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CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. § 119(e), this application claims priority from Provisional Application No. 60/149,841, filed Aug. 19, 1999. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to an improved gate device for preventing pedestrians and vehicular traffic from crossing railroad grades. Specifically, the present invention relates to gate devices that protect lowered railroad crossing gate arms from damage. 
     BACKGROUND OF THE INVENTION 
     Railroad crossing gate arms are lowered from a vertical position to a horizontal position to block traffic from crossing railroad tracks when a train is present. When lowered to their horizontal position, gate arms can suffer damage from passing vehicles, wind pressure and vandalism. Damage frequently results in broken gate arms that sever at their point of attachment to a crossing gate mechanism. Such damage risks exposing pedestrians and vehicular traffic to improperly guarded train crossings. To maintain safety and the integrity of grade crossing equipment, railroads expend substantial resources monitoring, repairing and replacing damaged crossing gates. Thus, in the first instance, it is advantageous to protect lowered gate arms from damage. 
     Various methods of protecting gate arms from damage were known to the prior art. Employing camblocks and ball bearings, U.S. Pat. No. 4,897,960 issued to Barvinek, et al., (hereinafter referred to as “Barvinek”) describes a mechanism designed to provide flexibility to lowered gate arms. Barvinek discloses a housing for pivotally mounting a support tube that swings a partially translucent, internally illuminated, impact-resistant gate arm away from an applied force. A camblock is mounted inside the housing, allowing the gate arm support tube, having a pair of ball bearings retained within, to rotate around a retaining pin that extends upwardly through the center of the camblock when force from a passing vehicle is applied. Downward force on the rotating gate arm support tube, applied by a coil spring mounted on the retaining pin, forces the arm to return to its original position parallel with the groove of the camblock when the force dissipates. However, Barvinek suffers from numerous problems. Relying on camblocks and ball bearings, Barvinek is expensive to manufacture, monitor and maintain. Moreover, Barvinek cannot return a displaced gate arm to a position parallel with the groove of the camblock if the gate mechanism rises while the gate is displaced. Finally, Barvinek provides no control over the rate of gate arm return and cannot prevent gate arm over travel into the flow of traffic. 
     Alternatively, U.S. Pat. No. 5,469,660, issued to Tamenne, (hereinafter referred to as “Tamenne”) employs a spring and hydraulic piston system. Tamenne discloses a pivot assembly allowing a lowered gate arm to rotate away from traffic when a passing vehicle applies pressure and then to return to its original position once pressure is removed. The pivot assembly is mounted on a counter-weighted gate arm mechanism and includes springs mounted on a shuttle post assembly to return the gate arm to a position perpendicular to the flow of traffic. The pivot assembly includes a hydraulic piston to buffer the rate of gate arm return and a weight channel to counterbalance the gate mechanism&#39;s main counterweight when the gate arm is rotated away from passing traffic. However, Tamenne also suffers from numerous problems. Tamenne&#39;s hydraulic piston system, like Barvinek&#39;s camblock and ball bearing system, is expensive to manufacture, monitor and maintain. Further, Tamenne&#39;s weight channel counterbalance places an imbalanced strain on the gate arm pivot assembly, risking damage to the gate arm mechanism. Tamenne also decreases safety at crossing grades when the gate arm is displaced, because the weight channel swings from a position generally parallel with the flow of traffic to a position generally perpendicular to the flow of traffic and through an area where pedestrians may be standing. Like Bamivek, Tamenne is incapable of returning a displaced gate arm back to its normal position if the gate mechanism rises while the gate is displaced. 
     Therefore, a need exists for a crossing gate mechanism that can rotate a crossing gate arm out of the way of a damaging force while safely and efficiently returning the gate to its normal position, that is capable of being adjusted for installation in conditions requiring varied gate arm lengths and flexibilities, that is capable of preventing excessive impact when the gate arm returns to its normal position, that prevents gate arm over travel upon return from a displaced position, that is capable of being adjusted for varying gate arm return force requirements, that is less expensive than existing spring-based crossing guard mechanisms, and that is not subject to the potential for deterioration of a cam-and-bearing based crossing gate mechanisms. 
     SUMMARY OF THE INVENTION 
     The present invention provides a crossing gate mechanism for use in a railroad crossing gate. In one embodiment, the crossing gate mechanism includes a gate arm adapter for receiving the gate arm and allowing rotation of the gate arm away from a normal operating position approximately perpendicular to a flow of traffic upon application of a displacement force. The gate arm adapter is capable of being pivotally mounted to a vertical support structure to allow the rotation of the gate arm. A return force mechanism coupled to the gate arm adapter provides for a return of a displaced gate arm adapter to the normal operating position upon removal of the displacement force. In the one embodiment, the crossing gate mechanism further includes a latch hook assembly that holds the gate arm adapter in its normal operating position in the absence of a displacement force. In another embodiment, the crossing gate mechanism further includes a drag brake that retards a rate of return of the gate arm adapter to the normal operating position from a displaced position upon removal of the displacement force. 
     In another embodiment, the crossing gate mechanism includes a crossing gate arm, the gate arm adapter, and a return force mechanism attachment point. The gate arm adapter receives the crossing gate arm and includes a hinge pin that allows rotation of the gate arm away from the normal operating position upon application of the displacement force. The return force mechanism attachment point is diametrically opposite the hinge pin from the gate arm, and the return force mechanism attachment point, the hinge pin, and the gate arm are disposed in a generally linear relationship. 
     In another embodiment, the crossing gate mechanism includes a latch hook assembly. The latch hook assembly includes a pivotally levered latch that selectively restrains the gate arm adapter in its normal operating position, and a latch hook pressure mechanism that applies a leveraging force to the pivotally mounted latch to produce a pivotally levered force of the latch. The latch hook assembly further includes a hook and drag surface that receives the pivotally levered force of the latch upon application of a displacement force to the crossing gate mechanism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial top view of a crossing gate mechanism in accordance with a preferred embodiment of the present invention. 
     FIG. 2 is a partial side view of a crossing gate mechanism in accordance with a preferred embodiment of the present invention. 
     FIG. 3 is a partial front view of a crossing gate mechanism in accordance with a preferred embodiment of the present invention. 
     FIG. 4 is a partial front view of a latch hook assembly when operating as a braking mechanism in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention can be more fully understood with reference to FIGS. 1-4. FIGS. 1 and 2 are a partial top view and a partial side view, respectively, of a crossing gate mechanism  100  in accordance with a preferred embodiment of the present invention. Crossing gate mechanism  100  is pivotally mounted to a vertical support that also typically serves as a mounting support for railroad crossing warning lights and signage. Crossing gate mechanisms such as crossing gate mechanism  100  are typically attached to the vertical support by two crossing gate support arms  102  (one shown). 
     The crossing gate support arms  102  are attached to crossing gate mechanism  100  at opposite ends of the mechanism and raise and lower the crossing gate mechanism, thereby raising and lowering a crossing gate arm  202  attached to the crossing gate mechanism, in a vertical plane. Normally, crossing gate mechanism  100  is in an upright position, holding crossing gate arm  202  in a generally vertical orientation and allowing vehicles to proceed through a railroad crossing in the absence of train traffic. When actuated by an oncoming train, crossing gate mechanism  100  lowers crossing gate arm  202 , bringing crossing gate arm  202  into a position approximately parallel to the ground, in order to block vehicular traffic from proceeding through the crossing. 
     As shown in FIGS. 1 and 2, crossing gate mechanism  100  includes an upper cross channel  104  and a lower cross channel  204 . Each cross channel  104 ,  204  is attached to each of the crossing gate support arms (e.g., crossing gate support arm  102 ), thereby pivotally affixing crossing gate mechanism  100  to the vertical support. Cross channels  104 ,  204  are fitted with an upper hinge bracket  106  and a lower hinge bracket  206  that are generally centered between crossing gate support arms  102 . Crossing gate mechanism  100  further includes a gate arm adapter  108  that is pivotally mounted to each cross channel  104 ,  204  via a hinge pin  110 . As shown in FIG. 2, hinge pin  110  is perpendicularly disposed between, and extends through an aperture in, each of cross channels  104 ,  204  and hinge brackets  106 ,  206 . 
     Crossing gate mechanism  100  further includes a return force mechanism that includes one or more, preferably three, spring assemblies  112 . Each spring assembly  112  is pivotally attached to the gate arm adapter  108  via a spring assembly hinge pin sleeve  115  and a spring assembly hinge pin  114 . Spring assembly hinge pin sleeves  115  fit over spring assembly hinge pin  114  acting as spacers to separate spring assembly adapters  117 . Using a fastener through a lower sleeve hole and the spring assembly hinge pin  114 , all parts stay in place within the top and bottom flanges of the gate arm adapter  108 . Spring assemblies  112  attach to the cross channels  104 , 204  via mounting flanges  116  using a similar pin and sleeve arrangement as just described. Spring assembly adapters  117  each provide an attachment point for the mounting of a spring assembly  112 , thereby providing for each spring assembly  112  to be pivotally attached to gate arm adapter  108 . In a preferred embodiment, gate arm adapter  108  is allowed to rotate about hinge pin  110  while the length of crossing gate arm  202 , hinge pin  110  and spring assembly hinge pin  114  and sleeve  115  maintain a generally linear relationship throughout rotation. 
     FIG. 1 further illustrates the typical operating positions of crossing gate mechanism  100  when it is in its lowered and approximately horizontal position relative to the ground. Reference position  118  indicates a normal operating position of lowered crossing gate mechanism  100 , wherein gate arm adapter  108  is generally perpendicular to the flow of vehicular traffic (as indicated by an approximately horizontal displacement force  120 ). Reference position  122  indicates a displaced position of lowered gate arm adapter  108 , achieved when displacement force  120  is applied to gate arm  202 , causing gate arm adapter  108  to rotate the gate arm  202  in an approximately horizontal plane about hinge pin  110 . By rotating crossing gate arm  202 , crossing gate mechanism  100  protects the gate arm  202  from potential damage due to the application of displacement force  120 . Preferably, the maximum angle of swing during displacement is approximately 68°; however, one of ordinary skill in the art realizes that other angles than 68° may be employed without departing from the spirit or scope of the present invention. 
     When displacement force  120  displaces gate arm adapter  108  from normal operating position  118 , each spring assembly  112  provides an approximately horizontal return force on gate arm adapter  108  at spring assembly hinge pin  114 . The return force causes gate arm adapter  108  and gate arm  202  to return from a displaced position  122  back into normal operating position  118  after displacement force  120  is removed. In a preferred embodiment, crossing gate mechanism  100  includes an interchangeable selection of spring assemblies  112  to provide more or less return force for returning longer or shorter gate arms  202  from the displaced position  122  to the normal operating position  118 . Spring assemblies  112  preferably provide adequate return force on gate arm adapter  108  so that gate arm  202  can be returned from a displaced position  122  to normal position  118  even if crossing gate mechanism  100  pivots in the vertical plane about its vertical support, as if to raise gate arm  202  while the gate arm is displaced. 
     In a preferred embodiment, crossing gate mechanism  100  further includes a shear pin  124  that is coupled between upper hinge bracket  106 , or alternatively lower hinge bracket  206 , and gate arm adapter  108 . Shearpin  124  provides crossing gate mechanism  100  with additional resistance to gate arm  108  rotation in high wind areas, yet will easily shear upon impact with displacement force  120 . 
     Referring now to FIGS. 1,  2  and  3 , wherein FIG. 3 is a partial front view of crossing gate mechanism  100  in accordance with a preferred embodiment of the present invention, crossing gate mechanism  100  further includes a latch hook assembly  126 . Latch hook assembly  126  latches gate arm adapter  108  in normal operating position  118  in the absence of displacement force  120  and serves to retard the rate of return of gate arm adapter  108  from displaced position  122 . Latch hook assembly  126  includes a latch hook  128  that is pivotally mounted to upper hinge bracket  106 , or alternatively to lower hinge bracket  206 , at a latch hinge  130 . Latch hook assembly  126  further includes a latch hook pressure mechanism  306  that applies a leveraging force to latch hook  128 . Latch hook pressure mechanism  306  includes a latch spring housing  132  attached to cross channel  104 , and/or cross channel  204 , and a latch spring  134  retained within a latch spring housing  132  by a latch spring retaining bolt  302 . Latch spring housing  132  includes one or more, preferably two, gate arm adapter stops  304  that serve as a positive return stop for the gate arm adapter  108  when the adapter is displaced by displacement force  120 , preventing gate arm  108  over travel beyond the normal operating position  118  upon return from displaced position  122 . 
     Latch hook assembly  126 , as shown in FIG. 3, latches gate arm adapter  108  in normal operating position  118  in the absence of displacement force  120 . Latch spring  134  transmits a leveraging force (in a direction indicated by arrow  307 ) to latch hook  128  via latch spring retaining bolt  302 . The leveraging force, transmitted by latch spring  134  through latch spring retaining bolt  302  to latch hook  128 , latches gate arm adapter  108  in normal operating position  118 . Preferably, latch hook  128  will remain latched to gate arm adapter  108  by the leveraged force of latch spring  134  through a minor rotation, such as 8° to 10°, out of the normal operating position  118  of gate arm  202 , allowing crossing gate mechanism to absorb a minor horizontal displacement force without unlatching. Those of ordinary skill in the art will realize that other angles than 8° to 10° may be employed without departing from the spirit or scope of the present invention. 
     FIG. 4 is a partial front view of latch hook assembly  126  when operating as a braking mechanism in accordance with a preferred embodiment of the present invention. Latch hook assembly  126 , as shown in FIG. 4, operates as a drag brake, retarding the rate of return of gate arm adapter  108  to normal operating position  118  when the adapter is in displaced position  122 . When displacement force  120  is applied to gate arm  108  causing gate arm adapter  108  to rotate out of its normal operating position  118 , gate arm adapter  108  applies an upward force on an end of latch hook  128  opposite the end disposed next to latch spring retaining bolt  302 . The upward force causes latch hook  128  to pivot about latch hinge  130 , depressing latch spring retaining bolt  302  and compressing latch spring  134  until latch hook  128  releases gate arm  108 . A brake plate  402 , fitted with a replaceable wear plate  404  that presents a hook and drag surface  406  to latch hook  128 , is mounted on gate arm adapter  108  to receive the pivotally levered force of latch hook  128  when gate arm adapter  108  is displaced from normal operating position  118 . 
     Pressure transmitted by latch spring  134  through latch hook  128  to gate arm adapter  108  via wear plate  404  causes a frictional contact between latch hook  128  and hook and drag surface  406  as the gate arm adapter  108  returns from displaced position  122  to normal operating position  118  and latch hook  128  correspondingly translates across hook and drag surface  406 . The frictional contact retards the return of gate arm adapter  108 . By retarding the rate of return of gate arm adapter  108  from displaced position  122  under power from spring assemblies  112 , latch hook assembly  126  operates as a drag brake and prevents excessive impact between gate arm adapter  108  and latch spring housing  132  at stops  304 . One of ordinary skill in the art realizes that a variety of latch springs  134  are available to provide more or less retarding force on gate arm adapter  108  and brake plate  402  through levered latch hook  128 . Upon return of gate arm assembly  108  to normal operating position  118 , latch hook assembly  126  returns to the position shown in FIG.  3 . 
     In sum, the present invention provides a crossing gate mechanism  100  that can rotate a crossing gate arm  202  out of the way of a damaging force while safely and efficiently returning the gate arm to its normal operating position  118 . Crossing gate mechanism  100  includes a latch hook assembly  126  that latches the gate arm in normal operating position  118 . Crossing gate mechanism  100  further includes a return force mechanism that includes multiple spring assemblies  112  that returns the gate arm  202  to the normal operating position after the gate arm has been displaced by a displacing force  120 . By varying the number of spring assemblies  112  used in the return force mechanism, or by using spring assemblies that apply a greater or lesser return force, crossing gate mechanism  100  is capable of being adjusted for installation in conditions requiring varied gate arm lengths and flexibilities and is capable of being adjusted for varying gate arm return force requirements. Latch hook assembly  126  also operates as a drag brake that is capable of preventing excessive impact when gate arm  202  returns to its normal operating position from a displaced position  122 . 
     Crossing gate mechanism  100  also includes return stops  304  that prevent gate arm over travel upon return from a displaced position  122 . By employing a drag brake, as opposed to a hydraulic piston of the prior art, to retard the rate of return of the gate arm  202  from a displaced position  122 , the present invention is less expensive than existing spring-based crossing guard mechanisms. Furthermore, by employing a return force mechanism that includes one or more spring assemblies applying an approximately horizontal return force when crossing gate mechanism  100  is in an approximately horizontal position, the potential for deterioration of a cam-and-bearing based crossing guard mechanism is eliminated. 
     While the present invention has been particularly shown and described with reference to particular embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

Summary:
A railroad crossing gate mechanism is provided that includes a gate arm adapter which is pivotally mounted to allow a lowered gate arm to rotate away from a generally perpendicular force in a generally horizontal plane. The gate arm mechanism further includes multiple interchangeable spring assemblies that generate a return force to bring a displaced gate arm back to its normal operating position, and a latch hook assembly for selectively latching the gate arm in its normal position and controlling the rate of return of the gate arm from a displaced position through application of a pivotally leveraged force to a braking surface.