GB2188407A

GB2188407A - Gas flow control apparatus

Info

Publication number: GB2188407A
Application number: GB08607471A
Authority: GB
Inventors: Ruey-Feng Fang
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-03-26
Filing date: 1986-03-26
Publication date: 1987-09-30
Also published as: GB8607471D0

Abstract

Apparatus for controlling flow of gas from a pressurised source thereof comprises a flow control valve arranged in a housing, a safety cut-off device 4 and a pressure gauge 2 arranged for communication with the gas source via a branch passage 1D in the housing so as to provide an indication of the pressure of the source. The safety device 4 comprises a normally open ball valve 5 in the gas flow path, the valve being movable by gas flow which exceeds a maximum rate to a position where it blocks said path, a passage 11 bypassing the ball valve and closed by a resiliently biased valve member 10, and a push rod 8 operable to move the valve member 10 against its resilient bias to open the bypass passage 11. When the ball valve is in the blocking position as a result of excessive gas flow, it can be caused to move to its open position by opening the bypass passage 11. <IMAGE>

Description

SPECIFICATION Gas flow control apparatus The invention relates to gas flow control apparatus and to safety devices for use therein.

It is known to provide apparatus for controlling the flow of gas from a pressurised source thereof e.g. a gas cylinder, such apparatus comprising a flow control valve in series with a safety cutoff device. If it is desired to obtain an indication of the gas pressure of the source an extra pipe has to be connected to communicate the gas source with a separate gas gauge. There is of course a certain amount of work involved in making the connection while the resulting arrangement can be inconvenient for a user.

Viewed from one aspect, the invention provides apparatus for controlling flow of gas from a pressurised source thereof, comprising a flow control valve arranged in a housing, safety cut-off means and a gauge arranged for communication with the gas source via a branch passage in the housing so as to provide an indication of the pressure of the source.

With such an arrangement it is possible for a user to check the pressure of the gas source. This will generally be a pressure vessel e.g. a tank or cylinder in which case the gauge can provide an indication of the stock of gas remaining in the vessel. The apparatus might be used to control the flow of natural or other gases.

Preferably the gauge is mounted on the housing and the branch passage is provided upstream of the flow control valve.

One type of known safety device comprises a ball valve including a ball movable under excess gas flow to engage a valve seat whereby the gas flow path is blocked. The device includes a rod for pushing the ball away from the seat when it is desired to unblock the flow path. However, frictional contact between the rod and the ball causes wear of the ball which can result in an inadequate seal with the valve seat.

Viewed from another aspect, the invention provides a safety device for limiting flow of gas to a maximum rate, comprising a normally open ball valve in the gas flow path, the valve being movable by gas flow which exceeds the maximum rate to a position where it blocks said path, a passage bypassing the ball valve and closed by a resiliently biased valve member, and means selectively operable to move said valve member against its resilient bias to open the bypass passage such that when the ball valve is in the blocking position it can be caused to move to its open position by opening the bypass passage.

With such an arrangement, if a leak or malfunction downstream of the safety device causes the gas flow rate to exceed the maximum the ball valve can operate to close the flow path. When it is desired to re-open the gas flow path the selectively operable means is used to open the bypass passage which tends to equalise the pressure on each side of the ball valve, thereby causing it to move to the open position. This is assisted by a drop in pressure on the upstream side of the ball valve caused by the flow of gas through the bypass passage. If the safety device is provided as part of the flow control apparatus discussed earlier, the safety device is normally arranged upstream of the flow control valve.

With this arrangement the flow control valve restricts the flow of gas so that during reopening of the ball valve positive gas pressure is provided immediately downstream thereof, thereby assisting the opening movement of the ball valve.

Once the gas flow path is re-opened normal flow is obtained provided the flow rate does not exceed the maximum set by the safety device.

Preferably the selectively operable means comprises a rod arranged to push the valve member and thereby open the bypass passage, the rod being resiliently biased away from said valve member. With this arrangement, when the rod has been used to open the bypass passage it can be simply released to move in the direction away from the valve member. In one compact and convenient arrangement the rod is connected to a manually operable push button and is biased away from the valve member by a spring acting on the push button.

Preferably the ball valve includes a ball provided in a chamber separate from the rod, so that the rod does not touch the ball at any time.

A preferred embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a partly sectioned elevation of one conventional gas flow control apparatus; Figure 2 is a partly sectioned elevation of a second conventional gas flow control apparatus; Figure 3 is a partly sectioned elevation of a third conventional gas flow control apparatus; Figure 4 is an elevation of a gas flow control apparatus in accordance with the invention; Figure 5 is a partly sectioned view of the apparatus of Figure 4; Figure 6 shows a section of a safety device in the open position thereof in accordance with the invention; Figure 7 shows a section similar to Figure 6 but showing the device in the blocked position and about to be re-opened; and Figure 8 is a perspective view of the apparatus of Figures 4 and 5.

Referring firstly to Figures 1, 2 and 3, these show known apparatus for controlling gas flow. Each apparatus has a flow control valve 1 which possesses only a depressurising device without a gas gauge.

A safety device 5 is connected upstream of each flow control valve 1 as shown in the crosssectional parts of Figures 1, 2 and 3.

When gas flow exceeds a set rate, that is, the strength of the gas flow is stronger than the rolling force of a ball 20, the ball 20 is pushed and moved by the gas to block an exit 30 thereby stopping the gas from flowing along the outflow path 40. When the ball 20 blocks the exit 30, it is located just below a push rod 50, generally in a straight line therewith. Although such a conventional device is simple and practical, if the safety device fails to operate or is detached, it cannot automatically cut off the gas flow. Moreover, as the ball 2 must be pushed away from the exit 30 by the push rod 50, the friction between them will cause gradual wear of the ball 20 and consequently the ball 20 cannot properly block up the exit.

The main improvements of the preferred embodiment shown in Figures 4 to 8 are that the flow control apparatus itself includes a gas pressure gauge 2 and that the safety device is substantially modified. Referring to Figures 4, 5 and 8, the flow control apparatus includes a flow control valve 1, a gas source connector 3, a gas gauge 2 and a safety device 4. The connector 3 is adapted to be connected with e.g. a gas tank and the downstream exit of the flow control valve 1 is at a relatively low pressure in use. Due to the depressurising effect of the flow control valve 1, the rate of gas flow normally permitted by the safety device 4 can be set relatively low, so that malfunction of the flow control valve or any leaks in the pipe downstream thereof which increases the gas flow rate will generally cause the safety device 4 to block the flow of gas.

As shown in figure 5, an inlet 1A of the flow control valve 1 receives the gas flowing out of an outlet 4A of the safety device 4.

The gas flow at the inlet 1 A is controlled by a leverage valve 1B which determines the gas flow from the outlet 1C, providing a depressurising function. In addition, a pressure detecting branch passage 10 is provided in the housing of the valve 1 and communicates with the safety device outlet 4A. The branch passage communicates with the gas gauge 2 mounted on the housing by a screw connection. Since the gas pressure in the branch passage 1D responds directly to that in the tank, so the gas gauge above the control valve 1 can indicate the gas stock in the tank, making it convenient for a user to know when refilling is necessary, as shown in Figure 8.

The right hand side of Figure 5 is a diagrammatic view of the structure of the safety device 4. Figure 6 shows an enlargement of this view, in which a ball 5 of a ball valve is away from the valve seat 4A1 to permit the gas to flow out of the tank up to a maximum flow rate. Under this condition, the gas pressure is not large enough to move the ball 5 to engage the valve seat 4A 1. At this time a spring 6 biases upwardly a push button 7 and push rod 8 and a spring 9 lifts a valve 10 up to close a bypass passage 11 which communicates the inlet and outlet of the safety device. The position of the ball 5 is at the inlet 1 1A of the bypass passage 11 and the bottom end of the rod 8 makes light contact with the valve member 10.The gas can then flow through the valve seat 4A1 and the outlet 4A to the inlet 1 A of the control valve and is depressurized by the controlling effect of the leverage valve 1B so as to flow from the outlet 1C for use. Thus Figure 6 shows the position of the ball 5 and the valve member 10 under normal use.

The valve member 10 is held in position by a screwed cap 12 which retains a compression spring 8. A valve chamber 10A is defined between the cap 12 and the safety valve housing and is sealed by an anti-leak packing 13. The bypass passage 11 connects the upstream side of the ball valve with the valve chamber 10A which is selectively connected with the downstream side of the ball valve depending on the position of the valve member 10. When, under normal conditions, the ball 5 is positioned away from the valve seat 4A1, the valve member 10 is pushed up by the spring 9 to block the bypass passage 11.

However, as the gas flow exceeds the-.maxi- mum rate e.g. because of pipe leakage or malfunction of the control valve 1, the ball 5 is immediately moved by high gas pressure to engage the valve seat 4A1, thereby blocking the normal gas flow path as shown in Figure 7. Once the above-mentioned irregularities have been rectified, it is necessary simpty t press down the push button 7 in order to make the ball 5 disengage the valve seat 4A 1. This is brought about by the downward action of the valve member 10, whereupon gas immediately flows through the bypass passage 11 to the outlet 4A. The instantaneous high-pressure gas is stopped by the control valve 1 causing a rebounding force which, together with the instantaneous strong suction force formed at the inlet to the bypass passage 11, move the ball 5 away from the valve seat 4A1 to locate itself on the inlet 1 1A of the bypass 11. Thus the normal gas supply is re-established. The safety device 4, due to the control of the bypass passage 11 and the valve member 10 pushed by the rod 8, is arranged to force the ball 5 away from the valve seat 4A1 without direct contact of the ball 5 with the rod 8, so that the ball 5 can continue to form an effective seal with the valve seat 4A1 without any wear and tear caused by friction with the rod 8.

It is to be clearly understood that there are no particular features of the foregoing specification, or of any claims appended hereto, which are at present regarded as being essential to the performance of the present invention, and that any one or more of such features or combinations thereof be included in, added to, omitted from or deleted from any of such claims if and when amended during the prosecution of this appliction or in the filing or prosecution of any divisional application based thereon.

Claims

1. Apparatus for controlling flow of gas from a pressurised source thereof, comprising a flow control valve arranged in a housing, safety cutoff means and a gauge arranged for communication with the gas source via a branch passage in the housing so as to provide an indication of the pressure of the source.

2. Apparatus as claimed in claim 1, wherein the gauge is mounted on the housing and the branch passage is provided upstream of the flow control valve.

3. A safety device for limiting flow of gas to a maximum rate, comprising a normally open ball valve in the gas flow path, the valve being movable by gas flow which exceeds the maximum rate to a position where it blocks said path, a passage bypassing the ball valve and closed by a resiliently biased valve member, and means selectively operable to move said valve member against its resilient bias to open the bypass passage such that when the ball valve is in the blocking position it can be caused to move to its open position by opening the bypass passage.

4. A safety device as claimed in claim 3, wherein said selectively operable means comprises a rod arranged to push the valve member and thereby open the bypass passage, the rod being resiliently biased away from said valve member.

5. A safety device as claimed in claim 4, wherein the rod is connected to a manually operable push button and is biased away from the valve member by a spring acting on the push button.

6. A safety device as claimed in claim 3, 4 or 5, wherein the ball valve includes a ball provided in a chamber separate from the rod.

7. Apparatus as claimed in claim 1 or 2, wherein the safety cut-off means is a safety device as claimed in any of claims 3 to 6.

8. Apparatus as claimed in claim 7, wherein the safety device is arranged upstream of the flow control valve.

9. Apparatus for controlling flow of gas from a pressurised source thereof, substantially as hereinbefore described with reference to Figures 4 to 8 of the accompanying drawings.

10. A safety device for limiting flow of gas to a maximum rate, substantially as hereinbefore described with reference to Figures 4 to 8 of the accompanying drawings.