US2038463A - Railway traffic controlling system - Google Patents

Description

A fil'Zl, 1936. w. w. WENHOLZ ET AL RA IL'WAY TRAFFIC CONTROLLING SYSTEM Filed Nov. 221929 2 Sheets$heet 1 .6 w. on mfiuqwm IVE 225 2- 257 MATTORNEY A ril 21, 1936. w. w. WENHOLZ ET Al,

RAILWAY TRAFFIC CONTROLLING SYSTEM Filed Nov. 22, 1929 2 Shets-Sheet 2 l l I rllllll llllllll w. llllk xm. ll x9 WE 2 W Iv O0 m 7+ rvm 11L |u 4 9: m lib 1. u 3

E W44206 M ATTORNEY ZUZUZU Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE RAILWAY TRAFFIC CONTROLLING SYSTEM Application November 22, 1929, Serial No. 409,010

20 Claims.

This invention relates to approach locking means for protecting the operation of poweroperated switches, and more specifically to approach locking circuits for power-operated switch machines at the ends of passing sidings on single track railroads equipped with a centralized control or dispatching system.

Where a power-operated switch is operated under manual remote control, for reasons familiar to those skilled in the art, it is important to provide suitable means to prevent operation of the switch in the face of a train approaching at high speed, in order to avoid the possibility that such train will pass over the switch in the wrong position, or in midstroke, or unlocked. Such desired protection may be obtained by what is commonly known as approach locking circuits.

One object of the present invention is to provide a simplified and improved form of such approach locking circuits, particularly applicable to a switch at the end of a passing siding on a single track railroad, which will afford the desired protection and at the same time will not interfere with the operation of the switch by manual control at such times and under such conditions as such operation is safe and proper.

One characteristic feature of the invention is the protection. afforded against failure. of the approach locking control by the momentary loss of shunting of a track circuit, such as sometimes may happen during movement of a car or short train from one track section to another, or under similar conditions.

Another feature of the invention is an improved form of release control for the approach locking,

Various other characteristic features, functions,

and advantages of the invention will be in part apparent, and in part pointed out as the description progresses.

In the accompanying drawings, which illustrate one specific embodiment of the invention,

applied to the control of a power-operated switch at one end of a passing siding on a single track railway equipped with a centralized control or dispatching system, Fig. 1 illustrates in a diagrammatic and conventional manner, the relays and circuits constituting the approach locking arrangement of this invention, together with some of the relays associated therewith; and Fig. 2

-.shows the circuits for the control of the signals governing traffic over the switch equipped with the approach locking of this invention, together with the control of the switch repeater relay, the various relays, circuits, and other devices illustrated in Figs. 1 and 2, together with others not shown, being employed to constitute a complete system of centralized control for a power-operated switch provided with the approach locking of this invention.

Fig. 1 shows a passing siding PS and portions of the adjacent stretches of the main track. Signals IIA, and signals 2-2A-govern west-bound and east-bound trafiic, respectively, over the switch SW at the east end of the passing siding PS; and signals 33A, and 4-4A govern westbound and east-bound trafiic, respectively, over the switch SW| at the other end of the passing siding PS. The stretch of main track is divided by insulated joints in the usual way to form track sections, designated 5 to H inclusive, each provided with a track battery, or other source of current, designated B, and a track relay, designated 5T, 6T, etc. The track sections 6 and 8 include the switch points and part of the track rails of the siding, up to the fouling point, with suitable cross bonding, in accordance with wellknown practice, so as to provide the usual detector track circuits at these switches.

The switch at each end of the passing siding PS is assumed to be operated by a suitable switch machine, preferably of the electrical type, such as shown and described, for example, in the patent to W. K. Howe, No. 1,466,903, dated September 4, 1923. The control circuits for the switch machine at each end of the passing siding,

and the approach locking protection therefor, are

the same; and for simplicity, the invention has been shown applied to the switch SW at the east end of the passing siding PS, the switch machine for this switch being illustrated conventionally and designated SM. 0

In the specific embodiment shown, where the invention is applied to a switch of a centralized control or dispatching system, the switch machine SM for operating that switch, and the signals governing traffic over that switch, are controlled in some suitable manner by an operator or dispatcher at a distant point, subject to automatic control by track circuits; and for the purposes of explanation, it is assumed that the switch machine SM, and the signals IIA and 2-2A, governing traffic over the associated switch SW, will be controlled by the distant operatorby the energizatlon or de-energization of a neutral-polar relay Z over a line circuit.

As shown in Fig. 2, this control relay Z is connected by line wires I4 and i5, one of which is ordinarily a common wire extending throughout the system, to the contacts 26 and I! of a control lever LV in the dispatchers office, the movement of these contacts l5 and I! from the middle position shown to either extreme position causing energization of the relay Z with direct current of one polarity or the other, as will be obvious from the drawings.

Such energization of the control relay Z causes operation of the switch machine SM to move the switch SW to the normal or reverse position, subject to detector track circuit and approach locking control presently to be described, and also governs the clearing of the signals l-IA and 2-2A governing traflic over the switch, subject to track circuit control. Also, the energization of this control relay Z, in co-operation with a similar control relay at an adjacent siding end, acts through the agency of the absolutepermissive-block signal circuits, to control the direction of trafiic between sidings, dependent upon the sequence in which these control relays are energized, in the manner shown and described in detail in the application of S. N. Wight, Ser. No. 120,423, filed July 3, 1926; but since'these specific means for controlling the direction of trafi'lc, and other features characteristic of a complete system of dispatching, are immaterial to the present invention, or essential to an understanding thereof, although preferably used therewith in some form in certain applications of the invention, no attempt has been made to illustrate and describe these features.

For the purposes of explanation of the present invention, it may be assumed that the switch machine SM is governed'by the control relay Z in the simple way shown in Fig. l, the battery l9 providing operating or control current for the switch machine SM over normal and reverse wires 23 and 2|, depending upon the polarity of current by which the relay Z is energized providing the approach locking relay LP is energized to close its front contacts 22, these circuits involved being readily traced on the drawings.

The switch machine SM includes suitable point detector contacts PD, such as shown and described, for example, in the patent to C. S. Bushnell, No. 1,517,236, dated November 25, 1924. These point detector contacts PD are shown diagrammatically in Fig. 2 as comprising two contact members 23 and 24, movable from the normal position shown to a reverse position, to open and close circuits through pairs'of contacts 25, 26, 21, and 28. These point detector contacts PD also preferably include shunting contacts, comprising movable arms 23 and 33, and cooperating stationary contacts 3l and 32. When the switch points are over and locked in the normal position, contact members 23 and 24 engage the pairs of contact fingers 25 and 23, the shunt contacts 293l are closed, and the shunt contacts 39-32 are open, providing a circuit for energizing the switch repeater relay WP with current of one polarity, which may be readily traced from the battery 33 through the contacts 24-26 to the wire 34 leading to the relay WP, and from this relay over wire 35, shunting contacts 293i and contacts 23-25 to the other terminal of said battery. When the switch points are over and locked in the reverse position, contact members 23 and 24 engage the pairs of contacts 21 and 28, shunting contacts 33-32 are closed, and shunting-contacts 293| are open, thereby energizing the relay WP with reverse polarity, over a circuit which may be readily traced by analogy to the one above pointed out. While the switch machine and switch points are in mid-stroke or unlocked, the contact members 2324 are in an intermediate position, disconnecting the battery 33 from the relay WP, and the shunting. contacts 29-3I and 3832 are both closed, so. as to provide a closed circuit for the relay WP, preventing its energization by extraneous current that might be applied to it by crosses or grounds. The switch repeater relay 'WP is assumed to be of the neutral-polar type, having two neutral armatures 36 and 31, and two polar armatures 38 and 39.

Considering now the control circuits for the signals l|A, and 22A, and referring to Fig. 2, the signals I- |A, governing west-bound traffic over the switch SW, are governed jointly by a line relay IHD and individually by relays IG and IAG. Similarly, the signals 2-2A, governing east-bound traflic over the switch SW, are governed jointly by line relay 2HD and individually by relays 2G and ZAG.

The line relay 2HD corresponds to'the line relay used in the absolutepermissive-block signal system, and is controlled by the track relays in advance of the signals 2'-2A, and between these signals and the next signalin-advance, such as l2 (see Fig. 1) governing traflic in the same east-bound direction, and-also by the line relay of that advance signal, or a circuit controller operated thereby, so as to provide for the "caution indication, all in a manner dis'closedin the patent to S. N. Wight, No. 1,294,736, dated-February 18, 1919.

The other line relay ll-ID is similarly controlled by the track circuits in advance of the signals l! A, and in accordance with the indication of the advance signal 3; but for purpose of economizing in line wire and relays, this line relay lHD-is also provided with special control to adapt it for use in connection with the approach locking.

The complete control circuit for the relay lHD is shown in Fig. l, the letter C indicating connections to the usual signal common; and this circuit may be traced as follows:--starting at C, relay !HD, Wire 46, front contact 4! of track relay 1T, wire 42, back contact 43 of relay 3G, corre spending to relay 2G of Fig.2 and controlling signal 3, wire 44, battery 45, wire 4'6, and thence either through the front contact 41 of track relay 5T, wire 48 to wire 49, or over wire 50, front contact 5| of the lock relay L l, and wire 52 to the same wire 49, thence through the front contact 53 of track relay 5T, wires 54 and 55, back contact 55 of relay- 3G to C.

In connection with this circuit, it should be understood that the relay L-l is. the lock relay for the switch SW'!, and is controlled in the same way as the lock relay L for the switch-SW, as hereinafter explained. It should also be noted that the energization of the-relay 3G, through the pole changing action of its contacts 43-56, reverses the polarity of the connection between the battery 45 and the relay IHD, thereby providing control for causing the signal I to indicate clear or caution depending upon the indication of signal 3.

Referring to Fig. 2, the control circuits for the signals l-IA and 22A are similar, and an explanation of one will sufiice for both, it 'being noted that the signal 2A is arranged to give three indications, while the signal IA, corresponding to the lower arm of an interlocking signal, merely gives two-indications. These signals are assumed to be of the color-light type, although semaphore signals, or signals of any other suitable type may, of course, be used. The circuits for lighting the lamps of these color-light signals are shown in dotted lines terminating at BX and OK; and it will be noted that, when the relay IG is deenergized, it closes a circuit for lighting the red lampto give a stop indication, and when energized, permits current to be supplied to the green or yellow lamps, giving clear or caution indications, depending upon the position of the polar armature 51 of the line relay IHD. Similarly, when the relay IAG is de-energized, the signal IA gives a stopindication, and when energized, gives a low speed proceed indication.

The energizing circuit for the relay IG may be traced (see Fig. 2) from relay IG, wire 69, front contact 6| of the detector track relay 8T, wire 62, front contact 63 of line relay IHD, wires 64 and. 65, polar contact 38 of the switch repeater relay WP to the right, corresponding with the switch SW normal, wire 66, polar contact 61 of the control relay Z to the right, wire 68, neutral contact 69 of relay Z, wire I0, and neutral contact 31 of relay WP, to The relay IAG has a similar energizing circuit through the other polar contact 39 of the relay WP, but does not include a front contact of the line relay IHD.

From these circuits, it can be seen that, when the control relay Z is energized with one polarity, it causes the switch SW to assume its normal position, and when the relay WP indicates that the switch points are actually in that position, the relay IG may be energized to clear signal I, subject to the usual block signal control of the line relay IHD; whereas if the control relay Z is energized with the opposite polarity, and the switch is in the reverse position, the signal I indicates stop and the signal IA is cleared to permit a slow speed movement onto the siding.

It should perhaps be explained that the signal control circuits, as shown in Fig. 2, would apparently provide for the clearing of opposite signals I and 2 at the same time, the energizing circuits for the relays IG and 2G being connected together, but it should be understood that the line relays IHD and ZHD are suitably controlled, as disclosed in the Wight application, Ser. No. 120,423, above mentioned, so that only one of these line relays is energized at a time, depending upon the sequence of operation of the control levers associated with adjacent ends of the passing sidings.

Considering now the approach locking circuits constituting the present invention, and referring to Fig. 1, the relay LP, which must be energized to permit operation of the switch machine SM, is controlled by the front contact 'II of the detector track relay 8T and the front contact 92 of a lock relay L, so that unless, the lock relay L is energized, and the detector track circuit is also unoccupied, the switch machine cannot be operated. The present invention deals more particularly with the control circuits for the lock relay L.

This lock relay L is a stick relay and when once energized by some one of its pick-up circuits, hereinafter pointed out, it is maintained energized by a stick circuit which may be traced front contact I3 of relay L, wires 14, I5 and 16, relay L, wires 11 and 18, back contact I9 of relayIAG, wire 80, back contact 8| of relay IG, wire 82, back contact 83 of relay ZAG, wire 84 and back contact 85 of relay 2G to Thus, once the lock relay L is energized, it is maintained energized so long as the signals I-IA-, and 22A, governing traffic over the switch SW, are held at. stop. Under such conditions, it is permissible to operate the switch SW, since any train approaching the switch on the main track will receive acaution indication, and will come to a stop.' Whenever one of these signals is cleared by the dispatcher, however, the lock relay L is de-energized, and operation of the switch is prevented, until all of these signals again assume the stop condition to block train movement over the switch. a.

' Since the dispatcher, after clearing one of the signals I-IA or 2-2A, may at any time thereafter put this signal back to stop, it is necessary to prevent re-energization of the lock relay Lin sucha case, unless or until it is assured that no train is approaching the switch in obedience to the previous received clear indication, and consequently may not have time to stop before reaching the switch and would encounter the switch in mid-stroke or unlocked.

If there is no such train approaching the switch in either direction, it will be evident that it is proper to permit re-energization of the lock relay L; and for this purpose the line relay I-HD and an approach relay A are employed in connection with the control of the relay L. The circuit for the approach relay A may be traced from relay A, wire 86, front contact 81 of track relay 9T, wire 88, front contact 89 of track relay IOT, wire 90, front contact 9| of track relay IIT, to Thus, if there is a west-bound train in either of the track sections 9 or II], which may have passed the signal I3 indicating proceed, or if there is a west-bound train in the track section II, which may be about to pass a signal I3, the approach relay A is de-energized. Similarly,

- from the control circuit for the line relay IHD hereinbefore traced, it can be seen that if there is aneast-bound trainin the section 5 approaching the switch SW under similar conditions, the relay L-I is de-energized if the signals 4 and 4A are cleared to permit such train to advance, and the relay IHD is de-energized. In this connection it is of course understood that the relay L-I is controlled by its associated relays and signals in the same way as is the relay L controlled by its associated relays and signals.

One of the pick-up circuits for the lock relay L, for permitting re-energizationthereof, is controlled by a suitable time element device TE,

which may be of any suitable construction, but

as shown is of the thermal element type, comconstruction, provided with a heating coil 95, and adapted to engage another contact finger 96, after the lapse of a predetermined time, such as (15 to 20) seconds, following the application of current to the heating coil 95. Such a time element device of thermal type is disclosed in the patent of S. N. Wight, Pat. No. 1,856,045, granted April 26, 1932.

Assuming now that the lock relay L has been de-energized by the clearing of one of the signals I, IA, 2 or 2A, and that the operator has caused the signal cleared to assume again its stop indication, and further assuming that there is no train approaching the switch SW, so that the approach ZAG, IG, and IAG, with the connecting wirespointed out, wire 91, back contact 98 of relay L, Wire 99., coil 95, wire I00, front contact IOI of a detector track circuit repeater relay 8TP, wire I02, front contact I03 of relay A, wires I04 and I05, and front contact I06 of relay IHD to Current flowingin this circuit heats the coil 95, and after the lapse of a suitable time interval, which may be assumed to be approximately (15 to 20) seconds, the contacts 94-96 of the time element device TE are closed, whereupon a pickup circuit for the relay L is established through the back contacts of signal control relays 2G, ZAG, IG and IAG, through the relay L, wires I6 and I01, contacts 94-96 of the time element device TE, and through the front contacts IOI, I03 and I06 of the relays BTP, A and IHD.

The time interval provided by the time element device TE, in the embodiment of the invention shown, performs two different functions. It will be noted that, even if the relays 8TP, A and IHD should be energized at the time the operator caused a clear signal to assume the stop position, the relay L is not at once re-energized, but only after the lapse of the time interval provided by the device TE. This assures-that any east-bound train on the siding PS, which is ordinarily not equipped with track circuits,,will have time to stop or advance into the detector track section 8, whereupon operation of the switch is directly prevented by de-energization of the relay LP, after the signal 2A is put to stop by the operator, if such train should happen to be in such position as to be making a low speed movement over the switch in obedience to a proceed indication of the signal 2A. In other words, the time element device TE provides time release for the approach looking to take care of the train movement 01f of the siding.

Another function of the time element device TE is to prevent energization of the lock relay L, in the event that either the approach relay A or the line relay IHD, while de-energized by an approaching train, should be momentarily picked up, due to the temporary loss of shunting of the track circuits, for any cause, as for example, due to the picking up of one track relay before the dropping of adjacent track relay by a short high-speed train or car. In other words, if an approaching car or train, which should maintain the lock relay L de-energized, should momentarily fail to keep the relays A, I I-ID de-energized, on account of the operating limitations of track circuits, the time element device TE affords the desired protection by preventing immediate response of the relay L. In this connection, it should be understood that the time interval for this purpose may ordinarily be much less than the time interval required to protect a train movement off of the siding; so that if desired, separate time element devices, with different time intervals of operation, may be employed to perform these two difierent functions; but it is preferred to employ a single time element device, as shown, since a reasonable delay in the re-energization of the lock relay L does not interfere with practicable operation.

Considering now the case of normal train movements, where a signal has been cleared by the operator and is left in that condition until a train has passed the switch and then returned to the stop position, the lock relay L is energized by another pick-up circuit which may be traced through the back contacts of the signal control relays 2G, etc., through the relay L, wires I6, I5, H0, through the back contact IOI of thedetector track circuit repeater relay BTP, wire I02, back contact I03 of approach relay A, wire III, another back contact II2 of relay 8TP, wires IZO-and I I3 (assuming switch normal), and-back contact I06 of line relay IHD, to If the switch is in'the reverse position, this pick-up circuit is over wires I20 and H4, polar contact II5 of the switch repeater relay WP in reverse position, wires H6 and I05, and front contact I06 of the line relay IHD. There is still another pickup circuit for relay L, which includes the back contact IilI of relay BTP and wire I'I0, but this circuit is more fully traced hereinafter.

To appreciate the significance of the control of this pick up circuit just traced, and the conditions under which it is established, assume a westbound train movement, with the switch SW in the normal position. This west-bound train de-energizes approach relay A, closing its back contact I03, and when this train enters the detector track circuit 8, it shunts the detector track relay 8T and in turn drops the repeater relay 8TP, closing its back contact I I2. As the train further advances and enters the track section I, the line relay IHD is de-energized, whereupon the complete pick-up circuit for the relay L is established.

If the switch SW is in the reverse position, the west-bound train would pass onto: the siding, and would not enter the track section I, so that the pick-up circuit for the relay L in this case is through the front contact I06 of the relay I HD, and includes the polar contact II5 of the relay WP.

An east-bound train on the main track establishes the pick-up circuit for the relay L, when it enters the track section 9, in the same way as a West-bound train, this because with relays 8'1? and IHD deenergized the relay A must also be deenergized to complete the pickup circuit for relay L. An east-bound train from the siding picks up the relay L through the back contact I9I of the relay BTP and the front contacts of the relays A and IHD, as soon as this train enters the detector track section 8, it being noted that such release will occur only if there is no other train within the approach locking limits in both directions, but will occur if there is a train in each of these approach sections at the same time, that is, with relays 8TP, A and IHD all down, and this is a safe condition for reasons given below.

It can be seen that this pick-up circuit for the relay L with an east-bound train on the main track is dependent upon the shunting of two or more track relays. This is done in order to avoid a possible unsafe condition by improper release of the approach locking, in the event that one track relay, such as the detector track relay 8T, should for some reason be shunted while there is a train within only one of the approach locking limits. For example, if the release of the approach locking were dependent only upon the shunting of the detector track relay 8T, it might happen that, While a train was approaching, 'this track relay would be shunted for some reason, as for instance, by a maintainer Working on the system; and the operator, believing that such accidental shunting of the detector track relay meant the arrival of the expected train, might change his control lever to operate the switch in the face of the approaching train. After a little consideration, it willbe appreciated that such an unsafe condition is obviated by making the re-energi'zation of the lock relay L dependent upon simulof circuits and devices shown and described is taneous shunting of a plurality of different track circuits.

In the case of a long train as above assumed, the track relays IT and 8T and 9T are simultaneously shunted to provide the pick-up circuit for the relay L, following change of the cleared signal toits stop condition upon entrance of the train into the track section 8. In the case of a single car, or a train shorter than the length of the detector track section, the relay L is picked up through the back contact IOI of the detector track circuit repeater relay 8TP and the front contacts I03 and I06 of the relays A and IHD. If the train should happen to be of such lengthand travelling at such a speed, that the relay IHD is dropping at the same instant the relay A is picking up, so that these relays A and IHD are not both either picked up or dropped at the same time, long enough to energize the relay L, then the desired release of the approach locking will not take place, but this combination of train length and speed is very remote and so rarely occurs in practice, it is found, that there is no practical limita tion imposed upon the operation.

In connection with this feature of re-energizing the relayL by a plurality of track circuits, it should perhaps be explained that, with a train on the track section I de-energizing the relay I I-ID,

and a west-bround train approaching the switch SW and de-energizing the approach relay A, dropping of the detector track circuit repeater relay 8'I'P under these conditions would energize the relay L, and might appear to cause an unsafe condition; but in this case, the train on the track section 1 holds at stop the signal I, and the west-bound train in question would receive at the signal l3 a caution indication, with this signal I at stop or with the signal IA cleared and consequently would be approaching the switch prepared to stop. Consequently, while in this particular case the relay L would be energized by accidental or improper shunting of the detector track relay 8T, this would take place under such conditions of train position and train movement that no train would be approaching at high speed. To provide for an emergency release of the approach locking, a contact l2| is preferably provided to close a circuit from over wires Ill and 16, to the relay L, and thence through the back contacts of the signal control relays 2G, etc., the same as if a train had passed the detector track section, or a time interval had elapsed. This contact I2l may be a push-button 01' hand switch, suitably housed and protected, or a contact on the dual control selector, which may be applied to the switch, in accordance with the disclosure of the patent of W. K. Howe, Pat. No. 1,852,573, granted April 5, 1932. It should be understood that this contact l2l isonly closed by a trainman at the switch, under the instruction andsupervision of the operator, who is in telephone communication with'the' siding in the usual way.

From the foregoing, it can be seen that there is provided by this invention a relatively simple and eflicient arrangement of circuits, relays and a time element device for affording the desired approach locking protection for a power operated switch, without interfering with the operators control of the switch at all times when safety permits, and at the same time affording a high degree of protection against improper operation due to unexpected or improper shunting of track relays.

- The particular combination and arrangement merely typical or illustrative-of one embodiment of the invention, and its application to one type susceptible of various modifications, adaptations,

and additions, without departing from the invention.

What we claim is:

1. In a system of approach looking for poweroperated switches, signals governing trafiic over the switch, a stick relay acting when de-energized to prevent operation of 'said'switch, a time element device having a circuit controller closed after the lapse of a predetermined time, contacts opened by a train approaching the switch, and a pick-up circuit for said relay including said circuit controller'and said contacts in series, said time element device being set into operation only if said signals indicate stop and said train governed contacts are closed.

2. In a system of approach looking, a stick lock relay, a detector track relay, approach relays respectively de-energized by a train approaching the switch from opposite directions, and a pick-up circuit for said stick relay including in series back contacts of said: detector track relay and of said approach relays.

3. A system of approach locking comprising, a lock relay, a detector track relay, two contacts separately closed by a train on opposite sides of the track section in which said detector track relay is located, and an energizing circuit for said lock relay including in series said two contacts and a back contact of said detector track relay.

4. In a system for protecting the operation of a power-operated track switch, the combination with a lock relay governing the operation of the switch, signals governing trafiic over the switch, three adjacent track circuitsassociated with said track switch, a stick circuit for said relay closed when said signals indicate stop, and a pick-up circuit for said relay closed after a predetermined time only if said signals indicate stop and three adjacent track circuits are simultaneously unfrom one direction and the other if deenergized manifesting the approach from the other direction, a circuit for said lock relay including front contacts of said detector track relay and front contacts of both of said approach relays in series, and another circuit for'said lock relay including back contacts of said detector track relay and back contacts of both ofsaid approach relays in series.

6. In a system of approach locking of the type described, the combination with a power-operated switch and manual control means for the switch, of a lock relay, a detector track relay associated with said switch, two approach relays one if deenergized manifesting the approach of a train from one direction and the other if deenergized manifesting the approach from the other direction, and means for energizing said lock relay requiring said detector and approach relays to 7; In a system. of approach locking of the typetherefor deenergized by a train approaching said i switch; a signal associated with said switch; and

for said stickrelayincluding in series acontact closed when said signal is at stop, a back contact of said detector track relay and back contacts of saidapp-roach relays.

9. In a system for protecting the-operationof a power-operated track switch; the combination with a stick lock relay governing the operation-of such switch; signals governing traffic over such switch; three adjacent track circuits associated with said switch and said signals; a stick circuit ior 'said relay closed when'said signals indicate stop; and a pick-up circuitfor said-relay closed by said signals indicating stop and-three adjacent track circuits simultaneously, occupied.

10. In a system for protecting the operation of a power-operated track switch; the .-combination with a :lock relay governing theroperation of such switch,- signals governing traiiiciover such switch,

three'adjacent track circuits associated with said switch and saidsignals; astick circuit for said relay closed when said signals indicate stopga pickup circuit forsaid relay closed' aftera-time only if said signals indicate stop and the middle one of said'three adjacent track-circuits -is-unoccupied and'theother-two track circuits. are also urr-- occupied, andv another pick up" circuit forsaid relay closed if said signals'indicate stop and-the:-

middle oneof said three adjacent track circuits is occupied and the other two track-circuits are unoccupied, saidanother pickup circuit actingwithout a time delay.

11-. Ina system for protectingrthe operation of a power-operated track switch, the combination with a lock relay governing the operation of such switch, signalsgoverning trafii'c: over such switch;

three adjacent track circuits associated with said switch and said signals;'a stick circuit for'said relay closed when said signalsindicate stop anda pick-up circuit-for-said relay closed if said Sig'-' nals-indicate stop and the middle oneof said three adjacenttrack circuits is occupied and the other two of said adjacenttrack circuits are unoccupied.

12.111 a system for-protecting the opera-tion' 'ot power-operated switches the: combination-with a lock relay'governing the operation ofasuclr switch;-a signal governing traffic over: such switch; a detector track section; an'approach' track section for said signal; a stick circuit for said relay'closed when said signals indicate stop; and a pick-up circuit for-said relay closed said signals indicate stop, said power-operated switch assumes the reverse position'and said detector track section associated with said switch and saidapproachqtrack section are bothoccupied;

13. In. combination, a main section of railwaytrack containinga switch, an approach section, a

track'circuit including a track relay for each section, a signal for-governing traffic into said main section, an approach locking relayfor the control of said switch, a slow-acting device having an energizing winding and a normally open contact,

described; the'combination with a power-oper atedswitch and a lock relay governing the operation of said switch; an approach relay means track containingra switch, an approach'section,

a track circuit including a track relay for each section, a signal for governing traffic into saidmain section, an approach locking relay for the control of said switch, a slow-acting device having an energizing winding and a normally open contact, means for energizing the winding of said slow-acting device when said signal indicates stop if and only if said approach locking relay is deenergized and the track relay for said main section is energized, and means for controlling said approach locking relay by said track relays by the contactof said-slow-acting device and by a contact reflecting; the indicating condition of said signal 15. In combination,--a-main section of railway track containing a switch, a track circuit including astrack relay for-said section, a'signal for governing traflic into said main section, an ap-' proach locking relay for the control of said switch, a slow-acting device having an energizing winding and a normally open contact, means for energizing the winding of said slow-acting device when said signalindicates stop if and-only if said approach locking relay is deenergized and the track'relay for said main section'is energized,

and an energizing circuit for said approach lock- I ing relay including a contact closed when said slow acting device is energized and a contact closed when said signal is at'stop.

16. In combination; a power operated track switch; approach track sections on opposite ends of said track switch; a stick lock relay for, when deenergized, preventing power operation of said track switch; signals for governing the movement of traific over said track switch; and two pick-up circuits for said stick relay, one out which is closedonly if all saidsignals are at stop and both-of said'approachsections are occupied, and the other o-f'which is closed only if all of said signals-iare at stop and both of said approach sections are unoccupied..-

1'7. In combination; a power operated track switch; approach track sections on opposite ends ofsaidtrack switch;a stick lock relay for when deenergized preventing power operation of said track switch; signals -f or governing the movement of trafiic over said track switch; two pick-up circuits for said-stick relay, one of which is closed only if all said signals are at stop and both of said approach sections are occupied, and the other of whichis closedonly if, all of said signals are at stop and both-of said approach sections are un-: occupied; and a stick .circuitfor said stick relay closed only if all of said signals are at stop.

18. In combination; a power operated track switch; approach track sections on opposite ends of said track switch; a stick lock relay for when deenergized preventing power operation of said track switch; signals for governing the movement of traffic over said track switch; two pick-up circuits for said stick relay, one of which'is closed only if all said signals are at stop and both of said approach sections are occupied, and the other of whichis closed only if. all of said signals are at stop and both of said approach sections are unoccupied; another pick-upcircuit for said stick relay closed only if a detector track circuit associated with said track switch is occupied and said signals are at stop; and a stick circuit for said stick relay closed only if all of said signals are at stop.

19. In combination; a power operated track switch; approach track sections on opposite ends of said track switch; a stick lock relayforwhen deenergized preventing power operation of saidtrack switch; signals for governing the movement of trafilc over said track switch; and two pick-up circuits for said stick relay, one of which is closed only if all said signals are at stop and both of said approach sections are occupied, and the other of which is closed only if. all of said signals are at stop and both of said approach sections are unoccupied; and another pick-up circuit for said stick relay closed only if one of said approach sections is occupied and the other is unoccupied providing said track switch assumes the reverse position.

20. In combination; a power operated track switch; approach track sections on opposite ends of said track switch; a stick lock relay for when deenergized preventing power operation of said track switch; signals for governing the movement of traffic over said track switch; two pick-up circuits for said stick relay, one of which is closed only if all said signals are at stop and both of said approach sections are occupied, and the other of which is closed only if; all of said signals are at stop and both of said approach sections are unoccupied; another pick-up circuit for said stick relay closed only if one of said approach sections is occupied and the other is unoccupied providing said track switch assumes the reverse position, and a stick circuit for said stick relay closed only if all of said signals are at stop.

WALTER W. WENHOLZ. CARL I. DE LONG.

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