US2337821A - Pump - Google Patents

Description

Dec. 28, 1943. M. w. HUBER PUMPY Filed Dec.V 2, 1942- Fie.5

attornegs erates successfully at against head pressures of' scribed arrangement l the complete pump.

Patented Dec.. 12943 iUNITED sTATEJs PATENT ol-*Fics Matthew W Huber, Chicago,

Ill., assignor to Hydraulic Controls, Inc., a corporation of Illinois f Application December 2, 1942, Serial No. 467,629

(Cl. 'I4-60) 3 Claims.

This invention relates to high pressure positive displacement pumps in which the' cylindersl are yarranged in circular series around the drive shaft andthe plungers are actuated by a swash plate (or other cam) mounted on said shaft.

`The pump is an improvement on that described in my copending application, Serial No. 462,563, led October 19, 1942.' That pump opnearly 4400 R. P. M. 1500 pounds per square inch,` and has the important characteristic of being indifferent to the direction of rotation of thedrive shafti l Where unidirectional rotation ofthe drive shaft is feasible, the present invention permits modication of the prior pump so as to operate gtiligher speeds or against higher pressures or The invention assures a more direct thrust reaction of the swash plate or cam upon the pump plungers by skewing the cylinder bores, so that the axis of each bore is tangent to a quick pitch helix concentric with the shaft axis instead of being parallel with the shaft axis. This disposition of the cylinders is such with reference to the cam angle that at mid stroke on the displacement stroke of each plunger the axis of the cylinder is nearly normal to the thrust face of the cam. Thusy the lateral thrust component of the cam on the plunger is reduced, as isthe total axial thrust. This consideration is important because anything which will reduce bearing loads in a type has a marked beneficialeiect. The de- .is practicable because -the displacement thrustA on the plungers is unidirectional. It gives a decided directional characteristic to the pump,` so that it is considered undesirable to permit the shaft to turn backward when the pump is under load.

A modification of the pump illustrated in -the prior application to incorporate the present invention, is illustrated in the accompanying drawing in which:

Fig. 1 is an approximately axial section of Fig.. 2 is a side elevation of the pump shown in Fig. 1 with a portion broken away to show one cylinder in section so that its inclination may be seen.

Fig. 3 is a section on line 3-3'of Fig. 1.

Fig. p4 is an end elevation of the cylinder block.

Fig. 5 is a perspective view of the swash plate.

Statements of direction in the following spe- III and I2 cii'lcation assume that the pump is positioned .as in Fig. 1. The direction of rotation of the shaft is indicated by an arrow placed on the shaft in Fig. 1.

The pump is lubricated by the hydraulic liqv mount (not shown).

The c'ylinder block I1 is cylindrical in form and has an axial bore to receive the bearing bushing hereinafter described. It also has a peripheral flange I8 which seats in a circular rabbet deeper than the ange and formed at the mating area vof the flanges I3 and I4.. The fiange I8 is sealed by a gasket I9 which lls the remaining space in the rabbet to the right of the flange I8. This gasket is initially of circular high pressure pump of this f cross section. The arrangement is such that the right hand end of the cylinder block is subject to pump discharge pressure so that the cylinder block is urged strongly to the left against the seat formed in the portion' I2 of the pump housing to receive flange I8.

A circular series of cylinder bores, eight of which are shown, are formed in the cylinder block. The axes of these bores may be considered as tangent to similar imaginary uniformly spaced quick-pitch helices generated around the axis of the pump shaft. The pitch of the imagmary helices can be estimated by an examination of Fig. 2. The cylinder block is of steel and suitably heat-treated.

Each cylinder bore receives a pump plunger 2l and the inclination of the bore and plunger is. such thatthe axis of each plunger is nearly but not quite normal-to the engaged surface of the actuating cam, hereinafter described, when the cam has moved the plunger to its mid stroke position in a displacingl direction. This is the position shown in Fig. 2.

The plungers 2l arepazdally bored as indicated at 22 in Fig. 1 and have radiating lubricating 4passages 23 which lead to circumferential grooves 24 cut in each plunger. AThis is the lubricating housing of the pump isv arrangement used in the structure of the earlier application. 'I'he grooves are so spaced that their traces overlap as the plungers reciprocate.

'I'here are also two cross bores 25 which are exposed when the plunger reaches its limiting position to the left. 'Ihe cross bores'thus serve as inlet ports. 'I'he open position is shown as to the lowermost plunger in Fig. 1. 'I'he cross which are formed both in the body andin the hub of the swash plate (see Fig. The purbores also assist in the lubrication of the plungers. The plungers are of steel andare suitably heat treated.

An automatic discharge valve of the disc type provided for each cylinder bore, the valve seating against the end face of the cylinder block I1. 'I'here is one valve 26 for each cylinder. each valve being cup-shaped and seated by a coil compression spring 21. Vents 28 (see Fig.

1) prevent liquid from being trapped behind the valves around the springs 21.

Each plunger has an enlarged head 29 on its outer end. A coil compression spring 3| encircles the outer end of the plunger behind the head and reacts between the head and the cylinder block to urge the plunger outward, i. e. to force it on its suction stroke. Each head 23 is provided with a spherical' socket whose depth exceeds its radius. Ball-like thrust heads 32 are pressed into these sockets and when pressed to place tilt freely and are retained because of the constricted entrance opening. Each such ball has a flat thrust face formed on a protruding boss which acts to limit the tilting motion of the ball to a little more than that necessary for the operation of the pump.

The cynnder block n is positioned m che hous-v ings II and I2 by means of a stake,4 not visible in the drawing, but of ordinary form. 'I'he stake engages the head portion of the housing I'I. The cylinder block is so closely clamped that the stake need perform little more than an initial positioning function. The space lbetween the head of the housing I I and the cylinder block.

I1 is the discharge space of the pump and communicates with a groove 34 `(see Fig. 2) cut in the periphery of the cylinder block and so located as to lead to the discharge port 35.

The pump shaft turns in a bearing bushing 31 which is pressed into the axial bore of the cylinder block I1 and thus is xed therein. 'Ihis bushing makes a close t with an aligned bore of the inner face of the head of body II and produces a seal therewith by sealing ring i3d received in a rabbet formed in the inner end of the bearing bushing. An oil groove 33 extends the entire length of the bushing 31 and supplies oil for lubrication at pump inlet pressure. Gasket 38 prevents leakage from the discharge pressure chamber to the interior of the bearing bushing. Both the gaskets I 3 and 38 are preferably formed of an oil resisting rubber substitute.

The drive shaft 39 carries an actuating cam,

the swash plate, which is a special type of cam.

'I'he shaft 33 is driven by a driving disc 45 which has a flattened hub I6 received within a cross slot at the end of the shaft and retained therein by the machine screw 41.

In'the example illustrated, the oil tQbepumped I enters the housing I2 through radial slots 48 76 pose in this arrangement is to ensure ample lubrication of the rotating hub and swash plate. Other arrangements to admit oil to the interior of the housing I2 are possible.

It is preferred to insert a oating annular disc 49 between the inclined face of the swash plate and the thrust heads 32. 'I'his plate rotates at a speed slower than that of the swash plate and serves to distribute Wear. As suggested in the earlierapplication, .a series of 'superposed discs can be used but the one shown is ordinarily sumcient. The use of such plates is not possible with disc cams having other than plane thrust surfaces.

The operation ofthe pump is not changed materially by duplicating these floating discs, though the wear is distributed because the motion bethis surface is retreating and the thrust load is at a minimum.

With this arrangement of the plungers, the pump is capable of sustained operation at somewhat higher speeds and at somewhat higher pressures than those permissible with the pump of the prior application. There is, however, the limitation that the pump should be driven in only vone direction. Where this-requirement can be met, the arrangement is desirable.

Generally stated, the design is worked on abasis such that the thrust of the swash plate on the plunger, and the lateral frictional drag which it exerts on the plunger, produce at mid-stroke a thrust which is practically coincident with the axis of the plunger. Thus the design is affected in some degree by the intended speed of operation and the intended' head pressure, each of which enters as a factor in determining the degree of lateral frictional drag.

The invention can be applied with various disc cams. The particular types of discharge valve and ball thrust head, though preferred, are subject to variation. The same applies to details of the bearings and similar components.

The illustrated embodiment above described inv detail is therefore to be taken as merely one possible embodiment of the general inventive principle.

What is claimed is:

1. The combination of a rotary shaft; a disc cam turning therewith; means forming a plurality of cylinders arranged in a circular series around said shaft, the axes of the cylinders being tangent to similar quick pitch helices surrounding said shaft; plungers in said cylinders; and means urging said plungers toward said cam, the pitch of said helices being such that the plungers are approximately normal to the surface of the cam at mid length of their displacing strokes.

2. The combination of a rotary shaft; a swash plate turning therewith; means forming a plurality of cylinders arranged in a. circular series around said shaft, the axes of the cylinders'being asentar Y A 1 A 3'.

aroimdsaid shaft, the axes of the cylinders being tangent to similar quick pitch helices surrounding said shaft; plunger-s in said cylinders: a iioat ing thrust plate interposed between the ends o! said plungers and said swash plate; and means urging said plungers toward the swash plate, the

tangent to similar quick pitch helices surround ing said shaft; piungers in said cylinders; and

means urging said plungers toward said cam, the pitch of said helices being such that the `combined effectr ofthrust and frictional drag on the plunger heads produces resultant forces approximately aligned with the axes of the plungers through the mid-ranges ofl their displacing it strokes.

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