Pressure compensated flow amplifying poppet valve

Flow amplifying poppet valves are useful in hydraulic circuits requiring low leakage when the circuit is in a load holding condition. Pressure compensation of the known flow amplifying poppet valves has not been totally successful and thus, the output flow varies somewhat with changing pressure drops across the poppet valve. The subject pressure compensated flow amplifying poppet valve utilizes a pressure compensating valve and a compensating orifice disposed in a compensating flow path disposed in parallel with a valve device for controllably regulating fluid flow through a flow regulating passage. Fluid flow through the compensating flow path is restricted by the orifice to a flow rate substantially equal to the amount of fluid that can flow through a flow control slot in a valve element at a closed position of the valve element. The addition of the compensating flow path and the compensating valve greatly increases the pressure compensating capability of the pressure compensated flow amplifying poppet valve so that the fluid flow through the poppet valve remains substantially constant for a given position of the valve means regardless of changing load conditions.

DESCRIPTION 
1. Technical Field 
This invention relates generally to poppet type hydraulic control valves 
and more particularly to a pressure compensated flow amplifying poppet 
valve. 
2. Background Art 
One type of low leakage hydraulic control valves is commonly referred to as 
a poppet valve. Such poppet valves typically include a cylindrical poppet 
valve element having a reduced diameter end seated against a valve seat in 
the valve. Fluid flow from an inlet port through the valve to an outlet 
port is controlled by controllably moving the valve element off the seat. 
A basic type of poppet valve has a throttling slot through the valve 
element to communicate the inlet port pressure to a control chamber at the 
back side of the valve element. The fluid pressure in the control chamber 
exerts a closing force on the valve element holding it against the valve 
seat. A spring is also generally used to hold the valve element against 
the valve seat when the inlet, control and outlet pressures are all equal. 
One method of controlling the opening position of the poppet valve element 
is to communicate the control chamber with the outlet port through a 
variable regulating orifice of a pilot valve. The variable regulating 
orifice is normally closed so that fluid pressure in the control chamber 
equals the inlet pressure and the poppet valve element is urged against 
the valve seat by the pressure in the control chamber. Opening of the 
poppet valve element is achieved by controllably opening the variable 
regulating orifice to communicate the control chamber with the outlet 
port. This creates a pressure drop through the throttling slot in the 
valve element such that the inlet pressure urges the valve element off the 
valve seat as the control pressure drops below the balance pressure. The 
degree of opening of the valve element is subsequently controlled by 
controlling the flow through the variable regulating orifice of the pilot 
valve to regulate the flow through the throttling slot. This method of 
control is described in U.S. Pat. No. 4,535,809. One of the problems with 
that design is that the flow through the poppet valve increases and 
decreases with increasing and decreasing pressure drops respectively 
between the inlet and outlet ports. The pressure drop between the inlet 
and outlet port changes with changing loads and/or pump pressure due to 
other circuits of the hydraulic system. 
Another method of controlling the position of the poppet valve element also 
described in U.S. Pat. No. 4,535,809 includes the addition of a pressure 
reducing valve in series with the variable regulating orifice described in 
the preceding paragraph. The pressure reducing valve maintains a constant 
pressure drop across the variable regulating orifice. The throttling slot 
of that design is always open to some degree to allow control fluid flow 
through the slot to pressurize the control chamber and urge the valve 
element against the seat. The amount of opening through the slot when the 
valve element is seated against the valve seat depends upon machining 
tolerances. However, due to this control flow, the outlet flow decreases 
with increasing pressure drop between the inlet and outlet ports. 
The present invention is directed to overcoming one or more of the problems 
as set forth above. 
DISCLOSURE OF THE INVENTION 
In one aspect of the present invention, a pressure compensated flow 
amplifying poppet valve comprises an inlet port, an outlet port, a 
cylindrical bore, and an elongate valve element having a spool portion 
slidably disposed in the cylindrical bore defining a control chamber. The 
valve element is movable between a closed position at which the inlet port 
is blocked from the outlet port and an open position to establish a main 
flow regulating orifice between the inlet and outlet ports. The valve 
element includes a variable orifice between the inlet port and the control 
chamber. A flow regulating passage means is provided for communicating the 
control chamber with the outlet port. A valve means controllably regulates 
the fluid flow through the flow regulating passage means. A means is 
provided for establishing a restricted compensating flow path from the 
control chamber to the outlet port parallel to the flow regulating passage 
means. 
It is desirable to have the flow amplifying poppet valves pressure 
compensated so that the output flow of the valve remains substantially 
constant for a given opening of a pilot valve regardless of changes in the 
load pressure or the input pressure.

BEST MODE FOR CARRYING OUT THE INVENTION 
A pressure compensated flow amplifying poppet valve is generally indicated 
by the reference numeral 10 and includes a composite valve body 11 and a 
valve element 12. The body includes a pair of concentric cylindrical bores 
13,14, a pair of axially spaced annuluses 16,17, an inlet port 19 in 
communication with the annulus 17, an outlet port 21 in communication with 
the cylindrical bore 14, and a value seat 22 between the cylindrical bore 
14 and the outlet port 21. The cylindrical bore 14 is formed in an annular 
sleeve 24 suitably seated in a bore 26. A plurality of flow modulating 
ports 27 extend through the sleeve 24 to communicate the annulus 17 with 
the cylindrical bore 14. 
The valve element 12 has a pair of concentric spool portions 28,29 slidably 
disposed in the cylindrical bores 13,14, respectively and define an 
annular reaction surface 31 therebetween. A control chamber 32 is defined 
by the annulus 16 and the end of the spool portion 28. The area of the end 
of the spool portion 28 is substantially larger than area of the surface 
31. The spool portion 29 terminates at a conical end portion 34 and 
cooperates with the ports 27 to provide a main flow regulating orifice 35. 
A pair of variable area flow control orifices 36 are provided in the spool 
portion 28 to communicate the inlet port 19 with the control chamber 32. 
The orifices 36 are in the form of a pair of axially extending rectangular 
slots 37 connected to the inlet port 19 through a pair of diagonally 
extending passages 38. As more clearly shown in FIG. 2, a minimum flow 
area "a" of the slots 37 is always open to continuously communicate the 
inlet port 19 with the control chamber 32. A light-weight spring 39 
disposed between the valve element 12 and the body 11 resiliently urges 
the conical end portion 34 into sealing engagement with the valve seat 22. 
A pressure compensated variable displacement pump 41 is connected to the 
inlet port 19 and a motor 42 is connected to the outlet port 21. 
The poppet valve 10 also includes a flow regulating passage means 43 
communicating the control chamber 32 with the outlet port 21, a valve 
means 44 for controllably regulating the fluid flow through the passage 
means 43, and means 45 for establishing a restricted compensating flow 
path 46 from the control chamber 32 to the outlet port 21 parallel to the 
passage means 43. The passage means 43 includes a regulating passage 47 
connected to and extending between the control chamber 32 and the outlet 
port 21. The valve means 44 includes a pressure reducing valve 48 and a 
flow regulating valve 49 serially disposed in the regulating passage 47. 
The flow regulating valve 49 is movable between a closed position blocking 
communication through the regulating passage 47 and an infinitely variable 
open position establishing a variable regulating orifice 50 for regulating 
fluid flow through the regulating passage 47. The pressure reducing valve 
48 maintains a substantially constant pressure drop across the regulating 
valve 49 at its open position. 
The flow path 46 includes a compensating passage 51 connected to the 
passage 47 on opposite sides of the valves 48 and 49. The establishing 
means 45 includes a means 52 for controlling fluid flow through the 
passage 51 of the flow path 46. The regulating means 52 includes a 
compensating orifice 53 and a compensating valve 54 serially disposed in 
the passage 51. The compensating valve 54 is movable between a closed 
position and an open position to modulatably control fluid flow through 
the passage 51. The compensating orifice 53 establishes a maximum flow 
area through the passage 51 at the fully open position of the compensating 
valve 54. 
In this embodiment the pressure regulating valve 48 and the compensating 
valve 54 are shown combined into a single valve movable between positions 
A, B, and C. Such movement can be by any convenient means such as pilot 
operation, electrical solenoid operation or mechanical operation. 
Alternatively, the flow regulating valve and compensating valve 54 may be 
separate valves which can be sequentially operated. Also, the orifice 53 
may be incorporated within the compensating valve 54 and be established by 
the maximum opening area of the compensating valve. 
Other embodiments of a pressure compensating flow amplifying poppet valve 
10 of the present invention are disclosed in FIGS. 3-6. It is noted that 
the same reference numerals of the first embodiment are used to designate 
similarly constructed counterpart elements of these embodiments. 
In the embodiment of FIG. 3, the compensating passage 51 connects the 
cylindrical bore 13 with the outlet port 21 and the compensating valve 54 
is formed by a slot 57 provided in the spool portion 28 of the valve 
element 12. The slot 57 is in continuous communication with the control 
chamber 32. Communication through the compensating passage 51 is blocked 
by the spool portion 28 when the end portion 34 is seated against the 
valve seat 22. 
The embodiment of FIG. 4 is similar to the embodiment of FIG. 3 with the 
exception that the establishing means 45 includes having the end portion 
34 of the valve element 12 axially separated from the spool portion 29 by 
a reduced diameter portion 58, the valve seat 22 axially spaced from the 
ports 27 by an annular chamber 59 formed in the sleeve 24, and the 
compensating passage 51 connecting the bore 13 with the annulus 59. 
In the embodiment of FIG. 5, the compensating passage 51, the orifice 53, 
and a compensating valve 62 are disposed within the valve element 12. More 
specifically, the compensating valve 62 includes a poppet valve 63 having 
a piston 64 slidably disposed in an axial bore 66 and defines an actuating 
chamber 67 in communication with the inlet port 19 through an opening 68. 
A conical valve portion 69 of the poppet valve 63 is biased against a 
valve seat 71 by a spring 72 disposed in a chamber 73 open to the control 
chamber 32. The compensating passage 51 connects the bore 66 adjacent the 
valve seat 71 with the outlet port 21. 
In the embodiment of FIG. 6, the valve means 44 includes a fixed orifice 74 
disposed in the regulating passage 47 and a pressure regulating valve 76 
also disposed in the regulating passage 47 upstream of the orifice 74 to 
controllably vary the pressure drop across the fixed orifice 74. The 
compensating valve 54 is built into the regulating valve 76 and is 
disposed in the passage 51 of the compensating flow path 46 similar to the 
embodiment of FIG. 1. 
INDUSTRIAL APPLICABILITY 
With respect to the embodiment of FIG. 1, when both the regulating valve 49 
and compensating valve 54 are in the closed position represented by the 
letter "A" as shown in the FIG. 1, fluid from the inlet port 19 passes 
through the passages 38 and the slots 37 into the control chamber 32. 
Since there is no fluid flow through the passages 47 and 51, the fluid 
pressure in the control chamber 32 is substantially equal to the fluid 
pressure in the inlet port 19. With the area of the valve element 12 
subjected to the fluid pressure in the control chamber 32 being greater 
than the area of the reaction surface 31, the valve element 12 is urged 
downwardly so that the end portion 34 remains sealingly engaged with the 
valve seat 22. If the fluid pressures in the inlet port 19 and the outlet 
port 21 are equal, the spring 39 holds the valve element in the sealing 
position. 
In the use of the embodiment of FIG. 1 of the present invention, actuation 
of the poppet valve 10 is initiated by initially controllably moving the 
compensating valve 54 from the "A" position to the "B" position. This 
controllably establishes fluid flow from the inlet port 19 through the 
passages 38, the aggregate open area "a" of the slots 37, the control 
chamber 32, the passage 51, the orifice 53, and the compensating valve 54 
to the outlet port 21. Movement of the compensating valve 54 between the 
"A" and "B" positions modulatably controls the fluid passing through the 
passage 51 while the orifice 53 generally limits the amount of fluid that 
can pass through the passage 51 of the flow path 46. In this embodiment, 
flow through the regulating valve 49 at the "B" position is still blocked. 
The fluid flow through the passage 51 is fairly low and generally does not 
generate a pressure drop sufficient to cause the valve element 12 to move 
upwardly to unseat the end portion 34 from the valve seat 22. Such low 
flow is referred to as impending flow. 
Upon further movement of the compensating valve 54 and the regulating valve 
49 from the "B" position to the "C" position, fluid flow through the flow 
path 46 does not increase due to the size of the orifice 53. However, 
movement of the regulating valve 49 between the "B" and "C" positions 
opens the regulating orifice 50 and establishes fluid flow through the 
passage 47 between the control chamber 32 and the outlet port 21 
sufficient to create a pressure drop between the inlet port 19 and the 
control chamber 32. At some small regulating flow through the regulating 
orifice 50 of the regulating valve 47, the valve element 12 moves upwardly 
and lifts the end portion 34 from the valve seat 22 but does not uncover 
any of the modulating ports 27 in the sleeve 24. With increasing 
regulating flow through the regulating orifice 50 and increasing movement 
of the valve element 12, the spool portion 29 begins uncovering the ports 
27 establishing fluid flow through the main flow regulating orifice 35 
from the inlet port 19 to the outlet port 21. The upward movement of the 
valve element 12 and thus the degree of opening of the ports 27 is 
determined by the flow between the inlet port 19 and the control chamber 
32 which in turn is modulatably controlled by the degree of opening of the 
flow regulating valve 49. At a steady state position of the regulating 
valve 49, the flow through the slots 37 equals the aggregate flow through 
the passages 47 and 51. Also the flow through the main orifice 35 is a 
proportional amount greater than the flow through the regulating orifice 
50. 
The pressure reducing valve 48 functions in its usual manner to maintain a 
constant pressure drop across the regulating valve 49. The combination of 
the compensating orifice 53 and the compensating valve 54 in the flow path 
46 disposed in parallel with the pressure reducing valve 48 and the 
regulating valve 54 makes the poppet valve substantially fully 
compensated. Thus, the fluid flow through the inlet and outlet ports 
remains substantially constant at a given setting of the regulating valve 
49 regardless of pressure differentials between the inlet and outlet ports 
19, 21. 
In general, to make the poppet valve fully compensated, the size of the 
compensating orifice 53 will be slightly less than the aggregate area "a" 
of the slots 37 that is always open. However, the size relationship 
between the orifice 53 and the aggregate area "a" can be varied to 
compensate for closing flow forces acting on the valve element 12 and the 
amount of fluid leaking between the valve element and the bore 13. 
Depending on the magnitude of the flow forces and the bore leakage, the 
size of the compensating orifice may be slightly less than, equal to, or 
slightly greater than the open area "a" of the slots. In actuality the 
size of the compensating orifice is preferably selected so that the end 
portion 34 remains seated when the compensating valve is at the "B" or "C" 
position and the fluid flow through the passage 51 is limited by the 
compensating orifice. 
Alternatively, the outlet flow from the outlet port 21 can be purposely 
made to increase or decrease with increasing pressure drop between the 
inlet and outlet ports by changing the size of the compensating orifice 53 
relative to the area "a" of the control slots 37 which is always open. 
In the use of the embodiment of FIG. 3, actuation of the poppet valve 10 to 
the open position is initiated by opening the flow regulating orifice 50 
of the regulating valve 49. At some small regulated flow through the 
regulating orifice 50, the valve element 12 moves upwardly to unseat the 
end portion 34 from the seat 22 and the slot 57 communicates with the 
compensating passage 51. A portion of the impending flow passes through 
the compensating passage 51 and the rest passes through the regulating 
passage 47. Increasing the regulating flow through the regulating orifice 
causes the valve element 12 to continue moving upwardly. At a 
predetermined position of the valve element 12, the fixed orifice 53 
limits the fluid flow through the passage 51. Shortly thereafter, the 
spool portion 29 begins uncovering the modulating ports 27 thereby 
allowing fluid flow from the inlet port 19 to pass through the ports 27 to 
the outlet port 21. 
Operation of the embodiment of FIG. 4 is essentially the same as the FIG. 3 
embodiment. However, with this embodiment, the compensating passage 51 is 
positively blocked from the outlet port 21 when the end portion 34 is 
seated against the valve seat 22. Thus, any leakage flow past the spool 
portion 28 is positively blocked from the outlet port 21. The initial 
upward movement of the valve element 12 unseats the end portion 34 thereby 
immediately establishing communication between the compensating passage 51 
and the outlet port 21. 
Referring to the embodiment of FIG. 5 with the regulating valve 49 in the 
blocked position and the end portion 34 seated against the valve seat 22, 
the pressure in the control chamber 32 equals the pressure in the inlet 
port 19. The poppet valve 63 is thus urged to the closed position shown by 
the spring 72. When the regulating orifice 50 of the regulating valve 49 
is initially opened to initiate regulating fluid flow through the 
regulating passage 47, the pressure in the control chamber 32 decreases 
due to the pressure drop across the slots 37. At some small pressure drop, 
the poppet valve 63 opens allowing fluid flow from the control chamber 32 
through the compensating passage 51 and the orifice 53 to the outlet port 
21. At some predetermined pressure drop, the poppet valve 63 will become 
fully open. The compensating orifice 53 limits the amount of fluid that 
can pass through the passage 51 at the open position of the compensating 
valve 53. After the maximum flow rate through the passage 51 has been 
reached and with some additional regulating flow, the valve element 12 
moves upwardly unseating the end portion 34 from the valve seat 22 and 
eventually the spool portion 29 will uncover the ports 27 to initiate the 
main flow between the inlet port 19 through the ports 27 to the outlet 
port 21. 
Operation of the embodiment of FIG. 6 is initiated by moving the combined 
pressure regulating valve 76 and the compensating valve 54 simultaneously. 
The initial movement of the compensating valve 54 permits fluid to flow 
through the compensating passage 51 from the control chamber 32 to the 
outlet port 21. At some predetermined point, the fluid flow rate through 
the passage 51 matches the size of the fixed orifice 53 so that further 
opening of the compensating valve 54 has no effect on fluid flow through 
the passage 51. Shortly after that occurs, the pressure regulating valve 
76 opens to allow fluid flow through the regulating passage 47 to create a 
pressure drop between the inlet port 19 and the control chamber 32. As 
previously described, with increasing flow through regulating passage 47, 
the valve element 12 initially moves upwardly sufficient to unseat the end 
portion 34 from the valve seat 22 with the spool portion 29 subsequently 
uncovering the ports 27 to initiate fluid flow from the inlet port 19 to 
the outlet port 21. The pressure regulating valve 76 is operative to 
controllably vary the pressure drop across the fixed orifice 74 in 
proportion to the input force applied to the regulating valve for moving 
it to the open position. 
In view of the foregoing, it is readily apparent that the structure of the 
present invention provides an improved pressure compensating flow 
amplifying poppet valve which makes the poppet valve substantially fully 
pressure compensated. This is accomplished by providing a compensating 
valve and compensating orifice in a compensating passage disposed in 
parallel with the valve means in the regulating flow passage such that the 
small flow through the compensating passage essentially equals the amount 
of flow that can pass through the slots in the main valve element before 
the main flow is established between the inlet and outlet ports. 
Other aspects, objects, and advantages of this invention can be obtained 
from a study of the drawings, the disclosure, and the appended claims.