Note: Descriptions are shown in the official language in which they were submitted.
iO9Z561
The present invention relates to a plunger for use in
excluding air from a contalner. The plunger is of value in
excluding air when filling and sealing a co~ltainer and is of
particular value when the container is a dispensing tube or a
cartridge tube of the type used for dispensing paste-like
materials from a dispensing gun.
The invention will be described with particular
reference to such cartridge tubes but is not limited to use
with containers of that description.
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Cartridge tubes of the type under discussion generally
have a plastics plunger inserted into their open ends after
being filled with the required material. A silicone jelly is
then applied to the exposed end of the plunger and the tube
end is sealed by any convenient means. In use, the sealed
end is opened and the cartridge inserted into the gun which
applies axial force to the plunger so as to expel the
contents of the tube in a controlled manner through a
dispensing nozzle located usually at the opposite end of the
tube from the plunger.
; When initially inserting the plunger prior to sealing
the end of the tube it is essential that substantially all of
the air trapped within the tube is expelled in order to
prevent the contents from hardening prematurely inside the
tube. It has been customary in the past to provide one or
more removable breather tubes which extend past the plunger ;;
to permit the escape of air durir.g its insertion and which
are withdrawn prior to sealing the tube.
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This process is cumbersome and it i8 an object of the
present invention to provide a plunger which enables a cartridge
to be filled in a much simpler operation.
According to one aspect the inventioniconsists in a
plunger adapted for insertion into a hollow tubular shape, said
shape having an open end and comprising at least a portion of
the internal surface of a container,
said plunger having a leading face and a peripheral
skirt, said skirt being insertable into said shape for a pre- -
determined distance from said open end without forming a seal
between said plunger and said shape,
said plunger being aAapted to provide a substantially
air tight seal with said tubular shape after insertion therein
of said leading face by said predetermined distance,
said leading face having means deformable in a
trailing direction after said plunger has been inserted into
said shape by at least said predetermined distance whereby said
plunger is moveable into said shape by a distance greater than
said predetermined distance,
saicl deformable means including a deformable domed
membrane having a dome protruding in the insertion direction and
being deformable to protrude in the trailing direction whereby,
said plunger may be employed to exclude air from an
, otherwise filled container.
j According to another aspect the invention consists in
a method for sealing extrudable contents in a container when ~ -
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said container has an inner surface a portion of which comprises
a tubular shape extending inwardly from a mouth thereof
comprising the steps of:
filling said container with said contents to a first
level,
thereafter inserting into said container the leading
face of a plunger according to the aspect and adapted to provide
said seal therewith, said first level being at a lesser distance
from said mouth than said predetermined distance,
advancing said leading face into said container by a
distance greater than said predetermined distance, to a position,
and ` ;
thereafter preventing movement in a trailing direction
beyond said position whereby air may substantially be excluded
from said container and the contents sealed therein.
By way of example, two embodiments of the invention
are illustrated in the accompanying drawings in which:
FIGURE 1 is a dual sectional side elevation showing a
plunger at two separate stages of its insertion into a tube end;
FIGURE 2 is a dual section taken on line 2-2 of Fig. l;
FIGURE 3 is a view taken on line 3-3 of Fig. 2 but
with the tube wall removed;
FIGURES 4, 5 and 6 correspond to Figs. 1, 2 and 3
respectively, but illustrate a second embodiment of the invention.
Referring to Figs. 1, 2 and 3 of the drawings, a plunger
indicated generally at 10 in the left-hand portion of Fig. 1
is shown partly inserted into the open end of a tube 11 which
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092561
forms part of a container 12 adapted for dispensing from a
nozzle 13. Nozzle 13 may be closed by means not illustrated
such as a frangible diaphragm, a screw cap or the like.
Plunger 10 has a leading face 14, and a side edge 15
extending in a trailing direction from leading face 14.
Plunger 10 is generally cup shaped having leading
face 14 and side edge 15 as outer surfaces and is a hollow
body open at its trailing end. Side edge 15 is generally
cylindrical in shape or may be slightly conical having a
least diameter at leading face 14.
Side edge 15 is provided with at least one, and
preferably two or more grooves 16 extending in a trailing
direction from leading face 14 longitudinally of tube 11.
Grooves 16 stop short of the trailing edge 17 of plunger side
edge 15.
Plunger side edge 15 has a diameter which at least
between the trailing edge 17 of side edge 15 and groove 16 is
of substantially the same diameter as the inner surface of
tube 11 so as to provide a sealing fit therewith.
Thus when plunger 10 is inserted into tube 11 leading
face 14 may first be inserted for a distance while groove 16
provides a communicatio~ from inside container 12 to
outside. If the tube is substantiàlly filled with
contents 19, for example a paste' any air trapped between
contents 19 and the leading face 14 is expelled via groove 16
and if the leading face comes in contact with contents 19, a
small amount of contents l9 may be extruded into groove 16
and even to outside container 12.
, , After insertion of leading face 14 into tube 11 by a
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distance determined by the length of the grooves the position
shown in the left-hand side of Fig. 1 is reached.
Groove 16 is then closed by virtue of the sealing fit of
side edge 15 of plunger 10 with tube wall 1'. Further
extrusion of contents and ingress of air is thereby prevented.
Preferably leading face 14 has integral therewith a
membrane portion 18 which is deformable in a trailing
direction. Further insertion of plunger 10 is possible for
at least a distance the pressure of contents 19 against the
leading face 14 causing distortion of the membrane in a
trailing direction, that is to say outwardly from the
container as shown in the right-hand side of Fig. 1. This
distortion compensates in container volume for a further
advance of leading face 14 against contents 19.
The plunger may then be prevented from retreat by any of
- a number of methods which will be apparent to those skilled
in the art. For preference the marginal edge of the tube
; ~ opening is rolled inwardly over the trailing edge 17 of the
~i plunger as shown at 20 and caused to gr~p with it so as to
, 20 seal the end of the tube.
, If tube 11 is a cartridge tube adapted for insertion in
~r a dispensing gun, the grip provided between plunger 10 and
rolled container wall 11 may be such that axial pressure
provided by a cartridge gun against the plunger can release
the grip whereby the plunger may be moved forwardly towards
nozzle 13 to expel contents from the nozzle.
Figs. 4, 5 and 6 are identical with Figs. 1, 2 and 3
except that the central portion of the leading face 14 of the
plunger is In the form of a dome 28 which initlally protrudes
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from the leading face 14 in the leading direction as shown in
the left-hand portion of ~ig. 4. After insertion of leading
face 14 by the predetermined distance at which communication
between the container volume and the exterior is cut
off,further insertion creates pressure which causes dome
shape 28 to deform in the manner of an oil can diaphragm
resulting in a dome protruding in a trailing direction, that
is to say, to form a concave depression in the leading face
as shown in the right-hand side of Fig. 4.
The increase in volume resulting from this distortion
enables plunger 10 to be further advanced into tube 11.
It will be understood that a container for use with a
plunger as described need not be of tubular shape throughout
its length and need not be provided with a dispensing nozzle.
Plungers according to the invention need not be hollow
but may be of a solid tubular shape and other forms of
passage communicating with the leading face and a side edge
may be provided instead of or in addition to a side edge
groove 16. For example the passage provided by groove 16 may
instead be provided by an annular space bounded by a
stepped-in portion of the side edge of the plunger and by the
wall of a tube in which it is inserted.
A plunger according to the invention may conveniently be
made from aluminum or an aluminum alloy by an impact extrusion
process and preferably has a thin distortable membrane
portion formed integrally therewith.
However in other embodiments a distortable diaphragm may
be inserted in the tube ahead of the plunger and the plunger
may be provided with a depression in its leading face, or
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~ 09Z561
with an orifice, so that tl~e diaphragm is distortable in a
trailing direction in a manner similar to that described for
membranes integral with the plunger. In that event the
diaphragm may also have a dome initially protruding in the
leading direction and distortable to a dome protruding in the
trailing direction.
While in its simplest form the plunger side edge
diameter is adapted to provide a sealing fit with the tubular
inner surface of a container, it is desirable to provide a
sealing compound or grease for example to that surface or at
the trailing edge of the plunger to make the seal airtight
when the plunger has been inserted into the tube sufficiently
to close the exit from passage 16. Other sealing means may
also be employed, for example, the plunger may be provided
¦ adjacent a trailing edge 17 with an O-ring sealed in a
circumferential groove adapted to receive it.
With dispensing cartridges it is desirable, after
~ insertion of the leading face of the plunger in the tube by
i at least the distance necessary to close air passages 16,
that retreat of the plunger be prevented by the roll forming
method described. However other methods may be used for
example the external skirt of the tube may be inwardly
crimped, or the skirt may be provided with inwardly crimpable
i tags, or the plunger may be sealed in place by other means
such as sealing compounds.
In other embodiments the plunger may be formed entirely
of plastics material or may be a composite form for example
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with a side edge of plastics and the leading edge or a
diaphragm portion thereoE of a soft metallic material either
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separate from or moulded illtO the wall of the plastic side
edge.
For use in cartridges the plunger may on its trailing
surfaces be adapted to engage with a cartridge gun
mechanism. When used in for example, a syringe, the plunger
may have a handle integral therewith or be adapted to receive
a handle at its trailing end. For use as a closure for a
container the plunger may be provided with a handle.
P~ungers according to the invention may advantageously
be used as a closure for a container when it is important to
exclude air from the contents at the time of sealing and to
maintain that exclusion until opening. In that event the
plunger after reaching a sealing position in which
passages 16 are closed, as described, may be adapted to be
locked against retreat by means permitting subsequent retreat
and removal of the plunger at a later date. For example a
baynet key formation of the plunger may engage with a groove
provided in the exterior skirt of the tube whereby the
plunger may be rendered immovable by twisting in the manner
of a baynet fitting light globe or the plunger may be held in
` place by screw and thread means.
Plungers according to the invention permit greatly
simplified filling and sealing methods in the case of
cartridge dispensers being filled for example with paste-like
materlals. The plungers enable air to be expelled prior to
~' sealing and enable an airtight seal to be maintained.
Plungers as described may also be used to prevent
o~erfilling of containers by expelling surplus content until
a level, determined by the insertion distance at which the
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10925~1
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plunger forms a seal with ~-he contaiher, is reached.
An added advantage of the use of deformable membranes
with plungers according to the invention is that expension of
contents, for example, due to temperature changes, is thereby
permitted without allowing air to enter the tube and no empty
space need be provided for expansion within the container.
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