SEALING GEOMETRY FOR A MOBILE POWER TOOL

Abstract

A sealing geometry for a mobile power tool is provided wherein the mobile power tool has a drive unit, wherein the sealing geometry is designed to seal off an interior (IB), containing a lubricant, of the drive unit from an exterior (AB) outside the drive unit. The sealing geometry has a seal that is contactless at least during operation of the drive unit.

Claims

1. A sealing geometry for a mobile power tool wherein the mobile power tool has a drive unit, wherein the sealing geometry is designed to seal off an interior (IB), containing a lubricant, of the drive unit from an exterior (AB) outside the drive unit, the sealing geometry having a seal that is contactless at least during operation of the drive unit.

2. The sealing geometry as claimed in claim 1, wherein the sealing geometry has a sealing lip that bears against a mating surface of the mobile power tool when the drive unit is at a standstill, in order to seal off the interior (IB) from the exterior (AB).

3. The sealing geometry as claimed in claim 1, wherein the sealing geometry has a sealing lip configured such that, during operation of the drive unit, the sealing lip comes away from a mating surface of the mobile power tool or that, during operation of the drive unit, a pressure force of the sealing lip on the mating surface is reduced at least compared with when the drive unit is at a standstill.

4. The sealing geometry as claimed in claim 2, wherein the sealing geometry has a seal carrier on and/or in which the sealing lip is arranged.

5. The sealing geometry as claimed in claim 2, wherein the sealing lip has a V-shaped or an at least substantially V-shaped cross section.

6. The sealing geometry as claimed in claim 1, wherein the sealing geometry is designed to create at least one vortex flow in the lubricant during operation of the drive unit, said vortex flow improving the sealing action of the sealing geometry.

7. The sealing geometry as claimed in claim 1, wherein the sealing geometry has a seal carrier having at least one vortex structure for creating the at least one vortex flow.

8. The sealing geometry as claimed in claim 1, wherein the sealing geometry is designed to have and/or to create a sealing fluid at least during operation of the drive unit.

9. The sealing geometry as claimed in claim 1, wherein the sealing geometry has a lubricant labyrinth seal.

10. The sealing geometry as claimed in claim 1, wherein the sealing geometry comprises an acrylonitrile butadiene.

11. The sealing geometry as claimed in claim 1, wherein the sealing geometry comprises a fluorine-containing material.

12. The sealing geometry as claimed in one claim 1, wherein the sealing geometry comprises a water-vapor-resistant material.

13. The sealing geometry as claimed in claim 1, wherein the sealing geometry comprises a high-temperature-resistant material.

14. The sealing geometry as claimed in claim 1, wherein the sealing geometry, has a coating.

15. A mobile power tool wherein the mobile power tool has a drive unit and a sealing geometry, wherein the sealing geometry is designed to seal off an interior (IB), containing a lubricant, of the drive unit from an exterior (AB) outside the drive unit, wherein the mobile power tool has the sealing geometry according to claim 1.

16. The mobile power tool as claimed in claim 15, wherein the lubricant is aqueous.

17. The mobile power tool as claimed in claim 15, wherein the lubricant comprises at least 5 percent water.

18. The mobile power tool as claimed in claim 16, wherein the lubricant comprises, in addition to water, at least one additive.

19. The sealing geometry of claim 4, wherein the sealing lip fits in an indentation in the seal carrier.

20. The sealing geometry of claim 8, wherein the sealing geometry is designed to have and/or create a sealing air at least during operation of the drive unit.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0044] In the figures:

[0045] FIG. 1 shows a hand-held power tool;

[0046] FIG. 2 shows a schematic illustration of a detail of a drive unit of the hand-held power tool having a sealing geometry and having lubricant.

DETAILED DESCRIPTION OF THE INVENTION

[0047] In order to make it easier to understand the invention, the same reference signs are used in each case for identical or functionally corresponding elements in the following description of the figures.

[0048] Although the invention generally encompasses mobile power tools and therefore for example construction robots or hand-held power tools, the invention is explained using the example of a hand-held power tool, only to make it easier to understand.

[0049] FIG. 1 shows a hand-held power tool 10. The hand-held power tool 10 is configured as a hammer drill. It is cordless. To this end, it has a rechargeable battery 14 in the region of a housing 12. The battery 14 exhibits lithium. The hand-held power tool 10 is configured as a portable device. It preferably has a weight of between 0.5 and 15 kg and generally of less than 25 kg.

[0050] The hand-held power tool 10 also has a tool fitting 16. A tool 18 is held in the tool fitting 16. The tool 18 has a diamond drill bit.

[0051] In a schematic illustration, a drive unit 20 of the hand-held power tool 10 is also discernible in FIG. 1. The drive unit 20 is located inside the housing 12 and is illustrated in a manner superimposed on the housing 12 only for reasons of illustration.

[0052] The drive unit 20 drives a shaft to which, in turn, the tool fitting 16 is coupled.

[0053] The drive unit 20 has an electropneumatic impact mechanism and a rotary drive, which drive the shaft in a striking and rotating manner, respectively. The impact mechanism and the rotary drive are mechanically connected via a transmission of the drive unit 20 to an electric motor of the drive unit 20 and are able to be driven thereby.

[0054] FIG. 2 shows a detail of the drive unit 20 in a schematic cross-sectional view.

[0055] In particular, a sealing geometry 22 is apparent, which is designed to provide sealing between a shaft 24 driven by the drive unit 20 and the housing 12, which is not illustrated in detail in FIG. 2. In particular, the sealing geometry 22 seals off an interior IB, containing a lubricant 26, of the drive unit 20 from an exterior AB. In FIG. 2, the lubricant 26 is indicated schematically in the form of a plurality of wavy lines. In this case, the lubricant 26 can in principle reach the entire free and continuous space within the interior IB and spread out within this space.

[0056] Ideally, the lubricant 26 cannot leave the interior IB.

[0057] The lubricant 26 is an aqueous lubricant. It contains 33 percent by weight water. Thus, the hand-held power tool 10 (FIG. 1) has the drive unit 20, wherein the drive unit 20 has the aqueous lubricant 26.

[0058] As will be explained in more detail below, the sealing geometry 22 is designed to be used to seal off the aqueous lubricant 26 and as a result is particularly suitable therefor.

[0059] The sealing geometry 22 is configured to radially encircle the shaft 24. In particular, the sealing geometry 22 and the shaft 24 are configured symmetrically to the longitudinal axis of the shaft 24.

[0060] The sealing geometry 22 has a seal carrier 28. The seal carrier 28 can be made from NBR. The seal carrier 28 is fixed to the shaft 24 by way of a press fit. Alternatively or additionally, the seal carrier 28 can be vulcanized onto and/or adhesively bonded to the shaft 24.

[0061] On its side facing the rest of the interior IB, the seal carrier 28 has at least one vortex structure 29 for creating at least one vortex flow within the lubricant 26. In particular, the seal carrier 28 has two vortex structures 29. The vortex structures 29 are configured in a channel-like manner. Their cross section can be configured in an elliptical, in particular circular, or at least substantially elliptical manner. The housing 12 can have a vortex structure configured so as to be complementary to at least one of the vortex structures 29. By way of the vortex structures 29, during operation of the drive unit 20, one or more vortex flows can form in lubricant 26 flowing toward the sealing geometry 22. In particular, vortex flows in opposite directions can form in the region of the vortex structures 29, as are marked by circular-arc arrows in FIG. 2. As a result of these vortex flows or as a result of the vortex structures 29, the sealing action of the sealing geometry 22 can therefore be further improved.

[0062] Fitted in an indentation 30 in the seal carrier 28 is a sealing lip 32. The sealing lip 32 has a V-shaped cross section. Its sealing lip wing 34 projects from the seal carrier 28 obliquely, in particular laterally, i.e. in a direction parallel to the longitudinal axis of the shaft 24, and in a radial direction relative to the shaft 24.

[0063] The sealing lip 32 is made from an elastomer. In one exemplary embodiment of the invention, to this end, the sealing lip 32 is made from NBR. In an alternative exemplary embodiment, the sealing lip 32 is made from a fluorine-containing rubber, in particular from an FKM. The sealing lip 32, in particular the sealing lip wing 34, can have a plasma coating, in particular for reducing the friction of the sealing lip wing 34 against the housing 12.

[0064] When the drive unit 20 is at a standstill, the free end of the sealing lip wing 34 and thus the sealing lip 32 bears laterally against the housing 12. In this respect, the housing 12 forms a mating surface for the sealing lip 32. In particular, the sealing lip wing 34 presses against the housing 12 with a, preferably low, pressure force. Therefore, when the drive unit 20 is at a standstill, the sealing lip wing 34 seals off the interior IB, which is delimited from the exterior AB by the housing 12 and the seal carrier 28, inter alia, from the exterior AB. The lubricant 26 located in the interior IB cannot escape into the exterior AB.

[0065] During operation of the drive unit 20 and therefore during rotation of the shaft 24, the sealing lip wing 34 is deformed in a direction radially away from the shaft 24 on account of centrifugal force. As a result, the pressure force of the sealing lip wing 34, with which the latter is pressed against the housing 12, is reduced. If the speed of the shaft 24 exceeds a minimum rotational speed, the sealing lip wing 34 is lifted at least slightly off the housing 12.

[0066] The friction between the sealing lip wing 34 and the housing 12 and therefore the otherwise locally arising relative temperature increase are, as a result, diminished or avoided. A local formation of water vapor in the region of the sealing lip wing 34 can therefore likewise be reduced in scope or even avoided entirely.

[0067] The sealing action of the sealing geometry 22 is maintained even in the event of the sealing lip wing 34 lifting off on account of the resultant centrifugal forces, as a result of which lubricant 26 flowing up is forced out of the boundary region between the seal carrier 28 and the sealing lip 32 and the housing 12.

[0068] In order to additionally support this dynamic sealing effect, a lubricant labyrinth seal 36 having a constriction 38 in the form of a narrow channel is formed between the housing 12 and the seal carrier 28.

[0069] At least one thread can be formed in the region of the lubricant labyrinth seal 36, in particular in the region of the constriction 38. By way of the thread, lubricant 26 can additionally be conveyed away from the sealing lip 32 during operation of the drive unit 20. To this end, the thread can preferably be formed so as to extend in a radial direction or at least so as not to extend axially with respect to the shaft 24.