US3542984A - Impact switch - Google Patents

Description

NOV. 24, 1970 K|RK ETAL IMPACT SWITCH 2 Sheets-Sheet 1 Filed July 24. 1.968

UTILIZATION CIRCUIT INVENTORS TURNER A. ROBIE ATTORNEY NOV. 24, 1970 I ET AL IMPACT SWITCH Filed July 24, 1968 2 Sheets-Sheet 2 INVENTORS TURNER A. ROBIE RUSSELL F. KIRK BY 2 flw %%M/&

ATTORNEY United States Patent O US. Cl. ZOO-61.45 6 Claims ABSTRACT OF THE DISCLOSURE This switch reacts to rapid acceleration or disturbance forces to irreversibly change from the open to closed state. A pair of conductive spheres or balls are supported against each other by a yieldable member having a circular seat in which one of the balls rests. A spring against the other ball presses the balls together so that the line of force through the balls intersects the surface of the seated ball within the perimeter of the seat. Deflection of the support due to a sudden impact against the assembly shifts the line of force outside the seat perimeter, unseating the ball and irreversibly moving it against a contact to close the switch.

BACKGROUND OF THE INVENTION This invention relates to electrical switches, and more particularly to an impact switch of the inertia type.

An impact switch is an electromechanical device which responds to acceleration forces applied to it or to a parent body by irreversibly closing electrical contacts to complete a circuit. The versatility and utility of such a switch depends upon its capability to react to forces applied to it in any direction and to remain locked in the closed state after tripping. Prior impact switches of this general type have been complex, costly structures which have not performed reliably.

A general object of this invention is the provision of a compact, simple, low cost impact switch.

A further object is the provision of an impact switch having a minimum number of parts which may be conveniently and quickly assembled.

SUMMARY OF THE INVENTION The movable contact of this impact switch comprises a pair of spring-loaded conductive balls supported on a yieldable member having a seat in which one of the balls rests. When the line of force between the balls intersects the seated ball on or within the seat perimeter, the switch is stable in the open state; when the point of intersection falls outside that perimeter due to a shift in the relative positions of the balls caused by an impact, the hall is unseated and moves into engagement with an adjacent stationary contact to close the switch. The other ball wedges the unseated ball against the contact, making the switch action irreversible.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an elevation of an impact switch embodying the invention;

FIG. 2 is a transverse sectison taken on line 22 of FIG. 1;

FIG. 3 is a section taken on line 33 of FIG. 2 showing the switch in the open position;

FIG. 4 is a transverse section taken on line 44 of FIG. 3;

FIG. 5 is a transverse section similar to FIG. 4 showing a modified form of the invention;

FIG. 6 is a section similar to FIG. 3 showing the switch in the closed position; and

FIG. 7 is a schematic representation of the switch bal s and the forces which act upon them.

3,542,984 Patented Nov. 24, 1970 A switch embodying the invention is shown at 10 in FIG. 1 and comprises a conductive casing 11, preferably cylindrical in form and open at one end, a coaxial terminal 12, and a second terminal 13 connected to casing 11 The switch terminals are connectable externally to utllization apparatus 14 which produces a desired effect upon closing of switch 10 when the latter receives a sudden jolt or impact.

Coaxially mounted in the casing 11 is a non-conductive block 15, see FIGS. 2, 3 and 6, having a central bore 16 with an axis coincident with the axis A of the casing. Block 15 has a main body portion 17 with an external diameter less than the internal diameter of the casing and has an enlarged rim 18 which engages shoulder 19 of casing 11 adjacent the open end of the latter. A washer 20 is mounted coaxially on the rim end of block 15 and the end portion 21 of the casing is spun over the washer to lock the latter and block rim 18 permanently to the casing. Terminal 12 extends through the central opening 20a of the washer for contact with other parts of the switch as explained below. Block 15 and washer 20 are made of suitable electrical insulating material such as polycarbonate or diallyl phthalate. It will be noted that casing 11 is cup-shaped and has its open end sealed by washer 20 and terminal 12 so as to protect the interior of the switch from moisture and foreign matter.

The end of block 15 opposite rim 18 has a foot 23 supported on the end wall of the casing. The main body 17 of the block has an intermediate surface 24 formed on a transverse plane inclined at an acute angle with axis A and intersecting bore 16 to form a lower bore opening 25 in the plane of that surface. Mounted on body 17 immediately below surface 24 as viewed in the drawings is a flexible or yieldable leaf member 27 having a circular opening or seat 28 offset from axis A. Member 27, which may be integral with the block as shown in FIGS. 3 and 6, is a cantilever designed to readily flex or bend about its connection 29 to the block and away from surface 24 when suflicient force is applied to the member.

An electrically conductive spring 30 is mounted in bore 16 of the block and abuts or is connected to an integral flange 32 on the inner end of terminal 12 under washer 20. The opposite end of spring 30 engages a conductive sphere or ball 34 in the lower end portion of the bore. A second sphere or ball 35 seated in opening 28 of member 27 and spaced from casing 11 engages sphere 34 at a point P on contact. Balls 34 and 35 preferably have equal diameters slightly less than the diameter of bore 16 and approximately twice the diameter of seat 28. Also, ball 35 when seated on member 27 is spaced slightly from block body 17 due to incline angle of surface 24 When switch 10 is in the open or non-conductive state as shown in FIG. 3, contact point P is located intermediate axis A and the center of seat 28 due to the offset position of the latter relative the axis. As a consequence of the relative dimensions of the balls, seat and offset, the direction of force from spring-loaded ball 34 to ball 35 causes the latter to be pressed securely into the seat. However, an acceleration force resulting from a jolt or impact applied to casing.11 causes member 27 to deflect away from surface 24, redirecting the line of force between the balls in such a manner as to dislodge ball 35 from seat 28 so that it engages the interior of casing 11 as shown in FIG. 6. With the balls in this position, electrical contact is made from terminal 12 through spring 30, balls 34 and 35, casing 11 and terminal 13 to complete a circuit. Ball 34 is essentially wedged between ball 35 and the wall of bore 16 so that neither ball can return to its initial position. The switch is thus locked in the closed position.

In order to improve the responsiveness of the switch to acceleration forces from any direction, member 27 may consist of a wire-like spring 37 formed in the shape of an eye hook as shown in FIG. 5. Such a member is equally responsive to forces in all directions transversely of the member.

The operation of the switch described above is based on the principle that a force applied between two balls is directed along a line of action through the centers of the balls. With one ball supported on a circular seat having a diameter smaller than that of the ball and with the other ball spring-loaded and engaging the first ball, the force is applied through the balls to the seat. If the force line through the ball centers intersects the surface of the seated ball within the perimeter of the seat, that ball is pressed more securely into the seat and the device is stable in that position. However, if the relative positions of the balls change so that the line of force intersects the seated ball externally of the seat perimeter, the resultant force moments move the seated ball outwardly from the seat. In other words, when the summation of force moments in the plane of the seat exceed the force moments normal to the seat, the seated ball overturns and moves outwardly.

This principle of operation is illustrated in FIG. 7 with the force of spring 30 indicated by arrow F and the force line between the balls indicated by the arrow P In the stable position as indicated by the parts in solid lines, the line of action F intersects the surface of ball 35 at or within the perimeter of engagement of that ball by the edges of opening 28in spring member 27. When the switch assembly is jolted, spring member 27 yields or bends to the broken line position shown and balls 34 and 35 move a corresponding amount. As a result of this movement, the line of action F shifts to intersect ball 35 externally of the perimeter of seat 28. This causes ball 35 to roll out of the seat against casing 11 to electrically connect terminals 12 and 13 as shown in FIG. 6.

A unique feature of the above described switch is that it responds to impact forces applied to it in any direction. Thus, the switch in any position instantly reacts to an impact force by snapping to the closed state. The spheres 34 and 35, preferebly are solid, react against each other under the loading of spring 30 and yieldable member 27 so that ball 35 is urged out from the seat 28 regardless of the direction of the impact force or the position of the switch.

We claim:

1. An impact switch comprising a block,

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surface of said one sphere substantially at the perimeter of the seat,

said member being mounted on said block to yield on impact and cause movement of the spheres and member relative to the block to a position such that the line through the centers of spheres and their point of contact intersects the surface of said one sphere externally of said seat,

an electrical conductor spaced from said one sphere by a distance less than the diameter of the latter,

a first switch terminal electrically connected to said one sphere, and

a second switch terminal electrically connected to said conductor.

2. The switch according to claim 1 in which said block is non-conductive and has a bore with an axis, said other sphere being disposed in said bore adjacent one end thereof, the center of said seat being offset from the axis of said bore.

3. The switch according to claim 2 with a compression spring in said bore engaging said other sphere and urging said spheres toward said member, said spring electrically connecting said second switch terminal to said other sphere.

a pair of electrically conductive spheres engagable with 4. The switch according to claim 3 in which said yieldable member is a leaf spring supported as a cantilever on said block, said seat consisting of a circular opening in said leaf spring.

5. The switch according to claim 3 in which said yieldable member is a wire-like element supported as a canti- -lever on said block, said seat consisting of a circular loop formed by said element.

6. An impact switch having first and second operating states, comprising a pair of electrically conductive balls,

means holding said conductive balls in engagement with each other,

a first switch terminal electrically connected to one of said balls,

a second switch terminal,

means mounting said second switch terminal adjacent to and spaced from the other of said balls for electrically making contact with said other ball when the switch is in the second operating state, and

said holding means including yieldable means engaging said other of said balls and restraining same from movement against said second terminal,

said yieldable means being responsive to a predetermined force by deflecting and thereby releasing said other ball for movement against said second terminal whereby to electrically connect said terminals through said balls.

References Cited

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