US2662167A - Highway crossing gate control system - Google Patents

Description

Dec. 8, 1953 J. c. LINDNER HIGHWAY CROSSING GATE CONTROL SYSTEM Filed June 18, 1949 u @N r I. L I. IL 25M??? 20 DE HEB jun Q2 E5: =0 26:

Ihwentor c. an m Patented Dec. 8, 1953 HIGHWAY CROSSING GATE CONTROL SYSTEM John C. Lindner, Rochester, N. Y., assignor to General Railway Signal Company,

Rochester,

Application June 18, 1949, Serial No. 100,066

1 Claim. 1

This invention relates to highway crossing protection mechanisms and the control of such mechanisms and more particularly pertains to the electrical control of gate arms which are lowered over a highway upon the approach of a train.

Varying conditions are often encountered in the use of gate arms of this type which greatly affect their operation. Under conditions of sleet and ice, for example, a gate arm may be frozen into its clear position so that it cannot drop by the force of gravity upon the approach of a train. In addition, a gate arm of this type may also be prevented from dropping due to the force of high winds. For this reason it is considered desirable to drive the gate arm downward during the first portion of its descent to assure it is not being held in the clear position.

On the other hand, a heavy load of ice upon the arm or a heavy wind may cause it to descend too rapidly. Or the wind blowing upon the gate arm may be of such a force and direction as to cause the arm to drop more slowly than it otherwise would. Either condition, 1. e. too fast or too slow dropping of the arm, is considered detrimental to safety because fast dropping of the arm may cause it to strike the tops of passing vehicles which have not yet come to a stop; whereas, slow movement of the gate arm might permit highway trafiic to cross the railroad tracks when the train is dangerously close to or actually at, the intersection. For these reasons a stand- 'ard, relatively uniform time of descent is considered advantageous in the operation of highway crossing gates.

In prior types of highway crossing gates in which the gate is driven downward during a portion of its descent, the rate of descent changes appreciably at the end of the drive-down period. Also, many of these gates are provided with some type of mechanical braking. In the gate arm mechanism of the present invention, however, the rate of descent is substantially constant during its entire travel and, in addition, only electrical braking is used so that less wearing of parts results.

A further object of the present invention is to provide a means of control for a highway crossing gate which will permit the gate to be raised immediately upon the passage of a train while yet permitting the descent of the gate to be delayed upon approach of a train so that highway traific may be warned of the gates impending descent.

Other objects, purposes, and characteristic features of the present invention will be in part matically and certain conventional illustrations have been employed, the drawings having been made more with the purpose of making it easy to understand the principles and mode of operation, than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner, and symbols are used to indicate connections to the terminals of batteries, or other sources of electric current, instead of showing all of the wiring connections to these terminals.

Although two crossing gates are commonly employed at a highway crossing, only the control apparatus and circuit for one gate 6 has been shown in the accompanying drawing. Except for certain of the equipment shown in the accompanying drawing which is common to both of the gate mechanisms at a typical highway crossing, the remainder of the equipment shown is associated only with one of the gate mechanisms with similar apparatus ordinarily being provided for the other gate. The equipment common to both of the gates includes the GP relay and its control circuit, the flasher relay and the relays TP and TPP.

Each gate mechanism has associated therewith a rotary contactor, various contacts of which are included in the circuit shown in the accompanying drawing. These contacts are illustrated diagrammatically by means of a revolving contact and a circular segment with which it makes contact, the revolving contact being operated from the. shaft 1 through the quadrant gears S and 9. In each of these diagrammatic illustrations the position of the revolving contact corresponds with the position of the gate and is shown in a vertical position when the gate 6 is cleared and in a horizontal position when this gate is lowered over the highway. The numerals associated with each contact indicate the angular position of the gate arm for which that particular contact is closed. Thus, the circuit of relay GP is shown as including contact 45 which is closed when the gate is in a position between 75 and 90, the zero degree position corresponding to the horizontal position of the gate and the 90 position corresponding, of course, to the gate arms vertical position.

An interlocking relay IR. is shown in the accompanying drawing and this relay is controlled by an associated track circuit in such a manner that either front contacts In and l l or front contacts l2 and i3 will become open when a train approaches the highway crossing. If, for example, an eastbound train approaches the crossing, the front contacts l2 and I3 will be opened and will remain open until the rear of the train has passed over the crossing. Because of the mechanical interlocking provided by this relay IR, contacts l and H will not be opened by the passage of this eastbound train beyond the highway crossing. Similarly, when a westbound train approaches the crossing, front contacts l0 and II will be opened. Since the contacts 10 and 12 are included in series to control the relay GP and the contacts H and iii are included in series to control the relay TP and relay TPP and since these relays are normally energized, the effect of the interlocking relay upon the approach of a train is to cause the deenergization of these relays when the train is at some specified distance in approach of the highway crossing and to condition the circuits for the reenergization of these relays when the rear of the train clears the crossing.

Under the normal condition shown in the accompanying drawing, the various contacts of the interlocking relay are shown closed so that relays GP, TP, and TPP are all picked up. When a train approaches the crossing, these relays will become deenergized as already described. Since the relay GP is a quick releasing relay, it will immediately drop away and close its various back contacts. The closing of its back contacts 14 and I will permit energy to be applied to the various lamps shown in accordance with the position of contact ll of the flasher relay. The closing of back contact IE will energize this flasher relay, and cause its armature to oscillate so as to intermittently close its front and back contacts. When front contact I! of this flasher relay is closed, the lamps 20 and 2| on the upright highway signal and the lamp 22 on the gate arm are energized through a circuit from back contact M of relay GP, front contact ll of the flasher relay; through the lamps 20, 2|, and 22, back contact l5 of relay GP, to Similarly, when the back contact I! of the flasher relay is closed, the lamps 23, 24 and 25 are similarly energized while the lamps 2B, 2 l, and 22 will then be deenergized. In this manner, the lights on the highway signal and on the gate arm are caused to flash intermittently. The lamp 26 located on the tip of the gate arm is continuously illuminated when back contacts 14 and I5 of relay GP are closed. The closing of back contact 21 of the relay GP energizes the bell 28 thereby producing an audible warning to approaching highway traflic of the approach of a train.

e e ys TP and TPP are both deenergized by the approach of a train as has been described. Although the relay TPP is of the ordinary type in that it has quick releasing characteristics, the relay TP, on the other hand, is provided with slow releasing characteristics as shown by the heavy base line for the symbol designating this relay. Thus, although the relay TPP will drop away quickly and open its front contact 30 upon the approach of a train, the relay TP will remain in its picked up position for a time interval corresponding to its slow releasing characteristics. Since the contact 30 of relay TPP and the contact 3| of relay TP are included in parallel in the circuit controlling the hold clear magnet I-IC, it is evident that even though the front contact 30 is quickly opened upon the approach of a train, the circuit to the hold clear magnet I-IC will not be interrupted. As will presently become apparent, the dropping away of the hold clear magnet HC causes the gate arm to drop. Therefore, the afiect of the slow releasing characteristics of the relay T? is to delay the descent of the gate 5 while the various lamps flash and the warning bell rings, thus warning approaching highway traffic that the gate is about to drop.

Under the normal condition as shown in the drawing, the hold winding 1-1 of the hold clear magnet HC is energized through contacts 39 and 3| of relays TPP and TP respectively. Consequently, with front contacts 29 of the hold clear magnet HC closed, the motor circuit cannot be energized since the contact 32 of the rotary contactor is open when the gate is in its normal, upright position. Also, with the hold clear magnet EC in its energized condition, the pawl I8 is moved into position so as to engage the ratchet wheel 33 on the motor shaft and in this way downward movement of the gate is prevented while the gate is in its normal position even though the motor including armature A and field windings UF and DF is deenergized.

Upon the release of front contact 3| of relay TP, the hold clear magnet EC is deenergized as has been described. As a result, both back contacts 29 and 34 will be closed and the pawl l8 will be released and biased by the spring 5 so as to disengage the ratchet wheel 33 so as to permit rotation of themotor armature A. A circuit for the motor will then be established from back contact 29 of the hold clear magnet HC, contact 35 of the rotary contactor, the down field winding DF and the motor armature A to Also a shunt field circuit will be established for the motor from the point 36, through the up field winding UF, back contact 34 of the hold clear magnet HC resistor 31 to Thus, in effect a short-shunt compound motor connection is provided in which the up field series winding UF for the motor is used as the shunt field. Since this field winding UP is of relatively low resistance as compared to an ordinary shunt field, the resistor 3'! is included in series with the winding in order to limit the current through it. As will presently be brought out, the direction of current flow through the up field winding UF (from left to right in the drawing) is opposite to the direction of current flow when thi winding U1? is used as a series field to drive the gate to its upward position. For this reason, the shunt field flux produced by this winding UP is of such a polarity as to aid the down field DF in driving the gate to the downward position. As shown in the drawing the motor armature A drives the gate arm 6 through the speed reducing gear box GB.

As is shown in the diagrammatic view of the gate in the accompanying drawing, the gate arm 6 is counterbalanced by a weight at to reduce the downward turning moment of the arm. In practice, the arm is so balanced as to have its maximum turning moment while in the clear position, reducing to a minimum value as the gate reaches the horizontal position. The reason for this arrangement is that a wind blowing upon the gate arm'will produce the least upward turning torque upon the gate when it is in its horizontal position and also the downward turning torque due to a heavy load of ice coating the gate is at a maximum when the gate is in its horizontal position. Therefore, although a large downward turning torque is desirable when the gate is in its clear position, such a large amount of torque is not required when the gate assumes lower positions for the reasons mentioned above and also because of the inertia of the gate as it revolves. The downward turning torque as the gate reaches its 45 position is such, however, that it will continue to drop of its own accord even when under the influence of various external forces and, for this reason, ener y is removed from the motor when the gate reaches this position as will presently be described. Depending upon the particular conditions encountered, however, the motor may actually function either as a generator or as a motor during the drive-down period depending on whether torque is being applied to the motor shaft or whether torque is being expended by the motor shaft upon the gate arm. The speedtorque characteristics of a compound machine of this type are such, however, that its speed will remain within a relatively narrow range even though the torque applied to or expanded by the motor should vary. Consequently, the gate will be lowered at a fairly uniform rate even under adverse conditions caused by ice, wind, or the like.

Referring again to the drawing, it can be seen that contact 35 of the rotary contactor opens when the gate arm is in its 45 position and that the contact 48 of the rotary contactor closes when the gate arm is in its 44 position. The opening of the contact 35, of course, removes energy from the motor armature and from the down field winding DF. This termination of the drive-down period, although shown in this particular embodiment as occurring at the 45 position of the gate arm may as well occur at some other position. The 45 position was here chosen because it can safely be assumed for reasons already mentioned that at this point the gate arm will continue to travel downwardly due to the force of gravity. In order to prevent a sudden change in the speed of descent of the gate arm when the drive-down period is ended, the contact 49 is closed just after the end of the drive-down period and by doing so connects the resistor 4! in parallel with the resistor 37. As a result, the total eifective resistance in series with the shunt field winding UF is decreased so that the total shunt field current may then increase. For this reason, the shunt field flux will also increase and this increase of flux will compensate for the removal of energy by the opening of contact 35. The proper value of resistance for the resistor 4| may most readily be determined by experiment for, with some particular value of resistance the speed of descent of the gate arm will be substantially unchanged at the end of the drivedown period.

The gate arm then continues to drop at a relatively uniform rate until it reaches a position '10 above the horizontal at which time contact 42 of the rotary contactor becomes closed. The closing of this contact 42 places a short circuit across both resistors 4i and 31. As a result, the braking action on the motor shaft is greatly increased so that its speed of rotation drops to a low value. ;By this .means, the gate arm is brought to its horizontal position with a minimum of shock to the mechanism. Also, as the gate arm reaches the 3 position, the circuit to the bell 28 is opened by the opening of contact 44 thereby preventing the bell from ringing and producing an unnecessary disturbance during the time that the gate arm remains in its horizontal position.

When the passing train recedes from the highway crossing and the front contacts of the interlocking relay IR which were previously opened by the approach of the train become closed. a circuit is established through the front contacts II and I3 of this interlocking relay IR to energize both relays TP and TPP. As was previously stated, the relay TP is provided with slow releasing characteristics. Although it is desired that this relay '1? be of the quick pick-up type, a relay of this type which is provided with slow releasing characteristics will also have somewhat slower pickup characteristics. For this reason, the relay TPP is provided which will quickly pick up upon the passage of the train thereby allowing the gate arm to be quickly raised so as not to obstruct highway traffic longer than is neces-' sary. Upon the closing of front contact 30 of relay TPP a circuit is established to energize the P Winding of the hold clear magnet HC. This hold clear magnet is of the type which employs two separate windings P and H; one (P) for picking up the armature and the other (H) for holding it up after it has once been picked up. The pick-up winding P of this hold clear magnet HC is of a lower resistance than the hold winding H so that a greater current and therefore more flux will be produced by this pick-up winding than by the hold winding H. The amount of flux thus produced by this winding P is sufficient to pick up the armature of the hold clear magnet when it is in its dropped away position. Circuit means, presently to be described, are included for deenergizing the pick-up winding P after it has once been picked up and for allowing the magnet to remain picked up by means of its higher resistance (lower power consuming) hold winding H.

When the armature of the hold clear magnet HC is picked up, and its front contacts 29 and 34 closed, a circuit is established to energize the motor from contact 32 of the rotary contactor, the up field winding UP, the motor armature A, to It will be noted that in this instance the direction of current through the up field UF was from right to left and thus opposite to the direction of current flow through this winding when it was used as a shunt field for driving the gate arm downwardly. Being thus energized, the motor operates to raise the gate arm to its vertical position. The picking up of the hold clear magnet HC also causes therpawl I8 again to engage with the ratchet wheel. Be-.

cause of the unsymmetrical shape of the teethof this ratchet wheel 33, however, the motor isrnot restrained fromdriving the gate to its upward position.

Examination of the circuit controlling the operation of relay GP shows that contact of the rotary contactor is open while the gate arm is in its horizontal position. Thus, when the contacts l0 and I 2 are both closed immediately following the passage of a train past this highway crossing location, the relay GP cannot become energized and, as a result, the lights on the gate closes and allows the relay GP to become energized. Back contacts I4, 15, and [6 of this relay GP are then opened with the result that the lights then no longer flash and the bell 28 stops ringing. Also, when the gate arm reaches its 75 po- ;sition, the contact 46 of the rotary contactor opens thereby deenergizing the pick up winding 'P. As has been described, this hold clear magnet HC, when in its picked up position, can be maintained in that position by the energization of the hold winding 1-1. As the gate arm continues to rise and finally reaches the 88 position, the contact 32 of the rotary contactor opens thereby deenergizing the motor. The inertia of the gate arm is of course sufficient to carry it to its vertical, 90 position even though it is deenergized at the 88 position.

It follows from the foregoing description then that the present invention provides an improved means for governing the operation of highway crossing gates in that it permits them to descend at a relatively uniform speed even while under the influence of various external forces. Also, this circuit for controlling a crossing gate is so arranged that the gate arm will quickly begin to rise upon the passage of a train even though it also embodies the provision of delaying the descent of the gate upon the approach of a train until the flashing lights and ringing hell have warned approaching trafl'icof the gates impending descent.

Having described a circuit for controlling a gate arm as one specific embodiment of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume; and it is to be further understood that modifications, adaptations, and alterations may be applied to the specific form shown without in any manner departing from the spirit or scope of the present invention.

What I claim is:

In a control system for a highway crossing gate, a normally energized hold clear magnet for mechanically latching said gate in an upright position, said magnet being deenergized only when a train is in approach to and crossing said highway, a rotary contactor having contacts whose operation is governed by the angular position 0! said gate, a motor including an armature and two field windings for driving said gate to selected upward and downward positions, circuit means governed by said hold clear magnet and efiective when said hold clear magnet is deenergized for energizing One of said field windings in series with said armature and for connecting the other 01' said field windings in shunt across said armature, the polarity of energization of said windings being chosen in relation to the polarity of current in said armature to cause said motor to drive said gate downwardly, said circuit means being effective when said hold clear magnet is energized and said gate is in its downward position to energize said armature in series with said other field winding, the polarity of energization of said other winding being chosen in relation to the polarity of current in said armature to cause said motor to drive said gate upward.

JOHN C. LINDNER.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 1,818,013 Smith Aug. 11, 1931 2,137,196 Sampson Nov. 15, 1938 20,154 Howe et al Nov. 5, 1940 2,310,694 Henry Feb. 9, 1M3

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