GB2481301A

GB2481301A - Percussion mechanism with recoil damping

Info

Publication number: GB2481301A
Application number: GB1109934.8A
Authority: GB
Inventors: Immanuel Werner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2010-06-14
Filing date: 2011-06-13
Publication date: 2011-12-21
Also published as: DE102010030026A1; CN102275153A; GB201109934D0

Abstract

A percussion mechanism, in particular of a hand tool such as a percussion and/or drilling hammer (10a fig. 1), includes a recoil damping device 12a that comprises at least one load transmission unit 14a and at least one damping unit 16a disposed at least partially radially outside the load transmission unit 14a. The damping unit 16a may be disposed entirely radially outside the load transmission unit 14a. The damping unit 16a may comprise at least one spring lock washer 28a split in a peripheral direction (22b fig 5b). The load transmission unit 14a may have a stop face 18a angled at less than 30Â° to an axial direction 26a and may comprise several load transmission elements 30a and a holding unit (32c fig. 6a) radially inside the damping unit (16c fig. 6a). A protective unit (34d fig. 7) may be provided between the damping unit (16d fig. 7) and the load transmission unit (14d fig. 7).

Description

Percussion mechanism

Background art

The invention proceeds from a percussion mechanism having a damping device according to the preamble of claim 1.

A percussion mechanism for a hand tool machine, in particular for a percussion-and/or drilling hammer, having a damping device for damping a recoil is already known, wherein the damping device comprises a load transmission unit and a damping unit. The damping unit in this case is disposed in an axial direction at a side of the load transmission unit remote from an insert tool.

Disclosure of the invention

The invention proceeds from a percussion mechanism, in particular of a hand tool machine, having a damping device for damping a recoil that comprises at least one load transmission unit and at least one damping unit.

It is proposed that the damping unit is disposed at least partially radially outside of the load transmission unit.

By "damping" is meant in particular the absorption of energy of the recoil and/or a decelerating of a component, in particular a snap die, over a defined distance, such as in particular over a distance that is greater than one hundredth of a millimetre and is preferably greater than one tenth of a millimetre, by means of the damping unit.

By "radially outside of" the load transmission unit is meant in particular that the damping unit is disposed in a radial direction, viewed radially outwards from a percussion axis of the percussion mechanism, at least preferably the load transmission unit and the damping unit are disposed in an axial direction in at least one common plane extending perpendicular to the percussion axis.

Here, by a "percussion axis" is meant in particular an axis, in which a percussion load is transmitted during operation. By the axial direction is meant in particular a direction parallel to the percussion axis. In the development according to the invention, the damping device may be advantageously integrated in the percussion mechanism, thereby making it possible to Save installati0n space particularly in axial direction.

A particularly advantageous saving of installation space in axial direction is achieved if the damping unit is disposed entirely radially outside of the load transmission unit.

It is further proposed that the load transmission unit has a stop face, which with the axial direction includes an angle in particular smaller than 50°. Here, by the stop face is meant in particular a face on an outer side of the load transmission unit, which the component, in particular the snap die, in an operating state of a hand tool machine touches the load transmission unit and via which the component, in particular the snap die, transmits at least part of a load of the recoil to the load transmission unit.

By an "angle" is meant in particular the angle between the axial direction and a, viewed in a longitudinal section, planar stop face or preferably the angle between the axial direction and at least one tangent, preferably a tangent of an in axial direction outermost region of a curved stop face facing the tool holder. If the angle between the stop face and the axial direction is smaller than 50°, an of fceF of a force F produced by the recoil may be achieved. This radial component of force F may then be advantageously taken up by the damping unit. By virtue of a corresponding development of the stop face an advantageously small axial component of force F may be achieved, with the result that it is advantageously possible to spare the load transmission unit As a result, an extended useful life of the iIF transmission unit may be achieved. If the angle between the stop face and the axial direction is in particular smaller than 450, preferably in particular smaller than 30°, the features described above may be advantageously improved.

It is proposed that the stop face is configured to be curved around at least one axis differing from the percussion axis, namely particularly preferably around axes that are perpendicular to the percussion axis. By virtue of the curvature of the stop face of the load transmission unit an advantageous guidance of the component, in particular of the snap die, may be achieved during damping.

Preferably at least two different radii of curvature are provided, with the result that damping properties of the damping device may advantageously be adjusted.

It is moreover proposed that the damping unit comprises at least one spring lock washer. By a "spring lock washer" is meant in particular an elastically deformable component that is in particular of an annular design. By virtue of the development according to the invention the damping unit is particularly easy and economical to manufacture.

ring that is split in a peripheral direction. By "split" ---is meant in particular that the spring lock washer has free ends, wherein the ends of the spring lock washer may be arranged in mutual contact or mutually spaced apart in peripheral direction, in axial direction and/or in radial direction. End regions of the split spring lock washer are

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direction, in an overlapping manner and are in mutual contact preferably in at least one overlap region in at least one operating state. By virtue of a corresponding development a friction in the overlap region during at least one operating state may advantageously be achieved, with the result that the component of force F may be absorbed and at least part of a recoil energy may be converted to frictional heat. It is also conceivable for the spring lock washer to be of a non-split design. By "non-split" is meant in particular that the ends of the spring lock washer are connected to one another or that the spring lock washer is of an integral construction and therefore has no ends. Other forms deemed meaningful by a person skilled in the art are however also possible.

In a further embodiment the damping unit may in particular comprise a metal spring lock washer. In this way, a particularly large component of force F generated by the recoil may advantageously be absorbed by the damping unit.

Furthermore, the metal spring lock washer may be of an advantageously thin design in radial direction and yet high stability and good damping properties may still be achieved. Thus, by virtue of a corresponding development installation space in radial direction may advantageously be saved. The spring lock washer may however be ___ meaningful by the -personskilled in the art, in-particular from an elastomer.

A composite of at least two different materials is however also conceivable for the spring lock washer, in which case advantageous damping properties may be combined.

It is moreover proposed that the load transmission unit -s±on_e.Leiments. Th load transmission elements in this case may be disposed side by side in axial direction and/or particularly preferably in peripheral direction. A long useful life, in particular as a result of an attainably low risk of fracture, may be achieved, namely particularly if the load transmission elements are disposed side by side in peripheral direction. The load transmission unit particularly advantageously comprises at least four, in particular at least eight load transmission elements, which are disposed side by side in peripheral direction.

It is further proposed that the load transmission unit comprises at least one holding unit, which is provided for holding the at least two load transmission elements in a position in a peripheral direction. By a "position" is meant in particular a relative position of the load transmission elements to one another in peripheral direction and/or in axial direction. The load transmission elements may be held by the holding unit preferably during an assembly, with the result that the assembly of the at least two, in particular at least four, advantageously at least eight load transmission elements may be facilitated.

The load transmission elements may be reliably prevented from slipping or falling out during the assembly.

inside of the damping unit.'"iàdiailfy inside of" the damping unit is meant in particular that the holding unit is disposed in radial direction, viewed radially outwards from the percussion axis of the percussion mechanism, at least partially in front of the damping unit. By virtue of the development according to the invention it is possible radial direction for the holding unit. The holding unit may preferably comprise a sleeve-shaped holding element, wherein by a s1eeve-shaped component" is meant in particular a component, the axial extent of which is at least 10% of a diameter of the component. It is however also conceivable for the holding element to be in particular of an annular construction. The holding element may in principle be manufactured from any material deemed meaningful by the person skilled in the art. If the holding element is formed in particular from a flexible material, preferably from an elastomer, it is possible to achieve an additional damping of the recoil in axial direction, with the result that an advantageous removal of load from the load transmission unit may be achieved.

It is moreover proposed that a protective unit is provided, 3D which is disposed between the damping unit and the load transmission unit. The protective unit is preferably disposed in radial direction between the damping unit and the load transmission unit. The corresponding protective unit may advantageously protect the damping unit from damage that may be caused in the operating state by an inward pressing of edges of the load transmission unit. In this way, an advantageously long useful life of the damping device, in particular of the spring lock washer, may be the cpnent of - - may bé antagebusl the load transmission unit, in particular from the load transmission elements, via the protective unit to the damping unit. The protective unit preferably comprises a sleeve-shaped protective element that extends at least partially, preferably entirely in axial direction along the h is way, a canting of the load transmission elements and/or damage to the damping unit may advantageously be avoided.

Drawings Further advantages emerge from the following description of drawings. In the drawings four embodiments of the invention are represented. The drawings, the description and the claims contain numerous features in combination.

The person skilled in the art will advantageously also consider the features individually and combine them into meaningful further combinations.

The drawings show: Fig. 1 a hand tool machine according to the invention in a side view, Fig. 2 a sub-region of the hand tool machine with a percussion mechanism according to the invention in a diagrammatic sectional view, Fig. 3 a section through a load transmission unit of the percussion mechanism, Fig. 4a a plan view of the load transmission unit of Figure 3 in a non-deflected position, Fig. 4b a plan view of the load transmission unit of Fig. 5a a further bödent of a percussion mechanism according to the invention in a diagrammatic sectional view, Fig. 5b a metal spring lock washer according to the invention of the percussion mechanism of Figure 5a, ion.rae canisrn according to the invention in a diagrammatic sectional view, Fig. 6b a damping device of the percussion mechanism of Figure 6a in a sectional view and Fig. 7 a further embodiment of a percussion mechanism according to the invention in a diagrammatic sectional view.

Description of the embodiments

In Figure 1 a hand tool machine lOa formed by a percussion-and/or drilling hammer is represented. The hand tool machine lOa has a housing 38a. Disposed in a front region 40a of the hand tool machine lOa is a tool holder 42a that is provided for receiving an insert tool 44a, in particular a drilling-or chipping tool. There is further disposed in the front region 40a of the hand tool machine lOa an additional handle 46a and on a side of the hand tool machine lOa remote from the front region 40a a main handle 48a, by means of which the hand tool machine lOa may be guided by an operator. The housing 38a of the hand tool machine lOa accommodates a drive unit 50a formed by an electric motor, which is not represented in detail. In the interior of the housing 38a a gear unit 52a is moreover provided, which may transmit a torque generated by the --drie iitQ papneumatic_percuqn_c nj_and to an output device formed by a hammer tube 54a that may be set in rotation.

In Figure 2 the pneumatic percussion mechanism according to the invention is represented in greater detail. In principle, instead of a pneumatic percussion mechanism skilled in the art are also conceivable. The percussion mechanism comprises a piston, which is not represented in detail and which in an operating state may be set by means of the drive unit 50a in linear reciprocating motion in the direction of a percussion axis 26a. Via an air cushion the piston accelerates a striker 56a of the percussion mechanism likewise in the direction of the percussion axis 26a. In an end position facing the tool holder 42a the striker 56a transmits a percussion load to a snap die 58a, which is guided in the tool holder 42a and in turn transmits the percussion load to the insert tool 44a. Once the snap die 58a has transmitted the percussion load to the insert tool 44a, the snap die 58a moves in an axial direction 20a back to the striker 56a. This movement of the snap die 58a, during which the snap die 58a moves in axial direction towards the striker 56a, is referred to hereinafter as recoil.

In order to prevent the recoil of the snap die 58a from striking a delimiting component in an unbraked manner and possibly causing damage to the delimiting component and to further components of the percussion mechanism of the hand tool machine lOa, a damping device 12a is provided. The damping device 12a for damping the recoil is disposed in axial direction 20a, viewed from the tool holder 42a in front of a side of the striker 56a facing the tool holder 42a and comprises a damping unit 16a and a load transmission unit l4a. The damping unit l6a is disposed entirely radially outside of the load transmission unit 14a. The damping unit 16a and the load transmission unit 14a extend in a peripheral direction 22a radially outside of the snap die 58a.

The load transmission unit 14a has a stop face 18a, which is configured to be curved around an axis differing from the percussion axis 26a, namely around an axis that is perpendicular to the percussion axis 26a. A tangent 60a of an in axial direction 20a outermost region of the stop face 18a facing the tool holder 42a includes an angle a with the axial direction. The angle a is smaller than 30°. Viewed from the tool holder 42a towards the striker 56a, angles between tangents of the stop face iSa and the percussion axis 26a continuously decrease.

The load transmission unit l4a comprises eight load transmission elements 30a in the shape of segments of a circle that are disposed side by side uniformly distributed in peripheral direction. When the snap die 58a is situated in axial direction 20a in an end position facing the tool holder 42a, the load transmission elements 30a lie adjacent to one another and form a closed ring (Fig. 4a) . When the snap die 58a is situated in axial direction 20a in an end position facing the striker 56a, the load transmission elements 30a are disposed in peripheral direction 22a in a mutually spaced position (Fig. 4b) . In this way, during damping a component of force F may be transmitted in a particularly uniform manner to the damping unit 16a.

a spring lock washer 28a, which is held by an intermediate flange 62a in a position radially outside of the load transmission unit 14a. The spring lock washer 28a of the damping unit l6a is formed in a closed and non-split manner from an elastomer and is provided for taking up and absorbing the component of force F. The spring lock washer 28a is held positively and non-

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groove base and is provided in the radially outer region of the load transmission unit 14a.

During the recoil of the snap die 58a a stop face 66a of the snap die 58a strikes the stop face 18a of the load transmission unit 14a. During a movement of the snap die 58a in axial direction 20a towards the striker 56a the stop faces 18a, 66a of the load transmission unit 14a and the snap die 58a slide past one another, wherein a force F caused by the percussion load of the recoil acts upon the load transmission unit 14a. The stop face 66a of the snap die 58a in this case presses the load transmission unit 14a outwards in radial direction 24a.

By means of the stop face l8a of the load transmission unit 14a that includes an angle a with the axial direction 20a the force F is split into a component of force F acting in axial direction 20a and a component of force F acting in radial direction 24a (Fig. 3). As the angle a included by the tangent 60a of the stop face 18a and the axial direction 20a is smaller than 30°, the component of force F is greater than the component of force F. The component of force F is taken up by the load transmission unit 14a. The component of force F is transmitted from the load transmission unit 14a to the damping unit l6a. The damping unit l6a is supported against the intermediate flange 62a and produces a counterforce to the component of force F and takes up and absorbs the component of force F. As a result, the snap die 58a may be decelerated over the distance 68a that it travels in the direction of the striker 56a after an .Loa transmission unit l4a.

Figures 5a and 5b, Figures 6a and 6b, and Figure 7 show alternative developments of the percussion mechanism of a hand tool machine lOa, lOb, lOc, lOd having a damping device l2a, 12b, l2c, 12d. Components and features that are substantially identical are in principle denoted by the same reference characters, wherein in order to distinguish between the embodiments the letters a (Figure 1 to Figure 4b), b (Figures 5a and 5b), c (Figures 6a and 6b) and d (Figure 7) have been added to the reference characters.

Furthermore, with regard to features and functions that remain the same reference may be made to the description of the embodiment in Figures 1 to 4b. The following description of Figures 5a to 7 is confined substantially to the respective differences from the embodiment in Figures 1 to 4b.

In Figure 5a an alternative development of a percussion mechanism of a hand tool machine lOb having a damping device 12b is represented. The damping device l2b comprises a load transmission unit 14a and a damping unit 16b, which comprises a metal spring lock washer 28b. The load transmission unit 14b comprises a rectangular groove 64b for the metal spring lock washer 28b, in which the metal spring lock washer 28b is held positively and non-positively.

The metal spring lock washer 28b is of a split design, wherein end regions 70b, 72b of the metal spring lock washer 28b overlap in peripheral direction and are disposed in a radial direction 24b one directly behind the other.

spring. lock washer 28b are in mutual contact in radial direction 24b in an overlap region 74b (Fig. 5b) . In an operating state of the hand tool machine lOb, as already described, a snap die 58b is driven and in the event of a recoil deflects the load transmission unit l4b radially outwards. In this case, the metal spring lock washer 28b is expanded in a peripheral direction 22b and the end regions 70b, 72b of the metal spring lock washer 28b are conveyed past one another in peripheral direction 22b. In this case, friction is generated between the end regions 70b, 72b of the metal spring lock washer 28b, thereby achieving an advantageous damping of a component of force F. In Figure 6a a further embodiment of a percussion mechanism of a hand tool machine lOc having a damping device 12c is represented, wherein a load transmission unit 14c of the damping device 12c additionally comprises a holding unit 32c. The holding unit 32c is provided for holding roller-shaped load transmission elements 30c of the load transmission unit l4c in a position mutually spaced apart from one another in a peripheral direction 22c. For this purpose, the holding unit 32c comprises a sleeve-shaped holding element 76c, which in peripheral direction 22c has recesses 78c for receiving the load transmission elements 30c. The number of recesses 78c corresponds to the number of load transmission elements 30c. The holding unit 32c is disposed radially inside of a damping unit 16c. The holding element 76c is formed integrally with a tool holder 42c and disposed in a region of the tool holder 42c that, viewed in an axial direction 20c from the tool holder 42c, faces a striker 56c.

--Figure---7-shows an embodiment ofa percussion mechanism of a hand tool machine lOd having a damping device 12d, in which a protective unit 34d is disposed in a radial direction 24d between a load transmission unit 14d and a damping unit 16d. The protective unit 34d comprises a sleeve-shaped protective element 36d, which in an axial direction 20d extends entirely over the damping unit 16d and over the load transmission unit 14d. The protective element 36d prevents a canting of load transmission elements 30d and damaging of the damping unit 16d by edges of the load transmission elements 30d during a movement of the load transmission elements 30d outwards in radial direction 24d.