Proportioning pump

951,019. Flexible tube pumps. TECHNICON INSTRUMENTS CORPORATION. July 17, 1962 [Aug. 1, 1961], No. 27347/62. Heading F1F. A flexible tube proportioning pump comprises a plurality of flexible tubes 16, Fig. 3, having the same wall thickness but of different diameter to enable them to be closed simultaneously whilst conveying different quantities of fluid. The tubes are placed side-by-side on a platen 14 resiliently supported by springs 20, on a base 12 and compressed by a tube compressing mechanism 18, Fig. 2, comprising a plurality of spaced apart transverse rollers 22 driven by sprocket chains 24 connected to their ends. The upper surface of the platen 14 is formed with a pressure relieving surface 34 and at either side of the platen a member 36 is fitted following the contour of the upper surface of the platen and of twice the thickness of the flexible tubes to prevent excessive pressure on the tubes. Pins 32 secure the members 36 to cross-members 30 which in turn hold the flexible tubes in position. To increase the closing pressure on the tubes the springs 20 may be replaced by stronger springs or alternatively extra springs 52 fitted between U-shaped abutment 44 may be fitted intermediate the springs 20. Specification 817,070 is referred to.