Threaded coupling assemblies for interconnecting fluid-carrying conduits

A threaded coupling assembly for interconnecting fluid-carrying conduit members, comprising

• a union having a fluid passage for passage of a fluid, an external tapered thread, and a receptacle;
• a machined tube end receivable in the receptacle of the union and having an internal passage for communicating with the fluid passage of the union, the tube end having a machined axially forward nose portion having a radially outer sealing surface that is configured to engage a radially inner sealing surface of the receptacle of the union, and the tube end having a machined radially outwardly protruding shoulder that is axially rearward of the forward nose portion;
• a coupling nut axially engageable with the shoulder of the tube end, the coupling nut being rotatable about the tube end and having an internal tapered thread for engaging the external thread of the union for securing the tube end to the union, wherein rotation of the coupling nut relative to the union causes the tube end to be forcibly drawn into the union from a partially assembled state to a fully assembled state for effecting a seal between the radially outer sealing surface of the tube end and the radially inner sealing surface of the union;
• and
• a pair of telescoping indicator rings respectively connected to the union and the coupling nut, the pair of telescoping indicator rings including a radially outer ring and a radially inner ring, the radially outer ring having at least one circumferentially extending window through which an arcuate segment of the radially inner ring can be viewed during relative of rotation of the union and coupling nut from the partially assembled state to the fully assembled state, the radially outer surface of the radially inner ring having over at least a first arcuate portion thereof a first visual characteristic contrasting with a second visual characteristic that extends over a second arcuate portion of the radially outer surface of the radially inner ring;
• wherein the shoulder of the tube end has an axially forwardly facing mating surface that is configured to interface with a mating face of the union to provide self-alignment of the respective tapered threads when the threaded coupling assembly is in the partially assembled state;
• wherein the first visual characteristic of the radially inner ring is circumferentially and axially aligned with and viewable through the window of the radially outer ring when the threaded coupling assembly is in the fully assembled state in which the seal is effected between the union and the tube end;
• and
• wherein the first visual characteristic of the radially inner ring is out of circumferential and axial alignment with the window of the radially outer ring when the threaded coupling assembly is not in the fully assembled state.