Abstract: An improved method and apparatus senses the extent of actual wear of a grinding wheel at an area where the wear will be the greatest during the grinding of a workpiece. The grinding wheel is dressed by removing material from the grinding wheel to an extent which is a function of the extent of sensed wear at the location where the wear is the greatest. The apparatus includes a probe member which is movable toward the circular working surface or side of the grinding wheel from a retracted position and a detector assembly which detects when the probe member initially engages the circular side of the grinding wheel. In some embodiments of the invention, the probe member is moved toward the grinding wheel in incremental steps with sufficient time between the steps to enable the grinding wheel to rotate through slightly more than one complete revolution. In one embodiment of the invention the detector assembly includes a mass which is connected with a probe member.

Abstract: An apparatus senses the extent of actual wear of a grinding wheel at an area where the wear will be the greatest during the grinding of a workpiece. The grinding wheel is dressed by removing material from the grinding wheel to an extent which is a function of the extent of sensed wear at the location where the wear is the greatest. The apparatus includes a probe member which is movable toward the circular working surface or side of the grinding wheel from a retracted position and a detector assembly which detects when the probe member initially engages the circular side of the grinding wheel. In some embodiments of the invention, the probe member is moved toward the grinding wheel in incremental steps with sufficient time between the steps to enable the grinding wheel to rotate through slightly more than one complete revolution. In one embodiment of the invention the detector assembly includes a mass which is connected with a probe member.

Abstract: A system for electrostatic printing including a corona source and electrode for coulombs/m.sup.a substantially uniform stream of ions in the direction of a print receiving medium and a multilayer apertured modulator interposed in the ion stream for modulating the cross-sectional flow density of ions in the stream in accordance with a pattern to be reproduced. A cloud of substantially uncharged liquid aerosol ink particles is introduced adjacent the print receiving medium whereby the modulated ion stream selectively impinges upon and charges particles in the cloud which are thereby accelerated and deposited on the print receiving medium in accordance with the pattern to be reproduced. The average surface charge density on liquid aerosol particles in the cloud is no greater than about 1 .times. 10.sup.-.sup.6 coulombs/m.sup.2, and preferably no greater than about 5 .times. 10.sup.-.sup.7 coulombs 2. The liquid aerosol droplets are in the range of from about 0.10 micron to 50.