Vacuum boxes for belt conveyors and belt conveyors for transporting plywood sheets

Abstract

A vacuum box (110) for a vacuum belt conveyor system (1000) for transporting veneer sheets (100) is provided, the vacuum box (110) comprising a housing having a top plate (212), wall plates (214), a bottom plate (210) and end plates, at least one opening (410) is provided along the length of the vacuum box (110) between the bottom plate (210) of the housing and each wall plate (214) of the housing, the shape of the bottom plate (210) being such that an edge area (EA) of the bottom plate (210) is farther away from an imaginary plane (IP) along which the veneer sheets (100) can be transported than a central area (MA) of the bottom plate (210). A vacuum belt conveyor system (1000) is also provided.

Description

[Technical Field]

[0001] The present invention relates generally to the technical field of handling veneer sheets. In particular, the present invention relates to the transport of veneer sheets. [Background technology]

[0002] One commonly used solution for transporting plywood sheets in a production line is to use a so-called vacuum belt conveyor, which consists of an elongated box structure inside which a vacuum can be placed. At least one lane-like perforation extends along the bottom of the box, through which the bottom region of the box can be placed under the effect of a vacuum that prevails within the case. The lane is bounded by a conveyor belt running along both edges thereof which is in dragging contact with the lower surface of the vacuum box. The veneer sheet to be transported is placed under vacuum effect on its upper surface through openings, so that the sheet is moved by the belt to the destination where it is released from the vacuum effect by stamping with a kicker arm provided on the conveyor. An example of such a vacuum belt conveyor is disclosed in document US Patent Application Publication No. 2009 / 0057102 A1.

[0003] Vacuum belt conveyors are commonly used, among other things, to transport veneer sheets, even in the embodiment where the veneer sheets are placed on the conveyor. A vacuum within the conveyor acts on the lower surface of the veneer sheet, holding it against the belt that carries it. In these embodiments, the belt is also positioned adjacent to and bounds the vacuum area.

[0004] Although known vacuum belt conveyors are an efficient solution for transporting veneer sheets, their energy efficiency is not optimal. In other words, the energy consumption, i.e., power consumption, of known vacuum belt conveyors is large compared to the vacuum effect and sheet lifting capacity required to keep the veneer sheets securely under suction, which is achieved by providing a partial vacuum, i.e., a pressure lower than ambient pressure. The main reason for the suboptimal energy consumption is that known solutions have been developed without paying sufficient attention to aspects related to air flow and its physical properties, which results in the need for a large volume flow to create a partial vacuum that is large enough to cause the lift required to transport the veneer sheets. This means that a large capacity blower is required to generate the required volume flow in the vacuum belt conveyor, which means additional costs not only in terms of the price of the blower but also in terms of the power required.

[0005] In view of the above, there is a need to introduce solutions such as vacuum boxes and belt conveyors equipped with such vacuum boxes that will alleviate the above mentioned problems and therefore at least partially improve the energy consumption of such systems. Summary of the Invention [Means for solving the problem]

[0006] SUMMARY The following presents a simplified summary in order to provide a basic understanding of some aspects of various embodiments of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplary embodiments of the invention.

[0007] SUMMARY OF THE INVENTION The object of the present invention is to provide a vacuum belt conveyor system for transporting vacuum boxes and plywood sheets.

[0008] The object of the invention is achieved by a vacuum box and a vacuum belt conveyor system for transporting plywood sheets as defined by the respective independent claims.

[0009] According to a first aspect, there is provided a vacuum box for a vacuum belt conveyor system for transporting veneer sheets, the vacuum box comprising a housing having a top plate, wall plates, a bottom plate and end plates, at least one opening being provided along the length of the vacuum box between the bottom plate of the housing and each of the wall plates of the housing, the shape of the bottom plate being such that edge regions of the bottom plate are farther away from an imaginary plane along which the veneer sheets can be transported than a central region of the bottom plate.

[0010] At least one opening provided between the bottom plate of the housing and each wall plate of the housing may have a width between 6 and 12 mm.

[0011] The wall panel may include a shoulder piece extending toward the outer edge of the base panel. For example, the length of the shoulder piece towards the outer edge of the base plate may be at least 10 mm.

[0012] The vacuum box may have a front opening that extends across the width of the base plate.

[0013] Furthermore, the height of the bottom plate can be between 4.5 and 28 mm.

[0014] The base plate may have at least one of the following shapes: at least partially V-shaped, at least partially curved, with a central region provided to run parallel to an imaginary plane along which the veneer sheet can be conveyed. For example, the base plate may have at least a central region with a V-shape, and the bending angle of the V-shaped central region may be between 150 and 175°.

[0015] According to a second aspect, there is provided a vacuum belt conveyor system for conveying plywood sheets, the vacuum belt conveyor system comprising: a vacuum box according to the first aspect defined above; several suction devices configured to suck air from the vacuum box through at least one conduit to create a vacuum effect through at least one opening provided between a bottom plate of the vacuum box housing and each wall plate of the vacuum box housing; and a plurality of belt conveyor devices coupled to the vacuum box on both sides thereof for transporting the plywood sheets by vacuum effect while suspended on the belts of the plurality of belt conveyor devices.

[0016] The base plate may be positioned such that a central region of the base plate runs above an imaginary plane defined by belt sections of a multiple belt conveyor device on which the plywood sheet can be suspended. For example, the distance between the central region of the bottom plate and the imaginary plane may be between 5 and 12 mm.

[0017] Furthermore, the vacuum belt conveyor system may further comprise several kicker arms for providing a force to the veneer sheets suspended by the vacuum effect to release them from the suspension.

[0018] Some suction devices may be at least one of the following types: blower, vacuum pump.

[0019] The term "several" as used herein refers to any positive integer starting from 1, for example 1, 2, or 3.

[0020] The term "plurality" as used herein refers to any positive integer starting from 2, for example 2, 3, or 4.

[0021] Various exemplary and non-limiting embodiments of the present invention, both as to structure and method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplary and non-limiting embodiments when read in connection with the accompanying drawings.

[0022] The verbs "comprise" and "include" are used in this document as open limitations that neither exclude nor require the presence of unrecited features. The features recited in the dependent claims are mutually freely combinable unless expressly stated otherwise. Furthermore, it must be understood that the use of "a" or "an", ie the singular, throughout this document does not exclude the plural. [Brief explanation of the drawings]

[0023] Embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

[0024] [Figure 1] 1 illustrates a schematic diagram of a vacuum belt conveyor according to an example. [Figure 2] 1 shows a schematic view of an example vacuum box from a first perspective; [Figure 3A] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3B] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3C] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3D] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3E] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3F] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3G]10A-10C illustrate various exemplary shapes of the base plate. [Figure 3H] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 3I] 10A-10C illustrate various exemplary shapes of the base plate. [Figure 4] 10 shows a schematic view of an example vacuum box from another perspective. [Figure 5] 10 illustrates a schematic diagram of a further aspect of a vacuum box according to an example; [Figure 6] 10 is a schematic diagram of another example vacuum belt conveyor; [Figure 7] 10 shows a schematic representation of a further embodiment of a vacuum box according to a further example; DETAILED DESCRIPTION OF THE INVENTION

[0025] The specific examples provided in the following description should not be construed as limiting the scope and / or applicability of the appended claims. The lists and groups of examples provided in the description below are not exhaustive unless otherwise specified.

[0026] FIG. 1 shows a schematic side view of a vacuum belt conveyor system 1000, or apparatus, according to one example of the present invention. The system 1000 is shown in a simplified manner and only a few features of the system are disclosed to provide a basic understanding of the system 1000 in which the veneer sheets 100 are transported to and from a stack of veneer sheets 100 by the vacuum belt conveyor system 1000. The vacuum belt conveyor system 1000 comprises a vacuum box 110, also known as a suction box, which defines a volume in which a partial vacuum, i.e. a pressure below the ambient pressure of the space outside the vacuum box 110, is created by several suction devices 120 configured to transport or suck air out of the vacuum box 110 as indicated by the arrows in FIG. 1 . The vacuum box 110 has a structure that improves air flow in the vacuum belt conveyor system 1000, thus at least partially reducing the energy consumption of the vacuum belt conveyor system 1000. An opening is provided at the bottom of the vacuum box 110 through which suction can be provided towards the veneer sheet 100, thus achieving gripping of the veneer sheet 100, and therefore a partial vacuum created inside the vacuum box 110 allows transport of the veneer sheet 100 below the vacuum box 110.

[0027] Furthermore, the vacuum belt conveyor system 1000 includes several belt conveyor devices 130 in which the conveyor belt moves in a loop between the running wheels. To achieve loop rotation of the conveyor belt, rotational force is applied to at least one of the wheels, for example by an electric motor. Typically, the vacuum belt conveyor system 1000 is provided with two belt conveyor devices 130 at a predetermined distance from each other. The lower part of the conveyor belt is adjusted vertically to run so that its contact surface for the veneer sheet 100 is at the same height as the bottom of the vacuum box 110 or slightly below it, and in either case the suction effect on the veneer sheet 100 is sufficient to keep it in contact with the contact surface of the conveyor belt. In the embodiment described, the veneer sheet 100 is kept suspended on a conveyor belt and can be transported to a desired location. Furthermore, the vacuum belt conveyor system 1000 may be equipped with several so-called kicker arms 140, for example on both sides of the vacuum box 110, so that the transported veneer sheets 100 can be kicked with a kicking force to release them from the suspension caused by the vacuum effect generated through the openings.

[0028] FIG. 2 shows a schematic diagram of an example of a vacuum box 110 according to the present invention. The vacuum box 110 in FIG. 2 is shown in cross section with respect to the conveying direction of the veneer sheet 100 . The example of Figure 2 also shows two belt conveyor devices 130 on either side of the vacuum box 110, towards which the veneer sheet 100 being transported, i.e., towards the belt of each belt conveyor device 130, is engaged by a partial vacuum provided inside the vacuum box 110. The vacuum box 110 has an elongated structure that forms the housing of the vacuum box 110 . The housing comprises at least a top plate 212, a wall plate 214 and a bottom plate 210, as well as end plates (not shown in Figure 2) that close the structure on both ends. The items of construction referred to may be formed, for example, from sheet metal by bending at least the top plate 212 and wall plates 214 into the shapes shown. The bottom plate 210 may be formed separately in that shape and coupled or secured to the vacuum box structure 110 by any known fastening solution, such as by applying applicable support structures and fastening devices such as screws. Alternatively, the base plate 210, shaped as described in the ensuing description, may be secured to other structures, for example, by welding to other items. In a further embodiment, the bottom plate 210 may also be formed from the same sheet metal as at least one other plate. The end plates may be secured in a similar manner. For clarity, it is worth mentioning that the top plate 212 and wall plates 214 may also be separate items that are fastened together, for example by welding, to form the elongated structure of the vacuum box 110. Thus, the use of the word "plate" should not be construed as covering only embodiments in which the plates are separate pieces fastened together; they, or at least parts of them, may be formed from one physical piece of, for example, metal sheet.

[0029] To enhance the vacuum effect directed towards the veneer sheet 100, the vacuum box 110 is configured such that the bottom plate 210 of the vacuum box 110 is molded to a predetermined shape. Advantageously, the shape or form of the base plate 210 is such that it aims to reduce the volume between the base plate 210 and the imaginary plane in which the veneer sheet 100 is conveyed. Advantageously, such a shape of the bottom plate 210 is such that its edges or edge regions are further from the imaginary plane along which the veneer sheet 100 is conveyed, in the conveying direction of the veneer sheet 100, than the central region of the bottom plate 210. In other words, the central region extends outward beyond the edges when viewed from the inside of the vacuum box 110.

[0030] According to one embodiment of the present invention, the shape of the bottom plate 210 is bent into a V-shape in the non-limiting example of FIG. 2 and is positioned so that the edge or bending edge of the V-shape runs along the length of the vacuum box 110, i.e. in the direction in which the veneer sheet 100 can be transported by the vacuum box 110 together with other entities. For example, as can be derived from FIG. 2, the apex or tip of the V-shaped bottom plate 210, i.e., the edge of the curved bottom plate 210, extends outward from the vacuum box 110, and the V-shape is symmetrical, with both sides of the curved bottom plate 210 having substantially the same length. The bending angle α of the bottom plate 210 forming the V-shape may be preferably close to a straight angle, for example between 150 and 175°, advantageously around 172°. In addition, the bottom plate 210 can be positioned relative to an imaginary plane along which the veneer sheet 100 is conveyed so that the edge of the V-shaped bottom plate 210 runs a predetermined distance above the imaginary plane, which distance can be, for example, between 5 and 12 mm, advantageously around 8.5 mm. The conveying plane of the veneer sheet 100 is defined by the belt section of the belt of the belt conveyor device 130, towards which the veneer sheet 100 can be suspended by suction achieved by a partial vacuum. The above values ​​are particularly applicable for a vacuum box 110 having a width of 226 mm and a height of 506 mm. When a V-shaped base plate 210 is used, the vacuum effect is greatest near the apex region of the V-shaped base plate 210 . This may cause some bending of the veneer sheet 100, especially in thin sheets, and the apex of the base plate 210 may provide support to the veneer sheet 100 during transport.

[0031] 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, and 31 schematically show some non-limiting examples of shapes of the base plate 210 according to the present invention. 3A to 3I, in order to improve the interpretation of each figure, an imaginary plane along which the plywood sheet 100 can be conveyed is indicated by a dashed line and is designated by the abbreviation IP. Furthermore, in Figures 3A-3I, the edge region of the floor plate is denoted by EA and the central region is denoted by MA. The shape of the bottom plate 210 in FIGS. 3A-3C is based on the V-shape already mentioned in the context of FIG. The central region MA in these embodiments can be considered the point within the base plate 210 that extends furthest outward from the inside of the vacuum box 110, or the point closest to the imaginary plane IP. The edge region EA is farther from the imaginary plane IP than the central region MA, and in the embodiment of Figures 3A-3C, the edge region is formed in a continuous manner, as in Figure 3A, or is composed of two or more sections connected together at different angles, as shown in Figures 3B and 3C. As can be seen from FIG. 3B, one section may be disposed substantially parallel to an imaginary plane IP. The embodiment of Figures 3D to 3F is based on an implementation in which the central region of the bottom plate 210 runs parallel to the imaginary plane IP, while the edge region EA consists of one or more sections arranged at various angles (singular or plural) to the imaginary plane IP. Additionally, Figures 3G-3I schematically illustrate an embodiment in which at least a portion of the base plate 210 is curved or arched, with the central region MA being the point of the curved section closest to the imaginary plane IP. As shown in Figures 3H and 3I, a portion of the edge region EA may be formed to be straight, while another portion of the edge region EA is provided to be curved. In Figure 3G, the entire bottom plate is curved. For clarity, it is worth mentioning that the bottom plate 210 shown at least in Figures 3A-3I is a cross-sectional view of the components mentioned, and their shapes are described accordingly. As can be derived from the description herein, the base plate 210 has a length in the conveying direction of the plywood sheet 100 (see, for example, FIG. 1), and the shapes described above are not related to the shape of the base plate 210 in that direction. Furthermore, the base plate 210 shown in Figures 3A-3I is a non-limiting example, and various other shapes may be provided under the present invention. As mentioned above, the shape of the bottom plate 210 in the context of the present invention is such that its edges or edge areas EA are further or more distant from the imaginary plane IP along which the veneer sheet 100 is conveyed, in the conveying direction of the veneer sheet 100, than the central area MA of the bottom plate 210. In a preferred embodiment, the height of the base plate 210, i.e. the distance between the plane passing through the edge of the base plate 210, i.e. through its outermost edge, and the plane passing through the central region MA at the point furthest from the plane passing through the edge of the base plate 210, may be between 4.5 mm and 28 mm, the mentioned planes being parallel to each other. For clarity, the height of the base plate 210 is indicated by the reference character h in Figures 3A to 3I. Such height can be provided, for example, on a V-shaped base plate 210 at an angle between 150 and 175°, where an angle of 172° would correspond to a height of 7.5 mm. Furthermore, as already mentioned in the description of FIG. 2, the apex of the V-shaped base plate 210 runs above the imaginary plane (IP) at a certain distance, which may be for example between 5 and 12 mm, advantageously around 8.5 mm. The same distance may apply with respect to any other mannerly shaped base plate 210, such as those shown as non-limiting examples in Figures 3A-3I.

[0032] FIG. 4 shows a schematic representation of the vacuum box 110 and the belt conveyor device 130 that can be seen below the vacuum box 110. The dimensions of the vacuum box 110 in Figure 4 do not necessarily correspond to an actual embodiment, and the purpose of Figure 4 is to specifically disclose how the openings 410 can be provided in the bottom plate 210 of the vacuum box 110 along the belt conveyor device 130. The bottom plate 210 in FIG. 4 has a V-shape. The opening 410 provides a path for suction to be applied inside the vacuum box 110 so that the veneer sheet 100 remains suspended against the conveyor belt of the belt conveyor device 130 during transport. The size of the opening 410 can be selected so that the combined area is optimal, such that the suction characteristics generated are as consistent and effective as possible, but also so that the size of the opening 410 at least partially prevents dirt from ending up inside the vacuum box 110, a non-limiting example of which is pieces of veneer moving along a production line. The width of the opening 410 (marked with "w" in FIG. 4) may be between 6 and 12 mm, such as 8 mm. The length of the opening 410 can be adjusted depending on the length of the vacuum box 210 . The bottom plate 210 of FIG. 4 may be secured to the wall plates 214, for example, by welding the bottom plate 210 to the respective wall plates 214 from bridge-like sections between the openings 410. As can be derived from the description herein, the number of openings 410 provided between the bottom plate 210 and the wall plate 214 of the vacuum box 110 can be implemented by manipulating the shape of the bottom plate 210 in a desired manner. Alternatively or additionally, the base plate 210 may be dimensioned in such a manner that openings 410 are formed between the noted components. This corresponds, for example, to the width of the base plate 210 being selected so that it does not extend to the wall plate 214 but is fixed in the desired position by an applicable support structure. Furthermore, to enhance the informational purposes of FIG. 4, the bent edges of the bottom plate 210 are also marked in FIG.

[0033] Although the openings 410 in FIG. 4 are longitudinal slots, the openings 410 may be provided in other ways. For example, the opening 410 may be formed from a number of smaller openings 410, such as by shorter slots, or by providing the openings 410 as a continuous series of holes in the shape of a circle. It is important that the openings 410 are implemented so that there are no long sections where there is no suction due to the absence of an opening in that area, and so that the combined area of ​​the openings 410 allows for sufficient suction for the purpose. In an advanced solution, the base plate 210 is attached to the rest of the vacuum box 110 by a bridge structure or other fastening means that has minimal effect on the air flow.

[0034] FIG. 4 also schematically illustrates a front opening 420, which is an area in the vacuum box 110 according to an example embodiment where suction can be provided in an enhanced manner so that the veneer sheet 100 can be captured, for example, from a stack or from another conveyor device. The width of the front opening 420 of the vacuum box 110 can be defined between the belt conveyor devices 130, i.e. extending across the width of the bottom plate 210, and the front opening is covered with an applicable mesh to prevent excessive amounts of dirt from ending up inside the vacuum box 110 due to suction. Additionally, the vacuum box 110 may include a support structure 430 that provides support to the veneer sheet 100 that is sucked by the partial vacuum in the front opening 420 . With respect to the front opening 420 and the support structure 430, it is worth mentioning that the belt of the belt conveyor device 130 is adjusted to provide primary support to the target veneer sheet 100 so as to enable transport of the veneer sheet 100 from the capture position along the length of the vacuum belt conveyor system 1000. Depending on the embodiment, the suction of the front opening 420 may be provided separately from other suctions of the other openings 410, for example by providing several dedicated suction devices 120 to serve the front opening 420.

[0035] In some example embodiments, a front opening 420 may be provided in the base plate 210 . This type of approach may be suitable for a vacuum box 110 in which the base plate 210 extends substantially the entire length of the suction box 110 . This front opening 420 may be machined into the base plate 210, for example, by cutting the front opening 420 into the edge of the base plate 210 that receives the veneer sheet 100. The size of the front opening 420 can be adjusted as needed, and its width is advantageously smaller than the width of the bottom plate 210 . Therefore, the support structure 430 may also be part of the base plate 210 . Also, in these embodiments, the front opening 420 can be covered with an applicable mesh so that the suction at the front opening 420 of the bottom plate 210 can be provided separately from other suctions to create enhanced suction to capture the veneer sheet 100.

[0036] The vacuum box 110 according to the present invention helps reduce the pressure drop in other areas other than the opening 410, which improves the hanging of the veneer sheet 100. This is achieved, at least in part, by providing a bottom plate that is shaped as described, thereby allowing the cross-sectional area of ​​the vacuum box 110 to be optimized, so that consistent suction is achieved.

[0037] FIG. 5 illustrates further aspects related to the shape of the vacuum box 110 according to at least some embodiments of the present invention when restricting air through the opening 410 enhances flow through the opening 410. As can be derived from FIG. 5, shoulder pieces 510 or treads are provided on the walls of the vacuum box 110 so as to extend towards the respective outer edges of the bottom plate 210 of the vacuum box 110 as shown in FIG. For example, the length of such a shoulder piece 510 may be 10 mm or more towards the outer edge of the bottom plate 210, and this kind of extension causes air restriction in an efficient manner at the opening 410 of the vacuum box 110. It is worth mentioning that at least one objective of the present invention is that the opening 410 is preferably implemented so that the edges of the opening 410 are sharp, thereby causing a pressure drop across the opening 410 in an efficient manner. This can be improved by a shoulder piece 510 as shown in FIG.

[0038] As already mentioned, the vacuum belt conveyor system 1000 comprises several suction devices 120 arranged to suck air out of the vacuum box 110 . A non-limiting example of such an embodiment is shown schematically in FIG. The purpose is to particularly disclose that several conduits 610 access the vacuum box 110 in order to convey air from the vacuum box 110 due to the suction caused by the several suction devices 120 thereof. The size of the conduits 610 , ie, in particular the diameter of each conduit 610 , is adjusted relative to the size of the opening 410 . For example, a rule of thumb may be applied such that the combined cross-sectional area of ​​the conduits 610 is doubled compared to the combined area of ​​the openings 410 . This causes air to flow through conduit 610 at half the speed compared to the flow through opening 410 . For clarity, the housing of the suction device 120 is provided so that air entrapped in the housing can be expelled from the housing in a desired manner. Also, depending on the size of the overall air flow path, the size of the suction device 120 may be selected to provide the power necessary to create a partial vacuum through the suction of air as needed.

[0039] The various embodiments of the present invention discussed thus far primarily refer to implementations in which the belt conveyor device 130 is coupled onto the outer surface of the vacuum box 110, as shown, for example, in FIGS. However, the invention is not limited to such implementations and other approaches may be taken. FIG. 7 shows a schematic example in which the belt conveyor device 130 is provided on the bottom side of the vacuum box 110. The belt conveyor device 130 may be secured thereto with a separate securing device, or in some embodiments, the ends of the wall panel 214 are bent inward and the belt conveyor device 130 is secured to the bent portion of the wall panel 214. By appropriately adjusting the components, the belt conveyor device 130 can be considered to form each shoulder piece 510 to achieve at least some of the effects achieved by the embodiment shown in FIG. 5.

[0040] In accordance with the present invention, a vacuum belt conveyor system 1000 is provided, which includes a vacuum box 110 as described herein, among other components. Other components may include, for example, several belt conveyor devices 130 arranged on either side of the vacuum box 110 in the manner described. Additionally, the vacuum belt conveyor system 1000 comprises several conduits 610 connecting the vacuum box 110 with each suction device 120 to form a flow path for air flow from the opening of the vacuum box 110 to the housing(s) of the suction device(s) 120 and ultimately out of the system. Of course, the vacuum belt conveyor system 1000 may include additional components to make the system fully operational.

[0041] As non-limiting examples of applicable suction devices 120 in the context of the present invention, mention may be made of one or more blowers or one or more vacuum pumps, with blowers being preferred. Other types of suction devices 120 may also be applied. Furthermore, the number of suction devices 120 may be selected depending on the desired suction power, but in practice it has been found that in situations where plywood sheets 100 are being transported, it is optimal to provide a suction device 120 every 2 to 4 meters along the length of the vacuum box 110.

[0042] From an operational standpoint, the vacuum belt conveyor system 1000 may be configured to operate such that the veneer sheet 100 to be transported is picked up by suction provided from the front opening 420 and the transport of the veneer sheet 100 along the vacuum box 110 is initiated by rotating the conveyor belt of the belt conveyor device 130 to which the target veneer sheet 100 is suspended so that it contacts it by suction. The openings 410 in the vacuum box 110 along the length of the vacuum box 110 as described allow the veneer sheet to remain suspended during transport, and once the veneer sheet is in the release position, the kicker arm 140 is commanded by a control signal to perform a kicking motion to release the veneer sheet from the suspension, resulting in the veneer sheet 100 dropping. The overall operation may be controlled by a control device of the system 1000 that is programmed to generate control signals to effect the transport operations.

[0043] The present invention offers many advantages over prior art solutions. Firstly, the overall system costs are reduced due to the improved vacuum effect provided by the solution according to the invention, which makes it possible to optimise the blower or any corresponding device. Additionally, because the overall air flow is reduced, smaller air filtration stations can be applied to purify the air in the production plant. Overall, the reduction in energy consumption in the transport operation and other operations associated therewith makes the entire system more environmentally friendly than prior art solutions.

[0044] The V-shaped base plate 210 has been found, based on measurements and testing, to be advantageous in a particularly efficient manner over other shapes. This relates to the partial vacuum effect achieved towards the veneer sheet 100 during transport. A further advantage of the V-shaped base plate 210 is that the sharp contact point on the veneer sheet 100, i.e. the apex of the V-shaped base plate 210, makes it possible to move the veneer sheet 100 as far away as possible from the base plate 210, which means that the suction acts on the target veneer sheet 100 over a correspondingly larger area than with other shapes of the base plate 210. The advantage of the V-shaped bottom plate 210, particularly with a wide angle α such as 172°, is that it is most common in vacuum belt conveyors that are provided to transport plywood sheets 100 with various properties such as rigidity.

[0045] The specific examples provided in the above description should not be construed as limiting the applicability and / or interpretation of the appended claims. The lists and groups of examples provided in the above description are not exhaustive unless expressly stated otherwise.

Claims

1. 1. A vacuum box (110) for a vacuum belt conveyor system (1000) for transporting plywood sheets (100), the vacuum box (110) comprising a housing having a top plate (212), wall plates (214), a bottom plate (210) and end plates, at least one opening (410) is provided along the length of the vacuum box (110) between the bottom plate (210) of the housing and each of the wall plates (214) of the housing, the shape of the bottom plate (210) being such that an edge area (EA) of the bottom plate (210) is farther from an imaginary plane (IP) along which the veneer sheets (100) can be transported than a central area (MA) of the bottom plate (210).

2. 2. The vacuum box of claim 1, wherein the at least one opening between the bottom plate of the housing and each wall plate of the housing has a width between 6 and 12 mm.

3. 3. The vacuum box (110) of claim 1 or claim 2, wherein the wall panel (214) comprises a shoulder piece (510) extending towards the outer edge of the bottom panel (210).

4. 4. The vacuum box (110) of claim 3, wherein the length of the shoulder piece (510) towards the outer edge of the bottom plate (210) is at least 10 mm.

5. The vacuum box (110) of any one of claims 1 to 4, wherein the vacuum box (110) comprises a front opening (420) for generating suction to capture the veneer sheet (100).

6. The vacuum box (110) according to any one of claims 1 to 5, wherein the height (h) of the bottom plate (210) is between 4.5 and 28 mm.

7. The vacuum box (110) according to any one of claims 1 to 6, wherein the bottom plate (210) has at least one of the following shapes: at least partially V-shaped; at least partially curved; the central region is arranged to run parallel to the imaginary plane along which the veneer sheet (100) can be conveyed.

8. 7. The vacuum box according to claim 6, wherein the bottom plate (210) comprises at least a central area (MA) having the V-shape, and the bending angle (α) of the V-shaped central area (MA) is between 150 and 175°.

9. A vacuum belt conveyor system (1000) for conveying plywood sheets (100), said vacuum belt conveyor system (1000) comprising a vacuum box (110) according to any one of claims 1 to 8; several suction devices (120) configured to suck air from the vacuum box (110) through at least one conduit (610) to create a vacuum effect through at least one opening (410) provided between a bottom plate (210) of the housing of the vacuum box (110) and each wall plate (214) of the housing of the vacuum box (110); a plurality of belt conveyor devices (130) coupled to the vacuum box (110) on both sides thereof for transporting the veneer sheet (100) suspended on the belts of the plurality of belt conveyor devices (130) by the vacuum effect; A vacuum belt conveyor system (1000) comprising:

10. 10. The vacuum belt conveyor system (1000) of claim 9, wherein the bottom plate (210) is positioned such that a central area (MA) of the bottom plate (210) runs above an imaginary plane (IP) defined by the belt sections of the plurality of belt conveyor devices (130) that can suspend the veneer sheet (100) in contact with the imaginary plane.

11. The vacuum belt conveyor system (1000) according to claim 10, wherein the distance between the central area (MA) of the bottom plate (210) and the imaginary plane (IP) is between 5 and 12 mm.

12. The vacuum belt conveyor system (1000) according to any one of claims 9 to 11, further comprising a number of kicker arms (140) for providing a force to the veneer sheet (100) suspended by the vacuum effect to release it from the suspension.

13. The vacuum belt conveyor system (1000) according to any one of claims 9 to 12, wherein the number of suction devices (120) is at least one of a blower, a vacuum pump.

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