SE544324C2 - A valve arrangement for an industrial dust extractor - Google Patents

Abstract

A valve arrangement (900) for generating a pulse of air (1100) to clean an air filter (125) of a pre-separator (120), the arrangement (900) comprising:a main valve closure body (950) arranged to seal a passage (951) between a high pressure (P2) side and a low pressure (P3) side of the valve arrangement (900),a control body (940), connected to the main valve closure body (950), such that a position of the main valve closure body (950) is determined by a position of the control body (940),a control chamber (930), partially defined by the control body (940), whereby a volume of the control chamber (930) is variable in relation to the position of the control body (940), anda control chamber valve (920) having an open state and a closed state for regulating a pressure (P1) in the control chamber,wherein the control chamber (930) is fluidly connected to the low pressure (P3) side via a connecting channel (935) configured with a connecting channel aperture (936),wherein the control chamber valve (920) is configured with an aperture larger than the connecting channel aperture (936) such that the control chamber valve (920) is arranged to overcome the connecting channel (935), and wherein the state of the control chamber valve (920) is determined by a trigger device (910, 980).Embodiments of the arrangement also comprises a resilient trigger membrane (980) arranged between the high pressure (P2) side and the low pressure (P3) side, wherein the state of the control chamber valve (920) is determined by the position of the resilient trigger membrane (980).

Description

TITLE A VALVE ARRANGEIVIENT FOR AN INDUSTRIAL DUST EXTRACTOR TECHNICAL FIELD The present disclosure relates to dust extraction devices for use withconstruction equipment. There are disclosed hatches for dumping dustaccumulated in a pre-separator such as a cyclone device into a dust container.There are also disclosed arrangements for cleaning pre-separator air filtersand other air filters.

BACKGROUND Dust and slurry are created by cutting, drilling, grinding and/or demolishingconcrete, brick, and other hard construction materials. The dust and slurry maybe collected by a dust extractor and removed from the construction site in acontrolled manner. Dust extractors collect the dust and slurry by generating avacuum by means of an impeller and motor arrangement, i.e., similar to avacuum cleaner for domestic use. Many industrial grade dust extractorscomprise a pre-separator or cyclone device followed by an essential filter such as a high-efficiency particulate air (HEPA) filter.

During operation, dust gradually accumulates inside the pre-separatorchamber and needs to be emptied regularly into a dust container such as adisposable bag or other type of dust container. One example of a disposabledust container is the Longopac® bagging system discussed, e.g., in US2018/0192838.

A hatch mechanism separates the pre-separator chamber from the dustcontainer. Several hatch mechanisms are known, such as hinged metalhatches, but such hatches have been known to damage and even puncturedust container bags and may not always be able to efficiently emptyaccumulated dust and slurry into the dust container. WO 2017/171596discusses a type of hatch mechanism based on an aperture with a grid or net in combination with a hose device made of a flexible material. This hatch mechanism is less likely to damage dust container bags.

Some forms of dust, such as fine concrete dust, tends to clot and lump whenaccumulated at the bottom of the pre-separator. lt may be difficult to efficientlyempty such accumulated dust from the pre-separator. The design proposed inWO 2017/171596 may not always provide optimal emptying performance.Thus, there is a need for improved pre-separator hatch mechanisms forindustrial grade dust extractors.

The pre-separator or cyclone normally comprises an air filter which graduallybecomes particle-laden, i.e., clogged, during operation. This filter thereforeneeds to be cleaned regularly. lt is known to clean the air filter in the pre-separator by means of a relief valve to generate a reverse thrust of air, or airpulse, as discussed in, e.g., WO 2017/171596, WO 2017/025305, andEP3619453. However, the design of a relief valve which generates this reversethrust of air is not straight forward. There is a need for improved valvearrangements for generating such pulses of air which allow efficient filter cleaning in a convenient manner.

SUMMARY lt is an object of the present disclosure to provide valve arrangements forindustrial grade dust extractors which alleviate at least some of the above- mentioned issues.

This object is obtained by a valve arrangement for generating a pulse of air toclean an air filter of a pre-separator. The arrangement comprises a main valveclosure body arranged to seal a passage between a high pressure side and alow pressure side of the valve arrangement, a control body connected to themain valve closure body, such that a position of the main valve closure bodyis determined by a position of the control body, a control chamber partiallydefined by the control body, whereby a volume of the control chamber isvariable in relation to the position of the control body, and a control chamber valve having an open state and a closed state for regulating a pressure in the control chamber. The control chamber is fluidly connected to the low pressureside via a connecting channel configured with a connecting channel apertureand the control chamber valve is configured with an aperture larger than theconnecting channel aperture such that the control chamber valve is arrangedto overcome the connecting channel when in the open state. The state of thecontrol chamber valve is determined by a trigger device.

Thus, a robust and simple mechanism is provided for generating a pulse of airto clean an air filter of a pre-separator. The arrangement does not requirecomplex three-way valves or the like, which is an advantage. The arrangementprovides a trigger mechanism able to generate an abrupt opening of the mainvalve closure body to generate a distinct air pulse.

According to some aspects, the trigger device comprises a resilient triggermembrane arranged between the high pressure side and the low pressure sidesuch that a position of the resilient trigger membrane is dependent on apressure difference between the high pressure side and the low pressure side,wherein the state of the control chamber valve is determined by the position ofthe resilient trigger membrane such that the control chamber valve is in theopen state when the pressure difference is above a threshold and in the closed state otherwise.

This mechanism provides an automatically triggered air pulse for cleaning anair filter, thus avoiding the need for an operator to manually trigger filtercleaning. The mechanism is mechanical in nature, voiding the need for complicated control units and sensor arrangements, which is an advantage.

According to aspects, a lever is arranged pivotable about an axis and arrangedto connect the resilient trigger membrane to the control chamber valve. Thislever provides leverage which can be tuned to the force requirements of theapplication at hand, which is an advantage. The lever also distances the triggermembrane from the control chamber, thereby simplifying functional layout ofthe design an providing a valve arrangement with reduced footprint, which isan advantage.

According to aspects, the valve arrangement further comprises a calibrationdevice configured to determine the threshold by biasing the lever to resistpivoting about the axis. This calibration device can be used in-field to adjustthe automatic triggering function of the valve arrangement.

According to aspects, the lever is operable by a manual control device to forcethe control chamber valve into the open state. Thus, the automatic triggering function can be overridden in a convenient manner.

According to aspects, the control chamber valve and the resilient triggermembrane are integrally formed. This further reduces footprint and provides acompact design, which is an advantage.

There are also disclosed herein pre-separators and dust extractors associatedwith the above-mentioned advantages.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined otherwiseherein. All references to "a/an/the element, apparatus, component, means,step, etc." are to be interpreted openly as referring to at least one instance ofthe element, apparatus, component, means, step, etc., unless explicitly statedotherwise. The steps of any method or process disclosed herein do not haveto be performed in the exact order disclosed, unless explicitly stated. Furtherfeatures of, and advantages with, the present invention will become apparentwhen studying the appended claims and the following description. The skilledperson realizes that different features of the present invention may becombined to create embodiments other than those described in the following,without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will now be described in more detail with reference tothe appended drawings, where Figures 1A-B show an example dust extractor; Figures 2A-C schematically illustrate a hatch mechanism; Figure 3 schematically illustrates a hatch mechanism in closed position;Figures 4A-C illustrate an example hatch mechanism in closed position;Figures 5A-C illustrate an example hatch mechanism in open position; Figure 6 illustrates an example dust container holder arrangement; Figure 7A-B shows a dust container holder attached to a hatch mechanism;Figure 8 schematically illustrates a dust container holder arrangement;Figures 9A-B illustrates an example dust extractor lid portion; Figures 10A-C show example valve arrangements for generating pulses of air;Figure 10D schematically illustrates a principle of a triggering membrane; and Figures 11A-C conceptually illustrate the generation of an air pulse; DETAILED DESCRIPTION The invention will now be described more fully hereinafter with reference to theaccompanying drawings, in which certain aspects of the invention are shown.This invention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments and aspects set forth herein;rather, these embodiments are provided by way of example so that thisdisclosure will be thorough and complete, and will fully convey the scope ofthe invention to those skilled in the art. Like numbers refer to like elementsthroughout the description. lt is to be understood that the present invention is not limited to theembodiments described herein and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

Figures 1A and 1B show an example dust extraction device 100. The dustextraction device can be connected via a hose to a dust generator (not shownin Figure 1), such as a core drill, a floor grinder, a concrete saw, or the like.The dust and slurry from the dust generator enters the dust extractor via an inlet 110. A pre-separator 120 is arranged after the inlet, i.e., downstream withrespect to the airflow direction into the inlet 110. The pre-separator maycomprise a cyclone with a pre-filter for separating out larger debris particlesfrom the particle-Iaden airflow entering the inlet 110. The larger debris particlesmay be collected via an outlet 130 of the pre-separator 120. A hatchmechanism 140 is arranged to close the outlet 130 during operation. Figure1A also shows a dust extractor lid 101 which forms an upper portion of the dustextractor 100. The lid 101 is not shown in Figure 1B.

The pre-separator 120 may also be referred to as a cyclone, a cyclone tank,or a filter tank. As noted above, the hatch mechanisms discussed herein areapplicable with most dust extractors for industrial use and need not bearranged to seal a pre-separator. Rather, the hatch mechanisms can be used to seal any filter tank structure.

The air flow continues from the pre-separator 120 via one or more conduits inthe lid 101 into one or more essential filters 150, here shown inside a filterholder 155. An essential filter is a filter designed to meet strict requirementson filtering function. Such an essential filter 150 may, e.g., be a High-Efficiency Particulate Air (HEPA) filter, but other air filters may also be used.

A blower arrangement 160 is arranged downstream from the pre-separator120 and from the one or more essential filters 150. The blower arrangementgenerates a suction force or vacuum which draws the particle-Iaden airflow inthrough the inlet 110, past the pre-separator 120, and through the one or moreessential filters 150. Herein, a vacuum or vacuum level indicates how far belowa reference pressure level, such as atmospheric pressure, the pressure in the airflow is.

The dust extractor 100 may also comprise a control unit 170 configured toperform various control actions, such as monitoring pressure levels at various places in the dust extractor 100 and controlling the blower arrangement 160.

The hatch mechanism 140 is an important part of the dust extractor 100. Thishatch is used when emptying the pre-separator chamber into a dust container which is arranged below the hatch (but not shown in Figures 1A-B). The dust container may, e.g., be a removable box structure or a plastic bag, such as theLongopac® bagging system mentioned above. lf the hatch mechanism is usedwith a non-rigid plastic bag dust container system, it is important that the dustbag is not sucked into the pre-separator chamber via the hatch. However, thisdoes not mean that the hatch needs to be air-tight during operation.

The present disclosure relates to hatch mechanisms which close to preventthe dust container from being sucked into the pre-separator during operation,while at the same time allowing for easy emptying of dust into the dustcontainer. The hatch mechanisms are designed so as to not damage a plasticbag dust container.

Figures 2A-C schematically illustrate a hatch mechanism according to thepresent disclosure. The hatch mechanisms 140 discussed herein are generallysuitable for use with pre-separators 120, such as the pre-separator exemplifiedin Figures 1A and 1B.

The mechanism comprises an aperture 210 having a perimeter 220 arrangedin a plane 230. lt is via this aperture that the accumulated dust and slurry isdumped into the dust container below the hatch mechanism. To empty the pre-separator chamber, the low operating pressure inside the chamber is firstincreased, e.g., by opening a conduit to outside atmosphere as during filtercleaning, or by turning off the blower arrangement 160. The plane 230 can bedefined freely to be some plane having the main emptying direction of thehatch as its normal. lt is appreciated that the perimeter need not be perfectly aligned with the plane along the entire circumference.

At least three elongated obturator elements 240 are pivotably attached 250along the perimeter 220 at respective hinge ends 241. Each obturator elementcomprises a distal end 242 arranged opposite to the hinge end along theextension direction of the obturator element 240. This means that eachobturator element is connected to the perimeter 220 in a way such that it canswing inwards with respect to the aperture.

Figure 3 shows an example hatch mechanism 140 in closed position where the pivoting motion 250 by the obturator elements 240 has been indicated.

Adjacent obturator elements 240 arranged along the perimeter 220 areconnected by foldable joining members 260 arranged to guide the distal ends242 to a common intersection point 270 distanced d from the plane 230,whereby the obturator elements 240 are arranged to fold about respectivehinge ends 241 to a position of mutual support to close the hatch mechanism140. Thus, the obturator elements swing inwards to a position of mutualsupport, forming an upside-down cone- or pyramid-like structure where thedistal ends meet at the pointy end. An obturator element 240 may, e.g., berealized by a rigid or semi-rigid batten structure, such as a metal bar structureor an elongated plastic structure.

When this structure is subject to a pressure gradient over the aperture, theobturator elements 240 and foldable joining members 260 will be suckedtowards the pre-separator chamber, i.e., in direction of the aperture 210. Thiswill cause the obturator elements 240 to pivot as illustrated in Figure 3 whichcloses the hatch, at least sufficiently in order for a dust container bag to notget sucked into the pre-separator chamber. When the low pressure in the pre-separator chamber is released, the obturator elements 240 will no longer beheld in closed position, but will swing radially outwards, thereby opening thehatch. According to some aspects the obturator elements 240 are configuredwith an increased weight in order to promote opening of the hatch bygravitational force.

This hatch mechanism is not rigid like other known hatch mechanism basedon metal lids and the like. Rather, the hatch can be integrally formed in aresilient material which moves and/or vibrates during operation, such as duringsmaller pressure differences over time in the pre-separator main chamber.This motion by the hatch mechanism prevents dust and slurry from formingmore solid lumps which are difficult to empty. Also, the hatch mechanism mayeven allow dust and slurry to penetrate the hatch mechanism despite apressure gradient over the aperture when the accumulated dust obtainssufficient weight to overcome the suction force which closes the hatch. Thismeans that the hatch mechanisms disclosed herein may automatically openas needed to dump dust and slurry into the dust container below the hatch.

This automatic opening may, e.g., take place when the air filter 125 is cleaned by a reverse thrust of air.

Figures 4A-C illustrate an example hatch mechanism in closed position.Figures 5A-C illustrate the same example hatch mechanism in open position. ln this example the aperture 210 has a circular shape and the commonintersection point 270 is located at the center of the aperture. However, othershapes are also possible. For instance, an elliptical aperture shape could beused, where the obturator members 240 are of different length in order to foldabout the respective hinge ends 241 to a position of mutual support to closethe hatch mechanism 140.

According to some other aspects, the aperture 210 has a polygonal shape withnumber of equal sized faces equal to the number of obturator elements 240.

The common intersection point 270 can be located anywhere in the aperture,e.g., offset to one side, as long as the common intersection point 270 isdistanced d from the plane 230. The obturator elements 240 are then matchedto meet at the common intersection point when pivoting about the hinge ends241. ln the example shown in Figures 4A-C and 5A-C, six obturator elements 240are arranged evenly spaced along the perimeter 220 of the aperture 210. Theobturator elements 240 are pivotably attached via a resilient portion at thehinge end 241 of each obturator element 240, i.e., a rubber or soft plastic partseparating the obturator member from the perimeter to allow pivoting by theobturator member. Each obturator element is configured with a distal end 242with a polygon shape matched to adjacent obturator elements. ln this case thepolygon shape has two opposing tangential sides 243 arranged at an acuteangle of about 60 degrees in order to interface with adjacent obturator elements, and two radial sides 244 as indicated in Figure 4C.

According to another example, the obturator elements 240 are pivotablyattached via a hinge at the hinge end 241 of each obturator element 240. This hinge may, e.g., be a piano hinge or the like.

The foldable joining members 260 are preferably but not necessarily made ofa flexible sheet material. As an alternative to using a flexible sheet material likerubber, hinges can also be used to allow folding. The important feature here isthat the folding members guide to obturator elements to the position of mutualsupport during pivoting about the respective hinge ends. ln the example shown in Figures 4A-C and 5A-C, the foldable joining members260 are arranged with a folding indication configured extending along a linefrom a point on the perimeter halfway between the adjacent obturator elementstowards a geometric center of the aperture 210. Preferably, the foldable joiningmembers 260 are integrally formed as a tubular element in a resilient material,such as rubber, i.e., a flexible structure resembling a hose or other resilientcylindrical structure, to which tubular element the obturator elements 240 areattached. The obturator elements 240 can also be molded into or otherwiseintegrally formed with the tubular structure. lt may as mentioned above beadvantageous to arrange the obturator elements with a relatively large weight,where the weight is configured in dependence of the power of the dustextractor, in order to promote opening of the hatch mechanism duringemptying of dust and slurry into the dust container.

With reference again to Figures 1A and 1 B, some dust extractors 100 comprisedust container holder arrangements 180. Figure 6 illustrates an example ofsuch a dust container holder arrangement 180. Some of the hatchmechanisms 140 disclosed herein are configured to hold a dust containerarrangement. According to such aspects, with reference to, e.g., Figure 4B and5B, the perimeter 220 of the hatch mechanism 140 comprises a rim portion410 with first 420 and second 430 flanges extending radially outwards from the rim portion with an axial separation a.

With reference also to Figure 6, the first flange 420 and the second flange 430are configured to mate with a flange portion 630 on the dust container holder180 which extends radially inwards Ri to mate with the first and second flangeson the hatch mechanism. 11 The dust container holder 180 comprises a tubular body 610 extendingbetween first 611 and second 612 end perimeters. The flange portion 630 isformed in a resilient material and extends radially inwards Ri in connection tothe first end perimeter 611. A groove portion 620 extends radially outwards Roin connection to the second end perimeter. This groove portion 620 isconfigured to hold a dust container 810, such as the Longopac® baggingsystem.

Figure 7A-B shows a dust container holder 180 attached to a hatch mechanism140 by these radial flanges.

Figure 8 schematically illustrates a dust container assembly 800 comprising adust container holder arrangement according to the present teaching fittedonto a hatch mechanism. Note how the dust container 810 is crimped 820 andfitted into the groove portion 620, with an end section 840 that is squeezedbetween the first flange 420 and the second flange 430 of the hatchmechanism 140, and the flange 630 of the dust container holder 180. The dustcontainer is sealed by a sealing member 830, such as a zip-tie, cable-tie, apiece of string, or the like.

The dust container holder 180 is arranged to be fitted onto the hatchmechanism 140 by pushing the first end perimeter 611 over the hatchmechanism, wherein the flange portion 630 is configured to hold the dustcontainer 810 in position between the flange portion and the hatch mechanism140. This way the dust container can be easily fitted onto the dust extractor.The dust container is held in position between the flanges, which voids theneed for additional fastening means to hold the dust container in position.

Figures 9A illustrates an example dust extractor lid portion 101. This lid portion101 comprises an example valve arrangement 900 for generating pulses of airto clean an air filter in the pre-separator 120. lt is appreciated that the principlesof the valve arrangements discussed herein are applicable in a wide variety ofapplications, and not limited to mounting in the exact manner illustrated by the drawings. 12 The valve arrangements 900 discussed herein are configured for automaticallygenerating an air pulse to clean the pre-separator air filter when needed, i.e.,when the air filter is starting to become too particle laden for efficient dustextraction operation.

Some of the valve arrangements are also possible to operate manually,overriding the automatic function. Towards this end, a manual control device910, such as a button or a knob, is arranged on the lid 101.

Figure 9B illustrates details of the valve arrangement 900 which will bediscussed in more detail below. Figures 10A-C show example valvearrangements 900 for generating a pulse of air to clean an air filter 125 of apre-separator 120. The arrangement 900 comprises a main valve closure body950 arranged to seal a passage 951 between a high pressure P2 side and alow pressure P3 side of the valve arrangement 900. The high pressure sidemay, e.g., be connected via fluid conduit 901 to atmospheric pressure, whilethe low pressure side may be associated with a machine operating pressure,i.e., be connected to a point in the dust extraction flow upstream from the airfilter 125.

The valve arrangement 900 also comprises a control body 940 connected tothe main valve closure body 950, such that a position of the main valve closurebody 950 is determined by a position of the control body 940. ln other words,if the control body 940 moves, so does the main valve closure body 950. Notethat this motion is longitudinal or normal with respect to a plane of the mainvalve closure body 950 in Figure 10A, but this exact configuration is not anecessary feature. The position of the main valve closure body 950 can bedetermined by the position of the control body 940 is many different ways, e.g., via a lever arrangement, via wire, or by some other form of mechanical linkage.

The control chamber 930 is partially defined by the control body 940. ln theexample of Figures 10A-B, the control chamber is a space which is sealed bya resilient membrane which is able to move up and down to restrict or expandthe volume of the control chamber. The volume of the control chamber 930 is therefore variable in relation to the position of the control body 940. Other ways 13 to implement this type of control chamber would, e.g., comprise a cylinder andpiston arrangement, or a balloon arrangement. lf pressure P1 inside the controlchamber 930 is smaller than pressure P2 outside the control chamber, thecontrol body 940 will move due to force F1 to restrict the volume in the controlchamber 930. This motion also pulls the main valve control body 950 intosealing position. Another force F2 acts on the main valve control body 950 dueto a pressure difference between the low pressure P3 side and the highpressure P2 side.

A control chamber valve 920 having an open state and a closed state forregulating the pressure P1 in the control chamber is furthermore comprised inthe valve arrangement 900. When this valve is opened to increase pressure inthe control chamber, e.g., from a machine operating pressure to atmosphericpressure, the main valve control body is shifted into a non-sealing position.The effective area of the control body 940 may be arranged larger than an effective area of the main valve control body 950.

This general type of control chamber mechanism for opening and closing amain valve closure body 950 has been proposed previously, see, e.g., WO2017/025305 and EP3619453 A1. lts basic mechanisms and principles ofoperation will therefore not be discussed in more detail herein, although anexample will be discussed in connection to Figures 11A-C below.

Differently from the known valve arrangements, this valve arrangement maybe automatically triggered when the air filter becomes particle laden and is inneed of cleaning, or when the operator blocks the inlet 110. Towards this end,the valve arrangement 900 optionally comprises a resilient trigger membrane980 arranged between the high pressure P2 side and the low pressure P3 sidesuch that a position of the resilient trigger membrane 980 is dependent on apressure difference between the high pressure P2 side and the low pressureP3 side. The state of the control chamber valve 920 in the valve arrangement900 is arranged to be determined by the position of the resilient triggermembrane 980 such that the control chamber valve 920 is in the open state 14 when the pressure difference is above a threshold and in the closed state otherwise.

Since the membrane is resilient, it will flex and be drawn towards the side ofthe membrane with Iowest pressure, as illustrated in Figure 10D. Thus, aconnecting member 981 attached to the membrane will move in dependence of the pressure difference on either side of the membrane 980.

The valve arrangement 900 illustrated in Figures 10A-C also differ from theknown valve arrangements in how the pressure P1 in the control chamber 930is regulated to trigger the air pulse for cleaning the air filter. The valvearrangement 900 comprises a connecting channel 935 which fluidly connectsthe control chamber 930 to the low pressure P3 side. The connecting channel935 is a relatively narrow conduit which extends from the low pressure P3 sideinto the control chamber 930 (the connecting channel aperture 936 opens upinto the control chamber 930 as can be inferred from, e.g., Figure 10A).

Thus, air is constantly drawn out from the control chamber 930 towards thelow pressure P3 side via the connecting channel 935 when the dust extractoris in use. A low pressure is thereby generated in the control chamber 930 aslong as the control chamber valve 920 is in the closed state. The controlchamber valve 920 is configured with an aperture that is larger than theaperture 936 of the connecting channel 935, which means that the controlchamber valve is arranged to overcome the connecting channel aperture 936when in the open state. ln this context, “to overcome” means that the pressureinside the control chamber increases if the control chamber valve 920 is opendespite that the connecting channel 935 constantly connects the controlchamber to the low pressure P3 side. lt is noted that the connecting channel935 is not closed when the air pulse is triggered, which means that no complexthree-way valve or the like is required as in WO 2017/025305.

For example, the diameter of the aperture of the control chamber valve 920may be on the order of 15mm for a circular aperture, which means that thearea is about 175 mm2. This large aperture easily overcomes an aperture of the connecting channel 936 which may be on the order of about 1.6 mm in diameter for a circular aperture corresponding to an area of about 2 mm2. lt is appreciated that the apertures of the control chamber valve 920 and theconnecting channel 936 need not be circular, or even regular in shape. lt is theaperture area which is important in order for the control chamber valve 920 tobe able to overcome the connecting channel 936. An aperture of the controlchamber valve 920 which is about two times larger in area may be sufficient,although a larger difference may be preferred, such as ten times larger ormore. The larger the difference in aperture is, the faster the response is to thetrigger. However, a too large control chamber valve aperture may result in structural difficulties.

When the control chamber valve 920 enters the open state the pressure in thecontrol chamber rapidly increases due to the open connection to atmosphericpressure, i.e., the pressure inside the control chamber quickly goes from amachine operating pressure to atmospheric pressure. The effect of theconnecting channel in reducing pressure is overcome, and the main valvecontrol body is therefore shifted into a non-sealing position whereby the airpulse is generated to clean the filter.

The mechanism may be automatically triggered using the trigger membrane980 when the air filter becomes particle laden and is in need of cleaning asdiscussed above, or it can be manually triggered by, e.g., the manual controldevice 910. The mechanism can also be triggered by an electrically actuatedcontrol device, such as a solenoid, arranged to force the control chamber valve920 into the open state in response to a wired or wireless control signal. Thus,the mechanism can be electrically triggered by the control unit 170, or evenremotely triggered via radio signal from a remote control device. lt is appreciated that the mechanism comprising the control chamber valve 920arranged with an aperture larger than an aperture of the connecting channelcan be used independently of whether the valve arrangement comprises theautomatic triggering device or not. l.e., the arrangement can also be used with the manual control device 910 as the only means for triggering the air pulse. 16 To summarize, with reference to Figures 10A-C, there is disclosed herein avalve arrangement 900 for generating a pulse of air 1100 to clean an air filter125 of a pre-separator 120. The arrangement 900 comprises a main valveclosure body 950 arranged to seal a passage 951 between a high pressure P2side and a low pressure P3 side of the valve arrangement 900, a control body940, connected to the main valve closure body 950, such that a position of themain valve closure body 950 is determined by a position of the control body940, a control chamber 930, partially defined by the control body 940, wherebya volume of the control chamber 930 is variable in relation to the position ofthe control body 940, and a control chamber valve 920 having an open stateand a closed state for regulating a pressure P1 in the control chamber. Thecontrol chamber 930 is fluidly connected to the low pressure P3 side via aconnecting channel 935 configured with a connecting channel aperture 936,and the control chamber valve 920 is configured with an aperture larger thanthe connecting channel aperture 936 such that the control chamber valve 920is arranged to overcome the connecting channel 935 when in the open state.The state of the control chamber valve 920 is determined by a trigger device910, 980.

Some optional details of the valve arrangement 900 are illustrated in 10C.Here, with reference also to Figure 10B, a lever 921 is arranged pivotableabout an axis 922 and arranged to connect the resilient trigger membrane 980to the control chamber valve 920. Thus, as the pressure difference P2-P3increases, the resilient trigger membrane 980 is drawn towards the low-pressure side (pressure P3, downwards in Figure 10C). This motion by theresilient trigger membrane 980 pulls the lever downwards via the connectingmember 981. The downward pulling force F4, when strong enough, translatesinto a pivoting motion by the lever 921, causing the control chamber valve 920to open abruptly.

An optional biasing member 925, here a leaf spring, is configured to resist thispivoting motion. This biasing member is part of an optional calibration device925, 990. Thus, according to some aspects, the valve arrangement 900 furthercomprises a calibration device 925, 990 configured to determine the threshold 17 by biasing the lever to resist pivoting about the axis 922. This calibration devicemay, e.g., be a resilient member like the leaf spring shown in Figures 10A and10C with a tuning screw 990 to determine the biasing force. A he|ica| spring orother resilient member can of course also be used for the same biasing effect.

The lever 921 is optionally arranged to be operable by a manual control device910 to force the control chamber valve 920 into the open state. This manualcontrol device 910 is exemplified by a push-button directly actuating the lever921 in Figure 10C. This manual control device then overrides the automatictriggering function to generate the pulse of air independently of the pressuredifference P2-P3.

According to other aspects, the control chamber valve 920 and the resilienttrigger membrane 980 are integrally formed. This means that the resilienttrigger membrane 980 directly pulls the control chamber valve 920 into theopen state as the pressure difference goes above the threshold, perhaps firstovercoming a biasing force exerted by a resilient member configured to biasthe control chamber valve 920 into the closed position.

With reference to Figure 10B, the valve arrangement 900 optionally comprisesa main valve biasing member 970 arranged to bias the main valve closurebody 950 into sealing the passage 951. This main valve biasing member canbe realized by a he|ica| spring as shown in Figure 10B.

Figures 11A-C conceptually illustrate the generation of an air pulse by thevalve arrangements disclosed herein. Figure 11A illustrates an operation statewhere the control chamber valve 920 is in closed position, and a low pressureprevails in the control chamber. This low pressure in the control chamber maybe obtained, e.g., by connecting the control chamber to the low-pressure sideof the dust extractor 100. The main valve closure body 950 is in sealingposition due to that the combination of force F1 generated by the control body940 and the optional biasing force F3 generated, e.g., by the resilient element970 overcomes the force F2 exerted on the main valve closure body 950 bythe pressure difference between the high pressure P2 (normally atmospheric pressure) and the pressure P3 (the vacuum generated by the blower 18 arrangement 160). Note that the effective area a1 of the control body 940 islarger than the effective area of the main valve closure body 950. This, for thesame pressure difference, when P1=P3, the force F1 will be larger comparedto force F2. ln Figure 11B, the control chamber valve 920 is opened to increase pressureP1 inside the control chamber 930, e.g., to atmospheric pressure P1 =P2. Theforce F1 therefore decreases such that the combination of F1 with F3 no longerovercomes the force F2. The main valve closure body 950 therefore abruptlyleaves the sealing position, whereby air forcefully enters the pre-separatorupstream from the air filter 125. This generates a pulse of air 1100 whichpushes particles away from the exterior filter wall, thereby cleaning the air filter125. ln Figure 11C, the pressure P3 has been increased such that F2 is reduced.The combination of F1 and F3 now overcomes F2 to once more place the mainvalve closure body 950 in sealing position. This process can be repeated untilthe air filter 125 is not particle laden anymore.

Claims (13)

1. A valve arrangement (900) for generating a pulse of air (1100) to cleanan air filter (125) of a pre-separator (120), the arrangement (900) comprising: a main valve closure body (950) arranged to seal a passage (951) between ahigh pressure (P2) side and a low pressure (P3) side of the valve arrangement(900), a control body (940), connected to the main valve closure body (950), suchthat a position of the main valve closure body (950) is determined by a positionof the control body (940), a control chamber (930), partially defined by the control body (940), wherebya volume of the control chamber (930) is variable in relation to the position ofthe control body (940), and a control chamber valve (920) having an open state and a closed state forregulating a pressure (P1) in the control chamber, characterized in that the control chamber (930) is fluidly connected to the low pressure (P3) side viaa connecting channel (935) configured with a connecting channel aperture(936), wherein the control chamber valve (920) is configured with an aperture largerthan the connecting channel aperture (936) such that the control chambervalve (920) is arranged to overcome the connecting channel (935) when in theopen state, and wherein the state of the control chamber valve (920) is determined by a triggerdevice (910, 980).

2. The valve arrangement (900) according to claim 1, wherein the triggerdevice comprises a manual control device (910) arranged to force the control chamber valve (920) into the open state.

3. The valve arrangement (900) according to claim 1 or 2, wherein thetrigger device comprises an electrically actuated control device arranged to force the control chamber valve (920) into the open state in response to a wired or wireless control signal.

4. The valve arrangement (900) according to any previous claim, whereinthe trigger device comprises a resilient trigger membrane (980) arrangedbetween the high pressure (P2) side and the low pressure (P3) side such thata position of the resilient trigger membrane (980) is dependent on a pressuredifference between the high pressure (P2) side and the low pressure (P3) side, wherein the state of the control chamber valve (920) is determined by theposition of the resilient trigger membrane (980) such that the control chambervalve (920) is in the open state when the pressure difference is above athreshold and in the closed state otherwise.

5. The valve arrangement (900) according to claim 4, wherein the controlchamber valve (920) and the resilient trigger membrane (980) are integrallyformed.

6. The valve arrangement (900) according to claim 4 or 5, wherein a lever(921) arranged pivotable about an axis (922) is arranged to connect theresilient trigger membrane (980) to the control chamber valve (920).

7. The valve arrangement (900) according to claim 6, further comprising acalibration device (925, 990) configured to determine the threshold by biasingthe lever to resist pivoting about the axis (922).

8. The valve arrangement (900) according to claim 6 or 7, wherein the lever(921) is operable by the manual control device (910) to force the control chamber valve (920) into the open state.

9. The valve arrangement (900) according to any previous claim,comprising a main valve biasing member (970) arranged to bias the main valveclosure body (950) into sealing the passage (951).

10. The valve arrangement (900) according to any previous claim, whereinthe low pressure (P3) side is associated with a pressure upstream from the airfilter (125) of the pre-separator (120), and wherein the high pressure side isassociated with atmospheric pressure. 21

11. The valve arrangement (900) according to any previous claim, whereinthe control chamber valve (920) is configured with an aperture area which is at least twice the aperture area of the connecting channel (936) aperture.

12. The valve arrangement (900) according to any previous claim, whereinthe control chamber valve (920) is configured with a circular aperture with adiameter between 10-20 mm and preferably about 15 mm, and wherein theconnecting channel (936) has a circular aperture with diameter between 1-3 mm, and preferably about 1.6 mm.

13. A valve arrangement (900) for generating a pulse of air (1100) to clean anair filter (125) of a pre-separator (120), the arrangement (900) comprising a main valve closure body (950) arranged to seal a passage (951) between ahigh pressure (P2) side and a low pressure (P3) side of the valve arrangement(900), a control body (940), connected to the main valve closure body (950), suchthat a position of the main valve closure body (950) is determined by a positionof the control body (940), a control chamber (930), partially defined by the control body (940), wherebya volume of the control chamber (930) is variable in relation to the position ofthe control body (940), a control chamber valve (920) having an open state and a closed state for regulating a pressure (P1) in the control chamber,characterized in that a resilient trigger membrane (980) is arranged between the high pressure (P2)side and the low pressure (P3) side such that a position of the resilient triggermembrane (980) is dependent on a pressure difference between the highpressure (P2) side and the low pressure (P3) side, wherein the state of the control chamber valve (920) is determined by theposition of the resilient trigger membrane (980) such that the control chambervalve (920) is in the open state when the pressure difference is above a threshold and in the closed state otherwise.