GB2041169A - Pilot-operated valve having varying bleed flow area - Google Patents
Pilot-operated valve having varying bleed flow area Download PDFInfo
- Publication number
- GB2041169A GB2041169A GB7942627A GB7942627A GB2041169A GB 2041169 A GB2041169 A GB 2041169A GB 7942627 A GB7942627 A GB 7942627A GB 7942627 A GB7942627 A GB 7942627A GB 2041169 A GB2041169 A GB 2041169A
- Authority
- GB
- United Kingdom
- Prior art keywords
- valve
- slot
- main valve
- bleed passageway
- chamber
- 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.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/12—Actuating devices; Operating means; Releasing devices actuated by fluid
- F16K31/36—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor
- F16K31/40—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor with electrically-actuated member in the discharge of the motor
- F16K31/406—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor with electrically-actuated member in the discharge of the motor acting on a piston
- F16K31/408—Actuating devices; Operating means; Releasing devices actuated by fluid in which fluid from the circuit is constantly supplied to the fluid motor with electrically-actuated member in the discharge of the motor acting on a piston the discharge being effected through the piston and being blockable by an electrically-actuated member making contact with the piston
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Fluid-Driven Valves (AREA)
Abstract
A valve has a valve body (10) formed with an internal orifice (14) between the valve inlet and outlet ports and a main valve member (42) for opening and closing the orifice (14). A chamber (26) above the valve member (21) is supplied with high pressure fluid through a bleed passageway (58) extending between the chamber (26) and the inlet port. A pilot valve (29) controls exhausting of the chamber (26) when the main valve is to be opened. The bleed passageway has a cross-sectional area which changes progressively along its length such that its flow area is smallest when the main valve is closed and largest when the main valve is open. The bleed passageway may be in the annular surface which guides the movement of the main valve member or in the cylindrical outer surface of the main valve member. The bleed passageway may be tapered either radially or axially with respect to the surface in which it is formed. <IMAGE>
Description
SPECIFICATION
Pilot-operated valve having varying bleed flow area
This invention relates to pilot-operated valves, and more particularly to an improvement in such valves whereby the rate at which they open and close is controlled in a special way.
A pilot op'erated valve includes a main valve member arranged to open or close an internal orifice so as to permit or prevent, respectively, fluid flow from the high pressure inlet port to the low pressure outlet port. A chamber on the side of the valve member opposite the orifice communicates through a bleed passageway with the inlet port. The chamber also communicates through a small pilot valve with a low pressure region, such as the outlet port.
When the pilot valve is closed, high pressure fluid fills the chamber through the bleed passageway, and when the pressure in the chamber rises to a high enough level, it forces the main valve member to close the orifice, thereby closing the main valve. When the pilot valve is opened, the fluid pressure in the chamber is relieved, since the pilot passageway is larger than the bleed passageway, and the main valve member moves to open the orifice.
In conventional valves of the type just described, the rate at which the main valve opens and closes, for any given differential in pressures at opposite ends of the valve, depends upon the ratio of the flow areas of the bleed and pilot passageways. For example, the larger the bleed passageway with respect to a particular pilot passageway, the slower the valve will open and the faster it will close.
The reason is that when the pilot valve is opened, the pressure in the chamber drops relatively slowly since high pressure fluid continues to enter the chamber through the bleed passageway at a relatively high rate. When the pilot valve is closed, high pressure fluid entering the chamber at a high rate quickly raises the pressure in the chamber. On the other hand, the smaller the bleed passageway with respect to a particular pilot passageway, the faster the valve will open and the slower it will close, The reason is that when the pilot valve is opened, the pressure in the chamber drops quickly since high pressure fluid continues to enter the chamber through the bleed passageway at a slow rate. When the pilot valve is closed, high pressure fluid entering the chamber at a slow rate slowly raises the pressure in the chamber, as a result of which the main valve closes slowly.
It is desirable, in most valve applications, for the main valve to open and close quickly in immediate response to opening and closing, respectively, of the pilot valve. However, such rapid movement of the main valve member is accompanied by an abrupt termination of movement in each direction, which is usually a disadvantage. Specifically, when a rapidly closing main valve member slams against the valve seat surrounding the orifice, fluid flow through the valve is stopped so abruptly as to cause a hydraulic shock, commonly referred to as "water hammer". Such a shock far exceeds the normal pressures in the system and consequently can cause damage to the fluid line and other equipment being controlled by the valve.In addition, when a rapidly opening main valve member strikes the abutment which limits any further travel, the parts tend to wear and hence reduce the useful life of the valve.
It is an object of the present invention to provide a pilot-operated valve in which the main valve member begins its opening and closing movements quickly, but slows as it approaches the ends of its opening and closing strokes, so that movement is not terminated abruptly. Consequently, water hammer and excessive wear of the parts is greatly minimized or even eliminated.
It is another object of the invention to provide such a valve wherein the bleed passageway has a cross-sectional area which changes progressively along its length such that its flow area is smallest when the main valve is closed and largest when the main valve is open.
Additional objects and features will be apparent from the following description in which reference is made to the accompanying drawings.
In the drawings:
Figure 1 is a fragmentary cross-sectional view of a pilot-operated valve incorporating the present invention showing both the main and pilot valves closed;
Figure 2 is a view similar to Fig. 1 showing the pilot valve open;
Figure 3 is a view similar to Fig. 1 showing the pilot and main valves open;
Figure 4 is an enlarged fragmentary crosssection view showing a portion of Fig. 1;
Figure 5 is a perspective view of the main valve member and seal which guides its movement, both of which are shown in Figs.
1-3;
Figure 6 is a view similar to Fig. 5 of an alternative embodiment of the invention;
Figure 7 is an elevational view, with a part broken away, of a main valve member and seal showing another alternative embodiment of the invention;
Figure 8 is a cross-sectional view taken along line 8-8 of Fig. 7; and
Figure 9 is a cross-sectional view of a pilot operated valve incorporating still another embodiment of the invention.
The pilot-operated valve shown in Fig. 9 comprises a valve body 10 surmounted by a bonnet 11. Body 10 has an inlet port 1 2 for connection to a source of high pressure fluid, an outlet port 1 3 for connection to a lower pressure region, and an orifice 14 between the ports 1 2 and 1 3 surrounded by an annular main valve seat 1 5. Bonnet 11 is formed with an interior bore accommodating a piston 1 8 slidable vertically within the bore. The lower face of piston 1 8 has a downwardly projecting peripheral lip 1 9 and a central downwardly projecting threaded stud 20.A resilient annular main valve disk 21, having a central hole, is accommodated within the annular recess defined between lip 1 9 and stud 20. Stud 20 passes through the hole in disk 21, and a nut 23 threaded on to stud 20 firmly secures the disk to piston 18. Disk 21 has an external diameter a little larger than the diameter of valve seat 1 5 so that when piston 18 is in its lowermost position, shown in Fig. 9, disk 21 engages seat 1 5 and closes the valve.
The region of the bore in bonnet 11 above piston 18 defines a chamber 26. A pilot passageway 27 extends completely through piston 1 8 from chamber 26 to the orifice 14 and the region beneath valve seat 1 5 opens to outlet port 1 3. An electrical solenoid 28 is mounted on bonnet 11, and surrounds a vertically movable armature 29. When solenoid 28 is deenergized, a compression spring 30 holds armature 29 down, and a pilot valve member carried by the lower end of armature 29 seats upon piston 1 8 to close the upper end of pilot passageway 27.In conventional valves, high pressure fluid constantly seeps between piston 1 8 and the wall of the bore in bonnet 11 from the inlet port 1 2 into chamber 26, so as to fill the chamber with high pressure fluid. Alternatively, a small diameter bleed passageway is often provided in bonnet 11 through which high pressure fluid continuously flows into chamber 26. As a result, a net downward force is applied to the piston which maintains the valve closed. When solenoid 28 is energized, armature 29 is lifted away from piston 1 8 so as to open pilot passageway 27.Since the flow area of seepage around piston 18, or of the bleed passageway, is smaller than the flow area of pilot passageway 27, the high pressure fluid in chamber 26 flows through passageway 27 to outlet port 1 3 faster than high pressure fluid seeps or flows through the bleed passageway into chamber 26, thereby reducing the pressure in chamber 26. As a result, the net force on piston 1 8 is now in an upwardly direction, and piston 18 rises lifting disk 21 away from seat 15, thereby opening the main valve. The valve remains open until solenoid 28 is deenergized, at which point the lower end of armature 29 again closes the upper end of pilot passageway 27.This prevents further flow of fluid from chamber 26 to outlet port 1 3. However, high pressure fluid continues to bleed into chamber 26, and hence fluid pressure builds up in the chamber causing piston 18 to move downwardly until disk 21 engages seat 1 5 and closes the valve.
Part of a valve, similar to that of Fig. 9, incorporating the present invention is shown in Figs. 1-5. An inverted cup-shaped holder 48 , having a top wall 49 and a continuous annular side wall 50, is slideable vertically within an annular guide and seal 51. The guide and seal includes an outwardly projecting flange 52, the outer margin of which is fixed between valve body 10 and bonnet 11, and a lip 53 concentric with valve seat 1 5.
Top wall 49 of holder 48 is formed with a hole 54 in registry with a hole 43 in a resilient disk 42. Holder 48 and disk 42 together constitute the main valve member of the valve. Top wall 49 is deformed into a frusto-conical shape around hole 54 so that the upper edge surrounding the hole defines a seat for cooperation with the pilot valve member carried by the lower end of armature 29.
Thus, aligned holes 54 and 43 correspond to pilot passageway 27 of Fig. 1.
A bleed passageway according to this invention is defined in part by a slot 57 formed in the outer surface of side wall 50 of holder 48. In this illustrative embodiment, slot 57 is of uniform width along its length but is tapered in depth, i.e., in the radial direction of annular side wall 50. The taper is such that the cross-sectional area of slot 57 is progressively larger from its end farthest from valve seat 1 5 to its end closest to the valve seat, i.e., from its upper end to its lower end in
Figs. 1-5. Bleed passageway 58 (see Fig. 4) is the area defined by slot 57 and the opposed inner surface 59 of lip 53 of guide and seal 51.
High pressure fluid flows from the high pressure region surrounding the exterior of valve seat 1 5 through bleed passageway 58 into chamber 26. When the main valve is closed (Figs. 1 and 4) the flow area of the bleed passageway is smallest, since the end of slot 57 having the smallest cross-sectional area is opposite surface 59 of lip 53. As the main valve member rises off valve seat 1 5 to open the valve, the flow area of bleed passageway 58 becomes progressively larger, since larger and larger cross-sectional areas of slot 57 move opposite surface 59. When the main valve member reaches the upper limit of its movement (Fig. 3), bleed passageway 58 having the largest cross-sectional area comes opposite surface 59. The larger the flow area of bleed passageway 58, the higher the rate of flow of high pressure fluid into chamber 26.
Thus, if the valve has been closed long enough to establish equally high pressures in the region surrounding the exterior of valve seat 1 5 and in chamber 26, and the pilot valve is then opened (Fig. 2), the high pressure fluid is chamber 26 immediately starts to flow out of pilot passageway 54, 43. Relatively little high pressure fluid enters chamber 26 through bleed passageway 58 since the flow area of the latter is a minimum. Consequently, the pressure in chamber 26 drops very rapidly and as a result the main valve member starts to rise off seat 1 5 very quickly after opening of the pilot valve. As the main valve member rises, the flow area of bleed passageway 58 increases and high pressure fluid enters chamber 26 at progressively higher rates.This increased flow of high pressure fluid into chamber 26 slows the movement of the main valve member, so that top wall 49 of holder 48 abuts wall 60, as shown in Fig. 3, while moving at a relatively low velocity.
If, when the valve is open (Fig. 3), the pilot valve is closed, i.e., armature 29 moves down so that its lower end engages the frustoconical portion of top wall 49 to close pilot passageway 54-43, high pressure fluid flows into chamber 26 at a relatively high rate, since the flow area of bleed passageway 58 is a maximum. Consequently, the pressure in chamber 26 rises very rapidly and as a result, the main valve member starts to move toward valve seat 1 5 very quickly after closing of the pilot valve. As the main valve member continues to move toward the valve seat, the flow area of bleed passageway 58 decreases and high pressure fluid enters chamber 26 at progressively lower rates.This decreased flow of high pressure fluid into chamber 26 slows the movement of the main valve member, so that disk 42 ultimately engages valve seat 1 5 while moving at a relatively low velocity.
Although only one slot 57 is illustrated in
Figs. 1-5, more than one could be provided at spaced points around the periphery of side wall 50.
In order to provide for more rapid opening of the valve, in response to opening of the pilot valve, and slower movement of the main valve member as it approaches valve seat 1 5 upon closing of valve, a slot 57' as shown in
Fig. 6 may be employed. Whereas slot 57 of
Figs. 1-5 extends for substantially the full height of wall 50, slot 57' of Fig. 6 extends for only a portion of the height of wall 50. As a result, after the pilot valve opens but before the main valve opens, only the high pressure fluid seeps between wall 50 and surface 59 enters chamber 26, and this seepage is at a very low rate, Hence pressure in chamber 26 drops very rapidly. Upon closing of the main valve from an open condition, the main valve member moves very rapidly at first, because pressure in chamber 26 builds up very quickly.However, the rate of pressure rise decreases when the main valve member nears valve seat 15, and hence the main valve member slows before engaging the seat. The length-of slot 57' can be tailored to the particular environment in which the valve will be used to give the precise desired speed of movement of the main valve member throughout its travel. The movement of the valve member can also be controlled by the number of slots 57' employed in each wall 50, and the angle of taper of the slot or slots. Furthermore, if more than one slot is employed, they
may be of different lengths.
In Figs. 1-6, slot 57, 57' is tapered in the
radial direction of wall 50 so that the slot varies in depth along its length. An alternative arrangement is illustrated in Figs. 7 and 8, wherein slot 1 57 is of uniform depth along its length (see Fig. 8) but tapers axially so that the slot varies in width along its length. The result on operation of the valve is exactly the same as described above with respect to slot 57. Here too, more than one slot may be employed, and the slot need not necessarily extend for the entire height of wall 50. Furthermore, it should be mentioned that a slot could be used which tapers in both width and depth.
In Figs. 1-8, slot 57, 57' is formed in the cylindrical outer surface of holder 48, i.e., in the outer surface of the main valve member.
Alternatively, a tapered slot may be formed in the annular surface guiding the movement of the main valve member. For example, as shown in Fig. 9, a slot 63, tapered in depth, is formed in the surface of the bore in bonnet
11 within which piston 18 slides. Slot 63 increases in depth with increased distance from valve seat 1 5. The bleed passage is defined by the slot and the portion of the outer surface of resilient O-ring seal 64, surrounding piston 18, opposite the slot. Hence, the farther piston 18, and hence valve disk 21, moves from valve seat 15, the larger the bleed passageway. Thus, the effect of the varying-flow-area bleed passageway will be exactly as described above with respect to
Figs. 1-5.
Furthermore, as mentioned above with respect to slot 57, 57', slot 63 can be made as long as desired for any particular use, to give the desired speed of movement of piston 1 8.
In addition, more than one slot 63, of the same or different lengths, can be employed.
Also, slot 63 could be tapered in width rather than depth, and the angle of taper varied to meet particular requirements.
The invention has been shown and described in preferred form only, and by way of example and many variations may be made in the invention which will still be comprised within its spirit. It is understood, therefore, that the invention is not limited to any specific form or embodiment except insofar as such limitations are included in the appended
Claims (9)
1. A valve comprising:
(a) a valve body having an inlet port for connection to a high pressure region, an outlet port for connection to a low pressure region, and an orifice between said ports surrounded by a valve seat,
(b) a main valve member movable into and out of engagement with said valve seat to close and open said valve respectively.
(c) a chamber within said valve body on the side of said main valve member opposite the side which faces said valve seat,
(d) a pilot valve for controlling communication between said chamber and a region where the pressure is low as compared to the high pressure at said inlet port, and
(e) a bleed passageway through which said inlet port communicates with said chamber,
CHARACTERIZED BY
said bleed passageway having a varying cross-sectional area which is progressively larger along its length such that the flow area through said bleed passageway is smallest when the main valve is closed and largest when the main valve is open.
2. A valve as defined in Claim 1 including an annular stationary surface for guiding the movement of said main valve member, said main valve member having a cylindrical surface in sliding contact with said stationary surface, and said bleed passageway comprises a slot formed in one of said surfaces.
3. A valve as defined in Claim 2 wherein said bleed slot is tapered from a maximum width at one end to a minimum width at its other end.
4. A valve as defined in Claim 2 wherein said bleed passageway slot is tapered radially with respect to the surface in which it is formed.
5. A valve as defined in Claim 2 wherein said bleed passageway slot is tapered axially with respect to the surface in which it is formed.
6. A valve as defined in Claim 1 wherein said main valve member is an inverted cupshaped member containing a resilient valve disk, and including an annular lip seal surrrounding said cup-shaped member for guiding the movement of the latter, said bleed passageway comprising a slot in the surface of said cup-shaped member facing said lip seal.
7. A valve as defined in Claim 6 wherein said bleed passageway slot is tapered from one on its ends to the other, the end closest to said valve seat being the largest.
8. A valve as defined in Claim 1 wherein said valve body has a bore within which said main valve member is slidable, said bleed passageway comprising a slot in the wall of said bore.
9. A valve as defined in Claim 8 wherein said bleed passageway slot is tapered from one end to the other, the slot being largest at its end most remote from said valve seat.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US774979A | 1979-01-30 | 1979-01-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2041169A true GB2041169A (en) | 1980-09-03 |
Family
ID=21727933
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7942627A Withdrawn GB2041169A (en) | 1979-01-30 | 1979-12-11 | Pilot-operated valve having varying bleed flow area |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE3003057A1 (en) |
| FR (1) | FR2450984A1 (en) |
| GB (1) | GB2041169A (en) |
| NL (1) | NL8000432A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2150712A (en) * | 1983-12-02 | 1985-07-03 | Glyco Antriebstechnik Gmbh | Controllable 2-way valve for regulating the pressure and flow of a flow of liquid |
| EP0211672A1 (en) * | 1985-08-10 | 1987-02-25 | Sanden Corporation | Scroll type compressor with variable displacement mechanism |
| EP0837275A1 (en) * | 1996-10-15 | 1998-04-22 | HEILMEIER & WEINLEIN Fabrik für Oel-Hydraulik GmbH & Co. KG | Solenoid actuated relief valve for electro-hydraulic lifting devices |
| WO2004104463A1 (en) * | 2003-05-26 | 2004-12-02 | Danfoss A/S | A servo valve for a vacuum system |
-
1979
- 1979-12-11 GB GB7942627A patent/GB2041169A/en not_active Withdrawn
-
1980
- 1980-01-23 NL NL8000432A patent/NL8000432A/en not_active Application Discontinuation
- 1980-01-28 FR FR8001731A patent/FR2450984A1/en not_active Withdrawn
- 1980-01-29 DE DE19803003057 patent/DE3003057A1/en not_active Withdrawn
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2150712A (en) * | 1983-12-02 | 1985-07-03 | Glyco Antriebstechnik Gmbh | Controllable 2-way valve for regulating the pressure and flow of a flow of liquid |
| EP0211672A1 (en) * | 1985-08-10 | 1987-02-25 | Sanden Corporation | Scroll type compressor with variable displacement mechanism |
| EP0837275A1 (en) * | 1996-10-15 | 1998-04-22 | HEILMEIER & WEINLEIN Fabrik für Oel-Hydraulik GmbH & Co. KG | Solenoid actuated relief valve for electro-hydraulic lifting devices |
| US6017015A (en) * | 1996-10-15 | 2000-01-25 | Heilmeier & Weinlein Fabrik Fur Oel-Hydraulik Gmbh & Co. Kg | Magnetically operated drain valve of an electrohydraulic lifting module |
| WO2004104463A1 (en) * | 2003-05-26 | 2004-12-02 | Danfoss A/S | A servo valve for a vacuum system |
| US7762520B2 (en) | 2003-05-26 | 2010-07-27 | Danfoss A/S | Servo valve for a vacuum system |
Also Published As
| Publication number | Publication date |
|---|---|
| NL8000432A (en) | 1980-08-01 |
| FR2450984A1 (en) | 1980-10-03 |
| DE3003057A1 (en) | 1980-07-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |