US2742056A - Open center control valve for double-acting motors - Google Patents

Description

P 395 s. G. WkLLlAMS 2,74%56 OPEN CENTER CONTROL VALVE FOR DOUBLE-ACTING MOTORS Filed July 1, 1954 Umted S t Patent cc .........iitti2 ii i narrow exhaustgrooves 21 and22 shown as symmetricall r spaced on opposite sides ofwgroiove 19. .Symrnetrical 2,742,056 U J spacing is not critical as the location ofyalve. ,ports. is a i p function-of the location of the coacting .seat, ports. sggg g 5 Through- ports 23, 24 ,leadjthrough', the sleeve zfrom.,,

. I v grooves 21, 22 respectively. I

Samuel G. Williams Cape Vincent, N. Y., assignor'to A centering spring 25 .biasesf th e ,sleeve ,18 fromany The New York Air BrakeC mpa y,1a corporation f position. toward the, open-center.,rnid?position il1ustrated New Jersey I v in Figure l. SpringZS .isa coil compression spring which II Application July 1 1954, SerialNm 440,653 I, reacts between two rings 26 each-slidable .on sleevef.18..-..; j The rings. 26 are. dimensioned-to engage,twowspaced. n-. 3l m (9 9 -5 w ternal shoulders 27 on leap L12 and bfidy ll.,IT6SPQ11Y1.,

and two similarly,spacedlexternal. shoulders lfi pn valve I I r v I r sleeve 18.- The shoulders; 28. are constructed .asfl snapv This invention relates tolcontrol valves for double- 15 rings seated in encircling grooves iriithe sleeve 18,..adetailm acting fluid pressure. motors, particularly hydraulic mofacilitating assembly. Observe thattheshouldersm need tors. i I I i I not be removable since parts 11, 12 ,on which? they are;1 The invention provides a balanced open-center valve formed are separable. i f having three functional positions useful whena double: I An actuator 31'for valve sleeve ;1;8,has a guidewayQZ}. acting motor is to be controlled and hydraulic liquid is for stem 16 and works through a. port in .theendofcapi supplied by a constantly runningpurnp- Th three Posi- 12. An O-ring 33'is used to resist "leakage. Theactufl: tions are. a mid-position in which the pump is unloaded M0 231 has a ported flange 34, which isseatedtin a.,,circu- (discharge Connected to inlet) and the motor y l lar recess in the left endvof sleeve-18 and .is thereretainede,

cally locked (both motor ports ;blanked) and.two.end by a Snap i 35. I I II a I I positions in which different onesof the twomotor ports h Sleeve 13InOrma11yseekS theIpIIositIl-on Ishgvmtin I:

are connected to supply whil'ethe other motor port s Figure l but may be moved a limitedfldistance dneither. connected tqdischarge, commonly to t p f m which direction by shifting actuator 31. Aconnection ssgleads the pump draws its supply.- i to the low pressure reservoir or sump so that the.. slee.ve 1,8

' Valves having the se functional characteristics are known is not subject to any significant hydr-aulicimbalance but as heretofore contrivedare expensive to construct, Theconstruction above described makes it possible .t 0 andsubj'ect to troublesome leakage... form theseat ports by simple drilling, operationseand to The-invention afi'ords a notably inexpensive construe-r. keep the diameter of seatlS to a reasonable, nimum. tion on which a balanced sleeve valve surrounds a cylin- Three longitudinal flo'w passages, parallel withfthe axis drical seat. In this seat adequate ports are formed by. are used. To conserve space andstill have passages of simple drilling operations. The exhaust passage sur- 3 substantial diameter, these are spaced at the corners of rounds the valve sleeve so that any leakage passes to exan equilateral triangle. They are all subject to the same haust (i. e. to the sump) and is wholly internal to the maximum pressure, i. e., the head pressure delivered by valve. I the pump.

The actuating stem which shifts the valve sleeve intro- The longest of the three is the passage 37 for the left duces a negligible unbalance and can be sealed very end ports 38 which are produced by cross drilling. (See effectively, because a negligible pressure acts upon it. Figure 4.) The shortest is passage 39 for the right end A preferred embodiment offering all the above-enumerports 41 also produced by cross-drilling, see Figure 6. ated advantages will now be described by reference to the The supply passage 42 has a length intermediate the accompanying drawing in which: lengths of passages 37 and 39 and supplies two sets of Fig. lis aview chiefly in axial section. f cross drilled ports, namely 43 which are motor supply Fig. 2 is an elevation of the right hand end of the ports (see Figure 5) and 44 which are the open center valve as positioned in Fig. l. unloading ports, (see Figure 7).

Figs. 3-7 respectively are sections through the sleeve Each of the passages 37, 39 and 42 has a radially exvalve and its seat on the planes 33, 44, 5--5, 6-6, tending connection 45, 46, 47 respectively. Plugs 48 and 77 indicated in Fig. l and looking in the direction (see Figures 1 and 2) are screwed into the ends of the of the arrows. passages 37, 39 and 42. This is because the passages are Fig. 8 is a miniature diagram showing one way in too closely spaced to permit convenient connection of which the valve may be connected between a constantly pipes at the end of head 11. I running pump and a double-acting piston motor. As a basis for explanation, one system developing the All statements of direction refer to the valve positioned utility of the valve is diagrammed in Figure 8. A sump as in Figure l. The hydraulic liquid is customarily an S serves as a reservoir for hydraulic liquid, receives this oil. Y n from discharge connection 36 and delivers it to the inlet The housing for the valve comprises a head 11 and a of pump P. The discharge of pump P is connected to cup shaped cap 12. The two are sealed together by a the supply connection 47. The opposite endsv of the toric gasket 13 and are held together by four machine double-acting piston motor M are connected respectively screws 14. to connections 45 and 46. This is one of several common Projecting from the head 11 and completely enclosed systems with which the valve may be used.

by cap 12 is the valve seat 15 which takes the form of a solid right circular cylinder integral with head 11 and spaced from cap 12 both peripherally and at its left hand In the position of Figure 1 ports 38, 41 and 43 are end. At its left hand end it carries a guide stem 16 for blanked, but 42 is connected to exhaust via 44, 22, 24 and Operation the valve actuator and this guide stem is ported axially and connection 36. This is the open-center path that unloads diametrically, as shown at 17, so that the actuator will not the constantly running pump P.

be oil-bound. Both sets of motor ports 38 and 41 are blanked. Hence The valve element is a sleeve 18 axially slida ble on 7 the connected motor M is hydraulically locked. Supply seat 15, and having three internal annular grooves, a passage 42 is connected to exhaust connection 36 via ports wide supply-groove 19 at mid-length and two relatively 44, 22, 24, so the pump P is unloaded.

To operate the motor M in one or the other direction, valve'sleeve 18'is moved in one or the other direction until groove 19 overlies one or the other set of motor ports 38 or 41. This occurs at one or the other limit of motion, as defined by collision ofsleeve valve 18 with head 11 or the cap 12. -At such time the set of ports 41 or 38 not in communication with groove19will communicate With exhaust groove 22 or 21 as the case may be. Hence a selected end of the motor M is connected to pump discharge and the other to pump suction.

The valve can be'produced with a very small number of machining operations and all of theseare simple and adapted tomass production. The only surfaces requiring high precision are the surface of seat 15 and the bore of sleeve 18. The grooves 19, 21 and 22 do not require precise machining and the ports and passages 23, 24, 37, 38, 39, 41, 42,43, and 44 are produced by simple drilling operations. Economy is thus had without detriment to performance.

The valve '18 is balanced to all intents and purposes and the seal 33 can be simple, since port 36 is under no appreciable pressure. Such valve leakage as may occur is strictly internal. It will be small if the mating surfaces are reasonably well fitted because adequate port spacing is afiorded.

The invention resides in the construction of the valve elements rather than in the function of the valve. The expedients used in the illustrated embodiment in mounting the centering spring and the actuator are subject to considerable variation.

I claim:

1. An open center balanced valve comprising a head having a projecting cylindrical valve seat; a cap attached to said head and enclosing said seat; a valve sleeve encircling said seat and shiftable axially thereon said sleeve 3 having Within its bore a supply-port recess substantially at mid-length and two exhaust-port recesses located between the supplyport recess and respective ends of the sleeve said exhaust port recesses each communicating with the space surrounding the sleeve; means affording a discharge connection to the space surrounding the sleeve and within the cap; and means attording seat ports and three distinct connections therefor, said means comprising three distinct parallel bores extending longitudinally from the head part-way through the cylindrical seat, of which one is a supply bore adapted for connection with pump discharge and communicating with two sets of crossports, a first set at. approximatelyrnid-length of the seat, and a second set positioned to communicate with an exhaust port recess in the sleeve when the latter is in midposition, and the second and third are motor bores each adapted for connection with a corresponding motor space and each communicating with corresponding cross-ports, said cross-ports being at opposite sides of the first set of supply cross-ports, and positioned between the supplyport recess and a corresponding exhaust-port recess of the sleeve, when the sleeve is in its mid-position.

2. The combination defined in claim 1 in which the supply port recess and the two exhaust port recesses in the sleeve are annular grooves encircling the bore of the sleeve.

3. The combination defined in claim 1 in which the cross-ports include a passage drilled diametrically through the valve seat, said passage in each instance intersecting one of said longitudinal bores and passing between the other two longitudinal bores or the geometrical projection of said longitudinal bores as the case. may be.

References Cited in the file of this patent UNITED STATES PATENTS

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