Two-stage Opening Valve

Abstract

A two-stage opening globe valve including the main valve member with a chamber therein receiving the valve stem to permit limited relative axial movement between them. Coaxial and lateral primer ducts connect the chamber to the upstream and downstream flow passages, and on the end of the stem is a primer valve that opens and closes the coaxial duct. When the stem is moved to open the valve it opens the primer valve first while an imbalance in opposing areas of the main valve closure which are exposed to upstream pressure produces a force differential biasing the valve toward closed position.

Description

BACKGROUND OF THE INVENTION

This invention relates to a two-stage opening valve and more particularly to a valve in which full capacity flow is normally delayed until upstream and downstream pressures are substantially equalized through a primer duct.

When a valve is opened to high-pressure differentials, the resultant sudden surge of high-velocity flow can cause severe erosion damage to the valve and may score or blow out a resilient seal ring. Moreover, when air or some other gas containing oxygen is being transmitted, the sudden rapid compression of the gas in the downstream line when the valve is opened may cause the gas to reach a dangerously high temperature level before heat can be dissipated. In the event a combustible is in the line or in the seal material, the sudden heat rise may cause a fire, or even an explosion.

Certain fluid systems have been designed to overcome this problem by providing a low capacity bypass line with a small valve which may be opened first to allow a low capacity flow around the main valve which causes downstream pressure to build up gradually. Then when upstream and downstream pressures are nearly equal, the main valve may be opened for full flow. However, such systems suffer the infirmities of the human factor, in that they are dependent upon the operator remembering the sequence of operation. Under certain hazardous circumstances, a single neglectful operation could produce devastating results.

OBJECTS OF THE INVENTION

It is, therefore, an object of this invention to provide a two-stage opening valve wherein the main valve remains closed if desired until throttled flow through a primer valve equalizes pressure.

It is a further object of this invention to provide a two-stage opening valve wherein opening of the main valve is resisted until a primer valve has equalized pressure.

It is a further object of this invention to provide a two-stage opening valve wherein the main valve is biased closed until a primer valve equalizes pressure.

It is a further object of this invention to provide a two-stage operating valve wherein a primer valve operates to equalize pressure before operation of the main valve regardless of the direction of pressure differential.

Other objects and advantages of this invention will become apparent from the detailed description to follow.

BRIEF SUMMARY OF THE INVENTION

In carrying out this invention, I provide a cylindrical globe valve member in a complementary bore. There is a chamber in the valve plug into which the valve operating stem extends with a limited amount of relative axial movement permitted between the stem and the valve member. A primer valve on the end of the stem uncovers a coaxial primer duct, connecting the chamber to a flow passage during initial operation of the valve stem. A second primer duct connects the chamber with the other flow passage so that fluid from the upstream passage flows at throttled rate to the downstream. In one embodiment of the invention, the bore in the main valve through which the stem extends is much larger than the coaxial outlet primer duct so that with a seal around the stem there is a greater area on the outlet side of the chamber exposed to upstream pressure, whereby the resultant force urges the valve closure toward its seat. Hence, the main valve is biased closed as the primer valve is opened by initial movement of the valve stem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of a valve embodying features of this invention mounted in a housing; and

FIGS. 2, 3 and 4 are partial section views showing other embodiments of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Embodiment of FIG. 1

Referring now more particularly to FIG. 1, the valve 10 of this invention is shown on a housing block 12 which is bored to provide inlet and outlet flow passage 14 and 16. A subassembly sleeve 18 forming part of the valve is received in a bore 20 in the housing block 12 with an O-ring 22 sealing around the upper portion thereof to prevent leakage.

A pin 24 locates the sleeve 18 with respect to the body block 26 and a second pin 28 locates the body block 26 with respect to the housing block 12 to insure alignment of the inlet port 30 with the upstream flow passage 14. When so retained, the body block is secured in place, as by means of capscrews 32.

Threadedly received in an upright cylindrical extension 33 of the body block 26 is stem screw 34 to which is fixed as by means of a setscrew 36 engaging a flat portion thereon is a handwheel 40 rotatably received on the upstanding cylinder portion 33. Formed on the lower end of the stem screw 34 is a receptacle 42 which receives the head portion 44 of a valve stem 46. A bearing member 48 having low friction characteristics is interposed between the receptacle 42 and the head 44 of the valve stem to minimize transmission of rotation from the threaded stem. A snapring 50 may be provided to retain the head 44 of the lower stem 46 in the receptacle 42. The lower stem 46 is slidably received in a bearing member 52 with an O-ring 54 sealing around it. The O-ring may be retained as by means of a low friction bearing ring 56 and a snapring 58, with an O-ring 60 being provided to seal around the bearing member 52.

Carried on a shoulder 62 formed at the lower end of a counterbore 64 is a seat ring retainer 66 of fairly rigid material substantially enclosing a seat ring of suitable plastic material, to prevent extrusion of the seat ring material into the flow line 16. An O-ring 70 is provided to insure against leakage around the seat ring 68. An annular lip 72 around the lower end of the main valve plug 74 seals against the seat ring 68 when the main valve is in its closed position as shown in FIG. 1.

Secured to the lower end of the valve stem 46 is an enlarged head 76 forming the primer plug, with an O-ring 78 sealing a trailing portion thereof 80 within a slide-bearing member 82 that is threaded into the main valve plug 74. A coil spring 84 may be provided to bias the main valve plug 74 away from the primer valve 76 and into its closed position, and a shoulder 86 will transmit upward movement of the primer valve 76 to the main valve plug 74 after limited relative movement of the primer valve away from its seat 88. A ring 89 of Teflon or the like, backed up by an O-ring 90 seals around the main valve plug 74.

The primer valve 76 when in the closed position shown in FIG. 1 engages the pilot valve seat to shut off an outlet primer duct 91 opening into the downstream flow passage. A second primer duct 92 brings the chamber 94 in communication with the upstream flow passage 14. The upstream pressure within the chamber 94 acts on the bottom surface thereof over the full area, i.e., the area of a circle of the bore diameter less the area of the primer duct 91. That same pressure acts against the top of the chamber only to the extent permitted by the O-ring seal 78 around the trailing portion 88 of the primer plug 76, i.e., the area of the annular lower end of the slide bearing 82. Hence, There is a substantially greater area which is exposed to upstream pressure in a direction forcing the main valve plug 74 toward the seat ring 68, and there is considerable resistance to opening the main valve.

In operation, the handwheel 40 is turned just enough to lift the primer valve 76 from its seat 88 with the shoulder 86 out of engagement with the slide bearing 82. The upstream pressure in the chamber 94 will hold the main valve plug 74 against its seat 68 as the upstream pressure passing through the restricted primer valve passage 91 builds up pressure in the downstream line 16. Then, when the upstream and downstream pressures are substantially balanced, the operator may again turn the handwheel 40 to lift the stem 46 whereby the shoulder 86 on the primer valve 76 will engage and open the main valve plug 76 for full capacity upstream flow. A bypass passage 96 through the main valve plug 74 maintains the cavity 98 above the main valve 74 at the level of the downstream pressure in order to prevent a high-pressure drop across the main valve which would generate high forces against the valve stem 46, and to prevent the entrapment and build up of pressure as the valve is opened.

The Embodiment of FIG. 2

Referring now to FIG. 2, the primer valve 100 may be provided with a bypass passageway 102 which permits venting of the cavity 98 by flowing through the threads 104 around the stem 46. In this case, the primer valve 100 is preferably provided with a nose 106 extending into the primer duct 108 so that a low-pressure area will not be created in front of the primer valve 100 as a result of the vacuum caused by high velocity flow past the bypass duct 102.

The Embodiment of FIG. 3

Referring now to the embodiment of FIG. 3, the main valve plug 110 is biased toward the seat 68 regardless of the direction of pressure differential. For this purpose, the subassembly 112 is provided with a counterbore 114 and the main valve plug has a reduced diameter trailing portion 116, forming a stepped configuration. Between opposed shoulder 118 and 120 on the subassembly sleeve 112 and on the main valve plug 110 is an O-ring 122 sealing between the concentric cylindrical surfaces 114 and 116. The sealing lip 124 on the main valve plug is of a sealing diameter intermediate that of the two cylindrical surfaces 114 and 116.

Assuming that passage on the left is the upstream passage, pressure acts around the main valve plug 110 to force the O-ring 122 up toward the shoulder 118 on the subassembly and asserts a downward force against the valve plug shoulder 120 over its full annular area. On the bottom of the plug it asserts an upward force, but does not act inward beyond the seal diameter, somewhere on the face of the seal lip 124 which is of a diameter greater than that of the smaller cylindrical surface 116. Within the chamber, the area of the bottom surface thereof 119 is greater than that of the top 121, so that, again, there is a difference in force. Therefore, with the upstream pressure coming from the left passage 14 the net force will tend to bias the main valve plug 110 against the seat 68.

If the lower passage is made the upstream passageway, pressure forces asserted through the bypass duct 125 and back around the valve plug, act downward to force the O-ring 122 and the primer valve tail O-ring 126 down in their recesses so that the pressure acts over an annular area between the inner O-ring recess, i.e., the diameter of the primer valve engaged by the O-ring 126 and the diameter of the larger bore 114. On the bottom of the valve, the pressure acts upward over the annular area between the primer port 91 and the main seal circular lip. Hence, downward force is unopposed between the bore diameter 114 and the main seal 124 while upward force is unopposed between the inner diameter of primer valve O-ring 126 and the primer port diameter. Hence, the diameters are established so that the first annular area described is the greater. This can be done without difficulty because the larger diameters produce greater differences in area per unit of diameter variance.

In either instance, without regard to the direction of pressure differential, the net force biases the plug 110 in its closed position until line pressure has been substantially equalized following opening of the pilot valve. Thereafter, the operator may continue rotation of the handwheel to open the main valve 110.

The Embodiment of FIG. 4

Referring now to FIG. 4, the main valve plug 130 is biased against its seat by means of a powerful spring 132. In this instance operation of the valve stem 46 is not opposed until the shoulder 134 on the primer valve 136 engages against the bearing member 138. Thereafter, operation will be more difficult, and the resistance to operation will serve as a signal to the operator to postpone operation until pressure has had an opportunity to equalize.

While this invention has been described in conjunction with preferred embodiments thereof, it is obvious that modifications and changes may be made by those skilled in the art without departing from the spirit and scope of this invention.

Claims

What is claimed is:

1. In a valve construction comprising:

a valve body,

inlet and outlet flow passages in said valve body,

a valve seat surface around one of said flow passages,

a valve closure movable axially into sealing engagement with said seat surface, and

a stem movable axially for operating said valve closure,

the improvement comprising:

a closed fluid chamber in said valve closure,

a coaxial primer port in said valve closure connecting said chamber with said one flow passage,

a second port connecting said chamber with the other flow passage,

a primer valve member on said stem and received in said chamber for limited axial movement relative to said valve closure to close and open said coaxial port,

a coaxial bore in said valve closure opening to said chamber,

said stem being slidably received in said coaxial bore, and

means sealing said bore around said stem,

said bore being opposite to and larger than said coaxial primer port whereby there is a larger area within said chamber exposed to pressure therein in a direction toward said port.

2. The valve construction defined by claim 1 including:

a bore in said valve body receiving said valve closure,

said other flow passage opening into said bore at one end thereof adjacent said valve seat,

means sealing around said stem at the other end of said bore,

means sealing around said valve closure intermediate said other flow passage and said other end, and

a balancing duct connecting said other end of the bore and said one flow passage.

3. The valve construction defined by claim 2 including:

a larger counterbore at said one end of the bore,

said valve closure being of complementary, stepped cylindrical configuration slidably received in said bore and counterbore,

said bore and valve closure presenting opposing radial shoulders, and

a seal ring received in said space to seal between the small diameter portion of said cylindrical closure and the wall of the large counterbore.

4. The valve construction defined by claim 3 wherein:

said valve closure seals against said valve seat on a diameter intermediate that of said small diameter portion and said counterbore.

5. The valve construction defined by claim 2 including:

a radial shoulder and stepped cylindrical surfaces on said valve closure,

complementary stepped cylindrical stationary surfaces forming with the valve closure an annular chamber between concentric cylindrical surfaces,

a seal ring sealing between said concentric surfaces,

the diameters of said concentric surfaces being selected relative to the sealing diameter of the valve closure sealing engagement with said seat surface that the net area acted on by fluid biasing said valve closure toward said seat surface is greater than the net area acted on in a direction biasing the valve closure away from said seat surface irrespective of the direction of pressure differential.