Abstract:
A plug arrangement in a machine tool comprises a primary plug part, which is associated with a drive motor, and a secondary plug part. According to the invention the primary and secondary plug parts are assembled to form a common plug part.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP2009/053230 filed on Mar. 19, 2009. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a plug arrangement in a power tool, in particular a hand-held power tool such as an angle grinder, equipped with a primary plug part, which is associated with a drive motor of the power tool, and a secondary plug part, which is associated with another component in the power tool. 
     2. Description of the Prior Art 
     There are known electric motor-driven hand-held power tools such as angle grinders that have a housing containing an electric drive motor that drives a tool shaft to which a tool is fastened. The electric drive motor is switched on and off by means of a manual switch that is usually connected via a plug part to an electronic component for controlling the drive motor. For speed control, the electric drive motor can be associated with a speed sensor and the sensor signals that represent the speed are supplied to the electronic component via another plug part. 
     With power tools of this kind, it is generally desirable to reduce the number of parts, both for cost reasons and to improve durability. In particular, the abrasive dirt particles produced during operation of the tool can penetrate into the housing interior of the power tool, leading on the one hand to an increased friction in the rotating parts and on the other hand, to undesirable bridging of the electrical contacts, which can result in a short circuit. A reduction in the number of parts also reduces the risk of undesirable dirt particles being deposited in the housing. 
     OBJECT AND ADVANTAGES OF THE INVENTION 
     The object of the invention is to create a plug arrangement in a power tool, in particular a hand-held power tool, by means of simple structural measures so that without limiting functionality, the number of parts is reduced and the service life is extended. 
     The plug arrangement according to the invention is used in a power tool, which is in particular a hand-held power tool such as an angle grinder. The power tool has a housing containing a drive motor, in particular an electric drive motor, that is associated with a primary plug part; electric connecting cables are routed between the drive motor and the primary plug part. In addition, a secondary plug part is provided, which is associated with another unit or electrical component of the hand-held power tool; in a preferred embodiment, this unit or electrical component is a speed sensor for determining the motor speed of the drive motor. Electrical cables are also provided between this other unit and the secondary plug part. The primary plug part and the secondary plug part are united to form a combined plug part. 
     This embodiment has the advantage that the plug arrangement, with the primary plug part and secondary plug part already in the form of a combined plug part, can be inserted into the housing of the power tool and mounted there. Uniting them to form a combined component not only reduces the number of parts, but also facilitates installation since essentially one combined connecting device suffices for mounting the plug part in the housing. In addition, the combined plug part has less surface area to be attacked by deposits of dirt, in particular abrasive dirt particles that are produced during the machining of a work piece. 
     In addition, it is possible to embody the primary plug part and secondary plug part as separate components that are connected to each other, thus constituting the combined plug part. For example, the secondary plug part can be placed onto the primary plug part by means of a plug connection; it is also conceivable to provide other connecting measures between the primary and secondary plug parts such as gluing, clamps, or the like. 
     According to an advantageous embodiment, however, the plug part is embodied of one piece so that the primary and secondary plug part have a combined plug housing. This is advantageously composed of plastic and can, for example, be manufactured using injection molding. 
     The combined plug part in which the primary and secondary plug parts are united can be provided with coding elements that make it possible to uniquely define the installation position of the plug part in the housing. For example, the coding element can be embodied in the form of a coding rib that protrudes from the outside of the combined plug part and in particular, corresponds to an associated coding recess in the housing so that it is only possible to install the combined plug part in the housing if the coding elements on the plug part and housing engage each other. Another possibility for uniquely defining the installation position lies in providing a coding element in the form of a coding pin that protrudes axially from the outside of the plug part and has either a non-round cross-sectional geometry and/or is positioned on the plug part off-center in the transverse or vertical direction. 
     According to another advantageous embodiment, the primary plug part and secondary plug part, on the same side of the combined plug part, have insertion openings situated above one another, provided either for installation in the housing or for accommodating electric connecting cables. 
     According to another advantageous embodiment, the housing of the power tool is composed of several parts and in particular, has a handle housing as well as a motor housing for accommodating the drive motor. The combined plug part is preferably situated in the handle housing; the electric connecting cables are routed from the plug part to at least one actuator in the motor housing, in particular to the electric drive motor, and to the additional electric unit, which is preferably embodied in the form of a speed sensor. Between the handle housing and the motor housing, a damping element can be provided to effectively reduce oscillations that are produced by the machining of the work piece and by the switched-on drive motor. The suitably annular damping element preferably has a central opening and a radial slot that extends to the central opening so that the connecting cables between the plug element and the drive motor and speed sensor can be inserted laterally via the radial slot until they reach the central opening in the damping element. Basically, however, it is also possible for the electric connecting cables to span the distance between the plug element and the drive motor and speed sensor on the outside of the damping element. 
     Other advantages and suitable embodiments can be inferred from the remaining claims, the description of the figures, and the drawings themselves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in further detail below in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a hand-held power tool, having a two-part handle housing and a motor housing for accommodating an electric drive motor, 
         FIG. 2  is a side view of the open handle housing, with a speed sensor that is situated in front of the handle housing and is connected via an electric connecting cable to an electronic component in the handle housing, 
         FIG. 3  is a perspective view of the open handle housing, with the electronic component, a manual switch for actuating the electric drive motor, and a plug part composed of a primary and secondary plug, 
         FIG. 4  is a depiction similar to  FIG. 3 , but from another perspective, 
         FIG. 5  is another depiction, but from another perspective, 
         FIG. 6  shows the entire plug part in a perspective detail view, 
         FIG. 7  shows the plug part from another perspective, 
         FIG. 8  shows the plug-part with different insertion openings in the end surface, which additionally function as coding elements that define the installation position, 
         FIG. 9  shows the plug part with a coding pin situated off-center, 
         FIG. 10  shows a plug part that has a coding pin with a non-round cross section, and 
         FIG. 11  shows an annular adapter part that includes a damping element for insertion between the motor housing and handle housing; a radial slot extending to a central opening is provided in the adapter part. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Components that are the same from one drawing to the next are provided with the same reference numerals. 
       FIG. 1  schematically depicts a hand-held power tool  1 , which is an angle grinder, for example. The housing  2  of the hand-held power tool  1  is composed of several parts and includes a motor housing  3 , and a handle housing  4  that is to be connected to the motor housing  4  and is composed of two handle shells  4   a  and  4   b . The motor housing  3  contains an electric drive motor  5 , which, via a drive connection  6 , drives a rotatably supported tool shaft  7  that supports a tool  8 . The motor housing  3  and handle housing  4  are connected to each other by means of a connecting device  9 . An adaptor part, which preferably has a damping element for vibration damping, can optionally be inserted into the region of the connection between the motor housing  3  and handle housing  4 . 
       FIG. 2  shows such an adaptor part  10  inserted between the motor housing  3  and handle housing  4 . The adaptor part  10  is embodied in an annular form and has a central opening through which is routed an electric connecting cable  13  that connects a speed sensor  11  to an electronic component  12 . The speed sensor  11  is situated in the motor housing  3  and is associated with the electric drive motor to measure its speed; the electronic component  12  is situated in the handle housing  4 . 
     As can be inferred from the various perspectives shown in  FIGS. 3 through 5 , the handle housing  4  contains a plug part  15  that is composed of two parts and includes a primary plug part  16  and a secondary plug part  17 . The primary plug part  16  and secondary plug part  17  are embodied of one piece and have a combined housing that constitutes the plug part  15 . The primary plug part  16  is associated with the electric drive motor and the secondary plug part  17  is associated with the speed sensor  11  ( FIG. 2 ). Both plug parts  16 ,  17  are also connected via electric connecting cables to the electronic component  12  that is situated in the handle housing  4 , directly under the plug part  15 . 
     The plug part  15  is situated in the upper section of the handle housing  4 , directly above a manual switch  14  for switching the electric drive motor on and off. For fastening and simple installation of the combined plug part  15  in the handle housing  4 , the plug part  15  has side walls  18  that protrude laterally from the housing of the plug part and can be bent open in opposition to a spring force acting in the transverse direction. These side walls  18  are each provided with a respective receiving opening that can be slid onto an associated raised area in the handle housing, as a result of which the plug part  15  assumes a detent-engaged position in the handle housing. 
     As can be seen in the detail view of the combined plug part  15  in  FIG. 6 , the top of the primary plug part  16 , on which the secondary plug part  17  is also positioned, has coding ribs  19  that protrude above the wall and are provided to precisely define the installation position of the plug part  15  in the housing of the hand-held power tool. Only a correct installation position prevents the coding ribs  19  from colliding with components in the housing. It can be useful to provide coding recesses in the housing, which are associated with the coding ribs  19  and in which the coding ribs engage in the correct installation position. 
     The end surface of the primary plug part  16  has insertion openings  20  that are preferably provided for the fastening of the plug part; in the installed position, mounting elements situated in the housing protrude into the insertion openings  20 . The insertion openings  20  can optionally also perform the function of accommodating electrical connecting elements. The side walls  18 , which are simultaneously used for installing the plug part  15 , protrude laterally beyond the end surface of the primary plug part  16  with the insertion openings  20  provided therein. 
     The secondary plug part  17  is provided with other insertion openings  21  that serve to accommodate electric connecting cables. The insertion openings  21  on the secondary plug part  17  are oriented toward the same end surface as the insertion openings  20  on the primary plug part  16 , but the end surface plane of the secondary plug part  17  is offset from the end surface plane of the primary plug part  16 . 
     As is clear from  FIG. 7 , other insertion openings  22  and  33 , respectively, that serve to accommodate electric connecting cables, are provided in the opposite end surface of the primary plug part  16  and secondary plug part  17 , i.e. on the end surface oriented away from the side walls  18 . 
     In the exemplary embodiment according to  FIG. 8 , the end surface of the plug part  15  oriented toward the side walls  18  is provided with two T-shaped insertion openings  20 ; by contrast with the exemplary embodiment according to  FIG. 6 , however, these T-shaped insertion openings  20  are not situated mirror-symmetrically to each other, but are instead rotationally offset from each other by 90°. The insertion openings  20  thus likewise function as coding elements, requiring a uniquely defined installation position of the plug part  15  in the housing of the hand-held power tool. 
     In the exemplary embodiment in  FIG. 9 , the end surface of the combined plug part  15  provided with the insertion openings  20  has a cylindrical coding pin  24  that protrudes axially from the end surface. The coding pin  24  is positioned on the plug part  15 , off-center in the transverse direction. This asymmetrical position of the coding pin  24  also assists in establishing a uniquely defined installation position of the plug part  15 . 
     In the exemplary embodiment according to  FIG. 10 , a coding pin  24  is likewise situated on the end surface of the combined plug part  15  provided with the insertion openings  20 . This coding pin  24 , however, has a non-round cross-sectional embodiment, in particular an asymmetrical cross section that requires a precisely defined angular position for the installation of the plug part. The coding pin  24  can be positioned either in the center or optionally also off-center in both the transverse and vertical directions. 
       FIG. 11 , shows an adapter part  10  that can be inserted between the motor housing and handle housing. The adapter part  10  is embodied in an annular form and is composed of a damping element  25  that is secured to an adapter ring  26 ; the adapter ring  26  is suitably composed of two parts and the damping element  25  is situated between the two parallel adapter ring parts. The adapter part  10  has a radial slot  27  that extends to a central opening  28  through which the electric connecting cables, which extend between the drive motor and speed sensor in the motor housing one the one hand and the electronic component and plug part in the handle housing on the other, are routed inside the handle housing. The radial slot  27  permits the connecting cables to be inserted into the central opening  28  radially from the outside. 
     The foregoing relates to the 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.