U.S. patent number RE28,842 [Application Number 05/489,589] was granted by the patent office on 1976-06-08 for unloader valve for spray guns.
This patent grant is currently assigned to Spraying Systems Co.. Invention is credited to Ted Lee Butterfield.
United States Patent |
RE28,842 |
Butterfield |
June 8, 1976 |
Unloader valve for spray guns
Abstract
An unloader type valve for spray guns supplied from pumps to
limit operating pressures of the pump when the spray gun is
stopped. The valve utilizes an adjustable spring to select pressure
forces for opening the valve and a variable flow passage from the
valve to an outlet when the valve is open, the allowing matching of
the valve to the precise operating pressures and flow rates in
spray gun and pumping system installations. UNLOADER VALVE FOR
SPRAY GUNS
Inventors: |
Butterfield; Ted Lee
(Naperville, IL) |
Assignee: |
Spraying Systems Co. (Wheaton,
IL)
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Family
ID: |
26856523 |
Appl.
No.: |
05/489,589 |
Filed: |
July 18, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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55319 |
Jul 6, 1970 |
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797196 |
Feb 6, 1969 |
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Reissue of: |
160014 |
Jul 6, 1971 |
03729018 |
Apr 24, 1973 |
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Current U.S.
Class: |
137/470 |
Current CPC
Class: |
F16K
17/0433 (20130101); F16K 17/082 (20130101); Y10T
137/7739 (20150401) |
Current International
Class: |
F16K
17/04 (20060101); F16K 17/08 (20060101); F16K
017/04 () |
Field of
Search: |
;251/284,285,20,22,23,119,121,118,122
;137/614.2,524,538,543.21,535,540,496,511,469,475,470,469,471,472 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Miller; Robert J.
Attorney, Agent or Firm: Mann, Brown & McWilliams
Parent Case Text
This application is a continuation-in-part of my copending
application filed July 6, 1970, under Ser. No. 55,319, now
abandoned, which in turn is a continuation of my earlier
application Ser. No. 797,196, filed Feb. 6, 1969, now abandoned.
Claims
I claim:
1. An unloader valve defined by a hollow valve body having an inlet
and an outlet leading to an interior working space in the body, a
pressure operated piston movably mounted in the interior space of
said body .Iadd.thereby subdividing said interior space into spaces
on the opposite sides of said piston.Iaddend., said valve body
having a valve seat of smaller cross-sectional area than said
piston and formed around said inlet .[.passage.]. , said piston
including a reduced portion adapted to engage said seat to close
off flow through said body, said valve body including .Iadd.a fluid
.Iaddend.passage .[.means.]. .Iadd.defined in said valve body
.Iaddend.communicating the space between said seat and said piston,
when said piston is away from said seat, with an outlet from said
body, .Iadd.said fluid passage being the sole source of fluid
communication between said inlet and said outlet, said passage
being in communication with a lower face of said piston at one end
and an upper face of said piston and said outlet at another
end.Iaddend., adjustable means .Iadd.disposed in said passage
between said lower face of said piston and said upper face of said
piston .Iaddend.for varying the flow area through said passage
.[.means.]. .Iadd.thereby providing variable control of the fluid
pressures exerted on said faces of said piston under maximum fluid
flow through said body.Iaddend., a spring positioned between said
piston and an abutment in said valve body to exert closing forces
on said piston, and means for adjusting the spring pressure to
adjust the closing forces exerted by said spring on said piston to
thereby vary the pressure force in said inlet .[.passage.].
necessary to move said piston away from said seat, the entire
cross-sectional area of said piston being subjected to the pressure
in said space when said piston is away from said seat to thereby
hold the piston away from said seat as long as the total force due
to pressure in said space exceeds the closing forces of said
spring.
2. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 1
wherein said passage .[.means.]. is defined by a passage positioned
laterally of said interior .[.space.]. .Iadd.spaces .Iaddend.and
communicating with said space on opposite sides of said piston.
3. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 2
wherein said adjustable means for regulating flow is defined by a
flow restricting element, and said element is variably positionable
across a portion of said passage .[.means.]. by an adjusting screw
carried by said body.
4. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 3
wherein said element is variably positionable across a portion of
said passage .Iadd., said portion of said passage
.Iaddend.extending transversely to the axis of said piston and said
passage has a shoulder positioned over said portion and limiting
movement of said element over said portion to a position providing
a small flow space through said portion.
5. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 1
wherein said means for adjusting spring pressure includes a movable
abutment engaging one end of said spring, said abutment being
axially movable against said spring by a screw threaded in said
body.
6. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 5
wherein said passage .[.means.]. is defined by a passage in said
body and positioned laterally of said interior space, said outlet
being defined by a bore opening into said .Iadd.interior
.Iaddend.space on the side of said piston opposite to the inlet
side, said passage communicating with said .Iadd.interior
.Iaddend.space by a first bore positioned transversely of said
passage and opening into said .[.working.]. .Iadd.interior
.Iaddend.space on the inlet side of said piston and a second bore
coaxial with said outlet bore and extending transversely of said
passage.
7. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 6
wherein said adjustable means for varying the flow area is defined
by an element positioned for movement axially of said passage and
movable across said second bore to restrict flow therethrough, said
valve including means for moving said element and stop means for
limiting movement across said second bore to a position leaving a
small flow space through said second bore.
8. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 7
wherein said stop means is defined by a shoulder in said
passage.
9. The .[.structure.]. .Iadd.unloader valve .Iaddend.of claim 7
wherein said means for moving said element is defined by a screw
threaded in said body and carrying said element.
Description
This application is directed to improvements in bypass or relief
valves of the type used with pump supplied spray guns.
Pump supplied spray guns of the type found in agricultural and
industrial applications include some provision for preventing
excessive build-up of pressure on the pump when the spray gun is
stopped. Usually it is not desirable to stop the pump at the time
the spray gun is stopped. Unless some provision is made for
relieving the pressure, the pressure can increase to a level where
the pump motor, pump and/or motor bearings may be overloaded and
seriously damaged or ultimately destroyed, particularly in positive
displacement pumps. Even centrifugal pumps or the drive therefor
may be damaged from an overloaded condition due to an increase in
pressure.
In the past, spring biased pressure relief valves have been used to
limit the pressure rise when spraying has stopped. These open at a
pressure somewhat above the normal spraying pressure and hence the
pressure and work of the pump are increased when the gun is idle.
Other types of valves such as unloaders use a bypass line and
spring biased valve system which opens the bypass when the pressure
increases at the time that the spray gun is stopped. The valve
arrangement is such as to reduce the pumping system pressure well
below the spraying pressure, once the spray gun is stopped and the
valve for the bypass is open.
The spring biased pressure relief valves are not desirable where
the spraying pressure is very close to the maximum rated pressure
for the pumping system and because of unnecessary wear of the
pumping system. Also, as pointed out in my earlier applications,
the opening and closing of the piston in the unloader type of valve
is dependent upon the relationships in flow area through the valve
as well as operating pressures and flow rates. These operating
pressures and flow rates may vary from one installation to the next
and may vary in the same installation from time to time due to wear
or changes desired by the operator. Hence, the unloader valve has
heretofore been designed for specific conditions of operating
pressures and flow rates. When so designed, the unloader valve is
not easily adaptable to other pressure and flow rate conditions and
does not accommodate changing conditions.
My earlier applications were directed to unloader valves
specifically designed to provide a variable orifice for the flow
passage through the valve to thereby vary the flow rate through the
valve. The valves were designed so that the same basic unloader
valve assembly could be utilized with a variety of variable
orifices, preferably in the form of removable orifice plates so
that the exact flow area required for proper operation of the valve
with any particular pumping system and spray gun could be
accommodated. The arrangement, however, was not easily adjustable
when the same pumping system is used with a different operating
pressure.
With the foregoing in mind, the major purposes of the present
invention are to provide a spring biased type unloader valve which
quickly reduces operating pressures on the pumping system when a
spray gun is stopped; to provide such a valve wherein the pressure
necessary to open the valve may be quickly and easily adjusted over
a wide range; to provide such a valve with variable flow facilities
so that the flow rate through the valve may be varied over a
relatively wide range while, when combined with the variable
pressure feature of the valve, permits an extremely wide range of
operating pressures and flow rates and a highly versatile
accommodation of different operating conditions; to provide such a
valve with built-in safety features which prevent adjustment of the
valve to a point where the pumping system could be damaged; to
arrange such a valve so that it can easily be adjusted in the field
by an operator so as to properly match the exact operating
conditions of the particular spray gun and pumping system with
which the valve is associated; and to arrange such a valve for
simple manufacturing techniques.
These and other purposes will appear from time to time in the
course of the ensuing specification and claims, when taken in
connection with the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of a typical spray gun and pumping
system therefor and with a valve incorporating the principles of
the present invention connected with the system and gun;
FIG. 2 is a perspective view of the unloader valve illustrated in
FIG. 1; and
FIG. 3 is a cross-sectional view of the valve illustrated in FIGS.
1 and 2.
Like elements are designated by like characters throughout the
specification and drawings.
With specific reference now to the drawings, and in the first
instance to FIG. 1, the numeral 10 generally designates a hand
manipulated spray gun of the type utilizing a trigger or lever to
open an outlet from the gun to direct a spray therefrom. A fluid
supply line 11 is connected to the gun and supplies fluid thereto
from a pump 12 which is illustrated as a positive displacement type
of pump. A motor 13 drives the pump. Spraying assemblies of this
type in the past have included unloader valves in a bypass line
from the fluid supply line 11 to the inlet of the valve. Such a
bypass line is designated at 14 with the unloader valve 15 of the
present invention connected in the bypass line. The inlet of the
valve is connected by a line 11a to supply line 11. The bypass line
14 is connected to the inlet line 16 for the pump. Inlet 16 is also
connected to a suitable fluid source (not shown).
In systems of this type, a pressure gauge 17 may be included in the
fluid supply line 11. Other optional facilities may be included in
the same line.
The unloader valve in systems of this general type are intended to
close under normal spraying conditions when the spray gun 10 is
open and delivering fluid therefrom. When the spray gun 10 is
closed, the pump 12 increases the pressure in the line 11
immediately and this immediately opens the unloader valve to divert
fluid back to inlet of the pump to prevent a pressure build-up.
The unloader valve of the present invention, as is seen in FIGS. 2
and 3 is defined by a hollow valve body 17 having an .[.outlet.].
.Iadd.inlet .Iaddend.fitting 18 threaded in an end bore of the body
and an outlet fitting 19. Inlet fitting 18 may be formed as an
exteriorly threaded plug having an internally threaded passage 20
communicating with an interior passage 21 of reduced diameter. The
inlet fitting may of course be provided with exterior threads to
receive a suitable hose coupling instead of the interior threads
shown. A variety of sizes and styles of inlet fittings may be
provided for the present valve to enable adaptation of the valve to
existing conduits of different styles and sizes. Outlet fitting 19
is defined by a threaded bore 22. The bore 22 extends at right
angles to the axis of the inlet fitting and communicates with an
interior operating chamber or space 23 in the valve body.
The valve body is formed with a tubular extension 24 axially
aligned with and opposite to the inlet fitting 18. The extension 24
carries an adjusting screw 25 for varying the operating pressure of
the valve in a manner which will be described. The valve body also
includes a tubular portion 26 on the side thereof opposite to the
outlet 19. The tubular portion 26 carries an adjusting screw 27 for
adjusting the flow rate through the valve in a manner which will be
described.
The operating chamber 23 of the valve has a piston 28 slidably
mounted in an enlarged portion of the chamber. The peripheral wall
of the piston has a groove in which an O-ring 29 is mounted for
sealing the piston to the chamber wall. Piston 28 has a portion of
reduced diameter 30 facing the inlet 21. The overall piston
cross-sectional area is considerably greater than the
cross-sectional area of the inlet passage 21. Reduced portion 30 of
the piston carries a long wearing insert 31 of Teflon or equivalent
material and this insert includes a projection 32 which is adapted
to seat against a valve seat 33 formed around the inlet passage 21
at the inner side thereof to close off flow through the inlet
passage 21 and to the interior space of the valve. A coil spring 34
biases the piston 30 to the closed position illustrated in FIG.
3.
In valves of this general type the piston will move to the right
(as seen in FIG. 3), when the force of the pressure in the inlet
passage 21 rises to a point exceeding the force of the spring 34.
When the piston moves to the right and thus opens the valve to
receive flow from inlet 21, the pressure required to hold the
piston in the open position is much less than the pressure required
to open the piston due to the fact that, when the piston is open,
the entire piston cross-sectional area is subjected to
pressure.
Spring 34 has one end thereof seated in a recess 35 in the piston
and the other end thereof carried by a spring retainer 36 which is
carried on the end of the adjusting screw 25. The spring retainer
36 has a groove in the peripheral wall thereof. An O-ring 37 is
seated in this groove to seal the bore of the tubular extension 24
against leakage. The exterior end of the screw 25 is slotted as at
38 to receive a screw driver or equivalent adjusting tool. By
rotating the screw, the spring retainer 36 is moved inwardly and
outwardly within the tubular extension to thereby adjust the force
developed by the spring 34 against the piston. A lock nut .[.38.].
.Iadd.38a .Iaddend.is carried by the screw 25 and is adapted to
bear against the end of the tubular extension 24 to thereby lock
the adjusting screw 25 in a selected axial position.
The end of the operating chamber 23 adjacent to the inlet passage
communicates with a bypass passage formed through the tubular
portion 26. The bypass passage is defined by a first bore 39
extending at right angles to the valve body and opening into the
chamber 23. Bore 39 communicates with a passage formed as bore 40
extending at right angles to the bore 39 and formed through the
tubular portion 26. Bore 40 communicates with another bore 41 which
is formed coaxially with the outlet 19 and which opens into the
operating chamber 23 on the side of the piston opposite to the
inlet side. The cross-sectional flow area of the passage means
defined by the bores 39, 40 and 41 should be at least as great and
preferably greater than the flow area of the inlet passage 21.
Adjusting screw 27 is threadably received in a plug 42 which is
threaded into an enlarged bore portion 43 in tubular portion 26.
Bore 43 is coaxial with bore 40. Screw 27 has a cylindrical
extension 44 with a flat end face 45. The extension 44 is sealed to
the wall of an interior bore in plug 42 by means of an O-ring 46
carried in a peripheral groove in the extension.
Screw 27 has a slotted exterior end as at 47 for receiving a screw
driver or similar adjusting tool. A lock nut 48 is carried by the
screw and is adapted to abut against the exterior end of plug 42 to
fix the screw in a selected axial position. The end face 45 of the
cylindrical portion 44 may be moved inwardly and outwardly over the
bore 41 to thus selectively vary the flow area through the bore 41
and thus vary flow rate through the valve.
It is preferred to form the cylindrical portion 44 on a diameter
slightly larger than the diameter of bore 40 while having the
enlarged bore portion 43 overlying the bore passage 41. This
enlargement commences at a shoulder 50 spaced within the outline of
bore 41. The cylindrical portion 44 may thus abut against this
shoulder, whereupon the inward adjustment of the cylindrical
portion 44 is limited to a position allowing some flow through the
valve. This prevents some accidental positioning of the cylindrical
portion 44 which would close off the bore 41 completely and thus
present dangerous pressure conditions in the pumping system. The
cylindrical portion is movable to the right (FIG. 3) to a position
fully opening bore 41.
In operation, and with the valve as disclosed in FIGS. 2 and 3
installed in a pump supplied spray gun assembly as illustrated in
FIG. 1, the adjusting screw 25 is moved to a position where the
spring force exerted on the piston is relatively light. The flow
rate adjusting screw 27 is rotated until the cylindrical portion 44
moves to its dead end position within the plug 42, thus fully
opening the bypass passage. The pumping system is then started and
the spray gun opened. Adjusting screw 25 is then rotated until the
force developed by spring 34 is sufficient to close the piston
inert 31 against the seat 33. The screw 25 is preferably turned
slightly more (as for example one-fourth or one-half turn) than
that just necessary to close the valve. The spray gun is then
turned off. With the bypass passage in a maximum flow rate
condition, flow through the bypass passage will be sufficiently
rapid to cause a large pressure drop and this will cause the piston
to close, whereupon pressure builds up and the piston will open.
This "open and closed" condition will be repeated in a cyclic
manner.
The flow rate adjusting screw 27 is then rotated to move the
cylindrical portion inwardly to gradually restrict flow. This
inward movement of the cylindrical portion 44 is continued until
the cyclic reciprocation of the piston stops. The screw 27 is then
rotated an additional small amount such as one-quarter turn,
whereupon the lock nut is rotated to fix the screw in the adjusted
position. The setting is then checked by opening and closing the
spray gun several times. If the piston should cycle between open
and closed positions when the spray gun is opened, the adjusting
screw 25 is then rotated inwardly to create additional closing
forces by the spring 34 until the cycling stops. If the piston
should continue to cycle when the spray gun is closed, the flow
rate adjusting screw 27 is then rotated to further restrict
flow.
In the event that no cycling of the piston occurs when the spray
gun is open but that the piston fails to close, unscrewing the
adjusting screw 27 to increase the flow through the bypass passage
will relieve the pressure conditions against the piston
sufficiently to allow the spring 34 to close the piston.
As may be noted in the foregoing, the valve is easily set up to
match exact operating conditions encountered in any spray gun and
pump assembly. It is adjusted in the field for proper conditions of
use. As these conditions change, due to wear or because of a
manmade change in conditions or any other cause, the adjustments
will enable proper use of the valve.
* * * * *