Dynamic mass balancer for a rotating power tool

Abstract

The present invention provides, in one aspect, a rotating power tool including a housing, a drive unit within the housing having an electric motor defining a rotational axis, and a drive shaft coupled to the electric motor to receive torque therefrom configured to rotate about the rotational axis, the drive shaft having an eccentric portion. The drive unit further includes an accessory tool configured to orbit about the rotational axis in response to rotation of the eccentric portion of the drive shaft, the accessory tool defining a rotational imbalance. The rotating power tool further includes a dynamic mass balancing system including an actively adjustable counterbalance mass to attenuate vibration caused by the rotational imbalance.

What is claimed is: 
     
         1 . An orbital sander comprising:
 a housing;   a drive unit within the housing, the drive unit including
 an electric motor defining a rotational axis, and 
 a drive shaft coupled to the electric motor to receive torque therefrom, the drive shaft rotatable about the rotational axis and having an eccentric portion; 
   an accessory tool configured to orbit about the rotational axis in response to rotation of the eccentric portion of the drive shaft, the accessory tool defining a rotational imbalance; and   a dynamic mass balancer system including an actively adjustable counterbalance mass to attenuate vibration caused by the rotational imbalance.   
     
     
         2 . The orbital sander of  claim 1 , further comprising:
 a battery pack coupled to the housing for providing power to the electric motor; and   a carrier coupled to the eccentric portion of the drive shaft for orbital motion about the rotational axis.   
     
     
         3 . The orbital sander of  claim 2 , wherein the counterbalance mass is a first counterbalance mass located on a first end of the drive shaft within the carrier. 
     
     
         4 . The orbital sander of  claim 3 , wherein the dynamic mass balancer system further comprises a second counterbalance mass located on a second end of the drive shaft opposite the first end. 
     
     
         5 . The orbital sander of  claim 1 , wherein the dynamic mass balancer system includes an annular dynamic mass balancer. 
     
     
         6 . The orbital sander of  claim 5 , wherein the annular dynamic mass balancer includes an annular main body having one or more moving elements comprising the first counterbalance mass are disposed therein. 
     
     
         7 . The orbital sander of  claim 6 , wherein the one or more moving elements include one or more balls, one or more cylindrical rollers, one or more sliding arcs, or a combination thereof. 
     
     
         8 . The orbital sander of  claim 1 , wherein the dynamic mass balancer includes a pendulum shaped mass balancer. 
     
     
         9 . The orbital sander of  claim 8 , wherein the pendulum shaped mass balancer includes a mounting portion, a swinging mass suspended from the mounting portion that comprises the first counterbalance mass, and a bearing between the mounting portion and the drive shaft. 
     
     
         10 . An orbital sander comprising:
 a housing;   a drive unit within the housing, the drive unit including
 an electric motor defining a rotational axis, and 
 a drive shaft coupled to the electric motor to receive torque therefrom, the drive shaft rotatable about the rotational axis and having an eccentric portion; 
   an accessory tool configured to orbit about the rotational axis in response to rotation of the eccentric portion of the drive shaft, the accessory tool defining a rotational imbalance; and   a dynamic mass balancer system including an actively adjustable counterbalance mass to attenuate vibration caused by the rotational imbalance, wherein the dynamic mass balancer system includes a first counterbalance mass located on a first end of the drive shaft within the carrier.   
     
     
         11 . The orbital sander of  claim 10 , wherein the dynamic mass balancer system further comprises a second counterbalance mass located on an opposite, second end of the drive shaft. 
     
     
         12 . The orbital sander of  claim 10 , wherein the dynamic mass balancer system includes an annular dynamic mass balancer having an annular main body in which one or more moving elements comprising the first counterbalance mass are disposed therein. 
     
     
         13 . The orbital sander of  claim 11 , wherein the one or more moving elements include one or more balls, one or more cylindrical rollers, one or more sliding arcs, or a combination thereof. 
     
     
         14 . The orbital sander of  claim 10 , wherein the dynamic mass balancer system includes a pendulum shaped mass balancer having a mounting portion, a swinging mass suspended from the mounting portion that comprises the first counterbalance mass, and a bearing between the mounting portion and the drive shaft. 
     
     
         15 . The orbital sander of  claim 10 , further comprising a plurality of compliant mounts disposed between the motor and the housing. 
     
     
         16 . The orbital sander of  claim 15 , wherein the compliant mounts permit the motor to move relative to the housing as the dynamic mass balancer system counterbalances vibration of the orbital sander during use. 
     
     
         17 . An orbital sander comprising:
 a housing;   a drive unit within the housing, the drive unit including
 an electric motor defining a rotational axis, and 
 a drive shaft coupled to the electric motor to receive torque therefrom, the drive shaft rotatable about the rotational axis and having an eccentric portion; 
   an accessory tool configured to orbit about the rotational axis in response to rotation of the eccentric portion of the drive shaft, the accessory tool defining a rotational imbalance; and   a dynamic mass balancer system including an actively adjustable counterbalance mass to attenuate vibration caused by the rotational imbalance, wherein the dynamic mass balancer system includes a first counterbalance mass located on a first end of the drive shaft within the carrier and a second counterbalance mass located on an opposite, second end of the drive shaft.   
     
     
         18 . The orbital sander of  claim 17 , further comprising a plurality of compliant mounts disposed between the motor and the housing. 
     
     
         19 . The orbital sander of  claim 18 , wherein the compliant mounts permit the motor to move relative to the housing as the dynamic mass balancer system counterbalances vibration of the orbital sander during use. 
     
     
         20 . The orbital sander of  claim 17 , wherein the dynamic mass balancer system includes an annular dynamic mass balancer, a pendulum shaped mass balancer, or a combination thereof.