FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Mechanism for Spring Guiding"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: Larsen & Toubro Limited
Electrical & Automation North Wing, Gate 7, Level 0, Powai Campus, Saki Vihar Road, Mumbai 400 072, INDIA
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Mechanism for Spring Guiding
Field of invention
The present invention relates to devices using springs, and more particularly, to a compression spring based mechanisms used in low voltage switch gear.
Background of the invention
In devices using compression springs, a spring guide is usually required to maintain a position of the spring. The function of the spring guide is to ensure location of the spring and to allow its smooth compression. The spring should in no way interfere with the guide.
US Patent No. 7294804 B1 talks about a ram assembly having a spring driven ram body as shown in figure 1. There is an energy dissipating spring seat provided. There is a guide assembly that includes a base plate and a stop plate. The ram assembly spring is placed between a ram body and the base plate and biases the ram body towards the stop plate. There is also a spring seat present between the ram assembly springs and the base plate intended to dissipate the energy released when the ram body impacts the stop plate. The disadvantage with such a construction is that only one end is pivoted on a pin whereas the other rests in a slot in the base plate. This makes the arrangement suitable only for applications where the spring assembly motion is limited.
Further, US Patent No. 3872269 talks about an electric switch with a lever that moves to open and close a switch with a rocking and sliding movement as shown in figure 2. There is a slot in the cover plate over which the slide moves when in operation. The spring is compressed in the lever and rocks the lever about a rotational axis of rollers.

This results in a combined rocking and sliding movement of the lever. The disadvantage with such an arrangement is that the lever encloses the spring making the design bulky. Also at the dead centre the lever projects out over that transverse pin for which additional space must be created.
Furthermore, a US Patent Application 2002/0092752 talks about a drive mechanism for a circuit breaker. The energy storage sub-assembly consists of a drive lever pivotally mounted around a fixed spindle. There is an energy storing spring inserted in a telescopic guiding arrangement. This arrangement consists of a guide that is pivotally mounted on a fixed spindle and a slide rack sliding with respect to the guide and pivoting with respect to a pin securely united to the drive lever. The problem with such an arrangement is that it cannot be used for smaller switches where space is a constraint. The guide and slide rack are expensive to manufacture and the cost is not justified for a smaller compact switch. The spring load is borne by the spring guide and the slide rack which may cause problems in a switch of smaller dimensions.
Conventionally, the compression spring uses a slider and slot arrangement. The spring guide (1) slides through a slot in the fixed spring rest (4) while the spring (3) is being compressed as shown in figure 4. One end of the spring rests on the fixed spring rest while the other rests on the arms provided on the spring guide itself. Thus the spring guide is allowed relief while the spring is compressed. The problem with such an arrangement is that the spring guide protrudes out of the spring rest as is shown in Figure 6. This results in unnecessary wastage of space and sometimes injury to the operator. Also the spring load is borne by the spring guide which is not the basic function of the guide and may be sometimes undesirable.
Accordingly, there is exists a need to provide a mechanism for spring guiding system, which overcomes the drawbacks of the prior art.

Object of the invention
An object of the invention is to provide a mechanism for spring guiding system which allows the compression of the spring without increasing the overall dimensions of the linkage.
Another object of the present invention is to provide a mechanism for spring guiding system which is less expensive to manufacture and suitable for smaller switches.
Summary of the invention
Accordingly, the present invention provides a mechanism for spring guiding in a circuit breaker, the mechanism comprising
a first end pin fixed to an housing;
a second end pin fixed to a moving link;
a slider pivoted on the first end pin, wherein the slider is capable of being rotated freely on the first end pin;
a slider guide having a slot configured therein, the slider guide pivoted on the second end pin, wherein the slider guide is capable of being rotated freely on the second end pin; and
a spring resting between the first end pin and the second end pin;
wherein the slider slides into the slot of the slider guide while the spring is being compressed and out of the slot when the spring expands, and wherein the first end pin and second end pin bears load of the spring.
Brief description of drawings
Figure 1 - 6 shows mechanism for spring guiding system the prior art;

Figure 7 shows a schematic drawing of a mechanism for compression spring guiding system in initial position, in accordance with the present invention;
Figure 8 shows a schematic drawing of a mechanism for compression spring guiding system in intermediate position, in accordance with the present invention;
Figure 9 shows a schematic drawing of a mechanism for compression spring guiding system in final position, in accordance with the present invention;
Figure 10 shows an assembly of the for compression spring guiding system without compression spring, in accordance with the present invention;
Figure 11 shows an assembly of the for compression spring guiding system with compression spring, in accordance with the present invention;
Figure 12 shows an exploded view of the mechanism for compression spring guiding system, in accordance with the present invention;
Figure 13 shows a mechanism for compression spring guiding system, when the compression spring is fully expanded;
Figure 14 shows a mechanism for compression spring guiding system, when the spring is fully compressed;
Figure 15 shows a slider of the mechanism for compression spring guiding system, in accordance with the present invention; and

Detailed description of the present invention
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with the prior art techniques and approaches are overcome by the present invention as described below in the preferred embodiment.
Accordingly, the present invention provides a mechanism for spring guiding system which allows the compression of the spring without increasing the overall dimensions of the linkage. The mechanism for spring guiding system is less expensive to manufacture and suitable for smaller switches.
Referring now to figure 7-15, there is shown a mechanism (100) and various components thereof for spring guiding in a circuit breaker, in accordance with the present invention. The mechanism (100) includes a first end pin (10), a second end pin (20), a slider (30), a slider guide (40) and a spring (50).
The first end pin (10) is fixed to an housing (not shown). In an embodiment, the first end pin (10) is fixed to any rigid body of the system wherein the compression spring is being used. Further, the second end pin (20) is fixed to a moving link (not shown).
The slider (30) is pivoted on the first end pin (10). The slider (30) is capable of being rotated freely on the first end pin (10). Further, the slider guide (40) includes at least one slot (42) configured therein. The slider guide (40) is pivoted on the second end pin (20). The slider guide (40) is capable of being rotated freely on the second end pin (40).
The spring (50) rests between the first end pin (10) and the second end pin(20). Specifically, the slider (30) slides into the slot (42) of the slider guide (40) while the

spring (50) is being compressed and out of the slot when the spring expands. The first end pin (10) and second end pin (20) bears load of the spring (50).
During the operation, the spring (50) may initially be in its fully expanded state as shown in figure 7. Further, figure 8 shows the aforesaid arrangement position when the spring (50) is fully compressed. It is from the former state to the latter that the aforesaid arrangement performs its function. The slider (30) (shown in figure 15) slides into the slot (42) provided in the slider guide (40) (shown in figure). As shown in figures 13 and 14, the slider (30) slides into the slot (42) while the spring (50) is being compressed and out of the slot (42) when the spring (50) expands.
In an embodiment, the slot (42) may be lubricated by means of a lubricant such as grease to reduce wear and friction. There is no change in overall dimension of the arrangement except for the compression of the spring, i.e., the entire arrangement remains perfectly contained between the two end pins (10, 20) and the is no protrusion of the spring guide from either end. In fact, in order to eliminate this protrusion, the overlap takes place within the dimensional length of the spring (50). The function of a guide and locator to the spring is performed by both the slider (30) and the slider guide (40). Neither the slider (30) nor the slider guide (40) are subject to the spring load, in theory.
Advantages of the invention
1. The mechanism (100) uses a novel dual spring guide concept wherein one of the slider guide slides over the other. This results in higher compactness of the system.
2. As the overlap is contained within the dimensions of the spring, chances of injury to the operator are eliminated.
3. In the mechanism (100), the entire spring load is borne by the end pins (10, 20) and spring guide (40) performs only the function of guiding.

4. The spring (50) rests on the end pins (10, 20) with a line contact between them. This creates an instability at the dead centre position that aids in toggling of the arrangement.
5. The components of the mechanism (100) are designed in such a way that they are easy to manufacture from sheet metal which is good for cheap and high quantity production.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We claim
1. A mechanism for spring guiding in a circuit breaker, the mechanism comprising
a first end pin fixed to an housing;
a second end pin fixed to a moving link;
a slider pivoted on the first end pin, wherein the slider is capable of being rotated freely on the first end pin;
a slider guide having a slot configured therein, the slider guide pivoted on the second end pin, wherein the slider guide is capable of being rotated freely on the second end pin; and
a spring resting between the first end pin and the second end pin; wherein the slider slides into the slot of the slider guide while the spring is being compressed and out of the slot when the spring expands, and wherein the first end pin and second end pin bears load of the spring.
2. The mechanism as claimed in claim 1, wherein the slot is lubricated by a lubricant to reduce wear and friction.