ABSTRACT
A turn signal indicator system (1A) for an automotive vehicle comprising a flasher unit (2) whose input terminal is connected to a terminal of a battery (4) of the vehicle through a main switch (5) and output terminal is connected to a flasher array (7) through a turn selector switch (8). The flasher array is connected to the other terminal of the battery. The flasher unit comprises a positive temperature coefficient resettable fuse (14) (Fig 1).

FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Turn signal indicator system for an automotive vehicle
INVENTOR
Name: Atkare Suresh Eknathrao
Nationality: Indian National
Address: Bajaj Auto Limited, Akurdi, Pune-411035,
Maharashtra, India.

APPLICANTS
Name: Bajaj Auto Limited
Nationality: Indian Company

Address: Akurdi, Pune- 411035, Maharashtra, India.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF INVENTION
4 This invention relates to flasher unit of a turn signal indicator system for an automotive vehicle.
BACKGROUND OF INVENTION
8
An automotive vehicle is provided with a turn signal indicator system to indicate the direction in which the motorist or driver intends to turn or proceed. A typical turn signal indicator system comprises a self-contained flasher unit whose input terminal is
12 connected to the positive terminal of the battery of the vehicle through a main switch and output terminal is connected to one end of flasher array through a turn selector switch. The flasher unit comprises a first coil connected to the input terminal and to the output terminal through a normally closed contact. The flasher unit also comprises a second coil
16 connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and the output terminal through a capacitor. The flasher unit also comprises a resistor connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and the
20 output terminal. The other end of flasher array is connected to the negative terminal of the battery. Manufacturing of flasher unit is well known and does not need detail explanation.
24 In such a turn signal indicator system, if faults like shorting of the filaments of any one of the lamps or touching of any one of the components of the flasher on the vehicle body or touching of the movable contact of the turn selector switch on the vehicle body occur, high currents will flow into the flasher unit due to which the normally closed contact may
28 melt and fuse thereby damaging the flasher unit and reducing its life. This may also lead to fire hazards.
2

To avoid high currents during fault conditions from reaching the normally closed contact of the flasher unit it is known to provide a glass fuse between the input terminal of the flasher unit and the main switch (that is the fuse is housed outside of the flasher unit).
4 The fuse is likely to be blown out often and needs to be replaced once it is blown out. This calls for frequent maintenance cost for the indicator system. Incorporation of fuse in the indicator system increases the size thereof. Also it becomes very essential that a fuse of accurate rating should be used. If a fuse of higher rating than the high currents likely
8 to be generated is used in the indicator system, such high currents would reach the normally closed contact and melt and fuse it, whilst fuses of too low a rating increase the likelihood of the fuse blowing.
12 Alternatively, to overcome above problem, a positive temperature coefficient resettable fuse can be used as a replacement in the flasher circuit of turn signal indicator system which cutoff the supply of electricity in the circuit as the temperature exceeds beyond certain limit. However insertion of this fuse in the circuit requires different type of wiring
16 harness which may disturb the existing wiring harness structure.
A positive temperature coefficient resettable fuse is a device wherein as the current flow increases through the fuse, the temperature of the fuse increase until the fuse ceases to
20 conduct current. Upon the temperature cooling below a certain point the fuse "resets" itself and is able to conduct electrical current once again.
OBJECTS OF INVENTION
24
An object of the invention is to provide a flasher unit of turn signal indicator system for an automotive vehicle, which prevents high currents from following into the flasher unit and damaging the flasher unit thereby increasing the life of the flasher unit.
28
Another object of the invention is to provide a flasher unit of turn signal indicator system, which is interchangeable in existing or old vehicle.
3

Another object of the invention is to provide a flasher unit of turn signal indicator system, which is compact.
4 Another object of the invention is to provide a flasher unit of turn signal indicator system, which is simple in construction and cost effective.
Another object of the invention is to provide an automotive vehicle comprising a flasher
8 unit of turn signal indicator system which prevents high currents from following into the flasher unit and damaging the flasher unit thereby increasing the life of the flasher unit.
Another object of the invention is to provide an automotive vehicle comprising a flasher 12 unit of turn signal indicator system, which is compact.
Another object of the invention is to provide an automotive vehicle comprising a flasher unit of turn signal indicator system, which is simple in construction and cost effective.
16
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a turn signal indicator system for an
20 automotive vehicle comprising a flasher unit whose input terminal is connected to the positive terminal of the battery of the vehicle through a main switch and output terminal is connected to a flasher array through a turn selector switch, the flasher array also being connected to the negative terminal of the battery, the flasher unit comprising a positive
24 temperature coefficient resettable fuse.
According to the invention there is also provided an automotive vehicle comprising a turn signal indicator system comprising a flasher unit whose input terminal is connected to the
28 positive terminal of the battery of the vehicle through a main switch and output terminal is connected to a flasher array through a turn selector switch, the flasher array also being connected to the negative terminal of the battery, the flasher unit comprising a positive temperature coefficient resettable fuse.
4

According to an embodiment of the invention the flasher unit comprises a first coil connected to the input terminal and to the output terminal through a normally closed
4 contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and the output terminal through a capacitor and a resistor connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and the
8 output terminal, the positive temperature coefficient resettable fuse being connected between the first coil and the normally closed contact.
According to another embodiment of the invention, the flasher unit comprises a first coil
12 connected to the input terminal and to the output terminal through a normally closed contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and output terminal through a capacitor and a resistor connected at the junction between the first coil and the
16 input terminal and the junction between the normally closed contact and output terminal, the positive temperature coefficient resettable fuse being connected between the normally closed contact and the output terminal.
20 According to another embodiment of the invention, the flasher unit comprises a first coil connected to the input terminal and to the output terminal through a normally closed contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and output terminal
24 through a capacitor and a resistor connected at the junction between the first coil and the
input terminal and the junction between the normally closed contact and the output
terminal, the positive temperature coefficient resettable fuse being connected between the
first coil and the input terminal.
28
According to an embodiment of the invention, the flasher array comprises four lamps,
two lamps in parallel connected to one fixed terminal of the turn selector switch and the
5

remaining two lamps in parallel connected to the another fixed terminal of the turn selector switch.
4 The following is detailed description of the invention with reference to the accompanying drawings, in which:
Figure 1 is circuit diagram of a turn signal indicator system for an automotive vehicle 8 according to an embodiment of the invention;
Figure 2 is circuit diagram of a turn signal indicator system for an automotive vehicle according to another embodiment of the invention; and
12
Figure 3 is circuit diagram of a turn indicator system for an automotive vehicle according to another embodiment of the invention.
16 Figure 4 is detail of view of flasher unit of a turn signal indicator according an embodiment of invention.
The turn signal indicator system 1A as illustrated in figure 1 of the accompanying
20 drawings comprises a flasher unit 2 whose input terminal 3 is connected to the positive
terminal of the battery 4 of the vehicle (not shown) through a main switch 5. The output
terminal 6 of the flasher unit is connected to a flasher array 7 through a turn selector
switch 8. The movable contact of the turn selector switch is marked 8a and the fixed
24 contacts of the turn selector switch are marked 8b and 8c. The flasher unit comprises a
first coil 9 connected to the input terminal and to the output terminal and to the output
terminal through a normally closed contact 10. A second coil 11 is connected at the
junction between the first coil and the normally closed contact and the junction between
28 the normally closed contact and output terminal through a capacitor 12. 13 is a resistor
connected at the junction between the first coil and the input terminal and the junction
between the normally closed contact and the output terminal. 14 is a positive
temperature coefficient resettable fuse connected between the first coil and the normally
6

closed contact. The flasher array comprises four lamps 15a, 15b, 15c and 15d. Two lamps 15a and 15b in parallel are connected to one fixed terminal 8b of the turn selector switch and the remaining two lamps 15c and 15d in parallel are connected to another
4 fixed terminal 8c of the turn selector switch. 8d is the neutral terminal of the turn selector switch. The lamps are also connected to the negative terminal of the battery. Manufacturing of flasher unit is well known and does not need detail explanation.
8 The turn signal indicator system IB as illustrated in Fig 2 of the accompanying drawings is similar to that of Fig 1 except that the positive temperature coefficient resettable fuse 14 is connected between the normally closed contact and the output terminal.
12 The turn signal indicator system 1C as illustrated in Fig 3 of the accompanying drawings is similar to that of Fig 1 except that the positive temperature coefficient resettable fuse 14 is connected between the first coil and the input terminal.
16 The flasher unit 2 of turn signal indicator system as illustrated in figure 4 of the accompanying drawings comprises input terminal 3, output terminal 6. The flasher unit 2 further comprises a first coil 9 connected to the input terminal and to the output terminal through a normally closed contact 10. A second coil 11 is connected at the junction
20 between the first coil and the normally closed contact and the junction between the normally closed contact and output terminal through a capacitor 12. A resistor 13 is connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and the output terminal. A positive temperature
24 coefficient resettable fuse 14 connected between the first coil and the normally closed contact.
The positive temperature coefficient resettable fuse 14 can be connected between first
28 coil and input terminal or can be connected between the normally closed contact and the output terminal inside the flasher unit. Such combinations or variations are construed as a part of invention.
7

Main switch 5 is normally closed when an automotive vehicle (not shown) provided with the turn signal indicator system is in the running mode. The movable contact 8a of the turn selector switch is in contact with the fixed neutral terminal 8d. The normally closed
4 contact 10 is also in the closed state. When the motorist or driver of the vehicle intends to take a turn or proceed in a particular direction, he operates or turns the movable contact 8a of the turn selector switch 8 to make contact with the respective fixed contact 8b or 8c of the turn selector switch. Current flows to the respective lamps through the flasher unit
8 causing the lamps to flash. During this time the capacitor 12 in the flasher unit charges. When the capacitor is fully charged, it starts discharging through the resistor 13 and the contact 10 opens as it is at a higher potential and the lamps turn off. When the capacitor is fully discharged, the contact 10 closes and the lamps are turned on and the capacitor
12 starts charging. When the capacitor is fully charged, it starts discharging and the lamps turn off. This sequence is repeated until the movable contact is turned back to the neutral terminal 8d. During the normal operation of the flasher unit, the positive temperature coefficient resettable fuse remains conductive and allows the flow of current
16 to the lamps. During operation of the turn signal indicator system, if faults like shorting of the filaments of anyone of the lamps or touching of the cable strands on the vehicle body or touching of the movable contact of the turn selector switch on the vehicle body occur, high currents are generated in the signal indicator system. Due to the high currents
20 the resistance of the positive temperature coefficient resettable fuse increases and the positive temperature coefficient resettable fuse becomes non-conductive thereby discontinuing the flow of current to the turn selector switch and the lamps and preventing damage to the flasher circuit and increasing its life. When the fault is rectified the
24 positive temperature coefficient resettable fuse becomes normal and conductive. The positive temperature coefficient resettable fuse is small in size as compared to the glass fuse. Therefore, the turn signal indicator system using this flasher unit of the invention is very compact. The flasher unit of the turn signal indicator can be replaced with the
28 flasher unit existing or old vehicle without disturbing the wiring harness of the system. The positive temperature coefficient resettable fuse can withstand high currents for longer periods as compared to glass fuse and does not fail as often as the glass fuse. Therefore, the signal indicator system of the invention does not call for frequent
8

maintenance and is cost effective. The signal indicator system of the invention is also simple in construction.

We Claim
4 1. A turn signal indicator system for an automotive vehicle comprising a flasher
unit whose input terminal is connected to a terminal of a battery of the vehicle through a main switch and output terminal is connected to a flasher array through a turn selector switch, the flasher array being connected to the other terminal of the battery, the flasher
8 unit omprising a positive temperature coefficient resettable fuse.
2. A turn signal indicator system as claimed in claim 1, wherein the flasher unit
12 comprises a first coil connected to the input terminal and to the output terminal through a normally closed contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and the output terminal through a capacitor and a resistor connected at the junction between the
16 first coil and the input terminal and the junction between the normally closed contact and the output terminal, the positive temperature coefficient resettable fuse being connected between the first coil and the normally closed contact.
20 3. A turn signal indicator system as claimed in claim 1, wherein the flasher unit
comprises a first coil connected to the input terminal and to the output terminal through a normally closed contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and
24 output terminal through a capacitor and a resistor connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and output terminal, the positive temperature coefficient resettable fuse being connected between the normally closed contact and the output terminal.
28
4. A turn signal indicator system as claimed in claim 1, wherein the flasher unit
comprises a first coil connected to the input terminal and to the output terminal through a normally closed contact, a second coil connected at the junction between the first coil
10

and the normally closed contact and the junction between the normally closed contact and output terminal through a capacitor and a resistor connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and
4 the output terminal, the positive temperature coefficient resettable fuse being connected between the first coil and the input terminal.
5. An automotive vehicle comprising a turn signal indicator system comprising a
8 flasher unit whose input terminal is connected to the positive terminal of the battery of
the vehicle through a main switch and output terminal is connected to a flasher array through a turn selector switch, the flasher array also being connected to the negative terminal of the battery, the flasher circuit comprising a positive temperature coefficient
12 resettable fuse.
6. An automotive vehicle as claimed in claim 5, wherein the flasher unit
comprises a first coil connected to the input terminal and to the output terminal through a
16 normally closed contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and the output terminal through a capacitor and a resistor connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and
20 the output terminal, the positive temperature coefficient resettable fuse being connected between the first coil and the normally closed contact.
7. An automotive vehicle as claimed in claim 5, wherein the flasher unit
24 comprises a first coil connected to the input terminal and to the output terminal through a
normally closed contact, a second coil connected at the junction between the first coil and the normally closed contact and the junction between the normally closed contact and output terminal through a capacitor and a resistor connected at the junction between the
28 first coil and the input terminal and the junction between the normally closed contact and output terminal, the positive temperature coefficient resettable fuse being connected between the normally closed contact and the output terminal.
11

8. An automotive vehicle as claimed in claim 5, wherein the flasher unit
comprises a first coil connected to the input terminal and to the output terminal through a
normally closed contact, a second coil connected at the junction between the first coil and
4 the normally closed contact and the junction between the normally closed contact and output terminal through a capacitor and a resistor connected at the junction between the first coil and the input terminal and the junction between the normally closed contact and the output terminal, the positive temperature coefficient resettable fuse being connected
8 between the first coil and the input terminal.
9. An automotive vehicle as claimed in anyone of claims 6 to 8, wherein the
positive temperature coefficient resettable fuse is made of a conductive polymer.
12
Dated this 29th day of March 2006

16 (Jose MA)
of Khaitan & Co Agent of the Applicants
12