The present invention relates to a method of producing a contain¬ er of plastic material capable of being oriented and/or crystallised, a substantially tubular blank being, in at least two mutually consec¬ utive shaping phases, reshaped into the container, and mechanical for-

5 ming elements stretching the material in the axial direction of the blank and in the circumferential direction of the blank.

It is previously known in this Art. to reshape blanks,, which in- - elude axially oriented material, into containers. In such a process, the reshaping is effected by means of a blowing process in which the

10 blank is brought into abutment against forming walls whose form

(configuration)- corresponds to the form of that container which is in the process of being produced. Patent Specification GB 2 076 731 de¬ scribes a technique for the production of a bottle-like container from a blank which includes axially oriented material.

15 Patent Specification GB 2052 364 discloses a technique in which an axially stretched blank is, by one or more mechanical reshaping phases, reshaped into a container. According to the technique shown- in this Patent Specification, a reduction only of the circumference of the container body takes place on reshaping of the blank into the

20 container.

Patent Specification GB 2 052 363 describes a technique in which a blank of axially oriented material is reshaped, by a blowing pro¬ cess, into a container. Also according to this Patent Specification, an axially oriented blank is reshaped into a container. There are pressing needs within this Art for a container of plas¬ tic material which is suitable for high-temperature applications and/or for the storage of liquids under pressure, eg. the storage of carbonated soft drinks, beer etc. The term high-temperature applica¬ tion is here taken to mean that the containers are used for eg. pas- teurisation (at 60-65°C) of the contents in the filled and sealed container, for h&t-filling, by which is- taken to mean that-the.liquid- is filled directly into the containers from boiling, or for sterili¬ sation (at least 121 C) of the contents of the filled and sealed containers. Further desires relating to containers αf pl stic materia-1 are that it must be possible to produce containers whose body is of a cross section which is independent of the mouth portion of the con¬ tainer, eg. that the body has a polygonal cross section, while the mouth portion of the container is circular. The circular configura- tion of the mouth portion of the container is desirable so as to facilitate closure of the container.

So as to reduce piece costs for the containers, it is further necessary that the material d stribution in the containers be adapted to meet calculated mechanical stresses in the different parts of the container (mouth portion, container body and bottom). Furthermore, it is also necessary that the material distribution in each region

(portion) of the individual container be as uniform as possible, since the thinnest - and thereby the weakest - part in each such region is determinati e of those stresses which the container can withstand. Apart from by the material distribution, the mechanical strength of the containers is, naturally, also determined by the orientation and/or thermal crystallisation of the material.

A further requirement placed on containers of the type contem¬ plated herein, and particularly on containers intended for high-tem¬ perature applications, is that the shrinkage which occurs on heating of stretched and oriented material must be eliminated or reduced to acceptable levels.

In the storage of liquids under pressure, it is a matter of pure Laws of Physics that when there is inner pressure within the con¬ tainer, its wall material is subjected to a stress which is approxi- mately twice, as great in the ci cumferential direction as in the axial direction. Ln order to improve the strength of the plastic material, it is known in the Art to shape the container by a blowing process, the temperature of the material being adapted to suit the properties of the material being employed in order, during the blow- ing process, to stretch the material and thereby orientate it.

The blow moulding technology suffers from the drawback that the material distribution on shaping of the container is not fully under control, since, on expansion of the blank into the form of the con¬ tainer, it is not possible to exactly determine and control where and how the stretching and thereby the orientation of the material take place. Normally, the stretching commences at a number of starting

points whose positions are determined by the prevailing temperature distribution in the material and the stretching forces arising therein. The extent of the expansion and the thus obtained stretch relationship is, moreover, temperature-dependent, which, together with the heating of the material which takes place when the material crystallises in consequence of the stretching, results in that the formed container has a material thickness which varies, i.e. in one section at right angles to the axial direction the thickness of the container wall varies in the circumferential direction. Corresponding variations also occur in the axial direction of the container, i.e. in axial sections- through regions of substantially the same size of - circumference there are. alternatingly thinner and. thicker materi l portions. Thus, the prior Art techniques call for a selection of the wall thickness of the blank with reference to the above-described uncertainty in the stretching and thinning of the material ,. which entails an over-dimensioning of the blank and, thereby, also a mate¬ rial surplus and spillage in the formed container.

In order to realise temperature stability in containers of thermo¬ plastic material capable of being oriented and/or crystallised, it is known in the Art to render the containers thermally stable by caus¬ ing, during blowing of the containers, the container material to meet hot moulding walls, against which the material abuts for a relatively long period of time (of the order of magnitude of 1-2 minutes). This is attained in that an inner excess pressure is maintained within the blown container and urges the wall material against the moulding walls. However, the long cycle times involved render this technique extremely costly.

The present invention relates to a technique in which the above-outl ned drawbacks are obviated. According to the present invention, the starting point is a blank of material capable of being oriented and/or crystallised. From the blank is produced a container of high mechanical strength and thermal stability, and with improved material distribution as compared with prior Art techniques. Accord¬ ing to the present invention, the time consumed for the production of each individual container is reduced in comparison with the time con¬ sumed in prior Art techniques, the present invention also entailing a simplified production equipment structure.

Thus _* , emp-loyment of the present invention will bring about, a re¬ duction of the requisite material requirement in each container, an attainment of desired thermal stability and a reduction of costs as compared with prior Art techniques currently in use. According to the present invention, a blank of a thermoplastic material which has the property of being able to be oriented by a mechanical processing and/or to be ther ocrystalli sed by a heat treat¬ ment, is reshaped into a container in a number of mutually consecu¬ tive reshaping phases which, in one preferred embodiment, take place in mutually separate substages. In each such phase or stage, the ma¬ terial is stretched either in the axial direction or in the circum¬ ferential direction of the future container. By stretching the materi¬ al each time to a regulated and controlled extent, there will be ac¬ cumulated in the material a total stretching which corresponds to the stretching required to impart to the material the desired and prede¬ termined orientation, and thereby the requisite strength properties.

In one preferred embodiment of the present invention, the blank is reshaped, in all substages, into the container by the use of mechanical forming elements. The mechanical stretching is effected in each stage w th the material at a determined and regulated tempera- ture which may be selected within a broad range, the temperature selection being, however, determined by the special effect it is de¬ sired to attain in the currently topical shaping stage under consid¬ eration. For materials with a distinct glass transition temperature, hereafter abbreviated to TG, for example the temperature of the a- terial at certain - and as a rule at the initial - shaping stages is lower than T&,. whil at. the final shaping, stage or stages, the tempe¬ rature as a rule exceeds TG. For the material polyethylene tereph- thalate, hereafter abbreviated to PET, the temperature, in one pre¬ ferred embodiment of the present invention, is selected in the range of between 70 and 160 C for the final shaping stages, while the initial shaping stages generally take place at a lower temperature.

In certain embodiments of the present invention, the container is given its final form in a concluding blow moulding stage. In this stage, but a miner change of shape will take place in the form of an expansion in the circumferential direction, eg. of the container body, so as to give the desired cross section (eg. polygonal), while retaining the circular configuration and diameter of the mouth portion.

In a first application of the present invention, the point of departure is a cylindrical blank of material with the properties stated above, eg. a thermoplastic material such as PET. The blank has

a bottom portion of a shape which substantially corresponds in its central bottom part to the shape of the central bottom part of the container which is under production. In a first shaping stage, the material is stretched by means of a draw ring which surrounds the blank and cooperates with an internal mandrel, in the axial direction of the blank in the region most proximal the bottom. The dimensions of the mandrel and the surrounding draw ring are selected such that there is formed, between the mandrel and the draw ring, a gap, whose width is less than the thickness of the material of the blank. The stretching is effected in that relative shifting takes place between draw ring and mandrel, with the result that the material in the blank wall is forced to. pass through the gaμ, whereby the material thick¬ ness in that portion of the blank wall which passes, through the gap is reduced, during simultaneous axial stretching of the blank. As a rule, the thickness reduction corresponds to that reduction imparted to the material on free stretching, which corresponds to material flow at the temperature employed. In this stage, a first preform is created which, in conjunction with its central bottom part, has a re¬ gion with axially stretched material. In, for example, Patent Speci- fication GB 2092 943, there is described a technique for stretching and orienting of plastic material by causing the material to pass through a gap.

In the next stage, the circumference of the body of the first preform is widened, this body essentially corresponding to the cylin- drical portion of the first preform, in that a mandrel is urged into the first preform, the material in the first preform undergoing a

certain stretching in the circumferential direction during simulta¬ neous reduction of the material thickness. Here, there will be formed a second preform. Those parts of the mandrel which widen the first preform most proximal i s central bottom part have, in an axial section, a profile length substantially corresponding to the length of the axially stretched material according to trie preceding para¬ graph. The transition between the axially stretched material and the non-ax ally stretched material constitutes, in the widened first preform - i.e. in the second preform - the defining line of the cylindrical portion of the second preform most proximal the bottom portion-

The material of the. cylindrical portion of the second preform is thereafter stretched in an axial direction (with the application of a technique corresponding to that described above) by means of a draw ring which, in cooperation with an internal mandrel, forms a gap. Here, the internal mandrel is preferably the same mandrel as realised the widening of the first preform as described in the preceding para¬ graph. On stretching, the material thickness is reduced during simul¬ taneous axial elongation of the second preform. As a rule, the thick- ness reduction which the material undergoes corresponds to the reduc¬ tion imparted to the material on free stretching corresponding to ma¬ terial flow at the temperature employed. Here, there will be created an intermediate preform whose bottom portion substantially has its counterpart in the material in the bottom portion of the blank and which otherwise consists of high-grade axially stretched material which, this apart, has a certain if albeit lesser stretching in the circumferential direction of the intermediate preform.

By means of a mandrel which is urged into the intermediate pre¬ form, this preform is further widened for further stretching of the material in the circumferential direction, so as to attain that material orientation which provides the requisite strength proper- ties. The reshaping described in this passage is generally effected with the mandrel at a raised temperature for shrinking in the axial direction of the blank of the stretched material during simultaneous thermocrystallisation of the material. The term shrinking is here taken to mean the length reduction which the stretched material undergoes as a result of the heating. In this shaping stage, the intermediate preform is reshaped, into.- final preform. In certain applications, the final preform also constitutes the contemplated finished product, i.e. constitutes the container proper, while in other applications, the mouth portion of the final preform is re- shaped in adaptation to serve its intended purpose, eg. by means of mechanical devices it is given the "neck-in" which is required in order that a cap, eg. fixedly-folded with the mouth flange shall not protrude beyond the container body. In those application examples where the body of the final preform has a polygonal cross section, ^' the mouth portion is, as a rule, reshaped so as to realise a circular opening.

The nature of the present invention and its aspects will be more readily understood from the following brief description of the accom¬ panying Drawings, and discussion relating thereto. In the accompanying Drawings:

Fig. 1 is an axial section through a blank placed in an apparatus for axial orienting of material in conjunction with its bottom portion;

Fig. 2 =■ is an axial section through a preform formed by the blank of Fig. 1;

Fig. 3 is an axial section through a widened preform, together with apparatuses for the widening of the preform and axial stretching of the material in the preform;

Fig. 4 shows the intermediate preform obtained on the stretching according to Fig. 3;

Fig. 5 is an axial sectioa through the intermediate-preform, to- _. gether with apparatuses for the reshaping of the interme¬ diate preform into a final preform;

Fig. 6 is an axial section through the reshaped intermediate preform;

Fig. 7 is an axial section through a container;

Fig. 8 is an axial section through a blank of other configuration than the blank of Fig. 1;

Fig. 9 is an axial section through the blank of Fig. 8, widened into a preform;

Fig. 10 is an axial section through the blank stretched to an intermediate preform; and

Fig. 11 is an axial section through a final preform obtained by reshaping of the intermediate preform of Fig. 10.

Referring to the Drawings, Fig. 1 shows a blank 1 with a tubular blank body 2 and a bottom 3. The blank consists of plastic material capable of being oriented and/or crystallised and is, for example, produced by injection moulding or thermoforming. Within the blank, there is a mandrel 30 which is disposed for cooperation with a draw ring 20 provided outside the blank. In the mandrel and the draw ring, respectively there are channels 31 and 21, respectively, for tempe¬ rature-regulating liquid.

The mandrel 30 and the draw ring 20 are disposed for axial ove- ment in relation to one another, there being formed a circumferential gap or space between the mandrel and the draw ring. The width of the gap is adapted to the thickness of the material wall in the blank body 2, in order, on movement of the draw ring in the direction of the arrows A in relation to the mandrel 30, to reduce the material thickness of the blank body in a transitional zone between thinner and thicker material, during simultaneous stretching and orienting of the material when the transitional zone is moved towards the mouth portion of the blank.

Fig. 2 shows one embodiment in which the material is stretched only in a limited region in conjunction with the bottom portion of the blank, there being formed a first preform 10 as shown in Fig. 2. Fig. 3 and 4 illustrate a mandrel 32 provided with te perature- -regulating channels 33. The mandrel is of greater circumference than the circumference of the previously-mentioned mandrel 30, and, more- over, the mandrel 32 has, in the transition to its bottom portion, a part curved inwardly towards the centre, whose length in the axial

direction of the mandrel corresponds to the length of the axially stretched material portion of the first preform 10. A mould bottom 40, also provided with temperature-regulating channels 41, is to be found at the bottom in the Figure. The mould bottom 40 is of a con- figuration which corresponds to the form of the bottom 3. The Figure also shows a draw ring 22 with temperature-regulating channels 23. The draw ring 22 is dimensioned so as to form, between itself and the mandrel 32, a gap which is moved in a direction towards the mouth portion of a widened preform 11 on movement in the direction of the arrows B in relation to the mandrel 32. On insertion of the mandrel 32 into the firs.t.preform LQ the widened, preform (second, preform) is. .. formed and on subsequent movement of the gap, the material of the body of the widened preform is stretched and oriented in accordance with that disclosed in conjunction with Fig. 2, during simultaneous axial elongation of the preform for forming an intermediate preform 12 (Fig. 4). In Fig. 4, the draw ring 22 is shown in a position where all material in the blank body 2.has undergone axial stretching and orienting. The gap 25 formed between the mandrel and the draw ring is also apparent from this Figure. Thus, the duty of the mandrel 32 is first to cooperate with the mould bottom 40 on the expansion of the widened preform into the in¬ termediate preform 12, and secondly to cooperate with the draw ring 22 so as to form the gap 25 through which the material of the contain¬ er body has passed so as to attain the desired axial stretching of the material .

Figs. 5 and 6 show elements for reshaping the intermediate pre¬ form 12 into the final preform 13. The Figures show a mandrel 34 pro¬ vided with channels 35 for temperature-regulating liquid, and with one channel 36 for a pressure medium. The channel for pressure medium discharges in the bottom portion 37 of the mandrel, where the mandrel is of a configuration which is adapted in conformity with the configu¬ ration of the bottom 3 of the blank.

Fig. 5 also shows an outer support member 42 which surrounds the intermediate preform 12 during its reshaping and which has a central cavity 44 through which the intermediate preform 12 and the mould bottom 40. - now operating as a press plunger - pass. In the upper region of the support member (with the orientation as shown in Fig. 5), the central cavity flares so as to form, between the inner defin¬ ing surface of the outer support member and the outer defining sur- face of the mandrel 34, a gap or space through which the wall of the intermediate preform passes on its reshaping into the final preform 13. For purposes of clarity, the outer support member 42 has been omitted from Fig. 6. In certain applications, the liquid temperature- -regulating channels 43 are used for regulating the temperature of the outer support member 42.

On reshaping of the intermediate preform 12 to the final preform 13, the intermediate preform is placed within the central cavity 44 of the outer support member and is pressed by the mould bottom 40 in a direction towards the mandrel 34. Since the mandrel 34 is of a greater circumference than the inner circumference of the intermedi¬ ate preform 12, the mouth edge of the intermediate preform is urged

into abutment against the outer surface of the mandrel 34 and is moved, on continued upward movement of the mould bottom 40, outwardly and upwardly in the Figure, during simultaneous stretching of the material in the circumferential direction of the intermediate pre- form. The abutment of the plastic material of the preform aga-inst surfaces of the mould bottom 40, the outer support member 42 and of the mandrel 34 regulates the temperature of the plastic material be¬ fore, during and after the reshaping of the intermediate preform into the final preform. To stabilise the intermediate preform mechanical- ly, a pressure medium is applied through the channel 36 to the inte¬ rior of the intermediate preform. During the upwardly-directed move¬ ment of the intermediate preform, pressure medium passes between the inner wall of the intermediate preform and the mandrel 34, and there¬ by reduces the friction between the plastic material and the inner de- fining surface of the outer support member 42. Once movement is com¬ pleted, the mould bottom 40 assumes the position illustrated in Fig. 6, in which the intermediate preform is reshaped into the final pre¬ form 13. In certain embodiments of the present invention, the inner excess pressure will entail that the material is brought into abut- ment against the outer support member at least in those regions where reshaping is about to take place.

In certain applications, a reduction of the circumference of the mouth portion then takes place, there being also formed a flared flange intended to be folded together with a cap or seal once the container has been filled with its final contents.

In certain applications, the mandrel 32 is also provided with a counterpart to the pressure medium channel 36, for cooperation with outer members corresponding to that described in conjunction with Figs. 5 and 6. Figs. 8-11 show an alternative embodiment of the present inven¬ tion. The Figures illustrate axial sections of the blank la during its reshaping into the container, while, on the other hand, only some of the devices, (mandrel, mould bottom, support member, etc.) which are required in conjunction with the reshaping, are shown. However, these devices, correspond fundamentally to those already described and it will be obvious to the. skilled reader of this specification that the previously-described devices are, after certain adaptation, also suitable for use in this embodiment of the invention.

The blank la shown in Fig. 8 is reshaped to the widened preform lla in that a mandrel 32a corresponding to the previously described mandrel 32 is urged down into the blank which is simultaneously sup¬ ported by a cup-like mould bottom 45. By means of draw rings 22a, the material is thereafter stretched in the axial direction of the blank, an intermediate preform 12a being formed. This is thereafter widened in its circumferential direction by means of a technique correspon¬ ding to that described in conjunction with Figs. 5 and 6, to reshape the intermediate preform 12a into the final preform 13a. By means of thermoforming between a die 46 and the mandrel 34a, the bottom por¬ tion 18a of the intermediate preform is reshaped to a form correspon- ding to the form of the central bottom part of the bottom portion 16 of the container. Reshaping of the final preform 13a into the contain

er 14 takes place in complete agreement and correspondence with the previous description and generally in the stage when the intermediate preform is reshaped to the final preform.

It will be clearly apparent from the body of this description

5 that, in certain applications, the shaping, as illustrated in Fig. 2, of the first preform 10 is not used, but that the blank 1 has a cir¬ cumference which is adapted to orienting the material as described in the discussion in conjunction with Fig. 3.

All drive means which realise the movements of the mechanical

10. elements have been omitted from the Drawings. It is obvious to the skilled reader of this specification that these may be arranged and provided according to prior Art techniques, eg. such as mechanical, hydraulic or pneumatic drive means.

The temperature of the material is set and adjusted as required

15 and intended for in each shaping and processing stage by means of the temperature-regulating liquid channels 212331,33,35,41,43 of the mechanical elements. It will also be apparent from this description that separate parts of the shaping apparatus are, if necessary, ad¬ justable to different temperatures at each individual processing oc- 0 casion or stage.

As has already been mentioned, the blank is expanded in its cir¬ cumferential direction, for stretching of the material in the wall of the blank. For materials with a distinct TG, at least the axial, and also the final stretchings, are generally effected at a temperature in

25 excess of TG. For, for example, PET, stretching generally takes place in the temperature range of between 70 and 130°C. In certain embodiments,

the expansion in the circumferential direction is effected in one single reshaping stage, whereas, in other embodiments, in which a greater degree of stretching is contemplated, the expansion takes place in several consecutive reshaping stages. It generally applies that a least the final shaping stage takes place, as a rule, at a raised temperature in order to thermocrystallise the plastic mate- rial .

By means of the mechanical reshaping process the stretching and * distribution of the material is exactly controlled both in the axial and circumferential direction of the blank or preform and also exact¬ ly controlled in each forming step. The final product will thus in each region (portion) possess a thickness, an orientation and/or a crystallisation adapted to the expected stresses in each specific region of the product. In contrary to a prior Art container, a con- tainer made according to the method now presented has, as an example, circumferential material sections at right angles to the axial direc¬ tion of the container, the sections consisting of material of uniform thickness, orientation and/or crystallisation. The term crystallisa¬ tion is related to the crystallisation produced by stretching and/or b heating the plastic material.

In certain embodiments of the present invention, an outer coating is onlaid onto the material, for example a barrier material prevent¬ ing the passage of light, radiation and/or gas, decorative artwork, etc., in conjunction with that stage in which the intermediate pre- form is reshaped into the final preform. In this instance, at least the surface material of the intermediate preform is rapidly heated,

for exmple by so-called flame treatment, whereafter the outer surface of the intermediate preform is provided with the desired coating, eg. by immersion dipping, by sprying, by roller coating, etc. The thus treated intermediate preform is subsequently pre-dried, eg. when PET is used, preferably at a temperature in the range of between 50 and 60 C, whereafter the thus treated intermediate preform undergoes the above-described mechanical reshaping into the final preform. The mechanical reshaping into the preform is preceded, in certain appli¬ cations, by a temperature conditioning of the material of the inter- mediate preform. However, as a rule, such temperature conditioning is concentrated to the bottom portion of the intermediate preform, in order, in those applications in which the bottom portion of the inter¬ mediate preform is reshaped on forming of the final preform, to facil¬ itate reshaping of the bottom portion. A considerable advantage inherent in the above-described tech¬ nique is that mechanical elements control and determine, on forming of the container, the stretching and the thickness reduction of the material in each individual material portion and at each individual shaping stage. The employment of an internal mandrel against which the material abuts also ensures a reliable and rapid thermal adjust¬ ment of the material to the temperature determined for each individ¬ ual shaping stage. In particular in the final shaping stages, the abutment against the internal mandrel makes for an extremely short material temperature adjustment time, eg. for shrinking and/or ther- mal crystallisation of the material, since the wall thickness in the final shaping stages is reduced. By combining this inner temperature

regulation with a temperature regulation acting against the outer sur¬ face of the material, eg. heating or cooling, the temperature adjust¬ ment time will be further reduced.

The above-described flame treatment of the material imparts to the surface layer an excellent adhesion capability of the on!aid layer. Any possible subsequent pre-drying in combination with pos¬ sible temperature conditioning of the intermediate preform prior to its reshaping into the final preform, and the above-described shrink¬ ing together with thermal crystallisation of the final preform all make for a reliable adhesion of the onlaid layer.

The above detailed description relates only to a limited number of embodiments of the present invention, but the skilled reader of this specification will readily perceive that the invention accomo- dates a great number of modifications in embodiments, without depart- ing from the spirit and scope of the appended Claims.