FIELD OF THE INVENTION
The present invention relates to a protection device for belt conveying system. More
particularly, the present invention is directed to providing an Anti Belt Snapping Device for
Belt Conveying System for application in Mining and other Material Handling Industries. The
anti belt snapping device according to the present invention is particularly suitable for
application in any down-hill conveyor which are prone to snapping due to uneven belt
tension under load and/or jamming of discharge chute, jerk of counter weight creating jerk
on return side belt or knocking the conveyor upper stringer structure etc, by automatically
stopping the conveyor before it is snapped.
BACKGROUND OF THE INVENTION
It is well known in Mining and other Material Handling Industries that belt conveyors are
widely used for transporting minerals and ores involving down-hill conveyors. Generally
down-hill conveyors cover long distance over undulating terrain and are placed in areas
difficult to approach. It is also a common experience that down-hill conveyor are prone to
snapping. Snapping of Down-Hill conveyors paralyses production and it takes huge time to
restore operation.
To solve the problems associated with frequent snapping of down-hill conveyors, a detailed
analysis were carried out to identify the reasons and forces involved. For this the
phenomena of operation of Down-Hill conveyor was observed and analyzed in details. It is a
fact that in Down-Hill conveyors the return side tension is greater than the carrying side
tension in the beginning when the conveyor is empty. Once the conveyor is loaded the belt
moves down by gravity, the material load starts driving the conveyor and the drive motor
tries to go beyond the synchronous speed. In this condition the motor starts working like
brake and does not allow the belt to move at higher speed ( More than the designed speed),
though the load always tries to move the belt at higher speed.
Another interesting phenomenon is the jamming of discharge chute. When the chute gets
jammed, the materials keep on accumulating in the chute/overflow the chute/starts
restricting the movement of discharge pulley and finally completely constrains the
movement of discharge pulley by stopping its movement. Now the drive pulley that is
located at the receiving end, takes power from the motor remains unaware of jamming/

stoppage of discharge chute; works/moves at normal speed. As the downward drag of
material acts downward there is no slip and material continue to accumulate at the
discharge point.
If the jamming is such that the discharge pulley movement is stopped and the drive pulley
does not slip on account of downward drag of conveyed material that maintains adequate
tension in the drive pulley; the counterweight develops a tendency to move in upward
direction. This causes momentary slip of belt in drive pulley which gives jerk in the
counterweight which is immediately taken care by the downward drag of material. If the
belt and joint condition is good, there is no problem till now. But if this continues further,
there is chance that the counterweight may hit the conveyor upper stringer structure/
tension bend pulley resulting in heavy jerk in the return belt. This jerk causes snapping of
belt. As already stated that such snapping of Down-Hill conveyors paralyses production and
it takes huge time to restore operation.
There has not been any device or method known in the prevailing practice to arrest such
occurrence of snapping in Down-Hill or in normal conveyors, except physical presence of
person who could stop the conveyor. Continuous presence of person just to watch the
jamming of the discharge chute and act promptly to stop the conveyor is not practically
possible. Moreover, such conventional human intervention for preventing belt snapping is
highly uncertain and unsafe. If the snapped belt or material conveyed hits the person
present in the conveyor gallery, it can be fatal.
There has been thus a persistent need in the art to developing a device to arrest snapping
of belt in Down-Hill or in normal conveyor systems which would be simple, safe and reliable
without needing any human intervention and stop the movement of conveyor belt before it
snaps by detecting any abnormal situation in operation in advance.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to providing an anti belt snapping
device to prevent snapping of down-hill conveyors by automatically stopping the conveyor
before any damage is done in a safe and reliable manner without any manual intervention.

A further object of the present invention is directed to providing an anti belt snapping device
to prevent snapping of down-hill conveyors wherein the device senses the chute jamming
condition automatically and stops the conveyor much before it causes failure of
equipment/major accident.
A still further object of the present invention is directed to providing an anti belt snapping
device to prevent snapping of down-hill conveyors wherein continuous manual presence for
monitoring conveyor operation/jamming is not required.
A still further object of the present invention is directed to providing an anti belt snapping
device to prevent snapping of down-hill conveyors wherein the device is totally safe as it
senses they abnormality in operating condition earlier and stops the drive.
A still further object of the present invention is directed to providing an anti belt snapping
device to prevent snapping of down-hill conveyors wherein operation of a selectively located
limit switch on the guiding channel of the counterweight beyond the safe movement span,
limit the counter weight movement on one hand beyond safe distance and on the other
hand also stops the drive motor to avoid major damage to the conveyor system.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to an anti-belt-snapping device for
down-hill conveyors comprising
a tension counter weight means cooperating interplay between carrying and return
side tension with pre-defined normal safe movement span of said counterweight for
operation;
a limit switch adapted to operate as a control switching based on any unusual
movement of the counterweight means beyond said safe limit;
means to activate the limit switch based on any noted unusual movement of the
counterweight means beyond said safe limit whereby the power to the drive motor is
cut-off to stop the conveyor thereby avoiding any unwanted snapping event.

A further aspect of the present invention is directed to an anti-belt-snapping device wherein
said means to activate the limit switch based on any noted unusual movement of the
counterweight means comprises a striker fitted to the counter-weight unit such that in case
of any unusual movement of counterweight said striker is adapted to hit/actuate the limit
switch thereby cutting power to the drive motor.
A still further aspect of the present invention is directed to an anti-belt-snapping device for
down-hill conveyors comprising
atleast one electrical limit switch in operative communication with the conveyor drive
motor selectively disposed on the guiding channel beyond the normal/safe
movement span of the counterweight attached to take-up pulley;
a striker fixed on the counterweight unit adapted to hit / actuate the limit switch in
case of unusual movement of counterweight including as in case of jamming of
discharge chute thereby cutting the power to motor through a motor control circuit
and stopping the conveyor before the counter weight striking/ hitting the stringer
structure/ tension bend pulley, thus preventing the belt snapping.
A still further aspect of t,he present invention is directed to an anti-belt-snapping device for
down-hill conveyors involving selective positioning of the limit switch obtained as a function
of belt speed, length of the belt, length of the take-up travel and weight of the counter
weight.
A still further aspect of the present invention is directed to an anti-belt-snapping device for
down-hill conveyors wherein the said limit switch is placed in such a way that it is actuated
by the said striker much before the take-up pulley reaches in the close vicinity of the upper
stringer structure of tension bend pulley.
A still further aspect of the present invention is directed to an anti-belt-snapping device for
down-hill conveyors wherein said striker is a mild steel striker, welded on the counter
weight that actuates the limit switch while the take-up pulley moves in upward direction.
A still further aspect of the present invention is directed to an anti-belt-snapping device for
down-hill conveyors wherein once the limit switch is actuated, it breaks the control circuit

and the Brake Motor Contactor (BMC) gets de-energized there by tripping the motor and
actuating the brake circuit that stops the motor.
Yet another aspect of the present invention is directed to an anti-belt-snapping device for
down-hill conveyors wherein Limit Switches and the strikers are fixed with welding or any
other fastening arrangement depending upon the site condition.
A still further aspect of the present invention is directed to an anti-belt-snapping device for
down-hill conveyors wherein to improve the reliability of the device, two parallel circuit
involving two limit switches and corresponding strikers are used to make it a "must work
device".
The objects and advantages of the present invention is described hereunder in greater
details with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic view of the conventional conveyor system for transporting
minerals/ores in mining industry involving down-hill conveyor subjected to belt snapping
due to chute jamming etc.
Figure 2: is the schematic arrangement of the anti belt snapping device according to the
present invention, installed in the down-hill conveyor system to avoid belt snapping,
showing the different components of the device.
Figure 3: is the schematic view of the control circuit diagram used in the anti belt snapping
device for down-hill conveyor system according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to an Anti Belt Snapping Device for Belt Conveying System
and more particularly to down-hill conveyors used in Mining and other Material Handling

Industries. The invented, device can be used for safe operation of any down-hill conveyors
which are prone to snapping.
Accompanying Figure 1 shows the schematic view of the conventional conveyor system for
transporting minerals/ores in mining industry involving down-hill conveyor subjected to belt
snapping due to chute jamming etc. In this conventional down-hill conveyors the problem of
discharge chute jamming and the resulting jerking of counter weight on return side
conveyor and frequent snapping of the belt conveyor occurs. Snapping of Down-Hill
conveyor paralyses production and it takes huge time to restore operation due to undulating
terrain and location in areas difficult to approach.
Accompanying Figure 2 is the schematic arrangement of the anti belt snapping device
according to the present invention, installed in the down-hill conveyor system to avoid belt
snapping, showing the different components of the device.
It can be seen in Figure 2, that when the chute gets jammed, the load / material keeps on
accumulating in the chute near Discharge pulley (1) / materials overflows the chute
/materials starts restricting the movement of the discharge pulley (1) / slows down or stops
the movement of the discharge pulley in extreme condition. Now the drive pulley(7)/drive
motor(9) unaware of the jamming keeps on moving at the normal speed as it is situated
near tail-end. As there is downward drag of material on the carrying side, the belt does not
slip and material keeps on accumulating near the discharge point.
If the jamming is so significant that the discharge pulley motion is hindered and the drive
pulley does not slip (because the material load on the carrying side of the belt maintains
tension), the result is movement of tension counter weight (5) in upper direction. During
this, the counter weight moves up gradually in the guiding channel / pipe (12) and slippage
occurs in the drive pulley momentarily. Due to this the take-up pulley (4) moves up along
with the counterweight (5) with the jerk. If the belt condition is good and the joints are also
in good condition, there is no problem till now. But if this continues for some time it may
happen that while moving up, the structure of the take-up pulley (4) hits the upper stringer
structure of tension bend pulley (2 and 6) resulting in heavy shock in the return belt. This
shock results in snapping of the belt.

In the device according to the present invention, a limit switch(lO) is put suitably on the
guiding channel / structure of the conveyor leaving sufficient space for counter weight to
move during normal operation. The positioning of the limit switch is the function of belt
speed, length of the belt; length of the take-up travel and weight of the counter weight.
At the time of starting of the belt conveyor the counterweight in the down-hill conveyor
moves upward usually. This movement can be calculated for each conveyor depending upon
the length, weight of the counter weight and type of starting ( DOL/ Soft) of the motor.
After calculating this normal movement span of the counter weight, a limit switch is fixed on
the guiding channel of the counterweight beyond the safe movement span. Also a striker is
fixed on the counterweight unit so that in case of unusual movement of counterweight ( As
in case of jamming of Discharge chute) the striker will hit / actuate the limit switch thereby
cutting the power to motor and the conveyor will stop before taking dangerous proportion
(Striking/ hitting the stringer structure/ tension bend pulley) as explained earlier, thus
preventing the belt snapping.
It can be seen in Figure 2 that there is a striker (11) welded on the counter weight (5) that
actuates the limit switch(lO) while the take-up pulley(4) moves in upward direction. The
limit switch(lO) is placed in such a way that it is actuated by the striker (11) much before
the take-up pulley reaches in the close vicinity of the tension bend pulley structure. The
moment the limit switch is operated, the motor stops and thus the heavy shock which is
responsible for the snapping of belt is eliminated. Thus by sensing the extreme condition of
jerk on the belt, the power to drive motor is cut with the help of limit switch. It will prevent
the occurrence of snapping of conveyor belt in down-hill conveyors where incidence of belt
snapping is more.
Accompanying Figure 3 shows the schematic view of the control circuit diagram for drive
motor used in the anti belt snapping device for down-hill conveyor system according to the
present invention.
Figure 3 shows the control circuit diagram for powering the motor (9). An additional
element is added i.e. a limit switch(4), that senses the jamming by getting actuated by the
actuator (11). Once the limit switch is actuated, it breaks the control circuit and the Brake
Motor Contactor (BMC) gets de-energized there by tripping the motor and actuating the
brake circuit that stops the motor. Thus the possibility of take-up pulley structure, hitting

the upper stringer structure is eliminated and hence the chance of belt snapping due to
chute jamming is avoided totally by incorporation of Anti-Belt Snapping mechanism in the
Down-Hill Conveyors.
It is thus possible by way of the present invention to providing a simple yet reliable anti belt
snapping device for down-hill conveyors wherein a selectively disposed limit switch in
operative communication with the counter weight and adjacent striker that stops the drive
motor of the conveyor in the event of chute jamming well in advance and thereby avoiding
snapping of the belt conveyor and thus avoiding down time and loss of production,
favouring wide application in Belt Conveying System for Mining and other Material Handling
Industries with significant cost advantage.

We Claim:
1. An anti-belt-snapping device for down-hill conveyors comprising
a tension counter weight means cooperating interplay between carrying and return
side tension with pre-defined normal safe movement span of said counterweight for
operation;
a limit switch adapted to operate as a control switching based on any unusual
movement of the counterweight means beyond said safe limit;
means to activate the limit switch based on any noted unusual movement of the
counterweight means beyond said safe limit whereby the power to the drive motor is
cut-off to stop the conveyor thereby avoiding any unwanted snapping event.
2. An anti-belt-snapping device as claimed in claim 1 wherein said means to activate
the limit switch based on any noted unusual movement of the counterweight means
comprises a striker fitted to the counter-weight unit such that in case of any unusual
movement of counterweight said striker is adapted to hit/actuate the limit switch
thereby cutting power to the drive motor.
3. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims
1 or 2 comprising
atleast one electrical limit switch in operative communication with the conveyor drive
motor selectively disposed on the guiding channel beyond the normal/safe
movement span of the counterweight attached to take-up pulley;
a striker fixed on the counterweight unit adapted to hit / actuate the limit switch in
case of unusual movement of counterweight including as in case of jamming of
discharge chute thereby cutting the power to motor through a motor control circuit
and stopping the conveyor before the counter weight striking/ hitting the stringer
structure/ tension bend pulley, thus preventing the belt snapping.

4. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims 1 to
3 involving selective positioning of the limit switch obtained as a function of belt speed,
length of the belt, length of the take-up travel and weight of the counter weight.
5. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims 1 to
4 wherein the said limit switch is placed in such a way that it is actuated by the said
striker much before the take-up pulley reaches in the close vicinity of the upper stringer
structure of tension bend pulley.
6. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims 1 to
5, wherein said striker is a mild steel striker, welded on the counter weight that actuates
the limit switch while the take-up pulley moves in upward direction.
7. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims 1 to
6, wherein once the limit switch is actuated, it breaks the control circuit and the Brake
Motor Contactor (BMC) gets de-energized there by tripping the motor and actuating the
brake circuit that stops the motor.
8. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims 1 to
7, wherein Limit Switches and the strikers are fixed with welding or any other fastening
arrangement depending upon the site condition.
9. An anti-belt-snapping device for down-hill conveyors as claimed in anyone of claims 1 to
8, wherein to improve the reliability of the device, two parallel circuit involving two limit
switches and corresponding strikers are used to make it a "must work device".

ABSTRACT

The present invention relates to an Anti Belt Snapping Device for Belt Conveying System for
application in Mining and other Material Handling Industries. The device according to the
present invention is particularly suitable for application in any down-hill conveyor which are
prone to snapping due to uneven belt tension or jamming of discharge chute by
automatically stopping the conveyor before it is snapped. The device of the present
invention is simple yet cost effective and reliable wherein a selectively disposed limit switch
in operative communication with the counter weight and adjacent striker that stops the
drive motor of the conveyor during upward movement of counterweight in the event of
chute jamming well in advance and thereby avoiding snapping of the belt conveyor and thus
avoiding down time and loss of production, favouring wide application in Belt Conveying
System for Mining and other Material Handling Industries with significant cost advantage.