Ammunition and explosives – Igniting devices and systems – Arming devices
Reexamination Certificate
2000-02-22
2001-11-06
Poon, Peter M. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Arming devices
Reexamination Certificate
active
06311622
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of munitions, and more particularly to an improved design for a secondary self-destruct fuze that functions in the event the primary fuze mode fails to function, and that meets the design requirements for a low cost, highly producible no-spin/low velocity operating environment.
BACKGROUND OF THE INVENTION
Dual Purpose Improved Conventional Munitions (DPICM) must have either a self-destruct capability or they must show dud rates not to exceed 1 in 500 as an operational requirement. Conventional designs proposed the development of a hybrid electromechanical fuze which is relatively complex with approximately 40 to 50 parts, with a costly production line. In addition, the no-spin/low velocity operational environments of grenades jeopardize the fuze reliability. Several projectiles have unique operational requirements that the current fuze design might not meet readily.
Some of the concerns facing current self-destruct fuze designs are listed below:
(1) The threads between the arming screw and the weight can be overtorqued.
(2) The fuze components may suffer collateral damage during ejection from the carrier.
(3) The fuze may impact the ground at oblique angles and the firing pin might not provide sufficient energy to the detonator.
(4) The fuze may operate poorly in a no-spin/low velocity environment.
Therefore, there is a still unsatisfied need for a fuze which, among other features, solves the no-spin/low velocity environment, significantly reduces the number of components, improves productivity, and increases the operational reliability of the primary arming mode.
Several engineering studies were conducted in the past two decades in an attempt to address the low reliability of existing mechanical fuzes. Although these ‘mechanical only’ solutions did improve the overall functional reliability of the fuze, there is still room for an improved design that fully addresses the no-spin/low velocity operational environment, and that significantly reduces the dud rate to the present ordnance requirements for self destruct fuzing of grenades.
A design that proposes a secondary self-destruct electrical mode of operation is described in U.S. Pat. No. 5,387,257. While the patented fuze provides an improvement in the relevant field, the activation of this self-destruct mode requires forces that are not available from no-spin/low velocity environment.
SUMMARY OF THE INVENTION
The present invention contemplates an improved design for a secondary self-destruct fuze that functions in the event the primary fuze mode fails to function, and that meets the design requirements for a low cost, highly producible no-spin/low velocity operating environment.
The fuze offers several features and advantages, among which are the following:
(1) It significantly simplifies conventional designs and the production process.
(2) It solves the functional reliability problems when operating in a no-spin/low spin environment.
(3) It uses a unique low cost mechanical/pyrotechnic design to provide a high functional reliability, in almost all operating environments.
(4) Its components and assemblies are made of readily available materials and are fabricated from stampings, die casting and precision molds.
(5) It meets all MIL-STD-1316D standards.
(6) It is compatible with almost all grenade configurations.
(7) It provides a self destruct delay of between 30-45 seconds.
(8) Its threads can be removed from a firing pin/weight and replaced by a one-piece threadless firing pin.
(9) It includes a mild firing pin spring, a heavier firing pin/weight, and a rotor lock out arming tab that mitigate the problem of grenade impact at oblique angles onto the ground.
The foregoing and other features and advantages of the present invention are realized by a fuze that includes the following components: a bottom plate, two spacers, a firing pin, a striker, a rotor, a pyrotechnic mix, a rotor spring, a striker spring, a weight with a firing pin, a weight spring, a bore rider, a bore rider spring, a housing, a handling safety pin, and a ribbon retainer. As it can be appreciated, the present fuze includes a minimal number of components.
In use, the handling safety pin is removed upon loading of the grenade in the main carrier. When the grenade is ejected in the air, the expulsion event forces the ribbon retainer to be uncovered and the ribbon to unfurl, which releases the safety lock feature. The unfurling of the ribbon in the air stream stabilizes the grenade by causing an upward pull force. Simultaneously, the air stream forces the bore rider, as well as the bore rider spring out of the fuze.
In addition, the upward pull force caused by the unfurling of the ribbon translates down to the weight firing pin and causes the latter to move up and away from the rotor. Both the rotor and the striker are free to move under the action of their respective springs. The burning of the pyrotechnic mix is initiated by the striker firing pin hitting the match tip (miniature detonator) at the open end of the channel in the rotor. After a delay of approximately 30-45 seconds, the main detonator (i.e., M55 detonator) is functioned. In the meantime, the rotor, together with the striker, have moved into their respective in-line positions. Upon impact, the firing pin of the weight is forced into the detonator, thereby igniting the lead charge of the grenade. This is the primary mode of operation. The secondary/self-destruct mode is the initiation of the main detonator by the burning of the pyrotechnic mix.
If, for any reason, the primary mode fails to function the grenade, the grenade is rendered safe to handle by the secondary/self destruct mode which sterilizes the main detonator.
REFERENCES:
patent: 3610154 (1971-10-01), Brown
patent: 3633510 (1972-01-01), Bernardin
patent: 3636880 (1972-01-01), Aske
patent: 3707912 (1973-01-01), Duncan et al.
patent: 3742854 (1973-07-01), Donahue et al.
patent: 4765245 (1988-08-01), Berube et al.
patent: 5387257 (1995-02-01), Tari et al.
patent: 5932834 (1999-08-01), Lyone et al.
patent: 6082267 (2000-07-01), Cooper
patent: 6237495 (2001-05-01), Hok et al.
Adimari Louis J.
Ball Marc E.
Cooper Edward F.
Donini Joseph A.
Fulton Keith R.
Lofdahl J
Moran John F.
Poon Peter M.
Sachs Michael C.
The United States of America as represented by the Secretary of
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