Magnetic junk basket assembly for drill strings

摘要

952,027. Boring earth &c. G. C. CROOKS. Oct. 9, 1962, No. 38141/62. Heading E1F. A magnetic junk basket assembly comprises a casing 10, a magnet carrier 18 slidable therein, spring loaded catching fingers 39SP1/SP, 39SP11/SP normally held against the casing but extending to span the casing when the carrier shears a pin 28 and is retracted into the casing by a spring 22, and a coring bit 35. The assembly is lowered on a drill string to the bottom of a well, and metallic junk is attracted to magnetic pole caps 33 on the carrier, the weight of the string shears the pin 28 and the carrier withdraws beyond the fingers which extend to close the casing end (Fig. 3). Alternatively tightly wedged junk may be 'cored' by the bit and forced past the fingers. The shear pin 28 may engage in any of a number of apertures 26 and grooves 25. The assembly is hollow so that mud or air may be pumped to remove loose material from the top of the junk, before the caps attact it.