GB1225908A - - Google Patents

Abstract

1,225,908. Self-processing cameras. POLAROID CORP. June 19, 1969 [June 21, 1968], No.31130/69. Heading G2A. In an apparatus in which an exposed photosensitive sheet and a copy sheet are passed together between a pair of pressure rollers 58, 60, a layer of processing liquid being spread between the sheets to effect an image transfer, the pressure between the rollers varies inversely as the ambient temperature, so as to compensate for temperature-related changes in the viscosity of the liquid. This is preferably of a thixotropic nature, and the arrangement enables the thickness of the processing liquid to be maintained at a constant value in spite of temperature variations. As shown, the drive to the rollers derives from a battery-driven motor 64 via a chain of gearwheels. Roller 60 is fixed, and roller 58 can be variably biased towards it by cantilever springs 62, fixed at one end and bearing at the other end against the shaft of rollers 58. A pair of bars 82 are each mounted at one end, adjacent the rollers, on a fixed pivot, and bear at their other ends 84 on the springs 62, being held thereagainst by fixed supports 86. The bars 82 are formed of an alloy having a high co-efficient of expansion. Thus as the bar varies in length with change of temperature, the point of engagement of end 84 with spring 62 will alter. This alters the effective length of the spring, and hence its effective force on roller 58. Hence an increase in temperature will cause an increase in the length of bars 82, and a corresponding increase in the effective length of springs 62, so reducing the spring bias acting on roller 58. Figs. 3 and 4 (not shown) are alternative methods of varying the effective length of the spring.