Abstract: A gas-blast type interrupter comprises first and second electrodes relatively movable between a closed position in which they are in mutual electrical engagement and an open position in which they are mutually separated, movement of the electrodes towards their open position causing an arc to be drawn therebetween. A tubular housing encloses the first electrode and has therein a first insulating orifice through which the second electrode substantially sealingly passes when the electrodes are in their closed position. A guide surrounds the tubular member and has therein a second insulating orifice through which the second electrode also substantially sealingly passes when the electrodes are in their closed position, the first and second orifices being co-axial and of essentially the same size.

Abstract: A circular saw blade having reduced vibration through increased damping by utilization of radial slots in the blade to form blade segments to interrupt circumferential vibration in the blade which may have blade segment stiffening means and having a damping collar axially aligned with said blade to provide a sink for dissipation of vibrational energy from the blade segments.

Abstract: A helical cutterhead for a wood planer for reducing noise level during planing by supressing vibration and sound radiation by having more than one knife blade engaged in the workpiece at any instant by satisfying the minimum condition of the formula L=.pi.D cot.phi./N is less than the workpiece width and in which L is the contact distance, D is the cutterhead diameter, N is the number of knife blades, and .phi. is the helix angle, and in which L is less than 4 inches.