A spool valve is provided with a stem portion that defines a fluid passageway formed by either (a) a single central support having a non-cylindrical curved surface shaped hydrodynamically, or (b) only a pair of sidewalls with, preferably, interior surfaces that are also shaped hydrodynamically. These stem passageways, which are designed to facilitate the flow of high-speed/high-pressure fluids controlled by the valve, are maintained in a predetermined orientation relative to the ports of the valve cylinders by a mechanism preferably including (a) a cam-following roller supported in a tang fixed to each spool and (b) a two-element cam that captures the roller within two of the parallel sides of a cam-track groove formed on the respective interior surfaces of each cam element.
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12. A spool for a valve for controlling the flow of fluids, said valve having a body including a cylinder having a cavity for receiving said spool, said cavity having an axis and at least one a first fluid port defining a first fluid passage, and said spool comprising:
a first port-blocking portion and a stem positioned around a central axis for alignment with the axis of said cavity;
said spool being movable axially within said cavity between first and second positions so that, when said spool is in said first position, said first fluid passage is blocked by said first port-blocking portion, and, when said spool is in said second position, fluids are permitted to move past said stem and through said first fluid passage; and
said stem defining a stem passageway formed by one of (a) no sidewalls with a central support, and (b) a pair of sidewalls with said stem passageway formed therebetween, said central support and said sidewalls, when viewed in cross section perpendicular to said central axis, having non-circular curved surfaces shaped aerodynamically, and said central support and said sidewalls also being positioned relative to said respective first fluid port of said cylinder to permit the flow of fluids through said stem passageway and through said first fluid port when said stem portion is aligned therewith.
1. In spool valve apparatus having a plurality of respective valves operated sequentially by the rotation of a drive shaft, each spool said valve comprising (a) a cylinder having at least a first fluid port defining a first fluid passage, and (b) a spool having a stem portion and at least one port-blocking portion, said spool being movable axially within the cylinder between first and second positions so that, when said spool is in said first position, said fluids are permitted to move past said stem portion and through said first fluid passage and, when said spool is in said second position, said first fluid passage is blocked, the improvement comprising:
a cam track rotated by said drive shaft and having at least two parallel surfaces; and
a plurality of cam followers, each cam follower being associated with, and aligned in a predetermined position relative to, a respective one of said spools, and each cam follower being captured between said parallel surfaces of said cam track for relative moving engagement therewith for controlling said axial motion of each respective spool and said sequential operation of said respective spool valves in response to the rotation of said drive shaft;
and wherein:
said stem portion of each respective spool defines a passageway formed by one of (a) no sidewalls with a central support comprising a non-cylindrical curved surface shaped hydrodynamically, and (b) a pair of sidewalls with said passageway formed therebetween, said central support and said sidewalls having interior surfaces shaped hydrodynamically, said sidewalls being positioned in a predetermined orientation relative to said respective first fluid port of said cylinder to facilitate the flow of fluids past said stem portion and through said first fluid port when said stem portion is aligned therewith.
0. 18. In spool valve apparatus having a plurality of valves operated sequentially by the rotation of a drive shaft, each said valve comprising (a) a cylinder having at least a first fluid port defining a first fluid passage, and (b) a spool having a stem portion and at least one port-blocking portion, said spool being movable axially within the cylinder between first and second positions so that, when said spool is in said first position, fluids are permitted to move past said stem portion and through said first fluid passage and, when said spool is in said second position, said first fluid passage is blocked, the improvement comprising:
a cam track rotated by said drive shaft and having at least two parallel surfaces; and
a plurality of cam followers, each cam follower being associated with, and aligned in a predetermined position relative to, a respective one of said spools, and each cam follower being captured between said parallel surfaces of said cam track for relative moving engagement therewith for controlling said axial motion of each respective spool and said sequential operation of said respective spool valves in response to the rotation of said drive shaft;
wherein:
said stem portion of each respective spool defines a passageway formed by no sidewalls with a central support comprising a non-cylindrical curved surface shaped hydrodynamically, said central support being positioned in a predetermined orientation relative to said respective first fluid port of said cylinder to facilitate the flow of fluids past said stem portion and through said first fluid port when said stem portion is aligned therewith;
said cylinder comprises a second fluid port spaced from said first fluid port and defining a second fluid passage;
when said spool is in said first position and fluids are permitted to move past said stem portion and through said first fluid port, said second fluid port is blocked;
when said spool is in said second position, said first fluid passage is blocked and fluids are permitted to move past said stem and through said second fluid port;
said predetermined orientation of said central support is positioned to facilitate the flow of fluids (a) past said stem portion and through said first fluid passage when said stem portion is aligned with said first fluid port and (b) past said stem portion and through said second fluid passage when said stem portion is aligned with said second fluid port;
wherein said central support forms a pair of passageways, each said passageway being oriented to direct fluid to and from a respective one of said fluid ports when said stem portion is aligned therewith.
2. The spool valve improvement of
said cylinder comprises a second fluid port spaced from said first fluid port and defining a second fluid passage; and
when said spool is in said first position and said fluids are permitted to move past said stem portion and through said first fluid port, said second fluid port is blocked;
when said spool is in said second position, said first fluid passage is blocked and fluids are permitted to move past said stem and through said second fluid port; and
said predetermined orientation of said central support and of said passageway between said sidewalls of said stem portion is positioned to facilitate the flow of fluids (a) past said stem portion and through said first fluid passage when said stem portion is aligned with said first fluid port and (b) past said stem portion and through said second fluid passage when said stem portion is aligned with said second fluid port.
3. The spool valve improvement of
4. The spool valve improvement of
0. 5. The spool valve improvement of
6. The spool valve improvement of
7. The spool valve improvement of claim 1 8 wherein said predetermined position of each said cam follower relative to its respective spool prevents rotation of each spool about the axis of its respective cylinder when said roller is in rolling engagement with said cam track and, thereby, maintains said predetermined orientation of said central support and said sidewalls of said stem portion to facilitate said fluid flow.
8. The spool valve improvement of claim 7 1 wherein each said cam follower comprises a roller captured for rolling engagement with said cam track.
9. The spool valve improvement of
10. The spool valve improvement of
11. The spool valve improvement of
13. The spool of
14. The spool according to
said orientation mechanism comprises a cam follower aligned in a predetermined position relative to said spool, said cam follower being captured between said parallel surfaces of said control cam for relative moving engagement therewith for controlling axial motion of said spool.
16. The spool according to
17. The spool according to
a second port-blocking portion separated from said first port-blocking portion by said stem and, when said spool is in said first position, said first port-blocking portion of said spool blocks said first fluid passage while fluids are permitted to move through said stem passageway and through said second fluid passage, and when said spool is in said second position, said second port-blocking portion of said spool blocks said second fluid passage while fluids are permitted to move through said stem passageway and through said first fluid passage; and
an orientation mechanism for positioning said stem passageway in a predetermined orientation relative to both said first fluid passage and said second fluid passage so that fluid flow through said stem passageway is facilitated at all times when said stem is aligned, respectively, with said first and second fluid passages.
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This invention relates to valving used to control the flow of fluids, e.g., radial valves incorporated as an integral part of hydraulic pump/motors; and, more particularly, it relates to apparatus for controlling the operation of spools used in such valves and to the shape of the spools themselves.
Valving using reciprocating spools to control the flow of fluids is well known in the hydraulics art. For instance, spool valves, arranged radially, are used as part of hydraulic pump/motor apparatus (e.g., see U.S. Pat. No. 5,513,553 entitled “Hydraulic Machine with Gear-Mounted Swash-Plate”). In most such known valving, each spool reciprocates axially within a cylinder formed in the valve body. Most commonly, each cylinder is provided with a pair of ports defining first and second fluid passages, and the spool has a pair of port-blocking portions separated by a stem so that, when the spool is moved axially to a first position, the first fluid passage is blocked while fluids are permitted to move past the stem and through the second fluid passage. Likewise, when the spool is moved axially to a second position, the second fluid passage is blocked while fluids are permitted to move past the stem and through the first fluid passage.
Traditionally in such valving, one end of the spool portion of the valve acts as a cam follower that rides on a revolving cam surface, and each spool is spring biased toward the cam surface so rotation of the cam controls the successive and continuous axial movement of the respective spools in each valve set. However, it is known that the response time and general operation of such spring-biased spool systems are often affected by dirt and counter-pressure problems. Also, it is well known that the individual spools of such known valving often rotate (albeit, very slowly) about their central axes when being operated within their respective cylinders. Therefore, the narrowed stem section of each spool has preferably been designed with a cylindrical shape (see
Valve design is of particular importance when the valving is used to control the flow of hydraulic fluids under high speed and high pressure conditions, e.g., in automotive pump/motors which are capable of developing high horsepower and must be able to achieve speeds as high as 4000 rpm and to withstand pressures as high as 4000 p.s.i. Consistent fluid flow under such conditions is critical.
The invention disclosed herein is primarily directed to such critical fluid flow. Valving according to the invention overcomes the response time problems of spring-biased valving and not only assures consistency of valve timing but also significantly increases the efficiency of fluid flow past the stem portion of each spool.
The general format of valving according to this invention follows the known conventional spool valve arrangements discussed above. Namely, each spool reciprocates axially within a cavity, preferably a cylinder, formed in the valve body. The cylinder may include ports forming only a single fluid passage. However, in the embodiments designed for use with hydraulic pump/motors (e.g., as disclosed in
However, in contrast to prior art arrangements, in the invention's valving, reciprocating axial motion of each spool is not controlled by a spring-biased cam follower. Instead, positive spool control is achieved with a cam follower captured within a cam track that is fixed to rotate with a drive shaft. The cam track has at least two parallel cam surfaces between which the cam follower is captured. In all preferred embodiments, the cam follower is a roller.
In the preferred valving arrangement illustrated in
The stem portion of each spool defines a passageway preferably formed by either (a) a single, central support which, when viewed in a cross section taken perpendicular to the central axis of the spool, has a non-circular curved surface shaped hydrodynamically, or (b) only a pair of sidewalls. Preferably, the interior surfaces of the sidewalls are also shaped hydrodynamically. The respective hydrodynamic shapes of the central supports and the sidewalls are designed to facilitate the high-speed/high-pressure flow of fluids through the fluid passages controlled by the valve. That is, these hydrodynamic surfaces are shaped to facilitate both (i) the flow of fluids through the spool and (ii) the direction of fluid flow to and from the fluid passageways defined by the respective cylinder ports when said stem portion is aligned therewith.
Of course, these hydrodynamic stem surfaces must be maintained in a predetermined orientation relative to the ports of the valve cylinders in order to assure maximum flow of fluid through these stem and cylinder passageways. The invention's orientation mechanism prevents any axial rotation of the spools. Namely, this mechanism includes the cam followers that are mounted on each spool. As just mentioned above, these cam followers (preferably, rollers) are captured between the parallel surfaces of a rotating cam so that each spool, while being positively driven by the cam track, cannot rotate about its axis, thereby maintaining the desired orientation of the spool's stem passageway.
The reciprocation of pump pistons 18, in response to the rotation of drive shaft 12, moves fluid into and out of pump cylinders 16 through an orifice 17. As each respective piston 18 moves to the right, low pressure fluid entering orifice 17 follows the piston to fill its respective cylinder 16; and, thereafter, as each respective piston 18 is driven back to the left, high pressure fluid is forced out of its respective cylinder 16 through orifice 17. This high speed flow of low and high pressure fluid is controlled by spool valving carried within a valve block 36 connected to the left end of cylinder block 14 by bolts 38.
Valve block 36 is bored with a plurality of valve cylinders 40 arranged about axis 42 of drive shaft 12, and the axis of each valve cylinder 40 extends radially from axis 42. Within each valve cylinder 40, a respective spool 44a is moved axially to sequentially open and close a pair of ports 46, 48 defining respective high and low pressure fluid passageways connecting with corresponding respective passageways 50, 52 in respective spiral manifolds 53 only one shown in hidden lines) formed in an end cap 54, which forms the left end of the housing of pump 10.
Operation of spool valves mounted in valve block 36 will first be generally described using spools according to a first embodiment of the invention. [NOTE: All of the valve spools of the invention share the same basic arrangement of similar elements which are generally identified by the same reference numerals, the elements of each different embodiment being differentiated by the use of letter suffixes (a through f) specific to each embodiment.]
Referring now to
As shown in
For assembly, after each spool 44a has been fitted within its respective valve cylinder 40, cam element 72 is keyed to shaft 12; and then each respective roller 66a is fitted through the respective guide hole 64 formed in the tang 62 of its respective spool 44. Each cam-following roller 66a is then positioned with one end within cam track 76 of cam element 72. Thereafter, cam element 70 is also keyed to shaft 12 so that the other end of each roller 66a is received within cam track 74 of cam element 70, and cam element 70 is suitably locked in position.
Since, as indicated above, tang 62a is fixed relative to spool 44a, and since cam-following roller 66a is captured within cam tracks 74 and 76 of cam elements 70, 72, spool 44a is prevented from rotation about the axis of its respective valve cylinder 40 at all times during operation. Further, since the position of stem 60a is also fixed relative to the other elements of spool 44a, the orientation of stem portion 60a is similarly prevented from rotation about the axis of its respective valve cylinder 40 at all times during operation.
A primary feature of the invention resides in the shape and orientation of the stem portion of each spool and in the facilitation of the flow and direction of fluid through the passageway formed by each stem portion when the latter is aligned with the port(s) of its respective valve cylinder 40. In this regard, it must be remembered that the axial movements of each spool 44a control sequential and bi-directional flows of fluids, i.e., flows into as well as out of each pump cylinder 16.
The importance of fluid flow facilitation is best appreciated when compared with prior art spools of the type illustrated in
As indicated in the Background above, each stem 60 of prior art spool 44 is centered on the axis of the spool and has a cylindrical form. Therefore, should spool 44 rotate axially within its respective valve cylinder during valve operation, the relative size and shape of the fluid passageway formed by the stem portion of spool 44 remain constant. As is well known in the art of hydraulics, when a fluid flows past a cylinder at high speed (e.g., the movement of air past a flag pole or the mast of a sailboat), eddies are formed in the moving fluid resulting in a rippling turbulence. The turbulence resulting from the movement of the fluid through the stem passageway of spool 44 is schematically illustrated in
The invention herein is directed to the reduction of such turbulence and, thereby, to an increase in the efficiency of high speed/pressure hydraulic pump/motors.
Reducing Turbulent Flow
Referring to a first embodiment of the invention's spool design illustrated in
A second embodiment of the invention's spool design is illustrated in
Enhancing Direction of Flow
As indicated above, spool valves find widespread use in hydraulic machines such as pumps and motors. As is well known in the hydraulic arts, pumps have pistons responsive to the rotation of a drive shaft, the latter being driven by an outside power source. The pistons draw low pressure fluid into the pump's cylinders and then force the fluid out of the cylinders at high pressure. In hydraulic motors, the reverse is true, i.e., high pressure fluid moves the motor's pistons, causing rotation of the motor's drive shaft, and the fluid then exits the cylinders at a lower pressure for return to a closed hydraulic loop shared with a mating hydraulic pump (or, in sonic cases, to a sump). The direction of rotation of the motor's drive shaft is reversed when the flow of the high pressure fluid is reversed in the hydraulic lines serving the motor, etc. In any event, hydraulic fluid enters and exits the cylinders of pump/motors through separate ports, and the direction of flow through these ports can be reversed.
Referring once again to the spool valve arrangement shown at the top left hand portion of the hydraulic machine illustrated in
For purposes of this explanation, it is assumed that pump 10 is being operated in a closed fluid loop arrangement with a matching hydraulic motor. Further, it is assumed that high pressure fluid is present in passageway 50 and in the duct connecting with port 46 and that lower pressure return fluid is present in passageway 52 and in the duct connecting with port 48.
The following embodiments relate to facilitation of the direction of fluid flow through the stem passageways of the invention's spools.
A third embodiment of the invention, spool 44c, is illustrated in
A fourth embodiment, spool 44d, is illustrated in
Finally,
In this sixth embodiment, a pressure-balancing channel 84 is formed around the entire exterior circumference of stem portion 60f. (NOTE: The depth of channel 84 is shown greatly exaggerated in the illustrations.) Although the width of channel 84 (in
As was explained above in regard to the first and third embodiments, spool 44f has no intermediate stem element (e.g., stem 60 of prior art spool 44), and fluid is free to move unimpeded and bi-directionally past stem portion 60f of spool 44f, as indicated schematically by fluid flow arrow 82f in
In the four latter embodiments, the orientation of the fluid passageways through the stem portions of the spools is once again critical. As explained in relation to the first and second embodiments, this critical orientation is maintained by a mechanism that prevents rotation of the individual spools 44a-f about the axis of their respective valve cylinders 40. Such an orientation mechanism might include some form of keyway arrangement using a key and slot/slide combination shared by each valve cylinder and spool. However, once again, the preferred orientation mechanism comprises a positively driven cam follower captured in a cam track and positioned in a fixed orientation relative to each spool as fully described above.
The invention as described above increases pump efficiency by (a) positively driving each spool, by (b) facilitating the direction of fluid flow past the stem portion of each spool, and by (c) using spool stem design to reduce fluid turbulence. The reduction of fluid turbulence in the valving system of hydraulic pump/motors not only increases machine efficiency but also significantly reduces the machine noise that accompanies all high speed movement of fluid.
Gleasman, Vernon E., Alexander, Warren R.
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Jan 21 1999 | GLEASMAN, VERNON | Torvec, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 026169 | /0887 | |
Jan 22 1999 | ALEXANDER, WARREN R | Torvec, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 026169 | /0887 | |
Sep 14 2004 | Torvec, Inc. | (assignment on the face of the patent) | / |
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