Abstract:
A multi-function power tool includes a motor, a control circuit, a variable speed gear box, a transmission unit, a bow member, and a module. The control circuit is connected to an input end of the motor. A rotating end of the motor is connected to an input end of the variable speed gear box. An output end of the variable speed gear box is connected to the transmission unit. One end of the bow member is mounted on the transmission unit. The module is sandwiched between another end of the bow member and the transmission unit. The transmission unit is a ball screw structure. The power tool has a simple structure and a low cost. The ball screw structure can greatly improve mechanical efficiency and save energy consumption. The module for machining a workpiece may be changed to realize punching, shearing, and pressure jointing functions accordingly.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a multi-function power tool, and more particularly to a handheld power tool for punching, shearing and pressure jointing. 
       BACKGROUND OF THE INVENTION 
       [0002]    Nowadays, power tools in the market, such as punching machines, shearing machines and pressure jointing machines, include a fluid pressure type and an oil pressure type. The fluid pressure type power tools and the oil pressure type power tools have good performance, but cost a lot. The mechanical type power tools usually apply common screw pairs to work in sliding friction way. However, the sliding friction produced by movement of the screw pairs is large, which reduces the mechanic efficiency of the power tool. In addition, each of the power tools only has a single function and is used for one purpose. If other operations are needed, another power tool should be used. This limits the application range of the power tools. 
       SUMMARY OF THE INVENTION 
       [0003]    Therefore, the object of the present invention is to provide a multi-function power tool for punching, shearing and pressure jointing. 
         [0004]    The present invention provides a multi-function power tool, which includes a motor, a variable speed gear box, a transmission unit, a bow member, a module and a control circuit. The control circuit is connected to an input end of the motor. A rotating end of the motor is connected to an input end of the variable speed gear box. An output end of the variable speed gear box is connected to the transmission unit. The transmission unit is a ball screw structure. One end of the bow member is mounted on the transmission unit. The module is sandwiched between another end of the bow member and the transmission unit. 
         [0005]    The transmission unit is a ball screw structure including a screw, a ball nut placed around the screw, and a connecting member slipped over the ball nut. An outer wall of the screw and an inner wall of the ball nut define spiral grooves for receiving a plurality of balls. The balls can circularly move in a closed passageway between the screw and the ball nut. One end of the screw adjacent to the variable speed gear box has an annular protrusion and a tenon formed on a top thereof. The tenon is inserted into a mortise of the output end of the variable speed gear box. The screw has a ring groove adjacent to the tenon. An elastic washer is engaged in the ring groove. A circular pressing plate, a first thrust ball bearing and a second thrust ball bearing are positioned between the annular protrusion and the elastic washer. An inner wall of the connecting member has a collar embedded between the first thrust ball bearing and the second thrust ball bearing. A stop block and an L-shaped groove are formed on the connecting member. The ball nut includes a larger diameter portion and a smaller diameter portion. A spring is mounted on the smaller diameter portion of the ball nut. One end of the spring abuts against a fringe of the larger diameter portion, and the other end thereof abuts against a stop tube placed around the smaller diameter portion. A stop ring is form on an inner wall of the stop tube. One side of the stop ring abuts against the spring, and the other side of the stop ring abuts against a steel stop ring mounted on the smaller end portion of the ball nut. 
         [0006]    The module is one of punching mold, shearing mold and pressure joint mold, and includes a male mold and a female mold. The male mold is connected to the ball nut through thread connection or fastener connection. 
         [0007]    A power of the control circuit is connected to the motor through a toggle switch and two limit switches. The control for the limit switches is realized through a latch pin and a limit block, wherein two ends of the latch pin are respectively inserted into the ball nut and the limit block, the latch pin moves in a guiding hole to bring the limit block to press the limit switches positioned at two sides of the limit block. Alternatively, the control for the limit switches is realized through two limit pins, wherein the ball nut includes two sloping surfaces between the limit pins to press the limit pins on the limit switches. A safety switch is connected to the input end of the motor. 
         [0008]    One end of the bow member is connected to the connecting member. A female mold of the module is directly mounted to another end of the bow member, or is attached to a manual sliding sleeve received in the end of the bow member. One end of the bow member defines a notch. An inner wall of the bow member defines an annular groove communicating with the notch. The manual sliding sleeve includes a protrusion and an L-shaped guiding slot. 
         [0009]    The advantage of the present disclosures has a simple structure and a low cost. The ball screw structure can greatly improve mechanical efficiency and save energy consumption. The module for machining the workpiece may be changed to realize punching, shearing, and pressure jointing functions according to the need. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
           [0011]      FIG. 1  is a schematic, cross-sectional view of a power tool according to a first exemplary embodiment of the present invention; 
           [0012]      FIG. 2  is a schematic view of a control circuit of the power tool shown in  FIG. 1 ; 
           [0013]      FIG. 3  is a schematic, cross-sectional view of a power tool according to a second exemplary embodiment of the present invention; 
           [0014]      FIG. 4  is a schematic view of a manual sliding sleeve of the power tool shown in  FIG. 3 ; 
           [0015]      FIG. 5  is a schematic view of a bow member of the power tool shown in  FIG. 3 ; 
           [0016]      FIG. 6  is a left view of the power tool shown in  FIG. 3 ; 
           [0017]      FIG. 7  is a schematic view of a control circuit of the power tool shown in  FIG. 3 ; 
           [0018]      FIG. 8  is a schematic, cross-sectional view of a power tool according to a third exemplary embodiment of the present invention; 
           [0019]      FIG. 9  is a schematic view of a bow member of the power tool shown in  FIG. 8 ; 
           [0020]      FIG. 10  is a schematic view of a connecting member shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0021]    The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
         [0022]      FIG. 1  is a schematic cross-sectional view of a punching power tool according a first embodiment of the present invention. A power supply circuit of the power tool is closed when a normally-opened toggle-switch  61  is pressed down, so as to drive a motor  50  to rotate in clockwise direction. The motor  50  drives a motor gear  51  fixed on a shaft of the motor  50  to rotate together. A gear box  05  includes a three-stage planetary gear mechanism. The gear mechanism includes two inner gears  58 . Each inner gear  58  includes a protrusion  581  extending from an end surface thereof. The protrusions  581  of the two inner gears  58  are respectively inserted into holes of a connecting member  21  and a housing of the gear box  05  for preventing the inner gears  58  from rotating. The motor gear  51  drives a first stage planet gear  52  engaged therewith in the gear box  05  to rotate. The first stage planet gear  52  drives a first stage central gear  55  to rotate. The first stage central gear  55  drives a second planet gear  53  to rotate. The second planet gear  53  drives a second stage central gear  56  to rotate. The second stage central gear  56  drives a third stage planet gear  54  to rotate. The third stage planet gear  54  drives a third stage central shaft  57  to rotate. A driving block  06  is firmly attached to the third stage central shaft  57  and is rotated with the third stage central shaft  57 . The driving block  06  includes a mortise  061  inserted into a tenon  10  of a ball screw  19 . After multi-stage transmission in the gear box  05  goes through, the rotating speed of the driving block  06  is slowed down and the rotating torque is increased. Torque output from the driving block  06  is transmitted to the ball screw  19 . 
         [0023]    The ball screw  19  defines a ring groove. An elastic washer  23  is engaged in the ring groove. The elastic washer  23  prevents the ball screw  19  from being pulled out when an outward force is applied to the ball screw  19 . A B thrust ball bearing  12  is attached to the ball screw  19 . The B thrust ball bearing  12  sustains the outward force applied to the ball screw  19  during working. The B thrust ball bearing  12  is rotated with the rotating ball screw  19  to reduce the rotating friction of the ball screw  19 , so as to increase the rotational efficiency of the ball screw  19 . An annular flange  14  is formed on the ball screw  19 . A circular pressing plate  13  and an A thrust ball bearing  11  are mounted on the ball screw  19  between the annular flange  14  and the B thrust ball bearing  12 . A collar  212  protruding from an inner wall of the connecting member  21  is mounted on the ball screw  19 . The collar  212  is sandwiched between the A thrust ball bearings  11  and the B thrust ball bearings  12 . During the punching process, the annular flange  14  of the ball screw  19  transmits the pressure thereon to the annular flange  14  and the A thrust ball bearing  11 . The A thrust ball bearing  11  rotates with the ball screw  19  to reduce the rotating friction of the ball screw  19 , so as to increase the rotational efficiency of the ball screw  19 . Since an outer diameter of the ball screw  19  is much small, an outer diameter of the annular flange  14  cannot be too large. Or else, the material would be wasted a lot in manufacture of the ball screw  19 , and the manufacture cost a lot. Thus, the annular flange  14  is configured for supporting the circular pressing plate  13 . 
         [0024]    A ball nut  20  is mounted on the ball screw  19 . An outer wall of the ball screw  19  and an inner wall of the ball nut  20  respectively define a spiral groove  201 . A plurality of balls  15  are received in the spiral grooves  201 . The above ball screw structure facilitates a horizontally movement of the ball nut  20  and reduces friction between the ball screw  19  and the ball nut  20 , thereby improving mechanical efficiency. The ball nut  20  includes a larger diameter portion and a smaller diameter portion. A spring  16  is mounted on one end portion of the ball nut  20 . A diameter of this end portion is smaller than that of another end portion of the ball nut  20  without the spring  16  mounted thereon. One end of the spring  16  abuts against the larger end portion of the ball nut  20 , and the other end thereof abuts against a stop tube  22  placed around the smaller end portion of the ball nut  20 . A stop ring  221  is form on an inner wall of the stop tube  22 . One side of the stop ring  221  abuts against the spring  16 , and the other side of the stop ring  221  abuts against a steel stop ring  18  mounted on the smaller end portion of the ball nut  20 . A male mold  41  is connected to the ball nut  20  by engagement between an outer thread defined in one end thereof and an inner thread defined in one end of the ball nut  20 . The connecting member  21  receiving the ball nut  20  therein defines a guiding hole  211 . One end of a latch pin  62  is inserted into a hole of the larger end portion of the ball nut  20  via the guiding hole  211 , for preventing the ball nut  20  from rotating with the ball screw  19 . The other end of the latch pin  62  is connected to a limit block  65 . The limit block  65  has a substantially inverse-trapezium shape, and includes two sloping surfaces. The two sloping surfaces are respectively configured for touching an A limit switch  64  and a B limit switch  63  positioned at two sides of the limit block  65 . A distance between the A limit switch  64  and the B limit switch  63  is substantially equal to a horizontal movement distance of the ball nut  20 . A bow member  30  has one end portion thereof attached to the connecting member  21 . An annular groove is defined in this end portion of the connecting member  21 . A fastener (e.g. screw, bolt . . . ) extends through the wall of the bow member  30  and is inserted into the annular groove of the bow member. The connecting member  21  has a protrusion at each of two sides thereof. When the bow member  30  rotates relative to a horizontal axis, the fastener is stopped by the protrusions. Thus, the rotation angle of the bow member  30  is limited, so that the protrusions can be completely engaged in the annular groove with a large enough contact area. A female mold  42  corresponding to the male mold  41  is attached to another end of the bow member  30 . The female mold  42  and the male mold  41  constitute a whole module. 
         [0025]      FIG. 2  is a schematic view of a control circuit of the power tool of this first exemplary embodiment. A power  60  includes two poles respectively connected to a first contact  1  and a fourth contact  4  of the toggle-switch  61 . A second contact  2  of the toggle-switch  61  is connected to a second contact  2  of the A limit switch  64 . A first contact  1  of the A limit switch  64  is connected to one end of a second resistor  82 , a sixth contact  6  of the toggle-switch  61 , and one end of the motor  50 . A fifth contact  5  of the toggle-switch  61  is connected to the first contact  1  of the B limit switch  63 , one end of the first resistor  81  and the other end of the motor  50 . The other end of the first resistor  81  is connected to an anode of a first diode  83 , and a cathode of the first diode  83  is connected to the third contact  3  of the A limit switch  64 . The third contact  3  of the toggle-switch  61  is connected to the second contact  2  of the B limit switch  63 . The third contact  3  of the B limit switch  63  is connected to a cathode of a second diode  84 . An anode of the second diode  84  is connected to the other end of the second resistor  82 . 
         [0026]    Referring to  FIGS. 1 and 2 , the work principle of the present embodiment is schematically illustrated as flow: A workpiece is placed between the male mold  41  and the female mold  42 . The bow member  30  is rotated, and one end of the toggle-switch  61  is pressed to electrically connect to the power supply circuit. Referring to  FIG. 2 , the power  60  supplies power to the motor  50  through the toggle-switch  61  and the A limit switch  64 . The motor  50  rotates clockwise, and drives the ball screw  19  to rotate through the gear box  05 . The rotation of the ball screw  19  causes the ball nut  20  to move forward. The spring  16  and the stop tube  22  also move forward. When the stop tube  22  touches and presses the workpiece, a resistance force is applied to the stop tube  22 . The resistance force and the thrust force of the ball nut  20  cooperatively compress the spring  16 , and the spring  16  is deformed. A restoring force of the deformation of the spring  16  is applied to the stop tube  22 , so that the stop tube  22  can tightly press the workpiece. As the ball nut  20  drives the male mold  41  and the latch pin  62  to move forward, the latch pin  62  keeps to horizontally move along the guiding hole  211 . When the male mold  41  touches and presses the workpiece for punching, the limit block  65  connected to the latch pin  62  can just press the A limit switch  64 . The second contact  2  of the A limit switch  64  is disconnected from the first contact  1  of the A limit switch  64 . The third contact  3  of the A limit switch  64  is connected to the first contact  1  of the A limit switch  64 . Thereby, the power supply circuit is broken. The first diode  83 , the first resistor  81  and the motor  50  cooperatively form a loop to immediately stop the motor  50  from rotating. This can prevents the male mold  41  from being further moved forward by the inertial rotation of the motor  50 , thereby attaining a precision control. Then, the other end of the toggle-switch  61  is pressed. The power  60  supplies power to the motor  50  through the toggle-switch  61  and the B limit switch  63 . The motor  50  reversely rotates and drives the ball screw  19  to rotate by the gear box  05 . The rotation of the ball screw  19  forces the ball nut  20  to horizontally move back. The latch pin  62  and the limit block  65  move with the ball nut  20 , and the latch pin  62  keeps to horizontally move along the guiding hole  211 . When the male mold  41  is separated from the processed workpiece, the stop tube  22  still abuts against the processed workpiece by the rebounding spring  16 , so as to prevent the processed workpiece from being deformed by an inertia force of the male mold  41 . After the ball nut  20  moves back for a predetermined distance, the spring  16  returns to its original state. The stop tube  22  returns back with the ball nut  20  through the protruding wall  221 . When the limit block  65  just touch the B limit switch  63 , the second contact  2  of the B limit switch  63  is disconnected from the first contact  1  of the B limit switch  63 , and the third contact  3  of the B limit switch  63  is connected to the first contact  1  of the B limit switch  63 . Thereby, the power supply circuit is broken. The second diode  84 , the second resistor  82  and the motor  50  cooperatively form a loop to immediately stop the motor  50  from rotating. This may prevent the male mold  41  from being further returned by the inertial rotation of the motor  50 , thereby attaining a precision control. 
         [0027]      FIG. 3  is a schematic cross-sectional view of a power tool according to a second exemplary embodiment of the present invention. The power tool is mainly similar to that the first exemplary embodiment. The difference is schematically illustrated as follow. The male mold  41  is interlocked with the ball nut  20  with a fastener (e.g. screw, bolt . . . ). The ball nut  20  defines an upper groove  225  and a lower groove  226  at two opposite sides thereof, correspondingly. The fastener is inserted into the upper groove  225  via a hole of the connecting member  21 , for stopping the rotation of the ball nut  20 . A first limit pin  641  has one end thereof inserted into the lower groove  226  via another hole of the connecting member  21 , and another end thereof connected to the A limit switch  64  by a helical spring, facing a button of the A limit switch  64 . A second limit pin  631  is positioned with a predetermined distance from the first limit pin  641 . The second limit pin  631  has one end of inserted into the connecting member  21 , and another end thereof connected to the B limit switch  63  by a helical spring, facing a button of the B limit switch  63 . The ball nut  20  has two sloping surfaces between the limit pins  63 ,  64 . The two sloping surfaces are configured for respectively pressing down the first limit pin  641  and the second limit pin  631 . A distance between the limit pins  631 ,  641  is substantially equal to a horizontal movement distance of the ball nut  20 . 
         [0028]    One end of the bow member  30  is integrally formed with the connecting member  21 . The other end of the bow member  30  is mounted on a manual sliding sleeve  100  and defines at least one notch  308  in an end surface thereof. An inner wall of the bow member  30  defines an annular groove  309  communicating with the notch  308 . The manual sliding sleeve  100  has a ring flange  101 . A diameter of the ring flange  101  is larger than that of the other portion of the manual sliding sleeve  100 . The ring flange  101  has a cutout portion  102 . Also referring to  FIGS. 4 and 6 , a safety switch  105  is positioned beneath the cutout portion  102 . The manual sliding sleeve  100  includes a protrusion  103  and an L-shaped guiding slot  104 . A fastener extends through a hole defined in a wall of the bow member  30 , and is engaged in the L-shaped guiding slot  104  as a guiding member. The manual sliding sleeve  100  is horizontally moved forward while the fastener slides in the L-shaped guiding slot  104 . The protrusion  103  is received in the notch  308 . When the manual sliding sleeve  100  cannot be further moved in a horizontal direction, the fastener guides the manual sliding sleeve  100  to rotate along a bending direction of the L-shaped guiding slot  104 . The protrusion  103  is locked in the annular groove  309  (referring to  FIG. 5 ). The female mold  42  is attached to the other end of the manual sliding sleeve  100 . 
         [0029]      FIG. 7  is a schematic view of a control circuit of the power tool of the second exemplary embodiment. This control circuit has a difference from that shown in  FIG. 2  is that the safety switch  105  is connected to the input end of the motor  50 . 
         [0030]    To punch a workpiece, the workpiece is disposed in the bow member  30 . The manual sliding sleeve  100  is horizontally moved inside, and then is rotated to allow the protrusion  103  to be locked in the annular groove  309 . Accordingly, the protrusion  103  has enough contact area for enduring impact. An edge of the cutout portion  102  of the ring flange  101  can press the safety switch  105  under the ring flange  101 . When the manual sliding sleeve  100  cannot be further moved in a horizontal direction, the toggle-switch  61  is pressed down to connect the power supply circuit. Then, the motor  50  rotates clockwise, and drives the ball screw  19  to rotate through the gear box  05 . The rotation of the ball screw  19  causes the ball nut  20  to horizontally move forward. A distance is decreased between the female mold  42  and the male mold  41  since the manual sliding sleeve  100  moves forward, and thus the ball nut  20  only needs to move a short distance to finish the punching process. After punching, one of the sloping surfaces of the ball nut  20  just press the first limit pin  641 . The first limit pin  641  is forced to move down to press the button of the A limit switch  64 . Then, the second contact  2  of the A limit switch  64  is disconnected from the first contact  1  of the A limit switch  64 . The third contact  3  of the A limit switch  64  is connected to the first contact  1  of the A limit switch  64 . Thereby, the power supply circuit is broken. The first diode  83 , the first resistor  81  and the motor  50  cooperatively form a loop to immediately stop the rotation of the motor  50  so as to prevent the male mold  41  from being further moved forward by the inertial rotation of the motor  50 , thereby attaining a precision control. Then, the other end of the toggle-switch  61  is pressed, the power  60  supplies the electric power to the motor  50  through the toggle-switch  61  and the B limit switch  63 . The motor  50  reversely rotates and drives the ball screw  19  to rotate through the gear box  05 . The reversely rotation of the ball screw  19  forces the ball nut  20  to horizontally move back. The portion including the sloping surfaces of the ball nut  20  moves toward the second limit pin  631  from the first limit pin  641 . The first limit pin  641  is moved back to an original position by the spring. When another one of the sloping surfaces of the ball nut  20  presses down the second limit pin  631 , the button of the B limit switch  63  is pressed down by the second limit pin  631 . The second contact  2  of the B limit switch  63  is disconnected from the first contact  1  of the B limit switch  63 . The third contact  3  of the B limit switch  63  is connected to the first contact  1  of the B limit switch  63 . Thereby, the power supply circuit is broken. The second diode  84 , the second resistor  82  and the motor  50  cooperatively form a loop to immediately stop the rotation of the motor  50  so as to prevent the ball nut  20  from being further moved back by the inertial rotation of the motor  50 , thereby attaining a precision control. Then, the manual sliding sleeve  100  is rotated to an original position, and the safety switch  105  is opened. Afterward, the manual sliding sleeve  100  is pulled out, and the processed workpiece may be taken out. 
         [0031]      FIG. 8  is a schematic cross-sectional view of a power tool according to a third exemplary embodiment of the present invention. This embodiment adopts a limiting route control method to control the route of the ball nut  20 . One end of the bow member  30  is mounted on the connecting member  21 , and can move along a horizontal direction. A stop block  288  is formed on the connecting member  21  to limit the movement distance of the connecting member  21  and position the connecting member  21 . Also referring to  FIG. 9 , an L-shaped groove  289  defined the connecting member  21  guides the movement direction of the bow member  30 . 
         [0032]    To punch a workpiece, the workpiece is placed in the bow member  30 , and the bow member  30  is horizontally moved forward. Also referring to  FIG. 10 , a stop block  288  of the connecting member  21  moves in a notch  308  of the bow member  30 . At this time, the bow member  30  cannot horizontally move forward under resistance, and the bow member  30  is moved along a bending direction of the L-shaped groove  289 . The stop block  288  is locked in the annular groove  309  communicating with the notch  308  of the bow member  30 , so that the bow member  30  does not move when an external horizontal force is applied thereon. When the bow member  30  rotates, the safety switch  105  located at a handle is pressed by a slope  301  on a corner of the bow member  30 , and the safety switch  105  is closed. The punching process is similar to the first exemplary embodiment, and is not detailed herein. After the punching process, the bow member  30  is returned, and the safety switch  105  is opened. The bow member  30  is pulled out, and the workpiece is taken out to finish the work. 
         [0033]    The second and third exemplary embodiments adopt a manual operation method to perform the processes. Pushing the ball nut  20  forward needs longer time, so the unloaded movement of the male mold  41  is replaced with the manual operation to effectively reduce the work time of punching process. Since the movement distance of the male mold driven by electric power is reduced and an output speed with an output force is an inverse ratio under the same power, the machining pressure may be increased according to the design for punching larger holes on a thicker steel plate. However, the operation of the first exemplary embodiment is more convenient than a manual operation of the second and third exemplary embodiments 
         [0034]    If more functions such as pressure jointing and shearing are needed, the punching mold of the above embodiments can be replaced with the pressure jointing mold or shearing mold. 
         [0035]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.