GB1054749A - - Google Patents

Abstract

1,054,749. Vacuum pumps, centrifugal pumps. NASH ENGINEERING CO. March 11, 1964 [March 18, 1963], No. 10329/64. Headings F1C and F1E. In a high vacuum system in which a primary vacuum pump 10, Fig. 4 creates the initial vacuum and an ejector 38 creates the final vacuum, a control valve 124 renders the ejector 38 inoperative during the initial vacuum stage and renders it instantly fully operative during the final vacuum stage. The primary pump 10 e. g. a liquid ring pump initially evacuates a chamber attached to flange 34. The flow is divided, one portion passing through conduit 120 and check valve 112 and the other portion passing through a supersonic diffuser 18. The pressure in manifold 114 is communicated to the upper side of piston 128, Fig. 3 (not shown) in valve 124. At a predetermined vacuum piston 128 is drawn to the top of its stroke, the movement being rapid because the pressure of ambient air from conduit 156 acts over the entire area of piston 128 when it leaves seat 142. The ejector begins functioning whilst simultaneously chamber 130 is cut off from conduit 96 and a port 160 is opened allowing atmospheric air to pass via channel 136, groove 140, and pipe 122 to the lower side of diaphragm 162 which closes valve 112. In another embodiment valve 112 is replaced by a gravity operated check valve 25, Fig. 1 (not shown), and the control valve 62, Fig. 2 (not shown), admits ambient air through an enlargement 108 of the valve housing adjacent the valve seat 82.