Handheld sander

Abstract

A handheld sander includes a main body, an extension arm, a follower draft, and a transmission shaft. The main body includes a housing and a drive shaft rotatably disposed in the housing. The extension arm includes a pivot portion rotatably connected with the housing in a way that the extension arm is rotatable relative to the housing, a distal portion opposite to the pivot portion, and an internal accommodation penetrating through the pivot portion and the distal portion. The follower shaft is rotatably disposed in the distal portion of the extension arm. The transmission mechanism is disposed in the internal accommodation and connected between the drive shaft and the follower shaft for transmitting a rotational power from the drive shaft to the follower shaft. As such, the handheld sander can perform a grinding work in a limit, narrow working space.

What is claimed is: 
     
         1 . A handheld sander, comprising:
 a main body including a housing and a drive shaft rotatably disposed in the housing in a way that the drive shaft is rotatable relative to the housing about a first axis;   an extension arm including a pivot portion rotatably connected with the housing of the main body in a way that the extension arm is rotatable relative to the housing about the first axis, a distal portion opposite to the pivot portion, and an internal accommodation penetrating through the pivot portion and the distal portion;   a follower shaft rotatably disposed in the distal portion in a way that the follower shaft is rotatable about a second axis that is parallel to and spaced from the first axis; and   a transmission mechanism disposed in the internal accommodation of the extension arm and connected between the drive shaft and the follower shaft for transmitting a rotational power from the drive shaft to the follower shaft.   
     
     
         2 . The handheld sander as claimed in  claim 1 , wherein the pivot portion of the extension arm has a tubular shape, through which the drive shaft extends into the internal accommodation. 
     
     
         3 . The handheld sander as claimed in  claim 1 , wherein the housing of the main body comprises a sleeve portion sleeved onto the pivot portion of the extension arm. 
     
     
         4 . The handheld sander as claimed in  claim 3 , wherein the pivot portion of the extension arm includes an outer periphery, on which a plurality of positioning holes are provided; the handheld sander comprises a first retaining member moveably disposed with the sleeve portion of the housing in a way that the first retaining member is selectively inserted into one of the positioning holes. 
     
     
         5 . The handheld sander as claimed in  claim 4 , wherein the sleeve portion of the housing includes a first through hole, through which the first retaining member extends; a first resilient member is disposed inside the first through hole and abutted against the first retaining member for imparting a spring force on the first retaining member toward the pivot portion of the extension arm. 
     
     
         6 . The handheld sander as claimed in  claim 1 , wherein the transmission mechanism comprises a first gear coaxially connected with the drive shaft, and a last gear coaxially connected with the follower shaft; the first gear is directly or indirectly meshed with the last gear. 
     
     
         7 . The handheld sander as claimed in  claim 6 , wherein the first gear and the last gear are spur gears. 
     
     
         8 . The handheld sander as claimed in  claim 6 , wherein the transmission mechanism comprises a middle gear located between and meshed with the first gear and the last gear. 
     
     
         9 . The handheld sander as claimed in  claim 6 , wherein the transmission mechanism comprises a plurality of middle gears located between the first gear and the last gear and meshed one after another in a way that one of the middle gears is meshed with the first gear and another one of the middle gears is meshed with the last gear. 
     
     
         10 . The handheld sander as claimed in  claim 8 , wherein the first gear, the middle gear and the last gear are spur gears. 
     
     
         11 . The handheld sander as claimed in  claim 8 , wherein a transmission shaft of the middle gear or the follower shaft is provided with a radial hole; the handheld sander comprises a second retaining member moveably disposed with the extension arm and optionally inserted into the radial hole. 
     
     
         12 . The handheld sander as claimed in  claim 11 , wherein the extension arm includes a second through hole in communication with the internal accommodation and an outside of the extension arm; the second retaining member extends through the second through hole; a second resilient member is disposed in the second through hole and abutted against the second retaining member for imparting a spring force on the second retaining member toward a direction away from the internal accommodation. 
     
     
         13 . The handheld sander as claimed in  claim 9 , wherein the first gear, the middle gears and the last gear are spur gears. 
     
     
         14 . The handheld sander as claimed in  claim 9 , wherein a transmission shaft of one of the middle gears or the follower shaft is provided with a radial hole; the handheld sander comprises a second retaining member moveably disposed with the extension arm and optionally inserted into the radial hole. 
     
     
         15 . The handheld sander as claimed in  claim 1 , further comprising an abrasive disc coaxially connected with the follower shaft. 
     
     
         16 . The handheld sander as claimed in  claim 1 , further comprising a guard rotatably disposed on the distal portion of the extension arm in a way that the guard is rotatable about the second axis.