US3853056A

US3853056A - Safety and arming device

Info

Publication number: US3853056A
Application number: US00334668A
Authority: US
Inventors: L Fisher
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1963-12-30
Filing date: 1963-12-30
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10

Abstract

1. A safety and arming device for underwater ordnance items comprising A HOUSING, A DETONATOR MOUNTED ON SAID HOUSING. A BOOSTER MOUNTED ON SAID HOUSING IN AXIAL ALIGNMENT WITH SAID DETONATOR, A SHUTTER MOVABLY MOUNTED ON SAID HOUSING BETWEEN SAID DETONATOR AND SAID BOOSTER, A TRANSMISSION CHARGE CARRIED BY SAID SHUTTER AND OPERABLE TO COMPLETE AN EXPLOSIVE TRAIN WHEN AXIALLY ALIGNED WITH SAID DETONATOR AND SAID BOOSTER. RESILIENT MEANS NORMALLY URGING SAID SHUTTER AND SAID TRANSMISSION CHARGE OUT OF AXIAL ALIGNMENT WITH SAID DETONATOR AND SAID BOOSTER WHEREBY THE EXPLOSIVE TRAIN IS INTERRUPTED AND THE ORDNANCE ITEM IS DISARMED, AND A FLOAT HAVING A SPECIFIC GRAVITY LESS THAN ONE POSITIONED WITHIN A CAVITY IN SAID HOUSING IN FLUID COMMUNICATION WITH THE WATER WHEN THE HOUSING IS IMMERSED THEREIN AND DIRECTLY CONNECTED TO SAID SHUTTER WHEREBY, UPON IMMERSION OF THE ORDANCE ITEM IN WATER, SAID SHUTTER IS MOVED BY SAID FLOAT AGAINST THE URGING OF SAID RESIIENT MEANS TO AXIALLY ALIGN SAID TRANSMISSION CHARGE WITH SAID DETONATOR AND SAID BOOSTER TO COMPLETE THE EXPLOSIVE TRAIN AND ARM THE ORDNANCE ITEM.

Description

United States Patent [191 Fisher Dec. 10, 1974 SAFETY AND ARMING DEVICE [7S] lnventor: Lyman C. Fisher, Silver Spring, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Dec. 30, 1963 [21) Appl. No.: 334,668

[52] US. Cl. 102/16 [51] Int. Cl. F42b 22/26 [58] Field of Search 102/7, 10, 13, 16

[56] References Cited UNITED STATES PATENTS 1,473,148 11/1923 Hammond, Jr. 102/7 2,960,030 11/1960 Semon 102/16 Primary Examiner--Verlin R. Pendegrass Attorney, Agent, or Firm-Q. B. Warner [57] ABSTRACT I. A safety and arming device for underwater ordnance items comprising a housing,

a detonator mounted on said housing.

a booster mounted on said housing in axial alignment with said detonator,

a shutter movably mounted on said housing between said detonator and said booster,

a transmission charge carried by said shutter and operable to complete an explosive train when axially aligned with said detonator and said booster.

resilient means normally urging said shutter and said transmission charge out of axial alignment with said detonator and said booster whereby the explosive train is interrupted and the ordnance item is disarmed, and

a float having a specific gravity less than one positioned within a cavity in said housing in fluid communication with the water when the housing is immersed therein and directly connected to said shutter whereby, upon immersion of the ordance item in water, said shutter is moved by said float against the urging of said resiient means to axially align said transmission charge with said detonator and said booster to complete the explosive train and arm the ordnance item.

l0 Claims, 5 Drawing Figures PATENIEU BE: 1 0 m4 NEH IN 2 FIG. I yman C. Fisher INVENTOR. JAMQ 4/1),

ATTORNEY PATENTED 3.853.056

SHEH 2 OF 2 FIG. 3

E FIG. 4 :l L FIG. 5 11"46 Lyman C. Fisher INVENTOR.

aid 0 mm) ATTORNEY SAFETY AND ARMING DEVICE 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.

This invention relates to safety and arming devices for underwater ordnance items, and more particularly to safety and arming devices for shallow water mines which operate independently of the ambient hydrostatic pressure.

ln the past, safety and arming devices for mines have normally used hydrostatic pressure to provide environmental safety, i.e., the mine had to be in the water and deep enough for hydrostatic pressure to move an explosive train into alignment or operate electrical safing and arming switches. In these prior art devices, hydrostatic pressure is normally opposed by a spring and whatever ambient pressure exists inside the sealed mine case. This internal pressure varies, depending on the atmospheric conditions of temperature and pressure existing when the case was sealed, relative to the condition of the air in the mine case at the time arming occurred. This variation is large enough so that production devices which will not arm in air, an unsafe condition, have been found to require submergence in as much as R8 to feet of water to insure arming. Designers have employed evacuated bellows in an endeavor to overcome this difficulty but again, in production, such devices have been found to require at least 12 feet submergence for reliable operation despite great care in design and manufacture.

The disadvantages and shortcomings of the prior art devices are apparent from the above discussion. The prior art devices will not provide safety and arming for tethered or free floating mines, or for moored or bottom mines in depths less than l2 to l8 feet. Yet there are many rivers and canals which could be mined which are not this deep. For these reasons. designers have long sought a device which would sense that a mine was really in water, not just wet by rain or spray to provide environmental safety in very shallow bottom mines and in tethered or free floating mines.

It is therefore a primary object of the present invention to provide new and improved safety and arming devices for underwater ordnance items which are independent of hydrostatic pressure.

It is another object of this invention to provide safety and arming devices for underwater ordnance items which will sense the immersion of the ordnance items in water as distinguished from the wetting of the ordnance items by spray or rain.

It is a further object of this invention to provide safety and arming devices for underwater ordnance items, the operation of which is independent of the orientation of the ordnance items.

It is yet another object of this invention to provide safety and arming devices for underwater ordnance items incorporating features which preclude arming of the ordnance items in air.

It is a still further object of this invention to provide safety and arming devices for underwater ordnance items which are readily adaptable for use in bottom, tethered, and free floating mines.

With these and other objects in view, the present invention contemplates safety and arming devices for underwater ordnance items which comprise an explosive detonator and an explosive booster charge mounted in axial alignment on a housing which may be attached to or formed in the casing of an underwater ordnance item. The detonator is intended for connection to the firing mechanism of the ordnance item and the booster charge is adapted to trigger the main charge of the ordnance item. The detonator and booster are spaced apart and a shutter carrying an explosive transmission charge is interposed therebetween. The shutter provides the principal safety feature of the invention by precluding ignition of the booster by operation of the detonator unless the shutter is so positioned that the transmission charge carried by the shutter is axially aligned with the detonator and booster to complete the explosive train. Resilient means are connected to the shutter and normally bias the shutter to a safe position wherein the transmission charge is out of axial alignment with the detonator and booster. A float having a specific gravity less than one is connected to the shutter and, upon immersion of the ordnance item in water, moves the shutter in opposition to the resilient means to an armed position wherein the transmission charge is axially aligned with the detonator and booster and the explosive train is completed. An arming wire, which is withdrawn just before the ordnance item is laid, is connected to the shutter and holds the shutter in the unarmed position prior to withdrawal thereof to preclude inadvertent arming of the ordnance item in air. A soluble washer is also connected to the shutter for holding the shutter in a safe position until the washer dissolves after immersion of the ordnance item. This feature permits the laying vessel time to leave the immediate vicinity of the ordnance item before the item is fully armed.

Other objects, advantages and novel features of the present invention will become readily apparent upon consideration of the following detailed description when read in conjuction with the accompanying drawings wherein:

FIG. 1 is a sectional view illustrating one embodiment of the present invention; and

FIGS. 2-5 illustrate other embodiments of the present invention and differ from FIG. 1 principally in the specific arrangements utilized for connecting the float to the shutter.

Attention now is directed to the drawings wherein like numerals of reference designate like parts throughout the several views, and more particularly to FIG. 1 wherein one embodiment of the safety and arming device of the present invention is illustrated and is designated generally by the reference numeral 10. The device 10 comprises a housing 11 adapted to be secured to a casing 12 of a mine or other underwater ordnance item by means of screws 14. A closure member 15 is secured to one end of the housing H by screws 16 and forms a part of the housing. An explosive detonator l8 and an explosive booster charge 19 are disposed in appropriately sized recesses in the member 15 in positions of axial alignment. The detonator I8 is provided with leads 20 which are provided for connecting the detonator to the firing mechanism (not shown) of the ordnance item. Booster charge 19 is adapted to initiate the main charge (not shown) of the ordnance item upon detonation thereof.

A shutter 21 is slidably disposed within a recess 22 formed in the member 15 and carries a transmission charge 24 in an appropriate recess therein. A second transmission charge 25 is positioned adjacent the booster 19 and is utilized merely for convenience in sealing. The second transmission charge 25 may be eliminated by relocation of the booster 19 adjacent the transmission charge 24 and the shutter 21. The detonator 18, transmission charges 24 and 25, and the booster 19 together constitute an explosive train which, when properly aligned, will serve to transmit a detonation initiated in the detonator 18 to the main charge of the ordnance item when the firing mechanism is actuated. The shutter 21 is so designed that, when the elements are positioned as shown in FIG. 1, the shutter forms a detonation barrier and a detonation wave will not be transmitted across the recess 22 and thus an accidental explosion of the ordnance item due to inadvertent firing of the detonator 18 is precluded.

A cork float 26 is secured in any suitable manner to the shutter 21 and serves to provide a buoyant force for moving the shutter, in the direction indicated by the arrow in FIG. 1, whenever the device is immersed in water. A guide pin 28 is fixed to the shutter 21 and rides in a slot 29 formedin one wall of the recess of 22 to maintain the transmission charge 24 axially oriented with respect to the detonator. 18 and second transmission charge 25. A compression spring 30 is interposed between the bottom of the recess 22 and one end of the shutter 21 and normally urges the shutter to the safe position shown in FIG. 1. The spring constant of the spring 30 is selected so that the spring will readily support the weight of the shutter 21 and float 26 in air and yet yield readily under the buoyant force applied to the shutter 21 by the float 26 when the device 10 is im-.

mersed water to permit movement of the shutter to align the elements of the explosive train.

A soluble washer 31 is disposed about one end of the shutter 21, and by engagement with a snap ring 32 carried by the shutter, precludes arming of the device 10 due to a buoyant force on the float 26 until the washer 31 has dissolved. This built-in delay permits the laying vessel to withdraw from the vicinity of the ordnance item prior to arming thereof so that the laying vessel itself does not actuate the firing mechanism of the ordnance item. An additional safety feature is provided by way of an arming wire 34 disposed in an aperture in the shutter 21 which precludes movement of the shutter to the armed position irrespective of other conditions until the arming wire is withdrawn.

In the embodiment shown in FIG. 2, the float 26 is connected to the shutter 21 by means of a connecting rod 35 and pivoted link 36. As isobvious from FIG. 2, movement of the float 26 in the direction indicated by the arrow will result in alignment of the elements of the explosive train. The shutter 21 and float 26 are connected to the casing 12 by means of expansible bellows 38 and 39, respectively. The bellows 38 and 39 perform the function performed by the compression spring in the embodiment of FIG. land additionally, these bellows. being oppositely acting, serve to offset the effects of hydrostatic pressure. In this embodiment, the shutter 21 extends through the opposite side of the casing 12 and is provided with a soluble washer 31, snap ring 32 and arming wire 34. These elements are not repeated in FIG. 2, for the purpose of simplifying the drawing, since their construction is adequately illustrated in FIG. I.

In the embodiment of the FIG. 3, the shutter 21 extends all of the way through the mine casing 12 to compensate for the effects of hydrostatic pressure and is directly connected to the float 26, movement of which in the direction of the arrow will align the explosive train. Flexible diaphragms 40 of rubber or other suitable material are connected to opposite ends of the shutter 21 to provide a fluid seal. Again the end of the shutter 21 opposite the float 26 would be provided with the soluble washer and arming wire in an arrangement similar to that illustrated in FIG. 1.

In the embodiment of FIG. 4, the float 26 is illustrated as spherical and is connected to" the shutter 21 by means of a flexible member 41. Brackets 42 are mounted on the casing 12 to support the float 26 in the position shown in FIG. 4. As is evident from the drawing, movement of float 26 in any of the three directions indicated by the arrows in the drawing would result in movement of the shutter 21 to the armed position wherein the explosive train elements are aligned. Again the other end of the shutter 21 is omitted for purposes of simplicity but would be provided with a soluble washer and arming wire arrangement as illustrated in FIG. 1.

FIG. 5 illustrates an embodiment which is omnidirectional in function. A spherical float 26 is mounted between a pair of L-shaped brackets 44 which are pivotedly connected by means of a pivot pin 45 and which are provided with open, circular loops 46 on the upper ends thereof. The loops 46 are of a lesser diameter than the float 26 and serve to confine the float therebetween. As before, the other end of the shutter 21 is pro vided with a soluble washer and arming wire arrangement similar to that shown in FIG. 1.

OPERATION In order that a better understanding of the invention might be had, the mode of operation of the various disclosed embodiments will now be described. Immediately before laying the ordnance item, the arming wire 34 is extracted from the aperture in the shutter 21. The ordnance item is then laid in the water in any fashion appropriate to the particular ordnance item. Immediately upon entry into the water, a buoyant force is applied to the float 26. However, immediate arming of the ordnance item is precluded by the action of the soluble washer 31 engaging the snap ring 32. Upon dissolution of the soluble washer 31, the float 26 is free to move in response to the buoyant force thereon. As will be evident from the drawings, the embodiments of FIGS. 1, 2 and 3 are limited to utilization in an ordnance item which will have a known orientation with respect to the vertical. That is, the final orientation of the ordnance item must be such that the buoyant force on the float 26 will be exerted in substantially the same direction as the arrows in these FIGS. The buoyant force on the float 26 will then move the shutters 21 in the direction indicated by the arrows against the urging of the compression spring 30, or in the case of FIG. 2 against the resistance of the

bellows

38 and 39, to axially align the transmission charge 24 with the other elements of the explosive train to complete the train and thus arm the ordnance item. The main charge of the ordnance item will than be initiated at such time as the detonator 18 is tired by the firing mechanism.

In the embodiment of FIG. 4, the orientation of the ordnance item is not as critical. As long as the buoyant force on the float 26 is not acting in a direction lying within the angle defined by the ends of the brackets 42 and the center of the float 26, the float will roll out of the socket defined by the ends of the brackets and move the shutter 21 against the urging of the compression spring 30 to align the elements of the explosive train. The member 41 is made flexible to accommodate movement of the float 26 in any direction other than the vertical direction as illustrated in FIG. 4.

On the other hand, the embodiment of FIG. 5 will function to arm the ordnance item irrespective of the direction of the buoyant force on the float 26. If the buoyant force on the float 26 is in either of the vertical directions, the loops 46 will be forced apart by the flaot causing the brackets 44 to pivot about their corners 48. This movement of the brackets 44 will cause the brackets to pivot about the pivot pin 45 with respect to each other and thus elevate the pivot pin. The shutter 21 is connected to the pivot pin 45 by means of the flexible member 41 and thus will be moved to the armed position by upward movement of the pivot pin. A flexible strap 49 interconnects the brackets 44 and limits the spreading thereof to preclude escape of the float 26 from the confining action of the loops 46.

if the buoyant force on the float 26 is in one of the lateral directions, the brackets 44 will move as a unit pivoting about one of the corners 48 and again raising the pivot pin 45 to extract the member 41 which is flexible to accommodate this movement. A buoyant force on this float 26 acting in a direction other than the mutually perpendicular directions shown in FIG. 5 will result in a movement of the brackets 44 which is a combination of the aforedescribed movements but which will still result in movement of the pin 45 away from the casing 12 and alignment of the elements of the firing train.

Consideration of the aforedescribed embodiments by those skilled in the art will result in additional variants immediately suggesting themselves. For example, internal operation of the device can also be accomplished by providing a float action which will result in rotary motion of the shaft, in which case hydrostatic forces are absent also. Additionally, internal motion can be effected through a lever pivoted in a ball or hinge type seal in the safety and arming device container wall and mounting the float on the outer end thereof. Another possibility would be to incorporate the major portion of the positive buoyancy in the float. In this case an ordnance item which sinks would do so because the float became flooded or ineffective and this would result in disarming or sterilizing of the ordnance item.

The linear motion of the float due to the buoyant force can also be applied in various ways which are well known to designers of safety and arming mechanisms to provide environmental safety, i.e., to operate switches, align explosive train shutters or rotors, or simply to remove a gag from one of these devices so that they can be operated from other sources. For example, in a moored mine the float could be used simply to unlock the shutter when the mine enters the water. The shutter could be moved to the armed position mechanically when the case separates from the anchor, or could be moved by an explosive driver initiated by a simple seawater cell uncovered when the case separates from the anchor, or initiated by an internal timer in the mine, started when the case separates from the anchor.

Also, it should be noted that while a cylindrical cork float was used as an example, there are many shapes and designs for floats equally suitable for this use, in-

cluding hollow spherical or cylindrical or irregularly shaped metal and plastic floats, foamed plastic filled floats having metal, plastic or rubber sheaths, and floats made solely of foamed plastic. The sole requirement is that the float be of low specific gravity so that it will provide the necessary positive buoyancy in water.

From the foregoing it will be readily apparent that the present invention provides numerous advantages not obtainable with prior art devices. The present invention provides safety in air, rain, spray and high humidity, yet at the same time it provides a known force to arm or permit arming of an ordnance item when just submerged in water or at any depth. That is, in contrast to known methods, it senses immersion in water with out dependence on submergence to some minimum depth for operation.

it is to be understood that the aforedescribed embodiments are simply illustrative of the principal features of the present invention. Numerous other arrangements may be readily devised by those skilled in the art to achieve a similar device which will still embody the principles of the present invention and fall within the spirit and scope thereof.

What is claimed is:

l. A safety and arming device for underwater ordnance items comprising:

a housing,

a detonator mounted on said housing,

a booster mounted on said housing in axial alignment with said detonator,

a transmission charge carried by said shutter and operable to complete an explosive train when axially aligned with said detonator and said booster,

a float having a specific gravity less than one positioned within a cavity in said housing in fluid communication with the water when the housing is immersed therein and directly connected to said shutter whereby, upon immersion of the ordnance item in water, said shutter is moved by said float against the urging of said resilient means to axially align said transmission charge with said detonator and said booster to complete the explosive train and arm the ordnance item.

2. A safety and arming device as defined in claim 1 wherein a soluble element is connected to said shutter for restraining said float from arming the ordnance item until said soluble element has dissolved whereby the arming is delayed.

3. A safety and arming device as defined in claim 1 wherein a removable arming wire is connected to said shutter for restraining said float from moving said shutter to the armed position prior to removal of said wire whereby inadvertent arming of the ordnance item is precluded.

4. A safety and arming device as defined in claim I wherein said float is formed of cork.

5. A safety and arming device as defined in claim 1 wherein said float is a hollow metal float.

6. A safety and arming device as defined in claim 1 wherein said float is formed of a foamed plastic material.

7. A safety and arming device for underwater ordnance items comprising:

a housing,

a detonator mounted on said housing,

a booster mounted on said housing in axial alignment with said detonator,

resilient means normally urging said shutter and said transmission charge out of the axial alignment with said detonator and said booster whereby the explosive train is interrupted and the ordnance item is disarmed,

a float having a specific gravity less than one positioned within a cavity in said housing in fluid communication with the water when the housing is immersed therein and directly connected to said shutter whereby, upon immersion of the ordnance item in water, said shutter is moved by said float against the urging of said resilient means to axially align said transmission charge with said detonator and said booster to complete the explosive train and arm the ordnance item,

a soluble washer connected to said shutter for restraining said float from arming the ordnance item until said soluble washer has dissolved whereby the arming is delayed, and

a removable arming wire disposed in an aperture in said shutter for restraining said float from moving said shutter to the armed position prior to removal of said wire whereby inadvertent arming of the 0rd nance item is precluded.

8. A safety and arming device as defined in claim 7 wherein said float is formed of solid cork.

9. A safety and arming device as defined in claim 7 wherein said float is a hollow metal float.

10. A safety and arming device as defined in claim 7 wherein said float is formed of a foamed plastic material.

Claims

1. A safety and arming device for underwater ordnance items comprising: a housing, a detonator mounted on said housing, a booster mounted on said housing in axial alignment with said detonator, a shutter movably mounted on said housing between said detonator and said booster, a transmission charge carried by said shutter and operable to complete an explosive train when axially aligned with said detonator and said booster, resilient means normally urging said shutter and said transmission charge out of axial alignment with said detonator and said booster whereby the explosive train is interrupted and the ordnance item is disarmed, and a float having a specific gravity less than one positioned within a cavity in said housing in fluid communication with the water when the housing is immersed therein and directly connected to said shutter whereby, upon immersion of the ordnance item in water, said shutter is moved by said float against the urging of said resilient means to axially align said transmission charge with said detonator and said booster to complete the explosive train and arm the ordnance item.

4. A safety and arming device as defined in claim 1 wherein said float is formed of cork.

7. A safety and arming device for underwater ordnance items comprising: a housing, a detonator mounted on said housing, a booster mounted on said housing in axial alignment with said detonator, a shutter movably mounted on said housing between said detonator and said booster, a transmission charge carried by said shutter and operable to complete an explosive train when axially aligned with said detonator and said booster, resilient means normally urging said shutter and said transmission charge out of the axial alignment with said detonator and said booster whereby the explosive train is interrupted and the ordnance item is disarmed, a float having a specific gravity less than one positioned within a cavity in said housing in fluid communication with the water when the housing is immersed therein and directly connected to said shutter whereby, upon immersion of the ordnance item in water, said shutter is moved by said float against the urging of said resilient means to axially align said transmission charge with said detonator and said booster to complete the explosive train and arm the ordnance item, a soluble washer connected to said shutter for restraining said float from arming the ordnance item until said soluble washer has dissolved whereby the arming is delayed, and a removable arming wire disposed in an aperture in said shutter for restraining said float from moving said shutter to the armed position prior to removal of said wire whereby inadvertent arming of the ordnance item is precluded.

10. A safety and arming device as defined in claim 7 wherein said float is formed of a foamed plastic material. >