Double-wall plastic produce container having ventilation holes therein, and mold for the manufacture thereof

Abstract

In this ventilated double-wall plastic container, each hole structure has a central hole surrounded by a solid flange extending along the inside wall of the double-wall structure. The hole structure also has a spacer portion connecting the solid flange to the outside wall of the double-wall structure. The wall segments of the hole structure between the spacer portion and the flange and between the spacer portion and the outside wall of the container define angles that are either obtuse angles or right angles. In another aspect, the mold for manufacturing the double-wall container has spaced-apart inside and outside metal walls, a plurality of openings in the outside metal wall, and hole-forming inserts mounted in the openings and projecting toward the inside wall. A projecting surface on each of the hole-forming inserts defines with the inside wall a space of even thickness surrounding a pin at the centre of the insert.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of a double-wall container having ventilation holes therein is illustrated in the accompanying drawings, with three preferred hole structures therefor being illustrated in greater details. In these drawings the same numerals are used to identify the same elements.

FIG. 1 is an isometric view of a stackable, double-wall, plastic produce container according to a preferred embodiment of the present invention;

FIG. 2 is a perspective view of a hole structure of the prior art;

FIG. 3 is a cross-section view of the hole structure of the prior art as seen along line 3-3 in FIG. 2;

FIG. 4 is a perspective view of a first preferred hole structure;

FIG. 5 is a cross-section view of the hole structure illustrated in FIG. 4, as seen along line 5-5 in FIG. 4;

FIG. 6 is a cross-section view of a second preferred hole structure, and a cross-section view of a hole-forming insert that is used for forming this second preferred hole structure;

FIG. 7 is a cross-section view of a third preferred hole structure, and a cross-section view of a hole-forming insert that is used for forming this third preferred hole structure;

FIG. 8 is a perspective view of the hole-forming insert for forming the second preferred hole structure;

FIG. 9 is a perspective view of the hole-forming insert for forming the third preferred hole structure.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described in details herein one specific embodiment of a double-wall ventilated container, with three different preferred ventilation hole structures, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and is not intended to limit the invention to the embodiment and preferred hole structures illustrated and described.

For reference purposes, FIG. 1 illustrates a stackable, double-wall plastic produce container 34 with ventilation holes 36 according to one of the preferred hole structures described and illustrated herein.

Referring now to FIGS. 4 and 5, the first preferred hole structure 40 is illustrated therein. The first preferred hole structure 40 is distinguishable from the hole structure 20 of the prior art, as shown in FIGS. 2 and 3, for having a flat disc-like solid flange 42 surrounding the hole 44, and extending at a right angle from the hole 44.

The first preferred hole structure 40 has a large hole 46 in the outside wall 48 of the double-wall structure of the container, and a conical section 50 extending from the outside wall 48 to the flange 42. The hole 44 has a cylindrical shape and extends through the centre of the flange 42. In this preferred hole structure, the flange 42 is integrated with the inside wall 52 of the container and is flush with the inside wall.

Preferably, the diameter ‘A’ of the disc-like flange 42 is about three times the diameter ‘B’ of the hole 44. The flange thickness ‘C’ is preferably equal to or larger than about 0.75 times the wall thickness ‘T’ of one of the walls 48, 52 in the double-wall structure of the container 34.

Preferably, the flange 42 is flush with the inside wall 52 of the container, as mentioned above, but can also be positioned at an intermediate distance between both walls, with two conical sections 50 extending respectively to each wall 48, 52.

Referring now to FIGS. 6-9, the hole-forming inserts 56, 58 for forming two of the preferred hole structures will be explained. In the first hole-forming insert 56, as illustrated in FIGS. 6 and 8, the insert comprises a cup-like member 60 which is adapted to be mounted in an opening 62 through the outside wall 64 of a mold. The cup-like member 60 is preferably welded to the outside wall 64 of the mold, as illustrated, but can also be mounted to the mold with fasteners.

The cup-like member 60 has a threaded hole 66 through its centre. A threaded plug 68 is mounted into the threaded hole 66 and is adjustable relative to the cup-like member 60. A locknut 70 on the threaded plug 68 is used to retain the plug 68 at a desired position relative to the cup-like member 60.

The threaded plug 68 has a hollow core 72. A spring 74 is mounted in the hollow core, and a metal pin 76 is slidably mounted in the hollow core below the spring. In a blueberry container, the metal pin 76 could have a diameter of ¼ inch for example. A head 78 on the pin 76 holds the spring captive against the bottom end of the hollow core 72. In use, the spring 74 pushes the pin 76 against the inside wall 80 of the mold, as illustrated in FIGS. 6 and 7.

It should be understood that the side walls 64, 80 of the mold are made of metal. The hole-forming inserts 56, 58 are also made of metal and are mounted to absorb heat from both side walls 64, 80.

The rate of the spring 74 is selected, and the initial compression of the spring may be adjusted by turning the threaded plug 68 and the locknut 70, to ensure that there is a good contact between the end of the metal pin 76 and the inside wall 80 of the mold when the mold in closed, such that there is good heat transfer coefficient between the inside wall 80 of the mold and the pin 76.

The hole-forming insert 56 is used for forming a ventilation hole that is enclosed by a spherical depression 82, as may be understood from the illustration in FIGS. 6 and 8. The second hole-forming insert 58 has a bar-like, trapezoidal body 90, as illustrated in FIGS. 7 and 9. This second hole-forming insert 58 can be used to form ventilation holes inside a reinforcing rib on a container, such as the rib 92 illustrated in FIG. 1.

It will also be appreciated that the hole-forming insert 56 can also be modified so that the cup-like member has a conical shape. The hole formed with it would have a same cross-section as in the illustration in FIG. 7, and an appearance as illustrated in FIGS. 4 and 5. It will also be appreciated that the spherical cup-like member 60 can also be replaced by a cylindrical shaped member (not shown) to obtain substantially the same advantageous results as those mentioned herein.

For reference purposes the conical section 50 and the spherical section 82 are also referred to herein as the spacer means because these elements are used for retaining both walls of the double-wall construction at a proper distance from each other around a hole 44.

Referring again to FIG. 7, it will be appreciated that the angles of the plastic walls around the third preferred hole structure, at ‘D’, ‘E’, ‘F’ and ‘G’ are obtuse angles or right angles. The same obtuse and right angles can be found in the first and second preferred hole structures as illustrated in FIGS. 5 and 6. The relatively large angles along the preferred hole structures are believe to be a contributing factor for preventing the formation of porosity in the plastic material during the molding process. A good heat transfer between the inside wall 80 of the mold and the pin 76 is also another important contributing factor for preventing the formation of porosity in the preferred hole structures.

While three hole structures for preventing the formation of porosity in the plastic material of a double-wall container, have been illustrated in the accompanying drawings and described herein above, it will be appreciated by those skilled in the art that various modifications, alternate constructions and equivalents may be employed without departing from the spirit and scope of the invention. Therefore, the above description and the illustrations should not be construed as limiting the scope of the invention, which is defined by the appended claims.

Claims

1. A double-wall plastic container having a double-wall structure comprising a first and second spaced-apart walls, and ventilation holes therein; each of said ventilation holes having a hole structure comprising a central hole surrounded by a flange made of solid plastic, and spacer means connecting said flange to said first wall, wherein segments of said spacer means connected to said flange and to said first wall define angles of 90° or more.

2. The double-wall plastic container as claimed in claim 1, wherein said flange extends perpendicularly from said central hole.

3. The double-wall plastic container as claimed in claim 2, wherein said central hole has a diameter and said flat flange has a width of about three times said diameter.

4. The double-wall plastic container as claimed in claim 3, wherein said first and second walls have a similar wall thickness and said flange has a flange thickness of at least 0.75 times said wall thickness.

5. The double-wall plastic container as claimed in claim 4, wherein said flange extends along and flush with said second wall.

6. The double-wall plastic container as claimed in claim 1, wherein said spacer means has a conical shape.

7. The double-wall plastic container as claimed in claim 1, wherein said spacer means has a spherical shape.

8. The double-wall plastic container as claimed in claim 1, further having ribs therein, and one of said ventilation holes is located in one of said ribs, and said spacer means define sides of said rib.

9. A double-wall plastic container having a double-wall structure comprising a first and second spaced-apart walls, and ventilation holes therein; each of said ventilation holes having a hole structure comprising a central hole surrounded by a flange made of solid plastic and extending along and flush with said first wall at a right angle from an axis of said central hole, said flange having a width of about three times a diameter of said central hole; andspacer means connecting said flange to said second wall, wherein segments of said spacer means connected to said flange and to said second wall define obtuse angles.

10. The double-wall plastic container as claimed in claim 9, wherein said first and second walls have a similar wall thickness and said flange has a flange thickness of at least 0.75 times said wall thickness.

11. The double-wall plastic container as claimed in claim 9, wherein said flange has a disc-like shape.

12. A mold for molding a ventilated, double-wall container by a rotational molding process; said mold comprising spaced-apart inside and outside walls;an opening is said outside wall;a hole-forming insert mounted in said opening;said hole-forming insert having a pin extending therefrom and against said inside wall, and a projecting surface extending toward said inside wall and defining with said inside wall a space of even thickness surrounding said pin.

13. The mold as claimed in claim 12, wherein said space of even thickness extends perpendicularly from said pin.

14. The mold as claimed in claim 12, wherein said hole-forming insert comprises a compression spring mounted therein against an end of said pin for pushing said pin against said inside wall.

15. The mold as claimed in claim 13, wherein said projecting surface has a spherical shape, a conical shape or a cylindrical shape.

16. The mold as claimed in claim 14, wherein said hole-forming insert comprises a threaded hollow plug adjustably mounted therein and said pin and said spring are mounted inside said threaded hollow plug.

17. The mold as claimed in claim 12, wherein said projecting surface makes obtuse angles with said outside wall and with said space of even thickness.

18. The mold as claimed in claim 12, wherein said hole-forming insert comprises a bar-like trapezoidal body defining said projecting surface.

19. The mold as claimed in claim 13, wherein said space of even thickness has a width of about three times a diameter of said pin.

20. The mold as claimed in claim 13, wherein said space of even thickness has a disc-like shape.