FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
CNG CYLINDER VALVES
VANAZ ENGINEERS LTD.
an Indian Company of
85/1, Paud Road, Pune-400 038, Maharashtra, India.
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 the field of manual valves for fuel cylinders.
In particular, the present invention relates to the field of manual valves for CNG cylinders.
BACKGROUND
Compressed Natural Gas (CNG) cylinders are containers in which natural gas is stored at very high pressure, around 200 -255 kg/cm . These cylinders are used for automotive applications, stationary applications as well as for storage purpose. A CNG valve is rigidly fitted to the cylinder prior to filling of the gas. CNG valve is an ON-OFF device that controls the flow of CNG by opening or closing the passageways and delivering it to a downstream system. As these cylinders and valves deal with very high pressures, safety features are incorporated in CNG valves to avoid mishap in case the pressure or temperature increases beyond safety limits. These are pressure relief devices that operate when the pressure and temperature both exceed permissible ranges.
There are typically two types of pressure relief devices (PRD):
1) Over Pressure Safety Devices:
In over pressure safety devices, a bursting disc or a rupture disc is used. When gas pressure in the cylinder increases beyond a pre-determined limit, the disc is ruptured and gas is vented to the atmosphere thus bursting of the CNG cylinder is prevented.

2) Over Temperature safety devices:
In over temperature safety devices, a fusible alloy is used. When temperature of the gas in the cylinder increases beyond a pre-determined limit, this alloy melts and enables the gas to release in to the atmosphere and prevents bursting of the CNG cylinder.
The CNG cylinder valves known in prior art are provided with both over-pressure and over-temperature safety devices combined together and acting as a single unit. As the temperature of the gas increases, its pressure goes on increasing due to expansion of the gas. Once the pressure and temperature increase beyond pre-determined limits, both the bursting disc and the fusible alloy operate to release gas to the atmosphere. However, in the event that the gas pressure in the cylinder increases up to the bursting pressure but the increase in temperature is not sufficient to melt the fusible alloy, the safety devices provided as a single unit do not operate, thus defeating the purpose of providing the safety devices. Thus the CNG cylinder valves known in prior art do not ensure complete safety and prevention of accidents when one of the conditions for bursting of the cylinder exists.
There is thus felt a need for CNG cylinder valves having a simple structural configuration and yet having discrete over-pressure and over-temperature safety devices which operate independent of one another.

OBJECTS OF THE INVENTION:
An object of the present invention is to provide a CNG cylinder valve with discrete over-pressure and over-temperature safety devices that operate independent of one another.
Another objective of the present invention is to provide a CNG cylinder valve that has a simple structural configuration.
Yet another object of the present invention is to provide a CNG cylinder valve that is compact.
Still another object of the present invention is to provide a CNG cylinder valve that is cost effective.
One more object of the present invention is to provide a CNG cylinder valve that is reliable.
Still one more object of the present invention is to provide a CNG cylinder valve that includes a provision for addition of an excess flow check valve.
An additional object of the present invention is to provide a common passage for venting of CNG upon operation of either an over-pressure or an over-temperature safety device.

SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a CNG cylinder valve for fitting on to at least one CNG cylinder, the valve comprising:
a valve body;
a hand wheel assembly adapted to facilitate opening and closing of the
valve, the assembly comprising:
■ a spindle inserted into the valve body;
■ a valve seat fitted to the spindle;
■ a hand wheel adapted to be mounted on the spindle;
an over pressure safety device adapted to be fitted to the valve body;
> an over temperature safety device adapted to be fitted to the valve body, the
over temperature safety device being further adapted to operate independent
of the over pressure safety device;
a common venting arrangement adapted to cooperate with the over temperature safety device and the over pressure safety device; and
at least one sealing assembly adapted to seal the valve and further adapted to
ensure venting through said common venting arrangement.
Additionally, in accordance with this invention, an excess flow check valve is fitted on a bottom face of the valve body and inside the CNG cylinder.
Preferably, in accordance with this invention, the sealing assembly comprises a combination of at least two elements selected from the group consisting of a plurality of washers, plugs and gland nuts.

Typically, in accordance with the present invention, when CNG cylinders are cascaded, a venting connector is connected to a venting pipe and a washer is provided at a joint of the valve body and the venting connector.
Typically, in accordance with the present invention, the hand wheel is adapted to be mounted on the spindle with a hex nut and a plurality of washers.
Preferably, in accordance with the present invention, the over temperature safety device is a fusible plug assembly comprising a fusible plug fitted with a fusible alloy adapted to have a pre-determined melting point; and the over-pressure safety device is a disc retainer assembly comprising a disc retainer fitted on to a bursting disc with a washer, the bursting disc adapted to burst at a pre-determined set point.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The invention will now be explained in relation to the accompanying drawings, in which:
FIGURE 1 illustrates a schematic arrangement of a CNG cylinder valve in accordance with an embodiment of the present invention; and
FIGURE 2 illustrates a schematic arrangement of a CNG cylinder valve in accordance with the present invention, when CNG cylinders are cascaded using suitable tubing.
DETAILED DESCRIPTION OF ACCOMPANYING DRAWINGS
The invention will now be described with reference to the embodiment shown in the accompanying drawings. The embodiment does not limit the scope and

ambit of the invention. The description relates purely to the exemplary preferred embodiment of the invention and its suggested applications.
Conventional CNG cylinder valves are designed in such a way that the overpressure safety device and the over-temperature safety device are in-line with each other and require both the temperature and pressure limits to be crossed for the safety devices to operate, thus hampering safety. Furthermore, not all possible causes of accidents have been taken into consideration. There is no provision for the incorporation of an excess flow check valve. The CNG cylinder in accordance with the present invention aims to overcome these drawbacks of the prior art and satisfy norms set up by relevant Standards.
The CNG cylinder valve in accordance with the present invention will now be explained with reference to FIGURE 1.
FIGURE 1 illustrates a schematic arrangement of a CNG cylinder valve, in accordance with embodiment of the present invention, wherein the CNG cylinder valve is generally indicated by the numeral 100.
The main components of the CNG cylinder valve illustrated in FIGURE 1 are referenced generally as given below:
a CNG cylinder 102;
a valve body 104;
a seat 106;
a spindle 108;
a washer (small) 110;
a packing washer 112;

a washer (big) 114;
a gland nut 116;
a hex nut 118;
a washer 120;
a spring washer 122;
a hand wheel 124;
a fusible plug 126;
a fusible alloy 128;
a washer 130;
a disc retainer 132;
a bursting disc 134;
a washer 136; and
an excess flow check valve 137.
The CNG cylinder 102 stores CNG at high pressure. The CNG cylinder valve 100 is mounted rigidly on the CNG cylinder 102. The CNG cylinder valve 100 facilitates opening and closing of the outlet of the CNG cylinder 102. The assembly and the operation of the CNG cylinder valve 100 are described herein below.
The seat 106 is fitted into the spindle 108 and the spindle 108 is inserted into the CNG valve body 104. After this, a sealing subassembly comprising the washer (small) 110, the packing washer 112, the washer (big) 114 along with the gland nut 116 are mounted on the valve body 104 as shown. Further, the hand wheel 124 is mounted on the spindle 108 with the help of the hex nut 118, the washer 120 and the spring washer 122. The fusible plug 126 is fitted with the special fusible alloy 128 and then fitted on to the valve body 104 along with the copper washer 130.

The fusible alloy 128 is a special alloy whose melting point is set to a desired limit. This fusible plug assembly serves as an over-temperature safety device.
The washer 136 and the bursting disc 134 are fitted on the valve body 104 on to which the disc retainer 132 is then fitted. The bursting disc 134 is designed to burst at a pre-determined set point. The disc retainer assembly serves as an over-pressure safety device.
The CNG valve 100 is fitted on the CNG cylinder 102 prior to the filling of the CNG. After filling the gas, the CNG valve 100 is closed with the help of the hand wheel assembly that includes mainly, the hand wheel 124, the spindle 108 and the seat 106. This hand wheel assembly facilitates opening and closing of the valve 100 by rotating the hand wheel 124 in an anti-clockwise or clockwise direction respectively. The excess flow check valve 137 is fitted on the bottom face of the valve body 104. This valve 137 operates on the principal of pressure difference. During normal operating conditions, CNG pressure inside the CNG cylinder 102 and at the outlet of CNG cylinder valve 100 is identical. When there is heavy leakage in the CNG system, may be due to rupture of downstream pipeline due to accident or any other reason, the pressure at the outlet of the CNG cylinder valve 100 suddenly reduces and is much lesser than the pressure of CNG inside the CNG cylinder 102. Due to this pressure difference, excess flow valve 137 operates and restricts the flow of CNG at the outlet of the CNG cylinder valve 100 and thus leakage rate is controlled. After taking corrective action to stop the leakage, pressure inside the CNG cylinder 102 and at the outlet of the CNG cylinder valve 100 becomes identical and excess flow valve will automatically operate in its normal state. This is an additional safety feature of the CNG cylinder valve 100 in

accordance with the present invention. The excess flow check valve 137 is fitted inside the CNG cylinder 102 thus making the CNG cylinder valve 100 compact.
Under normal operating conditions, both the over-pressure and the over-temperature safety devices remain passive. Both devices are discrete units and operate independent of each other. When the pressure of the gas in the cylinder 102 increases above a permissible limit, the bursting disc 134 is ruptured and gas bursts out of the valve body 104 to release into the atmosphere. When the temperature of the gas in the cylinder 102 increases above a permissible limit, the fusible alloy 128 melts and the gas releases into the atmosphere. Thus the CNG cylinder valve body 104 in accordance with the present invention eliminates all possibilities of failure of safety devices on occurrence of any event that could lead to bursting of the cylinder.
CNG cylinder valves also find application in heavy vehicles like buses where multiple higher capacity CNG cylinders are cascaded by using suitable tubing to increase storage capacity. In such applications, due to an increase in temperature or pressure beyond limits, gas is released in to the atmosphere. However, since the storage capacity of CNG cylinder is more, when used in such applications, CNG may accumulate in a nearby area and cause accident.
To avoid accumulation of CNG, venting through Pressure Relief Devices (PRD) is achieved in accordance with the present invention. FIGURE 2 illustrates a schematic arrangement of the CNG cylinder valve in accordance with the present invention, when CNG cylinders are cascaded using suitable tubing. A venting connector 140 is connected to venting pipe (not shown) by using suitable connectors and gas is released to a safe place. To avoid leakage through the joint of the valve body 104 and the venting connector 140, a copper washer 142 is used. In

accordance with the present invention, even though there are two discrete pressure relief devices, a single common venting arrangement 144 is provided which minimizes the number of connections for venting of gas and accordingly the size and weight of the valve and also the cost. In the event of over-temperature, the fusible alloy 128 melts and the gas releases into the atmosphere. However, in order to ensure that the gas vents only through the common venting arrangement 144 and does not release to the atmosphere, a plug 148 and a washer 146 are provided to seal the passage wherein the fusible alloy 128 is provided.
TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The technical advancements offered by the present invention which add to the economic significance of the invention include the realization of:
• a CNG cylinder valve that has a simple structural configuration;
• a CNG cylinder valve that eliminates all possibilities of accidents;
• a CNG cylinder valve that is reliable;
• a CNG cylinder valve with an innovative arrangement of safety devices that makes the CNG cylinder valve flawless and cost effective;
• a CNG cylinder valve that is compact in size; and
• a common passage for venting of CNG upon operation of either an overpressure or an over-temperature safety device.

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We Claim:
1. A CNG cylinder valve for fitting on to at least one CNG cylinder,
said valve comprising:
> a valve body;
> a hand wheel assembly adapted to facilitate opening and closing of the valve, said assembly comprising:

■ a spindle inserted into the valve body;
■ a valve seat fitted to the spindle;
■ a hand wheel adapted to be mounted on the spindle;
> an over pressure safety device adapted to be fitted to the valve body;
> an over temperature safety device adapted to be fitted to the valve body, said over temperature safety device being further adapted to operate independent of said over pressure safety device;
> a common venting arrangement adapted to cooperate with said over temperature safety device and said over pressure safety device; and
> at least one sealing assembly adapted to seal the valve and further
adapted to ensure venting through said common venting arrangement.
2. The CNG cylinder valve as claimed in claim 1 further comprising an excess flow check valve fitted on a bottom face of the valve body and inside the CNG cylinder.
3. The CNG cylinder valve as claimed in claim 1 further comprising a venting connector connected to a venting pipe and a washer provided at a joint of the valve body and the venting connector.

4. The CNG cylinder valve as claimed in claim 1, wherein the sealing assembly comprises a combination of at least two elements selected from the group consisting of a plurality of washers, plugs and gland nuts.
5. The CNG cylinder valve as claimed in claim 1, wherein the hand wheel is adapted to be mounted on the spindle with a hex nut and a plurality of washers.
6. The CNG cylinder valve as claimed in claim 1, wherein the over temperature safety device is a fusible plug assembly comprising a fusible plug fitted with a fusible alloy adapted to have a pre-determined melting point.
7. The CNG cylinder valve as claimed in claim 1, wherein the over-pressure safety device is a disc retainer assembly comprising a disc retainer fitted on to a bursting disc with a washer, said bursting disc adapted to burst at a predetermined set point.