This application claims priority, under 35 U.S.C. ยง119, to UK Patent Application No. GB 07 134 32.3, filed on Jul. 11, 2007, which is incorporated herein by reference.
This application relates to rotary hammer.
In a known rotary hammer (as described in DE 42 02 767 C2), an intermediate gear wheel is provided for coupling of both intermediate shafts which intermediate gear wheel is arranged coaxially to the armature shaft and rotatably mounted by means of a bearing which bearing is mounted in the housing of the rotary hammer. By means of this intermediate gear wheel the first intermediate shaft which is rotatably driven by the armature shaft in operation of the rotary hammer, is coupled with the second intermediate shaft. In this arrangement rotation of the intermediate shaft causes a certain undesired heating due to friction, and requires relatively precise machining of the intermediate gear wheel and the gear wheels or toothing of the intermediate shafts cooperating with the intermediate gear wheel.
In an aspect, a rotary hammer includes a motor with an armature shaft arranged perpendicular to the axis of rotation of the tool holder and comprising toothing, a first intermediate shaft forming part of the drive for the hammer mechanism which first intermediate shaft is provided at the side of the armature shaft facing away from the tool holder and is arranged in parallel to the armature shaft, and with a second intermediate shaft forming part of the rotary drive which second intermediate shaft is provided at the side of the armature shaft facing the tool holder and is arranged in parallel to the armature shaft. The toothing of the armature shaft meshes with a toothing of the first or the second intermediate shaft and the intermediate shafts are coupled so that the rotational movement of the intermediate shaft driven by the armature shaft is transmitted to the other intermediate shaft. Coupling of the intermediate shafts may be effected by a chain drive comprising a chain that interconnects the two intermediate shafts for driving purposes.
Implementations may include one or more of the following features. A bearing for the upper end of the armature shaft, i.e. the end nearer to the hammer mechanism, may be advantageously located between the toothing of the armature shaft and the plane of the chain. The toothing of the armature shaft may mesh with a toothing of the first intermediate shaft. The toothing of the first intermediate shaft may be formed by a gear wheel formed at the upper end of the intermediate shaft which gear wheel carries an eccentric pin which forms part of a crank drive. The chain drive may include sprockets secured to the intermediate shafts on the same height wherein the sprocket on the second intermediate shaft has a larger diameter than the sprocket on the first intermediate shaft.
Advantages may include one or more of the following. An intermediate gear wheel mounted coaxially with respect to the intermediate shaft is not required and heating generated by rotation of such an intermediate gear wheel as used in the prior rotary hammer is reduced. Further, the sprockets or the sprocket arrangements of the intermediate shafts need not to be manufactured with such a high precision, as this is required for the gear wheels provided in the known rotary hammer so that manufacturing costs are reduced. These and other advantages and features will be apparent from the description, the drawings, and the claims.
The rotary hammer shown in
The electric motor 10 is fixed in the motor housing 1. Its armature shaft 11 is supported in a lower ball bearing 40 which is mounted in the housing cap 3, and in an upper ball bearing 13 mounted in an upper housing 2. This upper housing contains, among other things, the pneumatic hammer mechanism. Such hammer mechanism is conventional for rotary hammers of this type and contains a fixed guiding tube 19 having its central axis arranged coaxially with respect to the longitudinal axis of the tool holder 6 and, thus, coaxially with respect to the axis of rotation of the tool holder. In the guide tube 19 a reciprocatingly drivable piston 18 is provided to which a rearwardly extending connecting rod 17 is pivotably mounted.
The rear end of this connecting rod 17 is pivotably connected to an eccentric pin 16 so that a crank drive is formed. Within the guide tube 19 an axially reciprocatable ram (not shown) is located in front of the piston 18. By the reciprocating movement of this piston generated by revolving of the eccentric pin 16 overpressure and underpressure is alternatingly generated between the piston 18 and the rear end of the ram, as well-known. Thereby the ram is driven forwardly to cause impacts on the rear end of the not-shown hammer drill bit provided in the tool holder 6 and is sucked back within the guide tube 19.
The armature shaft 11 of the electric motor 10 is arranged perpendicular to the axis of rotation of the tool holder 6. A first intermediate shaft 14 is arranged in parallel to the armature shaft 11 at its side facing away from the tool holder 6, i.e. at the right-hand side in
The first intermediate shaft 14 is rotatably mounted in a sleeve bearing 30 and comprises a gear wheel 14 at its upper end formed in one piece with the intermediate shaft. This gear wheel meshes with a pinion 12 formed on the armature shaft 11 which pinion is provided above the upper bearing 13 of the armature shaft 11. In the gear wheel 15 the eccentric pin 16 is mounted which extends in parallel to the axis of rotation of the first intermediate shaft 14. Thus, rotation of the first intermediate shaft 14 results in a revolving movement of the eccentric pin 16 and, therefore, in driving of the hammer mechanism.
The second intermediate shaft 23 which is mounted in ball bearings 26 and 27, comprises a bevel gear toothing 25 at its upper end which toothing meshes with the bevel gear toothing of a rotation sleeve 28. This rotation sleeve is mounted coaxially on the guide tube 19, and its rotational movement causes rotation of the tool holder 6.
A sprocket 20 is non-rotatably mounted on the first intermediate shaft by means of splines. At the same height as this sprocket a sprocket 24 is non-rotatably mounted on the second intermediate shaft 23. The diameter of the sprocket 24 is larger than the diameter of the sprocket 20. The sprockets 20 and 24 are coupled by means of an endless chain 22. Thus, when the first intermediate shaft rotates due to rotation of the armature shaft 11 so that the hammer mechanism is driven, also the sprocket 24 and, thus, the second intermediate shaft 23 are rotatingly driven through the chain 22 so that the tool holder 6 rotates. The chain 22 surrounds the first intermediate shaft, the second intermediate shaft and the armature shaft 11. The different diameters of the sprockets 20 and 24 cause a speed reduction of the second intermediate shaft 23 compared to the rotational speed of the first intermediate shaft 14.
Numerous modifications may be made to the exemplary implementations described above. These and other implementations are within the scope of the following claims.
Number | Date | Country | Kind |
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0713432.3 | Jul 2007 | GB | national |
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20090014195 A1 | Jan 2009 | US |