Patent GB-190824638-A (GB)
Title: Improvements in Safety Devices for Hoisting Apparatus.
Filed: 1908-11-16
Granted: 1909-03-11
Abstract: 24,638. Fraser & Chalmers, and Whitmore, F. L. Nov. 16. Overwinding, preventing; speed, governing.-In apparatus for preventing over winding and excessive speed in winding-engines, of the kind in which an operating-lever or the like is actuated by a rotary cam moving in fixed relation to the winding-drum, the cam or like part is so shaped that the operating- lever is moved at an increasing rate towards either end of the wind. Fig. 1 is a front view and Fig. 3 a back view of the safety gear, and Fig. 5 shows a detail. The winding drum is geared to a worm shaft a driving a worm-wheel c on the boss of which are mounted two cam levers d in a similar way to the jaws of a pair of pincers. The angle between the jaws is adjusted by movable blocks e, a spring d<2> keeping the jaws in contact with the blocks. The cams are so shaped as to give a slowly increasing rate of motion to the lever f during the greater portion of the wind, and a quickly increasing motion towards the end. The lever f has a roller for engaging the cam-surface and a pointed end adapted to catch a serrated floating lever h. The governor is connected to one end of this lever by a slotted link j, an arm k, a link k<1>, and a lever l. The opposite end of the lever is connected to a crank on a shaft g, which, by means of another crank g<2> and rod m<1>, controls the throttle and brake valves. In the event of excessive speed during the wind, the floating lever h falls and is caught by the point of the lever f which, by rocking the shaft g, operates the throttle and brake valves. To give a quick stoppage in the event of excessive speed occurring near the end of wind, the' governor is connected by a second slotted link k<2> to a toothed arm q<1> pivoted to a crank q mounted on a pin p<1>. A pawl p mounted on the pin p<1> supports an arm o the boss of which engages a lever g<3> acted on by a spring n. This lever is loosely mounted on the shaft g but is overhung by a projection on an arm g<5> keyed to the shaft. When the lever f engages the toothed arm p<1>, it rocks the pin p<1> and releases the pawl p from the arm o, thereby allowing the spring n to rock the shaft g and to apply the brakes and close the throttle instantly. Fig. 5 shows a device for allowing the cage to be lowered slightly after being brought to bank and for preventing the cage from being subsequently started upwards. The lever f is fitted with an adjustable set-screw f<5> adapted to engage the shoulder of a spring pawl q<3> mounted in the crank q. The pawl q<3> engages and normally retains in position a counterweighted toothed cam r<1> pivotally mounted on the same pin as the toothed arm q<1> and having a limited rotation relative thereto. When the cage is approaching its highest position the set-screw f<5> disengages the pawl q<3> and frees the toothed cam r'. It the cage is then lowered slightly to allow the higher decks to be unloaded the pointed end f<2> is slightly withdrawn, allowing the cam r' to rock upwards until it re-engages the point f If the engine is then reversed so as to start the cage upwards the lever f moves outwards and by rocking the crank q applies the brakes and closes the throttle. The cam r is re-set by a slotted link operated by an arm on the lever f or by a cam on the worm-wheel c. To prevent the arm o from being accidentally disengaged from the pawl p, it is locked in position by a detent s which is disengaged before the end of the wind by cam-surfaces on the worm-wheel c. The contour of the cam-levers d may be varied, or the worm-wheel c may be provided with a crank-pin or an eccentric connected by a rod to the lever f.