US 3812308 A
Description (OCR text may contain errors)
United States Patent 11 1 Bell et a1.
1 1 BALL ACTUATED INERTIA SWITCH Inventors: Lon E. Bell; William B. Gruber,
both of Altadena, Calif.
Assignee: Technar, Incorporated, Pasadena,
Filed: Aug. 23, 1972 Appl. No: 283,243
US. Cl.... ZOO/61.45 R, 200/61.52, ZOO/DIG. 2 Int. Cl. H0111 35/14, l-lOlh 1/16 Field of Search ZOO/DIG. 29, 61.11, 61.41,
ZOO/61.42, 61.43, 61.45 R, 61.48, 61.52
References Cited UNITED STATES PATENTS 11/1912 Myers 200/D1G. 29
[451 May 21, 1974 3,644,921 2/1972 Duggan et a1 ZOO/61.45 R X 1,662,979 3/1928 Nelson ZOO/DIG. 29
FOREIGN PATENTS OR APPLICATIONS 1,088,079 9/1954 France ZOO/61.11
Primary ExaminerJames R. Scott Attorney, Agent, or Firm-Jonathan Plaut 5 7] ABSTRACT Inertia switch with mass freely movable in chamber and energizing switch means upon reception in chamber.
3 Claims, 4 Drawing Figures BALL ACTUATED INERTIA SWITCH This invention relates to a G switch which embodies a mass removably mounted at the base of inclined apertured structure for biasing electrical contact means in one position when stationed partially within said aperture, and in a second position when said mass has moved from said aperture and is on the incline as a result of certain G forces.
Generally, the invention comprises a spherical mass or ball, in one embodiment, freely mounted for movement within a cylinder having an apertured inclined base. On the under-surface of the base is a contact wire biased into a position near the base which, when engaged by the spherical mass located within the aperture, moves to a position to engage another contact wire and implement the function of the switch.
When subjected to G forces of a certain predetermined level or greater, as a result of acceleration or deceleration, the mass moves from the apertured base up the incline and loses contact with the spring wire underneath the base. The fact that the spherical mass at a rest position is within the aperture and must first escape fromthe aperture provides a positive acting go:- no-go condition. The factor of escape from the aperture and that the mass must move up an incline on escaping the aperture under G forces, provides for not only positive action, but the filtering of those forces acting on the switch which are short duration pulses, as will be discussed later hereinafter. Since the contact wire against which the spherical mass abuts does lie against the mass until it moves from the aperture and a certain distance up the incline, such filtering effect is substantial.
The diameter of the aperture in the base in which the mass rests and the angle of incline determines the level of G forces needed to get and keep the spherical mass out of the apertured base and on the incline and thus out of contact with the contact wire.
In the usage of the sensor, the cylinder containing the mass is of such height that the mass may escape the aperture and incline entirely when the sensor is inverted, such as by a rollover of an automobile, to break contact with the contact wire.
The invention will now be described in more detail and further advantages understood with respect to the following drawings.
FIG. 1 shows the ball in rest position in one embodiment of the sensor;
FIG. 2 shows an end view of FIG. 1;
FIG. 3 shows the sensor of FIG. 1 with the mass having escaped the apertured base and on the incline thereof; and
FIG. 4 shows a second embodiment of the invention.
In the embodiment of FIG. 1 is shown a cylindrical casing 2 of an inertia sensor 1. Freely movable about within the casing, which forms a chamber 70, is a spherical mass or ball 3 which is held within the casing by its side wall 30, a base 4 integral therewith and a top 5 mounted on the side walls. The base 4 is inclined interior of the casing at an upward angle toward the side wall of the casing 2. The spherical member, when it rests, sits within the aperture or hole 7 in the base 4 and between the inclines 14 and extends therethrough at the bottom.
Mounted on the under surface 6 of the bottom of the base 4 is a spring contact wire 5a which is biased so as to tend to lie close to the base 4. The contact wire 5a may be preferably, in one embodiment, mounted in a groove 6 in the underside of the base 4 to enhance contact of the wire with the ball.
On one side of the aperture or hole 7 is mounted an electrical contact arm 8 which is in electrical contact with the wire 5a (see FIG. 2). In one embodiment, on the opposite side of the hole 7 from the contact arm 8 is a second contact arm 9 which has extending therefrom a contact wire 10 mounted so as to over-lie the contact wire 5a. The wire 5a may be fastened by welding to the contact arm 8 on the underside of the base at 12. In this embodiment, the wire 5a advantageously is free at the opposite end for movement under the influence of the mass 3. The contact wire 10 may be fastened to the base 4 at the end opposite to arm 9, as at 13, and is in electrical contact at the other end with arm 9.
When the spherical mass 3 is located in the hole 7, it bears against the contact wire 50 and pushes it against its own bias outward (away from the base) so as to be in contact with the wire 10 and complete the electrical circuit from the arm 8, through the wires 5 and 10 to the arm 9. When the spherical mass leaves the hole 7 and moves onto the incline (the incline being shown at 14), the contact wire 5a, under the influence of its bias, moves toward the base and out of contact with the wire 10, see FIG. 3.
In the embodiment of FIG. 4, the base 4 is substituted in function for the wire 10 so that the circuit is completed through the sphere 3, which must be conductive, from the base to the wire 50 when the sphere is in the hole 7.
In operation, such as, but not limited to, automotive useage as an inertia switch for locking seat belt retractors, the inertia sensor described is mounted so as to be sensitive to acceleration force in the vehicle. As a result of a sufficient enough G force level, the mass 3 moves from the hole up the incline breaking the electrical contact. In one embodiment, the inertia sensor could beutilized to look a seat belt retractor on occurrences of such G force, as disclosed in' US. Pat. No. 3,610,361, patented Oct. 5, 1971, for example.
The diameter of the hole and the angle of the incline will effect the forces necessary to move the mass against the forces of inertia and gravity out of the hole and up the incline. When such G forces have sufficiently declined or have disappeared, the mass will resettle in its rest position in the hole.
Because the spherical mass has to move out of the hole a certain distance before it no longer bears on contact arm 5, short duration pulses, such as caused by the effect of rough roads on an automobile driving thereover on which the sensor is mounted, will not cause the breaking of the contact between wires 5a and 10 in the sensor. There is insufficient duration and intensity to move the mass 3 out of the hole and away from the wire 5, so as to release that wire from the wire 10.
In its operation as a sensor for an automobile, as previously described, the normal functioning state of the sensor will be as shown in FIG. 1, the sensor being normally mounted so as to be horizontal on line AA when the vehicle is horizontal.
Electrical contact will be had in that state between the wire 5a and the wire 10.'When sufficient G force for a sufficient duration occurs so as to move the mass from the hole up the incline, contact between wire 5a and the wire is broken, and the circuit will be broken causing, for example, in the embodiment of the US. Patent cited above, the retractor to lock restricting movement of the passenger.
In the case of no net downward gravitational force in the mass, the wire pushes the mass upward thereby breaking the electrical contact. Such a case can occur during rollover, for example.
1. An inertia switch comprising an insulative chamber formed by top, sidewalls and base having a hole therein, a freely movable mass contained within said chamber and larger in diameter than said hole so as to be removably positioned in said hole under rest conditions, said chamber having inclined means for returning said mass to said position in said hole, switch means including a movable biased wire electrical contact underlying said hole mounted on said base for contacting a portion of said mass, said freely movable mass extending through said hole when in said hole and contacting said wire, said switch means moving as a result of said contact with said mass in a direction against its bias.
2. An inertia switch as claimed in claim 1, said switch means mounted outside of said chamber and underlying said base, a portion of said switch means being contacted by said biased wire on said movement.
3. An inertia switch as claimed in claim 1, said switch means consisting of said base, said mass, said fixed contact and said biased wire, said wireunderlying said hole.