Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to resistance welders, and more particularly, to a device for removing an electrode tip fitted to a tapered shaft of a shank in a resistance welder. 
     2. Background of the Related Art 
     As related art devices of this kind, there are a device in which an expandable member or wedge is inserted by force between a shank and an electrode tip for separating the electrode tip from the shank, and a device in which fine impacts are applied to the electrode tip for pulling the electrode tip from the shank. (see Japanese Laid Open Patent No. 3-291175, and Japanese Laid Open Patent No. 4-9285) However, because devices using the expandable member or inserting the wedge by force require disposition of an expandable part or a wedge part between the electrode tip and the shank by inserting the expandable part or the wedge part through an entire length of the electrode tip, and further require provision of a device for holding the removed electrode tip in place near to a fore end of the electrode tip, which causes the portion of the device in the vicinity of the electrode tip to leave a tight space to the shank disposed above and below thereof, employment of a robot becomes difficult. And, the type of devices applying impact suffer from the inconvenience of generating noise as the impacts are applied to the electrode tip repeatedly. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the invention, a device is disclosed for removing an electrode tip from a shaft of a resistance welder by turning the electrode tip. The device comprises a holding member having a center of rotation. The holding member defines a first hole sized to receive the electrode tip. The device also includes a claw disposed adjacent the first hole and mounted for rotation between an engagement position wherein at least a portion of the claw is positioned within the first hole to secure the electrode tip within the first hole, and a disengagement position wherein the at least a portion of the claw is displaced from the first hole. Additionally, the device includes a turning plate having a center of rotation coincident with the center of rotation of the holding member. The turning plate defines a second hole at the center of rotation. The turning plate is structured to move the claw from the disengagement position to the engagement position to secure the electrode tip in the first hole when the turning plate rotates in a first direction and to move the claw from the engagement position to the disengagement position to release the electrode tip from the first hole when the turning plate rotates in a second direction opposite the first direction. The device further includes a brake operatively engaging the holding member to substantially secure the holding member against movement during at least a first phase of movement of the claw from the disengagement position toward the engagement position. The holding member turns with the turning plate in the first direction after completion of the first phase of movement to turn the electrode tip. 
     Preferably, the claw has an axis of rotation and the axis of rotation of the claw is substantially parallel to an axis of the first hole. 
     In some embodiments, the first phase ends when the claw enters the engagement position. 
     Preferably, the first and second holes are coincident with the centers of rotation of the turning plate and the holding member. 
     Preferably, the second hole is sized to receive a portion of the holding member, the holding member includes an end portion projecting from the turning plate, and the brake cooperates with the end portion to apply the braking force to the holding member. In some such embodiments, the brake comprises a pair of brake arms engaging an outer surface of the end portion of the holding member; and a spring biasing the brake arms into frictional engagement with the end portion. 
     In some embodiments, the first hole has an inner wall and an inner diameter, and the inner diameter is sized such that, when the claw is in the engagement position and engages the electrode tip, a side of the electrode tip frictionally engages a portion of the inner wall. In some such embodiments, grooves are formed in the portion of the inner wall. In some such embodiments, the device includes only one claw and the portion of the inner wall is located opposite the claw. 
     In some embodiments, the claw comprises at least three claws, and the claws are spaced around the first hole such that, when the claws enter their engagement positions, the electrode tip is secured between the claws. 
     Preferably, the device includes a motor operatively coupled to the turning plate for rotating the turning plate in at least one of the first and second directions. In some such embodiments, the turning plate includes gear teeth, and the motor is operatively coupled to the gear teeth of the turning plate via at least one intermediate gear. 
     Preferably, the first hole is positioned to receive the electrode tip from two directions. 
     In accordance with another aspect of the invention, a device is disclosed for removing an electrode tip from a shaft of a resistance welder by turning the electrode tip. The device includes a holding member defining a first hole. It also includes a claw disposed adjacent the first hole and mounted for rotation between an engagement position wherein at least a portion of the claw is positioned within the first hole to secure the electrode tip within the first hole, and a disengagement position wherein the at least a portion of the claw is displaced from the first hole. The device also includes a turning plate cooperating with the claw to move the claw from the disengagement position to the engagement position to secure the electrode tip in the first hole when the turning plate rotates in a first direction and to move the claw from the engagement position to the disengagement position to release the electrode tip from the first hole when the turning plate rotates in a second direction opposite the first direction. Additionally, the device includes a brake operatively engaging the holding member such that, during a first phase of operation, the holding member does not rotate and the turning plate moves the claw from the disengagement position toward the engagement position, and during a second phase of operation, the holding member rotates with the turning plate to rotate the electrode tip. 
     In accordance with another aspect of the invention, a method of removing an electrode tip from a shaft of a resistance welder by turning the electrode tip is provided. The method comprises the steps of; inserting the electrode tip into a bore defined in at least one of a turning plate and a holding member; rotating the turning plate in a first direction without rotating the holding member to thereby move at least one claw into engagement with the electrode tip to secure the tip within the bore; and subsequently rotating the turning plate and the holding member in the first direction while the at least one claw secures the electrode tip in the bore to thereby turn the tip. 
     Preferably, the method also comprises the step of rotating the turning plate and the holding member in a second direction opposite the first direction to release the electrode tip from the bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the teachings of the invention and are incorporated in and constitute a part of this specification, illustrate devices constructed in accordance with the teachings of the invention and, together with the description, serve to explain the principles of the invention: 
     FIG. 1 illustrates a plan view of a first exemplary device for removing an electrode tip. 
     FIG. 2 illustrates a front view of the device of FIG.  1 . 
     FIG. 3 illustrates an enlarged sectional view taken across line III—III in FIG.  1 . 
     FIG. 4 illustrates an exploded perspective view of the device of FIG.  1 . 
     FIG. 5 illustrates a partial cross section of the device of FIG. 1 showing a state immediately before a clockwise turn of the turning plate is made to remove the electrode tip. 
     FIG. 6 is a view similar to FIG. 5, but showing a state immediately after a clockwise turn of the turning plate. 
     FIG. 7 is a view similar to FIGS. 5 and 6, but showing a state after FIG. 6 in removal of an electrode tip. 
     FIG. 8 is a view similar to FIGS. 5 and 6, but showing a state immediately before rotation of a holding member. 
     FIG. 9 is a view similar to FIGS. 5 and 6, but showing a state when the turning plate is turned in a reverse direction. 
     FIG. 10 illustrates a plan view of a second exemplary device constructed in accordance with the teachings of the invention for removing an electrode tip. 
     FIG. 11 illustrates a front view of the device of FIG. 10 
     FIG. 12 illustrates an enlarged sectional view taken across line XII—XII of FIG.  10 . 
     FIG. 13 illustrates an exploded perspective view of the device of FIG.  10 . 
     FIG. 14 illustrates a partial cross section of the device of FIG. 10 showing a state immediately before a clockwise turn is made of the turning plate to remove the electrode tip. 
     FIG. 15 is a view similar to FIG. 14, but showing a state immediately after a clockwise turn of the turning plate. 
     FIG. 16 is a view similar to FIG. 14, but showing a state right before rotation of a holding member. 
     FIG. 17 is a view similar to FIG. 14, but showing a state when the turning plate is turned in a reverse direction. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     The device disclosed herein can be used for removing an electrode tip, and includes a part near to the electrode tip which is made thin such that electrode tips which are fitted in a tight space between shanks can be removed with ease, and noise generation during the work can be prevented. 
     A device M 1  constructed in accordance with the teachings of the invention for removing an electrode tip is shown in FIGS. 1 and 2. The device M 1  is adapted for removing an electrode tip  4  fitted to a shank  1  and  2  of a welding robot as a resistance welder. The device M 1  includes a body  10  connected to an arm (not shown) of a working robot, and a fore end  13 . The fore end  13  projects from a side of a top surface of the body  10  in a horizontal direction for inserting between the shanks  1  and  2  and for mounting on the electrode tip  4  when the electrode tip  4  is to be removed. The reference numeral  5  denotes a tapered hole of the electrode tip  4  fitted to the tapered shaft  3  of the shanks  1  and  2 . 
     Referring to FIGS. 1-3, the body  10  has a driving motor (not shown) fitted with a reduction gear in a housing  11  for rotating a driving gear  12  (explained later) in a regular or reverse direction. The fore end  13  includes a case  14  fixed to the housing  11 , a holding member  20  and a turning plate  27  accommodated in the case  14 , a claw  25  held in the holding member  20 , an intermediate gear  29  engaged with the driving gear  12  for turning the turning plate  27 , and compression rings  18  screwed on top and bottom of the case  14 . 
     Referring to FIGS. 3 and 4, the turning plate  27  has a substantially disk form and includes a hole  27   a  with an inside diameter which is greater than an outside diameter of the electrode tip  4 . The turning plate  27  also includes a gear portion  27   e  on an outer circumference for engagement with the intermediate gear  29 , and cylindrical ribs  27   f  on top and bottom surfaces thereof. A center of rotation X of the turning plate  27  is provided in an up and down direction at the center of the hole  27   a.  A recess  27   b  is formed in an inner circumference of the turning plate  27  for placing the claw  25  therein. As shown in FIG. 5, one side surface of the recess  27   b  is an engagement pressing surface  27   c  for turning the claw  25  to an engagement region where a fore end  25   b  of the claw  25  engages with the electrode tip  4 . The claw  25  is turned to the engagement region by turning the turning plate  27  in a regular direction such that the engagement pressing surface  27   c  engages a convex portion  25   d  and a side surface  25   e  of the claw  25 . The other side surface of the recess  27   d  is a disengagement pressing surface  27   d  for turning the fore end  25   b  of the claw to a disengagement region in which the fore end  25   b  of the claw  25  makes no interference with the electrode tip  4 . The claw  25  is turned to the disengagement region by turning the turning plate  27  in a reverse direction such that the disengagement pressing surface  27   d  engages the convex portion  25   f  and a side surface  25   g  of the claw  25  (see FIG.  9 ). 
     Referring to FIGS. 3-9, the claw  25  includes a body  25   a  (e.g., a substantially rectangular plate), and a shaft  25   h  (e.g., a cylindrical column) on top and bottom surfaces of the body  25   a.  The fore end  25   b  of the body  25  has a sharp angled form, and a plurality of grooves taking the high friction with the electrode tip  4  into consideration. That is, in the first embodiment, the claw  25  is dimensioned such that its fore end  25   b  is projected into a pass through hole  22   j  in the holding member  20  when the claw  25  is turned into the engagement region. The shafts  25   h  of the claw  25  are disposed parallel to the center of rotation X. The shaft  25   h  is vertically disposed in a space  22   i  defined in the rib  22   f  (which will be explained later) on the holding member  20  in the vicinity of the fore end  25   b  such that a cross section of the claw  25  is projected from the recess  27   b  of the turning plate  27  into the hole  27   a  and into the space  22   i  defined in the rib  22   f.  A height h 1  of the body  25   a  (see FIG. 3) is slightly smaller than a thickness T 1  (FIG. 4) of the rib  22   f  on the holding member  20  (which will be explained later). 
     As shown in FIGS. 3 and 4, the holding member  20  has the same center of rotation X as the turning plate  27 . The holding member  20  includes a disk  21 , and a disk  22  with a stepped portion. The outside diameter of the disk  21  is dimensioned such that the disk  21  is rotatable in an inner circumference of the rib  27   f  on a top surface of the turning plate  27 . The disk  21  has a pass through hole  21   a.  The inside diameter of the hole  21   a  is slightly greater than the outside diameter of the electrode tip  4 . The disk  21  has a thickness which is greater than a height of the rib  27   f  so that an outer circumference of the disk  21  projects from the rib  27   f.  As explained below, this outer circumference serves as a braking surface  21   g  for engaging a brake arm  32 . The disk  21  also has a tapered surface  21   b  (see FIG. 3) at an upper edge around the pass through hole  21   a  to facilitate easy insertion of the electrode tip  4  from above. A holding hole  21   c  and two pair of fitting holes  21   e  located on opposite sides of the holding hole  21   c  are positioned around the pass through hole  21   a.  Each fitting hole  21   e  has a smaller inside diameter at a lower portion to form a stepped surface  21   f  (see FIG.  3 ). 
     The disk  22  has a disk portion  22   a  and a rib  22   f  projected upward from the disk portion  22   a.  The outside diameter of the disk  21   a  is dimensioned such that the disk portion  22   a  is rotatable in an inner circumference of the rib  27   f  on a bottom surface of the turning plate  27 . The disk  22  has a pass through hole  22   b  at a center thereof. The pass through hole  22   b  has an outside diameter which is slightly greater than the electrode tip  4 . The disk portion  22   a  has a thickness equal to a height of the rib  27   f.  A tapered surface  22   c  is formed at a bottom side edge of the pass through hole  22   b  to facilitate easy insertion of an electrode tip from below (see FIG.  3 ). The disk  22  includes a holding hole  22   d  adjacent the pass through hole  22   b  (see FIG.  3 ). The holding hole  22   d  is located in vertical alignment with the holding hole  21   c  in the disk  21 . The shafts  25   h  on the top and bottom of the claw  25  are respectively inserted in these holding holes  21   c,    22   d.  Accordingly, in the illustrated device M 1 , inside surfaces of the holding holes  21   c,    22   d  in a clockwise direction centered on the rotation center X form rotating action surfaces  21   d,    22   e  which take a torque when the turning plate  27  rotates in a regular direction. 
     As shown in FIGS. 3-5, the rib  22   f  has a substantially cylindrical form projected upward from a rim of the pass through hole  22   b  on a top surface of the disk portion  22   a.  A space portion  22   i  is defined in the rib  22   f  in the holding hole  22   d  region. The outside diameter of the rib  22   f  is selected such that the rib  22   f  can be inserted in the hole  27   a  in the turning plate  27 . As shown in FIG. 5, the rib  22   f  includes a pass through hole  22   j  having an inner diameter d 1  and an inner circumference which are formed equal to the pass through hole  22   b.    
     There are a plurality of grooves  22   k  (see FIG. 5) formed in the inner circumference of the pass through hole  22   j  at a portion opposite to the space portion  22   i.  The rib  22   f  has a thickness (height) t 1  (see FIG. 4) which is slightly greater than a thickness t 0  of an inside circumference of the ribs  27   f  on the turning plate  27 . The rib  22   f  also has four screw holes  22   g  on the top surface thereof. These holes  22   g  are aligned with the fitting holes  21   e  in the disk  21 . 
     As shown in FIGS. 5-8, a groove  22   h  is formed in one side surface of the space portion  22   i  of the rib  22   f  for preventing interference with the claw  25  until the claw is disposed in the engagement region. The inside diameter d 1  of the pass through hole  22   j  in the holding member  20  is dimensioned such that a portion (i.e., a groove side  22   k  portion) located opposite to the claw  25  at the inner circumference of the pass through hole  22   b  is pressed by the outer circumference of the electrode tip  4  when the claw  25  is brought into the engagement region and presses the tip  4 . In the illustrated device, the inside diameter d 1  of the pass through hole  22   j  is 17 mm, and an outside diameter of the electrode tip  4  is 16 mm. 
     As shown in FIGS. 1-4, the case  14  includes an upper case  15  and a lower case  16 . Each of the upper case  15  and the lower case  16  has an annular projection  15   b,    16   b  at the fore end side. The inner circumference of the annular projections  15   b,    16   b  form pass through holes  15   a,    16   a.  The pass through holes  15   a,    16   a  correspond to the outside diameter of the gear portion  27   e  in the turning plate  27 . Six screw holes  15   c,    16   c  for bolts (not shown) are formed in each of the annular projections  15   b,    16   b  for fitting the compression rings  18  thereto. Each of the upper case  15  and the lower case  16  has six connection holes  15   d,    16   d  in a periphery of the body  10  for connection to each other. In particular, the connection hole  15   d  is a simple pass through hole while the connection hole  16   d  is a threaded hole. Each of the upper case  15  and the lower case  16  has a fitting hole  15   e,    16   e  for fitting a holding bolt  33  for rotatably holding the intermediate gear  29  and a brake arm  32  of a brake device  31  explained later. The fitting hole  15   e  is a simple pass through hole while the fitting hole  16   e  is a threaded hole. Recesses  15   f  (see FIG. 3) and  16   f  for accommodating the intermediate gear  19  and recesses  15   g  (not shown) and  16   g  (see FIG. 4) for accommodating the driving gear  12  are formed in opposite surfaces of the upper case  15  and the lower case  16 . The recess  16   g  forms a pass through hole. 
     As shown in FIGS. 3 and 4, a compression ring  18  is provided for rotatably accommodating the turning plate  27  within the upper case  15  and the lower case  16 . The compression ring  18  includes a cylindrical portion  18   a  of a size which can be inserted in the inner circumference of the annular projections  15   b,    16   b  on the upper case  15  and the lower case  16 . It also includes a jaw portion  18   d  which is formed on an outer circumference of an end portion of the cylindrical portion  18   a.  Each of the jaw portions  18   d  has fitting holes  18   e  which correspond to the threaded holes  15   c,    16   c  in the upper case  15  and the lower case  16 . The compression rings  18  are fitted to the upper case  15  and the lower case  16  by bringing the jaw portions  18   d  into contact with the annular projections  15   b,    16   b  on the upper case  15  and the lower case  16  by means of bolts (not shown) threaded into the threaded holes  15   c,    16   c  via the fitting holes  18   e  such that end surfaces  18   c  of the cylindrical portions  18   a  spaced from the jaw portion  18   d  are at opposite sides. Each of the fitting holes  18   e  is provided with a stepped surface in an inside surface for receiving a bolt head to prevent projection of the bolt head when the compression rings  18  are fitted to the upper case  15  and the lower case  16 . Thus, when the upper case  15  and the lower case  16  are fitted, each of the compression rings  18  blocks the outer circumference of the cylindrical rib  27   f  of the turning plate  27  from the inner circumference of the cylindrical portion  18   a.  Also, when the upper and lower cases  16  are fitted, the top and bottom surfaces of the gear portion  27   e  of the turning plate  27  between the end surfaces  18   c  is rotatable under a condition of the turning plate  27 . 
     The braking device  31  includes one pair of brake arms  32  and a compression coil spring  34 . Each of the brake arms  32  has a semicircular compression piece portion  32   a  at a fore end thereof for covering one half of the braking surface  21   g  on the disk portion  21  of the holding member  20 . Each brake arm  30  also includes a spring seat  32   b  at a far end for disposing the compression coil spring  34  therebetween. A bolt  33  is located at a center portion of the arms  32  for rotably supporting the brake arm  32  on the case  14 . 
     In assembly of the fore end portion  13 , the turning plate  27  and the intermediate gear  29  are disposed between the upper and lower cases  15 ,  16 , the compression rings  18  are fitted to the upper and lower cases  15 ,  16  with bolts (not shown), and bolts are passed through the connecting holes  15   d,    16   d  to connect the upper and lower cases  15  and  16  to each other. Then, the claw  25  is disposed in the recess  27   b  of the turning plate  27  and, at the same time, the disk  21  and the stepped disk  22  are disposed from top and bottom of the turning plate  27 . In detail, the rib  22   f  is inserted into the pass through hole  27   a  from below, and at the same time, each of the fitting holes  21   e  are matched with the threaded holes  22   g,  and the shafts  25   h  are inserted into each of the holding holes  21   c,    22   d.  When each of the connecting bolts  23  are threaded into the threaded holes  22   g  through each of the fitting holes  21   e,  the disk  21  and the stepped disk  22  are fastened. In other words, the holding member  20  is assembled and is disposed to pass through the turning plate  27 . Since the height t 1  of the rib  22   f  of the holding member  20  is slightly greater than the height h 1  of the body  25   a  of the claw  25  and the inside surface thickness t 0  of the ribs  27   f  on the turning plate  27 , the claw  25  is rotatably held by the holding member  20  centered on the shafts  25   h.  The holding member  20  is secured within the case  14  by the rib  27   f  and the like such that the holding member can make a relative movement with the turning plate  27  by matching the rotation center X with the turning plate  27 . The assembly of the fore end portion  13  is completed by fitting the brake arm  32  to the case  14  by using the holding bolts  33 , by bringing the compression piece portions  32   a  into contact with the braking surfaces  21   g  on the disk  21  of the holding member  20 , and by positioning the compression coil spring  34  between the spring seats  32   b.  It is preferable that, after the fore end portion  13  is assembled, the intermediate gear  29  and the driving gear  12  are engaged, and the fore end portion  13  and the body  10  are assembled. 
     As shown in FIGS. 5-7, when removing an electrode tip  4 , the turning plate  27  is placed around the electrode tip  4  such that the electrode tip  4  is inserted in the pass through holes  21   a  and  22   b  in the holding member  20  which is concentric to the pass through hole  27   a  in the turning plate  27 . The driving motor in the body  10  is then driven to turn the turning plate  27  in a clockwise direction with reference to the center of rotation X by using the driving gear  12  and the intermediate gear  29 . Then, as shown in FIGS. 5-7, the engagement pressing surface  27   c  of the turning plate  27  is engaged with the convex portion  25   d  and side surface  25   e  of the claw  25  to turn the claw  25  in a clockwise direction taking the shaft as a rotation center. The claw  25  will turn until, as shown in FIG. 8, the claw  25  enters the engagement region where the fore end  25   b  of the claw  25  engages with the outer circumference of the electrode tip  4 , thereby securing the electrode tip  4  in the pass through hole  22   j.  The electrode tip  4  is engaged with the fore end of the claw  25  with the electrode tip  4  tilted slightly such that the electrode tip  4  presses against the groove portion  22   k  of the pass through hole  22   j.  Under this condition, if the turning plate  27  is further rotated in a clockwise direction, the fore end  25   b  of the claw  25  is directed toward a center direction of the electrode tip  4 , making a deeper engagement with the electrode tip  4  with a greater resistance of engagement of the claw  25 . When rotation of the claw  25  becomes difficult, a rotation torque applied to the turning plate  27  exerts a force on the rotating action surfaces  21   d,    22   e  which engage the claw  25 , so that the holding member  20  is rotated in a clockwise direction together with the turning plate  27  against a resistance of a rotation braking force of the brake arms  32 . As the holding member  20  rotates with the claw  25  engaging with the electrode tip  4  held in the pass through hole  22   j,  the electrode tip  4  is rotated in a clockwise direction with the turning plate  27 . Because even a slight rotation of the electrode tip  4  releases the fitting between the tapered shaft  3  of the shank  1  and the electrode tip  4 , if the fore end portion  13  is moved downward together with the body  10  from the fore end side of the shank  1 , the electrode tip  4  can be removed from the shank  1 . After the fore end portion  13  is brought over a collection box, the driving motor in the body  10  is driven in reverse, to cause a reverse rotation of the turning plate  27  and holding member  20  in a counterclockwise direction with reference to the center of rotation X. Then, as shown in FIG. 9, the disengagement pressing surface  27   d  of the turning plate  27  comes into contact with the convex portion  25   f  and the side surface  25   g  of the claw  25 . As a result, the claw  25  rotates in a counterclockwise direction about the shaft  25   h  so that the fore end  25   b  of the claw  25  releases the electrode tip  4  in the pass through hole  22   j,  and enters into the disengagement region. Because the electrode tip  4  is released from engagement with the fore end  25   b  of the claw and, thus, from the compression force into the groove portion  22   k  in the inner circumference of the pass through hole  22   j,  the tip  4  is dropped from the pass through hole  22   j  in the holding member  20  and the pass through hole  27   a  in the turning plate  27 , and the tip  4  falls into the collection box. After reversing the turning plate  27  reduces the engagement resistance of the claw  25 , the holding member  20  is no longer rotated because the rotation braking force of the compression piece portions  32   a  in the brake arms  32  act on the braking surfaces  21   g.  Continued rotation of the turning plate  27  rotates the claw  25  to the disengagement region. The electrode tip  4  on the lower shank  2  can also be easily collected into the collection box in the same manner as the electrode tip  4  on the upper shank  1  if the fore end portion  13  is brought around the electrode tip  4 , the turning plate  27  is rotated in a clockwise direction, the fore end portion is moved to a required position, and the turning plate  27  is reversed. 
     From the foregoing, persons of ordinary skill in the art will appreciate that the disclosed device M 1  can be made slim to permit easy removal of an electrode tip  4  fitted in a tight space between the shanks  1  and  2 . Moreover, since what is required in the removal of the electrode tip  4  is a simple engagement of the fore end  25   b  of the claw  25  with the electrode tip  4 , there is no noise of impact, and occurrence of noise during working is suppressed. As described above, the disclosed device has the holding member  20  disposed to pass through the pass through hole  27   a  in the turning plate  27 , the end portion  21   g  of the disk  21  projects from the turning plate  27 , and the rotation braking force applied to the holding member  20  is generated by the brake arms  32  pressing the outer circumference  21   g  to apply a friction force thereto by using the compression coil spring  34 . Accordingly, because the height of the brake arms  32  can be selected to be within the height of the outer circumferences  21   g,  and because portions of the braking device  31  other than the brake arms  32  can be disposed away from the vicinity of the electrode tip  4 , the thickness of the device M 1  in the vicinity of the electrode tip  4  can be made slim. This slimness permits easy removal of the electrode tip  4  fitted in the tight space between the shanks  1  and  2 . Moreover, as explained above, the inside diameter d 1  of the pass through hole  22   j  in the holding member  20  is dimensioned such that the side portion of the groove portion  22   k  opposite to the claw  25  in the inner circumference of the pass through hole  22  can be pressed by the outer circumference of the electrode tip  4  when the claw  25  is disposed in the engagement region and presses the tip  4 . Accordingly, since the electrode tip  4  is held in the pass through hole  22   j  in the holding member  20  such that the electrode tip  4  is gripped between two points, (i.e., the fore end  25   b  of the claw  25  and the groove portion  22   k  in the inner circumference of the pass through hole  22   j  in a manner that the fore end  25   b  of the claw is engaged with the electrode tip  4  only in one side), a stable hold of the electrode tip  4  is possible. Furthermore, because the groove portion  22   k  is formed in a portion of the inner circumference of the pass through hole  22   j  opposite to the claw  25  when the claw  25  is disposed in the engagement region, and because a convex portion  22   l  in a periphery of the groove portion  22   k  can also be engaged with the electrode tip  4  together with the fore end  25   b  of the claw when the electrode tip  4  is held, a further stable hold on the electrode tip  4  is possible. 
     Though the device M 1  has a system in which the electrode tip  4  is held by gripping the electrode tip  4  by means of the fore end  25   b  of the claw and the inner circumference surface of the pass through hole  22   j  in the holding member  20 , a system may also be provided in which the electrode tip  4  is held between the fore end  25   b  of the claw and the inner circumference of the pass through hole  27   a  in the turning plate  27  without departing from the scope or spirit of the invention. 
     Another device M 2  constructed in accordance with the teachings of the invention is shown in FIGS. 10-13. In the device M 2  shown in FIGS. 10-13, a system is provided in which only the claw  45  holds the electrode tip  4 . The device M 2  is different from the device M 1  in the claw  45 , the holding member  40  for holding the claw  45 , and the turning plate  47 . The upper and lower cases  15  and  16  in the case  14 , the compression rings  18 , the intermediate gear  29 , the brake device  31 , the driving gear  12 , and the body  10  are the same in both device M 1 , M 2 . Therefore explanations of those components will be omitted from the following discussion. 
     Referring to FIGS. 12-14, the turning plate  47  has a substantially disk form. It includes a pass through hole  47   a  formed in a central portion. The hole  47   a  has an inside diameter which is slightly greater than an outside diameter of the electrode tip  4 . The turning plate  47  also includes a gear portion  47   e  which is engaged with the intermediate gear  29 . The turning plate  47  is disposed in the pass through holes  16   a  of the upper and the lower cases  15 ,  16 , and is secured in up and down directions for rotation between the cylindrical end portions  18   c  of the upper and lower compression rings  18 . The center of rotation X of the turning plate  47  is set at the center of the pass through hole  47   a  in up and down directions. The turning plate  47  has annular ribs  47   f  on top and bottom surfaces for slidably engaging the inner circumferences of the cylindrical portions  18   a  of the compression rings  18 . The pass through hole  47   a  has three slots  47   b  for respectively disposing three claws  45  therein. The slots  47   b  are oriented in a radial direction and spaced in equal angles. 
     Each of the slots  47   b  has an engagement compression surface  47   c  for engaging the convex portion  45   c  and the side surface  45   d  of the claw to rotate the claw  45  until the fore end  45   b  of the claw is in an engagement region wherein the fore end  45   b  engages with the electrode tip  4  when the turning plate is turned in a regular (e.g., clockwise) direction. As shown in FIG. 17, the other side surface of the slot  47  is a disengagement compression surface  47   d  which rotates the fore end  45   b  of the claw to a disengagement region where no interference with the electrode tip  4  occurs by pressing the convex portion  45   e  and the side surface  45   f  of the claw  45  when the turning plate  47  reverses. 
     The turning plate  47  has these guide holes  47   g  of a circular arc form centered on the rotation center X of the turning plate  47  and located between the slots  47   b.  These guide holes  47   g  guide a rotation of the holding member relative to the turning plate  47 . 
     As shown in FIGS. 12-14, each claw  45  has a body  45   a  (e.g., a substantially rectangular plate), and shafts (e.g., circular columns) on top and bottom end surfaces of the body  45   a.  Fore end  45   b  of the body  45   a  forms a sharp angle. That is, each of the claws  45  in the device M 2  is dimensioned such that the fore end  45   b  is projected into the pass through hole  47   a  in the turning plate  47  when the claw  45  is rotated about the shafts  45   g  (which are parallel to the rotation center X). This is accomplished by disposing the upper and lower shafts  45   g  approximately midway between an origin side (convex portion  45   c  and  45   e  side, see FIGS. 15 and 17) and the fore end  45   b  side. The body  45   a  has a height h 2  (see FIG. 12) which is slightly smaller than a height h 3  (see FIG. 13) of the spacer  43  of the holding member  40 . 
     As shown in FIGS. 12 and 13, the holding member  40  of the device M 2  has a center of rotation which is concentric with the turning plate  47 . The holding member  40  includes two sheets of disks  41 ,  42 , three pieces of spacers, and six connecting bolts for connecting the above. Each of the disks  41 ,  42  has an outside diameter which is dimensioned such that the disks  41 ,  42  are rotatable in the inner circumference of the ribs  47   f  on the top and bottom of the turning plate  47 . Each of the disks  41 ,  42  also includes a pass through hole  41   a,    42   a  which has an inside diameter which is equal to the diameter of the pass through hole  47   a  in the turning plate  47  (i.e., slightly greater than the outside diameter of the electrode tip  4 ). Each of the disks  41 ,  42  has a tapered surface  41   b,    42   b  at an edge of the pass through hole  41   a,    42   a  in a surface facing outside of the disk for facilitating easy insertion of the electrode tips  4  from top and bottom thereof. The disks  41 ,  42  also have three holding holes  41   c,    42   c  and three fitting holes  41   e,    42   e  located around each of the pass through holes  41   a,    42   a  opposite each other respectively in concentric and radial direction. The holding holes  41   e,    42   e  rotatably hold the claws  45  by receiving the upper and lower shafts  45   g  of the claws  45  and act as rotation action surfaces  41   d,    42   d  which receive a rotation torque when a portion of an inner circumference of the holding holes  41   c,    42   c  is rotated together with the turning plate  47  turning in a regular (e.g., clockwise) direction. That is, the bearing surfaces  41   d,    42   d  are surfaces in the inner circumference of the holding holes  41   c,    42   c  facing a counterclockwise direction when the rotation center X of the turning plate  47  is taken as the center of rotation. Each of the fitting holes  41   e,    42   e  has a stepped surface for receiving a head of the connecting bolt  44 . This stepped surface is created by forming an inside diameter of a first inside portion smaller than the inside diameter of a second inside portion of the holes  41   e,    42   e.    
     The disk  41  has a thickness t 2  (see FIG. 13) which is greater than a height h 4  of the rib  47   f  on the top surface of the turning plate  47 . As a result, an outer circumference surface projecting above the rib  47   f  becomes a braking surface  41   f  interacting with the compression piece portion  32   a  on the brake arms  32 . The thickness of the disk  42  is equal to a height of the rib  47   f  on the bottom side of the turning plate  47 . Each of the spacers  43  have a cylindrical form with an outside diameter dimensioned so that the spacer can be inserted in the guide hole  47   g.  Each spacer  43  has a thread hole  43   a  for receiving the connecting bolt  44  in an inner circumference thereof. As already explained, each of the spacers  43  has a height h 3  (see FIG. 13) which is slightly greater than a height h 2  of the body  45   a  of the claw  45 , and which is slightly greater than a thickness t 3  of the inner circumference of the ribs  47   f  on the turning plate  47 . 
     The process for assembling the fore end portion  13  in the device M 2  will now be explained. Under a condition the turning plate  47  and the intermediate gear  29  are disposed between the upper and lower cases  15 ,  16 , the compression rings  18  are fitted to the upper and lower cases  15 ,  16  with bolts (not shown), and the bolts are passed through the connecting holes  15   d,    16   d  to connect the upper and lower cases  15 ,  16  to each other. Then, the claws  45  are disposed in the slots  47   b  in the turning plate  47 . At the same time, the spacers  43  are disposed in the guide holes  47   g  in the turning plate  47 , and the disks  41 ,  42  are disposed in the turning plate  47  from above and below, respectively. Then, the fitting holes  41   e,    42   e  and the thread holes  43   a  in the spacers  43  are matched, and the shafts  45   g  are inserted in the holding holes  41   c,    42   c.  When the connecting bolts  44  are screwed into the thread holes  43   a  through the fitting holes  41   e,    42   e,  the disks  41 ,  42  and the three spacers  43  are connected to assemble the holding member  40  as well as to dispose the holding member  40  in the turning plate  47  in a fashion to pass through the turning plate  47 . In this instance, because each of the spacers  43  in the holding member  40  has a height h 3  slightly greater than a height h 2  of the body  45   a  of each of the claws  45  and a thickness t 3  of an inner circumference of each of the ribs  47   f  on the turning plate  47 , each of the claws  45  is rotatably held by the holding member  40  centered on the shafts  45   g.  The holding member  40  is secured within the case  14  by the rib  47   f,  the guide holes  47   g,  and the like such that the holding member  40  can make a relative movement with the turning plate  47  by matching the center of rotation X with the turning plate  47 . The assembly of the fore end  13  is completed by fitting the brake arm  32  to the case  14  with the holding bolt  33 , bringing the compression piece portions  32   a  into contact with the braking surfaces  41   f  on the disk  41  of the holding member  40 , and locating the compression coil spring  34  between the spring seats  32   b.  It is preferable that, after the fore end portion  13  is assembled, the intermediate gear  29  and the driving gear  12  are engaged, and the fore end portion  13  and the body  10  are assembled. 
     As shown in FIGS. 14-17, when the device M 2  is employed to remove the electrode tip  4 , the turning plate  47  is placed around the electrode tip  4  such that the electrode tip  4  is inserted in the pass through hole  47   a  in the holding member  40 . The driving motor in the body  10  is then driven to turn the turning plate  47  in a counterclockwise direction with reference to the center of rotation X via the driving gear  12  and the intermediate gear  29 . Then, as shown in FIGS. 14 and 15, the engagement pressing surface  47   c  of the turning plate  47  is brought into contact with the convex portion  45   c  and side surface  45   d  of each of the claws  45 . Each of the claws  45 , therefore, turns in the counterclockwise direction about their shafts  45   g  until, as shown in FIG. 16, each of the claws  25  rotates into the engagement region where the fore end  45   b  of each of the claws  45  engages with the outer circumference of the electrode tip  4  to thereby hold the electrode tip  4  in the pass through hole  47   a.  Under this condition, if the turning plate  27  is rotated further in the regular (i.e., counterclockwise) direction, the fore end  45   b  of each of the claws  45  is directed toward a center direction of the electrode tip  4 , making a deeper engagement with the electrode tip  4  with a greater resistance of engagement of the claws  25 . When rotation of the claws  45  become difficult, the turning plate  47  exerts a torque on the rotating action surfaces  41   d,    42   d,  (which are a supporting portion of each of the claws  25 ) so that the holding member  40  is rotated in the regular (i.e., counterclockwise) direction together with the turning plate  47  against a resistance of a rotation braking force generated by the brake arms  32 . As the holding member  40  rotates with each of the claws  25  engaging the electrode tip  4 , the electrode tip  4  is rotated in a counterclockwise direction which is a regular rotating direction of the turning plate  47 . Because even a slight rotation of the electrode tip  4  releases the fitting between the tapered shaft  3  of the shank  1  and the electrode tip  4 , if the fore end portion  13  is moved downward together with the body  10  from the fore end side of the shank  1 , the electrode tip  4  can be removed from the shank  1 . After the fore end portion  13  is brought over a collection box (not shown), the driving motor in the body  10  is reversed, thereby causing a reverse rotation of the turning plate  27  and the holding member  40  (i.e., in a clockwise direction with reference to the rotation center X). Then, as shown in FIG. 17, the disengagement pressing surfaces  47   d  of the turning plate  47  come into contact with the convex portion  45   e  and the side surface  45   f  of each of the claws  45 , to rotate the claws  45  in a clockwise direction taking the shaft  45   g  as a rotation center so that the fore end  45   b  of each of the claws  45  releases the electrode tip  4  in the pass through hole  47   a  and enters the disengagement region. When the electrode tip  4  is released from the engagement of the fore end  45   b  of each of the claws  45 , it is dropped from the pass through hole  47   a  in the turning plate  47  into the collection box. After reversing the rotation of the turning plate  47  reduces the engagement resistance of each of the claws  45 , the holding member  40  is no longer rotated because the rotation braking force of the compression piece portions  32   a  in the brake arms  32  acts on the braking surfaces  41   f.  Continued rotation of the turning plate  47  rotates the claws  45  to the disengagement region. 
     The electrode tip  4  on the lower shank  2  can also be collected into the collection box with ease in a manner similar to the electrode tip  4  on the upper shank  1  if the fore end portion  13  is brought around the electrode tip  4 , the turning plate  47  is rotated in a regular direction, the fore end portion is moved to a required position, and the turning plate  47  is reversed. 
     From the foregoing, persons of ordinary skill in the art will appreciate that the device M 2  can be made slim to permit easy removal of the electrode tip  4  fitted in a tight space between the shanks  1  and  2 . Since what is required in the removal of the electrode tip  4  is a simple engagement of the fore end  45   b  of the claws  45  with the electrode tip  4 , there is no noise from impact, and occurrence of noise during working is suppressed. Moreover, because the height of the brake arms  32  can be restricted to be within the height of the outer circumferences  41   f,  and because portions of the braking device  31  other than the brake arms  32  can be disposed away from the vicinity of the electrode tip  4 , a thickness of the portion in the vicinity of the electrode tip  4  in the removing device M 2  can be made, not thick, but slim, to permit easy removal of the electrode tip  4  fitted in the tight space between the shanks  1  and  2 . Moreover, in the device M 2 , three claws  45  are provided in an inner circumference of the pass through hole  47   a  in the turning plate  47  in radial directions. As a result, since the fore ends  45   b  of the claws engage with the electrode tip  4  substantially equally in a circumference of the electrode tip  4 , tilting of the electrode tip  4  is prevented, and deformation of the tapered shaft  3  on the shanks  1  and  2  can also be prevented. Though the illustrated device M 2  includes three claws  45  provided on an inner circumference of the pass through hole  47   a  in the turning plate  47  in radial directions, persons of ordinary skill in the art will appreciate that four or more than four claws may be provided on the inner circumference of the pass through hole  47   a  without departing from the scope or spirit of the invention. As a variation of the first device M 1 , only one claw  45  with the fore end  45   b  projected slightly further than the claw of the second device M 2  may be provided, so that the outer circumference of the electrode tip  4  presses the inner circumference of the pass through hole  47  opposite to the claw  45  when the fore end of the claw comes into engagement with the electrode tip. Further, as a variation of the device M 1 , only two claws  45  of the second device M 2  can be used with no slot  47   b  for the rest of the claw  45  formed, so that the outer circumference of the electrode tip  4  presses the inner circumference of the pass through hole  47  when the fore ends of the claws come into engagement with the electrode tip. 
     Moreover, with regard to the rotation braking force of the brake arms  32  against the holding members  20 ,  40  in the first and second devices M 1 , M 2 , it is required that the holding member  20 ,  40  be turned together with the turning plate  27  in a regular direction against the rotation braking force of the brake arms  32  when the fore end  25   b,    45   b  of the claw  25 ,  45  is deeply engaged with the electrode tip  4  to increase a claw engagement resistance. This leads to difficulty in rotating the claw  25 ,  45  such that the rotation torque of the turning plate  27 ,  47  acts on the rotation action surfaces  21   d,    22   e,    41   d,    42   d  on the supporting portion of the claw  25 ,  45 . To do this, it is required that a compression force of the spring  34  be adjusted appropriately such that the rotation braking force of the brake arm  32  is not excessive for turning the turning plate  27 ,  47  in a regular direction by the holding member  20 ,  40  before the fore end  25   b,    45   b  of the claw  25 ,  45  is directed to a center direction of the electrode tip  4  (before the first engagement with the electrode tip  4 ). 
     The disclosed devices for removing an electrode tip brings the turning plate around the electrode tip such that the electrode tip is inserted into the pass through hole in the turning plate, and turns the turning plate in a regular direction. Then, the engagement compression surface of the turning plate is brought into contact with the claw to rotate the claw to an engagement region, such that the fore end of the claw is engaged with the outer circumference of the electrode tip, holding the electrode tip within the pass through hole. If the turning plate is rotated in a regular direction further, increased claw engagement resistance is encountered, and the holding member receives a rotating torque from the regular rotating turning plate, (taking the supporting portion of the claw as a rotation action surface) sufficient to rotate the holding member in the regular direction against the rotation braking force together with the turning plate. That is, because the holding member rotates together with the claw when the holding member makes the claw engage with the electrode tip to hold the electrode tip in the pass through hole, the electrode tip rotates in a regular direction of the turning plate. Even if the electrode tip rotates slightly, the fitting state of the electrode tip to the tapered shaft of the shank is released. Accordingly, if the turning plate and the holding member and the like are moved toward a fore end of the shank, the electrode tip can be removed from the shank. 
     After the turning plate and the holding member are disposed at predetermined positions, the turning plate is reversed. Then, the disengagement compression surface of the turning plate is brought into contact with the claw, to rotate the claw until the fore end of the claw is disposed in the disengagement region, the hold on the electrode tip in the pass through hole is released, and the electrode tip drops from the pass through hole in the turning plate into a predetermined position. That is, since the reversing of the turning plate is a rotation in a direction in which the engagement resistance of the claw is reduced, the holding member is not rotated on receiving the rotation braking force, but only the turning plate is rotated to rotate the claw(s) to the disengagement region. 
     From the foregoing, person of ordinary skill in the art will appreciate that, in a case when one claw is provided and a dimension of an inner diameter of the pass through hole in the holding member or the turning plate is dimensioned such that an outer circumference of the electrode tip pressed by the claw can be pressed onto a portion of an inner circumference of the pass through hole opposite to the claw, the holding on the electrode tip in the pass through hole in the holding member or turning plate is a two point gripping between the fore end of the claw and the portion of the inner circumference of the pass through hole in contact with the electrode tip. A stable holding on the electrode tip is, therefore, made available. In this instance, if grooves are formed in the portion of the inner circumference of the pass through hole opposite to the claw when the claw is disposed in the engagement region, convex portions at edges of the grooves also can come into engagement with the electrode tip together with the fore end of the claw when the electrode tip is held. A more stable holding on the electrode tip is, therefore, made available. In a case when three or more than three claws are provided on the inner circumference of the pass through hole in radial directions, since the fore ends of the claws preferably make engagement with the electrode tip at substantially equal intervals in a circumferential direction of the outer circumference of the electrode tip, tilting of the electrode tip is prevented, and deformation of the tapered shaft of the shank can, therefore, be prevented to the utmost. 
     It will be apparent to those of ordinary skill in the art that various modifications and variations can be made in the disclosed devices for removing an electrode tip of the present invention without departing from the spirit or scope of the invention. Thus, there is no intention of limiting the scope of this patent to the precise examples disclosed herein. On the contrary, it is intended that the present patent cover all devices falling within the scope of the appended claims and their equivalents.

Technology Category: 7