US3599572A

US3599572A - Safing and arming system for a munition

Info

Publication number: US3599572A
Application number: US868412A
Authority: US
Inventors: Donald A Brackman
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1969-10-22
Filing date: 1969-10-22
Publication date: 1971-08-17
Anticipated expiration: 1988-08-17

Abstract

A control apparatus comprising a safing and arming system for a munition wherein such apparatus requires only two sensors mounted about a reference axis in angularly spaced relation. The sensors are operatively connected to provide an effective arming signal for the munition only by the simultaneous provision of a signal from both sensors under conditions of sustained free fall and the sensors are incapable of providing signals simultaneously during normal handling of the munition, making it safe to handle.

Description

United States Patent Inventor Donald A. Brahman Englewood, Ohio App]. No. 868,412

Filed Oct. 22, 1969 Patented Aug. 17, I971 Assignee AVCO Corporation Richmond, Ind.

SAFING AND ARMING SYSTEM FOR A MUNITION l6 Clalma, 14 Drawing Flgs.

[1.8. CI 102/702, 102/76 Int. Cl. F421: 13/00, F4213 21/38 Field of 102/702, 76, 78, 79, 80

[56] References Cited UNITED STATES PATENTS 2.5 [5,043 7/1950 Jordan 102/702 3,167,018 1/1965 Brunner 102/702 3,292,537 12/1966 Goss, Jr. 102/28 3,332,354 7/1967 Silvers. Jr. et al l02/76 Primary xaminer-Samuel Feinberg Attorneys-Charles M. Hogan and Eugene C. Goodale ABSTRACT: A control apparatus comprising a safing and arming system for a munition wherein such apparatus requires only two sensors mounted about a reference axis in angularly spaced relation. The sensors are operatively connected to provide an effective arming signal for the munition only by the simultaneous provision of a signal from both sensors under conditions of sustained free fall and the sensors are incapable of providing signals simultaneously during normal handling of the munition, making it safe to handle.

PATENTEUAusmsn 3599572 SHEET 1 BF 3 kL -L j 52 INVENTOR. DONALD A. BRACKMAN BYW fi m

ATTORNEYS PATENIED we I 7 an SHEET 2 8F 3 FIG-4 FIG-3 FIG-9 O W L FIG-8 INVENTOR. DONALD A, BRACKMAN BY ,,1. H7

ATTORNEYS PATENIEI) M181 7 an SHEET 3 OF 3 N A RM O Wu T E NA ER r v8. W W flu T T A A D L A N O D FIG-l4 SPIN-REV] SEC.

SAFING AND ARMING SYSTEM FOR A MUNITION BACKGROUND OF THE INVENTION Munitions, such as bombs, missiles, and the like, which are designed for release from aircraft must be provided with suitable safing and arming means to assure safety of personnel during routine handling thereof, yet the system used to provide such safing and arming must be capable of arming the associated munition in a reliable manner after aerial release of such munition.

During the free fall of a munition, there are numerous environments acting on such munition and its control system and such environments include relative weightlessness of components, possible spin or rotation about a spin axis of the munition, and aerodynamic drag along such axis. However, in a so-called fin stabilized low-drag munition or bomb, the amount of drag may be less than 0.050 g., making it economically impractical to use drag as a control parameter.

Weightlessness, or zero g.," is the most logical control parameter which may be used in a safing and arming control system for a low-drag munition. However, previously proposed devices utilizing zero g. as a control parameter are unnecessarily complicated, expensive, and comparatively unreliable.

SUMMARY This invention provides a control apparatus sensing a lowdrag condition comprising a safing and arming system for a munition wherein the apparatus requires only two sensors mounted about a reference axis in angularly spaced apart relation and such control apparatus may be used to provide omnidirectional sensing. The sensors are operatively connected to provide an effective arming signal for the munition only by the provision of signals from both sensors simultaneously under conditions of sustained free fall and the sensors are incapable of providing signals simultaneously during normal handling of the munition. In addition, this invention provides an improved control apparatus in which the sensors are positioned about a reference axis of the control apparatus which may be spaced from the spin axis of an associated munition without adversely affecting the reliability of safing and arming the munition.

Other details, uses, and advantages of this invention will become apparent as the following description of the embodi ments thereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show present preferred cmbodiments ofthis invention, in which FIG. I is a schematic presentation, with certain parts shown in perspective, of one exemplary embodiment of a control apparatus of this invention having a reference axis mounted coaxially with the spin or longitudinal axis of an associated munition;

FIG. 2 is a view with parts in cross section and parts broken away taken essentially on the line 2-2 of FIG. 1',

FIG. 3 is an enlarged, fragmentary, cross-sectional view of one of the two identical magnetically controlled sensors illustrated in FIG. 2 particularly illustrating the flat parallel end walls of such sensor;

FIG. 4 is a view taken essentially on the line 4-4 of FIG. 3',

FIG. 5 is a cross-sectional view illustrating another embodiment of a magnetically controlled sensor which has a cylindricnl housing provided with opposed dishlike end walls which are particularly adapted to take into account spacing between the reference axis of a control apparatus and the spin axis ofa munition;

FIG. 6 is a cross-sectional view similar to FIG. 5 illustrating another embodiment of a magnetically controlled sensor which has a housing provided with end walls having another configuration;

FIG. I is a cross-sectional view similar to FIG. 5 illustrating still another embodiment of a magnetically controlled sensor which has a housing provided with still another configuration;

FIG. 8 is a schematic diagram illustrating "go" and "no go" areas ofa single sensor, in a l g. environment, having a housing comprised of a right circular cylindrical sidewall and flat end walls which utilizes a magnet capable of exerting a 0.5 g. force on a ferromagnetic spherical member carried within the housing of such sensor;

FIG. 9 is a schematic presentation illustrating the effect of spin of a munition about its spin axis when the spin axis coincides with the reference axis of an associated safing and arming apparatus and when the spin axis is spaced from such reference axis;

FIG. 10 is a schematic illustration showing a pair of cooperating sensors which are identical to the sensor illustrated in FIG. 3 with such sensors spaced apart to highlight that under no condition during normal ground handling will there be a simultaneous signal from both sensors to thereby provide an arming or "go" signal to an associated munition;

FIG. II is a schematic illustration similar to FIG. 10 showing a pair of cooperating sensors which are identical to the sensor of FIG. 5 with such sensors spaced 90 apart;

FIG. 12 is a schematic illustration similar to FIG. 10 showing a pair of cooperating sensors which are identical to the sensor of FIG. 5 with such sensors spaced apart;

FIG. 13 is a more detailed schematic analysis of the presentation ofFIG. l2; and

FIG. 14 is a graph showing the tolerance of various types of sensors to misalignment of the reference axis of a control apparatus in which such sensors are used with respect to the spin axis of an associated munition and spin of the munition about its spin axis.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Reference is now made to FIG. I of the drawings which il lustrates one exemplary embodiment of the control apparatus of this invention which is designated generally by the reference numeral 20 and is suitably supported within a munition 2! which has a longitudinal or spin axis 22. The munition 21 may be a missile, bomb, or similar device having any suitable configuration and in this example of the invention will be considered as being a fin stabilized low-drag bomb having a drag along its axis 22 which is too low to be used in an economical manner as a control parameter for the control or safing and arming apparatus 20 for the munition 2].

The control apparatus 20 is used for safing, i.e., assuring the munition 2i is safe and will not explode, the munition during normal handling and for arming such munition under conditions of sustained free fall. The apparatus 20 comprises first and second magnetically controlled sensors each designated generally by the reference numeral 24 and each capable of providing an electrical signal through an associated electrical line either 26 or 27 respectively to an AND electrical logic component 30. The AND component 30 operates in a manner well known in the art and requires that an electrical signal be provided from both sensors 24 simultaneously before it can provide an output signal through a line 31 to another AND logic component 32 which is similar in operation to component 30.

A portion of the electrical signal through the line 31 is trans mitted to a suitable time delay circuit 33 through a line 34 which then transmits the delayed signal to the AND component 32. Any suitable time delay may be introduced by circuit 33; however, a l-second delay is considered very conser' vative. It is also accepted practice to provide still another or third signal to the AND component 32 and this may be in the form ofa separate signal through a line 35 and such signal may be provided as long as 4 seconds after release of the munition 21 in order to enable arming of such munition.

From the above presentation it is apparent that three signals must be simultaneously provided to the AND component 32 to have an electrical output therefrom and such output is then suitably amplified through a power amplifier 36 and transmitted as an arming signal through a line 37 to a suitable fuze for the munition 21 during sustained free fall of such munition. The use of a time delay circuit 33 and the provision of a separate signal through a line 35 are, in essence, additional safeguards to assure against premature arming of the munition 21; however, this invention is directed to a safing and arming apparatus 20 which is utilized in providing

electrical output signals

26 and 27 to the AND component 30 and the operation of such apparatus is such that it is impossible as a practical matter to provide such signals in a simultaneous manner except during free fall of the munition 21 for sustained periods of time whereby such munition may be handled with optimum safety.

The apparatus 20 has means, in the form of a support 40, for supporting the sensors 24 an equal distance from a reference axis 4l of the apparatus 20 and in this example of the invention such reference axis coincides with the spin axis 22 of the munition 21 whereby the dot-dash line centrally through the munition 21 in FIG. I will also be designated by the reference numeral 41. The support 40 is fixed to a substantially tubular member 42 which is supported within the munition 21 in any suitable manner and member 42 may be supported at any desired axial position along the munition 21. The sensors 24 may be fixed to the support 40 using any known technique and may be angularly spaced apart between 90 and 180 depend ing on the configuration and positioning thereof in an associated munition. In the illustration of FIG. 1 the sensors 24 are spaced apart 90, placed an equal distance from their reference axis 41, and supported by the support 40 in a plane arranged perpendicular to the coinciding

axes

22 and 41.

The sensor 24 is in the form of a magnetically controlled sensor and comprises a magnetic member in the form of a spherical member or ferromagnetic ball 43 which is carried within housing means comprised of a member 44 which has a volume 45 which is greater than the volume of the member 43 and such volume allows unobstructed movement of the member 43 within housing member 44, see FIGS. 2 and 3. The member 44 illustrated in FIG. 2 of the drawings comprises a right circular cylindrical sidewall 46 and a substantially planar end wall 47 which is arranged parallel to and opposite a substantially planar wall 50 comprising the housing means and in this example is formed as an integral part of the support 40. However, the wall 50 need not necessarily be provided as an integral part of the support 40 and may be provided either as a separate member or as a part of housing member 44.

Electrical signal means in the form of an electrical device 51 is supported by the support 40 and the electrical device 51 includes a magnet 52 which is capable of exerting an attractive force against the ball 43 which is less than the weight of such ball and for a purpose which shall be apparent subsequently. The device 51 is a noncontact electrical device which provides an electrical signal therefrom when the ball 43 is in a centered condition essentially as illustrated for the top sensor 24 in FIG. 2. The manner in which each sensor 24 provides an electrical output signal through its associated line, either

line

26 or 27, upon centering of its associated magnetic ball 43 is well known in the art and hence will not be described in detail. Basically, all that is involved is that once the ball 43 is centered with respect to certain elements of the electrical device 51, magnetic and/or electrostatic fields surrounding the device 51 is altered thereby changing the effects of the device 51 on a control device (not shown) connected thereto.

The sensors 24 are angularly spaced apart 90 about the reference axis 41 and spaced an equal distance, indicated at 53, from such axis. Further, the AND logic component requires that signals be provided simultaneously from both sensors 24 in order to arm the munition 21 and this is only possible under conditions of sustained free fall. During ground handling the magnet 52 associated with each sensor 24 does not have sufficient strength to attract its ball 43 to the required centered position and must rely on orientation of the associated housing to help achieve centering. However, the

angular spacing of the sensors 24 assures that there is no handling condition where it is possible to center both balls 43 within their associated housings simultaneously whereby the munition 21 utilizing control apparatus 20 may be handled with optimum safety.

The detailed presentation will now proceed to highlight the manner in which the construction and arrangement of the sensors 24 will afiect the sensitivity of the apparatus 20 during normal handling thereof and particular reference is now made to FIG. 8 of the drawings which illustrates a single sensor 24 having a magnet which is capable of exerting a 0.5 g. force. The sensor is shown with its opposed parallel planar or flat walls initially arranged horizontally and with gravity acting vertically in a direction as indicated by the arrow G. The sensor 24 provides an effective output signal when it is moved through a 60 are indicated at 54 when it is arranged beneath its reference axis 41 and on either side of the vertically acting force of gravity g. The sensor of FIG. 8 also provides an effective output signal when it is arranged above the reference axis 41 and through an angle of 60 which will be designated by the reference numeral 55. The orientation of an associated munition so that a single sensor 24 would be placed in a position between the angles indicated at 54 and 55 would result in such sensor being in areas where it would be possible for the sensor to provide an efiective electrical arming signal to the munition whereby the sensor would be in areas popularly referred to as go" areas. The placement of a single sensor 24 within

angles

56 and 57 in FIG. 8 would result in such sensor being in areas where it would be impossible to provide an effective electrical arming signal from such sensor whereby the sensor would be in areas popularly referred to as "no go" areas.

However, the improved apparatus 20 shown in FIGS. 1 and 2 uses two sensors 24 spaced 90 apart whereby it is impossible to provide simultaneous centering of the balls 43 within their associated housing means during normal handling and this is highlighted in FIG. 10 of the drawings. In particular, the force of gravity acting on balls 43 is depicted as an arrow G initially acting vertically downwardly through the reference axis 41. Different orientations of the control apparatus 20 and hence munition 21 may be considered merely by considering the force of gravity as acting radially outwardly in different directions through 360 about axis 41 and this may be readily visualized by considering the shaded go" areas of FIG. 10 as remaining stationary while simultaneously rotating the arrow G and both sensors 24 whereby under no condition is it possible for both sensors 24 to provide output signals in a simultaneous manner therefrom. In particular. it is seen that for every instance where one sensor is in a go" area the other sensor is at least 30 away from "go" whereby for two sensors 24 having housing means comprised of right circular cylindrical sidewalls and planar end walls arranged in parallel relation the 90 separation represents optimum spacing to assure safe handling of the munition 21.

The utilization of only two sensors 24 spaced 90 apart enables easy installation of such sensors at precise positions away from the reference axis of the associated safing and arming apparatus and avoids the complications of attempting to install such sensors on such reference axis and coincident with the spin axis of an associated munition as is required by some systems in an efi'ort to provide the associated system with omnidirectional capabilities. Further, if an apparatus 20 could be installed so that its reference axis 41 coincided exactly with the spin axis 22 of a munition 21 such apparatus would be effective in arming the munition 21 during sustained free fall conditions even with the munition 2I spinning at comparatively high speeds about its spin axis 22.

As a practical matter, there will be some spin ofa munition 21 about its axis 22. If the axis 41 of the control apparatus 20 coincides exactly with the spin axis 22 the dominating force is centrifugal, as illustrated by the arrow 60 in FIG. 9, and is normal to the opposed end walls of each sensor 24 whereby it has virtually no effect on the centering of the associated ball 43. However, if the reference axis 41 and spin axis 22 are misaligned or spaced apart by an exemplary distance as indicated at 61 in FIG. 9 the centrifugal force 60 has a component 62 which tends to move the ball 43 within the housing means of its associated sensor away from the center and may thereby prevent the generation of a valid arming signal. Obviously. this objectionable condition may be avoided by utilizing special sensors constructed and arranged in accordance with the teachings of this invention and which will be described subsequently.

Reference is now made to FIGS. 5, 6, and 7 of the drawings wherein in each Figure a sensor is illustrated which is very similar in operation and construction to the sensor 24; therefore, each sensor of FIGS. 5-7 will be designated generally by the reference numeral 24 followed by a different letter designation for each different Figure and parts of the sensor in each Figure which are very similar to corresponding parts of the sensor 24 will be designated by the same reference numeral as in the sensor 24 followed by an associated letter designation and not described again. Only those parts of each sensor which are substantially different from corresponding parts of the sensor 24 will be designated by a new reference numeral also followed by an associated letter designation and described in detail. Thus, the sensors of FIGS. 5, 6, and 7 will be designated by the

reference numerals

24A, 24B, and 24C, respectively. Further, the sensors 24A-C may be used in the control apparatus 20 illustrated in FIG. 1 in lieu of the sensors In general, it will be seen that each sensor 24A-C has housing means comprised of a right circular cylindrical sidewall and dishlike or dished end walls arranged at opposite ends of an associated cylindrical sidewall with the dishlike end walls of a particular sensor having substantially identical configurations. Further, each end wall comprising the housing means of each

sensor

24A, 24B, and 24C is provided with an inclined peripheral portion which is preferably inclined at an angle ranging between I and 12 with respect to a plane extending perpendicularly through a central axis of the associated cylindrical sidewall and the manner of establishing the degree of inclination of the peripheral portion will be described in detail subsequently.

The sensor 24A is illustrated in FIG. 5 and is comprised of housing means or a housing 44A defined by a right circular cylindrical sidewall 46A and substantially identically contoured

end walls

63A and 64A arranged at opposite ends of the cylindrical sidewall 46A with end wall 64A and sidewall 46A being by way of an example made as a single member. The end wall 63A is dished or convex generally inwardly toward the center of the housing 44A while the end wall 64A is dished or convex generally outwardly from the center of such housing.

Each

end wall

63A and 64A has a planar central portion of circular outline designated in each instance by the reference numeral 65A and a substantially frustoconical peripheral portion 66A. The electrical signal device 51A for sensor 24A is provided in the central portion 65A of wall 64A.

The sensor 248 is illustrated in FIG. 6 and is comprised of housing means or a housing 443 defined by a right circular cylindrical sidewall 46B and end walls 678 and 70B of substantially identical configuration. In particular, each wall 678 and 70B is substantially arcuate as viewed in cross section and wall 708 has the electrical signal device 518 for sensor 248 provided in the central portion thereof.

The sensor 24C is illustrated in FIG. 7 and is comprised of housing means or a housing 44C defined by a right circuiar cylindrical sidewall 46C and a pair of end walls 71C and 72C of substantially identical configuration. Each end wall 71C and 72C has a substantially conical configuration. The signal device 51C for sensor 24C is provided in end wall 72C adjacent its apex.

The outer portion of each end wall comprising each sensor is inclined at an angle ranging between l0 and 12 with a plane arranged perpendicular to the central axis through the associated right circular cylindrical sidewall, as previously mentioned, and this inclination tends to compensate for the centrifugal forces tending to move the ferromagnetic ball of each sensor offcenter due to the utilization of sensors as part of a control apparatus which has its reference axis spaced apart from the spin axis of an associated munition. In particular, for each

wall

63A and 64A of sensor 24A frustoconical portion 66A has a corresponding frustoconical inside surface which is inclined between l0"l2 relative to the inside planar surface of planar portion 65A (which is parallel to the above-mentioned perpendicular plane), each

arcuate wall

67 B and 70B of sensor 24B has a corresponding arcuate inside surface which is generally inclined between l0l2 relative to such perpendicular plane, and each conical wall 71C and 72C of sensor 24C has a corresponding conical inside surface which is inclined between 10 l 2". The inclining of at least the peripheral portion of each end wall between 10 and 12 has been determined based upon angularly spacing a pair of identical sensors (whether

sensor

24A, 248, or 24C) between 90 and 100 and with each sensor of a cooperating pair positioned an equal distance from the reference axis of its associated control apparatus. Further, each sensor whether

sensor

24, 24A, 24B, or 24C is arranged so that a radial line from the reference axis coincides with the central axis for its right circular cylindrical sidewall.

The above presentation explains how the sensors may be physically altered to compensate for spin effects when the axis of the munition and the axis of the safing and arming apparatus are spaced apart. However, this physical alteration must be examined to determine its effect during normal han dling ofthe munition.

Accordingly, reference is now made to FIG. ll of the drawings which illustrates a pair of cooperating sensors 24A wherein the force of gravity is shown acting in the direction indicated by the arrow G and each magnet comprising each sensor 24A is capable of exerting a force of 0.5 g. The schematic presentation of FIG. II is similar to the presentation of FIG. It]; however, FIG. II has cross-hatched areas instead of shaded areas which are considered go areas for one sensor 24A and white for the other while shaded areas represent transition areas.

A typical control apparatus such as apparatus 20 would use a pair of sensors 24A mounted 90 apart in the manner illustrated in FIG. I]. In this exemplary presentation the inside surfaces of the peripheral portions of

end walls

63A and 64A are shown inclined at [2 which adds to the sensitive area on each side of vertical, for example, and this is due to the fact that the force component along each angled l2 surface is not greater than 0.5 g., or at 30 to the horizon, until the sensor central line moves through an angle of 42 on either side of vertical.

For a detailed understanding of FIG. ll consider the force of gravity as an arrow G acting downwardly through the lower sensor 24A. Rotating both sensors 24A coupled thereto counterclockwise moves the lower sensor 24A out of the right 42 "go area 73 into the 6 shaded area 74. At this point the upper sensor 24A is moving into the 1 3 shaded area 75 and is l8 away from the cross-hatched or go area 76 whereby there is an 18 safety margin.

In rotating the sensors 24A clockwise, as the lower sensor 24A reaches the closest line of the shaded area 77 the uppe. sensor 24A is within 6 of the area 74 which is considered a critical area because when gravity is acting in area 74 each sensor would be within 3 of a go" condition. Nevertheless, the shaded

areas

74, 75. 77, and 80 are transition areas n t go areas between both sensors being go. Thus, it is seen that during normal handling of a munition having a control system which uses a pair of sensors 24A spaced there is no condition where both sensors 24A would provide a go" signal whereby the associated control system would be considered safe. It will also be apparent from FIG. 11 that increasing the angle of inclination of the inside surfaces of opposed end walls of each sensor 24A to an amount greater than 12 would reduce the safety or "no go" areas and hence would not be considered practical.

The margin of safety may be increased by increasing the distance between a pair of sensors such as sensors 24A and this will be discussed in connection with FIG. 12 of the drawings where the angle of separation between sensors 24A is increased from 90 to l.

In considering the presentation of FIG. 12 is will be seen that the shaded transition area 82 is not critical since it extends through an angle of 16". However, two shaded transition 8 areas indicated at 83 and 84 require further analysis and for this analysis reference is also made to FIG. 13 of the drawings. When gravity is acting as indicated by the arrow G in FIG. 13 the bottom sensor 24A is 8 away from a go condition as indicated at 85. However, in the top sensor 24A it will be seen that the magnet surface is 30 away from a horizontal condition as indicated at 86 while the ball within the member 24A is resting against a surface at 42 to the horizontal plane as in dicated at 87: therefore, in this condition the top sensor must move another l2 to a cross-hatched or "go" area whereby the 8 safety ranges are effectively 20 from "no go" to go," i.e., 8 plus IT. From the above, it is seen that the l00 separation provides maximum safety.

In considering static and fractional G conditions, for exam ple, if the dish angle or inclination of the outer portions of the end walls for each sensor were IS, the 42 angles will be increased to 45 each. Then, in the 100 separation, the two 8 ranges decrease to each and the l6 angle reduces to l0, whereby any efi'ort to increase the most critical area back toward l6 by increased separation would reduce each of the 5 areas equally toward zero. This highlights that in using

sensors

24A, 24B, and 24C, and which have magnets which exert a 0.5 g. force, there should be no attempt to provide increased angular separation between a pair of cooperating sensors to angles greater than l00.

As previously indicated, it is impractical to attempt to place a safing and arming apparatus within an associated munition with its reference axis 41 coinciding exactly with the spin axis 22 of the munition. Thus, in case of a fin stabilized low-drag munition when zero g. sensors are utilized, it is much more realistic to design the sensors so as to offset the detrimental effect of centrifugal forces acting against each sensor and tend ing to move from center its associated ball. This invention provides three

sensors

24A, 24B, and 24C which enable comparatively great misalignment of

axes

22 and 41 without adversely affecting the reliability of the safing and arming system.

Reference is now made to FIG. 14 which presents four curves to highlight that by providing sensors having dishlike end walls essentially as shown for the

sensors

24A, 24B, and 24C and wherein a cooperating pair of each type of sensor are installed essentially as shown in FIG. 2, greater misalignment of the reference axis may be tolerated relative to the spin axis of an associated munition. In particular, it will be seen that each curve is a plot of distance of misalignment ofa reference axis of a control apparatus from a spin axis of an associated munition versus spin about such spin axis in revolutions per second.

Curve 90 is for sensor 24 having its ball initially displaced 0.1 inch from center, curve 91 is for sensor 24 having its ball initially on center, curve 92 is for sensor 24A with its ball initially displaced 0.1 inch from center, and curve 93 is for sensor 24C with its ball located centrally. From these curves it is apparent that a greater displacement of the reference axis ofa control system from the spin axis of a munition is possible using sensors having dishlike end walls of the character illustrated in FIGS. 5-7 of the drawings. Further, and as previ ously described in detail it will be apparent that a control system utilizing sensors 24A-C provides adequate safety during normal ground handling.

Thus, it is seen that this invention enables the utilization of only two magnetically controlled sensors in a control apparatus or system of the character described which are spaced from the reference axis of such control apparatus. Further, the two sensors may be spaced apart between 90 and 100, depending on the detailed configuration thereof. A pair of sensors 24 are preferably spaced apart 90 while a pair of

sensors

24A, 24B, and 24C may be spaced apart between and yet an associated safing and arming, i.e., control, apparatus using a cooperating pair of such sensors provides optimum safety during normal handling and provides reliable arming of the associated munition during sustained free fall while taking into account centrifugal forces acting on the control apparatus.

In this disclosure of the invention each electrical signal device 51A, 51B, and 51C of

sensors

24A, 24B, and 24C, respectively, is shown provided in an associated end wall, However, it will be appreciated that the signal device may merely associate with a particular end wall without being provided therein.

While present exemplary embodiments of this invention, and methods of practicing the same, have been illustrated and described, it will be recognized that this invention may be otherwise variously embodied and practiced by those skilled in the art.

What I claim is:

I. A control apparatus having a reference axis and comprising, a first sensor capable of providing a first electrical signal, a second sensor capable of providing a second electrical signal, and means supporting said sensors an equal distance from said reference axis and in angularly spaced apart relation, said sensors being operatively connected to provide an effective arming control signal only by the simultaneous provision of said first and second signals under conditions of sustained free fall and said sensors being incapable of providing said control signal during normal handling of said apparatus.

2. An apparatus as set forth in claim I in which said supporting means supports said sensors in a plane arranged perpendicular to said reference axis.

3. An apparatus as set forth in claim I in which said sensors are angularly spaced apart between 90 and ISO.

4. An apparatus as set forth in claim I in which each of said sensors comprises, a magnetic member, housing means for containing said magnetic member, said housing means having a volume which is greater than the volume ofsaid member and thereby allowing unobstructed movement of said member within said housing means, electrical signal means carried by said housing means and providing an associated electrical signal upon said member in operative association therewith, and a magnet for moving said member into said operative association, said magnet an attractive force against said member which is less than the weight of said member so that magnetic force from said magnet alone is effective in causing the provision of said associated electrical signal only under said conditions of sustained free fall.

5. An apparatus as set forth in claim 4 in which said member comprises a substantially spherical member and said housing means comprises a substantially right circular cylindrical sidewall having an effective height which is larger than the diameter of said spherical member.

6. In combination: a munition having a spin axis and an apparatus for saflng said munition during normal handling and arming said munition under conditions of sustained free fall, said apparatus having a reference axis and being supported by said munition and comprising, a first sensor capable of providing a first electrical signal, a second sensor capable of provid ing a second electrical signal, and means supporting said ser1- sors an equal distance from said reference axis and in angularly spaced apart relation, said sensors being operatively connected to provide an effective arming signal to said mun tion only by the simultaneous provision of said first and second signals under conditions of sustained free fall and said sensors being incapable of providing said first and second signals simultaneously during normal handling of said munition making it safe to handle.

7. A combination as set forth in claim 6 in which said sensors are angularly spaced apart between 90 and 8. A combination as set forth in claim 6 in which said supporting means supports said sensors in a plane arranged perpendicular to said reference axis.

9. A combination as set forth in claim 6 in which each of said sensors is magnetically controlled and comprises a magnetic member, housing means for containing said magnetic member, said housing means having a volume which is greater than the volume of said member and thereby allowing unobstructed movement of said member within said housing means, electrical signal means carried by said housing means and providing an associated electrical signal upon moving said member in operative association therewith, and a magnet for moving said member into said operative association, said magnet exerting an attractive force against said member which is less than the weight of said member so that magnetic force from said magnet alone is effective in causing the provision of said associated electrical signal only under said conditions of sustained free fall.

10. A combination as set forth in claim 9 in which said member comprises a spherical member and said housing means comprises a substantially right circular cylindrical sidewall having an effective height which is larger than the diameter of said spherical member.

ll. A combination as set forth in claim 9 in which said reference axis is spaced from said spin axis due to routine mounting of said apparatus within said munition and said housing means comprising each sensor comprises a cylindrical sidewall and a pair of dishlike end walls arranged at opposite ends of said cylindrical wall, one of said pair of walls having a surface which is convex inwardly toward the center of its sensor and the other of said walls having a cooperating surface which is concave inwardly toward said center, said housing means being fixed to said supporting means with a central axis through said cylindrical sidewall coinciding with a radial line arranged perpendicular to said reference axis and with said surface in said other wall being concave inwardly toward said reference axis, said surfaces serving to minimize the effect of centrifugal forces acting upon said sensors due to the spacing between said reference axis and said spin axis.

12. A combination as set forth in claim 11 in which said sensors are angularly spaced apart between and and each of said surfaces has an inclined peripheral portion which is inclined at an angle ranging between 10 and 12 with respect to a plane arranged perpendicular to said radial line.

13. A combination as set forth in claim ll in which each of said surfaces is substantially arcua as viewed in cross section.

14. A combination as set forth in claim ii in which each of said surfaces comprises a planar central portion of circular outline adjoined by a substantially frustoconical peripheral portion,

15. A combination as set forth in claim 11 in which each of said surfaces is substantially conical.

16. A combination as set forth in claim 9 in which each of said sensors is sensitive in a plurality of directions in an associated plane and said supporting means supports said sensors with the associated planes of each sensor arranged per pendicular to each other to effectively provide an omnidirectional sensing system using only said first and second sensors

Claims

1. A control apparatus having a reference axis and comprising, a first sensor capable of providing a first electrical signal, a second sensor capable of providing a second electrical signal, and means supporting said sensors an equal distance from said reference axis and in angularly spaced apart relation, said sensors being operatively connected to provide an effective arming control signal only by the simultaneous provision of said first and second signals under conditions of sustained free fall and said sensors being incapable of providing said control signal during normal handling of said apparatus.

2. An apparatus as set forth in claim 1 in which said supporting means supports said sensors in a plane arranged perpendicular to said reference axis.

3. An apparatus as set forth in claim 1 in which said sensors are angularly spaced apart between 90* and 180*.

4. An apparatus as set forth in claim 1 in which each of said sensors comprises, a magnetic member, housing means for containing said magnetic member, said housing means having a volume which is greater than the volume of said member and thereby allowing unobstructed movement of said member within said housing means, electrical signal means carried by said housing means and providing an associated electrical signal upon said member in operative association therewith, and a magnet for moving said member into said operative association, said magnet an attractive force against said member which is less than the weight of said member so that magnetic force from said magnet alone is effective in causing the provision of said associated electrical signal only under said conditions of sustained free fall.

6. In combination: a munition having a spin axis and an apparatus for safing said munition during normal handling and arming said munition under conditions of sustained free fall, said apparatus having a reference axis and being supported by said munition and comprising, a first sensor capable of providing a first electrical signal, a second sensor capable of providing a second electrical signal, and means supporting said sensors an equal distance from said reference axis and in angularly spaced apart relation, said sensors being operatively connected to provide an effective arming signal to said munition only by the simultaneous provision of said first and second signals under conditions of sustained free fall and said sensors being incapable of providing said first and second signals simultaneously during normal handling of said munition making it safe to handle.

7. A combination as set forth in claim 6 in which said sensors are angularly spaced apart between 90* and 180*.

8. A combination as set forth in claim 6 in which said supporting means supports said sensors in a plane arranged perpendicular to said reference axis.

11. A combination as set forth in claim 9 in which said reference axis is spaced from said spin axis due to routine mounting of said apparatus within said munition and said housing means comprising each sensor comprises a cylindrical sidewall and a pair of dishlike end walls arranged at opposite ends of said cylindrical wall, one of said pair of walls having a surface which is convex inwardly toward the center of its sensor and the other of said walls having a cooperating surface which is concave inwardly toward said center, said housing means being fixed to said supporting means with a central axis through said cylindrical sidewall coinciding with a radial line arranged perpendicular to said reference axis and with said surface in said other wall being concave inwardly toward said reference axis, said surfaces serving to minimize the effect of centrifugal forces acting upon said sensors due to the spacing between said reference axis and said spin axis.

12. A combination as set forth in claim 11 in which said sensors are angularly spaced apart between 90* and 100* and each of said surfaces has an inclined peripheral portion which is inclined at an angle ranging between 10* and 12* with respect to a plane arranged perpendicular to said radial line.

13. A combination as set forth in claim 11 in which each of said surfaces is substantially arcuate as viewed in cross section.

14. A combination as set forth in claim 11 in which each of said surfaces comprises a planar central portion of circular outline adjoined by a substantially frustoconical peripheral portion.

16. A combination as set forth in claim 9 in which each of said sensors is sensitive in a plurality of directions in an associated plane and said supporting means supports said sensors with the associated planes of each sensor arranged perpendicular to each other to effectively provide an omnidirectional sensing system using only said first and second sensors.