Actuating cylinder and manufacturing method of said actuating cylinder

Abstract

The present invention relates to an actuating cylinder having a cylinder 1 with a cylinder tube 3 and further having a piston unit 2, the cylinder 1 having a closure part 4a and a connecting part 7a with a cylinder tube end portion 5a, the cylinder tube end portion 5a having a threaded cylinder tube portion 5.1a, a cylinder tube intermediate portion 5.2a and a cylinder tube end portion 5.3a, the closure part 4a having an external thread 8a, the threaded cylinder tube portion 5.1a having an internal thread 9a corresponding to the external thread 8a, the external thread 8a and the internal thread 9a being connected to the closure part 4a. The closure part 4a and the cylinder tube 3 form a common threaded part designed to connect them with a form-fit, the cylinder tube end 5a being connected to the closure part 4a by an integral joint by a circumferential ring weld seam 10a, the ring weld seam 10a being designed as a ring weld seam produced by a laser and forming a sealing surface that is hermetic against pressure media, in an operating condition under relaxed load the common threaded part does not absorb axial tensile forces, and in an operating condition under load the ring weld seam 10a and the common threaded part each absorb axial tensile forces. The invention further relates to a method for the manufacture of such a cylinder.

Description

[Technical Field]

[0001] The present invention relates to actuation cylinders, in particular to hydraulic actuation cylinders. Furthermore, the present invention relates to a method for manufacturing such actuation cylinders. [Background technology]

[0002] Such actuating cylinders are known from the prior art and typically comprise a cylinder tube, a closure part connected to the cylinder tube, and a piston unit.

[0003] In the prior art, it is known to produce such actuating cylinders, for example, by screwing a closure part onto a cylinder tube, and therefore such actuating cylinders are also known as screw-type cylinders.

[0004] Another solution known in the prior art is to weld the cylinder tube and the closure part together.

[0005] Furthermore, combination solutions are also known from the prior art, in which the base closure part is connected to the cylinder tube by MAG welding and only the guide closure part is screwed in.

[0006] The threads on the cylinder tube and closure part are usually produced by a machining process.

[0007] Threaded cylinders and cylinders in which only one closure part is threaded and the other closure part is MAG welded are provided with high quality according to the prior art and have been found to be of excellent quality.

[0008] One manufacturing-related disadvantage is that cylinder tubes, especially those with threads machined using a subtractive process, require a large material thickness, i.e., a large tube wall thickness. This is because the threads necessarily weaken the cylinder tube. However, this results in a tube wall thickness that is significantly excessive for absorbing forces during operation (especially those exerted by the fluid's operating pressure). This undesirably increases material consumption and the final weight of the actuation cylinder. Another disadvantage of screw-type actuation cylinders is that a special thread length must be provided to allow for the absorption of large axial forces from the fluid's operating pressure and from prestress during screwing. The minimum thread length also increases the length dimension, which, depending on the installation situation, can have other disadvantages besides increased material consumption. Summary of the Invention [Problem to be solved by the invention]

[0009] It is an object of the present invention to provide a highly reliable actuation cylinder that can be manufactured in a material-saving and cost-effective manner. It is also an object of the present invention to disclose a method for manufacturing such an actuation cylinder. [Means for solving the problem]

[0010] This problem is solved with respect to an actuating cylinder according to the features set forth in claim 1 and with respect to a method for manufacturing such an actuating cylinder according to the features set forth in claim 8. Preferred embodiments follow from the corresponding dependent claims.

[0011] The actuating cylinder according to the invention has as its basic element a cylinder and piston unit, which is connected in a specific manner to the cylinder tube by a special connector of at least one closure part.

[0012] According to the present invention, the cylinder has a cylinder tube, a closure part, and another closure part.

[0013] Conventionally, a cylinder tube has a cylinder tube end and another cylinder tube end, and therefore has two opposing cylinder tube ends. A closure part is arranged at the cylinder tube end, i.e., the closure part is arranged at the cylinder tube end and the other closure part is arranged at the other cylinder tube end. The cylinder tube end and the other cylinder tube end are hereinafter collectively referred to as cylinder tube ends, and the closure part and the other closure part are hereinafter collectively referred to as closure part. The cylinder tube and the closure part arranged to be attached to the cylinder tube form the cylinder interior.

[0014] As another basic element, a piston unit forms at least one working chamber inside the cylinder. Preferably, the piston unit is designed as a piston and piston rod assembly, where the piston rod slides through one of the closure parts and thus represents the guide closure part. However, the piston unit can also be in the form of, for example, a plunger-piston of a plunger-cylinder or a piston unit of a cylinder with a continuous piston rod and thus two equally large effective surfaces for extension and retraction.

[0015] In particular, the actuation cylinder according to the invention is characterized by a specially designed coupling between the cylinder tube and the closure part, which are also collectively referred to as coupling partners.

[0016] For this design, the cylinder has a connecting portion, which is formed by the closure part and the cylinder tube end portion.

[0017] The cylinder-tube end portion has a threaded cylinder-tube portion, an intermediate cylinder-tube portion, and a cylinder-tube end portion.

[0018] The closure part has external threads and the threaded cylinder tube part has internal threads that correspond to the external threads, where the external and internal threads integrally form a common threaded part and are engaged with each other within the common threaded part.

[0019] The threaded part is designed to connect the closure part and the cylinder tube in a form-fit manner and therefore in particular to absorb the axial forces resulting from the operating pressure of the pressure medium when the actuating cylinder according to the invention is used as intended.

[0020] Additionally, the cylinder tube end is connected to the closure part in an object-locking manner (integral joint) at the end of the matching body on the cylinder tube side by a circumferential ring weld seam. The ring weld seam is designed as a laser ring weld seam. The ring weld seam forms a pressure-medium-tight sealing surface. The pressure-medium-tight sealing surface separates the working chamber from the environment and prevents pressure medium leakage.

[0021] The actuating cylinder according to the invention is designed to be in an unloaded operating state or in an underload operating state.

[0022] The unloaded operating state is understood to be an operating state in which no or only a low pressure medium operating pressure is applied. According to the invention, the connecting part is designed in such a way that in the unloaded operating state, axial tensile forces are not absorbed by the common threaded part. An axial tensile force is understood to be a force directed axially distal to the closure part, i.e., directed away from the center of the cylinder.

[0023] It is a given that the male and female threads exhibit a slight axial movement relative to one another, which in the case of an actuating cylinder is also known as breathing. This slight relative axial movement is hereafter referred to as axial clearance. When tensile forces are present, the male thread of the closure part is in the distal clearance end position, and when compressive forces, i.e. forces acting in the direction of the cylinder center, are present, the male thread of the closure part is in the proximal clearance end position. Between these positions there are intermediate clearance positions. In the operating condition under reduced load, the possible axial tensile forces are absorbed only by the ring weld seam. By definition, in the operating condition under reduced load, no axial tensile forces are absorbed by the common threaded part, where neither axial force is absorbed by the common threaded part and the closure part is in the intermediate clearance position, or conversely, axial compressive forces can be absorbed.

[0024] The operating state under load is understood to be an operating state in which the full operating pressure of the pressure medium or a large operating pressure is applied. The connecting part is designed so that in the operating state under load, the ring weld seam and the common threaded part each absorb the axial tensile force. This means that a portion of the large axial tensile force acting on the closure part due to the operating pressure of the pressure medium is absorbed by the ring weld seam, and another portion is absorbed by the common threaded part. According to the invention, this force distribution is achieved by the elastic deformation of the intermediate cylinder-tube part located between the threaded cylinder-tube part and the cylinder-tube end, which is accompanied by an increase in the axial tensile force during the transition from the operating state under unloaded load to the operating state under load. This change in length within its elastic limit guides the common threaded part to the distal clearance end position, from which point on it absorbs the axial tensile force. From this point onwards the intermediate cylinder-tube section is not elastically deformed and the ring weld seam as a substance-locking coupling and the common threaded section as a form-fit coupling together participate in absorbing the axial tensile forces.

[0025] According to the present invention, the boundary between the unloaded operating state and the loaded operating state is understood to be a state in which the operating pressure of the pressure medium is so great that the common threaded portion begins to absorb part of the axial tensile force.

[0026] The solution according to the invention has in particular the advantages explained below.

[0027] A first specific advantage is that the axial tensile forces that need to be absorbed by the common threaded part as a result of the operating pressure of the pressure medium during intended use are significantly reduced by two effects according to the invention.

[0028] First, as in the case of prior art screw-type actuating cylinders, the axial prestress caused by tightening the threaded connection by pressing the ring contact surfaces of the cylinder tube and the closure part is advantageously eliminated. This axial prestress must be absorbed in addition to the force from the operating pressure, reducing the force from the operating pressure (which can be absorbed to the maximum extent in prior art screw-type cylinders). Therefore, according to the present invention, only the axial tensile force resulting from the operating pressure needs to be absorbed by the common threaded part.

[0029] Secondly, the axial tensile forces resulting from the operating pressure are additionally reduced by a portion of the force being absorbed by the ring weld seam.

[0030] This is due, as another particular advantage, to the fact that the absorption of the forces of the axial tensile loads when the operating pressure is high can be allocated on the one hand to the ring weld seam and on the other hand to the common threaded part.

[0031] This force distribution results in the common threaded section being less stressed than in prior art screw-type cylinders. This has the advantage that the common threaded section can be designed to be shorter or the cylinder tube can be designed to have a thinner wall. These options can save expensive cylinder tube material, reduce the time required to machine the threads, and even allow the size of the working cylinder to be reduced for the same stroke.

[0032] This force distribution has the added effect of reducing the stress experienced by the ring weld seam compared to prior art welded cylinders, which advantageously allows for the use of thinner-walled cylinder tubes, thus saving material and reducing the weight of the actuating cylinder.

[0033] It is particularly advantageous here that the maximum axial force acting on the ring weld seam can be set by the geometry of the intermediate cylinder-tube section, in particular the length to wall thickness ratio can be selected in an advantageous manner that reliably maintains the elastic limit and limits the maximum axial force acting on the ring weld seam.

[0034] In comparison with threaded cylinders, the need for unscrewing protection is also advantageously eliminated, which is taken over by the functional integration of the ring weld seam.

[0035] According to a first advantageous further development, the actuating cylinder according to the invention is characterized in that, in the operating state under reduced load, the intermediate cylinder-tube section has a tensile prestress and the common threaded section absorbs axial compressive forces. According to this further development, in the operating state under reduced load, the common threaded section is in the proximal clearance end position. This further development therefore provides a solution in which the elastic strain path of the intermediate cylinder-tube section is realized as long as possible. In this way, a large portion of the axial tensile forces can be transmitted via the ring weld seam.

[0036] In another advantageous development, the actuating cylinder is characterized in that the intermediate cylinder-tube section is designed such that the axial strain is within its elastic limit when changing from an unloaded operating state to a loaded operating state.

[0037] The intermediate cylinder-tube portion may also be designed, for example, with a wall taper.

[0038] Furthermore, the intermediate cylinder-tube section can also be designed to be fully or partially integrated into the threaded cylinder-tube section. In this case, the internal thread of the cylinder-tube section can preferably have a thread pitch in the distal direction that is a slightly decreasing pitch in the unstressed state and a linear pitch in the elastically strained state. According to this further development, the flank surfaces of all turns of the thread are in full contact only in the operating state under load. This advantageously achieves a further structural reduction in the length of the cylinder-tube end section. Alternatively or additionally, the external thread of the closure part can also have this design.

[0039] According to another advantageous development, the working cylinder is characterized in that the intermediate cylinder tube section has a wall taper.

[0040] Wall taper is understood to mean a reduction in the wall thickness of the cylinder tube in the region of the intermediate cylinder tube section. Advantageously, the wall thickness of the intermediate cylinder tube section is less than 60%, particularly preferably less than 40%, of the wall thickness of the remaining cylinder tube. Furthermore, the length of the intermediate cylinder tube section in the region of the wall taper is preferably at least three times, and in particularly preferred designs at least five times, the wall thickness of the cylinder tube in the region of the wall taper. The wall taper offers a surprisingly simple yet highly reliable solution for reducing the load on the ring weld seam. This is based on the fact that, under load, the intermediate cylinder tube section elastically deforms in the axial direction and transmits tensile forces to the ring weld seam. A smaller wall thickness is selected, resulting in a reduced force being transmitted at the same elastic strain.

[0041] According to another advantageous development, the actuating cylinder is characterized in that the ring weld seam has a ring weld seam depth with a ratio to the cylinder tube wall thickness of 1.1 to 2.5.

[0042] In this further development, the ring weld seam has an inclination relative to a cross section perpendicular to the main longitudinal axis, which results in a depth of the ring weld seam beyond the cylinder tube wall thickness, which, depending on the angle of inclination, is 1.1 to 2.5 times the cylinder tube wall thickness. This particularly advantageously increases the connection area and strength of the object-locking connection of the closure part to the cylinder tube at its cylinder tube end.

[0043] According to another advantageous further development, the actuating cylinder is characterized in that the ring weld seam has a ring weld seam central axis with a ring weld seam inclination angle alpha of 20 to 70 degrees relative to the main longitudinal axis of the cylinder tube.

[0044] The central axis of the ring weld seam, which is V-shaped in its cross section, is inclined relative to the transverse plane, with a ring weld seam inclination angle alpha of 20 to 70 degrees relative to the transverse plane. It has been found that on the one hand, an additional increase in strength is achieved by the inclination in this region, since it results in a favorable distribution of the components of the multiaxial loads acting on the weld seam due to tensile and buckling stresses, and on the other hand, depending on the intended force distribution, a sufficiently low energy per unit length is achieved to avoid undesired excessive heating of the intermediate cylinder-tube section during welding.

[0045] According to another further development, the actuating cylinder has at its other cylinder tube end another connecting part which is designed similarly to the connecting part according to the invention, so that the contents of the description of the connecting part according to the invention and the contents of its advantages also apply to this other connecting part.

[0046] According to another aspect, the invention relates to a method for manufacturing an actuation cylinder according to the invention.

[0047] The working cylinder produced by this method has the above-mentioned characteristics, and therefore the description sections relating to the working cylinder according to the invention also apply to the method according to the invention, with the corresponding supplements.

[0048] The method according to the invention comprises the following process steps: a) threading the cylinder tube onto the closure part using a cylinder tube end portion of the cylinder tube to establish engagement between the internal threads of the threaded cylinder tube portion and the external threads of the closure part to create a common threaded portion; b) establishing a pressure fit at the axial ring contact surface between the cylinder tube end and the closure part; c) applying a tightening torque to generate an axial compressive force to establish axial compression of the intermediate cylinder-tube portion; d) performing laser welding of the cylinder-tube ends and the closure part at the axial ring contact surface, in which the cylinder-tube ends and the closure part are thermally softened and deformed in the area close to the axial ring contact surface, and the intermediate cylinder-tube part is thermally expanded, simultaneously relieving its axial compression; e) cooling with solidification of the cylinder-tube ends and closure parts in the area near the axial ring contact surface to establish a ring weld seam and axial heat shrinkage of the intermediate cylinder-tube section;

[0049] These process steps are described in more detail below.

[0050] a) threading the cylinder tube onto the closure part using a cylinder tube end portion of the cylinder tube to establish engagement between the female threads of the threaded cylinder tube portion and the male threads of the closure part to create a common threaded portion.

[0051] In process step a), the external thread of the closure part and the internal thread of the threaded cylinder-tube part are brought into engagement with each other. Then, screwing is performed, resulting in a common threaded part. Screwing continues until the cylinder-tube end of the cylinder-tube end part contacts the closure part.

[0052] b) establishing a pressure fit at the axial ring contact surface between the cylinder tube end and the closure part;

[0053] The cylinder-tube end has a distally oriented axial cylinder-tube ring surface and the closure part has a proximally oriented axial closure part ring surface, which are opposed and are pressed against each other in process step b), so that both ring surfaces form a common ring contact surface.

[0054] c) applying a tightening torque to generate an axial compressive force to establish axial compression of the intermediate cylinder-tube portion;

[0055] In process step c), a tightening torque is applied. This simultaneously generates an axial compressive force on the ring contact surface, resulting in an increased surface pressure there. The threads are in the distal clearance end position. Continued tightening of the threaded connection compresses the intermediate cylinder-tube section axially, preferably exclusively within the elastic range. After this process step, the actuation cylinder is in a state of axial prestress. The degree of compression can be used to influence the subsequent distribution of axial tensile forces between the ring weld seam and the common threaded section. As the compression increases, the portion of the axial tensile force transmitted through the ring weld seam in the finished actuation cylinder increases.

[0056] d) performing laser welding of the cylinder-tube ends and closure parts at the axial ring contact surface, wherein the cylinder-tube ends and closure parts are thermally softened and deformed in the area close to the axial ring contact surface, and the intermediate cylinder-tube part thermally expands, simultaneously relieving its axial compression.

[0057] In process step d), a welding laser is applied to the area of ​​the axial ring contact surface. The welding energy introduced by the laser beam causes heating and thus thermal softening of the material of the cylinder-tube end and closure part in the area close to the axial ring contact surface. This softening causes the material to yield, relieving the elastic compression of the intermediate cylinder-tube section. Furthermore, heat is applied to the intermediate cylinder-tube section by thermal conduction from the area close to the cylinder-tube end, which has the effect of thermal expansion. This length change due to thermal expansion is not hindered by the softening of the material in the laser weld zone, i.e., in the area close to the axial ring contact surface, so that a state of no axial tension can be achieved. The subsequent distribution of the axial tensile force absorbed by the ring weld seam and the common threaded section can be particularly influenced by the degree of heat applied to the intermediate cylinder-tube section. Intensified heating increases the portion of the axial tensile force transmitted through the ring weld seam in the finished working cylinder. Furthermore, the intermediate cylinder-tube may, in any case, be heated by the heat input generated by the laser welding. By pressing the material on the ring contact surface in process step c), a particularly reliable object-locking connection is also advantageously achieved during welding in process step d), and undesirable air inclusions are avoided, resulting in a highly robust ring weld seam.

[0058] e) cooling with solidification of the cylinder-tube ends and closure parts in the area near the axial ring contact surface to establish a ring weld seam and axial heat shrinkage of the intermediate cylinder-tube section;

[0059] In process step e), heat dissipates, resulting in the solidification of the softened material and the formation of a laser-welded ring weld seam in the region of the axial ring contact surface, thereby forming an object-locking connection between the closure part and the cylinder tube. Even during continued cooling after the ring weld seam has been formed, the cylinder tube end sections and, in particular, the intermediate cylinder tube section shrink. This axial portion of the thermal contraction causes the common threaded section to move from a distal clearance end position to an intermediate clearance position, or, depending on the length of the thermal contraction, to a proximal clearance end position. In this way, the common threaded section is reliably free of axial tensile prestress.

[0060] According to another advantageous development, the process is characterized in that process step e) is carried out as process step e1) and that in process step e1) the axial thermal shrinking continues until an axial tensile prestress occurs in the intermediate cylinder-tube section.

[0061] According to this further development, the common threaded portion is located at the proximal clearance end position. This particular further development has the advantage that when an axial force is applied as a result of the operating pressure, the tensile force is initially completely absorbed by the ring weld seam, and the common threaded portion remains free from the tensile force. As the elastic deformation of the intermediate cylinder-tube portion continues with an increase in the axial tensile force, the common threaded portion first reaches the clearance end position and then the distal clearance end position. Only with a further increase in the force does force transmission via the common threaded portion begin. At this point, force transmission begins to be divided between the ring weld seam and the common threaded portion. While force transmission via the ring weld seam does not increase significantly from this point on, further increases in the axial tensile force are transmitted via the common threaded portion.

[0062] The invention will be explained in more detail by way of exemplary embodiments with the aid of the following figures. [Brief explanation of the drawings]

[0063] [Figure 1] Schematic cross-sectional view showing the connecting portion of the actuation cylinder after process steps a) to c). [Figure 2] A schematic cross-sectional view showing the connecting part of the actuation cylinder after process step d). [Figure 3] Schematic cross-sectional view showing the connecting portion of the actuation cylinder after process step e). [Figure 4] 10 is a schematic cross-sectional view showing the connecting portion of the actuating cylinder transitioning from an operating state under unloading to an operating state under load. FIG. [Figure 5] 1 is a schematic cross-sectional view showing the connecting portion of the actuating cylinder in an operating state under load. [Figure 6] FIG. 10 is a schematic cross-sectional view showing another connection portion of the actuation cylinder in an operating state under load. DETAILED DESCRIPTION OF THE INVENTION

[0064] The same reference numbers in the various figures indicate the same features or components, and reference numbers are used in this description even if they are not included in the associated figures.

[0065] These figures show an exemplary embodiment of an actuation cylinder and an exemplary embodiment of the method in various process steps.

[0066] FIG. 1 shows the cylinder tube end portion 5a and the working cylinder in the region of the closure part 4a as process steps a) to c) are performed. The cylinder tube end portion 5a of the cylinder tube 3 is divided distally into the threaded cylinder tube portion 5.1a, the intermediate cylinder tube portion 5.2a, and the cylinder tube end portion 5.3a. The internal thread 9a of the threaded cylinder tube portion 5.1a and the external thread 8a of the closure part 4a are engaged in process step a), forming a common threaded part. In process step b), a pressure fit between the cylinder tube end portion 5.3a and the closure part 4a is established at the axial ring contact surface 11a by continued screwing. In process step c), an axial compression force is generated by applying a tightening torque, as indicated by the double arrow. With the common threaded part in its distal clearance end position, the intermediate cylinder-tube part 5.2a is subjected to tension between the threaded cylinder-tube part 5.1a and the axial ring contact surface 11a, thereby enforcing axial compression of the intermediate cylinder-tube part 5.2a as its elastic deformation. The geometry of the pair of internal and external threads 9a and 8a is shown in a greatly exaggerated and schematic manner in all figures to better visualize the clearance position. In the exemplary embodiment of the present invention, the closure part 4a is designed as a base closure part, which together with the cylinder tube 3 forms the working chamber 6.1 (in this case, the piston chamber) of the cylinder interior 6.

[0067] FIG. 2 shows the working cylinder when process step d) has been performed and at the start of process step e). Exposure to the laser in the area of ​​the axial ring contact surface 11a softens the material of the closure part 4a and the cylinder tube 3 at the cylinder tube end 5.3a, which is now deformed as a result of compressive stress and allows the axial extension of the intermediate cylinder tube section 5.2a under axial elastic re-deformation. Here, a ring weld seam 10a is created in the area of ​​the former axial ring contact surface 11a. The intermediate cylinder tube section 5.2a is now stress-free, and the common threaded section is in a clearance intermediate position due to its initial axial thermal contraction.

[0068] Figure 3 shows the working cylinder with varying tensile prestress in the intermediate cylinder tube section 5.2a after all process steps a) to e) have been completed. After continued axial thermal contraction of the intermediate cylinder tube section 5.2a after continued cooling in process step e), the common threaded section is at the proximal clearance end position. The tensile force acting on the ring weld seam 10a is indicated by the arrows above the ring weld seam 10a. The three opposing short arrows at the thread flanks represent the transmission of axial compressive force through the common threaded section.

[0069] Therefore, in operating conditions under unloading, small axial forces are transmitted only through the ring weld seam 10a.

[0070] Figures 4 and 5 show the working cylinder under load.

[0071] The illustrations in Figures 4 and 5 are based on the fact that the actuation cylinder of the exemplary embodiment of the present invention is equipped, as usual, with locking modules on both the piston rod and the base closure part (not shown). A locking module is understood to be a component for transmitting force from the actuation cylinder to a component of the application device. In a typical design, the locking module has a bore, often called an eye, into which a locking element, such as a bolt, can be inserted. The locking element connects the piston rod-side locking module to the component of the application device in a form-fit manner and ensures the transmission of force during operation. In particular, such a locking module can be designed as a spherical bearing. Figures 4 and 5 show the case where a pressure medium is pressurized in the piston rod chamber and relaxed in the piston chamber. Therefore, to perform the retraction movement, the actuation cylinder generates a tensile force between the locking modules. Pressure acting on the inner ring surface of another closure part 4b (in this case the guide closure part) generates a distal axial force which is transmitted to the cylinder tube 3 and from there to the connecting part 7a, where the tensile force transmitted to the application device by the fixing module of the closure part 4a is applied as an opposite tensile force to the closure part 4a.

[0072] Figure 4 shows the actuating cylinder in transition from a non-loaded operating state to a loaded operating state. The tensile force transmitted through the cylinder tube 3 is indicated by the arrow above the cylinder tube 3, while the tensile force acting on the closure part 4a via the fixing module is indicated by the arrow pointing in the opposite direction. The intermediate cylinder tube section 5.2a elastically deforms and distorts axially. However, the pressure of the pressure medium is not sufficient to reach the maximum axial extension of the intermediate cylinder tube section 5.2a and to bring the common threaded section into the clearance intermediate position. The force from the pressure medium is still absorbed exclusively by the ring weld seam 10a.

[0073] Figure 5 shows the actuating cylinder in an operating state under load. The large axial force indicated by the double arrow causes the intermediate cylinder-tube section to elastically stretch at the large or full operating pressure of the pressure medium in the piston rod chamber, to the extent that the common threaded section is in the distal clearance end position. Here, additional force is transmitted between the male thread 8a and the female thread 9a. The three short arrows on the thread flanks indicate the transmission of axial tensile force through the common threaded section. The transmission of force through the common threaded section prevents the intermediate cylinder-tube section 5.2a from further stretching, thereby preventing excessive loading of the ring weld seam 10a. Here, the total transmitted tensile force is divided into the force transmitted through the ring weld seam and the force transmitted through the common threaded section.

[0074] FIG. 6 shows an exemplary embodiment of an actuating cylinder with an alternative connecting part 7b, which is also shown in an operating state under load.

[0075] In the example shown in FIG. 6, the other closure part 4b is the guide closure part through which the piston rod of the piston unit 2 passes. Therefore, the other working chamber 6.2 is the piston rod chamber. The other cylinder tube end part 5b is designed similarly to the cylinder end part 5a and includes another threaded cylinder tube part 5.1b, another intermediate cylinder tube part 5.2b, and another cylinder tube end part 5.3b. Another external thread 8b and another internal thread 9b are engaged to form another common threaded part. At the same time, the cylinder tube 3 and the other closure part 4b are connected in a form-fit manner via another circumferential ring weld seam 10b. The pressure medium in the other working chamber 6.2 exerts a large operating pressure on the inner ring surface of the other closure part 4b under load, resulting in an axial distal force on the other closure part 4b (indicated by two parallel arrows). First, this force is transmitted to the cylinder tube 3 via the ring weld seam 10b (indicated by the long arrow in the other intermediate cylinder tube section 5.2b). This generates a tensile force in the area of ​​the other intermediate cylinder tube section 5.2b, which results in an elastic deformation of this section. Second, due to the resulting axial displacement between the other internal thread 9b and the other external thread 8b, a force is also transmitted to the cylinder tube 3 via the other common threaded section (indicated by the three short arrows at the thread flanks). Therefore, the structural and functional description of the connecting section 7a shown in Figures 1 to 5 also applies to the connecting section 7b shown in Figure 6. [Explanation of symbols]

[0076] 1 cylinder 2 piston units 3 Cylinder Tube 4a Closure Part 4b Alternate Closure Part 5a Cylinder tube end 5.1a Threaded Cylinder-Tube Section 5.2a Intermediate cylinder tube section 5.3a Cylinder tube end 5b Another cylinder tube end section 5.1b Another threaded cylinder tube section 5.2b Separate intermediate cylinder-tube section 5.3b Alternative Cylinder-Tube Ends 6 Inside the cylinder 6.1 Working chamber 6.2 Alternative working chambers 7a Connecting part 7b Another connecting part 8a male thread 8b Another male thread 9a female thread 9b Another female thread 10a ring welded seam 10b Another ring weld seam 11a Axial ring contact surface 12 Central axis of ring weld seam

Claims

1. A working cylinder comprising a cylinder (1) and a piston unit (2), The cylinder (1) comprises a cylinder tube (3), a closure part (4a) and another closure part (4b), the cylinder tube (3) has a cylinder tube end portion (5a) and another cylinder tube end portion (5b), the closure part (4a) is arranged on the cylinder tube end portion (5a), and the other closure part (4b) is arranged on the other cylinder tube end portion (5b); The cylinder tube (3) and the closure parts (4a, 4b) form a cylinder interior (6), The piston unit (2) defines at least one working chamber (6.1) within the cylinder interior (6), the cylinder (1) has a connecting part (7a) comprising the closure part (4a) and the cylinder tube end part (5a), the cylinder tube end portion (5a) comprises a threaded cylinder tube portion (5.1a), an intermediate cylinder tube portion (5.2a), and a cylinder tube end portion (5.3a); the closure part (4a) has an external thread (8a) and the threaded cylinder tube part (5.1a) has an internal thread (9a) corresponding to the external thread (8a), the external thread (8a) and the internal thread (9a) forming a common threaded part designed to connect the closure part (4a) and the cylinder tube (3) in a form-fit manner; The cylinder tube end (5.3a) is connected to the closure part (4a) by a circumferential ring weld seam (10a) in an object locking manner, the ring weld seam (10a) is designed as a laser ring weld seam and forms a pressure sealing surface that is tight against pressure media, The actuating cylinder is designed to be in an unloaded operating state or in an under-load operating state; In the unloaded operating state, the common threaded portion does not absorb any axial tension force; In the operating state under the load, the ring weld seam (10a) and the common threaded portion each absorb an axial tensile force. Working cylinder.

2. In the operating state under the unloaded condition, the intermediate cylinder-tube section (5.2a) has a tensile prestress and the common threaded section absorbs axial compressive forces.

2. The actuation cylinder according to claim 1, characterized in that:

3. In the operating state under the unloaded condition, the intermediate cylinder-tube section (5.2a) has a tensile prestress and the common threaded section absorbs axial compressive forces.

2. The actuation cylinder according to claim 1, characterized in that:

4. the intermediate cylinder-tube section (5.2a) is designed to undergo axial strains within its elastic limit when the unloaded operating condition changes to the loaded operating condition; 4. An actuating cylinder according to any one of claims 1 to 3, characterized in that it

5. 5. The actuation cylinder according to claim 1, wherein the ring weld seam (11a) has a ring weld seam depth with a ratio of 1.1 to 2.5 to the cylinder tube wall thickness.

6. the ring weld seam (11a) has a ring weld seam central axis with a ring weld seam inclination angle alpha of 20 to 70 degrees relative to the main longitudinal axis of the cylinder tube; 6. An actuating cylinder according to any one of claims 1 to 5, characterized in that it

7. The piston unit (2) forms a separate working chamber (6.2) within the cylinder interior (6), the cylinder (1) has another connecting part (7b) with the other closure part (4b) and the other cylinder tube end part (5b), the other cylinder-tube end portion (5b) comprises a other threaded cylinder-tube portion (5.1b), a other intermediate cylinder-tube portion (5.2b), and a other cylinder-tube end portion (5.3b); the other closure part (4b) has another external thread (8b), the other threaded cylinder tube end portion (5.1b) has another internal thread (9b) corresponding to the other external thread (8b), the other external thread (8b) and the other internal thread (9b) forming another common threaded part designed to connect the other closure part (4b) and the cylinder tube (3) in a form-fit manner, the other cylinder tube end (5.3b) is connected to the other closure part (4b) in an object-locking manner by another circumferential ring weld seam (10b); the further circumferential ring weld seam (10b) is designed as a laser ring weld seam and forms a sealing surface that is hermetic to pressure media. In the unloaded operating state, the other common threaded end portion does not absorb any axial tension force; In the operating state under the load, the another circumferential ring weld seam (10b) and the another common threaded portion each absorb an axial tensile force.

7. An actuating cylinder according to any one of claims 1 to 6, characterized in that it

8. 1. A method of manufacturing an actuation cylinder, comprising: The working cylinder is designed according to any one of claims 1 to 5, The process steps are as follows: a) threading the cylinder tube (3) onto the closure part (4a) using the cylinder tube end portion (5a) of said cylinder tube (3) to establish engagement between the internal thread (10a) of the threaded cylinder tube portion and the external thread (9a) of said closure part (4a) to create a common threaded portion; b) establishing a pressure fit at the axial ring contact surface (11a) between the cylinder tube end (5.3a) and said closure part (4a); c) applying a tightening torque to generate an axial compression force to establish axial compression of the intermediate cylinder-tube section (5.2a); d) performing laser welding of the cylinder-tube end (5.3a) and the closure part (4a) at the axial ring contact surface (11a), in which the cylinder-tube end (5.3a) and the closure part (4a) are thermally softened and deformed in the area close to the axial ring contact surface (11a), and the intermediate cylinder-tube section (5.2a) thermally expands, simultaneously relieving its axial compression; e) cooling with solidification of the cylinder-tube end (5.3a) and the closure part (4a) in the area near the axial ring contact surface (11a) to establish the ring weld seam (10a) and axial heat shrinkage of the intermediate cylinder-tube section (5.2a); A method comprising:

9. Process step e) is carried out as process step e1), and in process step e1) the axial heat shrinking continues until an axial tensile prestress is generated in the intermediate cylinder tube section (5.2a).

9. A method for manufacturing an actuation cylinder according to claim 8, characterized in that:

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