WORK CYLINDER

Description

[0001] The invention relates to a welded working cylinder with increased load capacity.

[0002] The state of the art describes hydraulic and pneumatic working cylinders in various variants.

[0003] In almost all designs, these working cylinders have a cylinder tube and locking parts.

[0004] To produce such working cylinders, the closure parts are coupled to the cylinder tube in different ways according to the state of the art.

[0005] A common method for positive coupling is screwing the locking parts to the cylinder barrel. Working cylinders manufactured in this way are therefore also known as screw cylinders.

[0006] It is also known from the prior art to first connect the bottom closure part to the cylinder tube by MAG welding and then to screw only the guide closure part.

[0007] Screw cylinders as well as 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.

[0008] Since the threads of the closure parts and the cylinder tube are usually formed using a machining process, this means that, especially for the cylinder tube, an allowance for the material thickness, i.e., the tube wall thickness, must be provided for the subtractive thread, because the thread inevitably weakens the cylinder tube. This results in a tube wall thickness that is significantly oversized to absorb the forces during operation, especially the forces caused by the operating pressure of the fluid. This disadvantageously leads to increased material consumption.

[0009] In addition, the machining processes used to create the thread require high precision and are therefore very demanding to manufacture. To ensure tightness, a seal must be regularly inserted between the cylinder barrel and the respective closure part as an additional measure.

[0010] Another disadvantage is that additional means must be provided to prevent the screw connection from loosening. Another disadvantage is that the changing operating pressures result in dynamic loads on the threads, which limit their service life. It is known from DE 10 2007 004666 A1, DE 20 2012 008320 U1, and DE 40 41 992 A1 to weld closure parts to the cylinder barrel using a laser process.

[0011] The object of the invention is to provide a working cylinder which is of particularly high quality and which is material-saving, simple and thus cost-effective to produce.

[0012] The problem is solved by the features listed in patent claim 1. Preferred developments arise from the subclaims.

[0013] According to the invention, the working cylinder comprises, as basic components, a cylinder tube, a first and a second closure part, and a piston unit. The first closure part and the second closure part are collectively referred to below as the closure parts.

[0014] The working cylinder according to the invention can be provided in various designs. In particular, the working cylinder can be a differential working cylinder, a plunger cylinder, a double-acting cylinder, a telescopic cylinder, a pull cylinder, or even a pneumatic working cylinder. If the working cylinder is designed as a double-acting cylinder, it is also referred to below as a steering cylinder. Working cylinders within the meaning of the present invention also include, in particular, accumulator cylinders, gas spring cylinders, and hydraulic shock absorbers.

[0015] A working cylinder according to the invention can in particular be double-acting or single-acting. A differential working cylinder, for example, is a double-acting hydraulic working cylinder with two working chambers, with differently sized piston contact surfaces in the two working chambers. At the same operating pressure, different forces act on the piston in the two actuating directions. In a double-acting cylinder, in contrast to a differential working cylinder, the piston rod is guided by guide closure parts arranged on both sides, so that the piston contact surfaces are of equal size and thus, at the same operating pressure, equal forces act in both actuating directions. With the result that double-acting cylinders are used in particular as steering cylinders.A plunger cylinder, on the other hand, is a single-acting working cylinder in which the pressure medium displaces the piston as a solid body, thus causing its extension. The same applies to a telescopic cylinder, in which several cylinder tubes are nested within one another, enabling particularly long working movements.

[0016] According to the invention, the cylinder tube has a first cylinder tube end and a second cylinder tube end. After assembly, the first closure part is arranged at the first cylinder tube end, and the second closure part is arranged at the second cylinder tube end. Both cylinder tube ends are preferably manufactured identically. Preferably, the two cylinder tube ends have beveled axial end faces, with the bevels having the same angle. The axial end faces thus preferably have the same cross-sectional area. However, it is also possible to design the cylinder tube ends differently.

[0017] According to the invention, the first closure part is arranged at the first cylinder tube end. The first closure part is preferably a guide closure part. A guide closure part is understood to be a closure part which receives a piston unit in a sliding and sealing manner. In a differential working cylinder, for example, the piston unit can consist of a piston and a piston rod, with the piston rod then being received by the guide closure part. In a plunger cylinder, the piston unit is in the form of a volume-forming piston, also referred to as a plunger piston, which is received by the guide closure part. The first closure part is designed such that it has a contact surface which, when placed against the first cylinder tube end, bears against a corresponding further contact surface of the first cylinder tube end.These contact surfaces preferably completely surround the first closure part and the cylinder tube. This creates a continuous annular surface against which the first closure part rests against the first cylinder tube end. The annular surface is inclined, so that in geometric terms it is a truncated cone surface. For simplicity, this surface will be referred to simply as the annular surface, regardless of its geometric configuration.

[0018] According to the invention, the second closure part is arranged at the second cylinder tube end. The descriptions of the first closure part in its relationship to the first cylinder tube end apply correspondingly to the second closure part in its relationship to the second cylinder tube end. The second closure part is designed analogously to the first closure part with regard to the contact surface. The second closure part is preferably a bottom closure part, which is then axially opposite the piston of the piston unit and axially delimits the at least one working chamber of the working cylinder according to the invention.

[0019] The working cylinder according to the invention further comprises the piston unit. Depending on the type of working cylinder, the piston unit can be formed from a piston and a piston rod—as is the case, for example, with a differential working cylinder or a double-action cylinder—or be formed solely by a piston—as is the case, for example, with a plunger cylinder—or have other configurations. If the piston unit comprises a piston and a piston rod, the piston and piston rod are in a fixed position relative to one another. Preferably, the piston and piston rod are firmly coupled to one another. The connection is preferably formed as a welded joint. The piston and piston rod can also be detachably coupled. In special cases, however, it is also possible for the piston unit to be formed in one piece, thus forming the piston and piston rod as sections of a monolithic component.

[0020] According to the invention, the cylinder tube and the closure parts form a cylinder interior when assembled. When the cylinder tube and closure parts are joined together, their inner surface sections define the cylinder interior. The cylinder interior extends up to the respective laser ring weld seam.

[0021] Furthermore, in the working cylinder according to the invention, the piston unit forms at least one working chamber in the cylinder interior. This is defined by the cylinder tube, a closure part, and the piston unit. The piston unit is arranged to be axially displaceable, wherein the main longitudinal axis of the cylinder tube and the axial direction of movement of the piston unit coincide. In this case, the piston unit preferably passes through the first closure part, at least in sections, in a sliding and sealing manner. A pressure medium connection is assigned to the working chamber, via which the pressure medium can enter or be led out of the working chamber, thus pressurizing the working chamber. The pressure medium can be hydraulic or pneumatic.

[0022] If the working cylinder according to the invention is, for example, in the form of a differential working cylinder, the following also applies.

[0023] The piston of the piston unit is arranged in the cylinder interior and divides the cylinder interior into a piston crown working chamber, hereinafter also referred to as the piston crown chamber, and a piston rod working chamber. The piston crown chamber is located between the piston and the second closure part, here designed as a crown closure part. The piston rod working chamber is located on the piston rod side between the piston and the first closure part, here designed as a guide closure part. The at least one working chamber is thus the piston rod working chamber. In addition, the piston crown working chamber forms another working chamber.

[0024] The piston is axially movable and positioned within the cylinder interior so that the main longitudinal axes of the piston and cylinder barrel overlap. The pressure medium connections are arranged on the cylinder so that the piston crown working chamber and the piston rod working chamber can be pressurized with operating pressure.

[0025] The piston can also have various guide, sealing, or piston rings. Various designs of a piston for a working cylinder are known in the art.

[0026] According to the invention, the piston rod slidably passes through the first closure part, here designed as a guide closure part.

[0027] The piston rod is slidably mounted in the guide closure part, which is designed to prevent the pressure medium, hereinafter also referred to as fluid, from escaping. This is achieved, for example, by means of appropriate ring seals.

[0028] The working cylinder according to the invention is characterized in particular in that both closure parts, for example in the case of a differential working cylinder both the guide closure part and the bottom closure part, are welded to the cylinder tube.

[0029] The first closure part is integrally connected to the cylinder tube by means of a first circumferential laser ring weld, and the second closure part is integrally connected to the cylinder tube by means of a second circumferential laser ring weld. The interconnected components are collectively referred to as the coupling partners. The two closure parts are joined to the cylinder tube using a laser welding process. The laser ring welds are fusion welds, without the addition of filler metals.

[0030] Laser welding advantageously creates a very narrow, tapered weld seam. The acute angle spanned by the lateral flanks of the essentially V-shaped laser weld seam is preferably less than 15 degrees and particularly preferably less than 10 degrees.

[0031] The two laser ring welds each form a fluid-tight sealing plane. This means that the first laser ring weld prevents the passage of pressure medium at the connection point between the cylinder tube and the first closure part, and the second ring weld prevents the passage of pressure medium between the cylinder tube and the second closure part, without the need for additional sealing means, such as a sealing ring.

[0032] The cylinder tube and closure parts, and preferably also the piston unit, are each made of a metal alloy, particularly preferably a steel alloy. The material composition of the individual components may differ slightly. Preferably, the mass fractions of the components of the cylinder's metal alloy differ from those of the closure parts by less than 10 wt.% of the metal alloy of the closure parts. Thus, the closure parts and cylinder tube have similar physical properties and can be welded together particularly well.

[0033] The steel alloy used preferably has a carbon content of less than 0.5 wt.%. The alloying constituents vanadium, chromium, and manganese are preferably present individually or in combination in a proportion of 0.01 to 2 wt.%.

[0034] Furthermore, the working cylinder is characterized in that at least one closure part has an axially opening, circumferential concave receiving contour into which the cylinder tube engages. The receiving contour radially overlaps the cylinder tube and a ring weld center axis, with the main longitudinal axis, encloses a ring weld inclination angle alpha of 110 to 160 degrees. This inclination exceeding 90 degrees is also referred to below as negatively inclined.

[0035] The axially opening, circumferential concave receiving contour is provided by an annular groove in the relevant closure part, which has radial side walls. The radially outer side wall is inclined and forms a conical shape. The concave receiving contour thus forms a radial overlap. The radially inner side wall is preferably not inclined and preferably forms a cylindrical shape. The cross section of the receiving contour therefore preferably corresponds to a concave wedge. The cylinder tube is designed at the corresponding cylinder tube end to correspond to the receiving contour and for this purpose has an inclined annular surface whose angle of inclination corresponds to the angle of inclination of the outer radial side wall of the receiving contour. The cross section of the wall of the cylinder tube end therefore preferably corresponds to a wedge that fits into the receiving contour.

[0036] The laser ring weld is positioned between the described inclined annular surfaces of the receiving contour and the cylinder tube. The angle of inclination of the laser ring weld corresponds to the angle of inclination of the two inclined annular surfaces.

[0037] The welded working cylinder according to the invention has a number of significant advantages over working cylinders according to the state of the art.

[0038] A first significant advantage is that the cylinder tube, in particular, requires little or no machining beyond cutting to length. This means that no threads need to be cut or grooves turned. Machining of the cylinder tube is advantageously limited to the formation of the inclined annular face.

[0039] This has the immediate advantage that the time, processing machines, tool costs and energy that would otherwise be required for machining can be saved.

[0040] Another advantage is drastic material savings and thus the conservation of raw material resources, because the cylinder tube only needs to have about half the tube wall thickness of a screwed differential cylinder. Allowances, for example, in the tube wall thickness to compensate for the material removal for a cut thread can be eliminated.

[0041] By eliminating the need for machining the cylinder tube and, preferably, also the piston rod, quality is also significantly improved. The axial concentricity is no longer impaired as a result of the elimination of force input through machining. Rather, the axial concentricity of the starting products for the cylinder tubes and, if applicable, also the piston rods is fully retained. The working cylinder according to the invention thus exhibits greater precision. The axial piston rod movement can also be provided without the problem of piston rod buckling in the end stop, which is known from the prior art. This also reduces wear on the cylinder guides in the guide closure part. By eliminating the need for machining the cylinder tube and, if applicable, the piston rod, reductions in load capacity due to notch effects are also avoided.

[0042] It has been found that the concave receiving contour in conjunction with the ring weld seam inclination angle according to the invention achieves three advantageous effects with the same means. Firstly, the radial overlap of the cylinder tube achieves a positive absorption of buckling forces caused by the working pressure of the pressure medium. The positive absorption of the radially acting buckling forces relieves the laser ring weld seam, so that the material-to-material force transmission at the laser ring weld seam is available almost exclusively for axial forces. Secondly, the inclination achieves a ring weld seam depth that exceeds the cylinder tube wall thickness without the need for additional measures, thus enabling a higher force transmission. Thirdly, an assembly advantage is achieved at the same time, since the cylinder tube and the relevant closure part center themselves automatically during an axial feed movement.

[0043] A further advantage is the absolute tightness of the differential power cylinder at the connection points between the cylinder barrel and the closure parts. Another advantage is that this tightness can be achieved without the seals otherwise required by state-of-the-art technology. The potential elimination of these aging-prone components not only results in cost savings, but also improves quality and extends service life. Furthermore, contamination from aging seals is eliminated.

[0044] A further advantage is increased operational reliability. This eliminates the axial play between the cylinder barrel and the locking components during load changes, as is the case with threads, or the loosening that can occur with threads. Furthermore, advantageous savings are achieved by eliminating the need for locking elements. This also eliminates the need for the actual locking elements, which is necessary for detachable connections. State-of-the-art technology achieves this by gluing the locking elements, for example. Eliminating the need for gluing brings with it other important advantages. Firstly, it eliminates the costs of very expensive threadlocking adhesives. Secondly, it eliminates the need to clean surfaces to ensure they adhere to the threadlocking adhesives; this cleaning chemicals, which are often hazardous to health, are required with state-of-the-art technology.This eliminates the need for special health and environmental protection measures. Third, it overcomes the problem that even detachable connections secured with threadlocking adhesives are at risk of loosening under impact loads.

[0045] Another aspect of the increased operational safety is the increased tamper resistance. Non-destructive interventions into the cylinder interior are impossible. Potential sources of injury associated with improper opening or improper reassembly of a differential cylinder by untrained personnel are eliminated.

[0046] The laser welding process results in only very localized heating of the material in the area of ​​the laser ring welds. This allows components made of thermally sensitive materials, such as seals, to be welded within a few millimeters of the planned weld, even though they would be damaged by other welding processes.

[0047] It also prevents scaling on the inner surface sections of the cylinder tube and the closure parts, especially near the weld seams, which would otherwise have to be laboriously removed according to the state of the art.

[0048] Another advantage is the reduction of thermal stresses in the coupling partners of the welded joint, since only a relatively low energy per unit length (amount of energy related to the length of the weld seam) needs to be introduced by means of laser welding.

[0049] A further advantage is that the path, weld depth, and angle of the laser ring welds can be largely determined by the movement, energy per unit length, and angle of the laser beam relative to the working cylinder being produced. This allows the path and angle to be precisely aligned, particularly by changing the position of the laser relative to the coupling partners.

[0050] In a first particularly preferred embodiment of the working cylinder according to the invention, the working cylinder is a double-acting working cylinder and is designed as a differential working cylinder.

[0051] In this embodiment, the first closure part is designed as a guide closure part, and the second closure part is designed as a base closure part. Therefore, the first cylinder tube end is referred to here as the guide-side cylinder tube end, and the second cylinder tube end is referred to as the base-side cylinder tube end. The first laser ring weld seam is thus arranged between the guide closure part and the guide-side cylinder tube end, and the second laser ring weld seam is arranged between the base closure part and the base-side cylinder tube end.

[0052] The piston unit in the differential working cylinder comprises a piston and a piston rod. For the structure of the piston unit thus formed, reference is made to the descriptions of the working cylinder presented above.

[0053] The piston of the piston unit is arranged in the cylinder interior and thus divides the cylinder interior into a piston crown working chamber, also referred to as the piston crown chamber for short, and a piston rod working chamber, also referred to as the piston rod chamber for short. The effective area of ​​the piston in the piston crown chamber is larger on the piston crown side of the piston than on the piston rod chamber side. At the same pressure of the pressure medium, a greater force acts on the piston on the piston crown chamber side than on the piston rod chamber side. A force acting on the piston is transferred from the cylinder interior to the outside by means of the piston rod, for which the piston rod slides through the guide closure part.

[0054] In a second particularly preferred embodiment of the working cylinder according to the invention, the working cylinder is also a double-acting working cylinder; however, here it is designed as a synchronous cylinder.

[0055] In the double-action cylinder according to this advantageous development, the first closure part is designed as a guide closure part, as in a differential cylinder. Furthermore, as a special feature, the second closure part is also designed as a further guide closure part. The guide closure part and the further guide closure part are collectively referred to below as the guide closure parts. The first laser ring weld seam is thus arranged between the guide closure part and the first cylinder tube end, and the second laser ring weld seam is arranged between the further guide closure part and the second cylinder tube end.

[0056] Here, too, the piston unit comprises a piston and a piston rod. The piston is arranged in the cylinder interior and divides it into a first and a second piston rod working chamber. To this end, the piston rod extends axially beyond the piston on both sides and is guided out of the piston interior through the closure parts, both of which are guide closure parts in this case. Thus, the piston rod slides through both guide closure parts.

[0057] Both piston rod working chambers have the same cross-section, providing the same effective contact surfaces for the pressure medium on both sides of the piston. The force acting on the piston and the length of the piston's travel are the same, regardless of whether a specific pressure flow of the pressure medium, with the same pressure and volume, acts on the first or the second piston rod working chamber. Because of this identical behavior in both actuation directions, the synchronized cylinder is often used as a steering cylinder and is therefore also referred to as a steering cylinder. In another embodiment, the working cylinder is designed as a plunger cylinder. This is a single-acting working cylinder.

[0058] According to this refinement, the first closure part is designed as a guide closure part, and the second closure part is designed as a base closure part. The first cylinder tube end is a guide-side cylinder tube end, and the second cylinder tube end is a base-side cylinder tube end. As with a differential working cylinder, the first laser ring weld is thus arranged between the guide closure part and the guide-side cylinder tube end, and the second laser ring weld is arranged between the base closure part and the base-side cylinder tube end.

[0059] The piston unit in the plunger cylinder is formed by a plunger piston. The plunger piston is arranged in the cylinder interior. Only one working chamber is formed in the cylinder interior. The plunger piston slides through the guide closure part. When the working chamber is subjected to a pressure flow of the pressure medium, the plunger piston is axially displaced in proportion to the volume of the pressure flow introduced and executes an extension movement. The retraction movement is caused by an external force acting in the opposite direction.

[0060] According to the invention, the working cylinder is characterized in that a first circumferential sealing ring is arranged in the cylinder interior between the first closure part and an inner wall of the cylinder tube at the first cylinder tube end thereof, axially spaced from the first laser ring weld seam, which forms a first pressure-separated ring section which is arranged between the first circumferential sealing ring and the first laser ring weld seam and / or that a second circumferential sealing ring is arranged in the cylinder interior between the second closure part and an inner wall of the cylinder tube at the second cylinder tube end thereof, axially spaced from the second laser ring weld seam, which forms a second pressure-separated ring section which is arranged between the second circumferential sealing ring and the second laser ring weld seam.

[0061] According to the invention, a circumferential sealing ring is positioned in front of at least one laser ring weld seam. Preferably, a circumferential sealing ring is positioned in front of each of the laser ring weld seams. The circumferential sealing ring is also referred to below as an O-ring.

[0062] The O-ring forms a pressure-tight seal between a ring section in front of the respective laser ring weld and the rest of the cylinder interior. It was surprisingly discovered that by forming a laser ring weld, the heat energy per unit length can be set so low that a thermally sensitive O-ring is not damaged even in the immediate vicinity of the laser ring weld. The immediate vicinity is defined as an axial distance between the laser ring weld and the O-ring that is less than the inner diameter of a cylinder tube and, more preferably, no more than four times the wall thickness of a cylinder tube.

[0063] The O-ring ensures that the ring section is separated from the working pressure of the pressure medium. This means that an axial section of the cylinder tube immediately in front of and at the laser ring weld seam is not subjected to the working pressure of the pressure medium from the inside and is therefore not subject to buckling stress. This advantageously prevents the otherwise occurring radial load on the laser ring weld seam using a very simple method. Instead, only the axial load exists. The axial load is based on the working pressure of the pressure medium acting on the base area of ​​the respective closure part. This advantageously prevents multi-axial loading of the laser ring weld seam and multi-axial material stress there.

[0064] At the same time, the upstream O-ring protects at least one working chamber, or depending on the type of working cylinder with O-rings on both sides, both working chambers, from contamination. Any emissions during laser welding or particles that could detach from the coupling partners in the area of ​​the laser weld seam are retained by the O-ring in the respective ring section before they enter the working chamber.

[0065] According to another advantageous development, the laser ring weld seams have a laser ring weld seam depth which is in a ratio of 1.1 to 2.5 to a cylinder tube wall thickness.

[0066] If the laser ring weld seam does not run vertically through the cylinder tube wall, the depth of the laser ring weld seam is greater than the thickness of the cylinder tube wall. This results in a particularly advantageous, higher-strength connection between the closure parts, as the force transmission in the weld seam is distributed over a larger area, thus optimizing the weld.

[0067] A further advantage is that the wall thickness of the cylinder tube can be further reduced for certain applications.

[0068] Furthermore, according to this advantageous development, it is also possible to make the laser ring weld depth greater than the cylinder tube wall thickness by inserting the laser ring weld deeper into the closure part than the cylinder tube is thick. This results in a deeper weld root. Preferably, the laser ring weld depth is at least 1.2 times the cylinder tube thickness. It was surprisingly found that the structural changes thus induced in the closure part result in an increase in the load-bearing capacity of the ring welds.

[0069] In general, the various advantageous developments of the laser ring weld seam design are not limited to specific cylinder types. Furthermore, different laser ring weld seam designs can be combined on one and the same working cylinder, provided the resulting working cylinder falls within the scope of protection defined by the following claims. II

[0070] The invention is illustrated by way of example with reference to Fig. 1 Double-action cylinder (overview), which is not covered by the claims Fig. 2 Enlarged section of Fig. 1 to show the concave recording contour Fig. 3Enlarged section of Fig. 1 in exploded view Fig. 4Enlargement of a laser weld seam to show the cross section and the ring weld angle beta explained in more detail.

[0071] Fig. 1 shows an embodiment in which the working cylinder is designed as a double-action working cylinder. In the double-action working cylinder, both closure parts 3, 4, i.e., the first closure part 3 and the second closure part 4, are designed as guide closure parts. The piston 5a is arranged in the axially central region of the piston rod 5b, which is guided by both closure parts 3, 4. Piston 5a and piston rod 5b together form the piston 5.

[0072] The first cylinder tube end 6 is connected to the first closure part 3 by means of the negatively inclined first laser weld seam 9 and the second cylinder tube end is connected to the second closure part 4 by means of the negatively inclined second laser weld seam 10.

[0073] The two closure parts 3, 4 each have a concave receiving contour 19 into which the obliquely formed annular surfaces of the respective cylinder tube ends 6, 7 are inserted and welded there by means of the laser welding process.

[0074] In Fig. 2 is the embodiment from Fig. 1 shown in more detail in an enlargement

[0075] The second cylinder ear end 7 is already inserted into the wedge-shaped concave receiving contour 19 and welded to the second closure part 4 by means of the second circumferential laser ring weld seam 10.

[0076] The ring weld center axis 13 and the main longitudinal axis 14 enclose the ring weld inclination angle alpha.

[0077] According to the invention, the ring weld angle alpha has an angle between 110 and 160 degrees, in the exemplary embodiment of approximately 120 degrees.

[0078] In Fig. 3 the coupling partners are in accordance with Fig. 1 additionally shown in a schematic exploded view. Fig. 1 shows the first cylinder tube end 6 and the first closure part 3 with the wedge-shaped concave receiving contour 19 before joining. The concave receiving contour 19 is designed such that it can accommodate the first cylinder tube end 6 and forms a common contact surface with it, on which the first laser ring weld seam 9 is then arranged. Fig. 3 shows that the concave receiving contour 19 opens axially in the direction of the cylinder tube 2. Buckling forces acting radially from the inside onto the cylinder tube 2 are thus positively absorbed by a radial overlap 20. This is the radially outer section of the concave receiving contour 19.

[0079] In Fig. 4 A laser weld seam is shown enlarged. The first laser ring weld seam 9 shown here, between the first cylinder tube end 2 and the first closure part 3, exemplifies a laser weld seam according to the present invention.

[0080] This first laser ring weld 9 has a ring weld depth 11 and a ring weld center axis 13. In this design, the ring weld depth 11 is greater than the cylinder tube wall thickness 12.

[0081] The laser weld seam has a slight conicity. If two tangents are placed on the edge contour of the laser weld seam, they intersect and enclose a ring weld seam angle beta. The ring weld seam angle beta is preferably no more than 15 degrees and particularly preferably no more than 10 degrees. The ring weld seam center axis 13 is simultaneously the angle bisector of the ring weld seam angle beta and, together with the main longitudinal axis 14, encloses the ring weld seam inclination angle alpha. Furthermore, the ring weld seam center axis 13 runs along the contact surface of the first cylinder tube end 6 and the first closure part 3. In this embodiment, the ring weld seam inclination angle alpha is 120 degrees.

[0082] At the same time, Fig. 4 an embodiment with a circumferential sealing ring 17 (O-ring) arranged upstream of the first laser ring weld seam 9, which seal separates the area upstream of the first laser ring weld seam 9 from the pressure medium in a pressure-tight manner. This area is the pressure-separated ring section 18. Viewed axially, the pressure-separated ring section 18 is located between the sealing ring 17 (O-ring) and the first laser ring weld seam 9. In this ring section 18, no radial forces act from the inside on the cylinder tube at its first cylinder tube end 6. The first laser ring weld seam 9 is therefore only subjected to an axial tensile stress. This means that in this area the cylinder bore 2 is not subjected to buckling forces and the first laser ring weld seam 9 is relieved. In this embodiment, the sealing ring 17 (O-ring) is made of an elastic polymer.The heat input during laser welding remains sufficiently low to avoid damage to the sealing ring 17 (O-ring) despite the proximity to the first laser ring weld seam 9. At the same time, . Fig. 4 combined with Fig. 3 It can be seen that due to the narrow design of the laser ring weld seams 9, 10 according to the invention, the material in the area of ​​the radial overlap 20 is only thermally stressed to a small depth, so that the corresponding closure part only needs to have a small material thickness at the radial overlap 20. Reference symbols used

[0083] 1Working cylinder 2Cylinder barrel 3First closure part 4Second closure part 5Piston unit 5aPiston 5bPiston rod 6First cylinder barrel end 7Second cylinder barrel end 8Cylinder interior 8aFirst working chamber 8bSecond working chamber 9First circumferential laser ring weld 10Second circumferential laser ring weld 11Ring weld depth 12Cylinder barrel wall thickness 13Ring weld center axis 14Main longitudinal axis 15Seal 16Guide 17Circular sealing ring 18Pressure-separated ring section 19Concave receiving contour 20Radial overlap αRing weld inclination angle alpha βRing weld angle beta

Claims

1. A working cylinder (1), comprising a cylinder tube (2) with a main longitudinal axis, a first closure part (3), a second closure part (4) and a piston unit (5), wherein the cylinder tube (2) comprises a first cylinder tube end (6) and a second cylinder tube end (7), wherein the first closure part (3) is arranged at the first cylinder tube end (6), wherein the second closure part (4) is arranged at the second cylinder tube end (7), wherein the cylinder tube (2) and the closure parts (3, 4) form a cylinder interior (8), wherein the piston unit (5) is arranged in the cylinder interior (8) such that it is axially displaceable along the main longitudinal axis and forms at least one working chamber in the cylinder interior (8), wherein the piston unit (5) slidingly passes through the first closure part (3), wherein the first closure part (3) is connected to the cylinder tube (2) by means of a first circumferential laser ring weld seam (9) and the second closure part (4) is connected to the cylinder tube (2) by means of a second circumferential laser ring weld seam (10) in a positive-substance manner, wherein each of the laser ring weld seams (9, 10) forms a fluid-tight sealing plane (10), characterized in that at least one closure part (3, 4) comprises an axially opening, circumferential concave receiving contour in which the cylinder tube engages, wherein the receiving contour radially engages over the cylinder tube, and that a ring weld seam centre axis (13) and the main longitudinal axis (14) enclose a ring weld seam inclination angle (alpha) which is 110 to 160 degrees, and that a first circumferential sealing ring (17) is arranged, axially spaced from the first laser ring weld seam (9), in the cylinder interior (8) between the first closure part (3) and a cylinder tube inner wall of the cylinder tube (2) at its first cylinder tube end (6) and forms a first pressure-separated ring section (18) which is arranged between the first circumferential sealing ring (17) and the first laser ring weld seam (9), and / or that a second circumferential sealing ring is arranged, axially spaced from the second laser ring weld seam (10), in the cylinder interior (8) between the second closure part (4) and a cylinder tube inner wall of the cylinder tube (2) at its second cylinder tube end (7) and forms a second pressure-separated ring section which is arranged between the second circumferential sealing ring and the second laser ring weld seam (10).

2. The working cylinder according to claim 1, characterized in that the working cylinder (1) is designed as a double-acting and differential working cylinder, wherein the first closure part (3) is designed as a guide closure part and the second closure part (4) is designed as a bottom closure part, wherein the first cylinder tube end (6) is a guide-side cylinder tube end and the second cylinder tube end (7) is a bottom-side cylinder tube end, wherein the piston unit (5) comprises a piston (5a) and a piston rod (5b), wherein the piston (5a) is arranged in the cylinder interior (8) and divides the cylinder interior (8) into a first working chamber (8a), designed as a piston rod working chamber, and into a second working chamber (8b), designed as a piston bottom working chamber, and wherein the piston rod (5b) slidingly passes through the guide closure part (3).

3. The working cylinder (1) according to claim 1, characterized in that the working cylinder (1) is designed as a double-acting and differential working cylinder, wherein the first closure part (3) is designed as a guide closure part and the second closure part (4) is designed as a further guide closure part, wherein the piston unit (5) comprises a piston (5a) and a piston rod (5b), wherein the piston (5a) is arranged in the cylinder interior (8) and separates the cylinder interior (8) into a first working chamber (8a), designed as a first piston rod working chamber, and a second working chamber (8b), designed as a second piston rod working chamber, and wherein the piston rod (5b) slidingly passes through the guide closure part and through the further guide closure part.

4. The working cylinder according to claim 1, characterized in that the working cylinder (1) is designed as a single-acting and plunger cylinder, wherein the first closure part (3) is designed as a guide closure part and the second closure part (4) is designed as a bottom closure part, wherein the first cylinder tube end (6) is a guide-side cylinder tube end and the second cylinder tube end (7) is a bottom-side cylinder tube end, wherein the piston unit (5) is designed as a plunger piston, wherein the plunger piston is arranged in the cylinder interior (8) and forms a working chamber in the cylinder interior (8), and wherein the plunger piston slidingly passes through the guide closure part (3).

5. The working cylinder according to claim 1, characterized in that each of the laser ring weld seams has a ring weld seam depth (11), wherein the ring weld seam depth (11) has a ratio of 1.1 to 2.5 with respect to a cylinder tube wall thickness (12).