US20030136586A1

US20030136586A1 - Holding device for the inner seal of a fluid-operated percussion drive

Info

Publication number: US20030136586A1
Application number: US10/337,283
Authority: US
Inventors: Hans-Jurgen Schneider; Thomas Deimel; Christian Dorsch; Markus Mellwig; Torsten Ahr
Original assignee: Atlas Copco Construction Tools GmbH
Current assignee: Construction Tools GmbH
Priority date: 2002-01-23
Filing date: 2003-01-07
Publication date: 2003-07-24
Also published as: ES2334897T3; DE10202648A1; ATE448915T1; JP2003220575A; EP1342539A1; JP4541648B2; EP1342539B1; DE50312123D1

Abstract

An apparatus having a housing (5) that shields a front of a percussion drive (1) against the environment, and into which a drive driven tool (3) projects. An exchangeable outer seal (10) is disposed at the housing opening (6 c) for the tool (3), surrounds the tool transversely to its longitudinal axis (3 a) with spacing, and is moveable in this transverse direction. An inner seal (11) is disposed behind the outer seal (10), and rests elastically against the tool (3) outside of its tool guide (2). The inner seal (11) is exchangeably secured to an elastic extension (12) of the tool guide (2) that surrounds the percussive tool (3) in the region of the inner seal (11) with a spacing larger than the largest transverse displacement of the tool (3). The extension (12) is an independent, elastic support that forms a detachable connection with the tool guide (2) at one end.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the priority date of German Application No. 102 02 648. 3, filed on Jan. 23, 2002, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a holding device for the inner seal of a fluid-operated percussion drive, having a housing part that shields the percussion drive, at least at the front, against the environment, and into which a percussive tool driven by the drive projects; an exchangeable outer seal, which is disposed at the opening provided in the housing part for the tool, the seal surrounding the tool transversely to its longitudinal axis with at least some spacing, and being embodied to move in this transverse direction; and having an inner seal, which is disposed behind the outer seal, seen counter to the direction of action of the tool, and rests in an elastic manner against the tool, outside of its guide. The inner seal is secured, so as to be exchanged, to an extension of the tool guide in the direction of action. This extension surrounds the percussive tool in the region of the inner seal, with a spacing that is larger than the largest possible transverse displacement of the percussive tool.

DE-A1-196 28 815, which was published prior to this application, discloses a generic holding device in connection with a protective device in a fluid-operated percussion drive. The known protective device is particularly intended to improve the functioning reliability of the percussion drive by decreasing the wear in the region of the tool guide, as well as to decrease repair and maintenance costs. The device accomplishes these objectives in that the outer seal—formed, for example, as a movably seated cross slide—simultaneously functions as a mechanical shield and an advance scraper, while the inner seal disposed behind the outer seal is intended to prevent the penetration of fine contaminants into the region of the tool guide.

The percussion drive can have an arbitrary form, provided that it includes a percussive tool that can be moved back and forth in a tool guide, driven by the percussion drive.

The known protective device is capable of considerably improving the functioning reliability of the percussion drive, but it is disadvantageous that the inner seal is secured to an extension of the tool guide that is an integral component of the tool guide itself. In the event of tool breakage, which cannot always be avoided, and may occur near the outer end segment of the outer tool guide, the extension of the tool guide may be destroyed or so heavily damaged that the tool guide must be disassembled and replaced, which is usually a cost- and labor-intensive process.

Because the production of the tool guide with the extension is relatively expensive, this guide is only used in fluid-operated percussion drives having an inner seal that is disposed behind the outer seal. Accordingly, different tool guides must be produced for percussion devices of the same structural size but different designs.

SUMMARY OF THE INVENTION

It is the object of the invention to improve the known protective device with respect to the holding device for the associated inner seal, and therefore make the percussion device more economically feasible.

In particular, the novel holding device is to be designed such that, in the event of serious malfunctions, especially tool breakage, the tool guide need not be disassembled and exchanged, provided that it is not also affected by the malfunction.

The above object generally is achieved according to the present invention by an apparatus comprising: a fluid-operated percussion drive; a housing part that shields the percussion drive, at least at the front, against the environment, and into which a percussive tool driven by the drive projects axially into a tool guide of the drive; an exchangeable outer seal disposed at an opening provided in the housing part for the tool, with the seal surrounding the tool, transversely to its longitudinal axis, with at least some spacing, and being seated for movement in the transverse direction; an inner seal disposed behind the outer seal, when seen counter to the direction of action of the tool, and resting in an elastic manner against the tool, outside of said guide, with the inner seal being secured, so as to be exchangeable, to an axial extension of the tool guide in the direction of the action of the tool, said extension surrounding the percussive tool in the region of the inner seal, with a spacing that is larger than the largest possible transverse displacement of the percussive tool in the housing; and wherein: the extension is an independent, elastic support element that, on its rear side facing away from the inner seal, has a beginning segment that forms a detachable connection with a receiving segment of the tool guide in the longitudinal and transverse directions; and, the extension latches in the receiving segment of the tool guide that is designed to secure the extension in a snap connection.

The essential concept of the invention lies in configuring the elastomer extension for supporting the inner seal as an independent, elastic support element which, on its rear side or end facing away from the inner seal, forms a detachable connection with the tool guide that is similar to a snap connection. Here, the extension latches in the receiving segment of the tool guide that is designed to secure it. In other words, the inner seal is connected to the tool guide, and the extension, which can be detached from the tool guide, is disposed between the seal and the guide. Furthermore, the elastic deformability of the extension allows it to engage the receiving segment designed to secure it, and maintain the connection through its elastic behavior, provided that no external forces are present that could overcome the retaining forces between the extension and the tool guide.

Due to the elasticity of the extension, the extension and the receiving segment of the tool guide are adapted to one another such that the extension is immovably connected to the receiving segment after being brought into the segment with the deformation necessary for latching, provided that no measures are undertaken to initiate the separation of the extension from the segment, or no circumstances occur that could trigger correspondingly large forces.

If tool breakage occurs outside of the outer end segment of the tool guide, the broken piece typically only damages the extension and the inner seal, so only the two aforementioned parts must be exchanged. The tool guide itself need not be disassembled.

It may be that the force originating from the broken piece merely causes the connection between the receiving segment of the tool guide and the extension to be broken; consequently, the extension may be latched to the receiving segment again and reused after the inner seal has been exchanged.

It is greatly significant that the elastic properties of the extension allow it to be inserted into the correspondingly adapted receiving segment of the tool guide and maintain the produced connection automatically, so to speak.

In accordance with the above discussion, it is especially simple to meet the requirements on the extension by using a thermoplastic elastomer, notably polyurethane. Of course, the extension can also be produced from other materials, should they yield comparable properties in the connection considered here.

The subject of the invention can be expanded to include forming the connection between the tool guide and the extension to be at least partially inside the tool guide, or supporting the extension on the outside of the tool guide, which faces away from the percussive tool.

As an alternative, the invention also relates to embodiments in which the extension is detachably supported on the inside of the tool guide, which faces the percussive tool.

In an especially simple embodiment of the subject of the invention, the tool guide has at least one annular-groove-like depression as a component of the connection. The elastic deformability of the extension allows it to latch in this recess, thereby creating a form-fit and/or a non-positive lockup with the tool guide.

Depending on the geometric relationships and other operating conditions, a plurality of annular-groove-like depressions can be provided, with spacing from one another, in the tool guide. In this instance, the extension is supported in the depressions by a plurality of adapted, annular projections.

The at least one annular-groove-like depression is preferably formed on the outside of the tool guide facing away from the percussive tool. The advantage of this arrangement is that the receiving segment of the tool guide is in a region of the percussion drive where it is less likely to be damaged.

Within the scope of the invention, the at least one annular-groove-like depression can, however, also be disposed on the inside of the tool guide facing the percussive tool.

The effect or operating reliability of the novel holding element may be further improved if the annular-groove-like depression is additionally undercut on at least the side facing the inner seal or the side facing away from it. In such embodiments, the annular-groove-like depression is partially closed by a circumferential protrusion, so in a cross-section, the depression has a hollow space with an opening that either faces the percussive tool or is on the side of the tool guide facing away from the tool.

Within the scope of the invention, the annular-groove-like depression can also be formed as a front-side depression that starts at the front side of the tool guide facing the inner seal. The advantage of this embodiment is that the extension, which has a countersurface that is adapted to a respective depression, can be connected to the tool guide without being severely deformed.

The front-side depression is advantageously undercut in the direction of the tool guide, so in a correspondingly adapted embodiment of the extension, a form-fit connection can be produced using the front-side depression.

The operating reliability of the novel holding device can also be increased, if necessary, by additionally holding the extension in position in the direction of the receiving segment of the tool guide by means of at least one annular securing element. Depending on how the receiving segment is oriented, the securing element is either pushed onto the outside or inside of the extension and supports the holding force originating from the extension itself.

The annular securing element can essentially have any other form or embodiment, for example, that of a bushing or a helix. The securing element is preferably formed as a spring element in order to ensure that the extension can detach from the tool guide in the event of an unacceptably high force, despite the use of the securing element, and avoid more extensive damage.

For producing a detachable connection with the receiving segment of the tool guide, the extension has at least one annular latch, which extends into the receiving segment of the tool guide.

In this case, at least one latch of the extension can be embodied or formed such that it is supported in a non-positive lockup on the receiving segment. This can be effected in a simple manner by dimensioning the latch to be larger than the annular-groove-like depression that receives it, so that the latch extends into the depression with a prestress.

Of course, it is possible within the spirit of the invention to combine the embodiments described above.

In particular, the tool guide can have at least one depression on the front side, and at least one annular-groove-like depression on either the outside facing away from the tool or the inside facing the tool, in which instance the extension is equipped with projections that are adapted to the relevant depressions and are supported in them.

The holding device can further be formed such that the wall thickness of the extension, with the exception of its beginning segment that forms the connection, and its end segment that supports the inner seal, decreases in the direction of the end segment. In the simplest case, the wall thickness changes in linear fashion. However, it can also follow a curved path.

It can be advantageous to dimension the inner diameter of the end segment of the extension that supports the inner seal to be larger than the inner diameter of the beginning segment that forms the connection.

The invention is described in detail below by way of embodiments that are illustrated schematically in the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial section through the lower part of a percussion drive having an associated housing part that receives an exchangeable component whose outer seal is seated so as to be displaced. [0034]
FIG. 2 is a partial section of the embodiment according to FIG. 1, on an enlarged scale. [0035]
FIG. 3 is a partial section through an embodiment similar to the one in FIG. 2, with the annular-groove-like depression that is formed on the inside of the tool guide being undercut in the direction of the tool guide. [0036]
FIG. 4 is a partial section in the region of the tool guide, the extension connected to the guide and the inner seal secured thereto, the tool guide being provided with an annular-groove-like depression on its outside. [0037]
FIG. 5 is a partial section through an embodiment similar to the one in FIG. 4, with the outside of the tool guide being provided with two annular-groove-like depressions that are spaced from one another. [0038]
FIG. 6 is a partial section through an embodiment similar to the one in FIG. 4, in which the annular-groove-like depression that is provided on the outside of the tool guide is undercut in the direction of the tool guide. [0039]
FIG. 7 is a partial section through an embodiment in which the extension supporting the inner seal is held by an annular-groove-like depression on the outside of the tool guide, on the one hand, and by an annular-groove-like, front-side depression that originates from the front side of the tool guide, on the other.[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Because the rest of the embodiment of the fluid-operated percussion drive is not of importance for the realization of the invention, FIG. 1 only illustrates the [0041] lower part 1 of the percussion drive, in which a tool guide 2 is immovably held. A percussive tool in the form of a chisel 3 and having the longitudinal axis 3 a is supported so as to move longitudinally in the guide 2. An arrow 4 indicates the direction of movement of the chisel 3 in the direction of action. The pendulous movements that the chisel 3 may perform are schematically indicated on an exaggerated scale by dashed lines 3 b and 3 c.
A [0042] housing part 5, which detachably receives an exchangeable component 6 at its front side (at the bottom in the figure), is secured as an extension to the lower part 1 of the percussion drive. For receiving the exchangeable component 6, the housing part 5 is provided with a recess 7 that is slightly deeper than the height of the component, and whose diameter is adapted to the diameter of the component. The parts 5 and 6 are detachably secured to one another by pins 8.
The exchangeable component [0043] 6 comprises a front plate 6 a and a rear plate 6 b. These plates have a sufficiently large passage 6 c for the chisel 3, and limit an annular chamber 9 transversely to the longitudinal axis 3 a. An outer seal in the form of a disk-shaped cross slide 10 is seated to move in this chamber 9.
The height of the [0044] annular chamber 9 in the direction of the longitudinal axis 3 a is slightly larger than the thickness of the cross slide 10, so the transverse movements of the chisel 3 relative to the housing part 5 cause the slide to move back and forth as a rigid unit.
Unlike in the schematic representation of FIG. 1, the [0045] wall 10 a of the cross slide 10, which limits the opening for the chisel 3, is formed such that transverse movements of the chisel 3 (indicated by the lines 3 b and 3 c) do not cause the parts 3 and 10 to become misaligned. For this purpose, the wall 10 a has a convex curvature in the direction of the chisel 3 (unlike in the illustration).
The parts [0046] 6 a and 6 b are connected (not shown). Accordingly, the exchangeable part 6 can be installed and removed as a unit with the cross slide 10 seated to move freely therein.
Inside the [0047] housing part 5, an inner seal 11 is disposed behind the cross slide 10, seen counter to the direction of action (arrow 4). The sealing lip 11 a of the seal rests in an elastic manner against the chisel 3, and acts as a scraper for contaminants that have entered the housing part 5.
The [0048] inner seal 11 is detachably secured to an extension 12 via a securing groove 12 b cut into the end segment 12 a of the extension (FIG. 2). In the region of the inner seal 11, the extension 12 surrounds the chisel 3 at a distance s, which is larger than the largest possible transverse displacement of the chisel in this region (indicated by the lines 3 b and 3 c).
To assure proper functioning of the [0049] inner seal 11 under different operating conditions, the length of the sealing lip 11 a should be selected so that the ratio of its length to the largest possible transverse displacement of the chisel 3 in the region of the sealing lip is a value greater than 2.
Unlike in the prior art, the [0050] elastomer extension 12 is formed as an independent, elastic support element. Its beginning segment 12 c, which rests on the rear side or end of the extension 12 facing away from the inner seal 11, can form a detachable, snap-like connection with a correspondingly adapted receiving segment 2 a, in the region of the front side or end 2 b of the tool guide (FIG. 2).
For this purpose, the receiving [0051] segment 2 a is provided with an annular-groove-like depression 13 that is spaced from the front side or surface 2 b and is oriented transversely to the longitudinal axis 3 a.
The beginning [0052] segment 12 c of the extension 12 has a circumferential latch 14, which is formed in the manner of an annular shoulder and is likewise spaced from the support surface 12 d of the extension 12 that cooperates with the front side 2 b.
The ability of the [0053] extension 12 to be elastically deformed allows it to be displaced relative to the tool guide 2 such that its latch 14 extends into the region of the annular-groove-like depression 13 and latches in the depression 13, thereby forming the aforementioned detachable connection.
The elastic deformability of the [0054] extension 12 maintains the connection formed in this manner between the receiving segment 2 a and the beginning segment 12 c as long as no external forces larger than the holding force that originates from the extension act upon the extension 12.
If tool breakage occurs in the region of the [0055] extension 12, the extension can first be deformed due to the effect of the transverse forces, or if the stress is excessive, it can detach from the receiving segment 2 a of the tool guide 2, which may prevent damage at least to the tool guide 2. Depending on the effects of the relevant malfunction, the detached extension 12 may be reused, that is, latched again with the receiving segment 2 a.
If necessary, within the scope of the invention, the connection between the receiving [0056] segment 2 a and the beginning segment 12 c may be further reinforced through the selection of the height of the circumferential (seen parallel to the longitudinal axis 3 a) latch 14 in the disassembled state to be larger than the height of the annular-groove-like recess 13 in the described direction (see FIG. 2 in particular). Accordingly, the latch 14 is compressed when brought into the depression 13, so the latch is also held with a non-positive lockup in the receiving segment 2 a.
In addition to or instead of this measure, the subject of the invention can also be embodied such that the annular groove formed between the [0057] latch 14 and the front side 12 d forms a non-positive lockup with the receiving segment 2 a.
As can be seen from FIGS. 1 and 2, the annular-groove-like depression [0058] 13 is disposed on the inside of the tool guide 2 facing the chisel 3. Furthermore, the effective inner diameter of the tool guide 2 and the inner diameter of the extension 12 in the region of its beginning segment 12 c are adapted to one another such that the tool guide 2 changes over into the extension 12, thereby forming a shoulder A. With the exception of the beginning segment 12 c in the region of the receiving segment 2 a, the wall thickness of the extension decreases continuously in the direction of the end segment 12 a, with a constant outer diameter.
This ensures that the [0059] extension 12 is located outside of the working region of the percussive tool 3 in the normal state (FIG. 1), and may be able to detach from the receiving segment 2 a of the tool guide 2.
FIG. 3 illustrates an embodiment of the invention in which the receiving [0060] segment 2 a of the tool guide 2 is provided with an annular-groove-like depression 15 that is undercut in the direction of the guide (toward the top in the drawing). As already explained in conjunction with FIGS. 1 and 2, the depression is disposed on the inside of the tool guide 2 facing the percussive tool 3, and thus the longitudinal axis 3 a.
Because of the aforementioned undercut, the [0061] depression 15 has an annular, circumferential shoulder 2 c in the direction of the longitudinal axis 3 a. Accordingly, the opening of the depression 15 (seen parallel to the longitudinal axis 3 a) is smaller than the total height in the described direction.
The beginning [0062] segment 12 c of the extension 12 is provided with a circumferential latch 16 that is spaced from the front side 12 d, and, seen in cross-section, is oriented essentially parallel to the longitudinal axis 3 a.
The dimensions of the [0063] latch 16 parallel to the longitudinal axis 3 a are shown in exaggerated form merely for illustration purposes. Of course, the depression 15 and the latch 16 must be adapted to each other in terms of size such that the latch 16 can be guided into the depression 15 and retain the assumed latched position, thereby producing the desired detachable connection, provided that no excessively high forces are exerted on the extension 12 and break the connection between the receiving segment 2 a and the beginning segment 12 c.
If necessary, the receiving [0064] segment 2 a and the beginning segment 12 c of the extension can be adapted to one another, especially in terms of the embodiment and dimensions of the depression 15 and the latch 16, such that the latch 16 is held in a non-positive lockup in the recess 15.
Unlike in the embodiment shown in FIGS. 1 and 2, the [0065] extension 12 forming an independent, elastic support element is formed such that its inner diameter, with the exception of the beginning segment 12 c, increases continuously in the direction of the end segment 12 a, with a constant wall thickness in the assembled state.
In the embodiment according to FIG. 4, the receiving [0066] segment 2 a for securing the elastic extension 12 has an annular-groove-like depression 17, which is formed on the outside of the tool guide 2 facing away from the percussive tool (FIG. 1), and is oriented transversely to the longitudinal axis 3 a. The extension 12 is thus adapted to the receiving segment 2 a such that its beginning segment 12 c has an annular latch 18 that projects in the direction of the longitudinal axis 3 a and has an inclined edge 18 a for facilitating the process of inserting the extension into the recess 17.
Because of the elastic deformability of the [0067] elastomer extension 12, the latch 18 can be displaced so far past the front side 2 b in the direction of the receiving segment 2 a that it eventually latches into the annular-groove-like depression 17 and detachably connects the extension to the tool guide 2 via the beginning segment 12 c.
This connection may be broken if desired, or in the event of a malfunction, by exerting sufficient transverse forces onto the [0068] extension 12.
If necessary, the connection produced between the [0069] segments 2 a and 12 c can be additionally supported by producing the latch 18 with excess material, and fitting it into the depression 17 with a non-positive lockup.
Furthermore, the discussed connection can be additionally reinforced by pushing a [0070] lock washer 19 onto the extension 12 from the outside at the height of the depression 17. This lock washer 19 additionally generates a force component that serves in keeping the latch 18 inside the recess 17.
To prevent an undesired displacement of the [0071] lock washer 19, the extension 12 should have a corresponding element for securing its position, such as the annular groove 20 indicated in FIG. 4, which receives the lock washer 19.
The [0072] extension 12 is otherwise formed such that its cross-section decreases continuously in the direction of the inner seal 11, with a constant inner diameter.
The inner diameter of the [0073] tool guide 2 changes over in conical fashion into the inner diameter of the extension 12 in the region of the receiving segment 2 a.
The embodiment according to FIG. 5 differs from the above-described embodiment in that the receiving [0074] segment 2 a of the tool guide 2 has annular-groove- like depressions 17 and 21, which are spaced from one another, and in which the elastically deformable extension 12 is detachably supported by annular latches 18 and 22, respectively.
As already explained in conjunction with FIG. 4, the connection between the [0075] segments 2 a and 12 c may additionally be secured by pushing a securing element, preferably one that can be elastically deformed, onto the extension 12 at the height of the receiving segment 2 a and fixing it appropriately to avoid undesired movements parallel to the longitudinal axis 3 a.
The holding device illustrated in FIG. 6 corresponds to the one in FIG. 3 insofar that the receiving [0076] segment 2 a likewise has an annular-groove-like depression 23, which is undercut in the direction of the tool guide 2 (toward the top in the drawing), and in which an annular latch 24 is supported in the assembled state. The latter can be pressed into the recess 23 with a corresponding prestress.
Unlike in the embodiment according to FIG. 3, the annular-groove-[0077] like depression 23 is formed on the outside of the tool guide 2 facing away from the percussive tool 3 (FIG. 1). Accordingly, the latch 24 also projects in the direction of the percussive tool 3, or the longitudinal axis 3 a, inside the depression 23.
With the exception of the embodiment and arrangement of the [0078] latch 24 in the region of the receiving segment 2 a, the elastic extension 12 with the inner seal 11 secured thereto is formed identically to the embodiment shown in FIG. 4.
In the embodiment of the invention shown in FIG. 7, the receiving [0079] segment 2 a of the tool guide 2 is provided with an annular-groove-like depression 25, which is oriented transversely to the longitudinal axis 3 a and is disposed on the outside of the tool guide 2. In the assembled state, an annular, circumferential latch 26 having an inclined edge 26 a (corresponding to the one in FIG. 4) projects into this depression 25.
The receiving [0080] segment 2 a further has an annular-groove-like front-side depression 27 that originates from the front side 2 b and becomes wider, that is, it is undercut, in the direction of the tool guide 2 (toward the top in the drawing).
Corresponding to the embodiment of the receiving [0081] segment 2 a, the beginning segment 12 c of the extension 12 is provided with a further annular latch 28, which has a head part 28 a with two holding surfaces 28 b.
In the illustrated assembled state, the head part is fixed inside the widened part of the front-[0082] side depression 27 by the holding surfaces 28 b.
The above-described holding device thus results from a combination of a [0083] latch 26 and a latch 28 that latch laterally and at the front side, respectively, in adapted, annular-groove-like depressions.
The particular advantage attained with the invention is that the tool guide provides more extensive protection against damage than before through the embodiment of the extension that supports the inner seal as an independent support element. The extension represents a relatively low-cost exchangeable part whose elastic deformability allows it to produce and maintain a detachable connection with the tool guide, provided that the extension is not acted upon by unacceptably high external forces. [0084]
In the event of a malfunction, the extension can detach from the tool guide, which may avoid further damage to the tool guide and, possibly, to the extension itself. [0085]
The invention now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein. [0086]

Claims

What is claimed is:

1. An apparatus comprising:

a fluid-operated percussion drive;

a housing part that shields the percussion drive, at least at the front, against the environment, and into which a percussive tool driven by the drive projects axially into a tool guide of the drive;

an exchangeable outer seal disposed at an opening provided in the housing part for the tool, with the seal surrounding the tool, transversely to its longitudinal axis, with at least some spacing, and being seated for movement in the transverse direction;

an inner seal disposed behind the outer seal, when seen counter to the direction of action of the tool, and resting in an elastic manner against the tool, outside of said guide, with the inner seal being secured, so as to be exchangeable, to an axial extension of the tool guide in the direction of the action of the tool, said extension surrounding the percussive tool in the region of the inner seal, with a spacing that is larger than the largest possible transverse displacement of the percussive tool in the housing; and wherein:

said extension is an independent, elastic support element that, on its rear side facing away from the inner seal, has a beginning segment that forms a detachable connection with a receiving segment of the tool guide in the longitudinal and transverse directions; and

the extension latches in the receiving segment of the tool guide that is designed to secure the extension in a snap connection.

2. The apparatus according to claim 1, wherein the extension is formed of a thermoplastic elastomer.

3. The apparatus according to claim 2, wherein the thermoplastic elastomer is polyurethane.

4. The apparatus according to claim 1, wherein the connection is produced at least partially inside the tool guide.

5. The apparatus according to claim 1, wherein the extension is supported on the outside of the tool guide facing away from the percussive tool.

6. The apparatus according to claim 1, wherein the tool guide has at least one annular-groove-type depression as a component of the connection.

7. The apparatus according to claim 6, wherein the at least one annular-groove-type depression is formed on the outside of the tool guide facing away from the percussive tool.

8. The apparatus according to claim 6, wherein the annular-groove-type depression is additionally undercut, at least on one of the side facing the inner seal and the side facing away from the inner seal.

9. The apparatus according to claim 7, wherein the annular-groove-type depression is additionally undercut, at least on one of the side facing the inner seal and the side facing away from the inner seal.

10. The apparatus according to claims 6, wherein the annular-groove-type depression is formed as a front-side depression that originates on the front side of the tool guide that faces the inner seal.

11. The apparatus according to claim 10, wherein the front-side depression is undercut in the direction of the tool guide.

12. The apparatus according to claim 1, wherein the extension is additionally held in position in the direction of the receiving segment of the tool guide by at least one annular securing element.

13. The apparatus according to claim 1, wherein the extension has at least one annular latch that extends into the receiving segment of the tool guide.

14. The apparatus according to claim 13, wherein at least one latch of the extension is supported in a non-positive lockup on the receiving segment.

15. The apparatus according to claim 1, wherein the wall thickness of the extension, with the exception of the beginning segment that produces the connection, and its end segment, that supports the inner seal, decreases in the direction of the end segment.

16. The apparatus according to claim 1, wherein an inner diameter of the end segment of the extension that supports the inner seal is larger than an inner diameter of its beginning segment that produces the connection.