EP0450501B1 - Actuator - Google Patents

Abstract

To limit the extension of its displaceable parts, in particular the telescopic tubes (14, 15) and the piston (16), the actuator has conventional stop rings (23, 28) of round spring steel. Intermediate stop rings (35) lying between them in the stop position are provided in order to reduce the radial forces. <IMAGE>

Description

The invention relates to a hydraulic piston-cylinder unit with a plurality of sealed and slidably arranged cylinder elements, such as an outer cylinder tube, telescopic tubes and pistons, which serve as a limit stop in the inner wall 21 of the respective larger part in the region of at least the front end in a part-circular groove have a front outer part stop ring and in the outer wall of the smaller element in the region of the rear end in a part-circular annular groove have a rear inner part stop ring which abut each other when the cylinder elements extend and limit the relative movement between the two parts in the axial direction.

Limit stops with spring washers, which have a circular cross section and are embedded in the cylinder walls, have long been known and are described, for example, in DE-A 3320 464. In many cases, however, they are also held stationary in an annular groove that has the same radius as the profile of the spring ring. Such rings must have a certain diameter to absorb the stop forces so that the groove shoulder can also absorb the forces that occur. It has hitherto been customary to provide the arrangement with such differences in diameter or gap widths that the line of the resulting forces of axial force and radial force extends at an angle of approximately 30 ° to the cylinder axis. A suitable space is left between the two cylinders, which is bridged by guide and sealing rings. A radial force occurs which is approximately 58% of the axial force. This results in considerable radial forces in the area of the stop rings, which are usually provided on both pipe ends, particularly in the case of telescopic cylinders, and these require a corresponding dimensioning of the telescopic cylinder walls. This also results in a corresponding share in the total weight of the piston-cylinder unit. From DE-C-2 649 524 a stop ring arrangement with inclined shoulders is known, which provides trapezoidal stop rings for receiving the forces, which lie loosely in their grooves, the two rings being intended to dampen the impact by elastic deformation. The rings are expensive to manufacture, the sharp-edged grooves lead to notch effects. This requires correspondingly strong cylinder walls.

The invention has for its object to design a piston-cylinder unit, preferably with telescopic cylinders, in such a way that the wall thickness of the cylinder parts can be reduced without impairing the function by suitable design of the stop rings.

According to the invention it is provided that at least one intermediate stop ring, the profile of which has a circular cross-section, is arranged between the stop rings which support one another when the stop is limited, with a diameter which is approximately the difference in radii or the gap width between a smaller and a larger part, possibly plus Depth corresponds to an associated intermediate ring holding groove or an intermediate ring holding and storage groove.

By inserting an intermediate stop ring, the support points of the stop forces to be transmitted are shifted such that the angle between the line of action of the resulting force and the cylinder axis is reduced compared to the angle in known arrangements without such intermediate stop rings. With reasonable and practically feasible dimensioning of the cylinder components, an angle between the axial direction and the resulting direction of force of about 20 ° to 13 ° can be maintained. That corresponds to a radial force of only about 36% to 23% of the axial force, so that about 38% to 60% can be saved compared to the radial force in constructions without an intermediate stop ring. Accordingly, the wall thickness of the cylinder tubes can be reduced considerably, which contributes to great material and weight savings for the entire cylinder and thus for the entire construction in which it is installed. The additional effort for the few, inexpensive to produce round wire rings per unit is insignificant in relation to the material and weight savings. As before, smooth pipes can also be used. As a result, the use of raw materials and processing costs are low.

The intermediate stop rings and stop rings made of round wire according to the invention with the associated part-toroidal ring grooves have the great advantage that they can all be produced inexpensively from round wire and that the grooves do not cause any particular peak effects and that this enables correspondingly small wall thicknesses.

In a further embodiment of the invention it can be provided that the intermediate stop ring lies in an intermediate ring holding groove adjacent to the stop ring groove. This makes it easier to hold the intermediate stop ring in position. Its size can be dimensioned according to needs and the force distribution can also be adapted to the circumstances in a more variable manner.

In order to keep the radial force as low as possible, it is advisable to provide two intermediate stop rings one behind the other. This leads to a particularly pronounced reduction in the radial forces and thus in the wall thicknesses and total weights, particularly in the case of intermediate stop rings located in holding grooves.

Further refinements, features, advantages, details and aspects of the invention also result from the further claims and the following description part dealt with on the basis of the drawings.

Embodiments of the invention are explained below with reference to the drawings.

Show it:

Fig. 1

A view with a half longitudinal section of a piston-cylinder unit in telescopic design;

Fig. 2

half a cross section along the line 2-2 in Fig. 1;

Fig. 3

an enlarged partial longitudinal section through the areas in which the stop rings on one side are in the inserted stop position.

Fig. 4

a representation corresponding to Figure 3 of an embodiment according to the prior art.

Fig. 5

a representation corresponding to Figure 3 of a further embodiment of the invention.

Fig. 6

a representation corresponding to Figure 5 of a further embodiment of the invention.

Fig. 7

a representation corresponding to FIG. 5 of a further embodiment of the invention.

The piston-cylinder unit 10 has an outer cylinder tube 11 with a screwed-on end and connecting base 12 of a conventional type. There, the line 13 is provided for the hydraulic connection. Telescopic tubes 14 and 15 and a piston 16 can be slid into each other with smaller diameters. The piston 16 has a connecting ball 17. The axis is designated 18. The displaceable components are guided and sealed into one another in the usual way with the aid of guide rings 19 and seals 20. A stop ring arrangement 25V or 25H is provided in the area of each end of each tube or the piston.

In the area of the front end V of each tube, an annular groove 22 is provided in the inner wall 21 - lying within the seals. This has a semicircular cross section and thus forms a partial torus. In it is a front outer part stop ring 23, which consists of a round spring steel wire and has a separation gap 24 (Fig. 2). In the outer wall 26 of the smaller part in each case there is a pair of annular grooves 27.1 and 27.2 spaced apart from one another in the region of the rear end H. These also have a semicircular cross section. Inside are the rear inner part stop rings 28.1 and 28.2. These also have a circular cross section and each have a separation gap. They are also made of round steel spring wire. Between them sits on the outer wall of the smaller part between the two walls 21 and 26 matching guide ring 19, for example made of bronze. The radius difference 29 between the outer radius 31 of the smaller part and the inner radius 32 of the larger part forms a free space or gap. As can be seen, this is bridged in the usual way with the guide rings 19 and suitably sealed with the seals 20. The radius difference 29, ie the gap width of the gap 33, is as large as the radius of the cross section of the stop rings 23 or 28, since the ring grooves 22 or 27 are usually designed as semicircular grooves.

In the area of the rear end H of each telescopic tube 14 or 15, an annular groove 22 of semi-circular cross-section is also formed for the inner stop in the respective inner wall 21, in which a stop ring 23H, which is also circular in cross section and made of spring steel, is inserted - as is the case with it 1 and 3 show.

In the first embodiment (FIGS. 1 and 3), there is an intermediate stop ring 35 in the gap 33, namely between the two stop rings 23V and 28.1, which are supported on each other in the respective stop position, on the one hand, and 23H and 28.2, on the other hand, that is to say in the telescopic tubes 14 and 15 both in the area of the front end V and in the area of the rear end H - as can be clearly seen from FIG. 3. The intermediate stop rings 35 are each assigned to the stop ring of the larger part and can be expediently installed with a preload to the outside. Their reference numerals are supplemented with the additional letters 'V' and 'H' to indicate their assignment, where it makes sense in the text.

1 and 3 are drawn with respect to the telescopic tubes 14 and 15 and the piston 16 in the retracted, rear stop position. The entire package of telescopic tubes and pistons is drawn slightly extended in relation to the outer cylinder tube 11 and its connecting base 12 in FIG. 1. It can hit the ground and support itself. Therefore, the ring 28H in the rear end H of the outer cylinder tube 11 does not require an outer part stop ring and essentially serves to hold and guide the adjacent guide ring 19, while the adjacent inner part stop ring 28.1 serves to limit the extension of the largest telescopic tube 14, as it is in connection was explained with the other pull-out parts.

3 shows in more detail how the stop ring 28.2 assigned to the smaller sliding part is supported on the rear intermediate stop ring 35H at the support point 39. The intermediate stop ring 35H is in turn supported on the support point 41 on the outer rear stop ring 23H assigned to the larger part. The diameters are chosen so that the center points 45.1 and 45.2 of the two stop rings 28H and 23H lie on a straight line with the support points 39 and 41. This takes an angle 49 to the axis 18. The axial force 51 and the radial force 52 together form the resulting force 50.

They are connected by the angle 49. This results from the dimensions. Here the angle 49 is 20 °, for example. As a result, the length of the section 52 is 36% of the length of the section 51, which are proportional to the magnitudes of the forces occurring.

In the upper part of FIG. 3 it is shown how the stop ring 28.1 assigned to the smaller part - here telescopic tube 14 - in the front extended stop position, in which it is designated 28.12, rests on its upper side at the support point 39.1 on the intermediate stop ring 35V of the front outer part stop ring 23 V is supported accordingly. The relationships in terms of angles and forces are the same as at the rear.

4 shows how the center of the stop rings and the only support point lie in relation to each other in the previously customary solution without an intermediate stop ring 35 and how the angle 49.1 between the resulting force 50.1 and the axis 18 is thereby much larger than in the new invention according to the invention 1 to 3 - with otherwise the same dimensions. For example, it is approximately 30 °, which means that the radial force is approximately 58% of the axial force. Thus, in the solution according to the invention according to FIGS. 1 to 3, the radial force is reduced by 37%. Accordingly, the wall thickness of the tubes 11, 14 and 15 of the new piston-cylinder unit 10 can be chosen to be thinner. This reduces the otherwise the same Performance of the piston-cylinder unit the total weight considerably, which has correspondingly favorable consequences for the entire construction in which the piston-cylinder unit is used.

The embodiment of FIG. 5 shows a variant in which the intermediate stop rings 35H and 35V are each located in an intermediate ring holding groove 55. These each directly adjoin the ring grooves 22 and are designed in such a way that the respective intermediate stop ring 35 is securely held on the stop ring 23 to which it is associated even when it is displaced. The intermediate ring holding grooves 55 are only a few mm deep into the inner wall 21 of the larger part. As a result, each intermediate stop ring 35 is somewhat larger in cross section and the centers of the three adjoining rings are no longer on a straight line, but on a line which is slightly bent in the center of the cross section of the intermediate stop ring 35. The angle 49.2 between the resultant 50 of the forces passing through the support point 39 and the axis 18 is significantly further reduced and is approximately 13 ° with practically feasible dimensions. The radial force 52 is then only 23% of the axial force 51. This leads to a reduction of the radial force compared to the previously known solution shown in FIG. 4 of 60%. In addition, the intermediate stop ring does not need to be installed with a correspondingly large tension and is included Security kept in place. Since the associated shoulder of the annular groove 22 is not loaded, a corresponding recess can be worked in right next to it. This advantageous solution seems particularly practical.

6 shows a further, particularly advantageous variant of the invention. A further intermediate stop ring is provided in a corresponding intermediate ring holding groove for each stop. Namely, a further intermediate stop ring 35H2 is now also provided in the smaller part 15 between the rear stop ring 28.2 and the rear intermediate stop ring 35H. This lies in a further intermediate ring holding groove 55.2, which adjoins the annular groove of the stop ring 28.2 in the outer wall 26 of the rear end H of the smaller part 15. Similarly, a further intermediate stop ring 35H3 is assigned to the rear stop ring 28.1 for striking the intermediate stop ring 35V of the front stop ring 23V. This lies in a further intermediate ring retaining groove 55.1, which adjoins the annular groove of the stop ring 28.1 in the outer wall 26 of the rear end H of the smaller part 15 to the front. The front stop position is indicated by dash-dotted lines only with the corresponding position of the additional intermediate stop ring 35H3 with the identification 35H3.2. As can be seen from Fig. 6 below - are the addition of the other Intermediate stop ring the center of all four rings in the stop position again on a straight line. This now takes the smallest possible angle 49.3 to the axis 18. With practically feasible dimensions, as in the embodiment of FIG. 5, this is again only about 13 °. In addition, radial forces are exerted on the intermediate stop ring. The radial force here is only 23% of the axial force. This solution can be provided in particular on the ends of thin tubes that are subject to high loads. As can be seen, it is designed as a double design, so that a rear guide ring 19.1 is also provided between the two stop rings of the smaller part. It is rectangular and rounded at the edges. It can consist of bronze and has the strength of the radius difference 29 of the gap 33.

The embodiment of FIG. 7 shows a further advantageous embodiment of the invention. The design is similar to that in FIGS. 5 and 6 with two rear stop rings 28.1 and 28.2 on the smaller part 15 and an intermediate guide ring 19.1 of the thickness of the gap 33. Here, the intermediate stop ring is no longer designed with approximately the thickness 29 of the gap 33 as in the first exemplary embodiment, but with the same thickness as the stop rings 23H and 23V or 28.1 and 28.2. The groove recess is correspondingly larger and it lies in its own part-circular intermediate ring retaining groove 55.3, which has the function of a storage groove because of the expansion and circumferential reduction of the intermediate stop ring. The intermediate stop ring 35.5 is biased outwards in the direction of the larger part 14 so that it detaches from the intermediate ring holding groove 55.3 for striking and rests against the support surface 57 of the inner wall of the larger part and arrives in the position suitable for supporting the stop forces . In order to make this possible, the support surface 57 is offset to the outside against the inner wall 21 of the larger part 14 by such an amount that the center point of the cross section of the intermediate stop ring 35.4 in the stop position shown in FIG. 7 again on a straight line through the centers of the two abutting support rings 23 and 28, on which the support points 39 and 41 are located.

In order to push the intermediate stop ring 35.5 back from the stop position into the intermediate ring holding groove 55.3 against its spring force and to enable the telescopic tubes 14, 15 or the piston 16 to be displaced, a run-up bevel 58 is provided which smoothly adjusts the diameter difference between the inner wall 21 and the supporting surface 57 compensates and by means of which the intermediate stop ring 35.5 between its rest position and the stop position is shifted radially and thereby stretched or reduced. Since the stop rings are only loaded on the shoulder facing away from the support point 41, corresponding grooves can be provided, as in the exemplary embodiments in FIGS. 5, 6 and 7. In this embodiment too, the cost of additional rings and incorporation of appropriately designed grooves is so low that it is worthwhile in any case for the considerable savings in material, wall thickness and weight of the overall arrangement in which the piston-cylinder unit is used.

In summary, the invention can also be described as follows:
The piston-cylinder unit has the usual stop rings (23, 28) made of round spring steel to limit its sliding parts, in particular the telescopic tubes (14, 15) and the piston (16). In order to reduce the radial forces, intermediate stop rings (35) are provided between them in the stop position.

Claims (7)

1. Hydraulic piston-cylinder unit (10), comprising a plurality of cylinder elements mounted displaceably one inside another in a sealed manner, such as an outer cylindrical tube (11), a telescopic tube (14, 15) and a piston (16), which have as a limit stop a front outer-part stop ring (23) in a part-circular groove (22) in the inner wall (21) of the respectively larger part near at least the front end (V), and a rear inner-part stop ring (28) in a part-circular annular groove (27) in the outer wall (26) of the respectively smaller element near the rear end (H), which stop rings come into contact with one another when the cylinder elements are extended and limit the relative motion between the two parts in the axial direction, characterised in that, between the stop rings (23, 28) that bear against one another when performing their limiting function, there is at least one respective intermediate stop ring (35) whose profile has a circular cross-section and whose diameter corresponds approximately to the difference in radius or the gap width (29) between the smaller and larger parts, plus if appropriate the depth of an associated intermediate ring holding groove (55) or an intermediate ring holding and storing groove (55.3).
2. Piston-cylinder unit according to claim 1, characterised in that the intermediate stop ring (35) lies in an intermediate ring holding groove (55) adjacent to the stop ring groove (22, 27).
3. Piston-cylinder unit according to at least one of the preceding claims, characterised in that two intermediate stop rings (35, 35.2, 35.3) lying one behind another are provided.
4. Piston-cylinder unit according to at least one of the preceding claims, characterised in that near the rear end (H) of the smaller part, two stop rings (28.1; 28.2) are provided in the outer wall (26), between which is a guide ring (19.1) and an intermediate stop ring (35V, 35H) is allocated to each stop ring.
5. Piston-cylinder unit according to at least one of the preceding claims, characterised in that the cross-section of the intermediate stop ring (35) has a diameter which is equal to the difference in radius (29) between the outer radius (31) of the smaller part and the inner radius (32) of the larger part.
6. Piston-cylinder unit according to at least one of the preceding claims, characterised in that the cross-section of the intermediate stop ring (35) has a diameter which is larger than the difference in radius (29) between the outer radius (31) of the smaller part and the inner radius (32) of the larger part.
7. Piston-cylinder unit according to at least one of the preceding claims, characterised in that the cross-section of the intermediate stop ring (35.5) has a diameter which is equal to the diameter of the cross-section of the stop rings (23, 28), and a support face (57) is provided, which is connected via a stop slope (58) to the inner wall (21) of the larger part, and the intermediate stop ring (35.5) has an outward bias, and the dimensions are such that, in the stop position, the centre points of the two stop rings (23, 28) bearing on one another via the intermediate stop ring (35.5) and of the associated intermediate stop ring (35.5) lie on a straight line (50) which is only slightly inclined relative to the axis (18) of the piston cylinder unit (10).

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