U.S. patent application number 11/452921 was filed with the patent office on 2007-12-20 for double-wall plastic produce container having ventilation holes therein, and mold for the manufacture thereof.
Invention is credited to Neri Jean.
Application Number | 20070289979 11/452921 |
Document ID | / |
Family ID | 38860551 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070289979 |
Kind Code |
A1 |
Jean; Neri |
December 20, 2007 |
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.
Inventors: |
Jean; Neri;
(Tracadie-Sheila, CA) |
Correspondence
Address: |
MARIO D. THERIAULT
812 HWY. 101 NASONWORTH
FREDERICTON
NB
E3C 2B5
US
|
Family ID: |
38860551 |
Appl. No.: |
11/452921 |
Filed: |
June 15, 2006 |
Current U.S.
Class: |
220/676 |
Current CPC
Class: |
B65D 19/04 20130101;
B65D 85/34 20130101; B65D 2519/00034 20130101; B29L 2031/7178
20130101; B29C 41/38 20130101; B29C 41/04 20130101; B65D 2519/00174
20130101; B65D 2519/00527 20130101; B65D 2519/00069 20130101; B65D
2519/008 20130101; B29C 33/0033 20130101 |
Class at
Publication: |
220/676 |
International
Class: |
B65D 6/00 20060101
B65D006/00 |
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.degree. 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; and
spacer 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.
Description
FIELD OF THE INVENTION
[0001] This invention pertains to double-wall produce containers
having ventilation holes therein, and more particularly it pertains
to double-wall plastic produce containers having porosity-free hole
structures therein. This invention also pertains to molds having
hole-forming inserts therein for manufacturing ventilated
double-wall plastic containers using a rotational molding
process.
BACKGROUND OF THE INVENTION
[0002] Fruits and vegetables are commonly harvested in plastic
containers that are stacked on a harvesting machine and transported
to a storage facility. These containers are generally made with a
double-wall structure for increased sturdiness, to better resist
stacking and handling stresses. These double-wall plastic
containers are generally manufactured using rotational molding
processes.
[0003] Fruits such as blueberries are harvested at the end of the
summer when ambient temperatures are relatively high. Therefore,
the containers that are used to harvest blueberries must have
ventilation holes therein to prevent deterioration of the fruits
due to heat and airless confinement. The surface of these
containers must be free of crevices and pin holes and must have an
overall surface texture that is well adapted to be disinfected with
steam or detergent and water for example.
[0004] The surface of these containers must also be sealed to
prevent moisture, dust, dirt or other impurities from migrating
into the plastic material, or from penetrating inside the hollow
space of the double-wall structure of the container.
[0005] It has always been a challenge in the rotational molding
industry to form ventilation holes in a double-wall plastic
container without causing porosity to occur around these holes.
[0006] Examples of prior art double-wall plastic articles having
holes therein are shown in the following documents:
U.S. Pat. No. 3,506,154 issued to Tracy W. Barnes on Apr. 14, 1970;
U.S. Pat. No. 6,155,580 issued to Ronny Symons on Dec. 5, 2000.
[0007] Both examples illustrate common hole structures in
double-wall plastic articles made by rotational molding processes.
For comparison purposes, the common hole structure 20 as found in
the prior art articles is illustrated in the accompanying drawings.
In FIGS. 2 and 3, the hole 22 in one wall 24 is larger than the
hole 26 in the other wall 28 of a double-wall article, and both
holes are joined by a conical section 30. This type of hole
structure makes it easy to remove a molded article from a mold, and
therefore, it has been widely used in the rotational molding
industry.
[0008] It has also been found that it is very difficult to
eliminate porosity from this type of hole structure, and especially
from the region identified by the detail circle 32 in FIG. 3. For
this reason, this type of hole structure has been found unsuitable
for application in a double-wall plastic container that is used for
carrying blueberries for example. As such it is believed that a
need still exists in the agricultural industry for double-wall
plastic produce containers having porosity-free ventilation holes
therein.
SUMMARY OF THE INVENTION
[0009] In the present invention, however, there is provided a
double-wall plastic container having porosity-free hole structures
therein. There is also provided a mold with hole-forming inserts
therein for molding a double-wall ventilated container in a
rotational molding process.
[0010] In one aspect of the container according to the present
invention, each hole structure comprises a central hole surrounded
by a flat solid plastic flange extending at right angle from the
central hole, and 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
of the container. 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. The thickness of the flange is at
least 0.75 times the thickness of one of the walls in the
double-wall structure. This hole structure is advantageous as it is
moldable without generating porosity around the central hole
thereof.
[0011] In another aspect of the present invention, the mold for
manufacturing the above-mentioned 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 metal wall.
[0012] The hole-forming inserts are made of metal and each has a
metal pin extending therefrom and against the inside wall. A
projecting surface on each of the hole-forming inserts extends from
the outside wall toward the inside wall and defines with the inside
wall a space of even thickness surrounding the pin. This projecting
surface on each of the inserts makes an obtuse angle with the space
of even thickness and a right angle with the pin.
[0013] When a container is formed therein, the hole-forming insert,
the pin and the space of even thickness define a region inside the
mold that is surrounded by hot metal and wherein plastic pellets or
plastic powder can easily penetrate and be evenly melted, for
preventing the occurrence of porosity in the molten plastic around
the hole.
[0014] In yet another aspect of the present invention, each
hole-forming insert has a spring mounted therein and this spring
acts against the metal pin for pushing the pin against the inside
wall of the mold. The force of the spring ensures a good contact
between the pin and the inside wall of the mold, and a better heat
transfer coefficient between the metal pin and the inside wall of
the mold.
[0015] This brief summary has been provided so that the nature of
the invention may be understood quickly. A more complete
understanding of the invention can be obtained by reference to the
following detailed description of the preferred embodiment thereof
in connection with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] 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.
[0017] FIG. 1 is an isometric view of a stackable, double-wall,
plastic produce container according to a preferred embodiment of
the present invention;
[0018] FIG. 2 is a perspective view of a hole structure of the
prior art;
[0019] FIG. 3 is a cross-section view of the hole structure of the
prior art as seen along line 3-3 in FIG. 2;
[0020] FIG. 4 is a perspective view of a first preferred hole
structure;
[0021] FIG. 5 is a cross-section view of the hole structure
illustrated in FIG. 4, as seen along line 5-5 in FIG. 4;
[0022] 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;
[0023] 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;
[0024] FIG. 8 is a perspective view of the hole-forming insert for
forming the second preferred hole structure;
[0025] FIG. 9 is a perspective view of the hole-forming insert for
forming the third preferred hole structure.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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 1/4 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
* * * * *