GB1389116A - Toner level control arrangements - Google Patents

Abstract

1389116 Examining a sheet or curtain of fluid RICOH KK 11 Oct 1972 [20 Oct 1971] 46808/72 Heading G1A [Also in Divisions G2 and G3 In a device for monitoring the optical density of a fluid by measuring the intensity of transmitted radiation the fluid is passed through a flexible tube 2, Fig. 3 one end 2b of which is squashed together to form a slit orifice so that a curtain 4 of fluid of uniform thickness over a predetermined area S is formed on discharge. The slit orifice can take several forms, each end of the slit may be enlarged to form two substantial square shaped or circular shaped areas, Figs. 4 & 6 respectively (not shown) the slit may be in a single plane Fig. 1 (not shown) or of arcuate form C Fig. 3 curving inwardly upstream. The internal surfaces of the tube may be electrically conductive and be coated with a water repelling substance Figs. 5 & 6 (not shown). The tube may be incorporated in an adjustable press Fig.7 (not shown) for varying the thickness of the slit, which may be controlled by a motor in response to measurements taken of the liquid concentration. In an embodiment Fig. 9 controlling the optical density of a toner solution light from a source 26 is received by a photo-resistor 24 after passing through the fluid curtain 4 and by a further photo-resistor 25. The two photo-resistors and a resistor and a variable resistor are connected into a wheatstone bridge circuit Fig.10 (not shown) the top of the variable resistor being connected to the base of a transistor. Thus, after the bridge has been balanced (and the transistor rendered non conducting), once the bridge is unbalanced the transistor becomes conducting activating a relay controlling a valve dispensing toner into the fluid until the initial optical density is reached.