The present invention generally comprises a counterbalancing assembly for a random orbital machine including an adapter and a counterweight. The adapter includes a recess and the counterweight is disposed in the recess and detachably fastened to the adapter. In some aspects, the counterweight is fully enclosed within the recess. The adapter is configured for connection to a drive means for the machine and for connection to an abrasive pad assembly. The drive means is rotatable about a first axis of rotation. The abrasive pad assembly is rotatable about a second axis of rotation disposed parallel to the first axis of rotation. The adapter and the counterweight are configured to substantially counterbalance portions of the abrasive pad assembly not disposed concentrically about the first axis of rotation and forces to which the abrasive pad assembly is subjected to during use.

The present invention relates to an anti-vibration arrangement (10) for a power sander (1) which comprises a housing (2), a motor (4) arranged in the housing (2), a rotary drive shaft (11), a first outer or ring-shaped pad surface (16) for attaching a first sanding paper (8) and a second inner or circular pad surface (22) for attaching a second sanding paper (9). The anti-vibration arrangement (10) serves to transfer energy from the motor (4) to the pads (16, 22) with out-of-phase motions to dynamically compensate for inertial and friction forces. For this purpose, twin cams (18a, 18b) are fixed on the rotary drive shaft (11). The cams (18a, 18b) rotate the central axes (15, 21) of the pads (16, 22) about the rotary drive shaft axis (12) with a phase differential of typically 180.degree.. Vibration which would otherwise be transmitted to the rotary drive shaft (11) and from there to the operator of the machine (1) are drastically reduced irrespective of whether or not the operator increases the applied force (1) in order to increase the sanding depth or to speed up the sanding operation.

A system for active dynamic balancing of a rotating tool driven by a motor having a shaft supported by a first and second bearing on opposing sides of the motor includes an acceleration sensing assembly configured to sense radial accelerations on the shaft producing an acceleration signal indicative of the radial accelerations. A correcting mass assembly is configured to rotate with the shaft and to move at least one mass radially to the shaft responsive to a correcting signal. A controller is configured to receive the acceleration signal generating a correcting signal by means of a closed loop iterative algorithm.

A system for active dynamic balancing of a rotating tool driven by a motor having a shaft supported by a first and second bearing on opposing sides of the motor includes an acceleration sensing assembly configured to sense radial accelerations on the shaft producing an acceleration signal indicative of the radial accelerations. A correcting mass assembly is configured to rotate with the shaft and to move at least one mass radially to the shaft responsive to a correcting signal. A controller is configured to receive the acceleration signal generating a correcting signal by means of a closed loop iterative algorithm.

A balancing method and apparatus is used for dynamically balancing an out of balance condition in a rotating body caused by resistance forces acting tangentially to the body. A device having a rotatable component and automatic or dynamic balancing includes a housing, a shaft rotatably mounted in the housing, the shaft supporting the component near one end of the shaft, at least one counterweight fixedly mounted on the shaft and at least one automatically adjusting balancer mounted on the shaft. The automatically adjusting balancer includes one or more compensating masses contained to move about a path relative to the shaft to compensate for variable imbalanced forces acting on the component.