Patent GB-563761-A (GB)
Title: Improvements in or relating to hook structures
IPC: E21B19/04
Filed: 1942-12-24
Abstract: 563,761. Hooks; locking nuts. BYRON JACKSON CO. Dec. 24, 1942, No. 18326. Convention date, Jan. 9, 1942. [Classes 89 (i) and 89 (ii)] [Also in Group XXXIV] A safety hook, for use in rotary well drilling, has resilient swivel suspension means with a catch for locking the swivelling motion and a mousing piece designed to prevent the trapping of the operator's fingers. The hook 1 is pivotally attached at 3 to a stem 2 mounted to swivel in a supporting casing 4 having a flange 8 at its lower end that acts as abutment for a spring 6 bearing also against a ball-race 66, Fig. 12, mounted in a recess of a nut 7, on the upper end of the stem, having a left-hand thread and locked by a second nut 14 with a different pitch. The nut 14 is further locked by a set-screw 17 tapped into the nut and engaging a plain end 15 on the stem. The setscrew is fitted with a lock-nut. The spring is sufficient to support one length of drill tubing or of casing during screwing into place. During drilling the spring is compressed till a second and heavier ball-race 69 contacts an intermediate flange 9 in the casing 4. Both ball bearings are mounted in a housing 62 with retaining shoulders 66, 68 against which the bearings are held with slight clearance by rolled over flanges 63, 64. Lubrication is provided for by a fitting 72 accessible through a plug (not shown) in the casing 4, the main bearing is lubricated through a fitting 74, Fig. 1 (not shown), in the casing, and in addition a lubricating fitting 75 may be provided accessible by removing a cover 76. A polygonal part 18 of the stem slides through a circular clearance hole in the bottom of the casing 4 and through a fitting hole in a casing 19 secured to the casing 4 by a split clamping ring 21 so that relative rotary, but not axial, movement is permitted. A cross shaft 35 mounted in an enlarged part 34 of the casing 19 has a non-circular portion 36 engaging a like opening on the boss of a catch 33 having a cam 45 engaging a roller 48 in a spring-controlled arm to give a load-andfire action to the catch when operated by a head projecting outside the casing. The surface 55 is parallel to the axis of the stem when in engagement with one of a number of slots 32 formed on the casing 4 and the surface 56 is parallel to the axis when riding on the outside of the casing preparatory to snapping into the next slot under the action of the spring and cam 45. Lateral lugs on the catch limit the entry into the slots. The mousing piece 83, Fig. 13, pivoted to the hook at 84 has a portion 86 that is engaged by the load-carrying member 82 to secure automatic closing and latching of the mousing piece, on application of the load, and that is curved at 88 both in the plane of section and in a plane perpendicular thereto to suit the curvature of the contacting part 80 of the hook. The upper surface is correspondingly .curved at 87, the two sets of curvatures being preferably concentric. Side wings of the portion 86 overlap the hook part 80 and are sufficiently deep to maintain overlap in the open position of the mousing piece and thus prevent trapping of the operator's fingers.