Railing

The present invention relates to a railing selected among hollow railings, grilles, tubes or the like in which a continuous sensor made of an optical fiber extends, which railing is filled with a suitable filling material, the sensor fiber being connected to outside control and/or alarm units to form a complete circuit. The optical fiber has advantageously a numerical aperture (NA) of 0.08.ltoreq.NA.ltoreq.0.5 preferably the following parameters: PA1 Bending loss .alpha.exp(-.beta.r), r-Bending radius .beta..alpha.N.A. (b/a) .gamma. b-cladding radius, a-core radius of the fiber, 0.1.ltoreq..gamma..ltoreq.3.0. The filling material has preferably the form of pellets and is suitably selected among glass, steel, ceramics or sand. The railing preferably comprises a binder selected among soft rubber and plastics, e.g. a polyester. The binder may comprise also a material selected among an irritating material and a dye. The railing may also be a system of railing wherein the sensor extends through all the railings.

BACKGROUND OF THE INVENTION 
The present invention relates to hollow railings, bars, grilles, tubes, 
etc., (hereinafter called "railings"), used as a protection from intruders 
to commercial buildings, to prevent escape in the case of a jail building, 
etc. 
There are known such railings being provided with an optical fibre or a 
wire threaded inside through hollow bars connected to discrete sensors 
and/or to a control and an alarm. Said "alarm" is activated upon cutting 
of the optical fibre or wire. 
The hollow section of these railings are optionally filled with protection 
material after the optical fibre or wire is inserted. 
The known railings are not entirely satisfactory for intrusion detection 
particularly as they require cutting of the fibre or wire. 
It has thus been desirable to develop a railing which overcomes the above 
drawback. Said railing should be very sensitive to activate the alarm not 
only while the fibre is cut, but also at an earlier stage or even when the 
railing is bent without any cutting. Said railing should be easy to 
manufacture and to mount on the site to be protected. 
SUMMARY OF THE INVENTION 
The present invention thus consists in a railing (as herein defined) in 
which extends a continuous sensor made of an optical fibre which railing 
is filled with a suitable filling material, said sensor fibre being 
connected to outside control and/or alarm units to form a complete 
circuit. 
The present invention consists also of a system comprising more than one 
railing, the sensor fibre extending through all said railings and being 
connected to the outside control and/or alarm unit. 
The railings may have any desired cross-section, e.g., be round, 
rectangular, etc. They may be made of any suitable material. e.g., steel, 
Suitable optical fibres for the railing according to the present invention 
have a numerical aperture (NA) of 0.08.ltoreq.NA.ltoreq.0.5. 
The optical fibre may be of a type having, for example, the required 
macro-bending sensitivity and have the following parameters: 
Bending loss .alpha. exp ( .beta.r), r-Bending radius .beta..alpha.N.A. 
(b/a) .gamma. b-bladding radium, a-core radius of the fibre 
0.1.ltoreq..gamma..ltoreq.3.0. 
The railing according to the present invention comprises advantageously 
besides the filling material, also a binding material. 
The binder and/or filler combination activates the sensor fibre and does 
not merely protect said fibres as is the case with the known railings. 
The binder may be made of any suitable elastic material, e.g., soft rubber, 
plastics such as polyester, etc., cast into the hollow space and after 
having been dried behaves as an elastic solid. Said casting is 
advantageously performed in a liquid state after the optical sensing fibre 
was threaded inside and the filling material was inserted. The binding 
material becomes after drying, solid (rigid or flexible). The binder and 
the filler become an integral part of the railing. 
The binding material may contain irritating materials such as C.S. 
(Orthochlorobenzalmalononitrile), C.N. (chloroacetophenone) or any other 
kinds of irritating or dye material. This may effect the intruder upon 
cutting the bar, and result in a desirable secondary effect. (Eye 
irritation, or dye marking that will allow easy identification of the 
intruder). 
The filling material has preferably the form of rigid pellets, grains, 
balls, rods, etc. (hereinafter called "pellets"). It may be for example, 
made of glass, steel, ceramic, sand, etc. Said pellets should be able to 
be displaced within the hollow railings when under an outside pressure, 
causing force that results in bending of the optical fibre thus activating 
it. 
Although it is preferred as indicated above, to use a combination of a 
binder and a filler, there may be used, if desired, filler pellets only. 
The sysstem will be activated when the wall of the hollow railing is cut 
and the forced pellets cause bending in the sensor fibre. 
Moreover, as the filler consists of hard material particles, the intruders 
device such as handsaw will not be able to cut easily through the hard 
material particles. In addition, the particles will resist cutting by 
their rotations about their own axis. 
In case of intruders cutting through the hard particles by using any other 
kind of cutting equipment including burner, the sensing fibre will 
activate the system by giving the signal, when cut.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The railing shown in FIGS. 1 to 3 comprises railing 1, optical fibre 2, 
hollow space 3 being filled with binding material 4 and pellets 5. 
When the railing is attached as shown in FIG. 3 the cutting equipment 6 
will push the hard pellets 5 through soft elastic binder 4 and the closed 
packed particles will activate sensin fibre 2 by bending it, long before 
the cutting equipment will reach sensor 2 by cutting through.