Patent GB-190722756-A (GB)
Title: Improvements in Apparatus for the Electric Lighting of Railway Carriages
Inventor: PRESTON EDWIN MUMFORD
Filed: 1907-10-15
Granted: 1908-10-15
Abstract: 22,756. Preston, E. M., and Kennard, A. E. Oct. 15. Lighting, systems of; switches.-A device of the type described in Specifications No. 5631, A.D. 1894, No. 1611, A.D. 1895 and No. 9882, A.D. 1899 for train-lighting system, with variable-speed generators consists of a pivoted or sliding support operated by a governor to insert plugs intocontacts, which are mounted upon a rocking support and are brought into position by friction between the brushes and commutator. In the arrangement shown in Figs. 1 and 2, an oscillating switch is also provided for changing the connexions between the dynamo and batteries. The rocker a, mounted concentric with the shaft b of a dynamo c, carries brush holders d and contacts e, f, g. The contacts e, g are connected to one brush of the dynamo, while the contact f is connected to the other brush. As the dynamo revolves, the friction between the brushes h and the commutator l move the rocker a in one direction or the other until it engages with a stop m, and the contacts e, f or f, g come opposite the contact-plugsj, k. A centrifugal governor w operates a sleeve x connected to the pivoted support n by means of a link 4 and lug 21. The support n carries contact-plugs j, k, which engage with the contacts e, f or f, g when the dynamo c is revolving fast enough to produce the required electromotive force, thereby causing the current in the external circuit to flow always in the same direction. When the dynamo c is arranged to supply both lamps and accumulators, a resistance is placed between the contacts 5, which are bridged when the dynamo is stopped and the accumulators supply the lamps. In a modification shown in Figs. 6 and 8, the rocker a carries two contacts 13, 14, while the pivoted frame n carries three contacts 15, 16, 17 each provided with a carbon break 18. The link 4 of the governor is made triangular with a spring 22 passing around a pin 23 while one end extends over a pivot pin 24 of the link 4 ; or, the ends of the spring may pass over both pins 24, 25. The pin 24 is formed with a notch by which it is locked by passing the spring through it. This arrangement diminishes the friction between the flange 1 and the projections z, after the governor has operated. When a "double battery" system is employed, a change-over switch is provided, the movable contacts 8<a> of which are mounted on arms 8 pivoted at the point 19 on the frame n. The arms 8 carry rollers 10 which engage with abutments 9, Fig. 4. When the rocker a has been operated to bring the abutment 9 opposite one of the arms 8 and the frame n moved towards the rocker, the arm 8 engages with the abutment 9 to operate the switch, thereby changing the connexions of the batteries at each-reversal of the dynamo. The system with three contacts on the rocker is shown in Fig. 10, in which the contacts 8<a> bridge the contacts 11, 38 and 12, 39, and the plugj is connected to the positive terminal of the dynamo. The circuits are then as follows: (1) contact 11, switch 32, field winding 34 of the dynamo, terminal 40 of the split resistance 29, lead 46, terminal t, and lead 26 ; (2) contacts 11, 8<a>, and 38, lead 27, terminals r and 41, upper part of battery 31, lead 42, terminal 40, lead 46, terminal t, and lead 26; (3) contacts 11, 8<a>, and 38, lead 27, terminals r and 41, resistance 29, terminal 43, lead 44, terminal u, lead 28, contacts 39, 8<a>, and 12, lead 29<1>, terminals s, 45, lamps 30, lead 42, and thence to lead 26 ; (4) contacts 11, 8<a>, and 38, lead 27, terminals r and 41, resistance 29, terminal 43, lower part of battery 31, lead 42, and thence to lead 26 and the negative plug k. When the dynamo reverses, similar circuits are made to charge the lower half of the battery. When the dynamo shows down, the switch 6, 6 short-circuits the greater part of the resistance 29 and the dynamo is d sconnected, the lamps being supplied from the battery. The system with two contacts on the rocker is shown in Fig. 11, in which the lead 26 is in connexion with the contact 16 which is always negative. The circuits to the terminal 40 of the split resistance 29 and thence by the leads 46, 26 to the negative terminal 16 are as follows: (1) contacts 15, 36, 35, switch 32, and field winding 34 ; (2) lead 27, terminals r, 41, upper part of battery 31, and lead 42 ; (3) lead 27, terminals r, 41, resistance 29, terminals 43, u, lead 28, contact 7', bar 20, lead 29<1>, terminals s, 45, lamps 30, and lead 42 ; (4) lead 27, terminals r, 41, resistance 29, terminal 43, and lower part of battery 31. When the dynamo is reversed, similar circuits are made to charge the lower part of the battery, and when it slows down the greater part of the resistance 29 is short-circuited and the dynamo is disconnected. The field winding 34 of the dynamo is always energized in the same direction, the switch 32 completing its circuit after a predetermined speed has been attained. A fuse 33 may be inserted in the negative conductor. In the change-over switch for the battery in the system shown in Fig. 11, the support n carries a pivoted bar 20 which engages with contacts 7, 7<1>, while a spring contact 20<a> connects the plate 35 to one of the plates 36 or 37, Fig. 8. The plate q may be mounted horizontally on the support n, instead of vertically as shown in Figs. 1 and 6.