Patent GB-190812176-A (GB)
Title: Improvements in Automatic Apparatus for Controlling the Speed of Trains and like Vehicles.
Inventor: BOULT ALFRED JULIUS
Filed: 1908-06-04
Granted: 1909-04-29
Abstract: 12,176. Boult, A. J., [Union Switch and Signal Co.]. June 4. Locomotives. - A mechanical track contact is moved laterally to the track into the path of one or other of two pivoted engine contacts, these positions corresponding respectively to home and distant signal indications. The home contact opens a valve and applies the brakes directly when the home signal is at ' danger,' and the distant contact reduces the speed by a predetermined amount by temporarily applying the brakes. The track contact is also pivoted, and is lowered out of the path of the engine contacts when the signals indicate ' safety.' Speed-responsive apparatus on the train co-operates with the engine contact apparatus so that the brakes shall not be applied when the distant signal indicates ' caution ' except when the speed is excessive under these circumstances. The home engine contact 2, Fig. 1, upon being actuated by the track trip 3, opens a valve 5 in the trainpipe or opens a pipe 6 communicating with any valve apparatus 7 which opens the train-pipe. The distant engine contact 8 upon being actuated breaks a circuit including a battery 19 and a magoet 18, which then opens a valve 16 in the train-pipe or opens a pipe 17 leading to the valve 7, which opens the train-pipe. If, however, the speed is not above a predetermined amount, the distant contact 8 is not actuated because it is normally slightly out of line with the track trip, and is only moved laterally on its spindle into line with the trip when the speed is high. For this purpose, the contact 8, Fig. 6, is normally retained in a vertical position by a spring 9 pressing between stops. A piston 12 mounted on the spindle 10 is moved against the action of a spring 13 by fluid pressure admitted through a valve 14<a> when a magnet 15 is energized. The fluid pressure moves the contact 8 into operative position. The magnet 15 is energized when the armature 28, Fig. 1, closes the circuit. This happens when the speed is not above a predetermined maximum, so that a dynamo driven from the wheels does not supply sufficient current to energize the magnet 24. A semicircular metal segment on the spindle 10, Fig. 6, is engaged by contact spring arms 20, 21, Fig. 1, and thus closes the circuit of the magnet 18 in the mid-position of the contact 8, but, if the contact 8 is deflected in either direction, the c'rcuit is broken at the contacts 20, 21, and the brakes are applied. In a modified form, any well-known form of centrifugal speed governor is employed to replace the dynamo driven from the train wheels, and the governor by its movement when the speed is too high opens the circuit of the magnet which admits fluid to the cylinder whereby the engine cont ict is moved into operative position. One such governor comprises a disk 31. Fig. 4, eccentrically pivoted with respect to the shaft on which it rotates. When the speed rises, the disk moves from the position shown in dotted lines to the position shown in full lines and moves an arm 31 against the action of a spring to open the circuit contacts as described above. In another form, a centrifugal governor 41, Fig. 5, moves a latch 43 to hold a bell-crank 44 in its operated position, shown in full lines, after the bell-crank 48 has moved it thereto by engagement with the track obstacle 3. Should the lever 48 engage the track obstacle while the speed is below the fixed limit, the valve 46 is merely opened and at once closed by the spring 49.