CA1273175A - Apparatus for the manufacture of a cup-like article from thermoplastic material - Google Patents
Apparatus for the manufacture of a cup-like article from thermoplastic materialInfo
- Publication number
- CA1273175A CA1273175A CA000560155A CA560155A CA1273175A CA 1273175 A CA1273175 A CA 1273175A CA 000560155 A CA000560155 A CA 000560155A CA 560155 A CA560155 A CA 560155A CA 1273175 A CA1273175 A CA 1273175A
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- Canada
- Prior art keywords
- zone
- blank
- press
- channels
- cup
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
The apparatus comprises a clamp for clamping a flat blank of amorphous thermoplastic material in a peripheral region thereof to form an inner zone completely surrounded by an outer clamped zone. A press engages the inner zone of the blank in a central region thereof smaller than the total area of the inner zone to form a band-like zone between the outer clamped zone and the central region in contact with the press. The press and the clamp should displace relative to one another and the material of the blank should be kept at a predetermined temperature, to produce free stretching by drawing of the blank in a drawing region between the outer surface of the press and the inner surface of the clamp without contact of the drawn material with the surfaces of the clamp and the formation in the drawing region of the material of a transition zone at which flow takes place in the material reducing the original thickness of the blank by a factor sufficient to effect crystallization of the material and substantially monoaxial orientation. This produces a drawn element which comprises an edge part composed of the clamped zone and a body which is drawn relative to the edge part and includes the monoaxially oriented crystallized material.
The apparatus comprises a clamp for clamping a flat blank of amorphous thermoplastic material in a peripheral region thereof to form an inner zone completely surrounded by an outer clamped zone. A press engages the inner zone of the blank in a central region thereof smaller than the total area of the inner zone to form a band-like zone between the outer clamped zone and the central region in contact with the press. The press and the clamp should displace relative to one another and the material of the blank should be kept at a predetermined temperature, to produce free stretching by drawing of the blank in a drawing region between the outer surface of the press and the inner surface of the clamp without contact of the drawn material with the surfaces of the clamp and the formation in the drawing region of the material of a transition zone at which flow takes place in the material reducing the original thickness of the blank by a factor sufficient to effect crystallization of the material and substantially monoaxial orientation. This produces a drawn element which comprises an edge part composed of the clamped zone and a body which is drawn relative to the edge part and includes the monoaxially oriented crystallized material.
Description
' 1~7~175 The invention relates to the manufacture of articles from a thermoplastic of polyester or polyamide type, preferably of polyethylene terephthalate, the art-icles being formed from an element which consists of an edge part which surr~unds a body in an arrangement in which the latter is sunk relativeto the edge part. The elementis formedfrom a blank of mainly amor~hous material or from a material having a crystallinity of less than 10%.
The blank consists, for example, of a flat plate, a blank shell or the like. The body or parts thereof are shaped by stretching the blank until that material flows which is located within the material sections of the blank~ which form the edge part in the element, the material stretched up to flowing in the body assuming a crystallinity of between lC%and 25%, whilst the crystallinity in the ~aterial in the edge ~, . .
part and in the unstretched parts retains its original value of less than lO~o. The edge part is severed from the body, the latter being elongated in the axial direction by a number of drawing steps, whilst the dimen-sions of the ~ody at right angles thereto are reduced at the same time. The body of the element of the drawn part is reshaped by a blow-mouldipg process to give the article.
In the manufacture of products from thermo-~r~
, 1~73175 plastics, the starting material is in most cases a virtually flat blank. Either an end product is formed here substantially in one deformation step, or a pre-moulding is formed for later reshaping to give the end product. The shaping of the blank is effected, according to methods known at present, either by the blow-moulding process or by the thermc-forming process.
In the blow-moulding process~ thick sections are as a rule obtained in the bottom. In the thermo-forming process, either so-called negative thermo-forming or so-called positive thermo-forming is used. In the negative thermo-forming process, a thin bottom is obtained, whilst a thick bottom is obtained in the posi-tive thermo-forming process.
- In negative thermo-forming, a warm sheet or a warm film is placed over cavities, after which the material of the film or the sheet is pressed and sucked into the cavities by external pressure and internal reduced pressure. This has the result that the material is stretched and becomes thin, when it is sucked into the particular cavities. If the cavity is a cup, a thin stretched bottom and a wall thickness increasing in the direction of the edge of the cup are obtained.
In positive thermo-forming the cup mould forms a projecting body and the material of the film or sheet is pressed and sucked over this projecting body. This has the result that the material on the upper part of the projecting body, that is to say the bottom of the cup, !
7317~i remains thick and essentially unstretched, whilst the thickness of the material decreases to-Yards the edge of the cup.
To obtain an adequate material thickness in the bottom part of the cup in negative thermo~forming, a sufficient thickness in the starting material must be chosen. To obtain an adequate thickness in the edge zone of the cup by positive thermo-forming, which is necessary for stability of the cup, a sufficient thick-ness of starting material must likewise be chosen.
In negative thermo-forming, the material zones between the shaped cups remain uninfluenced and are subsequently severed, after the manufacture of the actual cups.
In positive thermo-forming, the material between the cups is drawn into recesses and severed from the cups formed. In positive thermo-forming, cup bottoms are thus obtained which have substantially the same thick-hess as the starting material. Both forming processes require an unnecessarily high consumption of material, which is of economic importance in the mass production of articles.
The present invention eliminates certain disad-vantages connected with the technology hitherto known.
The invention is suitable preferably for the manufacture of articles from thermoplastics of the poly-ester or polyamide type. Examples of such materials are polyethylene terephthalate, polyhexamethylene-adipamide, polycaprolactam, polyhexamethylene-sebacamide, polyethylene 2,6- and l,~-naphthalate, polytetramethylene .
l,2-dihydroxybenzoate and copolymers of ethylene terephthalate, ethylene isophthalate and similar polymers. The description of the invention below relates mainly to polyethylene terephthalate, called PET in the further text, but the invention is not restricted exclusively to the use of either this material or other materials already mentioned; instead, it is also suitable for many other thermoplastics.
For a better understanding of the existing problem and of the invention, several characteristic properties of the polyester polyethylene terephthalate are described belcw. From the literature, for example Properties of Polymers, by D.W. van Krevelen, Elsevier Scientific Publishing Company, 1976, 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 3 7 and 319 in the book "Properties of Polymers".
The symbols used in the discussion below correspond to the symbols in the said book.
PET, like many other thermoplastics, can be oriented by stretching the material. Normally this stretching takes place at a temperature above the glass transition temperature Tg of the material. The strength properties of the material are improved by orienting. The literature shows that~ in the case of the thermoplastic PET, an increase in the stretching ratioJ~, that is to say the quotient of the length of the stretched material and the length of the unstretched
The blank consists, for example, of a flat plate, a blank shell or the like. The body or parts thereof are shaped by stretching the blank until that material flows which is located within the material sections of the blank~ which form the edge part in the element, the material stretched up to flowing in the body assuming a crystallinity of between lC%and 25%, whilst the crystallinity in the ~aterial in the edge ~, . .
part and in the unstretched parts retains its original value of less than lO~o. The edge part is severed from the body, the latter being elongated in the axial direction by a number of drawing steps, whilst the dimen-sions of the ~ody at right angles thereto are reduced at the same time. The body of the element of the drawn part is reshaped by a blow-mouldipg process to give the article.
In the manufacture of products from thermo-~r~
, 1~73175 plastics, the starting material is in most cases a virtually flat blank. Either an end product is formed here substantially in one deformation step, or a pre-moulding is formed for later reshaping to give the end product. The shaping of the blank is effected, according to methods known at present, either by the blow-moulding process or by the thermc-forming process.
In the blow-moulding process~ thick sections are as a rule obtained in the bottom. In the thermo-forming process, either so-called negative thermo-forming or so-called positive thermo-forming is used. In the negative thermo-forming process, a thin bottom is obtained, whilst a thick bottom is obtained in the posi-tive thermo-forming process.
- In negative thermo-forming, a warm sheet or a warm film is placed over cavities, after which the material of the film or the sheet is pressed and sucked into the cavities by external pressure and internal reduced pressure. This has the result that the material is stretched and becomes thin, when it is sucked into the particular cavities. If the cavity is a cup, a thin stretched bottom and a wall thickness increasing in the direction of the edge of the cup are obtained.
In positive thermo-forming the cup mould forms a projecting body and the material of the film or sheet is pressed and sucked over this projecting body. This has the result that the material on the upper part of the projecting body, that is to say the bottom of the cup, !
7317~i remains thick and essentially unstretched, whilst the thickness of the material decreases to-Yards the edge of the cup.
To obtain an adequate material thickness in the bottom part of the cup in negative thermo~forming, a sufficient thickness in the starting material must be chosen. To obtain an adequate thickness in the edge zone of the cup by positive thermo-forming, which is necessary for stability of the cup, a sufficient thick-ness of starting material must likewise be chosen.
In negative thermo-forming, the material zones between the shaped cups remain uninfluenced and are subsequently severed, after the manufacture of the actual cups.
In positive thermo-forming, the material between the cups is drawn into recesses and severed from the cups formed. In positive thermo-forming, cup bottoms are thus obtained which have substantially the same thick-hess as the starting material. Both forming processes require an unnecessarily high consumption of material, which is of economic importance in the mass production of articles.
The present invention eliminates certain disad-vantages connected with the technology hitherto known.
The invention is suitable preferably for the manufacture of articles from thermoplastics of the poly-ester or polyamide type. Examples of such materials are polyethylene terephthalate, polyhexamethylene-adipamide, polycaprolactam, polyhexamethylene-sebacamide, polyethylene 2,6- and l,~-naphthalate, polytetramethylene .
l,2-dihydroxybenzoate and copolymers of ethylene terephthalate, ethylene isophthalate and similar polymers. The description of the invention below relates mainly to polyethylene terephthalate, called PET in the further text, but the invention is not restricted exclusively to the use of either this material or other materials already mentioned; instead, it is also suitable for many other thermoplastics.
For a better understanding of the existing problem and of the invention, several characteristic properties of the polyester polyethylene terephthalate are described belcw. From the literature, for example Properties of Polymers, by D.W. van Krevelen, Elsevier Scientific Publishing Company, 1976, 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 3 7 and 319 in the book "Properties of Polymers".
The symbols used in the discussion below correspond to the symbols in the said book.
PET, like many other thermoplastics, can be oriented by stretching the material. Normally this stretching takes place at a temperature above the glass transition temperature Tg of the material. The strength properties of the material are improved by orienting. The literature shows that~ in the case of the thermoplastic PET, an increase in the stretching ratioJ~, that is to say the quotient of the length of the stretched material and the length of the unstretched
2 7 317 _ 5 material, also leads to an increase in the improvement of the material properties. When the stretching ratio is increased from about 2 to 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 317 that, after 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 sm~ll elongation, whilst the elonga-tion at ~ = 2.8 i$ substantially larger. In the further test, the term "step1' issometimes used to desig-nate orienting which is obtained by stretching, or a reduction in thickness by at least about 3 times, and which leads to the marked improvements of t~e material properties, indicated above.
The diagrams quoted abcve show changes which are obtained on mono-axial orientation of the material.
In biaxial orientation, similar effects are obtained in both directions of orientation. Orientation is carried out as a rule by successive stretchings.
Improved material properties, corresponding to those which are obtained by the "step" defined above, are also obtained if an amorphous material is stretc~ed until it flows and, before flowing, the ma~erial is at a tem-perature which is below the glass transition temperature Tg. In a rod being drawn, a reduction of the diameter ~2 7~17 J
~ about 3 times results in th~ flow zone. On drawing, the flow zone is continuously displaced into the a~orphous mat~rial, whilst at the same time the material, which has already undergone the state of flowing, absorbs the tensile forces of the test rod without an additio~al permanent stretching.
According to the invention, an element is pro-duced which consists of an edge part and a cup part, starting from a substantially flat blank of amorphous material or having a crystallinity of less than io%. The material in annular sections in ~he blank is transformed into the state of flow by a drawlng process. The cup part is formed in this way. In certain applications, the ratio between the radial and the axial expansion of the cup is such that production of the beaker in a single drawing step is not possible. According to tne invention, the desired ratios are obtained by a number of redrawing steps of the cup, the diameter of the cup being reduced in each redrawing step~ whilst the thickness of the material remains more or less unchanged.
The cup part of the element or the drawn cup is reshaped by a blow-moulding process to give the article According to the invention, an element is obtained which consists of an edge part and a cup part, the material preferably being of more or less uniform thickness and orientation in the entire bottom of the cup part (cup). In a certain embodiment of the invention, the material in the bottom part of the cup 1~7317Si moreover consists completely or partially of material of the same thickness as that of the material of the wall.
The remaining sections of ma*erial have the thickness and material properties of the material.
In certain applicat~ons, the bottom is more or less completely flat, whilst in other applications the bottom consists of parts which are axially displaced relative to the axis of the cup. In this case, in certain embodiments, annular edge sections are formed adjoining the lower edge of the wall, whilst in other embodiments central bottom sections are displaced further away from the upper opening edge of the element.
The element consists of an edge part which surrounds a ~ody which is sunk relative to the edge part. The material in the edge part is mainly amor-phous or has a crystallinity of less than 10%. The body has a wall part and a bottom part. The wall part consists of material which has been drawn at a tempera-ture below the glass transition temperature Tg, until flow sets in, and in which the crystallinity is between lOo~and 25%. In the basic design of the element, the bottom consists of mainly amorphous material or of material having a crystallinity of less than 10%. In embodiments of the invention, the bottom consists, as desired, of material which has been drawn at a tem-perature below the glass transition temperature Tg and at a crystallinity between 10%and 25%, until flow sets in, that is to say of a material having properties which 1~ 73 175 mainly are identical to the material properties of the wall part of the element,or of material sections which have been drawn until flow sets in and which alternate with material sections of mainly amorphous material or materlal having a crystallinity of less than 10%. In certain embodiments, the material zones already mentioned are displaced in the axial direction relative to the lower edge of the wall part.
During the production of an element, a mainly flat blank of thermoplastic, having a crystallinity of less than 10%,is clamped in ~t a temperature below the glass transition temperature Tg between counter-holders, so that a zone is formed which is completely surrounded by the clamped-in material sections. A press device the contact surface of which is smaller than the surface area of the zone, is applied against this zone. Thus, a closed strip-like material zone is formed between the clamped-in material sections of the blank and that part of the zone which is in contact with the press device.
Subsequently, a drive mechanism s~ifts the press device relative to the counter-holder, while the press device remains in contact with the zone. The material in the strip-like zone is thus stretched in such a way that flow of the material occurs, the material being oriented, whilst at the same time the thickness of the material is reduced by about 3 times in the case of PET. The wall part of the element is formed during the stretching pro-cess.
Since the circumference of the contact surface ~ ~ 73175 _ 9 _ of the press device is smaller than the inner circumference of the clamping devices, the material which adjoins the edge of the press device is subjected to the greatest stress, for which reason the flow of the material normally starts at this point.
The effect thus resulting is ~urther reinforced by the fact that the transition from the contact surface of the press device to the side walls of the press device is made relatively sharp-edged. When flow has set in, the zone of flow of the material is gradually shifted in the direction of the clamping devices. In certain application examples, the press step is interrupted when the flow zone has reached the press devices. In other application examples, the press step continues, renewed flowing of the material takir.g place adjoining the edges of the press device and being displaced from these zones towards the centre of the material. ~hen all the material which is in contact with the contact surface-of the press device has undergone flow, that -material between the clamping devices which is located next to the inner circumference of the clamping devices is utilised for a further drawing step in certain appli-cation examples. To make this possible, a somewhat elevated temperature in this material is normally required.
The starting temperature, however, is still below the glass transition temperature Tg.
- Incer~n a~plication examples, accelerated cooling of the drawn material is necessary. In this case, the press d~ioe is preferably provided with a cooling device ~ 73 175 which is arranged in such a way that the zones of the material, which flow during drawing of the material, are in contact with the cooling deviceL
In certain applications~ the flow of the material is caused to start adjoining the clamping devices.
This is accomplished by providing the clamping devices with heating devices which raise the temperature of those material sections where flow is to start. The tem-perature in the ma~erial, however, is still below the glass transiti~n temperature Tg of the material.
When flow has set in, this continues in the direction of the contact surface of the press device and, in some cases which may occur, it continues past the transition from the side walls to the contact surface of the press device. To ensure that the clamping devices retain the blank in the future edge sections of the element, the clamping devices are as a rule provided with cooling devices.
The concept of the invention also comprises the possibility that, by a number of drawing steps which are arranged onP after the other, both in the wall part and in the bottom p~rt of the body, material sections are obtained which alternately consist of material sections which have been drawn until flow sets in and have in this way been given a reduced wall thickness, and undrawn material sections which have retained their wall thick-ness. In material sections located in the bottom part of the body, a displacement of the material in the axial direction of the body also takes place in certain appli-', ~ ~731~S
cation examples in conjunction with the drawing step, The edge part is removed from the element formedand the element is reshaped by a number of drawing steps.
These drawing steps take place at a temperature below the glass transition temperature Tg and effect a reduction of the diameter of the cup, whilst the length of the body is extended at the same time in the axial direction T~e drawing step effects exclusively a redistribution of the material without flow setting in.
The cup formed after the end of the drawing step has an opening at one end, whilst it has a bottom part at the other end. ~epending on the manner in which the elementhasbeen shaped, the bottom part consists wholly or partially of amorphousmaterial orof unoriented material. In the first-mentioned case, the bottom part thus retains the thickness of the starting material in the amorphous zone or in the amorphous zones. The amorphous material is suitable for use as a fixing material for welding additional parts to the cup. This requirement will be present, for example, when the cup is used as a container and the bottom part of the cup simultaneously represents the bo'tom part.of the container. In this case9 it is advantageous to weld an external foot to the container.
The cup shaped in the manner described possesses an spening part which, if appropriate after reworking, is preferably expanded in such a way that a beaded edge results, the stability of the beaded edge being increased by heating up to the maximum crystallisation temperature of the material. The beaded edge is thus outstandingly ~ L~73175 suitable for fitting, for example, a loose lid of a suit-able material, for example metal, by crimping.
In another application example, the drawing step at the cup is interrupted so that parts of the cup have a reduced diameter compared with the initial diameter.
By removing the bottom from this part of smaller diameterJ
expanding the edge formed and stabilising the opening which has been formed in the manner described in the pre-ceding section, a mouth part is obtained which is suit-able for fitting, for example, a closure or a crown cap.
The other still open part of the cup is closed, for example, by an end disc, in a manner similar to that already described, In the blow-moulding process, the starting point is either a cup which has been severed in the normal way from the edge part of the element, or from a newly drawn cup. By blow-moulding against warm mould walls, the cup, the material of which is at a temperature above the glass transition temperature Tg, is reshaped in such a way that it has exactly the form of the intended end product. In certain applications, a warm blowing mandrel is used in order to prevent excessive cooling of the material during the blow-moulding step.
It can be seen from what has been said that the combination of drawing, until flow sets in to obtain an element, redrawing of the cup of the element formed and a blow-moulding step offers many optional possibilities for the shaping of different types of articles.
An article produced in the manner described 1, 73.1~5 above is thus not only suitable for use as a container, but many applications are possible.
The invention will be clescribed in more detail by reference to a number of illustrations in which Figures 1 - 2 show optional embodiments of bands suitable for reshaping, Figure 3 shows an element having a bottom part of the body, consisting mainly of amorphous .
material, Figures 4 - lO show the principles of devices for drawing of the element, Figure ll shows a part of a device for redrawing o~
the cup of the element, Fi~ure 12 shows the cup of the element before . redrawing, ; Figure 13 shows the cup of the element after partial redrawing, Figure 14 shows the cup of the element after complete redrawingj . Figure 15 shows the cup o~ the element, having the part of the cup, which was partially redrawn, according to Figure 13, after renewed redrawing, Figure 16 shows a container produced from a cup according to Figure 15~ .-Figures 17 - 19 show the counterparts to Figures 12 - 14, the bottom part of the cup having sections of amorphous material and Fi~ures20 - 22 show optional em~odiments of blow-moulded ~73~7,5 articles.
Figures 11 and 16 are on the same sheet of drawings.
Figures 1 - 2 show a band or a blank 14', 14" of thermoplastic, the bands or blanks being seen from above.
In the figures, annular material zones 16', 16" or 17', 17"
are represented. Moreover, a material zone 15', 15" is indicated which is surrounded by the original annular material zone 17', 17". The material zone 16 marks that zone which, cn drawing of the blank, is clamped in between the clamping devices 30 a-b (see Figure 4). The material zone 15 marks that zone which, on drawing of the blank, is in contact with the press face of the press device 20 (see Figure 4).
The material zone 17 marks that zone which, on drawing of the blank, is brought into the state of flow.
An element 10 consisting of an edge part 12 of the body 13 is seen in Figure 3. The body in turn consists of a wall part 18 and a bottom part 11. In the figure, the wall part consists of drawn material of reduced thickness compared with the thickness of the starting material. The bottom part 11 consists of material which, while retaining its material properties, has been displaced in the axial direction of the body. Moreover, a zone 19 is marked in which material belonging to the edge part 12 had been transformed into the state of flow.
In Figures 4-8, a number of clamping devices 30 which fix the blank 14 can be seen. A press device 20 having a press face 21 is located between the clamping devices 30. In Figure 4, the press device is in a ~ 73~75 position in which -the press.face 21 is located directly next to the upper surface of the blank 14. In Figure 5, the press device was shifted downwards, flow of the material.having started. In Fi~ure 6, the press device has been shi~ted to such an extent that an element according to Figure 3 has been formed. In Figure 7, the press device was yet further shifted, further flow of the material having taken place. An element 10'. has thus been formed, the body 13' of which has a bottom part llt the central sections of which consist of amorphous undrawn material which is surrounded by drawn oriented material in which flow has taken place. Finally, in Figure 8, the press device 20 has been shifted to such an extent that virtually the entire material in the bottom part 11" of the body 13" has undergone flow.
An element 10" has thus been formed in which both the wall part.and the bottom part o~ the body have a reduced wall thickness because the material has been in the state of flow and has-at the same time been oriented.: .
In Figures 9 - 10, an .optional embodiment of the cla.mping devices .~3 a-b is represented, which are pro-vided with cooling channels 31 and heating channels 34.
In.the figures, only the feedline for the heating channels is shown, whilst the di~charge line for the heating channels is located behind the feedline in the figu~es and is indicated by the upward-pointing arrow.
The cooling channels, like the heating channels, are covered by plate-like covers 35, the other surface of which at the same time represents the contact surface of the clamping devices for clamping the blank. An insulation 32 separates the cooled zone of the clamping devices from the heated zone. In certain applications, the heating channels are used as the cooling channe1s in the same way. I
Furthermore, the figures show an optional embodi- !
ment of a press device 20a which also has cooling channels 22. The cooling channels are covered by a cooling jacket 23 which at the same time represents the outer contact surface of the press device opposite the material during the process of drawing the latter.
Figure 9 shows a position of the press device, which corresponds to the position shown in Figure 5, and Figure 10 shows a position of the press device, which corresponds to the position in Figure 8. The press device is constructed with a face of rotationally symmetrical curvature, which is shaped in such a way that, on drawing within the flow range, the material is always in contact with the cooling Jacket, whilst that material which has not yet been in the state of flow is not in contact at any point with any device in the zone between the press device and the clamping devices.
- Heating of the material with the ~d of the heating channels 34 has the purpose of increasing the readiness of the material to flow.Heating is limited, how-ever, in such a way thatthe temperature of the material is always lower than the glass transition temperature Tg.
Heating makes it possible to allow the drawing step of the material to continue a little into the zone between 1273~7tj the jaws of the clamping devices, as shown in Figure 10.
Another optional application, where the increased readi-ness of the material to flow is exploited, is obtained when, during the drawing step, the zone of initial flow of the material is directed to the zone next to the inner edges of the clamping devices. After flow has taken place, the flow zone is gradually displaced in the direction away from the clamping devices towards the bottom of the press device, as the press device gradually shifts downwards as in the figures.
The result of this is that ~low always propagates in the same direction, and a new start of flow is avoided, such as takes place when the embodiment of the invention shown in ~igures 4 - 8 is used.
Figure 11 shows a device for redrawing the element formed before. In the figure which shows only a part of the device, a press plunger 40, a counter-holder ring 41, a clamping ring 42 and a wall part 18 i~
the element are seen, the wall part being in the process of shaping. Moreover, the bottom 11" in the body 13 of the element is seen. The clamping ring 42 is pro-vided with a calibration device 43 which determines the thickness o$ the material, drawn anew, in the wall part 18.
Figure 12 shows an element body 50 which has been formed by means of the press device 20a according to Figure 9 and in which the edge part of the element has been produced ~rom the body, In Figure 13, the shaping process of the body 50 was initiated with the aid of a 7~ ~75 device shown in Figure 11. The shaping process has progressed to such an extent that a mainly cylindrical larger part, having the same diameter as the body 50, and a shorter part 59 have been formed. In Figure 14, the shaping process has been completed, a mainly cylindrical body 52 of the same diameter as in the shorter part in Figure 13 having been formed.
Figure 15 shows a body 53, the shorter part 59 of which has been reshaped with the aid 'of a dev.-.
ice shbwn in Figure ll for the purpose of further reducing the diameter of the shorter part 59'. There is a transition 58 between the shorter cylindrical part 59' and the larger part of the body 53.
Figure 16 shows a bottle-like container 70~pro-duced from a body 53 according to ~igure 15. The bottom part of the shorter part 59' has been severed and replaced by a closure 55, for example a cap. The mouth edges formed on severing the bottom part were expanded and beaded, after which the material in the beaded material zones has preferably been givenan increased crystallinity as a result of heating the material up to the crystallisation temper~ture. This gives additional strength at the moubh edge so that the latter is well suited for closing the container, for example by means of a cap or a crown cork. The transition, already mentioned, between the shorter part and the larger part of the body now forms a bottle neck 58'. The figure also shows how an end disb 56 is fixed at the other end of the container ?~ after the container has ~ 73 17~
been filled. As a result of expanding, beading and heating of the material, material sections are here also obtained which are suitable, for example, for fitting an end disc. by crimping,in order to close-the container Figures 17 - 19 show counterparts to Figures 12 - 14. Thefigures showhow an element body, formed from the body 11' according to Figure 7, is subjected to an axial lengthening, with simultaneous reduction in the dia-meter of the body, and forms an almost completely cylin-drical body 61, the bottom part of this body consisting of a material section 62 of mainly amorphous material During the shaping process, an intermediate form of the body results, which is marked 60 in Figure 18.
In the embodiment of the invention in which a . body is formed which comprises an amorphous bottom sectlon,.
a.material zoneisa~.obtained which is suitable as a fixing .
material for welding on additional parts ~o- the body.
By rendering the material crystalline, a zone of extreme dimènsional stability is obtained, whereby it becomes possible to use the container for storing liquids under pressure, for example béverages to which carbonic acid has been added, without a risk of deforming the bottom part. The concept of the invention also comprises the replacement of the plane embodiment of the bottom part by a convex or concave face, depending on the particular wishes which apply corresponding to the individual appli-cations. -Figures 20 - 22 show.optional embodiments of 1~ 73 ~75 blow--moulded containers. - All the containers are closed by end discs in the manner already described in connec-tion with Figure 16. Of course, this combination of a blow-moulded container and an end disc is to be regarded only as an example of the possibilities avail-able for closure.
Figure 20 shows an embodiment in which all the material in the blow-moulded container consists of material previously drawn. The container is formed from a body part either according to Figure 12 or accord-ing to Figure 14 Figure 21 shows an embodiment of a blow-moulded container which has been formed from a body part accord-ing to Figure 17 or ~igure l9. On blow-moulding, the amorphous material zone 22 remained in the amorphous state without change, and it represents a thicker section in the bottom part of the container. In certain embodiments, this section is heated up to the crystal-lisation temperature of the material in order to form a bottom sectlon which is particularly suitable for withstanding deformation forces, for example~forces due to an internal pressure in the container. The amor-phous material is also suitable for the purpose of weld-ing additional plastic parts thereto.
Figure 22 shows an embodiment of a blow-moulded container ~Ihich has been formed from a body part, the bottom of the body part consisting alternately of material sections, which have been drawn until flow sets in, and of those material sections which have retained 1~ 73 ~75 their original thickness. In this way, a simple amorphous material section 21 has been formed which is surrounded by an annular amorphous section 72 which is located below the central section. The central section and the annular section are connected by material which has been drawn urt~ flowsets in. The a~nular material section thus forms standing surfaces for the container.
The parts forming the shell of the container are as a rule shaped from redrawn material. ~t least in the cases where the container has a relatively large a~ial dimension, such redrawing is necessary.
Blow-moulding is carried out in any known manner at a temperature of the material, which is above-the glass transition temperature Tg. Normally, blow- -moulding takes place against heated mould walls. In certain illustrative embodiments, a heated elongate blow mandrel is required in order to avoid excessive cooling of the material during the blow-moulding step.
The material oriented by flow possesses improved strength properties in the direction of orienting, which is largely the same as the direction of drawing the material Since the material has been heated to a temperature above the glass transition temperature Tg, there are no difficulties in a blow-moulding process with regard to reshaping the element by stretching the material in a direction which is mainly at right angles to the said direction of orienting. An element reshaped in this way forms, for example, a container having a central shell surface of a diameter which exceeds the ` 1~7;~175 diametPr of the opening, and havlng a bottom which con-sists of a standing surface which represents the tran-sition between the lower edge of the shell surface and the bottom surface, the bottom surface either being slightly concave or consisting of annular material sec-tions which are displaced relative to one another in the axial direction of the container.
The 2bove description merely represents examples for the application of the invention. The invention allows of course that a number of combinations of drawing steps take piace, zones of drawn and undrawn materlal also forming alternately. ~or example, the body con-~ sists of wall parts with sections which contain undrawn material, whilst the bottom part consists of sections, for example annular sections, which contain undrawn material and which are displaced in the axial direction of -the body relative to the lower edge of the wall part.
The concept of the invention comprises manv optional embodiments. According to one of these, drawing until the material in the body of the element flows is effected by a numberof successive drawing steps, the con-tact area of the press device decreasing for each drawing step. The result of this is t~at the width of the material zone 15 is adapted to the extent to which the drawing step has proceeded.
In addition to the above description, the inven-tion is also comprised by the attached patent claims.
This application is a division of Canadian Application No. 352,907 filed May 28, 1980~
I
1.
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 317 that, after 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 sm~ll elongation, whilst the elonga-tion at ~ = 2.8 i$ substantially larger. In the further test, the term "step1' issometimes used to desig-nate orienting which is obtained by stretching, or a reduction in thickness by at least about 3 times, and which leads to the marked improvements of t~e material properties, indicated above.
The diagrams quoted abcve show changes which are obtained on mono-axial orientation of the material.
In biaxial orientation, similar effects are obtained in both directions of orientation. Orientation is carried out as a rule by successive stretchings.
Improved material properties, corresponding to those which are obtained by the "step" defined above, are also obtained if an amorphous material is stretc~ed until it flows and, before flowing, the ma~erial is at a tem-perature which is below the glass transition temperature Tg. In a rod being drawn, a reduction of the diameter ~2 7~17 J
~ about 3 times results in th~ flow zone. On drawing, the flow zone is continuously displaced into the a~orphous mat~rial, whilst at the same time the material, which has already undergone the state of flowing, absorbs the tensile forces of the test rod without an additio~al permanent stretching.
According to the invention, an element is pro-duced which consists of an edge part and a cup part, starting from a substantially flat blank of amorphous material or having a crystallinity of less than io%. The material in annular sections in ~he blank is transformed into the state of flow by a drawlng process. The cup part is formed in this way. In certain applications, the ratio between the radial and the axial expansion of the cup is such that production of the beaker in a single drawing step is not possible. According to tne invention, the desired ratios are obtained by a number of redrawing steps of the cup, the diameter of the cup being reduced in each redrawing step~ whilst the thickness of the material remains more or less unchanged.
The cup part of the element or the drawn cup is reshaped by a blow-moulding process to give the article According to the invention, an element is obtained which consists of an edge part and a cup part, the material preferably being of more or less uniform thickness and orientation in the entire bottom of the cup part (cup). In a certain embodiment of the invention, the material in the bottom part of the cup 1~7317Si moreover consists completely or partially of material of the same thickness as that of the material of the wall.
The remaining sections of ma*erial have the thickness and material properties of the material.
In certain applicat~ons, the bottom is more or less completely flat, whilst in other applications the bottom consists of parts which are axially displaced relative to the axis of the cup. In this case, in certain embodiments, annular edge sections are formed adjoining the lower edge of the wall, whilst in other embodiments central bottom sections are displaced further away from the upper opening edge of the element.
The element consists of an edge part which surrounds a ~ody which is sunk relative to the edge part. The material in the edge part is mainly amor-phous or has a crystallinity of less than 10%. The body has a wall part and a bottom part. The wall part consists of material which has been drawn at a tempera-ture below the glass transition temperature Tg, until flow sets in, and in which the crystallinity is between lOo~and 25%. In the basic design of the element, the bottom consists of mainly amorphous material or of material having a crystallinity of less than 10%. In embodiments of the invention, the bottom consists, as desired, of material which has been drawn at a tem-perature below the glass transition temperature Tg and at a crystallinity between 10%and 25%, until flow sets in, that is to say of a material having properties which 1~ 73 175 mainly are identical to the material properties of the wall part of the element,or of material sections which have been drawn until flow sets in and which alternate with material sections of mainly amorphous material or materlal having a crystallinity of less than 10%. In certain embodiments, the material zones already mentioned are displaced in the axial direction relative to the lower edge of the wall part.
During the production of an element, a mainly flat blank of thermoplastic, having a crystallinity of less than 10%,is clamped in ~t a temperature below the glass transition temperature Tg between counter-holders, so that a zone is formed which is completely surrounded by the clamped-in material sections. A press device the contact surface of which is smaller than the surface area of the zone, is applied against this zone. Thus, a closed strip-like material zone is formed between the clamped-in material sections of the blank and that part of the zone which is in contact with the press device.
Subsequently, a drive mechanism s~ifts the press device relative to the counter-holder, while the press device remains in contact with the zone. The material in the strip-like zone is thus stretched in such a way that flow of the material occurs, the material being oriented, whilst at the same time the thickness of the material is reduced by about 3 times in the case of PET. The wall part of the element is formed during the stretching pro-cess.
Since the circumference of the contact surface ~ ~ 73175 _ 9 _ of the press device is smaller than the inner circumference of the clamping devices, the material which adjoins the edge of the press device is subjected to the greatest stress, for which reason the flow of the material normally starts at this point.
The effect thus resulting is ~urther reinforced by the fact that the transition from the contact surface of the press device to the side walls of the press device is made relatively sharp-edged. When flow has set in, the zone of flow of the material is gradually shifted in the direction of the clamping devices. In certain application examples, the press step is interrupted when the flow zone has reached the press devices. In other application examples, the press step continues, renewed flowing of the material takir.g place adjoining the edges of the press device and being displaced from these zones towards the centre of the material. ~hen all the material which is in contact with the contact surface-of the press device has undergone flow, that -material between the clamping devices which is located next to the inner circumference of the clamping devices is utilised for a further drawing step in certain appli-cation examples. To make this possible, a somewhat elevated temperature in this material is normally required.
The starting temperature, however, is still below the glass transition temperature Tg.
- Incer~n a~plication examples, accelerated cooling of the drawn material is necessary. In this case, the press d~ioe is preferably provided with a cooling device ~ 73 175 which is arranged in such a way that the zones of the material, which flow during drawing of the material, are in contact with the cooling deviceL
In certain applications~ the flow of the material is caused to start adjoining the clamping devices.
This is accomplished by providing the clamping devices with heating devices which raise the temperature of those material sections where flow is to start. The tem-perature in the ma~erial, however, is still below the glass transiti~n temperature Tg of the material.
When flow has set in, this continues in the direction of the contact surface of the press device and, in some cases which may occur, it continues past the transition from the side walls to the contact surface of the press device. To ensure that the clamping devices retain the blank in the future edge sections of the element, the clamping devices are as a rule provided with cooling devices.
The concept of the invention also comprises the possibility that, by a number of drawing steps which are arranged onP after the other, both in the wall part and in the bottom p~rt of the body, material sections are obtained which alternately consist of material sections which have been drawn until flow sets in and have in this way been given a reduced wall thickness, and undrawn material sections which have retained their wall thick-ness. In material sections located in the bottom part of the body, a displacement of the material in the axial direction of the body also takes place in certain appli-', ~ ~731~S
cation examples in conjunction with the drawing step, The edge part is removed from the element formedand the element is reshaped by a number of drawing steps.
These drawing steps take place at a temperature below the glass transition temperature Tg and effect a reduction of the diameter of the cup, whilst the length of the body is extended at the same time in the axial direction T~e drawing step effects exclusively a redistribution of the material without flow setting in.
The cup formed after the end of the drawing step has an opening at one end, whilst it has a bottom part at the other end. ~epending on the manner in which the elementhasbeen shaped, the bottom part consists wholly or partially of amorphousmaterial orof unoriented material. In the first-mentioned case, the bottom part thus retains the thickness of the starting material in the amorphous zone or in the amorphous zones. The amorphous material is suitable for use as a fixing material for welding additional parts to the cup. This requirement will be present, for example, when the cup is used as a container and the bottom part of the cup simultaneously represents the bo'tom part.of the container. In this case9 it is advantageous to weld an external foot to the container.
The cup shaped in the manner described possesses an spening part which, if appropriate after reworking, is preferably expanded in such a way that a beaded edge results, the stability of the beaded edge being increased by heating up to the maximum crystallisation temperature of the material. The beaded edge is thus outstandingly ~ L~73175 suitable for fitting, for example, a loose lid of a suit-able material, for example metal, by crimping.
In another application example, the drawing step at the cup is interrupted so that parts of the cup have a reduced diameter compared with the initial diameter.
By removing the bottom from this part of smaller diameterJ
expanding the edge formed and stabilising the opening which has been formed in the manner described in the pre-ceding section, a mouth part is obtained which is suit-able for fitting, for example, a closure or a crown cap.
The other still open part of the cup is closed, for example, by an end disc, in a manner similar to that already described, In the blow-moulding process, the starting point is either a cup which has been severed in the normal way from the edge part of the element, or from a newly drawn cup. By blow-moulding against warm mould walls, the cup, the material of which is at a temperature above the glass transition temperature Tg, is reshaped in such a way that it has exactly the form of the intended end product. In certain applications, a warm blowing mandrel is used in order to prevent excessive cooling of the material during the blow-moulding step.
It can be seen from what has been said that the combination of drawing, until flow sets in to obtain an element, redrawing of the cup of the element formed and a blow-moulding step offers many optional possibilities for the shaping of different types of articles.
An article produced in the manner described 1, 73.1~5 above is thus not only suitable for use as a container, but many applications are possible.
The invention will be clescribed in more detail by reference to a number of illustrations in which Figures 1 - 2 show optional embodiments of bands suitable for reshaping, Figure 3 shows an element having a bottom part of the body, consisting mainly of amorphous .
material, Figures 4 - lO show the principles of devices for drawing of the element, Figure ll shows a part of a device for redrawing o~
the cup of the element, Fi~ure 12 shows the cup of the element before . redrawing, ; Figure 13 shows the cup of the element after partial redrawing, Figure 14 shows the cup of the element after complete redrawingj . Figure 15 shows the cup o~ the element, having the part of the cup, which was partially redrawn, according to Figure 13, after renewed redrawing, Figure 16 shows a container produced from a cup according to Figure 15~ .-Figures 17 - 19 show the counterparts to Figures 12 - 14, the bottom part of the cup having sections of amorphous material and Fi~ures20 - 22 show optional em~odiments of blow-moulded ~73~7,5 articles.
Figures 11 and 16 are on the same sheet of drawings.
Figures 1 - 2 show a band or a blank 14', 14" of thermoplastic, the bands or blanks being seen from above.
In the figures, annular material zones 16', 16" or 17', 17"
are represented. Moreover, a material zone 15', 15" is indicated which is surrounded by the original annular material zone 17', 17". The material zone 16 marks that zone which, cn drawing of the blank, is clamped in between the clamping devices 30 a-b (see Figure 4). The material zone 15 marks that zone which, on drawing of the blank, is in contact with the press face of the press device 20 (see Figure 4).
The material zone 17 marks that zone which, on drawing of the blank, is brought into the state of flow.
An element 10 consisting of an edge part 12 of the body 13 is seen in Figure 3. The body in turn consists of a wall part 18 and a bottom part 11. In the figure, the wall part consists of drawn material of reduced thickness compared with the thickness of the starting material. The bottom part 11 consists of material which, while retaining its material properties, has been displaced in the axial direction of the body. Moreover, a zone 19 is marked in which material belonging to the edge part 12 had been transformed into the state of flow.
In Figures 4-8, a number of clamping devices 30 which fix the blank 14 can be seen. A press device 20 having a press face 21 is located between the clamping devices 30. In Figure 4, the press device is in a ~ 73~75 position in which -the press.face 21 is located directly next to the upper surface of the blank 14. In Figure 5, the press device was shifted downwards, flow of the material.having started. In Fi~ure 6, the press device has been shi~ted to such an extent that an element according to Figure 3 has been formed. In Figure 7, the press device was yet further shifted, further flow of the material having taken place. An element 10'. has thus been formed, the body 13' of which has a bottom part llt the central sections of which consist of amorphous undrawn material which is surrounded by drawn oriented material in which flow has taken place. Finally, in Figure 8, the press device 20 has been shifted to such an extent that virtually the entire material in the bottom part 11" of the body 13" has undergone flow.
An element 10" has thus been formed in which both the wall part.and the bottom part o~ the body have a reduced wall thickness because the material has been in the state of flow and has-at the same time been oriented.: .
In Figures 9 - 10, an .optional embodiment of the cla.mping devices .~3 a-b is represented, which are pro-vided with cooling channels 31 and heating channels 34.
In.the figures, only the feedline for the heating channels is shown, whilst the di~charge line for the heating channels is located behind the feedline in the figu~es and is indicated by the upward-pointing arrow.
The cooling channels, like the heating channels, are covered by plate-like covers 35, the other surface of which at the same time represents the contact surface of the clamping devices for clamping the blank. An insulation 32 separates the cooled zone of the clamping devices from the heated zone. In certain applications, the heating channels are used as the cooling channe1s in the same way. I
Furthermore, the figures show an optional embodi- !
ment of a press device 20a which also has cooling channels 22. The cooling channels are covered by a cooling jacket 23 which at the same time represents the outer contact surface of the press device opposite the material during the process of drawing the latter.
Figure 9 shows a position of the press device, which corresponds to the position shown in Figure 5, and Figure 10 shows a position of the press device, which corresponds to the position in Figure 8. The press device is constructed with a face of rotationally symmetrical curvature, which is shaped in such a way that, on drawing within the flow range, the material is always in contact with the cooling Jacket, whilst that material which has not yet been in the state of flow is not in contact at any point with any device in the zone between the press device and the clamping devices.
- Heating of the material with the ~d of the heating channels 34 has the purpose of increasing the readiness of the material to flow.Heating is limited, how-ever, in such a way thatthe temperature of the material is always lower than the glass transition temperature Tg.
Heating makes it possible to allow the drawing step of the material to continue a little into the zone between 1273~7tj the jaws of the clamping devices, as shown in Figure 10.
Another optional application, where the increased readi-ness of the material to flow is exploited, is obtained when, during the drawing step, the zone of initial flow of the material is directed to the zone next to the inner edges of the clamping devices. After flow has taken place, the flow zone is gradually displaced in the direction away from the clamping devices towards the bottom of the press device, as the press device gradually shifts downwards as in the figures.
The result of this is that ~low always propagates in the same direction, and a new start of flow is avoided, such as takes place when the embodiment of the invention shown in ~igures 4 - 8 is used.
Figure 11 shows a device for redrawing the element formed before. In the figure which shows only a part of the device, a press plunger 40, a counter-holder ring 41, a clamping ring 42 and a wall part 18 i~
the element are seen, the wall part being in the process of shaping. Moreover, the bottom 11" in the body 13 of the element is seen. The clamping ring 42 is pro-vided with a calibration device 43 which determines the thickness o$ the material, drawn anew, in the wall part 18.
Figure 12 shows an element body 50 which has been formed by means of the press device 20a according to Figure 9 and in which the edge part of the element has been produced ~rom the body, In Figure 13, the shaping process of the body 50 was initiated with the aid of a 7~ ~75 device shown in Figure 11. The shaping process has progressed to such an extent that a mainly cylindrical larger part, having the same diameter as the body 50, and a shorter part 59 have been formed. In Figure 14, the shaping process has been completed, a mainly cylindrical body 52 of the same diameter as in the shorter part in Figure 13 having been formed.
Figure 15 shows a body 53, the shorter part 59 of which has been reshaped with the aid 'of a dev.-.
ice shbwn in Figure ll for the purpose of further reducing the diameter of the shorter part 59'. There is a transition 58 between the shorter cylindrical part 59' and the larger part of the body 53.
Figure 16 shows a bottle-like container 70~pro-duced from a body 53 according to ~igure 15. The bottom part of the shorter part 59' has been severed and replaced by a closure 55, for example a cap. The mouth edges formed on severing the bottom part were expanded and beaded, after which the material in the beaded material zones has preferably been givenan increased crystallinity as a result of heating the material up to the crystallisation temper~ture. This gives additional strength at the moubh edge so that the latter is well suited for closing the container, for example by means of a cap or a crown cork. The transition, already mentioned, between the shorter part and the larger part of the body now forms a bottle neck 58'. The figure also shows how an end disb 56 is fixed at the other end of the container ?~ after the container has ~ 73 17~
been filled. As a result of expanding, beading and heating of the material, material sections are here also obtained which are suitable, for example, for fitting an end disc. by crimping,in order to close-the container Figures 17 - 19 show counterparts to Figures 12 - 14. Thefigures showhow an element body, formed from the body 11' according to Figure 7, is subjected to an axial lengthening, with simultaneous reduction in the dia-meter of the body, and forms an almost completely cylin-drical body 61, the bottom part of this body consisting of a material section 62 of mainly amorphous material During the shaping process, an intermediate form of the body results, which is marked 60 in Figure 18.
In the embodiment of the invention in which a . body is formed which comprises an amorphous bottom sectlon,.
a.material zoneisa~.obtained which is suitable as a fixing .
material for welding on additional parts ~o- the body.
By rendering the material crystalline, a zone of extreme dimènsional stability is obtained, whereby it becomes possible to use the container for storing liquids under pressure, for example béverages to which carbonic acid has been added, without a risk of deforming the bottom part. The concept of the invention also comprises the replacement of the plane embodiment of the bottom part by a convex or concave face, depending on the particular wishes which apply corresponding to the individual appli-cations. -Figures 20 - 22 show.optional embodiments of 1~ 73 ~75 blow--moulded containers. - All the containers are closed by end discs in the manner already described in connec-tion with Figure 16. Of course, this combination of a blow-moulded container and an end disc is to be regarded only as an example of the possibilities avail-able for closure.
Figure 20 shows an embodiment in which all the material in the blow-moulded container consists of material previously drawn. The container is formed from a body part either according to Figure 12 or accord-ing to Figure 14 Figure 21 shows an embodiment of a blow-moulded container which has been formed from a body part accord-ing to Figure 17 or ~igure l9. On blow-moulding, the amorphous material zone 22 remained in the amorphous state without change, and it represents a thicker section in the bottom part of the container. In certain embodiments, this section is heated up to the crystal-lisation temperature of the material in order to form a bottom sectlon which is particularly suitable for withstanding deformation forces, for example~forces due to an internal pressure in the container. The amor-phous material is also suitable for the purpose of weld-ing additional plastic parts thereto.
Figure 22 shows an embodiment of a blow-moulded container ~Ihich has been formed from a body part, the bottom of the body part consisting alternately of material sections, which have been drawn until flow sets in, and of those material sections which have retained 1~ 73 ~75 their original thickness. In this way, a simple amorphous material section 21 has been formed which is surrounded by an annular amorphous section 72 which is located below the central section. The central section and the annular section are connected by material which has been drawn urt~ flowsets in. The a~nular material section thus forms standing surfaces for the container.
The parts forming the shell of the container are as a rule shaped from redrawn material. ~t least in the cases where the container has a relatively large a~ial dimension, such redrawing is necessary.
Blow-moulding is carried out in any known manner at a temperature of the material, which is above-the glass transition temperature Tg. Normally, blow- -moulding takes place against heated mould walls. In certain illustrative embodiments, a heated elongate blow mandrel is required in order to avoid excessive cooling of the material during the blow-moulding step.
The material oriented by flow possesses improved strength properties in the direction of orienting, which is largely the same as the direction of drawing the material Since the material has been heated to a temperature above the glass transition temperature Tg, there are no difficulties in a blow-moulding process with regard to reshaping the element by stretching the material in a direction which is mainly at right angles to the said direction of orienting. An element reshaped in this way forms, for example, a container having a central shell surface of a diameter which exceeds the ` 1~7;~175 diametPr of the opening, and havlng a bottom which con-sists of a standing surface which represents the tran-sition between the lower edge of the shell surface and the bottom surface, the bottom surface either being slightly concave or consisting of annular material sec-tions which are displaced relative to one another in the axial direction of the container.
The 2bove description merely represents examples for the application of the invention. The invention allows of course that a number of combinations of drawing steps take piace, zones of drawn and undrawn materlal also forming alternately. ~or example, the body con-~ sists of wall parts with sections which contain undrawn material, whilst the bottom part consists of sections, for example annular sections, which contain undrawn material and which are displaced in the axial direction of -the body relative to the lower edge of the wall part.
The concept of the invention comprises manv optional embodiments. According to one of these, drawing until the material in the body of the element flows is effected by a numberof successive drawing steps, the con-tact area of the press device decreasing for each drawing step. The result of this is t~at the width of the material zone 15 is adapted to the extent to which the drawing step has proceeded.
In addition to the above description, the inven-tion is also comprised by the attached patent claims.
This application is a division of Canadian Application No. 352,907 filed May 28, 1980~
I
1.
Claims (8)
1. Apparatus for the manufacture of a cup-like article from polyethylene terephthalate or similar material comprising clamping means for clamping a substantially flat blank of amorphous, polyethylene terephthalate or similar material in a peripheral region thereof to form an inner zone completely surrounded by an outer clamped zone, press means for engaging said inner zone of said blank in a central region thereof smaller than the total area of said inner zone whereby a band-like zone is formed between said outer clamped zone and the central region in contact with said press means, said band-like zone having a radial extent substantially greater than the thickness of said blank, means for effecting relative dis-placement between said press means and said clamping means, means for maintaining the temperature of said blank below the glass transition temperature (Tg) of the material of the blank, the aforesaid clamping means, press means, relative displacement means and temperature maintaining means cooperatively constituting means for producing free stretching of the material of the blank in a drawing region by forming a transition zone in said material at which flow takes place in the material and the original thickness of the blank is reduced by a factor sufficient to effect orientation and crystal-lization of the material whereby a drawn element is formed which comprises an edge part composed of said clamped zone and a body which is drawn relative to said edge part and includes the oriented crystallized material, said temperature maintaining means including means in said press means so arranged as to provide for cooling the material of said blank at the temperature below Tg at least in the region of said transition zone to enable the material to be freely stretched thereat without undergoing compressive squeezing between the clamping means and the press means.
2. Apparatus as claimed in claim 1 wherein said press means has an outer surface which pro-gressively comes into contact with said material in the course of drawing thereof, said means for cooling the blank comprising channels in said press means proximate said outer surface for flow of a coolant therein.
3. Apparatus as claimed in claim 1 com-prising means for supplying a heat transfer fluid to said clamping means for controlling the temperature of said material in said clamped zone.
4. Apparatus as claimed in claim 3 wherein said heat transfer fluid is a coolant.
5. Apparatus as claimed in claim 3 wherein said means for supplying heat transfer fluid includes-a first set of channels for a cooling fluid and a second set of channels for a heating fluid and insulation means separating said first and second set of channels
6. Apparatus as claimed in claim 5 wherein said first set of channels is located in said clamping means at a location more remote from said press means than is said second set of channels.
7. Apparatus as claimed in claim 6 wherein said heating fluid in said first set of channels is at an elevated temperature below Tg to produce said transition zone within said clamping means.
8. Apparatus as claimed in claim 1 wherein said press means has a flat bottom surface which contacts said blank in said central region thereof.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000560155A CA1273175A (en) | 1979-06-11 | 1988-02-29 | Apparatus for the manufacture of a cup-like article from thermoplastic material |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7905047-2 | 1979-06-11 | ||
| SE7905047A SE424420B (en) | 1979-06-11 | 1979-06-11 | MANUFACTURING OF ARTICLES BY DRAWING AND BLASHING |
| CA000352907A CA1240114A (en) | 1979-06-11 | 1980-05-28 | Manufacture of articles by drawing and blow-moulding |
| CA000560155A CA1273175A (en) | 1979-06-11 | 1988-02-29 | Apparatus for the manufacture of a cup-like article from thermoplastic material |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000352907A Division CA1240114A (en) | 1979-06-11 | 1980-05-28 | Manufacture of articles by drawing and blow-moulding |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1273175A true CA1273175A (en) | 1990-08-28 |
Family
ID=25669090
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000560155A Expired - Fee Related CA1273175A (en) | 1979-06-11 | 1988-02-29 | Apparatus for the manufacture of a cup-like article from thermoplastic material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1273175A (en) |
-
1988
- 1988-02-29 CA CA000560155A patent/CA1273175A/en not_active Expired - Fee Related
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