U.S. patent number 3,775,030 [Application Number 05/203,562] was granted by the patent office on 1973-11-27 for diaphragm pump.
This patent grant is currently assigned to Wanner Engineering Inc.. Invention is credited to William F. Wanner.
United States Patent |
3,775,030 |
Wanner |
November 27, 1973 |
DIAPHRAGM PUMP
Abstract
An improved high pressure diaphragm pump comprising an improved
pumping unit including a pumping chamber, a transfer chamber, a
reciprocating piston means defining one end of the transfer
chamber, a diaphragm defining the other end of the transfer chamber
bias means urging the diaphragm toward the piston, and a stop for
limiting the movement of the diaphragm toward the piston; and an
improved pressure control and unloader valve incorporating a
floating check valve which is responsive to a gradual restriction
in the discharge line and is also responsive to the shock wave
formed as a result of a sudden shut-off of the discharge line.
Inventors: |
Wanner; William F. (Edina,
MN) |
Assignee: |
Wanner Engineering Inc.
(Hopkins, MN)
|
Family
ID: |
27560514 |
Appl.
No.: |
05/203,562 |
Filed: |
December 1, 1971 |
Current U.S.
Class: |
417/388 |
Current CPC
Class: |
F04B
1/14 (20130101); F04B 43/026 (20130101); F04B
43/0045 (20130101); F04B 43/067 (20130101); F16K
17/085 (20130101); F04B 49/24 (20130101); Y10T
137/2607 (20150401); Y10T 137/2615 (20150401); Y10T
137/2617 (20150401) |
Current International
Class: |
F04B
1/14 (20060101); F04B 43/06 (20060101); F04B
43/02 (20060101); F04B 49/24 (20060101); F04B
49/22 (20060101); F04B 43/00 (20060101); F04B
43/067 (20060101); F16K 17/08 (20060101); F16K
17/04 (20060101); F04B 1/12 (20060101); F04b
009/10 (); F04b 035/02 () |
Field of
Search: |
;417/388,385
;60/54.5R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,054,328 |
|
Apr 1959 |
|
DT |
|
1,034,030 |
|
Jul 1958 |
|
DT |
|
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Sher; Richard
Claims
I claim:
1. An improved diaphragm pump comprising:
a casing housing a pumping chamber adapted to contain the fluid to
be pumped, a transfer chamber adapted to contain hydraulic fluid,
and a hydraulic fluid reservoir;
a diaphragm means including a diaphragm having a transfer chamber
side and a pumping chamber side, said diaphragm being supported by
said casing, disposed between said pumping chamber and said
transfer chamber and adapted for reciprocation toward and away from
said pumping chamber;
piston means adapted for reciprocation between a power stroke and a
suction stroke and having one end in communication with said
transfer chamber;
means for reciprocating said piston means;
bias means for urging said diaphragm means away from said pumping
chamber with one end of said bias means connected with said
diaphragm means and the other end supported by said piston means
for movement therewith; and
means for replenishing the hydraulic fluid in said transfer chamber
including a stop means for limiting the movement of said diaphragm
means away from said pumping chamber and a valve means positioned
between said transfer chamber and said hydraulic fluid reservoir
for selectively allowing flow of hydraulic fluid from said
hydraulic fluid reservoir to said transfer chamber when said valve
means is open, the force needed to open said valve means and the
force exerted on said diaphragm by said bias means being such that
the sum of the said forces is greater than atmospheric
pressure.
2. The improved diaphragm pump of claim 1 wherein said diaphragm
means includes a stem extending from the transfer chamber side of
said diaphragm and into an opening in said piston means.
3. The improved diaphragm pump of claim 2 wherein said bias means
is a spring member disposed between said stem and said piston means
such that relative deflection of said spring member during
reciprocation of said piston means occurs only as a result of a
loss of hydraulic fluid in said transfer chamber.
4. The improved diaphragm pump of claim 1 wherein said bias means
is a coil spring.
5. The improved diaphragm pump of claim 1 wherein said stop means
includes an annular shoulder portion adapted to engage the transfer
chamber side of said diaphragm.
6. The improved diaphragm pump of claim 7 wherein said diaphragm
means includes a follower plate disposed on the pumping chamber
side of said diaphragm.
7. The improved diaphragm pump of claim 8 wherein said annular
shoulder portion and said follower plate include cooperating canted
surfaces adapted to engage opposing sides of said diaphragm.
8. The improved diaphragm pump of claim 1 wherein said first valve
means is a check valve which prevents flow of hydraulic fluid from
said transfer chamber to said hydraulic fluid reservoir, and which
allows flow of hydraulic fluid from said hydraulic fluid reservoir
to sad transfer chamber providing a preselected pressure
differential between said hydraulic fluid reservoir and said
transfer chamber is attained.
9. The improved diaphragm pump of claim 11 wherein said check valve
includes a valve member and a spring member urging said valve
member toward a closed position.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to an improved diaphragm
pump and more specifically to an improved high pressure diaphragm
pump having an improved pumping unit and an improved pressure
control and unloader valve.
The presently existing diaphragm pumps include a pumping chamber
containing an inlet passage and a discharge passage, a transfer
chamber filled with hydraulic fluid and separated from the pumping
chamber by a flexible diaphragm, and a piston defining one end of
the transfer chamber and adapted for reciprocating movement. During
operation, the piston reciprocates toward and away from the
diaphragm or into and out of the transfer chamber thereby causing
the recirpocating movement reciprocating the piston to be
transferred via the hydraulic fluid to the diaphragm. As the piston
moves away from the diaphragm, the diaphragm flexes away from the
pumping chamber and allows the fluid to be drawn into the pumping
chamber through the inlet passage. As the piston moves toward the
diaphragm, the diaphragm flexes toward the pumping chamber to
thereby force the fluid in the pumping chamber out the discharge
passage. The inlet and discharge passages each comprise a one-way
check valve. This cycle is then repeated.
SUMMARY OF THE INVENTION
In contrast to the high pressure diaphragm pumps of the past, the
present invention provides an improved hydraulic diaphragm pump in
which the reciprocating mechanism operates under ideal conditions,
in an oil bath and on the transfer chamber side of the diaphragm
while corrosive and abrasive solutions, exotic chemicals,
refrigerants and various other compositions are being pumped on the
pumping chamber side of the diaphragm. Thus the type of materials
pumped is limited by the composition of the diaphragm and the
materials of construction on the pumping chamber side of the
diaphragm. The present invention also provides a diaphragm pump in
which the hydraulic fluid contained in the transfer chamber is
designed to leak in a controlled manner from the transfer chamber
between the piston and the piston cylinder walls to provide
lubrication for the piston, and in which this hydraulic fluid which
has been allowed to leak from the transfer chamber is introduced
back into the transfer chamber prior to the next pumping stroke of
the piston. This continuous circulation of the hydraulic fluid also
tends to cool the hydraulic fluid and thereby reduce exposure to
vapor lock. Additionally, the present invention provides an
improved diaphragm pump having means for preventing cavitation of
the hydraulic fluid in the transfer chamber when the intake line of
the fluid being pumped is shut off, which in turn prevents
hydraulic lock of the transfer chamber.
The present invention also includes an improved pressure control
and unloader valve in communication with the outlet passage of the
pumping chamber for controlling the output pressure of the pump in
the event that the discharge end of the pump is shut off or
restricted. The improved unloader valve of the present invention
includes means utilizing a water hammer and a floating check valve
to open the unloader valve quickly as soon as the discharge end is
shut off and to keep the unloader valve open for recirculation of
the fluid being pumped until jthe discharge end is again
opened.
Accordingly, it is an object of the present invention to provide an
improved diaphragm pump which includes means for preventing
cavitation of the hydraulic fluid in the transfer chamber and
thereby preventing hydraulic lock from occuring in the transfer
chamber.
Another object of the present invention is to provide an improved
diaphragm pump in which the reciprocating mechanism operates under
ideal conditions in an oil bath on the transfer chamber side of the
diaphragm and the materials being pumped including corrosive and
abrasive solutions, exotic chemicals and other materials contact
only the pumping chamber side of the diaphragm.
Another object of the present invention is to provide an improved
diaphragm pump in which the hydraulic fluid in the transfer chamber
is allowed to controllably leak from the transfer chamber to a
reservoir and whereby this hydraulic fluid is allowed to leak out
is returned to the transfer chamber by a one-way check valve
thereby allowing for lubrication of the piston and cooling of the
hydraulic fluid in the transfer chamber.
A further object of the present invention is to provide a pump
having an improved pressure control and unloader valve which
utilizes a water hammer to open and keep open an elongated valve
upon sudden shut off of the discharge end of the outlet
passage.
Another object of the present invention is to provide a pump having
a pressure control and unloader valve which includes a floating
check valve.
Another object of the present invention is to provide an improved
pump having a pressure control and unloader valve in which the
unloader valve is controlled by the differential pressure between
the pressure at the outlet of the pumping chamber and atmospheric
pressure.
These and other objects of the present invention will become
apparent upon reference to the drawings, the description of the
preferred embodiment, and the appended claims.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the diaphragm pump of the present
invention.
FIG. 2 is a cross sectional view of the diaphragm pump of FIG. 1 as
viewed along the line 2--2.
FIG. 3 is a cross sectional view of the piston and diaphragm
assemblies of the diaphragm pump of FIG. 2.
FIGS. 4 and 5 are cross sectional views of alternative embodiments
of the diaphragm assembly.
FIG. 6 is a cross sectional view of the improved pressure control
and unloader valve.
FIG. 7 is a perspective view partially in section, of the manifold
casting of the improved diaphragm pump.
FIG. 8 is an exploded perspective view of the floating check
valve.
FIG. 9 is a cross sectional view of the strainer which is designed
to fit within the inlet to the pump.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIG. 1, the high pressure diaphragm pump 10 of
the present invention is a multi-piston pump. Generally, the pump
10 includes three piston assemblies, indicated by the broken lines
11, equally radially spaced from the center of the pump and each
separated from each other by 120 degrees. As will be explained more
in detail with reference to the other FIGURES, the piston
assemblies 11 are caused to reciprocate by a cam plate which is
rigidly secured to a cam shaft 12. The cam shaft 12 is located in
the center of the pump 10 and extends axially therethrough. The cam
shaft 12 includes a centrally located bore 14 for engagement with a
drive shaft 15, and further includes a longitudinal groove 16
adapted to receive a piece of conventional key stock thereby
causing the cam shaft 12 and the drive shaft 15 to rotate together.
The drive shaft 15 extends upwardly from the pump 10 and is driven
by an electric motor (not shown). The preferred embodiment of the
present invention is designed to be connected with a N.E.M.A. "C"
flange motor.
Also shown with reference to FIG. 1 are the relative positions of
the pumping fluid inlet 16, the pumping fluid discharge 18, and the
biasing means chamber 19 of the unloader valve. During operation,
the three piston assemblies 11 are sequentially reciprocated by the
rotating cam plate resulting in a relatively constant output of
fluid from the discharge 18.
Reference is now made to FIG. 2 which is a cross sectional view of
the pump shown in FIG. 1. The view in FIG. 2 is taken along the
line 2--2 of FIG. 1. Generally, the upper portion of the pump 10
includes an aluminum casting 23 serving as part of the pump case
and a cylinder sleeve holder casting 22 adapted to engage the
aluminum casting 23 to form the cam shaft case 17. As will be more
fully explained below, the cam shaft case 17 houses the cam
assembly and the piston assembly and is designed to be filled with
hydraulic fluid to a preselected level indicated on the sight glass
38. Connected below the cylinder sleeve holder casting 22 is a
valve plate casting 24 adapted to house the discharge valve
assembly 39 and the suction valve assembly 40. Disposed between the
castings 22 and 24 in a sealed relationship is a diaphragm 41
associated with each of the piston assemblies. Adjacent to the
valve plate casting 24 is the base or manifold casting 25. The
manifold casting houses the intake 16 (FIG. 1), the unloader valve
26 including the spring chamber 19 and the pump discharge 18. The
composition of the valve castings 24 and 25 depend upon the
corrosiveness and abrasiveness of the material being pumped.
Referring more specifically now to the internal structure of the
pump 10, each of the piston assemblies are reciprocated by a cam
assembly which includes the cam shaft 12 rotatably mounted within
the castings 22 and 23 and a cam plate 21 secured to the shaft 12,
rotatably mounted within the castings 22 and 23 and adapted to
engage an upper portion of each of the piston assemblies. As can be
seen, the cam plate 21 is canted with respect to the cam shaft 12.
Thus, as the cam shaft 12 and the cam plate 21 are rotated, the
piston assemblies are caused to reciprocate as a result of
engagement with the peripheral edge of the rotating plate 21.
The cam shaft 12 is journalled in the castings 22 and 23 by the
lower needle roller bearing 35 and the upper needle roller bearing
31 respectively. A suitable packing or shaft seal 20 is disposed
above the upper bearing 31 and between the outer surface of the
shaft 12 and the casting 23 to seal the cam shaft case 17 and thus
prevent hydraulic fluid in the case 17 from leaking between the
shaft 12 and the casting 23. The shaft 12 includes an inner
cylindrical bore 14 adapted to receive a drive shaft (not shown)
which in turn is designed to connect with a suitable motor. A
longitudinal key groove or channel 13 is cut into a portion of the
shaft 12 to permit a piece of conventional key stock to be inserted
therein to cause the drive shaft (not shown) and the cam shaft 12
and plate 21 to be rotated together.
The cam shaft 12 and the cam plate 21 are additionally supported by
a tapered thrust bearing 32 disposed between an upper surface of
the plate 21 and a portion of the casting 23. This bearing 32
counters the forces exerted by the plate 21 on the piston
assemblies. The bearings 32, 31 and 35 and the entire cam assembly
are lubricated by the hydraulic fluid in the cam shaft case 17.
When the fluid in the case 17 needs to be replenished or changed,
this is accomplished by draining the case 17 and refilling it
through the threaded opening 45 which is normally closed by the
plug 46.
Referring now to FIG. 3, each of the piston assemblies includes a
piston 48 and a cylindrical piston sleeve 49 associated with a
diaphragm assembly and a valve assembly. The cylindrical piston
sleeve 49 is securely fitted within the cylinder sleeve holder
casting 22 and is adapted to receive the piston 48. Threadedly
received by the piston at its upper end is a tappet 52 designed to
retain the upper bronze foot member 54 in proper association with
the cam plate 21. A lock-nut 55 is threadedly advanced over the
tappet 52 and jammed against the piston body 48 to prevent the
tappet 52 from loosening as a result of the vibratory movements of
the pump. The bronze foot 54 has a hemispherical shape and includes
a flat surface 56 adapted to slideably engage the upper surface of
the cam plate 21. The piston body 48 also houses a lower bronze
foot 58, similarly hemispherically shaped, and adapted to engage
the bottom surface of a pressure plate or ring 28. The plate 28 is
designed to remain stationary during operation of the pump and to
transfer the reciprocal movement of the cam plate 21 to the pistons
48. Disposed between the pressure plate 28 and a bottom annular
surface 59 of the cam plate 21 is a needle thrust roller bearing
34.
Each of the foot members 54 and 58 are hemispherically shaped to
accommodate the rotational movement of the canted cam plate 21 and
the reciprocating movement of the piston 48. Consequently, each of
the foot members 54 and 58 rotate reciprocally during the operation
of the pump 10. The foot members 54 and 58 and the needle bearing
34 are lubricated by the hydraulic fluid in the cam shaft case
17.
As can be seen in FIG. 3, the piston 48 is designed to slide fairly
tightly through the cylindrical piston sleeve 49. It should be
noted, however, that although the fitting relationship between the
piston 48 and the sleeve 49 is sufficiently tight so that
reciprocating movement of the piston 48 causes the diaphragm 41 to
also reciprocate, it is loose enough to allow some of the hydraulic
fluid to leak between the exterior cylindrical surface of the
piston 48 and the interior cylindrical surface of the sleeve 49 to
lubricate the same.
Contained within the casting 22, is a check valve assembly or first
valve means which includes a large passageway 60 extending from the
transfer chamber 61, a steel ball or valve 62, a sleeve spring 64
biasing the ball 62 upwardly, and a smaller passageway 66 extending
from one end of the passageway 60 to the cam shaft case 17. As a
result of the force exerted by the valve spring 64, the steel ball
62 is continually biased against the shoulder portion 68 connecting
the passageways 60 and 66 to control the passage of fluid from the
case 17 into the transfer chamber 61 and to prevent the flow of
hydraulic fluid from the transfer chamber 61 into the case 17. It
should be noted that fluid will pass from the case 17 and into the
transfer chamber 61 only if the pressure differential between the
hydraulic fluid in the case 17 and the transfer chamber 61 is
sufficiently large. This pressure differential is of course
determined by the size of the valve spring 64 and the size of the
passageway 66 against which the steel ball 62 is seated.
The diaphragm assembly includes a diaphragm 41 disposed in a sealed
relationship between the castings 22 and 24, a follower plate 69
secured to the bottom or pumping chamber side of the diaphragm 41,
and a plunger stem 70 secured to the upper or transfer chamber side
of the diaphragm 41. The follower plate 69 and the plunger stem 70
are securely connected in this arrangement by a screw 71 extending
through the plate 69 and a stem plate 73 disposed on either side of
the diaphragm 41 and into the plunger stem 70. The diaphragm
assembly further includes an annular stop member or shoulder
portion 74 formed within the transfer chamber 61 and designed to
engage a portion of the upper surface of the diaphragm 41 during
its upward movement. The shoulder portion 74 includes a bottom
canted surface 77 conforming substantially with the upper canted
surface 80 of the follower plate 69 between which the diaphragm 41
is disposed. At one point during each upward movement of the piston
48, the canted surface 80 and the diaphragm 41 are caused to be
seated against the canted surface 77 of the stop member 74. The
stop member 74 is positioned so that the diaphragm 41 seats against
the surface 77 just prior to the completion of the upward stroke of
the piston 48. Because of the further upward movement of the piston
48 after seating of the diaphragm 41 against the surface 77, a
suction is created in the transfer chamber 61 thereby caused
hydraulic fluid to flow from the case 17, through the check valve
assembly defined by the members 62 and 64 and into the chamber 61
to replenish the hydraulic cell. The amount of fluid replenished
conforms to the amount of fluid which leaked from the chamber 61
between the piston 48 and the cylinder 49 during the downward
stroke of the piston 48.
The plunger stem 70 is continuously biased upwardly by a plunger
spring or bias means 75 having one end disposed against the upper
surface of a piston nose plate 76 and the other end disposed
against the bottom annular surface of a plunger stem flange 78. The
flange 78 is integrally formed with the stem 70 and extends
outwardly therefrom. The nose plate 76 is securely connected with
the bottom portion of the piston 48 by a plurality of screws 79. In
the preferred embodiment, the spring 75 is a coil compression
spring. Although the actual size of the spring 75 may vary, the
force per unit area exerted by the spring 75 on the diaphragm plus
the force per unit area required to open the ball check valve 62
must be greater than the force per unit area exerted on the
diaphragm through atmospheric pressure. In the preferred
embodiment, the spring 75 exerts a force which develops a pressure
of 15-18 p.s.i. on the diaphragm 41 whereas the spring 64 exerts a
force on the ball 62 such that a pressure of about 3 p.s.i. is
required to move the ball off the seat. However, in accordance with
the limitation discussed above, the force exerted by the spring 75
on the diaphragm 41 may be less than atmospheric pressure,
providing, that force plus the force required to open the ball
check valve 62 is greater than atmospheric pressure.
With further reference to FIG. 3, the valve plate casting 24 houses
a pumping chamber 81 and a valve assembly. The valve assembly
includes a suction valve 40 and a discharge valve 39. The suction
valve 40 includes a valve seat 82, a valve plate 84, a spring
member 85 and a retainer member 86. These elements are oriented to
prevent the fluid in the pumping chamber 81 from passing through
the suction valve 40 and into the suction chamber 88 but to permit
fluid in the chamber 88 to flow through the valve 40 and into the
chamber 81. This flow will only occur, however, if the pressure
differential between the fluid in chamber 88 and the fluid in
chamber 81 is sufficient to overcome the force of the spring 85. Of
course, to maximize the efficiency of the pump, this pressure
differential is intended to be as small as possible. Therefore,
under ideal conditions, there is a continuous supply of fluid to
the pumping chamber 81. The chamber 88 is designed to be in
communication with a source of fluid to be pumped via the inlet 16.
As illustrated in FIGS. 7 and 9, the inlet 16 is connected with a
strainer for filtering impurities from the pumped fluid prior to
introduction into the pump. The strainer 131 includes a screen
which in the preferred embodiment is 100 mesh.
The valve plate 84 is positioned immediately above the valve seat
82 and engages the seat 82 to prevent fluid from passing between
the plate 84 and the seat 82. The plate 84 is biased against the
seat 82 by a compression coil spring 85 which is supported by the
spring retainer 86 and by the pressure of the fluid in the pumping
chamber 81. Although not clearly shown in the drawings, the spring
retainer 86 includes an opening which readily permits fluid to pass
into the pumping channel 40.
The discharge valve 39 is identical in construction to the suction
valve 40 except that its position is inverted. The discharge valve
39 includes a seat member 89, a valve plate 90, a spring 91, and a
retainer 92, which operate identically to their respective members
in the suction valve 40. However, the valve 39 allows fluid to pass
from the pumping chamber 81 and into the discharge chamber 94, but
prevents fluid from passing the discharge chamber 94 into the
pumping chamber 81.
The operation of the valve assembly and each of the valves 39 and
40 can best be understood by considering their operation in
conjunction with the movement of the diaphragm 41. When the
diaphragm 41 moves upwardly, a partial vacuum is created in the
pumping chamber 81 thereby causing fluid to flow from the suction
chamber 88, through the valve 40, and into the pumping chamber 81.
During the downward movement of the diaphragm 41, fluid is forced
from the chamber 81, through the valve 39, and into the discharge
chamber 94.
Reference is next made to FIG. 4 which shows an alternate diaphragm
arrangement with a spring loaded follower plate. In this
embodiment, the follower plate 120, and thus the diaphragm 122, is
biased upwardly via the spring or bias member 121 which is
supported at one end by a portion of the pumping chamber. This
arrangement will operate acceptably in the previously described
pump structure providing the springs 121 and 164 combined to exert
a pressure greater than atmospheric pressure.
FIG. 5 shows a further alternate diaphragm arrangement for use in a
long stroke pump diaphragm of the bellaphram type. In this
embodiment, the plunger stem 124 is secured to the followr 125 by
the screw 126. The diaphragm 128 is disposed between the castings
22 and 24 and is designed to reciprocate a considerably greater
distance than the diahragm 41 shown in FIGS. 2 and 3. The
embodiments in each of FIGS. 4 and 5 also include a shoulder or
seat member 129 against which the diaphragm is designed to seat
upon upward movement of the piston 130. Similar to the embodiment
described in FIGS. 2 and 3, the diaphragms in FIGS. 4 and 5 are
designed to seat against the seat member 129 slightly before the
end of the upward piston stroke. This allows for the hydraulic
fluid cell in the transfer chamber to be replenished with hydraulic
fluid which has leaked from the chamber during the downward stroke
of the piston 130.
With general reference to FIG. 2 and specific reference to FIG. 3,
the operation of the pump 10 may be described as follows: First of
all, as the cam shaft 12 and the cam plate 21 are rotated by the
motor (not shown), the three pistons 48 are caused to reciprocate.
Since the pistons 48 are positioned 120 degrees apart, the strokes
of the three pistons will also be 120 degrees apart. Therefore, as
one of the pistons 48 reaches the end of its upward stroke, the
second will be two thirds of the way toward completion of its
downward stroke and the third will be one third toward completion
of its upward stroke. This repeated and sequenced reciprocation
causes the output pressure and volumetric flow rate to be
maintained at a relative constant value.
Upon starting up the system, the case 17 is filled with oil to the
level indicated on the sight glass 38. The transfer chamber 61 is
full of air and the diaphragm 41 is against the diaphragm seat or
shoulder portion 77 regardless of the position of the piston 48.
Reciprocation of the piston 48 then forces the air in the chamber
61 up through the clearance space between the piston 48 and the
cylinder wall 49 until the chamber 61 is evacuated to a point where
the valve 62 opens and allows the chamber 61 to fill with oil from
the case 17. Shortly, all of the air will be displaced from the
chamber 61 and an oil cell is formed. From then on, the diaphragm
displacement is equal to the piston displacement less the oil which
leaks past the piston 48 on the pressure stroke. The leakage of
fluid past the piston 48 occurs during normal downward movement of
the piston.
On the return stroke the oil in the chamber 61 is replenished
whenever the diaphragm 41 engages the shoulder 77 thereby causing
the pressure in the chamber to drop below atmospheric pressure by
an amount greater than the pressure required to open the check
valve comprising the members 62, 64 and 68. As mentioned
previously, the diaphragm is designed to engage the surface 77
slightly before the end of the upward stroke of the piston 48 to
insure a replenishment of the oil in the chamber 61. This
controlled leakage past the piston 48 keeps the piston lubricated
and the oil in the chamber 61 cool.
As is evident from FIG. 3, the spring member 75 is disposed between
the diaphragm means, namely the stem 70 and the piston 48, and is
adapted for movement therewith. As is further evident, deflection
of the spring 75 will occur only when there is relative movement
between the piston 48 and the stem 70. In such cases, the magnitude
of the deflection will be equal to such relative movement. Relative
movement between the diaphragm means and the piston 48 can occur in
two ways. one is during the downward movement of the piston when a
small amount of hydraulic fluid leaks from the transfer chamber 61
between the piston 48 and the sleeve 49. In this situation, the
downward movement of the diaphragm means is less than the
corresponding downward movement of the piston 48 due to the small
amount of fluid which is lost. This results in a small extension of
the spring 75. The other is during the upward movement of the
piston 48 when the diaphragm 41 engages the shoulder 77. In this
situation, the piston 48 moves upwardly a small distance after
engagement of the shoulder 77 by the diaphragm. This results in a
small compression of the spring 75 and a replenishing of hydraulic
fluid in the chamber 61 through the ball check valve 62. It should
be noted that the loss of fluid from and the replenishing of fluid
to the chamber 61, as discussed above, and the relatively small
deflection of the spring 75, occurs during each normal stroke of
the piston 48.
Except for the time that the diaphragm 41 is supported by the
shoulder portion 77, the hydraulic pressure in the chamber 61 is
always greater than that on the pumping chamber side of the
diaphragm by an amount equal to the pressure exerted on the plunger
70 by the spring 75, which in the preferred embodiment is about
15-18 p.s.i. This pressure plus the pressure required to open the
check valve comprising the members 62, 64 and 68 is always above
atmospheric. Consequently, a full shut off in the suction line
causes a cavitation in that line rather than in the chamber 61.
This prevents the chamber 61 from ever becoming overfilled with
oil, which could cause a hydraulic lock on the pressure stroke.
During the upward movement of the piston 48 and thus the diaphragm
41, the discharge valve 39 is closed and the fluid to be pumped
flows from the suction chamber 88 through the suction valve 40 and
into the pumping chamber 81. During the downward movement of the
piston 48 and the diaphragm 41, the suction valve 39 is closed and
the fluid is pumped from the chamber 81, through the valve 40 and
into the discharge chamber 94.
For purposes of the description of the present invention, the
pressure control and unloader valve includes an inlet port disposed
between the pumping chamber 81 and the discharge chamber 94, an
outlet port disposed between the discharge chamber 94 and the pump
outlet 18 and comprising a portion of the pump outlet, and an
overflow or bypass port disposed between the discharge chamber 94
and the suction chamber 88. Referring specifically to FIG. 6, the
unloader valve assembly 26 of the present invention includes a
second valve means 42 disposed between the inlet port and the
bypass port and a spring cavity 44 housing a spring or bias member
95 urging the means 42 toward a closed position. The means 42
includes an end 96 having a valve portion 98 adapted for engagement
with a seat member 99 and an elongated stem 105. As illustrated in
FIG. 2, the valve and seat arrangement separate the fluid suction
chamber 88 from the fluid discharge chamber 94 when the valve 98
and seat 99 are in a closed position. When the end 96 is forced
rearwardly to an open position the chambers 88 and 94 are in
communication with each other. The valve end 96 is designed to
slidably engage the interior cylindrical surface of the spring
cavity 44 and engage one end of the spring member 95. The spring
member 95 is a conventional coil compression spring and is designed
to bias the end 96, and thus the valve portion 98, against the seat
99. One end of the cavity 44 includes an internally threaded
portion 100 adapted to threadedly receive a member 101 which may be
advanced along the threaded portion 100 to vary the force exerted
by the spring member 95 on the end 96. A suitable packing or
sealing 102 is disposed between the end 96 and the interior
cylindrical surface of the cavity 44 to prevent the fluid in the
chamber 88 from passing into the cavity 44.
Mounted to the other end of the valve means 42 is a floating check
valve disposed within the discharge chamber 94 and between the
inlet port and the outlet port and comprising a third valve means
which as best shown in FIGS. 6 and 8 includes a valve seat member
104 movably mounted within the discharge chamber 94 on the end of
the longitudinal stem 105. The stem 105 has a shoulder portion 106
against which the seat 104 is disposed. Around the peripheral edge
of the seat member 104 is a suitable "0" ring 108 or sealing
material designed to seal the discharge chamber 94 from the pump
outlet 18. A cylindrical bushing 109 abutts one side of the member
104 to tightly secure the member 104 against the shoulder 106. The
bushing 109 is in turn retained at its other end by the lock-nut
110 which is threadedly received by the end of the stem 105.
As best illustrated in FIG. 8, the seat member 104 includes a
plurality of openings 111 through which fluid may flow from the
discharge chamber 94 to the pump outlet 18. Adapted to seat against
the member 104 is a valve disk 117 which is urged toward the seat
member 104 by the spring 114. The disc 117 is composed of a
material having resilient properties and is a synthetic which has
been recognized by the trademark "Viton." In the preferred
embodiment, this material has a durometer of 90. The disc 117 is
backed by a stainless steel plate member 113. The spring member 114
is retained by a spring retaining member or step cap 115 which is
disposed between the bushing 109 and the lock-nut 110 and is
securely held there by the nut 110.
During normal operation fluid passes from chamber 94 through the
openings 111, between the valve disc 117 and the seat 114, through
the outlet 18 and into the discharge system. The restriction in the
discharge system causes the pressure in the chamber 94 to increase
until it overcomes the spring 95. The excess fluid passes through
the valve 26 to the chamber 88. If the discharge line (not shown)
is suddenly closed, a pressure wave will be formed in the discharge
line and will move from the discharge end toward the floating check
valve assembly. When it reaches the check valve assembly, the force
of the pressure wave acting on the floating check valve will cause
the entire valve assembly to move to the right as viewed in FIG. 6
to allow fluid to flow from the chamber 94 into the chamber 88. If
the discharge line is gradually closed, the pressure in the outlet
18 and the chamber 94 will gradually increase until the pressure is
sufficient to overcome the force of the spring 95. If this happens,
the valve assembly 26 will be forced to the right, thereby allowing
the fluid in the chamber 94 to by-pass into the chamber 88.
Referring now to FIG. 6, the operation of the pressure control and
unloader valve can be described as follows: During normal operation
of the pump, the outlet chamber 18 is in communication with an
outlet line and an operative device (not shown) which may, for
example, be a spray gun. When the spray gun is being operated,
fluid passes through the check valve which comprise the elements
114, 113, 117 and 104, and cut through the nozzle of the gun. Due
to the restriction in the nozzle, pressure builds in chamber 94
until it overcomes the spring 95. The excess fluid passes through
the valve 26 to the suction chamber 88. Thus, pressure control is
attained. Since the screw member 101 is adjustable, the pressure is
likewise adjustable.
When the spray gun is suddenly shut off, a pressure wave formed by
this sudden shut-off moves back along the outlet line toward the
pump at the speed of sound in water. The intensity of this wave is
always greater than the bypass pressure setting of the spring 95.
Consequently, when such a complete shut-off occurs, this pressure
wave exerts a sudden force against the plate 113 and thus the valve
117 and the seat 104 causing this entire arrangement and thus the
valve 26 to move to a wide open position thereby allowing the fluid
in the chamber 94 to freely bypass the valve assembly 26 and return
to the suction chamber 88 to be recirculated. Thus, through the use
of the moving pressure wave acting upon the movable check valve,
located in the discharge passage, a more responsive unloading
action is accomplished than that of a conventional unloader
valve.
As soon as the gun is opened, valve 26 returns to the normal
position and normal pressure control is reestablished.
Although the description of the present invention has been very
specific, it is contemplated that the present invention may be
embodied in other forms not specifically illustrated or described
in the present description. Consequently, the inventor intends that
the specific description has been illustrative only and intended
only to describe a working embodiment. Consequently, the scope of
the present invention should be determined from the appended claims
rather than from the description of the preferred embodiment.
* * * * *