Abstract:
A device is described for controlling the airflow through an airduct, the airduct having a housing, an inlet and an outlet. The device comprises a self-regulating valve having a diaphragm, the position of the diaphragm being determined by the difference between the pressure at the inlet and the pressure at the outlet. The diaphragm is rotatably suspended on a support so that, under influence of an increasing difference in pressure, the diaphragm can rotate between a minimum rotation angle and a maximum rotation angle over an intermediate rotation angle, the intermediate angle being situated between the minimum and maximum angle. The diaphragm is provided with a counterbalance and that, within the angle range between the intermediate rotation angle and the maximum rotation angle, the rotation movement of the diaphragm under influence of an increasing pressure difference is counteracted by an elastic resisting force.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a ventilation device which can regulate airflow as well as to a method of controlling air flow through a ventilation device and to an insert for a ventilation device that provides control of the air flow. 
       BACKGROUND TO THE INVENTION 
       [0002]    Ventilation devices are widely used in the walls and windows of buildings to allow fresh air to enter a building. In many countries, the use of a ventilator is recommended or mandatory. Standards can also define certain requirements for the performance of a ventilator. One such requirement defines the performance of the ventilator in terms of airflow rate versus pressure difference between the inlet and outlet of the device. Typically, there is a requirement for a constant, or a near constant, airflow rate across a range of pressure differences. This requirement will provide a user with a pleasing environment within a building, with a constant flow of air, regardless of weather conditions outside the building. One requirement is that the inflow of air should reach a limit as the incoming wind speed increases while maintaining good ventilation at low speeds. Hence, the flow characteristic of the valve should be non-linear and self-limiting. 
         [0003]    A ventilation device typically comprises a housing which defines an airflow duct. A valve is positioned within the flow duct. The position of the valve can be controlled by a pressure monitor and an actuator (e.g. an electrical actuator or motor) or the valve can be self-regulating, without the use of an actuator. A self-regulating ventilation device is described in EP 1 568 947 B1. A valve is rotatingly suspended about a suspension point in the air duct. The valve is arranged to move in the air duct. The valve firstly rotates to a maximum turning angle around the free suspension point, and then subsequently deforms, without further rotation about the free suspension point. Operation of this ventilation device relies on the flexibility of the valve, formed from plastic. However, as the properties of the valve part vary with temperature, the performance of this ventilation device can vary as temperature fluctuates. 
         [0004]    It is desirable that a ventilation device has a good performance (e.g. offering near-constant flow rate across a wide range of pressure differences) and is capable of being manufactured at low cost. 
       SUMMARY OF THE INVENTION 
       [0005]    A first aspect of the present invention provides a device for controlling the airflow through an airduct, the airduct having a housing, an inlet and an outlet, the device comprising:
       a self-regulating valve having a diaphragm, the position of the diaphragm being determined by the difference between the pressure at the inlet and the pressure at the outlet, the diaphragm being rotatably located, e.g. journalled or suspended, on a support so that, under influence of an increasing difference in pressure, the diaphragm can rotate between a minimum rotation angle and a maximum rotation angle over an intermediate rotation angle, the intermediate angle being situated between the minimum and maximum angle, and characterized in that the diaphragm is provided with a counterbalance and that, within the angle range between the intermediate rotation angle and the maximum rotation angle, the rotation movement of the diaphragm under influence of an increasing pressure difference is counteracted by an elastic resisting force.       
 
         [0007]    A ventilation device of this kind has been found to provide a well-regulated flow of air across a wide range of values of pressure difference. In particular, it has been found to offer a plateau at high pressure differences (i.e. values of external wind speed). The counterbalance helps to ensure that the valve member does not unduly restrict the air duct at low values of pressure difference, and can readily respond to changes in pressure difference at the lower values of pressure difference. 
         [0008]    The elastic resisting force can be generated by contact between the counterbalance, or the diaphragm, and a resilient means. The resilient means may be a spring of any suitable form. The resilient means can be attached to, or form part of, the housing. Alternatively, the elastic resisting force can be generated by contact between a part of the housing and a resilient means which forms part of, or is mounted to, the counterbalance or diaphragm. For example, the resilient means can be provided by a part of the counterbalance or diaphragm which is formed from a resilient material, such as a resiliently deformable plastic material. In either case, the resilient means can be a spring. 
         [0009]    Preferably, the resilient means provides substantially constant performance over a normal operating temperature range, e.g. −20° C. to +40° C. A resilient means formed of metal has been found to be particularly advantageous. The spring properties of the resilient means preferably change by less than 20%, or less than 10% over the range −20° C. to +40° C. or for some temperate countries 0-35° C. 
         [0010]    In an alternative embodiment of the invention, the elastic resisting force is provided by a part of the counterbalance which is formed from a resilient material, such as a resiliently deformable plastic material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which: 
           [0012]      FIG. 1  shows a first embodiment of a ventilation device in accordance with the present invention; 
           [0013]      FIGS. 2A-2C  show a second embodiment of a ventilation device in accordance with the present invention, in which the counterbalance is resiliently deformable; 
           [0014]      FIGS. 3A-3C  show a third embodiment of a ventilation device in accordance with the present invention; 
           [0015]      FIGS. 4A-4C  show a fourth embodiment of a ventilation device in accordance with the present invention; 
           [0016]      FIGS. 5A-5C  show a fifth embodiment of a ventilation device in accordance with the present invention, in which a spring is incorporated within a counterbalance; 
           [0017]      FIGS. 6A-6C  show a sixth embodiment of a ventilation device in accordance with the present invention, in which a spring is incorporated within a counterbalance. 
           [0018]      FIG. 7  shows test results on a ventilation device in accordance with the present invention. 
           [0019]      FIGS. 8A-8C  shows a seventh embodiment of the present invention for an acoustic ventilator device in accordance with the present invention. 
           [0020]      FIGS. 9A-9C  shows an eighth embodiment of a ventilation device in accordance with the present invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0021]    The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term “comprising” is used in the present description and claims, it does not exclude other elements or steps. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. 
         [0022]      FIG. 1  shows a first embodiment of the ventilation device. A housing  5  defines an airflow duct  4  having an inlet  1  and an outlet  2 . A valve  11 ,  12 ,  13  is fitted within the airflow duct  4 . The valve is mounted upon a hook-shaped support  10  which protrudes from an upper wall of the housing. The valve comprises a hooked part  11  which rests upon support  10 . The valve comprises two arms which are both connected to the hooked part  11  and which are aligned in mutually different directions. The first arm is a flap-like part  12  and the second arm is a counterbalance  13 . Flap  12  is shown as having a length  1  which is substantially equal to the height of the flow duct  4  in the region where it is fitted. Although shown only in cross-section, flap  12  also extends across the full width of the airflow duct  4 . Flap  12  extends upstream, towards the inlet  1 . In use, flap  12  can rotate in the direction of arrow  15  to restrict the height of the airflow duct  4 . Part  13  of the valve serves as a counterbalance. Flap  12  and counterbalance  13  are supported in a fixed relationship to each other, i.e. flap  12  and counterbalance  13  rotate as one unitary part about support  10 . Counterbalance  13  has a suitable dimension and weight, with respect to flap  12 , such that at low values of pressure difference between the inlet  1  and outlet  2  the counterbalance  13  serves to hold flap  12  in the position shown in  FIG. 1 , with the airflow duct  4  fully open. As pressure difference increases, flap  12  rotates about support  10  in the direction of arrow  15  and the duct  4  is progressively restricted by the flap  12 . A spring  14  is positioned in the uppermost corner of the housing, and lies in the path of the counterbalance  13 . As the valve rotates about support  10 , counterbalance  13  is moved towards the distal end of spring  14  and makes contact with the spring. The spring  14  provides a resilient force which serves to resist movement of the counterbalance  13 . At even higher values of pressure difference, flap  12  further rotates about support  10  in the direction of arrow  15 , causing spring  14  to compress. Advantageously, the properties of the spring  14  cause it to exhibit a non-linear response. 
         [0023]    Hooked part  11  of the valve is shaped to define the angular range over which the valve can move. Wall  17  of the hooked part  11  defines the rest position of the flap  12 , when there is little or no pressure difference. Wall  18  of the hooked part  11  defines the maximum turning position of the flap  12 , as the flap  12  rotates in the clockwise direction about support  10 . Additional stops can be provided, such as protrusions extending from the wall of housing  5  in the region of the resting position of the flap  12 . 
         [0024]      FIGS. 2A-2C  show a second embodiment of the ventilation device. As previously described for  FIG. 1 , a housing  105  defines an airflow duct  104  having an inlet  101  and an outlet  102 . A valve  111 ,  112 ,  113  is fitted within the airflow duct  104 . The valve is mounted upon an upwardly pointing hook-shaped support  110  which protrudes from an upper wall of the housing. The valve comprises a hooked part  111  which rests upon support  110 . The valve comprises two arms  112 ,  113  which are both connected to the hooked part  111  and which are aligned in mutually different directions. The first arm is a flap-like part  112  and the second arm is a counterbalance  113 . In use, flap  112  can rotate in the direction of arrow  115  to restrict the width of airflow duct  104 . Part  113  of the valve serves as a counterbalance. Flap  112  and counterbalance  113  are supported in a fixed relationship to each other, i.e. flap  112  and counterbalance  113  rotate as one unitary part about support  10 .  FIG. 2A  differs in that the counterbalance  113  is formed from a resiliently deformable material. This avoids the need to provide a spring ( 14 ,  FIG. 1 ).  FIGS. 2A-2C  show operation of the valve at increasing values of differential pressure between the inlet  101  and outlet  102 . In  FIG. 2A , the differential pressure is low. The counterbalance  113  serves to bias the flap  112  such that it lies parallel with the wall of the airflow duct. As differential pressure increases, the flap  112  moves in direction  115 , causing the flap  112  to begin to restrict the airflow duct  104 . In  FIG. 2B , the differential pressure has caused the valve to rotate about support  110  until the distal end of counterbalance  113  presses against the upper wall of airflow duct  104 . In  FIG. 2C , the differential pressure has caused the valve to rotate further about support  110 , with the counterbalance  113  deforming (resiliently) as it is pressed against the upper wall of airflow duct  104 . 
         [0025]      FIGS. 3A-3C  show a third embodiment of the ventilation device. This is similar to  FIGS. 2A-2C , in that a counterbalance  213  has a resiliently deformable portion. The rotatable mounting of the valve is different to that shown in  FIG. 1  and  FIGS. 2A-2C . The ventilation device has an inlet  201 , an outlet  202  and a flow duct  204 . The valve is rotatably supported by a socket  210  protruding from a wall of the housing. The socket has a generally annular cross-section. The annular socket has an open segment which defines end stops for controlling the angular path of the flap  212 .  FIG. 3A  shows the valve at a low (or zero) value of differential pressure, with the flap  212  pressed against one of the end stops of the socket  210 . As differential pressure increases, the flap  212  moves in direction  215 , causing the flap  212  to begin to restrict the airflow duct  204 . In  FIG. 3B , the differential pressure has caused the valve to rotate about socket  210  until the distal end  216  of counterbalance  213  presses against a stop  217 . In  FIG. 3C , increasing differential pressure has caused the valve to rotate further about socket  210 , with the tip  216  of the counterbalance  213  deforming (resiliently) as it is pressed against the stop  217 . It should be understood that the valve can, with increasing pressure difference, rotate between the positions shown in  FIGS. 3B and 3C  but that during this angular range of movement, the rotation is opposed by the resilient deformation of tip  216  of the counterbalance  213 . The socket  210  defines an end stop which limits the angular movement of the flap and counterbalance. This serves to limit deformation of the tip  216  to within a safe operating range (i.e. to prevent permanent deformation of the tip  216 . Tip  216  of the counterbalance can be co-extruded with the counterbalance, and can also be co-extruded with the flap  212 . 
         [0026]      FIGS. 4A-4C  show a fourth embodiment of the ventilation device. This has the same rotatable socket mounting as  FIGS. 3A-3C . In this embodiment, the counterbalance  313  carries a resilient, V-shaped, spring element  314 .  FIG. 4A  shows the valve at a low (or zero) value of differential pressure, with the flap support pressed against one of the end stops of the socket. As differential pressure increases, the flap  212  moves in direction  215 , causing the flap  212  to begin to restrict the airflow duct  204 . In  FIG. 4B , the differential pressure has caused the valve to rotate about socket  210  until a first part of the spring  314  presses against stop  217 . In  FIG. 4C , increasing differential pressure has caused the valve to rotate further about socket  210 , with the spring  314  carried by the counterbalance  313  deforming (resiliently) as it is pressed against the stop  217 , causing the two arms of the V-shaped spring  314  to press together. 
         [0027]      FIGS. 5A-5C  show a fifth embodiment of the ventilation device. The device has a housing which defines an airflow duct  404 , an inlet  401  and an outlet  402 . A valve  411 ,  412 ,  413  is rotatably mounted within the airflow duct. In common with  FIG. 1  and  FIGS. 2A-2C , the valve has a hooked part  411  which rests upon an upwardly pointing hook-shaped support  410  which protrudes from an upper wall of the housing. The valve comprises, on the remote side of the hooked part  411 , a counterbalance  413 . The counterbalance is generally V-shaped in cross-section, with two arms mounted in fixed relationship to one another. A V-shaped spring  414  is held between the arms of the counterbalance  413 .  FIG. 5A  shows the valve at a low (or zero) value of differential pressure. As differential pressure increases, the flap  412  moves in direction  415 , causing the flap  412  to begin to restrict the airflow duct. In  FIG. 5B , the differential pressure has caused the valve to rotate about support  410  until a first arm of the spring  414  presses against stop  417 . In  FIG. 5C , increasing differential pressure has caused the valve to rotate further about support  410 , with the arms of spring  414  having been pressed together. An end stop is defined by the counterbalance  413  pressing against the housing, and flap  412  pressing against support  410 . 
         [0028]      FIGS. 6A-6C  show a sixth embodiment of the ventilation device. This embodiment is similar to that previously described, except that instead of the counterbalance being located within a compartment above the air duct ( FIGS. 5A-5C ), the counterbalance is positioned within the airflow duct. The device has a housing which defines an airflow duct  504 , an inlet  501  and an outlet  502 . A valve  511 ,  512 ,  513  is rotatably mounted within the airflow duct  504 . As in  FIGS. 5A-5C , the valve has a hooked part  511  which rests upon an upwardly pointing hook-shaped support  510  which protrudes from a wall of the housing. The valve comprises, on the remote side of the hooked part  511 , a counterbalance  513 . The counterbalance is generally V-shaped in cross-section, with two arms mounted in fixed relationship to one another. A V-shaped spring  514  is held between the arms of the counterbalance  513 .  FIG. 6A  shows the valve at a low (or zero) value of differential pressure. As differential pressure increases, the flap  512  moves in direction  515 , causing the flap  512  to begin to restrict the airflow duct. In  FIG. 6B , the differential pressure has caused the valve to rotate about support  510  until a first arm of the spring  514  presses against stop  518 . In  FIG. 6C , increasing differential pressure has caused the valve to rotate further about support  510 , with the arms of spring  514  having been further pressed together.  FIGS. 6A-6C  also show a manually-operable flap  520  which can be operated to close the air duct completely, although this is optional. 
         [0029]    A further embodiment of the ventilation device (not shown) resembles the device shown in  FIG. 1 , but the spring  14  is replaced by a part of the housing, such as a wall or other component of the housing, which is formed from a resilient material. In use, increasing pressure difference rotates the counterbalance  13  towards the resilient part of the housing, until the counterbalance  13  presses against the resilient part of the housing. A further increase in pressure difference causes the resilient part of the housing to be compressed. 
         [0030]    Each of the illustrated embodiments show a counterbalance acting upon a resilient member, or a counterbalance which incorporates a resiliently deformable portion. However, this is not essential to the invention and, instead, the flap (diaphragm) can act upon a resilient member. 
         [0031]    In  FIG. 1  and  FIGS. 2A-2C , the valve has a hooked part  11  which rests upon a hooked support  10  on the housing, and part  1  is free to rotate about support  10 . This arrangement has the advantages of being cheap to manufacture and easy to assemble. In  FIGS. 3A-3C  and  4 A- 4 C the rotatable connection is achieved by a socket and pin. Any suitable alternative form of connection can be used which permits rotational movement between the valve and the housing. 
         [0032]    The ventilation device can be fitted to a building, with the housing  5  being adapted to fit within a wall of the building, in the frame of a window, or in the window itself. Portions  51 ,  52  of the housing fit within the wall, frame or window, with portion  53  extending into the interior of the building and portion  54  extending outside the building. The inlet  1 ,  101  to the device is preferably vertically oriented, which serves to prevent ingress of water.  FIG. 1  shows a hooded portion  7  extending upstream of the inlet, which serves to further limit ingress of water, although this is optional, particularly where the ventilation device is fitted at low levels. A grille  3  is fitted to the outlet of the ventilation device. 
         [0033]    In the illustrated embodiments, the counterbalance is arranged to position the valve member at an inclined position when the pressure difference has a low or zero value. This allows the exterior portion  54  of the housing surrounding the valve member to have a generally arcuate profile, which reduces the amount of material used to form this region (compared to a more rectangular profile), allows water to run off the housing and generally gives a more pleasing aesthetic appearance. 
         [0034]    Although a housing  5  has generally been described, this can be formed from a plurality of different physical parts which can be secured together, such as by snap fittings, screws, clips etc. For example, there can be an upper part and a lower part which, when fitted together, define the airflow duct. Parts can be formed from different materials. For example, the outermost shell of the housing can be formed from aluminum, with other parts formed in plastics materials such as PVC. 
         [0035]    Further embodiments of the ventilation device can comprise measures to acoustically dampen the air flow. Acoustic dampening can be achieved by lining the airflow duct  4 ,  104 , with acoustically absorbent material or by including acoustically absorbent material in the outlet  2  or grille  3 ; by including obstructions (or acoustically absorbent material) in the airflow duct etc. An embodiment of an acoustic device is shown in  FIGS. 8   a  to  c . As previously, a housing  605  defines an airflow duct  604  having an inlet  601  and an outlet  602 . A valve  611 ,  612 ,  613  is fitted within the airflow duct  604 . The valve is mounted upon a hook-shaped support  610  which protrudes from an upper wall of the housing. The valve comprises a hooked part  611  which rests upon support  610 . The valve comprises two arms which are both connected to the hooked part  611  and which are aligned in mutually different directions. The first arm is a flap-like part  612  and the second arm is a counterbalance  613 . Flap  612  has a length “ 1 ” which is substantially equal to the height of the flow duct  604  in the region where it is fitted. Although shown only in cross-section, flap  612  also extends across the full width of the airflow duct  604 . Flap  612  extends upstream, towards the inlet  601 . In use, flap  612  restricts the height of the airflow duct  604  as shown progressively in  FIGS. 8   a  to  c . Part  613  of the valve serves as a counterbalance. Flap  612  and counterbalance  613  are supported in a fixed relationship to each other, i.e. flap  612  and counterbalance  613  rotate as one unitary part about support  610 . Counterbalance  613  preferably has a suitable dimension and weight, with respect to flap  612 , such that at low values of pressure difference between the inlet  601  and outlet  602  the counterbalance  613  serves to hold flap  612  in the position shown in  FIG. 8 , with the airflow duct  604  fully open. A spring  614  is positioned in contact with the counterweight arm  613  but not touching a part of the housing  605  ( FIG. 8   a ). As the air pressure increase, the flap  612  rotates about support  610  and spring  614  makes contact with the part of the housing wall ( FIG. 8   b ). The spring  614  provides a resilient force which serves to resist movement of the counterbalance  613 . At even higher values of pressure difference, flap  612  further rotates about support  610  causing spring  614  to compress,  FIG. 8   c . Advantageously, the properties of the spring  614  cause it to exhibit a nonlinear response. The spring properties should also preferably be substantially constant over the operating temperature range. For example the spring may be made of metal. To provide acoustic damping air volumes may be provided in housing  605  that can be open to the duct  604 . These may be filled with sound damping material such as foam or fibres. 
         [0036]    Another embodiment of a ventilation device is shown in  FIGS. 9   a  to  9   c . As previously, a housing  705  defines an airflow duct  704  having an inlet  701  and an outlet  702 . A valve  711 ,  712 ,  713  is fitted within the airflow duct  704 . The valve is mounted upon a hook-shaped support  710  which protrudes from an upper wall of the housing. The valve comprises a hooked part  711  which rests upon support  710 . The valve comprises two arms which are both connected to the hooked part  711  and which are aligned in mutually different directions. The first arm is a flap-like part  712  and the second arm is a counterbalance  713 . Flap  712  has a length “ 1 ” which is substantially equal to the height of the flow duct  704  in the region where it is fitted. Although shown only in cross-section, flap  712  also extends across the full width of the airflow duct  604 . Flap  712  extends upstream, towards the inlet  701 . In use, flap  712  restricts the height of the airflow duct  704  as shown progressively in  FIGS. 9   a  to  c . Part  713  of the valve serves as a counterbalance. Flap  712  and counterbalance  713  are supported in a fixed relationship to each other, i.e. flap  712  and counterbalance  713  rotate as one unitary part about support  710 . Counterbalance  713  preferably has a suitable dimension and weight, with respect to flap  712 , such that at low values of pressure difference between the inlet  701  and outlet  702  the counterbalance  713  serves to hold flap  712  in the position shown in  FIG. 9 , with the airflow duct  704  fully open. A spring  714  is positioned in contact with the counterweight arm  713  but not touching a part of the housing  705  ( FIG. 9   a ). As the air pressure increase, the flap  712  rotates about support  710  and spring  714  makes contact with the part of the housing wall ( FIG. 9   b ). The spring  714  provides a resilient force which serves to resist movement of the counterbalance  713 . At even higher values of pressure difference, flap  712  further rotates about support  710  causing spring  714  to compress ( FIG. 9   c ). Advantageously, the properties of the spring  714  cause it to exhibit a non-linear response. The spring properties should also preferably be substantially constant over the operating temperature range, e.g. a temperature range of −20° C. to +40° C. For example the spring may be made of metal. 
         [0037]    A ventilation according to  FIGS. 9   a  to  c  has been tested in accordance with the Dutch test standard NEN  1087  (edition 05/1997) at varying pressure drops across the device (X axis). The flow rates vs. pressure differences are shown in  FIG. 7 . As can be seen the flow rate remains substantially constant over the range of pressures tested, e.g. between 4 and 7 litres/s over a pressure range of 2 to 25 Pa. The present invention provides a ventilation device with which the flow rate varies by less than ±60%, e.g. less than ±50% or less than ±40% over a pressure drop range ratio of 5:1, preferably 10:1 (e.g. from 2 to 20 Pa). 
         [0038]    The invention is not limited to the embodiments described herein, which may be modified or varied without departing from the scope of the invention.