MECHANICAL PERCUSSION MECHANISM

Information

  • Patent Application
  • 20080073092
  • Publication Number
    20080073092
  • Date Filed
    April 27, 2007
    17 years ago
  • Date Published
    March 27, 2008
    16 years ago
Abstract
A mechanical percussion mechanism for a percussion drive of a tool insert in a handheld power tool has a rotatably supported drive shaft, a percussion body connected to the drive shaft in a manner fixed against relative rotation and supported axially movable relative to the drive shaft, a rotatably supported driven shaft connected to the drive shaft in a manner fixed against relative rotation, the percussion body having drive cams and the driven shaft having drive cams, which drive cams of the percussion body and the driven shaft are bringable into operative connection for a percussion drive of the tool insert, and an axial stop provided for the percussion body.
Description

BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 shows the drive train of a handheld power tool in accordance with the present invention, with a mechanical rotary percussion mechanism, in an exploded view; and



FIG. 2 is a cross section through the mechanical rotary percussion mechanism of FIG. 1 in accordance with the present invention.





DESCRIPTION OF THE PREFERRED EMBODIMENT

In the exploded view of FIG. 1, the drive train of a rotary percussion screwdriver is shown, with a mechanical percussion mechanism 50. Hereinafter, only the essential components will be discussed.


An electric motor 10 (shown schematically) includes an armature shaft 12, on which a gear wheel, serving as a drive pinion 31, is located, in a manner fixed against relative rotation. The drive pinion 31 forms one part of a two-stage planetary gear 30 and drives planet wheels 32 with the first gear stage. The planet wheels 32 roll inside a ring gear 36. As a result, a first sun wheel 33 is rotated, which in turn, via a set of teeth 34, drives further planet wheels 35 of the second gear stage. The planet wheels 35 roll inside the ring gear 36 and drive a second sun wheel 37. The second sun wheel 37 is connected to the drive shaft 51 of the mechanical percussion mechanism 50 in a manner fixed against relative rotation.


To that end, in FIG. 1, the sun wheel 37 is embodied in the form of pins in one piece with the drive shaft 51. The drive shaft 51 is supported, on its end toward the gear, in a bearing 52, preferably a roller bearing, in particular a deep-groove ball bearing. The two-stage planetary gear 30, the bearing 52, and part of the drive shaft 51 are received in a separate housing 20 of plastic. On the gear end, the housing 20 is provided with a cap, also of plastic, as a cover element 22. The cover element 22 has a central opening 23 for receiving the armature shaft 12. On the diametrically opposed end, the bearing end, of the housing 20, the drive shaft 51 protrudes out of the housing 20.


The mechanical percussion mechanism 50 of FIG. 1 is a V-groove rotary percussion mechanism. It includes a rotatably supported drive shaft 51 with slaving elements 57 in the form of slaving balls in a V-groove 58. Via the slaving elements 57, a percussion body 56 is connected to the drive shaft 51 in a manner fixed against relative rotation, so that the drive shaft 51, driven by the electric motor 10 via the planetary gear 30, sets the percussion body into rotary motion. Simultaneously, the percussion body 56 is axially movably supported on the drive shaft 51. The percussion body 56 has drive cams 53. Via the percussion body 56 with the drive cams 53, a rotatably supported driven shaft 59 is connected to the drive shaft 51 in a manner fixed against relative rotation via driven cams 54.


In nonpercussive driving, the percussion body 56 is prestressed in the direction of the driven shaft 59 via a compression spring 55. Then the drive cams 53 engage the driven cams 54 in such a way that the rotary motion of the percussion body 56 is transmitted to the driven shaft 59. The driven shaft 59 is likewise supported in a bearing 61. A shim 24 serves to receive and fix the compression spring 55 and also to protect the housing 20 against heating and wear from the friction of the compression spring 55. For receiving a tool insert (not shown), the driven shaft 59 is connected to a tool receptacle 62. The percussion mechanism 50 is received in a housing part 63, preferably of metal. A housing screen 64 of an elastic plastic covers at least some of the housing part 63.


The mode of operation of a V-groove rotary percussion mechanism will not be discussed in detail here, since it is familiar enough to one skilled in the art. As to the mode of operation, it will merely be indicated that by means of a screw (not shown) contacting a workpiece, the torque demand increases abruptly, and the rotary motion of the driven shaft 59 is blocked. The percussion body 56 driven by the drive shaft 51 continues to rotate and is pressed by the slaving elements 57 in the V-shaped grooves 58 in the direction of the drive end of the drive shaft 51, counter to the restoring force of the compression spring 55. In the process, the drive cams 53 of the percussion body 56 meet the driven cams 54 of the driven shaft 59, and the energy of the percussion body 56, stored as a result of the rotation, is therefore transmitted to the driven shaft 59. As a result of this longitudinal motion, the drive cams 53 slip farther on the driven cams 54 and slide past them.


For the sake of greater simplicity, the mechanical percussion mechanism 50 is shown in FIG. 1 without a stop. However, in the cross section of FIG. 2 an axial stop 70 can be seen clearly. In the embodiment of FIG. 2, the axial stop 70 is formed by an annular or disklike spring element made from an elastomer. The diameter of the disklike elastomer spring element is less than the diameter of the compression spring 55, and thus the stop 70 can be located inside the compression spring 55. The stop 70 is supported on the drive shaft 51 in a manner fixed against relative rotation and rests on the shim 24. As a result, the maximum axial deflection of the percussion body 56 on the drive shaft 51 counter to the compression force of the compression spring 55 is limited in the direction of the drive end of the drive shaft 51.


Without an axial stop 70, the percussion body 56 could be moved still farther axially in the direction of the drive end of the drive shaft 51, so that the slaving elements 57 could be set free and fall out of the V-grooves 58.


It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above.


While the invention has been illustrated and described as embodied in a mechanical percussion mechanism, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.


Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

Claims
  • 1. A mechanical percussion mechanism for a percussion drive of a tool insert in a handheld power tool, the mechanical percussion mechanism comprising a rotatably supported drive shaft; a percussion body connected to said drive shaft in a manner fixed against relative rotation and supported axially movable relative to said drive shaft; a rotatably supported driven shaft connected to said drive shaft in a manner fixed against relative rotation, said percussion body having drive cams and said driven shaft having drive cams, which drive cams on said percussion body and said driven shaft are bringable into operative connection for a percussion drive of the tool insert; and an axial stop provided for said percussion body.
  • 2. A mechanical percussion mechanism as defined in claim 1, wherein said stop for said percussion body is configured as a spring element.
  • 3. A mechanical percussion mechanism as defined in claim 1, wherein said stop for said percussion body is composed of an elastic material.
  • 4. A mechanical percussion mechanism as defined in claim 3, wherein said stop for said percussion body is composed of an elastomer.
  • 5. A mechanical percussion mechanism as defined in claim 1, wherein said stop for said percussion body is configured as an annular stop.
  • 6. A mechanical percussion mechanism as defined in claim 5, wherein said annular stop is supported on said drive shaft.
  • 7. A mechanical percussion mechanism as defined in claim 1, wherein said percussion body is connected to said drive shaft in a manner fixed against relative rotation via at least one slaving element.
  • 8. A mechanical percussion mechanism as defined in claim 7, wherein said at least slaving element is configured as a roller body.
  • 9. A mechanical percussion mechanism as defined in claim 8, wherein said at least one slaving element is configured as a ball.
  • 10. A handheld power tool, comprising a tool insert which is percussively driven; and a mechanical percussion mechanism for a percussive drive of said tool insert, said mechanical percussion mechanism including a rotatably supported drive shaft, a percussion body connected to said drive shaft in a manner fixed against relative rotation and supported axially movable relative to said drive shaft, a rotatably supported driven shaft connected to said drive shaft in a manner fixed against relative rotation, said percussion body having drive cams and said driven shaft having drive cams, which drive cams of said percussion body and said driven shaft are bringable into operative connection for the percussion drive of said tool insert, and an axial stop provided for said percussion body.
Priority Claims (1)
Number Date Country Kind
202006014850.7 Sep 2006 DE national