Platemaker and contact frame exposure indicator

Details Platemaker and contact frame exposure indicator Platemaker and contact frame exposure indicator

1977-06-06

1978-09-05

Hix, L. T.

Photocopying

Projection printing and copying cameras

Illumination systems or details

356227, 355 83, 355120, G03B 2774, G01J 142

Patent

active

041115490

ABSTRACT:
An exposure indicator which is attachable to a hinged glass mask cover frame, the indicator comprising a light emitting diode having one end lead connected in series through a light sensitive cell; a sensitivity-controlling resistance and switch to the appropriate pole of a source of electrical potential, such as a battery, the other pole of the battery being connected to the other end lead of the diode; the switch being arranged so that it is closed when the glass mask frame is closed against the blanket frame on which there is loaded a light-sensitive printing plate, and onto which an activating light is adapted to be directed, whereupon the light-sensitive photo cell is activated (resistance decreased) so that current is allowed to flow from the battery, through the switch and the light-activated silicon controlled rectifier, causing the diode to glow, thus indicating that the material has been exposed, and thereby preventing a second exposure due to the inattentiveness or forgetfulness of the operator. The operator, to remove the exposed plate, must move the masking glass frame to open position, which opens the switch of the indicator and extinguishes the diode.

REFERENCES:
patent: 2510142 (1950-06-01), Richards
patent: 3351766 (1967-11-01), Weisglass
patent: 3458262 (1969-07-01), Greenlee
patent: 3682551 (1972-08-01), Bradley et al.

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