GB1296354A - - Google Patents

Abstract

1296354 Reciprocating pumps BRITISH UNITED SHOE MACHINERY CO Ltd 24 Oct 1969 [25 Oct 1968 17 May 1969] 50648/68 and 25242/69 Heading F1A [Also in Division B1] Apparatus for proportioning and mixing polyurethane resin constituents comprises two single acting pumping cylinders 52, 72 actuated by an operating cylinder 102 through a rocking lever 90 fulcrumed at 92; the cross-sectional areas of the pistons 54, 74 of cylinders 52, 72 are in inverse ratio to the distances of their pivot points 62, 82 from that 112 of the operating cylinder, the effect of which is that movement of the lever fulcrum 92 along its support 94 will alter the ratio of the respective constituents but not the total quantity pumped in a cycle. Supply to the pump cylinders is controlled by check valves 65, 66 and 85, 86, and supply of pressure fluid to the operating cylinder by a control mechanism including a micro-switch 120 and contacts 124, 126, the last being adjustable to alter the stroke of the operating cylinder. The control mechanism also supplies pressure fluid to a ram 20 which actuates a discharging piston 14 in the mixer 12. As shown the apparatus is at the extreme bottom of its stroke when it is maintained by the control mechanism during mixing and discharge. The cycle is then completed by the apparatus moving to its rest position indicated by broken lines, which dilutes the residual mixture in the mixer with further ingredient. The operating cylinder may be pivoted to the rocking lever between the pumping cylinders as shown, orits position may be interchanged with that of the fulcrum 92. In the embodiment shown each pumping cylinder fills and discharges in succession, but in another embodiment, see Fig. 3 (not shown) both cylinders are on the same side of the lever and fill and discharge in unison to a continuous discharge mixer. In this embodiment the cylinders discharge through two-way valves (166, 186) which are operated by a solenoid (132) so that the constituents can either be supplied to the mixer or re-circulated to their storage tanks.