US3386471A

US3386471A - Flow control and cushioning valve

Info

Publication number: US3386471A
Application number: US487018A
Authority: US
Inventors: James F King
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1965-09-13
Filing date: 1965-09-13
Publication date: 1968-06-04
Anticipated expiration: 1985-06-04

Description

June 4, 1968 1. F. KING FLOW CONTROL AND CUSHONING VALVE Filed Sept. 13, 1965 ATTORNEY United States Patent O 3,386,471 FLOW CONTROL AND CUSHIONING VALVE James F. King, St. Joseph, Mich., assignor toClark Equipment Company, a corporation of Michigan Filed Sept. 13, 1965, Ser. No. 487,018 7 Claims. (Cl. 137-5962) ABSTRACT F THE DISCLOSURE A ow control and cushioning valve have a spool slidable in a body to control iiuid communication between a pair of supply and return ports and a pair of motor ports and valve means in the spool for connecting the motor ports when a predetermined .pressure is reached.

`Backhoes conventionally are mounted on tractors and are arranged to be swung from side-to-side in an arc about a vertical axis. The mechanism for swinging the backhoe from side-to-side usually is a hydraulic circuit which includes a pair of single acting fluid motors. Such circuits are subject to problems caused lby the inertia of the backhoe. For example, when the backhoe is being swung through an arc and the pressure of the uid operating one of the fluid motors drops, the inertia of the backhoe will tend to keep the backhoe swinging with the result that cavitation may `occur in the fluid motor which had Ibeen powering the backhoe. Consequently, an object of my invention is to provide a ow control valve which prevents cavitation in the hydraulic circuit if the fluid pressure should drop while the backhoe is 'being swung.

Further, when the control valve in the hydraulic circuitry for swinging a backhoe is closed abruptly, the inertia of the backhoe tends to continue the swing of it with the result that there is an increase in pressure in the hydraulic circuitry and undesirable shock to the backhoe and related st-ructure due to the abrupt stop which tends to jerk violently the tractor and backhoe. Therefore, another object of my invention is to provide a valve which prevents an abrupt stopping of the swing of a backhoe and the associated fluid pressure build-up.

Another important object of my :invention is to provide a cushioning valve which functions independently of the working pressure of the associated hydraulic system.

While some of the objects of my invention have been set forth in regard to use with a backhoe, the valve is not limited to such use, but may be used in other applications also, such as in the hydraulic steering system of an articulated vehicle, for example.

In carrying out my invention Iin a preferred embodiment, I provide a valve having a body with a spool slidably disposed therein and held in a centered position by a pair of springs. The spool is responsive to fluid pressure supplied to the valve so that it shifts to communicate the uid supply and return ports to the valve with the ports to one or more fluid motors. Located in the spool is a pair of fluid pressure responsive valves which can communicate one of the fluid motor ports with the other huid motor port when the spool is in a substantially centered position.

The a'bove and other objects, features and advantages of my invention will be more clearly understood when the following detailed description is taken in conjunction with the accompanying drawing which shows a hydraulic circuit suitable for use with a backhoe and em- -bodying my invention.

Referring to the drawing, reference numeral 10 denotes a portion of the frame of a tractor, and numeral 12 denotes a portion of backhoe which is connected to frame 18 vfor pivotal movement about a vertical axis 14.

The backhoe 12 is swung from side-to-side about axis 3,388,471 Patented June 4, 1968 ICC 14 by a swing mechanism 16 which includes a pair of links 18 pivotally connected to backhoe 12 at 20 and a pair of links 22 pivot'ally connected to links 18 at 24 and pivotally connected to each other at 26. Connected to links 22, as shown, is a pair of single acting fluid moto-

rs

28 and 30 which also are connected to frame 10 at 32 and serve to actuate swing mechanism 16.

Fluid motors

28 and 30 form part of a hydraulic circuit 34 which includes a fluid reservoir or sump 36, a pump 38, a control valve 40 and a flow -control and cushioning valve 42. Pump 38 is disposed in a uid conduit 44 through which it draws liuid from sump 36 and supplies pressurized fluid to control valve 40 which is an open center, four way valve. An operator by manipulating control lever 46 Iof control valve 40 can direct pressurized fluid to fluid motor 28 via a conduit 48, valve 42 and conduit 50; direct pressurized fluid to fluid rnotor 30 via a conduit 52, valve 42 and a conduit 54; or return pressurized fluid directly to reservoir 36 via a conduit 56. By manipulating lever 46 to supply pressurized iiuid to conduit 48 and hence uid motor 28 the backhoe 12 will be pivoted in a clockwise direction as viewed in the drawing. Now on the other hand, if lever 46 is manipulated so that pressurized fluid is supplied to conduit 52 and hence fluid motor 30, the backhoe 12 will be pivoted in a counterclockwise direction as viewed on the drawing. It will be understood that when control valve 40 is manipulated so that one of the fluid motors is supplied with pressurized fluid that the other Huid motor is connected through the control valve to the reservoir.

Turning now to the details of the flow control and cushioning valve 42, it will be seen that the valve includes an elongated housing or body 58 through which a bore 60 extends longitudinally thereof and is closed at the ends by

caps

62 and 64 which threadably engage housing 58. Four longitudinally spaced apart

annular grooves

66, 68, 70 and 72 are cut in bore 60. A pair of

fluid ports

74 and 76 communicate with

grooves

66 and 72, respectively, the outermost two of the four grooves, and a pair of

ports

78 and 80 communicate with grooves 68 and 70, respectively, the innermost two of the four grooves. At this point it will be noted that

conduits

48, 50, 52 and 54 are connected to

ports

74, 78, 76 and 80, respectively.

Slidably ydisposed in valve xbore 60 is a spool 82 which includes an elongated body 84. A bore 86 extends longitudinally through spool body 84 and includes a reduced diameter portion 88 which defines a :pair of

shoulders

90 and 92. Sidably disposed in spool bore 86 is a pair of pistons 94 and 96 which are located longitudinally outwardly of

shoulders

90 and 92, respectively. Piston 94 has a reduced diameter portion 98 which is adapted to engage shoulder 90, forming la seal therewith, and piston 96 has a reduced diameter portion 100 which is adapted to engage shoulder 92, forming 'a seal therewith. Reduced diameter portion 98 of piston 94 defines therewith an annular face 102 and reduced diameter portion defines with piston 96 an annular face 104. The importance of these faces will become apparent when the operation 'of the valve is explained. A pair of helio-

al compression springs

106 and 108 are disposed in bore 86, and engage pistons 94 and 96, respectively. Springs 106 and 108 are held in bore 86 under compression by spring retainer members 110 and 112, respectively, which threadably eng-age spool body 84 with the result that pistons 94 and 96 tend to be biased into sealing relation with

shoulders

90 and 92.

Spool body 84 also includes three annular, longitudinally spaced apart lands 114, 116 and 118. Lands 114 and 116 define an annular groove 120 therebetween and lands 116 and 118 define an annular groove 122 therebetween. A plurality of fluid passages 124 connect groove 120 with bore 86 longitudinally outwardly of shoulder 90 and a plurality of fluid passages 126 connect annular groove 122 with bore 86 longitudinally outwardly of shoulder 92. The timing of lands 114, 116 and 118 with the grooves in Valve bore 6l), and thus the various ports is such that when spool 82 is in the centered position shown that land 114 blocks fluid communication between ports 74 and '78 and land 118 blocks fluid communication between ports 75 and 8G. Further, as spool 82 is shifted toward the right, fluid communication is established first between

ports

74 and 78 and then between ports 76 and 8G. Conversely, when spool 82 is moved toward the left fuid communication is established first between ports 76 and Sil and then between

ports

74 and 78.

Spool 82 tends to be held in a substantially centered position, as shown, by a pair of opposed

helical cornpression springs

128 and 130 which lare held in valve bore 60 by

caps

62 and 64 and engage the outer ends of lands 114 and 118, respectively.

In order to enable persons skilled in the art to understand my invention l will now explain the operation of it. lt will be assumed that an operator desires to swing the backhoe 12 in a clockwise direction as shown on the drawing, and so manipulates lever 46 to connect conduit 48 to the supply of pressurized fluid and to connect conduit 52 to return to sump 36. Pressurized fluid which is supplied to valve bore 60 through port 74 acts on the outer end of land 114 to cause spool 82 to shift toward the right as shown in the drawing. When spool 82 is shifted sufficiently far enough to the right land 114 will then uncover groove 68, and thus place port 74 in fluid communication with port 78 so that pressurized fluid then is supplied to fluid motor 28 which tends to cause it to retract. After a slight further rightward movement of spool 82 land 118 uncovers groove "l2, and so places port 76 and Y80 in fluid communication. When this occurs backhoe 12 will commence pivoting in a clockwise direction. Now, if fiuid pressure should suddenly drop, the inertia of backhoe 12 will tend to keep it pivoting in a clockwise direction, but spool 82 will shift back to the centered position, thereby preventing fiuid motor 28 from drawing a vacuum in the fluid circuit between it and control valve 40. Further, assuming that backhoe 12 is pivoting in a clockwise direction and the operator suddenly returns control valve 40 to the neutral position, the inertia of backhoe 12 will cause it to continue to pivot in a clockwise direction with a substantial fiuid pressure build up in conduit 54. However, when the fluid pressure in conduit 54 reaches a predetermined level the force caused by the pressure which acts on face 104 of piston 96 causes piston 96 to move toward the right so that fluid conduit 94 is placed in communication with reduced diameter portion 88. The fluid pressure then acts against the end of piston 94 causing it to move toward the left, thus placing conduit 50 in communication with reduced diameter portion 83. The result is that

conduits

50 and 54 are placed in communication with each other so that fluid which is being forced out of fiuid motor 30 simply is transferred into fluid motor 2.8. This avoids an undesirably high fluid pressure build up in either

conduits

50 or 54 and permits a gradual, rather than abrupt stopping of the swinging movement of backhoe 12. While the operation of the valve 42 has been explained only for one direction of pivotal movement of backhoe 12 it will be appreciated that since valve 42 is symmetrical that it will function in exactly the same manner for the opposite direction of pivotal movement of backhoe 12.

At this point it will be seen that when spool 82 is shifted toward the right, for example, so that port 74 is in communication with port 78 that land 114 blocks fluid communication between port 78 and groove 120. Similarly, when spool 32 is shifted toward the left so that

ports

76 and 80 are in fluid communication land 113 blocks fluid communication between port 76 and groove 122. Thus, pistons 94 and 96 are not effected by the liuid pressure in

ports

74 or 76. The importance of this is that pistons 94 and 96 can be set to open at fluid pressures which are substantially below the working pressure for the hydraulic system 34. For example, the working pressure of the hydraulic system may be 1500 psi., but springs 196 and 10S can be adjusted so that pistons 94 and 96 will open Linder 200 p.s.i. which will provide a very soft cushioned stop for the swing of the backhoe.

While l have described my invention in detail with rcgard to only a single preferred embodiment, it will be understood that modifications, changes, and other applications will appear to those skilled in the art which nonetheless will fall within the scope and spirit of my invention. Consequently, the above-detailed description is intended to be illustrative only, the limits of my invention being set out by the claims appended hereto.

l claim:

1. In a flow control and cushioning valve having an elongated body, a longitudinally extending bore in the valve body, first and second ports in the valve body which communicate with the valve bore and third and fourth ports in the valve body which communicate with the valve bore longitudinally inwardly of the said first and second ports, a spool comprising an elongated body, first, second, and third annular, longitudinally spaced apart lands on the said spool body, the said first and second lands defining a first annular groove and the said second and third lands defining a second annular groove, a longitudinally extending bore in the said spool body, the said spool bore including a reduced diameter portion which defines first and second shoulders in the said spool bore, a first fluid passage connecting the said first groove with the said spool bore longitudinally outwardly of the said first shoulder, a second iiuid passage connecting the said second groove with the said spool bore longitudinally outwardly of the said second shoulder, a first piston slidably and sealingly disposed in the said spool bore longitudinally outwardly of the first shoulder, the said first piston including a reduced diameter portion adjacent to the said first fluid passage and which seats against the said first shoulder to form a seal, a first spring disposed in the said spool bore which engages the said first piston to bias it into engagement with the said first shoulder, a second piston slidably and sealingly disposed in the said spool bore longitudinally outwardly of the said second shoulder, the said second piston including a reduced diameter portion adjacent to the said second fluid passage and which seats against the said second shoulder to form a seal, and a second spring disposed in the said spool bore which engages the said second piston to bias it into engagement with the said second shoulder.

2. A flow control and cushioning valve comprising lan elongated valve body, a longitudinally `extending bore in the said body, first and second ports in the said body which communicate with the said bore, third and fourth ports in the said body which communicate With the said bore longitudinally inwardly of the said first and second ports, a spool slidably disposed in the said bore, the -said spool including an elongated body, a longitudinally extending bore therein, the said second-mentioned bore having a reduced diameter portion which defines first and second shoulders therein, first and second fluid passages which `connect the exterior of the said spool with the said second-meiitioned bore longitudinally outwardly of the said first and second shoulders, respectively, first and second pistons slidably and sealingly disposed in the said second-mentioned bore, each piston having a reduced diameter portion adjacent one of the said shoulders and one of the said fluid passages and first and second springs disposed in the said second-mentioned bore which engage the said first and second pistons, respectively, and tend to bias the said piston into fluid sealing relation with the respective shoulders, and third and fourth springs fdisposed in the said first-mentioned bore which engage opposite ends of the said spool and tend to bias the said spool to a substantially centered position relative to the said ports.

3. A flow control and cushioning valve comprising an elongated valve housing, a longitudinally extending valve bore in the said housing, first, second, third and fourth ports in the said housing Which communicate with the said valve bore, the said second and third ports communicating with the said valve bore longitudinally inwardly of the said first and fourth ports, a spool slidably disposed in the said valve bore, the said spool including an elongated body, first, second and third lon-gitudinally spaced apart Ilands on the outer periphery of the said body, fluid passage means in the said body connecting the said outer spool periphery between the said first and second lands with the said outer spool periphery between the said second `and third lands and imperforate valve means sealingly disposed in the said fluid passage means, the said valve mean normally blocking fluid communication through the Isaid fluid passage means `and opening in response to a predetermined fluid pressure in the said fluid passage mean-s, and a pair of resilient means disposed in the said housing bore which engage opposite ends of the said spool and ten-d to :maintain the said spool in .a substantially centered position relative to the said ports.

4. A flow control and cushioning valve comprising an elongated valve 'ho-using, -a longitudinally extending valve bore in the said housing, first, second, third and fourth ports in the said housing which communicate with the said valve bore, the said second and third ports communicating with the said valve bore longitudinally inwardly of the said first and fourth ports, a spool sldably disposed in the said valve bore, the said spool including an elongated body, a longitudinally extending bore in the said body, the said spool bore having first and second shoulders therein, first, second and third longitudinally spaced apart lands on the outer periphery of the said body, the s'aid first and second lands defining a first groove therebetween, the said second and third lands defining a second groove therebetween, first fluid passage means connecting the said first groove with the said spool bore longitudinally outwardly of the said first shoulder, second fiuid passage means connecting the said second groove with the said spool bore longitudinally outwardly of the s'aid second shoulder, a first piston slidably 'and sea'- ingly disposed in the said spool bore longitudinally outwardly of the said first shoulder, the said first piston having a reduced diameter portion adjacent the said first shoulder and the said first fluid passage means, first resilient means which engages the said first piston `and tends to 'bias the said reduced diameter portion thereof into sealing relation with the said first shoulder, a second piston sldably and sealingly disposed in the said spool bore longitudinally outwardly of the said second shoulder, the -said second piston having la reduced diameter portion adjacent the said second shoulder and the said second fluid passage means and second resilient means which engages 'the said second piston land tends to bias the said -reduced diameter portion of the said second piston into sealing relation with the said second shoulder, and a pair of resilient .means disposed in the said housing bore which engage opposite ends of the Said spool and tend to maintain the `said spool in a substantially centered position relative to the said ports.

5. A fiow control and cushioning valve comprisin-g an elongated valve housing, a longitudinally extending valve bore in the :said housing, first, second, third, and fourth ports in the said housing which communicate with the said valve bore, the said second and third ports communicating with the said valve bore longitudinally inwardly of the said first and fourth ports, 'a spool slidably disposed in the said valve bore, the said spool including an elongated body, first, second, and third 1ongitudinally spaced apart lands on the outer periphery of the said body, the said first and second lands defining ya first -groove therebetween, the said second and the said third lands defining a second groove therebetween, the said lands being located so 'that when the said spool is in a substantially centered position relative to the said ports -communication between the said first and second ports and between the said third an-d fourth ports is blocked and when the said spool is shifted away from the said centered position a predetermined distance in either direction the said first and second ports and the said third and yfourth ports lare placed in communication, the said grooves being located so that when the said spool is in the said centered position the said first and second grooves are in communication with the said second and third ports, respectively, when the said spool is shifted in one direction from the said centered position the said predetermined distance communication between the said first groove and the said `second port is blocked and when the said spool is shifted in the other direction from the said centered position the said predetermined distance communication between the `said second groove and the said third port is blocked, Ifluid passage means in the said Ibody connecting the said first 4and second grooves and imperforate valve means sealin-gly disposed in the said fluid passage means, the said valve means normally blocking fluid communication through the said fluid passage means and opening in response to 'a predetermined fluid pressure in either of the said grooves, and a pair of springs disposed in the said housing bore which enga-ge opposite ends of the said spool and tend to maintain the said spool in a substantially centered position relative to the said ports.

6. A flow control and cushioning valve comprising an elongated valve housing, a longitudinally extending valve bore in the said housing, first, second, third and fourth ports in the said housing which communicate with the said valve bore, the said second and third ports communicating with the said valve bore longitudinally inwardly of the said first and fourth ports, a spool sldably disposed in the said valve bore, the said spool including an elongated body, a longitudinally extending bore in the said body, the said spool bore having first and second shoulders therein, first, second, and third longitudinally spaced apart lands on the outer periphery of the said body, the said first and second lands defining a first groove therebetween and the said second and third lands defining a second groove therebetween, the Said lands being located so that when the said spool is in a substantially centered position relative to the said ports communication between the said first and second ports and between the said third and fourth ports is blocked and when the said spool is shifted away from the said centered position a predeter mined distance in either direction the said first and second ports and the said third and fourth ports are placed in communication, the -said grooves being located so that when the said spool is in the said centered position the said first and second grooves are in communication With the said second and third ports, respectively, when the said spool is shifted in one direction from the said centered position the said predetermined distance communication between the said first groove and the said second port is blocked and when the said spool is shifted in the other direction from the said centered position the said predetermined distance communication between the said second groove and the said third port is blocked, a first fluid passage connecting the said first groove with the said spool bore longitudinally outwardly of the said first shoulder, a second fluid passage connecting the said second groove with the said spool bore longitudinally outwardly of the said second shoulder, a first piston sldably and sealingly disposed in the said spool bore longitudinally outwardly of the said first shoulder, the said first piston having a reduced diameter portion adjacent the said first shoulder and the said first fluid passage, a first spring which engages the said first piston and tends to bias the said reduced diameter portion thereof into sealing abutment with the said first shoulder, a second piston slidably and sealingly disposed in the said spool bore longitudinally outwardly of the said second shoulder, the said second piston having a reduced diameter portion adjacent the said second shoulder and the said second fiuid passage and a second spring which engages the said second piston and tends to bias the said reduced diameter portion of the said second piston into sealing abutment with the said second shoulder, and la pair of springs disposed in the said housing bore which engage opposite ends of the said spool and tend to maintain the said spool in a substantially centered position relative to the said Lports.

7. For use with a valve, a spool comprising an elongated body, a longitudinally extending bore therein, the said bore having first and second shoulders, first, second and third longitudinally spaced apart lands on the outer periphery of the said body, the said first and second lands defining a first groove therebetween, the said second and third lands defining a second groove therebetween, a first fiuid passage connecting the said first groove and the said bore longitudinally outwardly of the said first shou1- der, a second fluid passage connecting the said second groove With the said bore longitudinally outwardly of the said second shoulder, a first piston slidably and sealingly disposed in the said bore longitudinally outwardly of the said first shoulder, the said first piston having a reduced diameter portion adjacent the said first shoulder and the said first fluid passage, a first spring disposed in the said bore which engages the said first piston and tends to bias the said reduced diameter portion into sealing abutment with the said first shoulder, a second pistOn slidably and sealingly disposed in the said bore longitudinally outwardly of the said second shoulder, the said second piston having a reduced diameter portion adjacent the said second shoulder and the said second uid passage, and a second spring disposed in the said bore which engages the said second piston and tends to bias the said reduced diameter portion of the said second piston into sealing abutment with the said second shoulder.

References Cited UNITED STATES PATENTS 2,958,339 1l/1960 Meddock 137-596.12 3,255,777 6/1966 Rice et al 137-625.68 3,267,961 8/1966 Rice 137-596 HENRY T. KLINKSIEK, Primary Examiner.