Tread brake apparatus

Claim 2

A tread brake assembly for applying a braking force to a wheel of a railway vehicle truck, said assembly comprising: a. brake shoe means for applying a braking force to a vehicle wheel, and b. a pivoted lever effective upon rocking in one direction to apply said brake shoe means and upon rocking in the opposite direction to release said brake shoe means, wherein the improvement comprises: c. means for actuating said pivoted lever including: i. a proportioning lever operatively connected at one end to said pivoted lever, ii. a movable fulcrum means for said proportioning lever, iii. brake-applying spring means operatively connected to the other end of said proportioning lever, which means in one position of said movable fulcrum means transmits, via said proportioning lever, a moment of force to said pivoted lever that acts to rock said pivoted lever in a brake-releasing direction, and which in another position of said movable fulcrum means transmits, via said proportioning lever, a moment of force to said pivoted lever that acts to rock said pivoted lever in a brake-applying direction, and iv. power means for varying the position of said movable fulcrum means relative to said proportioning lever.

Claim 3

A tread brake assembly, as claimed in claim 1, further characterized in that said power means comprises: a. a control spring, b. a bell-crank lever, operably connected to said control spring and said movable fulcrum for varying the position of said fulcrum according to the compression of said control spring, and c. a torque motor so operably connected to said bell-crank lever as to vary the compression of said spring directly as the output torque of said motor is varied.

Claim 4

A tread brake assembly, as claimed in claim 1, further characterized in that said pivoted lever is pivoted intermediate its ends and operatively connected at one end to said proportioning lever, and by a rigid rod operatively connected to said brake shoe means and swivelly connected to the other end of said pivoted lever in a manner to move said brake shoe means into and out of braking engagement with the vehicle wheel upon corresponding pivotal movement of said pivoted lever in response to the moment of force transmitted thereto by said proportioning lever from said brake-applying spring means, the degree of said moment of force varying in accordance with the position of said fulcrum means relative to said proportioning lever.

Claim 5

A tread brake assembly, as claimed in claim 1, further characterized in that said movable fulcrum means comprises: a. stationary track means, and b. a wheeled carriage member carrying a fulcrum for said proportioning lever, said wheeled carriage member being borne by said track means and movable in opposite directions therealong to shift said fulcrum relative to said proportioning lever from a first position in which said moment of force transmitted to said pivoted lever acts to rock said pivoteD lever in said brake-releasing direction to another position in which said moment of force acts to rock said pivoted lever in a brake-applying direction, the value of said moment of force increasing as said fulcrum is shifted further from said first position.

Claim 6

A tread brake assembly, as claimed in claim 1, further characterized in that said pivoted lever comprises a hub from which extends a pair of spaced-apart parallel arms curved adjacent their outer ends and operatively connected to one end of said proportioning lever, the opposite end of which lever is disposed between said spaced-apart arms, and by a pivoted bell-crank lever having one arm operatively connected to said opposite end of said proportioning lever and another arm operatively connected to said brake-applying spring means, said bell-crank lever being effective to transmit said moment of force from said brake-applying spring means to said opposite end of said proportioning lever without substantial expansion of said brake-applying spring means.

Claim 7

A tread brake assembly, as claimed in claim 1, further characterized in that said proportioning lever is provided with a cam surface along which said movable fulcrum means travels, that portion of said cam surface initially traversed by said fulcrum means constituting an arc of a circle and the remaining portion being a straight line.

Claim 8

A tread brake assembly for applying a braking force to a wheel of a railway vehicle truck having a side frame, said brake assembly comprising in combination: a. a casing fixed with respect to the car truck side frame and having a chamber therein, said casing having two spaced walls in each of which is a bore coaxial with the bore in the opposite wall, b. a fulcrum member having its opposite ends disposed in said bores in said opposite walls, c. a brake lever disposed within said chamber and rockably mounted intermediate its ends on said fulcrum member, said brake lever having a pair of spaced-apart parallel arms extending in one direction from said fulcrum member and a single arm extending in the opposite direction, d. a brake shoe, e. a brake head carrying said shoe, f. a brake head hanger pivotally mounted at one end on said casing and pivotally connected at the other end in supporting relation to said brake head, g. a rigid rod member pivotally connected at its one end to the brake head and extending through one wall of said casing into said chamber, h. universal swivel means connecting the portion of said rigid rod member within said chamber to said single arm of said brake lever, whereby movement of the brake shoe out of and into braking contact with the tread surface of the car wheel is effected respectively by movement of said rigid rod member in one direction or in an opposite direction in response to rocking of said brake lever in said directions, wherein the improvement comprises: i. a brake-applying spring supported at one end on said casing, j. a first bell-crank lever pivotally mounted on said casing and having a pair of arms, one of which is operatively connected to the other end of said brake-applying spring, whereby said spring is effective to bias said bell-crank lever in one direction, k. a proportioning lever having thereon a cam surface, said lever being operatively connected at one end of said cam surface to said pair of spaced-apart parallel arms of said brake lever and connected intermediate the ends of said cam surface to the other arm of said first bell-crank lever, l. a track carried by said casing, m. a carriage member movably supported on said track and carrying a pair of fulcrum rollers that roll along said cam surface as said carriage member is moved along said track, n. a control spring supported at one end on said casing, o. a second bell-crank lever pivotally mounted on said casing and having a pair of arms, one arm being operatively connected to the other end of said control spring and the other arm to said carriage membeR, whereby the expansion of said spring is effective, via said second bell-crank lever, to move said carriage member along said track thereby to shift said pair of fulcrum rollers with respect to said cam surface from a first position in which said rollers abut said cam surface below the connection of said other arm of said first bell-crank lever with said proportioning lever to another position above this connection, thereby rendering said brake-applying spring ineffective to rock said proportioning lever in a brake-releasing direction and effective to rock said lever in a brake-applying direction, whereby the mechanical advantage provided by said proportioning lever is increased as said carriage member is moved along said track, and p. brake-release means including a torque motor and a reduction gear unit operatively connected to said second bell-crank lever for effecting rocking thereof in the direction to compress said control spring and shift said carriage member and pair of fulcrum rollers carried thereby to said first position in response to the supply of electric power to said torque motor.

Claim 9

A tread brake assembly for applying a braking force to a wheel of a railway vehicle truck having a side frame, said brake assembly comprising in combination: a. a casing fixed with respect to the car truck side frame and having a chamber therein, said casing having two spaced walls in each of which is a bore coaxial with the bore in the opposite wall, b. a fulcrum member having its opposite ends disposed in said bores in said opposite walls, c. a brake lever disposed within said chamber and rockably mounted intermediate its ends on said fulcrum member, said brake lever having a pair of spaced-apart parallel arms extending in one direction from said fulcrum member and a single arm extending in the opposite direction, d. a brake shoe, e. a brake head carrying said shoe, f. a brake head hanger pivotally mounted at one end on said casing and pivotally connected at the other end in supporting relation to said brake head, g. a rigid rod member pivotally connected at its one end to the brake head and extending through one wall of said casing into said chamber, h. universal swivel means connecting the portion of said rigid rod member within said chamber to said single arm of said brake lever, whereby movement of the brake shoe out of and into braking contact with the tread surface of the car wheel is effected respectively by movement of said rigid rod member in one direction or in an opposite direction in response to rocking of said brake lever in said directions, wherein the improvement comprises: i. a brake-applying spring supported at one end on said casing, j. a first bell-crank lever pivotally mounted on said casing and having a pair of arms, one of which is operatively connected to the other end of said brake-applying spring, whereby said spring is effective to bias said bell-crank lever in one direction, k. a proportioning lever having thereon a cam surface, said lever being operatively connected at one end of said cam surface to said pair of spaced-apart parallel arms of said brake lever and connected intermediate the ends of said cam surface to the other arm of said first bell-crank lever, l. a track carried by said casing, m. a carriage member movably supported on said track and carrying a pair of fulcrum rollers that roll along said cam surface as said carriage member is moved along said track, n. a control spring supported at one end on said casing, o. a second bell-crank lever pivotally mounted on said casing and having a pair of arms, one arm being operatively connected to the other end of said control spring and the other arm to said carriage membeR, whereby the expansion of said spring is effective, via said second bell-crank lever, to move said carriage member along said track thereby to shift said pair of fulcrum rollers with respect to said cam surface from a first position in which said rollers abut said cam surface below the connection of said other arm of said first bell-crank lever with said proportioning lever to another position above this connection, thereby rendering said brake-applying spring ineffective to rock said proportioning lever in a brake-releasing direction and effective to rock said lever in a brake-applying direction, whereby the mechanical advantage provided by said proportioning lever is increased as said carriage member is moved along said track, and p. brake-release means including a torque motor and a reduction gear unit operatively connected to said second bell-crank lever for effecting rocking thereof in the direction to compress said control spring and shift said carriage member and pair of fulcrum rollers carried thereby to said first position in response to the supply of electric power to said torque motor.

Claim 10

A tread brake assembly, as claimed in claim 7, further characterized in that said cam surface on said proportioning lever is formed on one side thereof and comprises two portions, one of which constitutes a straight line and the other an arc of a circle, and said other arm of said first bell-crank lever being pivotally connected to said proportioning lever intermediate the ends of said arc portion of said cam surface, whereby said pair of fulcrum rollers is shiftable from one side to the other of the connection of said one arm of said first bell-crank lever with said proportioning lever as said carriage member is moved from said first position to another position.

Claim 11

A tread brake assembly for applying a braking force to a wheel of a railway vehicle truck having a side frame, said assembly comprising: a. a casing immovably supported on said side frame, b. a brake-shoe-carrying brake head movably supported on said casing for movement into braking contact with said wheel, c. a brake-applying spring supported at one end on said casing, d. a brake lever rockably mounted intermediate its ends on said casing and operatively connected at one end to said brake head, e. a linkage operatively connecting the other end of said brake-applying spring to the other end of said brake lever, said linkage comprising: i. a bell-crank lever rockably mounted on said casing and having one arm connected to said other end of said brake-applying spring, whereby said spring is effective to rock said bell-crank lever in one direction, ii. a proportioning lever having formed thereon a cam surface, one portion of which constitutes a straight line and another an arc of a circle, iii. a first link pivotally connected at one end to one end of said proportioning lever and at the other to said other end of said brake lever, and iv. a second link pivotally connected at one end to the other arm of said bell-crank lever and having its other end rigidly secured to said proportioning lever intermediate the ends of said other cam portion, f. a shiftable fulcrum for contact by said cam surface on said proportioning lever and shifted to increase or decrease the moment of force transmitted to said proportioning lever by said brake-applying spring and from one position in which said moment of force is effective to rock said proportioning lever about said fulcrum in a brake-releasing direction to another position in which said moment of force is effective to rock said proportioning lever in a brake-applying direction, the value of said moment of force increasing accordingly as the distance between said shiftable fulcrum and the pivotal connection of said one end of said second link with said other arm of said bell-crank lever is increased, and g. power means selectively operable to cause shifting of said shiftable fulcrum in either direction along said cam sUrface on said proportioning lever.

Claim 12

A tread brake assembly for applying a braking force to a wheel of a railway vehicle truck having a side frame, said assembly comprising: a. a casing immovably supported on said side frame, b. a brake-shoe-carrying brake head movably supported on said casing for movement into braking contact with said wheel, c. a brake-applying spring supported at one end on said casing, d. a brake lever rockably mounted intermediate its ends on said casing and operatively connected at one end to said brake head, e. a linkage operatively connecting the other end of said brake-applying spring to the other end of said brake lever, said linkage comprising: i. a bell-crank lever rockably mounted on said casing and having one arm connected to said other end of said brake-applying spring, whereby said spring is effective to rock said bell-crank lever in one direction, ii. a proportioning lever having formed thereon a cam surface, one portion of which constitutes a straight line and another an arc of a circle, iii. a first link pivotally connected at one end to one end of said proportioning lever and at the other to said other end of said brake lever, and iv. a second link pivotally connected at one end to the other arm of said bell-crank lever and having its other end rigidly secured to said proportioning lever intermediate the ends of said other cam portion, f. a shiftable fulcrum for contact by said cam surface on said proportioning lever and shifted to increase or decrease the moment of force transmitted to said proportioning lever by said brake-applying spring and from one position in which said moment of force is effective to rock said proportioning lever about said fulcrum in a brake-releasing direction to another position in which said moment of force is effective to rock said proportioning lever in a brake-applying direction, the value of said moment of force increasing accordingly as the distance between said shiftable fulcrum and the pivotal connection of said one end of said second link with said other arm of said bell-crank lever is increased, and g. power means selectively operable to cause shifting of said shiftable fulcrum in either direction along said cam sUrface on said proportioning lever.

Claim 13

A tread brake assembly, as claimed in claim 9, further characterized in that said power means comprises: a. a rockable shaft, b. a second bell-crank lever rigidly mounted on said shaft and having one arm operably connected to said shiftable fulcrum, whereby said fulcrum is shifted in one direction or an opposite direction accordingly as said lever is rocked in said one or said opposite direction, c. a control rod operatively connected at one end to the other arm of said second bell-crank lever and having intermediate its ends a spring seat, d. a stop carried by said casing and disposed in the path of movement of said control rod for limiting movement of said rod in one direction, e. a control spring disposed about said control rod and interposed between said casing and said spring seat for moving said control rod in an opposite direction, and f. a torque motor operatively connected to said shaft, whereby rocking of said shaft and said second bell-crank lever in the direction to effect movement of said control rod in its said one direction to compress said control spring is effected by said torque motor, upon the supply of electric power thereto.

Claim 14

A tread brake assembly, as claimed in claim 10, further characterized by a hand brake lever pivotally mounted intermediate its ends on said casing, said hand brake lever having formed integral with one end thereof a pair of spaced-apart fingers which straddle said control rod and abut said spring seat upon rocking said hand brake lever in one direction to cause compression of said control spring and shifting of said shiftable fulcrum in a brake-releasing direction independently of said torque motor.