US2471320A - Railway braking apparatus - Google Patents

Description

May 24, 1949. R. M. GlLsoN RAILWAY BRAKING APPARATUS Filed Feb. 28, 1948 Patented May 24, 1949 RAILWAY BRAKING APPARATUS Robert M. Gilson, Pittsburgh, Pa., assignor to The Union Switch & Signal Company, Swissvalc, Pa., a corporation of Pennsylvania Application February 28, 1948, Serial No. 11,975

13 Claims.

My invention relates to railway braking apparatus, and particularly to braking apparatus of the type comprising wheel engaging braking bars located beside a track rail and movable toward the rail into braking positions by means of a fluid pressure operated motor and moved away from the rail into non-braking positions by suitable biasing means such as gravity.

In the form of braking apparatus described and claimed in Letters Patent of the United States No. 2,372,550, granted to Harold C. Clausen and Linnie K. Hedding, on March 27, 1945, for Railway braking apparatus, an electromagnetic inlet valve controls the supply of air to a fluid pressure motor which operates the brake, and another electromagnetic valve controls the exhaust of fluid from the motor. Three Bourdon tubes are provided which respond to the pressure of the fluid in the motor. Each Bourdon tube moves a movable contact between a low pressure stationary contact which it engages when the motor pressure is below a first predetermined value, and a high pressure stationary contact which it engages when the motor pressure is above another value substantially greater than said first predetermined value. The three Bourdon tubes are set to operate their movable contacts at different ranges of motor pressure. A remote manual electrical controller is connected to the Bourdon tubes and the valves through line wires. This controller has iive positions. In one extreme position, the electromagnetic exhaust valve is energized, and in the .other extreme position the electromagnetic inlet valve is energized. In each of the three intermediate positions, one of the three Bourdon tubes is placed in control of the two valves. A condenser is connected in parallel with the winding of the inlet valve to delay its closure when the valve controlling circuit is opened. This delay is provided to insure that when the inlet valve controlling circuit is opened by one of the Bourdon tubes, the motor pressure will be increased somewhat above the contact opening pressure, thereby preventing chattering of the Bourdon tube contact. Since a substantial amount of energy must be stored in this condenser, a condenser of large capacity is required. Ihe only commercially practicablel type of con- :lenser having the required large capacity is an electrolytic condenser, which has asymmetric :apacity characteristics. It is therefore essen- ;ial to the use of this type of condenser that it always be energized with current of the same `nolarity. The control circuits of the Clausen et al.

aatent are arranged so that the electrolyti condenser is always energized by current of the same polarity.

It is an object of my invention to provide an electrical control system of the type described, in which the number of line wires between the electrical controller and the valve winding is reduced below the minimum available on previous circuits.

Another object of my invention is to provide an improved remote electrical control system for an electrical device having asymmetric properties, including two selectively closable electrical circuits for energizing the device with current of the same polarity, both of which circuits include a line wire in which current flows in opposite directions in the two circuits.

I accomplish these objects of my invention by providing four line wires between the live-position controller and the electromagnetic valve, utilizing each line wire in at least two positions of the controller, and providing asymmetric units in the valve control circuits to block currents of one polarity and admit currents of the opposite polarity.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall describe one form of apparatus embodying my invention, and shall then point out the novell features thereof in claims.

The accompanying drawing is a somewhat diagrammatic illustration of one form of apparatus embodying my invention.

Referring to the drawing, the reference character I designates one track rail of a stretch of railway track, which track rail, as here shown, is secured to a rail support 2 mounted on an adjacent pairof the usual crossties 3, only one crosstie being visible in the drawing. Associated with the rail I is a car retarder comprising two braking bars AI and A2 locatedY on opposite sides of rail I. Each of these braking bars comprises, as usual, a brake beam 4 and a brake shoe 5.

The braking bars AI and A2 are arranged to be moved toward and away from the rail I through the medium of a lever 6 which is pivotally mounted at one end on a pivot pin 8 carried by the rail support 2, and a lever 8 which is pivotally mounted intermediate its ends on the pivot pin l. The lever 6 is inclined upwardly and extends away from the rail I and is provided in its upper surface with a groove 5a which receives the braking b-ar AI.. The one end 8a of the lever 8 is E Alikewise inclined upwardly and extends away from the rail I at the opposite side of the rail parts are so arranged and so proportioned that if i the outer or free ends of the levers 8 and 8 are moved apart, the braking bars will be moved toward the rails into their effective or braking positions. When the braking bars occupy their braking positions, the brake shoes will engage the opposite side faces of a car wheel traversing rail l, and will retard the speed of the car. The center of gravity of the lever and braking bar AI is considerably to the left of the pivot pin fl so that this lever will normally tend to rotate in a counterclockwise direction about the pivot pin.l

Similarly, the center of gravity of the lever 8 and braking bar A2 is to the right of the pivot pin 1 so that this lever will normally tend to rotate in a clockwise direction about the pivot pin. It will be apparent, therefore, than when no force is applied to the free ends of the levers 6 and 8 to move them apart, the free ends of these levers will move toward each other, thereby moving the braking bars to their ineiective or non-braking position in. which they are illustrated in the drawing.

The levers 6 and 8 are arranged to be moved apart by means of a fluid pressure motor M comprising -a cylinder 9 containing a reciprocable piston I8 which is attached to the inner end of a piston rod II. :The cylinder 9 is pivotally connected with the free end of the lever E by means of trunn-ionsIZ formed on the side of the cylinder and extending through bifurcations I3 formed on the lever E, while the piston rod II is connected at its free end withthe free end 8b of the lever 8 by means of an adjustable eyebolt I and pivot pin l5. Fluid pressure may be admitted to the cylinder -8 between the upper end of the cylinder and the piston Il) through an opening I8 which is threaded -to receive a pipe I'I. When fluid pressure is admitted to the cylinder 9 through the piper Il and opening I6, the piston Ill will be forced downwardly and the cylinder 9 upwardly, thereby-separating'the levers and 8, and hence moving the braking bars toward their elective or braking positions. It will be obvious-that when the braking bars are moved to their braking position, they will exert a braking force which is proportional to the pressure of the fluid supplied to the cylinder 9.

The supply of fluid pressure to the cylinder 9 of motor lVi is controlled b-y means of two fluid pressure operated poppet valves I8 and I9, which poppet valves,'in turn, are controlled by means of two electromagnetic valves VI and V2. These electromagnetic valves are similar and each comprises a valve stem 2l) biased to an upper position by means of a spring 2l, and provided with a winding 22 and an armature 23. When valve VI is energized, as shown in the drawing, valve stem 28 of this valve moves downwardly against the bias exerted by the associated spring 2l, and under theseconditions a pipe 2li is connected with a pipe 25 which is constantly supplied with iiuid pressure, usually compressed air, from a suitable source not shown in the drawing. When valve VI is deenergized, however, pipe 28 is disconnectedrfrom pipe 25 and is connected with atmospherethrough a port 26.

When valve V2 is energized, valve stem 28 of this valve moves downwardly, and connects the pipe 25 with a pipe 2l, but when valve V2 is deenergized, as shown in the drawing, pipe 21 is disconnected from the pipe 25 and is connected with atmosphere through a port 28.

The two fluid pressure operated poppet valves I8 and I8 are both located in the same Valve body 29, and associated-with each poppet valve is a spring lea or |90. which constantly biases the valvepto a closed position. Formed in the valve body 29 above the valve I9, and in axial alignment therewith., is a cylinder 38 containing a reciprocable-,piston y3i whichis operatively connectedL ywith the valve i9. The upper end of cylinderfiis connected with the previously referred to pipe 2l, and it will be apparent, therefore, thatwhen valve V2V is deenergized so that pipe 2'I is connected with atmosphere, spring I9a will hold valve I9 closed and piston 3| in its upper position, but that, when valve V2 is energized so that pipe 21 is connected with pipe 25, the fluid pressure which is then supplied to pipe 21 will force piston 3| to its lower position, thus opening valvev i9. When valve I9 is opened, cylinder 9 of motor M is connected4 to pipe 25 through pipe I1, a pipe-32, a chamber 33 formed in valve body 29, valve I9, and a chamber 34 formed in Vvalve body 32; but when this valve I9 is closed,.cylinder 9 is disconnected from pipe 25.

The valve body -29 is -also formed with a second cylinder35 containing a reciprocable piston 36 which is .operatively connected with the valve I8, andthe upper side of whichl is subjected to the pressurein the pipe 24. When valve VI is energized, the fluid pressure which is then supplied to pipe 24 forces piston 3S to its lower position thereby opening valve I8, and under these conditions, cylinder 9.0i' motor M becomes connected withatmosphere through pipes Il and 32, chamber 33, valve I8,- a chamber 3l formed in valve body 29, and a pipe 38. When valve VI is deenergized, howeverspring Ia moves valve I8 to its-,closed position, Aand piston 38 to its upper position.thus disconnecting vcylinder 9 from atmosphere.

It follows from the foregoing thatwhen valve V2 is energized, fluidpressure will be supplied to 4I, connected -to the pipe I'I, and hence subjected to the pressure 'of the iiuid in the region of cylinder Sfbetween piston I0 and the upper end of the cylinder. Each Bourdon tube positions a movable contact,'numbered respectively 39a, 48a., and 4Ia, iwhich respectively move between low pressure'stationary: contacts 39h, 48h, and lllb, and high pressure stationary contacts 39e, 40e, and 4Ic. The pressureresponsive devices P20- 30, PAE-A and P10- 80 are so constructed and so adjusted that they will operate successively as the pressure inthe region of cylinder 9 between the piston yIII and the upper end of the cylinder increases. For example, for all pressures below 20 pounds per square inch, the movable contact of each of these' devices is closed against its associated low pressure'contact. If the pressure exceeds 20 pounds per square inch, however, contact 39a--39b of device P2 [1 -30 opens, and if the pressureexceeds-SU pounds per square inch, contact 39e- 39e of device P20-30 closes. In a similar manner, the pressure responsive devices 1345-55 and P'l-B are adjusted to open their contacts 40u- Mib and dla- Mb at 45 and 70 pounds per square inch, respectively, and to close their contacts Mia-Mic and lla-Mc at 55 and 80 pounds per square inch, respectively. Of course, these specific pressures are not essential but are only mentioned for purposes of explanation.

The Valves V are also controlled by means of a manually operable lever L which, as here shown, is capable of assuming ve positions, indicated by dotted lines in the drawing, and designated by the reference characters pl to p5, inclusive. The lever L controls a plurality of contacts each designated by the reference character l2 with a distinguishing suiiX corresponding to the position of the lever in which the corresponding contact is closed. For example, contact i2- l is closed in the pl position of the lever, contact 42-2 in the p2 position of the lever, etc. Contacts l2-4a and i2-4b are both closed in the p4 position of the lever.

Lever L is usually located at a point remote from the braking apparatus, as in the control cabin of a classication yard car retarder system, and is connected with the braking apparatus by means of line wires extending from the control cabin to the braking apparatus. As shown in the drawing, lever L occupies its pl or off position, which is the position which it normally occupies when no cars are to be retarded, and all of the contacts of levers L with the exception of contact 42-I are therefore open.

Valve V2 is then deenergized, but valve V! is energized over a circuit which may be traced from the positive terminal of battery C, through common line wire 45, the winding 22 of valve VI, wire 44, an asymmetric unit Rl in its low resistance direction, line wire 43, and contact 42-I of lever L to the negative terminal of battery C. Since Valve V2 is deenergized, pipe 2 is cut off from the supply of iiuid pressure, and since valve VI is energized, cylinder 9 is connected with atmosphere. The braking bars are therefore held in their inefiective or non-braking positions by gravity. The low pressure contact of each of the pressure responsive devices is closed and the high pressure contacts are open.

A condenser D is connected in parallel with the winding 22 of valve V2 between a positive junction 46 and a negative junction All. The function of this condenser is to maintain the energization of the winding 22 of valve V2 for a time after its energizing circuit is opened. Since the condenser must store a substantial amount of energy if the winding energization is to be continued for an appreciable period, a condenser of large capacity is required. In one particular installation, a condenser of sixteen microfarads capacity was used in parallel with a Winding of one hundred and thirty ohms resistance. The necessity for a high capacity condenser makes it desirable to use an electrolytic condenser. Since such a condenser has asymmetric capacitance properties, it is desirable that it be energized by a potential of the same polarity at all times.

Now let it be assumed that the operator wishes to make a comparatively light brake application. To do this he moves the lever L from its pl position to its p2 position, thereby opening contact 42-l and closing contact i2- 2. The

5'* to the motor cylinder.

6 I, opening of contact 42-I interrupts the circuit which was previously closed for valve VI. closing of contact 42-2 places the valves Vl and V2 under control of the pressure responsive device P2 0-30.

Deenergization of valve VI disconnects pipe 24 from supply pipe 25 and connects pipe 24 with the atmosphere. The pressure inthe upper end of cylinder 35 therefore decreases rapidly, and as soon as this pressure has decreased to a predetermined value, for example, pounds per square inch, spring ita closes valve I8, thus disconnecting cylinder 9 from the atmosphere.

Since the pressure in cylinder 9 is at this time less than pounds per square inch, the closing of contact @i2-2 completed a circuit for valve V2.

This circuit may be traced from the positive terminal of battery B through contact 42--2, line wire '33, contacts 3Q@ and 39h of pressure responsive device P2il-39, wire 48, positive junction 46, winding 22 of valve V2 and condenser D in parallel, negative junction 4l, an asymmetric unit R2 in its low resistance direction, and common line wire 5.5 tothe common terminal of batteries B and Ck Valve V2 therefore becomes energized and connects pipe 2l with supply pipe 25 so that fluid at full line pressure is now supplied to the upper end of cylinder 3D, thus causing piston 3l to move downwardly and open valve I9. Pipe 25 thereby becomes connected with pipe l1 and cylinder E, so that air at full line pressure is supplied to cylinder t to move the braking bars to their effective or braking position. As soon as the pressure in the upper end of cylinder 9 reaches 20 pounds per square inch, contact 39a of pressure responsive device 12253- moves away from contact 39h, thereby opening the circuit just traced for valve V2. Because of the action of condenser D, winding 22 of valve V2 will remain energized for a short time after contact 39a separates from contact 39h, thereby causing the pressure in cylinder 9 to continue increasing suiciently to move contact 39a, a substantial distance away from contact 39h. As

' soon as energization of winding 22 of valve V2 is terminated, valve V2 returns to the position shown in the drawing, thereby venting cylinder Bti to atmosphere and allowing valve I9 to close under the inuence of spring I9a. The supply of fluid under pressure to cylinder 9 is thereby cut off. If the pressure in the motor cylinder 9 now decreases below 20 pound-s per square inch, then contacts 39a and 39h again close and valve V2 is again energized to supply air under pressure If the pressure in motor cylinder il should now increase above 30 pounds per square inch, then contact 39a would engage Contact 39o, thereby completing an energizing circuit for winding 22 of Valve VI. This circuit may be traced from the positive terminal of battery E through Contact @i2-2, line wire 43, contacts 3M and Stic of pressure responsive device PZt-B, wire lili, winding 22 of valve VI, common line wire d5 and the common terminal of batteries B and C. When valve Vl is energized,

valve I8 is opened, thereby venting the motor cylinder 9 to atmosphere until such time as the pressure in the motor cylinder again decreases below 30 pounds per square inch, whereupon contacts 39a and Sto again open. When this happens, valve Vl is again deenergized, thereby closing valve I8 and preventing further escape of the fluid from motor cylinder 9. It may therefore be seen that when lever L occupies its p2 position, the braking bars will be held in their braking posi- The4 7 tions byapressureof-.between 20 and 30 pounds per square inch.

Triez-circuits so4 farcie-scribed for the pl and p2 positions of .the-controller'Lare similar to those described in the Clausen et al. Patent No. 2,372,550,v previously-referred to. The circuits to bedescribedbelow..contain the novel features of my invention.

If theoperator.. moves vlever L to its p3 position, the valves VLandVZ are placed undercontrol vof thepressureresponsive device P45-55, which maintainsthe motor pressure between 45 and 55 pounds per .square inch. Under these conditions, the.. energizing circuit for valve V2 may be traced fromthe positive terminal of battery Bf through contact i2- 3, a line wire 49, an asymmetricunit R3 in its low resistance direction,.contacts 40a and 40hof pre-ssure responsive device P45-.55,V wire- 48, positive junction 46, winding 22 ofv valve V2 .and condenser D in parallel, negative .junction 41, asymmetric unit R2 in itslow resistance direction, and common wire 45 to the common terminal of batteries B and C. The corresponding. energizing circuit for valve Vl may be traced `alongthe circuit just described to contact. caandthence through contact 40e, wire 44,-.winding22` ofY valveVl, and common line Wire 45 to thecommon terminal of batteries B and C.

If the operator.-y moves lever L to position p4, the valves Vland V21 are placed under control of the Bourdon tube 4i, which maintains the motor cylinder pressure between 70 and 80 pounds per square inch. Under these conditions, the energizing .circuitfor Valve V2 may be traced from the commonterminal ofbatteries B and C through contact 42e-4b,.aline wire 5i), positive junction (116,.winding 22 of'valve V2 and condenser D in parallelnegative junction 4l, a Wire 5I, contacts4Ib..and.4la. operated by Bourdon tubev 4I, an asymmetriounit R4 in its low resistance direction, .line `wire. 49, contact l2-4a to the negative ,terminal oi battery C. The corresponding energizingicircuit for valve Vl may be traced from the common terminal of batteries B and -C along commonline wire 45, winding 22 of valve Vl, wire 44, vcontacts Mc and Ma, operated by. Bourdon tube 4I, asymmetric unit R4 in its low. resistance direction, line wire 59, and contact 42-4a to the negative terminal of battery C.

If ,the operator movescontroller L to position p5, then valve' V2 is energized independently of any oi theourdontubes. This energizing circuit for valve V2 may be traced -from the positive terminal of battery .B through contact 42-5, line wire 55, positive junction 46, winding 22 of valve V2 in parallel with` condenser D, negative junction 4l',asymmetric unit R2 in its low resistance direction, and common line wire 45 to the common terminal ofbatteries B and C.

It should be noted that in the positions p3, p4, and p5 of lever IL, all of the line wires are used for 'at least two positions. Line wire 49 is used in both positions p3 .and p4, and line wire 50 is used in both positionspland p5. It should also be noted that each energizing circuit for winding 22 of valve V2 supplies the condenser D with potential of the proper polarity. The asymmetric units R2, R3, and R4 block currents of improper polarity andadmit currents of proper polarity so that each of the line Wires 45, 49, and 5G may be used in two circuit controlling positions of lever L. The current -flows in line wire 49 in opposite directions in:positionsp3 and p4, but the asymmetric units`- are arranged sc that the.current flows through winding `22 of valve V2 in the same direction in both of those positions.

Although I have herein shown and described.

only one form of railway braking apparatus embodying my invention, it is understood that various changes and. modiications may be made therein within the scope of the appended claims without departing from the spiritand scope of my invention.

Having thus described my invention, what I claim is:

l. Control apparatus, comprising an electrical winding, an electrolytic condenser connected in parallel with said winding to delay deenergization thereof, two electrical circuits for energizing said winding and said condenserl from a remote point with direct electricv potentials of the same polarity, including a line wire extending between said winding and said point, direct electrical energy supply means, means at said point for connecting said line wire to said supply means so that at times a current of one polarity flows in the line wire and at other times a current of opposite polarity flows in the line wire, and means connecting said line wire to said winding including oppcsitely poled asymmetric units so that the current in the Winding is of the same polarity regardless of the polarity of the current in said one line wire.

2. Control apparatus, comprising an electrical device having asymmetric properties, two selectively closable electrical circuits for energizing the device from a remote point with direct electric potentials of the same polarity, including aline wire extending between the device and said point, direct electrical energy supply means, circuit controlling means at said point for connecting the line wire to the supply means so that when one of said circuits is completed a current' flows through the line wire in one direction and when the other circuit is completed a currentilows through the line wire in the opposite direction, and means connecting the line wire to the device including oppositely poled asymmetric'units so that the electric potential supplied to the device is of the same polarity when either circuit is completed.

3. Control apparatus comprising an electrical device having asymmetric properties, and means including two selectively closable electrical circuits for supplying to the device direct electric-potentials of the same polarity, including aline wire forming a part of both circuits and through which current flows in opposite directions in the-two circuits.

4. Control apparatus as in claim 3, including two oppositely poledv asymmetric units connecting said line wire to opposite terminals of said device.

5. Control apparatus comprising an electrical winding, means associated with said winding for delaying deenergization thereof when and only when said winding has previously been energized by direct current of a particular polarity, rst

` and second selectively closable electrical circuits for energizing the winding from a remote point with electrical current of said polarity, including a line wire forming. a part of both circuits and eX- tending between the Winding and said point, direct current supply means, circuit controlling means at said point for connecting the line wire to the supply means so that when one of said circuits is completed a current flows through the line wire in one direction and when the other circuit is completed a current flows through y.the

line wire in the opposite direction, and means connecting the line wire to the winding including oppositely poled asymmetric units so that the current flowing through the wire passes through the winding with said particular polarity regardless of its direction of ilow through the wire.

6. Control apparatus as in claim 5, including a fluid pressure motor, an electromagnetic valve having a winding and effective when the winding is energized to admit fluid to the motor, rst and second pressure responsive devices subject to the pressure in the motor, and rst and second contacts respectively opened by said rst and second pressure responsive devices at different pressures, in which said winding is connected in both said circuits, and said iirst and second contacts are connected in said iirst and second circuits, respectively, and in which said delaying means is effective to insure that the motor pressure continues to increase for a time after said contacts open.

7. Control apparatus as in claim 5, in which said first circuit includes a connection between the line wire and one terminal of the winding, a second line wire, and a first one oi said asymmetric units poled to pass current of said particular polarity; and in which said second circuit includes a connection between said first-mentioned line Wire and the opposite terminal of the Winding, a third line Wire, and another of said asymmetric units poled to pass current of said particular polarity.

8. Railway braking apparatus comprising a braking bar located in the trackway beside a track rail, and control apparatus for said bar as in claim 6, in which said fluid pressure motor is connected to said bar for moving it toward the track rail into a braking position in which it will engage a part of a car to retard the speed of the car.

9. Control apparatus, comprising an electrical device having asymmetric properties, a source of direct electrical energy, a line wire permanently connected at one end to a rst terminal on said source, means connecting the other end of the line wire to one terminal of said device including an asymmetric unit poled to pass current only in the direction corresponding to the asymmetric properties of said device, a first electrical circuit for at times energizing the device including the line wire, the asymmetric unit, and a connection between the opposite terminal of the device and a second terminal of said source having the proper polarity with respect to said first terminal to cause current to flow through said asymmetric unit, a second electrical circuit for at other times energizing the device including a connection between said opposite terminal of the device and said first terminal of the source and a connection between said one terminal of the device and a third terminal of the source having a polarity with respect to the first terminal opposite to that of the second terminal of the source, said asymmetric unit being effective at such other times to block the flow of current through said line wire from said :rst source terminal.

10. Railway braking apparatus comprising a braking bar located in the trackway beside a track rail, a fluid pressure motor for operating the bar toward the rail into a braking position in which it will engage a part of a car to retard the speed of the car, a valve for controlling the admission of fluid to the motor, an electrical Winding for operating the valve, first and second pressure responsive devices subject to the pressure in the motor, first and second contacts respectively opened by said iirst and second pressure responsive devices at different pressures, and control apparatus for said winding according to claim 9, in which said iirst and second contacts are connected in said rst and second circuits, and said electrical device is connected in parallel with the winding to delay deenergization thereof when said winding has previously been energized by direct current oi a particular polarity to insure that the motor pressure continues to increase for a time after the contacts open.

ll. Railway braking apparatus as in claim 10, in which said electrical device is an electrolytic condenser.

12. Railway braking apparatus comprising a braking bar located in the trackway beside a track rail, a uid pressure motor for operating the bar toward the rail into a braking position in which it will engage a part of a car to retard the speed of the car, a rst electromagnetic valve effective when energized to cause admission of fluid to the motor, a second electromagnetic valve eiective when energized to cause exhausting of fluid from the motor, rst and second pressure responsive devices subject to the pressure in the motor, rst and second contacts respectively opened by said iirst and second pressure responsive devices at different pressures, means associated with said rst valve to delay deenergization thereof when said winding has previously been energized by direct current of a particular polarity to insure that the motor pressure continues to increase for a time after the contacts open, a source of direct electrical energy, a first line wire permanently connected at one end to a first terminal on said source, means connecting the other end of the line wire to one terminal of said first valve including an asymmetric unit poled to pass current only in the direction corresponding to said particular polarity; a first electrical circuit for at times energizing the first valve including the line wire, the asymmetric unit, the rst valve, and a rst connection between the other terminal of said first valve and a second terminal on said source having the proper polarity with respect to said first terminal to cause current to flow through said asymmetric unit, said first connection including said rst' contact and a second line Wire; a second electrical circuit for at other times energizing the rst valve including a second connection between said other terminal of the irst valve and said iirst terminal of the source and a third connection between said one terminal of the first valve and a third terminal of the source having a polarity with respect to the rst terminal opposite to that of the second terminal, one of said second and third connections including said second contact, said asymmetric unit being effective at such other times to block the flow of current through said first line wire from said first terminal; a third electrical circuit for at still other times energizing the second valve including said first line Wire, said second valve, and a fourth connection between the second valve and said third terminal including said second line wire and a second asymmetric unit poled to pass current only from said first terminal to said third terminal, said first asymmetric unit being effective when said third circuit is completed and said first contact is closed to block the flow of current through said iirst circuit.

1'3. Control apparatus comprising a `controlled electric device havingasymmetric properties, a first circuit controller located adjacent said controlleddevice andV having a contact, a second circuit controller located remotelyfrom said controlled device and having two selectively `closable contacts, a rst line wire connected at one 'end to both contacts of said second cont-roller,

two oppositely poled asymmetric units connected to the other end of the linewire, afirst connecamig-32o circuit being effective when said other contact is tion'betv/een one asymmetric unit and one terf minal lof the controlled device including the contactI ofA said first controller, a second connection l vbetween the other asymmetric unit and the other terminal of the controlled device, second land third line Wires paralleling said rst linewirefand closed to control said controlled device independently of said rst controller, 'both of said circuits being effective When completed to supply electric potentials of the same polarity to the connected to said one terminal and said other terminal, respectively, of the controlled device, a'

firstelectric circuit for energizing said controlled device including one contact of said second concontrolled device, said first line Wire being effective to carry current in opposite directions in the two-circuits.

ROBERT M. GILSON.

No references cited.

Images