GB302436A - Improvements in braking mechanism - Google Patents

Abstract

302,436. Helps, A. O. Oct. 6, 1927. Actuated or applied by weights; force-transmitting mechanism.-Brake mechanism particularly for cranes and other lifting machinery comprises two brakes with a time lag or delay action between them so that one brake only is in operation at one time but such that in the event of failure of such brake the second brake will automatically come into operation. Means may be provided whereby the emergency brake may function for normal braking when the normal brake is required to be out of action. According to one arrangement, Figs. 12-14, a pair of shoe or post brakes disposed side by side, of which one a is shown, are applied by weighted levers a<2>, b<2>, one of which a<2> is secured to the shaft c while the other b<2> is freely mounted thereon. The brakes are controlled by a solenoid e connected to the lever a<2>. The shaft c has an arm k keyed thereon provided with a slot through which passes a pin l on the lever b<2>. A bent lever n pivoted to a fixed bracket normally has one arm engaging a pivoted arm n<2> so as to support the lever b<2>. The arrangement is such that if by reason of breakage of a pin or other connection in the brake a. the lever a<2> falls below the normal position for applying this brake, this lever disengages the lever n from the arm n<2> and permits the lever b<2> to apply the emergency brake. To enable the emergency brake to function for normal braking, when the normal brake is required to be out of action for repair &c., a collar of a size accurately to fit the slot in the arm k is placed therein on the pin l so as to prevent the lost motion normally allowed between these parts. This collar m may normally conveniently be carried on the end of the pin l. A lever o is provided for connection to a pedal by which the brake may be released. In another construction, Fig. 3, a pair of band brakes of which one b is shown have one end b<1> of each brake band fixed while the other ends are connected to arms b<2> on a shaft c to which is secured the weighted operating lever. The connection of the end of the band for normal operation to its lever is a simple pin connection but that of the emergency band is a pin-and-slot connection d, d<1> so that this band is applied only in the event of breakage of the normal band. A second hole is provided in the lever b<2> for the connection of the end of the emergency band when this is required to function as the normal brake without lost motion.