CA1073377A

CA1073377A - Plastic container

Info

Publication number: CA1073377A
Application number: CA264,688A
Authority: CA
Inventors: William A. Conrad; Erwin M. Raabe; Morris M. Knepp; George E. Trieschock; Albert F. Gerlovich; Benjamin F. Cake; Lee R. Layman; Jack M. Kamins; Eugene E. Stark
Original assignee: Rheem International Inc
Current assignee: Rheem International Inc
Priority date: 1975-11-05
Filing date: 1976-11-02
Publication date: 1980-03-11
Also published as: MX144391A; AU6010080A; AU531197B2; AU6009980A; DE2649721A1; AU511579B2; GB1572400A; NZ182487A; IT1066635B; NL7612246A; FR2330595B1; DE2649721B2; FR2330595A1; ZA766562B; MX164527B; AU531410B2; ES452981A1; MY8400072A; BR7607368A; MY8400073A

Abstract

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 so 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

~ '73377 This invention relates to containers or the storage and shipping of materials and to methods for container manuacture.
In its efforts to economize in cont.ainer manufacture while yet seeking to meet the demands of drop tests and like performance standards and to lessen container static weight and hence trans~
portation costs, the container industry has lnoked extensively to the use of non-metals. In industrial shipping containers, efforts to eliminate or lessen metal usage have taken wideLy diverse direc-tions. In Carpenter U.SO Patent 39357,626 a dr~m is disclosed having body or shell formed by winding la~inated l.ayers of fiber-board into an open-ended cylinder which is then sealed. With the shell placed in a press, a plastic parison is extruded inside the shell and beyond the ends thereof. Upon closure of the press 9 bottom and top portions of the parison are closed and the parison is blown to conform to the form defined by the shell and the bottom and top die faces of the press. End covers are secured to the lined fibrous shell by use of metal reinforcing chimes~ Other ~orms o such plastic-lined fibrous shell containers made in similar manner are shown in Carpenter U.SO Patents 3,4453049 and 3,266,390 and in Heisler et al. U.S. Patent 3,262,628.
In Moore U. S. Patent 2~8233826 a drum shell is formed of plural wall sections of fiberglass composition. Adjacent wall sections include interleaved margin portions which are interlocked by a common pin member. The shell interior i5 lined with imper-vious material to render it leak-proofO
A further drum, in present commercial use and known as the "Greif Plastic Drum", produced by Greif Bros. Gorporatlon, is com-prised of a plastic body or shell with plastic losure members ~0~33~7 secured to the ends of the shell, however, by steel reinforcing chimes which encircle the shell ends and are crimped over the closure members~ The top closure member has a dome-shaped central part continuous with a peripheral part which is engaged circumferentially by the upper reinforcing chime with spaced radially extending ribs connecting the central and peripheral parts to provide added strength for stacking and holding ~ontents.
In making containers of exclusive plastic composition, various blow molding practices are known wherein an ex~ruded parison is blown to conform to a mold cavity to provide a one-piece container. Unitarily molded shells with integral or de~
tachable bottom and/or top closure members are disclosed in various U~S. patents lncluding Reynolds 3,827,595, Ainslee 3,370,737, Sears, Jr. et alO 3,357,593, Somme 3,115,281, Hoeffelman 3,424,343, Rowe 3,826,404, Uemura 3,405,439 and N~ghes 3,524,568. Whiteford U.5. Patent 3,184,524 discloses a ~urther alternative wherein a pre~orm is peripherally clamped and centrally pressed into desired form defined by a mold.
The manl1facture of plastic containers by processing mold-20 ing material within forming dies has the evident disadvantage of rendering the production of different-sized containers quite costly.
Thus, molds of diverse length and volume are required for making each uniquely sized container. Waste also occurs since container thickness is not uniformly ma~ntainable in molding practice9 i.e., containers are unnecessarily thick-walled in corner and like areas.
Manufacture of containers by other above-discussed techniques is ~073377 "~ .
complicated by the need for ~orming fibrous shells ~y 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 further entails the need for reinforcing its closure member by radial ribs as above considered.
An object of the present invention is to provide improved plastic containers suited for storage of corrosive materials.
A urther 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 a container comprising an elongate cylindrical shell of plastics material having at least one open end and a closure member of plastics material closing such open end, said closure member comprising an exc~usively axially extending cylindrical rim portion encircling and sealingly secured exclusively to the radially outer surface of said shell about said open end, an annular hingedly deformable portion continuous with said rim portion extending radially inwardly from said rim portion to the interior of the shell and a central deformable portion of the closure continuous with the annular portion completing closing off said open end, said annular portion extending radially and axially inwardly of the open end edge of the shell deformably hingedly to support said central portion and including a first part continuous with said rim portion and extending radially of said shell, a second part continuous with said first part and extending axially of and substantially parallel to said shell and encircled by said shell and a third part continuous with said second part and extending ~ 73377 , - to end locations radially interiorly of and coa~ial with said shell, with said central portion being continuous with said third part and having a surface area greater than the planar area encompassed by the juncture of the annular and central portions, whereby the container is resistant to impact by deformation and hingedly unfolding of the annular and central portions.
In a further aspect, the invention provides fox 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 centxal portion can be omitted in certain applications. The invention further provid~s improved bonding apparatus for effecting such joinder of the closure member and shell.
In making containers from extruded sheets, the invention defines a preferred method wherein plastic sheet material is cut into a sheet of length equal to desired shell axial length or height and of width approximating the shell circumference. The sheet is next formed into a hollow cylinder with the cut ends of the sheet defining the cylinder ends and with a longitudinal slit extending axially of the cylinder and defined by the sheet side edges. Bonding material is preferably applied to the slit and processed to provide a continuous imper~ious seal whereby the seal is completed. Top and bottom closure members of above-discussed character are then secured to the shell ends.
The oregoing 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:

,' ,'~ . .

~L~i'733~7 Fig. 1 illus~rates schematically the extruding and cutting o~ sh~ forming sheet material.
Fig. 2 is a top plan view of the Fig. 1 sheet material formed into a hollow shell with a strip of bonding material dis-posed in the shell axial seam and subject to the action of fusing apparatus illustrated in section.
Fig. 2a is a perspectiv~ view showing a manner of energizing ~he Fig. 2 fusing apparatus.
Fig. 3 is a frontal elevation in section of the completed Fig. 2 shell with end closure members therefor.
Fig. 3a illustrates an alternate end closure member con-figuration for use with the Fig. 2 shell.
Fig. 4 is a bottom plan view of the Fig. 3 embodiment.
Fig. 5 is a top plan view of fusing apparatus for use in securing the Fig~ 3 end closure members to the shell.
Pig. 5a shows tube 40a of ~he Fig. 5 fusing apparatus removed therefrom.
Fig. 6 is an enlarged sectional view of the Fig. 5 apparatus as seen from the line VI-VI of Fig. 5 operative in a fusing operation.
Referring to Fig. 1, extruder head 10 dispenses from die lip slit opening lOa continuous sheet material 12 preferably com-prised o~ high molecular weight high density polyethylene. Cutting apparatus (not shown) selectively cuts sheet ma~erial 12 trans-versely of its issuing direction to form individ~al sheets 14 having length L and width W. The former of these dimensions is controlled by the cutting apparatus whereas the latt:er dimension may be varied together with sheet thickness T by substitution of ~ ~ 73~3~7 extruder heads or changing the die lip opening. Oppo~ed ~ide edges 14a and 14b of sheet 14 are mitered at an angle of from five to forty-five degrees (Fig. 2) and the sheet is then ~ormed into a hollow cylinder. As shown in Fig. 2, mitered edges 14a and 14b are spaced slightly from one another and a strip o bonding material 1~ is disposed therebetween. Strip 16 is preferably comprised o~ magnetizable particles, such as iron oxide, dispersed in a plastic base. With strip 16 and sheet 14 disposed as in-dicated in Fig. 2, holding fixtures 18a and 18b, both comprised of electrically insulative material, are clamped in pressure re-lation to one another. These fixtures support a continuous two-loop coil of axially extending hollow copper tubing 20 which is internally cooled and excited electrically by connection to a radio frequency supply whereby edges 14a and 14b of sheet 14 are fused together, appl;ed pressure causing the bonding agent to flow into intimate contact with the facing surfaces of the sheet edges.
Rubber hose 20a (Flg. 2a) conducts coolant (water) rom the right hand tubing 20 in fixture 18a to the left hand tublng 20 in fixture 18a, At the remote end of such left hand fixture 18a, the copper tubing conducts coolant and curre~t therefrom to the right hand tubing 20 in fixture l~b. Rubber hose 20b con-ducts coolant thence to the left hand tubing 20 in fixture 18b.
Switch plates 20g and 20h are movable horizontally 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 ver~ically to permit axial removal of the bonded shell.
Referring to Fig. 3, the above-discussecl seaming operation ~L~733'77 provides a completed container shell 22 having axially extending seam 22a. End closure members 24a and 24b, formed in configuration shown in Fig. 3 and preferably of like material to that of shell 22, are disposed in place on the ends o shell 22 with strips 26 of bonding material situated interiorly o~ the end closure members and exteriorly of shell 22 as illustrated. With shell 22~ members 24a and 24b and strips 26 so arranged, the member 24b ~nd of the assembly is placed in bonding apparatus as shown in Fig. 6. This apparatus has an outer fixture 28 (Fig. 5) supported in spaced 10 radially encircling relation to an inner fixture 30, both comprised of electrically insulative material. Fix~ure 28 is of segmen~ed type, including segments 28a and 28b each spanning approximately one hundred-twenty degrees and segm~nts 28c and 28d, each spanning approximately six~y degrees. The radially outward surfaces of segments 28a-28d ~ engage bladder 32 serviced on demand ~rom a supply of pressurized air through conduit 34 for displacing the segments radially inwardly. Rigid outer ring 36 provides a re-action bearing surface ~or bladder 32. At their radially interior suraces, segments 28a and 28b define grooves 38 (Fig. 5) a~d 20 fixture 30 defines grooves 39 for receiving double loop hollow copper tubes 40a and 40b ~Figs~ 5, 5a). Tubes 40a and 43b are used, as in the case of tubing 20 above-discussed for applying a radio frequency ind~ction field to unbonded assembl~s disposed in channel 42 established be~ween segments 28a-28d and fixture 30.
The manner in which the tubing is routed in the Fig. 5 apparatus is seen in ~ig. 5a which shows ~ube 40a removed rom the Fig. 5 apparatus. Tube 40a portion 40a-1 extencls into fixture 30 to locatinn Ll and the tubing then proceeds outwardly toward the 733~7 viewer of Fig. 5a to tube port'uon 40a-2 which extends in an upper groove of i~ture 30 clockwise circularly to location L2. At this location~ tube 4Qa proceeds inwardly awa1y from the viewer of Fig~
5a to tube portion 40a-3 which extends radially ou~wardly to segment 28a and thence to an upper groove in segmPnt 28a. Tube portion 40a-4 proceeds counterclockwise circularly in such segment 28a groove to location L3 and then proceeds inwardly away from the Fig. 5a viewer to tube portion 40a-5 which proceeds radially inwardly of segment 28a to a lower groove of fixture 30. There-upon tube 40a extends clockwise circularly in fixture 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 ~his location tube portion 40a-7 extends radially outwardly of segment 28a. Fixture 30 and segment 28a have grooves at locations Ll-L4 and elsewhere running transverse of and interconnecting their uppex and lower grooves to provide for travel of tube 40a between such upper and lower grooves.
With the unbonded assembly o~ bonded shell 22, closure member 24b and strip 26 disposed in channel 42 (Fig. 6), conduit 34 is posi~ively pressurized and segments 28a-28d press the assembly agains~ fix~ure 30O Segmen~s 28c and 28d serve to equalize pressure around the circumference of the unbonded assembly.
Tubes 40a and 40b are energized whereby the part ~f the assembly adjacent the tubes is fused together, the applied pressure causing the bonding agent to flow into intima~e contact with the surfaces of shell 22 and end closure member 24b which face strip 26.
In the embodiment shown in l~igs~, 5, 5a and 6, tubes 40a and 40b each encompass approximately one hundred degrees of arc, ~ la73377 mutually spaced by some ninety degrees, For a complete bonding opera~ion, the work is ro~ated and two passes are needed. The invention o~ course contemplates a single continuous double loop tubing assembly whereby the bonding oper,ation may be completed in a single pass mode for joining each closure member to the bonded shell.
Leaf ~pring 43 between base 44 and the segmen~s urges the segments radially ou~ardly o~ channel 42 when bladder 32 is de1ated to facilitate removal of bonded assemblies. For automated removal o~ bonded assemblies from the bonding apparatus, ram assembly 46 is slidably supported on sleeve 44a o~ base 44 for movement through base opening 44b into channel 42.
Referring to ~igs. 3 and 4, end closure members 24a and 24b include a ~irst (hinge) portion 24-1 having one part 24~1a ~tending axially of shell 22 and encircling the outer surface of the shell and another part 24-lb extending to end locations radially interiorly of and coaxial with the shell, i.e., as defined by circular locus 24-lc shown in broken lines. The closure members have a second (central) porticn 24-2 continuous with portion 24-1 e~clusively at such end locations in circle 24-lc whereby portion 24-2 is hingeably supported by portion 24-1. Portion 24-2 is itself preferably bowed axially of shell 22 such that it has linewise surface extent Sl between diametrically opposed ones, e.g., LA and LB, of end locations of portion 24-1 in excess of the diame~ric spacing S2 between such end locations. Closure member 24a may have bung hole fittings, one being shown a~ 24c in Fig. 3r By this arrangement, portions 24 1 and 24-2 are deformable or unfolding to a preselec~ed degree upon subjecting the Figo 3 container to drop testing, the extent of unfolding thereof being greater when portion 24-2 is bowed axially of the shell. As con-sidered in the examples below, the sealable relation of the closure members and the shell is thereby maintained throughout such testing. While portion 24~2 is bowed axially inwardly of shell 22 or dished in Fig. 3, the closure members may also have the configuration shown in Fig. 3a, i.e., with portion 24-2' bowed axially oukwardly of the shell or domed. In the Fig. 3a arrangement the linewise surface extent S3 of portion 24~2' between diametrically opposed end locations o hinge portion 24-1' !
exceeds the diametric spacing S2 between end locations~ As will be appreciated, the closure member hinge and central portions are preferably parts of an integral plastic structure formed by a molding operation.

~S~a~
The side edges of an e~truded sheet of high molecular weight high density polyethylene (HDPE), 38 inches in width, 70.5 inches in length and 0.135 inch in thickness are mitered at an angle of 10 and the sheet is ~ormed into a cylindrical shell as in Fig~ 2 having a diameter of 22.5 inches and an axially extend-ing slit between the mitered edges~ A strip of bonding material comprised o HDPE containing iron oxide particles and having a thickness of 0.015 inch and a width of 0.625 inch is placed in the slit and extends throughout the slit length. Bonding fixtures are next pressed against the shell slit as in Fig. 2 and ar,e energized from a radio-frequency supply to subject the bonding material to an electromagnetic field~ heating the material to its fusion ~3377 point and flowing the material into intirnate eontact with the mitered edges~ thus sealing the shell slit throughout its length.
End closure members are molded of high molecular weight HDPE in the configuration shown in Fig. 3 and have an average thickness of 0.187 inch. The line surfac:e extent of the end closure members (Sl in Fig. 3) is four percent longer than the spacing (S2 in Fig. 3) between diametrically opposed end locations of the hinge portion. The end closure members are assembled with the shell and with a bonding material strip therebetween as in Fig. 3, comprised of HDP~ containing iron oxide particles and having a thickness 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-~requency supply to subject the bonding material to an electromagnetic field, heating the ma~erial to its fusion point and flowing the material into intimate contact with the surfaces of the end closure members and shell ~acing the material.
Containers so formed and with bungs threaded into bung holes in one of the end closure members are subjected to internal hydrostatic pressure of 15 psi. No fluid leakage is observed on inspection. Containers so formed are filled through the bung holes with 55 gallons of water and water-methanol m~tures. Bungs are threaded into the bung holes and the containers are dropped from a height of 4 feet at an angle of 45 with respect to the container longitudinal axis at temperatures of 70F and 0F. No fluid leakage is observed on inspection of the dropped containers.

73~77 E~
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 ex~ent (S3 in Fig. 3a) four per-cent longer than the spacing (S2~ between diametrically opposed end locations of the hinge portion. End closure members so formed are secured to shells formed as in Example 1 in the manner set ~orth in Example 1. The resulting containers are subjected to the internal hydrosta~ic pressure and drop testing se~ forth in Example 1 without showing ~luid leakage.

Example 3 The side edges o~ an extruded sheet of high molecular weight HDPE, 13.5 inches in width, 36.5 inches in length and .085 inch in thickness are mitered at an angle of 10 and the sheet is formed into a cylindrical shell as in Fig. 2 having a diame~er of 11.5 inches and an axially extending slit between the mitered edges. A strip of bonding material comprised of HDPE containing iron oxide particles and having a thickness of .010 inch and a width o~ 0.375 inch is placed in the slit and extends throughout the slit length. The shell slit is sealed throughout its length in the manner set forth in ~xample 1.
End closure members are molded of high molecular weight HDPE in the configura~ion shown in Fig. 3 and have an average thickness of .085 ;nch. The line surface e~tent o~ the end closure members (Sl in Fig. 3~ is two percent longer than the spacing (S2 in Fig. 3) between diametrically opposed end locations o~ the hinge portion. The end closure members are assembled with the shell and with a bondîng material strip therebetween as in Fig. 3 -~2-` ~73377 comprised of HDPE containing iron oxide particles and having a thickness of .010 inch and a width of 0.5 inch. The assembly is secured in the manner set forth in Example 1.
Containers so ormed and with a bung threaded into a bung hole in o~e of the end closure members a:re subjected to internal hydrostatic pressure o~ 15 psi. No fluid leakage is observed on inspection. Containers so formed are filled through the bung hole wi~h S gallons of water and water-methanol mixtures. A bung is threaded into the bung hole and the containers are dropped from a height of 4 feet at an angle o 45 with respect to the container longitudinal axis at temperatures of 70 F and 0 F.
No fluid leakage is observed on inspection of the dropped con-tainers.
Exam~le 4 A high molecular weight HDPE shell is extruded in cylin-drical form through a circular die slot opening. The shell is 13.5 inches in length, having a diame~er of 11,5 inches and .085 inch in thickness. End closure members with an average thick-ness of .085 inch are molded of high molecular weight HDPE in the con~iguration of Fig. 3 except that their line surace extents (Sl in Fig. 3) are equal to the spacings (S~) between diametrically opposed end locations of the hinge portion, i.e., central portîon 24-2 is flat. End closure members so formed are secured to the shell in the manner set forth in Example 1. The resulting con-tainers are subjected to the internal hydrostatic pressure and drop testing set forth in Example 3 without showing fluid leakage.

EE~m~
A single end closure member o .085 inch av,erage thickness ~73377 is molded of high molecular weight HDPE in the configuration of Fig. 3 except that their line sur~ace extents (S3 in ~ig. 3~ are equal to the spacings (S2) between diametrically opposed end locations o the hinge portion, i.e., central portion 24-2 is flat. The end closure member is secured to a HDPE injection molded one-piece pail having a height of 13.5 inehes, a diameter of 11.5 inches and .085 inch i~ average thickness, using the bonding method set ~orth in Example 1. The resulting containè~s are subjected to the internal hydrostatic pressure and drop testing as set forth in Example 3 without showing fluid leakage.
White the invention has been disclosed by way of particu-larly preferred embodiments, various changes and modifications thereof will be evident to those skilled in the container, bond-ing and related arts. Where in extruded sheet form, the shell axial slit need not have mitered edges nor strip bonding material disposed therein but may have non-mitered edges joined directly to one another by ~usion or like techniques or by use of a common backing member joined thereto. The particularly disclosed embodiments are thus intended in an illustrative and not in a limiting sense, the true spirit and scope of the invention being set forth in the following claims.

Claims

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

1. A container comprising an elongate cylindrical shell of plastics material having at least one open end and a closure member of plastics material closing such open end, said closure member comprising an exclusively axially extending cylin-drical rim portion encircling and sealingly secured exclusively to the radially outer surface of said shell about said open end, an annular hingedly deformable portion continuous with said rim portion extending radially inwardly from said rim portion to the interior of the shell and a central deformable portion of the closure continuous with the annular portion completing closing off the said open end, said annular portion extending radially and axially inwardly of the open end edge of the shell deformably hingedly to support said central portion and including a first part continuous with said rim portion and extending radially of said shell, a second part continuous with said first part and extending axially of and substantially parallel to said shell and encircled by said shell and a third part continuous with said second part and extending to end locations radially interiorly of and coaxial with said shell, with said central portion being continuous with said third part and having a surface area greater than the planar area encompassed by the juncture of the annular and central portions, whereby the container is resistant to impact by deformation and hingedly unfolding of the annular and central portions.

2. The container of claim 1 wherein said closure member rim, annular and central portions are parts of an integral plastic structure.

3. The container claimed in claim 1 wherein said closure member central portion is bowed axially outwardly of said shell.

4. The container claimed in claim 1 wherein said closure member central portion is bowed axially inwardly of said shell.

5. The container claimed in claim 1 wherein said shell and said closure member are comprised of high molecular weight high density polyethylene.

6. The container claimed in claim 1 wherein said shell is cylindrical and has first and second open ends, said container having a first and a second said closure member respectively closing said shell first and second ends.

7. The container claimed in claim 1 wherein said shell is comprised of a shell of plastic material cylindrically formed and having opposed edges juxtaposed with bonding material therebetween and configured to define a miter joint extending axially of said shell.

8. The container claimed in claim 7 wherein said shell is comprised of an extruded sheet and wherein said opposed edges are spaced from one another in the direction of extrusion of said sheet.

9. The container claimed in claim 7 wherein said shell and closure member are comprised of high molecular weight high density polyethylene and wherein said bonding material comprises a plastic substance containing magnetizable particles.

10. A method for making a container comprising the steps of:
(a) cutting plastic sheet material into a sheet of predetermined length and width;
(b) forming such cut sheet into a hollow shell having a slit extending axially between open ends of said shell and defined by juxtaposed edges of said sheet;

(c) sealing said slit to provide an axially extending continuous sealed seam for said shell;
(d) forming a closure member for one of said shell open ends by shaping integral plastic material peripherally in hinge configuration and interiorly thereof in bowed configuration;
(e) forming an assembly wherein said closure member is disposed in encircling relation to said shell adjacent said one open end and wherein bonding material containing magnetizable particles is disposed between said closure member and said shell; and (f) securing said assembly by simultaneously applying pressure to said assembly and disposing a magnetic field generator in immediate juxtaposition with the periphery of said closure member, thereby heating said material to its fusion point for flowing thereof into intimate contact with said closure member and said shell adjacent said one open end.

11. The method claimed in claim 10 wherein said step (c) is practiced by disposing in said slit material containing magne-tizable particles and then subjecting said material to an electro-magnetic field thereby heating said material to its fusion point and flowing said material into intimate contact with said sheet edges.

12. The method claimed in claim 10 wherein said step (f) is practiced in successive practices and with a magnetic field generator comprised of generator segments, pressure being applied fully circumferentially of said assembly in each such practice, said assembly being rotatively moved between said successive practices for disposing said generator segments in immediate juxtaposition with successive periphery portions so as to cover the entire periphery of said closure member.