GB939598A - Improvements relating to the processing of sheet film - Google Patents

Abstract

939,598. Photographic processing tanks. KELVIN & HUGHES Ltd. May 8, 1962 [May 9, 1961], No. 16757/61. Class 98 (1). A tank for processing sheet film has two vertical plates, between the film sheet is located, and a surrounding container, so that the processing liquid flows over the top edges of the plates and down between them on both sides of the film; a pair of apertured baffles are provided within the container and just above the top edges of the plates, so as to maintain a top layer of the liquid free from turbulence. As shown in Fig. 4, the tank has front and back walls 27, 28, between which are two vertical glass plates 31, 32. The film sheet, suspended from a clip 23(1), hangs between the plates. The processing liquid is pumped in through a manifold 36, and passes through perforated baffles 37 up into the tank. As indicated by the arrows, it rises in the tank until it overflows between plates 31, 32, and flows down again on both sides of the film to an outlet manifold 34 and back to the pump. The rate of flow is such as to cause a high degree of turbulence, so as to avoid the forma-. tion of flow marks on the film. On the other hand, turbulence at the free top surface of the liquid would have the undesirable effect of entraining air and so tending to oxidise the developer solution. Just above the top of the plates 31, 32, therefore, are provided a pair of perforated baffles 38, so that a small head of still liquid, free from turbulence, is maintained at the top of the tank. Fig. 7 shows a complete processing unit comprising a sequence of such tanks, developing tank 10, followed by a drier 115, all housed in a light-tight enclosure 114. Since the turbulence and re-circulation would cause an undesirable temperature rise in the processing solutions, the water from the washing tanks is also circulated as cooling water round jackets 49 at the lower end of the tanks. The film sheets are suspended from a number of clips 23 spaced along an endless belt 120. The belts pass over pulleys 119, and the whole of this film-conveying arrangement can be reciprocated up and down, so as to lower the film sheets into the respective tanks, and then lift them out again. As the conveying system is lifted from its lower position, shown in broken lines, to its upper position, shown in full lines, a stud 134 on an arm 133 fixed to the shaft of the right-hand pulley 119 moves in a curved slot 132 in a cam plate 131, and so causes the pulley to index round through 90 degrees. This has the effect of moving the whole belt along one position, i.e. by the distance D between one tank and the next. When the film sheet is brought above the drier 115, it is released to fall therein, and is carried by rollers through an S-shaped path during which warm air is blown on to it. It is finally delivered into a box 147, and manually retrieved. The fixing tank 12 may have a conducting coating on the plates 31, 32, to co-operate with metal plates on the inside of the tank walls to provide electrolytic means for recovering silver.