Patent Publication Number: US-2004040161-A1

Title: Jigsaw comprising a stiff bearing for the saw moving mechanism

Description:
[0001] The invention relates to a jigsaw comprising a housing, an electric motor accommodated therein, an output shaft of the electric motor being coupled to a saw moving mechanism for driving a saw blade, and means for bearing mounting of the saw moving mechanism, wherein the bearing means comprise a bearing element which is stiff in relation to the housing.  
       [0002] Such a jigsaw is generally known from the prior art. The bearing means serve to support and guide the saw moving mechanism during the up and downward movement of the saw blade.  
       [0003] The object of the present invention is to provide a jigsaw with an improved construction for bearing mounting of the saw moving mechanism.  
       [0004] To this end the jigsaw is characterized according to the present invention in that the stiff bearing element is formed by a thin-walled and bent plate element arranged transversely of the walls of the housing. Such a thin-walled construction forms together with the walls of the housing a stiff box-like construction, whereby the walls of the housing can take a less rigid form. The desired stiffness is therefore provided in the situation of use so as to ensure that the saw moving mechanism is adequately bearing mounted.  
       [0005] The saw moving mechanism preferably comprises a drive rod which bears on its lower end a fixing for a saw blade, and converting means for converting a rotating movement of the motor into a reciprocating movement of the drive rod, which converting means comprise a gear transmission, wherein a gear shaft of the gear transmission is mounted in the bent plate element on either side of the gear wheel. The stiff bearing element in the form of the bent plate element provides a positioning of the gear shaft in relation to the housing.  
       [0006] In addition, the output shaft of the electric motor is preferably mounted at a distance from the gear shaft in the bent plate element. Thus is ensured that the positions of the output shaft of the electric motor and the gear shaft are fixed in relation to each other in the housing.  
       [0007] The bearing means preferably further comprise a wheel for supporting the saw blade. During sawing a force is exerted on the saw blade which is in a direction opposite to the sawing direction. The wheel then provides support for the saw blade during sawing.  
       [0008] The wheel is preferably located between two flanges to support the saw blade in a direction transversely of the sawing direction.  
       [0009] The flanges preferably form part of a fork which is pivotable relative to the housing. Such a fork is a component of a pendulum mechanism known from the prior art which serves to generate a reciprocating movement of the free end of the saw blade running in sawing direction. Additional sawing effect can be obtained using the pendulum mechanism by pressing in forward sawing direction on the saw blade during the sawing stroke (upward stroke) of the saw blade.  
       [0010] The plate element is preferably continued as a resilient element which is in contact with the drive rod of the saw blade. Use is advantageously made of the thin-walled material of the plate element to obtain a resilient bearing element. The resilient bearing element presses the drive rod with saw blade on the one side against the gear wheel located at the top of the housing and on the other side against the gear wheel located under or at the bottom of the housing.  
       [0011] Finally, the bent plate element is preferably manufactured from metal to enable discharge of the heat generated by the bearing(s) of the gear shaft. In order to discharge extra heat an airflow can be generated along the bent plate element.  
     
    
    
     [0012] The present invention will now be further elucidated with reference to the annexed drawing. In the drawings:  
     [0013]FIG. 1 shows a perspective view of the interior of a first embodiment of a jigsaw according to the invention;  
     [0014]FIG. 2 shows a view of the jigsaw of FIG. 1 in another operating position; and  
     [0015]FIG. 3 shows a view according to FIG. 1 of a second embodiment of a jigsaw according to the invention. 
    
    
     [0016] The jigsaw is provided with a housing  1 , a part of which is broken away in the drawing to provide a view of the interior of the jigsaw. In housing  1  is arranged an electric motor  2  for driving a drive rod  3  which bears on its lower end a fixing  4  for a saw blade  5 . Electric motor  2  is provided with a motor shaft  6 . Between motor shaft  6  and drive rod  3  for saw blade  5  are arranged converting means  7  for converting the rotating movement of electric motor  2  into a reciprocating movement of saw blade  5 . Converting means  7  comprise a gear transmission  8  consisting of a first gear wheel  9  connected to motor shaft  6  and a second gear wheel  10  co-acting therewith, and an eccentric  11  arranged on second gear wheel  10 . Eccentric  11  co-acts with drive rod  3  to transmit the rotating movement of the second gear wheel  10  as a reciprocating movement of saw blade  5 .  
     [0017] The second gear wheel  10  is supported rotatably in housing  1  by means of a gear shaft  12 . Gear shaft  12  is rotatably mounted in bearings  13  on either side of second gear wheel  10 . Gear shaft  12  herein extends through an opening  14  arranged in drive rod  3 . This opening  14  is slot-like, so that a bearing mounting of drive rod  3  on gear shaft  12  is obtained.  
     [0018] The jigsaw is further provided with a stiff bearing element  15  formed by a thin-walled and bent plate element arranged transversely of the walls of housing  1 . Plate element  15  is provided with two openings lying in line for passage of gear shaft  12 . In addition, plate element  15  contains a third opening for passage of the output shaft  6  of electric motor  2 . At the front of housing  1  the plate element  15  is continued as a resilient bearing element  16  which is in contact with drive rod  3  of saw blade  5 .  
     [0019] The bearing means further comprise a wheel  17  for supporting saw blade  5 . Wheel  17  lies between two flanges  18  which are part of a fork  19  pivotable relative to housing  1 . Fork  19  forms part of the pendulum mechanism for generating a reciprocating movement of saw blade  5  in sawing direction. In addition to the fork, the pendulum mechanism further comprises a pusher  20  which is in contact at its top with an eccentric  21  arranged on gear wheel  10 . The lower end of pusher  20  is provided with two shoulders  22  which can be placed in contact with the upper surface  23  of fork  19 , and a protrusion  24  which is placed in an opening in the upper surface  23  of fork  19 . Pusher  20  is finally provided with a hole  25  to allow undisturbed passage of motor shaft  6 .  
     [0020] In sawing direction the pusher  20  is retained at the top between gear wheel  10  and plate element  15  and at the bottom in the opening in upper surface  23  of fork  19  by means of protrusion  24 . Because pusher  20  is connected to eccentric  21  and retained in the sawing direction, it will execute an oscillating motion transversely thereof, wherein pusher  20  presses each time with its shoulders  22  on the upper surface  23  of fork  19 . Fork  19  will herein execute a pivoting movement around a point of rotation  26  by means of which fork  19  is mounted rotatably on housing  1 .  
     [0021] The pendulum mechanism can be disengaged by means of control member  27 . In the position shown in FIG. 1 the pendulum mechanism is disengaged in that the upper surface  23  of fork  19  is taken out of contact with shoulders  22  of pusher  20  by means of control member  27 . In FIG. 2 the shoulders  22  on the bottom end of pusher  20  can push on the upper surface  23  of fork  19  and saw blade  5  will execute a pendulum movement.  
     [0022]FIG. 3 shows a second embodiment of a jigsaw according to the invention. This differs from the first embodiment in that control member  27  for engaging respectively disengaging the pendulum movement of saw blade  5  is formed by a control pin  27   a  protruding partially from housing  1  and a control block  27   b  arranged slidably in housing  1 . In the position drawn in FIG. 3 the pendulum mechanism is on. The pendulum mechanism is disengaged by rotating control pin  27   a  from the position of FIG. 3, whereby control block  27   b  is pushed downward. With its bottom end the control block  27   b  herein takes the upper surface  23  of fork  19  out of contact with shoulders  22  of pusher  20 , whereupon the pendulum mechanism is off.  
     [0023] Finally, a guide element  28  is placed in housing  1  which serves to guide drive rod  3  when no saw blade  5  is placed in fixing  4 . Since drive rod  3  is not bearing mounted on its underside in housing  1  when this bearing mounting is performed by wheel  17  and flanges  18  of fork  19  when a saw blade  5  is connected to drive rod  3 , guide element  28  must perform this bearing mounting when there is no saw blade  5  placed in the machine. The resilient element  16  ensures that drive rod  3  with or without saw blade  5  is pressed rearward, and therein guides the up and downward movement of drive rod  3 .