GB801902A - Improvements in or relating to diaphragm pumps - Google Patents

Abstract

801,902. Diaphragm pumps. PLEUGER, F. W. [trading as PLEUGER & CO.]. Jan. 11, 1956 [Jan. 11, 1955], No. 1013/56. Class 102(1). [Also in Group XXVI] Pumping equipment comprises a pair of flexible diaphragms mounted in spaced relation between a pumping chamber and a driving means and having a pressure transfer chamber and a cylinder, filled with liquid, located between the diaphragms, the cylinder being in communication with the transfer chamber in which one diaphragm serves to seal the pumping chamber from the transfer chamber and the other diaphragm serves to seal the driving means from the cylinder. In the embodiment shown the pressure transfer chamber 15 and cylinder, formed as two concentric cylinders 16a and 16b, are sealed from the pumping chamber 12 and driving means 36, 37 by diaphragms 7 and 8a respectively. In operation the connecting rod 36 and drive shaft 37 reciprocate a two part crosshead 34, 34a which causes reciprocation of pistons 17a, 17b in cylinders 16a, 16b. As the piston 17a advances into the transfer chamber 15 the liquid in the chamber raises the diaphragm 7 and forces liquid out of the pumping chamber 12 past the usual non- return valve. As the piston 17a returns to the cylinder 16a the diaphragm 7 moves downwards and liquid is drawn into the pumping chamber. A recess 39 is provided at the bottom of cylinder 16a and liquid from the transfer chamber 15 which leaks past the piston rings 19a is returned to the transfer chamber 15 on the downward stroke of piston 17a through passageway 30a and non-return valve 31a. Liquid leaking past the piston rings 19b collects in recesses 29b and 29a and is forced past non- return valve 41 during the upward movement of the pistons by diaphragm 8a and joins the liquid collecting in recess 39. This leakage of liquid serves to lubricate the pistons 16a, 16b and crosshead member 34a. The lower crosshead member 34 may be lubricated either by grease provided in the bushing 35 or if the driving means in housing 11 operates under oil a lubrication recess 50 may be provided adjacent the lower face of the diaphragm 8a, and as the crosshead reciprocates the diaphragm 8a serves to pump the oil in the direction or the arrows 54, a non-return valve 51 being provided to prevent direct flow to the oil reservoir. A perforated plate 21 preferably provided with a resilient or elastic plastic coating 21a supports the diaphragm 7 when the pump is not in use or during the return stroke of the piston 17a. The diaphragm 7 and plate 21 may be set at an angle to the axis of the pump. In a modification the driving means may be a cam acting directly on the piston or on a ram in contact with the crosshead, the return stroke of the piston being effected by a compression spring in the transfer chamber. In a further modification the lower diaphragm is a complete circular member clamped at its outer end and lying between the ram and the lower piston, in this case the two concentric cylinders and pistons may be replaced by a single cylinder and piston, the piston being hollow.