A valve unit having a movement system for a shutter element

Abstract

A valve unit comprises: - a shutter element (2) shaped like a blade; - a frame (3) which defines an opening (4) through which a material can flow; - a motor unit (6) comprising an electric motor (7) for moving the shutter element (2) relative to the frame (3) from a closed position, in which the opening (4) is closed, to an open position, in which the opening (4) is open; - a motion transmission mechanism for transmitting motion from the motor unit (6) to the shutter element (2). The motion transmission mechanism comprises a transmission element (9, 10) which can be rotated by the motor unit (6). The transmission element (9, 10) is intended to engage with a track (11) associated with the shutter element (2). The track (11) has a curvilinear geometry so configured that the shutter element (2) is movable from the closed position to the open position by driving the electric motor (7) in the same rotation direction in which the electric motor (7) is driven for moving the shutter element (2) from the open position to the closed position.

Description

[0001] A valve unit having a movement system for a shutter element DESCRIPTION

[0002] The invention relates to a valve unit, in particular of the guillotine type. The valve unit according to the invention is in particular, but not exclusively, suitable for being mounted in plants for treating flowable materials comprising powder or granules. In particular, the valve unit according to the invention is suitable for being associated with silos or hoppers from which a flowable material can flow downwards. The valve unit according to the invention can be mounted at a lower opening of the silo or hopper and has a shutter element that is selectively moved between an open position and a closed position to control the flow of the flowable material.

[0003] Guillotine valves are known which comprise a shutter element, shaped like a blade, operated between an open position and a closed position by a pneumatic actuator.

[0004] The guillotine valves in which the shutter element is operated pneumatically generally function well. However, these valves have some drawbacks related to the use of compressed air.

[0005] For example, high costs are required to compress the air to a pressure sufficient to efficiently operate the shutter element. In addition, leaks of compressed air can occur in the circuit through which the compressed air flows, resulting in energy losses and wastage.

[0006] In addition, the compressed air must be treated to remove moisture and this treatment does not always provide adequate results.

[0007] In order to increase the efficiency of the prior art valves, it is therefore appropriate to replace the pneumatic actuator with a different type of driving mechanism, in particular with an electric driving mechanism.

[0008] However, in order to replace the pneumatic actuator with an electric actuator it is necessary to redesign the movement system with which movement is transferred from the actuator to the shutter element, in such a way that the movement system is compatible with an electric actuator.An object of the invention is to improve the valve units, in particular of the guillotine type.

[0009] Another object is to increase the efficiency of valve units, in particular of the guillotine type.

[0010] A further object is to provide a valve unit having a blade-shaped shutter element, wherein the shutter element is actuated electrically.

[0011] Another object is to provide a valve unit, in particular of the guillotine type, which requires reduced maintenance operations.

[0012] A further object is to provide a valve unit having a blade-shaped shutter element, wherein the shutter element moves easily between an open position and a closed position, minimising the risks of jamming.

[0013] According to the invention, a valve unit is provided comprising:

[0014] - a shutter element shaped like a blade;

[0015] - a frame which defines an opening through which a material can flow; - a motor unit comprising an electric motor for moving the shutter element relative to the frame from a closed position, in which the opening is closed, to an open position, in which the opening is open; - a motion transmission mechanism for transmitting motion from the motor unit to the shutter element;

[0016] wherein the motion transmission mechanism comprises a transmission element which can be rotated by the motor unit, the transmission element engaging with a track associated with the shutter element, the track having a curvilinear geometry so configured that the shutter element is moved from the closed position to the open position by driving the electric motor in the same rotation direction in which the electric motor is driven for moving the shutter element from the open position to the closed position.

[0017] In the valve unit according to the invention, an electric motor is provided which replaces the pneumatic actuator of the prior art. This allows to overcome the drawbacks related to the use of compressed air, which must be pressurised, dehumidified and circulated inside leak-free circuits.In the valve unit according to the invention, the electric motor rotates in the same direction both when the shutter element is brought from the closed position to the open position along an opening stroke, and when the shutter element is brought from the open position to the closed position along a closing stroke.

[0018] This makes it easier to control the electric motor and makes it unnecessary to use devices that allow the rotation direction of the electric motor to be reversed.

[0019] Using an electric motor allows the operation of the valve unit according to the invention to be controlled more efficiently. For example, it is possible to provide an electronic control circuit by means of which the position of the shutter element can be controlled remotely, in particular by connecting the valve unit to a central control unit.

[0020] The curvilinear geometry of the track allows the rotation of the electric motor to be efficiently transformed into a linear back and forth movement of the shutter element, optimising the distribution of forces on the shutter element. It is also possible to choke the valve unit, which would be complicated if a pneumatic drive were used.

[0021] The shutter element extends mainly in a plane.

[0022] The shutter element is movable along the opening stroke and along the closing stroke with a linear movement, back and forth, parallel to a movement direction.

[0023] In an embodiment, the track is symmetrical with respect to a plane of symmetry perpendicular to the plane defined by the shutter element, the plane of symmetry extending parallel to the movement direction.

[0024] The plane of symmetry divides the opening into two equal portions.

[0025] In an embodiment, the track is shaped as a circular arc having a concavity facing towards the opening.

[0026] The circular arc is centred at the point of application of a resistant force which opposes movement of the shutter element along the closing stroke or respectively along the opening stroke.In an embodiment, the transmission element comprises an arm having an end rotatably supported by the motor unit, and a further end, opposite said end.

[0027] In an embodiment, the transmission element further comprises an engagement element suitable for engaging with the track.

[0028] The engagement element may be supported by the further end of the arm. The circular arc may have a radius equal to the distance between the point of application of the resistant force and the centre of the engagement element, in a configuration in which the transmission element is arranged perpendicularly to the plane of symmetry.

[0029] This minimises the risk that, during the opening stroke or the closing stroke, the shutter element rotates in an undesired manner around an axis perpendicular to a plane defined by the shutter element. If this rotation occurs, angular zones of the shutter element could jam against the frame, for example against one or more gaskets supported by the frame, and damage these gaskets, in addition to sliding with difficulty along the movement direction.

[0030] In an embodiment, a closing portion of the shutter element suitable for engaging in the opening in the closed position is free of guide rolling elements.

[0031] Any guide rolling elements intended to enter the opening should be replaced or repaired frequently due to contact with material flowing through the opening in the open position. For this reason, eliminating guide rolling bearings from the closing portion allows the maintenance and repair operations of the valve unit to be simplified.

[0032] In an embodiment, the shutter element is provided with a pair of guide elements arranged to engage respective lateral guides.

[0033] The lateral guides extend along the movement direction.

[0034] The guide elements are supported by the shutter element at respective positions near two ends of the track.This further reduces the risks that the shutter element rotates around an axis perpendicular to the plane of the shutter element, jamming on a respective supporting structure.

[0035] The invention can be better understood and implemented with reference to the accompanying drawings which illustrate a non-limiting example embodiment of it and wherein:

[0036] Figure 1 is a plan view of a valve unit of the guillotine type, comprising a shutter element arranged in a closed position;

[0037] Figure 2 is a schematic plan view of the valve unit of Figure 1 , showing the shutter element in an open position;

[0038] Figure 3 is a view like that of Figure 2, showing the shutter element in the closed position;

[0039] Figure 4 is a view like that of Figure 2, showing the shutter element in an intermediate position between the open position and the closed position; Figure 5 is a cross-section along the plane V-V of Figure 1 ;

[0040] Figure 6 is a cross-section along the plane VI-VI of Figure 1.

[0041] Figures 1 , 5 and 6 show in detail a valve unit 1 of the guillotine type, particularly suitable for being installed in a plant for processing flowable materials, such as powders, or granules, or flakes.

[0042] The valve unit 1 can for example be installed at a lower end of a silo or hopper intended to contain the flowable material, in such a way as to allow the downward flow of the flowable material, or alternatively block such flow. However, the valve unit 1 can also be used in apparatuses other than those mentioned above, for example to control the flow of a liquid in a pipeline. The valve unit 1 comprises a shutter element 2, which can be shaped like a blade or plate. The shutter element 2 is slidable in a movement direction M between a closed position, shown in Figure 1, and an open position, shown schematically in Figure 2.

[0043] The valve unit 1 further comprises a frame 3, which defines an opening 4. For example, the frame 3 may surround the opening 4. In the example shown, the opening 4 has a quadrangular shape, in particular square, butother shapes are possible for the opening 4. The opening 4 could for example be rectangular, polygonal, circular, or other.

[0044] The shutter element 2 has a substantially flat geometry and extends mainly in a plane. The shutter element 2 therefore defines a plane. The shutter element 2 moves in the plane that the shutter element 2 defines for being displaced between the closed position and the open position. The movement direction M is therefore parallel to the plane defined by the shutter element 2.

[0045] In the closed position, the shutter element 2 is arranged at the opening 4 so as to close the latter, thereby preventing the passage of the flowable material through the opening 4. In the open position, the shutter element 2 is arranged outside the opening 4, in particular in a lateral position with respect to the opening 4, and allows the flowable material to flow through the opening 4.

[0046] In more detail, the shutter element 2 may comprise a closing portion 29 which is configured to be positioned at the opening 4 in the closed position, so as to close the opening 4. The shutter element 2 may further comprise an outer portion 12 which is arranged outside the opening 4, both in the open position and in the closed position. The outer portion 12 is a continuation of the closing portion 29.

[0047] If the valve unit 1 is associated with a silo or hopper, the valve unit 1 is positioned below the silo or hopper, in such a way that the shutter element 2 lies on a horizontal plane and is horizontally movable between the open position and the closed position. However, other arrangements are possible. For example, if the valve unit 1 is associated with a pipeline, the valve unit 1 could be mounted such that the shutter element 2 lies in a vertical plane and moves along a vertical direction while remaining parallel to itself.

[0048] The frame 3 comprises a supporting structure 18, for example metallic, and at least one gasket 19, supported by the supporting structure 18. In the example shown, the gasket 19 is an upper gasket, arranged above thesupporting structure 18. The gasket 19 is anchored to the supporting structure 18.

[0049] The gasket 19 surrounds the opening 4, so as to leave the opening 4 uncovered. The gasket 19 has a perimeter sealing zone 20 which, in the closed position, is arranged in contact with the shutter element 2. The perimeter sealing zone 20 may be shaped like a sealing lip. In an alternative embodiment, the perimeter sealing zone 20 may be shaped differently from what is shown in the drawings and may for example comprise two sealing lips.

[0050] The perimeter sealing zone 20 exerts a sealing action in contact with the shutter element 2, preventing the material contained in the silo or hopper (or, more generally, present upstream of the valve unit 1) from flowing past the shutter element 2 when the latter is in the closed position. The gasket 19 prevents that, in the closed position of the shutter element 2, there are leaks of material through the valve unit 1.

[0051] In the example shown, in which the opening 4 has a quadrilateral shape, the perimeter sealing zone 20 comprises a pair of longitudinal edges 21 , arranged parallel to the movement direction M, and a pair of transversal edges 22, arranged transversely, for example perpendicularly, to the movement direction M.

[0052] The longitudinal edges 21 may be straight and parallel to each other. The transversal edges 22 may also be straight and parallel to each other. The longitudinal edges 21 may be perpendicular to the transversal edges 22. A further gasket 34 may also be provided, the further gasket 34 being visible in Figure 5 and arranged below the supporting structure 18.

[0053] In the example shown, the further gasket 34 extends transversely to the movement direction M near an end of the opening 4 through which the shutter element 2 enters and exits the opening 4.

[0054] Other geometric shapes of the further gasket 34 are however possible. For example, the further gasket 34 could surround the opening 4 as does the upper gasket 19.More generally, if the valve unit 1 is installed with an orientation such that the shutter element 2 is not arranged horizontally (for example, it lies in a vertical plane), the gasket 19 may be arranged in contact with a face of the shutter element 2 facing upstream of the valve unit 1 with respect to a flow direction of the material flowing through the opening 4. The further gasket 34 may instead be facing downstream of the valve unit 1 with respect to the direction of flow of the material flowing through the opening 4.

[0055] A pair of lateral supports 23 is also provided, the lateral supports 23 being arranged below (or more generally downstream of) the shutter element 2 to support and guide the shutter element 2 while the latter is positioned at least partially at the opening 4.

[0056] The lateral supports 23 can extend along two sides of the opening 4 arranged parallel to the movement direction M, for example below the longitudinal edges 21 of the gasket 19. In the closed position, the shutter element 2 therefore has two longitudinal edge zones interposed between the lateral supports 23 and the longitudinal edges 21 of the gasket 19. The lateral supports 23 are arranged in a fixed position and can be fixed to the supporting structure 18.

[0057] The valve unit 1 further comprises a motor unit 6 for moving the shutter element 2 between the open position and the closed position.

[0058] The motor unit 6 comprises an electric motor 7. The motor unit 6 may further comprise a reducer 8 coupled to the electric motor 7 for providing as output a rotary motion having the desired characteristics as regards the speed of rotation, the rotation direction and the position of the axis about which rotation takes place.

[0059] Between the motor unit 6 and the shutter element 2 there is interposed a motion transmission mechanism, or movement system, for transmitting motion from the motor unit 6 to the shutter element 2, in such a way that the latter moves along a desired trajectory and with a predetermined law of motion.The motion transmission mechanism may comprise a transmission element, which may include for example at least one arm 9 connected to a drive shaft of the motor unit 6.

[0060] The transmission element may also comprise an engagement element 10, in particular supported at one end of the arm 9.

[0061] The engagement element 10 may comprise rolling means, for example at least one rolling bearing.

[0062] In a version not shown, it is also possible to use engagement elements other than the rolling bearing, for example a bushing made of a synthetic polymeric material having a low friction coefficient, or other.

[0063] The engagement element 10 is arranged for engaging a track 11 , which is fixed relative to the shutter element 2.

[0064] In the example shown, the track 11 is formed in the outer portion 12 of the shutter element 2.

[0065] In particular, the track 11 can be shaped as a slot formed in the outer portion 12. This condition is however not necessary and the track 11 could be shaped differently from a slot, for example it could comprise a groove not passing through the thickness of the outer portion 12, or other.

[0066] The track 11 has a curvilinear shape and can in particular be shaped as a circular arc, having a concavity facing the opening 4. The centre of the circular arc defining the track 11 may in particular lie within the opening 4. In the example shown, the track 11 is symmetrical with respect to a plane of symmetry P arranged perpendicularly to the plane identified by the shutter element 2.

[0067] The engagement element 10 engages with the track 11. In the example shown, in which the engagement element 10 comprises a rolling bearing, the latter is received in the slot which defines the track 11.

[0068] The transmission element or arm 9 can have an end 24 rotatably connected to the motor unit 6, so as to be rotatable about a rotation axis R. In the example shown, the end 24 is rotatably coupled with the reducer 8. The rotation axis R can be arranged vertically, in the event that - as shown inthe drawings - the shutter element 2 lies on a horizontal plane. The rotation axis R can be perpendicular to the plane defined by the shutter element 2. The transmission element or arm 9 also has a further end 25, opposite the end 24. The engagement element 10 can be mounted at the further end 25, for example in such away as to be freely rotatable about an axis R1 , parallel to the rotation axis R.

[0069] The valve unit 1 comprises a supporting arrangement 17 for supporting the motor unit 6 and the motion transmission mechanism. The supporting arrangement 17 extends outside the frame 3 and alongside the latter.

[0070] The supporting arrangement 17 may have the shape of a frame and may define an inner space 13 for receiving the shutter element 2 when the latter is in the open position and is therefore arranged outside the opening 4. The inner space 13 also houses the outer portion 12 of the shutter element 2, both in the open position and in the closed position. The supporting arrangement 17 may further comprise a transversal member 14 extending transversely to the movement direction M for supporting the motor unit 6. As shown in Figure 5, the valve unit 1 may further comprise two lateral guides 15 extending parallel to the movement direction M to keep the shutter element 2 parallel to the movement direction M while the shutter element 2 moves between the open position and the closed position. The lateral guides 15 can be shaped as rails formed along respective sides, arranged parallel to the movement direction M, of the supporting arrangement 17.

[0071] At least two guide elements 16 are furthermore provided, shown only partially in Figure 1 , the guide elements 16 engaging in the lateral guides 15. The guide elements 16 may comprise respective bearings, for example of the rolling type, supported by the outer portion 12 of the shutter element 2. When the shutter element 2 is moved back and forth along the movement direction M, the guide elements 16 slide within the lateral guides 15, so as to prevent the shutter element 2 from rotating about an axis perpendicular to the plane on which the shutter element 2 extends, which could lock theshutter element 2 in a rotated position and prevent the shutter element 2 from sliding correctly along the lateral guides 15.

[0072] In order to move the shutter element 2 from the closed position to the open position or vice versa, the electric motor 7 is driven and rotated in a predetermined rotation direction.

[0073] In the example shown, the rotation takes place in a clockwise direction, as shown by the arrow F in Figure 2, but this condition is not necessary and the rotation direction can be freely chosen depending on the geometry of the valve unit 1.

[0074] The electric motor 7 rotates the arm 9 about the rotation axis R in the predetermined rotation direction. The further end 25 of the arm 9, which supports the engagement element 10, is thus moved along a circular trajectory around the rotation axis R. During rotation around the rotation axis R, the engagement element 10, which is constrained to remain engaged with the track 11 , transmits to the shutter element 2 a force, having a driving component parallel to the movement direction M, which moves the shutter element 2 parallel to the movement direction M.

[0075] Depending on the position of the engagement element 10 along the track 11 , the driving component of the force transmitted to the shutter element 2 can be directed towards the opening 4, in which case the shutter element 2 is moved towards the closed position, or away from the opening 4, in which case the shutter element 2 is moved towards the open position.

[0076] In this way it is possible to move the shutter element 2 linearly back and forth, parallel to the movement direction M.

[0077] Figures 2 to 4 schematically show some significant positions reached by the shutter element 2 during operation.

[0078] In particular, Figure 3 refers to the closed position of the shutter element 2, also shown in Figure 1.

[0079] In this position, the engagement element 10 is arranged in the centre of the track 11. In particular, the axis R1 of the engagement element 10 lies on the plane of symmetry P of the track 11. As the arm 9 is rotated about therotation axis R by the electric motor 7, the engagement element 10 moves towards an end region of the track 11 , which in the example shown is the end region 26 shown in Figure 4. This Figure refers to an intermediate position that is reached while the shutter element 2 is moved from the closed position to the open position.

[0080] By continuing to rotate the arm 9, the engagement element 10 moves back towards the centre of the track 11 until it is positioned again at the plane of symmetry P of the track 11 , as shown in Figure 2. When this happens, the shutter element 2 has reached the open position.

[0081] The shutter element 2 has been moved along an opening stroke, to bring the shutter element 2 from the closed position to the open position.

[0082] In the closed position, as shown in Figure 3, the engagement element 10 is interposed between the opening 4 and the end 24 of the arm 9.

[0083] In the open position, as shown in Figure 2, the end 24 of the arm 9 is interposed between the opening 4 and the engagement element 10.

[0084] When it is desired to bring the shutter element 2 back to the closed position, the electric motor 7 is again rotated in the same rotation direction in which the electric motor 7 rotated when the shutter element 2 was brought from the closed position to the open position. The arm 9 is thus rotated about the rotation axis R. As a result, the engagement element 10 is moved along the track 11 towards a further end region 27 of the latter, opposite to the end region 26. By continuing to rotate the electric motor 7, the engagement element 10 moves away from the further end region 27 and returns to the centre of the track 11. At this point the closed position of the shutter element 2, shown in Figure 3, has been reached. The shutter element 2 has been moved from the open position to the closed position along a closing stroke. The shutter element 2 moves back and forth along the movement direction M with a speed that has a sinusoidal trend. The speed of the shutter element 2 starts from a zero value in the closed (or open) position, progressively increases until it reaches a maximum value and progressively returns to zero.The rotation direction of the electric motor 7 is the same both during the closing stroke that brings the shutter element 2 from the open position to the closed position, and during the opening stroke that brings the shutter element 2 from the closed position to the open position. It is therefore not necessary to reverse the rotation direction of the electric motor 7 depending on whether the shutter element 2 is moving along the opening stroke or along the closing stroke.

[0085] The electric motor 7 is rotated by a certain angle in a predetermined rotation direction along the closing stroke and stopped when the shutter element 2 has been brought to the closed position. When it is desired to reopen the opening 4, the electric motor 7 is again rotated, in the same direction as the previous rotation, and starting from the angular position that its drive shaft had reached when it had stopped in the closed position.

[0086] During rotation, the electric motor 7 has a substantially constant angular speed.

[0087] As previously mentioned, the track 11 may have the shape of a circular arc. In order to determine the curvature of the track 11 , that is, the radius of curvature of a median line thereof, it is possible to proceed as described below with reference to Figure 4.

[0088] The plane of symmetry P, which divides the shutter element 2 into two symmetrical parts, has been defined previously.

[0089] An axis of symmetry of the shutter element 2 is indicated with Y. The axis of symmetry Y, in a plan view, is defined by the intersection of the plane of symmetry P with the plane identified by the shutter element 2.

[0090] On the axis of symmetry Y a rotation point C lies, the rotation point C being defined as the intersection between the rotation axis R of the arm 9 and the plane identified by the shutter element 2 (plane of the sheet).

[0091] The distance between the rotation axis R of the arm 9 and the axis R1 of the engagement element 10 is indicated with d.

[0092] The position is considered in which the arm 9, schematically shown in Figure 4 as a segment of length d, is arranged perpendicularly to the axisof symmetry Y, which corresponds to the position of the engagement element 10 in which the engagement element 10 is arranged in an end region of the track 11 , for example at the end region 26.

[0093] In addition to the force transmitted by the motor unit 6 through the arm 9 and the engagement element 10, the shutter element 2 is acted upon by a total resistant force mainly related to the friction that opposes the movement of the shutter element 2 parallel to the movement direction M.

[0094] The total resistant force is determined by a plurality of contributions, which may include:

[0095] - a first resistant force acting along a lateral interaction zone, due to friction between the shutter element 2 and a longitudinal edge 21 of the gasket 19, as well as friction between the shutter element 2 and a lateral support 23;

[0096] - a second resistant force acting along a lateral interaction zone, due to the friction between the shutter element 2 and the other longitudinal edge 21 of the gasket 19, as well as to the friction between the shutter element 2 and the other lateral support 23; - a resistant force acting along a transversal interaction zone, due to the friction between the shutter element 2 and the transversal edge 22 of the gasket 19 closest to the motor unit 6, as well as to the friction between the shutter element 2 and the further gasket 34. This resistant force can be given by the sum of various components, in the event that, for example, the gasket 19 and / or the further gasket 34 have several sealing lips;

[0097] - a resistant force due to the weight of the flowable material weighing on the portion of the shutter element 2 positioned inside the opening 4.

[0098] The total resistant force is determined as well as its point of application, indicated with PT1 in Figure 4.

[0099] The track 11 is designed such that its median line has the shape of a circular arc whose centre is the point PT 1 and whose radius has a length L equal tothe distance between the point PT1 and the end of the segment of length d furthest from the axis of symmetry Y, in the configuration in which the segment of length d is perpendicular to the axis of symmetry Y.

[0100] In other words, the average radius of the track 11 is equal to the distance between the point of application (PT1) of the total resistant force and the axis R1 of the engagement element 10, in a position in which the arm 9 is arranged perpendicularly to the plane of symmetry P.

[0101] This position corresponds to the position in which the risk that the shutter element 2 may rotate around an axis perpendicular to the plane defined by it is greatest. If this happens, respective front angular areas of the shutter element 2, further away from the motor unit 6, may jam against the frame 3, that is, get stuck in contact with the latter, thereby damaging the gasket 19 and hindering the movement of the shutter element 2.

[0102] The position in which the arm 9 is arranged perpendicularly to the plane of symmetry P can also be defined as a maximum stress configuration, in which the effort that the electric motor 7 must make to rotate the arm 9 and then move the shutter element 2 in the movement direction M is maximum. By choosing the average radius of the track 11 as indicated above, the torque that would tend to rotate the shutter element 2 around the axis perpendicular to the plane defined by it (vertical axis) is minimised and the risk of jamming is consequently minimised.

[0103] It is thus possible to avoid using guide rolling bearings in the closing portion 29 of the shutter element 2. In other words, the closing portion 29 may be free of guide rolling bearings, which means that there are no guide rolling bearings associated with, for example supported by, the closing portion 29. This is appreciable, as any guide rolling bearings associated with the guide portion 29 would be soiled by the flowable material positioned upstream of the valve unit 1 and would have to be frequently replaced or serviced. The risk of jamming is also limited owing to the guide elements 16, which cooperate with the lateral guides 15 to keep the shutter element 2 parallel to itself.It is advisable to position the guide elements 16 as close as possible to the engagement element 10, along the movement direction M. In this way the guide elements 16 are arranged close to the point of application of the force that moves the arm 9. Furthermore, the guide elements 16 are external to the frame 3, that is, far from the zone where the flowable material passing through the opening 4 is present when the shutter element 2 is arranged in the open position. This prevents the guide elements 16 from being soiled by such material.

[0104] In particular, the guide elements 16 are positioned near the ends of the track 11 , in a position as close as possible to the end regions 26, 27 of the track 11 , along the movement direction M.

[0105] By so doing, the guide elements 16 keep the shutter element 2 guided in the movement direction M, both during the closing stroke and during the opening stroke.

[0106] The shutter element 2 is consequently moved between the open position and the closed position minimising the stresses acting on the components of the valve unit 1.

[0107] In an embodiment, the shutter element 2 can be stopped in an intermediate position between the open position and the closed position. This can be done if the valve unit 1 is to be “choked”. If the shutter element 2 is arranged in the intermediate position, the flow rate of material flowing through the opening 4 is lower than it would be if the opening 4 were fully open, that is, if the shutter element 2 were arranged in the open position.

[0108] In order to bring the shutter element 2 from the intermediate position back to the starting position (selected between the open position and the closed position) it is possible to operate the electric motor 7 in the rotation direction opposite to that used to reach the intermediate position itself. In fact, the reversal of the motion allows the stroke necessary to return the shutter element 2 to the starting position to be minimised.

Claims

CLAIMS1. A valve unit comprising:- a shutter element (2) shaped like a blade;- a frame (3) which defines an opening (4) through which a material can flow;- a motor unit (6) comprising an electric motor (7) for moving the shutter element (2) relative to the frame (3) from a closed position, in which the opening (4) is closed, to an open position, in which the opening (4) is open, or vice versa;- a motion transmission mechanism for transmitting motion from the motor unit (6) to the shutter element (2),wherein the motion transmission mechanism comprises a transmission element (9, 10) which can be rotated by the motor unit (6), the transmission element (9, 10) engaging with a track (11) associated with the shutter element (2), the track (11) having a curvilinear geometry so configured that the shutter element (2) can be moved from the closed position to the open position by driving the electric motor (7) in the same rotation direction in which the electric motor (7) is driven for moving the shutter element (2) from the open position to the closed position.

2. The valve unit according to claim 1 , wherein the track (11) is shaped like a circular arc having a concavity facing towards the opening (4).

3. The valve unit according to claim 2, wherein the shutter element (2) is movable in a movement direction (M) between the open position and the closed position, and wherein the circular arc is centred in the point of application (PT 1 ) of the resistant force which opposes the movement of the shutter element (2) along the movement direction (M) in a maximum force configuration, the maximum force configuration corresponding to the position in which the transmission element (9, 10) is positioned perpendicularly to a plane of symmetry (P) of the track (11 ).

4. The valve unit according to any preceding claim, wherein the transmission element (9, 10) comprises an arm (9) having an end (24) which can be rotated by the motor unit (6) and a further end (25) opposite said end (24), the transmission element (9, 10) further comprising an engagement element (10) supported by the end (24) and suitable for engaging with the track (11).

5. The valve unit according to claim 4, as appended to claim 3, wherein the circular arc has a medium radius equal to the distance (L) between the point of application (PT 1 ) of the resistant force and the centre of the engagement element (10), in the maximum force configuration which is defined when the arm (9) is positioned perpendicularly to the plane of symmetry (P).

6. The valve unit according to claim 4 or 5, wherein the engagement element (10) comprises rolling means supported by said further end (25) in such a way as to be freely rotatable relative to the arm (9).

7. The valve unit according to any preceding claim, wherein the shutter element (2) comprises a closing portion (29) which can be positioned at the opening (4) for closing the opening (4) and an outer portion (12) which is arranged outside the opening (4) both in the open position and in the closed position, the track (11 ) being formed in the outer portion (12).

8. The valve unit according to claim 7, wherein the track (11 ) is a slot which passes through the thickness of the outer portion (12).

9. The valve unit according to claim 7 or 8, wherein the outer portion (12) of the shutter element (2) supports a pair of guide elements (16) arranged on opposite sides of the shutter element (2) close to respective end regions (26, 27) of the track (11), each guide element (16) being arranged forengaging in a corresponding lateral guide (15) extending parallel to a movement direction (M) along which the shutter element (2) is movable between the open position and the closed position.

10. The valve unit according to claim 9, wherein each guide element (16) comprises a guide rolling bearing.

11. The valve unit according to any preceding claim, and further comprising a supporting structure (17) arranged alongside the frame (3), the supporting structure (17) having an aperture (13) for receiving the shutter element (2) when the opening (4) is open.

12. The valve unit according to claim 11, wherein the motion transmission mechanism and the motor unit (6) are supported by the supporting structure (17) and are positioned, in a plan view, within the dimensions of the supporting structure (17).

Images