Press molding apparatus and method

Abstract

A press molding device and method are described wherein the device comprises: a die element (2) for containing a dose of material suitable for press molding; a punch punch (5) which can be at least partially inserted into the die element (2) in order to press said dose of material and to produce a relevant product; wherein the punch (5) has an outer surface (10) for moulding the dose of material, and wherein the punch (5) comprises a first portion (6) that is slidable relative to at least a second portion (7) between a moulded state in which the second portion (7) radially presses the dose of material against the die element (2), and a retracted state in which the second portion (7) does not press the dose of material against the die element (2). The second portion (7) contracts radially away from the dose of material.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for compression moulding. More specifically, the present invention relates to the field of manufacturing by moulding concave objects, such as for example lids or containers of any type, such as glasses or bowls.

[0002] In more detail, these concave objects are made of a material capable of being compression moulded, generally a polymer-based material, in particular cellulose. Background Art

[0003] As is known, a moulding device for producing an object by pressing a given dose of a polymer-based material has a male mould element provided with a punch and a female mould element provided with a cavity.

[0004] A given dose of material is arranged between the cavity and the punch, and this material is pressed by inserting the punch into the interior of the above-mentioned cavity.

[0005] It should be noted that the outer surface of the punch and the inner surface of the cavity determine the shape of the product to be manufactured.

[0006] For example, it is possible to manufacture products provided with protrusions, such as, for example, to produce caps provided with threads, the threads being obtained in shaped cavities formed on the outer surface of the punch.

[0007] At the end of the pressing action, the punch and die elements are moved away from each other to allow extraction of the product thus obtained.

[0008] The extraction is actuated by an annular element which extends around the punch and which is pressed axially towards the end of the punch to allow the product to detach from the outer surface of the punch.

[0009] In this case, in the above-mentioned case of a product provided with a protrusion, such as, for example, a cap with an associated thread, the extraction step comprises a slight deformation of the product designed to release the protrusion from the shaped cavity formed on the punch.

[0010] However, this behavior leads to significant disadvantages, precisely due to the mechanical stresses to which the freshly formed product is subjected.

[0011] In fact, it should be noted that, if actuated with a certain force by the annular element, the deformation behavior may irreversibly destroy and deform a portion of the just-molded material, generally precisely the protrusion (the thread in the case of the cap).

[0012] In the case of moulding of certain materials, typically cellulose based materials, the above mentioned disadvantages are even more pronounced.

[0013] Indeed, in this case, the slight deformation designed to release the threads from the surface of the punch may tend to damage the cellulose material, which is notoriously more fragile than other polymer materials. Summary of the invention

[0014] It is therefore an object of the present invention to provide a device and an associated moulding method which do not have the above mentioned disadvantages.

[0015] More specifically, a first object of the present invention is to provide a press-molding apparatus and method capable of maintaining the state of a molded product during each production step of the molded product, particularly during a step for removing the molded product from a punch.

[0016] Still more specifically, an object of the invention is to provide a device and a related moulding method which do not require any (even minimal) deformation of the just moulded product.

[0017] Another object is to provide a device and a related compression moulding method suitable for any shape of product, which must be obtained from any polymer material, in particular cellulose-based material, and which can be applied.

[0018] According to a first aspect of the invention, there is a compression molding device comprising: a female mold element for receiving a dose of material suitable for compression molding; a male mold punch insertable at least partially into the female mold element for compressing the dose and manufacturing an associated product. The punch has an outer surface for molding the material of the dose and comprises a first portion slidable relative to at least a second portion between a molding state and a retracted state, in which the second portion radially compresses the dose against the female mold element and in which the second portion radially contracts away from the material of the dose.

[0019] Preferably, the first part has a cylindrical shape and has a plurality of seats arranged alternately with a plurality of outer surfaces. In this case, the punch comprises a plurality of second parts, each second part being accommodated in a corresponding seat of the first part.

[0020] Even more preferably, each second part comprises an outer surface adjacent to and between the two outer surfaces of the first part and having a cavity configured to define a thread of the product to be molded.In the molded state, the outer surfaces of the first and second parts define an outer molding surface.

[0021] According to a particular aspect of the invention, the plurality of seats of the first portion are arranged circumferentially along the cylindrical extension of the first portion, and the second portion is radially movable towards / away from the longitudinal extension axis of the first portion.

[0022] Preferably, each seat comprises a contact surface which is inclined and converges towards the end of the punch close to the bottom wall of the female die element. Each second portion also comprises a contact surface which is inclined and converges towards the end of the punch close to the bottom wall. In this way, the contact surface of each seat abuts against the contact surface of the corresponding second portion to slide thereon between the molding configuration and the retracted configuration.

[0023] According to another aspect of the present invention, there is provided a compression molding method comprising the steps of: preparing a female mold element for containing a dose of material suitable for compression molding; inserting a male mold punch at least partially into the female mold element for compressing the dose of material, the punch having an outer molding surface that defines the shape of a product obtained by compressing the dose in conjunction with an inner surface of the female mold element; separating the punch from the female mold element; and removing the molded product from the punch. After the step of inserting the punch and before the step of separating the punch, at least a second portion of the punch is retracted to define a retracted state of the punch in which the second portion moves away from the dose of material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention may be better understood and implemented with reference to the accompanying drawings, which show non-limiting example versions of the invention and in which:

[0025] Figures 1 to 3 is a side view and a longitudinal cross section of a compression molding apparatus according to the present invention in corresponding molding steps;

[0026] Figure 1 a to Figure 3 a shows the corresponding Figures 1 to 3 A magnified image of

[0027] 4a and 4b are perspective views of construction details of the molding device according to the present invention in corresponding operating steps. DETAILED DESCRIPTION

[0028] Referring to the drawings, reference numeral 1 generally designates a compression molding apparatus according to the present invention.

[0029] The device 1 comprises a female mould element 2 for containing a dose of material suitable for compression moulding (not shown in the drawings). In particular, the female mould element 2, schematically shown by way of non-limiting example in the drawings, has an internal compartment 3 defined by respective inner surfaces 3a for forming the product to be manufactured by moulding.

[0030] In the example shown, the compartment 3 and the corresponding surface 3a are configured so as to obtain a screw cap made of a polymer material, preferably a cellulose-based material.

[0031] In this case, it should also be noted that the compartment 3 has a bottom wall 4 on which an annular recess 4 a can be formed, designed to form a corresponding annular protrusion on the wall of the finished product (the lid).

[0032] The device 1 also comprises a male die punch 5 which can be at least partially inserted into the compartment 3 defined by the female die element 2 for compressing a dose of material and producing a corresponding product.

[0033] It should be noted that the figures do not show the step of inserting the punch 5 into the compartment 3 in order to better illustrate the structure of the punch 5. For this reason, the male punch 5 and the female die element 2 are always shown separated from each other by way of example in the figures.

[0034] In particular, the male punch 5 has an outer surface 10 for molding a dose of material, preferably having a cylindrical shape, which is designed to give shape to the finished product in conjunction with the surface 3a of the female die element 2. Advantageously, in the illustrated case where the device 1 is used to mold a threaded cap, the cylindrical outer surface 10 of the punch 5 defines the inner surface of the cap provided with the thread, while the surface 3a of the female die element 2 defines the appearance of the cap.

[0035] The punch 5 comprises a first portion 6 which can be in a molded state ( Figure 1 , Figure 1 a, Figure 4a) and retracted state ( Figure 2 , Figure 2 4b), in the molding state, the second part 7 radially presses a dose of material against the female die element 2, and in the retracted state, the second part 7 radially contracts away from a dose of material.

[0036] More specifically, as shown in more detail in FIGS. 4 a and 4 b , the first portion 6 has a substantially cylindrical shape, wherein a plurality of seats 8 are formed on respective outer extensions and are arranged alternately with a plurality of outer surfaces 9 .

[0037] It should be noted that a plurality of seats 8 arranged alternately with surfaces 9 are equidistantly spaced from each other and extend radially relative to the circular cross section of the cylindrical extension of the first portion 6. Furthermore, the seats 8 and the corresponding surfaces 9 extend along the longitudinal extension of the first portion 6.

[0038] Each seat 8 also has a contact surface 8 a which is inclined and converges towards the end 5 a of the punch 5 close to the above-mentioned bottom wall 4 of the die element 2 .

[0039] In other words, reference Figure 1 a to Figure 3In the cross-sectional view of a, it should be noted that the inclined contact surface 8a of each seat 8 is inclined relative to the longitudinal extension axis "X" of the punch 5 and defines a variation in the cross section of the first portion 6. In this way, the cross section of the first portion 6 decreases towards the end 5a of the punch 5 mentioned above.

[0040] Furthermore, in this case, it should be noted that the outer surfaces 9 of the first portion 6 protrude more than the inclined plane 8a of the seat 8. These outer surfaces 9 are located along the extension of the cylindrical outer surface 10 of the punch 5.

[0041] Advantageously, the punch 5 comprises a plurality of second portions 7 , each second portion being housed in a respective seat 8 of the first portion 6 .

[0042] As described in more detail below, the second portion 7 is radially movable towards / away from the longitudinally extending axis “X” of the first portion 6 .

[0043] In this case, it should be noted that each second portion 7 defines a section of the first portion 6 housed in a respective seat 8 , thus completing the cylindrical profile of the first portion 6 .

[0044] In more detail, each second portion 7 comprises an outer surface 11 adjacent to and between the two outer surfaces 9 of the first portion 6 .

[0045] To this end, in the molded state ( Figure 1 , Figure 1 a, FIG. 4 a ), the outer surfaces 9 , 11 of the first portion 6 and the second portion 7 define the above-mentioned outer molding surface 10 of the punch 5 .

[0046] Preferably, the outer surface 11 of each second portion 7 may have cavities 12 configured to define a thread or other finished shape of the product (cap) to be molded.

[0047] As in Figure 1 a to Figure 3 As better shown in the cross-sectional view of FIG. 1 a , each second portion 7 comprises an inclined contact surface 7 a opposite to the corresponding outer surface 11 and converging towards the end 5 a of the punch 5 .

[0048] In other words, the contact surface 7 a of each second portion 7 defines a variable cross section of the corresponding portion 7 , and this cross section increases towards the end 5 a of the punch 5 .

[0049] Advantageously, the contact surface 8a of each seat 8 abuts against the contact surface 7a of the corresponding second portion 7 for sliding thereon between the moulding configuration and the retracted configuration.

[0050] In other words, the respective contact surfaces 7 a , 8 a complement each other for radially moving the second part 7 following sliding of the first part 6 .

[0051] It should be noted that, in particular, the first portion 6 is movable along the longitudinal extension axis "X" towards or away from the female mould element 2 so as to define the moulding state and the retracted state mentioned above.

[0052] The movement of the first portion 6 away from the female mould element 2 causes the inclined surface 8 a of the seat 8 to slide on the inclined surface 7 a of each second portion 7 .

[0053] After sliding, Figure 2 a. Figure 3 a and 4b , the second portion 7 moves inside the seat 8 and radially towards the longitudinal axis "X".

[0054] In this case, better shown in FIG. 4 b , in the retracted state, the outer surface 11 of the second portion 7 is positioned within the retention space defined by the outer moulding surface 10 of the punch 5 .

[0055] It should be noted that the parts 7 are free to move radially towards / away from each other, but remain in place along the direction of movement of the first part 6 and along the axis "X". For this purpose, an annular sleeve 13 is provided, which is positioned above the second part 7 and is hollow inside to allow the first part 6 to slide inside it. Figures 1 to 3 The sleeve 13 , better shown in , is fixed and defines inside it a chamber 13 a for housing the top zone 6 a of the first portion 6 positioned above the seat 8 and the second portion 7 .

[0056] Furthermore, the sleeve 13 defines a stop for the second element 7 , preventing the second element from being raised and lowered as a result of the translational movement of the first element 6 .

[0057] Advantageously, in Figure 2 a and Figure 3 In the retracted state better shown in a, the second portion 7 has a corresponding contact surface 7a which abuts against an end region of a contact surface 8a of a corresponding seat 8 at a lower portion 6b of the first portion 6 opposite the top region.

[0058] The lower portion 6 b is positioned at the end 5 a of the punch 5 close to the bottom wall 4 of the die element 2 .

[0059] The radial movement of the second parts 7 towards each other, which occurs in the respective retracted state, is preferably actuated by an elastic actuator (not shown in the drawings) which exerts a pushing action of the second parts 7 towards the longitudinal extension axis “X” of the first part 6 .

[0060] Preferably, the elastic actuator comprises an elastic ring received in a groove 14 a formed on the protruding portion 14 of each second portion 7 .

[0061] The protruding portion 14 of the second part 7 defines an abutment wall abutting against the sleeve 13 and has a corresponding groove 14a arranged circumferentially around the punch 15. In this way, the elastic ring is received in the groove 14a so as to be coaxially positioned outside the first part 6.

[0062] The axial movement of the first portion 6 is preferably actuated by a lifting unit 15 , for example of electromechanical type, which acts on a top zone 6 a of the first portion 6 .

[0063] The lifting unit 15 comprises a tubular body 16 concentric with the longitudinal axis "X", provided with a slide 17 protruding from a respective end 16a close to the first portion 6. The slide 17 operates along the sleeve 13 on the top zone 6a so as to pull the first portion 6 in a linear movement towards / away from the female mould element 2.

[0064] Advantageously, the device 1 also comprises a third fixed portion 18 associated with the first portion 6 and having a pressing wall 19 positioned at the end 5 a of the punch 5 .

[0065] The pressing wall 19 has a substantially disc-shaped extension and is configured for pressing a dose of material onto the above-mentioned bottom wall 4 of the female die element 2 .

[0066] To this end, the pressing wall 19 defines, in conjunction with the outer surfaces 9 , 11 of the first portion 6 and the second portion 7 , the cylindrical outer surface 10 described above for molding a dose of material.

[0067] Preferably, the third portion 18 has a cylindrical body 20 coaxially inserted into the interior of the first portion 6 .

[0068] The cylindrical body 20 passing through the entire first portion 6 has a lower end 20a close to the female die element 2 on which the pressing wall 19 extends. On the opposite side of the lower end 20a, there is an upper end 20b rigidly engaged with the supporting body 21 of the entire punch 5.

[0069] The upper end 20 b extends in a chamber 13 a defined inside the sleeve 13 and closed by the support body 21 .

[0070] In this case, it should be noted that the first portion 6 slides in its axial displacement and is guided along the upper end 20 b of the cylindrical body 20 .

[0071] The device 1 also comprises an extraction unit 22 positioned around the punch 5 and movable axially along the longitudinal extension axis “X” of the first portion 6 .

[0072] The extraction unit allows the product to be removed from the punch 5 at the end of the pressing action, and comprises an annular element 23 extending around the moulding surface 10 and supported at the end of a support body 24 which is hollow inside and surrounds the tubular body 16 .

[0073] The supporting body 24 is moved by means of corresponding electromechanical actuators (not shown) for lifting and lowering the annular element towards / away from the female mould element 5 .

[0074] Advantageously, in the retracted state of the second portion 7, the annular element 23 moves ( Figure 3 and Figure 3 a) for removing the moulded product from the punch 5. For this purpose, the ring element 23 is provided with a circular push lip 25 configured to abut against the moulded product during the removal action.

[0075] The invention also relates to a compression molding method.

[0076] The method comprises the following steps: Preparing a female mould element 2 for receiving a dose of material, which is a material suitable for compression moulding, typically a cellulose based polymer.

[0077] Subsequently, the punch 5 and the female die element 2 are moved relative to each other in order to at least partially insert the punch 5 into the female die element 2 .

[0078] This behavior allows to compress a dose of material and manufacture a product according to the shape set by the outer molding surface 10 and by the inner surface 3 a of the female mold element 2 .

[0079] It should be noted that in this case, the punch 5 is in the corresponding molded state ( Figure 1 and Figure 2 a), in this molded state, the outer surfaces 9, 11 of the first part 6 and the second part 7 define the above-described mold surface 10. In this case, the contact surfaces 6a, 7a abut and match each other, and the first part is close to the pressing wall 19.

[0080] Subsequently, the punch 5 is separated from the die element 2 and the second portion 7 is contracted to define a retracted state of the punch 5. In this case, each second portion 7 is moved away from the previously molded product. In other words, the second portion 7 separates the corresponding outer surface 11 from the inner surface 3a of the die element 2.

[0081] The step of withdrawing the second portion 7 is simultaneously actuated by moving the first portion 6 axially away from the female mould element 2 .

[0082] In particular, due to the action of the lifting unit 15, the first part 6 moves along the end 20b of the cylindrical body 20 into the chamber 13 ( Figure 2 and Figure 2 a).

[0083] Thus, the contact surface 8a of the seat 8 is made to slide on the corresponding contact surface 7a of the second portion 7. This movement defines a retracted state in which the second portion 7 is contracted and positioned in the space defined by the cylindrical outer moulding surface 10 of the punch 5.

[0084] It should be noted that this movement of the second portion 7 makes it possible to release the cavity 12 formed on the second portion 7 from the protrusion (thread) formed on the product during the act of pressing a dose of material.

[0085] In other words, the movement of the second portion 7 allows the thread to be "released", thereby allowing the product obtained to be removed without deforming the thread.

[0086] Subsequently, the molded product is taken out from the punch 5 .

[0087] The extraction step is actuated by the annular element 23 which moves towards the end 5 a to remove the product from the punch 5 .

[0088] Subsequently, the first portion 6 returns to the initial state to define the outer cylindrical pressing surface 10, and a new molding action is performed.

[0089] The present invention thus overcomes the disadvantages of the prior art and brings important advantages.

[0090] Firstly, it should be noted that the retracted state of the punch 5 , in which the second portion moves radially inside the cylindrical moulding surface 10 , makes it possible to release any type of protrusion obtained on the side wall of the product, such as, for example, a thread.

[0091] Thus, the extraction action actuated simply by pushing the product out of the punch 5 allows the removal of the product just moulded.

[0092] Therefore, no area of ​​the product is subjected to any kind of stress and deformation, thus maintaining the perfect condition of the product.

[0093] To this end, the device 1 and the related method described above are particularly versatile since they allow the moulding of a wide variety of materials, even those that are most fragile and subject to deformation or damage, such as in particular cellulose-based polymers.

Claims

1. A compression molding device comprising: - a female mould element (2) for receiving a dose of material suitable for compression moulding; - a male punch (5) at least partially insertable into said female die element (2) for compressing said dose of material and producing the relevant product; - wherein the punch (5) has an outer surface (10) for molding the material of the dose, and wherein the punch (5) comprises a first portion (6) which is slidable relative to at least a second portion (7) between a molding state in which the second portion (7) radially presses the material of the dose against the die element (2) and a retracted state in which the second portion (7) radially contracts away from the material of the dose; The first part (6) has a cylindrical shape and has a plurality of seats (8) arranged alternately with a plurality of outer surfaces (9), wherein the punch (5) comprises a plurality of second parts (7), each second part being received in a corresponding seat (8) of the first part (6); And wherein the punch (5) further comprises a fixed third part (18) associated with the first part (6) and having a pressing wall (19) positioned at the end of the punch (5a) for pressing the dose of material against the bottom wall (4) of the die element (2).

2. The device according to the preceding claim, wherein Each second part (7) comprises an outer surface (11), the outer surface of the second part is adjacent to and between the two outer surfaces (9) of the first part (6), and the outer surface of the second part has a cavity (12), and the cavity is configured to define the thread of the product to be molded; in the molded state, the outer surfaces (9, 11) of the first part and the second part (6, 7) define the outer molding surface (10).

3. Device according to the preceding claim, wherein The plurality of seats (8) of the first portion (6) are arranged circumferentially along the cylindrical extension of the first portion (6); the second portion (7) is radially movable towards / away from the longitudinal extension axis (X) of the first portion.

4. The device according to any one of claims 2 to 3, wherein: Each seat (8) comprises a contact surface (8a), which is inclined and converges towards the end (5a) of the punch (5) close to the bottom wall (4) of the die element (2); and each second part (7) comprises a contact surface (7a), which is inclined and converges towards the end (5a) of the punch (5) close to the bottom wall (4); the contact surface (8a) of each seat (8) abuts the contact surface (7a) of the corresponding second part (7) to slide on the contact surface of the corresponding second part between the molding configuration and the retracted configuration.

5. Device according to the preceding claim, wherein The first portion (6) is movable along the longitudinal extension axis (X) to define the molded state and the retracted state; in the retracted state, the corresponding contact surface (7a) of each portion (7) abuts the end area of ​​the contact surface (8a) of the corresponding seat (8) close to the bottom wall (4).

6. The device according to any one of claims 2 to 5, wherein: The punch (5) further comprises an elastic push actuator associated with the second portion (7) for pushing the portion towards the longitudinal extension axis (X) of the first portion (6); in the retracted state, the outer surface (11) of the second portion (7) is positioned within a retention space defined by the outer molding surface (10) of the punch (5).

7. Device according to the preceding claim, wherein The elastic actuator comprises an elastic ring received in a groove (14a) formed in each second portion (7); The elastic ring is coaxially positioned outside the first portion (6).

8. Device according to the preceding claim, wherein The third part (18) has a cylindrical body (20) which is coaxial and at least partially inserted into the first part (6); the pressing wall (19) is associated with the end (20a) of the cylindrical body (20) close to the female mold element (2).

9. Device according to the preceding claim, wherein The pressing wall (19) defines, in conjunction with the outer surfaces (9, 11) of the first and second parts (6, 7), an outer surface (10) of a material for molding the dose.

10. Device according to the preceding claim, wherein In the retracted state, the second portion (7) is positioned within a perimeter defined by the peripheral edge of the pressing wall (19).

11. The device according to any one of claims 4 to 10, wherein: The device also comprises a removal unit (22) which is positioned around the punch (5) and is axially movable along the longitudinal extension axis (X).

12. The device according to the preceding claim, wherein: The removal unit (22) comprises an annular element (23) extending around the moulding surface (10); in order to remove the moulded product after the action of pressing the dose of material, the annular element (23) slides towards the end (5a) of the punch (5) in a corresponding retracted state.

13. A compression molding method comprising the steps of: - preparing a female mould element (2) for containing a dose of material suitable for compression moulding; - inserting a male punch (5) at least partially into the female die element (2) for compressing the dose of material, the punch (5) having an outer moulding surface (10) which, in conjunction with the inner surface (3a) of the female die element (2), defines the shape of the product obtained by compressing the dose of material; - separating the punch (5) from the die element (2); as well as - removing the molded product from the punch (5); - wherein, after the step of inserting the punch (5) and before the step of detaching the punch (5), at least a second portion (7) of the punch (5) is retracted to define a retracted state of the punch (5), in which the second portion (7) moves away from the dose of material; The method further comprises the following steps: withdrawing the plurality of second parts (7) by axially moving a first part (6) having a plurality of seats (8) for accommodating the second parts (7); The step of axially moving the first portion (6) is actuated by simultaneously sliding a plurality of inclined contact surfaces (8a) on the inclined contact surfaces (7a) of corresponding second portions (7), each of which is housed in a corresponding seat (8); in the retracted state, the second portion (7) is positioned in the space defined by the outer moulding surface (10) of the punch (5); The step of separating the punch (5) from the die element (2) comprises the step of moving the pressing wall (19) of the punch (5) away from the bottom wall (4) of the die element (2).

14. The method according to claim 13, wherein: The step of removing the molded product is actuated by axially moving an annular element (23) extending around the molding surface (10) towards the end (5a) of the punch (5) in the respective retracted state for removing the molded product after the act of pressing the dose of material.

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