Fiber optic cable sensor for movable objects

DETAILED DESCRIPTION OF THE PRESENT INVENTION Referring now to FIGS.
1 and 2, a fiber optic cable sensor 10 in accordance with a preferred embodiment of the present invention includes a cable housing 12 mounted adjacent to an interior manhole wall 25.
A fiber optic cable 14 runs through a pair of openings 16 disposed through the cable housing 12.
For an entire manhole system it is desirable to install a cable housing 12 of the present invention adjacent to each individual manhole cover 30 and run a single fiber optic cable 14 through each individual cable housing 12.
Thus, each manhole cover 30 of the system would be pre-assigned a specific location or length along the fiber optic cable 14, the reasons of which will become apparent with further reading.
A push/pull cable 24 extends through an opening 28 located at the top 29 of the cable housing 12 and contacts a bottom surface 31 of the manhole cover 30 which rests on an annular rim 32.
In the embodiment shown in FIGS.
1 and 2, the push/pull cable 24 is routed within a conduit 26 which runs through an opening 34 in the annular rim 32.
Alternatively, the conduit 26 may run to the inside of the annular rim 32 so that it is not necessary to install an opening 34 into an existing annular rim 32.
By routing the conduit 26 through the opening 34 in the annular rim 32, the conduit 26 becomes protected from unnecessary damage by those who seek access through the manhole, such as for maintenance.
Turning back to the cable housing 12, the fiber optic cable 14 is threaded through an opening 20 in a rigid linkage 18 disposed within the cable housing 12.
At an opposite end of the rigid linkage 18, the push/pull cable 24 is attached through a second opening 19 within the rigid linkage.
It should become readily apparent that other attaching methods may also be used to connect the push/pull cable 24 to the rigid linkage 18.
The rigid linkage 18 includes a threaded section 36 that allows fixed attachment to an elastic force compression cover 40 via a pair of locknuts 38