US3769472A

US3769472A - Inertia sensor switch

Info

Publication number: US3769472A
Application number: US00283241A
Authority: US
Inventors: L Bell; W Gruber
Original assignee: TRW Technar Inc
Current assignee: TRW Technar Inc
Priority date: 1972-08-23
Filing date: 1972-08-23
Publication date: 1973-10-30
Anticipated expiration: 1990-10-30
Also published as: JPS4985575A; CA999664A; DE2341862A1; FR2197221A1; FR2197221B1; GB1424056A; IT994638B

Abstract

Inertia switch with mass mounted between inclined structure and, when at rest, contacting spring switch extension means.

Description

United States Patent [1 1 Bell et al.

[ INERTIA SENSOR SWITCH [75] Inventors: Lon E. Bell; William P. Gruber,

both of Altadena, Calif.

[73] Assignee: Technar Incorporated, Pasadena,

Calif.

22 Filed: Aug. 23, 1972 211 Appl. No.: 283,241

[52] US. Cl. ZOO/61.45 R, ZOO/61.52 [51] Int. Cl. H0111 35/02 [58] Field of Search ZOO/DIG. 29, 61.11,

ZOO/61.41, 61.42, 61.43, 61.45 R, 61.48, v ZOO/6152,6153

[56] References Cited UNITED STATES PATENTS 3/1973 Suzuki et al. ZOO/61.45 R

[ 1 Oct. 30, 1973 11/1912 Myers ZOO/DIG. 29 3,484,571 12/1969 Williams 200/61.45 R X 3,644,921 2/1972 Duggan et a1.. ZOO/61.45 R X 1,662,979 3/1928 Nelson ZOO/DIG. 29 3,466,045 9/1969 Walton ZOO/61.1 l X 3,457,382 7/1969 Boswell ZOO/61.45 R

Primary Examiner-J. R. Scott Attorney-Jonathan Plaut [57] ABSTRACT lnertia switch with mass mounted between inclined structure and, when at rest, contacting spring switch extension means.

8 Claims, 6 Drawing Figures PAIENTEDncUo I913 3.769.472

4i 1 j JLC G-LEVEL FORCE v in O 5 IO l5 2O ANGLE OF DISPLACEMENT 1 INERTIA SENSOR SWITCH PLANAR SWITCH This invention relates to an inertia switch which embodies a mass movably mounted between inclined structure and, when at rest, on a fixed ring or other means providing an aperture for contact to spring extension means. The spring extension means applies a force on the mass with certain positive benefits to be discussed in detail hereinafter. In other positions, the mass is displaced from the aperture means as a result of certain G forces on the switch. The mass then is no longer in contact with the spring extension. In these positions, the electrical contact to which the spring extension is affixed is not in contact with its associated terminal and certain functions are rendered inoperative.

BRIEF DESCRIPTION OF INVENTION Generally, in the invention, the electrical contact which the mass presses into a contact position when the mass is at rest on the aperture means (in one embodiment, the ring) exerts .upward (against the force of gravity) force on the mass through the spring extension so that the mass is much more sensitive to G level force than otherwise. Likewise, when the mass has been removed from its position at rest as a result of G forces on the sensor and seeks to return-to its rest position, it must act against the force of the spring extension acting against it. By predetermining the force of the spring extension on the mass, the sensitivity of inertia switch is maximized and controlled, while still enabling a substantial and stable mass to be employed.

The details of the invention will be more fully understood with relation to the following drawings.

FIG. 1 shows one embodiment of the sensor with a spherical mass in rest position.

FIG. 2 shows a detailed embodiment of the invention with the spherical mass moved from its rest position and out of contact with the spring extension.

FIG. 3 shows a graph illustrating advantages of the invention.

FIG. 4 shows the sensor of FIG. 1 with an inertia mass of preferred configuration in the rest position.

FIGS. 5 and 6 show other embodiments of the sensor.

DETAILED DESCRIPTION OF INVENTION In FIG. 1 an inertia sensor 1 with cylindrical side walls 2 and a top 3 and bottom affixed thereto define a chamber 50. Mounted within the chamber 50, in this embodiment, is a ring 5 which forms an aperture adjacent the bottom 20 and preferably on the central vertical axis A-A of the sensor. The bottom 20 is provided with a hole 21 immediately below and contiguous with the aperture 7. A mass 4 is movably contained Within the aperture and normally rests in said aperture.

The inertia mass 4 in this embodiment is in the form of I a ball. The ring 4 may be dispensed with, as shown in Attached to the bottom 20 of the sensor is a base 6 .upon which the sensor normally stands in an attitude parallel with the horizontal. The base 6 and bottom 20 define an interior pocket which connects with the hole 21. Extending into the pocket 70 at one end thereof is a terminal contact 9 and extending from the pocket preferably on the opposite end thereof is a sec-' ond terminal contact 10. A leaf spring 1 l, which makes electrical contact from the terminal 9 to the terminal 10, directly extends across the pocket to make such contact. Contact is made by terminal contact point 12 on the leaf spring 11 touching the terminal 10. The leaf spring is pressed or otherwise in engagement with the terminal 9. The spring leaf extension 13, which is integral with the spring 11, in the preferred embodiment, projects from the leaf spring up into the aperture 7 and into contact with the ball 4 when it is resting in said aperture.

As previously discussed, the ball 4, when resting in the aperture, pushes down on the extension 13 to force contact at 12 of the spring 11 with the terminal 10. Simultaneously, because of a pre-set bias of the leaf spring 11 to move in a direction toward the chamber 50, the spring extension 13 exerts a force on the ball in an upward direction, causing the ball to be more sensitive to G forces than otherwise.

Because the extension 13 exerts a force on the ball in opposition to the force of gravity when the switch is in its normally deployed position, if the inertia switch 1 is inverted as a result of, say, a rollover when used in an automotive vehicle, the disengagement of the mass from the spring extension will occur as soon as the mass moves away from the spring extension and befor total inversion, as a result of the free-fall condition caused by the rapidly occurring inversion, causing opening of the contact between the spring at 12 and the terminal 10. In the case of automotive useage, as will be discussed hereinafter, such opening of the contact could result in locking of seat belt retractor.

In FIG. 2, the ball having moved out of the aperture and not in contact with the spring extension, the switch contact 12 is not in contact with the terminal 10 and thus is open. However, the ball 4 must move out of and a certain distance from its position of rest in the aperture before contact with the spring extension is lost, and this necessity for the G forces moving the ball to be sufficient to disengage the ball from the aperture and then move it such certain distance results in a filtering out of those G forces or pulsations which should not activate the sensing device (such as in the case of the effect of rough road shocksin automotive useage).

In the embodiment shown in FIG. 4, the mass 4 is shown as a cylindrical device 14 with a cone 15 at the top thereof and a section 16 at'the bottom thereof, shown'as located within the ring and in contact with the spring extension. The conical top has the advantage that, in one embodiment, when the mass is tipped and the top 3 is sufficiently low, the section 16 cannot fully disengage from the aperture 7 and contact with the spring extension may not therefore be lost.

In one embodiment the top 3 is located close enough to the ring 5, or other aperture forming means, so that the mass 4, in its rest position, when the inertia device is standing on its base 6 and not undergoing sufficient G forces, will have to rest in the aperture.

permanently In an alternative embodiment, shown in 5, the leaf extension is disposed with, and the leaf spring 11 is so positioned and biased so as to be in direct contact with I mass, the ball in this figure, when the mass is in the rest position in the aperture. In a like manner to that discussed heretofore with relation to the leaf extension, the spring 11 in this embodiment functions to exert force on the mass in the rest position.

In FIG. 3, G level forces are plotted against the angle of displacement of the mass 4 of FIG. 4 from its position of rest. As may be seen in the graph, the G level necessary to keep the mass displaced lessens as the angle of displacement'is increased, .the same spring force on the mass was utilized in each case (the spring force here being one-half of the weight of the mass). At the point after which the spring comes out of contact with the terminal 1 in FIG. 4, the G level force decreases more rapidly as the angle of displacementincreases, as shown beginning at A in FIG. 3, because the leaf spring 11 is no longer in contact with the terminal l0 and thus no longer is supporting the mass in contact with the extension 13. At the point C on the graph, the leaf extension 11 has risen from its position of terminal contact at 12 to a position where the terminal contact 12 has moved to the underside of the bottom 20 and no further substantial movement of the leaf spring or its extension is possible. Since the mass then is no longer supported by the spring extension, greater G level forces are necessary to increase the angle of displacement of the mass. Such displacement is shown by the portion B of the graph. Without the influence of the leaf spring on the mass, a plotting back on the graph to the initial G level forces required to initiate displacement of the mass, as shown by the dotted lines D on the graph, show the substantially higher initial force.

As an alternative embodiment, shown in FIG. 6, a contact terminal 17 may be placed adjacent to the terminal arm I0 and thereabove, said terminal arm 10 making contact with the leaf spring 11 at 12 when the mass has moved fully away from the leaf spring and its extension and substantial further movement of the leaf spring upward under its bias is impossible. Said terminal 17 leads, for example, to a signal which is electrically energized to show the G level condition or the failure of contact of the leaf spring 11 with terminal 17 (which might be the switchs own failure).

Although the disclosure of this patent application is not meant in any way to limit the uses of this inertia sensor, one application of the sensor would be as the inertia switch device utilized in the combination disclosed in US Pat. No. 3,610,361, patented Oct. 5, 1971, in which a seat belt retractor is locked as a result of sensor action.

I claim:

1. An inertia switch comprising achamber formed by top, side walls and base having an opening therein, a freely movable mass contained within said chamber and larger in diameter than said opening so as to be removably positioned as a result of inertial force in said opening under rest conditions, said chamber having inclined means for returning said mass to said position in said opening, biased means underlying said opening and mounted on said base for contacting and applying a predetermined force to a portion of said mass extending through said opening when in said opening, said mass moving from its rest position only on overcoming the combination of force thereon as a result of gravity, the incline and said bias, said biased means moving as a result of said contact in a direction against its bias, and switch means operatively associated with said biased means for contact therewith on movement in said direction.

2. An inertia switch as claimed in claim 1, said freely movable mass being in the shape of a sphere.

3. An inertia switch as claimed in claim 1, said freely movable mass being substantially cylindrical in shape.

4. An inertia switch as claimed in claim 3, said freely movable mass having at one end thereof a conical tip.

5. An inertia switch as claimed in claim 4, said chamber of such dimension that when said freely movable mass moves away from said position in said opening, the conical surface contacts the top of said chamber and thus maintains said mass in a position for re-entry into said opening on the resumption of rest condition.

6. An inertia switch as claimed in claim 1, said biased means consisting of a spring extending from said switch means and extending into said opening.

7. An inertia switch as claimed in claim 1, further comprising stop means on said base for limiting movement of said switch and said biased means operatively associated therewith in a direction toward the opening.

8. An inertia switch as claimed in claim 7, said biased means and said switch means located below the base and external to the chamber.

Claims

1. An inertia switch comprising a chamber formed by top, side walls and base having an opening therein, a freely movable mass contained within said chamber and larger in diameter than said opening so as to be removably positioned as a result of inertial force in said opening under rest conditions, said chamber having inclined means for returning said mass to said position in said opening, biased means underlying said opening and mounted on said base for contacting and applying a predetermined force to a portion of said mass extending through said opening when in said opening, said mass moving from its rest position only on overcoming the combination of force thereon as a result of gravity, the incline and said bias, said biased means moving as a result of said contact in a direction against its bias, and switch means operatively associated with said biased means for contact therewith on movement in said direction.