Patent Description:
Pneumatic systems using compressed air for actuation of different functions typically include an air supply unit, which is designed to treat the compressed air before introducing it into the pneumatic system. In particular, compressed air is usually required to be filtered and pressure regulated before it can be admitted into the distributors and actuators of the system. One example of an application in which an air supply unit is commonly required is stretch-blow molding (SBM), used for the production of containers, especially bottles, from plastic pre-forms.

Stretch-blow molding can be used in a variety of applications. However, one of the most likely used applications is in the production of polyethylene terephthalate (PET) products, such as drinking bottles. Typically, a stretch-blow molding process includes applying low pressured air via a pre-blow valve block, along with actuation of a stretch rod, during a so-called "pre-blow phase", to stretch the pre-form in a longitudinal direction and radially against walls of a mold. The stretch-blow molding process next uses high-pressured air supplied by the air supply unit, during a main blowing phase, to further expand the pre-form into the blow mold. The resulting product is generally hollow with an exterior shape conforming to the shape of the mold cavity. The stretch-blow molding process may further include a cold set stage during which cool air is introduced into the pre-form from a cooling valve and recovered by a recovery valve. This stretch-blow molding process is repeated for container and commonly has a cycle times in the order of seconds.

It will be appreciated that the air supply unit is a vital part of any high-pressure pneumatic system and particularly any stretch-blow molding process. Known air supply units are large and complex assemblies of various valves, filters and other functional parts. Thus, common air supply units are big in size and difficult to service. Often functional parts of the air supply units are positioned in hard to reach places. Moreover, the large size and positioning problems of the functional parts leads to poor aesthetic appearance, particularly when combined with ever smaller pneumatic systems.

Known systems are often depressurised manually. Manual depressurisation is achieved by placing manual valves in areas that will remain under high pressure after the system is closed off. For example, between stop-fill valves, upstream of stop-fill valves, and upstream of exhaust valves. An air supply unit must be depressurised between uses to prevent any build-up of dangerous high pressure air pockets within the system which could damage the apparatus and the operator.

Position sensors are commonly used to measure the position of a valve in air supply systems. Commonly the position sensors comprise of a Hall sensor and a magnet. If a valve were partially open, for example by <NUM> due to some dirt or grit in the valve, the position sensor would not be accurate enough to detect it as being open. The position sensor would still detect the valve as being closed. Even with this small gap of <NUM> highly pressurised air can still flow. This gap, and the high pressure air, are a potential hazard which may injure an operator.

A further main concern is the safety of existing air supply units and the machinery connected thereto. Particularly in high-pressure applications, such as stretch blow moulding systems, failure to exhaust compressed air in a fast and reliable manner can cause injury to the operator. Safety requirements for these operations can be found in the EN422:<NUM> standard. EN422:<NUM> outlines guidelines for the protection of people using high pressure air applications. For example, when operators open service doors of the high pressure system, it is paramount that pressurised air is vented before the access door or flap is opened. Furthermore, it is important to ensure that no further pressurised air can be supplied for as long as the system is being serviced, even in a failure situation. Known systems apply pressure regulators to ensure that pressurised air is exhausted before the operator gains access to the system. However, this known safety feature heavily relies on the correct function of one or more pressure regulator valves and is not available should one or more of the regulator valves fail. Document <CIT> discloses an air supply unit according to the preamble of claim <NUM>.

In view of the aforementioned problems, it is an object of the present invention to provide an air supply unit for high pressure applications, which has a simple, more compact design and is safe to use.

Aspects and embodiments of the invention provide an air supply unit for high-pressure applications as claimed in the appended claims.

According to a first aspect of the invention there is provided an air supply unit for high pressure applications according to claim <NUM>.

The air supply unit may be used in high pressure applications of up to <NUM> bar. The air supply unit may be used in high pressure applications greater than <NUM> bar. As will be appreciated, the first pilot valve can operably control both the shut-off valve and the exhaust valve. The first pilot valve is electrically actuated and is connected to a working pressure gas system which provides a pilot fluid to actuate the shut-off valve. This pilot fluid may be at <NUM> bar. The pilot fluid may be a low pressure gas, for example at <NUM>-<NUM> bar. When the shut-off valve is in an open position allowing the passage of air to the air outlet and the exhaust valve is shut preventing air from leaving the air supply unit. When the shut-off valve is shut the exhaust valve is open allowing air in the air supply system to be exhausted. The first pilot valve controlling both of the components reduces the number of components required to safely operate the air supply unit. This reduced number of components reduces the likelihood of failure of the air supply unit as there are less components that could break in operation. Controlling both the shut-off valve and the exhaust valve using a single pilot valve increases the safety of the air supply unit. The shut-off and exhaust valve may be poppet valves, ball valves or any other suitable valve. A second shut-off valve may be arranged between the air inlet and the air outlet of the air treatment unit. The second shut-off valve is controlled by a second pilot valve. The second pilot valve is electrically actuated and is connected to a working pressure gas source which provides a pilot fluid to actuate the second shut-off valve. This pilot fluid may be at <NUM> bar. The pilot fluid may be a low pressure gas, for example at <NUM>-<NUM> bar. The second shut-off valve may be arranged to move along a longitudinal valve access that is parallel to a longitudinal valve access of the first shut-off valve. In another embodiment, the two shut-off valves may have an identical construction and are received in parallel bores within the integrated air treatment unit. The bores may extend from the same surface of the integrated air treatment unit and may have substantially the same size and shape. The second shut-off valve may be arranged in parallel in both a mechanical and also a pneumatic sense. As such, the inlet and outlet ports of the two shut-off valves may be connected, providing a greater nominal diameter with minimal space requirements for the air treatment unit. Alternatively, to create redundancy, the second shut-off valve may be connected, pneumatically, in series with the first shut-off valve. In this case, the pressurised air supply could be disconnected by closing either or both of the first and second shut-off valve. Of course any number and combination of parallel and serial shut-off valves is feasible, depending on the operator's safety/air flow requirements. The second shut-off valve may be a poppet valve, a ball valve or any other suitable valve.

The air supply unit may comprise a low pressure outlet switch fluidly connected to the air outlet of the air treatment unit and configured to detect the pressure at the air outlet. The low pressure outlet switch gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the low pressure outlet switch was switched when the shut-off valve upstream of the air outlet is supposed to be closed it would indicate that in fact the shut-off valve was in fact open. The low pressure switch may occur at <NUM> bar and may output a voltage of 0V. The switch may return to its unactuated position at a pressure below <NUM> bar and may output a voltage of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch from oscillating in a hysteresis loop which may damage the pressure switch.

The air supply unit may comprise a high pressure outlet switch fluidly connected to the air outlet of the air treatment unit and configured to detect the pressure at the air outlet. The high pressure outlet switch gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the high pressure outlet switch was switched when the shut-off valve upstream of the air outlet is supposed to be closed it would indicate that in fact the shut-off valve was in fact open. The high pressure switch may occur at <NUM> bar and may output a voltage of <NUM> V. The switch may return to its unactuated position at a pressure below <NUM> bar and may output a voltage of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch from oscillating in a hysteresis loop which may damage the pressure switch.

The high and low output pressure switches may be provided in a single pressure switch. The single output pressure switch may be an analogue switch which can detect two different switch points. The pressure may be detected using mechanical, piezoelectric, or any other suitable means. The single output pressure switch may output two signal voltages, one indicating the state of the high output pressure and one indicating the low output pressure state as a function of the pressure.

The air supply unit may comprise a low pressure shut-off valve switch fluidly connected to detect the pressure between the first shut-off valve and the second shut off valve. The low pressure shut-off valve switch gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the low pressure shut-off valve switch was switched when the first shut-off valve is supposed to be closed it would indicate that the first shut-off valve is open. The low pressure switch may occur at <NUM> bar and may output a voltage of <NUM> V. The low pressure switch may return to its unactuated position at a pressure below <NUM> bar and output a signal of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch from oscillating in a hysteresis loop which may damage the pressure switch.

The air supply unit may comprise a high pressure shut-off valve switch fluidly connected to detect the pressure between the first shut-off valve and the second shut off valve. The high pressure shut-off valve switch gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the high pressure shut-off valve switch was switched when the first shut-off valve is supposed to be closed it would indicate that the first shut-off valve is open. The high pressure switch may occur at <NUM> bar and may output a voltage of <NUM> V. The low pressure switch may return to its unactuated position at a pressure below <NUM> bar and output a signal of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch from oscillating in a hysteresis loop which may damage the pressure switch.

The high and low shut-off pressure switches may be provided in a single pressure switch. The single shut-off pressure switch may be an analogue switch which can detect two different switch points. The pressure may be detected using mechanical, piezoelectric, or any other suitable means. The single shut-off pressure switch may output two signal voltages, one indicating the state of the high shut-off pressure and one indicating the low shut-off pressure state as a function of the pressure.

The air supply unit comprises a slow fill valve connected to the shut-off valve and the air outlet, a throttle which controls the fluid flow rate out of the slow fill valve, a second exhaust valve connected to the outlet port of the slow fill valve and the air outlet, the second exhaust valve comprising an outlet port connected to the exhaust outlet, and a slow fill pilot valve arranged to control the slow fill valve and the second exhaust valve.

The slow fill and second exhaust valve may be poppet valves, ball valves or any other suitable valve.

The first and second exhaust valves may be provided in parallel. By providing the exhaust valves in parallel it creates a redundancy that the air supply system can still be depressurised even if one of the exhaust valves does not open.

The slow fill valve and the slow fill valve throttle allows for a gradual increase in the pressure at the outlet rather than an instantaneous high pressure being output. The gradual ramping up in pressure prevents potentially dangerously high pressures flowing through the air outlet instantaneously. Controlling both the slow fill valve and the second exhaust valve using a single slow fill pilot valve increases the safety of the air supply unit and provides better protection for people. When the slow fill valve is closed the second exhaust will immediately open reducing the pressure in the system.

The first and second exhaust valves of the air supply unit may be arranged in parallel with each other. If one of the exhaust valves fails in use than the other can still safely depressurise the air supply unit. The exhaust valve may be a normally open valve. If a power failure occurs the exhaust valve will return or stay, respectively in its default open state, thereby safely venting the pressurised air.

The first and second shut-off valves of the air supply system and the first and second pilot valves may be provided in a normally closed position. Normalising the first and second shut-off and first and second pilot valves in a closed position increases the safety of the air supply unit. This closed normal position makes the system always return to the safest mode. If any electrical power or gas pressure is lost to the system so that the pilot valves cannot be used to actuate the shut-off valves, the shut-off valves may shut automatically. This may prevent any high pressure air continuing to flow through the system.

When the first shut-off valve and first pilot valve are closed the exhaust will immediately open reducing the pressure in the system. Exhausting the air supply unit means that when operation of the air supply unit is finished it is always returned to atmospheric pressure. This operation returns the air supply unit to a non-dangerous low-pressure state. There may be no pockets of high pressure air in the fluid lines of the air supply unit which may be hazardous to an operator or could potentially damage the machinery itself.

The slow fill valve and slow fill pilot valve of the air supply system may be provided in a normally closed position. Providing the slow fill valve and slow fill pilot valve in a shut position increases the safety of the air supply unit. This closed normal position makes the system always fail in the safest mode. If any power is lost to the system so that the pilot valves cannot be used to actuate the slow fill valve the slow fill valve may shut automatically. This may prevent any high pressure air continuing to flow through the system.

When the slow fill valve and slow fill pilot valve are closed the second exhaust valve will immediately open reducing the pressure in the system. Exhausting the air supply unit means that when operation of the air supply unit is finished it is always returned to atmospheric pressure. This operation returns the air supply unit to a non-dangerous low-pressure state. There may be no pockets of high pressure air in the fluid lines of the air supply unit which may be hazardous to an operator or could potentially damage the machinery itself.

The normally closed position used to make the valves return to a closed position may be provided by a spring and/or air pressure in one or more fluid lines which are connected to the inlet of the first and second shut-off valves and/or the slow fill valve. The use of both air pressure and a spring to provide means to normally return the valves to a closed position may provide an additional redundancy in case of either the spring failing or the fluid line being blocked. Having both of these features may increase the safety of the air supply unit.

The first and second shut-off valves, first and second exhaust valves, and the slow fill valve may be located in a valve block. The first and second shut-off valves, first and second exhaust valves, and the slow fill valve may be integral to the valve block. The valve block containing the first and second shut-off valves, first and second exhaust valves, and the slow fill valve may provide a compact assembly in the air supply unit. The compact assembly reduces the number of components required to use the air supply unit, which reduces the number of components that may fail and thus increases the reliability of the air supply unit. In particular it replaces connecting tubes or pipes with internal fluid passages which dramatically reduce the failure rate.

The pilot valves and the pressure switches may be located on the outside of a valve block of the air supply unit. Providing these components on the outside of the valve block allows them to be easily accessed, serviced and/or replaced. Pilot valves and pressure switches are relatively cheap to manufacture. Locating these components on the outside of the valve block allows them to be replaced without replacing the whole valve block or air unit assembly.

According to another aspect of the invention there is provided a method of self-testing the safety of an air supply machine comprising the steps of:.

The method tests whether the air supply system is safely depressurised after each cycle. The method of checking the safety of the air supply unit can be performed before each use of the air supply unit when it is first switched on. The steps can be used to check that the air supply unit is safe to use. Or, conversely, whether the air supply unit is not safe to use. If the air supply unit passes the safety test then the air supply unit can be operated. If the air supply unit fails the safety test then the air supply unit may not be operated. The operator may be prevented from using the device until a part is replaced and/or the air supply unit has been checked by a service person.

The sequence of method steps is predetermined and standardised by the manufacturer. The pilot valves in the air supply unit are actuated and the pressure at the output and between the first and second shut-off valves are measured. In this way the valves can be checked to see if they are: open, shut, or partially open. Pressure switches are advantageous over position sensors as if a valve were open by only a small magnitude, for example by <NUM>, then a position sensor would not be able to measure this. A pressure sensor however would be able to measure to pressure resulting from the fluid flow through this <NUM> gap.

By using a known test data set that the output of test can be compared against the ideal conditions known in the test data set. The test data set acts as an operational check list that a controller (such as a computer or other control device) and/or an operator know that the air supply unit is safe to use.

The method of testing the safety of an air supply unit can comprise the following predetermined sequence and predetermined times of:.

This predetermined sequence and steps can be used to check that the air supply unit is safe to operate.

According to another aspect not within the scope of the claims, there is provided an air supply unit for high-pressure applications, comprising an integrated air treatment unit with an air inlet, an air outlet, and an exhaust port. The air supply unit comprises a filter unit for treatment of pressurised air, the filter unit being arranged between the air inlet and the air outlet. At least one shut-off valve is provided having an inlet port connected to the air inlet and an outlet port connected to the air outlet of the integrated air treatment unit. The air supply unit also comprises an exhaust valve having an inlet port connected to the outlet port of the shut-off valve and the air outlet of the integrated air treatment unit, said exhaust valve comprising an outlet port connected to the exhaust port of the integrated air treatment unit. The filter unit, the at least one shut-off valve and the exhaust valve form part of the integrated air treatment unit.

As will be appreciated, all of the functional parts of the air supply unit of the present invention form part of a single, integrated air treatment unit, thereby significantly reducing the size of the supply unit. A reduced size is not only required in ever decreasing space envelopes but also has a more aesthetically pleasing appearance. The exhaust valve is connected to an outlet port of the shut-off valve and may thus quickly vent pressurised air passing the shut-off valve in a failure scenario. At the same time, the exhaust valve is connected to the air outlet of the integrated air treatment unit. As such, the exhaust valve can also be used to vent pressurised air supplied to elements of the air supply unit, which are not part of the integrated air treatment unit, as will be described in more detail below. In other words, the exhaust valve of the air supply unit can be considered as a central air vent, which reliably ensures the safety of all parts of the air supply unit of the present invention.

In this specification, the term "integrated air treatment unit" refers to a structure, in which the individual parts are in direct contact with each other. In other words, all of the individual components of the integrated air treatment unit are connected to each other via at least one flange surface, such that there are no tubes or pipes arranged between functional parts of the "integrated air treatment unit". In other words, while the integrated air treatment may or may not be a unitary structure, fluid lines between different functional parts of the "integrated air treatment unit" will only ever be cavities of a unitary or modular structure.

According to an embodiment not within the scope of the claims, the air supply unit comprises a first pressure regulator arranged downstream of the integrated air treatment unit, an inlet of said first pressure regulator being connected or connectable to the air outlet of the integrated air treatment unit. The first pressure regulator may comprise a bypass line connecting an outlet of the first pressure regulator with the air outlet of the integrated air treatment unit. As indicated hereinbefore, the exhaust valve within the integrated air treatment unit of the air supply unit may, thus, be used to vent pressurised air at the inlet and outlet of the first pressure regulator. The first pressure regulator can, therefore, be vented on both sides even if one or more of the valves of the pressure regulator fail at any point. It will be appreciated that, while the first pressure regulator is connected or connectable to the air outlet of the integrated air treatment unit, there may be other functional parts, such as further valves or filter arranged between the air outlet of the air treatment unit and the inlet of the first pressure regulator.

In another embodiment not within the scope of the claims, the bypass line comprises a check valve configured to enable fluid flow from the outlet of the first pressure regulator towards the inlet of the first pressure regulator. The presence of the check valve will stop treated pressurised air provided at the air outlet of the integrated air treatment unit from bypassing the pressure regulator between its inlet and outlet.

In another embodiment not within the scope of the claims, the first pressure regulator comprises a pilot operated pressure regulator valve. In particular, the first pressure regulator valve may be a <NUM>/<NUM>-way valve, the flow resistance of which can be adjusted via the input of a pilot valve. In more detail, the pressure regulator valve has a first open state, in which a pressure at its outlet port can be determined via the input of the pilot valve. In a second, closed state, the inlet and outlet ports of the pressure regulator valve are disconnected, such that no fluid flow is present at the outlet port of the pressure regulator valve. The pressure regulator valve, thus, also functions as a second safety valve of the air supply unit, in addition to the at least one shut-off valve of the air treatment unit.

In yet another embodiment not within the scope of the claims, the air supply unit comprises a second pressure regulator arranged outside of the integrated air treatment unit, an inlet of the second pressure regulator being connected or connectable to an outlet of the first pressure regulator. The second pressure regulator may comprise a bypass line connecting an outlet of the second pressure regulator with the outlet of the first pressure regulator. The configuration of the second pressure regulator may be substantially identical to the configuration of the first pressure regulator. By means of the two bypass lines, the outlet of the second pressure regulator is connected via check valves with the exhaust valve arranged as part of the integrated air treatment unit. As such, both the first and the second pressure regulator may be vented via the exhaust valve of the integrated air treatment unit.

According to another embodiment not within the scope of the claims, the at least one shut-off valve and the exhaust valve are arranged to move along parallel longitudinal valve axes. In one example, the shut-off valve and the exhaust valve may both be constructed as poppet valves, the opening and closing movements of which occur along parallel longitudinal valve axes. Arranging the shut-off valve and the exhaust valve along parallel longitudinal axes within the integrated air treatment unit results in an even more compact and simple construction of the air supply unit.

The integrated air treatment unit may comprise a valve block, housing the shut-off valve and the exhaust valve, wherein the integrated air treatment unit may further comprise a filter sleeve attached to the box-shaped valve block receiving the filter unit. The valve block may be a cast metal part or mainly machined out of a solid block of material. The valve block may be box-shaped. Attaching a removable filter sleeve to the valve block simplifies maintenance of the filter. In detail, the filter sleeve may be quickly and easily removed from and reattached to the valve block by means of a threaded connection.

The valve block may be a single piece structure. The term "single piece structure" in this specification refers to a structure that does not include any removable parts, except service caps, which are used to provide access to the functional parts housed within the valve block.

In another embodiment, the shut-off valve and the exhaust valve are received in bores extending from a first external surface of the integrated air treatment unit. In other words, both bores for the shut-off valve and the exhaust valve extend from the same external surface of the integrated air treatment unit. This arrangement reduces manufacturing times when machining the bores of the integrated air treatment unit, since the machining tools will only have to be applied on one surface of the integrated air treatment unit. Similarly, maintenance of the functional parts, such as the shut-off valve and the exhaust valve will be simplified, as access to the latter is provided via the same surface. The bores may be part of the valve block. Alternatively, the shut-off valve/valves and the exhaust valve may be received in bores arranged crosswise within the valve block. In other words, the bores may extend into the valve block from different surfaces. This crosswise arrangement may be beneficial in further reducing the size of the integrated air treatment unit.

A second shut-off valve may be arranged between the air inlet and the air outlet of the air treatment unit. The second shut-off valve may be arranged to move along a longitudinal valve access that is parallel to a longitudinal valve access of the first shut-off valve. In another embodiment, the two shut-off valves may have an identical construction and are received in parallel bores within the integrated air treatment unit. The bores may extend from the same surface of the integrated air treatment unit and may have substantially the same size and shape. The second shut-off valve may be arranged in parallel in both a mechanical and also a pneumatic sense. As such, the inlet and outlet ports of the two shut-off valves may be connected, providing a greater nominal diameter with minimal space requirements for the air treatment unit. Alternatively, to create redundancy, the second shut-off valve may be connected, pneumatically, in series with the first shut-off valve. In this case, the pressurised air supply could be disconnected by closing either or both of the first and second shut-off valve. Of course any number and combination of parallel and serial shut-off valves is feasible, depending on the operator's safety/air flow requirements.

According to yet another embodiment, the air supply unit comprises a fill pilot valve arranged to control the at least one shut-off valve, the pilot valve comprising an inlet port connected to an outlet of the filter unit. The pilot valve may be a two/two way solenoid valve with an inlet port connected to the pressurised air supply. If two shut-off valves are provided, the fill pilot valve may be used to actuate both shut-off valves simultaneously.

The fill pilot valve may form part of the integrated air treatment unit
The air supply unit may comprise an exhaust pilot valve arranged to control the exhaust valve. The exhaust pilot valve comprising an inlet port connected to an outlet of the filter unit. Similar to the fill pilot valve, the exhaust pilot valve may, therefore, have an inlet port connected to the pressurised air source, rather than a separate pilot air supply. The exhaust pilot valve may form part of the integrated air treatment unit.

The exhaust pilot valve may be a normally closed valve. The exhaust valve may be a normally open valve. As such, the exhaust pilot valve may be used to close the exhaust valve, when the system is fully operational. If an electrical power failure or a failure of the low pressure gas system occurs, the exhaust pilot valve will no longer actuate the exhaust valve, which will then move back into its default open state, thereby safely venting the pressurised air.

In another embodiment, the shut-off valve may include a pressure compensation bore extending between a first and second end of a valve piston, along the longitudinal valve axis. The shut-off valve can thus be actuated in very quick succession, substantially independent of the pressure provided by the fluid source.

One or more embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:.

Turning to <FIG> there is shown a schematic pneumatic diagram showing an embodiment of the air supply unit <NUM> not within the scope of the claims. The air supply unit comprises an inlet <NUM>, which may be connected to a pressurised air source. Inlet <NUM> is connected downstream to a manual valve <NUM> and two optional pre-filters <NUM>, <NUM>. Downstream of the second pre-filter <NUM> there is provided an integrated air treatment unit <NUM> with a variety of functional parts, which will be described in more detail below.

An air inlet <NUM> of integrated air treatment unit <NUM> is connected with an outlet of pre-filter <NUM>. An air outlet <NUM> of integrated air treatment unit <NUM> is connected to a pressure regulator <NUM> that is arranged downstream of the integrated air treatment unit <NUM>.

The integrated air treatment unit <NUM> includes a filter unit <NUM>, two fill valves, which are constructed as shut-off valves <NUM>, <NUM>, and an exhaust valve <NUM>. A fill pilot valve <NUM> is arranged as part of the integrated air treatment unit <NUM> and provided to control opening and closing of the shut-off valves <NUM> and <NUM>. An exhaust pilot valve <NUM> is also arranged as part of the integrated air treatment unit <NUM> and controls opening and closing of the exhaust valve <NUM>.

The filter unit <NUM> comprises an inlet port <NUM>, which is connected to the air inlet <NUM> of integrated air treatment unit <NUM> via fluid line <NUM>. Although in this embodiment not part of the integrated air treatment unit <NUM>, a pressure relief valve <NUM> is part of the air supply unit <NUM> and connected to fluid line <NUM> to act as excess pressure valve for the integrated air treatment unit <NUM>. Depending on the application, the magnitude of air pressure supplied by integrated air treatment unit <NUM> to pressure regulator <NUM> may vary significantly. In a stretch-blow molding example, the air pressure supplied may reach up to <NUM> bar such that a pressure of around <NUM> bar may be provided during a main blowing phase.

A pressure gauge <NUM> is provided outside of integrated air treatment unit <NUM> and connected to the inlet port <NUM> on one end and the outlet port <NUM> at the opposite end of the filter unit <NUM>. The pressure gauge <NUM> measures a pressure drop across filter unit <NUM> to monitor filter service requirements. If the filter unit <NUM> is contaminated, pressure gauge <NUM> will measure an increased pressure drop, which may be used to inform the operator that service of the filter is required. A filter drain valve <NUM> is provided outside of integrated air treatment unit <NUM> and connected to a drain port <NUM> of filter unit <NUM>.

The outlet port <NUM> of filter unit <NUM> is connected, on the one hand, to an inlet port <NUM> of fill pilot valve <NUM> and to inlet port <NUM> of exhaust pilot valve <NUM>. On the other hand, the outlet port <NUM> of filter unit <NUM> is connected to inlet ports <NUM> and <NUM> of shut-off valves <NUM> and <NUM> respectively. An outlet port <NUM> of fill pilot valve <NUM> is connected to pilot pressure faces of shut-off valves <NUM> and <NUM>. An outlet port <NUM> of exhaust pilot valve <NUM> is connected to a pilot pressure face of exhaust valve <NUM>.

The fill pilot valve <NUM> is a normally closed valve. As such, for as long as fill pilot valve <NUM> is not actuated, fill pilot <NUM> remains closed, resulting in no pressure being applied to the pilot pressure faces of the shut-off valves <NUM> and <NUM>. The shut-off valves <NUM> and <NUM> are also constructed as normally closed valves, such that, for as long as the fill pilot valve <NUM> remains closed, so are shut-off valves <NUM> and <NUM>. In other words, for as long as fill pilot valve <NUM> is in its closed state, no pressurised air will be supplied to air outlet <NUM> of integrated air treatment unit <NUM>. Once the fill pilot valve <NUM> is actuated, the pressurised fluid acting on the pilot pressure faces of the two shut-off valve <NUM> and <NUM> will move the latter into their open state. In the open state, the inlet ports <NUM> and <NUM> of shut-off valves <NUM> and <NUM> are connected to their respective outlet ports <NUM>, <NUM>. Both outlet ports <NUM> and <NUM> of the shut-off valves <NUM> and <NUM> are connected to air outlet <NUM> via fluid line <NUM>.

In the embodiment of <FIG>, the shut-off valves <NUM> and <NUM> are arranged downstream of the filter unit <NUM>. The advantage of this arrangement is that only clean air will be provided to the shut-off valves <NUM>, <NUM>, thereby avoiding debris from entering the latter. It is, however, also possible to place the shut-off valves upstream of the filter unit <NUM>, should this be required.

An inlet port <NUM> of exhaust valve <NUM> is also connected to the air outlet <NUM> of integrated air treatment unit <NUM> via fluid line <NUM>. In other words, the inlet port <NUM> of exhaust valve <NUM> is connected to both outlet ports <NUM>, <NUM> of the shut-off valves <NUM> and <NUM> and, at the same time, to air outlet <NUM> of integrated air treatment unit <NUM>. An outlet port <NUM> of exhaust valve <NUM> is connected to exhaust port <NUM> of integrated air treatment unit <NUM>. A silencer <NUM> is downstream of the exhaust port <NUM>.

The exhaust valve <NUM> is a normally open valve, which may be actuated by exhaust pilot-valve <NUM>. Exhaust pilot-valve <NUM> is a normally closed valve. An inlet port <NUM> of exhaust pilot-valve <NUM> is connected to outlet port <NUM> of filter unit <NUM>. An outlet port <NUM> of exhaust pilot-valve <NUM> is connected to a pilot pressure face of exhaust valve <NUM>. In its normally closed state, exhaust pilot-valve <NUM> interrupts the connection between inlet port <NUM> and outlet port <NUM>, thereby not providing any pressurised fluid to the pilot pressure face of exhaust valve <NUM>. As such, exhaust valve <NUM> remains open as depicted in <FIG>. As soon as exhaust-pilot valve <NUM> is actuated and moved into its open state, pressurised fluid acts on the pilot pressure face of the exhaust valve <NUM>, thereby transferring the latter into its closed state. It will be appreciated that, for as long as exhaust valve <NUM> is in its open state, only pressurised fluid at stagnation pressure can be supplied to outlet port <NUM>. In the example of a blow moulding system, the stagnation pressure may typically be in the region of <NUM>-<NUM> bar, rather than <NUM> to <NUM> as required for the main blowing phase. As such, whenever pressurised fluid is supplied to outlet port <NUM>, exhaust pilot-valve <NUM> is actuated in order to close exhaust valve <NUM>.

Treated pressurised air provided at air outlet <NUM> of integrated air treatment unit <NUM> is supplied to pressure regulator <NUM>. Pressure regulator <NUM> comprises a variable pressure regulator valve <NUM> and pilot valve arrangement <NUM>. An inlet port <NUM> of regulator valve <NUM> is connected to air outlet <NUM> of integrated air treatment unit <NUM>. Similarly, an inlet port <NUM> of pilot valve <NUM> is connected to air outlet <NUM> of integrated air treatment unit <NUM>. An outlet port <NUM> of pilot valve <NUM> is connected to pilot pressure face <NUM> of regulator valve <NUM>. An outlet port <NUM> of the regulator valve <NUM> is connected to outlet <NUM> of air supply unit <NUM>.

Pilot valve arrangement <NUM> is configured to determine an outlet pressure of regulator valve <NUM> via pilot pressure face <NUM>. Depending on the magnitude of pressure applied to pilot pressure face <NUM> by pilot valve <NUM>, the pressure regulator valve <NUM> determines the air pressure supplied to outlet <NUM> of air supply unit <NUM>.

The pressure regulator <NUM> further comprises a bypass line <NUM>. The bypass line <NUM> connects the outlet port <NUM> and the inlet port <NUM> of regulator valve <NUM>. A check valve <NUM> is provided in bypass line <NUM>. The check valve <NUM> stops pressurised fluid from bypassing the regulator valve <NUM> by flowing from its inlet <NUM> towards its outlet <NUM>. However, should an air pressure applied to inlet <NUM> of variable relief valve <NUM> be lower than an air pressure on the side of outlet port <NUM>, pressurised air may flow back to the air outlet <NUM> of integrated air treatment unit <NUM> via bypass line <NUM>. In other words, bypass line <NUM> is a return line, which enables pressurised fluid on the side of outlet port <NUM> to be vented via exhaust valve <NUM>.

In case of a sudden power failure of air supply unit <NUM>, shut-off valves <NUM> and <NUM> automatically return into their closed position shown in <FIG>, thereby disconnecting air inlet <NUM> of integrated air treatment unit <NUM> from air outlet <NUM>. At the same time, exhaust valve <NUM> will open and relieve pressurised air within fluid line <NUM>. Pressurised air downstream of pressure regulator <NUM> will also be vented via exhaust valve <NUM> by means of bypass line <NUM>. This is because once fluid line <NUM> is vented, there is no pressurised air supplied to inlet port <NUM> of regulator valve <NUM>. At this point, pressure on the outlet port side of regulator valve <NUM> exceeds the pressure on the inlet port side and check valve <NUM> opens, enabling pressurised fluid to flow between the outlet port <NUM> and the inlet port <NUM> of regulator valve <NUM>, ultimately venting said pressurised fluid via exhaust valve <NUM>. As will be appreciated, due to the presence of return bypass line <NUM>, pressure regulator <NUM> does not require a separate exhaust valve. Rather, exhaust valve <NUM> within integrated air treatment unit <NUM> acts as a centralised exhaust for all of the fluid lines.

<FIG> shows an embodiment of the integrated air treatment unit <NUM> schematically depicted in <FIG>. The integrated air treatment unit <NUM> is a compact, integrated unit including filter unit <NUM>, the shut-off valves <NUM>, <NUM>, exhaust valve <NUM>, and pilot valves <NUM>, <NUM>.

As shown in <FIG>, the integrated air treatment unit <NUM> includes a valve block <NUM>, a filter sleeve <NUM> and pilot valves <NUM>, <NUM>. In this specification, the term "integrated air treatment unit" refers to a multi-piece structure, in which the individual parts, such as pilot valves <NUM>, <NUM> and valve block <NUM> are in direct contact with each other, that is, fluid conduits connecting the functional parts are bores within the structure, rather than tubes connecting them. In other words, all of the individual components of the integrated air treatment unit are connected to each other with at least one contacting surface.

In the embodiment of <FIG>, the fill pilot valve <NUM> and the exhaust pilot-valve <NUM> re movably attached to a first exterior surface <NUM>, such as the top surface, of the valve block <NUM>. In particular, the pilot valves <NUM> and <NUM> may be bolted to the first surface <NUM> of valve block <NUM>. In this example, the valve block <NUM> is box-shaped, however any other suitable shape is also feasible. As will be shown in <FIG>, the filter sleeve <NUM> is removably attached to the box-shaped valve block <NUM> via a second, opposite, exterior surface. In particular, the valve sleeve is screwed into the bottom surface of the box-shaped valve block <NUM>.

Turning to <FIG>, there is shown a cross-sectional view through the upper part of the integrated air treatment unit <NUM> shown in <FIG> along lines A-A. As can readily be derived from <FIG>, the valve block <NUM> houses the two shut-off valves <NUM>, <NUM>. Although the shut-off valves <NUM>, <NUM> are usually actuated at the same time, and are thus usually in the same state, <FIG> shows the two shut-off valves <NUM>, <NUM> in different states to illustrate both states at the same time. Shut-off valve <NUM> is in its open state, whereas shut-off valve <NUM> is in its closed state.

Both shut-off valves <NUM>, <NUM> are biased towards their closed state by means of coil springs. The supply pressure acts on bottom surfaces <NUM>, <NUM> and, at the same time, on top surfaces <NUM>, <NUM> of the shut-off valves <NUM>, <NUM>. In the closed stage (cf. shut-off valve <NUM>) the effective surface area of the upper surface <NUM> is slightly larger than the effective area of lower surface <NUM>, resulting in a closing force acting on the respective valve piston.

The two shut-off valves include annular collars <NUM> and <NUM> respectively. The annular collars <NUM>, <NUM> create upper and lower control chambers, the air pressure in which acts on annular surfaces of the collars <NUM>, <NUM>. If the fill pilot valve <NUM> is opened, the lower control chambers of both shut-off vales <NUM> and <NUM> are provided with pressurised supply air via fluid channels <NUM>, <NUM>. The fluid pressure acting on the lower annular surface of the annular collars <NUM> and <NUM> respectively creates a force driving the respective piston of the first and second shut-off valves <NUM>, <NUM> upwards. A net force between the pressure acting on lower surface <NUM>, <NUM> and the annular collars <NUM>, <NUM> overcomes the closing force created by the coil spring <NUM>, <NUM> and the upper surfaces <NUM>, <NUM>. Accordingly, the valve will open, as represented by the first shut-off valve <NUM> in <FIG>.

Pressurised air enters the integrated air treatment unit <NUM> through air inlet <NUM>. Fluid line <NUM> will guide the pressurised air towards inlet port <NUM> of filter unit <NUM>. Pressurised air passing through filter unit <NUM> will be guided by filter sleeve <NUM> towards inlet ports <NUM> and <NUM> of the two shut-off valves <NUM>, <NUM>. Once the two fill/shut-off valves <NUM>, <NUM> are open, pressurised air can flow towards air outlet <NUM> without any restrictions.

Referring to <FIG>, fluid conduit <NUM> connects the two shut-off valves <NUM>, <NUM> with the air outlet <NUM> and inlet port <NUM> of exhaust valve <NUM>. In the illustration of <FIG>, exhaust valve <NUM> is in its open position. In this case, pressurised air in fluid conduit <NUM> will be vented via exhaust port <NUM>. As such, only stagnation pressure is available at air outlet <NUM>.

The exhaust valve <NUM> is biased towards its open position via coil spring <NUM>. In order to close exhaust valve <NUM>, exhaust pilot valve <NUM> is opened such that pressurised air can be introduced into upper control chamber <NUM> formed by annular collar <NUM>. Pressurised air in upper control chamber <NUM> will then act against the biasing force of coil spring <NUM> to close exhaust valve <NUM>.

Turning back to <FIG>, it will be appreciated that the first and second shut-off valves <NUM> and <NUM> have parallel longitudinal axes and move along said longitudinal axes between their open and closed position. Similarly, the exhaust valve <NUM> also moves along a longitudinal axis that is parallel to the longitudinal axes of the first and second shut-off valves <NUM>, <NUM>. A longitudinal axis of the filter unit <NUM> is further aligned with the longitudinal axis of the shut-off valves <NUM>, <NUM> and the exhaust valve <NUM>.

It is further derivable from <FIG> that the first and second shut-off valves <NUM>, <NUM> are both received within vertical bores extending from the first, top surface <NUM> of the valve block <NUM>. Caps <NUM>, <NUM> close the bores and complete the valve chambers. Similarly, as illustrated in <FIG>, the exhaust valve <NUM> is received in a vertical bore extending from the top surface <NUM> of the valve block <NUM>. An adaptor piece <NUM> is attached to the top surface <NUM> and engages with the exhaust valve bore. The adaptor piece <NUM> is configured to receive an exhaust silencer (not shown).

<FIG> shows a schematic pneumatic diagram of an air supply unit according to another embodiment not within the scope of the claims.

Part of the embodiment in <FIG> which perform an identical function as parts of the embodiment in <FIG> are labelled with identical reference signs. The air supply unit of <FIG> includes all of the elements described with reference to <FIG>. However, in addition, the embodiment of <FIG> includes a second pressure regulator <NUM>. The second pressure regulator <NUM> includes the same elements as the first pressure regulator <NUM>. In particular, a second pressure regulator pilot valve <NUM> determines the output pressure downstream of regulator valve <NUM>. Since the embodiment of <FIG> has two pressure regulators, <NUM>, <NUM>, the air supply unit <NUM> has two outlets <NUM> and <NUM> at different air pressures. A first air pressure at outlet port <NUM> of the first regulator valve <NUM> is available at outlet <NUM>, whereas a second, lower air pressure at outlet port <NUM> of second regulator valve <NUM> is available at outlet <NUM>. The lower pressure, which may be in the region of <NUM> to <NUM> bar, may be provided from second outlet <NUM> to a pre-blowing valve system <NUM>. The higher pressure at the first outlet <NUM>, which may by in the region of <NUM> bar, may be provided to a main blow-molding valve system <NUM> of blow molding valve arrangement <NUM>.

Similar to the first pressure regulator <NUM>, the second pressure regulator <NUM> comprises a bypass line <NUM> with a check valve <NUM>. As such, air pressure at the outlet port <NUM> of the regulator valve <NUM> can flow towards inlet port <NUM> of regulator valve <NUM> and outlet port <NUM> of regulator valve <NUM>. Accordingly, air pressure at the outlet port <NUM> of the second regulator valve can also be vented by exhaust valve <NUM> via bypass lines <NUM> and <NUM>. Exhaust valve <NUM>, therefore, acts as a central vent for the integrated air treatment unit <NUM>, the first pressure regulator <NUM> and the second pressure regulator <NUM>.

Turning to <FIG> there is shown a schematic pneumatic diagram showing an embodiment of the air supply unit <NUM> not within the scope of the claims.

The air supply unit comprises an inlet <NUM>, which may be connected to a pressurised air source. Inlet <NUM> is connected downstream to a manual valve <NUM> (not shown in <FIG>, but shown equivalently in the embodiment described in <FIG>) and two optional pre-filters <NUM>, <NUM>.

An air inlet <NUM> of the air supply unit <NUM> is connected with an outlet of pre-filter <NUM>. An air outlet <NUM> of the air supply unit is connected to a pressure regulator <NUM> (not shown in <FIG>, but shown equivalently in the embodiment described in <FIG>) that is arranged downstream of the air inlet <NUM>.

The air supply unit <NUM> includes a filter unit <NUM>, two fill valves, which are constructed as shut-off valves <NUM>, <NUM>, and an exhaust valve <NUM>. A first pilot valve <NUM> is arranged to control opening and closing of the shut-off valve <NUM> and the exhaust valve <NUM>. A second pilot valve <NUM> is arranged to control the opening and closing of the shut off valve <NUM>. The first and second shut-off valves <NUM>, <NUM> are arranged in series with the second shut off valve <NUM> being arranged between the first shut-off valve and the air outlet <NUM>.

The filter unit <NUM> comprises an inlet port <NUM>, which is connected to the air inlet <NUM> via fluid line <NUM>. A pressure relief valve <NUM> is part of the air supply unit <NUM> and connected to fluid line <NUM> to act as excess pressure. Depending on the application, the magnitude of air pressure supplied to pressure regulator <NUM> may vary significantly.

In a stretch-blow molding example, the air pressure supplied may reach up to <NUM> bar such that a pressure of around <NUM> bar may be provided during a main blowing phase.

The outlet port <NUM> of filter unit <NUM> is connected, on the one hand, to an inlet port <NUM> of first pilot valve <NUM> and to inlet port <NUM> of exhaust pilot valve <NUM>. On the other hand, the outlet port <NUM> of filter unit <NUM> is connected to inlet ports <NUM> and <NUM> of shut-off valve <NUM>. An outlet port <NUM> of first pilot valve <NUM> is connected to pilot pressure faces of shut-off valve <NUM>. An outlet port <NUM> of first pilot valve <NUM> is connected to a pilot pressure face of exhaust valve <NUM>.

The first pilot valve <NUM> is a normally closed valve. As such, for as long as first pilot valve <NUM> is not actuated, first pilot <NUM> remains closed, resulting in no pressure being applied to the pilot pressure faces of the shut-off valve <NUM> and exhaust valve <NUM>. The shut-off valves <NUM> and <NUM> are also constructed as normally closed valves, such that, for as long as the first and second pilot valves <NUM> and <NUM> remain closed, so are shut-off valves <NUM> and <NUM>. In other words, for as long as first and second pilot valves <NUM> and <NUM> are in their closed state, no pressurised air will be supplied to air outlet <NUM> of the air supply unit. Once the first pilot valve <NUM> is actuated, the pressurised fluid acting on the pilot pressure faces of the shut-off valve <NUM> will move the latter into their open state. In the open state, the inlet port <NUM> of shut-off valves <NUM> are connected to their respective outlet port <NUM>. Once the second pilot valve <NUM> is actuated, the pressurised fluid acting on the pilot pressure faces of the shut-off valve <NUM> will move the latter into its open state. In the open state, the inlet ports <NUM> of shut-off valve <NUM> is connected to their respective outlet ports <NUM>.

The air supply unit further comprises four pressure switches <NUM> and <NUM>: a low pressure outlet pressure switch <NUM>; a high pressure outlet pressure switch <NUM>; a low pressure shut-off valve pressure switch <NUM>; and a high pressure shut-off valve switch <NUM>.

The low pressure outlet pressure switch <NUM> is fluidly connected to the air output <NUM>. The low pressure outlet pressure switch <NUM> is configured to detect the pressure at the air outlet <NUM> of the air supply assembly. The low pressure outlet switch <NUM> gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the low pressure outlet switch <NUM> was switched when the shut-off valve upstream of the air outlet is supposed to be closed it would indicate that in fact the shut-off valve was in fact open. The low pressure switch may occur at <NUM> bar and may output a voltage of 0V. The switch may return to its unactuated position at a pressure below <NUM> bar and may output a voltage of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch from oscillating in a hysteresis loop which may damage the pressure switch.

The high pressure outlet pressure switch <NUM> is fluidly connected to the air output <NUM>. The high pressure outlet pressure switch <NUM> is configured to detect the pressure at the air outlet <NUM> of the air supply assembly. The high pressure outlet switch <NUM> gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the high pressure outlet switch <NUM> was switched when the shut-off valve upstream of the air outlet is supposed to be closed it would indicate that in fact the shut-off valve was in fact open. The high pressure switch may occur at <NUM> bar and may output a voltage of <NUM> V. The switch may return to its unactuated position at a pressure below <NUM> bar and may output a voltage of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch oscillating in a hysteresis loop which may damage the pressure switch.

The high and low output pressure switches <NUM> may be provided in a single pressure switch <NUM>. The single output pressure switch may be an analogue switch which can detect four different switch points. The pressure may be detected using mechanical, piezoelectric, or any other suitable means. The single output pressure switch <NUM> may output a signal voltage depending upon the pressure.

The low pressure shut-off valve switch <NUM> is fluidly connected to the inlet of the second shut-off valve <NUM>. The low pressure shut-off valve switch <NUM> is configured to detect the pressure at the inlet of the shut off valve <NUM>. The low pressure shut-off valve switch <NUM> gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the low pressure shut-off valve switch <NUM> was switched when the first shut-off valve is supposed to be closed it would indicate that the first shut-off valve is open. The low pressure switch may occur at <NUM> bar and may output a voltage of <NUM> V. The low pressure switch may return to its unactuated position at a pressure below <NUM> bar and output a signal of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch <NUM> from oscillating in a hysteresis loop which may damage the pressure switch.

The high pressure shut-off valve switch <NUM> is fluidly connected to the inlet of the second shut-off valve <NUM>. The high pressure shut-off valve switch <NUM> is configured to detect the pressure at the inlet of the shut off valve <NUM>. The high pressure shut-off valve switch <NUM> gives an indication, by means of an output voltage, to the safe and/or unsafe operation of the air supply unit. If for example the low pressure shut-off valve switch <NUM> was switched when the first shut-off valve is supposed to be closed it would indicate that the first shut-off valve is open. The high pressure switch may occur at <NUM> bar and may output a voltage of <NUM> V. The low pressure switch may return to its unactuated position at a pressure below <NUM> bar and output a signal of <NUM> V. The reverse is also possible. The <NUM> bar difference between the two switch points prevents the switch <NUM> from oscillating in a hysteresis loop which may damage the pressure switch.

The high and low shut-off valve pressure switches <NUM> may be provided in a single pressure switch <NUM>. The single shut-off valve pressure switch <NUM> may be an analogue switch which can detect four different switch points. The pressure may be detected using mechanical, piezoelectric, or any other suitable means. The single output pressure switch <NUM> may output a signal voltage depending upon the pressure.

An inlet port <NUM> of exhaust valve <NUM> is also connected to the air outlet. In other words, the inlet port <NUM> of exhaust valve <NUM> is connected to both outlet ports <NUM> and <NUM> of the shut-off valves <NUM> and <NUM> and, at the same time, to air outlet <NUM>. An outlet port <NUM> of exhaust valve <NUM> is connected to exhaust port <NUM>. A silencer <NUM> is downstream of the exhaust port <NUM>.

The exhaust valve <NUM> is a normally open valve, which may be actuated by first pilot valve <NUM>. First pilot valve <NUM> is a normally closed valve. An inlet port <NUM> of first pilot-valve <NUM> is connected to outlet port <NUM> of filter unit <NUM>. An outlet port <NUM> of first pilot-valve <NUM> is connected to a pilot pressure face of exhaust valve <NUM>. In its normally closed state, first pilot-valve <NUM> interrupts the connection between inlet port <NUM> and outlet port <NUM>, thereby not providing any pressurised fluid to the pilot pressure face of exhaust valve <NUM>. As such, exhaust valve <NUM> remains open as depicted in <FIG>. As soon as first pilot valve <NUM> is actuated and moved into its open state, pressurised fluid acts on the pilot pressure face of the exhaust valve <NUM>, thereby transferring the latter into its closed state. It will be appreciated that, for as long as exhaust valve <NUM> is in its open state, only pressurised fluid at stagnation pressure can be supplied to outlet port <NUM>. In the example of a blow moulding system, the stagnation pressure may typically be in the region of <NUM>-<NUM> bar, rather than <NUM> to <NUM> as required for the main blowing phase. As such, whenever pressurised fluid is supplied to outlet port <NUM>, exhaust pilot-valve <NUM> is actuated in order to close exhaust valve <NUM>.

The embodiment of <FIG> may comprise the following features which are not shown explicitly in <FIG> but are described here. These features are described in the embodiment shown in <FIG> and for consistency that numbering will be adhered to. Treated pressurised air provided at air outlet <NUM> is supplied to pressure regulator <NUM>. Pressure regulator <NUM> comprises a variable pressure regulator valve <NUM> and pilot valve arrangement <NUM>. An inlet port <NUM> of regulator valve <NUM> is connected to air outlet <NUM>. Similarly, an inlet port <NUM> of pilot valve <NUM> is connected to air outlet <NUM>. An outlet port <NUM> of pilot valve <NUM> is connected to pilot pressure face <NUM> of regulator valve <NUM>. An outlet port <NUM> of the regulator valve <NUM> is connected to outlet <NUM> of air supply unit <NUM>. Pilot valve arrangement <NUM> is configured to determine an outlet pressure of regulator valve <NUM> via pilot pressure face <NUM>. Depending on the magnitude of pressure applied to pilot pressure face <NUM> by pilot valve <NUM>, the pressure regulator valve <NUM> determines the air pressure supplied to outlet <NUM> of air supply unit <NUM>.

The pressure regulator <NUM> further comprises a bypass line <NUM>. The bypass line <NUM> connects the outlet port <NUM> and the inlet port <NUM> of regulator valve <NUM>. A check valve <NUM> is provided in bypass line <NUM>. The check valve <NUM> stops pressurised fluid from bypassing the regulator valve <NUM> by flowing from its inlet <NUM> towards its outlet <NUM>. However, should an air pressure applied to inlet <NUM> of variable relief valve <NUM> be lower than an air pressure on the side of outlet port <NUM>, pressurised air may flow back to the air outlet <NUM>. In other words, bypass line <NUM> is a return line, which enables pressurised fluid on the side of outlet port <NUM> to be vented via exhaust valve <NUM>.

In case of a sudden power failure of air supply unit <NUM>, shut-off valves <NUM> and <NUM> automatically return into their closed position shown in <FIG>, thereby disconnecting air inlet <NUM> of integrated air treatment unit <NUM> from air outlet <NUM>. At the same time, exhaust valve <NUM> will open and relieve pressurised air within fluid line <NUM>. Pressurised air downstream of pressure regulator <NUM> will also be vented via exhaust valve <NUM> by means of bypass line <NUM>. This is because once fluid line <NUM> is vented, there is no pressurised air supplied to inlet port <NUM> of regulator valve <NUM>. At this point, pressure on the outlet port side of regulator valve <NUM> exceeds the pressure on the inlet port side and check valve <NUM> opens, enabling pressurised fluid to flow between the outlet port <NUM> and the inlet port <NUM> of regulator valve <NUM>, ultimately venting said pressurised fluid via exhaust valve <NUM>. As will be appreciated, due to the presence of return bypass line <NUM>, pressure regulator <NUM> does not require a separate exhaust valve.

Turning to <FIG> there is shown a schematic pneumatic diagram showing an embodiment of the air supply unit <NUM> not within the scope of the claims configured substantially similar to the air supply unit <NUM> of <FIG>. The air supply unit of <FIG> further comprises a first redundant shut-off valve <NUM> and a second redundant shut-off valve <NUM> in comparison to <FIG>.

The first shut-off valve <NUM> and first redundant shut-off valve <NUM> form a first pair of valves <NUM>. The first pair of valves <NUM> are controlled by the first pilot valve <NUM>.

The second shut-off valve <NUM> and second redundant shut-off valve <NUM> form a second pair of valves <NUM>. The second pair of valves <NUM> are controlled by the second pilot valve <NUM>.

The first and second pair of shut-off valves <NUM>, <NUM> are arranged in series and are fluidly connected by a fluid line. Opening the first pair of valves <NUM> pressurises the fluid line between the first and second pair of valves.

Turning to <FIG> there is shown a schematic pneumatic diagram showing an embodiment of the air supply unit <NUM> according to the present invention configured substantially similar to the air supply unit <NUM> of <FIG>. The air supply unit of <FIG> further comprises a slow fill valve <NUM>, a slow fill pilot valve <NUM> and a second exhaust valve <NUM>.

The slow fill valve <NUM> comprises an inlet <NUM> and an outlet <NUM> and a throttle <NUM>. The throttle may be a variable orifice which may be used to control the fluid flow out of the slow fill valve <NUM>.

The slow fill valve inlet <NUM> is fluidly connected to an outlet of the first pair of shut off valves <NUM> at the fluid line connecting the first and second pair of shut-off valves <NUM> and <NUM>. The slow fill valve outlet <NUM> and slow fill valve throttle <NUM> are fluidly connected to the air outlet <NUM>. The slow fill valve <NUM> is in a normally closed position.

The second exhaust valve <NUM> has an inlet <NUM> and an outlet <NUM>. The second exhaust valve inlet is fluidly connected to the air outlet <NUM>. The second exhaust valve outlet <NUM> is fluidly connected to the exhaust outlet <NUM>. The second exhaust valve is in a normally open position.

The slow fill pilot valve <NUM> has an inlet <NUM> and an outlet <NUM>. The slow fill pilot valve inlet <NUM> is fluidly connected to the outlet port of the filter <NUM>. The slow fill pilot valve outlet <NUM> is connected to the slow fill valve <NUM> and the second exhaust valve <NUM> is used to operate both the slow fill valve and the second exhaust valve <NUM>.

The slow fill pilot valve <NUM> is in a normally closed position. The slow fill pilot valve <NUM> can be electrically actuated to open it. Opening the pilot valve <NUM> opens the slow fill valve <NUM> and closes the second exhaust valve <NUM>. Closing the slow fill pilot valve <NUM> causes the slow fill valve <NUM> to return to its normally closed position and the exhaust valve <NUM> to return to its normally open position.

The normally closed/open position used to make the valves, <NUM>, <NUM>, <NUM>, return to a closed/open position may be provided by a spring and/or air pressure in one or more fluid lines which are connected to the inlet of the first and second stop valves and/or the slow fill valve.

Turning to <FIG> there is shown a perspective view of a valve block <NUM> of an air supply unit <NUM> substantially similar to the embodiment described in <FIG>. The valve block <NUM> has an air outlet <NUM>, an air inlet <NUM> (not shown in this view) and a filter unit connection port (not shown). The valve block <NUM> may be a single component. The valve block <NUM> may be several components fixed together to form a valve block.

The valve block has bores which may receive the filter unit <NUM>, the first and second pilot valves (<NUM>, <NUM>) and the slow fill pilot valve (<NUM>), the outlet pressure switch <NUM>, and the shut-off valve pressure switch <NUM>.

The valve block <NUM> has internal bores which house the first and second pairs of shut-off valves <NUM>, <NUM>, the slow fill valve <NUM>, and the first and second exhaust valves <NUM>, <NUM>.

<FIG> shows a signal plan diagram and blow curves for the method of self-testing a air supply unit <NUM> substantially similar to the one disclosed in <FIG>. The diagram shows the change in electrical signal to actuate valves V1, V2 and V3, and the resulting pressure measured at the pressure switches <NUM>, <NUM>.

V1 is the signal for the first pilot valve <NUM>. The signal shows if the pilot valve <NUM> is open (V1 = On) or off (V1 = Off).

V2 is the signal for the slow fill pilot valve <NUM>. The signal shows if the pilot valve <NUM> is open (V2 = On) or off (V1 = Off).

V3 is the signal for the second pilot valve <NUM>. The signal shows if the pilot valve <NUM> is open (V3 = On) or off (V1 = Off).

Blowcurve S-X describes both the low and high pressure shut-off pressure switches <NUM>.

Blow curve S-O describes both the low and high pressure output pressure switches <NUM>.

V1 is the signal for the first pilot valve <NUM>.

V2 is the signal for the slow fill pilot valve <NUM>.

V3 is the signal for the second pilot valve <NUM>.

<FIG> describes a method of self-testing substantially similar to the signal plan diagram in <FIG>.

The signal SX1 and SX2 are the required output signal from the low and high pressure shut-off pressure switches <NUM> respectively.

The signal SO1 and SO2 are the required output signal from the low and high pressure shut-off pressure switch <NUM> respectively.

The method of the self-test involves the steps of:.

At each step the values of SX1, SX2, SO1 and SO2 are stored as a first, second, third and fourth data set respectively. The required values of SX1, SX2, SO1 and SO2 are stored in a test data set for comparison with the self-test outputs given in the first, second, third and fourth data sets.

If these criteria are all passed then a signal is indicated to the operator that the air supply unit <NUM> is safe to operate.

If these criteria are not passed then a signal is indicated to the operator that the air supply unit <NUM> is not safe to operate.

Claim 1:
An air supply unit (<NUM>) for high pressure applications, comprising:
an air inlet (<NUM>), an air outlet (<NUM>), and an exhaust outlet (<NUM>);
a shut-off valve (<NUM>) having an inlet port (<NUM>) connected to the air inlet (<NUM>) and an outlet port (<NUM>) connected to the air outlet (<NUM>);
a first exhaust valve (<NUM>) having an inlet port (<NUM>) connected to the air outlet (<NUM>), wherein the first exhaust valve (<NUM>) comprises an outlet port (<NUM>) connected to the exhaust outlet (<NUM>);
a pilot valve (<NUM>) arranged to control the shut-off valve (<NUM>);
wherein the pilot valve (<NUM>) is configured to control the shut off valve (<NUM>) and control the exhaust valve (<NUM>),
characterised in that
the air supply unit (<NUM>) further comprises:
a slow fill valve (<NUM>) connected to the shut-off valve (<NUM>) and the air (<NUM>);
a throttle (<NUM>) which controls the fluid flow rate out of the slow fill valve (<NUM>);
a second exhaust valve (<NUM>) connected to the outlet port (<NUM>) of the slow fill valve (<NUM>) and the air outlet (<NUM>), said second exhaust valve (<NUM>) comprising an outlet port (<NUM>) connected to the exhaust outlet (<NUM>); and
a slow fill pilot valve (<NUM>) arranged to control the slow fill valve (<NUM>) and the second exhaust valve (<NUM>).