Patent GB-998218-A (GB)
Title: Improvements in or relating to a force device
IPC: A61F5/04
Filed: 1963-07-09
Abstract: 998,218. Spring power-storing devices. AMETEK Inc. July 9, 1963 [July 12, 1962; Oct. 23, 1962], No. 27188/63. Heading F2S. An orthopaedic tensioning device 2, provided with means to indicate the tension comprises a cable 34 which has a ring 38 adapted to be connected, e.g. to an orthopaedic sling, not shown, and which is coiled upon a reel 21 rotatably mounted upon a bushing 22 fixed to a shaft 23 the latter being journalled at one end in a frame member 8 within a main casing 46 and at the other end in a cup member 24 fixed to a complementary frame member 10. A main power coil spring 30 is connected between the inner face of the reel 21 and the bushing 22 a relatively weaker initial tensioning coil spring 25 being connected between the fixed cup member 24 and the inner face of an open drum 27 secured to the reel 21 for rotation therewith. A worm gear 96 carried by the shaft 23 is engaged by a worm 98 which is splined on a shaft 100 mounted in brackets 102, 104, struck up from the main casing 4, 6 a finger 114, biased into a vertical position by the two arms of a torsion spring 118, being adapted to engage the worm 98 before it disengages from the worm gear 96. Before passing out of the main casing through a grommet 39 the cable 34 passes over a pulley 36 which is rotatably mounted in a pivoted frame 41 connected to a measuring spring 54 which is pretensioned by a weak spring 48, the frame 41 carrying a pin 60 which extends through an opening 62 in the frame member 10 and is secured to a lever 64 of a force indicator having a pointer 74. A centrifugal friction damper accommodated in a housing 138 at the upper end of the casing 4, 6 is driven through gears 132, 134 and a pinion 128 which is mounted on a shaft 130 and engages a ring gear 126 on the reel 21. The damper comprises a pair of semi-circular portions 150, 152 which are urged together around a shaft 160 by a garter spring 156, and which are moved radially outwardly to frictionally engage the inner face of the housing 138 if the reeling-in speed is too high. In operation, holes 15 in an extension 14 of the inner frame 10 are engaged by the arms 16 of a bracket 20 which is secured to a fixed support, e.g. a standard, not shown, and the worm 98 is retracted out of engagement with the worm gear 96 by rotating a crank 113 anti-clockwise when it is engaged in a recess 110 at the outer end of the splined shaft 100, the finger 114 ensuring continued retraction of the worm 98 until it is stopped by the bracket 104. With the main spring 30 out of action the cable 34 can be extended, against the winding- up force of the weaker spring 25 and connected to the sling, the tensioning force of the cable 34 being indicated by the pointer 74 or a dial 76. After the set-up has been accomplished the crank 113 is turned clockwise so that the worm 98 engages the worm gear 96, continued rotation of the crank 113 in the same direction causing the main power spring 30 to be wound up. Winding is continued until the spring 30 exerts a tension on the cable equal to that indicated by the pointer 74. The finger 114 may be replaced by a spring-loaded slide provided with a follower projection.