Abstract:
A drilling device includes an end cutting tool, a main housing, a motor, a transmission, and a dust collection unit. The end cutting tool processes a workpiece. The motor is provided in the main housing for generating a torque. The transmission transmits the torque to rotate the end cutting tool. The dust collection unit collects dust generated by the rotation of the end cutting tool. The dust collection unit includes a dust case for accumulating the dust therein. The dust case is detachable from the main housing and having an inlet and an outlet. The inlet and the outlet are oriented in a single direction.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a drilling device that has a motor for rotating a drill tip to form a hole in a workpiece such as a brick or a concrete block. More particularly, the invention relates to a drilling device that has a dust-collection mechanism for collecting dust generated by the drilling. 
       BACKGROUND 
       [0002]    A drill tool, a hammer drill (having a rotating hammer), and a vibrating drill have been used as drilling devices for forming a hole in a workpiece as a brick and a concrete block. The drilling device generates dust during the operation. A user therefore wears a dust mask and goggles, while using the drilling device. 
         [0003]    To suppress the generation of dust during the drilling operation, thereby to improve the work environment, a drilling device has been provided with a dust-collection mechanism. The dust-collection mechanism includes a housing and a dust-collection fan provided in the housing. The drilling device has a dust-collection pipe and a dust-collection adapter. The dust-collection pipe is connected to the housing and can slide with respect thereto. The dust-collection adapter is positioned near the drill tip. When the fan is driven, dust is drawn and collected through the dust-collection adapter and the dust-collection pipe into the housing. 
       SUMMARY 
       [0004]    An object of the present invention is to provide a drilling device to which a dust collection case can be easily secured in a simple manner. 
         [0005]    Another object of the present invention is to provide a drilling device in which a dust collection case can be easily sealed to a main unit. 
         [0006]    Another object of the present invention is to provide a drilling device that has a higher dust collection efficiency and a higher operating efficiency. 
         [0007]    Still another object of the present invention is to provide a drilling device that includes a main unit, a dust-collection device, and a dust collection case which is removably and firmly attached to the main unit or the dust-collection device. 
         [0008]    Another object of the present invention is to provide a drilling device in which a dust collection case is firmly sealed to a main unit, preventing dust from leaking out of the dust collection case. 
         [0009]    The present invention provides a drilling device including an end cutting tool, a main housing, a motor, a transmission, and a dust collection unit. The end cutting tool processes a workpiece. The motor is provided in the main housing for generating a torque. The transmission transmits the torque to rotate the end cutting tool. The dust collection unit collects dust generated by the rotation of the end cutting tool. The dust collection unit includes a dust case for accumulating the dust therein. The dust case is detachable from the main housing and having an inlet and an outlet. The inlet and the outlet are oriented in a single direction. 
         [0010]    The present invention provides a drilling device including an end cutting tool, a motor, a transmission, a dust collection unit, a dust collection adapter, and a support member. The end cutting tool processes a workpiece. The end cutting tool having an axis. The motor generates a torque. The transmission transmit the torque to rotate the end cutting tool. The dust collection unit collects dust generated by the rotation of the end cutting tool. The dust collection adapter is provided in proximity to the end cutting tool. The dust collection adapter is movable in an axial direction of the end cutting tool. The support member supports the dust collection adapter. The support member is retractable at a plurality of stages in the axial direction. 
         [0011]    The present invention provides a drilling device including an end cutting tool having an axis, a main housing, a motor, a transmission, and a dust case. The motor is provided in the main housing for generating a torque. The transmission transmits the torque to rotate the end cutting tool. The dust case accumulates dust generated by the rotation of the end cutting tool. The dust case is detachable from the main housing. The dust case has a center of gravity. The dust case includes a first engaging portion and a second engaging portion to be engaged with the main housing, respectively. The first and second engaging portions are positioned on an imaginary line connecting the first and second engaging portions through the center of gravity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
           [0013]      FIGS. 1 and 2  are partially sectional views illustrating a hammer drill according to one embodiment of the present invention; 
           [0014]      FIG. 3  is a partially sectional view illustrating a hammer drill according to another embodiment of the present invention; 
           [0015]      FIG. 4  is a vertically sectional view showing a dust collection case; 
           [0016]      FIG. 5  is a plan view illustrating a sealing member; 
           [0017]      FIG. 6  is a cross section taken along lines A-A shown in  FIG. 3 ; and 
           [0018]      FIG. 7  is a cross section taken along lines B-B shown in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    A drilling device according to an embodiment of the present invention will be described with reference to  FIGS. 1 and 2 . The expressions “front”, “rear”, “above” and “below” are used throughout the description to define the various parts when the drilling device is disposed in an orientation in which it is intended to be used. 
         [0020]      FIG. 1  shows a hammer drill  100  according to the present invention. The hammer drill  100  includes a gear housing  1 , a motor housing  2 , a handle  3 , a drill-tip holding unit  4 , and a dust-collection mechanism. The drill-tip holding unit  4  detachably supports a drill tip  26 . 
         [0021]    The hammer drill is configured to operate in at least three modes. These modes include a rotating-hammering mode, a rotating mode, and a hammering mode. In the rotating-hammering mode, the hammer drill  100  rotates and strikes the drill tip  26 . In the rotating mode, the hammer drill  100  rotates the drill tip  26 . In the hammering mode, the hammer drill  100  strikes the drill tip  26 . A switching member  6  is provided on one side of the gear housing  1 . When operated, the switching member  6  activates the mode-switching mechanism provided in the gear housing  1 . The mode-switching mechanism switches the operating mode of the hammer drill, from one to another. The hammer drill rotates and/or strikes the drill tip  26  to perform drilling. As the drill tip  26  performs drilling, the hammer drill is vibrated. More precisely, the hammer drill is vibrated as the drill tip  26  is moved back and forth repeatedly. 
         [0022]    The handle  3  has one end connected to the gear housing  1  and the other end connected to the motor housing  2 . The handle  3  has a power switch  3   a  and a power-supply cord  5 . 
         [0023]    The motor housing  2  contains a motor  18  that has a shaft  19 . A cooling fan  17  is mounted on and secured to the shaft  19  of the motor  18 . When the motor  18  is driven, rotating the cooling fan  17 , cooling-air flows into the motor housing  2  through the air-inlet port (not shown) formed in the tail cover  16  of the motor housing  2 . The cooling-air cools the motor  18  as the cooling-air passes by the motor  18 . The cooling-air then flows out of the motor housing  2  through the air-outlet port (not shown). 
         [0024]    The drill tip  26  includes a tip section  26   a  and a helical section  26   b . The drill tip  26  cuts the workpiece and forms a hole in the workpiece, as the drill chip is rotated by the motor  18 . 
         [0025]    The dust-collection mechanism has a dust-collection housing  8  as a main unit that is composed of two sections. The first section is interposed between the gear housing  1  and the motor housing  2 . The second section extends in the gap between the motor housing  2  and the drill tip  26 . As shown in  FIG. 2 , the dust-collection housing  8  has a first opening  8   a , a second opening  8   b , a third opening  8   c , and a recess  8   d.    
         [0026]    In the dust-collection housing  8 , a dust-collection fan  14  is mounted on the shaft  19  of the motor  18 , and can rotate integrally with the shaft  19 . As the motor  18  rotates to rotate the dust-collection fan  14 , air flows into the dust-collection housing  8  through the third opening  8   c  and flows to the outside from the dust-collection housing  8  through an air-outlet port (not shown). 
         [0027]    As shown in  FIGS. 2 and 4 , the dust collection case  12  has a projection  12   a  and a latch part  12   b . The projection  12   a  can be fitted in the recess  8   d  of the dust-collection housing  8 . The latch part  12   b  can be fitted in a recess  16   a  formed in the tail cover  16 . 
         [0028]    The projection  12   a  and the latch part  12   b  are provided on an imaginary line passing through the center of gravity of the dust collection case  12 . 
         [0029]    The latch part  12   b  of the dust collection case  12  is engaged in the recess  16   a  of the dust collection housing  8 . The projection  12   a  of the dust collection case  12  is engaged in the recess  8   d  of the dust collection housing  8 . 
         [0030]    When the projection  12   a  and the latch part  12   b  are disengaged from the recesses  8   d  and  16   a , respectively, the dust collection case  12  is removed from the dust collection housing  8 . 
         [0031]    The first opening  12   c  of the dust collection case  12  is formed in the top surface of the dust collection case  12 . The second opening  8   b  of the dust-collection housing  8  and the first opening  12   c  of the dust collection case  12  are communicated with each other. Further, the third opening  8   c  of the dust-collection housing  8  and the second opening  12   d  of the dust collection case  12  are communicated with each other. The first opening  12   c  of the dust collection case  12  is an inlet port through which air and dust enter the dust collection case  12 . The second opening  12   d  of the dust collection case  12  is an outlet port through which air comes out of the dust collection case  12 . 
         [0032]    A seal member  20  is provided between the dust collection housing  8  and the dust collection case  12 . The seal member  20  is contact with the top surface of the dust collection case  12  and can be deformable in the direction in which the dust collection case  12  is attached to the dust collection housing  8 . 
         [0033]    The seal member  20  seals the gap between the rim of the second opening  8   b  of the dust-collection housing  8  and the rim of the first opening  12   c  of the dust collection case  12 . The seal member  20  also seals the gap between the rim of the third opening  8   c  of the dust-collection housing  8  and the rim of the second opening  12   d  of the dust collection case  12 . The seal member  20  prevents air and dust from leaking through the connecting portion between the dust-collection housing  8  and the dust collection case  12 , which is positioned near the inlet port and the outlet port. 
         [0034]    The connecting portion that contacts the seal member  20  is located between the lower rim of the second opening  8   b  of the dust-collection housing  8  and between the upper rim of the first opening  12   c  of the dust collection case  12 . Another connecting portion that contacts the seal member  20  is located between the lower rim of the third opening  8   c  of the dust-collection housing  8  and the upper rim of the second opening  12   d  of the dust collection case  12 . 
         [0035]    The sealed connection of the second opening  8   b  of the dust-collection housing  8  and the first opening  12   c  of the dust collection case  12 , and the sealed connection of the third opening  8   c  of the dust-collection housing  8  and the second opening  12   d  of the dust-collecting case  12  are achieved when the latch part  12   b  of the dust collection case  12  is engaged in the recess  16   a  of the tail cover, as described above. 
         [0036]    As shown in  FIG. 5 , the seal member  20  has a flat shape. The seal member  20  is a single-piece component. As shown in  FIG. 2 , the first and second openings  12   c  and  12   d  are formed in an upper end of the dust collection case  12  and lie in an imaginary flat plane. 
         [0037]    Moreover, the connecting portion between the second opening  8   b  of the dust-collection housing  8  and the first opening  12   c  of the dust collection case  12  and the connecting portion between the third opening  8   c  of the dust-collection housing  8  and the second opening  12   d  of the dust collection case  12  lie in the same plane. 
         [0038]    As shown in  FIG. 6 , in the dust collection case  12 , a filter  13  is provided and fixed in position. In the dust collection case  12 , a dust storage unit  21  and an air passage  15  are provided. The filter  13  is provided between the dust storage unit  21  and the air passage  15 . Air can flow into the air passage  15  through the filter  13 . The filter  13  catches dust, which is collected in the dust storage unit  21 . 
         [0039]    The detailed structure of the dust collection case  12  will be described. 
         [0040]    As shown in  FIG. 6 , the dust collection case  12  includes a first dust-collection housing  12   x  and a second dust-collection housing  12   y . A filter holder  22  is interposed between the first dust-collection housing  12   x  and the second dust-collection housing  12   y . The filter  13  partitions the interior of the dust collection case  12  into two sections. One section is the dust storage unit  21 . The other section is the air passage  15 . As shown in  FIG. 6 , the filter  13  has a number of filter pleats  13   a , which extend in the axial direction of the drill tip  26 . Each filter pleat  13   a  has a space  13   v , which communicates with the air passage  15 . The filter  13  is fixed, at one side, to the filter holder  22 . The filter holder  22  is positioned near the junction between the air passage  15  and the dust storage unit  21 . The filter holder  22  firmly holds the filter  13 , preventing dust from moving into the air passage  15 . 
         [0041]    As shown in  FIG. 7 , each filter pleat  13   a  has a top member portion  13   x , a bottom member portion  13   y  and two filter wall portions  13   z.    
         [0042]    The filter wall portion  13   z  has an upper end connected to the top member portion  13   x  and an lower end connected to the bottom member  13   y . These connecting portions are achieved by adhesive. Hence, air cannot flow into the air passage  15 . As shown in  FIG. 7 , the space  13   v  surrounded by each filter pleat  13   a  communicates with the air passage  15 . A gap  13   w  is provided between the wall portion  13   z  of one filter pleat  13   a  and the wall portion  13   z  of the next filter pleat  13   a.    
         [0043]    The filer  13  has a large surface area in the dust storage unit  21 , because the filter  13  has filter pleats  13   a  and a narrow gap  13   w  is provided between any two adjacent filter pleats  13   a . In addition, the filter  13  has a large surface area in the air passage  15 , because the space  13   v  in each filter pleat  13   a  communicates with the air passage  15 . Air can flow through a large space, and thus very smoothly, into the air passage  15 . This enhances the efficiency of collecting dust. 
         [0044]    As shown in  FIG. 1 , the output axis of the motor  18  is arranged so as to extend at right angles with the longitudinal axis of the drill tip  26 . A support member  31  is attached between the drill tip  26  and the motor  18 . 
         [0045]    The support member  31  includes three hollow cylindrical members. More precisely, the support member  31  has a first slider  31   a , a second slider  31   b , and a hollow cylindrical member  31   c . The hollow cylindrical member  31   c  is secured to the gear housing  1  and the dust-collection housing  8 . The hollow cylindrical member  31   c  opens at the distal end. The second slider  31   b  is inserted in the hollow cylindrical member  31   c  and can slide therein and protrude therefrom. A dust-collection adapter  10  is provided at that end of the first slider  31   a , which faces away from the second slider  31   b . The first slider  31   a  and the dust-collection adapter  10  are secured to each other. The closer each hollow cylindrical member is located to the dust-collection adapter  10 , the smaller diameter the hollow cylindrical member has. The first slider  31   a  and the second slider  31   b  can be moved relative to each other. Since the first slider  31   a  and the second slider  31   b  are hollow cylindrical members and one slider is inserted in the other slider, the unit constituted by the sliders  31   a  and  31   b  can expand toward and contract from the drill tip  26 . 
         [0046]    Similarly, the second slider  31   b  and the hollow cylindrical member  31   c  can be moved relative to each other. Since the second slider  31   b  and the hollow cylindrical member  31   c  are hollow cylindrical members, and one slider  31   b  is inserted in the other slider  31   c , the unit constituted by the second slider  31   b  and the hollow cylindrical member  31   c  can expand toward, and can contract from, the drill tip  26 . Since the second slider  31   b  is supported in the hollow cylindrical member  31   c , the second slider can slide in the hollow cylindrical member  31   c.    
         [0047]    Thus, the support member  31  can change in length, or can expand and contract to and from the drill tip  26 . The length of the support member  31  in the longitudinal direction of the drill tip  26  is the sum of the length of the hollow cylindrical member  31   c , the length of the second slider  31   b  which protrudes from the hollow cylindrical member  31   c , and the length of the first slider  31   a  which protrudes from the second slider  31   b.    
         [0048]    The second slider  31   b  has an opening. The first slider  31   a  is inserted and can slide in the second slier  31   b  and protrudes from the opening of the second slider  31   b . The first slider  31   a , the second slider  31   b  and the hollow cylindrical member  31   c  define a continuous passage, in which a spring  32  is inserted. The spring  32  has one end abutting on the bottom of the hollow cylindrical member  31   c  and the other end abutting on that end of the first slider  31   a  which is an opposite side of the second slider  31   b . The spring  32  biases the first slider  31   a  to move from the hollow cylindrical member  31   c  to the dust-collection adapter  10 . The dust-collection adapter  10 , which is secured to the first slider  31   a , is therefore biased to the tip of the drill tip  26 . 
         [0049]    A dust-collection hose  11  has one end connected to the dust-collection adapter  10  and the other end connected to the first opening  8   a  of the dust-collection housing  8 . 
         [0050]    The dust-collection adapter  10  has a hole through which the drill tip  26  can pass. A brush (not shown) is provided in the hole in order to fill the gap between the drill tip  26  and the inner surface of the adapter  10 . The brush therefore prevents dust from leaking from the gap between the drill chip  26  and the hole. 
         [0051]    The operation of the hammer drill will be described as follows. 
         [0052]    The hammer drill can form a hole when the hammer drill is supplied with electric power through the power-supply cord  5 . When the user turns on the power switch  3   a  provided on the handle  3 , the motor  18  starts driving the drill tip  26 , which results in forming a hole in a workpiece. As the shaft  19  of the motor  18  rotates, the dust-collection fan  14  is driven to rotate, so that the dust generated during the drilling process is moved into the dust collection case  12  through the dust-collection adapter  10 , the dust-collection hose  11  and the dust-collection housing  8 , as the arrow indicated in  FIG. 1 . 
         [0053]    When the shaft  19  of the motor  18  rotates, the dust-collection fan  14  secured to the shaft  19  rotates. Then, the dust collection fan  14  guides the air together with the dust from the dust-collection adapter  10  in the direction of the arrow shown in  FIG. 1 . The air containing the dust flows from the dust-collection adapter  10  into the dust-collection hose  11 , as the arrow indicated in  FIG. 1 . Thereafter, the air containing the dust flows through the first opening  8   a  to the dust-collection housing  8  in the direction of the arrow shown in  FIG. 1 . Thereafter, the air containing the dust flows from the second opening  8   b  of the dust-collection housing  8  into the dust collection case  12  through the first opening  12   c  (shown in  FIG. 2 ) in the direction of the arrow shown in  FIG. 1 . In the dust collection case  12 , the filter  13  removes the dust from the air. At this time, the air containing dust may flow onto the top member portion  13   x , or the bottom member portion  13   y  of each filter pleat  13   a . The dust is accumulated in the dust storage unit  21 , whereas the air flows through the filter  13  into the air passage  15 . From the air passage  15 , the air flows through the second opening  12   d  (shown in  FIG. 2 ) of the dust collection case  12 , into the dust-collection housing  8  through the third opening  8   c , in the direction of the arrow shown in  FIG. 1 . Then, the air flown into the dust-collection housing  8  is discharged through the outlet port (not shown) in the dust-collection housing  8 . 
         [0054]    During the drilling, the user must keep pushing the hammer drill onto the workpiece. 
         [0055]    When the hammer drill  100   b  is pushed onto the workpiece, the tip section  26   a  of the drill tip  26  cuts the workpiece, forming a hole in the workpiece. 
         [0056]    As illustrated in  FIG. 1 , the dust-collection adapter  10  is positioned closer to the gear housing  1  than to the tip section  26   a  of the drill tip  26 . This is because the drilling has proceeded and the dust-collection adapter  10  has moved closer to the gear housing  1 . Thus, the dust-collection adapter  10  is positioned at the position where dust is generated at the surface of the workpiece. Unless the hammer drill is not used, or if the drill is not pushed onto the workpiece, the dust-collection adapter  10  is located near the tip section  26   a  of the drill tip  26 , because the first slider  31   a  is biased from the hollow cylindrical member  31   c  to the dust-collection adapter  10 . 
         [0057]    In the present invention, the spring  32  biases the dust-collection adapter  10  away from the gear housing  1 . Hence, the distance between the gear housing  1  and the workpiece gradually decreases as the drilling proceeds. As the tip section  26   a  of the drill tip  26  cuts the workpiece, the dust-collection adapter  10  is pushed to the gear housing  1  by the workpiece. 
         [0058]    As the drilling proceeds, the spring  32  is compressed with the elastic force generated between the gear housing  1  and the workpiece. The support member  31  therefore contracts in the direction away from the drill tip  26 . As a result, the support member  31  locates the dust-collection adapter  10  at a position according to the depth of the drill hole. 
         [0059]    The spring  32  biases the first slider  31   a  away from the gear housing  1 . As the drilling proceeds, the dust-collection adapter  10  gradually approaches the gear housing  1  because the adapter  10  is secured to the first slider  31   a . Once the drilling has proceeded to some extent, the second slider  31   b  can freely slide. 
         [0060]    When the tip section  26   a  of the drill tip  26  reaches the deepest position in the workpiece, the end of the second slider  31   b  which is opposite to the gear housing  1  abuts on the dust-collection adapter  10 . One end of the hollow cylindrical member  31   c  which is opposite to the gear housing  1  abuts on the dust-collection adapter  10 . Thus, the support member  31  has the length thereof reduced almost to the length of the hollow cylindrical member  31   c , when the drilling proceeds so much that the proximal end of the helical section  26   b  of the drill tip  26  reaches the surface of the workpiece. 
         [0061]    To remove the dust collection case  12  from the dust-collection housing  8 , as is illustrated in  FIG. 2 , the latch part  12   b  of the dust collection case  12  is disengaged from the recess  16   a  formed in the motor housing  2 . In order to disengage the latch part  12   b  from the recess  16   a , a larger force than the force with which the latch part  12   b  has been engaged in the recess  16   a  must be applied in the direction of arrow A shown in  FIG. 2 . When such a force is so applied, the dust collection case  12  is rotated around the projection  12   a  of the dust collection case  12  that is engaged with the recess  8   d  of the dust-collection housing  8 . 
         [0062]    After the latch part  12   b  has been removed from the recess  16   a , the projection  12   a  of the dust collection case  12  can be disengaged from the recess  8   d  of the dust-collection housing  8 . 
         [0063]    A second embodiment of the present invention will be described, with reference to  FIG. 3 . 
         [0064]    As shown in  FIG. 3 , a knob  33  is provided in the support member  31 . The knob  33  can be configured to adjust the position of the hollow cylindrical member  31   c  with respect to the dust-collection adapter  10  when the drilling is started. 
         [0065]    More specifically, the knob  33  has a screw that extends perpendicular to the axis of the support member  31 . The screw is set in engagement with a screw hole cut in the hollow cylindrical member  31   c . The lower end of the screw can abut on the second slider  31   b  which is inserted in the hollow cylindrical member  31   c . Because the screw abuts on the second slider  31   b , the second slider  31   b  remains at a specific position with respect to the hollow cylindrical member  31   c.    
         [0066]    The drill tip  26  of the hammer drill shown in  FIG. 3  is shorter than the drill tip  26  shown in  FIGS. 1 and 2 . In this case, if the drill tip  26  shown in  FIGS. 1 and 2  is used, the dust-collection adapter  10  and the support member  31  are pushed to the gear housing  1  for the distance equal to the difference between the drill tip  26  of  FIG. 3  and the drill tip shown of  FIGS. 1 and 2  in order to position the dust-collection adapter  10  in the vicinity of the tip section  26   a , before the drilling is started. Thus, until the adapter  10  is positioned near the tip section  26   a , the drilling is not started and no dust-collection process is performed. 
         [0067]    To eliminate the necessity of pushing the dust-collection adapter  10  and the support member  31  to the gear housing  1  before starting the drilling, the initial length of the support member  31  can be adjusted by using the knob  33  as shown in  FIG. 3 . 
         [0068]    As shown in  FIG. 3 , the use of the knob  33  sets the second slider  31   b  at a specific position with respect to the hollow cylindrical member  31   c , thereby shortening the distance for which the adapter  10  may move. In other words, the dust-collection adapter  10  can be positioned near the tip section  26   a  of the drill tip  26  by the knob  33  at the start of the drilling. 
         [0069]    The present invention can provide a drilling device in which the dust-collection adapter can be slidable for a longer distance, the support member does not protrude even if the dust-collection adapter is located near the main unit of the drilling device, and dust can therefore be efficiently collected even if the drill tip is relatively long, and which has a high operating efficiency. 
         [0070]    As described above, the spring  32  is provided to bias the support member  31  in the direction in which the dust-collection adapter is away from the main unit of the drilling device  100 . The dust-collection adapter  10  can therefore abut on the workpiece and is located near the drilling position. Hence, the present invention can provide a drilling device that can collect dust at high efficiency. 
         [0071]    Further, the support member is composed of a plurality of hollow cylindrical members. One hollow cylindrical member, which is closer to the tip end  26   a  of the drill chip  26 , slides in another hollow cylindrical member, which is closer to the gear housing  1 . The support member can therefore bear a load over a broad range, which is exerted as one hollow cylindrical member slides in another. Hence, the dust-collection adapter can smoothly move. The drilling device according to this invention can therefore have a higher operating efficiency. 
         [0072]    Moreover, the closer each hollow cylindrical member is located to a dust-collection adapter, the smaller diameter the cylindrical member has. Hence, the area in which the hollow cylindrical members slide in one another is smaller near the dust-collection adapter and is larger remote from the adapter. The load is therefore appropriately exerted on all hollow cylindrical members when each member slides in another. Hence, the drilling device can acquire a long lifetime. 
         [0073]    Since the spring  32  is arranged in the hollow cylindrical members, the spring does not contact any other components than the cylindrical members. Therefore, a deformation caused by he spring  32  is restricted at all. 
         [0074]    As described above, the support member  31  is composed of a plurality of members  32   a ,  31   b  and  31   c . Of these members, one member, which is closer to the tip end  26   a  of the drill chip  26 , can slide in the adjacent one, which is closer to the gear housing  1 . At least one member  31   c  has the restricting mechanism  33  for restricting the sliding distance. Hence, the slidable distance of the dust-collection adapter  10  can be limited, thereby restricting the depth of the hole in the workpiece formed by the drilling device  100 . 
         [0075]    The output axis of the motor is positioned at right angles with the longitudinal axis of the drill tip  26 , and the support member  31  is provided between the drill tip and the motor. This structure serves to downsize the drilling device in the drilling direction. The probability that the support member contacts any other members therefore decreases, ultimately increasing the operating efficiency of the drilling device. 
         [0076]    In the present invention, the dust collection case has an inlet port through which air and dust may flow into the case, and an outlet port through which air may flow from the case. Since these ports are oriented in a single direction, the dust collection case  12  can be attached to the dust-collection housing  8  if the dust collection case is moved to the housing  8  in one direction. Thus, the dust collection case  12  can be attached to the dust-collection housing  8  in a single manner. 
         [0077]    Moreover, the inlet port and the outlet port are provided in the same plane. The dust collection case  12  can therefore be attached to the dust-collection housing  8  in an easier manner than before. 
         [0078]    As the drill tip moves back and forth and strikes the workpiece, the hammer drill is vibrated due to the reaction the drill receives from the workpiece. The air containing dust is prevented from leaking in spite of the vibration of the hammer drill, because the flat seal member between the dust-collection housing and the dust-collection case is located in a direction parallel to the direction in which the drill tip moves back and forth. 
         [0079]    The inlet port is formed in the top surface of the dust-collection case as described above. Therefore, the dust does not leak from the dust collection case when the user detaches the dust collection case from the dust collection housing  8 . 
         [0080]    The seal member for both the inlet port and the outlet port is made from a single component. Therefore, the seal member contributes to manufacturing a drilling device having a simple configuration at a lower price with ease. 
         [0081]    In the present invention, the dust collection case is supported to the dust collection housing  8  with engaging portions  12   a ,  12   b  positioned on an imaginary line passing through the center of gravity of the dust collection case  12 . The vibration of dust collection case is suppressed, while the drilling device is performing drilling and is inevitably vibrating. This structure suppresses the leak of dust from the dust collection case and an accidental removal of the dust collection case from the dust collection housing. 
         [0082]    In another embodiment, electric power may be supplied from a battery to the drilling device. 
         [0083]    In another embodiment, the hollow cylindrical member  31   c  may be detachable from the gear housing  1  and the dust-collection housing  8 . Alternatively, the member  31   c  may be detachable from either one of the gear housing  1  and the dust-collection housing  8 . 
         [0084]    In another embodiment, the first slider  31   a  may slide on the outer surface of the second slider  31   b . The second slider  31   b  may slide on the outer surface of the hollow cylindrical member  31   c.    
         [0085]    In another embodiment, the first opening  12   c  and the second opening  12   d  may be formed in one side surface of the dust collection case  12  in order that the openings are oriented in the single direction. 
         [0086]    In another embodiment, the dust-collection hose  11  may be provided in the support member  31 . 
         [0087]    In the embodiment described above, the dust collection case  12  is attached to the dust collection case when the latch part  12   b  of the dust collection case  12  is engaged in the recess  16   a  of the tail cover and the projection  12   a  of the dust collection case  12  is engaged in the recess  8   d  of the dust-collection housing  8 . However, any structure for attaching the dust collection case  12  to the dust collection housing  8  other than the described above can be adopted. 
         [0088]    In another embodiment, the support member  31  may be composed of hollow members, having any other cross section such as a triangular one, a rectangular one or a keyhole-shaped one. 
         [0089]    It is understood that the foregoing description and accompanying drawings set forth the embodiments of the invention at the present time. Various modifications, additions and alternative designs will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the spirit and scope of the disclosed invention. Thus, it should be appreciated that the invention is not limited to the disclosed embodiments but may be practiced within the full scope of the appended claims.