Note: Descriptions are shown in the official language in which they were submitted.
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SPRAY GUN WITH DUAL MODE TRIGGER
Cross Reference To Related Ap~lication
This application is related in part to Canadian
application File No. 2,095,913 filed May 10, 1993.
Technical Field
The invention relates to paint spray guns and more
particularly to a hand held paint spray gun in which the
trigger has two operating modes for turning the gun on and
off.
Backqround Art
Many jobs require the use of hand held paint spray
guns. These include certain jobs in manufacturing and jobs in
automotive refinishing shops, for example. When an operator
is required to frequently use a spray gun over a long period
of time, the operator may develop fatigue in the hand and
wrist. Fatigue can be aggravated by repetitive motions, such
as by frequently squeezing the spray gun trigger with the same
finger motion, by unbalanced forces on the hand and wrist, by
the weight of the gun and by the force required to operate the
gun trigger.
A typical prior art hand held paint spray gun includes
a gun body having a nozzle assembly mounted on one end and
having a handle depending from adjacent an opposite end. A
trigger is attached to the gun body to pivot towards and away
from the handle. When an operator holds the gun by the handle
and squeezes the trigger, an air valve is opened and then a
valve needle is moved to open a fluid valve. The air valve
supplies any air required for atomization and for shaping the
spray pattern. If the trigger is only partially squeezed, the
fluid valve may be only partially opened to permit the
operator to apply a lighter coating, for example, for
feathering when touching up a coating. The spray gun also
includes an adjustable stop which limits either trigger travel
or the valve needle travel to adjust the maximum paint flow
from the gun when the trigger is fully squeezed. In the prior
art hand held spray gun, the trigger has a relatively long -~
travel. Consequently, the operator's fingers must move the
trigger over a relatively large arc when squeezing or
releasing the trigger. Also, a relatively high force has been
required to overcome friction when squeezing the trigger and
to assure that the gun turns off when the trigger is released.
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sclosure Of Invention
The invention in one broad aspect pertains to a hand
held liquid spray gun including a gun body having first and
second ends, a liquid atomization nozzle assembly secured to
the first end and a handle extending from adjacent the second
end for holding the spray gun. A main trigger controls the
discharge of liquid from the spray gun. The spray gun is
characterized by the trigger having first and second operating
modes with first means responsive to trigger movement for
varying the amount of liquid discharged from the spray gun as
a function of trigger movement between fully off and a
predetermined maximum liquid flow when the trigger is in the
first operating mode. Second means is responsive to a
predetermined small trigger movement when the trigger is in
the second operating mode for controlling the flow of liquid
discharged from the spray gun between fully off and the
predetermined maximum liquid flow. The trigger is moveable
over a greater range of movement in the first operating mode
than in the second operating mode.
More particularly the invention is directed to a hand
held palnt spray gun which reduces stress on the fingers and
hand of an operator. The spray gun has a gun body, a nozzle
assembly and a handle, as in prior art guns. According to the
invention, a trigger mounted on the gun body has two different
operating modes. The trigger is moved in a radial direction
towards and away from a pivot axis to select between the two
operating modes. In a first operating mode, the trigger is
squeezed to move over a predetermined arc in operating the
gun. When the trigger is partially squeezed, the paint flow
is reduced to permit feathering of the applied coating.
Movement of the trigger is connected through mechanical
linkages to move a valve needle. Friction on the valve needle
is minimized to minimize the required trigger force.
When the trigger is positioned for the second
operating mode, the trigger stroke is greatly reduced. In
this position, the mechanical linkage to the valve needle is
disengaged. Trigger movement over an arc significantly -
smaller than the predetermined arc for the first mode operates
a pneumatic valve assembly to cause the valve needle to be
opened. The pneumatic valve assembly has a low operating
force to reduce potential finger and hand fatigue. In the
second operating mode, the spray gun is either fully on or
fully off.
Accordingly, the invention seeks to provide ~n
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~_,proved hand held paint spray gun having a trlgger with dual
operating modes.
Other aspects and advantages of the invention will
become apparent from the following detailed description of the
invention and the accompanying drawings.
Brief Description Of The Drawings
Fig. 1 is a left side elevational view of a paint
spray gun according to the invention;
Fig. 2 is a is an enlarged vertical cross sectional
view throughout the center of the paint spray gun of Fig. 1;
Fig. 3 is an enlarged fragmentary cross sectional view
taken along line 3 - 3 of Fig. 2 showing a portion of the
mechanical linkage for moving the valve needle in a first
operating mode;
Fig. 4 is a cross sectional view through a trigger
actuated valve for operating the spray gun in a second mode,
with the valve shown closed;
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Fig. 5 is a cross sectional view through the trigger actuated valve,
similar to Fig. 4, but with the valve shown open;
Fig. 6 is a perspective view showing details of the actuator arm which
moves the valve needle;
Fig. 7 is a fragmentaly left side view showing details of the trigger, the
actuator arm and the valve needle assembly, with the trigger positioned for
operating the spray gun in the first mode;
Fig. 8 is a fragmentary left side view, similar to Fig. 7, but with the
trigger positioned for operating the spray gun in the second mode;
Fig. 9 is a fr~grnent~ry side elevational view of the spray gun with its
cover removed showing the trigger squeezed while in the first operating
mode;
Fig. 10 is a fragmentary side elevational view, similar to Fig. 9, but
showing the trigger squeezed while in the second operating mode;
Fig. 11 is a fragmentary side elevational view, similar to Fig. 9, but
showing the trigger in the first operating mode and positioned forward to
facilitate using an auxiliary trigger;
Fig. 12 is a fragmentary side elevational view, similar to Fig. 10, but
showing the trigger in the second operating mode and positioned forward to
20 facilitate using the auxiliary trigger; and
Fig. 13 is an enlarged cross sectional view showing details of the fluid
valve.
Best Mode For Carrvin~ Out The Invention
Turning now to Fig. 1 of the drawings, a hand held paint spray gun 10
25 is illustrated in accordance with a preferred embodiment of the invention.
The spray gun 10 generally includes a body 11 having a front end 12 to which
a fluid nozzle assembly 13 is secured and having a rear end 14. A knob 15 is
secured to the rear body end 14 for adjusting the maximum flow of paint from
the gun 10. A handle 16 depends from the body 11 adjacent the rear end 14.
30 A fluid hose 17 and a compressed air hose 18 are shown secured to a lower
free end 19 of the handle 16. However, it will be appreciated that the fluid
hose 17 and the air hose 18 may be secured to the rear body end 14 or that the
fluid hose 17 can be secured to a fitting 20 on the nozzle assembly 13 and
supported from the handle end 19. The spray gun 10 is shown as having a
main trigger 21 and an optional auxiliary trigger 22. The main trigger 21 is ---
mounted to pivot towards and away from the handle 16 and the auxiliary
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trlgger is mounted to pivot towards and away from a top 2~ of the gun body
As will be described in greater detail below and is shown in detail in
the other figures, the main trigger 21 has two distinct operating modes. When
5 the trigger 21 is positioned in the first operating mode as shown in solid andan o~cl~ol gradually squeezes the trigger 21, a mechanical linkage mounted
on the gun body 11 gradually opens a valve needle to provide an increasing
flow of fluid to the nozzle assembly 13. ~or the second operating mode, the
trigger 21 is pushed radially upwardly towards its pivot point on the gun body
10 11 and is moved towards the handle 16 to the position shown by the dashed
lines 24. When the trigger 21 is subsequently moved a short distance towards
the handle 16, the trigger 21 engages and moves a push bar 25 to open a valve
in the gun body. Opening the valve causes a piston to be pneumatically
moved to turn the spray gun 10 fully on. When the trigger 21 is released, the
15 spray gun 10 is turned off. Optionally, the trigger 21 may be pivoted forwardto the position shown by the dashed line 26. When the trigger is in the
forward position, an area 27 between the trigger 21 and the handle 16 is
opened up to permit the operator to grasp the gun body 11 in the area 27 for
using the auxiliary trigger 22. The auxiliary trigger 22 is parti~ularly useful
20 when the spray gun 10 is aimed downwardly for painting generally horizontal
surfaces.
Details of the spray gun 10 are shown in the cross sectional view of
Fig. 2. A molded plastic skeleton 28 and an outer cover 29 form the gun body
11 and ~e handle 16 as an integral unit. The no~zle assembly 13 consists of
25 a spray head 30 secured to the front body end 12 by a head retaiI~ing ring 31and arrair cap 32 secured to the spray head 30 by a retaining ring 33. The air
hose 18 is connected to a passageway 34 in the handle 16. The fluid hose 17
passes through a passageway 35 in the skeleton 2~ and connects to a passage
36 in the spray head 30. The passage 36 cormects with a chamber 37 which
30 leads to a fluid discharge orifice 38. Normally, a valve needle 39 is seated in
the spray head 30 to close the orifice 38. The valve needle 39 extends axially
through the gun body 11 to the knob 15.
Pressurized air is delivered to the handle passageway 34 from the air
hose 18. As shown in Figs. 2 and 3, a front surface 40 on a piston 41 is
35 normally seated against a surface 42 on an air valve bushing 43 to block the
flow of air to a passageway 44 in the gun body 11. The passageway 44 is -
connected for delivering ~o~ tion air and pattern shaping air to the spray
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head 30 and thence to the air cap 32. A knob 45 on the gun body 11 controls
a pattern shaping air valve 46 to control the discharge of such air from patternshaping orifices 47 on the air cap 32.
As best shown in Fig.3, the piston 41 is part of a piston assembly 48
5 which includes an air valve stem 49, a co~ res~ion spring 50, a retainer ring
51, a valve needle seal 52 and a plate 53. The piston 41 has a stepped axial
bore 54. The air valve stem 49 is generally tubular and slides in an axial
direction in the piston bore 54. An enlarged diameter end flange 55 retains
the air valve stem 49 in the bore 54. The retainer ring 51 is an internal
10 retainer ring which engages the piston bore 54. The coll.plt;s~ion spring 50 is
colllplessed between the air valve stem flange 55 and the retainer ring 51.
The seal 52 preferably has a U-shaped cross section and forms a low friction
sliding seal between the piston 41 and the valve needle 39 which extends
axially through the piston assembly 48. The seal 52 is retained by the plate
15 53. A compression spring 56 presses against the plate 53 to cause the piston
surface 40 to seat against the surface 42.
A T-block 57 is positioned to slide in an axial direction on the valve
needle 39 forward of the air valve stem 49. The T-b~ock 57 has an opening
58 through which the valve needle 39 passes and has two radially directed
20 lugs 59. Side portions 60 on an actuator arm 61 are moved to engage the lugs
59 for in turn moving the valve needle 39 to turn on the spray gun 10 when it
is operated in a first mode. As will be discussed in further detail below,
squeezing either the trigger 21 or the auxiliary trigger 22 rotates the actuatorarrn 61 to urge the T-block 57 towards the rear end 14 of the gun body 11.
25 This pushes on the air valve stem 49, moving the piston surface 40 clear of
the surface 42 on the air valve bushing 43. Air then flows between the
surfaces 40 and 42 to the passageway 44 and is discharged from the nozzle
assembly 13 for atomizing fluid and for shaping the pattern of the atomized
fluid in a known manner.
As the T-block 57 moves the piston assembly 48 further back, the plate
53 contacts a collar 62 which is secured to the valve needle 39. Further
movement of the piston assembly 48 causes the valve needle 39 to move and
ples~ ed fluid from the fluid hose 17 is discharged from the orifice 38 and
atoll~ized. The spacing between the piston assembly 48 and the collar 62
35 when the spray gun 10 is offassures that the flow of atomization and pattern
shaping air will start prior to the discharge of fluid from the orifice 38. The
amount of fluid discharged will depend on various factors, such as the fluid ~~
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pressure, the size of the orifice 38, the distance that the valve needle 39 is
moved and the properties of the fluid. A rear plug 63 is secured ~ the rear
body end 14 and the knob 15 is threaded into the rear plug 63. The knob 15
forms an adjustable stop against which the collar 62 abuts when the fluid
5 valve is fully opened. Rotating the knob 15 adjusts the m~ximllm travel of
the valve needle 39 when the fluid valve is opened. An annular seal 64 fits
between the knob 15 and the rear plug 63. The spring 56 extends between the
plate 53 and the seal 64. The spring 56 functions both as a return spring for
the piston assembly 48 and as a spring for m~int~ining a force on the seal 64
10 to forrn a self adjusting air tight seal between the rear plug 63 and the knob
15.
The spring 56 is located in a chamber 65. A small passage 66 in the
air valve bushing 43 connects the chamber 65 to the handle passage 34 to
allow a limited flow of the ~I~;s~ ed air into the chamber 65. A much
15 larger opening 67 in the air valve bushing 43 also allows the pressurized air to
flow from the handle passage 34 into a chamber 68 formed between the air
valve bushing 43 and the piston 41. Thus, air pl~s~ e is normally balanced
on both sides of the piston 41 and the piston 41 does not present an
irnpediment to axial movement of the piston assembly 48 when the spray gun
20 10 is turned on or off by movement of either of the triggers 21 or 22. The
rear chamber 65 is connected through a passage 69 to a normally closed valve
70 (Figs. 4 and 5). As will be ~liscllssed in greater detail below, when the
spray gun 10 is in the second operating mode and the trigger 21 is squeezed,
the valve 70 opens and the chamber 65 is vented to atmosphere, establishing
25 an air pres~ e dirrerelltial across the piston 41. The air p~C~SSUl~ differential
is sufficient to move the piston rearwardly until the collar 62 abuts the knob
15 and the valve needle 39 is fully opened.
Figs. 4 and 5 show details of the valve 70. The passage 69 connects to
a chamber 71 in the skeleton 28. An annular ridge 72 surrounds the passage
30 69 to form a seat for the valve 70. A co,lll ,~;s~.ion spring 73 is co,.lp-essed
between the valve 70 and a retainer ring 74 to urge the valve 70 to seal
against the ridge 72, closing the passage 69. A push bar 25 is secured to the
skeleton 28 to slide in an axial direction. An end 76 on the valve 70 is
engaged by a bumper 77 on the push bar 25. A co,l")lession spring 78 urges
35 the push bar 25 to the position shown in Fig. 4 wherein the push bar 25 does
not affect closure of the valve 70. When the trigger 21 is positioned for the
second operating mode and is squeezed, a surface 79 on the trigger 21
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Tages and moves a free end 80 of the push bar 25, thus
causing the valve 70 to tilt off of the ridge or seat 72, as
shown in Fig. 5. When this occurs, the passage 69 is vented
through the chamber 71 to atmosphere to in turn vent the
chamber 65 (Fig. 2). When the chamber 65 is vented, the air
pressure differential across the piston 41 moves the piston 41
against the force of the return spring 56 to cause the spray
gun 10 to be turned fully on. When the trigger 21 is released
and the valve 70 is again closed, the pressure in the chamber
65 will become equalized with the pressure in the chamber 68
and the spring 56 and a valve needle return spring 81, (Figs.
2 and 3), shut off the spray gun 10.
Details for the mechanism for mechanically operating
the spray gun 10 when either of the triggers 21 or 22 is
squeezed are shown in Figs. 2, 3, 6 and 7. As shown in Fig.
6, the actuator arm 61 has a generally U-shaped body 85. The
body 85 consists of an upper portion 86 from which two sides
87 and 88 depend. The sides 87 and 88 are spaced to straddle
the skeleton 28. Aligned openings 89 and 90 extend through
the sides 87 and 88, respectively and a tubular portion 91
extends outwardly from each side 87 and 88 around the opening
89 or 90. Each side 87 and 88 is shaped into a lower hooked
shaped side portion 60 which terminates at a gap 92. Finally,
a rearwardly opening recess 93 is formed in the upper portion
86, as best seen in the cross section of Fig. 2.
Two aligned pins 94 are integrally formed on opposite
sides of the skeleton 28 for mounting the actuator arm 61 and
the trigger 21 (one of the pins 94 is shown in Fig. 7). The
actuator arm 61 is positioned to straddle the skeleton 28 with
one of the pins 94 located in each opening 89 and 90 so that
the actuator arm 61 can pivot on the gun body 11. The trigger
21 has a U-shaped upper portion 95 with two parallel sides 96
which similarly straddle the actuator arm 61. The _wo sides
96 have aligned openings 97 which engage the projections 91 on
sides 87 and 88 of the actuator arm 61. The openings 97 are
formed with two overlapping lobes 98 and 99 with a small apex
100 on one side opposite a smoothly curved side 101. The
shape of the openings 97 permits the trigger 21 to be in a ----~
first position wherein the opening lobes 98 pivot on the
projections 91 when the spray gun is in a first operating
mode, as shown in Fig. 7. The trigger 21 may be pushed
upwardly until the projections 91 snap into the second lobe 99
to engage a second operating mode for the spray gun 10, as
shown in Fig. 8. Or, the trigger 21 may be pulled downwardly
to reengage the first operating mode.
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When the trigger 21 is positioned for the first operating mode,
inwardly directed tabs 102 on the trigger sides 96 abut the sides 60 of the
actuator arm 61, as shown in Figs. 3 and 7. When the trigger 21 is squeezed,
the tabs 102 push on and pivot the actuator arm 61. The lugs 59 on the T-
5 block 57 are confin~d within the curved actuator arm sides 60. Consequently,when the actuator arm 61 pivots due to squeezing the trigger 21, the T-block
57 is pushed towards the rear of the spray gun 10. This in turn pushes on the
air valve stem 49 to move the piston 41 for initi~ting air flow to the nozzle
assembly 13 and to move the valve needle 39 to initiate fluid discharge from
10 the nozzle assembly 13. As shown in Figs. 7 and 9, the surface 79 on the
trigger 21 is spaced to clear the push bar 25 so that the valve 70 is not
actuated when the trigger 21 is squeezed while in the first operating mode. ~~
A push rod 103 extends between the recess 93 on the top of the
actuator arm 61 and a recess 104 on the auxiliary trigger 22 (Fig. 2). When
15 the auxiliary trigger 22 is squeezed or pivoted towards the gun body 11, the
push rod 103 is moved towards the front of the spray gun 10 to pivot the
actuator arm 61. Consequently, either of the triggers 21 or 22 is capable of
pivoting the actuator arm 61 for turning on the spray gun 10. The amount of
fluid discharged from the spray gun 10 will depend upon how far either
20 trigger 21 or 22 is squeezed when the spray gun is in the first operating mode.
Fig. 8 is a fragmentary view showing details of the operation of the
trigger 21 when positioned in the second operating mode. The trigger 21 is
pushed upwardly until the actuator arrn projections 91 snap into the hole
lobes 99 on the trigger sides 96. When the trigger 21 is in this position, the
25 tabs 102 have the same radial spacing from the axis of the pins 94 and the
projections 91 as the gaps 92 on the sides 60 of the actuator arm 61.
Consequently, when the trigger 21 is squeezed towards the gun handle 16
(Figs 1 and 2), the tabs 102 move into the gaps 92 and the actuator arm 61 is
not pivoted to actuate the spray gun 10. However, when the trigger 21 is
30 positioned as shown in Fig. 8 and squeezed, the trigger surface 79 contacts
the push bar surface 80 and moves the push bar 25 for opening the valve 70,
as shown in Figs. 8 and 10. Consequently, the spray gun 10 will be turned
fully on by the resulting movement of the piston 41. When the main trigger
21 is positioned in the second operating mode, the auxiliary trigger 22 is still35 functional for operating the spray gun 10.
The trigger 21 has no separate return spring. When positioned in the ---~~
first operating mode as shown in Fig. 7, the spring S6 pushes the piston 41 to ~
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its normally closed position when the trigger 21 is released. The force of the
spring 56 through the piston 41, the air valve stem 49, the T-block 57 and the
actuator arm 61 pivots the trigger 21 to its released position. The trigger 21 is
held in this position by friction. When the trigger 21 is positioned in the
5 second operating mode as shown in Fig. 8, the spring 78 moves the push bar
25 to its normal position when the trigger 21 is released. The force of the
spring 78 also pivots the trigger to its released position. Since the push bar 25
only moves a short distance when the trigger is squeezed to actuate the gun
10, the released trigger will be returned only a short distance. Consequently,
10 the trigger 21 will be positioned close to the handle 16 and only require a
short movement to turn on the spray gun 10 when operated in the second
mode and only requires an operating force to overcome friction and the force
of the springs 78 and 73.
Figs. 11 and 12 show a fragmentary portion of the spray gun 10 with
15 the trigger 21 pivoted forward away from the handle 16 to open the area 27
between the handle 16 and the trigger 21. Fig. 11 shows the trigger 21
positioned for the first operating mode and moved forward and Fig. 12 shows
the trigger 21 positioned for the second operating mode and moved forward.
The trigger 21 is held in the forward position by friction or by a suitable
20 detent (not shown). When the trigger 21 is in the for~vard position, the spray
gun body 11 is easily grasped between the handle 16 and the trigger 21 to
facilitate using the auxiliary trigger 22, for example, when aiming the gun 10
downward to spray a horizontal surface.
Various techniques are used in the spray gurl 10 for mininli7ing the
25 force and the length of the stroke or arc required to operate the trigger 21 in
the first operating mode. Very low trigger force is required for the second
operating mode since only a low force is required to operate the valve 70. It
has been found that the trigger operating force is affected by various factors.
Reducing the diameter of the valve needle 39 to a smaller diameter than used
30 in prior art spray gun valve needles reduces the drag area and polishing the
valve needle 39 reduces packing friction. Preferably, the valve needle 39 has - ~-
a tliameter S0.1 inch (S2.54 mm) at least at the seals to reduce friction.
Fur~er, at the seals the valve needle 39 should be polished to an average
surface roughness of ~15 micro inch (S0.0000254 mrn). The use of a
polytetrafluoroethylene (Teflon) packing 105 which is loaded by a spring 106 ,_r~
(Fig. 2) reduces friction and a~ltorr~ahcally adjusts the packing 105 to controlpacking tightness and to control drag. The design of the trigger provides a
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mechanical advantage of about 7: 1, while m~int~ining ergonomic trigger
travel and form. The air valve formed between the piston surface 40 and the
air valve bushing surface 42 has a surface contour which allows full air flow
with a shorter trigger travel. Preferably, the air valve is constructed to open at
5 a rate which gives a ration of square inches of flow area per inch of travel for
the piston 20.65 (419 rnm2 of air flow area per 25.4 mm of piston travel),
which is 3 times greater than a typical prior art trigger operated air
atomization paint spray gùn.
The contour of the end of the valve needle 39 which seats in the spray
10 head 30 also provides quick opening of the fluid valve while m~int~ining
consistent feathering control of fluid flow in the first operating mode. Fig. 13shows details of the contours for a preferred design for fluid valve 110. At a
forward end of the fluid chamber 37 in the fluid head 30, the chamber is
curved with blend radii to a conic section 111 which connects to a straight
15 section leading to the fluid discharge orifice 38. The conic sectio:. 111 is in
the for~n of a frustum of a right circular cone having slightly tapered side
walls. The valve needle 39 has at its forward end, a first conic sectffon 112
which connects with a second, forward section 113. The first conic section
112 is in the form of a frustum of a right circular cone having sides tapered at20 an angle less than the sides of the fluid head sectffon 111. Preferably, the
spray head conic secffon 111 is tapered to have an included vertex angle of
about 20~ and the valve needle conic secffon 112 is tapered to have an
included vertex angle of about 12~. The valve needle sections 112 and 113
join at an annulus 114 which is of a diameter to seat against a central region
of the spray head section 111. The forward valve needle section 113 is a cone
terrnin~hng at a vertex 115. Preferably, the section 113 has a vertex angle of
about 40~. The forward sections 112 and 113 of the valve needle 39 may be
formed of a low friction material to minimi7e friction when the annulus 114 is
withdrawn from the spray head section 111 during triggering.
Finally, low friction seals~52 and 107 (Figs.2 and 3) which have U-
shaped cross secffons are used to reduce drag forces between the valve needle
39 and the piston 41 and between the piston 41 and the air valve bushing 43,
respectively. The spray gun 10 may be constructed to require an ~ct~l~ting
force no greater than 2 pounds (0.9 Kg.) to actuate the gun 10 in the first
35 operaffng mode and an actuaffng force no greater than 1 pound (0.45 Kg.)
when operaffng the gun in the second operating mode. Preferably, the trigger
21 pivots over an arc of at least 10~ when operated in the first mode to permit
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accurate control of fea~ering and the trigger~2Q p9iv7O~s8ov0er an arc of less than
10~ and preferably no greater than 5~ when operated in the second mode.
It will be appreciated that various modifications and changes may be
made to the above described preferred embodiment of a hand held spray gun
5 without departing from the spirit and the scope of the following claims.
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