U.S. patent application number 11/849161 was filed with the patent office on 2007-12-20 for method of blow-molding and blow-molded product.
This patent application is currently assigned to LINPAC ALLIBERT LIMITED. Invention is credited to Michael J. Melia.
Application Number | 20070292645 11/849161 |
Document ID | / |
Family ID | 29797741 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070292645 |
Kind Code |
A1 |
Melia; Michael J. |
December 20, 2007 |
METHOD OF BLOW-MOLDING AND BLOW-MOLDED PRODUCT
Abstract
A method of blow-molding comprising forming a parison (tube) of
a thermoplastics material, closing a mold around the parison,
injecting compressed gas into the parison through a blowing hole to
form a molded product that is shaped according to the shape of the
mold, then deforming a seal forming portion of the molded product
with a heated sealing tool to seal the blowing hole. The
seal-forming portion may comprise a tubular collar that surrounds
the blowing hole.
Inventors: |
Melia; Michael J.;
(Skelmersdale, GB) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
LINPAC ALLIBERT LIMITED
Birmingham
GB
B37 7YN
|
Family ID: |
29797741 |
Appl. No.: |
11/849161 |
Filed: |
August 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10968817 |
Oct 19, 2004 |
|
|
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11849161 |
Aug 31, 2007 |
|
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Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
B29C 49/04 20130101;
B29C 49/60 20130101; B29C 67/004 20130101; Y10T 428/1352 20150115;
B29C 2791/001 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 1/00 20060101
B65D001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2003 |
GB |
0327345.5 |
Claims
1. A blow-molded product comprising a hollow molded body portion
and a seal element that seals a blowing hole in the body portion,
wherein the body portion and the seal element are made of a
thermoplastics material and the seal element comprises a deformed
seal forming portion of the body portion.
2. The blow-molded product according to claim 1, wherein the
seal-forming portion is located within a recess provided in the
molded body portion.
3. The blow-molded product according to claim 1, wherein the
blow-molded product comprises a wall panel of a container.
4. The blow-molded product according to claim 1, wherein the
seal-forming portion is located adjacent the blowing hole.
5. The blow-molded product according to claim 1, wherein the seal
forming portion includes a tubular collar that surrounds the
blowing hole.
6. The blow-molded product according to claim 5, wherein the
tubular collar extends outward from the molded product.
Description
RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 10/968,817, filed Oct. 19, 2004, which claims priority to Great
Britain Patent Application No. 0327345.5, filed Nov. 25, 2003. The
contents of these applications are incorporated herein by reference
in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of blow molding
and to a blow-molded product.
[0004] 2. Description of the Related Art
[0005] Blow-molding processes are commonly used for manufacturing a
wide variety of hollow plastics products including, for example,
bottles and containers. Typically, a tube (or parison) is extruded
into a mold, which is then closed around the parison. A needle is
then inserted into the parison and compressed air is injected to
blow the parison into the shape of the mold. The needle is then
withdrawn, the mold is opened and the finished product is
removed.
[0006] Products made by the above process are left with a blowing
hole formed by the needle, which typically has a diameter of
approximately 5 mm. For certain products such as food containers,
this blowing hole may have to be sealed to prevent water and dirt
from entering and leaving the interior of the molding, as this
could contaminate foodstuffs within the container.
[0007] An example of a prior art blow-molded product made by the
process described above is shown in FIGS. 1 and 2 of the drawings.
The product 2 is a wall panel of a bulk container and the drawings
show a portion of the wall panel, partially broken away. The panel
includes two parallel rectangular side plates 4 that are
interconnected by a peripheral wall 6. A shallow recess 8 is
provided in one portion of the peripheral wall and a blowing hole
10 is located in that recess. To seal the blowing hole, a plug 12
is inserted and fixed in position. The recess allows the top of the
plug 12 to lie flush with the edge of the panel, as shown in FIG.
2.
[0008] Inserting a plug to seal the blowing hole in a blow-molded
product is a difficult and time-consuming process, which requires
an additional component and adds to the overall production costs.
There is also a risk that the blowing hole could be incompletely
sealed and/or that the plug could work loose during use. It is an
object of the present invention to provide a method of sealing the
blowing hole in a blow-molded product that mitigates at some of the
aforesaid disadvantages.
SUMMARY OF THE INVENTION
[0009] According to the present invention there is provided a
method of blow-molding, the method including forming a parison of a
thermoplastics material, closing a mold around the parison,
injecting compressed gas into the parison through a blowing hole to
form a molded product that is shaped according to the shape of the
mold, and deforming a seal forming portion of the molded product
with a heated sealing tool to seal the blowing hole.
[0010] The invention allows the blowing hole to be sealed quickly
and easily, without requiring an additional component. Production
costs are thereby reduced. There is also a reduced risk of an
incomplete seal and, because the seal is an integral part of the
molded product, it cannot work loose.
[0011] Advantageously, the mold is shaped to provide the molded
product with a seal-forming portion, which is preferably located
adjacent the blowing hole. The seal-forming portion may include a
tubular collar that surrounds the blowing hole and extends outwards
from the molded product. The tubular collar may for example be
molded between an orifice in the mold and a gas injection needle
that is inserted into the mold.
[0012] The mold is preferably shaped to form a locking element that
restricts movement between the tubular collar and the mold. The
locking element may include a flange element that is provided on
the tubular collar. This helps to prevent the tubular collar being
pushed into the molded product when the gas injection needle is
inserted.
[0013] Advantageously, the mold is shaped to provide the molded
product with a recess in the vicinity of the blowing hole and the
seal forming portion is deformed to form a seal element that is
located within the recess. This construction makes it possible to
avoid having a seal element that protrudes outwards beyond the
edges of the molded product.
[0014] According to a further aspect of the invention there is
provided a blow-molded product including a hollow molded body
portion and a seal element that seals a blowing hole in the body
portion, wherein the body portion and the seal element are made of
a thermoplastics material and the seal element comprises a deformed
seal forming portion of the body portion.
[0015] The blow-molded product can be sealed quickly and easily,
without requiring an additional component, with reduced production
costs. The risk of an incomplete seal or a loose plug is
significantly reduced.
[0016] Advantageously, the seal-forming portion is located within a
recess provided in the molded body portion.
[0017] The blow-molded product may for example comprise a wall
panel of a container, or any other suitable product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] An embodiment of the invention will now be described by way
of example, with reference to the accompanying drawings.
[0019] FIG. 1 is a broken away partial front elevation of a prior
art molded product, illustrating the insertion of the sealing
plug.
[0020] FIG. 2 is a broken away partial front elevation of the prior
art molded product, after insertion of the sealing plug.
[0021] FIG. 3 is a front elevation of one half of a blow-molding
tool according to an embodiment of the invention.
[0022] FIG. 4 is a side section showing an extruded parison located
between two halves of a molding tool according to the invention,
with the mold in an open position.
[0023] FIG. 5 is a side section showing the parison within the
closed molding tool.
[0024] FIG. 6 is a side section showing the molded product after
blowing (for clarity, the molding tool has been omitted).
[0025] FIG. 7 is a side section of the molded product after removal
from the mold, during a sealing operation.
[0026] FIG. 8 is side section of the finished molded product after
sealing.
[0027] FIG. 9 is a sectional front elevation of the finished molded
product after sealing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] The embodiment of the invention depicted in FIGS. 3 to 9 of
the drawings illustrates a method of molding a blow-molded product
14 such as a simple rectangular wall panel, which may for example
form part of a bulk container or crate. The wall panel, which is
shown in FIGS. 8 and 9, includes two parallel rectangular side
plates 16 that are interconnected by a peripheral wall 18. It will
be appreciated that many other products may also be made by
substantially similar processes and that the present application is
intended to cover such products and the processes for making
them.
[0029] The blow-molding tool 20 shown in FIGS. 3 and 4 includes two
symmetrically identical mold halves 22, each of which includes a
mating surface 24 that in use mates against a corresponding surface
on the other mold half and a substantially rectangular mold cavity
26 that comprises a side face 28 for molding a side plate 16 of the
blow-molded product and a surrounding peripheral face 30 for
forming the peripheral wall 18 of the product. The peripheral face
30 includes a portion 32 that protrudes inwards, to form a recess
34 in the peripheral wall of the molded product.
[0030] A channel 36 is provided in the mating surface 24 of each
mold half 22, at the location of the protruding portion. When the
mold halves 22 are brought together, these channels 36 form an
orifice 38 that extends through the mold tool 20 from the exterior
to the interior of the mold cavity 26. This allows an air injection
needle 40 to be inserted through the mold tool 20 into the mold
cavity, for blowing compressed air into the parison, to inflate the
molded product 14 within the mold.
[0031] The features of the blow-molding tool 20 as described above
are all conventional. Where the tool differs from prior art
blow-molding tools is in the shape of the orifice 38. In the prior
art, this orifice generally consists simply of a cylindrical bore
having a diameter slightly greater than that of the air injection
needle 40, so as to allow the needle to be inserted. In the
embodiment of the invention shown in the drawings, the orifice 38
includes an outer portion 38a comprising a cylindrical bore with a
diameter slightly greater than that of the needle 40 (for example
approximately 5 mm), an inner portion 38b of slightly larger
diameter (for example approximately 8 mm) and an intermediate
portion 38c of even larger diameter (for example approximately 10
mm). It will be appreciated that the dimensions quoted above are
only illustrative and are not intended to be limiting in
anyway.
[0032] The inner and intermediate portions 38b, 38c of the orifice
are therefore significantly larger than the needle 40, thus forming
an annular gap between the needle 40 and the sides of the orifice
38. During use, melted thermoplastics material is molded in this
gap to form a tubular collar, which is subsequently deformed to
seal the blowing hole.
[0033] The blow molding process will now be described in detail
with reference to FIGS. 4-7.
[0034] First, as shown in FIG. 4, a tube of heated thermoplastics
material is extruded through an extrusion nozzle 42 into a gap
between the two halves 22 of the mold, which at this stage is open.
The extruded material forms a parison 44 comprising a hollow tube
that is closed at its lower end.
[0035] The mold 20 is then closed as shown in FIG. 5. The upper
part of the parison 44 is nipped between the two halves of the mold
forming a plug of material within the orifice 38 in the upper part
of the mold. The air injection needle 40 is then inserted through
the orifice 38 into the parison 44 and compressed air is injected
to inflate the parison, so forming a molded product 14 matching the
internal shape of the mold, as shown in FIG. 6 (the mold tool has
been omitted in this drawing for the sake of clarity. Once the
thermoplastics material has set, the needle 40 is withdrawn,
leaving a blowing hole 45. The mold 20 is then opened and the
molded product 14 is removed.
[0036] As can be seen in FIGS. 6 and 7, the molded product 14
includes a tubular collar 46 that extends from the upper edge of
the molded product, this collar having been shaped within the gap
between the wall of the orifice 38 and the air injection needle 40.
The lower part of the collar 46 is substantially cylindrical,
having been formed by the inner portion 38b of the orifice, and at
its upper end the collar has an outwardly extending flange 48
formed by the intermediate portion 38c of the orifice. The collar
46 and the flange 48 provide a seal forming portion 49 of the
molded product, which may be deformed to seal the blowing hole
45.
[0037] After the blow-molded product has been removed from the mold
tool, it is subjected to a second processing step, in which a
heated sealing tool 50 is applied to the seal-forming portion 49.
The sealing tool 50 re-heats and melts the thermoplastics material
of the seal-forming portion 49 and squashes it downwards, thereby
sealing the blowing hole 45. The remelted material thus forms a
dome-like seal element 52 that is accommodated within the recess 34
in the edge of the molded product 14, the upper part of the seal
element 52 lying flush with or slightly below the edge of the
product, as shown in FIGS. 8 and 9.
[0038] The process described above thus provides a very simple
method for sealing the blowing hole 45. The seal element 52 is
formed as an integral part of the blow-molded product 14, thereby
obviating the need for a separate plug. Sealing the blowing hole 52
is a very simple process involving the application of a heated
sealing tool 50. This process can be carried out manually or it can
be automated, if desired.
[0039] The shape of the seal-forming portion 49 is important for
successful sealing of the product. We have found that the
seal-forming portion 49 preferably comprises a tubular collar 46
having a flange 48 at its outer end. The flange 48 supports the
collar 46 within the orifice 38 in the mold 20 and prevents it from
being deformed as the needle 40 is inserted. We have found that if
a flange 48 is not provided, the collar 46 tends to be forced
inwards as the needle 40 is inserted, which makes subsequent
sealing very difficult.
[0040] It will be appreciated that various modifications of the
process described herein may be made, the process described being
merely illustrative of one embodiment of the invention.
* * * * *