DE102012111136A1 - Producing pressure-tight hollow body to predetermined medium, comprises joining two body parts, which when assembled, form hollow body containing medium in gaseous and/or liquid form, or by sealing single body which forms hollow body - Google Patents

Abstract

Producing a hollow body (1) which is pressure-tight to a predetermined medium (2), comprises joining at least two body parts, which when assembled, form a hollow body containing the medium in a gaseous and/or liquid form, or by sealing a single body which forms the hollow body in the closed state and contains in the medium in gaseous and/or a liquid state normal conditions. At least two body parts are joined in a material fit manner. The body is sealed in a material fit manner. The medium which is in the solid or semi-solid state is placed in at least one part of a hollow chamber (7). Producing a hollow body (1) which is pressure-tight to a predetermined medium (2) comprises joining at least two body parts, which when assembled, form a hollow body containing the medium in a gaseous and/or liquid form, or by sealing a single body which forms the hollow body in the closed state and contains in the medium in gaseous and/or a liquid state normal conditions. At least two body parts are joined in a material fit manner. The body is sealed in a material fit manner. The medium which is in the solid or semi-solid state is placed in at least one part of a hollow chamber (7) of at least one body part and the medium are placed together prior to carrying out the material fit joining. The material fit joining is carried out. The medium which is in the solid or semi-solid state is used in hollow chamber of the body prior to carrying out the material fit joining. An independent claim is also included for a piston rod comprising pressure-tight hollow body having a hollow chamber forming body parts or a hollow body, where the hollow body is sealed in material fit manner and the hollow chamber contains the medium which is in gaseous and/or a liquid state.

Description

The present invention relates to a method for producing a pressure-tight for a predetermined medium hollow body and a piston rod.

Hollow bodies, which are pressure-tight for a predetermined medium which is arranged in the hollow inner region when the hollow body is used as intended, may be provided for various purposes. One possible use is the use of the hollow body as a heat pipe. In this application, due to movement of the heat pipe, the medium is reciprocated between a hot end and a cold end of the heat pipe, each receiving heat at the hot side and delivering it to the colder end. In this way, heat removal from the hot end is possible.

This application is for example from the DE 44 05 091 A1 known. There, a hollow body designed as a heat pipe is used as the piston rod of a crank-pulley motor. The piston rod connects the piston with the crank loop. The liquid located in the piston rod, which may be water, for example, absorbs heat at the piston end of the piston rod, evaporates and is then moved by the movement of the crank loop and thus the piston rod in the direction of the crank loop. This end of the piston rod is cooler or can even be cooled so that the liquid condenses there and thus gives off heat. The piston rod is integrally connected to the crank loop. The piston is screwed onto a plug inserted into the open end of the piston rod after the fluid has been introduced into the piston rod. However, such a screw connection may become leaky under the high load that occurs in a crank-type motor. This is further facilitated by the fact that due to the fast back and forth corresponding vibrations occur, whereby the screw can be solved gradually and may need to be tightened at certain intervals. Also, the plug closure itself can be leaking due to the vibrations and the associated wear.

Another application for a pressure-tight for a predetermined medium hollow body is the use as a valve for a reciprocating internal combustion engine. Such a valve is from the DE 2 324 850 known. In the method described there, the valve stem is gas-tight welded to the valve plate part. Subsequently, a Wärmeleitflüssigkeit, in particular sodium, is filled in a liquid state in an inner cavity of the valve stem. Thereafter, the heat transfer fluid must be cooled so that it assumes the solid state. After a complex cleaning, the valve end piece is inserted end into the inner cavity of the valve stem and then secured by electron beam welding to the valve stem. The process described is very complicated, since many process steps are necessary and during the production of a multiple heating with subsequent targeted cooling is necessary.

It is therefore an object of the invention to provide a process which can be carried out in a simple manner for producing a hollow body which is pressure-tight for a predetermined medium and in which an escape of the medium from the hollow space of the hollow body during production is prevented.

A further object of the invention is to make known methods for producing a hollow body which is pressure-tight for a predetermined medium more economical and easier to carry out.

A further object of the invention is to provide a method for producing a hollow body which is pressure-tight for a predetermined medium, in which also highly volatile and in particular non-metallic media can be used as a predetermined medium.

These objects are achieved by a method for producing a pressure-tight for a predetermined medium hollow body according to claim 1 and by a method for producing a pressure-tight for a predetermined medium hollow body according to claim 2.

It is a further object of the invention to provide a piston rod having a hollow body which is pressure-tight for a predetermined medium and which is easy to manufacture.

It is a further object of the invention to provide a piston rod having a hollow body which is pressure-tight for a predetermined medium and in which a sufficient amount of medium is present in the hollow body.

These objects are achieved by a piston rod according to claim 11.

Advantageous developments are the subject of the respective subclaims.

In a first alternative of the method according to the invention for producing a hollow body which is pressure-tight for a predetermined medium, at least two partial bodies are joined. The at least two sub-bodies form the hollow body in an assembled state, which contains the medium in the gaseous and / or liquid state when the hollow body is used as intended. This allows, for example, the use as a heat pipe in which the medium is evaporated at a hot end and condensed at a cooler end. The at least two partial bodies are joined cohesively. Before cohesive joining, the medium is used in partially solid or solid state in at least one partial cavity of at least one of the partial bodies. Subsequently, the cohesive joining is performed. In this way it is ensured that when carrying out the material-locking joining, the medium can not escape from the part cavity and in particular can not penetrate into the cohesive joint connection and contaminate it. By such contamination, the compound could, for example, become brittle or even fail.

It is not absolutely necessary that the medium is completely in solid state, and this is preferred. The medium can also be present as a gel, for example. It is crucial that the medium in the inserted state has sufficient rigidity or inertia, which prevents escape during the joining step. According to the invention, escaping is prevented in particular even if, for example, in the case of a piston rod, two substantially hollow-cylindrical partial bodies, which are each closed at one end, are joined by the method according to the invention, these partial bodies being in a horizontal position. If the medium were introduced in this case in the liquid state or in the gaseous state in the part body, so an escape would be easily possible. This is prevented by the method according to the invention.

In an alternative embodiment of the method according to the invention, a single body is closed cohesively. This body forms the pressure-tight for the predetermined medium hollow body. Also, this hollow body contains the medium when used properly in the gaseous and / or liquid state. Before the cohesive closing of the body, the medium is also used in this alternative in partially solid or solid state. Only then is the body closed materially closed. The advantages achieved correspond to those of the first alternative. Also in this alternative, escape of the medium during manufacture is effectively prevented.

In an advantageous embodiment of the method according to the invention, the part body according to the first alternative of the method according to the invention under the influence of heat material joined or in the case of the second alternative of the method according to the invention, the body is closed cohesively under heat. The term heat exposure is to be understood as meaning both processes in which heat is actively introduced into the part bodies or the body from a heat source, as well as processes in which the heat is transferred during the implementation of the process and in particular in the material to be sealed or sealed Body arises, as is the case for example in a friction welding. The joining or closing under the action of heat has been found to be particularly advantageous, since in this way a simple and process-reliable pressure-tight closure of the hollow body is possible.

In an advantageous development of the method according to the invention, in the case of the first alternative of the method according to the invention, the partial bodies are materially joined by means of deformation and / or material addition or, in the case of the second alternative of the method according to the invention, the body is firmly closed by means of deformation and / or material addition. In this way, a safe and economical joining or closing of the hollow body is possible. For example, after the medium has been introduced, a tube-like body open at only one end could be deformed at the open end such that this end is closed in a material-tight manner. In this way, a pressure-tight hollow body would have been produced by only a simple process step. The medium is used in this alternative before the deformation step in a solid or liquid state in the cavity of the body.

In the case of friction welding of the two partial bodies with each other, the hollow body would be produced even under the action of heat and by deformation. The friction welding method is particularly preferred, wherein basically a welding method for the cohesive joining or closing is to be regarded as advantageous. A likewise preferred method is the friction stir welding, since a secure connection in the sense of a cohesive joining or closure is also possible in this method.

In an advantageous embodiment of the method according to the invention, the medium which is arranged in the proper use of the hollow body in this, water and / or Diphyl and or perchlorethylene and / or trichlorethylene. The medium may consist of either one of these substances or of a mixture of these substances. These substances have according to the invention as for a heat transfer from one end of a heat pipe to another end of the Heat pipe proven effective media. If water is used, it is advantageously introduced in the process according to the invention in solid state, ie in the form of ice into the cavity or a partial cavity.

Surprisingly, it has been found that even with a cohesive joining or closing of the hollow body under heat, for example in a welding process, an ice volume melts so slowly despite the heat that an escape of water or water vapor is avoided during the process. Since a friction welding requires only a short time to perform, such a method has been found to be particularly advantageous because in this method, the medium does not have enough time to melt or evaporate, so that the escape of the medium can be effectively prevented.

In an advantageous embodiment of the method according to the invention, the medium is used together with a recording device receiving the medium in at least one partial cavity or in the cavity. This receiving device is used in particular to transport the medium to a predetermined location in the cavity or partial cavity and then advantageously also at least for a certain time to keep there, d. H. to be fixed. This additional support also ensures that the medium does not penetrate into the area during the production in which the joint or the closure is made.

The receiving device advantageously has a sleeve-like, spherical or rotationally elliptical spatial form. Additionally or alternatively, the receiving device is advantageously formed lattice and / or net-like. This embodiment ensures that the medium is held in partially solid or solid state of the receiving device, but not or hardly held by the receiving device in the liquid or gaseous state, so that, for example, when used as a heat pipe, a free flow of the medium is possible ,

In order to additionally ensure that the receiving device and the medium arranged therein does not enter the region of the cohesive closing or joining, it is provided in an advantageous development that the receiving device is resiliently biased, in particular biased in a radial direction. If the body or a partial body is formed as a tube-like component, then the receiving device is advantageously biased in the radial direction, so that it can be inserted into the cavity or partial cavity and then has a certain hold on the inner wall of the body or of the partial body by the acting force , The displacement of the receiving device in the cavity or partial cavity is made more difficult, which ensures that the medium does not enter the area of the cohesive connection or cohesive joining.

The piston rod according to the invention has a pressure-tight hollow body with a cavity-forming part body or a body having a cavity. The hollow body is closed by a material fit, with a hollow body joined from two or more partial bodies also being considered closed. The hollow space of the hollow body contains a medium that is liquid and / or gaseous when the hollow body is used as intended.

Unlike known piston rods, there is no risk in the piston rod according to the invention that the piston is released from the piston rod by shaking movements. In addition, the tightness of the piston rod according to the invention is significantly better than conventional piston rods, which have a medium in a cavity. The piston rod according to the invention can be advantageously produced by the process according to the invention in one of the above embodiments. As a result, an economical production of piston rods with a pressure-tight hollow body in which a medium is possible.

In an advantageous development of the piston rod according to the invention, the cavity has in at least one end region a retaining device for the medium and / or a receiving device receiving the medium. This retainer causes the medium or the receiving device remains in the end region during the production of the piston rod and thus does not come in the vicinity of the area in which the cohesive joint or the cohesive closure is made. Such a retaining device can also be provided within the scope of the method according to the invention in the cavity or a partial cavity, in particular in a respective end region of the cavity or of the partial cavity.

Advantageously, the retaining means is formed as an extended portion of the cavity or a partial cavity and further advantageously comprises retaining means, e.g. in the form of a retaining shoulder, a retaining collar or a retaining cone. These elements enhance the retention effect of the retainer, thereby additionally ensuring that the medium remains in the end region during manufacture.

In a further advantageous development of the piston rod according to the invention, the retaining device has a roughened surface area. This results in a greater resistance to the medium or the receiving device with respect to a movement away from the end region, which in turn prevents such movement.

In an advantageous development of the piston rod according to the invention, the cavity has a rib and / or lamellar structure in at least one end region. This structure may for example be in the form of a thread or in the form of longitudinal grooves or longitudinal webs. On the one hand, this rib or lamellar structure can likewise prevent or delay a movement of the medium or the receiving device away from the end region. However, a further significant advantage of the fin or lamellar structure is that an improved heat transfer between the medium and the hollow body is made possible, since a larger surface area of the hollow body, which can be in contact with the medium, is available through the rib or lamellar structure , This applies to both the transfer of heat at one end to the medium and heat from the medium to another end of the piston rod.

Particularly advantageous is the use of the connecting rod according to the invention has proven in a reciprocating piston engine, in particular a crank loop motor, in particular for the formation of piston rods of a crank loop. Due to the piston rod according to the invention, heat dissipation from the piston is possible in these applications and the piston rod is less susceptible to wear and requires less maintenance compared to known piston rods with a heat dissipation function.

The invention will be explained and illustrated by way of example with reference to seven figures. It show here

1 a partially cutaway plan view of a crank motor with piston rods according to the invention;

2 a detailed view of a composite of a crank, a piston rod according to the invention and a piston;

3 the individual parts of a hollow body produced by the process according to the invention in the form of a piston rod at the beginning of the process;

4 a further embodiment of a hollow body produced by the inventive method at the beginning of the process;

5 a further embodiment of a hollow body produced by the inventive method at the beginning of the process;

6 a receiving device for use in the inventive method with medium inserted therein;

7 a further embodiment of a recording device for the medium for use in the inventive method.

8A . 8B the production of a hollow body according to an embodiment of the method according to the invention

The 1 shows a crank motor with two working cylinders, in each of which a piston 14 running. Each of the pistons 14 is by a piston rod according to the invention 1 with a crank loop 13 connected to the crank loom motor.

In 1 The bottom cylinder is at the top and the top cylinder is at bottom dead center of the cycle of the crank motor.

When operating the crank loom motor, the pistons move 14 together with the piston rods 1 and the crank loop 13 back and forth, creating a cavity in each one 7 the piston rods 1 located medium 2 is moved back and forth. In this movement, the medium takes 2 which is water here, from the piston 14 Heat up and evaporate. Subsequently, the medium becomes 2 by the movement of the compound of the crank loop 13 with the piston rods 1 and the piston 14 in the direction of the crank loop 13 moves and gives heat to the surroundings of the crank loop 13 from. To improve the heat dissipation, the crank loop 13 z. B. be cooled by an oil bath or an oil jet. In the two cylinders, this process runs in opposite directions, ie while the medium 2 in the one piston rod 1 at the piston end of the piston rod 1 heated, gives the medium 2 the other piston rod 1 Heat to the surroundings of the crank loop 13 from.

The 2 shows in more detail the structure of the assembly of crank 13 , Piston rods 1 and on one side also a piston 14 , In the following, only the lower half of the composite shown will be discussed, since the upper half is constructed accordingly. The piston rod 1 has a cavity 7 on, extending over a large part of the piston rod 1 extends in a longitudinal direction. In the cavity 7 is a medium 2 , here water, arranged. Due to the operating temperatures of the crank motor, the water is liquid and / or gaseous when the piston rod is used as intended. In particular, this heats up medium 2 in one end area 8th the piston rod 1 through the piston 14 radiated or over the piston rod 1 supplied heat, so that the medium 2 goes into the gaseous state of aggregation.

By the subsequent movement of the composite of crank loop 13 , Piston rods 1 and pistons 14 becomes the medium 2 in the other end area 9 the piston rod 1 moves where the medium 2 Heat to the adjacent area of the piston rod 1 as well as the crank loop 13 and the surrounding area. Following this, the composite moves in the opposite direction, causing the medium 2 back in the end area 8th is moved and can absorb heat again.

In the end area 8th the piston rod 1 is the wall of the cavity 7 with a roughened surface area 11 Mistake. This surface area 11 causes in the production of the piston rod according to the invention 1 a retention of the semi-solid or solid state medium 2 but hinders the flow of the medium 2 not under normal use. Rather, the surface area improves 11 the heat transfer between the piston end of the piston rod 1 and in the end area 8th located medium 2 because the roughening provides a larger area for heat transfer.

The piston rod 1 according to 2 was prepared by the process of the invention. At the beginning of the process according to the invention were two partial bodies 3 . 4 present, in each of which a partial cavity 5 . 6 was present. These part bodies 3 . 4 are in 3 shown.

The part body 3 has the partial cavity 5 and the end area 8th with the roughened surface area 11 on. In the second part body 4 are the part cavity 6 and the end area 9 intended. The part body 4 is integral with the crank loop 13 made up and consists essentially of a short, tubular body, which at one end by a wall of the crank loop 13 is closed.

The connection of the two partial bodies 3 . 4 is carried out according to the method of the invention as follows:
First, the medium 2 in partially solid or solid state, for example as Eiszäpfchen, in the partial cavity 5 of the part body 3 used. Subsequently, the part body is rotated about its longitudinal axis X in rotation and from the in 3 shown position on the part body 4 moved. By when touching the part body 3 . 4 resulting heat and by a pressing pressure of the part body 3 . 4 against each other are the partial bodies 3 . 4 friction welded together. By the time the friction welding is completed, the medium is 2 not yet melted, so this throughout the manufacturing process in the end area 8th remained and therefore not from the resulting cavity 7 or the partial cavities 5 . 6 could escape.

The part body 3 is provided at its piston-side end with a threaded bore on which the piston 14 can be attached. While in the prior art for the connection of the piston rod to the piston, a plug was used, the piston rod according to the invention can be connected directly by a screw connection to the piston. As a result, this compound holds much longer than the known from the prior art connection. Due to the cohesive connection of the two part bodies 3 . 4 is the resulting hollow body 1 or the piston rod 1 pressure-tight for the medium 2 , causing an escape of the medium 2 from the cavity 7 is prevented.

The 4 shows a further embodiment of two partial bodies 3 . 4 with their partial cavities 5 . 6 , In the end area 8th of the part body 3 a medium retention means is provided as the extended area of the cavity 7 is trained. Will the medium 2 in the inventive production of the pressure-tight hollow body 1 in the partial cavity 5 of the part body 3 used, so can the medium 2 in the extended area in the end area 8th to lie down. By trained as a retaining collar holding means 15 it becomes the medium 2 difficult, from the end area 8th in a front area of the body part 3 to get. In this way it is ensured that in the subsequent friction welding process, the medium 2 not from the part cavity 5 can escape.

In the 5 is another embodiment of the body part 3 . 4 shown at the beginning of the process according to the invention. The part body 4 has no cavity. Thus, the later cavity becomes 7 of the hollow body 1 through the part cavity 5 of the part body 3 educated. In the end area 8th of the partial cavity 5 is a rib structure on the inner wall of the body part 3 present, which is formed by a thread located there. This rib structure enlarges the surface with which the medium 2 when used as intended the hollow body 1 with the part body 3 communicating what the heat transfer between the medium 2 and the part body 3 improved.

In the 6 is a recording device 12 for the medium 2 shown. The recording device 12 is formed like a lattice and has a sleeve-like spatial form with a diameter D on. The recording device 12 is biased in the radial direction, that is acted upon by a force from the outside in the direction of its longitudinal axis, so that the diameter D decreases. Will the recording device 12 in the inventive production of the hollow body 1 in a partial cavity 6 or cavity 7 introduced, the bias acts as a holding force of the receiving device 12 in the partial cavity 5 . 6 or cavity 7 , The recording device 12 thus holds the medium 2 and put this in one place in the part cavity 6 or cavity 7 firmly. This will prevent the medium 2 in the production of the pressure-tight hollow body 1 in the area that is joined or closed, moves.

The 7 shows a further embodiment of the receiving device 12 for use in a method according to the invention. The recording device 12 has a substantially rotationally-space-like spatial form and forms a kind of grid cage around the medium 2 , From the grid structure stand out single arms, which also has a holding force in a partial cavity 5 . 6 or cavity 7 cause the receiving device 12 and thus the medium 2 locally in the part cavity 6 or cavity 7 sets.

Because the medium 2 when used as intended the hollow body 1 is present in the liquid or gaseous state, hinders the receiving device 12 the movement of the medium 2 from an end area 8th to the other end area 9 not in normal use. Advantageously, the receiving device consists 12 made of a material which, at the temperatures used in the intended use of the hollow body 1 occur, does not melt. Melting material could adhere to the inner wall of the hollow body 1 put and thus the heat transfer to or from the medium 2 hinder. Alternatively, the receiving device 12 be formed from a material which, although at the temperatures in the normal use of the hollow body 1 occur, melts, but which has a sufficiently high thermal conductivity, so that the heat transfer between the hollow body 1 and the medium 2 not hindered.

In the 8A and 8B is an alternative of the method according to the invention for producing a pressure-tight hollow body 1 shown. The 8A shows a body 10 which is substantially tubular and closed at one end. The body 10 thus has a cavity 7 on. In the method according to the invention now the medium 2 in partially solid or solid state in the cavity 7 entered. Subsequently, the body becomes 10 deformed cohesively at the open end. This deformation can be done for example by heating this end and then pressing. The hollow body produced by these processes 1 thus has a cavity 7 with medium contained therein 2 on. The medium 2 can not leave the cavity 7 escape, causing the hollow body 1 is pressure-tight.

LIST OF REFERENCE NUMBERS

1

Hollow body / piston rod

2

medium

3

partial body

4

partial body

5

partial cavity

6

partial cavity

7

cavity

8th

end

9

end

10

body

11

surface area

12

recording device

13

crank loop

14

piston

15

holding means

X

 longitudinal axis

D

 diameter

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4405091 A1 [0003]
• DE 2324850 [0004]

Claims (16)

Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) by joining at least two partial bodies ( 3 . 4 ), in the joined state, the hollow body ( 1 ) forming the medium ( 2 ) in the intended use of the hollow body ( 1 ) in gaseous and / or liquid state, wherein the at least two partial bodies ( 3 . 4 ) are materially joined, wherein in at least one partial cavity ( 5 . 6 ) at least one partial body ( 3 . 4 ) before carrying out the material-locking joining the medium ( 2 ) is used in partially solid or solid state, and wherein thereafter the cohesive joining is performed. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) by closing a single body ( 10 ), which in the closed state, the hollow body ( 1 ), which forms the medium ( 2 ) in normal use in gaseous and / or liquid state, the body ( 10 ) is materially closed, wherein in a cavity ( 7 ) of the body ( 10 ) before carrying out the cohesive closure, the medium ( 2 ) is used in partially solid or solid state and wherein the cohesive sealing is carried out thereafter. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to claim 1 or 2, characterized in that the part bodies ( 3 . 4 ) are bonded by heat or the body ( 10 ) is closed materially under heat. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to one of the preceding claims, characterized in that the body ( 10 ) is materially closed by means of deformation and / or material addition or the partial body ( 3 . 4 ) are joined by means of deformation and / or material addition cohesively. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to one of the preceding claims, characterized in that the cohesive joining or closing by means of a welding process, in particular friction welding or friction stir welding, is performed. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to one of the preceding claims, characterized in that the medium ( 2 ) Water and / or diphyl and / or perchlorethylene and / or trichlorethylene. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to one of the preceding claims, characterized in that the medium ( 2 ) together with one the medium ( 2 ) receiving device ( 12 ) is used. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to claim 7, characterized in that the receiving device ( 12 ) is formed grid or net-like and / or has a sleeve-like, spherical or rotational elliptical spatial form. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to claim 7 or 8, characterized in that the receiving device ( 12 ) is resiliently biased, biased in particular in a radial direction, is used. Process for preparing a for a predetermined medium ( 2 ) pressure-tight hollow body ( 1 ) according to one of the preceding claims, characterized in that the medium ( 2 ) is used in solid state. Piston rod having a pressure-tight hollow body (in particular produced by a process according to one of the preceding claims) ( 1 ) with a cavity ( 7 ) forming partial bodies ( 3 . 4 ) or a cavity ( 7 ) having body ( 10 ), wherein the hollow body ( 1 ) is materially closed and wherein the cavity ( 7 ) a medium ( 2 ), which, in the intended use of the hollow body ( 1 ) is liquid and / or gaseous. Piston rod according to claim 11, characterized in that the cavity ( 7 ) in at least one end region ( 8th . 9 ) a retaining device for the medium ( 2 ) and / or a medium ( 2 ) receiving device ( 12 ) having. Piston rod according to claim 12, characterized in that the retaining means as an extended portion of the cavity ( 7 ) is formed and holding means ( 15 ), z. B. has a retaining shoulder, a retaining collar or a retaining cone. Piston rod according to claim 12 or 13, characterized in that the retaining device has a roughened surface area ( 11 ) having. Piston rod according to one of claims 11 to 14, characterized in that the cavity ( 7 ) in at least one end region ( 8th . 9 ) a rib or lamellar structure, z. B. in the form of a Has thread or in the form of longitudinal grooves or longitudinal webs. Use of the piston rod according to any one of claims 11 to 15 in a reciprocating piston engine, in particular a crank-belt engine, in particular for the formation of piston rods of a crank loop.

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