FR2629424A1 - Thermoplastic container and method of making such a container - Google Patents

Abstract

The thermoplastic container comprises a collar intended to receive a cover. The upper face of the collar is provided with a solid and continuous band 20 constituting, on the one hand, a seal between the container 1 and a cover and, on the other hand, a constant-thickness heat welding band of the said cover. The thermoplastic container is made from a thermoplastic strip or sheet 2. It is shaped in a mould 9, for example by stamping and blowing with pressurised air and, during the operation of shaping the container 1, the solid and continuous band 20 is formed on the upper face of the collar using a die.

Description

 The present invention relates to a thermoplastic container. more particularly a container provided with a flange or an internal shoulder, and a process for the continuous production of such a container from a strip or sheet of thermoplastic material.

 Processes are known for manufacturing containers intended, for example, for packaging solid, pasty and / or liquid products which comprise a phase of suction or blowing of pressurized air in order to apply a defined part of a strip. or sheet of thermoplastic material against the walls of a mold defining the outline of the container.

 The container thus formed is, after filling. closed by a cover which is fixed by heat sealing either on a flange formed around the opening of the container, or on a shoulder provided inside said container. In order to facilitate the welding of 1 cover, the collar # or 1 shoulder is provided with a continuous pleat which forms, on the upper face of said collar or of said shoulder, a projection and on the lower face, a hollow. of the heat sealing of 1 cover, the continuous fold is crushed and taking into account the hollow formed on the underside of the flange or the shoulder. it also crashes and may present, in certain cases, after welding of the cover. a more or less discontinuous deformation and punctual surface defects or flatness, which affects 1 seal between 1 seal and the container. In addition, the welded width of the cover is relatively large, which does not facilitate its tearing.

 The present invention aims to solve the aforementioned problem by providing a thermoplastic container and a method of thermoforming thermoplastic containers, from a thermoplastic strip.

 The subject of the invention is a thermoplastic container comprising a collar or a shoulder intended to receive a cover, characterized in that the upper face of the collar or the shoulder is provided with a full and continuous cord constituting on the one hand a seal between the container and a cover and on the other hand a strip of constant heat-sealing thickness of said cover.

 The invention also relates to a method of manufacturing thermoplastic containers as defined above, from a thermoplastic strip or sheet, according to which a container is formed in a mold by suction or by blowing of air under pressure. comprising a collar or a shoulder intended to receive a cover, characterized in that during the container forming operation, a solid and continuous bead is formed on the upper face of the collar or of 1 shoulder, constituting on the one hand a seal between said container and a cover and on the other hand a strip of constant heat-sealing thickness of said cover.

 The invention will now be described in more detail with reference to an embodiment given by way of example, without limitation, and represented by the accompanying drawings.

 Figures 1 to 3 are schematic sectional views of a stamping and blowing forming station showing the different phases of manufacturing a container according to the invention.

 Figure 4 is a schematic sectional view of a suction forming station showing the final phase of manufacturing a container according to the invention.

 Figure 5 is a partial schematic sectional view showing a container whose flange is provided with a cord according to 1 invention.

 Figure 6 is a partial schematic sectional view showing the container of Figure 5 after heat sealing a seal on the bead.

 Figures 1 to 3 schematically show three different phases in the manufacture of a container 1 from a thermoplastic strip 2 brought into a forming station 3 by stamping and blowing.

 Referring to FIG. 1, a forming station 3 composed of a mold 9 and a blowing box 10 will be described in more detail.

 Means not shown are connected to the mold 9 for its movement to the plane of the strip.

 The internal walls of the mold 9 define a forming chamber 12, the configuration of which is that of the container to be formed. In the example shown, the forming chamber 12 has the shape of a truncated cone, but it can naturally also be of cylindrical or parallelepiped shape.

 The mold 9 is provided with vents 13 putting the forming chamber 12 in communication with the outside in order to evacuate the air trapped between the strip 2 and the walls of the chamber 12 during forming.

 The blowing box 10 is mounted displaceable perpendicularly to the strip 2 and arranged opposite the mold while being separated from the latter by the strip which is transported between the two elements.

The walls of the 10 deli blowing box
put in a pressure chamber 14 into which pressurized air is injected through a duct 15. A stamper 16 is mounted vertically movable inside the blowing box. The stamper 16 is not necessary in cases where the depth of the container to be formed is small.

The end of the blowing box 10 in contact with the strip 2 is provided with a flat surface 17 intended to cooperate with a flat surface 18 at the open end of the mold 9 in order to seal between the blowing box 10 and the strip 2
when the mold is in the high position.

An annular groove 19 is formed in the flat surface 17 of the end of the blowing box.
10. The groove 19 constitutes means for forming a bead 20 on the container, more precisely on a collar 21 (see FIG. 5) formed at the open end of the container. The groove 19 has for example a triangular section.

 Referring to Figures 1 to 3, we will now describe the different sequences of operation and formation of a container.

 The continuous thermoplastic strip, brought to an appropriate temperature, is engaged under the blowing box 10. The mold 9 is then moved to the plane of the strip 2 by sealing with the blowing box 10. Then, the stamper 16 downwards in order to preform the part of the strip 2 delimited by the opening of the mold 9 inside the forming chamber 12 thereof (see FIG. 3).

Pressure air is then injected into the blowing box 10 (see FIG. 4) so as to press the preformed part of the strip 2 on the internal walls of the mold 9 to form a recess
pient 4.

 Then, the blowing box 12 is moved vertically towards the strip and a pressure is exerted on the part of the strip 2 comprised between the opposite ends of the blowing box 10 and of the mold 9. Thanks to this pressure, material penetrates in the groove 19 so as to form a full and continuous bead (FIG. 5) on the upper face of the strip, more precisely on the part which constitutes the flange 21 of the container.

 According to the variant illustrated in Figure 4, the forming station 22 operates by suction and comprises a mold 23 movable perpendicular to the strip 2. The mold 23 is here in its high position in contact with the strip 2. A chamber suction 25 is delimited by the internal walls of the mold 23.

 The mold 23 is provided with suction channels 25 opening into the suction chamber 24.

 A matrix 26 is mounted movable perpendicularly to the strip 2 and disposed opposite the mold 23 while being separated from the latter by the strip which is transported between the two elements.

 The end of the die 26 in contact with the strip 2 is provided with a flat surface 27 intended to cooperate with a flat surface 28 at the open end of the mold 23 in order to seal between the mold 23 and the strip 2 when the mold is in the high position.

 An annular groove 29 is formed in the flat surface 27 of the end of the matrix 26. The groove 29 constitutes means for forming a bead 20 on the container (see FIG. 5).

 A stamper may possibly be provided to preform the container.

 According to this variant, one begins by moving the mold 23 to the plane of the strip so as to seal with the matrix 26 and the air is drawn from the chamber 24 to press the part of the strip delimited by the opening of the mold 23 against the internal walls of the latter.

 Then, the matrix 26 is moved towards the strip and a pressure is exerted on the part of the strip 2 comprised between the opposite ends of the matrix 26 and of the mold 23. Material enters the groove 2S so as to form a full and continuous bead 20 on the upper face of the strip, more precisely on the part which constitutes the flange 21 of the container.

 According to all the variants, the operation of stamping a bead on a flange or shoulder of the container is carried out in the forming station.

The stamping can of course also be carried out immediately before forming the container or simultaneously.

 The container 1 thus obtained by one or other of the methods is then filled with a product and sealed with a cover 30 which is heat-sealed on the cord 20. During this operation, the cord 20 is flattened (FIG. 6 ) and there is a flow of the material over a determined width so as to constitute a well defined flat surface on which all the pressure forces are concentrated during the heat sealing of the seal. Thus, the flattened bead constitutes, on the one hand, a seal between the flange 21 of the container and the cover 30 and, on the other hand, a strip of constant heat-sealing thickness of said cover.

 Given the extra thickness of material constituted by the bead 20. the welding pressure generated on the material by a given application force can be greater with the method according to the present invention, so that the weld is of better quality.

 The ability to compensate for point surface defects or flatness is greater with the method according to the present invention, due to the higher pressures that can be implemented, and the obligation of creep of the material. The seal between the container and the seal is. therefore, better assured.

 Furthermore, another advantage of the invention resides in the reduced width of the weld bead between the flange of the container and the cover, so that the effort to be exerted for tearing off the cover and the opening of the container is small, which has a double advantage.

First of all an economic advantage, because it makes it possible to use lids which are less resistant than in traditional methods and an advantage for the user who tears off the lids more easily,
The cord thus formed on the collar of the container can, of course, have various shapes.

Claims (2)

 1.- Thermoplastic container comprising a collar (21) or a shoulder intended to receive a cover (30), characterized in that the upper face of the collar (21) or of the shoulder is provided with a full and continuous cord (20) constituting on the one hand a seal between the container (1) and a cover (30) and on the other hand a strip of constant thickness of heat-sealing of said cover.  2.- A method of manufacturing thermoplastic containers as defined in claim 1, from a thermoplastic strip or sheet (2), which is formed in a mold (23; 9 by suction or by blowing air under pressing a container (1) comprising a flange (21) or a shoulder intended to receive a cover (30), characterized in that during the operation of forming the container (1), the upper face of the flange (21) or the shoulder a full and continuous bead (20) constituting on the one hand a sealing joint between said container (1) and a cover (30) and on the other hand a strip of constant thickness of heat-sealing said cover.