US3495543A

US3495543A - Hydraulic apparatus

Info

Publication number: US3495543A
Application number: US685779A
Authority: US
Inventors: Dennis J Millard
Original assignee: Boulton Paul Aircraft Ltd
Current assignee: Boulton Paul Aircraft Ltd
Priority date: 1966-12-01
Filing date: 1967-11-27
Publication date: 1970-02-17
Anticipated expiration: 1987-02-17
Also published as: GB1201030A

Description

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' v 7 HYDRAULIC' APrARATUS Filed, Nov. 27. 1967 5 Sheets-Sheet 5 Head 43 Dav/w: Mmun ATTORNEY INVENTOR United States Patent US. Cl. 103162 8 Claims ABSTRACT OF THE DISCLOSURE A swash plate pump or motor comprising a rotary cylinder block, a tubular casing within which the block is rotatable, cylinders in the block disposed with their axes parallel to or inclined to the block rotation axis, pistons in the cylinders which extend to engage a swash plate located at a fixed inclination at one end of the block so that rotation of the block will cause reciprocation of the pistons, rotary bearing means such as taper roller bearings locating the block relative to the swash plate and acting at least in part to resist axial and radial movements of the block and a key which engages in a groove in the wall of the tubular casing to retain the swash plate in position and at the same time to exert a pre-load on the bearing means.

CROSS REFERENCES TO RELATED APPLICATIONS This invention may be applied to the pump or motor disclosed in United States application Ser. No. 570,385 I. D. North and D. J. Millard, now Patent No. 3,407,745.

FIELD OF THE INVENTION A swash plate pump or motor having a rotary cylinder block from whose cylinders pistons extend to a swash plate of fixed inclination, rotation of the cylinder block causing the pistons to reciprocate by engagement with the swash plate.

DESCRIPTION OF PRIOR ART It has been proposed in a swash plate pump having a tubular casing to close one end of the casing by means of a cover secured in position by a key. It has also been proposed in a swash plate motor to secure a drive shaft bearing housing into the tubular casing by means of a key. The point of using a key to secure the swash plate in position in the tubular casing is to reduce the overall dimensions of the pump or motor. In the proposal referred to above in which a drive shaft bearing housing is secured in position by a key there is no provision for pre-loading the hearings to ensure most efiicient bearing operation. The present invention proposes the use of a key to retain a swash plate in position in a tubular casing and also to apply a pre-load to the bearings or the rotary cylinder block to provide a more compact and efiicient construction of the swash plate pump or motor.

SUMMARY OF THE INVENTION In accordance with the present invention a hydraulic pump or motor includes a rotary cylinder block, a tubular casing within which the block is rotatable, cylinders in the block disposed with their axes parallel to or inclined to the block rotation axis, pistons in the cylinders, a swash plate disposed at one end of the block to engage the pistons either directly or through slippers or through hearings to cause reciprocation of the pistons during block rotation, rotary being means carried by the swash plate at least in part for locating the block for rotation so as to resist axial thrusts, and a key. engaging against the swash plate 3,495,543 Patented Feb. 17, 1970 ice and into the wall of the casing for retaining the cylinder block, swash plate and pistons within the casing and for exerting an axial pre-load on the said rotary bearing means.

The key may comprise an annulus engaged in a circular slot around the interior of the tubular casing.

The key may be formed in at least three separate parts arranged so that entry of the parts into the slot may be by radial sliding movement.

One of the parts may include parallel end surfaces so that when entered into position in the slot as the last part of the annulus there are substantially no gaps between adjacent parts of the annulus.

A drive shaft either rigidly attached to or integral with the cylinder block may extend through a central hole in the swash plate, rotary bearing means engaging between the drive shaft and the swash plate.

A second swash plate may be disposed at the other end of the block and secured in the casing to engage pistons projecting from cylinders opening into that end of the block either directly or through slippers or a bearing.

The second swash plate may include a bearing support arranged to engage with a second rotary bearing means within a recess in the said other end of the block.

The method of assembly of the pump or motor in accordance with the invention may comprise the steps of securing together the cylinder block, the one swash plate, the pistons and the rotary bearing carried by the swash plate to form a sub-assembly, entering the sub-assembly into the tubular casing, fitting the key into position, meas uring the axial movement of the block permitted by the bearing means, measuring an axial gap produced relatively between the bearing and the swash plate, and fitting a shim to act between the rotary bearing means and the swash plate whose thickness is slightly greater than the measured movement and locking the shim in position to provide a predetermined axial pre-load on the rotary bearing means.

BRIEF DESCRIPTION OF DRAWINGS How the invention can be carried into effect will now be particularly described with reference to the accompanying drawings in which,

FIGURE 1 is a cross-section through an assembled motor in accordance with the invention,

FIGURE 2 is a cross-section through a detail in FIG- URE 1,

FIGURES 3, 4, 5 and 6 are views of the motor of FIG- URES 1 and 2 in various stages of assembly, and

FIGURE 7 is a plan view of the key used in the motor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is made initially to FIGURES 1 and 2 of the' drawings. The motor casing is a tubular member of one piece of metal having at one end an inwardly directed flange 2. Within the tubular casing 1 the two end portions 3 and 4 are cylindrically bored to the same diameter. Within the bore 4 a groove 5 is formed by turning to extend continuously around the bore 4. A swash plate 10 fits in the bore 3 against the flange 2 being secured thereto by bolts 6. The swash plate 10 has a swash surface 7 inclined to the longitudinal axis of the casing 1. Also cen trally positioned in the swash plate is a bearing support member 8 integrally formed with the swash plate.

Within the bore 4 a swash plate 9 is located having a swash surface 11 also inclined to the axis of the tu'bular casing 1. The swash plate 9 is located in its angular position about the axis of a casing 1 by means of a dowel pin 12 and is retained in position in the bore 4 by means of a key 13 located within the slot 5. The key is formed in a number of parts illustrated more par- 3 ticularly in FIGURE 7. The parts of the key are so arranged that there is effectively no gap between them when they are located within the groove 5.

The cylinder block and piston assembly, within the casing 1 is substantially as disclosed in the specification filed in respect of our copending application 570,385. This assembly comprises a rotary cylinder block 14 having a plurality of cylinders 15 equally spaced around the rotation axis and each extending completely through the block in a direction parallel to the rotation axis. In each cylinder 15 a pair of

pistons

16 and 17 are located, being urged away from one another by means of a spring 18 trapped between them within the cylinder. Piston 16 has the slipper .19 secured thereto by a ball inint 21 to engage the swash surface 7. Piston 17 has a slipper 22 secured thereto by a ball joint 23 to engage the swash surface 11.

The support 8 enters a recess 24 centrally disposed within the cylinder block and a taper roller bearing 25 acts between the support 8 and the wall of the recess 24 to locate the block for rotation. A drive shaft 26 extends centrally from the block 14 through a central hole 27 within the swash plate 9, a taper roller bearing 28 acting between the swash plate 9 and the shaft 26 to locate the block and the shaft for rotation. The taper roller bearings are capable of withstanding both radial and axial thrusts and the arrangement illustrated ensures that the cylinder block within the casing is located for rotation without the possibility of either axial or radial movement. Hydraulic liquid passes to and from the cylinder by means of a valve plate 29 carried on the end of support 8 within the recess 24 and engaging a valve surface 31 of the cylinder block 14. The operation of the valve plate 29 is described in more detail in the said specification of our copending application 570,385.

During operation of the motor the slippers 19 and 22 will exert a considerable thrust in opposite directions on the two swash plates and 9 and these forces are transmitted through the casing 1 so as to equally oppose one another. The forces are transmitted from the swash plate 10 to the casing 1 by means of the flange 2. The forces are transmitted from the swash plate 9 to the casing 1 through the key 13 located in the slot 5 to engage against the swash plate 9.

As more particularly shown in FIGURE 7 the key is an annulus 13 comprised by four separate parts of substantially equal length. The end surfaces 65 and 66 of the part 62 are parallel to one another and parallel to a radius to the centre of the length of part 62. Similarly the end surfaces 67 and 68 of the part 64 are parallel to one another. When inserting the key into position in the groove 5 the parts of 61 and 63 are first inserted at opposing positions. The

parts

62 and 64 are then inserted. All parts are inserted by a radial sliding motion and it will be seen that after the last two

parts

62 and 64 have been inserted in position there will be substantially no gap between any adjacent pair of parts. This results from the fact that the end surfaces of the part 62 are parallel to one another and the end surfaces of the part 64 are parallel to one another. Whilst in this particular embodiment the annulus has been made in four separate parts it will be appreciated that the annulus could be made in any number of parts and the minimum number of parts being three. Provided that the last part to be inserted into the groove has a parallel end surface, it can be arranged that when the key is assembled there are substantially no gaps between adjacent pairs of the parts.

In order to maintain the key .13 in position a locking ring 32 is inserted in the bore 4. This locking ring includes a recess 33 formed in its periphery for engagement with the inner edges of the parts of the key 13 to maintain them within the grove 5. The locking ring 32 is secured in position by bolts 34 extending through it into the swash plate 9.

The outer race 35 of the bearing 28 is held within the hole 27 by means of a retaining ring 36 secured to the swash plate 9 by means of 'bolts 37. A sheet metal seal retainer 38 is clamped in between the ring 36 and the swash plate and extends to the shaft 26 to hold a low pressure seal 39 against the shaft 26 to retain low pressure leakage liquid 'within the casing 1. One or more drain holes 41 in the casing drains the liquid from the casing back to a suitable reservoir. The locking ring 36 reacts on the outer race 35 through shims 42 inserted during the assembly to ensure as substantial pre-load on the

roller bearings

28 and 25. Such pre-load will react through the swash plate 9 and key 13 on to the casing 1.

FIGURES 3, 4, 5 and 6 illustrate the method of assembly of the motor illustrated in FIGURES 1 and 2. The first stage in assembly is illustrated in FIGURE 3. The swash plate 9, piston 17, slippers 22 and bearing 28 are assembled on to the block 14 and a cup shaped bearing assembly tool 4 is positioned over the shaft, being secured thereto by a hollow stud 44 which extends from a screw threaded hole 45 in the shaft 26.

The next stage in assembly is shown in FIGURE 4. In this stage a rod 46 is passed centrally through the bore 35, which extends completely through the shaft and the block, and is used to retain the piston assembly tool 47 shown at the right end of FIGURE 4. In addition to the tool 47 a clamp 48 is secured to the right hand end of the cylinder block. The clamp includes a plurality of clips 49 adjustable to retain the individual pistons 16. Each clip 49 is held in place on clamp 48 by a knurl headed screw 50. The assembly tool 47 enables each piston 16 to be inserted against the compression of the enclosed spring 18, the clip 49 then being adjusted for each piston 16 to retain it in position. After all pistons have been retained the slippers 19 are inserted and the piston assembly tool 47 is removed. The swash plate 10 is then secured to the end of the rod '46 as shown in FIGURE 5, the support 8 being provided with a suitable centrally disposed screw-threaded hole for this purpose. The taper roller bearing 25 is fitted to the support 8 before the swash plate is offered to the end of the cylinder block 14 so that the bearing enters the recess 24. The clips 49 are then individually released so that the springs 18 urge the pistons 16 out- Wardly, forcing the slippers 21 to engage the swash plate 10. The clamp 48 is then removed. The whole of the interior parts of the motor are now held as one sub-assembly by means of the rod 46 and the tool 43. This whole sub-assembly can now be entered into the casing 1 and for this purpose the casing 1 is preferably supported with its axis vertical and the flange 2 lowermost so that the sub-assembly can be lowered into the easing "by means of lifting eye attached to the tool 43. The swash plate 10 is then bolted to the flange 2 by the bolts 6 and the key 13 is inserted into the groove 5. The rod 46 is then removed. The nut 52 which retains the hollow stud 44 under tension is then released allowing the swash plate 9 under the action of the springs 18 to move upwardly until the swash plate engages the key 13. At this position the nut 52 is tightened to finger tightness. As shown on the left-hand side of FIGURE 6 the outer race 35 Will now be out of contact with the rollers 28. Lift is now applied to the tool 43 so that the casing 1 is suspended. The lifting force will raise shaft 26 which initially will move slightly relatively to the casing until the rollers 28 engage the race 35. At this position the lifting force will be applied through swash plate 9 to the casing and a gap will be defined between the tool 43 and the swash plate 9. This gap is carefully measured and will represent the end float in the taper roller bearings. A shim 42 is then selected of annular shape to fit over the end surface of the race 35 within the bore 27 and the thickness of the shim is arranged to be slightly greater than the measured clearance. For example extra amount will be 0.003 inch. The unit is then lowered and the tool 43 is removed. The shim 42 is placed in position over the end of race 35 and the tool 43 is then replaced, a final drive tool 58 having been previously placed on the shim. The nut 52 is then tightened so that the final drive tool acting through the shim will push the outer race 35 further into the bore 27. At the stage when the surface of the shim is level with the outer surface of the swash plate 9, the

tools

43 and 58 are removed and the locking ring 36 and seal retainer 38 are clamped onto the swash plate 9 to ensure that the outer surface of the shim remains aligned with the outer surface of the swash plate 9. The taper roller bearings are then pre-loaded for eflicient operation, the pre-loading force reacting through the shim on to the swash plate 9 and from the swash plate 9 through the key 13 to the casing 1. The dowel 12 may now be entered in position to prevent rotation of the swash plate 9. The motor is then ready for operation.

I claim:

1. A hydraulic pump or motor including a rotary cylinder block, a one-piece tubular casing within which the block is rotatable, cylinders in the block, pistons in the cylinders extending from one end of the block, a nonrotatable swash plate disposed at the one end of the block to cooperate with the pistons to cause reciprocation thereof during block rotation, supply and return ports fixed relatively to the casing, a valve member hydraulically urged against the block during rotation thereof to connect the cylinders successively to the supply and return ports, tapered bearing means carried by the swash plate at least in part for locating the block for rotation to resist axial and radial thrusts, pre-loading means mounted on the swash plate to pre-load the said bearing means, and an annular key engaged against the swash plate, and into the wall of the casing, to transmit both piston thrust and pre-loading thrust between the swash plate and the casing.

2. A hydraulic pump or motor as claimed in claim 1, including a second swash plate disposed at the other end of the block, and an inwardly directed flange formed integrally with the casing to locate the second swash plate in position, pistons projecting from cylinders opening into that end of the block for co-operation with the second swash plate, and tapered bearing means engaging between the second swash plate and the other end of the block whereby the pre-loading force applied by the preloading means will act on both bearing means.

3. A hydraulic pump or motor according to claim 1 wherein one end portion of the casing is open-ended, and the swash plate is interposed between the block and the open end of the casing, to close the aforesaid one end portion thereof.

4. A hydraulic pump or motor according to claim 3 wherein the key is interposed between the open end of the casing and the swash plate, and abutted against the adjacent end face of the swash plate.

5. A hydraulic pump or motor as claimed in claim 1 wherein the key is formed in at least three separate parts arranged so that the entry of the parts into the wall of the casing may be by radial sliding movement.

6. A hydraulic pump or motor as claimed in claim 5 wherein one of the parts includes parallel end surfaces so that when entered into position in the wall of the casing as the last part of the key, there are substantially no gaps between adjacent parts.

7. A hydraulic pump or motor as claimed in claim 5 including a locking ring securable to the swash plate to engage the parts of the key to prevent movement thereof out of the wall of the casing.

8. A hydraulic pump 'or motor as claimed in claim 1 in which the tubular casing is of circular section and including a dowel pin engaged in the casing and at the edge of the swash plate to prevent rotation thereof.

References Cited UNITED STATES PATENTS 1,632,495 6/1927 Miller 308-236 X 2,296,620 9/1942 Tinker 292-566 X 2,342,186 2/1944 Fischer 292 256.6 X 3,191,543 6/1965 Harm e161. 10'3 162 3,200,762 8/1965 Thoma 103 162 3,265,008 8/1966 Ward 103-162 3,277,834 10/1966 Eickmann 103-161 3,356,037 12/1967 North 103-162 3,386,389 6/1968 Thoma 103162 3,407,745 10/1968 North 6161. 103 162 FOREIGN PATENTS 552,903 7/1932 Germany. 1,002,872 9/1965 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner IRWIN C. COHEN, Assistant Examiner US. Cl. X.R. 92--57