Gasketless Closure For Open-Top Pails

Abstract

A molded plastic closure is configured to provide a plug fit with the top rim of an open top container having an outwardly protruding rim flange. A two-part seal preventing leakage of fluid from the container is provided by means of a ridge structure on the inner wall of the inverted U-shaped channel of the closure peripheral structure as well as a flexible sealing wiper appendage which is formed integrally with the top of the inverted U-shaped structure and which deformingly contacts the top surface of the container rim when the rim is essentially fully inserted into the U-shaped channel. The wiper appendage is formed to angle toward the inner channel wall in the undeflected condition.

Description

FIELD OF THE INVENTION

This invention relates to closures; i.e., “lids,” for open-top pails and, more particularly, to a plug fit closure that provides an effective seal between the closure and the pail without the use of a conventional gasket.

BACKGROUND

Molded plastic closures for open-top pails are in wide spread use and are available from numerous manufacturers including the Letica Corporation of Rochester, Mich. The pails, also called “containers,” and closures are generally made from high density polyethylene, hereinafter “HDPE,” and are injection molded in a range of capacities from about one to six gallons and may or may not have pouring spouts and bails for carrying. The closures snap or “lock” firmly on the pails and may have various means such as tear bands on an outer skirt to aid in removal from the pail.

Where such pails are used to carry perishable goods or fluids, it is common to design the closure to provide a “plug fit” wherein the pail rim extends into and is trapped between the parallel walls of an inverted U-shaped annular channel formed in the peripheral portion of the closure structure. Conventional wisdom further calls for the use of a resilient gasket which is placed in the top of the channel and against which the top of the inserted pail rim bears to form a seal. An example of such a pail/closure combination is shown in U.S. Pat. No. 7,207,457 issued Apr. 24, 2007 to Stefan Schwarz and assigned to Letica Corporation.

The gasket itself adds to the cost of the product and the placement of the gasket into the channel is a secondary operation that adds still more cost and complexity to the manufacturing process. This presents a competitive disadvantage; moreover, recycling of the closure becomes more complex because of the different materials used to make the closure and the gasket.

As a result, various attempts dating back to at least 1976 have been made to eliminate the gasket while still providing an effective seal. One approach is to manufacture both the closure and the pail to close tolerances to provide a very tight fit and to design the mold to provide a complex and a conforming geometry between the pail rim and the closure. Again, this puts pressure on the design, manufacture, and maintenance of the tooling used to injection mold the HDPE lid and pail. Further, the seals can lose effectiveness due to age and/or damage to the pail rim or the closure channel through ordinary handling.

SUMMARY OF THE INVENTION

The invention here described follows conventional wisdom insofar as it utilizes a plug fit between the top rim of an open-top container provided by an inverted U-shape channel formed in the peripheral structure of the closure, but departs from the prior art in the manner in which a seal is provided.

The closure design contemplates use in combination with a pail or container having a sidewall ending at the top in an outwardly protruding rim having a top surface. The rim cooperates with a ledge on an interior wall of the closure to “lock” the closure on the container. The closure itself comprises a molded plastic body having a center deck and an integral peripheral channel portion with radially spaced apart inner and outer annular walls for receiving the top rim of the pail therein. The outer wall or “skirt” may have a tear strip on the lower end to facilitate the first removal of the closure from the pail.

The pail/closure embodiment used herein to explain the invention is generally cylindrical, albeit tapered. As a result, the pail rim and the peripheral channel of the closure are annular. However, the invention is not limited to cylindrical pails and can be used to advantage in oval, square, and rectangular pails.

The outer interior wall of the channel in the disclosed embodiment is formed with an annular ledge or “undercut” to lockingly receive and cooperate with the outwardly protruding annular pail rim when the pail rim is sufficiently inserted into the annular channel. The interior of the channel, particularly the surface of the inner wall, has a continuous annular rib configuration that provides a first primary seal in cooperation with the inner surface of the pail. In addition, the closure is molded to provide a sealing wiper appendage which is integral with the closure and depends downwardly and inwardly from the interior top wall of the channel; i.e., the appendage leans or curves toward the inner wall interior surface. When the seal wiper is deformingly contacted by the top surface of the pail rim upon insertion of the pail rim into the channel, the appendage bends further toward the inner wall to form a second seal.

The closure is preferably, but not necessarily, injection molded from HDPE. In addition, the sealing wiper appendage preferably has a ratio of length to root dimension of approximately 4.25:1 in a closure for a five-gallon pail, one of the most popular sizes, and has a 5° taper from root to distal end. As indicated above, and in accordance with prior practice, the container may be made in any of the commercially popular sizes and shapes, may be tapered or straight-walled, and the closure is designed and manufactured to correspond to the top configuration of the container.

As a result of the design of the closure herein described and the cooperation between the closure and the pail, a firm and reliable gasketless seal that can withstand rough handling without leakage is accomplished in a cost-efficient fashion. By virtue of the seal, air is prevented from entering container during storage to spoil or otherwise adversely affect perishable content, and leakage of fluids from the container in the event of tip overs, drops, and other handling events is substantially prevented.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an example of a molded plastic closure and pail combination of the type to which the invention can be practically applied;

FIG. 2 is a sectional view of a portion of the closure showing features of the invention;

FIG. 3 is a dimensioned detail of the closure channel;

FIG. 4 is a dimensional detail of the wiper appendage;

FIG. 5 is a perspective view of a portion of the closure channel; and

FIG. 6 shows the closure channel with the pail rim inserted and locked in place.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

Referring to FIG. 1 there is shown a molded plastic closure 10 for a five-gallon open-top molded plastic pail 12 having a tapered sidewall 14 and a wire bail 16. Both the closure 10 and the pail 12 are preferably injection molded from HDPE. Other plastics, such as polypropylene, can also be used.

The closure 10 has an annular peripheral portion 18 surrounding a generally circular inner deck portion 20 and is sized to fit on the pail 12 in such a way as to “lock” onto the pail and provide a seal to prevent both the ingestion of air into the pail 12 as well as to prevent leakage from any fluid carried by the pail in the fully closed condition. This representation is intended to be generic in nature; i.e., it shows a typical pail/closure configuration wherein the closure has a “plug fit” on the pail rim, and also has a “tear strip” on the outer skirt, details of which are omitted here but can be found in the Schwarz patent identified above, incorporated herein by reference.

Referring now to FIGS. 2-6, details of the annular peripheral portion 18 of the closure 10 are described. As stated above, the pail 12 has a slightly tapering sidewall 14 which ends in an annular top rim portion 15 with a generally a flat-top although the edges, both inner and outer, may be radiused. The top rim portion 15 is shown in FIG. 6 to have a rolled-over configuration but can also be flat-bottomed. The rolled-over configuration is preferred. The diameter of the rim 15 is about 11.5 inches.

The annular peripheral portion 18 of the closure 10 consists of an outer wall or “skirt” 26 and an inner wall 32 which, together with the top wall 36, define an inverted U-shaped channel into which the top rim portion of the pail 12 is inserted as best shown in FIG. 6 to provide a plug fit. This means that, in addition to an outer wall that captures only the outside of the pail rim, the closure has an inner wall that extends down into the container.

The inside surface of the outer wall or skirt portion 26 of the closure 10 is molded with an annular groove 28 which weakens the material to allow the lower portion 30 of the skirt to function as a “tear strip” in conventional fashion. Details of a tear strip structure can be found in the above-described Schwarz patent, incorporated herein by reference. A ledge 38 is formed below the top wall 36 of the inverted U-shape channel to lockingly interact with the undersurface of the top rim 15 of the pail 12 as shown in FIG. 6.

The inside surface of the inner wall 32 is molded to provide two vertically spaced continuous, annular seal ridges 40 that contact the inside surface of the container sidewall when sufficiently inserted into the U-shaped channel to provide a primary seal. See FIG. 6.

An inner structure 34 connects the inverted U-shaped channel to the center deck 20 in the manner shown to provide for stacking stability if desired.

The inner surface of the top wall 36 of the peripheral structure 18 has molded thereon a single circularly continuous sealing wiper 42 which depends downwardly and inwardly; i.e., toward the inner wall 32. The angle of the wiper appendage 42 is about 20° but this angle is not deemed critical so long as the appendage curves or angles inwardly toward the inner wall 34 and not outwardly toward the skirt wall 26. A practical lower limit would be about 15°.

The appendage 42 is thicker at the base or root; i.e., where it integrally joins the top wall 36, than it is at the distal end as shown in FIG. 4. The appendage 42 also has a length of about 0.170″ which is less than the distance between the inside surface of the top wall 36 and the ledge 38. The distance between the inside surface of the top wall 36 and the ledge 38 is also slightly greater than the distance between the top surface and the undersurface of the pail rim 15 so as to provide the slight clearance shown in FIG. 6. The ratio of the root thickness to the length of the appendage 42 is approximately 4.25:1. The overall length of the appendage 42 will depend on the size of the closure but is approximately 0.170″ for a closure that fits a standard five-gallon molded HDPE container with an 11.5″ diameter.

FIG. 6 shows the pail sidewall 14 with the top rim portion 15 essentially fully inserted into the U-shaped channel between the walls 26 and 32; i.e., inserted sufficiently far to seat the undersurface of the pail rim onto the top surface of the ledge 38 on the interior of the closure skirt portion 26, thereby essentially locking the closure 10 on to the pail rim 12. In this condition the inside surface pail sidewall fully contacts the ribs 40 to provide a primary seal therebetween. Furthermore, the top surface of the rim 15 deflects the sealing wiper appendage 42 inwardly, creating more annular surface area of contact with the surface of the rim 14 thus providing an additional seal.

In use, the pail and closure are shipped to the retailer unattached. The retailer fills the pail and firmly attaches the closure to the pail to complete the seal. Filled pails can be stacked to a degree depending on the design strength of the pail and closure, and the weight of the pail contents. The end user opens the pail by removing the tear strip. The closure can be reapplied to preserve unused content as needed.

It is to be understood that while the invention has been described in this document with respect to a specific but illustrative embodiment, various configurational and size changes may be made within the scope of the invention described and claimed herein. The drawings, although not fully dimensioned, are to scale.

Claims

1. A closure for a pail having a sidewall ending in an outwardly protruding top rim having a substantially flat top surface and a substantially flat undersurface wherein said closure comprises:

a molded plastic body having a center deck and an integral annular peripheral channel portion with radially spaced apart inner and outer annular walls defining an inverted annular U-shaped channel having an interior inner top and outer surfaces for lockingly receiving said top rim and a portion of said sidewall therein;

said outer wall having an annular ledge to lockingly abut the under surface of said outwardly protruding annular rim when the pail rim is inserted into said annular channel;

said interior inner surface having annular sealed ridges formed thereon to lie sealingly against an inner sidewall surface of said pail to form a first seal; and

a sealing wiper appendage integrally depending from the interior top wall of said inverted U-shaped channel and angled downwardly and inwardly toward said interior inner surface so as to deformingly contact the top surface of said outwardly protruding rim when said rim is inserted into said channel to form a second seal with said container.

2. A closure as defined in claim 1 wherein the entirety of the closure is molded from high density polyethylene (HDPE).

3. A closure as defined in claim 1 wherein the sealing wiper appendage has a root and a length and wherein the ratio of the length dimension to the root dimension is approximately 4.25:1.

4. A closure as defined in claim 3 wherein the length of the appendage is about 0.170″.

5. A closure as defined in claim 1 wherein the wiper appendage angles inwardly toward said inner wall by about 20°.