US2345125A - High pressure pump - Google Patents

Description

M. w. HUBER HIGH PRESSURE PUMP Filed oct. 9, 1942 March 28, 1.944.

Patented Mar. 28, 1944 HIGH PRESSURE PUMP Matthew W. Huber, Chicago, Ill., assignor, by mesne assignments, to The New York Air Brake Company, a corporation of New Jersey Application October 9, 1942, Serial No. 461,465

2 Claims.

This invention relates to high pressure, high speed pumps and particularly to the mechanism for actuating the pump plungers.

In hydraulic pumps operating against head pressures of the order of 2000 to 3000 pounds per square inch and at speeds of from 1750 to 3500 R. P. M., the unit pressures in the plunger drive mechanism are high, `and the lateral thrusts on the plungers are apt to be excessive, particularly near the end of the displacement stroke.

The present invention provides a pump in which the unit pressures are not unduly high and in which the use of an oblique plunger thrust face, preferably in conjunction with a cylinder which is offset from a radial line, affords thrusts which are better alined with the cylinder axes throughout the displacement stroke.

The invention produces a pump which is intended to be driven in one direction only, but whichrwill not be damaged by a few backward turns.

In the preferred embodiment, the plungers are of simple cylindrical form having a long guiding contact with the cylinders. Each cylinder is offset a uniform distance from and parallel with a radial line. Each of the plungers carries a head which has an oblique bearing surface contacting the corresponding face of a polygonal prismatic sleeve journaled on the driving eccentric. 'I'he 'offset of the cylinders is opposed to the direction of rotation of the eccentric, and the amount of such offset and the degree of Obliquity of the bearing surface on the thrust head are so chosen, that when Working against the normal pressure head, and with normal friction between the eccentric and the sleeve, and between the sleeve and the thrust head on respective plungers, the resultant displacement thrust on each plunger is nearly in the direction of its axis. The effect is to minimize the side thrust on the plungers.

Another and related eifect is that the tendency of the sleeve to rotate with the eccentric is so resisted that the unit pressure between the sleeve and the thrust head is, at least during the displacement stroke, approximately uniform over the area of engagement.

A successful embodiment of the invention in a multicylinder radial type pump will now be described by reference to the accompanying drawing, in which:

Fig. 1 is a *section of the pump on the plane of 4the plunger axes.

Fig. 2 is a section on the line 2-2 of Fig. l.

Fig. 3 is a perspective view of a plunger thrusthead.

Since the invention resides in the plunger actuating mechanism, a very simple inlet and dise charge arrangement is chosen for illustration This involves side inlet ports in the cylinder buiihings, controlled by the plungers, and spring pressed discharge valves sealing against the end. of the cylinder bushings. This is a known construction and any known valve arrangement can be substituted. Y

The pump body 6 has an inlet connection 1 which leads to the arcuate passages 8, and a discharge connection 9 which leads from the arcuate passages Il. A series of eight cylinder bushings I2 are pressed into approximately radial bores formed in body 6. The arrangement is such that the axis of each cylinder bushing is parallel with but displaced from a true radial line, and the displacement is opposed to the direction of rotation of the drive shaft of the pump, as will be explained in detail. I

Each bushing I2 has side inlet ports I3 in free communication with one of the passages 8, and is exposed at its outer end in one of the passages II. of corresponding bushings I2. They are urged in a seating direction by coil compression springs I5 which react against combined closure and valve guiding plugs I6 screwed into body 6. Each valve is freely guided by the corresponding guide plug. A plain cylindrical plunger I1 works in each bushing. A1; its innermost limit of motion it slightly overtravels the ports I3 and at its outermost limit forces the corresponding valve I4 from its seat.

No novelty is here claimed for this valve arrangement, nor is the invention limited to use with any particular type of valve.

The pump shaft I8 which, a's viewed in Fig. 1, turns counter-clockwise, is mounted in annular ball bearings, the main bearing I9 being mounted in body '5 and the outboard bearing 2I being mounted in the removable cap 22which is accurately centered on body `6 1by a flange 23, and is held in place by studs, as shown.

Between the two bearings, the shaft I8 carries an eccentric 24, and on this eccentric is swiveled an octagonal prismatic thrust block 25. Bearing rollers 2B (sometimes called needles) are interposed between the eccentric and the thrust block.

The thrust block is octagonal simply because the pump has eight cylinders I2 and plungers I1. Within reasonable limits any number of cylinders may be used, and there must be a thrust surface on the block to coact with the thrust head of each plunger I1.

'The plungers I1 and the thrust block 25 are of hardened steel, but each plunger I1 carries at its inner end a thrust head 21, preferably of bronze. The inner end of each plunger I1 makes a press t, and bottoms in a recess bored in the thrust head to receive it. Each block is Ialso pinned to its plunger as indicated at 28. Each head is rectangular in cross section and has a plane thrust face which is not normal to the axis of its plunger I1, but at a slight angle to a Cup-shaped valves I4 seat vagainst the ends.

normal plane. angle is Each thrust head with its plunger I1 is urged inward toward the thrust block by a coil compression spring 29. These springs seat at one en on external shoulder 3l on the bushings I2 an at the other end on the shoulders 32 on the heads 21.` As clearly indicated in the drawing, each spring is spaced from its plunger at all times, and so sustained that it has no tendency to bow laterally.

By a proper choice of dimensions of the thrust block and thrust heads, it is possible to cause the forward and rear edges of each thrust head to over-travel slightly the limits of the coasting surface on the thrust block. Fig. 1 illustrates this effect. This is desirable in the interests of uniform wear.

The important features of the invention are the oblique surfaces on the thrust heads, and the use of this type of thrust head in conjunction with offset cylinders. The Patent Office drawings, nled with the present application, show a pump whose bore and stroke are each 5/16 inch, the oifset being about %i inch and the thrust angle 5". These dimensions are typical but not limiting, for the optimum offset is a function of the friction between the eccentric and the polygonal thrust block, and the optimum thrust In the example illustrated, the

angle is a function of the friction between the4 thrust block and the thrust head. Further these two variables seem to be interrelated in some degree which makes definition of precise values impossible.

However, satisfactory values for these two variables can readily be determined by trial and error rectional.

if due consideration be given to the factors now y about to be outlined.

At high speeds and operating against high head pressures, there is considerable friction between the eccentric 24 and the thrust block 25 so that the thrust block tends to rotate with the eccentric. This tendency is resisted solely by the plunger heads. Irrespective of any Obliquity of 'thrust surfaces, if the plungers are radial to the axis of the shaft, the thrust block will be slightly displaced angularly when the pump runs, and the thrust faces on the thrust heads 21 will wear to a convex form. This results ultimately in high unit pressures because there is then practically only line contact. By offsetting the cylinders and consequently the plungers in the direction opposed to the direction of rotation of the shaft Il, the plungers are caused to develop a turning moment on the thrust block which opposes the rotary tendency. It is practically possible to neutralize the rotary tendency of the thrust block by properly offsetting the cylinders. Thus the amount of offset is primarily a function of the friction between the eccentric and the thrust block 25.

However, there are modifying factors such as the strength of the springs 29, the speed at which the pump is operated, and the head pressure against which the pump delivers. Experience has shown that for a given offset, there is a reasonable operating range as to the factors just mentioned. 'f

The Obliquity of the thrust facey on the thrust head of each plunger is effective to neutralize a condition set up by friction between the thrust block 2l and each thrust head 21. In a radial cation and extent of the side wear show that the wear-producing side thrust occurs in the latter half of the discharge stroke and hence is unidi- This makes it possible to neutralize this side thrust by the adoption of an oblique thrust surface.

Obviously the thrust between the thrust block 25 and the thrust surface on the head 2l is normal to the plane of the contacting surfaces. However, the frictional drag between the block 25 and the head 2l near the end oi Ithe displacement stroke introduces a lateral component. By proper choice of the angle of thrust, the resultant oi the thrust proper and of the frctional drag can be made 'to coincide approximately with the axis of the plunger so that the side Wear is greatly reduced.

The thrust obliquity is useful' even without any offset, but attains :its best effect when coordinated with oiset.

It will require only brief study to determine the fact that the motion of the plungers is harmonic. It is also obvious that the use of a spring retuirned plunger is not essential, the geometry of the movement being such that various other ways of causing the plunger head to follow the thrust surfaces on the thrust block may be used.

Thus while a preferred embodiment of the invention has been described iin great detail, this is intended to be illustrative only, and implies no limitations beyond those expressed in the claims.

I claim:

l. In a pump, the combination of a. rotary shait with eccentric; a block swiveled on the eccentric and having a plane thrust face parallel with the axis of the shaft; a cylinder mounted with its axis approximately radial to said shaft but oilset from a true radial line in a direction opposed to the direction of rotation of the shaft: a plunger working in said cylinder, and having a plane thrust surface on its end in contact with the plane face on the block, the plunger thrust surface being at an angle to a plane normal to the plunger axis; and means for maintaining the plunger and block in coactive relation.

2. A pump having a. rotary shaft: a plurality of cylinders each arranged approximately radially with respect to the shaft but each similarly offset from a true radial line in a direction opposite to the direction of rotation of the shaft; an eccentric turning with said shaft; a pris- `matic block swiveled on said eccentric and having plane sides, one corresponding to each cylinder.'

vsaid block, the cylinder offsetvand the angle of the plunger thrust surfaces being so chosen as to neutralize the lateral thrusts on the plungers otherwise caused by friction between eccentric and block and between the block and plungers.

MATTHEW W. HUBER.

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