US3128005A

US3128005A - Thin-walled containers and thin-walled closures for containers

Info

Publication number: US3128005A
Application number: US129318A
Authority: US
Inventors: Sherlock John Gerrard
Original assignee: Continental Can Co Inc
Current assignee: Continental Can Co Inc
Priority date: 1960-08-05
Filing date: 1961-08-04
Publication date: 1964-04-07
Anticipated expiration: 1981-04-07

Description

April 7, 1964 J. G. SHERLOCK 3,128,005

THIN-WALLED CONTAINERS AND THIN-WALLED CLOSURES FOR CONTAINERS Filed Aug. 4, 1961 2 Sheets-Sheet 1 JOHN G. SHERLOCK ATTORNEY April 7, 1964 J. G. SHERLOCK 3,123,005

THIN-WALLED CONTAINERS AND THIN-WALLED CLOSURES FOR CONTAINERS Filed Aug. 4, 1961 2 Sheets-Sheet 2 INVENTOR JOHN G. SHERLOCK United States Patent 3,128,005 THIN-WALLED CONTAINERS AND THW-WALLEB CLGSURES FOR CONTAINERS John Gerrard Sherlock, Feltham, England, assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Aug. 4, 1961, Ser. No. 129,318 Claims priority, appiication Great Britain Aug. 5, 1960 5 Ciairns. ((Zl. 229-39) This invention relates to thin-walled containers and thin-walled closures for containers, referred to generically as container means, made of resilient sheet material such as polystyrene by moulding, and has for its object to provide a container and/ or a closure for a container having a tubular part thereof formed with a screwthread for screwthreaded engagement with a cooperating part so that a container can be closed by a closure having screwthreaded engagement therewith, in which the appropriate tubular part of the container and/or closure can have the screwthread formed thereon in the moulding process, e.g. by expansion into a mould under the action of pressure and/ or vacuum while in a soft condition, while yet enabling the container or closure after moulding to be removed from the mould without the necessity for rotating it relatively to the mould to unscrew the screwthreaded part thereof from the part of the mould in which the screwthreaded part is formed.

Thus, an object of the invention is to enable containers and/ or closures for containers of the screwthreaded type to be formed by moulding, for example in batches from a piece of sheet material by expansion into moulds under air pressure, with or without initial expansion by mechanical means, followed by bodily removal of the articles thus formed from the moulds either still attached to the remainder of the sheet material or not, in the same general way as if the articles were of a form not provided with a screwthread.

In a thin-walled container or a thin-walled closure for a container made of resilient sheet material according to the present invention, the container or the closure includes a thin-walled tubular part having a screwthread of the reverse buttress type formed thereon by deformation of the material without substantial change in its thickness, the tubular part on which the screwthread is formed being of mean tapered form with the narrow flank of the reverse buttress thread facing towards the smaller end of the tubular part While the angle of the mean taper is such in relation to the axial length of the wider flank of the reverse buttress thread, the angle which this wider flank makes with the axis of the tubular part, and the mean taper of such tubular part, that, in cross-sections containing the axis of the tubular part, whereas the wider flank of the thread is inclined at a small angle to the said axis in one sense, the line representing the mean taper of the tubular part is inclined at a slightly larger angle to the said axis in the opposite sense and so that, as regards any two adjacent convolutions of the thread the crown of the convolution lying nearer the smaller end of the tubular part lies nearer to said axis than the root of the convolution lying nearer the larger end of the tubular part.

By the expression a screwthread of the reverse buttress type is to be understood a screwthread of which one flank has a relatively long axial length and lies at a small angle to the axis of the thread while the other flank has a negligible or relatively short axial length and lies at a relatively large angle to the axis of the thread, the relatively long flank being that which in use takes the axial thrust of the cooperating screwthreaded part, as opposed to a buttress thread in which the short flank takes such axial thrust.

By a thread formed by deformation of the material without substantial change in its thickness is to be understood a thread formed as a helical corrugation in the material so that the thread form appears on both the outside and the inside of the tubular part, although the thread under consideration will in each instance be only that appearing either on the outside or the inside of the tubular part, depending on whether this part constitutes or is arranged to constitute respectively a male or female threaded part. Thus, references to the screwthread herein are to be understood as referring to the thread form which is on that surface of the tubular part which in use cooperates with a cooperating thread form to form a screw connection between a container and a closure.

The construction is such that the screwthread can be formed by moulding and, following such moulding, the article and the mould can be separated by axial displacement without relative rotation, due to the fact that the resilience of the material coupled with the small angle which the wider flank makes with the axis of the tubular part allows each convolution of the thread to be withdrawn axially from the cooperating convolution on the mould while moreover after such withdrawal each convolution, having been separated from the convolution on the mould with which it originally made contact, can be moved clear of the die with little or no further contact with any of the other convolutions on the mould past which it then travels.

When the invention is applied to a container the screwthread might be formed within the bore of the open end of the container, in which case the container would preferably have an annular surface area adjacent to its end arranged to make sealing contact with a corresponding surface area on a flange or the like on an externally screwthreaded closure.

Preferably, however, in a container according to the invention the screwthreaded tubular part is in the form of a tubular collar or flange formed integral with the open end of the container and extending from such open end in the same direction as the body of the container so as to lie around and be spaced from the open end of the body portion of the container. In this case the screwthreaded part would be engaged by a corresponding screwthreaded part of an axially extending flange of a cap-like closure member and the cap-like closure would then preferably have a smooth externally tapered annular rib formed on its inner face and arranged to cooperate and make a sealing joint with a corresponding formation immediately within the open end of the container. Thus, the cooperating screwthreaded parts would serve to draw the rib into close sealing contact with the interior of the open end of the container.

In such a construction it would be understood that the screwthread on the flange of the closure member would conveniently also be formed in a similar manner to the screwthread on the container so that the closure member would itself also be in accordance with the invention.

Thus a preferred form of the invention would comprise a container and a cooperating closure member both according to the invention.

Containers and/or closure members according to the invention would conveniently be made of a thin resilient plastic material such as polystyrene or polyvinyl chloride and where :a container and a cooperating closure member, both according to the invention, are provided, different materials may be used for the two parts, for example, for the purpose of preventing or reducing binding of the lid on the container. In any event, the parts are conveniently formed by moulding in a manner generally known per se fromv a sheet of appropriate plastic material which, when in a soft deformable state, is disposed over one or more mould cavities or in contact with the end of a suitable die and then drawn or pressed into close contact with the surfiaces of such cavities or such die by the application of fluid pressure auid/ or vacuum, with or without an initial mechanical deformation of the material into the cavities or over the die before the application of such pressure or vacuum.

One example or a container and of a suitable cooperating closure, both according to the invention, is shown the accompanying drawings, in which FIGURE 1 is as to the lefthand half a cross-section on an enlarged scale containing the axis of the container, and as to the righthand half a side elevation on the sarne scale,

FIGURE 2 is a similar view to FIGURE 1 of the closure, the closure and container being shown as slightly separated from one another in readiness for application of the closure to the container, and

FIGURE 3 is a plan view of the closure member shown in FIGURE 2.

In the construction shown in the accompanying drawings, the container may be assumed to have a mean diameter of about 2 /2 inches and be made of polystyrene of a thickness of approximately .012". It comprises a body part 1 of somewhat tapered tubular tform closed at its lower end by an integral bottom wall 2 while its upper edge portion is turned over as shown to provide a tubular part 3 which is formed in the moulding process with a male screwthread of the reverse buttress type. The tubular turned-over edge portion 3 in which the screwthread is formed is of mean tapered form and the thread formed so that the narrow flank 4 of the thread faces towards the larger end of the aubular part 3. The angle of the mean taper is, as shown, approximately 8", while the engle which the wider flank 5 of the buttress thread makes with the axis of the tubular part 3 is 6. Moreover, the angles in question are such in relation to the axial length of the wider flank 5 of the reverse buttress thread that, as regards any two adjacent convolutions of the thread, eg. 6,

the crown of the convolution lying nearer the smaller end of the tubular part 3 lies nearer to the axis of the tubular part than does the root, e.g. 7, of the convolution lying nearer the larger end of the tubular part 3.

The axial length of the Wider flank in the example shown may be assumed to be that which will provide seven threads per inch while the radial depth of the narrow flank is approximately .002".

The construction shown is such that the screwthread can be formed by moulding, and so that following such moulding the container and the mould can be separated by axial displacement without relative rotation due to the fact that the resilience of the material, coupled with the small angle which the Wider flank 5 makes with the axis of the tubular part, allows the convolutions of the thread to be Withdrawn axially from the cooperating convolution on the mould, while moreover, aiter each convolution has by such withdrawal been separated from the convolution on the mould with which it originally made contact, it can be moved clear of the die with little or no further contact with any of the other convolutioos on the mould past which it then travels. The upper end of the con tainer is formed to provide a short firusto-conical internal surface 8 to provide substantially sealing contact with a corresponding surface on the closure as hereinatter described.

The closure comprises a disc-like part 9 anannular portion of which adjacent to its circumferential edge is formed with a downwardly projecting annular rib-like part 10 providing a conical surface to make sealing engagement with the surface 8 of the container referred to above. Depending from the extreme circumferential edge ct the disc-like part is a tubular flange 11 formed with a female sorewthread of the reverse buttress type similar in form to the screwthread on the container. Thus this tubular part is formed with a screwthread of mean tapered form, the angle of taper being 8 while the wider flank 12 of the reverse buttress screwthr'ead makes an angle with the axis of the screwthread of approximately 6. As shown, the larger diameter end of the Wider flank 12 adjacent to the smaller diameter end of the tubular part 11 as a whole.

The dimensions of the closure are such that when it is screwed on to the container, the tapered surface 8 and the part 10 come into closeengagcment approximately at the moment when during the screwing-down the screw-threads respectively :on the closure member and container grip one another over substantially their whole areas due to the 8 mean taper of the parts 3 and 11.

The container is provided with a circumferential rib 13 which when one container is nested in another similar container engages the surface 8 and thus prevents the containers jamming one the other, while the closure is provided with three downward projections 14 adjacent to its circumference similarly to prevent similar closure members jamming in one another when nested together, and with a ring of serrations as shown at 15.

In a typical example while the container is made of polystyrene the closure member might be made of a hard polyvinyl chloride.

What I claim as my invention and desire to secure by Letters Patent is:

1. A thin-walled container means made of resilient plastic sheet material, including a thin-walled tubular part having a screwthread of reverse buttress type formed thereon by deformation of the material without substantial change in its thickness, the tubular part on which the screwthread is formed being of mean tapered form and with the narrow flank of the reverse buttress thread facing towards the smaller end of the tubular part, while the angle of the mean taper is such in relation to the axial length of the wider flank of the reverse buttress thread, the angle which this wider flank makes with the axis of the tubular part and the mean taper of such tubular part that, in cross-sections containing the axis of the tubular part, whereas the wider flank of the thread is inclined at a small angle to the said axis in one sense, the line representing the mean taper on the tubular part is inclined at a slightly larger angle to the said axis in the opposite sense and so that, as regards any two adjacent convolutions of the thread, the crown of the convolution lying nearer the smaller end of the tubular part lies nearer to said axis than the root of the convolution lying nearer the larger end of the tubular part.

2. A container means as claimed in claim 1 in which the tubular screwthreaded part of the container means is in the form of a collar or flange which extends tirom the open end of the container means in the same direction as the body of the container means so as to lie around and be spaced from the open end of the body portion of the container means.

3. A container means as claimed in claim 2 including an approximately frusto-conical surface formed within the end part of the container means from which the screwthreaded tubular part extends, such surfiace being provided to form a seal with a cooperating surface on a second container means.

4. The combination of two container means as claimed in claim 1, in cooperation wherein the screwthreaded tubular parts of said container means are formed to engage one another.

5. A container means as defined in claim 3 compris ing a closure having an annular rib having a surface arranged to cooperate with the frusto-conicall surface on said container means (to form a substantially fluid-tight seal when the closure is fully screwed on to the container means.

References Cited in the file of this patent UNITED STATES PATENTS Pend'leton Sept. 28, 1897 Campbell Aug. 13, 1912 McLain Oct. 3, 1922 Nutter May 13, 1958 Aldington Jan. 26, 1960 Williamson Oct. 24, 1961

Claims

1. A THIN-WALLED CONTAINER MEANS MADE OF RESILIENT PLASTIC SHEET MATERIAL, INCLUDING A THIN-WALLED TUBULAR PART HAVING A SCREWTHREAD OF "REVERSE BUTTRESS" TYPE FORMED THEREON BY DEFORMATION OF THE MATERIAL WITHOUT SUBSTANTIAL CHANGE IN ITS THICKNESS, THE TUBULAR PART ON WHICH THE SCREWTHREAD IS FORMED BEING OF MEAN TAPERED FORM AND WITH THE NARROW FLANK OF THE REVERSE BUTTRESS THREAD FACING TOWARDS THE SMALLER END OF THE TUBULAR PART, WHILE THE ANGLE OF THE MEAN TAPER IS SUCH IN RELATION TO THE AXIAL LENGTH OF THE WIDER FLANK OF THE REVERSE BUTTRESS THREAD, THE ANGLE WHICH THIS WIDER FLANK MAKES WITH THE AXIS OF THE TUBULAR PART AND THE MEAN TAPER OF SUCH TUBULAR PART THAT, IN CROSS-SECTIONS CONTAINING THE AXIS OF THE TUBULAR PART, WHEREAS THE WIDER FLANK OF THE THREAD IS INCLINED AT A SMALL ANGLE TO THE SAID AXIS IN ONE SENSE, THE LINE REPRESENTING THE MEAN TAPER ON THE TUBULAR PART IS INCLINED AT A SLIGHTLY LARGER ANGLE TO THE SAID AXIS IN THE OPPOSITE SENSE AND SO THAT, AS REGARDS ANY TWO ADJACENT CONVOLUTIONS OF THE THREAD, THE CROWN OF THE CONVOLUTION LYING NEARER THE SMALLER END OF THE TUBULAR PART LIES NEARER TO SAID AXIS THAN THE ROOT OF THE CONVOLUTION LYING NEARER THE LARGER END OF THE TUBULAR PART.