Pipe swivel joint with improved bore seal

A pipe swivel joint with male and female hubs and an improved bore seal assembly having an anti-extrusion ring that axially energizes the swivel joint hubs toward their operational position as the joint is assembled.

BACKGROUND OF THE INVENTION 
This invention relates to pipe swivel joints, and more particularly to such 
joints with bore seals having anti-extrusion components. 
Many present pipe swivel joints are difficult and expensive to maintain in 
functional condition because of their relatively complex design and their 
large number of components including, for example, loose bearings, 
threaded locking mechanisms, and seals with non-integral anti-extrusion 
devices. The problems presented by these disadvantages, especially when 
amplified by the harsh environments encountered in the petroleum industry, 
have discouraged routine field maintenance of those swivel joints, thereby 
resulting in increased operating costs and greater potential for accidents 
or other safety-endangering problems. 
SUMMARY OF THE INVENTION 
The present invention provides a pipe swivel joint that has relatively few 
components, is quickly and easily assembled and disassembled even in the 
field, and that continues to function satisfactorily over longer time 
periods, thereby requiring servicing at less frequent intervals, than 
joints of more complex design. A swivel joint in accordance with the 
present invention includes male and female hubs, a strip-type load/bearing 
mechanism for interlocking the hubs in a rotatable manner while providing 
a thrust bearing therebetween, and an improved bore seal assembly with an 
anti-extrusion ring that axially energizes the hubs toward their 
operational position as the joint is being assembled. During the assembly 
process the anti-extrusion ring is subjected to compressive loading 
between the hubs and allows them to be axially overstroked past their 
normal operational position to facilitate installation of the load/bearing 
mechanism. Following installation of that mechanism the hubs are permitted 
to return axially to their normal operating position in which the joint 
can be rotated easily either clockwise or counter-clockwise.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As seen in FIGS. 1-4, the preferred embodiment of the present invention 
comprises a pipe swivel joint 10 that includes a female hub 12, a male hub 
14, a strip-type load/bearing mechanism 16 that locks the hubs 12, 14 
together yet facilitates their relative rotation, a radial bearing 18 
between the outer surface 20 of the inner hub and the inner surface 22 of 
the outer hub, and a bore seal assembly 24 that provides a fluid 
pressure-tight seal between the hubs 12, 14. An inner annular groove 26 
near the front end 27 of the female hub 12 provides a chamber for an 
annular dust seal (not shown) to isolate the radial bearing 22 and other 
internals from the external atmosphere, protecting them from dust, 
moisture and other contaminants. 
The strip-type load/bearing mechanism 16 may have a generally square cross 
section as illustrated, and may comprise a plurality of arcuate load 
elements interlocked in end-to-end manner as fully described in Witt et 
al. U.S. Pat. No. 4,867,483 (elements 17), or may comprise arcuate load 
elements secured together in the manner described in Ungchusri et al. U.S. 
Pat. No. 4,927,192, the content of both patents being incorporated herein 
by reference. 
The radial bearing 18 may comprise a dry film coating of 
polytetrafluoroethylene (PTFE), or a sprayed-on aluminum bronze coating, 
on either the outer surface 20 of the male hub 14 or the inner surface 22 
of the female hub 12, or on both surfaces. Also, a non-integral, press 
fitted journal bearing (not shown) may be used to support the radial load 
between the hubs 12, 14. 
The bore seal assembly 24 is similar in several respects to that described 
in Ungchusri et al. U.S. Pat. No. 4,930,791, the content of which is 
incorporated herein by reference, but has an anti-extrusion ring 28 of 
improved design and function. The seal assembly 24 comprises a sleeve-like 
plastic seal element 30, a sleeve-like finger spring 32, a wear sleeve 34, 
and the anti-extrusion ring 28, these elements shown properly assembled in 
the drawings. 
The seal element 30 comprises a central portion 36 with an outer annular 
groove 38 within which resides the anti-extrusion ring 28, two annular 
sealing lips 40, 42 extending axially from the central portion 36, the 
lips having annular radiused surfaces 40a, 42a for establishing a fluid 
pressure seal with the hubs 12, 14 respectively, and an inwardly oriented 
radial flange 44 at each end for retaining the finger spring 32 in proper 
position in the seal element bore 46. 
The finger spring 32 has a central annular continuous portion 48 and a 
plurality of circumferentially spaced spring fingers 50 extending axially 
in opposite directions from the portion 48. The spring fingers 50 support 
the seal element lips 40, 42 in fluid pressure tight contact with the 
adjacent bore surfaces of the hubs 12, 14, and also serve to provide the 
seal element with a memory property that is not affected by high pressure 
and/or temperature cycling. 
The wear sleeve 34 has a central portion 52 that fits against the finger 
spring central portion 48, and end portions 54 of lesser outside diameter 
that reside radially inward of the spring fingers 50. 
As illustrated best in the right half of FIG. 3, the annular space between 
the wear sleeve end portions 54 and the spring fingers 50 enable the 
fingers to flex radially inward during installation of the seal assembly 
24 into functional position between the hubs 12, 14 (FIG. 4). 
As seen best in FIGS. 3 and 4, the anti-extrusion ring 28 has cylindrical 
inner and outer surfaces 28a, 28b, and sloping side surfaces 28c, 28d that 
extend between the inner and outer surfaces at an angle in the range of 
about 30 to 45 degrees with respect to inner surface 28a. In its 
functional sealing position shown in FIGS. 1 and 4, the ring's side 
surfaces 28c, 28d are in contact with adjacent annular surfaces 12a, 14a 
of the female and male hubs 12, 14, and the inner cylindrical surface 28a 
is radially spaced from the bottom surface 38a of the annular groove 38 in 
the seal element 30. 
The procedure for assembling the swivel joint 10 is relatively simple and 
straightforward, and involves the following steps. The bore seal assembly 
24 is pressed into either the male hub 14 (FIG. 3) or the female hub 12, 
and the two hubs are then axially aligned and telescoped, thereby pressing 
the bore seal assembly fully into the other hub (FIG. 4) wherein both the 
hub surfaces 12a, 14a are in contact with the adjacent anti-extrusion ring 
surfaces 28c, 28d, respectively, and the ring is compressed radially 
inward in the groove 38. From this point the hubs are telescoped further 
to overstroke them until the inner annular groove 56 in the female hub 14 
and the outer annular groove 58 in the male hub 12 are aligned as shown in 
FIG. 2, thereby facilitating installation of the load/bearing mechanism 16 
into the grooves through a port (not shown) in the female hub 14. As the 
hubs undergo this further telescoping the anti-extrusion ring 28 is placed 
in compressive loading which energizes the hubs, i.e. tries to force them 
axially apart to their FIG. 4 position. Following installation of the 
load/bearing mechanism 16, the hubs 12, 14 are allowed to return to their 
functional operating position, as shown in FIGS. 1 and 4, in response to 
the energizing force of the anti-extrusion ring 28, and in this operating 
position the swivel joint 10 can be easily rotated both clockwise and 
counterclockwise. 
The anti-extrusion ring 28 is formed from a material of sufficient 
resiliency to undergo the above described compression and yet return to 
its original functional size and condition. The preferred material for the 
ring 28 is polyetheretherketone (PEEK). 
DESCRIPTION OF ADDITIONAL EMBODIMENTS 
FIG. 5 illustrates a modified version 124 of the bore seal assembly 24. In 
the assembly 124 the anti-extrusion ring 128 has a truncated triangular 
shape in cross-section, and surrounds a metallic or other relatively rigid 
annular support element 70 that resides in the groove 38 of the seal 
element 30. 
FIG. 6 shows a bore seal assembly 224 similar to that of FIG. 5, but 
wherein the anti-extrusion ring 228 has an annular ridge 72 that 
cooperates with an annular groove 74 in the male hub 214 to hold the ring 
in proper functional position as illustrated. 
FIGS. 7 and 8 illustrate yet another embodiment of bore seal assembly 324 
that resembles the assemblies of FIGS. 5 and 6, but wherein the 
anti-extrusion ring 328 has a serrated annular surface 328a that 
cooperates with a complementary surface 312a on the female hub 312 to 
secure the ring 328 in its proper operational position as shown. 
Although the best mode contemplated for carrying out the present invention 
has been herein shown and described, it will be apparent that modification 
and variation may be made without departing from what is regarded to be 
the subject matter of the invention.