Patent Publication Number: US-8113868-B2

Title: Electric device, in particular electric handheld power tool

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
     This application is a continuation application of U.S. patent application Ser. No. 11/412,687, filed Apr. 27, 2006 now U.S. Pat. No. 7,883,355 (“the parent application”). The invention described in the parent application, and described and claimed herein below is also described in German patent application DE 10 2005 020 358.2, filed May 2, 2005. This German patent application, whose subject matter is incorporated by reference herein, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
    
    
     BACKGROUND OF THE INVENTION 
     The invention is based on an electric device, in particular an electric handheld power tool. 
     From German Patent Disclosure DE 195 21 426 A1, a handheld power tool is known, with a receiving region on which a power supply unit for supplying an electric unit can be located. The handheld power tool is additionally provided with a contact means for making an electrical connection between the power supply unit and the electric unit, and this contact means is movable relative to the electric unit. To permit such a relative motion, clearance for the contact means is provided in the housing of the electric unit. By means of a guide means, the contact means is carried along with the power supply unit upon a motion of the power supply unit. As a result, abrasion and burnoff of contact elements of the contact means, which can be ascribed to vibration of the handheld power tool relative to the power supply unit, can be avoided. 
     SUMMARY OF THE INVENTION 
     The invention is based on an electric device, in particular an electric handheld power tool, including an electric unit having a receiving region for receiving a power supply unit, moved in a receiving direction to approach the receiving region, and including a contact means for making an electrical connection between the power supply unit and the electric unit. 
     It is proposed that the electric device has a means which is intended for counteracting a motion of the contact means, which is movable relative to the electric unit in the receiving direction, relative to the power supply unit located on the receiving region, and within a region intended for the motion. Particularly advantageously, wear of the contact means and/or of the power supply unit can be reduced. Moreover, unwanted burnoff of a contact element, such as a metal element, by way of which an electrical connection can be made between the power supply unit and the contact means, of the power supply unit and/or of the contact means can be reduced. 
     In this connection, the phrase “region intended for motion” is understood to mean in particular a region that offers clearance for a motion of the contact means and/or of the power supply unit located on the receiving region. The term “intended” should be understood in this context especially to mean “equipped” and/or “designed”. 
     It is also proposed that the means is intended for guiding the contact means along with the power supply unit located on the receiving region. This is especially advantageous if the electric device is used for tasks in which it may be stressed by strong vibrations and/or shocks. A burnoff of contact elements of the power supply unit and/or of the contact means can be further reduced or prevented, which is especially advantageous, if in operation of the electric device a current with high current intensity can flow between the contact elements. 
     Carrying the contact means along with the power supply unit located on the receiving region can be attained especially simply by providing that the means is intended for pressing the contact means against the power supply unit located on the receiving region. By means of a force exerted on the power supply unit by the contact means, a further force, which has a tendency to put the power supply unit and the contact means out of contact with each other can be counteracted. This is especially advantageous for instance if the power supply unit has an ejection spring for ejecting the power supply unit that exerts a force on the contact means when a power supply unit is located on the receiving region. 
     It is also proposed that the means is intended for counteracting a motion of the contact means relative to the electric unit and when the power supply unit has been removed. As a result, unwanted wobbling of the contact means, for instance in the receiving region, can be reduced, which is especially advantageous when the electric device is being transported without a power supply unit. 
     Advantageously, the means is formed at least by a spring. By the use of a spring, a motion of the contact means can be counteracted in a way that is especially protective of the contact means. Motions of the contact means, especially motions that can arise from strong vibrations and/or shocks of the electric device, can in fact be cushioned, for instance by tensing and/or bending of the spring. Moreover, existing elements that are especially simple, inexpensive, and/or space-saving can be used. 
     In a further feature of the invention, it is proposed that the spring, in a tensed state, is in contact with at least two portions of the electric unit. As a result, the spring can be braced on the electric unit, and the torque of a contrary force exerted on the spring by the electric unit can be kept slight. In this bracing, a rotary motion of the spring can thus be reduced and in particular prevented. The torque can be kept slight especially effectively if the portions are spaced apart from one another. In order to attain a long spring travel in addition, each end of the spring can be in contact with a respective one of the portions. To attain especially high stability of the contact means when the spring is braced on the electric unit, the portions can be located on both sides of the contact means. 
     Advantageously, the portions each have a rounded surface. As a result, wear to the spring, which can arise from repeated sliding of the spring on a portion, for instance in repeated tensing and untensing motions of the spring, can be advantageously averted. 
     It is also proposed that the means is formed at least by a leaf spring. By the use of a leaf spring, a long spring length and a compact design of the means can be attained. 
     It is furthermore proposed that the spring is kept with initial stress on the contact means. Especially effective retention of the spring can be attained, and additional retaining means for retaining the spring can be avoided. Moreover, wobbling of the contact means when a power supply unit has been removed can advantageously be further reduced and in particular prevented, because as a result of the initial tension of the spring and bracing of the spring on the portions of the electric unit, the contact means is pressed against the electric unit. 
     In a further variant embodiment, the spring is embodied as an ejection spring for ejecting the power supply unit. Installation space for an additional ejection spring can advantageously be avoided, making an especially compact arrangement of a power supply unit located on the receiving region possible. The embodiment as an ejection spring can also be attained in a simple way by providing that a spring is made to fit an ejection function by means of the choice of initial tension, for instance, and/or of a material. 
     Especially simple installation and/or effective retention of the spring can furthermore be attained by providing that the means is kept on the contact means by form-locking engagement. 
     Further advantages will become apparent from the ensuing description of the drawings. In the drawings, exemplary embodiments of the invention are shown. The drawings, description and claims include numerous characteristics in combination. One skilled in the art will expediently consider the characteristics individually as well and put them together to make useful further combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  is a section through an electric unit of a handheld power tool and through a power supply unit located on the electric unit; 
         FIG. 1   b  shows the arrangement of  FIG. 1   a , with a power supply unit displaced by a travel distance; 
         FIG. 2  shows a contact means, embodied as a contact plate, with a leaf spring, in perspective; 
         FIG. 3  shows the contact plate of  FIG. 2  in a further view; 
         FIG. 4   a  shows an electric unit of a further handheld power tool, having the contact plate of  FIG. 2 ; 
         FIG. 4   b  shows the arrangement of  FIG. 4   a  with a power supply unit attached; and 
         FIG. 4   c  shows the arrangement of  FIG. 4   b , with a power supply unit displaced by a travel distance. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1   a , part of an electric device, embodied as a handheld power tool  10 , is shown. Of the handheld power tool  10 , in a sectional view, an electric unit  12 , having a receiving region  14  and a lever  16 ; a contact means  18 ; and a means  20  embodied as a spring are shown. Located on the receiving region  14  is a power supply unit  22 , embodied as a battery pack, which has a guide groove  24  and a recess  26 . The contact means  18  is movable relative to the electric unit  12  in the receiving direction  28 , specifically within a region  30  intended for motion, which is defined by housing walls  32 . 1 ,  32 . 2  of the electric unit  12 . The contact means  18  also serves to make an electrical connection between the power supply unit  22  and the electric unit  12 . 
     When the power supply unit  22  is made to approach the receiving region  14 , a guide strip, not shown in the drawing, of the electric unit  12  is inserted into the guide groove  24  of the power supply unit  22 . The power supply unit  22  is then thrust in the receiving direction  28 , until a detent lug  34  of the lever  16  snaps into the recess  26  of the power supply unit  22 . During the displacement of the power supply unit  22 , metal contact blades  36  of the contact means  18  engage a gap, not identified by reference numeral in the drawing, of the power supply unit  22 . During the displacement of the power supply unit  22 , the contact means  18 , which when the power supply unit  22  has been removed rests on the housing wall  32 . 1  of the electric unit  12 , is struck by a side face  38  of the power supply unit  22  and is then displaced in the receiving direction  28 , until the motion of the power supply unit  22  is stopped by the snapping of the detent lug  34  into place. Upon the displacement of the contact means  18 , the means  20  embodied as a spring is tensed. In the process, the contact means  18  is pressed against the power supply unit  22  by a force exerted on the contact means  18  by the spring. 
     In operation of the handheld power tool  10 , an electrical connection is made between the power supply unit  22  and the handheld power tool  10 , specifically via the metal contact blades  36  of the contact means  18 , and an electrical connection, not shown in the drawing, between the contact means  18  and the electric unit  12  is also made. The power supply unit  22 , which is movable in the receiving direction  28  relative to the electric unit  12 , may, for instance because of vibrations and/or shocks that stress the handheld power tool  10 , be displaced briefly by a travel distance x in the receiving direction  28 . This displaced state can be seen in  FIG. 1   b . In this displacement, the contact means  18 , which is pressed against the power supply unit  22  by the spring force, is carried along with the power supply unit  22 . A motion of the contact means  18  in the region  30  relative to the power supply unit  22  can therefore be prevented by the means  20 , and as a result abrasion and/or burnoff of the metal contact blades  36  can be reduced. 
       FIGS. 2 and 3  show a contact means  40  in a further exemplary embodiment. It includes a plastic body  42 , in which three metal contact blades  44 . 1 ,  44 . 2 ,  44 . 3  are embedded, and also includes a means  46 , embodied as a leaf spring, that is retained in a receiving part  48  of the plastic body  42 . This receiving part  48  has two openings  50 . 1 ,  50 . 2  and two ribs  52 . 1 ,  52 . 2 . Upon installation of the leaf spring, this spring is introduced into the receiving part  48  through one of the openings  50 . 1 ,  50 . 2 , until a detent lug  54  of the leaf spring snaps into a gap  56 , formed by the ribs  52 . 1 ,  52 . 2 . After snapping into place, the means  46  embodied as a leaf spring is retained by form-locking engagement in the longitudinal direction of the receiving part  48 . 
     In  FIGS. 4   a ,  4   b  and  4   c , the contact means  40  is built into a further electric device, embodied as a handheld power tool  62 . The handheld power tool  62  includes an electric unit  64  with a receiving region  66  for receiving a power supply unit  68 , which is shown in  FIGS. 4   b  and  4   c . The contact means  40  is movable in the receiving direction  28  relative to the electric unit  64  within a region  70  intended for motion, the region  70  being defined by housing walls  72 . 1  and  72 . 2 . 
     In  FIG. 4   a , the handheld power tool  62  is shown with the power supply unit  68  removed. Ends  73 . 1 ,  73 . 2  of the leaf spring are braced on respective portions  74 . 1 ,  74 . 2  of the electric unit  64 , and as a result the leaf spring is kept under initial tension, which prevents rattling of the leaf spring. As a result, a slight pressure is furthermore exerted by the contact means  40  on the housing wall  72 . 1  of the electric unit  64 , which when the electric device is being transported with the power supply unit  68  removed reduces wobbling of the contact means  40  relative to the electric unit  64 . 
     When the power supply unit  68 , embodied as a battery pack, is brought toward the receiving region, the contact means  40  is displaced by the power supply unit  68  by a travel distance W, until the motion of the power supply unit  68  is stopped by a detent device, formed for instance by the lever  16  and the recess  26  of  FIG. 1   a . Upon this displacement of the contact means  40 , the leaf spring is accordingly tensed further, by means of a force exerted on the detent lug  54  by the ribs  52 . 1 ,  52 . 2 . This state of the handheld power tool  62 , with the power supply unit  68  in place, is shown in  FIG. 4   b . In this state, the contact means  40  is pressed against the power supply unit  68  by the bracing of the tensed leaf spring on the portions  74 . 1 ,  74 . 2 . Moreover, the metal contact blades  44 . 1 ,  44 . 2 ,  44 . 3  of the contact means  40  engage gaps  76 . 1 ,  76 . 2 ,  76 . 3  of the power supply unit  68 . 
     The power supply unit  68 , which is movable in the receiving direction  28 , may be offset relative to the electric unit  64  by a travel distance y, for instance because of vibrations and/or shocks of the electric device. This displaced state of the power supply unit  68  is shown in  FIG. 4   c . In the displacement, the contact means  40  is carried along with the power supply unit  68 , since the contact means  40  is pressed against the power supply unit  68  by the spring force, and the leaf spring becomes tensed further. In the process, the ends  73 . 1 ,  73 . 2  are displaced on the respective portions  74 . 1 ,  74 . 2 . To reduce abrasion of the ends  73 . 1 ,  73 . 2  of the leaf spring from repeated tensing and untensing motions of the leaf spring, the portions  74 . 1 ,  74 . 2  are each provided with a respective rounded surface  78 . 1  and  78 . 2 . 
     The leaf spring can additionally be used as an ejection spring. The force in  FIG. 4   b  exerted on the power supply unit  68  by the contact means  40  can be utilized, upon release of a detent connection, to eject the power supply unit  68 . In the process, the power supply unit  68  can be displaced by the travel distance W by the contact means  40 . 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in an electrical device, in particular electric handheld power tool, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.