CA1099187A - Control valve for use with variable displacement piston pump - Google Patents
Control valve for use with variable displacement piston pumpInfo
- Publication number
- CA1099187A CA1099187A CA299,762A CA299762A CA1099187A CA 1099187 A CA1099187 A CA 1099187A CA 299762 A CA299762 A CA 299762A CA 1099187 A CA1099187 A CA 1099187A
- Authority
- CA
- Canada
- Prior art keywords
- valve
- spool
- spring
- pressure
- orifices
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
ABSTRACT OF THE DISCLOSURE
For use with a variable displacement piston type pump, a valve responsive to pump discharge manifold pressure for controlling the pressure in the pump chamber, and which controlled pressure creates a force for regulating the stroke of the pump pistons to maintain a predetermined substantially constant pressure with a variable flow of fluid through the pump.
For use with a variable displacement piston type pump, a valve responsive to pump discharge manifold pressure for controlling the pressure in the pump chamber, and which controlled pressure creates a force for regulating the stroke of the pump pistons to maintain a predetermined substantially constant pressure with a variable flow of fluid through the pump.
Description
~099~L87 B~CKGROUND OF T~E INVENTION
Cross Reference to Related Applications ~ he valve disclosed hexe.in may he used in co~junction with a ~ariable displacement pi5ton pump ~uc]-l as descri~ed and claimed in commonly assignea coperldil-ly Canadian Application Serial No. 300,010, filed by Frank Woodruff on March 30, 1977.
Field of ~he Inven-tion - ' ~' ' This inventi.on relates generally ~o pump pressure control valves and, paxticularly, to a valve which controls A
'7 the discharge manifold pressure of the pump to provide a pressure for regulating the stroke of the pump pistons.
Description of the Prior Art The aforenoted copending Canadian ~pplicatlon Serial No. 300,010 describes a variable displacement piston pump including a shaft having a driven end and an opposite end arranged for supporting a swash plate to pivot about an axis displaced from the center line of the shaft and preferably, but not necessarily, normal thereto. A
plurality of pistons having hollow cylinders extending therethrough are arranged with corresponding check valves in a pump block. During the "delivery" stroke of the pistons the pressure in the cylinders becomes sufficient to actuate the check valves whereby fluid is delivered to a common discharge manifold.
When the manifold pressure approaches a predetermined value, a force is created which is transmitted to the swash plate and pivots the plate away from a maximum flow position. The pistons are arranged with the swash plate so that when the swash plate pivots r the stroke of the pistons is decreased to reduce fluid flow and pressure. Equili-brium is thus established and a reduced fluid flow at a predetermined substantially constant pressure is maintained.
The valve of the present invention is used in conjunction with a pump of the type described to control the pump manifold pressure Eor providing a pressure which creates the force transmitted to the swash plate. The valve herein described features a novel arrangemen-t including an elonyated spool section responsive to pump discharge manifold pressure for varying the area of a pair of orifices arranyed in series relation to provide a pressure which is transmitted to the pump chamber for regula-ting the stroke of the pump pistons.
According to the present inven-tion there is provided a pressure control valve having a valve cylinder including a bore extendiny therethrough with a pressure inlet port extending externally to the valve and communicating with the valve cylinder bore so that an inlet pressure is received by the valve. A spring loaded valve spool is disposed within the valve cylinder bore and is responsive to the inlet pressure for being displaced against the spring load. First and second orifices communicate with the valve cylinder bore and are arranged with the valve spool so that displacement of the spool increases the area of one of the first and second orifices and decreases the area of the other of the orifices to create a control pressure. A pressure outlet port extends external to the valve and means communicates the first and second orifices and the pressure outlet port with the control pressure transmitted through the means to the pressure outlet port and therefrom external to the valve.
In a specific embodiment of the invention, the spool includes an elongated section which varies the area of the pair of orifices arranged in series relation and used for inlet and exhaust of a control pressure generated by the valve. The orifices are of different diameters to permit tailoring of the control pressure in relation -to spool stroke for obtaining reasonably balanced slew rates toward or away from full pump flow. Means are provided for accommodating less than perfect spring force alignment along the spool axis.
One object of this invention is to provide a pressure control valve for a variable displacement piston type pump, whereby the pump is supplied with a pressure which crea-tes a force for regulating -the stro]ce of the pump pi.s-tons to provide a variable fluid flow at a substan-tially constant pressure.
-3a-~ Another object of this invention is to provide a valve of the type described which includes an elongated spool section responsive to pump discharge manifold pressure for varying the area of control pressure inlet and outlet orifices.
Another object of this invention is to provide the orifices of different diameters, with the area of the orifices being varied by the elongated spool section, whereby the control pressure in relation to the spool stroke can be tailored for reasonably balanced slew rates toward and away rom full pump flow.
Another object of this invention is to actuate the valve spool against a spring force and to accommodate misalignment of the spring force along the spool axis.
The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows taken together with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.
Description of the Drawings Figure 1 is a partially sectioned front plan view showing in substantial detail a pump pressure control valve according to the invention.
~7 Figure 2 is a schematic diagram illustrating the operation of the valve shown in detail in Figure 1.
Description of the Invention With reference first to Fi.gure 1, a pump pressure control valve designated by the ntlmeral 1 includes an inlet port 2! an outlet port 4 and an outlet port 6.
Inlet port 2 is connected to a pump discharge mani~old port whereby the pump discharge manifold pressure is transmitted to valve 1. Outlet port 4 i5 connected to a pump pressure control port whereby a control pressure is transmitted to the pump for creating a force or regulating the stro~e of the pump's pistons. The operation of the.
pump in this regard is described in the aforenoted copending Cdn. Application Serial No. 300,010. Outlet port 6 of valve 1 is connected to a pump inlet port for purposes to be hereinafter described.
Valve 1 includes a cylinder 8 having a bore 9 : extending therethrough, and havfng control pressure inlet orifices 10 and.control pressure outlet orifices 12 which .~0 are in communication with a channel 14. Channel 14 is in turn in communication with valve outlet port 4. Valve 1 further includes an orifice 16 which is in communication with valve outlet port 6. In this connection it is noted that orifices 10 and 12 are provided on both sides of
Cross Reference to Related Applications ~ he valve disclosed hexe.in may he used in co~junction with a ~ariable displacement pi5ton pump ~uc]-l as descri~ed and claimed in commonly assignea coperldil-ly Canadian Application Serial No. 300,010, filed by Frank Woodruff on March 30, 1977.
Field of ~he Inven-tion - ' ~' ' This inventi.on relates generally ~o pump pressure control valves and, paxticularly, to a valve which controls A
'7 the discharge manifold pressure of the pump to provide a pressure for regulating the stroke of the pump pistons.
Description of the Prior Art The aforenoted copending Canadian ~pplicatlon Serial No. 300,010 describes a variable displacement piston pump including a shaft having a driven end and an opposite end arranged for supporting a swash plate to pivot about an axis displaced from the center line of the shaft and preferably, but not necessarily, normal thereto. A
plurality of pistons having hollow cylinders extending therethrough are arranged with corresponding check valves in a pump block. During the "delivery" stroke of the pistons the pressure in the cylinders becomes sufficient to actuate the check valves whereby fluid is delivered to a common discharge manifold.
When the manifold pressure approaches a predetermined value, a force is created which is transmitted to the swash plate and pivots the plate away from a maximum flow position. The pistons are arranged with the swash plate so that when the swash plate pivots r the stroke of the pistons is decreased to reduce fluid flow and pressure. Equili-brium is thus established and a reduced fluid flow at a predetermined substantially constant pressure is maintained.
The valve of the present invention is used in conjunction with a pump of the type described to control the pump manifold pressure Eor providing a pressure which creates the force transmitted to the swash plate. The valve herein described features a novel arrangemen-t including an elonyated spool section responsive to pump discharge manifold pressure for varying the area of a pair of orifices arranyed in series relation to provide a pressure which is transmitted to the pump chamber for regula-ting the stroke of the pump pistons.
According to the present inven-tion there is provided a pressure control valve having a valve cylinder including a bore extendiny therethrough with a pressure inlet port extending externally to the valve and communicating with the valve cylinder bore so that an inlet pressure is received by the valve. A spring loaded valve spool is disposed within the valve cylinder bore and is responsive to the inlet pressure for being displaced against the spring load. First and second orifices communicate with the valve cylinder bore and are arranged with the valve spool so that displacement of the spool increases the area of one of the first and second orifices and decreases the area of the other of the orifices to create a control pressure. A pressure outlet port extends external to the valve and means communicates the first and second orifices and the pressure outlet port with the control pressure transmitted through the means to the pressure outlet port and therefrom external to the valve.
In a specific embodiment of the invention, the spool includes an elongated section which varies the area of the pair of orifices arranged in series relation and used for inlet and exhaust of a control pressure generated by the valve. The orifices are of different diameters to permit tailoring of the control pressure in relation -to spool stroke for obtaining reasonably balanced slew rates toward or away from full pump flow. Means are provided for accommodating less than perfect spring force alignment along the spool axis.
One object of this invention is to provide a pressure control valve for a variable displacement piston type pump, whereby the pump is supplied with a pressure which crea-tes a force for regulating -the stro]ce of the pump pi.s-tons to provide a variable fluid flow at a substan-tially constant pressure.
-3a-~ Another object of this invention is to provide a valve of the type described which includes an elongated spool section responsive to pump discharge manifold pressure for varying the area of control pressure inlet and outlet orifices.
Another object of this invention is to provide the orifices of different diameters, with the area of the orifices being varied by the elongated spool section, whereby the control pressure in relation to the spool stroke can be tailored for reasonably balanced slew rates toward and away rom full pump flow.
Another object of this invention is to actuate the valve spool against a spring force and to accommodate misalignment of the spring force along the spool axis.
The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows taken together with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.
Description of the Drawings Figure 1 is a partially sectioned front plan view showing in substantial detail a pump pressure control valve according to the invention.
~7 Figure 2 is a schematic diagram illustrating the operation of the valve shown in detail in Figure 1.
Description of the Invention With reference first to Fi.gure 1, a pump pressure control valve designated by the ntlmeral 1 includes an inlet port 2! an outlet port 4 and an outlet port 6.
Inlet port 2 is connected to a pump discharge mani~old port whereby the pump discharge manifold pressure is transmitted to valve 1. Outlet port 4 i5 connected to a pump pressure control port whereby a control pressure is transmitted to the pump for creating a force or regulating the stro~e of the pump's pistons. The operation of the.
pump in this regard is described in the aforenoted copending Cdn. Application Serial No. 300,010. Outlet port 6 of valve 1 is connected to a pump inlet port for purposes to be hereinafter described.
Valve 1 includes a cylinder 8 having a bore 9 : extending therethrough, and havfng control pressure inlet orifices 10 and.control pressure outlet orifices 12 which .~0 are in communication with a channel 14. Channel 14 is in turn in communication with valve outlet port 4. Valve 1 further includes an orifice 16 which is in communication with valve outlet port 6. In this connection it is noted that orifices 10 and 12 are provided on both sides of
2~ cylinder ~ to preclude a side load on the spool. As a design matter, more than one pair of orifices may be used .as may be desired.
A valve spool 18 is axially disposed within bore 9 and includes end sections 20 and 22 of a predetermined diameter and an elongated section 24 intermediate end sections 20 and 22. Section 24 is of a substantially larger diameter than sections 20 and 22. Section 24 is arranged with orifices 10 and 12 so as to vary the area of the orifices and to thereby provide a control pressure at valve outlet port 4 as will be hereinafter described.
Cylinder 8 terminates in an enlarged section 26 which is held in.place by a valve housing 28. A spring 30 is disposed within valve housing 28 intermediate a spring follower 32 disposed near section 26 and an oppositely dispo~ed.spring follower 34. Spring follower ~5 34 includes an axially extending portion 41 having a purpose which will be hereinafter described.
A free floating pin designated by the numeral 36 is disposed within bore 9 adjacent the end of spool `se~,tion 22 and intermediate said.end and spring follower '0 32. Pin 36 is designed to have sufficient strength and surface area to carry any sideload resulting from less than perfect alignment of the force of spring 30 along the common axis of pin 36 and spool 18. Bore 9 may or may not be enlarged in the area containing pin 36, as '5 dictated by.the proper design of the pin. As a design matter, diametral.clearance between pin 36 and bore 9 need not be closely held, since the clearance does not ,affect fluid leakage, and only nominal concentricity relative to spool 18 is required.
;~
A rod 40 extends through valve housing 38 and is adjustable through a thread and nut arrangement 42 for displacing spring follower 34 to adjust the tension on spring 30. Axially extending portion 41 of spring follower 34 which is arranged for sufficient clearance with spring fol10wer 32 so that compression of spring 30 beyond spool stroke requirements is precluded.
This is an optional design feature to protect the spring from over-stress and possible permanent deformation.
Operation of the Invention With the specific structural details of valve 1 illustrated and described with reference to Figure l!
the operation of the valve will next be described with i reference to the schematic diagram of Figure 2.
Thus, the pump discharge manifold pressure received by valve 1 through port 2, and which pressure may be for purposes of illustration 6,000 psi, forces spool 18 in bore 9 upward against the downward force extended by spring 30, relative to the illustration of Figure 2. This increases the area of orifices 10 which may have a diameter of .040 inches and decreases the area of orifices 12 which may have a diameter of .090 inches. Oriices 10 and 12, of different diameters and in the series arrangement as shown, create an intermediate control pressure in channel 14, which may be 500 psi, for transmission to the pump pressure control port via valve outlet port 4. With the arrangement shown, the 9~
pressure at valve outlet port 6 which is transmitted to the pump inlet port is substantially zero. The pressure at port ~ actuates a mechanism and c:auses the pump to de-stroke as described in the aforenoted Cdn- Application Serial No. 300,010.
With further reference to Figure 1, it will be seen that fluid leakage to vent must either go through the control pressure route or alon~ elongated section 24 of spool 18. The relatively long enlarged diameter of spool section 24 facilitates the use of separate orifices 10 and 12 which, in turn, facilita*e obtaining desired rates of change in the area of the orifices in relation to the stroke of spool 18. Elongated spool section 24 also permits a desired low fluid leakage with a practical diametral clearance with bore 8, the same being advantageous from a manufacturing standpoint.
The ratio of the diameters of orifices 10 and 12, orifices 10 being of the smaller diameter and orifices 12 being of the larger diameter, provides considerable flexibility in tailoring the control pressure in relation to the stroke of spool 18 to obtain both reasonably balanced slew rates toward or away from full pump flow and desired rates of change of the areas of the orifices.
This results in a desired change of control pressure in relation to spool stroke.
It is understood that the recited pressures and orifice diameters are for illustration purposes only and ,may be varied depending upon the size of the pump, the amount of fluid to be pumped, and the several other parameters which may be taken into account, the same being a matter of design.
It will now be seen from the aforegoing description of the invention that a fuel pump pressure control valve has been described which controls the pressure from the pump discharge manifold to proviae a pressure for regulating the stroke of the pump pistons. The valve as described minimizes ~luid leakage without extremely severe diameter tolerances and minimizes spring side loading. The spool diameter is chosen to:
a. provide sufficent force for an allowed change in pump discharge pressure to obtain a practical spool stroke with a spring rate-to-inertia ratio which puts the spring-mass resonance above the pump piston frequency for maY~imum pump speed;
b. minimize leakage by using minimum spool diameters; and c. allow sufficient area around spool portion 22 so as not to restrict flow through orifice 12.
9~87 . Although but a single embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.
A valve spool 18 is axially disposed within bore 9 and includes end sections 20 and 22 of a predetermined diameter and an elongated section 24 intermediate end sections 20 and 22. Section 24 is of a substantially larger diameter than sections 20 and 22. Section 24 is arranged with orifices 10 and 12 so as to vary the area of the orifices and to thereby provide a control pressure at valve outlet port 4 as will be hereinafter described.
Cylinder 8 terminates in an enlarged section 26 which is held in.place by a valve housing 28. A spring 30 is disposed within valve housing 28 intermediate a spring follower 32 disposed near section 26 and an oppositely dispo~ed.spring follower 34. Spring follower ~5 34 includes an axially extending portion 41 having a purpose which will be hereinafter described.
A free floating pin designated by the numeral 36 is disposed within bore 9 adjacent the end of spool `se~,tion 22 and intermediate said.end and spring follower '0 32. Pin 36 is designed to have sufficient strength and surface area to carry any sideload resulting from less than perfect alignment of the force of spring 30 along the common axis of pin 36 and spool 18. Bore 9 may or may not be enlarged in the area containing pin 36, as '5 dictated by.the proper design of the pin. As a design matter, diametral.clearance between pin 36 and bore 9 need not be closely held, since the clearance does not ,affect fluid leakage, and only nominal concentricity relative to spool 18 is required.
;~
A rod 40 extends through valve housing 38 and is adjustable through a thread and nut arrangement 42 for displacing spring follower 34 to adjust the tension on spring 30. Axially extending portion 41 of spring follower 34 which is arranged for sufficient clearance with spring fol10wer 32 so that compression of spring 30 beyond spool stroke requirements is precluded.
This is an optional design feature to protect the spring from over-stress and possible permanent deformation.
Operation of the Invention With the specific structural details of valve 1 illustrated and described with reference to Figure l!
the operation of the valve will next be described with i reference to the schematic diagram of Figure 2.
Thus, the pump discharge manifold pressure received by valve 1 through port 2, and which pressure may be for purposes of illustration 6,000 psi, forces spool 18 in bore 9 upward against the downward force extended by spring 30, relative to the illustration of Figure 2. This increases the area of orifices 10 which may have a diameter of .040 inches and decreases the area of orifices 12 which may have a diameter of .090 inches. Oriices 10 and 12, of different diameters and in the series arrangement as shown, create an intermediate control pressure in channel 14, which may be 500 psi, for transmission to the pump pressure control port via valve outlet port 4. With the arrangement shown, the 9~
pressure at valve outlet port 6 which is transmitted to the pump inlet port is substantially zero. The pressure at port ~ actuates a mechanism and c:auses the pump to de-stroke as described in the aforenoted Cdn- Application Serial No. 300,010.
With further reference to Figure 1, it will be seen that fluid leakage to vent must either go through the control pressure route or alon~ elongated section 24 of spool 18. The relatively long enlarged diameter of spool section 24 facilitates the use of separate orifices 10 and 12 which, in turn, facilita*e obtaining desired rates of change in the area of the orifices in relation to the stroke of spool 18. Elongated spool section 24 also permits a desired low fluid leakage with a practical diametral clearance with bore 8, the same being advantageous from a manufacturing standpoint.
The ratio of the diameters of orifices 10 and 12, orifices 10 being of the smaller diameter and orifices 12 being of the larger diameter, provides considerable flexibility in tailoring the control pressure in relation to the stroke of spool 18 to obtain both reasonably balanced slew rates toward or away from full pump flow and desired rates of change of the areas of the orifices.
This results in a desired change of control pressure in relation to spool stroke.
It is understood that the recited pressures and orifice diameters are for illustration purposes only and ,may be varied depending upon the size of the pump, the amount of fluid to be pumped, and the several other parameters which may be taken into account, the same being a matter of design.
It will now be seen from the aforegoing description of the invention that a fuel pump pressure control valve has been described which controls the pressure from the pump discharge manifold to proviae a pressure for regulating the stroke of the pump pistons. The valve as described minimizes ~luid leakage without extremely severe diameter tolerances and minimizes spring side loading. The spool diameter is chosen to:
a. provide sufficent force for an allowed change in pump discharge pressure to obtain a practical spool stroke with a spring rate-to-inertia ratio which puts the spring-mass resonance above the pump piston frequency for maY~imum pump speed;
b. minimize leakage by using minimum spool diameters; and c. allow sufficient area around spool portion 22 so as not to restrict flow through orifice 12.
9~87 . Although but a single embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.
Claims (8)
1. A pressure control valve, comprising:
a valve cylinder having a bore extending therethrough;
a pressure inlet port extending external to the valve and communicating with the valve cylinder bore whereby an inlet pressure is received by the valve;
a spring loaded valve spool disposed within the valve cylinder bore and responsive to the inlet pressure for being displaced against the spring load;
first and second orifices communicating with the valve cylinder bore and arranged with the valve spool so that displacement of the spool increases the area of one of the first and second orifices and decreases the area of the other of said orifices to create a control pressure;
a pressure outlet port extending external to the valve; and means communicating with the first and second orifices and the pressure outlet port, with the control pressure transmitted through said means to the pressure outlet port and therefrom external to the valve.
a valve cylinder having a bore extending therethrough;
a pressure inlet port extending external to the valve and communicating with the valve cylinder bore whereby an inlet pressure is received by the valve;
a spring loaded valve spool disposed within the valve cylinder bore and responsive to the inlet pressure for being displaced against the spring load;
first and second orifices communicating with the valve cylinder bore and arranged with the valve spool so that displacement of the spool increases the area of one of the first and second orifices and decreases the area of the other of said orifices to create a control pressure;
a pressure outlet port extending external to the valve; and means communicating with the first and second orifices and the pressure outlet port, with the control pressure transmitted through said means to the pressure outlet port and therefrom external to the valve.
2. A valve as described by claim 1, including:
a first spring follower;
a second spring follower in spaced relation to the first spring follower and near the valve spool;
a spring disposed in the space between the first and second spring followers, and loaded to provide a force; and means disposed intermediate the second spring follower and the valve spool for applying the force to the valve spool.
a first spring follower;
a second spring follower in spaced relation to the first spring follower and near the valve spool;
a spring disposed in the space between the first and second spring followers, and loaded to provide a force; and means disposed intermediate the second spring follower and the valve spool for applying the force to the valve spool.
3. A valve as described by claim 2, wherein the means disposed intermediate the second spring follower and the valve spool for applying the force to the valve spool includes:
a free floating pin member for carrying sideload resulting from misalignment of the force provided by the loaded spring and the axis of the spool.
a free floating pin member for carrying sideload resulting from misalignment of the force provided by the loaded spring and the axis of the spool.
4. A valve as described by claim 1, including:
means arranged with the first spring follower for displacing said follower to adjust the loading on the spring.
means arranged with the first spring follower for displacing said follower to adjust the loading on the spring.
5. A valve as described by claim 4, wherein:
the first spring follower includes a member extending therefrom toward the second spring follower and having a predetermined clearance therewith for limiting the displacement of the first spring follower.
the first spring follower includes a member extending therefrom toward the second spring follower and having a predetermined clearance therewith for limiting the displacement of the first spring follower.
6. A valve as described by claim 1, wherein:
the first orifice is a control pressure inlet orifice and is of a predetermined diameter; and the second orifice is a control pressure outlet orifice and is of a substantially larger predetermined diameter than the diameter of the first orifice.
the first orifice is a control pressure inlet orifice and is of a predetermined diameter; and the second orifice is a control pressure outlet orifice and is of a substantially larger predetermined diameter than the diameter of the first orifice.
7. A valve as described by claim 1, wherein:
the first and second orifices communicate with the valve cylinder bore on one side thereof; and corresponding orifices communicate with the valve cylinder bore on the opposite side thereof to minimize side loading on the spool.
the first and second orifices communicate with the valve cylinder bore on one side thereof; and corresponding orifices communicate with the valve cylinder bore on the opposite side thereof to minimize side loading on the spool.
8. A valve as described by claim 6, wherein:
the valve spool has opposite end sections of one predetermined diameter, and a section intermediate the end sections and of a substantially larger predetermined diameter; and.
the first orifice of the predetermined diameter and the second orifice of the substantially larger predetermined diameter are arranged with the intermediate section of the spool of the substantially larger predetermined diameter than. the end sections.
the valve spool has opposite end sections of one predetermined diameter, and a section intermediate the end sections and of a substantially larger predetermined diameter; and.
the first orifice of the predetermined diameter and the second orifice of the substantially larger predetermined diameter are arranged with the intermediate section of the spool of the substantially larger predetermined diameter than. the end sections.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US79477477A | 1977-05-09 | 1977-05-09 | |
| US794,774 | 1977-05-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099187A true CA1099187A (en) | 1981-04-14 |
Family
ID=25163635
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA299,762A Expired CA1099187A (en) | 1977-05-09 | 1978-03-28 | Control valve for use with variable displacement piston pump |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1099187A (en) |
-
1978
- 1978-03-28 CA CA299,762A patent/CA1099187A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |