US 3450387 A
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June 17, 1969 R. A. THOMAS HIGHWAY SAFETY FENCE POSTS Sheet 9133 Filed June 22, 1966 I nvenlor June 17, 1969 R. A. THOMAS 3,450,387
HIGHWAY SAFETY FENCE POSTS,
Filed June 22. 1966 59g 594 5px o Patfcu an) S Vii- I E) Attorneys June 17, 1969 R. A. THOMAS 3,450,387
' HIGHWAY SAFETY FENCE POSTS Filed June 22, 1966 Sheet 'L of 3 .Qtgl
INVENTOR. Robert Alb er-t Thomas United States Patent Int. Cl. 1501f 15/00 U.S. c1. 256-13.1
ABSTRACT OF THE DISCLOSURE A highway safety fence having an intermediate, thin- Walled post, cables attached to the post by means of devices which are releasable under an impact and wire netting stretched between the intermediate posts.
The present invention relates generally to safety fences and more particularly to fences erected along roads and highways. Such safety fences include posts to which cables and wire netting are attached in order to separate the opposite lanes of the road and stop any motor vehicle leaving its lane, because of a traflic incident occurring on the road or because the driver has lost the control of his motor vehicle.
Heretofore, posts, made of wood or of rigid steel, have been used for erecting safety fences of the aforementioned type, but in the event of a vehicle colliding with such posts, the posts are considerably damaged.
Summary This invention relates to highway safety fences and particularly to the intermediate posts to be used with such fences. The post is thin-walled and tubular, the cross section of which flattens locally when it is subjected to a shock, so that it immediately bends. The remainder of the fence includes netting and at least one cable attached to these posts as well as rigid end posts. The cable or cables are attached to the posts by a device which opens when subjected to a given force.
The safety fence made in accordance with the present invention is a fiexible one of the abovementioned type, made up of posts, cables and a wire netting. The cables of such a safety fence stretch to a greater extent on impact with a motor vehicle so that they absorb the energy and force the vehicle gradually back to the lane which it left.
To achieve this desired result, a post of an improved type has been designed for use as one of the intermediate posts, carrying the cables and the wire netting, whereas the rigid posts are only placed at the end of these cables and wire netting to stretch the latter.
The post, made in accordance with the present invention, is used for keeping the cable or the cables at a constant height, which particularly depends on the height at which the vehicles gravity center lies, the weights of said vehicles, their normal maximum speeds and the probable maximum impact angle. It is also used to force the cable or the cables and wire netting to follow the lane to be protected and to help absorb the energy of the shock of impact with a vehicle so that the vehicle will not rebound from the surface of the safety fence like a ball.
These results are achieved because the post made in accordance with the present invention is a tubular, thinwalled one. When hit by a motor vehicle, its cross-section flattens out locally, so that the tubular post bends immediately.
The hollow post may be coated with a protective layer of metal, plastic material, rubber or other material, to
6 Claims Patented June 17, 1969 prevent it from being corroded by atmospheric agents and also to reduce the risk of damaging the motor vehicle colliding with said post. The post also may be covered with a cap of plastic material, rubber or any similar material, to prevent said vehicle from coming into contact,
with the top part of the post, which is more or less sharpedged and consequently capable of seriously damaging said motor vehicle.
The hollow post may be of circular, square or any polygonal cross-section and may be set in the ground by means of a concrete block or other conventional means.
The safety fence made in accordance with the present invention is provided with intermediate posts of the abovementioned type.
According to another characteristic of the invention, the cables, which are preferably coated with an extruded plastic material, as defined in my co-pending application and relating to an improved cable for making safety fences to be erected along roads, are attached to the poles by means of improved devices.
The safety fence, made in accordance with the present invention, including the tubular posts, the cables coated with in extruded plastic material and the devices for attaching the cables, completely solves the problems inherent in such fences, because, on the one hand, due to the various coatings used, the vehicles cannot be caused serious damage by the elements of said safety fence, and on the other hand, this safety fence, being mainly a shock-absorbing one, cannot be destroyed when hit by a motor vehicle, even if the collision is a violent one.
When hit by the motor vehicle, the tubular post, made in accordance with the present invention, bends rapidly, simultaneously lowering the device used for attaching the cables, which device is attached to said post. This device opens and the cables may be replaced at their normal height, which position is determined by the devices used for attaching them to the adjacent posts and consequently the cables do not run the risk of being broken. Where the post bent after being hit by a motor vehicle, the remainder of the safety fence remains practically undamaged.
Various further and more specific purposes, features and advantages will clearly appear from the detailed description given below taken in connection with the accompanying drawings which form part of this specification and illustrate merely by way of example one embodiment of the device of the invention.
In the following description and the claims, parts will be identified by specific names for convenience, but such names are intended to be as generic in their application to similar parts as the art will permit. Like reference characters denote like parts in the several figures of the drawing.
In the drawings:
FIG. 1 is a front view in a partial section of a post made in accordance with the present invention, showing the adjacent parts of the cables, the device used for attaching the cables and the wire netting which parts make up the safety fence;
FIG. 2 is an enlarged detailed front view, in partial section, of the top part of the post;
FIG. 3 is a front section of another embodiment of a cap covering the top of the tubular post;
FIG. 4 is a perspective view of a safety fence supported by intermediate posts made in accordance with the present invention after a motor vehicle collides with said post;
FIGS. 5, 6 and 7 are cross-sections of the post taken along the lines 5-5, 6-6 and 7-7 in FIG. 4, showing how said post is deformed after a collision;
FIG. 8 is a schematic plane view of a safety fence after a motor vehicle has collided with a post;
FIG. 9 is a portion of the fence with the end posts partly broken away;
FIG. 10 is a cross-section of the cable with a protectective coating of an extruded plastic layer; and
FIG. 11 is a cross-section of a polygonal intermediate post with a protective coating.
Referring more particularly to the drawings, FIG. 1 shows a part of the safety fence, placed above the ground S and made up of an intermediate post P made in accordance with the present invention, two cables C (FIG. 4) attached to said post by means of a device A and a wire netting T attached to the cables and the post by means of fastening devices not shown in the drawing. Cables C and wire netting T are stretched at their ends by means of massive posts 15. Cables C are coated with a protective layer 16 preferably consisting of rubber or the like suitable resilient material.
Post P is made up of a thin-walled tube 1, preferably made of steel or any other suitable material. The thickness of the wall lies between 3% and 7% of the outside diameter of said tubular post, preferably thereof.
Post P is vertically tailed into ground S by any suitable means, such as a concrete block 2. Its outer surface is preferably coated with a protective layer, made of a metal, thermoplastic, rubber or other suitable material 17, to prevent corrosion by atmospheric agents. This coating is also desirable because such a surface more easily absorbs the impact of a colliding vehicle than an uncoated post, and the motor vehicle, colliding with it, would be much less damaged.
Post P is preferably covered with a cap 3, made of a plastic, rubber, or other suitable material, and fitted into the top part of said post. This avoids damaging the motor vehicles that would otherwise bump into the outside sharp edge 4 of the top section 5 of post P. The cap 3 may be either flat, as indicated by the numeral 6 in FIGS. 1 and 2, or convex, as shown by the broken and dotted lines 7 in FIG. 2. Cap 3 may be shaped, as shown in FIG. 3, with a projecting head 8 and top part 9, shaped like a cone. It may also be shaped like a hemisphere, as shown in broken and dotted lines 10 in FIG. 3.
FIGS. 4, 5, 6, 7 and 8 show what happens when a motor vehicle collides with intermediate tubular post P. Post Ps cross-section flattens at the point of impact indicated by section S in FIG. 7. The cross-section nearest the ground is appreciably deformed, indicated by section S in FIG. 5, whereas the intermediate portions, such as the one along lines 6-6, are more or less deformed, as indicated by the section S in FIG. 6.
The lower part a-b of post P bends outside the vertical longitudinal plane XX (FIG. 8) of the safety fence, whereas the upper end 0 nearly remains in this plane. Because of this, cables C between post P and the adjacent posts P and P which have not been displaced, are rapidly bent along the line A -AA when they are subjected to a shock, for instance, in the direction of the arrow f in FIG. 8. Because of the type of devices A used for attaching the cables, and the action of the forces exerted by cables C on the attaching device A, the bands 11, which keep cables C tightly attached, the upper half bushings 12, and the lower half bushings 13 are released.
.4 Cables C, being no longer integral with said attaching device A, slide along the part a-c of post P and come back into the horizontal plane, determined by the adjacent attaching devices A and A which yield elastically, so that the tractive force, exerted on each cable, is equalized by the resistance offered by the cable in a certain number of intervals between adjacent posts. Such resistance acts like a brake to prevent the cables from being broken.
The wire netting is itself deformed by the shock to which post P has been subjected as a consequence of its being hit by a motor vehicle, particularly in the vicinity of the elbow a of post P. However, neither the wire netting post P, nor cables C, will break.
Since the safety fence remains unbroken, it continues to fulfill its purpose should a new traflic incident or accident occur where a vehicle collides with one of the posts. The unbroken safety fence is still in a position to change the direction of the vehicle which has deformed a post P and bring this vehicle again into the lane that it has left.
1. A highway safety fence comprising a pair of spaced rigid end posts and at least one thin walled tubular deformable intermediate post adapted to be locally deformed and bent when subjected to impact, said intermediate post having its lower end anchored into the ground adjacent the highway, shock absorbing resilient cable means extending between and secured to said rigid end posts, break-away clamp means releasably securing said cable means to the intermediate posts, and a wire netting attached to said cable means and to said end posts and extending between said end posts.
2. A fence as set forth in claim 1 wherein said tubular post has a wall thickness of substantially 5% of the outside diameter of said intermediate post.
3. A fence as set forth in claim 1, wherein said breakaway clamp means comprises an upper and a lower elongated bushing half fitted about said cable means, and a breakable band holding said bushing halves together about the cable means and releasably securing the same to said intermediate posts.
4. A post according to claim 1, said post having a polygonal cross-section.
5. A post according to claim 1, said tube being coated with resilient material.
6. A safety fence according to claim 3, and said cable being coated with an extruded plastic material.
References Cited UNITED STATES PATENTS 1,106,826 8/1914 Michod 25613.1 1,897,250 2/1933 Frei 25613.1 X 2,093,577 9/1937 Shepherd 256-13.1 2,603,455 7/1952 Welch 256-13.1 3,077,339 2/1963 White 25613.1 3,185,445 5/1965 Broadway 256--13.1 3,207,478 9/ 1965 St. Pierre 256--l3.l 3,233,870 2/ 1966 Gerhardt 256-131 3,351,322 11/1967 Mueller 256-131 DENNIS L. TAYLOR, Primary Examiner.
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