GB2462938A

GB2462938A - Hand-held power tool with opening and cover

Info

Publication number: GB2462938A
Application number: GB0915147A
Authority: GB
Inventors: Florian Esenwein; Thomas Schomisch
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-08-29
Filing date: 2009-08-28
Publication date: 2010-03-03
Anticipated expiration: 2029-08-28
Also published as: GB2490069B; DE102008041720B4; GB2490069A; FR2935282B1; GB2462938B; DE102008041720A1; CN101659051A; FR2935282A1; CN101659051B; GB0915147D0; GB201213290D0

Abstract

A hand-held power tool 10 comprises a motor housing 16 that serves as a handle, which accommodates an electric collector motor 50. The interior of the motor housing is accessible via a servicing opening 26 of the motor housing, which is closable by a cover 22. The cover has an indentation 29 for engagement of a tool (58, fig 3) for opening the cover. The cover may be fixable to the motor by means of a screwed connection, where spring means (32, fig 4) are arranged between the cover and the housing, which are pre-loaded during the fixing of the cover. The cover may be provided with a plurality of peripheral seals. The cover may have a support element (50, fig 14) for holding down a carbon brush holder (54, fig 15). Preferably, the cover has holding means for holding a spare part, such as a spare carbon brush. The power tool may be an angle grinder.

Description

Description Title

Hand-held power tool with brush motor

Prior art

The present invention starts from a hand-held power tool according to the precharacterising clause of Claim 1.

Hand-held electric power tools are today usually driven by electric universal motors, i.e. by collector or brush motors. In the case of these motors, for the commutation, current is transmitted by the power cable via brushes to the motor collector, which rotates when in operation. The brushes are fixed by means of a brush holder in the motor housing, which in most cases is made of plastic. The brush holder has a well which axially guides the brush. It is provided with a spring which pushes the brush towards the collector. The brush wears down at its point of contact with the collector owing to friction and moves axially towards the collector under the action of the spring in accordance with the loss of length due to wear. As a result, the flow of current between collector and brush can be maintained. However, in most cases the brushes have to be replaced several times over the service life of the hand-held electric power tool.

To enable simple replacement of the brush, known motor housings have servicing openings, through which the carbon brush can be directly accessed. To ensure the electrical safety, the servicing openings can be closed in a water-and dust-tight manner via covers which can be fastened to the motor housing by screws or similar elements. The outer surfaces of these covers generally merge in a flush manner into the contour of the machine housing.

After detachment of the fastening screw, the cover which closes the servicing opening can be removed from the motor housing. For this purpose, the cover has at its outer edge an indentation or radial recess for engagement and levering-open of the cover by a screwdriver blade or similar tool. These indentations form a geometrical discontinuity of the cover edge and can impair the electrical safety if the seal with respect to the servicing opening is damaged there during the opening of the cover.

Electrically conductive dust and moisture can penetrate into the appliance interior there and form an electrical line connection which makes the outside of the appliance live, under the operating voltage of the electric tool.

Advantages of the invention The invention with the features of Claim 1 has the advantage that the new cover ensures the electrical safety of the hand-held power tool and at the same time is convenient and simple to open, so that the servicing work can be carried out more quickly.

By virtue of the fact that the motor housing according to the invention is structurally changed only in such a way that the demoulding, e.g. removal of the motor housing from the injection mould, can still take place at a 900 angle, the motor housing can be produced without an increase in cost.

By virtue of the fact that the cover according to the invention has a recess which is arranged at a distance from its outer edge oroutside the interface to the machine housing, it can be opened by means of a suitable tool without impairing the electrical safety.

By virtue of the fact that the cover according to the invention opens automatically during/after detachment of a captive fastening screw, the carbon brush is quickly accessible without further operating effort.

By virtue of the fact that at least one peripheral seal is arranged between the cover according to the invention and the servicing opening, the electrical safety and mechanical damping of the hand-held power tool is improved. Moreover, the cover screw is secured in position by elastic preloading by means of the seal, and rattling noises between motor housing and cover are precluded.

By virtue of the fact that the cover according to the invention is provided with rubber or similar damping elements in the region of contact with the motor housing, the cover serves as an anti-vibration cushion in the gripping region of the appliance housing, which cushion reduces the transmittable vibrations and thus the stress for the operator of the hand-held power tool, and thus increases the operating comfort and the operating safety.

By virtue of the fact that the cover according to the invention is captively seated on the machine housing after detachment of the fastening screw and opening of the cover, the operating convenience during brush replacement is markedly improved.

By virtue of the fact that the cover according to the invention forms a locking means for a further removable part, in particular a covering cap, of the machine housing, the interior of the motor housing is particularly easily accessible for inspections and servicing work.

By virtue of the fact that the cover according to the invention serves as a hold-down for the brush holder, a hitherto required, separate hold-down and its fastening screw can be dispensed with.

Drawing The invention is explained in more detail below using an exemplary embodiment with associated drawing, in which: Figure 1 shows an angle grinder according to the invention with a servicing opening and cover Figure 2 shows a detail of the motor housing of the angle grinder according to Figure 1 Figure 3 shows a longitudinal section of the motor housing in the region of the cover according to Figure 2 Figure 4 shows a further longitudinal section of the motor housing in the region of the cover Figure 5 shows a further longitudinal section of the motor housing with a variant of the cover Figure 6 shows a longitudinal section according to Figure 5 with a further variant of the cover Figures 7 and 8 show a longitudinal section with a sub-variant of the cover in two mounting steps Figure 9 shows a longitudinal section according to Figure 5 with a cover sealed by an 0-ring Figure 10 shows a longitudinal section according to Figure with a cover vibration-damped by elastic seals Figure 11 and 12 show a longitudinal section of a cover with a hinge connection to the motor housing Figure 13 shows a longitudinal section of a motor housing with 2 covers on opposite sides, which serve as holding means for a further housing part Figure 14 shows a bottom view of a cover with a supporting element Figure 15 shows a top view of the servicing opening of the opened motor housing with a view of the brush holder corrununicating with the cover and Figure 16 shows a side view of the motor housing with a cover and brush holder according to Figure 15.

Exemplary embodiment A hand-held power tool illustrated three-dimensionally in Figure 1 is configured as an angle grinder 10 and has at the front, on the left in the viewing direction, a gearbox housing 12, which is made of metal. Emerging downwards from the latter, parallel to the vertical axis 20 of the angle grinder 10 is an output shaft (not illustrated) for accommodating a grinding disc (not illustrated), around which extends a protective hood 14. At the rear, there is flange-mounted on the gearbox housing 12 a motor housing 16 of pot design, which accommodates an electric collector motor or brush motor referred to as a universal motor which is customary for hand-held power tools and from the rear of which emerges a cable 18 for the power supply of the motor.

The motor housing 16, which serves as a handle, carries centrally on its upper side a cover 22, which is fastened to the motor housing 16 in a contour-flush manner by a cover screw 24 and which thereby closes a servicing opening 26 in a dust-tight manner. Arranged diametrically opposite -not visible -on the lower side of the motor housing 16 is a second servicing opening 26 with an associated cover 22, so that the power supply of the motor is ensured, as usual, via two brushes offset by 1800 with respect to one another. The cover 22 bears, on the outside, three decorative grooves 28 which run transversely with respect to the longitudinal axis of the angle grinder and of which the decorative groove 28 nearest the cover screw 24 has at its base a central slot-like indentation 29 approximately 6 mm deep and 6 mm wide for engagement of a screwdriver blade or the like, e.g. a finger nail, a paper clip or a coin -for levering open the cover 22. The prerequisite is that the cover screw 24 is detached.

Figure 2 shows a detail of the motor housing 16 of the angle grinder 10 with the cover 22. In this case, the cover 22 with the three decorative grooves 28 running transversely with respect to the longitudinal axis and with the slot-like indentation 29 can be clearly seen. The indentation 29 lies within the outer contour of the motor housing 16 and is robustly impermeable towards the housing interior.

Also indicated are a lateral switching button 15 for actuating the on-and off-switch, as well as lateral ventilating slots 17 for sucking in motor cooling air, and three gripping regions 19 of the motor housing 16, the cover 22 itself and the region of the motor housing 16 which lies in front of and behind the cover being provided at least partly with a surface layer which improves the grip and reduces vibrations.

Figure 3 illustrates a longitudinal section of the motor housing 16 in the region of the cover according to Figure 2. Here, the cover 22 can be seen in longitudinal section, its decorative grooves 28, the indentation 29 and the screw hole 23 on its outside, and at the front edge the L-shaped end face for hinge-like engagement behind the adjacent housing wall. On its lower side, the cover 22 bears a downwardly projecting hollow-cylindrical region of the screw hole 23 for engaging over a screw dome 30 of the motor housing 16, into which dome the cover screw 24 can be screwed in order to fix the cover 22 to the motor housing 16. The cover 22 sealingly covers with its outer edge the servicing opening 26 and safeguards the electrical motor parts located thereunder, such as brush holder 54 and brush-holder screw 55, against contact and against ingress of dust and moisture. Also illustrated is a screwdriver 58 which is suitable for engaging in the indentation 29, the cover 22 being opened in the direction of the movement arrow 60 after insertion of the screwdriver blade.

In Figure 4 there is sketched a further longitudinal section of the motor housing 16 in the region of the cover 221, it being possible to discern the latter's L-shaped-bent cover edge 25 which serves for hinge-like engagement in a housing groove 34 in the edge of the servicing opening 26 or the adjacent housing wall. Also shown is a preloaded compression spring 32 which concentrically encompasses the screw dome 30 and is supported upwardly on the cover 221, and which pivots the cover 221 outwardly or upwardly during or after detachment of the cover screw 24. In this case, aids for lifting the cover and corresponding recesses are not required.

Figure 5 shows a further longitudinal section of the motor housing 16 in the region of the cover 222, its L-shaped cover edge 25 for hinge-like engagement behind the housing groove 34 of the adjacent housing wall, and a spring tongue 321 which is supported downwardly in a preloaded manner on a ramp 36 and pivots the cover 22 outwardly or upwardly after detachment of the cover screw 24. The ramp 36 is integrated in the motor housing 16.

In Figure 6, a spring tongue 322 is, in contrast to Figure 5, configured as a separate part made of steel or similar springy material and mounted on the cover 223. The details corresponding to Figure 5 are not recited again.

Figures 7 and 8 show a longitudinal section according to Figure 5 with a sub-variant of the cover 224. The latter's L-shaped cover edge 25 forms a preloaded spring tongue which, when being pressed into the housing groove 34, is loaded by the cover 224 and attempts to keep the cover 224 open. During detachment of the cover screw 24, the spring tongue, preloaded during mounting, bends back into its initial position and the cover 224 swings open.

Figure 9 shows a longitudinal section according to Figure 5 with a cover 225 which is sealed by an 0-ring 38 and the peripheral seal of which can be configured as an inserted rubber ring in the shape of the cover edge 25, of the servicing opening 26 or of the interface contour or else as a sealing edge directly injection-moulded onto the motor housing and/or onto the brush cover.

Figure 10 shows a longitudinal section according to Figure with a cover 226 which is vibration-damped by elastic seals and configured as a domed cushion with decorative grooves 28, and the damping of which with respect to the motor housing 16 and with respect to the screw dome 30 is effected by means of a suitable, ring-like damping means 40 selectively on the motor housing 16 or cover 225, assigned to the outer edge of the latter. This damping means can be attached to the cover 225 and/or motor housing 16 directly by two-component plastic injection moulding. Here, the damping means 40 can be designed such that one sub-region is more highly compressed than the other and that the cover 22 thereby opens in a pivoting manner as the cover screw 24 is being detached.

Figures 11 and 12 each show a longitudinal section of a cover 227, 228 with a hinge connection to the motor housing 16, 161 so that the cover is captively held in a manner movable for opening on the machine housing 16, 161 either as a rotary hinge 44, in the case of which the cover 227 is clipped in during initial assembly of the machine, or as a film hinge 46, in the case of which the cover 228 is injection-moulded directly onto the machine housing 16, 161.

Figure 13 shows a longitudinal section of the motor housing 16 with two covers 229 which are arranged on opposite sides and serve as holding means for a further housing part configured as a covering cap 161, which is readily detachable from the rest of the housing 16 after opening of the covers 229. The brush covers 229 form the locking means for the covering cap 161, for which no separate screwed connection or the like is therefore required.

The interior of the motor housing 16 in the region of its covering cap 161, e.g. the mains power line 18 with bush 181, the electric switch etc., is thus more easily accessible, e.g. for repair work and replacement.

To remove the covering cap 116, it is merely necessary to open both covers 229 after detaching the cover screws 24, so that the positive-locking connection between covers 229 and covering cap 116 is released. For this purpose, the covers 229 have a hook-like locking element 48 for engaging behind a matching, peripheral groove 49 of the covering cap 116. On opening of the covers 229, the covering cap 161 is then freed and can be removed. The covers 229 can be pivotably mounted in a hinge, a catch or the like.

Figure 14 shows the bottom view of a cover 2210 with prop-like supporting element 50, which serves as a hold-down of a brush holder 54 (Fig. 16). As a result, the brush holder 54 does not require a separate fixing element, such as, for example, its own screwed connection. For this purpose, the brush holder 54 has a counter-prop 52, on which the supporting element 50 is supported.

If, however, a separate screwed connection of the brush holder is provided, supporting element 50 and counter-prop 52 form an emergency stop, in case the brush-holder screw becomes detached from the screw hole, for example under extreme vibration or if the brush holder melts out of the motor housing 16, in the event of an overload and/or extremely high temperatures. A passage of the overheated brush holder through the motor housing 16 or the cover 2210 is thus prevented, since the counter-prop is located at a less temperature-loaded region of the brush holder and thus can act on the cover 2210 or the supporting element 50 with only a lower maximum temperature.

Figure 15 shows a top view of the servicing opening 26 of the opened motor housing 16 with the brush holder 54 communicating with the cover 2210 (Fig. 16) via the counter-prop 52. The brush holder can be fixed to the cover 2210 without a brush-holder screw 55 (Fig. 3) Figure 16 shows a side view of the motor housing 16 with the mounted cover 2210 with supporting element 50, which is supported on the counter-prop 52 of the brush holder 54 according to Figure 15.

The exemplary embodiments of the invention may be combined with one another relatively diversely, for example the supporting geometry of the cover 2210 for the brush holder 54 with a captive brush cover or else the recess for an aid for opening the cover with the damping.

Furthermore, as aids for opening the cover there are also possible square, hexagonal or other configurations.

Instead of the hand-held power tool described as an angle grinder, it is also possible for a hand-held drill, scraper, random orbit sander, jigsaw, etc. to be equipped with a motor housing configured as a handle and having the brush holder according to the invention, with or without servicing open and cover.