Forming station for a cardboard tray assembly machine

Abstract

The invention relates to a forming station for a cardboard tray assembly machine, which includes a mould (1b) comprising a base plate (4) with a central through-opening (29), in accordance with which a tray (3) is formed when a core (1a) descends. The base plate (4) is detachably coupled to two opposite support structures (18), which include first adjustment means arranged to move the base plate (4) in the horizontal plane in which the base plate (4) is located, and second adjustment means arranged to move the base plate (4) vertically, perpendicular to the base plate (4), to position same at the required height. The mould (1b) includes pairs of opposite adjustable benders attached to the top of the base plate (4) and pairs of opposite adjustable pressing mechanisms attached to the bottom of the base plate (4).

Description

Object of the invention

[0001] The present invention relates to a forming station for a cardboard tray assembly machine, preferably for assembling octagonal-shaped trays, where the vertical corners are chamfered, and where the trays further include a flange or rim delimiting the opening of the trays which allows the closure of each tray by means of a lid which is adhered to the flange by means of adhesive or by heat-sealing. The forming station presents substantial improvements both in the folding of the different parts of a cardboard sheet from which the tray is obtained, and in the capacity to adapt it to the forming of different formats of trays or boxes having an octagonal, quadrangular or rectangular geometry; all this based on a new concept in the way of assembling the different elements and mechanical devices responsible for forming said trays by collapsing and folding their corresponding parts.

[0002] It is particularly applicable in the industrial field related to the sector of forming cardboard boxes by means of folding.Technical problem to be solved and background of the invention

[0003] A trend in the current state of the art is aimed at mechanically solving the assembly of small cardboard trays, which include a flange folded outwards and delimiting an opening of the respective tray for the application of a laminar closure body in the form of a lid that is joined to said flange. These cardboard trays are assembled using conventional cardboard box forming machines, which have been around for years and in which a vertically moving core descends downwards to press a die-cut sheet with different glued areas into a forming mould to form the respective cardboard tray.

[0004] The mechanical improvements intended for the formation of cardboard trays have been focused on the assembly of trays with rectangular flanges. This trend has extended to the use of octagonal trays which, instead of the conventional four straight vertical corners where the side walls of the tray meet, have chamfers which constitute four additional portions of side walls and therefore imply having these four additional portions starting from the bottom of the tray which have to be correctly bent and glued.

[0005] The increase in side walls in the trays to be assembled implies that the forming station (mould and core) must be equipped with more mechanisms responsible for the actions of folding or collapsing and pressing the different parts of the tray. For example, in the case of octagonal trays, the mould must be equipped with four additional elements, which furthermore, together with the rest of the mechanisms, must be easy to assemble, disassemble and adjust in order to allow different tray formats or sizes to be assembled.

[0006] With current moulds, this necessary versatility is very limited, as can be seen, for example, in document P202230609 by the same proprietor of this invention, in which, although the assembly of trays of this type has been resolved quite effectively, it still lacks agility in format changes and in the optimal distribution and location of the different mechanisms involved in the forming of the tray.

[0007] The document with publication number ES1273399U discloses a forming machine for forming boxes with at least two side flaps, two front flaps and a base, where each flap incorporates a wing and both the flaps and the wings can be folded to form a box with a cavity open at an opening, and around the opening, the formed box comprises a support flange, formed by the wings of the flaps folded with respect to the walls, which allows the cavity to be closed by means of a lid joined by means of adhesive or heat-sealing, as well as correct storage and handling without altering either the condition of the box or its contents.

[0008] However, this machine is far removed from the state of the present application, as it does not allow the assembly of trays with chamfered corners and is focused solely on boxes with a rectangular bottom.

[0009] Document ES2839552 B2 discloses a machine and method for forming cardboard boxes from flat die-cut sheets. The machine comprises a core in the shape of an inverted truncated pyramid, movable in a linear Z (vertical) direction into a mould with forming stops, movable between respective retracted and stop positions for discharging the mould boxes through an outlet opening, the forming stops having concave curved surfaces, complementary to convex curved surfaces in the shape of an inverted conical section positioned in four corner areas of the core.

[0010] However, this invention does not provide optimal and novel solutions to the way of assembling the different folding or pressing mechanisms in the forming station, or mould, itself, resorting to traditional means, essentially consisting of using the chassis of the machine itself to anchor these mechanisms with the little versatility that this offers.

[0011] In this way, the aforementioned documents present many problems when it comes to adapting the different folding and pressing mechanisms located in the forming station to the assembly of octagonal trays or trays of any format or geometry, in that they require complex adjustments and operations for the assembly and disassembly of the aforementioned folding and pressing mechanisms.

[0012] The present invention presents a cardboard tray forming machine, with improvements focusing mainly on a new concept of a forming station as described below.Description of the invention

[0013] In order to achieve the objectives and avoid the drawbacks in the preceding sections, the invention proposes a forming station for a cardboard tray assembly machine comprising at least one core and one mould arranged to form a tray from a die-cut sheet supported on sections of two parallel longitudinal guide structures, and which is pulled downwards with the descent of the core into the mould to form of said tray.

[0014] The tray comprises at least a bottom, first opposite side walls and second opposite side walls.

[0015] The mould comprises a base plate with a central through-opening, in accordance with which a part of the tray is formed when a core descends; where said base plate includes an upper face and a lower face opposite the upper face.

[0016] The base plate of the mould is detachably coupled to two opposite support structures, which include first adjustment means arranged to move the heads in the horizontal plane to the dimensions of the base plate, and second adjustment means arranged to move the base plate vertically, perpendicular to the base plate, to position same at the required height.

[0017] The mould includes pairs of opposite adjustable benders attached to the base plate, located above said base plate; where said pairs of benders are arranged to initiate the forming of the tray during the descent of the core.

[0018] The mould includes pairs of opposite adjustable pressing mechanisms attached to the base plate, located below said base plate; where said pairs of pressing mechanisms are arranged to form the side walls of the tray.

[0019] Therefore, the forming station is arranged to form the tray inside an inner assembly space of the mould comprising the central opening of the base plate and an additional opening bounded at least between front surfaces of pairs of opposite adjustable pressing mechanisms; and where during actuation of the pairs of pressing mechanisms, the core is located inside the inner assembly space of the mould.

[0020] The first adjustment means for horizontally adjusting the base plate of each supporting structure comprise a spindle coupled to two nut elements integral with two heads which are coupled to a guide bar parallel to the spindle; where the two heads are linked to the base plate by means of vertical slide supports.

[0021] The second vertical adjustment means to adjust the positioning of the base plate vertically comprises the vertical slide supports which include vertical guides arranged to position the base plate at different heights.

[0022] The base plate, the nut elements, the heads and the vertical slide support, all of which elements form an integrally joined assembly arranged to move in the horizontal plane along the two parallel guide bars when the spindles rotate synchronously by means of a chain coupled to two sprockets fitted on said spindles of both support structures.

[0023] The sections of parallel longitudinal guide structures include movable guides with an angular profile which are associated with adjustment devices to rotate said movable guides to change their orientation around aligned articulated connections which are arranged parallel to the longitudinal guide structures.

[0024] Each of the adjustment devices comprises third linear actuators coupled in an articulated manner to fixed angle supports; where the shafts of the linear actuators articulate in turn in C-shaped end pieces, each of which is in turn connected to the respective articulated connection. The whole of each longitudinal guide structure runs through the opening of the C-shaped end pieces; where the movable guides are joined to pairs of C-shaped end pieces.

[0025] In one embodiment of the invention, the forming station comprises at least pairs of first benders arranged for the initial bending of the first and second side walls of the tray, and at least pairs of first pressing mechanisms arranged to form the first and second side walls of the tray.

[0026] In another embodiment of the invention, the forming station comprises: Pairs of first benders arranged for the initial bending of the first and second side walls of the tray. Pairs of second benders arranged for the initial bending of chamfered side walls of the tray located in accordance with the corner areas where the first and second side walls meet. Pairs of first pressing mechanisms arranged to form the first and second side walls of the tray. Pairs of second pressing mechanisms arranged to form the chamfered side walls of the tray located in accordance with the corner areas where the first and second side walls of the tray meet.

[0027] The first and second benders are attached to the base plate by means of adjustable guide pieces which are attached on the upper face of the base plate by means of screws passing through slots of said adjustable guide pieces; where the combination of screws and slots are arranged to position the first and second benders with respect to the perimeter edge of the central opening of the base plate to be adjusted to different sizes of tray to be obtained.

[0028] The second benders include downwardly inclined end-located extensions converging towards the centre of the central opening of the base plate; where said end-located extensions are flanked by pairs of side wings; and where said end-located extensions are located in accordance with chamfered corner portions that are part of the perimeter contour of the central opening of the base plate.

[0029] Each of the second pressing mechanisms comprises a separate module including a second frame structure formed by several pieces to which there is coupled by means of articulation a second linear actuator linked to a articulated quadrilateral mechanism including a second pusher with a front surface, arranged to contact with same the respective chamfered side wall of the tray during its forming inside the mould.

[0030] The articulated quadrilateral mechanism comprises two cranks in parallel and a connecting rod coupled to the two cranks by means of two articulated connections; where the second pusher is detachably attached to the connecting rod; where the two cranks are coupled to the second frame structure by means of two further articulated connections; and where one of the two cranks has an extension where it articulates one end of the shaft of the second linear actuator.

[0031] Next, to help better understand this specification and as an integral part thereof, a series of figures is attached in which the object of the invention is depicted in an illustrative and non-limiting manner.Brief description of the figures

[0032] Figure 1 shows a perspective view of the forming station for a cardboard tray assembly machine, object of the invention. This forming station produces trays with four side walls and four further chamfered side walls located at the meeting points of the ends of the other four side walls. Figure 2 shows an exploded perspective view of a part of what is represented in Figure 1, showing a base plate with a through-opening that is part of a mould and is the support for the necessary elements of the mould. Figure 3 shows a perspective view of two parallel opposite support structures associated by means of a chain. Figure 4 shows a perspective view of a first pressing mechanism. Figure 5 shows a perspective view of a second pressing mechanism. Figure 6 represents an exploded perspective view showing a rotation system for adjusting the position of a movable guide arranged parallel to longitudinal guide structures. Figure 7 shows a perspective view of a tray obtained in the forming station of the invention shown in Figures 1 and 2. Figure 8 shows a view of a die-cut sheet from which the tray of the invention is obtained. Figure 9 shows a perspective view of a mould for obtaining trays with four side walls and a quadrangular or rectangular bottom, without chamfered side walls; where the base plate comprises a structure adapted to obtain a tray without said chamfered side walls. Figure 10 represents a perspective view showing a part of what is shown in Figure 9, without the inclusion of the base plate. Figure 11 shows a perspective view of a tray obtained in the forming station shown in Figures 9 and 10. Figure 12 shows a schematic elevation view of the forming station and the longitudinal guide structures for transferring each die-cut sheet to the forming station. Description of an exemplary embodiment of the invention

[0033] Considering the numbering adopted in Figures 1 to 8, the forming station 1 for a cardboard tray 3 assembly machine comprises a core 1a and a mould 1b comprising improvements of the invention.

[0034] Once the tray 3 once is formed, it is like the one shown in Figure 7, for example, which is identical to that shown in patent P202230609, of the same proprietor as the present invention, and is formed from a die-cut cardboard sheet 6 as shown in Figure 8; where said tray 3 comprises a bottom 3a, two opposite first side walls 3b, two opposite second side walls 3c, and four chamfered side walls 3d located at the corner meeting points of the ends of the first 3b and second 3c side walls of the tray 3.

[0035] All the side walls 3a, 3b, 3c and 3d of the tray 3 include wings, so that once the tray 3 is assembled, an outwardly bent perimeter flange 3e is formed, delimiting the opening of the tray 3; where said perimeter flange 3e is arranged to join thereto a laminar lid (not represented in the figures) to close the opening of the tray 3.

[0036] Therefore, the flange 3e serves as a base to support the lid, which is joined to the tray 3 by means of adhesive or heat-sealing. Typically, the flange 3e is bent towards the outside of the tray 3, although it could also be bent towards the inside.

[0037] The machine to which the invention is applied incorporates an area for stacking cardboard sheets 6 which are then transferred individually by means of a pulling mechanism supported on longitudinal guides 2; where along the transfer there are glue injectors that deposit glue in certain areas of the sheet 6 until it reaches the forming station 1 where the sheet 6 stops and is located between the core 1a and the mould 1b of the forming station 1, which is precisely the main object of the invention, so that the core 1a pushes the sheet 6 downwards to a final position inside the mould 1b (inner assembly space) where pairs of first opposite adjustable pressing mechanisms 5 and second pairs of second opposite adjustable pressing mechanisms 9 push on different areas of the side walls 3b, 3c, 3d of the tray 3 during the assembly process to form said tray 3 in the inner assembly space of the mould 1b.

[0038] Specifically, the second pressing mechanisms 9 exert pushing on the chamfered side walls 3d, while the first pressing mechanisms 5 exert pushing on the first and second opposite side walls 3b, 3c two by two.

[0039] The mould 1b of the forming station 1 comprises a characteristic structure arranged on the basis of a rectangular base plate 4, which is attached on two of its opposite edges to two support structures 18 with first adjustment means, each of which comprises a spindle 20 coupled to two nut elements 21 integral with two heads 22 linked in turn to the base plate 4 by means of vertical slide supports 23; where the base plate 4 is coupled to the vertical slide supports 23 by means of a dovetailed vertical guide to position the base plate 4 at different heights; and where the vertical guide is part of second adjustment means to adjust the height of said base plate 4. The heads 22 mentioned in the preceding paragraph are coupled on a guide bar 24 which is part of the first adjustment means.

[0040] The first adjustment means are arranged to move the heads (22) in the horizontal plane with respect to the dimensions of the base plate (4) of the mould (1b).

[0041] The vertical slide supports 23 are detachably attached to the heads 22 by means of screws 31. Furthermore, it should be noted that stops 32 are provided to limit the maximum upward movement of the base plate 4; where said stops 32 are attached to the highest part of said vertical slide supports 23.

[0042] The base plate assembly 4 can move in the horizontal plane along the two guide bars 24 parallel to the two spindles 20 when the spindles rotate synchronously as they are linked by means of a chain 19 coupled to two sprockets 26 fitted on the spindles 20 of both first adjustment means.

[0043] In turn, the base plate 4 comprises strategically positioned fully adjustable anchoring means to assemble the first 5 and second 9 pressing mechanisms in different positions, as well as pairs of opposite first adjustable benders 7 adjustable to start the initial bending of the side walls 3b, 3c, and pairs of opposite second adjustable benders 8 to start the initial bending of the chamfered side walls 3d of the tray 3.

[0044] The first 5 and second 9 pressing mechanisms are attached on the lower face of the base plate 4, while the first 7 and second 8 benders have a half-round profile and are attached on the upper face of the base plate 4.

[0045] The base plate 4 further includes a central opening 29 through which the tray 3 is inserted during its assembly when the core 1a descends in the forming station, so that above the perimeter edge of said central opening 29 there are located, in principle, the first 7 and second 8 benders which are attached to the base plate 4 by means of adjustable guide pieces 27, 28 which are attached on the upper face of the base plate 4 by means of screws which pass through slots 27a, 28a of said adjustable guide pieces 27, 28 which allow the positioning of the first 7 and second 8 benders with respect to the perimeter edge of the central opening 29 of the base plate 4 to be adjusted to different sizes of tray 3 to be obtained and more specifically to be adjusted to the distance between pairs of opposite side walls of said tray 3, so that when the core 1a descends, pulling the die-cut sheet 6, it first contacts said benders 7, 8, starting the initial bends of the side walls of the tray 3.

[0046] The second benders 8 include downwardly inclined end-located extensions 17 converging towards the centre of the central opening 29; where said end-located extensions 17 are flanked by pairs of side wings 17a; and where said end-located extensions 17 are located in accordance with chamfered corner portions that are part of the perimeter contour of the central opening 29 of the base plate 4, which is quadrangular- or rectangular-shaped.

[0047] With this new configuration described, the forming station 1 is based fundamentally on the base plate 4, which can be adapted to a multitude of sizes and formats of tray 3 by allowing all the mechanisms and elements assembled on the base plate 4 to be moved together in both the vertical plane and horizontal plane, without the need for disassembly and all together by means of the first adjustment means for horizontally adjusting and the second vertical adjustment means. In turn, the horizontal structure of said base plate 4 allows the anchoring of the first 5 and second 9 pressing mechanisms and the first 7 and second 8 benders, both on the upper face and lower face of said base plate 4.

[0048] Of note is the great advantage of the new structure of the mould 1b of the forming station, where all the elements and mechanisms associated with it are much more accessible, and furthermore there is more open space than in the conventional configuration.

[0049] In a preferred embodiment of the invention, the base plate 4 has an H-shaped geometry, which allows for there to be better access to the folding mechanisms (benders 7, 8) and the pressing mechanisms 5, 9 assembled on same, and in turn for it to have the necessary extensions for assembling the vertical slide supports 23 for the vertical adjustment of the base plate 4.

[0050] Each of the first pressing mechanisms 5 comprises a separate module including a first frame structure formed by several pieces to which there is linearly coupled and guided a first mobile carriage 5b which moves by means of a first linear actuator 5a attached to the first frame structure; where the movement of the mobile carriage 5b is parallel to the movement of the first linear actuator 5a; and where said first mobile carriage 5b includes a first pusher 5c with a front surface, on which the respective side wall 3b or 3c of the tray 3 contacts during its forming inside the mould 1b. The first pushers 5c of the first pressing mechanisms 5 include lower ribs 16 on which opposite pairs of edges of the bottom 3a of the tray 3 act as a stop during the forming of said tray 3.

[0051] Conversely, each of the second pressing mechanisms 9 also comprises, in principle, a separate module including a second frame structure formed by several pieces to which there is coupled by means of articulation a second linear actuator 9a acting on an articulated quadrilateral mechanism 9b including a second pusher 9c with a front surface, on which the respective chamfered side wall 3d of the tray 3 contacts during its forming inside the mould 1b.

[0052] The articulated quadrilateral mechanism comprises two cranks 10 in parallel and a connecting rod 11 coupled to the two cranks 10 by means of two articulated connections; where the second pusher 9c is detachably attached to the connecting rod 11; where the two cranks 10 are coupled to the second frame structure by means of two further articulated connections; and where one of the two cranks 10 has an extension where it articulates one end of the shaft of the second linear actuator 9a.

[0053] Obviously, the first 5 and second 9 pressing mechanisms are attached to the base plate 4 by means of their respective frame structures, while the front surfaces of the first 5c and second 9c pushers comprise inclined planes in line with the side walls of the tray 3.

[0054] Moreover, each die-cut sheet 6 reaches the forming station 1 guided and supported by two parallel longitudinal guide structures 2 having an angular configuration; where each of said longitudinal guide structures 2 includes a movable guide 2a with an adjustable angular profile which can be rotated to change its orientation around an articulated connection 12, such that said variation is carried out by means of third linear actuators 13 coupled in an articulated manner to fixed angular supports 14; where the shafts of the linear actuators 13 articulate in turn in C-shaped end pieces 15, each of which is in turn connected to the respective articulated connection 12; where the whole of each longitudinal guide structure 2 runs through the opening of the C-shaped end pieces 15; and where the movable guides 2a are joined to pairs of C-shaped end pieces 15.

[0055] Therefore, the angular profiles 2a of the longitudinal guide structures 2, located above the base plate 4, can change their angle of rotation, so that in certain models of trays 3 or boxes it is possible to act beforehand on their different parts by pre-bending or pre-lifting to optimise the assembly operation on the mould 1b.

[0056] Figures 9 and 10 show an embodiment of the invention in which the mould 1b is intended to assemble trays 3' or boxes with four side walls and a quadrangular or rectangular bottom; where in this case the adjustable second benders 8 and the second pressing mechanisms 9 are dispensed with; conversely, there are four first benders 7' in line with the opposite first 3b' and second 3c' side walls two by two which are located above the base plate 4, and first pressing mechanisms 5' also in line with said side walls 3b', 3c' located below the base plate 4. The new tray 3' (Figure 11) also includes a bottom 3a' from which there emerge the side walls 3b', 3c' and a perimeter flange 3e' delimiting the opening of the tray 3'.

[0057] In this new embodiment of the invention being described, in accordance with two of the four side walls of the tray 3', there are provided two additional benders 7' positioned above the first two benders 7 which are practically flush with the upper face of the base plate 4, so that during the assembly of the tray 3' when the core 1a descends, dragging the die-cut sheet, two opposite zones first contact the two additional benders 7' and then contact the first benders 7 which are below the additional benders 7'.

[0058] In all cases it is possible to easily change a mould attached to the support structure 18 for another one in line with the dimensions and configuration of the tray or box to be obtained, so that this operation is very simple.

[0059] The mould 1b is change by removing the screws 31 attaching the whole of the mould 1b to the heads 22 by means of the vertical slide supports 23, and taking out the base plate 4 with respect to the heads 22 by moving the whole of the mould vertically upwards.

[0060] And secondly, in the case of the embodiment shown in Figures 9 and 10, the base plate 4 is to be detached from two side profiles 30 to which the base plate 4 is attached, so that in this embodiment the base plate 4 is also coupled to the vertical slide supports 23.

Claims

1. A forming station for a cardboard tray assembly machine, comprising at least one core (1a) and one mould (1b) arranged to form a tray (3, 3') from a die-cut sheet supported on sections of two parallel longitudinal guide structures (2), and which is pulled downwards with the descent of the core (1a), which is inserted into the mould (1b) to form said tray (3, 3'); where said tray (3, 3') comprises at least a bottom (3a, 3a'), first opposite side walls (3b, 3b') and second opposite side walls (3c, 3c'); characterised in that: - the mould (1b) comprises a base plate (4) with a central through-opening (29), in accordance with which a part of the tray (3) is formed when a core (1a) descends; where said base plate (4) includes an upper face and a lower face opposite the upper face; - the base plate (4) of the mould (1b) is detachably coupled to two opposite support structures (18), which include first adjustment means arranged to move heads (22) in the horizontal plane to the dimensions of the base plate (4) of the mould (1b), and second adjustment means arranged to move the base plate (4) vertically, perpendicular to the base plate (4), to position same at the required height; - the mould (1b) includes pairs of opposite adjustable benders attached to the base plate (4), located above said base plate (4); where said pairs of benders are arranged to initiate the forming of the tray (3, 3') during the descent of the core (1a); - the mould (1b) includes pairs of opposite adjustable pressing mechanisms attached to the base plate (4), located below said base plate (4); where said pairs of pressing mechanisms are arranged to form the side walls of the tray (3, 3'); where the forming station is arranged to form the tray (3, 3') inside an inner assembly space of the mould (1b) comprising the central opening (29) of the base plate (4) and an additional opening bounded at least between front surfaces of pairs of opposite adjustable pressing mechanisms; and where during actuation of the pairs of pressing mechanisms, the core (1a) is located inside the inner assembly space of the mould (1b).

2. The forming station for a cardboard tray assembly machine according to claim 1, characterised in that: - the first adjustment means for horizontally adjusting the base plate (4) to couple each support structure (18) to the dimensions of each base plate (4) comprise a spindle (20) coupled to two nut elements (21) integral with two heads (22) which are coupled to a guide bar (24) parallel to the spindle (20); where the two heads (22) are linked to the base plate (4) by means of vertical slide supports (23) which are detachably attached to the heads (22) by means of screws (31); - the second vertical adjustment means to adjust the positioning of the base plate (4) vertically comprises the vertical slide supports (23) which include vertical guides arranged to position the base plate (4) at different heights; where the base plate (4), the nut elements (21), the heads (22) and the vertical slide support form an integrally joined assembly arranged to move in the horizontal plane along the two parallel guide bars (24) when the spindles rotate synchronously by means of a chain (19) coupled to two sprockets (26) fitted on said spindles (20) of both support structures (18).

3. The forming station for a cardboard tray assembly machine according to any one of the preceding claims, characterised in that the sections of parallel longitudinal guide structures (2) include movable guides (2a) with an angular profile which are associated with adjustment devices to rotate said movable guides (2a) to change their orientation around aligned articulated connections (12) which are arranged parallel to the longitudinal guide structures (2).

4. The forming station for a cardboard tray assembly machine according to claim 3, characterised in that each of the adjustment devices comprises third linear actuators (13) coupled in an articulated manner to fixed angle supports(14); where the shafts of the linear actuators (13) articulate in turn in C-shaped end pieces (15), each of which is in turn connected to the articulated connection (12;) where the whole of each longitudinal guide structure (2) runs through the opening of the C-shaped end pieces (15); and where the movable guides (2a) are joined to pairs of C-shaped end pieces (15).

5. The forming station for a cardboard tray assembly machine according to any one of the preceding claims, characterised in that it comprises at least pairs of first benders (7, 7') arranged for the initial bending of the first (3b, 3b') and second (3c, 3c') side walls of the tray (3, 3'), and at least pairs of first pressing mechanisms (5, 5') arranged to form the first (3b, 3b') and second (3c, 3c') side walls of the tray (3, 3').

6. The forming station for a cardboard tray assembly machine according to any one of the preceding claims, characterised in that it comprises: - pairs of first benders (7) arranged for the initial bending of the first (3b) and second (3c) side walls of the tray (3); - pairs of second benders (8) arranged for the initial bending of chamfered side walls (3d) of the tray (3) located in accordance with the corner areas where the first (3b) and second (3c) side walls meet; - pairs of first pressing mechanisms (5) arranged to form the first (3b) and second (3c) side walls of the tray (3); - pairs of second pressing mechanisms (9) arranged to form the chamfered side walls (3d) of the tray (3) located in accordance with the corner areas where the first (3b) and second (3c) side walls of the tray (3) meet.

7. The forming station for a cardboard tray assembly machine according to claim 6, characterised in that the first benders (7) and the second benders (8) are attached to the base plate (4) by means of adjustable guide pieces (27, 28) which are attached on the upper face of the base plate (4) by means of screws passing through slots (27a, 28a) of said adjustable guide pieces (27, 28); where the combination of screws and slots are arranged to position the first (7) and second (8) benders with respect to the perimeter edge of the central opening (29) of the base plate (4) to be adjusted to different sizes of tray (3) to be obtained.

8. The forming station for a cardboard tray assembly machine according to claim 7, characterised in that the second benders (8) include downwardly inclined end-located extensions (17) converging towards the centre of the central opening (29) of the base plate (4); where said end-located extensions (17) are flanked by pairs of side wings (17a); and where said end-located extensions (17) are located in accordance with chamfered corner portions that are part of the perimeter contour of the central opening (29) of the base plate (4).

9. The forming station for a cardboard tray assembly machine according to any one of the preceding claims 6 to 8, characterised in that each of the second pressing mechanisms (9) comprises a separate module including a second frame structure formed by several pieces to which there is coupled by means of articulation a second linear actuator (9a) linked to an articulated quadrilateral mechanism (9b) including a second pusher (9c) with a front surface, arranged to contact with same the respective chamfered side wall (3d) of the tray (3) during its forming inside the mould (1b).

10. The forming station for a cardboard tray assembly machine according to claim 9, characterised in that the articulated quadrilateral mechanism comprises two cranks (10) in parallel and a connecting rod (11) coupled to the two cranks (10) by means of two articulated connections; where the second pusher (9c) is detachably attached to the connecting rod (11); where the two cranks (10) are coupled to the second frame structure by means of two further articulated connections; and where one of the two cranks (10) has an extension where it articulates one end of the shaft of the second linear actuator (9a).

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