WO2020079560A1

WO2020079560A1 - Method and apparatus for advancing products to be thermoformed

Info

Publication number: WO2020079560A1
Application number: PCT/IB2019/058731
Authority: WO
Inventors: Francesco Fiorentini
Original assignee: Cannon Ergos S.P.A.
Priority date: 2018-10-15
Filing date: 2019-10-14
Publication date: 2020-04-23
Also published as: IT201800009452A1

Abstract

A method is disclosed for advancing that uses an advancing apparatus (1) for advancing a plurality of sheet or plate-shaped products made of plastics to perform the following steps: conveying a first product (P1, P2, P3, P4) from a loading station (1) to a heating station (3, 6) along a main advancement direction by grasping and maintaining gripped two mutually opposite edges (2A, 2C) by conveying means which is movable parallel to said main direction; grasping in the heating station (3, 6) two further mutually opposite edges (2A, 2C) arranged transversely to the two edges (2A, 2C) by gripping means; heating the first product (P1, P2, P3, P4) and transferring the first product (P1, P2, P3, P4) from said heating station (3, 6) to a forming station (6) by maintaining the two further edges (2A, 2C) grasped with the gripping means, and the two edges (2A, 2C) with the conveying means; in the forming station (6) moving locking means in a direction that is transverse to said main advancement direction to make the locking means abut on the first product (P1, P2, P3, P4); releasing the further edges (2A, 2C) from the gripping means, maintaining the first product (P1, P2, P3, P4) gripped with the locking means; moving the gripping means away from the forming station (6) by displacing the gripping means in a direction opposite the main advancement direction, towards the heating station (3, 6) to grasp a second product (P1, P2, P3, P4) that in the meantime has been transferred from the loading station (1) to the heating station (3, 6). An advancement apparatus (1) is disclosed that comprises conveying means that is movable parallel to a main advancement direction that is able to convey a product (P1, P2, P3, P4) by grasping two longitudinal edges (2A, 2C) of a product (P1, P2, P3, P4) and gripping means that is suitable for grasping and conveying two further mutually opposite edges (2A, 2C) arranged transversely to the two opposite edges (2A, 2C).

Description

METHOD AND APPARATUS FOR ADVANCING PRODUCTS TO BE THERMOFORMED

BACKGROUND OF THE INVENTION

The invention relates to a method and/or an apparatus for advancing products to be formed.

Specifically, but not exclusively, the invention can be applied to advancing and thermoforming sheet or plate-shaped products made of plastics.

PRIOR ART

In the technical field of thermoforming, for manufacturing for example components for making household goods such as for example domestic refrigerators, portable refrigerators, freezers, and so on, the different markets require machines for thermoforming products made of plastics developed on different concepts; for example in America rotary forming machines have been developed whereas in Europa in line forming machines have been developed. In America, the chemical industry offers plastics at cheaper prizes of the type comprising polyolefins whereas in Europe plastics of the styrene type are more attractively priced.

In a softened state, styrenes (ABS and PS) retain greater structural properties than polyolefins (PP and PE) in the temperature range of the transformation window. The polyolefin plates undergo a deformation caused by great gravity and have to be conveyed to the thermoforming station with all four sides of the perimeter grasped; styrene plates do not undergo deformation to this degree immediately after the end of heating and can be conveyed to the forming station maintaining the grip only on the two longitudinal sides, i.e. the sides oriented parallel to a plate advancement direction.

If the grips are on four sides, it is possible to resort to thermoforming by using a rotary machine because it enables to avoid problems relating to recirculation of locking elements for the product.

Actually, the machines that have been most successful on the market are the in-line- machines since they permit flexibility in the layout and freedom in the number of operations to be performed, they also permit a more rational flow of materials because the entering material does not interfere with the exiting product.

This success of in-line machines has occurred for example in the domestic refrigerator manufacturing industry, so this type of machine is completely dominant.

In the context of in-line-forming machines, production lines are known comprising apparatuses for advancing sheet or plate-shaped products that are connectable to equally known thermoforming apparatuses.

The aforesaid production lines comprise a loading station, where the products to be thermoformed are loaded, and at least one heating station in which each incoming product is heated to a softening temperature, so as to permit subsequent thermoforming processing. Between the loading station and the heating station a pre heating station can be provided that is suitable for pre-heating each product to prevent the product being subjected to a too sudden temperature increase in the heating station.

Downstream of the heating station a forming station is arranged that is suitable for thermoforming each softened product, under pressure or in a vacuum condition, to obtain the desired product.

The advancement apparatuses can be inserted into the aforesaid thermoforming apparatuses and are able to convey, along a preset advancement direction, a plurality of products between the aforesaid loading, preheating, heating and thermoforming stations to perform several operations simultaneously.

The known advancement apparatuses comprise conveying means, for example chain conveying devices with tips or with pairs of grippers suitable for grasping the two mutually opposite edges that extend parallel to the advancement direction. Other means comprises pairs of grippers that move in a direction parallel to the advancement direction of the products and grasp the aforesaid products on the longitudinal edges, i.e. parallel to the advancement direction. The other edges, which are mutually opposite and arranged transversely to the advancement direction, are left free.

Advancement of the products by the aforesaid conveying means becomes extremely critical above all during the transfer from the (final) heating station to the forming station; in fact, the product in softened state, subject to the weight-force action, loses planarity, i.e. is deformed by the force of gravity, thus taking on a convex shape. Consequently, the two free transverse edges are deformed, thus adopting a convex profile, whilst the edges grasped by the conveying means undergo almost nil deformation, as illustrated in Fig. 1.

In Fig. 1 above, the same product Pl is in fact shown in four distinct instants of time, respectively in the loading station 1, pre-heating station 15, heating station 3 and forming station 6. It is noted that the free edges 2c and 2b of the product Pl, arranged transversely to the advancement direction D, are deformed progressively until the aforesaid product is given a plan shape, similar to the profile of an hourglass. This behaviour gives rise to the term“hourglass” phenomenon.

This deformation of the free edges 2c and 2d entails problems in the forming station 6, making thermoforming of the product difficult to perform; the effect that is obtained, depending also on the type of thermoplastic material, is that the grasping, necessary in a forming station, becomes a problem, especially in the central portion of the product, where deformation is greatest. If it is possible, the product is tensioned and consequently elongated so that the zone of maximum deformation, in the central portion, is in the area of action of a locking unit during forming. In all cases, a length of plate is used that this invention enables to be optimized.

Some technical solutions enable the deformation of the edges 2c and 2d of the product to be reduced before the product reaches the thermoforming station, using mechanical supports that are suitable for limiting the deformation of the product due to the force of gravity. The mechanical supports in fact extend parallel to the direction D and the product slides and rests on the mechanical supports. Nevertheless, on the portion of the face of the product abutting/sliding on the aforesaid mechanical supports, significant shape defects are generated, so that these supports can be used only when there is a multicavity forming.

Other technical solutions involve the use of a jet of hot air to support the sheet during conveying to the thermoforming station, or using chain conveying means with divergent guides. Nevertheless, if sheet-shaped products have a great thickness, the effect of reducing the deformation is limited, in addition to the fact that the edges 2c and 2d remain cold and thus not deformable/extendible in the forming station 6.

Examples of systems for grasping sheets made of plastics are known from EP0920975, EP 0330296 Bl, JPH0218969 and EP1153729. Nevertheless, such known systems have limits, given for example by the significant structural complexity, by the impossibility of intervening appropriately on the state of tensioning of the sheet and, where applicable, by an unsatisfactory method of transferring the sheet from the heating station to the thermoforming station.

In the light of what has been set out above, it is noticed that there is ample room for improvement for the current systems for advancing products to be thermoformed.

Although machines of rotating type enable the grasping frames to be maintained constantly engaged on the same product, these machines have limits with regard to the possibility of adapting the dimensions of the machine (or the frames) to the geometry of the products to be processed.

From US2009/104300 and US4944668 other devices for grasping sheets of plastics are known.

OBJECTS OF THE INVENTION One object of the present invention is to provide a method and/or an apparatus that is able to solve the aforesaid limits of the prior art.

Another object of the invention is to improve the methods and/or the apparatuses for advancing sheet or plate-shaped products made of plastics.

Still another object of the invention is to advance a product made of thermoformable plastics from a heating station to a thermoforming station, reducing the deformation of the edges.

A further object of the invention is to reduce deformation, caused by the weight force, of a heated product.

A still further object of the invention is to advance the heated product to the aforesaid thermoforming station and to release the heated product in the aforesaid thermoforming station in a simple way.

Such objects of the invention are achieved by a method and/or an apparatus for advancing products according to one or more of the claims set out below.

SHORT DESCRIPTION OF THE INVENTION

According to the invention, a method and an apparatus are provided for advancing and thermoforming sheet or plate-shaped products, according to what is defined in the attached independent claims.

The advancement apparatus, in particular, further comprises gripping means arranged transversely to the main advancement direction that is drivable to grasp in a heating station edges of the product arranged transversely to the aforesaid main advancement direction, to transfer the product from the heating station to the forming station, maintaining the aforesaid edges gripped, to release the product in the forming station, and move away in a direction opposite said main direction towards said heating station in order to grasp a second product. The advancement apparatus further comprises locking means arranged in the forming station to abut on the product, moving in a direction that is transverse to the main advancement direction, and to maintain the perimeter of the aforesaid product constrained both during the release of the transverse edges by the gripping means and during thermoforming of the product.

Owing to the invention, it is possible to advance a sheet-shaped product made of plastics that has been heated and brought to a soft state to a forming station, by minimizing deformation of the transverse edges, and it is possible to perform in a simplified and effective manner release and/or grasping of the sheet-shaped product, maintaining minimal deformation of the product caused by gravity during conveying to the forming station.

SHORT DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will be clearer from the following description with the help of the attached drawings that show an embodiment of the invention by way of non-limiting example, in which:

Fig. 1 is a schematic plan view that shows the evolution over time of the deformation of a product advanced in a thermoforming apparatus by an advancement apparatus of known type.

Figs 2 to 5 are schematic plan views of advancement steps of a plurality of products inside a thermoforming apparatus by an advancement apparatus according to the invention.

Figs 6A, 6B and 6C are schematic side views in a vertical elevation that show the moving away steps of the gripping means of the advancement apparatus according to the invention from the forming station.

Fig. 7 shows a detail of Fig. 6A.

Fig. 8 is a perspective view of locking means of the advancement apparatus according to the invention.

Figs 8A, 8B and 8C show sectioned details of portions of the locking means of Fig. 8.

Fig. 9 is another side view in a vertical elevation that shows the different advancement steps of a product inside a thermoforming apparatus by the advancement apparatus according to the invention.

Fig. 10 is a side view of gripping means of the advancement apparatus according to the invention.

Fig. 11 is a perspective view of the gripping means of Fig. 10.

Fig. 12 is a perspective view of a detail of the gripping means of Fig. 11.

Fig. 13 is a perspective section view of Fig. 11.

Fig. 14 is a view in a vertical elevation of the gripping means and of the conveying means of the advancement apparatus according to the invention.

Fig. 15 is a side view in a vertical elevation of the conveying means of the advancement apparatus according to the invention.

With reference to the attached figures, a forming apparatus, in particular a thermoforming apparatus, is shown schematically which includes an advancement apparatus for advancing sheet or plate-shaped products made of plastics, in particular a thermoplastic material that can cyclically soften under the action of the heat; be modelled or formed to adopt a desired shape and that, by cooling, becomes substantially stiff again. Each product, in particular having, on a plane view, a square or rectangular shape, can comprise a first edge 2a and a second edge 2b that are mutually opposite, a third edge 2c and a fourth edge 2d which are also mutually opposite and arranged transversely to the first edge 2a and to the second edge 2b.

The advancement apparatus, coupled with the stations of the forming apparatus, has the function of advancing a plurality of products Pl, P2, P3, P4,... in the form of a sheet or plates along the various process zones, as shown schematically in Figs 2-5. The thickness of the products can be variable, i.e. the advancement apparatus is able to advance products Pl, P2, P3, P4,... that have the thickness as of a film and/or a thickness that is greater but anyway suitable for carrying out thermoforming to obtain the required geometry of a product that is free of defects.

The forming apparatus can comprise a loading station 1 in which the plurality of products Pl, P2, P3, P4,...can be loaded, downstream of which a heating station 3 can be arranged for heating one product at a time of the plurality of products Pl, P2, P3, P4,.... In particular, in the heating station 3 an oven can be provided that is able to heat each product to bring the product to a softened state.

Downstream of the heating station 3, a forming station 6 can be arranged, in particular a thermoforming station for performing at least one thermoforming task on the product previously heated to the softening temperature. In the forming station 6 the product is shaped to obtain the desired product by pressing action, by a punch 6b insertable into a die 6a as shown in Fig. 9, in particular by stretch blow moulding, or also by the action of the vacuum.

Between the heating station 3 and the forming station 6, a pre-heating station 15 can be provided that is suitable for preheating each product for splitting up the heating in several steps, thus avoiding that the product is subjected to too sudden temperature increase in the heating station 6.

The advancement apparatus, as already said, can be connected to the aforesaid forming apparatus to advance along a main direction D at least one product at a time of the plurality of products Pl, P2, P3, P4,..., from the loading station 1 to the forming station 6, passing through the heating station 3 and the pre-heating station 15 (if provided).

The advancement apparatus can comprise conveying means 8 that extends and is movable longitudinally in a direction parallel to the main advancement direction D. The conveying means is configured for conveying a first product Pl of the plurality of products Pl, P2, P3, P4,... from the loading station 1 to the forming station by grasping and maintaining gripped the first edge 2a and the second edge 2b of the aforesaid first product Pl, as shown schematically in Fig. 2 and explained in detail below.

In one embodiment shown in Fig. 15, the conveying means 8 can comprise transmitting members, for example chain transmitting members 8a, each of which comprises a plurality of meshes 18 provided with an abutting tip 19.

In a version according to the invention, the chain transmitting members 8a can be positioned in the vicinity of the edge 2a and in the vicinity of the edge 2b to abut on an upper face F of the first product Pl.

The conveying means 8 can further comprise non-motorized contrasting rollers 8b arranged for cooperating with the chain transmitting member 8a for advancing the product Pl.

In the version shown, the contrasting rollers 8b can be arranged in the vicinity of the edge 2a and in the vicinity of the edge 2b to abut on another face G of the first product Pl opposite the face F.

In the side view of Fig. 15, only one chain transmitting member 8a is shown that is intended to abut on the first product Pl at the face F and near the first or the second edge, for example the first edge 2a, and a single unit of contrasting rollers 8b intended to abut on the product Pl at the other face G. In this manner, the abutting tips 19 and the contrasting rollers 8b grasp the first edge 2a, thus advancing the first product Pl along the main direction D. In a completely similar manner, the abutting tips 19 and the contrasting rollers 8b grasp the second edge 2b.

In other embodiments that are not illustrated, transmitting members can be of the toothed belt, belt, or“pilgrim step” gripper type known to expert persons, and so on.

The advancement apparatus can further comprise gripping means, in particular first gripping means 4 and second gripping means 5 drivable to grasp respectively the third edge 2c and the fourth edge 2d of the first product Pl of the plurality of products Pl, P2, P3, P4,... in the heating station 3, to transfer the product Pl along the main direction D from the heating station to the forming station 6, and move away from the forming station 6 in a direction opposite the main direction D to the heating station 3 to grasp a second product P2, as will be disclosed in detail below.

The first gripping means 4 is configured in a completely similar manner to the second gripping means 5 both at a structural and operational level, thus the same parts and/or components will have the same numeric reference and, in the course of the description, reference can be made to the first gripping means 4 or to the second gripping means 5 indifferently by the term“gripping means” 4, 5.

With reference to Figs 7 and 10 to 13, the gripping means 4, 5 can comprise elements suitable for grasping and maintaining gripped at least one edge of the product Pl, for example of the gripper, clamp, suction cup type, or elements equipped with openings placed in connection with sucking means.

The gripping means 4, 5 can be configured for adopting a disengaged position X and an operating gripping position Y with respect to the first product Pl, as will be explained in detail below.

In the disengaged position X, for example illustrated in Fig. 6C, the means 4, 5 are arranged in a first space volume that faces a face of the product Pl, for example the face F, whereas in the operating gripping position Y, for example illustrated in Fig. 6A and in detail in Fig. 7, the gripping means 4, 5 partially occupy the aforesaid first space volume and partially a second space volume opposite the aforesaid first space volume with respect to the first product Pl.

In the disengaged position X the gripping means 4, 5 can be arranged entirely above the first product Pl, for example on the face F of the first product Pl.

In other words, the first gripping means 4 comprises an abutting part 9 that is fixed with respect to the first product Pl - for example a fixed jaw of a gripper - intended in use to be placed in contact with the face F of the aforesaid first product Pl, and a further abutting part 10 that is rotatable around a rotation axis R - for example the movable jaw of a gripper - and is intended to exert a clamping pressure on the other face G of the aforesaid first product Pl and against the respective abutting part 9.

The rotation axis R of the first gripping means 4 and the rotation axis R of the second gripping means 5 are arranged parallel to an advancement plane for advancing the products Pl, P2, P3, P4, ... and transversely to the main advancement direction D. In disengaged position Y the abutting part 9 and the further abutting part 10 occupy the aforesaid space volume, i.e. are arranged entirely above the first product Pl.

In the operating gripping position, the abutting part 9 occupies the aforesaid first space volume with respect to the first product Pl, being in contact with the face F, whilst the further abutting part 10 is in contact with the other face G, thus occupying the second space volume.

The gripping means 4, 5 is further configured for reaching the operating gripping position Y when the gripping means 4, 5 is moved from the heating station 3 to the forming station 6 to minimize deformation of the third edge 2c and the fourth edge 2d, whilst the gripping means 4, 5 is configured for reaching the disengaged position X when the gripping means 4, 5 is moved from the forming station 6 to the heating station 3 to grasp a second product P2 that reaches the aforesaid heating station 3, without there being shocks or undesired contacts before grasping.

Each of the first gripping means 4 and of the second gripping means 5 are connected to a drive unit 17, illustrated in Fig. 7, configured for rotating the further rotatable abutting parts 10 from the operating position Y to the disengaged position X or from the disengaged position X to the operating gripping position Y. As illustrated in detail in Figs 10, 12 and 13, the drive unit 17 can comprise for example a motor 20 arranged inside a box body 21.

The motor 20 can be of the commercially known type, i.e. comprising an electric (or pneumatic) motor, speed reducing members and an output shaft 22. The shaft 22 can rotate around the rotation axis R.

A rod element 23 can be fitted to the output shaft 22 to connect and transmit motion from the shaft 22 to the further abutting part 10.

In use, the motor can be driven to rotate the connecting rod 23, taking the further abutting part 10 from the operating gripping position Y to the disengaged position X, and vice versa. As already said, the first gripping means 4 and the second gripping means 5 can grasp respectively the third edge 2c and the fourth edge 2d arranged transversely to the first edge 2a and the second edge 2b, i.e. transversely to the main advancement direction

D.

In a version according to the invention, the width of the gripping means 4, 5 cannot be varied; as a result, if the width of the product Pl (width is the dimension oriented parallel to the arrangement of the third edge 2c and the fourth edge 2d) varies, it becomes necessary to replace the gripping means 4, 5 with another similar gripping means that is configured identically but has different dimensions.

In another version that is not illustrated, the width of the gripping means 4, 5 can be modified, for example by using telescopic means to adapt to the width of the products to be advanced.

The advancement apparatus furthermore comprises first motor means 11 and second motor means 12 arranged respectively on the first gripping means 4 and on the second gripping means 5. The first motor means 11 and the second motor means 12 can be drivable for moving the gripping means 4, 5 from the heating station 3 to the forming station 6 and vice versa, along the aforesaid main advancement direction D at advancement speeds that are independent of one another. The first motor means 11 and the second motor means 12 can comprise an electric (or pneumatic) motor, speed reducing members and a further output shaft 25. A pair of pivots 26 can be fitted to the two ends of the further shaft 25. Each of the pivots 26 can rotate around another rotation axis S, parallel to the rotation axes R.

Each of the pivots 26 can engage a respective rack 24 to move the gripping means 4, 5 from the heating station 3 to the forming station 6 and vice versa.

In a version according to the invention, the motor means 11 is drivable for moving the first gripping means 4 at a speed that is greater than the speed at which the second motor means 12 moves the second gripping means 5, in order to subject the first product Pl to a tensioning state and reduce deformation (downward“bulging” effect) caused by the force of gravity during the transfer from the heating station 3 to the forming station 6.

In other words the distance between the gripping means 4 and the gripping means 5, evaluated in a direction parallel to the main direction D, can vary from a minimum distance, when the gripping means 4, 5 moves at the same advancement speed, to a maximum distance when the first gripping means 4 moves at a speed that is greater than the second gripping means 5.

The advancement apparatus also comprises third motor means 13, shown schematically in Fig. 14; the motor means 13 is fitted to the conveying means 8, in particular to the chain dragging members 8a, and is driven to move the aforesaid conveying means 8 from the loading station 1 to the forming station 6 along the main advancement direction D, at a further advancement speed different from the speed of the first gripping means 4 and of the second gripping means 5.

The advancement apparatus further comprises locking means 7 that can be arranged in the forming station 6 to abut on the first product Pl moving in a transverse direction T that is transverse to the main advancement direction D, and to maintain the first product constrained on the perimeter during the release of the third edge 2c by the first gripping means 4 and the fourth edge 2d by the second gripping means 5 and during thermoforming of the first product Pl.

The transverse direction T can be a perpendicular direction evaluated with respect to a resting plane on which the thermoforming apparatus rests, for example a vertical direction if the resting plane is arranged horizontally.

In other words, the locking means 7 comprises a frame element 7a connected to drive means of known type, for example of motors, drivable for moving the aforesaid frame element 7a along the transverse direction T to make the aforesaid frame element 7a abut on the other face G of the first product. In a version illustrated in Figs. 8, 8A, 8B and 8C, on the front portion and on the rear portion of the frame element 7 a (where the front portion and the rear portion are defined by considering as a reference the main advancement direction D of the product partially shown in Fig. 8) a groove 27 is provided extending transversely and parallel to the arrangement of the third edge 2c and of the fourth edge 2d.

On each groove 27, a plurality of orifices 16 can be provided that are placed in flowing communication with sucking means 14, for example a vacuum pump. The sucking means 14 is suitable for sucking air to exert, through the orifices 16, a retaining action on the aforesaid third edge 2c and fourth edge 2d of the first product Pl.

Through the orifices 16, the sucking means enables the first product Pl to be retained and maintained in position during the release of the third 2c and of the fourth edge 2d by the first gripping means 4 and by the second gripping means 5, as will be disclosed below.

The locking means 7 further comprises a further frame element 7b which is also connected to the aforesaid drive means that is drivable for moving the further frame element 7b along a further direction T’ parallel to and opposite the transverse direction T.

The further frame element is intended to abut on the face F and the first 2a, second 2b, third 2c and fourth edge 2d of the first product Pl against the frame element 7a after the release of the gripping means 4, 5, and permit thermoforming of the first product Pl.

On the front portion and on the rear portion of the further frame element 7b, protrusions 28 can be provided corresponding to the grooves 27.

In the context of the invention,“position corresponding to the grooves” means that the further frame element 7b abuts on the face F of the first product and simultaneously abuts on the first 2a, the second 2b, the third 2c and the fourth edge 2d against the frame element 7a, whereas each protrusion 28 engages the respective groove 27 to grasp and maintain gripped the third 2c and the fourth edge 2d of the first product Pl.

The frame element 7a and the further frame element 7b have dimensions that are such as to be able to abut on the first product Pl without entering into contact with the two chain dragging members 8a that grasp the first edge 2a and the second edge 2b, and with the first 4 and second 5 gripping means that grasp the third 2c and fourth 2d edge.

In other words the distance between the two chain dragging members 8a is greater than the width of the frame element 7 a and of the further frame element 7b, whereas the minimum distance between the first 4 and the second 5 gripping means is greater than the length of the frame element 7 a and of the further frame element 7b.

The frame element 7a and the further frame element 7b are intended to mutually couple, and in particular the groove 27 and the protrusion 28, in order to enable the first product Pl to be maintained locked during thermoforming and to counter the forming forces acting on the aforesaid first product Pl.

The sucking means 14 can be possibly driven to facilitate the retaining action exerted by the coupling between the frame element 7 a and the further frame element 7b, and in particular between the groove 27 and the protrusion 28, during the thermoforming operation.

Other temporary retaining means known to an expert, for example suction cup elements, claws elements and so on, can be provided on the frame element 7a to retain the third 2c and the fourth edge 2d.

With reference to Figs 2-6, the operation is disclosed of the advancement apparatus that has just been disclosed and thus the method according to the invention actuated by the advancement apparatus. The method comprises a first loading step for loading the loading station 1 with the plurality of products Pl, P2, P3, P4,

A second step is provided in which the first product Pl is transferred from the loading station 1 to the heating station 3 along a main advancement direction D by grasping and maintaining gripped the first edge 2a and the second edge 2b by the aforesaid conveying means 8.

The method provides for grasping, in the heating station 3, the third edge 2c and the fourth edge 2d by the first gripping means 4 and the second gripping means 5 respectively.

In Fig. 2 four products are shown in the respective four stations of the forming apparatus, the first product Pl is loaded in the loading station 1, a second product P2 is in the pre-heating station 15 (if envisaged), a third product P3 is in the heating station 3 and a fourth product P4 is in the forming station 6.

In Fig. 3, the product Pl is visible, advanced by the conveying means 8 from the loading station 1 to the heating station 3 (possibly passing from the pre-heating station 15) and the third edge 2c and fourth edge 2d of which are grasped by the first gripping means 4 and second gripping means 5.

A fourth heating step for heating the first product Pl in the heating station 3 is provided, maintaining gripped the first edge 2a and the second edge 2b with the conveying means 8, the third edge 2c and the fourth edge 2d with the gripping means 4, 5.

Subsequently, there is the transfer of the first product Pl from the heating station 3 to the forming station 6, keeping the third edge 2c grasped with the first gripping means 4, and the fourth edge 2d with the second gripping means 5. During the transfer of the first product Pl, the first edge 2a and the second edge 2b are also maintained gripped with the conveying means 8, as illustrated in Fig.4. A sixth drive step for driving the locking means 7 in the forming station 6, in a transverse direction T transverse to said main advancement direction D is provided to take the locking means 7 to abut on said first product Pl, and a subsequent release step for releasing the third edge 2c from the first gripping means 4 and releasing the fourth edge 2d from the second gripping means 5, keeping the first product Pl gripped with the locking means 7, as explained below in detail.

The frame element 7a can be brought into contact with a lower face G of the first product Pl, moving in the transverse direction T, and exerting a retaining action on the third edge 2c and the fourth edge 2d by sucking air through a plurality of orifices 16 obtained in the aforesaid frame element 7a to enable the third edge 2c and fourth edge 2d to be retained during the release step for releasing from the first 4 and second 5 gripping means.

The third 2c and the fourth edge 2d can be retained by other temporary retaining means provided on the frame element 7a that are known to an expert person, for example suction cup elements, gripping elements and so on.

An eighth step of removing the first gripping means 4 and the second gripping means 5 from the forming station 6 can be provided by moving the first gripping means 4 and the second gripping means 5 in a direction opposite the main advancement direction D, towards the heating station 3 to grasp the second product P2, which in the meantime has been transferred from the loading station 1 to the heating station 3, as illustrated schematically in Fig. 5.

The aforesaid step of removing the gripping means 4, 5 from the forming station 6 to grasp a second product P2 that has been transferred in the meantime to the heating station 3 can comprise the substeps of moving the gripping means 4, 5 from a disengaged position X that is disengaged from the first product Pl, in which the gripping means 4, 5 is completely located in a first space volume facing a face F of the first product Pl, to an operating gripping position Y in which the first 4 and second 5 gripping means partially occupy the first space volume and partially occupy a second space volume opposite the aforesaid first volume with respect to the first product Pl.

In particular, in the disengaged position X the gripping means 4, 5 can be arranged entirely above the first product Pl.

With reference to Figs 6A, 6B, 6C, the step is shown schematically of moving the gripping means 4, 5 from the forming station 6 and the passage from the operating gripping position Y to the disengaged position X.

In the operating gripping position of Fig. 6A, enlarged in Fig. 7, the first gripping means 4 and the second operating gripping means 5 have respective abutting parts 9 placed in contact with the face F of said first product Pl, whilst it is possible to rotate further pivotable abutting parts 10 to occupy the second space volume and to exert clamping pressure on another face G of the first product Pl against the respective abutting parts 9.

The further abutting parts 10 can be rotatable around respective rotation axes R arranged parallel to an advancement plane of products Pl, P2, P3, P4,... and transversely to the main advancement direction D.

In figure 6B, the further abutting parts 10 are rotated by an angle greater than or the same as 180° to occupy the aforesaid first space volume, permitting the first 4 and second 5 gripping means to release the third edge 2c and the fourth edge 2d of the first product Pl and move away from the forming station 6.

A ninth thermoforming step can be provided for thermoforming the first product Pl in the forming station 6, maintaining the perimeter of the first product Pl constrained by the locking means 7.

The further frame element 7b in fact comes into contact with the face F of the first product Pl along a further transverse direction T’, parallel to and opposite the transverse direction T, to abut simultaneously on the first 2a, the second 2b, the third 2c and the fourth edge 2d of the first product Pl against the frame element 7a. Coupling between the frame element 7a and the further frame element 7b enables the first product Pl to be maintained locked during the thermoforming step.

Locking the first product Pl can be facilitated by exerting the action of retaining the third 2c and the fourth edge 2d by the sucking of air through the plurality of orifices 16 obtained on the frame element 7a.

The step of transferring the first product Pl from the heating station 3 to the forming station 6, while maintaining the third edge 2c grasped with the first gripping means 4, and the fourth edge 2d with the second gripping means 5, can also comprise moving along the main advancement direction D the first means 4, 5 independently and autonomously at two advancement speeds that are different from one another.

In particular, it is possible to move the first gripping means 4 at a greater advancement speed than that of the second gripping means 5, in order to subject the first product Pl to a tensioning state during the aforesaid transferring step, limiting deformation thereof because of the force of gravity. Further, maintaining in a clamped position all the edges 2a, 2b, 2c, 2d during the transfer enables the products to reach the thermoforming station with the edges substantially undeformed and reduces the probability by preventing defects arising during the thermoforming step.

As can be seen from what has been disclosed, the apparatus and the corresponding method according to the invention enable the objects declared above to be reached.

Owing to the invention, it is possible to advance each sheet or plate-shaped product P, whilst the product P is in a softened thermal state, preventing deformation of the transverse edges.

The operations of release and/or grasping of the sheet- shaped product are moreover simplified and deformation of the product caused by the weight effect is limited equally effectively. It is further pointed out that great optimization and speeding up of the operations of transfer and handling of the products to be thermoformed are achieved.

The apparatus disclosed above is distinguished by great versatility of use, and is suitable for handling any format of plates/sheets made of plastics, owing to the easy adaptability of the various components, in particular the gripping means 3, 5 of the gripper type.

It is possible to configure and size the apparatus 1 in a desired manner according to the type of products to be advanced and variations on and/or additions to what has been disclosed and illustrated in the attached drawings are possible.

Claims

1. Method for advancing sheet or plate-shaped products made of plastics to be thermoformed, comprising the steps of:

a) loading a loading station (1) with a plurality of products (Pl, P2, P3, P4,...) each of which comprises a first edge (2a) and a second edge (2b) that are mutually opposite, a third edge (2c) and a fourth edge (2d) mutually opposite and arranged transversely to said first edge (2a) and said second edge (2b);

b) conveying a first product (Pl) from said loading station (1) to a heating station (3) along a main advancement direction (D) by grasping and keeping gripped said first edge (2a) and said second edge (2b) by conveying means (8) that extend and are longitudinally movable parallel to said main direction (D);

c) grasping, in said heating station (3), said third edge (2c) and fourth edge (2d) by first gripping means (4) and second gripping means (5) respectively;

d) heating said first product (Pl) in said heating station (3) while keeping gripped said first edge (2a), second edge (2b), third edge (2c) and fourth edge (2d); e) transferring said first product (Pl) from said heating station (3) to a forming station (6), while keeping said third edge (2c) grasped with said first gripping means (4), said fourth edge (2d) with said second gripping means (5) and while keeping said first edge (2a) and said second edge (2b) gripped with said conveying means (8); f) in the forming station (6), moving locking means (7) in a transverse direction (T) that is transverse to said main advancement direction (D) to make the locking means (7) abut on said first product (Pl);

g) releasing said third edge (2c) from said first gripping means (4) and said fourth edge (2d) from said second gripping means (5) and keeping said first product (Pl) gripped by said locking means (7);

h) removing said first gripping means (4) and said second gripping means (5) from said forming station (6) by moving them, in a direction opposite said main advancement direction (D), to said heating station (3) to grasp a second product (P2) that has been in the meantime transferred from said loading station (1) to said heating station (3);

i) thermoforming said first product (Pl) in said forming station (6) while keeping said first product (Pl) perimetrally constrained by said locking means (7).

2. Method according to claim 1, wherein said first (4) and second (5) gripping means are moved from a disengaged position (X) with respect to said first product (Pl), in which said first (4) and second (5) gripping means are completely located in a first space volume facing a face (F) of said first product (Pl), to a gripping operating position (Y) in which said first (4) and second (5) gripping means partially occupy said first space volume and partially a second space volume opposite said first volume with respect to said first product (Pl).

3. Method according to claim 2, wherein said first and second gripping means (4, 5), in said disengaged position (X), are arranged entirely above said first product

CP).

4. Method according to claim 2 or 3, wherein said first and second gripping means (4, 5), in said gripping operating position (Y), have respective abutting parts

(9) placed in contact with said face (F) of said first product (Pl), and in which further pivotable abutting parts (10) of said first and second gripping means (4, 5) are rotated to exert a clamping pressure on another face (G) of said first product (Pl) against the respective abutting parts (9).

5. Method according to claim 4, wherein said further pivotable abutting parts

(10) are rotated around respective rotation axes (R) arranged parallel to an advancement plane of said products (Pl, P2, P3, P4,...) and transversely to said main advancement direction (D).

6. Method according to any preceding claim, wherein during the step e) of transferring said first product (Pl) from said heating station (3) to said forming station (6), along said main advancement direction (D), said first (4) and second (5) gripping means are moved autonomously and independently of one another and at two respective advancement speeds different from one another.

7. Method according to claim 6 wherein said first (4) gripping means is moved at a higher speed than said second (5) gripping means to subject said first product (P) to a tensioning state during said step e) of transferring to said forming station (6).

8. Method according to claim 6, wherein during the step e) of transferring said first product (Pl) from said heating station (3) to said forming station (6), there is provided moving, along said main advancement direction (D), said first (4) and second (5) gripping means autonomously and independently by said conveying means (7) and at respective advancement speeds that are different from one another.

9. Method according to any preceding claim, wherein before said heating step d) there is provided a preheating step d’) in a preheating station (15) interposed between said loading station (1) and said heating station (3).

10. Method according to any preceding claim, wherein during said step f) a lower frame element (7a) of said locking means (7) is brought into contact with said other lower face (G) of said first product (Pl), and a retaining action is performed for retaining said third (2c) and fourth (2d) edges by sucking air through orifices (16) obtained on said lower frame element (7a) to permit the subsequent step g) of releasing said first (4) and second (5) gripping means.

11. Method according to claim 10, wherein there is provided bringing a further upper frame element (7b) of said locking means (7) into contact with said face (F) of said first product (Pl), to clamp simultaneously said first (2a), second (2b), third (2c) and fourth (2d) edges against said lower frame element (7a) to permit the subsequent step i) of thermoforming said first product.

12. Thermoforming apparatus comprising an apparatus for advancing sheet or plate- shaped products made of plastics, configured for implementing the method according to any preceding claim, and including:

- a loading station (1) arranged for being loaded with a plurality of products (Pl, P2, P3, P4,...) each of which comprises a first edge (2a) and a second edge (2b) that are mutually opposite, a third edge (2c) and a fourth edge (2d) that are mutually opposite and arranged transversely to said first edge (2a) and said second edge (2b);

- a heating station (3) arranged downstream of said loading zone (1) for heating a first product (Pl) of said plurality of products (Pl, P2, P3, P4,...);

- a forming station (6) arranged downstream of said heating zone (3) for performing a forming processing on said first heated product (Pl);

said advancement apparatus comprising:

- conveying means (8) extending and being movable longitudinally parallel to a main advancement direction (D), said conveying means (8) being configured for grasping and keeping gripped said first edge (2a) and said second edge (2b) to transport said first product (Pl) from said loading station (1) to said forming station (6) and;

- first gripping means (4) and second gripping means (5) drivable for grasping respectively said third edge (2c) and said fourth edge (2d) in said heating station (3), for transferring said first product (Pl) along said main direction (D) from said heating station (3) to said forming station (6) while keeping gripped said third edge (2c) and said fourth edge (2d), for releasing said third edge (2c) and said fourth edge (2d) in said forming station (6), and for moving away from said forming station (6) in an opposite direction to said main direction (D) towards said heating station (3) to grasp a second product (P2);

- locking means (7) arranged in said forming station (6) for abutting on said first product (Pl) moving in a transverse direction (T) that is transverse to said main advancement direction (D), and for maintaining said first product (Pl) constrained during the release of said third edge (2c) and of said fourth edge (2d) by said first (4) and second (5) gripping means and during thermoforming of said first product (Pl).

13. Apparatus according to claim 12, wherein said first gripping means (4) and said second gripping means (5) are configured to reach a disengaged position (X) with respect to said first product (Pl) in which they are completely arranged in a first space volume facing a face (F) of said product (Pl), and a gripping operating position (Y) in which they partially occupy said first space volume and partially a second space volume opposite said first volume with respect to said first product (Pl).

14. Apparatus according to claim 13, wherein said first gripping means (4) and said second gripping means (5), in said disengaged position (X), are arranged entirely above said first product (Pl).

15. Apparatus according to claim 13 or 14, wherein each of said first gripping means (4) and said second gripping means (5) comprise an abutting part (9) placed in contact with said face (F) of said first product (Pl), and a further pivotable abutting part (10) that is ratable around a rotation axis (R) intended to exert a clamping pressure on another face (G) of said first product (Pl) against the respective abutting part (9).

16. Apparatus according to claim 15, wherein the rotation axis (R) of said first gripping means (4) and the rotation axis (R) of said second gripping means (5) are arranged parallel to an advancement plane of said products (Pl, P2, P3, P4,...) and transversely to said main advancement direction (D).

17. Apparatus according to claim 15 or 16, comprising drive units (17) for rotating said further pivotable abutting parts (10) from the gripping operating position (Y) to the disengaged position (X) or from the disengaged position (X) to the gripping operating position (Y).

18. Apparatus according to any one of claims 12 to 17, further comprising first motor means (11) and second motor means (12) that are drivable for moving respectively said first gripping means (4) and said second gripping means (5) from said heating station (3) to said forming station (6), along said main advancement direction (D), at advancement speeds that are independent of one another.

19. Apparatus according to claim 18, wherein said first motor means (11) moves said first gripping means (4) at a greater speed than the speed at which said second motor means (12) moves said second gripping means (5), to subject said first product (Pl) to a tensioning state.

20. Apparatus according to any one of claims 12 to 19, further comprising third motor means (13) driven to move said third conveying means (8) from said loading station (1) to said forming station (6) along said main advancement direction (D), at a further advancement speed that is different from the speeds of said first (4) and second (5) gripping means.

21. Apparatus according to any one of claims 12 to 20, wherein said forming apparatus further comprises a preheating station (15) for preheating said plurality of products (Pl, P2, P3, P4, ...), arranged between said loading station (1) and said heating station (3).

22. Advancement apparatus according to any one of claims 12 to 21, wherein said locking means (7) comprises

- a frame element (7a) intended to abut on said other face (G) of said first product (Pl), said frame element (7a) being provided with orifices placed in flow- communication with sucking means (14) suitable for sucking air to exert a retaining action on said third (2c) and fourth (2d) edge to permit release by said first (4) and second (5) gripping means of said third (2c) and fourth (2d) edge of said first product

(Pi);

- a further frame element (7b) intended to abut on said face (F) to clamp simultaneously said first (2a), second (2b), third (2c) and fourth (2d) edge against said frame element (7a) to permit thermoforming of said first product (Pl).