Patent Publication Number: US-2005139021-A1

Title: Reciprocating mechanism

Description:
FIELD OF THE INVENTION  
      The present invention relations to a reciprocating mechanism for a power tool.  
     BACKGROUND OF THE INVENTION  
      Referring to  FIG. 1 , the prior art discloses a reciprocating mechanism for a power tool comprising a drive mechanism  10 , a reciprocating shaft  100  driven by the drive mechanism  10  and support bearings  200  mounted on each face of the reciprocative movement is “b”. The bearings  200  must be positioned within the middle section “c” of the reciprocating shaft  100  (where “c”=“a”−“2b”) otherwise the reciprocating shaft  100  will disengage the bearings  200  during reciprocation. However, if the bearings  200  are too close to the middle of the reciprocating shaft  100 , they will interfere with the drive mechanism  10 . Alternatively, increasing the distance between the two bearings  200  will lead to a need for the reciprocating shaft  100  to be lengthened to avoid the bearing s 200  dismounting during reciprocation. This will increase the overall size of the power tool which is not desirable. There is therefore a need to design a reciprocating mechanism for a power tool to overcome the disadvantages of the prior art.  
     SUMMARY OF THE INVENTION  
      The main object of the present invention is to provide a compact (in particular a laterally compact) reciprocating mechanism which performs effective reciprocating movement.  
      The viewed from one aspect the present invention provides a reciprocating mechanism for a power tool comprising: 
          a reciprocating rod including an elongate retaining portion;     a drive mechanism arranged to drive the reciprocating rod;     a coupling mounted on the reciprocating rod for intimately coupling the drive mechanism and the reciprocating rod; and     a carrier assembly including:     a fixed elongate carrier member arranged to be slidably retained at least partially in or on the elongate retaining portion and a fixing block for fixing the elongate carrier member.        

      In order to accomplish the object, the present invention may provide a reciprocating mechanism which comprises a drive mechanism, a carrier assembly comprising a carrier member and a fixing block and a reciprocating rod comprising a retaining portion for receiving the carrier member and a coupling for connecting the drive mechanism and the reciprocating rod.  
      The present invention exploits a carrier assembly in place of bearings which permits intimate coupling of the drive mechanism and the reciprocating rod (and therefore lateral compactness) without compromising the effectiveness of the reciprocative action.  
      Preferably the elongate retaining portion is an elongate retaining channel and the elongate carrier member is arranged to be slidably retained at least partially in the elongate retaining channel.  
      Preferably the elongate carrier member is circularly columnar and the elongate retaining portion is a hollow guide bore and the elongate carrier member is arranged to a slidably retained at least partially in the hollow guide bore.  
      Preferably the coupling is mounted tangentially on the reciprocating rod.  
      Preferably the coupling is mounted transversely on the reciprocating rod.  
      Preferably the coupling is an elongate U-shaped coupling.  
      Preferably the coupling is mounted perpendicular to the axis of the reciprocating rod.  
      Preferably the fixing block is a terminal fixing block.  
      In a preferred embodiment, the reciprocating mechanism further comprises: a pin for penetrating the fixing block to fix the carrier assembly on a part of the power tool.  
      In a preferred embodiment, the reciprocating mechanism further comprises; a holding rack in the form of a U-shaped channel. Preferably the holding rack includes: 
          an elongate base terminating proximally in a positioning portion     a first side portion extending conterminously from a first longitudinal edge of the elongate base and     a second side portion extending conterminously from a second longitudinal edge of the elongate base,     wherein each of the first and second side portions extends into a platform rim.        

      Preferably the fixing block has a first hole and the positioning portion has a second hole, wherein the first hole and the second hole are coincident to receive the pin.  
      Preferably the drive mechanism includes a gear wheel with an eccentric axle bearing a sleeve, wherein the gear wheel is connected to the coupling via the sleeve. Preferably the gear wheel is transversely mounted.  
      Viewed from a further aspect the present invention provides a power tool comprising: 
          a shell;     a reciprocating mechanism as defined hereinbefore housed in the shell, wherein the elongate carrier member is fixed to the shell.        

      In a preferred embodiment, the power tool further comprises: 
          a saw blade which extends exteriorly to the shell and     a connecting device which connects the saw blade to the reciprocating mechanism to enable the saw blade to follow the movement of the reciprocating rod.        

      Viewed from a yet further aspect the present invention provides a reciprocating mechanism for a power tool comprising: 
          a driving mechanism;     a rail set comprising a guide channel for receiving the rail portion of the rail set and a connect portion for connecting to the driving mechanism.        

      Viewed from an even yet further aspect the present invention provides a power tool comprising: 
          a shell;     a driving mechanism; and     a reciprocating mechanism comprising:     a carrier assembly comprising a carrier portion and a fixing portion for engaging with the shell;     a reciprocating rod comprising a guide channel for receiving the carrier portion of the carrier assembly and a connect portion for connecting to the driving mechanism.        

      The reciprocating mechanism in accordance with the present invention may be used in a power tool. Preferably the power tool is a jigsaw or a reciprocating saw. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a reciprocating mechanism of the prior art.  
       FIG. 2  shows a perspective exploded view of the reciprocating mechanism in accordance with an embodiment of the present invention.  
       FIG. 3  shows a front view of the reciprocating mechanism in accordance with an embodiment of the present invention.  
       FIG. 4  shows a cross-sectional view of the reciprocating mechanism in accordance with an embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      FIGS.  2  to  4  illustrate a jigsaw which comprises generally a shell  1 , a reciprocating mechanism in accordance with an embodiment of the invention which is housed within the shell  1 . The reciprocating mechanism comprises generally a carrier assembly  300 , a reciprocating rod  400 , a holding rack  500 , a pin  600  for fixing the carrier assembly  300  and the holding rack  500  to the shell  1  and a drive mechanism. A connecting device  800  connects the saw blade  900  to the reciprocating mechanism to enable the saw blade  900  to follow the movement of the reciprocating rod  400  (described below).  
      The drive mechanism comprises a transverse gear wheel  700  with an eccentric axle  710  disposed on one face a sleeve  720  mounted on the eccentric axle  710 .  
      The carrier assembly  300  comprises an elongate carrier member  310  which is circularly columnar and a terminal fixing block  320  which defines a fist hold  321  for receiving the pin  600 .  
      The reciprocating rod  400  defines a hollow guide bore  410  for freely receiving the carrier member  310  so as to guide the reciprocating rod  400  during reciprocative movement. Mounted tangentially on the reciprocating rod  400  substantially perpendicular to the direction of reciprocation is an elongate U-shaped coupling  420  which serves to couple the reciprocating rod  400  with the sleeve  720 .  
      The holding rack  500  is an elongate U-shaped channel comprising an elongate base  512  terminating proximally in a positioning portion  520  and two divergent side portions  510  extending conterminously from the longitudinal edges of the elongate base  512 . Each side portion  510  extends into a platform rim  511 . The positioning portion  520  defines a second hole  521  for receiving the pin  600 .  
      Referring to the reciprocating mechanism in assembled form illustrated in  FIGS. 3 and 4 , the pin  600  penetrates the first hold  321  and the second hole  521  and is fastened on the shell  1  to securely nest the carrier assembly  300  within the elongate U-shaped channel of the holding rack  500 . Concomitantly, the elongate U-shaped coupling  420  is seated on each platform rim  511 .  
      When the gear wheel  700  is powered by a rotary motor (not shown), the reciprocating rod  400  is driven reciprocatively (ie to-and-fro) causing the saw blade  900  to undergo a to-and-fro cutting action.