Note: Descriptions are shown in the official language in which they were submitted.
CA 02569369 2006-12-20
APPARATUS FOR SPRAYING LIQUIDS, AND DISPOSABLE CONTAINERS
AND LINERS SUITABLE FOR USE THEREWITH
The present invention relates to containers, more especially, disposable
containers
and to containers which can function as liners. The invention also relates to
apparatus for spraying liquids (for example, spray guns) and, more especially,
to the
liquid containers or reservoirs of such apparatus.
There are many uses, in many different fields, for disposable containers. For
example, many goods are packaged in disposable containers (e.g. bags) either
before or after purchase. When the disposable container is a plastic bag, it
will
often be re-used by the purchaser as a disposable liner for another
receptacle, for
example a refuse bin. In some cases, disposable liners are produced
specifically for
use in other, re-usable, receptacles: in those cases, the liner may be
intended to aid
disposal of the contents of the receptacle (as in the case of a liner in a
refuse bin); to
protect the receptacle or its contents; or to facilitate, or even eliminate,
the cleaning
of the receptacle.
The use of a liner in a receptacle in which a substance like glue, paint or
plaster is
mixed or contained for use can be particularly advantageous, in terms of
facilitating
the cleaning of the receptacle after use and of preventing substances in the
receptacle from being contaminated by the remains of other substances.
Receptacles in which paints are mixed or contained for use, for example, must
be
clean to ensure that the colour or quality of the paint is not altered by
traces of
other substances: that is particularly important, as explained above, when a
vehicle
is being re-painted and the paint is required to match an existing one. To
avoid
contamination problems when mixing paints, it is often the practice in vehicle
body
shops to use disposable waxed paper cups as mixing containers, particularly
when
only a small amount of paint is required. An alternative approach, proposed in
US-
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A-4 383 635, involves the provision of a disposable container which, for use,
is
located in a re-usable frame-like receptacle.
In the field of spray guns, it has been proposed for various reasons that a
disposable
liner should be used in the reservoir of the gun (see US-A-3 211 324, 3 255
972,
4 151 929, 4 951 875 and 5 143 294, and EP-A-0 678 334). Guns for spraying
liquids (e.g. paints, garden chemicals etc.) are generally well known and
typically
comprise a reservoir in which a liquid to be dispensed is contained, and a
spray
nozzle through which the liquid is dispensed, under pressure, under the
control of a
trigger mechanism. The liquid may be fed from the reservoir under gravity
and/or it
may be entrained in a stream of pressurized fluid, for example air or water,
which is
supplied to the gun from an external source.
When a user wishes to change the liquid in the reservoir of a spray gun, it is
usually
necessary to clean the gun very thoroughly to ensure that no traces of the old
liquid
remain in the gun to contaminate the new liquid. That applies particularly to
paint
spray guns because any traces of an old batch of paint remaining in a gun may
affect
the colour of a new batch of paint to the extent that the new batch of paint
becomes
useless. This can cause problems especially in vehicle body shops where the
paint
applied to a vehicle is often required to match existing paint work exactly.
Alternatively, if paint residues have been allowed to dry within the gun, they
may
flake and contaminate the new batch of paint. The cleaning of spray guns is,
however, a comparatively complex and time consuming operation. Moreover, in
the case of paint spray guns, the cleaning operation involves the use of
comparatively large amounts of solvents which, for environmental reasons,
should
be handled and disposed of with care. That, in turn, can add substantially to
the
cost of a painting operation. It has already been suggested (see, for example,
EP-A-0 678 334 mentioned above) that the use of a disposable liner in the
paint
reservoir (i.e. the paint pot) of a spray gun can simplify the cleaning of the
gun and
reduce the amount of solvent required.
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The present invention is concerned with the
provision of a container which is sufficiently inexpensive
to be disposable and which can preferably be collapsed when
it is to be disposed of but which, nevertheless, is
comparatively easy to handle and to fill when in use. The
invention is concerned, more especially, with the provision
of such a container which is suitable for use as a liner in
another receptacle. The present invention is also concerned
with enabling the cleaning of spray guns and like apparatus
to be simplified, and with thereby enabling the time and
expense associated with that operation to be reduced.
The present invention provides a container
comprising side walls and a comparatively-rigid base
thermo/vacuum-formed from a plastics material; wherein the
side walls are thin in comparison to the base and are
collapsible, but the container is capable of standing,
unsupported, on the base with the side walls extended and
upright.
More especially, the present invention provides a
container comprising a base, and side walls extending from
the base; wherein the base and side walls are thermo/vacuum
formed together from a plastics material in such a manner
that the base is comparatively rigid and the side walls are
thin in comparison to the base and are collapsible but the
container is capable of standing unsupported, on the base
with the side walls extended and upright.
A container in accordance with the invention may
be used as a liner for a receptacle, the liner having a
shape which corresponds to the interior of the receptacle.
As a modification, the invention also provides, in
combination with a receptacle, a disposable liner which fits
within and has a shape corresponding to the interior of the
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receptacle wherein the liner is thermo/vacuum formed from a
plastics material. The liner is preferably, but not
necessarily, collapsible.
In another aspect of the present invention, there
is provided a spray gun comprising: a fluid reservoir; a
removable, collapsible, liner having a base and at least one
side wall, wherein the liner has a shape corresponding to,
and is a close fit within, the interior of the reservoir,
and wherein the liner in its non-collapsed state is free of
pleats, corrugations, seams, joints or gussets, and also
free of a groove at the internal junction of the side wall
with the base; a removable lid secured by push-fit
connection to an opening in the reservoir, the lid
containing a fluid outlet; a removable collar located over
the lid, attaching the lid to the reservoir; and a spray gun
body including a spray nozzle for dispensing fluid from
within the liner, wherein the combination of reservoir and
liner has a fill opening which is inverted when connected to
the spray gun body in normal operation, with fluid passing
from within the liner to the spray gun body.
In yet another aspect, there is provided a
gravity-fed spray gun comprising: a fluid reservoir having
a closed bottom and sidewalls or a sidewall in the case of a
cylindrical container, the closed bottom and sidewall(s)
defining a fill opening for filling the reservoir with
fluid, a removable lid located in the fill opening of the
reservoir, the reservoir having a closable air vent in the
end of the reservoir remote from the lid; and a spray nozzle
for dispensing fluid drawn from within the reservoir through
an outlet in the lid; wherein the reservoir is removable
from the gun, and is capable of standing on its own to
enable fluid to be loaded into the reservoir through the
opening.
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The present invention also provides a spray gun
comprising a fluid reservoir; a removable, collapsible,
liner which has a shape corresponding to, and is a close fit
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within, the interior of the reservoir; wherein the liner is capable of
standing unsupported
by the reservoir; and a spray nozzle for dispensing fluid from within the
liner; wherein the
liner collapses when fluid is withdrawn from within the liner during operation
of the gun.
Also in accordance with the invention, there is provided a spray gun
comprising a
fluid reservoir having a removable lid located in an opening in the reservoir,
a
removable liner located within the reservoir and secured to the reservoir, by
the lid,
at the periphery of the opening; and a spray nozzle for dispensing fluid from
within
the liner; wherein the liner is removable from the reservoir together with the
lid.
The present invention also provides a gravity-fed spray gun comprising a fluid
reservoir having a removable lid located in an opening in the reservoir; and a
spray
nozzle for dispensing fluid drawn from within the reservoir through an outlet
in the
lid; wherein the reservoir is removable from the gun and is capable of
standing on
its own to enable fluid to be loaded into the reservoir through the opening.
The invention further provides a spray gun comprising a fluid reservoir, and a
spray
nozzle for. dispensing fluid from within the reservoir, the reservoir
comprising a self-
supporting container which is removable from the gun and is collapsible for
disposal.
In accordance with another aspect of the invention, there is provided a fluid
reservoir for attachment to a spray gun, the reservoir having a removable lid
which
is located in an opening in the reservoir and in which is formed a fluid
outlet for the
reservoir, the reservoir including a removable, collapsible, liner which has a
shape
corresponding to, and is a close fit within, the reservoir, wherein the liner
is secured
to the reservoir by the lid at the periphery of the opening and is removable
from the
reservoir together with the lid. The invention also provides a fluid reservoir
for
attachment to a spray gun, the reservoir having a removable lid which is
located in
an opening in the reservoir and in which is formed a fluid outlet for the
reservoir,
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the fluid outlet being shaped for attachment to the spray
gun; and a closable air vent in the end of the reservoir
remote from the lid.
In accordance with yet another aspect of the
invention, there is provided a liner for use in the
reservoir of a spray gun, the liner being formed from a
plastic material and being a close fit within the reservoir;
the liner having a comparatively rigid base, and side walls
which are thin in comparison to the base and are
collapsible.
The present invention also provides a spray gun
comprising a fluid reservoir, and a spray nozzle for
dispensing fluid from within the reservoir, the reservoir
having a removable lid and including a removable, generally
conical, mesh filter secured in the reservoir by the lid.
The present invention also provides a gravity-feed
spray gun comprising a fluid reservoir, and a spray nozzle
for dispersing fluid from within the reservoir, the
reservoir having a removable lid and a removable liner
secured in the reservoir by the lid.
In another aspect of the invention, there is
provided a gravity-fed spray gun comprising a fluid
reservoir having a removable lid located in an opening in
the reservoir; and a spray nozzle for dispensing fluid drawn
from within the reservoir through an outlet in the lid;
wherein the reservoir is removable from the gun, is capable
of standing on its own to enable fluid to be loaded into the
reservoir through the opening, and is collapsible for
disposal.
In a further aspect of the invention, there is
provided for use in a spray gun, a container for attachment
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to the spray gun to form, without the presence of any other
receptacle, a fluid reservoir for the gun; the container
being a sealed container and having fluid therein.
In a still further aspect of the invention, there
is provided a liner for use in the reservoir of a spray gun,
the liner being thermo/vacuum-formed from a thermoplastic
material and being a close fit within the reservoir; the
liner having a comparatively rigid base, side walls which
are thin in comparison to the base and are collapsible, and
a flat outwardly-extending rim portion which is shaped to
sit on the edge of an opening in the spray gun reservoir.
The term "thermo/vacuum-forming" as used herein
means a process by which a sheet'of material is heated to a
softened condition and formed into a required shape, defined
by a mould, while in that softened condition. It includes
the case in which the application of a differential air
pressure is used to assist in forming the material into the
required shape and, in particular, includes the case in
which a vacuum is produced on one side of the material to
assist in forming it into the required shape (also known
simply as "vacuum-forming").
The term "collapsible" as used herein with
reference to the side walls of a'container/liner in
accordance with the invention indicates that the side walls
can be distorted so that, by the application of moderate
pressure (e.g. hand pressure), the rim of the container can
be pushed towards the base of the container, without the
side walls being ruptured.
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The term "paint" is used herein to include all forms of paint-like coating
materials
that can be applied to a surface using a spray gun, whether or not they are
intended
to colour the surface. The term includes, for example, primers, base coats,
lacquers
and similar materials.
By way of example only, embodiments of the invention will be described with
reference to the accompanying drawings, in which:
Fig. 1 is a perspective view of a prior art spray gun, shown partly-
disassembled so
that it can be filled with paint;
Fig. 2 shows the components of an alternative form of paint reservoir for the
gun of
Fig. 1, in an exploded condition;
Fig. 3 shows the paint reservoir of Fig. 2 in an assembled condition, with an
adapter
for connecting the reservoir to a spray gun;
Fig. 4 shows a longitudinal cross-section through the paint reservoir and the
adapter
of Fig. 3;
Fig. 5 shows the paint reservoir of Fig. 4 being attached to a spray gun;
Fig. 6 shows the paint reservoir of Fig. 4 in use on a spray gun;
Fig. 7 shows components of the paint reservoir of Fig. 4 being removed after
use;
Fig. 8 is similar to Fig. 2 but shows a modified form of paint reservoir;
Fig. 9 shows a longitudinal cross-section through an alternative form of lid
for the
paint reservoirs of Figs. 2 to 4 and 8;
Fig. 10 is similar to Fig. 2 but shows another modified form of paint
reservoir;
Fig. 11 shows part of a longitudinal cross-section through the paint reservoir
of Fig.
10;
Fig. 12 shows a spray gun similar to that of Fig. 1 but with an alternative
form of
paint reservoir;
Fig. 13 shows the gun of Fig. 12 with a modified form of paint reservoir;
Fig. 14 illustrates a modification to the reservoir of the gun of Fig. 13.
Fig. 15 is a view, similar to Fig. 3, of an alternative form of paint
reservoir;
Figs. 16 and 17 show modified forms of a component of Fig. 15;
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Fig. 18 illustrates the use of a holder for the paint reservoir of Fig. 15;
Fig. 19 is a perspective view of a liner/container in accordance with the
invention;
Fig. 20 is a similar view but showing the liner/container in the process of
being
collapsed for disposal;
Fig. 21 (a) to (c) is a diagrammatic illustration of a method for producing a
liner for
the paint reservoirs of Figs. 2 to 4, and 10;
Fig. 22 illustrates a modification of the method of Fig. 21;
Fig. 23 shows a paint-mixing pitcher; and
Fig. 24 shows a liner in accordance with the invention, for use with the
pitcher of
Fig. 23.
Fig. 1 of the drawings illustrates a typical prior art paint spray gun 1 of
the gravity-
feed type. The gun I comprises a body 2, a handle 3 which extends downwards
from the rear end of the body, and a spray nozzle 4 at the front end of the
body.
The gun is manually-operated by a trigger 5 which is pivotally-mounted on the
sides
of the gun. The paint reservoir, or paint pot, 6 which contains paint (or
similar
material) to be discharged by the gun, is located on the top of the body 2 and
communicates with an internal passageway (not visible) for compressed air,
which
extends through the gun from a connector 7 at the lower end of the handle 3 to
the
nozzle 4. In use, the connector 7 is connected to a source of compressed air
(not
shown) so that, when the user pulls on the trigger 5, compressed air is
delivered
through the gun to the nozzle 4 and entrains and atomizes paint which is being
delivered under gravity from the pot 6. The paint is then discharged through
the
nozzle 4 with the compressed air, as a spray.
The paint which is contained in the pot 6 is often mixed by hand (for which a
separate receptacle, for example a jug, is required), and poured into the pot.
To
ensure that there are no unwanted particles in the paint, which would spoil
the finish
of the painted surface, the paint is usually poured into the pot 6 through a
filter.
Fig. 1 shows the cap 8 of the pot 6 removed for this purpose, and a conical
filter 9
about to be positioned on the open end of the pot. The filter 9 is shown as
being a
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known type of disposable conical filter, having solid sides and a filter mesh
portion
at the pointed end of the cone. When the pot 6 has been filled with paint, the
filter 9 is removed and discarded, and the cap 8 of the pot is replaced. If
the filter 9
is a reusable filter then, like the gun, it should be cleaned thoroughly
before it is
5 used with a different liquid (e.g. a paint of a different colour or a Iiquid
having a
different chemical composition).
Fig. 2 illustrates the components of an alternative form of paint pot 11 which
can be
used on the gun 1 of Fig. 1(or any similar gun) instead of the pot 6. The
alternative
10 form of paint pot 11 is shown assembled in Fig. 3 and (in cross-section) in
Fig. 4.
The paint pot 11 comprises an open container 12, comparable in size to a
conventional paint pot of a hand-held spray gun, having an air hole 12A in its
base
and provided with a disposable liner 13. The liner 13 corresponds in shape to
(and
is a close fit in) the interior of the container 12 and has a narrow rim 14 at
the open
end which sits on the top edge of the container. The container 12 also has a
disposable lid 15 which is a push-fit in the open end of the liner 13. The lid
15 has a
central aperture 16 (Fig. 4) from which extends a connector tube 17 provided,
at its
end, with outward extensions 18 forming one part of a bayonet connection. The
aperture 16 is covered by a filter mesh 19 which may be a push fit into the
aperture
or may be an integral part of the lid 15. The lid 15 is held firmly in place
on the
container 12 by an annular collar 20 which screws onto the container, on top
of the
lid.
The paint pot 11 is attached to the spray gun 1 through the use of an adapter
21
shown, separated from the paint pot, in Fig. 3 and (in cross-section) in Fig.
4. The
adapter 21 is a tubular component which, at one end 22, is formed internally
with
the other part of the bayonet connection for attachment to the connector tube
17 of
the paint pot 11. At the other end 23, the adapter is shaped to match the
standard
attachment of the spray gun paint pot (typically a screw thread).
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The liner 13 of the paint pot 11, as already mentioned, corresponds in shape
to the
interior of the container 12 and has a narrow rim 14 at the open end which
sits on
the top edge of the container. As described below, the liner is self-
supporting but is
also collapsible and, preferably, has a comparatively rigid base 13A and
comparatively thin side walls 13B so that, when it collapses, it is in the
longitudinal
direction by virtue of the side walls collapsing rather than the base. In
addition, the
liner 13 has no pleats, corrugations, seams, joints or gussets, and also no
groove at
the internal junction of the side walls 13B with the base 13A. A liner of that
type
will be described in greater detail later with reference to Figs. 19 and 20.
Also
described below is a thermo-forming process by which such a liner can be
produced.
The container 12 of the paint pot 11 is formed from a plastic material, for
example
polyethylene or polypropylene, and may be translucent (as shown in Fig. 2) or
opaque, and of any suitable size. For use with a paint spray gun, containers
having
a capacity of 250, 500 or 800 ml could typically be used, although other sizes
could
be used if required. The lid 15 is also formed from a plastic material, for
example,..
polyethylene or polypropylene, and may be formed by an injection moulding
process. The lid may be translucent or opaque and may be coloured. The collar
20
may be a moulded plastic component, or it may be a machined metal (for
example,
aluminium) component. The adapter 21 may be a machined metal component and
may, for example, be formed from aluminium and anodised.
To use the paint pot 11, the adapter 21 is attached (at the end 23) to the
spray gun
and is left in position. Then, with the paint pot 11 disassembled as shown in
Fig. 2,
the liner 13 is pushed inside the container 12. Paint is then put into the
container,
the lid 15 is pushed into place and the collar 20 is screwed down tightly to
hold the
lid in position. The top portion of the liner 13 is then trapped between the
lid 15
and the container 12, and the liner rim 14 is trapped between the top edge of
the
container and the collar 20, as shown in Fig. 4. Advantageously, the lid 15 is
formed with barbs (not visible) on its surface to engage and hold the top of
the
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liner. The spray gun 1 is then inverted from its normal operating position so
that
the end of the connector tube 17 can be attached to the adapter 21 as
illustrated in
Fig. 5, after which the gun can be returned to its normal position
(illustrated in Fig.
6) and is ready for use in the usual way. As paint is removed from within the
liner
13, the sides of the liner collapse as a result of the decreased pressure
within the
liner. The base of the liner, being more rigid, retains its shape so that the
liner tends
to collapse in the longitudinal rather than the transverse direction thereby
reducing
the possibility of pockets of paint being trapped in the liner.
The user can choose to evacuate the air from within the liner 13 before
operating
the spray gun 1 although that is not essential. It does, however, increase the
range
of angles at which the gun will function satisfactorily since there is no risk
of air
entering the gun from the paint pot 11. To evacuate the air from within the
liner 13,
the trigger 5 of the gun should be actuated while the gun is still in the
position
shown in Fig. 5.
After use, when the gun is to be cleaned, the gun can be re-inverted and the
trigger
5 can be actuated briefly to allow paint within the gun to drain back into the
liner in
the pot 11. The pot 11 is then removed from the gun by detaching the connector
tube 17 from the adapter 21 (which remains on the gun). The collar 20 is
removed
from the container 12, and the lid 15 is then pulled out, bringing with it the
collapsed liner 13, as shown in Fig. 7. The lid (including the filter 19) and
liner are
discarded, leaving the container 12 and collar 20 clean and ready for re-use
with a
fresh finer and lid. Or>ly the gun itself needs to be cleaned, resulting in a
substantial
reduction in the amount of solvent used. The risk of unused paint spilling
from the
pot 11 is also substantially reduced because the liner 13 is removed and
discarded
with the lid 15 in place. Moreover, because the liner is discarded in a
collapsed
condition, the amount of space required for collection of used liners is
minimized.
Because the liner 13, as described above, is an accurate fit inside the
container 12
and has a smooth internal surface, it is possible to mix paint in the
container 12 itself
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rather than in a separate receptacle. In that way, cleaning of a separate
mixing
receptacle can be eliminated to achieve a further reduction in the amount of
solvent
used. That possibility does not exist when using a gravity-feed gun with a
conventional paint pot, as shown at 6 in Fig. 1, because the latter is open at
both
ends. The possibility of the liner 13 being punctured or damaged by the mixing
implement is minimized, first because the liner fits inside the container 12
exactly
and, second, because the self-supporting nature of the liner (described below)
means that it is less likely to be dragged around inside the container during
the
mixing process. To facilitate the use of the container 12 as a mixing
receptacle, the
side walls of the container may be provided with markings 25 (Figs. 2 and 3)
enabling the volume of the contents of the container to be determined. The
general
shape of the container 12 and, in particular, the fact that it is flat-
bottomed and
stable when in the orientation shown in Fig. 2 makes it particularly suitable
for use
as a mixing receptacle, as does the fact that it is translucent as already
described. If,
however, the container 12 is opaque, it could be formed with slots in the side
wails,
through which the liner 13 could be viewed to enable the user of the spray gun
to
assess the amount of paint in the pot 11 at any time.
When paint is mixed in the container 12, the inclusion of the filter mesh 19
in the
container lid 15 prevents unwanted particles in the paint from entering the
spray
gun. The mesh 19 can be omitted, however, if the paint is textured, or if it
is mixed
in a separate receptacle and strained when it is transferred to the lined
container 12
or if the presence of contaminants in the paint is unimportant.
Although the collar 20 of the paint pot 11 is described above as being a
separate
item, it could be combined with the lid 15, in which case it would also be
disposable. As a further alternative, the lid 15 (with the connector tube 17
and the
mesh 19) could be formed as an integral part of the liner 13, to which it
could be
connected by a hinge joint 26 as illustrated in Fig. 8. In that case, there is
no need
for the lid to fit inside the mouth of the liner to ensure that the lid and
liner will be
removed together from the container after use: however, that would still be
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necessary if the lid were required to remain in place in the liner after use.
As yet
another alternative, the collar 20 could be replaced by a band secured around
the
top of the pot 11 to hold the lid 15 and liner 13 in place. The band could be
secured
to the pot 11 and could, for example, be formed from rubber or be part of a
metal
cfip arrangement of the type used to secure the tops ofjars and bottles.
If a more positive engagement is required between the lid 15 of Figs. 2 to 4
and the
liner 13, the lid could be a snap fit with the liner instead of a push-fit as
shown. The
liner could, for example, be formed with an internal circumferential rib
positioned to
engage in a corresponding groove on the adjacent surface of the lid.
As yet a further alternative, the push-in lid 15 could be replaced by a lid 27
having
the form shown in Fig. 9. The lid 27 is also a push-fit inside the liner but
is generally
conical in shape and at its upper end 28, corresponds in shape to the end of
the
connector tube 17 of Figs. 2 to 4 so that it will engage in the same adapter
21. The
lid 27 has an outwardly-extending rim 29 which will sit on top of the liner
rim 14,
and a shaped portion 29A which will engage the internal surface of the liner.
The
form of the shaped portion 29A allows the lid 27 to be pushed into the mouth
of the
liner and also provides a recess 29B into which the edge of the liner can the
contract so that the lid is securely located. The form of the shaped portion
illustrated in Fig. 9 is not essential, however, and alternatives could be
used
including, for example, barbs as described above with reference to the lid 15
of Fig.
4. The lid 27 is held in place on the container by a screw-on collar, similar
to the
collar 20, which will sit on top of the rim 29 of the lid. The lid 27 may
incorporate a
filter similar to the filter 19 of Figs. 2 to 5. Alternatively, in each case,
the filter may
be generally cylindrical in shape so that it can be inserted into the tubular
part of the
lid from the end adjacent the bayonet connection. In that case, the internal
shaping
of the tubular part of the lid should ensure that the filter remains in
position when
the spray gun is in use.
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The components of an alternative form of paint pot 30 are illustrated in Fig.
10.
The pot 30, like the pot 11 of Fig. 2, comprises a container 12 and a liner
13. In
this case, however, the filter 19 of the pot 11 is formed as a separate item
31 having
a diameter corresponding to that of the container 12 and including a
circumferential
sealing gasket 32. In addition, the lid 15 and collar 20 of the pot of Fig. 2
are
replaced by a generally-conical lid 33 which is a screw-fit onto the container
and
which, at its upper end has a tubular extension 34 of similar shape to the
connector
tube 17 of Fig. 3 so that it will engage in the same adapter 21. The pot 30 is
assembled by pushing the liner 13 inside the container 12 and then, after
paint has
been put into the container, placing the filter 31 on top of the container and
securing it in position by screwing down the lid 33. The rim 14 of the liner
13 and
the sealing gasket 32 of the filter 31 are then both trapped between the lid
33 and
the container 12, as illustrated in Fig. 11, thereby preventing the leakage of
paint
from the pot 30 at this location when the pot has been secured to a spray gun
and is
inverted for use.
The adapter 21 could be dispensed with by forming the ends of the tubular
parts 17,,
34 of lids of the containers 11, 30 with screw threads so that they can engage
directly in the standard paint pot attachment on the spray gun 1.
Fig. 12 illustrates an alternative spray gun in which the standard paint pot 6
of the
spray gun 1(see Fig. 1) is retained and is provided with a liner 35 which fits
inside
the pot and, preferably, extends into the connection with the body 2 of the
gun to
form a liquid-tight seal with the latter, for example through the use of a
flexible 0-
ring (not visible) between the gun and the liner. In this case, the liner 35
does not
collapse when paint is removed from within the pot and may be formed from a
more
rigid material to assist in positioning it within the pot 6. Once in position,
the liner
is held in place by the cap 8 which is screwed down onto an outwardly-
extending
rim 36 at the open end of the liner. The pot 6 of Fig. 12 is additionally
provided
30 with a filter 37 which is of generally conical shape and formed entirely of
mesh
material and which, in use, is positioned inside the liner 35. The filter 37,
like the
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liner 35, has an outwardly-extending rim 38 which lies on top of the liner rim
36 and
is likewise held in place by the cap 8 of the pot 6.
The pot 6 of Fig. 12, unlike the pot I 1 of Fig. 3 is intended to be filled
with paint
while attached to the spray gun 1. The liner 35 and filter 37 are placed in
position,
paint is poured into the pot, and the cap is fitted. During this operation,
there is no
risk of the filter being dislodged and, because the filter is formed entirely
of mesh
material, the user is always able to see the paint level while the paint is
being poured
into the pot. The gun 1 is then ready for use. All of the paint dispensed by
the gun
passes through the filter 37 and there is, accordingly, no need for the paint
to be
filtered when it is being poured into the pot 6. After use, the cap 8
unscrewed is to
allow the filter 3 7 and liner 3 5 to be removed. The liner 3 5 is discarded
and the
filter 37 is either also discarded or is cleaned, depending on whether or not
it is
disposable. The use of the liner 35 again reduces the amount of solvent
required to
clean the gun 1, with a further reduction being possible through the use of a
disposable filter 37.
The filter 37 can have any suitable shape and may, for example, have fluted
sides to
increase the effective surface area of the filter.
In a modified arrangement, illustrated in Fig. 13, the liner 35 and the filter
37 are
combined to form a single unit 39. In this case, the filter is discarded with
the liner.
In each of the arrangements shown in Figs. 12 and 13, the liner 35 and filter
37 can
be removed from the pot 6 with the lid 8. In that case, it is possible to
replace the
conventional lid 8 of the pot 6 by a disposable lid so that the lid 8, liner
35 and filter
37 can be discarded together.
The disposable unit 39 of Fig. 13 could be modified so that it would replace
the
paint pot 6 of the spray gun 1 instead of being fitted inside the paint pot.
In that
case, the unit 39 could be supplied as a sealed cartridge 50 already filled
with paint
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as illustrated in Fig. 14. Externally, the cartridge 50 is similar to the
paint pot 6 and
can be connected to the gun 1 in the same way. Because it is sealed, however,
the
outlet end 51 of the cartridge must be pierced and an air vent provided, for
example
at the other end 52 of the cartridge, to allow paint to flow into the gun. The
outlet
end 51 of the cartridge 50 could, for example, be pierced by the user before
the
cartridge (with the outlet end uppermost) is attached to the (inverted) gun.
A]ternatively, the gun I could be modified so that the outlet end 51 is
pierced
automatically when the cartridge 50 is attached to the gun. An air vent at the
other
end 52 of the cartridge 50 could then be formed after the cartridge has been
attached to the gun by piercing that end of the cartridge either manually or,
for
example, by attaching a separate cap 53 which is designed to pierce the
cartridge
when it is placed in position. Alternatively, an air vent, which simply needs
to be
opened when the gun is ready for use, could be pre-formed in the cartridge.
After use, the cartridge 50 is removed from the gun and discarded. Because the
cartridge 50 contains a filter, there is no need for the supplier to filter
the paint
before it is loaded into the cartridge. If, however,. the paint is pre-
filtered, then the
filter in the cartridge 50 can be omitted.
Fig. 15 illustrates an alternative form of paint pot 40 for a spray gun 1,
which is
entirely disposable. The paint pot 40 is generally similar to the pot 30 shown
in Fig.
10 except that the container 12 is replaced by a disposable container 41,
described
below, and the liner 13 is omitted.
The container 41 of Fig. 15 can be any conventional disposable container
suitable
for containing paint and for attachment to the paint pot lid 42. The container
41
may, for example, be formed from a thin plastic material, preferably
translucent (as
shown) so that the contents of the container are visible and preferably having
markings 43 on the side walls to enable the volume of the contents of the
container
to be determined. An air hole 44 is formed in the base of the container,
together
with some means for closing the air hole when desired. That means may take the
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form of a strip of adhesive tape (not shown) which is peeled back to open the
hole
44 and can be re-adhered to close the hole when required. Alternatively, a
flip-top
closure or some simple hand-operated valve mechanism may be provided. The
container 41 has an external screw-thread at its open end, for attachment of
the lid
42 which is generally similar to the lid 33 of Fig. 10 and is likewise shaped,
at its
upper end 42A, for attachment to a spray gun (if necessary by means of a
suitable
adapter). The lid 42 may be formed from the same material as the container 41
and,
as shown, may also be translucent. A flat filter mesh 45, which is also
disposable,
extends across the mouth of the container 41. The mesh 45 may be a separate
item,
held at its periphery between the lid 42 and the container 41, or it may be
formed
integrally with the lid.
To use the pot 40, the lid 42 and filter mesh 45 are removed from the
container 41
which is then filled with paint (care being taken that the air hole 44 in the
base of
the container is closed). It is unnecessary to strain the paint when it is put
into the
container 41 and, as described above, it is possible to mix the paint in the
container
thereby avoiding the need for a separate receptacle for that purpose. The lid
42 and
mesh 45 are then put back in position on the container 41, the lid 42 is
attached to
the (inverted) spray gun I which is then returned to its normal position, and
the air
hole 44 in the base of the container is opened. The spray gun I can now be
used in
the usual way. On completion of the spraying operation, the air hole 44 is
closed-
off again, the pot 40 is detached from the gun 1 and may then be discarded
leaving
only the gun to be cleaned. Before the pot 40 is detached, the spray gun 1 can
be
re-inverted and the trigger 5 of the gun operated to allow excess paint
remaining in
the gun to drain back into the pot. In either case, if sufficient paint
remains in the
pot 40, the pot could be re-sealed (instead of being discarded) and used
again.
Advantageously, the container 41 of the pot is formed so that it can be
collapsed
after use. In some cases, it may be possible for the lid 42 also to be
collapsible.
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As an alternative, the lid 42 could be a reusable component and would be
cleaned
with the gun. With an arrangement of that type, it is possible for the
disposable
container 41 to be supplied as a cartridge already filled with paint and
sealed by a
cover which would simply be removed before the container is attached to the
lid 42.
The filter mesh 45 could be either a disposable or a reusable component. As a
further alternative, the container 41 and lid 42 together could be supplied as
a
cartridge sealed by a removable cover, at the upper end 42A of the lid, which
would
be removed before the cartridge is attached to the gun. In that form, the
cartridge is
similar to the cartridge 50 of Fig. 14.
Through an appropriate selection of the dimensions of the lid 42 of the paint
pot 40,
it is possible for the one lid 42 to be used with containers 41 of different
sizes. The
user would then select, in each case, the container 41 that contains the most
suitable
amount of paint. It may also be desirable for a range of filters 45 having
different
mesh sizes to be provided so that the user can select the mesh size that is
best suited
to the type of paint that is being used. It is not essential for the filter
mesh 45 to
have the form and/or location shown in Fig. 15: it could, for example, have a
conical form as shown in Fig. 16 and/or it could be located in the outlet of
the lid
42, as shown in Fig. 17. Alternatively, the filter 45 can be omitted if the
paint is
filtered before it is put into the container 41, or if the presence of
contaminants in
the paint is unimportant.
The lid 42 need not have the exact shape shown in Fig. 15 and could, for
example,
be replaced by a push-in lid in combination with a screw-on collar as shown in
Fig.
2.
When the container 41 (with or without the lid 42) is supplied as a cartridge
containing paint (or other coating material) it may be desirable in some cases
for the
paint/coating material to be contained within a sealed collapsible liner
within the
cartridge. That may, for example, be desirable if it is necessary for the
paint/coating
material to be kept isolated, for example from the air or from light, until it
has been
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sprayed onto the surface to be coated. The air hole 44 in the container 41 can
then
remain open all the time, or may be omitted if the container 41 itself is not
airtight.
Depending on the shape of the container 41, it may be desirable to provide a
holder
in which the container can be located to ensure that it will not be knocked
over.
One suitable holder 50, shown in Fig. 18, comprises container portion 51 which
is
of similar shape to, but slightly larger than, the container 41 and is
provided with an
enlarged base 52. The container 41 is placed in the container portion 51 to
ensure
that it remains upright while it is being filled and/or attached to the spray
gun 1.
Although the above description refers to a paint spray gun, it should be
understood
that it applies also to other types of spray gun including, for example, guns
of the
type which are attached to water hoses (rather than air supply lines) for
spraying
substances such as garden chemicals. The description also applies to suction-
feed
guns, i.e. guns in which the liquid outlet from the reservoir is located at
the top of
the reservoir when the gun is in use and liquid is drawn from the reservoir
through a
supply tube by the action of the compressed air or other pressurized fluid
flowing
through the gun. In that case, when a liner is provided for the reservoir, the
construction of the liner and/or the supply tube should be such that the liner
can
collapse without blocking the supply tube. For example, a short supply tube
can be
used provided all air is exhausted from the liner before the gun is used.
Alternatively, a flexible supply tube could be used, which will collapse with
the
liner. As a further alternative, a modified liner which does not have a rigid
base
could be used, so that the liner collapses in a different manner from the
liner 13 of
Fig. 2. Since the reservoir of a suction-feed gun is not inverted during use,
as in a
gravity-feed gun, it is possible to omit the air hole in the reservoir,
provided the
connection between the reservoir and the gun permits air to enter the space
between the reservoir and the liner.
Returning now to the paint pot 11 of Fig. 2, the liner 13 will now be
described in
greater detail, together with a method by which it can be produced. The liner,
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shown in isolation in Figs. 19 and 20, is preferably transparent and is thermo-
formed from a single piece of plastics material, preferably polyethylene or
polypropylene. The shape of the liner is dictated by the internal shape of the
container 12. The comparatively rigid base 13A is circular and the liner 13,
like the
inside of the container 12, is generally cylindrical but tapers inwards
slightly from
the mouth towards the base 13A. The rim portion 14, like the base, is also
comparatively rigid but the side walls 13B are flexible and, as already
described, can
be made to collapse. Nevertheless, the liner 13 is capable of standing,
unsupported,
on the base 13A with the side walls 13B extended and upright as shown in Fig.
19.
When the liner 13 collapses, the comparatively rigid base 13A retains its form
but
moves towards the rim portion 14 of the liner as a consequence of the collapse
of
the side walls 13B, as illustrated in Fig. 20. The side walls 13B collapse in
a similar
fashion to a plastic bag without being ruptured (e.g. by splitting, tearing or
cracking).
In one form, the liner has a height of about 110 mm, a diameter at its base
13A of
about 78 mm and a diameter at its mouth (excluding the rim portion 14) of
about 86
mm. The base has a thickness of about 400 .m, the rim portion 14 has a
thickness ,
of about 900 m, and the side walls 13B have a thickness of about 150 m. In
another form, the liner has the same height and the same diameters at its base
and
mouth but the base has a thickness of about 300 m, the rim portion has a
thickness
of about 200 m, and the side walls 13B have a thickness in the range of from
50 to
250 m.
A method of producing a liner as shown in Fig. 19 will now be described with
reference to Fig. 21 (a)-(c).
A sheet 60 of low density polyethylene (LDPE), approximately 250 x 225 mm and
0.5 mm thick, was clamped at its periphery in the moulding frame 61 of a
vacuum-
forming machine. The LDPE material is commercially available from, for
example,
Plastech Extrusions Ltd. of Widnes, Cheshire, England and the vacuum-forming
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machine used was the model "FLB 725" from C.R.Clarke and Company Limited of
Ammanford, Carmarthenshire, Wales. It will be appreciated, however, that any
suitable plastics material could be used and that the method could be carried
out
using any suitable thermo/vacuum-forming machine.
After the sheet 60 had been placed in position, the bank of heaters 62 of the
vacuum-forming machine was moved into position above the sheet (as shown in
Fig. 21(a)), and the sheet was heated to a soft, pliable, state suitable for
vacuum-
forming. The fact that the sheet had reached the appropriate temperature could
be
seen by the change in its appearance from milky to transparent.
The bank of heaters 62 was then removed and the mould platen 63 was moved
upwards from below the sheet 60, bringing the mould 64 into contact with the
sheet
to deform the latter in an upwards direction. At this time, the vacuum pump of
the
machine was switched on to remove air from beneath the sheet 60. The upward
movement of the mould platen 63 was continued until the platen reached the top
of
its stroke, where it seals against the frame 61 holding the sheet 60 (Fig.
21(b)). The
mould 64 had a shape corresponding to the internal shape of the container 12
of the
spray gun paint pot 11.
Operation of the vacuum pump was continued with the mould platen sealed
against
the frame 61 and the pressure difference created between the upper and lower
sides
of the sheet 60 caused the latter (which was already in contact with the top
of the
mould 64) to move down into contact with the sides of the mould (Fig. 21(c)).
The
mould platen 63 was then moved away from the cooled sheet 60 leaving a moulded
portion 65 having the desired shape of the liner 13 and without any pleats,
corrugations, seams, joints or gussets, or any groove at the internal junction
of the
side walls 13B with the base 13A. Following removal from the frame 61, the
sheet
60 was trimmed around the mouth of the moulded portion 65 to form the rim 14
of
the liner 13. The width of the rim 14 is determined by the location at which
the
sheet 60 is trimmed at this stage, and can be adjusted as required.
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The above-described process was found to yield a moulded portion 65 (and hence
a
liner 13) in which that part of the plastics sheet 60 that had been in contact
with the
sides of the mould 64 during the forming process was substantially thinner
than the
part that had been in contact with the top of the mould. The process differs
from a
conventional vacuum-forming process which would aim to eliminate, as far as
possible, any differences in thickness in the moulded portion 65 and, to that
end,
would include the additional step of applying air pressure to the underneath
of the
heated sheet 60, after step (a) of Fig. 21, to cause the sheet to adopt a dome
shape
before the mould platen 63 seals against the frame 61: the thickness of the
sheet
would then be comparatively even when it moves into contact with the mould 64
in
step (c) of Fig. 21. Generally in the process illustrated in Fig. 21, for a
given size of
sheet 60, the size of the mould 64 has been found to affect the thickness of
the sides
of the resulting liner 13 more than the base. In other words, if the size of
the mould
64 is increased, the thickness of the base of the resulting liner 13 will be
about the
same but the sides of the liner will be much thinner. On the other hand, if
the size
of the mould is decreased, it may be found that a point is reached at which
longitudinal creases appear in the sides of the liner 13.
If a further reduction is required in the thickness of the sheet 60 where it
contacts
the sides of the mould 64 in step (c) of Fig. 21, the sheet 60 can be located
between
two thin metal plates 66 (Fig. 22) when it is clamped in the frarne 61 of the
forming
machine, each metal plate 66 having a hole 67 in the location of the mould 64
and
larger in size than the largest cross-section of the mould. The plates 66 are
also
clamped in the frame 61 and the process of Fig. 21 is then repeated. The
effect of
the plates 66 is that only the central portion of the sheet 60 is exposed
directly to
the heaters 62 and is drawn over the mould 64 when the latter has been moved
upwards (in this case, through the holes 67 in the plates 66). In that way,
less of the
sheet 60 is used in the formation of the moulded portion 65 and the resulting
liner
13 will have a slightly thinner base 13A and rim 14 and substantially thinner
side
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walls 13B. It is also possible to obtain a comparable result by using only the
upper
plate 66 shown in Fig. 22.
As a modification of the process illustrated in Fig. 22, the plastics sheet 60
can be in
the form of a circular disc of material which is clamped at its periphery
between the
two plates 66. Depending on the size of the disc, the clamped periphery may
then
form the rim 14 of the liner 13 and there may be no excess material to be
trimmed
away.
It has been found that a liner 13 produced by a process as described with
reference
to Figs. 21 and 22 will collapse as described with reference to Fig. 20 when
used in
the spray gun reservoir l 1 of Fig. 2. The liner 13 can also be collapsed by
hand by
pushing the base 13 A of the liner towards the rim 14. It has been found that
the
liner is typically capable of standing unsupported on its base 13 A and this
feature,
although not essential to the use of the liner in the spray gun reservoir 11,
may be of
use for storage purposes. The liner has no pleats, corrugations, seams, joints
or
gussets, and no groove at the internal junction of the side walls 13B with the
base
13A: consequently, there are no internal locations in which material within
the Iiner
can become trapped. The base 13A of the liner will, of course, occupy some
space
at the base of the container 12 of the spray gun reservoir 11 and the markings
on
the wall of the container 12 need to be positioned to take account of that
fact.
Although the liner 13 of Fig. 19 has been described for use specifically in
the paint
pot 11 of Fig. 2, the same or a similar article can be used in other ways
(subject, if
necessary to appropriate dimensional changes). For example, an article of the
type
illustrated in Fig. 19 can also be used as a liner in many forms of receptacle
other
than a spray gun reservoir. It is often desirable to provide a receptacle with
a
disposable liner, for example to keep the receptacle clean, to facilitate
cleaning, or
to protect the receptacle or its contents. A liner of the type illustrated in
Fig. 19 can
be used for any of those purposes and is especially useful in receptacles in
which
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substances are mixed together because there are no locations on the inside of
the
liner in which material can become trapped and remain unmixed.
An article of the type illustrated in Fig. 19 can, for example, be used as a
liner in a
receptacle intended for paint mixing in a vehicle body shop, in which case it
will
provide an attractive alternative to the disposable drinking cups which are
often
employed for that purpose. Prior to painting the repaired portion of a vehicle
in a
body shop, the repairer must mix-up a batch of paint of the required colour,
matching the colour of the surrounding portion of the vehicle. The various
components for a batch of paint should be measured accurately, either by
volume or
by weight, into a suitable receptacle in which they are mixed together
thoroughly
before being used. If the mixing is less than thorough, or if the receptacle
is not
absolutely clean, the colour/quality of the batch of paint (and, consequently,
the
quality of the repair) may be affected.
To enable paint mixing to be carried out conveniently, but effectively, a
liner of the
type illustrated in Fig. 19 can be used with a measuring vessel 70 as shown in
Fig.
23. The measuring vessel 70 is in the form of a pitcher having a spout 71 in a
shaped rim 72 and a handle 73. The pitcher is provided with markings 74 on the
side walls, enabling the volume of the contents of the pitcher to be
determined.
Using the method already described with reference to Fig. 21, liners of the
type
shown in Fig. 19 can be produced to fit accurately inside the pitcher 70 and,
by
utilizing such a liner, the various components for a batch of paint can be
assembled
and mixed together in the pitcher 70 without actually coming into contact with
the
latter.
A liner 75 suitable for use in the pitcher 70 is illustrated in Fig. 24. The
liner 75 has
a shape corresponding to the interior of the pitcher 70 and is generally
similar to the
liner 13 illustrated in Fig. 19 except that the thicker, outwardly-extending,
rim
portion 14 of the latter is omitted and the side walls 76 of the liner 75
include a
shaped rim 77 corresponding to the rim 72 and spout 71 of the pitcher. Because
the
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liner 75 fits the inside of the pitcher 70 exactly, the possibility that it
will be
punctured by the mixing implement when paint is being mixed in the pitcher is
minimized. In addition, because there are no locations in the interior of the
liner in
which material can become trapped, there is no barrier to the effective mixing
of all
the material that is measured into the pitcher. When the paint has been mixed
and
transferred from the pitcher 70 (for example, to the paint pot of a spray
gun), the
liner 75 is removed, preferably collapsed as shown in Fig. 20, and thrown
away,
leaving the pitcher 70 clean and ready for further use.
Because the base 78 of the liner 75 will occupy some space at the bottom of
the
pitcher 70, the markings 74 on the side walls of the pitcher may need to be
positioned to take account of that fact. It may also be desirable, depending
on the
shape of the pitcher 70, to provide an extension at the top of the liner 75
which can
be folded back over the rim 72 of the pitcher. Alternatively, or in addition,
it may be
desirable to seal the liner 75 to the pitcher 70 during use, for example by
providing
some form of shaping on the liner and the pitcher so that they can be snap-
fitted
together at the rims 77, 72.
Although it is desirable that the liner 75 of the pitcher 70 should be
collapsible so
that it occupies less space after use, that is not absolutely essential.
Moreover, since
the shape of the liner 75 is determined by the shape of the interior of the
receptacle
70 in which it is to be used, there may be cases in which the liner is not
capable of
standing, unsupported, outside the receptacle.
As a further alternative, an article of the type shown in Fig. 19 can be used
simply
as a container in which case it has the advantage that, although the walls 13B
are
comparable in flexibility to a plastic bag, the container will stand upright,
without
support, while it is being filled and also afterwards. The container can be of
any
appropriate size and can be used to contain many different types of items,
including
for example powders and liquids, or simply as an alternative to the
plastic/paper
bags provided to customers by retailers. In each case, the container has the
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advantage that there are no internal locations in which material within the
container
can become trapped. Depending on the contents of the container, it may be
desirable to be able to close the container mouth, in which case some
appropriate
form of closure can be provided. The closure may, for example take the form of
an
internal rib on the inside of the container around one half of the mouth, and
a
mating groove also on the inside of the container around the other half of the
mouth
into which the rib can be pressed to close the container. The flexibility of
the
container walls 13B additionally allows the walls to be pressed down around
the
contents, thereby reducing the air space within the container if required.
After use, when it is required to dispose of the container, the side walls 13B
can be
collapsed by hand by pushing the rim 14 towards the base so that the container
(now in the form illustrated in Fig. 20) requires less space for disposal. As
already
mentioned, the side walls 13B collapse in a similar fashion to a plastic bag
without
being ruptured (e.g. by splitting, tearing or cracking).
It will be appreciated that there are many other possible uses for articles of
the type
shown in Fig. 19. A liner of that type could, for example, be used simply as a
liner
for a refuse bin where it would offer the advantage of being a better fit
inside the
bin than a conventional bag-shaped liner, and of being easier to handle when
removed from the bin because it will stand upright on the base 13A. Similar
liners
could also be used in buckets or other containers for materials that harden
comparatively quickly (for example glue, wax or plaster): in some cases,
material
such as plaster is actually sold together with a mixing bucket, in which case
a supply
of liners could be included in the package. In some circumstances, it might be
appropriate to have a plurality of liners, stacked one inside another, in
position
inside a receptacle so that when one liner is removed the next is already in
position.
Moreover, since the receptacle is intended to contain a liner, it is not
essential for
the walls of the receptacle to be solid: the receptacle could, for example,
have the
form of a framework for containing the liner.
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Generally, in an article of the type shown in Fig. 19, the base 13A is
typically at
least 25 m thick, more typically at least 100 m thick. The side walls 13B
are thin
in comparison to the base 13A, to the extent that they can be collapsed as
described
to facilitate disposal of the liner/container: typically, the thickness of the
side walls
13B is less than half the thickness of the base 13A and may be less than one
fifth the
thickness of the base. Depending on the materials used, and the intended use
of the
liner/container, the side walls 13A will usually be less than 250 m thick.
For certain uses of an article of the type shown in Fig. 19, the rim portion
14 may
not be essential and can be omitted (as in the liner of Fig. 24). If no rim 14
is
required the sheet 60 of Fig. 21(c) would, of course, be trimmed immediately
adjacent the mouth of the moulded portion 65. It has been found that the self-
supporting nature of the liner/container can be retained even if the rim
portion 14 is
omitted.
It should also be noted that the base 13A of a container/Iiner of the type
shown in
Fig. 19 need not be circular but could have another shape, for example
rectangular
or triangular. In the case of a liner for a receptacle, that shape may be
dictated by
the shape of the receptacle particularly if the liner is required to fit the
interior of the
latter. In some cases, the base need not be rigid.
It will further be appreciated that the process illustrated in Figs. 21 and 22
is not
restricted to the production of liners for use in the paint pots of spray guns
and can
be adapted to produce liners/containers for other purposes. It will be
appreciated
that the process requires the mould 64 to have a slightly tapered shape with
the
largest cross-section being at the lower end (as seen in Figs. 21 and 22) to
allow the
sheet 60 to be removed when the forming operation is complete. When the
process
is used to produce of a liner which is required to fit inside a container,
that, in turn,
requires that the container should be similarly tapered internally. The
liner/container may be formed from any suitable thermoplastic material capable
of
fornvng a thin film which is impervious to the materials it is intended to
contain. In
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CA 02569369 2006-12-20
WO 98/32539 PCT/US98/00796
some cases, it may be desirable to use a material which is in the form of a
laminate.
For certain applications, such as food packaging, plastics with a low gas-
permeability may be preferred. For most applications, however, polyolefins
such as
polyethylene or polypropylene are preferred since these a relatively cheap,
are
readily thermo-formable, and are inert to most aqueous and organic fluids.
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