US2399990A - Automatic variable pump - Google Patents

Description

May 7, 1946. 9 M. M. CULVER v 9 2,399,990

AUTOMATIC VARIABLE PUMP Filed Nov. 12, 1943 4 sheets sheet 1 M y .M; M. CULVER 2,399,990

AUTOMATIC VARIABLE PUMP v Filed Nov. 12, 1943 4 Sheets-Sheet 2 Sums? err/9m 16 e011. 3/ 30 1.5 3mm Marg m. calm;

May 7, 1946. M. M. cum/ER AUTOMATIC VARIABLE PUMP 4 Sheets-Sheet 3 Filed Nov. 12, 1943 llli y 7, 1946. A M. M. CULVER 2,399,990

AUTOMATIC VARIABLE PUMP JFiled Nov. 12, 1945 4 Sheets-Sheet 4 Patented May 7, 9 1946 AUTOMATIC VARIABLE PUMP Merlyn M. Culver, Dayton, Ohio, assignor' to United Aircraft Products, 'Inc., Dayton, Ohio, a

corporation of Ohio Application November '12, 1943, Serial No. 510,003

2 Claims.

-.This invention relates to pumps, and has par-. ticular. reference to improvements in variablestroke, variable-capacity pumps of the type comprising a cylinder, a rotor rotatable therein and providedwith radial or transverse displacement chambers, pistons in said displacement chambers rotatable with said rotor, and means wherebysaid pistons are reciprocable in said chambers in response to their rotation with said rotor to accomplish their pumping function.

In many instances it is very desirable to employ a pump, the output of which may readily be varied to maintain the fluid being pumped under constantor substantially constant pressure despite variations in the demand upon the pump and without dependence upon sudden and more or less widely varying changes in the speed of operation of the pump. For example, in the internal combustion engine art in general and particularly in, the aircraft art, it is very desirable to employ an engine fuel pump which will deliver fuel to the engine under constant or substantially constant pressure and in accordance with more or less sudden and more or less wide variations in the fuel demands of the engine, whether variations in the fuel demands are due to more or less sudden and more or lesswidely varying changes in the speed of the engine, to variations in the load thereon, or to other causes.

Accordingly, one special and important object of the present invention is to provide a pump of the type mentioned, especially for use as a fuel pump for internal combustion engines in general and particularly for aircraft engines, but, 'of course, capable of various other uses, which is operable in response to variations in the pressure of the fluid being pumped rather than to variations in its speed of operation, to vary the stroke of its pistons and thereby vary its output, thus automatically to vary its delivery of fluid in accordance with variations in the demand therefor and to'maintain the delivered fluid under constant or substantially constant pressure.

Another special and important object of the invention is to provide a pump of the character mentioned which, in general, is of simple, practical construction and which embodies simple, practical means for varying the stroke of its pistons in response to variations in the pressure of the fluid being pumped.

Another special and important object of the invention is to provide a pump of the character mentioned which is reversible and which includes by-pass means whereby fluid may be pumped or otherwise circulated therethrough between the inlet and the outlet thereof when the same is idle. Another special and important object of the invention .i to provide a pump of the character mentioned embodying simple means to seal the same eifectively against. leakage of fluid therefrom.

Another special and important object of the invention is to provide a pump of the-character mentioned which is strong, rugged and thoroughly reliable and efficient in operation.

With the foregoing and other objects in view, the invention consists in a pump of the character mentioned embodying the various novel features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accompanying drawings and defined in the appended claims.

In the accompanyingdrawings, wherein like characters of reference denote; corresponding parts in the different views:

Fig. 1 is a side elevation of a pump constructed in accordance with one practical embodiment of the invention.

Fig. 2 is a diagrammatic view illustrating the pump embodied in a fuel feeding system of an aircraft engine.

Fig. 3 is a top plan view of the pump.

Fig. 4 is a central, vertical, longitudinal sec-' of the plug unit for closing the outer end of the pump cylinder.

Fig. 8 is a central. vertical, transverse section through the pump with the pressure responsive means for varying the stroke of the pistons positioned as shown in Fig. 4.

Fig. 9 is a perspective. view of the rotor and piston elements of the pump shown in separated relationship to each other; and

Fig. 10 is a perspective view of the closure cap unit illustrated in Fig. 7 with the parts thereof chamber, respectively, and either of which may be for the inlet of fluid to the pump and the other for the outlet of fluid therefrom.

At what may be termed its inner and its outer ends, the cylinder II is closed by what may be termed plug units I4 and i5, respectively, which are duplicates of one another except as regards the main element of each of them, which main elements merely are specifically different from each other to adapt the units for convenient and practical mounting in the respective ends of said cylinder. In other words, each of said plug units includes a main element in the form of a relatively thick, circular plate l6 fitted snugly in the cy1in--- der II, and whereas this plate of the unit l5 includes a flange I! to overlie and to be bolted against the outer end wall of the cylinder ID to secure said unit |5 firmly in place in closing relationship to the outer end of the cylinder II, the corresponding plate of the unit I4 is disposed entirely within the cylinder H and, therefore, is devoid of any such flange. In other respects the units l4, l5 are, in all essential respects and to all essential intents and purposes, reversed duplicates, or substantially reversed duplicates, of each other, the unit l4 being secured firmly in place in closing relationship to the inner end of the cylinder III by reason of the plate l6 thereof being disposed against an inwardly extending, annular, flange-like wall l8 of the casing l and by being fastened against said wall by bolts or screws |9.

Each plug unit |4, includes a block 20 securely fastened by means of screws 20 or inany other suitable manner against the inner face of its related plate l5 and having in the face thereof adjacent to its related plate I6 a channel 2| extending from top to bottom thereof. Thus, in each plug unit l4, l5, between the plate It and the block 20, is provided a guide channel extending from top to bottom of the'unit.

Slidably mounted in each guide channel 2| for vertical movement is a slide-piece 22, and projecting laterally inward from each slide piece through an opening 23 in the wall of the related block 20 defining the inner side of the channel 2| and inwardly beyond said wall, is a circular boss 24 on which is rotatably mounted a flat circular band 25. The openings 23 are of greater dimensions vertically than the diameters of the bands 25 to permit vertical movements of the slidepieces 22 and of the bosses 24 with the bands 25 thereon relative to the blocks 20.

Coaxial with the cylinder II is a shaft 25 which extends through openings 2!v in the slide-pieces 22 and the bosses 24 and which is journaled for rotation in central bearings in the plates l6. Carried by this shaft is the pump rotor, desigv pistons.

nated generally as 28. This rotor is of cylinthe shaft 25 extends, and said rotor is suitably fastened to said shaft for rotation therewith as,

for example,'by means of apin 32' extending transversely through alined holes in said hub and said shaft. I

The pump pistons 3| are of the same length as the rotor 29 and of the same width as the slots or displacement chambers 29, 30 so as to engage fluid-tightly at their sides with the walls defining the sides of said slots or displacement chambers and at their ends with the inner faces of the blocks 20, and are of lesser depth than said slots or displacement chambers 29, 30 so as to be reciprocable therein, their outer faces preferably being curved transversely on the same radius as the cylinder H and the rotor 28. These pistons are connected together in two opposite pairs, each pair by a. web 33 located adjacent to one end of the pair so as to clear the web or hub 32 of the rotor 29, and the two pairs are disposed in the slots or displacement chambers 29, 30 in right angular relationship to each other with the pistons of each pair occupying positions diametrically opposite of said slots or displacement chambers, the webs 33 of the respective pairs being disposed at opposite sides of the web or hub 32 of the rotor 28. In the webs 33 are openings 34 through which the shaft 25 extends and which are amply long so that said shaft does not interfere with reciprocation of the pistons. Obviously, when the rotor 28 rotates, the pistons 3| rotate therewith.

At their ends, the pistons of each pair straddle the bands 25 and contact with the peripheries thereof, the distance between the band contacting inner face portions 35 of each pair of pistons being equal to the diameters of said bands which are equal in diameter to each other. Accordingly, if the slide-pieces 22 are adjusted to dispose the bosses 24 and the bands 25 eccentrically with respect to the shaft "and the rotor 28, rotation of said rotor and the pistons 3| therewith will result in radial reciprocation of said pistons in the slots or displacement chambers 29, 30 due to the coacting cam action between the bands 25 and the end portions 35 of the pistons. If, on the other hand, the slide-pieces 22 are adjusted to dispose the bosses 24 and the bands 25 concentrically with respect to the shaft 26 and the rotor 28, rotation of said rotor and the pistons 3| will not result in any reciprocable movement of said It will be apparent, therefore, that the stroke of the pistons 3|, between zero and maximum, is variable by vertical sliding adjustments of the slide-pieces 22 in their channels 2|. 0bviously, the bands 25 may be eliminated and the ends of the pistons 3| may directly engage the bosses 24. The bands 25 preferably are used, however, because they may readily be hardened to reduce wear and because they may readily be removed.

Formed in the casing I0 at opposite sides of the cylinder II in alinement with the openings l2 and I3 and opening into said cylinder II, is a pair of circumferentially extending channels 36, 36 of any suitable width and depth the upper and lower ends of which, at the bottom and the top,

' respectively, of said cylinder II, are spaced apart ment chambers 29, 30. Thus, rotation of the asoaeoo a pair of arms 4|, 4| which are suitably connected,

to the slide-pieces 22 as, for example, by means of Preferably the piston 41 is bored from its top to accommodate the lower' end portion of the spring 43 and preferably means is provided to vary the strength of said spring to determine the pressure of the pumped liquid required to reduce the stroke of the pump pistons 3 I.

screws, rods or other suitable connecting elements 42 which extend slidably' through openings in the top wall of the casing I 3. Thus, flexure of the diaphragm 43 is effective to produce vertical adjustments of the slide-pieces 22 and of the bosses 24 and the bands 25 carried thereby to vary the stroke of the pump pistons. In this connection it will be observed that a spring 43 is provided to act downwardly upon the diaphragm 43 and the arms 4| to tend constantly to urge the slidepieces 22 to their limits of downward movement v for maximum stroke of the pump pistons and thatand that a pivoted or flap type check valve 43 is capable of being pivoted to either of a pair of supports 36, 43 in the chamber 33 so as to cooperate with either of the ducts 44 topermit'flow of fluid through the same into the pressure chamber 33 and to deny flow of fluid through the same from saidpressure chamber. This checkvalve is pivoted to cooperate with the duct 44 which is related to the channel 36 at whatever'ma'y be the inlet side of the pump, depending upon the direction of rotation of the rotor 28. Accordingly, the chamber 331s subjected to the pump outlet pressure of the fluid being pumped and if, for any reason, this pressure exerts a force upwardly upon the diaphragm 40 in excess of the spring pressure thereon, said diaphragm will flex upwardlywith consequent raising of the slide-pieces 22 and reduction in the stroke of the pump pistons commensurate with the difl'erence in pressures above and below said diaphragm. Thus, not only the quantity of fluid pumped by the. pump is controlled automatically in response to variations in the pressure of'the pumped fluid at the outlet side of the pump, but the consequent tendency is tomaintain a substantially constant or uniform pressure of the pumped fluid.

Preferably, but not necessarily, means isassociated with the diaphragm 43'to render the same smoothly acting in operation, and. this means may comprise, for example, a dash-pot consisting of a piston 41 suitably secured to said diaphragm and depending therefrom into a cylinder 41' formed in the upper wall of the casing III, the said cylinder being in communication at its bottom with the chamber 33 through a small duct 43.

- Conveniently, the arms 4| may be formed as integral parts of the piston 41. Conveniently, too,

the housing 31 may be of two-part construction comprising lower and upper parts 43 and 53. respectively, between which the diaphragm 43 may be marginally clamped.

While any suitabl means may be provided for varying the strengthof the spring 43, one suitable means for this purpose may comprise, as shown, an abutment disk 5| for the upper end. 01 said spring keyed or otherwise mounted in a vertical bore 52 of the upper housing part 53 for non-rotatable, vertical sliding movement in said bore, and a screw 53 swiveled to said upper housing part and threaded through said disk. Thus, by rotatably adjusting said screw, said disk may be adjusted vertically to var the strength of said spring 43. The screw 53 may have a flange 54 interposed between the top of an exteriorly threaded neck 55 at the top of the upper housing part and an inwardl extending flange 56 of a unit 51 threaded on said neck to provide a swiveled connection between said housing part and .said screw, this arrangement being simple and by tightening said nut, said screw may readily be fastened against rotation in any rotatably adjusted position thereof.

Th shaft bearing opening in the plate iii of the plug unit. I5 is closed at its outer end and therefore there is no possibility oi leakage of fluid from the pump around said shaft at this point.

: On the other hand, the shaft bearing opening in the plate l3 of the plug unit I4 extends entirely through said plate and therefore it is necessary to seal said opening against leakage of fluid from the pump therethrough. In this connection it this connection being afforded, for example, by a tongue 59 on the end of the shaft 28 engaged in a slot in the end of the shaft extension 26'.

In an annular channel in the inner face of thecap-piece 53 in surrounding relationship to the shaft extension 23' is disposed a suitable gasket 33, while on the shaft extension 26' is an annular flange 3i which bears against the inner edge of said gasket. In addition, a cup member 32 is mounted on the shaft 26 with its closed and facing inwardly and bearing against an annular rib 33 on the outer face of the plate It and with its open end facing outwardly. In this cup member and surrounding the shaft 26 is a suitable gasket 54, while between said gasket and the flange 3! is interposed an expansion coil spring 63 which tends constantly to urge the shaft extension 2-3' outwardly and the gasket 34 and the cup member 52 inwardly. Since inward movement of the cup member 32 is limited by the plate i3, one effect of the spring 35 is to maintain the gasket 34 under compression in tightly sealing. engagement with the shaft 23 and, at the same time, to maintain the inner face of the cap member 32 in tightly sealing engagement with the rib 33. The other effect of said spring 33 is to urge the shaft extension 23 outwardly, with V the result that the flange 3| maintains the gasket 33 under compression in tightly sealing engagement with said shaft extension and with the surrounding portion oi the cap=piece E8. Thus, even though. any fluid may lea-l2 the cylinder ii into the chamber containing the spring 65 and the seals, any leakage of fluid from said chamber eii'ectively is prevented.

The shaft extension 28 projects outwardly beyond the cap-piece 58 for connection with any suitable power unit for driving the pump, and openings 6? preferably are provided in the casing It for the supply of lubricant to the chamber 86 and for the drainage of said chamber.

Fig. 2 of the drawings illustrates a conventional fuel feeding system for an aircraft engine including a pump constructed in accordance with the invention. In Fig. 2 an internal combustion engine is indicated as A, a supercharger is indicated as B, a fuel tank is indicated as C, a power driven fuel pump constructed in. accordance with the invention islndicamcl as D, and. a hand= pump for use in the event of failure of the pump D or for engine starting or other purposes, is indicated as E.

A pipe at connects the fuel tank C with the inlet side of the hand=purop E, and the inlet side of said hand puznp is a bypass passageway b which is connected with the inlet side of the pump D by a pipe 6. Another pipe e connects the outlet side of the hand=pump with the inlet side of the pump a pipe fcoDnect-s the outlet side of the pump D with the e; ic A. Grdinarily, the pump D functions to fuel ss 2) under substantially constant or uniform pressure. At times, however, may he necessaiy or desirable to employ l1 d-pump E to deliver fuel to the engine, ch event the iiow is via the pipe (2 to the ini t side of said handpump, from the outlet side to the inlet side of the pump D via the pipe 2, through the channel 36 and the duct at the inlet si no of said pump D, then into the chamber past the check valve it, through duct i l and the channel the outlet side of said pump D, and then to engine the pipe f.

The superch. B is connected with the upper chamber 3 of the pump D by a pipe 9. Therefore, said chamber is subjected to supercharger pressure which acts downwardly upon the diaphragm 36 and augments the spring in this respect. Consequently, variations in the stroke of the pistons of. the D is a function ofthe difference between the pressm'e of the-fluid at the outlet side of said on the one hand, and the combined pressure of the spring and the supercharger B on. the other hand, in any instance where a supercharger or other pressure device is connected 4 the chamber 35?. In this cormectionit is manifest that, for many purposes, the chamber 59 may not he necessary and may be eliminated if desired.

From the foregoing description considered in connection with the accompanying drawings, it is believed thatthe construction and operation of the present pump will be clearly understood and its advantages appreciated. It is desired to point out, however, that while only a single, specific embodiment of the invention has ceen illustrated and descrihed, the same is readily capable of embodiment in various other specifically different mechanical form within its spirit and scope as defined in the appended claims.

1'. claim:

1. A variable capacity pump, comprising a housing defining a cylinder having inlet and outlet ports therein; a rotor in said. cylinder, the peripheral surface of which is in continuous contact with the wall of said cylinder; longitudinal slots in the peripheral surface of said rotor; pistons radially movable in said slots and carried by said rotor successively past said inlet and outlet ports; means eccentric with respect to the longitudinal axis of said rotor providing a mount for said pistons whereby to impart a pulsating motion thereto so that fluid is drawn into said slots at said inlet port and expelled therefrom at the outlet port, the length of strokes of said pistons determining the rate of flow of fluid through the pump; operating fingers extending into said cylinder into cooperative relation with said piston mounts for shifting said mounts toward and from a position more nearly coaxial with said rotor to shorten and lengthen the strokes of said pistons; and fluid pressure operated means for controlling action of said operating fingers.

2. A. variable capacity pump, comprising a housing defining a cylinder having inlet and outlet ports; a rotor in said cylinder movable about a fixed axis; a pair of diametrically opposed slots in said rotor; pistons in said slots connected for simultaneous operation, said pistons being movable transversely of the axis oi said rotor and carrim by said rotor successively past said inlet and outlet ports; a pair of cylindrical piston mounts at the opposite ends of said rotor and adjustable radially thereof toward and from positions coaxial with the rotor, the ends of said pistons being in sliding engagement with said cylindrical mounts and guided thereby through radim strokes which are variable in length in accordance with the position 05 the piston mounts with respect to the axis of the rotor; a single spring means pressing said piston mounts to positions effecting radial strokes of a maximum length of said pistons; and fluid pressure operuteri means opposing the action of said spring means.

I /LERLYN M. CULVER.

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