DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, a battery-operated right-angle screwdriver is shown, as an exemplary embodiment of a power tool 100 according to the invention. In the housing 10 of the power tool 100, an electric motor 12 for driving a drive spindle 14 is accommodated. The electric motor 12 may for instance be an electronically commutatable electric motor. Via the drive spindle 14, a tool insert (not shown) received in a tool receptacle 16 is driven. The electric motor 12 is supplied with power by a battery pack 11. The battery pack 11 also serves to supply voltage to an LED, which is provided as a lighting device 18 for illuminating the work area of the power tool 100. However, the invention is equally suitable for a power tool that has a power cord. The electric motor 12 and the lighting device 18 can be activated and deactivated via a contactless switch device 20 that has an actuating means 22 and a switch element 29, the latter including two sensor elements 21a and 21b and a signal transducer 24 (FIG. 2), in one housing 30.
FIG. 2 shows part of a first switch device 20 with the switch element 29 in perspective. The housing 30 comprises two housing parts 31, 32 in the form of half shells, of which in FIG. 2 only the housing part 32 is shown. In FIG. 2, a signal transducer 24 in the form of a permanent magnet is shown, which is movable linearly, in this case axially. The direction of motion of the signal transducer 24 is indicated by a double arrow 23. The signal transducer 24 is secured to a slide 25. The slide 25 is disposed axially movably in a guide element 26 in the form of a guide sleeve. The guide element 26, in the region of the signal transducer 24, has an opening 27, for instance in the form of a slot, window, or the like. The slide 25 protrudes partway out of the housing 30. Outside the housing 30, the slide 25 is rigidly connected to the actuating means 22, for instance by clips. Thus the slide 25 can be axially moved in that the user moves the actuating means 22 axially in the direction marked by the double arrow 23. The slide 25 is supported under spring loading, so that upon actuation of the actuating means 22 in the direction of the housing 30, the slide 25 is moved counter to the compressive force of a spring element 28, in this case a helical spring.
From FIG. 3, it can be seen that in the housing 30, at the level of the slide 25 with the signal transducer 24, two sensor elements 21a and 21b in the form of Hall sensors are disposed on a printed circuit board 33. The signal transducer 24 and the sensor elements 21a, 21b form the contactless switch element 29. By axial displacement of the slide 25 in the guide element 26, the signal transducer 24 is made to coincide first with the first sensor element 21a and then with the second sensor element 21b, as a result of which the two sensor elements 21a and 21b can be activated and deactivated in contactless fashion. The opening 27 is provided in the guide element 26 so that the signal transducer 24 and the sensor element 21 can be provided with electrical contact. In the position of the slide 25 as shown in FIG. 3, the first sensor element 21 a has just been made to coincide with the signal transducer 24. If the slide 25 is pressed onward as far as a stop counter to the compressive force of the spring element 28, the signal transducer 24 covers both sensor elements 21a, 21b. In the embodiment shown, two sensor elements 21a, 21b are thus associated with one signal transducer, and the sensor elements 21a, 21b are disposed side by side in such a way that by axial motion of the signal transducer 24 by means of the actuating means 22, the sensor elements 21a, 21b are activated and deactivated in succession. They are accordingly disposed one after the other in the axial direction 23. The first sensor element 21a serves for instance to turn the lighting device 18 on and off, and the second sensor element 21b serves to switch the electric motor 12 on and off.
In FIGS. 2 through 4, a second switch device 40 in a second embodiment is also provided, with an actuating means 42 and a contactless switch element 49. The contactless switch element 49 serves to select the clockwise/counterclockwise rotation of the right-angle screwdriver. The switch element 49 includes a sensor element 41 in the form of a Hall sensor and a signal transducer 44 in the form of a permanent magnet. The sensor element 41 is again disposed on a printed circuit board 33. The signal transducer 44 is connected to a lever 45, being secured to the lever 45. The lever 45 protrudes partway into the housing 30. On its free end outside the housing 30, the lever 45 is provided with an actuating means 42, which the user of the power tool 100 can actuate manually. The lever 45 is pivotably supported. It can be pivoted about an angle W about a pivot axis S between two positions A and B. In position A, the signal transducer 44 is brought into coincidence with the sensor element 41 without mechanical contact, as a result of which the switch element 49 is provided with electrical contact in contactless fashion. In position B, the signal transducer 44 and the sensor element 41 are spaced apart so far from one another that no electrical contact is made. A spring element 48 is disposed in the housing 30. It defines the terminal positions A and B of the lever 45; in the region of the end protruding into the housing 30, the lever 45 has indentations 47a and 47b into which the spring element 48 snaps.
Electronic components 34 are also disposed on the printed circuit boards 33. The electronic components 34 may for instance serve to control the electronically commutatable electric motor 12. If the electronic control unit is disposed in the region of the switch device 20, 40, then this has the advantage that they are located comparatively far away from the electric motor 12 and are thus not so markedly exposed to the electromagnetic interfering radiation of the electric motor 12. The printed circuit boards 33 are electrically connected to the power supply of the power tool 00, for instance to the battery pack 11, by means of voltage-carrying lines 36. Via electric lines 37, the electric motor 12 is electrically connected to the printed circuit board 33. The housing 30 surrounds the switch elements 29, 49 as well as the printed circuit boards 33 and the electronic components 34, and as a result the vulnerable components are better protected. The housing part 32 is of metal and can thus better dissipate the heat that is developed by the electronic components. In addition, a thermal conduction element 35 of metal is provided, which is connected to the metal housing part 32 on the one hand and to the printed circuit board 33 on the other in thermally conductive fashion, for instance by means of a thermally conductive adhesive.
The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
Patent Application
20080053805
