Electrostatic exposure time control

Claim 2

Apparatus for forming an electrostatic charge in a pattern on a sheet, comprising: charging means for forming an electrostatic charge on sheet material; first drive means for placing a sheet in charge receiving relationship to said charging means; second drive means spaced a distance from said first drive means a distance greater than one half the length of a sheet to be serviced; guide means for directing a sheet from said first to second drive means; sensing means adjacent said first drive means for detecting the arrival of a sheet at said first drive means; an exposure station located beyond said second drive means on the side of said second drive means opposite said first drive means, and means including a light source for exposing a transported sheet to a pattern of light and shadow; a first time delay control circuitry activated by said sensing means, a lamp and appropriate controls constituting said light source in said exposure station, said first time delay control circuitry causing said lamp to become energized a predetermined period of time after encounter of said sensing means by a sheet; a second time delay control circuitry activated by said sensing means, said second time delay control circuitry causing said lamp to become deenergized a predetermined period of time greater than that of said first time delay after encounter of said sensing means by the sheet; said period of time said lamp is energized being a minimum effective operating time; whereby the sheet is fully exposed in the exposure station with a minimum of heat build up.

Claim 3

In a photocopying machine having a supply of photosensitive material and means for transporting sheets of said material into an exposure station wherein it is exposed to a pattern of light and shadow, the improvement in the control of a light source in said exposure station comprising: a sheet conveyor means for transporting a sheet of said photosensitive material in a path from a sheet supply to an exposure station at a known rate of travel; a sensing means in said path between said sheet supply and exposure station for sensing the arrival of a leading edge of a sheet; a first time delay control circuitry activated by said sensing means, a lamp and appropriate controls constituting said light source in said exposure station, said first time delay control circuitry causing said lamp to become energized a predetermined period of time after encounter of said sensing means by a sheet; a second time delay control circuitry activated by said sensing means, said second time delay control circuitry causing said lamp to become deenergized a predetermined period of time greater than that of said first time delay after encounter of said sensing means by the sheet; said period of time said lamp is energized being a minimum effective operating time; whereby the sheet is fully exposed in the exposure station with a minimum heat build up.

Claim 4

In a photocopying machine having a supply of photosensitive material and means for transporting sheets of said material into an exposure station wherein it is exposed to a pattern of light and shadow, the improvement in the control of a light source in said exposure station comprising: a sheet conveyor means for transporting a sheet of said photosensitive material in a path from a sheet supply to an exposure station at a known rate of travel; a sensing means in said path between said sheet supply and exposure station for sensing the arrival of a leading edge of a sheet; a first time delay control circuitry activated by said sensing means, a lamp and appropriate controls constituting said light source in said exposure station, said first time delay control circuitry causing said lamp to become energized a predetermined period of time after encounter of said sensing means by a sheet; a second time delay control circuitry activated by said sensing means, said second time delay control circuitry causing said lamp to become deenergized a predetermined period of time greater than that of said first time delay after encounter of said sensing means by the sheet; said period of time said lamp is energized being a minimum effective operating time; whereby the sheet is fully exposed in the exposure station with a minimum heat build up.

Claim 5

In a photocopying machine having a supply of photosensitive material and means for transporting sheets of said material into an exposure station wherein it is exposed to a pattern of light and shadow, the improvement in the control of a light source in said exposure station comprising: a sheet conveyor means for transporting a sheet of said photosensitive material in a path from a sheet supply to the exposure station at a known rate of travel; a sensing means in said path betWeen said sheet supply and exposure station for sensing the arrival of a leading edge of a sheet; a first time delay control circuitry activated by said sensing means, a lamp and appropriate controls constituting said light source in said exposure station, said first time delay control circuitry causing said lamp to become energized a predetermined period of time after encounter of said sensing means by a sheet; a second time delay control circuitry activated by said sensing means, said second time delay control circuitry causing said lamp to become deenergized a predetermined period of time after encounter of said sensing means by the sheet; said first period of time before energizing said lamp being related to said conveyor means speed rate to delay the lamp energization with substantially only sufficient time for stabilization at full output prior to said arrival at said exposure station; and said second period of time before deenergization by said second time delay control circuitry being related to said conveyor speed to hold said lamp at full output until the sheet has fully traversed said station with a further period of time to assure against premature deenergization.

Claim 6

In a photocopying machine having a supply of photosensitive material and means for transporting sheets of said material into an exposure station wherein it is exposed to a pattern of light and shadow, the improvement in the control of a light source in said exposure station comprising: a sheet conveyor means for transporting a sheet of said photosensitive material in a path from a sheet supply to the exposure station at a known rate of travel; a sensing means in said path betWeen said sheet supply and exposure station for sensing the arrival of a leading edge of a sheet; a first time delay control circuitry activated by said sensing means, a lamp and appropriate controls constituting said light source in said exposure station, said first time delay control circuitry causing said lamp to become energized a predetermined period of time after encounter of said sensing means by a sheet; a second time delay control circuitry activated by said sensing means, said second time delay control circuitry causing said lamp to become deenergized a predetermined period of time after encounter of said sensing means by the sheet; said first period of time before energizing said lamp being related to said conveyor means speed rate to delay the lamp energization with substantially only sufficient time for stabilization at full output prior to said arrival at said exposure station; and said second period of time before deenergization by said second time delay control circuitry being related to said conveyor speed to hold said lamp at full output until the sheet has fully traversed said station with a further period of time to assure against premature deenergization.