Dispensing apparatus having nozzle for controlling heated liquid discharge with unheated pressurized air

A liquid dispensing apparatus for dispensing heated liquid, such as hot melt adhesive, onto a substrate includes a dispenser body with a liquid dispensing nozzle portion which has a liquid discharge passage and outlet communicating with the dispenser body. An air cap is mounted to the dispenser body and has an opening to receive the liquid discharge outlet of the nozzle portion. The air cap has an air discharge passage for directing air onto the heated liquid as it exits the liquid discharge outlet. The air discharge passage is thermally isolated from the liquid discharge passage to allow the use of air which is substantially cooler than the heated liquid.

FIELD OF THE INVENTION 
The present invention generally relates to a nozzle assembly for directing 
liquid onto a substrate and, more specifically, to nozzle assemblies that 
incorporate pattern air for developing specific liquid discharge patterns. 
BACKGROUND OF THE INVENTION 
It is known to discharge a bead of hot melt adhesive from a nozzle in a 
spiral pattern so that, for example, the bead is deposited in a series of 
overlapping loops. Such nozzles typically incorporate a plurality of air 
discharge passages surrounding an adhesive discharge passage. The air 
discharge passages direct so-called pattern air toward the discharged 
adhesive to cause it to take on a specific configuration or pattern on a 
substrate. When there is relative perpendicular movement between the 
adhesive bead and an underlying substrate, for example, a pattern of 
overlapping adhesive loops may be deposited on the substrate. Various 
apparatus and methods exist for applying liquids such as hot melt 
adhesives in overlapping, generally circular swirl patterns or other 
patterns using pressurized streams of air. 
In prior dispensing apparatus, the pattern air was typically channeled from 
an air source through air discharge passages surrounding the adhesive 
discharge outlet. The air discharge passages have been disposed adjacent 
to the adhesive discharge passage and in direct thermal communication 
therewith. As such, the temperature of the structure forming the air 
discharge passages has been substantially equal to that of the adhesive 
discharge passage and the adhesive. Unfortunately, if pattern air at 
relatively cool temperatures, such as ambient temperature, is circulated 
through the air discharge passages or other air passageways in the 
apparatus, the adhesive discharge outlet and other adhesive passageways 
can be cooled to unsatisfactory levels. Specifically, relatively cool 
pattern air can carry significant amounts of heat away from the nozzle 
assembly through heat transfer as it moves through the air discharge 
passages or other air passageways in thermal communication with the hot 
melt adhesive discharge orifices and/or other adhesive passageways. This 
cooling effect can cause the adhesive viscosity to increase and thus 
adversely affect the deposition of the adhesive onto a substrate in the 
desired pattern or patterns. 
To overcome the cooling effect, pattern air has been heated before its 
introduction into the nozzle assembly. It was found that to effectively 
minimize the cooling effect, the pattern air must be heated at least 
25.degree. F. to 50.degree. F. higher than the target adhesive temperature 
at the adhesive discharge outlet, which is typically about 300.degree. F. 
The heated pattern air effectively resolved the cooling effect created by 
the ambient temperature pattern air, but produced offsetting 
disadvantages. For example, heating the pattern air above the adhesive 
temperature increases the complexity of the adhesive dispensing apparatus 
and increases the cost and labor involved with set-up and operation of the 
apparatus. 
Adhesive or liquid dispensing apparatus of this general type which does not 
require heated pattern air would have several advantages over the prior 
designs. For instance, the time required to set up the adhesive dispensing 
apparatus would be reduced as the time needed to properly adjust the 
temperature of the air would be eliminated. Additionally, the cost of 
operation would be reduced due to the elimination of external heaters for 
the pattern air. Another advantage of using ambient temperature pattern 
air is that the air may desirably cool the extruded adhesive bead just 
prior to its contact with the substrate. Because cooler adhesive would 
contact the substrate, substrate burn-through caused by hot adhesive may 
be prevented and a thinner substrate could be used, for example, resulting 
in reduced material cost. 
For at least these reasons, it would be desirable to provide a hot melt 
adhesive or liquid dispenser capable of using ambient temperature pattern 
air or pattern air that at least does not have to be heated to a 
temperature approaching the hot melt adhesive or liquid temperature. 
SUMMARY OF THE INVENTION 
The present invention overcomes the foregoing and other shortcomings and 
drawbacks of previous liquid dispensing systems and methods involving the 
use of pressurized pattern air. While the invention will be described in 
connection with certain preferred embodiments, it will be understood that 
the invention is not limited to these embodiments. On the contrary, the 
invention includes all alternatives, modifications and equivalents as may 
be included within the spirit and scope of the present invention. 
The present invention is generally directed to a liquid dispensing 
apparatus for dispensing heated liquid, such as hot melt adhesive, on a 
substrate. The liquid dispensing apparatus includes a dispenser body with 
a liquid passageway adapted to be connected with a source of the heated 
liquid. A nozzle, which is connected to the dispenser body, has a liquid 
discharge passage communicating with the liquid passageway of the 
dispenser body. The nozzle also has at least one air discharge passage, 
and preferably a plurality thereof, positioned to direct pressurized air 
at the heated liquid as it exits the liquid discharge passage. Many nozzle 
configurations have from six to twelve air discharge passages. The air 
discharge passages are thermally isolated from the liquid discharge 
passage such that, for example, ambient air traveling through the air 
discharge passages does not substantially cool the liquid discharge 
passage and the liquid contained therein. This may be accomplished by 
incorporating a thermal insulator between the air discharge passages and 
the liquid discharge passage. In the presently preferred embodiments, this 
insulator is a space filled with an insulator located between the liquid 
and air discharge passages. The insulator may be air or some other 
thermally insulating material. 
In the preferred embodiments, the nozzle is made up of two separate pieces, 
i.e., a liquid dispensing nozzle portion and an air cap. The liquid 
dispensing nozzle portion is mounted to the dispenser body and has a 
liquid discharge passage with a liquid discharge outlet which communicate 
with the liquid passageway in the dispenser body. In a first embodiment, 
the air cap may be mounted to the dispenser body so as to also secure the 
liquid dispensing nozzle portion to the dispenser body. In another 
embodiment, the nozzle portion and air cap may have mating threaded 
portions to ensure proper alignment of the air discharge passages with 
respect to the dispensed liquid. The air cap has an opening that receives 
at least the end of the nozzle portion with the liquid discharge outlet 
and has a plurality of air discharge passages thermally isolated from the 
liquid discharge passage. The air discharge passages are positioned to 
direct pressurized air at the heated liquid as it exits the liquid 
discharge outlet. 
Methods of dispensing heated liquids using pattern air which is at a 
substantially cooler temperature than the liquid are also contemplated by 
the invention. The methods can involve dispensing heated liquids with 
apparatus constructed in accordance with the invention as generally 
described above. That is, the methods can include dispensing a heated 
liquid from a dispenser nozzle having a liquid discharge passage connected 
with a liquid discharge outlet each positioned adjacent to but thermally 
isolated from at least one air discharge passage. The methods can 
generally comprise the steps of discharging the liquid at a first 
temperature from the liquid discharge passage through the liquid discharge 
outlet and impacting the heated liquid exiting the liquid discharge outlet 
with at least one air stream directed through the air discharge passage at 
a second temperature which is substantially lower than the first 
temperature. The air in the air discharge passage should not cool the 
heated liquid in the liquid discharge passage by more than about ten 
percent. The second temperature may be substantially equal to ambient 
temperature or at least about 50% lower than the first temperature without 
adversely cooling the liquid in the nozzle. 
Accordingly, the present invention provides a liquid dispensing apparatus 
for depositing heated liquid on a substrate with a pattern generated by 
relatively cool air impacting the discharged liquid. Air discharge 
passages associated with the dispensing nozzle are thermally isolated or, 
in other words, insulated from the liquid discharge passage. Because of 
the thermal isolation, conventional heated pattern air may be replaced by 
ambient air or substantially cooler air to achieve advantages such as 
described above. For example, this can reduce the cost of labor and 
equipment in the set-up and operation of the liquid dispensing apparatus. 
Additionally, because the ambient temperature pattern air will partly cool 
the heated liquid just prior to contacting the substrate, substrate 
burn-through caused by hot liquid can be prevented and a thinner substrate 
may be used, resulting in reduced material cost. 
Various additional advantages and objects of the invention will become more 
readily apparent to those of ordinary skill in the art upon consideration 
of the following detailed description of the presently preferred 
embodiments taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, a liquid dispensing apparatus 10 is shown 
specifically adapted for dispensing a heated liquid onto a substrate in 
accordance with the principles of this invention. While it will be 
understood that any desired heated liquid may be dispensed in accordance 
with the invention, for the sake of simplicity, the present invention will 
be described more specifically in connection with dispensing so-called hot 
melt adhesives. These adhesives are typically dispensed at about 
250.degree. F. and above. The inventive principles will be described with 
reference to only two of many possible embodiments of dispensing apparatus 
and nozzle configurations falling within the scope of this invention. 
As shown in FIG. 1, liquid dispensing apparatus 10 includes a dispenser 
body 12 connected with a nozzle 14. Although a brief description of 
apparatus 10 and, specifically, of the interaction between body 12 and 
nozzle 14 will be given, it will be understood that many types of 
apparatus and dispensing bodies, including dispensing manifolds, modules 
or guns, may benefit from the present invention. The invention is 
therefore not limited to the specific type of dispenser shown in the 
drawings. In the embodiment shown in FIG. 1, for example, nozzle 14 
comprises a liquid dispensing nozzle portion 16 and an air cap 18 which 
will be described in more detail below. It will be appreciated that liquid 
dispensing nozzle portion 16 and air cap 18 could be constructed as one 
operative piece to function as nozzle 14, instead of the two separate 
pieces as shown. 
Dispenser body 12 includes a liquid passageway 20 which is in fluid 
communication with adhesive port 22. Adhesive port 22 is adapted to 
connect to a source of hot melt adhesive. Dispenser body 12 also includes 
an air chamber 24 in fluid communication with actuation air port 26. 
Actuation air port 26 is adapted to connect to a source of pressurized air 
(not shown). Dispenser body 12 further includes a valve member and piston 
assembly 28 which is moved to an open position by the actuation air coming 
from actuation port 26 and filling air chamber 24. The valve member 28 
provides a means to meter the viscous liquid flowing through the liquid 
dispensing apparatus 10. A conventional spring return mechanism 29 may be 
provided to close valve member 28 when air pressure through port 26 is 
turned off. These components of such dispensers are generally known in 
various forms and, therefore, further detailed discussion is not necessary 
for an understanding of the invention. 
With reference to FIGS. 1 and 2, liquid dispensing nozzle portion 16 
includes a adhesive discharge passage 30 which communicates with liquid 
passageway 20 of dispenser body 12. Liquid dispensing nozzle portion 16 
has an inlet end 31 which includes a liquid receiving inlet 32. Inlet end 
31 further includes an O-ring 34 externally positioned on the inlet end 31 
for sealing against leakage between the inlet end 31 and the adhesive 
discharge passage 30. Nozzle portion 16 further includes a discharge end 
35 which has a liquid discharge outlet 36 communicating with adhesive 
discharge passage 30 for extruding the liquid hot melt adhesive onto a 
substrate (not shown). 
With further reference to FIGS. 1 and 2, air cap 18 includes an opening 38 
that is adapted to receive at least the end of the liquid dispensing 
nozzle portion 16 having the liquid discharge outlet 36 (FIGS. 1-3). As 
will be appreciated from the assembled view of FIG. 2, opening 38 forms an 
insulating air space disposed between air channel 40 and liquid passage 30 
and also between air discharge passages 44 and liquid discharge passage 
30. This air space therefore serves as a thermal insulator, although other 
types of insulative materials may be used as well. Air cap 18 further 
includes an annular air channel 40 which is in fluid communication with 
air inlet port 42 which is adapted to connect to a source of pressurized 
air. Air cap 18 also has a plurality of air discharge passages or, more 
specifically, orifices 44 which are in fluid communication with air 
channel 40. Each air discharge passage 44 may be at a compound angle, for 
example, relative to a liquid extrusion axis 46. In the embodiment shown 
in FIG. 1, six air discharge passages 44 are equally spaced about the 
opening 38. With the air discharge passages 44 at compound angles to the 
liquid extrusion axis 46, the discharged pressurized air from the passages 
44 imparts a rotational movement into the liquid being extruded from 
liquid discharge outlet 36. It can be appreciated that the number of air 
discharge passages and their compound angles could be selected such that, 
upon discharge of the liquid hot melt adhesive from liquid discharge 
outlet 36, a rotational motion is imparted into the liquid. If the liquid 
dispensing apparatus 10 moves relative to a substrate during its 
operation, a series of overlapping adhesive loops will be formed on the 
substrate. 
Advantageously, and in accordance with the principles of the present 
invention, air discharge passages 44 are thermally isolated from the 
liquid dispensing nozzle portion 16 and its adhesive discharge passage 30. 
That is, for example, ambient temperature air entering through air inlet 
port 42 and traveling through air channel 40 and out of the air discharge 
passages 44 has little or no deleterious thermal influence on the liquid 
hot melt adhesive traversing through liquid dispensing nozzle portion 16 
or its adhesive discharge passage 30. Consequently, and in accordance with 
the principles of the present invention, even though the air flowing 
through the air cap 18 may be of ambient temperature or substantially 
cooler temperature than the liquid in passage 30, that air will not 
adversely reduce the temperature of the liquid prior to its discharge from 
outlet 36. Generally, the liquid in adhesive discharge passage 30 and 
upstream of outlet 36 should not be cooled by ambient pattern air by more 
than about 10% during continuous or intermittent operation. More 
preferably, the cooling should be less than about 5%. As one example, hot 
melt adhesive heated to 300.degree. F. before entering the dispensing 
apparatus 10 should exit the liquid discharge outlet 36 no cooler than 
about 275.degree. F. The present invention achieves this objective while 
enabling the use of pattern air which is introduced in port 42 at less 
than 50% of the hot melt adhesive temperature, e.g., at less than about 
100.degree. F. 
Air cap 18 connects to dispenser body 12 holding liquid dispensing nozzle 
portion 16 therebetween by means of screws 48 inserted through screw holes 
50. In the embodiment shown in FIGS. 1-3, a gasket 52 is inserted between 
liquid dispensing nozzle portion 16 and air cap 18. Gasket 52 can be any 
material suitable for thermally isolated one component from another, such 
as Teflon.RTM. or Rulon.RTM.. 
With reference to FIGS. 4 and 5, another embodiment is illustrated in 
accordance with the principles of the present invention. Although the 
structure is somewhat different than the first embodiment, the principles 
basic objectives are the same. In this embodiment, a nozzle 14a comprises 
a liquid dispensing nozzle portion 16a and an air cap 18a. Liquid 
dispensing nozzle portion 16a connects to dispenser body 12. The 
representative dispenser body 12 is common to both embodiments and details 
of its structure are basically described above. 
Liquid dispensing nozzle portion 16a includes an adhesive discharge passage 
30a which communicates with liquid passageway 20 of dispenser body 12. 
Liquid dispensing nozzle portion 16a has an inlet end 31a which includes a 
liquid receiving inlet 32a. Inlet end 31a further includes an O-ring 34a 
externally positioned on the inlet end for sealing against liquid between 
the inlet end and the adhesive discharge passage 30a. Nozzle portion 16a 
further includes a discharge end 35a which has a liquid discharge outlet 
36a communicating with adhesive discharge passage 30a for extruding the 
liquid hot melt adhesive onto a substrate (not shown). Liquid dispensing 
nozzle portion 16a further includes an air inlet port 54 communicating 
with air passageway 56. Air inlet port 54 is adapted to connect to a 
source of pressurized air. With respect to air inlet ports 42 and 54 of 
the respective first and second embodiments, it will be appreciated that 
these ports may be oriented according to the needs of the application. For 
example, an orientation to the rear of dispenser 12 can allow 
communication with an unheated or heated air manifold. Other orientations 
can allow connection with independent air supply lines. 
Discharge end 35 is connected to liquid dispensing nozzle portion 16a via a 
threaded portion 58. As such, replacement liquid discharge outlets can be 
easily installed into or removed from the liquid dispensing nozzle portion 
16a. Liquid dispensing nozzle portion 16a is secured to dispenser body 12 
by means of screws 60 insert into screw holes 62. When connected to 
dispenser body 12, adhesive discharge passage 30a is in fluid 
communication with liquid passageway 20 of the dispenser body. 
Again with reference to FIGS. 4 and 5, air cap 18a includes an opening 38a 
that is adapted to receive at least the end of the liquid dispensing 
nozzle portion 16a having the liquid discharge outlet 36a (FIG. 5). This 
opening 38a forms an insulating air space as discussed above with respect 
to the first embodiment. Air cap 18a further includes an annular air 
channel 40a which is in fluid communication with air passageway 56. Air 
channels 40 and 40a of the first and second embodiments act as 
distribution channels as well as air diffusers to help provide a uniform 
flow of air through air discharge passages 44 and 44a. Passageway 56 is 
adapted to connect to a source of pressurized air. Air cap 18a also has a 
plurality of air discharge passages or, more specifically, orifices 44a 
which are in fluid communication with air channel 40a. Each air discharge 
passage 44a is at a compound angle relative to the liquid extrusion axis 
46a. In the embodiment shown in FIG. 4, six air discharge passages 44a are 
equally spaced about the opening 38a. As described in the first embodiment 
above, air exiting air discharge passages 44a being at compound angles 
imparts a rotational movement into the liquid being extruded from liquid 
discharge outlet 36a to produce a series of overlapping loops of hot melt 
adhesive on a substrate moving relative to the liquid dispensing apparatus 
10. 
Air cap 18a is secured to liquid dispensing nozzle portion 16a via threaded 
portion 64 which screws into internal threads 66 of the nozzle portion. As 
such, the air cap 18a is aligned concentrically with the liquid discharge 
outlet 36a and liquid extrusion axis 46a. Advantageously, the air cap 18a 
can be repeatedly attached to the liquid dispensing nozzle portion 16a 
such that it is concentrically aligned each time with the liquid discharge 
or extrusion axis 46a. The concentrically aligned air cap 18a helps 
achieve precise and consistent rotational motion of the liquid hot melt 
adhesive such that the liquid can be accurately deposited onto a 
substrate. Advantageously, a washer 68 is positioned between air cap 18a 
and liquid dispensing nozzle portion 16a. Washer 68 establishes a 
substantially air-tight seal between it and the air channel 40a of air cap 
18a. Washer 68 has one or more throughholes 70 which permit fluid 
communication between air passageway 56 and annular air chamber 40a. 
Without the washer 68 or another suitable gasket or seal, air entering air 
channel 40a via air passageway 56 could escape through the screw holes 62 
because the outside wall of the air channel extends over the screw holes. 
Similar to the first described embodiment and in accordance with the 
principles of the present invention, air discharge passages 44a are 
thermally isolated from the liquid dispensing nozzle portion 16a and its 
adhesive discharge passage 30a. That is, the ambient temperature air 
entering through air inlet port 54 and traveling through air channel 40a 
and out of the air discharge passages 44a has little or no deleterious 
thermal influence on the heated liquid traversing through liquid 
dispensing nozzle portion 16a or its adhesive discharge passage 30a. 
Consequently, and in accordance with the principles of the present 
invention, even though the air flowing through the air cap 18a may be of 
ambient temperature, that air will not reduce the temperature of liquid at 
the liquid discharge outlet 36a by more than 10% of the temperature of the 
liquid coming from the liquid source. More preferably, the ambient pattern 
air will not reduce the temperature of liquid at outlet 36a by more an 5%. 
For example, adhesive heated to 300.degree. F. before entering the 
dispensing apparatus 10 will exit the liquid discharge outlet 36a no 
cooler than 275.degree. F., i.e., cooled less than about 10%. After the 
liquid has left outlet 36 or 36a, it may be advantageously cooled by the 
ambient pattern air as described above. 
In operation, liquid dispensing apparatus 10 deposits a bead of heated, 
viscous liquid, and more specifically an adhesive, in a series of 
overlapping loops onto a substrate moving relative to the dispensing 
apparatus. With reference to the operation of the embodiment shown in FIG. 
1, heated adhesive enters adhesive port 22 of dispenser body 12 from an 
external source. The adhesive is pushed under pressure through liquid 
passageway 20 and to adhesive discharge passage 30 of liquid dispensing 
nozzle portion 16. The adhesive is then discharged from liquid discharge 
outlet 36. Simultaneously, pressurized air enters air inlet port 42, flows 
through air channel 40 and is discharged through air discharge outlets 44. 
The discharged air impacts the heated adhesive, as it exits the liquid 
discharge outlet 36. As previously stated, the compound angles of air 
discharge outlets 44 impart a rotational motion into the adhesive 
discharged from liquid dispensing outlet 36. As such, if the target 
substrate moves in a line perpendicular to the liquid extrusion axis 46 of 
the liquid dispensing apparatus 10, the adhesive will form a series of 
overlapping loops of adhesive on the surface of the substrate. At the same 
time, the adhesive will be cooled by the pattern air as it leaves outlet 
36. It will be appreciated that the embodiment of FIGS. 4 and 5 will 
operate in an analogous manner.