THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
NATURE OF THE INVENTION

A FUEL METERING DEVICE FOR FUEL DISPENSER
A) FIELD OF THE INVENTION
1. This invention relates generally to an apparatus for metering liquids, and more particularly to, a flow sensing apparatus for a fuel dispenser in a fuel station.
B) BACKGROUND OF THE INVENTION
2. In general, a fuel dispenser normally consist of parts such as, an inlet port in the dispenser housing which connects the housing to the fuel source, an oudet port in the housing which connects the housing to the output device, a meter chamber in the housing, a pumping device, and a rotating wheel which measures the amount of fuel dispensed. A sensor is usually disposed outside and adjacent to the rotating wheel for sensing the rotation of wheel and hence fuel flow volume.
3. However, the above disclosed metering method is not accurate and rehable, and there is a need for having a metering device that would provide accurate and reliable metering.

C) OBJECTS OF THE INVENTION
4. An object of this invention is to provide a flow sensing apparatus for a fuel dispenser wherein the apparatus provides a reliable and accurate metering of dispensed fuel.
D) SUMMARY OF THE INVENTION
5. The above-mentioned shortcomings, disadvantages and problems are addressed herein, which will be understood by reading and studying the following specification.
6. In one embodiment, a fuel metering device for a fuel dispenser, comprises a rotating wheel member comprising a plurality of equidistant slots therein along the periphery and adapted for rotation in proportion to fuel flow volume, a first optical counter disposed in optically interrupting relationship with the slots and configured to output a first pulse indicating the fuel flow volume, and a second optical counter disposed near the first optical counter and configured to output a second pulse indicating the fuel flow volume, wherein the first and the second output pulse are configured to maintain a constant phase shift during forward rotation of the rotating wheel member.

E) BRIEF DESCRIPTION OF THE DRWAINGS
7. FIG. 1 shows a schematic diagram of one example of a fuel metering apparatus according this invention.
8. FIG. 2 shows an example of arrangement of slots according to this invention.
9. FIG. 3 shows pulse A obtained during forward rotation of rotating wheel member and pulse B obtained during reverse rotation of rotating wheel member.
10. FIG. 4 shows phase offset between pulse A and pulse B of FIG. 3, indicating tampered metering.
11. FIG. 5 shows a rotating wheel member having a reflective coating according to one embodiment of this invention.
12. FIG. 6 shows the output of first and second optical counters maintaining constant phase shift.

F) DETAILED DECRIPTION OF THE INVENTION
13. In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, ands it is to be understood that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.
14. Various embodiments of this invention provide a fuel metering apparatus for fuel dispenser.
15. Referring to Figure 1 to 4, a fuel metering device for a fuel dispenser, comprises a rotating wheel member 10 comprising a plurality of equidistant slots 40 (see FIG. 2) therein along the periphery and adapted for rotation on a shaft 11 in proportion to fuel flow volume. A first optical counter 12 is disposed in optically interrupting relationship with the slots 40 and configured to output a first pulse A (see FIG. 3) indicating the fuel flow volume. A second optical counter 14 is disposed near the first optical counter 12 and configured to output a second pulse B (see FIG. 3) indicating the fuel flow volume, wherein the first and the second output pulses A, B are configured to maintain a constant phase shift during forward rotation of the rotating wheel member 10.

16. In an embodiment, the positional offset between the first optical counter 12 and second optical counter 14 is about 90 degrees.
17. In another embodiment, the phase shift between the first optical counter 12 and second optical counter 14 is predetermined based on the number of slots 40 in the rotating wheel member 10. For example, the phase shift between the first output pulse A and second output pulse B is about 90 degrees. The phase shift between the first output pulse A and second output pulse B is configured to change during reverse rotation of the rotating wheel member 10. However, the number of first output pulse A and the second output pulse B is proportional to the amount of fiiel dispensed.
18. In a fiarther embodiment an infrared sensor 16 is disposed near one of the first and the second optical counters 12, 14. It should be noted that the infrared sensor 16 is configured to check and confirm the amount of fiael dispensed. The resolution of fuel metering is 1.2 ml. The slots 40 are provided at the outer circiomference of the rotating wheel member 10.
19. While the basic counting can be achieved with single counter, two counters namely, the first optical counter 12 and the second optical counter 14 are provided in order to overcome the following:
• NXTien the rotating wheel member 10 rotates in reverse direction [due to back pressure], a processor should not count corresponding number of pulses from the counter.
• To detect any tampering of the metering.

20. In an example for illustrating the working of the metering device according to one embodiment of this invention, the first optical counter 12 and the second optical counter 14 are placed in a processor board in an angle such that the
pulses coming from the sensors are phase shifted by 90°.
Example: The angle between the first and second optical counters 12,14 is calculated as follows:
Total no of slots 40 in the rotating wheel member 10 - X Therefore for 1 slot, 360/X=Y
For 90^ => Y/4 == Z
Multiples of Y + Z gives a Phase Shift of 90° as shown below
For a 50-slot rotating wheel member 10, angle calculations are as foUows
Total no of slots in the rotating wheel member = 50
Therefore for 1 slot, 360/50=7.2°
For 90° 7.2/4= 1.8
Multiples of 7,2 + 1.8 gives a Phase Shift of 90°
For Wider Spacing a factor of 4 is chosen (i.e 7.2*4)
So, (7.2*4)+ 1.8 = 30.60
21. When the rotating wheel member 10 rotates normally in the forward direction, the pulses will be as shown in FIG. 2. When the rotating wheel member rotates in reverse direction the pulses will be as seen in FIG 3.
22. Assume at the instance tl the rotating wheel member 10 has started to move backwards. At this point the pulse phases will be opposite which can be determined using known software. If any one tampers the rotating wheel member 10, then also the pulses will not be offset by 90°so that tampering is also detected. Thus the use of two counters, i.e. the first and second optical

counters 12, 14 gives dual advantage of counting the pulses as well as detecting any tamper.
23. It should also be noted that the infra red sensor 16 is implemented primarily to add more security for metering. In one example, the infra red sensor 16 may be of reflective type, A white reflective surface 20 may be provided on rotating wheel member 10 as shown in FIG. 5.
24. For example, for each rotation of the rotating wheel member, the infra red sensor 16 gives a pulse output. Between such two pulses, a fixed number of phase-shifted pulses will be obtained from the first and the second optical counters 12, 14. So if the number of pulses is more or less than this fixed number, then that particular counter section is said to be tampered. This acts as an additional security for metering.
25. In one example, fiael dispensed is set to 250ml for 1 rotation of the disc. Four edge sensing principle is used to detect the pulses. The four edges are detected in a sequence as shown in FIG. 6. By this way 200 edges are detected for every single rotation. Thus, the resolution of metering is 250/200 which is equal to 1.25 ml.
26. Thus, various embodiments of the present invention provide a fuel metering device for a fuel dispenser. It will be obvious for a person of skilled in the art to practice the invention with modifications. However, all those modifications will be deemed to be covered within the scope of the invention as covered in the claims hereunder.

G) WE CLAIM:
1 A fuel metering device for a fuel dispenser, comprising;
(i) a rotating wheel member comprising a plurality of equidistant slots therein along the periphery and adapted for rotation in proportion to fuel flow volume;
(ii) a first optical counter disposed in optically interrupting relationship with the slots and configured to output a first pulse indicating the fuel flow volume; and
(iii) a second optical counter disposed near the first optical counter and configured to output a second pulse indicating the fuel flow volume, wherein the first and the second output pulse are configured to maintain a constant phase shift during forward rotation of the rotating wheel member.
2 A fuel metering device as claimed in claim 1 wherein the positional offset between the first optical counter and second optical counter is about 90 degrees.
3 A fuel metering device as claimed in claim 1 wherein the phase shift between the first optical counter and second optical counter is predetermined based on the number of slots in the rotating wheel member.
4 A fuel metering device as claimed in claim 1 further comprising an infrared sensor disposed near one of the first and the second optical counters.

5 A fuel metering device as claimed in claim 1 wherein the phase shift
between the first output pulse and second output pulse is about 90 degrees.
6 A fuel metering device as claimed in claim 1 wherein the phase shift
between the first output pulse and second output pulse is configured to
change during reverse rotation of the rotating wheel member.
7 A fuel metering device as claimed in claim 1 wherein the number of first
output pulse and the second output pulse is proportional to the amount of
fuel dispensed.
8 A fuel metering device as claimed in claim 4 wherein the infrared sensor is
configured to check the amount of fuel dispensed.
9 A fuel metering device as claimed in claim 1 wherein the resolution of fuel
metering is 1.2 ml,
10 A fuel metering device as claimed in claim 1 wherein the slots are provided
at the outer circumference of the rotating wheel member.