WO2012046186A1 - Injection molding process and apparatus for carrying out said process - Google Patents

Injection molding process and apparatus for carrying out said process Download PDF

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Publication number
WO2012046186A1
WO2012046186A1 PCT/IB2011/054358 IB2011054358W WO2012046186A1 WO 2012046186 A1 WO2012046186 A1 WO 2012046186A1 IB 2011054358 W IB2011054358 W IB 2011054358W WO 2012046186 A1 WO2012046186 A1 WO 2012046186A1
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WO
WIPO (PCT)
Prior art keywords
die
matrix
punch
conformation
ceiling
Prior art date
Application number
PCT/IB2011/054358
Other languages
French (fr)
Inventor
Claudio Bariselli
Original Assignee
Borromini S.R.L.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Borromini S.R.L. filed Critical Borromini S.R.L.
Priority to EP11776888.7A priority Critical patent/EP2625016A1/en
Publication of WO2012046186A1 publication Critical patent/WO2012046186A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16—Making multilayered or multicoloured articles
    • B29C45/1615—The materials being injected at different moulding stations
    • B29C45/162—The materials being injected at different moulding stations using means, e.g. mould parts, for transferring an injected part between moulding stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D11/00—Producing optical elements, e.g. lenses or prisms
    • B29D11/00009—Production of simple or compound lenses
    • B29D11/0048—Moulds for lenses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
    • F21S43/00—Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights
    • F21S43/20—Signalling devices specially adapted for vehicle exteriors, e.g. brake lamps, direction indicator lights or reversing lights characterised by refractors, transparent cover plates, light guides or filters
    • F21S43/26—Refractors, transparent cover plates, light guides or filters not provided in groups F21S43/235 - F21S43/255
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2011/00—Optical elements, e.g. lenses, prisms
    • B29L2011/0016—Lenses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/30—Vehicles, e.g. ships or aircraft, or body parts thereof

Definitions

  • the present invention refers in general to an injection molding process and to an apparatus for carrying out said process.
  • the present invention is described below in connection with the production of a lens for a headlight of a vehicle but it is to be intended that the process according to the invention and the related apparatus can be utilized to carry out also whatever manufactured article in a plastic material for which two distinct injection phases are required.
  • the lenses of a headlight comprise a front part and a side part.
  • the front part which is called ceiling and corresponds to the portion in sight of the headlight, is transparent since this part has to be penetrated by the light emitted by a proper internal light source.
  • the side part which is called body of the lens, corresponds to the portion out of sight of the headlight and comprises one or more protruding elements fixing the whole lens on the headlight structure.
  • the side part of the lens usually is opaque but may also be transparent ; in case of an opaque lens, an opaque structure is mounted inside the headlight next to the side part of the lens so that there is no passage of light through the side part.
  • the injection molding process must be carried out in two subsequent plastic material-injection molding phases.
  • the molding process is implemented in two subsequent injection phases because the shape of the lens usually has an undercut and it is better to avoid internal movements of the molds which could provoke lines of division on the ceiling of the lens.
  • the ceiling of the lens must be perfectly homogeneous without any reliefs or lines of separation so as to avoid any minimal diffraction of the light that passes through the ceiling.
  • One of said methods provides, at first, the injection of a plastic material in a first cavity which is obtained between a matrix 12 and a first punch 14 in order to carry out a lens ceiling 10, as it appears from Figure 1.
  • the matrix 12 which receives the ceiling 10, as it appears from Figure 2
  • the matrix 12 is rotated and reaches a second die 16 in order to create a second cavity in which the plastic material is injected to obtain the body 18 of the lens, as it appears from Figure 3.
  • the matrix 12 must have projections 24, called claws, to rotate on dragging the lens ceiling 10 ( Figure 2) so that the matrix 12 holds the ceiling 10 when the matrix 12 is in motion.
  • Small cavities are thus created in the lens 20.
  • One of these cavities is indicated with reference number 26 in Figure 4. Although said cavities are small, they are unwished because in the following piece finishing phases, for instance during the treatment of the lens surface, substances could deposit in said small cavities.
  • the whole mold for carrying out the lens is rather delicate: in fact, it is necessary to reduce the dimensions of the claws 26 to the minimum but at the same time, it is necessary to guarantee a good fastening of the ceiling 10 on the matrix 12 in motion.
  • An aim of the invention is to remove the above mentioned disadvantages and further ones by carrying out a process and the related injection molding apparatus which allow to obtain a lens without cavities or chamfers to avoid an unwished deposit of substances or dust.
  • a further aim of the invention is to carry out a repeatable injection molding process which gives a measurable qualitative standard to the finished product so that the quality of the product can be easily controlled and reproduced.
  • a further aim of the invention is to carry out an apparatus for the production of a manufactured article through an injection molding, which apparatus is strong and not particularly delicate, the ordinary maintenance of the plant being thus reduced.
  • Another aim of the invention is to avoid the re-engineering of the lens and the consequent re-engineering of the whole headlight in order to maintain the production costs low.
  • first die comprises at least one pair of matrices formed by a first matrix and a second matrix, said matrices being identical and turned in the same direction, one matrix being turned about said direction 180 degrees in comparison to the other, and the second die comprises a first punch and a second punch;
  • the process according to the invention provides the simultaneous injection molding of the ceiling of a first lens and the body of a second lens for which the related ceiling had already been produced.
  • the ceiling and the body are obtained in two different cavities obtained between the first punch and a first matrix and between a second punch, which is different from the first punch, and a second matrix, which is shaped like the first matrix but comprises the ceiling which had been molded with the first punch previously, respectively.
  • the first die comprising at least one pair of matrices remains fixed while the second die is movable and rotating.
  • the finished lenses are thus extracted in each molding cycle from an only matrix of the pair, that is from the first matrix or second matrix, alternatively.
  • the process according to the invention can provide that when the first punch beats against the first matrix or second matrix, said first punch delimits the cavity showing the first conformation by means of a portion of surface on which the edge of union of the ceiling with the body is obtained; on the same portion of surface of the punch there is an opening of a tunnel obtained in the first punch and communicating with suitable conduits through which fluid plastic material to be injected in the cavity comes.
  • the second punch may comprise at least one molding element which forms, together with the second punch and the edge of union, the cavity showing the second conformation in which a lens body is molded through injection; in particular, before moving away the second die from the first die, said one or more molding elements being movable relative to the second punch are spaced from the so-obtained body, without touching the ceiling as carried out in the preceding injection molding phase.
  • the ceiling remains homogeneous and intact without the formation of reliefs or grooves owing to the presence of movable carriages permitting the displacement of the molding elements.
  • the process according to the invention may provide that after the injection molding of the ceiling, on moving the second die away from the first die, the first punch acts automatically as a riser remover.
  • an injection molding apparatus for the injection molding of a lens in a plastic material, for instance, for a headlight, comprising a first portion or ceiling for the passage of light, and a second portion or body for the coupling of the lens with the structure of the headlight, said ceiling and said body being attached to each other along an edge.
  • Said apparatus is characterized in that it comprises:
  • - a first die comprising at least one pair of matrices turned in the same direction; said at least one pair of matrices comprising a first matrix and a second matrix, which is shaped like the first matrix and is arranged on the first die so as to be rotated about an axis which is orthogonal to the plane of the first matrix, 180 degrees relative to the first matrix; - a second die comprising at least one pair of punches turned in the same direction; said at least one pair of punches comprising a first punch and a second punch;
  • - translation means for the translation of the second die relative to the first die so that the at least one pair of matrices is moved nearer or away from the at least one pair of punches so that when the second die beats on the first die, a cavity showing a first conformation is formed between the first punch and the first matrix and at the same time, a cavity showing a second conformation is formed between the second punch and the second matrix, or alternatively, according to the reciprocal rotation of said first and second die, a cavity showing the first conformation is formed between the first punch and the second matrix and at the same time, a cavity showing the second conformation is formed between the second punch and the first matrix;
  • - injection means for the injection of a plastic material in the inside of the cavities showing the first conformation and in the inside of the cavities showing the second conformation so that the ceiling of a lens is obtained in the cavities showing the first conformation and the body of a lens is obtained in the cavities showing the second conformation.
  • the injection molding apparatus may comprise first injection means for the injection of a first plastic material in the cavities showing the first conformation and second injection means for the injection of a second plastic material in the cavities showing the second conformation.
  • the ceiling of the lens and the body of the lens are made of two different plastic materials according to the need.
  • a tunnel is obtained in the first punch and the injection means introduce the first plastic material in the cavities showing the first conformation through said tunnel so that once the first plastic material has solidified, the removal of risers takes place automatically as the first punch is moved away from the first die.
  • the injection molding apparatus may provide that the communication opening of the tunnel for the communication of said tunnel with the cavity showing the first conformation is obtained in the sector of the surface portion of the first punch, such surface portion forming the edge of union of ceiling and body.
  • Figures 1 to 4 have been already described above and are schematic side views in section of a mold as utilized in the several molding phases to mold a lens according to the prior art;
  • Figure 5 is a schematic front view of the fixed part of a first die
  • Figure 6 is a schematic front view of the movable part of a second die
  • Figure 7 is a schematic side view in section of a first phase of the molding process according to the invention.
  • Figure 8 is a schematic side view in section of a second phase of the molding process according to the invention.
  • Figure 9 is a schematic side view in section of a lens obtained with the molding process according to the invention.
  • Figures 10 to 11 are schematic side views in section of two lenses as obtained with the molding process according to the invention.
  • number 31 denotes a first die (fixed part), fixed firmly on a molding plant.
  • the first die 31 is coupled with a second die 35 (movable part), as represented in
  • the lens 50 obtained in the process according to the invention comprises a transparent portion 30, called ceiling, and an opaque portion 40, called body.
  • the first die 31 comprises a first matrix 32 and a second matrix 33 which are put side by side, have the same shape and are turned 80 degrees to each other.
  • the first matrix 32 there are three conduits 54 for the feeding of an opaque plastic material and two conduits 56 for the feeding of a transparent plastic material.
  • the second matrix 33 there are three conduits 58 for the feeding of an opaque plastic material and two conduits 60 for the feeding of a transparent plastic material.
  • the total number of the conduits is five for each of the two matrices but obviously, the number of the conduits may vary according to the product to be carried out.
  • conduits 56, 60 for the transparent plastic material are connected with a first hot chamber, not represented in the figures, while the conduits 54, 58 for the opaque plastic material are connected with a second hot chamber, not represented in the figures, separated from the first hot chamber.
  • the second die 35 which is movable in comparison with the first die 31 , comprises a first punch 34, which corresponds to a first half of the second die 35, and a second punch 42, which corresponds to a second half of the second die 35.
  • Four outer molding elements 44, 46, 48, 52 are arranged on the second punch 42 and are movable by means of corresponding outer carriages, and two inner molding elements 61 , 62 are arranged on the second punch 42 and are movable by means of related inner carriages. Also in this case, the number of the molding elements may vary according to the product to be carried out.
  • the molding process according to the invention consists of a first phase in which the injection of the ceiling 30 of the lens 50 takes place as represented in Figure 7.
  • the first punch 34 is arranged at the first matrix 32 so as to obtain a closed cavity.
  • a transparent plastic material is injected in said cavity through a first conduit 36 and a tunnel 38 obtained in the first punch 34.
  • the plastic material is injected in the edge 37 of the closed cavity; said edge 37 corresponds to the portion of union of the ceiling 30 with the body 40 of the lens.
  • the tunnel 38 removes the risers automatically since in the moving away of the first punch 34 from the first matrix 32, the removal of the portion of plastic material injected from the point of injection to the edge 37 of the ceiling 30 is effected automatically.
  • the second phase of the molding process relates to a rotation of the second die 35 so that the second punch 42 is arranged at the first matrix, as represented in Figure 8.
  • the inner molding elements 44, 46, 48, 52 and the outer molding elements 61 , 62 move so as to form a second closed cavity together with the second punch 42 and the edge 37 of the ceiling 30, in which cavity the opaque plastic material is injected to obtain the body 40 of the lens 50.
  • This lens comprises a ceiling 30 in a transparent plastic material, and a body 40 in an opaque material, which are joined together along an edge 37.
  • a lens 50" may comprise a ceiling 30" and a body 40" which are joined together through an edge 37" having a more complex shape.
  • the molding process and the related apparatus provide at the same time the injection and molding of a ceiling 30 of a first lens in a first matrix 32, and the injection and molding of a body 40 in the other matrix 33 which already contains the previously obtained ceiling of a second lens.
  • one of the two matrices 32, 34 is in turn and at the same time adjacent to the first punch 34 while the other matrix is adjacent to the second punch 42 with the related molding elements 44, 46, 48, 52, 61 , 62.
  • the movements of the carriages and of the second punch are effected in a position which is slightly spaced from the ceiling so that the ceiling is not affected and is kept without any lines or reliefs.
  • a first die may comprise four or more matrices and a second die may comprise two or more first punches and two or more second punches.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Ophthalmology & Optometry (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

It refers to an injection molding process and to the related apparatus for carrying out a lens (50) in a plastic material, comprising a first portion or ceiling (30) for the passage of light, and a second portion or body (40) for the coupling of the lens (50) with the structure of the headlight. The process and the related apparatus allow to obtain a lens (50) in which the ceiling is perfectly homogeneous, without any reliefs or recesses.

Description

TITLE
INJECTION MOLDING PROCESS AND APPARATUS FOR CARRYING OUT SAID PROCESS
SPECIFICATION The present invention refers in general to an injection molding process and to an apparatus for carrying out said process.
More particularly, it refers to a particular injection molding process and to an apparatus for carrying out said process in which two distinct injection phases are provided and performed in succession.
The present invention is described below in connection with the production of a lens for a headlight of a vehicle but it is to be intended that the process according to the invention and the related apparatus can be utilized to carry out also whatever manufactured article in a plastic material for which two distinct injection phases are required.
As is known, the lenses of a headlight comprise a front part and a side part.
The front part, which is called ceiling and corresponds to the portion in sight of the headlight, is transparent since this part has to be penetrated by the light emitted by a proper internal light source.
The side part, which is called body of the lens, corresponds to the portion out of sight of the headlight and comprises one or more protruding elements fixing the whole lens on the headlight structure.
The side part of the lens usually is opaque but may also be transparent ; in case of an opaque lens, an opaque structure is mounted inside the headlight next to the side part of the lens so that there is no passage of light through the side part. In case the ceiling and the body of the lens are made of different materials, the injection molding process must be carried out in two subsequent plastic material-injection molding phases.
Even in case the ceiling and the body of the lens are made of the same material, the molding process is implemented in two subsequent injection phases because the shape of the lens usually has an undercut and it is better to avoid internal movements of the molds which could provoke lines of division on the ceiling of the lens.
In fact, the ceiling of the lens must be perfectly homogeneous without any reliefs or lines of separation so as to avoid any minimal diffraction of the light that passes through the ceiling.
Processes are known to produce headlight lenses, which allow the production of a lens in which the ceiling has no reliefs or lines.
One of said methods, as illustrated in Figures 1 to 4, provides, at first, the injection of a plastic material in a first cavity which is obtained between a matrix 12 and a first punch 14 in order to carry out a lens ceiling 10, as it appears from Figure 1. Once said first part 10 of the lens has been obtained, the matrix 12, which receives the ceiling 10, as it appears from Figure 2, is rotated and reaches a second die 16 in order to create a second cavity in which the plastic material is injected to obtain the body 18 of the lens, as it appears from Figure 3.
Thus, it is possible to produce a lens 20 comprising a ceiling 10 and a body 18, as represented in Figure 4.
According to this process of the prior art, the matrix 12 must have projections 24, called claws, to rotate on dragging the lens ceiling 10 (Figure 2) so that the matrix 12 holds the ceiling 10 when the matrix 12 is in motion. Small cavities are thus created in the lens 20. One of these cavities is indicated with reference number 26 in Figure 4. Although said cavities are small, they are unwished because in the following piece finishing phases, for instance during the treatment of the lens surface, substances could deposit in said small cavities.
Accordingly, the whole mold for carrying out the lens is rather delicate: in fact, it is necessary to reduce the dimensions of the claws 26 to the minimum but at the same time, it is necessary to guarantee a good fastening of the ceiling 10 on the matrix 12 in motion.
In addition, owing to the delicacy of the mold, the removal of risers must be effected with a complex automatic cutting system or even manually, especially to obtain a good finishing of the piece.
Another disadvantage of this process is the necessary re-engineering of the whole headlight. In fact, for the handling of the matrix, the matrix has to be positioned in such a way that the cavity corresponding to the lens ceiling is arranged according to an orthogonal direction as much as possible in respect to the translation and removal movement of the matrix from the punch. Consequently, both the lens body and the related connecting elements that connect the lens with the headlight have to be re-arranged and likewise, also the corresponding coupling elements in the structure of the headlight have to be rearranged.
An aim of the invention is to remove the above mentioned disadvantages and further ones by carrying out a process and the related injection molding apparatus which allow to obtain a lens without cavities or chamfers to avoid an unwished deposit of substances or dust. A further aim of the invention is to carry out a repeatable injection molding process which gives a measurable qualitative standard to the finished product so that the quality of the product can be easily controlled and reproduced.
A further aim of the invention is to carry out an apparatus for the production of a manufactured article through an injection molding, which apparatus is strong and not particularly delicate, the ordinary maintenance of the plant being thus reduced.
Another aim of the invention is to avoid the re-engineering of the lens and the consequent re-engineering of the whole headlight in order to maintain the production costs low.
All said aims and advantages are reached according to the invention through an injection molding process for the production of lenses in a plastic material, for instance lenses for headlights, comprising a first lens portion, designated as ceiling, allowing light to pass through, and a second lens portion, designated as body, for the coupling of the lens with the structure of the headlight. The process according to the invention is characterized by the fact of comprising the following phases:
- drawing a first die and a second die close to each other, in which the first die comprises at least one pair of matrices formed by a first matrix and a second matrix, said matrices being identical and turned in the same direction, one matrix being turned about said direction 180 degrees in comparison to the other, and the second die comprises a first punch and a second punch;
- beating the first die and the second die against each other so that the first matrix forms a cavity showing a first conformation with the first punch, and that at the same time, the second matrix forms a cavity showing a second conformation with the second punch, a first portion of lens (ceiling) being previously molded in the second'matrix;
molding through injection a first portion of lens (ceiling) in the cavity showing the first conformation, and at the same time, molding through injection a second portion of lens (body) in the cavity showing the second conformation, obtained with the second matrix so as to carry out a first complete lens with the first portion of lens (ceiling), previously molded;
moving the second die away from the first die;
removing the first lens from the second matrix and letting said second matrix empty;
rotating the second die 180 degrees relative to the first die about an axis which is parallel to the direction of translation of the two dies;
drawing the second die close to the first die (31 );
beating the first die and the second die against each other so that the second matrix, now empty, forms a cavity showing the first conformation with the first punch, and that at the same time, the second matrix comprising the previously molded ceiling forms a cavity showing the second conformation with the second punch;
molding through injection a first portion of lens (ceiling) in the cavity showing the first conformation, and at the same time, molding through injection a second portion of lens (body) in the cavity showing the second conformation, that is obtained between the second punch and the first matrix so as to carry out a second complete lens with the first portion of lens (ceiling), previously molded, in the sector of the first matrix; - moving away the second die from the first die;
- removing the second lens from the first matrix and letting said first matrix empty and ready to receive the first portion (ceiling) of a new lens.
Accordingly, the process according to the invention provides the simultaneous injection molding of the ceiling of a first lens and the body of a second lens for which the related ceiling had already been produced. The ceiling and the body are obtained in two different cavities obtained between the first punch and a first matrix and between a second punch, which is different from the first punch, and a second matrix, which is shaped like the first matrix but comprises the ceiling which had been molded with the first punch previously, respectively.
The first die comprising at least one pair of matrices remains fixed while the second die is movable and rotating. The finished lenses are thus extracted in each molding cycle from an only matrix of the pair, that is from the first matrix or second matrix, alternatively.
Advantageously, the process according to the invention can provide that when the first punch beats against the first matrix or second matrix, said first punch delimits the cavity showing the first conformation by means of a portion of surface on which the edge of union of the ceiling with the body is obtained; on the same portion of surface of the punch there is an opening of a tunnel obtained in the first punch and communicating with suitable conduits through which fluid plastic material to be injected in the cavity comes.
In this way, the injection of plastic material is done at the edge of union of the ceiling with the body, that is in a sector to be covered by the plastic material injected for the formation of the body itself, without letting any trace in sight on the surface. In addition, according to the injection molding process of the invention, the second punch may comprise at least one molding element which forms, together with the second punch and the edge of union, the cavity showing the second conformation in which a lens body is molded through injection; in particular, before moving away the second die from the first die, said one or more molding elements being movable relative to the second punch are spaced from the so-obtained body, without touching the ceiling as carried out in the preceding injection molding phase.
In this way, the ceiling remains homogeneous and intact without the formation of reliefs or grooves owing to the presence of movable carriages permitting the displacement of the molding elements.
Advantageously, the process according to the invention may provide that after the injection molding of the ceiling, on moving the second die away from the first die, the first punch acts automatically as a riser remover.
All the aims and advantages are reached according to the invention by an injection molding apparatus for the injection molding of a lens in a plastic material, for instance, for a headlight, comprising a first portion or ceiling for the passage of light, and a second portion or body for the coupling of the lens with the structure of the headlight, said ceiling and said body being attached to each other along an edge. Said apparatus is characterized in that it comprises:
- a first die comprising at least one pair of matrices turned in the same direction; said at least one pair of matrices comprising a first matrix and a second matrix, which is shaped like the first matrix and is arranged on the first die so as to be rotated about an axis which is orthogonal to the plane of the first matrix, 180 degrees relative to the first matrix; - a second die comprising at least one pair of punches turned in the same direction; said at least one pair of punches comprising a first punch and a second punch;
- a structure with which the first die and the second die (35) are coupled so that the at least one pair of matrices is in front of the at least one pair of punches;
- rotation means for the rotation of the second die relative to the first die so that the first punch is arranged in front of the first matrix and at the same time, the second punch is arranged in front of the second matrix or alternatively, the first punch is arranged in front of the second matrix and at the same time, the second punch is arranged in front of the first matrix;
- translation means for the translation of the second die relative to the first die so that the at least one pair of matrices is moved nearer or away from the at least one pair of punches so that when the second die beats on the first die, a cavity showing a first conformation is formed between the first punch and the first matrix and at the same time, a cavity showing a second conformation is formed between the second punch and the second matrix, or alternatively, according to the reciprocal rotation of said first and second die, a cavity showing the first conformation is formed between the first punch and the second matrix and at the same time, a cavity showing the second conformation is formed between the second punch and the first matrix;
- injection means for the injection of a plastic material in the inside of the cavities showing the first conformation and in the inside of the cavities showing the second conformation so that the ceiling of a lens is obtained in the cavities showing the first conformation and the body of a lens is obtained in the cavities showing the second conformation.
Advantageously, the injection molding apparatus according to the invention may comprise first injection means for the injection of a first plastic material in the cavities showing the first conformation and second injection means for the injection of a second plastic material in the cavities showing the second conformation.
In this way, the ceiling of the lens and the body of the lens are made of two different plastic materials according to the need.
In addition, as mentioned above, a tunnel is obtained in the first punch and the injection means introduce the first plastic material in the cavities showing the first conformation through said tunnel so that once the first plastic material has solidified, the removal of risers takes place automatically as the first punch is moved away from the first die.
The injection molding apparatus according to the invention may provide that the communication opening of the tunnel for the communication of said tunnel with the cavity showing the first conformation is obtained in the sector of the surface portion of the first punch, such surface portion forming the edge of union of ceiling and body.
In this way, it is possible to avoid the formation of reliefs or imperfections at the injection point in sight on the ceiling.
Besides, the presence of reliefs and cavities on the ceiling of the lens to be obtained is avoided because possible movable carriages at the second punch are put in motion at a short distance from the so-obtained ceiling.
Further features and details of the invention will be better understood from the following specification which is supplied as a non-limiting example, as well as from the accompanying drawings wherein:
Figures 1 to 4 have been already described above and are schematic side views in section of a mold as utilized in the several molding phases to mold a lens according to the prior art;
Figure 5 is a schematic front view of the fixed part of a first die;
Figure 6 is a schematic front view of the movable part of a second die;
Figure 7 is a schematic side view in section of a first phase of the molding process according to the invention;
Figure 8 is a schematic side view in section of a second phase of the molding process according to the invention;
Figure 9 is a schematic side view in section of a lens obtained with the molding process according to the invention;
Figures 10 to 11 are schematic side views in section of two lenses as obtained with the molding process according to the invention.
With reference to the accompanying drawings, in particular Figure 5, number 31 denotes a first die (fixed part), fixed firmly on a molding plant.
The first die 31 is coupled with a second die 35 (movable part), as represented in
Figure 6, and allows to carry out lenses 50 for headlights, a portion thereof being visible in section in Figure 9. In particular, the lens 50 obtained in the process according to the invention comprises a transparent portion 30, called ceiling, and an opaque portion 40, called body.
The first die 31 comprises a first matrix 32 and a second matrix 33 which are put side by side, have the same shape and are turned 80 degrees to each other. In the first matrix 32 there are three conduits 54 for the feeding of an opaque plastic material and two conduits 56 for the feeding of a transparent plastic material.
Likewise, in the second matrix 33 there are three conduits 58 for the feeding of an opaque plastic material and two conduits 60 for the feeding of a transparent plastic material. In the constructive system of the so-described invention, the total number of the conduits is five for each of the two matrices but obviously, the number of the conduits may vary according to the product to be carried out.
The conduits 56, 60 for the transparent plastic material are connected with a first hot chamber, not represented in the figures, while the conduits 54, 58 for the opaque plastic material are connected with a second hot chamber, not represented in the figures, separated from the first hot chamber.
The second die 35, which is movable in comparison with the first die 31 , comprises a first punch 34, which corresponds to a first half of the second die 35, and a second punch 42, which corresponds to a second half of the second die 35. Four outer molding elements 44, 46, 48, 52 are arranged on the second punch 42 and are movable by means of corresponding outer carriages, and two inner molding elements 61 , 62 are arranged on the second punch 42 and are movable by means of related inner carriages. Also in this case, the number of the molding elements may vary according to the product to be carried out.
The molding process according to the invention consists of a first phase in which the injection of the ceiling 30 of the lens 50 takes place as represented in Figure 7. In particular, the first punch 34 is arranged at the first matrix 32 so as to obtain a closed cavity. Then, a transparent plastic material is injected in said cavity through a first conduit 36 and a tunnel 38 obtained in the first punch 34.
The plastic material is injected in the edge 37 of the closed cavity; said edge 37 corresponds to the portion of union of the ceiling 30 with the body 40 of the lens. The tunnel 38 removes the risers automatically since in the moving away of the first punch 34 from the first matrix 32, the removal of the portion of plastic material injected from the point of injection to the edge 37 of the ceiling 30 is effected automatically.
The second phase of the molding process relates to a rotation of the second die 35 so that the second punch 42 is arranged at the first matrix, as represented in Figure 8.
The inner molding elements 44, 46, 48, 52 and the outer molding elements 61 , 62 move so as to form a second closed cavity together with the second punch 42 and the edge 37 of the ceiling 30, in which cavity the opaque plastic material is injected to obtain the body 40 of the lens 50.
In this way, a lens 50 as represented in Figure 9 is obtained. This lens comprises a ceiling 30 in a transparent plastic material, and a body 40 in an opaque material, which are joined together along an edge 37.
After the first injection of transparent plastic material at the edge 37, the imperfections in the point of injection of transparent plastic material are covered by the opaque plastic material injected in the second phase of the molding process. According to variants of the shape of the utilized molds, it is possible to obtain a flat edge 37' and a lens 50' which is formed by a ceiling 30' and a body 40', as represented in Figure 10.
Likewise, as represented in Figure 11 , a lens 50" may comprise a ceiling 30" and a body 40" which are joined together through an edge 37" having a more complex shape.
The molding process and the related apparatus provide at the same time the injection and molding of a ceiling 30 of a first lens in a first matrix 32, and the injection and molding of a body 40 in the other matrix 33 which already contains the previously obtained ceiling of a second lens.
In fact, through the rotation of the second die 35, one of the two matrices 32, 34 is in turn and at the same time adjacent to the first punch 34 while the other matrix is adjacent to the second punch 42 with the related molding elements 44, 46, 48, 52, 61 , 62.
During the second injection molding phase, namely, the phase in which the body of the lens is formed, the movements of the carriages and of the second punch are effected in a position which is slightly spaced from the ceiling so that the ceiling is not affected and is kept without any lines or reliefs.
It is to intended that the variants to the process and apparatus according to the invention regarding the injection molding of two or more lenses comprising a ceiling and a body are included in the scope of protection of the invention. For instance, a first die may comprise four or more matrices and a second die may comprise two or more first punches and two or more second punches.

Claims

1) Injection molding apparatus for the injection molding of a lens (50) in a plastic material, for instance, for a headlight, comprising a first portion called ceiling (30) for the passage of light, and a second portion called body (40) for the coupling of the lens (50) with the structure of the headlight, said ceiling (30) and said body (40) being attached to each other along an edge (37), said injection molding apparatus being characterized in that it comprises:
- a first die (31 ) comprising at least one pair of matrices (32, 33) turned in the same direction; said at least one pair of matrices comprising a first matrix (32) and a second matrix (33), which is shaped like the first matrix (32) and is arranged on the first die so as to be rotated about an axis which is orthogonal to the plane of the first matrix (32), 180 degrees relative to the first matrix (32);
- a second die (35) comprising at least one pair of punches (34, 42) turned in the same direction; said at least one pair of punches comprising a first punch (34) and a second punch (42);
- a structure with which the first die (31) and the second die (35) are coupled so that the at least one pair of matrices (32, 33) is in front of the at least one pair of punches (34, 42);
- rotation means for the rotation of the second die (35) relative to the first die (31) so that the first punch (34) is arranged in front of the first matrix (32) and at the same time, the second punch (42) is arranged in front of the second matrix (33) or alternatively, the first punch (34) is arranged in front of the second matrix (33) and at the same time, the second punch (42) is arranged in front of the first matrix (32);
- translation means for the translation of the second die (35) relative to the first die (31 ) so that the at least one pair of matrices (32, 33) is moved nearer or away from the at least one pair of punches (34, 42) and when the second die (35) beats on the first die (31 ), a cavity showing a first conformation is formed between the first punch (34) and the first matrix (32) and at the same time, a cavity showing a second conformation is formed between the second punch (42) and the second matrix (33), or alternatively, on the base of the reciprocal rotation of said first and second die, a cavity showing the first conformation is formed between the first punch (34) and the second matrix (33) and at the same time, a cavity showing the second conformation is formed between the second punch (42) and the first matrix (32);
- injection means for the injection of a plastic material in the inside of the cavities showing the first conformation and in the inside of the cavities showing the second conformation so that the ceiling (30) is obtained in the cavities showing the first conformation and the body (40) is obtained in the cavities showing the second conformation.
2) Injection molding apparatus according to claim 1 , wherein the injection means comprise first injection means for the injection of a first plastic material in the cavities showing the first conformation and second injection means for the injection of a second plastic material in the cavities showing the second conformation.
3) Injection molding apparatus according to claim 2, wherein a tunnel (38) is obtained in the first punch (34) and the injection means introduce the first plastic material in the cavities showing the first conformation through said tunnel (38) so that once the first plastic material has solidified, the removal of risers takes place automatically as the first punch (34) is moved away from the first die (31 ).
4) Injection molding apparatus according to claim 3, wherein the communication opening of the tunnel (38) for the communication of said tunnel with the cavity showing the first conformation is obtained in the sector of the surface portion of the first punch, such surface portion forming the edge (37) of union of ceiling (30) and body (40).
5) Injection molding apparatus according to any of the preceding claims, wherein the second die (35) comprises at least one movable molding element (44, 46, 48, 52, 61 , 62) next to the second punch (42), said at least one movable molding element (44, 46, 48, 52, 61 , 62) being spaced from the plastic material molded in the cavity showing the first conformation so as not to touch said plastic material, molded in the cavity showing the first conformation.
6) Injection molding process for the injection molding of a lens (50) in a plastic material, for instance, for a headlight, comprising a first portion called ceiling (30) for the passage of light, and a second portion called body (40) for the coupling of the lens (50) with the structure of the headlight, said ceiling (30) and said body (40) being attached along an edge (37), said injection molding process being characterized in that it comprises the following phases:
- approaching a first die (31 ) and a second die (35) to each other, the first die (31) comprising at least one pair of matrices comprising a first matrix (32) and a second matrix (33), which are identical to each other and are turned in the same direction, one of them being rotated, about said direction, 180 degrees relative to the other one; the second die (35) comprising a first punch (34) and a second punch (42);
- beating the first die (31 ) and the second die (35) against each other so that the first matrix (32) forms a cavity showing a first conformation with the first punch (34), and that at the same time, the second matrix (33) forms a cavity showing a second conformation with the second punch (42), a ceiling being previously molded in the second matrix (33);
- molding through injection a ceiling (30) in the cavity showing the first conformation, and at the same time, molding through injection a body (40) in the cavity showing the second conformation, obtained with the second matrix (33) so as to carry out a first complete lens (50) with the ceiling, previously molded;
- moving the second die (35) away from the first die (31 );
- removing the first lens (50) from the second matrix (33) and letting said second matrix (33) empty;
- rotating the second die (35) 180 degrees relative to the first die (31 );
- approaching the second die (35) to the first die (31 );
- beating the first die (31) and the second die (35) against each other so that the second matrix (32), now empty, forms a cavity showing the first conformation with the first punch (34), and that at the same time, the second matrix (33) comprising the previously molded ceiling (30) forms a cavity showing the second conformation with the second punch (42);
- molding through injection a ceiling in the cavity showing the first conformation, and at the same time, molding through injection a body in the cavity showing the second conformation, obtained with the first matrix (32) so as to carry out a second complete lens with the ceiling (30), previously molded, in the sector of the first matrix (32);
- moving away the second die (35) from the first die (31 );
- removing the second lens from the first matrix (32) and letting said first matrix (32) empty.
7) Injection molding process according to claim 6, wherein when the first punch (34) beats against the first matrix (32) or second matrix (33), said first punch (34) delimits the cavity showing the first conformation by means of a portion of surface on which the edge (37) of union of the ceiling (30) with the body (40) is obtained; the injection of plastic material being done through a tunnel (38) showing an opening communicating with said cavity showing the first conformation, said opening being obtained in said portion of surface of the first punch (34).
8) Injection molding process according to claim 6 or 7, wherein the second punch (42) comprises at least one molding element (44, 46, 48, 52, 61 , 62) which forms, together with the second punch (42) and the edge (37) of union, the cavity showing the second conformation in which a body (40) is molded through injection, said at least one molding element (44, 46, 48, 52, 61 , 62) being movable relative to the second punch (42).
9) Injection molding process according to claim 8, wherein before moving the second die (35) away from the first die (31), the at least one movable molding element (44, 46, 48, 52, 61 , 62) is spaced from the body (40) obtained, without touching the ceiling (30), previously obtained. )lnjection molding process according to any of claims 6 to 9, wherein after the injection molding of the ceiling (30) in a cavity showing the first conformation, the first punch (38) removes the risers automatically from the ceiling (30), obtained in said cavity as the second die (35) is moved away from the first die (31 ).
PCT/IB2011/054358 2010-10-05 2011-10-04 Injection molding process and apparatus for carrying out said process WO2012046186A1 (en)

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ITVR2010A000191 2010-10-05
ITVR2010A000191A IT1402358B1 (en) 2010-10-05 2010-10-05 INJECTION MOLDING PROCEDURE AND EQUIPMENT FOR THE IMPLEMENTATION OF THIS PROCEDURE

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IT1402358B1 (en) 2013-08-30
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