A FITTING FOR USE IN A PRESSURISED FLUID LINE

Abstract: A fitting for use in a pressurised fluid line comprises first and second adjacent sections (12, 14) of the line in co-axial and unconnected relationship to one another so as to define an axial joint (18) between the two sections. One of the sections (12) is able to rotate about its axis relative to the other section. Means (36, 48) support the two line sections in their co-axial and unconnected relationship with each other. A tubular sealing member (50) is disposed co-axially within the line and across the axial joint (18) betweeen and directly against the adjacent sections (12, 14) and joint (18), internally sealing the joint while allowing fluid within the line to pass from one section to the other.

Description: The present invention relates generally to a fitting for use in a pressurised fluid line for example a high pressure (over 68.95 MPa (10,000 psi)), high flow rate fluid line. In order to allow one section of a pressurised fluid carrying line to rotate about its axis relative to a co-axial section of the line, a joint between the two and some sort of means to seal that joint is necessary. One typical prior art way of accomplishing this in high pressure, high flow rate applications is to utilise a large diameter shaft containing the joint and a sealing member disposed around the outside diameter of the shaft over the joint. However, this type of approach has been found to result in high relative surface speed between the one section of the shaft and the sealing member which, in turn, tends to result in the generation of heat which exceeds the thermal capability of the seal, thereby causing the latter to fail. In addition, this type of configuration requires a relatively high driving torque to rotate one shaft section relative to the other, a larger housing to support the high internal pressure, and a large bearing to support the high thrust on the shaft (if only one seal is to be used rather than two for a balanced thrust fitting). A way to reduce the heat and high torque problems associated with the approach described immediately above and also to significantly reduce the overall size of the fitting is to locate the seal within the fluid line itself, as illustrated in U.S. Patent Specification No. 2421974 (Vandervoort). This shows that the two sections of a fluid carrying line are positioned in a co-axial relationship to each other so as to define an axial joint between the two and a combination packing gasket-metal ring is disposed within the line and across the joint. However, the metal ring itself extends across the joint between the latter and the packing gasket, as best illustrated in Figure 2 in the U.S. Patent specification. The sealing action will require that this metal ring be of precise dimensions especially on its outer diameter. The annular gap between this ring and the bores of the mating joint should be very small so that seal extrusion does not occur. As a result, the overall fitting is only capable of operating at relatively low line pressures. More specifically, if the internal pressure within the fitting becomes sufficiently large to cause the metal ring to deform outwardly, it will extrude into the joint between the two line sections and contact the bore walls of the two mating sections causing very high friction and thereby significantly hinder the rotary action of the fitting and possibly prevent the fitting from rotating altogether. The invention provides a swivel fitting for use in a pressurised fluid line, the fitting comprising: (a) first and second adjacent sections of the line in co-axial and unconnected relationship to each other so as to define an axial joint between the two line sections such that one section is able to rotate about its axis relative to the other section; (b) means supporting the first and second line sections in the co-axial and unconnected relationship; and (c) a tubular sealing member disposed co-axially within the line and across the axial joint between the adjacent line sections for internally sealing the joint while allowing fluid within the line to pass from one section to the other. Preferably the tubular sealing member is integrally formed with a sealing material which displays both sealing and bearing (low friction) characteristics, for example polytetrafluoroethylene (PTFE). Thus, the sealing member which is disposed in direct contact with the joint serves as both a seal and relatively low friction bearing surface. Moreover, if the member is caused to deform radially outwardly by internal pressure within the line, and thereby extrude into the joint between the line sections, it will extrude into the joint without adversely affecting the seal across the joint or the rotary action between the adjacent sections. Preferably, the axial section of the sealing member is greater along a segment thereof adjacent to the joint than on either side of that segment, so reinforcing the sealing member against radially outward extrusion into the axial joint due to internal line pressure. The axial section of the sealing member preferably defines a venturi across the joint in the direction of fluid flow through the line, thereby minimising any drop in pressure across the joint. Preferably, the sealing member extends further into the rotatable line section than into the other line section so that it will rotate about its own axis with the rotation of the rotatable line section without having to be bonded to it. On the other hand, if desired, the sealing member could be disposed further into the other line section so as to cause it not to rotate with the rotation of the rotatable line section, again without having to bond the sealing member in place. Preferably, the first and second line sections are supported in their co-axial, unconnected positional relationship to each other by means of a single radial bearing disposed co-axially around the outside of these sections and over the joint between the two. This helps to maximise co-axiality between the sections and minimise run out. Preferably, one of the line sections is divided into at least two sub-sections, one of which does not engage any bearings forming part of the overall arrangement. That particular sub-section is one which can be readily disengaged from the other, providing access to and allowing removal of the sealing member from its operating position. In that way, the sealing member can be replaced without disturbing the bearing system. In the accompanying drawings: Figure 1 is an axial sectional view of a rotary fitting which includes an in-line sealing member; Figure 2 diagrammatically illustrates the pressure distribution across an in-line sealing member during both leakage and non-leakage conditions; Figures 3, 4 and 5 are diagrammatic illustrations of different in-line sealing members; Figures 6, 7, 8 and 9 diagrammatically illustrate in axial section a number of rotary fittingss; Figure 10 is a diagrammatic illustration, in axial section, of a rotary fitting which includes an in-line sealing member and a cartridge to eliminate any gap in the joint; Figure 11A is a side view of a cartridge forming part of the of Figure 10, which cartridge is designed to be hydrostatically balanced; Figure 11B is an end view of the cartridge illustrated in Figure 11A; and Figure 12 is a side view of a modified cartridge for use in the fitting of Figure 10. Figure 1 illustrates a rotary fitting 10. This fitting, which is especially suitable for high pressure applications, includes first and second adjacent sections 12 and 14 which when assembled into their operating positions form part of a pressurised fluid line (not shown). A support assembly 16 to be discussed below for supports the sections 12 and 14 in a co-axial and unconnected relationship to one another so as to define an axial gap joint 18 between the two sections and such that the section 12 is able to rotate about its axis relative to the section 14. The non-confronting ends 20 and 22 of the line sections 12 and 14 are externally screw-threaded so that they can be thread connected into the line by means of co-operating internally screw-threaded end sections of the line (not shown). In that way, fluid under pressure can flow from one section to and through the other along a fluid carrying passage 24 defined by the line sections 12 and 14, as indicated for example by means of arrow 25. The support assembly 16 includes a main coupling 26 internally screw-threaded at opposite ends 28 and 30 so as to receive externally screw-threaded end plugs 32 and 34, respectively. The coupling 26 and end plugs 32 and 34 are positioned co-axially around the line sections 12 and 14 and gap 18, as shown. A single, tubular radial bearing 36 is disposed around the outside of and directly against adjacent segments of the line sections 12 and 14 and across the axial gap joint 18 in order to support the line section 12 for rotation relative to the section 14. Because of its position across both the line sections, the radial bearing 36 aids in maximising the co-axially of the two line sections and minimises run out as the line section 12 rotates about its axis relative to the section 14. The overall support assembly 16 includes a pair of axially spaced low pressure seal rings 38 on opposite sides of the gap 18 between the line sections 12 and 14 and the radial bearing 36. The purpose of the low pressure seal rings 38 is to keep the bearing surface free from foreign materials. Also, pre-loaded thrust bearings 46 and 48 are provided and along with the radial bearing 36 provide an overall bearing system for supporting the line section 12 for rotation. Inasmuch as the line section 14 is not designed to rotate, similar pre-loaded thrust bearings are not provided for that purpose. However, they could be so provided in order to allow the line section 14 to also rotate. The fitting 10 also includes a deformable sealing member 50 which is integrally formed of a material which is capable of not only providing a seal across the gap 18 but also one which is capable of serving as a relatively low friction bearing surface between the seal and one of the line sections 12 or 14 depending on which rotates and whether the seal rotates or is fixed. One particular material which meets both of the requirements just recited is polytetrafluoroethylene (PTFE), although there are other suitable materials such as nylon or polyacetal resin. The purpose of the sealing member 50 is to seal the gap 18 while at the same time allowing one of the line sections to rotate relative to the other. To minimise the pressure drop across the gap 18, the sealing member 50 is disposed within an enlarged axial section 52 of the overall fluid carrying passage 24 such that the inner diameter of sealing member 50 is at least approximately equal to the diameter of the passage 24. The sealing member 50 is able to radially outwardly deform and thus extrude into the gap joint 18 rather than crack in response to relatively large line pressures. Should the pressure within the sealing member increase to a level which does cause it to deform and thereby extrude partially into the gap 18, the rotary capability of the fitting will not be adversely affected to a significant degree. This is because the extruded segment of the sealing member nevertheless serves as a bearing surface. This deforming capability of the sealing member 50 also aids in eliminating leaks which occur along the outer surface of the sealing member between the passage section 52 and the gap 18. This is best illustrated by the pressure patterns within the interface between the sealing member 50 and the line sections 12 and 14 generally indicated at 56 and 58 in Figure 2. The pressure pattern 56 represents the pressure across the seal interface when no leaks are present. The pattern 58 corresponds to the pressure across the seal interface when a leak occurs. As a result of either pattern, the bore pressure within sealing member 50 will tend to deform the seal material radially outward so as to fill the void permitting any leak and thereby close the latter. The sealing member 50 may be positioned within the passage section 52 so as to control whether or not it rotates. This is best illustrated in Figure 2 where the sealing member is shown extending further into the line section 12 than into the line section 14. In other words, the sealing member extends further to the left of the gap 18 as viewed in Figure 2 than to the right of the gap. As a result of this positional relationship between the sealing member and the two line sections, the sealing member will tend to rotate with the line section 12 rather than remaining stationary with line section 14, without having to bond the sealing member to the line section 12. This presupposes that the sealing member fits approximately equally tight within both of the line sections. If the sealing member were positioned further into the line section 14, than into line section 12, the sealing member would remain stationary with section 14 as line section 12 rotates. In contrast to both of these extremes, if the sealing member were to extend into the two line sections equally, it could not be predicted whether it would rotate or not unless the sealing member were bonded to one or the other of the line sections. In this regard the sealing member should not be bonded in place since that makes it more difficult to remove the sealing member when the latter has to be replaced. At the same time, to be able to predict whether or not the sealing member will rotate is important in order to appropriately select the material it rotates against (or which rotates against it) so as to minimise friction between the two. For example, if the sealing member is going to rotate relative to the line section 14, the material making up this latter line section can be appropriately selected to provide a suitable bearing surface against the sealing member. One way of preventing the sealing member from extruding into the axial joint 18 as a result of relatively high line pressures is to design the cross-sectional configuration of the sealing member so that it is thicker at the gap than on either side thereof. Figure 3 shows a sealing member 60 which defines a venturi in the direction of the fluid flow through passageway 24. This provides the additional advantage of reducing the pressure drop across the gap 18 by providing pressure recovery downstream. Similar sealing member configurations 62 and 64 are illustrated in Figures 4 and 5, respectively. The configuration 62 includes an outermost cylindrical sealing member 66 constructed of a suitable sealing and bearing material, for example the same material forming the member 50. However, the configuration also includes an inner member 68 which is harder or more rigid than the member 66 and which does not have to provide either a sealing or bearing capability. Rather, the member 68 serves to prevent internal line pressures from causing the sealing member 66 to extrude into the gap 18. The member 68 also has a venturi type of axial section to minimise the pressure drop across the gap 18. The configuration 64 is similar to the configuration 62 to the extent that it includes a sealing member 70 and a reinforcement member 72 having a venturi type axial section. However, the member 72 extends axially beyond the sealing member 70 on one side thereof. Since the overall configuration 64 is arranged for rotation with the line section 12, the member 72 does not have to have bearing capabilities. An additional advantage to composing the seal insert as shown in Figures 4 and 5 is to be able to reuse the sections 68 or 72 in Figures 4 and 5 respectively. Only the sealing elements 66 or 70 which are in a simple cylindrical form need to be replaced after their useful lifetime. Figure 6 illustrates a rotary fitting 74 which includes co-axial and unconnected line sections 76 and 80 which together define a joint 82 and an in-line sealing member 84 extends across the joint. These line sections and the sealing member as a whole function in the same manner as the previously described sections 12 and 14 and sealing member 50 with the section 76 and the sealing member 84 being rotatable relative to the section 80. To this end, the fitting includes radial and thrust bearings 86 and 88 respectively disposed between the two line sections. The fitting 74 differs from the previously described fitting 10 in that the line section 80 is configured so that access to the sealing member 84 can be easily gained and it can be removed from its operating position without disrupting the bearings 86 and 88. To this end, the line section 80 is comprised of two sub-sections 90 and 92 which are disengageably connected to each other by means of screw-threads 94. The sub-section 90 is disposed co-axially around the radial bearing 86 and axially against the bearing 88 while the sub-section 92 does not engage any bearings at all. At the same time, the sub-section 92 can be disengaged from the sub-section 90 so as to expose the sealing member 84 to the ambient surroundings without affecting the bearings 86 and 88. This allows the sealing member 84 to be readily accessed and replaced when and if necessary without involving the bearings at all. Low pressure sealing rings 96 and 97 are provided between the line section 76 and the sub-section 92 of the line section 80, and between the line member 76 and the sub-section 90 of the line section 80 respectively. Figure 7 illustrates still another rotary fitting 98 which is slightly different from the fitting 74 described immediately above. The fitting 98 includes a line section 100 intended to rotate, a co-axial unconnected line section 102, an assembly of bearings 104 and 106, a low pressure sealing ring 108 and an in-line sealing member 110. The line section 102 is made up of three sub-sections, a first sub-section 112 designed to engage the bearings 104 and 106, and two further sub-sections 114 and 116 which do not engage the bearings. The sub-section 114 is disengageably connected to the sub-section 112 by means of screw-threads 118. The sub-section 116 which is in the form of a cartridge is disposed within a co-operating opening in the sub-section 114 which receives an end segment of the sealing member 110. With the sealing member 110 positioned in the manner shown, that is, further into the line section 100 than into the cartridge 116, the sealing member is intended to rotate with the line section 100. If the passageway 119 in the line section 100 has minimum or no run out, then the cartridge 116 can be configured to float in order to achieve maximum co-axiality. Otherwise, the cartridge 116 is fixedly held within the sub-section 114. In either case, the cartridge 116 can be readily removed (or replaced) to gain access to and replace the sealing member 110 without involving the bearings 104 and 106. Another advantage of using the cartridge 116 is that it can easily be made of a wear resistant material such as tool steel, tungsten or titanium carbide due to its simple shape. Figure 8 illustrates a rotary fitting 120 which is similar to the fitting 74 of Figure 6 in a number of respects. More specifically, the fitting 120 includes a line section 122 corresponding to the line section 76, a two-piece line section 124 corresponding to the two piece line section 80, radial and thrust bearings 126 and 128, respectively, and a sealing member 130. However, the radial bearing 126 is positioned axially closer to the joint than the thrust bearing 128. By providing the radial bearing closer to its sealing member, run out is reduced. Also, the radial bearing 126 is mounted in the section 124 Figure 9 illustrates a rotary fitting 130 similar in many respects to the fitting 98 illustrated in Figure 7. Like the fitting 98, the fitting 130 includes a rotatable line section 132 corresponding to the line section 100 of the fitting 98, a multi-piece line section 134 corresponding to the line section 102, radial and thrust bearings 136 and 138 respectively, a low pressure sealing ring 140 and a sealing member 142. In addition, the fitting 130 includes a plug 144 which forms part of the multi-piece line section 134 and which is disengageably connected to the rest of that line section. By removing the plug 144, access can be gained to the sealing member 142 and it can be readily replaced without involving the bearings or any of the tubing connected to the rotary fitting 130. In all of the fittings thus far described, none included active means to eliminate any gap at its axial joint, although all of the fittings described previously show such a configuration, except for the arrangement 10, which illustrates a gap at 18. Figure 10 illustrates a fitting 146 which does include positive means for ensuring no gap at its axial joint. The fitting 146 includes a rotatable line section 148 and an unconnected, co-axial multi-piece line section 150. This latter line section includes a first sub-section 156 which, while not shown, engages the necessary bearings forming part of the fitting, and two further sub-sections 160 and 162. The sub-section 160 functions as an end plug and supports one end of the sub-section 162 for axial slidable movement to a limited extent within a co-operating cavity 164. The other end of the sub-section 162 serves to contain one end segment of a sealing member 166. The sub-section 162 has an end surface 168 which is in confronting relationship with a corresponding end surface 170 of the line section 148. The two confronting surfaces 168 and 170 together define the axial joint. The sub-section 162, which serves as a cartridge, is axially biased in the direction of the surface 170 so as to eliminate any gap within the axial joint. The sub-section cartridge 162 is axially biased by means of a spring member 172 which is disposed co-axially around a reduced segment of the cartridge within the cavity 164 and between the larger segment of the cartridge and the end face of the plug 160. At the same time, the cartridge itself, due to is structural configuration, is hydrostatically balanced. In order to explain how the cartridge 162 is hydrostatically balanced, reference is made to Figures 11A and 11B. As seen in these figures, the right hand end of the cartridge has an outer diameter d while the left hand end has the same inner diameter. Flow within the fitting is from right to left in Figure 10 as indicated by arrow 174. The axial pressure forces acting on opposite ends of the cartridge are equal and opposite, thereby making the cartridge hydrostatically balanced. Referring to Figure 10, the cartridge 162 is prevented from rotating about its axis by means of a set screw 176 disposed with a co-operating opening in the sub-section 156 and engaging in an axial extending spline 178 in the cartridge 162. By making the cartridge 162 hydrostatically balanced, the spring force exerted by the spring member 172 will guarantee contact between the confronting surfaces 168 and 170 regardless of the line pressure within the overall fitting arrangement. This spring force will compensate for axial deflections and any gap increase due to pressurisation. The spring cavity 164 can be precharged with an adequate gas pressure to maintain higher contact force between the mating surfaces, if desired. Also, the cartridge can be configured to define an internal venturi to minimise pressure loss, as indicated by the modified cartridge 162′ illustrated in Figure 12. The sealing members have square ends but may have angled ends. Any sealing member may include either square ends or angled ends or one of each. The sealing members can be disposed equally on either side of their respective joints. Moreover, while each sealing member has a particular axial section, it could have other sections.

Claims: 1. An fitting for use in a pressurised fluid line, the fitting comprising (a) first and second adjacent sections (12, 13, Figure 1) of the line in co-axial and unconnected relationship to each other so as to define an axial joint (18, Figure 1) between the two line sections such that one section is able to rotate about its axis relative to the other section; (b) means (16, Figure 1) supporting the first and second line sections in the co-axial and unconnected relationship; (c) a tubular sealing member (50, Figure 1) disposed co-axially within the line and across the axial joint between the adjacent line sections for internally sealing the joint while allowing fluid within the line to pass from one section to the other. 2. A fitting according to Claim 1, wherein the sealing member (50, Figure 2) extends further into the rotatable line section than into the other line section. 3. A fitting according to Claim 1 or 2, wherein the sealing member (60, Figure 3) has an axial section which is thicker along a specific segment thereof directly adjacent to the joint (18) than along segments of the sealing member located on either side of the specific segment and spaced further from the joint. 4. A fitting according to Claim 1, 2 or 3 wherein the sealing member (60, Figure 3) defines a venturi across the joint (18) in the direction of fluid flow through the line. 5. A fitting according to any preceding claim, wherein the sealing material is PTFE. 6. A fitting according to any one of Claims 1 to 3, including means (68, Figure 4) more rigid than the sealing material located radially within and directly against the sealing member (66). 7. A fitting according to Claim 6, wherein the more rigid means (68, Figure 4) has an axial section which defines a venturi across the joint in the direction of fluid flow through the line. 8. A fitting according to any preceding claim, wherein the supporting means includes bearing means (86, 88, Figure 6) disposed between and in contact with co-operating surfaces of the first and second line sections (76, 80, Figure 6), and the second line section (80) includes a first sub-section (90) providing the co-operating surface or surfaces of the second section and a second sub-section (92) disengageably connected with the first sub-section, the sub-sections being configured such that the disengagement of the second sub-section (92) from the first sub-section (90) provides access to and allows removal of the sealing member (84) for replacement thereof without having to disturb the bearing means. 9. A fitting according to Claim 8, wherein the second line section (102, Figure 7) includes a third sub-section (114, Figure 7) only the second sub-section (116, Figure 7) is in direct contact with the sealing member (110) whereby disengagement of the second sub-section from the third sub-section provides access to and allow removal of the sealing member. 10. A fitting according to Claim 9, wherein the sealing member (110, Figure 7) is disposed within the line for rotation with the first line section (100, Figure 7) and the second sub-section (116) is connected with the third sub-section (114) such that the sealing member (110) rotates with the first line section relative to the second sub-section while the second sub-section is free to float radially to a limited extent relative to the third sub-section. 11. A fitting according to any preceding claim, wherein the second line section (150, Figure 10) includes a first sub-section (156, Figure 10), a second sub-section (162, Figure 10) located radially within and movable axially relative to the first sub-section (156), and spring means (172) biasing the second sub-section (162) in the direction of the first line section (148), the second sub-section being disposed in direct contact with the sealing member (166) and having a radially extending surface (168) in confronting relationship with a co-operating surface (170) of the first line section (148) such that the co-operating surfaces together define the joint, the spring means (172) serving to bias the co-operating surface of the second sub-section against the co-operating surface of the first line section to eliminate any gap between the two surfaces. 12. A fitting according to Claim 11, wherein the second sub-section (162) is configured to be hydrostatically balanced as a result of the internal pressure within the line. 13. A fitting according to any preceding claim, wherein the supporting means includes both radial and axial bearing means (126, 128, Figure 8), the radial bearing means (126) being positioned axially closer to the joint than the axial bearing means. 14. A fitting according to any one of Claims 1 to 12, wherein the supporting means includes a single, tubular radial bearing (36, Figure 1) disposed co-axially around the outside of adjacent segments of the first and second line sections (12, 14, Figure 1) and the joint (18).

Inventors: HASHISH, MOHAMED, OLSEN, JOHN H.
Applicants: FLOW INDUSTRIES INC.
Application year: 1987
Main classification: F16L27
IPC codes: F16L27