Improvements in plugs for use in cementing well casings

532,468. Cementing well casings. DYER, Z. A., LAMB, C., and RADFORD, D. R. July 29, 1939, No. 22086. [Class 85] Relates to lower plugs for use in cementing casing in wells. The plugs may be formed of rubber, "Bakelite" R.T.M., wood, &c. and comprise a cylindrical body 70, Fig. 6, with a central annular channel 32 and a groove 76 in which is a rubber washer 78 of greater outside diameter than the body and less normal inside diameter than the base of the groove 76 ; longitudinal passages 40 are formed in the outer surfaces of the body and central cavities 50 may be formed in the ends. The body may be integral, or formed in two parts with a threaded connection 74, or a frictional connection of smooth-walled or annularly corrugated parts. In Fig. 7, the upper part of the plug is replaced by a cap 80 which may be integral with the lower part or threaded thereto ; alternatively, the cap may be omitted, the washer then being vulcanized &c. to the lower part. Such plugs may be used in tandem. In Fig. 8, the washer has an inner flange 90 engaging corresponding grooves in the body ; such a washer may be used in the form of Fig. 7.