US2458474A - Centrifugally operated control device - Google Patents

Description

Jan. 4, 1949. J. D. JORDAN CENTRIFUGALLY OPERATED CONTROL DEVICE 3 Sheets-Sheet 1 Filed Feb. 23, 1943 ATTOR EY INVENTOR JAMES D. JORDAN BY %f f Jan. 4, 1949. J, JORDAN i 2,458,474

CENTRIFUGALLY OPERATED CONTROL DEVICE Filed Feb. 25, 1945 5 Sheets-Sheet 2 I//I/I /j w-u( w I ulllll mmm mm&I A

` 68 66 55 INVENTOR JAMES a 'JORDAN 4 Jan. 4, 1949. J. JORDAN 7 CENTRIFUGALLY OPERATED CONTROL DEVICE Filed Feb. 25, 1943 3 Sheefs-Sheet 3 F IG. /0

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"I F ORGE (POUVDS INVENTOR JAMES ,0. JORDAN ATTO NEY Patented `lan. 4, 1949 cEN'raiFUGALLr OPERATED coN'rRoL DEVICE James D. Jordan, Washington, D. Ca, assignor to the United States of America as represented by the Secretary of the Navy Application February 23, 1943, Serial No. 476371 8 Claims.

This invention relates to centrifugally operable control devices and has particular reference to a novel control device which is initially maintained inoperative by centrifugal force and operates upon a decrease in the centrifugal force below a predetermined value.

While the new control device is adapted for various uses, it may be used to particular advantage in the form of a safety switch for explosive projectiles of the rotary type. Accordingly, for illustrative purposes, the invention will be described in the form of a centrifugally controlled switch for this purpose, although it will be understood that the invention may take other forms as well One object oi the invention is to provide a novel control switch having means for securing it against operation due to an initial centrifugal force, but which operates in response to a decrease of the centriugal force. A switch made in accordance with the invention comprises a movable contact and means normally biasing the movable contact toward a fixed contact and operable by centrifugal force to move it away from the fixed contact. Closing of the Contacts is normally prevented by an element which is rendered inoperative when the movalole contact is initially actuated by centrifugal force. According'ly, when the centrifugal force diminishes sufficiently to allow the biasing means to return the movable contact toward the fixed contact, the Contacts are closed to operate an electrical device.

Another object of the invention resides in the provision of a novel centrifugally operated switch for automatically closing 'the circuit to a projectile detonator after the projectile has tra versed the useful part of its trajectory but before it is dangerously close to the earth.

A further object of the invention is to provide a switch operable by centrifugal force for use in measuring the muzz'le velocity of a projectile.

These and other objects of the invention may be better understood by reference to the accompanying drawings, in which:

Fig. 1 is a transverse sectional View of one form of the new control device for use in a rotary projeetile;

Fig. 2 is a sectional view on the line 2--2 in Fg. 1;

Fig. 3 is a transverse sectional View of part of the device shown in Figs. 1 and 2;

Fig. 4 is a plan view of another part of the device in one stage of its manufacture;

Fig. 5 is a side view of the part shown in Fi 4 after it is bent into final form;

Fig. 6 is a perspective view of one of the switch Contacts;

Fig. 7 'is a plan view, partly in section, of a modified form of the device;

Figs. 8 and 9 ar'e'sectionalviews on the lines 8--8 and 9- 9, respectively, in Fig. 7, and

Fig; 10 is a chart illustrating the operation of the device.

The control device in Figs. 1 to 6, inclusive, comprises a cylindrical housing made of metal or of an insulating material, such as lucite, the housing having a body 2! recessed in its `rear face, and a disk 22 secured to the rear face of the body and forming a covrfor the' recess. The cover may be secured'toathe body in any desired manner, and by means of studs 23 and 24 ex`- tending through the body and the cover and held by screws' %a and 2411 threaded into the studs. A shaft 25 extends :through 'the recss axially oi the housing and is seated at its ends in the body 2| and the cover. Rotatably mounted on the shaft 25 is a rotor arm 26 having -a central opening through'which the shaftextends. The arm is provided at its ends with rearwardly extending cars 21 and 28 inclined* at an angle to the longitudinal axis of the arni, as shown in Fig. 4, and having elong'ated openings 2'la and 28a, respectively.

A sprin .323 is coiled around 'the stud 23 in the housing recessand terminates at one'end in a leg 3! extending through the opening 21a in the rotor arm, thatis, through the ear of the' rotor armwhich is remote from the spring. The other end of the spring terminates in a leg 32 projecting along one side of the recess and confined between the bottom of the recess and the end of a cylindrical guide ss secured to the cover 22 by a screw 734. Due t o the tension in the spring 30, the leg a normally exerts a thrust on the rotor arm tending to move it in 'a clockwise direction and the force of the' thrust maybe adjusted by a screw' 35 threaded in the side' wall of the housin and engaging the leg 32 in a cutaway portion '36 of the cylindrical guide. By turning the screw 35, the position of the spring leg 32 may be varied so as to adjust the tension in'the spring' and the thrus't on the rotor arm 26. Diametrically opposite the spring 30' is a similar spring 38 coiled around the stud 24. One leg 39 of the spring 38 'extends through the rotor opening 28a, that is, through the ear 28 which is re'- mote from the spring 38. The other springleg 40 extends along the side 'of the recss and is confined between the bottom of the recess and the end of a cylindrical guide 4l. The leg 39, due to the tension in spring 38, normally exerts a thrust on the rotor arm tending to rotate it in a clockwise direction, and the force of the thrust may be adjusted by a screw :22 engaging the spring leg :29. i

The ree end of the leg 39 constitutes the movable contact of a switch having a cooperating fixed contact 4 5. The contact M has a base secured to the cover 22, and an arm 45 extending at right angles to the base through the housing.

recess and embedded in the bottom of the recess. A notch 43 is ormed in the contact arm 35 opposite the free end o'f spring arm 39, and the latter is provided with an insulating element ll normally held in the notch by the thrust of spring leg 39. The insulating member 41 fits loosey in the end of leg 39 and prevents ciosing of the switch by maintaining the leg 39 in spaced relation toxthe contact 9:2.. It will be apparent that clockwise rotation of the rotor 26 (Fig. 1) is limited by engagement of insulator 4'1 with contact arm 95.

A terminal plug 49 is connected through the insulating cover 22 to contact 44 and is adapted to ,be received in a terminal socket of an electrical detonating means (not shown) for the projectile. Thus, the switch is connected through the plug 49 in a detonating circuit including a battery 50, the detonator (not shown) and a wire 5! electrically connected to the spring leg 39 through shaft 25 and rotor arm 26.

Because of its cylindrical shape, the housing 20 may be readily fitted into the cylindrical casing of the preje-stile. The detonator circuit is normally broken by the insulating element 47 on the free end of the switch contact formed by the spring leg 39. The thrust of the leg 39 due to the tension in the spring Wedges the element 41 into the notch 45 of the fixed contact, so that the insulating element cannot be accidentally displaced due to rough handling of the projectile. When the gun is fired, the projectile attains a high rate of spinningin the gun barrel, and the resulting centrifugal force on the spring legs 3| and 39 overcomes the spring thrust of these legs and moves them outwardly from the axis of rotation of the projectile,-which corresponds to the shaft 25. As a re sult, the spring legs move to the position shown in dotted lines in Fig. 1 and rotate the arm 26 counterclockwise to the position shown in dotted lines (Fig. l). The outward movement of the spring legs is limited by a screw 52 forming an adjustable abutment for the leg 39, and when this leg engages the abutment 52 the free end of the leg lies opposite an enlargement 53 of the housing recess. When leg 39 engages abutment 52, the action of centrifugal force on the insulating element i? moves the element off the end of leg 39 into the recess extension 53. As the projectile continues its flight, the rate of its spin decreases and when the centrifugal force on legs 3! and 39 decreases to the point where it is overcome by the spring thrust of the legs, the legs snap the rotor arm 26 clockwise toward its starting position. However, since the insulating member 4'! is no longer on the free end of spring leg 39, the latter moves beyond its initial position` and is wedged in the notch 46 of contact arm 45, where it is held by the thrust of the spring legs 3! and 39. As a result, the switch is closed and causes energizing of the detonating circuit so as to explode the projectile.

It will be apparent that as soon as the centrifugal force on the spring legs 31 and 39 is suiciently great to overcome the biasing force of the springs, the legs move outwardly with a snap action, since the centrifugal force on the legs increases as the legs move away from the axis of rotation at the shaft While the biasing force of the spring legs also increases, due to distortion of the springs, as the legs move outwardly under centrifugal force, the rate of increase of the biasing force is -not as great as the rate of increase of the centrifugal force on the legs. When the rate of spin of the projectile decreases so that the centrifugal force on the spring legs 31 and 39 is overcome by the biasing tension in the springs, the latter return to their initial positions with a snap action, since the centrifugal force on the spring legs decreases faster than the biasing tension in the springs as the legs move toward the axis of rotation. Thus, the switch contact formed by the free end of the spring leg 39 moves in both directions with a snap action so that uttering of the switch is prevented. By employing two springs 30 and 38 on opposite sides of the axis of rotation, I provide automatic compensation for any off-center rotation of the device.

Referring now to the chart shown in Fig. 10, the abscissae are the radial distances of the spring legs 35 and 39 measured from the axis of rotation 25, O on the chart, and the ordinates are the centrifugal and the spring biasing forces on the legs 3i and 39. The vertical line from the point Ro on the abscissa represents the normal positions of the spring legs 3! and 39, and the line AD represents the increase in the spring biasing tension on legs 3! and 39 as the legs move from their normal positions to their outermost positions at R, the slope of the line AD being the spring constant in pounds per inch of deection. The inclinecl lines radiating from the point 0 represent the centrifugal force acting on the spring legs 3| and 39 at different rates of spin of the projectile and for different positions of the legs with reference to the axis of rotation O. With the projectile at rest, the spring legs are held in their normal position at Ro with a spring biasing force equal to OA measured vertically. Assuming that the muzzle spin of the projectile is 200 revolutions per second, the centrifugal force on the spring legs 3| and 39 is in excess of the spring tension by an amount represented by AB, and the legs move away from the axis of rotation to the stop 52 at Ri, the spring tension in this position of the legs being represented by RD. The rate of spin now decreases, and as soon as it falls to R. P. S. the centrifugal force becomes equal to the spring tension. Accordingly, a further reduction in the rate of spin leaves the springs with a tension greater than the centrifugal force, so that the spring legs start back toward the axis of rotation. As the radial distance R decreases, the excess of spring tension over centrifugal force increases so that the spring legs return to their initial position at Ro with a snap action. The area of the triangle ADE is a measure of the kinetic energy of impact When the switch is closed by return of the spring legs, and the distance AE represents the force holding the switch Contacts together at the instant they close. The total area under the line FD is a measure of the total resilience of the springs when defiected to their outermost positions, and the area Ro ADR represents the energy required to deflect the springs from their initial positions at Ra to their outer positions at R. The device may be cali- 'brated by exerting the proper force against the spring legs- Bl and 39, as by the use of a weight or other suitable means, and then adjusting the screw 52 to touch the leg 39.

It has been found .that a 5"/38 caliber projectile usually does not rotate about an axis greater than .01" from the projectile's geometric axis, and, thereiore, RI in the above analysis might vary im". I-iowever, the distance OR would normally be of such length that the percentage error due to this deviation is of no consequen'ce It should be noted that the angular deceleration of a projectile at the higher altitudes is less than at the lower altitudes, due to the decreased air resistance to its spin at the higher altitudes, and, therefore, the projectile has a more or less constant spin when it returns to earth, regardless of the angle of fire. Accordingly, if the device of my invention is made to operate at a predetermined rate of spin occurring at a safe altitude, there is no necessity for making it adjustable by means oi the screws 35, 42, and 52. However, the new device lends itself admirably to such adjustnient if it is desired. The adjustment could be accomplished in a uze setter by means of a cam operable to shift the screw 52 (R in Fig. or change the pre-tension on the springs 32 and 38 by shifting the screws 35 and 42.

The modified form of the device shown in Figs. 7, 8, and 9 comprises a housing 54 adapted to be received in a projectile casing and made up of a body 55 having an elongated recess 5511. in its rear face near one side, and a cover 56 for the recess. The cover 56 is Secured to the body 55 by headed studs 51' extending through the body and held by screws 58 in the cover, one of the studs being disposed near one end of recess 55a.

A spring E@ is coiled around the stud 51 and terminates at its front end in a leg Gi extending along the' side of the'recess adjacent the periphery of the body 55. -The position of leg Bl, and therefore the tension in spring 66, may be adjusted by means of a screw 52 threaded through the side wall of body 55 and engaging the leg. At its free end position, the leg El is confined between the bottom of the recess 550 and a guide bar 63 extending across the recess, whereby the leg is maintained 'in line with adjustment screw 62. The rear end of the spring terminates in a second leg 64 extending longitudinally of the recess adjacent the cover 56.

' The free end of spring leg 64 forms a movable switch contact coacting with a fixed contact 66 secured to the cover Et. The contact 66 projects into recess 55a and has an arm 61 extending across the recess and embodied in the bottom thereof. Intermediate its ends, the arm 61 is formed with a notch 68 which normally receives an insulating element 69 loosely mounted on the free end of the spring leg 54. The insulating element ta prevents closing of the switch 64, 66 and is normally wedged in the notch 68 by the biasing force of spring 60, so that the switch cannot be accidentally closed by displacement of the element 89 due to rough handling of the device.

A terminal plug 'lo on the cover 56 is electrically connected to the fixed contact 66 and is adapted to be received in a suitable socket for connecting the switch in circuit with a battery and a detonator (not shown). The circu't may be completed through a socket 'H in the body 55 electrically connected through a suitable conductor (not shown) to the spring leg 64.

In operation, when the projectile is fired from a gun, the high rate of spin acquired by the projectile as it moves through the rifled gun barrel results in a centrifugal force on the spring leg 6 3 which moves the leg outwardly against the :biasing force of the spring and away from the aXis of rotation of housing 54. Since the centrifugal force on the leg 64 as it moves outwarclly increases at a greaterrate than the blasing tension of the spring, the leg moves outwardly with a snap action. The outward movement of the spring leg te may be limited by a suitable abutment, such as an adjusting screw 73 threaded through the side 'wall of the body 55. When the insulating element te is withdrawn from notch 68, due to outward movement of the spring leg, the element moves on the free end of the spring leg under the action of the centrifugal force. Accordingly, when the rate of spin of the projectile decreases to the point where the centrifugal force on spring leg til is overcome by the biasing tension in the spring, the leg sa moves back toward contact 66 and closes the switch byengagement with the arm Bl. As the leg G i moves inwardly, the rate of decrease of the centrifugal force on the leg is greater than the rate of 'decrease of the biasing tension of the spring, and, therefore, the switch is closed with a snap action. The biasing tension in the spring Wedges the free end oi' leg se in the notch 53 so as to prevent accidental opening of the switch due to vibration, or the like. If the energy required to defiect the spring from its initial position is in excess of the kinetic energy acquired by dropping the device a distance of 40 feet, the device can be prevented from Operating accidentally without the use o'f a safety pin actuated by set-back.

The control device of my inVentio-n is simple and compact in Construction, includes relatively few moving parts, and is positive and reliable in operation. While I have described and illustrated the new device in the form of a switch for a seif-'destruction circuit in a projectile, it will be understood that the device may be used 'for other purposes as well. For example, the movable spring leg or legs may be arranged to open asquib unshorting device instead of closing a selfclestruction switch, or to trigger a ring pin. Also the device in the form illustrated may be used as annstrument for indicating the muzzle velocity of a gun. More particularly, since a projectile may be considered as being geared to the rifiing of a gun barrel while it passes through the barrel, the rate of spin of the projectile at the muzzle is proportional to the projectile's linear velocity. The device of my invention may be set to explode the projectile when it attains a predetermired rate of spin, and if the initial muzzle velocity is low, as occurs with a worn gun, the initial spin will be low and the elapsed time between firing and bursting will be correspondingly low. By using a stop watch to measure this elapsed time and plotting a -curve to show the relationship between time and muzzle velocity, the muzzle velocity of the gun may be determned. Knowledge of the muzzle velocity of the gun is desirable in the field to'permit correction of the trajectory so that the projectile will hit the target. The advantage of my control device when used in this manner is that no auxiliary equipment is needed. Even when the position of the gun is isolated, a box of fuzes containing the new device could always be kept near the gun for periodic checks on the muzzle velocity as the gun wears.

I claim:

1. In an initially inactive, oentrifugally operated, and automatically activated electrical switchthe combination with a fixed contact, of a movable contact having a separable insulator in frictioral engagement with the fixed contact, and yieldable activating means constantly tending to maintain said engagement, whereby the movable contact is operated to separate the insulator, and at deceleration of centrifugal force the movable contact is automatically moved into electrical connection with the fixed contact.

2. In an initially open, centrifugally operated and automatically closed electrical switch, the combination with a fixed contact, of a resiliently mounted movable contact and a separable insulator thereon in frictional engagement with the fixed contact, whereby the movable contact is operated to separate the insulator, and at deceleration of centrifugal force the movable contact automatically moves into electrical connection with the fixed contact.

3. In an initially open, centri-fugally operated and automatically closed switch, the combination with a fixed contact, of a pivoted rotor-arm and a movable contact operable therewith, a separable insulator mounted on the movable contact and in frictional engagement with the fixed contact, and resilient means c-o-acting with said arm constantly tending to maintain said engagement.

4. A safety clevice for rotary projectiles which comprlses an open switch including a movable contact and a fixed contact, means constantly basing the movable contact into engagement with the fixed contact, and said means actuated by centrifugal force to disengage the contacts, and an insulating element initially disposed between the contacts to secure the switch against closing and movable to an inoperative position on centrifugal actuation of said !biasing means.

5. An initially open, centrifugally operated and automatically closed electrical switch for a rotary projectile, which comprises a body, a fixed contact and a movable contact in the body, a spring for biasing the movable contact toward the fixed contact and operable by centrifugal force to separate the Contacts, and an insulated element co-acting with and normally securing said contacts against electrical connection and rendered inoperative upon movement of the spring by centrifugal force, whereby the spring causes the Contacts to engage upon a decrease in the centrifugal force.

6. A control device for a rotary projectile,

which comprises a body rotatable by the spin of the projectile, a rotor -piVoted on the axs of ro'- tation :of the body and having arms projecting laterally from said axis, a pair of springs mounted in the body connected to the rotor arms and normally biasing the rotor in one direction, the springs being operable by centrifugal force to turn the rotor in the opposite direction, an open switch including a fixed contact, and a movable contact operatively connected to the rotor and normally biased by the rotor toward the fixed contact, and an insuating element carried by the movable contact and movable to an inoperative position on actuation of the springs by centrifugal force, whereby the springs close the switch on reduction of the centrifugal force.

7. An initially open control switch for projectiles, which comprises a body, a rotor-arm in the body, a fixed contact, a spring having an operating leg forming a movable contact and connected with the rotor-arm, and an insuating sleeve mounted on said leg and dis-placeable there-from, the spring normally urging the leg toward the fixed contact for retainng the sleeve in engagement with said fixed contact, the spring and arm being movable on rotation of the body for displa-cing the sleeve from the leg, and the spring being operazble to engage the Contacts upon a. reduction in the speed of rotation of the body.

8. In an open centrifugally operable and automatically closed switch for a rotary pro jectile, a fixed contact, a movable contact, and means movable by centrifugal force for initially Shifting the movable contact from initially open position to a second open position, and automatic means for returning the movable contact to closed engagement with the fixed contact upon a decrease in the centrifugal force.

JAMES D. JORDAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,098,226 Charter Nov. 9, 1937 FOREIGN PATENTS Number Country Date 376,987 Italy Sept. 4, 1939

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