US3006280A - Fuze - Google Patents

Description

M. J. ROGERS ETAL 3,006,280

FUZE

Oct. 31, 1961 Filed April 13, 1954 2 SheetsSheet 1 I9 I r uxl/ $45 38 IGNITER DETONATOR BOOSTER EXPLOSIVE FIG. 1

MILTON J. ROGERS INVENTORS Oct. 31, 1961 M. J. ROGERS EI'AL 3,006,230

FUZE

Filed April 13, 1954 2 Sheets-Sheet 2 JEROME B. MEYER MILTON J. ROGERS INVENTORS Unitec'r states Pmerrt r r 3,006,280 FUZE Milton J. Rogers and Jerome B. Meyer, Baltimore, Md.,

assignors to Aircraft Armaments, Inc., Baltimore, Md. a corporation of Maryland Filed Apr. 13, 1954, Ser. No. 422,796 7 Claims. (Cl. 10270.2)

This invention relates generally to fuzes and more particularly to an acceleration sensitive fuze for bombs and the like, which employs a plurality of piezoelectric crystal units which will generate electrical energy in response to pressure exerted thereon.

In general, the fuze device comprises a hollow spherical housing with a ball carried therein so as to exert a force on at least one of a plurality of pressure sensitive piezoelectric crystals such as barium titanate ot produce electrical energy in amounts which vary directly with the acceleration of the fuze in any direction. By employing such a device in a bomb for effecting detonation of explosives it is not necessary that the bomb maintain a given attitude as is necessary in the case of bombs employing directional sensitive impact type fuzes. The bomb may first contact the target with its nose or side or tail and detonation will occur; the only requirement being that the bomb strike the object with sufiicient force to impart an acceleration, positive or negative, of sutficient magnitude to generate the required amount of electrical energy in the fuze for effecting detonation. Thus, even a glancing blow by the bomb on a target such as an enemy aircraft will cause the bomb to explode.

An object of this invention is to provide an acceleration sensitive fuze which will generate electrical energy in sufficient quantities A ithout amplifica ente'efieet eetena tion of common explosive material and which responsive to accelerations applied to the fuze from any direction.

Another object of this invention is to provide an acceleration sensitive fuze which is capable of withstanding very high accelerations without damage and which is small and compact by construction.

Another object of this invention is to provide an acceleration sensitive fuze which will operate under reasonably high temperature conditions, which is economical to manufacture and dependable in operation.

Still another object of this invention is to provide a fuze for bombs and the like of the type which is adapted to explode on impact, wherein the fuze may be mounted in any location within the confines of the device without affecting its operation.

Further and other objects will become apparent from a reading of the following description, especially when considered in combination with the acompanying drawings, wherein like numerals refer to like parts.

In the drawing:

FIG. 1 is an exterior view of the fuze, including a typical schematic circuit arrangement illustrating the use of the fuze in a bomb.

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1.

FIGS. 3 and 4 are sectional views showing modified forms of the piezoelectric crystal units.

Referring to FIGS. 1 and 2, the fuze includes a hollow spherical housing 1 which is made up of two hemispherical bodies 2 and 3 which are firmly secured together by suitable means such as bolt and bracket assemblies 4. A solid spherical ball 5 of material such as steel is carried within cavity 6 of housing 1. The diameter of ball Sis less than the diameter of cavity 6 by an amount which will allow sufiicient relative movement to properly load the piezoelectric crystal units 7 carried by housing 1 as hereinafter described.

A total of six piezoelectric crystal units 7 are carried by housing 1 and symetrically arranged relative to each r', I. I I I 1C6 Patented Oct. 31,

other on three mutually perpendicular axes. Threaded openings 8 are provided in the housing for receiving the units 7 and securing them in the proper position relative to ball 5. As best shown in FIG. 2 the piezoelectric 5 crystal units comprise an outer tubular sleeve 9 which threadedly engages housing 1 and telescopically receives an inner sleeve 10 of suitable electrical insulating material. The outer end of sleeve 9 is provided with a head 11 which projects beyond the outer surface of housing 1 to provide means for easily installing and removing the crystal units. An insert 12 of suitable electrical insulating material is arranged transversely of sleeve 10 to firmly abut head 11 and provide an insulated seat in the chamber for receiving a wafer 13 of piezoelectric crystal material such as barium titanate. A sliding washer 14 of electrical insulating material is located within sleeve 10 adjacent wafer 13 to completely insulate the barium titanate material and yet allow forces to be applied thereto by ball 5 through a piston-like member 15 which is slidably received by sleeve 10. A concave seating surface 16 is provided on the outer end of piston 15 for making surface to surface contact with ball 5. To avoid applying damaging shock loads on the barium titanate wafer 13, a layer 17 of sponge rubber or the like may be inserted between piston 15 and the insulating washer 14. The electrical potential developed by wafer 13 is picked up by a pair of electrical leads 18 and 19 which connect with the wafer on opposite sides thereof, wherein the opposite sides are transverse to the direction of the compressive force applied by piston 15. Holes 20 and 21 are tapped in head 11 and sleeve 9 to provide an exit for leads 18 and 19 from unit 7.

As shown in FIG. 2, piezoelectric crystal units 7 project into cavity 6 of housing 1 to suspend ball 5 centrally within the mity and out of contaet withthea'nner of housing 1.

The modified piezoelectric crystal unit 22 as shown in FIG. 3 is similar to unit 7 described above in connection with FIG. 2 except that piston 15 and sponge rubber insert 17 of unit 7 are replaced by a mechanical spring 23 and piston 24 assembly wherein piston 24 engages the insulating washer 14 directly and spring 23 projects into cavity'6 to engage ball 5. This arrangement shown in FIG. 3 will more efliciently absorb shock loads without danger of damaging the barium titanate wafer 13, but will allow greater freedom of movement of ball 5 within the cavity and therefore would be less desirable in applications where the fuze is subjected to vibrations of large amplitude.

A second modification of the piezoelectric crystal unit is shown in FIG. 4, wherein the openings 25 in housing 1 are tapered inwardly so that the barium titanate piezoelectric crystal material 26 may be wedged into a secure position for engaging ball 5 directly rather than through a piston and insulator as shown in FIGS. 2 and 3. As seen in FIG. 4, the barium titanate material 26 is electrically insulated from housing 1 through the use of sleeve 27 and insert 28. The barium titanate material 26, as well as the insulation 27 and 28, are secured in position relative to housing 1 by use of a cover plate 29 which is secured to the housing by suitable means such as screws 30. Since in the arrangement of FIG. 4, ball 5 contacts the piezoelectric crystal material 26 directly, the energy generated may be picked up by measuring the voltage potential between ball 5 and the outer surface of the barium titanate material 26. This may be done very simply by tapping a hole 31 in housing 1 and inserting a spring urged contact element 32 therein which contact ball 5 at all times, even though the ball may move relative to the housing. An output lead 33 firmly attached to contact member 32 is fed through an opening 34 in'housing 1. The lead 35 is firmly attached to the outer surface of the barium titanate material 26 and fed through a small opening 36 in cover plate 29. By conhousing 1. This arrangement, while being very simple in construction, has certain disadvantages over the configuration shown in FIG. 2 in that any oxidation on the surface of ball 5 or on pick-up element 32 will decrease the'output energy obtainable from the piezoelectric material 26. Also forming the piezoelectric material itself to the curved shape of ball 5 so that surface to surface contact may be obtained is quite difiicult and expensive to accomplish as compared with making flat wafers 13 as used in the forms shown in FIGS. 2 and 3. a

The operation of the fuze is believed obvious from a reading of the foregoing description. A force applied to any one of the piezoelectric crystal units will cause the latter to generate electrical energy in quantities varying directly with the magnitude of the force. Due to the pull of gravity, the fuze will produce a small output voltage even though it is not being. occelerated. However, this small output due to gravity is negligible when using the fuze for igniting the explosive in bombs and the like, since the accelerations imparted to the bomb, even when it strikes the target with only a glancing blow, will bemany times the 1 g loading due to gravity and hence a sufiicient diflference in the energy output of the fuze will be obtained to eifect detonation.

A typical circuit for use of the fuze in a bomb is shown in FIG; 1, wherein output leads 19 are fed to ground and output leads 18 connecting with the positive sides of the piezoelectric wafers are all connected to an arming switch 37 which, when closed, will allow the electrical energy generated by the fuze to be applied to an igniter 38 through lead 39. The agniter 38 in response to an electrical impulse of sufiicient magnitude from the fuze Will eiiect detonation of the bomb explosive 40 through conventional powder stages such as those identified in FIG. 1 as detonator 41 and booster 42.

Arming switch 37 is employed to prevent electrical communication between the fuze and igniter 38 while the bomb is being handled. This switch may be operated by any suitable device such as a mechanical actuator 43 which is responsive to releasing the bomb for closing the switch and completing a circuit from the fuze to igniter 38.

The efliciency of piezoelectric material such as barium titanate decreases with increasing temperatures and since in certain applications the fuze may be subjected to a considerable amount of heat such as that generated by skin friction on high velocity rockets and projectiles, it may be desirable to construct outer tube 9 and head 11 of the piezoelectric crystal units 7 from a ceramic type of material which possesses good heat insulating properties. If further insulation from heat should become necessary housing 1 could also be made from heat insulating materials.

The fuze described herein may be used not only to efiect detonation of explosives, but also to provide guidance information for controlling the movement of a body. That is, by measuring the difference in the outputs of the various piezoelectric crystal units 7 in the fuze, the change in movement of a body and the direction of that change may be determined.

It is to be understood that certain alterations, modifications and substitutions may be made to the instant disclosure without departing from the spirit and scope of this invention as defined by the appended claims.

We claim: 7

1. An acceleration sensitive fuze for generating electrical energy comprising, a housing having a generally spherically shaped cavity, a spherically shaped mass carried within said cavity, said mass having a diameter less than the diameter of said cavity, said housing having a plurality of openings formed therein in communication with said cavity, piezoelectric crystalunits carried by said housing within said openings and projecting into said cavity and engaging said mass to suspend the same within the cavity and out of contact with the housing wall, said crystal units being responsive to the forces exerted thereon by said mass due to accelerations in any direction for generating electrical energy, and means electrically con- .necting with said crystal units and completing an external circuit conducting electrical energy generated from within saidfuze.

2. An acceleration sensitive fuze for devices such as bombs and the like requiring an electrical impulse for actuation comprising, a housing forming a container, a

mass carried within said container, said mass being smaller than the inside dimensions of said container, at least four piezoelectric crystal units carried by said housing and engaging said mass to suspend the same within the container and out of contact with said housing, said crystal units being spaced so that the points of engagement with said mass of any three of said units be in one hemisphere of the imaginary sphere whose surface includes said points.

of engagement and the point of engagement with said mass of a fourth unit, and the point of engagement of said fourth unit lies in the other hemisphere of said sphere at a point not diametrically opposite to any one of the first said points of engagement, said crystal units each being responsive to forces exerted thereon by the acceleration of said mass in any direction for generating electrical energy, and means electrically connecting with said crystal units for conducting said energy exteriorly of said fuze and eiiecting actuation of the device.

3. An acceleration sensitive fuze for bombs and the like requiring an electrical impulse for detonating the same comprising, a housing forming a container, a mass carried within said container, said mass being smaller than the inside dimensions of saidcontainer, a plurality of piezoelectric crystal units carried by said housing and engaging said mass to suspend'the latter within the container and out of contact with the housing, each said unit including a tubular electrical insulator, a barium titanate wafer carried within said tubular insulator, a piston slidably received within said tubular insulator and responsive to accelerations of said mass for squeezing said wafer and generating electrical energy at a voltage varying directly with the squeezing force applied thereto, resilient means interposed between said mass and said wafer for reducing shock loads, and means electrically connecting with said wafers for conducting said energy exteriorly of said fuze and effecting detonation of said bomb.

4. An acceleration sensitive fuze for generating electrical energy, the voltage of which varies directly with the acceleration of said fuze comprising, an outer housing forming a container, a mass carried Within said container, said mass being smaller than the inside dimensions of said container, said housing having a plurality of openings formed therein, insulating means lining each said opening and forming a chamber communicating with the interior of said container, piezoelectric material carried within each said chamber and arranged to generate electrical energy in response to pressure applied thereto, and piston means slidably received within each said chamber and projecting into said container for engaging said mass and applying pressure to said piezoelectrical material in response to accelerations of said housing.

5. An acceleration sensitive fuze for generating elec trical energy, the voltage of which varies directly with the acceleration of said fuze comprising, an outer housing forming a container, a mass carried within said con tainer, said mass being smaller in size than the inside dimensions of said container, said housing having a plurality of openings formed therein, insulating means lining each said opening and forming a chamber communicating with the interior of said container, piezoelectric material carried within each said chamber and evil arranged to generate electrical energy in response to pressure applied thereto, shock absorbing piston means slidably received within each said chamber and projecting into said container for engaging said mass and applying pressure to said piezoelectric material in response to accelerations of said housing causing said mass to press against said piston means, and means electrically connecting with said piezoelectric material for conducting said electrical energy in a circuit exteriorly of said fuze.

6. An acceleration sensitive fuze for generating electrical energy, the voltage of which varies directly with the acceleration of said fuze comprising, a container, a mass of electrical conducting material carried within said container, said mass being smaller than the inside dimensions of said container, said container having a plurality of openings formed therein, insulating means lining each said opening and forming a chamber communicating with the interior of said container, a block of piezoelectric material secured'Witlain each aaid thamber and projecr ing into said container and engaging said mass to support the latter in a position out of contact with said housing, said piezoelectric material being responsive to pressure exerted by said mass for generating electrical energy, an electrical contact element carried by said container and engaging said mass to provide a common ground for all the blocks of piezoelectric material, and means connecting with each said block of piezoelectric material for completing an external circuit conducting electrical energy generated from within said fuze,

7. A fuze for eifecting detonation of explosives com- 30 and wiring'rneans eleetrieaiiy eormeeting wirh 'said 'piezo prising, a hollow spherical container, a ball carried within said container, said ball being smaller in diameter than the inside diameter of said hollow container, said container having a plurality of openings formed therein, a piezoelectric crystal unit carried by said container within each said opening, each said unit comprising an electrical insulating tubular member forming a chamber communicating with the inside of said hollow container, a water of piezoelectric material carried within each said chamber for generating electrical energy in response to pressure applied thereto, a piston assembly slidably received within each said chamber adjacent said water and projecting into said container for engaging said ball to support the latter in a position out of contact with the container Wall, each said piston assembly being responsive to inertia forces applied by said ball for applying pressure to said water, said assembly including cushioning means for absorbing shock loads applied by said ball,

electric material for conducting said electrical energy to the explosives for efiecting detonation.

References Cited in the file of this patent UNITED STATES PATENTS 2,488,586 Diemer NOV. 22, 1949 2,514,297 Smith et al. July 4, 1950 FOREIGN PATENTS 277,052 Switzerland Nov. 1, 1951

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