TECHNICAL FIELD

[0001] The present invention relates to the safety treatment for the ends of highway guardrails.

BACKGROUND

[0002] The terminal is the end of a guardrail and is often the part of the guardrail that, when struck by a moving vehicle, redirects the kinetic energy of the moving vehicle and its occupants. A guardrail terminal must serve two basic functions: (1) anchor the guardrail to allow the barrier to develop tension when struck on the traffic face and (2) mitigate the risks of serious and fatal crashes when struck on the end of the barrier.

Guardrail terminals generally fall one of three categories, non-energy absorbing, energy absorbing by tension, and energy absorbing by compression terminals. Energy absorbing terminals must be designed to provide a control deceleration for vehicle striking the terminal, Energy absorbing terminals have been shown by many studies to provide greatly improved safety performance compared to non-energy absorbing systems.

[0003] Many energy absorbing guardrail terminals rely on deformation of the guardrail to dissipate energy. Guardrail deformations were controlled by impact head that either flatten, cut, or kinked the rail elements as it was pushed down the rail during impact.

[0004] Most guardrails use a rail element in the shape of a "w" beam (W beam) which, when deformed or flattened dissipates a significant amount of energy. Unfortunately, the amount of energy dissipation during rail flattening is difficult to change from a basic level. As a result, designers of guardrail terminals cannot use flattening based designs when the impacting vehicle must be brought to stop over a short distance or the forces on the impacting vehicle need to be reduced. The impact head applies a compressive load to the W beam guardrail in order to produce these deformations. However, compression loads can become excessive and cause the guardrail to buckle. The buckled guardrail can then penetrate into the passenger compartment of the vehicle and impale the occupants.

[0005] Tension-based systems have been developed that incorporate a method for restraining the end of the W beam guardrail. The impact head slides down the rail and an anchor system pulls the rail through the impact. By keeping constant tension on the W beam guardrail, buckling of the rail is minimized or prevented entirely.

[0006] U.S. Patent No. 928, 928 describes a guardrail end plate that functions as a compression terminal that uses flattening of the W shaped guardrail as it slides down the rail after impact of a vehicle.

[0007] U. S. Patent Application No. US 200910272956 Al recites a tension method of flattening the guard rail in the vertical direction. This function is accomplished by forcing the guardrail element through a squeezer section that progressively reduces the height of the rail until it is virtually flat. Although this design does decrease impact forces, it provides a narrow range of energy dissipation. The embodiment described in this patent utilizes a channel through which the flattened rail element is pushed. Increasing the length of this channel will increase the impact force required to push the impact head down the rail. Unfortunately, this design directs the guardrail under the car and the top edge of the W beam can act as a knife and cut through vehicle components, such as a gasoline tank. Further, friction in the channel produces a force that resists impact head movement that is very close to the ground. This resisting force will produce an overturning moment that causes the impact face to lean backward and possibly allow the vehicle to vault over the top of the impact head.

[0008] U. S. Patent No. 7,883,075 B2 recites the use of the bended impact head using stacked plates, a V -shaped cutout, and tension. This guardrail terminal modifies at least one of the support post to an upper portion, a middle portion that is weekend, and a lower portion that remains in the ground when impact sheers away the upper portion.

[0009] U. S. Patent No. 6,173,943 Bl utilizes a flat end plate facing oncoming traffic with an array of vehicle deflecting rails secured to the support post extending along the roadway with the impact receiving element slid ably mounted, a stop coupled to at least one of the impact receiving elements, the impact receiving element coupled to the first post such that impact forces on the vehicle engaging portion are applied to the first post and break the first post before the stop limits sliding of the impact receiving element relative to the first rail.

[00010] U. S. Patent No. 6,220,5751 details an impact head assembly with the first support post attached to the rail so as to create tension that increases as the support post upper portion is sheared off.

[0001 1] U. S. Patent No. 7,699,293 B2 describes a guardrail cable routing means configured to form a torturous path through which a cable can be threaded. The torturous path includes a 1800 turn. As the guardrail is collapsed by a vehicle, the resistance caused by the cable applies tension in the direction opposite from the direction traveled by the impacting vehicle, slowing the collision.

[00012] U. S. Patent No. 5,797,591 describes bolting the impact head to a post mounted in the ground just in front of it and connecting it to the first post of the guardrail.

[00013] U. S. Patent No. 5,931,448 represents this inventor's previous collaborative attempt to address guardrail impact at the head by slowly tapering the head of the guardrail to ground level with a drop -down section that extends the guard rail to the ground.

SUMMARY OF THE INVENTION [00014] The current invention incorporates a novel way to implement tension; thereby representing an improvement on the current state of the art. This system utilizes an impact head to flatten the guardrail and also to guide the flattened guardrail through the front of the impact head, the tension is constantly maintained. Instead of passing the rail element out of the side of the terminal, as is done in several of the above mentioned methods, passing the flattened rail through the front of the terminal provides a superior structure for dissipating energy while minimizing the risk of the rail penetrating into the occupant compartment or cutting critical vehicle structural elements, such as the gasoline tank or brake lines. A connector member attached to the guardrail and secured to the ground provides tension to hold the guardrail and prevent buckling. The preferred connector is a plurality of flat steel straps attached to the leading edge a W beam and bolted to an anchor in the ground in front of the terminal head. The straps provide the tension necessary for the impact head flatten the guardrail. Further by twisting each strap 90° and bolting it to the top of the anchor post set into the ground in front of the terminal head, the guardrail element 1 is forced to twist ninety degrees until it is flat against the ground as it is pulled out the front of the terminal head.

[00015] The combination of using flat straps to enable the guardrail to twist and incorporating an oversized open front of impact head allows the new system to prevent the guardrail element from becoming entangled in front of the vehicle while it is in contact the impact head. The open front design enables a much stronger connection between the front of the impacting vehicle and the impact head that will assure the impact head does not twist as the guardrail passes through.

[00016] Further, the flattening and twisting of the W beam 1 as it passes through the impact head increase the energy dissipation of terminal system. It should be noted that placing the bottom of the impact head closer to the ground or passing the guard rail out of the bottom of the impact head increases the likelihood the vehicle will roll over the guard rail.

[00017] A further purpose and object of the invention is to address reverse direction impacts, that is, impacts to the guardrail from the direction opposite the one the guardrail is set up to primarily provide for. The present invention has additional structure is incorporated into the design to address this in an improved way. In this situation a vehicle that is traveling in the reverse direction strikes the face of the guardrail downstream from the terminal impact head.

[00018] When a vehicle strikes the rail in this manner at sufficient speed, the impact head can be projected to the end of the steel straps and become lodged on the anchor where it would again be struck by the impacting vehicle. Because the terminal head is likely to be essentially immovable when it is struck the second time, the guardrail rollover increases greatly. The solution to this problem is to provide a detachable connection between the guardrail and the end of the feeder chute on the impact head. Bolt slots in the guardrail impact head anchor bracket opening toward the front provide the secure fastening from one direction while allowing detachment in another direction. The impact head is securely anchored to the rail element during the reverse direction imp acts because the bolts between the guardrail and the reverse direction bracket bear against the impact head. When the impact head is pushed down the guardrail the bolts slide out of slots in the reverse direction bracket.

[00019] Another option for reducing the risk associated with a reverse direction (rearward) impact is to allow the bolts attaching steel straps to the anchor to release when the impact head is pushed between the anchor post straps. A hole with an oversized key way is sufficient to produce this behavior, as is turning the slots rearward. There are a number of detachment/ restraint system options which would prevent the head from moving off the guardrail.

BRIEF DESCRIPTION OF THE DRAWINGS

[00020] Referring to the drawings which are appended hereto and which form a portion of this disclosure, it may be seen that:

[00021] Fig. 1 shows a side view of the guardrail end, the last two support posts adapted to safely shear away and the post mounted in the ground in front of the impact head assembly with the flat strips anchored to it.

[00022] Fig. 2 is a top view of the guardrail end, the last two support posts adapted to safely shear away and a post mounted in the ground in front of the impact head assembly with the flat strips anchored to it.

[00023] Fig. 3 shows a reverse direction bracket.

[00024] Fig. 4 shows the fastening of the flat straps to a W beam guardrail.

[00025] Fig. 5 shows the bottom view of the impact head assembly with the interior throat which compresses the W beam and guides it to remain confined by the terminal impact head assembly.

DETAILED DESCRIPTION

[00026] One or more of the above objects can be achieved, at least in part, by providing a guardrail 1 , formed as a W (cross section) beam, which is supported by a plurality of support posts 2. Impact head assembly 35 is attached to the guardrail 1 by bolts, screws, rivets, nails, glue or welding. In the preferred embodiment, shearable bolts 13 are utilized to attach impact head assembly 35. Reverse direction bracket 4 connecting impact head 3 to guardrail 1 is provided with slots 42 such that the slots open forwardly (toward the oncoming traffic). Reverse direction bracket 4 is attached to impact head assembly 35 by attachments such as bolts, screws, or rivets passing through bolt holes 41. In the preferred embodiment bolts 1 1 are the attachment device. Reverse direction bracket 4 is then attached to guardrail 1 by bolts 12 captured the slots 42. Any slidab ly captured member would work including bolts, rivets, nails, or screws as long as the member fits into the slots 42 and as long as it allows for the reverse direction bracket to slide relatively easily when hit in the direction of oncoming traffic (forward). Near reverse direction bracket 4, impact head 35 is shearably attached to guardrail 1 in any suitable manner such as welding, screws, bolts, nails or glue. In the preferred embodiment, bolts 13 are the attachment members.

Reverse direction bracket 4 is adapted to be wedge shaped and attached with the wider part of the wedge shape at the forward end in order to channel the bumper or fender of a vehicle colliding with the guardrail from the opposite direction of the usual direction of travel.

[00027] Impact head assembly 35 is adapted to flatten the W beam guardrail 1 as it moves down the guardrail when impacted by an object in the front. This is

accomplished by the rear portion 15 of assembly 35 having the inside thereof shaped like a funnel with the narrow end facing the oncoming traffic direction (forward) as shown in Fig. 5.

[00028] At least one, but preferably a plurality, of flat strips 5, made of high toughness and tensile strength material, are attached to guardrail 1. Fig. 4 shows the strips attached to the W beam with boltsl4. Wire rope, cable, or other similar means of providing tension will suffice to create tension but will not twist the guardrail as it is moved under impact. Best results in protecting the occupants are obtained by flattening and twisting the guardrail ninety degrees during impact so it is roughly parallel to the road. Front anchor post 6 is embedded in the ground with only the connector plate portion of it above ground or under ground near the surface. Each of the flat strips 5 that are attached to guardrail 1 extend through the front of impact head 3, are twisted ninety degrees relative to the plane of guardrail 1 , and are attached to front anchor post 6. Any means of attachment is sufficient such as welding, rivets, bolts, screws, nails or glue. The preferred embodiment attaches flat strips 5 to front post 6 with bolts 14. First support post 7 is placed behind impact head 3 embedded into the ground and attached to guard rail 1.

[00029] From the forgoing it may be seen that I provide a twist box guardrail terminal including a guardrail beam 1 ; an impact head assembly 35 of open front configuration 3, adapted to flatten the beam 1 as it moves down the beam 1 when impacted by an object; shearable bolts 10 to attach the impact head assembly 35 to the guardrail 1 ; a front anchor 6 ; at least one connector 5; members 51 attaching the connector 5 to the guardrail 1 such that said connector 5 extends from the guardrail 1 through the open front of the impact head 3 and is attached to the front anchor 6 causing the front of the guardrail 1 to remain in tension during an impact.

[00030] The twist box guardrail terminal further includes a rear portion 15 shaped as a funnel disposed with the funnel tapering forwardly to a narrow end wherein the funnel is substantially planar along the top and bottom but sloped along the sides. The connector 5 is preferably at least one flat strip which is bolted or otherwise attached to the guardrail and extends from the guardrail through the rear portion 15 and out the open front of the impact head 4 for attachment to the front anchor 6. In a preferred embodiment connector 5 is a plurality of flat strips each attached to the beam 1 at vertically spaced points and then twisted 90 degrees relative to the plane of the beam before attachment to the front anchor post. Alternatively the connector 5 is a plurality of wire strips or cables attached to the guardrail and extending from the guardrail through the open front of the impact head for attachment to the front anchor.

Preferably, the front anchor is a post embedded in the ground with a connector plate secured thereto to facilitate attachment to connector 5. The connector plate may be at ground level, or below ground level.

[00031] My twist box guardrail terminal impact head 35 is preferentially connected to a reverse direction bracket 4 by a set of bolts 1 1 passing through the bracket 4 at apertures 41 and through complementary apertures in the head assembly 35. Bracket 4 uni-directionally connects the impact head assembly to guardrail 1 by virtue of a set of bolts 12 carried by guardrail 1 and captured in slots 42 which are open to the oncoming traffic direction.

[00032] The forgoing design is intended to permit the impact head assembly to move longitudinally along the rail upon frontal impact, thereby disengaging slots 42 from bolts 12 and deforming the guardrail to a flat or horizontal position near the ground by virtue of the movement of the impact head assembly, thereby absorbing energy from the impact and preventing the guard rail from imbedding into the vehicle. Contra -wise, in reverse direction impacts the impact head assembly is secured by the bolts 12 in slots 42 and constrained to prevent secondary collisions.

[00033] While in the foregoing specification this invention has been described in relation to certain embodiments thereof, and many details have been put forth for the purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.