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The present invention relates to a veneering machine, particularly for veneering parts made of wood, or other material, having a flat or variously shaped profile.
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As is known, the veneering of parts made of wood, or of other material, consists in covering said parts, produced using low-cost material, with a thin layer of fine material. The covering layer is made to adhere to the part by using appropriate adhesives and by pressing with high pressures the covering layer against the surface of the part, so that the covering layer follows the shape of the part as much as possible.
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The covering layer is compressed against the part to be covered, particularly when one face of the part has curved or shaped portions, by using specific machines. These machines are generally constituted by a main structure which supports a vat containing a liquid and being closed upwardly by an elastically deformable membrane. Above the vat there is a substantially horizontal abutment surface which is fixed to the supporting structure of the vat, and said vat can move vertically toward or away from said abutment surface. The part to be veneered, with the covering layer applied thereon, is placed on the membrane of the vat so that a substantially flat face is directed upwards, i.e. facing the abutment surface. The vat, with the part placed on the membrane, is then raised toward the abutment surface and is pushed against it by means of high-power hydraulic cylinders. The thrust applied by the hydraulic cylinders is transmitted through the part to the membrane, increasing the pressure of the liquid in the vat and consequently deforming the membrane, making it adhere to the surface of the part, or rather to the covering layer applied thereto. Obviously, in order to obtain an adequate pressure of the deformed membrane on the surface of the part, it is necessary to preset the degree of filling of the vat, which is changed in each instance according to the part by an operator.
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In practice, in known machines, the pressure required to make the covering layer adhere to the part to be veneered is obtained by moving the vat vertically by means of hydraulic cylinders which must be sized so as to ensure not only the movement of the vat but also the pressure required to make the covering layer adhere to the part.
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Furthermore, the force of the hydraulic cylinders is discharged onto the abutment surface and onto the supporting structure of the machine which accordingly must have an adequate strength. As a consequence of these requirements, known machines have considerably heavy supporting structures which significantly affect the production costs of these machines and make them difficult to transport and subsequently install.
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Another problem which can be observed in these known machines is the need to perform compensating filling of the vat in order to obtain adequate pressure in its subsequent lifting. This filling must be controlled manually, with evident problems in precision, and with the vat still spaced from the abutment surface. During this operation, the membrane may separate accidentally from the edge of the vat, since it is not contained by the abutment surface during its upward deformation, causing the spillage of the liquid and interrupting the production cycle. Even without membrane separation, the membrane in any case has a short life and is often overstressed during this step.
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Another problem of these machines is constituted by the time required to adequately heat the liquid in the vat. This heating, which is required to facilitate the adhesion of the covering layer to the part to be veneered, is usually obtained by using coils, arranged in the vat, in which a fluid is circulated; said fluid is preliminarily heated outside the machine, with unavoidable heat losses along the line and long times for the transmission of the heat to the liquid in the vat, which significantly affect the productive potentiality of these machines.
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An aim of the present invention is to solve the problems described above by providing a machine for veneering parts made of wood or other material having a flat or variously shaped profile, which can ensure a high operating pressure despite having a considerably simpler and lighter structure than conventional machines.
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Another aim of the present invention is to provide a machine having lower production and maintenance costs than known machines.
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Another object of the present invention is to provide a machine which is highly reliable and safe in operation.
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A further object of the present invention is to provide a machine requiring reduced maintenance operations while ensuring a long life.
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Another object of the present invention is to provide a machine having high productivity.
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These aims and others which will become apparent hereinafter are achieved by a veneering machine, particularly for veneering parts made of wood or of other material, having a flat or variously shaped profile, characterized in that it comprises: a main structure supporting a liquid containment vat, closed upwardly by an elastically deformable membrane, and slidably supporting, along a substantially vertical direction, a closure surface movable under control towards or away from the upper face of said vat; means for locking said closure surface in a position in which it rests against the upper edge of said vat; means, activable under control after locking said closure surface against the upper edge of said vat, for introducing a pressurized liquid into said vat to produce an increase in the pressure of the liquid contained in said vat which deforms said membrane so that it fits tightly, by pressure, to the membrane-facing surface of a part to be veneered, which is interposed between said membrane and said closure surface.
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Further characteristics and advantages of the present invention will become apparent from the following description of a preferred but not exclusive embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein:
- figure 1 is a partially sectional schematic lateral elevation view of the machine according to the present invention, with the closure surface raised above the vat;
- figure 2 is a schematic lateral elevation view of the machine according to the present invention with the closure surface rested on the vat edge;
- figure 3 is a bottom plan view of the machine, with some parts removed for greater clarity;
- figure 4 is an enlarged-scale sectional view of a detail of figure 1;
- figure 5 is an enlarged-scale view of another detail of the machine according to the invention;
- figure 6 is an axial sectional view of an air venting element connected to the bottom of the vat;
- figures 7 to 9 are schematic views of the operation of the machine according to the present invention, shown in vertical cross-section.
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With reference to the above figures, the machine according to the present invention, generally designated by the reference numeral 1, comprises a main structure 2 which supports a vat 3 preferably substantially shaped like a parallelepiped, delimited on its bottom and sides by rigid walls, and closed upwardly by an elastically deformable membrane 4.
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More particularly, the membrane 4 is connected to the vat 3 at a perimetric band thereof, which is clamped between the upper end of the side walls of the vat and an overlying frame-like edge 5. The frame-like edge 5 forms an upper inlet 6 of the vat which is closed by the membrane 4 and is shaped like an inverted truncated pyramid. The inside of the vat 3 is connected, through a duct 7, to a liquid tank 8, and a controllable valve 9 is arranged on the duct 7. In the case shown, the tank 8 is constituted by two containers, 8a and 8b, which are associated with the main structure 2 and are mutually connected.
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The main structure 2 also supports a closure surface 10 arranged horizontally above the vat 3. Said closure surface 10 is movable under control along a vertical direction towards or away from the upper face of the vat 3.
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A raised portion 11, shaped substantially like an inverted truncated pyramid, protrudes from the lower face of the closure surface; said raised portion is meant to couple inside the edge 5 of the vat, obtaining precise centering between the vat and the closure surface 10 when said surface is lowered.
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The closure surface 10 has a substantially rectangular plan shape, and four vertical posts 12 are fixed proximate to its corners, extend toward the underlying main structure and slidingly couple against vertical guides 13 which are rigidly coupled to the main structure 2.
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Conveniently, in order to obtain a correct vertical movement of the closure surface, a rack 14 is fixed to each post 12 and meshes with a gear 15, having a horizontal rotation axis and supported by the main structure 2. The rack 14 is fixed to the side of each post which is opposite with respect to the side which slides against the related guide 13, and the gears 15 are kinematically connected to each other so as to obtain an identical vertical movement of the four posts 12. As can be seen particularly from figure 3, there are two shafts 16 and 17 extending horizontally along the two shorter sides of the main structure, below the vat 3. Each shaft supports two of the gears 15, and the two shafts 16 and 17 are mutually connected, by means of bevel gear pairs 18 and 19 having a 1:1 transmission ratio, by a shaft 20 extending below the tank proximate to its main axis. The shafts 16, 17 and 20 are rotatably supported by the main structure 2 about their respective axes, by means of bearings not shown for the sake of simplicity.
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The vertical movement of the closure surface 10, which is made uniform by said racks and gears, is produced by two hydraulic cylinders 21 and 22 having a vertical axis, interposed between the main structure 2 and the closure surface 10, and arranged in a median region of the longer side of the main structure 2 on the outside of the vat 3.
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The machine according to the present invention is provided with means for locking the closure surface 10 in a position in which it rests on the edge 5 of the vat 3. Said locking means comprise a plurality of vertical pins 23, the upper ends whereof are fixed to the closure surface 10; said pins are slidably inserted within seats 24 formed in the main structure 2 parallel to the longer sides of the vat 3 outside said vat. Proximate to its lower end, each pin 23 has a region 23a having a smaller diameter. Proximate to the seats 24, along each longer side of the main structure 2, there is an element 25 for engaging the lower end of the pins 23 when the closure surface 10 is lowered against the edge 5 of the vat 3.
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The engagement element 25, for each longer side of the main structure 2, is constituted by a plate extending transversely to the axis of the pins 23 and longitudinally slidably supported by the main structure 2. In each plate 25 there is a plurality of holes 26 the diameter of which is substantially identical to that of the seats 24; said holes are mutually spaced in a corresponding manner so that they are aligned with said seats 24. Each hole 26 has, in a direction which is parallel to the longitudinal extension of the plate 25, a slot-shaped extension 26a the width whereof corresponds to the diameter of the region 23a of the pins 23 so that they can engage said region 23a of the pins by means of a longitudinal movement of the plate 25, producing a bayonet-like locking of the pins 23 when the closure surface rests on the edge 5 of the tank 3.
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The longitudinal movement of each plate 25 is obtained by means of a hydraulic or pneumatic cylinder 27 which is associated with the main structure 2, and each plate 25 is slidably accommodated in a guide 28 which is fixed to the main structure 2 so that the regions 23a of the pins 23 are located at the plates 25 when the closure surface 10 rests on the edge 5 of the vat 3.
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According to the present invention, the machine is provided with means for introducing a pressurized liquid into the vat 3. Said introduction means are constituted by a pump 29 which is connected to the tank 8 by means of its supply duct 30 and is connected to the bottom of the vat 3 with its delivery duct 31.
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A one-way valve 32 may be provided on the delivery duct 31 of the pump.
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Conveniently, the machine is also provided with means for heating the liquid contained in the vat 3, so as to facilitate the adhesion of the covering layer to the part 33 to be veneered. The means for heating the liquid, preferably a diathermic liquid of a known type, are constituted by electric resistors 34 inserted in tubular bodies 35 which are connected to the bottom of the vat 3 and in which part of the liquid contained in the vat circulates. The heat output by the resistors 34 is transmitted to the liquid contained in the vat by using the convective motion of the liquid. The tubular bodies 35 are in fact arranged so that at least one portion of their length, which accommodates the resistors, is inclined with respect to a horizontal plane. Furthermore, the resistors are powered so that their temperature rises progressively as one rises along the related tubular body. In this manner, a current of heated liquid is produced along the tubular bodies 35 and rises toward the vat 3, drawing toward the inlet of said bodies the colder liquid, which tends to sink toward the bottom of the vat, and so forth, so as to obtain the required temperature for the liquid inside the vat 3.
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The pump delivery duct 31 and the duct 7, lead into one of the tubular bodies 35 so that the liquid arriving from the tank 8 is heated before it reaches the vat 3. On the bottom of the vat 3 there is also an air venting element, designated by the reference numeral 36, for eliminating any air entering the vat 3. Said element 36 is simply constituted by an elongated body vertically slidable and provided with a head 37 in which a plurality of channels 38 is defined; said channels merge into a central channel 39 leading out at the opposite end of the element 36. When one wishes to vent the air which has accidentally entered the vat 3, the element 36 is pushed until its head 37 is proximate to the membrane 4, where the air is located, so that said air escapes from the vat through the channels 38 and 39. When air venting has ended, the element 36 is returned to a position in which its head is located in a seat 40 formed in the bottom of the vat 3, thus closing the channels 38 and closing the lower end of the element 36 for further tightness safety.
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The machine is also provided with means for conveying the parts 33 between the membrane 4 and the closure surface 10.
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Said conveyance means are preferably constituted by a conveyor belt 41 made of a material having high elastic deformability, such as for example the same material used to produce the membrane 4; said belt passes between the membrane 4 and the closure surface 10.
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The operation of the machine according to the present invention is as follows.
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The part 33, to which the covering layer has been applied, is rested on the conveyor belt 41 so that its shaped face, if any, faces downwards and so that a flat face is directed upwards. The conveyor belt carries the part 33 between the membrane 4 and the closure surface 10, which is in the raised position (figure 7). When the part 33 is correctly arranged, the cylinders 21 and 22 are actuated so as to lower the closure surface 10 toward the membrane 4, keeping the controllable valve 9 open until the closure surface 10 rests against the edge 5 of the vat 3. It should be noted that the tank 8 and the vat 3 act like two communicating vessels, and that the level of the liquid at rest in the tank 8 is set so that the membrane 4 is located against the closure surface 10, which is rested on the edge 5, in the absence of the part to be pressed.
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The presence of the part 33 while the valve 9 is open causes, during the lowering of the closure surface 10, the transfer of part of the liquid from the vat 3 to the tank 8 without requiring any compensating action (figure 8).
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After the closure surface 10 has been lowered, the cylinders 27 are actuated, locking the closure surface 10 and rigidly coupling it to the vat 3.
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At this point the valve 9 is closed and the pump 29 is actuated, so as to increase the pressure of the liquid inside the vat 3. This pressure increase is transmitted to the part 33 by the membrane 4, which deforms and follows the contour of said part 33, the flat face whereof is pushed against the lower side of the closure surface 10 (figure 9).
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During this operation, the conveyor belt 41 is arranged between the membrane 4 and the closure surface 10 and deforms like the membrane 4.
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Once the required pressure has been reached, the pump 29 is deactivated; after a preset time, which is sufficient to make the covering layer adhere to the part 33, the valve 9 is opened, returning the pressure in the vat 3 to the initial values.
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By proceeding in reverse with respect to what has been described so far, the closure surface 10 is raised and the finished part 33 is removed by means of the conveyor belt 41, introducing a new part 33 in the machine to start a new cycle.
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In practice it has been observed that the machine according to the present invention fully achieves the intended aims since, by directly increasing the pressure of the liquid in the vat, it avoids the use of high-power hydraulic pusher cylinders and avoids the discharge of the forces produced by the pressure increase in the vat onto the supporting structure. For this reason, the machine according to the present invention, for an equal power, is significantly lighter and less expensive than conventional machines.
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Furthermore, by virtue of the particular system for heating the working liquid, in addition to achieving a significant energy saving it reduces the time required to raise the liquid to the required temperature, also achieving higher productivity than conventional machines.
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A further advantage, arising from the fact that the liquid is pressurized only after the closure surface has been lowered, is that it produces no overstresses in the membrane, obtaining a longer life of said membrane and greater safety for operators.
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The machine thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may furthermore be replaced with other technically equivalent elements.
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In practice, the materials employed, as well as the dimensions, may be any according to the requirements and the state of the art.
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Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.
