US2434538A - Control device - Google Patents

Description

Patented Jan. 13, 1948 UN l TE D S TAT ES PATEN T OFF [C E CONTROL DEVICE Cyril E. Baston, Irwin, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa.-., a corporation of Pennsylvania I -'A-ppl i'cation May 16, 1944, Serial No. 535,837

2 Glaims.

My invention relates, generally, to -'contro1 devices and, more particularly, to fluid-pressure operated switches of the type utilized in railway control systems.

The use of groups of cam switche for the completion of electrical circuits in railway control systems has been somewhat restricted because of the diihculty of providing a means for driving the cam shaft which would not tend to stall and avoiding having two or more switches closedat the same time. In spite of thi problem, cam switch groups have been utilized since their use eliminates a large amount of electrical interlocking which is a potential cause of control failures.

An object of my invention, generally stated, is to provide "a control switch which shall be simple and efiicient in operation and which may be economically manufacturedand installed.

A more specific object of "my invention is to provide for accurately controlling the operation of a fluid-pressure operated switch.

Another object of my-inventionis to make the switch follow closely the movement of a controlling cam.

Other objects of my invention will be explained fully hereinafter orwi ll be apparent to those skilled in the art.

In accordance with one embodiment of my invention, the force for closing a switch is supplied by fluid pressure acting upon a piston in a cylinder, but the valve for admitting the fluid to the cylinder is controlled by a cam. The switch movement must follow that of the cam exactly or mechanical interference will stop any further motion of the cam, thereby preventing improper operation of other switches controlled by the same cam shaft.

For a fuller understanding of the nature and objects of my invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which the single figure is a View, partially in section and partially elevation, of a portion of a switch unit embodying my invention.

Referring to the drawing, the structure shown therein comprises a switch cylinder Ill, having a piston I I disposed therein for actuating a movable contact member I? into engagement with a fixed contact member 13 when a suitable pressure fluid, such as compressed air, is admitted into the cylinder ID. The piston H is attached to the lower end of a hollow piston rod l4, the upper end of which is attached to the moving contact member l2 by means of a bracket l5, an

insulator "f6 and a bracket I! for pivotally supporting the contact member 12. A piston spring I8 is disposed inside the cylinder Ill and i compressed when the piston is forced upwardly by the fluid pressure. The stored energy in the spring l8 forces the piston downwardly when the pressure fluid "is permitted to escape to atmosphere.

In'ord'er to control-the supply of 'presesur'e fluid to the cylinder H], a valve 21 may be disposed inside of the hollow piston rod [4. The valve 2| is providedwith ar'od'22, the upper end'of which is connected to one end of a lever 23 which is fulcrumed at '24. The other endof the lever 23 carries a roller25 which is disposed in a groove '26 in a plate cam 21. The cam 21 may be rotated by a shaft 28 which maybe driven by any suitable means, such as an electric motor.

In order to facilitate the manufacture and assembly of the hollow piston rod I4 and the valve 2|, the rod I4 may be con'structed of a plurality of sections which may be threaded together in the manner shown. When the piston rod and the valve are assembled, the piston l-l may be secured to the lower end of the rod by a nut 29 and the piston rod inserted int'o'the cylinder I 0 through the bottom of the cylinder, after which a'c'ap3l may be threaded ontothe lower end of the cylinder It. The rod 14 slides in suitable packing washers 32 and 33 which are retained in position in the lower and the upper ends of a sleeve 30 in the cylinder ill by threaded caps 34 and 35, respectively.

The operation of the switch is as follows: When the switch members are in the position shown, the space within the cylinder I0 is in free communication with the atmosphere through the hollow piston rod l4, past the valve 2| and the piston rod 22 and out through the bracket l5. Assume now that the cam '21 is rotated in the direction of the arrow until the roller 25 is at the point 31 in the groove 26. The first downward movement of the roller 25 moves the valve rod 22 upwardly, thereby closing th valve 2| against a seat 36 and removing it from a seat 38. This permits the pressure fluid to enter the cylinder l0 through a suitable connection 39, up past the valve seat 38, and down through the hollow piston rod M to the lower side of the piston ll.

As the piston H moves upwardly, the valv 2| is held against the upper seat 36 by the continued rotation of the cam 21. In order to insure that the valve 2| is held tightly against its seat at all times, the lever 23 may be constructed of spring steel and the cam 21 so de- 3 signed that the lever 23 is flexed slightly at all times to maintain pressure on the valve 2|.

The continued rotation of the cam 21' to a point 4| or rotation in the opposite direction moves the valve 2| against the valve seat 38 and away from the seat 36, thereby shutting oiI the supply of pressure fluid and venting the cylinder It) to atmosphere to permit the spring I 8 to open the contact members of the switch, as explained hereinbefore. It will be understood that the groove 26 may be so disposed in the cam 21 that the desired operation of the switch will be obtained as the cam 21 is rotated by the shaft 23.

It will also be understood that additional cams may be driven by the shaft 28 to control additional switch units of the type herein described. In this manner, a plurality of switch units may be operated in any desired sequence.

The force required to move the value 2! is relatively small, thereby requiring a relatively small motor or other device for driving the cam shaft 28. However, the force operating to close the switch may be made as large as required by proper proportioning of the cylinder and the piston H.- If for any reason the switch movement does not follow the movement of the cam after the valve 2! has been operated, further movement of the cam shaft is prevented by the roller 25 engaging the side of the groove 26, thereby stalling the shaft 28, and the improper operation of any additional switches, controlled by the cam shaft 28 is prevented. The shaft 28 may be released from its driving means by a slip clutch, or other. suitable device, which may be so constructed that it will not transmit sufiicient torque to overcome the force of the spring 18.

In this manner the advantages of a group of cam-operated switches are obtained without any of the attendant disadvantages of previously known structures. Furthermore, it is not necessary to provide a large number of electrical interlocks in order to insure the proper operation of a group of switches.

Since numerous changes may be made in the above-described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a fluid-pressure operated switch having a movable contact member, in combination, 9. cylinder, a piston disposed in the cylinder for actuating said movable contact member, valve means disposed within the cylinder and movable with said piston for controlling the supply of fluid to the cylinder, cam means disposed externally of the cylinder for controlling the operation of said valve means, and a resilient lever arm having one end engaging said cam means and the other end engaging said valve means.

2. In a fluid-pressure operated switch having a movable contact member, in combination, a cylinder, a piston disposed in the cylinder for actuating said movable contact member, valve means disposed within the cylinder and movable with the piston for controlling the supply of fluid to the cylinder, a rotatable cam disposed externally of the cylinder for controlling the operation of said valve means, a shaft for rotating said cam, and a resilient lever arm having one end engaged by said valve means for stopping the. rotation of said shaft, said lever arm being actuated by said cam to operate said valve means.

CYRIL E. BASTON.

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

UNITED STATES PATENTS Number Name Date {26,538 Lang Apr. 29, 1890 1,965,867 Vickers July 10, 1934 2,317,549 Muller Apr. 27, 1943 2,353,610 Chisholm July 11, 1944 1,959,786 Hodgkinson May 22, 1934 2,055,530 Hallenbeck Sept. 29, 1936 FOREIGN PATENTS Number Country Date 459,893 Great Britain Jan. 18, 1937

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