Patent GB-309065-A (GB)
Title: Improvements in automatic scotching mechanism for railway and like vehicles
IPC: B61H7/02
Filed: 1928-01-04
Abstract: 309,065. Stone & Co., Ltd., J., and Skinner, C. D. Jan. 4, 1928. Reverse movement, preventing by frictional devices; applied by weights; skid. - A scotch blockis adapted to be released for engagement between the wheel and the track by a tripping device actuated by the run-back of a railway vehicle on a gradient. A rail gripping device may be simultaneously operated. Means are provided for preventing the tripping device from being effective. A scotch block 1, suspended from the vehicle by an arm 2 pivoted at 3 is held in the normally raised position, Fig. 3, by a toggle 5, 6, held in the straightened condition by a load at the joint which when the mechanism is duplicated on the other side of the vehicle may take the form of a bar 8 extending between the two toggle joints. The joint is adapted to be broken to permit engagement of the scotch block by the engagement of a pawl 11 pivoted in a slot 10 in a bracket on the toggle link 5, with a ratchet wheel 12 on the wheel axle. In order that the apparatus may be " cocked " or set to permit of its operation by the trip device or be retained in the disengaged position, a toggle 37, 37a is connected to the shoe 1 and to an arm 36 on a shaft 34 provided with another arm to which is pivoted the forked ends 35<a> of a weighted arm 35. With this arm in the position shown, one limb of the fork 35<a> bears on the shaft 34 and the arm thus holds the shaft, the arm 36 and toggle 37, 37<a> in a position to permit the shoe 1 to fall into engagement when released by the trip device 11, 5, 6. If, however, the arm 35 is swung over the dead-centre position, the other limb of the fork 35<a> bears on the shaft 34 and the arm is operative to turn the shaft 34 and to pull the toggle into such a position as to hold the shoe 1 in the raised position even if the toggle 5, 6 is broken. The shaft 34 may be rocked by hand by the rod 41 and arm 42 prior to the ascent of a vehicle on an up-grade to set the mechanism for operation, but if this should be omitted it is done by the engagement of an arm 40 with an abutment 44 on the track, the arm 40 having a pivoted end so that it is effective only in one direction of travel. A cable 13 may extend from the pawl 11 to the arm 40 so that when the shaft 34 is turned to hold the shoe 1 in the raised position the pawl is disengaged from the ratchet 12. A rail gripping device may be combined with the shoe 1 and comprises oppositely threaded rail grippers 15, Fig. 2, on a screwed shaft 17 mounted in the shoe 1, The shaft 17 carries an arm 18 carrying a weighted roller 20, and when this arm is raised as by the winch 32 and cable 33 to disengage the rail grippers 15, the spindle of the roller 20 rides on a curved bracket 21 causing the raising of the brake shoe arm 2 and the straightening of the toggle 5, 6 while, at the same time, a pivoted catch 22 is set by a link connection 24 with the arm 2, to hold the arm 18 in the raised position. As shown in Fig. 6, the shoe 1 and rail grippers may be duplicated for the other pair of wheels. When the weighted arm 18 falls it rocks the pivoted double arm 29, 30 and thus lifts by a pm 31 on the arm 29, the end of a rod 25 connected to the arm 2a of the shoe 1<a> so as to disengage the end of this rod 25 from the shaft 27, thus permitting a spring 28 to pull the arm 2a into the operative position with the consequential release also of the arm 18<a> of the rail grippers. Two sets of tripping and scotching mechanism may be provided operative respectively in the one and the other directions of travel of the vehicle.