Piston-integrated overflow valve

Abstract

The invention relates to a piston-integrated overflow valve located in a piston (50) of a working cylinder, comprising a first valve plunger (10) and a first actuating tappet (14), a second valve plunger (20) and a second actuating tappet (24), a spring element (30), a valve chamber (40) and an end bush (70). The valve plungers (10, 20) are axially slidable in the valve chamber (40) and each provide a closed position in a distal end position and an open position in a proximally axially offset working position. The valve chamber (40) has a hollow-cylindrical basic shape formed by an inner lateral surface of an axial bore (60) in the piston (50), wherein an end bush (70) is located in the axial bore (60) at at least one axial bore end (61) and is welded to the piston (50) along an outer bush ring face (72) by means of a circumferential laser ring weld (73), the circumferential laser ring weld (73) forming a pressure-medium-tight sealing plane.

Description

[0001] Piston-integrated overflow valve

[0002] The invention relates to a double-acting overflow valve in a piston unit of a working cylinder, particularly designed for use in a master-slave working cylinder arrangement.

[0003] Overflow valves are known as such from the prior art. They are designed to control pressure fluid flows between adjacent working chambers of hydraulic devices, in particular between working chambers of a working cylinder separated by a piston.

[0004] For example, valves are known which have a movable element in an interior space to which an external force is applied, whereby a flow between inlet and outlet can be controlled due to pressure.

[0005] Such mechanically controlled valves can be used in working cylinders for pressure equalization between adjacent working chambers of a working cylinder or for pressure medium supply to pressure accumulators in order to compensate for pressure losses and leakage current losses that occur during operation.

[0006] In this regard, the publication DE 20 2004 011 532 U1 describes a valve in whose valve chamber a prestressed elastic molded body is arranged as a blocking element. To exert an axial force on the blocking element, a plunger that can be mechanically actuated from the outside is provided on at least one side of the valve. This is a structurally simple and cost-effective solution, although the blocking body, made of an elastomer, must withstand high mechanical loads during long-term use of the valve.

[0007] Confirmation copy. Furthermore, the document DE 10 2004 044 832 B3 discloses a backflow preventer having an inlet opening, an outlet opening, and a leakage opening arranged therebetween. Two check valves and a movable valve body are also provided. By means of a bypass channel that bypasses the two check valves, an excess pressure present in the outlet opening is at least partially transferred to the area of ​​the inlet opening.

[0008] Another solution for a double-acting overflow valve is shown in document DE 3 610 160 B1. This discloses a solution in which the overflow behavior can be adjusted separately according to pressure or volume, depending on the overflow direction.

[0009] The state of the art presented here demonstrates overflow valves that make an important contribution to solving the technical problem of pressure or volume equalization. These are technically sophisticated approaches, and sometimes correspondingly complex to implement.

[0010] The object of the invention is therefore to provide a double-acting overflow valve of a working cylinder which enables pressure-dependent control of the flow rate of the fluid, which ensures permanent and reliable sealing of the inlet and outlet, and which is particularly cost-effective and structurally simple to manufacture.

[0011] The problem is solved by the features listed in patent claim 1.

[0012] Preferred further training courses are set out in the subclaims.

[0013] The overflow valve according to the invention is based on the basic principle of a double-acting valve. The overflow valve according to the invention has two spring-loaded opposing valve pistons, each with an associated actuating plunger, which are arranged in the piston of a working cylinder and are actuated depending on the position of the piston.

[0014] The opening of the valve on the non-pressurized side, hereinafter also referred to as the depressurized side, is effected in one of the piston's end positions by the end-face stop of the plunger against the corresponding closure part of the depressurized working chamber of the working cylinder. At the same time, the valve piston on the pressurized side is lifted from its closed position due to pressure, thereby releasing a pressure fluid overflow from the pressurized working chamber through the now opened pressure fluid channel along the two valve pistons in the open position. In the opposite end position of the piston, this applies accordingly, resulting in an overflow in the opposite direction.

[0015] In all positions other than the end positions, the overflow valve is closed in both directions and the working chambers separated by the piston are reliably separated in a pressure-tight manner.

[0016] With the present invention, a solution was surprisingly found with which such an overflow valve can be provided in a particularly cost-effective, reliable and tamper-proof manner.

[0017] The piston-integrated overflow valve according to the invention enables these advantages according to the structure and mode of operation described below.

[0018] According to the invention, the piston-integrated overflow valve is arranged in the piston of a working cylinder and connects the working chambers of the working cylinder separated by the piston. For this purpose, the overflow valve is preferably arranged essentially axially parallel to the main longitudinal axis of the working cylinder. Its basic components include a first valve piston with an associated first actuating plunger, a second valve piston with an associated second actuating plunger, a spring element, and a valve chamber.

[0019] Both valve pistons are arranged axially opposite each other and with opposite orientations and opposite functions in the valve chamber. Both valve pistons preferably have the same basic structure; particularly preferably, for a cost-effective solution, they use the same components.

[0020] The detailed description is based on the first valve piston and the first actuating plunger and applies accordingly to the second valve piston and the second actuating plunger.

[0021] The first valve piston is arranged in the valve chamber for axial displacement. In a distal end position, it assumes a closed position and in the working position, an open position. The valve piston moves from the distal end position to the working position by a proximal axial displacement.

[0022] The position or direction "distal" refers to a position or direction directed axially outward from the center of the overflow valve or valve chamber. The position or direction "proximal" refers to the opposite position or direction, i.e., a position or direction directed axially from the outside toward the center of the overflow valve or valve chamber.

[0023] The valve piston preferably has a substantially radially symmetrical basic shape. On its distal side, a substantially circular surface is formed, which is referred to below as the first distal axial valve piston surface. In the distal end position, this first distal axial valve piston surface rests against a first axial chamber ring surface of the valve chamber, so that a first valve sealing plane is formed between these two surfaces and the closed position of the valve piston is present. If the first valve piston is brought into its working position by an axial proximal displacement, the first distal axial valve piston surface lifts off from the first axial chamber ring surface of the valve chamber, there is an axial spacing between the two surfaces and the first axial valve opening gap is formed there, so that the open position of the valve piston is present.In an overflow operating state, a pressure medium can flow through the first axial valve opening gap.

[0024] The radial surfaces of both valve pistons do not form a seal against the valve chamber's outer surface; rather, an axial overflow cross-section is always provided there. This can preferably be achieved in a particularly simple design by means of an annular gap with a sufficient clearance fit between the valve piston and the valve chamber's outer surface. However, it is also possible to provide one or more axial gaps or channels as an overflow cross-section, for example by means of a flattened area or axially extending milled recess. The two valve pistons are preferably designed as inexpensive and easy-to-manufacture plastic parts, so that a high level of tightness can be achieved without additional measures at the valve sealing levels.

[0025] The two actuating tappets also work in opposite directions, are arranged opposite each other and distally axially in front of the two valve pistons in a tappet bore and are preferably arranged coaxially.

[0026] The first actuating plunger has a first plunger base and a first plunger head and is associated with the first valve piston. It is arranged axially displaceably in the first plunger bore and is designed for a rest position and an actuated position.

[0027] In the rest position, no forces are transmitted via the actuating plunger. In the rest position, the first plunger foot protrudes distally from the plunger bore and thus into the respective working chamber of the working cylinder, so that, in the piston's end position, it can strike a stop surface, usually the inner side of the respective closure part of the working cylinder.

[0028] The actuating plunger is in its actuated position when the piston is in its end position on the side of the relevant working chamber. In the actuated position, the first plunger base is in pressure contact with the stop surface; the first actuating plunger is pressed in and thus displaced axially proximally relative to its rest position. The first plunger head is now in pressure contact with the first valve piston at its first distal valve piston surface. This causes an axial proximal change in position of the first valve piston from its distal end position to the working position, overcoming the spring force of the spring element. The first valve piston lifts off, and the first axial valve opening gap opens.

[0029] The second valve piston and the second actuating plunger have the same structure and function as the first valve piston and the first actuating plunger.

[0030] Like the valve pistons, the two valve tappets do not form a seal against the bore wall in their respective tappet bores, but rather provide an axial overflow cross-section there. This is preferably achieved through an annular gap with a sufficient clearance fit.

[0031] The spring element, another basic component, is designed to apply an axial force to the two valve pistons toward the closed position. By selecting the spring force, it is easy to determine the pressure difference at which the valve pistons can move into a pressure-actuated open position.

[0032] The spring element can preferably be designed as a simple spiral spring, which is arranged axially between the two valve pistons and whose first end springs onto the first valve piston and whose second end springs onto the second valve piston, thus pressing the two distal axial valve piston surfaces onto the respective corresponding axial chamber ring surface and thus forming the two valve sealing planes there in the closed positions. The cylindrical outer contour of the spiral spring corresponds to the shape and size of the valve chamber. Furthermore, the valve pistons can preferably each have a locking pin to fix the position of the respective spring end on the valve piston.

[0033] The valve chamber has a hollow cylindrical basic shape. It has a chamber surface and a first and a second axial boundary surface.

[0034] The chamber surface is advantageously formed directly by the inner surface of an axial bore in the piston. The axial bore is designed as a through-bore, creating an overflow channel. This channel can provide a pressure medium overflow controlled by the valve pistons.

[0035] The through-bore can be designed in a particularly simple manner with the same diameter over the entire length or can have a smaller diameter at the end on the bore exit side and thus form a final section there.

[0036] The piston-integrated overflow valve is characterized according to the invention in that a closure bush is arranged in the axial bore at at least one axial bore end

[0037] The end bushing has a bushing bore which forms the first tappet bore. The diameter of the bushing bore is dimensioned such that the valve tappet can pass through, whereby the bushing bore simultaneously guides the valve tappet and a gap remains between the valve tappet and the bushing bore through which the pressure medium can flow into or out of the valve chamber. The end bushing interacts with the first valve piston in such a way that the first axial chamber ring surface is also arranged on the axial inside bushing ring surface. Depending on the design, the first axial chamber ring surface can take up the entire axial inside bushing ring surface or just a narrow annular section, or it can even form a conical ring surface pairing with the first axial valve piston surface.

[0038] The invention is further characterized in that the end bushing is welded to the piston along an outer bushing ring surface by means of a circumferential laser ring weld seam, and the circumferential laser ring weld seam forms a pressure-tight sealing plane.

[0039] The overflow valve is designed for a first and a second overflow operating state as well as for a closing operating state.

[0040] In the first overflow operating state, the piston is in a first stroke end position. In this case, the first stroke end position is understood to be the end position at which the pressure medium has flowed out of the first cylinder working chamber and the piston rests against the first closure part, which, together with the piston, forms the first cylinder working chamber. The first cylinder working chamber is depressurized, and the second cylinder working chamber is pressurized, so that a pressure difference exists on both sides of the overflow valve.

[0041] In the first stroke end position, the actuating plunger is in pressure contact with its first plunger foot on a surface, referred to here as the first stop surface, on the first closure part. The first actuating plunger is pressed in and, via its plunger head, transmits the proximal axial movement via the first distal axial valve piston surface to the first valve piston. The first valve piston is thus displaced proximally from its distal end position to its working position, counteracting both the spring force of the spring element and the pressure difference between the two cylinder working chambers, which acts on the inside of the first valve piston. The first valve piston is now in the open position.Since pressure equalization has now been established between the first cylinder working chamber and the valve chamber via the first axial valve opening gap, the second valve piston is now subjected to the pressure from the pressure difference between the cylinder working chambers on the outside. According to the invention, the resulting force overcomes the spring force of the spring element, so that the second valve piston is pressure-actuated and lifts from its distal end position and transitions into its working position via a proximal axial movement. The second valve piston is therefore also in an open position, and pressure medium can flow from the second cylinder working chamber into the valve chamber via the second axial valve opening gap, passing through the overflow cross sections on the second actuating tappet and the second valve piston.From the valve chamber, the pressure medium can now flow further into the first cylinder working chamber via the first axial valve opening gap, passing through the overflow cross sections on the first valve piston and the first actuating tappet. This creates an overflow channel that is open across all sections of the overflow valve according to the invention, so that, in accordance with the intended function, pressure medium can flow from the second cylinder working chamber into the first cylinder working chamber, for example, to compensate for leakage losses.

[0042] In the second overflow operating state, the piston is in the second stroke end position on the second closure part, opposite the first stroke end position. In this second end position, the first cylinder working chamber is pressurized and the second cylinder working chamber is depressurized. The second tappet foot of the second actuating tappet is now in pressure contact with a second stop surface, so that the second actuating tappet is pressed in and opens the second valve piston. When actuated by pressure, the first valve piston now also opens, so that the overflow channel is opened and a pressure medium overflow occurs in the opposite overflow direction from the first cylinder working chamber into the second cylinder working chamber. Furthermore, the descriptions for the first overflow operating state also apply accordingly to the second overflow operating state.The closed operating state exists in any other piston position that is not one of the two stroke end positions. In the closed operating state, both actuating plungers are in their rest position. Depending on the direction of the pressure difference between the two cylinder working chambers, the pressure via the valve chamber acts on the inside of the valve piston facing the depressurized cylinder chamber, which additionally presses the piston into its distal end position, where it establishes the valve sealing plane and assumes the closed position.

[0043] In summary, in the first overflow operating state, the first valve piston is tappet-actuated and the second valve piston is pressure-actuated. In the second overflow operating state, the second valve piston is tappet-actuated and the first valve piston is pressure-actuated. In contrast, in the closed operating state, both valve pistons are closed.

[0044] Advantageously, a solution for an overflow valve is created that integrates the overflow valve into the piston as a permanent unit, enabling significantly more efficient production. The end bushing can be manufactured particularly cost-effectively.

[0045] By means of an interference fit of the end bushing during assembly, pre-positioning and position determination in the piston can be carried out as pre-assembly, so that the subsequent laser welding of the end bushing can take place without the need for measures to determine the relative positional relationship of the welding partners during the welding process. This makes it easier for the laser beam to access the weld seam and reduces the handling effort.

[0046] It was surprisingly discovered that laser welding allows for welded coupling despite the valve components already being pre-assembled. In particular, it was found that the axially directed, narrow laser weld seam allows the heat input per unit length to be kept so low and the heat-affected zone so small that any thermally sensitive parts of the valve, such as valve pistons made of plastic, are not damaged, that functionally impairing thermal distortion of the piston can be ruled out, and that complex rework, which is regularly required due to scaling or excessive weld seams, can be avoided. In particular, this prevents contamination from entering the valve chamber as a result of such rework, which could impair function.

[0047] Furthermore, it is advantageous that neither complex machining nor additional measures to prevent the connection from loosening are required, as is the case with state-of-the-art screw-in solutions.

[0048] Advantageously, a tamper-proof overflow valve is also provided.

[0049] Particularly advantageously, a solution is also provided which enables asymmetrical overflow behavior in a structurally simple and particularly cost-effective manner even with two identical valve pistons, in that a valve tappet protrusion can be adjusted by means of the length of the end bushing and the length of the opposite end section of the axial bore or an opposite further end bushing.

[0050] Furthermore, it is particularly advantageous that the piston body itself is used as the valve housing, reducing costs, eliminating the need for a separate valve housing component. The valve pistons can be manufactured cost-effectively as plastic parts. The spring element and the valve tappets can also be provided cost-effectively and preferably as commercially available standard components.

[0051] In an advantageous further development, the piston-integrated overflow valve is characterized in that the end bushing has a ring-shaped bushing head and the axial bore at the end of the axial bore has an axial bore widening corresponding to the bushing head. The bushing head rests with its lower ring surface on a resulting radial annular surface at the base of the axial bore widening and thus creates a reliable axial position fixation of the end bushing, which advantageously both simplifies assembly and limits the penetration depth of the laser weld seam towards the valve chamber. The valve pistons and the spring element are thus additionally protected from the effects of the welding. At the same time, the heat-affected zone is shifted further radially outwards from the center axis of the axial bore, thus improving heat dissipation via the piston body.Overall, the thermal load on the sensitive components is further reduced.

[0052] According to a further advantageous development, the end bushing additionally has an O-ring that rests on the inner wall of the axial bore, axially proximal to the axial bore expansion. Advantageously, the interior is additionally sealed against the circumferential ring weld seam, thus preventing unwanted ingress of contaminants, especially during laser welding. Furthermore, assembly is advantageously simplified, as the O-ring facilitates pre-positioning.

[0053] According to one aspect of the invention, the piston-integrated overflow valve is characterized in that, axially opposite the end bushing, the axial bore has a closing section with a closing section bore at a further axial bore end, which forms the second tappet bore, that an inner shoulder ring surface of the closing section forms the second axial boundary surface, and that the second axial chamber ring surface is arranged on the inner shoulder ring surface. Accordingly, the valve chamber is axially delimited on one side by a closing bushing and axially opposite on the other side by a closing section.The end section is achieved in a particularly simple manufacturing process by first constructing the axial bore as a blind hole and then concentrically drilling a through hole into the bottom of the blind hole with a diameter matched to the second valve tappet, extending to the other side of the piston. The diameter difference creates an inner shoulder, which forms the axial inner shoulder ring surface. This can preferably be designed with clearance symmetrical relationship to the axial inner bushing ring surface.

[0054] According to an alternative further aspect of the invention, the piston-integrated overflow valve has a further end bushing in the axial bore opposite the end bushing at the further axial bore end. The further end bushing has a further bushing bore that forms the second tappet bore. A further inner bushing ring surface of the further end bushing forms the second axial boundary surface. The second axial chamber ring surface is arranged on the further inner bushing ring surface of the further end bushing.

[0055] This further aspect is particularly characterized in that the further end bushing is welded to the piston along a further outer bushing ring surface by means of a further circumferential laser ring weld seam and that the further circumferential laser ring weld seam forms a further pressure-tight sealing plane.

[0056] The description of the end bushing also applies correspondingly to the additional end bushing. Accordingly, according to this alternative aspect, the valve chamber is also delimited on the side axially opposite the end bushing according to the invention by an end bushing—referred to here as the additional end bushing.

[0057] The geometry of the additional end bushing can, in particular, be designed in the same way as the end section according to the previously described aspect of the invention. Furthermore, it is possible for both end bushings to be designed identically.

[0058] According to a further advantageous development, the piston-integrated overflow valve is characterized in that the first or second or both valve pistons are formed as a plastic part. This is preferably a plastic with high strength and hardness as well as advantageous tribological properties such as a low coefficient of friction and high abrasion resistance, such as polyoxymethylene (POM). In this way, the valve pistons can be manufactured particularly cost-effectively and achieve a high level of tightness in the respective valve sealing plane without additional measures.

[0059] According to one development, the piston-integrated overflow valve is characterized in that an elastomeric seal is assigned to the first or second valve sealing plane. Preferably, an elastomeric seal in the form of a sealing ring is assigned to both valve sealing planes. Such an elastomeric seal enables particularly good sealing, but is also thermally sensitive. In this development, the particular advantages of the invention are particularly effective, since the low penetration energy and the local limitation of the heat-affected zone make the integration of elastomeric elements possible, even in the case of a welded connection. In a related development, the piston-integrated overflow valve is characterized in that the spring element is designed as an elastomeric component. The description of the elastomeric seal applies accordingly to this development.

[0060] The invention is illustrated by way of example with reference to

[0061] Fig. 1 Detailed view as a section as a longitudinal section in a first embodiment

[0062] Fig. 2 Exploded view in a first embodiment

[0063] Fig. 3 Detail enlargement without valve piston, spring element and end bushing in a first embodiment

[0064] Fig. 4 Detailed view as a section as a longitudinal section in a second embodiment

[0065] Fig. 5 Exploded view in a second embodiment

[0066] Fig. 6 Detail enlargement without valve piston, spring element and end bushing in a second embodiment

[0067] Fig. 7 Detail enlargement with a termination socket according to the second embodiment

[0068] Fig. 8 General view of a working cylinder with overflow valve

[0069] Fig. 9 Detailed enlargement with two end bushings without valve piston and spring element explained in more detail.

[0070] Identical reference symbols in the various figures refer to identical features or components. These reference symbols are used in the description even if they are not shown in the respective figure.

[0071] Fig. 1 and Fig. 4 show an enlarged section in two embodiments of a double-acting working cylinder, here as a differential working cylinder.

[0072] Fig. 2 and 5 each show an exploded view of the two embodiments and Fig. 3 shows an enlarged section of Fig. 2 and Fig. 6 shows an enlarged section of Fig. 5.

[0073] Fig. 7 shows a detailed illustration of a termination socket.

[0074] Figures 1 to 7 are summarized below.

[0075] The first embodiment according to Figs. 1 to 3 and the second embodiment according to Figs. 4 to 7 largely agree and differ only in the design of the end bushing 70 and the axial bore end 61.

[0076] An axial bore 60 is provided in the piston 50, connecting the two working chambers of the differential cylinder. In the illustrated embodiment, one axial bore end 61 leads to the piston working chamber, and another axial bore end 62 leads to the rod working chamber.

[0077] The axial bore 60 is formed in such a way that it continues into a terminal section 80, merely with a greatly reduced diameter, as the terminal section bore 82. The terminal section bore 82 is designed to accommodate the second valve tappet 24 and is matched to the diameter of the second valve tappet 24 in such a way that it is guided axially displaceably and that, at the same time, an annular gap remains as an overflow cross-section for a pressure medium overflow. It forms the second tappet bore 23. The terminal section 82 is represented by dashed lines in Figs. 3 and 6 and is not to be understood as a separate component, but rather as a functional section of the piston 50.

[0078] At the end of the full diameter, the axial inner shoulder ring surface 81 of the end section 80 is formed.

[0079] At the further axial bore end 62, Figs. 1 and 4—and enlarged in Fig. 7—also show the end bushing 70, which has an axial inner bushing ring surface 71 opposite the axial inner shoulder ring surface 81. In both embodiments, the bushing bore 74 leads to the piston working chamber. It is matched to the diameter of the first valve tappet 14 so that it is guided and, at the same time, an annular gap remains as an overflow cross-section for a pressure medium overflow. The bushing bore 74 forms the first tappet bore 13.

[0080] Thus, an interior space is formed in the piston 50, which is referred to here as the valve chamber 40 and has a hollow cylindrical basic shape due to the chamber jacket surface 43 and the first and second axial boundary surfaces 42, 43. The two axial boundary surfaces 42, 43 simultaneously form the first and second axial chamber ring surfaces 43, 44.

[0081] 1 and 4 show the arrangement of the first and second valve pistons 10, 20 and the spring element 30 in the valve chamber 40. In the present exemplary embodiment, both valve pistons 10, 20 are identically designed as POM plastic bodies. The first valve piston 10 forms the first distal axial valve piston surface 11 in the direction of the first tappet bore 13, which corresponds to the first chamber annular surface 43. In a closed position, both annular surfaces 11, 43 rest on one another in a sealing manner and form the first valve sealing plane 12a. In an open position, the first axial valve opening gap 12b is located there instead of the first valve sealing plane 12a. The same applies to the second distal axial valve piston surface 21 and the second chamber annular surface 44, which provide the second valve sealing plane 22a in the closed position and the second axial valve opening gap 22b in the open position.The first valve tappet 14 with first tappet foot 15 and first tappet head 16 is assigned to the first valve piston 10, and the second valve tappet 24 with second tappet foot 25 and second tappet head 26 is assigned to the second valve piston 20.

[0082] The spring element 30 is designed as a simple spiral spring and applies an axial force to the two valve pistons in opposite directions, acting toward the closed position. It is centered and guided to the pin on a proximal side of the valve pistons 10, 20.

[0083] As the exploded views in Fig. 2 and 5 show in particular, the piston-integrated overflow valve enables particularly effective and cost-effective production and assembly.

[0084] Prior to assembly, the axial bore 60 with end section 80 is machined into the piston in a first step.

[0085] For assembly, the second valve tappet 24 is now inserted into the second tappet bore 23. By means of a shaped section on the second tappet head 16 - in the exemplary embodiment in the form of a countersunk head - the valve tappet 24 is axially secured on one side and cannot slide out of the tappet bore 23. The second valve piston 20 is then inserted such that the second distal valve piston surface 21 rests against the second axial boundary surface 42 - here designed as the inner shoulder ring surface 81 of the end section 80. After the spring element 30 has been inserted, the first valve piston 10 is inserted into the axial bore 60 in an axially reversed position so that the first distal valve piston surface 11 is directed towards the axial bore end 61.Now, the end bushing 70, with the first valve tappet 14 previously inserted into the bushing bore 74, is inserted into the axial bore 60 such that the first valve tappet 14, with its first valve tappet head 16—here also with a countersunk head section—rests against the first distal valve piston surface 11. With the positioning of the end bushing 70, the valve chamber 40 is simultaneously closed axially by the inner bushing surface 71. The spring element 30 is thereby preloaded.

[0086] In the first embodiment according to Figs. 1 to 3, the end bushing 70 comprises an O-ring 76 and the flat-cylindrical bushing head 75. Matching this, the axial bore 60 has the axial bore widening 63 at the axial bore end 61, which provides support and together enable precise axial positioning of the end bushing. The O-ring supports the radial position determination and simultaneously creates a reliable barrier against any welding fumes entering the valve chamber 40 as a result of the subsequent welding.

[0087] In the second embodiment according to Fig. 4 to 6, the outer diameter of the end bushing 70 is matched to the inner diameter of the axial bore 60 by means of an interference fit so that the latter is already locked after its axial pressing in.

[0088] On the now externally accessible outer bushing ring surface 72, the laser ring weld seam 73 is applied to the annular butt joint gap, securely and irreversibly securing the end bushing in its positional relationship to the piston 50 and simultaneously creating a circumferential sealing plane. In the first embodiment, the enlarged diameter of the bushing head 75 and the axial bore expansion 63 additionally shift the heat-affected zone eccentrically during laser welding, thus further relieving thermal stress in the area in the valve chamber 40.

[0089] Fig. 8 shows the embodiment of a double-acting working cylinder, here as a differential working cylinder, in an overall view to illustrate the arrangement of the overflow valve in the piston 50 with the first and second valve pistons 10, 20. Furthermore, the position of the respective detail A enlarged in Fig. 1 and 4 is shown, wherein the overall view in Fig. 5 specifically represents the second embodiment according to Fig. 4.

[0090] Fig. 9 shows an alternative embodiment in which the axial bore 60 is initially designed as a simple through-bore with the same diameter over its entire length. Instead of the end section 80, a further end bushing 90 is arranged here, which is designed in the same way as the end bushing 70 and therefore has a further inner bushing ring surface 91, a further outer bushing ring surface 92 and a further bushing bore 94. The further end bushing 90 or the end bushing 70 can now be positioned first. For automated production, each of the two end bushings 70, 90 can also be used with the respective valve tappet 14, 24 as a prefabricated subassembly. The further circumferential laser ring weld seam 93 is designed in the same way as the laser ring weld seam 73 with the associated advantages.

[0091] In one embodiment, the mode of operation is explained using the second overflow operating state shown in Fig. 5 and Fig. 1, 4. In this operating state, the piston 50 is in a bottom-side end position and rests against the bottom closure part. The first tappet foot 15 of the first valve tappet 14 rests against the bottom closure part as a stop surface and is thereby pressed in. The rivet-head-shaped first tappet head 16 is engaged proximally and acts on the first distal axial valve piston surface 11 of the first valve piston 10, which is thereby also displaced proximally against the spring force of the spring element 30, so that the first axial valve opening gap 12b is formed.This creates pressure equalization between the unpressurized base working chamber and the valve chamber 40, so that the pressure difference between the operating pressure in the rod working chamber is now applied distally to the second distal valve piston surface 21, so that the second axial valve opening gap 22b opens on the second valve piston 20, overcoming the spring force of the spring element 30. Both valve pistons 10, 20 are now in the open state, so that an overflow channel is opened for the pressure medium, which flows from the rod working chamber into the base working chamber via the overflow cross-section on the second valve tappet 24, the second axial valve opening gap 22b, the overflow cross-section on the jacket of the second valve piston 20, the interior of the valve chamber 40, the overflow cross-section on the jacket of the first valve piston 10, the first axial valve opening gap 12b, and the overflow cross-section on the first valve tappet 14. (In Fig. 5 and Fig.1 , 4 the overflow in the second overflow operating state occurs from left to right.).

[0092] Reference symbols used

[0093] 10 first valve piston

[0094] 11 first distal axial valve piston surface

[0095] 12a first valve sealing level

[0096] 12b first axial valve opening gap

[0097] 13 first tappet bore

[0098] 14 first valve tappet

[0099] 15 first pushes If uß

[0100] 16 first ram head

[0101] 20 second valve piston

[0102] 21 second distal axial valve piston surface

[0103] 22a second valve sealing level

[0104] 22b second axial valve opening gap

[0105] 23 second tappet bore

[0106] 24 second valve tappet

[0107] 25 second ram foot

[0108] 26 second ram head

[0109] 30 spring element

[0110] 40 valve chamber

[0111] 41 first axial boundary surface

[0112] 42 second axial boundary surface

[0113] 43 first axial chamber ring surface

[0114] 44 second axial chamber ring surface

[0115] 45 chamber surface area

[0116] 50 piston axial bore

[0117] Axial bore end further axial bore end axial bore expansion

[0118] End bushing inside bushing ring surface outside bushing ring surface surrounding laser ring weld bushing bore

[0119] socket head

[0120] O-ring

[0121] End section inside shoulder ring surface End section bore further end bush further inside bush ring surface further outside bush ring surface further circumferential laser ring weld further bush bore

Claims

Patent claims 1. Piston-integrated overflow valve, arranged in a piston (50) of a working cylinder, comprising a first valve piston (10) and a first actuating tappet (14), a second valve piston (20) and a second actuating tappet (24), a spring element (30) and a valve chamber (40), as well as a closure bushing (70), wherein the first valve piston (10) is arranged axially displaceably in the valve chamber (40) and provides a closed position in a distal end position and an open position in a proximally axially offset working position, and has the first distal axial valve piston surface (11) on the tappet side, which, together with a first axial chamber ring surface (43), forms a first valve sealing plane (12a) in the closed position and a first axial valve opening gap (12b) in the open position, wherein the first actuating tappet (14) is assigned to the first valve piston (10),a first plunger foot (15) and a first plunger head (16) with a shaped section for a positive distal axial position determination of the first actuating plunger (14) and is arranged axially displaceably in a first plunger bore (13) and is designed for a rest position and an actuating position, wherein in the rest position the first plunger foot (15) extends distally out of the first plunger bore (13) and in the actuating position the first plunger foot (15) is designed for pressure contact with a first stop surface and the first actuating plunger is displaced axially proximally and the first plunger head (16) is designed for pressure contact with the first distal axial valve piston surface (11) for an axial change in the position of the first valve piston (10) from the distal end position to the working position, wherein the second valve piston (20) is arranged axially opposite the first valve piston (10) and displaceably in the valve chamber (40) and provides a closed position in a distal end position and an open position in a proximally axially offset working position, and has the second distal axial valve piston surface (21) on the tappet side, which, together with a second axial chamber ring surface (44), forms a second valve sealing plane (22a) in the closed position and a second axial valve opening gap (22b) in the open position, wherein the second actuating tappet (24) is assigned to the second valve piston (20), has a second tappet foot (25) and a second tappet head (26) with a shaped section for a positive distal axial positional determination of the second actuating tappet (24), and is arranged axially displaceably in a second tappet bore (23) and is designed for a rest position and an actuated position,wherein in the rest position, the second plunger foot (25) extends distally out of the second plunger bore (23), and in the actuating position, the second plunger foot (25) is designed for pressure contact with a second stop surface, the second actuating plunger is displaced axially proximally, and the second plunger head (26) is designed for pressure contact with the second distal axial valve piston surface (21) for an axial change in position of the second valve piston (20) from the distal end position into the working position, wherein the spring element (30) applies an axial force to the valve pistons (10, 20) in the direction of the closed position, wherein the valve chamber (40) has a hollow-cylindrical basic shape and comprises a chamber surface (45) and a first and a second axial boundary surface (41, 42), wherein the chamber surface (45) is formed by an inner surface of an axial bore (60) in the piston (50), wherein a closure bushing (70) is arranged in the axial bore (60) at at least one axial bore end (61), wherein the closure bushing (70) has a bushing bore (74) which forms the first tappet bore (13), and wherein an inner bushing ring surface (71) of the closure bushing (70) forms the first axial boundary surface (41) and the first axial chamber ring surface (43) is arranged on the inner bushing ring surface (71), and wherein the closure bushing (70) is welded to the piston (50) along an outer bushing ring surface (72) by means of a circumferential laser ring weld seam (73), and wherein the circumferential laser ring weld seam (73) forms a pressure-tight sealing plane, and wherein the piston-integrated overflow valve is designed for a closure operating state, a first and a second overflow operating state, wherein in the closure operating state the valve pistons (10, 20) are arranged in the closed position,wherein in the first overflow operating state, in a first end position of the piston (50), the first tappet foot (15) is in pressure contact with the first stop surface, the first actuating tappet (14) has the actuating position and the first valve piston (10) has the working position, the second actuating tappet (24) has the rest position and the second valve piston (20) also has the working position by means of a pressure medium pressure acting on the second axial chamber ring surface (44), wherein an overflow channel for the pressure medium is opened through the second tappet bore (23), through the second axial valve opening gap (22b), through the valve chamber (40), through the first axial valve opening gap (12b) and through the first tappet bore (13), wherein in the second overflow operating state, in a second end position of the piston (50), the second tappet foot (25) is in pressure contact with the second stop surface, the second actuating tappet (24) the, Actuating position and the second valve piston (20) has the working position, the first actuating tappet (14) has the rest position and the second valve piston (20) also has the working position by means of a pressure medium pressure acting on the first axial chamber ring surface (43), wherein an overflow channel for the pressure medium is opened through the first tappet bore (13), through the first axial valve opening gap (12b), through the valve chamber (40), through the first axial valve opening gap (22b) and through the second tappet bore (23).

2. Piston-integrated overflow valve according to claim 1, characterized in that the end bushing (70) has a ring-shaped bushing head (75) and the axial bore (60) at the axial bore end (61) has an axial bore widening (63) corresponding to the bushing head (75).

3. Piston-integrated overflow valve according to one of the preceding claims, characterized in that the end bushing (70) has an outer O-ring (76) which bears against the inner wall of the axial bore (60).

4. Piston-integrated overflow valve according to one of claims 1 to 3, characterized in that the end bushing (70) has, at a further axial bore end (62), a closing section (80) with a closing section bore (82) which forms the second tappet bore (23), that an inner shoulder ring surface (81) of the closing section (80) forms the second axial boundary surface (42), and that the second axial chamber ring surface (44) is arranged on the inner shoulder ring surface (81).

5. Piston-integrated overflow valve according to one of claims 1 to 3, characterized in that the end bushing (70) has a further end bushing (90) at a further axial bore end (62) opposite the end bushing (70), that the further end bushing (90) has a further bushing bore (94) which forms the second tappet bore (23), that a further inner bushing ring surface (91) of the further end bushing (90) forms the second axial boundary surface (42), that the second axial chamber ring surface (44) is arranged on the further inner bushing ring surface (91) of the further end bushing (90), and that the further end bushing (90) is welded to the piston (50) along a further outer bushing ring surface (92) by means of a further circumferential laser ring weld seam (93), and that the further circumferential laser ring weld seam (93) has a further forms a pressure-tight sealing layer.

6. Piston-integrated overflow valve according to one of the preceding claims, characterized in that an elastomeric seal is assigned to the first or the second valve sealing plane (12a, 12b).

7. Piston-integrated overflow valve according to one of the preceding claims, characterized in that the spring element (30) is designed as an elastomeric component. SIX PAGES OF DRAWINGS

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