EP4055279A1

EP4055279A1 - Working cylinder and method for the production thereof

Info

Publication number: EP4055279A1
Application number: EP20824436.8A
Authority: EP
Inventors: Josef Bueter
Original assignee: Buemach Engineering International BV
Current assignee: Buemach Engineering International BV
Priority date: 2019-11-08
Filing date: 2020-11-06
Publication date: 2022-09-14
Also published as: DE102019007754A1; CN114667397A; WO2021089069A1; JP2023502012A; US20220397128A1

Abstract

The invention relates to a working cylinder (1) having a cylinder tube (2), a first closure part (3), a second closure part (4) and a piston unit (5), wherein the cylinder tube (2) has a first cylinder tube end (6) and a second cylinder tube end (7), the first closure part (3) being arranged on the first cylinder tube end (6), the second closure part (4) being arranged on the second cylinder tube end (7), the cylinder tube (2) and the closure parts (3, 4) forming a cylinder interior (8), the piston unit (5) forming at least one working chamber in the cylinder interior (8), the piston unit (5) pushing slidingly through the first closure part (3), characterized in that the first closure part (3) is integrally joined to the cylinder tube (2) by means of a first peripheral laser ring weld seam (9) and the second closure part (4) is integrally joined to the cylinder tube (2) by means of a second peripheral laser ring weld seam (10) and the laser ring weld seams (9, 10) each form a fluid-tight sealing plane (10). The invention furthermore relates to a method for producing such a working cylinder.

Description

Working cylinder and process for its manufacture

The invention relates to a welded working cylinder and a method for its production.

Working cylinders are known as such from the prior art. The working cylinders can in particular be differential working cylinders, plunger cylinders, synchronous cylinders or telescopic cylinders.

A differential working cylinder, for example, is a double-acting hydraulic working cylinder with two working spaces, with the piston engaging surfaces of different sizes in the two working spaces. For the same operating pressure, different forces act on the piston in the two directions of actuation. In the case of a synchronous cylinder, in contrast to a differential working cylinder, the piston rod is guided by guide locking parts arranged on both sides, so that the piston engages the same size and thus the same forces act in both directions of operation at the same operating pressure, so that synchronous 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 volume body and thus causes its extension movement. The same also applies to the telescopic cylinder, with several cylinder tubes being pushed into one another and thus enabling particularly long working movements.

All such working cylinders have a cylinder tube and closure parts. According to the prior art, such working cylinders are usually manufactured by screwing the closure parts to the cylinder tube. These working cylinders are therefore also referred to as screw cylinders in the prior art.

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

The thread of the cylinder tube and closure parts is usually produced by a machining process.

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

On the manufacturing side, it should be noted that, in particular for the cylinder tube, an increase in the material thickness, that is to say the tube wall thickness, must be provided for the thread to be introduced subtractively because the thread inevitably weakens the cylinder tube. However, this then results in a pipe wall thickness which is considerably overdimensioned for absorbing the forces in working operation, in particular the forces due to the operating pressure of the fluid. This disadvantageously leads to increased material consumption and to an increased final weight of the differential working cylinder.

The machining processes for producing the thread also disadvantageously require high precision and are therefore very demanding in terms of production.

Furthermore, in order to achieve the tightness of the cylinder between the cylinder tube and the respective closure part, a seal must also be introduced regularly.

Furthermore, the final assembly requires a lot of time and skilled workers.

It is also disadvantageous that additional means must be provided to prevent the screw connection from loosening. Ultimately, it is disadvantageous that As a result of the changing operating pressures, there are dynamic loads on the threads, which limit their service life.

The object of the invention is to provide a working cylinder which is of particularly high quality and can be produced in a material-saving, simple and thus inexpensive manner. Furthermore, it is the object of the invention to provide a cost-effective method for producing such a working cylinder.

The object is achieved in relation to the working cylinder by the features listed in claim 1 and in relation to the manufacturing method by the features listed in claim 10. Preferred developments result from the respective subclaims.

According to the invention, the working cylinder has a cylinder tube, a first and a second closure part and a piston unit. The first closure part and the second closure part are also referred to collectively below as the closure parts.

The working cylinder according to the invention formed from these basic components can be in different designs. In particular, the working cylinder can be a differential working cylinder, a plunger cylinder, a synchronous cylinder, a telescopic cylinder, a pulling cylinder or a pneumatic working cylinder. If the working cylinder is designed as a synchronous cylinder, it is also referred to below as a steering cylinder. In the context of the present invention, working cylinders are also understood in particular as storage cylinders, gas spring cylinders and hydraulic shock absorbers.

The cylinder tube is designed as a hollow cylinder in a manner known per se and, according to the invention, has a first cylinder tube end and a second cylinder tube end. At the first end of the cylinder tube is after assembly the first closure part and the second closure part are arranged on the second cylinder tube end. Both cylinder tube ends are preferably made the same. The two cylinder tube ends preferably have beveled axial end faces, the bevels being at the same angle. The axial end faces thus preferably have the same cross-sectional area.

But it is also possible to design the cylinder tube ends differently.

According to the invention, the first closure part is arranged on the first end of the cylinder tube. The first closure part is preferably a guide closure part. In this context, a guide closure part is understood to be a closure part which receives a piston unit in a sliding and sealing manner. In this case, in the case of a differential working cylinder, for example, the piston unit can consist of a piston and a piston rod, the piston rod then being received by the guide closure part. In the case of a plunger cylinder, the piston unit is present as 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 in such a way that it has a contact surface which, when placed on 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 ring surface on which the first closure part rests on the first end of the cylinder tube. As far as the ring surface is inclined, it is present in the geometric sense as a truncated cone surface. For the sake of simplicity, this area is hereinafter simply referred to as an annular area, irrespective of the geometric configuration.

According to the invention, the second closure part is arranged on the second end of the cylinder tube. The contents of the description of the first closure part in its relationship to the first cylinder tube end apply in a corresponding manner to the second closure part in its relationship to the second cylinder tube end. The second closure part is analogous to the first with regard to the contact surface Closure part formed. 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 space of the working cylinder according to the invention.

The working cylinder according to the invention also has 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 synchronous cylinder - or it can be formed solely by a piston - as is the case with a plunger cylinder, for example - or have other designs . If the piston unit has a piston and a piston rod, the piston and the piston rod are in a fixed positional relationship relative to one another. The piston and the piston rod are preferably firmly coupled to one another. The connection is preferably formed as a welded connection in a materially bonded manner. The piston and piston rod can also be detachably coupled. In special cases, however, it is also possible for the piston unit to be designed in one piece and thus for the piston and piston rod to be sections of a monolithic component.

According to the invention, the cylinder tube and the closure parts form a cylinder interior in the assembled state. If the cylinder tube and the closure parts are assembled, their inner surface sections limit the interior of the cylinder. The interior of the cylinder leads to the respective laser ring weld seam.

Furthermore, in the working cylinder according to the invention, the piston unit forms at least one working space in the cylinder interior. This is delimited by the cylinder tube, a closure part and the piston unit. The piston unit is arranged to be axially displaceable, the main longitudinal axis of the cylinder tube and the axial direction of movement of the piston unit coinciding. Here the piston unit preferably passes through the first closure part in a sliding and sealing manner, at least in sections. A pressure medium connection is assigned to the working space, via which the pressure medium can reach the working space or can be routed out of it and the working space can thus be subjected to a pressure. The pressure medium can be in the form of a hydraulic or pneumatic pressure medium.

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

The piston of the piston unit is arranged in the cylinder interior and separates the cylinder interior into a piston head working chamber, also referred to below as the piston head chamber for short, and a piston rod working chamber. The piston head space is located between the piston and the second closure part, here designed as a base closure part. The piston rod working space is located on the side of the piston rod between the piston and the first closure part, here designed as a guide closure part. The at least one working space is thus present as the piston rod working space. In addition, the piston crown working space forms a further working space.

The piston is axially displaceable and is arranged in the cylinder interior in such a way that the main longitudinal axes of the piston and cylinder tube overlap.

The pressure medium connections are arranged on the cylinder in such a way that the piston head working space and the piston rod working space can be subjected to an operating pressure.

The piston can also have various guide, sealing or piston rings. Various designs of a piston for a working cylinder are known as such from the prior art.

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

The piston rod is slidably mounted in the guide closure part, the guide closure part being designed to prevent the pressure medium from escaping, hereinafter also referred to as fluid, to prevent. This is done, for example, using appropriate ring seals.

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

The first closure part is firmly connected to the cylinder tube by means of a first circumferential laser ring weld seam and the second closure part is firmly connected to the cylinder tube by means of a second circumferential laser ring weld seam. The components connected to one another are also referred to collectively below as the coupling partners.

The two closure parts are connected to the cylinder barrel using a laser welding process. The laser ring weld seams are fusion welded joints without the addition of welding consumables.

The laser welding advantageously forms 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.

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

The cylinder tube and closure parts as well as preferably also the piston unit each consist of a metal alloy and particularly preferably of one Steel alloy. The material composition of the individual components can differ slightly. The proportions by mass of the components of the metal alloy of the cylinder from those of the closure parts preferably differ by less than 10% by weight from the metal alloy of the closure parts. Thus, the closure parts and cylinder barrel have similar physical properties and can be welded together particularly well.

The steel alloy used preferably has a carbon content of less than 0.5% by weight. The alloy components vanadium, chromium and manganese are contained individually or in combination, preferably in a proportion of 0.01 to 2% by weight.

The welded working cylinder according to the invention has a number of significant advantages over working cylinders according to the prior art.

A first essential advantage is that the cylinder tube in particular hardly needs to be machined, or not at all, beyond being cut to length. In particular, no threads have to be cut or grooves turned. In the case of a welded piston unit, this also applies to the piston rod.

This initially has the immediate advantage that the otherwise required expenditure of time, processing machines, tool costs and energy for machining can be saved.

Furthermore, there is the advantage of a drastic saving in material 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 working cylinder. Supplements, for example in the pipe wall thickness to compensate for the material removal for a cut thread, can be dispensed with. By eliminating machining of the cylinder tube and preferably also the piston rod, the quality is also significantly increased. The axial run-out accuracy is no longer impaired due to the elimination of force inputs from machining. Rather, the axial concentricity of the starting products for the cylinder tubes and possibly also the piston rods is completely retained. The working cylinder according to the invention thus has a higher precision. In this way, the axial piston rod movement can also be provided without the problem, known from the prior art, of buckling of the piston rods in the end stop. This also reduces the wear on the cylinder guides in the guide locking part. By eliminating the machining of the cylinder tube and possibly the piston rod, reductions in load capacity due to notch effects are avoided at the same time.

Another advantage is the absolute tightness of the differential working cylinder at the connection points between the cylinder tube and the closure parts. It is also advantageous here that the tightness can be provided without the seals otherwise required according to the prior art. The possible elimination of these aging-prone components leads to cost savings, an improvement in quality and an increase in service life. In addition, contamination from aging seals is excluded.

Another advantage is the increased operational safety. There is no axial movement play between the cylinder barrel and the closure parts when there is a load change, as is possible with threads, or there is no loosening as with threads. Furthermore, savings result from the elimination of otherwise necessary securing elements. Ultimately, the securing of the actual securing elements, which is otherwise required, which is required in the case of detachable connections, is also dispensed with. According to the prior art, such securing takes place, for example, by gluing the securing elements. The elimination of gluing is associated with other important advantages. Firstly, there are no costs for the very expensive screw locking adhesives. Secondly, there is no need to clean the Surfaces for the production of their adhesion for the screw locking adhesives, which according to the state of the art often require cleaning chemicals that are harmful to health. This eliminates the special measures to ensure health protection and environmental protection. Thirdly, the problem is overcome that detachable connections secured by screw locking adhesives can be subject to the risk of loosening in the event of impact loads.

One aspect of the increased operational safety is also the increased manipulation safety. Non-destructive interventions in the interior of the cylinder are excluded. Possible sources of injury in connection with improper opening or improper reassembly of a differential working cylinder by untrained personnel are eliminated.

As a result of the laser welding process, there is only a very localized heating of the material in the area of the laser ring weld seams. In this way, components with thermally sensitive materials, such as seals in particular, can be welded within a few millimeters around the planned weld seam, which would be damaged in other welding processes.

Also, scaling on the inner surface sections of the cylinder tube and the closure parts, especially in the vicinity of the weld seams, which would otherwise have to be removed in a laborious manner according to the prior art, is avoided.

The reduction of thermal stresses in the coupling partners of the welded joint is also advantageous, since only a relatively small amount of energy per unit length (amount of energy related to the weld seam length) needs to be introduced by means of laser welding. Another advantage is that the course, the weld seam depth and the angle of the laser ring weld seams can be largely determined by the movement, the energy per unit length and the angle of the laser beam relative to the working cylinder to be produced. In this way, the course and the angle can be aligned in a targeted manner, in particular by changing the position of the laser relative to the coupling partners.

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

In these? Training, the first closure part is designed as a guide closure part and the second closure part as a bottom 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 as the bottom-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 thus arranged between the base closure part and the base-side cylinder tube end.

In the differential working cylinder, the piston unit has a piston and a piston rod. With regard to the structure of the piston unit embodied in this way, reference is made to the content of the description relating to the working cylinder above.

The piston of the piston unit is arranged in the cylinder interior and thus separates the cylinder interior into a piston crown working space, also referred to as piston crown space for short, and a piston rod working space, also referred to for short as piston rod space. The effective area of the piston in the piston crown space is larger on the piston crown side than on the piston rod space side of the piston. With the same pressure of the pressure medium, a greater force acts on the piston on the piston floor space side than on the piston rod space side. A force acting on the piston becomes transferred to the outside by means of the piston rod from the cylinder interior, for which the piston rod slidably penetrates the guide closure part.

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

In the synchronous cylinder according to this advantageous development, the first closure part is designed as a guide closure part, as in the case of a differential working cylinder. In addition, 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 also referred to collectively 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 thus arranged between the further guide closure part and the second cylinder tube end.

Here too, the piston unit has a piston and a piston rod. The piston is arranged in the cylinder interior and separates it into a first and a second piston rod working chamber. For this purpose, the piston rod projects axially beyond the piston on both sides and is guided out of the piston interior on both sides through the closure parts, which are both present here as guide closure parts. The piston rod thus slidably passes through both guide locking parts.

Both piston rod working spaces have the same cross-section and thus the piston on both sides have effective contact surfaces of the same size for the pressure medium. The force acting on the piston and the length of the working path carried out by the piston are the same, regardless of whether a certain pressure flow of the pressure medium, equal in pressure and volume, acts on the first or the second piston rod working chamber. Because of this in both Operating directions with the same behavior, the synchronous cylinder is often used as a steering cylinder and is therefore also referred to as a steering cylinder.

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

According to this development, the first closure part is designed as a guide closure part and the second closure part is designed as a bottom closure part. The first cylinder tube end was a guide-side cylinder tube end and the second cylinder tube end was a bottom-side cylinder tube end. As in the case of a differential working cylinder, 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 thus arranged between the base closure part and the base-side cylinder tube end.

The piston unit is formed by a plunger in the plunger cylinder. The plunger is arranged in the cylinder interior. Only one working space is formed in the cylinder interior. The plunger slidably penetrates the guide closure part. When a pressure flow of the pressure medium is applied to the working space, the plunger is axially displaced in accordance with the introduced volume of the pressure flow and executes an extension movement. The entry movement is brought about by an external force acting in the opposite direction.

According to an advantageous development, the working cylinder is characterized in that a first circumferential sealing ring is arranged in the cylinder interior between the first closure part and a cylinder tube inner wall of the cylinder tube at its first cylinder tube end axially spaced from the first laser ring weld seam, which forms a first pressure-separated ring section which is located between the first circumferential sealing ring and the first laser ring weld seam is arranged 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 axially spaced from the second laser ring weld seam a second circumferential sealing ring is arranged, which forms a second pressure-separated ring section, which between the second circumferential- Sealing ring and the second laser ring weld is arranged.

According to this development, a circumferential sealing ring is positioned in front of at least one laser ring weld seam. A circumferential sealing ring is preferably arranged in front of both laser ring weld seams. The circumferential sealing ring is also referred to below as an O-ring.

On the inside of the cylinder space, the O-ring separates a ring section in front of the respective laser ring weld seam from the rest of the cylinder interior in a pressure-tight manner. It has surprisingly been found that by forming a laser ring weld seam, the energy per unit length can be set so low that a thermally sensitive O-ring is not damaged even in the vicinity of the laser ring weld seam. The short range is understood to be an axial distance between the laser ring weld seam and the O-ring that is smaller than the inside diameter of the cylinder tube. The O-ring has the effect that the ring section is separated from the working pressure of the pressure medium. In this way, an axial section of the cylinder tube immediately in front of and on 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 a buckling load. In this way, an otherwise occurring radial load on the laser ring weld seam is advantageously avoided at the same time with a very simple means. Rather, there is only the axial load. The axial load is based on the fact that the working pressure of the pressure medium acts on the base of the respective closure part. A multi-axis loading of the laser ring weld seam and multi-axis material stress there is thus advantageously avoided. At the same time, the upstream O-ring protects the at least one working area or, depending on the type of working cylinder, in the case of O-rings on both sides, both working areas 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 in the respective ring section by the O-ring before they pass into the work area.

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.

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

The connection between the closure parts is particularly advantageously more stable, since the force transmission in the weld seam is distributed over a larger area and thus optimized.

This results in a further advantage that the tube wall thickness of the cylinder tube can be further reduced for certain applications.

In addition, according to this advantageous development, it is also possible to make the laser ring weld seam depth greater than the cylinder tube wall thickness, even with a substantially vertical alignment of the weld seam, by making the laser ring weld seam deeper into the closure part than the cylinder tube is thick. This means that there is a deeper-lying weld root. The laser ring weld depth is preferably at least 1.2 times the cylinder tube thickness. It was surprisingly found that the structural changes in the closure part brought about in this way lead to an increase in the load-bearing capacity of the ring weld seams.

According to a further advantageous development, the laser ring weld seams have an inclined laser ring weld seam central axis. According to the same advantageous development, the laser ring weld seam center axis includes a laser ring weld seam inclination angle alpha with a main longitudinal axis of the cylinder tube, with alpha being 20 degrees to 70 degrees.

The central axis of the laser ring weld seam runs through the center of the laser ring weld seam and divides its cross-section into equal parts. If the central axis of the laser ring weld seam is extended to the main longitudinal axis of the cylinder tube, which runs centrally and along the cylinder tube, this forms an angle with the main longitudinal axis. This angle is the laser ring weld inclination angle alpha.

The laser ring weld seam inclination angle alpha is between 20 degrees and 70 degrees, whereby the laser ring weld seam depth is generated with a ratio of 1.1 to 2.5 to the cylinder tube wall thickness.

Due to the greater depth of the laser ring weld seam and the raised ring weld seam center axis, the forces are better distributed during a load due to the angle and contact surface of the applied forces.

According to a further advantageous development, at least one closure part has an axially opening, circumferential concave receiving contour in which the cylinder tube engages, the receiving contour overlapping the cylinder tube radially and the annular weld seam inclination angle alpha being 110 to 160 degrees. This inclination beyond 90 degrees is also referred to below as a negative incline.

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 outwardly arranged side wall is inclined and forms a conical shape. The concave receiving contour thus forms a radial overlap. The radially inwardly arranged side wall is preferably not inclined and preferably forms a cylindrical shape. The cross section of the receiving contour thus preferably corresponds to a concave wedge. The cylinder tube is formed at the corresponding cylinder tube end to correspond to the receiving contour and for this purpose has an inclined annular surface, the angle of inclination of which 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 thus preferably corresponds to a wedge that fits into the receiving contour.

The laser ring weld seam is arranged between the described inclined annular surfaces of the receiving contour and the cylinder tube. The angle of inclination of the laser ring weld seam corresponds to the angle of inclination of the two inclined annular surfaces.

It has been found that three advantageous effects can be achieved at the same time with the same means through this further development. Firstly, the radial overlap of the cylinder tube results in a form-fitting absorption of buckling forces that are 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 force transmission at the laser ring weld seam is practically only available for axial forces. Secondly, the inclination achieves a ring weld depth that exceeds the cylinder tube wall thickness without additional measures and thus enables higher power transmission. Thirdly, an assembly advantage is achieved at the same time, since the cylinder tube and the relevant closure part center themselves automatically in the event of an axial feed movement.

According to another advantageous development, at least one of the laser ring weld seams is arranged axially on the end face and the ring weld seam inclination angle alpha is 180 degrees.

The laser ring weld seam thus has a cylindrical shape and is thus arranged radially between the cylinder tube and the relevant closure part. This development has the particular advantage that the annular end face on the cylinder tube does not require any special machining. Rather, only the edge of the inner jacket surface of the cylinder tube forms the contact surface with the relevant closure part and thus the surface to be welded for the laser ring weld seam. In addition, the closure part in question can advantageously be designed without a radial step. The outer diameter of the closure part only has to correspond to the inner diameter of the cylinder tube, which results in a considerable saving in material. In addition, a low level of precision is required in the formation of the length of the cylinder tube, since the exact spacing of the two closure parts can be set precisely during the joining.

According to another advantageous development, the angle of inclination of the ring weld seam is 90 degrees. This development has the advantage in terms of production that on the cylinder tube the annular end face formed by the cutting to length can already be used as the contact surface with the relevant closure part without further work steps.

In general, the different advantageous developments of the design of the laser ring weld seams are not restricted to certain types of cylinders. In addition, different designs of the laser ring weld seams can also be present in combination on one and the same working cylinder.

According to the invention, the method for producing a working cylinder has the following method steps: a) joining the cylinder tube, the first closing part, the second closing part and the piston unit to form a pre-assembly b) establishing a fixed relative positional relationship of the cylinder tube, the first closing part and the second closing part c) Performing the laser welding of the cylinder tube with the first closure part while producing the first laser ring weld seam and with the second closure part while producing the second laser ring weld seam

In process step a), the cylinder tube, both closure parts and the piston unit are arranged in their end position. The components arranged in this way are referred to below as pre-assembly.

The piston unit is inserted into the first closure part and introduced into the cylinder tube.

The first closure part is attached to the first end of the cylinder tube and the second closure part is attached to the second end of the cylinder tube.

As a preferred solution, all components are pre-assembled. This means that, for example, temperature-sensitive components such as the seal and the guide are also used in the first closure part designed as a guide closure part. The same applies to the guide and seal on the piston unit. The pre-assembly is preferably designed in such a way that the working cylinder according to the invention can be completely removed after method step c), that is to say the welding. Process steps such as processing the outer surface, in particular the application of a coating, can then follow.

In method step b), the cylinder tube and the closure parts of the pre-assembly are temporarily fixed and their positional relationship to one another is thus determined. The relative positional relationship of the cylinder tube and the closure parts in this process step corresponds to the relative positional relationship of these components in the finished working cylinder.

The closure parts are preferably designed in such a way that they are guided and fixed in their end position to the cylinder by an applied force along the main longitudinal axis of the cylinder tube. This is preferably done by means of a cylindrical section, which is precisely inserted into the cylinder barrel. and corresponding design of the axial contact surfaces of the closure parts achieved.

A force that acts along the main longitudinal axis of the cylinder tube is preferably applied by clamping in a chuck and, opposite, in a quill (or similar fixing elements) of a machine. Working cylinders to be manufactured with a high degree of slimness are preferably additionally guided through a steady rest.

With this device, the pre-assembly can preferably be rotated about the main longitudinal axis of the cylinder tube. However, temporary fixations are also possible, which do not provide for any rotation of the pre-assembly.

In process step c), the cylinder tube is welded to the two closure parts of the pre-assembly. According to the invention, this process step is carried out using a laser welding process.

The pre-assembly is preferably rotated about the main longitudinal axis of the cylinder tube during welding. The laser emitters are arranged in a stationary manner around the pre-assembly. In another variant of this method step, the pre-assembly is arranged in a stationary manner and the laser emitters are actively moved around the pre-assembly to produce the laser ring weld seams. The axial application of force is preferably maintained during the entire process step c), so that distortion of the coupling partners with respect to one another due to thermal stresses is advantageously prevented.

In both variants, a first laser ring weld seam is produced between the first closure part and the cylinder tube and a second laser ring weld seam between the second closure part and the cylinder tube.

The two laser ring welds connect the respective coupling partners of the pre-assembly in a materially and irreversibly. Irreversible is understood to mean that the connection cannot be undone without destroying it.

The first laser ring weld seam and the second laser ring weld seam can be produced one after the other or by means of several laser heads take place simultaneously. The welding work is preferably carried out by a fully automatic welding robot in a laser welding system.

The welding system works preferably under protective gas or under partial vacuum.

The manufacturing method is particularly characterized in that after method step c) there is no longer any access to the cylinder interior. Insofar as a closure part is welded to the cylinder tube according to the prior art, there is the problem that scaling occurs on the inner surface sections of the relevant closure part and the cylinder tube, i.e. the surface sections of the cylinder interior to be formed, which must be removed again in a further work step. Furthermore, according to the prior art, the seal and the guide, for example, can only be inserted into a first closure part designed as a guide closure part after cooling has taken place, since they would otherwise be thermally damaged.

The manufacturing method according to the invention shows a solution according to which welding is also possible with inserted thermally sensitive components such as seal and guide and without subsequent access to the inner surface sections and without their cleaning.

It was surprisingly found that laser welding with a small weld seam width, with a low thermal energy introduced per weld seam length (energy per unit length) and in connection with a high welding speed can achieve high temperature gradients in the pre-assembly, so that a high proportion of the thermal energy is immediately transferred again the surface surrounding the weld seam can be derived and at the same time the temperature on the inner surfaces and on the thermally sensitive components such as seals and guides can be kept so low that neither scaling of the inner surfaces nor thermal damage to the thermally sensitive components occurs. Furthermore, thermal stresses in the coupling partner are considerably reduced. This surprisingly shows a production method that was previously not possible, which enables a completely welded differential working cylinder, wherein the process step of welding can also take place simultaneously for both closure parts.

The method according to the invention enables, as an advantage, a high saving in production time, because machining of the cylinder tube can be dispensed with. In addition, it is only through the manufacturing method according to the invention that it is made possible to design the cylinder tube with a significantly smaller tube wall thickness than according to the prior art with positively coupled working cylinders. The parts of the description relating to the advantages of the working cylinder according to the invention also apply in a corresponding manner to the advantages of the manufacturing process.

The laser welding process thus has the advantage that the energy has a locally strongly limited effect on the components of the pre-assembly. Thus, a smaller amount of energy is required for a ring weld seam, which also leads to an advantageously lower heat input.

Thanks to the high precision of the lasers, they can be aligned very precisely. In this case, the emission direction of the laser preferably runs along the planned laser ring weld seam center axis, which in turn preferably runs along the contact surfaces of the coupling partners of the pre-assembly.

The laser is designed according to wavelength, power and operating speed to weld the material of the working cylinder.

According to an advantageous development, the method according to the invention relates to the production of a differential working cylinder. In this development, the method is characterized in that in method step a) the joining takes place in the following manner. The cylinder tube, the first locking part designed as a guide locking part, the second locking part designed as a bottom locking part and the piston unit formed from the piston and the piston rod are joined to form a pre-assembly of a differential working cylinder. The joining is done in such a way that the The piston rod slides through the first closure part, which is present here as a guide closure part.

According to another development, the method relates to the production of a synchronous cylinder, also referred to as a steering cylinder. According to this development, the method is characterized in that in method step a) the joining of the cylinder tube, the first closure part designed as a guide closure part, the second closure part designed as a further guide closure part and the piston unit formed from the piston and the piston rod to form a pre-assembly of a synchronous cylinder is carried out. The joining takes place in such a way that the piston rod slides through both closure parts.

According to a further development, the production method according to the invention is carried out in such a way that a plunger cylinder is produced. For this purpose, the joining is carried out as follows in process step a). The cylinder tube, the first locking part designed as a guide locking part, the second locking part designed as a bottom locking part and the piston unit designed as a plunger are joined to form a pre-assembly of a plunger cylinder. The plunger passes through the first closure part, which is designed as a guide closure part.

According to an advantageous development, in method step c) the laser welding for producing the laser ring weld seams is carried out with a ring weld seam inclination angle alpha of 20 to 70 degrees. The laser head is guided at this angle relative to the pre-assembly. In this way, a laser ring weld seam that is inclined at this angle of inclination of the ring weld seam is achieved.

According to another advantageous further development, in method step c) the laser welding for producing the laser ring weld seams is carried out with a ring weld seam inclination angle alpha of 110 to 160 degrees. Therefor at least one of the two closure parts is first provided with an axially open, circumferential concave receiving contour in preparation for work step a) which relates to joining. During the joining according to step a), the correspondingly designed cylinder tube end is then inserted into the receiving contour, with the corresponding design automatically centering being carried out, which advantageously further increases the precision.

The laser head is guided at this angle in process step c) relative to the pre-assembly. In this way, a laser ring weld seam that is inclined at this angle of inclination of the ring weld seam is achieved. The wedge-shaped joint is maintained under axial force during the entire process step c), so that distortion due to largely reduced but not completely ruled out thermal stresses during laser welding is avoided and a particularly precise and precisely positioned laser welded connection between the coupling partners is achieved.

According to another advantageous development, method step c) is carried out in such a way that at least one of the laser ring weld seams is introduced axially on the end face and the ring weld seam inclination angle alpha is 180 degrees. For this purpose, in method step c), the laser beam is aligned parallel to the main longitudinal axis of the working cylinder.

In process step a), the joining takes place, the exact axial spacing of the two closure parts being set here. This is based on the fact that the at least one closure part does not have a radial projection that would define the axial positional relationship of the two coupling partners.

In the method for producing a working cylinder, according to other advantageous developments, method steps a) to c) are also applied to at least one fastening module.

A fastening module is understood to be a component for transmitting power from the differential cylinder to components of an application device. In a In a common design, the fastening module has a bore - often also referred to as an eye - into which a locking element such as a bolt can be inserted. The locking element connects the fastening module on the piston rod side in a form-fitting manner with a component of an application device and ensures the power transmission during operation. In particular, the fastening module can be designed as a joint bearing.

The at least one fastening module is preferably the fastening module on the piston rod side. A fastening module which is arranged on the piston unit is referred to as a fastening module on the piston rod side. Furthermore, there can also or alternatively be a base-side fastening module. A fastening module which is arranged on the second closure part in a configuration as a base closure part is referred to as a base-side fastening module. However, it is also possible that the second closure part, if this is a floor closure part, is designed such that it includes the fastening module, so that the fastening module is only a section of a monolithic floor closure part.

The at least one fastening module is made of a weldable material, preferably metal.

A first variant of the development involves a fastening module on the piston rod side. A second variant of this development involves a fastening module on the bottom.

In method step a), the working step of joining also takes place here as joining a fastening module on the piston rod side to the relevant component of the pre-assembly. The pre-assembly formed in this way is referred to below as an extended pre-assembly. A fastening module on the piston rod side is arranged in method step a) on the piston rod of the piston unit on its part protruding from the cylinder tube. A base-side fastening module is arranged on the second closure part, which is designed as a base closure part.

In method step b), according to this advantageous development, the defined positional relationship is also established between the respective fastening module and the relevant component.

The fastening module is fixed temporarily and relative to the relevant component of the pre-assembly. The temporary fixation is carried out analogously to the methods already described. However, additional means for fixing can also be provided

In method step c), according to the first variant of this advantageous development, the fastening module on the piston rod side is welded while producing a first fastening module weld seam.

The fastening module on the piston rod side is welded to the piston rod in process step c). This is preferably done in the same way as welding the remaining components of the extended pre-assembly. The first fastening module weld seam produced connects the fastening module on the piston rod side to the piston rod.

According to the second variant of the same development, in method step c) the bottom closure part is welded to the mounting module on the bottom while a second mounting module weld seam is produced.

This is done in the same way as welding the fastening module on the piston rod side. The second fastening module weld seam connects the fastening module on the bottom with the bottom closure part.

The invention is illustrated as an exemplary embodiment on the basis of Fig. 1 differential working cylinder (overview)

Fig. 2 Enlarged section at the guide-side end of the cylinder tube

Fig. 3 Enlarged section at the bottom end of the cylinder tube

Fig. 4 Enlargement of a laser weld seam to illustrate the

Cross-section and the ring weld angle beta

Fig. 5 Plunger cylinder with a 90 degree weld seam and an O-ring in front

6 shows an enlarged detail of FIG. 5 to show the O-ring and the ring section

Fig. 7 synchronous cylinder with negatively inclined weld seam

8 shows an enlarged detail of FIG. 7 to show the concave receiving contour

9 shows an enlarged detail of FIG. 7 in an exploded view

Fig. 10 Telescopic cylinder with a combination of a 90 degree weld seam and angled seam

11 A schematic representation of a bottom closure part with a 0 degree weld seam explained in more detail.

Fig. 1 shows an overview of an embodiment of the

Working cylinder 1 as a differential working cylinder. The differential working cylinder 1 is composed of the cylinder tube 2, the first closure part 3, here designed as Guide locking part, the second locking part 4, designed here as a bottom locking part and the piston unit 5 together. The piston unit has the piston 5a and the piston rod 5b.

In this embodiment, the piston rod-side fastening module 15 is arranged on the piston rod 5b, and the base-side fastening module 17 is arranged on the second closing part 4, which is designed as a bottom closure part. The two fastening modules 15, 17 are each assigned fastening bolts 15a, 17a, which are not part of the invention and are only shown for better clarity.

The piston unit 5 is arranged in relation to the piston 5a and with sections of the piston rod 5b in the cylinder interior 8, the piston rod 5b slidingly penetrating the first closure part 3, which is 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, which is designed as a bottom closure part, closes the second cylinder tube end 7, here the bottom cylinder tube end.

The two cylinder tube ends 6, 7 are beveled and thus have a larger contact area with the two closure parts 3, 4. In this embodiment, the two closure parts 3, 4 are designed so that they protrude with a cylindrical section partially and precisely into the cylinder tube and thus can be more easily joined to the pre-assembly.

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

In Fig. 2 an enlargement of the area of the first cylinder tube end 6 is shown. This is the end of the cylinder tube on the guide side. The geometrical relationships of the first circumferential laser ring weld seam 9 are shown here in particular. In this embodiment, during welding, a laser is used to produce the first circumferential laser ring weld 9 along the central axis 13 of the ring weld. This runs along the Contact surface between the first cylinder tube end 6 and the first closure part 3. For this purpose, the previously assembled and temporarily fixed pre-assembly consisting of 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 moved around the main longitudinal axis of the Cylinder tube 14 and rotates in front of the laser.

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, includes the ring weld seam inclination angle alpha. 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. The ring weld depth 11 is longer than the cylinder tube wall thickness 12 due to the angling. The ring weld seam depth corresponds to the hypotenuse of a right-angled triangle formed by means of the ring weld seam, the cylinder tube wall thickness 12 and a perpendicular.

In this illustration, the first fastening module weld seam 16 can also be seen between the fastening module 15 on the piston rod side and the piston rod 5b. This is produced with the same laser welding process as the first circumferential laser ring weld 9.

Furthermore, the sliding mounting of the piston rod 5b in the first locking part 3, designed as a guide locking part, with guide 20 and seal 19 is also shown.

In Fig. 3, an area of the bottom-side cylinder tube end, which is the second cylinder tube end 7, is shown enlarged.

The structure of the illustration largely corresponds to FIG. 2. The connection of the second closure part 4, designed as a bottom closure part, to the second cylinder tube end 7 takes place analogously to the connection of the first closure part 3, designed as a guide closure part, to the first cylinder tube end 6 (see FIG. 2) by means of a Laser welding process. The second laser ring weld seam 10 is formed here.

In addition to FIG. 2, this illustration shows the piston 5a as it converts the cylinder interior 8 into a piston bottom working chamber 8a and a Piston rod working space 8b divides. A hydraulic pressure medium is applied to both working spaces 8a, 8b separately from one another via the fluid connections, as a result of which the working cylinder 1 designed as a differential cylinder is operated.

Analogously to the fastening module 15 on the piston rod side (see FIG. 2), the fastening module 17 on the bottom is also fastened by means of a laser weld seam, the second fastening module weld seam 18.

In Fig. 4, a laser weld 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 according to the present invention.

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

The laser weld seam has a slight taper. If you place two tangents on the edge contour of the laser weld seam, they intersect and form an annular weld seam angle beta. The ring weld seam center axis 13 is at the same time the bisector of the ring weld seam angle beta and encloses the ring weld seam inclination angle alpha with the main longitudinal axis 14. 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 90 degrees.

In Fig. 5, an embodiment of a working cylinder, 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 locking part is the second Closure part 4, here designed as a bottom closure part, is connected at the second cylinder tube end 7 to the cylinder tube 2 by the second laser ring weld 10. In this exemplary embodiment, both laser ring weld seams 9, 10 have a ring weld seam inclination angle of 90 degrees.

In addition, the reference numerals and descriptions given in FIG. 1 for a differential working cylinder apply.

The plunger working cylinder in the exemplary 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 tube 2 and the first closure part 3 and provides a pressure-tight seal which separates the second circumferential laser ring weld seam 10 in a pressure-tight manner from the pressure medium.

In FIG. 6, the area of the sealing ring 21 (O-ring) on the first closure part 3 from FIG. 5 is shown enlarged. The sealing ring 21 (O-ring) is shown here in more detail and is located in spatial proximity to the first circumferential laser ring weld seam 9. The sealing ring 21 (O-ring) in this embodiment consists of an elastic polymer. The heat input during laser welding remains sufficiently low in order not to damage the sealing ring 21 (O-ring) despite the 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 Cylinder tube 2 act. In this way, the cylinder tube 2 is not loaded with buckling forces in this area and the first laser ring weld seam 9 is relieved.

In this embodiment, the ring weld seam center axis 13 runs perpendicular to the main longitudinal axis 14 of the working cylinder 1.

Fig. 7 shows a synchronous working cylinder with a negatively inclined weld seam. In the case of the synchronous working cylinder, both locking parts 3, 4 designed as guide locking parts. The piston 5a is arranged in the axially central region of the piston rod 5b, which is guided through both closure parts 3, 4.

In this exemplary embodiment, the two cylinder tube ends 6, 7 are each pushed into a concave receiving contour 23 in the two closure parts 3, 4 and welded there by means of the laser welding process. The laser ring weld seam 9, 10 is inclined negatively here, which means an opposite bevel of the contact surfaces (compared, for example, to the exemplary embodiment according to FIG. 1) of the closure part 3, 4 and the cylinder tube end 6, 7.

In FIG. 8, the exemplary embodiment from FIG. 7 is shown in greater detail in an enlargement

The second cylinder tube end 7 is here already pushed into the wedge-shaped concave receiving contour 23 and welded to the second closure part 4 by means of the second circumferential laser ring weld seam 10.

The ring weld seam center axis 13 encloses the ring weld seam inclination angle alpha with the main longitudinal axis 14.

The ring weld angle alpha here has an angle greater than 90 degrees, in the exemplary embodiment of approximately 120 degrees.

In FIG. 9, the coupling partners according to FIG. 8 are additionally shown in a schematic exploded view. 8 shows the first cylinder tube end 6 and the first closure part 3 with the wedge-shaped concave receiving contour 23 before joining. The concave receiving contour 23 is designed in such a way that it can receive the first cylinder tube end 6 and forms a common contact surface with it, on which the first laser ring weld 9 is then arranged. 9 shows that the concave receiving contour 23 opens axially in the direction of the cylinder tube 2. Buckling forces acting radially from the inside on the cylinder tube 2 are thus positively locked by a radial overlap 24 added. This is the inclined section of the concave receiving contour 23

In Fig. 10 an embodiment is shown as a telescopic working cylinder. In comparison to the previously described cylinder types, the telescopic working cylinder has a further cylinder tube 2a, which is arranged in the cylinder tube 2, and a further closure part 3a. The first closure part 3 and the further closure part 3a are designed as guide closure parts. The further cylinder tube 2a is welded to the further closure part 3a via a further circumferential laser ring weld seam 9a.

In this exemplary embodiment, straight laser ring weld seams (ring weld seam inclination angle alpha = 90 degrees) are also combined with inclined laser ring weld seams (ring weld seam angle alpha <90 degrees).

In this embodiment, the first circumferential laser ring weld seam 9 on the first closure part 3 and the further circumferential laser ring weld seam 9a on the further closure part 3a are designed as an inclined laser weld seam and the second circumferential laser ring weld seam 10 on the second closure part 10 as a straight laser weld seam.

11 shows a schematic representation of a section of an exemplary embodiment in which the second circumferential laser ring weld seam 10 runs parallel to the main longitudinal axis.

The second closure part 4, designed as a bottom closure part, is encompassed radially by the second cylinder tube 2. In the 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 that one of the coupling partners protrudes axially or springs back from the other coupling partner.

The ring weld seam center axis 13 does not intersect the main longitudinal axis 14. The ring weld inclination angle alpha is 0 degrees. Reference symbols used

1 working cylinder

2 cylinder tube

2a another cylinder tube

3 first closure part

3a another closure part

4 second closure part

5 piston unit

5a piston

5b piston rod

6 first cylinder barrel end

7 second cylinder tube end

8 cylinder interior

8a piston crown working space

8b piston rod working space

9 first circumferential laser ring weld seam

10 second circumferential laser ring weld

11 Ring weld depth

12 cylinder tube wall thickness

13 Ring weld seam central axis

14 main longitudinal axis

15 Mounting module on the piston rod side

15a Fastening bolt of the fastening module on the piston rod side

16 first fastening module weld seam

17 bottom mounting module

17a Fastening bolts of the fastening module on the bottom

18 second fastening module weld seam

19 seal

20 leadership

21 circumferential sealing ring 22 pressure-separated ring section

23 concave mounting contour

24 radial overlap a ring weld angle alpha ß ring weld angle beta

Claims

1. Working cylinder (1), comprising a cylinder tube (2), a first closure part (3), a second closure part (4) and a piston unit (5), the cylinder tube (2) having a first cylinder tube end (6) and a second cylinder tube end (7), wherein the first closure part (3) is arranged on the first cylinder tube end (6), the second closure part (4) is arranged on the second cylinder tube end (7), the cylinder tube (2) and the closure parts (3 , 4) form a cylinder interior (8), the piston unit (5) forming at least one working space in the cylinder interior (8), the piston unit (5) sliding through the first closure part (3), characterized in that the first closure part (3) with the cylinder tube (2) by means of a first circumferential laser ring weld seam (9) and the second closure part (4) with the cylinder tube (2) by means of a second circumferential laser ring weld seam (10) and the Laserr ing weld seams (9, 10) each form a fluid-tight sealing plane (10).

2. Working cylinder (1) according to claim 1, characterized in that the working cylinder (1) is double-acting and designed as a differential working cylinder, the first locking part (3) being designed as a guide locking part and the second locking part (4) being designed as a bottom locking part, the first cylinder tube end (6) being a guide-side cylinder tube end and the second cylinder tube end (7) being a bottom-side cylinder tube end, the piston unit (5) having a piston (5a) and a piston rod (5b), the piston (5a) is arranged in the cylinder interior (8) and separates the cylinder interior (8) into a piston head working chamber (8a) and a piston rod working chamber (8b) and the piston rod (5b) slidingly penetrates the guide closure part (3).

3. Working cylinder (1) according to claim 1, characterized in that the working cylinder (1) is double-acting and designed as a synchronous cylinder, the first locking part (3) being designed as a guide locking part and the second locking part (4) being designed as a further guide locking part, wherein the piston unit (5) has a piston (5a) and a piston rod (5b), the piston (5a) being arranged in the cylinder interior (8) and separating the cylinder interior (8) into a first piston rod working chamber and a second piston rod working chamber, and the The piston rod (5b) slides through the guide locking part and the further guide locking part.

4. Working cylinder (1) according to claim 1, characterized in that the working cylinder (1) is single-acting and designed as a plunger cylinder, the first locking part (3) being designed as a guide locking part and the second locking part (4) being designed as a bottom locking part, the first cylinder tube end (6) being a guide-side cylinder tube end and the second cylinder tube end (7) being a bottom-side cylinder tube end, the piston unit (5) being formed by a plunger piston, the plunger piston being arranged in the cylinder interior (8) and forms a working space in the cylinder interior (8) and the plunger slidingly penetrates the guide closure part (3).

5. Working cylinder (1) according to one of the preceding claims, characterized in that in the cylinder interior (8) between the first closure part (3) and a cylinder tube inner wall of the cylinder tube (2) at the first cylinder tube end (6) axially spaced from the first laser ring weld (9) a first circumferential sealing ring (21) is arranged, which forms a first pressure-separated ring section (22), arranged between the first circumferential sealing ring (21) and the first laser ring weld seam (9), and / or that in the cylinder interior (8) between the second closure part (4) and a cylinder tube inner wall of the cylinder tube (2) at the second cylinder tube end (7) axially spaced from the second laser ring weld seam (10) a second circumferential sealing ring is arranged, which has a second pressure-separated ring section, arranged between the second circumferential sealing ring and the second laser ring weld seam (10).

6. Working cylinder (1) according to one of the preceding claims, characterized in that the laser ring welds each have a ring weld depth (11), the ring weld depth (11) to a cylinder tube wall thickness (12) having a ratio of 1.1 to 2.5.

7. Working cylinder according to one of the preceding claims characterized in that the laser ring weld seams (9, 10) each have a ring weld seam center axis (13), the ring weld seam center axis (13) with a main longitudinal axis (14) of the cylinder tube (2) enclosing a ring weld seam inclination angle alpha, where alpha is 20 to 70 degrees.

8. Working cylinder (1) according to one of the preceding claims 1 to 6, characterized in that at least one closure part (3, 4) has an axially opening, circumferential concave receiving contour in which the cylinder tube engages, the receiving contour overlapping the cylinder tube radially and that the ring weld inclination angle alpha is 110 to 160 degrees.

9. Working cylinder (1) according to one of the preceding claims 1 to 6, characterized in that at least one of the laser ring weld seams is arranged axially on the end face and the ring weld seam inclination angle alpha is 180 degrees.

10. A method for producing a working cylinder (1), wherein the working cylinder (1) is designed according to one of claims 1 to 8, comprising the following process steps: a) joining the cylinder tube (2), the first closure part (3), the second closure part (4) and the piston unit (5) to form a pre-assembly, b) Establishing a fixed relative positional relationship between the cylinder tube (2), the first closure part (3) and the second closure part (4) c) performing the laser welding of the cylinder tube (2) with the first closure part (3) producing the first laser ring weld seam (9) and with the second closure part (4) producing the second laser ring weld seam (10).

11. The method for producing a working cylinder (1) according to claim 10, characterized in that in process step a) the joining of the cylinder tube (2), the first closure part designed as a guide closure part (3), the second closure part (4) designed as a bottom closure part and the from the piston (5a) and the piston rod (5b) formed piston unit (5), wherein the piston rod (5b) sliding through the first closure part (3) takes place to a front assembly of a differential working cylinder.

12. The method for producing a working cylinder (1) according to claim 10, characterized in that in process step a) the joining of the cylinder tube (2), the first closure part designed as a guide closure part (3), the second closure part (4) designed as a further guide closure part and the piston unit (5) formed from the piston (5a) and the piston rod (5b) to form a pre-assembly of a synchronous cylinder, the piston rod (5b) sliding through both closure parts (3, 4).

13. The method for producing a working cylinder (1) according to claim 10, characterized in that in process step a) the joining of the cylinder tube (2), the first closure part (3) designed as a guide closure part, the second closure part (4) and the bottom closure part designed as a plunger piston unit (5) to a pre-assembly of a plunger cylinder takes place.

14. The method for producing a working cylinder (1) according to one of the preceding claims 9 to 12, characterized in that the working cylinder (1) is designed according to one of claims 1 to 7 and that in method step c) the laser welding for producing the laser ring welds (9 , 10) is carried out with a ring weld inclination angle alpha of 20 to 70 degrees.

15. A method for producing a working cylinder (1), characterized in that the working cylinder (1) is designed according to one of claims 1 to 6 and 8 and that in process step c) the laser welding for producing the laser ring welds (9, 10) with a ring weld inclination angle alpha is carried out from 110 to 160 degrees.

16. A method for producing a working cylinder (1), characterized in that the working cylinder (1) is designed according to one of claims 1 to 6 and 9 and that in process step c) the laser welding for producing the laser ring welds (9, 10) axially frontal and is carried out with a ring weld inclination angle alpha of 110 to 160 degrees.

17. The method for producing a working cylinder (1) according to any one of the preceding claims, characterized in that in method step a) the joining of a piston rod-side fastening module (15) to the pre-assembly also takes place, that in process step b) the production of the fixed relative positional relationship also takes place of the piston rod-side fastening module (15) and that in process step c) the welding of the piston rod (5b) to the piston-rod-side fastening module (15) takes place with the production of a first fastening module weld seam (16).

18. The method for producing a working cylinder (1) according to any one of the preceding claims, characterized in that in method step a) the joining of a bottom-side fastening module (17) to the sub-assembly also takes place, wherein in method step b) the establishment of the fixed relative positional relationship also takes place of the base-side fastening module (17) takes place, wherein in method step c) the welding of the second closure part

(4) is carried out with the fastening module (17) on the bottom, producing a second fastening module weld seam (18). ABOUT ELEVEN PAGE DRAWINGS