FR2917006A1 - Container manufacturing method, involves forming cut in junction zone between flange and warp, such that opening of container is defined by flange's free edge that is convex when viewed from exterior, for separating body from waste zone - Google Patents

Abstract

The method involves forming an annular flange (32) that is projected towards exterior on a lateral wall (34) of a container body (30) and connecting the flange to a waste zone (38) by a connecting warp (36) that is arranged in a manner to ensure axial spacing of the flange from the zone, for thermoforming the body in a thermoplastic sheet (10). A separation cut is formed in a junction zone (J) between the flange and the warp, such that an opening (30A) of a container is defined by a flange's free edge that is convex when viewed from the exterior, for separating the body from the zone (38). An independent claim is also included for a container manufacturing device comprising a thermoforming tool.

Description

The present invention relates to a method of manufacturing containers by

  thermoforming, in which is thermoformed, in a sheet of thermoplastic material, at least one container body having a bottom, a side wall and an opening axially opposed to the bottom, and said body is separated from a waste zone of the sheet by cutting. It is known to manufacture by thermoforming containers of various shapes. Because of the constraints of thermoforming and cutting the edges of the containers, these edges are generally in the form of a flat flange, perpendicular to the thermoforming direction, or slightly flared in the direction of their opening. On the other hand, the currently available methods do not make it possible to manufacture by thermoforming containers whose edge has the shape of a re-entrant flange. The invention aims to provide a method for manufacturing such containers.

  This object is achieved by the fact that the container body is thermoformed by forming an annular bead protruding outwardly on the side wall and connecting said bead to the waste zone by a connecting web arranged so as to space axially the bead of the waste zone, and the fact that, to separate the body from the waste zone, a separation cut is made in a junction zone between the bead and the connecting web, so that the opening of the container is delimited by a free edge of the bead which "seen from the outside is convex.So during thermoforming, not only the container body itself, but also the connecting web, is thermoformed, making so that the latter forms a spacer between the bead and the waste zone, a clearance allowing the introduction and activation of a cutting tool, to achieve the cut flush with the bead. cutting is in particular carried out in the inflection zone of the junction between the bead and the connecting web. Advantageously, to achieve the separation cut, a cutting tool is used comprising two tools that are respectively placed inside the container body and outside said body so that the junction zone is between these tools.

  This is a simple way of making the cut.

  Advantageously, the sheet of thermoplastic material is driven step by step between different stations of a manufacturing facility, the thermoforming is carried out in one of said stations and the separation cut is made in another station of the installation, located downstream of the thermoforming station. In this case, the thermoforming and the separation cut are made continuously, in two successive steps between which the thermoplastic material is advanced in one or more steps.

  Alternatively, to separate the container body from the waste zone, a first cut is first made in the waste zone to separate from the rest of the sheet an assembly comprising a container body with a connecting web and a flange. transverse, then the separation cutout is made on said set separated from the remainder of the sheet. In this case, the first cut can be carried out continuously with the thermoforming, in a different step, corresponding to a different pitch, and the separation cut can be performed in recovery, outside the installation.

  Advantageously, the material is stretched further in the region of the connecting web than in the region of the bead. Preferably, to do this, the thermoplastic material is thinned in an annular region prior to thermoforming the container body, and then said body is thermoformed by stretching the thermoplastic material, so that the bonding web is at least essentially formed by the stretched material in said annular region. This limits the amount of thermoplastic material forming the bonding web which will ultimately be eliminated. The invention also relates to a device for manufacturing containers by thermoforming, comprising a thermoforming tool having at least one thermoforming chamber and a piston that can be moved axially in this chamber for thermoforming in a sheet of thermoplastic material arranged across the tube. an opening of said chamber, a container body having a bottom, a side wall and an axially opposite opening at the bottom, and a cutting tool for separating said body from a waste zone of the sheet.

  The invention aims to provide a device for manufacturing, by thermoforming, a container body having a free edge which, seen from the outside, is convex. This object is achieved by the fact that the wall of the thermoforming chamber has an annular groove and a connecting portion located between said groove and the opening of the chamber, so that the container body has a projecting annular bead outwardly on its side wall, connected by a connecting web to a waste zone of the sheet by axially spacing said bead of said zone, and the fact that the cutting tool is able to perform a separation cut in a junction zone between the bead and the connecting web, so that the opening of the container is delimited by a free edge of the bead which, seen from the outside, is convex. It will be understood that the particular shape of the thermoforming chamber makes it possible to produce in this chamber not only the container body, but also the connecting web which connects this body to the waste zone and makes it possible to provide a clearance for making the flush with the bead. Advantageously, the cutting tool comprises two tools 20 adapted to be disposed respectively inside and outside the container body having the junction zone between them. Advantageously, the device of the invention is part of a container manufacturing installation comprising several stations between which the sheet of thermoplastic material is driven in step by step, and the thermoforming tool and the cutting tool are located. in two stations of this facility. In this case, the thermoforming and the separation cut are made in the same installation, with two different steps. According to a variant, the device of the invention comprises a pre-cutting tool capable of first making a first cut in the waste zone to separate from the remainder of the sheet, an assembly comprising a container body with a veil linkage and a transverse collar, and means for transferring this assembly into the cutting tool in which the separation cutout is made on said assembly. In this case, advantageously, the thermoforming tooling and pre-cutting tooling are located in two stations of a container manufacturing plant comprising a plurality of stations between which the sheet of thermoplastic material is driven in step. In this case, the separation cutout is performed in recovery, while the pre-cut can be performed in the same installation as that used for thermoforming. Advantageously, the device comprises a stamping tool capable of thinning the thermoplastic material in an annular region and means for disposing said thinned annular region in the thermoforming chamber, in the vicinity of the opening thereof and, during thermoforming, the piston is able to stretch said thinned annular region so that it comes against said connecting portion of the thermoforming chamber. This stamping is a simple way to further stretch the bonding web than other regions of the thermoformed material, so as to reduce the amount of waste, since this bonding web is finally cut. The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of an embodiment shown by way of non-limiting example. The description refers to the accompanying drawings in which: - Figure 1 is a schematic view of a thermoforming installation according to the invention and to implement the method of the invention; - Figure 2 shows in axial section a thermoformed assembly 25 comprising a container body and a connecting web attached to a waste zone; - Figure 2A shows the edge of the container after cutting flush with the bead; FIGS. 3A to 3C show three successive steps of the stamping process carried out using a stamping tool; - Figure 3D shows the shape of the sheet of thermoplastic material after stamping; FIG. 4 is a schematic view in axial section illustrating an exemplary embodiment for the cutting tool; Figure 5 is an enlargement of the area V of Figure 4; FIG. 6 is a diagrammatic view in axial section illustrating another embodiment of the cutting tool; FIG. 7 is an enlargement in zone VII of FIG. 6 for a variant; FIG. 8 schematically illustrates an operation of FIG. pre-cut ; and FIG. 9 shows, after this precut, an assembly consisting of a container body, its connecting web and a cut flange.

  Figure 1 shows a container thermoforming installation from a sheet of thermoplastic material 10 driven step by step between the different stations of the installation. This sheet is driven by any appropriate means, for example, when it is a continuous strip of material, by a chain or alternative clamps.

  It should be noted that the invention is not limited to the case where the sheet of thermoplastic material in which the containers are thermoformed is made in the form of a continuous strip. Indeed, the invention also applies to thermoforming containers from individual wafers of thermoplastic material, driven into the installation by any known means. The installation comprises, successively arranged in the forward direction F of the strip of thermoplastic material, a heating station 12 in which the thermoplastic material is brought to a temperature allowing its stretching, a thermoforming station 14, in which the containers are thermoformed and a cutting station 16. It may also include an intermediate station 18, located between the heating station and the thermoforming station, this station 18 being described below.

  Conventionally, the heating station can bring to the plastic deformation temperature, particular areas of the sheet 10 in which the containers are to be formed, while maintaining at a lower temperature other areas of the sheet which will form waste.

  In a manner known per se, the thermoforming station 14 comprises a thermoforming tool 20 which comprises a piston 22 movable back and forth perpendicularly to the plane P of the sheet 10 in a jacket 20. This station also comprises a thermoforming chamber 26. For thermoforming, the sheet 10 is pinched between the jacket 20 and the edge 26B of the chamber 26, so that the material to be thermoformed is held across this opening 26A. The piston is then moved to enter the chamber and push back into the latter the thermoplastic material. In known manner, air can be blown by the piston to press the thermoplastic material against the wall of the chamber. The displacement of the piston is operated in the axial direction A perpendicular to the plane P. Of course, although only one piston and one chamber have been shown, the installation may comprise a plurality of piston / piston assemblies. chamber, for example organized on at least one transverse row in the direction of driving the sheet 10.

  The chamber comprises a bottom 26C opposite the piston 22 and a side wall which has an annular groove 26D which extends transversely to the axial direction A and a connecting portion 26E connecting this groove to the edge of the opening 26A of the chamber ( that is, the inner edge of the edge 26B). Thus, the object thermoformed in this chamber has, as seen in Figure 2, a container body 30 with a bottom 40 and a side wall 34 which has a bead 32 projecting outwards, and a connecting web 36 which connects the container body to a waste zone 38 remained in the plane P of the strip. The opening 30A of the container body is delimited at the junction between the bead 32 and the connecting web 36. In this region, the curvature of the thermoformed object reverses, and the junction is in the inflection zone . Due to the presence of the connecting web 36, the bead 32 is maintained at a distance D from the waste zone 38. This makes it possible to form, between the waste zone 38 and the bead 32, a clearance serving to allow access at the junction area for the cutting tools. Referring to Figure 2A, it is understood that after cutting in the junction area, the edge 32A of the bead 32, which defines the opening 30A of the container body is convex from the outside. In this region, it has a radius of curvature R which is advantageously between 1 and 5 mm, preferably of the order of 1 to 3 mm. In axial section, the bead may have the shape of an arc of a circle, for example a semicircle, with a substantially constant curvature, or a variable curvature. In particular, its curvature R1 in the region of this bead which is opposite its free edge 32A may be smaller than in the region of this edge 32, that is to say that the radius of curvature may be greater, to achieve a smooth junction between the bead and the rest of the container body. The height H of the bead, measured parallel to the axial direction A, is advantageously of the order of 3 to 8 mm.

  With reference to FIGS. 3A to 3D, die stamping is now described to reduce the thickness of material in the region of the bonding web. This stamping can be performed in the station 18 of Figure 1, when this station is present. The stamping tool comprises two stamping tools, respectively 50 and 52 disposed on either side of the sheet of thermoplastic material 10. They each comprise a matrix, respectively 54 and 56, axially displaceable, that is to say perpendicularly to the plane P of the sheet 10, in a jacket, respectively 58 and 60. To allow the insertion of the thermoplastic sheet between the two stamping tools, they are first removed from the sheet as shown in FIG. Figure 3A. Then, the shirts 58 and 60 are brought closer to each other so as to pinch the sheet 10 between them as shown in Figure 3B. The dies 54 and 56 are then brought closer to each other in turn to crush between them an annular region 10A of the sheet 10 while flowing the thermoplastic material towards the inside of this annular region. It is found that the matrices 54 and 56, or at least one of them, have a forging edge, respectively 54A and 56A defining the aforementioned annular region, and a clearance, respectively 54B and 56B forming a refuge for the thermoplastic material after creep. One can imagine that only one of the dies has the leading edge and the clearance, while the other would be flat. Moreover, the clearance or clearances may, as seen in Figure 3C, have dimensions greater than those which would be sufficient to accommodate the thermoplastic material after creep, or otherwise the dimensions strictly adapted to the amount of thermoplastic material for give it a special shape. In any event, after stamping, the zone Z of the sheet 10 which will be arranged across the opening of the thermoforming chamber has the thinned annular region 10A in which the bonding web will be thermoformed, and a central region 10B of greater thickness, in which the container body will be thermoformed. This zone Z may be arranged across the opening of the thermoforming chamber by any appropriate means, in particular by the drive means of the sheet of thermoplastic material in the installation. Thus, the thermoforming performed in this chamber affects not only the central region 10B, but also the annular region 10A. Finally, the connecting web 36 may have a thickness e substantially less than the current thickness E of the wall of the container body 30, for example being at most of the order of half this thickness E. C FIG. 2 also shows that these two thicknesses are of course clearly less than the thickness EB of the sheet before thermoforming or in the areas of waste unaffected by the thermoforming. Of course, the stamping tool is compatible with any other known means of reducing the amount of waste, in particular means of stretching the strip of thermoplastic material parallel to its plane in the waste zones before thermoforming, as this is known from the patent application WO 03/006228. With reference to FIGS. 4 to 7, embodiments of the cutting tool which can be placed in the station 16 of the plant of FIG. 1 are now described in order to perform the separation cut.

  In FIG. 4, this tooling comprises a first cutting tool 60 which is disposed outside the container body, around the junction zone J, and a second cutting tool 62 which is disposed inside the body of the container, so as to be surrounded by this joining zone J. In the example of FIG. 4, the first cutting tool is integral with a jacket 64 which, to make the cut, is moved around the body of container. This jacket can be moved axially as indicated by the double arrow G for, in the retracted position, allow the container body to be brought into the cutting station and, in the active position, to be placed around this body. The first cutting tool may be formed of several tool segments that are transversely displaceable along the double arrow T to allow the insertion of the jacket 64 around the container body without the presence of areas against the latter's body. (in particular the bead 32) does not interfere with this positioning and the placement of this tool around the junction zone J. The first cutting tool can also be fixed relative to the sleeve 64, in which case the latter is made of several parts, for example two separable parts along the joint plane P3, parallel to the double arrow T, to be spaced from the wall of the container body so as to allow the insertion of the latter between these jacket halves 64 and for to be able to approach this wall in order to place the cutting tool 60 (then made in the form of two tool portions each secured to a half-sleeve) against the zone d J. The second cutting tool 62 is also movable axially along the double arrow G to be spaced from the sheet of thermoplastic material on the opposite side to the container body and to be placed inside this body, so as to be surrounded - by the junction zone J. In this case, the second cutting tool is made in the form of one or more knobs 62A rotatably mounted on a support 63, which is moved according to the double arrow G. The wheel or wheels 62A can be driven in eccentric rotation by means of a drive shaft 65 and an eccentric system, so as to roll on the inner periphery of the junction zone J to pinch the latter against the cutting edge 60A of the first cutting tool (see Figure 5) and thus cut the thermoplastic material. Of course, the dimensions of the wheel (s) 62A allow their insertion inside the container body. The wheel 62A has a groove 62B promoting the repelling of the thermoplastic material during cutting. Due to the shape of the cutting edge 60A of the cutting tool 60, the edge is cut cleanly to obtain the convex edge shown in Figure 2A.

  With the aid of Figures 6 and 7, there is described another embodiment of the cutting tool. This comprises a first cutting tool 70, which is placed around the junction zone J, outside the container body, and a second cutting tool 72 which penetrates inside this container. The first cutting tool is integral with a jacket 74, which also forms a support for the container after cutting. It is found that the inner wall of the liner 74 has a groove 75 of suitable shape to allow the retaining inside the bead 32 of the container body. As in the example of Figure 4, the sleeve 74 may be made of several separable parts in a joint plane to be placed around the container body. The second cutting tool is movable along the double arrow G to be placed inside the container body. The outer periphery of this tool 72 has a dimension adapted to the inner periphery of the junction zone J, and it comes into substantial contact with the latter. In particular, the end of the tool 72 is frustoconical to facilitate its insertion into the container body and this contact or quasi-contact. The second tool 72 may be a sonotrode, allowing ultrasonic cutting. In a variant, as indicated in FIG. 7, the second tool 72 may carry a heating part 72A which, by contact with the junction zone J during the movement of this tool towards the inside of the container body, carries out a fusion of the thermoplastic material and cut the latter. In general, all cutting means can be used, mechanical means, ultrasound or other, or even by heating. After cutting, the container body may be received in a tray or the like, as shown in FIG. 1, or, preferably, be held by grippers to be fed to filling, sealing and sealing stations. conditioning. As indicated above, the cutting tooling which has just been described can be arranged in the station 16 of the installation of FIG. 1. This makes it possible to continuously cut the manufacturing step by step.

  In a variant, it is possible to make a separation cut-out in recovery. This is illustrated in FIGS. 8 and 9. In FIG. 8, a conventional cutting tool is shown, which can be arranged in the station 16. The latter comprises, in a conventional manner, a first cutting tool 80 and a second cutting tool 82, disposed on either side of the sheet of thermoplastic material, around the container body, so as to make a cut in the plane P of this sheet. This is a precut tooling since, after pre-cutting, the assembly shown in FIG. 9, namely the container body 30, with the connecting web 36, and a flange 37, the latter being oriented transversely to the axial direction A. With the aid of transfer means comprising for example two jaws 83 and 84 adapted to be placed around the container body to seize the latter between them, all mentioned above can be transferred into a cutting tool, for example of the type shown in FIGS. 4 to 7, to make the separation cut-out in the junction zone between the flange 32 and the connecting web 36. These gripping jaws can be activated from the cut shown in Figure 8 to maintain the container body. Thus, the thermoforming tooling 14 and the precut tooling shown in FIG. 8 can be located in two stations of the container manufacturing facility, while the separation cutting tooling would be used in recovery.

Claims (13)

  A method of manufacturing containers by thermoforming, wherein is thermoformed, in a sheet of thermoplastic material (10), at least one container body (30) having a bottom (40), a side wall (34) and an opening (30A) opposed axially to the bottom, and said body is separated from a waste zone (38) of the sheet by cutting, characterized in that the container body (30) is thermoformed to form an annular bead (32) protruding outwards on the side wall (34) and connecting said bead to the waste zone (38) by a connecting web (36) arranged to axially distance (D) the bead of the waste zone , and in that, to separate the body from the waste zone, a separation cut is made in a junction zone (J) between the bead (32) and the connecting web (36), so that opening (30A) of the container is delimited by a free edge (32A) of the bead (32) which, seen from the outside it is convex.   2. Method according to claim 1, characterized in that, to achieve the separation cut, using a cutting tool comprising two tools (60, 62; 70, 72) which are placed respectively inside the body container (30) and outside said body so that the junction area (J) lies between these tools.   3. Method according to claim 1 or 2, characterized in that drives the sheet of thermoplastic material (10) in step by step between different stations (12, 14, 16) of a manufacturing facility, the thermoforming is carried out in one of said stations (14) and the separation cut is made in another station (16) of the installation, located downstream of the thermoforming station.   4. Method according to claim 1 or 2, characterized in that, to separate the container body (30) from the waste zone (38), is first made a first cut in the waste zone to separate from the rest of the sheet an assembly comprising a container body (30) with a connecting web (36) and a transverse flange (37), and then making the separation cut on said set separated from the remainder of the sheet.   5. Method according to any one of claims 1 to 4, characterized in that the bead (32) is produced with a radius of curvature (R) of between 1 and 5 mm, preferably between 1 and 3 mm, and a height H of between 3 and 8 mm.   6. Method according to any one of claims 1 to 5, characterized in that further stretches the material in the region of the connecting web (36) in the region of the bead (32).   7. Method according to any one of claims 1 to 6, characterized in that thins the thermoplastic material in an annular region (10A) prior to thermoforming the container body (30), then said body is thermoformed by stretching the thermoplastic material, such that the bonding web (36) is at least substantially formed by the stretched material in said annular region (10A).   8. Apparatus for producing containers by thermoforming, comprising a thermoforming tool (14) having at least one thermoforming chamber (26) and a piston (22) adapted to be axially displaced in this chamber for thermoforming in a sheet of thermoplastic material (10) disposed across an opening (26A) of said chamber, a container body (30) having a bottom (40), a side wall (34) and an axially opposed opening (30A) at the bottom, and a cutting tool (60, 62; 70, 72) for separating said body from a waste zone (38) of the sheet, characterized in that the wall of the thermoforming chamber (26) has an annular groove (26D) and a connecting portion (26E) located between said groove (26D) and the opening (16A) of the chamber, such that the container body (30) has an annular bead (32) projecting outwardly on its side wall (34) connected by a connecting web (36) to a zone of waste (38) of the sheet axially spacing (D) said bead (32) of said area, and in that the cutting tool (60, 62; 70, 72) is adapted to perform a separation cut in a junction zone (J) between the bead (32) and the connecting web (36), so that the opening (30A) of the container is delimited by a free edge (32A) of the bead which, seen from the outside, is convex.   9. Device according to claim 8, characterized in that the cutting tool comprises two tools (60, 62; 70, 72) adapted to be disposed respectively inside and outside the container body (30). having the junction zone (J) between them.   10. Device according to claim 8 or 9, characterized in that it is part of a container manufacturing installation comprising a plurality of stations (12, 14, 16) between which the sheet of thermoplastic material (10) is driven in steps. step, and in that the thermoforming tool (14) and the cutting tool (16) are located in two stations of this installation.   11. Device according to claim 8 or 9, characterized in that it comprises a pre-cutting tool (80, 82) adapted to first perform a first cut in the waste zone (38) to separate from the rest of the sheet (10), an assembly comprising a container body (30) with a connecting web (36) and a transverse flange (37), and transfer means (83, 84) of this assembly in the tooling of cutout in which the separation cutout is made on said assembly.   12. Device according to claim 11, characterized in that the thermoforming tooling (20, 26) and the pre-cutting tooling (82, 84) are located in two stations (14, 16) of a plant. manufacturing containers comprising a plurality of stations between which the sheet of thermoplastic material is driven stepwise.   13. Device according to any one of claims 8 to 12, characterized in that it comprises a stamping tool (50, 52) capable of thinning the thermoplastic material in an annular region (10A) and means for disposing said region ring thinned in the thermoforming chamber (26), in the vicinity of the opening (26A) thereof, and in that, during thermoforming, the piston (22) is able to stretch said thinned annular region (10A) to that it comes against said connecting portion (36E) of the thermoforming chamber (26).