SPRAY GUN

PISTOLET DE PULVERISATION

English Abstract

The present invention is a pneumatic spray gun for spraying a liquid medium,
wherein the spray
gun uses a flexible spray tube to control the spraying of the liquid medium.
The spray tube has
opposite first and second ends with a nozzle formed at the first end of the
spray tube and the
second end of the spray tube being removably coupled to a medium supply line
contained in the
housing. The spray gun further includes an actuator movable between a first
position wherein the
actuator pinches the spray tube closed and a second position wherein the
actuator permits the
spray tube to open, the actuator being operatively coupled to a trigger
mounted on the housing for
operating the actuator between its first and second positions.

Claims

Therefore, what is claimed is:
1. A pneumatic spray gun for spraying a liquid medium comprising:
a housing;
a resiliently flexible spray tube having opposite first and second ends, a
nozzle formed at
the first end of the spray tube, the second end of the spray tube being
removably coupled
to a medium supply channel contained in the housing, the medium supply channel
having
a coupling for connection to an external medium supply line;
an actuator movable between a first position wherein the actuator pinches the
spray tube
closed and a second position wherein the actuator permits the spray tube to
open, the
actuator being operatively coupled to a trigger for operating the actuator
between its first
and second positions.
2. The pneumatic spray gun of claim 1 wherein the spray tube is contained in a
compartment
of the housing having a removable cover, the compartment having a nozzle port
for
receiving the nozzle and directing it away from the spray gun, the actuator
pinching the
spray tube at a position on the spray tube adjacent the nozzle.
3. The pneumatic spray gun of claim 1 wherein the actuator is operatively
coupled to a first
switch, the first switch operating between an on state wherein the switch
causes the
actuator to move into its first position and a closed state wherein the first
switch causes
the actuator to move into its second position, the first switch being
positioned adjacent
the trigger such that the trigger, when depressed, causes the first switch to
change from its
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closed state to its on state.
4. The pneumatic spray gun of claim 3 wherein the actuator is a pneumatic
actuator and the
switch is a pneumatic valve.
5. The pneumatic spray gun of claim 3 wherein the gun further comprises an air
line for
supplying the gun with compressed air for atomizing the liquid medium and
further
comprising a second switch coupled to the air line, the second switch
operating between
an on state wherein air can flow through the air line to atomize the liquid
medium and a
closed state wherein the air line is closed, the second switch being mounted
to the
housing adjacent the trigger such that when the trigger is depressed, the
second switch is
placed in its open state.
6. The pneumatic spray gun of claim 2 wherein the removable cover has at least
one air
passage with an outlet for directing the sprayed liquid.
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Description

CA 02573868 2007-01-12
TITLE: SPRAY GUN
FIELD OF THE INVENTION
The invention relates generally to pneumatic spray guns for spraying liquid
materials that
can be atomized such as glue, paints and coatings.
BACKGROUND OF THE INVENTION
Pneumatic spray guns are used extensively to apply liquid adhesive solutions.
Traditionally, pneumatic spray guns included a metal or plastic grip having a
trigger operated
valve which, when opened by pressing on the trigger, permitted a stream of
atomized liquid to be
sprayed out of the spray gun's nozzle. The spray guns usually include two
lines, one for the
liquid medium being sprayed, and one for pressurized air to atomize the liquid
medium.
Traditional pneumatic spray guns as used for spraying paints have be
successfully used
for spraying solvent based liquid adhesives for many years. However, over the
past few years,
there has been an increased demand for water based liquid adhesives. Water
based liquid
adhesives behave very differently than solvent based adhesives. In particular,
solvent based
adhesives are much more stable, remaining liquid even when agitated. Water
based adhesives,
on the other hand, have a tendency to form clumps when the liquid experiences
sheer forces.
Unlike solvent based adhesives, clumps formed in liquid adhesives do not
dissolve back into
solution, and in fact tend to cause additional clumping. As a result, when
used in traditional
pneumatic spray guns, water based adhesives tend to cause the spray guns to
fowl quite badly
during use, resulting in the need for continuous adjustment, until becoming
inoperable. When a
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CA 02573868 2007-01-12
pneumatic spray gun is fowled by clumped adhesive, the gun must be
disassembled to be
cleaned. This is a laborious and time consuming task. Therefore, an improved
spray gun which
is not prone to fowling when used with water based adhesives is required.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a
pneumatic spray gun
for spraying a liquid medium, the spray gun including a housing containing a
resiliently flexible
spray tube. The spray tube has opposite first and second ends with a nozzle
formed at the first
end of the spray tube and the second end of the spray tube being removably
coupled to a medium
supply line contained in the housing. The spray gun further includes an
actuator movable
between a first position wherein the actuator pinches the spray tube closed
and a second position
wherein the actuator permits the spray tube to open, the actuator being
operatively coupled to a
trigger mounted on the housing for operating the actuator between its first
and second positions.
With the foregoing in view, and other advantages as will become apparent to
those skilled
in the art to which this invention relates as this specification proceeds, the
invention is herein
described by reference to the accompanying drawings forming a part hereof,
which includes a
description of the preferred typical embodiment of the principles of the
present invention.
DESCRIPTION OF THE DRAWINGS
FIGURE 1. is a side view of a spray gun made in accordance with the present
invention.
FIGURE 2. is a top view of the spray gun shown in figure 1.
FIGURE 3. is a cross sectional view of the spray gun showing only one medium
supply channel
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CA 02573868 2007-01-12
and one actuator.
FIGURE 4 is a cross sectional view of the spray gun showing two separate
medium supply
channels and two actuators.
In the drawings like characters of reference indicate corresponding parts in
the different
figures.
DETAILED DESCRIPTION OF THE INVENTION
Referring firstly to figure 1, a spray gun made in accordance with the present
invention is
shown generally as item 10 and includes a removable cap portion 12 fitted onto
body 14 which is
held in place by screws 42. Grip portion 16 is formed onto body 14 and is
adjacent trigger 34
which controls the flow of air and liquid spray medium through the gun.
Couplings 58 and 56
are adapted to couple to medium supply lines 57 and 55, respectively and
coupling 54 is
configured to couple to an air supply line 53.
Referring now to figure 3, spray gun 10 has internal medium supply channel 20
which is
continuous with coupling 58. Supply channel 20 is removably coupled to
coupling 21 onto
which coupling end 23 of flexible spray tube 22 is mounted. Flexible spray
tube 22 has nozzle
28 formed on the end opposite coupling 23. Flexible spray tube 22 is made of a
resilient yet
flexible material such as silicone rubber, flexible PVC, urethane or the like,
which is sufficiently
flexible to be pinched closed by actuator contact 40 of pneumatic cylinder
actuator 24. Actuator
contact 40 and actuator 24 are dimensioned and configured such that contact 40
is movable
between a first position, shown at 43 wherein the contact pinches tube 22
closed and a second
position, shown at dotted line 41, wherein the contact does not pinch tube 22
such that tube 22 is
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CA 02573868 2007-01-12
fully opened. In effect, actuator 24 and contact 40 act as a shut off valve
controlling the flow of
material through flexible tube 22 by pinching the tube closed. Preferably,
actuator contact 40
pinches tube 22 at point 26, which is immediately adjacent nozzle 28 to ensure
that no material
leaks out of the tube after the tube has been pinched closed.
Tube 22 is contained within a compartment 27 formed between cap 12 and body
14.
Tube 22 and coupling element 21 are continuous with supply channel 20. Tube 22
is formed as
an assembly with coupling element 21 so that the entire tube assembly is a
consumable item
which can be easily replaced when it gets worn or dirty. Removing and
replacing tube 22 and
coupling element 21 is easily achieved by simply removing screws 42 which
secure cap 12 to
gain access to compartment 27.
Actuator 24 is controlled by first valve 48 which is coupled to air channel
46, which is in
turn continuous with coupling 54. Valve 48 is a pneumatic control valve which
controls the
operation of actuator 24 by controlling the flow of air through air channel 38
which is coupled to
actuator 24. Valve 48 operates like an on off switch controlling the operation
of actuator 24 by
shutting off or turning on the flow of air through channel 38. Valve 48
operates between an on
state wherein the valve causes actuator 24 to move arm 40 into its first
position, and an off state
wherein the valve causes actuator 24 to move arm 40 into its second position.
Valve 48 has
valve actuator 50 which is mounted onto housing 14 adjacent trigger 34 such
that when the user
squeezes trigger 34, actuator 50 is engaged and the valve is placed into its
on state. Valve 48 is
configured to normally remain in its off state so that when the user releases
trigger 34, the valve
will return to its off state which in turn causes actuator 24 to close off
tube 22.
Gun 10 also has pneumatic valve 18 which controls the flow of air through
second air
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channel 36. Second air channe136 exits at port 52 which is positioned adjacent
nozzle 28 so that
the flow of compressed air through port 52 causes the atomization of the
liquid exiting nozzle 28.
Pneumatic valve 18 also has a valve actuator 44 which is mounted adjacent
trigger 34 which
when squeezed, depresses the actuator causing the valve to open to allow a
flow of air to pass
through air channe136. Preferably, actuator 44 of valve 18 is positioned
closer to switch 34 than
actuator 50 of valve 48 so that when the trigger is squeezed valve 18 is
activated immediately
before valve 48 is activated. This ensures that all of the fluid flowing from
nozzle 28 is
atomized.
Figure 4 illustrates how the present gun can be fitted with a secondary medium
flow
channe162 for delivering a second liquid material, such as an activator or
catalyst, to the
atomized stream of material flowing from the gun. The second flow channel
exits at port 64 and
the flow of material through the port is controlled by pneumatic valve 60.
Pneumatic valve 60
operates between an opened state wherein material can flow through channe162
and a closed
state wherein the valve closes off the flow of material through the cannel.
Pneumatic valve 60 is
coupled to pneumatic control valve 48 so that when control valve 48 causes
actuator 24 to open
tube 22, pneumatic valve 60 is simultaneously opened. In this way, two
separate flows of liquid
material are ejected through gun 10 simultaneously. Actuators 24 and 60 are
adjustable to
control the flow rate of both the medium and activator (or catalyst).
Atomization of the fluid is achieved by pressurized air which exits gun 10
through air
passages in the body 14 as well as air passages 9 and air openings 7 in cap
12. Air passages 9 in
cap 12 are coupled to air passage 36. The air passing from the passages in cap
12 contribute
greatly to the shape and size of the spray pattern. It is therefore possible
to offer various caps
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CA 02573868 2007-01-12
which would differ in configuration of the air passages, such as the size,
quantity, angle and
placement of the air passages. The advantage to users of the gun is to offer
various spray patterns
by interchanging the caps 12 only, without a need to change the entire gun.
The present invention has many advantages over the prior art. In particular,
flexible tube
22 and actuator 24 form a very effective valve which applies very weak sheer
forces onto the
liquid contained in tube 22. As a result, the liquid in tube 22 is far less
likely to congeal and
clump as a result of continuously operating the spray gun on and off.
Furthermore, since flexible
tube 22 is easily accessible and easily removed, it is easy for a user to
service the spray gun to
replace the tube in the event the gun becomes clogged.
A specific embodiment of the present invention has been disclosed; however,
several
variations of the disclosed embodiment could be envisioned as within the scope
of this invention.
It is to be understood that the present invention is not limited to the
embodiments described
above, but encompasses any and all embodiments within the scope of the
following claims.
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Representative Drawing