FORM 2 THE PATENTS ACT, 1970
(39 of 1970) & The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
Fastener-Less Hatch Cover Assembly for Pylons for Carriage Of External Stores On Aircraft
2. APPLICANT(S)
(a) NAME: HINDUSTAN AERONAUTICS LIMITED b) NATIONALITY: INDIAN
(c) ADDRESS: DAA, Aircraft Upgrade Research & Design Centre, (AURDC),
HAL, NASIK
3. PREAMBLE TO THE DESCRIPTION
PROVISIONAL The following specification describes the invention.
X COMPLETE The following specification particularly describes the invention and the manner in which is to be performed.
V
4. DESCRIPTION (Description shall start from next stage.) Refer Annexure I
5. CLAIMS (Not applicable for provisional specification. Claims should start with the preamble - "I/We claim" on separate page)
Refer Annexure II
6. DATE AND SIGNATURE (to be given at the end of last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on separate page)
Refer Annexure III
Note:-
*Repeat boxes in case of more than one entry.
*To be signed by the applicant(s) or by authorized registered patent agent.
*Name of the applicant should be given in full, family name in the
beginning.
*Complete address of the applicant should be given stating the postal
index no./code, state and country.
* Strike out the column(s) which is/are not applicable.

Complete Specification of
Fastener-Less Hatch Cover Assembly for Pylons for Carriage of External Stores on
Aircraft

1 Title of the Invention
Fastener-Less Hatch Cover Assembly for Pylons for Carriage of External Stores on Aircraft Field of the Invention
2 Field of Invention
The invention relates to Mechanical Hatch cover design specifically for hatch cover on pylon used for suspension of external stores on aircraft
3 Background of the Invention
External Stores such as drop tanks, articles, pods etc. are suspended under an aircraft with the help of external pylons/adapters (referred as pylons hereafter). These pylons act as an interface between the aircraft and the external stores/pods being suspended. In order to communicate between aircraft and external stores and to meet the power requirements of stores, one or more umbilical cables or looms are passed through these pylons. Through various openings/holes the looms reach out and are connected to the stores via end connectors. The pylon openings are covered with hatch covers to prevent entrance of any foreign bodies as well as to protect the internal components from any deliberate damage in flight or when stationed at ground. Moreover, the hatch covers not being the integral part of main structure of pylon and not being secured rigidly with pylon because of its regular removal and installation nature, are subjected to large vibrations during flight. This results in loosening the fasteners/components and dismantles the assembly leading to its failure.
4 Brief Summary of the Invention
The present invention relates to a fastener-less hatch cover assembly that requires no use of securing devices and that can be opened only through an alternative access window.
In the present invention, a hatch cover assembly is designed that comprises of a main cover (1), as shown in Figure 1 , Figure 2 and Figure3 with internal spaces to accommodate for stepped lock pins (2), arrestor

pins (3) and compression springs (4). It is a fastener-less assembly. Before installation of the hatch cover on the pylon structure (5) the stepped lock pins are retracted inside the main cover and after locating the hatch cover inside the openings of the pylon, an alternative access window is used to extend out the stepped lock pins instantly under the spring force to lock the hatch cover on the pylon structure. Similarly, the alternative access window is used to dismantle the hatch cover from the pylon.
5 Detail Description of the Drawings
The accompanying drawing is included to provide further understanding of the invention, illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. In the drawing, the same components have the same reference numerals. The illustrated embodiment is intended to illustrate, but not to limit the invention.
Figure 1 and Figure 2 are an illustration of "Fastener-less and restricted access hatch cover assembly". Figure 3 is an illustration of installation of Hatch cover assembly on a structure.
6 Detail Description of the Invention
In the present invention, a single machined plate called as main cover (1) is proposed with internal spaces to accommodate for stepped lock pins (2), arrestor pins (3) and compression springs (4). The main cover (1) is an oval or rectangular shaped plate, walled at periphery for sliding it easily into the pylon structure (5). More than one through and through holes from side of main cover as well as L-shaped slots on top are provided in the main cover (1). Stepped lock pins (2), arrestor pins (3) and compression springs (4) are installed in these spaces. Once the stepped lock pins (2) are located, the arrestor pins (3) are press-fitted into holes of respective stepped lock pins (2). It is a fastener-less assembly. The compression

springs (4) are selected so that the hatch cover locks can be easily operated by hand effort, Before installation of the hatch cover on the pylon structure (5) the stepped lock pins (2) with the help of arrestor pins (3) are pulled inside by hand and rotated in such a way that the arrestor pins (3) get arrested/hooked in the L-shaped slots. After locating the hatch cover inside the openings of the pylon (5), an alternative access window is used to pull back the arrestor pins (3) from the L-shaped slots, and under the spring (4) force all the stepped lock pins (2) are pushed out instantly to lock the hatch cover on the pylon structure (5). In a similar process, the alternative access window is used to dismantle the hatch cover from the pylon.

Title : Fastener-Less Hatch Cover Assembly for Pylons for Carriage
of External Stores On Aircraft
Claims
We Claim:
1. A fastener-less hatch cover assembly used for pylons attached under aircrafts comprising of:
- main cover (1) of oval or rectangular plate with internal cavities.
- stepped lock pins (2);
- arrestor pins (3);
- compression springs (4)
the main cover (1) is walled at periphery for sliding it easily up to the pylon structured) with more than one through and through holes from side of main cover(1) with L- shaped slots on top;
Stepped lock pins (2), arrestor pins (3) and compression springs (4) are installed in the internal cavities of the main cover (1). Once the stepped lock pins (2) are located, the arrestor pins (3) are press-fitted into holes of respective stepped lock pins (2) making it a fastener-less assembly;
Before installation of the hatch cover on the pylon structure (5) the stepped lock pins (2) with the help of arrestor pins (3) are pulled inside by hand against the compression springs (4) force and rotated in such a way that the arrestor pins (3) get arrested/hooked in the L-shaped slots;
After locating the hatch cover inside the openings of the pylon (5), an alternative access window is used to pull back the arrestor pins (3) from the L-shaped slots, and under the spring (4) force all the stepped lock pins (2) are pushed out instantly to lock the hatch

cover on the pylon structure (5) , further the alternative access window is used to dismantle the hatch cover from the pylon;
- the said hatch cover assembly (1) (2) (3) and (4) prevents the possibility of loosening of fasteners and components due to vibration during flight;
- avoids requirement of additional safety devices such as, but not limited to, wire-lock, locknut, and safety pins;
2. A hatch cover according to Claim 1 wherein the said hatch cover assembly can only be removed from the pylon structure (5) through an alternative restricted access window,.