Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DISPENSER
The present invention relates to an apparatus designed for dispensing a liquid
such as an adhesive system onto a substrate.
BACKGROUND
The dispensers referred to are frequently used in applications wherein a
liquid,
such as an adhesive or other liquid component included in an adhesive system,
such as
a resin component and a hardener component, is discharged to a surface of a
piece of
material that is successively combined with other such pieces in a laminated
structure,
such as a wood laminate. In the wood lamination industry, pieces of wood are
typically
conveyed below a dispenser by which the adhesive is distributed to the wood
pieces in
the form of curtains or parallel strings. Basically, liquid is supplied under
pressure to a
cavity in the dispenser from which the liquid is discharged through a
multiplicity of outlets
or nozzles arranged in one or several rows on the lower side of the dispenser.
The
dispensers are typically oriented horizontally and transversely to the general
direction of a
relative movement between dispenser and substrate.
A frequently occurring problem in this connection is the accumulation of gas
bubbles in the dispenser, forming pockets of gas in the dispenser cavity. The
gas, which
may originate from structural components building up the supplying system,
such as
stirrers, pumps, connectors etc. drawing air into the liquid, or from chemical
processes in
the liquid, disadvantageously affects the discharge of liquid through the
outlets.
Specifically, the occurrence of gas pockets may cause an uneven distribution
of liquid
through the outlets, resulting in uneven and unsatisfactory bonding between
the wood
pieces. The accumulation of gas bubbles in the dispenser is further supported
when the
inner structure of the dispenser gives rise to stagnant or trapped volumes of
liquid.
A non-homogenous distribution of liquid over the line of outlets is also
believed
to originate from a successively falling internal pressure in the liquid
filling the dispenser
cavity from an inlet end to the remote end. This shortcoming is further
expressed when
the pressure drop over the outlets is low, resulting in a heavier flow through
an outlet
close to the inlet than through the next outlet in the row.
SUMMARY OF THE INVENTION
The present invention aims to solve the problem discussed above and avoids the
formation of gas pockets within the apparatus. This object is met in a liquid
dispensing
apparatus comprising a cavity having an inlet connectable to a liquid source
operable for
supplying liquid under pressure to the cavity, and a number of outlets through
which the
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liquid is dispensable to a substrate, wherein each outlet individually
communicates with
the cavity through separate passages mouthing in the cavity, wherein each
passage
mouths in the cavity through a separate exit, each said exit intersecting
adjacent exits
arranged in a top of the cavity.
Briefly, an apparatus is arranged for dispensing a liquid, comprising a cavity
having an inlet connectable to a liquid source operable for supplying liquid
under
pressure to the cavity, and a number of outlets through which the liquid is
discharged to a
substrate which is provided below the apparatus in order to receive the
liquid. According
to the present invention, each outlet individually communicates with the
cavity through
separate passages, each said passage connecting individually to the top of the
cavity.
The liquid referred to is suitably an adhesive, or other liquid component
included
in an adhesive system such as a resin component and a hardener component.
Preferably, each outlet communicates with a separate exit, each said exit
intersecting with adjacent exits arranged in the top of the cavity.
Advantageously, the exits are formed in a lower side of a spreader insert
which
is mountable to cover an open top of the cavity.
The spreader insert preferably is formed with multiple through holes, each
through hole mouthing in a recess formed in the lower side of the spreader
insert, each
said recess transforming into adjacent recesses through an intersection line.
In an advantageous realization of the spreader insert, the recesses are formed
as inverted cones, or inverted spheres, or inverted pyramids having three or
more sides.
In effect of exiting the liquid from the top of the cavity, each outlet is
connectable
to an appurtenant exit via an interconnecting passage that is formed to turn
the flow
direction towards the outlets.
Advantageously, the passage is arranged to turn the liquid flow through 180
degrees from the exit to the outlet.
In one embodiment the passage is arranged initially to direct the liquid flow
upwards upon exit from the cavity.
In alternative embodiments, each outlet is connectable to an appurtenant exit
via
interconnecting conduits formed to turn the flow direction towards the
outlets.
The apparatus general structure comprises:
- a main block formed with a cavity and multiple outlets;
- a spreader insert receivable at the open top of the cavity, the spreader
insert having
multiple exits;
- a cover block mountable over the main block and the spreader insert, the
cover block
interconnecting the exits and the outlets for fluid communication, and
- snap lock means for mounting and dismounting the cover block from the main
block.
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The present invention further includes the use of the apparatus according to
the
present invention for applying a liquid onto a substrate. The liquid is
preferably an
adhesive, or other liquid component included in an adhesive system such as a
resin
component and a hardener component. The substrate is preferably a wood based
substrate.
The dispenser of the present invention will be more closely described below
with
reference to the accompanying drawings, wherein
Fig. 1 is a perspective view showing the dispenser of the present invention
from above;
Fig. 2 is an exploded top view showing the structural details of the
dispenser;
Fig. 3 is an exploded bottom view showing the same;
Fig. 4 is a transversal section through the dispenser, and
Fig. 5 is a longitudinal section through the same.
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the dispensing apparatus according to this invention is
shown in the drawings, from which it is readily apparent that the present
dispenser is
dismountable for maintenance. Typically, the dispensers referred to are
elongate bodies,
having a longitudinal dimension adapted for dispensing the liquid over the
total width of a
substrate that is provided below the dispenser. Nevertheless, multiple
dispensers may in
some applications be required to fully cover the width of a substrate.
With reference to the drawings, the dispenser comprises a main block 1,
forming
a base onto which the other details of the dispenser are attachable. The main
block 1 has
an elongate cavity 2 extended in the longitudinal direction of the main block.
The cavity 2
opens in the top side of the main block 1, and is supplied with liquid via an
inlet 3 which
opens in a side surface of the main block. Though not shown in the drawings,
the inlet 3
is connectable to a liquid source via pumping means which are operable to feed
the liquid
under pressure to the cavity 2. Advantageously, the sectional area of the
cavity 2 may be
reducing from an inlet end towards an opposite end of the cavity, preferably
realized
through a successively reducing depth or width in this direction of the
cavity. A plurality of
through holes or passages 4 connect the top side of the main block 1 with the
lower side
thereof, the passages 4 mouthing in the lower side in one or several rows of
individual
outlets 5 as is visible from fig. 3. The outlets may conventionally be adapted
to receive
separate nozzles, if appropriate. A groove 6 is formed to receive a sealing
member 7,
continuously encircling the cavity and passage openings in the top side of
main block 1.
An additional sealing member 8 is receivable to rest on a shoulder 9 which
runs
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continuously about an inner wall of the cavity 2, and which shoulder provides
a seat for a
spreader insert 10.
The spreader insert 10 forms a top cover for the cavity 2, and is receivable
to
rest on the shoulder 9 and sealing member 8 with its top surface leveling with
the top
surface of the main block 1. A number of through holes or passages 11 are
formed
through the spreader insert 10, equaling the number of passages 4 passing
through the
main block 1. Each passage 11 mouths in the lower surface of the spreader
insert 10
through a widened opening 12, visible in figs. 3-5. These openings 12,
constituting the
exit from the cavity, may be formed as conical or spherical cups, or inverted
pyramids
having three or more sides, recessed from the lower surface of the spreader
insert.
Advantageously, the recesses or exits 12 are dimensioned to overlap adjacent
exits such
that each exit 12 transforms into an adjacent exit 12 via an intermediate
intersection line
13, i.e. each exit intersects with adjacent exits without any substantial
interconnecting
surface between adjacent exits 12, as is notable from the drawings. On the top
side of the
spreader insert 10, the passages 11 mouth in a pattern that allows each
passage 11 to
be aligned with the top side opening of a an appurtenant passage 4 through the
main
block 1.
The passage 11 may be formed with a more or less accentuated vertical length
measured from the upper end of the corresponding exit 12 to the top side of
the spreader
insert 10. One embodiment of the present invention foresees that the flow of
liquid is
initially directed upwards through a vertical length of the passage 11, upon
exit from the
cavity, and turned twice through a total of 180 degrees before discharge via
the outlets.
A cover block 14 is arranged for connecting each passage 11 through the
spreader insert 10 with a corresponding passage 4 through the main block 1.
For this
purpose, the cover block 14 is formed in its lower surface with a number of
grooves 15,
the lengths of which are adapted for connecting a top side mouth of a passage
11 with
the appurtenant top side mouth of a passage 4. In its mounted position, the
grooves 15 in
the cover block complete the individual fluid passages from the exits 12 to
the outlets 5.
The cover block 14 is readily mountable and dismountable, respectively, on the
main block 1 through a snap connection. In one end, the cover block has a heel
16 which
is shaped to engage the lower side of a corresponding nose 17 arranged on the
main
block. The opposite end of the cover block is formed with a lug 18 which is
arranged for
engagement with an eccentric lock mechanism 19. In a snapped on position, the
lower
surface of the cover block is sealingly pressed towards the top surfaces of
the main block
1 and the spreader insert 10, respectively. A centering pin 20, threaded
through the cover
block, ensures the correct positioning and free passageways from the cavity's
exits to the
outlets, via passage sections 11, 15, and 4.
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For a full presentation of the illustrated embodiment, the nose 17 is bolted
to the
main block through a couple of screws 21 reaching through bores 22 formed in
the main
block. The eccentric lock mechanism 19 is bolted to the main block through a
couple of
screws 23, reaching through bores 24 and engaging an anchor 25 inserted in a
slot 26
5 which runs parallel to a seat 27 for the eccentric lock mechanism, the seat
27 being
formed in a side surface of the main block 1. On its top side, the cover block
comprises
means 28 adapted for installing the dispenser in a production line.
As apparent from the above description of the structural design, the liquid
passage through the dispenser from the inlet 3 to the outlets 5 contains no
obstructing or
entrapping formations where gas bubbles may accumulate, or formations that may
prevent any gas bubbles present in the liquid from being transported with the
liquid flow
through the passages. Moreover, the exits from the cavity are oriented in the
top of the
cavity, taking advantage of the natural rise of lighter gas bubbles eventually
enclosed in
the liquid. Furthermore, any gas bubble that rises through liquid standing in
the cavity
during intermittent operation is instantaneously introduced in a partial flow
and captured
in a flow of comparatively high velocity through the passages, directing the
flow from the
cavity to the outlets. The capacity to vent the dispenser apparatus is further
enhanced by
arranging separate passages initially to direct the liquid flow so as to exit
from the top of
the cavity, and successively to turn the partial flows towards the outlets.
In effect of exiting the liquid from the top of the cavity, the flow direction
must be
altered through 90 or 180 degrees in order to discharge the liquid from the
lower side of
the dispenser. The inevitable horizontal and vertical components of this
multidirectional
liquid flow results in added passage length from exit to outlet, generating a
corresponding
resistance and pressure drop over the passages. The raised drop in pressure
over the
passages advantageously reduces the influence of a falling pressure internally
in the
cavity, thus also reducing or avoiding a non-homogenous distribution of liquid
over the
line of outlets.
Another advantage achieved by the presented dispenser is a continuous and
complete liquid turnover in the cavity, resulting in part from the non-broken
exit area
facing the cavity from above, and in part from the reducing sectional area
from the inlet
towards the remote end of the cavity. In effect thereof the structure avoids
stagnant
volumes of liquid, and accordingly avoids the risk of entrapped volumes of
liquid impairing
the distribution of liquid as well as the risk of entrapped volumes of
adhesive curing in the
cavity.
The invention is illustrated with respect to an embodiment to which
modifications
are possible without departing from the basic solution. For example, instead
of
passageways that are machined as channels through block elements, the outlets
5 may
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be individually connectable with the exits from the cavity through separate
conduits
connecting to a distributor covering the top of the cavity.
