Electric power tool comprising a pneumatic percussion mechanism, comprising damping means on the tool holder side

Abstract

The invention relates to an electric power tool comprising a pneumatic percussion mechanism (3) for alternately applying impacts to a tool (6) clamped in a tool holder (5), wherein the tool holder (5) is mounted on a guide housing part (8) of the machine housing (7) associated with the pneumatic percussion mechanism (3) by inserting a rear-side connection sleeve (9) of the tool holder (5) into the distal end region of the guide housing part (8), wherein an elastomer sleeve (10) for damping vibrations introduced into the machine housing (7) from the tool side is arranged in a radial gap (11) between the connection sleeve (9) and the guide housing part (8).

Description

[0001] 2023P00228EP Hilti Aktiengesellschaft

[0002] Principality of Liechtenstein

[0003] POWER TOOL WITH A PNEUMATIC IMPACT MECHANISM, INCLUDING TOOL-SIDE DAMPING ELEMENTS

[0004] DESCRIPTION

[0005] The present invention relates to a power tool with a pneumatic impact mechanism for alternately striking a tool clamped in a tool holder, wherein the tool holder is attached to a guide housing part of the machine housing associated with the pneumatic impact mechanism, in which a rear connecting sleeve of the tool holder is inserted into the distal end region of the guide housing part.

[0006] The invention's scope of application extends primarily to handheld power tools, such as, in particular, rotary hammers, demolition hammers, and the like. A common feature of these power tools is a pneumatic impact mechanism for applying impact energy to the tool, for example, a hammer drill, chisel drill, or chisel. Mechanical loads generated during drilling and / or chiseling typically act back on the drive components, manifesting themselves, among other things, as disruptive vibrations.

[0007] State of the art

[0008] Based on generally known technology, power tools with pneumatic impact mechanisms are used, driven by an electric motor. The motor's rotary motion is converted via an eccentric drive into an alternating linear motion of an exciter piston within the pneumatic impact mechanism. The exciter piston is dynamically sealed within a guide tube and, via an internal column of compressed air, acts upon an opposing impact piston. This impact piston aligns with a coaxial impactor in the direction of action, and the impact energy generated by the impactor is then transferred coaxially to the tool held in the tool holder.

[0009] In the power tools of interest here, the tool holder is inserted into a distal end region of a guide housing component of the power tool via a rear connecting sleeve and is usually secured by a snap ring or similar device. In other known power tools as well, the tool holder is guided axially and radially within guide housings, gearbox housings, or bushings. This results in vibrations and static and dynamic bending loads generated during drilling / chiseling being transmitted directly to the adjacent components.

[0010] It is therefore the object of the present invention to further improve an electric tool of the generic type in such a way that the mechanical loads introduced by a tool are compensated in a simple manner.

[0011] Disclosure of the invention

[0012] The problem is solved starting from a power tool according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims describe advantageous embodiments of the invention.

[0013] The invention includes the technical teaching that an elastomer sleeve is arranged in a radial gap between the rear connecting sleeve of a tool holder and the machine housing, preferably the guide housing part adjacent to the tool holder, for radial damping of vibrations introduced into the machine housing on the tool side.

[0014] In other words, an elastomer sleeve establishes the connection between the tool holder, which is usually made of steel, and the guide housing part or the like, which is usually made of a light metal. To accommodate the elastomer sleeve according to the invention, a corresponding radial gap must be provided between the components that would otherwise be in direct contact with each other; this gap is referred to here as the radial gap.

[0015] The advantage of the solution according to the invention lies particularly in the fact that it enables backlash-free guidance of the connecting sleeve of the tool holder relative to the machine housing, compensating for geometric component tolerances. Simultaneously, axially acting forces, which arise especially from idle strokes or impacts, are transmitted and dampened. Furthermore, the static and dynamic bending loads generated during tool use are transmitted. Due to the elastic guidance of the tool holder in the guide housing part, all these mechanical loads on downstream components, in particular the guide housing part, a subsequent gearbox housing part, or an overall housing, as well as the drive, can be significantly reduced during operation. The damping properties of the elastomer sleeve further reduce the transmission of vibrations.

[0016] According to a preferred embodiment, the elastomer sleeve comprises a tool-side damping section with a greater wall thickness, to which a drive-side sealing section with a lesser wall thickness is attached. Thanks to the greater wall thickness of the tool-side damping section, significant vibration decoupling can be achieved. Since a lesser wall thickness is sufficient for sealing purposes, the coaxially adjoining drive-side sealing section is correspondingly thinner and can therefore be accommodated in a narrower annular gap. Furthermore, raised material features can also be provided on the drive-side sealing section, which can be used to secure the position of the elastomer sleeve relative to the adjacent components.

[0017] According to a further improvement of the invention, it is proposed to also mold at least one radially shaped sealing lip on the distal end region of the damping section of the elastomer sleeve for static sealing against the guide housing part. In this way, the elastomer sleeve seals in a functionally integrated manner against both the guide housing part and the tool holder, so that neither dust ingress into the machine housing nor oil leakage from the machine housing is possible.

[0018] According to another improvement of the invention, it is proposed that the elastomer sleeve has several longitudinal ribs spaced apart from one another along its circumference on the inner and / or outer surface, which engage in a form-fitting manner in corresponding recesses in the guide housing part or the connecting sleeve of the tool holder to prevent rotation. The molded longitudinal ribs prevent relative rotation between the adjacent components.

[0019] According to a further improvement of the invention, an additional guide section extending towards the guide tube can be integrally formed on the drive-side guide section of the elastomer sleeve. This guide section bridges a radial gap existing between the guide housing part and the adjacent tube end of the guide tube and thus provides at least radial guidance of the guide tube of the pneumatic impact mechanism relative to the guide housing part in a functionally integrated manner. This also results in radially elastic support of the guide tube. Bending stresses from the guide housing part to the guide tube are thereby significantly reduced.

[0020] According to a further improvement of the invention, it is proposed that the drive-side sealing section of the elastomer sleeve alternatively or additionally has an internally radially molded valve lip that resiliently rests against the outer surface of the guide tube to form a piston valve. When the piston moves forward during idle strokes, the air in front of the piston can escape through the valve into the impact chamber. During the subsequent return stroke of the piston, the valve closes, creating a braking vacuum in front of the piston.

[0021] According to a further improvement of the invention, an annular, metallic cooling element, attached to the connecting sleeve, can be installed in an axial gap between the tool holder and the guide housing part of the machine housing. The cooling element additionally cools the area of ​​the tool holder to counteract excessively high temperatures in the pneumatic impact mechanism. This additional measure may be necessary due to the thermally insulating effect of the elastomer sleeve, in order to protect its elastomer material. The annular metallic cooling element preferably has a round disc shape provided with cooling fins.

[0022] The elastomer sleeve consists of an elastomer material that is as temperature-resistant as possible, selected from an elastomer group comprising hydrogenated acrylonitrile butadiene rubber (HNBR) and fluorocarbon rubber (FPM). These materials have proven to be sufficiently temperature-resistant for the present application.

[0023] Detailed description based on drawing

[0024] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments of the invention, with reference to the figures. The figures show:

[0025] Fig. 1 shows a schematic, partially cut-away side view of a power tool, here in the form of a rotary hammer.

[0026] Fig. 2 shows a partial longitudinal section at the connection point between the tool holder and the guide tube housing part of the power tool in the area of ​​an elastomer sleeve arranged at this point,

[0027] Fig. 3 shows a detailed longitudinal section of the elastomer sleeve according to Fig. 2,

[0028] Fig. 4 shows a perspective view of the elastomer sleeve, Fig. 5 shows a partial longitudinal section in the area of ​​an elastomer sleeve according to an alternative embodiment,

[0029] Fig. 6 shows a partial longitudinal section in the area of ​​the interface between the tool holder and the guide housing part with a cooling element arranged at this point, and

[0030] Fig. 7 shows several side views of different embodiments of the heat sink according to Fig. 6.

[0031] According to Fig. 1, a power tool in the form of a rotary hammer essentially consists of an electric motor 1, the rotary motion of which is transmitted via an eccentric drive 2 into a linear alternating working motion on a pneumatic impact mechanism 3. The pneumatic impact mechanism 3 acts on a striker 4, the impact mass of which in turn acts backward on a tool 6 clamped in a tool holder 5. The aforementioned drive components, together with the pneumatic impact mechanism, are housed in a machine casing 7, from which the tool holder 5 protrudes.

[0032] According to Fig. 2, the tool holder 5 is mounted in a guide housing 8 of the machine housing (not shown here) such that a rear connecting sleeve 9 of the tool holder 5 is inserted into the distal end region of the guide housing part 8. A damping elastomer sleeve 10 fills an annular gap 11 between the connecting sleeve 9 and the guide housing part 8 in order to dampen vibrations introduced into the machine housing from the tool side.

[0033] In this embodiment, the guide housing part 8 encloses a tool-side tube end of a guide tube 11 of the pneumatic impact mechanism, as well as a stopper 12, which is housed and guided within the distal end region of the connecting sleeve 9 of the tool holder 5, for actuating the tool (not shown here). As shown in Fig. 3, the elastomer sleeve 10 comprises a tool-side damping section 13 with a greater wall thickness. This is adjoined by a drive-side sealing section 14 with a lesser wall thickness. The drive-side sealing section 14 has two radially molded sealing lips 15, which form a static seal against the connecting sleeve 9 of the tool holder 5. At the opposite end, the distal end region of the damping section 13 of the elastomer sleeve 10 has a pair of radially outward extending sealing lips 16 for a static seal against the guide housing part 8.

[0034] The drive-side sealing section 14 also has an internally radially molded annular rib 17 which engages in a corresponding circumferential groove on the connecting sleeve 9 to axially fix the elastomer sleeve 10 relative to the connecting sleeve. In conjunction with this, the elastomer sleeve 10 is axially fixed relative to the guide housing part 8 by means of a snap ring 18.

[0035] As can be seen from the perspective view of Fig. 4, the elastomer sleeve 10 has several longitudinal webs 19 (exemplary) arranged parallel to each other along the circumference on the outer surface, which engage in a form-fitting manner in corresponding recesses on the guide housing part - which is not shown here - to prevent rotation.

[0036] According to Fig. 5, a valve lip 20 extending inwards radially and resiliently is additionally formed on the drive-side sealing section 14, which comes into contact with the guide tube 10 on the outer shell side to form a piston valve.

[0037] According to Fig. 6, the distal end of the drive-side sealing section 14 can also be equipped with a guide function instead of the impact piston valve functionality described above. For this purpose, the elastomer sleeve 10 has a drive-side guide section 21 for the radial guidance of the enclosed guide tube 10 of the pneumatic impact mechanism (not shown). Furthermore, an annular metal cooling element, detachably attached to the connecting sleeve 9, is arranged in an axial gap 22 between the tool holder 5 and the guide housing part 8. The cooling element 23 dissipates heat generated in the area of ​​the tool holder 5 during operation, thus protecting the elastomer material of the elastomer sleeve 10 from overheating.

[0038] Figure 7 illustrates various geometries of such a heat sink 23. The specific design with regard to the heat sink surface area and the geometric dimensions depends on the design constraints of the power tool.

[0039] The invention is not limited to the preferred embodiments described above. Rather, variations thereof are also conceivable, which are also covered by the scope of protection of the following claims. In particular, it should be noted that the guide housing part referred to here as such can also be formed in one piece with the machine housing. Reference numeral list

[0040] 1 electric motor

[0041] 2 eccentric drives

[0042] 3 percussion instruments

[0043] 4 Döpper

[0044] 5 Tool holder 6 Tool

[0045] 7 Machine housing 8 Guide housing part 9 Connecting sleeve 10 Elastomer sleeve

[0046] 11 Radial gap

[0047] 12 Döpperkolben

[0048] 13 Damping section 14 Sealing section 15 Sealing lip

[0049] 16 Sealing lip

[0050] 17 Ringsteg

[0051] 18 snap ring

[0052] 19 Longitudinal web

[0053] 20 valve lip

[0054] 21 Guide section 22 Axial gap

[0055] 23 heat sinks

Claims

REQUIREMENTS 1. Power tool with a pneumatic impact mechanism (3) for alternately impacting a tool (6) clamped in a tool holder (5), wherein the tool holder (5) is attached to a guide housing part (8) of the machine housing (7) associated with the pneumatic impact mechanism (3), by inserting a rear connecting sleeve (9) of the tool holder (5) into the distal end region of the guide housing part (8), characterized in that an elastomer sleeve (10) for damping vibrations introduced into the machine housing (7) on the tool side is arranged in a radial gap (11) between the connecting sleeve (9) and the guide housing part (8).

2. Power tool according to claim 1, characterized in that the elastomer sleeve (10) comprises a tool-side damping section (13) of higher wall thickness, to which a drive-side sealing section (14) of lower wall thickness is attached.

3. Power tool according to claim 2, characterized in that the drive-side sealing section (14) forms a static seal against the connecting sleeve (9) of the tool holder (5) via at least one internally radially formed sealing lip (15), and / or is axially fixed against the tool holder (5) via at least one internally radially formed annular web (17) by engaging in a corresponding circumferential groove on the connecting sleeve (9).

4. Power tool according to one of claims 2 or 3, characterized in that the distal end region of the damping section (13) of the elastomer sleeve (10) has at least one externally radially formed sealing lip (16) for static sealing against the guide housing part (8).

5. Power tool according to one of the preceding claims, characterized in that the elastomer sleeve (10) has several longitudinal webs (19) arranged at intervals along the circumference on the inner and / or outer surface, which engage in a form-fitting manner in corresponding recesses on the guide housing part (8) or the connecting sleeve (9) of the tool holder (5) to prevent rotation.

6. Power tool according to one of the preceding claims, characterized in that the elastomer sleeve (10) is fixed in the axial direction via a snap ring (18) which engages in the distal end region of the guide housing part (8).

7. Power tool according to one of the preceding claims, characterized in that the elastomer sleeve (10) has a drive-side guide section (21) for radially guiding a guide tube (11) of the pneumatic impact mechanism (3) enclosed therein.

8. Power tool according to one of the preceding claims, characterized in that the drive-side sealing section (14) of the elastomer sleeve (10) alternatively or additionally has an internally radially formed valve lip (20) which resiliently comes into contact with the outer shell side of the guide tube (10) to form a piston valve.

9. Power tool according to one of the preceding claims, characterized in that an annular cooling element (23) made of metal is arranged in an axial gap (22) between the tool holder (5) and the guide housing part (8) of the machine housing and is detachably attached to the connecting sleeve (9).

10. Power tool according to one of the preceding claims, characterized in that the elastomeric sleeve (10) consists of a temperature-resistant elastomeric material selected from a Elastomer material group comprising hydrogenated acrylonitrile butadiene rubber (HNBR), fluororubber (FPM).

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