GB2121516A

GB2121516A - Fluid flow control valve

Info

Publication number: GB2121516A
Application number: GB08307542A
Authority: GB
Inventors: Richard Ward
Original assignee: Dobson Park Industries Ltd
Current assignee: Joy Global Industries Ltd
Priority date: 1982-04-13
Filing date: 1983-03-18
Publication date: 1983-12-21
Also published as: FR2524995A1; GB2121516B; GB2118688B; GB2118688A; GB8307542D0; GB8307541D0; DE3312996A1; FR2524995B1

Abstract

A fluid flow control valve has a valve closure member (15,16) which is operated by a rotatable eccentric (24) via the intermediary of a device such as a push rod (18). Two valve balls (15, 16) with an intermediate linking rod (17) are moved into and out of engagement with respective valve seats (13, 14) to control flow of pressure fluid between passages (8,9,10). The valve balls are moved via the intermediary of the push rod (18) by the action of the rotatable eccentric (24) which is driven by an electric motor (4). <IMAGE>

Description

1 GB 2 121 516 A 1

SPECIFICATION

Fluid flow control valve This invention relates to a fluid flow control valve.

1 n present day continuous mining at longwail coal faces it is common to use chock-type supports which supportthe roof and provide an overhead shield adjacent the face, such supports being advanced bodily togetherwith an associated coal conveyor as theface is cutaway. These supports incorporate hydraulic ramswhich are usual iy controlled with main valveswhich in turn may be controlled with solenoid operated pilotvalves. In orderto meetsafety require ments, the operating solenoids of the pilotvalves and all associated electrical equipment, haveto be "intrin sicallysafe" (IS),that is, in operation there should be no release of energy sufficientto give riseto any serious risk of explosion due to ignition of inflamm able gases likelyto be encountered in the coal mine environment (methane). It is customary therefore to operate the solenoidsfrom a relatively low-power electrical supply, e.g. a d.c. supply rated atsay 12V 0.5a. HoweverJor effective solenoid operation an appreciable currentflow is required and a serious limitation is therefore imposed on the number of solenoids which can be operated simultaneously from the same powersupply. Also a serious limitation is imposed in practical terms on the size of the valve orifice in so far as larger orifices give rise to higher power requirements. Commonly therefore operating currents of the order of say 125ma at 12V are used with valve orifices of the order of say 0.04!'(0.1 cm) diameter reduced bythe presence of a push rod therethrough of say 0.03Y (0.09cm) diameter giving atthe worst an annual flow path of only 0.000259 ins' (.0017cm') in area which can cause appreciable operational delays.

An object of the present invention is to provide a fluid flow control valve with which there is the possibility of achieving powerful effective operation without necessarily requiring the use of a direct acting solenoid for actuation purposes.

According to the invention therefore there is pro vided a fluid flow control valve having a first port, a second port, a valve closure member displaceable between different operative positions for controlling fluid flow between said ports, a valve operating mechanism comprising a rotatable eccentric, and a drive transmitting device between the eccentric and the valve closure member arranged to effect displace ment of said member in response to rotation of said eccentric.

With this arrangement, effective fluid flow control can be achieved without requiring the use of a relatively high power solenoid actuator. In particular 120 effective operation is possible using an electric motor as an actuator coupled to the rotary eccentric.

It is visualised thatthe valve of the invention will find particular application for controlling flow of fluid (directly orvia intermediate valves) to powerful 125 hydraulic rams of coal mining equipment as described above, and indeed the invention may be especially suited to this application in so faras a motor-operated valve can be readily made to conform to IS require ments. However, the invention is not intended to be 130 restricted to this field of application and the valve may be used for any suitable purpose in any suitable context and with any suitable actuator not necessarily comprising an electric motor.

The valve member of the valve of the invention may comprise a sealing element displaceable axially into and out of sealing engagementwith an associated valve seat, and said drive-transmitting device may comprise a longitudinally movable push rod arranged to act on said sealing elementthrough and axially of saidvalveseat.

In one embodimentthere aretwo said sealing elements axially displaceable into and out of sealing engagement with respective axially spaced said valve seats, said drive-transmitting device being arranged to act on one said element and there being a linking device between the elements to transmit said action from said one elementto the other element. In this case, the valve may have a third port and the arrangement may be such that one said valve seat is arranged between said first and second ports and the othersaid valve seat is disposed between said second and third ports.

The or each said valve element may comprise a ball.

In a preferred embodimentthe drive mechanism comprises a stop arranged to limitthe permitted maximum angle of rotation of the eccentric. In the case of a latching valve,the eccentric may be arranged to stop at or slightly over dead centre whereas in a non-latching valve it may stop before dead centre.

The invention will now be described further byway of example only and with reference tothe accompanying drawings in which:- Fig. 1 is a circuit diagram of a control system incorporating control valves according to one embodiment of the invention; Fig. 2 is an elevation of one of said valve of the system of Fig. 1, with parts broken away; and Fig. 3 is a sectional elevation of the valve of Fig. 2.

The system of Fig. 1 is for use in conjunction with a conventional chocktype powered support as used in -continuous- coal mining which is now generally applied in the case of longwall coal faces. With this mining procedure multiple chocks are disposed side- by-side in a line parallel to the coal face and alongside a coal conveyor. Each chock has an overhead shielding structure which is supported on upright hydraulic rams so as to act as a roof prop and protective cover. In use, coal is cut from the face and removed on the conveyor, and as the coal face is cut awaythe chocks are advanced stepwise togetherwith the conveyor, such advancement involving a number of procedures including for example: horizontal retraction and extension of overhead shield parts, vertical retraction and extension of the upright rams to allow movement of the chock awayfrom and up to the roof, and bodily movement of the entire chocktowards the coal face. Operations of the upright rams and also of auxiliary ramswhich effectthe other movements of the chock, are effected byfeed of hydrauiicfiuid to such ramsvia control valves and operation of thesevalves is controlled hydraulically with control systems incorporating pilotvalves. Unlike the conventional arrangementthe embodiment described with referenceto the accompanying drawings utilises a control system 2 GB 2121 516 A 2 incorporating motor-driven pilot valves ratherthan solenoid-operated valves.

The control system shown in Fig. 1 comprises a common electric power supply 1, a common switch ing control 2 and a plurality of valves 3 (only two of which are shown) each with a respective drive motor4 and regulating circuit5, which components are described in more detail hereinafter.

As shown in Figs. 2 and 3, each pilotvalve 3, which may have an aperture of say 0.04"(0.1 cm) and may be 75 arranged to operate with hydraulic fluid at a pressure of say 100 to 400 bar, is a three-port ball valve. The valve 3 comprises a cylindrical valve body 6 which is screwed into a solid housing 6a and has an axially extending bore 7 therethrough and three sets of 80 passages 8,9, 10 extending radially between the bore 7 and annularspaces which communicate with three ducts 8a, 9a, 10a extending radiallythrough the housing 6a at axially spaced positions. Within the bore 7there is adjustably mounted an encapsulated valve 85 assembly 11 comprising a tubularbody 12 with central valve seats 13,14atopposite ends thereof, two balls 15,16 movable respectively into sealing engagement with the two valve seats 13,14 and a push rod 17 extending axial ly between the bal Is 15,16. The valve 90 assemblyll is located within the bore 7 such that the two outermost sets of passages 8, 10 communicate respectively with the bore 7 beyond the two valve seats 13,14 and the central set of passages9 communicate with the bore 7 between such seats 13, 95 14. Above the valve assembly 11 afurtherpush rod 18 is axially slidably mounted within a bore 21. The upper end 19 of this rod 18 projects beyond the top 20 of the valve body 6. The lower end 22 of the rod is of reduced diameter and projects through the top valve seat 13 for 100 engagementwith the pertaining top ball 15.

On thetop end 20 of the valve body 6there is mounted a motor compartment 23. This compartment hastherein the pertaining regulating circuitry 5 and electric motor4described above. Also, the compart ment contains an eccentric 24and a geartrain 25. The eccentric 24 is fixed to a sleeve 26 which is fixed inturn to an axle 27 which is rotatably mounted between brackets 28 secured to the top of the valve housing 6a such thatthe periphery of the eccentric 24 engages the 110 top end 19 of the push rod 18. If desired, a return spring (notshown) may be coupled to the axle 27 to urge same in one direction of rotation. The axle 27 is drivably connected via the geartrain 25 to the motor 4 and a fixed stop 50 is provided for engagement with a 115 transverse pin 51 mounted on one end of the axle 27 for limiting the rotation of the axle in each direction.

The compartment 23 is seated and a screw socket 52 is provided to permit connection of an external cable to the internal circuitry 5 and motor 4. 120 The compartmentfurther contains a manual over ride device comprising a leaf spring 53 which is fixed at one end and at its opposite end fits freely beneath a push rod 54which is vertically slidable within a bore formed in the compartment structure. The push rod 54 125 is connected at its upper end to a button 55 which is covered by a flexible rubber boot 56. The leaf spring 53 passes overthe eccentric 24 and can be moved downwardly againstthe resilience of the spring, by pushing the button 55through the boot 56, to bear 130 against and effect rotation of the eccentric 24.

The bottom set of passages 10 of the valve is connected to a source of pressurised fluid and the upper and central sets of passages 8, 9 are connected respectivelyto a drain outlet and to a main valve (not shown) to be hydraulically controlled by the pilot valve 3. The valve 3 may be mounted near to the pertaining main valve and the motor 4 and regulating circuitry 5 may be connected remotelyto the control 2 and power supply 1 via IS leads, such remote control and supply being alongside the chock or an adjacent chock or at any other suitable position. The control 2 and/orthe power supply 1 may be common to all pilot valves of a single chock or of multiple chocks as desired. In particularthe control 2 may be connected to or mayform part of a central electronic control system.

Thepowersupplyl maybe of the kind conventionally used with solenoidoperated pilot valves and thus for example maybe of 5V to 12.5V 0.5a rating constructed to meet IS requirements. As indicated in Fig. 1, the regulating circuitry 5 comprises a constant current circuit based on an integrated circuit 29 (e.g. i.c. type 3347) with an external resistor30 (say 6.70) which setsthe value of the current (e.g. 10 ma). The motor 4 is a d.c. motorwhich may be capable of operation over a wide voltage range (say 3V to 30V) with a stalled torque which is dependent on the current and independent of the applied voltage within the operating range.

The arrangement may be such thatthe valve 3 is held in the "on" position when the motor 4 is powered. That is, the motor 4 drives the eccentric 24 (against any return spring) via the gearbox 25 to one limit position at which the push rod 18 is moved down to the lowermost position of its travel and the eccentric 24 is short of its dead centre position, such thatthe top seat 13 is closed and the bottom seat 14 is open therebyto permit flow of hydraulicfluid in through passage 10 and outthrough passage 9, and the motor 4 stalls in this position. Having regard to the nature of the motor 4 and the affect of the constant current circuit it is possibleto hold the motor in the stalled position for any required period oftime without damageto the motor or any overheating or other problem likelyto constitute a safety risk. When power is disconnected from the motor 4the push rod 18 rises to its uppermost position and the eccentric rotates backthrough slightly less than 180'to its other limit position atwhich the bottom seat 14 is sealed and the top seat 13 is open thereby permitting flow of fluid from the passage 9 to the passage 8. The push rod 18 is lifted by the fluid pressure, and rotation of the eccentric 24 is facilitated bythe action of the return spring, where fitted, (especially in low pressure applications) and also by the lowfriction contact between the eccentric 24 and the tip 19 of the push rod 18.

It is feasible to operate a numberof valves 3 simultaneously from the same powersupply l having regard to the relatively low power requirements of the motors 4, and such operation can be achieved effectively and at an acceptable speed. The actual power requirement of the motors and the speed of operation will depend upon various parameters such p i 3 GB 2 121 516 A 3 asthe operating characteristics of the motonthe valve aperture size, the ratio of the gears and (in the case of motorspeed only)the magnitude of the supply voltage. With a valve of 0.04"(0.1cm) orifice diameter, a miniature d.c. motortype Portescap 22 Cl 1-205 with gearbox B24of ratio 20:1 or32A, a hydraulic pressure of 400 bar, and a force multiplication atthe operating point duetothe action of the eccentric of 1.75:1 it is possibleto achieve a satisfactory valve opening and sealing force (of say 7.27 Ibs = 3.3kg) with a current of 1 Orna, and it is possible to achieve an acceptable operational speed (of the order of 0. 3 secs depending on the gearbox ratio) at a supplyvoltage of 1 OV. With regard to the force multiplication achieved with the eccentric, the eccentric gives a sinusoidal force distribution preferablywith maximum thrust positions coinciding with the limit positions of the push rod 18.

With the arrangementso fardescribed, duetothe low power requirements and constant current operating conditions, the use of remote electronic switching controls is pa rticu la rly facilitated. Moreover, due to theconstant current conditions, it is possible to determinethe number of valvesoperating at anytime by monitoring overall currentflow.

Valves of 0.04"(0.1 cm) orifice diameter are conventionally used as pilot valves but may be disadvantageous having regard to the close manufacturing tolerances and the limitations imposed on flow rate.

Larger orifice valves are also known buttheir use can raise problems with conventional solenoid-based systems dueto the relatively high power requirement. The control system described above advantageously renders feasiblethe use of largervalves in so far as the increased power requirement arising from a larger orifice is compensated by the reduced power requirement of the motor actuatorforthe valve. ThusJor example, it is possibleto use an orifice diameter as large as say 0.12Y (0.32cm) with an operating current of say 580ma although this might necessitate the use (alternatively to the above-described arrangement) of a storage battery alongside the motor, such battery being continuously trickle-cha rged from the IS supply and being switched in and out of circuit across the motor by logic pulses generated remotely and applied 110 to electronic switching circuitry adjacent and connected to the battery and the motor. With this trickle charge arrangement it maybe possible to power up to several hundred valves from the same power supply.

It may even be possibleto use valves of orifice diameter large enough for controlling fluid flow directlyto a ram in some circumstances.

Itis of course to be understood thatthe invention is not intended to be restricted to the details of the above embodimentwhich are described by way of example only.

Reference is made to ou r co-pending Application of even date also claiming priority from Applications Nos. 8210684 and 8210685 and which includes fu rther

Claims

description of control systems incorporating control valves as described above. CLAIMS

1. A fluid flow control valve having a first port, a second port, a valve closure member displaceable fluid flow between said ports, a valve operating mechanism comprising a rotatable eccentric, and a drive-transmitting device between the eccentric and the valve closure member arranged to effect displace- ment of said member in response to rotation of said eccentric.

2. A valve according to claim 1, wherein said valve member comprises a sealing element displaceable axially into and out of sealing engagement with an associated valve seat.

3. A valve according to claim 2, wherein said drive-transmitting device comprises a longitudinally movable push rod arranged to act on said sealing element through and axially of said valve seat.

4. A valve according to claim 2 or 3, wherein there are two said sealing elements axially displaceable into and out of sealing engagement with respective axially spaced said valve seats, said drive-transmitting device being arranged to act on one said element and there being a linking device between the elements to transmit said action from said one elementto the otherelement.

5. A valve according to claim 4, wherein said linking device comprises an axially movable rod.

6. Avalve according to claim 4 or5, wherein one said valve seat is arranged between said first and second ports and the other said valve seat is disposed between said second and third ports.

Printed for Her Majesty's Stationery Office byThe Tweeddale Press Ltd., BervAck-upon-Tweed, 1983. Publishedatthe PatentOffice, 25Southampton Buildings, London WC2A lAY, from which copies may be obtained.

GB 2 121 516 A 4 of i i2 A 1 j 1

6. Avalve according to claim 4or 5, having a third port and wherein one said valve seat is arranged between said first and second ports and the other said valve seat is disposed between said second and third ports.

7. A valve according to claim 6, wherein said sealing elements and linking device are arranged such that one said valve seat is open when the othervalve seat is closed and viceversa.

8. Avalve according to anyone of claims 2to 7, wherein the or each said valve element comprises a ball.

9. Avalve according to anyone of claims 1 to 8, wherein said drive mechanism further comprises a stop arranged to limitthe permitted maximum angle of rotation of the eccentric.

10. Avalve according to anyone of claims 1 to 9, wherein said drive mechanism further comprises an electric motor drivably connected to said eccentric.

11. A valve according to claim 10, wherein said drive mechanism further comprises a gear train between said motor and said eccentric.

12. Avalve according to claim 10 or 11, wherein said drive mechanism further includes a manual override for rotating said eccentric.

13. A valve according to claim 12, wherein said manual override comprises a leaf spring which can be pressed down onto said eccentric.

14. Avalve according to anyone of claims 1 to 13, including a compartment in which said drive mechan- ism is enclosed.

15. A valve according to claim 14, when dependent on claim 10, wherein said housing further contains an electrical control circuitfor said motor.

16. A valve according to claim 2 or any claim dependent thereon, wherein the said ports, and the or each said sealing element and associated valve seat are provided as an encapsulated cylindrical valve structure within a solid cylindrical valve body within a valve housing, there being passages extending between different operative positions for controlling 130- th rough said housing and valve body for commu nica- 4 is tion with said ports and there being a channel through said valve body and said valve structure for said drive-transmitting device.

17. A valve according to claim 16, when dependent on claim 14, wherein said compartment is attached to said 18. A valve substantially as herein before described with reference to and as illustrated in the accompanying drawings.

New claims or amendments to claims filed on 12 August 1983.

Superseded claims 1 and 6.

New or amended claims:- 1. Afluid flow control valve having a first port, a second port, a third port, a valve closure member displaceable between different operative positions for controlling fluid flow between said ports, a valve operating mechanism comprising a rotatable eccentric, and a drive- transmitting device between the eccentric and the valve closure member arranged to effect displacement of said member in response to rotation of said eccentric.