US 3452896 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
July 1, 1969 c, ELLIOT 3,452,896
CONTAINER Filed April 29. 1968 r Sheet 0r2 FIG] INVENTOR. NEIL C. ELLIOT ATTORNEY N. c. ELLIOT July 1, 1969 CONTAINER Sheet 2 of 2 Filed April 29, 1968 F/GIE F/GJZ Fla 1]? INVENTOR. 4 NEIL C. ELLIOT ATTORNEY- United States Patent U.S. 'Cl. 220-60 9 Claims ABSTRACT OF THE DISCLOSURE A plastic container lid which is stackable without wedging, is easily ejected from its forming mold, and is peripherally scalable to a container body. Sealing, which is in the corners for noncircular shapes, is accomplished by snapping relatively deep peripherally spaced sockets in the lid over a projection extending outwardly from the mouth of the container body.
This application relates to a container, and more particularly to a plastic lid for closing the opening of a complementary container body.
Thermoplastic containers are becoming increasingly useful in packaging and storage application of all types. These containers are usually closed with snap-on lids of the insert or of the over cap variety, which are made of relatively thin plastic to minimize material costs and to facilitate rapid production rates. The lids must seal tightly yet be easily removable by a consumer. However, it has been found that in high speed mass production operations, close tolerances cannot be consistently maintained on the mating peripheral sealing portions of the lid and container body which are adequate to provide a tight seal between the mating parts. Thus when the sealing portion of the body, for example, is oversize (or the lid is undersize) the lid will either not fit the body at all, or if it is forced onto the body by automated capping equipment in the filling line, will be too tight to be conveniently re moved by the consumer. On the other hand, if the sealing portion of the body is undersize (or the lid oversize) the lid fit is too loose and it may fall off during handling, or may inadequatelyprotect the packaged product. Frequently it is not possible for the consumer to know whether the lid is properly engaged on the body, or only partially engaged thereon.
In addition, lids and bodies of this nature must also be stackable without wedging together, since in high speed production operations they must be consistently individually fed successively from stacked formations. Ease of release of the container lid and body from their respective forming molds is also a design consideration, since projections extending opposite to the general outward flare of the sides of the parts inhibit axial ejection from the molds. With such configurations the molded part must be flexed laterally to permit the formed projection to proceed beyond the corresponding forming portion of the die. Sufficient lateral flexing to permit axial ejection from the mold without damaging the parts is especially difficult with relatively stiff thermoplastics. Design modifications to alleviate the initially mentioned production tolerance problem, therefore, cannot be made without considering the effect on the provisions made for stacking and releasing the lid and mating body parts from their forming molds.
'It has been found that this dilemma of difficulties has been effectively solved by the present invention. There is provided a stackable, snap-on, tight sealing, readily removable, plastic lid having peripherally spaced means for sealing to a complementary stackable container body. Both lid and body may be produced at high rates while consistently providing a seal between the parts.
Accordingly, it is an object of the present invention to provide an improved container lid which avoids the prior art difficulties discussed above.
It is an additional object of this invention'to provide a snap-on container lid which audibly permits knowledge of when the lid is in place on the container body.
It is another object of this invention to provide a container lid and body combination which permits relaxation of molding tolerances for the mating sealing portions of the parts, while still providing an effective container seal.
It is another object of this invention to provide an improved tight sealing, stackable container lid adapted for use in automated packaging operations, which can be manufactured at high production rates with a minimum of difficulty incurred in its ejection from the forming mold.
A further object of this invention is to provide a noncircular, snap-on container lid which accomplishes the above-described objects.
An additional object of this invention is to provide a snap-on container lid of relatively stiff thermoplastic material which fulfills the above-described objects.
These and other objects will in part be obvious and will in part appear hereinafter.
These and other objects are accomplished by providing a plastic container lid comprising a top wall and a skirt extending downwardly from the periphery of the top wall, the skirt having a plurality of peripherally spaced sockets which extend outwardly with respect to the periphery of the top wall, the sockets being adapted to confine a marginal portion situated adjacent the open end of a complementary container body, each socket having an upper wall portion, and a lower wall portion which extends substantially inwardly beyond the outer limit of the body margin, the skirt having a stacking abutment at its lower end beneath each socket which is adapted to support the lid in spaced relationship upon the upper wall portion of the socket of a similarly configured lid. The lids are preferably of noncircular configuration with the stacking abutments and sealing sockets located in each of the corners thereof. Strengthening furrows may be provided in the skirt above the sealing sockets to minimize lateral flexing of the lid in these areas.
In describing the overall invention, reference will be made to preferred embodiments illustrated in the accompanying drawings in which:
FIG. I is a top plan view of a lid embodying the invention;
FIG. 11 is a perpective view of the lid of FIG. I in closure sealing engagement on a container body;
FIG. III is an enlarged, partial, sectional view taken along the line 'IIIIII of FIG. II;
FIG. IV is a partial, sectional, elevational perspective view of a nested stack of the lids of FIG. I; and
FIG. V is a sectional elevational view taken along the line VV of FIG. IV.
With reference to the drawings, wherein identical numerals refer to identical parts, there is shown in FIGS. I and II a generally rectangular, thin wall, plastic stackable noncircular lid indicated as 10, for a container body generally indicated (FIG. II) as 12. As shown, container body 12 is of thin wall plastic, and is noncircular in horizontal cross section having a radially outwardly extending marginal projection 13 adjacent to and extending around an opening in the top portion thereof. Lid 10 comprises elongated, generally fiat top wall 14, having converging edges 16 defining corners 18 at the points of convergence of edges 16. Lid 10 further comprises a skirt 20 (FIG. III) extending downwardly from the periphery of top wall 14, having in each of its four corners 18, a radially outwardly opening vertically extending strengthening furrow 22 adjacent the periphery of top wall 14. A radially inwardly extending, generally U-shaped locking protrusion 24 is provided in skirt 20 spaced from and axially aligned below furrows 22 in each of corners 1-8 of lid 10. The innermost surface 26 of protrusion 24 is situated radially outwardly with respect to the innermost portion 28 of the outer surface of the furrow 22, as can be seen from FIGS. III and V. Between furrows 22 and protrusions 24 in each corner 18 of lid 11}, there is provided an intermediate, member 30 of L-shaped radial cross section having an upper leg 32, connected at the inner end thereof with the wall which defines furrow 22. Member 30, as shown, extends outwardly by means of upper leg 32 and downwardly along vertical leg 34, which in turn merges with the uppermost wall of locking protrusion 24. Intermediate member 30, and protrusion 24 in each of the four corners 18 of lid define socket 36 between protrusion 24 and furrows 22 for sealingly confining margin 13 of body 12 when the lid is in place on the body all as shown in the left side of FIG. III. Socket 36 extends outwardly with respect to the periphery of lid top wall 14.
The configuration of the remainder of peripherally extending skirt other than in the corners of lid 10 is depicted on the right of FIG. III. An intermediate member 38 is also provided having a shape similar to that in corners 18, in that horizontal portion 40 is connected at one end thereof to vertical wall 42 which. has a smooth outer surface, as opposed to the furrowed configuration of the corner skirt portion. Upright leg 44 of intermediate member 38 is jointed at its lower end to shallow C-shaped projection 46 which projects inwardly with respect to upright leg 44 to a lesser extent than does rounded protrusion 24 with respect to vertical leg 34 of intermediate member 30 in lid corners 18. Consequently cavity 48 along the sides of lid 10 is not nearly as confining by virtue of its lower configuration as are sockets 36 in the corners thereof. Lift tab 48 extending radially out from the end of lower leg 50 of U-shaped protrusion 24 may be provided to facilitate removal of the lid by the fingers of a consumer. This projection may be either continuous around the full periphery of the lid or situated only at spaced intervals there around.
To place lid 10 on body 12, the lid is initially rested atop peripheral projection 13 of the body in an aligned manner. Pressure is then exerted downwardly so that the rounded inner surface of protrusion 24 in each corner 18 of lid 10 is resiliently deflected outwardly or resilient body projection 13 deflected inwardly depending on which of the two is made of the stiffer material. The outer end 52 of projection 13 cammingly follows the rounded inner surface of substantially inwardly extending projection 24 as a result of downwardly exerted pressure, until it has moved beyond the longitudinally extending portion of projection 24, when it thereupon encounters no further resistance and expands against the upper wall of socket 36 with an audible snap. The body margin 13 is then confined within this socket on the upper side by the horizontal portion 32 of intermediate member 30, and on the lower side by the uppermost portion of U-shaped projection '24. This action occurs in each of the four corners of rectangular lid 10. When the lid is in place on the container body, a clearance 54 may exist between the inner surface of the lid skirt 30 and the outer end of the body peripheral margin or projection 13 as a result of relaxed tolerances on each of these parts, yet the lid is still held tightly in place in each of the deep corner sockets. As depicted in FIG. III, some locking may also occur around the remainder of the periphery to a lesser extent than in the corners, as a result of the position of shallow C-shaped projection 46 situated beneath and laterally inwardly of the outer end of projection 13.
To remove lid 10 from body 12, the bottom face of corner lift tab 48 of which there may be a plurality when the configuration is noncircular, i.e., one located in each corner, is gently pushed upwardly by the thumb or finger of a user in either of the four corners of the container,
while another finger laterally spaced inwardly presses down on the top surface of lid top wall 12. This results in a prying away of lid 10 from projection 13 of body 12 in the particular corner area chosen to be open, in a manner which is generally the reverse of the way in which the body projection was audibly snapped into the lid socket. After the lid has been pried away from the edge in the corner area it may then be easily grasped between the fingers and progressively peripherally peeled away from the remainder of the upper portion of body 12.
Stackability of lids 10 without resulting in a wedging action occurs as shown in FIGS. IV and V. Outer surface 56 of outwardly extending portion 32 of intermediate member 30 of the skirt 20 of a lower lid, in each of the four corners thereof, acts as a supporting surface for outer abutment surface portion 58 of the U-shaped protrusion of an upper lid so as to support the upper lid in stacked, spaced relationship with respect to the lower lid. The substantial inward extent of corner locks 24, with respect to the maximum lateral extent of the intermediate member provides considerable load bearing corner contact between surfaces 56 and 58 of adjacently stacked lids as shown in FIG. V. This results in a stable stack not susceptible to having the contacting parts of either of the lids forced beyond the other so as to provide undesirable wedging. Some stacking support may occur along the sides of the lids other than in the corners as depicted in FIG. IV, as a result of the contact between the lower side 60 of shallow C-shaped projection 46 of an upper lid and the outer surface of the horizontal portion of the intermediate member of a lower lid. Stackability (wedge resistance) is, however, primarily dependent on corner rather than side contact.
FIG. V also depicts the relationship between the projection 24 of an upper lid and furrow 22 of a lower lid with the latter functioning as a stacking aid when two lids are stacked together. Furrow 22 of the lower lid is in lateral alignment with projection 24 of the upper lid, so that projection 24 may if necessary at least partially fit within furrow 22 in the skirt of the lower lid. This provides corner clearance to permit the upper lid to stackingly fit over the lower lid should the dimensions of the two lids be such as to prevent this from otherwise occurring because of dimensional variations resulting from the relaxed tolerances between the adjoining parts. In other words, though projection 24 of the upper lid is not shown in FIG. V as fitting within furrow 22 of a lower lid, the space is available to achieve this should it be required for other adjacently stacked lids of slightly different dimensions. Furrow 22 because of its contour also provides strength in each corner to resist lateral lid deflection. This deflection, which is prone to occur because of the thin wall construction is problematical in that if it is excessive, wedging of the lids will occur. Furrow 22 also decreases the total amount of undercut which must be overcome in stripping thermoformed lids from their forming molds. Specifically, if the furrow were not present, the portion of the lid skirt where the furrow is now located would have to be forced laterally inwardly a sufficient amount to move it beyond the laterally inwardly extending mold projection defining deep U-shaped lid protrusion 24. This extra lateral movement which is more difficult to accomplish at the end of the skirt joined to the top wall than at the free lower end, would increase the forming cycle and therefore the manufacturing cost, since the lid would have to be left longer in the forming mold so as to cool and set it sufliciently to permit deflecting it laterally without permanently distorting it, which could occur if the plastic were in a softer, more pliable state. Furrows 22 appear only in the corners where stacking contact primarily occurs. The tendency toward lateral flexing of the sides other than in the corners during handling need not be of concern with the present design, and configurations to overcome it are unnecessary.
The above description and particularly the drawings are set forth for purposes of illustration only and are not to be taken in a limited sense.
The relatively deep, reversely angled, spaced corner locks of the lid of the present invention must extend laterally inwardly to a greater extent than that of the inwardly extending projections the remainder of the lid skirt since this is the area of the lid which is responsible for holding it onto the container body. The inward extent of these corner projections as well as the extent to which they are provided around the periphery must not be excessive, since difficulties could then be encountered in ejecting the lid from its forming mold. In general the maximum inward extent of the peripherally spaced lid skirt locking projections should extend to between about .015 to .030 inch inwardly beyond the maximum lateral dimension of the upper marginal projection of the container body. The inner surfaces of these relatively deep locking projections should be rounded to facilitate cammingly guiding the projections past the peripheral margin of the body or vice versa.
Since dependence for locking the lid onto the container body is based on peripherally spaced, reversely angled projections in the lid skirt, the peripheral configuration of the skirt between these projections may vary. In place of the shallow C-shaped configuration shown in the drawings, for example, a straight vertical portion could be used, or nothing at all, i.e., a discontinuity could be provided in this area of the lid. A peripherally continuous, shallow reversely angled projection is preferred, however, since this configuration can, to a degree, function in cooperation with the spaced locking projections to provide a stacking abutment and to assist in sealing the lid on the container body. Furthermore, it provides the same general outer appearance in the sides as that which is necessary in the corners, so as not to detract from the pleasing overall continuous aesthetic appearance of the lid.
The strengthening furrows peripherally located in the lid skirt at the points where locking and stacking primarily occur function to strengthen these areas against the tendency to flex laterally which may cause telescoping when a plurality of lids are stacked together, and which could result in a premature release of the lid from the container body. In addition these furrows provide insurance that the deep locking projections of one lid will clear the skirt of an adjoining lid when being stacked thereon without requiring tight molding tolerances to achieve this consistently. These furrows function also to minimize the extent of undercut which must be overcome during the mold ejection step of the fabricating process over that which would be encountered if they were not present. The furrows should extend inwardly from the remainder of the lid-periphery for between about .005 to .020 inch.
Positioning of the locking projections around the lid periphery may be according to any pattern desired. However, a particular problem occurs with noncircular shapes, Where due to the configuration the lid sides radially flex outwardly around the periphery, but at the same time are put under tension and even tend to flex slightly inwardly in the corner areas when pressure is exerted from above. Thisinherent characteristic of noncircular shapes is used to advantage in a preferred embodiment of the present invention, in that the locking projections, surfaces of which have a stacking function, are positioned in the area of the periphery where outward flexing is nonexistent or at a minimum, i.e., in the corner areas.
Though use of interrupted lid locking and stacking projections are uniquely applicable to noncircular type lids in the present invention, it should be understood that these may be used with circular lids, with ease of mold discharge being the primary consideration in such cases. Possible configurations include square, oval, oblong, triangular and the like.
The material from which the lid is formed may be any plastic capable of being molded from sheet material in accordance with the previously mentioned design parameters. Thermoplastics generally have the advantages of being tough, difficult to break under ordinary circumstances, and have sufficient strength to be fabricated relatively thinly from web stock for economy purposes, since the containers contemplated herein are of the throw away type which are generally meant to be nonreusable after consumption of the initial contents. The resulting lid, when formed in this manner is unitary in construction, has no seams, and is of the thin wall variety having a generally uniform thickness between about 2 to mils.
Usable thermoplastics are polymers based on styrene, polyolefins such as for example, polyethylene, or polypropylene, and polyvinyl chloride.
Particularly useful materials for forming these lids are relatively stiff thermoplastics having a flexural modulus in excess of about 100,000 p.s.i., and preferably between 250,000500,000 p.s.i., such as, for example, rubbermodified polystyrene or polystyrene which preferably has a rubber compound grafted or mechanically blended therein, e.g., acrylonitrile, butadiene, styrene copolymers. In addition, it has been found necessary to have at least one and preferably both of the mating portions of the container constructed of these materials in order to obtain the audible security snap feature which is heard when the lid is forced onto the container body. This feature of the invention clearly and decisively permits the user to know when the lid is sealed on the body. These materials are tough and resilient even when thin and kept at low temperatures, and are usually inert to most foods which may be packaged in the container. Unfortunately, however, these thermoplastics are relatively stiff and have very little tendency to shrink away from undercut portions of the forming mold on cooling, in comparison to the shrinkage obtained with softer materials. It has, therefore, been particularly difficult to mold reversely angled portions of these materials having a sufficient lateral extent tol resist wedging, yet which may be ejected from the mold without difliculty. The interrupted configuration of the present invention provides equivalent capabilities in this area for lids of thermoplastic materials having a flexural modulus in excess of about 100,000 p.s.i., with those of softer materials.
In general, the present lid finds particular utility in automated and semiautomated packaging lines for foods and other consumer items, and wherever storage space dictates that a plurality of lids must be stacked in telescoping relation. The assembled container comprising the lid and container body is tightly sealed, yet easily openable and resealable. The lids have improved structural stability, and may be easily dispensed with little or no difficulty from the bottom of a stack, while at the same time presenting fewer manufacturing difficulties in the molding operation, particularly with respect to with drawal of the lid from the mold. Consequently, high manufacturing rates may be maintained at very low costs. Dimensional tolerances'of the mating parts may be relaxed without a corresponding increase in reject rate or decrease in the sealing quality of the lid. These tolerances may range between about i040 inch whereas the tolerances for similarly positioned conventionally manufactured parts is about 1.020 inch.
It will be understood that many variations and modifications of the embodiments herein described will be obvious to those skilled in the art, and may be carried out without departing from the spirit and scope of the invention.
What is claimed is:
1. A plastic container lid comprising a top wall and a skirt extending downwardly from the periphery of the top wall, said skirt having a plurality of peripherally spaced sockets which extend radially outwardly with respect to the periphery of the top wall, said sockets being adapted to confine a radially outwardly extending marginal portion of a complementary container body, such portion being situated adjacent an open end of said body,
each socket having an upper wall portion and a lower wall portion, said lower wall portion being adapted to extend substantially inwardly beyond the outer limit of the body marginal portion, said skirt having a stacking abutment at its lower end beneath each of said sockets adapted to support said lid in stacked relationship upon the upper wall portion of the socket of a similarly configured lid.
2. The structure of claim 1 wherein the lid has a noncircular configuration, with the sockets located in the corners thereof.
3. A noncircular plastic container lid comprising:
(a) a top wall having converging edges defining corners;
(b) a skirt extending downwardly from the periphery of the top wall having in each corner:
(I) a radially outwardly opening vertically extending strengthening furrow adjacent the periphery of the top wall;
(II) an inwardly extending rounded protrusion below said reversely tapered furrow, the innermost surface of said protrusion being substantially radially inwardly of the maximum radial dimension of a peripheral marginal portion situated adjacent the opening of a complementary container body, said innermost surface of said protrusion being radially outward of the radially innermost portion of the outer surface of said vertically extending furrow;
(III) an intermediate member of L-shaped radial cross section connecting at the free edge of its long leg with the lower end of the wall of said furrow and extending outwardly and downwardly, the end of the downwardly extending portion connecting with the uppermost edge of said protrusion, said intermediate member defining a socket between the protrusion and the furrow into which may audibly snap said margin of the container body, the outer surface of said outwardly extending long leg portion of the intermediate member acting as a support on which rests the protrusion of an upper lid while said resting protrusion at least partially fits within the groove provided by the furrow in the skirt of a lower lid when two of such lids are stacked together, in order to maintain the top walls of said stacked lids spaced from each other.
4. The structure of claim 3 wherein the lid has a generally rectangular configuration.
5. A plastic container comprising:
(a) a thin wall, open top, plastic body of noncircular horizontal cross section having a projection extending radially outwardly around the opening in the top portion thereof;
(b) a thin wall plastic lid for the body having:
(A) a top wall having converging edges defining corners;
(B) a skirt extending downwardly from the periphery of the top wall having in each corner:
(I) a radially outwardly opening vertically extending strengthening furrow adjacent the periphery of the top wall;
(II) an inwardly extending U-shaped locking protrusion spaced from and axially aligned below said furrow, the innermost surface of said U-shaped protrusion being radially outward of the innermost portion of the outer surface of the furrow;
(III) an intermediate member connecting at one edge with the skirt at the lower end of said furrow and extending outwardly and downwardly, the end of said downwardly extending portion connecting with the uppermost leg of said U-shaped protrusion, said intermediate member defining a socket between the furrow and the U-shaped protrusion into which the projection at the top of the container body may be audibly snapped to sealingly confine said projection therein, the outer surface of said outwardly extending portion of the intermediate member acting as a support against which rests the lower leg of the U-shaped protrusion of an upper lid while said protrusion at least partially fits within the groove provided by the furrow in the skirt of a lower lid when two of such lids are stacked together, in order to maintain the top walls of said stacked lids spaced from each other.
6. The container of claim 5 wherein the peripheral portions of the skirt intermediate the U-shaped locking protrusions in the corners extend inwardly to a lesser extent than that of the locking protrusions.
7. The container of claim 5 wherein the plastic is a relatively stiff material having a fiexural modulus within the range of between about 250,000500,000 p.s.i.
8. The container of claim 7 wherein the plastic is an acrylonitrile, butadiene, styrene copolymer.
9. The container of claim 7 wherein the tolerances on' the lateral dimensions of the lid skirt and, the container body projection range between about 1.040 inch.
References Cited UNITED STATES PATENTS 3,077,284 2/ 1963 McLaughlin 220- 3,122,264 2/ 1964 Davis 220-60 X 3,178,051 4/1965 Edwards 220-60 3,237,803 3/ 1966 Edwards 220-6O X 3,351,227 11/1967 Collie 22060 FOREIGN PATENTS 1,141,584 12/ 1962 Germany.
JOSEPH R. LECLAIR, Primary Examiner.
J. R. GARRETT, Assistant Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,42%,896 Dated July 1, i269 Neil C. Elliot It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 7, line 21, Claim 3, delete the words "reversely tapered.
mUmLD NU SEALED FEB 171970 Amen:
Edward u Fletcher, 3:. -m. m.
oommissioner of Patents Attesting Officer