FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention - TAMPER PROOF OPTICAL ENCODER DISC FOR
USE IN FLUID DISPENSING DEVICES
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed :

FIELD OF THE INVENTION
The present invention relates to a tamper proof sensing device for use in fluid dispensers. More particularly, the invention relates to an improved sensing device comprising unique asymmetrical design of rings consisting of slots for use in fluid dispensers for facilitating tamper proofing while dispensing of fluids from dispensers.
BACKGROUND AND THE PRIOR ART
Tampering of sensor disc is a very common mechanism used by dealers to increase profits. The core of the Encoder is a rotating disc that quantifies the amount of fuel flowing. By tampering with this disc, it is possible to make the pump believe it is dispensing a different quantity of fuel than it actually is.
Generally, encoder/sensing device constitutes the major part of a fluid/liquid dispenser as it computes the amount of liquid that has been dispensed. The core of the encoder is a rotating disc that quantifies the amount of fuel/fluid flowing. By tampering with this disc, it is possible to make the pump believe it is dispensing a different quantity of fuel than it actually is.
There are two types of tampering:
• Disc replacement
• Disc damage/modification.
These are described in the following subsections. Disc Replacement


The Encoder disc traditionally meters fuel through a series of evenly-spaced slots on its outer rim. If this disc is replaced by a disc with a different number of slots, the subsequent measurements will be inaccurate.
Disc Damage
The Encoder disc may suffer damage either through accident or deliberate modification. This may lead to inaccurate metering or other errors in its activities.
US 4074356 discloses an improved fluid delivery control and registration system having notable utility in controlling and registering the cost and volume amounts of each fuel delivery of a fuel pump. Moreover the prior art provides an electronic fuel delivery control and registration system useful in providing for remote control of customer self-service delivery of fuel and in displaying the cost and/or volume amounts of the fuel delivered at the delivery station for customer use and at a remote controller's station for the controller's use in charging for the self-service delivery. It was not known in the prior art that a unique concentric design in the encoder disc could facilitate tamper proof fluid dispensing operation.
WO9210224 describes a device for liquid delivery comprising an expansible resilient liquid container for receiving liquid and for discharging it therefrom under pressure, tamper resistant means characterized in; rigid means comprising a conduit terminating in an elastic septum and said conduit also comprising means for connection to said liquid container, liquid for containment in said container being introducible into said conduit through said elastic septum and thence to said container, said elastic septum forming a closable end wall to said conduit and received within a cavity formed in


said rigid means, said cavity having an externally accessible opening; a cap to said septum receivable within and having an interference fit in said cavity, all parts of said cap being within said cavity when inserted therein through said opening and covering said septum to prevent access thereto; the rigid means including a passage connected to said conduit for flow of said liquid to a metering means for dispensing said liquid therefrom. It was not known in the prior art that a unique concentric design in the encoder disc could facilitate tamper proof fluid dispensing operation.
Thus there is a need to provide an improved sensing device comprising unique design of rings consisting of slots for use in fluid dispensers for facilitating tamper proofing while dispensing of fluids from dispensers.
The present inventors have found that an improved sensing device comprising unique design of rings consisting of slots when asymmetrically located can provide an encoded combination with slots surrounding them that will detect any change in either of the slots thereby facilitating tamper proofing while dispensing of fluids from dispensers. It has been found by the present inventors that by the sensing device of the present invention any tampering will become difficult and if done, controller on the encoder PCB will stop the flow of the fluid/liquid and indicate corresponding error on display panel.
OBJECTS OF THE INVENTION
Accordingly, one object of the present invention is to overcome the disadvantages prevailing in the prior art.


Another object of the present invention is to provide an improved sensing device for fluid dispensers for facilitating tamper proofing while dispensing of fluids from dispensers.
Another object of the present invention is to provide an encoded combination of slots so that on tampering of the slots fluid dispense will stop showing an error.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved sensing device for use in fluid dispensers for facilitating tamper proofing while dispensing of fluids from dispensers, said device comprising disc means;
said disc means consisting plural rings having slots such that said slots are substantially vertical to said disc, wherein plural rings comprises inner ring and outer ring maintaining an appropriate concentricity, said inner and outer rings generate waveforms when rotated during fluid dispensing operation, said waveforms being sensed by plurality of sensor means positioned on the disc means
wherein said slots on inner ring comprising asymmetrical spacing inbetween such that an arbitrary number of outer ring slots are located between any two inner ring slots such that said sensor means capture waveforms of inner ring against the outer ring wherein any change in number of slots in either rings will be immediately detected.
According to another aspect of the present invention there is provided a tamper proof fuel dispenser adapted for precise and accurate dispensing of fuel comprising a sensing device
comprising :


disc means; plural sensor means;
said disc means consisting plural rings having slots such that said slots are substantially vertical to said disc, wherein plural rings comprises inner ring and outer ring maintaining an appropriate concentricity, said inner and outer rings generate waveforms when rotated during fluid dispensing operation, said waveforms being sensed by said sensor means wherein said slots on inner ring comprising asymmetrical spacing inbetween such that an arbitrary number of outer ring slots are located between any two inner ring slots such that said sensor means capture waveforms of inner ring against the outer ring wherein any change in number of slots in either rings will be immediately detected.
The other objects and advantages of the present invention will be apparent from the detailed description and the description provided hereinbelow with reference to the accompanying figures.
DETAILED DESCRIPTION OF THE INVENTION
The present invention describes an improved sensing device for use in fluid/liquid dispensers for facilitating tamper proofing while dispensing of fluids from dispensers. The device comprises disc means which is rotatable that quantifies the amount of fuel flowing. By tampering with this disc, it is possible to make the pump believe it is dispensing a different quantity of fuel than it actually is.
In the present invention the disc means consists plural rings having slots which are substantially in the vertical direction to the plane of the rotating disc. The ring portions comprise


inner ring and outer ring with an appropriate concentricity. The said inner and outer rings generate waveforms when rotated during fluid dispensing operation which are sensed by plurality of sensor means positioned inside the dispenser. Slots on the inner ring comprises asymmetrical spacing in between such that an arbitrary number of outer ring slots are located between any two inner ring slots such that said sensor means capture waveforms of inner ring against the outer ring wherein any change in number of slots in either rings will be immediately detected. Preferably, a fixed number of outer ring slots are present in between two consecutive inner ring slots.
One embodiment of the present invention describes the inner ring of the encoder disc/sensing device is intended to tamper detection. The slots of the inner ring of the said encoder disc are placed at an interval of n, n+3, n+6, n+9 and n+12 positions corresponding to outer ring slots. Hereinabove, 3 is a factor of safety to prevent controller to get false trigger due to closely placed slots. However, such factor of safety should not be considered as any restriction of the present invention and said factor of safety can vary depending on the circumferential length of the rings.
Preferably, the encoder/sensing device comprises three sensors namely A, B and C which measures waveform of the inner ring against the waveform from the outer ring wherein Sensors A and B are placed such that when interrupter disc rotates through them, the pulses generated will have 90 degree phase shift. Sensors A and B are intended for flow counting. Sensor C is placed such that inner ring of the interrupter disc will pass though it.


The outer ring alone may be used to ascertain whether the disc is operating correctly in a factory setting. This is done by ensuring a constant rotational velocity for at least two slot/block groups of the disc and analyzing the resulting square waveform from sensors A and B.
The inner ring is intended to provide tamper detection. This is done through the use of asymmetrically spaced slots on the inner ring and an arbitrary number of outer ring slots between any two inner ring slots. The inner disc has total of five slots, which are unevenly spaced. Slots are in phase with outer ring slots but with greater slot width.
The rationale for this spacing is to provide an asymmetric arrangement of the inner ring slots. Then, when the Encoder sensor C measures the waveform of the inner ring against the waveform from the outer ring, any change in the number of slots in either ring will be immediately apparent.
The period for the waveform of sensor C is in a repeating sequence of 10-16-7-13-4-10-16-7-13-4- and so on. Any change in this sequence is an indication that the number of slots has changed in one or both of the rings.
Another embodiment of the present invention describes a fuel dispenser comprising the sensing device / encoder disc as described hereinabove.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figures la and lb illustrate isometric views of the arrangement of the slots of the two concentric rings


preferably the inner ring and the outer ring with respect to each other present invention.
Figure 2 illustrates a plan view of the sensing device of the present invention.
Figure 3 illustrates the cross-sectional view of encoder disc of the present invention.
Figure 4 illustrates the sensing device/encoder disc in a fuel dispenser.
Figure 5 illustrates the waveform of sensors A and B of the outer ring of the encoder disc.
Figure 6 illustrates the waveform of sensor C of the inner ring of the encoder disc.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figures la and lb illustrate the sensing device (6) / encoder disc comprising outer slots (1) along the outer ring (2) and inner slots (3) along with the inner ring (4). Inner slots (3) comprise asymmetrical spacing (7) in between. accordingly describes the encoder disc utilizing three sensors, labeled XA', ,B' and yC . The location of these within the Encoder is shown in the diagram below.
Fig. 2 accordingly illustrates the plan view of the encoder disc wherein the circumference of the disc is nd where d is the diameter of 52mm. Hence, the circumference is 163.43mm. This is made up of 50 slots and blocks, where a block is the solid portion of disc between slots. So, the sum of 50 slot


widths and block widths equals the circumference, meaning one slot and block width pair is equal to 3.27mm. Of this, the slot width is 1.4mm and the block width is 1.87mm.
Figure 3 illustrates the arrangement of slots of the inner ring wherein there is a fixed number of slots of the outer ring between each of the inner ring slots
Figure 4 illustrates fuel dispenser (5) comprising the sensing device (6) as described hereinabove.
Examples
The present invention is further described by way of non-limiting illustrative example in two parts.
Part 1
Considering that the disc is rotating as standard duty speed, which is 60 litres per minute, with a resolution of 250mL per revolution. This translates to 250mL every 250ms. For a 50-slot disc, this gives a period for each slot and block group of 5ms.
The resulting waveform is shown in figure 5, where Ton corresponds to the slot width while Toff corresponds to the block width.
Using the ring dimensions from section Error! Reference source not found., the block width is 1.33 times the slot width. Given that the disc is rotating at a constant speed, this ratio remains true for the Ton and T off period times. For the


slot/block group period of 5ms, this means Ton is 2.15ms and Toff is 2 . 85ms .
Using these values in the above timing diagram yields:
tl = 1.075 ms
t2 = 2.150 ms
t3 = 3.225 ms
t4 = 5. 000 ms.
Whilst these times will vary according to the rotational speed of the disc, the ratio between Ton and Toff remains constant, allowing for problem detection at any speed, provided the speed is constant for a sufficient period.
The precision of these values allows for the detection of any variation in the rotation of the disc. However, the requirement of a constant speed means it is a method only useful during assembly or under the control of a diagnostics application.
Part 2
The inner ring is intended to provide tamper detection. The method of tamper detection by the inner ring can be illustrated by way of example. The inner ring consists of 5 slots of width 2.2mm. These five slots are arranged in a way such that, there are 10, 16, 7, 13 and 4 slots of outer ring between each of the inner ring slots.
The Encoder sensor C measures the waveform of the inner ring against the waveform from the outer ring and any change in the number of slots in either ring will be immediately apparent.


The waveform for the example disc is shown in figure 6 :
The period for the waveform of sensor C is in a repeating sequence of 10-16-7-13-4-10-16-7-13-4- and so on. Any change in this sequence is an indication that the number of slots has changed in one or both of the rings.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The components herein described may be replaced by its technical equivalence and yet the invention can be performed. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.


WE CLAIM:
1. An improved sensing device for use in fluid dispensers
for facilitating tamper proofing while dispensing of
fluids from dispensers, said device comprising
disc means;
said disc means consisting plural rings having slots such that said slots are substantially vertical to said disc, wherein plural rings comprises inner ring and outer ring maintaining an appropriate concentricity, said inner and outer rings generate waveforms when rotated during fluid dispensing operation, said waveforms being sensed by plurality of sensor means positioned in the fluid dispenser
wherein said slots on inner ring comprising asymmetrical spacing in between such that an arbitrary number of outer ring slots are located between any two inner ring slots such that said sensor means capture waveforms of inner ring against the outer ring wherein any change in number of slots in either rings will be immediately detected.
2. Sensing device as claimed in claim 1, wherein the asymmetrically spaced inner slots comprises an encoded combination with the outer slots.
3. Sensing device as claimed in claims 1 and 2, wherein the inner ring comprises 5 slots.
4. Sensing device as claimed in claims 1 to 3, wherein the inner slots are in phase with the outer ring slots.
5. Sensing device as claimed in claims 1 to 4, wherein the
inner slots have greater slot width than the outer slots.


6. Sensing device as claimed in claims 1 to 5, wherein the slots of the inner ring being spaced such that there is a repetitive sequence of number of slots of the outer ring between each of the inner ring slots.
7. Sensing device as claimed in claim 4, wherein the repetitive sequence of numbers of slots of the outer ring is 10, 16, 7, 13 and 4 slots.
8. A tamper proof fuel dispenser adapted for precise and accurate dispensing of fuel comprising a sensing device as claimed in claim 1 comprising :
disc means;
plural sensor means;
said disc means consisting plural rings having slots such
that said slots are substantially vertical to said disc,
wherein plural rings comprises inner ring and outer ring
maintaining an appropriate concentricity, said inner and
outer rings generate waveforms when rotated during fluid
dispensing operation, said waveforms being sensed by said
sensor means
wherein said slots on inner ring comprising asymmetrical
spacing in between such that an arbitrary number of outer
ring slots are located between any two inner ring slots
such that said sensor means capture waveforms of inner
ring against the outer ring wherein any change in number
of slots in either rings will be immediately detected .
9. Fuel dispenser as claimed in claim 1, wherein the sensor means comprise encoded sensors.
10. An improved sensing device for use in fluid dispensers
for facilitating tamper proofing while dispensing of


fluids from dispensers and fuel dispensers as substantially herein described and illustrated with reference to accompanying figures.



ABSTRACT
TAMPER PROOF OPTICAL ENCODER DISC FOR USE IN FLUID DISPENSING DEVICES
The present invention relates to an improved sensing device (6) for use in fluid dispensers for facilitating tamper proofing while dispensing of fluids from dispensers. The device comprises disc means consisting plural rings having slots. Rings comprise inner ring (4) and outer ring (2) maintaining an appropriate concentricity. Waveform is generated from inner and outer rings when rotated during fluid dispensing operation. Waveforms are sensed by plurality of sensor means positioned in the fluid dispenser. The slots (3) on inner ring (4) comprises asymmetrical spacing (7) in between such that an arbitrary number of outer ring slots are located between any two inner ring slots such that said sensor means capture waveforms of inner ring against the outer ring wherein any change in number of slots in either rings will be immediately detected. The invention also relates to a fuel dispenser adapted for precise and accurate dispensing of fuel.
Figure la