FR2698037A1 - Method and device for producing by thermoforming a plastic foot cut and cut thus obtained. - Google Patents

Abstract

A method of making a plastic foot cutter which comprises the steps of: stamping a heated plastic film (10) by means of a stamping ring (130) in the extended position so as to introduce it in a cooled forming mold (200), while leaving a lower part of the plastic film free from contact with the interior side walls of said forming mold; creating a vacuum in a duct (230) provided in the forming mold and communicating with the inner side walls forming the cutting foot, so as to press a part of the plastic film on said inner side walls (210 ') to form the one of the faces of the cutting foot; injecting pressurized air onto the plastic film so as to press a part of the plastic film against the inner side walls (210) of the forming mold to form in particular the body of the cup; retract the stamping crown so that it is in the retracted position; injecting pressurized air onto the still hot free part of the plastic film so as to press at least part of it against the cooled face of the foot and form the other face of the cutting foot; unmold the plastic cup obtained. Application to the manufacture of foot cups intended to contain dessert creams or even yogurts.

Description

 The present invention relates generally to the field of the automatic manufacture of plastic footwear for the packaging of food materials such as dessert creams or yogurts and more particularly a new method of making such cuts as well as a device for carrying out implementation.

 The invention also relates to a new type of foot cutting plastic.

 A process for the industrial manufacture of molded foot sections is already known, which consists mainly in injecting thermoplastic materials in the liquid state into individual molds having the shape of the desired foot cut, and in demolding the preformed foot sections. obtained after a cooling phase.

 This type of process, however, has several disadvantages.

 First of all, according to this method it is necessary to produce pots or individual foot-cuts which require, for their grouping by two, four, six or more, the use of cartons or grouping caps.

These cartons or grouping caps having particular and complex shapes, require an expensive implementation which increases the cost of production of products packaged in these cuts. In addition, the introduction of these grouping caps on manufactured cuts adds an additional step in the overall manufacturing process, and conditions such products, which also increases their cost of implementation.

 In addition, by using this method of making footwear, it is known that the place of manufacture is then almost always different from that of filling and sealing preformed foot cups or pots. It is therefore easy to understand that the constraints of transporting and conveying these preformed pots or cups to the filling and sealing stations considerably increase the production costs of this type of product, especially if all the operations are to be considered. be conducted under conditions of perfect sterility. We need a high labor force.

 In order to overcome the aforementioned drawbacks of this type of manufacturing process by molding, techniques have been developed for manufacturing jars, cups or containers for yogurts or milk creams that are thermoforming techniques for sheets of polystyrene, polypropylene or the like, these techniques can then be performed directly before filling stations and sealing said pots.

 However, currently known thermoforming techniques and devices have only allowed to obtain pots very stripped form and in particular jars without feet because these thermoforming techniques have certain disadvantages that they do not allow the realization of cuts on foot.

 Indeed, the foot sections obtained by known conventional thermoforming techniques have inner corners due to the thermoformed foot. These recesses are places inaccessible to a consumer and yet fill with product when filling these cuts. These recesses therefore represent spaces lost to production.

 The present invention aims to propose a new thermoforming process for producing plastic foot-cuts, which makes it possible to obtain foot-cuts having a smooth, continuous interior surface and which does not comprise inaccessible spaces capable of fill with consumable material. In addition, the invention proposes a new device for implementing this method, which is a simple device and an apparatus which makes it possible, among other things, to manufacture, according to the process according to the invention, a plurality of cuts simultaneously, these cuts are automatically assembled and do not require the use of cardboard or grouping caps.

More particularly, the production method according to the invention comprises the steps of a) stamping a heated plastic film, by means of a forming punch provided at its lower end with a stamping ring in the outgoing position of for introducing it into a forming mold having cooled inner sidewalls, while leaving a lower portion of the plastic film free of any contact with the inner sidewalls of said forming mold, the forming punch being in the low position at the inside of the forming mold, with the projecting stamping crown holding the plastic film inside said forming mold
b) create a depression in a duct provided in the mold of
forming and communicating with the inner side walls forming
the cutting foot, so as to press a part of the plastic film on
said inner sidewalls to form one of the faces of the foot
cutting affecting the shape of the latter,
c) inject air under pressure on the plastic film so as to
press part of the plastic film against the side walls
mold forming molds to form in particular the body of the
cutting, d) retracting the stamping ring so that it is in the retracted position inside the forming punch held in the lower position inside the forming mold, e) while preferably maintaining the depression in said duct in the forming mold, injecting air under pressure on the still free hot part of the plastic film so as to press at least a portion against the cooled face of the foot and form the other face of the foot of cutting heat-welded to said cooled face, f) demolding the foot section of plastic obtained.

 According to another characteristic of the process according to the invention, in step c) the pressure of the air injected on the pressed plastic film is between approximately 1 × 10 5 Pa and 3 × 10 5 Pa; in addition, in step e) the injected air pressure is between about 1.105 Pa and 3.105 Pa.

 In addition, according to the invention, the device for implementing the method according to the present invention comprises two parts, a counter mold and a forming mold, able to move vertically relative to each other. to come against each other and pinch the plastic film positioned between them, the against-mold comprising a frame that pinches the plastic film and a forming punch placed inside the armature and able to move vertically so as to be introduced into the forming mold via an opening provided in the armature, the forming punch having at one of its ends a movable stamping crown adapted to protrude from said punch for deforming the heated plastic film into the forming mold when said forming punch moves vertically towards the forming mold, the forming die having inner side walls q They are substantially in the shape of a foot section, at least one outwardly directed lateral duct adjacent to said inner communicating side walls, and in which cold water circulates to cool the walls. internal side of said mold, at least one duct communicating on the one hand with a portion of the inner side walls forming the cutting foot, and on the other hand with the outside, in which a depression is created to press a part of the film plastic on said inner side walls forming the cutting foot, and a conduit which opens into the part of the cutting foot of the forming mold and in which air is injected under pressure to form the cutting foot.

 The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved.

 Figures 1 to 8 show, in vertical section, a first embodiment of the thermoforming device according to the invention, at different stages of the method of producing a foot section according to the invention.

 Figures 9 to 17 show, in vertical sectional view, a second embodiment of the device according to the invention, at different stages of the thermoforming method according to the invention.

 Figure 18 shows an embodiment of a foot section according to the invention.

 FIG. 19 represents a set of foot sections obtained by means of the method according to the invention.

 As a preliminary, it will be noted that from one figure to another, identical or similar elements or parts have been designated as far as possible by the same reference signs, and will not be described each time.

 Referring firstly to Figure 1, there is shown a device for implementing a method of making a plastic foot cup by thermoforming a film of thermoplastic material such as polystyrene or polypropylene. The different steps of the process will be explained later. This device comprises two parts, an upper part called against-mold 100 and a lower part called forming mold 200. These two parts are able to move along a vertical axis XX 'with respect to each other to come l against each other and pinch the plastic film 10 positioned therebetween.

The counter-mold 100 comprises a reinforcement 110 of substantially cylindrical shape positioned along the vertical axis XX 'of relative displacement of the counter-mold and the forming mold. This cylindrical armature 110 comprises an essentially cylindrical inner duct 112 which extends along the axis XX 'and which comprises an opening or upper orifice 113 which has a much smaller cross section than that of the duct 112 and a lower opening 111 which has the size of the section of the conduit 112. Inside this conduit 112 is positioned a forming punch 120 which comprises a handle 120a slidably mounted in a passage 114 provided in the upper part of the armature 110, adjacent to the orifice 113.Thus, this forming punch 120 is able to move vertically with respect to the reinforcement 110 in the duct 112 and towards the outside of said duct via the lower opening 111, with the aid of a jack placed at the outside of the armature and which is not shown in Figure 1. In addition, the forming punch 120 has at its lower end 121 a stamping ring 130 which comprises a base 130a connected to a cylinder 131 placed inside the body 120b of the forming punch 120 and controlled from outside the armature 110, so that said stamping ring 130 is able to move vertically relative to the punch 120 to occupy two positions
an output position in which the stamping crown 130
protrudes from the punch at its lower end 121,
a retracted position in which the stamping crown 130
is placed inside a housing 122 provided in the punch of
forming 120.

 It should be noted that the outer control cylinder of the forming punch 120 and the inner cylinder 131 are independent.

 In addition, the forming punch 120 has two inner vertical ducts 123,124, which extend in parallel in the handle 120a of the forming punch, the first vertical duct 123 opening inside the housing of the punch body containing the inner cylinder 131 and the second vertical conduit 124 opening into the housing 122 containing the stamping ring 131. These two vertical pipes 123,124 respectively have two upper openings positioned in the handle 120a of said punch outside the frame 110. The first conduit vertical 123 allows injection and evacuation of air under pressure for the actuation of the inner cylinder 131 which controls the displacement of the stamping ring 130. The second vertical duct 124 is intended, as will be explained in more detail later, to evacuate from above the air injected under pressure into the lower part of the forming mold through the duct provided for this purpose.

 Furthermore, the body 120b of the forming punch 120 comprises a lateral opening 125 which forms a communication duct between the duct 112 of the armature 110 and the housing containing the inner cylinder 131 in order to evacuate, if necessary, the air injected into the conduit 123 to the cylinder 131.

 It should be noted that the inner conduit 112 having a larger section than the section of the body of the forming punch 120, there remains a space between said punch and the inner side walls of the armature 110. As will be seen later, this space makes it possible to form an air passage conduit against the mold 100 to the forming mold 200 when they are placed against each other.

 The forming mold 200 has an inner portion open upward facing the lower opening 111 of the armature 110 against the mold 100. This inner portion has substantially the shape of a foot section. More particularly, the forming mold has inner side walls 210, 210 'which essentially have the shape of the side walls of the foot section. These side walls 210 have a substantially rounded shape forming the cutting body and extend downwardly by the side walls 21ri 'straight forming the cutting foot. These straight side walls 210 'forming the cutting foot are here fluted vertically for the formation of a fluted straight cutting foot. The upper opening of the forming mold 200 corresponds exactly to the lower opening 111 of the counter-mold 100. The lower inner part of the forming mold 200 placed below the inner part forming the foot of the foot cut is according to this embodiment a funnel-shaped portion which extends downwardly through a lower conduit 240 opening laterally outwardly. This duct 240 which has an opening in the foot part of the forming mold, is intended to receive air under pressure to form the foot of the cut. On the other hand, the forming mold 200 comprises two lateral ducts 220 which respectively comprise two inlets and two outlets placed in a symmetrically opposite manner with respect to the axis XX 'of relative displacement of the counter-mold 100 and of the forming mold 200 These lateral ducts 220 are positioned outside the inner part of the forming mold adjacent to said inner side walls 210, 210 '. Cold water circulates in these lateral ducts 220 so as to cool the inner walls 210, 210' of the forming mold 200. In addition, the forming mold comprises a conduit 230 which has a circular opening which communicates with the lower inner portion of the forming mold adjacent to the inner side walls 210 'of said mold forming the cutting foot, and an opening to the outside of the forming mold and by which a depression is created inside said duct to press a part of the plastic film tick on said inner side walls 210 'forming the cutting foot.

 According to an alternative embodiment shown in Figures 9 to 17, the portion forming the cutting foot always located in a lower portion of the forming mold has inner side walls 210 'having a flared shape from a central point in below the cutting body, down. As a result, the position of the ducts 240 and 230 is approximately inverted with respect to the embodiment of FIG.

Indeed, the duct 230 by which the depression is created to press the plastic film on said inner side walls 210 'forming the cutting foot, is located below the cutting foot portion and opens through small lateral ducts directly on the inclined side walls 210 'placed at the center and at the bottom of the inner part forming the section.

On the other hand, the air blowing duct 240 has a lateral inlet and an opposite lateral outlet with respect to the vertical axis X-X 'and opens laterally inside the forming mold facing said inclined walls 210'.

 The first embodiment shown in Figures 1 to 8 then allows to form, as we will see later, a right foot and the second embodiment shown in Figures 9 to 17 allows to form a flared bottom foot .

 Referring to Figures I to 8, we will now describe the method of making foot sections according to the invention.

 In a preliminary step shown in FIG. 1, a plastic film 10 is positioned against the reinforcement 110 of the counter-mold 100 in such a way that it obstructs the lower opening 111.

The two parts of the mold are then disjointed. The forming mold 200 then moves vertically upwards relative to the counter mold 100 which remains fixed, to come against the counter-mold, so that the plastic film 10 is clamped between the reinforcement 110 and the outer flanges of the forming mold 200. The plastic film 10 then has a portion which is positioned exactly at the joint of the lower opening 111 and the upper opening of the forming mold 200.

The entire device is brought to about 140 degrees, therefore when the plastic film 10 is clamped between the forming mold and the frame 110 of the counter-mold, it is itself carried by-conduction at a temperature of about 140 degrees.

 As shown more particularly in Figure 2, a certain amount of cold water circulates continuously in the conduits 220 so as to permanently cool the inner side walls 210,21ri 'of the forming mold. In a subsequent step, pressurized air is injected at approximately 6.105 Pa into the conduit 123 of the forming punch so as to compress the spring of the cylinder 131 which acts on the stamping ring 230 so that it comes into contact with exit position. Simulta does not lie under the action of the outer cylinder not shown, the forming punch 120 descends so that it enters the inside of the forming mold 200 via the opening 111 and stamps through the crown of drawing the heated plastic film to introduce it into the forming mold 200.

 As shown more particularly in FIG. 4, when the forming punch 120 is in the lower position, the stamping ring 130 has completely inserted the plastic film 10 inside the forming mold 200 in such a way that it a portion of said film 10 against the inner side walls 210 'forming the foot of the mold leaving a portion of the plastic film 10 free of any contact with the inner walls of said mold, this free portion corresponding to a bottom which extends between the two side walls 210 'forming the cutting foot.Simultaneously a vacuum is created in the conduit 230 provided for this purpose in the forming mold 200 and communicating with the inner side walls 210' forming the cutting foot so as to press the film on said inner side portions 210 'to form the outer face of the cutting foot, which is cooled in contact with said side walls 210' cooled in affect the shape of the cutting foot.

 In a subsequent step, as best shown in Figure 5, the stamping ring 130 is held in the extended position and the forming punch 120 in the down position so that it continues to hold a portion of the plastic film 10 against the inner side walls 210 'of the forming mold 200 forming the foot is injected through the upper orifice 113 of the frame 110 of the pressurized air at 2.105 Pa and in this way air is blown via the conduit 112 on the portion of the film 10 introduced into the forming mold 200 at the body of the cup so as to press said film against the inner side walls 210 of the forming mold 200 forming said cutting body. These inner side walls 210 being cooled, this part of the plastic film is thus cooled so that it takes the shape of said walls. Thus, the whole of the plastic film is plated and cooled against the inner side walls 210, 210 'forming the sectional cut. to form the plastic cup. Once the plastic film 10 is sufficiently cooled, injection of pressurized air at 2.105 Pa into the duct 112 and pressurized air at 6.105 Pa into the duct 123 is stopped in such a way that the jack 131 rises by expansion of the spring and repositioning the stamping ring 130 in the retracted position in the housing 122 of the forming punch 120 so as to leave the part of the film pressed against the inner side walls 210 'forming the outer face of the cutting foot. When the stamping ring 130 is positioned inside the housing 122, then at the end 121 of the punch 120 a flat surface is obtained. In a subsequent step, while maintaining the depression inside the conduit 230 and the circulation of cold water in the conduits 220, pressurized air is injected at approximately 2.105 Pa inside the conduit 240 so as to blow under the air under pressure under the free plastic film portion still hot inside the mold. In this way, a portion of this free hot film is pressed against the outside face of the cooled cutting foot to form the inner face of the cutting foot heat-sealed to said outer face and the other part then forms the bottom 320a of the cut on foot stretched between the walls of the foot cut by being positioned against said lower flat surface of the punch. It should be noted that the air blown through the duct 240 escapes to the outside by circulating in the duct 124 provided in the forming punch 120. Thus, it avoids the overpressures on the plastic film inside the mold. forming, which can cause tearing of it. This internal face of the cutting foot is cooled in contact with the cooled outer face. Similarly, the bottom 320a stretched between the walls of the foot cup cools. As a result, the forming punch 120 is pushed up inside the conduit 112 of the reinforcement 110 and when the cooling is sufficient, the forming mold goes back to its initial position so as to unmold the plastic foot section and obtained.

 Referring to Figures 9 to 17, we will now describe the method according to the invention by means of an alternative embodiment of the device of Figures 1 to 8.

 As can be seen in FIGS. 9 to 11, the plastic film is positioned against the reinforcement 110 of the counter-mold 100, and then the forming mold 200 rises to pinch the heated plastic film 10. The forming punch 120 descends with the stamping crown 130 projecting from its lower end 121 so as to stamp the heated plastic film 10 to introduce it into the forming mold 200.

 As best shown in FIG. 12, when the forming punch is in the lower position, the stamping ring 130 maintains a part of the plastic film free from any contact with the inner side walls 210, 210 'of the forming mold, this free part being extending in extension of the inner side walls 210 forming the body of the cut of the forming mold 200. In addition, a depression is created in the conduit 230 which communicates with the flared walls 210 'of the forming mold so that part of the film is pressed against said side walls flared down 210 'forming the cutting foot and against a horizontal wall forming the bottom of the section.

 In a subsequent step shown in Fig. 13, pressurized air is blown into the forming mold via the conduit 112 of the counter mold so as to press the film against the inner side walls 210 forming the body of the mold. the cup. With all of the interior walls of said mold being cooled, the film pressed against them hardens to form the body of the cup and the inner face of the cutting foot. Then, the stamping ring 130 retracts inside the housing 122 of the forming punch 120, and air is injected into the side duct 240 under pressure so as to press the free portion of the still hot film against the cooled internal face of the cutting foot to form the outer face of the latter heat-sealed to said inner face.In the same way, the pressurized air laterally escapes through the conduit 124 to the outside. The punch goes up inside the frame and when the entire film is cooled the forming mold 200 returns to its initial position to unmold the plastic cup obtained.

 Thus, according to the thermoforming process according to the invention, individual or grouped plastic foot sections having straight or flared feet are produced.

 As shown more particularly in Figure 18 with the device shown in Figures I to 8, a foot section is performed with a right foot 320 having a body 310 with a flange 315. It should be noted that the foot 320 has a size that is always smaller than the lateral size of the body of the cup 310. This foot is here fluted vertically on both sides. According to the embodiment of the device of Figures 9 to 17, the foot of the foot cut will flared shape down. In addition, the interior of the resulting cut foot has a smooth and continuous surface from the top to the bottom.

 According to the invention, it is possible to produce a device that is not shown and that allows the simultaneous manufacture of several foot sections. This apparatus then comprises several devices as previously described positioned in parallel and which act simultaneously on the same plastic film 10 positioned between the two parts of each of said devices. In addition, this apparatus comprises means for making a cutting line of lower strength between each foot cut performed. As is more particularly shown in FIG. 19, a set of four, six or eight assembled foot cups is obtained, with between each of the foot sections of the lower resistance lines which allow manual and easy cutting of the foot cups in a fashionable manner. to consume them individually.

Claims (17)

 A method of making a plastic foot cut, characterized in that it comprises the steps of a) stamping a heated plastic film (10) by means of a forming punch (120). provided at its lower end (121) with a stamping ring (130) in the extended position so as to introduce it into a forming mold (200) having cooled inner side walls (210, 210 ') while leaving a lower part of the plastic film (10) free of any contact with the inner side walls (210, 210 ') of said forming mold (200), the forming punch (120) being in the lower position inside the forming mold ( 200), with the embossing ring (130) projecting holding the plastic film (10) inside said forming mold (200)  b) creating a depression in a duct (230) provided in the mold of  forming (200) and communicating with the inner sidewalls  (210 ') forming the cutting foot so as to press a part of the  plastic film on said inner side walls (210 ') for  form one of the faces of the cutting foot affecting the shape of this  latest,  c) inject air under pressure on the plastic film so as to  press part of the plastic film against the side walls  interior (210) of the forming mold (200) to form in particular  the body of the cup, d) retracting the stamping crown (130) so that it is in the retracted position inside the forming punch (120) held in a low position inside the mold of forming (200), e) while preferably maintaining the vacuum in said conduit (230) in the forming mold (200), injecting pressurized air onto the still-hot free portion of the plastic film (10) in a manner such that to press at least a portion against the cooled face of the foot and form the other side of the heat-welded cutting foot to said cooled face, f) demolding the foot section of plastic obtained.  2. Production method according to claim 1, characterized in that in step c), the pressure of the air injected on the pressed plastic film is between about 1.105 Pa and 3.105 Pa.  3. Production method according to one of claims 1 or 2, characterized in that in step a), the stamping ring (130) is positioned a portion of the plastic film (10) heated against the side walls interior (210 ') forming the foot of the cut of the forming mold (200).  4. Production method according to claim 3, characterized in that in step a), the free portion of the plastic film (10) corresponds to a bottom which extends between the inner side walls (210) of the mold of forming (200).  5. Production method according to one of claims 1 or 2, characterized in that in step c), the air injected under pressure also allows to position a portion of the plastic film (10) heated against the inner side walls ( 210 ') forming the foot of the cut of the forming mold (200).  6. Production method according to claim 5, characterized in that the free portion of the plastic film (10) corresponds to a lateral portion which extends essentially in downward extension of the inner side walls (210) forming the body of the cutting of the forming mold (250).  7. Production method according to any one of claims 1 to 6, characterized in that in step e) the injected air pressure is between about 1.105 Pa and 3.105 Pa.  8. Apparatus for implementing the production method according to one of claims 1 to 7, characterized in that it comprises two parts, a counter-mold (100) and a forming mold (200), suitable for moving vertically relative to each other to urge against each other and pinch the plastic film (10) positioned therebetween, the counter-mold (100) comprising a frame (110) which pinches the plastic film (10) and a forming punch (120) placed inside the frame (110) and able to move vertically so as to be introduced into the forming mold (200) via an opening (111) provided in the armature (110), the forming punch (120) having at one of its ends (121) a movable stamping ring (130) adapted to protrude from said punch (120) to deform the heated plastic film (10) into the forming mold (200) when said forming punch (120) is e moves vertically in the direction of the latter, the forming mold (200) having inner side walls (210) which are essentially in the shape of those of a foot section, at least one lateral duct (220) located towards the external to said inner side walls (210) communicating with the outside, and in which cold water circulates so as to cool the inner side walls (210) of said mold (200), at least one conduit (230) communicating with on the one hand with a portion of the inner side walls (210 ') forming the cutting foot, and on the other hand with the outside, in which a depression is created to press a portion of the plastic film on said inner sidewalls (210 ') forming the cutting foot, and a conduit (240) which opens into the foot part of the forming mold (200) and into which air is injected under pressure to form the foot of the cut.  9. Device according to claim 8, characterized in that there is a space (112) between the armature (110) and the forming punch (120), this space (112) communicating with the opening (111) and an outwardly opening port (113) provided in said armature (110) opposite the opening (111), to form a counter mold passage conduit (100) to the forming mold ( 200) when they are against each other, into which pressure air can be injected via the orifice (113) to press the plastic film (10) stamped by the stamping ring (130). on the inner sidewalls (210) of the forming mold (200).  10. Device according to one of claims 8 or 9, characterized in that the stamping ring (130) is adapted to move vertically relative to the forming punch (120) by means of a control such as a cylinder (131), placed inside said punch, so as to occupy two positions  an output position in which the stamping ring (130)  projecting from said punch at one of its ends (121),  a retracted position in which the stamping crown (130)  is placed inside a housing (122) provided in the punch of  forming (120).  11. Device according to one of claims 8 to 10, characterized in that the forming punch (120) is slidably mounted on the armature (110), and in that its vertical movement is controlled by an external cylinder independent of the inner control (131) of the stamping ring (130).  12. Device according to one of claims 8 to 11, characterized in that the against-mold (100) is the upper part of the device, and the forming mold (200) is the lower part.  13. Apparatus for manufacturing a plurality of plastic foot cups, characterized in that it comprises a plurality of devices according to one of claims 8 to 12, which operate simultaneously on a single plastic film positioned in said devices, and in that it comprises a means for making a cutting line of lower strength between each foot cut performed.  14. Cutting foot (300) of plastic material made according to the method according to claims I to 7, characterized in that it comprises a main portion (310) whose base extends downwardly by a foot (320). , the foot (320) having two heat-sealed faces and the main part (310) having a smooth and continuous inner surface.  15. Cutting foot (300) according to claim 14, characterized in that its foot (320) is straight.  16. Cutting foot (300) according to claim 14, characterized in that its foot (320) has a flared shape downwards.  17. Cutting foot (300) according to one of claims 14 to 16, characterized in that the two faces of the foot (320) are fluted vertically.