Note: Descriptions are shown in the official language in which they were submitted.
Brief Description of the Prior Art
The closest patent is No. 1,926,869 issued to Galloway.
In that patent the rate of advance of a mechanical device which
is advanced by a hydraulic piston connected to a shaft is
controlled at preselected positions by a mechanical-hydraulic
circuit. The means of accomplishing the variation in advanced
speed, however, is radically different than that disclosed in this
invention. Galloway uses a sliding valve which opens various
ports to accomplish the variation in speed of the piston in a
control cylinder.
This invention, however, is an improvement over an
existing device manufactured by FISHER Controls, the best example
of which is shown in a catalogue bulletin 61.5:320 published
January, 1973, and specifically labeled 320 Series electro-
hydraulic actuator. In that apparatus a valve actuator is
illustrated using a mechanical feedback to an electro-servo valve.
The electro-servo valve is ported directly from the output to the
ports in the cylinder.
Brief Description of the Invention
This invention is an improvement on an electro-hydraulic
actuator similar to that manufactured by FISHER Controls and
above described. One of the basic problems with some applications
of the electro-hydraulic actuator described is the generation of
a severe water hammer when the valve contrGlled by the actuator
reaches its nearly closed position. The rapid shutoff of the fluids
fl~wing through the valve creates a damaging water hammer effect,
particularly in the downstream side of the control valve. The
water hammer can be so severe that the pumps, valves, and other
apparatus including the line can be stressed to the fracture point.
This invention
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provides a means for rapid closure of the valve which closure
rate is absolutely necessary under precision control condi-
tions, and yet prevents the water hammer effect by suddenly
slowing the closure of the valve when it reaches the point
where water hammer would be developed if the valve were
closed at that same rate.
The modification in closure rate is accomplished by
mechanically sensing the position of the shaft, coupling the
actuator cylinder to the valve, and, once a predetermlned
position is realized, an output is generated by the mechanical
sensing device which output is applied to a valve inserted in
series with one of the lines coupling the series hydraulic
valve output with one of the ports in the actuator cyl~nder.
The remotely-operated valve can be a solenoid valve which
is normally open when connected in parallel with a needle
valve which is ad~usted to provide a flow which will sub-
stantially reduce the closure rate of the actuator cylinder
shaft. If the valve can be opened at any rate without
ereating a water hammer~ a check valve can be inserted in
parallel with the needle valve in the direction to permlt
free flow of fluids through the check valve when the piston
in the actuator chamber is being repositioned in the direction
to open the valve. Instead of a solenoid valve, other
variations can be substituted to create other than linear
responses when a faster closure rate is necessary at the
critical point in the closure of the valve.
Brief Description of the Figures
FIGURE 1 is a schematic layout of the servo-con-
trolled valve illustrating the placement of the control
~0 valve an~ tne operation of the system in conJunction with
a slurry transportation mining system;
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FIGURE 2 is a graph showing the stroking speed versus
percentage closure of the shaft in relationship to the control
valve; and
FIGURE 3 is a modified form of the system shown in
FIGURE 1.
The invention consists in, in a control valve actuated
by a hydraulic system which includes a cylinder having first and
second ports on each side of the piston which is slidably
mounted therein, a shaft attached to said piston and mechanically
connected to said control valve, an electro-hydraulic servo-
control valve having an electrical and mechanical input and
first and second hydraulic output ports and means for hydraulic-
ally coupling said first and second output ports to each of
said first and second cylinder ports, respectively, a mechanical
feedback operatively coupled from said shaft to the mechanical
input of said servo-control valve, and an electrical control
apparatus connected to the electrical input of said servo-valve,
apparatus for controlling the rate of movement of said shaft
comprising control valve closure sensing means responsive to a
preselected closure of said control valve and developing an
output signal when said preselected closure is realized; a sole-
noid controlled valve and a controllable valve connected in
parallel said solenoid controlled valve and said controllable
valve connected in series with one of said means for hydraulic-
ally coupling said first or second output ports to said first
and second cylinder ports, respectively; a valve controller
having an input and an output, and means for coupling said valve
controller input to said sensing means and means for coupling
the output of said valve controller to said controllable valve;
and means having an input responsive to said sensing means
output signal for operating said solenoid controlled valve.
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Detailed Description of the Invention
Similar numbers will be used throughout the
specification for similar elements.
The electro-hydraulic actuator ordinarily includes
a servo-valve 10 which has an electrical control apparatus 11,
a mechanical input 12, and output hydraulic ports 13 and 14.
The servo-valve hydraulic ports are coupled through pipes 15
and 16, respectively, to input ports 17 and 18 of actuator
cylinder 19. Cylinder 19 contains a piston 20 slidably sealed
to cylinder 19 with an "O" ring 21, for example. A shaft 25
is axially coupled to piston 20 and to a control valve 26.
Valve 26 is the normal fluid type valve such as a"V"ball valve
which is actuated by rotating the valve stem. Several types
of valves could be used in place of the "V" ball valve 26 as
long as the valve is actuated either by a sliding type closure
or by rotation of the stem through suitable mechanical means.
A mechanical feedback 27 is coupled to shaft 25 by a clamp or
other suitable means 28 and to the mechanical feedback input 12
of servo-valve 10. A water source 30 is coupled through a
pipe 31 to the inlet 32 of control valve 26. The outlet 33 of
control valve 26 is coupled through a pipe 34 to a manifold 35
of a slurry hopper generally referred to by arrow 36. Slurry
hopper 36 is nearly filled with water which is maintained at
a proper height by a level sensor 37 which has an . . . . . . .
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electrical output ~8 coupled through a wire ~9 to controller
40. Controller 40 has a preselected set point 41 which
compares the voltage or signal through wire ~9 and generate~
an output on a wire 42 which is applled to an input 43 of
electrical control apparatus 11 of servo-valve 10. A mining
machine 45 removes coal in the ordinary manner with a plurality
of digger elements 46 and conveyæ dislodged coal 47 into a
crusher element 48, for example. The material, once crushed,
falls in the direction of arrows 49 into slurry hopper 36.
The material in slurry hopper ~6 is mixed with water and
removed by a pump 50 and discharged to an outlet line 51
where it is transported to the surface of the mine, for
example. One of the basic problems with the sy~tem as above
constructed is the excessive water hammer which developed
when control valve 26 was rapidly closed as was necessary
in order to prevent overflow of water from hopper ~6.
The invention primarily consists of a means for
preventing the creation of conditions which lead to the
generation of a water hammer in the ~ystem caused by the
rapid closure Or control valve 26. It was discovered that
the control valve 26 could be closed at a high closure rate
until the valve was approximately 75 percent closed. At that
point, if closure continued at the same rate, a water hammer
would develop. In order to slow down the clo~ure rate once
the valve was 75 percent closed, a shaft position sen~ing
circuit was installed WhiCh consi~t~ of a cam 55 adJustably
attached through a collar 56 to shaft 25. An electrical
switch 57 is positioned so that its switch arm 58 can be
operated by cam 55. An output circuit i5 coupled through a
~0 wire 59 to a solenoid 60 which operates a valve 61. Valve 61
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is connected through pipes 62 and 63 in series with pipe ~5
so that the fluid flowing through pipe 15 must flow through
valve 61. A second valve 64 is positioned parallel with
valve 61 and may be a needle valve which can be adjusted to
a predetermined flow or an electrically operated valve hav~ng
an input 65 which is coupled through a wire 66 to a valve
controller 67. An input 68 is, likewise, coupled from wire
59 to valve controller 67. A mechanical feedback 69 can also
be coupled to the mechanical feedback 27.
Depending upon the operations desired, a check
valve 70 can, likewise, be positioned in parallel with valves
61 and 64. Other combinations of valves can be utilized as,
for example, that illustrated in FIGURE 3. Such a system
can be installed in the circuit shown in FIGURE 1 at points
A-B and essentially consists of a solenoid 60 coupled to a
solenoid-operated valve 61 as previously described and a
needle valve 75 coupled in parallel with valve 61.
~ epending upon the operation desired, a check valve
76 can be positioned, likewise, in parallel with the previously
mentioned valves.
~E~eration
The operation will first describe the system as
used without the invention incorporated.
Water from source 30 travels through pipe 31 to
inlet 32 of control valve 26. From control valve 26 the
water travels out outlet 3~ through pipe 34 to mani~old 35
where lt is distributed into hopper 36. Level sensing ap-
paratus 37 measures the height of the water in hopper 36 and
develops an output 3~ corresponding to said height. The
neight will vary on occasions~ depe~.ding upon the a~lount of
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coal dislodged by mining machine 45 and conveyed into
crusher 48 which, as previously described, falls in the
direction of arrows 49 into hopper 36. ~s the water level
varies as a consequence in variation in the amount of coal
being deposited into hopper 36, level sensor ~7 will have
its output delivered through wire 39 to controller 40.
Set point 41 was previously set to a particular
water level which may, for example, be several inches below
the top of hopper 36. Thus as the signal through wire 39
varies, the variation will be compared with the set point
signal 41. Any error above or below the set point ~ignal 41
will be manipulated such that an output signal will be com-
municated from the controller 40 through wire 42 to input 43
of electrical control apparatus 11. Apparatus 11 will com-
municate this electrical variation to servo-valve 10 where
it will be converted to a hydraulic variation in pressure
and flow through outlet ports 13 and 14. As an example,
i~ the water level is getting too high in hopper 36, the
pressure in outlet 1~ will increase, causing a flow in pipe
15 to the inlet port 17 of cylinder 19. A reduction in
pressure will be exhibited at port 14, causing a drop in
pressure at port 18. With the increase in pressure at port
17 and a decrease in pressure at port 18, piston 20 will move
in the direction of arrow 80, causing a closure in control
valve 26. The amount that control valve 26 will close will
depend upon the magnitude of the signal being received by
electrical control apparatus 11. If the signal required
complete closure o~ the valve, once the valve reached 75 per-
cent closure and continued closing a severe water hammer did
~0 resul~. In order to eliminate the water hammer problem, a
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;h~ r ~ positi~n sensing apparatus was installed so that cam 55
would strike switch arm 58, signaling through wire 59 to
solenoid 60 that the shaft position had been reached at which
time solenoid 60 should operate valve 61. Upon closure of
valve 61 J fluid must then pass through valve 64 (check valve
70 is closed when the fluid is passing from port 13 to port 17).
If valve 64 is~ for example, a needle valve 75 (such a valve
is illustrated in FIGURE 3), then the ~luid will reduce by
a predetermined amount. See, for example, FIGURE 2 where
a stroking speed is illustrated vertically and percentage
closure o~ the valve is illustrated horizontally. Line 90
illustrates that full flow is realized until 75 percent
closure is reached. At this point, illustrated by No. 91,
solenoid 60 closes valve 61, and the pressure will drop
along lines 92 to a new level 93 until the valve is 100
percent closed. The drop is illustrated as half that
permitted when solenoid valve 61 is open. This, of course,
can be set at any level and not necessarily that illustrated
in the graph. When it is necessary to reverse the above
~0 process, that is, control valve 26 should now be opened, the
solenoid will of necessity remain closed until cam 55 moves
away from switch arm 5~. If check valve 70 is not in the
hydraulic circuit, the opening of valve 26 will be precisely
the same speed for percentage closure as was the closing of
the valve, that is, as it advances from 100 percent closure to
0 percent closure, it will overflow along lines 93, 92 and 90.
~Jith the check valve present in the hydraulic circuit, however,
the valve ~rill open along lines 94 and 95 to line 9~. If
valve 64 can be proportionately controlled by a valve con-
~0 troller circuit 67, then any actual curve can be utilized asillustrated, ~or example, by lines 96 or a7~
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Referring to FIGURE 3, fluid flowing in pipe 15
from "A" to "B" will flow freely through valve 61 and by
a predeter~ined amount through needle valve 75. No flow
will pass through check valve 70. When solenold valve 61
is closed by solenoid 60, the only flow is through valve 75.
A,curve similar to 90, 92, and 9~ in FIGURE 2 will result.
- When flow through pipe 15 is reversed, check valve 70 will
permit free flow as illustrated by curves 94, 95, and 90
of FIGURE 2.
Conclusions
Two modifications of the ramplng circuit have been
illustrated. It is obvious that other combinations of
circuits can be realized and still be within the spirit and
scope of the inventlon. It is further obvious that the ramp
circuit need not be supported in the particular hydraulic
line 15 illustrated but can be inserted in hydraulic llne
16 and work equally well. Furthermore, a single æhaft posi-
tion sensing circuit has been illustrated. It is further
obvious that several shaft positioning circuits could be
incorporated providing a plurality of steps for decreasing
the shaft closure rate and vice versa.
Although only the preferred embodiment of the
present invention has been illustrated and described, it
w111 be apparent to those skilled in the art that various
changes and modifications may be made therein without depart-
ing f rom the spirit and scope of the invention or from the
~cope of the appended claims.
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