MXPA97006060A

MXPA97006060A - Molded skirt without seams and proc

Info

Publication number: MXPA97006060A
Application number: MXPA/A/1997/006060A
Authority: MX
Inventors: Scheliga Werner
Original assignee: Unique Mould Makers Limited
Priority date: 1995-02-09
Filing date: 1997-08-08
Publication date: 1998-02-01

Abstract

The present invention relates to an injection molding method of a hollow body having an annular portion depending on a substantially planar crown portion, inside a mold containing an external one-piece mold and a shrinkable internal male mold, the portion The annular skirt has a projection molded on the external surface thereof by means of a slit in the inner face portion of the external mold, characterized in that said hollow body is a lock lid of a container and the skirt portion being annulled extends substantially normal to the crown portion, and the inner mold is substantially cylindrical, the projection molded on the outer surface of the skirt portion is discontinuous, this method includes the steps of: - assembling the outer mold and the internal male mold to form a cavity enclosed, - inject plastic form into the cavity, via a localized injection head to inside the internal male mold, - cool the plastic to form the lid by contracting the male mold out of contact with the portion of the skirt of the

Description

MOLDED SKIRT WITHOUT SEAMS AND PROCESS FIELD OF THE INVENTION This invention is directed to a molded plastic object having a seamless annular skirt, and to the apparatus and the process for injection molding.

BACKGROUND OF THE INVENTION Injection-molded lids with external notches are traditionally molded into mold cavities having a mold division divided into two or more arcuate segments. This usually results in visible mold or line spacings extending longitudinally along the skirt portion of the molded cover, coinciding with the lines of the mold and possibly resulting in leakage in the bond lines of the mold. mold.

A cap is usually expelled from its mold by means of its male mold which militates against the presence of any notch in the female mold of the skirt, which could sometimes cause an adhesion between the cap and the inner surface of the notches. of the mold. Thus, the only usual molding provides, on the outer surface of the skirt of the lid, transverse ribs, which can create a clean removal during ejection, or mold protrusions located in a small arc in the axis of extraction movement of a mold segment.

From the above it was concluded that the decoration of the outer surface of a mold skirt, without mold seams and resulting witness lines could not be satisfactorily performed.

DESCRIPTION OF THE INVENTION The present invention provides a method of molding a lid with an annular mold without seams. It was found, in the case of caps of 5.08 cm (2 inches) of or more in diameter, that a collapsible male mold can be used, where the male mold is formed by several segments, and can collapse inwards.

Inward retraction or collapse of the male mold while the cap is cooling inside its mold then allows thermal contraction of the molded article, particularly the skirt of the cap, radially inwardly of the inner peripheral wall of the skirt portion of the cap. mold, for the subsequent expulsion of the mold cavity.

It was found that in the extension of the radial contraction of the lid, in molds of around 5 cm (about 5 inches), a polypropylene lid can shrink approximately 0.762 mm, (0.030 inches), diametrically.

This in turn makes it possible to apply, in caps of around 5 cm in diameter or larger, to mold decorations on the peripheral outer surface of the skirt of the cap of about 0.36 mm (0.014 inches). The provision of such skirt decoration, and the absence of witness lines under the skirt is the greatest advantage of the user, to market the improved product.

The present invention, then, provides a molded cover with a dependent skirt, where the skirt has a surface without damage, free of witness lines.

The cover in question then has a dependent skirt where the outer peripheral surface of the skirt can be a continuous skirt without damage.

This cap may include shallow deviations integrally molded into or within the outer surface of the skirt.

The mentioned deviations can be molded around the periphery of the skirt, and can be in the form of desirable decoration so as not to prevent the radial contraction inwards of a notch of mold cavity.

The cover can also comprise letters, wording or other indicators with meaning. I The apparatus provided, to carry out the invention, should comprise a mold cavity having a removable male mold where the male mold is retractable outward together with its hollow molded product.

A three-piece collapsible matrix was found to be highly effective in this function.

The mold cavity may have a substantially cylindrical and continuous unitary wall to mold a hollow cylindrical object thereon.

The wall of the mold skirt may include portions of shallow grooves in it, to allow the molding of a hollow skirt article, where the skirt of the article includes low height protrusions extending outside the peripheral surface of the skirt in a surface relationship, and highlighted among them.

Alternatively, the skirt wall of the mold may include slightly pronounced protuberances extending inward, to mold notch portions within the skirt of the article.

Said raised protuberances are generally provided with a thin tapered taper or small inclination to facilitate radial separation between the skirt of the article and the surface of the skirt molding mold.

In one embodiment of the mold in question, the included male mold includes a plurality of collapsible skirt segments which, in an assembled, extended condition, provide an outer surface of the molding core. The use of three male mold segments are contemplated.

The outer mold surface of the male mold may include the necessary surface details such as ribs or screw cavities, for the production of ribs or screw threads on the inner surface of a cap molded into the mold.

In a preferred embodiment, a plurality of axially retractable, tapered male mold segments are provided, where the retraction of the male mold segments allows radial retraction inward of the remaining segments, to complete the radial cleaning, this making it possible to extract the Starting from the interior surface, from a lid or other hollow product molded into the mold, the interior surfaces of the article are molded, at least in part, by at least some of the portion of the inner surface of the male mold. , In an embodiment of the mold in question, the injection nozzle is located within the core of the mold, the core having an opening therein connected to the mold cavity-plastic transfer relationship.

The aforementioned nozzle is at least partially axially removable from the core of the mold, to facilitate the retraction of some of the segments of the female mold, thus making possible the radial contraction inwards of the remaining male mold segments, so as not to prevent the withdrawal of the male mold of a hollow molded object.

A mold constructed in accordance with the above may have an expeller incorporated as part of the mold, the expeller generally comprising an axially displaceable cylinder, the inner end surface of this cylinder forming at least a portion of the crown portion of the mold cavity, for molding at least a crown portion of a hollow object manufactured by the mold, and axially displacing the molded hollow object from the mold.

The present invention further provides a method of molding a hollow plastic object having a peripheral skirt portion comprised, including the steps of assembling a closed injection mold having a mold cavity including a portion of a male mold in the shape of the desired object. , inject hot plastic in a fluid state inside the mold, fill the cavity; removing the male mold from the hot plastic object; . cooling the object in order to promote inward contraction of the peripheral skirt portion in spaced relation to the adjacent inner mold surface; and unload the cooled object from the mold.

The inner skirt surface of the mold may include protuberances and / or notches of predetermined dimensions, relative to the main surface of the skirt, from which the molded article is free to contract thermally, for a subsequent displacement from the mold.

The ejector machine, the mobile air discharge head, the suction cup or the retraction of the male mold, are all possible objects of the unloading method.

In a preferred embodiment the inner skirt wall of the mold can be notched by one or more shallow decorations, from which the molded object is separated during cooling inside the mold.

It should be understood that the decorations may also consist of notches inserted into the thin wall of the skirt of the molded object.

The magnitude of the cooling affects the magnitude of the radial contraction. So a molding cycle time of 10 seconds can allow a retraction separation in the range of 0.127-0.25 mm (0.005-0.010 inches).

BRIEF DESCRIPTION OF THE FIGURES Certain embodiments of the state of the art are described, and of the invention, by way of illustration, and without further limitation of the corresponding invention, that established in the claims, references have been made to the accompanying drawings, where: Figures 1-4 show the injection molded covers of the state of the art; Figure 6 is a perspective view of a molded lid according to the present invention; Figure 7 is a diametrical section, in lateral elevation, of a simple cavity injection mold, in accordance with the present invention; Figure 8 is a view similar to that of Figure 7, with the plastic injector, and portions of the male mold in a retracted position; Figure 9 is a view similar to that of Figures 7 and 8, with the injector and male mold remote from the molded lid and the body of the mold; Figure 10 is a view similar to that of Figure 9, showing the ejector extended to its operative position and the treated molded cover expelled from the mold; Figure 1 1 is a view similar to Figure 8, showing the actuator mechanism for retraction of the male mold; Y Figure 12 is a diagrammatic plan view taken on the cut line 12-12 of Figure 1 1.

DETAILED DESCRIPTION OF THE INVENTION Referring to Figure 1, this lid 10 of the prior art, seen from the base, has a skirt portion 11 and crown 12. In the diametrical section of Figure 2, the SKIRT portion 11 has two turns of the start of a simple rope.

The perspective view of Figure 3 shows the skirt portion 11 without external decoration, and with a molding control line 14.

Figure 4 shows a regular lid having ribs 15 on the outside of the skirt; and Figure 5 shows a lid having decorations 16 on the outside of the skirt, being located substantially on the extraction axis of the mold under excision, from which the control line 14 originates.

Figure 6 is a perspective view of a lid molded according to the present invention, having absence of control lines, and decorations 17 distributed all around the skirt, in unrestricted relationship.

Referring to Figure 7, an injection mold 20 has a lower outer mold casing 22 with a cylindrical mold sleeve, without splits, in one piece 24, and an upper male mold assembly 25, having a segmented male mold 26. An injection head 28 is centrally located in the male mold 26.

The discharge opening 30 of the injection head 28 communicates with the mold cavity 32, located between the mold cover 24 and the male mold 26.

The male mold 26 is illustrated as having a plurality of three mold segments recessed, of which the segments 34, 38 and 39 can be seen.

The outer peripheral molding surface of the male mold 26 has strings of rope 40 and channels 42, for radially molding a thread on the inside face of the skirt of the lid to be molded.

The mold housing 22 has a releasable movable cylindrical portion 44, the axial end surface 46 of which the outer end face of the crown of the cover to be molded is formed.

Turning to Figure 8, this is shown after completing the injection to form the lid 48, having a single string start 50 on the inner side of the skirt.

The injection head 28 is in an axial separation position, together with a grooved mold part 38, such that the grooved mold part 34 and 39 are retracted radially inwardly. So the notches of shoulders 40 and channels 42 are withdrawn radially inward to undo the corresponding component parts of the newly molded cover 48.

In this condition the total of the male mold assembly 25, together with the injection head 28 can be axially separated from the mold housing 22, as shown in Figure 9. Also, in Figure 9, the molded cover 48 it is shown having cooled and being contracted radially inward, away from the notches or protuberances of the mold 24, such that the lid 48 is in a condition to be removed from the mold 24.

Turning to FIG. 10, the ejectable portion 44 of the mold housing 22 was directed upwards to discharge the lid 48 of the apparatus.

It can be seen that the lid 48 has a continuous arrangement of decorations 52 around the periphery of its skirt, which can be made on the surface of the skirt or be recessed therein.

A side air blast can displace the cover 48 on one side towards a collector, (not shown).

The radial extent of the decorations 52 is primarily a function of the diameter of the lid 48 and the shrinkage / expansion coefficient of the plastic with which the lid is molded. It will be noted that no control line necessarily exists, the cylindrical annular die mold 24 being in one piece. Alternative means of displacing the caps includes a moving air head arrangement for driving the lid 48 up and out of the under 22 assembly, or outward of the retractable suction extraction cups. -io Turning to Figures 11 and 12, the upper part of the mold head 56 is shown partially retracted, Including, first, the ejector of the injection head 28 and the mold segment 38 together. This action is completed by means of a pair of sequential cams (not shown), having a loss-of-motion connection with the upper half of the mold 56. A cam 54 (shown dotted) connected in sliding relation to the segment 39 of the mold male 26 is moved upwardly with the upper mold half unattached 56. This causes the cam face 58 to slide upwardly along the mold segment 39. The mold segment 39 is then 0 slid radially inward, towards its position retracted inwards to clean the molded lid 48.

The opposite mold segment 34 is similarly retracted inwardly by a cam (not shown).

COMMERCIAL UTILIZATION A lid having increased decorative capacity for the skirt portion, offers considerable incentives for sales promotion, along with a functional ability to print letters or labeling, such as secure labeling.

Claims

R E I V I N D I C A C I O N S

1. The method of injection molding a hollow body with a dependent skirt having shallow variations of the outer surface of the skirt portion, in a mold having a one-piece outer mold against which the skirt and its variations are molded, and a collapsible inner male mold that must be retracted from the body, including the steps of: assembling the inner and outer mold to form an enclosed cavity for said body; injecting plastic fluidly into the cavity to form the body; chill the plastic and contract the internal mold to increase the cooling of the molded body, thereby achieving the thermal contraction of the body to remove said skirt portion radially out of contact with said outer mold, and remove the molded body from the mold.

2. The method strongly stated in claim 1, wherein said internal male mold is contracted at sequential levels, to produce a radial separation effect between the molded inner portions of said body and the corresponding mold portions on which said inner portions were formed.

3. The method as claimed in claim 1, wherein said molded body is ejected from said external mold.

4. The method as claimed in claim 1, wherein said step of injecting the plastic into said mold cavity is performed through an injector extending through said male mold, and wherein said injector is removed from contact with said mold. mold cavity.

5. Molding apparatus for molding a hollow body comprising an outer mold having a one-piece mold skirt portion with a substantially cylindrical annular skirt wall portion; an inner male mold in tight relation with the outer mold to provide a mold cavity having a crown cavity portion and a skirt cavity portion; plastic injection means connecting with the mold cavity for the injection of fluid plastic therethrough; the internal male mold being segmented, to allow selective separations of its component parts for in this way, using the skirt molding surfaces of the internal male mold can be radially separated into the interior of the molded body; cooling means for cooling the molded body, to induce radial contraction towards the interior of said object, to cleanly separate said skirt wall portion from said mold skirt wall; Y means of removal of the object to remove the object from the mold.

6. The apparatus set forth in claim 5, including shallow molding details on the inside face of said mold skirt portion, the radial depth being less than the extension of the radial contraction into said object, thus, with its use, in the cooling of said object a free axial displacement can be given from said mold skirt portion.

7. The apparatus claimed in clause 6, wherein said plastic injection means being retractable from said mold through said inner mold.

8. Apparatus as claimed in claim 7, wherein said object removal means includes a crown portion of said outer mold.

9. Molding apparatus as set forth in claim 5, wherein said hollow body mold has a crown portion with a diameter of about 5 cm (2 inches) or more, and said portion of skirt mold cavity connected in dependent relationship.

10. A hollow body having a crown portion and a dependent skirt portion, said skirt portion having an external surface free of defects and without witness lines. eleven .

The body as claimed in clause 10, wherein said skirt portion having shallow radially formed decorations extended around the skirt.

12. The body as claimed in 11, wherein said skirt portion has a diameter of about 5 cm (2 inches) and more. SUMMARY A molded cap (48) for sealing a container, and having a profiled inner skirt portion that is injection molded into an annular seamless mold cavity (32), wherein the segmentation of the inner male mold portion (26) presents the internal shape of a thread of thyme for the inside of the skirt of the lid, allows its interior to unmold the lid after completing the injection cycle. Due to the seamless mold cavity (32) the lid has no external lines witnessing the mold along its skirt. The molded lid contracts radially with its cooling inside the mold, allowing molded parts and decorative characters (52) that can be on or in the skirt channel to radially withdraw its interior from the surface of the mold, in this way the lid can be cleanly expelled from the mold without damaging the fine or scratched details in the notches inside the face of the mold skirt.