US3672300A - Pressure actuated acoustic signal source - Google Patents

Abstract

A bomb-type underwater signal source is disclosed having a detonating mechanism wherein the rupture of a shear disk assembly at a predetermined ocean depth permits the ambient hydrostatic pressure to compress the gas within a cavity and raise the temperature at one end of this cavity to a level sufficient to detonate first a confined secondary explosive positioned at this end of the cavity and then the main charge.

Description

United States Patent Axelson et a1.

[451 June 27, 1972 Somerset, both of Mass; Elton Y. Mc- Gann, Williamsburg, Va.

[73] Assignee: The United States of America as represented by the Secretary of the Navy [22] Filed: Nov. 16, 1970 [21] App]. No.: 89,677

[52] U.S.Cl ..l02/10, 102/7, 102/16, 102/81 [51] Int. Cl ..F42b 21/00, F42b 22/36 [58] Field of Search ..l02/7, 10, 16, 81

[56] References Cited UNITED STATES PATENTS 3,391,639 7/1968 Bochman ..102/7 Primary Examiner-Benjamin A. Borchelt Assistant Examiner.lames M. Hanley Attorney-R. S. Sciascia and L. l. Shrago ABSTRACT A bomb-type underwater signal source is disclosed having a detonating mechanism wherein the rupture of a shear disk assembly at a predetermined ocean depth permits the ambient hydrostatic pressure to compress the gas within a cavity and raise the temperature at one end of this cavity to a level sufficient to detonate first a confined secondary explosive positioned at this end of the cavity and then the main charge.

5 Claims, 2 Drawing Figures PRESSURE ACTUATED ACOUSTIC SIGNAL SOURCE 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.

The present invention relates generally to underwater acoustics signal sources and, more particularly, to an acoustic signal source which utilizes only hydrostatic forces to detonate an explosive charge at a predetermined ocean depth.

In one common bomb-type underwater sound generator, hydrostatic pressures depress a plunger which contains a detonating charge and move it into alignment with a firing pin. When these pressures reach a predetermined magnitude corresponding to a prescribed firing depth, a shear disk assembly is ruptured and a firing pin is driven into the aligned detonating charge. This charge is set off and so is the remainder of the in line explosive train consisting of the lead cup, the booster and the main charge.

The safety feature in this type of sound signal source is provided by the plunger which normally maintains the detonating charge in a safe out of line" position. This plunger can be depressed only after an arming safety rod is withdrawn therefrom, either manually or by aerodynamic drag forces acting on the bomb during the air drop portion of the delivery. Furthermore, once armed, the bomb must reach a predetermined water depth sufficient to align the detonating charge with the explosive train. The many components required to achieve this degree of safety, as well as those necessary for arming and firing the bomb, result in a complicated and expensive device. Additionally, this complexity introduces the problem of reliability of operation of the sound source.

It is accordingly a primary object of the present invention to provide a simplified arrangement for detonating an explosive charge in an ocean environment.

Another object of the present invention is to provide a detonator which is inexpensive, compact, safe and highly reliable and which operates at relatively high, hydrostatic pressures.

Another object of the present invention is to provide a detonator for an explosive charge which utilizes hydrostatic pressures to increase the temperature at the explosive charge to a level sufficient to cause its detonation.

Another object of the present invention is to provide a bomb-type underwater signal source which cannot be accidentally detonated on the surface or in relatively shallow water but which requires substantial hydrostatic pressures for its operation.

Another object of the present invention is to provide a detonator for underwater explosives which eliminates the need of all sensitive initiators and the need for an out of line" safety feature and an in line" explosive train.

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

FIG. 1 is a schematic drawing showing the complete structure of a bomb-type acoustic signal generator utilizing the principle of operation of the present invention; and

FIG. 2. is a simplified drawing of a detonator which can be used in various explosive devices.

Briefly and in somewhat general terms, the above objects of invention are accomplished according to the present invention by utilizing the rupture of the shear disk assembly at a preselected ocean depth as a means for permitting the ambient hydrostatic pressures to compress the gas within a cavity and raise the temperature within this cavity to a level sufiicient to detonate a confined secondary explosive element which is positioned at the other end of the cavity. When the seawater rushes into the air cavity, the compression of the air therein which is in contact with the secondary explosive occurs sufficiently fast so as to be adiabatic and create a peak air temperature to cause deflagration. This defiagration, together with its instantaneous pressure rise and with a proper confinement of the explosive, results in the detonation of a secondary explosive column.

Referring now to FIG. 1 of the drawings, it will be seen that the bomb-type, underwater acoustic signal source includes a nose section I which houses a shear disk assembly 2 that is seated in place by a tensioningnut 3 against the back wall portion 4 of an inner central chamber 5.

A plurality of radial apertures, such as 6 and 7, are cut through the nose section to communicate with inner chamber 5. Likewise, suitable apertures, such as 8 and 9, are cut through a body portion of the tensioning nut 3 to communicate with a central bore 10 formed in one end of this nut. This arrangement of openings allows one face of the shear disk assembly 2 to be exposed to the ambient sea pressure when the sound signal source is immersed in the ocean.

Also communicating with inner chamber 5 and the back wall portion 4 thereof is a conical cavity 1 l, the base of which commences at this wall. The base of the cavity is effectively sealed off by the shear disk assembly so that the air contained therein is normally maintained at atmospheric pressure. The

apex of cavity 11 extends into one end of an explosive container 12 which has a circular flange that locks behind a backing plate 14 that is bolted or otherwise attached to the rear of nose section I. Contained within the explosive charge holder 12 in a central bore is the secondary explosive charge 13. A portion 16 of this charge serves to close the otherwise opened end of the apex of cavity 11. The secondary charge 13 is held in place by a spring cap 15 which clips over a reduced diameter end portion of the explosive container, forcing this charge to the left, as shown in the figure, so as to have it abut the apex of the cavity.

It would be pointed out that the shear disk assembly 2, together with the conical cavity 11, the secondary explosive container 12 and the secondary explosive column 13, constitute the detonating mechanism of the bomb-type signal source. This subassembly, that is, the nose section I with the explosive container 12 attached thereto and with the secondary explosive column 13 locked in place by spring cap 15, may be readily connected to any explosive device for detonation thereof at a predetermined ocean depth.

In the present case, the main explosive charge 17, which is of a plastic composition, is contained within a midsection 18 of the bomb and substantially fills the complete interior thereof except for the central cut-out section into which fits the secondary explosive container 12. The tail section of the bomb is filled with sponge rubber l9, and this rubber acts as a spring to compress the plastic explosive and keep it firmly abutted against the end cap 15 associated with the secondary explosive charge holder 12. The midsection and tail section of the bomb may be made of unitary construction, and a portion of the exterior casing 20 may be fabricated with an inner directed rim which snaps into a circumferential slot 21 formed in nose section I.

lt will be appreciated that the only explosive in the detonating mechanism is the secondary explosive column I3 and that there are no moving parts to this mechanism.

It will also be appreciated that the apparatus as described may be safely handled without any danger of its premature ignition since the temperature within the air cavity will be much below the level needed to ignite the secondary explosive column.

When the assembled apparatus, as shown in FIG. 1, is launched from an aircraft or dropped at the ocean surface, it falls within the ocean with seawater entering the nose portion through the various apertures, and the ambient ocean pressure acting against shear disk assembly 2. The air within cavity 1 1 remains at atmospheric pressure because of the barrier presented by this disk assembly. When the bomb reaches its preset depth as determined by the design of the disk assembly, the disk shears and seawater, because of the relatively great ambient hydrostatic pressure, rushes into the conical cavity. The converging walls direct this flow inwardly and the water, acting as a piston, causes the air within the cavity to be compressed into the apex. The compression of this air occurs fast enough to be essentially adiabatic. The magnitude of this compression at the depths involved is enough to create a peak air temperature in contact with the secondary explosive column 13 to cause deflagration. This deflagration and the confined condition of the secondary explosive column results in a transition from defiagration to detonation first of this column and then of the main explosive 17.

It can be shown by a mathematical analysis that if the final volume of the cavity is small compared to the original size of the cavity, then the increase in temperature, A! C. is equal approximately to 3.33 h, where h is the water depth at which the disk assembly is ruptured. Thus, for example, at a hundred feet, the temperature rise is 330.33 C., at 1,000 feet, 3,303.33 C. and at 10,000 feet 33,030.27 C. Likewise, it can be shown that the cavity need not have the conical shape shown in FIG. 1 but may be, for example, of cylindrical geometry.

One of the advantages of the arrangement hereinabove described is that the secondary explosive material is kept stationary and in a line with the main explosive charge at all times. The acoustic signal apparatus, since it needs no safety wire or other safety retaining device, is thus always ready for immediate use, a characteristic which is highly desirable in a combat or emergency situation.

In FIG. 2 there is disclosed the general details of the detonator which employs the operating principle of the present invention and which may be utilized to detonate a lead cup normally used with any explosive train. The apparatus consists of a secondary explosive charge holder 30 which, like its counterpart 12 in FIG. 1, has a central conical cavity 31 whose apex portion communicates with a longitudinal bore that con tains the secondary explosive column 32. A shear disk assembly 33 again closes ofi the circular base portion of conical cavity 31 and effectively entraps the air therein and maintains it at atmospheric pressure. A retaining cap 34 is screwed onto a reduced diameter end portion of the charge holder and serves to maintain the shear disk assembly in place. Formed in the head of the retaining cap is a central opening 35 which permits the ambient sea pressure to act on one face of the shear disk assembly.

In this particular modification, the explosive lead cup 41 fits into a recess in the rear of a plug 40 which is screwed into the base of charger holder 30. The explosive element 42 of this lead cup is maintained in alignment with an air passageway 43 cut through plug 40 which communicates with the secondary explosive column 32. An aluminum disk 44 is introduced behind plug 40 so as to block this air passageway and support the exploding column 32.

The rupture of the shear disk assembly at the preset depth again causes the temperature at the face of the secondary explosive column to increase to a level sufficient to cause detonation of this column. When this occurs, hot metal particles from aluminum disk 44, as well as the shock waves from the explosion, travel through passageway 43 and detonate the explosive lead cup 41. Detonation of this cup, of course, results in the subsequent detonation of any main explosive charge which is butted up against its output end.

In this modification, the detonator is positioned within a casing 50 and the main explosive charge occupies compartment 51 thereof.

The booster material in the usual underwater sound signal weighs approximately 31 grams. in the detonator above described, no such booster is required, and the explosive loaded pickup cup weighs only 3 grains. Total explosive weight of the assembled detonator is less than 1 gram.

Since the detonator of FIG. 2 has no moving parts, its reliability is of a high order. Likewise, its storage life is prolonged and little or no maintenance is required during the storage.

What is claimed is:

1. Apparatus for detonating an explosive charge at a predetermined depth comprising, in combination,

a member having a cavity formed therein which is open at both ends thereof;

a shear disk assembly closing one end of said cavity; an explosive charge confined within said member such that a portion of said charge closes the other end of said cavity; and

said shear disk assembly rupturing at said predetermined ocean depth and thereby allowing water to rush into said cavity, compress the gas present therein and raise the temperature thereof to a level sufficient to detonate said explosive charge.

2. In an arrangement as defined in claim 1,

wherein said cavity has a conical shape; and

wherein said shear disk assembly is positioned at the base and said explosive charge at the apex of said conical shape.

3. Apparatus for detonating an explosive charge at a predetermined ocean depth comprising, in combination,

an explosive charge holder having a cavity formed therein which is open at one end thereof and having a compartment which is in communication with the other end of said cavity;

an explosive charge confined within said compartment and effectively closing one end of said cavity; and

a shear disk positioned against the other end of said cavity and closing this end of said cavity; said shear disk maintaining the gas present within the interior of said cavity at atmospheric pressure until said shear disk assembly is ruptured at said predetermined ocean depth, whereupon water rushing into said cavity from said other end thereof compresses the gas present therein and raises the temperature thereof to a level sufficient to detonate said explosive charge.

4. In a bombdype underwater acoustic signal source, the combination of an explosive charge holder having a cavity formed therein which is open at opposite ends thereof;

a shear disk positioned against one end of said cavity and closing this end of said cavity, said shear disk being arranged so as to rupture at a predetermined hydrostatic pressure when said bombtype acoustic signal source is immersed in a fluid medium;

a secondary explosive charge confined within said explosive charge holder such that a portion thereof serves as a closure means for the other end of said cavity, whereby the gas present within said cavity is maintained at atmospheric pressure until said shear disk is ruptured;

a metallic disk contacting an end portion of said secondary explosive charge which is remote from that portion which serves as said closure means;

a cap attached to said explosive charge holder and maintaining said metallic disk in place, said cap having a passageway formed therethrough; and

a main explosive charge positioned against said cap whereby, when said shear disk is ruptured, water rushing into said cavity compresses the gas present therein and raises the temperature thereof to a level sufficient to detonate said secondary explosive charge and send particles from said metallic disk and shock waves through said passageway to denote said main explosive charge.

5. In an arrangement as defined in claim 4 wherein said cavity has a conical shape with said shear disk positioned at the base and said secondary explosive charge at the apex thereof.

Claims (5)

1. Apparatus for detonating an explosive charge at a predetermined depth comprising, in combination, a member having a cavity formed therein which is open at both ends thereof; a shear disk assembly closing one end of said cavity; an explosive charge confined within said member such that a portion of said charge closes the other end of said cavity; and said shear disk assembly rupturing at said predetermined ocean depth and thereby allowing water to rush into said cavity, compress the gas present therein and raise the temperature thereof to a level sufficient to detonate said explosive charge.

2. In an arrangement as defined in claim 1, wherein said cavity has a conical shape; and wherein said shear disk assembly is positioned at the base and said explosive charge at the apex of said conical shape.

3. Apparatus for detonating an explosive charge at a predetermined ocean depth comprising, in combination, an explosive charge holder having a cavity formed therein which is open at one end thereof and having a compartment which is in communication with the other end of said cavity; an explosive charge confined within said compartment and effectively closing one end of said cavity; and a shear disk positioned against the other end of said cavity and closing this end of said cavity; said shear disk maintaining the gas present within the interior of said cavity at atmospheric pressure until said shear disk assembly is ruptured at said predetermined ocean depth, whereupon water rushing into said cavity from said other end thereof compresses the gas present therein and raises the temperature thereof to a level sufficient to detonate said explosive charge.

4. In a bomb-type underwater acoustic signal source, the combination of an explosive charge holder having a cavity formed therein which is open at opposite ends thereof; a shear disk positioned against one end of said cavity and closing this end of said cavity, said shear disk being arranged so as to rupture at a predetermined hydrostatic pressure when said bomb-type acoustic signal source is immersed in a fluid medium; a secondary explosive charge confined within said explosive charge holder such that a portion thereof serves as a closure means for the other end of said cavity, whereby the gas present within said cavity is maintained at atmospheric pressure until said shear disk is ruptured; a metallic disk contacting an end portion of said secondary explosive chArge which is remote from that portion which serves as said closure means; a cap attached to said explosive charge holder and maintaining said metallic disk in place, said cap having a passageway formed therethrough; and a main explosive charge positioned against said cap whereby, when said shear disk is ruptured, water rushing into said cavity compresses the gas present therein and raises the temperature thereof to a level sufficient to detonate said secondary explosive charge and send particles from said metallic disk and shock waves through said passageway to denote said main explosive charge.

5. In an arrangement as defined in claim 4 wherein said cavity has a conical shape with said shear disk positioned at the base and said secondary explosive charge at the apex thereof.

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