U.S. patent number 3,568,705 [Application Number 04/851,288] was granted by the patent office on 1971-03-09 for hydraulic system circuit breaker.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to George I. Boyadjieff, Robert K. Van Ausdal, Ralph L. Vick.
United States Patent |
3,568,705 |
Boyadjieff , et al. |
March 9, 1971 |
HYDRAULIC SYSTEM CIRCUIT BREAKER
Abstract
A hydraulic circuit breaker or fail-safe device is disclosed for
sensing leaks in lines to and from hydraulic actuators or the like.
Flow through the line is sensed across a restriction on a piston
valve member movable to close the line, the size of the restriction
being such that flow in excess of normal requirements causes a
significantly increased pressure drop, which drop is sensed across
a quantity measuring piston movable in a chamber within the
piston-valve, and causing the latter piston to move within its
chamber at a rate controlled by the area of a control orifice. As
this latter piston moves, it carries a shaft which is spring biased
to resist movement until the pressure drop across the restriction
reaches a value indicative of a leak. Two spool valve members are
carried on the shaft whose function in the two embodiments shown is
to direct either supply pressure or lower pressure against
operating areas of the piston-valve to control its movement to open
or close the line. A check valve is placed in a return line and an
additional piston in contact with the biasing spring senses a leak
in the return line as indicated by a changed pressure drop across
the check valve and moves to either remove the effective spring
bias on the shaft or to move the shaft directly such that the spool
valve members direct flow to cause the piston-valve to close the
line.
Inventors: |
Boyadjieff; George I. (Woodland
Hills, CA), Van Ausdal; Robert K. (La Crescenta, CA),
Vick; Ralph L. (Granada Hills, CA) |
Assignee: |
The Bendix Corporation
(N/A)
|
Family
ID: |
25310417 |
Appl.
No.: |
04/851,288 |
Filed: |
August 19, 1969 |
Current U.S.
Class: |
137/87.04;
91/468; 137/460 |
Current CPC
Class: |
F15B
20/005 (20130101); Y10T 137/7727 (20150401); Y10T
137/2705 (20150401) |
Current International
Class: |
F15B
20/00 (20060101); F16k 017/22 () |
Field of
Search: |
;137/87,460,487
;91/446,447,468 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nilson; Robert G.
Claims
We claim:
1. A hydraulic safety device for connection between a source of
hydraulic fluid under pressure and a device to be controlled
comprising:
a housing having an inlet port connected to said source, a high
pressure outlet port connected to said supply controlled device,
and a return port for receiving return flow from said device;
a chamber in said housing connecting said inlet port and said high
pressure outlet port;
a first piston movable in said chamber between a first position in
which flow passes between said inlet port and said high pressure
outlet port and a second position where said high pressure outlet
port is blocked; said piston including ridge means cooperating with
the walls of said chamber to form a restricted passageway, and a
second chamber within said piston;
resilient means in said housing urging said piston toward said
first position;
a shaft and a second piston in said second chamber carried on said
shaft and first and second passages communicating opposite sides of
said second piston with opposite sides of said ridge means;
a third piston on said shaft positioned in normal operation to
permit communication between the inlet pressure side of said second
piston and one end of said first piston, and movable with said
second piston to a second position to interrupt said communication
and to open communication between said one end of said first piston
and a source of hydraulic fluid at return pressure;
a fluid chamber adjacent said shaft and an orifice positioned to
control the rate of flow out of said chamber and, therefore, the
movement of said shaft; whereby when a leak occurs downstream of
said high pressure outlet port the resulting fluid pressure
differential across said restricted passageway is sensed across
said second piston causing said second and third pistons to move
against the force of said resilient means and at a rate controlled
by said orifice until said third piston reaches its second
position, causing said first piston to be moved by the force of
inlet pressure from said first position to said second
position.
2. A hydraulic safety device as set forth in claim 1 wherein a
check valve is located between said return port and the return side
of said source, a fourth piston is positioned coaxially with said
shaft and fluid conduits are provided connecting opposite sides of
said fourth piston across said check valve, such that upon the
occurrence of a substantial loss of pressure upstream of said
return port, said check valve will close and said fourth piston
will sense the differential across said check valve and will move
to compress said spring, moving said shaft until said third piston
blocks communication between said inlet port and said one end of
said first piston thus releasing the high inlet pressure acting
against said one end and causing said first piston to move to said
second position.
3. A device for blocking a flow of fluid from a high pressure
source to a utilization device in response to excessive flow
indicating a leakage comprising:
a housing;
an inlet conduit connecting said source with said housing;
an outlet conduit connecting said housing with said utilization
device;
a return conduit connecting said utilization device with said
housing;
first valve means in said housing movable from a first position
permitting flow from said inlet conduit to said outlet conduit to a
second position in which flow from said inlet conduit to said
outlet conduit is blocked, and flow restriction means associated
with said first valve means;
second valve means including pressure responsive means for sensing
the pressure drop across said flow restriction means and flow
directing means movable with said pressure responsive means to a
first position to connect one side of said first valve means with
fluid pressure in said inlet conduit to maintain said first valve
means in its said first position or to a second position to direct
fluid pressure acting against said one side of said first valve
means to said return conduit which permits said first valve means
to be moved to said second position;
a chamber containing fluid in contact with said second valve means
and orifice means restricting flow from said chamber to control the
rate of movement of said second valve means; and
resilient means urging said second valve means toward a position
where inlet conduit pressure is directed against said one side of
said first valve means.
4. A device for blocking a flow of fluid as set forth in claim 4
including a check valve connected between said return conduit and
the return side of said source; pressure responsive means connected
across said check valve to sense the pressure drop across said
check valve and movable in response to a substantial drop in
pressure in said return conduit in a direction to oppose said
resilient means, thereby moving said second valve means such that
said flow directing means connects said one side of said first
valve means with said return conduit, thus causing said first valve
means to be moved to its second position.
5. A device for blocking a flow of fluid as set forth in claim 3
wherein said first valve means includes a piston having said one
side, an opposite side and in inner chamber, and said second valve
means includes a second piston movable within said inner chamber
and communicating with opposite sides of said flow restriction
means.
6. A device for sensing a flow of fluid as set forth in claim 5
wherein said piston is fastened to a shaft movable therewith, said
flow directing means constitutes a spool valve member on said
shaft, a chamber communicating with the opposite side of said
piston is provided containing fluid communicating with said return
conduit, and an additional spool valve member is carried on said
shaft such that when said second valve means is in its first
position, it blocks flow between said outlet conduit and said
chamber, and when said second valve means is in its second position
it permits flow between said outlet conduit and said chamber.
7. A device for sensing a flow of fluid as set forth in claim 6
wherein said first valve means encloses said first named chamber
which communicates with said return conduit, and a second piston is
carried on said shaft and movable within said first named chamber,
said piston including said orifice means.
8. A device for blocking a flow of fluid as set forth in claim 5
wherein said piston is fastened to a shaft movable therewith, said
flow directing means constitutes a spool valve member on said
shaft, said first named chamber forms part of said inner chamber, a
third piston forms one end of said inner chamber, a passageway is
provided in said third piston communicating said first named
chamber with said return conduit and said orifice means is
positioned in said passageway.
9. A device for blocking a flow of fluid as set forth in claim 8
including a check valve connected between said return conduit and
the return side of said source, a fourth piston is connected across
said check valve to sense the pressure drop across said check valve
and movable in response to a substantial drop in pressure in said
return conduit in a direction to oppose said resilient means,
thereby moving said second valve means such that said spool valve
member connects said one side of said first named piston with said
return conduit thus causing said first piston to be moved to its
second position.
Description
BACKGROUND OF THE INVENTION
In large aircraft currently available and under development many
separate hydraulic actuators are used to operate control surfaces,
landing gear, and other hydraulically operated devices. In the case
of actuators for control surfaces, it has become a rather common
feature of design to include paralleled actuators arranged for
redundant control such that if one actuator fails or sticks,
another will make possible either partial or complete operation of
the control surface. This large number of hydraulic actuators, of
course, requires that a source of a good quantity of hydraulic
fluid under pressure be available, and it is apparent that the loss
of a substantial proportion of the available hydraulic fluid may
cause impairment of a number of the actuator functions, even though
redundancy is provided. There is, therefore, a need for means which
will sense a loss or leakage of fluid and will act to block certain
passages to eliminate this fluid loss so that a sufficient supply
will remain to operate other control surfaces even though one or
more may be inoperative. Such a sensing and control device should
not introduce substantial problems of its own, either as to
operation or as to safety.
SUMMARY OF THE INVENTION
Two embodiments of our hydraulic circuit breaker design are shown
which include three basic elements: (1) a pressure line shutoff
valve; (2) a flow rate/quantity sensor; and (3) a return line check
valve. The units operate to trip and block flow from a source to a
downstream utilization device upon the occurrence of either excess
supply flow or a loss of return line pressure. Either case requires
a fixed quantity of flow to pass through the circuit breaker after
sensing a loss before the unit trips.
The flow rate and quantity sensor, built into the shutoff valve
spool, operates by sensing supply line pressure drop across the
shutoff valve lands. This pressure drop, a square root function of
the supply flow rate, drives a small piston inside the spool
against a larger piston with a trapped volume behind it. The
trapped fluid flows through a restricting orifice, proportional to
the square root of the developed pressure. This developed pressure
is related to the supply flow pressure drop by the area ratio of
the pistons, and hence, cancels out, and the bleed flow through the
restriction will be directly proportional to the supply flow rate.
Thus the movement of the pistons is a measure of the supply flow
quantity and is used as a quantity sensor. Another embodiment makes
use of a bleed in a small conduit communicating with a chamber
containing the sensing piston without utilizing the larger piston
and bleed arrangement.
The pistons are preloaded by a caged spring which determines the
threshold or tripping flow rate. For pressure drops below the
spring preload, no piston motion occurs. For pressure drops above
the preload, this piston moves at a rate proportional to the supply
flow rate and hence reaches the end of its stroke at a given
quantity of flow. The piston rod also carries small shuttle valves
that port supply pressure to the ends of the supply shutoff valve.
At the end of the quantity-measuring stroke, supply pressure is
shuttled from holding the shutoff valve open to forcing it closed.
Finally, as the shutoff valve closes, it locks the pistons in the
tripped position, preventing recycling. Resetting of the circuit
breaker occurs automatically when the supply pressure is reduced to
zero by shutting off the engine-driven pump. The preloaded
threshold spring will drive the pistons and shutoff spool to their
initial position. Also, if the overload flow quantity is
insufficient to fully stroke the pistons and the supply line
pressure drop decreases below the threshold pressure, the spring
will reset the pistons. This feature prevents a series of transient
overloads such as start-up flow in excess of rated amounts, due to
air in the lines, from tripping the circuit breaker.
Return line failure is sensed by comparing the pressure drop across
the return line check valve. When the check valve closes and the
load side of the return line pressure drops a given amount below
the reservoir pressure, the return failure sensor decoupled the
threshold spring from the supply flow sensor. When the supply flow
quantity accumulates to the tripping quantity under this condition,
the circuit breaker trips. The flow sensor can no longer reset;
hence, it trips on accumulated quantity when return failure occurs.
This accumulated supply flow trip in necessary for return failures
because excess flow does not occur due to return line failure.
From the foregoing, it will be apparent that our hydraulic circuit
breaker either senses excess supply flow indicating a loss
downstream from itself and trips to close off the line or it
responds to return line failure to close off the line. It resets in
normal operation when the system is shut down because the supply
pressure is reduced to zero, but so long as there is any
substantial supply pressure it does not reset and there is,
therefore, no inadvertent reset in operation. Reset occurs normally
without specific crew action, and the device does not react to
short term pressure fluctuations and cause a shutoff prematurely
since a significant amount of flow must occur simultaneously with a
lower pressure downstream of the actuator before shutoff will
occur.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of an embodiment of our hydraulic
circuit breaker;
FIG. 2 is a partial sectional view somewhat enlarged, of the device
of FIG. 1 showing the circuit breaker in tripped position;
FIG. 3 is a sectional view of another embodiment of our hydraulic
circuit breaker.
FIG. 4 is a partial sectional view of the device of FIG. 3 wherein
the device is shown tripped in response to pressure line
failure.
FIG. 5 is a partial sectional view of the device of FIG. 3 shown in
tripped position in response to a return line pressure failure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, a circuit breaker is depicted in section
in connection with a housing 10. Operating fluid from a high
pressure source enters an inlet passage 12 where it communicates
with a cylindrical chamber 14. An outlet passage 16 communicating
with an actuator or other utilization device downstream from the
housing 10 also communicates with cylindrical chamber 14. Axially
movable within the chamber 14 is a piston member 18 carrying on its
surface a land 20 which operates in conjunction with the surface of
cylindrical chamber 14 to provide a metering passageway. A pair of
ports 22 and 24 provide access to the interior of piston 18 which
contains a cylindrical chamber 26 and a piston 28 reciprocates
within chamber 26. Piston 28 is carried on a shaft 30 which also
carries pistons 32 and 34, a spool member 36 at the left end
containing a spring retainer 39 and at the opposite end a larger
piston 38 positioned within a cylinder 40 formed in an enlarged
extension of piston member 18, the piston 38 containing a bleed 42.
Also positioned within piston 18 is a cylindrical chamber 44 which
communicates with a chamber 46 and a port 48 communicating with a
larger chamber 50 exterior of piston member 18. Also positioned
within piston 18 is an additional small cylindrical chamber 52
which communicates with the cylindrical chamber 26, as well as with
a larger diameter chamber 54 through a passageway 56. A spring 58
is positioned within a chamber 60 in housing 10 and urges piston 18
to the right away from retainer member 39. Also positioned in
cylindrical chamber 60 is a slide valve member 62 which
communicates through a passage 64 with return fluid pressure in a
return passage 66. A check valve 68 in the return line 66 to a
reservoir (not shown) is biased against pressure from the return
side of the actuating device in conduit 69 by means of a spring 70.
Chambers 50 and 60 communicate with the load side of the return
line through conduits 72 and 74, respectively.
Under normal operating conditions the flow from inlet passage 12 to
outlet passage 16 across land 20 will be limited to that required
by the necessary displacement of the associated actuator or other
device. The pressure drop across land 20, which is sensed by means
of piston 28, will be insufficient to cause a significant movement
of piston 28 and, hence, shaft 30. In the event of a substantial
leak downstream of land 20, the pressure drop across this orifice
will increase substantially, causing piston 28 to begin moving
toward the right. As piston 28 carries shaft 30 toward the right,
it also carries piston 38 in cylindrical chamber 40 at a rate
controlled by the area of bleed 42. Bleed 42 is sized such that the
flow through this restriction will be directly proportional to the
supply flow rate, and thus the movement of the piston is a measure
of the supply flow quantity which is passing orifice 20. As shaft
30 moves toward the right, it carries with it pistons 32 and 34
which, as they approach the end of their stroke, open certain
passageways and close others to cause changes in the pressures
operating on the various effective areas of piston 18. As
specifically shown in FIG. 2, as piston 32 moves toward the right
it blocks communication between inlet passage 12 and chamber 52 and
at the same time opens communication between chamber 52 and the
return pressure conduit 74. Similarly, as piston 34 moves to the
right it interrupts communication between chambers 44 and 46 and
passageway 48 communicating with the low pressure in passage 50 and
opens communication between chambers 44 and 46 and a higher
pressure in passageway 16. This permits the higher pressure in
passageway 16 to be communicated into chamber 46 while at the same
time the pressure in chamber 54 is reduced to return line pressure,
and this pressure differential forces piston 18 to the left such
that it reaches a position where it completely blocks flow out of
passageway 16 as shown in FIG. 2.
A substantial loss of fluid can also occur from a break in the
return line 69. When the pressure sensed in line 69 drops to a low
value, this pressure loss is communicated through lines 72 and 74
to chambers 50 and 60. Since piston 62 has a substantial area in
communication with a low, but still significant pressure in line
66, piston 62 will be forced to the right carrying retainer 39 to
remove the preload on piston 28 caused by the caged spring 58. The
piston 28 acting in conjunction with bleed 42 will again
effectively measure the flow across land 20 as it moves, and when a
given flow has occurred, it will reach a position such that the
higher pressure from conduit 16 is communicated to chambers 44 and
46 while the pressure in chamber 54 is exhausted through conduit
74. This pressure differential forces the piston 18 to the left
such that it blocks communication between passages 12 and 16 as
shown in FIG. 2.
Another embodiment of our invention appears in FIGS. 3, 4 and 5.
FIG. 3 is a sectional view of our device shown in normal position.
FIG. 4 is a partial sectional view of this device with the parts in
tripped position in response to a failure in a pressure line, and
FIG. 5 is a similar partial sectional view with the parts shown
after the device has been tripped in response to a return line
pressure failure.
In FIG. 3 an inlet conduit 80 provides actuating fluid under high
pressure to a housing 82 having a port 84 communicating the fluid
with a cylindrical chamber 86. Also communicating with chamber 86
is a port 88 connected to a pressure outlet conduit 90 to provide
supply flow to an associated actuator. A conduit 92 is connected to
receive return flow from the associated actuator or other
utilization device which flow is connected through a line 93 to a
reservoir (not shown) through a check valve 94 biased against
return pressure by means of a spring 96.
A cylindrical piston 98 is arranged to be reciprocable in chamber
86 and includes a land 100 on its surface which cooperates with the
wall of chamber 86 to form a restriction of a desired area. Within
the piston 98 is a cylindrical chamber 102 and a timing piston 104,
having the same function as piston 28 of FIG. 1, which is movable
within chamber 102. The left side of piston 104 is in communication
with inlet pressure in port 84 through a passageway 106 which
communicates with a chamber formed by a groove 108 on the surface
of piston 98 and this chamber, in turn, communicates with the left
side of piston 104 through ports 110. On the right side of piston
104 the chamber 102 communicates with the pressure outlet port 88
through a passage 112, a chamber formed by a groove 118 in the
surface of a piston 120, a port 122, and a passageway with a timing
bleed 124.
Piston 104 is carried on a rod 126 which also carries an elongated
smaller diameter piston 128, a smaller piston 130 and a spring
retainer 132 which operates to retain a spring 134 between itself
and an extension 136 of piston 98, slidable within a small diameter
chamber 138 in housing 82. Movable in chamber 138 is a piston 140
which communicates at its left end with reservoir pressure through
a conduit 142. A conduit 144 communicates chamber 138 with return
flow conduit 92 through a short passage 146. Also connected to
passage 146 through a conduit 148 is an annular chamber 150
positioned between the end of piston 98 and a flange on piston 120.
A plurality of small ports 152 provide communication between
chamber 150 and a large chamber 154 at the right end of piston
120.
With the system of FIG. 3 operating normally, the assembly will be
in the position shown with a limited amount of flow permitted
across the restriction between the inside wall of chamber 86 and
the land 100. High pressure from inlet port 84 is communicated
through passages 106 and 110 and groove 108 to the left side of
piston 104 from whence it flows through an annular passageway 156
and a port 158 to the left end of piston 98. Since chamber 150 on
the right end of piston 98 is connected to return pressure, a
substantial pressure differential holds piston 98 toward the right,
as shown. In the event of a break or substantial leak downstream of
port 88, a reduced pressure will appear on the downstream side of
land 100 which is transmitted through passage 112, annulus 118,
radial passage 122, and bleed 124 into chamber 102 on the right
side of piston 104, causing increased flow across land 100, with
accompanying increased pressure drop thereacross, which increased
pressure drop causes piston 104 to begin moving toward the right.
The return pressure is maintained in chambers 138 and 150 through
passageways 144, 146 and 148; and through ports 152 to chamber 154.
As piston 104 moves to the right it carries shaft 126, piston 130,
and retainer 132 compressing spring 134. As it approaches the end
of its travel piston 130 passes port 158 permitting the high inlet
pressure at the left end of piston 98 to be vented into chamber 138
which is effectively at return pressure. Piston 128 also moves
toward the right, finally approaching the end wall of chamber 154,
where, as shown in FIG. 5, it opens an annular passageway
connecting with radial passage 122 and which bypasses bleed 124,
thus exhausting the pressure on the right side of piston 104 to the
outlet port 88. With a large leak downstream of port 88, the
pressure on the right side of piston 104 drops to a very low value
while pressure on the left side is maintained at a higher value by
land 100. With piston 128 bottomed against the end of chamber 154,
the high fluid pressure on the left side of piston 104 acts to
force piston 98 to the left to its maximum travel, thereby blocking
port 88. Piston 120 will also move to the left because it has
return pressure on its right face and a very low opposing pressure
in chamber 102. With port 88 blocked, pressure on the right side of
piston 104 will rise to a value approaching supply pressure because
of communication through port 112, annulus 118, port 122 and
orifice 124. This increasing pressure will then force piston 120 to
the right with the ports finally assuming the positions shown in
FIG. 4.
The device of FIG. 3 also blocks flow when a substantial leak or
rupture occurs in the line 92 between the associated actuator or
other device and the check valve 94. In this condition there will
be a substantial reduction in the pressure in line 92 while the
pressure in the return line to the reservoir 93 remains at a
significant value. This pressure differential will cause check
valve 94 to be held closed and the lowered pressure in line 92 will
be communicated to chambers 138 and 150 through lines 144, 146 and
148. This pressure differential also appears across piston 140,
causing it to move toward the right, compressing spring 134 and
moving shaft 126 with pistons 104, 128 and 130 to the right. Again,
the rate of movement of piston 104 is limited by the area of
orifice 124 and the pressure drop thereacross so that a given
significant amount of flow across land 100 will occur before piston
128 is bottomed against the right end of chamber 154. As piston 130
moves to the right it passes orifice 158 thus interrupting
communication between the inlet pressure on the left side of piston
104 and the left end of piston 98, and moving further, opening
communication between the left end of piston 98 and chamber 138.
This exhausts the high pressure acting on the left end of piston 98
into chamber 138 which is at a very low pressure reflecting the
leak in line 92. With piston 128 anchored, piston 104 cannot move
further to the right and inlet pressure will then force piston 98
to its limit of travel toward the left, blocking outlet port 88.
Because inlet pressure will be communicated through port 112,
annulus 118, passage 122 and orifice 124, piston 120 will be
retained in the position shown in FIG. 5. The movable parts will
all remain in this position until the inlet pressure is removed,
thus avoiding a possible inadvertent reset.
From the foregoing it will be appreciated that applicants' device,
in both embodiments shown, operates to block the flow of operating
fluid when leaks of significant size occur while at the same time
providing assurance that operation of the associated hydraulic
system is not interrupted or impaired from normal startup flows or
normal leakage such as would be expected from servo valves, etc.
Once a substantial leak has been sensed, the devices effectively
measure the flow quantity past the metering orifice before closing
the outlet and will not reset until supply pressure is removed.
* * * * *