US2348679A

US2348679A - Pump

Info

Publication number: US2348679A
Application number: US383258A
Authority: US
Inventors: Groves Warren Wilfred
Original assignee: Yale and Towne Manufacturing Co
Current assignee: Yale and Towne Manufacturing Co
Priority date: 1941-03-14
Filing date: 1941-03-14
Publication date: 1944-05-09
Anticipated expiration: 1961-05-09

Description

May 9, 19440 w. w. GROVES I 2,343,679

PUMP

Filed March 14, 1941 v 4 $heets-Sheet 1 INVENTOR 2w zfxfl mo ATToRNY May 9, 1944. w. w. GROVES I 2,343,679

PUMP

Filed March 14, 1941 4 Sheets-Sheet 2 'l i t. BYv

' ATTORNEY y w. w. GROVES 2,348,679

ATTORNEY May 9, 1944. w. w. GROVES;

PUMP

Filed Mafch 14, 1941 4 Sheets-sheaf! INVENTOR ATTORNEY Patented May Warren Wiiired Groves, Stamford, Conn, assignor to The Yale & Towne Manufacturing Company, Stord, 601mm,, a corporation of (Ionnecticut application can, ran, Serial ssazss as one. (ma-3s) This invention relates to a pump, and more particularly to a pump adapted for supplying gasoline to the carburetor of an airplane engine.

More particularly, my invention relates to a pump in which a positioning member is used for positioning certain of the pumping elements of the pump to vary the pumping volume, the positioning member in turn being preferably moved towards ful! pumping position by a spring, and away from pull pumping position by the pressure generated by the pump. It is an object of my invention to adapt such a pump for use in an airplane engine. It is known to those skilled in the art that in an airplane, a supercharger is utilized to supply air to the carburetor whereby to compensate for the decrease in atmospheric pressure as the airplane gains altitude. Since the pump suppliesi'ue1 directly to the carburetor at the pressure of the carburetor, the discharge pressure of the pump is of course superimposed on the air pressure at the carburetor, which'pressure tends to remain at ground atmospheric because of the action of the supercharger.

Because in a variable volume pump of the class described, the discharge pressure acts against the force of a spring to reduce the volume pumped by the pump, the discharge pressure will have greater effect in decreasing the pumped volume as the airplane gains altitude, since the discharge pressure is superimposed on the pressure developed by the supercharger and acts against the decreased atmospheric pressure of high altitudes. This condition I have found undesirable, and to eliminate it, I apply the pressure generated by the supercharger of the airplane so as to compensate for its effect on the discharge pressure of the pump.

As a feature of my invention, I utilize a diaphragm against which the discharge pressure of the pump operates, this diaphragm being connected with the positioning member by novel means. As a further. feature of my invention, it

is against this-diaphragm that the supercharger pressure is directed to compensate for its effect on the discharge pressure oi the pump.

As a detailed feature of my invention, the diaphragm is secured with its open end about the periphery of a pressure chamber so as to efiectively seal'that pressure chamber from the inside of the diaphragm, the inside of the diaphragm being exposed through suitable passages to the discharge pressure of thepump. The pressure chamber is in commun cation with the supercharger, so that the pressure of the supercharg er will act against the diaphragm in a direction directl opposite that of the discharge pressure of the pump. 1

As still a further feature of my invention, I utilize a diaphragm so mounted and so constructed as to increase its effective area as it operates, this being accomplished by me through a sidewise as well as endwise expansion of the diaphragm. This result is preferably obtained partially through the use of a diaphragm formed of a resilient rubber-like material, such as Buna, which is resistant to deterioration by gasoline. Because the diaphragmis adapted for sidewise I as well as endwise expansion, it is obvious that the action of the discharge pressure of the pump effects an increase in the area against which the discharge pressure may operate as the diaphragm is expanded. This increase of area results in an increase in the over-all pressure applied against the positioning member by the diaphragm, and compensates for the additional pres sure of the spring or other pressure mea'ns against the positioning member as the positioning member is moved away from full pumping P sition by the pump discharge pressure actingagainst the diaphragm.

I a further feature of my invention, I use a novel arrangement of a torsion spring for pressing the positioning member to full pumping position, and a very novel manual means for adju'sting the tension in said spring.

' As still a further feature of my invention, 1 have a nulel form of adjustable stop mechanism for limiting the throw of the positioning member towards full pumping position. In this way, I can readily predetermlne the maximum throw of the positioning member and the maximum volume of the pump, it being understood that the pressure generated by the pump, if greater than that for which the spring is set, will force the positioning member away from its full pumping position.

As an additional feature of my invention, I arrange for a'novel form of by-passso that should the pump be rendered ineffective for some reason, it is possible to feed the gasoline to'the carburetor through utilization of an auxiliary pump.

As a further feature of my invention,- 1 use a shuttle block of novel form for actuating the pistons of my pump, this shuttle block being formed so as to facilitate its movement relatively to the rotor and pistons, all as will be indicated hereinafter.

I have thus described generally the important features of my invention in order that a better appreciation may be had of the detailed description of those features which follows. One preferred form of the means which I have devised, is shown in the accompanying drawings, and will be described in this specification, but

it should be understood that I consider my invention to be a relatively broad one, and that I expect to obtain claims which will prevent the utilization of my contribution to the art in physical forms other than that herein shown and described.

-Referring now to the drawings, Fig. l is an elevation of a pump embodying my invention.- Fig. 2 is a view looking downwardly on Fig. 1.

tain of the parts in dlfierent operating positions:

Referring now more particularly to the drawings and especially to Figs. 1 and 2, it will be noted that the casing of my pump is built up of a series of separate castings held together by bolts. There is thus the casting ill to which is secured the casting l l by the bolts i2. The casting i3 is in turn secured to the casting H I by the bolts it. The casting i5 is in turn secured to the casting H by bolts Id. In describing my invention, I shell, for the purpose of simplicity, consider the pump casing as formed of a single casting.

Referring now more particularly to Figs. 3, 4 and 6, the drive shaft of my pump is designated by reference numeral 97, and has a splined connection I 8, is, with the rotor 28 of the pump. The rotor 20 rotates relatively to a lining 21 outlining a cylindrical chamber,'and cut away at 22 for the intake side of the pump, and at 23 for the discharge side of the pump. As best illustrated in Fig. 3, a locating pin 26 fits 'into a slot 25 of the lining 2i and serves to maintain it in proper position. An endwise lining member 26 is also utilized, and is located by pins 27, all as is best seen from Fig. 3. I

The rotor 20 is of the usual type formed with cross slots for the reciprocation of

pistons

28 and 29 through the rotation of the rotor as the pistons are in contact with a cross-shaped eccentric shuttle block 30. The shuttle block 30 is maintained in varying eccentric positions by a pin 3| which is controlled in a manner to be hereinafter set forth. So far as I have described my rotor, its pistons and its shuttle block, they resemble structures well known in the art. A feature of novelty resides in the forming of bores 32 in the four arms of the shuttle block 30, these bores facilitating the flow of fluid from one side of the arms to the other as the shuttle block reciprocates relatively to the pistons.

Thus, any fluid which enters between the shuttle block and the pistons, as within the spaces designated by reference numerals 33 in Fig. 4, may

move freely from one side to the other of the flow from the intake side of the pump to the discharge side, that is, in the direction of the two arrows I and D in Fig. 4, denoting respectively, intake and discharge. In an emergency of this sort, it is necessary that fluid be bypassed relatively to the rotor and its pistons, and for this purpose, I provide the casing with passages35, 36 and 31, best shown in Figs. 4

. of the pump to the intake side of the pump when the pump rotor and pistons are operating normally. However, with the rotor and pistons not operating normally, fluid submitted under pressure against the rotor and pistons will act against the valve 88, moving it from its seat 39 against the force of the spring 36 so that gasoline may be forced through the

passages

35, 38 and 37 to the discharge side of the pump, and thence to the carburetor, all as will be quite apparent to those skilled in the art.

A suitable mechanical seal is provided for the pump rotor, and is best illustrated in Figs. 3 and 6. This mechanical seal camprises a disk at, a spring :33 and a further disk 68, as well as the ring packing 85. I do not believe a further description of the construction of my seal is necessary, since I do not claim any particular novelty therein.

For disposing of any gasoline which may leak past the mechanical seal described, the casing is formed with four .bores 48, terminating in threaded counter bores M. In normal use, all but one of the bores 48 and the counterbores 41 will be plugged by screw threaded plugs 68. The lowermost bore 48, depending upon the position of the pump unit when assembled in the airplane, will have leading therefrom a pipe 49, as best shown in Fig. l, the pipe returning to the gasoline supply line such fuel as may leak past the mechanical seal. The utility of this construction will of course be readily understood by those skilled in the art.

As was indicated earlier in the specification, the eccentricity of the shuttle block 36 is determined by a shuttle pin H. I shall now describe the means whereby the eccentricity of the shuttle pin is itself determined in accordance with the setting of a spring, and in further response to he discharge pressure, with the variations in atmospheric pressure compensated for by a superchargers 4 Referring now more particularly to Figs. 3, 6, 9 and 10, and especially to Fig. 6, it will readily be noted that the pin II forms part of a lever 50 which through a shaft portion 5| integral therewith, is pivoted to the casing through the intermediary of a bushing 52. The lever 50 is bifurcated as at 54 for cooperation with a pin 55 extending laterally from a disk 56. The disk 56 has an integral shaft portion 51, best seen in Fig. 3, whereby it is rotatably mounted on bushings58 relatively to a bored abutment 59 formed as a part of the pump casing. Mounted about the outside of the abutment 59 through the intermediary of the bushing 60 is what I term'a spring winding disk 6|, which as best illustrated in Fig. 7, has .teeth 62 formed on its periphery for cooperation with the worm shaft 63. The

ascaevo shaft extends outwardly of the casing through a suitable seal M and a cap 65, and is formed with a knob 66 whereby the shaft 63 may be rotated. Its rotation in turn, of course, rotates the disk El to adjust the tension in aspring Gl positioned between the disk 56 and the spring windingdisk 6!.

One end of the spring 67, seen best in Fig. 7 and there designated by reference numeral E8, fits into a suitable notch 69 in the spring winding disk El whereby rotation of the disk winds the spring. The other end of the spring bl, as best seen in Fig. 6, fits into a notch ill in the disk 56 and tends therefiore to rotate the disk in accordance with the pressure predetermined by the torsion of the spring 67. It is obvious that the spring til will tend to rotate the disk 56; and therefore .through the pin 55, rotate the lever in a clockwise direction, looking at Figs. 9 and 10. When so rotated, the lever 59 and its shuttle pin 3! will position the shuttle block 30 in an eccentric pumping position. The most extreme eccentric position to which the lever 56, and therefore the shuttle block to, may be moved, is determined by a shoulder ll formed on the casing and limiting the throw of the lever till.

Should less than maximum volume be desired, a movable stop may be utilized, this stop taking the form of a shaft it which has threads at it for threaded engagement with the casing of the pumps The shaft 72 extends outwardly through the casing, and is equipped with a square head id for ready manual adjustment, as is probably best seen in Figs. 3 and 9. A cap it is threaded on to the casing as at it for normally preventing access to the shaft l2 and its head iii, a suitable seal l'i being provided between the cap'lfi and the casing. For maintaining the shaft 12 in any position to which it is adjusted, the end surface it of the casing through which the shaft 72 extends, has projecting therefrom a pin 2?, with of a disk 88 which is slidable on the square end portion id of the shaft, and which must rotate with the disk. Those skilled in the art will readdoes upon the application of pressure thereto,

and assumes a position such as that oiFig. 10,

' through its pin ill from the eccentric position which may cooperate any one of the holes ill whereby the diaphragm is secured to those plates and the rod W, are very clearly shown in the sev eral drawings, and need not be further described here.

It is obvious from a study of the parts in Figs. 3 and 9, that the diaphragm at is capable oi expanding sidewise as well as endwise. This it when the discharge pressure is suficiently great to overcome the pressure of the spring fill maintaining the parts in the position of Figs. 3 and 9. The rod W is pinned at 9b to the lever 5E so that the movement of the diaphragm to the position of Fig. 10 will force the lever 5t) to theposition of Fig. 10 against the force of the spring bl. This efiects a movement of the shuttle block 8t! which is predetermined by the positioning of the fliniit shaftllt, and cuts down the volume which will be pumped by the rotor 2E and its pistons. Thus, if the throttle is closed and less gasoline is required by the carburetor, the pressure on the mscharge side of the pump will increase and will act on the diaphragm moving it from the position of Fig. 9 toward the position of Fig. 10, to decrease the eccentricity oi the shuttle block lit and the pump volume.

Those skilled in the art will readily appreciate that in moving from the position of Fig. 99 to the position of Fig. lilthe lever 5!? acts through the pin as to wind the spring t'l, thereby in creasing the effective pressure which is transmitted by the spring. Since it is the initial pressure setting of the spring which determines the maximum pressure at which a predetermined volume is pumped, and since it is desirable that the pressure acting on the diaphragm iltshall be in a predetermined proportion at all times to the force of the spring til, I utilizethe sidewise expansion of the diaphragm to apply there I diaphragm against which the discharge pressure ular adjusted position. It will now be readily understood that through rotation of the shaft t2, the maximum volume of the pump. dependout on the maximum eccentricity which may be imparted to the shuttle block Elli, may be predetel-mined.

Referring now to Figs. 3, 9 and 10, it will be noted that my casing includeswhat I term a pressure chamber 82 which is in communication through passages 83 and 8d (Figs. 6 and 8) with the discharge side of the pump. The pressure chamber 82 is effectively formed in two parts sealed from one another by a, diaphragm 85 secured at at relatively to the casing through the joining together of-the casting id of the cas-.

ing and the casting H by the series of bolts it, as has already been described. The diaphragm such as Bunaf which is resistant to deterioration by gasoline, and is secured at its pressure end relatively to a cup-shaped plate or and the d5 is preferably formed of a rubber substitute.

threaded end of a rod 88; through the intermediary of a nut 89 and a circular plate 9E. The shapes of the plates El and $90 and the means sure.

of the pump acts, is greater than it is in Fig. 9, so that the total pressure exerted by the die phragrh is also greater, and compensates for the greater tension in the spring. This particular feature oi, my invention I consider of considerable importance.

That portion of the pressure charcher it? outside the diaphragm has formed therein a series of threaded openings to. It will be well to consider what would happen were these openings allowed to remain open and exposed to the atmosphere. As'the airplane gains altitude, the decrease in atmospheric pressure on the car-l buretor is compensated for by a supercharger, so that the fluid pressure developed by the pump is superimposed on the supercharger pressure, rather than on the decreased atmosphericpres- It isthis compensated fluid pressure, as we may call it, which is applied against the inside of the diaphragm 85 to move the shuttle block 38 to decrease the pumping volume. Since this compensated iiuid pressure, at high altitudes, operates against a decreased atmospheric pressure on the outside of the diaphragm Q, the pumping volume will be decreased to a greater degree than is desirable. To ofiset this phenomenon, I connect the supercharger to. the pressure chamber through at least one of the threaded openings 95, closing the others with'plugs lit.-

It is quite clear that with such an arrangement, the compensated fluid pressure always acts against a compensated atmospheric pressure on the outside of the diaphragm 85 so that it is the increased fluid pressure only which really acts to cut down the pump volume. thought that in view of the several general ex planations previously presented and the specific description now presented, this feature of the invention which is highly important, will be fully appreciated and understood.

I now claim:

1. In a pump of the class described, a positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a spring for pressing said positioning member into a predetermined volume position, an expansible and contractible diaphragm, said pump having passages connecting the discharge pressure of said pump to said diaphragm whereby said pressure acts against the diaphragm to expand it, means whereby the diaphragm effects the movement of said positioning member against the pressure of said spring toward non-pumping position, and means mounting said diaphragm so that the eifective area thereof against which said discharge pressure is applied increases through the deforming of said diaphragm as said positioning member is moved by said dia- Dhragm against the pressure of said spring whereby to compensate for the increasing pressure of said spring.

2. In a pump of the class described, a position- .ing member for a pump mechanism adapted to determine the volume pumped by said mechanism, a spring for pressing said positioning member into -a predetermined volume position, an expansible and contractible diaphragm, said pump having passages connecting the discharge pressure of said pump to said diaphragm whereby said discharge pressure acts against the diaphragm to expand it, means. connectin phragm to said positioning member for moving said member against the pressure of said spring toward non-pumping position, and means mounting said diaphragm for sidewise as well as end- It is the diawise expansion by said discharge pressure so member into predetermined volume position, an

expansible and contractible diaphragm formed of a flexible resilient material such as rubber adapted when expanded as by the application of pressure thereto to increase the effective area against which the pressure acts to, further expand said diaphragm, said pump having passages connecting the discharge pressure of said pump to said diaphragm whereby said discharge pressure acts against the diaphragm to expand it, means connecting the diaphragm to said positioning member for moving said member against the pressure of said spring toward nonpumping position as said diaphragm is'expanded, the increase or the size of said effective area as said diaphragm is expanded acting to increase the effective area against which said discharge pressure is applied as said positioning member is moved against the pressure of said spring, whereby to compensate forthe increasing pressure of said spring.

4. In a pump of the class described compriscasing whereby rotation thereof adjusts said stop, and a portion of said shaft extending outwardly of said casing for manual manipulation.

5. In a pump of the classdescribed, a posi-.

tioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a torsion spring, means whereby said positioning member is secured relatively to one end of'said spring whereby to be pressed into a predetermined volume position, and means secured to the other end of said spring for winding said spring and determining the pressure under which said pdsitioning member is urged to said predetermined volume position.

6. In a pump of the class described, a positioning member for a pumpmechanism adapted to determine the volume pumped by said mechanism, a torsion spring, means whereby said positioning member is secured relatively to one end of said spring whereby to be pressed into a predetermined volume position, a rotatable adjusting member secured to the other end of said spring for winding said spring and determining the pressure under which said positioning member is urgedto said predetermined volume position, and means for rotating said adjusting member and for maintaining it in adjusted position.

7. In a pump of the class described, a positioning lever for a pump mechanism adapted to determine the volume pumped by said mechanism, a torsion spring, a disk secured to one 7 tioning lever for a pump mechanism adapted to determine the volume pumped by said mechanism, a torsion spring, a disk secured to one end of said spring, a connection between said disk and lever whereby said spring urges said lever toward a predetermined volume position,

an adjustable stop against which said spring presses said lever to determine said volumeposition, and a winding disk secured to the other end of said spring for winding said spring and determining the torsion therein and therefore the pressure under which said lever is urged by said spring to said predetermined volume position.

9. In a pump 'of the class-described, a posi- I tioning lever for a pump mechanism adapted to determinethe volume'pumped by said mechanism, a torsion spring, a disk secured to one end or said spring, a connection between said disk and lever whereby said spring urges said lever toward a predetermined volume position, an expansible and contractible diaphragm, said pump having passages connecting the discharge pressure to said diaphragm whereby saidpressure acts against the diaphragm to expand it, means connecting the diaphragm to said positioning lever for moving said lever against the pressure of said spring toward non-pumping position, and

a winding disk secured to the other end of said spring for determining the torsion therein and,

nism, a torsion spring, a disk secured to one end of said spring, a connection between said disk and lever whereby said spring urges said lever toward a predetermined volume position, an expansible and contractible diaphragm, said pump having passages connecting the discharge pressure to said diaphragm whereby said pressure acts against the diaphragm to expand it, means connecting the diaphragnfto said positioning lever for moving said lever against the pressure of said spring toward non-pumping position, a winding disk secured to the other end of said spring for determining the torsion therein and therefore the pressure under which said lever is urged, by said spring to said predetermined volume position, and a hand rotated shait having a worm gear connection with the periphery of said disk for rotating said disk into a particular spring torsiorn'ng position and thereafter maintaining the said spring in that position.

11. In a pump of the class described a rotatably mounted positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a torsion spring, a

connection between said spring and member whereby said spring rotates said member toward a predetermined volume position, an expansibie and contractible diaphragm, said pump having passages connecting the discharge pressure oi said pump to the interior of said diaphragm whereby said pressure acts against the diaphragm to expand it, means connecting the diaphragm to said positioning member for moving said mem- 'ber against the pressure of said spring toward non-pumping position,.and a pressure chamber formed with the exterior of said diaphragm defining part thereoi whereby said diaphragm may be subjected to pressure to ofiset said pump fluid pressure. v

12. In a pump of the class described, a rotor, a pair oi reci rocating pistons carried by said rotor and Slldfifle relatively thereto and to one another, an eccentrically positioned shuttle block having four arms in the form of a square cross and having the opposed parallel surfaces of its arms in contact with said pistons for reciprocating said pistons as said rotor is rotated to contribute a pumping effect, said block sliding relatively to said pistons while reciprocating said pistons, an eccentric pin for determining the eccentricity of said shuttle block, and passages through the arms of the said shuttle block to allow the passage of fluid as said block slides relatively to said pistons.

it. In apump or the class described, a casing,

a rotary pump mechanism in said casing, a positioning lever for said pump mechanism pivoted in said casing and adapted to determine the volume pumped by said mechanism, a spring chamber having a torsion spring therein, a rotary shaft in said spring chamber and extending outwardly thereof for manual adjustment, means spring, means of connection between said spring and lever whereby said spring rotates said lever in one direction corresponding to full pumping of said pump mechanism, an adjustable stop against which said lever is pressed by said spring, said stop extending outwardly of said casing for manual adjustment, a rod pivotally secured to said lever at one end, a pressure diaphragm to which said rod is secured at its other end,

said pump having passages connecting the pressure side or said pump with the interior of said diaphragm whereby said pressure acts against said diaphragm to move said lever against said spring toward non-pumping position, and a chamber in which the outside of said diaphragm is exposed for the application of pressure to offset said fluid pressure. I a

is. in a pump of the class described, a rotatably mounted positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a torsion spring,

means whereby said positioning member is secured relatively to one end of said spring whereby to be rotated into a predetermined volume position, and means secured to the other end of said spring for winding said spring and determining the pressure under which said positioning member is rotated to said predetermined volume position.

15. In a pump 9f the class described, a rotatably mounted positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a torsion spring, means of connection between said spring and member whereby said spring rotates said mem= ber toward a predetermined volume position, an expansible and contractible diaphragm, said pump having passages connecting the discharge pressure to said diaphragm wherebysaid discharge pressure acts against the diaphragm to expand it, means whereby the diaphragm urges the rotation of said positioning member agains the pressure of said spring toward non-pumping position when the discharge pressure is applied thereagainst, and a winding means secured to a portion oi said spring for determining the tin-- sion therein and therefore the pressure under which said positioning member is rotated by said spring toward said predetermined volum position.

.16, in a pump of the class described, a rotor, a pair oi reciprocating pistons carried by said rotor and slidable relatively thereto and to one another, an eccentrically positioned shuttle block having four arms in the form oi a square cross and having the opposed parallel surfaces of its arms in contact withsaid pistons for reciprocating said pistons as said rotor is rotated to contribute a pumping efiect, said block sliding relatively to said pistons while reciprocating said pistons, and passages through the arms of the said shuttle bloclsto allow the passage of fluid as said block slides relatively to said pistons.

17. In a pump of the class described, a rotor, a reciprocating piston carried by said rotor and slidable relatively thereto to contribute a pumping action, an eccentrically positioned shuttle block having surfaces adapted to contact opposed surfaces formed on said piston for reciprocating said piston relatively to said rotor as said rotor is rotated, said shuttle block sliding relatively to other of said shuttle block as it slides relatively to said surfaces.

18. In a pump of the class described, a rotor, a reciprocating piston carried by said rotor and slidable relatively thereto to contribute a pumping action, an eccentrically positioned shuttle block positioned within a slot formed in said piston and contacting opposed surfaces of the said piston defining the said slot for reciprocating said piston relatively to said rotor as said rotor is rotated, said shuttle block sliding relatively to said surfaces while reciprocating said piston; and passages through said shuttle block to allow the passage of fiuid from one side to the other of said shuttle block as it slides relatively to said surfaces.

19; In a pump of the class described, a positioning member for a pump mechanism adapted to deterngine the volume pumped by said mechanism, a spring for pressing said positioning member into a predetermined volume position,

it, and means connecting the bottom of said diaphragm and said plate portion to said positioning member for moving said positioning member against the pressure of said spring toward nonpumping position as said diaphragm is expanded.

21. In a pump of the class described, a positioning member for a pump mechanism adapted to determine the volumepumped by said mechanism, an expansible and contractible diaphragm, said pump having passages connecting the discharge pressure of said pump to said diaphragm whereby said pressure acts against the diaphragm to expand it, means whereby the diaphragm eflects the movement of said positioning member, and means mounting said diaphragm so that the eifective area thereof against which said discharge pressure is applied increases an expansible and contractible diaphragm of cup a shape having a bottom portion and a side portion and with said side portion adapted to extend into said bottom portion as said diaphragm is exdiaphragm and thereby to increase the area of its bottom portion, means whereby the expansion of said diaphragm efiects the movement of said positioning member against the pressure of said spring toward non-pumping position, the increase of the area of said bottom portion acting to increasethe efiective area againstr which said discharge pressure is applied as said positioning member is moved against the pressure of said spring, whereby to compensate for the increasing pressure of said spring.

20. In a pump of the class described, a positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a spring for pressing said positioning member into a predeterminedvolume position, a cupshaped expansible and contractible diaphragm having a bottom portion and a side portion, a metal plate against which the bottom portion of said cupshaped diaphragm presses when acted upon by fluid pressure, said plate being somewhat larger than the normal area of the bottom of the diaphragm, the application of fluid pressure to said diaphragm acting to expand said diaphragm and to force the side thereof to move against said plate to form in eflfect a part of the bottom thereof whereby to increase the area of the botthrough the deforming of said diaphragm as said positioning member is moved by said diaphragm. 22. In a pump of the class described, a positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, an expanslble and contractible diaphragm having a bottom portion and a side portion and with said side portion adapted to extend into said bottom portion as said diaphragm is expanded, said pump having passages connecting the discharge pressure of said pump to said diaphragm whereby said pressure acts against the bottom portion of said diaphragm to expand said diaphragm and thereby to increase the area of its bottom portion, means whereby the expansion of said diaphragm effects the movement of said positioning member, the increase of the area of said bottom portion acting to increase the eifective area against which said discharge pressure is applied.

23. In a pump of the class described, a positioning member for a pump mechanism adapted to determine the volume pumped by said mechanism, a cupshaped expansible and contractible diaphragm having a bottom portion and a side portion, a metal plate against which the bottom portion of said cupshaped diaphragm presses when acted upon by fluid pressure, said plate being somewhat larger than the normal area of the bottom of the diaphragm, the application of fluid pressure to said diaphragm acting to expand said diaphragm and to force the side thereof to move against said plate to form in effect a part of the bottom thereof whereby to increase the area of the bottom of said diaphragm, said pump having passages connecting the discharge pressure of said pump to. said diaphragm whereby said discharge pressure acts against the diaphragm to expand it, and means connecting the bottom of said diaphragm and said plate portion to said positioning member for moving said positioning member.

WARREN WILFRED GROVES.