FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
DIFFERENTINAL MECHANICAL INTERLOCK ASSEMBLY FOR
CONTACTORS
APPLICANT: LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001 Maharashtra
INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The present invention generally relates to the electrical
switching systems and particularly to the interlocking mechanisms in the electrical switching systems. The present invention more particularly relates to the mechanical interlocks for preventing the simultaneous switching ON of the two electromagnetically operable contactors.
B) BACKGROUND OF THE INVENTION
[0002] In electrical systems, which include equipments such as multi-
phase reversible AC motors, it is often necessary to provide one contactor for controlling the rotation of the motor in forward direction and another contactor for controlling the rotation of the motor in reverse direction. If, inadvertently, both contactors were simultaneously energized, a short circuit would have occurred between the motor phases which could result in serious equipment damage. To avoid the undesired simultaneous actuation of the contactors, various interlocking mechanisms have been devised, the majority of which are typified by mechanical interlocking mechanisms.
[0003] To avoid such equipment damages, the provision of a
mechanical interlock is frequently used due to its more positive action. A mechanical interlock provides a restraining force to prevent the physical movement of a movable magnetic member of one of the contactors from the de-energized position to the energized position when a movable magnetic

member of the other contactor is already moved from the de-energized position to the energized position.
[0004] The mechanical interlocks known in the prior art are
cumbersome due to the assembly of numerous component parts. Hence there is a need to provide an improved mechanical interlock device for electromagnetic contactors for simultaneous interlocking of the contactors without requiring any additional circuitry.
[0005] The above mentioned shortcomings, disadvantages and
problems are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECT OF THE INVENTION
[0006] The primary object of the present invention is to develop an
improved differentia] mechanical interlock assembly for contactors for interlocking the operation of the contactors without requiring any additional circuitry.
[0007] Another object of the present invention is to develop an
interlock assembly for contactors, which is assembled easily.
[0008] Yet another object of the present invention is to develop a
compact interlock assembly for contactors.

[0009] Yet another object of the present invention is to develop an interlock assembly for interlocking electromagnetic contactors of different ranges and sizes.
[0010] Yet another object of the present invention is to develop an
interlock assembly to prevent a concurrent closure of the electromagnetic contactors.
[0011 ] These and other objects and advantages of the present invention
will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0012] The above mentioned shortcomings, disadvantages and
problems are addressed herein and which will be understood by reading and studying the following specification,
[0013] The various embodiments of the present invention provide a
mechanical interlock assembly for contactors. The interlock assembly includes a base plate, a first electromagnetic contactor mounted on the base plate and a second electromagnetic contactor mounted on the base plate. An actuator assembly is coupled with the two electromagnetic contactors. The base plate further includes two shaft assemblies mounted on the base plate. The shaft assembly includes two flaps and one cam attached to the shaft. The

energization of one of the electromagnetic contactors causes a rotation of the cam. The rotation of the cam changes the position of the cam to interlock the operations of the first electromagnetic contactor or the second electromagnetic contactor.
[0014] According to one embodiment, the actuator assembly is coupled with a moving bridge of both the first electromagnetic contactor and the second electromagnetic contactors mounted on the top surface of the base plate. Two shaft assemblies are mounted on the base plate using brass brackets and connected to the two electromagnetic contactors. Each shaft assembly includes two flap on which the actuator assembly rests and the cam which rotates with the movement of the bridge.
[0015] A change in position of the cam caused by the rotational movement when the first contactor is in an energized state and the second contactor in de-energized state, as the bridge movement of the second contactor is restricted. The change in position of the cam associated with the first contactor restricts the movement of the cam connected to the second contactor. This in turn restricts the movement of the shaft assembly. As the actuator assembly is coupled with the moving bridge of the first contactor, it prevents the energization of the second contactor. Similarly, the change in position of the cam associated with the second contactor restricts the movement of the cam connected to the first contactor. This in turn restricts the movement of the actuator assembly coupled with the moving bridge of

the second contactor, thereby preventing the energization of the first contactor. Thus the mutual locking of the first electromagnetic contactor and the second electromagnetic contactor is achieved.
[0016] On de-energization of the at least one contactor, the shaft assembly resumes to its normal position due to a spring mechanism placed between the respective shaft assembly and the base plate.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0018] FIG. 1 illustrates a top view of a differential mechanical
interlock assembly for contactors, according to one embodiment of the present invention.
[0019] FIG. 2 illustrates a top view of a base plate assembly mounted
with actuator assembly in a differential mechanical interlock assembly for contactors, according to one embodiment of the present invention.
[0020] FIG. 3 illustrates a bottom view of a base plate assembly
mounted with two shaft assemblies in a differential mechanical interlock assembly for contactors, according to one embodiment of the present invention

[0021 ] FIG. 4 illustrates an isometric view of a differential mechanical interlock assembly showing the arrangement of the shaft assembly and the cam in an open condition, according to one embodiment of the present invention.
[0022] FIG. 5 illustrates a sectional view of a differential mechanical
interlock assembly showing one shaft assembly in an actuated condition making the other shaft assembly inoperative, according to one embodiment of the present invention.
[0023] FIG. 6 illustrates a perspective view of a differential
mechanical interlock assembly having at least one of the contactor in an energized condition, according to one embodiment of the present invention.
[0024] Although specific features of the present invention are shown in
some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0025] In the following detailed description, reference is made to the
accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These

embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical. mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0026] The various embodiments of the present invention provide a differential mechanical interlock assembly for electromagnetic contactors. The interlock assembly is capable of providing a mechanical interlocking of the electromagnetic contactors simultaneously without the need for any additional circuitry. The differential mechanical interlock assembly uses a system comprising a plurality of shaft assemblies and cam assemblies which are interlocked during system operation so that the closure of one electromagnetic contactor prevents the closure of the other electromagnetic contactor.
[0027] FIG.l illustrates a front view of a differential mechanical interlock assembly for contactors, according to one embodiment of the present invention. The interlock assembly includes a base plate 3 mounted with a first electromagnetic contactor 1 and a second electromagnetic contactor 2. The base plate 3 further includes an actuator assembly 4 coupled with the second electromagnetic contactor 2 and an actuator assembly 5 coupled with the first electromagnetic contactor 1. The actuator assemblies 4 and 5 are mounted on the top surface of the base plate 3. When at least one of the

electromagnetic contactor's coil is energized, the contactor operates and thus disabling the closing of other contactor. On energization of the first electromagnetic contactor 1, the actuator assembly 5 coupled with the moving bridge on both sides of the contactor move along the bridge resulting in a rotatary movement of the shaft assembly 32.
[0028] FIG.2 illustrates a top view of the base plate according to one embodiment of the present invention. The base plate as shown in FIG. 2 includes a plurality of actuator assemblies 4, 5 mounted on the top surface of the base plate 3. The actuator assemblies 4 and 5 are coupled with the moving bridge of the first electromagnetic contactor 1 and the second electromagnetic contactor 2 respectively.
[0029] FIG. 3 illustrates the bottom view of the base plate assembly according to one embodiment of the present invention. As shown in FIG.3, a first shaft assembly 31 and a second shaft assembly 32 are mounted on the base plate 3 using brass brackets 33. The first shaft assembly 31 includes a flaps 11 on which the actuator assembly 4 is placed. The first shaft assembly 11 further includes a cam 12 which rotates with the movement of the moving bridge of the contactor.
[0030] On energisation of the first electromagnetic contactor 1, the actuator assembly 5 coupled with the moving bridge on both sides of the first electromagnetic contactor 1 move along with the bridge resulting in a rotation movement of the second shaft assembly 32. The rotation movement

of the second shaft assembly 32 causes a rotation of the cam 22 connected to it. The rotation in turn provide for a change in position of the cam 22 which prevents the energization of the second electromagnetic contactor 2 by restricting the rotation movement of the shaft assembly 31.
[0031] The second shaft assembly 32 also includes a flaps 21 and a cam 22. The second shaft assembly 32 works in a similar manner as that of the first shaft assembly 31. Similarly, on energization of the second electromagnetic contactor 2, the actuator assembly 4 coupled with the moving bridge of the second electromagnetic contactor 2 moves along with the movement of the moving bridge of the second electromagnetic contactor 2 during a rotation movement of the first shaft assembly 31. The rotation movement of the first shaft assembly 31 causes a rotation of the cam 12 connected to it. The rotation in turn provide for a change in position of the cam 12 which prevents the energization of the first electromagnetic contactor 1 by restricting the rotation movement of the second shaft assembly 32.
[0032] The rotational movement of the cam 12 during an energization of electromagnetic contactor 1 provides for mutual interlocking of the first electromagnetic contactor 1 and the second electromagnetic contactor 2. Also, the rotational movement of the cam 22 during an energization of electromagnetic contactor 2 provides for mutual interlocking of the first electromagnetic contactor 1 and the second electromagnetic contactor 2.

[0033] FIG.4 illustrates an isometric view showing the arrangement of the shaft assembly and the cam in an open condition according to one embodiment of the present invention. The first shaft assembly 31 includes a cam 12 which rotates with the movement of the moving bridge of the first electromagnetic contactor 1. Similarly, the second shaft assembly 32 includes a cam 22 and it works in similar manner as that of the shaft assembly 31. The shaft assemblies 31 and 32 are mounted on the base plate 3 with the brass brackets 33.
[0034] FIG.5 illustrates a sectional view of the differential mechanical
interlock assembly showing one shaft assembly in an actuated condition while making the other shaft assembly inoperative according to one embodiment of the present invention. The energization of the second electromagnetic contactor 2 causes a movement of the actuator assembly 4 coupled with the moving bridge of the second electromagnet contactor 2. As the actuator assembly 4 rests on the flaps 11 as shown in FIG. 3, the linear movement of the actuator assembly 4 is transferred into a rotary movement of the flaps 11. The rotation movement of the flap 11 in turn provides for the rotation of the first shaft assembly 31. The rotation of the first shaft assembly 31 actuates the cam 12 associated with the first shaft assembly 31. A change is position of the cam 12 due to the rotation of the cam 12 restricts the movement of the second electromagnetic contactor 2. This in turn helps to maintain the first electromagnetic contactor 1 in an energized state.

[0035] FIG.6 illustrates a detailed view showing the differential mechanical interlock assembly with one of the electromagnetic contactor in an energized condition. The first electromagnetic contactor 1 and the second electromagnetic contactor 2 are mounted on the base plate 3. The actuator assembly 4 is coupled with a moving bridge of the second electromagnetic contactor 2 and the actuator assembly 5 is coupled with a moving bridge of the first electromagnetic contactor 1. The first shaft assembly 31 includes one flap 11 on which the actuator assembly 4 rests and the cam 12 which rotates with the movement of bridge. The change in position of the cam 12 will restrict the movement of cam 22 which in turn restricts the movement of actuator assembly 5. The actuator 5 is further coupled with the moving bridge of the first electromagnetic contactor 1 and hence the energisation of the second electromagnetic contactor 2 is prevented as shown in FIG. 5. The same functioning is repeated and vice versa. Thus the mutual locking of the first electromagnetic contactor 1 and the second electromagnetic contactor 2 is achieved.
[0036] On de-energisation of the first electromagnetic contactor, the
shaft assembly 31 resumes to its normal position as shown in FIG. 4 due to the action of a return spring placed in between the first shaft assembly 31 and the base plate 3.
G) ADVANTAGES OF THE INVENTION

[0037] The differential mechanical interlock assembly for contactors according to the present invention is compact and is easy to assemble. The interlock assembly of the present invention doesn't require any additional circuitry for interlocking the contactors. The interlock assembly is used for interlocking the electromagnetic contactors of different ranges and sizes. The interlock assembly prevents simultaneous actuation of the actuating assemblies associated with both the first electromagnetic contactor and the second electromagnetic contactor thereby preventing the simultaneous closure of the two contactors.
[0038] Although the invention is described with various specific
embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0039] It is also to be understood that the following claims are
intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
What is claimed is:
1. An mechanical interlock assembly for contactors, the assembly
comprising: a base plate;
a first electromagnetic contactor mounted on the base plate; a second electromagnetic contactor mounted on the base plate; a first actuator assembly coupled with the first electromagnetic contactor; a second actuator assembly coupled with the second electromagnetic
contactor;
a first shaft assembly mounted on the base plate; a second shaft assembly mounted on the base plate; at least two flaps provided both in the first shaft assembly and in the second
shaft assembly; and
a first cam attached to the flap in the first shaft assembly ; a second cam attached to the flap in the second shaft assembly; wherein the simultaneous energisation of the first electromagnetic contactor
and the second electromagnetic contactor is prevented.
2. The interlock assembly according to claim 1, wherein the simultaneous closure of the first electromagnetic contactor and the second electromagnetic contactor is prevented, even when an input signal is applied to both the first electromagnetic contactor and the second electromagnetic contactor.
3. The interlock assembly according to claim 1, wherein the first shaft assembly and the second shaft assembly are mounted on the base plate through atleast one fixing means.

4. The interlock assembly according to claim 1, wherein the fixing means is a brass bracket.
5. The interlock assembly according to claim 1, wherein the first actuator assembly is mounted on the flap in the first shaft assembly.
6. The interlock assembly according to claim 1, wherein the second
actuator assembly is mounted on the flap in the second shaft assembly.
7. The interlock assembly according to claim 1, wherein the first actuator
assembly is coupled to a moving bridge of the first electromagnetic
contactor
8. The interlock assembly according to claim 1, wherein the second actuator assembly is coupled to a moving bridge of the second electromagnetic contactor.
9. The interlock assembly according to claim 1, wherein the first electromagnetic contactor is energized to move the first actuator assembly so that the linear movement of the first actuator assembly is transferred into a rotational movement of the first shaft assembly to provide a rotary change in the position of the first cam to prevent the energisation of the second electromagnetic contactor as the movement of the moving bridge of the second electromagnetic contactor is restricted by the change in position of the first cam in the first shaft assembly and vice versa.

10. The interlock assembly according to claim 1, further comprising a first spring mechanism placed between the base plate and the first shaft assembly.
1 1. The interlock assembly according to claim 1, further comprising a second spring mechanism placed between the base plate and the second shaft assembly.
12. The interlock assembly according to claim 1, wherein the first shaft
assembly returns to a normal position due to the return action of the first
spring mechanism during the de-energisation of the first electromagnetic
contactor.
13. The interlock assembly according to claim 1, wherein the second shaft
assembly returns to a normal position due to the return action of the second
spring mechanism during the de-energisation of the second electromagnetic
contactor.