Abstract:
The invention relates to a hand machine-tool, especially electrical shears, comprising a housing ( 13 ) provided with a tool head ( 14 ) and a grip part ( 15 ), an electric motor ( 18 ) arranged in the housing ( 13 ), a switch ( 22 ) for the electric motor ( 18 ), and a drive shaft ( 16 ) mounted in the tool head ( 14 ), transversally to the housing axis. The drive shaft can be driven by the electric motor ( 18 ) by means of a transmission ( 19 ). The hand machine-tool also comprises a rotary tool ( 11 ) that can be fixed to the drive shaft ( 16 ). The aim of the invention is to create a compact, structurally small and lightweight hand machine-tool for work without generating fatigue. To this end, a small-volume, rechargeable energy accumulator, preferably a lithium ion accumulator ( 20 ), which feeds the electric motor ( 18 ) and has a high charging capacity, is arranged in the grip part, together with an electronic plate ( 21 ) and the switch. The transmission ( 19 ) and at least part of the electric motor ( 18 ) are arranged in the tool head ( 14 ).

Description:
CROSS-REFERENCE 
     The invention described and claimed hereinbelow is also described in PCT/EP2007/060580, filed on Oct. 5, 2007 and DE 10 2006 048 315.4, filed on Oct. 12, 2006. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention is directed to a hand-held power tool, in particular electrical shears. 
     Known electrical shears for cutting sheet material, such as cloth, paper and cardboard webs and the like (SU 1 768 384 A1), include a longitudinal housing with a tool head and a grip part. A drive shaft, which is oriented transversely to the housing longitudinal axis and extends laterally out of the tool head, is supported in the tool head. A disk-shaped polygonal cutting disk is non-rotatably accommodated on the drive shaft. The upper—as viewed in the working position—edge of the polygonal cutting disk is covered by a protective collar—which is formed on the housing—around a circumferential angle that is greater than 180°. A downwardly extending, angular blade holder is attached to the tool head, which carries a counter-blade that interacts with the cutting disk, and on which a supporting base is formed that is located opposite to the lower edge region of the cutting disk. The blade holder is located on the housing such that the supporting surface of the supporting base and the longitudinal axis of the housing form an acute angle. An electric motor and a transmission for driving the drive shaft on which the cutting disk is mounted are located in the grip part. Power is supplied to the electric motor via an electrical device cable. 
     SUMMARY OF THE INVENTION 
     The inventive hand-held power tool, in particular electrical shears has the advantage that it is compact, small in size, and lightweight, thereby enabling a user to operate it without becoming tired. The housing is composed only of the tool head and the grip part designed as one piece therewith, and it accommodates all necessary components, including the wireless power supply. The displacement of the electric motor and the transmission into the tool head creates space for the energy accumulator and the electronics, and it moves the center of gravity of the hand-held power tool very far downward into the tool head and, therefore, closer to the work piece, which improves the handling ergonomics. The ergonomics are also greatly improved by the fact that, according to a preferred embodiment of the present invention, the housing is designed such that it curves like a banana, thereby resulting in the grip part being located—in an ergonomically favorable position—at a distinct distance away from the surface of the work piece to be machined, so that the fingers of the operator of the hand-held power tool may never come in contact with the surface of the work piece while work is being performed. 
     All of the measures stated in the further claims regarding the design and placement of the machine components and components of the hand-held power tool contribute to a smaller space and a lighter weight of the hand-held power tool, and ensure that the machine may be manufactured in a cost-favorable manner, which keeps the overall costs low. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventive hand-held power tool is described in greater detail in the description below with reference to an exemplary embodiment shown in the drawing. 
         FIG. 1  shows a side view of electrical shears, 
         FIG. 2  shows a perspective side view of the electrical shears in  FIG. 1  after removal of a housing shell of the housing and a grip cover, 
         FIG. 3  shows a longitudinal sectional view of the electrical shears along the cutting plane labelled III-III in  FIG. 2 , 
         FIG. 4  shows a sectional view along the line IV-IV in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The electrical shears—which are also referred to as an electrical multipurpose blade, and which are depicted in various views and cross sections in the drawing—serves as an exemplary embodiment of a general hand-held power tool with a rotating tool, which may be a cutting disk or a circular saw blade. In the exemplary embodiment of the electrical shears, disk-shaped rotatable tool  11  is a polygonal cutting disk  12 , specifically a 10-sided cutting disk. The electrical shears include a housing  13 , which is composed of two housing shells  131 ,  132 . Housing  13  includes a tool head  14 , on the side of which rotatable tool  11  is located, and a grip part  15  adjacent thereto. Tool head  14  and grip part  15  are connected with each other as one piece, so that each housing shell  131 , 132  forms a part of tool head  14  and grip part  15 . A drive shaft  16  that is oriented transversely to the housing longitudinal axis is rotatably supported in tool head  14 , and extends with a projecting end out of tool head  14  in a flattened region  17  ( FIG. 4 ) of front housing shell  132  in  FIG. 1  and accommodates rotatable tool  11  in this case. Drive shaft  16  is driven in a rotary manner by an electric motor  18  via a transmission  19  ( FIG. 2 ). Transmission  19  and electric motor  18  are located in tool head  14 . Electric motor  18  is powered by a chargeable, small-volume energy accumulator  20  with a high charging capacity. A lithium-ion rechargeable battery is preferrably used as an energy accumulator of this type. The energy accumulator will therefore be referred to below simply as a rechargeable battery  20 . Rechargeable battery  20  is integrated—along with an electronics printed circuit board  21  and an on/off switch  22  for the hand-held power tool—in grip part  15  of housing  13 . Rechargeable battery  20  is located above electronics printed circuit board  21 . An on/off switch  22  is composed of a not-shown electrical switch that is located in the circuit of rechargeable battery  20  and electric motor  18  and on electronics printed circuit board  21 , and it is composed of an actuating element  23  that is designed as a large-area button  24  that projects from the underside of grip part  15  and actuates the electrical switch via a plunger  25  located on the underside of electronics printed circuit board  21  ( FIG. 3 ). Button  24  is pivotably supported in grip part  15  and is held in an “off” position of on/off switch  22  via a return spring  26 . The pivot support of button  24  advantageously results in short travel for the electrical switch and in long travel for return spring  26 . Due to the large surface area of button  24 , the operator may actuate on/off switch  22  in an ergonomically advantageous manner. 
     A circuit for charging and monitoring the state of charge of rechargeable battery  20  is located on electronics printed circuit board  21 . A charging socket  27 , which is mounted on electronics printed circuit board  21  and is accessible—via a recess  31  located on the rear end of grip part  15 —to a charging plug of a charging device, is connected with the circuit. A start-of-charge display  28 , which is also connected with the circuit, is located in a region of housing  13  that is visible to the operator when the electrical shears are held in the working position. In the exemplary embodiment shown, state-of-charge display  28  is located on the top side of the end of tool head  14  that faces grip part  15  ( FIGS. 1 through 3 ). Rechargeable battery  20  is contacted with electronics printed circuit board  21  via terminals  29 , and electric motor  18  is contacted with electronics printed circuit board  21  via terminals  30 . A grip cover  32  with a golf ball-type structure is attached to the top side of grip part  15 , which faces away from button  24  ( FIG. 1 ). Grip cover  32  ensures that the electrical shears may be held and guided in a secure manner without slipping. 
     Transmission  19 , which is located in tool head  14 , is composed of a reduction gear and a deflecting gear, which are located downstream in the power flow ( FIGS. 3 and 4 ). A transmission design of this type is very compact. The reduction gear is designed as a multi-staged—two-staged in the present exemplary embodiment—planetary gear set  34  with an input stage and an output stage. The deflecting gear is designed as a bevel gear set  35 , which includes two meshed bevel gears  36 ,  37 , whose gear axes are oriented at right angles to each other. The input stage of planetary gear set  34  is coupled to motor shaft  33  of electric motor  18 , and the output stage of planetary gear set  34  is coupled to first bevel gear  36  of bevel gear unit  35 . Bevel gears  36 ,  37  have the same number of teeth and are made of brass. First bevel gear  36  is accommodated in a ball bearing  38  mounted in housing  13 , and second bevel gear  37  is pressed onto drive shaft  16 . Drive shaft  16  itself is supported on one side in a ball bearing  39 , which serves as a fixed bearing, and in a sintered bushing  40  on the other side ( FIG. 4 ). Sintered bushing  40  is pressed into housing shell  131 , and ball bearing  39  is pressed into housing shell  132 . 
     In planetary gear set  34 , all gear stages share the same internal gear  41 , which is mounted in housing  13 , and which extends across the axial length of planetary gear set  34 . Each gear stage includes a sun gear  42 , with planetary gears  43  (three planetary gears  43  in the exemplary embodiment) that mesh with sun gear  42  and internal gear  41 , and a planetary gear carrier  44  that carries planetary gears  43 . Sun gear  42  of the input stage is inserted on motor shaft  33  in a driving manner, while sun gear  42  of the output stage is part of planetary gear carrier  44  of the input stage. If planetary gear set  35  has more than two gear stages, sun gear  42  of the next gear stage is mounted on each planetary gear carrier  44 , or it is designed as a single piece therewith. If there are three gear stages, sun gear  42  of the middle gear stage would be combined with planetary gear carrier  41  of the input stage, and sun gear  42  of the output stage would be combined with planetary gear carrier  44  of the middle gear stage. Planetary gear carrier  44  of the output stage is fixed on a peg-type output shaft  58 , on which first bevel gear  36  of bevel gear unit  35  is non-rotatably mounted. Planetary gears  43  of the gear stages are made of sintered steel, and internal gear  41  is a sintered part, aspects that reduce weight and costs. The shaft section of drive shaft  16 , which extends laterally out of housing  13 —specifically, out of housing shell  132 —in flattened region  17  of tool head  14  includes a bearing flange  44  ( FIGS. 2 and 4 ) with an integral driving element  46  ( FIG. 1 ) for rotatable tool  11 . An axial threaded bore  47  that is formed from the free end face inward is provided in drive shaft  16 . A panhead screw  48  ( FIGS. 1 and 4 ) is screwed into threaded bore  47 , thereby securing disk-shaped, rotatable tool  11 —a polygonal cutting disk  12  in this case, and which bears non-rotatably against bearing flange  45 —in the axial direction. 
     An angular blade retaining plate  49  is detachably attached ( FIGS. 1 and 4 ) to housing  13 —specifically, to housing shell  132 —in flattened region  17 , which is somewhat larger than the diameter of rotatable tool  11 . 
     A supporting base  50  is formed on blade retaining plate  49 , with which the electrical shears may be guided when cutting is performed on a guide plane. A rectangular counter-blade  51  is located nearly parallel with contact surface  501  of supporting base  50  and forms a wedge-shaped groove  52  ( FIG. 1 ) with rotatable tool  11  and/or polygonal cutting disk  12 , whose opening points in the working direction. Counter-blade  51  is riveted to a leaf spring  53 , which is attached to the side of supporting base  50  that is not shown in  FIG. 1 . 
     Blade retaining plate  49  is detachably attached to housing shell  132  and may be replaced with a spring-loaded protective bracket, which is not shown here. This protective bracket covers the lower edge region of rotatable tool  11  and/or polygonal cutting disk  12  that is exposed by blade retaining plate  49 , and ensures that the electrical shears may not be touched when they are not in use. Using this protective clamp, the electrical shears may be used to perform cutting work without counter-blade  51 . 
     A guard  54  is also pivotably mounted on flattened region  17  of housing shell  132  ( FIG. 1 ). Guard  54  covers the upper edge region of rotatable tool  11  that faces away from supporting base  50 , so that it may not be touched. Guard  54  extends around a circumference of greater than 180°. Guard  54  is spring-loaded and, when the electrical shears are not in use, it slides over wedge-shaped gap  52 , so that rotatable tool  11  is completely covered at the edge by supporting base  50  and guard  54 . Via a lever mechanism or cable tension, guard  54  is coupled with on/off switch  22  such that, when button  24  is actuated to switch on electric motor  18 , guard  54  in  FIG. 1  is swiveled in the clockwise direction to the extent that wedge-shaped gap  52  between rotatable tool  11  and counter-blade  51  is exposed. As an alternative, guard  54  may also be integrally formed as a single piece with housing shell  132 , in which case its coverage of rotatable tool  11  ends before wedge-shaped gap  52 . 
     As shown in  FIGS. 1 and 3 , a suspension eye  55  is integrally formed with the rear end of housing  13 , which faces away from tool head  15 . Instead of a suspension eye  55 , it is possible for set-down strip to be formed on housing  13 . 
     As shown in  FIGS. 2 and 3 , at least one electrical lamp—which is preferably designed as an LED  56 —is located in the front side of tool head  15 , which points in the working direction. LED  56  is connected via a connecting line  57  with electronics printed circuit board  21 , where it is connected to the circuit. The electrical switch of on/off switch  22  is designed with two stages. When button  24  is actuated, the electrical switch moves into stage “ 1 ” and stage “ 2 ” in succession. In stage “ 1 ”, LED  56  is switched on. In stage “ 2 ”, in addition, the circuit between rechargeable battery  20  and electric motor  18  is closed. As an alternative, LED  56  may also be connected to a separate switch, which is accessible on housing  13 , so that LED  56  may be switched on and off, independently of starting up the electrical shears. In this case, the electrical shears may also be used as a flashlight.