US3396271A - Railroad-wheel operated controlsignal generator - Google Patents

Description

Aug. 6, 1968 c. A. GALLAGHER 3,396,271

RAILROAD-WHEEL OPERATED CONTROL-SIGNAL GENERATOR Filed March l5, 1967 TTORNE United States Patent O 3,396,271 RAILRGAD-WHEEL OPERATED CONTRGL- SIGNAL GENERATOR Cornelius A. Gallagher, Syosaet, N.Y., assignor to Servo Corporation of America, Hicksville, N.Y., a corporation of New York Filed Mar. 15, 1967, Ser. No. 623,253 5 Claims. (Ci. 246-249) ABSTRACT OF THE DISCLOSURE This invention is concerned With a particular interconnection of two magnetic-induction wheel-trip devices capable of responding to railroad-wheel movement and so interconnected as to effectively nullify or buck-out spurious signals induced by electric currents passing down the rails, as in electrified territory. The arrangement is such that not only are the spurious signals eliminated, but a control signal is developed in a polarity which is insensitive to the particular direction of traffic passing the wheel-trip location.

This invention relates to a particular forni of signal generator for use in conjunction with railroad tracks to enable the automatic generation of a control signal based on the instant when a moving railroad Wheel passes the detection region.

Devices of the character indicated include magnetic-induction devices wherein a polarized air gap is established at the rail, the reluctance of the gap being modified as the wheel or its flange effectively changes the physical proportions of the air gap. An electric coil linked to the magnetic core develops an Output voltage characterized by a first swing of one polarity, followed by a similar swing of opposite polarity, as when the wheel flange enters and then (later) leaves the gap.

In electrified territory, heavy electrical currents passing down the rails may induce undesirable spurious responses from such magnetic-induction wheel trips, and it is desirable etfectively t-o neutralize such responses while at the same time providing a suitable time-identifying controlsignal output to mark the passage of each wheel. lt is desirable that such control signals be of the same polarity regardless of the direction of traflic movement past the detection point.

It is, accordingly, an object of the invention to provide an improved device of the character indicated lending itself particularly to use in electrified territory and accommodating itself inherently to traffic, regardless of the direction of traffic movement.

Another object is to meet the foregoing objects with a device having an inherent capacity to produce the same apparent control signal output rregardless of the direction of tratlic movement.

A further object is to meet the foregoing objects with a device producing a control-signal output magnitude greater than that produced by prior wheel trips and uniquely identifying an instant of time when a wheel center is passing.

A general object is to meet the foregoing objects with a structure which is inherently simple, which is a passive in the sense that it requires no external source for derivation of basic signal inputs, and which may utilize existing components to the largest extent possible.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a -reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show for illustrative purposes only, preferred forms of the invention.

3,396,271 Patented Aug. 6, 1968 ICC FIG. 1 is a diagram schematically showing electrical components of one form of the invention shown in application to a section of railroad track;

FIG. 2 is a series of graphs depiciting, on the same time base, voltage fluctuations encountered in the operation of the device of FIG. l; and

FIG. 3 is a simplified diagram showing a modification of FIG. 1.

Briefly stated, the invention contemplates the employment of two magnetic-induction wheel-trip devices of the variety which have heretofore been bolted to a rail so as to enable characteristic output pulses to be generated to mark the instant of time when a railroad wheel passes the wheel-trip location. The two trips, in the present case, are spaced from each other by an amount so related to wheel diameter that the flux in the air gap for one of the trips is undergoing its greatest change due to a given wheel-flange entering that gap, while flux in the other wheel trip is undergoing its greatest change due to the same flange leavn'g the latter gap. The number of turns on the output coils of both these devices are matched and connected so that their output voltages normally buck or balance out.

The circuitry for generating a suitable control signal includes the relay responsive to the thus-combined outputs of the two coils, and this relay produces an output signal of the same polarity for each passing wheel, regardless of the direction of passage of the wheel.

Referring to FIG. 1 of the drawings, the invention is shown in application to a railroad rail 10 having a head 11 on an upstanding web and resting on a flat base 13. Two permanently polarized magnetic cores 14-15 are mounted adjacent the web and beneath the head 11 so that the outer poles 16-17 of each core are spaced laterally to generally the same extent with respect to the head and web 11-12 of the rail. Longitudinally, the cores 14-15 are spaced a distance D. Separate like output coils 18-19 are linked to the respective cores 14-15 and are so interconnected that for simultaneously induced voltages due to the same cause, these output voltages buck out or are self-cancelling. In the form shown, both coils 18-19 have turns in the same direction and, therefore, their output connections are opposed.

The parts thus far described may be all combined within a single assembly suggested by phantom outline 20 of generally rectangular prismatic form, being preferably a plastic potting fully sealing and enclosing the coils and their cores, the potting being secured by means (not shown) to the web section of the rail. In this circumstance the output of the assembly may be contained in a single two-conductor cable, suggested by the loop 21.

The spacing D is determined by considerations of greatest flux change in the respective magnetic circuits due to passage of particular railroad wheel, it being understood that railroad wheels are of magnetic-flux conducting material. In the form shown, the variety of wheel-trip element suggested at 14-15 is such that the polarized air gaps are defined between the outboard pole faces 16-17 and the nearest adjacent edge of the head 11 of the rail. These polarized gaps are located on the inside of the rail and are poised to undergo marked change in reluctance as wheel flanges of passing wheels enter and leave the polarized air gaps. In the event of such wheel-flange operated devices, the spacing D is such that the wheel flange for a given wheel is entering the polarized gap for ore wheel trip while it (the same wheel flange) is leaving that for the other. The significance of this relationship will be explained in conjunction with curves a and b of FIG. 2.

Assume a wheel on the rail 1t) and moving from left to right. Its flange will first change the reluctance of the polarized gap associated with core 14, and the direction of this change may be such as to induce a first voltage swing 25 in a negative polarity in the output of coil 1-8. The wheel will progress down the track until a time comes when the ange leaves the polarized gap associated with core 14, at which time the same coil 18 will develop a similar but oppositely poled voltage swing 26 in its output.

In the same manner, the same wheel flange will induce rst a negative and then a positive voltage swing in the output of coil 19 in connection with traversal of the polarized gap associated with core 15. However, due to the bucking or opposed-phase connection of the outputs of coils 18-19, the sequence of pulse outputs at coil 19 for the same wheel-ange will appear to be of polarity opposed to that of coil 18. This relationship is suggested in curve b of FIG. 2, wherein the iirst pulse at the output of coil 19 is shown as being electively a positive pulse 27 and is followed by a negative pulse 28, as the wheel ange leaves the polarized gap associated therewith.

Now, in electrified territory where track currents may be severe, as due to operation of electric traction locomotives, a given current in the track may induce a voltage in the outputs of coils 18-19. However, the voltages thus induced at coils 18-19 will be simultaneously induced and because of the similarity of the coils to each other these voltages wll be equal and opposite. This relation being suggested by a dashed outline graph 29-30 at FIG. 2A.

The net result is to neutralize such rail-induced voltages and to discriminate for pulses due to wheel-ange passage, it being noted that the pulses 26-27, due to the same ilange leaving the gap associated with core 14 while it is also entering the gap associated with core 15, are effectively simultaneous and of the same polarity. Thus, due to the interconnection already described for the coil outputs, these outputs combine additively to produce a pulse substantially exceeding the output of either one of the coils 18, and amounting to substantially double the output of either coil.

The additive response is suggested at curve c for the assumed condition of the wheel moving from left to right in the sense of FIG. l. This response is seen to comprise the rst negative swing 25 associated with coil output at 18, followed by a double-amplitude central pulse 31 representing the combined outputs 26-27 from both coils, and terminated by another lesser-magnitude negative pulse 28, representing that due to the ange leaving the polarized gap associated with core 15.

For trai-lic proceeding in the opposite direction along the rail 10, the polarized gap associated with core is the one rst to be traversed. A similar pattern of signalpulse development will occur as the wheel proceeds into and beyond the distance D, but due to the opposed-phase connection of the outputs of coils 18-19, the combined output-pulse pattern will be the mirror image of that described at FIG. 2c for the case of left-to-right tratiic movement. Curve d of FIG. 2 suggests this mirror-image pattern, being characterized by a rst minor positive pulse followed by a double-amplitude negative pulse 31', and ending with another minor positive pulse 28'.

The present invention concerns itself with accepting either one of the pulse patterns displayed at curves c and d of FIG. 2 and deriving therefrom a control pulse which is unrelated to the particular polarity of the pattern at FIG. 2c or 2d. Specifically, if desired, the control-pulse output from my circuitry can be of positive polarity whether or not the input pulse pattern is that displayed at FIG. 2c or FIG. 2d.

FIG. 2e represents one such control pulse (of positive polarity) which may for certain specific control purposes be adequate, and which will certainly be generated, regardless of whether the input pulse pattern is that of FIG. 2c or that of FIG. 2d. Such an output pulse is generated by the circuit of FIG. 3.

In FIG. 3, the two spaced cores 14-15 are schematically shown, together with their associated output windings 18-19 connected in phase opposition. The combined outputs of these coils are connected by lines to a polarized relay having an actuating coil 36 and an armature 37 movable between interconnected 4lrst and second (e.g., front and back) contacts 38-39. These interconnected contacts form part of a circuit including a suitable source 40 and the armature 37 to provide an output in line 41 to a utilization device, which may be the input relay for a roadtraic grade-crossing gate or the like.

In operation, the polarized relay will function to produce three discrete and closely associated successive output pulses in line 41, namely the pulses 42-43-44 of the same polarity. Strictly speaking, a small time interval (suggested by dashed lines 45-46) will interrupt or intervene between pulses 42-43-44, but it will be understood that the mechanical and inductive yinertia of the control relay of the utilization device will effectively ignore these short interruptions so that the net result of signal-development in line 41 to effectively produce a single elongated pulse 42-43- 44, of single polarity, regardless of direction of wheel movement.

In other applications, it is important that there be better identification of the instant of time when the wheel center for each passing wheel is passing a given location on the track, and in the present case the ldescribed interconnection of wheel trip components for the spacing D enables this instant of time to be identiiied when the wheel center is substantially midway along the distance ID, as suggested by the D/Z designation in FIG. l to identify the longitudinal location X. The circuitry shown in HG. l enables substantially this instant of time to be identied.

In the circuit of FIG. 1, the ultimate device to be controlled or operated is `designated at 50 and denominated a relay or gate. It may thus represent the gate-opening (or the gate-closing) function for a hotboX-detector circuit, as of the variety shown and described in greater detail in U.S. Patent No. 2,880,309.

Control circuitry for the signal supplied to relay 50 is such as to effectively ignore or exclude the minor opening and closing pulses for each wave train, regardless of the direction of passing tratiic, and on the other hand to accentuate and respond essentially only to the double amplitude central pulse 31 (or 31') regardless of the direction of traflic.

For this purpose, the control-signal circuitry may utilize a double-throw relay 51, having rst and second contacts (front and back) determining a rst direct input connection 52 (to output 55) and a second input connection 53 (to output 55) based on the combined outputs of coils 18-19. The input connection 53 is shown with an inverter 54 so that the polarity of signals in lines 52 and 53 is always in opposed phase. For purposes of simplifying discussion the legend '.E has been employed to suggest that the line 52 accommodates eastbound traffic (left to right in the sense of FIG. 1) while W suggests that line 53 accommodates westbound traine, this accommodation function contemplating the particular instantaneous connection of front or back contacts at relay 51. The particular actuation of relay 51 will be described, but it assures that regardless of the direction of passing tra'ic, the output 55 of relay 51 will be characterized by pulse trains in which the central pulse attributable to eastbound double-pulse development 31 or to westbound doublepulse development 31 will appear in the same polarity, so that a half wave rectifier 56 may electively cut oi minor-pulse components and thus accentuate just the double-pulse components.

'For eastbound traffic, let it be assumed that the relay 51 has a normal position establishing direct connection of rectier 56 to the line 52. -In that event, there is no need to operate relay 51, and rectifier 56 is eiective to select the double-pulse positive swing 31 for an identification of the instant of time at which the Wheel center passes 'location X, so that relay or gate 50 may respond in synchronism with this determination.

On the other hand, for westbound tratiic, the desired double-pulse amplitude 31' is of undesired polarity, so that the relay 51 must be operated to invert the pulse 31'. To achieve this operation in the form shown, a suitable poled amplifier 60 responds to the initial positive minor pulse 25', signifying a westbound signal development to actuate the first of two inputs 61-62, to a bi-stable multivibrator 63. This first input 61 will be understood to be operative to change the state, say from a first state in which relay 51 is not operated to a second state in which relay 51 is operated. The second input connection 62 to multivibrator 63 is shown connected to a reset circuit which will be described. (The reset function is generated as a marker of the termination of the trip pulse wave train generated for each wheel passing the distance D.)

In the `form shown, the reset pulse is developed by -a full-wave rectifier 65 responding to the combined outputs of coils 18-19. The rectifier output is shaped at 66 into an elongated square Wave which may be of the nature shown at 42-43-44 in curve e of lFrIG. 2, which constitutes one single square wave of this duration. The square-wave output from circuit 66 may be differentiated at 67 to develop a pulse of unique polarity to mark the end 0f the square-Wave. A poled diode 68 is shown selecting this response and therefore developing a reset pulse in line 69 to return multivibrator 63 to its normal first state, at which time relay 51 will be de-energized, thus restoring connection of rectifier 56 to the input line 52.

In order that the first negative minor pulse 25 for eastbound trafiic shall be ineffective to `operate the multivibrator 63, -I show a lock-out circuit for biasing the amplifier 60 below cut-ofi in this circumstance. The lock-out circuit is shown to include a poled diode 70 connected to the combined outputs of coils 18-19 and selective to respond to the initial negative swing 25 for a wave train attributable to eastbound traffic. Diode 70 then supplies to a second bi-stable multivibrator 71 a first control signal determining change of state to eect a cut-oli signal in line 72 to amplifier 60.

Multivibrator 71 will remain thus actuated in spite of succeeding pulses from diode 70 until a reset pulse in line 73 (to the other input connection of multivibrator 71) is operative to again change the state of multivibrator 71, thus restoring amplifier 60 to its original operative condition.

It will be seen that I have described an inherently simple connection of magnetic-induction wheel-operated devices which is inherently self-compensating for railinduced currents, but which on the other hand is operative to generate control signals of a given polarity, regardless of the direction of passing traiiic. These control signals may be so refined in terms of the timing of their development as to utilize inherent signal-to-noise enhancement attributable to the spacing D for wheel passage, and to inherently effectively split the distance D for wheel-center identification.

What is claimed is:

1. Control means responsive to trafiic movement along a railroad track, comprising two rail-mounted magnetic wheel-trip devices secured in spaced relation along the same track, each of said devices presenting a magnetized air gap for interception of a wheel ange, the spacing between said trips being such that a Wheel ange on a given axle is leaving the gap for one wheel trip as a wheel fiange on the same axle is entering the gap for the other wheel trip, each of said wheel-trip devices including an electrical output coil, said coils being connected in phase-opposition, whereby signals induced in said coils due to rail currents are effectively bucked-out, whereas a passing railroad Wheel ange will induce output-coil voltages which are additive for the entering pulse of the second-traversed trip and the leaving pulse of the first-traversed trip, and connecting means including a relay responsive to the thus-combined output of said coils, said relay producing an output signal of the same polarity for each passing wheel regardless of the direction of passage of the wheel.

2. Control means according to claim 1, in Which said relay is a polarized double-throw relay with inter-connected front and back contacts, and a control-signal output circuit including a voltage source and the inter-connected contacts of said relay.

3. Control means according to claim 1, in which said relay is of the double-throw variety having front and back contacts and an output circuit including an armature normally engaging one of said contacts to the exclusion of the other, first and second connections of said contacts to the combined output of said coils, one of said connections to one of said contacts being of inverted polarity with respect to the other of said connections to the other of said contacts, and actuating means for said armature including polarity-sensitive connection to the combined output of said coils.

4. Control means according to claim 3, in which said polarity-sensitive connection includes a bi-stable multivibrator having an output connected `for operation of said re'lay, said multivibrator having a first state which is inoperative to actuate said relay and a second state which is operative to actuate said relay, said multivibrator having a first input connection for actuation of said multivibrator from said first to said second states and having a second input connection for actuation from said second to .said first state, means responsive to a first polarity of combined coil signal output and connected to said first input connection, said last-defined means including means responsive to an opposite polarity of combined signal output voltage and effective to lock-out operation of said polarity-sensitive means, and reset means for said multivibrator connected `to said second input connection thereof and including means detecting completion of each detected wave train in the combined output of said coils.

5. Control means according to claim 4, in which said reset means includes a full-Wave rectifier connected to said combined signal output, wave-shaping means associated with said rectifier for developing an elongated square wave for wave train in said output, and differentiating means connected to said wave-shaping means.

References Cited UNITED STATES PATENTS 3,281,593 10/ 1966 Mendelsohn 246-249 3,359,417 12/ 1967 Gallagher 246-249 FOREIGN PATENTS 730,359 5/ 1955 Great Britain. 1,147,728 6/1957 France.

ARTHUR L. LA POINT, Primary Examiner.

S. T. KRAWCZEWICZ, Assistant Examiner.

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