CA1191501A - Control valve - Google Patents
Control valveInfo
- Publication number
- CA1191501A CA1191501A CA000443372A CA443372A CA1191501A CA 1191501 A CA1191501 A CA 1191501A CA 000443372 A CA000443372 A CA 000443372A CA 443372 A CA443372 A CA 443372A CA 1191501 A CA1191501 A CA 1191501A
- Authority
- CA
- Canada
- Prior art keywords
- valve
- opening
- valve stem
- interior
- thread
- 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.)
- Expired
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
- F16K41/00—Spindle sealings
- F16K41/10—Spindle sealings with diaphragm, e.g. shaped as bellows or tube
-
- 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
- F16K31/44—Mechanical actuating means
- F16K31/50—Mechanical actuating means with screw-spindle or internally threaded actuating means
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Details Of Valves (AREA)
- Lift Valve (AREA)
Abstract
ABSTRACT
A control valve is disclosed for precisely controlling the flow of a liquid in a pipe using a housing having liquid inlet and outlet openings and a side opening, with a wall structure across the housing having an opening for passage of liquid from the inlet opening to the outlet opening.
A valve closure mechanism is positioned in relation to the opening for controlling flow through the opening, with a flange positioned over the side opening and having a portion extending into the interior of the housing towards the valve closure mechanism, said flange and its extended portion having a circular cross-section opening therethrough, said opening having an interior predetermined pitch thread over a lower portion of its length. There is also provided a primary valve stem rotatably mounted in the circular cross-section opening and having an exter-ior thread adapted to co-act with said interior thread, said valve stem having a concentric circular opening in its lower portion containing an interior pre-determined pitch thread and having an upper portion adapted to be connected to a valve drive system, a secondary valve stem rotatably mounted in the concentric circular opening and having an exterior thread over its upper end adapted to co act with the interior thread in the circular opening in the primary valve stem and having a lower section connected to the valve closure mechanism, and a cylindrical metal bellows position-ed over the primary and secondary valve stems and sealably connect-ed at its upper end to the said flange and at its lower end to the lower end of the secondary valve stem such as to isolate liquid flow in the interior of the valve from the valve stems, said bellows being of a length to allow movement of the primary valve stem from a fully valve closed position to a fully open position.
A control valve is disclosed for precisely controlling the flow of a liquid in a pipe using a housing having liquid inlet and outlet openings and a side opening, with a wall structure across the housing having an opening for passage of liquid from the inlet opening to the outlet opening.
A valve closure mechanism is positioned in relation to the opening for controlling flow through the opening, with a flange positioned over the side opening and having a portion extending into the interior of the housing towards the valve closure mechanism, said flange and its extended portion having a circular cross-section opening therethrough, said opening having an interior predetermined pitch thread over a lower portion of its length. There is also provided a primary valve stem rotatably mounted in the circular cross-section opening and having an exter-ior thread adapted to co-act with said interior thread, said valve stem having a concentric circular opening in its lower portion containing an interior pre-determined pitch thread and having an upper portion adapted to be connected to a valve drive system, a secondary valve stem rotatably mounted in the concentric circular opening and having an exterior thread over its upper end adapted to co act with the interior thread in the circular opening in the primary valve stem and having a lower section connected to the valve closure mechanism, and a cylindrical metal bellows position-ed over the primary and secondary valve stems and sealably connect-ed at its upper end to the said flange and at its lower end to the lower end of the secondary valve stem such as to isolate liquid flow in the interior of the valve from the valve stems, said bellows being of a length to allow movement of the primary valve stem from a fully valve closed position to a fully open position.
Description
:a ~.''3~
This invelltion relates to a control valve and more particular~
ly to a valve operable by a micro-adjustable actuator.
In fluid systems there is a need for accurate and reliable valves to control flow and balance system loads. This need exists in all types of systems for low pressure and flow, domestic, general, commercial, industrial and high pressure systems more particularly in industrial chemical and nuclear applicakions.
In the present state of the art, electro~mechanical, hydraul-ic or pneumatic actuators are cumbersome~ frequently unreliable over the comple~e open~to closed range, and fail to provide a repeatably accurate positioning of the plug and rapid response to calls for flow variations.
Presently available 10w control valves have packed stems which require a build-up of force (normally provided by solenoid, or pneumatic actuators) in order to overcome packing friction on the valve stem which leads to sluggish response and jerking motion of the valve plug~ In the case of solenoid or pneumatic operators~
the plug is snapped closed by fluid flow when the actuator brings the plug toward the closed position.
In the case of large control valves in hiyh pressure applica-tions, the large material mass of a valve bonnet and actuator off-set in many cases several feet from the center line of the pipe is of grave concern to the design engineer who must provide for suitable hangers and snubbers to stabilize the non-symmetric mass in the event of severe earthquake activity. This concern i5 doubly important in the design of chemical and nuclear stations.
Bellows sealed control valves are not widely used because of the necessity to provide bonnet containment of a very long bellows to provide reasonable life expectancy in view of the frequent motion of a control valve stem.
A control valve design which provides for rapid response and a plug actuator capable of a smooth, even motion is not presently availabl~.
It is an object of the present invention to provide a control valve in which the position of the plug is micrometer controlled throughout the whole of its axial stroke, i.e. it canno-t snap closed even when pressure builds behind it while it is only - allowing a trickle flow.
It is a further object of the invention to provide 3:~5~
a control valve that is leak-proo:~ to the exterior over its complete operating range. It is a fur-ther object oE -the invention to provide a valve containing mechanism built into the valve stem.
It is a further object of the invention to provide a valve having a high ratio jacking capability which can overcome back pressure on a large diameter plug when opening the valve f.rom a fully closed position.
It is a further object of the invention to provide a control valve that requires only a relatively short bonnet and small actuatorO
These and other objects of the invention are achieved by a control valve for precisely controlling the flow of a liquid in a pipe comprising:
~a) a housing having liquid inlet and outlet openings and a side opening, (b) a wall structure across the housing having an opening for passage of li~uid from the inle~ opening to the outlet opening, ~c) a valve closure mechanism positioned in relation to the opening for controlling flow through the opening~
(d) a flange positioned over the side opening and having a portion extending into the interior of the housing towards the valve closure mechanism, said flange and its extended portion having a circular cross-section opening therethrough, said opening having an interior pre-determined pitch thread over a lower portion of its lengthr (e) a primary valve stem rotatably mounted in the circular cross section opening and having an exterior thread adap-ted to co-ac-t with said interior thread~ said valve stem having a concentric .30 circular opening in its lower portion containing an intexior pre-determined pitch thread and having an upper portion adapted to be connected to a valve drive sys~em, ~f) a secondary valve stem rotatably mounted in -the concentric circular opening and having an exterior thread over its upper end :35 adapted to co-act with the interior thread in the circular opening in the primary valve stem and having a lower section connected to the valve closure mechanism, (g) a cylindrical metal bellows positioned over -the primary and secondary valve stems and sealably connected at its upper end ~10 to the said flange and at its lower end to the lower end of the secondary valve stem such as to isolate liqui~ flow in t~e interior of the valve from the valve s-tems, said bello~s being of a length to allow movement of the secondary valve s-~em from a fully valve closed position to a fully open position.
(h) said pre-determined pi-tch threads on the valve stems being chosen such as to give an increased mechanical advantage, micrometer movement to the secondary valve stem on rotation of the primary valve stem.
In drawings which illustrate embodiments of the invention, Figure 1 is a cross-section of a double plug version of the control valve, Figure 2 is an end view of the valve of Figure 1, Figure 3 is a cross-section of a single plug verslon of a fully designed control valve, Figure 4 is a cross-section of the valve used as a flow mixer, and Figures 5 and 6 are cross-sections of a gate valve version of the device. Referring to the drawings, Figure 1 shows a valve housing 1 in which a double plug 2 has a square or suitably splined or keyed section 3 which pilots the seating rings of the plug and also prevents torque being applied to a metal bellows 4 which is welded to the upper face of the plug a~ one end and to the sleeve housing flange 6 a~ the other.
When the flange 6 is clamped to the valve housing 1 and sealed with a suitable gasket the fluid containment envelope is complete.
A primary valve stem 5 has an internal for example, 16 threads per inch hole into which is screwed a secondary valve stem 5A
which is connected to the double plug or poppet 2.
The lower part of the outside diameter of the primary valve stem 5 is threaded with, for example, 12 threads per inch and is screwed into a threaded inwardly ex~ended portion of flange 6. In actual construction these parts would be pre-~s~mhled before the bellows is welded to the plug and after it is welded to the flange.
In operation it can be seen that when the flange 6 is fixed to the valve hou~ing 1 and plug 2 is located and prevented from rotating by the spline or other means 3, then rotation of the primary valve stem 5 will produce motion of secondary valve stem 5A and double plugs 2 in either direction equivalent to the difference for example b~tween the two thread pitches, i.e.
12 TPI 0.0833 inches and 16 TPI 0.0625" = 0~0208" per revolution of the valve stem 5.
The micro mechanism is therefore cont.ained inside the bellows ,.;, :1 3 and can be sealed with packing 7 which would also act as the mandatory back-up seal which i9 required in nuclear applications to prevent catastrophic leakage .in the event of bellows failure.
A moisture sensor housed inside the bellows could also be installed to warn of failureO
Also shown in Fig. 1 is a, for example, secondary 50:1 worm reduction unit which also further reduces the size of the actuator motor 10 which could be electrical, mechanical, or pneumat.ic/ and is coupled to the drive shaft with a coupling 9 and housed by bracket attachment 11 to the gear box 8. As shown .in Figure 2 an anti~rotation device 12 operating Qn restraint brackets 12A
attached to the valve body restrains the torque generated through the gear box.
The valve body 1 is more bulbous than a conventional control valve body but is basically symmetrical around the center line of the pipe except for penetration of the actuator and a sma~l penetration of the twin plug pressure balancing line 13 which would be used if desirPd to adjust pressure differentials between valve plug regions.
It is also pointed out that except for very high pressure systems, a single plug control valve is easily operated due to the high jacking capability of the micro mechanism. A version of this type of valve is shown in Figure 3O
In this design the input line 14 and output line 15 are not co-linear but the drive motor and control structure lie parallel to and closely adjacent to the flow linesO This allows a very compact design set up with no need for a long valve actuating mechanism standing off at right angles to the flow lines. As in figure 1, bellows 4 isolates the liquid flow from the micrometer actuating mechanisms giving substantially leak proof operation with stem packing 7 xequired chiefly for con'caining lubricating oils inside the micrometer mechanism. ~econdary valve stem 5A
carries annular valve facing 16 wo.rking into valve seat 16A and also splined or keyed sections 3 into a sui-table opening 17.
This construction provides precision operation of the valve face against the seat but also prevents wear caused by rot.ation of these against each other, and prevents torque being transmitted - to the bellows.
Secondary valve stem 5A is mounted in a screw thread 18 inside primarty valve stem 5 which in turn is mounted in a screw ~5--thread 19 in the inner portion of flange 6. rrhe primary valve s-tem is actuated by a drive motor (not shown) driving worm gear mechanism 20. The outside housing of this mechanism is prevented from rotation by arm 21 bearing on pipe 14.
The bellows used should be of high quality and capable of large numbers of recycling actions~ A suitable bellows would be o the type produced by the method of Canadian Patent No. 1,033~199 issued June 20, 1978 to Atomic Energy of Canada Limited, Ottawa, Canada on an invention by the present applicant.
Figure 4 is similar to Figure 3 but shows a valve h~ving three input or output lines 14,15 and 22O This version can be used as a flow mixer with flow from one line being injected into flow via the other two linesO
Figure 5 and 6 are cross-sections of the invention applied to a gate valve constructionO The valve opera~ing mechanisms are similar to that shown in Figure 3 but with the secondary valve stem 5A connected to a gate valve closure 23. The inlet and output lines are tapered from circular cross-section shown dotted as 24 to flattened oval 25. Thls construction provides for minimal stroke of the valve stem.
In all of the versions of the invention described herein, the micro~adjustable and high jacking load capabllities of the actuator mechanism provide absolute control over the movement of the plug or valve closure mechanism even against high back pressuresO This is not possible with conventional valve actuatorsO
The closure mechanism can therefore be sized to allow for minimal axial stroke of the valve stem which in turn permits the use of a much shorter bellows and therefore smaller valve ~onnet -than is normally required in conventional valvesO
This invelltion relates to a control valve and more particular~
ly to a valve operable by a micro-adjustable actuator.
In fluid systems there is a need for accurate and reliable valves to control flow and balance system loads. This need exists in all types of systems for low pressure and flow, domestic, general, commercial, industrial and high pressure systems more particularly in industrial chemical and nuclear applicakions.
In the present state of the art, electro~mechanical, hydraul-ic or pneumatic actuators are cumbersome~ frequently unreliable over the comple~e open~to closed range, and fail to provide a repeatably accurate positioning of the plug and rapid response to calls for flow variations.
Presently available 10w control valves have packed stems which require a build-up of force (normally provided by solenoid, or pneumatic actuators) in order to overcome packing friction on the valve stem which leads to sluggish response and jerking motion of the valve plug~ In the case of solenoid or pneumatic operators~
the plug is snapped closed by fluid flow when the actuator brings the plug toward the closed position.
In the case of large control valves in hiyh pressure applica-tions, the large material mass of a valve bonnet and actuator off-set in many cases several feet from the center line of the pipe is of grave concern to the design engineer who must provide for suitable hangers and snubbers to stabilize the non-symmetric mass in the event of severe earthquake activity. This concern i5 doubly important in the design of chemical and nuclear stations.
Bellows sealed control valves are not widely used because of the necessity to provide bonnet containment of a very long bellows to provide reasonable life expectancy in view of the frequent motion of a control valve stem.
A control valve design which provides for rapid response and a plug actuator capable of a smooth, even motion is not presently availabl~.
It is an object of the present invention to provide a control valve in which the position of the plug is micrometer controlled throughout the whole of its axial stroke, i.e. it canno-t snap closed even when pressure builds behind it while it is only - allowing a trickle flow.
It is a further object of the invention to provide 3:~5~
a control valve that is leak-proo:~ to the exterior over its complete operating range. It is a fur-ther object oE -the invention to provide a valve containing mechanism built into the valve stem.
It is a further object of the invention to provide a valve having a high ratio jacking capability which can overcome back pressure on a large diameter plug when opening the valve f.rom a fully closed position.
It is a further object of the invention to provide a control valve that requires only a relatively short bonnet and small actuatorO
These and other objects of the invention are achieved by a control valve for precisely controlling the flow of a liquid in a pipe comprising:
~a) a housing having liquid inlet and outlet openings and a side opening, (b) a wall structure across the housing having an opening for passage of li~uid from the inle~ opening to the outlet opening, ~c) a valve closure mechanism positioned in relation to the opening for controlling flow through the opening~
(d) a flange positioned over the side opening and having a portion extending into the interior of the housing towards the valve closure mechanism, said flange and its extended portion having a circular cross-section opening therethrough, said opening having an interior pre-determined pitch thread over a lower portion of its lengthr (e) a primary valve stem rotatably mounted in the circular cross section opening and having an exterior thread adap-ted to co-ac-t with said interior thread~ said valve stem having a concentric .30 circular opening in its lower portion containing an intexior pre-determined pitch thread and having an upper portion adapted to be connected to a valve drive sys~em, ~f) a secondary valve stem rotatably mounted in -the concentric circular opening and having an exterior thread over its upper end :35 adapted to co-act with the interior thread in the circular opening in the primary valve stem and having a lower section connected to the valve closure mechanism, (g) a cylindrical metal bellows positioned over -the primary and secondary valve stems and sealably connected at its upper end ~10 to the said flange and at its lower end to the lower end of the secondary valve stem such as to isolate liqui~ flow in t~e interior of the valve from the valve s-tems, said bello~s being of a length to allow movement of the secondary valve s-~em from a fully valve closed position to a fully open position.
(h) said pre-determined pi-tch threads on the valve stems being chosen such as to give an increased mechanical advantage, micrometer movement to the secondary valve stem on rotation of the primary valve stem.
In drawings which illustrate embodiments of the invention, Figure 1 is a cross-section of a double plug version of the control valve, Figure 2 is an end view of the valve of Figure 1, Figure 3 is a cross-section of a single plug verslon of a fully designed control valve, Figure 4 is a cross-section of the valve used as a flow mixer, and Figures 5 and 6 are cross-sections of a gate valve version of the device. Referring to the drawings, Figure 1 shows a valve housing 1 in which a double plug 2 has a square or suitably splined or keyed section 3 which pilots the seating rings of the plug and also prevents torque being applied to a metal bellows 4 which is welded to the upper face of the plug a~ one end and to the sleeve housing flange 6 a~ the other.
When the flange 6 is clamped to the valve housing 1 and sealed with a suitable gasket the fluid containment envelope is complete.
A primary valve stem 5 has an internal for example, 16 threads per inch hole into which is screwed a secondary valve stem 5A
which is connected to the double plug or poppet 2.
The lower part of the outside diameter of the primary valve stem 5 is threaded with, for example, 12 threads per inch and is screwed into a threaded inwardly ex~ended portion of flange 6. In actual construction these parts would be pre-~s~mhled before the bellows is welded to the plug and after it is welded to the flange.
In operation it can be seen that when the flange 6 is fixed to the valve hou~ing 1 and plug 2 is located and prevented from rotating by the spline or other means 3, then rotation of the primary valve stem 5 will produce motion of secondary valve stem 5A and double plugs 2 in either direction equivalent to the difference for example b~tween the two thread pitches, i.e.
12 TPI 0.0833 inches and 16 TPI 0.0625" = 0~0208" per revolution of the valve stem 5.
The micro mechanism is therefore cont.ained inside the bellows ,.;, :1 3 and can be sealed with packing 7 which would also act as the mandatory back-up seal which i9 required in nuclear applications to prevent catastrophic leakage .in the event of bellows failure.
A moisture sensor housed inside the bellows could also be installed to warn of failureO
Also shown in Fig. 1 is a, for example, secondary 50:1 worm reduction unit which also further reduces the size of the actuator motor 10 which could be electrical, mechanical, or pneumat.ic/ and is coupled to the drive shaft with a coupling 9 and housed by bracket attachment 11 to the gear box 8. As shown .in Figure 2 an anti~rotation device 12 operating Qn restraint brackets 12A
attached to the valve body restrains the torque generated through the gear box.
The valve body 1 is more bulbous than a conventional control valve body but is basically symmetrical around the center line of the pipe except for penetration of the actuator and a sma~l penetration of the twin plug pressure balancing line 13 which would be used if desirPd to adjust pressure differentials between valve plug regions.
It is also pointed out that except for very high pressure systems, a single plug control valve is easily operated due to the high jacking capability of the micro mechanism. A version of this type of valve is shown in Figure 3O
In this design the input line 14 and output line 15 are not co-linear but the drive motor and control structure lie parallel to and closely adjacent to the flow linesO This allows a very compact design set up with no need for a long valve actuating mechanism standing off at right angles to the flow lines. As in figure 1, bellows 4 isolates the liquid flow from the micrometer actuating mechanisms giving substantially leak proof operation with stem packing 7 xequired chiefly for con'caining lubricating oils inside the micrometer mechanism. ~econdary valve stem 5A
carries annular valve facing 16 wo.rking into valve seat 16A and also splined or keyed sections 3 into a sui-table opening 17.
This construction provides precision operation of the valve face against the seat but also prevents wear caused by rot.ation of these against each other, and prevents torque being transmitted - to the bellows.
Secondary valve stem 5A is mounted in a screw thread 18 inside primarty valve stem 5 which in turn is mounted in a screw ~5--thread 19 in the inner portion of flange 6. rrhe primary valve s-tem is actuated by a drive motor (not shown) driving worm gear mechanism 20. The outside housing of this mechanism is prevented from rotation by arm 21 bearing on pipe 14.
The bellows used should be of high quality and capable of large numbers of recycling actions~ A suitable bellows would be o the type produced by the method of Canadian Patent No. 1,033~199 issued June 20, 1978 to Atomic Energy of Canada Limited, Ottawa, Canada on an invention by the present applicant.
Figure 4 is similar to Figure 3 but shows a valve h~ving three input or output lines 14,15 and 22O This version can be used as a flow mixer with flow from one line being injected into flow via the other two linesO
Figure 5 and 6 are cross-sections of the invention applied to a gate valve constructionO The valve opera~ing mechanisms are similar to that shown in Figure 3 but with the secondary valve stem 5A connected to a gate valve closure 23. The inlet and output lines are tapered from circular cross-section shown dotted as 24 to flattened oval 25. Thls construction provides for minimal stroke of the valve stem.
In all of the versions of the invention described herein, the micro~adjustable and high jacking load capabllities of the actuator mechanism provide absolute control over the movement of the plug or valve closure mechanism even against high back pressuresO This is not possible with conventional valve actuatorsO
The closure mechanism can therefore be sized to allow for minimal axial stroke of the valve stem which in turn permits the use of a much shorter bellows and therefore smaller valve ~onnet -than is normally required in conventional valvesO
Claims (5)
1. A control valve for precisely controlling the flow of a liquid in a pipe comprising:
(a) a housing having liquid inlet and outlet openings and a side opening, (b) a wall structure across the housing having an opening for passage of liquid from the inlet opening to the outlet opening, (c) a valve closure mechanism positioned in relation to the opening for controlling flow through the opening, (d) a flange positioned over the side opening and having a portion extending into the interior of the housing towards the valve closure mechanism, said flange and its extended portion having a circular cross-section opening therethrough, said open-ing having an interior pre-determined pitch thread over a lower portion of its length, (e) a primary valve stem rotatably mounted in the circular cross-section opening and having an exterior thread adapted to co-act with said interior thread, said valve stem having a concentric circular opening in its lower portion containing an interior pre-determined pitch thread and having an upper portion adapted to be connected to a valve drive system, (f) a secondary valve stem rotatably mounted in the concentric circular opening and having an exterior thread over its upper end adapted to co-act with the interior thread in the circular opening in the primary valve stem and having a lower section connected to the valve closure mechanism, (g) a cylindrical metal bellows positioned over the primary and secondary valve stems and sealably connected at its upper end to the said flange and at its lower end to the lower end of the secondary valve stem such as to isolate liquid flow in the interior of the valve from the valve stems, said bellows being of a length to allow movement of the primary valve stem from a fully valve closed position to a fully open position, (h) said pre-determined pitch threads on the valve stems being chosen such as to give an increased mechanical advantage, micrometer movement to the secondary valve stem on rotation of the primary valve stem.
(a) a housing having liquid inlet and outlet openings and a side opening, (b) a wall structure across the housing having an opening for passage of liquid from the inlet opening to the outlet opening, (c) a valve closure mechanism positioned in relation to the opening for controlling flow through the opening, (d) a flange positioned over the side opening and having a portion extending into the interior of the housing towards the valve closure mechanism, said flange and its extended portion having a circular cross-section opening therethrough, said open-ing having an interior pre-determined pitch thread over a lower portion of its length, (e) a primary valve stem rotatably mounted in the circular cross-section opening and having an exterior thread adapted to co-act with said interior thread, said valve stem having a concentric circular opening in its lower portion containing an interior pre-determined pitch thread and having an upper portion adapted to be connected to a valve drive system, (f) a secondary valve stem rotatably mounted in the concentric circular opening and having an exterior thread over its upper end adapted to co-act with the interior thread in the circular opening in the primary valve stem and having a lower section connected to the valve closure mechanism, (g) a cylindrical metal bellows positioned over the primary and secondary valve stems and sealably connected at its upper end to the said flange and at its lower end to the lower end of the secondary valve stem such as to isolate liquid flow in the interior of the valve from the valve stems, said bellows being of a length to allow movement of the primary valve stem from a fully valve closed position to a fully open position, (h) said pre-determined pitch threads on the valve stems being chosen such as to give an increased mechanical advantage, micrometer movement to the secondary valve stem on rotation of the primary valve stem.
2. A control valve as in claim 1 wherein the valve closure mechanism is a plug or poppet valve working in relation to a valve seat formed in the wall structure.
3. A control valve as in claim 1 wherein the valve closure mechanism is a gate valve structure.
4. A control valve as in claim 1 further comprising means for preventing rotation of the secondary valve stem in relation to the housing on rotation of the primary valve stem.
5. A control valve as in claim 4 wherein the means for preventing rotation of the secondary valve stem is a shaped or splined extension on the valve closure mechanism working into a similarly shaped close ended opening built into the housing wall.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000443372A CA1191501A (en) | 1983-12-15 | 1983-12-15 | Control valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000443372A CA1191501A (en) | 1983-12-15 | 1983-12-15 | Control valve |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1191501A true CA1191501A (en) | 1985-08-06 |
Family
ID=4126752
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000443372A Expired CA1191501A (en) | 1983-12-15 | 1983-12-15 | Control valve |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1191501A (en) |
-
1983
- 1983-12-15 CA CA000443372A patent/CA1191501A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |