Piston unit of working cylinder

Abstract

The invention relates to a piston unit of a working cylinder, comprising a piston (1) and a piston rod (2), wherein the piston has an axial hole (3) in which the piston rod (2) is accommodated, wherein the piston rod (2) and the piston (3) are connected in a material-locked manner by means of an annular laser annular weld (4), and wherein the laser annular weld (4) forms a sealing plane that seals against pressure medium.

Description

Technical Field

[0001] The invention relates to a piston unit of a working cylinder, which is formed by a piston and a piston rod. Background Art

[0002] Different solutions for connecting a piston to a piston rod are known from the prior art. Here, form-locking, force-locking and material-locking connections are known.

[0003] Positive-locking and non-positive-locking connections usually have the problem that additional measures are required to prevent the connection of piston and piston rod from loosening. In addition, positive-locking connections usually have the disadvantage that, due to the profiled sections, such as grooves or threads, introduced into the piston rod, the piston rod must be solid or at least have a large wall thickness in order to achieve sufficient stability. In addition, notch effects can be disadvantageous. In addition, the production costs for the usual machining of piston rods and pistons are relatively high. It is also expensive to provide a gap-free positive-locking connection.

[0004] Furthermore, it is known in principle to connect the piston and the piston rod to each other in a materially bonded manner. Loosening can thus be prevented, but this leads to other disadvantages. If this is done by gluing, there are the disadvantages of relatively low strength and low safety against failure of the connection. Gluing is therefore only feasible in certain application cases.

[0005] In particular, welded connections are known in principle, which however require considerable expertise and are complex. In particular, there is the disadvantage of thermal loading of the connecting parts, which can lead to changes in the material structure of the piston rod, in particular, requiring a thick-walled piston rod or a piston rod made of solid material. Summary of the invention

[0006] The object of the present invention is to specify a piston unit of a working cylinder which is formed by a connection of a piston and a piston rod which can be produced cost-effectively and ensures a particularly high degree of operational safety.

[0007] This object is achieved by the features described in detail in embodiment 1. Preferred developments are found in the subordinate embodiments.

[0008] According to the invention, the piston unit of the working cylinder has a piston and a piston rod. Here, the piston and the piston rod are particularly preferably made of steel.

[0009] In the piston unit according to the invention, in particular, it can be a piston unit of a differential cylinder, a synchronous cylinder or other working cylinder type, such as, for example, a pneumatic cylinder or a pulling cylinder. Likewise, the piston unit is particularly comprised of an energy storage cylinder, a hydraulic buffer or a gas spring cylinder, as long as it has a piston connected to a piston rod.

[0010] According to the invention, the piston has an axial bore in which a piston rod is received. The axial bore in the piston is designed such that the piston rod can be received therein. The axial bore preferably has a circular cross section.

[0011] According to the invention, the piston rod and the piston are integrally connected by means of an annular laser girth weld.

[0012] The laser girth weld is therefore provided at mutually opposing contact surfaces of the piston and the piston rod, wherein usually the outer cylindrical side of the piston rod and the inner cylindrical side of the piston are opposite each other. However, other configurations of the contact surfaces are also possible.

[0013] The laser girth weld is characterized in particular by the fact that a particularly narrow, tapering and essentially V-shaped weld is advantageously formed by laser welding. The lateral flanks of the laser weld form an acute weld angle of preferably less than 15 degrees and particularly preferably less than 10 degrees.

[0014] According to the invention, the laser annular weld forms the sealing surface for the pressure medium seal.

[0015] The laser annular weld is arranged without interruption along the contact surface between the piston and the piston rod. Thus, it forms a sealed material-locked connection that prevents the pressure medium from passing through, without requiring additional devices, such as, for example, seals.

[0016] The following essential advantages are found with the piston unit according to the invention, in particular compared to the prior art.

[0017] The first advantage of the piston unit produced in this way is the high precision and coaxiality accuracy. Since only a small amount of energy must be introduced for welding per unit weld seam length (small segment energy), significantly smaller thermal stresses occur, which can cause deformation of the piston rod.

[0018] Another advantage is that, in particular at the piston rod, no material removal is required to reduce the cross section, which increases the mechanical load capacity with less material consumption.

[0019] Furthermore, apart from the cutting of the piston rod, almost no material machining of the piston rod is required, which advantageously reduces the expenditure on machining technology, tool costs, time and energy.

[0020] A particularly important advantage is the high strength. The laser girth weld has a small width, but nevertheless has a large weld depth. Due to the large weld depth, a large area is welded, so that with the same mechanical stresses at the laser girth weld, particularly high forces can be transmitted, or conversely, with the same forces, lower mechanical stresses occur at the laser girth weld.

[0021] Advantageously, a particularly high operational safety is achieved thereby, since due to the low mechanical stresses there is a particularly high margin up to overload. In particular, the connection is reliable and permanently stable with respect to the dynamic loads with frequent load changes that typically occur in hydraulic working cylinders.

[0022] At the same time as the relatively large weld depth, there is advantageously a small width of the weld. By means of a small weld width, the material of the connecting partner is only thermally loaded near the surface, which is particularly advantageous particularly with regard to the piston rod, since the piston rod is hardly weakened or thermally deformed as a result.

[0023] Overall, the laser girth weld also has a small volume, so that the total heat input is small. Due to the small heat input, no oxidation of the material occurs, which would otherwise have to be removed again in other work steps.

[0024] In particular, due to the surprisingly achievable interaction of the advantages described, the piston rod can be designed to be particularly material-saving, so that raw material resources are conserved.

[0025] Furthermore, it is advantageous that no additional means need to be provided for the seal between the piston rod and the piston. In comparison with a sealing ring, the sealing surface of the pressure medium seal produced by the laser annular weld between the piston rod and the piston is also not subject to wear.

[0026] In terms of production technology, there are also the advantages of the high speed of laser welding and, due to the low energy input, the particularly short time required for cooling until further processing.

[0027] A further advantage in terms of production technology is that thermally sensitive components, such as guide elements or elastomeric seals, can already be mounted on the piston before laser welding of the piston to the piston rod.

[0028] According to an advantageous development, the laser girth weld is arranged on the bottom side at the end and with the weld seam center axis parallel to the main longitudinal axis of the piston rod.

[0029] The weld seam center axis is parallel to the main longitudinal axis of the piston rod and is arranged along the contact surface between the piston and the piston rod. In this development, the weld seam center axis extends in accordance with the course of the contact surface of the connecting partner.

[0030] If the laser extends exactly along the contact surface, the piston and the piston rod are melted with essentially the same partial thermal load and with the same material quality in a symmetrical weld seam along the weld seam center axis.

[0031] This development thus makes it possible to achieve a particularly large-area connection of the contact surfaces in a particularly advantageous and reliable manner with simultaneously low thermal loading of the connection partner.

[0032] This development can be realized particularly advantageously if there is sufficient movement play for the laser along the weld seam center axis and above the contact surfaces to be connected, as applies in particular to the bottom side of the piston.

[0033] According to a further advantageous development, the laser girth weld is arranged on the piston rod side with the weld center axis inclined at an inclination angle α of 2 to 15 degrees relative to the main longitudinal axis.

[0034] In order to be able to weld the piston rod side, the laser must be positioned so that the weld center axis, which also corresponds to the incident path of the laser, encloses an inclination angle α with the main longitudinal axis.

[0035] In this development, the angle of inclination α is between 2 and 15 degrees, preferably between 4 and 8 degrees and particularly preferably 5 degrees.

[0036] In order to achieve a stronger connection between the piston and the piston rod, the largest possible melting area along the contact surface between the two connecting parts is sought. It has been found that sufficient melting is achieved by the conical cross section of the laser girth weld when its edge region extends along the contact surface. Therefore, the inclination angle is preferably not greater than half the weld angle of the laser girth weld.

[0037] The advantage of this development is that even with low movement play of the laser, such as in particular along the piston rod, a laser girth weld with a large effective weld depth can be provided.

[0038] According to an advantageous development, the piston unit has a first laser girth weld and a second laser girth weld.

[0039] According to this advantageous development, a first laser girth weld is arranged on the bottom side at the end side and with its weld center axis parallel to the main longitudinal axis of the piston rod, and a second laser girth weld is arranged on the piston rod side at the piston rod side and with its weld center axis inclined at an inclination angle α of 2 to 15 degrees relative to the main longitudinal axis. The inclination angle α of the second laser girth weld is preferably 4 to 8 degrees and particularly preferably 5 degrees.

[0040] In this development, the two advantageous developments described above are combined.

[0041] In an advantageous forming variant, the weld depths of the first laser girth weld and the second laser girth weld extend generally over the entire contact surface between the piston and the piston rod, so that the integrally bonded connection between the piston and the piston rod utilizes the entire contact surface, thereby achieving maximum loadability of the connection.

[0042] It is also possible that two laser girth welds connect the piston and the piston rod only partially along the contact surface. The two annular surfaces formed in this way via the two laser girth welds supplement the axial force transmission and also provide a particularly high loadability of the connection. Here, the heat input is smaller than in the case of conventional welded contact surfaces.

[0043] According to a further advantageous development, the piston unit is designed as a piston unit of a synchronous cylinder.

[0044] The piston unit of the synchronous cylinder is designed so that the piston is fixed centrally on the piston rod. The piston rod is here completely guided through the piston and axially protrudes beyond the piston on both sides.

[0045] According to this advantageous development, the piston has a first piston rod side and a second piston rod side. Due to the specific design of the synchronization cylinder, the piston has no bottom side and instead has two piston rod sides.

[0046] According to an advantageous development, the piston unit has a first laser girth weld and a second laser girth weld, wherein the laser girth welds are arranged opposite each other.

[0047] The piston is fixed to the piston rod by means of two annular laser ring welds.

[0048] According to this advantageous development, the first laser girth weld and the second laser girth weld are each arranged on the piston rod side and their weld center axes are each arranged obliquely at an angle α of 2 to 15 degrees relative to the main longitudinal axis.

[0049] Since the piston rod extends through the piston, the two laser girth welds are extended by means of the weld center axis inclined at an angle α. The angle α is between 2 and 15 degrees, preferably between 4 and 8 degrees and particularly preferably 5 degrees. Thus, for this piston design, an optimized connection is advantageously achieved between the piston and the piston rod.

[0050] According to a further advantageous development, the piston rod has a chrome-plated outer surface.

[0051] Due to the special load, the piston rod is usually formed with a chrome-plated outer surface. Here, the piston rod is chrome-plated as a rod stock, cut and then further processed with the chrome-plated surface.

[0052] In terms of production technology, there is the problem that the chrome-plated outer surface does not allow welding according to the prior art in practice.

[0053] It has been found that by means of the thermal action of the laser annular weld on the chrome-plated outer surface, such a structural change of the chrome layer is caused that it is structured between the steel of the piston and the piston rod in such a way that a high lateral static friction is achieved on the opposite contact surfaces, i.e. between the outer cylindrical side of the piston rod and the inner cylindrical side of the piston. This provides a sufficiently high axial force transmittance between the piston and the piston rod.

[0054] A particular advantage of this development is that the otherwise necessary removal of the chrome-plated outer surface can be dispensed with.

[0055] According to a further advantageous development, the chrome-plated outer surface has a non-chrome-plated ring section of reduced cross-section.

[0056] For this purpose, the chrome layer is removed in the ring section by means of a cutting method, preferably grinding or turning. There is a ring section surrounding the piston rod, the cross section of which is reduced at least by the thickness of the removed chrome layer.

[0057] According to this advantageous development, an annular compensation layer is arranged between the piston and the ring section of reduced cross section. The compensation layer compensates for the diameter difference between the non-chrome-plated ring section of reduced cross section and the rest of the piston rod and can also exceed the difference if necessary. For this purpose, the annular compensation layer, which is preferably formed from at least one shaped body, is inserted into the ring section of reduced cross section and the piston is pushed onto it. It is also possible to introduce the annular compensation layer as a cutting ring.

[0058] In this advantageous development, the piston rod is connected to the annular compensation layer by a radially inner laser annular weld, and the annular compensation layer is connected to the piston by a radially outer laser annular weld. To this end, the material of the annular compensation layer is matched not only to the material of the piston but also to the material located below the chrome-plated outer surface of the piston rod so that melting can take place.

[0059] Advantageously, components of the piston unit which have an additional surface treatment, such as chrome plating, can therefore also be welded.

[0060] According to an advantageous development, the piston is designed to be case-hardened.

[0061] The surface of the piston is hardened by methods known from the prior art, such as nitriding. Such changes in the material properties at the surface make welding connections more difficult or preclude welding connections according to the prior art.

[0062] According to an advantageous improvement, the piston rod has an axial contact surface at the end. Preferably, it is a flat surface arranged orthogonally to the main longitudinal axis of the piston rod. Here, it is an unhardened contact surface. In the middle of the contact surface, a centering pin is preferably arranged.

[0063] According to this advantageous development, the piston has a flat cylindrical profiled section on the piston rod side, the end face of which forms the axial counter-contact surface on the piston rod side.

[0064] The counter-contact surface is likewise preferably oriented orthogonally to the main longitudinal axis and is designed as a flat surface.

[0065] In this case, the centering hole is preferably located centrally in the flat cylindrical profile section, into which the centering pin of the piston rod engages, so that the piston and the piston rod are fixed radially to one another during the connection.

[0066] When connected, the contact surface and the counter-contact surface bear flat against one another.

[0067] According to this advantageous development, the counter contact surface has a surface reduction, wherein the hardened surface is removed by the surface reduction.

[0068] In the region of the counter-contact surface, the hardened surface is preferably removed by surface grinding until the base material is reached.

[0069] According to this advantageous development, the laser girth weld is arranged transversely to the main longitudinal axis and connects the contact surface and the counter-contact surface in a materially bonded manner.

[0070] This improvement is particularly advantageous in the case of a piston unit of a micro cylinder. A micro cylinder is understood in this context to be a working cylinder having a piston diameter of up to 50 mm. In this improvement, there are the advantages of high production efficiency and at the same time sufficient loadability of the piston unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The present invention is explained in detail as an embodiment according to the following figures.

[0072] Figure 1 Showing the piston unit of the working cylinder (welding on the bottom side)

[0073] Figure 2 Showing the piston unit of the working cylinder (welding on the piston rod side)

[0074] Figure 3 Showing the piston unit of the working cylinder (closed piston)

[0075] Figure 4 The piston unit of the working cylinder is shown (welding on both sides)

[0076] Figure 5 Showing the piston unit of the synchronous cylinder (welding on both sides)

[0077] Figure 6 The piston unit of the working cylinder is shown (with an annular compensation layer)

[0078] Figure 7Showing the piston unit with hardened piston surface (exploded view)

[0079] Figure 8 Showing piston unit with hardened piston surface (weld) DETAILED DESCRIPTION

[0080] The above description of the solution according to the invention thus includes in particular the various combinations of features defined by the embodiments which are subsequently numbered consecutively:

[0081] 1. A piston unit of a working cylinder,

[0082] It comprises a piston (1) and a piston rod (2),

[0083] The piston has an axial hole (3), in which the piston rod (2) is accommodated.

[0084] The piston rod (2) and the piston (1) are connected in a material-locking manner by means of an annular laser ring weld (4), and

[0085] The laser annular weld (4) forms a sealing plane for sealing the pressure medium.

[0086] 2. The piston unit of the working cylinder according to embodiment 1,

[0087] The laser annular weld (4) is arranged on the bottom side (5) at the end and has a weld center axis (6) arranged parallel to the main longitudinal axis (7) of the piston rod (2).

[0088] 3. The piston unit of the working cylinder according to embodiment 1 or 2,

[0089] The laser ring weld (4) is arranged on the piston rod side (8) and the weld center axis (6) is arranged obliquely with respect to the main longitudinal axis (7) of the piston rod (2) at a weld inclination angle α of 2 to 15 degrees.

[0090] 4. The piston unit of the working cylinder according to any one of the above embodiments,

[0091] The piston unit has a first laser ring weld (4.1) and a second laser ring weld (4.2).

[0092] The first laser ring weld (4.1) is arranged on the bottom side at the end side and with its weld center axis (6) parallel to the main longitudinal axis (7) of the piston rod (2), and the second laser ring weld (4.2) is arranged on the piston rod side (8) and with its weld center axis (6) inclined at an angle α of 2 to 15 degrees relative to the main longitudinal axis (7).

[0093] 5. The piston unit of the working cylinder according to any one of the above embodiments,

[0094] The piston unit is designed as a piston unit of a synchronous cylinder,

[0095] The piston (1) has a first piston rod side (8.1) and a second piston rod side (8.2),

[0096] The piston unit has a first laser ring weld (4.1) and a second laser ring weld (4.2),

[0097] The laser annular welds (4.1, 4.2) are arranged axially opposite to each other.

[0098] The first laser ring weld (4.1) is arranged on the first piston rod side (8.1) and the second laser ring weld (4.2) is arranged on the second piston rod side (8.2), respectively, and the weld center axes (6) of the laser ring welds (4.1, 4.2) are arranged at an inclination angle α of 2 to 15 degrees relative to the main longitudinal axis (7).

[0099] 6. The piston unit of the working cylinder according to any one of the above embodiments,

[0100] Wherein, the piston rod (2) has a chrome-plated outer surface.

[0101] 7. The piston unit of the working cylinder according to embodiment 6,

[0102] wherein the outer surface has a non-chrome-plated ring section (9) of reduced cross-section,

[0103] wherein an annular compensation layer (10) is arranged between the piston (1) and the ring section (9) of reduced cross-section,

[0104] The piston rod (2) is connected to the annular compensation layer (10) via a radially inner laser annular weld (11), and the annular compensation layer (10) is connected to the piston (1) via a radially outer laser annular weld (12).

[0105] 8. The piston unit of the working cylinder according to any one of the above embodiments,

[0106] The piston (1) is designed to be surface-hardened.

[0107] - wherein the piston rod (2) has an end-side axial contact surface (13),

[0108] - wherein the piston (1) has a flat cylindrical profiled section (14) on the piston rod side, the end face of which forms an axial mating contact surface (15) on the piston rod side,

[0109] - wherein the mating contact surface (15) has a surface reduction, wherein the hardened surface is removed by the surface reduction,

[0110] The laser annular weld (4) is arranged transversely to the main longitudinal axis (7) and connects the contact surface (13) and the counter-contact surface (15) in a material-locking manner.

[0111] exist Figure 1 , a first embodiment of a piston unit of a working cylinder is shown as a schematic sectional view. The piston unit has a piston 1 and a piston rod 2. The piston 1 has an axial bore 3, in which the piston rod 2 is accommodated. It has a bottom side 5 and a piston rod side 8.

[0112] The piston unit has a laser circumferential weld 4 which connects the piston 1 and the piston rod 2 in a materially bonded manner. The laser weld 4 is arranged on the bottom side 5 .

[0113] In this case, the laser girth weld 4 has a weld center axis 6 which extends centrally through the cross section of the laser girth weld 4 .

[0114] The laser weld seam center axis 6 is parallel to the main center axis 7 of the piston rod 2 and extends along corresponding contact surfaces of the piston 1 and the piston rod 2 .

[0115] In this embodiment, welding is performed by means of laser welding starting from the bottom side 5. Laser welding in which the weld seam center axis 6 runs parallel to the main longitudinal axis 7 is possible on the bottom side due to the required freedom of movement of the laser emitter.

[0116] exist Figure 2 , another embodiment of a piston unit is shown, which is welded on the piston rod side. The laser annular weld 4 is tilted at an inclination angle α of 5 degrees. Figure 2 The piston unit is Figure 1 The piston units shown in are constructed identically.

[0117] Due to the piston rod 2, the laser is tilted at an angle of inclination α relative to the main longitudinal axis 7 of the piston rod 2. As a result, the weld center axis 6, which extends in accordance with the path of the laser beam, is not as good as in Figure 1 As in FIG. 1 , it extends parallel to the main central axis 7 and encloses an inclination angle α therewith.

[0118] In this embodiment, the edge region of the laser annular weld 4 overlaps the contact surface between the piston 1 and the piston rod 2 , thereby producing a connection therebetween.

[0119] exist Figure 3 , a piston unit with a closed piston 1 is shown. In contrast to the previous piston unit, the axial bore 3 does not penetrate the piston 1 but is designed as a blind bore. The piston rod 2 is not completely guided through the piston 1 here.

[0120] Laser girth weld 4 is similar to Figure 2 It is arranged on the piston rod side with an inclined weld seam center axis 6, which encloses an inclination angle α with the main center axis 7. The inclination angle α is also 5 degrees here.

[0121] exist Figure 4 In the example, the piston unit basically corresponds to Figure 1 and Figure 2 The piston unit in the

[0122] In this embodiment, the connection between the piston 1 and the piston rod 2 is formed via a first laser girth weld 4 . 1 and a second laser girth weld 4 . 2 .

[0123] Here, the first laser ring weld 4.1 corresponds to Figure 1 The laser girth weld 4 in FIG. 5 is a laser girth weld, wherein the weld center axis 6 extends parallel to the main longitudinal axis 7 and the laser girth weld is welded starting from the bottom side 5 .

[0124] The second laser ring weld 4.2 corresponds to Figure 2 and Figure 3 The laser girth weld 4 in the embodiment of the present invention is shown, wherein the weld center axis 6 forms an inclination angle α with the main longitudinal axis 7. The inclination angle α is also 5 degrees here. The welding is performed from the piston rod side 8.

[0125] In this embodiment, the first laser girth weld 4.1 and the second laser girth weld 4.2 touch or overlap, so that the connection is made over the entire cylindrical contact surface of the piston 1 and the piston rod 2. This achieves the highest loadability of the connection.

[0126] exist Figure 5 . The synchronous cylinder is characterized in that it has no bottom side 5 due to the through-going piston rod 2. For the reasons mentioned, two sides are defined as a first piston rod side 8.1 and a second piston rod side 8.2. In this embodiment, the two piston rod sides 8.1, 8.2 are identically constructed.

[0127] Unlike other embodiments of the piston unit, the first laser girth weld 4.1 and the second laser girth weld 4.2 are inclined relative to the main longitudinal axis at an inclination angle α. The inclination angle α is also 5 degrees here. Here, the first laser girth weld 4.1 is laser welded from the first piston rod side 8.1 and the second laser girth weld 4.2 is laser welded from the second piston rod side 8.2.

[0128] exist Figure 62 shows a piston unit with an annular compensation layer 10. In this embodiment, the surface of the piston rod 2 is chrome-plated.

[0129] The surface is removed in the ring segment 9 by turning, so that a segment with reduced cross section is formed. The extent of the cross section reduction is Figure 6 1 is shown too high for reasons of clarity. An annular compensation layer 10 is inserted into the ring segment 9 of reduced cross section, which in this embodiment is designed as a segmented steel sleeve. The piston 1 is pushed onto the annular compensation layer 10 .

[0130] The piston rod 2 is welded to the annular compensation layer 10 by means of a radial inner laser weld 11. The annular compensation layer 10 is homogeneous in material with the piston rod 2 below the chrome layer and with the piston 1. The weld center axis 6 is tilted here at an angle of inclination α. ​​The angle of inclination α is 5 degrees. The piston 1 is welded to the annular compensation layer 10 by means of a radial outer laser weld 12. The weld center axes 6 of the radial outer laser weld and the radial inner laser weld 11 extend parallel.

[0131] exist Figure 7 2 shows a piston unit having a piston 1 which has a hardened surface 16 .

[0132] The piston 1 also has a flat cylindrical profile section 14 which slightly projects beyond the remaining contour of the piston 1 on the piston rod side 8. The hardened surface is removed from the axial mating contact surface 15 by surface grinding in the region of the flat cylindrical profile section 14. In the middle of the flat cylindrical profile section 15 there is a centering hole which corresponds to a centering pin in the middle of the axial contact surface 13 of the piston rod 2.

[0133] Thus, the piston 1 can be placed on the piston rod 2, whereby the two are fixed in their relative radial position.

[0134] exist Figure 8 Shown in Figure 7 The piston unit is mounted in the embodiment of the present invention. The piston 1 is axially placed on the piston rod 2, so that the contact surface 13 and the matching contact surface 14 are in contact with each other. The centering pin is engaged with the centering hole.

[0135] The piston 1 and the piston rod 2 are connected along corresponding contact surfaces 13, 14 by means of a laser girth weld 4. In contrast to the piston units described above, the weld center axis 6 is perpendicular to the main longitudinal axis.

[0136] List of reference numerals:

[0137] 1 Piston

[0138] 2 Piston rod

[0139] 3 Axial hole

[0140] 4 Laser girth weld

[0141] 4.1 First laser ring weld

[0142] 4.2 Second laser ring weld

[0143] 5 Bottom side

[0144] 6 Weld centerline

[0145] 7 Main longitudinal axis

[0146] 8 Piston rod side

[0147] 8.1 First piston rod side

[0148] 8.2 Second piston rod side

[0149] 9 Ring segment with reduced cross section

[0150] 10 Annular compensation layer

[0151] 11 Radial internal laser weld

[0152] 12 Radial external laser weld

[0153] 13 Axial contact surface

[0154] 14 Flat cylindrical profile section

[0155] 15 Axial mating contact surface

[0156] 16 Hardened surface

[0157] α Tilt angle α

Claims

1. A piston unit of a working cylinder, It comprises a piston (1) and a piston rod (2), The piston has an axial hole (3), in which the piston rod (2) is accommodated. The piston rod (2) and the piston (1) are connected in a materially bonded manner by means of an annular laser girth weld (4), and The laser annular weld (4) forms a sealing plane for sealing the pressure medium. The piston rod (2) has a chrome-plated outer surface. wherein the outer surface has a non-chrome-plated ring section (9) of reduced cross-section, - wherein an annular compensating layer (10) is arranged between the piston (1) and the ring section (9) of reduced cross-section, The piston rod (2) is connected to the annular compensation layer (10) via a radially inner laser annular weld (11), and the annular compensation layer (10) is connected to the piston (1) via a radially outer laser annular weld (12).

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