GB2414868A

GB2414868A - Electric tool with light source generator

Info

Publication number: GB2414868A
Application number: GB0511262A
Authority: GB
Inventors: Christoph Cramer; Wolfgang Hirschburger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-06-05
Filing date: 2005-06-02
Publication date: 2005-12-07
Also published as: GB0511262D0

Abstract

In an electric tool having a power generating arrangement, wherein the power generating arrangement comprises a magnet rotatable about an axis of rotation, as well as a means of generating power with the aid of the magnetic field of the magnet, a construction that is particularly space-saving in terms of width is achieved in that the distance of the means from the axis of rotation of the magnet corresponds to the distance of the magnet from the axis of rotation.

Description

24 1 4868 Electric tool with light source

Background art

The invention proceeds from an electric tool having the generic features of claim 1.

From EP 1 287 98 A2 an electric tool having a light source is known, which light source has its own power generation inside the tool independently of external voltage sources.

This power generating arrangement comprises a magnet, which rotates during operation of the electric tool and hence at a defined location generates a time-varying magnetic field.

The known power generating arrangement moreover comprises induction coils, which are disposed in the vicinity of the magnet that rotates during operation. The varying magnetic field of the rotating magnet generates in the induction coils a current, which is used to supply the light sources of the electric tool.

In this known power generating arrangement, however, the magnet and the induction coils are disposed radially side by side. This means that both the magnet and the induction coils are situated at right angles to the axis of rotation of the magnet in the same plane. Consequently, the known power generating arrangement takes up a lot of room in radial direction at right angles to the axis of rotation of the magnet. Indeed, the electric tool around its axis of rotation has to have a specific minimum width to be able to accommodate both the magnet and the coils disposed adjacent thereto. This is disadvantageous above all in the case of tools where only a low width around the axis of rotation is desired. It is therefore impossible, for example, for an electric tool having the known power generating arrangement to be used in narrow gaps or the like because of the required minimum width.

Advantages of the invention In contrast, an electric tool according to the invention having the features of claim 1 has the advantage that, because the distance of the means from the axis of rotation of the magnet corresponds to the distance of the magnet from the axis of rotation, the power generating arrangement according to the invention does not increase the dimensions of the electric tool in radial direction. The head of the electric tool is not widened unnecessarily by this advantageous arrangement. Consequently, an electric tool having the power generating arrangement according to the invention is also eminently usable in confined spaces. The axial arrangement according to the invention of the magnet and the power generating means is advantageous particularly for electric tools that are required to have as small a width as possible.

Here, by an electric tool is meant any tool that is operated electrically and in particular has a shaft that executes a rotational or rotary movement.

According to the invention, the distance of the means from the axis of rotation of the magnet corresponds to the distance of the magnet from the axis of rotation. This means that the means of generating power is seated in axial direction in front of or behind the magnet. It could also be said that the magnet and the means of generating power are disposed successively along the length of the electric tool. In other words, the means of generating power is at the same distance from the axis of rotation as the magnet.

It is advantageous when the magnet is magnetized along its axis of rotation. In particular, the lines of force of the magnet may extend at least partially parallel to the axis of rotation. The arrangement of the magnetization and/or of the lines of force of the magnet is then at least partially axial. Such magnetization guarantees a good penetration of the means of generating power, with the result that power may be generated reliably during rotation of the magnet.

The axial magnetization may be realized in an advantageous manner by disposing a north and a south pole of the magnet successively in the direction of the axis of rotation.

In a preferred manner, the means of generating power is an induction coil, in particular a reactance coil.

When the magnet in particular takes the form of a ring, a particularly good magnetic field may be achieved. The magnet may however alternatively comprise one or more rod magnets, or present a different configuration.

When the magnet is disposed in particular on the tool holder or on the tool attachment and/or tool of the electric tool, the path between the power generating arrangement and the light source is advantageously minimized as the light source is generally disposed in the area surrounding the tool holder or the tool attachment.

In this case, there is no need to provide long leads between the power generating arrangement and the light source because these are then situated in the immediate vicinity.

It is advantageous when the electric tool according to the invention has a light source that is supplied with power by the power generating arrangement.

By a light source is meant any light-emitting element that is powered by electric current. In a preferred manner, the light source is a lightemitting diode, in particular a coloured light-emitting diode, although the light source may alternatively be an incandescent bulb.

In a preferred manner, the electric tool is a cutter, in particular a routing cutter.

Drawings There now follows a detailed description of embodiments of the invention with reference to the accompanying drawings.

The drawings show: Fig. 1 a cross section through a tool holder of an electric tool according to the invention, Fig. 2 a cross section according to the arrows A-A of Figure 1, Fig. 3 a cross section of a ring according to the invention with magnets disposed therein, Fig. 4 a side view showing the alignment of two magnet coils in relation to the magnet ring according to Fig. 3, Fig. 5 the two magnet coils according to Fig. 4 viewed from above, Fig. 6 a circuit diagram comprising the two coils according to Fig. 4 and two light-emitting diodes, Fig. 7 a perspective view of a further magnet ring with magnetic lines of force.

Fig. 1 shows a cross section of the tool holder 100 of an electric tool according to the invention. In the tool holder 100 two light-emitting diodes lOla and lOlb are situated as light sources. The two lightemitting diodes lOla and lOlb are disposed on a printed circuit board 102. The electrical connections to the light- emitting diodes lOla and lOlb are made via the printed circuit board 102. Also shown is a ring 103, which is disposed around the shaft 104 of the electric tool.

Fastened to the ring 103 is a likewise ring-shaped magnet 105.

In the further sectional view (see Fig. 2) according to the section A-A shown in Fig. 1 it is moreover possible to see a reactance coil 106. The reactance coil 106 is disposed in such a way that it is disposed, in the direction of the longitudinal axis of the shaft 104, behind the magnet 105.

There now follows a description of the mode of operation of the power generating arrangement with light-emitting diodes that is illustrated in Figures 1 and 2.

When the electric tool is set in operation, the shaft 104 starts to rotate. The ring 103 seated on this shaft and hence the magnet 105 fastened on the ring 103 are driven by, and rotate with, the shaft 104. Consequently, at the location of the reactance coil 106 a time-varying magnetic

field is produced. In the reactance coil 106 an

alternating current is accordingly generated. The coil 106 is connected in an electrically conducting manner by the non-rotating printed circuit board 102 to the light emitting diodes 101a and 101b, so that the alternating current generated by induction in the reactance coil 106 is carried to the light-emitting diodes 101a and 101b. Owing to the supplied current, the light-emitting diodes 101a and 101b emit light. Through the rotation of the magnet 105, therefore, an alternating current is induced in the coil 106 and supplied to the light- emitting diodes 101a and 101b. During rotation of the shaft 104, i.e. during operation of the electric tool, light is accordingly generated. The generated light illuminates the work area of the electric tool, thereby allowing the electric tool to be used also under poor light conditions.

Fig. 3 shows a ring 203, which is a modification of the ring 103 illustrated in Fig. 1. The ring 203 is a nut made of non-magnetic material, in which magnets 205 are glued.

The ring 203 has an annular recess 207, in which the rod magnets 205a and 205b are situated. To put it more precisely, two rod magnets 205a and two rod magnets 205b are provided, which lie in each case opposite one another.

The two rod magnets 205a are of identical polarity. The two rod magnets 205b are likewise of identical polarity, wherein however the two magnets 205b are of the opposite polarity to the two magnets 205a.

Fig. 4 shows a lateral cross section of the ring 203 together with two coils 206a and 206b disposed therebelow.

Fig. 4 further shows the axis of rotation 208 of the ring 203. The two reactance coils 206a and 206b lie directly below the ring 203 around its axis of rotation 208. As is evident from Fig. 4, the coils 206a and 206b are disposed in such a way that they lie directly opposite and underneath the rod magnets 205. When the ring 203 then rotates about its axis of rotation 208 during operation of the electric tool, while the two coils 206a and 206b remain stationary, there is always alternately a north and a south pole of a corresponding rod magnet 205 situated above one of the coils 206. The coils 206a and 206b are accordingly exposed to a time-varying magnetic field, with the result that an alternating current is induced in these coils.

Fig. 5 shows the two coils 206a and 206b in a view from above, without the ring 203. In Fig. 5 the inside diameter 209 of the ring 203 is indicated. The coil 206a is at a slight distance a from the inside diameter 209. The two coils 206a and 206b are disposed at an angle a relative to one another, wherein this angle is preferably 45 .

Fig. 6 reveals how the two coils 206a and 206b are connected to two lightemitting diodes 210a and 210b to form a circuit. The two light-emitting diodes 210a and 210b are connected in parallel.

Fig. 7 shows a second modification 303 of the ring 103. In the case of the ring 303, there is no longer any separation between a ring element and a magnet element, as there was with the rings 103 and 203. Instead, the ring 303 is constructed entirely as a magnet. The ring magnet 303 has an axis of rotation Z. Fig. 7 shows the polarity and the lines of force of the magnet 303. The lines of force of the ring magnet 303 extend partially in Z direction, i.e. axially. By virtue of the axial arrangement of the lines of force, a coil situated in Z direction above or below the magnet ring 303 is penetrated particularly well by the lines of force. It is thereby ensured that power is reliably generated when the magnet rotates about the axis of rotation Z. The described power generating arrangement for an electric tool for supplying a light source has the advantage that the magnet and the associated coils are disposed adjacent to one another along the axis of rotation. This means that an electric tool having the described power generating arrangement is scarcely wider than a standard electric tool. The described power generating arrangement with its axial juxtaposition of the magnet and the coils is particularly space-saving and particularly advantageous for electric tools that may have only a low width. The described power generating arrangement may be fitted in a space-saving manner particularly in electric tools, which have sufficient room lengthwise in their housing but in which no room is available widthwise.

List of reference characters tool holder 101 light-emitting diodes 102 printed circuit board 103 ring 104 shaft magnet 106 reactance coil 203 ring 205 rod magnets 206 coils 207 recess 208 axis of rotation 209 inside diameter 210 light-emitting diodes 303 magnet ring distance angle axis of rotation

Claims

Claims 1. Electric tool having a power generating arrangement (105, 106;

205, 206), wherein the power generating arrangement (105, 106i 205, 206) comprises a magnet (105, 205, 303) rotatable about an axis of rotation (208, z) as well as a means (106, 206) of generating power with the aid of the magnetic field of the magnet (105, 205, 303), characterized in that the distance of the means (106, 206) from the axis of rotation of the magnet (105, 205, 303) corresponds to the distance of the magnet (105, 205, 303) from the axis of rotation (208, z).
2. Electric tool according to claim 1, characterized in that the magnet (105, 205, 303) is magnetized along its axis of rotation (208, z).
3. Electric tool according to claim 1 or 2, characterized in that the lines of force of the magnet (105, 205, 303) extend at least partially parallel to its axis of rotation (208, z).
4. Electric tool according to one of the preceding claims, characterized in that a north and a south pole of the magnet (205) are disposed successively in the direction of the axis of rotation (208).
5. Electric tool according to one of the preceding claims, characterized in that the means (106, 206) is an induction coil, in particular a reactance coil.
6. Electric tool according to one of the preceding claims, characterized in that the magnet (303) takes the form of a ring.
7. Electric tool according to one of claims 1 to 5, characterized in that the magnet (205) comprises one or more rod magnets (205a, 205b).
8. Electric tool according to one of the preceding claims, characterized in that the magnet (105, 205, 303) is disposed on the tool holder (100) or on the tool attachment of the electric tool.
9. Electric tool according to one of the preceding claims, characterized in that the electric tool has a light source (101, 210) that is supplied with power by the power generating arrangement (105, 106; 205, 206).
10. Electric tool according to one of the preceding claims, characterized in that the electric tool is a cutter, in particular a routing cutter.
11. An electric tool substantially as herein described with reference to the accompanying drawings.