GB2295054A

GB2295054A - Hand-held power tool

Info

Publication number: GB2295054A
Application number: GB9521935A
Authority: GB
Inventors: Gerhard Haeusser; Guillermo Havenstein; Ottmar Seel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-11-05
Filing date: 1995-10-26
Publication date: 1996-05-15
Anticipated expiration: 2015-10-26
Also published as: NL1001578A1; DE4439590A1; NL1001578C2; CN1130556A; ES2128213A1; GB2295054B; CN1052933C; DE4439590C2; GB9521935D0; ES2128213B1

Description

Hand-held power tool 2295054

Prior art

The invention starts from a hand-held power tool according to the generic definition of the main claim. A hand-held power tool of this type is already known (DE 35 40 964 Al) which is provided with operating elements which can be moved into corresponding easing openings. An operating element of this type in for example in the f orm of a locking button, such as is widely used in hand-held power tools, for the mains switch, said button being able to be operated when the mains switch is depressed and then locking-the latter so that the operator of the hand-held power tool does not need to hold the mains switch continuously depressed during continuous operation. To switch off, the mains switch has to be depressed again, whereupon the locking button -A brought back from its locking position to its starting position by spring force and releases the mains switch. A disadvantage of operating elements of this kind is that foreign bodies can penetrate into the gap between the wall of the casing opening and the operating element, and then become jammed between the latter and the wall of the caning opening, thereby making it impossible for the operating element to be returned by spring force alone.

Advantages of the invention The hand-held power tool according to the invention, which has the characterizing feature of the main claim, has in contrast thereto the advantage that the risk of the jamming of the operating element Inside the casing opening is reduced. The operating elements of the handheld power tool can thus be reliably handled, even after a lengthly period of continuous operation in an R. 27387 environment heavily laden with grinding or drilling dust. Through the measures indicated in the subclaims advantageous developments and improvements of the handheld power tool according to the invention are achieved.

it is particularly advantageous for guide ribs having guide surfaces extending parallel to the wall of the casing opening to be arranged on the outer periphery of the tapering region of the operating element, since in this way the operating element is guided in the Casing opening and at the same time the jaming of the operating element by foreign bodies is prevented by the tapering in -the other regions of the operating element. Furthermore, the formation of openings in a bottom or on the wall of the casing opening to enable the foreign bodies to pass -out of-the casing opening is advantageous.

Drawings Two exemplary embodiments of the invention are illustrated in the drawings and expla - inedin greater detail in the following dearription. Figure 1 shows an elevation of a hand-held power tool equipped with an operating element, Figure 2 shows an operating element of the hand-held power tool according to a first exemplary embodiment, Figure 3 shows an operating element according to a second exemplary- embodiment and Figure 4 shows a three-dimensional representation of the operating element according to Figure 3.

Description of the exemplary embodiments

Figure 1 shows, as an example of a hand-held power tool, a hand-held drill 10 which has a casing 11. From the casing 11 projects a front part of a drive spindle 12, with the tool holder 13, into which a tool 14 can be inserted, fastened on it. The drive spindle 12 can be driven rotationally by means of a drive motor 15 with the aid of a gear unit 16. The drive motor 15 can be switched on and off by operation of a switch handle 17, for example in the form of a trigger-type push switch 18. The switch handle 17 or the trigger-type push switch 18 is - 3 R. 27387 here preferably arranged on a handgrip 19 of the hand held drill 10, said handgrip being formed by the caning 11 or possibly being attached to the latter. By means of an operating element 20 arranged on the side of the handgrip 19 the trigger-type push switch 18 can be locked in a designated switch position, particularly in the Oonn position of the drive motor 15, in known manner. This kind of locking of the trigger-type push switch 18 in useful for continuous operation of the hand-held' drill 10, since then the operator does not need to hold the trigger-type push switch 18 continuously depressed.

The operating element 20 shown in greater detail in Figure 2 in in the form of a locking button 21, which can be moved axially in a caning opening 22 in the hand-grip 19 or caning 11, and partly projects out of said opening.

The locking button 21 has a conical head part 21a and a cylindrical actuating part 21b which has a smaller cross section than the head part and on the end -of which a collar 21c in formed. The head part 21a has a conical shape such that it tapers in the direction of the actuating part 21b, that In to say in the operating direction. A gap 24 having a certain gap width a, which is forme-1 between a predominantly cylindrical wall 23 of the casing opening 22 and the head part 21a, therefore widens in the direction of the actuating part 21b. The locking button 21 cooperates with a locking part 25, which in connected to the trigger-type push switch 18 for translation therewith and in which a catch through opening 26 in provided. The locking part 25 in mounted for longitudinal movement in bearing points 27. The trigger-type push switch 18 together with the locking part 25 is loaded by a return spring 28 in the direction of the return position of the trigger-type push switch 18. The return spring 28 in in the form of a compression spring and is supported at one end against the casing 11 and at the other end against the trigger-type push switch 18. The locking button 21 is in turn loaded by a return element 29 in the direction of its starting position, said element likewise being in the form of a compression R. 27387 spring. This return element 29 in supported on a bottom of the casing opening 22 and on the end face of the head part 21a of the locking button 21. The actuating part 21b extends through the bottom 30.

In the actuating position shown in Figure 2 the actuating part 21b of the locking button 21 engages positively in the catch opening 26 in the locking part 25, so that the trigger-type push switch 18 cannot be returned by the return spring 28. The collar 21c here projects beyond the edge of the catch opening 26, so that the locking button 21 is likewise held fast in this position. In this locking position an electric switch, not shown in detail in Figure 2, in for example switched to continuous operation of the drive motor 15 (Figure 1).

is If it is desired to return the trigger-type push switch 18 from this position, that is to say to switch off the drive motor 15, the trigger-type push switch 18 must first be pushed slightly more deeply into the caning 11, against the force of the return spring 28, until the collar 21c no longer projects beyond the edge of the catch opening 26. The locking button 21 in then free and can be moved axially by the return element 29 towards the outside of the caning 11. The actuating part 21b together with the collar 21c then snaps axially out of the catch opening 26, so that the trigger-type push switch 18 in likewise released and can be returned by the return spring 28 to its starting position.

The conically shaped outer periphery of the head part 21a here has the effect of preventing foreign bodies 31, which may have penetrated into the gap 24 between the head part 21a and the wall 23 of the casing opening 22, from becoming jammed, since during the axial return of the locking button 21 the gap width a between the head part 21a and the wall 23 of the caning opening 22 continuously increases.

In order to guide the locking button 21 in its axial movement inside the casing opening 22, in the exemplary embodiment according to Figure 3 guide ribs 32 are formed on the outer periphery of the conical head part 21a of R. 27387 the locking button 21; the guide ribs 32 extend approximately parallel to the cylindrical wall 23 of the casing opening 22 and form guide surfaces 33 on their exterior. Since the head part 21a is predominantly, that is to say in the peripheral regions situated between the guide ribs 32, conical in shape, foreign bodies 31 which have penetrated into the gap 24 between the head part 21a and the wall 23 of the caning cannot become jammed therein. In the region of the guide surfaces 33 there in admittedly still a possibility of the jamming of foreign bodies 31, but this guide region is relatively small in _comparison with the total peripheral area, so that the advantageous action of the invention in also retained in _-the exemplary embodiment according to Figure 3. Since the is critical area, in which the jamming of foreign bodies 31 can occur, has as a whole been significantly reduced, faultless return of the locking button 21 by the return element is ensured, particularly as jamming in usually caused by a multiplicity of foreign bodies 31, consisting for example of drilling oz grinding dust, possibly combined with moi-sture. It has been possible to verify this by means of practical tests.

In the exemplary embodiment according to Figure 3 at least one opening 34 for the foreign bodies 31 to pass out is provided in the bottom 30 of the caning opening 22 (Figure 2), so that the caning opening 22 will not become clogged after after a lengthy period of operation in a dust-laden environment. The opening 34 leads into a compartment 35 in the casing (Figure 2), in which the foreign bodies 31 can be dispersed without difficulty.

In Figure 4 is shown a three-dimensional view of the operating element 20 according to Figure 3. The predominantly conical head part 21a of the locking button 21 can clearly be recognized, with four guide ribs 32 distributed over the periphery, said button tapering conically in the peripheral regions between the guide ribs 32. The cylindrical actuating part 21b adjoins the head part 21a and is provided with the collar 21c at its end.

- 6 R. 27387 The invention is not restricted to the exemplary embodiments illustrated. Its application is obviously advantageous not only for hand-held drills, but for all hand-held power tools, particularly those operated continuously in a dust-laden environment, such as for example grinding tools and the like. in addition, the locking button 21 may also have any other desired shape whereby it encloses, with the wall 23 of the casing opening 22, a gap 24 which, viewed in the operating 10 direction, has an increasing gap width a. The increasing of the gap width 9 can here also be achieved by a corresponding conical widening of the wall 23 in the operating direction of the operating element 20, while the head part 21a is cylindrical. The openings 34 can is also be provided in the wall 23 of the casing opening 22. The invention is also not restricted to locking buttons for trigger-type push switches, but can also be appropriately applied to other operating elements returnable by spring loading, such as for example locking 20 slides on switch handles or trigger-type push switches.

CLATMS 1. Hand-held power tool having a casing (11) which is provided with a casing opening (22) for the at least partial reception of an operating element (20), preferably for an electric switch, which operating element can be moved more deeply into the casing opening -(22) in its operating direction relative to a wall (23) of the casing opening (22) and in loaded by a return force of a return element (29) oppositely to the operating direction, while a part, projecting into the - casing opening (22), of the operating element (20) forms with the wall (23) of the casing opening (22) a gap (24) of a certain width (9), characterized in that the gap width (a) between the operating element (20) and the wall (23) of the casing openiffg (22) increases in the operating direction of the operating element (20).

Claims

2. Hand-held power tool according to Claim 1, characte-ized in that the

operating element (20) in in the form of a locking button (21), which, in the position in which it has been moved into the casing opening (22), locks a trigger-type push switch (18) for controlling a drive motor (15) of the hand-held power tool.

3. Hand-held power tool according to Claim 1 or 2, characterized in that the gap (24) between the operating element (20) and the wall (23) of the casing opening (22) runs around at least partly in the form of a ring.

4. Hand-held power tool according to Claim 3, char acterized in that the gap width (s) increases conically in the operating direction.

S. Hand-held power tool according to one of the preceding claims, characterized in that the wall (23) of the casing opening (22) has a cylindrical shape in that part of the operating element (20) which projects into the casing opening (22), and the operating element (20) - a - tapers the operating direction in this part.

6. Hand-held power tool according to Claim 5, characterized in that on the periphery of the operating element (20) a plurality of distributed guide ribs (32) project radially, each of them being provided on its radially outer sides with guide surfaces (33) which extend parallel to the cylindrical wall (23) of the casing opening (22).

7. Hand-held power tool according to one of the 10 preceding claims, characterized in that the return element (29) is supported on a bottom (30) of the casing opening (22), which bottom in provided with at least one opening (34) to enable foreign bodies (31) to pass out of the casing opening (22).

8. A hand-held power tool substantially as herein described with reference to Figures 1 and 2, or Figures 3 and 4, of the accompanying drawings.