US3483436A

US3483436A - Voltage compensated series flasher circuit

Info

Publication number: US3483436A
Authority: US
Inventors: Hemming G Siiberg
Original assignee: Wagner Electric Corp
Current assignee: Cooper Industries LLC
Priority date: 1967-08-21
Filing date: 1967-08-21
Publication date: 1969-12-09
Anticipated expiration: 1986-12-09
Also published as: GB1190168A; FR1579177A; DE1766952B1

Description

Dec. 9, 1969 H. G. SIIBERG VOLTAGE COMPENSATED SERIES FLASHER CIRCUIT Filed Aug. 21,` 1967 2 Sheets-Sheet 1 Dec. 9, 1969 H. G. snBERG 3,483,436

VOLTAGE COMPENSATED SRIES FLASHER CIRCUIT Filed Aug. 21, 1967 2 Sheets-Sheet 2 Tmp, @y

United States Patent O U.S. Cl. 317-123 6 Claims ABSTRACT F THE DISCLOSURE An electromagnetic relay having a spring-loaded armature is connected in series with a llasher so as to cause the llasher to be shunted for a portion of the llashers normal ON time when the lamp to be flashed is illuminated. This has the effect of maintaining a constant ON time within a range of applied voltages, as a result of shunting the large initial surge current past the llasher. As the lamp resistance increases with increasing incandescene, the current through the relay winding and the shunting path decreases to the point where the relay will become vde-energized, at which time sulliciently greater current will llow through the llasher to cause it to begin its operation.

It is desirable to employ series-connected snap-action flashers in automotive vehicle turn signal circuits and the like because of their simplicity and low power dissipation, which make this type of llasher very reliable. However, such llashers have the dis-advantage that they are very sensitive to fluctuations in the applied voltage. A higherthan-normal voltage results in a proportionately higher current, thereby causing more rapid heating of the pull ribbon of the llasher and consequently a shorter ON time and a faster flashing rate. Conversely, a lower-thannormal voltage produces a proportionately lower current, resulting in slower heating of the pull ribbon and consequently a longer ON time and a slower flashing rate. OFF time usually remains constant over the range of voltages normally encountered in the electrical system of au automotive vehicle.

The present invention achieves a voltage compensation within the normal range of lluctuation of a l2 volt automotive system, viz. from ll to volts (D.C.). Such voltage compensation results in a constant ON time and a constant flashing rate.

FIG. l is a schematic drawing of a preferred embodiment of the invention.

FIG. 2 shows the relationship between lamp current and llasher ON time for three values of applied voltage, with superimposed energization and de-energization levels of the magnetic relay.

FIG. 3 shows the voltage drop across the pull ribbon of a series llasher for the same three values of applied voltage as a function of flasher ON time with voltage compensation and without voltage compensation.

FIGS. 4 and 5 `show the dellecting member of the llasher preferred for utilization in the present invention.

FIG. 6 shows the deilecting member-pull ribbon assembly of the llasher preferred for utilization in the present invention.

FIGS. 7, 8, 9 and l0 diagrammatically show the dellecting member-pull ribbon assembly of FIG. 6 associated with the other cooperative parts of the flasher at various times during the operating cycle of the llasher.

Referring now to FIG. 1, terminal 10 connects the winding 12 of relay 14 in series with a power source 15. Winding 12 is connected to armature 16 and to a terminal of llasher 18. The relay 14 further comprises contacts 20, which, when closed, establish a shunt path around flasher ice 18. Armature 16 is spring loaded by adjustable spring 22 connected to the frame 24. Core 26 serves to concentrate magnetic flux resulting from current passing through winding 12. Series llasher 18 is connected through switch 28 to lamp load 30 and then to ground 32.

The operation of the circuit may be best understood by a brief explanation of the initial circuit conditions upon closing of switch 28 with the relay 14 eliminated and substituted by an assumed direct connection between terminal 10 and llasher 18 as is used in conventional series-connected llasher circuits. In such a circuit, a surge current `of a magnitude of approximately five to seven times that of the steady state lamp load current would be produced when switch 28 is closed, due to the nonlinear resistance characteristic of the lamp load. This surge current, which is caused primarily by the low initial resistance of lamp load 30, has a duration of between to 200 milliseconds, depending upon the characteristics of the lamp filament, and remains fairly constant for a range of applied voltages from 11 to 15 volts. Since series flashers usually have an ON time which ranges between 350 milliseconds and 600 milliseconds, the surge current lasts for a signilicant part of the ON time. The curves in FIG. 2 show the relationship between lamp current and ON time of a llashing lamp for three values of applied voltage. From that graph of FIG. 2, it may be readily seen that ON time decreases as applied Voltage and the resulting surge current increase. Thus, the ON time lluctuates undesirably as the applied voltage varies, which is a common occurrence in automobile circuits.

The present invention introduces a variable time delay between the closing of switch 28 and the full energization of yseries llasher 18, so as to delay the opening of the series llasher contacts and thereby maintain a constant ON time, regardless of applied voltage. In the embodiment illustrated in FIG. 1, this variable time delay is provided by the relay 14 which is adjusted so as to cause contacts 20 to close below the peak surge current produced by the lowest value of applied voltage encountered in the circuit.

The de-energization current level of relay 14 is set at a specific current level higher than the highest steady state lamp current, which will result in a variable time delay during which the llasher is shunted, thereby producing a constant ON time. The effect of the adjustment of the de-energization level of relay 14 is illustrated in the 4graph of FIG. 2, which shows the levels at which the relay is under-compensated, fully-compensated, or over-compensated. The relay 14 may be adjusted by varying the tension of the spring 22 or the width of the gap between the contacts 20.

When relay 14 is properly adjusted, the circuit will operate as follows:

When a voltage within the range for which the circuit is designed to operate is applied to terminal 10, the aforementioned surge current will pass through winding 12 of relay 14, thereby causing a concentration of magnetic llux in the core 26. As a result, the armature 16 will be drawn to the core 26 against the bias of spring 22, thereby causing contacts 20 to close. Flasher 18 is thereby almost completely by-passed by the low resistance paths through armature 16 and contacts 20 to the switch side of the llasher. As the resistance of lamp load 30 increases, load current will decrease, eventually reaching the de-energization level of relay 14. Contacts 20 will then open, thereby breaking the shunt path around llasher 18, with a resultant increase in current through the series flasher 18. Heating of the pull ribbon of the llasher will become greatly accelerated by this increase in current and, after the pull ribbon has relaxed sullciently, the contacts of the llasher 18 will open. When the contacts 3 of the flasher 18 close due to cooling of the pull ribbon, a large surge current will again pass through the winding 12 and the aforementioned cycle will continue to repeat itself as long as switch 28 remains closed.

Referring now to FIG. 3, the series of graphs produced by an uncompensated circuit lacking relay 14 show a steady decrease of ON time with increasing values of applied voltage, whereas the series of graphs produced by the compensated circuit of FIG. 1 shows a constant ON time for the range of applied voltages from 1l to 15 volts. Thus, the advantage of the invention is lforcefully and dramatically demonstrated.

Although the invention can employ any known snapaction flasher, it has been found that the flasher disclosed in my co-pending application, Ser. No. 638,856, filed on May 16, 1957 gives the best results to date when utilized in the circuit of this invention. This flasher is shown in FIGS. 4 through 10, and is described in the following paragraphs.

Referring now to FIGS. 4, 5 and 6, the blade 10 has a rectangular portion 12 and a tapered portion 14. The rectangular portion 12 has a tab 16 to facilitate the mounting of the pull ribbon. The narrow tip of the tapered portion 14 serves the sarne function.

A deformation 18 extends along an axis in the central region of the blade and is made after the formation of the cutout area 20 which produces the tongue 22. The blade is made of a conducting spring material such as steel, duranickel, or the like. A preferred range of the included angle formed by the rectangular and tapered portions after the deformation has been made is from approximately 160 to 170, although angles outside of this range may also used. The two portions of the blade on either side of the deformation 18 are bowed reversely to the direction of bend of the deformation by attaching a pull ribbon 24 under tension to the blade as shown in FIG. 6. By tapering one portion of the blade 14, a more constant radius of curvature is produced in that portion when the blade is subjected to the tension of the pull ribbon and other functional advantages are achieved also. The function of the cutout is to permit the pull ribbon 24 to pass just below the crest of the deformation in the blade 10.

Contact 26 is mounted on the pull ribbon 24 in proximity to the deformation 18 of the blade 10. The contact 26 is preferably centrally located on the pull ribbon 24 so as to provide the maximum rate of heating of the pull ribbon, which results in faster starting of the flasher. The pull ribbon 24 is preferably welded to the blade 10 at

points

16 and 28, which form convenient tabs for mounting. Tab 28 is simply the tip of the tapered portion 14 of the blade 10.

FIG. 7 illustrates the pull ribbon-blade member assembly of FIG. 6 diagrammatically associated with other parts in an operative flasher mechanism which is in a cold position. The blade 10 is attached to a mount 34 which is electrically connected to terminal 37 and electrically insulated from a supporting frame 36. Terminal 37 is in turn connected to a lamp load 38 which 1s grounded at 40. The movable contact 26 is engaged with a stationary contact 32 which is electrically connected to terminal 33 and electrically insulated from frame 36. Terminal 33 is in turn connected through an on-off switch 31 to a source of electric current 30, such as an automobile battery. The stop 42 for the free end of the blade 10 is mounted on the frame 36 and the function of the stop will be explained in greater detail below.

In the FIG. 7 cold position of the flasher mechanism, the mechanical energy stored in the blade 10 under the tension of the pull ribbon 24 urges the pull ribbon upward to generate the pressure necessary to maintain the

contacts

26 and 32 firmly engaged and to prevent arcing between these contacts upon disengagement thereof. When the switch 31 `is closed, an electrical circuit is .established whereby Current HOW@ tra@ oure ,39 through 3,483,436 I Y l switch 31, terminal 33,

contacts

32 and 26, pull ribbon 24, blade 10, mount 34, terminal 37 and load 38 to ground 40. Current flow through the ribbon 24 generates heat which causes the ribbon to expand in length wherebv the distance between points A and C increases. As this expansion occurs, the previously-stored energy of the blade 10 causes the crest of the deformation v18 (point B) to move towards the ribbon 24. When the ribbon 2.4 is substantially coincident with the crest of deformation 18, a functional intermediate or equilibrium position is reached (FIG. 8) and thereafter, when the ribbon moves just past the equilibrium position, a sudden release of energy occurs to produce a snap action movement which disengages

contacts

32 and 26 and moves the pull ribbonblade assembly into the hot position shown in FIG. 9.

In this position, the pull ribbon '24 is prevented from going too far below the crest of deformation 18 (point B) by the cutout portion 20 and the tongue 22 therein (FIGS. 4 and 5) and by mechanical stop 42. If the pull ribbon 24 were allowed to pass too far below point B, the forces exerted by the pull ribbon upon cooling would tend to pull points A and C down further below point B, rather than upward. Mechanical stop 42 is adjustable, so as to provide a control over the amount of potential energy in blade 10 which is to be released. This adjustment will control the rate at which the flasher operates,

With the flasher mechanism in the hot position shown in FIG. 9, the electric circuit for energizing the load 38 and heating the pull ribbon 24 is broken, so that the load is extinguished and the ribbon begins to cool and contact. This forces the crest (point B) to again move toward the ribbon 24, this time in an opposite direction as compared to the sequence of FIGS. 7 and 8, until a functional intermediate or equilibrium position is again reached, as shown in FIG. 10, with the ribbon being substantially coincident with the crest. When the ribbon 24 moves just 'beyond the equilibrium position, there is again a sudden release of energy which causes the pull ribbon and blade 10 to return to the cold position shown in FIG. 7 to re-engage the

contacts

26 and 32.

The cycle described in connection with FIGS. 7 through 10 repeats as long as switch 31 is maintained closed.

It will be understood that it is intended to cover all changes and modifications of the preferred embodiment of the invention, herein chosen for the purpose of illustration, which do not depart from the spirit and scope of the invention.

What is claimed is:

1. A voltage-compensated flasher circuit comprising:

(a) a power source,

(b) an electromagnetic relay connected to said power source,

(c) a flasher connected to said relay,

(d) a load having a non-linear resistance characteristic connected to said flasher, and

(e) a switch for completing and opening said circuit; said relay being operative when said switch is closed to shunt said flasher during an initial portion of the time period when the flasher contacts are closed.

2. A voltage-compensated flasher circuit according to claim 1, wherein said flasher comprises:

(a) a deflecting member having a deformation extending along an axis thereof,

(b) an expansible pull member attached under tension to said deflecting member to hold portions of said deflecting member bowed on opposite sides of said deformation reversely to the direction of bend of said deformation,

(c),y a movable contact mounted on the deflecting member-pull member assembly,

(d) a stationary contact positioned for cooperative make-and-break electrical connection with said moys .able cantata and (e) means for electrically heating said pull member intermittently in order to alternately expand and contract said pull member whereby said pull member moves reciprocally in opposite directions through an equilibrium position located approximately at the 5 crest of said deformation to produce snap actions which correspondingly cause said make-and-break electrical connection between said contacts without substantial change in the directions of bend of said deformation and bowed portions of said deflecting lo member.

3. A voltage-compensated flasher circuit according to claim 1, wherein said electromagnetic relay comprises:

(a) a winding having rst and second terminals, said iirst terminal being electrically connected to said power source and said second terminal being electrically connected to a first terminal of said asher,

(b) a magnetic core,

(c) an armature electrically connected to said second terminal of said electromagnetic relay, and 2O (d) irst and second contacts, said rst contact being electrically and mechanically connected to said armature and said second contact being electrically connected to a second terminal of said flasher.

4. A voltage-compensated flasher circuit according to claim 3, wherein said armature is mechanically biased by adjustable spring means so as to hold said rst and second contacts open when the current flowing through said winding is below the relay energization thershold.

5. A voltage-compensated asher circuit according to claim 3, including means for adjusting the gap between said first and second contacts.

6. A voltage-compensated flasher circuit according to claim 3, wherein said flasher comprises:

(a) a blade member having a linear crease transverse to its longitudinal axis, a cutout portion forming a tongue which partially coincides with said linear crease, a tapered portion extending from the bows of said linear crease, and integral tabs positioned at opposite ends of said blade member along said longitudinal axis,

(b) an expansible pull member attached under tension to said integral tabs of said blade member to bow the portions of said blade member on opopsite sides of said linear crease reversely to the direction in which said portions were inclined by the introduction of said linear crease,

(c) a movable contact mounted on the blade memberpull member assembly,

(d) a stationary contact positioned for cooperative make-and-break electrical connection with said moveable Contact, and

(e) means for electrically heating said pull member intermittently in order to alternately expand and contract said pull member, whereby said pull member moves reciprocally through an equilibrium position located approximately at the locus of said deformation to produce snap actions which cause cyclical making and breaking of an `electrical connection through said contacts, without substantial change in the congurations of said linear crease and of said bowed portions of said blade member.

References Cited UNITED STATES PATENTS 3,302,057 1/1967 Siiberg 315-77 LEE T. HIX, Primary Examiner U.S. Cl. X.R.