Patent Application
20070252124
1. Field of the Invention
The present invention relates to guardrail systems having impact absorbing end units.
2. Description of the Prior Art
Guardrails are commonly provided along the sides of roadways to prevent vehicles from going off the roadway in the event of the driver losing control of the vehicle. In particular, where a precipice is located adjacent the roadway a guardrail can save the lives of a vehicle's occupants by preventing the vehicle from going over the edge of the precipice in the event of the driver losing control of the vehicle. It is desirable for guardrail systems to also have impact absorbing properties to minimize the risk of injury to the occupants of a vehicle that impacts the guardrail system. Where one roadway intersects another roadway, for example, a break is created in the guardrail system resulting in the creation of guardrail system terminal portions. The impact absorbing properties of the guardrail system are particularly important at these end or terminal portions of the guardrail system because vehicles can potentially impact the terminus of the guardrail system head on resulting in far higher impact energies that are further concentrated by a relatively small impact area at the terminus of the guardrail system. Consequently, the potential for catastrophic injuries to a vehicle's occupants are far greater at the terminus of a guardrail system. For this reason guardrail systems having impact absorbing terminal portions have been proposed in the art. However, none are seen to have the unique structure and advantages of the present invention as will become apparent from the detailed description below.
The present invention is directed to a guardrail system having an impact absorbing terminal portion and to novel components parts useful with a guardrail system.
The present invention includes a sled designed to receive the impact of a vehicle. The sled forms part of the terminal portion of the guardrail system. The terminal portion of the guardrail system also includes one or more cables that are anchored to the ground and pass through the sled. The sled supports a cable break that is in engagement with the cable. The sled is supported by a releasable post that is released from its base upon the impact of a vehicle. The cable or cables extend for some distance from the sled along the guardrail system. Once the post supporting the sled is released from its base due to the impact of a vehicle, the sled can move along the cable with the friction between the cable brake and the cable gradually dissipating the energy from the impact. Thus the guardrail system greatly reduces the effect of the impact on the vehicle and its occupants, which in turn reduces the likelihood of serious injury to the occupants of the vehicle.
An advantage of the impact absorbing guardrail terminal portion according to the present invention over the prior art is that the cable of the present invention is routed along a non-tortuous path as it passes through the cable brake. The known prior art maintains the cable in a tortuous configuration such that upon impact the cable is subjected to severe bends or changes in direction that can excessively strain the cable, which can lead to breakage and fraying of the cable.
The invention also encompasses several novel and unique components that could have utility in various other contexts in addition to the guardrail system of the present invention. These unique components include a cable brake system, a releasable guardrail post, and a frangible guardrail post.
Accordingly, it is an object of the present invention to provide a terminal portion for a guardrail system that has impact absorbing properties.
Another object of the present invention is to provide an impact-absorbing guardrail terminal portion that includes a cable and a cable brake means, in which the cable follows a non-tortuous path through the cable brake means.
Another object of the present invention is to provide a guardrail system that incorporates an impact absorbing terminal portion.
A further object of the present invention is to provide a cable brake system.
Yet another object of the present invention is to provide a releasable guardrail post.
Yet another object of the present invention is to provide a yieldable guardrail post.
These and other objects of the present invention will become apparent from the detailed description below.
Similar reference characters denote corresponding features consistently throughout the drawings.
Referring to
In the illustrated example, the guardrail system 100 is provided with two cables 108 and 110. The cables 108, 110 are preferably steel cables that are made from multiple strands of steel wire that are woven, twisted or braided together to form a steel cable. Each of the cables 108, 110 has a portion extending between the sled 102 and the guardrail post 104 closest to the sled 102. Each of the cables 108, 110 also has a portion extending between the sled 102 and a respective ground anchor location 116, 118. In use the sled 102 is positioned between the guardrail post 104 that is closest to the sled and the ground anchor locations 116, 118.
The cable brakes 112 and 114 are supported by the sled 102. The cable brakes 112 and 114 are structurally identical to one another. Each of the cable brakes 112 and 114 comprise at least a first brake pad 120 and a second brake pad 122 positioned on opposite sides of a respective one of the cables 108, 110. The first brake pad 120 and the second brake pad 122 of each of the cable brakes 112 and 114 frictionally engage a respective one of the cables 108, 110 in use.
When the guardrail system is installed on a side of a road, the sled 102 can move along the cables 108, 110 upon impact of a vehicle (not shown) on the sled 102. The vehicle would impact the sled 102 with kinetic energy that must be dissipated gradually in order to bring the vehicle to a stop in a manner that reduces the likelihood and severity of injuries to the occupants of the vehicle. The frictional forces between the cables 108, 110 and the first and second brake pads 120, 122 of the cable brakes 112, 114, respectively, dissipate at least a portion of the kinetic energy of the vehicle on impact as the sled 102 moves along the cables 108, 110 from its initial position toward the guardrail post 104 nearest the sled 102. By selecting a sufficiently large predetermined value for the frictional forces between the cables 108, 110 and the first and second brake pads 120, 122 of the cable brakes 112, 114, respectively, and selecting a sufficiently long distance between the sled 102 and the guardrail post 104 nearest the sled 102, a very substantial portion of the kinetic energy of the vehicle on impact can be dissipated by the frictional engagement between the cables 108, 110 and the brake pads 120, 122.
Each of the cable brakes 112, 114 includes a cable brake housing 124, 126, respectively, that is incorporated in the sled 102. The first brake pad 120 and the second brake pad 122 for each of the cable brakes 112, 114 are received in the respective cable brake housing 124, 126.
Each of the cable brake housings 124, 126 has a cable inlet 128, a cable outlet 130, and opposing sidewall portions 132 and 134 that are tapering from the cable inlet 128 to the cable outlet 130 such that the opposing sidewall portions 132, 134 are closer together near the cable outlet 130 as compared to the opposing sidewall portions 132, 134 near the cable inlet 128. The tapering sidewall portions 132, 134 of each cable brake housing 124, 126 engage the first and second brake pads 120, 122 of the respective cable brake 112, 114 as the sled 102 moves along the cables 108, 110 upon impact of a vehicle on the sled 102. Furthermore, the engagement of the tapering sidewall portions 132, 134 of each cable brake housing 124, 126 with the first and second brake pads 120, 122 of the respective cable brake 112, 114 moves the first and second brake pads 120, 122 of the cable brakes 112, 114 with the sled 102 along the cables 108, 110 as the sled 102 moves along the cables 108, 110 upon impact of a vehicle on the sled 102.
As the sled 102 moves along the cables 108, 110 due to the impact of a vehicle on the sled 102, the tapering opposing sidewall portions 132, 134 of each cable brake housing 124, 126 tend to more forcefully squeeze the respective first and second brake pads 120, 122 toward one another such that the frictional forces between the respective cable 108, 110 and the respective first and second brake pads 120, 122 are increased.
The first brake pad 120 of each cable brake 112, 114 has a threaded hole 136 provided at a location that is at spaced separation from a surface portion 138 of the first brake pad that is in contact with the respective cable 108, 110 when the cable brake is in use. Similarly, the second brake pad 122 of each cable brake 112, 114 has a threaded hole 140 provided at a location that is at spaced separation from a surface portion 142 of the second brake pad 122 that is in contact with the respective cable 108, 110 when the cable brake is in use. The surface portions 138 and 142 are in the form of tapering channels that are narrower at their end closest to the cable outlet of the respective brake housing 124, 126 as compared to their end that is farthest from the cable outlet of the respective brake housing 124, 126. The surface portions 138 and 142 have cross sections that are in the form of circular arcs.
Each of the cable brakes 112, 114 further includes a collar 144, a pair of wedges 146, 148, and a pair of bolts 150, 152. The collar 144 has a first surface 154 that faces away from the first and second brake pads 120, 122 when the respective cable brake 112 or 114 is fully assembled. The first surface 154 of the collar 144 is inclined from the centerline 156 toward either side 158, 160 of the first surface 154, such that the centerline 156 of the first surface 154 of the collar 144 is depressed relative to both of the sides 158, 160 of the first surface 154 of the collar 144. Therefore, the first surface 154 of the collar 144 slopes forward toward the nearest guardrail post 104 on either side of the centerline 156. The collar 144 also has an elongated slot 162 extending on either side of the centerline 156. The slot 162 has a widened middle portion 164 through which the respective cable 108 or 110 passes when the cable brakes 112, 114 are in operation. The widened middle portion 164 has an outline that follows a circular arc on either side of the slot 162. The widened middle portion 164 has a diameter that is large enough to allow the cable 108 or 110 to pass through the middle portion of the slot 162.
Each of the pair of bolts 150, 152 has a head 166 and a shaft 168 that is threaded at least in part. Each of the pair of wedges 146, 148 has a hole 170, 172, respectively, that is sized to provide clearance for the shaft 168 of a respective one of the pair of bolts 150, 152. The slot 162 is sized to provide clearance for the shaft 168 of each of the pair of bolts 150, 152 and a respective one of the cables 108, 110, such that the shaft 168 of each of the pair of bolts 150, 152 can pass through the hole 170, 172 of a respective one of the pair of wedges 146, 148 and the slot 162 to engage a respective one of the threaded holes 136, 140 of the first and second brake pads 120, 122. In the illustrated embodiment, the slot 162 is sized to be wide enough on either side of the middle portion 164 to provide clearance for the shaft 168 of a respective one of the pair of bolts 150, 152.
To assemble one of the cable brakes 112, 114 each of the pair of wedges 146, 148 is positioned in contact with a respective sloping portion of the first surface 154 of the collar 144 on either side of the centerline 156 of the first surface 154 of the collar. Then each of the pair of bolts 150, 152 is positioned such that its shaft 168 passes through the hole 170, 172 of the respective one of the pair of wedges 146, 148 and the slot 162 and engages a respective one of the threaded hole 136 of the first brake pad 120 and the threaded hole 140 of the second brake pad 122. Tightening the pair of bolts 150, 152 with the head 166 of each of the bolts 150, 152 being in contact with the respective one of the pair of wedges 146, 148 tends to force the first and second brake pads 120, 122 toward one another such that frictional forces between the cable 108 or 110 and the first and second brake pads 120, 122 of the respective cable brake are increased.
Each of the cables 108, 110 has a longitudinal axis 182, 184, respectively. Each of the pair of wedges 146, 148 of each cable brake 112, 114 has a thick side 174 and a thin side 176. The thin side 176 is thinner or narrower than the thick side 174 and can be so narrow as to form a sharp edge. The pair of wedges 146, 148 are positioned on opposite sides of the centerline 156 of the first surface 154 of the collar 144 with a respective one of the cables 108, 110 passing between the pair of wedges 146, 148. Each of the pair of wedges 146, 148 is placed in contact with the respective sloping portion of the first surface 154 of the collar 144 with its thick side 174 being positioned closer to the centerline 156 of the first surface 154 of the collar compared to its thin side 176, such that in operation the head 166 of each of the pair of bolts 150, 152 is in contact with a front surface 178, 180 of a respective one of the pair of wedges 146, 148 that is essentially perpendicular to the longitudinal axis 182, 184 of the respective cable 108, 110.
As an alternative to the illustrated example, the cable brakes could be assembled with the surface 154 facing the first and second brake pads 120, 122, if the brake pads 120, 122 are provided with beveled surfaces that match the slope of the inclined surfaces on either side of the centerline of the surface 154 of the collar 144. Thus, the bolts 150, 152 can extend through the collar 144 and engage the threaded holes in the brake pads 120, 122 directly in order to provide the required clamping action upon tightening of the bolts. As yet another alternative, the collar 144 could be provided surfaces on both sides that are bilaterally inclined in relation to the centerline of the surface like the surface 154. In this case brake pads having the beveled surfaces would be positioned on one side of the collar and the wedges 146, 148 would be positioned on the other side of the collar. The bolts 150, 152 can then extend through the wedges 146, 148 and the collar 144 and engage the threaded holes in the brake pads in order to provide the required clamping action upon tightening of the bolts.
The guardrail system 100 further includes a base 186 adapted for being anchored or fixed to the ground. The base 186 includes a base plate 188 and an elongated base post 190. The base post 190 is adapted for being buried at least in part in the ground to thereby anchor the base 186 to the ground in the illustrated embodiment. The base post 190 has a top that remains above ground. The base plate 188 can be attached to the top of the base post 190 by, for example, welding. In the illustrated example, the base plate 188 has a sleeve 187 welded to its bottom surface. The sleeve 187 fits into the top of the base post 190, and the sleeve 187 and the base post 190 each have one or more holes such that the holes of the sleeve 187 register with the holes of the base post 190 to allow pins, rivets, bolts or the like to be used to attach the base plate 188 to the base post 190.
The sled 102 further includes at least one skid plate 192 capable of being supported on top of the base plate 188 for essentially rectilinear movement parallel to the base plate 188 upon the impact of a vehicle on the sled 102. Once the guardrail system 100 is installed at a site, the cables 108, 110 will be in tension. In the illustrated embodiment, the base plate 188 is inclined such that it slopes upward or rises in the direction of oncoming traffic shown by arrow T.
The base plate 188 is provided with a guide 194 that assists in guiding the skid plate 192, and thus the sled 102, during the initial rectilinear movement of the skid plate 192 and sled 102 relative to the base plate 188 due to the impact of a vehicle. The guide 194 can take a variety of forms as shown in the drawings. The guide 194 can be in the form of a channel 196 that receives a portion of the skid plate 192 once the guardrail system 100 is installed at a given site. The channel 196 is provided on one side of the base plate 188 and is coextensive with the side of the base plate 188 that is substantially perpendicular to the cables 108, 110 and is upstream of the other sides of the base plate 188 in relation to the direction of flow of traffic. In other words, the channel 196 is coextensive with the side of the base plate 188 that is closest to the ground anchor locations 116, 118 after installation. The ends of the channel 196 can be closed off as shown in the drawings to form a pocket 196. The channel or pocket 196 receives the portion of the skid plate 192 that includes the side or edge of the skid plate 192 that is closest to the ground anchor locations 116, 118 after installation. The pocket 196 and the sloping base plate 188 can cooperate to keep the sled 102 in position over the base 186 during assembly and thus can facilitate the installation of the guardrail system 100.
In another one of the illustrated embodiments, the guide 194 is in the form of a channel 198 that receives a portion of the skid plate 192 once the guardrail system 100 is installed at a given site. In this instance, the guide 194 is in the form of two opposing channels 198 provided on either side of the base plate 188 that receive portions of the skid plate 192 on either side of the skid plate 192. The opposing channels 198 are provided on either side of the base plate 188 such that they extend substantially parallel to the cables 108, 110.
The sled 102 further includes a beam 200. The beam 200 supports the cable brake housings 124, 126 and the skid plate 192 is attached to the beam 200 at the lower end of the beam 200. The guardrail system 100 further includes a catch member 202 that is pivotally attached to the beam 200. The catch member 202 pivots about a horizontal pivot axis and the catch member 202 is pivotally movable between a raised position and a lowered position.
The sled 102 is mounted on the base 186 with the catch member 202 positioned substantially on the side of the beam 200 that faces toward oncoming traffic. When the catch member 202 is in the lowered position, the catch member 202 has a portion 204 that overlaps at least a portion of the base 186, such as the base plate 188, as seen from the view of oncoming traffic such that movement of the sled 102 relative to the base 186 in the same direction as oncoming traffic would essentially be prevented by interference between the catch member 202 and the base 186.
The guardrail system 100 further includes a lever arm 206 that is attached to the catch member 202 such that lever arm 206 and the catch member 202 move as a unit. The catch member 202 is movable between the lowered position and the raised position responsive to the lever arm 206 moving between a first position and a second position. The catch member 202 is in the lowered position when the lever arm 206 is in the first position. The catch member 202 moves toward the raised position as the lever arm 206 is moved toward the second position which is closer to the beam 200 compared to the first position.
After installation of the guardrail system 100 at a site, the sled 102 is mounted on the base 186 with the catch member 202 positioned substantially on the side of the beam 200 that faces toward oncoming traffic. The catch member 202 is normally in the lowered position and the cables 108, 110 are in engagement with the cable brakes 112, 114. When vehicle is about to collide with the sled 102, the vehicle first impacts the lever arm 206 and moves it to the second position before the vehicle impacts the sled 102. Therefore, the catch member 202 is moved to the raised position before the vehicle impacts the sled 102. Accordingly, the sled 102 is first freed for rectilinear motion relative to the base 186 before the vehicle impacts the sled 102, such that the sled 102 can move relative to the base due to impact energy being imparted to the sled 102 by the vehicle and thus gradually slow down the vehicle.
The catch member 202 includes two parallel plates 208, 210 that are spaced apart from one another and a catch plate 212 that extends between the parallel plates 208, 210. Each of the parallel plates 208, 210 is provided with a hole 214 and 216, respectively. The hole 214 of the first one of the parallel plates 208 is in registry with the hole 216 of the second one of the parallel plates 210. Each hole 214, 216 in each parallel plate 208, 210 is located at spaced separation from the catch plate 212. One or more shafts or pins 218 pass through one or more openings, there are two openings 220, 221 in the illustrated example, in the beam 200 and through each hole 214, 216 in each parallel plate 208, 210 to thereby pivotally attach the catch member 202 to the beam 200. An impact plate 222 is preferably attached to the lever arm 206 to provide a larger surface area over which the impact of a vehicle can operate the lever arm 206 and consequently the catch member 202.
The guardrail system 100 may also include one or more guardrail sections 224. The guardrail sections 224 are preferably of the type having a W-shaped cross section. Each guardrail section has a front side 226 and a back side 228. The front side 226 has a central valley or trough 230 that extends longitudinally along the length of the guardrail section 224 and the front side 226 also has a pair of peaks 232, 234 on either side of the valley that also extend along the length of the guardrail section. The back side 228 has a central peak 236 that extends longitudinally along the length of the guardrail section 224 and the back side 228 also has a pair of valleys 238, 240 on either side of the peak 236 that also extend along the length of the guardrail section 224.
Each of the cables 108, 110 has a first end and a second end. The first end of each cable 108, 110 is anchored to the ground at the respective ground anchor location 116, 118 and the second end of each cable 108, 110 is anchored in place at a location 242, 244, respectively, over the back side 228 of the guardrail section 224 when the guardrail system is installed on the side of a road.
In the illustrated embodiment, the guardrail system 100 includes a plurality of guardrail sections 224. At least one of the guardrail sections 224 is supported at least in part by the guardrail post 104 nearest to the sled 102. The second end of each cable 108, 110, near the locations 242, 244, respectively, is anchored in position in the respective trough 238, 240 of one of the plurality of guardrail sections 224 when the guardrail system 100 is installed on the side of a road.
The second end of each cable 108, 110, near the locations 242, 244, respectively, is provided with a threaded shaft 246, 248, respectively, that is essentially coaxial with the respective cable 108, 110. The guardrail system 100 further includes a mounting bracket 250. The mounting bracket 250 is used for attaching at least one of the plurality of guardrail sections 224 to one of the guardrail posts 104, 106. In particular, the mounting bracket 250 is used for attaching at least one of the guardrail sections 224 to one of the guardrail posts 104, 106 corresponding to the locations 242, 244 where the second ends of the cables 108, 110 are anchored. The mounting bracket 250 includes at least one sleeve having a bore with a diameter that is large enough to allow one of the threaded shafts 246, 248 to extend through the bore of the sleeve. In the illustrated embodiment, the mounting bracket 250 includes two sleeves 252, 254, corresponding to the two cables 108, 110. Each sleeve 252, 254 has a bore 256, 258, respectively, with a diameter that is large enough to allow a respective one of the threaded shafts 246, 248 to extend through the bore of the sleeve 252, 254.
One threaded nut 260, 262 capable of engaging the threaded shaft 246, 248, respectively, is provided for each threaded shaft 246, 248. Each nut 260, 262 is too large to pass through the bore 256, 258 of the respective sleeve 252, 254. Each nut 260, 262 engages the respective threaded shaft 246, 248 with the cables 108, 110 extending toward the sled 102, on an opposite side of the sleeves 252, 254 relative to the nuts, to thereby anchor the second end of each of the cables 108, 110 in position over the back side of one of the guardrail sections 224, when the guardrail system 100 is installed on the side of a road.
The mounting bracket 250 has a bottom plate 251 and two side plates 253, 255 on either side of the bottom plate 251. The two side plates 253, 255 are at angles of greater than 90° with respect to the bottom plate 251 to give the mounting bracket 250 an approximately V-shaped cross section. The mounting bracket 250 is dimensioned and configured to fit over the middle peak 236 of the back side 228 of the guardrail sections 224. The bottom plate 251 has holes that allow it to be bolted to the guardrail posts 104, 106. The side plates 253, 255 have holes that allow the guardrail sections 224 to be bolted to the mounting bracket 250. Standard or frangible bolts may be used as necessary, both to bolt the guardrail sections 224 to the mounting bracket 250 and to bolt the mounting bracket 250 to the guardrail posts 104, 106, depending upon the location of the mounting bracket 250 in the guardrail system 100 as will be described later. The mounting bracket 250 also has flanges 257, 259 provided at the edges of the side plates 253, 255 that are distal from the bottom plate 251. The flanges 257, 259 are positioned approximately in the valleys 238, 240 on either side of the middle peak of the back side 228 of the guardrail sections 224 when a guardrail section 224 is bolted to the mounting bracket 250. Each of the sleeves 252, 254 is attached, for example by welding, to the mounting bracket 250 at the angle formed between a respective one of the flanges 257, 259 and a respective one of the side plates 253, 255.
The guardrail system 100 also includes an anchor structure 264 for anchoring the first end of each of the cables 108, 110 to the ground at the ground anchor locations 116, 118, respectively, when the guardrail system 100 is installed on the side of a road. The anchor structure 264 includes an anchor post 266, a pair of bars 268 and 270, and at least one angled plate. In the illustrated embodiment, there are two angled plates 272 and 274, one provided for each of the cables 108, 110. The anchor post 266 is adapted for being buried at least in part below ground to thereby anchor the anchor post 266 to the ground. In use the anchor post 266 is positioned upstream of the base post 190 relative to the direction of traffic flow in a lane of the road nearest the guardrail system 100 as indicated by the arrow T.
The bars 268, 270 extend in parallel between the anchor post 266 and the base post 190. Each of the pair of bars 268, 270 has a longitudinal axis, a first end, and a second end. Each of the pair of bars 268, 270 is attached to the anchor post 266 proximate its first end, and each of the pair of bars 268, 270 is attached to the base post 190 proximate its second end. The pair of bars 268, 270 can be attached to the anchor post 266 and the base post 190 using means that include but are not limited to bolts, rivets, and welding. In the illustrated example, the pair of bars 268, 270 are attached to a cap 267 that fits over the top of the anchor post 266. The cap 267 has three sides and the pair of bars 268, 270 are welded to the cap 267 on either side to for a five sided box that fits over the top of the anchor post 266. The pair of bars 268, 270 and the top of the anchor post 266 have holes that register with one another, and one or more bolts or rivets can be used to attach the pair of bars 268, 270, the cap 267, and the anchor post 266 together. Alternatively, the cap 267 can be five sided and also have holes that register with the holes in the pair of bars 268, 270 and the top of the anchor post 266. Again, one or more bolts or rivets can be used to attach the pair of bars 268, 270, the cap 267, and the anchor post 266 together. The angled plates 272, 274 extend like rungs in a ladder between the pair of bars 268, 270 at positions intermediate the anchor post 266 and the base post 190. The angled plates 272, 274 are spaced apart from one another. Each of the angled plates 272, 274 has an inclined portion 276, 278, respectively, that is angled relative to the longitudinal axis of each of the pair of bars 268, 270 such that in use the inclined portion rises upward relative to the ground with decreasing horizontal distance from the anchor post 266. The inclined portions 276, 278 can be attached to the pair of bars 268, 270 using means that include but are not limited to bolts, rivets, and welding. Each of the cables 108, 110, is provided with a threaded shaft 280, 282, respectively, at its first end. Each of the inclined portions 276, 278 has an opening 284, 286, respectively, that is large enough to allow the respective threaded shafts 280, 282 to extend through the openings 284, 286 of the inclined portions 276, 278.
A pair of threaded nuts 288 and 290 capable of engaging the threaded shafts 280, 282, respectively, are provided for anchoring the first ends of the cables 108, 110 at the ground anchor locations 116, 118. The threaded nuts 288, 290 are too large to pass through the respective openings 284, 286 of the inclined portions 276, 278. Each of the nuts 288, 290 engages a respective one of the threaded shafts 280, 282 at the first ends of the cables 108, 110 with the cables 108, 110 extending between the inclined portions 276, 278 and the sled 102 on the sides of the inclined portions 276, 278 opposite the sides on which the nuts 288, 290 are located to thereby anchor the first ends of the cables 108, 110 in position at the ground anchor locations 116, 118 once the guardrail system 100 is installed on the side of a roadway. In the illustrated embodiment, the openings 284, 286 in the inclined portions 276, 278 are in the form of U-shaped slots to provide for greater ease of assembly of the guardrail system 100.
The manner in which the base post 190 or any of the guardrail posts 104, 106, or the anchor post 266 are fixed to the ground can vary depending upon the requirements of the particular location where the guardrail system 100 is being installed, especially the nature of the surface over which the guardrail system 100 is to be installed. For example, if the guardrail system 100 is being installed over a concrete foundation, the elongated portions of the base post 190, the guardrail posts 104, 106, and the anchor post 266 that are intended for being buried under the ground surface can be replaced by a flange or plate having a plurality of holes attached to the bottom of these various posts. Each of these various posts can then be positioned on the concrete foundation such that anchor bolts embedded in the concrete foundation extend through the holes in the flange or plate attached to the bottom of the post. Threaded nuts engaging the anchor bolts can then be tightened down over the flange or plate attached to the bottom of the post in order to secure or fix the post in place over the concrete foundation. As yet another alternative, the elongated portions of the base post 190, the guardrail posts 104, 106, and the anchor post 266 that are intended for being buried under the ground surface can be placed in holes in the ground that are backfilled with concrete. Furthermore, one or more of the various modes for securing or fixing the various posts in place that are mentioned above can be combined as conditions require in a given installation of the guardrail system 100.
As a way of conveniently referencing parts of the invention, the cable 108, the cable 110, the cable brake 112, the cable brake 114, the sleeve 252, the sleeve 254, the angled plate 272, the angled plate 274, the threaded shaft 246, the threaded shaft 280, the threaded shaft 248, the threaded shaft 282, the nut 260, the nut 288, the nut 262, the nut 290, the ground anchor location 116, the location 242, the ground anchor location 118, the location 244, the brake pad 120 of the cable brake 112, the brake pad 122 of the cable brake 112, the brake pad 120 of the cable brake 114, and the brake pad 122 of the cable brake 114 are respectively referred to as the first cable, the second cable, the first cable brake, the second cable brake, the first sleeve, the second sleeve, the first angled plate, the second angled plate, the first threaded shaft, the second threaded shaft, the third threaded shaft, the fourth threaded shaft, the first threaded nut, the second threaded nut, the third threaded nut, the fourth threaded nut, the first anchor location, the second anchor location, the third anchor location, the fourth anchor location, the first brake pad, the second brake pad, the third brake pad, and the fourth brake pad in some of the appended claims.
In the illustrated embodiments of the guardrail system, one or more of the guardrail posts nearest the sled 102 are yieldable guardrail post 104 designed to yield at a predetermined impact force. The guardrail posts 106 are standard guardrail posts. The use of yieldable guardrail post 104 for the several guardrail posts nearest the sled 102 provides an added measure of safety in the event that the energy from the impact of the vehicle is not completely dissipated before the sled 102 reaches the nearest guardrail post 104 by providing for continued gradual dissipation of the impact energy. Thus vehicles with a wider range weights and speeds can more safely be brought to a stop in head-on collisions with the end unit or portion of the guardrail system 100.
Each yieldable guardrail post 104 includes a first elongated member 292, a second elongated member 294, and a reinforcement plate 296. The first elongated member 292 has an elongated back plate 298 and two side plates 300, 302 that are parallel to one another. The side plates 300, 302 project at right angles to the back plate 298 on either side of the back plate 298 to thereby give the first elongated member 292 a channel-shaped cross section. The second elongated member 294 has an elongated back plate 304 and two side plates 306, 308 that are parallel to one another. The side plates 306, 308 of the second elongated member 294 project at right angles to the back plate 304 of the second elongated member 294 on either side of the back plate 304 of the second elongated member 294 to thereby give the second elongated member 294 a channel-shaped cross section The first elongated member 292 and the second elongated member 294 are attached together with their respective back plates 298, 304 in abutting contact so as to form a beam 310 having an H-shaped cross section. The second elongated member 294 has a slit 312 transverse to the longitudinal axis of the second elongated member 294 that transects the second elongated member. When the post 104 is installed, the side with the slit 312 faces toward oncoming traffic.
The reinforcement plate 296 is attached to the back plate 298, 304 of one of the elongated members 292, 294 proximate the slit 312 in the second elongated member 294. In the illustrated embodiment, the reinforcement plate 296 is attached to the back plate 304 of one of the second elongated member 294 and faces toward oncoming traffic when the beam 104 is installed. In the illustrated embodiment, two rows of rivets 314, 316 distributed along the length of the beam 310 and passing through back plates 298, 304 are used to attach the first elongated member 292 and the second elongated member 294 together. There is a gap in the rows of rivets 314, 316 corresponding to the location of the reinforcement plate 296 along the beam 310. The reinforcement plate 296 is attached to the back plate 304 of the second elongated member 294 by two rows of rivets 318, 320. The two rows of rivets 318, 320 are distributed along the length of the reinforcement plate 296 and pass through back plate 304. The two rows of rivets 318, 320 are spaced more closely together compared to the rows of rivets 314, 316. The gauge, i.e. thickness, of the steel used and the dimensions of the first elongated member 292, the second elongated member 294, and the reinforcement plate 296 can be varied to determine the predetermined threshold impact energy at which the post 104 will yield. A specific predetermined threshold impact energy at which the post 104 will yield can be determined for a specific application by routine experimentation.
In the illustrated embodiment, each of the guardrail sections 224 overlaps a portion of each adjacent guardrail section 224 over at least one guardrail post 104, 106 that is a common support for both adjacent guardrail sections 224. Beginning with the guardrail section 224 that is closest to the sled 102, a portion of each guardrail section 224 covers over a portion of the front side 226 of the succeeding guardrail section 224. The guardrail sections 224 are attached to the guardrail posts 104 and at least the guardrail post 106 nearest to the guardrail posts 104 by frangible fasteners such that the guardrail sections 224 will collapse in a roughly telescoping fashion in the event that the energy from the impact of the vehicle is not completely dissipated before the sled 102 reaches the nearest guardrail post 104 and the sled 102 is pushed beyond the nearest guardrail post 104 by the impacting vehicle. Thus the spearing of the impacting vehicle by the guardrail sections 224 is prevented. The cables 108, 110 should extend from about the ground anchor locations 116, 118 to at least the guardrail post 104 that is nearest the sled 102. In the illustrated example, the cables 108, 110 extend from proximate the ground anchor locations 116, 118 to the guardrail post 104 that is nearest the sled 102 and continue to extend over the distance covered by the guardrail sections 224 that are supported in whole or in part by the yieldable guardrail posts 104. Accordingly, the cables 108, 110 extend from proximate the ground anchor locations 116, 118 to the guardrail post 106 that is nearest the guardrail posts 104.
The guardrail system 100 also includes a cable guide 322. The cable guide 322 includes a wedge-shaped cap 324 and two tubular sleeves 326, 328. The cap 324 is made of sheet metal and has a wide end 330 and a narrow end 332 with the cap 324 tapering from the wide end to the narrow end. The wide end 330 of the cap 324 is dimensioned and configured to fit over the end nearest the sled 102 of the guardrail section 224 nearest the sled 102, and the cap 324 is fixed to that end of that guardrail section using nuts and bolts. With the cap 324 fixed to the end of the guardrail section, the sleeves 326, 328 will be in registry with the interior of the valleys 238, 240, respectively, on the back side 228 of the guardrail nearest the sled 102. Accordingly, the cables 108, 110 can be routed through the sleeves 326, 328, respectively, so that the cables 108, 110 can be maintained in a close relationship to the back side of the guardrail section 224 nearest the sled 102.
The guardrail system 100 is also provided with a protective sheet metal covering 334 that covers the cable brakes 112, 114. The covering 334 provides some measure of protection from the elements to the cable brakes 112, 114.
The guardrail system 100 has the desirable feature that the cables 108, 110 follows a non-tortuous path as they pass through the cable brakes 112, 114. Subjecting the cables 108, 110 to extreme bends or changes in direction, particularly upon vehicle impact, can excessively strain the strands in the cables 108, 110. Such excessive strain can lead to the fatigue and breakage of the strands, which would ultimately lead to the fraying of the cables 108, 110. The terminology “non-tortuous” as used herein means that any bends at least in the portion of the cables 108, 110 passing through the sled 102 and within at least six inches of the sled 102, as measured along the respective cable, form internal angles that are all greater than or equal to 100° and less than or equal to 180°. More preferably the internal angles formed by any bends in the aforementioned portion of the cables 108, 110 are in the range of greater than or equal to 110° to less than or equal to 180°. Of course, the definition of “non-tortuous” includes the case where there are no bends in the aforementioned portion of the cables 108, 110. In the illustrated embodiments, the portion of the cables 108, 110 passing through the cable brake housings 124, 126 follow a substantially straight path, the only significant bend in this portion of each cable occurring near the cable outlet 130 of each respective cable brake housing 124, 126.
In cases were the bend is well defined, as in the illustrated examples, the internal angle formed by any bend in the cables 108, 110 should be readily apparent. In cases where the cables may follow a curved path through the bend or bends, the angle formed by the bends is more complex to define. In such cases, a portion of a cable follows a “non-tortuous” path when there are no two points along the portion of the cable such that direction vectors corresponding to the direction of the central longitudinal axis t of the portion of the cable at each of the two points, respectively, that are both directed in the direction of increasing distance measured along the cable from a common origin point that is located outside the portion of cable in question and corresponds to a distance of zero along the cable, when translated while preserving their direction to be placed in tip to tail relationship define an internal angle that is acute. In other words, for each and every point β within the cable portion 105 in question if the direction vector 107 of the cable at a selected end point a of the cable portion in question is placed in tip to tale relationship with the direction vector 109 of the cable at the point β within the cable portion in question then the two vectors would define an obtuse internal angle θ. This of course requires that the two direction vectors are both directed in the direction of increasing distance measured along the cable from a common origin point that is located outside the portion of cable in question (see
An optional method for installing the guardrail system 100, provided as an example of final assembly and constructability, will now be described. The guardrail is constructed in the normal except for the terminal portion of the guardrail. One or more, preferably several, guardrail posts 104 are fixed to the surface proximate the roadway upstream of the last guardrail post 106 in relation to the direction of flow of traffic. The guardrail sections 224 are mounted to the guardrail posts 104, 106 such that at least all the distances between the guardrail posts are spanned by guardrail sections 224. The guardrail sections 224 should be mounted to one or more of the guardrail posts 106 near the guardrail posts 104 with a mounting bracket 250 having the sleeves 252, 254. At those guardrail posts 104, 106 where the sleeves 252, 254 are not required, a mounting bracket similar to the mounting bracket 250 but lacking the sleeves 252, 254 is used to attach the particular guardrail section 224 to the guardrail post 104, 106. In the illustrated example, a mounting bracket 250 is used to attach the guardrail section 224 to the guardrail posts 106 nearest the guardrail posts 104. The cable guide 322 can now be fixed to the end of the guardrail section 224 that is farthest upstream of the other guardrail sections 224 in relation to the direction of the flow of traffic in the lane nearest the guardrail system 100, i.e. the guardrail section 224 that is to eventually be the closest to the sled 102.
The guardrail posts 104, 106 are fixed to the surface proximate the roadway downstream of the sled 102 in relation to the direction of the flow of traffic in the lane nearest the guardrail system 100. Accordingly, the base 186 is fixed to the surface proximate the roadway upstream of the guardrail posts 104, 106 in relation to the direction of the flow of traffic in the lane nearest the guardrail system 100.
The anchor structure 264 can then be fixed to the surface proximate the roadway upstream of the base 186 in relation to the direction of the flow of traffic. The base 186 and the anchor structure 264 may be prefabricated into a single assembly prior to being fixed to the surface proximate the roadway. The sled 102 can then be positioned atop the base plate 188.
The shafts 246, 248 at the second ends of the cables 108, 110 are then inserted through the sleeves 252, 254 of the mounting bracket 250 that is located farthest from the sled 102 and the nuts 260, 262 are engaged to the shafts 246, 248, respectively, to thereby anchor the second ends of the cables 108, 110 at an anchor location corresponding to the location of the mounting bracket 250 that is located farthest from the sled 102. The cables 108, 110 are then routed through the valleys 238, 240 on the back side 228 of the guardrail sections 224 and through the sleeves 326, 328 of the cable guide 322. Each of the collars 144 is then placed around a respective one of the cables 108, 110 and then each of the cables 108, 110 is routed through the respective cable brake housing 124, 126 of the sled 102. Thus the cables 108, 110 are routed through the sled 102. Each of the collars 144 is placed around a respective one of the cables 108, 110 such that the first surface 154 of the collar 144 faces away from the sled 102.
The shafts 280, 282 at the first ends of the cables 108, 110 are then positioned so as to extend through the slots 284, 286 in the angled plates 272, 274 and the nuts 288, 290 are engaged to the shafts 280, 282, respectively, to thereby anchor the first ends of the cables 108, 110 at an anchor location near the surface proximate the roadway and upstream of the sled 102 relative to the direction of traffic flow in a lane of the road nearest the guardrail system 100. Accordingly, a portion of the cables 108, 110 extends between the sled 102 and the guardrail post 104 nearest the sled 102. The collars 144 are positioned intermediate the sled 102 and the cable guide 322.
Next a pair of brake pads 120, 122 are placed around the cable 108 such that the brake pads 120, 122 are positioned at least in part in the brake housing 124. The collar 144 on cable 108 is then brought into contact with the brake pads 120, 122 on either side of the cable 108, with the first surface 154 of the collar 144 facing away from the brake pads 120, 122. The pair of wedges 146, 148 of the cable brake 112 are each positioned in contact with a respective sloping portion of the first surface 154 of the collar 144 on either side of the centerline of the first surface 154 of the collar 144. Each of the pair of bolts 150, 152 of the cable brake 112 is positioned such that its shaft passes through the hole 170, 172 of the respective one of the pair of wedges 146, 148 and the slot 162 of the collar 144 and engages a respective one of the threaded holes 136, 140 of the first and second brake pads 120, 122. The pair of bolts 150, 152 are tightened, with the head of each of the bolts being in contact with the respective one of the pair of wedges, to force the first and second brake pads 120, 122 toward one another such that the cable 108 is clamped between the first and second brake pads 120, 122 of the cable brake 112, and thus frictional forces between the cable 108 and the first and second brake pads 120, 122 of the cable brake 112 are set at a predetermined level.
Similarly, a pair of brake pads 120, 122 are placed around the cable 110 such that the brake pads 120, 122 are positioned at least in part in the brake housing 126. The collar 144 on cable 110 is then brought into contact with the brake pads 120, 122 on either side of the cable 110, with the first surface 154 of the collar 144 facing away from the brake pads 120, 122. The pair of wedges 146, 148 of the cable brake 114 are each positioned in contact with a respective sloping portion of the first surface 154 of the collar 144 on either side of the centerline of the first surface 154 of the collar 144. Each of the pair of bolts 150, 152 of the cable brake 114 is positioned such that its shaft passes through the hole 170, 172 of the respective one of the pair of wedges 146, 148 and the slot 162 of the collar 144 and engages a respective one of the threaded holes 136, 140 of the first and second brake pads 120, 122. The pair of bolts 150, 152 are tightened, with the head of each of the bolts being in contact with the respective one of the pair of wedges, to force the first and second brake pads 120, 122 toward one another such that the cable 110 is clamped between the first and second brake pads 120, 122 of the cable brake 114, and thus frictional forces between the cable 110 and the first and second brake pads 120, 122 of the cable brake 114 are set at a predetermined level.
In each of the cable brakes 112, 114, the pair of wedges 146, 148 are positioned on opposite sides of the centerline of the first surface 154 of the collar 144 with the respective cable 108, 110 passing between the pair of wedges 146, 148, and such that each of the pair of wedges 146, 148 is placed in contact with the respective sloping portion of the first surface 154 of the collar 144 with its thick side being positioned closer to the centerline of the first surface 154 of the collar than its thin side. Thus, in operation the head of each of the pair of bolts 150, 152 is in contact with a front surface of a respective one of the pair of wedges 146, 148 that is essentially perpendicular to the longitudinal axis of the respective cable 108, 110.
Loosening the nuts 260, 262 and tightening the nuts 288, 290 moves the brake pads 120, 122 of the cable brake 112 and the brake pads 120, 122 of the cable brake 114 such that the brake pads 120, 122 of the cable brake 112 and the brake pads 120, 122 of the cable brake 114 are positioned snugly within the respective brake housings 124, 126.
Thus the brake pads 120, 122 of the cable brake 112 and the brake pads 120, 122 of the cable brake 114 are frictionally engaged to the cables 108, 110, respectively, with the brake pads 120, 122 of the cable brake 112 and the brake pads 120, 122 of the cable brake 114 positioned relative to the sled 102 such that the brake pads 120, 122 of the cable brake 112 and the brake pads 120, 122 of the cable brake 114 would interfere with movement of the sled 102 toward the guardrail post 104 nearest the sled 102 over at least a substantial portion of a distance between the sled 102 and the nearest guardrail post 104 upon impact of a vehicle on the sled 102.
Furthermore, the interference with the movement of the sled 102 toward the nearest guardrail post 104 due to the engagement of the brake pads 120, 122 of the cable brakes 112, 114 is of such a nature that the sled 102 can move along the cables 108, 110 upon the impact of a vehicle on the sled 102, when the vehicle impacts the sled 102 with energy above a predetermined threshold level, while the frictional forces between the cables 108, 110 and the brake pads 120, 122 of the cable brakes 112, 114 dissipate at least a portion of the energy from the impact.
The distance between the sled 102 and the nearest yieldable post 104, the threshold impact energy level for overcoming the friction due to the cable brakes 112, 114, the number of yieldable guardrail posts 104 that should be used and the distance that they cover, can all be determined by routine experimentation involving crash testing and taking into account the applicable mandatory safety regulations and if necessary the average speed and weight of vehicles expected at a particular site.
Referring to
The sled 402 does not have a protective cover 334, and the sled 402 lacks the catch member 202 and lever arm 206. The sled 402 is provided with a fixed impact plate 522. The base plate 488 lacks any kind of guide like guide 194. The sled 402, and consequently the skid plate 492, simply rests atop the base plate 488. The skid plate 492 has a forward portion that is turned up in a manner resembling skis to prevent the sled 402 from digging into the ground and getting stuck after impact.
In the guardrail system 400 the angled plates 272, 274 are replaced by tubular structures 572, 574 that function in a manner similar to tubular sleeves 252, 254. The various components and features from the guardrail systems 100 and 400 can be used in any combination to construct a variety of guardrail systems within the scope of the appended claims.
Referring to
The skid plate 792 is attached to the lower end of the beam 800. The catch member 802 is pivotally attached to the beam 800 such that the catch member 802 pivots about a pivot axis. The catch member 802 is pivotally movable between a raised position and a lowered position. When the base post 790 is buried at least in part below ground and the beam 800 is mounted on the base plate 788 with the skid plate 792 supported by the base plate 788 and the catch member 802 is in the lowered position, the catch member 802 has a portion that overlaps at least a portion of at least one of the base plate 788 and the base post 790 such that rectilinear movement of the beam 800 relative to the base post 790 in a predetermined direction would essentially be prevented by interference between the catch member 802 and at least one of the base plate 788 and the base post 790. A lever arm 806 is attached to the catch member 802. The catch member 802 is movable between the lowered position and the raised position responsive to the lever arm 806 moving between a first position and a second position. The catch member 802 moves toward the raised position as the lever arm 806 is moved toward the second position which is closer to the beam 800 as compared to the first position.
When the catch member 802 is in the lowered position, an impact on the lever arm 806 that moves the lever arm 806 to the second position frees the beam 800 for rectilinear motion relative to the base post 790 in the predetermined direction. In most applications the predetermined direction would be the same as the direction of on-coming traffic.
The catch member 802 is similar to the catch member 202 and the catch member 802 includes two parallel plates 808, 810 that are spaced apart from one another and a catch plate 812 that extends between the parallel plates 808, 810. Each of the parallel plates 808, 810 is provided with a hole 814 and 816, respectively. The hole 814 of the first one of the parallel plates 808 is in registry with the hole 816 of the second one of the parallel plates 810. Each hole 814, 816 in each parallel plate 808, 810 is located at spaced separation from the catch plate 812. One or more shafts or pins 818 pass through one or more openings, there are two openings 820, 821 in the illustrated example, in the beam 800 and through each hole 814, 816 in each parallel plate 808, 810 to thereby pivotally attach the catch member 802 to the beam 800. A bumper 822 is preferably attached to the lever arm 806 to minimize damage to the releasable post 700.
In the illustrated example, the base plate 788 is inclined such that it slopes upward in the predetermined direction when the base post 790 is buried at least in part below ground. The base plate 788 is provided with a guide 794 that guides the skid plate 792 during the rectilinear movement of the skid plate 792 relative to the base plate 788. All the same types of guides 194 discussed in relation to the base plate 188 may also be used with the base plate 788. In the illustrated example, the guide 794 is in the form of a pocket 796 that receives a portion of the skid plate 792. The guardrail sections 224 can be attached to the beam 800 in the same manner in which they are attached to the guardrail posts 104 and 106.
The beams 200 and 800, the lever arms 206, 806, the skid plates 192 and 792, the catch members 202 and 802, the impact plate 222, and the bumper 822 may be provided with various slots, holes, or openings, for example the slots 824, 826, 828 and 830, as necessary to provide clearance for cables that may be part of the guardrail system in which these components are used.
In some applications it may be desirable to use washers between the nuts 260, 262, 288, or 290 and the corresponding sleeves or angled plates. The washers may prevent damage to contact surfaces when the nuts are tightened, may provide greater surface area for better distribution of forces, and may be needed to enhance the size of the nuts where the nuts are smaller than would be desirable relative to the size of the corresponding openings in the sleeves and angled plates.
It should be noted that the sled and cable brake system of the present invention can be used in conjunction with a variety of barrier systems. The sled and cable brake system of the present invention can be used with barriers in the form of corrugated metal beams including “W-Beam” or “Thrie-Beam” barriers such as shown in
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
