A REGULATOR ASSEMBLY FOR A PRESSURISED GAS CYLINDER
The present invention relates to a regulator assembly for a pressurised gas cylinder.
Such a regulator is fitted on the outlet of gas cylinders in order to reduce the pressure from the gas cylinder (often at a pressure of 300 bar or more) down to an outlet pressure, typically below 10 bar.
Although reference is made to a "cylinder", it will be understood that the invention is applicable broadly to all portable pressurised gas containers including gases stored under pressure as liquids whether they are strictly in the form of a cylinder or not.
Such cylinders are used to supply gas for a range of applications including welding and cutting hoses and
torches, gas packaging machines and laboratory equipment. The regulator needs to be adjustable to allow a user to supply gas at the required pressure and flow rate for a given application. For example, different flow rates of shielding gas are normally requires for different material thicknesses during welding processes. Further, the majority of regulators need adjusting several times a day to alter the pressure or flow rate as the cylinder pressure drops and consequently outlet pressure increases. Conventionally in a regulator, the force required to adjust the outlet pressure of the regulator is provided by the application of a
manually applied torque rotating a hand wheel. The pressure required is dependent upon the outlet pressure requirements and increases as the outlet pressure increases. This torque
demand can often be demanding for the user, particularly when dealing with a high outlet pressure. If the regulator is intended to be operated using an electric motor
controlled by on-board power supply, the torque and
therefore energy requirement of the regulator may become prohibitive in terms of the capacity required from the on¬ board power supply.
According to the present invention there is provided a regulator as defined in claim 1.
By including a pilot regulator into the regulator housing to supply a control pressure to the regulator, the torque or power required to adjust the outlet pressure setting is greatly reduced. In the case of a manually activated device, this makes it far easier for a user to make the required adjustment to the regulator. For an electronic actuator, this reduces the demand on the on-board power supply .
Pilot operated pressure regulators are known in other fields. However, these are generally large scale devices in which the pilot valve is a separate component in its own housing which is connected to the regulator via a pipe.
Such pilot operated regulators are designed for applications which require a high level of outlet pressure accuracy.
They are not used to reduce the operating torque required to adjust the regulator as the regulators are operated using mains power. They are not used in pressurised cylinder applicators as these rely on direct action mechanical means for valve closure/opening and pressure adjustment.
Therefore, existing pilot valves are not configured in the
same manner as in the present invention in that they are not within the housing containing the regulator. As well as being configured differently, they are used in an entirely different field for an entirely different purpose.
The primary drivers of the present invention are to make a small device as it is required to fit on a cylinder and to reduce the torque necessary to operate the regulator. Preferably, therefore, the pilot regulator has a positive seat valve element. The positive seat valve element is one which seats on the low pressure side of its corresponding valve port as opposed to a reverse seat valve which passes through the port and seats on the high pressure side. Such a valve element requires a significantly smaller diameter seat than a reverse seat valve for the same flow
requirement. This allows a smaller piston size for the same accuracy. The smaller piston size reduces the upward force from the gas pressure which allows the biasing springs to be smaller and requires less torque to adjust.
The pilot regulator preferably has an inlet port in
communication with high pressure gas from the cylinder and a pilot valve element biased towards the inlet port by a biasing element to control the flow of gas through the inlet port, the biasing force provided by the biasing element being adjustable by an actuator to control the pressure of pilot gas passing through the inlet port to the regulator to vary the force on a restricting element in the regulator. The biasing element may be a single spring positioned between the actuator and the pilot valve element. However, preferably, the biasing element is arranged to bias the
pilot valve element open while a balancing biasing element is positioned between the pilot actuator and the pilot valve inlet to provide an opposing force on the pilot valve element. The presence of the balancing element allows a smaller package for the pilot regulator.
The pilot valve element may be manually operated, in which case it requires less effort from a user to adjust the regulated pressure. Alternatively, the pilot valve element is operated by a motor. In this case, there may further comprise a control system to control the operation of the motor, the control system including a transmitter and receiver to receive and transmit data concerning the control of the pilot valve element.
An example of a regulator will now be described with
reference to the accompanying drawings, in which:
Fig. 1 is a schematic cross-sectional view showing the regulator connected to a shut off valve of a pressurised gas cylinder; and
Fig. 2 is a more detailed cross-section of the pilot
regulator .
The improvement provided by the present invention is the introduction of a pilot regulator into the regulator housing and the description below will focus on this and the manner in which it interfaces with the regulator and the shut off valve of the pressurised cylinder. This shut off valve is not part of the invention, but will be described first to provide context for the invention.
The shut-off valve 1 has a generally conventional construction. It comprises a shut-off valve element 2 urged onto a valve seat 3 by a spring 4. The shut-off valve element 2 and spring 4 are within a chamber which is exposed to high pressure cylinder gas at pressure PI as described in greater detail below. This pressure exerts a closing force on the shut off valve element 2. The shut-off valve element 2 is displaced from the valve seat 3 by the depression of a spindle 5 which is pushed downwardly by the operation of a lever or hand wheel (not shown) . The return spring 7 biases the spindle upwardly to assist in the closure of the valve.
Depressing the spindle 5 opens the shut-off valve element 2 against the action of the spring 4 and cylinder pressure PI. This causes gas at the cylinder pressure PI to be emitted from the outlet 8.
The high pressure PI is regulated by a combination of the regulator 10 and pilot regulator 30 as described below.
These are both housed in a single housing to which is connected to a cylinder outlet 8 via a releasable connection 9. The connection 9 may be one which is known in the art to connect a conventional regulator such as a screw thread or quick release coupling . Both the regulator 10 and the pilot regulator 30 receive high pressure cylinder gas at a
pressure PI .
The regulator 10 has a regulator element in the form of a piston 11 slidable within a regulator chamber 12.
Alternatively, a flexible diaphragm or bellows could be used. The chamber 12 has a stepped bore with a smaller
diameter portion 13 on the high pressure side and a larger diameter portion 14 on the regulated pressure side. The piston 11 has a correspondingly stepped construction with a smaller diameter portion 15 sealed by an O-ring 16 with the smaller diameter portion 13 of the chamber. A larger diameter portion 17 of the piston 11 is sealed by an O-ring 18 with respect to a large diameter portion 14 of the chamber. A bore 19 extends axially down the centre of the piston 11 connecting the high pressure side PI of the regulator with the regulated pressure side P2 as described below. A bleed port 30 is provided through the larger diameter portion 14 of the piston 11. The bleed port 30 allows a flow of gas from the pilot pressure P3 to the lower regulated pressure P2 and enables the pilot control pressure to continuously vary. The piston 11 is urged downwardly by a spring 21 urging a tapered lower end 22 towards a seat 23.
The chamber 12 above the piston 11 is connected to the pilot regulator 30 via a regulated pressure line 24 and is
connected to the downstream equipment via a regulated pressure outlet line 25. This may be a conventional
regulator quick connect outlet to which a flexible outlet tube is attached. The large diameter portion 14 of the regulator chamber 12 below the large diameter portion 17 of the piston 11 is provided with gas at a pilot pressure P3 via a line 26.
The downward force (using the orientation of Fig. 1) on the piston 11 is a combination of the spring force provided by spring 21 together with the regulated pressure P2 acting on the available upwardly facing piston surface. The upward
force on the piston 11 is provided by a combination of the pilot pressure P3 on the downwardly facing surface of the piston and the cylinder pressure PI on the downwardly facing portion of the smaller diameter portion 15 of the piston.
One example of the pilot regulator 30 will now be described. The pilot regulator 30 comprises a pilot regulator element in the form of a piston 31 which is housed in a pilot regulator chamber 32, the piston 31 is biased upwardly (in the orientation shown in Fig. 1) by a pilot regulator spring
33 and is biased in the opposite direction by a balancing spring 34. The force balance on the piston 31 is adjustable via actuator stem 35 which bears against the top of
balancing spring 34. The net effect of the pilot regulator spring 33 is less than that of the balancing spring 34. A downward force is exerted by the pressure P2 and an upward force by the pilot regulator sping 33. The balancing spring
34 serves to reduce the net effect of the pilot regulator spring 33 and therefore provides a simple method of
adjusting the overall force balance. The actuator stem 35 is the means by which the user adjusts the regulated
pressure P2 and this is done using a very small force as described in greater detail below. This either makes the manual adjustment of the regulated pressure easier for a user or reduces the power consumption of any electronic actuation assembly.
The surface of the piston 31 in the upper part of chamber 32 receives the regulated pressure P2 via the regulated
pressure line 24, while the downwardly facing surface of the piston 31 is open to atmosphere via vent 36. A positive seat pilot regulator valve element 37 extends downwardly from the
piston 31 and seats on a valve seat 38 which can be
significantly smaller than the valve seat 23 of the
regulator 10. The positive seat pilot regulator valve element 37 passes through an O-ring seal 39 to seal the valve seat 38 from being exposed to atmospheric pressure.
As a result of this, the region in the vicinity of the valve seat 38 is held at the pilot pressure P3 which is
transmitted to the regulator along the pilot pressure line 26.
The piston 31 is therefore biased downwardly by a
combination of the spring force from the balancing spring 34 and the relatively low regulated pressure P2 acting on the large piston surface 31. It is biased upwardly by a
combination of the biasing force from the pilot regulator spring 33, atmospheric pressure on the lower surface of the piston 31 and the high cylinder pressure PI acting on the positive seat pilot regulator valve element 37. Raising the actuator stem 35 opens the pilot regulator valve element 37. This causes P3 to rise, this increases the pressure beneath piston 11 lifting it and causing the regulated pressure P2 to rise. A gauge may be present on the regulator to display the regulated pressure. The pilot regulator valve element is significantly smaller than the smaller diameter portion 15 of the regulator 10 so that the surface area exposed to high pressure acting on the piston 31 is significantly less than the high pressure acting on the piston 11. As a result if this, the spring force required to bias the piston 31 can also be
significantly reduced in comparison to a standard regulator construction .
Although one example has been described here, other
variations are contemplated. The valve elements in the regulator and pilot regulator could be reverse seat valves, and the pistons in the regulator and pilot regulator could be replaced by a diaphragm or bellow.