CA1210915A - Process for the production of a blank for containers and blank produced by the process - Google Patents
Process for the production of a blank for containers and blank produced by the processInfo
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- CA1210915A CA1210915A CA000487316A CA487316A CA1210915A CA 1210915 A CA1210915 A CA 1210915A CA 000487316 A CA000487316 A CA 000487316A CA 487316 A CA487316 A CA 487316A CA 1210915 A CA1210915 A CA 1210915A
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- tube
- moulding
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- thickness
- glass transition
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Abstract
ABSTRACT OF THE DISCLOSURE
There is described an apparatus for the manufacture of a tubular pre-moulding from a thermo-plastic material. The apparatus can axially stretch a tube of the thermoplastic material to a substan-tially reduced material thickness in at least a cen-tral zone of the tube while substantially maintaining the diameter of the tube in the axially stretched section in the central zone. The reduction is by a factor sufficient to cause yielding and orienting of the material substantially in the axial direction of the future pre-moulding. The apparatus can also effect the axial stretching of the tube at a temperature not greater than the glass transition temperature of the thermoplastic material. A mould surrounds the tube, and the material is heated in one of the oriented zones to a temperature above the glass transition temperature. The material is expanded in the radial direction of the tube until it makes contact with the mould to form a mouth part with adjacent neck section of the pre-moulding, the material then being cooled to a temperature below the glass transition tempera-ture, thereafter heated at one end of the tube to a temperature above the glass transition temperature and formed as a closure at the one end for the pre-moulding.
There is described an apparatus for the manufacture of a tubular pre-moulding from a thermo-plastic material. The apparatus can axially stretch a tube of the thermoplastic material to a substan-tially reduced material thickness in at least a cen-tral zone of the tube while substantially maintaining the diameter of the tube in the axially stretched section in the central zone. The reduction is by a factor sufficient to cause yielding and orienting of the material substantially in the axial direction of the future pre-moulding. The apparatus can also effect the axial stretching of the tube at a temperature not greater than the glass transition temperature of the thermoplastic material. A mould surrounds the tube, and the material is heated in one of the oriented zones to a temperature above the glass transition temperature. The material is expanded in the radial direction of the tube until it makes contact with the mould to form a mouth part with adjacent neck section of the pre-moulding, the material then being cooled to a temperature below the glass transition tempera-ture, thereafter heated at one end of the tube to a temperature above the glass transition temperature and formed as a closure at the one end for the pre-moulding.
Description
~ 5 This appllcation is a divi.sion of application Serial No. 466,796, filed October 31, 1984.
I~e lnvention relates to a tubular pre-moulding of a thermoplastic, suitable for subsequent shaping to give containers by a blow-moulding process, and to a process and eaAuipment for producing the pre-moulding.
~ a tube, future mouth parts and parts o~ adjacent neck sections are moulded to pre-m~uldings, from two blank parts joined to one another, by an axial stretch process and a blow-moulding process, the parts in the transition between the two mouth parts being severed in order to form two separate blank parts which~ after closing at one of the ends and subsequent reworking to produce the re~uisite closing surfaces at the respective ~ther ends, each alone form a tubular pre-moulding~
- Xn a production process used for the manufacture of containers from a thermoplastic, blanks normally called p~e-mouldings for containers are produced from severed parts of extruded long tubes of an amorphous thermoplastic. At one end, the severed pieces are shaped in such a way that they form the future mouth part of the container, whilst they are closed at the opposite endO
~ he present invention eliminates certain disad-vantages connected with the production process indicated above, according to the known terhnology. ~X~
.. _ . . . _ . .. .
The invention is suitable especially for the manufac~ure of containers ~rom a thermoplastic of the p~lyes-~er or polyamide type. Examples of such materials are polye~hylene terephthalate, polyhexamethylene-adipamide, polycaprolactam, polyhexamethylene-sebacamide, polyethylene 2,6- and 1,5-naphthalate, polytetramethylene 1~2-dihydroxybenzoate and copolymers of ethylene terephthalate, ethylene isophthalate and similar .polymers. T~e description of the invention below relates mainly to p~lyethylene terephthalate, called -PET in the further text, but the invention is not restricted only to the use of either this material or one of the other materials already mentioned; instead, it is also applicable to many other thermoplastics.
For a better understanding of the existing .problem and of t~e invention, several characteristic properties of the polyester polyethylene terephthalate ~re described below. From the literature, lor exam~le Properties of Polymers, by D.W. van Krevelen, Elsevier Scientific ~ublishing Company, 1976J it is known that the properties of the material change when amorphous poly-ethylene terephthalate is oriented. Some of these changes are shown in the diagrams, Figures 14.3 and 14.4 on pages 317 and 31g in the book "Properties of Polymers".
The symbols used in the discussion oelow correspond to - . the symbcls in the said bo~k.
- PET, like many other thermoplastî.cs, can be ~ oriented by stretc~ing the material. Nvrmally this stretching takes place at a temperature abo-ve the glass transiti~n temperature Tg of the material. The strength properties of the material are improved by orienting. The literature shows that, in the case of ~he thermoplastic PET, an increase in the stretching ratio~ that is to say the quo~ient of the length of the stretched material and the length of the unstretched material, also leads to an increase in the impro~ement of the material properties~ When the stretching ratio J~ is increased from about 2 tu a little more than 3~
particularly large changes in the material properties are obtained~ The strength in the direction of orien-tation is here markedly improved, whilst at the same time the density-~ and likewise the crystallinity Xc rises and the glass transition temperature Tg is raised. It can be seen from the diagram on page ~17 that3 a~ter stretch-in~ with~ assuming the value of 3.1, the material with-stands a force per unit area, which corresponds to ~ = 10 coupled with a very small elongation, whilst the elonga-tion at~ 2.B is substantially larger. In the further text, the term "step" is sometimes used to designate orienting which is obtained by stretching, or a reduction in thickness by about 3 times, and which leads to the-marked improvements of the material properties, indicated above.
The diagrams quoted above show changes which are obtained on mono-axial orientation of the material.
In biaxial orientation, similar effects are obtained in S
both directions of orienta~ion. - Orientation is carried out as a rule by successive stretchings.
Improved material propertie.s, corresponding to th~se which are obtained by the ~Istep~ defined above, are also ~btained if an amorphous ma~erial is st~etched until it ~lows and, before flowing, the material is at a tem-perature which is below the glass transition temperature Tg, In a rod being drawn9 a reduction of the diameter of.about 3 times results in the flow zoneO On drawingg the flow zone i5 continuously displaced into the amorphous material, whilst at the same time the material~ which has already undergone the state of flowing, absorbs the tensile forces of the test rod w;thout an additional permanent stretchingO
For bottlesS defined external diameters of the mouth with the associated thread are standardised and, in the technology known at present when using the moulding .process described as an introduction, this determines the.
greatest diameter which is permissible in the blow .moulded container body. The reasons for this are explained in more detail in the following text. In order to obtain an amorphous starting material for the pieces of tube, which are to be shaped into pre-mouldings, .~he material must be cooled rapidly to below the glass transition temperature Tg after extruding - in ~he case of ext~uded tubes from which the pieces of tube are severed. In the case of excessive wall thickness, the materi~l does not possess adequate heat conductîvity t~
, .
enable the central sect.ions of the wall ~o ~e cooled as rapidly as required, so that the material located in the centre becomes crystal~ine ancl opaqueO For this reason 9 viewed theoretically, the largest possible wall thickness of the extruded tubes.is less than about ~ mm.
In practice, however, wall thicknesses of less than 4 mm are used as a rule. In fact, in blow-moulding of a pre-moulding having wall material of excessive thickr.ess, problems arise due to the cooling of the material during the actual blow-moulding step and be~ore the material reaches the wall of the mould. The blow-moulded con-tainer is no longer clear as glass and, instead 9 contains opaque white sections. In blow-moulding, in order to obtain containers having the requisite resistance against stresses and penetration o~.the container..wall, the wall thickness of the finished container must not fall below a defined value. Moreover, a reduction of the external diameter of the tube during the shaping of the mouth part of the pre-moulding is not possible in accordance with known technology. The result is that the desired mouth diameter of the blow-moulded container is decisive for the diameter of the pre-moulding and thus for the maximum diameter of the blow-moulded container body.
If bottles of large capacity are required, these bottles are extended, according to known technology, in the axial direction after they have reached the maximum possible -diameter.-- In additiQn to the disadvantage of a certain instability, the extension represents an unsatisfactory utilisation of the quantity of material in the container body since the re~uisite quanlity of mate~ial per unit volume of storage capacity is greater than would be necessary if ~oth the diameter and the length of the container body were adapted to the actual volume required.
Moreover, the unnecessarily large sur~ace of the con-tainer leads to a corresponding increase in the overall penetration of carbon dioxide during the storage of beverages containing carbonic acid.
To utilise the material properties of the material in the best way, it is desirable that the diameter of those parts of the pre-moulding which, after the blow-moulding step, represent the actual container body, is given a value which has the result that the material in the blow-moulded container body assumes the desired orientation. In containers of PET it is desirable that the material, in conjunction with blow-moulding7 is biaxially stretched in such a way that the product of the stretchings is about 9.
The above shows that, according to known teoh-nology, the quantity of material in the mouth part is not determined by the calculated stresses but by the maximum diameter of the container body. As a rule, this leads to a considerable excess of material in the mouth part.
For example, in a PET bottle of 1 litre capacityy the mouth part can, according to known technology, contain up to 25-30% of the total ~uantity of ~aterial. Dis-regarding the unpl-easant appearance of the oversizing sf the mout~ part, this fact also results in a waste of material, which i5 of importance in the mass production s of articles.
. In the technology applied at present, the m~uth part and adjacent neck partsconsist of unoriented material, that is to say amorphous matlerial. This means that the material in the mouth par~ including the adjacent neck parts has properties which differ from those of the con-tainer body. In containers of, for example, PET, the material in the mouth part has a glass transition tem-perature Tg of 71C, whilst the glass transition tempera-ture ~f the material in the container body is about 81C.
It follows from this that the material in the mouth part so~tens at a lower temperature than the material in the container body.
It is already known, by cold-forming of the m~uth part of the blank, to displace material downwards ~rom th~
mouth part into the sections of the blank, which later represent the wall sections of the container body. In this way, a certain matching of the quantity of material in the mouth part to the ~uture stresses is achieved but, between the actual container body and the mouth part 5 neck sections are formed in which the material is stre~ched by a factor of less than 3. These neck sections in the moulded container thus consist of inadequately oriented material, whilst at the same time the wall thickness is undesirably large. This metho~ is also known from Canadian Application No. 322,4~9, filed Fëbruary 28, 1979, inventor, Kjell M. Jakobsen. British Patent Specification 1,536,194 puhlished December 20, 1978 to Carnaud Total Interplastic has disclosed a method wherein a tubular blank, which is closed at one end and which is provided at the other ena with ` E3 --beading for fixing the blank :in a downstream blowing element, is injection-moulded and wherein the tubular blank is blow-moulded after-a certain reshaping to give a container. Material in the tubular part of the blank is expanded in the radial direction at a temperature abo~e tlle glass transition temperature Tg in order thus to form the mouth part of the container. A container ~ormed in the manner described possesses a mouth part and a neck section in which the material has been exposed to only very slight s~retching and hence orienting, 50 that the disadvantages, already indicated, with respect to the mouth part of the known containers are also present in this container.
The invention described in-Bri~tish Patent Specifica-tion 1,536,194 also has the disadvantage that only a part of the material content of th~ injection-moulded tubular blank is utilised when reshaping the blank to give the finished con~ainer. It is obvious that the losses of materiaL, ~ich occur in this process, represent an economic disadvan'cage in the mass production of articles.
From Federa~ German Of~enlegungsschrift DOS
I~e lnvention relates to a tubular pre-moulding of a thermoplastic, suitable for subsequent shaping to give containers by a blow-moulding process, and to a process and eaAuipment for producing the pre-moulding.
~ a tube, future mouth parts and parts o~ adjacent neck sections are moulded to pre-m~uldings, from two blank parts joined to one another, by an axial stretch process and a blow-moulding process, the parts in the transition between the two mouth parts being severed in order to form two separate blank parts which~ after closing at one of the ends and subsequent reworking to produce the re~uisite closing surfaces at the respective ~ther ends, each alone form a tubular pre-moulding~
- Xn a production process used for the manufacture of containers from a thermoplastic, blanks normally called p~e-mouldings for containers are produced from severed parts of extruded long tubes of an amorphous thermoplastic. At one end, the severed pieces are shaped in such a way that they form the future mouth part of the container, whilst they are closed at the opposite endO
~ he present invention eliminates certain disad-vantages connected with the production process indicated above, according to the known terhnology. ~X~
.. _ . . . _ . .. .
The invention is suitable especially for the manufac~ure of containers ~rom a thermoplastic of the p~lyes-~er or polyamide type. Examples of such materials are polye~hylene terephthalate, polyhexamethylene-adipamide, polycaprolactam, polyhexamethylene-sebacamide, polyethylene 2,6- and 1,5-naphthalate, polytetramethylene 1~2-dihydroxybenzoate and copolymers of ethylene terephthalate, ethylene isophthalate and similar .polymers. T~e description of the invention below relates mainly to p~lyethylene terephthalate, called -PET in the further text, but the invention is not restricted only to the use of either this material or one of the other materials already mentioned; instead, it is also applicable to many other thermoplastics.
For a better understanding of the existing .problem and of t~e invention, several characteristic properties of the polyester polyethylene terephthalate ~re described below. From the literature, lor exam~le Properties of Polymers, by D.W. van Krevelen, Elsevier Scientific ~ublishing Company, 1976J it is known that the properties of the material change when amorphous poly-ethylene terephthalate is oriented. Some of these changes are shown in the diagrams, Figures 14.3 and 14.4 on pages 317 and 31g in the book "Properties of Polymers".
The symbols used in the discussion oelow correspond to - . the symbcls in the said bo~k.
- PET, like many other thermoplastî.cs, can be ~ oriented by stretc~ing the material. Nvrmally this stretching takes place at a temperature abo-ve the glass transiti~n temperature Tg of the material. The strength properties of the material are improved by orienting. The literature shows that, in the case of ~he thermoplastic PET, an increase in the stretching ratio~ that is to say the quo~ient of the length of the stretched material and the length of the unstretched material, also leads to an increase in the impro~ement of the material properties~ When the stretching ratio J~ is increased from about 2 tu a little more than 3~
particularly large changes in the material properties are obtained~ The strength in the direction of orien-tation is here markedly improved, whilst at the same time the density-~ and likewise the crystallinity Xc rises and the glass transition temperature Tg is raised. It can be seen from the diagram on page ~17 that3 a~ter stretch-in~ with~ assuming the value of 3.1, the material with-stands a force per unit area, which corresponds to ~ = 10 coupled with a very small elongation, whilst the elonga-tion at~ 2.B is substantially larger. In the further text, the term "step" is sometimes used to designate orienting which is obtained by stretching, or a reduction in thickness by about 3 times, and which leads to the-marked improvements of the material properties, indicated above.
The diagrams quoted above show changes which are obtained on mono-axial orientation of the material.
In biaxial orientation, similar effects are obtained in S
both directions of orienta~ion. - Orientation is carried out as a rule by successive stretchings.
Improved material propertie.s, corresponding to th~se which are obtained by the ~Istep~ defined above, are also ~btained if an amorphous ma~erial is st~etched until it ~lows and, before flowing, the material is at a tem-perature which is below the glass transition temperature Tg, In a rod being drawn9 a reduction of the diameter of.about 3 times results in the flow zoneO On drawingg the flow zone i5 continuously displaced into the amorphous material, whilst at the same time the material~ which has already undergone the state of flowing, absorbs the tensile forces of the test rod w;thout an additional permanent stretchingO
For bottlesS defined external diameters of the mouth with the associated thread are standardised and, in the technology known at present when using the moulding .process described as an introduction, this determines the.
greatest diameter which is permissible in the blow .moulded container body. The reasons for this are explained in more detail in the following text. In order to obtain an amorphous starting material for the pieces of tube, which are to be shaped into pre-mouldings, .~he material must be cooled rapidly to below the glass transition temperature Tg after extruding - in ~he case of ext~uded tubes from which the pieces of tube are severed. In the case of excessive wall thickness, the materi~l does not possess adequate heat conductîvity t~
, .
enable the central sect.ions of the wall ~o ~e cooled as rapidly as required, so that the material located in the centre becomes crystal~ine ancl opaqueO For this reason 9 viewed theoretically, the largest possible wall thickness of the extruded tubes.is less than about ~ mm.
In practice, however, wall thicknesses of less than 4 mm are used as a rule. In fact, in blow-moulding of a pre-moulding having wall material of excessive thickr.ess, problems arise due to the cooling of the material during the actual blow-moulding step and be~ore the material reaches the wall of the mould. The blow-moulded con-tainer is no longer clear as glass and, instead 9 contains opaque white sections. In blow-moulding, in order to obtain containers having the requisite resistance against stresses and penetration o~.the container..wall, the wall thickness of the finished container must not fall below a defined value. Moreover, a reduction of the external diameter of the tube during the shaping of the mouth part of the pre-moulding is not possible in accordance with known technology. The result is that the desired mouth diameter of the blow-moulded container is decisive for the diameter of the pre-moulding and thus for the maximum diameter of the blow-moulded container body.
If bottles of large capacity are required, these bottles are extended, according to known technology, in the axial direction after they have reached the maximum possible -diameter.-- In additiQn to the disadvantage of a certain instability, the extension represents an unsatisfactory utilisation of the quantity of material in the container body since the re~uisite quanlity of mate~ial per unit volume of storage capacity is greater than would be necessary if ~oth the diameter and the length of the container body were adapted to the actual volume required.
Moreover, the unnecessarily large sur~ace of the con-tainer leads to a corresponding increase in the overall penetration of carbon dioxide during the storage of beverages containing carbonic acid.
To utilise the material properties of the material in the best way, it is desirable that the diameter of those parts of the pre-moulding which, after the blow-moulding step, represent the actual container body, is given a value which has the result that the material in the blow-moulded container body assumes the desired orientation. In containers of PET it is desirable that the material, in conjunction with blow-moulding7 is biaxially stretched in such a way that the product of the stretchings is about 9.
The above shows that, according to known teoh-nology, the quantity of material in the mouth part is not determined by the calculated stresses but by the maximum diameter of the container body. As a rule, this leads to a considerable excess of material in the mouth part.
For example, in a PET bottle of 1 litre capacityy the mouth part can, according to known technology, contain up to 25-30% of the total ~uantity of ~aterial. Dis-regarding the unpl-easant appearance of the oversizing sf the mout~ part, this fact also results in a waste of material, which i5 of importance in the mass production s of articles.
. In the technology applied at present, the m~uth part and adjacent neck partsconsist of unoriented material, that is to say amorphous matlerial. This means that the material in the mouth par~ including the adjacent neck parts has properties which differ from those of the con-tainer body. In containers of, for example, PET, the material in the mouth part has a glass transition tem-perature Tg of 71C, whilst the glass transition tempera-ture ~f the material in the container body is about 81C.
It follows from this that the material in the mouth part so~tens at a lower temperature than the material in the container body.
It is already known, by cold-forming of the m~uth part of the blank, to displace material downwards ~rom th~
mouth part into the sections of the blank, which later represent the wall sections of the container body. In this way, a certain matching of the quantity of material in the mouth part to the ~uture stresses is achieved but, between the actual container body and the mouth part 5 neck sections are formed in which the material is stre~ched by a factor of less than 3. These neck sections in the moulded container thus consist of inadequately oriented material, whilst at the same time the wall thickness is undesirably large. This metho~ is also known from Canadian Application No. 322,4~9, filed Fëbruary 28, 1979, inventor, Kjell M. Jakobsen. British Patent Specification 1,536,194 puhlished December 20, 1978 to Carnaud Total Interplastic has disclosed a method wherein a tubular blank, which is closed at one end and which is provided at the other ena with ` E3 --beading for fixing the blank :in a downstream blowing element, is injection-moulded and wherein the tubular blank is blow-moulded after-a certain reshaping to give a container. Material in the tubular part of the blank is expanded in the radial direction at a temperature abo~e tlle glass transition temperature Tg in order thus to form the mouth part of the container. A container ~ormed in the manner described possesses a mouth part and a neck section in which the material has been exposed to only very slight s~retching and hence orienting, 50 that the disadvantages, already indicated, with respect to the mouth part of the known containers are also present in this container.
The invention described in-Bri~tish Patent Specifica-tion 1,536,194 also has the disadvantage that only a part of the material content of th~ injection-moulded tubular blank is utilised when reshaping the blank to give the finished con~ainer. It is obvious that the losses of materiaL, ~ich occur in this process, represent an economic disadvan'cage in the mass production of articles.
From Federa~ German Of~enlegungsschrift DOS
2,540,930, published April 8, 1976, a process is known where-in a tubular blank of PET is resha~ed to give a container and wherein the container w~l consi~ts of a material which is stretched by a factor of, for example, more than 1.5. The bottom part o~ the container consists of an amorphous unoriented material, whilst the neck sections of the container con-sist of material which has been oriented only to a slight extentO As a result of heating and crystallisation, ~ 5 caused thereby, the strength of the material is improved in the unoriented zone6 which at the same time become opaque. Furthermore, a combinatlon of the methods indicated above results in an undesired oversizing of the neck sections of the containers, whilst the latter at the same time have poorer properties tnan the material in the actual container body.
- The invention provides a blank which makes it possible that, in a container formed from the blank, bot~
the mouth part and the neck sections and also the container body consist of a material which is adapted to the occurring stresses and in which the material in the said parts is oriented to a satisfactory ~xtent in such a way that the material is stretched, at least in the axial direction, by a factor ol more than 3.
This results in the advantage o~ a raised glass .
transition temperature Tg in all the said parts of the container. This means that all thesa~ parts will have the same heat resistance, and this is a great advantage compared with containers which are ~ormed according to the known technology and which, at least as far as con-tainers with mainly clear and transparent materials are concerned, have neck sectlons and mouth parts which are more sensitive to heat stresses than the actual container body.
Moreover, the invention enables a.container o~
sm~L~rmouth diameter to be manu~actured, the length and diameter of the container body being matched to the storage capacity of the con-tainer in such a way that the .
~2~
smallest possible ~lantity of material per unit volume of storage space results.
In a~dition, the invention enables a container of any desired shape of the neck part to be formed from the blank, the container material in the mouth part and in the neck part also being orientPd and having a crystallinity of more than l~/o~ this was achieved by stretching the material to the requisite extent, ~or example in the case of con-tainers of PET by stretching in the axial direction by a factor of more than 3. According to known technology it was hitherto not possible to obtain such a degree of orienting, unless the mouth part and neck sections of the containers were to consist of mainly unoriented material, in which case the neck sections merge in the shortest possible distance with oriented sections of the container body, where the wall thickness has been reduced by a factor of at least 3. This shaping represented an attempt to reduce the size of that zone in the neck part, which has mainly amorphous material and low ori.entation and hence a low glass transition temperature Tg~
In accordance with one aspect of the invention, there is provided a tubular pre-moulding of a thermoplastic material, the pre-moulding having a mouth part with adjacent neck sections at one end, a closure at the other end and a tubular section between the two ends, and the closed end and the tubular section of the pre-moulding consisting mainly of amorphous unoriented material having a ~Z~15 crystallinity of less than 5~0 The tubular pre-moulding of the invention is characterized :in that the mouth part w.ith adjacent neck sections of the p:re-moulding are orient~d mainly in the axial direction o:E th~ pre-moulding by reducing the wall thickness by a factor corresponding to the reduction of thickness obtained in a sheet of the material monoaxially stretched into yielding, the crystal-.linity of the material in the mouth part and in the adjacent neck sections being at most 50~0.
According to a further aspect of-the invention, there is provided in a tubular pre moulding of a thermo-plastic of polyester or polyamide type, the pre-moulding having substantially uniform initial thickness and comprising a mouth part with adjacent neck sections at one end, a closure at the other end and a tubular section between the two end~, the closed end and the tubular section of the pre-moulding consisting mainly of amorphous unoriented material having a crystallinity of less than 5%, the improve-ment wherein the mouth part of the pre-moulding, with adjacent neck sections, consists of material which is oriented substantially by a reduction in the thickness of the material while the remainder of the pre-moulding retains its original thickness and, at least in the mouth part, the material has a lower degree of orientation in the circum-ferential direction of the pre-moulding as compared to the axial direction. The crystallinity of the material in the mouth part is at most 5~/0, the orientation of the mouth -part and adjacent neck section~ of the pre-moulding by the thickne~ reduction providing an increased glass transition temperature Tg in the mouth part and neck sections which is substantially equal to the glass transition temperature of the tubular section when the amorphous material of the tubular section is oriented by a subsequent blowing of the pre-moulding to a container.
Accordiny to the invention! the tube of thermo-plastic material is clamped in between two mutually separate clamping devices. The material in the zone between the two cla~ping devices is stretched in the axial direction of the tube by shifting the clamping devices in the direction away from one another. When PET is used, stretching by a factor of at least 3 takes placeO
According to one embodiment of the invention, the
- The invention provides a blank which makes it possible that, in a container formed from the blank, bot~
the mouth part and the neck sections and also the container body consist of a material which is adapted to the occurring stresses and in which the material in the said parts is oriented to a satisfactory ~xtent in such a way that the material is stretched, at least in the axial direction, by a factor ol more than 3.
This results in the advantage o~ a raised glass .
transition temperature Tg in all the said parts of the container. This means that all thesa~ parts will have the same heat resistance, and this is a great advantage compared with containers which are ~ormed according to the known technology and which, at least as far as con-tainers with mainly clear and transparent materials are concerned, have neck sectlons and mouth parts which are more sensitive to heat stresses than the actual container body.
Moreover, the invention enables a.container o~
sm~L~rmouth diameter to be manu~actured, the length and diameter of the container body being matched to the storage capacity of the con-tainer in such a way that the .
~2~
smallest possible ~lantity of material per unit volume of storage space results.
In a~dition, the invention enables a container of any desired shape of the neck part to be formed from the blank, the container material in the mouth part and in the neck part also being orientPd and having a crystallinity of more than l~/o~ this was achieved by stretching the material to the requisite extent, ~or example in the case of con-tainers of PET by stretching in the axial direction by a factor of more than 3. According to known technology it was hitherto not possible to obtain such a degree of orienting, unless the mouth part and neck sections of the containers were to consist of mainly unoriented material, in which case the neck sections merge in the shortest possible distance with oriented sections of the container body, where the wall thickness has been reduced by a factor of at least 3. This shaping represented an attempt to reduce the size of that zone in the neck part, which has mainly amorphous material and low ori.entation and hence a low glass transition temperature Tg~
In accordance with one aspect of the invention, there is provided a tubular pre-moulding of a thermoplastic material, the pre-moulding having a mouth part with adjacent neck sections at one end, a closure at the other end and a tubular section between the two ends, and the closed end and the tubular section of the pre-moulding consisting mainly of amorphous unoriented material having a ~Z~15 crystallinity of less than 5~0 The tubular pre-moulding of the invention is characterized :in that the mouth part w.ith adjacent neck sections of the p:re-moulding are orient~d mainly in the axial direction o:E th~ pre-moulding by reducing the wall thickness by a factor corresponding to the reduction of thickness obtained in a sheet of the material monoaxially stretched into yielding, the crystal-.linity of the material in the mouth part and in the adjacent neck sections being at most 50~0.
According to a further aspect of-the invention, there is provided in a tubular pre moulding of a thermo-plastic of polyester or polyamide type, the pre-moulding having substantially uniform initial thickness and comprising a mouth part with adjacent neck sections at one end, a closure at the other end and a tubular section between the two end~, the closed end and the tubular section of the pre-moulding consisting mainly of amorphous unoriented material having a crystallinity of less than 5%, the improve-ment wherein the mouth part of the pre-moulding, with adjacent neck sections, consists of material which is oriented substantially by a reduction in the thickness of the material while the remainder of the pre-moulding retains its original thickness and, at least in the mouth part, the material has a lower degree of orientation in the circum-ferential direction of the pre-moulding as compared to the axial direction. The crystallinity of the material in the mouth part is at most 5~/0, the orientation of the mouth -part and adjacent neck section~ of the pre-moulding by the thickne~ reduction providing an increased glass transition temperature Tg in the mouth part and neck sections which is substantially equal to the glass transition temperature of the tubular section when the amorphous material of the tubular section is oriented by a subsequent blowing of the pre-moulding to a container.
Accordiny to the invention! the tube of thermo-plastic material is clamped in between two mutually separate clamping devices. The material in the zone between the two cla~ping devices is stretched in the axial direction of the tube by shifting the clamping devices in the direction away from one another. When PET is used, stretching by a factor of at least 3 takes placeO
According to one embodiment of the invention, the
3~
~ 13 material in the tube is stretched, while the material is at a temperature aboYe the glass transition temperature Tg~ whereas in another embodiment the'material is stretched in the cold state~ which means that the material is at a temperature below the glass transition temperature Tg at the beginning of the stretching step. On stretching "in the cold state", the materia'l is drawn until flow sets i~l .
After stretching, at least the central sections of the drawn material are blow-moulded at a temperature above the glass transition temperature Tg against a mould, in order to form, for example, threads and9 in some cases which may occur, parts of'the adjacent neck sections, while two future mouth parts are in adjacent posiiions.
Subsequently, the tube is severed at the transition between the two future mouth parts. Each of the two severed blank parts thus produced form a tubular pre-moulding, after closing at one end and 9 if appropriate, reworking at the other end in order to obtain the requi'red closure surfaces.
In optional embodiments of the invention, the material is heated before the axi~l stretching to a tem-perature above the glass transition temperature Tg, or the stretching step is preceded by a blow-moulding step in which the heated material is subjected to a certain expansion in order to increase the diameter of the zone.
In another embodiment of the invention7 the mouth parts of the pre-mouldings are shaped'by simultaneous axial stretching, and blow-moulding for the purpose of a radial expansion of the heated material-In certain application examples, the heatedmaterial zone has a temperature profile such that one or several annular zones are at a temperature which exceeds the temperature of the adjacent material by ~-20C 9 pre-ferably 10-15C. l~le actual drawing or stretching step starts in the material ~ones of higher tempera~ure.
In an application of the invention, wherein the material in the tube is,a* the start of axial stretching of the maleria~ at a temperature which is less than the glass transition temperature Tg, the drawing or stretching step is initiated, according to an optional embodiment of the invention, with the aid of pressure forces. This is achieved, for example, by means of a ring which sur-rounds the tube, the inner surface of thering being brough~
into contact with the outer surface of the tube by reducing the internal diameter of the ring.
On axial stretching of the material, the external diameter of the tube is reduced. As a result of the invention, it is thus possible to produce a pre-moulding, the mouth part of which has an external diameter which is less than the çxternal diameter of the tu~e.
Equipment ~or carrying out the process comprises a number of stretching and blow-moulding devices, which are each provided with two clamping devices which are located at a certain spacing from one another. The clamping devices are provided for clamping a tube in, and the two sets of clamping devices are arranged in such a way that they can be shifted towards one another or away ~63 ~5 from one another. The contact surfaces ~f the cla~ping devices with the tube are oooled. Appro~
priate devices are provided fs~r heating the material in the tube be~ween the said sets ofclamping devices, and also the blow-moulds against which the heated material is blown. Moreover, the equipment comprises elements for closin~ the tro ends of the tube before blow-moulding and also elements fsr applying an elevated pressure to the slosed cavlty formed in this way. In certain illustrative embodiments, a cylindrical rod is also fitted axially in the tube. Finally, an element for severing the tube into two pre~erably equal parts is present.
In an embodiment of the invention, the clamping devices are arranged in such a way that ~he tube can rotate about its own axis. In this way 9 heating of the material in the zone between the two sets of olamping devices and also the severing of the tube into ~wo eq~al --parts are facilitated.
In ~orming a blank, the tube is f ixed between the two clamping devices, after which the latter are shifted in the direction ~way from one another, in oertain illus-trative embodiments after the material between the two sets of clampin~ devices has first been heated to the desired temperature profile and, in cer-tain application cases, with simultaneous radial expansion of the material in the tube or after a first radial expansion of the material in the tube has taken place. The length of displacement relative to the length of the part of the tj tube, -~he material of which is stretched3 is selected in the case of PET in such a way that the material reaches a crystallinity of at least 10% on axial orientation.
In some cases w~ich may occur, the cylindrical rod is introduced intc the tu~e before'the material is stretched.
In certain application examples, the rod is heated. To effect radial expansion, the two ends of the tube are closed, the material between the two sets of clamping devices is'heated'in some cases which may occur, and the closed space in the tube is subjected to pressure, the heated material expanding in such a way that it makes contact with the mould surfaces, for example for the pur-pose of moulding the mouth thread and adjacent neck sections. When the material has cooled to a sufficient extent to reach dimensional stability, the tube is severed into two parts in the severing element. - Each of the two parts is closed at one end by reshaping and, if appro-priate, reworked at the other end, that is to say the mouth end, in order to produce th~ requisite closing sur-faces~ Thus, the pre-moulding is completed.
According to the process described above, ea~h drawing step with subsequent severing results in ~ro blan~
parts which~ after a certain rewor,king and reshaping 9 each form a blank. In this manner, no losses of material arise in the production of pre-mouldings. Of course, the stretched material formed during the drawirg step can be adapted in such a way that it is used for forming exclusively one single future mouth part with adjacent future neck sections. Due ~o ~he severing of parts of ~ 17 -the piece of tube, which can :not be used for further production of the pre-moulding, however, this leads to undesired losses of material, so ~hat this embodiment of the invention is only used in special cases~ for example in the production of pre-mouldings which are.intended ~or contalners having long mouth sections and neck sections.
Figure 1 shows, in perspective view, a stretching and - blov-moulding device having ~wo sets of clamping devices, and with the two sets o~ clamping devices o~ the stretching device bei.ng in the position ior receiving a piece of tube, Figure 2 shows, in perspective view, a stretching and blow-moulding device, with the clamping devices in the position ~or fixing a piece of tube, .Figure 3 shows a sectional view of the stretching and . blow-moulding device during the heating o~ a central part of a piece of tube, Figure 4 shows a sectional view of a stretching and blow-moulding device with the piece o~ tube fixed and drawn, Figure 5-shows a sectional view of a stretching and blow-moulding device with the internal volume of the piece of tube subjected to pressure in order ~o form the mouth sections and adjacent neck sections, ~igure 6 shows a device for severing ~he piece o~ tube - - into two separate blank parts, ~igure 7 shGws, in diagrammatic view~ a device for the stepwise produ~tion of blank parts for pre-18 _ mouldingsO
Figure 8 shows a sectional view of a stretching and - blaw-moulding device having a device for heating an annular sestion in the piece of tube, Figure 9 shows a secti~nal view of a stretching and .
blow-~oulding device during the cold-~rawing .
step of the piece of tube, Figure 10 shows a sectional view of a stretching and - blow-moulding device a~ter the cold-drawing step of the piece of tube has been carried out, Figure 11 shows a sectional view of a stretching and blow-moulding device with the length of the axially drawn zone increased, Figure 12 shows a partial section through a stretching and blow-moulding device according to Figure 11, in which the internal volume c~ the piece-of tube has been subjected to pressure, and in particular the forming of the neck sections - adjacent to the mouth part, Figure 13 shows a completed tubular pre-moulding which has been shaped from a blank part according to Figure ~, and - Figure 14 shows a completed tubular pre-moulding which has been shaped from a blank part according to Figure 12.
Figures 1 and 2 show a frame on which two separate sets of clamping devices 20 a-b and 21 a-b are located.
I~ principle, the two sets of clamping devices consist of an upper clamping part 20a, 21a and a lower clamping part ~lq3~ ~5 20b, 21b. In both sets of cl~mping devices~ the upper part can be shifted between an open positlon and a closed position. In ~e closed position, the particular set o~ clamping devices fixes one end of a tube 50 in each case~ The two sets o~ clamping devices can be shifted from their starting positions (Figure 1) towards one another up to a smallest distance ~Figure 2) which matches the length of the tube 50, and from there they can be shifted back again into the particular starting position.
-In the starting position, the particular upper part assumes the open posi~ion and remains in the latter until the two sets of clamping devices have been shifted towards one another up to the said smallest distance. In this position, the particular upper parts assume the closed position and thus cover a relatively large part o~ ~he tube 50, the latter being surrounded at the same time and being fIxed by the particular set of clamplng devices.
While the upper parts are still in the closed position, the two sets o~ clamping devices are subsequently shifted back to the starting position. The shift of the upper parts 20a, 21a of the-~wo sets of clamping devices is effect~d by means of drive mechanisms 25, 26, and a drive mechanism 24 is provided for shifting the two sets of clamping devices towards one another. The two upper parts slide in the grooves 22, 23 provided in the lower parts; whilst the lower parts slide in grooves 13 a-b provided in the frame llo . ~.
A gripper 28 is provided ~or inserting the tube 50 into the clamping devices or removing it from the ~2~
clamping devices. When the tWG sets-of clamping devices are at their smallest distance from one anothrr, a heating element consisting ~f the two heating jaws 29 a-b is brought int~ a position in which it can heat the cen-tral sections o~ the tube 50. The motion of the heating ja~s is effected by means of a drive mechanism 33 with a push-and-pull bar. A lead 31 for heating the, heating jaws, ~or example by means of electric power, is shown in the figures.
Adjoining one o~ the two sets of clamping devices, a cylindrical forming and blowing mandrel 27 is provided.
This mandrel is moved by means of a drive mechanism 39 from and to a position in which the cylindrical part of the mandrel protrudes a little into the opening of the other set of clamping devices. The mandrel protrudes into the said opening even when the two sets of clamping devices are in their starting positions.
The external di~meter of the mandrel and the -internal diameter of the tube 50 are matched in such a way that the mandrel can be introduced into the tubeO
Moreover, the mandrel is provided with a row of orifices 40 which lead to a cavity in the interior of the mandrel~
which cavity is connected to a line 32 for a pressure medium.
A pressure medium is fed via the lines 30a, b, c, e (the pressure line 30d is not shown in the figure) to the indivldual drive mechanisms 24, 25, 26, 33 and ~9.
In Figure 3, the two sets of clamping devices 20 a-b, ~1 a-b are shown in the position for the smallest _ 21 -distance between the sets. In addition, the figure shows the said cavity 42 in the mandrel 27, a gasket 41 between one end o~ the tube 50 and t,he set of clamping devices 21 a-~ a~d a gasket 34 ~e~ween the other end of the tube 5G and the set of clamping devices 20 a-b.
A gasket 35 between the mandrel 27 and the set of clamping devices 20 a-b can also be seen. An outle-t valve 36 is located in thP lower clamping device 21b. - In this way, the closed space which can be subjected to pressure through the orifices 40 is formed in the mandrel 27.
Figure 4 shows the two sets of clamping devices shifted back into their starting positions, while the surrounded parts o~ the tube 50 are still held firmly as before. The Figure shows that the mandrel 27 continues to projectinto the set ofclamping devices 21a-~ A central zon~
510fthe tube 50has been stretched inthe axial directionand hasasmaller wall thicknessthan theremainderof the tube.
In Figure 5 7 the central zone 51 has been blow-moulded against the mould 57 a-~. The shaping surface o~ the mould corresponds to the form of two mouth parts 52 a-b, facing one another, for containers which are tobe formed fromthe blanksand arein the process ofmanufact-~re.
Figure 6 shows the mandrel 27 in its siarting position. A severing disc 58 is located in the position for severing the tube 50, that is to say at the transition between the two moulded mouth parts 52 a-b.
Figure 7 shows a turntable 7 which rotates about a bearing 12~ Next to the turntable, a number o~
positions A-U is indicated. One frame 11 with the associated set of c~amping devioes, drive mechanisms, tubu~ar mandrel, heating device and the like according to Figures 1-2 is located on the turntable for each position.
In the positions, the particular working step is indicated diagrammatically by the posi'tion of mandrel, heating jaws, sets of clamping devices and the like.
~ igure 8 shows an embodiment of the invention, which is adapted preferably for so-calle~ cold-drawing of the tube. An annular heating element 38 lS locatea be~ween the two sets of clamping devices. By means o~
this heating element, the central sections of the tube 50 are heated to an elevated temperature over an annular zone.
Fig~res9-lQ relate to the cold-drawing of the tube 50. In Figure 9, the formation of a centrally located drawn zone 53 has started, whilst in Figure 10 the entire centrally located dra~m zone 54 has been formed.
`Figures 11 and 12 relate to a variant of ~he invention wherein the centrally located zone 51a of the tube 50 is longer than in the previously described embodiments of the invention. The figures show only one of the ~wo sets of clamping devices. Figure 11 sh~ws the position after drawing of the tube has been completed, whilst Figure 12 shows the central zone-51a (Figure 11) after it has been blow-moulded against an outer mould 59. The moulding surface of the outer mould corresponds tothe shape of t~ro mutually facing mouth parts (only one, 52a, is shown in the figure) and parts of the adjacent future neck section 60a of the containers which are to be formed from the blanks and are i~ the ~rocess of product;ion~ A zone 567 having the~largest diameter in the moulded future neok sections, pre~erably has a diameter which is at least three times the original diameter of the tub~.
Figures 1~ and 14 show comp~et~rl tubular pre mouldings, the pre-moulding according to Fi~lre 13 haying been-formed from~a blank part shown in Figure 5 and a pre-moulding according to Figure 14:having been formed from a.
blank part shown in Figure 12. At one end, the pre-mouldings have a mouth part 62a, b with adaacent neck sections 63a, b. At the other end the pre-mouldings have a closure 61a, b. A tubular section 64a, b can be seen between the closure 61a, b and the neck sections 63a1 b r In the production ol a pre-moulding according to the invention$ a tube 50 is brought into the position sho~m in Figure 1 with the aid of the gripper 28. The -two sets of clamping devices 20 and 21 are shifted towards one another with the aid of the drive meohanism 24 until the ~wo ends of the tube are in contac~ with the gaskets 34 and 41. The upper clamping devices are brought into their closed position with the aid of the drive mechanisms 25, 26, the tube 50 being firmly held at both its ends and at the same time being enclosed over a relatively large part. This situation is ~hown in Figure 2. As an alternative, the mandrel 27 was already in this phase brought beforehand into the position 6~s~ a ~
- ~4 -which is shown in Figure 3~ The heati~g jaws 29 are -brought into the heating position and remain in this position for such a perio~ as-is necessary for heating the material in the c`en~ral-sections o~ the tube to a temperature below the glass transition temperature Tg~
The drive element 24 now shifts the ~wo sets of clamping devices in the direction away from one another~ the central sections of the tube being stretched; with ~simultaneous thinning of the tube wall, in such a way that the tube is given the appearance shown in Figure 4.
Preferably, stretching amounts to at least a factor of 3, and the reduction in thickness thus also amounts to a factor of 3. During the entire drawing step; the mandrel 27 is located in the interior of the tube, within the stretched zone9 and thls prevents the stretched zone from assuming an undesirably small diameter.
The closed space in the interior of the tube is subjected to pressure, the material being expanded into the zone concerned until it makes contact with t~e outer mould 57. In~this step9 the future mouth parts and parts of the adjacent neck sections in two blank parts connected to ~ne another are shaped to give pre-mouldings.
On contact with the-surfaces of the outer mould, the material in the tube is cooled so that it becomes dimen-sionally stable. With simultaneous retraction of the mandrel 27 into its starting position, the outer mould is opened and a severing disc 28 divides the tube at the transition be~een the two future mouth parts. This produces two separate blank parts ~Jhich are closed at one 91.S
end by reshaping and are provided with the requisite closing sur~aces a~ the other end by reworking. In this way, a tubular-pre~moulding as shown in Figure 13 is obtained.
The design of the equipment for closing one end~
and likewise for the reworking, which may be necessar~, of the mouth part7 is not shown in the figures~ but this can be in accordance with any technology already known and used. Normally~ closing is effected by ~eating the material at one end of the tube u~ to a temperature above the glass transition temperature Tg. after which the end is forced in the axial direction against a substan-tially spherical shell which compresses the soft material and closes the end~ Subsequently, the gripper 28 takes the two blank parts ~ormed out of the production equipment after the two sets of clamping devices have released the pre-mouldings. Subsequen~ly, the course of the pro-cess described above is repeatea.
According to a pre~erred embodiment of the inven-tion, the production step described above is carried out with the aid of the equipment shown in ~igure 70 In position A, th~ tube is fed to the t~Jo sets of clamping devices, in position B the two sets of clamping devices are shifted in the direction towards one another, whilst simultaneously the mandrPl is introduced into the tube, and in position C-E the central zone of the tube is heated, whilst in positio~ ~ the heating process is interrupted.
In p~sitions G-H, the central sections of the tube are stretched, irl position I the outer moulds move into the ~2~ iS
moulding position 7 in position J the interior o~ the tube is subjected to pressure and is formed to give the future mouth parts with the acljacent nec~ sections.
In position ~, the oute.r moulds open, whilst in position L the mandrel is retracted into its starting position.
Position M is a cooling position for stabilising the form o~ the tube or, alternatively, is a reserve position, whils~ i~ position N the tube is severed into ~wo blank parts. In position 0, the -~wo future mouth parts are heated for.reworking, i~ appropriate, and they obtain their final form in position P. In position R, the devices for reworking the mouth parts have assumed . -again their starting position, and subsequently, in position S~ the blank parts have been shifted in the direction towards one another in order~to enable the gripper to engage in position T and to enable ihe clamping devices to open in position U, so tha~ the mouldings formed can be removed ~r~m the production equipment according to ~igure 7. Advanta~eously, the gri~per device here transfers the blanks ~o devices for closing one of their ends. Such devices can either be pro-vided independently of the equipment described in this paragraph, or they can form part of this equipment.
In the latter case, this equipment must be pro-vided with a further number of positions.
During cold-drawing of the oentral zone of the tube, the material is heated before the drawing step with the aid of an annular heating element 38 (~igure 8~ over an annular ~one within the central zone.. This heating element is preferably designed to heat the central zone as ~ar as one of the sets v~ clamping devices. To con~rol the direction of displacement during the flow which sets in on drawing 9 the material is normally cooled immediately next to the heated annulus-in that dIrection in which it is intended that the flow step should not propagate. In the embodiments in which t,he entire material of the tube is to be drawn between the two sets of jaws, the required cooling is obtained by the cooled jaws. In other embodiments, annular cooling devices are used which, in princlple, are arranged in a manner corresponding to the arrangement of the heaiing device 38.
On warm-drawing of the central zone o~ the tube, one or several annular heating elements are used in cer-tain application examples in order to produce the desired temperature profile in the central zone of the tube before the latter is drawn. The annular heating elements here ~requently consist o~ zones of elevated temperature in the heating jaws 29.
On cold-drawing of the material in the central zone o~ the tube, flow of the material sets in first in the annular zone which has been heated by the annular heating element ~8. On further stretching o~ the cen-tral zone o~ the tube, the flow zone of-the material is displaced in the direction of the other set of clamping devices, comPare Figure 9 9 SO that, after completion of the stretching step, a central drawn zone has formed, the appearance of which is shown in Figure 10. On cold-drawing, the central zone has no tendency towards a .
reduction of the internal diiameter of the tube, as long as stretching is~limited to ~bout a ~actor of 3. In . this embodiment of the lnven-tion,-lt is ~hus not-necessary to cause the mandrel 27 to assume its positivn in the tube .
- before the actua7 stretching step~ Figures 11-12 show an embodiment of the invention in which the stretched central zone 51a has a greater leng-th than in the embodi-men*s of the invention so far described. ~en the interlor of the tu~e is subjected to pressure, parts of . .... ~ .. .
adjacent neck sections are:also formed, in addition *o the two future mouth parts, these neck sections being given a greater diameter than that of the actual mouth part.
At this stage, it is pre~erable to allow the future neck section to be shaped to such an extent that the greatest rise in diameter is at ieast 3-fold. This-ha-s *he advantage *hat a relatively dimensionally stable neck section is formed which, during the subsequent heating in conjunction with the shaping o~ the remaining part o~-the container~ is affected only to a small ex~enc. ~he appearance of a pre-moulding, which was formed from a blank part partially shown in Figure 12, can be seen in Figure 14.
In the above description9 it was explained how the blank parts are formed by severing the drawn and shaped tube. In a preferred embodiment of the invention, severing of the blank parts from one another is effected with the aid of one or several severing discs which revolve under pressure about the circumferential surface of the tube formed at the.transition between the ~wo s future mouth parts.
It was ass~ed in the above description that heating of the centra~ material sections of the tube is ef~ected-by heating jaws. To obtain the most uniform heating of the material possible, the tube should pre-ferably rotate relative to the heating element. To make this possible, the clamping devices are moAi~ied 7 if appropriate having cone type bearings or having heating jaws which revolve about the tubeO
In the case where the central sections of the tube are drawn at an initial temperature which is below the glass transition temperature Tg, the material is heated after the drawing step to a temperature above ~he glass transition temperature Tg, after which the ~uture mouth part and parts of the adjacent neck sections are shaped.
- I~ addition to the above description, the inven-tion is also comprised by the attached patent claims.
~ 13 material in the tube is stretched, while the material is at a temperature aboYe the glass transition temperature Tg~ whereas in another embodiment the'material is stretched in the cold state~ which means that the material is at a temperature below the glass transition temperature Tg at the beginning of the stretching step. On stretching "in the cold state", the materia'l is drawn until flow sets i~l .
After stretching, at least the central sections of the drawn material are blow-moulded at a temperature above the glass transition temperature Tg against a mould, in order to form, for example, threads and9 in some cases which may occur, parts of'the adjacent neck sections, while two future mouth parts are in adjacent posiiions.
Subsequently, the tube is severed at the transition between the two future mouth parts. Each of the two severed blank parts thus produced form a tubular pre-moulding, after closing at one end and 9 if appropriate, reworking at the other end in order to obtain the requi'red closure surfaces.
In optional embodiments of the invention, the material is heated before the axi~l stretching to a tem-perature above the glass transition temperature Tg, or the stretching step is preceded by a blow-moulding step in which the heated material is subjected to a certain expansion in order to increase the diameter of the zone.
In another embodiment of the invention7 the mouth parts of the pre-mouldings are shaped'by simultaneous axial stretching, and blow-moulding for the purpose of a radial expansion of the heated material-In certain application examples, the heatedmaterial zone has a temperature profile such that one or several annular zones are at a temperature which exceeds the temperature of the adjacent material by ~-20C 9 pre-ferably 10-15C. l~le actual drawing or stretching step starts in the material ~ones of higher tempera~ure.
In an application of the invention, wherein the material in the tube is,a* the start of axial stretching of the maleria~ at a temperature which is less than the glass transition temperature Tg, the drawing or stretching step is initiated, according to an optional embodiment of the invention, with the aid of pressure forces. This is achieved, for example, by means of a ring which sur-rounds the tube, the inner surface of thering being brough~
into contact with the outer surface of the tube by reducing the internal diameter of the ring.
On axial stretching of the material, the external diameter of the tube is reduced. As a result of the invention, it is thus possible to produce a pre-moulding, the mouth part of which has an external diameter which is less than the çxternal diameter of the tu~e.
Equipment ~or carrying out the process comprises a number of stretching and blow-moulding devices, which are each provided with two clamping devices which are located at a certain spacing from one another. The clamping devices are provided for clamping a tube in, and the two sets of clamping devices are arranged in such a way that they can be shifted towards one another or away ~63 ~5 from one another. The contact surfaces ~f the cla~ping devices with the tube are oooled. Appro~
priate devices are provided fs~r heating the material in the tube be~ween the said sets ofclamping devices, and also the blow-moulds against which the heated material is blown. Moreover, the equipment comprises elements for closin~ the tro ends of the tube before blow-moulding and also elements fsr applying an elevated pressure to the slosed cavlty formed in this way. In certain illustrative embodiments, a cylindrical rod is also fitted axially in the tube. Finally, an element for severing the tube into two pre~erably equal parts is present.
In an embodiment of the invention, the clamping devices are arranged in such a way that ~he tube can rotate about its own axis. In this way 9 heating of the material in the zone between the two sets of olamping devices and also the severing of the tube into ~wo eq~al --parts are facilitated.
In ~orming a blank, the tube is f ixed between the two clamping devices, after which the latter are shifted in the direction ~way from one another, in oertain illus-trative embodiments after the material between the two sets of clampin~ devices has first been heated to the desired temperature profile and, in cer-tain application cases, with simultaneous radial expansion of the material in the tube or after a first radial expansion of the material in the tube has taken place. The length of displacement relative to the length of the part of the tj tube, -~he material of which is stretched3 is selected in the case of PET in such a way that the material reaches a crystallinity of at least 10% on axial orientation.
In some cases w~ich may occur, the cylindrical rod is introduced intc the tu~e before'the material is stretched.
In certain application examples, the rod is heated. To effect radial expansion, the two ends of the tube are closed, the material between the two sets of clamping devices is'heated'in some cases which may occur, and the closed space in the tube is subjected to pressure, the heated material expanding in such a way that it makes contact with the mould surfaces, for example for the pur-pose of moulding the mouth thread and adjacent neck sections. When the material has cooled to a sufficient extent to reach dimensional stability, the tube is severed into two parts in the severing element. - Each of the two parts is closed at one end by reshaping and, if appro-priate, reworked at the other end, that is to say the mouth end, in order to produce th~ requisite closing sur-faces~ Thus, the pre-moulding is completed.
According to the process described above, ea~h drawing step with subsequent severing results in ~ro blan~
parts which~ after a certain rewor,king and reshaping 9 each form a blank. In this manner, no losses of material arise in the production of pre-mouldings. Of course, the stretched material formed during the drawirg step can be adapted in such a way that it is used for forming exclusively one single future mouth part with adjacent future neck sections. Due ~o ~he severing of parts of ~ 17 -the piece of tube, which can :not be used for further production of the pre-moulding, however, this leads to undesired losses of material, so ~hat this embodiment of the invention is only used in special cases~ for example in the production of pre-mouldings which are.intended ~or contalners having long mouth sections and neck sections.
Figure 1 shows, in perspective view, a stretching and - blov-moulding device having ~wo sets of clamping devices, and with the two sets o~ clamping devices o~ the stretching device bei.ng in the position ior receiving a piece of tube, Figure 2 shows, in perspective view, a stretching and blow-moulding device, with the clamping devices in the position ~or fixing a piece of tube, .Figure 3 shows a sectional view of the stretching and . blow-moulding device during the heating o~ a central part of a piece of tube, Figure 4 shows a sectional view of a stretching and blow-moulding device with the piece o~ tube fixed and drawn, Figure 5-shows a sectional view of a stretching and blow-moulding device with the internal volume of the piece of tube subjected to pressure in order ~o form the mouth sections and adjacent neck sections, ~igure 6 shows a device for severing ~he piece o~ tube - - into two separate blank parts, ~igure 7 shGws, in diagrammatic view~ a device for the stepwise produ~tion of blank parts for pre-18 _ mouldingsO
Figure 8 shows a sectional view of a stretching and - blaw-moulding device having a device for heating an annular sestion in the piece of tube, Figure 9 shows a secti~nal view of a stretching and .
blow-~oulding device during the cold-~rawing .
step of the piece of tube, Figure 10 shows a sectional view of a stretching and - blow-moulding device a~ter the cold-drawing step of the piece of tube has been carried out, Figure 11 shows a sectional view of a stretching and blow-moulding device with the length of the axially drawn zone increased, Figure 12 shows a partial section through a stretching and blow-moulding device according to Figure 11, in which the internal volume c~ the piece-of tube has been subjected to pressure, and in particular the forming of the neck sections - adjacent to the mouth part, Figure 13 shows a completed tubular pre-moulding which has been shaped from a blank part according to Figure ~, and - Figure 14 shows a completed tubular pre-moulding which has been shaped from a blank part according to Figure 12.
Figures 1 and 2 show a frame on which two separate sets of clamping devices 20 a-b and 21 a-b are located.
I~ principle, the two sets of clamping devices consist of an upper clamping part 20a, 21a and a lower clamping part ~lq3~ ~5 20b, 21b. In both sets of cl~mping devices~ the upper part can be shifted between an open positlon and a closed position. In ~e closed position, the particular set o~ clamping devices fixes one end of a tube 50 in each case~ The two sets o~ clamping devices can be shifted from their starting positions (Figure 1) towards one another up to a smallest distance ~Figure 2) which matches the length of the tube 50, and from there they can be shifted back again into the particular starting position.
-In the starting position, the particular upper part assumes the open posi~ion and remains in the latter until the two sets of clamping devices have been shifted towards one another up to the said smallest distance. In this position, the particular upper parts assume the closed position and thus cover a relatively large part o~ ~he tube 50, the latter being surrounded at the same time and being fIxed by the particular set of clamplng devices.
While the upper parts are still in the closed position, the two sets o~ clamping devices are subsequently shifted back to the starting position. The shift of the upper parts 20a, 21a of the-~wo sets of clamping devices is effect~d by means of drive mechanisms 25, 26, and a drive mechanism 24 is provided for shifting the two sets of clamping devices towards one another. The two upper parts slide in the grooves 22, 23 provided in the lower parts; whilst the lower parts slide in grooves 13 a-b provided in the frame llo . ~.
A gripper 28 is provided ~or inserting the tube 50 into the clamping devices or removing it from the ~2~
clamping devices. When the tWG sets-of clamping devices are at their smallest distance from one anothrr, a heating element consisting ~f the two heating jaws 29 a-b is brought int~ a position in which it can heat the cen-tral sections o~ the tube 50. The motion of the heating ja~s is effected by means of a drive mechanism 33 with a push-and-pull bar. A lead 31 for heating the, heating jaws, ~or example by means of electric power, is shown in the figures.
Adjoining one o~ the two sets of clamping devices, a cylindrical forming and blowing mandrel 27 is provided.
This mandrel is moved by means of a drive mechanism 39 from and to a position in which the cylindrical part of the mandrel protrudes a little into the opening of the other set of clamping devices. The mandrel protrudes into the said opening even when the two sets of clamping devices are in their starting positions.
The external di~meter of the mandrel and the -internal diameter of the tube 50 are matched in such a way that the mandrel can be introduced into the tubeO
Moreover, the mandrel is provided with a row of orifices 40 which lead to a cavity in the interior of the mandrel~
which cavity is connected to a line 32 for a pressure medium.
A pressure medium is fed via the lines 30a, b, c, e (the pressure line 30d is not shown in the figure) to the indivldual drive mechanisms 24, 25, 26, 33 and ~9.
In Figure 3, the two sets of clamping devices 20 a-b, ~1 a-b are shown in the position for the smallest _ 21 -distance between the sets. In addition, the figure shows the said cavity 42 in the mandrel 27, a gasket 41 between one end o~ the tube 50 and t,he set of clamping devices 21 a-~ a~d a gasket 34 ~e~ween the other end of the tube 5G and the set of clamping devices 20 a-b.
A gasket 35 between the mandrel 27 and the set of clamping devices 20 a-b can also be seen. An outle-t valve 36 is located in thP lower clamping device 21b. - In this way, the closed space which can be subjected to pressure through the orifices 40 is formed in the mandrel 27.
Figure 4 shows the two sets of clamping devices shifted back into their starting positions, while the surrounded parts o~ the tube 50 are still held firmly as before. The Figure shows that the mandrel 27 continues to projectinto the set ofclamping devices 21a-~ A central zon~
510fthe tube 50has been stretched inthe axial directionand hasasmaller wall thicknessthan theremainderof the tube.
In Figure 5 7 the central zone 51 has been blow-moulded against the mould 57 a-~. The shaping surface o~ the mould corresponds to the form of two mouth parts 52 a-b, facing one another, for containers which are tobe formed fromthe blanksand arein the process ofmanufact-~re.
Figure 6 shows the mandrel 27 in its siarting position. A severing disc 58 is located in the position for severing the tube 50, that is to say at the transition between the two moulded mouth parts 52 a-b.
Figure 7 shows a turntable 7 which rotates about a bearing 12~ Next to the turntable, a number o~
positions A-U is indicated. One frame 11 with the associated set of c~amping devioes, drive mechanisms, tubu~ar mandrel, heating device and the like according to Figures 1-2 is located on the turntable for each position.
In the positions, the particular working step is indicated diagrammatically by the posi'tion of mandrel, heating jaws, sets of clamping devices and the like.
~ igure 8 shows an embodiment of the invention, which is adapted preferably for so-calle~ cold-drawing of the tube. An annular heating element 38 lS locatea be~ween the two sets of clamping devices. By means o~
this heating element, the central sections of the tube 50 are heated to an elevated temperature over an annular zone.
Fig~res9-lQ relate to the cold-drawing of the tube 50. In Figure 9, the formation of a centrally located drawn zone 53 has started, whilst in Figure 10 the entire centrally located dra~m zone 54 has been formed.
`Figures 11 and 12 relate to a variant of ~he invention wherein the centrally located zone 51a of the tube 50 is longer than in the previously described embodiments of the invention. The figures show only one of the ~wo sets of clamping devices. Figure 11 sh~ws the position after drawing of the tube has been completed, whilst Figure 12 shows the central zone-51a (Figure 11) after it has been blow-moulded against an outer mould 59. The moulding surface of the outer mould corresponds tothe shape of t~ro mutually facing mouth parts (only one, 52a, is shown in the figure) and parts of the adjacent future neck section 60a of the containers which are to be formed from the blanks and are i~ the ~rocess of product;ion~ A zone 567 having the~largest diameter in the moulded future neok sections, pre~erably has a diameter which is at least three times the original diameter of the tub~.
Figures 1~ and 14 show comp~et~rl tubular pre mouldings, the pre-moulding according to Fi~lre 13 haying been-formed from~a blank part shown in Figure 5 and a pre-moulding according to Figure 14:having been formed from a.
blank part shown in Figure 12. At one end, the pre-mouldings have a mouth part 62a, b with adaacent neck sections 63a, b. At the other end the pre-mouldings have a closure 61a, b. A tubular section 64a, b can be seen between the closure 61a, b and the neck sections 63a1 b r In the production ol a pre-moulding according to the invention$ a tube 50 is brought into the position sho~m in Figure 1 with the aid of the gripper 28. The -two sets of clamping devices 20 and 21 are shifted towards one another with the aid of the drive meohanism 24 until the ~wo ends of the tube are in contac~ with the gaskets 34 and 41. The upper clamping devices are brought into their closed position with the aid of the drive mechanisms 25, 26, the tube 50 being firmly held at both its ends and at the same time being enclosed over a relatively large part. This situation is ~hown in Figure 2. As an alternative, the mandrel 27 was already in this phase brought beforehand into the position 6~s~ a ~
- ~4 -which is shown in Figure 3~ The heati~g jaws 29 are -brought into the heating position and remain in this position for such a perio~ as-is necessary for heating the material in the c`en~ral-sections o~ the tube to a temperature below the glass transition temperature Tg~
The drive element 24 now shifts the ~wo sets of clamping devices in the direction away from one another~ the central sections of the tube being stretched; with ~simultaneous thinning of the tube wall, in such a way that the tube is given the appearance shown in Figure 4.
Preferably, stretching amounts to at least a factor of 3, and the reduction in thickness thus also amounts to a factor of 3. During the entire drawing step; the mandrel 27 is located in the interior of the tube, within the stretched zone9 and thls prevents the stretched zone from assuming an undesirably small diameter.
The closed space in the interior of the tube is subjected to pressure, the material being expanded into the zone concerned until it makes contact with t~e outer mould 57. In~this step9 the future mouth parts and parts of the adjacent neck sections in two blank parts connected to ~ne another are shaped to give pre-mouldings.
On contact with the-surfaces of the outer mould, the material in the tube is cooled so that it becomes dimen-sionally stable. With simultaneous retraction of the mandrel 27 into its starting position, the outer mould is opened and a severing disc 28 divides the tube at the transition be~een the two future mouth parts. This produces two separate blank parts ~Jhich are closed at one 91.S
end by reshaping and are provided with the requisite closing sur~aces a~ the other end by reworking. In this way, a tubular-pre~moulding as shown in Figure 13 is obtained.
The design of the equipment for closing one end~
and likewise for the reworking, which may be necessar~, of the mouth part7 is not shown in the figures~ but this can be in accordance with any technology already known and used. Normally~ closing is effected by ~eating the material at one end of the tube u~ to a temperature above the glass transition temperature Tg. after which the end is forced in the axial direction against a substan-tially spherical shell which compresses the soft material and closes the end~ Subsequently, the gripper 28 takes the two blank parts ~ormed out of the production equipment after the two sets of clamping devices have released the pre-mouldings. Subsequen~ly, the course of the pro-cess described above is repeatea.
According to a pre~erred embodiment of the inven-tion, the production step described above is carried out with the aid of the equipment shown in ~igure 70 In position A, th~ tube is fed to the t~Jo sets of clamping devices, in position B the two sets of clamping devices are shifted in the direction towards one another, whilst simultaneously the mandrPl is introduced into the tube, and in position C-E the central zone of the tube is heated, whilst in positio~ ~ the heating process is interrupted.
In p~sitions G-H, the central sections of the tube are stretched, irl position I the outer moulds move into the ~2~ iS
moulding position 7 in position J the interior o~ the tube is subjected to pressure and is formed to give the future mouth parts with the acljacent nec~ sections.
In position ~, the oute.r moulds open, whilst in position L the mandrel is retracted into its starting position.
Position M is a cooling position for stabilising the form o~ the tube or, alternatively, is a reserve position, whils~ i~ position N the tube is severed into ~wo blank parts. In position 0, the -~wo future mouth parts are heated for.reworking, i~ appropriate, and they obtain their final form in position P. In position R, the devices for reworking the mouth parts have assumed . -again their starting position, and subsequently, in position S~ the blank parts have been shifted in the direction towards one another in order~to enable the gripper to engage in position T and to enable ihe clamping devices to open in position U, so tha~ the mouldings formed can be removed ~r~m the production equipment according to ~igure 7. Advanta~eously, the gri~per device here transfers the blanks ~o devices for closing one of their ends. Such devices can either be pro-vided independently of the equipment described in this paragraph, or they can form part of this equipment.
In the latter case, this equipment must be pro-vided with a further number of positions.
During cold-drawing of the oentral zone of the tube, the material is heated before the drawing step with the aid of an annular heating element 38 (~igure 8~ over an annular ~one within the central zone.. This heating element is preferably designed to heat the central zone as ~ar as one of the sets v~ clamping devices. To con~rol the direction of displacement during the flow which sets in on drawing 9 the material is normally cooled immediately next to the heated annulus-in that dIrection in which it is intended that the flow step should not propagate. In the embodiments in which t,he entire material of the tube is to be drawn between the two sets of jaws, the required cooling is obtained by the cooled jaws. In other embodiments, annular cooling devices are used which, in princlple, are arranged in a manner corresponding to the arrangement of the heaiing device 38.
On warm-drawing of the central zone o~ the tube, one or several annular heating elements are used in cer-tain application examples in order to produce the desired temperature profile in the central zone of the tube before the latter is drawn. The annular heating elements here ~requently consist o~ zones of elevated temperature in the heating jaws 29.
On cold-drawing of the material in the central zone o~ the tube, flow of the material sets in first in the annular zone which has been heated by the annular heating element ~8. On further stretching o~ the cen-tral zone o~ the tube, the flow zone of-the material is displaced in the direction of the other set of clamping devices, comPare Figure 9 9 SO that, after completion of the stretching step, a central drawn zone has formed, the appearance of which is shown in Figure 10. On cold-drawing, the central zone has no tendency towards a .
reduction of the internal diiameter of the tube, as long as stretching is~limited to ~bout a ~actor of 3. In . this embodiment of the lnven-tion,-lt is ~hus not-necessary to cause the mandrel 27 to assume its positivn in the tube .
- before the actua7 stretching step~ Figures 11-12 show an embodiment of the invention in which the stretched central zone 51a has a greater leng-th than in the embodi-men*s of the invention so far described. ~en the interlor of the tu~e is subjected to pressure, parts of . .... ~ .. .
adjacent neck sections are:also formed, in addition *o the two future mouth parts, these neck sections being given a greater diameter than that of the actual mouth part.
At this stage, it is pre~erable to allow the future neck section to be shaped to such an extent that the greatest rise in diameter is at ieast 3-fold. This-ha-s *he advantage *hat a relatively dimensionally stable neck section is formed which, during the subsequent heating in conjunction with the shaping o~ the remaining part o~-the container~ is affected only to a small ex~enc. ~he appearance of a pre-moulding, which was formed from a blank part partially shown in Figure 12, can be seen in Figure 14.
In the above description9 it was explained how the blank parts are formed by severing the drawn and shaped tube. In a preferred embodiment of the invention, severing of the blank parts from one another is effected with the aid of one or several severing discs which revolve under pressure about the circumferential surface of the tube formed at the.transition between the ~wo s future mouth parts.
It was ass~ed in the above description that heating of the centra~ material sections of the tube is ef~ected-by heating jaws. To obtain the most uniform heating of the material possible, the tube should pre-ferably rotate relative to the heating element. To make this possible, the clamping devices are moAi~ied 7 if appropriate having cone type bearings or having heating jaws which revolve about the tubeO
In the case where the central sections of the tube are drawn at an initial temperature which is below the glass transition temperature Tg, the material is heated after the drawing step to a temperature above ~he glass transition temperature Tg, after which the ~uture mouth part and parts of the adjacent neck sections are shaped.
- I~ addition to the above description, the inven-tion is also comprised by the attached patent claims.
Claims
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-1. Apparatus for the manufacture of a tubular pre-moulding from a thermoplastic material comprising means for axially stretching a tube of the thermo-plastic material to a substantially reduced material thickness in at least a central zone of the tube while substantially maintaining the diameter of the tube in the axially stretched section in said central zone, the reduction being by a factor sufficient to cause yielding and orienting of the material substan-tially in the axial direction of the future pre-moulding, means for effecting the axial stretching of the tube at a temperature not greater than the glass transition temperature of the thermoplastic material, a mould surrounding the tube, means for heating the material in one of the oriented zones to a temperature above the glass transition temperature and means for expanding said material in the radial direction of the tube until it makes contact with said mould to form a mouth part with adjacent neck section of the pre-moulding, the material then being cooled to a tempera-ture below the glass transition temperature, there-after heated at one end of the tube to a temperature above the glass transition temperature and formed as a closure at said one end for the pre-moulding.
2. Apparatus as claimed in claim 1, wherein said mould is formed such that during the radial expansion of the material, two adjoining mouth parts with respective adjacent neck sections for two future pre-mouldings are formed, the apparatus further com-prising means for severing the tube between the two future mouth parts to form two separate blanks, each of the latter itself forming a tubular pre-moulding.
3. Apparatus as claimed in claim 1, comprising means for locally heating the material in the zone envisaged for axial stretching to a temperature above the glass transition temperature before the material is stretched in the axial direction of the tube.
4 Apparatus as claimed in claim 1, comprising means for forming a local annular zone of reduced thickness in the zone of axial stretching of the tube before stretching such that upon stretching, the material is caused to flow, at least in said annular zone in the axial direction of the tube with simul-taneous substantial reduction in the thickness of the tube wall.
5. Apparatus as claimed in claim 1, comprising means for applying local external pressure to the tube in an annular region in the zone envisaged for axial stretching such that flow during the axial stretching of the material commences in the region subjected to external pressure.
6. Apparatus as claimed in claim 1, wherein said mould has walls positioned relative to the tube such that the neck section formed by the radial expan-sion of the material in the zone of reduced thickness of material is stretched in the circumferential di-rection of the material by a factor of more than 2.
7. Apparatus as claimed in claim 1, comprising means for locally heating the material in the zone envisaged for axial stretching in at least one annular region in which the temperature exceeds the tempera-ture of the adjacent material by from 3 to 20°C., the flow during the axial stretching of the material starting in the region of elevated temperature.
8. Apparatus for the manufacture of a tubular pre-moulding from a tube of thermoplastic material comprising a pair of separate clamping means each for holding one end of a tube, means supporting the clamp-ing means for movement towards and away from one another, drive means for moving the clamping means toward and away from one another, each clamping means having an open position for receiving one end of the tube and a closed position for holding said end in clamped position, the tube being stretched in the zone between the clamping means upon movement of the clamp-ing means away from one another whereby the thickness of the stretched material in said zone is reduced, the reduction being by a factor sufficient to cause yield-ing and orienting of the material substantially in the axial direction of the future pre-moulding, a blow mandrel insertable through one of the clamping means into the interior of the stretched zone of the tube, a mould surrounding said stretched zone of the tube, the blow mandrel radially expanding the stretched material to bring the material into contact with the mould to form a mouth part and adjacent neck section for the future pre-moulding means for severing the future pre-moulding from the remainder of the material at said mouth, the material then being cooled to a temperature below the glass transition temperature, thereafter heated at one end of the tube to a tempera-ture above the glass transition temperature and formed as a closure at said one end for the pre-moulding.
9. Apparatus as claimed in claim 8, wherein said mould is formed such that during the radial expan-sion of the material, two adjoining mouth parts with respective adjacent neck sections for two future pre-mouldings are formed, said severing means cutting the material between the two future mouth parts to form two separate blanks, each of the latter itself forming a tubular pre-moulding.
10. Apparatus as claimed in claim 8, comprising means for locally heating the material in the zone envisaged for axial stretching to a temperature above the glass transition temperature before the material is stretched in the axial direction of the tube.
11. Apparatus as claimed in claim 8, comprising means for forming a local annular zone of reduced thick-ness in the zone of axial stretching of the tube before stretching such that upon stretching, the material is caused to flow, at least in said annular zone, in the axial direction of the tube with simultaneous substan-tial reduction in the thickness of the tube wall.
12. Apparatus as claimed in claim 8, comprising means for applying local external pressure to the tube in an annular region in the zone envisaged for axial stretching such that flow during the axial stretching of the material commences in the region subjected to external pressure.
13. Apparatus as claimed in claim 8, wherein said mould has walls positioned relative to the tube such that the neck section formed by the radial expan-sion of the material in the zone of reduced thickness of material is stretched in the circumferential direc-tion of the material by a factor of more than 2.
14. Apparatus as claimed in claim 8, comprising means for locally heating the material in the zone envisaged for axial stretching in at least one annular region in which the temperature exceeds the temperature of the adjacent material by from 3 to 20°C., the flow during the axial stretching of the material starting in the region of elevated temperature.
15. Apparatus as claimed in claim 8, comprising a turntable supporting said clamping means, said sup-porting means therefor, said drive means, said mould and said blow mandrel, the turntable being movable through successive angular positions at which succes-sive operations are carried out.
16. Apparatus for producing a tubular pre-moulding of a thermoplastic of polyester or polyamide type from a tubular blank in which the pre-moulding comprises a mouth part with adjacent neck section at one end, a closure at the other end and a tubular section between the two ends, the closed end and the tubular section of the blank consisting mainly of orientable material, said apparatus comprising means for reducing the thickness of the mouth part and adjacent neck section of said blank to orient the material by the reduction of the thickness of the material, means for maintaining the remainder of the blank with its original thickness to form said pre-moulding, such that at least in the mouth part, said material has a lower degree of orientation in the circumferential direction of the pre-moulding as compared to the axial direction, and means for con-trolling the orientation of the mouth part and adja-cent neck section of the pre-moulding by the thickness reduction to provide an increased glass transition temperature Tg in said mouth part and neck section which is substantially equal to the glass transition temperature of said tubular section when the orient-able material of said tubular section is oriented by a subsequent blowing of the pre-moulding to a con-tainer.
17. Apparatus as claimed in claim 16 wherein the orientable material of the blank is substantially amorphous with a crystallinity of less than 5%.
18. Apparatus as claimed in claim 16 further comprising means for maintaining the material of the blank at a temperature below the glass transition temperature in said mouth part and adjacent neck re-gion at the commencement of reducing the thickness thereof.
19. Apparatus as claimed in claim 16 further comprising means for radially expanding the axially oriented material of the mouth part and adjacent neck section after heating said material to a temperature above the glass transition temperature.
20. Apparatus as claimed in claim 16 wherein said thermoplastic material is selected from the group consisting of polyethylene terephthalate, polyhexa-methylene adipamide, polycaprolactam, polyhexamethy-lene sebacamide, polyethylene 2,6- and 1,5-naphthalate, polytetramethylene 1,2-dihydroxybenzoate and copoly-mers of ethylene terephthalate and ethylene isophtha-late.
21. Apparatus as claimed in claim 16 wherein said thermoplastic material is polyethylene tereph-thalate and is reduced in thickness by at least about 3 while concurrently being stretched axially.
22. Apparatus as claimed in claim 16 wherein the orientation of the mouth part and adjacent neck section obtained by reduction of thickness provides a crystallinity of between 10 and 20%.
23. Apparatus as claimed in claim 16 wherein said thickness reducing means comprises means for applying local radial pressure to said blank in the region thereof in which mouth part and adjacent neck section are to be formed to initiate said reduction of thickness thereof.
24. Apparatus as claimed in claim 23 wherein said thickness reducing means causes said material to undergo axial stretching in said region concur-rently with the reduction of thickness, said stretch-ing commencing at the location of application of local radial pressure.
25. Apparatus as claimed in claim 23 wherein said means for applying local radial pressure to said blank comprises a roller having a cylindrical central pressure surface, an inclined transition surface and a cylindrical bearing surface of smaller diameter than that of said pressure surface.
25. Apparatus as claimed in claim 25 wherein said thickness reducing means further comprises means supporting said roller for radial and axial travel relative to said blank.
27. Apparatus as claimed in claim 26 wherein the difference in diameter between the central pres-sure surface and the bearing surface of said roller is equal to twice the reduction in thickness of said material, said transition surface extending at an angle of about 45° relative to said surfaces.
2. Apparatus as claimed in claim 1, wherein said mould is formed such that during the radial expansion of the material, two adjoining mouth parts with respective adjacent neck sections for two future pre-mouldings are formed, the apparatus further com-prising means for severing the tube between the two future mouth parts to form two separate blanks, each of the latter itself forming a tubular pre-moulding.
3. Apparatus as claimed in claim 1, comprising means for locally heating the material in the zone envisaged for axial stretching to a temperature above the glass transition temperature before the material is stretched in the axial direction of the tube.
4 Apparatus as claimed in claim 1, comprising means for forming a local annular zone of reduced thickness in the zone of axial stretching of the tube before stretching such that upon stretching, the material is caused to flow, at least in said annular zone in the axial direction of the tube with simul-taneous substantial reduction in the thickness of the tube wall.
5. Apparatus as claimed in claim 1, comprising means for applying local external pressure to the tube in an annular region in the zone envisaged for axial stretching such that flow during the axial stretching of the material commences in the region subjected to external pressure.
6. Apparatus as claimed in claim 1, wherein said mould has walls positioned relative to the tube such that the neck section formed by the radial expan-sion of the material in the zone of reduced thickness of material is stretched in the circumferential di-rection of the material by a factor of more than 2.
7. Apparatus as claimed in claim 1, comprising means for locally heating the material in the zone envisaged for axial stretching in at least one annular region in which the temperature exceeds the tempera-ture of the adjacent material by from 3 to 20°C., the flow during the axial stretching of the material starting in the region of elevated temperature.
8. Apparatus for the manufacture of a tubular pre-moulding from a tube of thermoplastic material comprising a pair of separate clamping means each for holding one end of a tube, means supporting the clamp-ing means for movement towards and away from one another, drive means for moving the clamping means toward and away from one another, each clamping means having an open position for receiving one end of the tube and a closed position for holding said end in clamped position, the tube being stretched in the zone between the clamping means upon movement of the clamp-ing means away from one another whereby the thickness of the stretched material in said zone is reduced, the reduction being by a factor sufficient to cause yield-ing and orienting of the material substantially in the axial direction of the future pre-moulding, a blow mandrel insertable through one of the clamping means into the interior of the stretched zone of the tube, a mould surrounding said stretched zone of the tube, the blow mandrel radially expanding the stretched material to bring the material into contact with the mould to form a mouth part and adjacent neck section for the future pre-moulding means for severing the future pre-moulding from the remainder of the material at said mouth, the material then being cooled to a temperature below the glass transition temperature, thereafter heated at one end of the tube to a tempera-ture above the glass transition temperature and formed as a closure at said one end for the pre-moulding.
9. Apparatus as claimed in claim 8, wherein said mould is formed such that during the radial expan-sion of the material, two adjoining mouth parts with respective adjacent neck sections for two future pre-mouldings are formed, said severing means cutting the material between the two future mouth parts to form two separate blanks, each of the latter itself forming a tubular pre-moulding.
10. Apparatus as claimed in claim 8, comprising means for locally heating the material in the zone envisaged for axial stretching to a temperature above the glass transition temperature before the material is stretched in the axial direction of the tube.
11. Apparatus as claimed in claim 8, comprising means for forming a local annular zone of reduced thick-ness in the zone of axial stretching of the tube before stretching such that upon stretching, the material is caused to flow, at least in said annular zone, in the axial direction of the tube with simultaneous substan-tial reduction in the thickness of the tube wall.
12. Apparatus as claimed in claim 8, comprising means for applying local external pressure to the tube in an annular region in the zone envisaged for axial stretching such that flow during the axial stretching of the material commences in the region subjected to external pressure.
13. Apparatus as claimed in claim 8, wherein said mould has walls positioned relative to the tube such that the neck section formed by the radial expan-sion of the material in the zone of reduced thickness of material is stretched in the circumferential direc-tion of the material by a factor of more than 2.
14. Apparatus as claimed in claim 8, comprising means for locally heating the material in the zone envisaged for axial stretching in at least one annular region in which the temperature exceeds the temperature of the adjacent material by from 3 to 20°C., the flow during the axial stretching of the material starting in the region of elevated temperature.
15. Apparatus as claimed in claim 8, comprising a turntable supporting said clamping means, said sup-porting means therefor, said drive means, said mould and said blow mandrel, the turntable being movable through successive angular positions at which succes-sive operations are carried out.
16. Apparatus for producing a tubular pre-moulding of a thermoplastic of polyester or polyamide type from a tubular blank in which the pre-moulding comprises a mouth part with adjacent neck section at one end, a closure at the other end and a tubular section between the two ends, the closed end and the tubular section of the blank consisting mainly of orientable material, said apparatus comprising means for reducing the thickness of the mouth part and adjacent neck section of said blank to orient the material by the reduction of the thickness of the material, means for maintaining the remainder of the blank with its original thickness to form said pre-moulding, such that at least in the mouth part, said material has a lower degree of orientation in the circumferential direction of the pre-moulding as compared to the axial direction, and means for con-trolling the orientation of the mouth part and adja-cent neck section of the pre-moulding by the thickness reduction to provide an increased glass transition temperature Tg in said mouth part and neck section which is substantially equal to the glass transition temperature of said tubular section when the orient-able material of said tubular section is oriented by a subsequent blowing of the pre-moulding to a con-tainer.
17. Apparatus as claimed in claim 16 wherein the orientable material of the blank is substantially amorphous with a crystallinity of less than 5%.
18. Apparatus as claimed in claim 16 further comprising means for maintaining the material of the blank at a temperature below the glass transition temperature in said mouth part and adjacent neck re-gion at the commencement of reducing the thickness thereof.
19. Apparatus as claimed in claim 16 further comprising means for radially expanding the axially oriented material of the mouth part and adjacent neck section after heating said material to a temperature above the glass transition temperature.
20. Apparatus as claimed in claim 16 wherein said thermoplastic material is selected from the group consisting of polyethylene terephthalate, polyhexa-methylene adipamide, polycaprolactam, polyhexamethy-lene sebacamide, polyethylene 2,6- and 1,5-naphthalate, polytetramethylene 1,2-dihydroxybenzoate and copoly-mers of ethylene terephthalate and ethylene isophtha-late.
21. Apparatus as claimed in claim 16 wherein said thermoplastic material is polyethylene tereph-thalate and is reduced in thickness by at least about 3 while concurrently being stretched axially.
22. Apparatus as claimed in claim 16 wherein the orientation of the mouth part and adjacent neck section obtained by reduction of thickness provides a crystallinity of between 10 and 20%.
23. Apparatus as claimed in claim 16 wherein said thickness reducing means comprises means for applying local radial pressure to said blank in the region thereof in which mouth part and adjacent neck section are to be formed to initiate said reduction of thickness thereof.
24. Apparatus as claimed in claim 23 wherein said thickness reducing means causes said material to undergo axial stretching in said region concur-rently with the reduction of thickness, said stretch-ing commencing at the location of application of local radial pressure.
25. Apparatus as claimed in claim 23 wherein said means for applying local radial pressure to said blank comprises a roller having a cylindrical central pressure surface, an inclined transition surface and a cylindrical bearing surface of smaller diameter than that of said pressure surface.
25. Apparatus as claimed in claim 25 wherein said thickness reducing means further comprises means supporting said roller for radial and axial travel relative to said blank.
27. Apparatus as claimed in claim 26 wherein the difference in diameter between the central pres-sure surface and the bearing surface of said roller is equal to twice the reduction in thickness of said material, said transition surface extending at an angle of about 45° relative to said surfaces.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000487316A CA1210915A (en) | 1979-06-11 | 1985-07-23 | Process for the production of a blank for containers and blank produced by the process |
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7905043-1 | 1979-06-11 | ||
| SE7905043A SE424287B (en) | 1979-06-11 | 1979-06-11 | PREFORMED PREFORM AND PROCEDURE AND DEVICE FOR PREPARING THIS AGREEMENT |
| CA000352909A CA1190365A (en) | 1980-05-28 | 1980-05-28 | Process for the production of a blank for containers and blank produced by the process |
| CA000466796A CA1205264A (en) | 1979-06-11 | 1984-10-31 | Process for the production of a blank for containers and blank produced by the process |
| CA000487316A CA1210915A (en) | 1979-06-11 | 1985-07-23 | Process for the production of a blank for containers and blank produced by the process |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000466796A Division CA1205264A (en) | 1979-06-11 | 1984-10-31 | Process for the production of a blank for containers and blank produced by the process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1210915A true CA1210915A (en) | 1986-09-09 |
Family
ID=27166692
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000487316A Expired CA1210915A (en) | 1979-06-11 | 1985-07-23 | Process for the production of a blank for containers and blank produced by the process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1210915A (en) |
-
1985
- 1985-07-23 CA CA000487316A patent/CA1210915A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |