US3089934A

US3089934A - Flasher switch

Info

Publication number: US3089934A
Application number: US24724A
Authority: US
Inventors: Gustaf R Lawson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1960-04-26
Filing date: 1960-04-26
Publication date: 1963-05-14
Anticipated expiration: 1980-05-14

Description

May 14, 1963 G. R. LAWSON 3,089,934

FLASHER swucu Filed April 26, 1960 2 Sheets-Sheet 1 'NCREAS'NG MAGNETIC FORCE vs GAP 4 CONTACT HOLDING FORGE i 0 SPRING FORCE vs GAP AT FORCE VARIOUS HOT WIRE TEMPERATURES f/n emon' 60 1 1?. Lad/sol? GAP 'r o gw AcT OPENING GAP INCREASE DU -4 GAP DUE TO CONTACT THK. /J' Z 1/778;

G. R. LAWSON FLASHER SWITCH May 14, 1963 2 Sheets-Sheet 2 Filed April 26, 1960 f/n/e/rzar 605/6) ,6 Zea/s0 Afar/75y United States Patent Oiiiice 3,.fid9,934i Patented May 14, 1963 3,089,934 FLAEEHER WHTCH Gustaf R. Lawson, West Warwick, 13.1., assignor to General Electric Company, a corporation of New York Fiied Apr. 26, 19nd, Ser. No. 24,724 16 Claims. (Cl. zen-422) The present invention relates to an electrical timing switch of the type sometimes referred to as a flasher switch; more particularly, the invention relates to a timing switch to control the flashing of automobile turn indicator lights.

The present invention has as one of its objects to provide an improved electrical timing switch in which the timing cycle can be readily adjusted.

Another object of the present invention is to provide an electrical timing switch in which the switch contacts have snap action.

A further object of the invention is to provide an electrical timing switch which may be readily assembled from a minimum number of parts.

Other objects of the invention will become apparent from a perusal of the following specification considered in conjunction with the attached drawing wherein FIG. 1 is a perspective view of a timing switch made in accordance with this invention;

FIG. 2 is an exploded perspective View of the switch illustrated in FIG. 1;

FIG. 3 is an enlarged view of a portion of the switch illustrating an alternative structure;

FIG. 4 is a diagram of Force v. Armature Gap Distance illustrating the snap action of the switch of this invention;

FIG. 5 is an alternative embodiment of the invention wherein a pilot light circuit is included in the switch;

FIG. 6 is a bottom view of the embodiment of FIG. 5 showing the blade spacing;

FIG. 7 is a schematic diagram of a circuit including the switch of FIG. 5;

FIG. 8 is an additional embodiment showing a switch which includes a pilot light circuit;

FIG. 9 is a bottom view of the embodiment of PEG. 8 showing the contact blade spacing; and

FIG. 10 is a schematic diagram of a circuit including the switch of FIG. 8.

Briefly stated, in accordance with one of its aspects, the timing switch of this invention comprises a nonconducting bar magnet, a first and a second pole piece mounted on the opposite poles of the magnet, an armature centrally mounted on the second pole piece, the armature having a first leg disposed to make bridging engagement with the first pole piece and an oppositely extending second leg, and a resistance wire electrically connected between the pole pieces and mechanically connected between the second pole piece and theproiecting end of the second leg of the armature, the resistance wire when cold biasing the first leg of the armature out of contact with the first pole piece whereby when the first and second pole pieces are connected in an electric circuit the resistance wire is heated to expand and release the bias in the first armature leg enabling the magnet to attract the first armature leg to make contact with the first pole piece to establish a circuit which shunts the re istance wir Referring to the drawing, and particularly to FIGS. 1 and 2, a very important element of the invention consists of a bar magnet 16, here shown in cylindrical form with the poles located at the ends of the cylinder. Since this magnet electrically insulates the other elements of the switch from each other, a preferred form the so-called ceramic magnet which consists of powdered magnetic metal materials molded into a ceramic substance. Such magnets are non-conducting, relatively inexpensive, and easily molded to any desired shape. While they are preferred for use in this invention, it is understood that a conventional metal bar magnet can be used provided it is electrically insulated from the other elements of the structure.

Connected to one pole of the bar magnet 10 is a first pole piece 11 which has a portion extending transversely outward from the magnet and which is then flared at the end. The opposite pole of the magnet is has a second pole piece 12 extending transversely outward in the same direction as the first pole piece and which likewise has a flared end. It will be noted that the flared portion of the second pole piece is much greater in area than the flared portion of the first pole piece.

A first terminal 13 is in engagement with the first pole piece 11 and a second terminal 14 is in engagement with the second pole piece 12. The magnet 1d, pole pieces 1.1 and 12, and

terminals

13 and 14 comprise an assembly which is mounted upon a mounting base is composed of an insulating material such as a molded phenolic. The assembly is maintained on this mounting base as by a fastening screw 16. The first terminal 13 has a portion extending through the mounting base 15 to form a contact blade 17, and the second terminal 14 has a portion extending through the mounting base 15 to form a contact blade 18.

A resilient armature i9 is mounted upon the flare portion of the second pole piece 12. The armature 19 has a first leg 21 disposed to engage the flared portion of the first pole piece 11 and an oppositely disposed second leg 22 having an end portion 23 bent over the magnet 10 at about a -degree angle containing a notch 24. A portion of the material of the second leg 22 of the armature 19 has been removed to expose a center finger 25 and it is this finger 25 which mounts the armature on the flared portion of the second pole piece 12, as by welding. The use of the finger 25 as the mounting means increases the resilience of the armature 19 so that it readily has motion with respect to the pole piece.

Connected between the

terminals

13 and 14 is a resistance wire 26 having a top portion 27 and a coiled portion 28 separated by a glass head 29 positioned in the notch 24 of the armature 19. \Nhen cold, the top por- .tion 27 of the resistance wire 26 serves to bias the armature 19 out of engagement with the first pole piece 11. The purpose of the coiled portion 28 is to provide easy means to vary the length of the resistance wire 26 in order to vary the heating time of the resistance wire 26 and thus the timing cycle of the switch.

The embodiment illustrated in FIG. 3 is similar to the embodiment of FIGS. 1 and 2 except that an armature 31 is composed of rigid sheet metal which fulcrums off of an end portion of the second pole piece 12. The rigidity extends only to the first leg 32 of the armature 31. A second leg 33 may be of resilient material as in the case of the armature 19.

The embodiments of P168. 5 and 8 are similar to the embodiment of FIG. 1 except that an additional contact 35 is present to provide a pilot light circuit. In both embodiments this contact 35 is substituted for the stop member 34 of FIGS. 13. The contact 35 terminates in a third contact blade as through which connection to an external pilot circuit is made in the FIG. 5 embodiment.

In the embodiments of FIGS. 1-3 the

contact blades

17 and 18 are spaced 90' degrees from each other. In order to permit the contact blade configuration to conform to established standards of use, the three-blade switches of FIGS. 5 and 8 have two blades oppositely disposed to each other and the third contact blade positioned at right angles thereto.

The operation of the switch embodiments of FIGS. 13 is substantially the same and will now be described. The switch is piugged into a turn indicator circuit of an 3 automobile by means of the contact blades 17 and 1'3. :When the turn indicator switch is now operated, a circuit is established from the first terminal 13 through the resistance wire 26 and the second terminal M. This also f-completes a circuit to operate the turn indicator lights of the automobile but due to the high resistance of the resistance wire 26, the lights are not operated sufficiently to be visible. However, the resistance wire 26 at once heats up and in so doing the top portion 27 expands sufficiently to release its bias holding the first leg of the armature out of engagement with the first pole piece. Magnetic attraction then pulls the first leg of the armature into engagement with the first pole piece and this est-ablishes an electrical circuit from the first terminal 13, through the first pole piece 11, first leg of the armature, second pole piece 12, and second terminal 14 which shunts out the resistance wire 26. At once, the turn indicator lights of the automobile come on full and the resistance wire 26 beings to cool. When it has cooled sufiiciently, it contracts to restore the first leg of the armature to its initial position out of engagement with the first pole piece ill and the cycle is now ready to commence once again. The length and diameter of the resistance wire 25 may readily be adjusted to provide for flashing of the turn indicator lights one to two cycles per second.

As iilustnated in FIG. 7, the operation of the switch "9f the HS. embodnnent is the same as that described above for FIGS. 1-3 except that a pilot lamp 357 is energized as soon as the turn indicator circuit of the automobile is closcd. At the same time, the resistance wire 26 is energized through a circuit which includes signal lamps 38 but the signal lamps do not emit a significant quantity of light due to the voltage drop across the resistance wire 26. However, the wire 26 heats up and lengthens to release the armature 19 which makes contact with the pole piece 11 to shunt the wire 26 which then cools and contracts to restore the switch to the position illustrated in FIG. 5.

As shown in FIG. 10, the embodiment of FIG. 8 has the portion 27 of the resistance wire in series with the terminal 14. The signal lamps 38 in this embodiment are energized when the armature it? is in the position illustrated in FIG. 7 and the pilot lamp 37 is energized when the armature i9 is drawn to the second pole piece 12. The wire 27 in this embodiment is given a low resistance and this does away with the necessity of the glass bead 29 but makes it necessary to include insulating

washers

39 and 41 to insulate the terminals from the pole pieces. When the automobile turn signal switch is operated, the signal lamps 38 come on full brilliance and the wire 26 heats from the full load current. This heat lengthens the wire 26 which relaxes its hold on the armature 19 to enable it to be drawn into contact with the first pole piece 11. This breaks the circuit to the signal lamps 38 and closes the circuit energizing the pilot lamp 37 which goes on. While the wire 26 is also in the pilot lamp circuit, the current drawn by the pilot lamp is so small that the wire 26 cools and contracts to draw the armature 19 away from the pole piece 11 and into engagement with the contact 35 to restore the switch to the position illustrated in FIG. 7.

It has previously been mentioned that the switch of this invention has snap actiona very desirable feature which lengthens the life of the contacts. This action will be described with reference to FIG. 4. The snap action of the switch is accounted for by the difierence in behavior of the Spring force of the resilient armature 19 :and the magnetic force. The magnetic force is inversely proportional to the square of the distance between the pole piece and the armature. The spring force of the resilient armature, on the other hand, varies linearly in proportion to the strain placed upon it by the wire provided the range of this strain is not too great. Thus, it is possible to correlate the contact gap distance (distance between the first leg of the armature and first pole piece), magnetic strength, and spring gradient such that the armature connect be held suspended in the gap but will always move into engagement with the first pole piece or out of engagement to a stop 34 on the mounting base 15 depending upon how the armature i9 is flexed by the resistance wire 26.

in FIG. 4, if the straight sloping lines become steeper than the curve at the point of operati0n-a condition brought about when the spring is too stifior if the curve becomes less steep than the sloping lines-a condition brought about when the magnetic field is too wealrthe switch will not operate with a snap action. Therefore, the gap, magnetic field, armature stiffness, and resistance wire tension must be correlated to give the force conditions illustrated at a, b, c, and d of FIG. 4. The force illustrated at a in FIG. 4 is the contraction of the resistance wire upon cooling. At 17, the contacts snap open. At c, the resistance wire has expanded upon heating to release its tension tending to hold the contacts in open position. At d, the magnetic attraction has snapped the contacts into closed position.

While the invention has been described with reference to certain specific embodiments, it is obvious that there are a number of possible variations which would still fall within the spirit of the invention. Therefore, the invention is properly limited in scope only as may be necessitated by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical timing switch comprising a non-conducting bar magnet, a first and a second pole piece mounted on the opposite poles of said magnet, an armature centrally mounted on said second pole piece, said armature having a first leg disposed to make bridging engagement with said first pole piece and an oppositely ex tending second leg, and a resistance wire electrically connected between said pole pieces and mechanically connected between said second pole piece and the projecting end of the second leg of said armature, said resistance Wire when cold biasing the first leg of said armature out of contact with said first pole piece whereby when said first and second pole pieces are connected in an electric circuit said resistance wire is lengthened by heating to release the bias on said first armature leg enabling said magnet to attract said first armature leg to make contact with said first pole piece to establish an electrical circuit which shunts said resistance wire.

2. An electrical timing switch as claimed in claim 1 wherein the resistance wire has a taut portion and a coiled portion, the length of the coiled portion being adjustable.

3. An electrical timing switch as claimed in claim 2 wherein the pole pieces are flared outward and the second leg of the armature has a notched end portion bent at an angle of about toward the magnet.

4. An electrical timing switch as claimed in claim 3 wherein the taut portion of the resistance wire is separated from the coiled portion by a glass bead positioned in the notched portion of the armature second leg.

5. An electrical timing switch as claimed in claim 1 wherein the armature is resilient and fixedly mounted on the second pole piece.

6. An electrical timing switch as claimed in claim 1 wherein the armature is rigid and fulcrum-mounted on the second pole piece.

7. An electrical timing switch comprising a non-conducting bar magnet, a first conducting pole piece attached to one pole of said magnet and a second conducting pole piece attached to the other pole of said magnet, a terminal mounted on each pole piece, a mounting base of insulating material on which said magnet, pole pieces, and terminals are mounted, each terminal having a contact blade portion extending through said mounting base, an armature centrally mounted on said second pole piece, said armature having a first leg disposed to make engagement with said first pole piece and an oppositely disposed second leg, and a resistance wire insulatingly connected to the end of said second armature leg and extending to the terminal adjacent said second pole piece, said resistance wire when cold biasing said armature out of engagement with said first pole piece and releasing said armature when heated whereby said armature engages said first pole piece to close a circuit shunting said resistance wire.

8. An electrical timing switch as claimed in claim 7 wherein the armature is resilient and fixedly mounted on the second pole piece.

9. An electrical timing switch as claimed in claim 7 wherein the armature is rigid and fulcrum-mounted on the second pole piece.

10. An electrical timing switch as claimed in claim 7 wherein the pole pieces are flared and the second leg of the armature has a notched end portion bent at an angle of about 90 toward the magnet.

11. An electrical timing switch as claimed in claim 10 wherein the resistance wire has a taut portion and a coiled portion separated by a glass bead and the said glass bead is positioned in the notched portion of the second leg of the armature.

12. An electrical timing switch comprising: a mounting base of insulating material; an assembly comprising a nonconducting bar magnet, a first pole piece, an oppositely disposed second pole piece, a first terminal attached to said first pole piece, and a second terminal at tached to said second pole piece mounted on said mounting base, said pole pieces extending transversely across said bar magnet and being flared at one end; an armature mounted on the flared portion of said second pole piece, said armature having a first leg disposed to engage the flared portion of said first pole piece and an oppositely disposed second leg notched at the end and folded at said end in the direction of said magnet; a resistance wire connected between the end of said second leg of said armature and said second terminal for biasing said armature to a position out of engagement with said first pole piece; and a glass bead on said resistance wire for positioning said wire in the notch at the end of the second leg of said armature, said glass bead dividing said resistance wire into a taut portion and a coiled portion.

13. An electrical timing switch as claimed in claim 12 wherein the first and second terminals include Contact blades which extend through apertures in the mounting base.

14. An electrical timing switch as claimed in claim 12 wherein the armature is resilient and fixedly mounted on the second pole piece.

15. An electrical timing switch as claimed in claim 12 wherein the armature is rigid and fulcrum-mounted on the second pole piece.

16. An electrical timing switch comprising a non conducting bar magnet, a first and a second pole piece mounted on opposite poles of said magnet, an armature centrally mounted on said second pole piece, said armature having a first leg disposed to make bridging engagement with said first pole piece and an oppositely extending second leg, a contact spaced from said first pole piece, said contact being engageable by said first leg of said armature, and a resistance wire electrically connected between said pole pieces and mechanically connected between said second pole piece and the projecting end of the second leg of said armature, said resistance wire when cold biasing the first leg of said armature out of engagement with said first pole piece and in engagement with said contact whereby when said first and second pole pieces are connected in an electric circuit said resistance wire is lengthened by heating to release the bias on said first armature leg enabling said magnet to attract said first armature leg to make contact with said first pole piece to establish an electrical circuit which shunts said resistance wire.

References Cited in the file of this patent UNITED STATES PATENTS 2,103,276 Schmidinger Dec. 28, 1937 2,172,666 Michel Sept. 12, 1939 2,639,345 Sitzer May 19, 1953 2,715,187 Schmidinger Aug. 9, 1955 2,735,967 Lew'us Feb. 21, 1956 2,747,052 Blume May 22, 1956 2,749,404 Flubacker June 5, 1956

Claims

1. AN ELECTRICAL TIMING SWITCH COMPRISING A NON-CONDUCTING BAR MAGNET, A FIRST AND A SECOND POLE PIECE MOUNTED ON THE OPPOSITE POLES OF SAID MAGNET, AN ARMATURE CENTRALLY MOUNTED ON SAID SECOND POLE PIECE, SAID ARMATURE HAVING A FIRST LEG DISPOSED TO MAKE BRIDGING ENGAGEMENT WITH SAID FIRST POLE PIECE AND AN OPPOSITELY EXTENDING SECOND LEG, AND A RESISTANCE WIRE ELECTRICALLY CONNECTED BETWEEN SAID POLE PIECES AND MECHANICALLY CONNECTED BETWEEN SAID SECOND POLE PIECE AND THE PROJECTING END OF THE SECOND LEG OF SAID ARMATURE, SAID RESISTANCE WIRE WHEN COLD BIASING THE FIRST LEG OF SAID ARMATURE OUT OF CONTACT WITH SAID FIRST POLE PIECE WHEREBY WHEN SAID FIRST AND SECOND POLE PIECES ARE CONNECTED IN AN ELECTRIC CIRCUIT SAID RESISTANCE WIRE IS LENGTHENED BY HEATING TO RELEASE THE BIAS ON SAID FIRST ARMATURE LEG ENABLING SAID MAGNET TO ATTRACT SAID FIRST ARMATURE LEG TO MAKE CONTACT WITH SAID FIRST POLE PIECE TO ESTABLISH AN ELECTRICAL CIRCUIT WHICH SHUNTS SAID RESISTANCE WIRE.