Volume increasing flasher unit for turn signal system

A flasher unit is provided which can plug into the standard flasher receptacle of a turn signal system of a vehicle. When the vehicle operator selects a turn signal lamp by operation of the turn signal switch, the flasher unit will cycle the chosen lamp on and off at a predetermined rate for as long as the turn signal switch is closed. The flasher unit will also operate an audible signal to indicate that the turn signal system is in operation, with the level of the audible signal progressively increasing in the event that the operator forgets to restore the turn signal switch to the off position.

BACKGROUND OF THE INVENTION 
This invention relates to turn signal systems for vehicle and more 
particularly to an improved flasher unit for such systems. 
A typical turn signal system for a vehicle includes a switch (usually 
actuated by a wand on the steering column) which is moved by the driver 
from a neutral position to one position wherein the right turn signal 
lamps are operated or a second position wherein the left turn signal lamps 
an operated. The system also includes a flasher unit that operates to turn 
the selected signal lamps on and off at a repetition rate within the range 
specified by the vehicle code. The flasher unit is located in the driver's 
compartment and emits an audible signal, usually a clicking sound in each 
cycle of operation, to help advise the driver that the turn signal system 
in operation. 
Flasher units do wear out or otherwise become inoperative and accordingly 
the turn signal systems are designed with a standard two terminal 
receptacle into which the flasher unit is plugged. Thus, if a flasher unit 
fails, it is removed and a replacement flasher unit is plugged back in. 
The turn signal system is turned off in two ways First, if the steering 
wheel has been rotated a sufficient amount when making a turn, a return of 
the steering wheel will automatically move the wand and turn signal switch 
back to their neutral positions. Secondly, the wand may be moved back to 
its neutral position by the driver. 
Very often, and particularly when driving on highways or freeways, the 
driver may turn on the turn signal system when changing lanes. The amount 
of steering wheel movement in a lane change is usually very little, and 
the turn signals system will not be automatically restored when the lane 
change has been completed. With traffic noise, or with a sound system 
turned up high, the low level clicking sound of the flasher unit may not 
be heard. If distracted, the driver may forget to move the wand back to 
neutral position. As a consequence, the turn signal system will continue 
in operation, indicating to others that the driver may be going to make a 
turn or change lanes again. Reliance by other drivers on the unintended 
operation of the turn signal system can create hazardous situations. 
It is an object of the present invention to provide a flasher unit which 
provides a more perceptible warning to the driver if the turn signal 
system has been left on for an extended time. 
It is a further object of the invention to provide such a flasher unit as 
can be plugged into a standard flasher receptacle, with no other 
connection to the electrical system of the vehicle. 
SUMMARY OF INVENTION 
The present invention is directed towards meeting the above objects. 
In the main aspect of the present invention, a flasher unit is provided 
having means to cyclically operate the chosen signal lamp on and off for 
as long as the turn signal switch is on, means to generate audible signals 
during operation of the signal lamps, and means for progressively 
increasing the volume level of the audible signal during the time that the 
turn signal switch remains closed. 
A more specific aspect of the invention is the provision of a flasher unit 
which can plug into the conventional two terminal flasher plug receptacle 
of a turn signal system, the flasher unit having switching means for 
connecting the terminals directly together, a diode and capacator 
connected in series across the terminals, a signal generating means for 
generating an audible signal, a control circuit connected across the 
capacitor and powered by the capacitor voltage, the control circuit having 
means to cycle the switching means on and off at a predetermined rate, 
means to cyclically connect the signal generating means to the capacitor 
voltage, and means for progressively increasing the power applied to the 
signal generating means. 
Other aspects and advantages of the invention will become apparent in the 
course of the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the drawings, wherein a preferred embodiment of the present invention is 
disclosed, the reference number 10 indicates a typical turn signal system 
for a vehicle, such system having a battery 11, connected to the chassis 
ground 12 of the vehicle and a turn signal switch 13 which enables the 
driver selectively to actuate the right turn signal lamps 14 or the left 
turn signal lamp 15. Such a system will include terminals 16 and 17 of a 
standard flasher receptacle into which a conventional flasher unit (not 
shown), may be connected. Such units typically include a bi-metallic strip 
through which battery current can flow, with the strip bending away from a 
contact when heated by the current and returning to the contact when 
cooled, so that the selected signal lamp will flash on and off at a 
desired rate. Such flasher unit will also generate relatively low 
intensity sounds for each cycle of flashing, to indicate to the driver 
that a signal lamp is flashing. 
The flasher unit 20 of the present invention has two connectors 21 and 22 
adapted to plug into the terminals 16 and 17 of a standard flasher 
receptacle. No other electrical connection is made between the flasher 
unit 20 of the present invention and the electrical circuits of the 
vehicle. The ground plane 23 of the flasher unit 20 is connectable to the 
chassis ground 12 of the vehicle only through one or the other of the 
signal lamps 14 or 15. The operating voltage, Vcc, of the flasher unit 20 
is obtained from the positive side of battery 11 through diode 26. The 
control circuit for the flasher unit 20 includes a clock 27 which 
generates square-wave clock pulses at a rate of 300 Hz to clock the 
counter means 29 made up of four binary counters U1, U2, U3 and U4 daisy 
chained together. 
In operation of the flasher unit 20, operation of the turn signal switch 13 
will connect the ground 23 of the flasher unit through one of the 
relatively low resistance (typically 3 ohms) lamps 14 or 15. With this 
connection, battery current can now flow through diode 26 to charge the 
high capacitance capacitor 31. The inherent time required for the 
integrated circuits of the flasher unit 20 to come up will enable the 
capacitor 31 to become almost fully charged in the initial operation of 
the flasher unit 20. 
In due course, inverter 32 will have a high output so that low power relay 
coil 33 is energized to close its contacts 34. This in turn energizes the 
high power relay coil 36 to close its contacts 37 so that the battery 
current is now applied through switch 13 to the chosen signal lamp. Diode 
26 will prevent capacitor 31 from discharging through the now closed relay 
contacts 37, and this capacitor will maintain the voltage Vcc high enough 
to power the control circuits of the flasher unit 20 while the relay 
contacts 37 are closed. 
The clock pulses from clock 27 are applied at a 300 Hz rate to the clock 
input of binary counter U1. Carry pulses will be delivered from the carry 
output RCO of U1 to the clock input of counter U2 at a rate of 18.75 Hz, 
and the Q4 output of counter U2 will cycle at a rate of about 1.17 Hz. 
Therefore, after about 0.4 seconds, the Q4 output of counter U2 will go 
high, the output of inverter 32 will go low, and the relay coils 33 and 36 
will be deenergized. Contacts 37 open to disconnect the battery 11 from 
the chosen indicator lamp 14 or 15. Capacitor 31 will now recharge. The U1 
and U2 counters will continue to count, and in approximately another 0.4 
seconds, the Q4 output of counter U2 will go low. The Q4 output of counter 
U2 will thus serve to cyclically operate the relay contacts 37 between 
closed and open positions so that the chosen indicator lamps will flash on 
and off at a rate of about 1.17 Hz, for as long as the turn signal switch 
13 is closed. 
The ripple carry pulse from counter U1 is applied to one of the inputs of 
OR gate 38, causing its output to go high (and remain latched high since 
its output is connected to one of its inputs). The high output of this 
gate resets both counters U3 and U4. 
The Q1 and Q4 outputs of counter U1 and the Q4 output of counter U2 are 
connected to the AND gate 39. As shown in FIGS. 2 and 3, the Q1 and Q4 
outputs of counter U1 have frequencies of 150 and 18.75 Hz respectively, 
while the Q4 output of counter U2 has a frequency of 1.171875 Hz. When all 
of these outputs are combined, the output of AND gate 39 will be a series 
of eight bursts of 150-Hz pulses during the approximately 0.4 seconds that 
the chosen signal lamp is on. The pulses are applied to the clock input of 
the 1-of-4 decoder U5. A 1-of-4 decoder functions so that, when the 
decoder is clocked, one only of the four outputs 01, 02, 03, 04 will be 
high, depending on the state of the A and B inputs. For example, when both 
A and B inputs are low, output 01 is enabled and will go high when the 
decoder is clocked. The A input is connected to the Q3 output of counter 
U4 and will have half a cycle of operation of approximately one minute, 
while the B input will go from low to high, or vice versa, in 
approximately 2 minutes. 
The decoder outputs are connected to transistors 41, 42, 43 and 44 to 
progressively connect the coil 46 of speaker 47 through resistors 51, 52 
and 53, or directly, to circuit ground, resistors 51, 52 and 53 having 
decreasing values of resistance. For example, if the resistance of the 
speaker coil 47 is 8 ohms, the resistance of resistors 51, 52 and 53 
should preferably be about 10, 8 and 3 ohms, respectively. 
During the initial operation of the flasher circuit 20, the bursts of 
150-Hz pulses applied to the clock input of decoder U5 will turn 
transistor 41 on and off at a 150 Hz rate, and the speaker will produce a 
relatively low level 150 Hz audible signal while the chosen signal lamp is 
on. The 150 Hz sound of the speaker is relatively low in frequency and 
generally simulates the clicking sound of a conventional flasher unit. 
If the turn signal switch 13 is left closed, after about a minute the 02 
output of the decoder U5 will be enabled so that the transistor 42 will be 
switched on and off at the clock input rate. Since resistor 42 is of 
lesser resistance, the level of the audible signal from speaker 47 will 
increase. After about another minute, the 03 output will be enabled and 
the output level from the speaker will again increase. If the turn signal 
switch 13 is still not opened, after about another minute the 04 output of 
the decoder U5 will be enabled and the speaker coil 46 will be connected 
through transister 44 directly to ground to produce the maximum output 
level of the speaker. The 04 output of the decoder is connected to OR gate 
56 so that as soon as the 04 output goes high the output of OR gate 56 
will go high (and will latch high because the output is connected to one 
of the inputs of the OR gate). This will cause the output of inverter 57 
to go low. This grounds the enable input of counter U4 so that it will 
cease to count, leaving both Q3 and Q4 outputs of decoder U5 enabled. 
Speaker 47 will then continue at its maximum volume until turn signal 
switch 13 is opened. 
As mentioned previously, when relay contacts 37 are closed, capacitor 31 
will maintain the Vcc voltage of the flasher unit 20 sufficiently high for 
operation of the flasher unit 20 during the approximately 0.4 seconds that 
the lamp is on. During the succeeding 0.4 seconds, when contacts 37 are 
open, capacitor 31 will recharge. 
At any time after the turn signal switch 13 has been closed to initiate 
operation of the flasher unit 20, the operator may open the switch. Such 
opening will immediately stop the lamps from flashing. Such opening will 
also disconnect the ground 23 of the flasher unit 20 from the chassis 
ground 12 so that capacitor 31 cannot now be recharged from battery 11. 
The value of capacitor 31 is selected so that the voltage Vcc will decay 
to an inoperable level in about twice the normal 0.4 seconds on-time of an 
indicator lamp. Thus, when switch 13 is opened, the speaker 47 will 
normally not sound more than once. If the capacitor 31 is charged 
sufficiently so that there is still enough operating voltage to energize 
the speaker coil for a second time, the sound level will be very low and 
will decrease rapidly because of the drain of the speaker coil and of the 
relay coils 37 and 36 from the unrecharged capacitor 31. 
Merely for purposes of disclosure, an operating embodiment of the flasher 
unit has been made with 4161 integrated circuits for the four-bit binary 
counters U1, U2, U3 and U4, a 4555 integrated circuit for the 1-of-4 
decoder U5, and a 10,000 microfarad capacitor 31. 
In the flasher unit 20 shown and described herein, the relay contracts 37 
function as a switching means to connect terminals 16 and 17 together or 
to disconnect them from each other. Other devices may be used, if desired 
to perform this switching function. For example, a silicon controlled 
rectifier (SCR) may be used and controlled in response to the cycling Q4 
output of counter U2. 
The foregoing description of a preferred embodiment of the invention has 
been presented for purpose of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed. Obviously many modifications and variations are possible in 
light of the above teaching. The embodiment was chosen and described in 
order to best explain the principles of the invention and its practical 
application to thereby enable others in the art to best utilize the 
invention in various embodiments and with various modifications as are 
suited to the particular use contemplated. It is intended that the scope 
of the invention be defined by the claims appended hereto.