piston seal for hydraulic props of coal mine

摘要

933,136. Piston packing. BWG BERGWERKUND WALZWERK-MASCHINENBAU G.m.b.H. March 7, 1962 [March 21, 1961], No. 8775/62. Class 122(1). The piston 11 of an hydraulic pit prop is sealed by a rubber &c. packing ring 12 backed by an anti-extension ring 13 of polyurethane.