CA1074072A - Plastic container - Google Patents

Abstract

PLASTIC CONTAINER

Abstract of the Disclosure Plastic containers include a shell an open end of which is sealably closed by a closure member having a peripheral hinge portion secured to the shell and an inner expanse which may be bowed axially of the shell. The closure member is unfolding or deformable in drop testing such that sealable closure of the shell is maintained.

Description

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This invention relates to coneainers for the ~torage and shipping of materials and to method~ for container m2nufacture.
In its efforts to economize in container manufacture while yet seeking to meet the demands of drop tests and like performance ~tandards and to lessen container static weight and hence trans-portation costs, the contalner industry has looked exten~ively to the u~e of non-metals. In industrlal shipping container~, efforts to eliminate or lesseQ metal usage have taken widely diverse direc-tions. In Carpenter U.S. Patent 3,357,626 a drum is disclosed having body or shell formed by winding laminated lay~r~ of fiber-board i~to an open-ended cyllnder which i8 then ~ealed. With the ~hell placed in a pre~s, a plastic parison is e~truded inside the shell and beyond the ends thereof. Upon closure of the press, bottom ant top portions of the parison are closed and the parison i8 blown to conform to the form defined by the ~hell and the bo~tom and top die faces of the press. End covers are ~ecured to the lined fibrous ~hell by u~e of metal reinforcing chimes. Other forms of ~uch plastic-lined fibrous shell containers made in similar manner are shown in Carpenter U.S. Patents 3,445,049 and 3,266,39 and in Heisler et al. U.S. Patent 3,262,628.
~n Moore U. S. Patent 2,823,826 a drum ~hell i9 formed of plural wall sections of fiberglass compo~ition. Ad~acent wall --section8 include interleaved ma n in port$ons which are interlocked by a common pin member. The ~hell interior is lined with imper-vious material to render it leak-proof.
A further drum, in pre~ent commercial use and known a~ the "Gre~f Plastic Drum", producet by Greif Bros. Corporation, i8 com-prised of a plastic body or ~hell with pla~tic closure members 107~q~7Z

~ecured to the ends of the ~hell, h~wever, by steel reinforcing chimeR which encircle the shell ends and are crimped over the closure member~. The top closure member has a dome-shaped central psrt continuous with a peripheral part which i8 engaged circumferentially by the upper reinforcing chime with ~paced radially extending ribs connect~ng the central and peripheral parts to provide added strength for stacking ant holding content~.
In making containers of exclusive plastic composition, var~ou3 blow molding practices are known wherein an extruded parison i8 blown to conform to a mold cavity to provide a one-piece container. Unitarily molded ~hell~ with integral or de-tachable bottom and/or top clo~ure members are disclosed in various U.S. patents including Reynolds 3,827,595, Alnslee 3,370,737, Sears, Jr~ et al. 3,357,593, Somme 3,115,281, Hoeffelman 3,424,343, Rowe 3,826,404, Uemura 3,405~439 and NugheJ 3,524,568. Whiteford U.S. Patent 3,184,524 d~scloses a further alternative wherein a preform is perlpherally clamped and centrally pressed into desired form defined by a molt.
The manufacture of plastic containers by processing mold-20 ing material within forming dies ha8 the evident disadvantage of rendering the production of different-sized containers quite co~tly.
Thus, molds of diver~e length and volume are required for making each uniquely sized container. Wa~te also occurs since contalner thickness i8 not uniform~y ma~ntainable in molding practice, i.e., containers are unnece8sarily thic~-walled in corner and like areas.
Manufacture of containers by other above-discussed techniques i8

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complicated by the need for forming fi~rous shells by winding and sealing laminates or joining sections and then applying a sealing lining thereto. Regarding the reference commercially-available drum, the same is a metal-reinforced plastic drum and its manufacture furt~er entails the need for reinforcing its closure member ~y radial ribs as above considered.
An object of the present invention is to provide improved plastic containers suited for storage of corrosive materials.
A further object of the invention is to provide improved methods for the manufacture of containers impervious to materials storable therein.
In accordance with one broad aspect, the invention relates to apparatus for use in securing a closure member to an open end of a shell including a first fixture and a second fixture supported coaxially interiorly of said first fixture, said fixtures being supported for relative movement to jointly define a radially extending space therebetween for receiving an unbonded assembly of said closure member and said shell, at least one of said fixtures being comprised of separate segments, first means for displacing said fixtures relative to one another whereby said fixtures apply pressure to said assembly, and second means for subjecting such pressed assembly to heat energy, the improvement wherein said second means comprises an electromagnetic field generator supported at the pressing periphery of at least one of said fixtures immediate to the pressed assembly and adapted for flexure relative to its supporting fixture and bonding material including magnetizable particles dispersed in plastic, said particles being responsive to such generated electromagnetiF field to heat sald plastic to

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its fusion point for flowing thereof into intimate contact with surfaces o~ said shell and said closure member in facing relation to said ~onding material.
In a further aspect, the invention provides for joinder of a container closure member to the exterior of a container shell in a manner minimizing constraints on movement of the closure member hinge portion whereby the above-discussed excess linewise surface extent of the closure member central portion can be omitted in certain applications. The invention further provides improved bonding apparatus for effecting such joinder of the closure member and shell.
The foregoing and other objects and features of the invention will be evident from the following detailed discussion of preferred embodiments thereof and from the drawings wherein like reference numerals identify like parts throughout.
In the drawings:

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Flg. 1 lllustrates schematically the extruding and cutting of shell-forming sheet material.
Fig. 2 is a top plan view of the Fig. 1 ~heet material formed into a hollow shell with a ~trip of bonding material dis-posed in the shell a~ial seam and sub~ect to the action of fusing apparatus illustrated in section.
Fig. 2a i9 a perspective view showing a manner of energizing the Fig. 2 fusing apparatu~.
Fig. 3 i8 a frontal elevation in section of the completed Fi8. 2 shell with end closure members therefor.
- Fig. 3a illu~trates an alternate end closure member con-figuration for u~e with the Fig. 2 ~hell.
Fig. 4 i8 a bottom plan vlew of the Fig. 3 embodiment.
Fig. 5 is a top plan view of fusing apparatu~ for use in securing the Fi8. 3 end clo~ure members to the shell.
Fig. 5a shows tube 40a of the Fig. 5 fusing apparatus removed therefrom.
Fig. 6 i8 an enlarged sectional view of the Fig. S
apparaeus as seen from the line VI-VI of Fig. 5 operative in a fu~ing operation.
Referring to Fi8. 1, e~truder head 10 dispense~ from die lip slit opening lOa continuous sheet m terial 12 preferably com-pri~ed of high molecular weight high den~ity polyethylene. Cutting apparatus (not shown) ~electively cut~ ~heet material 12 trans-~ersely of its issuing direction to form individual sheets 14 having length L and width ~. The former of these dimension~ i~
controlled by the cutting apparatus whereas the latter dimension may be varied together with sheet thic~ne~ T by ~ubstitution of ~074~7Z

extruder heads or changing the die lip opening. Qpposed side edges 14a and 14b of sheet 14 are mitered at an angle of from five to forty-five tegrees (Fig. 2) and the sheet is then formet into a hollow cylinder. As shown Ln Fig. 2, mitered edges 14a snd 14b are ~paced slightly from one another and a gtrip of bonding material 16 i8 disposed therebetween. Strip 16 is preferably comprised of m~gnetizable particles, ~uch as iron oxide, di~persed in a plastic base. With strip 16 and sheet 14 disposed as in-dicatet in Fig. 2, holding fixtures 18a and 18b, both compr~et of electrically insulative material, are clamped in pressure re-lation to one another. The~e fixtures support a continuous two-loop coil of axially extending hollow copper tubing 20 ~hich i8 internally cooled and excited electrically by connection to a radio frequency supply whereby ed8es 14a and 14b of sheet 14 are fu~ed together, applied pre~ure cau~ing the bonding agent to flow into intimate contact with the facing surfaces of the sheet edges.
Rubber hose 20a (Fig. 2a) conducts coolant ~water) from the right hand ~ubing 20 in fixture 18a to the left hand tubing 20 in fixture 18a. At the remote end of such left hand fixture 18a, the copper tubing conduct~ coolant and current therefrom to the ri8ht hand tubing 20 in fixture 18b. Rubber hose 20b con-ducts coolant thence to the left hand tubing 20 in f~xture 18b.
Switch plates 20g and 20h are movable horiæontally in Fig. 2a to engage switch plates 20c-20f to energize the tubing. On completion of the fusing operation, plates 20g and 20h are moved vertically to permit axial removal of the bonded shell.
Referring to Fig. 3, the above^di~cussed seaming operation 1074~72 provides a completed container ~hell 22 having axially extending ~eam 22a. End cloYure members 24a and 24b, formed in configuration ~ho~n in Fig. 3 and preferably of like ~aterial to that of ahell 22, are disposed in place on the end~ of shell 22 with strips 26 of bonding material situaeed lneeriorly of the end clo~ure members and exteriorly of shell 22 as illustrated. With shell 22, members 24~ and 24b and strips 26 80 arranged, the member 24b end of the aJ~elDbly i8 placed ln bonding apparatus a~ sho~n in Fig. 6. This app~ratus has an oueer fi~cture 28 (Fig. 5) supported ln ~paced 10 radlally encircllng relation to an inner fixture 30, both comprised of electrically insulative material. Fisture 28 i~ of Jegmented t~pe, including segments 28a and 28b each ~panning approximately one hundred-twenty de8rees and ~egments 28c and 28d, each spannlng appro~cimately si~cty degreeJ. The radially oueward surfaces of ~egments 28~-2~d engage bladder 32 serviced on temand from a ~upply of pre3surized air through conduit 34 for displacing the ~egments radially in~srdly. Rigid outer ring 36 provldea a re-sctlon bearing ~urface for bladder 32. At their radially interior ~urface~, ~egmentJ 28a and 28b define groove~ 38 tPig. S) and 20 fixture 30 defines grooves 39 for receiving double loop hollo~
copper tubes 40a and 40b (Figs. 5, 5a). Tubes 40a and 40b are used, a~ in the case of tubing 20 above-discu~sed for applying a radio frequency induction field to unbonded a~sen~ie~ ti~posed in channel 42 established between ~egments 28a-28d and fixture 30~
me manner in which the tubing i~ routed in the Fig. 5 spparatus i9 seen in Fig. 5a which sho~s tube 40a removed from the Fig. 5 apparatus. Tube 40a port$on 40a-l extends into fi~ture 30 to location Ll and the tubing then proceeds outwardly toward the ~7-- - ;

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viewer of Fig. 5a to tube port~on 40a-2 which e~tends in an upper groove of fixture 30 clockwi~e circularly to location L2. At this location, tube 40a proceeds inwardly away from the viewer of Fig.
5a to tube portion 40a-3 which extend~ radlally outwardly to segment 28a and thence to an upper groove in segm2nt 28a. Tube portio~ 40a-4 proceed~ counterclockwise circularly in such segment 28a groove to location L3 snd then proceeds inwardly away from the Fig. 5a viewer to tube portion 40a-5 wh~ch proceeds radially inwardly of segment 28a to a lower groove of fixture 30. There-upon tube 40a extend~ clockwise c$rcularly in fi~ture 30 tolocation L4 whereupon tube portion 40a-6 proceeds radially out-wardly to a lower groove of segment 28a and therein to location L5.
At thi~ location tube portion 40a 7 extends radially out~ardly of ~egment 28a. Fi~ture 30 and ~egment 28a have groove~ at location~
Ll-L4 and elsewhere running transver~e of and interconnecting their upper ant lower grooves to provide for travel of tube 40a between ~uch upper snd lower grooves.
With the unbonded a~embly of bonded shell 22, cloJure member 24b and strip 26 diJposed in channel 42 (Flg. 6), condult 34 is po~itively pr~urized and segments 28a-28d press the a~sembly against fixture 30. Seg~ents 28c and 28d ~erve to equalize pre~sure around the circumference of the unbonded a~sembly.
Tube~ 40a and 40b are energi2ed whereby the part of the a~sembly ad~acent the tubes i~ fused together, the applied pre~sure caw ing the bonding agent to flow into intimate contact with the surfaces of ~hell 22 and end closure member 24b which face trip 26.
In the embodiment shown in Figs. 5, 5a and 6, tubes 40a and 40b each encompass approximately one hundred degrees of arc, 0 7 4~7 ~
mutually spaced by 80me ninety degrees. For a complete bonding operation, the work i8 rotated and two passes are needed. The invention of course contemplates a single continuous double loop tubing as~embly whereby the bonding operation way be completed in a ~ingle pa~s mode for ~oining each closure member to the bonded ~hell.
Lea~ spring 43 bet~een ba~e 44 and the segments urge~ the ~egments radially out~ardly of channel 42 ~hen bladder 32 i8 dsflated to facilitate removal of bonded assemblies. For automated removal of bonded assemblies from the bondlng apparatu~, ram a~sembly 46 1~ slidably ~upported on sleeve 44a of base 44 for movement through ba~e opening 44b into channel 42.
R~ferring to Figs. 3 and 4, end closure ~ember~ 24a and 24b include a fir8t (hinge) por~ion 24-1 having one part 24-la tending a~ially of ~hell 22 and encircling the outer surface of the ~hell and another part 24-lb extending to end locations radially lnteriorl~ of and coaxial with the shell, i.e., a~ defined by circul~r locu~ 24-lc sho~n in broken lines. The closure members ha~ a second (central) portion 24-2 continuous with portion 24-1 exclusiv~ly at such eod locations in circle 24-lc whereby portion 2~o-2 i~ hingeably supported by portion 24-1. Portion 24-2 is i~Jelf preferably bowed a~ially of ~hell 22 such that it has llne~i~e ~urface extent Sl between diametrically opposed ones, e.g., LA and LB, of end locations of portion 24-1 in excess of the diametric spac~ng S2 between such end locations. Closure member 24a may have bung hole fitting~, one being shown at 24c in Fig. 3.
By this arrangement, portions 24-1 and 24-2 are deformable - 10 7 4~7'Z

or unfoldlng to a preselected tegree upon subJecting the Fig. 3 container to drop tes~ing, the extent of unfolding thereof being greater ~hen portion 24-2 i8 bowed axially of the shell. As con-sideret in the examples below, the sealable relation of the clo~ure members ant the shell i8 thereby maintained throughout such testing. While portion 24-2 i8 bowed axially i~wartly of shell 22 or dished in Fig. 3, the closure member~ may al8o have the configuraeion ~hown in Fig. 3a, i.e., with portion 24-2' bowed sxially outwardly of the s~ell or domed. In the Fig. 3a arrangement the linewi~e surface e~tent S3 of portion 24-2~
bet~een diametrically opposed end locations of hinge portion 24-1' exceed~ the diametric spacing S2 between end locations. As will be appreciated, the closure member hinge and central portions are preferably psrts of a~ integral plastic ~tructure formed by a molding operation.

ExamDle 1 The side edges of an e~truded sheet of high molecular weight high density polyethylene (HDPE), 38 inches in width, 70~5 inches in len~th a~d 0.135 inch in thickness are mitered at an angle of 10 aad the sheet i~ formed into a cylindrical ~hell as in Fig. 2 having a diameter o~ 22.5 inches and an axially extend-ing alit between the mitered edges, A ~trip of bonding material comprised of HDPE containing iron oxide particle~ and having a thickne~s of 0.015 inch and a width of 0.625 inch i9 placed in the slit and extends throughout the 81ie length. Bonding fistures are next pressed again~t the shell ~lit as in Fig. 2 and are energized from a radio-frequency supply to sub~ect the bonding material to an electromagnetic field, hesting the material to its fusion .:

~07 40,~2 point and flowing the msterial into intimate contact with the mitered edges, thus sealing the shell slit throughout it8 length.
End clo~ure members are molded of high molecular weight HDPE in the configuration ~hown in Fig. 3 and have an average thickne~s of 0.187 inch. The l$ne surface extent of the end clo~ure members (Sl in Fig. 3) i8 four percent longer than the ~pacing (S2 in Fig. 3) between diametrically opposed end locations of tho hinge portion. The end closure members are assembled ~ith the shell and ~ith a bonting material strip therebetween as in Fig. 3, comprised of HDPE containing iron oxide part~cles and having a thic~ess of 0.015 inch and a width of 0.750 inch. Bond-ing fixtures are next pressed against the assembly as in Fig. 6 and are energized from a radio-frequency supply to sub~ect the bonding material to an electromsgnetic field, heating the ~aterial to its fusion point and flowing the material into intimate contact ~ith th~ ~urfaces of the end clo~ure members and sholl facing the mater$al.
Container~ ~o formed and ~ith bungs thresded into bung holes in one of the end closure members are sub~ected to internal hydrostatic pressure of 15 p8i. No fluid leaksge Ls ob~erved on inspection. ContainQrs 80 formed are filled through the bung holes with 55 gsllonJ of water and water-methanol mlxtures. Bungs are thre-ded into the bung hole~ and the contsine~s are dropped from a height of 4 feet at an angle of 45 with respect to the container longitudinal axi~ at temperature~ of 70F and 0~. No fluid leakage i8 observed on inspection of the dropped container~.

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Example 2 End closure members are molded of high molecular weight HDPE in the configuration shown in Fig. 3a with average thickness of 0.187 inch and line surface extent (S3 in Fig. 3a) four per-cent longer than the spacing (S2) between diametrically opposed end locations of the hinge portion. End closure member~ 80 formed are 8ecured to ~hells formed as in Example 1 in the manner ~et forth in Example 1. The resulting containers ~re sub~ected to the internal hydrostatic pressure and drop te~ting ~et forth in Example 1 without showlng fluid leakage.
ExamPle 3 The side edge~ of an extruted sheet of high molecular weight HDPE, 13.5 inche~ in width, 36.5 inches in length and .085 inch in th$ckne~s are mitered at an angle of 10 and the sheet i8 formed into a cg~indrical shell ~8 in Fig. 2 having a diameter of 11.5 inches and an axially extending slit between the mitered edges. A strip of bonding material comprised of HDPE containing iron oxlde particles and having a thicknes~ of .010 inch and a width of 0.375 inch i8 placed in the slit and extends throughout the slit length. The shell ~lit i8 sealed throughout its length in the manner set forth in Example 1.
Ent closure members are molded of high molecular weight HDPE in the configuration shown in Fig. 3 and have an average thicknes~ of .085 inch. The line surface extent of the end closure members (Sl in Fig. 3) i~ t o percent longer than the ~paclng (S2 in Fi8. 3) between di~metrically opposet end locations of the hinge portion. The end clo~ure me~bers are a~embled with the ~hell and with a bonding material strip therebetween as in Fig. 3 :- :
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" ' 10 7 4~7 2 comprised of HDPE containing iron oxide particle~ ant having a thicknes~ of .010 inch and a width oX 0.5 inch. The assembly is secured in the manner ~et forth in E~ample 1.
- Container~ ~o formed and ~ith a bung threaded into a bung hole in one of the end clo~ure members are ~ub~ected to internal hydrostatic pre~sure of 15 p8i. No fluid leakage i8 observed on inspection. Containers 80 formed are filled through the bung hole with 5 gallons of water and ~ater-methanol mixture~. A bung i~ threated into the bung hole and the containers are dropped from a height of 4 feet at an angle of 45 with respect to the container longitudinal axi8 at temperatures of 70 F and 0F.
No fluid leakage i~ observed on inspection of the dropped con-tainer~.
Exam~le 4 A high molecular weight HDPS shell i8 extruded in cyll~-drical form through a circular die slot opening. The shell i8 13.5 inche~ in length, having a diameter of 11.5 inches and .085 inch in thickness. End closure members with an average thick-ne~s of .085 inch are molded of high molecular w~ight HDPE in the configuration of Fig. 3 except that their line surface extent3 (Sl in Fig. 3) are equal to the pacing~ (S2) between diametrlcally oppo~ed end location~ of the hinge portion, i.e., central portion 24-2 i~ flat. End clo~ure member~ ~o formed are secured to the ~hell in the manner set forth in Example 1. The resulting con-tainers are sub~ected to the internal hydrostatic pressure and drop testing set forth in Exanple 3 without showing fluid leakage.
ExamDle 5 A single end closure member of .085 inch average thickne~

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10 7 4~ 7 2 i~ molded of high molecul~r weigh~ HDPE in the configuration of Fig. 3 except that their line surface e~tent~ (S3 in Fig. 3) are equal to the spacings (S2) between diametrically opposed end location~ of the hinge portion, i~e., central portlon 24^2 i8 flat. The end clofiure ~ember is ~ecured ~o a HDPE in~eetion ~olded one-piece p~il having a height of 13.5 inches, a dlameter oi 11.5 inches and .085 inch in average thicknes~, using the bondin~ method set forth in Example 1. The re~ulting contain~r3 are ~ub~ected to the internal hydrostatic pres~ure and drop 0 testing as set forth in E~ample ~ without ~howing fluid leakage.
White the invention ha~ been disclo~ed by way of particu-lfirly preferred embodimentJ, various change~ snd modification~
thereof will be evident to those skilled in the contai~er, bond-ing and related art~. Where in e~eruded sheet form, the shell a~al ~lit need not h~ve mi~ered edges nor ~trip bonding msterial di~posed therein but ~ay h~ve non-mitered edge~ ~oined directly to one another by fusion or like techniques or by u~e of a common`b~cking member ~oined thereto. The particularly di~closed embodiment~ are thus intended in an illustrative ~nd not in a limiting ~ense 9 the true spirit and qcope of the invention being ~et forth in the foll~wing claims.

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In apparatus for use in securing a closure member to an open end of a shell including a first fixture and a second fixture supported coaxially interiorly of said first fixture, said fixtures being supported for relative movement to jointly define a radially extending space there-between for receiving an unbonded assembly of said closure member and said shell, at least one of said fixtures being comprised of separate segments, first means for displacing said fixtures relative to one another whereby said fixtures apply pressure to said assembly, and second means for sub-jecting such pressed assembly to heat energy, the improve-ment wherein said second means comprises an electromagnetic field generator supported at the pressing periphery of at least one of said fixtures immediate to the pressed assembly and adapted for flexture relative to its supporting fixture and bonding material including magnetizable particles dis-persed in plastic, said particles being responsive to such generated electromagnetic field to heat said plastic to its fusion point for flowing thereof into intimate contact with surfaces of said shell and said closure member in facing relation to said bonding material.

2. The apparatus claimed in claim 1, wherein said first fixture is segmented and wherein said first means comprises inflatable means situated radially in-wardly of and engageable with said segments and rigid means disposed radially outwardly of said inflatable means for defining a bearing reaction surface for said in-flatable means.

3. The apparatus claimed in claim 1 wherein said second means comprises radio-frequency energizable tubing means supported by at least one of said fixtures and defining an interior hollow for receiving a cooling medium.

4. The apparatus claimed in claim 1 wherein said second means comprises radio-frequency energizable tubing means supported by at least one of said fixtures and of extent less than the perimeter of said assembly and thereby adapted for said flexture relative to its supporting fixture for movement into confronting relation with said assembly in the course of pressing thereof.