Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to shuttle valves, and more
particularly to a shuttle valve having improved operating
characteristics.
In a shuttle valve, a valve member, which may be in the
form of a spool or two pistons joined by a xod, slides axially
within an elongated bore in a valve body. The bore has a number
of ports in its side wall which are typically connected to a
source of pressurized fluid, a low pressure region, and a working `~
device of some kind, respectively. ~he valve member has two `
stable positions within the bore and controls communication
between the ports, In one position of the valve member, the
pressure port is connected to one of the working device ports and ~`~
the exhaust port is connected to another of the working device
ports. In the other position of the shuttle valve member, the
working device port which was connected to the pressure port is
connected to the exhaust port and the working device port which
was connected to the exhaust port is connected to the pressure
port.
Movement of the shuttle valve member is controlled by
pressurizing and exhausting two chambers located at the two ends
of the bore in the valve body. More specifically, the two
chambers are fed with pressurized fluid through bleed passageways.
A control port is provided at each end of the bore, and by means
of a control valve one of the control ports is opened to a low
pressure region while the other control port is blocked, or vice
versa. As a result, the shuttle valve member is always pushed
toward the end of the bore whose control port is open, and hence
at a lower pressure, and away from the end of the bore whose
control port is blocked, and hence at a higher pressure,
A problem prese~ted by such valves i9 that when the con-
trol valve, which may be manually operated, or remotely operated,
such as by an electrical solenoid, changes its state to cause
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movement of the shuttle valve member, the pressurized chamber at
one end of the bore slowly exhausts and the exhausted chamber
slowly becomes pressurized. Thus, the shuttle valve member starts
to move gradually from one end of the bore toward the o~her end,
and completes the movement at a slow speed. Furthermore, a
dashpot effect of the valve member in the chamber being slowly
exhausted contributes to the slow and possibly unsteady movement
of the shuttle valve member. This slow movement has a number of
disadvantages, including the possibility that the valve member may
actually get stuck at an intermediate poin~ in its movement due
to the presence of dirt between the sliding valve member and the
stationary seals within which it slides, or the valve member
seizing within or sticking to those seals. Also, the quicker the
movement of the shuttle valve member, the more positive and surer
will be the response of the wor~ing device being controlled by
the shuttle valve.
One way of solving the problem and providing more rapid
movement of the shuttle valve member is to make the control ports
at the ends of the bore very large, so t hat the chambers exhaust
rapidly and become pressurized rapidly upon a change of state of
the control valve. However, a disadvantage of this solution is
that with larger control ports, and assuming a solenoid operated
control valve, a larger solenoid requiring more electric power ~
to operate it would be necessary, or alternatively, with the same ~ ;
size solenoid only lower fluid pressures could be controlled. :
It is an object of the pre~ent invention to overcome these
problems by providing a shuttle valve in which movement of the
shuttle valve member is positive and rapid without employing con-
trol ports of increased size.a
This objective is accomplished by providing a valve
seat around each control port which has a relatively large dia-
meter, i,e., significantly larger than the cross-sectional size
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of its respective control port, and such that there is a relatively
small ratio between the cross-sectional sizes of the valve member
and each valve seat, As a result of employing large valve seats,
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one of which is engaged by an end of the shuttle valve member in
each stable position of the valve member, upon a change of state
of the control valve, the shuttle valve member does not begin to
move until a significant proportion of the pressure in the chamber
toward which the valve member will move is exhausted. The reason
is that only a relatively small annular area at the end of the
shuttle valve member outside the valve seat with which that end
is in contact is exposed to the pressure in the chamber away from
which the valve member will move. When the shuttle valve member
does begin to move, the pressure in the chamber away from whi-ch
it i~ moving is high and the pressure in the chamber being exhausted
is re~atively low, so that the shuttle valve member is moved very
rapidly by the relatively large pressure differential between the
two chambers.
Additional objects, features, and explanation of the
invention will be apparent from the following description in which
reference is made to the accompanying drawings.
In the drawings:
Fig. 1 is a schematic longitudinal cross-sectional view
of a spool-type shuttle valve according to the present invention;
Fig. 2 is a cross-sectional view taken along line 2-2
of Fig. l;
Fig. 3 is a view similar to Fig. 1 showing the control
valve and the shuttle valve member in an alternative position to
that shown in Fig. l;
Fig. 4 is a cross-sectional view taken on line 4-4 of ;
Fig. 3; and
Fig. 5 is a schematic longitudinal cross-sectional view
of a piston-type shuttle valve according to the present invention.
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The shuttle valve chosen to illustrate the present
invention, and shown in Figs. 1-4, includes a valve body 10 having
an elongated bore 11. Bore 11 is closed at one end by an end
plate 12 and at the other end by the valve body 13 of ~'~control
means in the form of a solenoid operated valve 14. End plate 12
and valve body 13 are mounted on valve body 10 in a fluid tight `
manner by suitable fasteners (not shown). Body 10 is formed, in
this example, with five ports 15, 16, 17, 18, and 19 in the side
wall o~ bore 11. Projecting into bore 11 are six annular seals
20, formed for example of rubber or plastic, one seal being located
between each two successive bores, and two seals being arranged
beyond the extreme bores 15 and 19, respectively.
At each end, bore 11 is provided with an orifice. One
of the orifices 23 is formed in end plate 12 and communicates
with a passageway 24 formed in end plate 12 and body 10. The
other end of passageway 24 terminates at the face of valve body
D0 on which control valve body 13 is mounted~ The second orifice -
25 is formed in control valve body 13. Orifice 23 is surrounded
by an annular valve seat 26, and orifice 25 is surrounded by an
annular valve seat 27, both valve seats~projecting into bore 11.
The end portion of bore 11 between valve seat 26 and
the seal 20 to the left of port 15 defines a chamber 28, and the
other end portion of bore 11 between valve seat 27 and the seal
20 to the right of bore 19 defines another chamber 29.
Valve body 10 is mounted on a ba~e 32 having five
passageways 33, 34, 35, 36, and 37 aligned and communicating with ;
the five ports 15-19, respectively. Passageway 35 is ¢onnected ;
to a source of pressurized fl~id, such as compressed air, and
passageways 33 and 37 are connected to a low pres~ure region,
such as the atmosphere, where the fluid whose flow is being con-
trolled is air, or a re~ervoir, where the fluid is a liquid.
Passageways 34 and 36 are connected to a working device being
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controlled by the shuttIe valve, such as the opposite sides of apiston within a cylinder (not shown). To insure a fluid tight
connection between valve body lO and base 32, a gasket 38 (Figs.
1 and 2) is provided between the body and base. Gasket 38 has
five holes through it, aligned with ports 15-19, respectively,
and two slots 39 and 40. Slot 39 establishes communication
between the hole in gasket 38 aligned with pressure passageway 35
and a hole 41 in valve body 10 which extends through the valve
body to chamber 28, Slot 40 establishes communication between
the same hole in gasket 38 and a hole 42 in body 10 which extends
through the valve body to chamber 29. Thus, slot 39 and hole 41
define a bleed passageway for continuously supplying high pressure
fluid to chamber 28, and slot 40 and hole 42 define a bleed
passageway for continuously supplying high pressure fluid to
chamber 29.
A shuttle valve member 45 is slidably supported within
seals 20 for axial movement within bore 11. Valve member 45 is,
in this example, in the form of a generally cylindrical spool
having two reduced diameter regions 46. ~lthough valve member
45 is slidable, its engagement with each of seals 20 is fluid tight
in~ ature, At each of it~ ends, valve member 45 carries a disk
47 of a material capable of forming a good seal when pressed
against one of the valve seats 26 and 27. Valve member 45 has two
stable positions shown respec*ively in Figs. 1 and 3. In the
position shown in Fig. 1, valve member 45 engages valve seat 27
and is spaced from valve seat 26. In this position, pressure
passageway 35 communicates with working device passageway 34
through port 17, bore 10, and port 16. At the same time, exhaust
passageway 37 communicates with working device passageway 36
through port 19, bore 10, and port 18. When valve member 45
moves to the position shown in Fig. 3, valve member 45 engages
valve seat 26 and is spaced from valve seat 27, In this position,
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pressure passageway 35 communicates with working device passage-
way 36 through port 17, bore 10, and port 18. At the same time,
exhaust passageway 33 communicates with working device passageway
34 through port 15, bore 10, and port 16.
Movement of shuttle valve member 45 may be controlled by
a three-way solenoid operated valve 14 of the type shown in U.S.
Patent ~o. 3,303,854. Body 13 of valve 14 is formed with a bore
49 from which a passageway 50 e~tends to the end of passageway 24
and from which orifice 25 extends. Also extending from bore 49 is
a vent port 51 which, in the case o~ air opens to the atmosphere,
as shown, but in the case of a liquid would open to a reservoir.
Fixed within bore 49 is a fitting 52 (Figs. 1, 3, and 4) having a
T-shaped passageway for establishing communication between passage-
way 50 and the region of bore 49 above fitting 52, and another T-
shaped passageway for establishing communication between orifice 25
and the region of bore 49 below fitting 52. The vertical stems 53
and 54 of the T-shaped passageways constitute control ports of the
valve. Fitting 52 also has a vertical through hole 55 (Fig. ~)
through which the regions above and be~ow fitting 52 are in constant
communication~ CQnse~uently,~ the region~ of bore 49 above and
below fitting 52 are always in communication with vent port 51.
Mounted on body 13 is an electrical solenoid 58 having
a depending armature 59 spring biased in a downward direction.
The lower end of armature 59 serves as a valve member for clo~ing
and opening the upper end of control port 53. Three vertical pins
60 are slidably arranged in three holes in fitting 52, the pins
carrying a valve member 61 at their lower ends. Valve member 61
serves to close and open the lower end of control port 54. The
upper ends of pins 60 abut the lower face of solenoid armature 59,
and a compression spring 62 constantly urges valve member 61 and
hence pins 60 upwardly. However, the spring (not shown) biasing
armature 59 downwardly i9 stronger than spring 62. Hence, when
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solenoid 58 is deenergized (Fig. 1), armature 59 closes control port
53 and pushes valve member 61 downwardly, via pins 60, to open con-
trol port 54. As a result, orifice 25 is exhausted through passage-
way 54, bore 49 and port 51, and orifice 23 is blocked, since it
communicates with closed control port 53 through passageways 24
and 50. In this condition, high pressure fluid bleeding into
chamber 28 from passageway 35 builds up pressure in that chamber
and holds shuttle valve member 45 against valve seat 27.. The
high pressure which was also bleeding into chamber 29 was just as
quickly exhausted through orifice 25 until the end of valve member
45 engaged valve seat 27. With equal pressures in chambers 28
and 29, thereis a net force toward the right on valve member 45,
because the entire left end face of the valve member is exposed
~o the pressure while only the annular area of the right end
face of the valve member radially outwardly of valve seat 27 is -
exposed to the pressure.
When solenoid 58 is energized (Fig. 3), armature 59 is
pulled upwardly opening control port 53 and permitting spring 62 to
cause valve member 61 to close control port 54. As a result, control
port 54 and hence orifice 25 are blocked. On the other hand,
orifice 23 is opened to exhaust through passageways 24 and 50, con-
trol port 53, bore 49, hole 55, and vent port 51. The pressure in
chamber 28 diminishes because control port 53 and all the passage-
ways with which it is connected are larger than bleed passageway
39, 41. High pressure remains, howeve~ in chamber 29. When the
pressure in chamber 28 decreases to the point where there is a net
leftward force on valve member 45, the valve member moves away
from valve seat 27 and into engagement with valve seat 26. In
this condition, although the same high pressure eventually exists
in both chambers 28 and 29, there is a net leftward force on valve
member 45, for the reasondescribed above. When solenoid 58 is
again deenergized, valve member 45 again moves to the right into
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the position shown in Fig. lo
According to the present invention, each valve seat 26,
27 is made considerably larger than its respective control port 53,
54, i,e., the cross~sectional area of the valve seat is at least
fifty tLmes larger, and even 100 or more times larger, than,the
cross-sectional area of the control port. The valve seats 26, 27
are also relatively large with respect to the cross-sectional dimen-
sion of the shuttle valve member 45 as compared to conventional ;~
valves of this type, Thus, according to the present invention the
cross-sectional area of the portion of valve member 45 within
chamber 28, 29 is no more than four times the cross-sectional area
of the valve seat 26, 27, and is no less than twice the area of the~
valve seat. Preferably, the ratio of the cross-sectional area of ;;~
the valve member to the cross-sectional area of the valve seat is
three to one.
To understand the advantages of the area relationships
described immediately above, consider the situation when the area
of the valve seat is very small with respect to the area of the
shuttle valve member. In such a case, when one end of the shuttle
valve member is seated against a valve seat, almost as much sur-
face area at the seated end face of the valve member is exposed
to high pressure as at the unseated end face of the valve member. ~~
Hence, when the control valve changes state, the shuttle valve
member begins moving almost immediately after the pressure begins
to drop in the chamber whose control port had been blocked, but
is now open, and movement continues very slowly, as described in
the introductory portion above.
In contrast, in a valve according to the present invention,
when the valve is in the condition shown in Fig. 1, a much larger
surface area at the end of valve member in chamber 2~ is exposed
to high pressure than at the end of the valve member in chamber
29. The reason is that the relatively large area valve seat 27
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keeps high pressure fluid in chamber 29 from contacting 25% to 50%of the surface area of the end face of valve member 45 in chamber
29. Thus, when control valve 14 shifts from its condition shown
in Fig. 1 to its Fig. 3 condition, valve member 45 will not move
right after pressure in chamber 28 begins to drop. Instead, the
pressure in chamber 28 will have to drop considerably before a net
leftward force develops on valve member 45. Once valve member 45
begins to move, its movement is very rapid for two reasons. First,
there is already low pressure in chamber 28, so little or no
dashpot effect occurs in that chamber. Secondly, as soon as valve
member 45 moves the slightest distance away from valve seat 27,
the entire right end face of valve member 45 is exposed to high ;
pressure fluid, and hence a large net leftward force is suddenly
applied to the shuttle valve member. This sudden rapid movement
of shuttle valve member 45 eliminates, or at least greatly mini-
mizes, the chance that the valve member will get stuck bet~een its
two stable positions. The description given immediately above
obviously applies as well when valve member 45 is moving from its ;;
Fig. 3 position to its Fig. 1 position.
The invention has been described in connection with a ~;
spool-type shuttle valve member. It is equally applicable to a
piston-type shuttle valve member as shown in Fig. 5. In Fig. 5,
parts corresponding to those shown in Figs. 1-4 bear the same
reference numerals followed by a prime. Shuttle valve member 45'
comprises two spaced-apart pistons 65, snugly but slidably
arranged in bore 11', joined together by a central rod 66 of
smaller diameter. The space between pistons 65 is filled with
high pressure fluid through port 35'. In this example, high
pressure fluid bleed into chambers 28' and 29' through bleed
passages 67 extending through the pistons, Rod 45' carries a ;~-
cup-like element 68 which causes either working device port 37' ~
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to communicate with exhaust port 34', as shown in ~'ig 5, or work-
ing device port 33' to communicate with exhaust port 34'. The
working device port not communicating with exhaust port 34'
communicates with pressure port 35'. In all other respects, the
shuttle valve of Fig. 5 functions in the same manner as the valve
of Figs. 1-4. ;~
Ports 53 and 54 have been referred to as the "control
ports" of the valve, since in a commercial valve these would
ordinarily be the passageways ofrsmallest cross-sectional area
between each of chambers 28 and 29 and vent port 51. ~owever, if
for some reaso~ some other portion of the communication passageway
between either chamber and the vent port were the portion of
smallest cross-sectional area, that smallest portion would be con-
sidered the control port. For example, if orifices 23 and 25 were ~-
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smaller than ports 53 and 54, respectively, orifices 23 and 25
would be considered the control ports.
The invention has been shown and described in preferred
form only, and by way of example, and many variations may be made -~
in the invention which will still be comprised within its spirit.
It is understood, therefore, that the invention is not limited to
any specific form or embodiment except insofar as such limitations
are included in the appended claims.
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