US2029634A

US2029634A - Pneumatic drive system

Info

Publication number: US2029634A
Application number: US637025A
Authority: US
Inventors: Peter Charles
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1932-10-10
Filing date: 1932-10-10
Publication date: 1936-02-04
Anticipated expiration: 1953-02-04

Description

c. PETER PNEUMATIC DRIVE SYSTEM Filed oct, 1d, 1952 Feb.. 4, 1936.

Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE PNEUlVIATIC DRIVE SYSTEM Application October 10, 1932, Serial No. 637,025

3 Claims.

This invention relates to improvements in servo-motors and servo-motor controlled systems and more particularly to fluid pressure operated servo-motors when used in connection with elec- 5 trical control apparatus.

Servo-motors operated by fluid pressure are employed in many ways to secure control or operation of apparatus or mechanisms particularly when such apparatus is located at points remote from the point in which the operator is located.

Such servo-motors are usually provided with pistons acting in both directions to secure forward or reverse operation of the apparatus which such motors serve. Such double acting servo-motors,

however, heretofore required duplicate pressure lines and control valves and greatly complicated the control equipment and the control operations for the apparatus. Such duplication not only increases the expense but also increases the possibilities of failure of equipment, thus preventing the design of rugged and absolutely trustworthy systems.

It is, therefore, among the objects of the present invention to provide a fluid pressure operated servo-motor which will require only a single connection with the fluid pressure source and which is provided with a single valve to control both the supply to and the discharge of fluid from the servo-motor.

Another object of the invention is to provide a single piston fluid pressure operated servomotor to operate a control system requiring reversal of operation of the apparatus to be controlled.

Another object of the invention is to provide a single piston fluid pressure operated servomotor to operate a control system requiring reversal of operation of the apparatus to be controlled in which the conditions for reversal are fulfilled and such reversal takes place prior to the occurrence of the need therefor.

Objects and advantages other than those above described will be apparent from the following description when read in connection with the accompanying drawing, in which:

Fig. l diagrammatically represents one embodiment of a servo-motor illustrating the present invention as applied to control apparatus of individually electrically driven railway cars to be controlled from a remote point on a train composed of such cars;

Fig. 2 is a vertical cross sectional view of the servo-motor taken on the plane II-II of Fig. 3 and illustrating the manner of engagement of the main piston of the servo-motor with one of the control drums of a multiple unit train for operation of the traction motor on the particular car on which the servo-motor is located;

Fig. Bis a vertical longitudinal section of the main piston of the servo-motor taken on the 5 plane III-III of Fig. 2 and illustrating in detail the operating connection between the main piston and one of the control drums of a multiple unit car; and

Fig. 4 is a vertical longitudinal sectional view of 10 the auxiliary piston of the servo-motor taken on the plane IV-IV of Fig. 2 to illustrate the manner in which the control drum, operated by the main piston of the servo-motor, is retained in the presently attained position upon return of the 15 main piston to its starting position in preparation for another operating stroke thereof.

Referring more particularly to the drawing by characters of reference, the reference numeral II designates a supply line which may be either an 20 overhead trolley line or a third rail as desired. Current is drawn from the line I I by current collecting means I2 such as a pantograph or a third rail shoe and is supplied to traction motors I3 through a main switch I4 and a reversing switch 25 or controller IB which reverses the connection of the motor with the current collector from forward to reversing positions or vice versa as will be set forth hereinafter. Reverser I6 is operated by a servo-motor, to be speciiically described herein- 30 after, operated by fluid pressure from a suitable source (not shown) under the control of a magnet valve Il. The coil of valve I1 is connected to be energized from a source of current I8 and opens the connection with the fluid pressure 35 source against the action of a spring upon cooperative action of a selector switch I9 associated with the reverser I6 and a main controller 20, of which only one contact or switch portion is shown, located on the car to be controlled. The 40 main controller 20 is in turn controlled by a master controller 2| and the entire control operation takes place as will be described. Reference numeral 22 designates a socket through which the servo-motors of other cars may be connected 45 with battery I8 and through which the main controller 20 of such other cars may be controlled by a single master controller 2|.

The servo-motor is formed with a main piston 3| and an auxiliary piston 32 which are preferably 50 arranged in side-by-side relation in a common block or casing 33 although shown diagrammatically, for the purposes of clearness, in Fig. l as being arranged in separate blocks. The cylinders within which the pistons are arranged are connected to receive fluid under pressure from the same source (not shown) through valve I1. The pistons are associated with

springs

36 and 31 respectively which are arranged within the cylinders and tend to return the pistons to the neutral position against the pressure of the fluid from the fluid pressure source.

A slot is formed in one side of piston 3| and receives a pin 38 extending thereinto to permit longitudinal movement of the piston but prevent rotating movement thereof. A stud 39 with a transverse pin 4| is attached to piston 3| and exten-ds upward therefrom through a slot in the cylinder containing the piston 3| ,and engages with a forked double plate 42 which is rotatably mounted on the shaft 43 oi the reverser-selector drum I6, I9, one end of the shaft being supported in a bearing 44 formed integral with the servo-motor block. The plate 42 carries a pawl 46 held under the pressure of spring 41 and arranged to engage with a ratchet wheel 48 keyed on shaft 43 and having four teeth. Reverserselector I6, I9 is thus rotated one-quarter revolution, by ratchet 48 and pawl 46, for each stroke of the piston 3|v by engagement of pin 4I with plate 42 and the consequent engagement of pawl 46 with-wheel 48.

The auxiliary piston is provided with a recess into which a latch 5| extends, such latch being pivotally mounted on the block 33. The latch is arranged to engage a latch wheel 52 which is keyed to the shaft 43 and is provided with four notches corresponding in position with the positions of the teeth of the ratchet 48. Thus when piston 3| rotates drum I6, I9 by one-quarter revolution, piston 32 is likewise operated thereby withdrawing latch 5I from engagement with latch wheel 52.

In operation, when the several portions of the system are in the position shown, master controller 2| is in the zero position and main controller 20 is likewise in the zero position. Reverser I6 is then in position to connect the eld and the armature of the motors I3 in series for reverse operation of the car. Selector I9 is in such position that the circuit to valve I1 is interrupted and the spring connected with such valve has, therefore, connected the cylinders containing pistons 3| and 32 with the discharge port from the valve. Movement of master controller 2| into the first forward operation position completes a circuit from the battery I8 with the coil of the valve I1 excepting that the main controller 26 is still in the neutral position. Upon movement of controller 2B into an operating position, the coil of valve I1 is energized and the position of the valve is changed to permit connection of the cylinders containing the pistons 3| and 32 with the source of fluid pressure. Both pistons of the servo-motor then receive fluid under pressure. Main piston 3| moves plate 42 and pawl 36 to the end of its stroke, thus causing movement of the drum I 6, I9 to the next following position. Movement ofthe master and maincontrollers into an operating position interrupts the circuit to the coil of valve I1 and the valve is reversed under the action of the spring to permit the cylinders to discharge under the actions of the spring and to thus cause preparation for a new movement. Continued movementV of main controller 2i through the operating positions is followed by movement of main Vcontroller 20 through its operating positions until the neutral positions of both the master controller and the main controller are again reached. When the master controller and the main controller 2U and 2l respectively are again in the neutral position, motor I3 being still connected for further forward operation of the car, and the circuit to valve I1 being open, movement of master controller 2| into position for reverse operation closes the circuit from battery I8 over main controller 2D to the coil of valve I1 which again admits fluid under pressure to the servo-motor thus causing reversal of the connection of the motor I3 and interruption of the circuit to the coil of valve I1 as described above. After such operation of the servo-motor, the connections of the motor I3 having been changed and the connection between battery I8 and coil of valve I1 having been interrupted, movement of master controller 2| through the reversing positions and the resulting movement of main controller 20 through the reversing positions permits reverse movement of the car.

At each movement of the .drum I 6, I9 which reverses the connection of the motor I3 and interrupts the circuit from Vbattery I8 to the coil of valve I1, the spring connected with the valve I1 reverses the position of the valve which opens the connection with the cylinders containing the pistons 3| and 32 and the

springs

36 and 31 return the pistons to their previous position. Latch 5| then reengages wheel 52 and retains drum I6, I9 in the presently attained position. 'Ihe connections to the motors I3 having been reversed, a circuit to the valve is prepared to repeat operation of the servo-motor as above described, such circuit being completed upon movement of master controller 2| into the first position and before movement of main controller into such rst position. It will thus be seen that the present system provides means whereby the connections oi the motor are prepared for reversal of operation only after such operation has been initiated at the master controller and before current has been applied to the motor I3 by the main controller. Consideration of the particular construction of the servo-motor involved shows that it is impossible for vibration to disturb the positive operation of the servo-motor and that the valve controlling the flow of lluid pressure to the servomotor and the discharge therefrom is interlocked with both the main and the master controllers to avoid operation thereof excepting in the sequence above set forth.

Although but one embodiment of the present invention has been illustrated and described, it

will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit o1' the invention or from the scope of the appended claims. Y

It is claimed and desired to secure by Letters Patent: Y

l. In a fluid pressure operated system, a shaft to be rotated, a fluid pressure operated motor and a single valve controlling the ilow of uid under pressure to said motor, said motor comprising a main piston for stepwise rotation of said shaft in the same direction, a ratchet mounted on said shaft to drive the same, a pawl arranged for operation by the main piston for engagement with the ratchet, an auxiliary piston, said main and said auxiliary pistons moving along parallel axes, a latch wheel mounted on said shaft, and a latch arranged for movement by the auxiliary piston and for engagement with the latch wheel to retain said shaft in position.V

2. In a fluid pressure operated system, a shaft to be rotated, a uid pressure operated motor and a single valve controlling the flow of uid under pressure to said motor, said motor comprising a main piston for driving said shaft step by step vin the same direction, a ratchet mounted on said shaft to drive the same., a pawl arranged for operation by the main piston for engagement with the ratchet, an auxiliary piston, a latch wheel mounted on said shaft, and a latch arranged for movement by the auxiliary piston, and a plurality of springs for severally returning the pistons to inoperative positions.

3. In a uid pressure operated system, a shaft to be rotated, a single fluid pressure operated motor and a single valve controlling the flow of fluid under pressure to said motor, said motor comprising a main piston, and an auxiliary piston, said main and said auxiliary pistons being operable alternately in the same direction along parallel axes, a ratchet Wheel mounted on said shaft to drive the same, a paWl arranged for operation by the main piston for engagement with the ratchet wheel, a latch Wheel mounted on said shaft, and a latch arranged for movement by the auxiliary piston and for engagement with the latch Wheel to retain said shaft in position between driving operations of the main piston.

CHARLES PETER.