HYDRAULIC DRIVE

Abstract

In a hydraulic drive of a tool piston in a cylinder first and second flat contact areas each are contiguous, when moving into and in the open position of the valve member between the detent element and the valve member, wherein a pressure-limiting valve that can be loaded with the pressure in the cylinder from a closed position to an open position and a detent element loaded by a spring in the locking direction to positively hold a neck of a valve member of the pressure-limiting valve are arranged in the open position, wherein the detent element at least via the tool piston at its return to a released position can be moved and, when moving the valve member to the open position of the pressure-limiting valve, non-positively acts on the valve member.

Claims

1. A hydraulic drive of a tool piston in a cylinder that can be loaded against a return spring by a pump, in particular of a pressing tool, wherein there are provided a pressure-limiting valve, wherein the pressure-limiting valve can be loaded with the pressure in the cylinder from a closed position to an open position against spring force, and a detent element, wherein the detent element is loaded by a spring to a locked position, to hold a valve member of the pressure-limiting valve lifted from a seat in the open position, and wherein the detent element that is arranged transversely to the valve member can be moved from the locked position to a released position at least via the tool piston at its return stroke, in the locked position does support the valve member positive and non-positive, and when moving the valve member to the open position of the pressure-limiting valve does non-positively act on the valve member laterally, wherein at least when moving the valve member into and in its open position first and second flat contact areas of the detent element and of the valve member each are contiguous.

2. The hydraulic drive according to claim 1, wherein the second contact areas being contiguous in the open position of the pressure-limiting valve and in the locked position of the detent element on the valve member and the detent element are even and in parallel to each other, preferably each approximately circular.

3. The hydraulic drive according to claim 1, wherein the first contact areas being contiguous, when moving the valve member to the open position of the pressure-limiting valve, on the valve member and the detent element are partially cylindrical.

4. The hydraulic drive according to claim 1, wherein axes of a pump port, a housing hole of the detent element and a hole for the valve member intersect at right angles in one point, wherein the housing hole and the hole are preferably arranged in a valve insert having the seat.

5. The hydraulic drive according to claim 1, wherein the detent element is a longitudinally drilled cylindrical detent sleeve that is penetrated by the valve member in a transverse passage and the through-hole of which forms a part of a pressure line and a part of a return line.

6. The hydraulic drive according to claim 4, wherein the valve insert is built into a hydraulic drive block containing the pump port and being connectable preferably to the cylinder via a single hydraulic interface, and that a bypass of the valve insert extends from the pump port to the through-hole.

7. The hydraulic drive according to claim 5, wherein the valve member has a guided neck of small diameter, a shank carrying a sealing surface and therebetween a collar having a diameter that is at least larger than that of the neck and having a cylindrical outer circumference, and can be displaced with the collar in the transverse passage of the detent sleeve.

8. The hydraulic drive according to claim 5, wherein in the detent sleeve the even second contact area is restricted by the transverse passage, the bottom of an even flattening in the cylinder jacket of the detent sleeve and a recess in the flattening.

9. The hydraulic drive according to claim 7, wherein the transverse passage is a cross hole of a diameter that corresponds at least to the outer diameter of the collar, that the arc curvature of a cross hole side having the wall thickness of the detent sleeve corresponds to the cylinder curvature of the outer circumference of the collar and forms the first flat contact area of the detent sleeve.

10. The hydraulic drive according to claim 5, wherein axes of a pump port, a housing hole of the detent sleeve and a hole for the valve member intersect at right angles in one point, wherein the housing hole and the hole are preferably arranged in a valve insert having the seat.

11. The hydraulic drive according to claim 10, wherein the detent sleeve is guided without a seal with a slide fitting in the housing hole.

12. The hydraulic drive according to claim 4, wherein the detent element is a longitudinally drilled cylindrical detent sleeve that is penetrated by the valve member in a transverse passage and the through-hole of which forms a part of a pressure line and a part of a return line, and the valve member has a guided neck of small diameter, a shank carrying a sealing surface and therebetween a collar having a diameter that is at least larger than that of the neck and having a cylindrical outer circumference, and can be displaced with the collar in the transverse passage of the detent sleeve.

13. The hydraulic drive according to claim 12, wherein in the valve insert between the shank of the valve member having a sealing surface and the hole for the valve member a space forms a further part of the return port up to the seat.

14. The hydraulic drive according to claim 12, wherein the diameter of the seat in the valve insert is larger than the diameter of the neck of the valve member guided in the hole.

15. The hydraulic drive according to claim 6, wherein the spring loading the detent element is assigned to the end of the detent element that protrudes into the cylinder or the other end facing away from the cylinder and is preferably supported in the block.

16. The hydraulic drive according to claim 5, wherein the detent sleeve has inlets to the through-hole that are distributed in the circumferential direction and offset to each other toward the axis of the detent sleeve.

17. The hydraulic drive according to claim 1, wherein the height of the hydraulic drive seen in the longitudinal direction of the cylinder is smaller than the diameter of the tool piston.

18. A hydraulic drive of a tool piston in a cylinder that can be loaded against a return spring by a pump, the hydraulic drive comprising: a pressure-limiting valve that can be loaded with pressure in the cylinder from a closed position to an open position against spring force; and a detent element that is loadable by a spring to a locked position, to hold a valve member of the pressure-limiting valve lifted from a seat in the open position, wherein the detent element is arranged transversely to the valve member and can be moved from the locked position to a released position at least via the tool piston at its return stroke, wherein, in the locked position, the detent element is configured to support the valve member positively and non-positively, and when moving the valve member to the open position of the pressure-limiting valve, the detent element is configured to non-positively act on the valve member laterally, wherein when moving the valve member into its open position, and when the valve member is in its open position, first and second flat contact areas of the detent element and of the valve member each are contiguous.

Description

DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows a part of a pressing tool equipped with a hydraulic drive in section and in an operating phase before reaching a required pressing power;

[0024] FIG. 2 shows a sectional view turned by 90 over FIG. 1 in the operating phase of FIG. 1;

[0025] FIG. 3 shows a sectional view corresponding to FIG. 2, but in an operating phase after the pressing power has been reached;

[0026] FIG. 4 shows a valve member of a pressure-limiting valve and a detent sleeve of the hydraulic drive; and

[0027] FIG. 5 shows a perspective plane view of the detent sleeve shown in FIG. 4.

DETAILED DESCRIPTION

[0028] FIGS. 1 to 5 illustrate a hydraulic drive H of a pressing tool W as well as components of the hydraulic drive H. Such pressing tools W are used to press cable lugs, fittings, clamps and the like, for example, are usually portable, and are hydraulically driven. In order to generate sufficient pressing forces pressures up to 700 bar are used that are applied by a pump that is electrically driven (from a net or a power pack), for example. As soon as in a press cycle the required pressing power has been reached that is generated by a tool piston 2 that is slidable against a return spring 3 in a cylinder 1, the pressing tool W switches off independently and the tool piston 2 returns under the force of the return spring 3. Then, the pressing tool W is ready for a new press cycle. Here, the important thing is i.e.,, that the set pressing power is precisely achieved over many press cycles, the tool piston 2 return with a set return velocity, and in a new press cycle the pressing power is reached again as soon as possible.

[0029] On the pressing tool W on the cylinder 1 at a single hydraulic interface 4 there is mounted the hydraulic drive H the components of which are accommodated in a block 5 that is surrounded by a reservoir (not shown) for a hydraulic fluid, for example made of an elastic material, and carries or contains the pump (not shown) with its drive motor.

[0030] In block 5 a pump port 6 is laterally drilled into which the pump P feeds hydraulic fluid for a press cycle (arrows in FIG. 1). Pump P sucks in from the reservoir via a not shown suction valve and presses the hydraulic fluid via a not shown pressure valve into the pump port 6. In a housing hole 7 in block 5 a detent element R, here a longitudinally drilled detent sleeve 11, is slidably guided (e.g., slide fitting without a seal) that penetrates a valve insert 16 mounted in a hole 24a. In the valve insert 16 holes 24, 25 with a seat 18 for a valve member 15 of a pressure-limiting valve D are provided. The valve member 15 is loaded by a spring 21 in the direction of the arrow in FIG. 2.

[0031] Axes 8, 9, 10 of the pump port 6, the housing hole 7, and the hole 24a, 24, 25 for example are at right angles to one another and intersect in one point, for example. Block 5, which in FIG. 2 has a rounded circumference in the sectional plane, for example in the direction of the cylinder has a height that may be smaller than the diameter of the tool piston 2, for example.

[0032] In the hydraulic drive H a through-hole 12 of the detent sleeve 11 simultaneously serves as pressure line and return line into and out of the cylinder 1. The through-hole 12 via inlets 13 and a bypass 17 of the valve insert 16 communicates with the pump port 6. Further, the return port extends from the through-hole 12 via the seat 18 of the pressure-limiting valve D in FIG. 2 upwards into the not shown reservoir. The detent sleeve 11 is loaded by a spring 14 toward the valve member 15. In the embodiment shown, the spring 14 is assigned to the end of the detent sleeve 11 facing the tool piston 2. Alternatively (not shown), the spring 14 could also be assigned to the opposite end of the detent sleeve 11. The spring 14 supports itself on or in block 5.

[0033] The valve member 15 of the pressure-limiting valve D has a neck 23 of a small diameter that is guided in the hole 24 in the valve insert 16, for example with a slide fitting; a cylindrical collar 22 having a larger diameter than the neck 23, as well as a shank 19 having a larger diameter than the neck 23. A conical sealing surface 20 is arranged on the shank 19 that cooperates with seat 18 at the upper end of the hole 25 in the valve insert 16. The valve member 15 is pressed by the spring 21 in the direction of the arrow into the closed position of the pressure-limiting valve shown in FIG. 2 onto the seat 18, namely against the pressure prevailing in the cylinder 1 that acts onto an annulus surface, resulting from the diameter of the seat 18 minus the diameter of the neck 10, via the through-hole 12 of the detent sleeve 11, a transverse passage 27 of the detent sleeve 11 and a clearance 26 between the shank 19 and the wall of the hole 25.

[0034] The valve member 15 penetrates the passage 27 of the detent sleeve 11. The purpose of the detent sleeve 11 is to lock the valve member 15 in the open position of the pressure-limiting valve D against the force of the spring 21 so that the hydraulic fluid at the return stroke of the tool piston 2 can unrestrained flow from the valve member 15 through the seat 18 rapidly into the reservoir.

[0035] FIGS. 1 and 2 show the pressure-limiting valve D in the closed position and the detent sleeve 11 in a released position in which the left end of the detent sleeve 11 penetrates the cylinder 1 less than in the open position of the pressure-limiting valve D and the locked position of the detent sleeve 11. In the open position shown in FIG. 3 the detent sleeve 11 protrudes into the cylinder 1 to such an extent that the tool piston 2 at its return stroke pushes out hydraulic fluid under the action of the return spring 3, but towards the end contacts the detent sleeve 11 in order to push it back into the released position shown in FIGS. 1 and 2 against the force of the spring 14 from the locked position shown in FIG. 3.

[0036] The passage 27 of the detent sleeve 11 for example is in the form of a keyhole and is explained in detail with reference to FIGS. 4 and 5. In the jacket of the detent sleeve 11 that faces the collar 22 of the valve member 15 there is formed a flattening 29 the even bottom of which includes the passage 27 and that is in parallel to the even bottom side of the collar 22. The passage 27 (FIGS. 4 and 5) in the embodiment shown is a transverse hole having at least the outer diameter of the cylindrical collar 22 of the valve member, wherein on a side of the cross hole in the flattening 29 an approximately semicircular recess 28 having the wall thickness of the detent sleeve 11 leads to the through-hole 12 and interrupts the transverse hole wall.

[0037] In FIGS. 1 and 2 a press cycle is initiated (hydraulic fluid flows according to the arrows in FIG. 1 in the cylinder 1), wherein the pressure-limiting valve D is in the closed position, the tool piston 2 moves to the left, and the detent sleeve 11 by the spring 14 with the transverse hole wall in the passage 27 is pressed to the cylindrical outer circumference of the collar 22.

[0038] On the other hand, in FIG. 3 the press operation is completed and the set pressing power has been achieved, wherein the pressure-limiting valve D went into the shown open position in which the sealing surface 20 was lifted from the seat 18 by a given opening stroke, and thereby the detent sleeve 11 slid into the locked position shown in FIG. 3 by the action of the spring 14 in which the bottom of the flattening 28 from two sides reaches under the parallel bottom side of the collar 22 and then, when the pressure in the cylinder 1 decreases, absorbs the force of the spring 21. Under the force of the return spring 3 the tool piston 2 with the pump being switched-off now performs its return stroke, thereby pushing hydraulic fluid out through the open pressure-limiting valve D into the reservoir. As soon as the tool piston 2 at the return stroke contacts the detent sleeve 11 this is pushed to the right with the bottom of the flattening 28 against the force of the spring 14 until the cross hole of the passage 27 aligns with the collar 22 and the valve member 15 is pressed by the spring 21 into the closed position according to FIG. 2 onto the seat 18. Thus, the tool piston 2 has completed its return stroke and is ready for a new press cycle.

[0039] The cylindrical outer circumference of the collar 22 on the valve member 15 as well as the even bottom side of the collar 22 form first and second flat contact areas A1, A2 of the valve member 15. The bottom of the flattening 28 and the wall of the cross hole of the passage 27 form first and second flat contact areas B1, B2 of the detent sleeve 11. The first contact area A1 of the valve member 15 approximately corresponds to half of the circumference of the collar 22 over its height and is a cylinder sub-surface. The first contact area B1 of the detent sleeve 11 in its curvature corresponds to the curvature of the outer circumference of the collar 22, so that in the released position of the detent sleeve 11 two cylinder sub-surfaces adapted to each other are contiguous under the force of the spring 14 (FIG. 1). The second flat contact area A2 of the valve member 15 is defined by the even bottom side of the collar 22 and corresponds to about half of an annulus. On the other hand, the second flat contact area B2 of the detent sleeve 11 is defined by the even bottom of the flattening 28 and the recess 29, and is in parallel to the bottom side of the collar 22, so that in the open position of the pressure-limiting valve D (FIG. 3) and the locked position of the detent sleeve in FIG. 3 on both sides of the valve member 15 there is symmetrical flat contact.

[0040] In FIGS. 4 and 5 the first and second flat contact areas A1, A2 and B1, B2 of the valve member 15 and the detent sleeve 11 are partially brought out by hatchings. FIG. 5 in the perspective view shows the relative assignment of the first and second flat contact areas B1, B2 of the detent sleeve 11. Among the inlets 13 one is indicated in FIG. 5. Suitably, several inlets 13 are distributed in the circumferential direction of the detent sleeve 11 that may optionally also be offset to each other toward the axis of the detent sleeve 11.

[0041] The concept of the three axes 8, 9, 10 intersecting in one point at right angles reduces the size of the hydraulic drive H and offers advantages in production. The spring 21 of the pressure-limiting valve that is accessible on the block 5 (FIG. 2) allows the pressure-limiting valve, if necessary, to be moved manually to the closed position, provided that the detent sleeve 11 is in the position of FIG. 1.

[0042] The hysteresis of the pressure-limiting valve D is optimally low. The compact design of the hydraulic drive saves weight and above all length on the pressing tool W. Further, the chosen concept results in the single hydraulic interface 4 to the cylinder 1. The detent sleeve 11 fulfills a multiple function, because it functions both as pressure line and return line. The valve insert 15 is an easy-to-manufacture member and guides, centers and secures the valve member 15 and the detent sleeve 11. The positive locking of the valve member 15 in the open position of the pressure-limiting valve D is based on a surface contact. Also, when moving the valve member 15 from the closed position shown in FIG. 2 into the open position shown in FIG. 3 there is a surface contact, i.e., the detent sleeve 11 fitting under the force of the spring 14 ensures a constant friction on the valve member 15 over many press cycles, so that the pressure-limiting valve D always exactly opens at the set pressing power.

[0043] The valve member 15 has an optimally small diameter and acts with a relatively small annulus surface, while the detent sleeve 11 of a large diameter for the purpose of the large cross section of the passage receives the valve member 15 and makes the mentioned flat contacts. Also, when the second flat contact area B2 slips off the second flat contact area A2 over the edge of the collar 22 there is not generated a wear-promoting point contact, but a long line contact. The symmetric locking effect of the detent sleeve 11 at the valve member 15 like its transfer to the released position is always ensured. This increases the operational reliability of the hydraulic drive H.

[0044] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms according to the disclosure. In that regard, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Additionally, the features of various implementing embodiments may be combined to form further embodiments according to the disclosure.