FIELD OF THE INVENTION
The present invention relates to a low cost but highly reliable optical (phototransistor)
based detection device /system for identification/measurement of the angular
displacement of motor/rotating shaft in which free end of shaft is not available for
mounting the conventional known shaft encoder, without the need for any flexible
coupling. More particularly, the present phototransistor based detection device for
measuring the angular displacement of shaft is also capable to detect its direction of
rotation, being mounted on the shaft surface at intermediate location, particularly in
situations when end of shaft is not exposed. The device according to the present invention
has been developed comprising a lightweight perforated disk mounted around the said
shaft. The disk is made of either plastic or wooden or tin material depending on the
working environment. A light emitting diode and a corresponding phototransistor have
been put on opposite sides of said perforated disk. The plastic disk consists of two halves
in order to facilitate its mounting around the shaft which has no free ends. Two halves of
the disk is united and mounted on shaft by fixing with two clamps. For avoiding the slip
and ensuring proper gripping between shaft and disk, an adhesive is applied at the
mounting location. Also two fabricated halves (C1 and C2) made up of tin or plastics, are
used for cover and protect the disk, LEDs, and phototransistors. On rotation of shaft at a
given RPM, the pulses are generated at the output of phtotransistor and the same are sent
through cable to 4-digit standard counter which is located at control pulpit, to display the
measure of angular displacement. Further to detect the direction of rotation of shaft, a
Light sources e.g. a separate LED and corresponding two phototransistors are put one side
of disk in such a manner that said Light Emitting Diode (LED) throws light beam at
particular point on a mirror which is mounted on the circumference of said disk and two
phototransistors kept selectively apart, receive the light after reflection from a mirror and
they are used to detect the displacement in clockwise direction if light falls earlier on one
phototransistor and anticlockwise if the light falls first on the other phototransistor. The
pulses so obtained at output of phototransistors are sent to control pulpit for indicating
clockwise rotation (LED red) and anticlockwise rotation (LED green) of shaft after
processing through AND gate (IC 7408) and inverter gate (IC7404). While for a non-
critical application, a single mirror is sufficient since a measuring delay in direction of
rotation does not affect much, but for higher accuracy and fast response specially for
detecting the direction of rotation such as in the present device, 8 mirrors, 45 degrees
apart, are mounted on the disk. The present invention is thus adapted to measure angular

shift as well as direction of shift of rotating shaft with desired accuracy even at high
temperature work environment and the same is readable from pulpit itself, particularly
where the ends of shafts are not exposed and as such use of conventional end coupled
shaft encoders are prohibitive. In absence of any flexible coupling, the measuring accuracy
is consistently maintained.
BACKGROUND ART
It is known in the art of measuring angular motion of rotating shafts/rollers or similar
components, encoders are used to measure the angular displacement of rotating shaft of
drive / roller or flying shear motor of billet mill etc. at different sections of steel plants and
rolling mills. Normally, shaft encoders are put on free end of motor/roller shaft.
Importantly, sometimes free end of motor/ roller shaft is not available or may not be
easily accessible for mounting/coupling with common shaft encoders for desired
measurement of angular shift/rotation. Moreover, in the conventional configuration of
encoders, its components such as either its light source or its receiver or its rotating
perforated disc or mirrors develops fault over a span of time and it becomes difficult to
rectify/replace items since the entire unit remains sealed. Also, with the use of
conventional shaft encoders, usually coupled with rotating shaft at ends using a flexible
coupling do not provide means for detecting angular shifts of very small magnitude and
neither helps detecting the direction of rotation at any instant. No means/device found
available in the existing art for serving the function of encoder by mounting the same at
the intermediate position of shaft when the ends are not exposed or are inaccessible for
flexible coupling with end mounted encoders.
There had been thus a compelling need to develop a device for measuring the magnitude
of angular displacement/rotation of shafts or roller drives and similar other applications, as
well as provide means to detect the direction of rotation of such rotating machine parts,
where ends of shaft is not exposed to implement a flexible connection with a conventional
shaft encoder. Hence, as an alternative to traditional shaft encoder, a LED activated photo
sensor/transistor based device is mounted at any intermediate accessible location of shaft
by using suitable clamps, avoiding slipping, such that both the measurement of angular
shift as well as the direction of rotation is measured/detected with desired degree of
accuracy even from the location of the display device at a long distant: place at the pulpit,

in a safe, reliable and cost effective manner, ensuring ease and speed of maintenance of
parts in case of any failure of the device.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to a device/system for
measuring/identifying the angular displacement and direction of rotation of rotating
shaft/rollers, flying shear motors of billet mills or other machine parts in steel mill or allied
industry, without using any flexible coupling, when ends of shaft is not: approachable.
A further object of the present invention is directed to mounting said system, using simple
LED and a perforated disk adapted to send the light based signal to phototransistors, such
that the same is suitably mounted/clamped at any intermediate location of the rotating
shaft and facilitate measurement/detection or direction of rotation with desired accuracy.
A still further object of the present invention is thus directed to a system for measuring
the angular displacement and direction of rotation of rotating shaft/rollers, where in the
display of measured value of angular displacement or the direction of rotation is
readable/detectable from the pulpit itself through a standard counter or any suitable
coloured illumination based display means.
A still further object of the present invention is thus directed to a device/system for
measuring/identifying the angular displacement and direction of rotation of rotating
shaft/rollers, wherein the mounting of the device on the shaft and the cover placed over
the assembly is done in such a manner so that the maintenance and servicing in case of
failure of parts can be easily and quickly attended, reducing down time.
A still further object of the present invention is thus directed to a device for measuring the
angular displacement and direction of rotation of rotating shafts/rollers, wherein the
elimination of use of any flexible coupling help avoiding the reading errors and favour
achieving more accurate measurement.
A still further object of the present invention is thus directed to a device for measuring the
angular displacement and direction of rotation of rotating shafts/rollers, wherein the LED

and phototransistor based measuring/rotation direction detection device is directly
mounted on the shaft using clamps, without the need of using any coupling between shaft
and the encoder and thus do not involve any error due to play or backlash in coupling,
particularly when the rotation direction is reversed.
A still further object of the present invention is thus directed to a device for measuring the
angular displacement and direction of rotation of rotating shafts/rollers, wherein no
electronic component is used in the encoder side and the angular displacement or direction
of rotation detection signals are sent to a distance of nearly 100m for display at pulpit,
without using any amplifier.
A still further object of the present invention is thus directed to a device for measuring the
angular displacement and direction of rotation of rotating shafts/rollers, wherein for higher
accuracy and fast response specially for knowing of angular shift or rotation of screw down
mechanism spontaneously, encoder devices are used having multiple perforations on disc.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a system for identifying
angular displacement of shaft comprising:
a perforated split disk adapted to be mounted around said shaft with clamping
together of the split portions;
a light source preferably an LED and a phototransistor disposed on opposite
sides of the said disk such that on the rotation of shaft, the pulses are
generated at the output of phototransistor; and
means to identify the angular displacement of said shaft based on said
phototransistor output.

Another aspect of the present invention is thus directed to a system for identifying angular
displacement of shaft comprising means to identify the direction of angular displacement
of the shaft comprising:
a Light source preferably an LED and a pair of phototransistors are put one side
of disk;
a mirror mounted on the same side as that of said pair of phototransistors on
the circumference of the disk whereby said phototransistors are adapted to get
light after reflection from a mirror and favour identification of whether the
displacement of the shaft is clock wise direction or anticlockwise based on the
relative position of the two phototransistors and which of the two lights up first
based on said reflected light from the mirror.
A further aspect of the present invention is thus directed to a system for identifying
angular displacement of shaft wherein said means for identification of the angular
displacement comprises cable to digit counter located at control pulpit.
A further aspect of the present invention is thus directed to a system for identifying
angular displacement of shaft wherein said disk is either plastic or wooden or metal based
upon the working environment.
A still further aspect of the present invention is thus directed to said system for identifying
angular displacement of shaft comprising preferably split disk comprising of two halves
adapted to be put around the shaft having no free ends with the said two halves of the
disk operatively connected by clamps.

According to yet another aspect of the present invention directed to said system for
identifying angular displacement shaft wherein for ensuring proper gripping between shaft
and disk, an adhesive is provided.
A still further aspect of the present invention is directed to a system for identifying angular
displacement of shaft wherein the pulses at output of said pair of phototransistor are sent
to control pulpit for indicating said clock wise rotation preferably by glowing of LEDs red
and said anti clock wise rotation preferably by glowing of LED green.
Another aspect of the system according to the present invention directed to identifying
angular displacement of shaft comprising said means for indicating angular displacement
of the shaft comprises of AND gate and inverter gate.
A still further aspect of the present invention is directed to said system for identifying
angular displacement of shaft wherein for enhancing the glowing of respective LED, a
mono-stable multi vibrator circuit is provided and the glowing time of LED is based upon
time circuit C and R and speed of rotation and wherein for non critical application, a single
mirror is provided since a measuring delay in direction of rotation does not affect much
and for higher accuracy and fast response specially for knowing the direction of rotation of
screw down mechanism spontaneously the number of mirrors on the circumference is
more preferably 8 such that on passing the individual mirror before LED-2 the respective
mirror is adapted to reflect light on said pair of phototransistors, said 8 mirrors being
fixed after every 45 degrees.
The present invention and its objectives and advantages are described in greater details
with reference to the accompanying non limiting illustrative figures.

BRIEF DESCRIPTION OF FIGURES
Figure 1: is the illustration of the conventional shaft encoder using flexible coupling for
coupling of encoder at the end of shaft to measure rotation/detect direction.
Figure 2: is the illustration of the improved and modified shaft encoder device according
to the present invention adapted to be mounted on the intermediate shaft surface with the
LED and phototransistors selectively placed on either side of the rotating disk having
perforations selectively located at the periphery of the disk.
Figure 3: is the illustration of the mounting arrangement of encoder disk of the present
invention in two halves on the shaft surface and fixed by means of two clamps.
Figure 4: is the schematic illustration of the encoder device according to the present
invention comprising LED light sources selectively disposed and spaced apart, plurality of
mirrors, along the perimeter of disk mounted on shaft surface and the phototransistors for
detection and sending signal for display of measured/detected data.
Figure 5: is the illustration of the protection means by way of cylindrical covers mounted
in two halves (Cl and C2) to guard the encoder disk and other electronic components used
in the device to protect from shock, heat or dust.
Figure 6: is the illustration of the circuit diagram for detection of direction of rotation of
shafts, by the illumination of either Red or Green LED, using signals received by two
phototransistors.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention is directed to development of simple low cost device for knowing the
angular displacement shaft and its direction of rotation without using flexible coupling,
particularly under situation where the end of the shaft are not exposed or accessible and
as such cannot adopted by attaching conventional encoder through flexible coupling at the

end of the shaft. The present invention relates to design and development of a very
simple, low cost but highly reliable optics based system for measuring the angular speed
of motor/ rotating shaft in which free end of shaft is not available.
Reference is first invited to the accompanying Figure 1 that illustrates the conventional
Shaft encoder for coupling at the end portion of any shaft to measure its angular
displacement. It is apparent from the figure that the encoder is essentially coupled to the
shaft end by a flexible coupling such that the encoder runs co-axially with the shaft of
motor or other machine.
To overcome this limitation with respect to mounting at end of shaft, the novel low cost
device comprising a perforated disk, LED light source and phototransistor based sensors as
illustrated in the accompanying Figure 2, has been configured. The perforated disk
mounted around the rotating shaft favor sensing of interrupted light from the LED by the
phototransistors, which then generate signals to measure the rate of angular displacement
or detect the direction of rotation. The schematic illustration of the working principle of the
device according to present invention is shown in Figure 2. The figure schematically
illustrates the light interruption based signal generation by the phototransistor receiving
incident light rays through the perforation on the disk from the LEDs located at the other
side of the rotating disk having selectively located perforation on it, and thereby
measuring either angular shift or direction of rotation of said shaft.
The experimental observations established that the material of disk has to be light in
weight such as made of either plastic or wooden or tin material depending upon the
working environment. Reference is now invited to the accompanying Figure 3 that
illustrates an embodiment of the device according to the present invention and the
arrangement of its mounting on the shaft. The plastic disk is consisting of two haves in
order to put it around the shaft at any suitable intermediate location, which has no free
exposed ends. Two halves of the disk is united by fixing with two clamps. For avoiding the
slip and ensuring proper gripping between shaft and disk, an adhesive is put. The figure
also shows the circumferential location of a plurality of perforations for allowing passage of
light incident from the LED source to any selectively located phototransistor.
Reference is now invited to the accompanying Figure 4 which is the schematic illustration
of the manner of implementation of the encoder device according to the present invention

comprising LED light sources and phototransistors selectively disposed and spaced apart,
plurality of mirrors along the perimeter of disk mounted on shaft surface and the
phototransistors for detection and sending signal corresponding to measured/detected
rotaion/ direction data for display at the pulpit. The figure shows how a light emitting
diode LED-1 and phototransistor PT-1 have been put on the opposite sides of the
perforated disk, co-operatively generating angular displacement measurement data by the
light interruption principle as already explained. During the rotation of shaft along with the
device mounted on it, the pulses are generated at the output of phtotransistor and same
are sent through cable to 4-digit counter which is located at control pulpit, counting the
number of pulses by using the standard counter which has in built relay output, preset up
to 9999 events through thumb wheel switches and with a counting reset facility.
Two halves Cl and C2 are used for protecting the disk LED and phototransistors,
preferably made up of tin or plastic: in two halves and mounted on shaft covering the
encoder disk and associated components providing a complete enclosure, as illustrated in
accompanying Figure 5, and protecting the encoder device comprising sensible
components from harsh work environment, shock or heat.
In order to obtain/detect the direction of rotation of shaft, a Light sources such as the
Light emitting diode LED- 2 and two corresponding phototransistors PS-2.a and PS-2.b are
put on one/same side of disk. The Light emitting diode LED-2 throws light beam at
particular point on a mirror which is mounted on the circumference of disk and
phototransistors PS-2.a and PS-2.b get light after reflection from a mirror and they are
used to know the displacement in clock wise direction if light falls earlier on PS2-a and
displacement of shaft is anticlockwise if PS2-b gets light earlier to PS2-a, as illustrated in
the accompanying Figure 4.
The pulses so obtained at output of phototransistor PT-2-a and PT-2.b are sent to control
pulpit for indicating clock wise rotation by glowing a LED red and anti clock wise rotation
by LED green, of shaft after processing through AND gate (IC 7408) and inverter gate
(IC7404). For enhancing the glowing of respective LED, a mono-stable multi vibrator
circuit by using IC 4011 is used as illustrated in the accompanying circuit diagram in
Figure 6. The glowing time of LED depends upon time circuit C and R and speed of
rotation. For non-critical application, a single mirror M-1 is sufficient since a measuring
delay in direction of rotation does not affect much. For higher accuracy and fast response,

especially for determining the direction of rotation of screw down mechanism
spontaneously, the number of mirrors on the circumference should be more and in a
preferred embodiment of the invention such mirrors are 8 in numbers. Upon passing an
individual mirror before LED-2 while the disk is rotating, the respective mirror will reflect
the light incident from LED on PT-2.a and PT-2.b. The mirrors Ml, M2, M3, M4, M5, M6,
M7, and M8 are fixed at every 45 degrees intervals along the perimeter of disk, to ensure
desired accuracy of measurement/detection at any instant.
The present invention is thus directed to providing a simple cost effective device for
measuring angular displacement of shafts and determine or indicate the direction of
rotation, particularly shafts of heavy equipments in steel rolling mills or flying shear of
billet mill and the like, whereby following advantages are achieved:
-the encoder device is adapted to work efficiently even if no free end of motor/ gear and
shaft encoder disk is capable of being mounted on the shaft of the motor itself.
-no coupling in between shaft and shaft encoder is required.
-no wear and tear of coupling as use of coupling is eliminated.
-no play in the coupling therefore no measuring error during change in direction of
rotation of shaft.
-no harmonics due to presence of old coupling.
-device gives direction of rotation of shaft and corresponding signals are sent 100m
distance without using any amplifier
-no electronic components are used related to signal conditioning at Shaft encoder side.
- the direction of rotation of shaft is processed by a very simple circuit and display of
coloured LED- Red or green.
-faulty components, when detected, can be easily attended.
It is thus possible by way of the present invention to develop a device to overcome the
limitations of conventional end mounted shaft encoder, particularly under situations when
such end of shaft is either unexposed or inaccessible for mounting of such encoders
coupled to the shaft end by means of a flexible coupling. More particularly, the present

device is adapted to measure the angular displacement of shaft with desired accuracy
and/or providing means for detecting the direction of rotation-whether clockwise or
anticlockwise rotation, avoiding errors induced by conventional flexible coupler based
application, by the pulse/signal generated by light interruption principle operatively by LED
light source on one side of a perforated rotating encoder disk mounted on the shaft at a
suitable intermediate location and a phototransistor located on the opposite side of disk.
The direction of rotation is also detected and displayed by sensing reflection of light from
LED by selectively disposed mirror on the disk and processing the signals through a simple
circuit to indicate either Red LED or Green LED. Both the angular displacement/rotation
and its direction are displayed right in the pulpit through standard display means,
facilitating ease and accuracy of operation of equipments. Moreover, the device according
to the invention provide a low cost alternative for faster, economic and safe means of
operating rotary equipments by knowing and controlling the operating parameters for a
longer life with fast and easy repair and maintenance of components in case of any failure.
The device of the present invention is thus having potential for wide industrial application
in steel or other heavy industry in applications like the motor shaft, rolling drive or flying
shear in billet mill, whereby safe and reliable measurement of angular displacement of
shafts and/or determining the direction of its rotation is detected and displayed in a user
friendly manner to the operator at a safe distant place/pulpit.

WE CLAIM:
1. A system for identifying angular displacement of shaft comprising:
a perforated split disk adapted to be mounted around said shaft with clamping
together of the split portions;
a light source preferably an LED and a phototransistor disposed on opposite
sides of the said disk such that on the rotation of shaft, the pulses are
generated at the output of phototransistor and
means to identify the angular displacement of said shaft based on said
phototransistor output.
2. A system for identifying angular displacement shaft as claimed in claim 1
comprising means to identify the direction of angular displacement of the shaft
comprising:
a Light source preferably an LED and a pair of phototransistors are put one side
of disk;
a mirror mounted on the same side as that of said pair of phototransistors on
the circumference of the disk whereby said phototransistors are adapted to get
light after reflection from a mirror and favour identification of whether the
displacement of the shaft is clock wise direction or anticlockwise based on the
relative position of the two phototransistors and which of the two lights up first
based on said reflected light from the mirror.
3. A system for identifying angular displacement shaft as claimed in anyone of
claims 1 or 2 wherein said means for identification of the angular displacement
comprises cable to digit counter located at control pulpit.

4. A system for identifying angular displacement shaft as claimed in anyone of
claims 1 to 3 wherein said disk is either plastic or wooden or metal based upon
the working environment.
5. A system for identifying angular displacement shaft as claimed in anyone of
claims 1 to 4 comprising preferably split disk comprising of two halves adapted
to be put around the shaft having no free ends with the said two halves of the
disk operatively connected by clamps.
6. A system for identifying angular displacement shaft as claimed in claim 5
wherein for ensuring proper gripping between shaft and disk, an adhesive is
provided.
7. A system for identifying angular displacement shaft as claimed in anyone of
claims 1 to 6 wherein the pulses at output of said pair of phototransistor are
sent to control pulpit for indicating said clock wise rotation preferably by
glowing of LEDs red and said anti clock wise rotation preferably by glowing of
LED green.
8. A system for identifying angular displacement shaft as claimed in claim 7
comprising said means for indicating angular displacement of the shaft
comprises of AND gate and inverter gate.
9. A system for identifying angular displacement shaft as claimed in anyone of
claims 7 or 8 wherein for enhancing the glowing of respective LED , a mono-
stable multi vibrator circuit is provided and the glowing time of LED is based
upon time circuit C and R and speed of rotation and wherein for non critical

application, a single mirror is provided since a measuring delay in direction of
rotation does not affect much and for higher accuracy and fast response
specially for knowing the direction of rotation of screw down mechanism
spontaneously the number of mirrors on the circumference is more preferably 8
such that on passing the individual mirror before LED-2 the respective mirror is
adapted to reflect light on said pair of phototransistors, said 8 mirrors being
fixed after every 45 degrees.
10. A system for identifying angular displacement of shaft substantially as
hereindescribed and illustrated with reference to the accompanying figures.

A system for identifying angular displacement of shaft comprising a perforated split disk
mounted around said shaft with clamping together of the split portions, a light source
preferably an LED and a phototransistor disposed on opposite sides of the said disk such
that on the rotation of shaft, the pulses are generated at the output of phototransistor
adapted to identify the angular displacement of said shaft based on said phototransistor
output. Importantly, a Light source preferably an LED and a pair of phototransistors are
put one side of disk and a mirror selectively spaced apart along circumference of disc,
mounted on the same side of phototransistors, adapted to get light after reflection from a
mirror and favour identification of whether the displacement of the shaft is clockwise
direction or anticlockwise based on the relative position of the two phototransistors and
which of the two lights up first based on said reflected light from the mirror.