Note: Descriptions are shown in the official language in which they were submitted.
~1-
TI'rL~ GUN FOR DISP~NSING A YLURAL COMPO,Y~NT
SYSTEkS
BASK~ûUND OF T~ N~ lTION
This inven~ion ~ d~rec~d to a ~un for di~-
pensi~g a plural compon~nt sy~tem which inclucle5 ~
~alYe carrier mo~ablo within the gun such that both
th~ compon~nt con~rol ~alve5 and an air csrltrol
S ~ral~ are movabl~ in response to ~he valve carrlsr.
In o~o pO~3itiOlI o th~ ~alve carrier tho compo~ent~
a~e dî~p~n~d throu~ll a mixing chambsr and in anoth~r
position of the ~alv~ carrier the mixing chamber i5
pur~ed o any rssidual components by dispensing air
10 into the mixin~ ch~mber~
For dispensing polyurethan~ foam sy~t~ms and
other plural comp~nent systems wherein two or more
compoll~nts ~re mixed immediately prior to dispensin~,
15 seYeral dispensi~g g~Ul~ arc hlowil. These gun~ hav~
beeTI dereloped b~cau~ tho components of the respec-
tiv~ plural componcllt system polymeriz~ very rapidly
upon m~xing. Upon polymerlzation the componen~s set
up into masses which cannot bg conv~eniently dis~nsod~
20 Any atte3npt to mix~n~ th~ compone~lts pr ior to
dispelasing inevi~bly le~ds to clogging or plugging
o:E the disperl~ing 5y~'c~lll.
~n any dispsnsing syst~m for plural co~apol~nt~
25 it i~ u~c~s~ary ~o mix thus~ compon~ts svmel,lhoru i~
thu disp~n~ing syst~m. Thls r~quir~s 5011;el fo~m of
mixing cllamber to always be inclu~ in th~ di~p~n~n~
~yste~,, Upon cessat~on of us~ of the pluF31 compon~nts
~omo m~rial romai~ the) mixing chamb~r and if not
~0 r~mo~sd will polym~r~zc ir~ th~ mixillg chamb~r illtO a
used mass which must be m~chanically remoYed. Thi~
of sours~ ~ s impractlcal to do. Fur~he~ tho~o
~k
~7~ Z
systems wherein the dispensing unit is continually being cycled
off and on, it is of course impractical to have to repeatedly
clean the mixing chamber~
In order to circumvent these problems spray guns have
been devised which provide for cleaning of the mixing chamber
with either a mechanical plunger or a blas~ of pressurized air
each time the stream of the individual members of the plural
component system is interrupted. One such system relies on a
piston which is machined to fit the walls of the mixing chamber
and mechanically forc~s out any remaining portions of a plural
component system upon returning the trigger of the spray gun to
an off position. Unfor~unately, the utility of this system
requires maintaining of close tolerances between the mixing
chamber and the cleansing piston. This system deteriorates
with age and wear.
U.S. Patents 3,799,403 and 3~873,023 describs spray gun
type apparatuses which utilize an air blast to purge their mixing
chambers. Both of these utilize a movable mixing chamber having
a T-shaped passage located therein. The individual components
of ~he plural component system are injected into the arms at
the top of the T and they exit out of the base of the T. In
both of these, the mixing chamber moves between a position
wherein the components of the plural component system are in-
jected into the arms of the T and a position wherein air is
injected into the arms of the T. One of the patents describes
a spray gun wherein the mixing chamber moves radially between
these two positions and in the other the mixing chamber moves
axially. In both of these, since ~he mixing chamber in fact
moves either some machining to close tolerances of those areas
of the mixing chamber wherein the openings of the arms are
located and those areas of the housing wherein both the air
and the plural components exit into the arms of the mixing
chamber must be done or seals must be used in these areas.
;2
If the parts are machined, the machine parts of course are
also susceptible to wear and any leakage between the movable
mixing chambers and other components of the housing require
disassembly of the unit to effect cleaning. If seals are used,
the seals are continuously exposed to abrasion by the edges
formed by the openings of the passageways moving across them
each time the mixing chamber moves. This of course leads to
early failureof the seals.
In any spray gun or similar device wherein the individual
components of a plural component system are injected into passage-
ways which are directly opposed to each other such as the passage-
ways in the arms of the T's of the mixing chambers of the above
noted patent, should the nozzle of the device become clogged
one individual component can be injected into or flow into the
passageway of the other components and thus mix with the other
components within its passageway. Since the noæzle is clogged
once mixing has been effected polymerization quickly follows
and these passageways become clogged. Further, since these
passageways are located in movable mixing chambers the length
Of the passageways is restricted by the size of the mixing chamber.
Th~ls, the passageways are inevitably quite short. This makes
it easier for one component to contaminate not only the passageway
of th~ other components within the mixing chamber, but also the
passageway o~ tha other components within the housing and even
into the supply lines.
In view of these problems with the prior art d~vices
it is evident there exists a need for a dispensing system for
plural component systems which utilize an air purge of the
mixing chamber thus eliminating the need for high tolerances
required in mechanical purge systems, but does not rely on a
movable mixing chamber thus eliminating the need for close
-- 3 --
X
~ ~ ~7~
tolerances between the mixing chamber and the housing and
allowing for longer component supply ducts or passageways.
Further, since different plural component systems are sprayed
under di~ferent pressure, the mechanics of the dispensing
system must be adaptable to handle different pressures and
different plural component systems.
BRIEF SUMMARY OF THE INVENTION
It is an object of this invention to provide a dispensing
system which utilizes the features outlined in the prec2ding
paragraph~ It is a further object of this invention to provide
a plural component dispensing system which is readily adaptable
to a hand-held, lightweight gun yet is foolproof in its operation
and self-purging. I~ is a further object to provide a plural
component dispensing system which is simple in its operation and
thus economically manufactured and capable of sustained use and
easy replacement of parts.
These and other objects as will become evident from a
remainder of the specification are provided in a gun for dis~
pensing a plural component system which comprises: a housing
incl'uding a first component receiving means, a second component
receiving means and a gas receiving means, said first component
receiving means connectable to a pressurized source o~ a first
component of said plural component system, said second component
receiving means connectable to a pressurized source of a second
component of said plural component system and said gas receiving
means connectable to a source of pressurized gas; a fi-st
component feed port means connected to said first component
receiving means and receiving a pressurized supply of said first
component of said plural component system from said first
component receiving means; a second component feed port means
, . .. .. . . . . . . ..... .. .. .
connected to said second component receiving means and receiving
a pressurized supply of said second component of said plural
component system from said second component receiving means;
a first valve means located in said first component feed port
means; a second valve means located in said second component
feed port means; a valve carrier means movably located in said
housing; said fi.rst valve means and said second valve means
operatively connec~ed to said valve carrier means and movable
within said first and said second component feed port means
respectively in response to movement of said valve carrier means;
a gas passage means connected to said gas receiving means and
receiving a supply of pressurized gas from said gas receiving
means, said gas passage means including a gas valve means, said
gas valve means operatively connected to said valve carrier
means and moving in response to movement of said valve carrier
means; a static mixing chamber means attaching to said housing
and including a mixing chamber, a discharge outlet connecting
to said mixing chamber, a first component inlet means connecting
to said mixing chamber, a second component inlet means connecting
to said mixing chan~er and a gas inlet means connecting to said
mi.xing chamber, said gas inlet means operatively connected to
said gas passage means, said first co~lponent inlet means opera-
tively connected to said first component feed port means and
said second component inlet means operatively connected to said
second component feed port means; trigger means movably mounted
on said housing, said valve carrier means operatively associated
with said trigger means and moving between a first position and
a second position in response to movement of said trigger means;
said first and said second valve means prohibiting the flow of
said first and said second component from said first and said
second component feed port means, respectively, into said first
and s~id second inlet means, respectively, and said gas valve
means allowing flow of said pressurized gas from said gas passage
~.~7~
means into said mixing chamber through said gas inlet means
when said valve carrier means is in said first position and
~aid first and said second valve means allowing flow of said
first and said second components from said first and said second
component feed port means into said first and said second
component inlet means, respectively, and into said mixing chamber
and controlling the flow of said pressurized gas from said gas
passage means into said gas inlet means when said valve carrier
means is in said second position; said firs~ and said second
component flowing into said mixing chamber and being discharged
out of said discharge outlet when said valve carrier means is in
said second posi~ion and said pressurized gas flowing into said
mixing chamber and discharging the contents of said mixing chamber
out of said discharge outlet when said valve carrier means is in
said first position.
Preferredly the first and second valve means include
first and second valves respectively, each having a valve head
and the first and second feed port means each include a valve
seat which the valve heads seal againstO Each of the component
inlets include a passageway leading betw~en the mixing chamber
and the respective valve seats. Each of the valves attach to
the valve carrier means and move in conjunction with movement
of the valve carrier means.
The component feed ports each comprise a closed chamber
and include openings wherein the stems of the valves pass through.
Surrounding the openings are sealing means which seal against
the valve stems.
The valve carrier means preferably includes a carrier
member, at least a portion of which is slidably mounted in a
cylindrical chamber ~orming part of the receiving chamber means.
The trigger means includes a trigger pivotally mounted to the
housing and operatively contacting the carrier member. The
~7~
carrier member includes an elongated shaft having an axially
oriented gas passageway along at least a portion of its length.
Located on the shaft is an annular flange and an annular piston.
The annular piston is sized to fit into the cylindrical chamber.
The first and se~ond valves attach to the annular flange. The
gas valve means preferably includes an elongated gas valve having
an axially extending gas passageway along at least a portion of
the length of its stem. The gas passageway in the gas valve
seals with and communicates with the gas passageway in the
carrier member. The gas valve includes a valve head which seals
against a sealing means located in the rear of the mixing chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention described in this specification will be
more fully understood when taken in conjunction with the draw-
ings wherein:
Figure 1 shows an isometric view of the plural component
dispensing gun of the invention;
Figure 2 is a side elevational view in section of one
embodiment of the dispensing gun o~ Figure l;
Figure 3 is a side elevational view also in section of
the émbodimen~ shown in Figure 2 excep~: that certain components
of the gun are shown in a different spatial relationship;
Figure 4 is an end eleva~ional view in section about
the line 4-4 of Figure 2;
Figure 5 is a side elevational view in section of a
second embodiment of the gun of Figure l; and
Figure 6 is a side elevational view in section showing
an enlargement of the forward end of the gun shown in Figure 5
and additionally showing certain components of the gun in a
different spatial relationship.
The dispensing gun shown in the figures and described
in this specification utilizes certain principles and/or concepts
as set forth and defined in the c~aims appended to this speci-
fication. Those skilled in the dispensing arts will realize
that these principles and/or concepts could be utilized in a
number of differently appearing embodiments differing from the
exact embodiment herein disclosed; however, not differing from
the principles and concepts embodied in the claims. For this
reason this invention is understood to be defined by the claims
and is not limited to the exact embodiment described in this
specification and shown in the figures.
10 DETAILED DESCRIPTION
The dispensing gun 10 shown in Figure 1 has a housing
12 made up of several component parts. These component parts
include rear section 14~ rear midsection 16, front midsection 18
and front section 20. These sections are all machined with
appropriate interlocking bosses and annuluses (not numbered)
which interlock to maintain the sections in relation to one
another. Attaching to the rear section 14 is a trigger 24.
~ttaching ~o the uppermost surface of front midsection 18 are
component inlet nipples 26 and 28. Located in the rear end of
rear,section 14 is a gas receiving port 30.
While the gun 10 of this invention can be used for dis-
pansing ma~y plural componen~ systems, it is primarily envisioned
that the gun 10 will be used for dispensing two separate types
of plural component systems. The firs~ of these systems is
generally identified as a packaging system. In this system the
individual components of the plural component system are supplied
to the nipples 26 and 28 of the gun 10 at pressures of approxi-
mately 200 pounds per square inch. Generally the packaging
system would dispense what are known in the art as f lexible poly-
urethane foam. The second of these systems is generally identi-
fied as a spray system. In the spray systems the individual
components of ~he plural component system would be delivered to
!j),~
.. , ,, .: ~ . . . . ... .
~ :~7~5~
the nozzles 26 and 28 at pressures upward of 1000 pounds per
square inch. Generally, polyurethane spray foams would be
produced by this spray system.
Because of the high pressures utilized in the spray
system certain considerations must be made which are best made
by providing certain design featur~s in the mixing chamber.
Because of the high pressures it is considered advantageous to
maintain the volume of the mixing chamber as small as possible.
This alleviates problems resulting from back pressure if clogging
occurs within the mixing chamber or down~stream from the mixing
chamber. For those plural component systems falling under the
category of packaging systems, the design features utilized for
the spray systems could be used. However, since the working
pressures are much lower it is generally not required to minimize
the size of the mixing chamber as per the case of the spray system.
To better effect mixing of the components of the plural component
system of the packaging system, it is preferable to utilize a
slightly larger mixing chamber. Since back pressures are not a
problem in the packaging system increase in size of the mixing
chamber is not a problem.
Because of these consideratiorls certain components of
the gun 10 of this invention are described as separate embodi-
ments. Other components of the gun 10, however, find dual
utility in both the spray system and the packaging system, and
in the interes~ of brevity their description will not be repeated
for both embodiments.
The embodiment pictured in Figures 2 and 3 is directed
to the packaging system. The embod~ment pictured in Figures 5
and 6 is directed to the spray system. The end elevational view
of Figure 4 is universal for both systems as is the outside
appearance of the gun 10 illustrated in Figure 1.
X - g _
Located in the front section 20 as illustrated in
Figures 2 and 3 is the mixing chamber 32. Mixing chamber 32
includes an outlet 34 through which the comple~ed plural
component system is discharged. Two dump tubes 35 and 38 lead
into the mixing chamber 32. The dump tubes 36 and 38 are set
at an oblique angle to each other. The placement of the dump
tubes 36 and 38 at an oblique angle accomplishes several things.
First of all, a turbulent flow of the individual comp~nents of
the plural component system is achieved by this oblique dis-
placement. Secondly, because the dump tubes 36 and 3B areplaced at an oblique angle with respect to one another, they
do not feed directly into one another. Additionally, placement
of the dump tubes 36 and 38 at an oblique angle allows for
elongation of these dump tubes.
In combination, the elongation of the dump tubes 36
and 38 and the lack of direct feeding into one another serve
as a preventive measure to inhibit contamination of the component
in one of the dump tubes and other portions of the system up-
stream from the dump tubes with the component flowing through
the other dump tube. As noted previously, contamination of one
component with another component in any of the lines of a plural
component dispensing system results in polymeri~ation in that
line and plugging of the line. As hereinaf~er described nipples
26 and 28 feed dump tubes 36 and 38. Should the pressure of
the component supplied to either nipples 2G or 28 be slightly
different than the pressure of the other component and should a
plug or a ¢log occur within the mixing chamber 32 or the outlet
34, the components feeding out of the dump tubes 36 and 3a into
the mixing chamber 32 will be fed at different pressures. It is
theoretically possible that should the dump tubes 36 and 38 be
in direct alignment with one another the component at a higher
X - 10 -
~ ~7'~5~
pressure could feed or be injected into the dump tube holding
the component at a lower pressure. By setting the dump tubes
36 and 38 at an angle this possibility is minimized.
Because the dump tubes 36 and 38 can be elongated even
if cross contamination occurred in one of the dump tu~es,
elongation of, coupled with the small diameter of, the dump tubes
would result in restricted flow within the contaminated dump
tube, thus also inhibiting polymerization of the plural component
system upstream from the dump tubes.
Ends 40 and 42 respectively of the dump tubes 36 and
38 feed into mixing chamber 32. The other ends 44 and 46 of
the dump tubes 36 and 38 feed into drillings 48 and 50 in front
section 20 in which seals 52 and 54 are inserted. Preferredly
the seals 52 and 54 are teflon O-rings. Front midsection 18
contains appropriate drillings 56 and 58 which lead into drill-
ings 48 and 50. The seals 52 and 54 form a fluid impervious
seal between the drillings in the respective front section 20
and front midsection 18.
The drillings 56 and 58 lead to feed chambers 60 and
20 62, respectively. l'he feed chambers 60 and 62 serve as feed
ports for the dump tubes 36 and 38. Located in one end of the
feed chambers 60 and 62 are valve seat rings 64 and 66 respec-
tively. The rings 64 and 66 are preferredly teflon rings which
are appropriately shaped to accept valve heads 68 and 70 mounted
on valve stems 72 and 74 respectively. As with the seat rings
the valve heads 68 and 70 are preferredly formed of teflon and
are shaped to form fluid impervious seals with the seat rings
64 and 66. Not shown in the figures is the fact that the valve
stems 72 and 74 are threaded and the valve heads 68 and 70 screw
on to these threads. This allows for easy replacement of the
valve heads 68 and 70 when required because of wear.
'7'~
Front midsection 18 mates with rear midsection 16.
Machined into rear midsection 16 are drillings 76 and 78 which
accept seals 80 and 82 and valve stem O-rings 84 and 86 resp~c-
tively~ In combination the seals 80 and 82 and the O-rings 84
and 86 effectively seal the feed chambers 60 and 62 with respect
to both alignment of the sections 16 and 18 and seal between the
valve stems 70 and 72 and section 16.
As seen in figure 4 leading from chamber 60 to nipple
26 is a supply passageway 88. Likewise, leading from chamber
10 62 to nipple 28 is a supply passageway 90. One of the components
of the plural component system is fed to dump tube 36 via nipple
26 by a route taking it through passageway 88 to chamber 60 pa3t
valve head 68 through seat ring 64. Likewise, the other com-
ponent is fed through nipple 28 to dump tube 38 by the corres-
ponding component associated with chamber 62.
The gun 10 illustrated in the figures and described in
this specification is adapted to dispense a two-component plural
component system. The current state of the art of plural com-
ponent sys~ems is based on two component systems. The gun 10,
20 however, could be readily adaptable to more complex component
systems by incorporating additional chambers, valves, etc.
corresponding to the two herein described. Thus, in place of
two chambers 60 and 62, three, ~our or more chambers could be
utilized. Appropriate extra nipples~ dump tubes, etc. wauld
be analogously placed in the sections 16 and 18. Additionally,
as hereinafter described, valve stems for the additional valves
could be attached to the controlling components as is herein-
after described for the attachment of valve stems 72 and 74.
As can be seen in the side elevational view in the
30 drawings, section 16 is bolted to section 18 via two hex head
bolts 92 spaced 180 degrees apart from each other. Likewise,
~ ~ 7'~j2
section 20 is attached to section 18 and section 16 attached
to section 14. These attachments, however, would be 90 degrees
out of phase from the bolts 92. The bolts used to attach the
front section 20 would be of such a length that they would not
interfere with the bolts used to attach section 16 to section 14.
Rear section 14 contains several drillings aside from
the gas receiving port 30. The gas receiving port 30 is appro-
priately threaded to receive a connecting nippleO Extending
forward from port 30 is a gas duct 94. Forward of gas duct 94
is cylindrical chamber 96. Forward of cylindrical chamber 96
and extending to the front of rear section 14 is void area 98.
An end of cylindrical chamber 96 is continuous with area 98.
Void area 98 is open at opening 100 at the bottom of the gun 10
allowing for projection of trigger 24 downwardly. In essence
the opening 100 is a rectangular passageway opened on its forward
end extending downwardly from void area 98. Opening upwardly
from void area 98 are two openings collectively identified by
the numeral 102 having a bridge 104 between them. The top of
the trigger 24 is bifurcated to fit around bridge 104 allowing
20 trigger 24 to be pivotally mounted to bridge 104 via a bolt 106.
- A valve carrier 108 fits within the interior of the
gun 10 axially centralized within sections 14 and 16. Valve
carrier 108 has a central shaft 110 which is hollow forming a
gas passageway 112 extending axially along its longitudinal axis.
Pocitioned near the forward end of the shaft 110 is an annular
flange 114. Positioned near the rearward end of the shaft 110
is an annular piston 1160 Piston 116 includes an appropriate
annular slot (not numbered) in its surface which receives an
O-ring 118. That portion of the valve carrier 108 including
30 piston 116 and the shaft 110 extending rearwardly from it fits
X - 13 -
within the cylindrical chamber 96. Piston 116 is sized to just
fit within chamber 96 and O-ring 118 makes the seal which is
impervious to pressurized gas between the piston 116 and the
walls of the chamber 96. A compression spring 120 fits between
the piston 116 and the rear wall 122 of chamber 96 biasing the
valve carrier 108 to the front of ~he gun 10 ~o a first position.
The ends of valve stems 72 and 74 are threaded and are
received in holes 124 and 126 in the flange 114. The holes 124
and 126 are threaded such that the valve stems 72 and 74 can be
fixedly located with respect to the annular flange 114 by secur-
ing nuts collectively identified by the numeral 128. By so
securing the valve stems 72 and 74 this way, the valve heads 68
and 70 can be positioned to correctly seal with the seats 64
and 66.
Trigger 24 has an arcuate area 130 on its rear surface
which fits against the fron~ portion of piston 116. Normally
the valve carrier 108 is biased forward into the first position
by spring 120. When trigger 24 is squeezed toward handle 22
against the bias of spring 120, the trigger 24 pivots about
20 bolt 106 contacting area 130 against the piston 116 depressing
the valve carrier 108 rearwardly in the housing 12 into a second
position.
Except for certain features in the front section 20
relating to the mixing chamber 32 all of the components as
hereintofore described are identical in the embodimenks as
exemplified by figures 2 and 5. These embodiments dîffer,
however, in regard to certain features specific to the air
passage systems. Further, in Figures 2 and 5 the valve carrier
108 is in the first position and in Figures 3 and 6 it is in
the second position.
~ - 14 -
In the packaging system embodiment illustrated in
Figures 2 and 3, an air valve 132 having threads on its stem
135 screws into appropriate threads on the front of valve
carrier 108. A gas passage 134 extends axially along the length
of the stem 135 of air valve 132. The gas passage 134 is con-
tinuous with the gas passage 112 in valve carrier 108. The head
136 of valve 132 flares out wi~h regard to the stem 135 of this
valve. Located behind the head is a gas port 138 which extends
transversely to the longitudinal axis of the valve and communi-
cat~s with the gas passage 134. Thus, gas passing through thevalve carrier 108 will be transmitted via passage 134 to port
138. The valve 132 fits into a drilling 140 extending through
sections 16 and 180 The drilling 140 is slightly larger than
both valve stem 135 and valve carrier 108, allowing them to
freely slide within it.
In the front of section 18 is a drilling 142 wherein an
O-ring 144 is located. When the trigger 24 is pulled toward the
rear of the gun moving valve carrier 108 backwardly to its second
position, the air valve 132 also moves rearwardly. The head 136
of this valve seals against O-ring 144 and prevents escape of
gas 'through the gas port 138 into the mixing chamber 34. Simul-
taneously valve stems 72 and 74 have been drawn toward the rear
of the gun 10.
This unseats valve heads 68 and 70 from seat rings 64
and 66. The components of the plural component system located
in the chambers 60 and 62 are thus allowed to feed into the
mixing chamber 32 through the dump tubes 36 and 38. As long as
the trigger 24 is maintained in its rearward position, the com-
ponents are fed to the mixing chamber and the appropriate plural
component system is formed therein and is ejected out of the out-
let 34. When the trigger 24 is released spring 120 pushes the
valve carrier 108 forward to its first position. In so doing
X - 15 -
~7~
valve heads Ç8 and 70 seal against seat rings 64 and 66 closing
off the supply of the components of the plural component system
feeding into mixing chamber 32. This allows compressed gas to
be fed past the air valve head 136 into the mixing chamber 32.
The compressed gas flows past the valve head 136 and purges the
mixing chamber 32 of any residual portion of the plural component
system located thereinO
In certain environments it is desirable to limit the
amount of noise polution. When the trigger 24 is in the second
position, and the valve head 132 is sealed against the O-ring
144, a small amount of pressurized gas will leak down the drill-
ing 140 into the void area 98. This inevitably produces a certain
amount of noise. For both the embodiments illustrated in Figure
2 and Figure S a noise suppression system can be incorporated.
This system is only illustrated in Figure 2, but is equally
applicable to the embodiment shown in Figure 5.
Communicating with gas passage 112 in valve carrier 108
is a transver~e gas port 146 leading into cylindrical chamber 96.
At the wall wherein cylindrical chamber 96 is connected with gas
20 duct 94 an annular teflon bushing 148 is insexted. The rear
end of the gas passage 112 is threaded to receive a hex head
bolt 150. When the valve carrier 108 is in the second position
the position of hex head bolt 150 is appropriately adjusted by
turning it into or out of the gas passage 112 such that the
head of the bolt 150 seats against the annular bushing 148 at
the same time that the head 138 of the air valve 132 seats
against the O-ring 144~ The adjustment is easily done by using
a hex key inserted through port 30. This cuts off the supply of
pressurized gas to the gas passage 112 since its open rear end is
30 now effectively plugged by the bolt 150. When the trigger 24 is
released and the valve carrier 108 moves forward, compressed gas
- 16 -
X
~:~7~
fills the chamber 96 and flows into the gas passage 112 via
the gas port 146.
While not forming a part of this invention, an appro-
priate air timing or logic system can be incorporated to the
line connecting to the gas receiving port 30. Such an air logic
system senses the increase in pressure within the gas duct 94
when it is sealed off by the interaction of bolt 150 with bushing
148. This control device then shuts off the supply of pressurized
air to the gas duct 94 after a predetermined time has expired.
Normally gas pressure will be maintained in the line for a limited
amount of seconds, such as 10 to 15 seconds. On release of the
trigger 24 and movement of the valve carrier 108 forward in
response thereto, bolt 150 no longer seals against bushing 148
and the air logic system senses the change in pressure caused by
this movement and again supplies pressurized gas to the gun 10.
In the spray gun illustrated in Figure 5 certain features
of the air injection system and mixing chamber are modified to
accommodate high pressure gas utilized in spraying systems. The
front section 20-a is modified to include screw threads 152 allow-
ing for a spray nozzle to be mounted over the outlet 34-a. Before
describing other modifica~ions to the front section 20-a the gas
valve 154 will be described. The gas valve 154 has a head 156
which is somewhat smaller than the heacl of th~ gas valve 132
shown in the other embodiments~ The valve stem 158 is threaded
to be received into the valve carrier 108 as before. Extending
behind the head 156 down a portion of the length of the stem 158
is a throated or waisted section 160. Section 160 is of a smaller
diameter than either the head 156 or the rear portion of the stem
158~ A gas passageway 162 extends through the rear portion of
the stem 158 and then branches off in a Y and opens up into the
frustro-conical shaped shoulder 164 located between the waisted
section 160 and the remainder of the stem 158.
17
-~7'~
18
~,
Referring to the detail shown in ~ig. 6, front section
20 has an annular f]ange 164 which projects inwardly at
the rear of th~ mixing chamber 32 ~orming an annular
should~r 166. m e annular shoulder 166 has an inside
diameter ~hich is slightly larger than the outside diameter
of th~ head 156 such that the head 156 can be drawn into
the an~ular shoulder 166. A curtain o~ bushing 170 fits
into an appropriate drillin~ 172 in the front section 20-a.
It s~ats against the back of annular shoulder 166 and is
retained there by sleeve 171. When the gas valve 154 is
pulled to the rear of the gun lO in response to movement
of the valve carrier 108, the head 156 fits into the
shoulder 166 and makes a gas impervious seal against the
bushing 170, e.g., Fig. 6. When the valve carrier lO~
is slid forward the head 156 moves away from the bushing
170, e.g., Fig. 5. The diameter of the centralized
opening 174 in the bushing 170 is generally slightly
larger than the diameter of the waisted section 160 of
the gas .valve 154. This allows gas to flow up the gas
passage 162 through the drilling 140, through the
opening 17A in the bushing 170, and fi~ally through
the center of the shoulder 166 into the mixing
chamber 32-a to purge or clean the mixing chamber.
The mixing chamber 32-a in the embodiment
illustrated in ~igs. S and 6 is generally of a
smaller diameter than the mixing chamber illustrated
in the embodiment in Fig. 2. Further, its diameter
is only slightly larger than the diameter of the hea~
156 of the gas valve 154. For example, the ~iameter
of the chamber 32-a could be 0.140 inches and the
diameter of tlle hea~ 156 coul~ be 0.125 inches.
Because of thc hi~h pressure whicl- thc componcl~ts
of the plural componcnt system are subjected ~o in
a spray system, maintaining the si~e relationship
between the mixing chamber 32-a, the head 156, as well as
locating the opening oE the dump tubes 36-a and 38-a close to
the rear of the mixing chamber 32-a results in minimizing back
pressure and increased efficiency of the gun 10. Because the
bushing 170 is made of teflon it is easily slid over the head
156 even though the head 156 is of a slightly larger diameter
than the diameter of the opening 174 in the bushing.
In operation, the nipples 26 and 28 are connected to
appropriate supplies of the components of the plural component
system. A pressuri~ed gas system with or without an air logic
control is attached to the gas receiving port 30. When the
trigger 24 is forward of the handle such that the valve carrier
108 is in a forward or first position, air is ejected into the
mixing chamber cleansing i~. When the trigger is depressed
toward the handle, the air cleansing of the mixing chamber is
halted and the valves controlling the components of the plural
component system open allowing the individual components to feed
into the mixing chamber and be expelled from the outlet. When
the trigger is released it returns to its irst position halting
the flow of the components to the mixing chamber and starting
the flow of the air to pùrge the same.
-- 19 --
