Patent GB-924644-A (GB)
Title: Well tools
Inventor: SCHWAB CARL MILTON
IPC: E21B23/02
Filed: 1959-09-25
Abstract: 924,644. Well tools. OTIS ENGINEERING CORPORATION. Sept. 25, 1959, No. 32772/59. Class 85. A stop is located in a well flow conductor, e.g. to prevent tools from falling to the bottom of the well, by dogs which engage internal recesses in the conductor, e.g. the recesses in the coupling collars, the dogs being kept inwardly retracted by a keeper which is released by an upward movement of the stop. The stop comprises a mandrel 37 connected by a shear pin 39 with the running tool 31, a sleeve 47 with a split collar 42 welded thereto, being slidable on the mandrel between shoulders 41, 44. A shear pin 48 secures the sleeve 47 to the mandrel 37 whilst the stop is run into the conductor, the dogs 56, which are formed on resilient fingers 45, 46 on the sleeve, being held in inwardly flexed state by a U-shaped keeper 50 pivoted to one of the dogs at 51 and embracing the other with the cross-member of the U. A spring 57 secured to the cross-member is flexed inwardly during downward movement past the recesses 62a in the coupling collar 35, but when the tool is pulled upwardly past a selected coupling, the spring 57 is held and swings the member 50 downwardly thereby permitting the dogs 56 to pass into the recess. The square shoulders 60 on the dogs prevent the stop from moving downwards whilst jars from the running tool shear the pin 48 and force the enlargement 40 of the mandrel down to cam the dogs firmly into the recess. The enlargement 40, which has a tapered camming surface 65 and a bevelled end 67 which rests finally on shoulders 68 of the dogs, is retained in locking position by lugs 62 on the fingers 45, 46 engaging the top bevelled shoulder of the enlargement, and the pin 39 is sheared by jars to permit removal of the running tool. The stop is removed by a fishing tool pulling on the head 44 of the mandrel. In Fig. 6 the dogs 89 have surfaces 92 which are initially confined within a cylindrical keeper 90 having springs 98 secured thereto to engage in the recess on upward movement of the stop. The dogs have vertical slots 95 in which diametral guide pins 96 are slidable. When the stop is pulled up, the keeper is arrested by the springs 98 and the dogs slide up until the shoulders 92a come above the top of the keeper and are released. Continued upward pulling on the stop breaks off the springs 98 and the stop is then lowered until the dogs 89 rest with their square shoulders on the top of pipe section 34. The dogs are kept positively in locking position, as before, by forcing down the mandrel. In another modification, the dogs are formed on members pivoted on the sleeve 47 and the spring fingers 45, 46 are dispensed with. A spring between the dogs separates them when a keeper, similar to the keeper 50, is released. The mandrel has fingers, depending therefrom, whi h engage the backs of the pivoted dogs and hold them in locked position, detents on the fingers snapping into retaining recesses in the backs of the dogs. In the modification shown in Fig. 13, dogs 157 are radially slidable on guides 159, and are urged outwardly by a split spring ring 161. The guides 159 pass through slots in extensions of the dogs, and are secured in a sleeve 153 carrying springs 168. The mandrel 151 has depending fingers 163 which initially lie outside the dogs and keep them retracted. When the springs 168 engage the recess 62a, the sleeve is held stationary whilst the mandrel 151 continues to rise until the fingers 163 release the dogs. Further raising of the mandrel breaks off the springs 168 and the sleeve and dogs rise until the latter engage in the recess 62a. The mandrel is now forced down until lugs 166 on the fingers snap into retaining grooves 164 in the dogs. The springs separating the dogs may be modified, or the dogs may be magnetized and thereby moved apart.