Patent Abstract:
A hammer drill ( 2 ) includes a clockwise and counterclockwise driven tool spindle ( 28 ), a drive pinion ( 70 ) operatively connectable with the tool spindle ( 28 ) for transmitting a torque thereto, a separate control handle ( 6 ) for selecting one of the hammer drill functions including a pure drilling operation, a pure percussion operation, and a rotary-percussion operation), and a switching device ( 8 ) which is adjustable in accordance with a position of the control handle ( 6 ) and which is shiftable by the control handle ( 6 ) in a clockwise rotation position for effecting a pure drilling operation in a clockwise direction and in a counterclockwise rotation position for effecting a pure drilling operation in a counterclockwise direction.

Full Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a hammer drill including a clockwise and counterclockwise driven tool spindle, a drive pinion operatively connectable with the tool spindle for transmitting a torque thereto, a separate control handle for selecting one of drill functions including a pure drilling operation, a pure percussion operation, and a drilling or rotary and percussion operation, and a switching device adjustable in accordance with the position of the control handle.  
         [0003]     2. Description of the Prior Art  
         [0004]     Hammer drills of the type described above are very operator-friendly because switching between all three drill functions with the same control handle is possible. Moreover, the control handle can be easily arranged in such a way that switching of the drill functions takes place at an easily accessible and well visible location.  
         [0005]     German Publication DE-195 45 260 discloses a hammer drill in which switching between a pure drilling operation, a rotary-percussion operation, and a pure percussion operation is effected with a single rotary switch. The rotary switch is connected with a rotatable body for joint rotation therewith. The rotatable body displaces a shifting bushing arranged on an intermediate shaft and shifting sleeve arranged on the tool spindle. The percussion mechanism of the hammer drill is actuated and deactuated dependent on the position of the shifting bushing. Simultaneously, dependent on the position of the shifting sleeve, the tool spindle rotates or is secured to the housing without a possibility of rotation. Further, the hammer drill has an actuation member which is provided on an on-off switch and which serves for switching between clockwise and counterclockwise rotation of the tool spindle by changing the polarity of the drive motor.  
         [0006]     The drawback of the known hammer drill consists in that a separate switch should be provided for effecting the clockwise and counterclockwise operations and which is poorly visible. Further, in such a hammer drill, because of two rotational directions of the motor, the fan likewise should be adapted for operation in opposite directions. This reduces the power of the fan and thereby its cooling effect.  
         [0007]     Accordingly, an object of the present invention is to provide a hammer drill in which the drawbacks of the known hammer drill are eliminated and the operating convenience is increased.  
       SUMMARY OF THE INVENTION  
       [0008]     This and other objects of the present invention, which will become apparent hereinafter are achieved by providing a hammer drill in which the switching device is shiftable by the control handle in a clockwise rotation position for effecting a pure drilling operation in a clockwise direction and in a counterclockwise rotation position for effecting a pure drilling operation in a counterclockwise direction.  
         [0009]     With such a switching device, the switching between clockwise and counterclockwise operations can be effected with the same control handle that is used for selection of an operational function, which insures a better handling of the hammer drill. Further, the switching between the clockwise and counterclockwise operations is clearly visible and, generally, the operating convenience of the hammer drill is increased.  
         [0010]     Advantageously, the switching device includes clockwise gear means and counterclockwise means for alternating forming a clockwise rotational connection and a counterclockwise rotational connection between the tool spindle and the drive pinion in the pure drilling operation. Such gear drive means for switching of a rotational direction can be particularly easy, in comparison with the switching of the rotational direction by changing the polarity of the drive motor, integrated in the switching device for performing an additional switching function. In addition, the switching of the rotational direction with the same function—selecting control handle reduces manufacturing and operational costs, which further increases the operating convenience of the hammer drill. Moreover, with switching of the rotational direction with drive gear means, the motor and the fan, which is driven by the motor, can be operated only in one direction. Thereby, the shape of the fan, in particular, the shape of the fan lamellas can be optimized in order to achieve a better cooling efficiency.  
         [0011]     Advantageously, the switching device is brought by the control handle in an additional position in which both the clockwise and counterclockwise drive gear means occupies a position in which both the clockwise rotational connection and the counterclockwise rotational connection between the drive pinion and the tool spindle are broken, and the tool spindle is rotatable relative to a hammer drill housing.  
         [0012]     Thus, the control handle provides an adjusting or set-up position of the switching device in which the tool used in the hammer drill, e.g., a flat or spade-shaped chisel, can be rotated relative to the hammer drill into a desired position.  
         [0013]     According to a particular advantageous embodiment of the present invention, the clockwise drive gear means and the counterclockwise gear means include, respectively, a first drive gear and a second drive gear both driven by the drive pinion and both having, respectively, tooth surfaces arranged opposite each other. In this way, an easy switching between clockwise and counterclockwise rotational directions with the control handle can be effected.  
         [0014]     Advantageously, both first and second drive gears are permanently engaged with the drive pinion, and are alternatively rotatably connected with the tool spindle by the switching device. Thereby, an easy and disturbance-free switching between clockwise and counterclockwise rotational directions becomes possible.  
         [0015]     Advantageously, the switching device has a sleeve-shaped shifting member for rotatably connecting the tool spindle alternatively with one of the first and second drive gears. The shifting member is supported on the tool spindle for joint rotation therewith and for axial displacement relative thereto. Thereby, different positions of the switching device can be precisely and reliably retained.  
         [0016]     Advantageously, the switching device has a chiselling position in which a pure chiseling operation takes place in which the tool spindle is operatively connected to the hammer drill housing without a possibility of rotation relative thereto. Thereby, in a simple way, rotation of a chisel tool during a chiseling operation is prevented so that a precise chiseling operation can be carried out.  
         [0017]     Advantageously, the shifting member has engagement means engaging matching engagement means fixedly secured to the housing in the chiseling position of the switching device for preventing rotation of the tool spindle relative to the housing. Thereby, a particularly reliable securing of a chisel tool against rotation is achieved.  
         [0018]     It is particularly advantageous when the percussion mechanism is operated by an eccentric member driven by a drive member. Between the eccentric member and the drive member, there is provided separable coupling means operated by the switching device. Thereby, an easy actuation and deactivation of the percussion mechanism with the switching device is achieved.  
         [0019]     It is advantageous when the coupling means is formed as a coupling member permanently rotatably connected with one of the eccentric member and the drive member and rotatably disconnected from another of the eccentric member and the drive member in a switch-off position. Thereby, a disturbance-free actuation and deactuation of the percussion mechanism becomes possible.  
         [0020]     According to a particularly advantageous embodiment of the coupling means, the coupling member has a ramp profile that can be abutted by a movable bearing region of the switching device and which presses the coupling member back in an axial direction upon its rotation. Thereby, in a simple way, a separation movement of the coupling member for decoupling the eccentric member from the drive member is generated.  
         [0021]     Advantageously, the bearing region is formed on a shift plate supported in the hammer drill for linear displacement and which is displaceable by the control handle. This likewise insures a disturbance-free actuation and deactuation of the percussion mechanism.  
         [0022]     It is particularly advantageous when the shift plate is translationally connected with the sleeve-shaped shifting member of the switching device. Thereby, the shift plate is used for both switching the drive gears and for actuation and deactuation of the percussion mechanism, which noticeably simplifies the construction of the switching device and reduces the manufacturing costs.  
         [0023]     Further, the shift plate advantageously has a tooth profile connected, directly or indirectly, with a rotatable matching tool profile provided on the control handle. This insures a particularly precise shifting of the switching device and thereby a reliable switching between the different hammer drill functions.  
         [0024]     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  
       [0025]     The drawings show:  
         [0026]      FIG. 1 a  side view of a hammer drill according to the present invention;  
         [0027]      FIG. 2 a  side, partially cross-sectional view of the eccentric drive of the hammer drill shown in  FIG. 1  in its operational position in a set-up according to  FIGS. 8 and 9 ;  
         [0028]      FIG. 3 a  side, cross-sectional view of a switching device with the eccentric drive according to  FIG. 2  in a set-up according to  FIG. 5 ;  
         [0029]      FIG. 4 a  side view of the shifting member of the switching device shown in  FIG. 3 ;  
         [0030]      FIG. 5 a  side, partially cross-sectional view of the switching device shown in  FIG. 3  in a chiseling position;  
         [0031]      FIG. 6 . a side, partially cross-sectional view of the switching device shown in  FIG. 3  in a position during shifting to the chiseling position;  
         [0032]      FIG. 7 . a side, partially cross-sectional view of the shift in device according to  FIG. 3  in a position for effecting a drilling and percussion operational;  
         [0033]      FIG. 8 . a side, partially cross-sectional view of the switching device shown in  FIG. 3  in a clockwise drilling position; and  
         [0034]      FIG. 9 a  side, partially cross-sectional view of the switching device shown in  FIG. 3  in a counterclockwise drilling position.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0035]     A hand-held, electrically driven hammer drill  2  according to the present invention, which is shown in  FIG. 1 , has a housing  4  on which there is provided a control handle  6  in form of a rotary switch for setting up a desired drill function. The control handle  6 , together with an arrow symbol P, can be rotated relative to the housing  4 , to one of five switching positions which are shown with corresponding symbols on the housing  4 . Each switching position corresponds to a different drill function. There are provided chiseling position M, shifting-to-chiseling position MV, rotary-percussion position HB, clockwise drilling position RB, and counterclockwise drilling position LB.  
         [0036]     As shown in  FIGS. 2 and 3 , the control handle  6  is used for actuation for a switching device  8 . The switching device  8  has a pinion  10  connected with the control handle  6  for joint rotation therewith and engaging a tooth profile  12  provided on a shift plate  14 . The shift plate  14  has an elongate opening  16  through which a guide member  18 , which is fixedly secured to the housing extends. In this way, the shift plate  14  is supported for a linear displacement relative to the housing  4  along a displacement path SR.  
         [0037]     At its rear, with respect to the operational direction AR of the hammer drill  2 , end, the shift plate  14  of the switching device  8  forms a bearing region  20 . At a corresponding positioning, the shift plate  14  lies on a ramp profile  22  that is formed on a displaceable coupling member  24  of an eccentric drive  26 .  
         [0038]     The eccentric drive  26  forms part of a percussion mechanism (not shown in detail) that applies blows to a tool spindle  28  in the operational direction AR upon its reciprocal movement during chiseling and rotary-percussion operations. The eccentric drive  26  includes an eccentric member  30  which, upon its rotation applies a reciprocating movement to a piston rod  32  in the operational direction AR.  
         [0039]     The coupling member  24  connects the eccentric member  30  with a drive member  34  for joint rotation therewith. The drive member  34  is permanently engaged with a pinion  38  of a motor  36 . As shown in  FIG. 2 , the coupling member  24  engages, with a rib  40 , in a groove  42  that is formed in an axle  44  connected with the eccentric member  30  for joint rotation therewith. The drive member  34  is rotatably supported on the axle  44 . The torque transmission from the drive member  34  to the eccentric member  30  takes place only when the coupling member  24  is displaced along the groove  42  into a position in which an engagement member  46  of the coupling member  24  engages the matching engagement element  48  of the drive member  34 . The coupling member  24  is preloaded in the engagement position with a spring  50 .  
         [0040]     As further shown in  FIG. 3 , the shift plate  14  has, at its front, with respect to the operational direction AR of the hammer drill  2 , end, an adjusting region  52  that is translationally connected with a sleeve-shaped shifting member  54  of the switching device  8 . E.g., the adjusting region  52  applies a sidewise pressure to the shifting member  54  when, simultaneously, a biasing force is applied to its opposite side. As shown in  FIG. 3 , the adjusting region  52  is engageable with the shifting member  54  on both side of the operational direction AR. In this way, the shifting member  54  is displaceable on the tool spindle  28  by the adjusting region  52  of the shift plate  14 .  
         [0041]     The shifting member  54  is shown in detail in  FIG. 4 . As shown in  FIG. 4 , there are provided, on the circumferential surface of the shifting member  54 , engagement bays  56 . There are further provided, on one end surface of the shifting member  54 , engagement cams  58  and on the other, opposite end surface thereof, there is provided a crown formed of engagement elements  60 .  
         [0042]     As shown in  FIGS. 2-3 , in a respective position of the shifting member  54 , the crown with engagement elements  60  can be brought into engagement with matching engagement elements  62  which are formed on an intermediate ring  64  secured to the housing  4 . The shifting member  54  is supported on the tool spindle  28  for joint rotation therewith. Thereby, the tool spindle  28  can be secured against rotation by the shifting member  54  when the engagement elements  60  to engage the matching engagement elements  62  that are provided on the intermediate ring  64  which is fixedly secured to the housing  4 .  
         [0043]     The shifting member  54  also connects the tool spindle  28  with first or second drive gear  66 ,  68  which are connected by a drive pinion  70  with the motor pinion  38 . The first drive gear  66  has a tooth surface  67  that is arranged opposite a tooth surface  69  of the second drive gear  68 . The drive pinion  70  extends between the two surfaces  67 ,  69  and permanently engages the first and second drive gears  66 ,  68 , forming a clockwise drive with the first drive gear  66  and counterclockwise drive with the second drive gear  68 .  
         [0044]      FIGS. 5-9  show functioning of the switching device  8  in separate shift positions.  
         [0045]      FIG. 5  shows the switching device in a position corresponding to chiseling operation of the hammer drill  2 , which position is also shown in  FIG. 3 . This position is obtained by switching the control handle  6  into a chiseling position M. The switching of the control handle  6  leads to rotation of the rotation of the pinion  10  which is engaged with a tooth profile  12  of the shift plate  14 . As a result of rotation of the pinion  10 , the shift plate  14  is displaced in the displacement direction SR until it reaches its outmost position in the operational direction AR. Upon its displacement, the shift plate  14  displaces, with its adjusting region  52 , the shifting member  54  in the operational direction AR, resulting in engagement of the elements  60  with the engagement elements  62  of the intermediate ring  64 . This results in connection of the tool spindle  28  with the housing  4 , so that the tool spindle  28  cannot rotate relative to the housing  4 . In this position of the spindle  28 , the drive gears  66 ,  68  are rotationally decoupled from the shifting member  54 , and no rotational coupling exists between the drive pinion  70  and the tool spindle  28  with which a torque can be transmitted to the tool spindle  28 .  
         [0046]     Simultaneously, the displaceable coupling member  24  of the eccentric drive  26  is biased by the spring  50  into engagement with the drive member  34  in this position of switching device  8 . With the motor  36  being turned on, a torque is transmitted to the eccentric member  30  via the motor pinion  38 , drive member  34 , coupling member  24 , and the axle  44 , and the eccentric member  30  actuates the percussion mechanism that is (not shown).  
         [0047]     In this position, the hammer drill  2  has a pure chiseling function at which the tool spindle  28  performs only the percussion movement in the operational direction AR, without being rotated.  
         [0048]     Upon rotation of the control handle  6  into the shifting-to-chiseling position MV, the switching device  8  assumes a position shown in  FIG. 6 . In this position of the switching device  8 , the shift plate  14  is displaced by the pinion  10  in a direction opposite the operational direction AR. Simultaneously, the shifting member  54  becomes disengaged from the intermediate ring  64 . In this position, the shifting member  54  is rotationally decoupled from the drive gears  66 ,  68 , and no torque is transmitted to the tool spindle  28 .  
         [0049]     In this position, the hammer drill  2  has a shifting-to-chiseling function at which a chisel (not shown) is inserted into the tool spindle  28  that can be pivoted to any arbitrary position. Thereby, e.g., a flat or spade-shaped chisel can be so aligned with respect to the hammer drill  2  that the hammer drill  2  is conveniently held during operation.  
         [0050]     Upon rotation of the control handle  6  to the rotary-percussion position, the switching device  8  occupies a position shown in  FIG. 7 . In this position of the switching device  8 , the shift plate  14  is displaced even further in the direction opposite the operational direction AR, and the shifting member  54  is displaced so far that the engagement cams  58  engage the matching engagement profile  72  of the first drive gear  66 . In this way, a clockwise rotational connection is formed between the motor pinion  38  and the tool spindle  28  via the drive pinion  70 , the first drive gear  66 , and the shifting member  54 , which insures a clockwise rotational movement of the tool spindle  28 . Simultaneously, the motor  36  also drives the percussion mechanism.  
         [0051]     In this position, the hammer drill  2  performs both drilling and percussion functions, so that both clockwise rotation and percussion movement in the operational direction AR are imparted to the tool spindle  28 .  
         [0052]     Upon rotation of the control handle  6  to the clockwise drilling position RB, the switching device  8  occupies a position shown in  FIG. 8 . In this position of the switching device  8 , the clockwise rotational connection of the tool spindle  28  with the motor pinion  38  is retained, but the shift plate  14  is displaced so far in the direction opposite the operational direction AR that its bearing region  20  abuts the ramp profile  22 . During the rotation of the eccentric drive  26 , the coupling member  24  applies pressure to the bearing region  20  only through the ramp profile  22  and is displaced out of the engagement with the drive member  34  against the biasing force of the spring  50 . In this way, the eccentric member  30  becomes rotationally disengaged from the drive member  34 , and the percussion mechanism is deactivated.  
         [0053]     In this position of the switching device  8 , the hammer drill  2  has a clockwise drilling function at which the tool spindle  28  performs a simple clockwise rotation.  
         [0054]     Upon rotation of the control handle  6  to the counterclockwise rotation position LB, the switching device  8  occupies a position shown in  FIG. 9 . In this position of the switching device  8 , the eccentric member  30  remains rotationally decoupled from the drive member  34 . The shifting member  54  is in its outmost position in the direction opposite the operational directional AR. In this position of the shifting member  54 , the engagement cams  58  are disengaged from the matching engagement profile  72  of the first drive gear  66 , and only the engagement bays  56  form an engagement connection with the matching engagement profile  74  of the second drive gear  68 . Thereby, only a counterclockwise rotational connection is formed between the motor pinion  38  and the tool spindle  28  via the drive pinion  70 , the second drive gear  68 , and the shifting member  54 , which results in the counterclockwise rotation of the tool spindle  28 .  
         [0055]     In this position of the switching device  8 , the hammer drill  2  has a counterclockwise drilling function at which the tool spindle simply performs a counterclockwise rotational movement.  
         [0056]     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 limited 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.

Technology Classification (CPC): 8