FR2817793A1 - Mould for injecting plastic packaging tube blank has body with recess adjoining main cavity to receive centering peg on mobile core - Google Patents

Abstract

The injection mould for plastic packaging tube blanks consists of a body (12) with a cylindrical cavity (24) and an axially moving core (16) forming an injection gap for the blank inside the cavity, a drive with supports (42) and power cylinders (44) to move the core relative to the body, and one or more injectors (38). The body of the mould has a recess (34) in line with the cavity's axis, and the core has a centering peg (52) on its end opposite the drive which fits into the recess to align the core with the cavity. The recess and peg are cylindrical in shape, with the peg made from the same material as the rest of the core and having a maximum diameter greater than half that of the core. The core and cavity have channels (30, 48) in the peg zone to make a neck on the tube, and the injected plastic enters the mould in that zone.

Description

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 The present invention relates to a mold for injecting a blank for a packaging tube comprising: - a body delimiting a generally cylindrical cavity; - a generally cylindrical core, movable axially with respect to the cavity, between a position engaged inside the cavity, in which the core and the cavity define an injection space for the tube blank, and a released position , in which the core is outside the cavity, allowing withdrawal of the injected tube blank; - a device for axial displacement of the core relative to said cavity, which displacement device is connected to a first axial end of the core; and - at least one injection nozzle in the injection space.

 It further relates to a method of manufacturing a blank for a packaging tube.

 The packaging tubes are commonly used for packaging cosmetic or pharmaceutical products, detergents, or soapy solutions.

 The packaging tubes are appreciated because of their low manufacturing cost.

 The tubes currently known are generally produced from an extruded tubular section of constant section at one end of which is attached a dispensing head, this head being for example injected onto the tubular section. After filling, the tubular section is closed by a transverse weld at its end opposite to that having the dispensing head.

 Attempts have been made to form tube blanks not from extruded sections, but by direct injection of the tube blank into a mold.

 However, this technique for manufacturing a tube blank has encountered the difficulty of guaranteeing a constant thickness of the side wall of the tube over its entire surface.

 The object of the invention is to propose a mold and a method for manufacturing a tube using this mold which make it possible to obtain blanks of

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 tubes whose wall thickness is substantially constant over the entire surface of the tube.

 To this end, the subject of the invention is a mold for injecting a blank for a packaging tube, of the aforementioned type, characterized in that the body has, in the axial extension of said cavity, a recess, and in that that the core has, at its second axial end, opposite the first axial end, a centering pin integral axially and transversely with the rest of the core, which centering pin is adapted to be received in the recess when the core is in its engaged position, said centering pin and the recess having complementary transverse profiles suitable for axial support of the core from its second end by fitting the centering pin into the recess.

 According to particular embodiments, the mold comprises one or more of the following characteristics: - the centering pin and the recess are generally cylindrical and extend along the axis of the cavity; - the centering pin came integrally with the rest of the core; - the maximum diameter of the centering pin is greater than 0.5 times the maximum diameter of the core; - The core and the cavity comprise, in the vicinity of the second end of the core, corresponding sections of reduced diameter adapted to form a neck of the tube blank, and the or each injection nozzle opens into the space injection only in the region delimited by the corresponding sections of reduced diameter; - The body comprises at least one movable drawer transversely to the axis of movement of the core, which drawer is movable between an injection position in which it partially delimits the surface of the cavity and a retracted position in which it is set back of the cavity; - It comprises a sleeve for ejecting the tube blank, which sleeve internally has a profile complementary to that of the core and is engaged around the core, the sleeve being axially displaceable along the core between an injection position in which he is away from the

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 second axial end of the core and an ejection position in which it is in the vicinity of the second axial end of the core; and - it comprises at least one relief suitable for the formation on the tube blank of a projecting or hollow profile suitable for the elastic engagement of a dispensing capsule.

 The invention also relates to a method for injecting a blank for a packaging tube, characterized in that it comprises a step of injecting liquid material inside a mold as described above. .

 The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings, in which: - Figure 1 is a schematic view in longitudinal section of a mold d injection of a packaging tube blank according to the invention, immediately before injection; - Figure 2 is a view identical to that of Figure 1, immediately after injection; - Figure 3 is a view identical to that of Figure 1, during the initial phase of demolding of the tube blank; - Figure 4 is a view similar to that of Figure 1, during the final phase of demolding of the tube blank; and - Figure 5 is a view identical to that of Figure 1, during the ejection of the tube blank.

 The mold 10 shown in FIG. 1 is intended for the manufacture of a blank for a packaging tube, in particular for cosmetic products. Such a tube blank is made of a polymeric material such as polyethylene or polypropylene.

 The tube blank comprises a flexible tubular body open at a first end and having, at a second end, a neck of reduced diameter. This neck has externally a thread allowing the subsequent screwing of a dispensing head. The first end of the tube is intended to be closed by a transverse weld, after filling.

 The mold 10 essentially comprises a body 12 internally delimiting a cavity 14, and a core 16 which can be moved inside the body,

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 an injection space 18 being delimited between the core and the body, when the core is in its injection position.

 The body 12 is formed from a solid metal block in which the cavity 14 is machined. The latter has a generally cylindrical shape with a longitudinal axis X-X. The cavity 14 opens onto a face 20 of the body through an opening 22 allowing the evacuation of the blank of injected tube.

 The cavity 14 is delimited by a cylindrical side wall 24. In this region, the section of the cavity 14, transverse to the axis X-X, is constant.

 At its end opposite the opening 22, the cavity 14 has a shoulder 26 partially delimited by a set of radially displaceable drawers 28.

 These drawers 28 can be moved between an injection position, as illustrated in FIG. 1, and a retracted position allowing the evacuation of the tube blank, as illustrated in FIG. 2.

 The drawers 28 have, on their face 30 facing the axis X-X, imprints adapted to form an external peripheral projection on a neck of the tube blank. This projection constitutes a peripheral rib adapted to allow a snap-fitting of a dispensing capsule onto the tube blank, this capsule comprising an internal groove in which the peripheral rib elastically engages. This snap-fit ensures axial retention of the capsule on the body.

 In addition, the drawers 28 have longitudinal recesses 31 adapted to form stops for blocking the capsule in rotation relative to the tube blank.

 The cavity 14 has, behind the drawers 28, a bottom 32. An axial recess 34 is provided in the bottom 32. This recess extends the cavity 14 axially.

 This recess is generally cylindrical with an X-X axis. It is for example generally circular in section.

 Advantageously, the maximum diameter of the recess 34 is greater than half the maximum diameter of the cavity 24.

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 The body 14 also comprises conduits 36 for the arrival of liquid polymer intended to fill the space 18. These conduits 36 open onto the bottom 32 by the supply nozzles 38.

 The core 16 is generally cylindrical and extends along the axis XX. At a first end denoted 40, the core 16 is secured to a support crown 42. The support crown and the core 16 which is integral therewith are displaceable in translation along the axis XX, under the action of jacks 44 shown diagrammatically . These jacks 44 ensure an axial displacement of the core 16 between a position engaged inside the cavity 14, in which the space 18, which is delimited between the core and the cavity, strictly has the shape expected for the roughing of tube, and an open position, illustrated in Figure 4, in which the core extends outside the cavity.

 More specifically, the core 16 has a main section 46 extending along the length of the cavity 24. The profile of the section 46 is generally cylindrical and follows the shape of the cavity 24 with slightly smaller dimensions making it possible to define a space 18 d substantially constant thickness between the core and the body.

 In particular, the core 16 has, in its main section 46, a segment 48 of reduced diameter adapted to delimit, with the drawers 28, the neck of the tube blank.

 According to the invention, at its second axial end 50, opposite its end 40, the core is extended axially by a centering pin 52 adapted to fit into the recess 34. The centering pin 52 is axially integral with the rest of the core 16 and in particular of the main section 46. The centering pin and the rest of the core have, for example, come in one piece. The centering pin is generally cylindrical and has a shape complementary to that of the recess 34. In particular, their cross sections are substantially complementary, in order to ensure centering and support of the core from its second end by fitting the centering pin 52 in the recess 54.

 Finally, a sliding ejection sleeve 56 is mounted movable along the core 54 from its first end to its second end.

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 moth. This sleeve 56 has internally a profile complementary to that of the core 16. Means for moving the sleeve 56 relative to the core are interposed between the sleeve 56 and the support ring 42.

These displacement means 58 are formed for example by jacks.

 For the manufacture of a tube blank, the mold is initially in the position illustrated in FIG. 1. In this position, the interlocking of the centering pin 52 in the recess 34 and the maintenance of the first end of the core by the support 42 ensures that the core 16 is held strictly along the axis XX. The core 16 being held at its two ends, the spacing between the core 16 and the body 12 is ensured with precision, thus guaranteeing an adequate and advantageously constant wall thickness.

 Liquid polymers are introduced into the space 18 through the conduits 36.

 At the end of the injection of the liquid polymers, the space 18 is completely filled, as illustrated in FIG. 2. After a sufficient cooling time, the drawers 28 are separated, as illustrated in FIG. 3.

 After the drawers 28 have been retracted, the core 16 is extracted from the cavity 24 by the action of the jacks 44, as illustrated in FIG. 4.

 The sleeve 56 is then moved from its initial position to its final position under the action of the jacks 58, as illustrated in FIG. 5. During its movement, the sleeve 56 releases the tube blank from the core 16 pushing it back towards the second end of the nucleus.

 After removal of the tube blank, the core is again introduced into the cavity 24, for the injection of a new tube blank.

 It is understood that with a mold according to the invention, the core being supported at each of its ends, it extends exactly along the axis of the cavity, thus guaranteeing a controlled thickness of the walls of the tube blank injected.

 The centering pin having a large diameter relative to the diameter of the rest of the core, the centering obtained by the cooperation of the centering pin 52 and the recess 34 is of very good quality.

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 As the centering pin is permanently fixed to the rest of the core, and that these advantageously come from one material, no play exists between the centering pin and the rest of the core, thus guaranteeing very reliable axial guidance.

Claims (9)

CLAIMS 1. - Injection mold (10) of a blank for a packaging tube, of the type comprising: - a body (12) delimiting a generally cylindrical cavity (24); - a generally cylindrical core (16) movable axially relative to the cavity (24), between a position engaged inside the cavity (24), in which the core (16) and the cavity (24) define a space for injecting the tube blank, and a cleared position, in which the core (16) is outside the cavity (24), allowing the withdrawal of the injected tube blank; - a device (42,44) for axial displacement of the core (16) relative to said cavity (24), which displacement device (42,44) is connected to a first axial end (40) of the core (16); and - at least one nozzle (38) for injection into the injection space (81), characterized in that the body (12) has, in the axial extension of said cavity (24), a recess (34) , and in that the core (16) comprises, at its second axial end (50), opposite the first axial end (40), a centering pin (52) integral axially and transversely with the rest of the core, which pin centering (52) is adapted to be received in the recess (34) when the core (16) is in its engaged position, said centering pin (52) and the recess (34) having complementary transverse profiles adapted for a axial support of the core (16) from its second end (50) by fitting the centering pin (52) into the recess (34).  2. - Mold according to claim 1, characterized in that the centering pin (52) and the recess (34) are generally cylindrical and extend along the axis (X-X) of the cavity (24).  3.-Mold according to claim 1 or 2, characterized in that the centering pin (52) came integrally with the rest of the core.  - 4. - Mold according to any one of the preceding claims, characterized in that the maximum diameter of the centering pin (52) is greater than 0.5 times the maximum diameter of the core (16). <Desc / Clms Page number 9>  5.-mold according to any one of the preceding claims, characterized in that the core (16) and the cavity (24) comprise, in the vicinity of the second end (50) of the core (16), sections ( 30,48) correspondents of reduced diameter adapted to form a neck of the tube blank, and in that the or each injection nozzle (38) opens into the injection space (18) only in the delimited region by the corresponding sections (30,48) of reduced diameter.  6.-mold according to any one of the preceding claims, characterized in that the body (12) comprises at least one drawer (28) movable transversely to the axis (XX) of displacement of the core (16), which drawer ( 28) is movable between an injection position in which it partially delimits the surface of the cavity (24) and a retracted position in which it is set back from the cavity (24).  7.-Mold according to any one of the preceding claims, characterized in that it comprises a sleeve (56) for ejecting the tube blank, which sleeve (56) has internally a profile complementary to that of the core ( 16) and is engaged around the core (16), the sleeve (56) being axially displaceable along the core (16) between an injection position in which it is away from the second axial end (50) of the core (16) and an ejection position in which it is in the vicinity of the second axial end (50) of the core (16).  8.-Mold according to any one of the preceding claims, characterized in that it comprises at least one relief (30) suitable for the formation on the tube blank of a projecting or hollow profile specific to the elastic engagement of a dispensing capsule.  9.-A method of injecting a tube blank, characterized in that it comprises a step of injecting liquid material inside a mold (10) according to any one of the preceding claims.