US3654410A

US3654410A - Pivoted inertia switch self-orienting along a line of deceleration in a prescribed angular pattern

Info

Publication number: US3654410A
Application number: US96108A
Authority: US
Inventors: James R Miller
Original assignee: Aerodyne Controls Corp
Current assignee: Aerodyne Controls Corp
Priority date: 1970-12-08
Filing date: 1970-12-08
Publication date: 1972-04-04
Anticipated expiration: 1989-04-04

Abstract

An inertia switch assembly includes a support in the form of a casing in which an inertia switch body is mounted for free swinging in an angular pattern so that the switch body aligns itself with the direction of an applied force. Inertia means in the switch body responds slower to the applied force than the switch body. The inertia means include a conductive member which contacts terminal pins pivotally supporting the switch body.

Description

United States Patent Miller [54] PIVOTED INERTIA SWITCH SELF- ORIENTING ALONG A LINE OF DECELERATION IN A PRESCRIBED ANGULAR PATTERN [72] inventor:

[73] Assignee:

James R. Miller, Huntington, N.Y.

Aerodyne Controls Corporation, Farmingdale, N.Y.

[22] Filed: Dec.8, 1970 [21] Appl.No.: 96,108

[52] U.S. Cl. [51] Int. Cl. [58] Field of Search ..200/6l.45-61.53;

[56] References Cited UNITED STATES PATENTS 2,972,134 2/1961 McKay ..200/61.45 X

[is] 3,654,410 [451 Apr. 4, 1972 3,571,538 3/1971 Swanson ..200/61.47

3,049,700 8/1962 Du Plooy ..340/261 2,974,529 3/1961 Brueggeman et al. ..200/61.53 X

FOREIGN PATENTS OR APPLlCATlONS 386,034 1/1933 Great Britain ..340/262 Primary Examiner-Robert K. Schaefer Assistant Examiner-M. Ginsburg Attorney-Edward H. Loveman [57] ABSTRACT An inertia switch assembly includes a support in the form of a casing in which an inertia switch body is mounted for free swinging in an angular pattern so that the switch body aligns itself with the direction of an applied force. lnertia means in the switch body responds slower to the applied force than the switch body. The inertia means include a conductive member which contacts terminal pins pivotally supporting the switch body.

10 Claims, 6 Drawing Figures PATENTEUAPR 41972 SHEET 1 0F 3 INVENTOR. .JAMES R. MILLER FIG.5

ATTORNEY" PATENTEDAPR 4 4972 SHEET 2 UF 3 INVENTOR. JAMES R. MILLER ATTORNEY PATENTEU PR 41912 SHEET 3 OF 3 INVENTOR. JAMES R. MILLER ATTORNEY PIVOTED INERTIA SWITCH SELF-ORIENTING ALONG A LINE OF DECELERATION IN A PRESCRIBED ANGULAR PATTERN This invention concerns a switch for triggering instant operation of a safety device when a vehicle is involved in an accident and more specifically involves an inertia switch which will respond to a force of deceleration encountered by the vehicle involved in an accident.

Inertia and acceleration switches heretofore known may be categorized by their response to a force applied in either a uniaxial direction of a multi-direction. These switches, however, are completely unsatisfactory for use in triggering a safety device when a vehicle is in an accident. That is, a switch of the character described must meet two basic requirements:

a. It must respond to decelerations or accelerations in a horizontal plane for preset angular extent at each side of a direct forward line of motion, and

b. it must not respond to any force having a magnitude less than a predetermined adjustable amount for a duration less than a desired period.

The prior art switches will not meet the first of the two basic requirements mentioned above, because their response is not limited to a prescribed angular extent in one or more planes. Furthermore, the prior art switches will not meet the magnitude and time discriminatory requirements and also permit wide angle equal response over a wide operating temperature range.

In accordance with the present invention an inertia switch assembly which meets both basic requirements is comprised of a casing in which is a pivotably mounted inertia switch having a cylindrical body containing switch terminals and a movable conductive member which bridges the switch terminals. The switch terminals themselves serve as pivots for the cylindrical body which is free to turn in a plane so that the switch can align itself axially with a line of deceleration in a prescribed angular pattern. The limits of free swing of the switch body may be set by abutments provided in the casing. A preferred form of the inertial switch is a gas damped switch having a hollow piston with an orifice at one end with the piston being movable axially in a hollow cylindrical gas-filled body, opposed in its motion by a spring or other elastic means. Movement of the piston in response to applied forces of acceleration or deceleration is gas damped. The piston carries a conductive plate or disk to bridge the switch terminals.

The pivotable mounting of the switch body is such that the switch body will align itself with the direction of applied force faster than the piston in the switch body will respond to the applied force. Stated another way, the pendulous response rate of the switch body is faster than the linear response of the gasdamped inertia element in the switch body. The natural frequency and damping ratio of the air damped inertia element are adjusted to make the switch respond to any magnitude of acceleration larger than a prescribed minimum limit, so as to obtain discrimination between a crash situation and a noncrash situation when the switch assembly is installed in a vehicle.

It is therefore, a principal object of the present invention to provide an inertial switch assembly for triggering a safety device in a vehicle collision.

It is another object of the present invention to provide inertial switch which will align itself with the direction of an applied force.

It is still another object of the present invention to provide an inertial switch which is pendulously mounted and wherein the pendulous response rate is faster than the response of the inertial switch.

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

FIG. 1 is a prespective view of an inertia switch assembly embodying the invention;

FIG. 2 is another perspective view of the inertia switch assembly shown in an inverted position;

FIG. 3 is a top plane view of the inertia switch assembly with part of the casing broken away to show internal construction;

FIG. 4 is an enlarged central sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a fragmentary cross sectional view on a reduced scale taken along line 5-5 of FIG. 4; and

FIG. 6 is an exploded perspective view of parts of the switch assembly.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout, there is illustrated an inertia switch assembly generally designated as reference numeral 10 having a flat cylindrical casing 12. The casing 12 has a cylindrical wall 14 and opposite

circular end walls

16, 18. If desired the wall 16 may be integral with the wall 14 and wall 18 may serve as a closure plate and seat on a shoulder 20 formed in the end wall 14. A mounting bracket plate 21 is secured to end wall 16 and has apertured tabs 23 for mounting the assembly 10 in a vehicle. A pair of

stationary metal cups

22, 24 are set in

respective holes

25, 26 centrally aligned with each other in respective end walls l6, 18 but offset radially from the center or central axis of the cylindrical casing 12.

lnsulative disks

28, 30 are set in the

cups

22, 24 and have respectively secured thereto and extending

therethrough metal pins

32, 34. If desired each combination of disk, cup and pin may comprise a fused ceramic to metal header for hermetically sealing the casing 12. These pins are axially aligned and serve as electrical terminals for a switch which is normally open (electrically) and also serve as pivots for the cylindrical switch 35.

The switch 35 as best shown in FIGS. 3-6 includes a tubular or cylindrical body 36 made of a plastic or of a metal such as aluminum. Set in holes 38 in opposite sides of body 36 are insulative trunnions 40 provided with axial holes 42 which receive the

pins

32, 34. The trunnions serve as bearing members permitting free swinging of switch 35 in a plane perpendicular to the aligned axes of the pins 32 34 and parallel to the

end walls

16, 18 ofthe casing 12.

When the casing 12 is axially vertical as shown in FIG. 3, the tabs 23 will be vertical and may be secured by suitable screws to a fire wall or other appropriate surface S in a vehicle. The switch 35 will then be free swinging in a horizontal plane. Resilient abutment blocks 44 made of felt, urathane foam or rubber are secured to the inside of cylindrical wall 14 at points spaced apart. These blocks serve as stop members to limit the free swinging movement of the switch 35. The mounting of the assembly will be such that direction D represents the forward direction of movement of the vehicle carrying the assembly 10. The switch 35 is shown in FIG. 3 as axially oriented in direction D and is free to swing laterally to the right or left in angle A which is shown as approximately 120. In order to effect closure of an external circuit (not shown) connected to

pins

32, 34 there is provided as inertia means comprising a movable switch ring 50. The switch ring is a thin flat elec trically conductive metallic member mounted at one end 51 of a mass or piston 52 which is cylindrical and is slidably disposed in an axial, cylindrical passage in the switch body 36 (FIGS. 4-6). Piston 52 is hollow and receives a coil spring 56 which extends axially out of the open end 57 of the piston 52 and seats around a stud 58 formed on the inner end of a plug 60. If desired the plug 60 may have an external thread 61 adapted to mate in a threaded hole 62 at the distal end of the body 36. The switch ring 50 is engaged on a shoulder 64 defined by a neck 66 at the proximal end 51 of the piston 52. On this neck is a coil spring 68 held in compression by the head 70 of a screw 72 and yieldably bearing on the switch ring 50. The shank of the screw 72 is engaged in the internally threaded neck 66 of the piston 52. An axial hole 74 extending entirely through the screw 72 communicates with the interior of a chamber 75 in the piston 52. The hole 74 permits air flow between chamber 75 and a chamber 76 at the adjacent end of the body 36. Chamber 76 is closed by a circular disk or plate 78 set in the end of the body 36.

Referring to FIG. 4 it will be noted that the switch ring 50 is normally spaced to the right of the aligned pins 32, 34 when the assembly is stationary and when it is moving in the forward direction D. If a mechanical impulse due to collision or a sudden deceleration of the assembly 10 occurs, the body 36 will first respond by swinging freely to align itself axially with the direction of applied impulse. Then the piston 52 will respond by compressing the spring 56 and moving axially in body 36 until the switch ring 50 contacts both

pins

32, 34 to close the electric circuit in which the pins will be connected. The spring 68 insures contact of the switch ring 50 with both pins in the event the

pins

32, 34 are not axially aligned or the switch ring is not flat, etc. The response time of the piston 52 to the applied pulse is determined by a number of factors such as mass of the piston, stiffness of the spring 56 and size of the hole 74 in the screw 72. The stiffness of spring 56 may be adjusted most conveniently by substituting or selecting a spring of desired length and stiffness. Similarly a piston of greater or lesser mass may be selected, and/or a screw having an axial hole 74 of greater or lesser diameter may be selected. The largest measure of control of the switch assembly is exerted by the air damping (due to air trapped in the chamber 75 in the piston 52) and this insures that the body 36 will align itself first in the direction of the applied impulse before the piston 52 moves to close the circuit terminals 32 34 via the conductive switch ring 50. I

It is possible that other types of inertia switch elements can be employed in the switch body 36, such as those operating in a magnetic field or those having movable mercury contacts, etc. However, regardless of the particular type of inertia switch employed it must meet the basic requirement of response only to an impulse of a magnitude greater than a predetermined limit, and its response must be somewhat slower than the response time of the free swinging body 36.

The switch assembly 10 has particular utility in vehicles equipped with automatic systems for inflating protective plastic cushions in the event of an accident. The switch assembly may be used to trigger operation of the system. However the switch assembly is of general utility and may be used wherever an impulse responsive inertia switch is required to respond to an impulse in a prescribed angular pattern in a plane. The principles of the invention may be applied to switch assemblies wherein the inertia switch body 36 may be mounted by universal joint means to swing in a desired spherical angular vector pattern.

It should be understood that the foregoing relates to only a preferred embodiment of the invention, and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

The invention claimed is:

1. An inertia switch assembly comprising a support means subject to an applied directional impulse;

an impulse responsive switch body pivotally carried by said support means to swing freely thereon for self-orientation in the direction of application of said impulse; and

impulse responsive inertia means in said switch body arranged to move in said direction to close an external electric circuit and means whereby said inertia means respond slower to said impulse than said switch body so that said inertia means will close said external electric circuit only after said body orients itself in said direction.

2. An inertia switch assembly as defined in claim 1, further comprising stop means carried by said support means and disposed to limit swinging of said switch body to a prescribed angular pattern.

3. An inertia switch assembly as defined in claim 1, further comprising pivot means pivotally mounting said body on said support means and arranged so that free swinging of said body is limited to at least one plane.

4. An inertia switch assembly as defined in claim 3, wherein said support means is a cylindrical casing mountable in an axially vertical os ition and includes ivot means dis osed axially vertrcal 0 limit free swinging 0 said body to a orrzontal plane.

5. An inertia switch assembly as defined in claim 4, wherein said pivot means comprises axially aligned pins carried by said casing, said switch body comprising a cylindrical member containing said inertia means; and trunnions on said cylindrical member receiving said pins so that said cylindrical member swings freely thereon.

6. An inertia switch assembly, as defined in claim 4, further includes stop means spaced apart circumferentially of and within said casing for limiting angular movement of said switch body to a prescribed angular pattern.

7. An inertia switch assembly as defined in claim 5, wherein said inertia means comprises a conductive element movably disposed inside said cylindrical member, said pins being electrically conductive and extending into said cylindrical member; and biasing means in said cylindrical member normally holding said conductive element spaced from said pins in such a way that said conductive element contacts said pins to bridge the same mechanically and electrically in response to said applied impulse.

8. An inertia switch assembly as defined in claim 7, wherein said inertia means further comprises a mass movable in response to said impulse only after said cylindrical member orients itself in said direction, said mass carrying said conductive element.

9. An inertia switch assembly as defined in claim 8, wherein said mass is a gas-damped cylindrical piston, said cylindrical member having an axial passage slidably supporting said piston; said biasing means comprising a spring engaged between said body and said piston for yieldably holding said conductive element spaced from said pins.

10. An inertia switch assembly as defined in claim 9, wherein said piston is hollow to define a first gas-containing chamber, said axial passage in said cylindrical body defining a second gas-containing chamber, and means defining an aperture in said piston to provide restricted communication between said chambers for limited passage of said gas therebetween, whereby movement of said piston in response to said impulse is gas-damped.

Claims

1. An inertia switch assembly comprising a support means subject to an applied directional impulse; an impulse responsive switch body pivotally carried by said support means to swing freely thereon for self-orientation in the direction of application of said impulse; and impulse responsive inertia means in said switch body arranged to move in said direction to close an external electric circuit and means whereby said inertia means respond slower to said impulse than said switch body so that said inertia means will close said external electric circuit only after said body orients itself in said direction.

4. An inertia switch assembly as defined in claim 3, wherein said support means is a cylindrical casing mountable in an axially vertical position, and includes pivot means disposed axially vertical to limit free swinging of said body to a horizontal plane.