Safety arrester for arresting a hydraulically operated lifting ram of a hydraulic elevator

In a hydraulic elevator drive of the type including a hydraulic cylinder, a piston movable in said cylinder by hydraulic fluid from a fluid pressure source, a lifting ram connected to said piston, and a safety arrester for arresting movement of said ram;

• the improvement wherein said safety arrester comprises:
• an arrester body having an upper end and a lower end, said body having extending upwardly therethrough a passage, said ram being received in said passage, said body having therein a cavity surrounding a portion of said passage, said cavity being partially defined by planar walls of said body, said planar walls being inclined inwardly from said upper end to said lower end;
• a plurality of brake shoes positioned in said cavity, said brake shoes comprising segments of a ring surrounding said ram, each said brake shoe having an outer surface including an inclined planar portion corresponding to and cooperating with a respective said planar wall of said body;
• a plurality of spring means, one each directly connected to a respective of said brake shoes, for biasing said brake shoes toward said lower end of said body into sliding relationship with said inclined planar walls, and for thereby forcing said brake shoes inwardly into locking frictional engagement with said ram;
• and
• a plurality of hydraulic actuator means, one each directly connected to respective of said brake shoes, actuatable by the pressure of said hydraulic fluid in said hydraulic cylinder for urging said brake shoes toward said upper end of said body against the force of said spring means only when said pressure is above the level sufficient to move said piston and ram.