FIELD

The present disclosure relates to the field of material handling devices.

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.
In vehicle manufacturing and assembly plants, overhead conveyors are the conveyor mechanisms used for moving a vehicle chassis around for performing various operations thereon. After a vehicle chassis is fitted with heavy components such as an engine and a differential, the chassis is loaded onto the overhead conveyor (OHC) at the backend loading station of the paint shop. The OHC loaded with the chassis is driven by an electric motor, which is driven by a drive unit, through a transmission mechanism. The OHC has a plurality of tackles, each tackle moving in a closed loop, through the operations of pre-treatment, water dry-off, painting, flash removal, paint baking, the unloading station where the tackle is unloaded and then the tackle returns back to the backend loading station. The transmission mechanism is a heavy-duty reduction gear set driven by an electric motor which is coupled to a driver and a driven gear placed one above the other, and the driven gear is coupled to the dock chain, wherein the dock chain eventually meshes with the OHC and moves the OHC.
A shear pin is inserted between the sprocket and the driven gear of the drive unit for engagement and disengagement of the dock chain with the transmission mechanism. Under normal load conditions, the torque is transmitted from the driven gear to the sprocket through the shear pin. When overload occurs, the shear pin is configured to shear off first, due to which the mechanical power supply to the chain and thereby to the OHC is cut off. An overload condition may occur due to mechanical failure occurring within the mechanical power transmission mechanism, such as due to a ball element of a bearing falling off from its location, due to improper loading of the OHC, due to jamming occurring due to an object

getting trapped in the drive or due to one of the chassis mounted on the OHC getting stuck with an obstacle, due to electrical failure and so on.
When an overload condition occurs, the drive unit draws electric current of a high value to provide for the additional torque. Even though the shear pin is configured to break, it may not completely cut off mechanical power transmission. Ultimately, the OHC and the transmission mechanism may undergo heavy damage. The OHC may also roll off leading to heavy damage to the OHC, damaging the chassis mounted thereon as well as to any structures and equipment that the load of the chassis collides with. Repair of components of the transmission mechanism may require considerable time leading to a long stoppage time, causing production losses.
Hence, there is felt a need for an overload detection and power cut-off ability for a material handling system which ameliorates the aforementioned issues.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a material handling system with an overload detection and power cut-off ability.
Another object of the present disclosure is to provide a material handling system with an overload detection and power cut-off ability wherein the overload detection and power cut-off is reliably implemented.
Yet another object of the present disclosure is to provide a material handling system with an overload detection and power cut-off ability wherein the overload detection and power cut-off ability can be easily retrofitted in an existing material handling system.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure envisages a material handling system with an overload detection and power cut-off ability. The material handling system comprises a conveyor mechanism, an electric motor, a drive unit and a control unit. The conveyor mechanism is configured to convey articles from one location to another. The electric motor is coupled to the conveyor mechanism. The drive unit is configured to supply electric power to the motor. The control unit is configured to control electrical power supplied to the drive unit. The control unit is further configured to sense the instantaneous electrical output of the drive unit, to compare the sensed instantaneous electrical output of the drive unit with a predetermined threshold value and to cut off electrical power supply to the drive unit when the sensed instantaneous electrical output of the drive unit exceeds the predetermined threshold value. In an embodiment, the conveyor mechanism comprises an overhead conveyor.
In an embodiment, the control unit comprises a signal conditioning module, a repository, a comparison module and a control module. The signal conditioning module is configured to sense instantaneous electrical output of the drive unit and generate an instantaneous digital feedback signal of amplitude proportional to a parameter of the electrical output. The repository is configured to store the predetermined threshold value. The comparison module is configured to receive and compare the instantaneous digital feedback signal with the predetermined threshold value and generate a comparison signal. The control module is configured to receive the comparison signal and send a control signal to the drive unit based on the value of the comparison signal. In an embodiment, the predetermined threshold value is in units of electric current.

In an embodiment, the system comprises an input unit. The input unit is configured to receive the predetermined threshold value from a user and transmit the predetermined threshold value to the control unit.
In an embodiment, the drive unit is a variable frequency drive.
In an embodiment, the material handling system comprises a power transmission mechanism which transmits mechanical power generated by the motor to the conveyor mechanism. In an embodiment, the power transmission mechanism comprises a first coupling element, a gear set, a second coupling element and a chain drive mechanism. The first coupling element is configured to couple the motor to the gear set. The gear set comprises a drive gear and a driven gear. The chain drive mechanism comprises a chain and at least two sprockets including a first sprocket and a second sprocket. The chain is configured to mesh with the conveyor mechanism. The second coupling element is configured to couple the driven gear with the first sprocket of the chain drive mechanism. In an embodiment, the system comprises a sensor configured to generate a signal on detecting absence of the second coupling element between the driven gear and the first sprocket and transmit the signal to the control unit. The control unit is configured to cut off power supply to the drive unit on receiving the signal from the sensor. In an embodiment, the second coupling element is a shear pin. .
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
A material handling system with an overload detection and power cut-off ability of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a schematic view of the material handling system of prior art;
Figure 2 illustrates a block diagram of a material handling system according to an embodiment of the present disclosure;

Figure 3 illustrates a block diagram of the control unit according to an embodiment of the control system of the present disclosure;
Figure 4 illustrates a schematic view of the material handling system of the present disclosure;
5 Figure 5 illustrates a flow diagram of an overhead conveyor in a paint shop of a
vehicle manufacturing plant; and
Figure 6 illustrates a block diagram of a material handling system according to another embodiment of the present disclosure.
LIST OF REFERENCE NUMERALS
10 1000’ material handling system of prior art
10’ conveyor mechanism of prior art
20’ electric motor of prior art
30’ power transmission mechanism of prior art
305’ first coupling of prior art
15 310’ gear set of prior art
312’ drive gear of prior art
314’ driven gear of prior art
320’ second coupling (= shear pin) of prior art
330’ chain drive of prior art
20 332’ chain of prior art
334’ first sprocket of prior art
336’ second sprocket of prior art
6

1000 material handling system of the present disclosure
10 conveyor mechanism
20 electric motor
30 power transmission mechanism
5 305 first coupling
310 gear set
312 drive gear
314 driven gear
320 second coupling (= shear pin)
10 330 chain drive
332 chain
334 first sprocket
336 second sprocket
40 drive unit
15 50 control unit
52 signal conditioning module
54 repository
56 comparison module
58 control module
20 60 input unit
70 sensor
7

DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the
5 present disclosure to the person skilled in the art. Numerous details are set forth,
relating to specific components, and methods, to provide a complete
understanding of embodiments of the present disclosure. It will be apparent to the
person skilled in the art that the details provided in the embodiments should not be
construed to limit the scope of the present disclosure. In some embodiments, well-
10 known processes, well-known apparatus structures, and well-known techniques
are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the
15 forms “a”, “an” and “the” may be intended to include the plural forms as well,
unless the context clearly suggests otherwise. The terms “comprises”, “comprising”, “including” and “having” are open-ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or
20 addition of one or more other features, integers, steps, operations, elements,
components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
25 When an element is referred to as being “mounted on”, “engaged to”, “connected
to” or ‘coupled to” another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.
8

The terms first, second, third, etc., should not be construed to limit the scope of
the present disclosure as the aforementioned terms may be only used to
distinguish one element, component, region, layer or section from another
component, region, layer or section. Terms such as first, second, third etc., when
5 used herein do not imply a specific sequence or order unless clearly suggested by
the present disclosure.
Terms such as “inner”, “outer”, “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures.
10 A material handling mechanism such as an overhead conveyor (OHC) is usually
driven by electric motors which in turn are controlled by a control unit (not shown in Figure 1). Figure 1 illustrates a schematic view of the material handling system 1000’ of prior art. The control unit controls the mechanical power output of an electric motor 20’ by controlling at least one of the current and the voltage
15 supplied to the electric motor 20’. A typical OHC 10’ is driven by the electric
motor 20’, wherein the power output of the motor 20’ is given to the OHC 10’ through a transmission mechanism 30’ comprising a gearbox and a chain drive. The driven gear 314’ of the gear set and the input sprocket 334’ of the chain drive are coupled using a shear pin 320’. The shear pin 320’ is configured to be the
20 weakest link that is supposed to fail in conditions of overload, so as to protect the
rest of the mechanical components of the system 1000’. However, it has been observed that, despite failing, the shear pin 320’ may still transmit mechanical power to the chain 332’ of the chain drive. Hence, a shear pin arrangement cannot be completely relied upon in case of power supply during overload condition, for
25 protection of components in a material handling system.
The present disclosure envisages a material handling system 1000 with an overload detection and power cut-off ability, as illustrated through Figure 2 to Figure 6. Figure 2 illustrates a block diagram of the system 1000 according to an embodiment of the present disclosure. The system 1000 comprises a conveyor
9

mechanism 10, an electric motor 20, a drive unit 40 and a control unit 50. The
conveyor mechanism 10 is driven by the electric motor 20 through a power
transmission mechanism 30. The conveyor mechanism 10 conveys articles from
one location to another as the conveyor mechanism 10 goes around in a loop. The
5 power transmission mechanism 30 transmits mechanical power generated by the
electric motor 20 to the conveyor mechanism 10 at a reduced speed of rotation. The electrical power is supplied to the motor 20 through the drive unit 40. The control unit 50 is configured to control the electrical power supplied to the drive unit 40. Further, the control unit 50 is configured to sense instantaneous electrical
10 output of the drive unit 40. The control unit 50 compares the instantaneous value
of the electrical output of the drive unit 40 with a predetermined threshold value. The control unit 50 cuts off electrical power supply to the drive unit 40 if the instantaneous value of the electrical output exceeds the threshold value. Thus, by cutting off the power supply to the motor 20 as soon as the electric current drawn
15 by the electric motor 20 overshoots due to overload, the conveyor mechanism 10
as well as the moving components of the transmission mechanism 30 are protected from damage.
In an embodiment as illustrated in Figure 3, the control unit 50 comprises a signal conditioning module 52, a repository 54, a comparison module 56 and a control
20 module 58. The signal conditioning module 52 is configured to sense
instantaneous electrical output of the drive unit 40, generate an instantaneous digital feedback signal of amplitude proportional to a parameter of the sensed electrical output and transmit the instantaneous feedback signal to the comparison module 56. The repository 54 is configured to store a predetermined threshold
25 value. The comparison module 56 is configured to receive the instantaneous
digital feedback signal, compare the instantaneous digital feedback signal with the predetermined threshold value and generate a comparison signal and transmit the comparison signal to the control module 58. The control module 58 is configured to receive the comparison signal and send a control signal to the drive unit 40
30 based on the value of the comparison signal. In an embodiment, the signal
10

conditioning module 52 is an analog-to-digital convertor. Further, the signal conditioning module 52 comprises a current measurement module (not shown in Figure 3).
In an embodiment, the comparison signal generated by the comparison module is
5 a rectangular wave, wherein the higher level of voltage indicates that the
instantaneous value of the feedback signal is greater than the threshold value. In
another embodiment, the comparison signal is a sawtooth wave. Thus, in the
embodiment where a rectangular wave is used to represent the comparison signal,
the control module 58 cuts off power supply to the drive unit 40 when a voltage of
10 higher level in the comparison signal is received.
In an embodiment, the current measurement module is an ammeter. In another embodiment, the current measurement module is a digital ammeter.
For a constant supply voltage, load driven by an electric motor is proportional to
the supplied electric current. Hence, preferably, the parameter of electrical output
15 which the feedback signal is proportional to is the electric current output of the
drive unit 40. Thus, the predetermined threshold value is in units of electric current.
In an embodiment, the material handling system 1000 comprises an input unit 60.
The input unit 60 is configured to receive at least the predetermined threshold
20 value from a user and transmit the predetermined threshold value to the control
unit 50.
In an embodiment, the conveyor mechanism 10 is an overhead conveyor. Figure
4 illustrates a schematic view of the material handling system 1000 of the present
disclosure. The conveyor 10 has a plurality of tackles (not shown in Figure 4)
25 mounted thereon, wherein each tackle holds an object/material to be transported
from one location to another. In a vehicle manufacturing plant, the tackle holds a vehicle chassis which is often loaded with heavy components such as an engine assembly, a differential mechanism and so on. The material handling system 1000
11

comprises a gear set 310 and a chain drive mechanism 330 together defining a
mechanical power transmission mechanism 30. The gear set 310 includes a drive
gear 312 and a driven gear 314. The chain drive mechanism 330 comprises a
chain 332 and at least two sprockets including a first sprocket 334 and a second
5 sprocket 336. The electric motor 20 is coupled to the drive gear 312 using a first
coupling element 305. The drive gear 312 meshes with the driven gear 314, which in turn is coupled through a second coupling element 320 to the first sprocket 334 of the chain drive mechanism 330. The chain 332 in turn meshes with the conveyor mechanism 10. A typical vehicle manufacturing plant includes a paint
10 shop, and each tackle moves in a closed loop in the paint shop, through the
operations of pre-treatment, water dry-off, painting, flash removal, paint baking, the unloading station where the tackle is unloaded and then the tackle returns back to the backend loading station, as illustrated in the flow chart of Figure 5. The conveyor 10 also goes along an upward elevation after the tackle is loaded and a
15 slope before the tackle is unloaded. Through this loop, the conveyor 10 makes at
least three turns. The tackle is highly likely to get stuck at these turns. Also, obstacles may come in front of the moving chassis or an object such as a dislodged ball of a bearing or the like getting caught in between the conveyor’s moving parts. Any blockage to the movement of the mechanical components
20 increases the load on the motor 20. The overload is compensated for by increase
in the current drawn by the motor 20, resulting in increase in the instantaneous output current of the drive unit 40. The control unit 50 senses the instantaneous electrical output of the drive unit 40. In an embodiment, control unit 50 senses the instantaneous current output of the drive unit 40. The control unit 50 of the
25 present disclosure compares the instantaneous current output with a
predetermined threshold value by the user. An input unit 60 is configured to be communicatively coupled to the control unit 50. The threshold value in units of current has been input by the user using the input unit 60. If the control unit 50 determines that the value of the instantaneous current output of the drive unit 40 is
30 greater the threshold value, the control unit 50 cuts off electric power supply to
the drive unit 40 and thereby to the motor 20. Hence, the gears 312 and 316, the
12

chain drive mechanism 330 and the conveyor mechanism 10 stop moving.
Further, to counter the inertia of the chassis, particularly when the loop of the
conveyor mechanism 10 goes through an upward elevation and a downward slope,
mechanical stoppers (not illustrated in Figures) are provided for the conveyor
5 mechanism 10. Thus, any rolling forward down the downward slope or roll back
along the upward elevation of the conveyor mechanism 10 is also prevented, thereby ensuring complete stoppage of any movement of the mechanism 10.
In an embodiment, the drive unit 40 comprises a switch (not shown in Figures).
When the switch is in an OFF state, the power supply to the drive unit is cut off.
10 The control unit 50 is configured to change states of the switch. Thus, the control
unit 50 turns the switch into an OFF state when the control unit 50 determines that the value of the instantaneous current output of the drive unit 40 is greater the threshold value, thereby cutting off the power supply to the drive unit 40 and thus to the electric motor 20.
15 In an embodiment, the second coupling element 320 is a shear pin, which couples
the driven gear 314 with the first sprocket 334 of the chain drive mechanism 330. The shear pin 320 is configured to break when a predetermined threshold load (i.e., torque) is applied by the driven gear 314 through the shear pin 320 on the first sprocket.
20 In an embodiment, as illustrated in Figure 6, a sensor 70 is configured to generate
a signal on detecting absence of the shear pin 320 between the driven gear 314 and the first sprocket 334 and transmit the signal to the control unit 50. The control unit 50 cuts off power supply to the drive unit 40 on receipt of a signal corresponding to detection of absence of the shear pin 320 from the sensor 70. In
25 an embodiment, the signal generated by the sensor 70 is selected from a group
consisting of a square wave, a rectangular wave, a pulse. In an embodiment, the sensor 70 is an optical sensor. In another embodiment, the sensor 70 is an electromagnetic sensor.
In an embodiment, the drive unit 40 is a variable frequency drive.
13

In an embodiment, the control unit 50 is a programmable logic controller (PLC).
In another embodiment, the control unit 50 is implemented as one or more
microprocessors, microcomputers, digital signal processors, central processing
units, state machines, logic circuitries, and/or any devices that manipulate signals
5 based on operational instructions.
The time taken by the control unit 50 between sensing the instantaneous current
output of the drive unit 40 and cutting off electric power supply to the drive unit
40 is estimated to be less than 1.9 ns. Thus, practically, the control unit 50 of the
present disclosure cuts off power supply to the motor 30 as soon as it senses
10 overcurrent supplied to the drive unit 40.
Thus, the material handling system of the present disclosure protects the conveyor mechanism and the transmission mechanism from damage by sensing the electrical power supplied to the electric motor (i.e., the prime mover) and cutting off the electrical power supply in case an overload current sensed to be drawn by
15 the motor. Hence, the system does not rely completely on a shear pin for
protection of mechanical components against overload. Therefore, the system becomes highly reliable. The shear pin can still function as a secondary means for protection against overload. Moreover, an existing material handling mechanism such as an OHC system can easily be retrofitted with the overload detection and
20 power cut-off ability of the present disclosure, by configuring the existing control
system to sense the electrical output of the drive unit, to compare the sensed electrical output with a threshold value input by the user and to cut off electrical power supply to the drive unit on detection of excessive value of a parameter (preferably, current) of the sensed power output of the drive unit.
25 The foregoing description of the embodiments has been provided for purposes of
illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a
14

departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages 5 including, but not limited to, the realization of a material handling system with an overload detection and power cut-off ability, wherein:
• the overload detection and power cut-off is reliably implemented; and
• the overload detection and power cut-off ability can be easily retrofitted in an existing material handling system.
10 The foregoing disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following
15 description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples
20 should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and 25 modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description
15

and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

WE CLAIM:

A material handling system (1000) with an overload detection and power cut-off ability, said material handling system (1000) comprising:
• a conveyor mechanism (10) configured to convey articles from one location to another;
• an electric motor (20) coupled to said conveyor mechanism (10);
• a drive unit (40) configured to supply electrical power to said motor (20);
• a control unit (50) configured to control electrical power supplied to said drive unit (40);
characterized in that:
said control unit (50) is configured to sense the instantaneous electrical output of said drive unit (40), to compare said sensed instantaneous electrical output of said drive unit (40) with a predetermined threshold value and to cut off electrical power supply to said drive unit (40) when said sensed instantaneous electrical output of said drive unit (40) exceeds said predetermined threshold value.
The system (1000) as claimed in claim 1, wherein said conveyor mechanism (10) comprises an overhead conveyor.
The system (1000) as claimed in claim 1, wherein said control unit (50) comprises:
• a signal conditioning module (52) configured to sense
instantaneous electrical output of said drive unit (40) and generate
an instantaneous digital feedback signal of an amplitude
proportional to a parameter of the sensed electrical output;

• a repository (54) configured to store said predetermined threshold value;
• a comparison module (56) configured to compare said instantaneous digital feedback signal with said predetermined threshold value and generate a comparison signal; and
• a control module (58) configured to receive said comparison signal and send a control signal to said drive unit (40) based on the value of said comparison signal.
The system (1000) as claimed in claim 1, wherein said system (1000) comprises an input unit (60), said input unit (60) configured to receive said predetermined threshold value from a user and transmit said predetermined threshold value to said control unit (50).
The system (1000) as claimed in claim 1, wherein said drive unit (40) is a variable frequency drive.
The system (1000) as claimed in claim 1, wherein said system (1000) comprises a power transmission mechanism (30) which transmits mechanical power generated by said motor (20) to said conveyor mechanism (10).
The system (1000) as claimed in claim 6, wherein said power transmission mechanism (30) comprises a first coupling element (305), a gear set (310), a second coupling element (320) and a chain drive mechanism (330), said first coupling element (305) configured to couple said motor (30) with said gearbox (310), said gear set (310) comprising a drive gear (312) and a driven gear (314), said chain drive mechanism (330) comprising a chain (332) and at least two sprockets including a first sprocket (334) and a second sprocket (336), said chain (332) configured to mesh with said conveyor mechanism (10), and said shear pin (320) configured to couple

said driven gear (314) with said first sprocket (334) of said chain drive mechanism (330).
The system (1000) as claimed in claim 7, wherein said system (1000) comprises a sensor (70) configured to generate a signal on detecting absence of said second coupling element (320) between said driven gear (314) and said first sprocket (334) and transmit said signal to said control unit (50), wherein said control unit (50) is configured to cut off power supply to said drive unit (40) on receiving said signal from said sensor (70).
The system (1000) as claimed in claim 8, wherein said second coupling element (320) is a shear pin.