Abstract:
A portable hand-held power tool ( 2 ), especially in the form of a drilling or chisel hammer, includes a drive assembly ( 8 ) located in the tool housing ( 10 ) for driving a tool spindle ( 4 ) along an operational axis (A), a first handle ( 16 ) which is rotatable around a first pivotal axis (S 1 ) by a first handle suspension ( 22 ), a second handle ( 20 ) located on the opposite sides ( 14.1, 14.2 ) of the housing which is rotatable around a second pivotal axis (S 2 ) by a second handle suspension ( 24 ), and spring elements for retaining the handles ( 16, 20 ) in their initial position, with the first and second handle suspensions ( 22, 24 ) extending partially circumferentially about the drive assembly ( 8 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a portable hand-held power tool, especially in the form of a drilling or chisel hammer and including a drive assembly for driving a tool spindle along an operational axis, which comprises a drive assembly in the form of an electric motor and a movement converter in the form of a percussion mechanism, if necessary in combination with a transmission. The drive assembly is located in the tool housing. Further, the hand-held power tool includes a first handle pivotable by a first handle suspension around a first pivotal axis, and a second handle pivotable around a second pivotal axis by a second handle suspension. Both handles extend from the opposite sides of the housing and are respectively held in their initial position by spring means. 
     2. Description of the Prior Art 
     Hand-held power tools of the type discussed above generate strong vibrations during operation along the operational axis in the housing. As a result of the spring-loaded handle suspensions, these vibrations are transmitted at considerably reduced intensity to the handles. 
     From U.S. Pat. No. 4,576,241, a pneumatic chisel and drilling hammer is known in which two handles project from opposite sides of the housing. Both handles are provided at the free ends of levers, pivotally supported at the head of the housing. Furthermore, between the levers and the housing, respective helical springs are provided, which extend parallel to the operational axis, which insulate the corresponding handles from the head of the housing against vibrations acting in the direction of the operational axis. 
     In this case, the head and the handle assembly are formed as an assembly unit, in order to enable their retrofitting at the existing chisel or drilling hammer. 
     This type of handle assembly, however, has the disadvantage that the constructional length of the disclosed tool increases considerably at the end remote from the working tool. In particular, with electropneumatic hand-held power tool, which, in addition to a percussion device and, possibly, an additional transmission, also includes a drive motor in the housing, the increased constructional length at the remote end of the housing would result in a very inconvenient form of a hand-held power tool that would not allow comfortable handling. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to avoid the disadvantages discussed above in a portable hand-held power tool with spring-loaded handles, and in particular, to ensure a compact form of a hand-held power tool with an electropneumatic drive. 
     According to the invention, this and other objects of the present invention, which will become apparent hereinafter, are achieved in that both handle suspensions extend over both spacial axes extending transverse to the operational axis, sectionwise around the drive assembly, i.e., that the first handle suspension and the second handle suspension partially circumferentially surround the drive assembly. For this purpose, the handle suspensions, for example, can include two forked arms or only one bent arm, which extends around the handle suspension. Consequently, the handles with the respective related handle suspensions can easily be arranged, with respect to the operational axis at the height of the drive assembly, which includes an impact device, a drive motor, and, if necessary, a transmission, which can be accommodated in an interior of the housing. Since the handle suspensions in certain regions can be extended around the drive assembly, the handle suspensions can be so arranged in the housing in such a way that they will not cause or cause only a minor additional constructional length. In this way, a compact hand-held power tool is obtained in spite of the spring-loaded suspension of both handles, which can be handled comfortably. 
     According to an advantageous embodiment of the present invention, a first damping body is provided between the first handle suspension and the second handle suspension, which forms a first end stop against which the first handle suspension can be put up and a second end stop against which the second handle suspension can be put up. Consequently, at extreme load conditions of the hand-held power tool, at which a pivot range of the handle suspensions provided for isolating the vibration can be exceeded, the pivot range is limited by a damping end stop. Consequently, in the case of extreme loads, only noticeably reduced vibrations are transmitted from the hand-held power tool to the handle. 
     Advantageously, both a pivot motion of the first handle suspension and a pivot motion of the second handle suspension in both directions are limited by the damping body, as a result of which both end stops of the handle suspensions have damping properties, which reduces the energy of the vibrations which are transferred to the handles in the case of extreme loads. 
     Advantageously, the damping body is diamond-shaped in cross-section, as a result of which the handle suspensions in both directions can be put up against opposite surfaces of the one-piece damping body. In this way, handle suspensions can support each other on both sides of the end stops by using washers as damping bodies and, thus, reducing energy. Furthermore, this produces a highly compact and stable form of the damping body. 
     Advantageously, the handle suspensions each include a fork-shaped support which is connected, at a first side of the drive assembly and at a second side of the drive assembly opposite the first side, respectively, with a pivot support around a respective pivot axis. In this way, the handles can be so arranged that they intersect in the longitudinal direction of the operational axis. The two-side encompassing of the drive assembly provides for a particular stable pivotal support of the handle suspensions with respect to the remainder of the hand-held power tool. 
     Advantageously, the pivot axes are spaced from respective effective application points, at which a contract pressure is applied by the operator to the respective handle, by a distance of 13 to 19 cm. The effective application point, for example, essentially corresponds to a geometric center of the handle. Consequently, this produces a comfortable holding of the hand-held power tool with good vibration reduction at the handles. By maintaining a distance in the range between 15 and 18 cm, the vibration transmission to the handles can be reduced to a minimum intensity. 
     Advantageously, elastomer rings are provided between the pivot axes and the handle suspensions, respectively, whereby a primary vibration transmission to the handle assembly can be markedly reduced by the damping characteristics of the elastomer rings. 
     It is advantageous when there are provided a first damping body at the first side of the drive assembly and a second damping body at the second side of the drive assembly. This produces a two-part end stop for both handle suspensions in two pivot directions, respectively, which can be arranged geometrically. In this way, the forces or torques to be absorbed by the handle suspensions can be reduced considerably. 
     In a particularly advantageous embodiment, the spring means includes two helical springs, which are provided, transversely to the operational axis, respectively, between spring supports, which are solidly fixed to the housing, and a respective handle suspension. Consequently, only a very small additional construction space is required for the spring means, as the result of which a more compact design of the hand-held power tool is possible overall. 
     The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  shows a schematic view of a hand-held power tool with a vibration-reducing handle assembly according to the present invention; and 
         FIG. 2  shows a perspective view of the handle assembly according to  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a portable hand-held power tool  2  in the form of an electropneumatically operated chisel hammer, which carries a tool holder  6  on a tool spindle  4  to which blows are imparted by a drive assembly  8 , not shown in detail, along an operational axis A. 
     As an alternative to the design of the chisel hammer, the hand-held power tool  2  can also be formed as a drilling hammer or a combination chisel and drill hammer, in which the tool holder  6  in addition to being imparted with percussion motion, is also imparted with a rotating motion around the operational axis A. In this case, the drive assembly  8  comprises an additional transmission (not shown in detail). 
     The hand-held power tool  2  comprises a tool housing  10  in which the drive assembly  8  is located. Furthermore, a handle assembly  12  is provided, which comprises a first handle  16  projecting from a first side  14 . 1  of the housing  10 , which is provided with a first effective point of application G 1  which is formed by a geometric center of the handle. On the first handle  16 , a push button  18  is provided for activating the drive assembly  8 . Furthermore, the handle assembly  12  comprises a second handle  20  which projects from a second side  14 . 2  of the housing  10  opposite the first side  14 . 1  and defines a second effective point of application G 2 , which is formed by a geometric center of the handle. 
     Further, the first handle  16  is rotatable via a first handle suspension  22  around a first pivot axis S 1 , which is formed by a first pivot support  21 . 1 , and the second handle  20  is rotatable via a second handle suspension  24  around a second pivot axis S 2 , which is formed by a second pivot support  21 . 2 , along a path of motion B 1  and B 2 , respectively. The pivot supports  21 . 1 ,  21 . 2  essentially are designed as pins solidly fixed to the housing, which project through the drive assembly  8 . As an alternative to the illustrated embodiment, both handle suspensions  22 ,  24  can be pivotally supported on a common pivot support (not shown), which essentially is formed by a single pin projecting through the drive assembly  8 . 
     A distance a between the first effective point of application G 1  and the first pivot axis S 1 , as well as between a second effective point of application G 2  and a second pivot axis S 2  in this case amounts to between 13 and 19 cm, respectively, especially to 15 and 18 cm. Furthermore, vibration-damping elastomer rings  22  are provided between the pivot axes S 1 , S 2  and the respective handle suspension  22 ,  24 , as is illustrated in  FIG. 2 . 
     Furthermore, as is disclosed especially in  FIG. 2 , the first handle suspension  22  comprises a fork-shaped branching first support  25  at the ends of which two first application arms  26  are provided. These first application arms  26  essentially extend transversely to a longitudinal axis L 1  of the first handle  16  and form an upper application region  28 . 1  and a lower application region  28 . 2 . The application regions  28 . 1 ,  28 . 2  abut, respectively, correspondingly arranged, first upper end stop surface  30 . 1  and a first lower end stop surface  30 . 2  of a first damping body  32 . 1  and a second damping body  32 . 2 , which are made of elastomer. For this purpose, both damping bodies  32 . 1 ,  32 . 2  essentially are diamond-shaped, in which the first damping body  32 . 1  is positioned at a first side  34  of the drive assembly  8  and the second damping body  32 . 2  is positioned at a second side  36  of the drive assembly  8 . 
     On the side remote from the handle suspension  22 , the damping bodies  32 . 1 ,  32 . 2  also comprise second upper end stop surfaces  38 . 1  and second lower end stop surfaces  38 . 2  which corresponding upper application regions  40 . 1  and lower application regions  40 . 2  of the second handle suspension  24  abut. Further, the application regions  40 . 1 ,  40 . 2  are formed on second application arms  42  and are held, at the ends of a fork-shaped branched second support  44 , essentially transversely to a longitudinal axis L 2  of the second handle  20 . 
     Furthermore, a helical spring  48  of spring means  46  engages, respectively, at least one of the first application arms  26  and at least one of the second application arms  42 . As shown in  FIG. 1 , the helical spring  48  extends transverse to the operational axis A and is supported on spring supports  50  fixedly secured to the housing. As an alternative, the helical springs  48  at both ends can be supported at one of the handle suspensions  22 ,  24 . In each case, the handle suspensions  22 ,  24 , or rather the handles  16 ,  20  attached thereto, are preloaded in an initial position, in which, for example, the upper application regions of application  28 . 1 ,  40 . 1  abut the upper end surface  30 . 1 ,  38 . 1 , as shown in  FIGS. 1 and 2 . 
     During the operation, a contact pressure D is applied in the direction of the operational axis A, while at the same time, the drive assembly  8  is actuated via the push button  18 . The pulse-like application of blows to the tools spindle  4  and holding fixture  6 , as well as the counter forces generated by a to-be-treated workpiece (not shown) generate vibrations in the hand-held power tool  2 , which, in particular, act in the direction of the operational axis A. 
     The vibration-damping elastomer rings between the pivot axes S 1 , S 2  and the handle suspensions  22 ,  24  ensure a reduced primary vibration transmission to the handles  16 ,  20 . 
     The spring means  46  are so designed that with a regular contact pressure D, all application arms  26 ,  42  are spaced from respective end stop surfaces  30 . 1 ,  30 . 2 ,  38 . 1 ,  38 . 2 , and both handle suspensions  22 ,  24  are able to rotate freely around the respective pivot axes S 1  or S 2  along the respective paths of motion B 1 , B 2 , in order to uncouple the handles  16 ,  20  from the housing  10  in terms of the vibrations occurring along the operational axis A. 
     In exceptional cases, at a particularly high contact pressure D or particularly high reaction forces of the treated workpieces, the paths of motion B 1 , B 2  are extended by the stronger vibrations to such an extent that the upper application regions  28 . 1 ,  40 . 1  ultimately come in contact with the lower application regions  28 . 2 ,  40 . 2  at the respective damping bodies  32 . 1 ,  32 . 2 . Also in this case, the vibrations, which are transmitted from the housing  10  or from the drive assembly  8 , to the handle assembly  12 , are noticeably reduced by the damping effect of the damping bodies  32 . 1 ,  32 . 2 . 
     The essentially diamond-shaped form of the damping bodies  32 . 1 ,  32 . 2  and the matching shape of the application arms  26 ,  42  result in the upper application regions  28 . 1 ,  40 . 1  being simultaneously pressed against the upper end stop surfaces  32 . 1 ,  38 . 1  and the lower application regions  28 . 2 ,  40 . 2  being pressed simultaneously against the lower end stop surfaces  32 . 2 ,  38 . 2 . 
     This has the effect that the press-on forces of both handle suspensions  22 ,  24 , depending on the nature and positioning of the damping bodies  32 . 1 ,  32 . 3 , cancel each other out. 
     Further, the fork shape of the supports  25 ,  44  enable an optimized positioning of the handles  16 ,  20  with stable mounting. The axial positioning at the height of the drive assembly  8  provides for a compact form and a good balance of the hand-held power tool  2 . The radial distance of the effective points of application G 1 , G 2  of 15 to 18 cm to the respective pivot axis S 1 , S 2  guarantees a particularly low vibration transmission. 
     Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be ended to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.