US3631370A

US3631370A - High-current, hot wire relay and flasher

Info

Publication number: US3631370A
Application number: US862812A
Authority: US
Inventors: Arthur J Hollis
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1969-10-01
Filing date: 1969-10-01
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: AU2051870A

Abstract

A monostable snap vane of a high-current flasher is held just beyond its snap point in an open contact position by an expansion ribbon fastened to opposite corners of the vane. Upon the passage of electric current through a resistance wire wrapped around the ribbon, the ribbon thermally expands, thereby permitting the vane to snap to a closed contact position and shorting out the current flow to the resistance wire. Cooling of the ribbon causes the vane to snap back to its open contact position.

Description

United States Patent 3,218,415 11/1965 Voorman 337/136 3,246,181 4/1966 Bleiweiss 337/135 3,225,165 12/1965 Bleiweiss et al.... 337/138 3,505,642 4/1970 Siiberg 337/136 FOREIGN PATENTS 605,950 8/1948 Great Britain 337/101 Primary Examiner-Bernard A. Gilheany Assistant Examiner-F. E. Bell Attorneys-Norman J. OMalley and James Theodosopoulos ABSTRACT: A monostable snap vane of a high-current flasher is held just beyond its snap point in an open contact position by an expansion ribbon fastened to opposite corners of the vane. Upon the passage of electric current through a resistance wire wrapped around the ribbon, the ribbon thermally expands, thereby permitting the vane to snap to a closed contact position and shorting out the current flow to the resistance wire. Cooling of the ribbon causes the vane to snap back to its open contact position.

PATENTEnniczsnan ARTHUR J. HOLLIS INVENTOR BY TWO,

AGE NT 1 HIGH-CURRENT, IIOT WIRE RELAY AND FLASHER BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to the field of electrical control devices, such as relays and automotive flashers, and particularly to such devices wherein an electrical circuit is opened and/or closed by the movement of a resilient, snap-acting vane.

2. Description of the Prior Art For the past decade or two, automobiles have been equipped with flashers for energizing directional signal lamps. Such flashers are generally of the snap-acting vane type, an example of which is shown in US. Pat. No. 2,861,149 issued on Nov. I8, 1958 to Hollis et al.

Recently the automotive industry has been required to supply all road vehicles with hazard warning signal flashers. Such flashers generally flash all the directional signal lamps of an automobile and must flash a minimum of four directional lamps. The electrical load, then, of a hazard flasher is about double that of a directional flasher.

Most hazard flashers currently in use are simply modified directional flashers. The higher electrical load on these flashers substantially limits their reliability and life. There are other devices, such as electromagnetic flashers, which will provide adequate reliability and life under a high electrical load, but they are quite expensive. It is an object of this invention to provide a reliable, low-cost, high-current flasher.

Directional flashe'rs of the type shown in US Pat. No. 2,86 I ,l49 have several disadvantages when adapted to handle the high current of a hazard flasher. First, the flasher is sensitive to the amount of current drawn by the load and the flashing rate can vary if the load current changes, such as by, for example, one lamp being burned out. The reason for this is that all the load current passes directly through the expansion ribbon and controls the rate at which the ribbon is heated and expanded. If one lamp is burned out, less current will pass through the ribbon and the ribbon will require more time to heat up and expand, thereby increasing the cycle time of the flasher.

Another disadvantage of the prior art flasher is that the metal comprising the expansion ribbon must be selected to have sufficient electrical resistivity to insure proper operation of the flasher. Such a requirement precluded the use of metals that have higher tensile strength and faster thermal response than the commonly used metals.

Also, the snap-acting vanes of the prior art flashers were generally made of high carbon steel. Because of variations in the metal structure, such vanes had to be aged or operated for at least 1 hour in order to obtain uniformity in the flashing cycle. In addition such vanes did not have adequate resistance to work hardening to provide the desired reliability and life for the high-current hazard flashers of the instant invention.

SUMMARY OF THE INVENTION A relay or flasher in accordance with this invention includes a substantially rectangular monostable snap vane. An expansion ribbon is disposed on one face of the vane, substantially diagonally thereto, the ends of the ribbon being fastened to the ends of the vane. The intermediate portions of the ribbon and the vane are free to move or flex relative to each other.

Disposed on the opposite face of the vane is a shunt made of a highly electrically conductive material, such as copper. Only the ends of the shunt are connected to the vane and the shunt has a loop at about its center in order to not inhibit the snap action of the vane.

One end of the shunt and vane assembly is fastened to a rigid blade terminal which, in turn, is mounted on an insulated base. The other end of the shunt and vane assembly is movable and, in the monostable position of the vane, is in contact with a contact terminal supported in the insulated base. Preferably electrical contact therebetween is established through an arcresistant contact mounted on the shunt and a similar contact mounted on the contact terminal.

A heater in the form of an insulated resistance wire is wrapped around the expansion ribbon along the length thereof. One end of the heater is electrically connected to the blade terminal and the other end of the resistance wire is electrically and flexibly connected to the contact terminal.

The device can be housed in a suitable protective container having means for externally connecting the terminals in an electrical circuit.

As normally assembled, the expansion ribbon maintains the vane in an open contact position, that is to say, the contact on the shunt is spaced slightly from the contact on the contact terminal. Upon electrical energization of the device through its terminals, current flows through the contact terminal, the flexible heater connection, the heater and the blade terminal. The heater rapidly heats the expansion ribbon, causing it to expand sufficiently to release its constraint of the vane and permitting the vane to snap to a closed contact position. In this position the low-resistance shunt shorts out the heater, thereby permitting the expansion ribbon to cool and contract and snap the vane back into its open contact position. Current then immediately flows through the heater again thereby repeating the cycle, which continues as long as electrical power is supplied to the device.

For use as a hazard flasher, the device is placed directly between an automobile power supply and the lamps to be flashed. When a suitable external switch is closed, current initially flows through the heater as mentioned above and the circuit is completed through the lamps. However the resistance of the heater is so high that the current flow through the lamps is insufficient to light them.

When the contacts of the flasher close, the shunt resistance thereof is so low that the lamps become the only effective load across the power supply and, consequently, they light up. The lamps will flash in this manner as long as the external switch is closed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view ofa flasher in accordance with this invention, showing the container in phantom.

FIG. 2 is a side elevational view of the flasher showing the vane in an open contact position.

FIG. 3 is the same view showing the contacts closed.

FIGS. 4 and 5 are front and back elevational views, respectively.

FIG. 6 is a top view of the flasher.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings a hazard flasher I in accordance with this invention comprises an electrically insulating base 2 holding blade terminal 3 and contact terminal 4 in fixed relationship to each other. In the example shown base 2 is molded around

terminals

3 and 4 which extend completely therethrough. An electrical contact 5 is connected to the inner end of terminal 4.

Fastened to the inner end of terminal 3 is an assembly comprising snap vane 6, shunt 7 and expansion ribbon 8. Vane 6 is a rectangular strip of 6 mil stainless steel having dimensions of about W4 inch by one-half inch. A 3/32-inch diameter hole ll extends through the center of vane 6. Preset deformations extend along the longitudinal center line of vane 6 from the edge of the vane to within about three thirty-seconds inch of hole 11. Similar deformations may extend along the minor axis of vane 6 for the purpose of increasing the snap differential of the vane.

Shut 7 is a flexible rectangular strip of 4 mil copper, threesixteenths inch wide by I inch long, and is positioned along a longitudinal edge of vane 6. Shunt 7 is disposed on the face of vane 6 wherein the above-mentioned preset deformations are concave.

Vane 6 and shunt 7 are spot welded to a protruding tab 9 of terminal 3, one end of shunt 7 being sandwiched between tab 9 and vane 6. Tab 9 is about one-fourth inch square and covers one end of shunt 7. A backup pad 10 is fastened to the opposing surface of vane 6, in line with tab 9, at the time of welding. The purpose of pad I is to strengthen the welded area of relatively thin vane 6 in the event that weld brittleness occurs.

The ends, only, of shunt 7 are fastened to vane 6; therefore the shunt does not substantially inhibit the snapping movement of vane 6. A 3/32-inch loop l2 at the center of shunt 7 further decreases the possibility of shunt 7 interfering with the snapping movement of vane 6.

A contact 13 is fastened to the opposite end of shunt 7 which, in turn, is welded to vane 6 and contact 13 is in alignment with contact on terminal 4. When vane 6 is in its monostable position, contacts l3 and 5 are in electrical contact with each other, and when vane 6 is in its secondary restrained position,

contacts

13 and 5 are spaced apart from each other.

Expansion ribbon 8 is tautly secured to diagonally opposite comers of vane 6 on the face thereof opposite that on which shunt 7 is disposed. The corners of vane 6 to which the ends of ribbon 8 are welded are bent slightly away from ribbon 8 in order to insure that the tensile force on the ribbon welds is parallel to the blade surface. This orients the welds in their strongest position.

In operation, ribbon 8 is not part of an electrical circuit and, therefore, need not satisfy any particular electricalconductivity requirement. However, because of the high stored energy level in stainless steel vane 6, ribbon 8 should have a high hot tensile strength. In addition, ribbon 8 should have a high temperature coefficient of expansion and very little creep. Also, the mass of ribbon 8 should be small in order to provide a fast cycle rate. I have found that a supersteel alloy, so called, which is a steel alloy containing chromium, nickel, molybdenum and titanium, was satisfactory for this purpose. In the example described, ribbon 8 was 4 mils thick by 0.025 inch wide by 1% long.

Wrapped around ribbon 8 is heater l4 consisting of a length of glass-insulated, lifi-mil, iron-nickel-chromium resistance wire having a resistance of 46 ohms. One end of heater 14 is electrically connected to pad and the other end is electrically connected to terminal 4 by means of a flexible connector 15. The flexibility of connector 15 permits the heater to move in conjunction with vane 6 without mechanical or electrical disruption of the heater connections.

An aluminum container 16, shown in phantom in FIG. 1, is attached to base 2 and encloses the flasher assembly for environmental protection thereof.

The use of a stainless steel vane eliminates the need of aging the flasher, as was commonly required in prior art flashers having the usual high carbon steel vane, since stainless steel can be stress-relieved at a temperature higher than the normal operating temperature of the vane. in addition the lower thermal conductivity of the stainless steel vane results in less heat being lost from expansion ribbon 8 to vane 6, thereby producing a faster initial cycle.

The use of shunt 7 with vane 6 dispenses with the need of selecting the vane material for its electrical conductivity. The high electrical conductivity of shunt 7 reduces the voltage drop across the flasher to an extremely low level, even at currents as high as amperes. And the relatively large surface area of shunt 7 effectively cools contact 13, which is mounted thereon, and permits the use of a smaller vane contact.

I have found it desirable to match the thermal coefficients of expansion of the base and the terminal materials to prevent relative movement between the terminals because of varying ambient temperatures. The combination of a mineral-filled phenolic resin base with a 70-30 brass terminal which has an offset equal to the distance between the two terminals was satisfactory in this respect.

For DC current applications, contacts 5 and I3 are preferably polarized and made of dissimilar materials to produce optimum contact life. Where the load is resistive, such as automobile lamps, the positive contact can be a high melting point material, such as palladium, and the negative contact can be a low electrical resistance material, such as silver.

The flasher was tested in a circuit comprising a l3 volt DC supply and eight automotive lamps, each rated at 2.l amperes. With vane 6 in the closed contact position, the voltage drop across the flasher was under 0.4 volts, and in the open contact position, the voltage drop across the flasher was 12.9 volts.

In performance testing, flashers in accordance with this invention successfully flashed a 17 ampere lamp load at l4 volts DC at selected rates between 60 and cycles per second for l to 2 million cycles. Prior art flashers, when tested under the same conditions, failed at less than z-million cycles.

For use of the device as a three-terminal relay, one end of heater 14 can be isolated from the load contact circuit. For example, connector l5 could be directly connected to a third terminal instead of the terminal 4, and for use as a four-terminal relay, each end of heater 14 could be connected to separate terminals.

lclaim: 1

' l. A control device comprising: an insulating base; a monostable snap vane; a first terminal supporting said vane in spaced relation with said base; an expansion ribbon disposed on one face of said vane and connected thereto at the ends of said ribbon only; a shunt of highly electrically conductive material disposed on the opposite surface of said vane and connected thereto at the ends of said shunt only; a resistance heater disposed on said expansion ribbon and electrically insulated therefrom; a second terminal supported in said base; a flexible electrical connection between one end of said heater and said second terminal; and a welding tab, the point of connection between said shunt and said vane being sandwiched between said first terminal and said welding tab.

2. The device of claim 1 wherein said vane consists ofa strip of stainless steel having a stress relief temperature higher than the normal operating temperature of said vane.

3. The device of claim l wherein said shunt comprises an elongated strip of copper having a loop at its center.

4. The device of claim 1 comprising, in addition, a first and a second contact, said first contact being disposed on said shunt, said second contact being disposed on said second terminal, said contacts being in electrical engagement with each other only when said vane is in its monostable position.

5. The device of claim I wherein said vane comprises a substantially rectangular strip of stainless steel having a central circular opening therethrough and having preset deformations extending longitudinally from each short edge of said strip to within about one diameter of said opening.

6. A control device comprising: an insulating base; a monostable snap vane; a first terminal supporting said vane in spaced relation with said base; an expansion ribbon disposed on one face of said vane and connected thereto at the ends of said ribbon only; a shunt of highly electrically conductive material disposed on the opposite surface of said vane and connected thereto at the ends of said shunt only; a resistance heater disposed on said expansion ribbon and electrically insulated therefrom; a second terminal supported in said base; a flexible electrical connection between one end of said heater and said second terminal; and a first and a second contact, said first contact being disposed on said shunt, said second contact being disposed on said second terminal, said contacts being in electrical engagement with each other only when said vane is in its monostable position, said shunt having a large surface area to effectively cool said first contact, thereby permitting the use ofa smaller contact.

Claims

1. A control device comprising: an insulating base; a monostable snap vane; a first terminal supporting said vane in spaced relation with said base; an expansion ribbon disposed on one face of said vane and connected thereto at the ends of said ribbon only; a shunt of highly electrically conductive material disposed on the opposite surface of said vane and connected thereto at the ends of said shunt only; a resistance heater disposed on said expansion ribbon and electrically insulated therefrom; a second terminal supported in said base; a flexible electrical connection between one end of said heater and said second terminal; and a welding tab, the point of connection between said shunt and said vane being sandwiched between said first terminal and said welding tab.

2. The device of claim 1 wherein said vane consists of a strip of stainless steel having a stress relief temperature higher than the normal operating temperature of said vane.

3. The device of claim 1 wherein said shunt comprises an elongated strip of copper having a loop at its center.

5. The device of claim 1 wherein said vane comprises a substantially rectangular strip of stainless steel having a central circular opening therethrough and having preset deformAtions extending longitudinally from each short edge of said strip to within about one diameter of said opening.

6. A control device comprising: an insulating base; a monostable snap vane; a first terminal supporting said vane in spaced relation with said base; an expansion ribbon disposed on one face of said vane and connected thereto at the ends of said ribbon only; a shunt of highly electrically conductive material disposed on the opposite surface of said vane and connected thereto at the ends of said shunt only; a resistance heater disposed on said expansion ribbon and electrically insulated therefrom; a second terminal supported in said base; a flexible electrical connection between one end of said heater and said second terminal; and a first and a second contact, said first contact being disposed on said shunt, said second contact being disposed on said second terminal, said contacts being in electrical engagement with each other only when said vane is in its monostable position, said shunt having a large surface area to effectively cool said first contact, thereby permitting the use of a smaller contact.