US3041424A - Magnetomotive and thermomotive flasher - Google Patents

Description

June 26, 1962 R. B. GRONTKOWSKI MAGNETOMOTIVE AND THERMOMOTIVE FLASHER Filed July 17, 1959 FIG.1

INVENTOR.

Raymond B. Gronrkowski ATTORNEY3 United States Patent ()fiice 3,041,424 MAGNETGMOTIVE AND THERNIDMOTIVE FLASHER Raymond B. Grontkowski, Bronx, N.Y., assignor to Signal-Stat Corporation, Brooklyn, N.Y., a corporation of New York Filed July 17, 1959, Ser. No. 827,946 3 Claims. (Cl. 200113) This invention relates to thermomotive circuit breakers, such as the flashers commonly used in automotive vehicle signalling systems, and more particularly to a thermomotive flasher embodying novel, simple and readily adjustable means for pre-setting the limits of movement of the separable contacts and the frequency of operation of the flasher.

In the co-pending application of James W. Welsh, Serial No. 734,471, filed May 12, 1958, and now Patent No. 2,900,474, issued August 15, 1959, as Well as in the copending application of James W. Welsh, Serial No. 1,064, filed January 7, 1960, there is described a novel type of thermomotive flasher in which a combination of magnetomotive and thermomotive forces are used to effect snap separation and snap engagement of the contacts thereby to increase the contact life. In the latter of said applications, there is described an improved flasher arrangement wherein, during the break cycle of the flasher, the contact pressure is actually increased up to the point of actual snapping apart of the contacts, and the contacts, when reengaged in the made portion of the cycle, are reengaged under full and increasing contact pressure.

Both of these types of flashers have proven effective in operation. However, when produced as a commercial item, it is important that such flashers be designed for ready and easy setting of the limits of movement of the movable contact, for ready and easy setting of the rate of operation or cycling frequency of the flasher, and for accurate and precision joining of parts. For example, in these flashers a relatively rigid magnetic armature is secured to the free end of a relatively flexible bimetallic thermomotive element or strip. It is important that the fixed end of this strip be welded or brazed to its support at a precise location in order that the distance between the point of joining the bimetallic strip to its support and the point of joining the free end of the bimetallic strip to the magnetic armature be maintained accurately to preset the desired operating values of the flasher. While, by the use of jigs and the like, a welded or brazed joint can be readily and accurately located in joining the armature to the bimetallic strip before the latter is mounted to its support, it is diflicult, in a production operation, to accurately fix the location of the Welded or brazed joint securing the bimetallic strip to its support so that it will be at a pre-set distance from the joint securing the strip to the magnetic armature.

In order to take full advantage of the magnetomotive effect of the magnet on the armature, it is highly desirable that provision be made for accurately and precisely presetting the range of movement of the armature toward and away from its associated permanent magnet. It is also desirable to provide means for readily and easily setting accurately the cycling rate or frequency of operation of the flasher.

In accordance with the present invention, the several mentioned factors are provided for in a novel and simple manner. The control of the limit of movement of the magnetic armature with respect to its magnet is provided by an arm positioned adjacent the free end of the armature and having a pair of bendable tabs projecting into the path of movement of the armature. By suitable bending of these tabs, the range of movement of the magnetic armature with respect to its magnet may be accurately and very simply pre-set. The striking of the armature against these tabs produces an audible indication of the flasher operation, which is highly desirable. Also, when the armature engages a tab, a magnetic circuit is closed except for the gap between the armature and the magnet. This improves the snap action of the flasher.

The bimetallic strip to which the magnetic armature is secured is mounted on a support bracket having a shoulder or tab projecting therefrom. This shoulder acts as a stop against which the fixed end of the bimetallic strip may be positioned for precise location of the strip during forming of the welded or brazed joint anchoring the bimetallic strip to its support. Thereby, accurate-location of this joint is provided for in a simple and easy manner particularly adapted to production line assembly of the flasher. 1

Adjustable pre-sett-ing of the frequency of the flasher is also effected in a novel and simple manner. -More particularly, the aforementioned shoulder for positioning the bimetallic strip for welding or brazing is bent over the bimetallic strip so as to overlie the same. By bending the tab or shoulder to project over the strip, the rapidity of cycling or the frequency of the flasher may be readily and easily adjusted to a pre-set value by adjusting the distance between the overlying tab and the bimetallic strip.

For an understanding of the invention principles, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a side elevation view of a thermomotive flasher embodying the invention, the cover thereof being broken away to illustrate the components of the flasher;

FIG. 2 is a plan view of the flasher with the cover recover removed; and

FIG. 3 is an end elevation View of the flasher with the cover again partly broken away.

Referring to the drawings, a flasher embodying the invention is illustrated as comprising a dielectric base 10 and acover 15 which may be of metal. Three prongs or terminal lugs 11, 12 and 13 project from base 10 whereby the flasher may be suitably disengageably mounted in a receptacle for connection into the signalling circuit of an automotive vehicle. The terminal lugs 11, 12 and 13 are respectively secured to base 10 by means of rivets 16, 17, and 18. Rivets 16 and 17, and thus lugs 11 and .12, are electrically interconnected by a flat L-shaped piece of conductive metal 14.

An electrically conductive metal mounting member 20 has a strip portion 21 secured beneath rivet 18 and by a fastener 22 to base 1 0. Adjacent the end of base 10,

bracket 20 has a flange 23 bent upwardly at right angles and extending laterally over and in spaced relation to rivet 17. A platform 24 is bent outwardly from extension 23 parallel to base 10 and a shoulder or tab 25 is bent upwardly from the free end of shelf 24, tab- 25 preferably having a tapered or pointed free end. The purpose of shelf 24 and 25 will be described more fully hereinafter.

Beyond rivets 16 and 18 toward the other end of base 10, and centered transversely of the base, a permanent magnet 30 is set into base 10. This permanent magnet may be of any magnetic material having a long life and capable of retaining its strength under adverse operation conditions, such as in the presence of elevated temperatures. Also, it should be a magnetic material which is not substantially subject to deterioration by aging. A suitable permanent magnet may be one of the Alnico permanent magnets manufactured by the General Electric Company. Beyond magnet 30, a paramagnetic meta1 L-shaped bracket 31 is secured to base 10 by a fastener Patented June 26, 1962 3 32 and has an upstanding arm 33 from which are. struck two vertically spaced tabs 35U and 35L.

The circuit making and breaking portion of the flasher comprises a magnetic armature 40 secured to the free end of a bimetallic strip 45. Bimetallic strip 45 is, in turn, secured to platform or shelf 24. Magnetic armature 40 has an offset bend or loop 41 transversely aligned with rivets 16 and 18. A resilient conductor 42 is brazed or Welded into off-set loop 41 and extends laterally over rivet 16. The free end of strip 42 has secured thereto a contact 43 which is normally engaged with a bar-shaped contact 44 brazed or welded to rivet 16. The free end of armature 40 extends between tabs 35U and 35L, and in alignment with the upper end of permanent magnet 30, but stops short of arm 33 of bracket 31.

As stated, it is very important that the parameters of the circuit maker and breaker, and particularly the effective length of bimetallic strip 45 be accurately set in a simple manner. The accurate assembly of the free end of strip 45 to the end of armature 40 is relatively easily effected by placing these two parts in a jig and brazing and welding the same together as indicated at 46. However, it has been diflicult to accurately locate the welded or brazed joint securing the fixed end of bimetallic strip 45 in position. In the present invention, such accurate location is effected in an easy and simple manner. The bent up shoulder or tab 25 is precisely positioned relative to shelf 24 to provide a fixed abutment against which bimetallic strip 45 is abutted and held while a welded or brazed joint 47 is formed. The distance between welded or brazed joints 46 and 47 determines the effective length of bimetallic strip 45, which effective length is important to the proper functioning of the flasher.

Shoulder or tab 25 has a further function. It is desirable to accurately set the operating frequency or cycling rate of the flasher and, in the present invention, this is done by bending tab 25 downwardly over bimetallic strip 45. The distance between the free pointed end of tab 25 and the bimetallic strip 45 determines the frequency of cycling of the flasher by controlling the. degree of deflection of the bimetallic strip when the latter is heated. Such frequency can be easily adjusted or regulated by varying the amount by which tab 25 is bent over strip 45.

It is also important to the proper functioning of the flasher in providing the snap engagement and snap separation of contacts 43 and 44 that the limits of movement of armature 40 relative to the magnetomotive force of permanent magnet 30* be set. Thus, it is important to be able to easily adjust the minimum spacing of the armature from the magnet and also to be able to easily adjust the maximum spacing of the armature from the magnet. In the illustrated flasher, this is effected by the two tabs 35U and 35L. These tabs may be bent in either direction to accurately set both the minimum spacing of armature 40 from magnet 30 and the maximum spacing of armature 40 from magnet 30, and such spacing may be easily re-adjusted at any time by further bending of the tabs 35U and 35L.

When the armature 40 engages tab 35L, the magnetic flux flows into the tab and bracket 35. This augments the magnetomotive force holding the armature down, and thus increases the snap action on contact separation. Engagement of armature 40 with tabs 35U and 35L produces distinctly audible clicks which are indicative of flasher operation.

It will be thus seen that a flasher is provided in which the effective length of the bimetallic strip is accurately pre-determined, in which the frequency of the flasher can be accurately pre-set and accurately adjusted, and in which the relative range movement of the circuit breaker can be effectively controlled as to limits of operation in both directions.

In the operation of the illustrated flasher, when a potential is applied between contacts 11 and 13, current 4 will flow through bracket to shelf or platform 24 and enter the bimetallic strip 45 and flow from this strip through armature 40, normally closed contacts 43 and 44, and rivet 16 to lug 11. A parallel circuit, such as a pilot lamp circuit, may also be connected to lug 12 which is secured by rivet 17 to conductor strip 14. The current flow heats the bimetallic strip which bows and deflects to build up kinetic energy in a direction tending to separate normally closed contacts 43 and 44. However, the magnetomotive force exerted by magnet on armature 40, assisted by the magnetic flux path into tab L, maintains the contacts fully engaged under pressure until such time as the kinetic energy in strip 45 has built up to a value exceeding the force of the magnet on the armature. At this time, the normally closed contacts 43 and 44 are snapped apart and, with the distance of armature from magnet 30 rapidly increasing with a corresponding even more rapid decrease in the effective magnetomotive force on the armature, the separation is accelerated. The limit of separation, of course, is pre-set by adjustment of tab 35U. With the opening of contacts 43 and 44, the circuit is broken and bimetallic strip cools. This tends to move armature 40 toward magnet 30 and, after a predetermined movement with the magnetomotive force increasing inversely as the square of the distance from the magnet to the armature, the movement of the armature is accelerated so that contacts 43 and 44 are re-engaged with a snap action as soon as the magnetomotive force exceeds the residual kinetic energy in bimetallic strip 45.

While a specific embodiment of the invention has been shown and described in order to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

l. A normally closed thermomotive circuit breaker comprising, in combination, a dielectric base; a first relatively fixed terminal on said base; a relatively elongated thermomotive element electrically and mechanically fixed at one end relative to said first terminal; a magnetic armature secured to and extending from the free end of said element; a second relatively fixed terminal on said base; a relatively fixed contact electrically connected to said second terminal; a relatively movable contact carried by said armature in alignment with said relatively fixed contact; a magnet on said base aligned with the free end of said armature and biasing said armature toward said base to normally engage said contacts; said element, upon establishment of an electric potential between said terminals, being heated by the flow of current therethrough and tending to deflect in a contact separating direction; the holding action of said magnet on said armature resisting such deflection of said element until the energy stored in said element exceeds the magnetomotive holding force whereupon said element deflects its free end away from the base to snap said contacts apart at an accelerating rate; said element, upon interruption of current flow therethrough, deflecting toward said base and the increasing magnetomotive force upon said armature overbalancing the energy stored in said element to snap said contacts into engagement; and a bracket secured to said base and having an arm projecting from the base adjacent the free end of said armature; said arm having a pair of tabs adjustably bent therefrom into the path of movement of the free end of the armature relative to said magnet to pre-set the range of movement of said armature.

2. A normally closed thermomotive circuit breaker comprising, in combination, a dielectric base; a first relatively fixed terminal on said base; an electrically conductive bracket electrically and mechanically secured to said first terminal and having a shelf extending substantially parallel to said base; said shelf having a shoulder tab extending outwardly from its outer end; a relative- 1y elongated thermomotive element having a fixed end lying along said shelf and secured thereto by a fused metal joint, the location of said joint being accurately predetermined by engagement of said element with said shoulder and said joint electrically and mechanically connecting said element to said bracket; a magnetic armature secured to and extending from the free end of said element; a second relatively fixed terminal on said base; a relatively fixed contact electrically connected to said second terminal; a relatively movable contact carried by said armature in alignment with said relatively fixed contact; a magnet on said base aligned with the free end of said armature and biasing said armature toward said base to normally engage said contacts; said element, upon establishment of an electric potential between said terminals, being heated by the flow of current therethrough and tending to deflect in a contact separating direction; the holding action of said magnet on said armature resisting such deflection of said element until the energy stored in said element exceeds the magnetomotive holding force whereupon said element deflects its free end away from the base to snap said contacts apart at an accelerating rate; said element, upon interruption of cur- References Cited in the file of this patent UNITED STATES PATENTS 1,477,350 Hoeschen Dec. 11, 1923 1,943,656 Doman et a1. Ian. 16, 1934 1,997,604 Stewart Apr. 16, 1935 2,236,282 Ayers Mar. 25, 1941 2,338,474 Wilson Jan. 4, 1944 2,484,145 Bader Oct. 11, 1949' 2,900,474 Welsh Aug. 18, 1959 2,953,664 Mitick Sept. 20, 1960

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