Piston unit of a working cylinder

Abstract

A piston unit of a working cylinder has first and second coupling partners. The first coupling partner is a piston. The second coupling partner is a piston rod. The piston rod is inserted axially into the piston. Each of the coupling partners has an annular groove, the groove of the piston rod is an external groove, the groove of the piston is an internal groove. The grooves of the coupling partners lie opposite one another. The unit has a spring-loaded coupling ring. The coupling ring, when deformed in a tensioning direction, is fully accommodated by the groove of one coupling partner and which, when deformed in a release direction, engages in the grooves of both coupling partners. The engagement of the coupling ring in the grooves produces a form-locking connection between the partners. The piston rod is oversized in relation to the piston and provides an additional frictional connection.

Claims

1. A piston unit of a working cylinder, comprising: a piston and a piston rod, said piston rod being axially inserted into said piston; said piston and said piston rod each having a respective annular groove formed therein, said annular groove of said piston rod being an external groove and said annular groove of said piston being an internal groove, said annular grooves of said piston and said piston rod being disposed opposite one another; and a coupling ring for being resiliently braced, said coupling ring, when deformed in a bracing direction, being fully received in said annular groove of one of said piston and said piston rod and said coupling ring, when deformed in a relaxation direction, engaging into said annular grooves of said piston and said piston rod in an engagement, the engagement of said coupling ring into said annular grooves of said piston and said piston rod effecting a positively locking connection between said piston and said piston rod; said piston rod having an oversize in relation to an internal diameter of said piston, for providing a non-positively locking connection between said piston and said piston rod, said piston and said piston rod having different moduli of elasticity, a first area of overlap between said engaged coupling ring and a side wall of said annular groove of one of said piston or said piston rod, having the higher modulus of elasticity, being smaller than a second area of overlap between said coupling ring and a side wall of said annular groove of the other of said piston or said piston rod, having a lower modulus of elasticity.

2. The piston unit according to claim 1, wherein said piston rod is hollow, and said coupling ring is fully received by said annular groove of said piston.

3. The piston unit according to claim 1, wherein said coupling ring or one of said piston or said piston rod which does not fully receive said coupling ring has a run-on bevel, said run-on bevel causes said coupling ring to be fully received in said annular groove of a coupling partner which fully receives said coupling ring.

4. The piston unit according to claim 1, wherein said piston and said piston rod has a further, axially offset annular groove for receiving a further, coupling ring.

5. The piston unit according to claim 1, wherein said coupling ring has a circular cross section.

6. The piston unit according to claim 1, wherein said annular groove in said piston or said piston rod, which fully receives said coupling ring is provided with an elastic element which acts radially on the coupling ring.

7. The piston unit according to claim 1, wherein said piston has access openings, said access openings permit manipulation of the coupling ring from an outside thereof.

8. A piston unit of a working cylinder, comprising: a piston and a piston rod, said piston rod being axially inserted into said piston; said piston and said piston rod each having a respective annular groove formed therein, said annular groove of said piston rod being an external groove and said annular groove of said piston being an internal groove, said annular grooves of said piston and said piston rod being disposed opposite one another; and a coupling ring for being resiliently braced, said coupling ring, when deformed in a bracing direction, being fully received in said annular groove of one of said piston and said piston rod and said coupling ring, when deformed in a relaxation direction, engaging into said annular grooves of said piston and said piston rod in an engagement, the engagement of said coupling ring into said annular grooves of said piston and said piston rod effecting a positively locking connection between said piston and said piston rod; said piston rod having an oversize in relation to an internal diameter of said piston, for providing a non-positively locking connection between said piston and said piston rod, said coupling ring being of conical and segmented form.

9. The piston unit according to claim 8, wherein said piston rod is hollow, and said coupling ring is fully received by said annular groove of said piston.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) The invention will be explained in more detail below, on the basis of exemplary embodiments, with reference to:

(2) FIG. 1 which shows a sectional illustration of a piston unit with a coupling ring,

(3) FIG. 2 which shows a half-section of a piston unit with two coupling rings,

(4) FIG. 3 which shows a half-section of a piston unit with circular coupling ring cross section,

(5) FIG. 4 which shows a half-section of a piston unit with a conical coupling ring,

(6) FIG. 5 which shows a half-section of a piston unit with a conical coupling ring and an elastic element,

(7) FIG. 6 which shows a half-section of a piston unit with a coupling ring and an access opening,

(8) FIG. 7 which is a detail illustration of the coupling partners in a clearance end position,

(9) FIG. 8 which shows a cross section of hollow piston rod, and

(10) FIG. 9 which shows a segmented coupling ring.

DESCRIPTION OF THE INVENTION

(11) FIG. 1 shows a piston unit according to the invention of a working cylinder in a full section.

(12) The piston unit is of multi-part form and has a piston 1 and a piston rod 2, wherein the piston rod 2 has been partially inserted into the piston 1.

(13) Below, the piston 1 and the piston rod 2 will also be described collectively as coupling partners.

(14) According to the invention, the piston 1 and piston rod 2 are coupled to one another by means of a positively locking connection.

(15) The positively locking connection is in the present case achieved by virtue of a coupling ring 4.1 being arranged within the piston unit.

(16) In the present case, the coupling ring 4.1 has a rectangular cross section, wherein according to the invention, coupling rings with other forms of cross section may also be used.

(17) To receive the coupling ring 4.1, the piston 1 has a first annular groove 3.1 and the piston rod 2 has a first annular groove 3.3, wherein the first annular groove 3.1 of the piston 1 is in the form of an encircling internal groove and the first annular groove 3.3 of the piston rod 2 is in the form of an encircling external groove.

(18) The first annular groove 3.1 of the piston 1 is, in the present exemplary embodiment, designed such that it can receive the coupling ring 4.1 fully, and in particular to such an extent as to ensure that the piston rod 2 can be inserted into the piston 1 without complications.

(19) As the piston rod 2 is inserted into the piston 1, the coupling ring 4.1 is pushed into the first annular groove 3.1 of the piston 1 and, in the process, is braced in its bracing direction.

(20) When the piston rod 2 reaches its final assembled position in the piston 1, with the annular grooves 3.1 and 3.3 being situated correspondingly opposite one another, it is made possible for the coupling ring 4.1 to relax in its relaxation direction, enabling the coupling ring 4.1 to engage simultaneously into the annular grooves 3.1 and 3.3.

(21) The positive locking of the coupling of the piston 1 and of the piston rod 2 is realized according to the invention in that, in the final position of the piston rod 2 in the piston 1, that surface of the coupling ring 4.1 which faces toward the piston-side end of the piston rod 2 bears against those walls of the annular grooves 3.1 and 3.3 which face toward the coupling ring 4.1.

(22) The piston rod 2 is thus prevented in an effective manner from possibly being pulled out of the piston 1, in particular during use of a working cylinder which has a piston unit according to the invention.

(23) In order that, as the piston rod 2 is inserted into the piston 1, the coupling ring 4.1 is pushed into the annular groove 3.1 of the piston 1, the piston rod 2 additionally has, on the end facing toward the piston 1, a run-on bevel 5 of encircling form.

(24) As a special technological feature, the external diameter of the piston rod 2 has an oversize in relation to the internal diameter of the piston 1. The oversize has the effect that, in the final assembled position of the piston rod 2, an interference fit and thus frictional locking is produced between said piston rod and the piston 1.

(25) Owing to the frictional locking that is provided, the piston rod 2 and the piston 1 are axially fixed in their position relative to one another without a clearance, whereby the piston 1 is prevented in an effective manner from moving axially relative to the piston rod 2. In this way, abrasion grinding phenomena can be prevented.

(26) For illustration, reference is made to FIG. 7, which shows, in a detail view, the piston 1 and the piston rod 2 in their clearance end positions and the coupling ring 4.1 in its final position in the annular grooves 3.1 and 3.3 and an oversizeillustrated on an exaggerated scale for illustrative purposesof the annular grooves 3.1 and 3.3 in relation to the coupling ring 4.1.

(27) FIG. 7 shows the relative position assumed by the piston 1 and piston rod 2 owing to the load in an axial clearance end position.

(28) As a further advantage, the frictional locking that is provided makes it possible for axially acting forces when the working cylinder is subjected to load to be accommodated and for undesired twisting of the piston 1 relative to the piston rod 2 to be prevented.

(29) In particular, owing to the additional accommodation of axial forces by way of the frictional locking, the maximum load and endurance strength of the working cylinder can be optimized.

(30) FIG. 2 shows an exemplary embodiment of a piston unit according to the invention in half-section, wherein, to increase the axial load-bearing capacity, the piston unit has two coupling rings 4.1 and 4.2.

(31) In the present case, the coupling ring 4.1 is arranged in a first annular groove 3.1 of the piston 1 and in a first annular groove 3.3 of the piston rod 2.

(32) By contrast, the coupling ring 4.2 is arranged in a second annular groove 3.2 of the piston 1 and in a second annular groove 3.4 of the piston rod 2.

(33) To ensure complete insertion of the piston rod 2 into the piston 1, an annular groove bevel 7 is provided on the annular groove 3.3 of the piston rod 2.

(34) Said annular groove bevel 7 has the effect, in a particularly advantageous manner, that the second coupling ring 4.2, after it relaxes into the annular groove 3.1, can be pushed back by the annular groove bevel 7 into the annular groove 3.3 of the piston 1 again, and thus the insertion of the piston rod 2 into the piston 1 can be continued.

(35) In a further exemplary embodiment as per FIG. 3, the coupling ring 4.1 has a circular cross section.

(36) Such a circular cross section is, in a particularly advantageous manner, associated with a reduction in production costs for the coupling ring 4.1 and with an optimization of the profile of the internal stresses on the coupling ring 4.1 during the bracing thereof.

(37) To realize as large a region as possible in which there is a positive locking action between the coupling ring 4.1 and the annular groove 3.3 of the piston rod 2, said annular groove is adapted in terms of its contour to the cross-sectional geometry of the coupling ring 4.1.

(38) The adaptation of the annular groove contour to the cross section of the coupling ring 4.1 furthermore has the technological advantage that, owing to the resulting roundings of the annular groove contour, notch effects that arise when the positively locking connection is subjected to load can be substantially eliminated.

(39) Furthermore, the annular groove 3.1 has, in its groove base, a rounded contour for preventing notch effects from occurring.

(40) As a further exemplary embodiment, FIG. 4 shows a piston unit according to the invention with a coupling ring 4.1 which is of conical form and which has multiple segments.

(41) In this case, the annular grooves 3.1 and 3.3 are of a geometrical form such that, when the piston rod 2 reaches the final assembled position in the piston 1, the segments of the coupling ring 4.1 at least partially pivot into the annular groove 3.3 of the piston rod 2.

(42) FIG. 5 shows a refinement of the piston unit as per the exemplary embodiment from FIG. 4.

(43) In this case, a piston unit as per FIG. 5 additionally has an elastic element 6 which, according to the invention, is arranged in the annular groove 3.1 of the piston 1.

(44) According to the invention, the elastic element 6 acts radially on the coupling ring 4.1 and thus assists the relaxation thereof when the piston rod 2 reaches the final position in the piston 1.

(45) Furthermore, the elastic element 6 ensures correct seating of the coupling ring 4.1 in the annular grooves 3.1 and 3.3 even in the event of insufficient relaxation of the coupling ring 4.1.

(46) According to the invention, the elastic element 6 may for example be formed by an elastomer element with circular cross section or by a similarly shaped rubber element.

(47) Furthermore, depending on the application, use may also be made of elastic elements with other cross sections.

(48) FIG. 6 shows a further exemplary embodiment of a piston unit according to the invention.

(49) In this case, the exemplary embodiment as per FIG. 6 provides firstly that the annular groove which fully receives the coupling ring 4.1 is formed by the annular groove 3.3 of the piston rod 2, and that, in the piston 1, access openings 8 are provided which make it possible for the coupling ring 4.1 to be manipulated from the outside for example by means of a suitable tool (not illustrated) or a screw (not illustrated). The access openings are preferably each arranged with a 120-degree offset.

(50) By means of such external manipulation of the coupling ring 4.1, it is possible for said coupling ring to be pushed back into the annular groove 3.3 of the piston rod 2 again, and thus for the engagement of the coupling ring 4.1 into the annular groove of the piston 1 to be eliminated, in a particularly advantageous manner.

(51) Thus, as a special technological advantage, a releasable connection between the piston 1 and the piston rod 2 is provided.

(52) In a particularly advantageous embodiment, the access openings 8 may be provided with a thread into which a screw (not illustrated) can be screwed, which screw in turn causes the coupling ring 4.1 to be pushed back into the annular groove 3.3 of the piston rod 2.

REFERENCE NUMERALS USED

(53) 1 Piston 2 Piston rod 3.1 First annular groove, piston 3.2 Second annular groove, piston 3.3 First annular groove, piston rod 3.4 Second annular groove, piston rod 4.1 First coupling ring 4.2 Second coupling ring 5 Run-on bevel 6 Elastic element 7 Annular groove bevel of the first annular groove, piston rod 8 Access openings