US2199952A - Railway traffic controlling apparatus - Google Patents

Description

y 7. 1 40. c. M. HIM-=5 ET AL 2199.952

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed D86. 14, 193'? 2 Sheets-Sheet 1 Dual selectozy Contact Fig 2. I

lNVENTORS Fig? E. ()Hqgan BY THEJR ATTORNEY I K?: J Claude M Hines and v Bern May 7, 1940. c. M H|NEs AL 2,199,952

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Dec. 14, 19s? 2 Sheets-Sheet 2 Fl .4. r 57 WRS 55 0H6 i? I I 9 I C M 54 53 Dual selector comaczs INVEN TOR'5 Claude-1M Hznes and Ber .By v THEIRATTORNEY Patented May 7, 1940 UNITED STATES PATENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Application December 14, 1937, Serial No. 179,704

13, Claims.

Our invention relates to railway traflic controlling apparatus, and' has for an object the provision of novel and improved apparatus for the protection of a railway switch operating moe tor against overload conditions, and which apparatus provides resetting thereof subsequent to an overload condition.

We shall describe'five forms of apparatus embodylng our invention, and shall then point out the novel features thereof in claims.

Figs. 1, 2, 3, 4 and 5 of the accompanying drawings are diagrammatic views of specific forms of apparatus each form of which embodies our invention. v

Similar reference characters refer to similar parts in each of the different views.

Referring to Fig. 1, the reference character S designates a railway track switch whichis actuated by .an electric motor M through the mein dium of a suitable switch operating mechanism SM, the motor M being here shown as a reversible direct current motor having an armature 5 and a field winding 6. The mechanism SM maybe of any of the standard types, and is 2:, shown conventionally for the sake of simplicity.

The switch S operatesa-circuit controller E comprising a contact 'l8 closed in all positions of the switch except in the extreme-normal position,

that is, in the position shown in Fig. 1, and a so contact 'l9 closed in all positions of the switch except in the extreme reverse position, that is, in the position opposite that shown in Fig. .1.

The motor M is reversibly operated by means of a normal and a reverse operating circuit, which :27. circuits are controlled by a direct current polarized relay WR. In Fig. l, relay WR is provided with twooperating windings I2 and I3. An auxiliary or overload relay OR is associated with relay WR for protecting the motor M under overload conditions in a manner to be later described.-

In this form of the invention, the relay OR is a direct current neutral relay provided with two energizing windings l4 and I5. I

The relay WR is controlledover a pole changer CL which may-be located at any convenient point such as an operators oifice remote from the track switch S. The pole changer CL may be actuated by a switch lever .of an interlocking machine. The control of relay WR is effected from the pole changer CL'over a pair of control linewires'lll and I l which are reversibly connected with a source of direct current such as a battery 10 through the medium of the pole changer CL.

' The arrangement is such that the battery 10- is .55 connected with the control wir'es l0 and II to supply current of one polarity, which we'shall term normal polarity, when the pole changer CL is set at the position indicated by the solid lines, and to supply current of the other polarity, which we shall term reverse polarity, when the pole changer is set at the position indicated. by the dotted lines. The winding l2 of relay WR is permanently connected across the control wires llland'll, but the winding ['3 of relay WR is connected across the wires lll'and ll over pole changing contact fingers l6 and ll of the overload relay OR. When relay OR is deenergized and released so that the contact fingers I 6 and I1 are in engagement with back contacts IB and I9, respectively, the windings l2 and [3 of relay WR are connected with the control wires l0 and II as required for the magnetic fluxes created thereby to add their effects, and relay WR is effectively energized and picked up to close front neutral contacts and 2|, as well as to operate polar contact fingers 22 and 23. With current of normal polarity supplied to the control wires l0 and I, and the relay OR released, the energization of relay WR is of normal polarity, and the polar contact fingers 22 and 23 are shifted to the left-hand position, that is, to the position shown in Fig. 1. With current of reverse polarity supplied to the wires I0 and I l and relay OR released, the energization of relay WR is of the reverse polarity, and the polar contact fingers 22 and 23 are shifted to the right-hand position, that is, the position opposite that shown in Fig. 1.

Under conditions that cause the relay OR to be effectively energized and picked up so that the contact fingers l6 and I! are in engagement with front contacts 24 and 25, respectively, the connection of winding l3 of relay WR is reversed, and'the energization of winding l3 opposes that of winding l2 and relay WR is deenergized and released, opening its front neutral contacts 20 and 2|, the polar contact fingers 22- and 23 preferably remaining in the position to which they were last moved.

When relay WR. is energized with current of normal polarity, a normal motor operating circuit is formed from the B terminal of a current source, such as a battery not shown, over polar contact finger '22 in its normal position, front neutral contacts 20 and 2| in multiple, motor armature 5, a resistor R to be referred to later, polar contact finger 23 in its normal position, contact 1-8 when closed, field winding 6, and to the C terminal of the current source. With motor M thus supplied lwithcurrent, it is rotated in a iii direction as required to move the track switch S to the normal position. When relay WR is energized with current of reverse polarity, a reverse motor operating circuit is formed from B terminal over polar contact finger 23 in its reverse position, resistor R, motor armature 5, front neutral contacts 20 and 2i in multiple, polar contact finger 22 in the reverse position, contact 'I9, field winding 6, and to the C terminal, 7

the resistor R and the winding I4 in multiple, 7

the magnitude of the current flowing in the winding is depending upon the relative value of the resistor R. The parts are so constructed and proportioned that, when the motor current flowing to resistor R and the winding I4 in multiple does not exceed that required to operate mo tor M and in turn the track switch S under usual operating conditions, the potential drop across resistor R is relatively low and the energization of winding I4 is insufiicient to pick up the relay OR. However, under overload conditions such as occur in the event the track switch S is obstructed, the motor current is relatively large and the resistor R quickly heats up to materially increase its resistance so that the potential drop across the resistor R soon exceeds a predetermined value and the winding I4 of relay OR is energized sufficiently to pick up that relay, c1osing its front neutral contacts. The parts are further so proportioned that surges of current which are high in value but of relatively short duration, such as starting and reversal surges, are

not effective to pick up the relay OR.

It is clear that under usual operating conditions the relay WR follows as to normal and reverse positions the corresponding movements of the pole changer CL, and the relay WR in turn causes corresponding normal and reverse operations of, the motor M to actuate the track switch S, the operation of motor M being terminated at the extreme position of the track switch through the medium of controller E. In the event the track switch meets an obstruction so that an overload on the motor M occurs, the potential drop across the resistor R soon exceeds a predetermined value and relay OR is picked up in response to the increased energization of winding I I. Relay O-R, on picking up, shifts the pole I changing contact fingers I6 and H from engage-.

ment with the respective back contacts to engagement with the respective front contacts, causing a reversal in the connection of winding I3 of relay WR, with the result that relay WR is deenergized and released, opening its front neutral contacts 20 and 2| to interrupt the motor operating circuit. When relay OR is picked up, the front contact 28 is closed and completes a stick circuit easily traced by which the winding I is connected across control wires I0 and I I so that the relay OR is retained energized and held picked up by current supplied from battery T0 over the pole changer CL and the wires I0 and II, notwithstanding the fact that winding I4 of relay OR is deenergized when the motor operating circuit is interrupted. It follows that an overload condition which causes the relay OR to be picked up to interrupt the motor operating the relay OR is reset.

After such an interruption due to an overload condition, the apparatus can be reset by the pole changer CL being operated. Operation of the pole changer CL causes a reversal in the polarity of the current supplied to the control wires Ill and II, and the energization of winding I5 of relay OR is reversed. During the interval the magnetic flux passes through zero, relay OR is released, opening the front contact 28 by which the winding I5 is connected with the control wires I0 and II. With relay OR released, the connection of winding I3 of. relay WR'is changed so that the two windings I2 and I3 are now in agreement and the relay WR at once responds to the new setting of the pole changer CL. Since the current supplied to the wires I0 and II is opposite that supplied to the wires in and II prior to the overload condition, the relay WR reverses its position and causes the motor M to move the switch S back to the position it occupied prior to the overload condition.

With the apparatus of Fig. I, there are two alternative arrangements for the relay WR. The preferred arrangement is to have the windings I2 and I3 so proportioned that both windings must be energized to operate the relay. This arrangement assures the'detection of a fault in the control circuit at the first operation after a fault occurs. A second arrangement is to have the windings I2 and I3 so proportioned that energization of either winding alone is effective to operate the relay.

There is a third arrangement for relay WR that would be at times useful. This third arrangement would be to omit the winding I2 and operate the relay by winding l3 alone. Under this arrangement, the operation of the apparatus would be modified to the extent that, when an overload occurs and the overload relay OR picks up reversing the position of its contact fingers I6 and H, the relay WR is reversed and the motor M is operated at once to return the switch to the position it occupied prior to the overload condition. To regain control, the operator would reverse the position of the pole changer CL to re lease relay OR and to bring the pole changer CL into agreement with the relay WR and the switch.

In Fig. 2, the track switch S is operated by the motor M through the medium of a switch operating mechanism SM,the same as in Fig. -1, except for the fact the switch mechanism of Fig. 2 would preferably be of the dual type having the usual dual selector lever (not shown). The controller E of Fig. 2 is operated from the track switch S, the same as in Fig. 1. The motor circuits are governed by a relay WRI, which relay is a direct current polarized relay having a single operating winding 30. For protection to the motor under overload conditions, .a slow acting direct current neutral relay ORI is provided. The relay WRI is controlled over the remote pole changer CL and control wires I0 and II, the

One terminal of winding 30 of v is connected with control wire I I over a normally closed contact 3| operated'by the dual'selector lever of the switch mechanism SM and a back contact 32 of the overload relay ORI. It follows that, as long as relay ORI is deenergized and re-- leased and the dual selector is set for power operation closing contact 3|, the relay WRI follows as to position the movements of I pole changer CL. With relay WRI energized by current of normal polarity, a normal motor operating circuit is formed from B terminal over front neutral contacts 33 and 34 in multiple, polar contact finger 35 in its normal position, a resistor RI, motor armature 5, polar contact finger 35 in its normal position, contact 'I-8 when closed, field winding 6 and C terminal. With relay WRI energized by current of. reverse polarity, a reverse motor operating circuit is formed from B terminal over front neutral contacts 33 and 34 in multiple, polar contact finger 3B in its reverse position, motor armature 5, resistor RI, polar contact finger 35 in its reverse position, contact 'I9, field winding 6, and to the C terminal.

The resistor RI is similar in construction to resistor R of Fig. 1, and is common to both motor operating circuits. The operating winding 31 of relay ORI is connected in multiple with resistor RI over front contacts 38 and 39 of relay WRI, as will readily be understood by an inspec- I tion of Fig. 2. The parts are so proportioned that the potential drop across resistor RI caused by the usual motor operating current produces a flow of current inwinding 3'I- insufllcient to energize relay ORI at its pick-up value, but that an overload current flowing in the motor circuit causes the resistor RI to quickly heat up, in-

creasing its resistance to the point wherethe potential drop across the resistor is abovea predetermined value and relay ORI is energized sufficiently to pick up and close the front contact 40. Furthermore, as pointed out in Fig. 1, the parts are so proportioned and adjusted that starting and reversal surges of current do not last for a sufiicient period to cause relay ORI to be picked up. v j

When relay ORI is picked up, opening its back contact 32, thewindingBU ofrelay WRI is disconnected from the wires I and I l, and relay WRI is released, interrupting the motor circuit at front contacts 33 and 34. When relay WRI is released, one terminal of winding 31 of relay ORI is connected with the control wire. I0 over back contact 4| of relay WR'I and a current limiting resistor 42, and the other terminal of winding 31 is connected with control wire II over back contact 12 of relay WRI and the front contact 40 of relay ORI. 7 Consequently, with theapparatus constructed as disclosed in Fig. 2, an overload condition on the motor M that raises the potential drop across resistor RI above a predetermined value causes relay ORI to be picked up to deenergize relay WRl,'and relay WRI upon releasing interrupts at its front neutral-contacts the overloaded motor circuit. The relay WRI,

upon releasing, also shifts. the connectionfor winding-31 of relay ORI to the control wires I0 and II so that relay ORI 'is retained energized by current supplied over a'stick circuit comprising the pole changer CL, the line wires I0 and I I and its own front contact 40 and winding 31, with the result the relay WRI remains deenergized, holding the overloaded motor circuit open. r

The operator can regain control ,of relay WRI subsequent to an overload condition by shifting the pole changer CL to reverse'the polarity of the current supplied to the wires I0 and I I, the relay ORI being released during the reversal .of its energization opening its own front contact 40 interposed in the connection of winding 31 with the control wires. When relay ORI is released, the relay WRI is again connected with the control wires III'and I I and is operated to the position corresponding to the polarity of the current supplied to the control wires, so that the motor M is operated to move the switch back to the position it occupied prior to the overload condition.

In case the dual selector of the switch machine SM of Fig. 2.is set for hand operation of switch 5, the shifting of contact 3| deenergizes the relay WRI, and the shifting of the normally open contact 43 of the dual selector completes the connection of -winding 31 to the control wires I0 and II, so that relay ORI is picked up, closing its stick circuit at front contact 40, over which it is then retained energized. Consequently, when the dual selector is returned to normal after hand operation, the relay WRI remains deener'gizedand motor M is inactive until such time as the operator at the remote office reverses the pole changer CL to cause the relay ORI to be released.

In Fig. 3, the apparatus is similar to that of Fig. 2 exceptthe overload relay 0R2 is provided with twoenergizing windings 56 and 51, and is not controlled over contacts of the motor operating relay WR2.

The winding 56 of relay 0R2 is connected in multiple with resistor R2, which resistor is common to both motor operatingcircuits, as will be readily understood by an inspection of Fig. 3. The winding 51 of relay 0R2 is normally shortcircuited over its own back contact 58 to provide slow pick-up characteristics. To energize wind- 5 ing 5'Iat times fromthe control wires Ill and II,

one terminal of winding 51 is connected with wire I'll over a current limitingresistor, 59-, while the other terminal of winding 5'! is connected with wire II over transfer contact 60 and front con- .tact SI of a continuity transfer contact of relay The parts are so proportioned thatan overload current flowing in resistor R2 causes it to heat up, raising its resistance,fand :in turn the potential drop across the resistor, .so that the potential drop across the resistor exceeds a predetermined value, with the'"result that winding 56 of relay 0R2 is energized to the pick-up value 'of the relay, and relay ORZ-is picked up. Overload relay 0R2, on picking up, opens the connection of vwinding 62 of relay'WRZ with wire -II at the back contact 63 of relay 0R2. Relay WRZ, when thus deprived of energizing current, quickly releases, interrupting the motor operatlng'circuit at its front neutral contacts 64 and 65. It is to be noted that the short circuit connection for winding 51 of relay 0R2 at back contact 58 causes the relay 0R2 to be slow acting, and operation of'relay 0R2 due to the starting and reversal surges of current is avoided. When relay ORZ is picked upfthe closing of contact 60--6I completes the connection of winding 51 across the control wires II and II, and relay 0R2 is retained energized'by a stick circuit comprising the polechanger CL, wires Ill and II, front contact 60'-6I and winding 51, subsequent to the interruption of the motor circuit.

Operation of the pole changer CL of Fig. 3,

subsequent to an overload condition, reverses the polarity of the current supplied to the control wires, and relay 0R2 is released.v during the; re-" versal'of its energization." With relay 0R2 released, the connection of relay WRZ is restored and relay WRZ is in turn operated to the position corresponding to the new position of the pole changer, so that the motor M is operated to restore the track switch S to the position it occupied prior to the overload condition.

In Fig. 4, the motor M operates the track switch S through the medium of a switch operating mechanism SM, the same as in Fig. 1, the motor operating circuit being governed by a direct current polarized relay WR3 having a single operating winding 44. The normal and reverse motor circuits controlled by relay WR3 are similar to those described in Figs. 1 and 2, and it is thought unnecessary to repeat their description in detail, except to point out that the resistor R3 of Fig. 4 is common to both motor circuits.

Overload protection of motor M of Fig. 4 is accomplished through the medium of an overload relay 0R3 having a single operating winding 45. To control relay WR3 by the remote pole changer CL, one terminal of the winding 44 of relay WRS is connected directly with the control wire in, and the other terminal of winding 44 is connected with the wire ll over back contact 46 of the overload relay 0R3. It is clear that, as long as relay 0R3 is deenergized and its back contact 46 closed, the relay WR3, and in turn the motor M, are responsive to operation of the pole changer CL.

The resistor R3 is preferably constructed and proportioned similarly to the resistor R of Fig. 1. One terminal of winding of relay 0R3 is connected at one end of the resistor R3 ov'er transfer contact 41 and back contact of the relay, While the'other terminal of Winding 45 is connected with the other terminal of resistor R3 over transfer contact 49 and back contact 50 of the relay. The parts are so proportioned and adjusted that the potential drop across resistor R3 caused by the usual operating current is less than that required to energize relay 0R3 to the point where it picks up, but the larger value of current flowing in the motor circuit under overload conditions soon creates a potential drop across resistor R3 above a predetermined value and relay CBS is energized sufiiciently to pick up. The

picking up of relay 0R3 to open its back contact- 46 causes the relay W'R3 to become deenergized, and relay WR3 on releasing interrupts the motor circuit at the neutral front contacts 5| and 52. When relay 0R3 is picked up, the connection of its winding 45 is shifted fromresistor R3 to the control wires Ill and ll through the medium of the front contacts 54 and 55. The connection from wire ID to the left-hand terminal of winding 45 includes resistor 53, front contact 54 and the transfer contact 41, while the connection from wire l I to the right-hand terminal of winding 45 includes front contact 55 and transfer contact 49. It follows that relay 0R3, when once picked up, due to the potential drop created across resistor R3 by an overload current, is retained picked up by a stick circuit comprising the pole.

changer CL, control wires l0 and ll, front contacts 54 and 55 and winding 45.

Operation of the pole changer CL of Fig. 4 subsequent to an overload condition reverses the polarity of the current supplied to wires l0 and l l and reverses the energization of relay 0R3 which is released during the interval the magnetic flux passes through zero. With relay 0R3 and reversal current surges do not cause an operationof the overloadrelay 0R3.

In Fig. 5, the switch S is operated by the moe tor M through the medium of a switch mechanism SM, the same as in the other cases, the

mechanism SM in Fig. 5 being of the dual selector type, the same as in Fig. 2. The controller A El of Fig. 5 comprises two movable contact members 90 and 9|. Contact member 90 makes engagement with a stationary contact 92 in all the positions of the switch except the full normal position, and contact member 9| engages a stationary contact 93 in all the positions except the full reverse position.

A polarized relay-WR4 controls the motor M through the medium of twocontactors NC and RC, the relay WR4 in turn being governed over thecontro'l wires l0 and H from the remote pole changer CL. The contactor NC is governed by relay WR4 by virtue of a circuit which includes the normal polar contact 94 of relay WR4, contact 90-92 of controller El, winding of contactor NC, and the backcontact 95 of an associated overload relay 0R4. The control circuit 5 of contactor RC involves reverse polar contact 66 of relay WR4, contact Ell-93 of controller,

El, winding of contactor RC, and the back contact 95 of relay 0R4. With contactor NC energized, the normal motor operating circuit is completed at front contact 61 of contactor NC and back contact 68 of contactor RC, as will be readily understood by an inspection of Fig. 5. With contactor RC energized, the reverse motor operating circuit is completed at front contact 69 of contactor RC and back contact 96 of contactor NC. A resistor 2 R4 is common to both motor operating circuits, the same as in other forms of the invention.

The overload relay 0R4 is provided with a single operating winding ll which is connected across the resistor R4 over back contactsof the relay. To be specific, the right-hand terminal of winding H is normally connected with the lefthand terminal ofresistor R4 over transfer contact 91 and back contact 13 of the relay and a normally closed. contact 14 of the dual selector lever of the mechanism SM. The left-hand ter minal of winding 'H is connected over transfer contact 15 and back contact 16 of the relay with the right-hand terminal of resistor R4. The parts are so proportioned that the potential drop across resistor R4 caused by the usual motor operating current does not shunt sufficient current through winding H to pick up the relay 0R4. An overload current flowing in themotor circuit causes resistor R4 to heat up, however, raising its resistance so that sufficient current is shunted through winding ll to pick up the overload relay.

no I

With the relay 0R4 picked up, the connection When overload relay 0R4 contactor NC or'RC, as the case may be, is de- 7 energized -to interrupt the overloaded motor circuit. With the winding of relay R4 shifted to the control wires I0 and H the overload relay isretained energized by the stick circuit including the pole changer, and the overloaded motor circuit is held open until such time as the pole changer CL is shifted to cause the release of relay 0R4.

With the dual selector shifted for hand operation, a connection is closed at the contacts 80 and 8| whereby the winding ll of relay 0R4 is connected with the control wires I 0 and II, and relay 0R4 is picked up and then retained energized over the stick circuit including its front contacts H and 18. Thus, when. the dual selector is returned to its normal position subsequent to hand operation, the overload relay 0R4 remains energized so that the operator to regain control of the switch must first shift the pole changer CL to cause the release of the overload relay.

Although we have herein shown and described only five forms of apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

1. In combination, a reversible electric motor, a normal and a reverse operating circuit for the motor, control means including a current source and a manually operable pole changer as well as a pair .of control wires for selectively governing said motor operating circuits, a resistor common to both of the motor circuits, a neutral relay having a winding connected across said resistor, said relay and resistor proportioned and adjusted to pick up the relay only when an overload current flows through the resistor for a predetermined interval, means controlled by the relay when picked up to interrupt the overloaded motor circuit; and a stick circuit for said relay comprising said current source, pole changer and control wires as well as a front contact and a winding of the relay for holding the overloaded circuit open until the pole changer is operated.

2. In combination, a reversible electric motor, an" operating circuit means for said motor, a manually operable pole changer for reversibly governing the supply of current to said circuit means for operating the motor, a resistor having a positive temperature coefficient interposed in said circuit means, a relay having a winding connected across said resistor, said relay adjusted to pick up only when an overload current flows through said resistor and the resistor heats up to increase its resistance so that the potential drop across the resistor exceeds a predetermined value, means controlled by said relay when picked up for interruptlng said motor circuit means, and a stick circuit for said relay including said pole changer and a winding of the relay as well as a front contact of the relay.

3'. In combination, a track switch having operatively connected therewith a reversible electric motor, a normal and a reverse operating circuit for the motor, a direct current polarized relay for selectively governing said circuits, a control circuit for, said relay including a polechanger and a pair of control wires, a neutral overload relay having a winding common to both said :motor operating circuitasaid overload relay adjustedgto pick up only when an overload current flows in a motor operating circuit for a given period, meanscontrolled by the overload relay when picked, up to interrupt the overloaded motor circuit, and a stick circuit for said overload relay comprising said pole changer and said control wires as well as a front contact and a winding of the relay for holding the overloaded circuit open until the pole changer is operated to reverse the polarized relay and operate the .motor to move the track switch to the position it occupied priorto the overload condition.

' 4, In combination, a reversible electric motor, a direct current polarized relay, a control circuit including a pole changer for controlling said relay, a normal motor operating circuit including a normal polar contactand a front neutral contact of said relay, a reverse motor operating circuit including a reverse polar contact and a front neutral contact of said relay, a resistor having a positive temperature coefficient common to both of said motor circuits, a neutral relay having a Winding connected across said resistor and which relay is picked up only when an overload current flows in a motor circuit and the potential drop across said'resistor exceeds a predetermined value, means including a front contact of said neutral relay operative to deen'ergize said polarized relay for interrupting the overloaded motor circuit, and a stick circuit for said neutral relay connected with said control circuit'for holding the overloaded circuit open until the pole changer is operated. '5. In combination, a reversible electric motor, a direct current polarized relay, a pole changer, circuit means including said pole changer for reversiblyenergizing said polarized. relay, a'

'single winding slow acting overload relay having a back contact interposed in said circuit means for at times deenergizing said polarized relay, motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of said polarized relay, a resistor characterized by a positive temperature coefficient interposed in said motor operating circuit means, means includinga contact of said polarized relay to connect said single winding of said slow acting relay across said resistor to pick up said slow acting relay when an overload current flows in said motor operating circuit means to deenergize the polarized relay for int'errupting theoperating circuit means, and a r stick circuit for said slow acting relay including said pole changer, another contact of said polarized relay and said single Winding of the relay.

6. In combination, a reversible electric motor,

a direct current polarized relay, a pole changer,

a control circuit including said pole changer and a winding of said relay for reversibly energizing said relay, a slow pickup slow release neutral relay having a back contact'interposed in said control circuit, motor operating circuit means ineluding normal and reverse polar contacts as welldrop across the resistor exceeds a predetermined value to deenergize the polarized relay for interrupting the overloaded motor circuit, means in- ,cludingfa back contact of said polarized relay and another resistor to connect a winding of the neu: tral relay-with said'control circuitto retain energized the neutral relay for holding the polarized relay deenergized and the overloaded circuit open, and a front contact of said neutral relay interposed in the connection of the winding of the neutral relay to said control circuit to release the neutral relay when the pole changer is operated.

7. In combination, a reversible electric motor, a direct current polarized relay provided with two windings, a direct current neutral relay provided with two windings, a pole changer for reversibly connecting a pair of control wires with a source of direct current, a first means to connect'one of the windings of said polarized relay across said control wires, a second means including pole changing front and back contacts of said neutral relay to connect the other winding of said polarized relay across said control wires, said windings of the polarized relay connected to aid when said neutral relay is released and to oppose each other when the neutral relay is picked up, motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of said polarized relay, a resistor having a positive temperature coefiicient interposed in said motor operating circuit means, means to connect one of the windings of said neutral relay across said resistor to pick up said neutral relay when the current flowing through said resistor exceeds a predetermined value and the potential drop across the resistor exceeds a given value, and means including a front contact of the neutral'relay to connect the other winding of said neutral relay across the control wires.

8. In combination, a reversible electric motor, a direct current polarized relay, a neutral relay, motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of said polarized relay, a pair of control wires, a pole changer for connecting a source of direct current with said control wires, means including a back contact of said neutral relay to connect a winding of the polarized relay across said control wires to reversibly energize the polarized relay for operating the motor in response to operation of said pole changer, a resistor interposed in said motor operating circuit means, means including a front neutral contact of the polarized relay to connect a winding of theneutral relay across said resistor for picking up said neutral relay in response to an overload current flowing in the motor operating circuit to deenergize the polarized relay and interrupt the motor operating circuit, and means including aback contact of the polarized relay and a front contact of the neutral relay to connect the winding of said neutral relay across said control wire to retain the motor operating circuit interrupted until the pole changer is operated.

9. In combination, a reversible electric motor, a direct current polarized relay, a neutral relay,

motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of said polarized relay, a pair of control wires, a pole changer for connecting a source of direct current with said control wires, means including a back contact of the neutral relay to connect a winding of the polarized relay across said control wires, a resistor having a positive temperature coefiicient interposed in the motor operating circuit means, means to connect, a winding of the neutral relay across said resistor including aback contact of the neutral relay and arranged to pick up said neutral relay when the voltage drop across said resistor exceeds a predetermined value for 'deienergi'zing said polarized relay to interrupt the motor operating circuit, and

means including a front contact of the neutral relay to connect its winding across said control wires to retain the motor operating circuit interrupted until the next operation of the pole changer.

10. In combination, a reversible electric motor, a direct current polarized relay, a neutral relay, motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of the polarized relay, a pair of control wires, a pole changer for connecting a source of direct current with said control wires, means including a back contact of the neutral relay to connect a winding of the polarized relay across said control wires, means controlled by the polarized relay when energized to associate a winding of theneutral relay with said motor operating circuit means to pick up the neutral relay when an overload current flows in the motor and deenergize the polarized relay to interrupt the overloaded motor circuit, other circuit means controlled by the polarized relay when deenergized to connect a winding of the neutral relay across the control wires to hold the overloaded motorcircuit open, and a front contact of the neutral relay interposed in said other circuit means to restore the relays by an operation of the pole changer.

11. In combination, a reversible electric motor, a direct currentpclarized relay, a neutral relay, motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of the polarized relay, a pair of con trol wires, a pole changer for connecting a source of direct current across the control wires, means including a back contact of the neutral relay to connect a winding of the polarized relay across said control wires for governing the polarized relay by operation of the polechanger, means including a back contact of the neutral relay to associate a winding of the neutral relay with the motor operating circuit means for picking up the neutral relay when an overload current flows in the motor for a predetermined interval, and a stick circuit for the neutral relay including the winding and a front contact of'the relay as well as said control wires and the pole changer.

12. In combination, a reversible electric motor, a direct current polarized relay, a neutral relay, a manually operable selector havinga firstand a second position and normally set at its first position, a control circuit including a pole changer and a pair of control wires, means including a contact of the selector closed at its first position and a back contact of the neutral relay to connect a winding of the polarized relay across said control wires to operatethe polarized relay by said pole changer, motor operating circuit means including normal and reverse polar contacts as well as a front neutral contact of thepolarized relay, a pick-up circuit to associate a winding of the neutral relay with the motor 'operatingicircuit means to pick up the neutralirelay in response'to an overload current flowing in' the motor'tolinterrupt such overloaded motor circ'uit by deenergizing the polarized relay, a stick circuitto connect the winding of the neutral relayacrossthe control wires to hold the overloaded" circuit open until the pole changer is nextoperated;*and other circuit means including a contact'of said selector closed at its second position to connect ,the winding of the neutral relay across the-controlwir es to hold the neutral relay energized by said stick "circuit and the polarized-relaydeenergized =sub'sequent to an operation of the selector to its second position and back to its first postion until the pole changer is Operated.

13. In combination, a current source, a pair of control wires, a pole changer for reversibly supplying current from said source to said wires at one end, a direct current polarized relay having a winding connected with the wires at said other end for reversibly energizing said relay, areversible electric motor having a normal and a reverse operating circuit controlled by said relay, a resistor having a positive temperature coefiicient common to both said motor circuits, a neutral relay having a winding connected across said resistor, said neutral relay adjusted to pick up only when a motor overload current flows through said resistor and the resistor heats up to increase its resistance so that the potential drop across the resistor exceeds a predetermined value, means including a contact of said neutral relay effective when the neutral relay is picked up to interrupt the overloaded motor circuit, and. a stick circuit for said neutral relay to connect a Winding of that relay across said control wires at said other end for holding said overload relay energized and to assure release of the overload relay when the pole changer is next operated.

CLAUDE M. HINES. BERNARD E. OHAGAN.

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