CA1222211A - Preform for blow molding spherical containers - Google Patents
Preform for blow molding spherical containersInfo
- Publication number
- CA1222211A CA1222211A CA000425495A CA425495A CA1222211A CA 1222211 A CA1222211 A CA 1222211A CA 000425495 A CA000425495 A CA 000425495A CA 425495 A CA425495 A CA 425495A CA 1222211 A CA1222211 A CA 1222211A
- Authority
- CA
- Canada
- Prior art keywords
- preform
- wall section
- container
- curved
- constant thickness
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
Abstract A thermoplastic polymer preform, more especially a polyethylene terephthalate preform, particularly structured and configured for producing a spherical container is provided. The spherical container, useful for holding beverages, more especially beer, is produced by a blow molding method employing such particularly structured and configured preform.
Description
Z2~21~1 Preform ~or Blow Molding Spherical Contalners Field oE Invention This inventlon relates to injection ~olded, test tube shaped, thermoplastic pol~ner preEorms useful in the blow molding of plastic containers. Additionally, this invention relates to a method of blow molding containers uslng a preform adapted to produce spherical containers particularly useful for holding beverageR such as carbonated soft drinks or beer.
Background Blow molded plastic contalners (e.~. bottles) for holding food and beverages are well known in the art. Generally such contalners have a cylindrical body, however, in some cases they have a rectangular body.
Thcse containers are required to have VariOUS properties suitable to their commercial use for packaging ~arious materials including foods and beverages. Among such properties impact resistance, creep resistance and the resistance to the passage of various substances (e.g. water, carbon dioxide and oxygen) through the walls of the container (i.e. barrier properties) are of particular importance. To achieve such properties it is required not only to choose the appropriate plastic for making the container but lt is important to achieve the neeessary cross sectional structure, configuration and uniEormity from container to container.
Poor impact resistance renders the container susceptible to fracture failure when dropped. Poor creep re~istance causes the container to change shape with time and may even cause the container to be unable to stand upright. Poor barrier propertles result in the loss of essential cornponellts from the contents of the container or allows the penetration of sul~taslces (e.g. oxygen) into tlle contailler with ~he su~sc~ ent deterloration oE the containerts corltents. ~lolecular orientation of the plas~ic forming the container, in particular uniaxial and biaxial orlen ~tion ..
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of the plastic-formin~ the walls of the container is known to significantly impro~e the barrier properties, impact resistance and creep resistance of these containers. Such orientation is achleved by stretching the plastic during the formation (i.e. blow molding) of the container.
Blow molded uniaxially or biaxially oriented containers are generally made from plastic preforms. These preforms are usually prepared from thermoplastlc pol~ners by various techniques including for example by injection molding and by the thermoshaping (i.e. heating in a mold) of an extruded tube. Quite often the preforms wlll have a test t~lbe shape (i.e. an elon~ated tubular or cylindrical shape open at one end and closed at the other end), although other shapes are also known and usedO
In known method~ for making blow molded containers there may be used a reheated previously molded preform. The heated preform, at the appropriate temperature is inserted into a mold, the mold halves closed around the body of the preform and blowing fluid (e.g. air) introduced into the preform to expand it against the cavity walls of the mold. The cooled blow molded container is then removed from the mold.
The blow molding of con~ercially acceptable containers (i.e.
containers having the required shape and properties with respect to the intended end use) is, once the polymeric material is selected, a function of various factors. For example factors such as temperat~re9 blow rate and blow pressure have to be considered. Along with these factors consideration is to be given to the degree of extension of the preform, the amount of orientation achieved in the plastic, the shape of the container and the distribution of material in the container walls. Poor or impropèr distribution of plastic material in the container walls n~ay lead to weak spots in the container, an improperly shaped container and premature failure of the container. Too l~ttle or too much orientation may result in reduced barrier properties, impact resistance and creep
Background Blow molded plastic contalners (e.~. bottles) for holding food and beverages are well known in the art. Generally such contalners have a cylindrical body, however, in some cases they have a rectangular body.
Thcse containers are required to have VariOUS properties suitable to their commercial use for packaging ~arious materials including foods and beverages. Among such properties impact resistance, creep resistance and the resistance to the passage of various substances (e.g. water, carbon dioxide and oxygen) through the walls of the container (i.e. barrier properties) are of particular importance. To achieve such properties it is required not only to choose the appropriate plastic for making the container but lt is important to achieve the neeessary cross sectional structure, configuration and uniEormity from container to container.
Poor impact resistance renders the container susceptible to fracture failure when dropped. Poor creep re~istance causes the container to change shape with time and may even cause the container to be unable to stand upright. Poor barrier propertles result in the loss of essential cornponellts from the contents of the container or allows the penetration of sul~taslces (e.g. oxygen) into tlle contailler with ~he su~sc~ ent deterloration oE the containerts corltents. ~lolecular orientation of the plas~ic forming the container, in particular uniaxial and biaxial orlen ~tion ..
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of the plastic-formin~ the walls of the container is known to significantly impro~e the barrier properties, impact resistance and creep resistance of these containers. Such orientation is achleved by stretching the plastic during the formation (i.e. blow molding) of the container.
Blow molded uniaxially or biaxially oriented containers are generally made from plastic preforms. These preforms are usually prepared from thermoplastlc pol~ners by various techniques including for example by injection molding and by the thermoshaping (i.e. heating in a mold) of an extruded tube. Quite often the preforms wlll have a test t~lbe shape (i.e. an elon~ated tubular or cylindrical shape open at one end and closed at the other end), although other shapes are also known and usedO
In known method~ for making blow molded containers there may be used a reheated previously molded preform. The heated preform, at the appropriate temperature is inserted into a mold, the mold halves closed around the body of the preform and blowing fluid (e.g. air) introduced into the preform to expand it against the cavity walls of the mold. The cooled blow molded container is then removed from the mold.
The blow molding of con~ercially acceptable containers (i.e.
containers having the required shape and properties with respect to the intended end use) is, once the polymeric material is selected, a function of various factors. For example factors such as temperat~re9 blow rate and blow pressure have to be considered. Along with these factors consideration is to be given to the degree of extension of the preform, the amount of orientation achieved in the plastic, the shape of the container and the distribution of material in the container walls. Poor or impropèr distribution of plastic material in the container walls n~ay lead to weak spots in the container, an improperly shaped container and premature failure of the container. Too l~ttle or too much orientation may result in reduced barrier properties, impact resistance and creep
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re6istance. Most, if not all, of these Iactors ma~y be tr aceable back to tlle preform as tlle source of contr ol. Thus appropriate preiorm coilstruction and configuration is necessary and important to achieve Lhe desired blow molded container.
Sumnlary of lnventiorl There has now been discovered a thermoplastic polymer pr erorm having a cor~iguration and cross section particularly adapted to the ~low molding of a spherical container Ior packaging beverages, more especially l~eer.
It is, therelore, an object of this invention to provide an injection molded, thernloplastic polymer, essentially test tube shaped preforrrl .
It is another object of this invention to provide an injectioll molded, thermoplastic polyrrler, essentially test tube shaped preform for blow rnolding a spherical container.
These and other objects, as will be apparent to one skilled in the art from the following description, are achieved by an injection molded, essentially test tube shaped, polyethylene terephthalate preform for blow molding a spherical container, said preform having an open end and a curved closed end and comprising a neck portion at said open end, l~aving a continuous flange for positioning said preform in a mold for blow molding the container and having an acljoining elongated, cylindrical body portion containing said closed end wherein the body portion comprises a) a tapered wall section adjoining sclid neck portion and tapering toward and abutting said flange, said tapered wall section constituting a minor segment of the length of the overall body portion, b) adjoining the tapered wall section (a) a sul~stanlicllly constant thickness wall section and c) a curved closed end ~`OIItainillg 'I ('Ul'V((] tapere(l wall sectioll joining the constant thickness wall section (b) to a curve(l substantillly conslanl lhickness closed secliorl, said (~urved substarltially constant thiclu~ess elosed section havitlg a thickncss less thall the thickness of the constant thiekness wall section (b), but at least one halt the thickness of the constant tllickness wall seclion (b), said curved closed end having at its bottorn a flat spot approximately 1/~ lo 1/4 inch in diameter.
Brief Description of Drawings In the following description of this invention referenee will be made lo the accompanying drawings wherein:
Figure 1 is a front view, partly in seetion, of a preform aceording to this invelltion;
I~'igure 2 is a front view, partly in section, of a spherieal container obtained from a preform aceording to this invention, shown in phantom in the intel ior of the spherical container.
Description of the Invention There is now provided in aeeordanee with an aspeet of this invention an injeetion molded, essentially test tube shaped, thernloplastic molecularly orientable polymer preform for blow molding a spherical container, said preform having an open end and a eurved closed end and eomprising a neek portion, at said open end, having a locating means for positioning said preform in a mold for blow molding the container and an adjoining elongated eylindrical body portion containing saicl closed end wherein the body portion eomprises a) a tal)ered wall section adjoining said neek portion, b) adjoining the tapered wall section (a) a substantially constant thickness wall seetion and e) a curvecl closed end containing a curved tapered wall seetion joining the constant thiclilless wall section (b) to a curved substantially constant ~hi(kl-less closed section, said curved substantially constant thickness k)sed section having a thickness less than the thiclcness of the ol~sLant thic~klless ~ all sectioll (b) but ~I
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at least one half the thic~ness of thè constant thickncss wall sectlon (b). Additionally, there is provided in accordance with this invention a method for blow molding a spherical container comprising the steps of I) positioning a heated preform according to the afore description in an open mold having a spherical cavity9 II~ closing ~he mold, III) lntroducing a blowing fluid into the lnterior of said preform, IV) expanding said preform to and against the walls of said savity, V) opening said mold and VI) removing the blown container from the mold.
In a particular aspect there i~ provided in accordance with this invention an injection molded, essent-lally test tube shaped, polyethylene terephthalate preform according to the above description and the method, as described above, of blow molding a polyethylene terephthalate spherical container. A further aspect of this invention provides the preform in accordance with the above description wherein the tapered wall section (a) adioining the neck portion of ~he preform tapers toward (i.e. narrows toward) and abuts the locating means of the neck portion of the preform.
This aspect is particularly applicable to the afore described polyethylene terephthate preform of this invention. ~s a still further aspèct of this invention there i6 provided a preform according to the above description wherein the thermoplastic polymer is a stretch orientable thermoplastic polymer more particularly a blow stretch biaxially orientable thermoplastic polymer. Another aspect of this lnvention provides a preform according to the above description wherein the tapered wall section (a~ adjoining the neck portion is a minor segment of the wall length of the body portion of the preform. In a even further aspect of this invention there is provided a preform according to the above description wherein the locating means is a segmented or a continuous r;ng or Elange~ more particularly a contilluous ring or flange.
The injection molding of the preform according to this invention often produces a gate pro~ection (15 of Fig. 2~ at the bottom of the curved closed end of the preform. Such a gate projection when removed from the preform for subscqucnt blow molding operations may create a ,,, __ 122:Z211 small flat spot at the bottom of the closed end of the preform. Therefore, an aspect of the preform accordin~ to ~his inventlon includes ~he afore described preform wherein the curved closed end contains a small, for example about 1/~ to 1j4 inch diameter, flat spot at ~he bottom of the curved closed end.
The neck portion of the prefo~m of this invention may be conventional in configura~ion and cross section e~cept that in accordance w$th this invention there iR required that the neck portlon contai~ a locating means. Such locatlng means serves to position the preform in the blow mold for blow molding the spherical container. This neck portion remains substantially unchanged in configuration during the blowing of the preform to form the spherical shaped container and forms the neck of the container which engages a closure for retaining the contents of the container. The body portion of the preform of this invention, containing the closed end~ i6 the portion of the preform that exapands in the mold to form the spherical shaped container.
By virtue of its shape the blow molding of a spherical container is markedly different from the blow molding of a conventional bottle and, therefore, re~uires special considerations in the cross sectional structure and configuration of the preform for producing the spherical container as compaLed to a preform for producing a bottle. Generally bottles taught in the prior art have a cylindrical shape and in that respect bear some resemblence to many of the prior art preforms that are used to produce them. However; the preform of this invention bears very llttle geometric resemblence to the spherical container ~hich is produced therefrom. Because of many self-evident geometric distinctions between bottles taught in the prior ar; and the spherical container produced in accordance with this invention there is established the need for a preform not only to produce a sp~lerical contain~r, but also to produce a plleriCal CODtaiOe~ h~ving a unilo~ all structure (e. g. thickn2ss~ an~
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provide molecular orlentation in the contalner wall needed to obtain commercially acceptable physical properties ~e.g. impact strength, tensile strength and barrier properties). The preform of this invention has the configuration to meet those needs (i.e. to produce a spherical container having commercially acceptable structure and properties).
The preform according to this invention and described herein is made by the in~ection molding method commonly known in the art for molding thermoplastic articles.
In the practice of this invention the preform disclosed herein i5 especially useful for making a hollow spherical container. Such container is useful for packaging beverages, such as for example beer.
A variety of thermoplastic polymers may be used for the practice of the preform and method of thls lnvention. Such thermoplastic polymers include, but are not limited to, for example, homopolymers and copolymers of vinyl monomers (e.g. polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinyl acetate copolymer and ethylene/vinyl chloride copolymer)~ homopolymers and copolymers of acrylonitrile (e.g. polyacrylonltril and acrylonitrile/styrene copolymer), homopolymers and copolymers of mono~olefin monomers (e.g. polyethylene, polypropylene, ethylene/vinyl acetate copolymer and ethylene/propylene copolymer), linear thermoplastic satllrated polyesters (e.g. polyethylene terephthalate and polybutylene terephthalate),homopolymers and copolymers of acrylic acid esters or lower alkyl substituted acrylic acid esters (e.g. polymethyl acrylate and polymethyl methacrylate), polystyrene and polycarbonate. Physical mix~ureff of thermoplastic polymers may also be used. In the practice of the preform and method of this lnvention there is preferably used a stretch orientable thermoplastic polymer, more preferably a thermoplastic linear saturated polyester and most preferably polyethylene terephthalate.
There also is conte~plated in the practice of this invention a preforin, as disclosed herein, and the metllod of making a spherical lZ;~;211 conta~ner wherein the preform has à barrier coating on the outside surface or the ins-lde surface or both the outside surface and inside surface thereof. Further, there is contemplated in the practice of this invention a preform, as disclosed herein, and the method of making a spherical container wherein the preform is a multi-layer wall preform having two or ~ore layers of different the~oplastic polymers forming the walls of ~he prefor~ and spherlcal container.
Thi8 invention is further described with reference to the non-li~iting figures 1 and 2.
In Fig. l iB shown a preform 3, according to this invention for producing a spherical container as shown in Fig. 2, having a neck portion 4 with ring locating means 7 and a body portion 5 containing a curved closed end section 6. The body portion 5 comprise~ a tapered wall section 8 tapered toward and abutting the ring locating means 7 from the axially straight, substantially constant thickness wall section 9 The substantially constant thickness wall section 9 in turn joins and leads into the curved, tapered wall section lO tapering toward and blending into the curvedJ substantially constant thickness closed end wall section 11. Curved substantially constant thickness, closed end wall section ll has a thickness less than the thickness of the constant thickness wall section 9 but at least one half the thickness of the constant thickness wall section 9. Ring locating means 7 of neck portion 4 is used to position preform 3 in the spherical cavity of a blow mold for blowing a spherical container shown in Fig. 2. Tapered wall sections 8 and lO in combination with the axially straight substantially constant thic~ness wall section 9 and the curved substantially constant thickness closed end~sectlon 11 provide the configuration in preform 3 for producing a uniform spherical wall 17 in spherical container 13 of Fig. 2. The neck port on 14 of the spherical container 13 of Fig. Z is substantially the same as the neck portion 4 of prefon~ 3 of Fig. l. ~ase 16 of . ,, 2~
~ ., spherical container 13 i8 C0}2figUred ~0 allow container 13 to stand unsupported on a flat surface. In Fig. 2 a preform according to this invention for producing spherical container 13 is shown in phantom in the interior of the container to depict a b~fore and after condition (i.e.
the condition prior to and after the blow molding operation) In the preferred practice of this invention the preform as disclosed herein is a stretch orientable thermoplastic polymer preform more preferably a polyethylene terephthalate preform.
There ls ~ow provided i~ accordance with this invention a Method Eor producing a spherical container`comprising the steps of I) positioning a heated preform in an open blow mold having a spherical cavity, II) clo.slng the blow mold around the body of the preform, III) introducing a blowing fluid lnto the inside of the preform, IV) expanding the body of the preform to and against the walls of the cavity, V) op~ning the mold and VI) removing the spherical container from tle mold, wherein said preform is an injection molded, essentially test tube shaped, thermoplastic poly~ler preform having an open end and a curved closed end and comprising a nec~ portion, at said open end, having a locating means for positioning said preform in the mold and an adjoining elongated cylindrical body portion containing said closed end wherein the body portion comprises a) a tapered wall section adjoining said neck portlon, b) adjoining the tapered wall section ta) a substantially constant thickness wall section and c) a curved closed end containing a curved tapered wall section ~oining the constant thickness wall section (b) to a curved constant thickness wall closed section, said curved constant thickness wall closed section having a thickness less than the thickness of the constant thickness wall scction (b) but at least one half the thickness of the constant thickness wall section (b).
In the practice of the mcthod of this invention tlle hcated preform may be a heate~ preform resulting from a heating step wherein a cold previously inJection rnolded preform is heated to a predetermined (i.e. desired~ temperature or temper~ture profile ~i.e. speclfic varlatlon of temperatures over the configuration of the preform). Durlng the heating of the preform the neck portion thereof is maintained at a temperature substantially below the softening or glass transition temperature of the thermoplastic polymer, preferably below 150F. The positioning step of the afore described process may be accomplished by well known methods such as, for example, by the use of a collar that grasps the exterior neck of the preform and may become part of the blow ~old or a mandrel which grasps the interior of the neck of the preform. Preferably the positioning step is accomplished by a metllod us;ng a collar to ~rasp the exterior of the neck of the preform. There may be used as the blowing fluid in the practice of the step of lntroducing a blowing fluid into the preform, a liquid or a gas. Preferably there is used a gas, more preferably air, as the blowing fluid.
Various thermoplastic polymer~ usable in the practice of the afore described method of this invention include, for example, those thermoplastic polymers exemplified herein with respect to the preform of this invention. Preferably the thennoplastic polymers used in the practice of the method of this invention are molecularly orientable thermoplastic polymers9 more preEerably a polyethylene terephthalate polymer.
In the preferred practice of the method of this invention a heated polyethylene terephthalate preform having a temperature profile is positioned in the biow mold, the mold closed, air under pressure introduced into the ;nside of the preform, the preform expanded to and against the cavity walls of the blow mold, the mold opcned and the spherical container removed. rne spherical container produced by the ~netllod of this invention is useful for the packaging of bevera~es, partic~larly beer.
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As used in this di6closure the phrase spherical container denotes a container having substantially a ball shape.
While this invent~on has been described above with rPspect to various embodiments, which are intended to be non-limiting, it is recognized that those skill~d in the art may practice further embodlments of this invention wlthout departing from the splrlt and scope of the inventlon as set forth and claimed herein.
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re6istance. Most, if not all, of these Iactors ma~y be tr aceable back to tlle preform as tlle source of contr ol. Thus appropriate preiorm coilstruction and configuration is necessary and important to achieve Lhe desired blow molded container.
Sumnlary of lnventiorl There has now been discovered a thermoplastic polymer pr erorm having a cor~iguration and cross section particularly adapted to the ~low molding of a spherical container Ior packaging beverages, more especially l~eer.
It is, therelore, an object of this invention to provide an injection molded, thernloplastic polymer, essentially test tube shaped preforrrl .
It is another object of this invention to provide an injectioll molded, thermoplastic polyrrler, essentially test tube shaped preform for blow rnolding a spherical container.
These and other objects, as will be apparent to one skilled in the art from the following description, are achieved by an injection molded, essentially test tube shaped, polyethylene terephthalate preform for blow molding a spherical container, said preform having an open end and a curved closed end and comprising a neck portion at said open end, l~aving a continuous flange for positioning said preform in a mold for blow molding the container and having an acljoining elongated, cylindrical body portion containing said closed end wherein the body portion comprises a) a tapered wall section adjoining sclid neck portion and tapering toward and abutting said flange, said tapered wall section constituting a minor segment of the length of the overall body portion, b) adjoining the tapered wall section (a) a sul~stanlicllly constant thickness wall section and c) a curved closed end ~`OIItainillg 'I ('Ul'V((] tapere(l wall sectioll joining the constant thickness wall section (b) to a curve(l substantillly conslanl lhickness closed secliorl, said (~urved substarltially constant thiclu~ess elosed section havitlg a thickncss less thall the thickness of the constant thiekness wall section (b), but at least one halt the thickness of the constant tllickness wall seclion (b), said curved closed end having at its bottorn a flat spot approximately 1/~ lo 1/4 inch in diameter.
Brief Description of Drawings In the following description of this invention referenee will be made lo the accompanying drawings wherein:
Figure 1 is a front view, partly in seetion, of a preform aceording to this invelltion;
I~'igure 2 is a front view, partly in section, of a spherieal container obtained from a preform aceording to this invention, shown in phantom in the intel ior of the spherical container.
Description of the Invention There is now provided in aeeordanee with an aspeet of this invention an injeetion molded, essentially test tube shaped, thernloplastic molecularly orientable polymer preform for blow molding a spherical container, said preform having an open end and a eurved closed end and eomprising a neek portion, at said open end, having a locating means for positioning said preform in a mold for blow molding the container and an adjoining elongated eylindrical body portion containing saicl closed end wherein the body portion eomprises a) a tal)ered wall section adjoining said neek portion, b) adjoining the tapered wall section (a) a substantially constant thickness wall seetion and e) a curvecl closed end containing a curved tapered wall seetion joining the constant thiclilless wall section (b) to a curved substantially constant ~hi(kl-less closed section, said curved substantially constant thickness k)sed section having a thickness less than the thiclcness of the ol~sLant thic~klless ~ all sectioll (b) but ~I
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at least one half the thic~ness of thè constant thickncss wall sectlon (b). Additionally, there is provided in accordance with this invention a method for blow molding a spherical container comprising the steps of I) positioning a heated preform according to the afore description in an open mold having a spherical cavity9 II~ closing ~he mold, III) lntroducing a blowing fluid into the lnterior of said preform, IV) expanding said preform to and against the walls of said savity, V) opening said mold and VI) removing the blown container from the mold.
In a particular aspect there i~ provided in accordance with this invention an injection molded, essent-lally test tube shaped, polyethylene terephthalate preform according to the above description and the method, as described above, of blow molding a polyethylene terephthalate spherical container. A further aspect of this invention provides the preform in accordance with the above description wherein the tapered wall section (a) adioining the neck portion of ~he preform tapers toward (i.e. narrows toward) and abuts the locating means of the neck portion of the preform.
This aspect is particularly applicable to the afore described polyethylene terephthate preform of this invention. ~s a still further aspèct of this invention there i6 provided a preform according to the above description wherein the thermoplastic polymer is a stretch orientable thermoplastic polymer more particularly a blow stretch biaxially orientable thermoplastic polymer. Another aspect of this lnvention provides a preform according to the above description wherein the tapered wall section (a~ adjoining the neck portion is a minor segment of the wall length of the body portion of the preform. In a even further aspect of this invention there is provided a preform according to the above description wherein the locating means is a segmented or a continuous r;ng or Elange~ more particularly a contilluous ring or flange.
The injection molding of the preform according to this invention often produces a gate pro~ection (15 of Fig. 2~ at the bottom of the curved closed end of the preform. Such a gate projection when removed from the preform for subscqucnt blow molding operations may create a ,,, __ 122:Z211 small flat spot at the bottom of the closed end of the preform. Therefore, an aspect of the preform accordin~ to ~his inventlon includes ~he afore described preform wherein the curved closed end contains a small, for example about 1/~ to 1j4 inch diameter, flat spot at ~he bottom of the curved closed end.
The neck portion of the prefo~m of this invention may be conventional in configura~ion and cross section e~cept that in accordance w$th this invention there iR required that the neck portlon contai~ a locating means. Such locatlng means serves to position the preform in the blow mold for blow molding the spherical container. This neck portion remains substantially unchanged in configuration during the blowing of the preform to form the spherical shaped container and forms the neck of the container which engages a closure for retaining the contents of the container. The body portion of the preform of this invention, containing the closed end~ i6 the portion of the preform that exapands in the mold to form the spherical shaped container.
By virtue of its shape the blow molding of a spherical container is markedly different from the blow molding of a conventional bottle and, therefore, re~uires special considerations in the cross sectional structure and configuration of the preform for producing the spherical container as compaLed to a preform for producing a bottle. Generally bottles taught in the prior art have a cylindrical shape and in that respect bear some resemblence to many of the prior art preforms that are used to produce them. However; the preform of this invention bears very llttle geometric resemblence to the spherical container ~hich is produced therefrom. Because of many self-evident geometric distinctions between bottles taught in the prior ar; and the spherical container produced in accordance with this invention there is established the need for a preform not only to produce a sp~lerical contain~r, but also to produce a plleriCal CODtaiOe~ h~ving a unilo~ all structure (e. g. thickn2ss~ an~
:lZ~Z~
provide molecular orlentation in the contalner wall needed to obtain commercially acceptable physical properties ~e.g. impact strength, tensile strength and barrier properties). The preform of this invention has the configuration to meet those needs (i.e. to produce a spherical container having commercially acceptable structure and properties).
The preform according to this invention and described herein is made by the in~ection molding method commonly known in the art for molding thermoplastic articles.
In the practice of this invention the preform disclosed herein i5 especially useful for making a hollow spherical container. Such container is useful for packaging beverages, such as for example beer.
A variety of thermoplastic polymers may be used for the practice of the preform and method of thls lnvention. Such thermoplastic polymers include, but are not limited to, for example, homopolymers and copolymers of vinyl monomers (e.g. polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinyl acetate copolymer and ethylene/vinyl chloride copolymer)~ homopolymers and copolymers of acrylonitrile (e.g. polyacrylonltril and acrylonitrile/styrene copolymer), homopolymers and copolymers of mono~olefin monomers (e.g. polyethylene, polypropylene, ethylene/vinyl acetate copolymer and ethylene/propylene copolymer), linear thermoplastic satllrated polyesters (e.g. polyethylene terephthalate and polybutylene terephthalate),homopolymers and copolymers of acrylic acid esters or lower alkyl substituted acrylic acid esters (e.g. polymethyl acrylate and polymethyl methacrylate), polystyrene and polycarbonate. Physical mix~ureff of thermoplastic polymers may also be used. In the practice of the preform and method of this lnvention there is preferably used a stretch orientable thermoplastic polymer, more preferably a thermoplastic linear saturated polyester and most preferably polyethylene terephthalate.
There also is conte~plated in the practice of this invention a preforin, as disclosed herein, and the metllod of making a spherical lZ;~;211 conta~ner wherein the preform has à barrier coating on the outside surface or the ins-lde surface or both the outside surface and inside surface thereof. Further, there is contemplated in the practice of this invention a preform, as disclosed herein, and the method of making a spherical container wherein the preform is a multi-layer wall preform having two or ~ore layers of different the~oplastic polymers forming the walls of ~he prefor~ and spherlcal container.
Thi8 invention is further described with reference to the non-li~iting figures 1 and 2.
In Fig. l iB shown a preform 3, according to this invention for producing a spherical container as shown in Fig. 2, having a neck portion 4 with ring locating means 7 and a body portion 5 containing a curved closed end section 6. The body portion 5 comprise~ a tapered wall section 8 tapered toward and abutting the ring locating means 7 from the axially straight, substantially constant thickness wall section 9 The substantially constant thickness wall section 9 in turn joins and leads into the curved, tapered wall section lO tapering toward and blending into the curvedJ substantially constant thickness closed end wall section 11. Curved substantially constant thickness, closed end wall section ll has a thickness less than the thickness of the constant thickness wall section 9 but at least one half the thickness of the constant thickness wall section 9. Ring locating means 7 of neck portion 4 is used to position preform 3 in the spherical cavity of a blow mold for blowing a spherical container shown in Fig. 2. Tapered wall sections 8 and lO in combination with the axially straight substantially constant thic~ness wall section 9 and the curved substantially constant thickness closed end~sectlon 11 provide the configuration in preform 3 for producing a uniform spherical wall 17 in spherical container 13 of Fig. 2. The neck port on 14 of the spherical container 13 of Fig. Z is substantially the same as the neck portion 4 of prefon~ 3 of Fig. l. ~ase 16 of . ,, 2~
~ ., spherical container 13 i8 C0}2figUred ~0 allow container 13 to stand unsupported on a flat surface. In Fig. 2 a preform according to this invention for producing spherical container 13 is shown in phantom in the interior of the container to depict a b~fore and after condition (i.e.
the condition prior to and after the blow molding operation) In the preferred practice of this invention the preform as disclosed herein is a stretch orientable thermoplastic polymer preform more preferably a polyethylene terephthalate preform.
There ls ~ow provided i~ accordance with this invention a Method Eor producing a spherical container`comprising the steps of I) positioning a heated preform in an open blow mold having a spherical cavity, II) clo.slng the blow mold around the body of the preform, III) introducing a blowing fluid lnto the inside of the preform, IV) expanding the body of the preform to and against the walls of the cavity, V) op~ning the mold and VI) removing the spherical container from tle mold, wherein said preform is an injection molded, essentially test tube shaped, thermoplastic poly~ler preform having an open end and a curved closed end and comprising a nec~ portion, at said open end, having a locating means for positioning said preform in the mold and an adjoining elongated cylindrical body portion containing said closed end wherein the body portion comprises a) a tapered wall section adjoining said neck portlon, b) adjoining the tapered wall section ta) a substantially constant thickness wall section and c) a curved closed end containing a curved tapered wall section ~oining the constant thickness wall section (b) to a curved constant thickness wall closed section, said curved constant thickness wall closed section having a thickness less than the thickness of the constant thickness wall scction (b) but at least one half the thickness of the constant thickness wall section (b).
In the practice of the mcthod of this invention tlle hcated preform may be a heate~ preform resulting from a heating step wherein a cold previously inJection rnolded preform is heated to a predetermined (i.e. desired~ temperature or temper~ture profile ~i.e. speclfic varlatlon of temperatures over the configuration of the preform). Durlng the heating of the preform the neck portion thereof is maintained at a temperature substantially below the softening or glass transition temperature of the thermoplastic polymer, preferably below 150F. The positioning step of the afore described process may be accomplished by well known methods such as, for example, by the use of a collar that grasps the exterior neck of the preform and may become part of the blow ~old or a mandrel which grasps the interior of the neck of the preform. Preferably the positioning step is accomplished by a metllod us;ng a collar to ~rasp the exterior of the neck of the preform. There may be used as the blowing fluid in the practice of the step of lntroducing a blowing fluid into the preform, a liquid or a gas. Preferably there is used a gas, more preferably air, as the blowing fluid.
Various thermoplastic polymer~ usable in the practice of the afore described method of this invention include, for example, those thermoplastic polymers exemplified herein with respect to the preform of this invention. Preferably the thennoplastic polymers used in the practice of the method of this invention are molecularly orientable thermoplastic polymers9 more preEerably a polyethylene terephthalate polymer.
In the preferred practice of the method of this invention a heated polyethylene terephthalate preform having a temperature profile is positioned in the biow mold, the mold closed, air under pressure introduced into the ;nside of the preform, the preform expanded to and against the cavity walls of the blow mold, the mold opcned and the spherical container removed. rne spherical container produced by the ~netllod of this invention is useful for the packaging of bevera~es, partic~larly beer.
~ -10-~Z;2~
As used in this di6closure the phrase spherical container denotes a container having substantially a ball shape.
While this invent~on has been described above with rPspect to various embodiments, which are intended to be non-limiting, it is recognized that those skill~d in the art may practice further embodlments of this invention wlthout departing from the splrlt and scope of the inventlon as set forth and claimed herein.
Claims
1. An injection molded, essentially test tube shaped, polyethylene terephthalate preform for blow molding a spherical container, said preform having an open end and a curved closed end and comprising a neck portion at said open end, having a continuous flange for positioning said preform in a mold for blow molding the container and having an adjoining elongated, cylindrical body portion containing said closed end wherein the body portion comprises a) a tapered wall section adjoining said neck portion and tapering toward and abutting said flange, said tapered wall section constituting a minor segment of the length of the overall body portion, b) adjoining the tapered wall section (a) a substantially constant thickness wall section and c) a curved closed end containing a curved tapered wall section joining the constant thickness wall section (b) to a curved substantially constant thickness closed section, said curved substantially constant thickness closed section having a thickness less than the thickness of the constant thickness wall section (b), but at least one half the thickness of the constant thickness wall section (b), said curved closed end having at its bottom a flat spot approximately 1/8 to 1/4 inch in diameter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000425495A CA1222211A (en) | 1983-04-08 | 1983-04-08 | Preform for blow molding spherical containers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000425495A CA1222211A (en) | 1983-04-08 | 1983-04-08 | Preform for blow molding spherical containers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1222211A true CA1222211A (en) | 1987-05-26 |
Family
ID=4124970
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000425495A Expired CA1222211A (en) | 1983-04-08 | 1983-04-08 | Preform for blow molding spherical containers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1222211A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2361875A1 (en) * | 2005-11-29 | 2011-08-31 | Petainer Lidköping AB | Container, system and method for distribution and dispensing of beverages |
-
1983
- 1983-04-08 CA CA000425495A patent/CA1222211A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2361875A1 (en) * | 2005-11-29 | 2011-08-31 | Petainer Lidköping AB | Container, system and method for distribution and dispensing of beverages |
| EP1954624B1 (en) * | 2005-11-29 | 2016-06-15 | Petainer Lidköping AB | System and method for distribution and dispensing of beverages |
| EP3100975A1 (en) * | 2005-11-29 | 2016-12-07 | Petainer Lidköping AB | System and method for distribution and dispensing of beverages |
| US9725293B2 (en) | 2005-11-29 | 2017-08-08 | Petainer Lidkoping Ab | System and method for distribution and dispensing of beverages |
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