Abstract:
The invention relates to a hand tool machine ( 2 ), in particular a drilling and/or percussion hammer, with a housing ( 4 ) and a vibration-damped handle ( 10 ) elastically supported relative to the housing ( 4 ) with two essentially parallel legs ( 20, 22 ) and a coupling element ( 44  or  46 ) between each leg ( 20  or  22 ) and the housing ( 4 ) that is pin-jointed to the leg ( 20  or  22 ) and the housing ( 4 ). The coupling elements ( 44, 46 ) are connected to each other by a connector ( 48 ) that synchronizes the movements of the coupling elements ( 44, 46 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2006 021 307.6 filed on May 8, 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 relates to hand-held power tool, in particular a rotary hammer and/or a percussion hammer, with a housing and vibration-damped handle that is spring-supported against the housing. 
     With hand-held power tools with an impact drive in particular, such as rotary hammers, chisel hammer, and the like, the hand-held power tool may be subjected to considerable vibrations. When these vibrations are transferred to a handle that is used to press the hand-held power tool against a work piece, the operator perceives the vibrations to be uncomfortable, and long-term exposure thereto may even result in injury. For this reason, double-shelled housings, with which the entire hammer is suspended in an outer shell such that it is resilient in the working direction, have been used to provide linear vibration damping of rotary hammers. This design is relatively complex and expensive, however. 
     Publication WO 03/011532 makes known a machine tool of the type described initially, which includes a vibration-damped, C-shaped handle that supported via springs against the housing. This handle includes two essentially parallel legs, which are guided into complementary recesses in a grip end of the housing in the working direction of the machine tool such that they are linearly movable. To ensure that the two legs do not tilt in the recesses and then move in a synchronous manner with each other relative to the housing when the operator applies a compressive force to the handle on only one side or not parallel to the working direction of the machine tool, the two legs are connected with the housing via a lever, the outer ends of which are hingedly connected to the particular legs, while their inner ends are hingedly connected to a region of the machine housing located between the two legs of the handle. Since there is no direct connection between the handle and the housing of the machine tool, a good decoupling of the handle from the vibrating housing is attained. The lever design also increases the stability of the handle. 
     In addition, publication DE 10 2004 019 776 A1 has also already made known to hingedly connect the two legs of a handle of a machine tool with the housing of the machine tool, to dampen vibrations using coupling elements. 
     In addition, a machine tool with a vibration-damped handle is made known in DE 101 38 123 A1, with which one of the coupling elements that is hingedly connected with the handle and the housing is accommodated inside the hollow handle in a space-saving manner, and the other is accommodated inside the housing. 
     While these designs make it possible to attain satisfactory vibration damping and decoupling of vibrations, it is not always possible to integrate these designs in the housing and/or the handle, or to accommodate them inside the housing and/or the handle such that they take up a small enough space in the working direction of the machine tool that they do not result in an increase in the overall length of the machine tool. 
     SUMMARY OF THE INVENTION 
     Based thereon, the object of the present invention is to improve a machine tool of the type described initially such that the components required to decouple vibrations from the handle may be accommodated inside the housing and/or the handle in a space-saving manner, and, in particular, such that they require very little space in the working direction of the machine tool, thereby making it possible to reduce the overall length of a grip region of the machine tool—which is composed of the handle itself and a part of the machine tool housing used to accommodate the legs of the handle, the coupling elements, and the spring—to the greatest extent possible. 
     In keeping with these objects and with others which shall become apparent hereinafter, one feature of the present invention resides, briefly stated, in that the coupling elements are interconnected via a connecting element that synchronizes the motions of the coupling elements. 
     The present invention is based on the finding that the space required by the components designed to decouple vibrations from the handle may be kept very small when the motions of the two legs of the handle are not synchronized by the coupling elements themselves, but rather by an additional connecting element between the coupling elements, which is hingedly connected only to the two coupling elements, and is not connected with the housing or the handle. In this manner, the shape of the coupling elements may be better adapted to the space available in the grip region of the machine tool, thereby making it possible to provide a compact, cost-favorable design. 
     According to a preferred embodiment of the present invention, the connecting element is designed as a connecting rod, the opposing ends of which are advantageously hingedly attached to the coupling elements such that the connecting rod is oriented essentially transversely to the working direction of the machine tool, which contributes to a reduction in the overall length. 
     According to a particularly space-saving version, the connecting element and parts of the coupling elements are located inside the hollow, C-shaped handle, thereby making it possible to move some of the required components out of the housing of the machine tool. The two coupling elements advantageously extend through the open ends of the legs of the C-shaped handle and into the interior of the handle, where they are coupled by the connecting element, which advantageously extends through the hollow yoke of the handle. 
     In this case, at least one coupling element is advantageously designed as a two-armed lever, whose one lever arm is hingedly connected with the housing, and whose other lever arm is hingedly connected to the connecting element inside the hollow handle, the lever between the two lever arms being hingedly connected with a leg of the handle. Advantageously, the other coupling element is also designed as a two-armed lever, whose one lever arm is hingedly connected with a leg of the handle, and whose other lever arm is hingedly connected to the connecting element inside the hollow handle, while the lever itself between the two lever arms is hingedly connected to the housing. 
     As an alternative, at least one coupling element may be designed as a disk that is pivotably connected at its center with the housing and that, at a distance from its center, is hingedly connected with one of the legs and the connecting element. The springy support of the handle against the housing is advantageously achieved using a compression spring located between the handle and the housing, and which is preferably located next to the two legs along at least a portion of its length. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The present invention is described in greater detail below with reference to an exemplary embodiment shown in the drawing. 
         FIG. 1  shows a simplified, schematic side view of a hand-held power tool; 
         FIG. 2  shows a partially cut-away, enlarged side view of a rear grip region of the hand-held power tool in  FIG. 1 , with no force applied to the handle; 
         FIG. 3  shows a view similar to  FIG. 2 , but after the hand-held power tool has been pressed against a work piece, with a compressive force applied to the handle; 
         FIG. 4  shows a partially cut-away, enlarged side view of the rear grip region of another exemplary embodiment of the hand-held power tool, with no force applied to the handle; 
         FIG. 5  shows a view similar to  FIG. 4 , but after the hand-held power tool has been pressed against a work piece, with a compressive force applied to the handle; 
         FIG. 6  shows a partially cut-away, enlarged side view of a rear grip region of a further exemplary embodiment of the hand-held power tool, with no force applied to the handle; 
         FIG. 7  shows a view similar to  FIG. 6 , but after the hand-held power tool has been pressed against a work piece, with a compressive force applied to the handle. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hand-held power tool  2 , which is depicted schematically in  FIG. 1  and is designed as a rotary hammer or a percussion hammer, is essentially composed of a housing  4 , a tool holder  6  for accommodating a tool  8 , and a drive device (not shown) enclosed by housing  4  that drives tool  8  installed in tool holder  6  in a rotating and/or percussive manner. 
     The drive device is composed—in a known manner—of an electric drive motor that drives tool holder  6  via reduction gears and a transmission in a rotating manner, and an impact mechanism that is also driven by the drive motor, and with which tool  8  in tool holder  6  may be acted upon with an impact force that acts in a working direction A of machine tool  2 . 
     Housing  4  is provided with a C-shaped handle  10  on its end face that faces away from tool holder  6 . C-shaped handle  10  is used—together with an additional handle  14  detachably installed near tool holder  6  or  12 —to grip and hold machine tool  2 . Together with housing  4 , C-shaped handle  10 , which extends beyond housing  4 , encloses a grip opening  16  for a hand of an operator and makes it easier for him to hold and guide machine tool  2 , particularly during vertical operation, i.e., in vertical working direction A and with tool  8  oriented downward, while additional handle  14  is used mainly when working direction A is oriented horizontally or flat. 
     As shown best in  FIGS. 2 through 7 , C-shaped handle  10  is composed mainly of a yoke part  18  and two legs  20 ,  22 , which are parallel to working direction A of machine tool  2 , the free ends of which extend through two openings  24 ,  26 —located adjacent to each other, with distance between them—in a wall part  28  of housing  4  that bounds grip opening  16  toward the front, and into a chamber  30  inside a grip region  32  of housing  4  that faces away from tool holder  6 . 
     Chamber  30 , which is enclosed by housing  4 , contains a helical compression spring  34  located between a part of C-shaped handle  10  and housing  4 , and at least a portion of which is preferably located next to legs  20 ,  22 . Spring  34  presses C-shaped handle  10 —when in the unloaded state—backward into a rear end position ( FIGS. 2 ,  4 , and  6 ), in which rear-facing stop surfaces  36  on legs  20 ,  22  of C-shaped handle  10  come in contact with complementary stop surfaces  38  of housing  4  that face forward, in working direction A, stop surfaces  38  being formed around openings  24 ,  26  on the inner side of wall part  28 . When a compressive force is applied to C-shaped handle  10 —as indicated by arrow F—by the operator&#39;s hand when tool  8  is pressed against a work piece, C-shaped handle  10  is pressed against the force of spring  34  in working direction A. When spring  34  is compressed in a front end position ( FIGS. 3 ,  5 , and  7 ), C-shaped handle  10  comes in contact via the front end faces of legs  20 ,  22  with a stop surface  40  that is perpendicular to the working direction, stop surface  40  being formed by an inner boundary wall  42  of chamber  30  that is parallel with wall part  28 . 
     To prevent the vibrations—caused, e.g., by the impact mechanism of the machine tool—of housing  4  from being transferred to C-shaped handle  10 —the vibrations not only being perceived as uncomfortable by the operator but also possibly resulting in injury after long-term exposure—the two legs  20  of handle  10  are not guided directly in housing  4 , nor are they connected directly with housing  4 . Instead, their connection with housing  4  is established via a coupling element  44  or  46 , which is hingedly connected to adjacent leg  20  or  22  and to housing  4 , and which, together with helical compression spring  34 , ensures that vibrations are decoupled between housing  4  and handle  10 . 
     To prevent C-shaped handle  10 —which is decoupled from housing  4 —from tilting when moved from a rear end position in the direction toward the front end position when force F is applied to handle  10  on only one side or not parallel to working direction A, the motions of legs  20 ,  22  relative to housing  4  are synchronized. This takes place, according to the present invention, with the aid of connecting element  48 , which connects the two coupling elements  44 ,  46  and ensures that the swivelling and rotary motion of coupling elements  44 ,  46  is synchronized and, therefore, that the linear motions of legs  20  and  22  of handle  10  hingedly connected to coupling elements  44  and  46  are synchronized. 
     With the exemplary embodiment of machine tool  2  presented in  FIGS. 2 and 3 , which includes a hollow C-shaped handle  10  that is open at the ends of legs  20 ,  22 , coupling elements  44 ,  46  are each composed of a two-armed lever  50 ,  52 , whose two lever arms  54 ,  56  and  58 ,  60  are oriented at nearly right angles to each other near a pivot axis  62  of lever  50 ,  52 . One lever arm  54  or  58  of each lever  50 ,  52  is located inside chamber  30 , which is enclosed by grip region  32  of housing  4 . When handle  10  is located in the center, lever arm  54  or  58  is located in the middle between the front and rear end positions, essentially perpendicular to working direction A of machine tool  2 , while second lever arm  56  or  60  of each lever  50 ,  52  extends through the open end face of adjacent leg  20  or  22  into hollow handle  10 , where the free ends of these lever arms  56 ,  60  are interconnected via connecting element  48 , but not with handle  10  or housing  4 . 
     Lever  50  (shown at the top in  FIGS. 2 and 3 ) is pivotably connected via its pivot axis  62  at the free end of adjacent leg  20  of C-shaped handle  10 , and at the free end of its lever arm  54  to a wall projection  64  of boundary wall  42 . Lever arm  56  inside handle  10  is bent nearly parallel to lever arm  54  as it extends into hollow handle  10 . Bent part  66  in the rear end position of C-shaped handle  10  is oriented nearly perpendicularly to working direction A. In contrast, the other lever  52  (shown at the bottom in  FIGS. 2 and 3 ) is hingedly connected at its pivot axis  62  to an adjacent wall projection  68  of boundary wall  42 . Its two lever arms  58 ,  60  are designed as straight lines, and lever arm  58  is pivotably and hingedly connected at a projection  70  of C-shaped handle  10  that extends perpendicularly to working direction A beyond the end face of leg  22  and into chamber  30 , projection  70  serving simultaneously as a support bearing for the rear end face of helical compression spring  34 . 
     Connecting element  48  has the shape of a longitudinally-extended, straight connecting rod, which is located in hollow yoke part  18  of C-shaped handle  10  and is oriented essentially perpendicular to working direction A of machine tool  2 . Its opposing end faces are each hingedly connected with the free ends of lever arms  56  and  60  of levers  50  and  52 . Pivot axes  62  of levers  50 ,  52  and the pivot joints at the free ends of lever arms  54 ,  56 ,  58 ,  60  are oriented perpendicularly to a plane passing through yoke  18  and legs  20 ,  22  of C-shaped handle  10 . 
     The width of legs  20 ,  22  and yoke part  18  of handle  10  is adapted to the shape and dimensions of the two levers  50 ,  52  such that they may swivel—when C-shaped handle  10  moves—between the front and rear end positions inside chamber  30  and hollow handle  10  along a swivel path that corresponds to the path of travel of handle  10 . 
     In contrast, in the exemplary embodiments of machine tool  2  with a solid C-shaped handle  10  depicted in  FIGS. 4 through 6 , coupling elements  44 ,  46  are designed as two circular disks  72  and  74 , each of which is rotatably supported on a wall projection  76 ,  78  of boundary wall  42  adjacent to the inner side of leg  20  or  22 , the rotation axes of disks  72 ,  74  extending through their centers. Both disks  72 ,  74  include—at a radial distance from their centers—a pivot pin  80  that extends over a broadside surface, and that rotatably engages in a complementary bore in adjacent leg  20  or  22  located near the free end. 
     The two disks  72 ,  74  are coupled via connecting element  48  such that a swiveling or rotary motion of one disk  72  or  74  results in a corresponding swiveling or rotary motion of the other disk  74  or  72 , i.e., a rotation around a related swivel angle. In this case as well, connecting element  48  is designed as a straight, longitudinally extended connecting rod  82 , the opposite end faces of which are hingedly connected to disks  72  and  74  and, in fact, at a radial distance from the center of disks  72 ,  74 , and at an angular distance of approximately 90 degrees from pivot pin  80 . In this case as well, the rotation axes of disks  72 ,  74  and the pivot axes of pivot pins  80  and the pivot points of connecting rod  82  on disks  72 ,  74  are perpendicular to a plane that passes through C-shaped handle  10 . 
     While connecting rod  82  in the exemplary embodiment shown in  FIGS. 4 and 5  is oriented perpendicularly to working direction A of machine tool  2 —its pivot points being located on the two disks  72 ,  74  behind the center of disks  72 ,  74 , as viewed in working direction A of machine tool  2 —in the exemplary embodiment shown in  FIGS. 6 and 7 , connecting rod  82  is slanted at a shallow angle toward working direction A of the machine tool. As viewed in working direction A of machine tool  2 , one of the end faces of connecting rod  82  is located in front of the center of adjacent disk  72 , and the other is located behind the center of adjacent disk  74 . 
     In both cases, the pivot points of connecting rod  82  on disks  72 ,  74  move—when C-shaped handle  10  moves—between its two end positions along a trajectory that is nearly perpendicular to working direction A or machine tool  2 , and they are displaced toward opposite sides of wall projections  76  and  78 . In contrast, pivot pins  80  move along a trajectory that is nearly parallel to the working direction of machine tool  2 .