here's an explanation......I don't know if this is the right term but at least you can read about couplers

Why a Flexible Coupling?
A flexible coupling connects two shafts, end-to-end in the same line, for two main purposes. The first is to transmit power (torque) from one shaft to the other, causing both to rotate in unison, at the same RPM. The second is to compensate for minor amounts of misalignment and random movement between the two shafts. Belt, chain, gear and clutch drives also transmit power from one shaft to another, but not necessarily at the same RPM and not with the shafts in approximately the same line.

Such compensation is vital because perfect alignment of two shafts is extremely difficult and rarely attained. The coupling will, to varying degrees, minimize the effect of misaligned shafts. Even with very good initial shaft alignment there is often a tendency for the coupled equipment to "drift' from its initial position, thereby causing further misalignment of the shafts. If not properly compensated, minor shaft misalignment can result in unnecessary wear and premature replacement of other system components.

In certain cases, flexible couplings are selected for other protective functions as well. One is to provide a break point between driving and driven shafts that will act as a fuse if a severe torque overload occurs. This assures that the coupling will fail before something more costly breaks elsewhere along the drive train. Another is to dampen torsional (rotational) vibration that occurs naturally in the driving and/or driven equipment.

Each type of coupling has some advantage over another type. There is not one coupling type that can "do it all". There is a trade-off associated with each, not the least of which can be purchase costs. Each design has strengths and weaknesses that must be taken into consideration because they can dramatically impact how well the coupling performs in the application.


could be: break-point coupling

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Note added at 1 hr 50 mins (2005-09-02 19:11:45 GMT)
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OK

I think it is:

misalingnment couplers


now that makes sense! In light of the above article!

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Note added at 1 hr 50 mins (2005-09-02 19:12:06 GMT)
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Final: misalingnment couplers

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Note added at 1 hr 55 mins (2005-09-02 19:16:33 GMT)
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More about this:

Couplers
Shaft misalignments are unavoidable due to fabrication tolerances.Common shaft misalignment problems include parallel, angular, and endfloat misalignment.
Parallel misalignment is the offset of two shaftcenter lines where the center lines remain parallel to each other.
Angular misalignment occurs when the shaft center lines are not parallel, butintersecting at some angle not equal to 0°.
End float misalignment is a variance in the relative distance between the ends of the two shafts.Couplings can help you accommodate these misalignment problems whilemaintaining desired torque. Several coupling types are available.t
Single-flext
Double-flextRigidA single-flex coupler will correct only for angular misalignment while adouble-flex handles both angular and parallel problems. Depending upontheir design both types may or may

That seems to be it....

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Note added at 1 hr 55 mins (2005-09-02 19:17:10 GMT)
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Final: misalignment couplers [for drives shafts]

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Note added at 2 hrs 45 mins (2005-09-02 20:06:35 GMT)
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mine is wrong..I was thinking about parts