GB1021552A - Improvements in or relating to braking mechanisms - Google Patents

Abstract

1,021,552. Safety brakes for lift cages. A. LODIGE. Aug. 20, 1962 [Aug. 18, 1961], No. 31896/62. Heading B8L. [Also in Division F2] A safety brake mounted on a lift cage or the like comprises two brake shoes interconnected by a link and adapted to be applied against opposite sides of a guide by tilting of the link to brake the cage upon a predetermined value of a parameter, such as the speed of the cage, being exceeded wherein one brake shoe is connected with an initiating device and the other brake shoe is attached to the cage through the intermediary of a pre-stressed spring, the arrangement being such that the brake shoes transmit a high initial braking force which is subsequently decreased, but not reduced to zero. In the embodiment shown in Fig. 1, one brake shoe 5 has a conical surface 7, which is urged downwardly into a recess 8 in the cage 2 by a spring 9, and is pivotedly connected at 12 to a link 11 provided with a roller 14 which engages wedge surfaces 16, 20 on a brake shoe 15. A speed-responsive device 18 mounted on the cage and engaging the guide 1 raises the shoe 15 by means of a link 19 when a predetermined speed is attained. In the inoperative position, the link 11 is supported by the shoe 5 and by an adjustable stop 4 and the base 96 of the shoe 15 rests in a recess 97 in the cage chassis so that the shoe is displaced away from the guide 1 and the roller 14 is disposed at the upper end of the wedge surface 16. When the braking operation is initiated, the link 19 raises the shoe 15 relative to the link 11 and the roller 14 rolls down the wedge surface 16 and moves the shoe into engagement with the guide 1. During this movement, the link 11 is tilted and pulled bodily to the right, as shown, and raises the shoe 5 against the action of the spring 9 into engagement with the guide. When the shoe 15 engages an abutment 3 on the cage, the braking becomes self-regulating in dependence upon the adjusted force of the spring 9. In a modification, Fig. 2 (not shown), the roller 14 is replaced by a two-arm lever provided at one end with a roller engaging the wedge surface 16 and at the other end with friction teeth engaging the guide 1, and the shoe 5 is pivotally mounted on an upright fork member which is urged downwardly by the spring 9. The lower end of the shoe 15 is provided with balls which are spring-urged against the guide 1 for cleaning the guide. In a further modification, Fig. 3 (not shown), three further brake shoes are connected by links between the two original brake shoes. In the embodiment shown in Fig. 6, one shoe 205 is urged downwardly by a spring and is provided with a cam surface 206 on which runs a roller 208 provided on the other shoe 209, the shoes being pivotally connected by a link 203. An acceleration-responsive device, Fig. 20, for initiating the braking action comprises a weight Q supported by a spring 53 on the cage 2. On a sudden increase in speed, the spring is extended or compressed and the relative movement of the weight Q is transmitted through a linkage 55, 56 to a double-wedge shoe 87 coupled to a spring mounted shoe 87<SP>1</SP>. A speed-responsive device, Fig. 9 (not shown) comprises a cam wheel rotatable with a wheel engaging the guide and engageable by a roller mounted on a. pivoted arm, the arrangement being such that when a critical speed is attained, the radial deflection of the roller causes engagement of a pawl with a ratchet wheel on the same axle thereby swinging the support of the pivoted arm about the axle and initiating the operation of the brake through a linkage. An alternative speed-responsive device, Fig. 27, comprises an arm 275, supporting a roller 278 running on the guide surface 279, pivoted on the cage 277. A two-arm lever 263 is pivoted at 265 on the arm 275 and supports a roller 262 which is spring- urged against a cam 260. When the cage attains a predetermined critical speed, the radial displacements of the lever 263 become sufficiently large for a spring-supported detent 270 on the other end of lever 263 to engage teeth 261 formed on the cam 260, the lever 263 with the arm 275 pivot about the pivot point of the latter on the cage and thereby raise a link 272 to initiate the braking action. A further speed-responsive device, Fig. 24 (not shown), comprises a plate, pivoted to the cage about a horizontal axis and provided with a counterweight so dimensioned that when the cage attains a predetermined speed, the air flow pivots the plate which is coupled to one of the brake shoes by a linkage. An electromagnetic speed-responsive device, Fig. 25 (not shown), is also described.