US2853022A - Control means for positive displacement rotary pumps and hydraulic motors - Google Patents

Description

p 23, 1953 E. E. WAGNER 2,853,0221.

' CONTROL MEANS FOR POSITIVE DISPLACEMENT ROTARY PUMPS AND HYDRAULIC MOTORS Filed June 17, 1955 2 Sheets-Sheet 2:

IN VEN TOR.

United States Patent() CONTROL MEANS FOR POSITIVE DISPLACEMENT ROTARY PUMPS AND HYDRAULIC MOTORS Ernest E. Wagner, Santa Ana, Calif.

Application June 17, 1955, Serial No. 516,167

8 Claims. (Cl. 103-120) This invention relates to a control means for positive displacement rotary pumps and hydraulic motors of the variable volume type.

In pumps and hydraulic motors of the type referred to, all looseness, deflection and sponginess, collectively designated as backlash, interferes with the smooth and efficient operation and hence is detrimental to the pumps and hydraulic motors and to their performance; and therefore an essential object of the invention is to provide a means by which backlash is eliminated for the life of the unit.

In conventional units of this type the resistance to movement of the stroke adjusting means is objectionable and therefore, an additional object of this invention is to provide a stroke adjusting mechanism in which resistance to movement under load is reduced to a minimum.

A further object of the invention is to provide a device of the character referred to, which is of great simplicity, ease of manufacture and assembly.

Since the traverse of the inlet-outlet passageways from the intake side to the outlet side of a unit of the character referred to results in an imbalance of the control means along the line of its movement, it is a further and important object of the invention to provide means for eliminating the effects of this imbalance, or so reduce them as to be negligible and more closely offset than is possible with conventional means.

It is a further object of this invention to provide control means wherein surfaces which must slide are not subjected to loads due to the operating pressure when moving, and wherein surfaces which are necessarily subjected to loads due to the operating pressure when moving, do not slide, but roll.

Other objects and advantages will become apparent from the following description in connection with the accompanying drawings, in which,

Fig. 1 is an enlarged transverse sectional view taken on line 1-1 of Fig. 5.

Fig. 2 is a view of a unit looking at the inlet-outlet end.

Fig. 3 is an enlarged fragmentary sectional view through a set of rack and gear teeth. t

Fig. 4 is an enlarged longitudinal vertical section through a unit on line 4-4 of Fig. 2.

Fig. 5 is a view of the left side, facing the shaft end.

In rotary pumps and hydraulic motors which displace fluid by radial action, due to excentricity between rotor and housing, there are alternating forces of considerable magnitude along the line F-F of Fig. 1, which line must pass through the center of rotation B of the rotor and the center A of the ring 13. The distance A-B or AL-B is variable, equal to the pump excentricity and proportional to the stroke of the control means, which is a stroke adjustor as hereinafter pointed out. The pump excentricity is responsible for the pumping action.

The load on the unit, caused by the operating pressure, oscillates as the pumpingchambers are alternately loaded and unloaded upon entering and leaving the pressure 2,853,022 Patented Sept. 23, 1958 ice side of a pump or hydraulic motor of the radial displacement type. One component of the load, by far the greatest proportion, is transferred to the pump housing through a stroke adjustor and the other component is transferred at right angles along the line F-F to a stroke actuating mechanism presently referred to. This latter component represents the alternating force or forces responsible for the imbalance.

The forces are large, diametrically opposed and therefore capable of setting up a violent, disturbing and destructive pounding action. To prevent this, no looseness can be tolerated and all parts of the stroke adjusting mechanism should be preloaded at all times, the preload to exceed the magnitude of the reciprocating forces.

Referring more particularly to the drawings, my invention comprises a circular, rollable stroke adjustor 10 with antifriction elements 11 and 12 supporting the ring 13 of a cartridge type pump or hydraulic motor, the rotor assembly 14 of which is carried in antif'riction bearings 15-16 in a suitable housing 17.

For such other adjuncts as may be employed to form the composite unit shown in Fig. 4, but which form no part of the present disclosure, reference is made to my co-pending applications Ser. No. 468,815, filed November 15, 1954 covering Rotary Device and Ser. No. 490,605 filed February 25, 1955 covering Plate Valve for Rotary Units.

Therollable stroke adjustor 10 has an exterior cylindrical surface 23, which surface coincides with the pitch line of a gear with standard involute teeth, said teeth having been modified by decapitating their tops 24 at the pitch line to form a partial gear composed of not less than two of said modified teeth, diametrically opposed. Racks 26-27 have teeth 30-31 which have been correspondingly modified by leaving the normal profile 25 solid below their pitch lines 28-29 in order to form surfaces 38-39 upon which the decapitated teeth may truly roll, so that the center of the stroke adjustor 10, upon rolling, will generate a straight line that is common to both the center of the rotor and said center of the stroke adjustor, for which reason the pitch lines 28-29 of the racks 26-27 must be parallel to said straight line.

The rack teeth 30-31, Fig. 3, adjacent to the stroke adjustor tooth 34 engage the gear tooth spaces 32-33 in such a manner that the points of contact 36-37 between the mating tooth fianks touch first, before the load causes the tooth 34 to contact its mating surface at the point 38.

A preload is thereby established between the rack and the gear teeth which effectively eliminates all lateral play by means of the load imposed on the stroke adjustor by the fluid pressure of the pump, without impairing the freedom of the stroke adjustor to roll and thereby vary the distance between the center of the rotor and the center of the stroke adjustor for the purpose of varying the displacement of the pumping cartridge.

A further and important function of the preload is to reduce minute lateral movements due to elastic deformations under load changes.

For conditions of clockwise rotation, per arrow, the unit operating as a pump with the stroke adjustor so positioned that the center of excentricity A is to the right of B, the vane pockets 22, see Fig. 1, below the line F-F, are decreasing in size and therefore generating pressure, the result of which is principally a downward pressure on the stroke adjustor 10 and its tooth 34. The load on the tooth is transferred to the rack and through it to the stationary cover plate 93 and the housing 17. Friction between rack and cover plate, due to the load, effectively locks the two against movement when' such movement is not a normal operating function.

Upon moving the stroke adjustor to the left, Fig. 1, the center, point A, passes through B to the position AL, to the left of B, which, as has been shown in the references mentioned results in a flow reversal when operating as a pump, or a reversal in the direction of rotation when assembled for operation as a hydraulic motor.

To simplify matters the description following pertains to a unit functioning as a pump. It is obvious, that the principle underlying the operation as a pump applies equally to a unit operating as a hydraulic motor, except for certain self-evident differences.

'I have shown that when the stroke adjustor center A is positioned to the right of B there results a downward pressure on the stroke adjustor for clockwise rotation.

With the stroke adjustor center A positioned to the left of B the pockets 40, above the line FF, are decreasing in size and are therefore generating pressure, the result of which is principally an upward pressure on the stroke adjustor 10, its tooth 35, the rack 27 and the cover plate 88, therefore movement of the rack is effectively prevented by friction with the cover plate in a like manner to that for the downward load.

This alternately loads rack 26 for discharge from pockets 22 and rack 27 for discharge from ockets The design is therefore arranged to index rack 26 against stop 41, where it remains when under load, while the rack 27, guided by the rack teeth and the surface 90 on the cover 88, but under no direct load from the downward pumping pressure, regulates the stroke from B to A. The design is likewise arranged for rack 27 to index against stop 42, where it remains when under load, while the rack 26, guided by the rack teeth and surface 89 on the cover 93, but under no direct load from the upward pumping pressure, regulates the setting of the stroke adjustor for all positions between points B and AL. It must be understood that whenever the stroke adjustor moves from a position concentric to the rotor center B, even if only .001", one or the other of the racks is always under load and, that, whichever rack is so loaded, that rack is also effectively held against movement by friction with its coverplate. The stroke adjustor 10 is held in alignment axially by the housing surfaces 91-92, Fig. 4. With the foregoing requirements and actions in mind, the stroke actuating means functions as follows:

Light springs 43-44 bearing against plates 4546 on the racks 2627 keep them in contact with the stops 41-42 whenever the plungers 47-48, within the cylinders 83-84, which are bolted to the housing 17, Fig. 2, are de-energized, that is, whenever the inlet-outlet connections 49-50 to the plunger-s are connected to the atmosphere.

Two types of stroke adjusting means are shown in Fig. 1.

v The first type is shown in the upper right hand corner wherein the cover plate 51 contains a screw 52, axially adjustable in the threaded portion 55 of the cover plate 51. An internal spline 53 in the screw 52 is slidably engaged by a mating spline on the end of the stroke adjusting shaft 54 which is journaled in bearing 56. O-ring 57 in an enlarged portion of the shaft prevents oil from escaping. The outer end of the stroke adjusting shaft 54 is arranged to receive a gear 58, as shown, but other actuating means better suited to the conditions encountered may be substituted. The bearing 56 prevents shaft 54 from moving axially. Actuating the gear 58 causes the screw 52 to move in or out as the mating splines 53 slide axially thereby adjusting the position of the stop surface 59 with respect to the neutral position, in which position the rack 27 is against stop 42. The distance the rack is free to move between the stop surfaces 42 and 59 is therefore a measure of the setting of the stroke adjustor center A, which setting is proportional to the rate of discharge of the pump.

The second type is shown in the lower left hand corner wherein the cover plate 60 blanks off a stroke adjusting means functioning as follows: The screw 61 operates in a manner identical to that of the screw 52. The stop surface 62 is positioned by the stroke adjusting shaft 63, which has an O ring 66, and is journaled in bearing 64 in the cover plate 65. It is provided with a splined inner end 82 and is made identical to the stroke adjusting shaft 54, except for its extension 85 through a hole 64a in the rack 26 in order to bring both stroke controls to the same side of the unit. Screw 61 is carried in mating threads in a differential piston 67 which is provided with an 0 ring 68 on its large diameter. The annular space 69 has an inlet-outlet connection at 70. O ring 71 is a static seal and O ring 72 a seal between the flanged cover 73 and the movable differential piston 67. A stop ring 74 accurately locates the position of the differential piston axially, when fluid pressure is applied to the. annular space 69, therefore, actuating shaft 63 positions screw 61 and its stop surface 62 to the position giving the desired discharge rate. For any position of the stop surface 62, corresponding to a position of the stroke adjustor 10 short of the maximum stroke, and assuming plunger 47 to be energized, then, release of fluid pressure from the annular space 69 lets the differential piston 67 move back, carrying the screw and the stop surface 62 with it, which action frees the stroke adjustor 10 to move to its maximum position against stop 81, corresponding to a maximum rate of flow, without in any way disturbing the setting for the lower rate. Upon re-establishing fluid pressure on the differential piston 67 the pump again operates at the lower originally selected rate.

For machine tool applications this arrangement results in a selective feed rate over a wide range, coupled with a constant speed rapid transverse by means of an on-off control.

The four bores 7576-7778 are identical in diameter and permit assembly or reassembly, for right or left hand rotation, using the same parts. Cover plate 65 with shaft 63 can be substituted for cover plate 79, so that rack 27 is adjustable from either side. Likewise, cover plate 60 may be removed and another one, including a stroke adjusting shaft 54, substituted.

The plungers 47-48 are so proportioned that, in combination with the hydraulic pressure behind them, they exert a force against the stroke adjustor 10 which is always greater than the alternating force against it.

With plunger 47 de-energized and plunger 48 energized by a suitable supply of hydraulic pressure fluid, the center A of the stroke adjustor 10 will move from the neutral position to the right and the stroke adjustor itself will roll with a clockwise motion because rack 26, under the action of spring 44, is against the stop 41, while rack 27 is free to move away from its stop 42, being held there only lightly by the spring 43. Movement of the stroke adjustor will continue until movement of the rack is arrested by the stop surface 59 on the end of screw 52.

Fig. 1 shows the screw set for maximum stroke. Should a screw setting exceed the maximum permissible, the stroke adjustor is then arrested in its movement by a safety stop, either or 81, as the case demands.

Upon de-energizing plunger 48 the stroke adjustor returns to the neutral position under the action of spring 43 or returns at an accelerated rate if plunger 47 is energized. In so doing the stroke adjustor rolls with an anti-clockwise movement on rack 26 until the rack 27 is arrested in its neutral position by stop 42. Rack 26 is prevented from moving by reason of the friction between it and its cover plate, due to the pressure generated by the hydraulic fluid, whenever and as long as the stroke adjustors position is excentric to the rotor. Plunger 47 continues to move the center of the stroke adjustor, therefore, with rack 27 arrested, rack 26 moves against the light force of spring 44 and causes the stroke adjustor to roll with a clockwise movement on rack 27, transporting its center to the left, until stopped by the surface 62 on the end of the screw 61.

We have already described the action and function of the diflerential piston 67, the proportions of which must be such, that the force it exerts, in conjunction with the hydraulic pressure, is great enough to return it to its initial position as dictated by the stop 74, while overcoming the reciprocating force along the center line heretofore referred to and moving the stroke adjustor against the opposing force of the plunger 47.

Seepage is drained from the unit via pipe connections 86-87 and covers 88 and 93 when bolted in place complete the enclosure of the unit, see Fig. 2.

I claim as my invention:

1. In combination with a rotary unit including a rotor, radial members movably disposed in said rotor and a ring surrounding said members and forming pumping chambers developing a pressure differential, thereby generating a radial force on said ring: a housing having covers, a circular stroke adjustor in said housing and held in axial alinement therein by surfaces in said housing, the exterior surface of said circular stroke adjustor at diametrically opposite points having a gear tooth decapitated at its pitch line, racks disposed within said housing and slidable on said covers, said racks having teeth adapted to mesh with the teeth on said stroke adjustor and providing surfaces between said teeth upon which the tops of said decapitated teeth of said circular stroke adjustor may truly roll, while said radial force holds stationary the companion rack associated with said adjustor, fixed stops in said housing for each of said racks, springs to hold said racks against said stops while one or the other rack is free to move away from its stop and means to roll said member to vary the eccentricity of said rotary unit.

2. Means to control the volume and the direction of fluid flow in a rotary hydraulic unit which includes a rotor, radial members movably disposed in said rotor and a ring surrounding and cooperating with said members to form pumping chambers generating a radial force on said ring: said means comprising a circular stroke adjustor surrounding said ring and having a gear tooth at diametrically opposite sides, a housing, racks slidably disposed within said housing and in mesh with said teeth and movable in opposite directions, means for limiting the movement of said racks and thereby controlling the magnitude of the stroke and the volume of fluid flow, the radial force of said pumping chambers holding one of said racks stationary whereas the other rack is free to move, and means to actuate said stroke adjustor in opposite directions and force said adjustor to roll one way or another, thereby to control the direction of fluid flow.

3. In combination with a rotary unit including a rotor, radial members movably disposed in said rotor and a ring surrounding said members to form pumping chambers: a housing, a stroke adjustor in said housing surrounding said ring, two modified gear teeth upon the circumference of said stroke adjustor and concentric with said ring, racks in said housing on diametrically opposite sides of said stroke adjustor and in engagement with said teeth, said stroke adjustor adapted to roll with one of said teeth upon one of said racks to vary the eccentricity between rotor and stroke adjustor in one direction and to roll with the other of said teeth upon the other of said racks to vary the eccentricity between rotor and stroke adjustor in the opposite direction; said stroke adjustor, when displaced by rolling, being guided by said racks in a straight line, parallel to a line common to the centers of said stroke adjustor and rotor, means to selectively control said eccentricity, and means to roll and automatically clamp said stroke adjustor in the position of eccentricity selected,

4. In combination with a rotary unit including a rotor, radial members movably disposed in said rotor and a ring surrounding said members: a housing, a stroke adjustor surrounding said ring, said stroke adjustor having two teeth, one diametrically opposite the other, two racks within said housing, said stroke adjustor engaging and being rollable upon one or the other of said racks for varying the eccentricity of said ring with respect to said rotor, means engaging said stroke adjustor substantially midway between said teeth for rolling said adjustor one way for varying the flow in one direction, and means diametrically opposite for rolling said adjustor the opposite way for varying the flow in another direction and means adapted to co-operate with said racks to control the eccentricity of said ring.

5. In combination with a rotary unit including a rotor, radial members movably disposed in said rotor and a ring surrounding said members to form pumping chambers developing a pressure differential and thereby gen erating an outwardly directed radial force on said ring; a housing, a stroke adjustor surrounding said ring, said stroke adjustor having a single gear tooth substantially in line with said radial force and a second gear tooth diametrically opposite, a slidable rack meshing with each or said gear teeth for adjusting the stroke, adjustable stops cooperating with said racks, fixed neutral stops, springs indexing said racks against said fixed stops, said radial force holding stationary the rack co-acting with said force whereas the opposite rack remains free to move, means for moving said stroke adjustor thereby to roll it on said rack held stationary and slide said free rack until arrested by one of said adjustable stops, said means also clamping said stroke adjustor to said housing.

6. In combination with a rotary unit including a rotor, radial members movably disposed in said rotor, a ring surrounding said members and forming pumping chambers: a housing, a circular stroke adjustor having two decapitated gear teeth, one diametrically opposite the other on the circumference thereof, racks in said housing, anti-friction means between said ring and said stroke adjustor, said gear teeth meshing, free of backlash, with said racks, the tops of said teeth adapted to roll on the bottom of the spaces between the teeth of said racks, means for rolling said stroke adjustor, and means in said housing co-operating with said racks, selectively limiting the travel of said stroke adjustor.

7. A rotary unit including a housing having safety stops, a rotor therein having radial vanes and a ring surrounding said vanes and displaceable to vary the displacement of said rotor, a cylindrical stroke adjustor surrounding said ring and having two gear teeth, one diametrically opposite the other, racks meshing with the teeth on said stroke adjustor to make it roll, diametrically opposed plungers of equal area in said housing bearing against said stroke adjustor midway between the pitch lines of said teeth, said plungers adapted to be actuated alternately, one rolling said stroke adjustor in one direction, first on one rack and as zero stroke is passed, on the other rack, the other of said plungers rolling said stroke adjustor in the opposite direction, first on one rack and upon passing zero stroke, upon the other rack, adjustable stops for limiting the travel of said racks, shafts for operating said stops, a piston carrying one of said stops, said piston being adapted to be held extended and to move back with said stop when fluid pressure is released, thereby permitting said stroke adjustor to move to its maximum position against one of said safety stops under the force of one of said plungers.

8. Means to control the volume and direction of fluid flow in a rotary hydraulic unit which includes a rotor, radial members movably disposed in said rotor, and a ring surrounding said members to form. pumping chambers developing a pressure differential and thereby generating a radial force on said ring; a circular stroke adjustor having two teeth, a housing, a pair of racks slidable in said housing and each engaging one of said teeth on diametrically opposite sides of said stroke adjustor, one of said racks being held stationary by the radial force generated by said pumping chambers, the other of said racks remaining free to move and permit the stroke adj'usftoi f0 r611 6'11 said staticnafy rack, and inans to' aict'fiat e sai dtrok ddjustbi in opposite dir'etions to regulate the fiowih one of another dire'ction.

References Cited in the file of this patent 5 UNITED STATES PATENTS I Antonelli -1 Sept. 17, 1929 Rayburn Ian. 16, 1934 Ott Jan. 15, 1935 10 Clark 1 July 18, 1939 Whitmo're Nov. 14, 1944 Dillon Aug. 26, 1947 French June 17, 1952 Erns't Sept. 30, 1952 Garner Oct. 27, 1953 FOREIGN PATENTS Great Britain Aug. 22, 1956 France Jan. 10, 1951

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