Working cylinder, in particular a hydraulic working cylinder

Abstract

The invention relates to a working cylinder, wherein the cylinder, for coupling a closure part to a cylinder tube end portion, has a coupling portion with a coupling ring and a locking body, wherein, on the cylinder tube end portion, the cylinder tube has a circumferential inner annular groove and the closure part is pushed axially into the cylinder tube end portion and has an outer annular groove axially open at one side distally, wherein the inner annular groove and the outer annular groove form an annular groove space in which the coupling ring is arranged and radially enclosed by the inner annular groove, wherein the coupling ring is designed, in a segmented form consisting of a plurality of coupling ring segments, by separating cuts, wherein the coupling ring segments are arranged abutting one another at the separating cuts, and the separating cuts of at least one piston ring segment are designed parallel to one another or opening in a concentric direction, wherein the closure part is form-fittingly secured at one axial end by the coupling ring in a distal direction, wherein the locking body is arranged axially distally on the closure part and has a circumferential ring surface which forms a pressure contact with the coupling ring and form-fittingly secures the coupling ring in the annular groove space, wherein the locking body form-fittingly secures the closure part at one axial end in a proximal direction by means of the pressure contact with the coupling ring.

Description

[0001] Working cylinder

[0002] The invention relates to a working cylinder, in particular a hydraulic working cylinder.

[0003] Working cylinders are known as such from the state of the art. They typically comprise a cylinder barrel and locking components coupled to it.

[0004] According to the state of the art, a detachable coupling of the locking parts to the cylinder tube for the production of such working cylinders is generally achieved by screwing the locking parts to the cylinder tube. These working cylinders are therefore also referred to as screw cylinders in the state of the art.

[0005] For example, it is also known from the prior art to connect the bottom closure part to the cylinder tube by MAG welding and then only to screw the guide closure part.

[0006] Both screw cylinders and cylinders with screw connection of only one locking part and MAG welding of the other locking part are provided in high quality according to the state of the art and have proven themselves to be high-quality and reliable products.

[0007] A disadvantage from a manufacturing perspective is that it is difficult to match the threads of the closure parts and the cylinder tube to each other in such a way that, in the case of a desired special angular position of the closure parts to each other or to the cylinder tube, a suitable tightening torque is applied when screwing.

[0008] A solution that overcomes this problem is known, for example, from EP 2 898 224 B1. It is a hybrid coupling in the interaction of a positive coupling by means of a resilient coupling ring and a

[0009] Confirmation copy of a force-lock coupling using a press fit. This is also a high-quality solution for a detachable and highly resilient coupling, although special fixtures are required for assembly and disassembly.

[0010] It is the object of the invention to provide a working cylinder which is highly reliable, can be manufactured cost-effectively and can be dismantled.

[0011] The problem is solved with respect to the working cylinder by the features listed in patent claim 1. Preferred developments arise from the subclaims.

[0012] According to the invention, the working cylinder comprises a cylinder and a piston unit as basic components. It is characterized in particular by a specially designed coupling section.

[0013] The cylinder of the working cylinder according to the invention has a cylinder tube, a closure part and another closure part.

[0014] As is common with working cylinders, the cylinder tube has two opposing cylinder tube end sections: a cylinder tube end section and a further cylinder tube end section. The closure part is arranged at the cylinder tube end section, and the further closure part is arranged at the further cylinder tube end section. The cylinder tube end section and the further cylinder tube end section are collectively referred to below as the cylinder tube end sections. Accordingly, the closure part and the further closure part are collectively referred to as the closure parts.

[0015] The cylinder tube and the closure parts arranged thereon form a cylinder interior. The piston unit forms at least one working chamber within the cylinder interior. The piston unit is preferably designed as an assembly consisting of a piston and piston rod, with the piston rod sliding through one of the closure parts, which then serves as a guide closure part. However, the piston unit can also be designed, for example, as a plunger piston or as a piston unit of a double-action cylinder.

[0016] Furthermore, the working cylinder according to the invention is characterized by a coupling section designed in a special way.

[0017] The coupling section according to the invention comprises the closure part, the cylinder tube end section, a segmented coupling ring and a locking body.

[0018] The elements of the coupling section and their interaction are described below.

[0019] The closure part is inserted axially into the cylinder tube end section. The closure part has a cylindrical outer surface, also referred to as the closure part outer surface, and the cylinder tube has a cylindrical inner surface, also referred to as the cylinder tube inner surface. The closure part is thus radially enclosed by the inner surface. Both surfaces correspond in diameter, whereby the closure part is fixed in its position relative to the cylinder tube, with the exception of the axial positional relationship, i.e., except for the linear degree of freedom along the cylinder's longitudinal axis. A supporting press fit is also optionally available.

[0020] At the cylinder end section, the cylinder tube has a circumferential inner ring groove on the inner surface. The contour corresponds to the cross-section of the coupling ring and is preferably substantially semicircular in the case of a circular coupling ring cross-section.

[0021] At the same time, the closure part has an outer ring groove on its outer surface that is open axially distally on one side. "Axially distal" is understood to be the direction away from the axial cylinder center. Here, too, the contour corresponds to the cross-section of the coupling ring and, in the case of a circular coupling ring cross-section, is preferably essentially quarter-circular.

[0022] The inner ring groove and the outer ring groove form an annular groove space in which the coupling ring is arranged. The coupling ring is radially enclosed by the outer ring groove. Since the outer ring groove on the closure part is axially open on one side, the annular groove space spanned by the two annular grooves is not completely enclosed by the annular grooves, but is accessible axially distally.

[0023] According to the invention, the coupling ring is segmented by means of separating cuts. It consists of several coupling ring segments, hereinafter also referred to as ring segments.

[0024] The ring segments are arranged in a butt-jointed manner at the separating cuts. Essential to the invention is that, due to the butt-jointed arrangement, the ring segments abut one another with virtually no gaps. The opposing surfaces of the separating cuts at the butt joint are essentially parallel to one another. Furthermore, it is essential to the invention that all ring segments together form a virtually gap-free ring body and span an angle of 360 degrees.

[0025] This provides a particular advantage over a resilient piston ring with a piston ring gap in that a continuous ring surface or ring line for force transmission is provided on the one hand between the groove wall of the inner ring groove and the coupling ring and on the other hand between the coupling ring and the groove wall of the outer ring groove.

[0026] According to the invention, the separating cuts of at least one piston ring segment are designed to open parallel to one another or concentrically. A solution has thus surprisingly been found which, with an eccentric joining direction, allows the coupling ring to be arranged in the outer ring groove with virtually no gap, whereas this is not possible with radial separating cuts. Parallel design means that the separating cuts at one end of a ring segment and at the other end of a ring segment have surfaces parallel to one another. Concentric design means that the separating cuts at one end of a ring segment and at the other end of a ring segment have surfaces whose flat planes are, on the one hand, essentially parallel to the longitudinal axis of the cylinder and, on the other hand, at an angle which enables the ring segment in question to be inserted in a radially eccentric direction.

[0027] In conjunction with the outer ring groove and the inner ring groove, the coupling ring secures the closure part axially and positively on one side in a distal direction. The full load resulting from the operating pressure is absorbed in this direction. The annular surface sections of the inner ring groove and the outer ring groove, which are adapted to the coupling ring, are advantageous here, so that undesirably high surface pressures are avoided by sufficiently large surfaces.

[0028] Furthermore, the locking body is arranged axially distally on the closure part by means of a releasable fastening. An axially distal arrangement means that the locking body is arranged opposite the axially distal one-sided opening of the outer ring groove. A releasable fastening is understood in particular to mean a screw connection of the locking body to the closure part. The locking body can in particular be designed as an annular body if the closure part is a guide closure part, so that a free space remains for the piston rod. In the case of a bottom closure part, the locking body can also be designed as a flat cylindrical body. Furthermore, the locking body can also be made up of several parts.

[0029] The locking body has a circumferential annular surface that forms a pressure contact with the coupling ring and secures the coupling ring in the annular groove space with a positive fit. The contour of the annular surface can preferably correspond to the cross-section of the coupling ring and, for example, be essentially quarter-circular in shape. The locking body can thus cover the remaining open section of the annular groove space. However, other contours are also possible, for example, part-circular contours of less than 90 degrees, inclined annular surfaces without curvature, or part-circular contours with a radius that deviates from the coupling ring cross-section, for example to optimize the pressure contact and thus the positioning of the coupling ring.

[0030] The locking body secures the closure part axially and positively in a proximal direction by means of pressure contact with the coupling ring. The load is transferred indirectly via the detachable fastening, which is advantageous but unproblematic, since only small forces, for example, from the friction of the piston unit in a guide closure part, need to be absorbed in this direction.

[0031] Since the axially distal position is already established through the interaction of the outer ring groove, coupling ring, and inner ring groove, the locking body also provides the positional relationship to the cylinder tube in the remaining axially opposite direction. As a result, the closure part and the cylinder tube are now fully coupled in a form-fitting manner.

[0032] The solution according to the invention has the following advantages in particular.

[0033] The continuous annular surface or annular line for force transmission, on the one hand between the groove wall of the inner ring groove and the coupling ring, and on the other hand between the coupling ring and the groove wall of the outer ring groove, prevents uneven stresses in the groove areas of the coupling partners, reduces notch stresses, for example, and thus increases the maximum load capacity. Another advantage is the high load capacity possible, since the coupling ring does not need to be spring-loaded due to its segmentation and can have a large cross-section.

[0034] Another advantage is the particularly easy detachability of the coupling. With the appropriate design, it is possible to disassemble the locking body using a screwdriver or wrench with a standard drive, remove the ring segments, and thus remove the locking part for inspection or repair purposes.

[0035] Another advantage is easy assembly, as the ring segments are already secured radially outward by the outer ring groove and radially inward by the locking part before the locking body is inserted. Another advantage is the low susceptibility to assembly errors, as the locking body cannot be inserted if the ring segments are not properly seated.

[0036] The structural simplicity of the solution is also particularly advantageous, since both the cylinder barrel, the closure part and the locking body can be produced using a conventional turning and milling process.

[0037] According to a first advantageous development, the working cylinder is characterized in that the piston ring has four piston ring segments and all separating cuts are formed parallel to one another.

[0038] According to this refinement, there are two identical ring segments of the first type and two identical ring segments of the second type. The ring segments of the same type are arranged opposite one another. After the two ring segments of the first type are positioned in the inner ring groove, the two ring segments of the second type can be inserted from the center in a radially eccentric direction thanks to the parallel separating cuts. Thus, using the four ring segments, the coupling ring can be joined to form a completely closed, virtually gap-free ring body over 360 degrees.

[0039] According to another advantageous development, the working cylinder is characterized in that the locking body is arranged in the proximal direction with an axial elastic prestress.

[0040] Especially in hydraulic cylinders, the coupling between the cylinder barrel and the locking parts is subject to high mechanical stress due to the high and changing operating pressures and the associated dynamic loads. In positive-lock couplings, this can lead to undesirable play, also known as breathing. Such play can occur when the groove walls of the ring grooves and the coupling ring conform to each other.

[0041] The elastic preload of the locking body ensures a permanent force is applied to the annular surface of the locking body against the coupling ring. As the coupling ring and the groove walls conform to each other, this force presses the coupling ring deeper into the annular grooves, thus maintaining a zero-backlash condition.

[0042] According to an advantageous further development based on this, the working cylinder is characterized in that the detachable fastening of the locking body is formed by means of head screws, the respective screw head of which has a one-sided support on the locking body and an axial force applied to the support, and in that the head screws have an elastic bending to their longitudinal axis.

[0043] According to this refinement, the screw heads only partially, preferably approximately halfway, rest on the locking body. When the head screws are tightened with a tightening torque, the screw head is loaded off-center, causing the screw to bend at the free shaft end toward the non-supporting side of the screw head. According to the refinement, this bending lies within the limits of elastic deformation, whereby the screw advantageously acts like a spring element to exert axial elastic preload on the locking body in the proximal direction and simultaneously secures itself against unscrewing.

[0044] With this structurally simple further development, a surprisingly reliable solution was found to counteract breathing and achieve a particularly longevity of the coupling.

[0045] According to a further advantageous development based on this, the working cylinder is characterized in that the circumferential annular surface of the locking body is designed as a cone.

[0046] According to the invention, the circumferential annular surface forms a pressure contact with the coupling ring. In conjunction with the axial elastic preload of the locking body in the proximal direction, the conically inclined annular surface distributes the force on the coupling ring into an axial and a radial portion. The axial portion presses the piston ring, particularly into the outer annular groove of the closure part, and the radial portion presses the piston ring, particularly into the inner annular groove of the cylinder, thus counteracting the formation of play and breathing.

[0047] According to another development, the working cylinder is characterized in that a coupling section according to the invention is arranged at each of the two cylinder tube end sections. Both coupling sections have the same basic structure, so that the description of the coupling section also applies correspondingly to the further coupling section at the opposite end of the cylinder tube. This advantageously provides a solution that allows access for inspection or repair purposes at both ends of the working cylinder. Furthermore, it is advantageously possible to design the cylinder tube identically at both ends, thus simplifying production.

[0048] The invention is illustrated by way of example with reference to

[0049] Fig. 1 Sectional view of the coupling section

[0050] Fig. 2 Enlarged section of the coupling section

[0051] (Shown without coupling ring)

[0052] Fig. 3 Enlarged section of the coupling section (shown with coupling ring and axial preload)

[0053] Fig. 4 Sectional view of a working cylinder

[0054] (Overall view)

[0055] Fig. 5 Coupling ring with separating cuts

[0056] (Top view and cut)

[0057] Fig. 6 Coupling ring with parallel separating cuts (schematic representation)

[0058] Fig. 7 Coupling ring with opening cuts (schematic representation)

[0059] Fig. 8 Axial view of the coupling section

[0060] (Illustration without piston unit) is explained in more detail. The same reference symbols in the various figures refer to the same features or components. The reference symbols are used in the description even if they are not shown in the respective figure.

[0061] Fig. 1 shows, in one exemplary embodiment, a guide-side section of a working cylinder with the coupling section 7 arranged there on the cylinder 1. The cylinder 1 has a closure part 4a, designed here as a guide closure part, and a cylinder tube 3. The cylinder tube end section 5a, which in this case is designed as a separate sleeve, is arranged at the guide-side end of the cylinder tube 3. Alternatively - not shown here - the cylinder tube 3 can also be designed monolithically. The closure parts 5a, 5b form an interior space 6. Furthermore, the piston rod of the piston unit 2 and the at least one working chamber 6.1 thus formed, in the exemplary embodiment the piston rod chamber, are shown.

[0062] The coupling section 7 has, in addition to the cylinder tube end section 5a, the coupling ring 8 and the locking body 9 with the releasable fastening 10.

[0063] Fig. 2 shows the coupling section in an enlarged view, wherein Fig. 2 initially shows a representation without the coupling ring 8.

[0064] The cylinder tube 3 has an inner annular groove 11.1 on its cylinder tube end section 5a, which is arranged on the inside of the cylindrical cylinder tube inner surface. Corresponding to the circular cross-section of the coupling ring 8 in the exemplary embodiment, the inner annular groove 11.1 has a substantially semicircular contour. Radially opposite, the closure part 4a has the outer annular groove 11.2 on its cylindrical outer surface, which has a substantially quarter-circular contour and is thus open on one side in the distal axial direction. The two annular grooves 11.1, 11.2 span the annular groove space 11.3. The locking body 9 is annular in the exemplary embodiment and is mounted axially such that its circumferential annular surface 9.1 covers the quadrant of the annular groove space still left open by the two annular grooves 11.1, 11.2. Furthermore, the axial directions are indicated distally and proximally by arrows.

[0065] Fig. 3 essentially corresponds to Fig. 2, wherein the arrangement of the coupling ring 8 in the annular groove space 11.3 and the interaction of the releasable fastening with the locking body 9 for generating an axial elastic preload are additionally shown here.

[0066] The support cone for the countersunk head screw of the releasable fastening 10 is designed asymmetrically, with a support section on the closure part 4a being axially recessed compared to a support section on the locking body 9. When the countersunk head screw is screwed in, there is thus one-sided support 10.1 on the locking body 9. When a tightening torque is applied, the countersunk head screw bends due to the one-sided force acting on the screw head, as shown by the auxiliary lines (dashed lines). The upper section bends against the longitudinal axis and the axial flat surface of the screw head is inclined. With an even higher tightening torque, the screw head is now additionally supported on the deeper support zone on the closure part. This prevents bending beyond the elastic range and at the same time secures the countersunk head screw against loosening.

[0067] As a result of the releasable connection 10 acting as a spring-loaded tensioning element, the locking body 9 is elastically pre-tensioned in the axially proximal direction and transmits a force to the coupling ring 8 via the circumferential annular surface 9.1. The circumferential annular surface 9.1 is designed as a cone and thus has an inclined contour which advantageously acts as an inclined plane to transform the force and thus increases the force for pressing the coupling ring into the annular grooves 11.1, 11.2. This advantageously prevents play from developing as a result of the high and dynamic operating loads acting axially distally, which could cause the working cylinder to breathe. Fig. 4 shows, in addition to Fig. 1, an overall view which also shows the further cylinder tube end section 5b and the further closure part 4b, which is present as a base closure part. In the embodiment shown in Fig.In the embodiment shown in Figure 4, however, there is no coupling according to the invention between the further cylinder tube end section 5b and the further closure part 4b, but rather a laser welding coupling.

[0068] Fig. 5 shows a four-part design variant of the coupling ring 8. Here, all separating cuts 8.1 are aligned parallel. The four separating cuts 8.1 form four coupling ring segments 8.2.

[0069] Fig. 6 shows, in addition to Fig. 5, a schematic representation of the embodiment with parallel separating cuts 8.1. There are two coupling ring segments 8.2 of the same type in each case. First, the two coupling ring segments of the first type (shown left and right) can be positioned in the inner ring groove 11.1. Subsequently, the two coupling ring segments of the second type (shown above and below) can be inserted between the coupling ring segments 8.2 of the first type by means of an eccentric radial joining movement. The respective joining movement of the coupling ring segments 8.2 of the second type is shown by the two arrows. After joining, there is a butt-jointing, gap-free contact between all coupling ring segments 8.2, so that a practically uninterrupted force transmission between the cylinder tube 3 and the closure part 4a is provided over a range of 360 degrees.

[0070] Fig. 7 essentially corresponds to Fig. 6, so the descriptions therein apply accordingly. Deviating from the embodiment in Fig.

[0071] 6, however, the separating cuts 8.1 in Fig. 7 are formed in a radially concentrically opening angular position.

[0072] During the joining movement of the coupling ring segments 8.2 of the second type, on the one hand, the joining between the coupling ring segments 8.2 of the first type is facilitated and, on the other hand, the wedge-shaped inlet creates a pressure contact at the separating cuts 8.1, which supports the gap-free positioning of the coupling ring segments 8.2 to one another.

[0073] Fig. 8 finally shows an axial view of the cylinder 1, whereby the piston unit 2 is not shown here. The coupling ring 8, which is not visible, is represented by the two concentric dashed lines.

[0074] The locking body 9 is designed here as a ring body that surrounds the piston rod passage. The detachable fastening 10 is formed by three screws arranged at an angle of 120 degrees, the heads of which rest on the locking body with the one-sided support 10.1 on one side and on the axially lower support of the closure part 4a.

[0075] Reference symbols used

[0076] 1 cylinder

[0077] 2 piston unit

[0078] 3 cylinder barrel

[0079] 4a closure part

[0080] 4b additional locking part

[0081] 5a Cylinder tube end section

[0082] 5b further cylinder tube end section

[0083] 6 cylinder interior

[0084] 6.1 Workspace

[0085] 7 Coupling section

[0086] 8 coupling ring

[0087] 8.1 Separation cuts

[0088] 8.2 Coupling ring segments

[0089] 9 locking bodies

[0090] 9.1 circumferential ring surface

[0091] 10 removable fastening

[0092] 10.1 one-sided edition

[0093] 11.1 Inner ring groove

[0094] 11.2 Outer ring groove

[0095] 11.3 Annular groove space

Claims

Patent claims 1. Working cylinder comprising a cylinder (1) and a piston assembly (2), wherein the cylinder (1) comprises a cylinder tube (3), a closure part (4a) and a further closure part (4b), wherein the cylinder tube (3) comprises a cylinder tube end section (5a) and a further cylinder tube end section (5b), wherein the closure part (4a) is arranged on the cylinder tube end section (5a) and the further closure part (4b) is arranged on the further cylinder tube end section (5b), and wherein the cylinder tube (3) and the closure parts (4a, 4b) form a cylinder interior (6), wherein the piston assembly (2) in the cylinder interior (6) comprises at least one working chamber (6).1) forms, wherein the cylinder has a coupling section (7) which has the closure part (4a), the cylinder tube end section (5a), a coupling ring (8) and a locking element (9), wherein the cylinder tube (3) has a circumferential inner ring groove (11.1) on a cylinder tube inner surface at the cylinder tube end section (5a), wherein the closure part (4a), having a cylindrical closure part outer surface, is inserted axially into the cylinder tube end section (5a) and is radially enclosed at the closure part outer surface by the cylindrical cylinder tube inner surface of the cylinder tube end section (5a) and has an axially distal outer ring groove (11.2) open on one side. wherein the inner ring groove (11.1) and the outer ring groove (11.2) form an annular groove space (11.3) in which the coupling ring (8) is arranged and radially enclosed by the inner ring groove (11.1), wherein the coupling ring (8) is segmented by means of separating sections (8.1) and consists of several coupling ring segments (8.2), wherein the coupling ring segments (8.2) are arranged butt-jointed at the separating sections (8.1) and the separating sections (8.1) of at least one piston ring segment (8.2) are formed parallel or opening concentrically to each other, wherein the closure part (4a) is axially and unilaterally secured by the coupling ring (8) in a distal direction, wherein the locking element (9) is arranged axially distally on the closure part (4a) by means of a releasable fastening (10) and has a circumferential annular surface (9.1) comprising a pressure contact with the coupling ring (8) and positively locking the coupling ring (8) in the annular groove space, wherein the locking element (9) axially locks the closure part (4a) in a proximal direction in a one-sided manner by means of the pressure contact with the coupling ring (8). Working cylinder according to claim 1, characterized in that the coupling ring (8) comprises four coupling ring segments (8.2) and all separation cuts (8.1) are parallel to each other. Working cylinder according to one of the preceding claims, characterized in that. that the locking element (9) is arranged in the proximal direction with an axial elastic preload.

4. Working cylinder according to claim 3, characterized in that the releasable fastening (10) of the locking body (9) is formed by means of cap screws, the respective screw head of which has a one-sided support (10.1) on the locking body and an axial force application at the one-sided support and that the cap screws have an elastic bending to their longitudinal axis.

5. Working cylinder according to claim 3 or 4, characterized in that the circumferential annular surface (9.1) of the locking body (9) is designed as a cone.

6. Working cylinder according to one of the preceding claims, characterized in that the cylinder (1) has a further coupling section which has the further closing part (4b), the further cylinder tube end section (5b), a further coupling ring and a further locking element and that the further coupling section is designed in the same way as the coupling section (7a). INCLUDES SIX PAGES OF DRAWINGS

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