Patent Document

This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2011/059871, filed on Jun. 15, 2011, which claims the benefit of priority to Serial No. DE 10 2010 038 753.3, filed on Aug. 2, 2010 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The present disclosure relates to an electric machine tool, in particular a drill and/or a chipping hammer, comprising a tool housing and a handle casing disposed on the tool housing, wherein a first actuating device is disposed in the tool housing and wherein a second actuating device is disposed in the handle casing. 
     For portable power tools, in particular for drills and/or chipping hammers, it is known to damp the vibrations in the handle through the use of an elastic element between the handle and the tool housing of the electric machine tool. Such handles are also referred to as anti-vibration handles. The elastic element allows the handle to be moved relative to the tool housing in the horizontal and/or vertical direction. An electric machine tool comprising an elastic element of this kind is shown by printed publication WO 2008/000543 A1. 
     In order to enable easy operation of a portable power tool, it is further known to dispose in the handle a mechanical switch, with which an electric motor switch disposed in the tool housing can be actuated. Printed publication DE 10 2005 021 731 A1 shows an electric machine tool in which the mechanical switch in an anti-vibration handle is connected by means of a Bowden cable to the electric motor switch disposed in the tool housing. Although the Bowden cable enables a connection between the mechanical switch and the electric motor switch via curved paths, the provision of a Bowden cable, due to the receiving fixtures which are necessary for the absorption of the arising compressive and tensile forces, and due to the sheath which acts as counterbearing for the tensile forces transmitted by the Bowden cable, is complicated. 
     In drills and/or chipping hammers, a switch disposed in the handle is frequently lockable in “chipping operation” in order that the operator does not have to keep the switch in this operating mode constantly pressed. However, the switch must not be able to be locked in “drilling operation” or “hammer drilling operation”, in order that the portable power tool can be switched off by the user as quickly as possible should the drill tilt and does not twist uncontrollably, so that the operator does not get injured. 
     However, a switch disposed in the handle calls for a switch connection into the tool housing. In electric machine tools having an anti-vibration handle, the displacement between the tool housing and the handle casing which is caused by the relative movement can be, however, in the order of magnitude of a few millimeters, so that such a switch connection between machine components disposed in the handle casing and machine components disposed in the tool housing are traditionally complicated and therefore expensive. 
     SUMMARY 
     The object of the disclosure is to provide an electric machine tool which enables uncomplicated and very cheap mechanical switch connection between machine components which are disposed, for instance, in a handle casing and machine components which are disposed, for instance, in the tool housing. 
     The object is achieved with an electric machine tool, in particular a drill and/or a chipping hammer, comprising a first actuating device and a second actuating device distanced from the first actuating device, wherein the first actuating device is mechanically connected to the second actuating device by means of a switching connector which is to be subjected only to tensile load. 
     Such a switching connector which must be subjected only to tensile load requires, in comparison to a Bowden cable, no sheath which absorbs counterforces, nor does it require any correspondingly complicated receiving fixtures, disposed, for instance, on the housing of the electric machine, for the Bowden cable and sheath, since the switching connector does not have to be designed to absorb compressive forces. The disclosed mechanical switching connector can therefore be realized considerably more cheaply. 
     The switching connector preferably has a first end and a second end, wherein it likewise preferably is fixed by its first end to the first actuating device and also preferably is fixed by its second end to the second actuating device. 
     It is herein preferred that the first actuating device is adjustable by adjustment of the second actuating device and/or the second actuating device is adjustable by adjustment of the first actuating device, in that the switching connector is subjected only to tensile load. Particularly preferably, both the first actuating device is adjustable by adjustment of the second actuating device and the second actuating device is adjustable by adjustment of the first actuating device through only tensile loading of the switching connector. 
     The switching connector is preferably invariable in length, so that it is at least designed such that it does not, or not substantially, change its length as a result of the normally arising tensile load. Particularly preferably, the switching connector is a band or wire. Likewise preferably, the switching connector is configured as a stamped bent part. In the embodiment as a band, it is produced, for example, from a plastic. Alternatively, it can also be made, however, from a natural fiber or a fabric. In the embodiment as a wire or as a stamped bent part, it is preferably produced from a sheet-metal semifinished product or a composite material. 
     Preferably, the electric machine tool has a tool housing and a handle casing disposed on the tool housing, wherein the first actuating device is disposed in the tool housing and the second actuating device is disposed in the handle casing. Particularly preferably, the handle casing is an anti-vibration handle casing. Quite especially preferably, the anti-vibration handle casing is supported on the tool housing by means of an elastic connecting means, wherein the switching connector bears against the elastic connecting means. Also preferably, the stretched length of the elastic connecting means is constant here. 
     In a preferred embodiment, the elastic connecting means is a leaf spring. This embodiment has the advantage that the switching connector, due to the spring preload, bears against the leaf spring. Since, despite the deformation of the leaf spring which occurs upon the movement of the handle casing relative to the tool housing, the length of the leaf spring does not change, the length of that part of the band which bears against the leaf spring also remains virtually unchanged. Furthermore, the leaf spring is preferably of thin configuration, so that the switching connector, close to the neutral axis of the leaf spring, bears against the latter and, also for this reason, the length of that part of the switching connector which bears against the leaf spring remains virtually unchanged. In the event of a relative movement of the handle casing to the tool housing, the distance between the first end of the switching connector and the second end of the switching connector also therefore remains unchanged, so that a switch setting of the first and/or second actuating device cannot be influenced by the relative movement. Despite the relative movement of the handle casing to the tool housing, that operating state of the electric machine tool which has been set by means of the first and/or second actuating device does not therefore change and operating reliability is ensured. 
     Further alternative embodiments of the elastic connecting means, in which the distance present between the first end of the switching connector and the second end of the switching connector remains unchanged, or at least virtually unchanged, are also preferred. For instance, an alternative embodiment in which the elastic connecting means is formed by an articulately mounted lever attached to the handle casing is preferred. The lever is preferably designed such that a change in length of the lever and/or band in the event of compression of the handle casing is prevented, or at least reduced to a reasonable minimum. 
     In a first preferred embodiment, the first actuating device comprises an operating mode switch, with which the electric machine tool can be switched between at least two operating modes. The second actuating device of this embodiment is preferably a locking device, with which a switching device can be fixed in a switch-on position. In this embodiment, the switching connector is therefore at least indirectly fixed by its first end to the operating mode switch and, at the same time, is fixed by its second end to the locking device. 
     The electric machine tool of this embodiment is, for instance, a hammer drill, wherein a “drilling operation”, a “chipping operation” and a combined “hammer drilling operation” are preferably provided as the operating modes. 
     By adjustment of the operating mode switch, for instance from “drilling operation” or “hammer drilling operation” into “chipping operation”, the locking device can be adjusted by means of the switching connector such that it locks the switching device in the switch-on mode. Conversely, by adjustment of the switching device, the locking device can be reset into the switch-off position, so that the operating mode switch is resettable, for instance, from “chipping operation” into “drilling operation” or “hammer drilling operation”. 
     The switching device is preferably realized as a pawl having a first pawl part and a second pawl part, wherein, by actuation of a first pawl part, the pawl can be adjusted into the switch-on position and, by actuation of the second pawl part, the pawl can be adjusted into the switch-off position. 
     According to the application, an embodiment in which the locking device locks the switching device in the switch-off position by adjustment of the operating mode switch is also, however, preferred. Furthermore, an embodiment in which the locked switching device is released by adjustment of the operating mode switch is also preferred. 
     In a second preferred embodiment, the first actuating device is an electric motor switch, while the second actuating device is a mechanical switch. For instance, the electric machine tool can be switched on and off by actuation of the mechanical switch. 
     Further embodiments of electric machine tools, in which, by adjustment of a first actuating device, a second actuating device is adjustable by a switching connector subjected only to tensile load, and/or vice versa, are preferred. 
     The first actuating device preferably comprises a slide bar, which, in the adjustment of the operating modes, is adjustable in a sliding direction. The first end of the switching connector is here preferably fixed to the slide bar. 
     Particularly preferably, by displacement of the slide bar, further motor functions are switchable. For instance, by displacement of the slide bar, a Hall sensor of a speed control unit is switchable, so that as an additional operating mode a “turbo mode” can be activated in “chipping operation” through the use of the slide bar. 
     The connection of the first to the second actuating device by means of a switching connector subjected only to tensile load can be realized in an uncomplicated and very cheap manner and enables reliable switching of the first and/or second actuating device, ensuring operating reliability. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The disclosure is described below with reference to the FIGURE. The FIGURE is merely illustrative and does not restrict the general concept disclosed. 
       The FIGURE shows an electric machine tool  1  comprising a handle casing  3  configured as an anti-vibration handle casing. 
     
    
    
     DETAILED DESCRIPTION 
     The handle casing  3  is supported on a tool housing  2  by means of an elastic connecting means  7 , here a leaf spring. Below, the terms elastic connecting means  7  and leaf spring are used synonymously. The leaf spring  7  here has a first end (non-visible) and a second end  72 , wherein it is connected by its first end fixedly to the tool housing  2 . The handle casing  3  is supported at the second end  72  of the leaf spring  7  on the top side  73  thereof, so that it can compress both in the horizontal and in the vertical direction. A relative movement of several millimeters between the tool housing  2  and the handle casing  3  is thereby possible. Between the tool housing  2  and the handle casing  3  is provided a bellows element  21 , so that the relative movement between the tool housing  2  and the handle casing  3  is possible without damaging the tool housing  2  or the handle casing  3 . 
     Inserted detachably in the handle casing  3  is a grip molding  31 , so that machine components disposed in the handle casing  3  are accessible from outside. 
     The electric machine tool  1  of this illustrative embodiment is a hammer drill, which can be adjusted by means of an operating mode switch  41  into the “drilling”, “hammer drilling” and “chipping” operating modes. The operating mode switch  41  is a component part of a first actuating device  4 , which further comprises a slide bar  42 . The slide bar  42  is displaceable by adjustment of the operating mode switch  41  in or counter to a sliding direction  43  from one of the operating modes into another of the operating modes. 
     For this, the operating mode switch  41  comprises cams (not visible), which displace the slide bar  42  against the force of a compression spring  44 , supported on the tool housing  2 , in the displacement direction  43  when adjustment is made from one operating mode into the other operating mode. 
     To the slide bar  42  is fixed a first end  61  of a switching connector  6 . In the present illustrative embodiment, the first end  61  is hooked on under the preload of a spring  63 . However, embodiments in which the switching connector  6  is fixedly connected to the slide bar  42 , for instance by screwing or clipping, are also preferred. 
     A second end  62  of the switching connector  6  is fixed to a tilt lever part  51  of a second actuating device  5 , of which only the tilt lever part  51  is visible here. The second actuating device  5  of this illustrative embodiment is a locking device. Below, the terms second actuating device  5  and locking device are used synonymously. 
     To be precise, the second end  62  is hooked here in the tilt lever part  51 , which is of hook-shaped configuration. It is also preferred, however, to fixedly connect the second end  62  to the second actuating device  5 . Also preferred is an embodiment in which the second actuating device  5  comprises, instead of a tilt lever part  51 , a sliding part (not represented), to which the second end  62  of the switching connector  6  is fixed. 
     By means of the locking device  5 , a switching device  9 , configured here as a pawl, can be locked in a switch-on position. Below, the terms switching device  9  and pawl are used synonymously. The pawl  9  here has an upper pawl part  91  for the adjustment into the switch-on position and a lower pawl part  92  for the resetting into the switch-off position. By means of the pawl  9 , an electric switch  8  can be switched, wherein the electric switch  9  switches a circuit (not shown), which in the switch-on position of the pawl  9  is closed, so that the electric machine tool  1  is driven, and in the switch-off position of the pawl  9  is open, so that the electric machine tool  1  is switched off. 
     When the operating mode switch  41  is adjusted from “drilling operation” or from “hammer drilling operation” into “chipping operation”, the slide bar  42  is displaced in the displacement direction  43  by means of the cam contour of the operating mode switch  41 . The slide bar  42  thereby pulls on the switching connector  6 , so that the locking device  5  is adjusted out of a basic position against an adjusting force (here indicated by the arrow  52 ) by means of the tilt lever part  51  into a locking position. When the upper pawl part  91  is pressed, or if the upper pawl part  91  is already pressed, the pawl  9  is thus locked in the switch-on position. By pressing of the lower pawl part  92 , the pawl  9  is adjusted from the switch-on position into the switch-off position. 
     When the operating mode switch  41  is reset from “chipping operation” into “drilling operation” or into “hammer drilling operation”, the slide bar  42  is displaced against the sliding direction  43  with the aid of the compression spring  44 . Since the switching connector  6  is invariable in length, it follows the sliding movement of the slide bar  42 , so that the locking device  5  is reset from the locking position into the basic position. The locking device  5  is here drawn back into the basic position by means of the adjusting force  52 , whereupon the switching connector  6  is subjected to tensile load. 
     Both in the adjustment of the locking device from the basic position into the locking position and in the resetting from the locking position into the basic position, the switching connector  6  is therefore subjected only to tensile load. Moreover, the switching connector  6 , in the embodiment as a band, can also withstand only tensile load. 
     The electric switch  8 , the pawl  9  and the locking device  5  are here accessible from outside by detachment and removal of the grip molding  31 . 
     The switching connector  6  is supported on the leaf spring  7 . Due to the spring preload of the leaf spring  7 , the switching connector  6  also bears against the leaf spring  7  in the event of relative movements of the handle casing  3  in relation to the tool housing  2 . Since the length of the leaf spring  7  does not change, that part of the switching connector  6  which bears against the leaf spring  7  also remains unchanged or substantially unchanged. The distance between the first end  61  of the switching connector  6  and the second end  62  of the switching connector  6 , despite the relative movement of the handle casing  3  to the tool housing  2 , therefore also remains unchanged or virtually unchanged, so that both the slide bar  42  and the locking device  5  remain in their position and the operating mode of the electric machine tool  1  does not change. 
     Upon the displacement of the slide bar  42 , a magnet  10 , with which a Hall sensor (not represented) disposed in the speed control unit (not represented) is switched, is here simultaneously displaced. In chipping operation, the “turbo mode” motor function of the electric machine tool  1  can hence additionally be activated.

Technology Category: b