Abstract:
The present invention relates to a drilling hammer comprising a hammer tube ( 13 ) that is rotationally drivable inside a housing ( 10 ), a striking tool ( 14 ) located in the hammer tube ( 13 ) and provided with a piston ( 15 ) that can driven with a reciprocating motion, and an operating mode change-over switch ( 35 ) for the “impact drilling” and “chiseling” operating modes. The hammer tube ( 13 ) is decoupled from its rotary drive when in the “impact drilling” operating mode and is secured in the housing ( 10 ) in a non-rotative manner when in the “chiseling” operating mode. To obtain a switching mechanism ( 37 ) of the operating mode change-over switch ( 35 ) having a very flat design and requiring little installation space, an actuator ring ( 48 ) is fixed on the hammer tube ( 13 ) in an axially displaceable and torsion-proof manner, the actuator ring including at least one radially projecting locking spline ( 51 ) on its outer side facing away from the hammer tube ( 13 ), the locking spline being capable of engaging in at least one axial recess ( 52 ) in the gearbox and in locking toothing ( 53 ) in the housing. Rotational motion of a control button ( 36 ) of the operating mode change-over switch ( 35 ) is converted to axial displacement of the actuator ring ( 48 ) on the hammer tube ( 13 ) by the switching mechanism ( 37 ). In addition, the operating mode change-over switch ( 35 ) can be used to activate a “drilling” operating mode, in which the striking tool ( 14 ) is decoupled on the drive side.

Description:
BACKGROUND INFORMATION  
       [0001]     The present invention is directed to a drilling hammer according to the definition of the species of Claim  1 .  
         [0002]     It is commonplace today to equip drilling hammers having a certain rating such that they can be used in the “impact or hammer drilling” operating mode, in which the striking tool hammers the work piece in the axial direction while the tool is simultaneously started rotating using the tool holder, and they can be used in the “chiseling” operating mode, in which only the striking tool is activated and the rotational drive for the tool holder is turned off. Since a single electric motor drives, via a gear unit, a hammer tube that is connected with the tool holder in a torsion-proof manner, and it drives the striking tool via a crank driving mechanism, the piston of which makes a reciprocating stroking motion in the hammer tube and acts on a beater which, in turn, transfers the impacts to the end of the tool via a snap die, an operating mode change-over switch is provided that separates the hammer tube from the gear unit in the “chiseling” operating mode and secures it against rotation in the housing. In this mode, the rotatably supported driven gear of the gear unit encompassing the hammer tube is separated from the hammer tube.  
       ADVANTAGES OF THE INVENTION  
       [0003]     The drilling hammer according to the present invention having the features of Claim  1  has the advantage that the switching mechanism of the operating mode change-over switch is very flat in design and the axial extension of the operating mode change-over switch can be kept small due in particular to a narrow actuator ring. The flat design allows the housing cover on which the manually operated control button is mounted to have a low profile and the width across corners of the drilling hammer, i.e., the distance between the center of the switching mechanism and the upper edge of the housing, to be kept small. A single locking spline is sufficient to establish a torsion-proof connection between the actuator ring fixed on the hammer tube in a torsion-proof and axially displaceable manner and the driven wheel of the gear unit. Preferably, a large number of locking splines distributed around the circumference of the actuator ring is provided, the locking splines being axially insertable into a correspondingly large number of axial recesses in the driven wheel. As a result of the large number of locking splines and axial recesses, the actuator ring—which is made of metal—can transfer higher torque, and may also be made of plastic. In addition, given the non-aligning orientation of locking splines and axial recesses, a very small path of rotation of the hammer tube is required to snap the actuator ring into the drive wheel. If the guide splines on the actuator ring provided for a torsion-proof connection and guide grooves in the hammer tube are equidistant, the actuator ring can be slid onto the hammer tube in any relative position, which makes installation easier. The switching mechanism can be designed to be very compact and stable despite the small overall size, thereby ensuring a long service interval.  
         [0004]     Advantageous further developments and improvements of the drilling hammer indicated in Claim  1  are possible due to the measures listed in the further claims.  
         [0005]     According to an advantageous embodiment of the present invention, the actuator ring is located on the side of the driven wheel facing away from the control button and is connected in a fixed manner—underneath the drive wheel and past it—with a coupling ring slid onto the hammer tube on the other side of the driven wheel, the coupling ring being coupled to the control button such that switching the control button brings about an axial displacement of the actuator ring. Due to this structural design, the switching mechanism on the hammer tube is located under the driven wheel of the gear unit so that the width across corners of the drilling hammer is determined only by the outer diameter of the driven wheel—which is typically designed as a ring gear—and is minimized by it.  
         [0006]     According to an advantageous embodiment of the present invention, the connection with the coupling ring, which is preferably made of plastic, is realized using two cantilevers, which extend integrally with the coupling ring axially away from said coupling ring and accommodate the actuator ring in recesses located near its ends. The actuator ring can be installed easily by pressing the two elastically outwardly preloaded cantilevers together. The circumferential play of the cantilevers is kept greater than that of the actuator ring on the hammer tube, so that the cantilevers need not transfer any torque.  
         [0007]     According to an advantageous embodiment of the present invention, the coupling ring is coupled to the control button via a shift fork that is guided with a projection in an annular groove in the coupling ring, whereby the coupling takes place via a synchronizing spring retained on the shift fork and an eccentric pin located on the control button, on which said eccentric pin the legs of the shifter fork bear in a non-positive manner at diametral points. The large synchronizing spring allows the operating mode change-over switch to be changed over easily and reliably. The shift fork and the coupling ring can be fabricated economically out of plastic. The size of the control button makes operation easier and also permits handling using work gloves.  
         [0008]     According to an advantageous embodiment of the present invention, a further setting position for the “drilling” operating mode is assigned to the control button; in this mode, the striking tool is decoupled from its drive when the hammer tube rotates. This decoupling is not brought about by the axial displacement of the actuator ring on the hammer tube, but rather by the displacement—at a right angle thereto—of a switching mechanism part that separates a coupling located in the drive chain of the striking tool. To this end, a switching ramp which extends across an angle of rotation is configured on the control button, preferably on its underside, the switching ramp rising in the direction of the axis of rotation of the control button. The switching mechanism part is preferably configured as an axially displaceable separating slide, which bears against the switching ramp in a non-positive manner and against a displaceable coupling part of the coupling that, when displaced axially against the force of a coupling spring, the coupling can be released. The low spring force of the coupling spring and a spring provided on the separating slide for bearing against the switching ramp in a non-positive manner permits the operating mode change-over switch to be operated in an easy yet reliable manner. 
     
    
     DRAWING  
       [0009]     The present invention is explained in greater detail in the description below with reference to an exemplary embodiment presented in the drawing.  
         [0010]      FIG. 1  shows, in sections, a longitudinal sectional view of a drilling hammer with an operating mode change-over switch,  
         [0011]      FIG. 2  shows a perspective drawing of a switching element of the operating mode change-over switch in  FIG. 1 ,  
         [0012]      FIG. 3  shows the switching element according to  FIG. 2 , in a perspective drawing, the switching element having been partially extracted from a hammer tube of the drilling hammer,  
         [0013]      FIG. 4  shows a top view of a control button of the operating mode change-over switch in  FIG. 1 ,  
         [0014]      FIG. 5  through  8  show a top view of a control button lower part and a coupled shift fork of the operating mode change-over switch in  FIG. 1  in four different setting positions of the control button,  
         [0015]      FIG. 9  shows a profile of the control button lower part with switching ramp for actuating a vertical separating slide of the operating mode change-over switch in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0016]     The drilling hammer shown in a sectional view in  FIG. 1  with its rear region in a longitudinal sectional view includes a housing  10  with a housing opening  11  that is closed by a housing cover  12 . A tool holder extends out of housing  10  at its left end, which is not shown in  FIG. 1 , on which a tool is mounted in a limited axially displaceable manner. The tool holder is connected in a torsion-proof manner with a hammer tube  13  rotatably supported in housing  10 . An air cushion striking tool  14  with a piston  15  capable of being displaced axially in hammer tube  13  is located in hammer tube; the air cushion striking tool can be brought into reciprocating motion using a crank driving mechanism  16  located in a drive chain between an electric motor  27  and piston  15 . Air cushion striking tool  14  further includes a beater driven by piston  15 , the beater acting via a snap die on the end of the tool mounted in the tool holder. To this extent, the drilling hammer described here conforms with the drilling hammer described in DE 38 26 213 A1, whereby the arrangement and configuration of the tool holder, hammer tube  13  and air cushion striking tool  14  with piston  15  described there also apply to the drilling hammer described here.  
         [0017]     Crank driving mechanism  16  includes a crank wheel  18  with an integral bearing tube  181  and a crank pin  19  positioned eccentrically to the axis of rotation, on which a push rod  20  bears in a rotatable manner, the push rod being connected with piston  15  of air cushion striking tool  14  in a swivelling manner. Crank wheel  18  is supported in a rotational manner with its bearing tube  181  on an axis  17  in the housing. A gear wheel  21  with external teeth  22  is situated on bearing tube  181  in a rotatable and axially displaceable manner. A coupling spring  23  configured as a coil compression spring bears between crank wheel  18  and gear wheel  21 , the coupling spring pressing gear wheel  21  on the front side against a separating slide  24  described in detail hereinbelow. In this displacement position of gear wheel  21  shown in  FIG. 1 , a torsion-proof connection between crank wheel  18  and gear wheel  21  is established via a tooth system  25  between gear wheel  21  and bearing tube  181  of crank wheel  18 ; the torsion-proof connection can be released by sliding gear wheel  21  in  FIG. 1  upward. A coupling is therefore located in the drive chain, one coupling part of which is formed by crank wheel  18  with bearing tube  181 ; the other coupling part, which can be actuated by separating lever  24 , is formed by gear wheel  21 . The coupling is held closed by coupling spring  23 . Gear wheel  21  meshes with its outer teeth  22  in a drive pinion  28  formed on a driven shaft  26  of electric motor  27 . It should be noted that, in  FIG. 1 , crank driving mechanism  16  is shown in a position in which piston  15  assumes its anterior dead-center position, shown at the left in  FIG. 1 . To ensure clarity in the drawing, piston  15  is shown further to the left than it would be under actual circumstances, however.  
         [0018]     Hammer tube  13 , which is rotatably supported in housing  10 , is started rotating by electric motor  27  via a gear unit  30 , so that the tool, which is axially displaceable with limitation in the tool holder and is mounted in a non-rotative manner, also rotates. Gear unit  30  includes a ring gear located on hammer tube  13 , the ring gear being retained on hammer tube  13  in an axially displaceable and rotatable manner, a bevel gear  32  meshing with teeth on ring gear  31 , and a gear wheel  33  with external teeth  34  that is connected with bevel gear  32  in torsion-proof fashion. Bevel gear  32  and gear wheel  33  are rotatably retained in housing  10 , and external teeth  34  mesh with drive pinion  28  on driven shaft  26  of electric motor  27 .  
         [0019]     The drilling hammer described in this manner can be used in three operating modes. In the “impact drilling” operating mode, electric motor  27 , which has been turned on, brings hammer tube  13  into rotation and activates air cushion striking tool  14 ; for this purpose, the coupling in the drive chain of air cushion striking tool  14  (as shown in  FIG. 1 ) is closed and ring gear  31  is connected with hammer tube  13  in a torsion-proof manner. In the “chiseling” operating mode, only the air cushion striking tool  14  is activated; for this purpose, the coupling in the drive chain of air cushion striking tool  14  is closed and ring gear  31  is decoupled from hammer tube  13 . In the “drilling” operating mode, air cushion striking tool  14  is idled and hammer tube  13  is started rotating; for this purpose, the coupling in the drive chain of air cushion striking tool  14  is opened and ring gear  31  is connected with hammer tube  13  in a torsion-proof manner.  
         [0020]     An operating mode change-over switch  35  serves to set these three different operating modes of the drilling hammer, the operating mode change-over switch including a single, manually operated control button  36  and a switching mechanism  37  having a stable and compact design. Control button  36  is located in housing cover  12  such that it is protected and user-friendly. It includes a control button lower part  38  and a control button cap  39  that overlaps a collar  121  formed on housing cover  12 . Control button lower part  38  is inserted in a multi-step bore encompassed by collar  21  and secured to the underside of control button cap  39 . Control button lower part  38  includes an eccentric pin  40  that extends at a right angle from the underside of control button lower part  38 , and a switching ramp  41  that is located on the underside of control button lower part  38 , extends in the circumferential direction of control button lower part  38 , thereby rising in the direction of the rotational axis of control button  36 , i.e., downward in  FIG. 1 .  
         [0021]     Switching mechanism  37  also includes separating slide  24  mentioned above; the separating slide is guided in housing  10  in a vertically displaceable manner and bears with a U-bent slide end  241  on the underside of control button lower part  38  or switching ramp  41 , and, with its other U-bent slide end  242 , it overlaps gear wheel  21  that forms the displaceable coupling part of the coupling in the drive chain of air cushion striking tool  14 . Upper slide end  241  is pressed by a spring  41  shown only schematically in  FIG. 1  against the underside of control button lower part  38  and/or against switching ramp  41 , whereby the spring force of spring  42  is greater than the spring force of coupling spring  23 , so that, in the range of rotation of control button lower part  38  in which upper slide end  241  leaves switching ramp  41 , gear wheel  21  is slid upwardly by spring  42  and lower lever end  242 —while tensioning coupling spring  23  in  FIG. 1 —so far that toothed connection  25  between crank wheel  18  and gear wheel  21  is released, the coupling in the drive chain of air cushion striking tool  14  is therefore opened and striking tool  14  is turned off. As illustrated in the profile of switching ramp  41  in  FIG. 9 , the switching ramp extends across an approximately 270° circumferential angle of control button lower part  38 , so that separating slide  24  is released to be displaced by spring  42  only in a range of rotation of approximately 90° of control button  36 .  
         [0022]     Switching mechanism  37  also includes a switching element  43  slid onto hammer tube  13 , which is shown in a perspective drawing in  FIGS. 2 and 3 , and a shift fork  44  that connects switching element  43  to control button  36 . Switching element  43  is composed of a coupling ring  45  made of plastic, from which two diametrally located cantilevers  46  integral with coupling ring  45  extend axially. Each cantilever  46  is provided with a recess  47  on its free end opposite the ring and are pretensioned outwardly in the radial direction of coupling ring  45 . When the two cantilevers  46  are pressed together, an actuator ring  48  can be inserted into recesses  47 , the actuator ring being composed preferably of metal. On its inside facing hammer tube  13 , actuator ring  48  includes two diametrally located, radially projecting guide splines  49  that are positioned in corresponding guide grooves  50  recessed in the outside of hammer tube  13 . Two further guide grooves  50  are recessed in hammer tube  13 , each of which accommodates one of the two cantilevers  46 . The dimensions of cantilevers  46  and guide splines  49  are preferably the same, so that all four guide grooves  50  can be configured identically. On its outside facing away from hammer tube  13 , actuator ring  45  includes a plurality of equidistantly spaced, radially projecting locking splines  51  that are configured such that they can be inserted axially in corresponding axial recesses  52  on the underside of ring gear  31  facing hammer tube  13 . A locking part  53  in the housing is diametrically opposed to the insertion openings of axial recesses  52  in ring gear  31 , the locking teeth of which are configured such that locking splines  51  can be inserted axially into locking part  53  and can be positioned in a form-locked manner in the direction of rotation. Locking part  53  is located with axial clearance from axial recesses  52  in ring gear  31  such that, once actuator ring  48  slides out of ring gear  31 , actuator ring  48  can still assume a position in which its locking splines  51  do not yet engage in locking part  53 . In this “neutral” or “zero” position of actuator ring  48 , hammer tube  13  is not coupled to ring gear  31  or locking part  53  in the housing, enabling hammer tube  13  to rotate freely. Coupling ring  45  includes a recess or an annular groove  54  into which a radially directed projection  45  of shift fork  44  engages.  
         [0023]     Flat shift fork  44 , which is shown in a sectional view in  FIG. 1  and a top view in  FIGS. 5 through 8  and is preferably made of plastic, extends with its free end on which the projection is located over hammer tube  13  to annular groove  54  in coupling ring  45 ; it turns downward at the end of hammer tube  13  and extends underneath control button lower part  38 . The coupling of shift fork  44  to control button  36  takes place via a synchronizing spring  56  and eccentric pin  40  on control button lower part  38 . Synchronizing spring  56  is configured as a coil spring with long legs  561 ,  562  U-bent at a right angle to the spring axis, the spring being slid onto a bolt  57  projecting upward at a right angle from shift fork  44  and bearing with its two long legs  561  and  562  on diametral points of eccentric pin  40  in a non-positive manner, the points nearly aligning with each other in the sliding direction of shift fork  44  ( FIGS. 5 through 8 ). Eccentric pin  40  is located on control button lower part  38  at an angle α relative to the longitudinal axis of shift fork  44  such that, when control button  36  rotates by 90°, four rotated positions of eccentric pin  40  result, each being offset from the other by a distance a/2 as viewed in the sliding direction of shift fork  44 , as shown in  FIG. 5 . The overall displacement travel of shift fork  44  is a, after which shift fork  44  bears against a stop  59  in the housing. The upper slide end  241  of separating slide  24  is shown in the illustrations in  FIGS. 5 through 8 , the slide end extending past the underside of control button lower part  38  and bearing on switching ramp  41  across a circumferential angle of nearly 270°.  
         [0024]     Control button cap  39  is shown in a top view in  FIG. 4 . It includes a gripping segment  58  on which a marking tip  581  is configured. Marking tip  581  indicates the setting position of control button  36 , that is, the “chiseling” mode (M), the “impact drilling” mode (S), and the “drilling” mode (B), which are set by operating mode change-over switch  35 . In addition, a “neutral” or “zero” position (0) is provided, in which only the air cushion striking tool  14  is active but not the rotary drive for hammer tube  13 , and hammer tube  13  can rotate freely and at random in housing  10 .  
         [0025]     The mode of operation of operating mode change-over switch  35  is as follows:  
         [0026]     If control button  36  is set, as shown in  FIG. 4 , such that marking tip  581  points to position M, shift fork  44  is displaced furthest to the left in  FIG. 1  along the maximum displacement travel a, as shown in  FIG. 5 . Accordingly, switching element  43  is displaced by shift fork  44  as far to the left as possible; as a result, actuator ring  48  with its locking splines  51  is pressed into locking part  53  in the housing. Hammer tube  13  is fixed in housing  10  in a torsion-proof manner by the torsion-proof connection of actuator ring  48  with hammer tube  13  via guide splines  49 , cantilevers  46  and guide grooves  50 , and there is no connection between hammer tube  13  and ring gear  31 . When electric motor  27  is turned on, freely rotating ring gear  31  and air cushion striking tool  14  are driven by gear unit  30 , since separating slide  24  bears with its upper slide end  241  on switching ramp  41  and, as shown in  FIG. 1 , is displaced downward so that coupling spring  23  holds the coupling between crank wheel  18  and gear wheel  21  closed. Since only air cushion striker train  14  is activated, the tool is driven only by air cushion striker train  14  with an axial striking motion.  
         [0027]     If control button  36  is turned out of position M into position 0 by 90° in  FIG. 4  in the counter-clockwise direction, shift fork  44  is displaced by eccentric pin  40  and synchronizing spring  56 —as shown in  FIG. 6 —to the right along displacement travel a/2 in  FIG. 1 . Switching member  43  in  FIG. 1  is displaced to the right along the same displacement path by coupling ring  45 ; as a result, locking splines  51  on actuator ring  48  disengage from locking part  53 , and actuator ring  48 —as shown in  FIG. 1 —assumes a central position between locking part  53  and ring gear  21 . Hammer tube  13  is released to rotate freely, but is not started rotating by electric motor  27 . Air cushion striking tool  14  remains activated, since separating slide  24  is also held in this rotational position of control button  36  by switching ramp  41  in the position shown in  FIG. 1 .  
         [0028]     If control button  36  is turned to control button position SB, shift fork  44  is displaced to the right along displacement path a/2 in  FIG. 1  and, after eccentric pin  40  covers half of the rotation path, it contacts stop  59  in the housing. Eccentric pin  40 , which moves further, deflects spring leg  561  of synchronizing spring  56  ( FIG. 7 ). Shift fork  44 , which is being displaced by the distance a/2, pushes actuator ring  48  in  FIG. 1  so far to the right that locking splines  51  slide into axial recesses  52  in ring gear  31  in a form-locked manner and therefore connect hammer tube  13  to ring gear  31  in a torsion-proof manner. Electric motor  27  now brings hammer tube  13  and, therefore, the tool holder and the tool retained in the tool holder in a torsion-proof manner into rotation. Air cushion striking tool  14  remains activated, since upper slide end  241  of separating slide  24  has not yet left switching ramp  41  (refer to position SB in  FIG. 9 ).  
         [0029]     If control button  36  is now turned further by 90° into setting position B, eccentric pin  40  returns along rotation distance a/2. Since eccentric pin  40  in setting position SB had previously moved rotation distance a ( FIG. 7 ) given a displacement travel of shift fork  44  by a/2 while deflecting spring leg  561 , this return of eccentric pin  40  does not cause shift fork  44  to become displaced. Actuator ring  48  therefore retains its engaged position in ring gear  31 . As a result of the rotation of control button lower part  38  around this further 90°, switching ramp  41  has slid out of the region of the upper lever end  241  of separating slide  24 , so that separating slide  24  is pushed upward by spring  42  in  FIG. 1  until it bears against the switching ramp-free region of control button lower part  38  and, thereby, its lower lever end  242  pushes gear wheel  21  upward while pressing coupling spring  23  together, so that the external teeth between gear wheel  21  and bearing tube  181  of crank wheel  18  become disengaged and the coupling in the drive chain of air cushion striking tool  14  is opened. Air cushion striking tool  14  is therefore decoupled from electric motor  27  and, finally, hammer tube  13  is started rotating by electric motor  27 . Pure drilling work can now be carried out with the tool retained in the tool holder in a torsion-proof manner.  
         [0030]     It is possible, of course, to turn control button  36  out of its setting position M in the opposite direction of rotation directly into setting position B and then, from here, further to setting position SB and then 0. Nothing about the mode of operation of switching mechanism  37  changes as a result.