US2407232A - Impulse actuated timing means - Google Patents

Description

Sept. 10, 1946.

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INVENTOR HIS ATTORNEY Patented Sept. 10, 1946 UNITED STATES iPATENT OFFICE IMPULSE ACTUATED TIMING MEANS of Pennsylvania Application July 14, 1943, Serial No. 494,753

4 Claims. 1

My invention relates to impulse actuated timing means.

In certain forms of railway signaling systems such for example as that shown and described in an application for Letters Patent of the United States, Serial No. 452,894, filed by F. H. Nicholson and C. E. Staples on July 30, 1942, one signal indication is provided by means of a standard code consisting of regularly recurring code cycles each consisting of a current pulse followed by an off interval of the same duration as the current pulse in which interval the supply of current is interrupted, and another indication is provided by a modification of this code in which a code cycle is modulated at regularly recurring intervals usually by shortening the off time and lengthening the on time the same amount that the off time is shortened.

One object of my invention is to provide improved timing means capable of distinguishing between the modulated and regular code cycles in a signaling system of the type above-described.

Another object of my invention i to provide improved timing means including a highly damped resonant circuit, and a relay which will pick up and subsequently release in response to the first half cycle of each train of current oscillations set up in said oscillating circuit and will thereafter remain released.

A further object of my invention is to provide improved timing means including a relay the release time of which is substantially unaffected by changes in temperature or voltage, and which relay is immune to rectifier ripple.

Timing means embodying my invention are an improvement upon that shown and described in an application for Letters Patent of the United States, Serial No. 452,902, filed by Carl Volz on July 30, 1942, for Code detecting means.

According to my invention, I supply energy to I.

a highly damped oscillating circuit including the primary winding of a transformer, over a contact of a code following relay, and I supply the energy which is induced in the secondary windin of said transformer by the oscillatin current flowing in said primary winding, to a timing relay which will respond to current of one polarity only, the parts being so proportioned and so arranged that said timing relay will pick up and release in response to the first half cycle of said induced lease control relay jointly by a contact of said code following relay and a contact of said timing relay in such manner that saidcontrol relay will pick up the first time the above referred to modulated code cycle is supplied to said code following relay and will subsequently remain picked up as long as said modulated code cycle continues to be. supplied to said code following relay at regularly recurring intervals.

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

In the accompanying drawing, Fig. 1 is a diagrammatic view showing one form of timing means embodying my invention applied to a portion of a coded signaling system for railways for distinguishing between two codes used for obtaining two different signal indications. Figs. 2 and 3 are diagrammatic views illustrating two code patterns of the type between which timing means embodying my invention are capable of distinguishing. Fig. 4 is a diagrammatic view showing the energy impulses to which the timing relay of my invention responds.

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

Referring first to Fig. 1, the reference character TR designates a relay which is at times supplied with coded signaling current of the type shown in Fig. 2 and at other times with coded signaling current of the type shown in Fig. 3. As shown in Fig. 2, the signaling current consists of recurring code cycles each having an equal on and off time, while as shown in Fig. 3, the signaling current consists of a code pattern made up of a predetermined number of code cycles each similar to the cycles of the current shown in Fig. 2, followed by a modulated cycle formed usually by shortening the off time and lengthening the on time of the normal cycle, although the modulated cycle might equally well be formed by shortening the off time and lengthening the on time. The number of code cycles per minute may be varied as conditions require, the particular code shown consisting of 75 cycles per minute, so that each cycle is of .8 second duration. In the code shown in Fig. 3, a modulated cycle occurs every third cycle, and consists of an off period of approximately onethird the length of the 01f period of a normal cycle followed by an on period of approximately one and two-thirds the normal period. The above described codes are standard codes in widespread commercial use in railway signaling systems wherein they are usually referred to respectively as the '75 and 75M codes. A complete signaling system employing these codes is described and claimed in the above referred to Nicholson and Staple application Serial No. 452,894, and also in the above referred to Volz application, Serial No. 452,902, wherein the track relay IZTR corresponds to the herein designated relay TR. The signaling current is usually obtained by interrupting 100 cycle alternating current by means of contacts which open and close the circuit for the proper time intervals, and supplying the resulting interrupted current to the relay through a full wave rectifier. Inasmuch as the source of the coded current is immaterial to my present invention, it is deemed unnecessary to describe it herein.

Associated with the code following relay TR are timing means comprising a timing unit TU and a timing relay TRA,

The timing unit TU includes a transformer TA and a condenser Q. The condenser Q is connected across the terminals of the primary winding l of transformer TA to form an oscillating circuit for a purpose which will appear presently, and this circuit is arranged to be supplied with energizing current when the relay TR is picked up and the relay IRA is released over an energizing or exciting circuit which passes from one ter minal B of a suitable source of direct current not shown in the drawing through front contact 3 of relay TR, a wire 4, a back contact 5 of relay TRA and thence through the upper portion of primary winding I, in multiple with condenser and the lower portion of primary winding 1 in series, to the other terminal of the same source.

The secondary winding 2 of transformer TA is included in an energizing circuit for relay TRA. This circuit becomes closed whenever relay TR closes its back contact 6, and may be traced from terminal C of the source through secondary winding 2, back contact 6 of relay TR and the winding of relay TRA back to terminal C. It will be noted that when this circuit is closed, the sec ondary winding 2 and the winding of relay TRA are connected in series so that any current which flows in secondary winding 2 will be supplied to the winding of relay TRA.

The relay TRA is also provided with a stick circuit which becomes closed when relays TR and TRA are both picked up, and which passes from Y terminal B through front contact 3 of relay TR, wire 4, front contact 5 of relay IRA, and the winding of relay TRA to terminal C. For reasons which will appear presently the relay TRA is of a quick acting type which will respond to current of one polarity only, and the relay is connected in the stick circuit just traced in such manner that when this circuit is closed the relay will be supplied with current of the polarity to which it responds. It will be seen, therefore, that if relay TRA is picked up when front contact 3 of relay TR becomes closed, it will subsequently be held in its picked-up position until front contact 3 subsequently opens.

The relays TR and TRA jointly control a slow releasing relay HB by virtue of a circuit which becomes closed when and only when relays TR and TRA are both picked up, and which passes from terminal B through front contact 3 of relay TR, wire 4, front contact 5 of relay TRA, front contact 6 of relay TR and the winding of relay HR to terminal C. Relay HE is made sufficiently slow releasing so that when it becomes deenergized it will retain its front contacts closed for a time interval slightly longer than that which oocurs between the long on periods of the 75M code. The reason for this will be made clear presently.

The parts are shown in the positions they assume when the relay TR is being supplied with the 75M code. The relay TR is so constructed that its contacts will follow the alternate on and off times of either the '75 or 75M code, and each time relay TR closes its front contact 3 in response to the on period of the 75M code, if back contact 5 of relay TRA is then closed as will be the case if the on period is of normal duration, energizing current will be supplied to the oscillating circuit comprising the condenser Q and primary winding I of transformer TA. A part of this energizing current will flow through the upper portion of primary winding l, and the remainder of this current will flow through the condenser Q and lower portion of primary winding I in series. The upper portion of the primary winding l is preferably formed of a relatively few turns of low resistance so that the current can build up in this portion sufficiently quickly to insure that the transformer core will become saturated with flux during the brief interval of time that the contact 3 remains closed irrespective of any variations in voltage which may be expected to occur in the current source from which energy is supplied to the oscillating circuit, while the lower portion of the primary winding is preferably formed of a relatively large number of turns of fine wire so that this portion of the winding does not take up much core space yet has a sufiiciently high inductance to enable the oscillating circuit to be tuned to resonance at the desired frequency with a condenser of relatively small capacity.

On the supply of energy to the primary winding i an electromotive force is induced in the secondary winding 2, but no current flows since the circuit for relay TRA including secondary winding 2 is then open at back contact 8 of track relay TR.

When track relay releases following an on time of normal length the resultant opening of front contact 3 of relay TR interrupts the exciting circuit which was previously closed at this contact while the resultant closing of back contact 6 of this relay completes the previously traced energizing circuit for relay TRA. As soon as the exciting circuit for the oscillating circuit is interrupted, the flux in the core of transformer TA starts to decay and condenser Q starts to discharge through the primary winding. The collapse of the flux in the transformer core and the discharge of the condenser through the transformer primary winding causes oscillations to be set up in the oscillating circuit formed by condenser Q and the primary winding, and these oscillations in turn cause an oscillating electromotive force to be induced in the secondary winding 2 of transformer TA.

It i obvious that each time relay TR releases a brief interval of time will elapse between the opening of its front contacts and the closing of its back contact, and it follows, therefore, that the electromotive force which is induced in secondary winding 2 due to the opening of contact 3 will not cause any current to be supplied to relay TRA during the brief interval of time between the opening of contact 3 and the closing of back contact 6.

However, as soon as back contact 6 closes, this electromotive force will then cause current to be supplied to relay TRA. A was previously pointed out, relay IRA is of a quick actin type which will respond to current of one polarity only, and the parts are so proportioned and relay TRA is connected in its energizing circuit in such manner that it will pick up and release in response.

to the first half cycle of this current, which half cycle for purposes of explanation I shall assume to be positive. The second half cycle of current supplied to relay TRA will of course be negative, and since relay TRA will only pick up on current of positive polarity, it will not respond to this half cycle. The next half cycle will again be a positive half cycle but the oscillating circuit is so highly damped that any current which flows during the third half cycle will not have sufficient magnitude to cause relay TRA to again pick up.

The parts are so proportioned that when relay TRA once picks up, it will remain picked up for a period of time which is longer than the short off period in the 75M code but which is shorter than the off periods of the normal code cycles in either the 75M or '75 code.

It will be seen, therefore, that when the release period in the code during which relay TRA becomes energized is the short off period in the 75M code, the front contact 5 of this relay will still be picked up when track relay TR next closes its front contacts. Under these conditions, the closing of front contact 3 of relay TR will not complete the energizing circuit for the oscillating circuit because this energizing circuit will then be open at back contact 5 of relay TRA, but the closing of contact 3 will complete the previously traced stick circuit for relay TRA includin front contact 5 of relay TRA, and also the previously traced energizing circuit for relay I-IB including front contact 5 of relay TRA and front contact 6 of track relay TR. The energy supplied to track relay TRA over its stick circuit keeps this relay energized during the long on period following the short off period, and since the circuit for relay HB remains closed as long a relays TR and TRA are both picked up, it follows that relay HB will be supplied with energizing current throughout the long on period which follows the short off period in the modulated code cycle. The closing of the energizing circuit for relay I-IB causes this relay to pick up if it is not already picked up, and, due to the slow release characteristics of relay HB pointed out previously, when relay HB once becomes picked up it will retain its front contacts closed for a time interval which is slightly longer than the intervals between the long on periods in the 75 code.

On release of track relay TR followin each long on period in the 75M code, contact 3 will interrupt both the stick circuit for relay TRA and the energizing circuit for relay HB, while the opening of front contact 6 of relay TR will additionally interrupt the energizing circuit for relay HB. A soon as the stick circuit for relay TRA becomes interrupted, this relay will release, but relay HB will remain picked up even though its energizing circuit is then interrupted for the reasons pointed out in the preceding paragraph.

When back contact 5 of relay TR becomes closed following the long on period in the 75M code, it again completes the energizing circuit for relay TRA, but inasmuch as energy was not supplied to the oscillating circuit during the preceding picked-up period of relay TR, no energy is present in the timing unit, and relay TRA therefore remains released.

When relay TR picks up in response to the first on period of the code following the long on period, back contact 5 of relay TRA will be closed, and the closing of front contact 3 of relay TR will therefore again complete the exciting circuit for the oscillating circuit to again store energy in this latter circuit. Accordingly on the subsequent off period of the code, relay TRA will again pick up. However, this relay Will release before the end of this 0 r period, so that during the next picked-up period of relay TR energy will be again stored in the timing unit TU.

The next off period in the code will be the short off period, and when track relay TR releases due to this off period, the stored energy in the timing unit will pick up relay TRA. Due to the short off period, relay TRA will still be picked up when relay TR next picks up due to the long on period, and relay HB will therefore again be supplied with energy to maintain it in its picked-up position.

It will be seen, therefore, from the foregoing that when relay TR is being supplied with the 75M code, energy will be stored in the timing unit TU during each on? period of normal length, and will be supplied to the relay TRA during the succeeding off period. The energy supplied to relay TRA will cause this relay to pick up and again release at the expiration of a time interval which, as will be described presently, depends upon the frequency of the oscillating current induced in the secondary winding 2 of transformer TA, and which frequency is so chosen that the relay will maintain its front con-- tact closed during the short off periods in the code but will open its front contact and close its back contact in a time interval which is less than the duration of the off period of normal length. Accordingly, each time the relay TR closes its front contacts following a short 01f period in the 75M code, the contacts of relay TRA will still be picked up, and the picking up of relay TR under these conditions will complete both the stick circuit for relay TRA and the energizing circuit for relay HB. However, each time the relay TR closes its contacts following an off period of normal length, relay TRA will be released, and no energy will be supplied to either relay TRA or relay HB during the next on period in the code, but energy will be supplied to the timing unit TU to cause relay TRA to pick up during the next off period. he energy supplied to relay BB is supplied throughout the long on period in the code, and is of sufficient magnitude to cause it to remain picked up until the next long on period occurs.

When 75 code is supplied to relay TR, relay TRA picks up during each on period and releases during the next off period, and since relay TRA is always released when relay TR picks up, the energizing circuit for relay HE remains open at front contact 5 of relay TRA. Relay HB therefore remains released under these condi-- tions.

It will be apparent, therefore, that relay HB will be picked up when 75M code is being supplied to relay TR, and will be released when '75 code is being supplied to this relay. It will also be apparent that the picking up of relay HB depends upon the release time of relay TRA, and that it is therefore necessary that this release time should insofar as possible be independent of changes in the voltage of the source B-C or changes in ambient temperature. The release time of relay TRA depends for the most part on the frequency of the energy impulse supplied thereto and is independent of the magnitude or this current. This can best be seen from an examination of Fig. 4 which is a diagram illustrating the energy impulses which are supplied to relay TRA from the timing unit. Referring to Fig. 4, it will be seen that as soon as back contact 8 of relay TR closes, current having a magnitude considerably greater than the pickup current of relay TRA is supplied thereto. This is due to the fact that the oscillating electromotive force which gives rise to this current starts to build up in secondary winding 2 when front contact 3 of relay TR opens, and as a result by the time back contact 6 closes, this electromotive force has already reached a relatively high value. The relay TRA being quick acting responds quickly to this impulse, although the relay can pick up at any time while the current in the impulse remains above the pick-up current of the relay, and this time is more than adequate to insure adequate response of th relay even though the magnitude of the current should decrease considerably below that shown. However, the magn tude of the current is not likely to decrease to any great extent because the transformer TA is so designed that its core will become saturated at a voltage of the source BC considerably below that likely to be encountered in practice, and the energy stored in the transformer is therefore substantially constant regardless of voltage variation. Some of the energy supplied to relay TRA is of course due to that stored in the condenser Q, and while the amount of this energy is effected by variations in the Voltage of the cource of energy, the amount of energy stored in the condenser is relatively small compared to that stored in the transformer so that variations in the energy stored in the condenser will have negligible effect on the magnitude of the current supplied to relay TRA to pick it up.

Relay TRA will start to release as soon as the current impulse supplied thereto decreases below the release value. The actual time required for the relay to release after the current decreases below its release value will depend on the inertia of the moving parts, and on the speed with which the flux decreases. If the relay is a polar biased relay and the armature has not released by the time the current reverses in direction, the rowth of current in the reverse direction will act to accelerate the release of the relay. The portion of the current curve which occurs after the current decreases below the release current of the relay is very steep, and it will be seen, therefore, that positive rapid release is assured and that the release time is controlled almost entirely by the frequency of the oscillation and is practically independent of the magnitude of the current. Furthermore, considerable latitude may be permitted in the degree of damping of the oscillation since it is only necessary that the current of the third half cycle be below the pickup value of relay TRA.

The frequency of oscillation of the oscillating circuit can readily be varied to vary the release time of the relay TRA, and it follows that I have provided a convenient and highly accurate form of impulse actuated timing means. While this timing means is particularly suitable for use in a coded signaling system for railways, it is not limited to this use, and may be employed whenever it is desired to accurately time relatively short time intervals.

The relay HB may be used to control signals for indicating traffic conditions in the manner described in either the Nicholson and Staples application, Serial No. 452,894, or the V012 application, Serial No. 452,902, referred to hereinbefore.

Although I have herein shown and described only one form of apparatus embodying my 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 my invention.

Having thus described my invention, what I claim is:

1. Impulse actuated timing means comprising a relay which will respond to current of one polarity only, an oscillating circuit, means for at times setting up oscillations in said circuit, and means for supplying said relay with an oscillating current in response to the oscillations set up in said circuit, said circuit being highly damped and said means being connected with said relay in such manner and the parts being so proportioned that said relay will pick up and again release in response to the first half cycle of said current and will thereafter remain released.

2. Impulse actuated timing means comprising a highly damped oscillating circuit including an inductance and a capacitance, means for at times setting up oscillations in said circuit, a winding inductively coupled with said circuit, and arelay capable of responding to current of one polarity only at times connected with said winding in such manner that the first half cycle of the current supplied thereto in response to oscillations set up in said oscillating circuit will flow in the direction to pick up said relay, the parts being so proportioned that said relay will pick up and release in response to said first half cycle of current and will thereafter remain released.

3. Impulse actuated timing means comprising a relay which will respond to current of one polarity only, an oscillating circuit including capacitance and inductance, means for at times supplying said circuit with current impulses which saturate said inductance to cause said circuit to oscillate at its natural period, and means for supplying said relay with an oscillating current in response to the oscillation set up in said circuit, said circuit being highly damped and said means being connected with said relay in such manner that said relay will pick up and release in response to the first half cycle of said current and will thereafter remain released, whereby the release time of said relay will depend upon the frequency of the oscillation induced in said circuit and will be unailected by changes in temperature or the voltage of the exciting source.

4. Impulse actuated timing means comprising a transformer having a primary winding and a secondary winding, said primary winding being divided into two portions one of which has a low inductance and the other of which has a relatively high inductance, a condenser connected across said primary winding and forming with said primary winding a highly damped oscillating circuit, means for at times supplying said oscillating circuit with current impulses to cause said circuit to oscillate at its natural period, a part of said current being caused to flow through the low inductance part of said primary winding and being of sufficient magnitude to saturate the core of said transformer, a timing relay which responds to current of one polarity only, and means for supplying said relay with the current which is induced in said secondary winding when said os- 9 cillating circuit is oscillating in such manner that the first half cycle of current supplied to the relay will have the polarity to which said relay responds, the parts being so proportioned that said timing relay will pick up and release in response to said first half cycle of current and will thereafter remain released, whereby the release time 10 of said relay will depend upon the frequency of the oscillations induced in said oscillating circuit and will be unafiected by changes in temperature or the voltage of the source from which current impulses are supplied to said oscillating circuit to cause it to oscillate.

CI-IALMERS W. GILBERT.

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