File belt sander

Abstract

A belt sander for sanding a workpiece including a main housing, a motor having a motor shaft disposed within the main housing, a gear assembly driven by the motor shaft, and a drive assembly coupled to the gear assembly for driving a sanding belt. The drive assembly includes a hammer coupled to the motor shaft, an anvil configured to receive rotational impacts from the hammer, and a spring biasing the hammer towards the anvil. The drive assembly is configured to convert the continuous torque provided by the motor and gear assembly to intermittent applications of torque to the anvil. The sanding belt is coupled to the anvil, such that the sanding belt is intermittently driven by the drive assembly when an abrasive load between the sanding belt and a workpiece causes a reaction torque exerted on the anvil to exceed a biasing force of the spring.

What is claimed is: 
     
         1 . A belt sander for sanding a workpiece, the belt sander comprising:
 a main housing;   a motor having a motor shaft disposed within the main housing;   a gear assembly driven by the motor shaft; and   a drive assembly coupled to the gear assembly for driving a sanding belt, the drive assembly including
 a hammer coupled to the motor shaft, 
 an anvil configured to receive rotational impacts from the hammer, and 
 a spring biasing the hammer towards the anvil, 
   wherein the drive assembly is configured to convert the continuous torque provided by the motor and the gear assembly to intermittent applications of torque to the anvil, and   wherein the sanding belt is coupled to the anvil, such that the sanding belt is intermittently driven by the drive assembly when an abrasive load between the sanding belt and a workpiece causes a reaction torque exerted on the anvil to exceed a biasing force of the spring.   
     
     
         2 . The belt sander of  claim 1 , further comprising a belt drive system driven by the drive assembly, wherein the belt drive system includes a drive wheel that is driven by the anvil, a driven wheel that is driven by the drive wheel via the sanding belt, and a platen disposed between the drive wheel and the driven wheel. 
     
     
         3 . The belt sander of  claim 2 , wherein the sanding belt has teeth on the inner periphery to intermesh with corresponding teeth of the drive wheel that, in turn, is directly coupled to the anvil, such that a positive engagement is established from the anvil to the sanding belt. 
     
     
         4 . The belt sander of  claim 3 , wherein the driven wheel has teeth that intermesh with the teeth on the inner periphery of the sanding belt. 
     
     
         5 . The belt sander of  claim 1 , further comprising a camshaft that is directly driven by the gear assembly and drives the hammer. 
     
     
         6 . The belt sander of  claim 1 , further comprising hammer lugs disposed on the hammer that engage with anvil lugs disposed on the anvil. 
     
     
         7 . The belt sander of  claim 6 , wherein the drive assembly is capable of transitioning between an engaged state, in which the hammer lugs are meshed with the anvil lugs, and a disengaged state, in which the hammer lugs are no longer meshed with the anvil lugs. 
     
     
         8 . The belt sander of  claim 7 , wherein the hammer lugs cam against the anvil lugs, causing the hammer to retract away from the anvil against the bias of the spring when the reaction torque exerted on the anvil exceeds the biasing force of the spring. 
     
     
         9 . The belt sander of  claim 7 , further comprising a camshaft that is directly driven by the gear assembly and drives the hammer, wherein the camshaft includes cam grooves and cam balls that rotationally couple the hammer to the camshaft and allows for relative axial movement of the hammer relative to the camshaft between the engaged state and the disengaged state while the camshaft continues to rotate. 
     
     
         10 . The belt sander of  claim 1 , wherein the biasing force of the spring can be adjusted by an adjustment mechanism, allowing the spring to either be expanded or compressed. 
     
     
         11 . A belt sander for sanding a workpiece, the belt sander comprising:
 a main housing;   a motor having a motor shaft disposed within the main housing;   a contact arm extending from the main housing for driving a sanding belt, the contact arm is moveable relative to the main housing; and   a drive assembly disposed between the motor and the contact arm and including
 a hammer driven by the motor shaft about a drive axis, 
 an anvil configured to receive rotational impacts from the hammer and coupled to the sanding belt, and 
 a spring biasing the hammer towards the anvil, 
   wherein the drive assembly is configured to convert the continuous torque provided by the motor to intermittent applications of torque to the anvil, and   wherein the sanding belt is intermittently driven by the drive assembly when an abrasive load between the sanding belt and a workpiece causes a reaction torque exerted on the anvil to exceed a biasing force of the spring.   
     
     
         12 . The belt sander of  claim 11 , further comprising a drive wheel that is coupled to the anvil and disposed at one end of the contact arm, a driven wheel that is driven by the drive wheel via the sanding belt and disposed at another end of the contact arm, and a platen disposed on the contact arm and between the drive wheel and the driven wheel. 
     
     
         13 . The belt sander of  claim 12 , wherein the drive wheel and the driven wheel both have teeth that intermesh with corresponding teeth on the inner periphery of the sanding belt, such that a positive engagement is established from the drive wheel to the sanding belt. 
     
     
         14 . The belt sander of  claim 11 , further comprising a camshaft that is driven by the motor and coupled to the hammer. 
     
     
         15 . The belt sander of  claim 14 , wherein the camshaft includes cam grooves and cam balls that are received within the cam grooves, wherein the cam balls rotationally fix the hammer to the camshaft while also enabling the hammer to translate relative to the camshaft along the drive axis. 
     
     
         16 . The belt sander of  claim 11 , further comprising hammer lugs disposed on the hammer that engage anvil lugs disposed on the anvil. 
     
     
         17 . The belt sander of  claim 16 , wherein the drive assembly is capable of transitioning between an engaged state, in which the hammer lugs are meshed with the anvil lugs, and a disengaged state, in which the hammer lugs are spaced away from the anvil lugs in a direction parallel with the drive axis. 
     
     
         18 . The belt sander of  claim 17 , wherein the hammer lugs cam against the anvil lugs, causing the hammer to retract away from the anvil against the bias of the spring when the reaction torque exerted on the anvil exceeds the biasing force of the spring. 
     
     
         19 . The belt sander of  claim 11 , wherein the biasing force of the spring can be adjusted by an adjustment mechanism, allowing the spring to either be expanded or compressed. 
     
     
         20 . The belt sander of  claim 11 , wherein the contact arm is pivotable relative to the main housing about the drive axis.