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Патент USA US2411451

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NOV; 19, 1945-
R. J. DEMARTINI EI‘AL
2,411,451
CONTROL APPARATUS FOR TESTING MACHINES
Filed March 31, 1945
wml
Inventors :
' Robert J. Demar‘tini,
Henry H. Leigh ,.
Then" Attorney
Patented Nov. ‘1%), i946
'1 11,45
UNITED STATES PATENT OFFICE
2,411,451
CONTROL APPARATUS FOR TESTING
MACHINES
Robert J. Demartini, Schenectady, and Henry H.
Leigh, Scotia, N. Y., assignors to General Electric Company, a corporation of New York
1
,
Application March 31, 1945, Serial No. 585,962
11 Claims. (Cl. 73-90)
2
This invention relates to the'testing of ma
terials, more particularly to apparatus vfor test
ing material samples, and it has for an object
.
to provide a reference voltage, and an induction
the provision of a'simple, reliable, inexpensive,
and improved apparatus of this character.
In the testing of many materials such as textile
of application Of load. In one speci?c embodi
ment of the invention a potentiometer is used
5
fabrics,the apparent strength'of the material as
voltage regulator, and resistance capacitance cir
cult-associated therewith supplies to a secorid
_ potentiometer a signal voltage which is propor
tional to the rate of application of load to the.
determined by a testing machine varies ma
material specimen. The difference of these two
terially with variations in the rate at which load
voltages is utilized to control suitable electric
is applied to the test sample. The rate of ap
plication of load to the material sample, in turn, 10 valve apparatus to control the supply of current
to the motor which drives the testing machine to
depends upon the elasticity or “stretchiness” of
equalize the two voltages, thereby to e?ect ap
the material sample. Consequently, markedly
plication of load to the specimen at a constant
different indications of tensile strength are ob
rate.
.
tained from material samples having the same
15
For
a
better
and
more
complete
understand
actual tensile strength but having different elas
ing of the invention, reference should now be had
ticities. Accordingly, a further object of this
to the following speci?cation and to the accom
invention is the provision» of means'for con
panying drawing of which the single ?gure is a .
trolling a testing machine in‘such a manner that
simple,
diagrammatical sketch of an embodiment
the 'rate of application of load to the test sample
of the invention.
-
is independent of the elasticity of the material 20
and therefore reproducible from'sample to sam
ple.
.
Referring now to the drawing, a material test
ing machine is illustrated as being provided with
two members I and 2 for holding a sample of
the material which is to'sbe tested for tensile
machine in such a manner that the application 25 strength. Each of the members I and 2 may be
a conventional pair of jaws for securely gripping
of load is substantially uniform for all materials
the sample. The lower pair of jaws 2 is mounted
irrespective of their elasticity.
on a'screw 3 which is in threaded engagement
Another object of the invention is the provi
sion of improved apparatus of the character 30 with a nut (not shown) within the gear box 4.
The nut is connected through a gear train and
described in the foregoing in which the initial
a chain and sprocket drive 5 to the shaft of an
rate at which load is imposed on the sample is
electric motor 6. Although the motor 6 may be
low so that substantially all possibility of shock
of any suitable type, it is illustrated as a sep
is eliminated.
.
arately excited D.-C‘. motor.
A still further object of the invention is the
The upper pair of jaws l is connected through
provision- of means for- compensating for the 35
Another object of the invention is the provision
of improved means for controlling the testing
a chain 1 to a drum 8 which is rotatably mount
ed on the frame of the machine. Secured to
the drum is a pendulum 9 comprising an arm
of load.
‘
I
9c having a weight 912 on the free end.
40
In order to cause the load to be applied to
In carrying the invention into effect in one form
the test sample at a uniform rate, suitable means
thereof, a testing machine is utilized which has
are provided for comparing the rate of applica
a pair of members for holding the test sample.
tion of load to the test sample with a constant
One of these members is‘driven by an electric
motor in a direction to apply a force to the sam 45 reference rate, and utilizing the di?‘erence to
control the speed of the motor 6.
ple. Meansare provided for producing a con
The load on the test sample varies with the
stant reference voltage which corresponds to a
angular position of the pendulum. Since the
predeterminedconstant rate. Additional means
weight of the pendulum remains constant, the
are provided for producing a signal voltage which
load on the sample varies with the length of the
corresponds ‘to the rate of application of load
or force to the material sample. The difference
RI drop 01' the motor which drives the testing
machine when the stretch is being taken out of
the material specimen prior to the application
between the two voltages is utilized to control
is proportional to the sine of the angle 0 between
the motor which drives the testing machine to
the arm of the pendulum and the vertical.
equalize the rate at which the loadis being ap
The reference voltage which corresponds to a
plied tofthe sample with the predetermined rate 55
predetermined rate of application of load to the
2,411,451 _
.
material specimen is derived from the source
of alternating voltage ill by means of a trans
former H, a recti?er l2 and a potentiometer £3.
The transformer has a primary winding Ma and
three secondary windings lib, lie, and lid. The
recti?er i2 is illustrated as a diode electric valve.
It is connected in series with the potentiometer
I3 across the secondary winding l lb and supplies
a recti?ed voltage to the potentiometer which is
maintained substantially constant by the'capaci
tor during the half cycle of anode-voltage in
which the recti?er is not conducting. The volt
age which appears across the potentiometer i3
is the reference voltage.
'
‘
d
in which C is the capacity of the capacitor 22 and
iv
dT
" is the rate of change of the voltage impressed
on the capacitor. The capacity C is ?xed, and
since the voltage impressed on the capacitor is
proportional to the load applied to the material
specimen, the current I is proportional to‘ the
rate of change, i. e., rate of application of load on
10 the material specimen.
This current ?owing
through the potentiometer 23 produces a signal
,voltage dropvacross the potentiometer which is
proportional to this current. This signal volt
age is thus'proportional to therate of application
For the purpose of providing an indication of 15 of load to the material specimen.
'
the rate of application of load to the material
- For the purpose of providing a control voltage
specimen an induction voltage regulator 15 is
for the operation of the control switches, voltage
provided. This induction voltage regulator has
buses 25 and 28 are provided. Aisubstantially
a stator coil Mia and an inductively related rotor
constant direct voltage is supplied to the control
20
voltage buses 25 and 26 by means of suitable
coil 15?) mounted upon the‘ rotor member. The
stator coil is supplied with alternating voltage
rectifying means which‘ is illustrated as a double
from a suitable source such as represented by the
diode electric valve 2? of which the anodes 21a
two supply lines it. This source may be and
and 21b are connected to opposite terminals of
the secondary winding Me of the supply trans
preferably is the same source as that represented
by the supply lines it. The rotor member upon 25 former H, and the cathode is connected to the
bus 25. The bus 26 is connected to the center tap
which the. rotor coil Hub is mounted is me
of the secondary winding tic of the supply transé
chanically connected by means of a shaft H or
other suitable coupling to the shaft of the test
former. As thus connected, the valve Zl op
ing machine drum 8. When the axis of the rotor
erates as a full wave recti?er to supply a rec
coil 15b is at right angles to the axis of the stator 30 ti?ed voltageto the buses 25 and 26. As shown,
coil l5a the voltage induced in the rotor coil is
the separately excited ?eld winding 6a of they
zero. For all 01,481‘ positions of the rotor coil
motor 6 is connected across the buses 25 and 26.
The armature 6b of the motor 6 is supplied
the induced voltage is proportioned to the sine
from suitable electric valve means illustrated as
of the angle between the axis of the rotor coil
and its zero position. The connection between 35 a pair of thyratrons 28 andZS. I The anodes 28a.
and 29a of these thyratrons are connected to op
the shaft of the drum 8 and the shaft of the rotor‘
coil is made so that the axis of the rotor coil
posite terminals of the supply transformer sec
is perpendicular to the axis'of the stator coil
ondary winding H0, and the cathodes 28b and
when the pendulum is in its vertical or zero posi
292) are connected through conductor 30 and the
tion. Since the rotor coil is rotated in response 40 'main contacts 3 lb of contactor 3! to one terminal
to rotation of the pendulum, the voltage induced
of the motor armature 6b. The other terminal
in the secondary winding is proportional to the
of the armature is connected to bus 25 which, as
sine of angle ¢. Thus it is proportional to the
pointed out in the foregoing, is connected to the
‘
center tap of the secondary winding i la. As thus
load
applied to the material sample. '
This alternating voltage is supplied to the pri
connected, the thyratrons 28 and 29 rectify both
mary winding We of a transformer H8. The volt
half-waves of the ‘alternating voltage and sup—
age induced in the secondary winding lab is rec
ply the recti?ed voltage to the armature 6b.
ti?ed by means of a recti?er Hi. This recti?er is
The speed of the motor 6 is adjusted by varying
illustrated as a double diode electric valve of
the average current conducted by the thyratrons.
which the anodes 09a and i912 are connected to
Although the thyratrons may be controlled by
opposite terminals of the secondary winding lI8b.
any suitable method, it is preferred to use the
A resistor 20 is connected between the cathode
method of phase shift control of the grid volt
49c and the center tap of the secondary‘winding.
age. For the carrying out of this method of con
As a result of this connection a direct voltage is
trol, a phase shifting resistance-reactance net
supplied to the resistor 20 which is proportional
work is provided. This network comprises the
to the alternating voltage supplied-to the pri
secondary winding lid of the transformer H, re
mary winding 05 the transformer. This direct
sistors 3'2 and 33, and capacitors 3t and 35. The
voltage is therefore proportional to the load ap
resistors and capacitors are connected in series
plied to the material specimen. This voltage is
relationship across the secondary windingv lid.
smoothed by means of a capacitor 2! which is 60 The circuit is traced from the left-hand terminal
connected in parallel with the resistor 20.
' of the secondary winding ll d through resistor 32,
A capacitor, 22 and a potentiometer 23 having
capacitor 34, the common cathode connection 38,
a slider 23a are connected“ in series in a circuit
capacitor 35, and resistor 33 to the opposite ter
across the terminals of resistor-20, and thus the
minal of the secondary winding lid.
voltage across resistor 20 which is proportional to
The common point 32a of resistor 32 and ca
the load on the material specimen is supplied to
pacitor 34 is connected through a resistor 3'! to
this circuit. When the load varies, i. e. when it is
the grid 280 of thyratron 28. Similarly, the com
I being applied to the material specimen, the volt
mon point 33;; between resistor 33 and capacitor
age across resistor 20. varies correspondingly.
35 is ‘connected through a. resistor 38 to the grid
As a result of the variation of this voltage a
290 of thyratron 29. The capacitative reactance '
charging current I ?ows through the capacitor
X0 or the capacitors 34 and 35 is chosen rela
.22 and potentiometer‘ 23 which is de?ned by the
tively small incomparison with the resistance R
equation:
of resistors 32 and 33. ' Thus the alternating volt;
V
(1)
1: (TT
34 and 35-lag the volt
75 ages across'the capacitors
'
. ..
tors élo and 3
-.
e
are, the voltages of girls
voltages of the anodes
and
approximately so degrees.
-
v
and
a
is connected
"
lag the
respectively,
cco
,.-.
a result the conductivity {is val".
and the phase of the arid. vol
l ..
- e ti yra»
trons
and
is advanced to increase the volt
age supplied to the armature thereby coonteie
The effect of phase shift of the grid voltage
acting or compensating for
drop
the
is produced by applying a variable component of
armature. The amount of ccmpensation'niay he
direct voltage to the grids in addition to the 90=
I degree lagging alternating voltage component.
adjusted as desired ‘by adjustment of resistor fill.
10
With the foregoing understanding oi.’
ele»
This is accomplished by means of a pair of elec
ments and their organization in the completed
tric valves 39 and (‘it connected in series rela
system, the operation of the system itself will
tionship- across the transformer secondary lid.
readily be understood from the following details
The valve 39 is preferably a trlode valve and the
valve ?ll is preferably a diode valve. The circuit 15 description. It is assumed that the apparatus .s
in the position in which it is illustrated in the
is traced from the left-hand terminal or the sec=
drawing with the lower jaws 2 in their uppermost
ondary winding lid to the anode 39a of valve 39,
position. At the lowermost position of the lower
cathode 3gb, resistor M, conductor 3% to the com
jaws 2 during the previous test run, the limit
mon cathode connection 36, resistor d2, anode
switch 48 which is actuated by the screw closed
40a of valve $0, cathode 49b to the opposite ter
minal of the secondary winding lid. Thus, the 20 its contacts to complete an energizing circuit for
the operating coil 49a of the ?eld contactor as.
triode valve 3% is in parallel circuit relationship
In response to energization, contac'tor [it closed.
with capacitor 354 and the diode valve to is in
its normally open contacts 39?}, ‘89c, and dad and
parallel circuit relationship with capacitor 35.
When the valves 39 and at are conducting, 25 opened its normally closed contacts tile and def.
The opening of contacts its and F35)’ and the
charges are placed on the capacitors til and 35,
closing of contacts tab and tile reversed the con
and as a result, a component of direct voltage
nections of the ?eld winding to to provide for.
is applied to the grids 28c and 29a. The combi
nation of this direct voltage component with the
lagging alternating component produces the effect 30 the lower jaws 2 toward their uppermost posi~
tion. The closing of contacts sea completed a
of phase shift of the grid voltage and correspond
sealing-in circuit for the operating coil ll?a in
ing variation of the average current transmitted
by the thyratrons.
1
parallel with the contacts of the limit switch ‘i8
so that the contactor remained picked up- after
The amount of phase shift Of the grid voltage
the contacts of the limit switch to opened in re
of the thyratrons, and consequently the amount
sponse to the upward movement of the jaws 2.
of current transmitted by the thyratrons, can ‘be
varied by varying the relative conductivities of
the triode valve 39 and the diode valve til. This
is accomplished simply by varying the conductiv
In the uppermost position of the lower jaws 2, a ‘
clutch (not shown) in the testing machine is dis
engaged to interrupt the driving connection be
ity of the triode valve. For this purpose, the 44 tween the motor 5 and the screw 3. Assuming
that the motor 6 was stopped with the machine
cathode 39b of the triode valve is connected to
in this position by pressing the stop pushbutton
the upper or positive terminal of the reference
switch 50, it is now necessary to restart the motor
voltage potentiometer l3 and the control grid
This is done by momentarily depressing the
390 is connected to the slider 23a of the signal
start pushbutton switch '55
voltage potentiometer 23.
and thereby complete anenergizing circuit for the
If the voltage of the grid 39c becomes less neg‘
operating coil 35a of the line contactor
In
ative or increasingly positive with respect to the
response to energization, the line contactor closes
voltage of the cathode 3812, the conductivity of
its main contacts 3th and interlock contacts 35c
valve 39 is increased. This has the effect of re
and opens its normally closed dynamic braking
tarding the phase of the grid voltage of the
contacts, (lid. The contacts 3i in opening inter
‘thyratrons 28 and 2t thereby to decrease the cur
rupt the dynamic braking circuit through the dy~
rent supplied to the armature G?) or“ the motor
namic braking resistor 52 in parallel with the ar
mature, and the main contacts 53 l b in closing- com
plete the connections of the armature to the cath
odes 28?) and 29b of the thyratrons 28 and
The
is advanced and the current supplied to the ar
closing of contacts ‘sic in parallel with the con—
mature is correspondingly increased.
tacts of the start pushbutton switch 5% completes
For the purpose of compensating for R1 volt
a holding circuit for the operating coil of the line
age drop in the armatureoi the motor when oper
ating at low speed, a resistor Q3 is ‘connected in 60 contactor so that the start pushbutton switch may
now be released. With the contacts of the limit
series with resistor All across the motor anna
switch 58 in the closed position in which they are
ture 6b. These two resistors thus constitute a
illustrated, the voltage of the grid 3710 of the valve
voltage divider connected across the armature.
37? is adjusted with respect to the voltage of its
A third resistor all is connected
series with the
cathode so that the valve is nearly fully conduct
armature between the cathode of the thyratrons
ing. As a result, the grid voltages of the thyra
and the positive terminal of the armature. The
trons 2t and 29 are retarded to such an extent
cathode 39b of the triode valve is connected to
that the thyratrons supply only a small current
theintermediate point 431; of the. voltage divider
to the armature of the motor which therefore ro
and the grid 390 is connected through resistor to,
tates at a low creeping speed. For the purpose of
the contacts of limit switch #38 and an adjustable
maintaining the speed of the motor constant at
potentiometer lll to the lower terminal‘ or" arma- '
this low value, the portion of the armature voltage
ture voltage drop resistor Ms. Any change in cur-:
which appears across the resistor 5i less the RI
rent ?owing in the armature circuit produces a
drop voltage across the resistor 4Q produced by the
corresponding change in th voltage drop across
resistor 64. Thus if the armature current in~ 75 armature current is compared with the reference
Conversely, if the grid voltage becomes in
creaslngly negative. with respect to the cathode
voltage, the phase of the tyratron grid voltage
voltage across the potentiometer l3 and the dif~
anneal
ferenc'e is utilized to control the .electric valve 89
in such a manner as to correct for any variations
~
29 is advanced. The advance in phase of the grid
voltages of the thyratrons increases the current
the motort thereby
. supplied to'the armature of
The direction of rotation is such as'to drive the
increasing the speed of’ the motor 6 and also the
downward speed of the jaws ? driven thereby. The
ever, as pointed out; the lower pair ofdjaws 2 are
in ‘their uppermost position with the clutch be
increasing downward speed of the jaws 2 increases
the speed of the counterclockwise rotation of the
pendulum 85 so that the signal voltage increases
tween the motor and the screw 3 disengaged so
and approaches equality with the reference volt
- in‘ the. speed of the motor.
.
g
, ' ‘lower pair of'jjaws 2 in an upward
direction.
How»
- that there is no movement of. the jaws at this
point in the operation.
' The test sample is now
firmly secured in the -
upper and lower jaws i and 2. The test run is
initiated by shifting the lever 53 to engage‘the
clutch to complete the driving connections be
'
‘ tween the motor 6
age.
.
Who the two voltages become substantially
equal, there will be no further increase in the
speed of the motor 6. This is an indication that
the rate of application of load to the test sample,
i. e., the rate of increase of load on the test sam
and the screw 3. The shifting 15 pie, "is equal to the predetermined rate which
of the clutch lever 53 opens contacts 56 to inter
corresponds to the magnitude of the reference
rupt the holding circuit for the operating coil of
voltage and is therefore uniform.
_
the ?eld contact'or $9. In response to .deener
If the sample has a high elongation character
gization, the ?eld c'ontactor drops out to open its
istic, the rate of application of load to the test
normally open ‘contacts @911, 69c, and 49d'and .to. 20' sample tends to decrease and the signal voltage
69c and 49,1‘.
tends to become smaller than the reference volt
'close its normally closed contacts
interrupt the holding
age. :I‘he result is that the voltage applied to the
. Contacts sec in opening
circuit for the ‘coil 69a so that the contactor 49
- grid 39c becomes negative with respect to the
cannot ‘be picked up by a subsequent movement of
voltage of the cathode. Consequently, the‘cone
ductivity of the valve 39 decreases thereby to ad
the lever dd.
'
The lower jaws 2 start downwardly at a‘very
low speed to remove the stretch from the’sample.
vance the phase of the grid voltage of the thyra
trons 28 and 29 and to increase the speed of the
During this operation the wide variations in the
motor sand the rate of application of load.
friction of the parts of the testing machine pro
On the other hand, if the sample has a low
30
duce corresponding variations in the loading of
elongation characteristic, as is the case when a
the motor. The speed of the motor tends to vary
in load,_
erratically in response to these variations
_
high count fabric is tested at short gauge, the
‘tervening between the time the driving gears are
with respect to the voltage of the cathode 39b. '
This increases the conductivity‘of the valve 39
and retards the phase of the grid voltages of the
thyratrons thereby to decrease the speed of the
load on the sample increases at a rate faster than
but this tendency is effectively counteracted by
thatdetermined by the reference voltage with the
the RI 'd'rop compensating control circuits de 35 result that the signal voltage ‘tends to become _
scribed in the foregoing. Thus, the provision is
greater than the reference voltage and the volt‘ made foridling speed during the few seconds in
age of the grid 39c becomes increasingly positive
engaged and the instant when load is applied to
the specimen. No matter how carefully the op
erator inserts the sample in the jaws, factors such
_
as slack in the textile specimen and backlash in
' motor 6 and the rate of application of load.
the mechanism of the testing machine
remain ‘of
to
beginning
cause a shock-load bump at the
the loading cycle. Because the motor speed is
Thus, the rate of application of load to the test
sample is maintained uniform throughout the
maintained constant at a low value the lower jaw as ' At some point in the downward‘travel of the
continues to move downward at a, very slow rate
lower jaws 2, the test sample is ruptured. Fol
and stretch
lowing the rupture of the sample the pendulum
“ while backlash, is taken up and'slack
are removed from the sample. When the stretch
and the induction voltage regulator remain sta
is completely removed, the pendulum 9 beginsto
tionaryrin the positions they occupied at the inrotate in a counterclockwise direction thereby to . stant of rupture. Consequently the recti?ed volt
apply load to the test sample. After a very small
age from the induction voltage regulator remains
amount of rotation of the pendulum 9, the con
constant and consequently the signal voltage
tacts of limit switch 55 actuated by the pendulum
across the potentiometer 23, which is proportional
e are opened to interrupt the RI drop compensat
to the rate of change of the recti?ed voltage,
est.
55
I
1 ing circuit.
As the pendulum rotates in a counterclockwise
direction, the rotor of the induction voltage regu
lator is correspondingly rotated from its zero po-.
'sition and. a signal voltage proportional to the
rate of application of load appearsacross the sig 60
nal .voltage potentiometer 23. Since the negative
terminals of the reference and signal voltage po
tentiometers. i3 and 23 are connected together
and their ‘positive terminals are connected to the
cathode and grid respectively ‘of valve 39 the dif 85
is .zero.
-
"
.
'
Therefore the difference between the
rate of change signal voltage and the reference .
‘ voltage is a maximum and thus the voltage of the
cathode of the valve 39 becomes so positive with
respect to the voltage of its grid that the valve
becomes non-conducting, , This causes the thy
ratrons to supply maximum voltage to the motor,
thereby causing the motor to drive the lower pair
of jaws 2 to the lower end of the downward travel
at maximum speed. At the lower end of the
downward travel of the laws 2, the limit switch
- ference of the reference and signal voltages is
48 closes its contacts to complete an energizing
supplied between the grid ‘and cathode of the
circuit for the operating coil ‘to of the field con
valve._ At the instant of opening the limit switch
tactor as which responsively to energization re
contacts the rotation of the rotor of the induc
verses the ?eld connections of the ?eld winding
tion voltage regulator is relatively slow and conse 70 6a to the source. This reverses the direction of
quently the signal voltage is low.- Consequently
rotation of the motor 6 and causes it to drive the
the difference voltage is large and the voltage of
screw 3 and the pair of jaws 2 in an. upward di
' the grid 390 is strongly negative. As a result, the
rection. This continues until the jaws 2 reach
conductivity of the valve 39 is decreased and the
their uppermost position and the clutch in the ‘
phase of the grid voltages of the thyratrons 28 and (5
machine is disengaged to interrupt the driving
connections between the motor and' the screw 3.
The pendulum, which is held in its upper posi~
tion by means of a pawl and ratchet mechanism,
is manually returned by the operator to its initial
position. In returning to its initial position, the
ohms comprising an electric motor
, lying
a. load to a material specimen, a source or l'efEl‘e
ence voltage corresponding to a predetermined
rate or" application of load to a material speci=
men, means for producing a direct voltage vary~
ing with the magnitude of the load applied to
contacts of the limit switch it are closed to re
said specimen, means responsive to the rate of
establish the armature voltage and RI drop com~
change of said direct voltage for producing a sig
pensating circuit connections to the grid tee of
nal
voltage having a magnitude corresponding to
valve 39 thereby leaving the system in a reset 10
the rate of application of load to said specimen,
condition for a subsequent test.
and electric valve means responsive to the differ
Thor-ate of application of load to the material
ence
of said reference voltage and said signal
specimen may be adjusted to any desired value
voltage for controlling said motor'to equalize said
within a wide range by adjusting either the ref
rate of application of load with said predeter
erence voltage or the signal voltage. This is 15 mined
rate.
preferably accomplished by adjusting the position
5.
Control
apparatus for a material testing ma
of the slider 23a of the signal voltage potentiome
chine comprising an electric motor for applying
ter which as shown is provided with a cooperat
a load to a material specimen, a source of refer
ing dial calibrated in terms of rate of application
ence
voltage, means for producing a voltage vary
of load.
'
'
'
20 ing with the magnitude of the load applied to said
Although in accordance with the provisions of
specimen, a control circuit including a capacitor
the patent statutes this invention is describedas “responsive to the rate of change of said varying
embodied in concrete form and the principle
voltage for producing a signal voltage having a
thereof has been explained, together with the
magnitude corresponding to the rate of applica
best mode in which it is now contemplated apply
tion of load to said specimen, and means respon~
ing that principle, it will be understood that the
sive to the di?erence of said reference and sig
apparatus shown and described is merely illus
nal voltages for controlling said motor to main
trative and that the invention is not limited
tain said rate of application of load to said speci
thereto, since‘alterations and modi?cations will
men substantially constant.
readily suggest themselves to persons skilled in 30 6. Control apparatus for a material testing
the art without departing from the true spirit
machine comprising an electric motor for ‘apply
of this invention or from the scope of the‘ an
nexed claims.
What we claim as‘ new and desire to secure by
Letters Patent oi the United States, is:
1. Control apparatus for a material testing ma
chine comprising an electric motor for applying
a load to a material specimen, a source of refer
ence voltage, means for producing a voltage vary
ing with the load applied to said specimen, means
for deriving from said varying voltage a signal
voltage corresponding to the rate of application
of load to said specimen, and means responsive
to the difference of said reference. voltage and
said signal voltage for controlling said motor to
maintain the rate of application of load to said
specimen constant.
2. Control apparatus for a material testing ma
chine comprising an electric motor for applying
ing a load to a material specimen, a potentiom
eter for providing a reference voltage correspond
ing to a predetermined rate of application of load
to said material specimen, a second potentiometer,
means for supplying to said second potentiometer
a voltage corresponding to the rate of application
of load to said specimen by said motor thereby to
provide a signal voltage, means responsive to the
difference of said reference and signal voltages
for controlling said motor to equalize said rate
of application of load with said predetermined
rate, and means for adjusting one of said poten
tiometers to adjust said predetermined rate to a
desired value.
'7. Control apparatus for a material testing
machine comprising an electric motor for apply
ing a load to a material specimen, a potentiometer
for providing a reference voltage corresponding
a load to a material specimen, a source of refer» 50 to a predetermined rate of application of load
ence voltage having a magnitude corresponding
to a predetermined rate of application of load to
said material specimen, means for producing a
signal voltage corresponding to the rate of ap
plication of load to said specimen by said motor,
means responsive to the difference of said Volt
ages for controlling said motor to equalize said .
to-said material specimen, means for producing
a voltage varying with the magnitude of the
load applied to said material specimen, means
responsive to the rate of change of said varying
voltage for producing a signal voltage corresponding to the rate of application of load to
said specimen comprising a capacitor and a sec
rate of application of load with said predeter
mined rate, and means for adjusting one of said
ond potentiometer connected in circuit and sup
voltages to adjust said predetermined rate to a
desired value.
means responsive to the di?erence of said refer- .
3. Control apparatus for a material testing ma
chine comprising an electric motor for applying
a load to a material specimen, a source of ref
erei ce voltage, means for producing a voltage
plied with said varying voltage, electric valve
ence voltage and said signal voltage for control
ling said motor to equalize said rate of appli
cation of load with said predetermined rate, and
means for adjusting one of said potentiometers
thereby to adjust said predetermined rate to a
varying with the magnitude of the load applied
desired value.
_
to said specimen, means responsive to the rate of
8.
Control
apparatus
for
a
material
testing
change of said varying voltage for producing a
machine comprising an electric motor for ap
signal voltage having a magnitude corresponding
to the rate of application of load to said specimen, 70 plying a load to a material specimen, a source of
reference voltage, means comprising an induc~
and means responsive to the difference of said
tion voltage regulator responsive to the load
reference and signal voltages for controlling said
applied to said specimen for producing an alter
motor to maintain said rate of application of load
nating voltage, means for rectifying said alter
to said specimen substantially constant.
nating voltage'to produce a direct voltage vary~
4. Control apparatus for a material testing me. 76
ing with the load applied to said specimen, ca
2,_d11,451
__pacitor means responsive to the rate of change
ptv said direct voltage for producing a signal
voltage corresponding to the rate of application
of load to said‘ specimen, and means responsive to
apparatus to compensate for the RI voltage drop
in said, armature, means responsive to the ap
plication of load to said specimen for rendering
said compensating means ineffective, a source
of referencevoltage, means responsive to the
load applied to said specimen for producing a
signal voltage corresponding to the rate oi ap
- . feet application of load to said specimen at a e
plication of load to said specimen, and connec
constant rate.
tions for supplying the di?erence of said reference
9. Control apparatus for a material testing
voltage and said signal voltage to control said
machine comprising an electric motor for apply 10 motor to eiiect application of load to said speci
ing a load to a material specimen, a potentiometer
men at a constant rate.
_ for providing a reference voltage corresponding
11. Control apparatus for a material testing
to a predetermined rate of application of load to
machine comprising an electric motor for ap
a material specimen, means comprising an in
a load to a material specimen, electric
duction voltage regulator responsive to the load 15 plying
valve means for controlling the supply of current
applied to said specimen for producing an al
to said motor for operation at a relatively slow
ternating voltage, means for rectifying said alterspeed, a resistor connected in the armature cir
nating voltage to produce a direct voltage vary
cuit of said motor, means responsive to the volt
ing with the load applied to said‘ specimen, a
age drop across said resistor for controlling said
' second potentiometer, capacitor means respon
electric valve apparatus to compensate for the
, sive tothe rate of change of said varying direct
RI drop in said armature, limit switch means
voltage for supplying to said second ~potentiom
responsive to the application of load to said
eter a signal voltage corresponding to the rate
specimen for rendering said compensating means
the di?erence of said reference voltage and said
signal voltage for controlling said motor to ei—
of application of load to said specimen, and elec
tric valve means responsive to the difference of
said reference voltage and said signal voltage
- for controlling said motor to effect application
ine?'ective, a source of reference voltage, means '
responsive to the load applied to said specimen
for producing a signal voltage corresponding to
the rate of application of load to said specimen,
01 load to said specimen at a constant rate.
and ‘connections for supplying the difference of '
10. Control apparatus for a material testing
said reference voltage and said signal voltage to
machine comprising an electric motor for ap 30 control said motor to effect application of load
plying a load to a material specimen, electric
to said specimen at a constant rate.
.valve means for controlling the supply of current
to said motor for operation at a relatively=slow
ROBERT J. DEMARI'INI.
speed. means responsive to the armature current
HENRY H. LEIGH.
35
of said motor for controlling said electric valve
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