Abstract:
An injection mould component for moulding the outer surface of a preform neck, which allows improved cooling of the preform neck inside the mould, while at the same time reducing the mould cycle time. A related production process of said injection mould component, which allows the section of the cooling channels to be optimised, determining a more effective cooling, is also described.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to PCT International Application No. PCT/IB2012/052974 filed on Jun. 13, 2012, which application claims priority to Italian Patent Application No. RM2011A000303 filed Jun. 14, 2011. 
     
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to an injection mould component for moulding the outer surface of a preform neck of a container made of plastic material, in particular a bottle. The invention also relates to a production process of said injection mould component. 
         [0005]    2. State of the Art 
         [0006]    An example of a bottle preform made of plastic material is illustrated in  FIG. 1   a.  This preform, globally indicated with the numerical reference  1 , comprises an elongated cylindrical portion  2 , that is closed at one end, and a neck  3 . The elongated cylindrical portion  2  is then stretched and blown in the stretch-blow process to form a bottle for drinks or more generally for liquids. The neck  3 , provided with an open end  4 , has an outer surface comprising: 
         [0007]    a threaded end portion  5 , onto which the cup-shaped cap is screwed; 
         [0008]    a first annular flange or support ring  7 , that acts as a support for transport and seal, shaped in such a way as to be able to slide on longitudinal guides that support the neck of the bottle from both sides to support and retain the bottle as it advances downstream of the container production plant; 
         [0009]    a possible second annular flange  6 , that acts as seal tearing, shaped in such a way as to retain, once the cap has been inserted into the neck  3  of the bottle, the annular seal placed at a preset position between the first flange  7  and the second flange  6 ; 
         [0010]    a possible slightly conical annular portion  8 , beneath the first annular flange or support ring  7 , which has the function of cooperating, in the handling operations before the blowing, with said support ring  7  to slide on the longitudinal guides of advancement and transport of the bottle downstream of the container production plant. 
         [0011]    Where only one of the two annular flanges is provided, this flange may have the dual function of “support ring” and “seal tearing”. In this case, following coupling of the cap onto the neck  3  of the bottle, the annular seal is placed at a preset position beneath the flange at the conical annular portion  8 . 
         [0012]    In greater detail, the conical annular portion  8  is defined by the tubular stretch of preform comprised between the annular flange  7  and the joint section  9 , placed between the lower end of the neck  3  and the elongated cylindrical portion  2  defining the containment body of the bottle. 
         [0013]    The preform  1  is normally produced by means of an injection process into an injection mould  10  primarily comprising the components shown in  FIG. 2 . The cooling function is exercised by the respective cooling system that each of these components has. 
         [0014]    The main components of the injection mould  10  are: 
         [0015]    a first mould component  11 , called external mould component of the neck or more simply “neck ring”, which defines the shape of the outer surface of the preform neck  3 , including the threaded portion  5 ; 
         [0016]    a second mould component  12 , called internal mould component of the preform or more simply male component (or elongated core), which defines the inner surface of the entire preform; 
         [0017]    a third mould component  13 , called external mould component of the cylindrical portion  2  of the preform or more simply cavity, which defines the outer surface of the cylindrical portion  2 . 
         [0018]    The first component  11  consists of two separate threaded half-inserts, the internal curved surfaces of which define, once the two half-inserts are mounted together in the rest of the mould ( FIG. 2 ), a through opening to mould the outer surface of the preform neck  3 . Each threaded half-insert is provided with a cooling circuit within its body. 
         [0019]    The third component  13  may also, in certain cases, consist of two separate half-inserts that are cooled by means of two independent cooling circuits or by a single circuit that provides for the passage in series from one half-insert to the next. 
         [0020]    Taking into consideration the external part of the preform neck  3 , comprising the threaded portion  5 , the first annular flange or support ring  7  and the conical annular portion  8  up to the level of the plane P indicated in  FIG. 2 , it emerges that the preform neck is cooled by the first mould component  11  and by the third mould component or cavity  13 . However, the greatest weight in terms of cooling capacity is to be attributed to the first mould component  11 . 
         [0021]    It is imperative that the cooling function at the level of the preform neck is achieved in an optimal manner before extracting the preform from the mould, in order to ensure the high quality of the injected product and at the same time a contained cycle time. 
         [0022]    Having the shortest possible cycle time in fact permits greater profitability, particularly in the mass productions that are typical of these products. 
         [0023]    The cooling channels  14 ,  15  can be seen in the section of  FIG. 2  in the half-inserts of the neck ring  11  and in the cavity  13  respectively. In particular, the cooling channels  14  are produced in such as way as to effectively cool only one part of the outer surface of the preform, in particular the part at the level of the support ring  7  (zone indicated by K in  FIG. 1 ), while the zones marked with the rectangles  16 ,  17  in  FIG. 2  (corresponding to the zones indicated by J and L of the preform in  FIG. 1 ) are away from cooling channels and are not therefore adequately cooled. 
         [0024]    For this reason such zones are critical from the point of view of cooling, and the moulding cycle time will depend in a determining way on the capacity of the mould to evacuate heat from said zones. 
         [0025]    The same drawback can also be found in the case of a preform with unthreaded neck, illustrated by way of example in  FIG. 1   b.    
         [0026]    Alternative solutions to the conventional solution described above are already on the market. For example, the document EP0768164A2 describes a mould component, formed by two separate threaded half-inserts, for moulding the outer surface of a preform neck. This component partially resolves these drawbacks but has the following limitations. 
         [0027]    Disadvantageously, the cooling channels are completely external to the upper and lower truncated cone end zones of said mould component, determining a low cooling in the corresponding zones of the preform neck. The arrangement of the two pieces of each half-insert, in fact, determines a space insufficient for the production of the channels in said truncated cone end zones by conventional processing technologies. 
         [0028]    In addition, since the cooling channels are entirely produced by means of the normal stock-removal process, they cannot be created very close to the moulding surface and the section of these channels cannot be adequately optimised whereby they present unconnected edges that cause stagnation points of the cooling liquid and consequent low cooling in particular zones. 
         [0029]    A further disadvantage is represented by the fact that each half-insert of said component is produced by joining two pieces by braze-welding, determining a limited structural resistance. 
         [0030]    There is therefore a need to provide an injection mould component to mould the outer surface of the preform neck, which allows the aforementioned drawbacks to be overcome. 
       SUMMARY OF THE INVENTION 
       [0031]    The main aim of this invention is that of providing for an injection mould component for moulding the outer surface of a preform neck, which allows an improved cooling of the preform neck inside the mould, at the same time reducing the mould cycle time. 
         [0032]    A further aim of the invention is that of providing for a related production process of said injection mould component, which allows the section of the cooling channels to be optimised, determining a more effective cooling. 
         [0033]    The present invention, therefore, proposes to achieve the aforementioned aims by providing an injection mould component that, according to claim  1 , comprises a pair of half-inserts that define, once assembled in the injection mould, a moulding surface of said outer surface of the neck; 
         [0034]    said moulding surface defining a longitudinal axis and comprising a first annular groove for making a first annular flange of the preform neck; 
         [0035]    a cylindrical end portion, arranged at a first side of said first annular groove, for making a corresponding cylindrical end portion of the preform neck; 
         [0036]    and a portion proximal to said first annular groove and arranged at a second side of said first annular groove, for making a corresponding portion proximal to the first annular flange, 
         [0037]    wherein each half-insert is provided with an internal circuit for the passage of a cooling liquid; said internal circuit being provided with a first curved stretch and with a second curved stretch provided in proximity of said first annular groove of the moulding surface; a third curved stretch provided in proximity of said cylindrical end portion of the moulding surface; a fourth curved stretch provided in proximity of said tapered portion of the moulding surface; and wherein third curved stretch and fourth curved stretch are branches of said first curved stretch and converge in said second curved stretch. 
         [0038]    The first curved stretch and the second curved stretch have a respective curvilinear axis, arranged on a first plane substantially perpendicular to a plane containing the longitudinal axis of the moulding surface, and can be symmetrically arranged with respect to a centre-line plane Z of the half-insert. The third curved stretch has a curvilinear axis arranged on a second plane and the fourth curved stretch has a curvilinear axis arranged on a third plane, said second plane and third plane being substantially parallel to said first plane. 
         [0039]    The internal circuit is also provided with a longitudinal inlet stretch and a longitudinal outlet stretch for the cooling liquid, defining respective axes which are substantially parallel to each other and to the longitudinal axis of said moulding surface. A first longitudinal connection stretch connects the longitudinal inlet stretch to the first curved stretch and a second longitudinal connection stretch connects the second curved stretch to the longitudinal outlet stretch, said longitudinal connection stretches being arranged on said first plane. 
         [0040]    The moulding surface can include a second annular groove for providing a second annular flange of the preform neck, provided between said first annular groove and said cylindrical end portion. 
         [0041]    A second aspect of this invention provides a manufacturing process for an injection mould component comprising a pair of half-inserts, each half-insert consisting of two parts integrally connected to each other; the process comprising, according to claim  13 , the production, starting from metal powder, of at least a first part of each half-insert, comprising the first curved stretch, the second curved stretch, the third curved stretch and the fourth curved stretch, by means of Sintering Laser Melting or Laser Cusing. 
         [0042]    The cooling capacity is function of various parameters, such as the proximity of the cooling channels to the moulding surface and the inner surface of said channels, the latter being in turn function of the cross section and of the length of the channels themselves. 
         [0043]    Advantageously the mould component, object of the present invention, is provided with cooling circuits, one for each half-insert, configured in such a way as to adequately cool all the critical zones of the preform neck (zones indicated by J, K and L in  FIG. 1 ). Indeed, such cooling circuits are provided with at least one branch of the cooling circuit both in proximity of the portion of moulding surface corresponding to the, possibly threaded, cylindrical end portion of the neck and in proximity of the portion of moulding surface corresponding to the support ring and in proximity of the portion of moulding surface corresponding to the substantially conical portion of the neck. In this way, the cooling channelling is in proximity of the entire moulding surface of the mould component of the neck and cooling will therefore be optimal. 
         [0044]    Furthermore, the arrangement of the stretches or branches of the cooling circuit in proximity of all the zones where the preform is thickest allows a better evacuation of the heat and consequently greater advantages in terms of the moulding cycle time and the quality of the preform. 
         [0045]    A further advantage is represented by the fact that the cooling channels are produced by means of technologies such as SLM (Sintering Laser Melting), Laser Cusing or equivalent technologies that allow products to be produced starting from metal powder. Compared to traditional stock-removal processes, these technologies allow: 
         [0046]    the obtainment of cooling channels, with circular or elliptical section for example, well connected to each other, allowing a better flow of the cooling liquid, less load losses and a better heat transfer; 
         [0047]    the production of part of the cooling system also inside the upper and lower truncated cone end parts of the component of the invention. 
         [0048]    The mould component of the invention allows the obtainment of moulded products having a temperature profile at the outlet of the mould that is significantly lower with respect to the moulded products obtained with mould components provided with conventional cooling channels This also allow temperature gradients on the moulded product to be avoided; this condition normally occurs on conventional moulded products due to the non-optimal distribution of the cooling. 
         [0049]    Translating this in performance terms, the greater cooling obtainable with the mould component of the invention translates into a variable reduction in the cycle time of between 5% and 15% depending on the profile of the preform, into a greater compliance with the dimensional tolerances of the product and into a better preform quality (less stresses, better quality of the PET or of another suitable material). 
         [0050]    The dependent claims describe preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0051]    Further characteristics and advantages of the invention will become clearer in the light of the detailed description of a preferred but non-exclusive embodiment of an injection mould component for preforms, illustrated by way of a non-limiting example, with the assistance of the accompanying drawings, wherein: 
           [0052]      FIG. 1   a  represents a perspective view of a bottle preform; 
           [0053]      FIG. 1   b  represents a perspective view of a further bottle preform; 
           [0054]      FIG. 2  represents a cross section of an injection mould of the prior art; 
           [0055]      FIG. 3  represents a portion of the mould component according to the invention; 
           [0056]      FIG. 4  represents a schematic front view of the cooling circuit provided in the component according to the invention; 
           [0057]      FIG. 5  represents a schematic top view of the cooling circuit provided in the component according to the invention; 
           [0058]      FIG. 6   a  represents a cross section of a portion of a first variant of the component according to the invention; 
           [0059]      FIG. 6   b  represents a cross section of a portion of a second variant of the component according to the invention. 
       
    
    
       [0060]    The same reference numbers in the drawings identify the same elements or components. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0061]    With reference to Figures from  3  to  6 , these represent an embodiment of an injection mould component for moulding the outer surface of the neck of a preform made of plastic material said component being known as “neck ring”. 
         [0062]    The mould component, object of the present invention, comprises two separate threaded half-inserts  18 ,  19 , the internal curved surfaces  20  thereof define, when one the two half-inserts  18 ,  19  have been mounted together in the rest of the mould (as in  FIG. 2  for example), a through opening and a moulding surface for moulding the outer surface of the neck of a preform such as, for example, the one illustrated in  FIG. 1   a.    
         [0063]    Each internal curved surface  20  has a substantially semi-circular profile and is provided with: 
         [0064]    a semi-circular groove  7 ′, half of an annular groove having a profile corresponding to the profile of the annular flange or support ring  7  of the preform neck to be moulded; 
         [0065]    a possible further semi-circular groove  6 ′, half of a further annular groove having a profile corresponding to the profile of the possible annular seal-tearing flange  6  of said neck; 
         [0066]    a semi-cylindrical, entirely threaded, end portion  5 ′, half of the cylindrical end portion having a profile corresponding to the profile of the threaded end portion  5  of the neck to be moulded, which extends between the groove  7 ′ or the groove  6 ′ and one end  4 ′ of the curved surface  20 . 
         [0067]    Each half-insert  18 ,  19  is also provided with portions of tapered flange  22 ,  23 , having for example a truncated cone shape. When the two half-inserts  18 ,  19  are mounted together in the rest of the mould, they are fixed together to form a seal by means of said portions of tapered flange  22 ,  23 , these portions  22 ,  23  being restrained by the rest of the mould ( FIG. 2 ). In this position, the respective internal flat contact surfaces  24 ,  25  of each half-insert rest on each other and the curved surfaces  20  combine to form the moulding surface and define the aforementioned through opening in which, during the moulding, the internal mould component or elongated core extends to form the inner surface of the preform. 
         [0068]    Each threaded half-insert  18 ,  19  is provided within its body with a cooling circuit inside which a cooling liquid, such as water, can flow. Said cooling circuit comprises (Figures from  4  to  6 ): 
         [0069]    a longitudinal inlet stretch  30  for the inlet of the water, defining an axis that is substantially parallel to the longitudinal axis of the through opening defined by the curved surfaces  20 , i.e. parallel to the longitudinal axis of the preform when it is present within the injection mould; said stretch  30 , extending from an inlet section  40  provided on an outer surface  42  of the central portion  43  of the threaded half-insert that is intermediate to said portions of tapered flange  22  and  23 ; 
         [0070]    a longitudinal outlet stretch  37  for the outlet of the water, also defining an axis that is substantially parallel to the longitudinal axis of the through opening defined by the curved surfaces  20 , i.e. parallel to the longitudinal axis of the preform when it is present within the injection mould; said stretch  37  extending from one outlet section  41  provided on said outer surface  42 ; 
         [0071]    a curved stretch  32 , the curvilinear axis thereof is arranged on a first plane which is substantially perpendicular to a plane containing the longitudinal axis of the stretch  30 , has an extension equal to the width of a circular sector having an angle of around 80+90° at the centre and is substantially equidistant from a corresponding portion of the semi-circular groove  7 ′; 
         [0072]    a longitudinal connection stretch  31  for connecting the stretch  30  to the stretch  32 , arranged on said first plane; 
         [0073]    a curved stretch  33 , which is a branch of the curved stretch  32 , having a curvilinear axis arranged on a second plane which is substantially perpendicular to a plane containing the longitudinal axis of the stretch  30  and positioned above the first plane; the curvilinear axis of said curved stretch  33 , having an extension equal to a circular section of around 170+180°, is substantially equidistant from a lateral semi-cylindrical surface  50  ( FIG. 6   a ) comprising the base surface on which the threading of the internally threaded portion  5 ′, the semi-circular groove  7 ′ and the possible semi-circular groove  6 ′ are formed; 
         [0074]    a curved stretch  34 , which is a branch of the curved stretch  32 , having a curvilinear axis arranged on a third plane which is substantially perpendicular to a plane containing the longitudinal axis of the stretch  30  and positioned beneath said first plane; the curvilinear axis of said curved stretch  33 , having an extension equal to a circular sector having an angle of around 170+180° at the centre, is substantially equidistant from said lateral semi-cylindrical surface  50  ( FIG. 6   a ); 
         [0075]    a first joint stretch  32 ′ connecting said curved stretch  32  on the first plane to said curved stretch  33  on the second plane; 
         [0076]    a second joint stretch  32 ″ connecting said curved stretch  32  on the first plane to said curved stretch  34  on the third plane; 
         [0077]    a curved stretch  35 , in which the curved stretch  33  and the curved stretch  34  converge, the curvilinear axis thereof is arranged on said first plane, is substantially equidistant from a corresponding portion of the semi-circular groove  7 ′ and has an extension equal to a circular sector having an angle of around 80+90° at the centre, 
         [0078]    a third joint stretch  35 ′ connecting said curved stretch  33  on the second plane to said curved stretch  35  on the first plane; 
         [0079]    a fourth joint stretch  35 ″ connecting said curved stretch  34  on the third plane to said curved stretch  35  on the first plane; 
         [0080]    a longitudinal connection stretch  36  for connecting the stretch  35  to the stretch  37 , arranged on said first plane. 
         [0081]    The joint stretches  32 ′,  32 ″,  35 ′,  35 ″ are also curvilinear, thus preventing the formation of stagnation points of the cooling liquid. 
         [0082]    The flow of the cooling liquid, generally water, is indicated by the arrows visible in  FIG. 4  and in  FIG. 5 . The cooling liquid enters the cooling circuit through the inlet section  40 ; it flows through the longitudinal inlet stretch  30 , the longitudinal stretch  31  and the curved stretch  32 ; it subdivides into two flows, flowing through the curved stretch  33  and the curved stretch  34 ; said two flows again converge into a single flow in the curved stretch  35 ; said single flow finally flowing through the longitudinal stretch  36  and the longitudinal outlet stretch  37  up to reach the outlet section  41  of the cooling circuit. 
         [0083]    Advantageously, all the stretches of the cooling circuit in each of the half-inserts  18 ,  19  have a circular or elliptic section and are perfectly connected whereby the cooling circuit presents no edges that can create stagnation points of the cooling liquid and consequent low cooling. 
         [0084]    A further advantage is represented by the fact that the distance between the curved stretches  32 ,  33 ,  34 ,  35  and the moulding surface of the mould component of the invention is considerably reduced compared to the distances between the stretches of the cooling circuit and the moulding surface of the mould components known in the prior art. 
         [0085]    In particular, the minimum distance d1 between the curved stretch  32  or the curved stretch  35  and the semicircular groove  7 ′ can vary from 0.8 to 5 mm, determining an optimal cooling of the preform at the support ring  7 . 
         [0086]    Advantageously, the minimum distance d3 between the curved stretch  33  and the semi-circular groove  6 ′ can also vary from 0.8 to 5 mm, determining an optimal cooling of the preform above the support ring  7 ; while the minimum distance d4 between the curved stretch  34  and the half-portion  8 ′ of moulding surface, corresponding to the annular portion  8  of the preform, can vary from 0.8 to 5 mm, determining an optimal cooling of the preform below the support ring  7 . Said annular portion  8  of the preform, which in  FIGS. 1   a  and  1   b  is represented tapered converging towards the longitudinal axis of the preform, can be either cylindrical or tapered in the direction diverging from the axis of the preform, depending on the type of preform that is to be moulded. 
         [0087]    In a first variant, the distances d1, d3 and d4 are equal to each other; in a second variant the distances d1, d3 are d4 are different from each other. 
         [0088]    Advantageously, the minimum distance d2 between the curved stretch  32  and the lateral semi-cylindrical surface  50  can vary from 0.8 to 9 mm, depending on the depth of the semi-circular groove  7 ′; the minimum distance d5 between the curved stretch  33  and the lateral semi-cylindrical surface  50  can vary from 0.8 to 9 mm, depending on the depth of the semi-circular groove  6 ′. 
         [0089]    With reference to the section of  FIG. 6   a,  the curved stretch  33  crosses a zone of the half-insert adjacent to the moulding surface of the preform above the groove  7 ′, i.e. in proximity of the moulding surface of the threading of the preform neck; while the curved stretch  34  crosses a zone of the half-insert adjacent to the moulding surface of the preform below the groove  7 ′. 
         [0090]    Advantageously, at least one or both of the stretches  33 ,  34  are, at least partially, provided in the respective portion of the tapered flange  23 ,  22 . In the example of  FIG. 6   a,  the curved stretch  33 , having for example an elliptic section, is partially provided in the tapered flange portion  23  and partially provided in the central portion  43  of the threaded half-insert, while the curved stretch  34 , having for example an elliptic section, is partially provided in the tapered flange portion  22  and partially provided in the central portion  43 . 
         [0091]    One or both of the stretches  33  and  34  may be entirely produced within the volume of the tapered flange portions  23  and  22 , respectively. In the example of  FIG. 6   b,  the curved stretch  33 , having for example an elliptic section, is entirely provided in the tapered flange portion  23 , while the curved stretch  34 , having for example an elliptic section, is entirely provided in the tapered flange portion  22 . 
         [0092]    In the event in which the neck of the preform to be moulded is unthreaded ( FIG. 1   b ), one variant of the invention provides that the separate half-inserts  18 ,  19  not be threaded; therefore the cylindrical end portion  5 ′ of the moulding surface of the component of the invention is not internally threaded. Furthermore, in this event, a further semi-circular groove in the curved inner surface  20  is half the size of a further annular groove having a profile corresponding to that of the possible annular flange  6 ″ for restraining the cap in the event in which the neck is not provided with threading ( FIG. 1   b ). 
         [0093]    The above-described cooling circuit, in all its variants, allows the cooling of the preform within the mould in the neck zone  3  ( FIG. 1 ) to be significantly improved. 
         [0094]    As regards the production process for the mould component of the invention, each half-insert  18 ,  19  can be formed by two parts  44 ,  45 . 
         [0095]    In a first variant of the production process, the outermost part  44 , comprising the longitudinal stretches  30 ,  31 ,  36  and  37  of the cooling circuit, is produced by means of a stock-removal process or EDM (Electrical Discharge Machining), while the innermost part  45 , comprising the portions of truncated cone flange  22 ,  23  and the curved stretches  32 ,  33 ,  34  and  35 , is advantageously produced by means of Sintering Laser Melting or Laser Cusing or equivalent technologies that allow products of this type to be produced starting from metal powder. 
         [0096]    In a second variant of the production process, both the outermost part  44  and the innermost part  45  of the threaded half-inserts  18 ,  19  are advantageously produced by means of Sintering Laser Melting or Laser Cusing starting from metal powder. 
         [0097]    Application of the Sintering Laser Melting or Laser Cusing technology allows at least the curved stretches  32 ,  33 ,  34  and  35  of the cooling circuit to be produced without sharp edges, while perfectly joined together, and much closer to the moulding surface of the mould component of the invention, therefore determining a more effective cooling of the preform being formed within the injection mould. 
         [0098]    These technologies can be combined with conventional process such as milling, turning, grinding, polishing, thermal treatments provided for the material used, any thermochemical surface treatments, as well as coatings such as PVD, PACVD, chromium plating, etc.