US3074345A - Hydraulic pump - Google Patents

Description

Jan. 22, 1963 o. w. scHEFLow 3,074,345

HYDRAULIC PUMP t. a a L INVENTOR. oLlvER' w. scHEFL-ow BY M ATTORNEY Jan. 22, 1963 o. w. scHr-:FLOW

HYDRAULIC PUMP 3 Sheets-Sheet 2 Filed July 27, 1959 INVENTOR. OLIVER SCHEFLOW A Tram/E( Jan. 22, 1963 o. w. SCHL-:FLOW 3,074,345

HYDRAULIC PUMP Filed July 27, 1959 3 Sheets-Sheet 3 INVENTOR. OLIVER W. SCHEFLOW wmf ATTORNEY United States @arent @ffice lfatenteel Jan, 22, lg3d 3,074,345 HYDRAULIC PUB/m @liver Waller Seheflow, Kalamazoo, Mich., assigner, by mesne assignments, to Pneumolynamics Corporation, Cleveland, Ghia, a corporation of Delaware Filed July 27, 1959, Ser. No. 829,864 7 Claims. (Si. 103-37) This invention relates generally to hydraulic pumps and more particularly to a new and improved hydraulic pump incorporating a valve mechanism which operates to change the effective displacement.

It is an important object of this invention to provide a new and improved valving mechanism for a wobble plate type pump.

It is another object of this invention to provide a valving mechanism for wobble plate type pumps which can be adjusted or operated to change the effect of displacement of the mechanism.

lt is another object of this invention to provide a wobble plate pump with a new and improved valve structure which can be operated to change the effective displacement of the pump in response to predetermined operating conditions.

It is still another object of this invention to provide a wobble plate pump in combination with a new and improved valve device which operates to maintain a predetermined maximum output pressure in the pump.

It is still another object of this invention to provide a wobble plate pump in combination with a vali/ing device which is operable while the pump is functioning to change the effective displacement of the pump from zero to the maximum pump displacement.

Further obg'ects and advantages will appear from the following description and drawings, wherein:

FIGURE l is a longitudinal section of a preferred wobble plate pump incorporating this invention;

FIGURE 2 is an exploded perspective view of the valve control structure;

FGURE 3 is a cross section taken along 3 3 of FIG- URE l illustrating `the valving operation in a full ilow position;

FIGURES 4A through 4J are schematic illustrations of the progressive valving operation under a full ow condition;

FIGURE 5 is a View similar to FIGURE 3 showing the valving structure operated to a position wherein the effective displacement of the pump is zero; and

FIGURES 6A through 6I are schematic illustrations of the progressive valving operation under a zero ilow condition when the etfective displacement of the pump is zero.

In the past, variable displacement wobble plate type pumps have normally achieved their variable displacement function by changing the angle of the wobble plate. However, the mechanisms for changing the angular position of the wobble plate to change the displacement of the pump produces structural mounting and adjustment problems. In a wobble plate pump incorporating this invention, the wobble plate is maintained in a fixed angle regardless of the required displacement of the overall devices so that the wobble plate can be securely and rigidly mounted.

The pump includes a housing or body lul) formed with an axially extending bore ill in which the pump mechanism is positioned. The outer end of the bore ll is closed by an end cap l2 through which a rotatable drive shaft E3 projects. One end of a cylinder block ld is held against a thrust member i6 by a spacer 17. One end of the spacer 17 engages a radial wall 18 on the cylinder` block 14 and the opposite end of the spacer 17 engages the outer race 19 of the ball bearings 2l. The outer race 1Q is in turn held in position by the end cap 12. Connected by a spline 22 to the drive shaft i3 is a rotor shaft 23 to which is keyed a wobble plate 24. The wobble plate 2liis provided with a bearing race 26 along which the ball bearings 2l, move. A forward bearing 4.3 is positioned between the rotor shaft 23 and the cylinder block 14 and co-operates with the `bearings 2l. to support the rotor shaft 23 for rotation about its axis.

A thrust bearing 27 is mounted on the forward face of the wobble plate 2d so that it is inclined relative to the axis of rotation of the wobble plate. An advanced slipper 23 is positioned against the thrust bearing 27 and is formed with a groove 2@ adapted to receive a spherical end 3l on each of a plurality of pistons 32 which move in individual cylinder bores 44- in the cylinder block 14. A return slipper 33 is formed with a bore 3d for each piston 32 and a socket 3o which engages the opposite side of each spherical end and cooperates with the advance slipper 28 to clamp the spherical ends in position. The return slipper 33 is also formed with a central socket 57 which engages a spherical end 33 formed on a spring member 3%. The spring member 3f should be either a wave sprinty or Belleville spring. The spring member 39 is in turn positioned by engagement with the wall of a central bore il formed in the cylinder block ital and the outer race i2 of the forward antifriction bearing 43. The engagement of the spherical end 38 with the central lsocket 37 produces a force to hold the return slipper 33 in tight `engagement with each of the spherical ends 3i on the pistons 32 and in turn maintains them in engagement with the advance slipper 28. This force also operates to maintain the advance slipper 28 in Contact with the thrust bearing Z7.

The cylinder yblock ltdoes not rotate with the rotor shaft 23 so rotation of the rotor shaft, and in turn the wobble plate 242A, produces reciprocating motion of the pistons 32 relative to the cylinder block la. The cylinder bores 2l/l are parallel and symmetrically arranged around the rotor shaft axis 23. The number of pistons 32 is determined by the particular ydesign requirement of the pump. ln the illustrated embodiment, there are eight pistons and cylinder bores, so each of the pistons is displaced 45 in its cycle of operation from the adjacent piston and relatively even llow characteristic is provided. lf a 'smaller number of pistons are used, the cycle spacing between adjacent pistons will be greater.

Each of the cylinder bores la is open at a port or valving face lo formed in the cylinder block ld. A valve ring i7 is positioned between the valving face ad and the thrust member 16 and operates to sequentially provide communication between the cylinderbores and the high and low pressure zones which will be discussed below. The valve ring i7 is iiournalled on the outer cylindrical surface 48 of an eccentric or cam member 49. As best shown in FIGURE 3, the eccentric member i? is formed with an inner cylindrical surface 5l having an axis 52 displaced from the axis 53 of the outer cylindrical face 48. A sleeve bearing S4 is positioned within the inner cylindrical surface 5l and is in turn mounted on the forward end of the rotor shaft 23.

Referring again to FGURE l, the eccentric member 49 and the sleeve bearing 54 are secured in position on the rotor shaft 23 by a nut 56. A pin 57 extends through a rst slot 5S in the rotor shaft 23 and the sleeve bearing 5d into an axial slot 59 in the eccentric member 49. Therefore, the eccentric member 49 rotates with the rotor shaft 23 and causes the valve ring d'7 to move eccentrically around the axis 53 as the rotor shaft 23 rotates. This causes radial movement of the valve ring 47 relative to the cylinder bores 44 and produces the desired valving operation.

Liquid at low pressure is supplied to the pump through an inlet port 6I in the housing 1i) and a radial port 62 in the spacer I7 so that the inner cavity of the pump is lled with liquid at low pressure. The spacer I7 is formed with a rib 63 which engages the housing 10 and in `co-operation therewith, forms a forward or high pressure chamber 64 which is open through its high pressure or outlet port 66. The high pressure chamber communicates through the plurality of inclined ports 68 with an annular cavity 67 ,defined in part by the outer surface of the valve ring 47. Communication with an inner portion of the valving ring 47 and `an inner cavity 69 is provided through a plurality of low pressure passages 7l. The valve ring 47 is formed with an annular groove providing an inner face Til and a plurality of axial ports 72 so that liquid at low pressure is provided on both sides of the valve plate along the inner portion thereof. Supply of low pressure liquid passes through the ports 6l and 62V to the inner cavity 69. From the inner cavity 69, it passes through the low pressure passages 71 to the inner area of the valve ring 47'.

In FIGURE l, both of the cylinder bores 44, which are shown in the plane of the section, are closed by the valve ring 47. However, reference to FIGURES 3 and 4 will illustrate how the valve ring operates. The lowermost piston 32 is in the forward or dead center position as illustrated in FIGURE l and is closed by the valve ring 47.V

Also, the uppermost piston 32 is in the top dead center position yand is also closed by the valve ring 47. However, the three pistons 32 and their cylinder bores 44, which are located to the right of the centerline as viewed in FIGURE 3, are open to the low pressure zone. At the same time, the three cylinder hores 44 to the left of the centerline are open to the high pressure zone in the annular cavity 67. If lthe direction of the rotation of the rotor shaft 23 is conntercloclrwise as viewed in FIGURE 3, liquid is drawn into each of the cylinder bores 44 as the pistons 32 move from the bottom dead center position to the top dead center position. Then, as the pistons in the left side from the centerline move forward pressurizing the liquid -in the cylinder bores, liquid is pumped out of the cylinder bores into the high pressure zone in the cavity 67 around the valve ring 47.

The operation of a piston through one complete cycle is illustrated in FIGURES 4A through 4]. In FIGURE 4A, the piston 32 is in the bottom dead center position and the valve ring 47 closes the cylinder bore 44. As the piston 32 starts to move back toward the top Vdead center position, the valve ring 47 operates to provide communication with the low pressure zone withinthe valve ring so liquid is drawn into the cylinder bore 44 as indicatedv by the arrows. This condition continues through FIG- URES 4B, 4C, and 4D. When the piston 32 reaches the top dead center position, the cylinder is filled with liquid and the valve ring 47 again closes the cylinder bores 44 as shown in FIGURE 4E. On the forward stroke illustrated in FIGURES 4F, 4G, and 4H, the valve ring 47 provides communication between the cylinder bores 44 and the high pressure zone around the valve ring so the liquid in 4the cylinder is pumped into the high pressure zone. Again, when the piston 32 is in the bottom dead center position of FIGURE 4I, the original condition, as shown in FIGURE 4A, is again reached and the valve nng 47 closes the cylinder bores 44.

In order to vary the effective displacement of the pump, la pressure operated mechanism illustrated in FIGURES 1 and 2 is utilized. Located in the outer end of the housing is a piston 73 the right end of which is maintained at a pressure equal to the pressure in the high pressure or forward chamber 64 by a liuid connection through the passages 74 and 76. The piston 73 engages a plunger 77 through which the pin S7 projects. The plunger 77 is positioned within an axial bore 78 in the rotor shaft 23 and is resiliently urged toward the piston 73 by a spring 79 also positioned in the bore 78. The slot 53 formed in the rotor shaft 23 is inclined relative to the rotor shaft as best illustrated in FIGURE 2 so that axial movement of the plunger 77 and pin 57 relative to the rotor shaft 23 causes the plunger 77 and pin 57 to rotate relative to the rotor shaft 23. Normally, the spring 79 maintains the pin 57 in the positions of FIGURES 1 and 3 so that the eccentric member 49 is positioned as shown in FIGURE 3, which is the full dow position. If the high pressure exceeds a predetermined value, the piston 73 operates to overcome the spring 79 and move the plunger 77 inward along the bore 78. This causes the pin 57 to ride along the slot 58 and rotate relative to the rotor shaft 23. Because the slot 59 on the eccentric member 49 extends axially, rotation of the pin S7 relative to the rotor shaft 23 produces relative rotation between the eccentric member 49 and the rotor shaft 23. ThisV changes the orientation of the eccentric axis 53 of the eccentric member 49 relative to the central axis 52 and at a maximum movement of the plunger 77 toward the spring 79, moves the elements to the position shown in FIGURE 5. The sleeve bearing 54 is formed with a slot 55 to permit axial movement of .the plunger 77. At this time, the uppermost piston is in communication with the high pressure zone and the lowermost piston is in communication with the low pressure zone even though the upper and lower pistons are in their dead center positions at this point.

Reference to FIGURES 6A through 6J will illustrate the valving operation when the piston 73 has operated to change the orientation of the eccentric member 49 to the position of FIGURE 5. Here again, the operation of the device is schematically illustrated to show one piston 32 in progressive positions through one complete cycle. In FIGURE 6A, the piston 32 is in the bottom dead center position and the valve ring 47 provides communication between the cylinder bores 44 and the low pressure zone. Therefore, as the piston moves toward its top dead center position as shown in FIGURE 6B, liquid is drawn into the cylinder bores 44 from the low pressure zone. However, when .the piston 32 is in a midposition of its stroke as shown in FIGURE 6C, the valve ring 47 closes the cylinder bores 44. Further movement of the elements causes them to reach the condition of FIGURE 6D at which time the piston 32 is still moving toward the top dead center position. However, the cylinder bore is now open to the high pressure zone so liquid is drawn from the high pressure zone into the cylinder bore rather than from the low pressure zone. Communication is maintained between the cylinder bore 44 and the high pressure zone through, the top dead center position of FIGURE 6E and until the piston 32 returns to a midposition on its inward stroke shown in FIGURE 6G. Since the highl pressure zone is maintained in communication with the cylinder bore 44 from `the positions of FIGURES 6C through 6G, the liquid which is received from the high pressure zone is merely returned to the high pressure zone causing a zero elective displacement relative to the high pressure zone. As lthe piston 32 continues to move toward its bottom dead center position through the positions of FIGURE 6H, communication is again established between the cylinder bore 44 and the low pressure zone. Therefore, the liquid received during the initial inward stroke from the low pressure zone is returned to the low pressure zone. The piston 32 therefore has an effective displacement of zero since the liquid received from the low pressure zone is returned to the low pressure zone and the liquid received from the high pressure zone is returned to the high pressure zone.

Normally, the piston 73 will not move the plunger 77 through a suiicient distance to cause the pump to reach the zero displacement condition. However, it does function to automatically change the eifective displacement of the pump to regulate or maintain a predetermined pressure in the high pressure zone. I This predetermined pressure is determined by thev area of the piston 73 in relationship to the force of the spring 79. Because the J piston 73 operates to rotate the eccentric member 49 gradually from the full ilow condition of FIGURE 3 toward the zero ow condition of FlGURE 5, an infinitely variable effective displacement can be achieved so that the output pressure of the pump can be maintained at the desired level. A pressure sensitive valve may be used in the passage 76 to port pressure to the piston 73 to decrease pressure differential between full flow and zero ow. Also, a ow sensitive valve could be used at this point to maintain constant flow regardless of speed or pressure. ther sensing devices may be used as required to change tlovv.

lt should be understood that the above sequence discussed in connection with one piston 32 is repeated by each of the pistons as the pump functions. VBecause the valve is operated automatically to change the effective displacement of the pump through an infinite number of conditions between the full flow or full displacement condition and the zero displacement condition, complete control is provided even though the wobble plate 24 is xed in its angular position.

Although a preferred embodiment of this invention is illustrated, it will be realized that various modifications of the structural details may be made without departing from the mode of operation and the essence of the invention. Therefore, except insofar as they are claimed in the appended claims, structural details may be varied widely without modifying the mode of operation. Accordingly, the appended claims and not the aforesaid detailed description are determinative of the scope or" the invention.

l claim:

1. A hydraulic mechanism comprising a body, a rotary shaft rotatably mounted in said body, a plurality of cylinders having their longitudinal axes arranged in parallel relation, a piston reciprocable in each cylinder, means mounted on the shaft and engaging the pistons producing reciprocation of said pistons upon rotation of said shaft, a port open to each cylinder symmetrically positioned at equal distance from the axis of said shaft, a member concentrically mounted on said shaft for rotation therewith having a bearing surface eccentric relative to said shaft, an annular valve journalled on said bearing surface and abutting adjacent ends of the cylinders, separate high and low pressure zones leading to said valve with one portion of the valve forming a bounding surface of the high pressure zone and another portion of the valve forming a bounding surface of the low pressure Zone, said valve by virtue of rotation of said member progressively connecting said cylinders to said low and high pressure zones, and means engaging said member and shaft responsive to pressure variations Within said high zone to change the eccentric orientation of said member and valve relative to said shaft.

2. A hydraulic mechanism comprising a body, rotary shaft rotatably mounted in said body, a plurality of cylinders having their longitudinal axes arranged in parallel relation, a piston reciprocable in each cylinder, means mounted on the shaft and engaging the pistons producing reciprocation of said pistons upon rotation of said shaft, a port open to each cylinder symmetrically positioned at equal distance from the axis of said shaft, a circular valve having a central axis and inner and outer faces mounted on said shaft with its central axis eccentric relative to the axis of said shaft and abutting adjacent ends of the cylinders, a high pressure zone cornmunicating with one of said valve faces, a low pressure zone communicating with the other of said valve faces, the eccentric mounting of said valve causing said valve to progressively connect said cylinders to said high and low pressure zones upon rotation of said shaft, and pressure responsive means connected to said high pressure zone and said valve operable to change the eccentric orientation of said valve relative to said shaft at a predetermined pressure in the high pressure zone.

3. A hydraulic mechanism comprising a body, a rotary shaft rotatably mounted in said body, a wobble plate member nonrotatably mounted on the shaft, a stationary cylinder block member disposed in the body and formed with a plurality of parallel cylinders, a piston reciprocable in each cylinder, the wobble plate member engaging the pistons and producing reciprocation of said pistons upon rotation of the wobble plate member, a port open to each cylinder symmetrically positioned at equal distance from the axis of said shaft, a circular valve having a central axis and inner and outer faces mounted with its central axis eccentric relative to the axis of said shaft and abutting adjacent ends of the cylinders, a high pressure zone communicating with the one of said valve faces, a low pressure Zone communicating with the other of said valve faces, the eccentric mounting of said valve causing said valve to progressively connect said cylinders to said high and low pressure zones upon rotation of said shaft, and pressure responsive means connected to the high pressure zone and to said valve operable to change the eccentric orientation of said central axis of said valve relative to the axis of said shaft at a predetermined pressure in the high pressure zone.

4. A hydraulic mechanism comprising a body, a wobble plate rotatably mounted in said body, a plurality of parallel cylinders, a piston reciprocable in each cylinder, the wobble plate engaging the pistons producing reciprocation of said pistons upon rotation of said wobble plate, a port open to each cylinder symmetrically positioned at equal distance from the axis of rotation of said wobble plate, a circular valve having a central axis and inner and outer faces mounted with its central axis eccentric relative to the axis of rotation of said wobble plate and abutting adjacent ends of the cylinders, a high pressure zone communicating with one of said valve faces, a low pressure zone communicating with the other of said valve faces, the eccentric mounting of said valve causing said valve to progressively connect said cylinders to said high and low pressure zones upon rotation of said wobble plate, and pressure responsive means connected to the high pressure zone and to said valve operable to change tne eccentric orientation of said central axis of said valve relative to the axis of rotation of said wobble plate at a predetermined pressure in the high pressure zone.

5. A hydraulic mechanism comprising a body, a shaft rotatably mounted in. said body, a plurality of parallel cylinders, a piston reciprocable in each cylinder, means connecting said shaft and pistons producing reciprocation of the pistons in the cylinders in response to rotation of said shaft, a valve surface, a plurality of ports in said valve surface symmetrically positioned at equal distance from said axis, each of said ports providing communication with one of said cylinders, a member concentrically mounted on said shaft having a bearing surface eccentric relative to said shaft, an annular valve journalled on said bearing surface engaging said valve surface and abutting adjacent ends of the cylinders, separate high and low pressure zones leading to said valve with one portion of the valve forming a bounding surface of the high pressure zone and another portion of the valve forming a bonn g surface of the low pressure zone, a connecting mechanism between said shaft and member including means responsive to pressure variations in said high pressure zone operable to change the rotational orientation of said member relative to said shaft at a predetermined pressure in the high pressure zone.

6. A hydraulic mechanism comprising a body, a shaft rotatably mounted in said body, a plurality of parallel cylinders, a piston reciprocable in each cylinder, means connecting said shaft and pistons producing reciprocation of the pistons in the cylinders in response to rotation of said shaft, a valve surface, a plurality of ports in said valve surface symmetrically positioned at equal distance from said axis, each of said ports providing communication with one of said cylinders, a member concentrically mounted on said shaft having a bearing surface eccentric relative to said shaft, an annular valve journalled on said bearing surface engaging said valve surface and abutting adjacent ends of the cylinders, separate high and.

low pressure zones leading to said valve with one portion of the valve forming a boundingsurface of the high pressure zone and another portion of the valve forming a bounding surface of the low pressure zone, an operator connected to the high pressure zone axially movable rela tive to said shaft at a predetermined pressure in the high pressure zone, and connecting means between said shaft and member connected to the operator and operable to change the rotational orientation of said member relative t0 said shaft in response to axial movement of said.

operator.

7. A hydraulic mechanism comprising a body, a shaft rotatably mounted in said body, arplurality of parallel.

cylinders, a piston reciprocable in each cylinder, means connecting said shaft and pistons producing reciprocation of the pistons in the cylinders in response to rotation of said shaft, a valve surface, a plurality of ports in said valve surface symmetrically positioned at equal distance.

from said axis, each of said ports providing communication with one of said cylinders, a member concentrically mounted on said shaft having a bearing surface eccentric relative to said shaft, an annular valve journalled on said bearing surface engaging said valve surface and abuttingV adjacent ends or" the cylinders, separate high and low pressure zones leading to said valve with one portion of the valve forming a bounding surface of the high pressure zone and another portion of the valve forming a bounding surface of the low pressure zone, said valve by virtue of rotation of said member progressively connecting the cylinders to the low and high pressure zones a bore in said shaft, an inclined groove through the wall of said shaft open to said bore, an axial groove in said mem er, a. plunger axially movable in said bore and connected to the high pressure zone and provided with a projection extending through said inclined groove into said axial `groove connecting said member for rotation with said shaft and the plunger movingvaxially in the bore at a predetermined pressure in the high pressure zone causing the projection to move along the inclined groove in the shaft and compelling the axial groove in the member to follow the projection to provide rotation of the member relative to the shaft.

References Cited in the tile of this patent v- UNITED STATES PATENTS 2,280,875

" (Addition to No. 1,146,899)

Claims (1)

1. A HYDRAULIC MECHANISM COMPRISING A BODY, A ROTARY SHAFT ROTATABLY MOUNTED IN SAID BODY, A PLURALITY OF CYLINDERS HAVING THEIR LONGITUDINAL AXES ARRANGED IN PARALLEL RELATION, A PISTON RECIPROCABLE IN EACH CYLINDER, MEANS MOUNTED ON THE SHAFT AND ENGAGING THE PISTONS PRODUCING RECIPROCATION OF SAID PISTONS UPON ROTATION OF SAID SHAFT, A PORT OPEN TO EACH CYLINDER SYMMETRICALLY POSITIONED AT EQUAL DISTANCE FROM THE AXIS OF SAID SHAFT, A MEMBER CONCENTRICALLY MOUNTED ON SAID SHAFT FOR ROTATION THEREWITH HAVING A BEARING SURFACE ECCENTRIC RELATIVE TO SAID SHAFT, AN ANNULAR VALVE JOURNALLED ON SAID BEARING SURFACE AND ABUTTING ADJACENT ENDS OF THE CYLINDERS, SEPARATE HIGH AND LOW PRESSURE ZONES LEADING TO SAID VALVE WITH ONE PORTION OF THE VALVE FORMING A BOUNDING SURFACE OF THE HIGH PRESSURE ZONE AND ANOTHER PORTION OF THE VALVE FORMING A BOUNDING SURFACE OF THE LOW PRESSURE ZONE, SAID VALVE BY VIRTUE OF ROTATION OF SAID MEMBER PROGRESSIVELY CONNECTING SAID CYLINDERS TO SAID LOW AND HIGH PRESSURE ZONES, AND MEANS ENGAGING SAID MEMBER AND SHAFT RESPONSIVE TO PRESSURE VARIATIONS WITHIN SAID

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