Patent Description:
More particularly, the disclosure relates to a cleaning valve for a separator, i.e. to a valve that is used to create a reverse burst of air through a filter of a separator, in order to clean the filter.

Separators are used for separating particles (including powder, granules, debris, etc.) from a flow of fluid, such as air, oil or water.

Some separators make use of a permeable separator body which traps the particles as the flow is directed through the separator body. The separator body may take the form of a grille, a net or a filter medium. A filter medium may comprise a porous material that ideally is permeable to the fluid but not to the particle that is to be separated. In many applications, the filter material may be a woven or non-woven material fiber material.

As particles become trapped in the separator body, the separator body will gradually become clogged, leading to an increase in pressure drop over the filter, which affects the efficiency of the entire system.

Hence, it may be necessary to maintain the separator body, e.g. by exchanging it or by cleaning it.

In many applications, cleaning the separator body is the method of choice, since the separator body as such has a life which is substantially greater than the time it takes for it to clog.

There are various methods of cleaning the separator body, some of which include removing it from its place of operation, and others including cleaning the separator body in situ. The latter may involve various methods of scraping, striking or agitating the separator body.

A particular way of cleaning a separator body is by subjecting it to a reverse burst of the fluid. That is, fluid is caused to rapidly flow backwards through the separator body, whereby particles that are trapped on the separator body side which is upstream in normal operation are released from the separator body, and preferably collected and removed.

Directions "upstream" and "downstream" are defined relative to the normal flow of fluid and material in the separator, during a normal separating operation.

In heavy duty separators for separating particles from air (essentially heavy duty "vacuum cleaners"), e.g. in connection with grinding of stone or concrete, a suction generator is normally arranged downstream of the separator, such that the suction generator draws air through the separator and thus through the separator body.

Referring to <FIG>, such heavy duty separators may comprise a pre-separator, which may have the form of a settling chamber, coarse filter, a cyclone separator or a centrifugal separator, and a post-separator, such as a HEPA filter for separating out the finest particles not caught by the main separator. The suction generator would then typically be situated downstream of the main separator, and in many cases also downstream of the post-separator.

In order to clean the separator body, the separator inlet is typically closed, while the suction generator is allowed to operate, such that an underpressure (i.e. pressure lower than ambient pressure) is built up inside the separator. Once the underpressure has been established, a valve at the downstream side of the separator body, a "cleaning valve" is quickly opened, connecting the downstream side of the separator body to higher pressure air, such as ambient air, whereby air will rush backwards through the separator body, cause agitation of the separator body and release particles caught on the upstream side of the separator body. If the separator body is appropriately oriented, then the particles will drop to the bottom of the separator, where they may be collected and removed.

As an option, it is possible to provide an accumulated volume of pressurized air, which may be applied in the reverse direction of the separator body.

Hence, the cleaning procedure makes use of two valves: an inlet valve at the upstream side of the separator body and a cleaning valve on the downstream side of the separator body.

The inlet valve should provide sufficient shut-off of the incoming flow to the separator.

It is desirable to provide a cleaning valve, which is robust and which can be manufactured at low cost. Preferably, the cleaning valve should also be possible to open very quickly, such that a sudden burst of reverse flow can be achieved. Preferably, the cleaning valve should also be easy to maintain and allow for automation. That is, it should be possible to operate the valve through numerical control, such that a cleaning operation can be entirely automated and initiated by a controller when needed or when ordered by an operator.

While a very well-functioning cleaning valve is disclosed in <CIT>, there is still room for improvement.

<CIT> discloses a valve arrangement for a suction cleaner. The valve arrangement is configured to generate a reverse burst of air to clean a permeable separator body (a filter) of a suction cleaner such as a separator.

It is an object of the present invention to provide an improved cleaning valve, and in particular an inlet valve which at least partially meets the criteria set forth by way of introduction.

The invention is defined by the appended independent claims, with embodiments being set forth in the dependent claims. The attached drawings and in the following description are used to interpret the claims.

According to a first aspect, there is provided a valve having a predetermined low pressure side, comprising a main valve closure body, arranged on a low pressure side of the valve and moveable to open towards the low pressure side, a control body, fixedly connected to the main valve closure body, such that a position of the main valve closure body is fixed relative to a position of the control body, a control chamber, partially defined by the control body, whereby a volume of the control chamber is variable in relation to the position of the control body, a control fluid connector for controlling a pressure in the control chamber, and a trigger valve which is movable between an open state and a closed state and which, in its open state, connects the control chamber to a pressure which is sufficiently high to allow the main valve closure body to open, wherein said trigger valve is a pressure balanced valve comprising a trigger space that comprises a first trigger chamber, a second trigger chamber and a third trigger chamber, a first trigger closure body operable on a first trigger seat facing outwardly of the first trigger chamber, and a second trigger closure body, rigidly connected to the first trigger body and operable on a second trigger seat facing inwardly of the second trigger chamber, where the control connection is connected to the third trigger chamber and where, when the trigger valve in its closed state, the first trigger chamber is open to the third trigger chamber, such that vacuum applied through the control connector is applied to the control chamber through the first and third trigger chambers, and the second trigger chamber is open to the third trigger chamber, such that vacuum is applied to the control chamber through the second and third trigger chambers.

By the valve being able arranged to open towards a low-pressure side, the external force required to open the valve can be kept very low, and the lower pressure is effectively used to force the valve open.

By controlling the position of the main valve closure body based on a control body whose position is set relative to a pressure in a control chamber, it is possible to use a small air volume to control the main valve closure body, and thus to achieve a rapid opening of the main valve closure body.

The control body may have an effective area exposed to the control chamber which is greater than an effective area of the main valve closure body exposed to the low pressure side of the valve.

The term "effective area" relates to the area on which the pressure operates to provide a resulting force.

The control chamber may be defined by the control body, a base body and a flexible membrane sealingly connecting the control body with the base body, such that a volume of the control chamber is variable.

The main valve closure body may be formed as a substantially planar member.

The control body may be formed as a substantially planar member and oriented parallel with the main valve closure body.

Alternatively, the control chamber may be defined by the control body forming a piston and a cylinder in which the control body is movable, such that a volume of the control chamber is variable.

The valve may further comprise at least one spacer connecting the main valve closure body and the control body.

The main valve closure body may be biased towards its closed position.

The main valve closure body may be biased by the tension of the membrane, or bladder, as the case may be, or by a separate biasing device, such as a spring.

The trigger closure bodies may present areas exposed to the trigger space, wherein the areas are equal or wherein the areas differ +/- less than <NUM> %, preferably +/- less than <NUM> % or +/- less than <NUM> %.

The first trigger seat may be arranged on an inside of a trigger chamber while the second trigger seat may be arranged on an outside of the trigger chamber.

Hence, an underpressure (or vacuum, partial vacuum) on the inside of the trigger valve will operate to draw the first trigger closure body towards the first trigger seat, thus providing a force operating to close the trigger valve.

Simultaneously, the underpressure on the inside of the trigger chamber will operate to draw the second trigger closure body away from the second trigger seat, thus providing a force operating to close the trigger valve.

By selecting areas of the trigger closure bodies and connecting the trigger closure bodies to each other, the forces operating to open and close, respectively, the trigger valve may balance each other.

Depending on the design, the trigger space may be permanently open to the control space, with the first trigger seat facing ambient pressure.

Alternatively, the trigger space may be permanently open to the ambient pressure, with the second trigger seat facing ambient pressure.

The valve may further comprise a trigger member which is rigidly connected to the trigger closure bodies and exposed for manual operator interaction.

The valve may further comprise a trigger actuator, configured to control a state of the trigger valve.

The actuator may be a linear actuator arranged for causing the trigger closure bodies to move relative to the trigger seats.

According to a second aspect, there is provided use of a valve as described above in a separator for separating particles from a particle-laden fluid flow, wherein the valve is arranged on a downstream side of a separator body.

The separator body may take the form of a grille, a net or a filter medium.

In such use, fluid may be drawn through the separator by a suction generator arranged downstream of the separator.

In such use, the control connector may be in fluid connection with the suction generator at a point downstream of the separator, such that a pressure applied to the control connector is lower than a pressure applied to the separator space.

As an alternative, the control connector may be connected to a separate pump device, arranged to supply a vacuum and/or a pressure to the control chamber and/or to the trigger space.

In such use, a pressure applied to the control connector and thus to the control chamber, may be sufficient to provide a control body closing force which is greater than a force provided by the suction force applied to the separator operating on the main valve closure body.

In such use, the separator may be adapted for separating particles from particle-laden air.

According to a third aspect, there is provided a separator for separating particles from a fluid flow, comprising a separator housing enclosing a separator body, a suction generator, connected to the separator housing at a downstream side of the separator body, an inlet for particle-laden fluid, the inlet connecting to the separator housing at an upstream side of the separator body, and a valve as described above, wherein the main valve closure body is openable inwardly into the separator housing.

The separator may further comprise an inlet valve, adapted for closing the inlet.

The separator may further comprise a separate pump device, arranged to supply a vacuum and/or a pressure to the control chamber and/or to the trigger chamber.

The separator may further comprise an accumulator arranged to accumulate a vacuum and/or a pressure, and selectively connected to the control chamber and/or to the trigger chamber, to apply said vacuum and/or pressure to the control chamber and/or trigger chamber.

According to a fourth aspect, there is provided a method of operating a separator having a separator body arranged in a separator space, with a separator space inlet arranged upstream of the separator body and a separator space outlet arranged downstream of the separator body. The comprises providing a valve as described above on a downstream side of the separator body, such that the valve in its closed state prevents communication between the separator space and an outside of the separator space, and in its open state allows communication between the separator space and the outside, applying a suction to the separator space outlet, applying a pressure to the control chamber that is sufficiently low for a resulting force generated on the control body to be higher than a force generated by the suction on the main valve closure body, and causing the trigger valve to shift from a closed position to the open position, whereby the force generated on the control body is reduced, such that the suction applied to the main valve closure body causes the main valve closure body to open the valve to the outside.

In the following description, the valve will be described with reference to its use in a separator that forms part of a heavy duty vacuum cleaner useful in a floor grinding context.

Referring to <FIG>, a system comprises a floor grinding machine <NUM>, which may be any type of floor grinding machine having a connection for evacuation of grinding residues. The system further comprises a heavy duty vacuum cleaner unit <NUM>, which comprises a pre-separator <NUM> illustrated as a cyclone type separator; a main separator <NUM> comprising an inlet <NUM>, an outlet <NUM>, an inlet valve <NUM>, a cleaning valve <NUM>, and a separator body <NUM>, such as a filter. The system further comprises a post-separator <NUM>, such as a HEPA filter and a suction generator <NUM>, which may comprise a motor driving a fan to create an airflow.

<FIG> schematically illustrates the separator <NUM> with the separator inlet <NUM>, the outlet <NUM>, the inlet valve <NUM> and a housing <NUM>. The cleaning valve <NUM> is also visible at the top of the housing <NUM>.

Referring to <FIG>, there is illustrated an upper portion <NUM> of the separator housing <NUM> with a cleaning valve assembly <NUM> mounted thereto.

Referring to <FIG>, the cleaning valve <NUM> comprises a valve base <NUM>, which may be formed as a separate member, that is adapted for being mounted to an opening in the separator housing <NUM>, <NUM>. Alternatively, the valve base <NUM> may be integrated with the separator housing <NUM>, <NUM>, such as formed in one piece therewith.

The valve base <NUM> comprises one or more valve openings <NUM>, which provide a flow area that is sufficiently large to allow the air volume necessary to rapidly flow into the separator housing <NUM>.

The valve base <NUM> also provides a valve seat <NUM>, i.e. a seat against which the valve closure <NUM> member is to cooperate in its closed position (<FIG>). This valve seat <NUM> is arranged on the face of the valve base <NUM> which is to face the interior of the separator housing <NUM>, which will be a low pressure side of the valve <NUM>.

In the illustrated example, the valve base <NUM> is formed as a base plate, made of a piece of sheet metal. Moreover, in the illustrated example, the valve base <NUM> has a generally circular shape, i.e. a circular outer perimeter and the openings <NUM> are formed as segments of a circle or of an annulus.

The valve <NUM> further comprises a valve closure body <NUM>, which cooperates with the valve seat <NUM> when the valve is in its closed position (<FIG>).

A seal <NUM> may be arranged at to seal between the valve seat <NUM> and the valve closure body <NUM>, attached either to the seat or to the valve closure body (as illustrated).

The valve closure body <NUM> may also be formed as a generally planar member, having a shape that is adapted to that of the opening and being slightly larger than the opening <NUM>, such that it can cover the opening to provide a sufficiently air-tight seal.

Spaced from the base, there is a control base <NUM>. The control base may be rigidly mounted to the valve base <NUM> by means of one or more base spacers 1244a, 1244b, 1244c 1244d, such that a flow area Af is provided between the valve base <NUM> and the control base <NUM>.

The control base <NUM> defines, together with a control body 1247a, 1247b and a flexible membrane <NUM>, a control chamber Cc. The control body 1247a, 1247b is connected to the control base <NUM> via the membrane <NUM>, such that the control body 1247a, 1247b is movable relative to the control base <NUM> while a volume of the control chamber Cc varies.

The control body 1247a, 1247b is rigidly connected to the valve closure body <NUM> by means of one or more valve spacers 1243a, 1243b, such that the control body 1247a, 1247b and the valve closure body <NUM> always maintain a predefined distance and orientation relative each other.

The control body 1247a, 1247b may also be formed as a planar member, such as from a piece of sheet metal.

As one design example, an effective area of the control body 1247a, 1247b exposed towards the control chamber Cc may be greater than an effective area of the valve closure body <NUM> that is exposed to the low pressure side of the separator housing <NUM>.

The membrane <NUM> may be an elastically flexible membrane, such as a rubber elastic membrane.

The membrane <NUM> may be formed as an annular member, with its radially outer edge attached and sealed against an outer portion of the control base <NUM> and with its radially inner edge attached and sealed against an outer portion of the control body 1247a, 1247b.

Alternatively, the membrane <NUM> may be a circular member, which is connected to the 1247a, 1247b.

As yet another alternative, the membrane <NUM> may be wholly or partially sandwiched between a pair of control body members 1247a, 1247b.

The control base <NUM> may be formed as a substantially planar member. In the alternative, it may be formed or mounted so as to define a chamber. For example, the base <NUM> may present side walls so as to define a substantially cylindrical control chamber, defined by the side walls, an axial wall, the membrane <NUM> and the control body 1247a, 1247b, with the membrane and the control body 1247a, 1247b being movable relative to the control base <NUM>.

A fluid connector <NUM> is arranged to provide a fluid connection to the trigger chamber Ct1, Ct2, Ct3 and from there to the trigger chamber/control chamber, such that a vacuum can be drawn in the control chamber Cc in order to close the valve closure body <NUM>.

The axial wall of the control base <NUM> may also present a trigger opening <NUM>, i.e. an opening through which the control chamber Cc may be connected to ambient pressure Aa, such that the valve closure body <NUM> may open. This opening may be provided with any type of valve that can be opened sufficiently quickly to allow enough air to flow into the control chamber Cc to rapidly increase pressure therein so that the vacuum in the separator housing <NUM> will cause the valve closure body <NUM> to open.

In the following, a trigger valve <NUM>, that can be used to control this trigger opening <NUM>, will be described.

Referring to <FIG>, the trigger valve <NUM> may comprise a trigger valve housing 12481a, 12481b defining at least one trigger chamber Ct1, Ct2, Ct3, that is connected to the control chamber Cc.

In the illustrated example, there are three interacting trigger chambers Ct1, Ct2, Ct3 provided.

The first trigger chamber Ct1 provides a constant (i.e. always open) connection to the control chamber Cc. and present port openings towards ambient pressure Aa and towards the third trigger chamber Ct3.

The port opening from the first trigger chamber towards the ambient pressure Aa is regulated by a first trigger closure body <NUM>, which is arranged on the outside of the first trigger chamber Ct1, where it cooperates with a first trigger valve seat St1 to regulate the connection between the first trigger chamber Ct1 and the ambient pressure Aa.

The second trigger chamber Ct2 provides a constant connection to the control chamber Cc and houses the second trigger closure body <NUM>, which cooperates either with the second trigger valve seat St2 to regulate a connection to the ambient pressure Aa, or with the third trigger valve seat St3 to regulate a connection to the third trigger chamber Ct3.

The third trigger chamber Ct3 provides a constant connection to the control connector <NUM> and houses the third trigger closure body <NUM>, which cooperates with the fourth trigger valve seat St3 to regulate the connection to the first trigger chamber Ct1.

In the closed position (<FIG>, <FIG>) of the cleaning valve <NUM>, the first trigger chamber Ct1 is open to the third trigger chamber Ct3, such that vacuum (suction from e.g. the suction generator <NUM>) applied through the control connection <NUM> may be applied to the control chamber Cc through the first and third trigger chambers Ct1, Ct3, as illustrated by arrow V1 in <FIG>.

Further, in the closed position of the trigger valve, the first trigger chamber Ct1 is sealed off from ambient pressure by the first trigger valve body <NUM> interacting with the first trigger valve seat St1.

Moreover, in the closed position of the trigger valve, the second trigger chamber Ct2 is sealed off from ambient pressure by the second trigger valve body <NUM> interacting with the second trigger valve seat St2.

Also in the closed position of the trigger valve, the second trigger chamber Ct2 is open to the third trigger chamber Ct3, such that vacuum applied by the suction generator <NUM> may be applied to the control chamber Cc through the second and third trigger chambers Ct2, Ct3, as illustrated by arrow V2 in <FIG>.

In the open position (<FIG>, <FIG>) of the trigger valve, the first trigger chamber Ct1 is sealed from the third trigger chamber Ct3 by the third trigger valve body <NUM> interacting with the fourth trigger valve seat St4, such that no vacuum is applied to the control chamber Cc through the first and third trigger chambers Ct1, Ct3.

Further, in the open position of the trigger valve, the first trigger chamber Ct1 is open to ambient pressure by the first trigger valve body <NUM> being spaced from the first trigger valve seat St1.

Moreover, in the open position of the trigger valve, the second trigger chamber Ct2 is open to ambient pressure by the second trigger valve body <NUM> being spaced from the second trigger valve seat St2.

Also in the open position of the trigger valve, the second trigger chamber Ct2 is sealed off from the third trigger chamber Ct3 by the second trigger valve body <NUM> interacting with the third trigger valve seat St3, such that no vacuum is applied to the control chamber Cc through the second and third trigger chambers Ct2, Ct3.

Hence, in the open position of the trigger valve, the control connection <NUM> only draws a vacuum in the third trigger chamber Ct3, but not in the control chamber Cc.

With the third trigger valve seat St3 operating on the outside of the third trigger valve chamber Ct3 and the fourth trigger valve seat St4 operating on the inside of the third trigger valve chamber Ct3, the force provided by the vacuum connection <NUM> is balanced.

Likewise, with the first trigger valve seat St1 operating on the ambient pressure side of the trigger valve, and the second trigger valve seat St2 operating on the inside that is subjected to vacuum from the suction generator <NUM> when the trigger valve is in the closed position, the forces provided by the vacuum connection <NUM> are balanced.

It is noted that at each area of interaction between a trigger valve seat St1, St2, St3, St4 and a trigger valve body <NUM>, <NUM>, <NUM> a seal may be provided. Such seal may be arranged on the valve seat and/or on the valve body.

It is noted that the second trigger valve body <NUM> may be provided by one or two separate valve bodies.

The trigger valve bodies <NUM>, <NUM>, <NUM> are rigidly connected to each other by a trigger axle <NUM>. For example, the trigger valve closure bodies <NUM>, <NUM>, <NUM> may be aligned with each other in an axial direction of the trigger valve, whereby the valve closure bodies are movable back and forth along that axial direction.

That is, the lower pressure inside the trigger chamber Ct1, Ct2, Ct3 will operate to pull the first trigger valve closure body <NUM> towards the first trigger valve seat St1 and simultaneously, it will pull the second trigger valve closure body <NUM> inwardly, away from the valve second seat St2.

Since the trigger valve closure bodies <NUM>, <NUM>, <NUM> are rigidly connected to each other, the forces operating on the respective body will balance each other.

When the trigger valve closure bodies <NUM>, <NUM>, <NUM> are in the valve's <NUM> closed position, the pressure inside the trigger chamber Ct1, Ct2, Ct3 will be the same as in the control chamber Cc, due to the connection to the control chamber.

When the trigger valve closure bodies are in the open position, the trigger chamber Ct1, Ct2, Ct3 will communicate with ambient air pressure, and so will also the control chamber Cc.

In order to control the position of the trigger valve closure bodies <NUM>, <NUM>, <NUM>, there may be provided an operating member <NUM>, which may comprise a pin that may be pushed or pulled by hand by an operator to close or open the trigger valve.

A spring (not shown) may be provided to slightly bias the trigger valve closure bodies <NUM>, <NUM>, <NUM> towards the closed position of the trigger valve (<FIG>, <FIG>).

An actuator <NUM> may be provided to control a position of the trigger valve closure bodies <NUM>, <NUM>, <NUM>. Such actuator may, as an example, be formed as a coil providing a linear movement of the trigger valve closure bodies along the axial direction.

The cleaning valve <NUM> may be operated as follows.

The cleaning valve <NUM> is mounted to an opening in a wall <NUM> of the separator <NUM>, at the downstream side of the separator body <NUM>, such that the inside of the valve <NUM> faces inwardly into the separator chamber and the outside of the valve is exposed to ambient air pressure.

A fluid connection <NUM> is provided to the trigger chamber/control chamber Cc via the control connector <NUM> and connected to the suction generator <NUM> of the separator <NUM> at a point that is closer to the suction generator than a separator outlet <NUM>. For example, another separator, such as a post-separator <NUM> may be arranged between the separator outlet <NUM> and the connection to the suction generator <NUM>, such that a lower pressure will be provided to the control chamber Cc than to the separator outlet <NUM>. As an alternative, the control connection may be connected to a separate pump (not shown) for drawing a vacuum and/or for applying a pressure to the trigger chamber/control chamber.

The connection <NUM> between the connector <NUM> and the suction generator <NUM> may be controlled by a valve <NUM>, which may be arranged to selectively connect the trigger chamber/control chamber Cc to the suction generator <NUM> or to ambient pressure.

In an embodiment with the trigger valve, the valve <NUM> is not necessary.

In an embodiment without the trigger chamber, the connection <NUM> may be connected directly to the control chamber Cc, with the valve <NUM> being used to trigger the valve <NUM> to open. In such case, the underpressure to the control chamber may be supplied directly from the suction generator <NUM> or from an accumulator <NUM>.

During normal operation, the inlet valve <NUM> will be held open, as will the cleaning valve <NUM> by virtue of the suction drawn at the control connection <NUM> being greater than the suction provided at the separator outlet <NUM>.

With the separator <NUM> running, i.e. the suction generator <NUM> activated, an inlet valve <NUM> is closed, such that a very low pressure is provided in the separator <NUM> chamber. Simultaneously, an even lower pressure is provided in the control chamber Cc, due to its connection to the suction generator <NUM>.

Through the lower pressure in the control chamber Cc, and optionally also the larger effective surface area of the control body 1247a, 1247b, the suction force provided on the control body 1247a, 1247b will be greater than the suction force provided on the valve closure body <NUM> by the vacuum inside the separator housing <NUM>. Hence, the valve closure body <NUM> will be kept in the closed position, as illustrated in <FIG>, <FIG>, <FIG>.

Faces of the members 1247a, 1247b forming the control body may be slightly convex, such that the membrane may be fixedly attached to the control body at a central portion thereof, while, at the edges of the control body 1247a, 1247b, the membrane may move relative to the control body, to further enhance its flexibility.

As another option, or additionally, edges of the membrane may be formed creases such as to provide a bellows, to further increase its mobility.

Once a sufficiently low pressure has been built up in the separator chamber, and/or after a predetermined time of operation with the inlet valve <NUM> closed, the trigger valve <NUM> is caused to open. When the trigger valve is opened, ambient air pressure flows into the control chamber Cc, as illustrated by arrows V3, V4 in <FIG>, such that the pressure in the control chamber Cc rapidly increases. When the pressure in the control chamber Cc reaches a sufficient level (which it does very quickly due to the small size of the trigger chamber Ct1, Ct2, Ct3 and the control chamber Cc and the relatively large trigger valve openings), the force provided on the control body 1247a, 1247b will decrease, whereby the lower pressure in the separator chamber <NUM> will force open the valve closure body <NUM>, to rapidly allow air to burst in, as illustrated by arrows V5, V6, such that a reverse flow through the separator body <NUM> is achieved, and optionally, the separator body <NUM> is agitated. In practice, this is a very rapid sequence.

After the cleaning operation, the trigger valve <NUM> is allowed to return to its closed state (<FIG>, <FIG>), whereby the pressure in the control chamber Cc is again reduced until the suction force operating on the control body 1247a, 1247b is sufficient to cause the valve closure body <NUM> to return to its closed position.

The cleaning procedure may then be repeated, if desired.

If the cleaning is deemed to be completed, the inlet valve is opened and normal operation is resumed.

Optionally, an accumulator <NUM> may be provided between the suction generator <NUM> and the control connection <NUM>. By allowing the suction generator <NUM> to operate via the accumulator <NUM> and a non-return valve <NUM>, it is possible to accumulate a vacuum so that a faster response time for the valve may be provided when it is desired to open the valve.

The connection <NUM> between the connector <NUM> and the suction generator <NUM> may be controlled by the valve <NUM>, which may be arranged to selectively connect the trigger chamber/control chamber to the accumulator <NUM> or to ambient pressure.

As yet another option, the accumulator <NUM> may be arranged to provide a pressure higher than ambient pressure, to further speed up the opening of the valve <NUM>.

Claim 1:
A valve (<NUM>) having a predetermined low pressure side, comprising:
a main valve closure body (<NUM>), arranged on the low pressure side of the valve and moveable to open towards the low pressure side,
a control body (1247a, 1247b), fixedly connected to the main valve closure body (<NUM>), such that a position of the main valve closure body is fixed relative to a position of the control body,
a control chamber (Cc), partially defined by the control body (1247a, 1247b), whereby a volume of the control chamber (Cc) is variable in relation to the position of the control body (1247a, 1247b),
a control fluid connector (<NUM>) for controlling a pressure in the control chamber (Cc), and
a trigger valve (<NUM>), which is movable between an open state and a closed state and which, in its open state, connects the control chamber (Cc) to a pressure (Aa) which is sufficiently high to allow the main valve closure body to open,
characterized in that the trigger valve is a pressure balanced valve comprising
a trigger space (Ct1, Ct2, Ct3) that comprises a first trigger chamber (Ct1), a second trigger chamber (Ct2) and a third trigger chamber (Ct3),
a first trigger closure body (<NUM>) operable on a first trigger seat (St1) facing outwardly of the first trigger chamber (Ct1), and
a second trigger closure body (<NUM>), rigidly connected to the first trigger body (<NUM>) and operable on a second trigger seat (St2) facing inwardly of the second trigger chamber (Ct2), where the control fluid connector (<NUM>) is connected to the third trigger chamber (Ct3) and where, when the trigger valve in its closed state,
the first trigger chamber (Ct1) is open to the third trigger chamber (Ct3), such that vacuum applied through the control connection (<NUM>) is applied to the control chamber (Cc) through the first and third trigger chambers (Ct1, Ct3), and
the second trigger chamber (Ct2) is open to the third trigger chamber (Ct3), such that vacuum is applied to the control chamber (Cc) through the second and third trigger chambers (Ct2, Ct3).