GB2334630A - Actuating member for rotatably displacing brush support in a power driven hand tool - Google Patents

Abstract

A power driven hand tool is provided with a electric universal motor for clockwise and anti-clockwise rotation. The hand tool comprises a device 22' for displacing the brush support 23. The device 22' is actuated by means of an actuating member 16' which is accesible from outside the housing of the hand tool. An intermeadiate member 33 is provided between the actuating member 16' and the brush support 23. The intermeadiate member 33 turns the brush support 23 in a direction opposite to the direction of actuation when the actuating memebr 16' is actuated.

Description

Power-driven Hand Tool The invention relates to a power-driven hand tool according to the precharacterising clause of claim 1. It is known to use universal motors to drive power-driven hand tools, the direction of rotation of said motors being reversible.

Such motors comprise a commutator which is electrically contacted by means of brushes. To achieve optimum commutation in both directions of rotation of the motor, it is known to displace the brush holders, together with the brush supports supporting them, in the circumferential direction of the commutator when the direction of rotation is changed from clockwise to anti-clockwise and vice versa.

This movement displacing the brush support is accompanied simultaneously by pole reversal of the motor connections.

A brush displacement device of this type has already been proposed in EP-A-329 249. An actuating member is used to initiate a turning movement of the brush support with respect to the housing of a power tool. The actuating member extends through the wall of the power-driven hand tool housing and is thus accessible from the outside. To change the direction of rotation, the power tool operator adjusts the actuating member, wherein the brush support then effects a turning movement in the same direction as the direction of actuation.

In power-driven hand tools, the direction of rotation of the tool is dependent on both the running direction of the drive motor and the number and type of gear stages interposed between the drive motor and the tool spindle.

Consequently, when the known changeover device is used with power tool types differing from the point of view of gear arrangement, the same actuating member switch positions may correspond to different directions of rotation of the tool.

Thus, in power tools of different types produced by the same manufacturer, the same actuating member switch position may bring about clockwise or anticlockwise rotation depending on the number or type of interposed gear stages.

This increases labelling requirements for the devices and makes unreasonable demands of the operator, who will assume that all devices operate in the same direction of rotation when the direction of rotation changeover switch is in a particular switch position.

In contrast, the power-driven hand tool according to the invention and having the features of claim 1 has the advantage that all the power-driven hand tools in any one manufacturer's range, irrespective of the type and number of gear stages arranged therein, may be equipped in such a way that the tool is always driven in the same direction when the actuating member is in the same switch position. The devices may advantageously always be operated in the same way by the user. Owing to this uniformity of operation, the devices do not require different or supplementary labelling. Assembly of all the devices is substantially the same. In particular, the electrical connections of motors with the same polarity may be of uniform design.

Advantageous modifications and improvements of the power-driven hand tool according to the invention are provided by the measures indicated in the dependent claims.

A known solution and an exemplary embodiment of the invention are shown in the drawings and described in more detail in the description which follows: Figure 1 is a front view of a hand drill; Figure 2 shows a device for displacing the brushes of a universal motor with actuating member arranged thereon according to the prior art; Figure 3 is a view of the actuating member of Figure 2; and Figure 4 is a view of a device for brush displacement according to the invention with an actuating member to be arranged thereon.

In Figure 1, a power-driven hand tool is designated 10 and is constructed in the known way as a hand drill. The hand drill comprises a housing 11, which develops, in a rear part thereof, into a handle 12 of the pistol grip type.

A pressure-operated trigger switch 13 is located on the handle 12 and carries an adjusting wheel 14 for preselecting rotational speed. On the side of the handle 12 there is located a push button 15, by means of which the pressure-operated trigger switch 13 may be locked. At the top of the handle 12 where it emerges from the housing 11 there is arranged a bar-shaped actuating member 16, which projects transversely from the housing 11. The actuating member 16 serves to change the direction of rotation of the power-driven hand tool 10 and, to this end, may be displaced in the direction of the arrow 17 between the control position shown and a control position indicated by broken lines 18. In addition, a tool holder 19 projects forwards from the housing 11, which tool holder 19 may be driven in anticlockwise or clockwise rotation depending on the switch position of the actuating member 16.

Figure 2 shows a known device 22 for changing the direction of rotation of the power-driven hand tool 10, which may be actuated by means of the actuating member 16. As far as its function is concerned, the device 22 corresponds substantially to the changeover device known from EP-A-329 249, such that for the purposes of disclosure reference is here made expressly to the content of said application. The device 22 shown in Figure 2 comprises a diskshaped brush support 23, on which two brush holders 24 with brushes 25 inserted therein are arranged opposite one another. The brushes 25 serve to contact the commutator 26, indicated by broken lines, of the electric drive motor of the powerdriven hand tool 10, which takes the form of a universal motor providing clockwise and anti-clockwise rotation. The brush support is mounted so as to be able to turn to a limited extent relative to an annular holder 27 fixed to the housing.

Figure 3 shows the actuating member 16, by means of which the brush support 23 may be turned relative to the holder 27. The actuating member 16, which is in itself bar-shaped, has projecting laterally from it a changeover member 28 constructed at the end as a fork 28', which engages directly with a peg .29 on the brush support 23. The connection between the brush support 23 and the actuating member 16 is rigid, such that when, for example, the actuating member 16 is displaced out of the position shown in Figure 2 in the direction of the arrow 30, the brush support 23 is rotated in the same direction in the direction of the arrow 31. The changeover device 22 shown in Figures 2 and 3, which is already known in relation to power-driven hand tools 10 available on the market, thus corresponds in function to the changeover device known from EP-A-329 249.

Thus, for example, the tool holder 19 of the power tool 10 operates in the clockwise direction when the actuating member 16 is in the right-hand position, wherein the brush support 23 will likewise have been swivelled into the right-hand position. This brush adjusting device is unsuitable, however, in the case of power tools which operate in the anti-clockwise direction when the brush support is in this position.

In contrast, the changeover device 22' according to the invention, shown in Figure 4, reverses the direction of rotation when the actuating member 16' is actuated. Components which are the same and operate in the same way as in the exemplary embodiment according to Figure 2 are given the same reference numerals.

In Figure 4, the brush support 23 and the holder 27 are of the same construction as the exemplary embodiment according to Figure 2, but are viewed from the opposite direction. The brushes 25 are therefore hidden by the holder 17 and are therefore not visible. Only the radially outer end of the brush holder 24 projects beyond the outer circumference of the holder 27.

The peg 29, by means of which a movement displacing the brush support 23 is initiated, is also visible. An intermediate member 33 is provided between the actuating member 16' and the peg 29 on the brush support 23 and comprises fork-like notches 34 at each of its ends. An inner notch 34a surrounds the peg 29 in articulated manner. An outer notch 34b is provided to cooperate with a link pin 35 on the actuating member 16', which is moved out of the position shown in Figure 4 in the direction of the arrow 36 and brought into engagement with the outer notch 34b for assembly with the brush support 23. The intermediate member 33 is mounted with respect to the holder 27 and thus with respect to the housing 11 of the power-driven hand tool 10 in articulated manner via a pin 37.

II; after assembly with the brush support 23, the actuating member 16' is displaced in the direction of the arrow 30, first of all the outer notch 34b is displaced in the same direction. Because it is mounted rotatably on the pin 37, the inner notch 34a, on the other hand, is moved in the opposite direction, such that the brush support 23 is turned altogether in the opposite direction in the direction of the arrow 31'. To compensate for the different paths followed, when they are moved, by the link pin 35, the intermediate member 33 and the peg 29, the notches 34a, b take the form of longitudinal slots, such that the peg 29 and the link pin 35 have the necessary play available to them.

Connection with the brush support 23 is effected by the actuating member 16' instead of by the rigid actuating member 16, i.e. it is necessary merely to install a different actuating member in the power-driven hand tool, which is otherwise structurally virtually unchanged.

Claims (6)

1. CLAIMS 1. A power-driven hand tool, in particular a drill or hammer drill, comprising a housing (11), an electric drive motor accommodated therein for clockwise and anti-clockwise operation, at least two brushes (25) for electrically contacting a commutator (26) of the drive motor, which brushes (25) are held by a brush support (23), and a changeover device (22') for turning the brush support (23) relative to the housing (11) in the circumferential direction of the commutator (26) to change clockwise rotation into anti-clockwise rotation and vice versa, wherein at least one actuating member (16') accessible from outside the housing (11) is provided for initiating the turning movement of the brush support (23), characterised in that reversing means (32) are arranged between the actuating member (16') and the brush support (23), which means (32) turn the brush support (23) in a direction opposite to the direction of actuation when the actuating member (16') is actuated.
2. 2. A power-driven hand tool according to claim 1, characterised in that the reversing means (32) take the form of an intermediate member (33) acting as a two-armed lever, which is mounted centrally in articulated manner with respect to the housing (11).
3. 3. A power-driven hand tool according to claim 2, characterised in that the intermediate member (33) is mounted in articulated manner by means of a pin (37) which is held in a holder (27) for the brush support (23).
4. 4. A power-driven hand tool according to claim 2 or claim 3, characterised in that the intermediate member (33) comprises a notch (34a, b) at each end, in which there engage pegs (29 or 35 respectively) on the brush support (23) and the actuating member (16').
5. 5. A power-driven hand tool according to any one of the preceding claims, characterised in that the reversing means (32) may optionally be installed in the housing (11) instead of the left-hand actuating member (16) with rigid connection of the brush support (23).
6. 6. A power-driven hand tool substantially as herein described with reference to the accompanying drawings.