FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Screw Cap for Captive Screw Arrangement for Accessories"
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,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Screw Cap for Captive Screw Arrangement for Accessories
Field of the invention
The present invention relates to captive screw arrangement, and more particularly, to a captive screw arrangement for internal accessories of a circuit breaker.
Background of the invention
Accessories are provided for a circuit breaker for enhancing protection ability thereof. There are internal and external accessories which are provided separately with the circuit breaker. These accessories are not always meant to be factory fitted, and customer can mount the accessories as per his requirement at site. Accordingly, means of connecting the accessories with the circuit breaker should be provided such that they are easy to assemble as well as fail proof.
Generally, the interna! accessories are the ones which are mounted inside a circuit breaker by means of snap fit arrangement, screws and the like. Out of these means, screws are highly preferred because of high reliability thereof. Therefore, most of the accessories are provided with screws for mounting, in addition to snap fitting or any other locking means known in the art.
Any mounting components, such as screws for internal accessories, may pose danger if they become loose, as such loose components can get detached and fall on any live parts, and can cause severe/irreparable damage to the power system/any functional part. Secondly, in case of custom-made screws, missing of screws would lead to issues and difficulties in mounting of accessories - for instance, screws of necessary standard/specification may not be available in market. Hence, making the screws "captive" is essential for avoiding the above-mentioned problems.
Generally, captive screw arrangement is achieved by making the screw mounting hole oblong so that screw does not fall even though it is free to move. In this arrangement,

the screw should be such that the total length of the screws is the sum of total threaded length and axial free movement required for the assembly. Hence, there is twice the space requirement for a given thread length. Also, screw should have equal lengths of threaded and unthreaded length.
Accordingly, there exists a need to provide a captive screw arrangement which overcomes drawbacks of the prior art.
Objects of the invention
An object of the present invention is to address issues of mounting accessories with a circuit breaker at customer end, by providing captive screw arrangement.
Another object of the present invention is to provide such a captive screw arrangement in the form of a screw cap, which would occupy lesser space and would work for smaller screw length than conventional type.
Summary of the invention
Accordingly, the present invention provides a screw cap for providing captive arrangement for mounting screw of internal accessories of a circuit breaker. The screw cap comprises a hollow housing having a first opening at a top portion, a second opening at a bottom portion and an open side-portion. The hollow housing is capable of being secured to a wall of the internal accessory. The screw cap further includes a first member configured across an internal diameter of the hollow housing thereby forming a first ridge therein. The screw cap further comprises a second member configured above the first member across the internal diameter of the hollow housing thereby forming a second ridge therein - wherein, the screw cap covers the screw from three sides and the fourth side is covered by the wall of the internal accessory, holding the screw tight along the wall of the accessory while mounting, and the axial movement of the screw is prevented by restraining a screw head movement by the second member, thereby making the screw captive.

Brief description of the drawings
Figure 1 shows a screw cap for providing captive screw arrangement, in accordance with the present invention;
Figure 2 shows a screw cap for providing a captive screw arrangement, in another embodiment of the present invention;
Figure 3 shows an assembled view of the accessory mounted with a screw captured by the screw cap of the present invention;
Figure 4 shows exploded view of the screw cap and the accessory, in accordance with the present invention; and
Figure 5 shows mounting of the screw cap with the accessory, in an embodiment of the present invention.
Detailed description of the invention
The foregoing objects of the present 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 embodiments.
Referring now to Figure 1, there is shown a screw cap (100) for providing captive screw arrangement for internal accessories of a circuit breaker. Generally, as shown in Figure 3, the internal accessory (60) is connected to the circuit breaker with the help of a screw (50). The screw (50) would be tightened when the accessory (60) would be fitted to circuit breaker (not shown in the figures). Till then, the screw cap (100) ensures presence of the screw (50) by making it captive, in a way that does not create any difficulty in tightening the screw while fitting the accessory to circuit breaker. The screw cap (100) is connected to the accessory, preferably by press-fit arrangement.

The screw cap (100) covers the screw (50) and has sufficient space for the screw (50) to travel axially depending upon the required movement.
Referring again to figure 1, the screw cap (100) in preferred embodiment of the present invention is shown. The screw cap (100) includes a housing (10). a first member (20), a second member (30) and a third member (40).
The housing (10) is hollow rectangular housing. In an embodiment, the housing (10) may be of any other shape such oval, square and the like. The housing (10) includes a first opening (12) at top portion, a second opening (14) at bottom portion and an open side portion (16). The first opening (12) provided at the top of the housing (10) is smaller than a screw head (not numbered) but sufficient for a tool entering therein for tightening the screw (50). Further, height of the housing (10) is such that a bottom tip of the screw (50) cannot move above the bottom end thereof.
The housing (10) is capable of securing to a wall of the accessory (60) of circuit breaker. In an embodiment, the housing (10) is capable of being secured to a wall of the accessory (60) by any one of press fit and tight fit mechanisms.
The first member (20) is configured across an internal diameter of the housing (10) thereby forming a first ridge therein. The first ridge is formed in such way as to provide a lower surface (not numbered) and an upper surface (24).
Further, the second member (30) is configured above the first member (20) across the internal diameter of the housing (10) thereby forming a second ridge therein. The second ridge is formed in such a way as to provide a lower surface (32) and an upper surface (34),
Furthermore, the third member (40) is configured above the second member (30) across the internal diameter of the housing (10) such that the upper portion (not numbered) of the third member (40) faces the first opening (12) of the housing (10), wherein the third member (40) also forms a lower surface (42).

Specifically, the screw cap (100) covers the screw (50) from three sides and the fourth side is covered by the accessory (60) wall. Further, the upper surface (24) of the first member (20) and a lower surface (32) of the second member (30) prevent axial movement of the screw (50). The screw head is trapped between a lower surface (42) of the third member (40) and the upper surface (34) of the second member (30). Thus, the screw (50) is made captive from all sides, eliminating possibility of the screw getting displaced from its location and remaining loose in the accessory/circuit breaker.
The housing (10), the first member (20), the second member (30) and the third member (40) are configured as a single unit by moulding process known in the art. In another embodiment, the screw cap (100) is made of PVC grade plastic material. However, it may be evident to those skilled in the art that any other material for construction of the screw cap (100) may be used.
In an embodiment of the present invention as shown in figure 2, the screw cap (100) includes housing (10) with first member and a second member. The first member and the second member are similar to first member (10) and the second member (20) of figure \ and are not described herein again for the sake of brevity of the description. In this embodiment, the axial movement of the screw (50) is prevented by restraining a screw head movement by the second member, thereby making the screw captive.
Though the screw cap (100) described herein provides captive screw arrangement for internal accessories of the circuit breaker, it may evident to those skilled in the art that the screw cap (100) may be used for providing captive screw arrangement for screws of other devices as well.
Advantages of the invention
1. The screw cap (100) provides for captive screw requirement in lesser space and smaller screw length than conventional type.

2. The screw cap (100) addresses issue of mounting accessories with a circuit breaker at customer end.
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 persons with average skill 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 screw cap for providing captive arrangement.for mounting screw of
internal accessories of a circuit breaker, the screw cap comprising:
a hollow housing having a first opening at a top portion, a second opening at a bottom portion and an open side-portion, the hollow housing being capable of secured to a wall of the internal accessory;
a first member configured across an internal diameter of the hollow housing thereby forming a first ridge therein; and
a second member configured above the first member across the internal diameter of the hollow housing thereby forming a second ridge therein,
wherein the screw cap covers the screw from three sides and the fourth side is covered by the wall of the internal accessory, holding the screw tight along the wall of the accessory while mounting, and the axial movement of the screw is prevented by restraining a screw head movement by the second member, thereby making the screw captive.
2. The screw cap as claimed in claim 1, further comprising a third member configured above the second member across the internal diameter of the housing such that the third member communicates with an open upper portion of the housing.
3. The screw cap as claimed in claim 1, wherein the housing is capable of being secured to the wall of the accessory by any one of press fit and tight fit mechanisms.
4. The screw cap as claimed in claim 1, wherein the opening provided at the top of the housing is narrower than the screw head but wide enough to admit any screw-operating tool entering therein.
5. The screw cap as claimed in claim 1, wherein height of the housing is such that a bottom tip of the screw cannot move above the bottom end of the housing.