FR2917329A1 - Joint hinge's rectilinear score forming method for e.g. file folder, involves exerting pressure on sheet surface to conform score along direction in thickness of sheet, while permitting only joint portion to be subsisted on bottom of score - Google Patents

Abstract

The method involves supporting a thermoplastic sheet (2) that is found in a pasty state, on an upper metal rotary thermostated cooling roller (6) that drives the sheet during fabrication of the sheet. A predetermined confined collapsing pressure is exerted on a surface of the sheet to conform a rectilinear score (10) along a direction that is parallel to a displacement direction of the sheet on the roller, in the thickness of the sheet in the pasty state, while permitting only a thin joint portion to be subsisted on bottom of the score. An independent claim is also included for a rectilinear score forming device comprising a rotary thermostated cooling roller.

Description

The present invention relates to a method and a device for producing

  at least one rectilinear groove constituting a hinge hinge on a sheet of thermoplastic material.

  It applies in particular, but in a nonlimiting manner, to filing and presentation articles, such as for example binders, and to packaging, which are often made from a thermoplastic sheet generally based on polyolefin, more particularly polypropylene of the family of polyolefins. These classification or document presentation articles consist of different parts with flaps and / or flaps of more or less complex shape connected to each other by hinge hinges for opening or folding these parts. FIG. 1 represents an extrusion machine 1, known per se, for continuous shaping of a thermoplastic sheet 2. The various components, especially those based on polypropylene for producing the thermoplastic sheet, are introduced into an extruder 3 by means of a hopper. feed 4 in which they are mixed and melted and converted into a fluid mass conveyed by an Archimedean screw extruder 3 through a flat die 5 providing at the outlet of the die lips a continuous sheet 2 made of materials heated above its melting point and having an average thickness determined by the setting of the die. The soft sheet thus obtained passes between two metal calendering rollers 6, 7 for regulating the thickness of the sheet, cooling it and giving it its final surface appearance. Then, the sheet thus formed passes over other rollers 8 and is cut into several sheets 9 at a cutting station 10.

  These cut sheets are then stored. Alternatively, the sheet from the rollers 8 can be wound. The filing or document presentation articles are made from the sheets 9 by an adapted press of very high power, hydraulic or mechanical type of cardboard, manual or automatic, equipped with adapted tools consisting of steel nets cutting for cutting the shape contours of these articles and grooving threads allowing the realization of hinge hinges of different parts of these articles. These hinges can be made at the same time as cutting or during a second subsequent operation, recovery. In both cases, the cutouts and hinge hinge grooves can be made cold or hot. These very high power presses are extremely delicate to adjust, especially in the case of hot presses.

  Whatever the method used hot or cold, the shaping operation of a hinge groove is to practice a localized crushing of the thermoplastic sheet leaving only a thinned residual portion or hinge film of a thickness that can be between 100 and 300 microns. Generally, a hinge hinge is easily made cold on a thermoplastic sheet with a thickness ranging from 0.2 mm to 1.2 mm, but it is preferable to make this hinge hot if it is desired to obtain a hinge better quality. According to the method of hot forming a hinge, the surface of the sheet is more or less softened in contact with the heated grooving tool, but because of high production rates, this tool can not transfer its temperature to any the thickness of the sheet, the latter can not reach its softening temperature, or melting of the plastic material used. To achieve this calorie transfer goal, it is necessary to allow the grooving tool to penetrate more slowly into the thermoplastic sheet and to leave it in the down position for a certain time in the thickness of the sheet in order to transfer the calories of the the grooving tool at the part of the grooving sheet, which has the major disadvantage of significantly reducing production rates. In addition, if such a hot method allows for very flexible hinge hinges likely to retain their properties of flexibility over time, this type of press is extremely expensive and difficult to implement especially for large formats of sheets thermoplastics. Moreover, during the shaping operation of the cold or hot grooves on a sheet produced several days or even weeks before and crystallized molecular structure, the molecules constituting the hinge film thus produced are oriented during the course of the operation. thinning by crushing of the sheet, the grooving net causing a stretching of the sheet on either side of the net with thinning of the sheet at the hinge. The flexibility of the hinge thus produced will depend on many parameters that are not always controllable or known to the operator who performs this groove conformation operation. These parameters are related to the operating conditions of the hinge, such as for example the profile of the tool used which will influence the shape of the hinge and its flexibility, the temperature of the sheet during the grooving, the tool temperature grooving, the pressure applied during grooving, the speed of penetration of the grooving tool into the sheet, the rate of grooving, and the wear of the grooving tool. These parameters are also related to the characteristics of the sheet, such as its thickness, its variable hardness according to the colors and qualities of the polymer used and the extrusion conditions of the sheet, conditions which considerably influence the qualities and characteristics of the sheet, and the direction of extrusion (direction of manufacture) of the sheet relative to the direction of formation of the groove, the flexibility of the hinge is not the same if it is parallel or perpendicular to the direction of extrusion. Finally, these parameters are related to the quality and the characteristics of the groove obtained, namely the thickness of the residual hinge film which must be fine for a flexible hinge at the outlet of the press, the thickness regularity of this hinge and the straightness hinge. It therefore appears from the foregoing that it is very difficult to obtain large quantities of articles having the same characteristics of hinges, and the same hinge flexibilities. In addition, it is found after a few days or weeks of formation of a hinge, that it becomes less flexible and has a phenomenon of spring effect incompatible with a quality product, even if in its manufacture, the hinge was achieved with its desired flexibility characteristic.

  Indeed, if after manufacture, the hinge has not been solicited and stretched by manipulations, as is the case for filing articles or filing cabinets that are stored, shipped and sold to end consumers many weeks after their manufacture it can be seen that the hinge has become harder and therefore less flexible.

  This type of hinge shows a spring effect very detrimental to the desired use and no longer has the same characteristics of flexibility in opening and closing than those found during the manufacture of the hinge. For example, a binder with two hinges connecting two flanks on the back of the binder will no longer open flat and will tend to close on its own, or will not close properly, because of the spring effect of the two hinges very detrimental the good use of this workbook. If necessary, it will be further noted that the two sides of the binder are bent around a rigid hinge. This change in time hinges that are made on a sheet formed a few weeks ago and already crystallized, is due inter alia to the elastic component of the thermoplastic sheet used, the molecular crystallization of the sheet having organized and frozen the molecular orientation during and after the calendering. During the abrupt and rapid thinning mentioned above, the molecules of the hinge film thus produced are oriented and stretched on either side of the longitudinal central axis of the hinge, but over time, by memory and elastic effect of the materials. some of these molecules thus oriented and stretched during the grooving operation will tend to resume their original positions and shapes. Thus, the hinge film will lose its flexibility and gradually regain an unwanted spring effect for use. Therefore, products made from a thermoplastic sheet including polypropylene, such as filing cabinets or filing items, have not achieved the expected commercial success or have been classified by the customer user as low quality products .

  The present invention aims to overcome all the drawbacks mentioned above. For this purpose, the invention proposes a method of producing at least one rectilinear groove constituting a hinge hinge on a sheet of thermoplastic material and which is characterized in that it consists, on the production line of the sheet thermoplastic, to bring the sheet of thermoplastic material in a pasty state in bearing contact on at least one thermostatic cooler and rotary drive roll of the sheet, to exert on the face of the sheet opposite to that in support on the temperature-controlled roll a localized crushing pressure predetermined to conform in the thickness of the sheet in the pasty state a groove in a direction parallel to the direction of movement of the sheet on the roll leaving only the bottom groove that a thinned portion of articulation. The method consists in simultaneously forming a plurality of parallel grooves in the thickness of the sheet in the pasty state resting on the thermostatic roll, respectively exerting several localized and predetermined crushing pressures in the thickness of the sheet.

  The method consists in exerting each conformation crushing pressure of a groove as close as possible to the upstream contact entry location of the sheet in the pasty state on the thermostatic roll. The invention also proposes a device for producing at least one rectilinear groove constituting a hinge hinge on a sheet of thermoplastic material and which is characterized in that it comprises, on the manufacturing line of the thermoplastic sheet, at least a thermostatic sheet thermostatic roll and driven rotary drive carried in support thereon to a pasty state, a forming tool comprising at least one outer circular projection which extends in a plane perpendicular to the longitudinal axis of the thermostatic roll and can be applied by the tool at a predetermined pressure on the face of the sheet opposite to that resting on the thermostatic roll to form in the thickness of the sheet a groove of shape conjugate to the circular sheet and following a direction parallel to the direction of movement of the sheet on the roll leaving no trace at the bottom of the groove e a thinned portion of articulation. According to a first embodiment, the forming tool is constituted by an idler roller parallel to the thermostatic roller, of smaller diameter than the latter, and whose circular projection extends radially and externally on the rim of the forming roll. . Advantageously, the shaping roll comprises a plurality of axially spaced outer radial radial projections that can be applied by the shaping roll on the face of the sheet opposite to that resting on the thermostatic roll to form in the thickness of the sheet respectively several grooves of forms conjugated to the circular projections and parallel to the direction of movement of the thermoplastic sheet. According to an alternative embodiment, the device comprises a single thermostatic roll and the forming roll is arranged in line with the upstream contact entry location of the sheet in the pasty state on the thermostatic roll. In the context of this variant, a flat extrusion die is disposed upstream of the thermostatic roll to continuously produce the thermoplastic sheet deposited on the rotary thermostatic roll and applied thereto in particular by blowing a film of air. According to another alternative embodiment, the device comprises a second rotary thermostatic roll parallel to the first thermostatic roll and between which is introduced the thermostatic sheet in the pasty state which is subjected to a pressure exerted by the two rollers and the forming roll is disposed at an outlet of the sheet between the two thermostated rolls close to the second thermostatic roll. According to a second embodiment, the device comprises a second rotary thermostatic roll parallel to the first thermostatic roll and between which is introduced the thermoplastic sheet in the pasty state which is subjected to a pressure exerted by the two rollers and the forming tool is constituted by the second thermostatic roll and whose circular projection extends radially outwardly on the rim of this roll. The second thermostatic roll advantageously comprises a plurality of axially spaced outer radial radial projections and the height of the radial projections cut off at the air gap of the two thermostated rollers determines the depth of the articulation grooves. According to a third embodiment, the shaping tool comprises at least one rotating disc extending in a plane perpendicular to the longitudinal axis of the thermostat roll and whose outer edge constitutes the circular conformation projection of the groove. Advantageously, the shaping tool comprises a plurality of parallel disks perpendicular to the longitudinal axis of the thermostatic roll and whose outer edges respectively constitute circular protrusions of conformation of the corresponding grooves. Each disk is mounted loosely on a controlled displacement yoke between an inactive position and a pressure bearing position on the thermoplastic sheet.

  The yoke is movable in rectilinear translation perpendicular to the roller by a pneumatic or hydraulic cylinder. The yoke is part of a pivoting 5-counterweight assembly for bringing each disk into a pressure bearing on the thermoplastic sheet. According to the third embodiment, the device comprises a second rotary thermostatic roll parallel to the first thermostatic roll and between which is introduced the thermoplastic sheet in the pasty state which is subjected to a pressure exerted by the two rollers and each forming disc is applied to the thermoplastic sheet at an exit location of the sheet from between the two thermostatic rolls close to the second thermostatic roll. Each disc is movable in a direction parallel to the longitudinal axis of the thermostatic roll so as to adjust the conformation position of the hinge in the thermoplastic sheet. Each circular projection is shaped like a torus sector. Each circular projection has a profile for printing visual and / or tactile patterns on the hinge and / or on one or both sides of the hinge. Advantageously, each circular projection is shaped to print in the hinge hinge repetitive reliefs projecting or hollow transverse to the longitudinal axis of the hinge and limiting the tear of the hinge. The invention also relates to a hinge made of thermoplastic material, in particular intended to connect two elements of thermoplastic material articulated to each other, such as two flaps or flaps of a file folder, and which is characterized in that it is made from the method or device defined above.

  The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the following explanatory description made with reference to the accompanying schematic drawings given solely by way of example relating to several embodiments of the invention and in which: - Figure 1 generally shows a known calendering extrusion machine for manufacturing a continuous thermoplastic sheet; - Figure 2 is a perspective view of a first embodiment of the device of the invention for producing hinge hinges; - Figure 3 is a sectional view along the line III-III of Figure 2; - Figure 4 is a perspective view of a second embodiment of the device of the invention for producing hinge hinges; - Figure 5 is a perspective view of a third embodiment of the device of the invention for producing hinge hinges; - Figure 6 is a perspective view of a fourth embodiment of the device of the invention for producing hinge hinges; FIG. 7 is a perspective view of an alternative embodiment of the articulation hinge forming device of FIG. 6; FIG. 8 is a partial perspective view of a shaping tool of the invention provided with ridges for producing visual and / or tactile patterns in hinge hinges; and FIG. 9 is a plan view of a hinged hinge sheet shaped by the tool of FIG. 8.

  Figures 2 and 3 show a first embodiment of the device of the invention for conforming on a sheet of thermoplastic material 2 at least one rectilinear groove 10 constituting a hinge hinge. According to this embodiment, each groove 10 is shaped on a calendering extrusion line where only the flat die 5 at the end of the extruder, not shown, preforming its exit lips the thermoplastic sheet 2, and the first two rollers rotating metal calendering 6, 7 being shown. Thus, the sheet 2 from the flat die 5 is introduced in a pasty state between the two rollers 6, 7 of the calender to finalize and regulate the thickness of the sheet 2 and give it the surface appearance conferred by the surface aspects of these two rollers which are thermostated to maintain in the pasty state the sheet 2 partially wound on the upper roll 6 before being transferred to other rolls of the calender. According to the invention, the grooving operation of the sheet 2 is performed while the sheet is still in the pasty state and in contact between the two rolls of the shell. For this purpose, the upper cooling roll 6 comprises at least one circular projection 11 extending radially on the rim or peripheral surface 6a of the roll 6 on the outside of this rim. As shown, the chill roll 6 comprises two identical circular protrusions 11 axially spaced from each other along the roll 6, but it is understood that this roll may comprise a different number of circular projections depending on the number of hinges. articulation that one wishes to realize in the sheet 2.

  Each of these projections 11 has a shape conjugate to that of the groove 10 which it is desired to make on the sheet 2 and a radial height determining the depth of the groove 10 so as not to remain during the production of the groove 10 at the bottom of the latter a thinned portion 10a in the form of a hinge film. Each of the projections 11 extends in a plane perpendicular to the longitudinal axis of the roll 6 and is a sort of tool for shaping the groove 10. The circular projections 11 can be made by an etching technique to reduce the thickness of the peripheral roll wrapper 6, but other techniques may be used. The two rollers 6, 7 are set at a position parallel to each other so as to exert on the sheet 2 introduced between them a pressure allowing in particular to regulate the thickness of this sheet.

  As shown in FIG. 3, the thickness e 1 of the hinge film 10 a formed by the corresponding circular projection 11 is equal to the value of the air gap e 2 between the two rollers 6, 7 corresponding to the thickness of the sheet 2 coming out of these rollers, reduced by the radial height of the circular projection 11 from the rim 6a of the roller 6. This figure shows for the sake of clarity the two rollers completely separate from each other, but in reality they are pressed towards each other at the position in phantom of the rim 6a of the roller 6 corresponding to the gap e2. Thus, during the passage of the sheet 2 between the two rollers 6, 7 in the sheet extrusion direction indicated by the arrow F, each radially outer circular projection 11 is applied under a predetermined pressure of thickness equalization of the sheet 2 on the face of this sheet opposite to that resting on the other antagonist thermostat roller 7 so as to form in the thickness of the sheet 2 in the pasty state a rectilinear groove 10 of shape conjugate to the projection 11 and following a direction parallel to the direction of displacement or extrusion of the sheet 2 on the roll 6 so as to leave at the bottom of the groove 10 only the hinge hinge film 10a. By way of example, the temperature of each calender roll 6, 7 directly at the outlet of the die 5 is regulated at a value of approximately 130 ° C. for a temperature of the sheet 2 coming out of the die 5 of approximately 230 ° C. in order not to create a thermal shock on the sheet 2 and to keep it in a pasty state between the rollers 6, 7 and on the roll 6. Of course, these temperature values are given for information only and can vary according to the components of the material constituting the sheet 2 or the extrusion process retained. The hinge 10a of the invention formed in the pasty material of the thermoplastic sheet 2, is produced before it is crystallized in its thickness and it retains in time its flexibility required qualities without encountering any phenomenon. retraction as is the case in the conventional processes mentioned above to achieve hinges. Indeed, during the operation of making each of the grooves 10 by the method of the invention, the molecules of the sheet 2 undergo virtually no orientation and no stretching, the grooves 10 being only thermoformed by the radially outer circular projections 11 used for this purpose. As shown in FIG. 3, the circular projection 11 has a profile in the form of a toroidal sector, but it is understood that it may have different profiles that are more or less complex depending on the needs, as will be seen later.

  Thus, the sheet 2 will comprise one or more parallel continuous and flexible hinges parallel to the extrusion direction and disposed on the sheet according to the implantation of the circular projections 11 on the calender-cooler roll 6 bearing these projections. According to an alternative embodiment, the radially outer circular projections 11 may be formed on the roller 7, the roller 6 then serving as an opposing roller for shaping the grooves 10 in the pasty material of the sheet 2. Although the device of FIGS. and 3 gives neither production flexibility in terms of thermoplastic sheet thickness 2 due to the presence of circular protrusions 10 of a given height, nor production flexibility in terms of position of the circular protrusions, it nevertheless considerably simplifies the adjustments that the operator must make since he does not have to worry about the position relative to the sheet 2 of the circular groove conforming projections, but only the gap between the second roll 7 of the shell and each circular projections 11 of the other roll 6 to produce a sheet having continuous hinge hinges with thicknesses s of the sheet 2 and the hinge joint film 10a very regular. The second embodiment of the invention shown in FIG. 4 makes it possible, on the thermoplastic sheet 2, to produce grooves 10 for shaping hinge hinges at the desired depth values and to position the grooves to be formed at the desired location. parallel between the two longitudinal edges of the sheet 2, that is to say in the direction transverse to the extrusion direction F of this sheet. As in the embodiment of Figures 2 and 3, the device of Figure 4 is part of a calendering extrusion line of which only the two rotary calendering rollers 6, 7 are shown. According to this embodiment, the groove forming tool 10 comprises two parallel rotating discs 12 extending in a plane perpendicular to the longitudinal axis of the upper thermostat roll 6 and whose respective outer circular edges have a profile to achieve respectively two hinge hinge grooves 10 on the sheet 2 still in the pasty state between the two thermostatically controlled cooling rollers 6, 7 and in its wound part on the roll 6. The two discs 12 are mounted idle on a clevis 13 to a controlled displacement between an inactive position released from the roll 6 and a position in which the two disks are pressing against the thermoplastic sheet 2 itself bears on the roll 6 to form the two grooves 10. More specifically, the clevis is movable in rectilinear translation perpendicular to the longitudinal direction of the roll 6 by a pneumatic jack or hy hydraulic 14 or any other equivalent means. In addition, the clevis assembly 13 for supporting the discs 12 and control jack 14 can be mounted on a carriage, not shown, for moving this assembly in a direction parallel to the longitudinal axis of the roll 6 so as to adjust the position of the discs 12 relative to the rollers and, therefore, adjust the two grooves 10 on the sheet 2 at desired locations in the direction transverse to the direction of extrusion or displacement of the sheet 2 symbolized by the arrow F. Preferably , the disks 12, in the position of the grooves 10, are located at an outlet location of the thermoplastic sheet 2 between the two thermostated rolls 6, 7 and close to the lower thermostatic roll 7.

  In operation, the discs 12 are applied to a determined pressure on the face of the thermostatic sheet in the pasty state 2 emerging from between the two rollers 6, 7 and whose opposite face is in rolling support on the roll 6 to thereby penetrate into the thickness of the sheet 2 and create the desired hinge hinge, the sheet 2 is always applied to the counter roller 6. This embodiment allows to adjust the pressure exerted by the discs 12 in the thickness of the sheet 2 in the pasty state and, consequently, to modify the thickness of the hinge hinge without being constrained by the thickness of the extruded sheet. Of course, adjustable mechanical stops may be used to limit the displacement of the discs 12 in the sheet 2 and to adjust the depth of the grooves relative to the rim of the roll. The device of Figure 4 is very flexible in use since it allows not only to adjust the depth of the grooves, but also to change the position of the hinge hinges. Of course, the device of FIG. 4 may comprise a single disk or more than two disks according to the number of hinge hinges that one wishes to make on the sheet 2. FIG. 5 represents another embodiment of the invention. invention also using rotating shaping discs of grooves 10 in the pasty material of the thermoplastic sheet 2 as in the embodiment of FIG. 4. The difference between these two embodiments is that the two discs 12 are part of a E crew pivoted about a horizontal axis YY 'parallel to the rollers 6, 7 and comprising on either side of this axis the clevis 13 for supporting the discs 12 and a counterweight 15 for exerting on the discs 12 a predetermined pressure allowing them to tilt the discs 12 resting on the sheet 2 and to penetrate into the thickness of the thermostated sheet 2 in the pasty state to achieve a groove depth corres ponding.

  The two forming discs 12 are applied at an outlet location of the sheet 2 between the two rollers 6, 7 and close to the roll 7. The crew E can be mounted on a carriage allowing it to be moved in a manner direction parallel to the longitudinal axis of the roller 6 to thereby allow to modify the hinge to a desired position of formation in the sheet 2 parallel to the extrusion direction F. Inactive position, the crew E can be tilted around the YY 'axis for disengaging the discs 12 of the roll 6. According to the two embodiments of Figures 4 and 5, the shaping discs 12 of the grooves 10, instead of being mounted on a single yoke 13 to be applied under pressure together simultaneously on the outer face of the sheet 2 wound on the roll 6, can be individually mounted on a yoke so as to be applied to the sheet 2 independently of each other. Such a modification makes it possible, for example, to provide a plurality of discs 12, some of which are used to produce corresponding grooves on a thermoplastic sheet, the others being provided to make other grooves on another thermoplastic sheet. FIG. 6 shows a fourth embodiment of the device of the invention which is used for shaping hinge hinge grooves on a thermoplastic sheet 2 obtained on a calendering extrusion line, as in the embodiments of FIGS. 5.

  According to this embodiment, the groove forming tool 10 is constituted by a single roll 16 of smaller diameter than the two calendering rollers 6, 7 and which is mounted idler about its longitudinal axis. The roller 16 is provided with two radially outer circular projections 17 of the thermally controllable roll rim 16 which are applied at a predetermined pressure in the thickness of the pasted sheet 2 to provide two conformal grooves. hinge hinges. Of course, the roller 16 may comprise a single circular projection or more than two circular projections located in one or more planes perpendicular to the longitudinal axis of the roll 6. Each of these projections 17 may have a profile in torus section as for the embodiment of the device of Figures 2 and 3. The forming roller 16 is disposed parallel to the roller 6 at an outlet location of the thermoplastic sheet 2 between the two rollers 6, 7 and close to the lower roller 7 so that the circular projections 17 of the roller 16 are applied under pressure in the thickness of the thermostatic sheet 2 in a state as pasty as possible. Of course, the forming roll 16 is applied by any suitable means to a predetermined pressure on the thermoplastic sheet 2 partially rolled on the upper roll 6 to shape the grooves 10 extending parallel to the extrusion direction F of the sheet 2. Such means could be constituted by a roller bearing fork 16 with controlled displacement perpendicular to the longitudinal axis of the roller 6, for example using a hydraulic or pneumatic jack in the manner of the clevis 13 for supporting the disks. 12 of the embodiment of FIG. 4.

  Because the radially outer circular projections 17 of the roller 16 are integral with this roller respectively in planes perpendicular to the longitudinal axis of the calendering roller 6, the operator does not have to worry about their respective positions relative to the roller. 6 so that any risk of error in making the grooves at a precise and desired location is greatly reduced. Further, because the forming roll 16 is extremely small in diameter with respect to the two calender rolls, it is inexpensive, and it is furthermore possible to multiply the number thereof, i.e. a roll by position of circular shaping protrusions and profile type thereof. Advantageously, each forming roll 7 may comprise an internal thermostatic cooling or heating means for optimizing the settings according to the production conditions. If necessary, the roller 16 can receive several removable folders with different profiles of circular grooving protrusions so that changing the sleeve, one changes grooving projection profile.

  FIG. 7 represents an alternative use of the roller 16 of FIG. 6 applied to an extrusion line called "cast" used in particular for the production of thin sheets or thin films the thickness of which would not be compatible with FIG. use of two air gap calender rollers too low and uncontrollable up to cause deterioration of these two rollers if they came to touch. Unlike the calendering extrusion, the thin sheet or continuous thin film coming out of the die lips is cast or deposited on a single rotating metal roll 18 shown in FIG. 7, the sheet or film 2 being applied to this roll by an air film, a continuous metal strip or another roller whose surface is of a sufficiently flexible material to be applied to the metal roller 18 and not to deteriorate the latter in case of sudden thinning or breaking the sheet or thin film. Of course, the sheet or thin film 2 thus supplied then passes on other cooling rollers 19, possibly thermostatically, of which only one is shown in FIG.

  This figure shows that the roller 16 provided with its two radially outer circular projections 17 is arranged parallel to the roller 18 above it to the right of the upstream contact entry location of the sheet in the pasty state 2 on the rotary thermostatic roll 18 so that the two projections penetrate under pressure into the thickness of the sheet 2 in a pasty state resting on the counter-roller 18 to achieve in the best possible conditions the shaping grooves of articulation hinges parallel to the direction of extrusion F. The devices which have been described in the various embodiments of Figures 2 to 6, instead of being used on a calendering extrusion line, can be used on a conventional calendering line without depart from the scope of the invention. Each of the external circular projection forming tools described in the various embodiments of the invention may have a profile provided with regular patterns or ridges throughout its periphery as shown in FIG. 8 showing a circular projection 11 of the embodiment. FIG. 3. These drawings or ridges 20 which can protrude from the profile of the protrusion itself 11 or be hollowed out in it, will engrave hollows or repetitive reliefs on the articulation hinge, such as by Examples of lines perpendicular to the longitudinal direction of the hinge or a chevron pattern, providing a visual and tactile effect of the hinge hinge. In addition, the tear strength of the hinge hinge will be considerably increased in the longitudinal direction of this hinge, the latter being no longer composed of a smooth film of fixed thickness, but a regular succession small reliefs or recesses 10b in the hinge film 10a and transverse to the longitudinal direction of the hinge to limit the propagation of the tear. An example of such a hinge providing a tear resistance thereof is shown in Figure 9 which also shows the impression of other visual and / or tactile patterns on both sides of the hinge 10a in order to improve the visual and / or tactile effect of the latter. In this case, the circular rim portion of a shaping roll located on either side of the circular projection will comprise a printing etching of the drawings or patterns 10a on either side of the hinge hinge 10a. and may be dot-shaped as shown in FIG.

Claims (23)

  A method of producing at least one rectilinear groove (10) constituting a hinge hinge on a sheet of thermoplastic material (2), characterized in that it consists, on the manufacturing line of the thermoplastic sheet (2). ), to bring the thermoplastic sheet (2) in a pasty state into bearing contact on at least one rotary thermostatic cooling roll (6; 7; 18) for driving the sheet (2), to exert on the face of the sheet (2) opposite to that resting on the thermostatic roll (6; 7; 18) a predetermined crushing localized pressure allowing to conform in the thickness of the sheet in the pasty state (2) a groove ( 10) in a direction parallel to the direction of movement of the sheet (2) on the roll leaving only a thin portion of articulation (10a) remaining at the bottom of the groove.   2. Method according to claim 1, characterized in that it consists in simultaneously forming several parallel grooves (10) in the thickness of the sheet in the pasty state (2) resting on the thermostatic roll (6; 7; 18) respectively exerting several predetermined localized crushing pressures in the thickness of the sheet (2).   3. Method according to claim 1 or 2, characterized in that it consists in exerting each conformation crushing pressure of a groove (10) closest to the upstream contact input location of the sheet to the pasty state (2) on the thermostatic roll (18).   4. Device for producing at least one rectilinear groove (10) forming a hinge hinge on a sheet of thermoplastic material (2), characterized in that it comprises, on the production line of the thermoplastic sheet (2) at least one rotary thermostatic chill roll (6; 7; 18) for driving the thermostatic sheet (2) fed thereon to a pasty state; a forming tool (6; 12; 16,17); comprising at least one outer circular projection (11; 17) which extends in a plane perpendicular to the longitudinal axis of the thermostatic roll (6; 7; 18) and can be applied by the tool according to a predetermined pressure on the face of the sheet (2) opposite to that resting on the thermostatic roll (6; 7; 18) to form in the thickness of the sheet (2) a groove (10) of shape conjugate to the circular projection and in a direction parallel to the direction of movement of the sheet (2) on the roll (6; 7; 18) leaving only a thinned portion of articulation (10a) at the bottom of the groove.   5. Device according to claim 4, characterized in that the forming tool is constituted by an idler roller (16) parallel to the thermostatic roll (6; 7; 18), of smaller diameter than the latter and whose protrusion circular member (17) extends radially and externally on the rim of the forming roll (16).   6. Device according to claim 5, characterized in that the shaping roll (16) comprises a plurality of axially spaced outer radial radial projections (17) which can be applied by the shaping roll (16) to the face of the sheet (2). opposite to that resting on the thermostatic roll (6; 18) to form in the thickness of the sheet (2) respectively several grooves (10) of forms conjugated to the circular projections (17) and parallel to the direction of movement of the sheet theoplastic (2).   7. Device according to claim 5 or 6, characterized in that it comprises a single thermostatic roll (18) and in that the forming roll (16) is disposed in line with the upstream contact entry location of the pasty sheet (2) on the thermostatic roll (18).   8. Device according to claim 7, characterized in that a flat extrusion die (5) is arranged upstream of the thermostatic roll (18) to continuously produce the thermoplastic sheet (2) deposited on the rotary thermostatic roll (18). ) and applied thereto in particular by blowing an air film.   9. Device according to claim 5 or 6, characterized in that it comprises a second rotary thermostatic roll (7) parallel to the first thermostatic roll (6) and between which is introduced the thermoplastic sheet (2) in the pasty state which is subjected to a pressure exerted by the two rollers (6,7) and in that the shaping roll (16) is arranged at an outlet of the sheet (2) between the two thermostated rollers (6,7). ) close to the second thermostatic roll (7).   10. Device according to claim 4, characterized in that it comprises a second rotary thermostatic roll (6) parallel to the first thermostatic roll (7) and between which is introduced the thermoplastic sheet in the pasty state (2) which is subject at a pressure exerted by the two rollers (6,7) and in that the forming tool is constituted by the second thermostatic roll (6) and whose circular projection (11) extends radially and externally on the rim of this roll.   11. Device according to claim 10, characterized in that the second thermostat roll (6) comprises a plurality of outer radial radial projections (11) axially spaced and in that the height of the radial projections (11) entrenched at the air gap of the two rollers thermostats (6,7) determines the depth of the hinge grooves (10).   12. Device according to claim 4, characterized in that the shaping tool comprises at least one rotating disc (12) extending in a plane perpendicular to the longitudinal axis of the thermostat roll (6) and whose outer edge constitutes the circular protrusion of the groove (10).   13. Device according to claim 12, characterized in that the forming tool comprises a plurality of parallel discs (12) perpendicular to the longitudinal axis of the thermostatic roll (6) and whose outer edges respectively constitute circular groove conformation projections. corresponding (10).   14. Device according to claim 12 or 13, characterized in that each disc (12) is mounted loosely on a yoke (13) controlled displacement between an inactive position and a pressure bearing position on the thermoplastic sheet (2).   15. Device according to claim 14, characterized in that the yoke (13) is movable in rectilinear translation perpendicularly to the roller (6) by a pneumatic or hydraulic cylinder.   16. Device according to claim 14, characterized in that the yoke (13) is part of a counterbalanced pivoting assembly (14) for bringing each disc (12) into a pressure bearing on the thermoplastic sheet ( 2).   17. Device according to one of claims 12 to 16, characterized in that it comprises a second rotary thermostatic roll (7) parallel to the first thermostatic roll (6) and between which is introduced the thermoplastic sheet in the pasty state ( 2) which is subjected to a pressure exerted by the two rollers (6, 7) and in that each forming disc (12) is applied to the thermoplastic sheet (2) at an exit location of the sheet of between two thermostatic rolls (6,7) close to the second thermostatic roll (7).   18. Device according to one of claims 12 to 17, characterized in that each disc (12) is movable in a direction parallel to the longitudinal axis of the thermostat roll (6) so as to adjust the hinge of the conformation position in the thermoplastic sheet (2).   19. Device according to one of claims 4 to 18, characterized in that each circular projection is in the form of torus sector.   20. Device according to claim 9, 10 or 16, characterized in that the thermoplastic sheet (2) comes from a flat extrusion die (5).   21. Device according to one of claims 4 to 18, characterized in that each circular projection has a profile for printing visual and / or tactile patterns on the hinge and / or one side or each side of the hinge.   22. Device according to claim 21, characterized in that each circular projection is shaped to print in the articulation hinge (10a) protruding relief projections or recesses (10b) transverse to the longitudinal axis of the hinge and limiting the tearing of the hinge (10a).   23. Hinge made of thermoplastic material, in particular intended to connect two thermoplastic elements hinged to each other, such as two flaps or flaps of a file folder, characterized in that it is made from the process according to one of claims 1 to 3. tIt