Abstract: An active stack height sensing mechanism that operates through a cam off a disc stacker which performs one cycle per sheet stacked. After a sheet is stacked, a stack height clamp contacts the stack and stops. If the stack height is too low or within a predetermined range, a flag attached to the clamp will block a light beam path between an emitter and receiver and trip the stack height sensor. If the stack height is too high, the stack height sensor will not be made indicating that the stacker should be indexed down.

Abstract: A technique is provided for controlling the interposition of one or more special sheets into a stream of regular imaged substrates. In one example, a point in time at which a special insert sheet should be fed from a special insertion sheet subsystem to the stream is determined by reference to plural sets of preset time periods. In this example, the preset time periods can be adjusted to accommodate print engine/interposing module machine clock fluctuations. In another example, interposition of a special insert sheet with the stream of regular imaged substrates is maintained at an acceptable level by comparing a distance between a special insert sheet fed to the stream and an adjacent regular imaged substrate with a predefined tolerance. The comparison can then be used to adjust feed times of special insert sheets subsequently fed to the stream.

Abstract: An apparatus in which a stack of sheets is detected at a preselected location. An air jet is directed towards an edge of the stack of sheets at a preselected location. A pressure transducer is located at the prescribed location and positioned to have the air jet at impact thereon. The pressure transducer is enabled to transmit a signal indicative of the absence of the stack of sheets at the preselected location in response to the air jet impacting thereon. The pressure transducer is inhibited from transmitting the signal in response to the stack of sheets blocking the air jet. When the stack of sheets blocks the air jet, the signal from the pressure transducer indicates the presence of the stack of sheets at the preselected location. A pneumatic stack height detector of this type may be used to regulate the movement of a stack of sheets used in electrophotographic printing machines.

Abstract: A trail edge transport belt is provided over the elevator platform which receives sheets from a disk stacker. The trail edge transport belt engages and ensures the proper inversion of sheets moved by the rotating disk regardless of the size and weight of the sheet. To ensure that long, light weight sheets do not collapse on themselves prior to inverting, the trail edge transport belt is rotated at a velocity which is greater than the velocity which the sheets are fed to the disk and/or is arranged at an angle to the elevator platform so that a distance between the transport belt and the elevator platform decreases as the transport belt extends away from the rotatable disk.