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:
TORSION SPRING BASED LOAD ADJUSTMENT
SYSTEM
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 a torsion spring load
adjustment and particularly to a torsion spring load adjustment mechanism which requires an increment or decrement of a torsion spring torque by increasing or decreasing a spring deflection for a load adjustment.
B) BACKGROUND OF THE INVENTION
[0002] A torsion spring is a spring that works by torsion or twisting; that
is, a flexible elastic object that stores mechanical energy when it is twisted. The amount of force the spring exerts is proportional to the amount the spring is twisted.
[0003] Usually, in the torsion spring, the coils forming the torsion spring
are wound together with less spacing or no spacing between the turns of the coil. When these closely wound torsion springs are used in devices whose application is in load adjustment such as MCCB (Moulded Case Circuit Breaker), the friction between the coil turns of the torsion spring increases and decreases during loading and unloading process thereby decreasing the consistency of the spring in a load offered at a particular deflection and depends on whether the spring is being loaded or unloaded.
[0004] Further, a spring hysteresis is the mechanical energy loss that
always occurs under cyclic loading and unloading of a spring, proportional to the area between the loading and unloading load-deflection curves within the elastic range of a spring. When the torsion spring whose pitch is equal to the wire diameter is used, the level of inaccuracy and inconsistency is proportional to the spring hysteresis loss.

[0005] Hence there exists a need to provide a torsion spring load
adjustment mechanism which increases the accuracy of load adjustment. There also exists a need to provide a torsion spring load adjustment mechanism which reduces spring hysteresis for load adjustment in various devices.
[0006] The above mentioned shortcomings, disadvantages and problems
are addressed herein and which will be understood by reading and studying the following specification.
C) OBJECTS OF THE INVENTION
[0007] The primary object of the present invention is to provide a
torsion spring load adjustment mechanism which improves the accuracy of the load adjustment.
[0008] Another object of the present invention is to provide a torsion
spring load adjustment mechanism which reduces spring hysteresis loses.
[0009] Another object of the present invention is to provide a torsion
spring load adjustment mechanism to obtain a consistency in load adjustment irrespective of whether the spring is being loaded or unloaded.
[0010] Yet another object of the present invention is to provide a torsion
spring load adjustment mechanism with ease of adjustment with respect to a load.
[0011] Yet another object of the present invention is to provide a torsion
spring load adjustment mechanism which reduces iterations required for a load adjustment.

[0012] 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
[0013] The various embodiments of the present invention provide a spring
based load adjustment mechanism comprising a torsion spring, a part or body of mechanism on which a load of defined weight needs to be applied, a screw attached to the load taking /application part having a groove in the head to hold one of the legs of torsion spring, a bracket to hold the load taking/application part; and a pin assembled in the bracket to guide the torsion spring wherein the torsion spring is provided with a preset profile to reduce spring hysteresis during a spring deflection when the screw is rotated in at least one of clockwise direction and anticlockwise direction for load adjustment.
[0014] According to an embodiment of the present invention, the spring is
open wound torsion springs wherein one end of the torsion spring rests on the bracket and other on the groove on the head of the screw; and the open wound torsion spring includes inter turn spacing between each of its coil.
[0015] According to an embodiment of the present invention, the pitch of
the open wound torsion spring is higher than a wire diameter.
[0016] According to an embodiment of the present invention, the screw
which is connected to the load taking/application body/part or loaded body wherein the screw is moved in clockwise direction and anticlockwise direction using a metric thread tapped on the ioad taking body/part and the required load is applied on the head of the screw which is connected to a load taking body.

[0017] According to an embodiment of the present invention, the screw is
rotated in an anti-clockwise direction to decrease the spring deflection when the load is greater than the defined weight.
[0018] According to an embodiment of the present invention, the screw is
rotated in a clockwise direction to increase the spring deflection when the load is lesser than the defined weight.
[0019] According to an embodiment of the present invention, the inter
turn spacing between the spring coils reduces the inter turn friction thereby improving the consistency in a load offered irrespective of whether the spring is being loaded or unloaded.
E) BRIEF DESCRIPTION OF THE DRAWINGS:
[0020] 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:
[0021] FIG. 1 illustrates a front perspective view of the torsion spring load
adjustment mechanism according to an embodiment of the present invention.
[0022] FIG. 2 illustrates a side perspective view of the torsion spring load
adjustment mechanism according to one embodiment of the present invention.
[0023] FIG. 3 illustrates the front perspective view of a close wound
torsion spring according to an embodiment of the present invention.
[0024] FIG. 4 illustrates the front perspective view of an open wound
torsion spring according to an embodiment of the present invention.

[0025] FIG. 5 is a graph illustrating the spring hysteresis loop for a closed
wound torsion spring in accordance with an embodiment of the present invention.
[0026] FIG. 6 is a graph illustrating the spring hysteresis loop for an open
wound torsion spring in accordance with an embodiment of the present invention.
[0027] 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
[0028] 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.
[0029] The various embodiments of the present invention provide an
improved torsion spring based load adjustment system in devices such as circuit breakers. According to one embodiment of the present invention, the torsion spring based load arrangement comprises of a torsion spring, a part or body on which load of a defined weight is applied, a screw attached to the load taking/application body/part having a groove in its head to hold one of the legs of torsion spring, a bracket to hold the bad taking body/part; and a pin assembled

with the bracket to guide the spring. The torsion spring is guided over a pin which is assembled to the bracket resting one leg of the torsion spring on the bracket of the assembly and the other leg on the screw. The screw is connected over the load taking body/part and the screw can be moved in a clockwise direction and in an anticlockwise direction using a metric thread tapped on the load taking body/part. A definite load is to be adjusted on the load taking body/part which may be anything depending on the application in which such torsion spring based load adjustment system is used. The torsion spring applies the required load on the head of the screw which is connected to the load taking body/part on which load is to be applied. The load adjustment is done by rotating the screw in a clockwise direction or in an anti clockwise direction thereby moving the screw in and out of the load taking body/part. This increases or decreases the deflection of the spring and hence the load applied on the load taking body/part.
[0030] FIG. 1 illustrates a front perspective view of the torsion spring load
adjustment system according to one embodiment of the present invention. With respect to FIG. I, the torsion spring based load arrangement comprises of a torsion spring 103, a load taking/application part/ body 101 on which a load of a defined weight needs to be applied, a screw 104 attached to the load taking body/part 101, a bracket 105 to hold the load taking body/part 101; and a pin 102 which is assembled to the bracket 105 to guide the spring 103.
[0031] The torsion spring 103 is guided over the pin 102 which is
assembled to the bracket 105 resting one leg of the torsion spring 103 on the bracket 105 of the assembly and the other leg on the screw 104. The screw 104 is connected over the load taking body/part 101 and can be moved in the clockwise direction and in the anticlockwise direction using a metric thread tapped on the load taking body/part 101. A definite load is to be adjusted on the load taking body/part 101 which may be anything, depending on the application in which such torsion spring based load adjustment system is used. The torsion spring 103 applies the required load on the head of the screw 104 which is connected to the

load taking body/part 101 on which the load is to be applied. The load adjustment is done by rotating the screw 104 in the clockwise direction or in the anti clockwise direction thereby moving the screw 104 in and out of the load taking body/part 101. This increases or decreases the deflection of the spring 103 and hence the load applied on the load taking body/part 101.
[0032] To apply the required load on the particular part after the assembly
of all the components, the screw 104 is used for an adjustment. The screw 104 is rotated in the clockwise direction or in the anticlockwise direction so that the screw 104 is moved in or out of the load taking body/part lOland the load applied on load taking body 101 is checked. If the load on load taking body 101 is greater than the required value, then the screw 104 is rotated in the anticlockwise direction so that the deflection of the spring 104 is decreased and the load on the load taking body/part 101 is checked again. But if the load on the load taking body 101 is lesser than the required value, then the screw 104 is rotated in the clockwise direction so that the deflection of the spring 103 is increased and the load on load taking body 101 is checked again. This process of adjustment and the load checking is carried out until the required load is set on the particular part.
[0033] The process of load adjustment requires a loading and unloading of
the spring 103 due to which the spring hysteresis occurs and hence the accuracy and the consistency of load adjustment are reduced during such adjustment. This implies that the load 101 applied at a particular spring deflection in loading direction is different from that in unloading direction. So the process of load adjustment which requires such loading and unloading process exhibits an error in the adjustment due to spring hysteresis.
[0034] Generally, the level of inaccuracy and inconsistency is proportional
to the spring hysteresis loss. According to the embodiment herein, the torsion spring for load adjustment is provided with an open wound profile.

[0035] In the open wound torsion springs 103, the inter turn spacing i.e.
spacing between the coils is provided and hence the inter turn friction is negligible which improves the consistency in the load offered irrespective of the loading and unloading directions.
[0036] FIG. 2 illustrates the side perspective view of the torsion spring
load adjustment system according to an embodiment of the present invention. With respect to FIG. 2, the torsion spring 103 is guided by a pin 102 assembled to the bracket 105 wherein one leg of the torsion spring 103 rests on the bracket 105 and the other leg of the torsion spring 103 rests on the head of the screw 104. The screw 104 is used to apply the required load on the particular part for load adjustment. The screw 104 is rotated in the clockwise direction or in the anticlockwise direction so that the screw is moved in or out of the load taking bodypart 101 and the bracket 105 (refer arrows of FIG. 2). The load on the load taking body/part 101 is checked. If the load on the load taking body 101 is greater than a required value, then the screw 104 is rotated in the anticlockwise direction so that the deflection of the spring 103 is decreased and the load on load taking body 101 is checked again. But if the load on load taking body 101 is lesser than required value, then the screw 103 is rotated in the clockwise direction so that the deflection of the spring 103 is increased and the load on load taking body 101 is checked again. This process of adjustment and load checking is carried out until the required load is set on the particular part.
[0037] FIG. 3 illustrates the front perspective view of the close wound
torsion spring according to an embodiment of the present invention. The close wound torsion spring 103 does not include any gap between the turns of the coil. The close wound torsion spring 103 shown here is a helix shaped spring with an inter-turn coil 302 and with no gap between the inter-turn coils 302 of the torsion spring 103 and two legs 301 of the torsion spring 103. The level of inaccuracy and inconsistency in load adjustment is proportional to the spring hysteresis loss. This error in adjustment is more in case of close wound torsion spring 103 wherein the

pitch is equal to the wire diameter. There is an increase in friction between the turns of the close wound torsion spring 103 as it is loaded. But during unloading of the close wound torsion spring 103, the friction is reduced. So the load 101 offered by the close wound torsion spring 103 is different in loading and unloading directions.
[0038] FIG. 4 illustrates a front perspective view of an open wound
torsion spring according to an embodiment of the present invention. The torsion spring shown here is a helical shaped spring with inter-turn coil 402 and with gap 403 between the inter-turn coils 402 of the torsion spring 103 attached to the two legs 401. The torsion spring 103 used in the load adjustment system has a pitch greater than the wire diameter i.e. open wound design so as to reduce the spring hysteresis occurring during cyclic loading and unloading of spring while the adjustment of had on load taking body/part 101 is done which increases the accuracy of load adjustment.
[0039] FIG. 5 illustrates a graph illustrating the spring hysteresis loop for
a closed wound torsion spring in accordance with an embodiment of the present invention. Spring hysteresis is the mechanical energy loss that always occurs under cyclic loading and unloading of a spring, proportional to the area between the loading and unloading load-deflection curves within the elastic range of the spring. Spring hysteresis leads to different load of the spring at a particular deflection under cyclic loading and unloading of the spring. A variety of closed wound torsion springs with same specifications and torque were selected and experiments were carried out to simulate the phenomenon of cyclic loading and unloading which happens in any torsion spring based load adjustment system requiring increasing and decreasing the deflection of the spring for load adjustment. The torque value v/s spring deflection is plotted for slight increment in spring deflection in one direction and then for decrement in the spring deflection in the reverse direction without any time interval. The graph of the nature as illustrated in FIG.5 was obtained each time when multiple samples of

close wound torsion springs were tested and observed that the difference in load is more from the point of reversal of the loading.
[0040] FIG. 6 is a graph illustrating the spring hysteresis loop for open
wound torsion spring in accordance with an embodiment of the present invention.
Spring hysteresis is the mechanical energy loss that always occurs under cyclic
loading and unloading of a spring, proportional to the area between the loading
and unloading load-deflection curves within the elastic range of the spring. Spring
hysteresis leads to different load of the spring at a particular deflection under
cyclic loading and unloading of the spring. A variety of open wound torsion
springs with same specifications and torque were selected and experiments were
carried out to stimulate the phenomenon of cyclic loading and unloading which
happens in any torsion spring based load adjustment system requiring increasing
and decreasing the deflection of the spring for load adjustment. The torque value
v/s spring deflection is plotted for slight increment in spring deflection in one
direction and then for a decrement in spring deflection in the reverse direction
without any time interval. The results showed observed that the difference in load
is negligible irrespective of the reversal of loading as shown in FIG.6.
G) ADVANTAGES OF THE INVENTION
[0041] The various embodiments of the present invention provide an
improved torsion spring based load adjustment system in devices such as circuit breakers. The use of torsion spring in open wound form with interspacing between each coil turn leads to load adjustment system with reduced spring hysteresis losses. The embodiment disclosed herein increases improved accuracy in load adjustment, provides consistency in load adjusted irrespective of direction of loading the torsion spring. The embodiments according to the present invention further provide for easy adjustment and reduce the iterations required for load adjustment.

[0042] 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.
[0043] 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. A torsion spring based load adjustment mechanism comprising:
a torsion spring;
a load application part;
a screw attached to the load application part;
a bracket to hold the screw and the load application part; and
a pin to guide the spring to the bracket;
Wherein the torsion spring is provided with a preset profile to reduce
spring hysteresis so that the screw is rotated in a clock wise direction or in
an anticlockwise direction to control a deflection of the spring to apply a
desired load.
2. The torsion spring based load adjustment mechanism according to claim !, wherein the preset profile includes an open wound torsion spring design.
3. The torsion spring based load adjustment mechanism according to claim 2, wherein the open wound torsion spring includes inter-turn spacing between each turn of the coil.
4. The torsion spring based load adjustment mechanism according to claim 3, wherein the inter turn spacing between the spring coils reduces the inter-turn friction thereby improving a consistency in the load applied

irrespective of a loading direction and an unloading direction of the torsion spring to the bracket.
5. The torsion spring based load adjustment mechanism according to claim 1, wherein a pitch of the open wound torsion spring is higher than a wire diameter.
6. The torsion spring based load adjustment mechanism according to claim 1, wherein the screw is moved in a clockwise direction and in an anticlockwise direction using a metric thread tapped on the load.
7. The torsion spring based load adjustment mechanism according to claim 1, wherein the required load is applied on a screw head which is connected to the load.
8. The torsion spring based load adjustment mechanism according to claim 1, wherein at least one end of the torsion spring rests on the bracket.
9. The torsion spring based load adjustment mechanism according to claim 1, wherein the screw is rotated in anti-clockwise direction to decrease the spring deflection when the applied load is greater than the desired load value.

10. The torsion spring based load adjustment mechanism according to claim 1, wherein the screw is rotated in a clockwise direction to increase the spring deflection when the applied load is lesser than the desired load value.