US3699893A

US3699893A - Ignition band and cover assembly

Info

Publication number: US3699893A
Application number: US129436A
Authority: US
Inventors: Daniel Meraz Jr; Anthony J Simshauser
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1971-03-30
Filing date: 1971-03-30
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

An ignition band and nozzle cover assembly for use on rocket motors. A cover molded from high impact strength plastic is provided with a groove around its outside diameter and recessed areas in its top. An ignition band is positioned within the groove and is provided with a contact band and shorting tab which fit into the recess on the cover top. Removal of the shorting tab unshorts the ignition band and, thus, the rocket motor. To reshorten the rocket motor, a shorting clip is provided which fits beneath the contact band and into the recess in the cover top. The cover assembly protects against dust and/or moisture entering the inside of the rocket motor and acts as a high impact protection for the aft end of the motor by absorbing impact. The ignition and contact bands are also shielded from damage by being positioned within recesses in the cover assembly.

Description

United States Patent Meraz, Jr. et al.

[ Oct. 24, 1972 1 IGNITION BAND AND COVER ASSEMBLY [72] Inventors: Daniel Meraz, Jr.; Anthony J. Simshauser, both of China Lake, Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: March 30, 1971 [21] App1.No.: 129,436

[52] US. Cl. ..102/70.2, 102/49.7, 89/1.814 [51] Int. Cl. ..F42c 19/06 [58] Field of Search ..89/1.807, 1.813, 1.814; 102/49.7, 70.2 A; 60/256, 39.82 E

[56] References Cited UNITED STATES PATENTS 2,645,999 7/1953 Bogard ..89/1.814 2,828,692 4/1958 Webster ..102/70.2 A 3,039,363 6/1962 Grillo etai ..89/1.814 3,194,119 7/1965 Robert et al. ..102/49.7 X

FOREIGN PATENTS OR APPLICATIONS 996,829 6/1965 Great Britain ..89/1 .807

Primary Examiner-Merlin R. Pendegrass Attorney-11. S. Sciascia and Thomas 0. Watson, Jr.

[57] ABSTRACT An ignition band and nozzle cover assembly for use on rocket motors. A cover molded from high impact strength plastic is provided with a groove around its outside diameter and recessed areas in its top. An ignition band is positioned within the groove and is provided with a contact band and shorting tab which fit into the recess on the cover top. Removal of the shorting tab unshorts the ignition band and, thus, the rocket motor. To reshorten the rocket motor, a shorting clip is provided which fits beneath the contact band and into the recess in the cover top. The cover assembly protects against dust and/or moisture entering the inside of the rocket motor and acts as a high impact protection for the aft end of the motor by absorbing impact. The ignition and contact bands are also shielded from damage by being positioned within recesses in the cover assembly.

10 Claims, 9 Drawing Figures PATENTEU 0m 24 1972 SHEET 1 0F 3 INVENTORS DAN/EL MERAZ,JR ANTHONY .1 smsmusm ATTORNEY IGNITION BAND AND COVER ASSEMBLY STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates generally to rocket motors and more particularly to an ignition band and cover assembly for such motors.

Those concerned with the storage and handling of rocket assemblies, have found it advantageous to provide such assemblies with dust and moisture protecting rear closures. Generally, these closures were snapped into position on the aft end of the rocket motor. They have proven acceptable but, their performance in several areas has not proven totally satisfactorily. For example, when the rocket assembly is dropped during handling, the prior art closures have had a tendency to either come off or be damaged. Additionally, they provided little or no protection to the rocket assembly itself.

Typically, the prior art closures were provided with a V groove in which a shorting band is wrapped. In one form, this shorting band has a wide end with a series of slits and a narrower end which is weaved in and out of the slits. The shorting band is exposed and is easily damaged during handling. Also, these prior art closures and shorting band assemblies were difficult to assemble and have a high cost relative to the present invention.

The nozzle cover of the present invention protects the ignition-contact band assembly from damage during handling. In addition, a more certain dust and moisture seal is provided because of the nature of assembly with the rocket motor. Also, the nozzle cover of the present invention acts as a high impact protection cover for the nozzle assembly by absorbing the impact on it during handling.

OBJECTS OF THE INVENTION An object of the present invention is the provision of a rear closure for a rocket motor having a reliable dust and moisture protection capability.

Another object is to provide a rear closure for a rocket motor which is capable of providing a high impact protection for the nozzle assembly.

A further object of the invention is the provision of a rear closure for a rocket motor which has the capability of protecting the ignition band assembly during handling and storage.

A still further object of the present invention is the provision of an ignition band and cover assembly which is simple to assemble.

Still another object of the present invention is the provision of an ignition band and cover assembly which has a low cost relative to prior art devices.

Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a rocket motor assembly employing a preferred embodiment of the present invention.

FIG. 2 shows a cross-section of a preferred embodiment of the present invention.

FIG. 3 shows a top view of a preferred embodiment of the present invention.

FIG. 4 shows a shorting clip used in the preferred embodiment of FIG. 3.

FIG. 5 shows the preferred embodiment of FIG. 3 with the shorting tab removed.

FIG. 6 shows a top view of a second preferred embodiment of the present invention.

FIG. 7 shows a bottom view of the preferred embodiment of FIG. 6.

FIG. 8 shows a third preferred embodiment of the present invention.

FIG. 9 shows the bottom view of the preferred embodiment of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1, which illustrates a rocket motor assembly employing a preferred embodiment of the present invention, shows a motor tube 10 having a propellant grain 11 disposed therein. On the aft end of the motor tube 10 is disposed the ignition band and cover assembly 13 of the present invention. This assembly is connected by lead wires 14 through the motor tube 10 to an ignitor 15. The ignitor 15 is held in place on the motor tube 10 by a pressurization ring 16 and a support ring 17.

Referring now to FIG. 2, there is shown a cross-section of a preferred embodiment of the cover assembly 13 of the present invention. The body of the cover assembly 20 is generally cupped shaped and has an inwardly extending central portion 21. The outer wall is provided with a recessed area in its outer surface in which is located an ignition band 24. This band 24 completely surrounds the cover assembly 20. A plurality of slots 25 are placed in the wall to facilitate the positioning of cover assembly over the aft end of the rocket motor.

Extending into the cup portion of the cover assembly 20, is a circular projection 27. This projection 27 is concentric with both the outer cover assembly wall, and the extending central portion 21. The projection 27 is the means by which the cover assembly 20 is held in position on the rocket motor. The surface shown at 28 is an interference fit with the structure of the rocket nozzle, and both the surfaces shown at 28 and 29 are coated with an adhesive sealant prior to assembly, to better hold the cover assembly 20 in position. A contact band 30 is shown recessed within the top surface of the cover assembly and extending over the central bore 31. The function of the contact band 30 and central bore 31 is explained in detail below.

FIG. 3 shows a top view of a preferred embodiment of the present invention. Here, there is shown the body of the cover assembly 20 with the ignition band 24 extending around its circumference. The integral contact band 30 is shown extending from the ignition band 24 and lying within a recess (see FIG. 2) in the top of the cover assembly. Two

rivets

33 and 34 are used to attach the contact band 30 to the top of the cover assembly. At a location between the two

rivets

33 and 34, the contact band 30 is connected to a shorting tab 36 which lies within a recess 35 in the top of the cover assembly. This shorting tab 36 may be integral with the contact band or connected to it by any suitable means such as welding. Also, the contact band may be weakened at one or more locations to assure that it will separate in the desired locations. In any of these configurations, removal of the shorting tab 36 causes a break in the contact band 30 (see FIG. 5).

A second recess 38 is provided in the top of the cover assembly which has two extending portions spanning the portion of the contact band which contains the

rivets

33 and 34. This recess 38 is designed to accept a shorting clip 39 (see FIG. 4) whose function is to reshorten the rocket motor once the shorting tab 36 has been removed. As shown in FIG. 5, the shorting clip 39 fits beneath the contact band 30 and lies flat within the recess 38. The shorting clip 39 is made of a low carbon steel. A third recess is shown at the center of the cover assembly 20 over which the contact band 30 extends. This recess leads to the central bore 31 (see FIG. 2) which is designed to accept a grounding screw 40 which extends through the contact band 30 and bore 31 to make electrical contact with the nozzle of the rocket motor.

To assemble the ignition band and cover assembly, the shorting tab 36 is first fixed in position on the contact band 30 at the location shown in FIG. 3. Next, the ignition band 24 is slipped over the cover 20 with the ignition band 24 fitting into the outside diameter groove in the nozzle cover (see FIG. 2). The integral contact band assembly 30 is next bent into the groove in the top of the cover assembly 20 with the shorting tab 36 fitting into the recessed area (see FIG. 3). Two

rivets

33 and 34 are used to secure the contact band 30 to the cover assembly 20 with one rivet being placed on each side of the shorting tab 36. An electrical lead 14 (see FIG. 1) extends from each of these rivets through the rocket motor to the ignitor. An adhesive sealant is then applied to the surfaces 28 and 29 (see FIG. 2) and the assembly is placed on the rocket nozzle with the lead wires extending through the rocket motor. The rivet 34 is considered the live contact and the other rivet 33 is considered the ground contact. A grounding screw extending through the central bore 31 connects the contact band 30 to the motor nozzle plate assembly.

With the grounding screw 40 in position, the motor is shortened and thus, inoperable. To make the motor live and ready to fire, the ignition band 24 must be unshorted. This is accomplished by removing the shorting tab 36 which breaks the connection to the ground screw 40. By pulling the shorting tab 36 the narrow strip between the two

rivets

33 and 34 is removed (see FIG. 5). To reshorten the motor, the shorting clip 39 is inserted in the grooves underneath the contact band 30.

The advantages of the present invention are the ease of unshorting the rocket motor for use and the speed with which it can be reshorted by the use of an inexpensive shorting clip. In addition, the invention acts as a dust and moisture cover and provides a high impact protection for the contact band and nozzle assembly.

There is no pre-ignition problem as the cover assembly is able to withstand all the standard drop tests from various heights and attitudes.

The nozzle cover 20 is made of a new plastic material which is a very high strength impact ABS (acrylonitrilebutadiene-styrene) injection molded plastic. The use of this material eliminates the cost of applying protective painting to a major metal part. Also, the material is much lighter than other potential materials for this application.

The new ABS plastic can be electroplated. By electroplating with copper, nickel, or chrominom in thicknesses of 10 to 40 millionths of an inch, parts or all of the contact band assembly can be eliminated. This method pre-etches the ABS plastic part and deposits a conductive coating on its surface. A plated ABS plastic has a strong chemical bond or high adhesion of metal to plastic. It is galvanic corrosion resistant because the plastic is non-conductive and there is no galvanic action between the metal plate-plastic subtrate. This is a decided advantage on applications where a corrosive environment, such as salt spray, has previously necessitated the use of brass, stainless steel, or other expensive metals.

A second embodiment of the present invention is shown in FIG. 6 and 7. Here an outside contact band 46 is shown as being connected to the top of the cover assembly by two rivets 41 and 42. Two other rivets 43 and 44 are located on either side of the contact band 46. As shown in FIG. 7, the rivets 43 and 44 are connected to the hole for the grounding screw 48 by an inside contact band 50. An RF filter is directly connected to the inside contact band 50 and to the rivet 42 by the electrical lead 55.

A shorting pin 45 is inserted through the hole 47 to make contact with both the inside contact band 50 and the outside contact band 46 thus shorting the rocket motor in a manner similar to that of the first embodiment. By removing the shorting pin 45, the motor is then in open firing position. The rocket motor is reshorted by inserting the pin 45 back in the hole 47.

FIGS. 8 and 9 show a modification of the embodiment of FIGS. 3 and 5. As shown in FIG. 8, an added shorting strip 58 extends from a rivet 50 to the center of the cover where it is in electrical contact with the contact band 30 and ground screw 40. This shorting strip 58 allows for the motor to be checked for continuity in the ignition circuit. FIG. 9 shows the lead wires of a shield penetration filter (RF filter) 59 connected to the

contacts

34 and 60 for the lead wires of the ignition system. The shield penetration filter (RF filter) will take 500 volts which means it would have to take over 500 volts to set off the ignition system by accident. Resistance of the RF attenuated squib can be measured through the shield penetration filter. The shield penetration filter is mounted in a cavity as shown in FIG. 9 for support against vibration.

Obviously many modifications and variatlons of the present invention are possible in the light of the above teachings.

What is claimed is:

1. An ignition band and cover assembly for the aft end of the rocket motor which comprises:

a cup shaped member having a circumferential groove around the outer surface of its side;

an ignition band within said groove;

a contact band formed at least in part by a first band extending along the top side of said cup shaped member, said contact band being electrically connected to said ignition band; and

means for breaking the electrically continuity of said contact band.

2. The assembly of claim 1 further comprising a recess along the top of the cup shaped member, the contact band lying at least partially within the recess.

3. The assembly of claim 2 wherein the breaking means is in the form of a metal tab mounted on the contact band such that removal of the tab causes a part of the contact band to be removed also.

4. The assembly of claim 3 further comprising a second recess on the top of the cover assembly, the metal tab lying within the second recess.

5. The assembly of claim 4 further comprising a third recess in the top of the cover assembly, the third recess having portions extending under the contact band at each side of the metal tab.

6. The assembly of claim 5 further including a metal clip which is generally U-shaped and having dimensions which conform to the third recess, the metal clip having a configuration such that positioning of the clip within the third recess provides an electrical connection from one portion of the contact band to another through the metal clip.

7. The assembly in claim 6 wherein the sides of the cup shaped member are slotted.

8. The assembly of claim 7 wherein the cup shaped member is made from acrylonitrile-butadiene-styrene plastic.

9. The assembly of claim 1 wherein the contact band further comprises the second band through which an RF filter is incorporated into the electrical circuitry formed in part by the contact band and the ignition band.

10. The assembly of claim 9 wherein the second band lies on the underside of the cup shaped member.

Claims

1. An ignition band and cover assembly for the aft end of the rocket motor which comprises: a cup shaped member having a circumferential groove around the outer surface of its side; an ignition band within said groove; a contact band formed at least in part by a first band extending along the top side of said cup shaped member, said contact band being electrically connected to said ignition band; and means for breaking the electrically continuity of said contact band.