Power sanders have been used for years to eliminate laborious hand sanding. The handheld Rotary Drum Sander from Frank Houghton uses a novel method to fix and rotate the sanding drum and smooth curved surfaces. Here’s a short description of how the sander works. The unit consists of a main housing, which contains a mount for the battery, motor assembly, hand grip, circuit board, trigger, and end cover. The battery plugs into a connector on the circuit board and provides the power to rotate the motor assembly (which sits inside the sanding drum). In turn, a rubber sleeve surrounds the outside of the sanding drum. Each sander comes with several 50-mm-diameter sandpaper cylinders of different grits.
Inside the rotary drum, sits a fixed-shaft motor. The motor shaft is press-fit into a sleeve molded into the housing and the motor stator is press-fit onto the shaft. The stator is laminated with wires wound in the lamination slots to provide a rotating magnetic field near the rotor. The attractions and repulsions of the rotating magnetic fields power the tool.
On setup, the user pops off the end cap and places a sandpaper cylinder over the rubber sleeve. The user then tightens the clamp nut on the end of the motor assembly. Tightening the nut shortens the rubber sleeve. The resulting displaced volume of rubber reduces the sleeve’s inside diameter and enlarges its outside diameter. This swelling action clamps the sandpaper against the sanding drum. The operator then replaces the end cap and tightens it on with a screw. When the operator depresses the sander’s trigger, the motor assembly activates and the drum rotates.
The relatively small curvature of the drum (50 mm) lets the drum sander make full contact with the curved surface of, say, a gun stock or chair leg. Belt or disk sanders have flat sanding surfaces or an infinite radius and, therefore, cannot make contact with a curved workpiece.
The Rotary Drum Sander is patent pending. Reach Frank Houghton at firstname.lastname@example.org.