US1824146A - Interlocking system for railroads - Google Patents

Description

Sept. 22, 1931. w. K. HOWE INTERLOCKING SYSTEM FOR RA ILROADS Filed Feb. 2, 1929 Patented Sept. 22, 1931 warren STATES PATENT OFFICE v WINTER/OP K. HOWE, F ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK INTER-LOCKING SYSTEM FOR RAILROADS Application filed February 2, 1929. Serial No. 337,000.

This invention relates to a power-operated switch machine, together with the necessary control and indlacting circults and ancillary apparatus to protect against the 5 operation of the switch machine by unauthorized current.

A switch machine for'operating a track switch of a railway system is usually controlled from a distant point, and it is highly important that such switch machine should not be permitted to operate by unauthorized or accidental application of current thereto, because 1f this were posslble it might operate in the face of an approaching train-mom 1 mg at high speed. Further, if the switch machine is operated by a lever in an interlocking plant an indication of the position of the switch machine should be given in such interlocking plant and this indication should be obtained in a manner so that it is highly improbable for a false indication to be given.

In accordance with the present invention it is proposed to construct a switch machine. so that itwill automatically open its oper-v ating circuit upon completion of an operating stroke and at the same time to make it possible to operate a switch machine in either direction when in anintermediate position. ize the control circuits that energy applied at the control lever of such switch machine must pass through suitable overload circuit brakin means such as a fuse orla circuit vide an electro-magnetio brake of the type,

which is only released it current is applied thereto, this electro-magnetic brake to be.

connected in serieswith the motor for op crating the swi; ch machine and having such pick-up and drop-away value thatthis brake will only release if approximately full volt age is applied to the switch machine with a motor locked by such brake,,and this brake iI" once released not applying so long as norlt is further proposed to so organ- 'can possibly take place.

mal current for the switch machine motor is flowing. Further, it is proposed to provideindicatingmeans in which the polarity of the current applied to two wires is reversed upon reversal of the switch machine. This in order that an ordinary cross or ground cannot efi'ect a false indication.

ther objects, purposes and characteristic features of the present invention will appear as the description thereof progresses and in part from the showing in the drawing.

In describing the invention in detail reference will be made to the accompanying single drawing in which one embodiment of the invention has been conventionally shown.

The switch machine has been conventionally shown by the apparatus contained within the rectangle SM. The indication relay is designated IR, and the normal and re-v verse locking magnets are designated NM and RM respectively and are associated with theswitch machine lever L. This lever L operates movable contacts 1 and 2, these movable contacts being connected to the lever in such a way that their relation with respect to the lever will never change, that is, the construction'is that no breakage between either of these contacts and the lever Further, the stationary jumpers and contactsB, 4, 5, and 6 are made of heavy straps of brass or copper or other suitable metalpand are constructed so heavy that their presence and contacting quality may be relied upon. If it is desired these movable contacts 1 and 2 as well as stationary contacts 3, 4:, 5, and 6 may be duplicated and connected in multiple so that the failure of one contact would not be detrimental to the functioning of the contact mechanism.

The switch machine motor comprises a reversible direct current series motor of the two-field winding type, in which the field windings are so ,wound that current flowing through the normal field winding NF and the armature A causes the motor to operate the switch machine to the normalposition, and current flowing through the reverse field winding RF and the armature A causes the switch machine to be operated to the reverse position. In this connection it will be noted that the movable contacts of the switch machine 10, 11, 12, and 13 assume the solid line position when the switch machine is in the normal position, assume the light dotted position when the switch machine is in an intermediate position and assume the heavy dotted position when the switch machine is in the reverse position. This switch ma chine includes an electro-magnetic brake BR, comprising a brake shoe 15 held against a brake drum 16 by a compression spring 17, and includes a winding 18 which if energized with suflicient current moves the brake shoe 15 away from the brake drum 16. This electro-magnetic brake BB is so designed that it will only release the brake shoe 15 if approximately full battery voltage is applied to the switch machine with the motor stationary. It is believed that the characteristic features of the system are best understood by considering the operation of the 7 system.

0pe1'ate'0n.Let us assume that the operator wishes to operate the switch machine to the reverse position. In order to do so he must first energize the normal indicating magnet NM. He must therefore press the energy saving push button PB, whereupon the magnet NM is energized through a circuit readily traced in the drawing, provid ing the indication relay IR is then assuming its left-hand position. relay IR will assume the left hand position if the switch machine is then assuming the normal position. In this connection it should be understood that if desired the circuit for the winding 20 of the indicating relay IR may be carried through front contacts of track relays to protect against operation of the switch machine during the approach of a train. With the lock magnet NM energized and the lock plunger 21 raised the operator is free to move the lever L from the normal position N to the half reverse. position HR, beyond which position movement of the lever L is preventedby the lock plunger 22 of the reverse magnet RM engaging the lock lug 23 of the lever L. With the lever L in the half reverse position HR the following circuit for the switch machine is completed :-beginning at the battery 25, wire 26, fuse or circuit breaker 27, wire 28, contacts 5, Land 4, reverse wire RW, contact 13, field winding RF, armature A, magnet winding 18, common return wire C, contact 6, wire 29, fuse or circuit breaker 30, wire 31, back to the battery 25. With this circuit completed the switch machine is started, and as soon as it has been unlocked, by suitable locking means, not shown, the contacts 10, 11, 12, and 13 are shifted to the light dotted or intermediate position, but as soon as the switch machine has com- This indicating pleted its stroke and has assumed the reversed locking position the contacts 10, 11, 12 and 13 are moved to the heavy dotted position, thereby opening the circuit ust traced at the contact 13. Also when the switch machine has reached its extreme reversed position and has been locked up the contacts 10 and 11 have reached their heavy dotted position thereby applying alternating current of reversed relative polarity from the trail?- former 33 to the winding 20 of the relay IR. This causes the indicating relay IR to assume the dotted position and with the push button PB depressed the reverse magnet RM is energized, thereby permitting the operator to operate the lever to the position R in which it unlocks conflicting levers and permits clearing of certain signals and the like,

in accordance with usual interlocking practice. With the lever L moved to the position R the following partial circuit is completed from-the normal wire to the negative side of the battery 25 :beginning at this normal Wire NW, contacts 3, 2 and 6, wire 29, fuse 30, wire 31, to the negative side of battery 25. This partial circuit is conveniently called the safety circuit. It is thus seen, should the positive side of battery 25 be accidentally connected to the normal wire NW current could readily flow through this safety circuit back to the battery 25. This flow of' current would not only blow the fuses 27 and 30, but would allow insufficient current to flow through the motor of the switch machine to release its brake BR.

In the same way as above explained the lever L cannot be moved from the full reverse position R to the half normal position HN until the reverse magnet RM has been energized, and then cannot be moved from the half normal position HN to the normal position N until the switch machine has been operated back to its normal position and has re-energized the indicating relay IR back to its normal position. This circuit for operating the switch back to its normal position may be traced as follows beginning at the battery 25, wire 26, fuse 27, wire 28, contacts 5, 1 and 3, wire NW, contact 12, field winding NF, armature A, magnet 18, wire C, contact 6, wire 29, fuse 30. wire 31, back to the battery 25.

The most common application of unauthorized current is due to a cross between the wires NW and RW. With the switch machine in the normal position, as shown, it is noted that if there were a cross between these wires RVV and NW that current could flow through the motor of the switch machine. It is, however, also noted that current can flow through a partial or safety circuit of low resistance similar to the one heretofore traced but including the contact 4, instead of the contact 3, and that this partial circuit is of much lower resistance machine in question.

than the switch machine circuit, and for this reason insuficient current will flow to release the brake BR of the switch machine. In this connection it should be noted that this partial circuit of low resistance, conveniently called the protection or safety circuit is only present when the lever L assumes either of its extreme positions N or R, and not when it assumes the half normal HN or the half reverse HR position. The lever L in practice, will however, assume one or the other extreme positions because it will be locked in such position by other levers unless it is permissible to operate the switch Another protective feature of the present invention resides in the provision of switch machine contacts and field windings so organized and connected,'that when the switch machine assumes an intermediate position the motor armature is included in two circuit branches one of which includes the normal wire and the normal field winding and the other of which includes the reverse wire and the reverse field winding, and since these field windings are wound oppositely they will neutralize each other when the two circuits including the two circuit branches are simultaneously energized, and this happens when a cross occurs between the normal and reverse wire with the switch machine in an intermediate position. It is thus apparent that a cross between the normal and reverse wire can only operate the switch machine from its extreme position to an intermediate position, for thereafter the field flux of the motor is substantially zero and no torque is produced by the motor. In practice the switch machine lock bolt will unlock after the contacts 12 and 13 open during movement of the switch machine from its extreme position. It is of course understood that the brake BR may be omitted and the feature of bucking fields maybe relied upon to prevent operation of the switch machine due to a cross between the normal and reverse wire, if desired. This feature also affords reversibility of the switch machine in mid-stroke, that is when assuming an intermediate position.

The characteristic features of the present invention reside in a construction of lever contacts that always can be relied upon, the

safety circuit of low resistance in multiplewith the switch machine motor when current is applied in an unauthorized way, 111- cluding overload circuit interrupting means,

and in the electro-magnetic brake constructed to have a pick-up current characteristic, so that the brake is only released in the event that a full normal application of current is made to the motor when at stop. Other features include the pole changing indication circuit associated therewith and the indication locking.

circuit breaker is once installed its adjustment cannot be changed as by tampering or unauthorized adjusting.

Attention is again directed to applicants safety and checking circuit, which when a cross between wires NW and RVV occurs, extend'sfrom the positive terminal of battery 25, 26, 27, 2S, 5 to NW and RW (crossed) through contact 2, wires 29, 30 and 31 to the negative terminal of battery 25. It should be noted that with the lever L in the normal position only the movable contact 2 is unchecked, and with the lever L in the reverse position only the contacts 2 and 8 are unchecked, and for this reason the contacts 2 and 3 are constructed either of a size to allow a large factor of safety (as shown) or with many branches in multiple, so that their presence and functioning can be relied upon. F or convenience the contacts 4%, 5 and 6 have also been shown very heavy. It should be noted that circuit portions 29, 30 and 31 are self checking or self betraying, in that, failure of these parts not only break the safety circuit, but also prevent the flow of unauthorized current through the motor due to the cross above mentioned.

Having thus shown and described one specific form of the present invention, it is desired to be understood that the particular exemplificat-ion of the invention has been selected to facilitate description of its nature, its operating characteristic and the safety features thereof, and the illustration is not intended to show the scope of the invention or the specific manner in which the invention is to be practiced; and that various changes, modifications, and additions may made to meet the requirements when practicing the invention or idea of means underlying thesame, except as demanded by the scope of the following claims.

What I claimis:

1. Apparatus for operating a distant track switch comprising, a. switch machine, a normal and a reverse wire leading to said switch machine, a reversible motor for said switch machine including two field windings one or the other of which is connected in series with the armature of such motor depending upon whether the normal wire or the reverse wire is connect-ed to a source of current, contacts operated by said switch machine included in said normal and said reverse wire of which the contact in the normal wire is closed in any intermediate and reverse position of the switch machine and in which the in an intermediate position through both field windings, thus preventing operation of the switch machine by such accidental cross between wires.

2. Aoparatus for operating a distant track i switch comnrisin a switch machine a nor- A. CD7 7 mal and a reverse wire leading to said switch machine, a reversible motor including two field windings one or the other of which is connected in series with the armature of 5 such motor depending upon whether the normal wire or the reverse wire is connected to a source of current, contacts operated by said switch machine included in said normal a and said reverse wire of which the contact in the normal wire is closed in intermediate and reverse position of the switch machine and in which the contacts in the reverse wire are closed in the normal and 7 any intermediate position of the switch machine, a common wire connecting said armature to one side of a source of current, a lever for connecting the other side of said source to either the normal or the reverse wire, whereby an accidental cross between the normal and the reverse wire will cause current applied to said motor when in an intermediate position through both field windings, thus preventing operation of the ,4 switch machine by such accidental cross between wires, and other contacts operated by said lever for causing said source of current to be short-circuited when said normal and said reverse wire are accidentally connected together while said lever is assuming one or the other extreme position.

3. Apparatus for operating a distant track switch comprising, a normal wire, a reverse wire, a switch machine having a reversible ,motor including two field windings one or the other of which is connected in ser es with the armature of such motor depending upon whether the normal wire or the reverse is connected to a source of current, con acts ope 'ated by said switch machine ini cluded in said normal and said reverse wire of which the contact in the normal wire is closed in intermediate and reverse position of the switch machine and in which the contacts in the reverse wire are closed in the normal and any intermediate position of the s 'itch machine, common wire connecting said armature to one side of a source or": current, a lever for connecting the other side of said source to either the normal or he reverse wire, whereby an accidental cross between the normal and the reverse wire will cause current applied to said motor when in an intermediate position through both field windings, thus preventing operation of the switch machine by such accidental cross between wires, and an electro-magnetic brake for said motor which is normally active and which is rendered inactive only if full voltage is applied to said motor when at rest. 7

4t. Apparatusfor operating a distant track switch comprising, a normal and a reverse wire, a switch machine having a reversible motor including two field windings one or the other of which is connected in series ith the armature oi such motor depending upon whether the normal wire or the reverse wire is connected to a source of current, contacts operated by said switch machine included in said normal and said reverse Wire of which the contact in the normal wire is closed in any intermediate and reverse position of the switch machine and in which the contacts in the reverse wire are closed in the normal and any intermediate position of the SWiJCh machine, a common wire connecting said armature to one side of a source of current, a level for connecting the other side of said source to. either the normal or the reverse wire, whereby an accidental cross between the normal and the reverse wire will cause current applied to said motor when in an intermediate position through both field windings, thus preventing operation of the switch machine by such accidental cross between wires, and an electro-magnetic brake for said motor which is normally active and which is rendered inactive only if full voltage is applied to said motor when at rest, said electro-magnetic brake if once operated to its release position remaining in its inactive position by the current flowing through said motor when operating at full speed. 7

5. Apparatus for operating a distant track switch comprising, a normal and a reverse wire, a switch machine having a reversible motor including two field windings one or the other of which is connected in series with the armature of such motor depending upon whether the normal wire or the reverse wire is connected to a source of current, contacts operated by said switch machine included in said normal and said reverse wire of which the contact in the normal wire is closed in any intermediate and reverse position of the switch machine and in which the contacts in the reverse wire are closed in the normal and any intermediate position of the switch machine, a common wire connecting said armature to one side of a source of current, a lever for connecting the other side of said source to either the normal or the reverse wire, whereby an accidental cross between the normal and the reverse wire will cause current applied to said motor when in an intermediate position through both field windings, thus preventing operation of the switch machine by such accidental cross between Wires, other contacts operated by said lever for causing said source of current to be short-circuited when said normal and said reverse wire are accidentally connected together while said lever is assuming one or the other extreme position, and two electric locks for said lever one of which can be energized only when the switch machine assumes one extreme position and the other of which can be energized only if the switch machine assumes the other extreme position.

6. Apparatus for operating a distant track switch comprising, a normal and a reverse wire, a switch machine having a reversible motor including two field windings one or the other of which is connected in series with the armature of such motor dependin upon whether the normal wire or the reverse wire is connected to a source of current, contacts operated by said switch ma chine included in said normal and said re verse wire of which the contact in the normal wire is closed in any intermediate and reverse positionof the switch machine and in which the conctacts in the reverse wire are closed in the normal and any intermediate position of the switch machine, a common wire connecting said armature to one side of a source of current, a lever for connecting the other side of said source to either the normal or the reverse wire, whereby an accidental cross between the normal and the reverse wire will cause current applied to said motor when in an intermediate position through both field windings, thus preventing operation of the switch machine by such accidental cross between wires, other contacts operated by said lever for causing said source oi current to be short-circuited when said normaland said reverse wire are accidentally connected together while said lever is assuming one or the other extreme position, two electric locks for said lever one of which can be energized only when the switch machine assumes one extreme position and the other of which can be energized only if the switch machine assumes the other extreme position, and an indication circuit for controlling said lock magnets controlled from a distant point by the application of current of a polarity corresponding to the position of the switch machine.

7 Apparatus for operating distant traffic controlling devices; the combination with a switch machine including the usual revers-r ible motor having a normal circuit and a reverse circuit and contacts for opening said normal or the reverse circuit of said motor when the corresponding operating stroke of the motor has been completed; of a lever for applying current from a local source to said motor through said normal or said reverse circuit when said lever assumes respectively the half normal or the half reverse position, and a protective circuit of low resistance for connecting said reverse wire or said normal wire to the common return wire leading from said motor to said local source when said lever assumes respectively said full normal or said full reverse said lever assumes respectively the half normal or the half reverse position, a protective circuit of low resistance for connecting said reverse wire or said normal wire to'the common return wire leading from said motor to said local source when said lever assumes respectively said full normal or said full reverse position and circuit interrupting means connected in series with said local source of current.

9. Apparatus for operating distant trafiic controlling devices; the combination with a switch machine including the usual reversible motor having a normal and a reverse circuit and contacts for opening said normal or the reverse circuit of said motor when the corresponding operating stroke of the motor has been completed; of a normally active spring actuated brake for said motor, an electro-magnet for rendering said brake inactive connected in series with said motor, said electro-magnet being constructed to have a pick-up characteristic so that said brake will release it full normal starting current flows through said motor, means for applying current to said motor, and a protective circuit in multiple with said motor closed only when unauthorized current is applied to said motor.

10. Apparatus for operating distant traffic controlling devices; the combination with a switch machine including the usual reversible motor having a normal and a reverse circuit and contacts for opening said normal or the reverse circuit of said motor when the corresponding operating stroke of the motor has been completed; of a normally active spring actuated brake for said motor, an electro-magnet for rendering said brake inactive connected in series with said motor, said electro-magnet being constructed to have a pick-up characteristic so that said brake will only release it full normal starting current flows through said motor, means for applying current to said motor, a protective circuit in multiple with said motor closed only when unauthorized current is applied to said motor, and means for indicatingthe position of said switch machine.

11. Apparatus for operating distant traffic controlling devices; the combination with a switch machine including the usual reversible motor having a normal and a reverse circuit and contacts for opening said normal or the reverse circuit of said motor when the corresponding operating stroke of the motor has been completed; of a normally active actuated brake for said motor, an electro magnet for rendering said brake inactive connected in series with said motor, said electro-magnet being constructed to have a pick-up characteristic so that said brake will only release it full normal starting current flows through said motor, a lever which it moved to the half-normal or halireverse position applies current to said normal or said reverse circuit respectively, and indication locking means for preventing saidlever being moved to the full normal or full reverse position until said switch machine has assumed the corresponding position.

12A switch machine comprising, a reversible motor, a normal circuit which if energized operates said motor toward the normal position and including contacts opened only when said switch machine assumes the full normal position, a reverse circuit which if energized operates said motor toward the reverse position and including contacts opened only when said switch machine assumes the full reverse position, a spring actuated brake normally -I holding said motor at rest, an electro magnetfor rendering said brake inactive connected in series with said motor said electro-magnet having operating characteristics to permit release of said brake only it full normal starting current is flowing in saidmotor, whereby said motor will not be operated if unauthorized current of less than full normal current value is applied to said motor. v

13. A switch machine comprising, a reversible motor, a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the I full normal position, a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse position, a normal field winding '1 in said normal circuit, and a reversely wound field winding in said reverse circuit, whereby a cross between said normal circuit and said reverse circuit energizes said motor through both of said fieldwindings as soon as said switch machine assumes a position other than saidfull normal or said'full reverse position thus preventing material operation ofsaid switch machine with a cross between said normal and said reverse circuit.

14. A switch machine comprising, a reversible motor; a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position, a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse positions; and a lever for energizing said normal circuit when said lever assumes the half normal position, energizing said reverse circuit when it assumes the half reverse position, short-circuiting said reverse circuit when in the full normal position and short-circuiting said normal circuit when in the full reverse position.

15. A switch machine comprising, a reversible motor, a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position, a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse positions; and a lever for energizing said normal circuit when said lever assumes-either the half normal or the full normal position, energizing said reverse circuit when it assumes either the half reverse or the full reverse position, short-circuiting said reverse circuit when in the full normal position and short-circuiting said normal circuit when in the full reverse position.

16. A switch machine comprising, a reversible motor, a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position, a reverse circuit which if energized operates said. motor toward the reverse position and including contacts open only when said switch machine assumes the full reserve positions; and a manually operable switch comprising four rigid stationary contacts and a lever having two movable contacts for energizing saidnormal circuit when said lever assumes either the half normal or the full normal position, energizing said reverse circuit when it assumes either the half reverse or the full reverse position, short-circuiting said reverse circuit when in the full normal position and short-circuiting said normal circuit when in the full reverse position.

17.vA switch machine comprising; a reversible motor; a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position; a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse position; and a manually operable switch comprising four one piece stationary contacts and a lever having two movable contacts for controlling the energization of said normal circuit and said reverse circuit; said switch energizing said normal circuit when assuming the half normal position, energizing the reverse circuit when assuming the half reverse position, short-circuiting the normal circuit when in the full reverse position and short-circuiting the reverse circuit when assuming the full normal position.

18. A switch machine comprising; a reversible motor; a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position; a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse position;a manually operable switch comprising four one piece stationary contacts and a lever having two movable contacts for controlling tne energization of said normal circuit and said reverse circuit; said switch energizing said normal circuit when assuming the half normal position, energizing the reverse circuit when assuming the half reverse position, short-circuit the normal circuiting when in the full reverse position. and short-circuiting the reverse circuit when assuming the full normal position, and an electrically operated brake effective when de-energized to brake said motor including a winding connected in se ries with said motor.

19. A switch machine comprising; a reversible motor; a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position; a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse position; a manually operable switch comprising four one piece stationary contacts and a lever having two movable contacts for controlling the energization of said normal circuitand said reverse circuit; said switch energizing said normal circuit when assuming the 'half normal position, energizing the reverse circuit when assuming the half reverse position, short-circuiting the normal circuit when in the full reverse position and shortcircuiting the reverse circuit when assuming the full normal posltlon; and locking means for preventing movement of said lever to the full normal or full reverse position respectively unless said switch machine assumes the corresponding position.

20. A' switch machine comprising, a reversible motor, a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position, a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse position, a normal field winding in said normal circuit, and a reversely wound field winding in said reverse circuit, whereby a cross between said normal circuit and said reverse circuit energizes said motor through both of said field windings as soon as said switch machine assumes a position other than said full normal or said full reverse position, thus preventing material operation of said switch machine with a cross between said normal and said reverse circuit and under normal conditions affording reversibility of the switch machine in midstroke.

21. A switch machine comprising, a reversible motor, a source or current for operating said motor, a normal circuit which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position, a reverse circuit which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse positions;excess current circuit interrupting means in series with said source; and a lever for energizing said normal circuit when said lever assumes the half normal or full normal position, energizing said reverse circuit when it assumes the half reverse or full reverse position, short-circuiting said reverse circuit when in the full normal position and short-circuiting said normal circuit when in the full reverse position.

22. A switch machine comprising, a reversible motor, excess current circuit interrupting means included in series with a source of current for operating said switch machine, a normal circuit including a normal wire which if energized operates said motor toward the normal position and including contacts open only when said switch machine assumes the full normal position, a reverse circuit including a reverse wire which if energized operates said motor toward the reverse position and including contacts open only when said switch machine assumes the full reverse positions; and a lever for energizing saidnormal circuit when said lever assumes either the half normal or the full normal position, energizing said re verse circuit when it assumes either the half reverse or the full reverse position, short-cireuiting said reverse circuit when in the full normal position and short-cireuiting said normal circuit When in the full reverse position, whereby said source is short-oircuited through said circuit interrupting means if said normal and said reverse Wires are connected together With said lever assuming either 01 said full positions. I

In testimony whereof I afiix my signature.

WVINTHROP K. HOWVE.

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