FIELD OF THE INVENTION
This invention relates to a device for measuring convergence of the roof in a
mechanized or semi mechanized coal mine workings. This invention particularly
relates to a simple device which is easy to install, capable of maintaining
alignment as per requirement, provides accurate measuring and easy reading
and also provides a visual warning..
BACKGROUND OF THE INVENTION & DESCRIPTION OF PRIOR ART
In underground coal mining technology, bord and pillar mining method is one of
the major technology being used in India, it has lion's share of about 91% of the
underground production, employing about 57% of total work force. In terms of
number of mines, out of about 595 operating mines, about 384 are underground
mines. In this method, numbers of tunnels are formed at certain intervals called
roadways and thus underground pillars are formed all around. These pillars are
extracted by retreating away from dip most side using different types of
machinery in mechanized or semi-mechanized district. The stability of the
roadways is measured by roof convergence which takes place due to
redistribution of stresses over the pillars and roadways during adjoining pillar
extraction. The different machineries are allowed to move in the roadways
frequently by which floor of the roadways get damaged. Therefore, measurement
of roof convergence with respect to the floor reference point, otherwise
necessary to be put, by using telescopic convergence meter or other existing
convergence-measuring device may not be so accurate. The convergence of the
roof strata and its rate is an important parameter in prediction of roof failure and
subsequent obviation of an accident occurring in mines. Also, this convergence
rate is helpful in deciding the type of support system to be installed in the
roadways for better safety of men, machines and materials.
@ An existing telescopic type convergence indicator is depicted in figure 1. In case
of such existing telescopic type convergence indicator, to measure convergence
or convergence rate in a roadway, one has to decide and make arrangement for
two-reference points, one in the roof surface and another vertically below in the
floor level. For this purpose, two iron nails having central punch mark on its top
surface are grouted into roof and floor aligned vertically to each other. The
observations are to be taken between these two reference points. Therefore,
both the reference points should not be disturbed to get error free convergence.
This type of telescopic convergence indicator is good where mining operation is
performed manually. In case of mechanized or semi-mechanized mines where
heavy machines like SDL's, LHD's, Continuous miners etc. are operated,
reference points on floor of the roadways will always get disturbed. Therefore,
accurate measurement may not be possible and thus stability of the roadways
can not be predicted precisely.
Reference may also be made to US patent no. 4514905, titled: Convergence
extensometer for measuring mine roof subsidence, wherein is disclosed an
,extensometer for measuring changes in the vertical distance between the roof
and floor of a mine opening which comprises; a pair of rigid telescoping
members, a tension spring securing said members to each other in a telescoping
relationship, a hook for attaching a non-extensible cable to each of said
members, and an indicator for determining telescoping movement of said
members. The extensometer of this invention is utilized by securing one of said
telescoping members to the roof of the mine and other telescoping member to
the floor of the mine with the axis of said member being disposed along the
vertical. The telescoping members are secured, under tension, to the mine roof
and floor by means of non- extensible cables such as a steel cable. The indicator
for determining the telescopic movement of the members may be pair of lugs or
flanges or other indicating marks, each member of which pair is affixed to a
separate telescoping member.
Reference may also be made to JP patent no. 2001165656, titled: Automatic
measurement system for tunnel convergence, wherein is disclosed an a three
dimensional automatic tracking optical wave rage finder having automatic
collimating function is permanently set on the mine wall surface of a tunnel, and a
plurality of round slice sections are set at prescribed intervals on the tunnel inner
wall surface within the measuring visual field range of the automatic collimating
function by use of the three dimensional automatic tracking optical wave range
finder as an automatic tacking total station. A plurality of target device is
permanently set on each round slice section. The station of each target device is
successively automatically tracked by remote control and collimated, and the
displacement quantity of the station of each target device is automatically
measured.
Reference may also be taken from US patent no. 6480289, titled: Position
measuring apparatus and optical deflection angle measuring apparatus for
underground excavators, wherein is disclosed an optical deflection angle
measuring apparatus which, upon optically measuring a deflection angle, does
not require an operation for directing a light onto a position detecting element and
makes it possible to obtain measurement results without being affected by
external force such as vibration. It consists of a detector containing common lens
for converging diffuse lights from light source. Position detecting elements
receive the converged lights from light sources and detect received positions of
the converged lights. Reflecting prisms allow the diffuse lights from the light
sources to be transmitted and guided so that the diffuse light from the light
sources are converged by the lens onto the position detecting elements. The
respective position detecting elements are arranged so as not to interface with
convergence of the lights by the lens. The deflection angle PHI can then be
measured by computation.
Reference may also be taken from JP patent no. 2001004369, titled: Method for
measuring convergence of excavation cross-section, wherein is disclosed a
control part is electrically connected to sensor heads. A laser beam is emitted to
each of corresponding reflecting sheet from each of the sensor heads. By
individually receiving the reflected laser beam, the distance between the sensors
heads and the reflecting sheets are each computed on the basis of the phase
difference between the emitted and received laser beams etc. The distances are
automatically and continuously measured at all times during sampling time. By
continuously obtaining distances between three points in an excavation cross
section with time, it is possible to obtain the convergence of the excavation
cross-section from the principle of the triangulation.
Reference may also be taken from JP patent no. 2000329554, titled: Measuring
method for convergence in excavation section, wherein is disclosed when the
setting operation of bench marks and measuring reference points id finished, a
photographing operation is performed in a state that they are inclined
simultaneously, and an imaging screen immediately after an excavating
operation is imaged. The excavating operation progresses and it reaches a
second point from a first point in which the imaging screen is obtained. Then an
excavating section as an object to be measured is photographed again. When a
second imaging screen after the elapse of a prescribed time is obtained, the two
imaging screen are overlapped. When the two imaging screens are mutually
superposed, the measuring reference points are made to agree because the
reference points are photographed in the respective imaging screens. When an
overlapped screen is obtained, the convergence in the excavating section on the
respective bench marks is detected.
Reference may also be taken from JP patent no. 9329422, titled: Height
measuring method and device, wherein is disclosed an X-Y-Z stage is moved so
that an image formed on the light receiving surface of a CCD is converged at
three points on the plane of an object to be measured, and the coordinates for
the position of the stage when convergence is established are determined,
followed by determination of the plane in which the three points exists, and a light
@ spot is formed on the object by a projecting I sub-scanning part, and the height of
the light spot is sensed on the basis of the output from sensing of the light spot
made by a light position sensor while the object is photo-scanned by an acousticoptical
deflector and the stage, and the obtained height is put in correspondence
to the position of the stage at the time an output is given from the sensing so that
height of the light spot when light spot formed on the object by the part is sensed
by a light spot sensor in the converged condition is put in correspondence to the
converging position of the object.
Reference may also be taken from US patent no. 5418758, titled: Distance
measurement system, wherein is disclosed an apparatus and a method using
ultrasonic signals to determine the distance between the displacement of two
points in space. An ultrasonic distance measurement unit generates frequency
modulated ultrasonic waves using binary shift keying. The signals are transmitted
by the transmitting transducer towards a reflector assembly, preferably
comprised of two reflectors. One of the reflectors is smaller than the other
reflector, and the smaller reflector is positioned in front of the larger reflector. The
reflected signals are received by the receiving transducer. The unit phase
digitizes and processes the received signals by recording time stamps of zero
crossing of the received signal. The speed of sound may be determined by a
temperature measurement system and 1 or by measuring the transit time
difference between the two reflectors of the assembly. The distance between the
unit and the assembly can then be determined from the speed of sound and time
taken for an ultrasonic signal to travel between the unit and assembly.
Displacement of the assembly relative to the unit can be determined by making
distance measurement over a period of time.
Reference may also be taken from GB patent no. 2280513 titled: Tape
extensometer or convergence meter with tension measurement, wherein is
disclosed a tape extensometer or convergence meter has a tension sensor that
illuminates a coloured light when the correct tension on the tape thereof is
attained and illuminates a second coloured light if the correct tension is
exceeded. The extensometer has a digital or analog vernier to indicate the
distance by which it has been reduced to apply the correct tension to the tape
thereof. The tape extensometer has a metal tape in which holes are punched at
regular intervals which can be hooked onto an eye bolt and placed over a pin,
then tensioned by means of a winding handle which reduces the length of the
extensometer. The extensometer has a similar hook by which it is attached to the
second eye bolt from which the measurement of the distance to the first eye bolt
is to be taken.
Reference may also be taken from DE Patent no. 4129562 titled: Borehole strain
meter arrangement using conventional vertical or mechanical strain motors -
measures convergence movement between roof and floor of underground
chamber and swelling movements in the suspended and supported layers,
wherein is disclosed a borehole strain meter arrangement uses conventional,
vertical or mechanical Harwardt strain meters with inductive, capacitive or other
measurement transducers. For vertical installation in underground measurement
chambers both convergence movements between reference points in the roof
and floor and swelling movements of the suspended and supported layers are
measured. This technique enables approximate separation to be achieved
between the local motion components from the geo-mechanically interesting
strain variation of regional relevance.
Reference may also be taken from JP patent no. 4279806 titled: Light beam
scanning type measuring device, wherein is disclosed laser beam emitted from a
semiconductor laser is shaped into parallel light by means of a beam regulating
lens and reflected by means of a rotary scanning mirror and radiated to the inner
wall of a measured tube. A photo spot is formed on the inner wall surface of the
pipe and part of light scattered to the perimeter from the photo spot is reflected
by means of a rotary scanning mirror and converged by means of a convergence
lens and reaches a two-dimensional semiconductor position detection element
@ and a photo spot image is formed on the light receiving surface of the PSD.
Convergence positions outputted from the PSD are converted into distance by
means of two - axial calibration curves and vector operation is conducted and
measurement is calculated.
Reference may also be taken from US patent no. 5345685 titled: Strata
movement indicator, wherein is disclosed an apparatus which includes at least
two lengths of suspension wire respectively for remote and near anchors
locatable in the same borehole. Each wire carries a cylinder provided with
indicator markings, the cylinders being movable with respect to one another and
a reference tube fixed in the mouth of the borehole. Relative movement of the
cylinders with respect to one another andlor to the reference tube indicates the
degree of strata movement.
Reference may also be taken from US patent no. 6334260 titled: Strata
movement indicator, wherein is disclosed an apparatus which includes a strata
movement indicator suspended within a borehole is provided with a drive
element and a reference element, relative movement between the elements
being translated into rotary motion to give a visual indication on an indicator on
the respective elements.
Reference may also be taken from US patent no. 7324007 titled: Instrumented
rock bolt, data logger and user interface system, wherein is disclosed an
apparatus which includes a hollow body and a gap along a length of the hollow
body. At least one strain gauge is affixed to an inner surface of the rock bolt and
is accessible from the gap. The rock bolt may include a data logger within the
hollow body and coupled to receive signals from one or more strain gauges, and
to record these signals in a memory. The data logger may comprise a data port
adapted to be accessible from the outside of a bore hole into which the rock bolt
is inserted. The data logger also may include at least one of a visual and auditory
alarm. A graphic user interface software program can be used to download data
from the data logger and set certain operating parameters of the data logger.
Reference may also be taken from US patent no. 6674396 titled: System and
method for distance measurement by in-phase and quadrature signals in a radio
system, wherein is disclosed a system and a method for distance measurement
utilizes a radio system. The distance is measured by determining the time it takes
a pulse train to travel from a first radio transceiver to a second radio transceiver
and then from the second radio transceiver back to the first radio transceiver.
The actual measurement is a two step process. In the first step, the distance is
measured in coarse resolution, and in the second step, the distance is measured
in fine resolution. A first pulse train is transmitted using a transmit time base from
the first radio transceiver. The first pulse train is received at a second radio
transceiver. The second radio transceiver synchronizes its time base with the first
pulse train before transmitting a second pulse train back to the first radio
transceiver, which then synchronizes a receive time base with the second pulse
train. The time delay between the transmit time base and the receive time base
can then be determined. The time delay indicates the total time of flight of the
first and second pulse trains. The time delay comprises coarse and fine distance
attributes. The coarse distance between the first and second radio transceivers is
determined. The coarse distance represents the distance between the first and
second radio transceivers in coarse resolution. An in-phase (I) signal and a
quadrature (Q) signal are produced from the time delay to determine the fine
distance attribute. The fine distance indicates the distance between the first and
second transceivers in fine resolution. The distance between the first and second
radio transceivers is then determined from the coarse distance and the fine
distance attributes.
Reference may also be taken from US patent no. 5825496 titled: Borehole
optical lateral displacement sensor, wherein is disclosed an apparatus which
includes an optical displacement sensor that utilizes a reflective target connected
to a surface to be monitored to reflect light from a light source such that the
reflected light is received by a photoelectric transducer. The electric signal from
the photoelectric transducer is then imputed into electronic circuitry to generate
an electronic image of the target. The target's image is monitored to determine
the quantity and direction of any lateral displacement in the target's image which
represents lateral displacement in the surface being monitored.
Reference may also be taken from US patent no. 5629480 titled: Rock
extensometer, wherein is disclosed an apparatus which includes an
extensometer for use in a borehole comprises a combination of linear motion
transducers located with daisy wheel anchors, which may be attached together if
desired with extension bars. Linkages are used to connect the transducers to the
daisy wheel anchors. The transducers are set up to measure distance changes
both axially along the hole or radially. The extensometer includes at least one
axially measuring transducer, and at least two radially measuring transducers.
The transducers change in value according to changes in borehole dimensions;
the transducer values are monitored electrically
Reference may also be taken from US patent no. 5284107 titled: Cable bolt
monitoring device, wherein is disclosed an apparatus which includes a
monitoring unit for installation on a cable bolt comprises a tube designed to fit
within a cable bolt hole and having a collar at one end thereof, a cable bolt
adapted to be grouted in the rock at the centre of the tube, a base plate placed
tightly against the tube collar adjacent the rock face, a centralizer sleeve
designed to fit over the cable bolt to keep the cable centralized within the base
plate and tube, an elongated measuring plate having a centre hole for insertion of
the cable bolt to fit tightly against the base plate and a groove cut at equal
distances from each side of the centre hole for allowing the measuring plate to
bend if the rock moves with respect to the cable bolt, and a cable clamp for fixing
the measuring plate tight against the base plate.
Reference may also be taken from US patent no. 4410296 titled: Rock bolt
overload warning device, wherein is disclosed an apparatus which includes a
washer which is used in the construction of the support for the roof of a mine.
9 The washer is fabricated such that finger like projections rupture in stages as the
tension on bolts and pressure in the strata of the roof of the mine increases
beyond structurally safe limits. The rupturing of the washer emits audible warning
signals and also provides a visual indication of an unsafe condition.
Reference may also be taken from US patent no. 4318302 titled: Method of
determining mine roof stability, wherein is disclosed a method of testing mine
roof stability, comprising the steps of exciting the mine roof bolt to vibration at the
natural occurring frequencies by normal tightening of the roof bolt, detecting the
natural occurring frequency vibrations, and analyzing spectrally to determine the
predominance of frequency distribution within the range of natural occurring
frequencies between zero and 1,000 Hz. to provide an indication of roof bolt
tension thereby to derive an indicator of mine roof stability.
Reference may also be taken from US patent no. 4136556 titled: Device to
monitor movement of a surface, wherein is disclosed an apparatus which
includes a device to monitor movement of a surface such as, for example, the
roof of a mine tunnel or the like and to provide an indication if that movement
exceeds some predetermined creep rate or velocity. The device includes a
sensing member formed of a material whose precise creep characteristics as a
function of stress and strain are known. The device includes a sensing member
formed of a material whose precise creep characteristics as a function of stress
and strain are known.
Reference may also be taken from US patent no. 4127788 titled: Piezoelectric
stress indicator for mine roofs, wherein is disclosed an apparatus which includes
a device for detecting deformations in mine roofs wherein an open cylindrical
casing having inner and outer threaded surfaces is threaded into the mine roof. A
piezoelectric crystal is mounted within the casing to sense the deformations and
stresses in the mine roof. Provision is made for mounting a plurality of
piezoelectric crystals within the casing whereby stresses at varying locations are
sensible.
Reference may also be taken from US patent no. 4097854 titled: Sensing
mechanism for mine roof bolting apparatus, wherein is disclosed an apparatus
which includes a sensing mechanism of the present invention includes a probe
electrically connected to a mine roof bolting apparatus and adapted to be
embedded within a mine roof to sense any shifting of the apparatus during an
operative cycle. The probe is linked to a 360" rotational toggle switch mechanism
which controls an alarm means. The probe is pivotably mounted within the roof
bolting apparatus and consequently, any effective movement of the apparatus
along any direction within a horizontal plane pivotably displaces the probe and
actuates the switch mechanism, energizing the alarm. In this manner, personnel
are apprised of conditions warranting corrective measures in order to re-position
the bolting apparatus or the apparatus may be automatically halted so as to
prevent damage from being imparted thereto.
Reference may also be taken from US patent no. 4058079 titled: Movement
indicator, wherein is disclosed an apparatus which includes a device for
indicating a preset amount of relative movement between two points, an indicator
sleeve axially movable in a cylindrical bore in a housing fixed to one of the points
remains flush with the housing until the preset amount of movement is reached at
which point the sleeve pops up to give a positive, easily identifiable indication of
the movement. An actuating rod which bears against and follows the second
point is axially slidable in the sleeve and operates a ball bearing mechanism
which locks the indicator sleeve in the retracted position. The amount of
movement required to generate the discrete indication is easily variable and
monitoring of the actual displacement is always available.
Reference may also be made to Patent Application no. 1890lDEU2006 titled:
Device for measuring roof convergence in underground coal mines or tunnels,
wherein is disclosed an apparatus which includes a device for indicating relative
movement between two points comprise of a frame, which can be fixed vertically
in one side of the mine roadway wall 1 pillar with a horizontal frame which can
9 swing horizontally for alignment and is fixed in the bottom of vertical frame with
the help of a bolt. A graduated vertical scale, which can move freely in a slot,
provided in the horizontal frame and a link rod, which can swing freely, and
having fixed length with a socket head. A nearly L-shaped socket head is
provided which can be fixed in the mine roof. A telescopic rod having graduation
at one end is also provided which can be easily fixed between the two socket
heads.
There are various types of instruments available, in the hitherto known prior art,
such as telescopic type convergence indicator, remote convergence indicator to
measure the daily convergence of given strata in an underground mine. Although
remote convergence indicators are used widely, these are costly and generally
left in goaf to collect cumulative data for longer period of time. For their
installation, one has to create notches in the pillar, which is a cumbersome task.
At the same time if the wires connected to the remote convergence indicator are
faulty or damaged by any means, it becomes impossible to take reading out of it.
From the hitherto known prior art, it is seen that the instruments are either optical
or electronics based and are very costly and are not easy to handle or operate
particularly in coal mine workings.
From the hitherto known prior art it is also seen that the instruments are grouted
in the roof rock and if roof departed from a point above the grouted point no roof
movement will be recorded by the instruments. At the same time if the immediate
roof is laminated in nature, then one has to drill a longer borehole so that
instruments can be grouted in strong roof bed. Drilling of long vertical hole is a
very cumbersome task.
From the hitherto known prior art it is also seen that there is a definite need to
provide a device for measuring convergence of the roof in a mine, which is
economical, easy to assemble and dismantle, maintains verticality, provides
' accurate measurement, easy accessibility, capable of indicating the convergence
fast and accurate and provide visual warning when reaches a pre determined cut
off value.
I OBJECTIVES OF THE PRESENT INVENTION
The main objective of the present invention is to provide a device for
measuring convergence of the roof in a mine, quickly and accurately
Another objective of the present invention is to provide a visual warning
when reaches a pre determined cut off value and give convergence of the roof
irrespective of the position of the roof bed from where it is separated.
Still another objective of the present invention is to know the true
convergence of the mine roof which will be helpful to predict the roof fall.
SUMMARY OF THE PRESENT INVENTION
Accordingly the present invention provides a device for measuring convergence
of the roof in a mine,, which consists of a horizontal frame (1) which is fixed
horizontally in between the mine roadway walls / pillars just below the roof level
by tensioned wires (2) that is anchored in the drilled hole provided in both side of
the mine walls/pillars with the help of butterfly springs (3) wherein an extendable
and movable rod (4) is passing through the said frame (1) having gear teeth's at
lower end which will mesh with the teeth's of the spur gear (5) connected with the
pointer (6) provided in the graduated circular scale (7) by a connecting rod (8).
Another embodiment of the present invention is to provide a device wherein a
simple electrical circuit (9) in the said frames (1) connected with a battery (10)
and an LED bulb (1 1) for providing a visual warning of impeding roof failure.
Another embodiment of the present invention is to provide a device wherein an
umbrella type frame (12) connected with the rod (4) placed above the said
horizontal frame (1).
10 Another embodiment of the present invention is to provide a device wherein the
horizontal frame (1) is fixed below the roof level by means of tensioned wires (2)
Another embodiment of the present invention is to provide a device wherein
horizontal frame (1) is anchored in the drilled hole provided in both side of the
mine walls/pillars with the help of butterfly springs (3).
Still another embodiment of the present invention is to provide a device wherein
teeth's of the spur gear (5) are connected with the pointer (6) by means of
connecting rod (8)
Still another embodiment of the present invention is to provide a device wherein
the roof convergence is measured using the inter-related movement of rod (4),
spur gear (5), connecting rod (8) and pointer (6) in the circular graduated scale
(7) attached with the said horizontal frame (1).
Yet another embodiment of the present invention is to provide a simple electric
electrical circuit is used for providing a visual warning of impeding roof failure
Yet another embodiment of the present invention is to provide a device that is
made up of material aluminum for making it lighter in weight
FIGURE 1: An existing telescopic type convergence indicator is depicted in
figure 1. In case of such existing telescopic type convergence indicator, to
measure convergence or convergence rate in a roadway, one has to decide and
make arrangement for two-reference points, one in the roof surface and another
vertically below in the floor level. For this purpose, two iron nails having central
punch mark on its top surface are grouted into roof and floor aligned vertically to
each other. The observations are to be taken between these two reference
points. Observation can be taken with the help of a telescopic measuring rod
which can move freely in an external tube and can be fixed at required position
with the help of a clamp provided with the external tube.
Figures 2, 3 and 4- The device of the present invention is shown in figures 2, 3
and 4 of the drawings accompanying this specification, which consists of a
horizontal frame (I) which can be fixed horizontally in between the mine roadway
walls 1 pillars just below the roof level by means of tensioned wires (2) that can
be anchored in the drilled hole provided in both side of the mine wallslpillars with
the help of butterfly springs (3). An extendable as well as movable rod (4) is
provided which is passing through the horizontal frame (1) at lower end of which
gear teeth's are provided which can mesh with the teeth's of the spur gear (5)
which is connected with the pointer (6) provided in the graduated circular scale
(7) by means of a connecting rod (8). A simple electrical circuit (9) is provided
inside the horizontal frame (I) which is connected with a battery (10) and an LED
bulb (1 1). An umbrella type frame (12) is also provided which is connected with
the rod (4) and is placed just above the horizontal frame (1).
DETAILED DESCRIPTION OF THE INVENTION
This device consists of a horizontal frame, which can hang horizontally from both
sides of the mine roadway walls I pillars just below the roof level by means of
tensioned wires so that the extendable rod provided with the frame can touch the
roof. A graduated circular scale is provided in which a pointer can rotate freely
and is attached with the frame. A LED bulb is provided at the base of the
horizontal frame which will illuminate when a pre determined amount of roof
convergence takes place. An umbrella type frame is also provided over the
horizontal frame to protect it from water trickling from mine roof.
9 The device of the present invention is shown in figures 2, 3 and 4 of the drawings
accompanying this specification, which consists of a horizontal frame (1) which
can be fixed horizontally in between the mine roadway walls I pillars just below
the roof level by means of tensioned wires (2) that can be anchored in the drilled
hole provided in both side of the mine wallslpillars with the help of butterfly
springs (3). An extendable as well as movable rod (4) is provided which is
passing through the horizontal frame (1) at lower end of which gear teeth's are
provided which can mesh with the teeth's of the spur gear (5) which is connected
with the pointer (6) provided in the graduated circular scale (7) by means of a
connecting rod (8). A simple electrical circuit (9) is provided inside the horizontal
frame (1) which is connected with a battery (10) and an LED bulb (11). An
umbrella type frame (12) is also provided which is connected with the rod (4) and
is placed just above the horizontal frame (1).
To measure the convergence of the roof in a mine, a point is located in the roof
at the particular place where measurement is required. Then the horizontal frame
(1) is hanged horizontally in between the mine roadway walls 1 pillars just below
the roof level by means of tensioned wires (2) which are grouted in the drilled
holes provided in both side of the mine walls with the help of butterfly springs (3).
The extendable rod (4) is then so adjusted that it touches the roof properly. Now
as the roof converges, the rod (4) is pushed in downward direction. Downward
movement of the rod (4) provides a rotary movement to the spur gear (5) as their
teeth's are meshed with each other. As the connecting rod (8) is attached with
the spur gear (5), the rotary movement of the spur gear (5) also provides a rotary
movement to the connecting rod (8). Since pointer (6) is connected with the
connecting rod (8), the rotary movement of the connecting rod (8) provides a
rotary movement to the pointer (6) which can be measured from the circular
graduated scale (7) attached with the frame (1). Now as the roof convergence
increases it pushes the rod (4) further downward and ultimately a time comes
when the tip of the rod (4) touches the electrical circuit (9) and completes the
circuit and electrical power flow from the battery (10) and thus illuminating the
LED bulb (1 1). Illumination of LED bulb (11) indicates the reaching of cut off
value of roof convergence for that particular mine and thus providing a visual
warning of impending roof failure.
EXAMPLES
The following example is given by way of illustration of the working of the
invention in actual practice and therefore should not be construed to limit the
scope of the present invention.
Example-I
Convergence measuring device of the present invention for measuring
convergence of the roof in a mechanized or semi mechanized coal mine
workings, quickly and accurately in accordance with the specification were
manufactured as mentioned in the drawings accompanying this specification.
Field trials in Dhori Khas colliery of CCL was conducted where conventional
method of mining with caving was being used. The results of the experiments
such as installation and convergence measurement with this device at site were
studied and are detailed below.
Convergence measuring device was installed in mine roadways and reading was
taken as per the accompanying specification.
It was found that the device give more accurate results very quickly as compared
to existing convergence measuring device as it eliminated the requirement of a
reference point in the floor of a roadway whose position is liable to be disturbed
due to movement of heavy machines (SDULHD) in a semi mechanized coal
mine district. The convergence per unit time provided the convergence rate,
which was useful in predicting roof failure 1 fall. Also the visual warning provided
by this instrument helps in withdrawal of men and equipments in time to safe
place.
NOVELTY OF THE PRESENT INVENTION
The novelty of the present invention resides in enabling measuring convergence
of the roof in a mine as well as providing visual warning when a pre determined
cut off value is achieved, which is economical, easy to assemble and dismantle,
maintains verticality, provides accurate measurement, easy reading and is
capable of indicating the convergence quickly and accurately without any
requirement of a reference point in the floor of a roadways whose position may
be disturbed due to movement of heavy machines and also gives convergence of
the roof irrespective of the position of the roof bed from where it is separated.
The working principle of the operation of the device of the present invention for
measuring convergence of the roof in a mine, quickly and accurately, is detailed
below.
ADVANTAGES OF THE PRESENT INVENTION
The main advantages of the present invention for measuring convergence of the
roof in a mine are:
1. Simple mechanism.
2. It is cost effective.
3. Installation is very easy.
4. It does not require any reference point in the floor.
5. It gives true convergence.
6. Easy accessibility of convergence reading.
7. Speedy measurement of convergence for a particular point in a mine roof.
8. Provides visual warning when roof convergence reaches a pre determined cut
off value.
9. It doesn't disturb the deployment of different heavy earth moving machines.
10. It can be used in caverns, tunnels and other under ground civil construction.
11. It is a fast, reliable and appropriate roof fall predicting device.
12. Robust in nature.
13. It does not require any vertical hole in the roof for grouting purpose.
14.lt gives convergence of the roof irrespective of the position of the roof bed
I from where it is separated.
15.lt does not use roof as a reference point against which roof convergence is I
measured.
16.Since roof is not used as a reference point for convergence measurement, it
will give more reliable roof convergence informa

WE CLAIM
1. A device for measuring convergence of the roof in a mine,, which consists
of a horizontal frame (1) which is fixed horizontally in between the mine
roadway walls / pillars just below the roof level by tensioned wires (2) that
is anchored in the drilled hole provided in both side of the mine
walls/pillars with the help of butterfly springs (3) wherein an extendable
and movable rod (4) is passing through the said frame (1) having gear
teeth's at lower end which will mesh with the teeth's of the spur gear (5)
connected with the pointer (6) provided in the graduated circular scale (7)
by a connecting rod (8).
2. A device as claimed in claim 1 wherein a simple electrical circuit (9) in the
said frames (1) connected with a battery (10) and an LED bulb (1 1) for
providing a visual warning of impeding roof failure.
3. A device as claimed in claim 1 wherein an umbrella type frame (12)
connected with the rod (4) placed above the said horizontal frame (1).
4. A device as claimed in claim 1 wherein the horizontal frame (1) is fixed
below the roof level by means of tensioned wires (2)
5. A device as claimed in claim 1 wherein horizontal frame (1) is anchored in
the drilled hole provided in both side of the mine walls/pillars with the help
of butterfly springs (3).
6. A device as claimed in claim 1 wherein teeth's of the spur gear (5) are
connected with the pointer (6) by means of connecting rod (8)
7. A device as claimed in claim 1 wherein the roof convergence is measured
using the inter-related movement of rod (4), spur gear (5), connecting rod
(8) and pointer (6) in the circular graduated scale (7) attached with the
said horizontal frame (1).
8. A simple electric electrical circuit as claimed in claim 2 is used for
providing a visual warning of impeding roof failure
9. A device as claimed in claim 1 is made up of material aluminum fir
making it lighter in weight
Dated the ------ 4-b ---- 1 -------- day of --------- ------20-13- -----.
L) Scientist
Intellectual Property Management Division,
Council of Scientific and Industrial Research.
+om I CHETAN KUMAR
?krrFmlScientist
&. a. y, (3R.w.d.m.)
I.P.U. (C.S.I.R.)
14,- fam Tfll4,Satsang Vihar Mai L; 4 m-1100671 New Delhi-110067