A threaded connection that provides high sealing performance is provided. A threaded connection (10) includes a pin (1) and a box (2). An inner male thread (13) of the pin (1) includes a parallel portion (131). The parallel portion (131) is located at an end portion of the inner male thread (13) adjacent to the pin inner sealing surface (11), and has thread roots parallel to the pipe axis. An inner female thread (23) of the box (2) includes a tapered portion (231). The thread height in the tapered portion (231) is larger than that in the parallel portion (131). Da<Db is satisfied, where Da is the difference in diameter between adjacent thread crests (231a) in the tapered portion (231) in a longitudinal cross section of the pin (1) and box (2) as found when the connection is not made up, and Db is the difference between the diameter of the thread root (131a) in the parallel portion (13) and the maximum diameter of the pin inner sealing surface (11).

A pipe coupling is described comprising an outer tubular part (1) with threads inside, an inner tubular part (10) with threads outside, and a sleeve (5) where on a first half of the sleeve there are external and inner threads which fit in the threads of the outer and inner tubular parts, respectively, so that the sleeve (5) can be screwed into the outer tubular part (1) while it is simultaneously screwed onto the inner tubular part (10) and the outer and inner tubular parts are firmly connected to each other through the threads on the sleeve (5).

The present disclosure provides couplers used to connect one length of rigid electrical conduit to another length of rigid electrical conduit. The couplers include a body having a first coupling portion, a second coupling portion, a stop portion positioned between the first coupling portion and the second coupling portion, and a longitudinal bore extending from the first coupling portion through the stop portion to the second coupling portion. The longitudinal bore within the first coupling portion is a threaded bore capable of receiving a threaded end of a first threaded electrical conduit. The longitudinal bore within the second coupling portion has a diameter capable of receiving a threaded end of a second threaded conduit or an unthreaded end of an unthreaded conduit. The longitudinal bore within the stop portion has a diameter that provides a wire passage between the first threaded conduit and the second threaded conduit or the unthreaded conduit.

A pipe-fitting device according to the present invention includes a fitting body, a fixing nut, and a collet. A first end of the fitting body is rotatably connected to an outer circumferential surface of a first pipe, and a second end of the fitting body surrounds an outer surface of a second pipe. A first end of the fixing nut is rotatably connected to an outer circumferential surface of the fitting body, and a second end of the fixing nut surrounds the outer surface of the second pipe. The collet is provided inside the fixing nut and presses the second pipe when the fixing nut is rotated and tightened. The collet includes a seating portion provided inside the fixing nut, a bending portion in which a bending groove is formed, a pressing portion which presses and seals the second pipe, and a protecting portion which protects the pressing portion.

Provided is a hose including a first connector assembly including a regulator assembly, a second connector assembly, and a hose assembly coupled to the first and second connector assemblies. The hose assembly includes an inner hose member having first and second ends, an outer hose member having first and second ends, a first hose connector assembly coupled to the first ends of the inner hose member and outer hose member and the first connector assembly, and a second hose connector assembly coupled to the second ends of the inner hose member and outer hose member and the second connector assembly.

A coupling nut (108) for joining a pair of conduits (104, 106) is provided. The coupling nut includes a first end (124) and a second end (126). An opening extends between the first end and the second end. The opening has an interior surface. A first coupling nut thread (114) extends along the interior surface at the first end and is constructed and arranged to receive a first conduit thread (110) having a first length (L1). A second coupling nut thread (116) extends along the interior surface at the second end and is constructed and arranged to receive a second conduit thread (112) having a second length (L2). A non-threaded central portion (118) extends between the first coupling nut thread and the second coupling nut thread. The non-threaded central portion (118) has a third length (L5). The third length (L5) of the non-threaded central portion is less than the sum of the first length (L1) of the first conduit thread and the second length (L2) of the second conduit thread.

A threaded joint for oil well steel pipe is provided. The threaded joint includes a pin provided with a male thread, and a box provided with a female thread threadedly engaged with the male thread, and at an outer periphery side sealing portion, a cross-sectional area S1 of the pin at a seal point, and a cross-sectional area S0 of a pipe body portion, which is an unprocessed pin portion, satisfy an expression (S1/S0)10015(%), at an inner periphery side sealing portion, a cross-sectional area S2 of the box at a seal point, and a cross-sectional area S0 of a pipe body portion, which is an unprocessed box portion satisfy an expression (S2/S0)10020(%), and a surface area S3 of a contact portion of an intermediate shoulder between thread rows and the cross-sectional area S0 satisfy the expression (S3/S0)10010(%).

A threaded connection comprising a pin connecting having dual tapered threads and a box connection having mating dual tapered threads. There is an internal torque shoulder in the box connection, the torque shoulder having a negative angled surface which mates with an angled surface on the nose of the pin connection. The pin connection has an external torque shoulder having a negative angled surface which is engaged and mates with a negative angled surface formed on the face of the box connection.

In a threaded connection for pipe with a two-step thread construction, including intermediate shoulders, during stabbing, the internal-pressure sealing surface of the pin near its tip is prevented from contacting the intermediate shoulder of the box and thus receiving damage. L.sub.P, L.sub.B, h.sub.P and h.sub.B shown in FIG. 2 satisfy Expressions (1) and (2), provided below. ?.sub.seal is the angle of slope of the straight line connecting the two ends, as determined along the axial direction, of the internal-pressure sealing surface of the pin. Expression (3), provided below, is also satisfied.
L.sub.P<L.sub.B(1)
h.sub.B<h.sub.P(L.sub.B?L.sub.P)?tan ?.sub.seal(2)
L.sub.SP<L.sub.B?L.sub.P(3)

A pipe assembly includes a first pipe, a second pipe, and a collar. The first pipe has a first external thread and a first rim that has a bearing surface. The second pipe has a second external thread and a second rim that has a bearing surface. The collar is threadedly coupled to the first pipe and the second pipe to form a threaded connection. The collar has a first internal thread that corresponds with the first external thread, and a second internal thread that corresponds with the second external thread. The collar has an inwardly-projecting annular shoulder residing between the first internal thread and the second internal thread. The shoulder has two bearing surfaces that face away from each other and each bear, with the threaded connection formed, against a respective one of the bearing surfaces of the first and second rims.