close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3088071

код для вставки
April 30, 1963
3,088,061
E. c. SMITH
SHEET THICKNESS SENSING SERVOMECHANISM
4 Sheets-Sheet 1
Filed May 6, 1959
__Z
AH
(I'l
IN VEN TOR.
50/74/90 C. J/l/f/f
BY
maM
ATTORNEY
April 30, 1963
3,088,061
E. c. SMITH
SHEET 'mxcxmzss SENSING SERVOMECHANISM
Filed May 6, 1959
4 Sheets-Sheet 2
QMeww
§RQ
§R»§
on
Q
In
/
0
co
JOKFZUkwntmo:w
INVENTOR.
50/1445’? ‘6. sw/r/f
BY
'
m 0. ébi
ATTORNEY
April 30, 1963
i
E. c. SMITH
3,088,061
SHEET THICKNESS SENSING SERVOMECHANISM
ATTORNEY
United States Patent 0 "ice
3,088,061
Patented Apr. 30, 1963
2
1
' ness of a sheet of stock produced by a calender, which
3,088,061
has the above-mentioned desired operational character
SHEET THICKNESS SENSING SERVOMECHANISM
istics.
Edward C. Smith, Ramsey, N.J., assignor to United States
Rubber Company, New York, N.Y., a corporation of
New Jersey
Filed May 6, 1959, Ser. No. 811,397
30 Claims. (Cl. 318-28)
indicating the distance of a material surface from a ref
erence point comprises ‘a movable nozzle with an ori?ce
adapted to discharge a stream of gas against the material
of pneumatically actuated positioning servomechanism in
also includes mounting means, in ?xed spatial relation
ship to the reference point, upon which the nozzle is so
In a particular form of the invention, a device for
surface, and thereby develop within the nozzle a back
pressure of a magnitude dependent upon the distance be
This invention relates to servomechanisms with nega
tive velocity feed-back and, more particularly, to a type 10 tween the material surface and the ori?ce. The device
which a control means acts to control .a motive means
which positions a movable member at a desired position,
the control means being actuated by a pneumatic pressure
representative of the instantaneous position and velocity
mounted as to be movable relative to the material sur
face. The device also includes control means primarily
actuated by the back pressure within the nozzle, and hav
ing an output adapted to reposition the nozzle so as to
maintain within the nozzle a substantially constant pre
determined back pressure corresponding to a predeter
lar to that of the present invention, and in some respects
distance between the surface :and the ori?ce. The
resembling the devices of the present invention in struc 20 mined
device also includes means responsive to the rate of
of the ‘movable member.
The prior art discloses devices having a purpose simi
ture and operation. The present invention pertains to
change of position of the nozzle for modifying the back
the incorporation of negative velocity feed-back in a pneu
pressure in such a sense as to counteract the motion of
matically actuated servomcchanism, with resultant greatly
the nozzle, thereby providing negative velocity feed back
improved operational characteristics; to the means used
to incorporate the negative velocity feed-back; and to the 25 in the device and conferring upon the device desired
operational characteristics.
adaptation and application of such servomechanisms to
For a better understanding of the present invention,
a variety of purposes. The term “negative velocity feed
together with other and further objects thereof, refer
back,” as used in this application, refers to means where
ence is made to the following description taken in con
by the above-mentioned pneumatic pressure which actu
nection with the accompanying drawings, in which:
ates the control means is modulated in accordance with 30
FIGURE 1 represents, in part diagrammatically, a de
the velocity of the movable member, in such a sense as
vice according to the invention for automatically posi
to counteract the motion of the member. By the use
tioning a movable member at a desired position;
of negative velocity feed-back, it is possible to obtain
desirable operational characteristics of high sensitivity,
accuracy, and speed of response, combined with sta
bility, to a degree heretofore unknown in devices of the
FIGURE 2 is a view, partly in section and partly dia
grammatic, of a stock thickness-indicating device con
structed in accordance with the invention;
FIGURE 3 is an end view of a preferred nozzle utilized
in
the FIGURE 2 device;
‘Devices embodying my invention are useful for a num
FIGURE 4 is a side view of the FIGURE 2 device
ber of purposes, such as for continuously indicating or
recording the distance of a material surface from a ref 40 and its mount;
FIGURE 5 is a top view of the FIGURE 2 device
erence point, and more particularly for continuously in
and its mount;
dicating or recording the thickness of a moving sheet of
FIGURE 6 is a schematic diagram of a portion of a
material, for example a sheet of rubber or other material
servomechanism for controlling the gage of a calendered
type under consideration.
formed by a machine such as a calender, an extruder, a
spreader, etc.
My invention is also useful in servomechanisms for pc
stock utilizing the FIGURE 2 device;
FIGURE 7 is a circuit diagram of the control system
utilized in the FIGURE 6 servornechanism; and
FIGURE 8 shows the adaptation of the FIGURE 1
device to an instrument for the indication and recording
sitioning a member relative to a material surface, and
‘for controlling the thickness of a moving sheet of material
formed by a machine of the type mentioned. Other use
pneumatic pressure.
ful ‘applications of my invention, and its advantages over 50 of Referring
to FIGURE 1, there is shown therein a
devices previously used, will become evident in the fol
source B of supply of gas as a closely regulated constant
lowing.
pressure, which discharges gas to the atmosphere at D
It is therefore an object of the present invention to
through a passageway containing a ?xed flow resistance
provide ‘a pneumatically actuated servomechanism with
and a variable flow resistance R2. The passageway
negative velocity feed-back, having desired operational 55 R1
is connected at a point between the two ?ow resistances
characteristics of high sensitivity, accuracy, speed of re
R1 and R2 to a chamber V having means P for varying
sponse, and stability.
its volume (represented in the ?gure as a movable pis
It is a further object of the invention to provide a
ton), and to the controller C at 1. R1 has a large resist
pneumatically actuated servomechanism for positioning a
ance compared with R2, so that, under operating condi~
movable member at a desired position, having the above 60 tions, a relatively large pressure drop occurs across R1,
rnentioned desired operational characteristics.
and the gas ?ows through R1 at a substantially constant
It is another object of the invention to provide a new
rate, regardless of the relatively small pressure variations
and improved device for indicating the distance of a ma—
which occur in the region of system between R1 and R2.
terial surface from a reference point, which has the above
Thus the pressure in this region, which is applied to the
rnentioncd desired operational characteristics.
65
controller C at I, will, in the absence of any change in
It is another object of the invention to provide a new
volume of the chamber V, be determined by the flow of
and improved device for indicating the thickness of a
gas at a constant rate through R2, and so will be propor
moving sheet of stock produced by a calender, which
tional to the resistance R2. If the volume of V is de
has the above-mentioned desired operational charac
teristics.
70 creasing, the ?ow rate through R2 will be increased by
It is another object of the invention to provide a new
and improved servomechanism for controlling the thick
an amount equal to the rate of change of volume, and
hence the pressure applied at I will be increased as com
1%
3,088,061
pared with the “stationary” value. The movable mem
ber O is moved upwards or downwards by the motor M,
4
may take various forms, according to the particular ap
plication.
which receives power from a source S through the power
The device of FIGURE 1,, can be adapted to a wide
variety of useful purposes. . By way of illustration, im
supplied with a control reference pressure, corresponding
portant applications of the device are shown in FIGURES
ot the pressure at I when the movable member is sta
2—5, which show a device for indicating the thickness of
tionary and in the desired position. This control refer
a sheet of material, and in FIGURES 6 and 7 which illus
ence pressure may be furnished at an input port, indicated
trate the adaptation of the device of FIGURES 2-5 to
by A in FIGURE 1; or in some cases it may be gen
the control of the thickness of a calendered sheet of rub
erated within the controller. Means are provided for 10 ber or the like.
varying the resistance R2 in response to changes in posi
Referring now more particularly to FIGURE 2 of the
outlet Z of the controller C. The controller C is also
tion of the movable member 0, thereby developing at I
a pressure representative of the position of O. The ar
rangement is such that, as 0 moves upwards, R2 is in
drawings, there is represented a device 10 for indicating
the distance of the surface 94 of rubber stock 92 from
a reference point A at the surface 93 of a calender roll
creased. Means are also provided for moving the piston 15 as represented in fragmentary view. The device 10 thus
P in correspondence with the motion of 0, thereby modi
is effective to indicate the thickness of the stock. The
fying the pressure at I in proportion to the velocity of O.
device 10 includes movable means for discharging a gas
The operation of the device in FIGURE 1 can best
stream against the surface of the stock to develop within
be understood by ?rst considering how it would operate
the discharging means a back pressure of a magnitude
if the volume of the chamber V remained constant, and 20 dependent upon the distance between the surface of the
then considering how this operation is modi?ed when the
stock and the discharging means and upon the velocity of
volume of V is varied as speci?ed above. In the ab
the discharging means. The discharging means com
sence of any change in volume of the chamber V, gas
prises a nozzle 11 with an ori?ce 12 adapted to discharge
flows at a constant rate through the resistance R2, causing
an air stream supplied from a source of compressed air
a back pressure which depends only on the position of 25 33 through line 22a and restriction 99. The nozzle pref
the movable member 0. This back pressure is com
erably has a multihole ?at face 13, represented in FIG
pared in the controller C with the control reference pres
URE 3, for discharging a diffuse air stream against the
sure. When the movable member 0 is at the desired
surface of the stock without distorting the surface. The
position, these two pressures correspond, and the con
nozzle is slidably movable towards and away from the
troller operates to hold the motor M stationary. When 30 surface of the calender roll in the plate 15 of the device
the member 0 is not at the desired position, the two pres
10, which is mounted in ?xed spatial relationship to the
sures do not correspond, and the controller operates to
surface of the calender roll, all as more fully explained
drive the motor in such a direction as to restore the de
sired position of the member 0; the motor speed is
hereinafter. Thus, the ori?ce of the nozzle discharging
gas against the surface which is at a variable distance
higher, the greater the deviation of the back pressure 35 from the nozzle constitutes a variable ?ow resistance, the
from correspondence with the control reference pressure.
magnitude of which depends upon the distance from the
Thus the mechanism operates to maintain the movable
face 13 of the nozzle to the stock surface.
member 0 in the desired position. However, in the ab
The thickness-indicating device 10 also includes con
sence of negative velocity feed-back as furnished by the
means, actuated by the back pressure in the nozzle,
chamber V, the accuracy, sensitivity, speed or response, 40 trol
and having an output adapted to reposition the nozzle 11
and stability of the device are not satisfactory for many
so as to maintain within the nozzle a substantially con
purposes.
stant predetermined back pressure corresponding to a pre~
Considering now the effect of varying the volume of V,
determined distance between the nozzle face 13 and the
it is apparent that, if 0 is moving upwards in FIGURE
surface of the stock. More particularly, the control means
1 (in response to a decrease in pressure I), the volume 45 includes a pneumatic controller 14 actuated by the back
is decreasing, and the air ?ow through R2 is increased,
pressure for developing an output pressure adapted to
thereby increasing the pressure at I over that correspond
reposition the nozzle. The controller shown is a pneu
ing to the existing position of the member 0 with the
matic controller which is commercially available from
member 0 stationary. Similarly, if 0 is moving in the
opposite direction (i.e. downwards in FIGURE 1), the
pressure at I is decreased. The arrangement is such that
in both cases the pressure at I is modi?ed in such a sense
the Moore Products Company, Philadelphia, Pennsyl
vania. The controller 14 includes a chamber 50‘ bounded
by diaphragms 51 and 52 and connected to an adjustable
source 53 of control pressure of suitable magnitude (for
as to partially counteract the change in pressure which
initiated the action of the control means. The pressure
example, 3-5 pounds per square inch). The magnitude
results in negative velocity feed-back.
chamber 20 of the pneumatic motor (described below)
of this control pressure determines the distance between
change due to the volume change in chamber V is pro 55 the nozzle and the stock surface, as will be made clear
portional to the velocity of the movable member 0.
below. The controller also includes a chamber 54
Thus incorporation of the variable-volume chamber V
bounded by diaphragms 52 and 55 and connected to the
My invention as illustrated in FIGURE 1 is not limited
by means of line 22. The pressures of the chambers 50
to any particular type or form of any of the component 60 and 54 are balanced when the nozzle 11 is at a predeter
parts. The controller C and the motor M may be of any
mined distance, for example, 0.012 inch from the surface
types which, by suitable arrangement, can be adapted to‘
of the stock. A chamber 56, bounded by the diaphragm
cause appropriate motion of the motor M at a rate and in
55 and the outer wall, connects with control pressure
a direction determined by the extent and direction of the
deviation of the pneumatic pressure applied at the con
troller input I from correspondence with the control
reference pressure. For example, the controller C may
source 53, through a restriction 57. The diaphragm
assembly consists of the diaphragms 51, 52 and 55, dia
phragm stiffening discs 51a and 55a, and spacer rings
58a, all rigidly assembled on member 58 as shown. The
assembly is positioned between a leaf spring 59 and a
coil spring 60. One end 581) of the member 58 serves as
70 a pilot to open or close the ori?ce 61 of the pilot valve
ume of the chamber V is shown in FIGURE 1, for illus
62. The air source 33 is connected through a line 64, a
trative purposes, as a movable piston; but it is obvious
control the power delivered from an electrical source S
to an electrical motor M. The means for varying the vol
that other devices, such as liquid displacement piston,
a ?exibly mounted movable diaphragm, or a bellows-like
chamber could be used. The variable ?ow resistance R2
passageway 65, and a restriction 66 to a chamber 67
bounded by a diaphragm assembly 68.
The diaphragm assembly 68 comprises a porous inner
layer 680, communicating with the atmosphere, between
3,088,061
5
an impermeable layer 68a adjacent to chamber 67, and
an impermeable layer 68c, adjacent to another chamber 70
and having an aperture 72 connecting chamber 70 with
porous layer 680. Aperture 72 is opened or closed by
relative motion of diaphragm assembly 68 and valve stem
72a.
Valve stem 72a also carries ball valve" 74, which is
held in a normally closed position by coil spring 73.
6
opens valve 41—-41-a, allowing air to escape from chamber
47 to chamber 46, and thence to the atmosphere through
vent 38, and allows valve 39 to close under the action of
spring 39a. The pressure in chamber 47 is the output
pressure representative of the position of the nozzle
and operates the pressure gage 24, which indicates the
gage of the stock. The operation of the motion trans
mitter is as follows. Movement of the nozzle 11 to the
right causes pilot 29 to further obstruct the flow of air
valve stem 72a, valve 74 admits air from the source 33 10 from bellows unit 30. The resulting pressure increase in
bellows unit 30 and in chamber 45 moves diaphragm 36
through passageway 64 to chamber 70. The chamber 70
When opened by motion of diaphragm 68b acting through
communicates with chamber 71 through passageway 70a,
and with chamber 56 through passageway 70a and valve
to the left, opening valve 39 and thus increasing the pres
sure in chamber 47 and in connecting chamber 48. The
increased pressure in chamber 48 moves the bellows unit
70b. The pressure in chamber "70‘ is the output pressure
of the controller. Valve 70b controls the proportional 15 30 to the right against the force exerted by range spring
28a, repositioning port 29a to its original position with re
band of the controller and may be preset or adjusted to
spect to pilot 29. Air then escapes from bellows 30 and
provide, for example, a 12 pound per square inch pres
chamber 45 allowing diaphragm 36 to return to substan
sure change in the output in response to a .72 pound per
tially its original equilibrium position. The increase in
square inch pressure change in the input with a 6% pro
pressure in chambers 47 and 48‘, and in the gage 24, is
portional band setting. Restriction 57 is used in conjunc
directly jproportional to the distance which pilot 29
tion with valve 7% so that the pressure in chamber 56
is intermediate the control reference pressure and the
pressure in line 70a.
moves; thus both the pressure and the gage indication are
a measure of the gage of the sheet 92.
Referring now more particularly to FIGURES 4 and 5
A pneumatic motor for positioning the nozzle 11 is
driven by the output pressure of the controller. The 25 of the drawings, the stock thickness indicating device
10 is represented together with its associated mounting
motor comprises a movable member 18 attached to the
nozzle 11, and a ?exible diaphragm 19 attached to one
surface of the movable member 18 for forming one wall
means. The mounting means comprises a suitable I-bar
80, having a mounting bracket 81 for the device 10, and
attached at each end by suitable brackets 82 to a side
of the power chamber 21, of the pneumatic motor. The
pressure output of the controller is supplied to chamber 30 mounting plate 83. The mount has at each end a shoe
84 having a curved surface in contact with a surface 93a
21 by pipe 90. A cup-shaped member 17 attached to the
of the calender roll, and it is maintained in position by
nozzle and a coil spring 16 operating to push the nozzle
means of springs 85. (The surface 93a is preferably on a
assembly to the left are included in the means for posi
shoulder turned on the end of the calender roll as shown,
The device 10 also includes means responsive to the 35 to avoid clogging the contact area between 84 and 93a
with rubber.) Thus, the body of the device 10 is main
rate of change of position of the nozzle for providing neg
tioning the nozzle.
tained in ?xed spatial relationship with the surface of
the calender roll, following any variations of position
of the surface of the calender roll due to, for example,
be explained more fully hereinafter. This means com~
prises the chamber 20‘ in front of the diaphragm 19 and 40 displacements of the roll during rotation.
Considering now the operation of the FIGURE 2 de
the member 18 of the pneumatic motor. ‘The chamber
ative velocity feed-back in the device, thereby conferring
upon the device desired operational characteristics, as will
vice, -air at a pressure, for example, of 35 pounds per
square inch is supplied from source 33 through the re
striction 99, which maintains a substantially constant ?ow
10' also includes a pneumatic connection or air line 22 45 to line 22, and thence to chamber 20‘ and nozzle 11. The
20 has a volume which varies with displacements of the
diaphragm 19, and the chamber communicates pneumat
ically with the nozzle through passage 12a. The device
nozzle discharges the air against the surface of the stock,
for applying the pressure developed in the nozzle and the
developing a back pressure in the range of, for example,
chamber 20 to the controller chamber 54.
3-5 pounds per square inch in the chamber 20, which is
The device preferably also includes means associated
applied through line 22 to the controller. As will be ex
with the nozzle for visually indicating the gage of the
stock. As illustrated in FIGURE 2, this consists of means 50 plained more fully subsequently, the back pressure is com
pared with the control pressure in the controller, which
for developing an output pressure representative of the
delivers an output pressure in the range of, for example,
position of the nozzle relative to the mounting means,
0 to 35 pounds per square inch through line 98‘ to the
and pneumatic means responsive to this output pressure
chamber 21 of the pneumatic motor. The force thus
for indicating the position of the nozzle relative to the
mounting means, thereby indicating the thickness of the 55 developed is counteracted by the spring 16 acting against
cup-shaped member 17, causing the diaphragm 19, with
stock. The indicating means shown comprises in part a
the attached member 18 and nozzle 11, to assume its rest
motion transmitter which is commercially available from
position at a predetermined distance from the surface of
Moore Products Company. The motion transmitter com
the stock.
prises a housing 25 enclosing a chamber 26‘ having a
As the calender roll rotates and the thickness of the
vent 27 to the atmosphere. A shaft 28 is attached to‘ the 60
stock varies, the nozzle 11 follows the variations. As
nozzle 11, and supports a pilot 29 within a valve port 29a
usming that the stock moves away from the nozzle 11
in the bellows unit 30, which is connected pneumatically
due to a ‘decrease in stock thickness, the back pressure in
through a passageway 31, a pressure-dropping valve 32,
the nozzle ‘and the chamber 20 drops. This drop in back
and a line 31a to the source of compressed air 33. Cham
bers 45, 46 and 47 and 48 of the motion transmitter are 65 pressure is applied to chamber 54 of the controller, caus
ing the pilot 58b to move toward the nozzle ori?ce 61,
separated by a rigid plate 35 and ?exible diaphragms 36',
because the area of diaphragm 55 is twice the area of
37. The chamber 45 communicates with passageway 31.
diaphragm 52, and hence a decrease in pressure in cham
The chamber 46 has an exhaust vent 38' to the atmosphere.
ber 54 causes a net increase in the force acting to move
The flow of air into and out of chamber 47 is governed by
the position of diaphrams 36 and 37, acting through valve 70 the diaphragm assembly to the left. When the pilot 58b
more fully ‘obstructs the nozzle ori?ce 61, the flow of air
stem 41. Motion of ‘diaphragms 36 and 37 to the left
from source 33 through line ‘64, passageway 65 and re
seats stem 41 in valve seat 41a, closing the connection
striction 66 to the chamber 67 bounded by diaphragm
between chamber'47 and chamber 46, and opens valve 39,
admitting air from passage 31a to chamber 47 and con
68a causes an increase in the back pressure of the nozzle
necting chamber 48. Motion of diaphragm 36 to the right 75 62 and forces the assembly 68 into a position which tends
7
to close valve 72. This action also opens the valve 74',
allowing air to How from line 64 to chamber 70 and thus
increasing the pressure in the chamber 21 and moving
the diaphragm 19 and nozzle 11 toward the calender roll.
When the nozzle reaches the predetermined distance from
FIGURES 2-5 to this use will be described and dis
cussed with reference to FIGURES 6 and 7.
Referring to FIGURE 6 of the drawings, there is rep—
resented schematically a portion of a servomechanism for
the stock, the back pressure in chamber 20 returns to sub
thickness of the stock substantially constant. The out
put pressure in chamber 47 of the thickness-indicating
device or gage 10 of FIGURE 2 is connected to indicator
24, to a recorder 96 of conventional construction for
stantially its initial value, and the pressure in chamber
21 has increased enough to hold the nozzle assembly in its
new position. Since the pressures in chamber 50 and
adjusting the nip of the calender rolls to maintain the
chamber 54 are now substantially balanced, the con 10 recording the variations of thickness of the stock, and to
troller acts to maintain the new output pressure in
a differential pressure transmitter 97‘ of conventional con
chamber 21. The system then is in a condition of balance.
struction. An adjustable source (97a) of constant pres
When the nozzle 11 is acted upon by the control
sure equal to the output pressure of the thickness gage
means as described above, and moves toward the calen
corresponding to the desired stock thickness is also con
der roll while seeking its new position of balance, the dis—
phragm 19 moves toward the wall 15, descreasing the
volume of chamber 20. The decrease in volume of the
chamber 20 causes a component of pressure increase to be
developed in the chamber 20. This component of pres
nected to the differential pressure transmitter 97, which
thus develops an output pressure dependent upon the dif
ference between the two pressures supplied to it, and
hence representative of the deviation of the actual stock
thickness from the desired stock thickness. The output
sure increase partially nulli?es the decrease in back pres
sure which has occurred, due to the reduced thickness of
the stock. The component of pressure increase is directly
propertional to the rate of change of volume of the front
to four pressure-actuated switches 101, 102, 103, 104
which start and stop the calender roll screw-down motor
chamber, that is, proportional to the velocity of the dia
phragm 19. Thus the effect of the action is to reduce
operate and are actuated in a manner to be described
the actuating force exerted in chamber 54 of the control
ler by an amount which is proportional to the rate of
correction of the position of the nozzle. This constitutes
negative velocity feed-back.
In greater detail, the back pressure of the nozzle 11
can be expressed as a function of the ?ow rate through
the nozzle and the distance between the nozzle and the
stock surface. The ?ow rate can be expressed as the
sum of the constant flow from the restriction 99' supplying
air to the nozzle 11 and the ?ow due to the rate of
change of volume of the chamber 20. The back pres
sure, therefore, has a component which is a function of
the rate of change of volume of the chamber. This com
ponent is in opposition to the change in back pressure
caused by motion of the stock relative to the nozzle
mount, and is proportional to the velocity of the dia
phragm and nozzle. When ampli?ed and applied to
line of the differential pressure transmitter is connected
116 (shown diagrammatially in FIGURE 7), and which
presently.
The action of the differential pressure transmitter 97
is such that, when the stock has the desired thickness, the
output pressure of 97 has a de?nite value; and when
the stock thickness is greater (or less) than desired, the
output pressure of 97 is respectively less (or greater)
than this de?nite value by an amount which is larger,
the larger the deviation of the stock thickness. For def
initeness in this discussion, the following typical values
will be used for the relationship between stock thickness
35 and output pressure of 97:
Stock thickness deviation (mils)..
Output pressure of 97 (p.s.1.)
—2
--0.
11
9.
Ed
1
0
+0. 75
+2
9
8.25
7
The four pressure-actuated switches are then chosen and
adjusted to open and close, when the applied pressure
changes, in accordance with the following schedule:
chamber 21, this component provides negative velocity
Switch 101--open below 9.75 p.s.i.; closed above 9.75
feed-back. The necessity for, and the functioning of,
negative velocity feed-back in obtaining desirable opera 45 p.s.i.
Switch 102—-open above 8.25 p.s.i.; closed below 8.25
tional characteristics may be explained as follows. To
p.s.1.
'
obtain high accuracy and speed of response in the gage
Switch 103-open below 11 p.s.i.; closed above 11 p.s.i.
in following changes in stock thickness, it is necessary
Switch 104—open above 7 p.s.i.; closed below 7 p.s.i.
that a small change in the pressure in chamber 20, ap
plied to chamber 54 of the controller, shall result in 50 Comparison of this schedule with the output pressure vs.
a much larger change in the pressure in chamber 70, which
stock thickness relationship will show that for stock
operates the motor. That is, the controller should have
a high ampli?cation factor for speed and accuracy. How
ever, a system with a high ampli?cation factor is inherently
thickness deviations of 0.75 mil or less, all the switches
are open. For stock thickness deviations between 0.75
and 2 mils, switch 102 only is closed if the deviation is
unstable, and liable to uncontrolled oscillations, unless 55 positive, switch 101 only is closed if the deviation is
damping is present. Frictional damping is undesirable
negative. For deviations of more than 2 mils, switches
since it reduces the sensitivity. Negative velocity feed
102 and 104 are closed with positive deviations, switches
back, when properly adjusted, supplies damping in just
101 and 103 with negative deviations. These switches
the degree required vfor stability, without reducing the
are connected in a circuit shown in FIGURE 7 which
sensitivity. Negative velocity feed-back in effect con 60 operates to energize the screw~down motor 116 in a
tinuously and practically instantaneously varies the overall
suitable direction and at a suitable rate to correct the
ampli?cation factor inversely to the velocity of the nozzle.
stock thickness.
Thus corrections are made quickly and positively, but
In FIGURE 7, lines 108 and 110 carry the line voltage;
without loss of control.
106 is a relay which, when energized, closes contacts
When the thickness of the stock on the calender roll 65 1060 which energize the screw-down motor 116 so as
increases, the nozzle 11 moves away from the calender
to reduce the spacing of the calender rolls 117; 106 also
roll and assumes a new position at the predetermined
opens normally closed switch 106a and closes normally
distance from the surface of the stock. This operation
open switch 106k. Relay 109, when energized, closes
is analogous to that previously described and will not be
contacts 1090 which energize the screw-down motor 116
described in detail.
70 so as to increase the calender roll spacing; 109 also opens
A thickness indicating instrument, such as that of
normally closed switch 109a, and closes normally open
FIGURE 1 or FIGURES 2-5, may be used in a means
switch 10%. Switch 107, normally open, is closed for
for automatically controlling the gage of a sheet of a
a short time periodically (e.g. once each revolution of
plastic material formed ‘by a machine (for example a
the calender roll) by a suitable mechanical arrangement.
calender). 0ne method of applying the instrument of 75 Switch v105a, normally closed, is opened by time delay
3,088,061
relay 105 at a predetermined and adjustable time interval
after 105 is energized. Switch 113 connects either the
automatic control system at terminal 114 or the manual
control system at terminal 115 as desired, and push-button
10
As a further example of an application of the device
of FIGURE 1, FIGURE 8 shows, in part diagrammati
cally, a device for indicating or recording the variations
in a pneumatic pressure, or by extension the variations
in ‘any quantity which can be made, by suitable arrange
ment to manifest themselves as variations in a pneumatic
switches 111 and 112 are provided for manual operation
of the screw-down motor.
pressure. The elements of the device, and their mode of
It is evident that the automatic control system functions
operation, correspond closely to those of the FIGURE 1
as follows. If the stock thickness deviation is less than
device; corresponding parts in the two ?gures are corre—
0.75 mil, switches 101, 102, 103, and 104 are open, and
the screw-down motor remains stationary. If the devia 10 spondingly identi?ed.
In the FIGURE 8 device, the pressure which it is de
tion is greater than 2 mils, switches 102 and 1041‘ close
sired to indicate or record is applied to the controller C’
for positive deviations, and switches 101 and 103‘ close
as the reference pressure at the input port A’; the pointer
for negative deviations, the other two switches in each
E carrying a pen and connected to the shaft 0' of the
case remaining open; the screw-down motor operates
continuously in the proper direction to correct the devia 15 motor 1 ’ is moved over the chart G to record the pres
sure variations as shown :by line L. The motor M’ is
tion. For deviations between 0.75 and 2 mils, either
a pneumatic motor of the type shown in FIGURE 2, hav
switch 102. (positive deviations) or switch 101 (negative
ing a piston travel great enough to give the requisite range
of motion to‘ B. Low mechanical motion magni?cation
or 109 is energized only intermittently, when switch 107 20 may be used in linking M’ with E. The tapered rod R
attached to the shaft 0’ and moving in the hole H forms
momentarily closes, and the relay remains energized
deviations) is closed, the other three pressure-operated
switches remaining open. The corresponding relay 106
(through the holding action of relay 10Gb or 1091;) only
until time delay relay 105 opens switch 105a. Thus the
screw-down motor operates to correct the deviation only
the variable flow resistance R’z. As in the FIGURE 1
device, the pressure in the chamber V’ and connecting
(In the case under discussion, 105 would be set to give
about 0.6 mil correction in the stock thickness.) Switches
106:! and 109a insure against energizing both relays 106
pressure at A’, the device is in a balanced condition; the
pressure at 1’ corresponds to the input pressure, and the
controller C’ holds the motor M’ stationary. If now the
portions depends upon the value of the variable ?ow resis
periodically and intermittently, for periods of time de 25 tance R’2, and so is representative of the position of the
pointer E. When the pointer E indicates the value of the
termined by the setting of the time delay relay 105.
and 109v at the same time.
Switches 10Gb and 10% en 30 input pressure applied at A’ increases, the resulting un
ergize 105 at the proper time.
The above-described system for calender stock thick
ness control combines rapid correction of large devia
tions with freedom from over-shooting and “muting”
balance in the controller causes the motor to move to the
right, thereby increasing the How resistance R’2, and
causing the pressure at I’ to increase until balance once
more is reached. The change in volume of the chamber
V’ when the motor moves acts as in the previously de
in correcting small deviations. Using this system, it
has been possible to hold the gage of calendered stock
scribed devices to provide negative velocity feedback.
Thus the position of the pointer E substantially follows
within tolerances of plus or minus 1 mil.
From the foregoing description, it will be apparent
the pressure variations at A’ providing an indication and
that a stock thickness indicating device constructed in
a record thereof. This device is much superior to a sim
accordance with the invention has several advantages. 40 ple, direct-acting pressure gage in showing, on a large,
The device is ‘accurate, stable and has good speed of
easily-read scale, rapid changes of pressure, with a mini
response.
It is suitable for use in a servomechanism
mum of error due to time lag in response.
effective to control the nip of calender rolls to maintain
While there have been described what are at present
the thickness of the stock substantially constant. A plu
considered to be the preferred embodiments of this inven
rality of such gages, for example, one at each end of 45 tion, it will be obvious to those skilled in the art that
the calender rolls, may be employed to control a like
various changes and modi?cations may be made therein
number of independent adjustments to the calender, for
without departing from the invention, and it is, therefore,
example, separate screw-down action at the two ends.
aimed to cover all such changes and modi?cations as fall
While applicant does not wish to be limited to any
within the true spirit and scope of the invention.
particular set of parameters and operating character 50
Having thus described my invention, what I claim and
istics, the following have been successfully employed in
desire to protect by Letters Patent is:
a stock thickness-indicating gage constructed in accord
1. A servomechanism with negative velocity feedback
for positioning a member comprising: a motor adapted
ance with the invention.
to position said member; a controller actuated by a
Air pressures:
Supply-50 p.s.i. or higher. Source 33-3 5—40 p.s.i. 55 pneumatic pressure representative of the position and
velocity of said member and adapted to control said
(regulated to +03% ).
_
motor so as to maintain the desired position of said mem
Control pressure source 53—-adjustable 3-5 p.s.l.
ber; and means for developing the actuating pressure for
(regulated to +03%).
Nozzle ori?ce: 13 holes, 0.035" diameter, in ?at surface 60 said controller comprising a passageway for gas com
municating with said controller and having an entrance
0.250" diameter.
and an exit, means for introducing gas at the entrance to
Performance: Range-up to 0.25 inch thickness (range
said passageway at a constant rate of ?ow, means com
depends upon dimensions and design of the pneumatic
municating with said passageway for changing the rate
motor).
of ?ow of gas therein by an amount proportional in mag
Accuracy: -_t—0.5% of full range.
Speed of response-1 inch of nozzle travel per 65 nitude to the velocity of said member and in such a sense
as to counteract the motion of said member, a variable
second.
Stability of operation-excellent.
?ow resistance at the exit of said passageway, and means
including said motor for varying said variable ?ow resis
In comparison with the manual and automatic methods
of the prior art for indicating, adjusting, and controlling 70 tance in correspondence with the position of said member.
2. A servornechanism with negative velocity feedback
the gage of calendered sheets, the instrument of the present
for
positioning a member comprising: a motor adapted
invention is far superior in accuracy, reliability, and speed
to position said member; a controller actuated by a pneu
of operation, resulting in substantial savings in labor,
matic pressure representative of the position and velocity
material, and machine operating time, and improvements
in product quality.
75 of said member and adapted to control said motor so as
3,088,061
11
to'maintain the desired position of said member; and
means for developing the actuating pressure for said con
troller comprising a passageway for gas communicating
with said controller and having an entrance and an exit,
a ?xed flow resistance at the entrance of said passageway,
means for supplying ‘gas from a constant pressure supply
through said ?xed flow resistance to said passageway,
means communicating with said passageway for changing
12
with an ori?ce adapted to discharge a stream of gas
against the surface of said stock to develop within said
nozzle a back-pressure of a magnitude dependent upon
the distance between said surface and said ori?ce and
upon the velocity of said nozzle; mounting means, main
tained in a ?xed spatial relationship with the surface of
said calender roll, upon which said nozzle is so mounted
as to be movable relative to said stock surface; control
means actuated by said back-pressure and having an out
in magnitude to the velocity of said member and in such 10 put adapted to reposition said nozzle so as to maintain
a sense as to counteract the motion of said member, a
within said nozzle a substantially constant predetermined
variable ?ow resistance at the exit of said passageway, and
back-pressure corresponding to a predetermined distance
means including said motor for varying said variable ?ow
between said stock surface and said ori?ce; and means
resistance in correspondence with the position of said
responsive to the rate of change of position of said nozzle
member.
15 for providing negative velocity feed-back in said device,
the rate of ?ow of gas therein by an amount proportional
3. A servomechanism with negative velocity feed-back
for positioning a member comprising: a motor adapted
to position said member; a controller actuated by a pneu
matic pressure representative of the position and velocity
thereby conferring upon said device desired operational
characteristics.
7. A device for indicating variations of position of a
material surface comprising: movable means for dis
of said member and adapted to control said motor so 20 charging a gas stream against said material surface to
as to maintain the desired position of said member; and
develop a back-pressure dependent in magnitude upon
means for developing the actuating pressure for said con
vthe distance between said material surface and said dis
troller comprising a passageway for gas communicating
charging means and upon the velocity of said discharging
with said controller and having an entrance and an exit,
means; means for mounting said discharging means mov
a ?xed ?ow resistance at the entrance of said passageway, 25 ably relative to said material surface; a pneumatic con
means for supplying gas from a constant pressure sup
troller actuated by said back-pressure for developing an
ply through said ?xed flow resistance to said passageway,
a chamber communicating with said passageway and hav
ing a wall movable with said member for varying the
output pressure representative of said back-pressure;
means actuated by said output pressure of said pneu~
matic controller for repositioning said discharging means
volume of said chamber to change the rate of ?ow in said 30 so as to maintain a substantially constant predetermined
passageway by an amount proportional in magnitude to
back-pressure within said discharging means, the posi
the velocity of said member and in such a sense as to
tion of said discharging means thus being representative
counteract the motion of said member, a variable ?ow
of the position of said material surface; and means re
resistance at the exit of said passageway, and means in
sponsive to the rate of change of position of said dis
cluding said motor for varying said variable ?ow resist 35 charging means for developing negative velocity feed-back
ance in correspondence with the position of said member.
4. A device for indicating the distance of a material
surface from a reference point comprising: a movable
nozzle with an ori?ce adapted to discharge a stream of
gas against said material surface to develop within said
nozzle a ‘back-pressure of a magnitude dependent upon
in said device, thereby imparting to said device desired
operational characteristics.
8. A device for indicating variations of position of a
material surface comprising: movable means for dis
charging a gas stream against said material surface to
develop a back-pressure dependent in magnitude upon
the distance between said material surface and said ori?ce
and upon the velocity of said nozzle; mounting means,
in ?xed spatial relationship to said reference point, upon
the distance between said material surface and said dis
which said nozzle is so mounted as to be movable relative
ably relative to said material surface; a pneumatic con
troller actuated by said back-pressure for developing an
output pressure representative of said back-pressure; a
pneumatic motor, actuated by said output pressure of
said controller, having a movable member attached to
said discharging means for repositioning said discharging
to said material surface; control means actuated by said
back-pressure and having an output adapted to reposition
said nozzle so as to maintain within said nozzle a sub
stantially constant predetermined back-pressure corre
sponding to a predetermined distance between said sur
face and said ori?ce; and means responsive to the rate
of change of position of said nozzle relative to said sur
face for providing negative velocity feed-back in said de
vice, thereby conferring upon said device desired oper
ational characteristics.
5. A device for indicating variations of position of a
charging means and upon the velocity of said discharging
means; means for mounting said discharging means mov
means so as to maintain a substantially constant prede
termined back-pressure within said discharging means,
the position of said ‘discharging means thus being repre~
sentative of the position of said material surface; and
means responsive to the rate of change of position of
said discharging means for providing negative velocity
feed-back in said device, thereby imparting to said device
desired operational characteristics.
material surface comprising: movable means for dis
charging a gas stream against said material surface to
develop within said discharging means a back-pressure of
7 9. A device for indicating variations of position; of a
a magnitude dependent upon the distance between said
60 material surface comprising: movable means for dis
material surface and said discharging means and upon
charging a gas stream against said material surface to
the velocity of said discharging means; means for mount
develop a back-pressure dependent inmagnitude upon
ing said discharging means movably relative to said ma
the distance between said material surface and said dis
terial surface; control means actuated by said back-pres
charging means and upon the velocity of said discharg
sure for repositioning said discharging means so as to
maintain a substantially constant predetermined back— 65 ing means; means for mounting said discharging means
movably relative to said material surface; a pneumatic
pressure within said discharging means, the position of
controller actuated by said back-pressure for developing
said discharging means thus being representative of the
an output pressure representative of said back-pressure;
position of said material surface; and means responsive
a pneumatic motor having a diaphragm attached to said’
to the rate of change of position of said discharging means
discharging means and actuated by said output pressure
for providing negative velocity feed-back in said device,
thereby imparting to said device desired operational
characteristics.
6. A device for indicating the thickness of moving
of said controller for repositioning said discharging
means so as to maintain a substantially constant prede
termined back-pressure within said discharging means,
stock on a calender roll comprising: a movable nozzle 75 the position of said discharging means thus being repre
sentative of the position of said material surface; and
3,088,061
13
means comprising a chamber of variable volume, com
municating with said discharging means and with said
controller and responsive to the velocity of said dis
charging means for varying the volume of said chamber
to develop a component of flow rate through said dis
for providing negative velocity feed-back in said device,
thereby conferring upon said device desired operational
characteristics; means associated with said nozzle for de
veloping an output pressure representative of the position
of said nozzle relative to said mounting means; and pneu
matic means responsive to said output pressure for indi
charging means proportional to said velocity and in such
cating the position of said nozzle relative to said mount
direction as to provide negative velocity feed-back in the
ing means, thereby indicating the distance of said material
device, thereby imparting to the device desired opera
surface from said reference point.
tional characteristics.
13. A servomechanism for positioning a movable mem
10. A device for indicating the thickness of moving 10
stock on a calender roll comprising: movable means for
discharging a stream of gas against the surface of said
stock to develop a back-pressure dependent in magnitude
upon the distance between said surface of said stock and
said discharging means and upon the velocity of said dis
charging means; means for mounting said discharging
means movably relative to said surface of said stock; a
pneumatic controller actuated by said back-pressure for
ber at a predetermined distance from a surface compris
ing: movable means for discharging a gas stream against
said surface to develop within said discharging means a
hack-pressure dependent in magnitude upon the distance
between said surface and said discharging means and upon
the velocity of said discharging means; means for mount
ing said discharging means movably relative to said sur
face; means for moving said movable member in direct
correspondence with the motion of said discharging
developing an output pressure representative of said
control means actuated by said back-pressure
back-pressure; a pneumatic motor having a diaphragm 20 means;
and having an output adapted to reposition said discharg
attached to said discharging means and actuated by said
ing means so as to maintain with said discharging means
output pressure of said controller for repositioning said
a substantially constant predetermined back-pressure cor
discharging means so as to maintain a substantially con
stant predetermined back-pressure within said discharg
responding to said predetermined distance between said
surface and said movable member; and means responsive
ing means, the position of said ‘discharging means thus 25 to the rate of change of position of said discharging
eing representative of the position of said surface of
means for providing negative velocity feed-back in said
said stock; means, comprising a chamber of variable
servomechanism, thereby conferring upon said servo‘
volume bounded at one side by said diaphragm and hav
mechanism desired operational characteristics.
ing a volume which varies with displacements of said
14. A servomechanism for positioning a movable mem
30
diaphragm and communicating pneumatically with said
ber at a predetermined distance from a surface compris
nozzle and with said controller, responsive to the velocity
ing: a movable nozzle having a multiholed ?at face for
of said discharging means for varying the volume of said
discharging a diffuse stream of gas against said surface
chamber to develop a component of ?ow rate through
without distorting said surface to develop within said
said discharging means proportional to said velocity and
nozzle
a back-pressure dependent upon the distance be
in such direction as to provide negative velocity feed 35 tween said surface and said nozzle and upon the velocity
back in the device, thereby imparting to- said device de
of said nozzle; means for mounting said nozzle movably
sired operational characteristics.
relative to said surface; means for moving said movable
11. A device for indicating the distance of a material
member in direct correspondence with the motion of said
surface from a reference point comprising: a movable
nozzle; control means actuated by said back-pressure
40
nozzle with an ori?ce adapted to discharge a stream of
and having an output adapted to reposition said nozzle so
gas against said material surface to develop within said
as to maintain within said nozzle a substantially constant
nozzle a back-pressure of a magnitude dependent upon
predetermined back-pressure corresponding to said prede
the distance between said material surface and said ori?ce
termined distance between said surface and said movable
and upon the velocity of said nozzle; mounting means,
member; and means responsive to the rate of change of
in ?xed spatial relationship to said reference point, upon 45 position of said nozzle for providing negative velocity
which said nozzle is so mounted as to be movable relative
feed-back in said servomechanism, thereby conferring
to said material surface; control means actuated by said
upon said servomechanism desired operational character
back-pressure and having an output adapted to reposition
istics.
said nozzle so as to maintain within said nozzle a sub
15. A servomechanism for controlling the position of
stantially constant predetermined back-pressure-corre
sponding to a predetermined distance between said surface
and said ori?ce; means responsive to the rate of change
of position of said nozzle relative to said surface for pro
viding negative velocity feed-back in said device, thereby
conferring upon said device desired operational character
istics; and means for indicating the position of said nozzle
relative to said mounting means, thereby indicating the
distance of said material surface from said reference
a surface relative to a reference point comprising: a
?rst portion comprising movable means for discharging
a gas stream against said surface to develop within said
discharging means a back-pressure dependent in magni
tude upon the distance between said surface and said dis
charging means and upon the velocity of said discharg
ing means; means, in ?xed spatial relationship to said
reference point, for mounting said discharging means
movably relative to said surface; control means actuated
point.
12. A device for indicating the distance of a material 60 by said back~pressure and having an output adapted to
surface from a reference point comprising: a movable
nozzle with an ori?ce adapted to discharge a stream of
gas against said material surface to develop within said
nozzle a back-pressure of a magnitude dependent upon
the distance between said material surface and said ori?ce
and upon the velocity of said nozzle; mounting means, in
?xed spatial relationship to said reference point, upon
reposition said discharging means so as to maintain with
in said discharging means a substantially constant pre
determined back-pressure corresponding to a predeter
mined distance between said discharging means and said
surface; means responsive to the rate of change of po
sition of said discharging means relative to said surface
for providing negative velocity feed-back in said ?rst
portion; and a second portion comprising means respon
sive to the position of said discharging means for chang
which said nozzle is so mounted as to be movable rela
tive to said material surface; control means actuated by
said back-pressure and having an output adapted to re 70 ing the position of said surface; whereby said servomech~
anism maintains said surface substantially at a predeter
position said nozzle so as to maintain within said nozzle
mined position relative to said reference point.
a substantially constant predetermined back-pressure cor~
16. A servomechaninsm for controlling the position of
responding to a predetermined distance between said sur
a
surface
relative to a reference point comprising: a
face and said ori?ce; means responsive to, the rate of
change of position of said nozzle relative to said surface 75 movable nozzle with an ori?ce adapted to discharge a
3,088,061
16
stream of gas against said surface to develop within said
nozzle a back-pressure of a magnitude dependent upon
the distance between said surface and said ori?ce and
means movably relative to said surface of said stock; a
pneumatic controller actuated by said back-pressure for
developing an output pressure representative of said back
pressure; means actuated by said output pressure of said
pneumatic controller for repositioning said discharging
upon the velocity of said nozzle; means, in ?xed spatial
relationship to said reference point, ‘for mounting said
nozzle movably relative to said surface; a pneumatic con
means so as to maintain a substantially constant predeter
troller actuated by said back-pressure for developing an
output pressure representative of said back-pressure; a
pneumatic motor having a diaphragm attached to said
mined back-pressure within said discharging means, the
position of said discharging means thus being representa
tive of the position of said surface of said stock; and
nozzle and actuated by said output pressure of said con
means responsive to the rate of change of position of
troller for repositioning said nozzle so as to maintain
said discharging means for developing negative velocity
feed-back in said device, thereby imparting to said device
desired operational characteristics.
20. A device for indicating the thickness of moving
within said nozzle a substantially constant predetermined
back-pressure corresponding to a predetermined distance
between said surface and said nozzle; means, compris
ing a chamber of variable volume, communicating with
stock on a calender roll comprising: movable means for
said nozzle and with said controller and responsive to
discharging a stream of gas against the surface of said
the velocity of said nozzle relative to said surface, for
varying the volume of said chamber to develop a com
ponent of ?ow rate through said nozzle proportional to
said velocity and in such direction as to provide negative 20
stock to develop a baclopressure dependent in magnitude
upon the distance between said surface of said stock and
said discharging means and upon the velocity of said dis
charging means; means for mounting said discharging
velocity feed-back in the servomechanism; and means
responsive to the position of said nozzle for changing
means movably relative to said surface of said stock; a
pneumatic controller actuated by said back-pressure for
developing an output pressure representative of said back
pressure; a pneumatic motor, actuated by said output pres
the position of said surface so as to maintain said sur
face substantially at a predetermined position relative to
25 sure of said controller, having a movable member attached
said reference point.
to said discharging means ‘for repositioning said discharg
17. A device for indicating the thickness of moving
stock on a calender roll comprising: a movable nozzle
ing means so as to maintain a substantially constant pre
having a multiholed ?at face for discharging a diffuse
stream of gas against the surface of said stock without
distorting said surface to develop within said nozzle a
back-pressure dependent upon the distance between said
surface and said nozzle and upon the velocity of said
determined back-pressure within said discharging means,
the position of said discharging means thus being repre
sentative of the position of said surface of said stock; and
nozzle; mounting means, maintained in a ?xed spatial
relationship with the surface of said calender roll, upon
which said nozzle is so mounted as to be movable rela
tive to said stock surface; control means actuated by said
back-pressure and having an output adapted to reposition
said nozzle so as to maintain Within said nozzle a sub
stantially constant predetermined back-pressure corre
sponding to a predetermined distance between said sur
face and said nozzle; and means responsive to the rate
of change of position of said nozzle relative to said sur
means responsive to the rate of change of position of said
discharging means for providing negative velocity 'feed
back in said device, thereby imparting to said device de
sired operational characteristics.
35
21. A device for indicating the thickness of moving
stock on a calender roll comprising: movable means for
discharging a stream of ‘gas against the surface of said
stock to develop a back-pressure dependent in magnitude
upon the distance between said surface of said stock and
said discharging means and upon the velocity of said dis
charging means; means -for mounting said discharging
means movably relative to said surface of said stock; a
face for providing negative velocity feed-back in said de
vice, thereby conferring upon said device desired op
pneumatic controller ctuated by said back-pressure for
with an ori?ce adapted to discharge a stream of gas
ing means so as to maintain a substantially contsant pre
developing an output pressure representative of said back
45 pressure; a pneumatic motor having a diaphragm attached
erational characteristics.
to said discharging means and actuated by said output
18. A device for indicating the thickness of moving
pressure of said controller for repositioning said discharg
stock on a calender roll comprising: a movable nozzle
determined back-pressure within said discharging means,
against the surface of said stock and thereby develop with
in said nozzle a back-pressure of a magnitude depend 50 the position of said discharging means thus being repre
sentative of the position of said surface of said stock;
ent upon the distance between said surface of said stock
means, comprising a chamber of variable volume, com
and said ori?ce and upon the velocity of said nozzle;
municating with said discharging means and with said
mounting means, including a member in contact with said
controller
‘and responsive to the velocity of said discharg
' calender roll and responsive to movements thereof ‘for
55 ing means for varying the volume of said chamber to de
maintaining said mounting means in ?xed spatial rela
velop a component of ?ow rate through said discharging
tionship to said calender roll, upon which said nozzle is
means proportional to said velocity and in such direction
so mounted as to be movable relative to said surface of
as to provide negative velocity feed-back in the device,
said stock; control means actuated by said back-pres
thereby imparting to said device desired operational char
sure and having an output adapted to reposition said noz 60 acteristics.
zle so as to maintain within said nozzle a substantially
constant predetermined back-pressure corresponding to
a predetermined distance between said surface and said
ori?ce; and means responsive to the rate of change of
22. A device for indicating the thickness of moving
stock on a calender roll comprising: a movable nozzle
with an ori?ce adapted to discharge a stream of gas
against the surface of said stock to develop within said
position of said nozzle relative to said surface for provid 65 nozzle a back-pressure of a magnitude dependent upon the
ing negative velocity feed-back in said device, thereby
distance between said surface of said stock and said ori?ce
conferring upon said device desired operational character
and upon the velocity of said nozzle; mounting means,
istics.
in ?xed spatial relationship with the surface of said cal
19. A device for indicating the thickness of moving
ender roll, upon which said nozzle is so mounted as to be
stock on a calender roll comprising: movable means for 70 movable relative to' said surface of said stock; control
discharging a stream of gas against the surface of said
means actuated by said back-pressure and having an out
stock to develop a back-pressure dependent in magnitude
put adapted to reposition said nozzle so as to maintain
upon the distance between said surface of said stock and
said discharging means and upon the velocity of said dis
charging means; means for mounting said discharging
Within said nozzle a substantially constant predetermined
back-presure corresponding to: a predetermined distance
between said surface and said ori?ce; means responsive to
3,088,061
17
the rate of change of position of said nozzle relative to
said surface for providing negative velocity ‘feed-back in
said device, thereby conferring upon said- device desired
operational characteristics; and means for indicating the
position of said nozzle relative to said mounting means,
thereby indicating the thickness of said stock.
18
to the velocity of said nozzle relative to said surface, for
varying the volume of said chamber to develop a com
ponent of flow rate through said nozzle proportional to
said velocity in such direction as to provide negative ve
locity feed-back in the servomechanism; and means re
sponsive to ‘the position of said nozzle for adjusting the
nip of said calender rolls so as to maintain the thickness
of the said stock substantially constant.
stock on a calender roll comprising: a movable nozzle
26‘. Apparatus for automatically controlling a dimen
with an ori?ce adapted to discharge a stream of gas
sion of a material produced by a machine in continuous
against the surface of said stock to develop within said
lengths comprising: gaging means for developing a pneu
nozzle a back-pressure of a magnitude dependent upon
matic pressure representative of said dimension of said
the distance between said surface of said stock and said
material; means for supplying a pneumatic pressure repre
ori?ce and upon the velocity of said nozzle; mounting
sentative of the desired value of said dimension; a differen
means, in ?xed spatial relationship with the surface of
said calender roll, upon which said nozzle is so mounted 15 tial pressure transmitter actuated by said pressures and
adapted to furnish an output pressure representative of
as to be movable relative to said surface of said stock;
the deviation of the value of said dimension from said de
control means actuated by said back-pressure and having
sired value; and means responsive to said output pres
an output adapted to reposition said nozzle so as to main
sure of said differential pressure transmitter adapted to
tain within said nozzle a substantially constant prede
effect an adjustment of said machine and thereby bring
termined back-pressure corresponding to a predetermined
said dimension of said material to said desired value.
distance between said surface of said stock and said ori
27. Apparatus for automatically controlling a dimen
?ce; means responsive to the rate of change of position of
sion of a material produced by a machine in continuous
said nozzle relative to said surface for providing negative
lengths comprising: gaging means for developing a pneu
velocity feed-back in said device, thereby conferring upon
said device desired operational characteristics; means as 25 matic pressure representative of said dimension of said
material; means for supplying a pneumatic pressure repre
sociated with said nozzle for developing an output pres
sentative of the desired value of said dimension; a dif
sure representative of the position of said nozzle relative
ferential pressure transmitter actuated by said pressures
to said mounting means; and pneumatic means responsive
and adapted to furnish an output pressure representative
to said output pressure for indicating the position of said
nozzle relative to said mounting means, thereby indicating 30 of the deviation of the value of said dimension from said
desired value; electrically energized motor means for ad
the thickness of said stock.
justing said machine to change said dimension of said ma
24. A servomechanism for controlling the thickness of
terial; and an electrical circuit comprising a plurality of
stock moving between calender rolls comprising: a ?rst
pressure-operated electrical switches actuated by said out
portion comprising movable means for discharging a
stream of gas against the surface of said stock to develop 35 put pressure and adapted to energize said motor means
in such a sense as to adjust said dimension of said mate
within said discharging means a back-pressure dependent
rial to said desired value.
in magnitude upon the distance between said surface of
23. A device for indicating the thickness of moving
said stock and said discharging means and upon the ve
28. Apparatus for automatically controlling the gage
of sheet stock produced by a calender comprising gaging
locity of said discharging means; means, in ?xed spatial
relationship to the surface of one of said calender rolls, 40 means adapted to furnish a pneumatic pressure repre
sentative of the gage of said stock; means for supplying
for mounting said discharging means movably relative to
a constant pneumatic pressure representative of the de
said surface; control means actuated by said back-pressure
sired gage of said stock; a differential pressure transmitter
and having an output adapted to reposition said discharg
actuated by said pressures and adapted to furnish an
ing means so as to maintain within said discharging means
a substantially constant predetermined back-pressure cor 45 output pressure representative of the deviation of the
actual stock gage from the desired stock gage; electrically
responding to a predetermined distance between said sur
energized motor means for opening and closing the nip
face of said stock and said discharging means; means re
sponsive to the rate of change of position of said discharg
of the calender rolls; and an electrical circuit, comprising
ing means relative to said surface for providing negative
a plurality of pressure-operated switches actuated by said
velocity feed-back in said ?rst portion; and a second por
output pressure and adapted to energize said motor means
tion comprising means responsive to the position of said
to change the nip separation in such direction and to
discharging means for adjusting the nip of said calender
such extent as to correct for the deviation of the actual
rolls so as to maintain the thickness of the said stock sub
stock gage from‘ the desired stock gage, when said devia
stantially constant.
tion exceeds a predetermined amount.
'25. A servomechanism for controlling the thickness of 55
29. Apparatus for ‘automatically controlling the gage
stock moving between calender rolls comprising: a mov
of sheet stock produced by a calender comprising gaging
able nozzle with an ori?ce adapted to discharge a stream
means adapted to furnish a pneumatic pressure repre
of gas against the surface of said stock to develop within
sentative of the gage of said stock; means for supplying
said nozzle a back-pressure of a magnitude dependent
upon the distance between said surface of said stock and 60 a constant pneumatic pressure representative of the de
sired gage of said stock; a differential pressure transmitter
said ori?ce and upon the velocity of said nozzle; means in
actuated by said pressures and adapted to furnish an
?xed spatial relationship to the surface of one of said
output pressure representative of the deviation of the
calender rolls for mounting said nozzle movably relative
actual stock gage from the desired stock gage; electrically
to said surface of said stock; a pneumatic controller actu
65
energized
motor means for opening and closing the nip
ated by said back-pressure for developing an output pres
of the calender rolls; and an electrical circuit, comprising
sure representative of said back-pressure; a pneumatic
a ?rst pressure-operated on-off switch, actuated by said
motor having a diaphragm attached to said nozzle and
output pressure, which is closed only when said output
actuated by said output pressure of said controller for
pressure exceeds a predetermined value corresponding to
repositioning said nozzle so as to maintain within said
a predetermined deviation of the stock gage in one sense,
nozzle a substantially constant predetermined back-pres
and a second such switch which is closed only when said
output pressure is less than a predetermined value cor
responding to a predetermined deviation of the stock gage
prising a chamber of variable volume, communicating
with said nozzle and with said controller and responsive 75 in the opposite sense, whereby said motor means is ener
sure corresponding to a predetermined distance between
said surface of said stock and said ori?ce; means, com
19
3,088,063 1
gized in such sense and to such extent as to correct said
deviation, when it exceeds a predetermined amount.
30. An apparatus as in claim 29 in which said elec
trical circuit includes a normally closed timer switch de
signed to open the supply line to said circuit at a pre
determined time interval after energiz-ation of said motor
means, a normally open ‘sampling switch in ‘series with
said timer switch, means for momentarily closing said
sampling switch at periodic time intervals, and a normally
. open holding-relay switch shunting ‘said sampling switch.
20
References Cited in the ?le of this patent _
UNITED STATES PATENTS ~
1,317,956
2,156,895
2,244,864
2,295,399
2,43 8,696
2,763,278
2,83 8,028
2,927,455
Carlstedt _____________ __ Oct. 7,
Godat ________________ __ May 2,
Witham _____________ __ June 10,
Hanna _______________ __ Sept. 8,
Fox et a1 _____________ __ Mar. 30,
Eller et a1. ___________ __ Sept. 18,
1919
1939
1941
1942
1948
1956
Erbguth _____________ __ June 10, 1958
Outterson _____________ __ Mar. 8, 1960
Документ
Категория
Без категории
Просмотров
4
Размер файла
1 997 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа