Charles J Hagen, Age 5213208 Coralberry Dr, Fairfax, VA 22033

5119030, Jun 2, 1992

May 18, 1990

7/526063

Peter R. Bossard - Langhorne PA
Kevin D. Brown - Gasport NY
Charles Hagen - Lockport NY

Trek, Inc - Medina NY

G01N 2761

324456

Apparatus for determining the physical uniformity of a charged drum surface wherein current signals are induced in sensing electrodes in response to variation in drum surface charge. The sensing electrodes are on a detector assembly which is movable toward the drum for inspection of the surface and movable away from the drum after inspection when the drum is to be ejected from the apparatus. The detector assembly is movable through another degree of freedom to accommodate irregularities in drum geometry encountered during rotation thereof. The detector assembly also is provided with structure for maintaining a predetermined spacing of the sensing electrodes from the drum surface during relative movement therebetween. The drum is received, held, and rotated by co-operation between a drum retention assembly and a drum clamping mechanism. The retention assembly includes an arrangement of retainer arms which contact the drum inner surface and which are collapsed in response to forcible engagement of the drum by the drum clamping mechanism to allow rotation of the drum.