US2467026A

US2467026A - Control system for electric locomotives

Info

Publication number: US2467026A
Application number: US584378A
Authority: US
Inventors: Giger Walter
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1944-03-03
Filing date: 1945-03-23
Publication date: 1949-04-12
Anticipated expiration: 1966-04-12

Description

April 12, 1949. w G|GER 2,467,026

CONTROL SYSTEM FOR ELECTRIC LOCOMOTIVES Filed March 23, 1.945

HH H N Patented Apr. 12, 1949 CONTROL SYSTEM FOR ELECTRIC LOCOMOTIVES Walter Giger, Zurich, Switzerland, assignor to Aktiengesellschaft Brown,

Baden, Switzerland Boveri & Cie.,

Application March 23, 1945, Serial No. 584,378 In Switzerland March 3, 1944 7 Claims.

Control systems for electric locomotives are known where by moving a hand controller drum on the operating platform the main controller which regulates in steps is actuated by a doubleacting compressed air motor and the positions of the main controller are clearly determined by the engagement of a pawl. The same pawl can also act as a control element for the valves of the compressed air motor and can also be controlled by an electromagnet or compressed air. In order to avoid impacts the ratchet wheel with which the pawl engages is connected by means of a spring coupling with the shaft of the main controller. This known arrangement can also be used formultiple-way control systems.

Systems operated by compressed air possess certain disadvantages, however, which prevent their universal application. Since the compressed air motor is lubricated with oil or grease its operation depends very much on the ambient temperature and in cold weather the resistance which the motor has to overcome is many times greater than that occurring during warm weather. In cold weather the required air pressure is therefore considerably greater and the motor operates jerkily, so that the pawl and ratchet teeth are subjected to sudden high stresses which easily result in tooth fractures.

With control systems which operate with pressure oil these disadvantages do not occur. The pressure oil systems used up to the present are, however, very complicated and difl'icult to supervise and employ at least three valves; furthermore due to the differential pistons incorporated in the system the switching times vary according to the position, the recall motions are not uniform and the operation of the contacts is sluggish, so that the accuracy of the control system is detrimentally afiected and the wear on the contacts is excessive.

According to the present invention all the aforementioned disadvantages are avoided. This is achieved by the fact that the smaller cylinder of the difierential-servomotor which is operated by pressure oil is maintained continuously under oil pressure, and the main switch shaft which is actuated by the servomotor is provided with a single-acting ratchet disc for the individual switch positions, the pawl associated with the ratchet when engaging this latter at the same time opening the pressure oil outlet below the larger piston of the dilrerential motor, whereby the smaller piston of the differential motor presses the tooth of the ratchet disc corresponding to the switch position in question against the pawl.

A constructional example of the invention is illustrated in diagrammatic form in the accompanying drawing which shows an electro-magnetically operated pressure oil control system for a thermal-electric locomotive.

By rotating the main control shaft l the fuel supply to the thermal prime mover which can be either a turbine or an internal combustion engine is regulated or its speed governor influenced, and if desired the generator and when necessary the traction motors of the locomotive are also controlled simultaneously. For transmitting control orders, there is provided a controller drum 2 rotatable by a manually operable crank 2a. Drum 2 contains a stepped contact plate 2b, each step in the plate 21) corresponding to a separate switching position, these being designated on the drawing by the vertical dash-dot lines I-V. AS- sociated with the rotatable plate 2b are stationary brushes 20, there being a brush for each of the several steps in the plate 212, and also a brush for connecting the positive side of a power supply to plate 2?).

A stationary switch movement indicating controller drum 3 having arcuate contact rows 0,. d, e and f, interconnected as shown, is supported coaxially with the shaft l. A rocker arm 21 is see cured to and rotates with shaft I, arm 2! bearing a plurality of insulated brushes 28 which make contact with the several contact segments on rows 0- as the arm 2'! rotates. The several switch positions of rocker arm 21 relative to drum 3 are indicated by the horizontal dash-dot lines labeled O-V and these correspond to the various switching positions of the manually rotated crank 2a. The several brushes 2c of controller 2 are connected, in order, to successive contact segments of contact row 0 by conductors IV. As the drum 2 is rotated step by step, a circuit is completed from the positive side of the power supply through contact plate 2b through each of the brushes 2c, in order, and from these brushes through conductors IV', and contact rows 0, d, e and f to the coil of an electromagnetically operated valve 4 which controls a hydraulic motor 5. Hydraulic motor 5 is a differential motor with a large cylinder 6 and a small cylinder 1 the pistons of which by means of the toothed rods 8 and 9 act in opposite directions on the common toothed wheel I ll which drives the main control shaft l in the switching up (a) or down b) direction. In order to ensure that the switch positions are exactly adhered to a ratchet wheel ll operating in one direction only is provided-on shaft I, this wheel I I being engaged by a pawl l2. This pawl I2 is brought into engagement with ratchet wheel I l by electromagnetic means or by hydraulic cylinder l4 which is controlled by electromagnetic valve 13 and is provided with a counter-spring l5, whereby under the action of spring- II and only during the last part of its stroke auxiliary contact I6 is opened or closed. Valve l3 which controls cylinder I4 is actuated by electro-magnet l8, Whilst valve 4 for controlling difierential motor is actuatedby two elec tro-magnetic coils, a main coil [9 and an auxilia ry coil 20, and is provided with a counter-spring 2] and a self-holding contact 22for auxiliary coil 26; in the circuit of coil lies auxiliary contact 16. The current supply which is not shown in the drawing is connected to the system at"+ and The direction of flow of the pressure oil is indicated by the arrows shown in the figure, A low pressure relief valve 23 and two

throttle valves

24, 25 are located in the pipes between valve 4 and hydraulic motor 5. The main control and regulating apparatus is coupled to shaft I at 26.

The method of operating the control system, which in the drawing is shown in the zero position, is' as follows. If controller drum 2, which hasfive switch positions I-V, is for instance moved. from position 0 to position I, then the circuit. to the excitation coil [9 of valve 4' is closed over both outer contact brushes of controller 3. The piston of valve 4 is raised against the pressure exerted by spring 2! and thus allows pressure oil to flow tocylinder 6 of motor 5 whilst at the same time closing the oil outlet; valve 25 enables the switching-in speed to be regulated. Due to the excess power. of the large piston 6 control shaft I is rotated in the switching-up direction indicated by the arrow a. When drum 2 is moved into position I and closes the circuit of coil l9 associated'with valve 4, the circuit of coil l8 associated with valve I3 is also closed over brushes (1 and e of controller 3, and therefore the oil supply to valve I3 is shut off and its outlet. opened, so that spring l5 in cylinder l4 presses pawl l2 against ratchet wheel H which rotates in a clockwise direction, whereby auxiliary contact I6 still remains closed due to Spring I1.

Contact H5 is only opened when pawl l2 slips into notch I in ratchet H. In the meantime brush 0 has moved away from the top-most contact segment of contact row 0 of controller 3 and has interrupted the circuit of the main energizing coil H) for valve 4, so that this latter is then only held by auxiliary coil 29 in conjunction with auxiliary contact 22. As soon as pawl l2 slips into a notch in ratchet wheel H, the opening of. auxiliary contact l6, however, also interrupts the circuit of coil 20 and valve 4 is then forced by spring 2! into the discharge position shown in the figure. The piston of the smaller cylinder 'l' is subjectedto a continuous oil pressure and causes tooth I of ratchet wheel H to be pressed sharply against pawl.|2 so that this switch position is adhered to with great accuracy and as long as no further order is given by controller drum 2. As a result of the interruption of the contact row d of controller 3 the current in coil i8 is interrupted for a short time when between two switch positions and valve l3 is movedinto-the position shown so that cylinder I4 is. supplied with pressure oil, pawl I2 is disengaged from-ratchet wheel H and auxiliary contact lfirclosed.

When moving up to higher switching positions the operation is performedin an analogous manner andindependently of the fact whether the downwards.

. cannot rotate in the direction indicated by arrow 17. When drum 2 is moved back into position IV conductor V and coil 18 are no longer under voltage. Cylinder l4 thus receives pressure oil and disengages pawl I2 from the tooth on ratchet wheel H, so that the piston of the smaller cylinder 1 ca turn shaft l backwards. Wheel H) by means of toothed rod 8 thus also causes the pistons of the larger-cylinder E to be pressed Since the main coil IQ of valve 4 is not excited-th oil outlet from cylinder 6 over the switching-out speed regulating valve 2d and minimum pressure valve 23 is open. Valve 23 is adjusted to a pressure slightly above atmospheric so that cylinder 6 and the pipes between it and valve 3 are not completely emptied, even when the control system is out of operation.

After the switching-down operation has been initiated the brush associated with contact row at of controller 3 moves away from the last segment on contact row d which is without voltage and touches the next above contact segment of row (1. This latter is, however, still connected with conductor IV which is under voltage, so that coil is is excited again and pawl I2 pressed against ratchet wheel i'l. As soon as position IV is reached, shaft l is blocked by pawl l2 which engages with notch IV on ratchet wheel H, and since piston I exerts a constant torque on wheel ll position IV is maintained until the next switching order is given.

If the control current fails, piston i4 remains constantly under pressure, so that pawl l2 remains disengaged and shaft 1 is returned to zero position by piston l.

The most important advantage of the system described. is that due to the constant pressure which prevails in cylinder i any desired switch position of shaft 5 can be adjusted for and adhered to with great accuracy. This is of particular importance as regards the control of speed governors for thermal prime movers. With this arrangement the ambient temperature and therefore the viscosity of the pressure fluid has no effect on the accuracy of the control system. Even poor joints in the pressure oil system or slight leakages past the pistons and glands do not. affect the operation. The control cannot overrun the position for which it is adjusted or stop before it has reached the desired position. With a maximum simplicity of apparatus optimum safety of operation of the vehicle is thus obtained. The described system is quite suitable as a multiple-way control for the fine adjustment of the individual drives of several traction vehicles which are coupled together.

I claim:

1. In a hydraulic pressure operated switching control system, a manually operable controller having a plurality of operating positions, a rotatable shaft, a control device adapted to be rotated by said shaft, said control device having a plurality of operating positions each corresponding to' an operating position on said controller, a ratchet wheel mounted onsaid shaft, said wheel having a plurality of notches therein each cor-' responding to an operating position of said control device, a pawl cooperative with said notches, a hydraulic differential servo motor, said motor including pistons of different areas arranged to apply torque in opposite directions to said shaft, a source of hydraulic pressure, a conduit between said pressure source and the smaller of said pistons to maintain the latter under constant pressure, a second conduit between said pressure source and the larger piston, a valve in said second conduit, control means for said valve responsive to operation of said controller, control means for said pawl responsive to controller operation, said valve and pawl control means hav ing an inter-relation such that when the pawl is engaged in a notch of the ratchet wheel, pressure is removed from the larger servo motor piston whereby the torque exerted by the smaller piston on said shaft causes the edge of said notch to be pressed against said pawl.

2. A control system as defined in claim 1 characterized by the feature that said pawl control means comprises an electrically controlled auxiliary hydraulic servo motor the piston of which actuates said pawl,

3. A control system as defined in claim 1 wherein said valve control means comprises an electro responsive device connected through a circuit which includes contacts actuated by operation of said pawl.

4. A control system as defined in claim 1 wherein said valve control means comprises an electro responsive device having a main coil and an auxiliary holding coil, the circuit to said holding coil including contacts actuated by operation of said pawl.

5. A control system as defined in claim 1 and further including a regulating valve in said second conduit for determining the switching-in speed of said control device between operating positions.

6. A control system as defined in claim 1 and further including a by-pass conduit from said second conduit through said valve to the low pressure side of said source, said by-pass conduit including a regulating valve which determines the switching-out speed of said control device.

7. A control system as defined in claim 1 characterized by the feature that said valve control and pawl control means comprise electrically operated devices energized over circuit means controlled by said controller, and further including an auxiliary controller actuated by said shaft, said auxiliary controller including contacts connected in said circuit means.

WALTER GIGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,476,703 Forman Dec. 11, 1923 1,683,175 Falcke Sept. 4, 1928 1,766,510 Gregory June 24, 1930 1,847,688 Couwenhoven 1 Mar. 1, 1932 1,851,902 Haeghen Mar. 29, 1932 2,029,634 Peter Feb. 4, 1936 FOREIGN PATENTS Number Country Date 445,400 Germany June 13, 1927