GB2136870A

GB2136870A - Pressurised spherical interfaces

Info

Publication number: GB2136870A
Application number: GB08400424A
Authority: GB
Inventors: Ernest James Burles
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-01-10
Filing date: 1984-01-09
Publication date: 1984-09-26
Also published as: GB8400424D0; GB2136870B

Abstract

A flexible joint has two rotatable shafts 10,12 with a central passage 15, 17 through which fluid under pressure can pass. Flexibility while rotating is provided by a spherical cup end 42 on the shaft 12 engaging sealingly in a mating cavity 40 at the end of the shaft 10. A duct 64 connects the high pressure fluid in the central passage with a recess 66 at a spherical interface between cup 42 and cavity 40 so as to counteract the force applied to the joint by the high pressure fluid in the central passage. A ball valve can be constructed on the same principle (Figs. 2 and 3 not shown). <IMAGE>

Description

SPECBFICATION Pressurised spherical interfaces This invention relates to the design of spherical interfaces, such as in flexible joints and ball valves, in which a fluid under pressure acts upon the spherical interface.

The fluid under pressure can apply considerable force to the interface, with the result that appreciable wear occurs between the relatively moving parts. Also, the force can reduce the effectiveness of any seal between the parts if it tends to force them apart, or it can make movement between the parts more difficult if it tends to force the parts together.

According to the present invention there is provided an assembly comprising two relatively movable components having mating surfaces providing a first spherical interface at which movement occurs and which is exposed to a passage between the two components, which passage can contain fluid under pressure; a duct within one of the components communicating at one end with said passage and at the other end with a second spherical interface between the two components, concentric with and opposed to the first interface, whereby high pressure fluid from the passage extending through the duct applies pressure to said second interface so as to oppose the force applied by the high pressure fluid in the passage on the first interface. Suitably, the area of one of both interfaces on which high pressure fluid can act is bounded by one or more seals.

One embodiment of the invention takes the form of a flexible joint between two rotating components whose axes of rotation intersect but need not be coaxial, the spherical interfaces being centred on the point of intersection of the axes of rotation so that they maintain a seal with respect to high pressure fluid flowing through a passage between the two components during rotation of the components about their respective axes whether coaxial or not.In this embodiment, one component may have a cup-shaped end which provides opposed external spherical surfaces, and the other component has a mating cupshaped cavity providing opposed internal spherical surfaces, in which cavity the cupshaped portion of the first component is received with the spherical surfaces mating and is rotatable about the centre of curvature of the spherical surfaces which lies on the point of intersection of the axes of the two components. Suitably, the high-pressure fluid passage is coaxial with the axes of rotation of the two components.A sealing ring may be provided in the first interface so as to define the outer boundary of the first interface upon which the high-pressure fluid in the passage can act, and said conduit extends from said passage in one of the components to an annular space at the second interface lying between two concentric sealing rings in the second interface.

A second embodiment of the invention takes the form of a ball valve, in which a spherical valve member is rotatable within a valve housing, and a bore in the valve member transverse to the axis of rotation is, by rotation of the valve member, brought into and out of register with bores in the housing so as to establish or shut off respectively a passage for fluid through the valve; said conduit extending from one of the bores in the housing to a portion of the spherical interface between the valve member and the housing remote from said one bore of the housing so that fluid under pressure in said one bore when the valve is closed is communicated to said remote spherical interface portion which thereby applies a force on the valve member opposing the force applied on the valve member by fluid under pressure in said one bore in the housing.Said remote interface portion is preferably bounded by one or more sealing rings. More than one said remote portion may be provided, occupying discrete areas of the interface at different locations about the other bore in the housing.

In order that the invention may be more clearly understood, two embodiments will now be described with reference to the accompanying drawings, wherein: Figure 1 shows a longitudinal cross-section through a rotary joint, Figure 2 shows a diagrammatic cross-section through a ball valve, and Figure 3 shows a diagrammatic cross-section at right-angles to that of Fig. 2 through a ball valve which may be a modification of that shown in Fig. 2.

Referring to the drawings, and firstly to Fig.

1; a flexible joint is provided between two parts 19, 21, which are rotatable about respective axes 14, 16. The joint comprises two components 10, 12 secured to the parts 19, 21 respectively. The component 10 has flanges 18, 20 at opposite ends of a shaft 22.

The flange 18 is adapted for attachment, for example by bolts, to the part 19, and is sealed thereto by an O-ring 24 concentric with the axis 14. The flange 20 is bolted to an annular block 26, with O-rings 28, 30 between them. A boss 32 at the end of the component 10 beyond the flange 20 has a convex spherical surface 34 with its centre of curvature 36 on the axis 14. The block 26 is provided with a concave spherical surface 38 which is concentric with the convex surface 34 so as to define a cup-shaped cavity 40 between the block 26 and the boss 32. In this cavity is slidably located a cup-shaped portion 42 provided at the end of a shaft 44 of the other component 12 of the joint.The cup-shaped portion 42 thus has an outer convex spherical surface 46 which mates with the concave surface 38 of the block 26 and an inner concave spherical surface 48 which mates with the convex spherical surface 34 of the block 32. The cavity 40 has a somewhat greater circumferential extent than the cupshaped portion 42, so that the component 12 can swivel with respect to the component 10 about the centre of curvature 36, which lies on the point of intersection between the two axes 14, 16. This allows the two components to rotate when the axes are not coaxial. The end of the component 12 remote from the joint can likewise be secured to the part 21 by means of a ring 50 bolted to said member and trapping a flange 52 of a split collet 54 around the shaft 44.

The dot-dash line A-A demarcates an alternative design for this end region of the component 12. Above the line A-A the split collet is shown as butting against an end flange 56 on the shaft 44, and an O-ring 58 establishes a seal between the flange 56 and the part 21 to which it is joined by the ring 50. Below the line A-A the collet is shown as sealing directly against the part 21, with an O-ring 60, and is also an axial sliding fit on the shaft 44, with an O-ring 62. In the latter arrangement, since the collet can be slid directly onto the end of the shaft, it is not a split collet, and indeed it need not have a mounting ring 50, but its flange 52 could be extended so as to be bolted directly to part 21. It is of course to be understood that these different constructions represented on either side of the line A-A are alternative designs.

Passages 15, 17 are coaxial with the axes of rotation 14, 16 respectively, and provide a through passage for high pressure fluid between the parts 19, 21. Fluid under pressure in this passage can enter the spherical interface between the surfaces 34 and 48, and tends to force the surfaces apart. To counteract this a conduit 64 extends from the passage 15 through the flange 20 and the block 26 to an annular recess 66 at the spherical interface between the surfaces 38 and 46.

The high pressure fluid entering the recess 66 this applies a force opposite to that applied between the surfaces 34 and 48. The force applied between the surfaces 34 and 48 is limited by a sealing ring 68 at the interface, and the force applied at the recess 66 is similarly limited by concentric sealing rings 70, 72 on either side of the recess. The axial force applied by the fluid in the recess 66 is a function of the difference between the squares of the radii of the sealing rings 70, 72.The axial force applied between the surfaces 34 and 48 is a function of the difference between the square of the radius of the sealing ring 68 and the square of the internal radius of the passage 17 in the case of the construction shown above the line A-A, or the square of the internal radius of the collet 54 in the case of the construction shown below the line A-A where the fluid pressure acts also on the end of the shaft 44 remote from the joint. The opposing forces applied to the spherical interface can be arranged so as to be substantially balanced, or to result in a limited net force in either direction, according to the location of the sealing rings 68, 70, 72.

Since there will inevitablty be a small leakage of fluid past these sealing rings and into the cavity 40, a drain conduit 74 is provided from the cavity 40 to atmosphere. To prevent the ingress of solid contaminants, a reinforced flexible shield 76 connects the two parts of the joint, and the drain conduit 64 opens into the space within the shield, which is atmospheric pressure, if necessary a small aperture in the shield being provided for this purpose.

Referring now to Figs. 2 and 3; a ball valve comprises a spherical valve member 77 located in a valve housing 79 and rotatable about an axis 81. A bore 82 transverse to the axis 81 extends through the valve member and, on rotation of the valve member, is brought into and out of communication with opposed first and second bores 84, 86 in the housing 79, so as to open and close the valve. When the valve is closed, as shown in Fig. 1, high pressure fluid at the inlet bore (in this case the bore 84) applies a force to the surface of the valve member 77 which closes the bore. This force is maintained during rotation of the valve element until the bore 82 connects the bores 84 and 86. This can result in undue wear and friction in the valve.The present invention provides a conduit 89 extending from the inlet bore 84 to a portion 90 of the spherical interface between the valve member and the housing remote from the inlet bore 84. This portion 90 can take the form of an annular recess, as with the recess 86 in Fig. 1, located between two coaxial sealing rings 92, 94. The resulting force applied to the annular surface 90 can counterba lance the force applied to the surface of the valve member closing the bore 84, so that there is little or no net force on the valve member. Alternatively, the area 90 could be a discrete area to one side of the outlet bore 86, as shown in Fig. 3. In order that the counter-balancing force should be coaxial with the inlet bore 84, a second surface portion 90 (see Fig. 3) can be provided on the opposite side of the outlet bore 86, and connected to the inlet bore 84 by a second conduit 89, shown in dot-dash lines in Fig. 2. These discrete areas 90 can be individually bounded by single sealing rings 96 as shown in Fig. 3.

Claims

1. An assembly comprising two relatively movable components having mating surfaces providing a first spherical interface at which movement occurs and which is exposed to a passage between the two components, which passage can contain fluid under pressure; a duct within one of the components communicating at one end with said passage and at the other end with a second spherical interface between the two components, concentric with and opposed to the first interface, whereby high pressure fluid from the passage extending through the duct applies pressure to said second interface so as to oppose the force applied by the high pressure fluid in the passage on the first interface.

2. An assembly according to claim 1 wherein the area of one or both interfaces on which high pressure fluid can act is-bounded by one or more seals.

3. An assembly according to claim 1 or claim 2 in the form of a flexible joint between two rotating components whose axes of rotation intersect but need not be coaxial, the spherical interfaces being centred on the point of intersection of the axes of rotation so that they maintain a seal with respect to high pressure fluid flowing through a passage between the two components during rotation of the components about their respective axes whether coaxial or not.

4. An assembly according to claim 3 wherein one component has a cup-shaped end which provides opposed external spherical surfaces, and the other component has a mating cup-shaped cavity providing opposed internal spherical surfaces, in which cavity the cup-shaped portion of the first component is received with the spherical surfaces mating and is rotatable about the centre of curvature of the spherical surfaces which lies on the point of intersection of the axes of the two components.

5. An assembly according to claim 3 or claim 4 wherein the high-pressure fluid passage is coaxial with the axes of rotation of the two components.

6. An assembly according to any one of claims 3, 4 and 5 wherein a sealing ring is provided in the first interface so as to define the outer boundary of the first interface upon which the high-pressure fluid in the passage can act, and said conduit extends from said passage in one of the components to an annular space at the second interface lying between two concentric sealing rings in the second interface.

7. An assembly according to claim 1 or claim 2 which takes the form of a ball valve, in which a spherical valve member is rotatable within a valve housing, and bore in the valve member transverse to the axis #of rotation is, by rotation of the valve member, brought into and out of register with bores in the housing so as to extablish or shut off respectively a passage for fluid through the valve; said conduit extending from one of the bores in the housing to a portion of the spherical interface between the valve member and the housing remote from said one bore of the housing so that fluid under pressure in said one bore when the valve is closed is communicated to said remote spherical interface portion which thereby applies a force on the valve member opposing the force applied on the valve member by fluid under pressure in said one bore in the housing.

8. An assembly according to claim 7 wherein said remote interface portion is bounded by one or more sealing rings.

9. An assembly according to claim 7 or claim 8 wherein more than one said remote portion is provided, occupying discrete areas of the interface at different locations about the other bore in the housing.

10. An assembly having a spherical interface, substantially as described herein with reference to the drawings.