Optical monitoring chamber unit for toner density controls

Claim 1

A disposable combined toner optical monitoring and toner concentrate injecting device for use in an electrophotographic liquid developing system including a tank of liquid developing toner and a circulating pump located in the tank, said device comprising: A. a unitAry, generally elongate and vertically oriented housing being removably supported by a portion of the toner tank, B. wall means forming a portion of said housing to define a first vertical passageway extending substantially the height of said housing through which toner in the tank is adapted to pass, at least a portion of said first vertical passageway being formed of transparent material and defining a monitoring chamber for permitting optical monitoring the opacity of toner passing therethrough, the lower end of said first vertical passageway having means removably connected to an outlet of the pump in the toner tank, C. additional wall means of said housing defining a lateral passageway communicating at one end with the upper end of said first vertical passageway, D. further additional wall means of said housing defining a second vertical passageway which communicates with the other end of said lateral passageway, the lower end of said second vertical passageway being adapted to communicate with the interior of the toner tank whereby toner in the tank is pumped through said first vertical passageway, said lateral passageway and said second vertical passageway back into the tank without passing outside of said housing, E. means in said vertical passageway defining a restricted orifice through which the toner passes to form a suction chamber in said second vertical passageway adjacent said orifice, F. means defining a first inlet to said suction chamber and adapted to be normally connected to atmosphere for venting said suction chamber, and G. means defining a second inlet to said suction chamber and adapted to be connected to a source of toner concentrate whereby toner concentrate is drawn into said suction chamber through said second inlet and injected into the toner passing therethrough when said first inlet is blocked to prevent the venting of said suction chamber.