U.S. patent number 3,589,610 [Application Number 04/824,856] was granted by the patent office on 1971-06-29 for variable flow rate spray gun with pressure relief.
This patent grant is currently assigned to Spraying Systems Co.. Invention is credited to Ted Lee Butterfield, Fred W. Wahlin.
United States Patent |
3,589,610 |
Wahlin , et al. |
June 29, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
VARIABLE FLOW RATE SPRAY GUN WITH PRESSURE RELIEF
Abstract
A variable pressure spray gun with an unloader valve built into
the gun so that when the spray pressure is turned off fluid
circulated to the gun is returned to the fluid system. Movable
valves in the gun selectively direct all of the fluid developed in
the pressure system through the outlet of the gun or through a
bypass return line to the system and are arranged to selectively
vary the pressure of the fluid delivered by diverting selected
amounts of the pressurized fluid to the return line. The gun is
arranged with counterbalancing fluid forces aiding a gun closing
spring and with stop means for selectively limiting pressures
delivered by the gun.
Inventors: |
Wahlin; Fred W. (St. Charles,
IL), Butterfield; Ted Lee (Naperville, IL) |
Assignee: |
Spraying Systems Co.
(N/A)
|
Family
ID: |
25242491 |
Appl.
No.: |
04/824,856 |
Filed: |
May 15, 1969 |
Current U.S.
Class: |
239/125;
239/583 |
Current CPC
Class: |
B05B
1/3093 (20130101); B05B 9/01 (20130101) |
Current International
Class: |
B05B
9/01 (20060101); B05B 9/00 (20060101); B05B
1/30 (20060101); B05b 009/00 () |
Field of
Search: |
;239/124,125,126,127,526,527,528,583,412 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Love; John J.
Claims
We claim:
1. A spray gun including a gun barrel having a fluid chamber
defined within the barrel and spaced valve seats in the chamber,
one of said valve seats defining a nozzle supply seat and being
formed and adapted to afford communication with a nozzle on the
barrel, the other of said valve seats defining a fluid return seat
and being formed and adapted to communicate with a fluid return
line opening into said barrel, a fluid pressure supply line
connected with said barrel and opening into said chamber, a movable
valve operating member in said chamber and having spaced valve
portions cooperable with said valve seats, said valve portions
being spaced so that when one of said portions is seated against
said one valve seat, the other portion is spaced from the other
valve seat and so that when said other portion seats against said
other valve seat, said first named portion is spaced from said
first named valve seat, a second chamber defined within said
barrel, said operating member being in the form of a rod extending
within said second chamber, a piston on said rod within said second
chamber, means communicating the pressure within said first named
chamber to said second chamber so as to exert closing forces
against the piston within said second chamber and nozzle closing
forces on said rod, and actuating means connected with said valve
operating member to move the member respectively so that said valve
portions move toward and away from said valve seats.
2. The structure of claim 1 wherein the valve portion adapted to
seat against the fluid return seat of the chamber is tapered and
movable gradually within said seat to provide a metered opening
through said seat until said valve portion moves fully against the
said seat.
3. The structure of claim 1 characterized by and including spring
means for biasing said rod toward the nozzle supply seat.
4. The structure of claim 1 characterized by and including guiding
and supporting elements on said rod in said first named chamber and
supported by the wall of said first named chamber.
5. The structure of claim 1 wherein said valve portion which is
cooperable with said return valve seat has a tapered portion
adapted to progressively move within said seat and eventually
completely close said seat, said tapered portion being effective to
gradually close the outlet area through said seat as said portion
moves within said seat, and adjustable stop means are associated
with said actuating means so as to adjustably limit the travel of
said tapered portion within said seat and thus limit the flow of
fluid through said return seat and vary the outlet pressure through
said nozzle seat.
6. A spray gun including a gun barrel having a fluid chamber
defined within the barrel and spaced valve seats in the chamber,
one of said valve seats defining a nozzle supply seat and being
formed and adapted to afford communication with a nozzle on the
barrel, the other of said valve seats defining a fluid return seat
and being formed and adapted to communicate with a fluid return
line opening into said barrel, a fluid pressure supply line
connected with said barrel and opening into said chamber, a movable
valve operating member in said chamber and having spaced valve
portions cooperable with said valve seats, said valve portions
being spaced so that when one of said portions is seated against
said one valve seat, the other portion is spaced from the other
valve seat and so that when said other portion seats against said
other valve seat, said first named portion is spaced from said
first named valve seat, a second fluid chamber defined within said
gun barrel, said operating member being in the form of a rod
passing through said second chamber and having a piston fixed
thereto and subject to the pressure forces developed within said
second chamber, said rod being hollow and having a first pressure
inlet located within said first chamber and a fluid pressure outlet
located within said second chamber so that the pressure in said
first chamber is communicated through the hollow portions of said
actuating rod to said second chamber to exert nozzle closing forces
on said actuating rod, and actuating means connected with said
valve operating member to move the member respectively so that said
valve portions move toward and away from said valve seats.
7. The structure of claim 6 characterized by and including spring
means for biasing said rod toward the gun closing position.
8. A spray gun including means defining a manipulating handle and a
barrel carried by said handle, an actuating rod reciprocably
mounted for movement within said barrel, said barrel having a
nozzle outlet at one end thereof, said barrel having a fluid
chamber in one end thereof with spaced valve seats at opposite ends
of said chamber, seat, of said seats nearest the nozzle outlet
defining a nozzle outlet seat and the other seat defining a fluid
return seat, a fluid pressure supply line communicating with said
chamber between said valve seats, said actuating rod extending
within said chamber and having a first valve closure element
cooperable with said nozzle outlet seat and a second valve closure
element cooperable with said fluid return seat, a fluid return line
connected to said barrel and communicating with a passage within
said barrel aligned with said fluid return seat, means on said
handle for reciprocating said rod, said valve portions being spaced
so that when said first element is seated against its nozzle seat,
the second valve element is spaced from said return seat so as to
allow fluid from said inlet to pass through said fluid return seat,
and so that when said second valve element seats against said
return seat, said first named valve element is spaced away from
said nozzle outlet seat to allow supply of the full inlet pressure
through said chamber and through said nozzle, a second chamber
within said barrel and a piston carried by said actuating rod and
positioned within said second chamber, and means for communicating
said first chamber with said second chamber in a manner such that
the pressure within said first chamber operates against said piston
to provide forces on said operating rod in a direction tending to
close said first valve element against its associated seat, the
effective cross-sectional area of said piston being such that the
pressure exerted thereaginst essentially balances the opposite
pressure forces exerted on said rod when said first valve element
is away from its seat.
9. A spray gun including a gun barrel having a fluid chamber
defined within the barrel and spaced valve seats in the chamber,
one of said valve seats defining a nozzle supply seat and being
formed and adapted to afford communication with a nozzle on the
barrel, the other of said valve seats defining a fluid return seat
and being formed and adapted to communicate with a fluid return
line opening into said barrel, a fluid pressure supply line
connected with said barrel and opening into said chamber, a movable
valve operating member in said chamber and having spaced valve
portions cooperable with said valve seats, said valve portions
being spaced so that when one of said portions is seated against
said one valve seat, the other portion is spaced from the other
valve seat and so that when said other portion seats against said
other valve seat, said first named portion is spaced from said
first named valve seat, the valve portion cooperable with said
return valve seat having a tapered portion adapted to progressively
move within said return seat and eventually completely close said
seat, said tapered portion being effective to gradually close the
outlet area through said return seat as said tapered portion moves
within said seat, actuating means connected with said valve
operating member to move the member respectively so that said valve
portions move toward and away from said valve seats, and adjustable
stop means associated with said actuating means so as to adjustably
limit the travel of said tapered portion within said return seat
and thus limit the flow of fluid through said return seat while
establishing a maximum pressure in said chamber and through said
nozzle seat.
Description
The present invention is directed to new and useful improvements in
spray guns.
A number of spray gun arrangements are known to the art. When using
spray guns with relatively high pressure pump systems the overall
fluid system is usually sensitive to the specific components
utilized. For example, the pump supplying the pressure usually has
a particular rated flow rate at a particular pressure and the
nozzle orifices used with the guns have particular ratings in terms
of pressures and flow rates. Previous spray gun systems have been
more or less sensitive to the specific components in the system in
that for particular pumps particular nozzle orifice ratings must be
utilized. If the nozzle orifice and pump are not properly matched,
as, for example if a nozzle orifice is too small for the rating of
its supply pump, the nozzle may cause a buildup in pump pressure
with a resultant overloading of the pump and a possible "burnout"
of the pump motor and/or bearings. Also, in previous spray gun
systems it has been customary in many installations to utilize some
form of bypass or unloader valve in the system and arranged so
that, when the spray gun is turned off, the valve opens and diverts
fluid from the pressure side of the pump supplying the fluid to the
gun to the return side of the system so as to avoid pump damage.
This has required use of a separate valve in the fluid system. When
such valves are utilized, they must be matched in terms of pressure
and flow rate with the other components in the system so that they
operate properly to divert fluid from the high pressure side of the
system to the return line when the gun is turned off.
With the foregoing in mind, the major purposes of the present
invention are to so arrange a spray gun that the fluid system is
far less sensitive to specific pressure and flow ratings of nozzles
and pumps, to so arrange a spray gun that the outlet pressure and
flow rate of the gun are variable and easily controllable between
zero pressure and a preselected maximum pressure which may be
selected by the operator of the gun to be the same as the rated
pressure of the pump or a lesser pressure which is within the
capabilities of the pump, to so arrange a spray gun that shock
forces on the gun are minimized when the spray gun is turned off,
to so arrange a spray gun that pressure forces acting on a valve
controlling member within the gun are essentially balanced, and to
so arrange a spray gun that the valve elements which are used to
control pressure are also used to return fluid from the pressure
side of the system to the return side when the spray gun is turned
off.
These and other objects and purposes will become more apparent in
the course of the ensuing specification and claims when taken with
the accompanying drawings, in which:
FIG. 1 is a diagrammatic view of a typical spraying system with
which the present invention is concerned;
FIG. 2 is a sectional view through the barrel of the gun
illustrated in FIG. 1 and illustrating the gun in a closed
position;
FIG. 3 is a sectional view similar to FIG. 2 and illustrating the
barrel of the spray gun in the fully open position;
FIG. 4 is a sectional view similar to FIGS. 2 and 3 but
illustrating a valve controlling member of the gun in a partially
open position;
FIG. 5 is an enlarged elevation of the spray gun of FIGS. 1--4;
FIG. 6 is a sectional view of a portion of the spray gun;
FIG. 7 is a detailed view of a trigger stop assembly utilized in
the invention; and
FIG. 8 is another view of the trigger stop utilized in the present
invention.
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 spray gun
defined by an operating handle 11, a gun barrel 12, a nozzle
orifice member 13 at the outlet end of the gun barrel, and an
operating trigger 14. The trigger is pivotally mounted on the gun
for reciprocating an actuating or control rod 15 to open and close
the gun for flow through the nozzle orifice 13. A fluid supply line
16 is connected to the gun barrel and supplies fluid under high
pressure from a pump 17 which is driven by a motor 18. A fluid
return line 19 is also connected to the barrel 12 and leads to a
suitable reservoir or drain in the fluid system. The pump 17 has an
intake line 20 supplied with fluid from a suitable source.
As will be noted in FIGS. 3 and 5, the spray gun includes a barrel
support 21 which projects forwardly from handle 11 and which is
formed integrally therewith. The barrel support 21 may have a
depending collar 22 formed on the end thereof which collar receives
one end portion of the barrel and which is held fixed thereto as by
a nut 23. Trigger 14 is pivotally mounted on the barrel support 21
as by a pivot pin 24 and is connected to the actuating rod 15 as by
means of a connection generally designated at 25. Spray gun handles
for connection with a barrel and with a trigger connected to an
actuating rod for the gun are known to the art as, for example, in
Wahlin et al. U.S. Pat. No. 3,181,798, issued May 4, 1965, and
Williams et al. U.S. Pat. No. 3,379,376, issued Apr. 23, 1968, the
disclosures of which are hereby incorporated by reference.
In accordance with the present invention, the barrel 12 is hollow
and the actuating and control rod 15 extends within the opening
therein and generally coaxially with the barrel. The hollow
interior of the barrel at the outlet end portion thereof is formed
on a somewhat larger diameter then the remainder of the hollow
opening through the barrel and defines a first fluid chamber 26.
The outlet end of this chamber includes a first valve seat element
27 disposed across the end of the chamber. The valve seat element
may be a screw machine part with a passage 28 formed therethrough
and with a ring 29 of nylon or other soft material surrounding the
opening 28 and opposed to the chamber. The element 27 may be held
in position by a coupling 30 which is threaded onto the outlet end
of the barrel and which is used to hold the nozzle element 13 at
the end of the barrel. A flange 31 of the nozzle element may abut
against the valve seat element 27 so as to hold the valve seat
element in abutting relation against the end of the gun barrel. The
other end of the chamber 26 is defined by a tapered valve seat 32.
A ring of nylon or other soft material may be positioned in this
tapered valve seat, although it is not necessary with accurately
machined valving surfaces. The valve seat 32 may, if desired, be
defined by a separate replaceable insert so that a worn valve seat
is easily replaced. The opening within the gun barrel is of a
reduced diameter rearwardly of the chamber 26 as designated at
33.
An inlet fitting 34 is connected to the gun barrel intermediate the
ends of the chamber 26 and has the inlet pressure fluid supply line
16 coupled thereto by a suitable coupling fitting (not shown in
FIGS. 2, 3 and 4) so as to afford communication between the
pressure side of the pump and the chamber 26. An outlet fitting 35
is fixed to the gun barrel at a position spaced rearwardly from the
inlet fitting 34 and is adapted to afford communication between the
passage 33 and the return conduit 19 which may be coupled to the
fitting 35 through means of a suitable coupling.
The hollow part of the barrel rearwardly of the passage 33 may have
a slightly larger diameter so as to define a second pressure
chamber 36 which is axially spaced rearwardly of the first chamber
26 and the passage 33. The rear end of this chamber may be closed
by an insert 37 through which actuating rod 15 passes in a sealing
relation.
The control rod 15 includes spaced valve closure elements 38 and 39
within chamber 26 and adapted for selective cooperation with the
valve seats 29 and 32 at the ends of the chamber 26. For example,
the valve element 38 on the forward end of the control rod may be
tapered or flat so as to seat against the ring 29 and thus close
the opening through the ring. The valve element 39 on the other
hand is preferably tapered so as to allow movement of the extreme
rearward end of the valve element 39 within the valve seat 32 and
progressively restrict flow area between the valve element 39 and
the valve seat as the valve element 39 moves within the seat under
influence of movement of the control rod 15 to the right as appears
in FIG. 2. The larger diameter of the frustoconical shape of the
valve element 39 is sufficiently large so as to seat fully against
and fully close the valve seat 32 when the control rod 15 is moved
to the extreme right-hand position as is illustrated in FIG. 3.
Valve closure element 39 thus meters and varies the flow through
the valve seat 32 as it moves within the seat. While it is
preferred to use a tapered valve 39, a flat valve surface may be
used to abut against seat 32 to close the bypass opening
therethrough. A flat valve surface will also perform some metering
of the flow as it moves toward and away from the valve seat.
Square or hexagonal guiding portions 40 and 41 are formed on the
control rod 15 within the chamber 26 for a sliding and supporting
engagement with the cylindrical wall of chamber 26.
It should be understood that the chamber 26, passage 33, chamber 36
and the remainder of the hollow interior of the gun barrel may be
formed by boring and counterboring the gun barrel to the
appropriate diameters as illustrated, followed by machining the
barrel at the inner end of the chamber 26 so as to define the valve
seat 32.
The valve elements 38 and 39 are spaced from one another so that
when one valve element, as, for example, the gun closing element
38, seats against the ring 29, fluid from the inlet is passed to
the chamber and is then diverted through the fluid return seat 32
and passes through passage 33 to the return line 19 through the
fitting 35. By pulling trigger 14 towards the handle 11 of the gun,
the tapered portion of the valve element 39 gradually moves within
valve seat 32 so as to gradually restrict the outlet opening
through the valve seat 32. This movement pulls the valve element 38
away from its associated seating ring 29 and opens chamber 26 to
the nozzle 13 so that fluid from the chamber 26 may pass through
the valve seat 39 and through the nozzle orifice 13a. At the same
time, since the flow area through valve seat 32 is partially open
as is illustrated in FIG. 4, part of the fluid is diverted through
passage 33 for flow through the fitting 35 and to the return line
19.
When the control rod 15 is withdrawn to the maximum under influence
of trigger 14, the valve element 39 closes against the seat 32 as
is illustrated in FIG. 3. At this time all of the fluid from inlet
conduit 16 passes through the chamber 26 and through the opening in
the valve seat 27 and through the orifice 13a of the nozzle. By
setting the control rod at a particular axial position between the
extreme positions of FIGS. 2 and 3, the pressure of the fluid
delivered through the outlet orifice 13a may be selectively varied
between zero and the full operating pressure developed by the pump
of the system (as when the valve element 39 fully closes against
seat 32).
Also, when the gun is turned off and the valve element 39 seats
against the seating element 29, all of the liquid from the pump for
the system is returned through the return conduit 19 so as to avoid
pressure buildup and damage to the pumping system.
In further accordance with the invention, the control rod 15 is
hollow through a portion of its length to define a passage 42
therethrough and extending between an inlet opening 43 in the rod
between the guiding and supporting elements 40 and 41 and an
aperture 44 which is positioned in the actuating rod at a location
such that it is within the chamber 36. A piston 45 is defined on
the control rod 15 forwardly of the aperture 44. The piston 45 may
include an O-ring 46 which is adapted to make good bearing contact
with the opposed cylindrical wall of the chamber 36 within the
barrel. Pressure in the chamber 26 is thus communicated through the
opening 43 and through the hollow portion of the control rod 15
into chamber 36. This pressure works against the piston 45 in a
direction tending to force the control rod 15 to the left in FIG. 2
or in a gun closing direction. The pressure developed within the
chamber 36 thus counteracts or counterbalances the pressure acting
on the control rod when the gun is in an open position as
illustrated in FIG. 3. In FIG. 3 it will be noted that the pressure
acting on the effective seal area of valve element 39 and the valve
seat 32 tends to move the control rod 15 to the right in FIG. 3 or
in a gun opening direction.
The cross-sectional areas may be calculated so that the pressure
forces within chamber 36 approximately balance the pressure forces
in chamber 26. The cross-sectional area of chamber 36 minus the
cross-sectional area of control rod 15 where it passes through
element 37 should equal the effective cross-sectional seal area of
valve element 39 and seat 32. It should be noted here that by
providing the area relations as thus stated, operating pressures
less than the full operating pressure, as for example when the
control rod is in an intermediate position as illustrated in FIG.
4, will still produce opposite forces on the rod in the chambers 26
and 36 which substantially balance one another. The counterbalance
thus provided allows use of a light spring to bias the trigger
toward the closed position.
In further accordance with the invention, a pring 47 is used to
bias the trigger and the control rod 15 toward the closed position.
This spring biases an auxiliary rod 47a which is axially aligned
with the control rod 15. Rod 47a is slidably supported in a sleeve
48 which extends into a bore in the gun handle 11. Sleeve 48 is
slidably mounted in the bore. A second sleeve 48a is axially
aligned with sleeve 48 in the bore. Sleeve 48a has a threaded
exterior portion as does a portion of the bore threadably received
within the gun handle. The spring 47 is positioned within aligned
bores in the sleeves 48 and 48a. The extension of sleeve 48 within
the bore is limited by the position of sleeve 48a. Sleeve 48a has a
knurled knob 48b on the end thereof to enable rotation of the
sleeve and adjustment of the position of sleeve 48.
The end of sleeve 48 adjacent trigger 14 is enlarged to define a
stop element 49. As may be appreciated in FIGS. 6, 7 and 8, stop
element 49 includes a pair of parallel flats 50 and 51 positioned
on opposite sides of rod 47a at equal spacings. The flats 50 and 51
are spaced a distance such that flanges or sidewalls 52 and 53 of
the trigger 14 may pass over these flats when they are in the
relationship shown in FIG. 7. A manipulating element 54 may be a
separate part which is held on sleeve 48 by a set screw 54a.
Element 54 may be knurled to permit the operator to easily rotate
it and the stop element 49 together.
For operator convenience the element 54 may have spaced shoulders
54b and 54c which abut against the gun handle and limit rotation of
the element between the two positions illustrated. The portions of
the stop element 49 between the flats 50 and 51 are positioned a
greater distance from the axis of rod 47a than are the flats 50 and
51. When the stop element 49 is rotated through 90.degree. from the
position illustrated in FIG. 7 to the FIG. 8 position, the element
49 blocks the rearward movement of the trigger as by abutment of
the trigger flanges against the element. In the position of FIG. 7,
the trigger may be pulled back until seat 32 is completely closed.
Thus, two distinct spraying pressures may be provided through
selective axial positioning of the sleeve 48 and element 49. A
maximum degree of spraying pressure is provided by positioning the
stop element 49 as illustrated in FIG. 7 wherein the trigger 14 and
the control rod 15 may be withdrawn toward the handle and thus open
the seat 29 and close seat 32 so that all of the flow from the pump
must pass through the nozzle 13. A lesser degree of operating
pressure is afforded by rotating the stop element to the position
illustrated in FIG. 8. In FIG. 8 the trigger flanges abut against
the element 49 at a lesser degree of pivotal movement of trigger 14
with an attendant lesser degree of opening movement of control rod
15 which allows seat 29 to open and seat 32 to partially close,
thereby allowing part of the flow to pass through the nozzle and
part to pass through seat 32. The lower pressure obtainable may be
regulated through axial adjustment of the sleeve 48 as by rotating
the knurled control knob 48b on the end of the sleeve 48a. Rotation
in opposite directions positions the stop element 49 at varying
axial positions toward and away from the handle 11 and the trigger
14, so as to thus allow the user to selectively set a lower
operating pressure for the gun. As the trigger is allowed to move
further back, the flow through seat 32 becomes more restricted and
the operating pressure increases.
By virtue of the arrangement of the spray gun as disclosed herein,
exact matching of the nozzle orifice with the supply pump in terms
of flow rates and pressures is not as critical as in the case of
prior spray guns. For example, if the nozzle orifice used with the
gun is too small for the rated pressure and flow rate of the
pumping system, and causes a buildup in pressure which might
overload the pumping system (with return valve closed or with a
small return valve opening), the maximum pressure may be easily
reduced to a safe value as By (a) operator manipulation of the
control rod so that it is at a safe pressure position, or (b) by
setting the stop 49 in the trigger blocking position of FIG. 8 and
setting the stop 49 at an axial position such that valve 39 never
fully closes against seat 32 and the bypass through seat 32 is
sufficient to provide a safe maximum operating pressure.
If desired, the stop 49 and manipulating element 54 may be arranged
so that the trigger flanges abut against the manipulating element
54 when the stop element is in the FIG. 7 position. Then, by proper
axial positioning of stop element 49 and manipulating element 54,
two distinct spraying pressures may be provided below the maximum
pressure obtainable with the valve seat 32 fully closed. For
example, a lower pressure limit is obtainable when the stop element
is in the trigger blocking position of FIG. 8 and a higher pressure
limit is then obtained when the stop element is in the position of
FIG. 7. When arranged this way, the gun provides three distinct and
settable spraying pressures, namely a maximum pressure when the
stop element is withdrawn sufficiently as to allow valve element 39
to fully close seat 32, and two distinct lower pressures by axial
positioning of the stop element so that stop element 49 and the
manipulating element 54 block and limit trigger movement at two
distinct positions corresponding to two distinct and different
relief outlet areas through the valve seat 32.
The spray gun arrangement also provides for a bypass of the
pressure fluid when the gun is turned off. In this regard it should
be noted that the pressure developed by the spraying system is
gradually reduced as the control rod 15 is moved toward a nozzle
closed position, because, as this happens, the flow area through
valve seat 32 gradually increases. When the gun is fully shut off,
the pressure in the pumping system is much lower than the normal
spraying pressure.
* * * * *