WO2012024843A1

WO2012024843A1 - Striking mechanism

Info

Publication number: WO2012024843A1
Application number: PCT/CN2010/076412
Authority: WO
Inventors: Bo Zhen
Original assignee: Bosch Power Tools China Co Ltd
Current assignee: Bosch Power Tools China Co Ltd
Priority date: 2010-08-27
Filing date: 2010-08-27
Publication date: 2012-03-01
Anticipated expiration: 2013-02-27
Also published as: CN103079771A

Abstract

The invention relates to a striking mechanism for a hand-held power tool, in particular a drill hammer and/or a chipping hammer. The striking mechanism of the present inven- tion comprises a piston (12a; 12b) to produce a striking pulse and a drive unit (14a; 14b) to drive the piston (12a; 12b). The drive unit (14a; 14b) according to the invention com- prises at least one gear wheel (16a; 16b) that is rotatably driven. The gear wheel (16a; 6b) comprises an eccentric driving groove (18a; 18b) which is provided to convert a rotary motion of the gear wheel (16a; 16b) into a reciprocating motion of the piston (12a; 2b).

Description

Striking Mechanism

Field of Invention

The invention relates to a striking mechanism for a hand-held power tool, in particular a drill hammer and/or a chipping hammer.

Background Art

Striking mechanisms for hand-held power tools, in particular for drill hammers and/or chipping hammers, which comprise a piston to produce a striking pulse and a drive unit to drive the piston, are well-known.

Summary of the Invention

The invention relates to a striking mechanism for a hand-held power tool, in particular a drill hammer and/or a chipping hammer. The striking mechanism of the present invention comprises a piston to produce a striking pulse and a drive unit to drive the piston.

The drive unit according to the invention comprises at least one gear wheel that is ro- tatably driven. The gear wheel comprises an eccentric driving groove which is provided to convert a rotary motion of the gear wheel into a reciprocating motion of the piston. In this context, the term "piston" shall define a part which is provided to produce a striking pulse in cooperation with a hammer, in particular an axial striking pulse, and/or to directly or indirectly transmit a striking pulse, in particular an axial striking pulse, to a tool of a hand-held power tool which is inserted into a tool holder of the hand-held power tool. The tool can be configured as a drill and/or a chisel. To indirectly transmit the striking pulse to the tool, the striking mechanism further comprises a striker that is formed by a part which is separate from the hammer. The striker directly contacts the tool to transmit the striking pulse when the striking mechanism is operated. The piston according to the invention is preferably configured as a pot-shaped piston. It is also possible to configure the piston in another shape which is considered expedient by a person skilled in the art. Furthermore, in this context a "drive unit" shall define a unit which comprises at least a motor, especially an electric motor, and a transmission unit that comprises the gear wheel to transmit a force and/or a torque from the motor to the piston or to transmit and/or reduce a rotational speed. The gear wheel of the drive unit according to the invention can be embodied as a crown gear, as a spur gear or as a bevel gear. Therefore, a rotation axis of the electric motor can be orientated substantially per- pendicular to a striking direction of the piston or parallel to the striking direction. The reciprocating motion of the piston proceeds along an axis which is substantially parallel to a rotation axis of a tool holder in which a tool is inserted to work on a workpiece. Moreover, in this context an "eccentric driving groove" shall define a recess in the gear wheel preferably in a plane perpendicular to a rotation axis of the gear wheel. It is also possible that the eccentric driving groove is formed by two annular- shaped ribs which extend in the plane perpendicular to the rotation axis of the gear wheel and which are located distantly from each other in the plane perpendicular to the rotation axis. Thereby, an advantageously simple and compact structure of the striking mechanism according to the invention can be achieved.

In a preferred embodiment of the striking mechanism according to the invention the eccentric driving groove has an annular shape and comprises a center which is located eccentrically to a center of rotation of the gear wheel. The center of rotation of the gear wheel is located on the rotation axis of the gear wheel. Thereby, a simple structure of the eccentric driving groove can be achieved.

In addition, the striking mechanism further comprises at least one connecting rod to connect the gear wheel to the piston. The transformation of the rotary motion into the reciprocating motion is essentially generated by the cooperation of the gear wheel, especially the eccentric driving groove, and the at least one connecting rod. It is also possible to provide more than one connecting rod to generate the reciprocating motion of the piston. A person skilled in the art is undoubtedly able to select a suitable number of connecting rods that meets the requirements for the specific use of the striking mechanism. Thereby, an advantageous transformation of a rotary motion of the gear wheel into a reciprocating motion of the piston can be achieved.

In a preferred embodiment of the striking mechanism of the present invention the connecting rod is embodied L-shaped. In this context, the term "L-shaped" shall define a geometrical shape which has at least two legs deviated from each other. The two legs enclose an angle between 60° and 120°. Preferably the two legs enclose an angle of 90°. It is also possible that the connecting rod has another shape. A person skilled in the art is undoubtedly able to select a suitable shape of the connecting rod that meets the requirements for the specific use of the striking mechanism. Thereby, a simple combination of a supporting structure and a transmission structure of the connecting rod can be advantageously achieved. Moreover, the connecting rod comprises a first leg and a second leg. The first leg is orientated substantially perpendicular to a striking direction of the piston and the second leg is orientated substantially parallel to the striking direction of the piston. The striking direction of the piston is at least parallel to a rotation axis of a tool holder. In this context, the term "substantially parallel" shall define an orientation of a first direction relative to a second direction wherein the first direction has a deflection relative to the second direction which is smaller than 5° and preferably smaller than 2°. Thereby, packaging space can advantageously be saved.

In addition, the connecting rod is supported with an end of the first leg of the connecting rod in the eccentric driving groove. The end of the first leg can be supported via a bearing in the eccentric driving groove to achieve less friction between the first leg and the eccentric driving groove. In a preferred embodiment the end of the first leg is directly supported in the eccentric driving groove. Thereby, an advantageous connection between the gear wheel and the piston can be achieved. Moreover, a simple structure to convert a rotary motion into a reciprocating motion can be achieved.

Furthermore, the striking mechanism further comprises a guidance element that is provided to guide an end of the second leg of the connecting rod along the striking direction of the piston. The guidance element can be embodied as bush or the like which is provided to guide a part along a direction. It is also possible that the end of the second leg is mounted in the housing and that the first leg and the second leg are connected via a hinge. Thereby, an advantageous guidance of the connecting rod, especially of the second leg, can be achieved.

Moreover, the present invention relates to a hand-held power tool, in particular a drill hammer and/or a chipping hammer, which comprises a striking mechanism according to the present invention. Thereby, a hand-held power tool with a compact and simple structure can be advantageously achieved.

Brief Description of the Drawings

Other objects, features and advantages of the present invention will become apparent from a reading of the following detailed description when taken in conjunction with the accompanying drawings wherein two particular embodiments of the invention are disclosed as illustrative examples. Fig. 1 shows a hand-held power tool that comprises a striking mechanism according to the invention in a schematic representation,

Fig. 2 shows a detail view of a first embodiment of the striking mechanism according to the invention in a schematic representation, and

Fig. 3 shows a detail view of an alternative embodiment of a striking mechanism according to the invention in a schematic representation.

Detailed Description of the Invention

Figure 1 shows a hand-held power tool 38a that comprises a striking mechanism 10a according to the invention. The hand-held power tool 38a is configured as a drill hammer 40a. Alternatively, the hand-held power tool 38a can also be configured as a chipping hammer (not shown). The drill hammer 40a comprises a housing 42a to accommodate the striking mechanism 10a. Moreover, the drill hammer 40a comprises a handle 44a which can be gripped by an operator using the drill hammer 40a. The handle 44a essentially extends perpendicular to a main extension direction 46a of the drill hammer 40a. Furthermore, the drill hammer 40a comprises a tool holder 48a to accommodate a tool 50a. The tool holder 48a is located on a side 52a opposite to the handle 44a of the drill hammer 40a. The drill hammer 40a further comprises a detachable accessory handle 54a which can also be gripped by the operator for a guidance of the drill hammer 40a.

Figure 2 shows a detail view of the striking mechanism 10a according to the invention. The striking mechanism 10a comprises a piston 12a to produce a striking pulse along a striking direction 30a. The striking direction 30a is essentially parallel to the main extension direction 46a of the hand-held power tool 38a. The piston 12a is slidably supported in a hammer tube 60a. The hammer tube 60a has a cylindrical shape and is embodied in a well-known manner. In a striking position the striking pulse is transmitted from the striking mechanism 10a to the tool 50a.

Moreover, the striking mechanism 10a comprises a drive unit 14a. The drive unit 14a has a gear wheel 16a embodied as a bevel gear that is rotatably driven by an electric motor 56a of the drive unit 14a. Therefore, the electric motor 56a comprises a pinion 58a embodied as a conical gear. The electric motor 56a is supported in the housing 42a of the drill hammer 40a via bearings (not shown). A rotation axis 64a of the electric motor 56a is orientated parallel to the striking direction 30a and perpendicular to a rota- tion axis 62a of the gear wheel 16a. The gear wheel 16a of the drive unit 14a has an eccentric driving groove 18a which is provided to convert a rotary motion of the gear wheel 16a into a reciprocating motion of the piston 12a. The eccentric driving groove 18a has an annular shape. A center 20a of the eccentric driving groove 18a is located eccentrically to a center of rotation 22a of the gear wheel 16a.

The striking mechanism 10a further comprises a connecting rod 24a to connect the gear wheel 16a to the piston 12a. The connecting rod 24a is embodied L-shaped. Hence, the connecting rod 24a comprises a first leg 26a and a second leg 28a, wherein the first leg 26a is orientated substantially perpendicular to the striking direction 30a of the piston 12a and the second leg 28a is orientated substantially parallel to the striking direction 30a of the piston 12a. The first leg 26a is connected to a supporting part of the piston 12a. Moreover, the connecting rod 24a is supported with an end 32a of the first leg 26a in the eccentric driving groove 18a. The end 32a of the first leg 26a is slidably supported in the eccentric driving groove 18a.

Furthermore, the striking mechanism 10a comprises a guidance element 34a that is provided to guide an end 36a of the second leg 28a of the connecting rod 24a along the striking direction 30a of the piston 12a. The guidance element 34a is embodied as a bush that is supported in the housing 42a of the drill hammer 40a. It is also possible that the guidance element 34a is embodied in another form which is considered expedient by a person skilled in the art. For example the guidance element 34a can be formed as one piece with the housing 42a of the drill hammer 40a.

When the gear wheel 16a is driven by the electric motor 56a via the pinion 58a the gear wheel 16a rotates around the rotation axis 62a. The center 20a of the eccentric driving groove 18a of the gear wheel 16a eccentrically rotates around the rotation axis 62a. At this, the connecting rod 24a causes a movement of the piston 12a along the striking direction 30a by the connection of the end 32a of the first leg 26a of the connecting rod 24a and the eccentric driving groove 18a. The end 32a of the first leg 26a of the connecting rod 24a is guided in the eccentric driving groove 18a. During a rotation of the gear wheel 16a the end 32a of the first leg 26a slides inside the eccentric driving groove 18a so that the connecting rod 24a carries out a linear movement along the striking direction 30a during a rotation of the gear wheel 16a. The connecting rod 24a is moved linearly in a plane which extends through the rotation axis 62a of the gear wheel 16a and through the rotation axis 64a of the electric motor 56a. The linear movement of the connecting rod 24a is enabled by the conjunction of the guidance of the end 32a of the first leg 26a in the eccentric driving groove 18a and the guidance of the end 36a of the second leg 28a of the connecting rod 24a in the guidance element 34a. The connecting rod 24a causes a reciprocating motion of the piston 12a when the gear wheel 16a is rotated around the rotation axis 62a. It is also possible that the connecting rod 24a carries out a heterodyne movement. Then the connecting rod 24a will be pivotably moved in a first plane perpendicular to the striking direction 30a and will be linearly moved along the striking direction 30a to cause a reciprocating movement of the piston 12a.

Figure 3 shows an alternative embodiment of the present invention. Parts, features and functions which are essentially the same are numbered with the same reference numerals. For differentiation of the embodiments, letters a and b are added to the reference numerals. The following description is restricted to the differences between the embodiments shown and described in figures 1 and 2. With regard to the parts, the features and the functions which are unchanged, it is pointed out that the description of the embodiment of figures 1 and 2 already describes these parts, features and functions.

Figure 3 shows a detail view of a striking mechanism 10b according to the invention. The striking mechanism 10b comprises a piston 12b to produce a striking pulse along a striking direction 30b. Moreover, the striking mechanism 10b comprises a drive unit 14b. The drive unit 14b has a gear wheel 16b embodied as a spur gear that is rotatably driven by an electric motor 56b of the drive unit 14b. Therefore, the electric motor 56b comprises a pinion 58b embodied as a spur gear. A rotation axis 64b of the electric motor 56b is orientated perpendicular to the striking direction 30b and parallel to a rotation axis 62b of the gear wheel 16b. The gear wheel 16b of the drive unit 14b has an eccentric driving groove 18b which is provided to convert a rotary motion of the gear wheel 16b into a reciprocating motion of the piston 12b.

Thus, the present invention may be practiced and/or configured otherwise than as specifically described above. Many changes, alternatives, variations, and equivalents to the various structures shown and described will be apparent to one skilled in the art. Accordingly, the present invention is not intended to be limited to the particular embodiments illustrated but is intended to cover all such alternatives, modifications, and equivalents as may be included within the spirit and broad scope of the invention as defined by the following claims. All patents, patent applications, and printed publications referred to herein are hereby incorporated by reference in their entirety.

Claims

1. A striking mechanism for a hand-held power tool, comprising:

a piston (12a; 12b) to produce a striking pulse; and

a drive unit (14a; 14b) to drive said piston (12a; 12b);

wherein said drive unit (14a; 14b) comprises at least one gear wheel (16a; 16b) that is rotatably driven; wherein said gear wheel (16a; 16b) comprises an eccentric driving groove (18a; 18b) which is provided to convert a rotary motion of said gear wheel (16a; 16b) into a reciprocating motion of said piston (12a; 12b).

2. The striking mechanism as defined in Claim 1, wherein said eccentric driving groove (18a; 18b) has an annular shape and wherein a center (20a; 20b) of said eccentric driving groove (18a; 18b) is located eccentrically to a center of rotation (22a; 22b) of said gear wheel (16a; 16b).

3. The striking mechanism as defined in one of the preceding Claims, further comprising at least one connecting rod (24a; 24b) to connect said gear wheel (16a; 16b) to said piston (12a; 12b).

4. The striking mechanism as defined in Claim 3, wherein said connecting rod (24a; 24b) is embodied L- shaped.

5. The striking mechanism as defined in Claim 4, wherein said connecting rod (24a; 24b) comprises a first leg (26a; 26b) and a second leg (28a; 28b), wherein the first leg (26a; 26b) is orientated substantially perpendicular to a striking direction (30a; 30b) of said piston (12a; 12b) and wherein the second leg (28a; 28b) is orientated substantially parallel to said striking direction (30a; 30b) of said piston (12a; 12b).

6. The striking mechanism as defined in Claim 5, wherein said connecting rod (24a; 24b) is supported with an end (32a; 32b) of said first leg (26a; 26b) of said connecting rod (24a; 24b) in said eccentric driving groove (18a; 18b).

7. The striking mechanism as defined in Claim 5, further comprising a guidance element (34a; 34b) that is provided to guide an end (36a; 36b) of said second leg (28a; 28b) of said connecting rod (24a; 24b) along said striking direction (30a; 30b) of said piston (12a; 12b).

8. A hand-held power tool, in particular a drill hammer and/or a chipping hammer, comprising:

a striking mechanism as defined in one of the preceding Claims.