Highway crash cushion and components thereof

A highway crash cushion includes a single, central, rigid, guide tail that guides the crash cushion in axial collapse. Diaphragm assemblies are each provided with recessed legs, and a central guide that slides along the rail while locking against the rail in a lateral collision. The diaphragm assemblies support fender panels that include four longitudinally extending ridges, a central slot, and a tapered trailing edge that reduces vehicle snagging. Energy absorbing elements are disposed between the diaphragm assemblies, and each includes an indicator that clearly indicates when the element has been compressed and possibly damaged.

BACKGROUND OF THE INVENTION

The present invention relates to improvements to a highway crash cushion of the type having an array of diaphragms, a plurality of energy absorbing elements disposed between the diaphragms, and an array of fender panels extending alongside the diaphragms.

Highway crash cushions of this general type have proven to be successful in a wide variety of applications. Walker U.S. Pat. No. 3,982,734 describes one early version of such a crash cushion, and Meinzer U.S. Pat No. 4,321,989 discloses another. Typically, such crash cushions are used alongside highways in front of obstructions such as concrete walls, toll booths and the like.

In the event of an axial impact, the crash cushion is designed to absorb the kinetic energy of an impacting vehicle as the crash cushion collapses axially. In such an axial collapse, the diaphragms move closer to one another, the fender panels telescope over one another, and the energy absorbing elements are compressed. After such a collision many of the component parts can be reused by repositioning the diaphragms and fender panels in the original position, and replacing the energy absorbing elements and other damaged components.

The performance of such a highway crash cushion in lateral rather than axial impacts is also significant. When an impacting vehicle strikes the fender panels obliquely, it is desirable that the crash cushion act as a guard rail, which redirects the impacting vehicle without sending it back into traffic at a steep angle, and without allowing the impacting vehicle to move into the region on the other side of the crash cushion protected by the crash cushion.

Another aspect of such crash cushions is the need for simple maintenance and repair. Typically, such crash cushions are positioned alongside a high speed roadway, and it is therefore important to minimize traffic disruption and to minimize exposure of maintenance personnel to the hazards of adjacent traffic in maintenance and repair procedures.

In view of the foregoing operational and maintenance requirements for crash cushions, there is a need for an improved crash cushion that provides increased rigidity in a lateralimpactsimpactthat decelerates an impacting vehicle in a more controlled manner in a lateral impact, both when the vehicle is moving along the fender panels in a forward and in a reverse direction, and to provide a crash cushion which is simpler to install and easier to maintain.

SUMMARY OF THE INVENTION

The present invention is directed to a number of separate improvements to a highway crash cushion of the type defined initially above. These improvements are preferably used together as described below. It should be clearly understood, however, that these improvements can be used separately from one another and in various subcombinations in alternative applications.

According to a first aspect of this invention, a highway crash cushion of the type described above is provided with a single rail disposed under the crash cushion and anchored to a support surface. A plurality of guidesareisprovided, each coupled to a respective one of the diaphragms and each substantially centered with respect to the respective diaphragm. The guides are mounted to the rail to slide along the rail in an axial impact, and to restrict movement of the diaphragms with respect to the rail in both lateral directions. The rail is substantially centered with respect to the diaphragms, thereby reducing any tendency of an impacting vehicle to snag on the rail. Furthermore, since a single, centered rail is used, installation is simplified.

According to a second aspect of this invention, a highway crash cushion as described above includes an improved diaphragm assembly. Each diaphragm assembly includes an upper part that comprises a diaphragm adapted to apply compressive loads to an adjacent energy absorbing element, and a lower part secured to the upper part. The lower part comprises a leg assembly comprising an upper portion mounted to support the upper part, a lower portion, two side portions and a centerline extending between the side portions. Each lower portion is connected to two feet shaped to support the leg assembly on a support surface. The feet extend outwardly from the respective leg assembly, away from the centerline, such that the feet are separated from the respective centerline by a distance DF, the side portions are separated from the respective centerline by a distance DL, and the ratio DF/DLis greater than 1.1. Alternately, the difference DF-DLcan be maintained greater than 4 cm. By recessing the legs with respect to the feet, there is a reduced chance that an impacting vehicle will snag on the legs in a lateral impact. In this way, any tendency for the impacting vehicle to be decelerated in an uncontrolled manner is reduced.

Preferably, each leg assembly supports a removable guide on the centerline. This guide includes a first pair of spaced plates facing the centerline on one side of the centerline, and a second pair of spaced plates facing the centerline on the other side of the centerline. This guide cooperates with the guide rail described above to provide rigidity in the crash cushion in a lateral impact.

According to a third aspect of this invention, a fender panel for a highway crash cushion as described above includes a trailing edge, a leading edge, and a side edge. The trailing edge is tapered such that the first and second portions of the trailing edge are separated from a reference line transverse to the side edge by lengths L1and L2, respectively. The length L1is greateristhan the length L2by at least 10 cm. Preferably, the fender panel defines a plurality of ridges extending generally parallel to the side edge, and the first portion of the trailing edge is positioned in a groove of the fender panel between adjacent ones of the ridges. The tapered trailing edge has been found to reduce the tendency of an impacting vehicle to snag on the fender panel when the impacting vehicle approaches the fender panel from the direction of the trailing edge.

According to a fourth aspect of this invention, a fender panel for a highway crash cushion as described above comprises four parallel ridges separated by three parallel grooves. The grooves comprise a central groove and two lateral grooves. The central groove forms a slot extending parallel to the ridges, and the slot extends over a length of at least one half the length of the fender panel. The grooves each have a respective width transverse to the slot, and the central groove width is greater than each of the lateral groove widths. In use, a fastener passes through the slot and is secured to the crash cushion to allow the fender panel to slide relative to the fastener. This arrangement has been found to provide increased strength to the fender panel with respect to bending, flattening out, and tear-out, and increased pull-out resistance to the fastener.

According to a fifth aspect of this invention, a highway crash cushion energy absorbing element is provided with an indicator movably mounted on the energy absorbing element to move between first and second positions. This indicator is visible outside of the energy absorbing element in at least the second position. A retainer is coupled to the energy absorbing element to retain the indicator in the first position prior to distortion of the energy absorbing element. The retainer is positioned and configured such that distortion of the energy absorbing element by more than a selected amount releases the indicator from the retainer. In the preferred embodiment described below, a spring is coupled to the indicator to bias the indicator to the second position, and the energy absorbing element includes a housing that forms a zone of increased compressibility in the region between the mounting location for the indicator and the mounting location for the retainer.

In use, a maintenance inspector can readily determine remotely whether an individual energy absorbing element has been deformed (as for example in a low speed collision). Such deformation releases the indicator from the retainer and allows the indicator to move to the second position, where it can readily be seen.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Turning now to the drawings,FIG. 1shows a perspective view of a highway crash cushion10that incorporates a presently preferred embodiment of this invention. The crash cushion10is mounted to slide axially along a guide rail12. The crash cushion10includes an array of spaced, parallel diaphragm assemblies14. Fender panels16are secured between adjacent diaphragm assemblies14, and the fender panels16and the diaphragm assemblies14form an array of enclosed bays. An energy absorbing element22is disposed within each of the bays, between an adjacent pair of diaphragm assemblies14. A nose fender24extends around the forwardmost energy absorbing element22.

The following discussion will take up each of the major components of the crash cushion10.

The Guide Rail

FIGS. 2-5show various views of a portion of the guide rail12. In this embodiment, the guide rail12is made up of two or more segments26. Each of the segments26includes an upper plate28and two side plates30. The upper plate28forms two opposed, horizontally extending flanges29. The side plates30are secured to a series of lower plates32. Each of the lower plates32defines at least two openings34sized to receive a respective ground anchor (not shown in FIGS.2-5). Bracing plates36are secured between the side plates30and the lower plates32to provide additional rigidity.

As shown inFIG. 4, one end of the segment26defines a central recess38which in this embodiment is generally rectangular in shape. As shown inFIGS. 2,3, and5, the other end of the segment26defines a central protrusion40. The central protrusion40is generally rectangular in shape, but it defines a sloping lower surface42. In this embodiment the central protrusion40is welded in position in the rearward end of the segment26.

Depending upon the application, the crash cushion10can have a varying number of diaphragm assemblies14. In the example shown inFIG. 1, there are five separate diaphragm assemblies14, and the guide rail12is made up of two segments26. The central protrusion40of the forward segment fits into the central recess38of the rearward segment to maintain alignment of the two segments26.

Simply by way of example, and without intending any limitation, the following exemplary dimensions have been found suitable. The upper plate28can be formed of steel plate 10 cm in width and 1.3 cm in thickness. The side plates30can be formed of flat bar 7.6 cm in height and 0.95 cm in thickness. The lower plates32can be 13 cm in thickness. A hot rolled steel such as ASTM A-36 or AISM 1020 has been found suitable, and standard welding techniques are used to secure the various components together.

The segments26are shorter and therefore more easily transported and installed than a one-piece guide rail. Furthermore, in the event of damage, only the damaged segment26must be replaced, and maintenance costs are thereby reduced. The sloping lower surface42of the central protrusion40and the slots in the lower plate32near the central protrusion40allow the damaged segment26to be removed by lifting up the end forming the central recess38.

By providing three separate segments, having lengths appropriate for one bay, two bays, and three bays, respectively, crash cushions of varying lengths between one bay and twelve bays can readily be assembled.

The Diaphragm Assemblies

FIGS. 6 and 7show front and side views, respectively, of a diaphragm assembly14. Each diaphragm assembly14includes an upper part44and a lower part46. The upper part44forms a diaphragm, and includes a central panel48, which in this embodiment is a ridged metal plate, identical in cross section to the fender panels described below. The panel48is rigidly secured at each end to a respective metal plate50. Support brackets52can be secured to the lower edge of the panel48to support the energy absorbing elements. Alignment brackets54can be secured to the panel48to locate the energy absorbing elements laterally in the bay.

The lower part46of the diaphragm assembly14includes a leg assembly56. The leg assembly56in this embodiment includes two rectangular-section legs58which are rigidly secured to the upper portion44, as for example by welding. The leg assembly56forms an upper portion60that is secured to the diaphragm of the diaphragm assembly14, two side portions62, and a lower portion64. The side portions62are symmetrically positioned with respect to a centerline66that is vertically oriented in this embodiment.

Each of the legs58supports a respective foot68. The feet68extend downwardly and outwardly from the lower portion64of the legs58. Each of the feet68terminates in a lower plate70and a pair of side plates72. The lower plate70is shaped to support the diaphragm assembly14on a support surface S, and to slide freely along the support surface S. This support surface S can be formed for example by a concrete pad. The side plates72form ramps extending upwardly from the lower plate72to the foot68. These ramps reduce snagging of the tire or wheel of an impacting vehicle on the lowermost portion of the foot68.

InFIG. 6the reference symbol DFis used to designate the distance of the outermost edge of the foot from the centerline and reference symbol DLis used to designate the distance of the outermost portion of the side portion62from the centerline66.

As shown inFIG. 6 and 7, the legs58are recessed with respect both to the feet68and the panel48. This way, any tendency of the wheel or tire of a vehicle moving along the fender panels to snag on the legs58is substantially reduced. The ratio DF/DLis greater than 1.1, preferably greater than 1.4, and most preferably greater than 1.8. In this way, the legs58are substantially recessed. Similarly, the difference between DF/DL, is greater than 4 cm, preferably greater than 8 cm, and most preferably greater than 12 cm to obtain this advantage. In this preferred embodiment the ratio DF/DLis 1.85 and the difference DF-DLis 14.8 cm.

As shown inFIG. 6, two guides74are removably secured between the legs58, as for example by fasteners76. Each of the guides74includes a respective pair of spaced, horizontal plates78,80facing the centerline66. The plates78,80receive the flanges29therebetween, with the upper plates78resting on the upper surface of the flanges29and the lower plates80positioned to engage the lower surface of the flanges29.

During operation, the weight of the diaphragm assemblies14is supported by the feet68and the plates78. The plates80prevent the diaphragm assemblies14from moving upwardly with respect to the guide rail12in an impact.

Because the guides74are held in place in the diaphragm assembly14by removable fasteners76, the guides74can be replaced if damaged in an impact without removing the diaphragm assemblies14.

As the crash cushion10collapses in an axial impact, the diaphragm assemblies14slide down the guide rail12, while the guide rail12prevents substantially all lateral movement of the crash cushion10. Preferably, the guides74have a substantial length, and can for example be 20 cm in length and approximately 1.3 cm in thickness. A hot rolled steel such as ASTM-36 or AISM 1020 has been found suitable. The length of the guides74reduces any tendency of the diaphragm assemblies14to rock and bind to the guide rail12in an axial collapse, thereby insuring a stable, consistent axial collapse of the crash cushion. Because the lower plates80engage the underside of the flanges29, overturning of the crash cushion10is prevented. The upper plates78of the guides74maintain the diaphragm assemblies14at the proper height relative to the guide rail12, in spite of irregularities in the support surface S. The guide rail12and the guide74provide lateral restraint guided collapse, and resistance to overturning throughout the entire axial stroke of the collapsing crash cushion10.

Furthermore, in the event of a side impact against the fender panels16, the guides74tend to lock against the guide rail12as they are moved by the impacting vehicle into a position oblique to the guide rail12. This locking action provides further lateral rigidity to the crash cushion10in a lateral impact.

The wide separation between the feet68increases stability of the crash cushion10and resistance to overturning in a lateral impact.

The Fender Panels

Turning now toFIGS. 8 and 9, the fender panels16have been improved to provide increased rigidity and improved operation to the crash cushion10.FIG. 8is a cross-sectional view through one of the fender panels16. As shown inFIG. 8, the fender panel16includes four parallel ridges82and three parallel grooves. These grooves are not identical to one another, and the central groove84is in this embodiment wider than the lateral grooves86. The groves84,86define lower-most portions that are co-planar, and the ridges82are uniform in height.

Because the fender panel16includes four ridges82instead of the conventional three, it is symmetrical about the central groove84. This allows the longitudinally extending slot88to be positioned on the flat portion of the central groove84. It has been discovered that for a fender panel of the same height, material and thickness as in a prior art thrie beam, the improved geometry discussed above increases the section modulus and the tensile strength of the panel, by approximately 20% for the section modulus, and approximately 15% for the tensile cross section. Furthermore, by having three grooves rather than two as in the prior art thrie panel, an additional fastener can be used to secure the fender panel16to the adjacent diaphragm assembly14, thereby increasing tear out strength by 50%.

Simply by way of example, preferred dimensions for the fender panel16are listed in the attached Table 1. In this embodiment, the fender panel can be formed of a 10 gauge, cold rolled steel such as that identified as alloy ASTM-A-570, grade 50. This material has a yield strength of 50,000 psi.

FIG. 9shows a fender panel metal plate90in plan view, prior to formation of the ridges82and grooves84,86. This metal plate90defines a longitudinal slot88and three attachment apertures92. The metal plate defines a leading edge94, a trailing edge96and two side edges93. In the following discussion the leading edge94will be considered to define a reference line that is perpendicular to the side edges98. In alternate embodiments it is not required that the leading edge94be shaped in this manner. The apertures92are used to fasten the fender panel to a forward diaphragm assembly14, and the slot88is used to fasten the fender panel to a rearward diaphragm assembly14. The slot88extends over more than one-half the length of the plate90.

As shown inFIG. 9, the trailing edge96is tapered, and it includes a first portion100and a second portion102. In this embodiment the trailing edge96is symmetrical, and the first portion100is aligned with the slot88, while the second portion102is formed in two parts, one adjacent each of the side edges98. The symbol L1is used for the separation between the first portion100and the leading edge94, and the symbol L2is used for the separation between the second portion102and the leading edge94. In this embodiment the difference L1minus L2is greater than or equal to 10 cm. Preferably this difference is greater than 20 cm, and most preferably it is greater than 30 cm. In this embodiment L1equals 131 cm, L2equals 98 cm and L1-L2equals 33 cm. The slot88can be 85 cm in length. As shown inFIG. 1, the first portion100of a given fender panel16is disposed in the central groove84of the fender panel16that is adjacent to the rear.

It has been discovered that this arrangement reduces vehicle snagging in a wrong-way impact, where the impacting vehicle slides along the side of the crash cushion10, approaching the fender panels16such that the trailing edges96make initial fender panel contact with the vehicle (from left to right with respect to the side of the crash cushion10shown in FIG.1). Because the first portions100are disposed in the central grooves84, they are somewhat recessed and less likely to snag the vehicle. The trailing edge96is tapered, sloping upwardly on the upper portion of the trailing edge and downwardly on the lower portion of the trailing edge. This tapered arrangement for the trailing edge has been found to reduce vehicle snagging. When the vehicle sheet metal begins to tear as it slides longitudinally down one side of the crash cushion10, the vehicle sheet metal encounters an upward or downwardly sloping portion of the trailing edge96. This causes the tearing action to cease. Snagging of the vehicle tends to be self-releasing, and not to become progressively worse as the vehicle proceeds down the crash cushion10in a wrong-way impact.

Though the trailing edge96discussed above is symmetrical about the centerline of the fender panel16, this is not required in all embodiments. If desired, various asymmetrical arrangements can be used. Also, if desired the fender panel can define multiple first portions, each disposed in a respective groove, and each separated by a substantially constant distance from the reference line.

As shown inFIG. 1, the rearward portion of the fender panel16is secured to the rearward adjacent diaphragm by a fastener104, whichincludes a plate106. This plate106has sides shaped to conform to the adjacent ridges82, and forward and rearward edges that are bevelled to reduce vehicle snagging. The plate106is relatively large, and can for example be 25 cm in length, and can define a lug extending downwardly into the respective slot88. This arrangement provides a system in which the fender panels telescope smoothly against one another in an axial collapse, and in which pull out of the fastener104is substantially prevented.

The improved geometry of the fender panel16is not restricted to use with highway crash cushions, but can be used with a variety of other roadside barriers, including guard rails. In some of these applications the slot88may not be required.

The Energy Absorbing Element

FIG. 10shows an exploded view of one of the energy absorbing elements22. This energy absorbing element22includes an outer housing108that is formed in two parts that meet at a horizontally oriented seam110. The housing defines front and rear surfaces112,114that are positioned against the adjacent diaphragm assemblies14. Each housing108also defines a respective top surface116. The top surface116defines a zone of increased compressibility118that in this embodiment defines an array of parallel pleats or corrugations120. These corrugations120extend generally parallel to the front and rear surfaces112,114. The zone of increased compressibility118ensures that in the event the housing108is compressed axially between the front and rear surfaces112,114, this compression is initially localized in the zone118. Simply by way of example, the housing108can have a length, height and width of about 82, 57, and 55 cm, and the zone118can have a width of about 11 cm.

The housing108can be molded of any suitable material, such as linear, low-density polyethylene having an ultraviolet inhibitor for example. The housing108can contain any suitable energy absorbing components109, and this invention is not limited to any specific choice for these components149. For example, the energy absorbing components can be formed as described in U.S. Pat. No. 4,352,484, using a paper honeycomb material (5 cm cell diameter and 5 cm layer thickness) and a polyurethane foam. Alternately, the energy absorbing elements109can be formed as four metal honeycomb elements111, each 17.8 cm thick, with a cell diameter of 3.8 cm. The elements are preferably formed of low carbon, fully annealed steel sheets (0.45 mm thick in one element and 0.71 mm thick in the other three). In the embodiment described here, the forward energy absorbing elements use the paper honeycomb material and the rearward energy absorbing elements use the steel material, both as described above. If desired, the brackets52,54can be deleted and replaced with brackets (not shown) on the panels48that support the housing108at the lower, protruding edge of the upper part of the housing, adjacent the seam110.

FIGS. 11 and 12show two views of an indicator122that is mounted on the top surface116of the energy absorbing element. This indicator22includes a plate124that has an outer surface. This outer surface can for example be covered with a reflective material. The plate124is mounted for pivotal movement by a mounting126on a first side of the zone118. The indicator122includes a lip128on the opposite end of the plate124. A retainer130is mounted to the top surface116on the opposite side of the zone118. As best shown inFIG. 12, the indicator122is pivotally movable between a first position in which the plate124is alongside and recessed into the top surface116, and a second position in which the plate124is pivoted upwardly and outwardly to a position substantially perpendicular to the top surface116. The first and second positions can each correspond to a range of positions. In the second position the plate124is clearly visible from outside the energy absorbing element122. A spring132biases the indicator122to the second, more visible position.

As shown inFIG. 12, the indicator122is initially installed in the first or lower position. In this position the retainer130overlaps the lip128by a selected distance, which can correspond to a range of distances. In this embodiment, the selected distance is about 1 to 2 cm. The indicator122is mounted to the housing108at a first location, and the retainer130is mounted to the housing at a second location.

In the event that the housing108is distorted even temporarily in a low speed event such that the first and second locations approach one another by more than the selected distance of overlap between the lip128and the retainer130, then the indicator128moves out of engagement with the retainer130, and the spring132moves the indicator122to the upper position shown in FIG.11.

A maintenance inspector can readily determine if any of the energy absorbing elements22has been compressed excessively simply by looking for indicators122in the extended position. This can be done at a considerable distance, and does not require close inspection.

Of course, many alternatives to the indicator122are possible. For example, the spring does not have to be a separate element, and the desired biasing force can be obtained by bending of the indicator122itself. Furthermore, the zone of increased compressibility can be formed with many geometries, and corrugations are not always required. If desired, the retainer130can engage the indicator122along the side rather than the end of the indicator122. Furthermore, the indicator can move between the first and second positions with translational rather than pivoting movements.

Conclusion

From the foregoing detailed description it should be apparent that an improved crash cushion has been described. The central guide rail reduces vehicle snagging and simplifies installation while providing excellent rigidity against lateral movement and controlled axial collapse. The improved diaphragm assembly utilizes recessed legs that again reduce vehicle snagging. These assemblies are rigid, and are designed to lock against the guide rail in a lateral impact. The improved fender panels are stronger, with an improved cross-sectional shape that increases pull out resistance and enhances a controlled axial collapse. The tapered trailing edge further reduces vehicle snagging in a wrong-way collision. The energy absorbing element indicator indicates remotely to a maintenance inspector that the element has been compressed and possibly damaged, and is therefore in need of replacement.

Of course, it should be understood that a wide range of changes and modifications can be made to the preferred embodiment described above. It is therefore intended that the foregoing detailed description be considered as illustrative and not as limiting. It is the following claims, including all equivalents, that are intended to define the scope of this invention.