WORK CYLINDER

Description

[0001] The invention relates to a welded working cylinder.

[0002] Working cylinders are known as such from the state of the art in various designs.

[0003] All such working cylinders comprise a cylinder barrel and locking components. According to the state of the art, such working cylinders are usually manufactured by screwing the locking components to the cylinder barrel. These working cylinders are therefore also referred to as screw cylinders in the state of the art.

[0004] Furthermore, it is 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.

[0005] The thread of the cylinder barrel and closure parts is usually produced by a machining process.

[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] From a manufacturing perspective, it should be noted 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 fluid's operating pressure. This disadvantageously leads to increased material consumption and a higher final weight of the differential cylinder.

[0008] The machining processes used to produce the thread also require a high level of precision and are therefore very demanding to manufacture.

[0009] Furthermore, to ensure that the cylinders are leak-tight, an additional seal must be regularly inserted between the cylinder tube and the respective closure part.

[0010] Furthermore, final assembly requires a lot of time and skilled workers.

[0011] Another disadvantage is that additional means must be provided to prevent the screw connection from loosening. Finally, the changing operating pressures place dynamic loads on the threads, which limit their service life.

[0012] DE 40 41 992 A1 proposes using a drawn hollow profile as the cylinder tube and inserting a cover and base as the closure parts in alignment, and welding them together in a ring-shaped manner in the fitting gap without filler metal. The disadvantage of this approach is that the weld seam is subjected to considerable stress due to buckling forces.

[0013] Another solution is described in DE 10 2007 004 666 A1 for a gas spring. The locking parts are inserted into a cylinder bore. They have a protruding rim, which, together with the annular end faces of the cylinder bore, forms a radially directed fit gap, which is then laser-welded. Due to the intended application, this is a coupling designed only for low loads.

[0014] Document US 2004 143953 A1 discloses the integral coupling of a closure part to a cylinder barrel of a hydraulic working cylinder by means of a weld seam. The weld seam is formed as a solid weld seam with filler metal, which is disadvantageous due to high heat input, which places significant stress on thermally sensitive parts.

[0015] Furthermore, EP 3 260 705 A1 also discloses a closure part arranged on a cylinder tube, which is welded by a radially directed weld seam. The disadvantage is that the weld seam is subject to both tensile and shear stress.

[0016] 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.

[0017] The problem is solved by the features listed in patent claim 1. Preferred developments arise from the subclaims.

[0018] According to the invention, the working cylinder comprises 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.

[0019] The working cylinder according to the invention, formed from these basic components, can be available in various designs. In particular, the working cylinder can be a differential working cylinder, a plunger cylinder, a synchronized cylinder, a telescopic cylinder, a pull cylinder, or even a pneumatic working cylinder. If the working cylinder is designed as a synchronized 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.

[0020] 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 actuation 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 actuation directions. With the result that double-acting cylinders are used particularly 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.

[0021] The cylinder tube is formed as a hollow cylinder in a conventional manner and, according to the invention, 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. Thus, the two cylinder tube ends preferably have beveled axial end faces, with the bevels having the same angle. The axial end faces thus preferably have the same cross-sectional area.

[0022] However, it is also possible to design the cylinder tube ends differently.

[0023] 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 that accommodates a piston unit in a sliding and sealing manner. For example, in a differential cylinder, the piston unit can consist of a piston and a piston rod, with the piston rod then being accommodated by the guide closure part. In a plunger cylinder, the piston unit is a volume-forming piston, also referred to as a plunger piston, which is accommodated by the guide closure part.

[0024] The first closure part is designed such that it has a contact surface which, when placed against the first cylinder tube end, rests 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 results in a continuous annular surface against which the first closure part rests against the first cylinder tube end. If the annular surface is inclined, it is geometrically present as a truncated cone surface. For simplicity, this surface will be referred to below simply as the annular surface, regardless of its geometric design.

[0025] 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.

[0026] 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 has 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.

[0027] 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.

[0028] 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.

[0029] If the working cylinder according to the invention is, for example, in the form of a differential working cylinder, the following also applies.

[0030] The piston of the piston unit is arranged in the cylinder interior and separates the cylinder interior into a piston crown working chamber, hereinafter also referred to as piston crown chamber, and a piston rod working chamber.

[0031] The piston crown chamber is located between the piston and the second closure part, designed here 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, designed here 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.

[0032] The piston is axially movable and is arranged in the cylinder interior in such a way that the main longitudinal axes of the piston and cylinder barrel overlap.

[0033] The pressure medium connections are arranged on the working cylinder in such a way that the piston crown working chamber and the piston rod working chamber can be pressurized with an operating pressure.

[0034] 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.

[0035] According to the invention, the piston rod slidably passes through the first closure part, here designed as a guide closure part.

[0036] 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.

[0037] The first closure part is integrally connected to the cylinder tube by means of a first circumferential laser ring weld. 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 below as the coupling partners.

[0038] 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.

[0039] 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.

[0040] The two laser ring welds each form a fluid-tight sealing plane. This means that the first laser ring weld prevents pressure medium from passing through the connection point between the cylinder tube and the first closure part, and the second ring weld prevents pressure medium from passing through the cylinder tube and the second closure part, without the need for additional sealing means, such as a sealing ring.

[0041] 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 metal alloy of the cylinder 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.

[0042] 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.%.

[0043] The working cylinder is further characterized in that the laser ring weld seams (9, 10) each have a ring weld seam center axis (13), wherein the ring weld seam center axis (13) encloses a ring weld seam inclination angle alpha (α) with a main longitudinal axis (14) of the cylinder tube (2), wherein alpha (α) is 20 to 70 degrees, and in that in the cylinder interior between the first closure part and a cylinder tube inner wall of the cylinder tube at the first cylinder tube end thereof, axially spaced from the first laser ring weld seam, a first circumferential sealing ring is arranged, 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 in the cylinder interior between the second closure part and a cylinder tube inner wall of the cylinder tube at the second cylinder tube end thereof, a second circumferential sealing ring is arranged, 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.

[0044] According to this refinement, 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 as an O-ring.

[0045] 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.

[0046] The O-ring ensures that the ring section is separated from the working pressure of the pressure medium. The ring section is therefore an axial section of the cylinder tube immediately in front of and on the laser ring weld seam, which is not subjected to the working pressure of the pressure medium from the inside and is therefore not subject to buckling loads. 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 avoids multi-axial loading of the laser ring weld seam and multi-axial material stress there.

[0047] 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.

[0048] According to the invention, the laser ring welds have an inclined laser ring weld center axis. According to the invention, the laser ring weld center axis encloses a laser ring weld inclination angle alpha α with a main longitudinal axis of the cylinder tube, where alpha α is between 20 degrees and 70 degrees. The laser ring weld center axis runs centrally through the laser ring weld and divides its cross-section into equal parts. If the laser ring weld center axis is extended to the main longitudinal axis of the cylinder tube, which runs centrally and longitudinally of the cylinder tube, it forms an angle with the main longitudinal axis. This angle is the laser ring weld inclination angle alpha α. The laser ring weld inclination angle alpha α is between 20 degrees and 70 degrees, whereby the laser ring weld depth is produced with a ratio of 1.1 to 2.5 to the cylinder tube wall thickness.Due to the larger laser ring weld depth and the adjusted ring weld center axis, the forces are better distributed during loading due to the angle and area of ​​the acting forces.

[0049] The welded working cylinder according to the invention has a number of significant advantages over working cylinders according to the state of the art.

[0050] A first significant advantage is that the cylinder barrel, in particular, requires little or no machining beyond cutting to length. This means that no threads need to be cut or grooves turned. In a welded piston unit, this also applies to the piston rod.

[0051] This has the immediate advantage that the time, processing machines, tool costs and energy that would otherwise be required for machining can be saved.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The working cylinder according to the invention also has advantages in manufacturing. In particular, it is possible to weld both closure parts because, unlike the prior art, access to the cylinder interior is no longer required after welding. This is based, firstly, on the fact that the laser welding process only results in very localized heating of the material in the area of ​​the laser ring welds. This means that components made of thermally sensitive materials, such as seals in particular, can still be welded within a few millimeters of the planned weld seam, which would be damaged with other welding processes. In addition, scaling on the inner surface sections of the cylinder barrel and the closure parts, particularly near the welds, is avoided, which would otherwise have to be laboriously removed using the prior art.Secondly, this is based on the fact that any material emissions from the area of ​​the laser ring weld are retained in the annular space by the upstream O-ring.

[0058] Preferably, the working cylinder according to the invention also makes it possible to weld both closure parts in one operation.

[0059] 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.

[0060] 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.

[0061] Another particularly advantageous feature is a particularly long service life, as the laser ring weld seams are largely protected from dynamic radial loads caused by the varying working pressure of the pressure medium and thus from multiaxial stresses by the O-ring in front. Since exclusively axial loads are advantageous, a significantly higher number of load cycles and thus a significantly longer service life can be achieved with the same dimensions.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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, and a piston rod working chamber, also referred to as the piston rod chamber. 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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 double-action cylinder is often used as a steering cylinder and is therefore also referred to as a steering cylinder.

[0070] According to another development, the working cylinder is designed as a plunger cylinder. This is a single-acting working cylinder.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] If the laser ring weld seam does not run vertically through the cylinder tube wall, the laser ring weld seam depth is greater than the thickness of the cylinder tube wall.

[0075] The connection between the closure parts is particularly advantageous in terms of greater stability, as the force transmission in the weld seam is distributed over a larger area and thus optimized.

[0076] A further advantage is that the wall thickness of the cylinder tube can be further reduced for certain applications.

[0077] The invention is illustrated by way of example with reference to Fig. 1Differential working cylinder (overview) Fig. 2Enlarged section of the guide-side cylinder tube end showing the sealing ring and the ring section Fig. 3Enlarged section of the guide-side cylinder tube end showing the ring weld angle Fig. 4Enlargement of a non-inventive laser weld to show the cross section and the ring weld angle beta Fig. 5Plunger cylinder with a non-inventive 90 degree weld and upstream O-ring Fig. 6Enlarged section of Fig. 5 to show the O-ring and the ring section Fig. 7Schematic representation of a bottom closure part not according to the invention with 0 degree weld seam explained in more detail.

[0078] Fig. 1 shows an overview of an embodiment of the working cylinder 1 as a differential working cylinder. The working cylinder 1 comprises the cylinder tube 2, the first closure part 3, designed here as a guide closure part, the second closure part 4, designed here as a base closure part, and the piston unit 5. The piston unit 5 consists of the piston 5a and the piston rod 5b.

[0079] In this embodiment, the piston rod-side fastening module 15 is arranged on the piston rod 5b, and the bottom-side fastening module 17 is arranged on the second closure part 4, designed as a bottom closure part. Fastening bolts 15a, 17a are assigned to each of the two fastening modules 15, 17. The fastening modules 15, 17 and the fastening bolts 15a, 17a are not part of the invention and are shown merely for clarity. The piston unit 5 is arranged in the cylinder interior 8 with respect to the piston 5a and with sections of the piston rod 5b, wherein the piston rod 5b slidably passes through the first closure part 3, designed as a guide closure part.The first closure part 3, designed as a guide closure part, closes the cylinder tube 2 at the first cylinder tube end 6, here the guide-side cylinder tube end, and the second closure part 4, designed as a base closure part, closes the second cylinder tube end 7, here the base-side cylinder tube end. In this embodiment, the two closure parts 3, 4 are designed such that they have a cylindrical section that projects precisely into the cylinder tube. The two cylinder tube ends 6, 7 are chamfered and thus have a larger contact surface with the two closure parts 3, 4. The laser ring welds 9, 10 run along the contact surfaces, with the first laser ring weld 9 connecting the first closure part 3 to the first cylinder tube end 6, and the second laser ring weld 10 connecting the second closure part 4 to the second cylinder tube end 7. The laser ring welds 9, 10 each form a fluid-tight sealing plane.In addition, a circumferential sealing ring 21 is arranged in an annular groove (without reference symbol) of the first closure part 3, axially upstream of the first laser ring weld seam 9 in the direction of the cylinder center. Viewed axially, the annular section 22, here the first annular section, is located between the sealing ring 21 and the laser ring weld seam 9.

[0080] The main longitudinal axis 14 of the cylinder tube 2 runs centrally and longitudinally through the working cylinder 1.

[0081] Fig. 2 shows an enlarged section of the area of ​​the first laser ring weld 9. Here, the circumferential sealing ring 21 is shown in particular in its positional relationship to the cylinder tube 2, the first closure part 3 and the first laser ring weld 9. The circumferential sealing ring 21 is embedded in a circumferential outer ring groove of the first closure part 3. It seals the area up to the first laser ring weld 9 in a pressure-tight manner from the rest of the cylinder interior 8. The vertically drawn arrows symbolize the forces of the pressure medium acting radially from the inside on the cylinder tube 2, wherein the ring section 22 is excluded from this radial force due to the pressure-tight separation by means of the circumferential sealing ring 21.

[0082] In Fig. 3 An enlargement of the area of ​​the first cylinder tube end 6 is shown. This is, as in Fig. 2 around the guide-side cylinder tube end. Here, the geometric relationships of the first circumferential laser ring weld seam 9 are particularly illustrated. During welding, in this embodiment, the first circumferential laser ring weld seam 9 is created with a laser along the ring weld seam center axis 13. This runs along the contact surface between the first cylinder tube end 6 and the first closure part 3. For this purpose, a previously assembled and temporarily fixed subassembly comprising the cylinder tube 2, the first closure part 3, the second closure part 4, the piston unit 5, and the two fastening modules 15, 17 is preferably rotated around the main longitudinal axis of the cylinder tube 14 and in front of a laser inclined by the ring weld seam inclination angle alpha.

[0083] The ring weld seam center axis 13 runs centrally through the first circumferential laser ring weld seam 9 and, in its extension with the main longitudinal axis of the cylinder tube 14, encloses the ring weld seam inclination angle alpha α. The ring weld seam depth 11 is the length of the ring weld seam center axis 13, which runs in the actual laser ring weld seam 9. Due to the angulation, the ring weld seam depth 11 is longer than the cylinder tube wall thickness 12. The ring weld seam depth corresponds to the hypotenuse of a right-angled triangle formed by the ring weld seam, the cylinder tube wall thickness 12, and a perpendicular. This illustration also shows the first fastening module weld seam 16 between the piston rod-side fastening module 15 and the piston rod 5b. This is produced using the same laser welding process as the first circumferential laser ring weld seam 9.

[0084] Furthermore, the sliding bearing of the piston rod 5b in the first closure part 3 designed as a guide closure part with guide 20 and seal 19 is also shown.

[0085] In Fig. 4 A laser weld seam not according to the invention is shown enlarged. The first laser weld seam 9 shown here, between the first cylinder tube end 2 and the first closure part 3, shows an example of a laser weld seam.

[0086] This first laser weld seam 9 has a ring weld seam depth 11 and a ring weld seam center axis 13. In this design, the ring weld seam depth 11 is greater than the cylinder tube wall thickness 12.

[0087] The laser weld seam exhibits 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 β. The ring weld seam center axis 13 is simultaneously the bisector of the ring weld seam angle beta β and, together with the main longitudinal axis 14, encloses the ring weld seam inclination angle alpha α. 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 design, the ring weld seam inclination angle alpha is 90 degrees.

[0088] In Fig. 5 an embodiment of a working cylinder not according to the invention, which is designed as a plunger working cylinder, is shown. Here, the piston unit 5, which is designed as a plunger piston, is guided in the cylinder tube 2. In addition, the piston unit 5 is guided in the first closure part 3, which is designed as a guide closure part. For this purpose, the plunger cylinder has the guides 20. The guide closure part is connected to the cylinder tube 2 at its first cylinder tube end 6 by means of the first laser ring weld seam 9. Opposite the guide closure part, the second closure part 4, designed here as a base closure part, is connected to the cylinder tube 2 at the second cylinder tube end 7 by the second laser ring weld seam 10. In this embodiment, both laser ring weld seams 9, 10 have a ring weld seam inclination angle of 90 degrees.

[0089] In addition, the provisions in Fig. 1 Reference symbols and description contents listed for a differential working cylinder.

[0090] The plunger working cylinder in the embodiment according to Fig. 5 also has an additional first circumferential sealing ring 21 on the first closure part 3. This additional sealing ring 21 is also referred to as an O-ring and is arranged radially between the cylinder bore 2 and the first closure part 3 and provides a pressure-tight seal that separates the second circumferential laser ring weld seam 10 from the pressure medium in a pressure-tight manner.

[0091] In Fig. 6 the area of ​​the sealing ring 21 (O-ring) on ​​the first closure part 3 is made of Fig. 5 shown enlarged. The sealing ring 21 (O-ring) is shown in more detail here and is located in spatial proximity to the first circumferential laser ring weld seam 9. In this design, the sealing ring 21 (O-ring) is made of an elastic polymer. The heat input during laser welding remains sufficiently low so as not to damage the sealing ring 21 (O-ring) despite the close proximity to the first laser ring weld seam 9. Viewed axially, there is a pressure-separated ring section 22 between the sealing ring 21 (O-ring) and the first laser ring weld seam 9. In this pressure-separated ring section 22, the operating pressure of the pressure medium is not applied on the inside of the cylinder tube, so that no radial forces from the pressure medium act on the cylinder tube 2 in this area. This means that the cylinder bore 2 is not subjected to buckling forces in this area and the first laser ring weld seam 9 is relieved.

[0092] In this design, the ring weld center axis 13 runs perpendicular to the main longitudinal axis 14 of the working cylinder 1.

[0093] Fig. 7 shows a schematic representation of a section of an embodiment not according to the invention, in which the second circumferential laser ring weld seam 10 runs parallel to the main longitudinal axis.

[0094] The second closure part 4, designed as a bottom closure part, is radially encompassed by the second cylinder tube 2. In this exemplary embodiment, the second closure part 4 and the annular surface of the cylinder tube 2 form a common end face. However, it is also possible for one of the coupling partners to protrude or recess axially relative to the other coupling partner.

[0095] The ring weld center axis 13 does not intersect the main longitudinal axis 14. The ring weld inclination angle alpha α is 0 degrees. The second circumferential sealing ring 23 forms an axial section up to the weld root of the second laser ring weld 10, which is the second pressure-separated ring section 24. The second circumferential sealing ring 23 and the second pressure-separated ring section 24 are designed in the same way as the first circumferential sealing ring 21 and the first pressure-separated ring section 22, so that the descriptions there also apply here accordingly. Reference symbols used

[0096] 1 Working cylinder 2 Cylinder barrel 2a Further cylinder barrel 3 First closure part 3a Further closure part 4 Second closure part 5 Piston unit 5a Piston 5b Piston rod 6 First cylinder barrel end 7 Second cylinder barrel end 8 Cylinder interior 8a Piston crown working chamber 8b Piston rod working chamber 9 First circumferential laser ring weld 10 Second circumferential laser ring weld 11 Ring weld depth 12 Cylinder barrel wall thickness 13 Ring weld center axis 14 Main longitudinal axis 15 Piston rod-side fastening module 15a Fastening bolt of the piston rod-side fastening module 16 First fastening module weld 17 Bottom-side fastening module 17a Fastening bolt of the bottom-side fastening module 18 Second fastening module weld 19 Seal 20Guide 21First circumferential sealing ring 22First pressure-separated ring section 23Second circumferential sealing ring 24Second pressure-separated ring section αRing weld 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 axially displaceable along the main longitudinal axis in the cylinder interior (8) 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 in a positive substance manner 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), wherein the laser ring weld seams (9, 10) each form a fluid-tight sealing plane, characterized in that the laser ring weld seams (9, 10) each have a ring weld seam centre axis (13), wherein the ring weld seam centre axis (13) and a main longitudinal axis (14) of the cylinder tube (2) enclose a ring weld seam inclination angle alpha (a), wherein alpha (a) is 20 to 70 degrees, and that a first circumferential sealing ring (21) is arranged 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), axially spaced from the first laser ring weld seam (9), and forms a first pressure-separated ring section (22) which is arranged between the first circumferential sealing ring (21) and the first laser ring weld seam (9), and / or a second circumferential sealing ring (23) is arranged 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), axially spaced from the second laser ring weld seam (10), and forms a second pressure-separated ring section (24) which is arranged between the second circumferential sealing ring (23) and the second laser ring weld seam (10).

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

4. The working cylinder (1) according to claim 1, characterized in that the working cylinder (1) is single-acting and designed as a 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 base-side cylinder tube end, wherein the piston unit (5) is formed by 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 (1) according to one of the preceding claims, characterized in that the laser ring weld seams each have a ring weld seam depth (11), wherein the ring weld seam depth (11) has a ratio of 1.1 to 2.5 to a cylinder tube wall thickness (12).