Note: Descriptions are shown in the official language in which they were submitted.
:~25~
BIRD:007
IMPROVED MUD PUMP
The present apparatus is directed to a fluid mud pump
and, more particularly, to a mud pump to be utllized to
int~nsly ~luid pre3sure ~or use in drlllin~ Qil well5 or
in conclitioning oil. wells such as fracturing with
extremely high pressure or abrasive fluids. Various mud
pumps and pressure intensification pumps are already known
to exist that employ various and sundry means to overcome
the difficulties encountered in prolonged pumping of high
volume, high pressure, and abrasive materials. The - -
present invention is an apparatus which will provide
improvement in mud pumping operations in such areas as
reduced mud pressure pulsation, less operating energy
re~uired for fluid pressure intensification, slower
operating piston speeds and longer piston strokes thus
resulting in extended life of all operating parts, wider
range of mud flow and pressure controllability, greater
simplicity of manufacture, improved adaptability and
operation, plus other less apparent improvements. Thus
the context of the problem to be dealt with in the present
invention is that of providing a non-pulsating output,
highly efficient and controllable hydraulic powered fluid
pump.
6~i
-- 2 --
Fig. l is a plan view of multicylinder mud pump
system in accordance with the teachings of the present
invention.
Fig. 2 is a section view taken along the line 2-2 of
Fig. l.
.'
Fig. 3 is a schematic drawing showing a hydraulic
circuit and power system used to power a typical mud pump
of the present invention.
Fig. 4 is an end view of the independent driven
metering valve that is used to distribute hydraulic fluid
to the hydraulic drive cylinders of Fig. 3.
Fiy. 5 i.~ a ~ection vieW t~ken along the line 5-5 of
Fig. 4,
Fig. 6 is a section view taken along the lines 6-6 of
Fig. 5.
Fig. 7 is a section view taken along the lines 7-7 of
Fig. 6.
Fig. 8 is a schematic drawing showing hydraulic line
interconnection between Fig. 6, Fig. 7, and the hydraulic
drive cylinder of Fig. 3.
Fig. 9 is a view of the reciprocating mud piston and
valve drawn to a larger scale than shown in Fig. 2.
Fig. 10 is a view, drawn to a larger scale than shown
in Fig. 2 of the mud piston rod seal that is shown in
Fig. 2.
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- 3 -
Attention is first directed to Fig. 1, of t~e
drawings where the numeral 10 generally identifies a mud
pump according to the present invention. In this
- illustrated embodiment a plan view of a mud p~mp employing
~ 5 three pumping cylinders is shown. Three or more pumping
cylinders is a preferred embodiment of this pump. Each
pumping cylinder is the same in cross section and is
connected to a common mud inlet manifold and to a common
mud outlet manifold. Attention is also directed to Fig. 2
which is a section view taken along the lines 2-2 of
Fig. 1. This section view is the same for each of the
three pumping cylinders that comprise a mud pump according
to the present invention.
~eferring now to FIG. 2, a mud suction manifold 11 is
connected by bolts 12 to valve housing 13, manifold 11
connects to valvo housing 13 of each pumplng section and
has an annulus 14 which is common to all valve inlets.
Flange 15 is located on each end of manifold 11 to aliow
connection of annulus 14 to a suitable mud supply source.
Valve housing 13 is a circular member with a circular bore
16 therethrough that is formed to receive unidirectional
inlet valve assembly 17, valve assembly 17 consists of a
valve seat, a spring loaded valve spool, and a compression
spring element. Valve housing 13 is sealingly connected
to a head flange 18 by bolts 19 and seals 20. Head flange
18 is elongated rounded member with a flat 21 on one side
to receive member 13. The flat surface 21 has a rounded
bore 22 extending inward therefrom which is concentric to
3C and communicate with annulus 16. Within bore 22 a
circular shaped valve retainer plate 23 is positionad and
held in place by snap ring 24 to retain unidirectional
valve assembly 17 in position. Valve assembly 17 is
positioned to allow relatively free fluid flow from
annulus 14 to annulus 16 and to block fluid flow from
annulus 16 to annulus 14.
...~,
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,,
-- 4 --
Head flange 18 contains a circular recess 31 on one
end into which is fitted one end of a spacer tube 32, the
second end of spacer tube 32 is likewise fitted into a
-- circular recess 34 of one end of a head cap 33. An access
opening 180 is provided through the side of member 32.
Head cap 33 also contains a circular recess 35 on its
second end into which is fitted a tubular shaped cylinder
adaptor member 36. An access opening 181 is provided
through the side of member 36. Members 18, 32, 33 and 36
are held together by tie rods 37 which are connected by
threads to member 18 on one end and pass through member 33
and 36 on the second end. The second end of tie rod 37 is
threaded to receive a nut 38 which tighten against member
3~ to clamp together and retain members 18, 32, 33, and 36
as a single unit with a concentric bore therethrou~h.
Head 1an~e 18 contains a circular annulus 25
therethrough which communicates with annulus 22. Within
annulus 25 an end cap 26 is slidably fitted and held in
place by a circular retainer plate 27 and bolts 28. End
cap 26 is an elongated circular member with a raised __ __
flange on each end that contains circular seals 29 on one
end and circular seals 49 on the other end. Seals 29 and
49 form slidable sealing contact with the walls of annulus
25. The diameter of the flange that holds seals 29 is of
a slightly reduced size than the diameter of the flange
that holds seals 49, these seals also mate with
correspondingly different sized diameters in annulus 24.
These different sized sealing surfaces are to facilitate
ease of assembly. End cap 26 also contains a recessed
bore 30 on its inner face and side part 48 which
communicates with annulus 25. The inner face of end cap
26 has a smooth, concentric circular tapered face 3g
against which is fitted a correspondingly tapered face on
the first end of a tubular shaped piston liner 40. The
tapered face of the liner 40 contains a circular groove 41
~25S~
-- 5
into which a circumferential seal 50 is fitted to form a
static seal between liner 40 and end cap 26. The second
end of liner 40 contains a similar tapered face and
- sealing element 51 which mate with a corresponding tapered
face 42 on an end seal member 43. Member 43 slidably and
sealingly fits within a circular bore 44 of member 33.
- Member 43 is an elongated circular member with raised
flanges on each end which each contain seals 121 fitted in
circumferential grooves to form slidable seals within the
bore 44 of member 33. Member 43 seats against a shoulder
45 of member 36 that limits its movement in one direction.
Seal member 43, liner 40, and end cap 26 are pulled
together by retainer plate 27. Retainer plate 27 being so
positioned as to provide a space 46 that allow~ plate 27
to tighten a~ains-t end cap 26 as bolts 28 are ticJhtened~
Lin~r 40 ha~ a smoo~h lnner bore 47 that is corlc~ntric
with both tapered end faces. End cap 26 and its tapered
bore 39 is positioned to be concentric with seal cap 43
and its tapered face 42. Thus as plate 27 is moved inward
by tighting bolt 28, liner 40 will assume a concentric and
sealed position with respect to end cap 26 and seal cap
42. Thus liner 40 can be of a wide range of bore
diameters and maintain stable, concentric sealing contact
with end cap 26 and seal cap 43. End cap 26 and seal cap
43 are positioned to maintain concentric positions through
concentric alignment of annulus 25 and annulus 44.
End cap 43 has concentric bore 52 therethrough and a
recessed groove 53 on its diameter which are in
communication through part S4. Head cap 33 has a flat
surface 55 on one side through which extends a port 56.
Port 56 is in communication with groove 53. The flat
surface 55 of head cap 33 is fitted to receive an outlet
manifold 57 which is sealingly connected to number 33 by
bolts 58 and circular seals 59. Manifold 57.connects to
each of the ~hree pumping cylinder assemblies and has a
-- 6 --
contained bore 60 therethrough which sealingly mates with
bore 56 of each pumping cylinder to form an outlet annulus
60 that is common to each pumping cylinder. Manifold 57
-- is also fitted with flange 61 on each end for-connection
to a suitable outlet supply line.
Liner 40 houses a member 62 which is a combination
piston and unidirectional flow valve. Attention is
additionally directed to Fig. 9 where an enlarged view of
member 62 is shown. Member 62 connects to piston rod 63
by threads 64 and is secured by snap ring 65. Member 62
consists of valve housing 66, piston seal 67, cap ring 68,
piston backup ring 69, retainer cap 70, valve seat 72,
seal 74, and valve plug 75. Member 66 is an elongated
rounded memher that is fitted on one end with a pliable
sealincJ el~ment 67. Element 67 is further positioned a~
held in pLace by a cap ring 68 and a backup ring 69.
Backup ring 69 being secured by a thread at 71. Retainer
cap 70 further holds in place a valve seat 72. Valve seat
72 is a circular ring type member with a smooth, hardened
and tapered face 73 that houses a seal 74. Face 73 and
seal 74 are fitted to receive a valve plug 75 that is
slidably fitted into an annulus 76 of member 66. Valve
plug 75 contains a smooth and hardened face 77 that is
tapered to mate with face 73 and seal 74 to form a seal
between member 75 and member 72. Member 75 is further
fitted with a spring 78 that tends to exert a slight ~orce
against member 75 to position member 75 in normally sealed
position against face 73, but which may be compressed to
allow member 75 to assume a non-sealed position relative
to face 73. Member 66 is fitted with slots 79
therethrough which are in communication with annulus 76.
Member 70 has a bore 80 therethrough which becomes blocked
when valve plug 75 is in a sealed position against face 73
but which is in communication with slots 79 when valve
plug is not in a sealed position with face 73. When valve
5~
cap 75 is in a sealed position against face 73, then the
annulus of liner 40 is separated into two distinct
pressure chambers shown as a second pressure chamber 81 on
- the rod end of member 62 and as a first pressure chamber
82 on the back side of member 62. Un:idirectional valve
member 62 will open when pressure is applied from the
first chamber R2 and allow flow from chamber 82 into
chamber 81. Valve member 62 will close and hold pressure
when flow attempts to travel from chamber 81 to chamber
82. Seal 67 is slidable within piston liner 40. Piston
rod 63 extends forward from member 62, through a piston
rod seal member 83 and connects by thread 122 to a
cylinder rod 84. Cylinder rod 84 is the piston rod of a
hydraulic cylinder assembly 85. Hydraulic cylinder
assembly 85 consists of plston rod 8~, piston rod seal 86,
piston as~embly 87, piston retainer cap 88, cylinder
barrel 89, end cap 90, head cap 91, tie rod 92, and tie
rod bolts 93. Tie rods 92 extend through end cap 90 and
head cap 91 and are threadingly connected to an adapter
flange 94. Adapter flange 94 is concentrically fitted to
cylinder adapter 36 and retained in place by bolt 95. _ _
Thus as nuts 93 are tightened, piston cylinder 85 is
secured and concentrically positioned with piston rod 63.
Piston assembly 87 is fitted to slidably and sealingly
form two pressure chamber within cylinder assembly 85; A
rear chamber 96 with fluid inlet ports 97, and a front
chamber 98 with fluid inlet ports 99. Thus as hydraulic
fluid under pressure is directed to either chamber 96 or
chamber 98, then piston 87 and piston rod 84 will respond
with movement as directed by hydraulic fluid flow and
pressure~
Attention is further directed to Fig. 10 which is an
enlar~ed view of seal assembly 83. Assembly 83 is
concentrically and sealingly fitted to end seal member 43
by bolts 100 and circumferential seal 101. Assembly 83
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- 8 -
consists of a housing 102, end cap 103, slidable seal ring
104, seal end ring 105, seals rings 106, seal head ring
107 and retainer ring 108. Retainer ring 108 is a flat
~ rounded ring that is centrally retained within member 43
by a shoulder 110 and member 102. Ring 108 positions in
place a wiper ring 109 and retains member 107 from
- movement in a one direction. Housing member 102 is a
rounded member with a bore therethrough into which is
fitted seal head ring 107, seals 106, seal end ring 105,
slidable seal ring 104, and end cap 103. End cap 103 is
sealably connected to member 102 by seal 111 and bolts
112, and is fitted to exert slight compression pressure on
member 108, 107, 106, 105, and 104 as bolts 112 are
tightened. Seal 106 is a rod seal which creates a
slidable seal contact with piston rod 63 as co~pression
pressure i~ e~erted against the seal ends. Mem~er 10~ is
a flat rounded plate wlth a slidable seal 113 on its outer
circumference and a rod seal 114 on its inner
circumference. Member 104 also contains a small diameter
oriface 115 therethrough which forms an annular
communication with a recessed circumferential groove 116
that is formed in the face of member 103. Ori~ace 115
creates an annular communication between groove 116 and
the surfaces surrounding member 105 and 106. Groove 116
further communicates with a small port 117 extending
through the wall of member 102. Port 117 being threaded
on the outer end at 118 to receive a suitable hydraulic
connection for supply of pressurized hydraulic fluid. End
cap 103 is a somewhat rounded member with a bore
therethrough which is fitted with seals 119 and 120 to
slidably seal against piston rod 63.
Thus as pressurized hydraulic fluid is supplied to
connection 118 it will flow through port 117 to groove 116
where it will pressurize seal ring 104 thus exerting added
pressure against seal 106. Pressurized fluid will further
~2~iS~6~-~
flow through oriface 115 and surround and lubricate seal
105. This process being continual with a minimum of
leakage of hydraulic fluid across seal 106 as long as the
- pressure differential between groove ]16 and pressure
chamber 81 is held to a minimum. Seal 106 can be supplied
with hydraulic fluid containing good lubricating
characteristics and this supply of hydraulic fluid can be
at a controlled pressure slightly higher than the mud
pressure in chamber 81; thus seal 106 will effectively
seal against mud leakage from chamber 81 as piston rod 63
reciprocates. Seal 106 will function with less îriction
and wear thus giving longer life and better sealing
characteristics than if it were not lubricated by
hydraulic fluid. The loss of hydraulic fluid will be held
to a minimum due to the compression that is actincJ aqainst
seal 106.
Referriny now to FIG. 2 as pressurized hydraulic
fluid is supplied to Ports ~9 and 97 of hydraulic cylinder
85 in such a manner to cause piston 87 to be powerly
reciprocated, then piston rod 63 will cause piston _ _
assembly 62 to likewise reciprocate. As piston 62 moves
toward the rod end or to decrease chamber 81, then valve
plug 55 will assume a closed position and pressurized
fluid will be forced out of chamber 81 through annulus 60
of outlet manifold 57. Simultaneously chamber 82 will
create a vacuum due to the displacement of piston 62 and
will pull in fluid from annulus 14 of inlet manifold 11.
Incoming fluid will flow across inlet valve assembly 17,
through annulus 16, 22, 25, through ports 48, and into
chamber 82 to replace fluid that is being discharged from
annulus 60. The amount of fluid drawn into chamber 82
will be greater than the amount displaced from chamber 81
by an amount equal to the volume determined by the area
decreased due to piston rod 63.
~ 25Si~
- 10 -
Correspondingly as piston 62 moves away from the
piston rod end or in the direction to decrease chamber 82,
then the movement of member 62 will be in a direction to
: compress the entrapped fluid in chamber 82 a~~thus the
fluid will flow through valve member 62 into chamber 81
and out annulus 60. In this direction of piston 62
movement the pressure in both cham~ers 82 and chambers 81
will be equal to the discharge pressure of annulus 60, and
the fluid flow from chamber 81 to annulus 60 will be e~ual
to the volume of fluid displaced due to the area of piston
rod 63. Thus it is shown that as piston rod 63
continually reciprocates, fluid will be displaced from
pressure chamber 81 to the discharge annulus 60 in both
diroctions o~ travel of piston rod 63. ~lso that the
lS pressure in chamber 81 and discharcJe annulus 60 will be
e~ual in e~th~r directions o travel o~ piston rod 63.
Attention is next directed to Fig. 3 which is a
schematic drawing of a typical hydraulic circuit employed
to power the hydraulic cylinders 85 of this mud pump. In
this circuit only two cylinders 85 are illustrated for _ __
clarity of explanation, addition of a third or more
cylinders 85, will be explained in later descriptions.
~he main components of this circuit are: a main pump 125
that is driven by a prime motor 126; a charge pump 127
that is also driven by prime motor 126; one way check
valves 128 and 129; high pressure relief valve 130;
independently driven metering valve 132 that is driven by
prime mover 133; one way check valve 134; flow control
valve 135; flow control valve 136; one way check valve
137; relief valve 138; pneumatic type accumulation 139;
hydraulic piston 85; hydraulic reservoir 140; high
pressure supply line 141; low pressure hydraulic return
line 142; hydraulic flow lines 143, 144, 145, 146, 147,
148 and 149; and low pressure relief valve 131. The
hydraulic system shown is a closed loop, charged type
~55~
-- 11 --
hydraulic system employing a variable volume one direction
main pump. Most of the components in this hydraulic
circuit and the usage thereof are well known by anyone
: versed in the art, so I will give detailed ex~Ianation
only of unique and ~ew pressurized fluid control means
disclosed by this hydraulic circuit.
Attention is further directed to Fig. 4 which is an
end view of metering valve 132. Fig. 5 is a section view
taken along the line 5-5 of Fig. 4. Fig. 6 is a section
10 view taken along the line 6-6 of Fig. S. Fig. 7 is a
section view taken along line 7-7 of Fig. 5. Fig. 8 is a
schematic drawing imposed between Fig. 6 and Fig. 7
showing hydraulic line connections between Fig. 6, E'ig. 7
and hydraulic cylinders 85.
Referrirl~ now to FIC. 5, valve 132 contains a hous.ing
lSO with a finely finished central bare 151 therethrough.
Housing 150 has an end plate 152 on one end which retains
in place a seal 153 for sealing against flows
therebetween. End plate 152 also contains a thrust
20 bearing 154 which is fitted into a recessed counterbore
for containment, and a fluid return port 155 which passes
`~ therethrough and is fitted on its outer end for receipt of
hydraulic fluid return line 142. End plate 152 is
retained in place by bolts 156. On the other end, housing
25 150 has a second end plate 157 which is retain~d in
position by bolts 158 and which retains in place a seal
159. End plate 157 also contains a central bore
therethrough into which is fitted a second thrust bearing
~2~
- 12 -
160 and a shaft seal 161. Seal 161 is retained in place
by snap ring 162.
- Mounted within bore 151 of housing 150 is a rounded
rotatable ~alve spool 163 which is fitted to make
rotatable sealing contact with the walls of bore 151.
- Spool 163 has a drive shaft 164 of reduced diameter
extending from one end which extends through the bore of
plate 157 and thus through seal 161 to form a drive
connection means to rotate spool 163 about a rotational
centerline 176 by an external rotary drive means;
contained within valve spool 163 is a groove 164 that
circles the circumference and continually communicates
with an inlet port 165 that is positioned ln housing 150
and that is fitted to receive pressure line 1~1. Leadin~
inward from groove 164 is a roun~ed annulus 166 which
connects to an annulus 167. T~le centerline of annulus 167
passes through the rotational centerline of spool 163 and
is perpendicular to the rotational centerline of spool 163
thus forming two equal annulus outlets from spool 163
which are at 180 degree spacing. The outer ends of _ _ _
annulus 167 is finely finished to form s~uare like and
equal recesses 168 into, spool 163. Housing lS0 contains a
first bore 169 therethrough and a second bore 170
therethrough being positioned in line with bore 169 but at
a 90 spacing to bore 169, both bore 169 and bore 170 being
positioned perpendicular to the rotational centerline of
spool 163. Bores 169 and 170 are positioned to
alternately mate with annulus 167 of spool 163 as spool
163 rotates thus forming two alternating fluid outlet
connections to annulus 167. Bore 169 is fitted on each
end for hydraulic line connections to line 149. Bore 170
- is fitted on each end for hydraulic line connection to
line 148. Thus as spool 163 is rotated and pressurized
hydraulic fluid is supplied to inlet port 165 it is
equally and alternately distributed to ports 169 and 170.
~Z55~
- 13 -
Further it is distributed with no hydraulic prassure
originated side loading being applied to spool 163 as the
pressure outlets are directly opposecl. Further a
~- relatively large quantity of fluid can be distributed from
spool 163 since it is being distributed simultaneously at
two outlets.
Valve spool 163 further contain a second annulus 171
there through whose centerline passes through the
rotational centerline of spool 163 and is perpendicular to
the rotational centerline of spool 163. Annulus 171 is
positioned at a 90 degree spacing relative to the
centerline of annulus 167. The outer ends of annulus 171
are finely finished to form s~uare line and equal recesses
].72 into spool 163 and 180 degree spacing. Housing 150
contains a third bor~ 173 the~ethrou~ and a fourth bore
174 therethrough, bore 173 being in the same pl~n~ as bore
174 but at a 90 degree spacing from bore 17g. Both bore
173 and bore 174 being a plane perpendicular to the
rotational centerline of spool 163. Bore 173 is fitted at
each end to receive hydraulic line connection from line _ _
149. Bore 174 is fitted at each end to receive hydraulic
line connection from line 148. Bores 173 and 174 are
positioned to alternately mate with annulus 171 of spool
163 as spool 163 rotates thus forming two alternating
fluid inlet connections to annulus 171. Spool 163 further
contains a centrally located end port 175 which
communicates with annulus 171 and continually communicates
with fluid return port 155 in end plate 152. Bore 169 and
bore 173 are positioned in the same longitudinal plane
relative to rotational axis 176. Thus as spool 163 is
rotated fluid return port 155 will equally and alternately
be in communication with exhaust bores 173 and 174.
Recess 168 and recess 172 can be sized to regulate the
timing of fluid distribution as re~uired.
55~ ;D
-- 14 -~
Attention is directed to Fig. 8 and Eig. 5 where it
is clearly shown that as spool 163 is rotated, ~ressure
inlet port 165 of valve 150 is firstly in communication
~ through line 149 with the pressure chamber on~the rod end
of a first cylinder 85 while simultaneously fluid return
port 155 of valve 150 is first in communication through
lines 148 with the pressure chamber on the rod end of a
second cylinder 85. Secondly inlet port 165 is in
communication through line 148 with the pressure chamber
on the rod end of the second cylinder 85, while
simultaneously fluid return port 155 of valve 150 is
secondly in communication through line 149 with the
pressure chamber on the rod end of the first cylinder 85.
Thus as the spool 163 of valve 132 is rotated and
pressurized fluid is applied to inlet port 165, then the
pressure chamber of a one cylinder 85 can be supplied
fluid to cause it to expand while the p~essure chamber of
a second cylinder 85 can exhaust the same amount of fluid
through return port 155. It will be noted that a third
cylinder 85 can be added to operate from valve 132 by
addition of a third bore through housing 150 in a plane of
Fig. 6 and in the plane of Fig. 7 and thusly positioning
the three through bores at a 60 degree spacing relative to
the rotational axis. The same is true for a fourth or
more cylinder. In the case of a fourth cylinder 85, then
four through bores positioned at 45 degrees, etc.
However, three of cylinders 85 must be employed, or to be
more precise three or more pressure chambers o~ equal
displacement unless outside make-up fluid is employed, to
allow uninterrupted and continuously equal flow into inlet
port 165 and from outlet port 155 of valve 132 without
fluid flow bypassing said cylinders 85. Thus the mud pump
of this invention will normally employ three or more
cylinders 85, the circuit of figure 3 illustrating two
cylinders 85 only for ease of explanation. Also in the
circuit of figure 3 outlet 169 and 173 are illustrated
emerging from one side only of valve 132 for simplicity
reason as are also outlets 170 and 174. It is obvious
that lines 149 and 148 could be so internally ported
~-- within housing 150 as to eliminate excessive outside
piping.
To this end, prime motor 126 powers charge pump 127
to precharge the hydraulic circuit to a pressure as
determined by the setting of relief valve 131, preferably
in the 200 P.S.I. range. Motor 126 also powers main pump
125 to supply pressurized fluid to line 141. Pressurized
fluid travels through line 141 and enters valve 132 at
port 165. Valve 132 being controllably rotated by motor
133, this rotation being independent of fluid flow or
fluid pressure. Pressurized fluid is first directed to
line 14Y by ~alv~ 132 to pressuri~e chamb~r 9~ of ~ ~ir~t
hydraulic cylinder 85 while chamber 9~ of a second
hydraulic 85 is vented by valve 132 to hydraulic return
line 142 through outlet 155. Chambers 96 of cylinders 85
are connected by a common fluid line 146, thus as
pressurized fluid enters chamber 98 of first cylinder 85
it will force fluid out of chamber 96 of said first
cylinder and into chamber 96 of a second cylinder 85. The
fluid entering chamber 96 of said second cylinder 85 will
in turn force fluid from chamber 98 of said second
cylinder, which fluid will be returned to line 142 through
port 155 to be repressurized by pump 125. The amount of
fluid returning to line 142 will be the same as is leaving
from line 141, less leakage which -~s made up by charge
pump 127. This process is alternately and continually
repeated by cylinders 85 thus continually powerly stroking
cylinder rods 84 of cylinder 85. The stroke length of
cylinder rod 84 being determined by the amount of fluid
passed through line 141, or by the rotational speed of
valve 132. The pressure within hydraulic line 146 and
thus within chamber 96 of cylinder 85 is controlled by
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- 16 -
relief valve 138. Thus fluid pressure is applied to
chamber 98 of a first cylinder ~5 to powerly drlve piston
rod 84. In a one retracting direction the secondary
: pressure created in chamber 96 can powerly drive piston
rod 84 of a second cylinder in a second extending
direction. Thus work can be performed simultaneously by
all cylinders 85. When 3 cylinders 85 are employed as is
normally done in the mud pump of this invention, then the
pressure chamber 98 of two cylinders 85 can simultaneous
be receiving pressurized fluid while the chamber 98 of the
third cylinder 85 is exhausting fluid. Conversely the
pressure chamber 98 of one cylinder 85 can be receiving
pressurized fluid while the chamber 98 of the second and
third cylinder 85 are simultaneously exhausting fluid.
It will again be pointed out and stressed that valve
132 of thls lnvention is an independently driven valv~,
which means that its rotation is completely independent
from the movement of the piston 87 within cylinder 85.
This independently driven control valve 132 as employed in
the hydraulic circuit of Fig. 3 to effectively control the
movement of free floating pistons 87 is a new, innovative
and advantageous concept of hydraulic powered cylinder
control. The two major difficulties that have hindered
development of high horsepower hydraulic driven
reciprocating piston in the past has been the seemingly
impossible solution of supplying a large ~uantity of non-
pulsating pressurized flow to the cylinder while
controlling the timing of the cylinder stroke. This I
have accomplished in a relatively simple and practical
manner by adaptation of independent driven control valve
132 combined with several other techniques that will be
described in the following disclosures.
Referring to the hydraulic circuit of Fig. 3 it will
be pointed out that for the circuit to be operable from
.
., .
~55~
practical standpoint then piston 87 of cylinder 85 must be
in a position to move when pressurized fluid is admitted
to chamber 98 or stated in another manner, since piston 87
- is not positively timed in relation to valve ~32, then on
start-up if piston 87 is positioned at the expanded
directional end of its stroke and pressuri7ed hydraulic
fluid is directed to said expanded chamber, then damaging
pressure pulsation will occur as the pressure will surge
to the relief setting of high pressure relief valve 130.
To assure that this situation does not normally arise, a
variable volume pump 125 is employed as the fluid power
source, and the pressurized driving fluid is directed to
the rod end of cylinder 85. Note from the circuit of
Fig. 3 that on start up or at any time that prime motors
lS 126 and 133 ar~ operating a~d hydr~ulic pump 125 is
positioned in lts neutral or no flow position, th~n the
charge pump 131 will charge the complete system to the
pressure as dictated by the low pressure 131 relief valve
setting. This puts the same pressure on chambers 96 and
98 of cylinder 85, thus tending to expand chamber 96 due
to the area of piston rod 84, thus piston 87 will always
tend to position itself into a position to allow chamber
98 to be in a position to expand and thus automatically
assume a timed cycle relative to valve 132 as valve 132
rotates, without causing a high pressure surge. A low
pressure source will occur which is determined by the
relief valve setting of relief valve 138. Further, since
pump 125 is a variable volume pump, the flow going to
cylinders 85 is gradually increased which correspondingly
gradually increases the stroke length of piston 87 and
allows piston 87 to automatically assume a timed
relationship to valve 132 as piston 87 starts
reciprocating. Further when the system is operating and
the piston stroke length of cylinder 85 is decreased to
zero by changing the output of pump 125 to zero, then the
pistons 87 will automatically assume a near centered
. .
~ 2~ 5~`D
-- 18 --
position relative to cylinder 85 thus providing for piston
87 to be in a position to expand and automatically assume
a timed position with valve 132 as flow is again increased
: from pump 125.
,
As previously disclosed, the mud pump of this
- invention is a double acting pump which means that
cylinder rod 84 must supply force in each direction of
travel. This force re~uirement depends upon the mud
pressure being pumped and thus varies greatly. Therefore,
the pressure requirements within pressure chamber 96 and
thus line 146 varies considerably. The fluid reservoir
created by chambers 96 and lines 1~6 is a constant volume
for a given cylinder stroke length and is in essence a
closed re~ervoir; however, the reservoir o~ chamb~rs 96
are sub~ected to sliding seals and to leakage so make up
fluid must be continually supplied to this closed
reservoir from a source of higher pressure. This is done
by allowing a small volume of fluid to continually flow
from high pressure line 141 to line 146 through and
adjustable metering valve 135. __
..
Since there is no practical way to always supply the
! correct amount of make-up fluid to the closed reservoir of
~5 chamber 96 and line 146, and since this reservoir must
remain at or above the required volume, then an excessive
amount of fluid must be allowed to flow across metering
valve 135 and a suitable means provided to allow this
excessive fluid to discharge from chamber 96 without
causing excessive pressure surges. Note that the
excessive fluid passed therethrough chamber 96 is also a
means to provide cooling to chamber 96.
Piston 87 of cylinder 85 will automatically force
fluid from chamber 96 across relief valve 138 as the
piston strokes and chamber 96 will automatically assume
~5~
- 19 -
the correct volume. However, there will be damaging
pressure surges on the complete high pressure circuit
unless valve 138 is set to dump fluid at a pressure only
~ slightly above the pressure that is required in chamber
96. The required pressure in chamber 96 being that
pressure that is necessary to move piston rod 84 against
its load. Its load being varied as previously described.
Thus relief valve 138 must be capable of sensing the
loading requirement of chamber 96 and adjusting to allow
fluid bypass therethrough at a pressure slightly higher
that the load requirement, if this system is to function
with a minimum of pressure surges. It will be noted that
the pressure surge required to remove fluid from chamber
96 can be excessive, if not controlled, due to t.he larger
pi~ton area of piston 87 that it is acting against, and
also due to ~he ~act ~hat the su~ge i8 ~uddon bec~u~o the
excess fluid will be discharged very suddenly when one of
pistons 87 has reached the end of its stroke. When above
said piston 87 has reached the end of its stroke as
described, then the pressure in chambers 96 will suddenly
jump from whatever the required pressure to move piston
rod 84, to whatever the relief valve 138 is set to
relieve.
To overcome the above described conditions and
maintain the said pressure surge to an acceptable and
workable range, unique circuitry employing a gas operated
accumulator 139 is used. Accumulator ~39 contains a
pressure chamber 177 filled with a compressible gas, a
pressure chamber 178 for connection to hydraulic fluid,
and moveable piston or diaphragm element 179 sealably
separating the two chambers. Chamber 177 is filled with a
compressible gas and pressuri~ed to approximately the same
pressure as the charge relief valve 131. Chamber 178 is
connected through check valve 137 and metering valve 136
to the closed reservoir formed by chamber 96 of cylinder
5~
- 20 ~
85. A line 147 connect the vent port of relief valve 138
to hydraulic chamber 178. As anyone versed in the art of
hydraulic is aware, the vent port of a relief valve 138
-- can be utilized to control the pressure at wh~-ch said
relief valve allows flow to pass therethrough. Flow will
pass across said relief valve at a pressure equal, or just
above due to a spring loaded plunger within said valve, to
the pressure at which flow is allowed to pass from the
vent port. I will not describe the internal operations or
relief valve 138 as this is a well known art. Chamber 178
of accumulator 139 is connected to chamber 96 of cylinder
85 through a one way check valve 137 that allows flow from
chamber 178 to chamber 96 but blocks 10w in the opposite
direction, chamber 178 is also connected to chamber 96
through a variable volume metering valve 136. 'rhus when
pump 125 i~ suppl~ing pr~ss~ri~ed flow to l~nes 1~1 then
the pressure formed by chamber 96 will continually be
maintained at a pressure as required to cause piston rod
84 to move against its load through metered pressurized
flow across valve 135. The pressure in chamber 178 of
accumulator 139 will also be equal to or slightly above _ _
through valve 137 and valve 136, the said required
pressure of chamber 96. If chambers 96 contain an
excessive amount of fluid then as a one piston 87 of
cylinder 85 reaches the end of its stroXe in the rod end
direction, then the pressure in chamber 96 will start to
rise. The rise in pressure will cause fluid to flow from
the vent port of relief valve 138 to chamber 178 of
accumulator 139 and thus allow relief valve 138 to pass
flow therethrough to low pressure line 142 thus allowing
the excessive fluid to be dumped from chamber 96 at a
pressure just higher than the required pressure in chamber
96. Chamber 178 will assume the pressure of chamber 96
through a valve 137 and valve 136, however, chamber 178
will not be subject to a sudden pressure surge due to
blockage of flow at valve 137 and a metering of flow at
. "
- 21 -
valve 136 and also vent flow from valve 138 is internally
metered within valve 138. Thus due to the compressibility
of the gas in chamber 177, the fluid pressure in chamber
- 178 will rise at a slower rate that the pressure in
chamber 96, thus allowing valve 138 to dump excess fluid
from chamber 96. This process is continually repeated,
- thus keeping the fluid volume and pressure requirement of
chamber 96 as necessary to continually operate cylinder
rod 84 in a powerly reciprocating manner.
Thus it is noted that as a quantity of pressurized
fluid is supplied to valve 132 by pump 141, and valve 132
distributes this fluid to chamber 98 of cylinder 85, then
piston 87 will assume a stroke that is synchronized with
the rotation of valve spool 163. This synchronization
will occur, pulse ~ree, A~ long as chamber 98 is free to
expand and piston rod 8~ has equal loading, an~ the
correck pressure is maintained in chambers 96. The
pressurized fluid within chamber 96 assures that piston 87
either assumes a somewhat centralized position or a rod
end position within cylinder 85 whenever the fluid flow to ___
cylinders 98 is decreased thus decreasing the stroke.
Thus piston 87 will always assume a position to allow
surge free synchronization with valve 132 and to allow
25 surge free increase and decrease of its stroke length.
The requirement for surge-free synchronization between
piston 87 and valve 132 being that the stroke length of
piston 87 be reduced to a given amount prior to cease of
stroking of pistons 87 and that on start of stroking of
30 piston 87 the supply of pressurized fluid to chamber 98 be
at a given minimum. The given minimum being dependent
mainly upon the rotational speed of valve 132. However, a
surge free synchronization can always be assured by
bringing the pressurized fluid flow supply to valve 132 to
a zero value at a reasonable reduction rate to cause
piston 87 to cease stroking, while correspondingly
- 22 -
increasing the pressurized fluid flow rate to valve 132 at
a reasonable increase rate to commence stroking of pistons
87.
Thus it has been shown that independent operated
valve 132 can receive, distribute, and return a large or a
varying quantity of pressurized fluid without flow
interruption or without damaging pressure side loading
effect upon said valve; that free floating piston 87 and
thus cylinder rods 84 can be reciprocally and alternately
powered in both directions of travel by said large or
varying quantity of pressurized fluid, that the piston
stroke length of piston 87 is controllabl0 as desired and
that said piston stroke length can be started, stopped, or
operated continuously without excessive pressure surges
and with an automatically assumed synchronization between
the rotation of valve 132 and the stroke c~cl~ o~ piston
87.
It has additionally been shown from previous
discussion that the loading upon each piston rod 84 will
be equal when the above reciprocating piston system is
employed to drive the mud pump of this invention. This
e~ual loading of piston rod 84 being obvious from the
~5 disclosure that each piston of said mud pump discharges
its flow directly into a pressure chamber common to all
pistons of said mud pump.
Further unique operating characteristics of this pump
are provided by the illustrated circuitry of Fig. 3
combined with the independent operated rotary valve. In
the operation of the hydraulic drive system, t~ere can
actually be two distinct modes of operation - depending
upon the start up relation between valve and cylinder. If
the cylinders are all retracted completely, then the
actual timing position between valve and piston can be
I
~ '`'
~2~5~
- 23 -
slightly different from what it is if the pistons are
positioned near mid range and free to move in each
- direction. The preferred mode of operation is with the
~- pistons starting from a position not completeE~ retracted.
There are numerous means to assure that t~e pistons are in
the preferred position at start up. It would normally
- occur when the circuitry is arranged as shown in Fig. 3
because valve 131 would normally be set at a low enough
pressure so that frictional forces upon the cylinder
piston rod would be enough to keep the piston of cylinder
85 in the "stopped" position unless drive pressure were
applied to line 141. Another means that could be employed
would be to remove check valve 134 and block line 146 at
this position, then install a shut off valve on one side
o valve 135 with thls shut off valve being arranged to
open when pump 125 applies pre~sure to line 141 and to
close when pump 125 returns to zero flow, thus the pistons
of cylinder 85 would be "locked" into the "stopping"
position until the system is again started. It will also
be noted that the line 145 leading from high pressure
relief valve 130 can be connected to line 142 if desired
to prevent a pressure drop in line 142 when fluid is by-
passed across valve 130. It is also noted that the line
leading from relief valve 138 can be connected to line 142
if desired instead of to reservoir 140 as illustrated to
assist in prevention of a pressure drop in line 142.
It is additionally pointed out that the two modes of
operation as discussed above actually encompass two
different methods of the excess fluid being dumped from
the interconnect chamber 96. In one case - the preferred
case, the excess fluid is forced from the interconnected
cylinder spaces as the valve is relatively closing against
flow from a cylinder 98 space; in the second case, when
the system is started with the cylinders in the fully
retracted position, then the valve can assume a relative
i5~
- 24 -
.position where the excess fluid is dumped prior to the
opening of a cylinder 98 space. The degree of change
between the relative position of valve and piston is
~- small; however, the degree of operational cha~acteristics
is large as the preferred case, the ~irst case, allows a
much broader range of cylinder piston speed and stroke
: length adjustment without system malfunction.
A pump according to the present invention has the
capability to operate effectively at a large horsepower
capacity. Oilfield mud pumps generally need to operate at
a horsepower capacity of anywhere from l00 to 2000
horsepower. Thus when operating a hydraulic system of
this type it is an absolute re~uirement rom a practical
lS standpoint to have a system that does not experience
sudden ~luid 1Ow blocka~e or doe~ not exp~ri~nc~ a
continued bypas~ of a large quantity of pressurized fluid.
For example a l000 horsepower system would require a fluid
flow of approximately 500 gallons per minute at 3000
p.s.i. pressure. This represents a tremendous amount of
flowing energy and the machinery required to produce this _ __
energy cannot in actual application withstand shocks or
heat that is generated from such practices as sudden flow
stoppage to allow a valve to shift, or for a piston to
move from a dead ended position, or for venting back to
tank a large quantity of pressurized fluid to control a
piston stroke length. For e~ample, if hal the above said
flow was vented to tank to cause a piston stroke length to
change by one half, then it would require an additional
500 horsepower system to control the cooling of the vented
fluid. To this end the pumping system that I have
disclosed is an extremely versatile and controllable fluid
pumping system that is relatively simple and can
effectively and in a practical manner be continually
operated to transmit a high horsepower capacity.
2~55~
- 25 -
The foregoing is directed to the preferred
embodiment, but the scope of the present invention is
determined by the claims which follow.
.
