WO2006083163A1

WO2006083163A1 - Hydraulic device

Info

Publication number: WO2006083163A1
Application number: PCT/NL2005/050062
Authority: WO
Inventors: Peter Achten
Original assignee: Innas Bv
Priority date: 2004-12-06
Filing date: 2005-12-05
Publication date: 2006-08-10
Also published as: NL1027657C2

Abstract

The invention relates to a hydraulic device, such as a pump or a hydromotor, comprising pistons which can rotate in a first plane, piston sleeves which are arranged around the piston's in a sealing manner and which each form a chamber together with a piston, a drum plate for supporting the piston sleeves, in which the piston sleeves can rotate in a second plane, coupled to the pistons, and in which the first plane is at an angle to the second plane so that the volume of the chamber changes during rotation of the piston, and means for clamping the piston sleeves against the drum plate. According to the invention, each piston sleeve is clamped against the drum plate in a sealing manner by individually acting spring means.

Description

HYDRAULIC DEVICE

The invention relates to a hydraulic device in accordance with the preamble of Claim 1. A device of this type is known, inter alia, from WO 03/058035 by the same applicant. In the known device_/ the piston sleeves 11 are clamped against the drum plate 7 by a sleeve holder 18. Since a common ring is used for clamping all the piston sleeves 11 against the drum plate 1, the ring will only clamp some piston sleeves

11 against the drum plate 7 and there will be some play on the other piston sleeves 11 as a result of dimensional tolerances. As a result of this play, there is a gap between most piston sleeves 11 and the drum plate 7. In order to prevent leaks along this gap, the piston sleeves 11 are pressed against the drum plate 7 through the pressure in the chamber 9 in the existing device . In this case, the pressing force depends on this pressure and thus changes with the rotation of the shaft . When the oil pressure is relatively low, the pressing force is very low and this may lead to a tilting of the piston sleeve 11 as a result of centrifugal forces, enlarging the gap. This will lead to oil leaking from the gaps . At reduced pressure, such as when oil is sucked into the chamber 9, there is no pressing force, which may also lead to tilting and possible leaking of oil between the piston sleeve 11,

12 and the drum plate 7. Any resulting leak lowers the efficiency of the device, which is a drawback.

In order to overcome this drawback, the device is designed in accordance with Claim 1. As a result, each piston sleeve is clamped against the drum plate with more or less the same force, even with a relatively low pressure in the chamber, thus always sealing the latter sufficiently against the drum plate.

According to a refinement, the device is designed in accordance with Claim 2. As the pressure at the position of the sealing ring between the piston sleeve and the drum plate decreases more or less linearly with the diameter from the pressure in the chamber to the pressure outside the chamber, the mean pressure between the drum plate and the piston sleeve across the surface of the sealing ring is approximately half the pressure in the chamber. Making the non-pressurecompensated surface on which the pressure in the chamber presses in the direction of the drum plate about half the size of the surface of the sealing ring results in the force with which the piston sleeve presses on the drum plate being independent of the pressure in the chamber. According to the invention, this force is only dependent on the force exerted by the spring means on the piston sleeve and this ensures less leakage as well as less friction at high pressures.

According to a refinement, the device is designed in accordance with Claim 3. Consequently, the movement between the piston sleeves and the drum plate is more or less limited to the eccentric movement due to the angle between the first surface and the second surface. This movement takes place at a low speed, as a result of which there is hardly any oil leakage between the piston sleeve and the drum plate.

According to a refinement, the device is designed in accordance with Claim 4. Consequently, the exterior of the piston sleeve can be designed to foe cylindrical, so that the piston sleeves can be positioned closer together and/or can be of larger diameter. This makes it possible to produce a smaller device having the same capacity.

According to a refinement, the device is designed in accordance with Claim 5. Consequently, the piston sleeve can rotate below the spring means as a result of which the abrasion between piston and piston sleeve is distributed evenly over the circumference . According to a refinement, the device is designed in accordance with Claim 6. Consequently, tilting of the piston sleeves resulting from an acceleration or deceleration of the rotation of the pistons is prevented, thus in turn preventing leaks between piston sleeve and drum plate in this situation.

According to a refinement, the device is designed in accordance with Claim 7. Consequently, a force is exerted on the piston sleeve which counteracts the tilting moment due to the centrifugal force which may act on the piston sleeve. Leakage between piston sleeve and drum plate is thereby reduced further.

According to a refinement, the device is designed in accordance with Claim 8. Consequently, it is possible to press each of the piston sleeves individually against the drum plate with more or less the same spring force using one single component .

According to a refinement, the device is designed in accordance with Claim 9. Consequently, the spring force can be set at a lower level, as a result of which less friction loss occurs, or higher, as a result of which the rotary speed can be increased without the piston sleeves tilting as a result of the centrifugal forces .

According to a refinement, the device is designed in accordance with Claim 10. The locking means ensure that the piston sleeves cannot tilt due to centrifugal forces and break free from the drum plate in case the pressing force of the spring means is insufficient due to an unexpectedly high circumferential velocity of the pistons .

According to a refinement, the device is designed in accordance with Claim 11. Consequently, the locking means can be realised without the use of additional components.

According to a refinement, the device is designed in accordance with Claim 12. Consequently, a locking action is provided which also prevents the tilting of the piston sleeves as a result of acceleration and deceleration.

According to a refinement, the device is designed in accordance with Claim 13. Consequently, the piston sleeves can be produced in a simple manner as the sleeve jacket can be made from tube material and the sleeve bottom can be made in a simple manner from sheet or strip material .

According to a refinement, the device is designed in accordance with Claim 14. The sleeve bottom can be pressed into the sleeve jacket in this manner without deforming the sleeve jacket, the pressure prevailing in the chamber pressing the thin edge down on the sleeve jacket.

According to a refinement, the device is designed in accordance with Claim 15. This makes it possible to manufacture the sleeve jacket from precision tube.

According to a refinement, the device is designed in accordance with Claim 16. This makes it possible to design the cylindrical jacket to be especially thin and mass equilibrium of the piston sleeve is approached by the supporting ring on both sides of the sealing with the piston and a wider supporting surface for the spring means can be achieved.

According to a refinement, the device is designed in accordance with Claim 17. This prevents pressure from building up in the gap between the sleeve bottom and the sleeve jacket, as a result of which these could be pushed apart . According to a refinement, the device is designed in accordance with Claim 18. Consequently, the drum plate can be made from steel while no additional sliding resistance occurs, thus enabling a cost saving.

According to a refinement, the device is designed in accordance with Claim 19. As a result of the stiffness of the material, the diameter of the sleeve jacket changes as little as possible by the effect of the pressure in the chamber, as a result of which leakage along the piston is prevented.

According to a refinement, the device is designed in accordance with Claim 20. As a result of the relatively thin wall, the weight can be better distributed over the height, the relatively great wall thickness on the side remote from the drum plate adding additional mass which compensates for the additional mass of the bottom and approaches mass equilibrium on both sides of the piston sealing.

The invention will be explained in more detail below with reference to an exemplary embodiment by means of a drawing, in which:

Fig. 1 shows a perspective view of the internal parts of a pump or hydromotor;

Fig. 2 shows a top view of a spring plate as used in the pump or hydromotor of Fig. 1; and

Fig. 3 shows a cross section of a sleeve jacket as used in the pump or hydromotor of Fig. 1.

Fig. 1 shows the internal parts of a hydraulic device, such as a pump or hydromotor, which can be fitted into a casing (not shown) in a known manner . With regard to the method of fitting the internal parts, which will be known to those skilled in the art, reference is here made, for the sake of completeness, to prior publications by the applicant, such as WO 03/058035.

The internal parts are provided with a first face plate 4 and a second face plate 17 which are fitted inside the housing. Bearings 2 are fitted inside the housing on both sides of the housing. The housing is provided on the one side with an opening with a shaft seal in a known manner, as a result of which the end of the shaft 1, which is provided with a toothed shaft end 18, protrudes from the housing. A motor can be coupled to the toothed shaft end 18 if the hydraulic device is a pump, and a driven tool can be coupled thereto if the hydraulic device is a motor.

Approximately in the centre between the bearings 2, the shaft 1 is provided with a flange 14. Pistons 13 are fitted on both sides of the flange 14; in the embodiment shown, twelve pistons 13 on either side. The pistons 13 rotate in a plane of rotation 9 which is at right angles to the shaft 1. A piston sleeve 11, 12 is fitted around each piston, the piston sleeve 11, 12 consists of a sleeve bottom 11 and a sleeve jacket 12. The interior of the piston sleeve 11, 12 forms a chamber 10 together with the piston 13. The piston sleeve 11, 12 is fastened in a sealing manner around a spherical seal 28, which forms part of the piston 13. On the one side of the pump or hydromotor, the sleeve bottom 11 rests against a first drum plate 7 and on the other side of the pump or hydromotor, against a second drum plate 16. The first drum plate 7 and the second drum plate 16 are fitted around the shaft 1 by means of a ball hinge 23 and are coupled to the shaft 1 by means of coupling means, such as a key connection, so that the first drum plate 7 and the second drum plate 16 rotate with the shaft 1.

The first drum plate 7 rests on a supporting surface 5 of the tapering first face plate 4 by the side remote from the piston sleeve 11, 12, so that the first drum plate 7 pivots about the ball hinge 23 during rotation with the shaft 1. A wedge angle α is situated between the plane of rotation 9 and the supporting surface 5, the wedge angle α being approximately 9 degrees .

K spring plate 24 is connected to the first drum plate 7. The drum plate 24 is provided with spring arms 25 having contact surfaces 15 which press against a top edge 33 of the sleeve jacket 12 on two sides and thus press the piston sleeves 11, 12 against the first drum plate 7. In the embodiment shown, the contact surfaces 15 are designed as small pads of material having a low sliding resistance which are connected to the spring arms 25 by riveting. If desired, the contact surfaces 15 can be formed by local deformation of the spring arm 25.

The piston sleeves 11, 12 are also pressed against the pivoting first drum plate 7 during rotation of the shaft 1, so that the volume of the chamber 10 changes . The chamber 10 having a volume which changes during rotation of the shaft 1 is in communication with line connections for the supply and discharge of fluids, such as oil, in a known manner via a drum plate gate 6 and a face plate gate 3.

If the shaft 1 rotates quickly or if the rotational speed of the shaft 1 changes rapidly, the piston sleeve 11, 12 may tilt about the spherical seal 28 by the effect of centrifugal forces or by the effect of acceleration forces and deceleration forces . This is prevented by the fact that the piston sleeve 11, 12 is pressed against the first drum plate 7 by the spring arms 25. However, if the forces become too great, there would still be a risk of tilting. In order to prevent such tilting, which may seriously hamper the operation of the pump or motor, ^■ from happening, a lock is provided, in the embodiment shown, by arranging a positioning sleeve 8 in the first drum plate 7 - An opening in the sleeve bottom 11 fits around the positioning sleeve 8 with play, so that the piston sleeve 11, 12 is able to slide relative to the first drum plate 7 and the piston sleeve 11, 12 can perform the required sliding movements over the first drum plate 7, which result from the wedge angle α and the swivelling of the first drum plate 7 during rotation of the shaft 1.

The piston sleeve 11, 12 seals against the first drum plate 7 having an annular sealing surface 21, which forms part of the side of the sleeve bottom 11 facing the first drum plate 7. In order to further reduce tilting, the outermost circumference of the sleeve bottom 11 forms a supporting surface 22. A relieving groove 20 is provided between the supporting surface 22 and the sealing surface 21 in order to prevent pressure building up between the supporting surface 22 and the drum plate 7 - The dimensions of the sealing surface 21 are chosen such that the resultant of all the forces acting on the piston sleeve 11, 12 and depending on the pressure in the chamber 10 equals zero, so that the piston sleeve 11, 12 is pressed against the first drum plate 7 only by the force exerted by the contact surfaces 15.

It will be clear to those skilled in the art that the details as discussed in connection with the first face plate 4, the first drum plate 7 and the piston sleeves 11, 12 resting on them apply to the second face plate 17 and the second drum plate 16 in a corresponding manner.

Fig. 2 shows a plan view of the spring plate 24. A clamping surface 26 is attached to the first drum plate 7 by means of attachment means to be described below in more detail . In Fig. 2 , a radius Rl denotes the radius of the centre points of the pistons 13. The centre points of the piston sleeves 11, 12 will move in a path which touches these centre points . Each piston sleeve 11, 12 is pressed towards the drum plate 7 by two spring arms 25 having contact surfaces 15. As two spring arms 25 press against the top edge of the sleeve jacket 12, tilting as a result of acceleration and deceleration of the rotation of the shaft 1 is prevented. The contact surfaces 15 press on the sleeve jacket 12 at a radius which, depending on the masses of the sleeve bottom 11 and the sleeve jacket 12, is for example 10-15% larger than the radius Rl of the centre of the pistons . This greatly reduces the risk of the piston sleeve 11, 12 tilting as a result of the centrifugal forces. As the spring arms 25 press against the top edge 33 of the sleeve jacket 12, the piston sleeve 11, 12 is able to rotate about its axis, so that wear resulting from friction between the inside of the sleeve jacket 12 and the spherical seal 28 is distributed evenly over the circumference. Since each piston sleeve 11, 12 is pressed towards the drum plate 7 by designated spring arms 25, the height tolerance of the piston sleeves 11, 12 can be chosen to be higher, since the dimensions of one piston sleeve 11, 12 do not affect the pressing force on another piston sleeve 11, 12.

Fig. 3 shows the piston sleeve 11, 12 and the drum plate 7 in more detail . The sleeve bottom 11 is provided with a thin clamping edge 27 which is clamped in the inner diameter of the sleeve jacket 12. Radial grooves 32 are provided between the sleeve bottom 11 and the sleeve jacket 12 which ensure that no build-up of pressure occurs between the underside of the sleeve jacket 12 and the sleeve bottom 11. The thin clamping edge 27 is deformable and increases its clamping force as the pressure in the chamber 10 increases, so that the clamping action between the sleeve bottom 11 and the sleeve jacket 12 is maintained even as the pressure increases . Since the clamping edge 27 is thin and the sleeve jacket 12 is much thicker, the clamping edge 27 thus follows the increase in diameter of the sleeve jacket 12 by the effect of the pressure .

The dimensions of the clamping edge 27 and the supporting surface 21 are in addition matched to one another such that the surface of the clamping edge 27 , when viewed as a projection on the drum plate 7, is approximately half the size of the surface of the sealing surface 21. Because the pressure between the chamber 10 and the relieving groove 20 decreases more or less linearly along the drum plate 7, the forces directed at the drum plate 7 acting on the clamping edge 27 are approximately equal to the forces directed away from the drum plate acting on the sealing surface 21 and no forces which are dependent on the pressure in the chamber 10 are exerted on the piston sleeve 11, 12.

In the embodiment shown, the piston sleeve 11, 12 is designed in two parts . This has the advantage that both parts can be produced differently and may be made of different materials . The sleeve jacket 12 may be made from tube in a simple manner with an exactly calibrated inner diameter and a height which is ground to size. Preferably, the sleeve jacket 12 is made of material of as high a stiffness as possible, such as steel, so that as little deformation as possible occurs in the chamber 10 by the effect of the pressure. The sleeve bottom 11 may be made of flat material, the clamping edge 27 being formed by pressing. The chosen material may be a type of bronze as this has good sliding properties and can slide over the drum plate 7 with little resistance. The drum plate 7 may in that case be made from steel and the face plate 4 may, in turn, be for example made from bronze. An additional advantage of the use of bronze as material is that the material is less stiff, as a result of which the clamping edge 27 is better able to follow the increase in diameter of the sleeve jacket 12 when the pressure increases and the clamping between the sleeve jacket 12 and the sleeve bottom 11 is tighter.

It will be clear to those skilled in the art that the piston sleeve 11, 12 consisting of two parts can also be used in embodiments in which no spring plate 24 is used, for example as described in document WO 03/058035, or in embodiments in which the spring arms 25 are placed between the sleeve jackets 12 and the contact surfaces press against a protruding edge of the sleeve bottom 11.

The spring plate 24 is attached to the drum plate 7 by means of bolts 31. In this case, washers 30 are arranged between the spring plate 24 and the drum plate

7. By making the washers 30 thicker or thinner, the force used to press the spring arms 25 against the piston sleeve 11, 12 can be adjusted- If the pump or hydraulic device has to be suitable for relatively high rotary speeds, a relatively large pressing force is selected and relatively thin washers 30 are used; if this is not required, a relatively small pressing force is selected, so that less friction occurs between the piston sleeves 11, 12 and the drum plate 7. In this case, relatively thick washers 30 are selected.

Fig. 3 also shows a keyway 29 which is arranged in the drum plate 7 and interacts with a key placed in the shaft 1, and which ensures that the drum plate 7 rotates together with the shaft 1.

In the exemplary embodiments described above, the sleeve jacket 12 has a constant wall thickness. In order to reduce the centrifugal forces which are being exerted on the piston sleeves 11, 12, it has proved to be desirable to reduce the wall thickness of the sleeve jacket 12. As a result, the mass of the sleeve bottom 11 as a proportion of the mass of the piston sleeve 11, 12 would increase and thus the tendency to tilt about the spherical seal 28 by the effect of the centrifugal forces increases . In order to prevent this, the mass of the piston sleeve 11, 12 which, relative to the spherical seal, lies on the side remote from the sleeve bottom 11 of the piston sleeve 11, 12, is increased. This can be achieved by making the wall thickness of the sleeve jacket 12 on the open side of the piston sleeve 11, 12 thicker than on the side of the sleeve bottom 11 and/or by making it thinner near the sleeve bottom 11. When using a sleeve jacket 12 with constant wall thickness, it is also possible to provide a supporting ring {not shown) around or in the sleeve jacket 12 on the open side of the piston sleeve 11, 12. This supporting ring may, if desired, be dimensioned such that this supporting ring forms a top edge 33 which is wider than the wall thickness of the sleeve jacket 12 and which supports the contact surfaces 15 of the spring arms 25 in a stable manner.

Claims

Claims :

1. Hydraulic device comprising pistons (13) which can rotate in a first plane (9) , piston sleeves ( 11, 12) which are arranged around the pistons in a sealing manner and which each form a chamber (10) together with a piston, a drum plate (7, 16) for supporting the piston sleeves, in which the piston sleeves can rotate in a second plane (5) , coupled to the pistons, and in which the first plane is at an angle (α) to the second plane so that the volume of the chamber changes during rotation of the piston and spring means (24 ) for clamping the piston sleeves against the drum plate, characterized in that each piston sleeve (11, 12) is clamped against the drum plate (7, 16) in a sealing manner by individually acting spring means (15, 25) .

2. Hydraulic device according to Claim 1, in which a ring (21) of the piston sleeve (11, 12) sealing against the drum plate (7, 16) has a surface which is approximately twice as large as a projection of the surface of the piston sleeve directed at the drum plate (7, 16) and non-pressure-compensated, viewed at right angles to the drum plate (7 , 16) .

3. Hydraulic device according to Claim 1 or 2, in which the drum plate (7, 16) can rotate parallel to the second surface (5) and the rotation of the drum plate is coupled to the rotation of the pistons (13) .

4. Hydraulic device according to Claim 1, 2 or 3, in which the spring means ( 15, 25) press against a top edge (33) of the piston sleeve (11, 12) .

5. Hydraulic device according to Claim 4, in which the top edge (33) is flat . _f

6. Hydraulic device according to Claim 4 or 5, in which spring means (15, 25) press against two points on the piston sleeve (11, 12) which are more or less on the same radius .

7. Hydraulic device according to Claim 6, in which the radius on which the spring means press against the piston sleeve {11, 12) is larger than the radius (Rl) of the centre of the pistons (13) .

8 - Hydraulic device according to one of the preceding claims, in which the spring means comprise a spring plate {24) which is coupled to the drum plate (7, 16) and which comprises spring arms (25) on the outer circumference which press against the piston sleeves (11, 12) .

9. Hydraulic device according to Claim 8, in which adjusting means (30, 31) are provided for adjusting the spring force with which the spring plate (24 ) presses against the piston sleeves (11, 12) .

10. Hydraulic device according to one of the preceding claims, in which locking means (8) are provided for limiting the outwardly directed movement of the piston sleeves (11, 12) .

11. Hydraulic device according to Claim 10, in which the locking means comprise a supporting edge on the outer circumference of the drum plate (7, 16) and/or on the inside of a housing surrounding the drum plate .

12. Hydraulic device according to Claim 10 or 11, in which the locking means comprise locking pins or locking sleeves (8) fitted in the drum plate (7, 16) , around which the piston sleeves (11, 12) can be placed.

13. Hydraulic device according to one of the preceding claims, in which the piston sleeve (11, 12) is made from a cylindrical sleeve jacket (12) and a sleeve bottom (11) which is fitted in the sleeve jacket in a sealing manner.

14. Hydraulic device according to Claim 13_r in which the sleeve bottom (11) has a thin clamping edge (27 ) which is pressed into the sleeve jacket (10) with a slight press fit .

15. Hydraulic device according to Claim 13 or 14, in which the cylindrical sleeve jacket (12) has a constant wall thickness .

16. Hydraulic device according to Claim 13, 14 or 15, in which a supporting ring is arranged in or around the cylindrical sleeve jacket at the end of the cylindrical sleeve jacket (12) which is remote from the drum plate (7, 16) .

17. Hydraulic device according to one of Claims 13-16, in which radial pressure-relieving grooves (32) are arranged in the sleeve jacket (12) and/or the sleeve bottom (11) in order to prevent a build-up of pressure between the sleeve jacket and the sleeve bottom.

18. Hydraulic device according to one of Claims 13-17 , in which the sleeve bottom (11) is made of bronze or of a material with similar properties .

19. Hydraulic device according to one of Claims 13-18 , in which the sleeve jacket (12) is made of steel or of a material of similar stiffness.

20. Hydraulic device according to one of the preceding claims, in which the wall of the piston sleeve (11, 12) has a relatively small wall thickness near the drurn plate (7, 16) .