Patent Abstract:
A hand-held power tool, has a housing, at least one partially hollow U-shaped C-shaped handle with a yoke part and two parallel leg parts and supported in a resilient manner such that the handle is movable relative to the housing in order to dampen vibrations, at least one coupling element accommodated at least partially inside the C-shaped handle to synchronize motion between the two leg parts and having a recess, and a switch arranged in a vicinity of the coupling element and having a switch housing extending in an interior of the handle and accommodated in the recess of the coupling element.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2006 051 924.8 filed on Nov. 3, 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 a hand-held power tool, in particular a rotary hammer and/or a percussion hammer, with a housing and a vibration-damped, U-shaped handle that is resiliently supported and is movable relative to the housing. 
     With hand-held power tools with an impact drive in particular, such as rotary hammers, chisel hammers, 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 its working direction, have usually been used to provide linear vibration damping of rotary hammers. This design is relatively complex and expensive, however. 
     Publication EP 1 529 603 makes known a hand-held power tool that includes a vibration-damped C-shaped handle that is supported against the housing via springs. With this hand-held power tool, extensions of two leg parts of the C-shaped handle extend into a cavity in the housing, where they act via connecting elements on swivel arms, the motion of which is damped via springs. To synchronize the motion of the swivel arms and, therefore, the two leg parts, the two swivel arms are connected via a coupling element designed as an axle. A switch for switching the hand-held power tool on and off is located inside the hollow handle. 
     Publication DE 101 38 123 A1 makes known a hand-held power tool of the type described initially with a vibration-damped C-shaped handle, with which one of the leg parts is supported against the housing via a spring, and with which the motion of the two leg parts is synchronized via two coupling elements, which are hingedly connected with the handle and the housing, one of which is accommodated in the interior of the hollow yoke part in a space-saving manner. 
     In addition, a hand-held power tool of the type described initially was proposed in the two unpublished German patent applications that belong to this applicant, with which two coupling elements are located inside the yoke part of a hollow C-shaped handle. 
     By accommodating one or more coupling elements in the interior of the hollow C-shaped handle, the amount of space required inside the housing of the hand-held power tool and, therefore, their overall length, may be reduced, which, in turn, enables the amount of force required to handle the hand-held power tool to be reduced. Previously, however, a design of this type was only possible with those hand-held power tools with which a switch was not provided on the C-shaped handle, since the space available inside of it was not sufficient to accommodate an inwardly extending housing of the switch or one or more coupling elements. 
     SUMMARY OF THE INVENTION 
     The object of the present invention, therefore, is to find a solution that makes it possible to equip the C-shaped handle of hand-held power tools of the type described initially with a switch without impairing the function of a coupling element located in the region of the switch. 
     In the present invention the coupling element is provided with a recess in the vicinity of the switch, into which a switch housing of the switch may extend into the interior of the C-shaped handle, and therefore the switch may be installed on the handle using simple means and without hindering the function of the coupling element. 
     According to a preferred embodiment of the present invention, the coupling element is designed as a hollow profile open on the side, along a portion of its length, while the rest of the coupling element may be designed as a solid component or as a hollow profile that is closed on all sides, in order to provide the coupling element with great bending resistance. 
     The coupling element is preferably designed as a rectangular box profile along at least a portion of its length, the opposite side walls of which are advantageously parallel with each other and are oriented toward adjacent outer sides of the switch housing, while the base of the box profile is located on the side of the coupling element facing away from the switch housing. In this manner, the switch housing may extend far into the coupling element, which has strong bending resistance despite its longitudinal extension, therefore allowing considerable contact forces to be transmitted from the C-shaped handle into the housing of the hand-held power tool. 
     According to a further advantageous embodiment of the present invention, the switch is located in the vicinity of a pivot joint of the coupling element, where it bears inside the handle and receives additional reinforcement due to the support, and where the path of travel of the coupling element during a motion of the C-shaped handle relative to the hand-held power tool is at a minimum, thereby enabling the penetration depth of the switch housing into the recess and, therefore, the depth of the recess, to be reduced. 
     To provide good support of the coupling element in the rocker pivot, the coupling element advantageously includes two flush pivot pins that are coaxial with the pivot axis of the rocker pivot, which extend beyond the opposite side walls of the box profile and into opposite bearing openings in the C-shaped handle. 
     The switch is preferably inserted into an opening in a front boundary wall of the C-shaped handle facing the housing of the machine tool, and includes an actuating element that extends beyond the yoke part of the C-shaped handle and is swivelable against the force of a spring relative to the switch housing, the actuating element extending into a grip opening between the C-shaped handle and the housing. 
    
    
     
       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 an enlarged sectional view along the line III-III in  FIG. 2 . 
     
    
    
     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 percussive manner. 
     The drive device is composed—in a known manner—of an electric drive motor that drives tool holder  6  in a rotating manner via reduction gears and a transmission, 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 auxiliary handle  14  that is detachably installed near tool holder  6  or  12 —to grip and hold machine tool  2 . Together with housing  4 , C-shaped handle  10  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 auxiliary handle  14  is used preferably when working direction A is oriented horizontally or flat. 
     C-shaped handle  10  is provided with a switch  18  on its side facing grip opening  16 , with which hand-held power tool  2  may be switched on and off without releasing handle  10 . 
     As shown best in  FIG. 2 , housing  4  includes two parallel projections  20 ,  22 , which project rearwardly beyond the rear end face of housing  4 , are rigidly connected with housing  4 , and extend into the hollow interior of C-shaped handle  10 . 
     C-shaped handle  10  is essentially composed of a hollow yoke  24  that extends perpendicularly to working direction A of hand-held power tool  2  and is gripped with one hand by the operator in order to use hand-held power tool  2 . C-shaped handle  10  is also composed of two hollow legs  26 ,  28  that extend parallel to working direction A and are open at their end faces adjacent to housing  4 , thereby enabling projections  20 ,  22  of housing  4  to enter legs  26 ,  28 . 
     To prevent the vibrations—caused, e.g., by the impact mechanism of machine tool  4 —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 ,  22  of housing  4  extend into hollow legs  26 ,  28  of C-shaped handle  10  with a great deal of lateral play S. In addition, C-shaped handle  10  does not bear directly against projections  20 ,  22  or housing  4 , but rather via a helical compression spring  30 , which serves to decouple vibrations between C-shaped handle  10  and housing  4 . 
     To prevent C-shaped handle  10 —which has been decoupled from housing  4  in this manner—from tilting while work is performed with the hand-held power tool in working direction A and a compressive force is applied to C-shaped handle  10 —this compressive force being introduced such that it is not entirely parallel to working direction A, or it is applied to C-shaped handle  10  on one side of a longitudinal central plane  32  ( FIG. 1 ) of hand-held power tool  2 —the motions of the two hollow legs  26 ,  28  along projections  20 ,  22  are synchronized with the aid of two coupling rods  34 ,  36 . 
     The two longitudinal coupling rods  34 ,  36  are accommodated in the hollow interior of yoke  24  of C-shaped handle  10  and are generally oriented transversely to working direction A and longitudinal central plane  32  of hand-held power tool  2 . Each of the two coupling elements  34 ,  36  is designed as a two-armed lever that is supported near its center in a pivot joint  38  or  40 , so that it may swivel relative to C-shaped handle  10 . The end face of each coupling element  34 ,  36  that points outwardly away from longitudinal central plane  32  is hingedly connected via a pivot joint  42  and  44  to the free end of adjacent projection  20  and  22 , while the opposite, inner end faces of coupling elements  34 ,  36  form a knuckle joint  46 . To form knuckle joint  46 , the end face of one coupling element  34  is designed as a fork  48 , into which a spherical wide section  50  on the end face of the other coupling element  36  engages in a movable manner. Knuckle joint  46  enables the two coupling elements  34 ,  36  to be displaced longitudinally to a certain extent relative to each other when they are swiveled around the swivel axes of pivot joints  38  and  40  when relative motion takes place between C-shaped handle  10  and housing  4 . 
     While coupling element  36  is designed as a solid coupling rod, which is provided with a wide section on its inner end face, as well as in the center and on the outer end face, in order to form pivot joints  40 ,  44 , coupling element  34  is designed—on a portion of its length between its outer end face that is hingedly connected to projection  20  and its inner, forked end face—as a hollow box profile that is open on one side and includes two parallel side walls  54  and a perpendicular base  56 , as shown in  FIG. 3 . In addition, pivot joint  40  includes a projection  51 —which extends into the hollow interior of C-shaped handle  10 —of a front boundary wall  52  of yoke  24  that faces housing  4 , while pivot joint  38  of coupling element  34  includes two opposing, flush, cylindrical bearing openings  62  in opposite boundary wall parts of C-shaped handle  10 , and two pivot pins  60  that extend outwardly beyond side walls  54  and extend into bearing openings  62 . 
     The two side walls  54  and base  56  border a recess  58 , which has a rectangular cross section and is open toward front boundary wall  52  of yoke  24 , and which accommodates switch housing  64  of switch  18 —which extends inwardly beyond boundary wall  52 —in a manner such that the swivel motion of coupling element  34  is not hindered by switch  18 . To this end, recess  58  extends away from pivot joint  38 —whose swivel axis  66  passes through switch housing  64 —toward both sides and beyond the opposite end faces of switch housing  64 . 
     To attach switch  18  to C-shaped handle  10  in such a manner that its switch housing  64  extends into the hollow interior of yoke  24  and/or into recess  58  of coupling element  34 , and an actuating element  68  of switch  18  that may be tilted or swiveled relative to switch housing  64  extends outwardly past boundary wall  52  and into grip opening  16 , switch housing  64  including—on its side adjacent to actuating element  68 —a cover plate  70 , the outer edge of which extends beyond the lateral sides and end faces of housing  64  and, when switch  18  is installed in C-shaped handle  10 , is inserted into a complementary recess  72  formed in an edge of an opening  74  in boundary wall  52  that serves to accommodate switch  18 . 
     To enable coupling elements  34 ,  36  and switch  18  to be installed in C-shaped handle  10 , C-shaped handle  10  is composed of two mirror-image half shells  76 ,  78 , which are joined after coupling elements  34 ,  36  and switch  18  are installed in one of the two half shells  76 ,  78 , which are then welded together along a central plane  80  of C-shaped handle  10 , as shown in  FIG. 3 . 
     The present invention may also be used in an analogous manner with a hand-held power tool whose C-shaped handle includes a coupling element that extends into the handle only partially, as does the C-shaped handle of the hand-held power tool described in DE 101 38 123 A1.

Technology Classification (CPC): 1