CA1052323A - Plastic lids and pails - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

This invention concerns plastic pails having rein forcement members about their top section. When in combination with plastic lids, these assemblies have increased resistance to de-flection from impact forces.

Description

~05~3'~3 BACKGROUND O~ THE INVENTION

Large thick-walled plastic containers are used for packaging and transpoxting materials in the form of liquids and solids~ These materials may be solids, liquids or pastes, aqueous or organic, acidic or alkaline, e.g., detergent solutions, latices, foods or condiments, fine chemicals, etc. Three and a half, five-and six-gallon sizes are most common Because of inertness and toughness, plastics such as high density polyethylene or other inert moldable thermoplastic resins are preferred materials. The contain-ers are filled with the contents, capped, perhaps stored, and ship-ped~ After they are transported to the user, he may also store them.
In storage, these containers are stacked one upon the other. After being opened, they may be reopened and closed as the contents are used. There are two common types of container constructions: the wide mouth or open-head pail and the closed mouth or tight-head pail.
This invention relates to constructions for open-head pails so that they may have the structural characteristics associated with tight-head pails yet retain the wide mouth access of the open-head pails.

1 _ ~.05~3Z3 SUMMARY OF THE INVENTION

In this invention, plastic pails have thin rein-forcing members in their top section. This stiffens the top section against deflection to protect the seal bet:ween the lid and the pail.
When screw threads are used on the pails, the reinforcement members support the threads so that corresponding lids can be made with out-wardly flaring rims. In addition, the lids may have enhanced struc-tural features for stackability and for dissipating impact forces.

BRIEF DESCRIPTIO_ OF THE DRAWINGS
The features of the invention are illustrated in Figures 1 3.
Figure 1 is a cross section in elevation of a lid according to this invention.
Figure la is a plan view of the lid shown in Figure 1.
Figure lb is an elevation in full of a,quarter section of the lid shown in Figure 1.
Figure 2 is an elevation, partly in cross section of a plastic pail according to this invention.
Figure 3 is an elevation of an enlarged cross sec-tion showing the lid of Figure 1 combine~ with the pail of Figure 2.

DETAILED DESCRIPTION OF THE INVENTION
-Plastic containers constructed in accordance with ~05f~3Z3 this invention comprise a pail or receptacle body, a gasket and a lid. The lid is securely fastened to the pail, while the gasket forms the seal between the lid and the pall. The pail will have an opening at its top substantially the width of the pail, a fastening mechanism will be located at or near the top of the pail. The lid will cover the open top of the pail and will have a fastening mechanism about its periphery to cooperate with the mechanism on the pail for securing the lid to the pail.
The pails of this invention are generally cylindric-al in shape and are made of moldable thermoplastic resins. Prefer-red materials are inert polyolefin resins such as high density polyethylene and polypropylene. The volumetric capacities are typ ically 3.5, 5 and 6 gallons. The pails are generally tall and wide compared to their wall thickness.
The plastic pail structures of particular interest are those having a wide-mouth opening, open-head pails. As shown in Figure 2, the pail 200 has a topmost section 210, an intermediate section 220 and a bottom section 230. The topmost section has the matching engagement means for the lid located at the mouth of the pail.
Reinforcing members 212 in the form of thin integral-ly molded elements extending outwardly from the outer sidewall of the pail to the mid region of the engagement means and extending through the vertical segment of the topmost section can be used with engagement means both in the form of screw threads and snap fit beads. These members 212 tend to stiffen the topmost section of the pail against deflection and from impact forces and transfer or distribute such deflection to the intermediate section.
These reinforcement members are disposed about the circumference of the pail. They project out from the sidewall of the top section 21Q. By having them extend down from the top edge 211 of the pail to a circumferential shoulder 213, the vertical deflection of the top section can be transferred to the intermediate section 220. This will protect the enga~ement between the lid and the pail from suffering deflection which causes leakage. The number of the members and the width to depth ratio of the members are selected to stiffen the top section while avoiding a material increase in the mass of the top section. By forming an open frame-work around the top section with the reinforcing members, substan-tial rigidity is created yet the added mass of plastic is only about 10 to 15% of the mass of the top section. Because of the minimal increase in mass, shrinkage of the circular hot top section in the pail while cooling from its molding temperature is minimized.
This pail construction is particularly suitahle for use with lid structures having engagement means in the form of screw threads. By integrally molding the screw thread on the pail and the reinforcing member, the screw thread can be supported with ~)5'~3Z3 sufficient rigidity so that it will engage the lid at a position exterior of the inner face of the outer leg in the inverted U~shaped rlm. As illustrated in Figure 3, the reinforcement members 212 can extend outwardly to the outer surface of the rolled edge forming the rim 211. The screw threads 215 extend beyond the reinforcing members and can terminate interiorly of the shoulder 213. This has the important benefit in that the corresponding rim of the lid is now wide enough so that the mold for making it can have a shaped metal mass to form the rim that is rigid and easily cooled. The effect of such a core piece in the mold is that it helps to maintain the dimensional tolerances for production and also can operate for a long period of service without distortion. As well, it shortens the cycle time required to mold the lid.
In one form of mold for the pail, rotating mold sections can be used to shape the threads and the topmost section of the pail.
In this case, it is convenient to have the reinforcing members ter-minate interiorly of the outer surface of the rolled top edge 213 of the pail.
Where the wall thickness of the pail, the thickness of the screw threads and the thickness of the reinforcing members are about equal, the pail can be molded with minimum distortion in the top section. The thickness of the reinforcing member adjacent to the top edge of the pail can be less than that of the remainder of the element so that the upper edge of the pail in contact with ~OS,Z3~3 gasket material is smooth and free from depressions or sinkholes which may arise from cooling thicker masses of plastic~
When used with screw threads, it is prefeLred that the reinforcement members extend into the screw thread a distance sufficient to reduce deflection of the individual thread. As shown in Figure 3, the reinforcing membars form a girder-work projecting radially to about midway of the thread. This increases the stiff-ness of the free end Qf the thread. The thread can extend outwardly of the rim 211 of the pail. As a consequence, the interior of the arch in the lid and the arrangement of the top section of the pail can be dimensioned so that the engagement means of the lid and the pail are mated at a position that is exterior of the rim 211 of the pail. Thus the lateral dimensions for the engagement means can be independent of the lateral dimension of the interior of the U-shaped arch in the lid and the pail which hold the compression on the gasket. The result is a wider manufacturing tolerance in the dimensions of the molded plastic parts while the mating engagement parts can be securely fastened.
The reinforcing members on the pail may be oriented in the direction of draw o the mold which forms the pail. Then, these members will form an acute angle with a radius through the axis of the pail which passes through the intersection of the pail and the members. The members are arranged to form a stiff reinforcing ~0~'~3Z3 action in the topmost section of the pail without a substantial mass of resin being present. A preerred assembly is for vertical members to extend down from the top of the pail to a peripheral shoulder 213 extending outwardly Erom the pail. The threaded engage-ment means will be disposed as a helix upwardly along the pail axis and will extend from the top of the pail to the peripheral shoulder.
The reinforcing elements may have a uniform thickness or may be thicker in the portion above the thread and thinner below the thread.
The bottom section 230 of the pail has a vertical sidewall section 231 and a horizontal bottom wall section 232 which is dis-posed above the lower edge 233 of the sidewall section 231. The low-er edge 233 of the sidewall section is shaped to repose within the peripheral rim o a lid similar to that described above. The stack-ing feature of the lid and pail combination is illustrated in Figure 3 with the adjacent pail bottom shown in phantom outline.
The lid structures are illustrated in Figures 1, la ~nd lb.
The plastic lid 100 has a central closing portion 101. An inverted U-shaped rim 102 surrounds the central closing portion 101. The rim 102 contains the engagement means for ~astening the lid to an open-head pail. The interior of the rim is shaped to include spacing fora gasket 300 to be fitted between the lid and the pail. Projecting from the rim are a plurality of thin plastic members 105. These members are located on the periphery of the rim and extend both from ,~LoS6,~3Z3 the outer wall 107 of the outer leg of the arch in the xegion of the arch and upwardly above wall 106 forming the top of -the arch of the inverted U. By this arrangement, the thi~ elongated plastic members are in a position to initia~ly absorb and dissipate impact forces directed to the rim of the lid~ Th:is d,istributes the shock of such impact over a broad region of the lid and causes a reduction in the intensity of forceper unit area so that the seal formed by the combination of lid, gasket and pail will be able to maintain its integrity after such shocks. The thinness and spacing of the upstanding members is selected according to the mass of the container and the curvature of the rim. These members are thin enough and long enough so that upon impact they defect rather than rigidly transmit the forces to the rim proper.
A standard test for tight-head pails, the D.O.T. four foot drop test, can be used to good advantage for observing the bene-fits of this invention. In both versions of the test, the assembly of pail and lid is dropped from a height of four feet onto a floor.
In one version, the direction is such that the corner of the lid stri~es the floor at an angle of 45 In the other version, the direction is such that the axis through the center of the pail is parallel to the floor. Usually, the container is filled with water.
At the time of impact, noticeable deflection occurs in the conven-tional lids with open-head pails that causes the circular shape to become wrinkled. In the pail, there is also a noticeable deflection - ~o~ 3,'~3 or kink at the top section. Fur-thermore, leakage from the assembly is shown by spillage of liquid. Bv using this invention, the deflec-tion of both the lid and the pail can be controlled as well as avoidance of leakage.
A particularly advantageous construction results when the upstanding members 105 of the lid are combined with a second inverted U-shaped portion 120 adjacent to the rim of the lid. This second portion 120 extends above the central closing portion and ends below the outer wall 106 forming the top of the inverted U section of the rim. The upstanding members together with the second U-shaped por-tion form a receptacle for receiving the bottom section 230 of a pail200, the bottom being shown in phantom outline in the partial cross section of the lid in Figure 3. With this construction, several closed pails can be assembled on top of each other. The lower pail will securely hold the next adjaGent upper pail and the inverted U
shaped portion of the lid can withstand heavy loads without deflection of the lid. By having the upstanding members 105 formed integral with the outer wall 110 of the inner leg of the rim and the outer leg o the second inverted U-shaped portion, the resulting lid struc-ture tends to act as a unit in dissipation of impact forces on the rim and the resistance to vertical loads.
The lids are astened to the pails with engagement means in the outer leg 113 of the inverted U-shape of the rim. These are 3~3 adapted to mate with corresponding devices on the pail, In one form the engagement means may be screw threads 111, 112. Those shown in Figure 1 have a generally buttress form and a long pitch and each thread extends about one-quarter of the circumference of the lid~ This gives a large mechanical aclvantage (9/1 or greater);
the lid can easily be engaged or disengaged with high compression on the gasket. Another form of engagement means is a peripheral bead extending inwardly from the inner wall of the outer leg of the in-verted U in the rim. With the upstanding members of the lid, the seal between lid, gasket and pail is protected. The threads may be disposed with one of a full section 111 and one with a half section 112 as the next adjacent thread face. Inasmuch as the lids are made by injection molding, a preferred form of lid having screw threads for engagement also has the outer wall 113 of the inverted U in the rim 115, 116 contoured to follow in parallel the upwardly rising threads 113 as shown in Figure lb. This simplifies the manufacturing techniques and allows a uniform wall thickness over the whole cross section of the lid. Furthermore, when polyethylene or a similar resin with high slippage is the material of construction, the lids having screw threads should also have a secondary locking device so that vibration during transportation does not cause the lid and pail to loosen by slippage. One such device is notches 114 formed in the lower edge of the outer wall of the lid for locking onto short posts ~o5~,~3Z3 or bars 214 on the pail. When the lid is in its tightly closed position on the pail, the bar or posts will be just tall enough to penetrate and engage the notches for a completely secure container.
Rather than mechanical structures such as notches t light coating o adhesives will secure th~ lid against vibration during shipment. The lid may also ~e disengaged by hammer blows,, An integrally formed handle in ~he central closing portion of the lid may be in the form of a hollo~ bar 130 rising above and across the central closing portion. The sidewalls 131 of the bar present large flat vertical areas for closing or opening the contain-er. In closing, automatic cappers having rotating grippers or bars can bear on the flat surfaces of the handle and quickly close ths lid. In opening, automatic machinery or simple tools such as hammers can be used to overcome the locked notch and post and then unspin the lid. By having lids with the screw threads, the containers may be opened without the use of pry bars, knives, etc., to cut away por-tions of the lid and may readily be reclosed and reopened.
An illustrative example of a specific container having a capacity of 6 gallons and constructed according to this invention with the configuration shown in Figures 1-3 would have the following representative dimensions, the Fiyures themselves being approximately to scale. High density polyethylene would be injection molded to form the lid 100 and the pail 200. The lid has an overall diameter of 12.5", the central closing portion is 9.38" in diameter. The ~OS'~3Z3 inverted U-shaped rim has an in-t:erior span o 0.624" The thread depth is 0.175l'. The span between the outer wall of the inner leg of the U-shaped rim and the wall of the adiacent wall of the invert-ed U-shaped portion is 0.275". The entire span of the U-shaped por-tion is 0.70". The typical wall thickness for the lid is 0.10".
The upstanding members 105 may be spaced at 10 intervals, they are 0.07 inches thick. The overall height of the member is 1.175".
The inverted U-shaped rim is about 1.575 inches high, while the adjacent inverted U-shaped portion is 0.70". ~s shown, the adjacent U-shaped portion is elevated from the mid point of the rim. The thread is 0.100 inches thick and rises 0.50 inches in each arcuate segment. The handle portion is about 0.60 inches high.
The pail is 17.5 inches high overall with an average wall thickness of 0.10 inches~ The topmost section would be 6.225 inches rorn the rim to the circumferential shoulder section bearing the handle. The intermediate section is about 11.5 inches and the bottom-most section is about 0.75 inches. In the bottommost section, the outer walls extend about 0.~ inches below the floor of the pail.
The top of the pail is 11.8 inches in diameter. The rim diameter of the top is 11.25 inches. The rim has a radius of 0.156 inches. The screw threads are 0.10 inches thick and extend 0.79 inches from the sidewall. These threads are disposed to match those on the lid. There is a taper in the width of the pail so that it is ~QS~323 10.5 inches in diameter at its bottom.
The reinforcing members 212 project about 0.55 inches from the sidewall and extend down from the rim for about 1.125 inches.
These are oriented at a slight angle to the surface of the sidewall so that when the pail is molded, segmented mold ~arts can move rad-ially away from the pail These members are 0.05 inches thick and there are thirty-six in number, spaced about the circum-ference of the pail. On the~shoulder 213, small posts extend upwardly about 0.1 inch. These are to engage the notGhes which are found in the bottom of the rim on the lid. In the arch of the lid, space is provided between the compression member 1~4 and the rim of the pail to allow about 0.06 inches for the compressed gasket. The compress-ion member causes the gasket to initially squeeze when the lid is first fitted to the pail. The further engaging of the lid and the pail results in a fully compressed gasket which forms an especially effective seal.
It has been found that when the assembled lid and con-tainer are subjected to impact force, e.g., by being dropped to land on its corner, there is a further tightening of lid and pail. In the event it is desired to quickly loosen the threaded engagement, slots can be provided in the lid so that implements such as screwdrivers can be used to make an initial separation between the lid and the pail. As an alternative, by deliberately applying a separate impact , ~.os'~:3z3 force to the assembled lid and pail, the seal between them can be further improved.
It is contemplated that the lid may contain smaller pour openings as part of its structure. In this manner, the open-head pail structure can be used with the small pour opening fittings common for tight-head pails~
The common capacity for the pail.s of this invention are 3.5, 5 and 6 gallons. Other sizes can be made utilizing the advan-tages of this invention. As well, variations in the size and shape of the parts of the lid and the pail can be made. These and other changes such as materials of construction as would be apparent to those versed in this field are within the invention set forth in the ollowing claims.

Claims (5)

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

1. In a molded flexible thermoplastic open top pail having a top section, a middle section and a bottom section, said top section having engage-ment means for assembly with a lid having an inverted U-shaped rim portion that contains mating engagement means in the outer leg of said rim, said middle section being the predominant volumetric portion of said pail, the improvement comprising a top section with a plurality of integrally molded reinforcement members disposed about the circumference of said pail, said members projecting outwardly from the sidewall of said pail and extending downwardly from the open end of said pail a distance sufficient to transfer vertical deflection to said middle section, the number of said members and the width to depth ratio of said members being sufficient to stiffen said top section without a material increase in the mass of said top section and wherein said engagement means are in the form of screw threads, said threads extending outwardly from the sidewall of said top section for engagement with said lid at positions outwardly of the inner face of the outer leg of said inverted U-shaped rim, said threads being integrally molded with said reinforcing members whereby the free edge of said threads is stiffened.

2. The pail of claim 1 wherein said top section includes a circum-ferentially extending shoulder and said threads extend upwardly between said shoulder to the top edge of said pail and said threads extend radially out-wardly beyond said top edge and terminate before the outer edge of said shoulder.

3. The pail of claim 2 wherein said reinforcing members extend from said shoulder to said top edge of said pail and terminate radially inwardly of the inner leg of said U-shaped rim.

4. The pail of claim 3 wherein said top edge is the end surface of a rolled edge surrounding said pail.

5. The pail of claim 4 wherein said reinforcing members terminate radially outwardly at the outer surface of said top edge.