CN114423580A

CN114423580A - Moulding method and apparatus

Info

Publication number: CN114423580A
Application number: CN202080065258.3A
Authority: CN
Inventors: 大卫·潘纳利; 史戴芬诺·伯加米; 里卡多·潘卡斯泰利
Original assignee: Sacmi Imola SC
Current assignee: Sacmi Imola SC
Priority date: 2019-12-05
Filing date: 2020-11-27
Publication date: 2022-04-29
Also published as: EP4028234A1; IT201900023139A1; WO2021111268A1; TW202128389A

Abstract

The invention describes a compression moulding method and apparatus, wherein a dose of plastic is deposited on a bottom portion of a first lower half-mould, wherein the dose is laterally encumbered by lateral encumbering members comprising at least three elongated elements protruding from the bottom and arranged along a circumference, then the dose is compression moulded between the first half-mould and a second upper half-mould, wherein the lateral encumbering members are moved by a retractable slide into the bottom of the first half-mould in order to allow compression of the dose.

Description

Moulding method and apparatus

Background

The present invention relates to a compression moulding method and apparatus, particularly for moulding doses of plastics.

In particular, but not exclusively, the invention can be used for moulding flat articles (for example discoid) made of plastic and usable, for example, as internal gaskets for caps for closed containers, such as metal caps, in particular articles having a relatively small thickness and weight.

Patent publication US 2004/130068 a1 discloses a compression mould in which a dose of plastic is first deposited on a support at a distance from the bottom of the female half-mould, which support is formed by three pins defining the three base points of the dose, and then, by virtue of the fact that the pins slide and can sink through the inside of the bottom, the dose of plastic is released on the bottom of the female half-mould immediately before or at the beginning of the compression.

Each of patent publications EP 2889116 a1, US 2010/084788 a1 and US 2011/018166 a1 discloses the preamble of claim 1.

A problem with the prior art relating to compression moulding of at least one dose of plastic is that it is difficult to ensure accurate and correct positioning of the dose in the mould before the compression dose, while also obtaining a relatively high productivity.

Disclosure of Invention

It is an object of the present invention to provide a method and/or apparatus that solves the aforementioned problems of the prior art.

The aim is to provide an alternative solution to the problem of depositing a dose of plastic in a compression mould.

The aim is to allow a dose of plastic to be deposited in the compression mould quickly and with precise positioning.

The advantage is that a dose of plastic is deposited in the desired location in a reliable and conventional manner.

The advantage is to make an easy and simple constructed apparatus for compression moulding plastics.

An advantage is that it allows a simple and safe transfer of the molded product from the mold, wherein the compression is performed towards one or more areas where the product can be further processed.

The advantage is to ensure easy handling of the molded article, which can be held and moved by one of the half molds forming the mold itself after opening the compression mold.

The advantage is that it is ensured that the molded product can be transferred away from the compression mold even in the case of particularly light products and/or in the case of relatively small thicknesses.

Such objects and advantages, and other objects and advantages, are obtained by a method and/or apparatus according to one or more of the claims reported below.

In one example, a molding method includes the steps of: depositing at least one dose of plastic on a bottom portion of the first half mould, wherein the dose deposited on the bottom portion is laterally enclosed by a lateral enclosing member protruding from the bottom, and moulding the dose between the first half mould and the second half mould, wherein the lateral enclosing member is moved into the bottom of the first half mould, for example by means of a retractable sliding movement, so as to allow compression of the dose.

When the lateral containment member is in a protruding position projecting itself from the bottom of the first half-mould, it can be configured so as to operate as a stop member which, when the dose is deposited on the bottom of the first half-mould, prevents the movement of the dose on the bottom caused by the inertial forces applied to the dose. In particular, such a movement may have at least one movement component in a direction parallel to the bottom of the first mold half. In particular, such inertial forces may comprise centrifugal forces caused by the rotational movement performed by the dose as it is deposited on the bottom of the first half mould.

Drawings

The invention will be better understood and implemented with reference to the accompanying drawings, which show some non-limiting specific examples, in which:

FIGS. 1A-1E are five sections showing, in sequence, five steps of a compression molding method according to the present invention;

FIG. 2 shows an enlarged detail of FIG. 1A, in which a portion of the lower mold half of the compression mold is presented;

FIG. 3 shows an enlarged detail of FIG. 1A, in which a portion of the upper mold half of the compression mold is presented;

FIG. 4 shows an enlarged detail of FIG. 1C including a dose of compression-formed regions;

FIG. 5 shows an enlarged detail of FIG. 1C including a dose of compression-formed regions;

FIG. 6 shows an enlarged detail of FIG. 1D, in which a portion of the lower mold half of the compression mold is presented;

FIG. 7 shows an enlarged detail of FIG. 1D, in which a portion of the upper mold half of the compression mold is presented;

FIG. 8 shows an enlarged detail of FIG. 1E, in which a portion of the upper mold half of the compression mold is presented;

FIG. 9 shows a molded product obtained by the compression molding method of FIGS. 1A to 1E;

FIG. 10 shows some examples of molded products that can be obtained by the compression molding method according to the present invention;

fig. 11 is a top plan schematic view of a molding apparatus having an insert carousel that inserts doses into a molding carousel that includes the molding apparatus of fig. 1A-1E;

FIG. 12 is a vertical elevational side view, partially in section, of a conveyor transferring molded products from the molding carousel of FIG. 11 to an area where the molded products may be further processed;

fig. 13 is a top plan view of the conveyor of fig. 12.

Detailed Description

With reference to the accompanying drawings, a compression-moulding apparatus particularly suitable for moulding doses of plastics is indicated as a whole by 1. The molding apparatus 1 can be used in particular for molding flat articles, such as disc-shaped articles (of relatively small thickness and/or particularly light), made of plastic and as can be used as internal gaskets for caps (e.g. metal caps) for closed containers, as in the specific example.

In detail, the molding apparatus 1 can comprise at least one compression mold having at least one first half-mold 2 and at least one second half-mold 3 cooperating therebetween to define a shaped cavity for compression molding at least one dose D of plastic. In detail, the first and

second mold halves

2 and 3 may comprise a lower mold half and an upper mold half, respectively. In detail, the first half-mould 2 and the second half-mould 3 may comprise at least one die and one punch, respectively, cooperating therebetween.

In detail, the molding apparatus 1 may comprise deposition means for depositing at least one dose of plastic in the first half-mold 2 so that the dose is later compressed in a forming cavity defined between the first half-mold 2 and the second half-mold 3 in a closed mold configuration (see fig. 5). In particular, the means for depositing may comprise means for extruding plastic, such as an extrusion nozzle, provided with separate means configured to separate a dose of plastic from an extruder flow of plastic (e.g. movable elements that periodically open and close the extrusion nozzle). The means for depositing may comprise, for example, an extrusion means of known type and/or a separate means of known type.

In detail (see fig. 10), the means for depositing may comprise an insertion carousel a rotatable about a vertical rotation axis and comprising a plurality of pick-up devices (arranged angularly spaced apart from each other on the insertion carousel a, and wherein the circumferential trajectory is schematically indicated in the figure by a), each of which picks up a dose of material from the extrusion means to leave it later on to the compression-moulding means. In detail, the compression-moulding means may comprise a moulding carousel B rotatable about a vertical rotation axis and comprising a plurality of moulding apparatuses 1 (arranged angularly spaced apart from each other on the moulding carousel, and with a circumferential trajectory schematically indicated in the figure by B), each of which comprises a first half-mould 2 and a second half-mould 3. The pick-up device inserted in carousel a is configured to release and insert a dose of plastic into the molding apparatus 1 of molding carousel B.

In detail, each molding apparatus 1 can comprise lateral containment members 4, said lateral containment members 4 being configured to take at least one protruding position (see fig. 2, 4 and 6), in which they protrude beyond the bottom 5 of the first half-mold 2 so as to delimit a bottom portion, and at least one recessed position (see fig. 5), in which they enter the bottom 5 so as to allow compression of the dose D on the bottom 5, which bottom delimits underneath a forming cavity. In detail, the lateral containment members 4 can be configured to take at least one protruding position in which they protrude outside the bottom 5 of the first half-mould 2 and are internally located at a distance from the peripheral edge of the bottom 5 itself, wherein this distance is considered in a direction transverse to the direction of protrusion of the lateral containment members 4. In detail, in the protruding position, the lateral containment members 4 may be distanced from the centre of the bottom. In detail, in the protruding position, the lateral containment members 4 can be distanced from the periphery of the bottom. In detail, in the protruding position, lateral containment members 4 may be exposed to a height both from the central bottom portion and from the peripheral bottom portion. In the protruding position of the lateral containment members from the bottom 5, the lateral containment members 4 are arranged above the bottom 5 itself (inside this bottom).

In particular, the lateral containment members 4 may comprise at least one, or two, or more than two elongated elements extending along a longitudinal direction (parallel to the mold axis and/or the direction of opening and closing the mold halves, as in this example). In detail, the elongated elements can be spaced apart from each other so as to delimit a bottom portion on which the dose D is deposited. In particular, the elongate elements may be parallel therebetween. In detail (see fig. 2), the maximum size of the dose D deposited by means of the means for depositing may be lower than the minimum distance between the elongated elements, considered in a direction transverse to the longitudinal direction of the elongated elements, so that the dose deposited on the bottom portion is arranged between the elongated elements. In detail, in other examples (see fig. 11), the maximum dimension of the dose D deposited by means of the means for depositing, considered in a direction transverse to the longitudinal direction of the elongated elements, may be higher than the minimum distance between the two elongated elements, so that the dose deposited on the bottom portion and possibly pushed to move on the bottom due to inertial forces is prevented by the two elongated elements.

The elongated elements may be arranged on the bottom 5 such that, when said elongated elements are in the protruding position, at least one or at least two of the elongated elements may act as a member for blocking the movement of the dose D, which, once deposited on the bottom 5, may be subjected to an inertial force tending to move the dose according to a direction of movement at least partially parallel to the bottom 5.

In detail, the lateral containment means 4 may comprise at least three elongated elements (parallel to each other) arranged circumferentially (as in the example of fig. 1A to 1E), whereby the dose D deposited on the bottom portion may be surrounded by the collection of elongated elements. In detail, lateral containment members 4 may comprise elongated elements arranged angularly equidistant from each other.

In particular, in other examples, the lateral encirclement member 4 may comprise only two elongated elements, or four or more elongated elements, for example arranged along a circumference having a diameter higher than that of the dose D, so that the dose D may be deposited on the bottom of the shaped cavity and be laterally encirclement therein by the elongated elements.

In detail (see fig. 11), the lateral containment means 4 can comprise at least one or at least two elongated elements (for example parallel therebetween) arranged in an off-centre or asymmetrical manner with respect to the axial centre of the compression mould, so as to form lateral abutment or stop means against the movement of the dose D inside the forming cavity.

In particular, such movement may be generated by a combination of forces generated on the dose (e.g., due to the dynamics and kinematics of the various devices interacting with the dose).

Among these forces, mention may be made, without limitation, of the centrifugal force generated by the rotating stacks used to transfer or insert the dose, and/or the force by which the dose is transferred by the rotating stacks used to transfer or insert to the forming cavity in the molding rotating stacks, and/or the adhesive force exerted by the dose on all the surfaces with which it is in contact, and/or the centrifugal force generated by the molding rotating stacks, and/or the elastic force accumulated by the dose, etc.

A combination of one or more of these forces and/or other possible forces will produce at least one predominant direction of movement over the dose that will be impeded by the lateral contrast or lateral stop member, which may comprise (in particular) at least one or at least two elongate elements, as seen. The lateral contrast or stop means are configured so as to prevent the movement of the dose D, in particular on the bottom 5 (i.e. in a direction substantially parallel to the bottom 5), due to the combination of forces acting on the dose D.

With reference to the example of fig. 11, the lateral containment members 4 comprise two elongated elements arranged at an angular distance from each other (wherein the vertex of the angle may be the geometric centre of the shaped cavity) lower than 180 °, or lower than 90 °, or lower than 60 °.

In this case, the elongated element laterally blocks the dose D positioned on the bottom 5 by the insertion carousel a by means of the generated force F acting on the dose D, so that the elongated element is arranged on the bottom 5 of the forming cavity, off-centered, e.g. towards the direction of the generated force F, to block the movement of the dose D on the bottom 5, which movement may comprise at least a radial component and at least a tangential component, as in the specific example. In detail, two elongated elements can be arranged alongside one another on the bottom 5 of the forming cavity of the molding carousel B to form an obliquely arranged barrier which opposes the movement of the dose D having at least a radial component and at least a tangential component.

In these particular examples, the lateral containment members 4 comprise elongated elements in the form of pins or rods. In particular, in other examples, not shown, the lateral containment members may comprise one, or two, or three or more than three elongated elements in a shape different from that of the pins (e.g., in the shape of a flat plate, or in the shape of a circular segment, or pairs of walls joined at an angle, etc.).

As in the particular example illustrated herein, the lateral containment members 4 can be set for a retractable movement inside the bottom 5 of the first half-mould 2, in particular by means of an axial sliding inside sliding holes arranged on the bottom 5 of the first half-mould 2.

In detail, the lateral containment members 4 can be supported by support elements 6 axially sliding and arranged below the bottom 5 of the first half-mould 2 which delimits the compression-forming cavity at the bottom.

In detail, the lateral containment members 4 can be fixed to an annular portion 7 of the first half-mould 2, which surrounds the bottom 5 of the first half-mould 2 and can slide axially in a direction parallel to the opening and closing direction of the mould formed by the first half-mould 2 and the second half-mould 3. As in this example, the annular portion 7 can be fixed to the support element 6 of the lateral containment member 4. During the step of closing the mould (see fig. 4 and 5), the sliding annular portion 7 of the first half-mould 2 comes into contact and interacts with the annular portion 8 of the second half-mould 3, whereby the sliding annular portion 7 of the first half-mould 2 can slide downwards with respect to the bottom 5 of the first half-mould 2 (see fig. 4 and 5), so that the lateral containment member 4 can perform a retractable movement in which it descends below the bottom 5 of the first mould 2, penetrating the bottom 5 itself and exiting the forming cavity for the free compressed dose D.

In detail, the first half-mould 2 may comprise elastic means 9 (for example arranged between the sliding annular portion 7 and the supporting portion 10 of the first half-mould 2) configured to exert a force against the retractable movement, i.e. a force tending to move the lateral containment member 4 towards the convex position (in this case, upwards).

The means for depositing the dose D of plastic are configured to deposit the dose D on the bottom portion (see fig. 2 or 11), so that the dose D deposited on the bottom portion is laterally encumbered by the lateral encumbering means 4 and is thus held in the desired position.

In detail, the lateral encirclement member 4 can be configured to assume a convex position when the deposition member deposits the dose D on the bottom portion such that the dose D deposited on the bottom portion is laterally encirclement by the lateral encirclement member 4, and a concave position when compressing the dose D.

In detail, the lateral encirclement means 4 can comprise two elongated elements arranged alongside one another at a distance lower than the transverse dimension of the dose D, so as to form a barrier against a force F (which, as mentioned above, can be generated by a greater force acting on the dose D) which is applied to the dose D and tends to move it on the bottom 5. In the specific example (fig. 11) in which the carousel a is inserted to transfer the dose D to the molding carousel B, the two elongated elements are arranged off-centre both with respect to the circumferential trajectory of the carousels a and B and with respect to the radial direction of the molding carousel B.

In detail, the forming cavity may be set such that the molded product G (see fig. 7 to 9) comprises at least one undercut surface 11, wherein "undercut" is intended with reference to the mold opening and/or closing direction. In detail, the undercut surface 11 can engage at least one counter-surface of the second half-mould 3. In detail, the molded product G may comprise at least one lateral projection and/or at least one lateral recess of the undercut surface 11, and the at least one lateral projection and/or at least one lateral recess is formed by at least one corresponding recess and/or at least one corresponding projection of the second half-mold 3.

In detail, the undercut surface 11 may be configured such that the molded product G remains engaged with the second half mold 3 when the first half mold 2 and the second half mold 3 are moved away from each other in the mold opening direction (see fig. 7). In detail, the undercut surface 11 may be disposed on the peripheral edge of the molded product G.

In detail, the forming cavity may be set such that the molded product G comprises a second surface opposite and substantially symmetrical to the undercut surface 11, wherein "symmetrical" is intended with reference to a plane orthogonal to the mold opening and/or closing direction. In detail, the undercut surface 11 and the aforementioned second surface opposite to the undercut surface 11 may comprise two tapered surfaces (e.g. truncated cones) inclined in opposite directions.

In the particular example described herein, the lateral containment members 4 adopt the recessed position by means of axial sliding, in particular through holes made on the bottom 5 of the first half-mould. In other non-illustrated examples, it is possible to envisage lateral containment members capable of assuming a recessed position by means of other types of movement (such as rotation or a combined movement of translation and rotation) and/or capable of assuming a retractable recessed position, for example lateral containment members capable of being retracted into the housing on the bottom of the forming cavity.

The molding apparatus 1 can implement a compression molding method by its operation, which in detail can include the steps of: the lateral containment members 4 are positioned in a protruding position (fig. 6), in which the lateral containment members 4 protrude from the bottom 5 of the first half-mould 2 so as to delimit a portion of the bottom of the first half-mould 2.

In detail, the compression molding method may include the steps of: when the lateral containment member 4 is in the projecting position (fig. 2 or 11), at least one dose D of plastic is deposited on the aforesaid bottom portion, so that the dose D deposited on the bottom portion is laterally contained and retained on the bottom portion by the lateral containment member 4.

In detail, the dose D deposited on the aforesaid bottom portion can be arranged inside the delimited space (arranged between or surrounded by the elongated elements) by means of the lateral containment member 4 and/or the dose D can be laterally stopped by means of the lateral containment member 4 acting as a stop member.

In detail, the compression moulding process may comprise, after the step of depositing the dose D on the bottom 5, the following steps: the lateral containment member 4 is positioned in a recessed position, wherein the lateral containment member 4 enters the bottom 5 of the first half-mould, so as to allow compression of the dose. Fig. 4 shows the annular portion 7 of the first half-mould 2 in contact and interacting with the annular portion 8 of the second half-mould 3, which determines the retractable movement of the lateral containment members 4 from the convex position (fig. 4) to the concave position (fig. 5).

In detail, the compression molding method may include the steps of: a dose D (fig. 5) is molded in the forming cavity defined between the first half-mold 2 and the second half-mold 3, to obtain a molded product G with the lateral containment members 4 in the recessed position.

When the first half-mould 2 and the second half-mould 3 are in the closed position (fig. 5), with the dose D compressed in the forming cavity to form the moulded product G, the lateral containment means 4 are in a recessed position, whereby, in principle, the upper end of the lateral containment means 4 is very close to the bottom surface 5 of the first half-mould 2, i.e. against the lower surface of the forming cavity, so as to provide continuity on the bottom 5 and not to adversely interfere with the forming.

In detail, the compression molding method may include the following steps after the step of molding: the mold is opened (fig. 6 in relation to the first mold half 2 and fig. 7 in relation to the second mold half 3), i.e. the first mold half 2 and the second mold half 3 are moved away from each other in the mold opening direction. In detail, it is possible to make the molded product G remain engaged to the second half-mould 3 during the step of moving away, by virtue of the fact that the molded product G comprises undercut surfaces 11 which engage with the facing surfaces of the second half-mould 3 (fig. 7). As described above, the undercut surface 11 may be provided on the peripheral edge of the molded product G, and even other positions are possible.

In detail, the compression molding method may comprise the following steps after the step of opening the mold or moving the

half molds

2 and 3 away from each other: the moulded product G is removed from the second mould half 3 by means of a separating force capable of disengaging the undercut surfaces 11.

In detail, such a separating force can be generated by a relative movement between two portions of the second half-mould 3, in particular of the annular portion 8 and the central portion 12 (see the passage from fig. 7 to 8), wherein in detail the central portion 12 can comprise a punch portion having a surface transverse to the mould axis and compressing the material during the moulding step. In practice, in a particular example, the aforesaid relative movement is carried out by a descending movement of the central portion 12.

In detail, such a separation force can be generated in addition or alternatively by means of the aforesaid relative movement between the annular portion 8 and the central portion 12 of the second half-mould 3, a fluid jet (fluidjet), for example a compressed air jet, of the self-aligned moulded product G, passing through a circuit arranged in the second half-mould 3 and ending in an outlet member arranged on the wall of the second half-mould 3, which delimits the forming cavity when the mould is closed. In particular, such outlet means may further have the function of a vent forming a cavity.

In particular, such outlet and/or vent members may include at least one void (annular) formed on an exterior surface of the central portion 12 or punch portion (e.g., a void between the central portion 12 and the annular portion 8). In particular, such outlet and/or vent gaps may have dimensions equal to or lower than 0.02 mm.

As mentioned above, the molded product G may comprise a second surface opposite and similar to the undercut surface 11, wherein in particular the undercut surface 11 and the second opposite surface may comprise two tapered surfaces (e.g. truncated cones) inclined in opposite directions (see e.g. fig. 9) in order to provide some overall symmetry feature of the molded product G. The two tapered surfaces may be convex, such as in the example of fig. 9.

Six different examples of molded products G that can be made are shown in fig. 10, where from top to bottom of fig. 10, the peripheral edge of the molded product G includes: (i) a series of alternating ridges and depressions such as serrations or knurls, (ii) an annular recess with symmetrical and curved edges, (iii) two convex frustoconical surfaces on a non-planar but curved disc-shaped molded product, (iv) two concave frustoconical surfaces, (v) a central annular protrusion, (vi) a central annular depression.

In detail, the molding apparatus 1 may comprise a conveying device for conveying the molded product G from the compression mold to one or more operative areas below. In detail (see fig. 12 and 13), the conveying device can comprise a first transferring carousel 13 which rotates about a vertical rotation axis and picks up the molded products G released by the molding apparatus 1. In detail, the first transferring carousel 13 may be provided with first holding and suction means which hold the molded products G by suction pressure. In a specific example, the molded product G is released by the molding apparatus 1 in a direction from above towards below, and the first suction holding means creates a suction pressure on the underside of the molded product G. In detail, the first suction-holding means can comprise at least one body 14 having a plurality of orifices or holes (angularly spaced apart arranged on the first transferring carousel 13) connected to vacuum-generating means by means of a fluid circuit at least partially inside the first transferring carousel 13 to generate a suction pressure on the plane on which the moulded products G (released by the moulding apparatus 1) are placed. In detail, the aperture or hole on the body 14 may be arranged in communication with the vacuum generating means, each time limited to the angular section of interest.

In detail, the conveying device may comprise a second transferring carousel 15, which rotates about a vertical rotation axis and picks up the molded products G released by the first transferring carousel 13. In detail, the second transferring carousel 15 may be provided with second holding and suction means which hold the molded products G by suction pressure. In a particular example, the molded product G is released by the first transferring carousel 13 in a bottom-up direction, and the second suction holding means generate a suction pressure on the upper side of the molded product G. In detail, the second suction holding means may be configured to hold the molded product G from above (i.e., on the upper side thereof). In detail, the second suction-holding means comprise a body 16 having a plurality of orifices or holes (angularly spaced apart arranged on the second transferring carousel 15) connected to the vacuum-generating means by means of a fluid circuit at least partially inside the transferring carousel 15 to generate a suction pressure on the upper side of the molded products G. In particular, an aperture or hole on the body 16 may be placed in communication with the vacuum generating means, each time limited to the angular section of interest.

In detail, the conveying means can comprise a suction conveyor 17 (for example linear) picking up the molded products G from the second transferring carousel 15. In the specific example, the molded product G is released by the second transferring carousel 15 in a direction from above downwards, and the suction conveyor 17 generates a suction pressure on the lower side of the molded product G. The conveyor 17 may comprise, for example, a suction conveyor belt that generates suction pressure on the underside of the molded product G.

Claims

1. A compression molding process comprising the steps of:

providing a compression mould comprising at least one first half-mould (2) and at least one second half-mould (3);

positioning the lateral containment member (4) in a protruding position in which it protrudes from a bottom (5) of the first half-mould (2);

depositing at least one dose (D) of plastic on the bottom (5), wherein the lateral containment member (4) is in a protruding position, so that the dose (D) deposited on the bottom (5) is at least partially laterally contained by the lateral containment member (4);

moulding the dose (D) in a shaped cavity between the first half-mould (2) and the second half-mould (3) to obtain a moulded product (G);

characterized in that it comprises, after the deposition step, the following steps: positioning the lateral containment member (4) in a recessed position in which it enters the bottom (5) of the first half-mould (2) so as to allow compression of the dose (D), the step of moulding the dose (D) being carried out with the lateral containment member (4) in the recessed position.

2. The method of claim 1, wherein the lateral containment member (4) comprises a plurality of elongated elements spaced apart from each other extending in a longitudinal direction.

3. The method of claim 1 or 2, wherein the lateral containment member (4) prevents, in the protruding position, a movement of the dose (D), on which a force acts tending to move the dose (D) on the bottom (5).

4. The method of claim 3, wherein the lateral containment member (4) comprises at least two elongated elements cooperating in the protruding position to prevent the movement of the dose (D) in a direction at least partially parallel to the bottom (5).

5. A method according to claim 4, wherein said two elongated elements are arranged alongside each other to form a barrier against said force tending to move said dose (D) on said bottom (5).

6. The method of any one of the preceding claims, wherein the lateral containment member (4) comprises at least three elongated elements arranged in a circumferential manner, such that the dose (D) deposited on the bottom (5) is surrounded by said elongated elements.

7. The method according to any one of the preceding claims, wherein the step of positioning the lateral containment member (4) in a recessed position comprises a movement of the lateral containment member (4) sinking below the bottom (5) penetrating the bottom itself.

8. The method of any one of the preceding claims, comprising the step of moving the first and second half-moulds (2 and 3) away from each other in a mould opening direction after the moulding step, wherein during the moving away step the moulded product (G) remains engaged to the second half-mould (3) as the moulded product (G) comprises at least one undercut surface (11) engaging with at least one counter-surface of the second half-mould (3), wherein "undercut" is intended with reference to the mould opening direction.

9. The method of claim 8, wherein the undercut surface (11) is arranged on a peripheral edge of the molded product (G).

10. The method according to claim 8 or 9, comprising, after the step of moving away, a step of moving the molded product (G) out of the second half-mold (3) by means of a separating force capable of disengaging the undercut surface (11), wherein the separating force is generated by a relative movement between an annular portion (8) and a central portion (12) of the second half-mold (3) and/or by a fluid jet directed at the molded product (3).

11. The method of any one of claims 8 to 10, wherein the molded product (G) comprises a second surface opposite and substantially symmetrical to the undercut surface (11), wherein "symmetrical" is intended with reference to a plane orthogonal to the mold opening direction.

12. The method of claim 11, wherein the undercut surface (11) and the second surface comprise two tapered surfaces, such as truncated cones, inclined in opposite directions.

13. The method of any one of the preceding claims, comprising, after the step of moulding the dose (D) to obtain a moulded product (G), the steps of:

transferring the molded product (G) from the compression mold to a first suction conveying member (13) which generates a suction pressure on an underside of the molded product (G);

transferring the molded product (G) from the first suction conveying means (13) to second suction conveying means (15) which generate a suction pressure on an upper side of the molded product (G); and

transferring the molded product (G) from the second suction conveying member (15) to a third suction conveying member (17) which generates a suction pressure on the lower side of the molded product (G).

14. Compression molding apparatus (1) comprising:

at least one first half-mould (2) and at least one second half-mould (3) cooperating with each other to define a forming cavity for compression moulding at least one dose (D) of plastic;

-lateral containment means (4) configured to take at least one protruding position, in which they protrude from a bottom (5) of the first half-mould (2), and at least one recessed position, in which they enter the bottom (5) to allow compression of the dose (D) on the bottom (5);

means for depositing at least one dose (D) of plastic on the bottom (5), so that the dose (D) is subsequently compressed in the forming cavity between the first half-mould (2) and the second half-mould (3);

the lateral containment member (4) is configured to assume the convex position when the means for depositing deposits the dose (D) on the bottom (5), so that the dose (D) deposited on the bottom (5) is laterally contained by the lateral containment member (4), and to assume the concave position when the dose (D) is compressed.

15. The apparatus of claim 14, wherein the lateral containment member (4) comprises a plurality of elongated elements spaced apart from each other extending in a longitudinal direction; in detail, the plurality of elongated elements comprises at least three elongated circumferentially arranged elements, so that the dose (D) deposited on the bottom (5) is surrounded by said elongated elements.

16. Apparatus according to claim 15, wherein a maximum dimension of the dose (D) deposited by the means for depositing, considered in a direction transverse to the longitudinal direction, is smaller than a minimum distance between said elongated elements, so that the dose (D) deposited on the bottom (5) is arranged between said elongated elements.

17. The apparatus of any one of claims 14 to 16, wherein the shaped cavity is configured such that the molded product (G) comprises at least one undercut surface (11) engaging with at least one opposing surface of the second half-mold (3), wherein "undercut" is intended with reference to a mold opening direction such that the molded product (G) remains engaged with the second half-mold (3) when the first half-mold (2) and the second half-mold (3) are moved away from each other in the mold opening direction; in detail, the undercut surface (11) is arranged on a peripheral edge of the molded product (G).

18. The apparatus according to any one of claims 14 to 17, wherein the lateral containment member (4) is configured so as to be capable of a retractable movement inside the bottom (5).

19. The apparatus of any one of claims 14 to 18, wherein the lateral containment member (4) is configured so as to assume a retracted position by means of an axial sliding through one or more holes made in the bottom (5).

20. The apparatus of any one of claims 14 to 19, in combination with a transfer device comprising:

first suction conveying means (13) which generate a suction pressure on an underside of the molded product (G) and are configured to receive the molded product (G) from the compression molds of the apparatus;

second suction conveying means (15) generating a suction pressure on an upper side of the molded product (G) and configured to receive the molded product (G) from the first suction conveying means (13); and

third suction conveying means (17) generating a suction pressure on the lower side of the molded product (G) and configured to receive the molded product (G) from the second suction conveying means (15).