Abstract: Selected points in a copier are monitored by signal lines connected to a computer. If a signal is detected on a signal line, the time of occurrence is stored in the computer's memory at a location associated with the point that caused the signal. Eventually an array of the times of operation of each monitored point will be stored. The computer then calculates the difference between the times stored for selected pairs of the monitored points and stores these, as intervals, in additional locations of the memory. The intervals are combined to give calculated statistical results (mean, deviation, etc.) each of which is then compared against predetermined values normal for correctly operating copiers also stored in the memory. The results of the comparison set error flags if the limits are exceeded indicating possible future copier failures.

Abstract: An electrophotographic copier's magnetic brush roller applies developer material to the surface of a photoconductor drum. Two parallel centerlines define the photoconductor drum surface a fixed gap distance from the magnetic brush roller's mating surface. Moving the magnetic brush roller adjusts the gap distance between the mating surfaces. Two sandwiches of conventional, standard-thickness, flexible, plastic sheets form tools; one having a total thickness slighty larger than the desired gap between the mating surfaces of the drum and roller, and the other having a thickness slightly less than the desired gap. The desired gap is set by separating the drum and roller surfaces, inserting the tool that is slightly smaller than the gap and closing the gap sufficiently so that each of the mating surfaces on the drum and roller contacts one surface of the tool.