Source: http://www.google.com/patents/US4512735?ie=ISO-8859-1
Timestamp: 2014-07-28 05:26:59
Document Index: 73034109

Matched Legal Cases: ['art.\n12', 'art 24', 'art 24', 'art 24', 'art 24', 'art 24', 'art 24', 'art 53', 'art 53', 'art 53', 'art 57', 'art 58', 'arts 61', 'art 57', 'art 53', 'art 34', 'art 53', 'art 57', 'arts 61', 'art 53', 'art 34']

Patent US4512735 - Apparatus for blow molding a container having an upward bulged bottom - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA mold, for forming a container by fluid pressure, having two mold halves and two axially movable plungers, the plungers forming the bottom of the container therebetween, an inner plunger or mandrel having a concave end and a second plunger, hereafter called "the bottom part", having a convex end....http://www.google.com/patents/US4512735?utm_source=gb-gplus-sharePatent US4512735 - Apparatus for blow molding a container having an upward bulged bottomAdvanced Patent SearchPublication numberUS4512735 APublication typeGrantApplication numberUS 06/443,938Publication dateApr 23, 1985Filing dateNov 23, 1982Priority dateNov 26, 1981Fee statusPaidAlso published asCA1216719A1, CA1232555C, DE3243908A1, US4704243, US4991734Publication number06443938, 443938, US 4512735 A, US 4512735A, US-A-4512735, US4512735 A, US4512735AInventorsTorsten Nilsson, Kjell M. JakobsenOriginal AssigneePlm AbExport CitationBiBTeX, EndNote, RefManPatent Citations (4), Referenced by (8), Classifications (47), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetApparatus for blow molding a container having an upward bulged bottomUS 4512735 AAbstract A mold, for forming a container by fluid pressure, having two mold halves and two axially movable plungers, the plungers forming the bottom of the container therebetween, an inner plunger or mandrel having a concave end and a second plunger, hereafter called "the bottom part", having a convex end.
What is claimed is: 1. Apparatus for forming a container from a cylindrical preform having a side wall and a bottom closure, said apparatus comprising an internal mandrel on which the preform is fitted, a mold including two mold halves, and a bottom part in said mold in axial opposition to said mandrel, said mandrel and bottom part being movable axially of the mold relative to each other and relative to the mold halves for shaping the preform into a container, said mandrel having a concave end surface, said bottom part having a convex end surface facing said concave surface for enclosing and reshaping the bottom closure of the preform, said mold halves together defining a mold inner surface for engaging the wall of the preform at the outer surface thereof proximate said end closure, said mandrel having an outer surface engaging the wall of the preform at the inner surface thereof, the engagement of the inner and outer surfaces of the preform in region of said end closure being without clearance to maintain the wall thickness of the preform during reshaping of the bottom closure of the preform, said end surfaces of said mandrel and said bottom part including respective central regions which a opposite one another and define a substantially uniform gap for engaging the inner and outer surfaces of the bottom closure of the preform to turn the bottom closure inwardly, said end surfaces further including peripheral regions which are opposite one another and of differing curvature to form an annular ring-shaped region in which the material of the preform in a ring-shaped transition region between the inwardly bulged bottom closure and the side wall is stretched and becomes oriented so that the inward bulged shaped of the bottom closure is stabilized and prevented from turning inside-out said bottom part being positionable within said mold inner surface such that said mold inner surface and said convex end surface define an annular molding recess therebetween.
2. Apparatus as claimed in claim 1 wherein the central region of the end surface of the mandrel is concave and the central region of the end surface of the bottom part is convex, the peripheral region of one of said end surfaces being convex while the peripheral region of the other of the end surfaces is concave.
3. Apparatus as claimed in claim 1 wherein the central region of the end surface of the mandrel is concave and the central region of the end surface of the bottom part is convex, the peripheral region of one of said end surfaces having an annular recess.
4. Apparatus as claimed in claim 1 comprising means for effecting thermal crystallization of the material of said bottom closure of the container.
5. Apparatus as claimed in claim 4 wherein the thermal crystallization means effects the thermal crystallization of the bottom closure simultaneously with the reshaping of said bottom closure.
6. Apparatus as claimed in claim 1 wherein said mold halves include extension portions shaped to form a body part of said container which is joined to said bottom closure by said ring shaped transition region.
7. Apparatus as claimed in claim 1 comprising means for effecting heat transfer between the mandrel and the preform.
8. Apparatus as claimed in claim 1 comprising means for effecting heat transfer between the bottom part and the closure of the preform.
9. Apparatus as claimed in claim 1 comprising means for effecting heat transfer between the mold parts and the preform.
10. Apparatus as claimed in claim 1 wherein said mold parts include means for forming a mouth part on the container.
11. Apparatus as claimed in claim 1 comprising means for blow-molding the preform to the shape of the mold parts to form said body part.
12. Apparatus as claimed in claim 1 wherein the relative displacement of the mandrel and the bottom part is coordinated with the blow molding so that the profile length of the container substantially corresponds to that of the preform.
FIELD OF THE INVENTION The present invention relates to apparatus for producing a container of thermoplastic material, preferably of polyethylene terephthalate or similar material having a central bottom part of amorphous, oriented and/or thermocrystallized material which forms a bulge directed towards the interior of the container which merges into an area of material around the central bottom part. Said area of material has undergone material flow through stretching and/or reshaping and has been contracted and/or acquired built-in stresses through heating whereby said area of material prevents the inward bulge from straightening out or turning inside out when the pressure inside the container is increased and/or in connection with heating of the same.
PRIOR ART In the field of packaging there exists a need for containers of thermoplastic material capable of resisting an internal pressure of at least about 7 kgf/cm2 for the storage of carbonated beverages, e.g. beer or soft drinks. It has so far not been possible at reasonable cost to achieve can-shaped free-standing containers, for example, which under unfavorable conditions, e.g. at high temperature, are deformed by such a negligible degree that the deformation can be accepted in regard to shape change, volume change, standing stability, etc.
In accordance with known techniques it is possible to produce bottles with a mouth portion of monoaxially oriented material normally with a cylindrical container body of biaxially oriented material and with a central bottom part of amorphous or thermal crystallized material. Such containers have a body in which biaxial stretching of the material is obtained through a process in which the degree of stretching of the material in the axial direction of the container body and in the circumferential direction of the container body is mainly determined by the ability of the material itself to elongate when the preform is subjected to internal pressure in conjunction with being blown into the shape of the container. As a rule, insufficient stretching of the material along the axis of the container is obtained although in certain applications attempts have been made to improve this stretching by means of a mechanical device in the form of a mandrel which extends the preform along its axis in the initial stage of blowing it into the shape of the container. Examples of this technique will be found in GB No. 1 536 194 and GB No. 2 052 367. The known technique described is solely related to the production of bottles and not to the production of containers in the nature of cans.
It is known that polyethylene terephthalate, henceforth abbreviated to PET, which is stretched monoaxially and particularly biaxially about three times in the direction of each axis acquires extremely good material properties, see U.S. Pat. No. 4,152,667, for example. An extremely sure and effective technical method of achieving such stretching is to stretch the material until it undergoes flow. Examples of techniques where such stretching occurs are given in GB No. 2 052 365 and GB No. 2 052 367.
The physical properties mentioned above do not apply solely to PET but to a greater or lesser degree also to many other thermoplastic materials. Examples of such materials are polyhexamethylene-adipamide, polycaprolactum, polyhexamethylene-sebacamide, polyethylene-2.6-naphthalate and polyethylene-1.5-naphthalate, polytetramethylene-1.2-dioxybenzoate and copolymers of ethylene terephthalate, ethylene isophthalate and other similar polymer plastics.
SUMMARY OF THE INVENTION An object of the present invention is to provide apparatus for producing a container of can-shape.
The container has a central bottom part which consists chiefly of amorphous, oriented and/or thermocrystallized material, the said central bottom part being surrounded by a ring-shaped area of oriented material. The central bottom part is displaced inwards towards the center of tne container and as a result a ring-shaped standing surface is created adjacent to and principally outside the central bottom part. The ring-shaped area of material is formed through stretching to flow of mainly amorphous material which, as in a tubular blank, is situated adjacent the bottom closure of the blank and which before stretching is a ring-shaped and mainly amorphous part of material in the blank. In certain applications the ring-shaped part of material in the blank is at least partially situated at a shorter distance from the axis of the blank than the material forming the mainly cylindrical walls of the blank. Through stretching to flow, the material in the ring-shaped section is oriented chiefly along the axis of the container, to which is added a certain preferably lesser orientation in the circumferential direction of the material. The ring-shaped area of material accordingly forms in the container a transition between the material in the container body and the central bottom part of the container.
Depending on which alternative version of the bottom part is chosen, crystallization in the material of the bottom part varies from a few percent up to about 25-30%, where the thermal-conditioned crystallization is usually less than 10-15%.
In a preferred version of the invention the material is stretched by passing the whole blank through a draw ring at the same time as a mandrel occupies the interior of the blank. In this way the blank is elongated by an amount corresponding to the reduction in the thickness of the walls of the blank. In the case of PET the elongation is about three times. During the passage of the blank through the draw ring, at the transition between the material that has already passed through the draw ring and the material that is just about to pass through it, a transitional zone is formed between material stretched along the axis of the blank, i.e. oriented material, and material which has not yet been stretched, i.e. chiefly amorphous material. Heat is released in connection with the molecular restructuring, which takes place during the passage of the material through the draw ring. Both the internal mandrel and the draw ring are maintained at a temperature in the vicinity of or in the range of the glass transition temperature of the material, henceforth designated TG. As a rule, passages for this purpose are arranged in both the mandrel and the draw ring to carry liquid for regulating the temperature of the mandrel and draw ring respectively. In the event of excessively high temperature in the material at the transitional zone, contact between the material and the draw ring is lost in parts of the transitional zone, which leads to unwanted effects in the material that is to pass through, or has passed through, the draw ring. In conjunction with its passage through the draw ring the material is temporarily allowed to assume a temperature somewhat in excess of TG. In the case of PET, temperature in excess of 105� C. are as a rule unsuitable. Described in patent application DEOS No. 31 21 524.6 is a version of material stretching using draw rings as described in brief above.
FIGS. 5a-c show versions of a container formed through reshaping of the mouth portion of the preform as in FIG. 4,
In another version the bottom part 24 is reshaped with the material at a temperature within the thermoelastic temperature range of the material. As a result, the profile length of the bottom part increases in conjunction with reshaping as the thickness of the material in the bottom part decreases during simultaneous elongation of the material. The equivalent to the ring-shaped transition of materia1 which is stretched to flow as described in the previous paragraph consists of a ring-shaped area of material stretched to flow which was formed during the passage of the blank through the draw ring and which is situated adjacent the bottom part 24 of the blank. FIGS. 3 and 3a are also representative of the ring-shaped area of material which is formed according to this version and which is accordingly assigned reference number 25a in the figures.
FIGS. 4 and 4a show the preform as in FIGS. 3 and 3a which has been heated to a temperature higher than the TG range of the material. In the case of PET the material has been heated to a temperature preferably higher than the TG range by at least about 40� C., i.e. has been heated to at least about 120� C. Through heating, the preform is given a smaller axial length and the cylindrical portion 22b a smaller diameter (cf. the figures). The reduction of the diameter of the ring-shaped transition 25a results in the bottom part 24b of the preform 20b being given a sharper bend than the bottom part 24a and it consequently bulges deeper into the cylindrical portion than the bottom part 24a. In the version of the invention where the ring-shaped transition 25a is formed by amorphous material closer to the axis of the blank than the material in the cylindrical walls of the blank, the contracting effect in the ring-shaped transition 25a is intensified, which as a rule results in greater inward bulging of the bottom part 24b into the cylindrical portion 22b.
The figures show a blowing mould 50 with two mould halves 51a, b. At the lower part of the blowing mould is a cylindrical cavity 52 bounded by the two mould halves 51a, b with a diameter adapted to the diameter of preform 20b in order to permit the preform to pass into the cavity. In the cavity the blowing mould is arranged with a bottom part 53 which is movable in the cavity and in the direction of the arrow D to assume the position shown in FIG. 10 at one of its end positions. The bottom part 53 corresponds to the previously-mentioned second forming element 43 and like it is arranged with a convex forming surface 55. Bottom part 53 is relieved about its periphery to from a narrow radially extending annular surface and a slight annular recess between said convex surface and said radially extending annular surface. A mainly cylindrical mandrel 56 with a diameter mainly coinciding with the inside diameter of preform 20b and adapted to permit the mandrel to pass into the preform corresponds to the previously-mentioned first forming element 42 and like it is arranged with a concave forming surface 54. At its upper part the mandrel is arranged with a part 57 of larger diameter and terminates in a flat-like part 58 with a lower contact surface 59 adapted to abut against an upper contact surface 60a, b on the mould halves 51a, b. The mandrel 56 is capable of moving back and forth in the direction of arrow C to assume the position shown in FIGS. 9 and 10 at one of its end positions. The blowing mould halves 51a, b have at their upper parts 61a, b a shape adapted to the shape of the mandrel in part 57 of larger diameter whereby, with the mandrel 56 in the end position shown in FIGS. 9 and 10, a forming space adapted to the shape of the mouth portion of the future container is formed between the mandrel and the upper parts of the blowing mould halves. Further, with the mandrel and bottom part 53 in the positions shown in FIG. 10, a corresponding forming space for the central bottom part 34c of the future container is formed.
Liquid passages 62a, b, 63 and 64 are arranged in the mould halves 51a, b, in the bottom part 53 of the blowing mould, and in the mandrel 56 for heating or cooling of the respective elements.
When using a device as shown in FIGS. 8-10 the mouth portion of the future container is also formed during the initial stage of reshaping the preform through part 57 of the mandrel 56 having a larger diameter moving the material radially outwards towards the upper parts 61a, b of the mould halves. The preform is then as a rule able to withstand the axial forces without undergoing deformation. In cases where the processing temperature and the material have been so chosen that the axial strength of the preform is insufficient, forming of the mouth portion of the future container can be carried out more suitably in a separate device having a cylindrical cavity for supporting the preform more or less along its entire length.
In the event that a container 30d is to be produced, the interior of the container 30b, which is now to be regarded as an intermediate product, is pressurized and as a result the walls of the intermediate product are blown out or expanded to make contact with the forming surfaces of the mould halves 51a, b at the same time as the bottom part 53 of the blowing mould is moved upwards and so permits reshaping to take place with retention of the profile length of the section of material of the intermediate product consisting of material stretched to flow. In its upper position (FIG. 10) the concave forming surface 54 and the convex forming surface 55 interact for the formation of a forming space adapted to the shape of the central bottom part 34d of the desired container.
The liquid passages 62a, b, 63 and 64 then carry hot or cold liquid, depending on which of the versions mentioned in the introductory part of the description is aimed at in the individual application example. Through simultaneous retention of the internal pressure in the formed container and supplying heat to the forming surfaces, a container is producted where thermal crystallization is also obtained in the parts of the material which are crystallized through stretching of the material.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3329996 *Oct 10, 1963Jul 11, 1967Dow Chemical CoApparatus for scrapless blow molding of plastic receptaclesUS3661483 *Aug 8, 1969May 9, 1972Bose Robert NApparatus for controlling the flow of liquidUS3806587 *Dec 31, 1969Apr 23, 1974Continental Can CoApparatus for forming oriented containersUS3981668 *Jan 31, 1975Sep 21, 1976Farrell Patent CompanyApparatus and method for longitudinal stretch for blow molding* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS4725219 *Jun 17, 1986Feb 16, 1988Plm AbDevice for the stretching of thermoplastic materialsUS4927591 *Aug 14, 1986May 22, 1990Petainer S.A.Container, method and apparatus for manufacturing the sameUS5067888 *Jul 3, 1990Nov 26, 1991Petainer S.A.Apparatus for shaping a tubular preform into a hollow bodyUS6082991 *Jun 26, 1998Jul 4, 2000Rozenberg; OlegInjection blow molding machineUS6358038Jun 28, 2000Mar 19, 2002Oleg RozenbergInjection stretch blow molding machineUS20130244050 *Nov 3, 2011Sep 19, 2013Husky Injection Molding System Ltd.Preform and a mold stack for producing the preformWO2004014631A1 *Aug 4, 2003Feb 19, 2004Juergen WeissMethod and device for producing a plastic preformWO2005120806A1 *Jun 3, 2005Dec 22, 2005Graham Packaging Pet TechStretched container and method of manufacture* Cited by examinerClassifications U.S. Classification425/526, 425/533International ClassificationB29C49/58, B29C65/00, B29C51/08, B29C49/00, B65D1/16, B65D1/02, B29C43/36, B29C49/48, B65D1/00, B29C49/08, B29C51/34, B29C49/64, B29C55/30, B29C49/54, B29C49/02Cooperative ClassificationB29C2043/3631, B29C2043/3618, B29C2049/548, B29B2911/1402, B29C49/02, B29C43/361, B29L2031/716, B29C49/541, B29K2995/004, B29B2911/14033, B29B2911/1404, B29B2911/14026, B29C49/0073, B29B2911/14906, B29C51/343, B29B2911/1442, B65D1/165, B29C51/08, B29B2911/14486, B29B2911/14426, B29C55/30, B29B2911/14333, B29B2911/14326European ClassificationB29C51/34B, B29C49/02, B29C55/30, B65D1/16B, B29C51/08, B29C49/54B, B29C49/00GLegal EventsDateCodeEventDescriptionSep 23, 1996FPAYFee paymentYear of fee payment: 12Oct 13, 1992FPAYFee paymentYear of fee payment: 8Sep 30, 1988FPAYFee paymentYear of fee payment: 4Feb 14, 1983ASAssignmentOwner name: PLM AB; MALMO, SWEDEN A CORP OF SWEDENFree format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:NILSSON, TORSTEN;JAKOBSEN, KJELL M.;REEL/FRAME:004092/0194Effective date: 19821206RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google