Abstract: A method of treating piston rings to render their surfaces extremely hard-wearing, wherein the rings are assembled in batches on a tubular mandrel which is then surrounded by a matching cylinder, the mandrel bearing the rings and the cylinder being subjected to relative cyclical motion while a slurry of hard silicon carbide particles is poured into the cylinder. Either the wall of the tubular mandrel, or the wall of the cylinder, or both, are provided with holes to allow the slurry to flow away. The cyclical motion may consist of relative rotation at 170 r.p.m. and simultaneous relative reciprocation at 5 cycles per minute. The slurry may consist of 220 mesh silicon carbide powder in oil, with the treatment lasting for one minute, and preferably this is followed by a further treatment of one minute with a 400 mesh silicon carbide particle slurry.

Abstract: An optical mouse utilizing a linear array of photodiodes is provided with circuitry to correlate during each self-timed cycle a new image with a stored image from the previous cycle with the new image offset relative to the stored image one pixel (photodiode signal) to the right, one pixel to the left, and also with no offset. All three correlations are done at the same time in separate correlators. Decision as to motion to the right, to the left or no motion is made on the basis of maximum correlation output. The new image is not stored in a second store array for use during the next cycle until any motion is detected, but it is stored in a first store array during the cycle when half the precharged photodiodes discharge below a predetermined level in response to incident light. A new cycle is initiated by precharging the photodiodes when any decision of motion or no motion is made.

Abstract: In a process for forming an extremely hard-wearing rubber or bearing surface on a metal machine part, particles of hard grit, such as carbide grit, are deliberately formed into the surface using a resiliently-loaded tool, so that the surface becomes permanently impregnated with the hard particles. During the operation the particles can conveniently be contained in a slurry that flows over the surface. After impregnation, a lapping operation is performed on the impregnated surface using a fine carbide grit.