Collapsible road barrier

A collapsible road barrier comprises a foundation pit, a frame located in the foundation pit, an expandable barrier element mounted in the frame, at least one energy absorption element extending from a rear wall of the foundation pit to a rear side of the frame, and at least one stretching element connected between the front side of the frame and the front wall of the foundation pit, such that vehicle impact against the barrier element will cause the frame to first move towards the rear wall of the foundation pit, causing the energy absorption element(s) to compress and the stretching element(s) to extend and eventually break, and then pivot upwardly to stop the vehicle.

The invention relates to a retractable road barrier comprising an 
expandable barrier element and at least one energy absorption element. 
Such a road barrier is known from GB-A-No. 2 165 569. 
The object of the invention is to improve this known road barrier in such a 
way that with a light construction of the barrier element, which has a 
small mass and consequently can be erected quickly from the retracted 
position to the blocking position--something which is very important in 
use--the energy of a vehicle driving onto the expanded road barrier is 
absorbed in controlled fashion in the optimum manner. 
The accumulated energy in a vehicle driving onto the road barrier is first 
partially absorbed by deformation of the front side of the vehicle and of 
the barrier element; before the vehicle has come to a standstill, the 
whole frame will, in a subsequent phase, shift in the direction of travel, 
while energy is absorbed by the energy absorption element (for example one 
or more energy absorption pipes which are known per se), by the 
displacement of the frame and by the stretching element. The latter will 
break when a specific tensile loading is reached, the consequence being 
that the barrier element on the drive-on side is no longer fixed in the 
vertical direction and will start to tilt about an axis near the drive-off 
side of the barrier, as a result of which the initial horizontal movement 
of the vehicle is converted into a movement with a considerable vertical 
component. The remaining vehicle energy is thereby absorbed and the 
vehicle falls back on the road barrier. Of course, the number and shape of 
the energy absorption elements and stretching elements can be chosen as 
desired, so that the road barrier can be adapted optimally to the 
requirements set for it--for a road barrier which is intended only to 
impede the passage of motor cars will have different dimensions from those 
of the road barrier which also has to be capable of stopping armored 
vehicles. 
It is pointed out that DE-A-No. 3 112 717 described a road barrier with 
chains provided on the front side, the sole object of which is to limit 
the maximum angle of expansion of the barrier element: the insight to 
provide on the front side of the road barrier a downward-running 
stretching element which not only absorbs energy, but also breaks when a 
particular load is reached and permits tilting of the whole independent 
frame is not found in this publication.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The illustrated road barrier according to the invention comprises a 
foundation pit 2 accommodating an independent frame 4, which on the top 
side 6 rests with the plate 8 on the front edge 10 of the foundation pit 
2, and with the two longitudinal edges 12 and 14 also rests with cover 
plates (not shown) on the edges of the foundation pit. The frame 4 carries 
on its rear end a corner bar 16. The latter has on both ends short 
counter-corner sections 22 and 24, which are each reinforced with section 
parts 18, 20 which are welded crosswise therein, and which--as shown in 
FIG. 2--project on either side over a short distance beyond the frame and 
are guided in guide tracks 26, 28 recessed in the foundation pit 2 and 
thus form the sliding pivot points. A foundation pit cover plate 30 
competes the whole unit. 
The frame 4 has the usual elements, known per se from, for example EP-A-No. 
0 092 282, in the name of applicant, such as the expandable barrier 
element 30, made up of the usual barrier element cover plate 32, which 
covers the road barrier in the normal passing position and has on the 
front side thereof the closure element 34; by means of the hinges 36, this 
barrier element is carried by the frame 4. The expansion takes place 
through the action of the pneumatic cylinder 38 in combination with the 
run-on rollers 38a, 38b fixed on the piston rod 39 thereof, the run-on 
plates 40a, 40b and the hinge arm 42a, 42b; the compressed air is supplied 
by a compressor (not shown) via a buffer tank 44, so that even when the 
compressor cuts out the barrier can still be operated a number of times, 
while there are also the schematically shown compression springs 46, which 
are known per se. 
According to the invention, the rear side 4a of the frame 4, in fact the 
corner bar 16, is by means of a number of energy absorption elements 
50a-50h, here designed as the "crumple pipes" which are known per se (only 
one of which is shown schematically), supported against the rear wall 2a 
of the foundation pit 2, while the front side 4b is connected to the front 
wall 2b of the foundation pit by means of a number--in this case 4--of 
stretching strips 52a-52d breaking at a specific load. They run from the 
top edge 4c of the frame to the bottom edge 2c of the foundation pit in 
which they are fixed with anchors 54a-54d, so that when the stretching 
strips are intact the top side of the frame is fixed in the vertical 
direction. It will be clear from the above that the invention deliberately 
creates the possibility that, when a great force is exerted on the road 
barrier in the direction of the arrow 56, the whole frame can move 
backwards in the direction of arrow 56 against the action of the crumple 
pipes 50a-50h and with stretching of the stretching strips 52a-52d. When 
the latter finally break, the front side of the frame is no longer fixed 
in the vertical direction, and the whole frame can tilt upwards around the 
corner sections 22, 24, constituting guide elements projecting in the 
guide tracks, 26, 28 respectively. The fact that this results into optimum 
energy absorption and blocking action is explained below with reference to 
FIGS. 3 to 8. 
In these figures are, for the sake of clarity, only the elements of the 
road barrier which are necessary for a good understanding of the 
functioning, shown. 
FIG. 3 shows the situation in which a heavy motor vehicle 58 is driving 
onto the expanded road barrier in the direction of the arrow 60. This 
vehicle has a certain kinetic energy which according to the invention is 
deliberately absorbed in a number of phases. 
The first phase, shown in FIG. 4, is the contact between the front side 62 
of the vehicle 58 and the closing element 34, resulting in a slight 
deformation of the two elements. 
The second phase, shown in FIG. 5, is that in which both the front side 62 
of the vehicle and the closing element 34 are deformed to a great extent. 
This already permits a small displacement of the frame in the direction of 
the arrow 60, with a slight deformation of the crumple pipes 50a-50b and a 
slight elongation of the stretching strips 52a-52d. FIG. 6 shows the next 
phase, in which the stretching strips 52a-52d are stretched even further 
and the crumple pipes 50a-50h are pressed down over an appreciable 
distance. In the following phase, shown in FIG. 7, the stretching strips 
52a-52d finally break, and the crumple pipes 50a-50h are completely 
crushed; the breaking of the stretching strips results in that the front 
side of the road block is no longer fixed in the vertical direction. As a 
result of the difference in height between the guide elements 22, 24 in 
the guide tracks 26, 28 respectively, on the one hand, and the action 
point, on the other and the kinetic energy of the vehicle is at that 
moment not entirely absorbed, the frame 4 will tilt upwardly. This 
situation is shown in FIG. 8, wherein the upward movement is indicated by 
the arrow 64; the movement takes place around the guide parts 22 and 24 
(see FIG. 2), thereby causing the front of the vehicle to be lifted up and 
the residual energy acting in the horizontal direction to be absorbed by 
the lifting of the front of the vehicle. The latter will eventually rise 
up virtually vertically with its front, and will finally fall back without 
the road barrier having been passed. 
It is clear that after such an event the road barrier can be restored 
quickly to its original state at relatively low cost: only the closing 
element 34, the crumple pipes 50a-50h and the stretching strips 52a-52d 
need replacing.