Overspeed safety braking device
AssigneeD. Wickham and Company Limited
InventorsDerek J. Martin, Michael D. Barker
Life of this patent
Estimating the term…
Abstract
An overspeed safety braking device comprising an input shaft, the speed of which is to be braked when it exceeds a limit value, a rotary friction brake having a fixed part and a rotary part, the input shaft being permanently coupled for rotation with the rotating part of the rotary friction brake, a control device for applying the brake, and centrifugal activated structure comprising a braking member which rotates with the input shaft when the speed is below the limit value, a weight pivotally mounted on the braking member and biasing spring coupled to the weight and arranged to bias the weight toward the axis of rotation of the shaft when the speed is below the limit value and away from the axis of rotation when the speed is above the limit value.
Claims27
An overspeed safety braking device comprising an input shaft, the speed of which is to be braked when it succeeds a limit value, a rotary friction brake having a fixed part and a rotary part, the input shaft being permanently coupled for rotation with the rotating part of the rotary friction brake;
- a control device for applying the brake;
- and centrifugal activating means for activating said control device, said centrifugal actuating means comprising a support member which rotates with the input shaft when the speed is below the limit value, a weight pivotally mounted on said support member, an overcenter biasing means coupled between said weight and said support member, said biasing means being arranged to bias the weight toward the axis of rotation of the shaft until the speed has exceeded the limit value and to bias the weight away from the axis of rotation after the speed has exceeded the limit value, thereby irreversibly applying the brake so that even when the speed of the shaft is slowed down below the limit value, the overcenter biasing means remains in an overcenter position.
An overspeed safety braking device comprising an input shaft, the speed of which is to be braked when it exceeds a limit value, and which is permanently coupled for rotation with the rotating part of a rotary frictional brake, means responsive to the speed of rotation of the front shaft exceeding the limit value for activating a control device to apply the brake and thus brake the input shaft, means for biassing the rotating part and a fixed part of the brake into engagement and the control device includes means for compressing the biassing means when activated, the means for compressing comprising a first member with a screw-thread which is engaged with a complementary screw-thread on a second member fixed to the input shaft, the first screw-threaded member being arranged to rotate with the second screw-threaded member and the input shaft when the speed is below the limit but being prevented from rotation by the activating means at speeds above the limit whereby the first threaded member travels axially on the second screw-threaded member to compress the biassing means, the activating means comprising a member which is fixed to the first screw-threaded member and which carries a weight biassed towards the axis of rotation and which can move away from the axis of rotation against the action of the biassing means as the speed of rotation increases, a catch being carried by the weight, the catch engaging a fixed stop when the speed of the shaft exceeds the limit value to prevent rotation of the first screw-thread member, and a first locking member fixed to the weight and a second locking member fixed to the second screw-threaded member, the first locking member engaging the second locking member to prevent relative rotation of the first and second screw-threaded members, the first locking member disengaging the second locking member when the weight has moved a certain distance away from the axis of rotation.
Dependencies are inferred from the claim text.