Dual action sander

Abstract

A dual action sander includes a housing, a motor shaft balancer, a balancer shaft, an engaging member and a control rod unit. The motor shaft balancer is disposed in the housing, and is rotatable about a first axis. The control rod unit is movable along the first axis between a locked position, where the balancer shaft is not permitted to rotate about a second axis that is parallel to and spaced apart from the first axis, and an unlocked position, where the balancer shaft is permitted to rotate about the second axis. The engaging member is mounted to one of the balancer shaft and the control rod unit, and is engaged with the other one of the balancer shaft and the control rod unit when the control rod unit is in the locked position.

What is claimed is: 
     
         1 . A dual action sander comprising:
 a housing;   a rotating unit disposed in said housing, and including
 a motor shaft balancer that is rotatable relative to said housing about a first axis, and that has
 a balancer portion defining a receiving space that extends along a second axis which is parallel to and spaced apart from the first axis, and 
 a motor shaft portion extending from said balancer portion along the first axis, and defining a through hole that extends along the first axis and that is spatially communicated with said receiving space; 
 
   a driving unit disposed in said housing for driving the rotation of said motor shaft balancer about the first axis;   a balancer shaft extending into said receiving space of said motor shaft balancer, and being co-rotatable with said motor shaft balancer about the first axis;   a control rod unit extending along the first axis through said through hole of said motor shaft portion of said motor shaft balancer, and being movable along the first axis between a locked position, where said control rod unit is secured to said balancer shaft so that said balancer shaft is not permitted to rotate about the second axis, and an unlocked position, where said control rod unit is separated from said balancer shaft so that said balancer shaft is permitted to rotate about the second axis; and   an engaging member mounted to one of said balancer shaft and said control rod unit, and engaged with the other one of said balancer shaft and said control rod unit when said control rod unit is in the locked position.   
     
     
         2 . The dual action sander as claimed in  claim 1 , wherein:
 said balancer shaft has a base segment and a shaft segment extending from said base segment along the second axis and disposed in said receiving space of said motor shaft balancer; and   said rotating unit further includes a bearing received in said receiving space and sleeved on said shaft segment of said balancer shaft.   
     
     
         3 . The dual action sander as claimed in  claim 2 , wherein:
 said shaft segment of said balancer shaft has a mounting protrusion that is not surrounded by said bearing and that has a non-circular cross section;   said engaging member has
 a non-circular mounting hole that extends along the second axis and that is engaged fittingly with said mounting protrusion of said shaft segment of said balancer shaft such that said engaging member is co-rotatable with said balancer shaft, and 
 at least one positioning slot that is spaced apart from said mounting hole; 
   when said control rod unit is in the locked position, said control rod unit extends into said at least one positioning slot of said engaging member to be engaged with said engaging member; and   when said control rod unit is in the unlocked position, said control rod unit is separated from said at least one positioning slot of said engaging member.   
     
     
         4 . The dual action sander as claimed in  claim 3 , wherein said engaging member has an inner surface surrounding the second axis and defining said mounting hole, an outer surface opposite to said inner surface, and a connecting surface interconnecting said inner and outer surfaces, said at least one positioning slot of said engaging member being formed in said connecting surface and extending outwardly through said outer surface. 
     
     
         5 . The dual action sander as claimed in  claim 4 , wherein said engaging member is formed with a plurality of said positioning slots surrounding said mounting hole and spaced apart from each other. 
     
     
         6 . The dual action sander as claimed in  claim 2 , wherein:
 said shaft segment of said balancer shaft has a mounting protrusion that is not surrounded by said bearing and that is provided with an external thread;   said engaging member has
 an inner surface that defines a mounting hole extending along the second axis, and that is provided with an internal thread engaged threadedly with said external thread of said mounting protrusion of said shaft segment of said balancer shaft such that said engaging member is co-rotatable with said balancer shaft, and 
 at least one positioning slot that is spaced apart from said mounting hole; 
   when said control rod unit is in the locked position, said control rod unit extends into said at least one positioning slot of said engaging member to be engaged with said engaging member; and   when said control rod unit is in the unlocked position, said control rod unit is separated from said at least one positioning slot of said engaging member.   
     
     
         7 . The dual action sander as claimed in  claim 2 , wherein:
 said shaft segment of said balancer shaft has a mounting protrusion that is not surrounded by said bearing and that has a non-circular cross section;   said engaging member is mounted co-movably to said control rod unit, and is formed with a non-circular mounting hole that extends along the second axis;   when said control rod unit is in the locked position, said mounting hole is engaged fittingly with said mounting protrusion of said shaft segment of said balancer shaft; and   when said control rod unit is in the unlocked position, said mounting protrusion is disengaged from said mounting hole.   
     
     
         8 . The dual action sander as claimed in  claim 2 , wherein:
 said shaft segment of said balancer shaft is formed with an elongated recess that is exposed from said bearing;
 said engaging member is mounted in said motor shaft portion of said motor shaft balancer and is formed with a non-circular mounting hole that is eccentric from the first axis and that is in spatial communication with said receiving space; 
   said control rod unit has an eccentric portion that has a non-circular cross section, that is eccentric from the first axis, that extends through said mounting hole of said engaging member, and that is movable relative to said engaging member;   when said control rod unit is in the locked position, said eccentric portion of said control rod unit extends into said recess of said shaft segment to be engaged with said shaft segment; and   when said control rod unit is in the unlocked position, said eccentric portion of said control rod unit is separated from said recess.   
     
     
         9 . The dual action sander as claimed in  claim 1 , wherein said control rod unit includes a first rod and a second rod resiliently connected to said first rod along the first axis, said first rod being operable to bias said second rod along the first axis.