FIELD OF APPLICATION
The present invention relates to a device for detecting the presence of hot stocks
in rolling mills of steel and metal industry.
The detection electronics can be kept at a remote location from the hot metal.
Radiation from the hot stock can be carried to the detection electronics by optical
fiber.
The device of the present invention comprises light capturing optics an optical
fiber conduit for carrying radiation from a hot stock to a far off place where the
detection electronics is provided and detection electronics.
Thus the present invention provides a device for detecting presence of hot stocks
in rolling mills in steel and metal industry, said device comprising light capturing
optics provided in a housing for capturing radiation from said hot stocks; an
optical fiber conduit for carrying said radiation from hot stocks to a remote place;
and an electronic circuitry for detecting presence of hot stocks by detecting a
high or low radiation signal.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The present invention will now be described with the help of the accompanying
drawings where

Figure 1 shows light capturing optics of the present invention.
Figure 2 shows the sensor holder for connecting the optical fiber
conduit to a silicon photodiode.
Figure 3 shows a housing for the light capturing optics of Figure 1.
Figure 4 shows the design of the ferrule for optical fibre bundle end.
Figure 5 shows the detection electronics of the device.
DETAILED DESCRIPTION
The light capturing optics is shown in Figure 1 and Figure 3 shows the housing
for the light capturing optics of Figure 1.
Light capturing optics consists of a biconvex lens along with optical fibre conduit
at the other ends as shown in Figure 1. The specification of the lens shown in
Figure 1, i.e. diameter 23 mm and focal length 14 mm can be different if
specified by the user or depending on the application. The capturing optics
focuses the light signal on the optical fibre conduit which actually carries it to the
electronic signal detector. In this way the electronic circuitry is shielded from the
high temperatures of the hot stocks.

The optical fibre conduit consists of a bundle of multimode optical fibre strands
(50 or more in number), 10 to 20 m long each depending on the length of optical
fibre conduit, enclosed in a spiral, flexible, mild steel hollow wire with plastic
sheath. The coating of the optical fibre strands is not removed which makes it
resistant against easy breakage.
The fibre bundling method of the present invention uses a spiral, flexible, mild
steel hollow wire with plastic sheath which is an economical enclosure for optical
fibre strands (50 or more in number). The method consists of pulling out a
copper wire inserted inside the spiral hollow wire enclosure and attached to the
bundle of optical fibre strands at one end. As the copper wire is pulled out, the
optical fibre strands are pulled inside the spiral hollow wire casing. The ends of
the optical fibre strands are then inserted inside ferrules (Figure 4) and glued
together using a heat resistant and waterproof standard epoxy. The inclined
ends are then polished flat using 5 µm polishing papers.
The optical fibre conduit is connected to a silicon photodiode through a sensor
holder as shown in Figure 2 (sensor holder). The optical fibre conduit consists of
specially designed ferrules at both ends. The design of the ferrule is shown in
Figure 4. The dimension of the ferrule can be decided on the basis of the size of
fibre conduit and the number of fibre strands in the fibre conduit. This method
facilitates fabrication of the fibre bundles with the fibre strands as close as
possible at the extremities. Along the length of the conduit, the optical fibres are
splayed out which makes the arrangement flexible and less liable to breakage.

The detection electronics is shown in Figure 5 and consists of conversion of
optical signal to electrical signal using a silicon photodiode. The electrical signal
is amplified and fed to three channels, a comparator which provides level
detection output in the form of relay, open collector output and green LED
indication; a differentiator which provides edge detection output in the form of
relay, open collector output and yellow LED indication; and a LED bar graph
which indicates the analog voltage level.
The comparator provides a level detection i.e. a high or a low signal depending
on the presence or absence of hot metal respectively. The comparator has been
designed using a quad opamp IC like an LM 324 and a Schmitt trigger
configuration. The turn off time is adjustable in discrete steps as
3.9ms/8.2ms/15ms/33ms/68ms/120ms/250ms/500ms/1.2s/3.3s. This is achieved
using a timer like an LM 555 in a monostable configuration. This is required to
account for random interruptions in the signal. The level detection output can be
accessed via a relay or an open collector configuration. A green LED gives an
indication of the output.
The differentiator provides an edge detection (i.e. a pulse of 23ms duration)
whenever a change in the captured radiation has occurred between 1V/ms and
50V/ms. The differentiator is designed using the quad opamp IC like an
LM 324. The output of the differentiator is fed to a timer like an LM 555 in a
monostable configuration to generate a pulse. The edge detection output can be
accessed via a relay or an open collector configuration, A yellow LED gives an
indication of the output.

WE CLAIM;
1. A device for detecting presence of hot stocks in plants like rolling mills of
steel and metal industry, characterized in that said device comprises :
- light capturing optics (1) provided in a housing for capturing radiation
from said hot stocks;
- an optical fibre conduit (3) for carrying said captured radiation from
hot stocks to a remote place; and
- an electronic circuitry (Fig.5) provided in said remote place for
detecting presence of hot stocks from a high or low radiation signal
received.
2. The device as claimed in claim 1, wherein said electronic circuitry is
provided with a comparator for detecting if the radiation signal received is
high or low, using a quad opamp IC.

3. The device as claimed in claim 1, wherein said electronic circuitry is
provided with a differentiator for providing edge detection output
wherever a change in the capture radiation signal has occurred
between 1 V/ms and 50 V/ms.
4. The device as claimed in claim 1, wherein said electronic circuitry is
provided with a driver connected to a LED bar graph for displaying
the analog level.
5. The device as claimed in claim 1, wherein said optical fibre conduit
comprises a bundle of multi mode optical fibre strands enclosed in a
spiral, flexible, mild steel hollow wire with plastic sheath.
6. The device as claimed in the preceding claims, said optical fibre
conduit is connected to a silicon photodiode through a sensor holder.

7. The device as claimed in claim 6, wherein said optical fibre conduit
comprises specially designed ferrules provided at the two ends of said
conduit.
8. The device as claimed in claim 7, wherein dimension of said ferrules can
be decided on the basis of the size of fibre conduit and the number of
optical fibre strands in the fibre conduit.
9. The device as claimed in claim 1, wherein the spectral response of said
device is 350 - 1050 nm and the response time is 7 µs for analog output
and 100 µs for level detection and edge detection output.
10. A device for detecting presence of hot stocks in for examples, rolling mills
in steel and metal industry, said device, substantially as herein described
and illustrated in the accompanying drawings.

This invention relates to a device for detecting presence of hot stocks in for
example, rolling mills in steel and metal industry, said device comprising: light
capturing optics provided in a housing for capturing radiation from said hot
stocks; an optical fibre conduit for carrying said radiation from hot stocks to a
remote place; and an electronic circuitry arranged in said remote place for
detecting presence of hot stocks from a high or low radiation signal received.