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Perhaps best directed at Phil, but posted to the list in case anyone
is interested: I was looking at some of the old ADS suit joint patents, and I noticed that the old Nuytten patent (CA 1296032) describes a degree of freedom in axial alignment of 1.5 - 3 degrees per joint. By inspection, it appears that this is the result of the movement of lower member 2 in this patent, although I could be mistaken. In any case, this permissible misalignment is touted as a design advantage in the patent, although it is not clear whether this allowable flex is by design intent, or merely an unintended consequence of the assembly. In the subsequent Humphrey patent (CA 2485908), this degree of freedom is characterized as undesirable, and indeed the joint described in this patent specifically attempts to eliminate it and establish axial rigidity, in an attempt to prevent any bending load on the joint from causing seal leakage. Intuitively this makes some sense, although the Nuytten patent describes a cumulative flexing ability of 18 degrees over a seven-joint conduit; this is not insignificant. I presume that this difference would need to be accommodated by adjusting the wedge angles and/or rotary limits of each joint such that the necessary range of motion of the operator is not impacted. I'm not entirely sure what I'm asking here - other than to get some idea of whether flex is an important design objective, or whether it is simply the result of holding looser assembly tolerances than a design using fully rigid joints which relies upon joint rotation exclusively? -Sean |