A dust extractor with improved dust handling function

Abstract

A dust extractor (100) comprising at least one cyclone tank (110), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140), and a control unit (150) arranged to control a solenoid arrangement configured to actuate a pressure release valve (220, 310, 320) of the dust extractor (100), where the pressure release valve (220) is arranged to connect an internal volume (V) of the cyclone tank (110) to an external volume (E) of the dust extractor (100), the solenoid arrangement comprising a solenoid device (340) and a remanence mitigation circuit (155) configured to generate a reverse current through a coil of the solenoid device (340) after actuation of the solenoid device (340) by a forward current through the coil.

Description

[0001] TITLE

[0002] A DUST EXTRACTOR WITH IMPROVED DUST HANDLING FUNCTION

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to dust extraction devices for use with dust generating construction equipment. There are disclosed functions for improved handling of dust accumulated in the dust extractor.

[0005] BACKGROUND

[0006] Dust and slurry are created by cutting, drilling, grinding and / or demolishing concrete, brick, and other hard construction materials at a construction site. The dust can be collected in an efficient manner by a heavy-duty dust extractor, accumulated in a dust container of the dust extractor, and removed from the construction site in a controlled manner. Dust extractors are heavy- duty vacuum devices which collect dust and slurry by generating an underpressure in a cyclone tank by means of a fan or impeller and motor arrangement. This allows the dust extractor to collect larger quantities of dust compared to domestic vacuum cleaners which normally lack a cyclone tank. Some dust extractors comprise a coarse pre-filter arranged inside the cyclone tank, followed by a finer filter downstream of the pre-filter, such as a high- efficiency particulate air (HEPA) filter. The fine filter in a heavy-duty dust extractor is normally referred to as an essential filter, e.g., in IEC 60335-2- 69:2021 (Ed. 6.0).

[0007] Commonly used dust containers comprise plastic bags and buckets, such as the Longopac plastic bag system, which must be emptied regularly. It is desired to provide more efficient methods for handling dust containers.

[0008] There is also a general desire to improve performance in heavy-duty dust extractors. SUMMARY

[0009] It is an objective of the present disclosure to provide improved dust extractors and methods for operating dust extractors, in particular regarding handling of dust accumulated in the dust extractor and management of dust containers in general. This object is at least in part obtained by a dust extractor according to claim 1 .

[0010] Aspects of the present disclosure relate to dust extractors comprising a control unit, a cyclone tank, and a blower system. The blower system is arranged downstream from the cyclone tank to generate an air flow through an inlet opening in the cyclone tank, via an internal volume of the cyclone tank to an outlet passage leading away from the cyclone tank towards the blower system. The dust extractor is arranged to support a dust container underneath the cyclone tank in use, for receiving dust accumulated in the cyclone tank. The dust container may, e.g., be a plastic bag, a bucket, or the like. The Longopac plastic bag system is a popular dust container that sees widespread use together with heavy-duty dust extractors. The dust extractor comprises a pressure release valve that is arranged to connect the internal volume of the cyclone tank to an external volume when in an open state, and also an air flow blocking valve configured to restrict air flow via the outlet passage when in a blocking state. The pressure release valve is arranged to abruptly release an under-pressure in the cyclone tank, whereby the pressure in the cyclone tank increases, hence its name. Upon activation of a bag swap mechanism of the dust extractor, the pressure release valve is set in the open state and the air flow blocking valve is set in the blocking state, until deactivation of the bag swap mechanism when the pressure release valve is moved away from the open state and the air flow blocking valve is moved away from the blocking state. This way the pressure inside the cyclone tank increases rapidly due to the inflow of gas via the pressure release valve and the cessation of suction via the outlet passage. The increase in pressure allows an operator to manage the dust that has been collected by the dust extractor. The operator may, e.g., conveniently remove a full dust bag from the dust extractor and configure a new empty bag. The external volume is normally an ambient environment comprising air at atmospheric pressure, but it may also be a pressure vessel comprising gas at a pressure above atmospheric pressure. Air or some other gas rushes into the cyclone tank from the ambient environment or from the pressure vessel upon manipulation of the pressure release valve.

[0011] The pressure release valve and the air flow blocking valve may be arranged as separate valve mechanisms. However, additional advantages are obtained if they are actuated by a joint valve actuation mechanism, such that both valves are operated more or less synchronously by the same valve control device. In this case the bag swap mechanism can be activated by manual manipulation of a single joint valve actuation mechanism in a convenient manner. An operator wishing to replace a full Longopac bag with a new empty bag simply manipulates the joint valve actuation mechanism to activate the bag swap mechanism. Once activated the pressure in the cyclone tank increases almost instantaneously, whereupon the new Longopac bag can be deployed in a convenient and efficient manner. The bag swap mechanism is deactivated once the empty dust container is in place. The pressure release valve and the air flow blocking valve may also share a common valve disc configured to engage a first valve seat and a second valve seat in reciprocating motion. The pressure release valve is in a closed state and the air flow blocking valve is in a non-blocking state when the valve disc engages the first valve seat. The pressure release valve is in the open state and the air flow blocking valve is in the blocking state when the valve disc engages the second valve seat.

[0012] According to some aspects, the control unit is configured to manipulate the state of the pressure release valve and the state of the air flow blocking valve by sending electronic control signals to at least one automatic valve actuator, such as a solenoid device, upon activation of the bag swap mechanism of the dust extractor. This way an automated bag swap mechanism is obtained, which further increases the convenience and efficiency of the dust management. The operator does not need to manually operate valves of the dust extractor to activate the bag swap mechanism. According to some aspects, the bag swap mechanism is arranged to be activated in response to user manipulation of a user interface of the dust extractor, such as a touchscreen, a button, or some other electronic control input device.

[0013] In case the system uses solenoid devices to operate one or more valves, the dust extractor preferably comprises a remanence mitigation circuit that is configured to generate a reverse current through a coil of the solenoid device after actuation of the solenoid device by a forward current through the coil. The remanence mitigation circuit improves the function of the solenoid device by reducing remaining pull force by the solenoid after deactivation of the solenoid, which improves the actuation of the valves controlled by the control unit.

[0014] According to some examples, the dust extractor also comprises a solenoid activation circuit configured to generate an initial forward pull current through a coil of the solenoid followed by a forward hold current through the coil, where the forward pull current is of larger magnitude compared to the forward hold current. The strong pull current causes the valve to change state in a reliable and speedy manner, while the weaker hold current conserves energy, which is an advantage. The weaker hold current also prevents the solenoid device coil from becoming overheated.

[0015] The control unit can also be arranged to automatically deactivate the bag swap mechanism after a predetermined time period. For instance, the control unit can be arranged to automatically deactivate the bag swap mechanism in case a temperature of the blower system fails to satisfy a temperature acceptance criterion, such as a threshold or a more advanced acceptance criterion, thereby preventing the blower system from overheating. It may also be undesired to leave the bag swap mechanism in the activated state indefinitely, where the dust extraction capability of the dust extractor is limited.

[0016] The control unit can also be arranged to automatically deactivate or reduce power of a drive motor of the blower system in case a temperature of the blower system fails to satisfy a temperature acceptance criterion, thus preventing overheating of the drive motor.

[0017] The control unit is optionally arranged to trigger generation of a notification signal such as a notification light prior to automatically deactivating the bag swap mechanism, this way an operator is informed about the upcoming deactivation of the bag swap mechanism and is not taken unawares.

[0018] According to some aspects, a drive motor of the blower system is arranged to generate a cooling air flow that is separate from the air flow through the air flow blocking valve. The cooling air flow is independent of the working air flow used by the dust extractor to suck dust and particulate matter in through the inlet opening. This is an advantage since the cooling air flow will not be obstructed by operations and events related to the dust extraction air flow. Rather, cooling of the electric machine or machines of the blower system will remain effective even if the air flow blocking valve is in the blocking state, which is an advantage.

[0019] The control unit may also be arranged to decrease a fan speed of the blower system in response to activation of the bag swap mechanism, and to restore fan speed in response to deactivation of the bag swap mechanism. The reduced fan speed may be a low speed, such as half of a normal operating speed, or one third of a normal operating speed. This way the fans are not operated at full force when the dust suction air flow is not needed, which is an advantage. The fans may experience an increase in operating temperature when the air flow blocking valves are in the blocking state, since there is less air flow that transports heat away from the fan arrangement. By reducing the fan speed this increase in temperature may be avoided, or at least mitigated, which is an advantage.

[0020] A one-way valve can be arranged in connection to the inlet opening of the cyclone tank. The one-way valve is arranged to allow passage of the air flow into the cyclone tank and to resist air flow out from the cyclone tank via the inlet opening. The one-way valve prevents dust from escaping out from the cyclone tank through the inlet opening, which is an advantage. The one-way valve also allows the dust extractor to be used in a system with other dust extractors connected to the same suction hose. The one-way valve optionally comprises a flap valve with a flap arranged to engage a valve seat in sealing position to resist air flow out from the cyclone tank via the inlet opening. The one-way valve is preferably biased towards a sealing position of the valve where air flow out from the cyclone tank via the inlet opening is prevented. The one-way valve is particularly advantageous during activation of the pressure release valve discussed above. When the pressure release valve is actuated the pressure inside the cyclone tank rises abruptly, which may push some dust out through the inlet opening. This is highly undesired since the dust collected in the cyclone tank may be harmful to persons in vicinity of the dust extractor. The one-way valve mitigates this effect, and prevents dust from escaping out through the inlet opening as the pressure release valve is actuated.

[0021] The objective is also at least in part obtained by a cyclone tank bottom closure valve arrangement for a dust extractor having a cyclone tank. The closure valve arrangement comprises a fixed part arranged to be attached to the cyclone tank, and a moving part arranged floating in relation to the fixed part. The moving part comprises an outlet valve arranged to allow air and dust to pass through the closure valve arrangement in direction away from the fixed part, and to resist a flow of air through the closure valve arrangement in direction towards the fixed part in use. The fact that the closure valve arrangement moves relative to the cyclone tank means that the dust inside the cyclone tank is unsettled in use, e.g., as the prefilter is cleaned by reverse thrusts of air and as the pressure inside the cyclone tank is released. This reduces the risk that the dust forms a hard cake which can be difficult to remove from the cyclone tank. The motion of the moving part in relation to the fixed part is preferably restricted in the direction away from the fixed part. The motion of the moving part in relation to the fixed part can also be restricted in use to a range in a vertical direction which is at least 0,5cm, and preferably larger than 1 ,0cm.

[0022] The moving part may also comprise an integrated dust container holder arranged to support a dust container. This means that the dust container also moves relative to the cyclone tank in use, which is an advantage due to that the dust in the dust container may also be unsettled due to the movement of the moving part. The integration of dust container holder and closure valve arrangement also forms a spatially efficient design. The dust container holder can for instance be arranged to support a replaceable dust bag such as a Longopac plastic bag system, or a bucket.

[0023] The outlet valve can, e.g., be a duckbill valve, a flap valve, or a hatch arranged to allow passage of the air flow into the cyclone tank and to resist air flow out from the cyclone tank via the inlet opening. The designs proposed herein have been found to be particularly efficient when used together with a duckbill valve, which comprises an inherently movable structure. The outlet valve may also comprise a combination of a grate which covers the bottom aperture of the cyclone tank and a soft bag dust container, such as a plastic bag, configured to be sucked up against the grate in use.

[0024] According to some aspects, the moving part is biased in a direction away from the fixed part by a resilient member such as a spring. This biasing force enhances the jerk as the moving part encounters the stop at the end of the displacement range.

[0025] There are also disclosed herein control units, methods and systems associated with the above-mentioned advantages.

[0026] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will now be described in more detail with reference to the appended drawings, where

[0028] Figures 1 A-C show an example dust extractor;

[0029] Figure 2A schematically illustrates a cyclone tank with valves;

[0030] Figure 2B shows an example dust extractor with a cyclone tank and valves;

[0031] Figure 3 shows a cross-section view of part of an example cyclone tank;

[0032] Figures 4A-B show a valve arrangement in connection to a cyclone tank;

[0033] Figures 5A-B illustrate an example remanence mitigation circuit;

[0034] Figures 6A-B schematically illustrate an example one-way valve;

[0035] Figure 7 shows a dust extractor system;

[0036] Figure 8 is a flow chart illustrating methods;

[0037] Figure 9 shows an example control unit; and

[0038] Figures 10-12 illustrate a closure valve arrangement for a cyclone tank.

[0039] DETAILED DESCRIPTION

[0040] The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0041] It is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. Figures 1A-C show an example dust extractor 100. The dust extractor can be connected via a hose to a dust generator (not shown in Figures 1A-C), such as a core drill, a floor grinder, a concrete saw, or the like. The hose is secured to the dust extractor by means of an optional locking mechanism. The dust and slurry from the dust generator enters the dust extractor via an inlet 160 which opens up into a cyclone tank 1 10 configured to separate out larger debris and particles from the particle-laden airflow that enters the inlet 160. The material accumulated in the cyclone tank 110 can be emptied into a dust container 1 15, such as a plastic bag or a bucket, located underneath the cyclone tank 1 10.

[0042] Figure 2B illustrates another dust extractor 100 where at least some of the techniques discussed herein are applicable.

[0043] The Longopac plastic bag system is a well-known dust container option suitable for heavy-duty dust extractors of the kind exemplified in Figures 1 A-C and Figure 2B. The Longopac plastic bag system essentially comprises a long plastic tube which is folded into an annular form. A part of the plastic tube is pulled out and sealed at one end, whereby an amount of dust can be held in the pulled out part. The pulled out part is then sealed at its upper end and cut from the rest of the tube, whereby a new part can be pulled out.

[0044] The dust extractor 100 in Figures 1 A-C comprises a frame structure 180, 181 , 182, 185 and is supported on wheels 195, 196, where at least some of the wheels are braked by a brake mechanism 190.

[0045] The frame structure 180, 181 , 182, 185 is a rigid structure made of, e.g., rigid tubular members that extend around the dust extractor to form a cage around the dust extractor 100, thereby protecting the dust extractor from impact at the work site. A rear part 180 of the frame structure extends vertically (Vd) along the dust extractor to form a rail which the dust extractor can slide on, e.g., when the dust extractor 100 is loaded or unloaded to / from a trailer or other elevated platform. The rear part 180 forming the rail constitutes the extreme distal portion of the dust extractor 100 along the side of the rail, thereby allowing the dust extractor 100 to slide on the rail over, e.g., a ledge. An operator can then pull on the upper part 181 of the rear part 180 of the frame structure which form a handle, while letting the rear part 180 of the frame structure slide on the edge of the elevated platform.

[0046] In other words, at least part of the rear side of the dust extractor is defined by the rear part 180 of the frame structure. The rear part 180 of the frame structure is straight along a section, forming a rail upon which the dust extractor may slide, as illustrated in Figure 1 C.

[0047] A side part 185 of the frame structure extends horizontally along both sides of the dust extractor at a height of about 0,6-1 ,0m, and at least less than 1 ,5m. Note that only one side of the dust extractor is shown in Figure 1A. This relatively low side part 185 of the frame structure allows an operator to lift the dust extractor 100 from the ground in a convenient manner. Two operators can grip the side parts 185 on both sides in order to jointly lift the dust extractor from the ground.

[0048] A front part 182 of the frame structure extends across the dust extractor front, as shows in Figure 1A. The front part of the frame structure protects the dust extractor, e.g., in case it tips over. The front part 182 of the frame structure also protects the inlet opening 160, which is an advantage.

[0049] A wheel brake 190 is arranged in connection to the rear wheels 195 of the dust extractor 100. This wheel brake 190 prevents the rear wheels from moving when in its locked position, thereby immobilizing the dust extractor 100. According to a preferred embodiment, the wheel brake mechanism implements an auto-latch function, whereby the wheel brake engages the wheel in locking position in response to a vertical impact force acting on the dust extractor 100. This auto-latch function of the wheel brake 190 is particularly useful when the dust extractor is lowered from an elevated platform such as a loading bay or a trailer. The operator can then use the rear part 180 of the frame structure to slide the dust extractor along the edge of the elevated platform. Once the rear wheels 190 hit the ground surface, an impact force is generated which triggers the auto-latch function of the wheel brake 190, thereby automatically immobilizing the dust extractor on the ground surface below the elevated platform such that the operator can climb down from the elevated platform and continue to relocate the dust extractor 100 in a safe manner. The auto-latch function is preferably triggered by gravity. Thus, as the dust extractor hits the ground, the inertia of a wheel brake components causes the brake to automatically engage. The operator can then disengage the wheel brake when he or she has climbed down from the elevated platform.

[0050] An auto-latching brake of the type discussed herein can be implemented by adding a weight on a lever connected to the brake device, where the weight is calibrated to the expected impact force. The downwards directed impulse force when the dust extractor rear wheels hit the ground will urge this weight downwards, manipulating the lever, thereby engaging the wheel brakes.

[0051] A prefilter 120 is arranged in the cyclone tank 1 10 after the inlet 160, i.e., downstream with respect to the airflow direction. The example prefilter 120 in Figure 1 B is a split filter, i.e., a pre-filter divided into two filter sections. Each filter section has a respective suction valve 125 which draws air from the cyclone tank 1 10, through the filter media, and onwards to the blower system 140 of the dust extractor 100. This type of split filter arrangement was described in detail in Swedish application no. SE2250866-7 and will therefore not be discussed in more detail herein. Figure 2B shows an example without split filter, i.e., where the prefilter 120 comprises a single filter compartment.

[0052] The dust extractor 100 comprises a lid 101 which is closed in Figure 1A and open in Figure 1 B and in Figure 2B to expose the pre-filter 120 located inside the cyclone tank 1 10. The lid 101 in Figures 1A-C comprises a suction valve arrangement that was described in detail in SE2250866-7. The air flow in through the inlet 160 passes through the cyclone tank 1 10, through the prefilter 120, and onwards through air conduits formed in the lid towards the blower system 140. There are two air flows through the lid in Figures 1A-C. Each such air flow passes a respective essential filter 130 located in the volume behind the cyclone tank 1 10. The air flows through the two essential filters then enter into the blower system 140 which will be discussed in more detail below. One or more finer air filters 130 may be arranged downstream from the prefilter 120. Such an air filter 130 may, e.g., be a High-Efficiency Particulate Air (HEPA) filter, but other air filters may also be used. HEPA, also known as high- efficiency particulate absorbing and high-efficiency particulate arrestance, is an efficiency standard of air filters. Filters meeting the HEPA standard must satisfy certain levels of efficiency. It is noted that the techniques disclosed herein can be applied to dust extractors with any number of air filters, including dust extractors comprising combinations of different air filters.

[0053] Generally, downstream refers to a relative location along the air flow, while upstream is a relative location in direction against the air flow. Thus, the blower system 140 is located downstream from the inlet 160, while the inlet 160 is located upstream from, e.g., the cyclone tank 1 10.

[0054] The dust extractor 100 also comprises a control unit 150, schematically shown in Figures 1A-C. The control unit 150 is configured to control various operations of the dust extractor such as activating the motor of the blower system 140 to drive the fan of the blower system 140. The control unit 150 may also control the state of valves in the dust extractor, e.g., by activating currents in solenoid coils or by controlling other types of actuators such as servos. An example realization of this control unit will be discussed in more detail below in connection to Figure 9.

[0055] An optional user interface 105 allows an operator to activate various functions on the dust extractor 100, configure different operating parameters of the dust extractor, and receive notification messages and other types of information about the current status of the dust extractor.

[0056] According to some aspects, the dust extractor 100 comprises a status indicator light 170 arranged to emit a plurality of different and selectable colors of light. This means that the light source is configured to emit light in more than one color, such as red, green, and orange. The selected type of light to be emitted is determined by a control signal from the control unit 150. The control unit 150 is configured to activate the status light in a first color, such as a green or white color, in case the blower system 140 is activated. The control unit 150 is also configured to activate the status light in a second color, such as an orange color, in case a magnitude of the air flow does not satisfy an acceptance criterion. This way an operator can verify visually that the dust extractor is active, and that the dust extraction capability of the dust extractor is sufficient for the work task. It is an advantage that the same light source is used to indicate that the dust extractor is active and also to indicate that air flow is sufficient. It is particularly advantageous to combine the status light 170 with the brushless motor blower systems discussed herein, since these drive units are relatively quiet when active. It may be difficult for an operator to hear if the dust extractor 100 is active at a work site since it often does not make enough noise to be heard over the other sounds at the work site. The status light activated in the first color, such as a green or white color, ensures that personnel at the work site knows that the dust extractor is actively extracting dust, as opposed to being turned off or otherwise inactivated. There is preferably one status light on each side of the dust extractor 100, to ensure visibility from all sides. Note also that the status light 170 protrudes slightly from the dust extractor body, to ensure that it can be seen also from the front and rear of the dust extractor 100. A flow sensor and / or a pressure sensor can be used to detect when insufficient air flow is being generated. The control unit 150 controls the status indicator light 170 to emit light of the second color in case insufficient air flow is detected.

[0057] According to some aspects, the control unit 150 is configured to activate the status light in a third color, such as a red color, in case the control unit has detected malfunction in the dust extractor 100. A malfunction condition may, e.g., be a loss of power, insufficient electrical power in terms of voltage and / or current, overheating of the blower drive system, and so on.

[0058] The present disclosure relates to dust extractors 100 comprising a control unit 150, a cyclone tank 1 10 and a blower system 140, where the blower system 140 is arranged downstream from the cyclone tank 1 10 to generate an air flow A through an inlet opening 160 in the cyclone tank 1 10 via an internal volume V of the cyclone tank 1 10 to an outlet passage 210 leading away from the cyclone tank 1 10 towards the blower system 140. To operate with satisfactory performance, it is desired to generate an air flow through the dust extractor system of at least 500 m3 / h, and preferable at least 700 m3 / h.

[0059] The dust extractor 100 is arranged to support a dust container 1 15 underneath the cyclone tank 1 10 in use, for receiving dust accumulated in the cyclone tank 110. The example dust container 1 15 is a plastic bag. However, buckets and other types of bags can also be used. Dust and debris accumulates inside the cyclone tank during operation. To empty the dust into the dust container 1 15, pressure is released in the cyclone tank 1 10, and a hatch or other cyclone tank closing mechanism then opens up to allow the accumulated dust to fall down into the dust container.

[0060] With reference to Figure 2, the dust extractor 100 comprises a pressure release valve 220 which is arranged to connect the internal volume V of the cyclone tank 110 to an external volume E when in an open state. Example pressure release valves 310, 320 will also be discussed in more detail below in connection to Figures 3A-B. The external volume E comprises gas, such as air or some other gas, at a higher pressure compared to the pressure inside the cyclone tank during operation. Thus, when this connection is open the gas rushes into the cyclone tank 1 10, thereby increasing the pressure in the cyclone tank. It is known to use this type of valve to generate pulses of air to clean the pre-filter 120, as described in, e.g., SE2250866-7.

[0061] The external volume E is normally an ambient environment comprising air at atmospheric pressure. I.e., the pressure release valve 220 opens up a passage between the internal volume V of the cyclone tank 1 10 and atmospheric pressure when in the open state. However, the external volume E can also be a pressure vessel comprising gas at a pressure above atmospheric pressure. The pressure release valve then opens up a passage between the internal volume V and the pressure vessel, which allows gas from the pressure vessel to rush into the cyclone tank, thereby rapidly increasing the pressure inside the cyclone tank 1 10. It is appreciated that the pressure release valve 220 is a valve that releases an under-pressure in the internal volume V of the cyclone tank 1 10, i.e., a valve that increases the pressure inside the cyclone tank 1 10 when operated. The pressure release valve may also be referred to as a dump valve since it normally causes dust in the cyclone tank to be dumped into the dust container when actuated.

[0062] The dust extractor 100 also comprises an air flow blocking valve 230, 310, 330 configured to restrict air flow via the outlet passage 210 when in a blocking state. When the air flow blocking valve 230, 310, 330 is closed, the blower system 140 no longer draws air out from the cyclone tank internal volume, thereby promoting the increase in pressure inside the tank. The air flow blocking valve 230, 310, 330 can be arranged downstream from the dirty side of the prefilter 120. The suction valves 125 are examples of the air flow blocking valve. However, the air flow blocking valve can be arranged anywhere along the air flow from the part of the cyclone tank where dust accumulates to the blower system, i.e., downstream from the cyclone tank, or even downstream from the essential filter or filters 130.

[0063] Figure 2B shows an example dust extractor with a less advanced implementation of the pressure release valve 220 and the air flow blocking valve 230. The dust extractor in Figure 2B comprises a prefilter 120 with a single compartment, i.e., the prefilter 120 in Figure 2B is not a split filter. The pressure release valve 220 opens up a passage to atmospheric pressure, thereby increasing the pressure inside the cyclone tank 1 10. The air flow blocking valve 230 is a valve arranged in the outlet passage 210 from the cyclone tank 1 10 towards the blower system 140, not shown in detail in Figure 2B. Both valves 220, 230 may be manually operated by levers or buttons, or automatically operated by the control unit 150 using actuators, such as solenoids.

[0064] A sensor may, generally, be arranged in connection to the air flow blocking valve 230 to sense whether it is in the blocking state or not, and trigger transmission of a signal indicative of the air flow blocking valve state to the control unit 150. The control unit may also obtain information about the state of the air flow blocking valve 230 in case it controls the state of the air flow blocking valve 230 via an actuator. The control unit 150 may be configured to reduce a power or a motor speed of the drive motor of the blower system in case the air flow blocking valve 230 is in the blocking state, and thus also a fan speed of the blower system 140. This prevents the drive motor and the fan of the blower system 140 from overheating, which is an advantage. This feature is not inextricably linked to any other features described herein but can be used with advantage on its own.

[0065] The dust extractor 100 implements a special bag swap mechanism which allows an operator to more efficiently replace and / or empty a dust container 115. Upon activation of this bag swap mechanism of the dust extractor 100, the pressure release valve 220, 310, 320 is set in the open state and the air flow blocking valve 230, 310, 330 is set in the blocking state, until deactivation of the bag swap mechanism when the pressure release valve 220, 310, 320 is moved away from the open state and the air flow blocking valve 230, 310, 330 is moved away from the blocking state. In other words, when the bag swap mechanism is activated, the pressure release valve is opened for an extended duration of time to let gas from the external volume into the cyclone tank and remains in the open state. The air flow blocking valve is also closed for an extended period of time when the bag swap mechanism is activated, which means that the suction of air from the cyclone tank ceases. It is appreciated that the pressure release valve and the air flow blocking valve are actuated with time overlap, such that the pressure release valve is open at the same time as the air flow blocking valve is closed. As a result, the pressure inside the cyclone tank 1 10 increases fast and remains above normal cyclone tank operating pressure until the bag swap mechanism is deactivated again. When the bag swap mechanism is activated, the pressure release valve and the air flow blocking valve changes state and remains in this state until the bag swap mechanism is deactivated.

[0066] Activation of the bag swap mechanism allows an operator to empty the dust container 1 15 underneath the cyclone tank 1 10, e.g., by manipulating a Longopac system to deploy a new plastic bag section. The pressure release valve may remain open and the air flow blocking valve remain closed for more than 10 seconds following activation of the bag swap mechanism, or even longer. In other words, the pressure release valve is open while the air flow blocking valve is closed with a time overlap of at least 10 seconds. Thus, it is appreciated that the bag swap valve actuation differs from a normal filter cleaning air pulse valve actuation, in that the bag swap mechanism involves a much longer time period of increased cyclone tank pressure compared to normal pulse cleaning cyclone tank pressure increases. The bag swap valve actuation also differs from a dust dumping operation for the same reasons, i.e., the dust dumping sequence does not involve leaving the cyclone tank at atmospheric pressure for an extended period of time. In other words, an important difference between the bag swap mechanisms discussed herein and a filter cleaning operation involving generation of a short burst of air in reverse through the prefilter is that the bag swap mechanism involves actuation of the valves over a much longer time span, such as more than ten seconds or so. Thus, the bag swap mechanism is not intended to generate a burst of air followed by continued dust extraction, but a more permanent or long-time increase in cyclone tank pressure to facilitate dust container management.

[0067] The pressure release valve 220, 310, 320 and the air flow blocking valve 230, 310, 330 are optionally actuated by a joint valve actuation mechanism, such as a lever, a pushbutton, or some other mechanical device. The bag swap mechanism can then be activated by manual manipulation of the joint valve actuation mechanism, whereupon the bag swap mechanism will stay in the activated state until the operator manually deactivates the bag swap mechanism by manipulating the joint valve actuation mechanism.

[0068] According to another example, the bag swap mechanism is arranged to be activated in response to user manipulation of a user interface 105 of the dust extractor 100. The operator can operate the user interface 105 of the dust extractor 100 to activate the bag swap mechanism, whereupon the control unit 150 generates the necessary control signals to control valves etc. to activate the bag swap mechanism and to keep the bag swap mechanism active until it is deactivated. The control unit 150 is optionally arranged to automatically deactivate the bag swap mechanism after a predetermined time period, e.g., in case no deactivation signal is obtained. The predetermined time period may be about 10-30 seconds.

[0069] The control unit 150 is, according to an example, arranged to automatically deactivate the bag swap mechanism in case a temperature of the blower system 140, such as a motor temperature or a fan temperature fails to satisfy a temperature acceptance criterion. The motor temperature and the fan temperature can be determined by temperature sensors arranged in connection to the motor of the blower system and / or in connection to the fan of the blower system.

[0070] The blockage of the suction air conduits on the dust extractor may lead to an increase in rotation speed of the blower system fans and drive motors, which may cause a rise in operating temperature of one or more blower system components. The blockage of the suction air conduits on the dust extractor primarily leads to an increase in temperature of the fans, which rotate fast without much air flow to transport heat away from the blower system when the air flow blocking valve 230, 310, 330 restricts air flow. By deactivating the bag swap function in response to high temperature, damage to the blower system can be avoided.

[0071] According to some aspects, the control unit 150 is arranged to decrease a fan speed of the blower system 140 in response to activation of the bag swap mechanism, and to restore fan speed in response to deactivation of the bag swap mechanism. This saves energy, and also keeps the blower system 140 from overheating as a consequence of the disruption of the suction air flow through the suction valves 125.

[0072] According to some aspects, the fan motor arrangement of the blower system 140 comprises a separate cooling air flow which is generated by a fan on the drive motor independently of the working air flow that is used for dust extraction. The cooling air flow of the blower system drive motor or motors is not restricted during activation of the bag swap mechanism, and in fact often increases in magnitude when the suction valves 125 are blocked, due to the increased motor drive axle speed that results from restricting the air flow through the suction valves 125.

[0073] The control unit 150 can furthermore be arranged to trigger generation of a notification signal such as emission of a notification light signal by the status indicator light 170 prior to automatically deactivating the bag swap mechanism. This way an operator receives notification about an imminent deactivation of the bag swap mechanism and is not taken unawares when the bag swap mechanism is automatically deactivated.

[0074] Figure 3 shows a cross-section view of the dust extractor 100, seen from the front side of the dust extractor 100. The two separate suction valves 125 are configured in respective parts of the pre-filter to clean the filter parts, and to realize the bag swap mechanism of the dust extractor 100. The spatially efficient configuration of the valves and the suction conduits integrated in the lid 101 of the dust extractor 100 are particularly noted.

[0075] With reference also to Figures 4A-B, each of the suction valves 125 comprises a main valve closure body 310 arranged to move between a first position and a second position (up and down in Figure 3), where, in the first position, the main valve closure body 310 is arranged to seal a passage between the external volume E and the internal volume V (up), and where, in the second position, the main valve closure body 310 is arranged to seal a passage between the internal volume V and the outlet passage 210 towards the blower system 140 (down). In this example the first position is associated with a seat 320 against which the main valve closure body 310 seals the passage between the external volume E and the internal volume V, while the second position is associated with a seat 330 against which the main valve closure body 310 seals the passage towards the blower system 140. Note how the suction conduits are arranged at least partly inside the pre-filter interior.

[0076] Upon activation of the bag swap mechanism of the dust extractor 100, both suction valves 125 are placed in their second position (down) for an extended period of time during which an operator can replace or empty the dust container 1 15. The pressure release valve is set in the open state and the air flow blocking valve is set in the blocking state. The suction valves 125 will remain in this state until deactivation of the bag swap mechanism whereupon the valves are moved into their first positions where the pressure in the internal volume V of the cyclone tank drops down to a low operating level.

[0077] In other words, according to some aspects, the pressure release valve 220 and the air flow blocking valve 230 share a common valve disc 310 configured to engage a first valve seat 320 and a second valve seat 330 in reciprocating motion. The pressure release valve 220 is in a closed state and the air flow blocking valve 230 is in a non-blocking state when the valve disc 310 engages the first valve seat 320. The pressure release valve 220 is in the open state and the air flow blocking valve 230 is in the blocking state when the valve disc 310 engages the second valve seat 330.

[0078] The control unit 150 is, according to some aspects, configured to manipulate the state of the pressure release valve 220 and the state of the air flow blocking valve 230 by sending electronic control signals to at least one automatic valve actuator upon activation of the bag swap mechanism of the dust extractor 100. The at least one automatic valve actuator may for instance comprise a solenoid device 340, as illustrated in Figures 4A-B. Solenoid devices are well known and will therefore not be discussed in more detail herein. A solenoid device may also be referred to as an electromagnet, or an electromagnetic actuator.

[0079] The suction valve arrangement 125 in Figures 4A-B comprises a control body 360, connected to the main valve closure body 310, such that a position of the main valve closure body 310 is determined by a position of the control body 360. In other words, if the control body 360 moves, so does the main valve closure body 310. Note that this motion is vertical in the normal operating position, or normal with respect to a plane of the main valve closure body 310, but this exact configuration is not strictly necessary for the arrangement to function. The position of the main valve closure body 310 can be determined by the position of the control body 360 is many different ways, e.g., via a lever arrangement, via wire, or by some other form of mechanical linkage. An electric or electromechanical control actuator can also be used to control the position of the control body 360, such as a solenoid or electromagnet 340.

[0080] The mechanism in Figures 4A-B uses differential air pressure to actuate the valve mechanism. In the example, a control chamber 361 is partially defined by the control body 360, and a volume of the control chamber 361 is variable in relation to the position of the control body 360. There is also a control chamber valve 362 having an open state and a closed state for regulating a pressure P1 in the control chamber. Thus, by a change of pressure in the control chamber, the control body can be made to move, which will cause a corresponding motion of the main valve closure body 310. The state of the control chamber valve 362 is determined by a trigger device which can be a solenoid device or other electronic actuator 340, or a button 350 for manual manipulation of the state of the suction valve 125.

[0081] In the example of Figure 3 and Figures 4A-B, the control chamber 361 is a space which is sealed by a resilient membrane which is able to move up and down to restrict or expand the volume of the control chamber. The volume of the control chamber 361 is therefore variable in relation to the position of the control body 360. Other ways to implement this type of control chamber would, e.g., comprise a cylinder and piston arrangement, or a balloon arrangement.

[0082] If the pressure P1 inside the control chamber 361 is smaller than the pressure outside the control chamber 361 , the control body 360 will move to restrict the volume in the control chamber 361. This motion also pulls the main valve control body 310 towards the valve seat 320, since a smaller counter-force acts on the main valve control body 310 due to the pressure difference.

[0083] When the control chamber valve 362 is opened to increase pressure in the control chamber 361 , e.g., from a machine operating pressure to atmospheric pressure, the main valve control body is shifted into the non-sealing position, and now instead seals the suction conduit towards the blower system 140, at least in part due to being sucked against the vale seat 330. The effective area of the control body 360 is in this example larger than an effective area of the main valve control body 310. A problem which may arise when using solenoid devices, such as the solenoids 340 that control the suction valves 125, is that the solenoid retains some magnetization after the current through its coil has ceased. This effect is known as magnetic remanence. The remanence causes the solenoid to retain undesired pull force. To mitigate this remanence, the dust extractor 100 may comprise an optional remanence mitigation circuit 155 configured to generate a reverse current through a coil of the solenoid device 340 after actuation of the solenoid device 340 by a forward current through the coil. It is appreciated that this remanence mitigation circuit 155 is not inextricably linked to any of the other features of the dust extractors discussed herein. Thus, the remanence mitigation circuit 155 can be applied to control solenoid devices in other types of equipment, in particular in dust extractors that lack the bag swap mechanisms discussed herein.

[0084] Figure 5A shows an example solenoid system that comprises a remanence mitigation circuit 155 suitable for use with heavy-duty dust extractors. The solenoid coil L1 is powered by a power source V1 , and has a free-wheeling diode arrangement D1 , D2. The capacitance C1 complements the power source V1 in providing current though the solenoid coil upon solenoid actuation. Breaker U1 is used to actuate the solenoid device. When the solenoid device is released and current stops flowing through the coil L1 in the forward direction F, the capacitance C1 is charged from the power source V1 via current circuits 11 and I2, where current circuit I2 feeds current in reverse direction R through the coil L1 to remove or at least suppress remanence in the coil. The balance between the two charging paths from the power source V1 to the capacitance C1 is determined by the current regulating circuits 11 and I2.

[0085] There are many ways in which the current balancing circuits 11 and I2 can be realized in practice. Figure 5B provides one example. In Figure 5B, R1 -R6 are resistances which are determined in order to balance the charging current to the capacitance C1 and the drive current of the coil L1 . The diode D2 together with transistor Q3 will generate a fixed charging current to capacitance C1 . This current will be drawn from the gates of Q4 and Q5 in dependence of the balance point that is set by selection of the different resistances. The balance point can be set by computer simulation or by laboratory experimentation. The constant current through transistor Q3 and the resistor R1 is used to obtain current balance between transistors Q4 and Q5. Transistor Q4 controls the gate of switch M1 and hence the current to C1 . The voltage drop over resistor R2 will control how much Q4 respective Q5 opens and hence control how much current is passed through M1 .

[0086] An H-bridge circuit can be used instead of the example remanence mitigating circuits in Figures 5A-B. H-bridge circuits are generally known and will therefore not be discussed in more detail herein.

[0087] When using solenoid devices and other electronic actuators to control valves as in the different applications discussed herein, it is often desired to generate a strong initial actuation or valve pull force, followed by a less strong holding force. This generates less heat in the solenoid coils, and also conserves energy in the system. Thus, according to some aspects, the dust extractor 100 comprises a solenoid activation circuit configured to generate an initial forward pull current through the coil of the solenoid followed by a forward hold current through the coil, where the forward pull current is of larger magnitude compared to the forward hold current. This effect is obtained by the circuit in Figure 5A, due to the capacitance C1 .

[0088] Generally, there is disclosed herein a dust extractor 100 comprising a control unit 150 arranged to control a solenoid arrangement configured to actuate a valve of the dust extractor. The solenoid arrangement comprises a remanence mitigation circuit 155 configured to generate a reverse current through a coil of the solenoid device 340 after actuation of the solenoid device 340 by a forward current through the coil.

[0089] According to some aspects, the solenoid arrangement is configured to generate an initial pull current upon activation that is stronger than a hold current applied after a time period. The initial strong pull current improves actuation of the valve, while the less strong hold current is sufficient to keep the valve in position. The remanence mitigation circuit 155 may comprise first and second current balancing circuits 11 , I2 arranged to balance a charge current to an energy storage device C1 of the remanence mitigation circuit 155. An example of the balancing circuits 11 , I2 is shown in Figures 5A-B.

[0090] The dust extractor 100 may also comprise an H-bridge circuit configured to generate the reverse current through the coil of the solenoid device 340 after actuation of the solenoid device 340 by a forward current through the coil. The H-bride implementation can be combined with the current balancing circuits, although it is often used on its own to provide the reverse and the forward currents through the solenoid coil.

[0091] Figures 6A-B illustrate an optional one-way valve 600 that can be arranged in connection to the inlet opening 160 of the cyclone tank 1 10. The one-way valve 600 is arranged to allow passage of the air flow into the cyclone tank 1 10 and to resist air flow out from the cyclone tank 1 10 via the inlet opening 160.

[0092] The one-way valve may for instance comprise a flap valve with a flap 610 arranged to engage a valve seat 620 in sealing position to resist air flow out from the cyclone tank 1 10 via the inlet opening 160. The flap 610 may be biased towards its closed position by force of gravity or by some form of resilient member such as a spring. This way the flap 610 closes the inlet 160 when the dust extractor is not in use, which means that less dust, or even no dust, escapes out from the cyclone tank 110 through the inlet 160 during transport and handling of the dust extractor 1 10.

[0093] Figure 7 shows a dust extractor system 700 comprising two or more dust extractors 100. The inlet openings 160 of the two or more dust extractors are joined into a common suction conduit. When one of the dust extractors activates a bag swap mechanism or a dust dumping operation involving release of underpressure inside the cyclone tank, the suction from the dust extractor ceases due to the blockage of the suction valves and the increase in the cyclone tank pressure. This causes a pressure difference over the oneway valve which quickly closes the valve as in Figure 6B, such that no dust escapes from the cyclone tank 110 out through the inlet 160. The suction through the hose is maintained by the other dust extractor during the bag swap operation.

[0094] To further improve the dust extractor system 700, the control units 150 of the dust extractors can be arranged to communicate with each other, e.g., by exchanging wireless signals, and to coordinate activation of the respective bag swap mechanisms of the dust extractors such that the bag swap mechanism of at least one dust extractor is not active at any given point in time. In this case, the control units 150 of the dust extractors will verify that the other dust extractor does not have an activated bag swap mechanism before it activates its own bag swap mechanism.

[0095] The two or more dust extractors 100 may also coordinate dust dumping operations, and or prefilter cleaning operations, such that the combined dust extraction performance is not overly affected by the maintenance operations.

[0096] Figure 8 is a flow chart illustrating methods that summarize the discussions above. There is illustrated a method of operating a dust extractor 100, where the dust extractor comprises a control unit 150, a cyclone tank 1 10 and a blower system 140, where the blower system 140 is arranged downstream from the cyclone tank 1 10 to generate an air flow A through an inlet opening 160 in the cyclone tank 1 10 via an internal volume V of the cyclone tank 1 10 to an outlet passage 210 leading away from the cyclone tank 1 10 towards the blower system 140, the dust extractor 100 being arranged to support a dust container underneath the cyclone tank 1 10 in use, for receiving dust accumulated in the cyclone tank 1 10.

[0097] The dust extractor 100 comprises a pressure release valve 220, 310, 320 arranged to connect the internal volume V of the cyclone tank 110 to an external volume E when in an open state, the dust extractor 100 also comprising an air flow blocking valve 230, 310, 330 arranged downstream from the cyclone tank 1 10 and configured to restrict air flow via the outlet passage 210 when in a blocking state.

[0098] The method comprising, in response to activation SO of a bag swap mechanism of the dust extractor 100, setting S1 the pressure release valve 220, 310, 320 in the open state, setting S2 the air flow blocking valve 230, 310, 330 in the blocking state, and maintaining S3 the pressure release valve 220, 310, 320 in the open state and the air flow blocking valve 230, 310, 330 in the blocking state until deactivation of the bag swap mechanism.

[0099] Figure 9 schematically illustrates, in terms of a number of functional units, the general components of a control unit 150. Processing circuitry 910 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 930. The processing circuitry 910 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[0100] Particularly, the processing circuitry 910 is configured to cause the control unit 150 to perform a set of operations, or steps, such as the methods discussed herein. For example, the storage medium 930 may store the set of operations, and the processing circuitry 910 may be configured to retrieve the set of operations from the storage medium 930 to cause the device to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 910 is thereby arranged to execute methods as herein disclosed.

[0101] The storage medium 930 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0102] The control unit 150 may further comprise an interface 920 for communications with at least one external device. As such the interface 920 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication. The processing circuitry 910 controls the general operation of the control unit 150, e.g., by sending data and control signals to the interface 920 and the storage medium 930, by receiving data and reports from the interface 920, and by retrieving data and instructions from the storage medium 930.

[0103] The present disclosure also relates to various forms of computer readable media carrying respective computer programs comprising program code means for performing methods and / or for executing the various functions discussed above, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product.

[0104] The cyclone tank 1 10 of most heavy-duty dust extractors comprises a cylindrically shaped main tank which tapers off at the bottom end towards an aperture or dust outlet. A cyclone tank outlet valve is normally arranged in connection to the bottom aperture.

[0105] An inlet 160 opens up into the interior volume V of the cyclone tank 110 and at least one outlet passage 210 leads away from the cyclone tank towards the blower system 140 of the dust extractor. The outlet passage is normally arranged in connection to the top side or at least the upper side of the cyclone tank in use. The working air flow used for dust extraction enters the cyclone tank 110 via the inlet 160 and exits the cyclone tank 1 10 via the one or more outlet passages 210. Dust is deposited in the cyclone tank as a result of the working air flow passing the cyclone tank.

[0106] The aperture located at the bottom of the cyclone tank is used to evacuate the accumulated dust from the cyclone tank into a dust container, such as a bag or a bucket, arranged underneath the cyclone tank. The bottom aperture of the cyclone tank is normally closed by a cyclone tank outlet valve that prevents air from being drawn into the cyclone tank during dust extraction when the pressure inside the cyclone tank is well below atmospheric pressure. The outlet valve is arranged to allow a flow of air and dust out from the cyclone tank, and to resist a flow of air into the cyclone tank during dust extraction, at least after a transient phase when the pressure inside the cyclone tank drops. The outlet valve of the cyclone tank may also be referred to as a cyclone outlet one-way valve.

[0107] Figures 10-12 illustrate aspects of an example closure valve arrangement 1000 suitable for use with the cyclone tanks discussed herein, and also with other cyclone tanks, i.e., the closure valve arrangements discussed herein are not limited in use to the dust extractors disclosed herein and illustrated in the drawings. It is appreciated that the features discussed in connection to Figures 10-12 is not inextricably linked to any of the other dust extractor features discussed herein. Thus, even though the different closure valve arrangements 1000 can be advantageously combined with at least some of the designs and techniques discussed above, they are also applicable on their own.

[0108] Dust which has accumulated inside the cyclone tank during use of the dust extractor must regularly be emptied from the cyclone tank 1 10 into the dust container 1 15 arranged underneath the cyclone tank 1 10. An issue which is sometimes encountered is that the dust accumulated inside the cyclone tank interior volume V forms a “cake”, which may be difficult to dislodge and evacuate from the cyclone tank. Other issues that may be encountered are so- called rat-holes which is when the dust cake forms a channel between the bottom aperture of the cyclone tank and the internal volume of the cyclone tank. This can make it difficult to evacuate the dust from the cyclone tank. The dust may also form a bridge or separation which separates the internal volume of the cyclone tank from a smaller volume located just above the bottom aperture of the cyclone tanks. These types of bridges may also complicate emptying the dust from the cyclone tank.

[0109] It has been realized that a floating outlet valve, i.e., an outlet valve which can move in relation to the cyclone tank, helps in evacuating dust from the cyclone tank into the dust container arranged underneath. A floating bottom portion of the cyclone tank has a similar effect. When the dust extractor is actively extracting dust, and the pressure inside the cyclone tank is well below atmospheric pressure, the floating outlet valve or bottom portion is forcefully sucked up towards the cyclone tank bottom aperture. Once the cyclone pressure is released, e.g., by opening up the pressure release valve 220 discussed above, the outlet valve falls forcefully downwards away from the cyclone tank. This relative movement between cyclone tank and outlet valve has been found beneficial when it comes to emptying dust from the cyclone tank into the dust container underneath. As the outlet valve moves downwards it eventually encounters a stop at the end of the displacement range of the floating attachment between the valve and the outlet valve. This causes a jerk which propels the dust downwards and out from the cyclone tank. This way, even dust that has formed a cake is evacuated from the cyclone tank.

[0110] The outlet valve will also move forcefully upwards towards the cyclone tank as the pressure inside the cyclone tank drops (which happens when dust extraction is initiated). This movement will also cause a jerk as the outlet valve encounters the stop at the other end of the outlet valve displacement range, which unsettles any dust in the cyclone tank, making it easier to evacuate from the cyclone tank.

[0111] The relative movement of the floating outlet valve in relation to the cyclone tank may also happen during cleaning of the prefilter 120 by reverse bursts of air through the prefilter (from the clean side to the dirty side of the prefilter 120). This movement by the outlet valve disturbs or unsettles the dust accumulated inside the cyclone tank 1 10, in particular dust that has settled on top of the outlet valve, thereby mitigating dust cake formation, which is an advantage.

[0112] With reference to Figures 10-12, there is disclosed herein a closure valve arrangement 1000 for a cyclone tank 1 10 of a dust extractor 100, such as the dust extractors discussed generally herein or some other dust extractor. The closure valve arrangement 1000 comprises a fixed part 1010 that is arranged to be attached to the cyclone tank 1 10 and a moving part 1020 that is arranged floating F in relation to the fixed part 1010 over a displacement range R. The fixed part can be a separate part that is secured to the cyclone tank 1 10, or form part of the cyclone tank 1 10. According to a preferred embodiment, the fixed part is an annular member that is secured around the bottom aperture of the cyclone tank 1 10, as illustrated in Figures 10-11. According to some aspects, the fixed part 1010 is constituted by the cyclone tank 110, and the moving part 1020 forms a bottom portion of the cyclone tank. The moving part may be attached to the fixed part by a resilient member, such as a bellows connecting the fixed part and the moving part, to allow the moving part to float relative to the fixed part over a displacement range R in the vertical direction Vd. The moving part 1020 may also be arranged to slide relative to the fixed part 1010. The moving part may, e.g., comprise a cylinder section or annular member having a radius slightly larger than that of the cyclone tank 110, allowing a lower part of the cyclone tank to be received in the moving part in sliding relation. A sliding seal may be arranged between the cyclone tank and the moving part to prevent air from entering into the cyclone tank via the gap formed between the moving part and the cylinder tank constituting the fixed part.

[0113] That two objects are arranged floating in relation to each other means, generally, that the two are not fixedly attached to each other, but may move at least in one dimension over a predetermined displacement range R. The relative motion of the two objects may be constrained to some range in case of one-dimensional motion or some volume in case of motion in more than one dimension. The moving part 1020 may move relative to the fixed part in a vertical direction Vd, and also in a horizontal direction Hd, although the movement in the vertical direction is often the most pronounced.

[0114] The moving part 1020 is preferably arranged to move at least 0,5cm relative to the fixed part 1010 in the vertical direction Vd, and preferably more than 1 ,0cm, and even more preferably more than 2,0cm or even 3,0cm in the vertical direction Vd. The moving part 1020 is preferably arranged to move at least 0,5cm relative to the fixed part 1010 in a horizontal direction Hd perpendicular to the vertical direction Vd, and more preferably at least 1 ,0cm.

[0115] The fixed part 1010 and / or the moving part 1020 may be formed in a resilient material, such as rubber or a polymer.

[0116] Generally, there is disclosed herein a dust extractor 100 comprising a cyclone tank 110 with a fixed portion and a movable bottom portion, wherein the movable bottom portion comprises a dust container, where the movable bottom portion is movably attached to the fixed portion of the cyclone tank so as to allow the movable bottom portion to move a limited distance relative to the fixed portion in response to a pressure change in the cyclone tank. It is appreciated that the fixed portion and the movable portion can be realized in a number of different ways. According to a first example the fixed portion is a part of the cyclone tank, or a component fixedly attached to the cyclone tank, while the moving part forms a bottom part of the cyclone tank and comprises the outlet valve of the cyclone tank, as exemplified in Figure 10. According to another example the fixed part is an upper part of the cyclone tank, for example comprising the inlet 160, the prefilter 120 and the outlet passage 210, while the bottom portion is a cylindrical tank bottom part that is attached to the fixed part via bellows or the like. According to a third example the fixed part is an upper part of the cyclone tank, for example comprising the inlet 160, the prefilter 120 and the outlet passage 210, while the bottom portion is a cylindrical tank with a larger diameter than the upper part of the cyclone tank, allowing it to receive part of the upper cyclone tank in sliding relation, where a sliding seal prevents air from entering into the cyclone tank internal volume via the gap formed between the two parts.

[0117] The moving part 1020 comprises an outlet valve 1030 arranged to allow a flow of air and dust through the closure valve arrangement 1000 in direction D1 away from the fixed part 1010, and to resist a flow of air through the closure valve arrangement 1000 in direction D2 towards the fixed part 1010. The outlet valve 1030 may comprise a one-way valve such as a duckbill valve, a flap valve, a hatch, or some other type of one-way valve. The outlet valve may also comprise a grate which covers the bottom aperture of the cyclone tank where it is configured to prevent a dust bag from being sucked into the cyclone tank. The combination of the grate and the dust container bag forms a type of oneway valve which allows a flow of air and dust through the closure valve arrangement 1000 in direction D1 away from the fixed part 1010 and resists a flow of air through the closure valve arrangement 1000 in direction D2 towards the fixed part 1010. Figure 10 and Figure 12 shows a duckbill valve in closed state. Both duckbill valves, flap valves, and hatch valves are known and will therefore not be discussed in more detail herein. A grate, beam, or other obstructing member, can be arranged across the bottom aperture 1060 of the cyclone tank 1 10 to prevent the outlet valve 1030 from being sucked into the internal volume of the cyclone tank during dust extraction.

[0118] With reference to Figure 1 1 , the motion of the moving part 1020 in relation to the fixed part 1010 is restricted E at least in the direction D1 away from the fixed part 1010. The motion of the moving part 1020 in relation to the fixed part 1010 is preferably restricted in use to a displacement range R in the vertical direction Vd. This restriction will cause the moving part to stop abruptly on its way downwards away from the fixed part, thereby jettisoning the dust on top of the outlet valve downwards and out from the cyclone tank in direction D1 , as explained above.

[0119] The moving part 1020 can also be biased in the direction D1 away from the fixed part 1010 by a resilient member such as a spring. This enhances the unsettling of the dust during pressure release in the cyclone tank 1 10, since it increases the jerk that happens when the moving part 1020 hits the end E of the vertical displacement range R.

[0120] According to some aspects, the moving part 1020 comprises an integrated dust container holder 1040 arranged to support a dust container 1 15. The example illustrated in Figures 10-12 shows an integrated Longopac dust container system holder. The dust container holder 1040 can, more generally, be arranged to support a replaceable dust bag such as a Longopac plastic bag system or a dust container bucket, or some other type of dust container. It is appreciated that the dust container holder may also be otherwise supported, e.g., fixedly secured onto the cyclone tank, integrated with the fixed part of the closure valve arrangement 1000 or in some other way in relation to the fixed and the moving parts of the closure valve arrangement 1000.

[0121] The fixed part may also comprise a resilient tubular member 1050 arranged to cover a Longopac dust container system. The tubular member 1050 folded down over an installed Longopac plastic bag system in order to protect the Longopac material from damage.

[0122] The fixed part 1010 optionally comprises a perimeter with at least one perimeter flange 1 110 extending radially outwards Ro from the rim portion, the perimeter flange 1 110 being configured to mate with a flange portion 1 120 on the moving part 1020 that extends radially inwards Ri.

Claims

CLAIMS1. A dust extractor (100) comprising at least one cyclone tank (1 10), a prefilter arrangement (120), an essential filter arrangement (130), a blower system (140), and a control unit (150) arranged to control a solenoid arrangement configured to actuate a pressure release valve (220, 310, 320) of the dust extractor (100), where the pressure release valve (220) is arranged to connect an internal volume (V) of the cyclone tank (1 10) to an external volume (E) of the dust extractor (100), the solenoid arrangement comprising a solenoid device (340) and a remanence mitigation circuit (155) configured to generate a reverse current through a coil of the solenoid device (340) after actuation of the solenoid device (340) by a forward current through the coil.

2. The dust extractor (100) according to claim 1 , where the solenoid arrangement is configured to generate an initial pull current upon activation that is stronger than a hold current applied after a time period.

3. The dust extractor (100) according to claim 1 or 2, where the remanence mitigation circuit (155) comprises a first current balancing circuit (11 ) and a second current balancing circuit (I2) arranged to balance a charge current to an energy storage device (C1 ) of the remanence mitigation circuit (155).

4. The dust extractor (100) according to any of claims 1 -3, comprising an Id- bridge circuit configured to generate the reverse current through the coil of the solenoid device (340) after actuation of the solenoid device (340) by a forward current through the coil.

5. A dust extractor (100) comprising a control unit (150), a cyclone tank (1 10) and a blower system (140), where the blower system (140) is arranged downstream from the cyclone tank (1 10) to generate an air flow (A) through an inlet opening (160) in the cyclone tank (1 10) via an internal volume (V) of the cyclone tank (1 10) to an outlet passage (210) leading away from the cyclone tank (110) towards the blower system (140),the dust extractor (100) being arranged to support a dust container underneath the cyclone tank (1 10) in use, for receiving dust accumulated in the cyclone tank (110), the dust extractor (100) comprising a pressure release valve (220, 310, 320) arranged to connect the internal volume (V) of the cyclone tank (1 10) to an external volume (E) when in an open state, the dust extractor (100) also comprising an air flow blocking valve (230, 310, 330) configured to restrict air flow via the outlet passage (210) when in a blocking state, where, upon activation of a bag swap mechanism of the dust extractor (100), the pressure release valve (220, 310, 320) is set in the open state and the air flow blocking valve (230, 310, 330) is set in the blocking state, until deactivation of the bag swap mechanism when the pressure release valve (220, 310, 320) is moved away from the open state and the air flow blocking valve (230, 310, 330) is moved away from the blocking state.

6. The dust extractor (100) according to claim 5, where the external volume (E) is an ambient environment comprising air at atmospheric pressure.

7. The dust extractor (100) according to claim 5, where the external volume (E) is a pressure vessel comprising gas at a pressure above atmospheric pressure.

8. The dust extractor (100) according to any of claims 5-7, where the pressure release valve (220, 310, 320) and the air flow blocking valve (230, 310, 330) are actuated by a joint valve actuation mechanism, where the bag swap mechanism is activated by manual manipulation of the joint valve actuation mechanism.

9. The dust extractor (100) according to any of claims 5-8, where the pressure release valve (220) and the air flow blocking valve (230) share a common valve disc (310) configured to engage a first valve seat (320) and a second valve seat (330) in reciprocating motion,where the pressure release valve (220) is in a closed state and the air flow blocking valve (230) is in a non-blocking state when the valve disc (310) engages the first valve seat (320), where the pressure release valve (220) is in the open state and the air flow blocking valve (230) is in the blocking state when the valve disc (310) engages the second valve seat (330).

10. The dust extractor (100) according to any of claims 5-9, where the control unit (150) is configured to manipulate the state of the pressure release valve (220) and the state of the air flow blocking valve (230) by sending electronic control signals to at least one automatic valve actuator upon activation of the bag swap mechanism of the dust extractor (100).

11. The dust extractor (100) according to claim 10, where the at least one automatic valve actuator comprises a solenoid device (340).

12. The dust extractor (100) according to claim 1 1 , comprising a remanence mitigation circuit (155) configured to generate a reverse current through a coil of the solenoid device (340) after actuation of the solenoid device (340) by a forward current through the coil.

13. The dust extractor (100) according to claim 1 1 or 12, comprising a solenoid activation circuit configured to generate an initial forward pull current through a coil of the solenoid followed by a forward hold current through the coil, where the forward pull current is of larger magnitude compared to the forward hold current.

14. The dust extractor (100) according to any of claims 10-13, where the bag swap mechanism is arranged to be activated in response to user manipulation of a user interface (105) of the dust extractor (100).

15. The dust extractor (100) according to any of claims 10-14, where the control unit (150) is arranged to automatically deactivate the bag swap mechanism after a predetermined time period.

16. The dust extractor (100) according to any of claims 10-15, where the control unit (150) is arranged to automatically deactivate the bag swapmechanism in case a temperature of the blower system (140) fails to satisfy a temperature acceptance criterion.

17. The dust extractor (100) according to any of claims 10-16, where the control unit (150) is arranged to automatically deactivate or reduce power of a drive motor of the blower system (140) in case a temperature of the blower system (140) fails to satisfy a temperature acceptance criterion.

18. The dust extractor (100) according to any of claims 15-17, where the control unit (150) is arranged to trigger generation of a notification signal such as a notification light (170) prior to automatically deactivating the bag swap mechanism.

19. The dust extractor (100) according to any of claims 5-18, where a drive motor of the blower system (140) is arranged to generate a cooling air flow that is separate from the air flow through the air flow blocking valve (230, 310, 330).

20. The dust extractor (100) according to any of claims 5-19, where the control unit (150) is arranged to decrease a fan speed of the blower system (140) in response to activation of the bag swap mechanism, and to restore fan speed in response to deactivation of the bag swap mechanism.21 . The dust extractor (100) according to any of claims 5-20, where a oneway valve (600) is arranged in connection to the inlet opening (160) of the cyclone tank (1 10), the one-way valve (600) being arranged to allow passage of the air flow into the cyclone tank (1 10) and to resist air flow out from the cyclone tank (1 10) via the inlet opening (160).

22. The dust extractor (100) according to claim 21 , where the one-way valve comprises a flap valve with a flap (610) arranged to engage a valve seat (620) in sealing position to resist air flow out from the cyclone tank (110) via the inlet opening (160).

23. The dust extractor (100) according to claim 21 or 22, where the one-way valve is biased towards a sealing position of the valve where air flow out from the cyclone tank (1 10) via the inlet opening (160) is prevented.

24. A dust extractor system comprising two or more dust extractors according to any of claims 21 -23, where the inlet openings (160) of the two or more dust extractors are joined into a common suction conduit.

25. The dust extractor system according to claim 24, where the control units (150) of the dust extractors are arranged to communicate with each other, and to coordinate activation of the respective bag swap mechanisms of the dust extractors such that the bag swap mechanism of at least one dust extractor is not active at any given point in time.

26. A method of operating a dust extractor (100), where the dust extractor comprises a control unit (150), a cyclone tank (1 10) and a blower system (140), where the blower system (140) is arranged downstream from the cyclone tank (1 10) to generate an air flow (A) through an inlet opening (160) in the cyclone tank (110) via an internal volume (V) of the cyclone tank (110) to an outlet passage (210) leading away from the cyclone tank (1 10) towards the blower system (140), the dust extractor (100) being arranged to support a dust container underneath the cyclone tank (1 10) in use, for receiving dust accumulated in the cyclone tank (110), the dust extractor (100) comprising a pressure release valve (220, 310, 320) arranged to connect the internal volume (V) of the cyclone tank (1 10) to an external volume (E) when in an open state, the dust extractor (100) also comprising an air flow blocking valve (230, 310, 330) configured to restrict air flow via the outlet passage (210) when in a blocking state, the method comprising, in response to activation (SO) of a bag swap mechanism of the dust extractor (100), setting (S1 ) the pressure release valve (220, 310, 320) in the open state, setting (S2) the air flow blocking valve (230, 310, 330) in the blocking state, and maintaining (S3) the pressure release valve (220, 310, 320) in the open state and the air flow blocking valve (230, 310, 330) in the blocking state until deactivation of the bag swap mechanism.

27. A dust extractor (100) comprising a control unit (150), a cyclone tank (1 10), a pre-filter (120), at least one essential filter (130), and a blower system (140), where the blower system (140) is arranged downstream from the cyclone tank (1 10), the pre-filter (120) and the at least one essential filter (130), to generate an air flow (A) through an inlet opening (160) in the cyclone tank (1 10), where the dust extractor (100) is arranged to support a dust container (1 15) underneath the cyclone tank (1 10) in use, for receiving dust accumulated in the cyclone tank (1 10), the dust extractor (100) comprising a pressure release valve (220) arranged to connect an internal volume (V) of the cyclone tank (1 10) to an external volume (E) when in an open state, where a one-way valve (600) is arranged in connection to the inlet opening (160) of the cyclone tank (1 10), the one-way valve (600) being arranged to allow passage of the air flow into the cyclone tank (1 10) and to resist air flow out from the cyclone tank (1 10) via the inlet opening (160).

28. The dust extractor (100) according to claim 27, where the one-way valve comprises a flap valve with a flap (610) arranged to engage a valve seat (620) in sealing position to resist air flow out from the cyclone tank (110) via the inlet opening (160).

29. The dust extractor (100) according to claim 27 or 28, where the one-way valve is biased towards a sealing position of the valve where air flow out from the cyclone tank (1 10) via the inlet opening (160) is resisted or prevented.

30. A dust extractor system comprising two or more dust extractors according to any of claims 27-29, where the inlet openings (160) of the two or more dust extractors are joined into a common suction conduit.31 . The dust extractor system according to claim 30, where the control units (150) of the dust extractors are arranged to communicate with each other, and to coordinate activation of respective bag swap mechanisms of the dustextractors such that the bag swap mechanism of at least one dust extractor is not active at any given point in time.

32. A cyclone tank bottom closure valve arrangement (1000) for a dust extractor (100) having a cyclone tank (1 10), the closure valve arrangement (1000) comprising a fixed part (1010) arranged to be attached to the cyclone tank (1 10), and a moving part (1020) arranged floating (F) in relation to the fixed part (1010), the moving part (1020) comprising an outlet valve (1030) arranged to allow air and dust to pass through the closure valve arrangement (1000) in direction (D1 ) away from the fixed part (1010), and to resist a flow of air through the closure valve arrangement (1000) in direction (D2) towards the fixed part (1010) in use.

33. The closure valve arrangement (1000) according to claim 32, where a motion of the moving part (1020) in relation to the fixed part (1010) is restricted (E) in the direction (D1 ) away from the fixed part (1010).

34. The closure valve arrangement (1000) according to claim 32 or 33, where the motion of the moving part (1020) in relation to the fixed part (1010) is restricted in use to a range (R) in a vertical direction (Vd).

35. The closure valve arrangement (1000) according to claim 34, where the range is at least 0,5cm, and preferably larger than 1 ,0cm.

36. The closure valve arrangement (1000) according to any of claims 32-35, where the moving part (1020) comprises an integrated dust container holder (1040) arranged to support a dust container (1 15).

37. The closure valve arrangement (1000) according to any of claims 32-36, where the dust container holder (1040) is arranged to support a replaceable dust bag such as a Longopac plastic bag system, or a bucket.

38. The closure valve arrangement (1000) according to any of claims 32-37, where the fixed part (1010) is an annular member comprising a perimeter with at least one perimeter flange (1 1 10) extending radially outwards (Ro) from therim portion, the perimeter flange (1 1 10) being configured to mate with a flange portion (1 120) on the moving part (1020) that extends radially inwards (Ri).

39. The closure valve arrangement (1000) according to any of claims 32-38, where the outlet valve (1030) is a duckbill valve, a flap valve, or a hatch arranged to allow passage of the air flow into the cyclone tank (1 10) and to resist air flow out from the cyclone tank (1 10) via the inlet opening (160).

40. The closure valve arrangement (1000) according to any of claims 32-39, comprising an obstructing member such as a grate or a beam arranged to prevent the outlet valve from entering into the cyclone tank internal volume (V).41 . The closure valve arrangement (1000) according to any of claims 32-38, where the outlet valve (1030) is a combination of a grate which covers the bottom aperture (1060) of the cyclone tank (1 10) and a soft bag dust container such as a plastic bag configured to be sucked up against the grate in use.

42. The closure valve arrangement (1000) according to any of claims 32-41 , where the fixed part (1010) comprises a resilient tubular member (1050) arranged to cover a Longopac dust container system in use.

43. The closure valve arrangement (1000) according to any of claims 32-42, where the moving part (1020) is biased in a direction away from the fixed part (1010) by a resilient member such as a spring.

44. A moving part (1020) for a cyclone tank closure valve arrangement (1000) of a dust extractor (100), the moving part comprising an outlet valve (1030) arranged to allow a flow of air and dust to pass the outlet valve (1030) in a first direction (D1 ), and to resist a flow of air through the outlet valve (1030) in a second direction (D2) opposite to the first direction (D1 ), the moving part (1020) also comprising an integrated dust container holder (1040) arranged to support a dust container (1 15), where the moving part (1020) is arranged to mate with a fixed part (1010) of the cyclone tank closure valve arrangement (1000) in floating relation (F).

45. A dust extractor (100) comprising a cyclone tank (110) with a fixed portion and a movable bottom portion, where the movable bottom portion comprises a dust container, where the movable bottom portion is movably attached to the fixed portion of the cyclone tank so as to allow the movable bottom portion to move a limited distance (R) relative to the fixed portion in response to a pressure change in the cyclone tank (110).

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