DE102015222862A1 - Method for coating at least one piston groove provided on a piston with a protective coating and coating device, in particular for carrying out the method - Google Patents

Abstract

The invention relates to a method for coating at least one piston groove (3) provided on a piston (2) with a protective coating (16) comprising the following steps: a) arranging the piston (2) with the piston groove (3) to be coated in one Coating device (1), b) fluid-tight sealing of a gap (13), which is formed in the region of the piston groove (3) to be coated between the piston (2) and the coating device (1), by means of a sealing element that can be filled and expanded with a fluid ( 10a), c) applying the protective coating (16) by introducing a coating material (17) into the intermediate space (13) so that a surface of the piston groove (3) is coated with the coating material (17).

Description

The invention relates to a method for coating at least one provided on a piston for an internal combustion engine piston groove with a protective coating. The invention further relates to a coating device, which is set up in particular for carrying out this method.

Pistons used in the cylinders of an internal combustion engine are exposed to considerable mechanical and thermal stresses during operation of the internal combustion engine. This is especially true for pistons of a piston material with low weight such as aluminum, as it is used for weight reasons in piston bodies of modern internal combustion engines. However, those areas of the piston surface on which are mounted in a known manner sealing rings for sealing the combustion chamber against the environment of the cylinder, however, are subject to considerable thermal and mechanical stresses due to strong temperature variations in the combustion chamber and due to strong vibrations of the sealing rings during operation of the internal combustion engine. These effects can lead to significant damage to the surface of the piston during long-term operation of the internal combustion engine.

It is therefore known from the prior art, with the aid of a suitable coating method, to provide the region of the piston surface, which is mechanically in contact with said sealing rings, typically piston grooves provided on the circumferential side of the piston, with a protective coating increases the wear resistance of the piston material.

Against this background, the DE 10 2008 038 323 A1 a coating device in the form of a coating mask for the electrolytic coating of a piston ring groove of a piston. The coating mask consists of an elastically yielding material. The elastic material can be stretched by means of several spikes of a stretching device, whereby the radial diameter of the coating mask can be increased. This facilitates the introduction of the piston in the coating mask.

A disadvantage found in conventional methods for applying the protective coating that they are feasible only with great technical effort and thus associated with considerable costs.

It is therefore a first object of the invention to provide an improved method for applying a protective coating to the piston groove of a piston, in which the above-mentioned disadvantage could be largely or even completely eliminated. It is also a second object of the invention to provide an improved embodiment of a coating device which is adapted to carry out the method.

These objects are achieved by the subject matter of the independent claims. Preferred embodiments are the subject of the independent claims.

The basic idea of the invention is therefore to provide a coating device for coating a piston groove of a piston with an expandable sealing element which can be filled with a fluid. This sealing element can be converted by filling with a pressurized fluid from a non-expanded to an expanded state in which there is a gap in which the actual coating of the piston groove is to take place, hermetically isolated from the outer environment of the coating device. For this purpose, the sealing element can be pressed in the expanded state against the piston surface of the piston, and preferably in the immediate vicinity of the piston groove to be coated. The gap formed in this way is then according to the invention limited not only by the expanded sealing element, but also by a piston portion of the piston, in which the piston groove to be coated is provided on the piston surface of the piston. By introducing the coating material into the space defined by the sealing element and the piston, for example in the course of a galvanic or chemical coating process, the piston groove can then be coated with the desired protective coating. Since an undesired fluid connection of the intermediate space with the outer environment of the coating device is prevented, the coating material remains exclusively in the typically very small-sized gap and thus in the immediate area around the piston groove to be coated. An undesirable, extensive coating of further area of the piston surface can be avoided in this way. It is also possible to prevent dirt particles or the like from being applied during the application of the protective coating. From the environment of the coating device into the space and affect the coating process can affect. Finally, after completion of the coating operation, by removing the pressurized seal member and the associated transfer of the seal member to the unexpanded state, the plunger can be easily removed from the coater.

An inventive method comprises the following steps: In a first step a), the piston is arranged with the piston groove to be coated in a coating device. In a second step b), a gap formed between the coating device and the piston to be coated is hermetically sealed, that is, fluid-tight. This means that said gap is fluidly separated from the outer environment of the coating device. The fluidic sealing takes place with the aid of a fluid-filled and expandable sealing element. In a third step c), a surface of the piston is coated with the coating material on the piston groove to be coated by introducing a coating material into the intermediate space, at least in the region of the piston groove. After applying the coating on the piston groove, the seal described in step b) can be canceled again and the coated piston can be removed from the coating device again.

In a preferred embodiment, the method comprises an additional step c0), which is carried out before the implementation of step c). According to step c0), the space is purged with a cleaning fluid. In this way, the gap and thus also the surface to be coated of the piston groove are cleaned before the actual protective coating is applied. This results in improved adhesion of the protective coating on the piston groove.

In a preferred embodiment of the method according to the invention, the expandable sealing element is arranged on the coating device and has an elastic sheath which delimits a sealing element interior. The sealing element interior is filled in this variant in step b) of the process with a fluid and pressurized. As a result, the envelope expands while increasing the volume of the seal member interior. In such a state expanded from the initial state, the sealing member is pressed against an outer peripheral side of the piston, thereby effecting the desired sealing of the clearance from the external environment.

Suitably, the fluid for filling the sealing element interior gas, preferably air, be.

In an advantageous development, two sealing elements are used in step b), which are arranged in an axial direction of the piston at a distance from each other. The axial arrangement of the two sealing elements takes place in such a way that the piston groove to be coated is arranged axially between the two sealing elements. In this way, the volume of the gap and thus the surface area of the piston around the piston groove can be kept small, so that only a relatively small surface area is coated around the piston groove. This leads to considerable cost advantages in the coating of the piston.

Particularly preferably, the coating of the piston groove takes place galvanically, in particular by means of hard anodization of the surface of the piston groove. In this case, the coating material is the electrolyte required for plating. If the aluminum piston is made of aluminum and if this is to be galvanized to aluminum oxide, it is possible to introduce into the intermediate space as a coating material, for example an aluminum electrolyte. As an alternative to electroplating, the coating can also be carried out chemically, in particular by applying a nickel coating. Instead of nickel, another suitable material may be used, such as chromium, iron, copper or tin. Together with all mentioned materials, solid or lubricant particles can be introduced as dispersion.

The invention further relates to a coating device for coating at least one piston groove provided on a piston. The coating device according to the invention is set up in particular for carrying out the above-presented. The coating device comprises a receiving device for receiving the piston during the performance of the coating process. On the receiving device, a fillable with a fluid and expandable sealing element is arranged. The sealing element is designed in such a way that a gap formed between the receiving device and the piston received in the receiving device, in which the piston groove to be coated is arranged, can be hermetically insulated from the surroundings of the receiving device. This space is partially limited by a piston portion of the piston, on which the piston groove to be coated is arranged.

In a preferred embodiment, a second sealing element is present in the coating device in addition to the first sealing element. In this variant, the two sealing elements are arranged on the pot collar at a distance from each other. In addition, the second sealing element is arranged at a distance from the bottom of the pot. In this way, the volume of the gap and thus the surface area of the piston around the piston groove can be kept small so that only a reduced surface area of the piston is coated around the piston groove becomes. This leads to further cost advantages in the coating of the piston. Since the second sealing element is intended to have the same effect as the first sealing element, the second sealing element preferably corresponds essentially to the first sealing element in terms of its construction and its construction. Particularly preferably, the first and the second sealing element are realized as equal parts.

Preferably, the first sealing element has an expanded and a non-expanded state and is adjustable between these two states. In the expanded state, the hermetic isolation described above is present. In the unexpanded state this hermetic isolation is abolished.

Particularly suitably, the sealing element is formed with air inflatable. In this way, the sealing element can be technically easily realized, which has an advantageous effect on the manufacturing cost.

Particularly preferably, the receiving device is pot-shaped and has a pot bottom and a protruding from the bottom of the pot pot collar. The pot bottom and the pot collar together partially define a receiving interior, in which the piston for carrying out the coating method according to the invention is receivable. In this variant, the expandable sealing element is arranged on the pot collar. The arrangement on the pot collar takes place in this embodiment in such a way that the sealing element projects into the receiving interior in the expanded state.

In a particularly preferred embodiment, the expandable sealing element has an elastic sheath which delimits a sealing element interior. This sealing element interior can be filled with a pressurized fluid for expansion of the sealing element.

Particularly suitably, the sealing element is designed such that it is pressed in the expanded state and arranged in the receiving device piston against an outer peripheral side of the piston when it is arranged in the receiving device. In this way, a particularly effective sealing of the gap between receiving device and piston is achieved.

For the purpose of an advantageous adaptation to the geometry of the piston to be coated is proposed to form the pot collar and / or the at least one sealing element substantially annular.

For the purpose of effective introduction of the layer material in the space hermetically isolated from the external environment of the receptacle, it is proposed to provide a fluid passage on the receptacle. This fluid passage serves to introduce into the sealing element a reservoir which is not associated with the coating device and in which the fluid, preferably air, required for expansion of the sealing element is stored, if necessary. This can - as well as the discharge of the fluid from the sealing element - done with the help of a suitable pumping device. With the piston received in the receiving device, the fluid passage communicates fluidically with the intermediate space formed between the receiving device and the piston.

Particularly suitably, the fluid passage is formed as a passage opening, which passes through the pot collar and opens at one end to an outer peripheral side of the pot collar and the other end to an inner peripheral side of the pot collar. Such a way of implementation is technically easy to implement and thus associated with cost advantages in the production of the coating device.

In a further preferred embodiment, an annular receiving groove is provided for the sealing element on an inner peripheral side of the pot collar, in which the at least one sealing element is at least partially accommodated. This measure allows a space-saving attachment of the sealing element on the pot collar.

In a preferred embodiment, the receiving groove is dimensioned such that the sealing element protrudes in the expanded state partially out of the receiving groove inwardly into the receiving interior. In its non-expanded state, however, the sealing element is completely received in the receiving groove. In this way it is achieved, on the one hand, that the sealing element mechanically comes into contact with the surface of the piston even at a relatively small volume expansion for sealing the intermediate space. On the other hand, it is ensured that the sealing element in its unexpanded state is not arranged in a disturbing manner in the receiving interior when the piston is to be introduced into this or removed therefrom.

In a further preferred embodiment, an additional passage opening is formed on the pot collar for each sealing element. The Through opening thereby passes through the pot collar and opens at one end to an outer peripheral side of the pot collar and the other end to an inner peripheral side of the pot collar. In this case, the sealing element is fluidly connected to the passage opening. This facilitates easy filling of the sealing element with the fluid when it is to change from the non-expanded to the expanded state.

Particularly expedient opens the additional passage opening in the receiving groove. The provision of additional fluid lines in the pot collar can be omitted in this way.

In an advantageous embodiment, the sheath consists of a resilient material, preferably of an elastomer. In this way, the invention-essential adjustability of the sealing element between the expanded and the non-expanded state can be realized particularly cost-effective.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

The only 1 shows a schematic representation of an example of a coating device according to the invention 1 , The coating device 1 serves to coat one on a piston 2 piston groove provided for an internal combustion engine 3 with a protective coating against wear. The piston groove 3 serves to receive a sealing ring when the piston 2 is installed in the cylinder of an internal combustion engine (not shown), and typically extends annularly on a circumferential contour of the piston 2 ,

The coating device 1 includes a receiving device 4 for picking up the piston 2 during the performance of the coating process. Corresponding 1 is the recording device 4 pot-shaped and has a pot bottom 5 and one from the bottom of the pot 5 protruding pot collar 6 on. The bottom of the pot 5 and the pot collar 6 are preferably formed integrally with each other. The bottom of the pot 5 and the pot collar 6 partially limit a reception interior 8th in which the piston to be coated 2 is arranged to carry out the coating process. The pot collar 6 may be as extending along an axial direction A hollow cylinder 9 be formed, which at a first axial end 7a from the bottom of the pot 5 is closed. A first axial end 7a opposite, second axial end 7b of the hollow cylinder 9 is open, so that the piston to be coated 2 into the recording interior 8th can be introduced. Is the piston 2 as in 1 shown in the recording interior 8th placed so the axial direction A of the piston extends 2 , whose position through a central longitudinal axis M of the piston 2 is defined, perpendicular to a plane E, in which the pot bottom 5 is arranged. The one in the recording interior 8th recorded pistons 2 can be in the distance to the pot bottom 5 can be arranged so that between an end facing the bottom of the pot 28 of the piston 2 and the bottom of the pot 5 a gap 29 is formed.

As 1 recognize, are at the receiving device 4 at the pot collar 6 a first sealing element 10a and a second sealing element 10b arranged axially spaced from each other. The pot collar 6 and the two sealing elements 10a . 10b may have a substantially annular geometry. The two sealing elements 10a . 10b are filled with air or other suitable fluid. Furthermore, both have sealing elements 10a . 10b each an elastic sheath 11a . 11b on which a sealing element interior 12a , respectively. 12b limited. The serving 11a . 11b may consist of a resilient material, preferably of an elastomer. Will the sealing element interior 12a . 12b filled with air and pressurized in this way, so the respective elastic envelope expands 11a . 11b , The sealing elements 10a . 10b are "inflatable" with air. In the expanded state, the sealing elements protrude 10a . 10b into the recording interior 8th into it. The first sealing element 10a is designed such that it is a between the receiving device 4 and in the recording interior 8th recorded piston 2 formed gap 13 against the outside environment 14 the recording device hermetically isolated. Said gap 13 is doing by a piston section 27 of the piston 2 in which the piston groove to be coated 3 is arranged, limited.

This scenario is in 1 shown: The in the seal element interior 12a existing, pressurized air 15 ensures expansion of the elastic covering 11a of the sealing element 10a , so that these in the expanded state against an outer peripheral side 30 of the piston 2 is pressed, preferably adjacent to the piston groove to be coated 3 ,

Will air 15 from the sealing element interior 12a discharged, so pulls the elastic envelope 11a again together, ie she is punished, so that the wrapping 11a no longer on the piston 2 is applied. In this, non-expanded state of the sealing element 10a is the gap 13 fluidic with the external environment 14 connected. Therefore, the piston can 2 to carry out the coating process comfortably in the receiving device 4 positioned and after performing the process again from the receiving device 4 be removed.

The first sealing element 10a thus has an expanded state in which said hermetic isolation of the gap 13 given is. Accordingly, the first sealing element 10a an unexpanded state in which this isolation is canceled again, by introducing or discharging air into the elastic sheath 11a can the sealing element 10a be adjusted between the two states.

In the expanded state of the first sealing element 10a the actual coating process is carried out. The coating of the piston groove 3 can be galvanic, in particular by means of hard anodizing the surface of the piston groove 3 respectively. In this case, the coating material 17 the electrolyte required for electroplating. In the course of a hard anodization, the piston material of the piston 2 , typically aluminum, are oxidized. Alternatively, the coating may also be chemical, in particular by applying a nickel coating to the surface of the piston groove 2 respectively. To the piston groove 3 with a protective coating 16 can be provided in the interspace 13 a coating material 17 from a suitably executed, in 1 only roughly sketched indicated reservoir 18 in the gap 13 be introduced. The person skilled in various forms of realization of the reservoir 18 known, so that a more detailed description is omitted here. In the gap 13 introduced wets the coating material 17 the surface of the piston groove 3 and thus forms the desired protective coating 16 out. It is clear that in the course of this coating not only in the piston groove 3 a protective coating 16 is generated, but also in those areas of the piston surface of the piston 2 that the gap 13 limited. For introduction of the coating material 17 in the gap 13 is on the pot collar 6 the receiving device 4 a fluid passage 19 educated. Is the piston 2 in the recording interior 8th received and is the first sealing element 10a in the expanded state, leaving the hermetically isolated space 13 is formed, so the coating material 17 from the reservoir 18 over the fluid passage 19 in the gap 13 be initiated.

As the 1 clearly demonstrated, the fluid passage 19 as a passage opening 20 be formed, which the pot collar 6 interspersed. Said passage opening 20 opens at one end on an outer peripheral side 21 of the pot collar 6 and at the other end on an inner peripheral side 22 of the pot collar 6 , The fluid passage 19 can also be used to clear the gap 13 before the introduction of the coating material 17 to rinse and clean in this way. For example, water may be considered as cleaning fluid.

It is clear that through the fluid passage 19 the invention essential hermetic isolation of the gap 13 is not affected, since the fluid passage 19 only with the reservoir 18 communicates, but not with the external environment 14 ,

The 1 shows the second sealing element 10b exemplarily in the unexpanded state in which the wrapper 11b not against the piston 2 is pressed, but is arranged at a distance to this.

The second sealing element 10b serves to, in its expanded state (in 1 not shown) the volume of the gap 13 Keep as small as possible, so that only the smallest possible area of the piston surface around the piston groove 3 with the protective coating 16 is provided. Is the second sealing element 10b in its expanded state (in 1 not shown), so no layer material 17 in the gap 29 to penetrate, as illustrated in 1 for a non-expanded second sealing element 10b is shown. In this way, the cost of coating the piston groove 3 be kept low. In particular, the between the front side 28 of the piston 2 and the bottom of the pot 5 formed gap 29 hermetically from the gap 13 isolated, leaving in the gap 29 no coating material 17 can penetrate.

In the example of 1 are on the piston 2 in addition to the piston groove 3 two more piston grooves 23 shown by the expanded first sealing element 10a be covered and therefore not coated. It is clear that by suitable arrangement of the first sealing element 10a at the receiving device 4 a gap relative to the piston 13 can be generated, the coating of two or more piston grooves 3 allowed (in 1 Not shown).

For the two sealing elements 10a . 10b is on the inner circumference side 22 of the pot collar 6 in each case an annular receiving groove 24a . 24b provided in which the sealing elements 10a . 10b are receivable. The two grooves 24a . 24b are dimensioned such that the respective sealing element 10a . 10b in the expanded state partially from the receiving groove 24a . 24b out inside, into the reception interior 8th protrude so they are on the piston 2 issue. This is in 1 exemplary for the first sealing element 10a shown. In the non-expanded state, ie without pressurization, the sealing elements 10a . 10b - in 1 exemplary for the second sealing element 10b shown - but completely in the receiving groove 24a . 24b added. This facilitates the introduction or removal of the piston into or out of the receiving interior 8th ,

Is the piston 2 in the recording 4 received and are the two sealing elements 10a . 10b in the expanded state, so does the gap 13 axially through the two sealing elements 10a . 10b and radially through the receiving device 8th , in particular through their pot collar 6 , as well as by the piston section 27 of the piston in which the piston groove 3 is arranged, limited. Are the two sealing elements 10a . 10b in their expanded state, in which they are against the surface of the piston 2 are pressed, so limit the two sealing elements 10a . 10b in the axial direction A of the piston 2 , In other words, the piston groove 3 is in the axial direction A between the two sealing elements 10a . 10b arranged.

For filling or for pressurizing the seal element interior 12a . 12b with air is on the pot collar 6 for each sealing element 10a . 10b an additional passage opening 25a . 25b formed, which the pot collar 6 interspersed. The additional passages 25a . 25b open at one end to the outer circumference 21 of the pot collar 6 and at the other end on the inner circumference side 22 of the pot collar 6 , The two sealing elements 10a . 10b are fluid with the respective additional passage opening 25a . 25b connected. The additional passages 25a . 25b open for this purpose in their assigned grooves 24a . 24b , By connecting the two through holes 25a . 25b to suitable pressurizing devices - these are in 1 only roughly schematic in the form of two arrows 26a . 26b indicated - can air in the respective sealing element interior 12a . 12b be introduced and removed again. The pressure-sensitive devices known to the person skilled in the art 26a . 26b For example, a reservoir for storing a supply of air and a pump device cooperating with the reservoir, including suitable fluid lines (in 1 for the sake of clarity, not shown). In this way, the two sealing elements 10a . 10b between the expanded and unexpanded states.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102008038323 A1 [0004]

Claims (21)

Method for coating at least one on a piston ( 2 ) provided for an internal combustion engine piston groove ( 3 ) with a protective coating ( 16 ), comprising the following steps: a) arranging the piston ( 2 ) with the piston groove to be coated ( 3 ) in a coating device ( 1 ), b) fluid-tight sealing of a gap ( 13 ), which in the region of the piston groove to be coated ( 3 ) between the piston ( 2 ) and the coating device ( 1 ) is formed by means of a fluid-filled and expandable sealing element ( 10a ), c) applying the protective coating ( 16 ) on the piston groove ( 3 ) by introducing a coating material ( 17 ) into the space ( 13 ), so that a surface of the piston groove ( 3 ) with the coating material ( 17 ) is coated. Method according to Claim 1, characterized in that the method comprises the following additional step c0), which is carried out before carrying out step c): c0) purging the interspace ( 13 ) with a cleaning fluid. Method according to claim 1 or 2, characterized in that the expandable sealing element ( 10a ) an elastic sheath ( 11a ) having a sealing element interior ( 12a ), which is pressurized with a fluid in step b), so that the elastic envelope increases in volume of the sealing element interior ( 12a ) expands and adjacent to the piston groove ( 3 ) against an outer peripheral side ( 30 ) of the piston ( 2 ) is pressed. Method according to one of claims 1 to 3, characterized in that the fluid is a gas, preferably air. Method according to one of the preceding claims, characterized in that in step b) two sealing elements ( 10a . 10b ) used in an axial direction (A) of the coating device ( 1 ) are arranged at a distance to each other, such that the piston groove to be coated ( 3 ) of the piston ( 2 ) axially between the two sealing elements ( 10a . 10b ) is arranged. Method according to one of the preceding claims, characterized in that the coating of the piston groove ( 3 ) galvanically, in particular by means of hard anodization of the surface of the piston groove ( 3 ), or chemically, in particular by means of applying a nickel coating occurs. Coating device ( 1 ) for coating at least one on a piston ( 2 ) provided piston groove ( 3 ), in particular for carrying out the method according to one of the preceding claims, - with a receiving device ( 4 ), in which a piston ( 2 ) is receivable for performing a coating process, - with a on the receiving device ( 4 ), filled with a fluid and expandable (first) sealing element ( 10a ), such that a between the receiving device ( 4 ) and in the receiving device ( 4 ) received piston ( 2 ) formed space ( 3 ), which of a piston section ( 27 ) of the piston ( 2 ) with the piston groove ( 3 ) is partially limited, against the external environment ( 14 ) of the recording device ( 4 ) is hermetically isolable. Coating device according to claim 7, characterized in that in addition to the (first) sealing element ( 10a ) an additional (second) sealing element ( 10b ), the sealing elements ( 10a . 10b ) on the pot collar ( 6 ) are arranged at a distance to each other and at a distance to the pot bottom ( 5 ) are arranged. Coating device according to claim 7 or 8, characterized in that the sealing element ( 10a . 10b ) has an expanded state in which the hermetic isolation of the interspace ( 13 ) to the environment ( 14 ), and has an unexpanded state in which this hermetic insulation is removed, wherein the sealing element ( 10a ) is adjustable between the two states. Coating device according to one of claims 7 to 9, characterized in that the sealing element ( 10a . 10b ) is formed with air inflatable. Coating device according to one of claims 7 to 10, characterized in that the receiving device ( 4 ) pot-shaped and a pot bottom ( 5 ) and one from the bottom of the pot ( 5 ) protruding pot collar ( 6 ), which together form a receiving interior ( 8th ) in which the piston ( 2 ) is receivable, wherein the expandable sealing element ( 10a . 10b ) on the pot collar ( 6 ) is arranged such that it in the expanded state in the receiving interior ( 8th ) protrudes. Coating device according to one of claims 7 to 11, characterized in that the expandable sealing element ( 10a . 10b ) has an elastic envelope, which has a sealing element interior ( 12a . 12b ), wherein the sealing element interior ( 12a . 12b ) for expansion of the sealing element ( 10a . 10b ) can be filled with a fluid and pressurized. Coating device according to one of claims 7 to 12, characterized in that the sealing element ( 10a . 10b ) is designed such that it in the expanded state and in the receiving device ( 4 ) arranged piston ( 2 ) against an outer peripheral side ( 30 ) of the piston ( 2 ) is pressed. Coating device according to one of claims 7 to 13, characterized in that the pot collar ( 6 ) and / or the sealing element ( 10a . 10b ) are formed substantially annular. Coating device according to one of claims 7 to 14, characterized in that on the receiving device ( 4 ) a fluid passage ( 19 ) formed in the receiving device ( 4 ) received piston ( 2 ) fluidly with the gap ( 13 ) communicates. Coating device according to claim 15, characterized in that the fluid passage ( 19 ) as a passage opening ( 20 ) is formed, which the pot collar ( 6 ) and at one end on an outer peripheral side ( 21 ) of the pot collar ( 6 ) and at the other end on an inner peripheral side ( 22 ) of the pot collar ( 6 ) opens. Coating device according to one of claims 11 to 16, characterized in that for the sealing element ( 10a . 10b ) on an inner peripheral side ( 22 ) of the pot collar ( 6 ) an annular receiving groove ( 24a . 24b ) is provided, in which the sealing element ( 10a . 10b ) is at least partially included. Coating device according to claim 16, characterized in that the receiving groove ( 24a . 24b ) is dimensioned such that the sealing element ( 10a . 10b ) in an expanded state partially from the receiving groove ( 24a . 24b ) inside, into the recording interior ( 8th protrudes in a non-expanded state completely in the receiving groove ( 25a . 25b ) is recorded. Coating device according to claim 18, characterized in that on the pot collar ( 6 ) for each sealing element ( 10a . 10b ) an additional passage opening ( 25a . 25b ) is formed, which the pot collar ( 6 ) and at one end on an outer peripheral side ( 21 ) of the pot collar and the other end on an inner peripheral side ( 22 ) of the pot collar ( 6 ), wherein the sealing element ( 10a . 10b ) fluidly with the passage opening ( 25a . 25b ) connected is. Coating device according to claim 19, characterized in that the additional passage opening ( 25a . 25b ) in the receiving groove ( 24a . 24b ) opens. Coating device according to one of claims 7 to 20, characterized in that the envelope ( 11a . 11b ) consists of a resilient material, preferably made of an elastomer.

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