Inertia type switch having bridging ball contactor and plural, concentric conductive ring array

Abstract

A device responsive to acceleration in any direction in which a ball rests on an upwardly facing seat in a housing and is moveable laterally on the seat when acted on by a predetermined force of acceleration. When the ball moves laterally on the seat an electric circuit is completed which can be employed for signalling or control purposes. One of the preferred embodiments consists of a bridging conductive ball engaging a plural, concentric conductive ring array.

Description

The present invention relates to an acceleration and retardation responsive electric control device which is intended preferably for installation in vehicles, especially motor vehicles, airplanes, ships, and the like, and which is provided with a ball acting as mass inertia body and movable from its stabile rest position to different sides when the acceleration or retardation exceeds a predetermined fixed minimum value, the control device cooperating with at least one electric contact which is arranged in spaced relationship to the ball when the latter is in its rest position.

Control devices of this type are frequently employed for quickly and safely initiating the winding-up of automatic systems of safety belts in case of danger when the vehicle which is equipped with such safety belts is subjected to a certain limit acceleration or retardation. Devices of this type are frequently called sensors.

It is an object of the present invention to provide a simple and safely operating control device of the above mentioned general character in which the limit value of acceleration or retardation is adjustable at which the control operation is to be initiated.

It is a further object of this invention to realize a control device as set forth in the preceding paragraph in which the control function will equally well be assured in all directions in the horizontal or at least approximately horizontal plane.

A still further object of the present invention consists in that when the device according to the invention is fixedly installed in motor or rail vehicles, the device will, when the vehicle is driven over inclines or in inclined position, not show any material deviation as to its control precision over situations in which the vehicle is driven on horizontal planes.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a sensor according to the present invention which shows the fundamental principle of the invention.

FIG. 2 illustrates a longitudinal section through a sensor according to the invention with contact ring path extending conically toward the outside.

FIG. 3 is a cross section through another embodiment of the invention which embodiment includes a cushioning member.

FIG. 4 represents a longitudinal section through a device according to the invention with a cushioning member which is designed for extreme vertical accelerations exerted upon the mass ball.

FIG. 5 is a longitudinal section through a liquid-cushioned sensor according to the invention.

FIG. 6 illustrates a section through a sensor according to the invention in which the cushioning member has the form of a brush holder.

FIG. 7 illustrates a modification of a sensor according to the invention in which a control plate is arranged over the mass ball which control plate is operatively connected to a microswitch.

FIG. 8 shows a section through a further embodiment of the invention in which the cushioning member is formed by a permanent magnet and cooperates with a dry-reed contact.

FIG. 9 shows a sensor of a construction similar to that of FIG. 8 in which the permanent magnet cooperates through a mass ball with field plates.

FIG. 10 shows a longitudinal section through another sensor according to the invention with a cushioning member formed by a soft iron core which immerses into an induction coil.

FIG. 11 is a longitudinal section through still another embodiment of the invention with a permanent magnet arranged below the mass ball.

FIG. 12 is a further embodiment of the invention with an outer cushioning contact ring.

FIG. 13 shows another control device according to the invention which is connected in a cushioning and/or resilient manner.

FIG. 14 represents still another control device according to the invention with an oscillation cushioning suspension, the device being shown as a vertical section.

FIG. 15 is a vertical section through a modified control device according to the invention.

As numerous tests have shown, in case of a collision between vehicles it is always of foremost importance that the safety devices in such vehicles respond in a minimum of time. Collision sensors have become known in which the mass inertia body in the form of a ball is in its starting position subjected to the thrust of a spring. In practice, however, such control devices have shown the drawback that their response precision is not sufficient because it depends too much on the influence of the spring force. Moreover, when manufacturing such devices, it is difficult so precisely to tune such springs that only minor deviations from the desired limit value of acceleration or retardation will occur.

The above mentioned drawbacks have been overcome by the acceleration and retardation responsive control device according to the invention which is characterized primarily in that the ball in its rest position rests upon the confining edges of a cutout which edges extend at least approximately in a horizontal plane, while the cutout is designed with a radius determining the engaging depth of the ball, this radius being smaller than that of the ball. With such an arrangement, the ball extends in its rest position with a downwardly pointing sherical section into the cutout. Out of this stabile rest position the ball can be lifted and moved toward the side, in view of its mass inertia force, only when an acceleration or retardation is exerted upon the support containing the cutout which acceleration or retardation exceeds the limit value derived from the dimensions of the ball and the dimensions of the cutout. For this limit value there exists the relationship according to which the product of ball weight and radius of the cutout must equal the product of the mass of the ball, the acceleration or retardation and the vertical distance of the center of gravity of the ball and the plane passing through the confining edges. This will precisely furnish the control resolution of the control device. Particularly stable conditions will be obtained when, according to a further development of the invention, the radius of the cutout amounts to from 0.1 to 0.45 times the diameter of the ball, preferably to from 0.2 to 0.4 times the diameter. If, for instance, the radius of the cutout amounts to 30% of the ball diameter, the vertical distance of the center of gravity of the ball amounts to 30% of the ball diameter. The control resolution lies in this instance at an acceleration or retardation of 75% of the acceleration due to gravity.

When the limit value derived from the geometry of the ball and of the cutout is exceeded, the ball moves out of its rest position and rolls toward the outside from the center of the cutout. On its way toward the outside, the ball can carry out a mechanical or electric control function. A safe and proper control function can be realized with simple means when, according to a further development of the invention, a metallic supporting member is provided which contains the cutout and when the supporting member is connected to a source of current. When in this connection the ball has a metallic conductive surface, it will in view of its engagement with the metallic confining edges likewise receive voltage. Expediently, the supporting member may be designed as a ring or as a tube, and the cutout intended for partially receiving the ball may be formed by the bore of the ring or of the tube. A particularly simply and effective control arrangement is obtained when as control contacts, according to a further development of the invention, there are provided two contact devices in the form of concentric rings insulated with regard to each other. Expediently, between these two concentric rings there is arranged a tube section of insulating material which tube section has its end face which faces the ball ending at a slight axial distance below the end faces of the two rings so that between the two rings there is formed a groove. When due to horizontal acceleration or retardation the ball is lifted out of its rest position because the control resolution has been exceeded, the ball will roll radially outwardly and will establish an electrically conductive connection between the two concentric rings which consist of metal or have a metallic cover. This operation practically corresponds to a pulse control operation with closing contacts. Inasmuch as it is structurally possible without difficulties to obtain very short distances, the control retardation can be fixed for very small values. If the end face of the inner ring toward the ring axis is provided with a inclination which corresponds to the conditions encountered by the vehicle when driving uphill or downhill, it will be appreciated that, when a distinct resting point for the stable starting position of the ball is provided which resting point determines the control resolution, the limit values for the acceleration and retardation vary in conformity with the cosine value of the angle of inclination and thus can be practically neglected for small angles of inclination.

When the two rings acting as contact devices are provided with end faces which are perpendicular to their axes and which extend in a common horizontal plane, the mass ball will not be able, after it has been controlled out of its starting position, to return to its starting position without outside help but will remain in its control position in which the ball engages the groove between the two rings. This so to speak bistable behavior may be disturbing in such instances of application of the control device in which a contact is desired only as long as the acceleration or retardation exceeds the adjusted or set limit value. To make sure that the ball will, after effected control, automatically return to its starting or rest position, the end face of at least one of the rings, preferably of the inner ring, may, according to an advantageous design of the device according to the invention, form the mantle of a cone which is coaxial with the ring and which has the point of the cone directed downwardly. In this connection, the line of intersection of the end face and of the bore will be located at the outer ring on the conical mantle, and the radial width of the groove between the two rings will be sufficiently small. Expediently, walls may be provided outside the outer contact ring which walls limit the stroke of the ball radially toward the outside. The angle at which the mantle surface of the cone is inclined toward the horizontal plane is advantageously selected slightly smaller than the angle of inclination which the ball will still be able to overcome after it has been lifted out of its stabile rest position due to the force of acceleration. In this way it will be assured that the ball will be able, after it has been lifted out of the cutout, to roll toward the outside until contact is established.

When installing a control device according to the present invention in vehicles which, in addition to the acceleration or retardation in approximate horizontal plane, are also subjected to shock-like accelerations acting perpendicularly with regard to this plane, additional steps might be necessary for the mass ball in order to stabilize the same in vertical direction. This can be realized in a simple manner according to the present invention by arranging a shock-absorbing or cushioning element which acts in a vertical direction and which is arranged above the ball when the latter is in its rest position, said cushioning element acting upon the ball by its weight. In this way it can be realized that with acceleration shocks acting in a vertical direction, the ball is held in the cutout acting as contact resolution. Expediently, such cushioning element may consist of synthetic material. In particularly difficult instances, very short vibrations may occur in vertical direction which make it necessary to provide a cushioning element adapted to perform an increased cushioning operation. This can be realized according to a further development of the invention by designing the cushioning element as a sleeve and closing the same at its lower section by a bottom on which the ball rests. Expediently, in the interior of the sleeve, small balls of synthetic material or steel may be filled in which in response to a corresponding acceleration shock exert a friction upon each other and thereby consume working energy so that with this consummation of energy, the mass ball is safely held in its stabile starting position in the cutout of its support, namely, the bottom of the sleeve. According to a preferred embodiment of the invention, the bottom serving as support for the ball may consist of a cushioning material, for instance, of synthetic material. Furthermore, the said bottom may contain a central ring or tube section acting as contact surface and may also contain a lining of insulating material, which lining is arranged within said ring and has a central longitudinal bore which forms the cutout for the ball. In this way it can be realized in a simple manner that also with increased vertical accelerations, the ball will always safely remain in its starting position without carrying out control operation and will only in response to correspondingly high acceleration values or retarding values leave its support on the lining when, for instance, an accident occurs.

According to a further suggestion in conformity with the present invention, a liquid medium may, for increasing the cushioning effect, be introduced into the chamber which receives the mass ball. As liquid medium in this instance there is employed a medium which has no electric conductivity as, for instance, transformer oil. When the chamber surrounding the ball is filled with oil, the static pressure of the liquid will act above the ball and also the dynamic cushioning in view of the viscosity of the liquid will be effective. The ball will in this way be pressed into the cutout in the supporting surface or supporting body therefor, and will undergo a high cushioning in case shocks occur in vertical direction. This shock absorbing effect depends to a great extent on the viscosity of the employed liquid. The reduced control speed resulting therefrom during horizontal acceleration and retardation may be disadvantageous in various instances of application. For purposes of increasing the control speed and for avoiding control sparks or arcs during the establishment and interruption of contacts, it may be advantageous in conformity with a further development of the invention with the design described above to greatly evacuate the chamber surrounding the ball so that preferably an absolute pressure of 100 Torr or less is obtained. Advantageous, with regard to the sine curve, is an inner pressure of approximately 10 Torr which can relatively easily be maintained and over a normal atmospheric pressure brings about the advantage that only at considerably increased voltages, sparkovers or light arcs may occur at the contacts or terminals. According to a further suggestion in conformity with the present invention, a permanent magnet may be arranged in the bore on the confining edges of which the mass ball rests. The ball which has a cover layer of ferromagnetic material, or which consists of ferromagnetic material will then be attracted by the permanent magnet.

While using the principle of the invention above referred to, it is additionally possible above the mass ball to provide a pressure plate which is mechanically connected to a micro-switch. This micro-switch is actuated when the mass ball leaves its cutout defining the stabilizing starting position of the ball, and is lifted upwardly. According to a further development of the invention, a permanent magnet may be arranged above the ball which will act as cushioning element and which, in response to exceeding the limit acceleration, is lifted off the mass ball to such an extent that a reed contact arranged above the permanent magnet will be moved into its closing or turning-on position. Moreover, this is also possible according to a further development of the invention by employing a magnet which is arranged above the ball and is operatively connected thereto, and by controlling by means of said magnet a so-called field plate and to initiate by the latter a fast control action. According to a still further development of the invention, it is possible instead of the above described permanent magnet, to provide a soft iron core which immerses at its upper end section into an induction coil. When this mass ball is controlled in the above mentioned manner and lifts the soft iron core, there will in this instance, a change of induction occur, by means of which it is possible safely and quickly to obtain a control pulse in a manner known per se. Finally, according to the invention it is also possible for cushioning the mass ball to provide a cushioning element of the type of a brush holder which is under vertical spring force and which is provided with a cable connection that will assure that the ball in response to the limit value of a horizontal acceleration or retardation gets into contact with a radially spaced ring zone, thereby carrying out the control function.

When installing a device according to the invention in a motor vehicle, the following conditions will result. When the vehicle drives straight ahead, and when the fixed acceleration or retardation value is exceeded, a signal will be emitted which brings about, for instance, the blocking of the rolling-up kinematics for the provided safety belts. When the vehicle drives through curves at high speed, the mass ball will, due to the centrifugal force acting thereupon, be lifted out of its rest position and will move outwardly whereby likewise a contact will be closed. If, however, it is desired that the device should not respond, for instance, when driving through a bank or canted curve, there exists the possibility so to design the supporting edges for the ball that the control device will not respond as long as the critical centrifugal force has not been reached. It is thus possible within the horizontal plane of function, to set or determine a desired acceleration or retardation value at which the device will respond.

Advantageously, the supporting member for receiving the ball may be produced by injection molding or pressing for which purpose no complicated or expensive tools are required.

Referring now to the drawings in detail, FIG. 1 shows a longitudinal section through a sensor which illustrates the principle of the control device according to the invention that is responsive to an accelerating and/or retarding action. The pot-shaped housing 1 is connected to a non-illustrated vehicle. A mass ball 2 rests in the bore 3 of an inner contact ring or device 4 on a ring edge or internal periphery 5. Between the outer contact ring or device 6 and the inner contact ring or device 4 there is provided an insulating intermediate layer 7. When considering the limit situation of the ball control, the center of gravity of the mass ball 2 is located at S. By "limit situation" is meant that the housing 1 is suddenly stopped at a certain retardation, as a result of which the mass ball, due to its inertia moves on in its inertia direction. In this connection, the following relationship exists: The weight G of ball 2 times the radius r of bore 3 must equal the product of mass times acceleration times the vertical distance h from the supporting ring edge 5. If this limit situation is exceeded, the mass ball 2 is lifted out above the edge or inner periphery 5 and rolls over the two ring contacts so that these contacts are bridged and a control pulse is emitted. Radially outwardly, the stroke of the mass ball 2 is limited by the inner wall of the pot-shaped housing 1. According to FIG. 1, the two annular contacts 4 and 6 are located along one and the same plane. In practice the result of this is that the moved-out or controlled-out mass ball 2 is located in the groove between the two contact rings 4 and 6 and remains there, and that outer forces must be applied in order to return said ball 2 to its starting position. Control conduits 11 and 12 for conveying the control pulses are firmly connected to the contact rings 6 and 4 respectively.

If, after the mass ball has been moved out from the first contact ring or device 4, and it is desired to have the ball automatically returned to its starting position, an inclined plane is taken advantage of.

According to the embodiment of FIG. 2, the contact surfaces of the inner ring or first contact device 13 and the outer ring or second contact device 14 are located in a common conical mantle or inclined surface 15 and thus form the angle 16. The control pulse can be conveyed from the contact rings or devices through the conductors 17 and 18. The conical angle 16 is so dimensioned that it can easily be overcome by the force exerted by the retardation or acceleration upon the mass ball 2. In FIGS. 1 and 2, the mass ball is indicated in dash lines 2' in that position in which the ball 2 moves in and establishes contact with the outer ring 14. If strong forces occur which act upon the mass ball 2 in a direction perpendicularly with regard to the acceleration or retardation direction 19, steps have to be taken for cushioning these forces. This has been realized in connection with the embodiment of FIG. 3.

According to FIG. 3, above the mass ball 2 there is provided a pushrod 20 which may, for instance, be cylindrical and which is displaceable in a cover plate 21 fixedly connected to the housing. Preferably, the pushrod 20 is made of a synthetic material, such as polyamide, which has good cushioning properties. When providing an additional cushioning element, the supporting zones have to be corrected correspondingly because additionally a further weight acts upon the ball, and the conditions of friction change within the region where the cushioning element engages the ball. If extreme strong accelerations in vertical direction occur and if the suggested solution according to FIG. 3 is no longer sufficient, it is suggested according to a further development of this invention that in conformity with FIG. 4, the cushioning element is formed substantially by a closed thin-walled hollow cylinder 22 which is filled with small frictional bodies 23. Expediently, for this purpose small balls are employed while in case of possibly occurring vertical accelerations, these filling bodies will perform a frictional action so that the ball 2 has no possibility to overcome this frictional work in upward direction.

As will be evident from FIG. 4, the inner ring contact 13 may be lined with a sleeve 24 made of a highly cushioning material, such as polyamide. In this way a maximum cushioning of the mass ball 2 can be obtained.

FIG. 5 shows a further embodiment of a sensor according to the invention in which the desired cushioning effect is obtained by liquid means. Similar to the embodiments described above, the ring contacts or devices 13 and 14 in FIG. 5 are designed similar to those of FIGS. 1 to 4. Merely the housing is so designed that it is completely closed at the bottom 1'. The interior of the housing is filled with a liquid, for instance, transformer oil 24 and is closed by means of a cover 25 in a liquid-tight manner. The static pressure which is effective through the liquid column above the mass ball 2 sees to it that with vertical accelerations, the ball 2 will be safely held and kept upon the inner contact ring 13.

FIG. 6 shows a sensor in which the cushioning element is formed by a brush holder 26, the free end 27 of which has connected thereto a flexible conductor 28. The brush holder 26 is made of an electrically conductive material and rests upon the mass ball 2. A ball 2 rests on an insulated ring 29 which has its outer periphery surrounded by a contact ring 30. The outer contact ring 30 is fixedly connected to a conductor 31 so that when the mass ball is moved out of its rest position a control pulse is, through brush holder 26 and ball 2 as well as contact ring 30 conveyed through conductors 28 and 31.

The embodiment of FIG. 7 comprises a housing 32 which is advantageously made of an electrically non-conductive material. The housing 32 has a bore 33 engaged by the ball 34 which rests against the ring edge 35. Above the ball 34 there is provided a pressure plate 36 which is designed in the manner of a lever 37. When a predetermined acceleration or retardation has been exceeded, ball 34 moves over the inclined conical surface 38 in the direction of the arrow 39 so that the pressure plate 36 is lifted and actuates the pushrod 40 of the micro-switch 41, which latter is firmly connected to the housing 32. The control pulse is conveyed through the conductors 42 and 43.

The housing 44 of the embodiment according to FIG. 8 is substantially of the same general construction as the housing 32 of FIG. 7. The only difference consists in that the housing 44 is closed by a cover 45 which is fixedly connected to the housing. Above the mass ball 46 there is provided a cushioning element 47 which is vertically displaceably arranged in the cover 45 and is formed by a permanent magnet. In cover 45, and more specifically, in a glass tube, there are arranged reed contacts 48 which, when the mass ball 46 is controlled out of its rest position will, in view of the permanent magnet 47 move to mutual contact. In this instance, the control pulse is conveyed by the conductors 49, 50.

As will be seen from FIG. 9, the construction representing a modification of the design of FIG. 8 may be so selected that the permanent magnet 47 acting as cushioning element will act, not upon a reed contact, but upon two field plates 51, 52 and will convey the control pulse through control conductors 53 and 54.

FIG. 10 shows still another embodiment of a sensor according to the invention, in which the lower portion corresponds substantially to that of FIGS. 7 - 9. In the closure cover 55 and, more specifically, in the center thereof, a soft iron core 56 is displaceably arranged and surrounded by a coil 57. When controlling the mass ball 46 out of its rest position, the soft iron core 56 is displaced upwardly in the direction of the arrow 58 so that a control pulse is emitted by the change in the induction.

The device according to FIG. 11 shows a substantially open pot-shaped housing 59 of electrically insulating material, in which the ring contacts or devices 60 and 61 are arranged so as to be insulated from each other. The inner ring contact device 61 is lined with a thin-walled part 62 of synthetic material, such as polypropylene, on which the mass ball 63 rests at the ring zone 64. In order safely to hold the mass ball 63 in its position when vertical accelerations occur, a permanent magnet 65 is provided below the ball 63. The lines of force of said magnet 65 act continuously upon the metallic ball and pull the same downwardly. When controlling the ball out of its rest position, the control pulse is conveyed through conductors 66 and 67 which are connected to the contact rings 60 and 61.

The device according to FIG. 12 has a housing which in its pot-shaped inner portion comprises a contact ring 69 which is lined with a cushioning or resilient material 70, such as polyurethane foam. The inner contact ring 71 is designed similar to the ring 13 of FIG. 2. When the mass ball 72 moves into the dash-line position 73, it will be appreciated that between the contact ring 71 and the contact ring 69 arranged in the pot-shaped portion, the control function is initiated over the connected conduits 73 and 74. The lining 70 of the contact ring 69 brings about the advantage that at an accelerated rolling out of the mass ball 72 no hard shocks are exerted upon the contact ring 69. The forces which act in a direction perpendicular to the acceleration plane, and which may subject the mass ball to oscillations, can be absorbed by suspending the entire sensor system in a resilient or elastic manner in the vehicle approximately perpendicularly with regard to the vehicle plane. Any possible influences exerted upon the mass ball which may be produced by the cushioning elements depending on their arrangement need no longer be taken into consideration. Therefore, by a clear calculation, the corresponding supporting position for the mass ball can be predetermined.

A suspension of the type referred to in the preceding paragraph is illustrated in FIG. 13. According to FIG. 13, the sensor housing 75 is closed by a cover 76. Arranged on the cover 76 is a guiding pin 77 for receiving a pressure spring 78. At the bottom of the sensor there is likewise provided a guiding pin 79 for receiving and guiding a pressure spring 80. The pressure spring 80 is, in a dish-shaped manner, held in a supporting cap 81, and the pressure spring 80 is held in a supporting cap 82. The supporting caps 81 and 82 are connected in a U-shaped manner to the web 83 which is firmly connected to the vehicle 84. In the driving direction indicated by the arrow 85 which driving direction simultaneously illustrates the acceleration plane and the plane in which the device responds, the device must not carry out any relative movement with regard to the vehicle. Perpendicularly to this plane in the direction of the arrow 87, the complete device is resiliently supported by pressure springs 78 and 80 to cushion any oscillations so that the mass ball 88 when the vehicle drives through holes in the road will safely remain in its supporting position without the necessity of providing inner cushioning elements.

FIG. 14 shows a further development of the design according to the invention in which the suspension and outer cushioning means are particularly favorably designed. The sensor housing 89 is principally of the same construction as described. Merely the length is somewhat greater. At its open top side the sensor housing 89 is closed by means of a snap cover 90 which consists of rubber elastic material, especially synthetic material, such as polyvinylchloride. The cover 90 has at its top side a neck 91 and merges with a ball head portion 92. The connecting lines 93 and 94 are flexible and pass toward the outside through the ball head portion 92. A bearing plate 95 has in its center a spherical supporting surface 96 for pivotally journaling the sensor. The bearing plate 95 is in a resilient cushioning element 97 fastened in the cushioning housing, said cushioning element 97 advantageously embraces the bearing plate 95 in a U-shaped manner. This cushioning housing may, by means of an element 92 be fixedly connected to the vehicle. The cushioning housing 98 contains a cushioning liquid 100. Due to this arrangement, the sensor will, during normal driving operation, always carry out a pendulum movement in the direction of the forces of gravity. When suddenly changes in the vehicle speed occur, the sensor housing will, in view of the outer liquid cushioning maintain its inertia and the mass ball 101 will control the control pulse. At the bottom side of the sensor housing 89 an additional mass 102 may be provided for a better tuning, or adaptation. By determining the diameter of the cushioning housing, the maximum position of inclination 103 is determined, which maximum position of inclination is shown by dash lines.

The embodiment of FIG. 15 is similar to that of FIG. 14, but differs therefrom in that it has an outer liquid cushioning which is effective in all directions. The sensor corresponds to a major extent to that of FIG. 14. The cushioning housing 14 has a bottle-neck-like snap cover 105. The bore 106 is slightly greater than the ball head 92 so that the sensor can be displaced axially. Moreover, the sensor can be pivoted in conformity with the angle 103. If a cushioning liquid 107 is filled into the container 104, it will be appreciated that with a corresponding design, the sensor housing 89 is subjected to a buoyancy and thus floats. In this way, an outer liquid cushioning is realized in all locations of operations of the device.

It is, of course, to be understood that the present invention is, by no means, limited to the particular embodiments illustrated in the drawings, but also comprises any modifications within the scope of the appended claims.

Claims

What is claimed is:

1. An acceleration responsive electric control device in combination comprising a mass inertia element in the form of a ball having a surface of conductive material, a support member having a seat supporting said ball seated thereon, said member comprising a first fixed contact device having a circular internal periphery of substantially less diameter than said ball normally lying in a horizontal plane, the top of said device forming a ring surrounding the lower portion of the ball resting thereon, said contact device having conductive material on its surface to contact the ball in engagement with said ring, a second fixed contact device having a second circular periphery forming a second ring coaxial with said first ring and spaced radially outwardly and upwardly of said first ring, a distance less than the diameter of said ball, and normally lying in a horizontal plane, said second contact device having conductive material on its surface to contact a ball in engagement with said second ring, said ball being displaced from said first ring by acceleration to span the space between said two contact devices and engage said two rings, the lines of contact of said rings engageable by said ball lying in a surface inclined downwardly toward the axis of said rings, so that the ball returns to its seat on said first ring when said acceleration ceases, and means to retain said ball in association with said contact devices.

2. A device according to claim 1 in which the radius of the seat is from about 0.10 to about 0.45 times the diameter of said ball.

3. A device in combination according to claim 1 in which said support member and ball are located in housing and at least the outer surface of said ball is electrically conductive, said support member being electrically conductive and forming one terminal of said switch means, and an electrically conductive annular member surrounding said support member and forming the other terminal of said switch means, said ball bridging between said support member and said annual member when the ball moves laterally on said seat.

4. A device in combination according to claim 3 in which said annular member is a sleeve supported in said housing and in turn insulatingly supporting said support member.

5. A device in combination according to claim 4 in which said support member is also a sleeve, and a ring of insulating material interposed coaxially between said support member and said annular member.

6. A device in combination according to claim 4 in which said support member is a sleeve element, said seat being formed cup-shaped on the upper end of said sleeve element and being upwardly concave.

7. A device in combination according to claim 3 in which said housing is closed, and a damping medium in the form of a dielectric liquid provided for cushioning in said housing.

8. A device in combination according to claim 3 in which said housing is closed, and a chamber therein with subatmospheric pressure of from about 10 Torr up to about 100 Torr in said housing.

9. A device according to claim 3 in which said housing is cup shaped so as to have a bottom wall and a side wall extending upwardly from the periphery of the bottom wall, said support member being a conductive ring mounted in said bottom wall, said ball being conductive, and a conductive sleeve resistently supported on the inside of said side wall, said support member and said sleeve forming the terminals of said switch means and said ball bridging therebetween upon lateral movement of the ball on said seat.

10. A device according to claim 1, in which said control device is mounted in a housing, and said housing has a bottom wall formed of synthetic material, said support member being mounted in said bottom wall of said housing.

11. A device according to claim 10 which includes a metal ring in said bottom wall, a ring of insulating material in said metal ring and having said seat on the upper end thereof, said ball being electrically conductive and forming one switch terminal and said metal ring forming the other switch terminal.

12. A device according to claim 1, in which said control device is mounted in a housing, and said housing has a bottom wall, at least said bottom wall being formed of electrically nonconductive synthetic material, said bottom wall forming said support member, and a vertical hole in said bottom wall the upper end of which forms said seat.

13. A device according to claim 10 which includes at least one metal ring in said bottom wall for cooperation with said ball.

14. An acceleration responsive electric control device in combination comprising a mass inertia element in the form of a ball having a surface of conductive material, a support member having a seat supporting said ball seated thereon, said member comprising a first fixed contact device having a circular internal periphery of substantially less diameter than said ball normally lying in a horizontal plane, the top of said device forming a ring surrounding the lower portion of the ball resting thereon, said contact device having conductive material on its surface to contact the ball in engagement with said ring, a second fixed contact device having a second circular periphery forming a second ring coaxial with said first ring and spaced radially outwardly and upwardly of said first ring, a distance less than the diameter of said ball, and normally lying in a horizontal plane, said second contact device having conductive material on its surface to contact a ball in engagement with said second ring, said ball being displaced from said first ring by acceleration to span the space between said two contact devices and engage said two rings, the lines of contact of said rings engageable by said ball lying in a surface inclined downwardly toward the axis of said rings, so that the ball returns to its seat on said first ring when said acceleration ceases, force applying means acting on said ball to resist displacement from its seat on said first ring, and means to retain said ball in association with said contact devices.