PROCESS AND APPARATUS FOR THE MANUFACTURE OF SHAPED ARTICLES OR PIECES FROM A SHEET OF ORIENTABLE PLASTIC MATERIAL

Abstract: Shaped articles are manufactured from a thin band (2) of orientable plastic material by stamping the band between two dies (15, 33) having complementary profiles, these dies being carried by parallel plates (6, 27), at least one of these plates being movable with respect to the other, so as to press the plastic band around the area to be stamped or embossed. One (27) of the plates (6, 27) comprises a fixed part (29, 30) to which is fixed one (33) of the dies (15, 33) and which elastically supports a movable plate (47) cooperating with one (6) of the plates (6, 27) for pressing the plastic band during the interpenetration of the dies (15, 33) which locally deform permanently the plastic band.

Description: PROCESS AND APPARATUS FOR THE MANUFACTURE OF SHAPED ARTICLES OR PIECES FROM A SHEET OF ORIENTABLE PLASTIC MATERIA . This invention relates to a process and to an apparatus for the manufacture of shaped pieces or articles from a plastic sheet or film, said plastic material having some degree of crystallinity and being therefore orientable when it is subjected to stretching or tensile forces. Plastic materials which may be used whithin the scope of this invention are, for example, polypropylene or polyesters, such as polyethylene terephthalate. The pieces or articles manufactured by the process and by means of the apparatus according to this invention may have various shapes , such as the shape of cups, the shape of discs provided with concentrical pleats and forming a flat bellow piece or generally the shape of circular or polygonal articles having portions which are raised and/or lowered with respect to their central plane. It is known to manufacture articles made from a ther osetting plastic material by injection of such a material into a mold. However, this process cannot be used for obtaining pieces or articles having very thin walls, since it is difficult and even impossible to fill in the mold even by injecting plastic material under a very high pressure into said mold, when the walls of said mold are near each other. The injection molding is therefore not suitable for the manufacture of thin-walled articles. The manufacture of such thin- walled pieces or objects is frequently desirable for economical reasons, for example when these objects or pieces are disposed off after use. It is also known to manufacture plastic shaped pieces or articles by thermoforming. When it is desired to use plastic materials having a well de- fined melting point, such as polypropylene, the thermo¬ forming process requires a very precise control of the temperature at which the plastic material is molded, so that an expensive equipment is needed. Moreover, even very small variations of the temperature of the surface of the articles made by thermoforming cause important variations of the thickness of said articles, the flui¬ dity of the plastic material being very dependent on the temperature which is applied thereto. When thin- walled shaped articles or pieces are manufactured by thermo orming, the percentage of wastes i.e. of defec¬ tive articles, is frequently important, even when using a thermoforming apparatus equipped with expensive means for adjusting and distributing the preparation to which the plastic material, for example in the form of a sheet or strip, is subjected during the thermoforming step. It has now been found that it is possible by using a purely mechanical process to manufacture, at a very high speed and without any heating, from a very thin plastic sheet or strip, shaped pieces or articles of very good quality, the thickness of said sheet or strip being for example of 200 to 300 microns. It is possible, by the mechanical moldin process and apparatus according to this invention, t obtain at room temperature shaped articles or pieces having very thin walls, the capital investment needed b the process and apparatus being lower than that neede by the thermoforming process and the results being more reproducible than the results obtained by the know thermoforming process. This is due to the fact that th process according to this invention does not need an heating of the plastic material and that the resul obtained by this process only depend on mechanica parameters which can be more easily controlled than th temperature, these parameters being, among others, th form of the used dies and the molding speed. According to the invention, the process fo manufacturing shaped articles or pieces from a sheet o film of a plastic material having some degree o crystallinity, by permanent local deformation of sai plastic sheet or film by means of two dies havin complementary profiles, is essentially characterized b the fact that it comprises the following steps : (1) the plastic sheet is immobilized by pressin together two plates which support each one of sai dies and between which the plastic sheet i located, so that the opposite surfaces of sai sheet is firmly squeezed between said plates i the area or areas of the sheet where n deformation must occur ; (2) the plastic sheet is locally stamped by causing an interpenetration of the dies, between which are located the areas of the immobilized sheet which must be deformed, by moving at least one of said dies with respect to its support plate, so as to stretch and orient the plastic sheet beyond its elastic limit in the areas of the sheet which are deformed by the dies ; (3) the dies and the plates supporting the latter are moved away from each other, and (4) the deformed areas or parts of the plastic sheet are ejected from the dies. In accordance with a feature of the process, the plastic sheet is preferably a continuous band which is moved step by step from a supply source consisting in a roll or reel delivering such a plastic band. According to another feature of the process, one of the plates supporting a die is maintained in a fixed position, whereas the other plate supporting the other die is movable with respect to the first plate, at least one of dies being movable with respect to its support plate against the action of springs. The apparatus for carrying out the process according to the invention is essentially characterized by the fact that it comprises a device for stamping a sheet or band of plastic material, this device compri¬ sing a first movable plate, to which is fixed a first die, and a second composite plate which is parallel to the first plate and to which is fixed a second die having a profile which is complementary to that of the first die, the composite plate comprising a fixed base part to which the second die is fixed and a movable part elastically supported by the fixed base part, means being provided for moving the plates supporting the dies toward and away from each other. Each die is preferably provided, on the profiled side, with a central bore which opens into the face of the die contacting the plastic sheet, a core subjected to the action of a spring being mounted in said bore, so as to be able to move therein on a distance limited by a stop. The composite plate comprises preferably a first fixed base plate to which a die is fixed and which supports elastically a movable plate, one face of which is intended to contact one face of the plastic sheet or band. The movable plate is connected to the first plate by rods having one end fixed to the movable plate and the other end of which carries a head which is slidable in a bore of the lower plate against the action of springs . These springs may be helical springs or Belleville discs bearing, on the one hand, against the base plate and, on the other hand, against the movable plate. As a whole, the apparatus according to the invention comprises a source for the supply of a continuous band of plastic material, a supporting table on which said continuous band is moved forward, a stamping device as defined hereabove, a device for causing the plastic band to advance step by step and a device for cutting shaped pieces or articles from said band downstream the stamping device. Other features and details of the invention will appear in the following detailed description, in which reference is made to the attached schematic drawings, in which : Fig 1 is a schematic side elevation of an apparatus for the manufacture of shaped pieces or articles from a sheet or band of plastic material ; - Fig 2 is a section showing the stamping device in the open position ; - Fig 3 is a section showing the stamping device in the closed position ; Fig 4 is a view of the stamping device in the direction of arrow X in fig. 3 ; Figs 5 and 6 show, respectively in cross-section and plane view, an example of a shaped article manufactured by the process according to the inven¬ tion, and Fig 7 shows a plastic band in which articles have been made by stamping, at the outlet of the stamping device and before these articles are separated from the band by punching. In these various figures, the same references designate identical elements. The apparatus shown in fig. 1 comprises a source 1 for supplying a band of plastic material having some degre of crytallinity, such as a polypropylene band, which may, for example, have a width of 75 mm and a thickness of 200 to 300 microns. The supply source may be a reel from which the band of plastic material 3 is unrolled, said reel 1 having a rotating core 3, the ends of which are supported by known means (not shown). The band of plastic material 2 which leaves the reel 1 passes onto cylinders 4, between which it forms a downwardly directed loop. This loop is formed by means of a ring 5 having a large diameter, which is applied, under its own weight, on the band and is maintained in a vertical position between two paral¬ lel walls (not shown). After it has passed onto the second cylinder 4, the plastic band passes through the stamping device 6, whereafter the band in which shaped pieces or articles have been formed advances onto the longitudinal supporting table 7 which may be provided with side guides (not shown). A device 8 is provided for causing the plastic band 7 to advance step by step in the direction of arrow Y, so that said band 2 remains stationary in the stamping device 6 during the time (4 or 5 seconds) which is necessary for shaping the arti¬ cle, which may be a cup or an article comprising a multiplicity of concentric plies, as explained herein¬ after. A punching or cutting device 9 is used for separating the shaped articles from the plastic band, these articles being collected in a container 10 located below the table 7. The plastic band 2 wherein holes are provided at the places where the articles have been removed therefrom by cutting or punching is collected in a second container 11. Instead of being collected in the container 11, the perforated plastic band may be wound on a band or bobbin which may be caused to rotate by means of a winding device subjected to an intermittent rota¬ tion, the latter device replacing then the device 8. As shown in figures 2 and 3, the stamping device 6 comprises essentially an upper plate 12 which is movable in the direction of arrows Z. This plate 12 has preferably a rectangular shape and has a width which slightly exceeds that of the plastic band 2. This upper plate 12 has a central part 13 having a smaller thickness than its peripheral part 14, so that a downwardly open cavity is formed in said plate 12. An upper die 15 is removably fixed by screws 16 to the central part 13 of the upper plate. The upper die 15 may have a cylindrical or polygonal (for example a square or rectangular) shape, according to the form to be given to the article to be obtained in the plastic band 2. In the embodiment shown in figs. 2 and 3 of the upper die 15, the latter is provided with a central bore 17. This bore comprises an upper part 18 having a larger diameter than a lower part 19. This bore 17 comprises an upper part 18 having a larger diameter than a lower part 19, this bore 17 having thus a circular flange 20. A sliding cylindrical core 21 is located in the bore 17. The functions of this core 21 will be explained later. The core 21 has a head 22 having a larger diameter than the remaining part or shank 23 of said core 21. A spring 24 bears, on the one hand, on the central part 13 of the upper plate 12 and, on the other hand, on the head 21 of the core 21, so that this core 21 is permanently urged downwardly, the downward movement of the core 21 being limited by the circular flange 20 on which the head 22 of said core 21 bears, when the spring 24 is allowed to act fully. As shown particularly by fig. 2, wherein the parts of the stamping device are removed from each other (open position of this stamping device), the upper die 15 is provided with a series of projections 25 separated from each other by recesses 26 forming the profiled or shaped part of said upper die 15. Furthermore the stamping device comprises a lower composite plate 27 which is parallel to the upper plate 12 and has also preferably a square or rectangular shape. This lower composite plate 27 comprises a fixed plate 29 and a upper plate 30, the upper plane face of the lower plate 29 being applied against the lower plane face of the upper plate 30. Screws 31 (for example four screws) maintain the plates 29, 30 fixed or attached to each other. A lower die 33 is fixed by means of screws 32 to the upper plate 30, the upper face of said lower die 33 having a profile which is complementary to that of the lower face of the upper die 15. This means that the upper face of the lower die 33 has projections 35 alter- nating with recesses 36, the form and arrangement of which being such that an interpenetration of the upper die 15 and of the lower die 33 is possible, as shown in fig. 3. In the same manner as the upper die 15, the lower die 33 has a central bore 37 which comprises a lower part 38 having a larger diameter than an upper part 39, a flange 40 being provided between said parts 38, 39. A sliding cylindrical core 41, cooperating with the core 21 is placed within the bore 37. The core 41 has a head 42 of a larger diamater than the remaining part or shank 43 of said core 21. A spring 44 bears, on the one hand, against a central part 45 of lower thickness of the peripheral part 46 of the upper plate 30, and, on the other hand, on the head 42 of the core 41, so as to urge permanently said head against the flange 40 of the bore 37. The upward sliding of the core ' 41 is thus limited by the flange 40 of the cylindrical bore 37. The lower composite plate 27 comprises also a movable plate 47 carried by rods 48 which are screwed therein (49) and are each provided with a cylindrical head 50 which is slidable in coaxial bores 51 provided in the plates 29, 30 which constitute the lower fixed part 28 of the stamping device 6. A plurality of Belleville springs 52 surround each rod 48, said springs 52 bearing, on the one hand, on the lower face 53 of the movable plate 47 and, on the other hand, on the upper face 54 of the fixed plate 30. Instead of superimposed Belleville springs 52, helical springs may of course be used. The stroke of the rods 48 is limited by a circular recess or flange 55 provided in the bores 51, the latter having a part of larger diameter 56 opening into the lower face 57 of the lower fixed plate 29 and the other end of said bores 51 opening in the upper face 54 of the upper fixed plate 30. In fig. 2, the stamping device is shown in the open position, i.e. in the position in which its upper plate 12 and the upper die 15 are distant from the lower composite plate 27 and from the lower die 15 during one step of the intermittent advancing movement of the plastic band 2 in the direction of arrow Y. Each time that the plastic band 2 is stopped by the device 8 which causes it to advance step by step, the upper plate 12 is lowered by a mechanical device (such as a piston or a cam) or by a pneumatic or hydraulic device (such as a jack) so that the plastic band 2 is firmly pressed and immobilized between, on the one hand, the lower face 59 of the upper plate 12, the projections 25 of the upper die 15 and the free end 60 of the upper core 21 and, on the other hand, the upper face 61 of the movable plate 47 of the lower composite plate 27 and the free face 62 of the lower core 41. The faces 59, 60, 61, 62 have preferably a high friction coefficient, so as to inhibit any sliding of the plastic band 2 pressed between them, during the stamping operation. These faces 59 to 62 are preferably made of stainless steel. When the plastic band 2 is so pressed between the two parts of the stamping device, the downward movement of the upper plate 12 continues, so that the projections 25 of the upper die 15 penetrate into the recesses 36 of the lower die 33, whereas the projections 35 of the latter penetrate into the recesses 26 of the upper die 15, as shown in fig.3. Due to this interpenetration of the projections and recesses of the dies 15 and 33, the plastic band 2 is locally subjected to a permanent deformation, at these interpenetration places, so that concentric circular grooves 63 alternating with concen¬ tric circular projections 64 are formed therein. The side walls 65 of the grooves 63 and of the projections 64 are stretched during the interpenetration of the dies 15 and 33, so that the thickness of said side walls 65 is slightly diminished (as shown in fig. 5), said stretching exceeding the elastic limit of the plastic material, so that the latter becomes oriented. Under these circumstances, when a normally transparent crystalline plastic material, such as polypropylene, is used, the side walls 65 of the recesses 63 and of the projections 64 of the shaped article designated by the general reference 66 in figures 5 to 7 are white, whereas the remaining parts of said article, namely those designated by 67, 68, 70, which have not been stretched, have kept their thickness and have not been oriented. It is to be noted that, during the interpene¬ tration of the recessed and projecting parts of the dies 15 and 33, the movable plate 47 is lowered against the action of the Belleville springs 52, so that, in the completely closed position of the stamping device 6, the part of the lower die 33 which is provided with the projections 35 and the recesses 36 extends at a higher level than that of the upper face 61 of said movable plate 47 (see fig. 3). When the stamping operation is finished, the cores 21 and 41, which had been pushed back in their respective bores 17 and 37, against the action of the springs 24 and 44 are released, when the upper die 15 and the lower die 33 are moved away from each other. Under these circumstances, the cores 21 and 41 are pushed by their respective springs 23,44 toward the outside of their bores 17, 37 and eject the stamped article 66. Thus, the cores 21 and 41 have two functions : on the one hand, they are used for immobilizing and centering the articles 66 during the stamping thereof and, on the other hand, they act as ejector ' s after the stamping operation. As soon as the cores 21 and 41 have ejected a shaped piece, the device 8 causes the plastic band to advance by a step, the length of which slightly exceeds the diameter of a shaped piece. A new shaped piece can then be formed by a further stamping operation. Down¬ stream the stamping device 6, the plastic band 2 appears as shown in fig. 7, said band carrying a series of shaped articles which can be separated therefrom by a cutting operation at station 9. In the embodiment shown in figures 5 and 6, the shaped article 66 is a small disc having circu¬ lar concentric grooves 63 alternating with circular concentric projections in zigzag form. This disc can be easily deformed by applying a pressure upon its central plane part 68. This shaped article may, for example, form the bottom of a plastic container and may be welded by its peripheral edge 67 to the side walls of said container. This container may itself contain a bottle containing a pharmaceutical product and having a pierca- ble neck. When a pressure is applied upon the central part 68 of the disc 66, it is thus possible to move said bottle so that its neck is pierced by a sharp-pointed hollow needle or rod, so that the pharmaceutical product can be transferred from said bottle into a container, such as a flexible bag, to which said needle or rod is connected. This system described in the PCT/BE patent application n c 85/0001 of January 23, 1985 allows to dissolve or disperse a pharmaceutical product in a li¬ quid carrier, under perfect aseptic conditions, for example for the purpose of an intravenous or intramuscu- lar injection of the drug. It is obvious that the process and the appa¬ ratus according to the present invention can be used for manufacturing other articles than the article shown in figures 5 to 7. They can indeed be used for giving any shape comprising at least one projection and/or one recess to a plastic sheet projection and/or one recess to a thin plastic sheet which can be oriented and permanently deformed by stamping. In the process and apparatus according to the invention, the components of the stamping device may be in a vertical position instead of an horizontal posi¬ tion. In this case, the plastic band to be stamped follows a vertical path upstream and downstream of this stamping device, as well as within this device. The stamping device contained in the appara¬ tus according to this invention may also comprise more than a pair of dies, so as to enable the stamping, during one step, of several pieces on the width or length of the plastic band. The apparatus according to this invention may be used for forming, by a stamping operation, pieces having forms and arrangements which are different from those of the article shown in figures 5 and 6. The dies 15 and 33 shown in figures 3 and 4 may indeed be easily replaced by dies having other profiles than those designated by references 25,26 - 35,36, for enabling the stamping of different articles. The use of the process and of the apparatus according to the present invention has shown that it is possible to obtain from a very thin film or sheet of orientable plastic material, with a capital investment substantially lower than that needed for the thermoforming process , shaped pieces which are free from defects, these pieces being formed at very precise identical distances (constant interaxis distance A - A ; see fig.7), so as to allow a correct stamping of the pieces. The process and apparatus according to the invention thus allow the production, at a very quick cadence, of inexpensive articles having a better quali¬ ty than those which can be obtained by the thermoforming process.

Claims: CLAIMS Process for the manufacture of shaped pieces ■ or articles from a plastic sheet or film, said plastic material having some degree of crystallinity, by permanent local deformation of said plastic sheet by means of two dies having complementary profiles, said process comprising the following steps : the plastic sheet is immobilized by moving toward each other two plates which support each one of said dies and between which the faces sheets extends, so that the opposite faces of said sheet is firmly pressed between said plates in the part or parts of the sheet which are not intended to be deformed ; the plastic sheet is locally stamped by causing an interpenetration of the dies, between which are located the areas of the immobilized sheet which must be deformed, by moving at least one of said dies with respect to its support plate, so as to stretch and orient the plastic sheet beyond its elastic limit in the areas of the sheet which are deformed by the dies ; the dies and the plates supporting the latter are moved away from each other, and the deformed areas or parts of plastic sheet are ejected from the dies. 2. Process according to claim 1, comprising the additional step of separating the shaped article or piece from the plastic sheet by a cutting operation. 3. Process according to claim 1, in which the plastic sheet is a continuous band which is moved step by step from a supply source consisting in a roll or reel delivering such a plastic band. 4. Process according to claim 1, in which the movements of the plates supporting the dies toward each other or away from each other are controlled by mechanical, hydraulic or pneumatic means. 5. Process according to claim 1, in which one of the plates supporting a die is maintained in a fixed position, whereas the other plate supporting the other die is movable with respect to the first plate. 6. Process according to claim 1, in which at least one of these dies is allowed to move with respect to a plate supporting the plastic sheet, against the action of springs. 7. Apparatus for carrying out the process according to any one of the preceding claims, said apparatus comprising a device for stamping a sheet or band of plastic material, this device comprising a first movable plate, to which is fixed a first die, and a second composite plate which is parallel to the first plate and to which is fixed a second die having a profile which is complementary to that of the first die, the composite plate comprising a fixed base part to which the second die is fixed and a movable part elastically supported by the - fixed base part, means being provided for moving the plates supporting the dies toward and away from each other. 8. Apparatus according to claim 7, in which each die is provided on the profiled side, with a central bore which opens into the face of the die contacting the plastic sheet, a core subjected to the action of a spring being mounted in said bore, so as to be able to move therein on a distance limited by a stop. 9. Apparatus according to any one of claims 7 and 8, in which an interchangeable die is fixed to each of said plates. 10. Apparatus according to claim 7, in which the composite plate comprises a first fixed base plate to which a die is fixed and which supports elastically a movable plate, one face of which is intended to contact one face of the plastic sheet or band. 11. Apparatus according to claim 10, in which the movable plate is connected to the fixed plate by rods having one end fixed to the movable plate and the other end of which carries a head which is slidable in a bore of the lower plate against the action of springs . 12. Apparatus according to claim 11, in which said rods are surrounded by a helical spring or Belleville springs bearing, on the one hand, against the base plate and, on the other hand, on the movable plate. 13. Apparatus according to any one of claims 7 to 12, in which the faces of the plates and dies intended to contact the plastic sheet or band have a friction coefficient which is high enough to inhibit a sliding of said plastic sheet or band with respect to said faces when the latter are applied on this plastic sheet or band. 14. Apparatus according to claim 10, in which the fixed base plate is a double plate, the two parts of which are in contact which each other by two opposite faces. 15. Apparatus according to any one of claims 7 to 14, further comprising also a source for the supply of a continuous band of plastic material, a supporting table on which said continuous band is moved forward, a stamping device as defined to any one of the claims 7 to 14, a device for causing the plastic band to advance step by step and a device for cutting shaped pieces or articles from said band downstream the stamping device. 16. Apparatus according to claim 15, further comprising means for adjusting the forward step by step movement of the plastic band, so that the distance between the axis of the pieces or articles shaped in said band is constant.

Inventors: HEREMANS ALPHONSE, KERSTEN JEAN, MATHIAS JEAN-MARIE, HEREMANS, ALPHONSE, KERSTEN, JEAN, MATHIAS, JEAN-MARIE
Applicants: TRAVENOL EUROP RES & DEV, TRAVENOL EUROPEAN RESEARCH AND DEVELOPMENT CENTRE
Application year: 1986
Main classification: B29C51
IPC codes: B29C43, B29C51