Abstract:
A cutter driving apparatus has a spindle, a base, and a transmission shaft. The spindle has a cutter attached thereto. The base moves along the axis of the spindle. The spindle moves integrally with the base along the axis of the spindle. The base has a pair of support rods. The support rods are disposed apart from the spindle. The transmission shaft transmits a power to the base through the support rods so as to move the base along the axis of the spindle. This structure provides the cutter driving apparatus that facilitates boring operations by boring machines.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a cutter driving apparatus to be incorporated into a boring machine. 
   A boring machine provided with a cutter driving apparatus shown in  FIGS. 7(   a ) and  7 ( b ) is disclosed in the specification of U.S. Pat. No. 6,280,123. In this cutter driving apparatus, a cutter  114  is attached to a spindle  112 , which rotates integrally with a drive shaft  106  disposed in a housing  105 . 
   Since the drive shaft  106  and the spindle  112  are connected to each other with a spline  113 , the spindle  112  can move relative to the drive shaft  106  along the axis  106   a  thereof. A quill  115  rotatably surrounds the spindle  112  and is movable integrally with the spindle  112  along the axis  106   a . A pinion  118  is meshed with a rack  119  provided on the quill  115  and is rotated by operating an operation handle (not shown). Thus, when the pinion  118  rotates, both the quill  115  and the spindle  112  move along the axis  106   a.    
   When the spindle  112  moves along the axis  106   a , the distance over which a cutter  114  attached to the spindle  112  moves, the stroke S shown in  FIG. 7(   a ), depends upon the length of the rack  119 . However, the length of the rack  119  is subject to the design limitation so as to avoid interference of the rack  119  with members located around the drive shaft  106  and spindle  112 . Thus, the stroke S is not very long. Therefore, the conventional boring machine is unable to form deep bores. 
   SUMMARY OF THE INVENTION 
   Accordingly, the object of the present invention is to provide a cutter driving apparatus that facilitates boring operations by boring machines. 
   To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a cutter driving apparatus is provided to be incorporated into a boring machine. The cutter driving apparatus includes a spindle rotating around its own axis, a moving member moving along the axis of the spindle, and a transmission member transmitting a power to the moving member so as to move the moving member along the axis of the spindle. The spindle has a cutter attached thereto. The spindle moves integrally with the moving member along the axis of the spindle. The moving member has a peripheral part disposed apart from the spindle. The transmission member transmits the power to the moving member through the peripheral part. 
   The present invention provides another cutter driving apparatus, which includes a spindle, a moving member, an operation member, a transmission member, and a joint. The spindle rotates around its own axis. The spindle has a cutter attached thereto. The moving member moves along the axis of the spindle. The spindle moves integrally with the moving member along the axis of the spindle. The operation member is operated so as to move the moving member along the axis of the spindle. The transmission member is located between the operation member and the moving member. The operation member is removably connected to the transmission member. The joint connects the operation member with the transmission member. The joint is shifted selectively between an admissible state where the joint admits transmission of a power from the operation member to the transmission member and an inadmissible state where the joint does not admit transmission of a power from the operation member to the transmission member. The power transmitted to the transmission member is transmitted to the moving member to move the moving member along the axis of the spindle. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1  is a side view showing a boring machine according to one embodiment of the present invention; 
       FIG. 2  is a plan view of the boring machine shown in  FIG. 1 ; 
       FIG. 3  is a partly cut-away front view of the cutter driving apparatus to be incorporated into the boring machine of  FIG. 1 ; 
       FIG. 4(   a ) is a partly cut-away side view of the cutter driving apparatus shown in  FIG. 3 ; 
       FIG. 4(   b ) is a side view showing a part of the cutter driving apparatus shown in  FIG. 3 ; 
       FIG. 5(   a ) is a partly cut-away side view showing a handle provided in the cutter driving apparatus shown in  FIG. 3 , assuming the locked state; 
       FIG. 5(   b ) is a cross-sectional view taken along the line A—A in  FIG. 5(   a ); 
       FIG. 6(   a ) is a partly cut-away side view of the handle shown in  FIG. 5(   a ), assuming the unlocked state; 
       FIG. 6(   b ) is a cross-sectional view taken along the line B—B in  FIG. 6(   a ); and 
       FIG. 7(   a ) and  FIG. 7(   b ) are cross-sectional views each showing a part of the cutter driving apparatus incorporated into the boring machine of the prior art. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   One embodiment of the present invention will be described referring to  FIG. 1  to  FIG. 6(   b ). 
   As shown in  FIG. 1  and  FIG. 2 , the boring machine  1  according to this embodiment is provided with a grip  2  facilitating portage of the boring machine  1  and a magnet  3  facilitating mounting of the boring machine  1  onto a workpiece W. The boring machine  1  is also provided with an electric motor  4  and a cutter driving apparatus to be disposed inside and outside of a housing  5  attached to the external side of the electric motor  4 . 
   The cutter driving apparatus will be described below in detail. 
   A drive shaft  6  shown in  FIG. 3  and  FIG. 4(   a ) is disposed inside the housing  5 . The drive shaft  6  is supported by bearings  7 ,  8  to be rotatable around the axis  6   a  thereof. The drive shaft  6  is provided with a bevel gear  9 , which rotates integrally with the drive shaft  6  around the axis  6   a . As shown in  FIG. 4(   a ), the bevel gear  9  meshes with a bevel gear  11  of the electric motor  4 . The bevel gear  11  is attached to an output shaft  10  of the electric motor  4  and rotates integrally with the output shaft  10  around the axis  10   a  thereof. Thus, the rotation of the output shaft  10  around its axis  10   a  causes the drive shaft  6  to rotate around its axis  6   a . The axis  6   a  of the drive shaft  6  intersects orthogonally with the axis  10   a  of the output shaft  10 . 
   A spindle  12  shown in  FIG. 3  and  FIG. 4(   a ) is supported to be rotatable around the axis  12   a  thereof by a bearing  17  contained in a base  16  disposed on the external side of the housing  5 . The axis  12   a  of the spindle  12  is in alignment with the axis  6   a  of the drive shaft  6 . 
   As shown in  FIG. 3  and  FIG. 4(   b ), the base  16  has a pair of support rods  15  as peripheral parts. The axis  15   a  of each support rod  15  is parallel to the axis  12   a  of the spindle  12 . As shown in  FIG. 3 , the spindle  12  is located between these two support rods  15 . A predetermined clearance is secured between the spindle  12  and each support rod  15 . In other words, each support rod  15  is located apart from the drive shaft  6  and from the spindle  12 . As shown in  FIG. 4(   b ), each support rod  15  is provided with a rack  19  extending along the axis  15   a  thereof. 
   A transmission shaft  18  shown in  FIG. 3  and  FIG. 4(   b ) is rotated around the axis  18   a  thereof by operating a handle  21  (see  FIG. 2  and  FIG. 3) . The axis  18   a  of the transmission shaft  18  intersects orthogonally with the axis  10   a  of the output shaft  10  and with the axis  6   a  of the drive shaft  6 . As shown in  FIG. 4(   b ), the transmission shaft  18  is provided with a pair of pinions  20 , which rotate integrally with the transmission shaft  18  around the axis  18   a  thereof. The pair of pinions  20  is meshed with the racks  19  respectively. Thus, rotation of the transmission shaft  18  around the axis  18   a  thereof causes the support rods  15  and the base  16  to move along the axis  12   a  of the spindle  12 . More specifically, the support rods  15  and the base  16  function as moving member that move along the axis  12   a  of the spindle  12 . Both end portions  22  of the transmission shaft  18  are located outside the housing  5 . 
   As shown in  FIG. 3  and  FIG. 4(   a ), the spindle  12  is connected to the drive shaft  6  with a spline  13 . Thus, the spindle  12  can move along its axis  12   a  relative to the drive shaft  6  and also rotates integrally with the drive shaft  6 . Therefore, movement of the base  16  along the axis  12   a  of the spindle  12  causes the spindle  12  to move along its axis  12   a , and rotation of the drive shaft  6  around its axis  6   a  causes the spindle  12  to rotate around its axis  12   a.    
   A cutter  14  can be removably attached to the distal end of the spindle  12 . The cutter  14  attached to the spindle  12  is located outside the housing  5  to rotate and move integrally with the spindle  12 . 
   Therefore, a torque output from the electric motor  4  through the output shaft  10  is transmitted through the drive shaft  6  to the spindle  12 . Then, the cutter  14  attached to the spindle  12  rotates integrally with the spindle  12  around the axis  12   a , depending on the torque. 
   When the spindle  12  moves along its axis  12   a , the distance over which the cutter  14  attached to the spindle  12  moves, the stroke S shown in  FIG. 3 , is greater than that in the conventional cutter driving apparatus shown in  FIG. 7(   a ). This is because the rack  19  shown in  FIG. 4(   b ) is longer than the conventional rack  119  shown in  FIG. 7(   a ). Since the rack  19  is provided on each support rod  15  located apart from the drive shaft  6  and apart from the spindle  12 , it does not interfere with members disposed around the drive shaft  6  and spindle  12 . 
   As shown in  FIG. 5(   a ) to  FIG. 6(   b ), both end portions  22  of the transmission shaft  18  have a substantially square cross section. In other words, each end portion  22  has four plane surfaces  22   a  arranged around the axis  18   a  at 90° intervals. Each end portion  22  has a pin  31 , a helical compression spring  32 , and a movable part. In this embodiment, the movable part is a ball  33 . The pin  31  has a large-diameter portion  31   a  formed on the proximal end side thereof and a small-diameter portion  31   b  formed at an intermediate part in the axial direction thereof. The pin  31  moves between a protrusion position (see  FIG. 5(   b )) and a retraction position (see  FIG. 6(   b )). At the protrusion position, the tip of the pin  31  protrudes from the end face of the transmission shaft  18 , while the tip of the pin  31  at the retraction position does not protrude from the end face of the transmission shaft  18 . When the pin  31  is located at the protrusion position, the large-diameter portion  31   a  is abutted against the ball  33  to urge the ball  33  such that a part of it protrudes from the plane surface  22   a . Meanwhile, when the pin  31  is located at the retraction position, the small-diameter portion  31   b  is abutted against the ball  33 , so that the ball  33  does not protrude from the plane surface  22   a . The helical compression spring  32  urges the pin  31  located at the retraction position toward the protrusion position. 
   The handle  21  has a main body  23  and a joint  25  attached to one end portion thereof. The joint  25  contains a center hole  26 , and the axis of the center hole  26  intersects orthogonally with the major axis of the main body  23 . The joint  25  is rotatable around the axis of the center hole  26  relative to the main body  23 . The center hole  26  has a substantially square shape. In other words, the center hole  26  is defined by planes containing four plane surfaces  26   a  arranged around the axis thereof at 90° intervals. Each plane surface  26   a  has a recess  30  defined thereon. The center hole  26  permits insertion of the end portion  22  of the transmission shaft  18 . The end portion  22  inserted to the center hole  26  enables the transmission shaft  18  to rotate integrally with the joint  25 . 
   If the pin  31  is located at the protrusion position when the end portion  22  of the transmission shaft  18  is inserted to the center hole  26 , a part of the ball  33  protruding from the plane surface  22   a  is brought into the recess  30 . Thus, the transmission shaft  18  becomes unable to disengage from the joint  25 . Meanwhile, when the pin  31  is located at the retraction position, the part of the ball  33  protruding from the plane surface  22   a  retracts from the recess  30 . Thus, the transmission shaft  18  becomes disengageable from the joint  25 . 
   A plurality of recesses  34  is formed on the peripheral surface of the joint  25 . The main body  23  is provided with a movable part in the vicinity of the joint  25 . In this embodiment, the movable part is a pin  35 . The pin  35  moves between a protrusion position (see  FIG. 5(   a )) and a retraction position (see  FIG. 6(   a )). At the protrusion position, the tip of the pin  35  is located in one of the recesses  34 , while the tip of the pin  35  at the retraction position is located in none of the recesses  34 . When the pin  35  is located at the protrusion position, the joint  25  can rotate around the axis of the center hole  26  integrally with the main body  23 . Meanwhile, when the pin  35  is located at the retraction position, the rotation of the main body  23  is not transmitted to the joint  25 . More specifically, the main body  23  runs idle relative to the joint  25 . A helical compression spring  36  urges the pin  35  located at the retraction position toward the protrusion position. A knob  35   a  moves between a locking position and an unlocking position. When the knob  35   a  is located at the locking position, the pin  35  is brought to the protrusion position, whereas when the knob  35   a  is located at the unlocking position, the pin  35  is brought to the retraction position. 
   When the cutter  14  attached to the spindle  12  is to be moved along the axis  12   a  of the spindle  12 , the handle  21  is fitted to one end portion  22  of the transmission shaft  18 . Then, after the knob  35   a  is brought to the locking position, the handle  21  is rotated around the axis of the center hole  26 . Thus, the transmission shaft  18  rotates integrally with the handle  21  to cause the cutter  14  to move along the axis  12   a  of the spindle  12 . 
   In the case where rotation of the handle  21  in a desired direction is interfered by an obstacle, the knob  35   a  is brought to the unlocking position, and the handle  21  is rotated in the direction opposite to the desired direction. The knob  35   a  is then returned to the locking position, and the handle  21  is rotated in the desired direction. Thus, the cutter  14  moves in one direction by reciprocating the handle  21  without detaching the handle  21  from the transmission shaft  18 . 
   When the handle  21  is detached from the transmission shaft  18 , the pin  31  is brought to the retraction position from the protrusion position resisting against the urging force of the helical compression spring  32 . Thus, the handle  21  can be disengaged from the transmission shaft  18 . 
   The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.