Patent GB-1286914-A (GB)
Title: Improvements in or relating to an earth excavator
Inventor: ALLARD PIERRE JEAN-MARIE THEOD
IPC: E21B27/00
Filed: 1970-04-14
Abstract: 1286914 Grabs P J M T ALLARD 14 April 1970 [28 April 1969 22 Oct 1969] 17678/ 70 Heading E1F An earth excavator comprises a grab having a cylindrical body 1 in which is slidably mounted a piston 2 connected by links 50 to shovels 3 pivotally carried by the body, locking means including a pin 101 for retaining the piston in its lowermost position with the shovels open for digging, a device including cams 105, 110 for unlocking the piston after the shovels have engaged the earth and so that lifting of the body 1 by a cable 17 is preceded by upward movement of the piston 2 to close the shovels 3, the piston being retained in its raised position by means including a stud 8, and means including a rod 38 which when engaged by a stop member when the body is raised releases the piston so that it falls and opens the shovels 3, the body 1 dropping to a limited extent simultaneously with the piston whereby earth is released from the body. The cable 17 is anchored to the periphery of a spring-loaded drum 5 rotatably carried on a sleeve which is rotatably mounted on a shaft 4 fixed to the body 1. The stud 8 is slidably and rotatably carried by a member 9 fixed to the sleeve 6, the stud being spring-urged into releasable engagement with a ball bearing 35 mounted in the drum 5, and the stud carrying a pinion 120 engaging a rack 121 on a ratchet wheel 7 rotatably mounted on the sleeve 6, the ratchet being resiliently engaged by the bottom end of the rod 38. The piston is supported by chains 10 anchored at one end to pulleys fixedly carried by the sleeve 6 and at the other to the body 1. The pin 101 is rotatably carried by a bearing 102 fixed to the body 1 and is provided at its bottom with splines or the like 104 for engaging complementary openings in the top of the piston 2, and the cam 105 is spring-urged to dispose the splines or the like out of alignment with said openings. In operation the grab is dropped to engage the earth with the shovels locked in the open position. When the earth takes the weight of the body, the drum 5 is rotated by its spring until the stud 8 engages the ballbearing 35 and until the cam 110 engages the cam 105 and rotates the pin 101 to free the piston 2. The cable 17 is then hoisted which rotates the drum 5 and the sleeve 6 to lift the piston in the body and close the shovels 3; the cable 17 is not completely unwound, the position being adjustable by selective connection of the cable 17 to holes spaced round the drum periphery. Further hoisting of the cable 17 lifts the grab until the stop member 39, Fig. 12 (not shown), engages the rod 38 to rotate the ratchet and disengage an offset conical end of the stud 8 from the ball-bearing 35 to free the piston so that it falls to open the shovels. The unwinding of the cable 17 is consequently completed so that the body 1 also falls a small distance. A cable clamp 22 may be operated to retain the shovels in their open position. The earth is discharged from the grab onto a spring-loaded chute which is moved to and from an operational position by vertical movement of the grab, Figs. 19 and 20, and Figs. 21 to 24 (not shown).