WO2011045739A1

WO2011045739A1 - Preform of plastic material with recesses formed on the head thereof

Info

Publication number: WO2011045739A1
Application number: PCT/IB2010/054607
Authority: WO
Inventors: Gianfilippo Pagliacci
Original assignee: Concordia Development S.R.L.
Priority date: 2009-10-16
Filing date: 2010-10-12
Publication date: 2011-04-21
Also published as: ITMI20091782A1; TW201139096A; AR078661A1

Abstract

Preform (1) of plastic material for the manufacture of bottles by means of a blow-moulding process, comprising a substantially cylindrical central body (3) having an open end (2) and an opposite end closed by a head (4). In correspondence of said head (4) there are provided multiple adjacent recesses (5), said recesses (5) having corresponding projections (6) towards the inside of the preform (1) such as preform thickness at said recesses (5) is substantially equal to preform thickness at the remaining adjoining portions of said head (4) and such as to allow the passing between said projections (6) of a stretching rod of said preform. The remaining lateral portion of the head (4) may have a spherical, conical, elliptical or parabolic shape and may be provided with a central and projecting appendix of a rounded shape.

Description

PREFORM OF PLASTIC MATERIAL WITH RECESSES FORMED ON THE HEAD THEREOF

DESCRIPTION

FIELD OF THE INVENTION

The present invention refers to an improved preform for the manufacture of hollow bodies and, in particular, of bottles of any kind and size, by means of a blow-moulding process.

STATE OF THE PRIOR ART

As it is well known to people skilled in the field, the manufacture of bottles or jars of plastic material today is almost exclusively carried out by means of a 2-phase process which comprises the production and use of hollow semi-finished raw pieces having a substantially cylindrical shape, known as preforms or parisons. In the first phase of such process production is hence carried out - in a strongly centralised way, i.e. at few specialised manufacturers - almost always by injection moulding, of large-thickness hollow preforms having longitudinal and transversal size in a ratio of about 1:2 to 1:4 with respect to those of the finished bottle. In the second phase of the process - which instead is usually carried out at the same plant where bottling of the liquid to package is carried out - the hollow preforms are heated to a temperature sufficient to obtain the necessary softening thereof, inserted in a blowing mould, stretched to the final bottle length by means of a stretching rod which is inserted into the preform, and hence blow-moulded by introducing into the heated and stretched preform one or more compressed air flows.

This manufacturing system allows remarkable and various advantages in the entire manufacturing chain, well-known to the people skilled in the field and which it is hence not necessary to recall here, which advantages have determined - as stated above - the almost general adoption, at global level, of this manufacturing system to obtain hollow bodies and in particular bottles of any kind, shape and size.

In particular, the above described process has found a particularly effective application with the use of crystal plastic materials, such as for example PET (polyethylene- terephtalate) , which during the blowing process undergo orientation of the crystal structure such as to impart the bottle particularly satisfactory mechanical features, even with extremely low final thicknesses of the material.

Precisely for this type of bottle constant research has hence developed for optimising the manufacturing process so as to reduce - the final bottle volume being equal - the amount of plastic material used which represents about 90% of the final cost of the bottle. Up until today such research has mainly addressed on the one hand shape changes of the finished bottle (in order to create greater shape stability) and, on the other hand, the implementation of the various moulding parameters (stretching ratio of the preform, heating temperature, pressure of the blowing air and the like) .

Substantially unchanged has instead remained over time the preform shape which - as stated - consists of a hollow cylindrical body, with constant or varying thickness, the open end of which already has the final shape of the bottle neck area - and hence also provided with the necessary threading for the coupling with the screw cap - and the closed end of which has in most cases the shape of a hemisphere.

In order to reduce the amount of plastic material which, in the finished bottle, remains in the central area of the bottom of the same, preforms with non-spherical head have furthermore been proposed and partly used and, in particular, with a head having a conical, elliptical or parabolic shape. However, while preforms of this type have actually allowed some advantages in terms of preform moulding, allowing a modest reduction of moulding times due to the smaller amount of plastic molten material to be injected corresponding to the different geometry of the preform, they have not allowed instead appreciable results in terms of weight reduction in the above-said central area of the bottom of the bottle, since the distribution of material in the finished bottle was not finally significantly different from that of the bottles obtained from preforms with a hemispherical head.

More recently, in EP-2077934 in the name of the same Applicant, a preform provided with a projecting, rounded, central appendix has been suggested, by which it was possible to achieve a remarkable weight reduction of the preform, the performances of the same being equal.

PROBLEM AND SOLUTION

The object of the present invention is hence that of providing another type of improved preform which has a remarkably reduced weight - the features of size and resistance of the bottle obtained therefrom being equal - with respect to that of currently used known-type preforms, similarly to what occurred for the preform described in EP-2077934, but with a different construction solution which may have a more immediate application in replacing traditional preforms and which may furthermore arise a smaller resistance to change in the affected sectors .

Another object of the invention is that of providing an improved preform which may be used in replacing traditional, known preforms, while maintaining unchanged the stretching ratios in the blowing procedure.

A further object of the invention is that of providing an improved preform by which it is possible to obtain a weight reduction of the bottle obtained therefrom, such reduction being concentrated in correspondence of a central area of the bottom of the bottle.

Such objects are achieved, according to the present invention, by means of a preform having the features defined in the attached claim 1. Further features of the preform of the invention are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention are in any case more evident from the following detailed description of a preferred embodiment, given purely by way of a non-limiting example and illustrated in the attached drawings, wherein:

fig. 1 is a schematic side elevation view of an improved preform according to the present invention; and

figs. 2A, 2B and 2C are longitudinal-section, partial views of various embodiments of the preform according to the present invention .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As appears clearly from the drawing, preform 1 according to the invention has a completely traditional structure, both in terms of the shape of open end 2, provided in a known way with threading and ribbings for the housing and abutment of the bottle cap, and in terms of the elongated, cylindrical shape of body 3 of the preform.

As a matter of fact, the innovation of the preform of the invention lies exclusively in the shape of the closed end or head 4 of the preform, opposite to its open end 2, normally of a semi-spherical shape. As stated above, the preform head may also have a conical, elliptical or parabolic shape and also have a projecting central appendix of the type described in EP-2077934; however, for simplicity's sake, in the following reference will be exclusively made to the semi-spherical head, by this term hence intending all the possible head shapes mentioned above.

As a matter of fact, head 4 has a series of recesses 5, preferably evenly distributed on the lateral surface of head 4, in correspondence of a spherical segment of said head - i.e. in an area lying between two mutually parallel planes and perpendicular to the preform axis - said recesses 5 being adequately joined to the remaining lateral portion of head 4 and having corresponding projections 6 towards the inside of the preform so that preform thickness at said recesses 5 is substantially equal to preform thickness at the remaining adjoining portions of said preform head 4. Maintaining a substantially constant thickness of the preform in correspondence of recesses 5 is in fact a preferred requirement for obtaining good performances of the bottles obtained by the preform of the invention. First of all, a narrowed cross section of the preform head in correspondence of said recesses could give rise to a partial crystallization of the preform in the injection moulding phase thereof; secondly, a different thickness in different portion of the preform head will give rise to a bottle having a varying thickness in its bottom; thirdly, during the preheating step of the blow-moulding process thinner parties of the preform head could become soft in too a short time and require therefore adjustment of the moulding parameters to avoid any irregularities or defects in the finished bottle, in particular as far as regards burst resistance and stress-cracking resistance of the finished bottle. The remaining lateral portion of head 4 may have any one of the known shapes described above and, preferably, has a hemispherical shape.

The shape of recesses 5, the number and size thereof are not particularly limited, being it only necessary that in the correspondence of such recesses no substantial preform thickness changes occur and that the part most projecting towards the inside of head 4 of projections 6 leaves a central space sufficiently large to allow the passage of the stretching rod of the preform (not shown), at the beginning of the moulding phase. In the various embodiments illustrated in section, recess 5 has a concave shape (fig. 2A) , an even shape (fig. 2B) , and a double-convexity shape (fig. 2C) , respectively. Other shapes are of course possible, for example by means of a combination of various curvatures among those mentioned above, as it is also possible to vary widely the height of the spherical segment occupied by recesses 5, which may also extend until it occupies entire head 4. In other words, recesses 5 may extend from one side to the top of head 4 and from the other side to the circumference joining head 4 and cylindrical body 3.

Within the above-said variability ranges, the sizes and shape, as well as the number of recesses 5 may be varied at will, depending on the desired results, for example for the purpose of concentrating the weight loss of the preform in correspondence of the central area of the bottom of the bottle formed with the same, or for other objects which from time to time become useful or convenient for the individual, various applications .

Due to the particular, above-described shape of the preform of the invention, the extraordinary result is obtained of a preform having a considerably reduced weight with respect to a known-type preform of equal thickness and height, due to the fact that the overall surface of the preform of the invention evidently has a smaller development than that of a corresponding traditional preform with fully hemispherical head and of equal height, considering that for each point of head 4 the areas affected by recesses 5 develop along more internal circumferences and hence shorter ones than those of the corresponding hemispherical surface. This remarkable result is furthermore obtained without having to vary in the least the other features of the preform, and in particular the axial stretching ratio of the same, due to the fact that the stretching rod may pass through projections 6 until it touches the internal vertex of the preform and it hence determines an elongation of the preform of the invention identical to the one which it would determine in a conventional preform with hemispherical head of equal overall height.

The preform of the invention can hence replace a traditional preform without the need to carry out a new calibration of the blow-moulding process - also due to the fact that the hemispherical areas of head 4 lying between adjacent recesses 5 represent a sort of reticular structure joining to the below-lying cylindrical body 3, whereto they hence transfer the stretching action induced by the stretching rod in a way substantially identical to what occurs in a traditional preform - and thereby obtaining, in a simple and direct way, a remarkable reduction of the preform weight, and hence of the finished bottle, thus reaching the first and the second object of the invention.

Moreover, by suitably adjusting the size parameters, shapes and the number of recesses 5 it is furthermore possible to concentrate the weight reduction in correspondence of the central part of the bottom of the bottle obtained by blow- moulding said preform, thereby reaching also the third object of the invention.

The head of the preform of the present invention, as stated above, may be used also in combination with a rounded central appendix as described in EP-2077934, thus obtaining an even more marked overall weight reduction of the preform.

The present invention has been described with reference to a preferred embodiment of the same, but it is clear that a number of other embodiments which use the principle of the invention can differ therefrom. The invention is hence in no way limited by the features of the described embodiment, but only by the definitions of the invention supplied in the attached claims .

Claims

1) Preform (1) of plastic material for the manufacture of hollow bodies through a blow moulding process, wherein said preform (1) comprises a substantially cylindrical central body (3) having an open end (2) and an opposite end closed by a rounded head (4) , characterised in that in correspondence of the lateral surface of said head (4) a plurality of spaced apart recesses (5) are provided, said recesses (5) having corresponding projections (6) towards the inside of the preform (1) such as preform thickness at said recesses (5) is substantially equal to preform thickness at the remaining adjoining portions of said head (4) .

2) Preform as claimed in claim 1), wherein said hollow body is a bottle or a jar and said open end (2) makes up the neck area of the finished bottle, intended to form the seat of application of a cap.

3) Preform as claimed in claim 2), wherein said head (4) has a spherical, conical, elliptical or parabolic shape.

4) Preform as claimed in claim 3), wherein said recesses (5) are formed in correspondence of a head area comprised between two mutually parallel planes which are perpendicular to the preform axis.

5) Preform as claimed in claim 4), wherein said recesses (5) have a concave, planar, convex or mixed shape.

6) Preform as claimed in claim 5) , wherein said recesses

(5) are joined, in correspondence of the periphery thereof, to the remaining portion of said head (4) .

7) Preform as claimed in claim 6), wherein said recesses

(5) extend as far as the vertex of the preform head (4) .

8) Preform as claimed in claim 6), wherein said recesses extend as far as the connecting circumference between said preform head (4) and said cylindrical body (3) .

9) Preform as claimed in any one of the preceding claims, wherein the portions of said projections (6) which extend furthest towards the preform (1) inside determine a minimal inner port sufficient for causing the free end of a stretching rod of said preform (1) to pass through between them,

10) Preform as claimed in any one of the preceding claims, wherein said head (4) has a rounded appendix projecting in correspondence of its vertex.