Self-leveling Anti-disturbance Device

Abstract

A normally open self-leveling anti-disturbance device which includes a base having a generally hemispherical recess and closed by a cover or lid provided with an outwardly directed hemispherical protuberance for providing a hemispherical channel between the cover and the base. The surface of the recess is provided with a conducting coating which is divided into two separate electrical circuits by etching. The circuits are physically isolated by a continuous serpentine-like raised narrow rib which is formed with a central insulated crack or depression. A metallic sphere is disposed within the channel and is free to translate therein. When the device is moved or disturbed the sphere will move across the raised rib and in so doing will temporarily short the two circuits. In its normal or undisturbed position the sphere will contact only one of the circuits. There is also provided a plurality of bumpers or deflectors to prevent the sphere from translating only within the clear paths between the adjacent portions of the isolating rib.

Description

The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION

The present invention relates to an anti-disturbance device and more particularly pertains to a self-leveling, anti-disturbance device whose parameters and characteristics may be selectively varied while retaining the inherent self-leveling feature.

In the field of anti-disturbance mechanisms, it has been the general practice to employ standard anti-disturbance devices and to physically level the device when it is actually employed or emplanted. In general, for an anti-disturbance device to function properly it must be leveled in order to provide a uniform overall sensitivity. One such present component includes a gooseneck that is incorporated into mine systems to provide for manual leveling to compensate for a variety of terrains. These prior art devices inherently add to the cost, to the time involved in the physical emplacement and are sensitive to the extreme military environments encountered in the field. Clearly, the number of moving parts of these present devices all introduce operational limitations and increase the cost of manufacture even when produced in large quantities. Although it is desirable to use a normally open circuited anti-disturbance apparatus, those now available do not in general possess this unique property. The present invention fills these apparent needs.

SUMMARY OF THE INVENTION

The general purpose of this invention is to provide an anti-disturbance device that has all the advantages of similarly employed prior art devices and has none of the above described disadvantages. To attain this, the instant invention provides a unique arrangement wherein a base having a hemispherical recess whose surface has been coated or etched with a pair of conducting areas separated a by serpentine narrow raised rib. The rib is formed with an etched channel extending lengthwise thereof thus electrically isolating the circuits. Raised deflectors are also provided in order to prevent the metallic sphere disposed on the surface from limiting its travel only along one circuit. The base is closed across the hemispherical recess by a cover formed with a hemispherical protuberance so that the sphere will be confined to translate therebetween. In use the subject device is self-leveling in that the sphere will assume an initial stationary position on the hemispherical surface in contact with only one of the surfaces. Upon being disturbed, the device will deflect from its initial position and cause the sphere to translate over the rib and as it passes over the depression it will momentarily and simultaneously contact both circuits.

An object of this invention is to provide a simple, economical, reliable and normally open circuited anti-disturbance device.

Another object is the provision of a self-leveling anti-disturbance device characterized by its employment of only one moving part and which is insensitive to extreme military environment.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of an embodiment made in accordance with the principle of this invention;

FIG. 2 is a view of the embodiment taken approximately along 2--2 of FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken approximately along 3--3 of FIG. 2;

FIG. 4 is a schematic diagram of an external electronic sensor which may be employed in conjunction with the anti-disturbance device of the present invention.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT

In the illustrated embodiment of FIG. 1 an insulating base 10 is formed with a central hemispherical recess or depression 11 which is closed by a cover 12 that is provided with a complementary generally hemispherical protuberance 13 thereby forming a semi-spherical space 14 therebetween. Disposed for movement within space 14 is a metallically surfaced contact sphere 15 which is free to roll therein. The surface of the recess 11 has deposited thereon an electrically conducting layer 16 which is physically divided into a pair of conducting surfaces 17 and 18 forming separate contact circuits. These circuits are best illustrated by way of FIG. 2 where the circuits 17 and 18 are physically separated by a serpentine channel 19 extending through the layer 16 and into the base 10. An insulator strip 20 is disposed on the base of the channel 19. A relatively simple structure would encompass a base 10 of a material that is an electrical insulator and whose surface is coated with a conductive layer except along a line dividing the circuits thus created. The spacing between adjacent linear sections of the channel 19 is sufficient to permit the sphere to translate therealong and thus create a path. If the entire hemispherical recess surface where uniform or smooth the metallic sphere could readily come to rest directly on the channel 19 and since the width of the channel 19 is extremely narrow, the circuits would be short circuited by the sphere. For this purpose, and to alleviate such a problem, the area of the surface immediately adjacent the channel 19 is raised to form a longitudinally extending raised rib 21. The raised rib, thus not only insures that the sphere will not position itself directly on the channel 19 but, also that the sphere requires a certain amount of energy to cross over the rib. In so doing it momentarily shorts the two circuits. This energy is provided by movement of the base or disturbance thereof. Upstanding bumpers or deflectors 22 are formed in regions along the conductors 17 and 18 in order to prevent the sphere, when in motion, to limit its translation to a path only along each conductor and not transversely. Each circuit terminates in a connector strip 23 and 24 which is provided with a wire 25 and 26 or the like for external connection to a control or switch means responsive to the momentary shorting of the circuits.

FIG. 3 shows in detail a cross section of a typical raised rib 21 and the sphere 15 in two positions. As the sphere rolls under a disturbing deflection along a path intermediate the adjacent portions of the rib 21 it remains in contact with circuit 18. If it has sufficient energy it will climb over the rib and at one point along its motion it will assume a position of straddling the channel 19 and simultaneously contact both circuits.

The particular circuit design configuration of the anti-disturbance device described hereinabove provides relatively uniform sensitivity over the full effective area. The following calculations indicate that for the different or possible travel paths of the sphere, the energy (deflection of the device) required for activation varies but for all situations where the device would be employed, this difference in sensitivity results in only a negligible effect. The sensitivity of the specific embodiment can be calculated as follows:

1. Since the anti-disturbance device must conform to Military Specifications it is assumed that a stainless steel sphere (MS 19060 grade 10) having a diameter of 0.1875 inches and a density of 0.284 lbs/in.sup.3 so that its weight is:

wt = 0.5236(0.1875).sup.3 .times. 0.284 .times. 454 gm/1b = gms = 0.445 gms

by goldplating the sphere its total weight becomes:

wt = 0.4445 + 0.0321 = 0.4766 gms.

2. Assuming the raised strip is 0.002 inches high then the energy required to lift the sphere over the strip in ergs (dyne/cm) is:

Height .times. weight = energy

[0.002 .times. 2.54] .times. [0.4766 .times. 981] = 3.56 ergs.

3. Assuming the maximum clear distance 0.459 cms of travel for the sphere and an activation tilt angle of 1.degree.19' then the energy is:

[sin 1.degree.19' .times. 0.459] [0.4766] .times. 981 = 6.8 ergs.

It should be noted that for the highest or maximum sensitivity the amount of energy for the sphere to travel over the 0.002 inch strip is 3.56 ergs.

Since the anti-disturbance hereinbefore described is normally in the open circuit condition an external electronic sensor as shown in FIG. 4 can be employed in conjunction therewith. Upon activation of the device which is effectively, the equivalent, of a switch 40, transistor device 41 commences conducting and the other transistor 42 ceases conducting. This in sequence turns the silicon controlled rectifier 43 "on" thus providing a signal for the indicator 44 which may be of the visual type. Analyzing the circuit it is evident that the shorting of the anti-disturbance circuit need not be a low resistance since any contact resistance encountered will be insignificant with respect of the resistance of resistor 45 and the input resistance of transistors 41 and 42.

I wish it to be understood that I do not desire to be limited to the exact method and detail of construction described for obvious modification will occur to persons skilled in the art.

Claims

I claim:

1. A self-leveling anti-disturbance device comprising:

a. a base member of electrically insulating material having a generally hemispherical recess formed therein, the surface of said recess being formed with a continuous serpentine raised rib extending entirely across said recess and having a relatively-narrow central channel along its entire length, the surface of said recess including said rib but excluding said channel being coated with electrically conducting material to form two separate conducting coatings isolated by said channel;

b. an electrical conductor connected to each of said coatings for external connection therewith;

c. a cover formed with a hemispherical protuberance disposed across and closing said base member to provide a hemispherical space therebetween;

d. a sphere, having an electrically conducting coating, disposed in said space for translation therein;

said channel having a width to permit said sphere to simultaneously contact both of said conducting coatings, and the portions of said surface adjacent to said channel being tapered upwardly toward said channel; whereby said sphere will initially assume a rest position in contact with only one of said coatings, and upon being disturbed said sphere will move across said rib and channel and momentarily short circuit said coatings.

2. The device as in claim 1, wherein adjacent portions of said channel are spaced apart a distance greater than the diameter of said sphere.

3. The device as in claim 2, further comprising a continuous insulator strip disposed on the base of said channel.

4. The device as in claim 1, further comprising upstanding bumper means for preventing said sphere, when in motion, from limiting its translation to a path only along each coating instead of transversely thereof.

5. The device as in claim 1, wherein said coatings are etched on said surface.