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Патент USA US2407926

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Sept. 17,1946.
‘ 2,407,925
original Fiied‘Mavrch’27, 1943
2 Sheets-Sheet 1
31%7,wmiw f .50.2“
seppdv, 1946.’
. 23071925
Original Filed March
2 Sheets-Sheet 2 '
Zm. “3%.
Patented Sept. 17, 1946
1 L
M We;
error. ]
Henry W‘. Gil?llan, Detroit, Mich, assignor to
Chrysler Corporation, Highland Park, Mich, a
corporation of Delaware
()‘riginal application March 27, 1943, Serial No.
480,786. Divided and this application Decem
ber 31, 1943, Serial No. 516,423
11 Claims.
This application is a, division of Gil?llan et al.,
application Serial No. 480,786, ?led March 27,
1943. Copending application Serial No. 518,829,
?led January 19, 1944:, in the name of David M.
Borden relates broadly to a type of pumping-limit
detector such as shown in the drawings as D in o
especially when the plane participates in‘ aerial
combat. Accordingly, a coordinated control sys
tem, subject in some respects to the pilot’s super
vision, but otherwise as automatic in its reac
tions as may be, is indicated.
It will have been observed that use has been
made of the ten , “pumping limit.” When the
characteristic curve for a supercharger, operat—
the present application. The present application
relates to this speci?c form of pumping-limit detector and to certain details thereof that may
at some designated speed, is plotted, it is read
have use in other than a pumping-limit detector. 10 ily noticeable that a point is reached where fur
The pumping-limit detector for a supercharger
thcr reductions in the quantity of air passing
disclosed herein is based on the discovery that
through the machine fail to produce proportion
pumping limit is reached when a, certain relation
creases in the difference between the de
is reached between increase in pressure produced
y and inlet pressures. Tins point is some
by the supercharger and velocity head of gas en
.- es called the surge point, and, With respect
tering the supercharger, Velocity head is actu
to axial ?ow compressors, its existence may be
ally a very small quantity in relation to increase
explained by considering the character of flow
in pressure, and thus if a balancing of one against
through. the supercharger. Too- low a velocity of
the other is to be obtained as is the case in the
with respect to the rotational speed of
present application, it is necessary to ?nd some 20
iblades and their formation, causes the air to
practical way of multiplying‘in effect, the force
meet the blades at too- great an angle of attack,
developed by the velocity head in relation to the
aerodynamic how is interrupted and the machine
force developed by the increase in pressure. The
stalls. This condition produces noises and vibra
means developed in the invention of the present
tions and pulsations which may cause physical
application for carrying this out is of special ad 25 failure of the parts, with attendant disruption of
vantage with the particular type of pumping
the entire power plant, Accordingly, operation
limit detector disclosed, but may be employed
of the supercharger at or beyond the surge point
is to be avoided.
On the other hand, the supercharger has the
just as well in other situations, where it is neces
sary to balance a small force against a large force
or to make comparisons between large and small
As herein employed, the term “power plant”
embraces the internal combustion engine proper,
the propeller connected to the engine, and the
supercharger which compresses the relatively rare
air for delivery with the fuel to the engine inlet
duty of supplying to the engine that quantity of
air, under suitable pressure, which is needed under
its Wide range of operating speeds and horse
pcwer demands.
’ ince the aircraft operates from
sea level to very high altitudes, it is apparent
that the density, and therefore the mass, of in
ducted air is also a variable. Presupposing a
supercharger designed to supply enough low den
manifold. rThese units are often interconnected
by gearing for simultaneous rotation. For satis
sity air, compressed to a suitable pressure, for
factory performance, it is necessary to correlate
an open throttle condition of the engine, then
a number of variables, such as engine or propeller 40 the samesupercharger may not operate effec
speed the amount of fuel mxture and the pro
tively with denser air at the same speed, nor
portions of air and fuel in such mixture delivered
with the
rare?ed air at a lower speed, since
to the engine, the actual speed of the super
a change in either of these factors may adversely
charger and its ratio to the engine speed, and
effect the angle of attack.
When the surge points for the same super
the pressure at which the fuel mixture is sup 45
plied. The wide variations in speed and power
charger, subjected to changes in these variables,
are plotted, it is found that they lie in or along
loads on the
and the variations in the
air supply due to changes in‘ density andf’tem
another curve, which establishes the “pumping
limit”. for the supercharger throughout the
perature with changes in altitude, coupled with
range of operating conditions which it may en
the incidents of ?ight service, make the integra-'
tion and resolution. of these variables an extremely
counter. In practice, it means that; a certain
difficult task. Independent manual adjustments,
relationship must be maintained between the
made by the‘ pilot or crew in‘ response to indicat
pressure rise through the machine, and the
quantity of air which passes through the super
ing dial readings, are too dependent on human
frailties and preoccupations to be satisfactory, 55 charger. Mathematically, the relationship may
be expressed, with su?icient accuracy for present
D insures the operation of the supercharger S
purposes, by a simple equation in this form:
within its pumping limit‘. The unit E, on the
righthand side of the control rotor A, is pro
vided to govern the speed ratio between the
where P2 is the pressure of the discharged air; '
P1 is the inlet or barometric pressure; p is the
supercharger S and the engine (not, shown).
density of the inducted air; 1) its velocity; and
K, K’, are constants. This relation may also be
expressed by the equation:
. In one aspect, this invention contemplates a
control system in which the supercharger is
made to operate within the pumping limit. The
principles and means hereinafter discussed in 15
detail will disclose how such result is obtained.
An object of the present invention is to provide
improvement in a pumping-limit detector.
Another object is the provision of improve-'
ment in a pumping limit detector of the type 20
functioning on a relation of pressure increase
With this unit is associated a solenoid control
valve H and electrical circuits illustrated dia
grammatically at the upper right of the ?gure.
The unit M is a mechanism provided to adjust
the fuel mixture and it is also responsive 'to the
setting of the rotor A. The linkage L, also con
nected to the rotor A, is connected at its oppo
site end to the propeller governor (not shown)
of the engine in'such manner as to govern the
speed of the engine.
Supercharger discharye'pressure regulation
Air enters the supercharger S through an inlet
line H, ?owing through a venturi l2 and thence
into the inlet of the supercharger for delivery into
a line 13 which is connected to the engine inlet
manifold at a point not shown. The line I3 is
provided with a lateral or spill pipe Ill in which is
and velocity.
.A further object is to provide an improved
device for balancing or comparing large and
rotatably mounted the waste gate or spill valve G.
Additional objects, and the advantages to be 25 An open position of the valve G permits the super
charger discharge to bleed to the atmosphere, a
derived from the practice of the invention, both
position of the valve G directs all of the
' in its entirety or by use of its several components,
discharge to the engine manifold, and interme
will become apparent from a perusal of the fol
lowing description of a preferred embodiment, 30 diate‘ positions of the valve permit proportionate
withdrawals of the compressed air, either to
read in connection with the accompanying draw
diminish its quantity or its pressure.
The system is such that the pilot may manually
For the purposes of clarity and simplicity,
position the gate G. For this purpose a link l5,
there are omitted from the drawings representa
small forces against one another.
tions of various standard parts, accessories, and
design details, since these, as such, form no part
operable from the pilot’s position, is connected. by
35 a clevis to a radial arm l6 extending from the
outer surface of the unit A. The unit A comprises
of the present invention and are here unneces
a pivotally mounted rotatable member having a
sary for a full presentation of the subject to
plurality of cams formed on its external periphery,
those skilled in the art. For like reasons, no
attempt has been made to illustrate an airplane 40 and internally divided into two chambers by
means of inwardly extending sectors H and 18.
engine, nor the details of a supercharger, nor
These are cut away at the center to receive a
themechanism interconnecting the same.
diametrically extending vane l9, rotatable within
Fig. 1 is a diagrammatic view partially in sec
and with respect to the casing of the rotor A.
tion of controls for a supercharger; Fig. 2 shows
‘an airplane propeller and pitch control there 45 There are thus formed pairs of opposed chambers
2| and 22, the chambers in each pair being con
for; and Fig. 3 is a sectional view of a pumping
limit detector.
In approaching a consideration of the draw
' ings, it may be initially helpful to designate cer
tain of the units by reference letters, the de 50
tails of which will be presented hereinafter. The
unit A is a rotary member manually operable
by the pilot into various positions and, the auto
matic control features are, to a large extent,
governed by the setting of this control instru V55
The unit B is a valve including member, man
ually operable by reason of its connection to the
unit A, and further subject to automatic adjust
nected by holes 24 diagonally drilled through the
hub of the vane IS. The several chambers 2| and
22 are ?ooded with hydraulic pressure ?uid ad
mitted from a suitable source through the oil
?lter F and normally blocked off from free flow
by valve mechanism hereinafter described. Ad
mission or withdrawal of the pressure ?uid to the
chambers is effected by piping 25 and 25 entering
the pairs of chambers through ducts formed in
the rotor casing wall. The vane I9 is, of course,
rotatably pivoted for motion relative to the rotor
casing, and the unit as illustrated is also pro
vided with a cover plate in order to close the
ment. The unit C is a valve device responsive 60 chambers and preclude oil leakage. _
i It will be observed that, with the parts in the
to excess changes in the pressure conditions oc
position illustrated, a left hand movement of the
curring therein. The three units A, B, and C
link 15 will effect a counter-clockwise rotation of
operate conjunctively with a supply of hydraulic
the rotor A. Since it has been assumed that the
pressure ?uid entering the units through a ?lter
F, and in such manner as to establish the posi 65 chambers 21 and. 22 are blocked against ?ow of oil,
then such movement will drag the vane [9 also
tion of a waste gate or spill valve G positioned
in a counterclockwise direction to rotate an at
in the supercharger delivery line. These units,
tached shaft 21 upon which is mounted the'gate
therefore, modulate the discharge pressure of
valve G. counterclockwise rotation of the valve
the ‘supercharger, which is designated by the
reference letter S.
70 will close the lateral l4, and thereby operate to
build up rapidly the pressure in the engine inlet
The unit D at the left of the ?gure is a pump
line 13. Conversely clockwise rotation of the unit A
ing limit detector whose function it is to super
would, under the same blocked condition for the
vise, and even to overrule, the decisions made by
*vane 19, open the valve G to its limiting position.
the foregoing units in connection with the set
ting of the valve G. In other words, the detector 75 A gear segment 28 is formed on the lower external
portion of the rotor A and its teeth'engage with
a rack 29 included in the unit B.
This unit comprises a stationary cylindrical
housing 3| (note, for example, the ‘securing lugs
32 at the extreme right). The cylinder 3| is suit
ably cut away at its mid portion to permit en
gagement of the teeth of the gear and rack
.28 and 29, while the right hand portion 33 is
to the‘ left. The ?ow into and away from the
rotor would now be reversed, admission being
effected through the ports 42 and 54, and dis
charge occurring through the ports 53 and 45.
The remainder of the circuits is the same as here
tofore noted. ‘Too rapid overtravel of the vane IS
in‘ either rotational direction is forestalled, how
ever, by the operation of the stabilizing unit C.
A‘rapid increase in pressure in either chamber
enlarged. Within the bore of the cylinder 3| is
a longitudinally movable sleeve 34 having on its 10
58‘ or 59, coupled with a sudden release of hy
external surface the rack 29. The sleeve 34 in
draulic pressure in the opposite chamber, creates
turn receives a valve unit 35 provided with a stem
momentarily a substantial pressure di?erential
36 which extends to the right hand section 33
on the opposite ends of the piston 51. This pres
where it is coupled with a bellows assembly in~
cluding the bellows 31 and 33. The left hand 1-5 sure differential, therefore, drives the piston into
one chamber or the other, to close, by means of
section of. the sliding sleeve 34 is provided with
abutting valve discs 62, one or the other of the
ports and ?uid pressure line connections adapted
. connections to the ports 53 or 54. Accordingly,
to be opened or closed by relative movement of the
the outwardly ?owing oil develops a back pres
valve 35.
in the discharging chambers 2| or 22, and
Pressure ?uid is admitted to the unit B through
a pressure line 4! into’ any inlet chamber 42 con 20 in this way prevents the vane l9 from going to
its extreme position too rapidly. Obviously, the
nected to the clear space between the valve'discs
action of the piston 51 is the same, except for its
43 and 44. Similarports 45 and 41 are provided
direction‘ of motion, irrespective of the applica
for normal connection to the space between discs
tion of the hydraulic pressure to either side of
43 and 48 and 44 and 49 respectively. These last
mentioned ports are coupled together by tubes 25 the vane member I9. Accordingly, the valve G
will initially move to that position determined
5l-which in turn are connected to a drain line
by the manual setting of the control unit A and
52. The sleeve 34 is also provided, at a radially
will thereafter tend to creep forward to its limit
remote region, with two additional ports 53 and
ing position.
54. These ports are normally covered by the valve
Opposition to overtravel, and restoration of
discs 43 and 44. ‘Thus, in the position shown, pres 30
the valve G1 to ‘a ‘suitable position, is effected
sure ?uid may enter the region between the discs
through the bellows assembly contained'in the
43 and 44 via the port 42, but it cannot go any
right hand section 33 of the unit B. The bellows
where because the exit ports 53 and 54 are blocked
38 is secured at one end to the wall 65, and, at
by these discs.
to in its opposite end, it is joined to‘ the bellows 31,
The ports 53 and 54 are connected by suitable
tubing to opposed chambers formed within the
casing of the unit C. This casing has a central
shoulder portion 56 receiving a piston 51 which is
being sealed therefrom by the disc 66. Before
sealing, the bellows 38 is evacuated to a very
low or negative gauge pressure. The bellows 31,
normally maintained in its centralized position 40 which is free to ?oat in the casing 33, is connected
at its opposite end to the valve stem 35, and it
by the hydraulic pressure exerted on its ends,
is also provided with a vent 61 of small diameter.
which are in communication with the opposed
The space between the bellows and the inner
chambers 58 and 59. Each chamber also re
wall of the casing 33 is connected to the super
ceives a spring 6|. The chamber 58 is connected
charger. discharge line I3 by a conduit 58. An
to the chambers 2| of the unit A by the ‘above
end wall 59, positioned between the casing 33 and
mentioned piping 25, while the chambers 22 are
the sleeve 34, and formed with a‘ suitable gland
connected to the chamber 59 by the piping 26.
to receive the stem 35, prevents manifold pressure
Since, as previously noted, ports 53 and ,54 of the
from being exerted on ‘the valve disc 49.
unit B are normally blocked by the valve discs 43
' Increase in the manifold pressure, caused by
and 44, it will now be apparent ,why there can
closing the gate G, therefore causes an increased
be no displacement of the pressure ?uid in the
pressure to be exerted on the sealed bellows 38,
chambers 2| and 22, and why thevane l9 must,
to contract its length. This movement draws the
under these conditions, turn with the unit A.
valve stem 36 to the right, and therefore replaces
However, while initial rotation of the manually
operable rotor A causes the valve G to shift, due 55 the discs 43 and 44 over the ports 53 and 54.
Flow of the hydraulic ?uid is accordingly ar
to the drag on the vane l9, rotation of the unit A
and the valveG is ?xed in position. Con
(in a counterclockwise direction, for example)
versely, had the rotor A been turned to open the
also draws the longitudinally movable sleeve 34 to
gate G, then the sleeve 34 would have been shifted
the right, due to the intermeshing ofdthe segment
the left, and the diminution of manifold pres
28 with the rack 29. This motionconnects the 60 sure
would have permitted the bellows 38 to ex
port'53 with the port 42, and the port 54‘with
pand. The valve discs 43 and 44 would again
the port 41. Accordingly, pressure ?uid may now
have followed after the ports 53 and 54 to restore
?ow through the line 4|, ports 42 and 53, chamber
maintain the balanced condition.
59, and line 25, to the pair of chambers 22. The
is apparent that any condition causing a
chambers 2| are concurrently connected to the 65
drain line 52 through the piping 25, chamber 58,
ports 54' and 41, and lateral 5|. Hydraulic pres
sure is now applied through the chambers. 22 to
cause the vane l9 to move in a counterclockwise
direction to its limiting position, or, the move
ment of the rotor A brings into play mechanism
causing the rotor l 9 to overtravel.
Conversely, if the rotor A were rotated in a
clockwise direction, as by pulling the link l5 to
the right, then the sleeve 34 would be shifted
change in the manifold pressure is re?ected by
the extension or contraction of the bellows 38,
with compatible readjustments of the valve mech
anism in the unit B, and the positioning of the
gate G. Regulation of the manifold discharge
pressure, and its maintenance at a substantially
constant value, is thereby effected.
Such regulation is not, however, necessarily
instantaneous, because of the action of the bellows
31. Since both interior and exterior of this bel
lows“ are’normally subjected to equal pressures,
byreason cfthe vent 61, relatively slow or small
changes in manifold pressure have no signi?cant
effect on thebellows 31. When rapid pressure
changes tend to occur, as for example, during a
power dive or steep climb, the rapid change in
the pressure on the exterior of the bellows 31
creates a pressure differential, due to therestrict
ing effect of the ori?ce 61. The bellows 31~will
once in the areas of the diaphrag-msiill-a and 18.
Since the diaphragm-13 is only slightly larger in
area than the diaphragm 11a, the ‘difference be
tween these areas is small and the force exerted
to the left, on the valve stem 84 is only a small
multiplication of the difference in pressures. .
In contrast therewith, the area of the dia
phragm 1-5 ‘is larger than that of diaphragm 18
and ‘many ‘times larger than the difference in the
then tend to expand or collapse, as the case may
areas of ‘the diaphragms 11a and 13. Conse
be, and thereby add to or subtract from the force
quently, the velocity head in the inlet l i measured
acting on the valve stem 36.
by the difference in pressures in the pipes 16 and
It will be noted that thebellows 31, which is
11 is multiplied considerably by the large area of
sensitive to the ‘rate of change of manifold pres
the diaphragm 1-5 to an appreciable total force
sure, eifects a rapid adjustment of the valve unit
to the ‘right on the valve stem 81%.
" 5 :in anticipating the adjustments to be secured 15
What is accomplished is the use of a small area
:by'the .bellcws 38. Thus, in a power dive, the
for one unitiforce and of a large area-tor another
manifold pressure increases,
smaller unit force to establish a relation between
transferto a region of denser air. The pressure
the two unit forces depending upon a multiplica-
increase operatesto foreshorten the bellows 31,
thus admitting pressure ?uid through port 54 to
chambers 2i, to open the spill valve G, as pre
viously described. As the pressures within and
tion of the smaller unit force. This. might have
been accomplished by the use of a very small dia
phragm, but this would increase the possibility’ of
errors very considerably. Instead, I have accom
plished the same result by the use of two rela
tively large diaphragms 11a, and 1,8, which "are of
In fact, due to the falling external pressure, 25 slightly different areas and are opposed to one
caused by the opening of gate G, the bellows may
another, so that they have the effect of one small 7
actually be extended beyond its free length. By
this time, however, the bellows 38v has taken a
This arrangement‘ is ‘of special advantage with
new position to govern the setting of the gate,
pumping-limit detector disclosed‘hcrein, for
and the combined ‘assembly therefore works to 30 the
this detector functions by vbalancing velocity
meet a rapid pressure change with a rapid read
head, a Very small ‘quantity, against pressure
justment, followed by rapid dampening to pre
difference, :a more appreciable quantity. How
outside of the bellows‘?! become equalized, by
flow through the orifice 61, the bellows expands.
' vent hunting of the valve 35.
Pumping limit detector
The pumping limit detector D best shown in
Fig. 3 is provided to supervise the performance
of the units A, B and C, as just described, and
ever, it should be’ understoodthat this arrange
ment is not limited to pumping-limit detectors
of this type vorpumping-limit detectors of any
type, for it may be applied ‘as well to other
It should ‘bev noted that a bellows 91 ‘is secured
element of the combinations constituting a part 40 to the right end of the chamber 113 and to the
outer side of the diaphragm 1.8,. reducing the
of this invention.
effective or pressure-responsive area of the outer
The unit D comprises a cylinder 1| provided
side of diaphragm. Without the bellows-91 the
with left and right hand chambers 12 and 13 of
pumping-limit detector ‘D would operate accord
different diameters, and a central bore 14. The
chamber 12 is divided into two parts by a dia 45 ing to the equation:
it will be herein treated insofar as it forms an
phragm 1-5, the left hand part being connected to
inlet pressure by a pipe 16 leading to the super
charger inlet .l i. The right hand part is con
With the bellowsthe equation ‘is either
nected by a pipe 11 to the venturi l2. The dia
phragm 15 is, therefore, subject to an unbalanced 50
pressure proportionate to the pressure drop be
tween the upstream and throat regions of the
ventur-i, which pressure tends .to force the dia
The diaphragms 11a and 18 have members
or portions secured to their inner sides, which
‘The right hand chamber 13 is divided into three 55 abut one another and transmit the forces exerted
sections by two spaced diaphragms 11a and 18.
upon one diaphragm to the votherdiaphragm and
The middle chamber, between the two dia
phragms, is subjected to inlet pressure by a con
Interposed between the two chambers 12 and 1.3,
duit 19 leading to the pipe 16. The right hand
and in the bore 14, is a valve unit whose stem
section of the chamber 13 is connected to the 60 84 abuts both the vd-iaphragms 15 and 11a.v A
supercharger discharge line 13 by a pipe 8|, and
centrally located valve disc -85 normally uncovers
to the left hand section by a duct 82. Thus, the
a port ‘86., which ‘is connected to high pressure
same high pressure is applied in opposing direc
hydraulic ?uid by a branch $1. The liquid is thus
tions on the diaphragms 11a and 18 against the
admitted to the clear space between the disc 85
relatively low resistance of inlet pressure in the 65 and another disc 88, which space is connected to
phragm 15 to the right.
space between the diaphragms.
the pressure line 4| by a port .89. > ‘The previously
The area of diaphragm 18 is slightly larger than
described drain line '52 is coupled to a port Bi
that of diaphragm 11a. Since the inlet pressure
leading torthe clear space between the "disc »85
in pipe ‘i9 is applied in opposed directions on the
and a third disc 92, for connection to a port 93 in,
diaphragms Tia and 18 in the chamber between 70 communication with the master drain line 94.
these diaphragms, and the outlet pressure in pipe
Another drain line‘95 leads through an additional
8i'is. applied in opposed directions on the outer
port Q6 tothe :clear space between the discs 85
sides .of diaphragms 11a and’ 18, the net thrust
and 588,110 become effective when the valve assem
to the left due‘to these pressures is a product of
blyzpushed over to the left. At that time, the
‘the difference in these pressures and the differ
inlet line 87 is coupled to the li' e
while the
master drain is connected to the line ill
Any sh"ting of the valve stem
which makes:
the line
a drain, and the line 52 a pressure
supply line, of course completely reverses the
direction of application of force on the vane it of
unit A, as heretofore described. I“ o’her word‘
the val Ye settings of u it D, in
existing pressure cond- ‘>
iiiil, pulling it along to close the damper I06,
and thereby additionally throttle the engine.
pressure line, v hereby the units A, a;
late the setting of the gate G as forme
When the settings are reversed, then 1. - vane
nected to a linkage 5'95, which is connected in
turn to a damper 5G5 pivoted in the manifold line
is. Normal :back and forth motion of the rod
lei? simply causes the pin iiiil to ride in the slot
m3. Under these conditions the damper I05
hangs wide open, and is not aifected at all.
However, if the link it is pulled to its extreme
position, the end of the slot
engages the pin
Restoration of the link iii to a normal operating
range permits the‘ damper’ to open, restoring the
control ofthe air supply to the units heretofore
tion, for example, will move it an open posit on.
The detector D may therefore on .pletely l'illillfy .15
the natural inclination of the or its A, B and C
Supcrchargerdrive control
instead of moving the gate G to
in actuating
the valve
closed pom..
The supercharger ‘S is driven from the engine
through a drive unit H2, which, as herein indi
The detector operates to overrule the waste
cated includesnuid coupling members and gearing
gate regulator, and reverse its action, when the
amount of delivered
is so small, with respect
to the pressure rise, that the pumping limit of
the supercharger is reached. Such a situation
may arise under variation in the controlling fac
tors heretofore discussed.
Referring again to the left hand chamber 72
permitting the supercharger to run at one or the
other of two speed ratios. Normally, the gearing
will be set to drive in the low speed ratio. ‘How
, ever, when high altitudes are
encountered, it may
be necessary to shift to the higher speed ratio,
.25 so that the supercharger may deliver an adequate
quantity of air and still operate safely ‘within the
pumping limit. The particular drive just re
ferred to is not the subject matter of this inven
cf the unit D, it will be seen that the force ex~
erted in the right hand direction, which tends
to keep the main pressure line in communica
ticn with the line ill, is proportional to the work
of the diaphragm "l5 and to the pressure
drop from atmosphere to the‘ Venturi throat l2.
vThe ‘pressure drop is in turn proportional to the
density of the air, and its velocity. Hence,
tion, and therefore, is not shown in detail. Here,
the description is concerned with the control of
the drive, and, since a fluid coupling is involved,
the control means is made to» govern the supply
oi'hydraulic ?uid to thegcoupling.
There are two hydraulic pressure fluid lines,
2' 53, l Hi, which lead from the unit H to the cou
pl'ng ! l2, and a main feeder i it extends‘ from the
expression: [p02]. The left hand thrust is simi
F to the unit H. When the feeder H5 is
larly proportioned to the ‘pressure rise (Pg-$1),
connected to the line M3, the unit H2 is in low
since the middle section of chamber l3 is con
when the unit H is actuated to couple
nected to atmosphere, while the other faces of 40 speed,
the lines 5 l5 and i it, the supercharger S is driven
the differential diaphragms l'lc
‘iii are sub?
through the high speed ratio. Selection of the
jected to the supercharger discharge pressure.‘
of the unit l-I may be effected either man
Accordingly, under normal conditions of op
the mean effective thrust on the left hand end
of the valve stem 3% may be proportioned to the
eration, or over that range of pressure quantity
ratios within the pumping limit, thedetector D 45
p rinits admission of ‘the hydraulic pressure ?uid L
to the line Ill. The units A, B and ‘C then ‘func
tion as ?rst described, the manifold pressure‘ is
regulated, and any excess air delivered at that
pressure, which is not needed by the engine, passes
to waste through the partially open spil1 valve ‘
G. When this relationship changes in such man~
nor as to cause the supercharger S to approach
its pumping limit, the gate
rather than ‘being
ually, or automatically through the unit E. The
comprises a fixed cylindrical casing l2!
' <3: a movable follower :22 projecting from
end thereof, and held in engagement with
a cam
on the rotor unit ‘A by means of a
spring‘ 3
disposed in the casing l2! between
end wall and the inner end of the follower.
is ?xed to the free end of
he follower i223, and it abuts a push pin I26 of
.is electric switch 523. The follower ‘122 is open
‘he atmosphere, and the bellows E25 isevacu
Hence, atmospheric pressure tends to col
turned to
closed po tion in the manner ?rst .55
lapse the bellows
withdraw its inner end from
outlined, will new ‘so ti‘: rust toward an open posi
tion, The resulting reduction of discharge pres
sure head, 1by the relief of the compressed air,
is re?ected in the line
and on the diaphragms
engagement with the push pin 52%‘. At higher
altitudes the bellows will expand, due to the lower
air density, and may do so even to a point where
it can press the pin i255 sufficiently hard to shift
Tia and id, as well as the bellows ‘3i and 38. fit)
the switch till, everything else disregarded. Nor
mally, the parts
so proportioned that, at sea
restoring to line Iii its function as a pressure ?uid
Valve stem tbl may then move toward the right,
supply line, and thereby making the unit 13 once
more the control instrumentality.
It may ‘be assumed that operation of the air
craft causing the detector D to cut in and out
of service will be accompanied by other conditions
observed by the pilot. He may then elect to» shift
the link 55 to the extreme right, thereby .to open
the gate G, manually, and he may moreover de
level, the maximum lift of the cam £23, brought
by rot on of unit A, is insu?cient to
offset the contraction of the bellows 125. As
higher altitudes are reached, extension of the ‘bel
lows E25 permits the actuation of the pin I26
diirerent settings of the cam I23, until ?nally
a point is reached where actuation of the rotor
A becomes _ unnecessary, as just pointed out.
Thus, theswitch l2? will shift at some predeter
sire to throttle the engine to an even greater
mined altitude,"established by the setting of the
extent. For this purpose, the arm it, connected
rotor A and the barometric pressure. Or,~stated_
to the link i is vpcovided with a pin illl, to
otherwise, each setting of the rotor A, by ‘the
which is attached a, rod it? formed with a termi
‘ nal slot ‘I93. The slot receives a pin lllll con
manual lever i5, determines the altitude at which
75 the supercharger may go into high speed.
high speed line H4, and blocking line II3 except
The switch I21, as shown in the diagrammatic
repetition in the drawings, is of a single pole, dou
for the reduced lubricating flow alluded to. On
the next energization, the motion is reversed and
the stem I5I is pushed up to restore it to‘the
ble throw type, wherein inward movement of
the pin I26 forces the resiliently supported lever
I28 into engagement with a high speed contact
7 I29, while withdrawal of the pin I26 permits the
position illustrated.
' The stem I5I carries spaced conductive discs
I64 and I65, which respectively bridge either’
lever I28 to move forward against a low speed
contacts I66 and I61 or contacts I69 and I69,
depending upon the position of the valve. Con
contact I3I.l Manual control over the electrical
circuit is obtained through a switch having a
tacts I66 and I69 are connected by a common
pivoted arm I33 which maybe selectively set 10 wire IN to the solenoid I63, the other side of
on an automatic control contact I34, a low speed
contact I35, or a high speed contact I36. When
which is grounded.’
Let it be assumed that the machine has been
running in the lower speed ratio, the parts of
the arm is in the position shown, the gearing I I2
may be in either high or low ratio; when point
the solenoid valve unit H being as shown, and
I35 is used only a low ratio is available, and 15 that the pin I26 has just been moved to force
when point I36 is connected, the high speed ratio
is selected, subject to certain limitations here
after stated.
the switch arm I28 into engagement with the
high speed contact I29, the switch arm I33 then
contacting the automatic control point I34. A
The circuits established by the vsettings of
circuit for energizing the solenoid I63, thereby
switches I33 and I21 (which will be traced di 20 to shift the valve member 539, is now established
rectly) determine whether ?uid will flow from
as follows:
line II5, through unit H, to line H3 or line II4.
, From the power source through arm I33, con
This unit comprises a housing I31 formed with a
tact I34, wire I12‘ to arm I28 and high speed
bore I38 in which is slidably mounted a valve
contact I29, thence via wire I13 and junction, I14
member I39. The feeder line II5 connects to a
to wire I15 into the armature I16 of a relay R,
port I4I, communicating with the bore I38, while
then engaging contact I11 connected to wire
I18 leading to contact'stem I5I; thence
through disc I64 to contact I66 and wire I1I to
the winding of the solenoid I63, to ground and
.the lines H3 and H4 are respectively connected
to axially spaced ports I42 and I43.
The valve member carries a series of spaced
discs which serve to direct pressure ?uid to the 30' return. Plunger I62 is thereupon lifted to pull
line H3 or II4, depending upon their relation
down the Valve I39 as previously described, the
disc I64 being separated from contacts I66 and
‘to the port MI. The structure is so similar to
I61 to break the circuit just traced when the
the valves heretofore described that it is believed
links I6I approach dead center. The disc I65
unnecessary to elaborate thereon. It may, how
35 will accordingly engage contacts I68 and I69
ever,'be noted that the unit is formed with addi
tional, similar ports I45 which seem to re-open
the feeder II5 to the line from which it other
when the parts have come to rest.
When the pin I26 is withdrawn, switch arm
I28 engages low speed contact I3I, and a re
wise would be, blocked. This, however, is desir
able, since the short-circuiting connection is 40 versal of the ?uid connections, to restore the low
taken through a restricted ori?ce, as shown.
speed ratio, is effected through the following
Admission of a limited amount of ?uid to the
blocked line H3 or II4 assures lubrication and
cooling of the coupling then’ out of service, but
the total flow is too small, for power transmission
The valve member I39 has an extended stem
I5I terminating in a olevis I52, the pin of which
is positioned in a slot I53 of a lever I54, pivoted
on a fulcrum I55. The opposite arm of the lever
is formed with a fork I56, in which may ride a
From the power source to contact I3I,
wire I19, junction IBI, wires I82 and I83, thence
through disc I65 and contacts I58 and I6g9'to
the solenoid I63.
Let it be assumed that the pilot selects the low
speed contact I35 for the switch arm I33. Cur
rent then ?ows through contact I35 and wire
I83 to contact I69, thereby to establish a circuit
low speed position of the unit E. If it be as
sumed that the high speed contact I36 is selected,
the solenoid valve unit will (subject to a subse
pin I51 extending from a rocker segment. The
segment, which is centrally pivoted on a stud
quently stated limitation) remain in the desired
position, being actuated through the following
I59, carries a pair of links I6I at one corner,
which extend to a plunger I62 of a solenoid I63. 55 circuit: Contact I36, wire I15, .armature I16
When the solenoid is energized, the plunger is
and contact I11 of relay R, thence via- wire I18
pulled up, thereby to rotate the segment I58 and
‘to contact I61, etc.
to bring the links I6I into a substantially verti
The relay R is introduced into the ‘high speed
cal position. As will presently appear, such move
circuit to enforce a low speed gearing when the
ment simultaneously breaks the energizing cir
compressed air in the delivery line I3 exceeds
a predetermined temperature.~ The relay in
cuit, permitting the plunger I62 to drop away.
Due to the inertia of the moving parts, however,
the segment does not fall back to its starting
position, but continues its travel to the opposite
upper quadrant from which it started. Thus, 65
through a thermostatic" switch I88 positioned
in the pipe I3. Thus, the coil I85 will be ener
each energization of the solenoid shifts the pin‘
gized whenever switch I88 closes at a predeter
I51 up or down.
mined temperature.
r This motion is transmitted through the lever
cludes a coil I85, connected directly to the power ,
source by a wire I86 and a wire I61 leading
I54 to shift the valve stem I5I either down or
For example, the draw
up, as the case may be.
ings show the links I6I in the second quadrant
and the valve discs I44 so located as to supply
pressure ?uid to the low speed-line II3. Upon,
energizing the solenoid I63, links I6I swing to
the ?rst quadrant, and stem I5I is pulled down
to connect ports MI and I43, thereby supplying
Armature I16 is then'pulled down against the
.urge of its holding spring I89 to‘ engage contact
70 I9l, which leads via wire I92 to junction I8I,
and so into the low speed selecting circuit.
The armature I16 is latched into this posi
tion by an armature I93 of a second coil I94,
which must be energized to permit the armature '
75 I16 to return into engagement with contact I11,‘
“ 13
after the switch l88 has opened. A circuit for
this coil is established by contacts I95 andvl??,
connected to the coil, and adapted to be bridged
by a manually depressiblo switch arm £91.
It will thus be seen that the control of the
supercharger speed ratio .is quite ‘?exible, the
pilot may insist ‘on a low ratio, or a high ratio
subject to the thermostatic supervision; or he
may let the ratio be ‘determined automatically
but still subject to his positioning of the rotor A.
Engine regulation
' 14
crease the speed. This can :be done by changing
the propeller pitch.
. V
The ,unit L is therefore provided to adjust the
propeller and engine speeds in response to the
manifold pressure. The periphery .of they rotor
of unit A is formed with a milled cam slot M5, to
which ‘is connected a bellcrank lever ‘M6, the
upper arm of which is pivoted to a linkf I]. This
link extends to a control mechanism 218 fora
propeller governor speed control, the propeller
being indicated by 21 9. Hence, an extreme move
ment of the rotor A, representing a high or low
The engine of the power plant is supplied with
air ?owing past the damper Hi6, and fuel which V
is later mixed with such air. It is common in
the art to include, with the engine, a propor
‘manifold pressure, will affect the propeller pitch,
while in intermediate positions the inner end of
“the vlever lid is free to ride in the slot 215. The
slot EI‘S is advantageously ‘so cut as to insure a
tioning device through which the relative per
de?nite relationship between engine speed and
centages of fuel and air are determined and
manifold pressure, the curve being laid out from
knowledge of the engine characteristics. In such
maintained. However, it is desirable to super
vise the performance cf such device in response
to the manifold pressure, as determined by the
instrumentalities heretofore considered.
if the manifold pressure becomes either high or
low, a rich mixture is indicated, while at inter
mediate pressures, the mixture may be lean.
Means for assuring the rich mixture are pro
vided by the unit M, operating in conjunction
with the manifold control unit A.
The unit M
comprises a valve casing 29! enclosing a spring ,
loaded piston 282, whose stem 253 extends be
yond the casing for connection to the carbu
retor controls, not shown;
The casing 2!!! also contains a bore 2% re
case, intermediatesettings of the rotor A cause
the lever M6 to be'positoned so as to follow the
speed and pressure relationship.
It will thus be seen that the present invention
provides an integrated control, automatic in oper
ation, for the various components of the power
plant, and accordingly relieves the pilot of the ,
necessity-of making a large number of independ
ent adjustments. He is, however, free to'super
vise many such adjustments by his overriding
‘manual controls, and he may therefore exercise
his judgment with considerable latitude. The
system is obviously directed to one wherein the
supercharger is regulated by control of ‘the dis
ceiving a plunger 205, formed with a stem ace .
charge pressure, rather than by throttling the
which normally engages the dwell portion be
supercharger inlet, and any excess of air deliv
ered at the predetermined pressure is according
ly sent to waste. Such plan of control admits of
tween two similar cams 201 on the rotor A. The
bore 2% is formed with ports on either side of
the head on the plunger 285, one of which is
connected by a pipe 285 to the main hydraulic
feeder line H5. The other port is connected to
a drain line, and it also communicates with the l
upper side of the piston 2E2 through a duct 289.
Hydraulic pressure therefore urges the plunger
295 to the right, bringing the stem 2535 into en 45
gagement with the periphery of the unit A.
The plunger?d? normally partially uncovers
a port 2“ below the piston 2&2‘, thereby en
abling pressure ?uid from the line 238 'to urge
the piston and its stem ‘2.93 ‘upward. This posi
tion, by connection to any suitable linkage, sets
the carburetor for operation in the usual ‘manner.
If, however, the rotor A is moved to either ex
treme position, the stem .236 rides up on one or
the other of the cams Zill, and moves to the left
to block the line 208, and connect the port 2-H
to drainage. This permits the piston .262 to drop.
If the rotor A is rapidly shifted from one extreme
the simultaneous governing of the other related
Variables, as hereinabove explained.
While the invention has been described with
reference to one embodiment only, it will be ap
parent that numerous changes and modi?cations
may be made without departure from its prin
ciples, or the scope of ‘the following claims.
I claim:
1. A device for comparing a small pressure
quantity with a much larger pressure quantity
by causing the small quantity to act against a
“much ‘larger area than that acted against by the
much ‘larger quantity, said device comprising
?rst and second diaphragms positioned opposite
one another, the pressure-responsive area of the ,
?rst diaphragm being larger than that of the sec
ond diaphragm, means for causing the much
larger pressurequantity to apply force in one di
rection against the outer side of the ?rst dia
phragm, means for causing the much larger pres
sure quantity to apply force in the opposite ‘di- ,
position to the other, the piston 2532 will not,
however, be signi?cantlly affected. This is due 00 rection against the second diaphragm, members
secured to the inner sides of the first and sec
to the fact that the admission of pressure ?uid
ond .diaphragms and abutting one another for
through the port Eli is slow, in comparison to
causing ‘the forces ,to act in opposition to one
the drainage rate. Accordingly, the valve unit
another and to be resolved to a small force act
protects against sudden mixture changes which
one direction and being propor
might be conducive to creating backfires. When G 5 ing in vthe
tional ‘to the product of the much larger pressure
the piston 2'52 drops, the corresponding move
quantity and the difference in the pressure-re
ment of the stem 2% sets the carburetor unitin
sponsive areas of the ?rst and second diaphragms,
such position that only a rich fuel mixture can ‘
a ‘third diaphragm, means ,for applying the small
be supplied. Since the extreme movement of
pressure quantity against the third diaphragm in
unit A corresponds to a high or low manifold
pressure, the apparatus therefore achieves the
purpose intended.
the said opposite direction, and means connecting
the third diaphragm with the ?rst and second
Under take-oil conditions, a relatively high
.2. A device for comparing a large difference in
propeller, and engine, speed are desirable, while
pressures between two regions at high and low
under flight conditions it may be better .to .de 75 pressures with a small difference in pressure be
tween two regions at high and low pressures; said
device comprising ?rst and second diaphragms
having inner and outer pressure-responsive areas
and being positioned with inner pressure-respon
sive ‘areas opposite one another, the ?rst dia
f phragm having larger pressure-responsive areas
than the second; means for applying in opposite
directions against the inner pressure-responsive
the high pressure of the other of the two regions
having the low difference in unit pressures, the
last mentioned high and low pressures producing
a resultant force directed toward the ?rst and
second diaphragmsand beingproportional to thev
product of the area of the third diaphragm. and
the small difference in pressures; and means
connecting the third diaphragm with the ?rst
and second diaphragms for balancing the result
areas of the ?rst and second diaphragms the low
pressure of the one of the two regions having a 10 ant force produced at the third diaphragm
against the resultant force produced at the ?rst
large difference in pressures; means for applying
and second diaphragms.
in opposite directions. against the outer pressure
4. A device for comparing a large difference in
responsive areas of the ?rst and second dia
between two regions at high and low
phragms the high pressure of the other of the two
regions having a large difference in pressures; 15 pressures with a small di?erence in pressures be
tween two regions at high and low pressures, said
'means connecting the diaphragms for causing
device comprising a ?rst means providing inner ‘
the said large difference in pressures to produce
and outer pressure-responsive areas, a second
aresultant force acting‘ in a direction from the
means providing inner and outer pressure-respon
?rst diaphragm toward the second diaphragm
and proportional to the product of the said large 20 sive areas somewhat larger than the pressure
responsive areas of the ?rst means, the two inner
difference in pressures times the difference be
pressure-responsive areas being opposite one an
tween the pressure-responsive areas of the ?rst
other, means for applying in opposite directions
and second 'diaphragms; a third diaphragm dis
against the inner pressure-responsive areas of
posed on the outer side of the second diaphragm
in spaced relation thereto; means for applying 25 the ?rst and second means the low pressure of
the one of the regions having a large difference in
against the side of the third diaphragm facing
pressures, means for applying in opposite direc
the second diaphragm the low pressure of one
tions against the outer pressure-responsive areas
of the two regions having the low difference in
of the ?rst and second means the high pressure
pressures; means for applying against the other
side of the third diaphragm the high pressure 30 of the other of the two regions having a large dif
ference in unit pressures, means connecting the
of the other of the two regions having the low
?rst and second means for causing the said high
di?erence in pressures, the last mentioned high
and low pressures to produce a resultant force act
and low pressures producing a resultant force
ing in a direction from the second means toward
directed toward the ?rst and second diaphragms
and being proportional to the product of the area 35 the ?rst means and proportional to the product
of the said large difference in pressures times the
of the third diaphragm and the small difference
di?erence between the areas of the ?rst and sec~
in pressures; and [means connecting the third
0nd means, a third means having opposed pres
diaphragm with the ?rst and second diaphragms
sure-responsive areas, means for'applying against
for balancing the resultant force produced at the
‘third diaphragm against the resultant force pro 40 one area of the third means the low pressure of
the one of the two regions having the low differ
duced. at the ?rst and second diaphragms.
3. A device for comparing a large di?erence in ‘ ence in pressures, means for applying against the
other area of thethird means the high pressure
pressure between two regions at high and low
‘ . pressures with a small difference in pressures be
tween two regions at high and low pressures; said '
device. comprising ?rst and second diaphragms
having inner and outer pressure-responsive areas
I and being positioned with inner pressure-respon
sive areas opposite one another, the ?rst dia
phragm having larger pressure-responsive areas
then the second; means for applying in opposite
directions against the inner pressure-responsive
of the other of the two regions having the low
difference in pressures, the last mentioned high
and low pressures producing a resultant force op
posed to the resultant force produced at the ?rst
and second means and being proportional to the
area of [the third means times the small differ
ence in pressures, and means connecting the third
means with the ?rst and second means for bal
ancing the aforesaid resultant forces.
5. A device for comparing a small pressure dif
areas of the ?rst and second diaphragms the low
ference representing velocity head of gas entering
pressure of the one of the two regions having a
large difference in pressures; means for applying 55 a supercharger with a large pressure difference
equal to the pressure of gas discharged from the
in opposite directions against the outer pressure
supercharger minus the pressure of gas entering
responsive areas of the ?rst and second dia
the supercharger, said device comprising a ?rst
phragms the high pressure of the other of the two
means providing inner and outer pressure-respon
regions having a large difference in pressures;
members secured to the inner sides of the ?rst 60 sive areas, a second means providing inner and
outer pressure-responsive areas somewhat larger
and second diaphragms and abutting one an
than the pressure-responsive areas of the ?rst
other for causing the said large difference in
means, the two inner pressure-responsive areas
pressures to produce a resultant force acting in a
opposite one another, means for applying
direction from the ?rst diaphragm toward the
65 the pressure of entering gas in opposite directions
second diaphragm and proportional to the prod
against the inner pressure-responsive areas of the
uct of the said large difference in pressures
?rst and second means, means for applying the
times the difference between the pressure-respon
pressure of discharged gas in opposite directions
sive areas of the ?rst and second diaphragms; a
third diaphragm disposed on the outer side of ' against the outer pressure-responsive areas of the
and second means, means, connecting the
the second diaphragm in spaced relation thereto; 70 ?rst
?rst and second means for causing a resultant
means for applying against the side of , the third
force proportional to the diiference in pressures
diaphragm facing the second diaphragm the low
times the di?erence between the pressure-respon
pressure of one of the two regions having the low
sive areas of the ?rst and second means and act
vdifference in pressures; meanszfor applying
against the other side of the third diaphragm 75 ing in a direction from the second means toward
the ?rst means, a third means having pressure
responsive areas, means for applying against the
pressure-responsive areas of the third means the
small pressure difference representing veloc
discharged from the supercharger and pressure
of entering air, to reverse control apparatus for
the supercharger by switching certain lines of
the control apparatus from a source of fluid
pressure to exhaust and vice versa, said detector
the resultant force produced at the ?rst and sec
comprising a ?rst means having inner and outer
ond means, and means connecting the third means
pressure-responsive areas, a second means having
with the ?rst and second means for balancing the
inner and outer pressure-responsive areas larger‘
aforesaid resultant forces against one another.
than those of the ?rst means, means for applying
6. A device for comparing velocity head of gas 10 the pressure of entering air against the inner
entering a supercharger represented by a small
areas of the ?rst and second means, means for
ity head .to produce a resultant force opposed to
pressure di?erence between a, pressure at one
applying the pressure of discharged air against
region of entering air and a pressure at another
the outer areas of the ?rst and second means,
region of entering air, with a large pressure dif
means connecting the ?rst and second means to
ference between the pressure of air discharged 15 produce a resultant force proportional. to the '
from the supercharger and the pressure of enter
large pressure difference times the di?erence
ing air, said device comprising ?rst and second
between the pressure-responsive areas of the >
diaphragms having inner and outer pressure»
?rst and scond means, a third means having
responsive areas and being positioned with inner
opposed pressure-responsive areas, means for
pressure-responsive areas opposite one another, 20 applying the pressures having the small di?er~
the ?rst diaphragm having larger pressure-re
ence in pressure against the areas of the third
sponsive areas than the second, means for apply
means to produce a resultant force opposed in
ing the pressure of entering air in opposite direc
direction to the resultant force produced at the
tions against the inner pressure-responsive areas
?rst and second means, and means connecting
of the ?rst and second diaphragms, means for ap
the third means with the ?rst and second means
plying the pressure of discharged air in opposite
for balancing the resultant forces against one
directions against the outer pressure-responsive
another and including valve means for switch
areas of the ?rst and second diaphragms, means
ing the said certain lines of the control appa
connecting the diaphragms for producing a re
ratus from pressure to exhaust and vice versa,
sultant force proportional to the difference in pres 30 depending upon the relative sizes of the result
sure-responsive areas of the ?rst and second dia
ant forces produced at the ?rst and second means
phragms times the large difference in pressure
and at the third means.
7 between discharged air and entering air to pro
8. A device as speci?ed in claim 3, the outer
duce a resultant force acting in a direction from
pressure-responsive area of the ?rst diaphragm
the ?rst diaphragm toward the second diaphragm, 35 being smaller than the inner pressure-responsive
a third diaphragm, means for applying against
area of the ?rst diaphragm.
the opposite sides of the third diaphragm the
9. A device as speci?ed in claim 3 and further
pressures having the small di?erence in pressures
including a bellows means ?xed to the outer side
representing the velocity head of entering air to’
of the ?rst diaphragm for making the said outer
produce a resultant force proportional to the area 40 pressure~responsive area smaller than the inner
of the third diaphragm times the small difference
pressure-responsive area of the ?rst diaphragm.v
in pressures and opposed to the resultant force
10. A device as speci?ed in claim 5, the outer
produced at the ?rst and second diaphragms, and
pressure-responsive area of the second means
means connecting the third diaphragm with the
being smaller than the inner pressure-responsive
?rst and second diaphragms for balancing the 45 area of the second means.
aforesaid forces against one another.
11. A device as speci?ed in claim 5 and fur
'7. A pumping-limit detector for a supercharger
ther including a bellows means ?xed to the outer
operating by comparison of 'a small di?erence
side of the second means for making the outer
between pressures at one region of entering air
pressure-responsive area of the second means
and another region of entering air representing 50 smaller than the inner pressure-responsive area
velocity head of gas entering the supercharger
of the second means.
with a large di?erence between pressure of air
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