Scoop-controlled fluid couplings

A fluid coupling, comprising coaxially supported impeller and runner elements which are independently rotatable about a coupling axis, each said element being in the form of a dished shell having vanes and said elements together defining a working circuit for a working liquid, an impeller casing supported on said impeller element for rotation therewith and extending around said runner element so as to define a fluid-flow space between said impeller casing and the exterior surface of said runner element, a reservoir for holding working liquid at a location outside said working circuit, leak-off means for defining a restricted flow path from said working circuit to said reservoir, and means for controlling the volume of liquid in said reservoir and for collecting surplus liquid from said reservoir and supplying said surplus liquid to said working circuit, wherein the outer profile diameter of said runner element is from 5 to 15% less than the outer profile diameter of said impeller element, the radially outermost part of said shell of said impeller element lies radially beyond said runner element, said runner element has angularly spaced holes through its shell in the region thereof having the greatest axial width, said holes communicating directly with said space, and said radially outermost part of said impeller element communicating through said space with said holes in said runner element so that working fluid which flows from the working circuit through the holes then flows through the space and can communicate with the working circuit through the radially outermost part of the impeller element.

In a scoop-controlled fluid coupling which includes:

• an impeller and a runner which are supported coaxially with respect to and for independent rotation about a coupling axis, said impeller and runner each being a dished shell having plural angularly spaced vanes and together defining a working circuit for a working liquid;
• an impeller casing supported on said impeller for rotation therewith;
• a reservoir casing rotatable with said impeller for holding a quantity of the working liquid radially outside said working circuit;
• and means which includes a radially movable scoop having a scooping tip adjustable to different radial positions in said reservoir casing for collecting liquid from a rotating ring of the liquid held in said reservoir casing and for supplying it to said working circuit, from which the working liquid can return to said reservoir casing through a restricted outlet;
• the improvement comprising means for preventing any significant increase in the torque transmitted during prolonged acceleration of the coupling due to thermal expansion of the working liquid, said means including the outer profile diameter of said runner being from 5 to 15% smaller than the outer profile diameter of said impeller and the radially outermost part of said impeller lying radially beyond said runner, said impeller casing extending around said runner and projecting inwardly so as to radially overlap the exterior side of the runner to define a space therebetween, said space communicating with the radially outermost part of the impeller, said runner having first and second sets of holes provided through said shell thereof for direct communication with said space, the centres of said holes of said first set being spaced from said coupling axis by a distance in the range of 53 to 63% of the outer profile radius of said runner, and the centres of said holes of said second set being spaced from said coupling axis by a distance in the range of 65 to 75% of the outer profile radius of said runner, said holes in said runner communicating with said radially outermost part of said impeller through said space as provided between said impeller casing and said runner.