Automatic replenisher system for a photographic processor

An automatic replenisher system for photographic film processors of the type having a liquid confining processing tank and a conveyor system defining a film path extending through the tank and therebeyond, said system comprising,

• a normally de-energized replenisher pump for supplying replenishing liquid to the tank,
• means for automatically periodically energizing the pump at predetermined intervals regardless of the density of the film processed in said tank,
• light-sensitive film density scanning means positioned in the film path beyond the tank for measuring the image density of the processed film and for producing an electrical control signal responsive to the density of said processed film,
• comparator circuit means receiving said signal for comparing the same to a reference signal and de-energizing said replenisher pump, as a function of the comparing, whereby the time duration between energizing and deenergizing is a function of measured image density of the processed film,
• said means for automatically periodically energizing the pump at predetermined time intervals comprising:
• a two phase oscillator circuit for producing a first phase signal and second phase signal, said phase signals being in fixed consecutive relation to each other, and the frequency of said phase signals determining said predetermined time intervals,
• means for supplying said second phase signal to energize said replenishment pump,
• said comparator circuit means comprising:
• an accumulator which accumulates said electrical control signal and produces an output signal,
• a sample and hold circuit which acquires and holds the output signal of said accumulator when said first phase signal is applied to said sample and hold circuit,
• a timing integrator circuit which produces a present reference current and integrates said reference current to produce an output reference voltage,
• a comparator circuit which compares the electrical control signal to the output reference of said timing integrator circuit, and
• means to deenergize said replenishment pump when the output voltage level of said timing integrator circuit corresponding to said replenishment pump exceeds the voltage level of said electrical control signal.