A
universal joint between adjacent, electrically connected instrument housings for downhole well operations allow the connected housings to bend longitudinally as required to
traverse an arced section of a well bore but does not permit relative elongation or twisting about the longitudinal axis of the housings. I one embodiment, a fluid impermeable open passage space at
atmospheric pressure surrounds electrical
signal carriers linking the instrument circuitry within the two housings. The passage is constructed as a high-pressure flexible
bellows or as a braided or
spiral wound high-pressure fluid hose. In another embodiment, a fluid impermeable sheath surrounds the
signal carriers and encapsulates the
signal carriers by a resilient
solid. The articulation structure comprises a Cardan-type of
universal joint wherein two fingers project longitudinally from the end of each of the housings. The fingers are meshed and pivotally joined to respective spindles projecting radially from the open center of a ring spyder. The protective
bellows, hose or resilient compound filled sheath is secured at opposite ends to bore plugs in the respective instrument housings. Between the instrument housings, the hose,
bellows or filled sheath passes through the open center of the spyder ring.