Note: Descriptions are shown in the official language in which they were submitted.
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STATIC CONTROLLED DISCHARGE SPOUT
TECHNICAL FIELD
This invention relates to a collapsible receptacle
which is useful in handling flowable materials in
semi-bulk quantities, and more particularly to a
collapsible plastic ~abric recep~acle having a
discharge spout with a metalized outer surface to
discharge static electricity.
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BACKGROUND
There has been increasing interest in the use of
flexible, collapsible containers for handling semi-bulk
quantities of particulate, granular and other ~lowable
materials such as chemicals, minerals, fertili~ers,
S foodstuffs, grains, and agricultural products. The
advantages of such receptacles include relatively low
weight, reduced cost, better versatility, and low
return freight costs in the case of reusable
receptacles.
Fabrics are often used in the construction of such
containers for strength, flexibility and durability.
Traditionally, fabrics have been constructed of natural
fibers; however, in recent years synthetic fibers
manufactured from polypropylene or other plastics have
come into extensive use because they are generally
stronger and more durable than fabrics made of natural
fiber.
The electrical characteristics of fabrics make
their use undesirable in some circumstances. For
~ example, many qranular and liquid materials develop a
static-electric charge through friction as they are
poured into, discharged from or vibrated within a
receptacle. Because ~.lbrics are not electrically
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conductive, discharge of static-electricity rom such
materials contained by ~a~ric receptacles is difficult,
if not impossible, poslng the danger of explosion or
fire caused by an electrical spark.
Previously, to reduce static electricity problems,
a layer of metalized fabric or a metallic laminate such
as an aluminum or other electrically conductive metal
foil has been secured to the fabric and the fabric was
used to construct a receptacle and a discharge spout
with the foil laminate or metalized layer comprising
the interior surface of the receptacle and the
discharge spout. The metal layers were then grounded
to eliminate static electricity.
Foil la~inates and metalized fabrics are, however,
susceptible to abrasion, tearing and separation ~rom
the underlying fabric, particularly along the edges of
the foil laminate due to contact with the contents of
the receptacle as the receptacle is filled, emptied or
transported. Such abrasion quickly reduces the
effectiveness of the foil layer as a grounding surface
and often results in unwanted contamination of the
contents of the bag with foil particles or flakes.
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SUMMARY OF THE INVENTION
The present invention comprises a collapsible receptacle
for handling materials in semi-bulk quantities having a
metallized fabric discharge spout which eliminates statlc
electric charge from the collapsible receptacle as flowable
materials are discharged. The receptacle may have any of
those designs known in the art such as those disclosed in U.~.
Patent No. 4~457,456. The receptacle is formed primarily of
rectangular panels of flexible but substantially inextensible
material such as woven polypropylene or woven polyethylene.
In accordance with one aspect of the invention there is
provided a collapsible product receptacle comprising: a
tu~ular side wall; a bottom wall secured to the side wall
around the lower end thereof for closing the lower end of the
receptacle to retain the product; a generally pliable
cylindrical discharge spout located in the bottom wall for
dispensing the product, the discharge spout comprisi.ng a
continuous inner layer for contact with the product to be
dispensed and a continuous outer layer having a continuous
inner non-metallized surface securely bonded substantially
throughout to the continuous inner layer and a continuous
outer surface metallized to a level that is electrically
conductive to the static electricity generated by contact of
the dispensed product with the inner layer, said inner layer
and said inner surface of said outer layer protecting said
conductive metallized surface of said spout from wear and tear
.
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induced by direct contact with the dispensed product; and
means for connecting the outer conductive surface of the
discharge spout to a source of predetermined electrical
potential to control the buildup of static electricity in the
receptacle.
In accordance with another aspect of the invention there
is provided a collapsible product receptacle comprising: a
tubular side wall; a bottom wall secured to the side wall
around the lower end thereof for closing the lower end of the
receptacle to retain the product; a pliable discharge spout
located in the bottom wall for dispensing the product, the
discharge spout comprising a continuous inner layer of plastic
fabric for contact with the product being dispensed and a
continuous outer layer of plastic material having a continuous
inner surface securely bonded substantially throughout to the
plastic fabric by lamination and a continuous outer surface
metallized to a level that is conductive to the static
electricity generated by contact of the dispensed product with
the plastic fabric; and means for connecting the electrically
conductive outer layer of the discharge spout to a source of
predetermined electrical potential to control the buildup of
static electricity in the receptacle.
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BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention can
be had by reference to the following Detailed
Description in conjunction with the accompanying
Drawings, wherein:
FIGURE 1 is an illustration of the lower portion of
a collapsible receptacle incorporating the discharge
spout o the present invention for static electric
charge elimination;
FIGURE 2 is an enlarged partial sectional view
showing part of the bottom wall and part of the
discharge spout of the receptacle of FIGURE l;
FIGURE 3 is a sectional view through the discharge
spout of the receptacle of FIGURE l; and
FIGURE 4 schematically illustrates a preferred
method of construction of fabric for the discharge
spout.
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DETAILED DESCPcIPT~ON
Referrinq now to the Drawings, wherein like
reference numerals designate like or corresponding
parts throughout the several views, and particularly
referring to F~GURE 1, there is shown the lower portion
of a collapsible receptacle 10 incorporating a static
controlled tubular discharge spout 12 according to the
present invention. The receptacle 10 has a side
wall 14 and a bottom wall 16 both formed from fabric
material, preferably woven polypropylene or woven
polyethylene. The side wall 14 compri~ses a ractangular
piece of fabric material rolled into a tubular
configuration with the overlapping edges secured to
each other by sewing, adhesives or a combination of
both techniques. The bottom wall 16 is secured to the
lower end of the side wall 14 to close the bottom of
the receptacle 10.
The bottom wall 16 comprises a fabric layer 18
which is secured to the side wall 14, such as by means
of sewing. Perpendicular slits are formed in the
fabric layer 18 to de~ine a plurality of flaps 22 which
in turn define a rectangular opening 26 in the fabric
layer 18. The tubular discharge spout 12 is provided
with a flange at its upper end which is secured to the
interior of the ~abric layer 18 along a line of
stitching 34.
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As illustrated in FIGURES 1, ~ and 3, the discharge
spout 12 has a woven fabric interior layer 38 and an
electrically conductive exterior layer 40. As is best
shown in FIGURE 3, the discharge spout lZ is formed
5 from a rectangular piece o~ ~abric rolled into a
cylinger with the edges joined by means of a seam 42.
A typical alligator-type connector 44 forms an
electrical connection with the conductive layer 40 and
is in turn connected by a lead 46 to a source of ground
potential. Those skilled in the art will appreciate
the fact that various other conventional techniques may
be used to ground the discharge spout 12 and conductive
layer 40.
In earlier collapsible receptacles with no grounded
conductive layer, static charges of up to 200,000 volts
developed. This static electricity created a
significant fire and safety hazard. In the the
receptacle shown in FlGURES 4~-50 of U.S. Patent No.
4,457,456, a grounded inner conductive layer is used to
eliminate the static electric charge. However, the
inner layer of the receptacle is subject to
deterioration through abrasive wear and tear.
The conductive l~yer 40 of the disch~rge spout 12
is grounded during ~he discharge o~ material
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therethrough. This prevents a buildup of static
electric charge within the material as it is discharged
from the collapsible receptacle 10 through the
discharge spout 12. ~y maintaining the conductive
layer 40 at ground potential, the static electric
charge buildup from material flowing out of the
receptacle lO is grounded and eliminated. In the
present invention, grounding the conductive layer 40
eliminates the static electricity problem without wear
and tear on the conductive layer 40 because the
conductive layer 40 is not in contact with the material
moving through the spout 30. It is presently not
understood exactly why grounding the exterior surface
of the discharge spout results in the elimination of
static.
The receptacle 10 is preferably manufactured as
described in U.S. Patent No. 4,457,456. Discharge
spout 12 is similar to the discharge spout assembly 582
illustrated and described in FIGURES 48-50 of U.S.
Patent No. 4,457,456.
~ollapsible receptacle 10 may be constructed of any
strong, flexible and substantially inextensible
material. Natural or synthetic woven material such as
jute, cotton, polyethylene, or polypropylene are
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examples of such materials. Woven polypropylene
material is advantageous because of its strength,
durability and puncture resistance.
The receptacle 10 is useful for handling semi-bulk
quantities of virtually any flowabl-e material,
including minerals, chemicals, fertilizers, foodstuffs,
agricultural products and the like. The receptacle 10
is simply constructed and is therefor-e less expensive
than collapsible receptacles incorporating other static
discharge methods.
FIGURE 4 schematically illustrates the construction
of the metalized fabric preferably used in constructing
the discharge spout 12 of the present invention. A
roll 50 comprises a length of plastic fabric 52, such
as woven polyethylene or polypropylene, having an upper
surface 54 and an opposing lower surface 56. Supported
above the roll 50 of plastic fabric is a roll 58
comprising a length of plastic film 60 having a
metalized upper surface 64 and a lower sur~ace 66. The
length of fabric 52 and the length of film 60 are
manufactured from the same type of plastic. The
film 60 is oriented in two substantially perpendicular
directions, thereby strengthening the film against
tearing or breaking.
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The upper surface 64 of the length of film 60 is
metallized continuously along its entire length by
conventional methods to a level which is electrically
conductive. For example, one such method includes
vaporization of an electrically conductive metal in a vacuum.
The surface 64 of the length of film 60 is exposed to the
metallic vapors within the vacuum while opposing electrical
charges are imposed on the metal vapor and the film 60. The
opposing charge causes the vapor to deposit or plate onto the
film, forming a strong bond therebetween.
Typically, a metallic layer no more than one or two atoms
thick is required to provide an electrically conductive
surface. In the embodiment shown, aluminum is deposited on
the length of film 60 due to its relatively low melting point
and low cost. However, other electrically conductive metals,
such as gold, silver, chromium, and the like may be used.
The film 60 is extrusion laminated to the fabric 52 by
drawing the fabric 52 and the film 60 from rolls 50 and 58,
respectively, through the nip between two compression rollers
68 and 70. Prior to passage of the film 60 and fabric 52
between the rollers 6 and 70, a thin layer of molten plastic
of the same type from
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which the fabric 52 and the film 60 are manufactured is
interposed between the lower, non-metalized surface of
the film 60 and the upper surface 54 of the fabric 52
by a nozzle 72. Molt~n plastic is provided to the
nozzle 72 from a supply 74 through a tube 76. As the
fabric 52 and the metalized film 64 are compressed
together between the rollers 68 and 70, the molten
plastic partially melts both the non-metalized surface
of the film 60 and the upper surface 54 of the
fabric 52, resulting in a homogeneous layer of molten
plastic which hardens when cooled to securely bond the
film 60 to the underlying fabric 52. The resulting
metalized fabric 78 exits from the compression
rollers 68 and 70 and is collected on a take-up roll 80.
The fabric 78 may be cut into lengths of material
to form discharge spout blanks. The discharge spout
blank is rolled into a cylinder and the ends joined by
the seam 42 to form a discharge spout 12 with an
electrically conductive layer 40. The fabric 78 may
also be used in the construction of a receptacle having
an electrically conductive surface by using the
techniques disclosed by U.S. Patent No. 4,457,456. The
metalized surface will also protect the fabric 78 from
the harmful effects o~ sunlight, ultraviolet radiation
~: 25 or other similar radiation.
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Although a preferred embodiment of the invention
has been illustrated in the accompanying Drawings and
described in the foregoing Detailed Description, it
will be understood that the invention is not limited to
the embodiment disclosed, but is capable of numerous
rearrangements, modifications and substitutions of
parts and elements without departing from the spirit of
the invention.
