Abstract: An adjustable viscous shear coupling comprises a housing containing a viscous fluid therein, an inner part such as a shaft extending into the housing, a set of outer disks non-rotatably connected to the housing, a set of inner disks non-rotatably connected to the inner part, the inner disks and the outer disks being interleaved so that adjacent disks are separated by a gap, and an axially movable piston which acts on the disks to adjust the width of the gaps. The adjustable viscous shear coupling is constructed so that sealing intervals are formed between the outer disks and the inner part and between the inner disks and the housing so that the overflow of viscous fluid from one gap to another is greatly inhibited. In a preferred embodiment, the adjustable viscous shear coupling includes inner choke elements disposed between the outer disks and the inner part, and outer choke elements disposed between the inner disks and the housing, the choke elements creating the sealing intervals.

Abstract: An adjustable viscous shear coupling suitable for use in a high performance four-wheel drive vehicle comprises a housing containing a viscous fluid therein, a shaft extending into the housing, a set of outer disks non-rotatably connected to the housing, a set of inner disks non-rotatably connected to the shaft and interleaved with the outer disks, and an axially movable pressure piston which bears against the disks and adjusts the gap width between the inner and outer disks. One of the sets of disks is provided with frictional linings. The disks are brought to bear against each other in a controlled manner so that torque can be transmitted therebetween in a smooth, hump-less manner by a combination of frictional engagement and viscous shear.

Abstract: A liquid friction coupling comprises a housing that contains a viscous liquid, a shaft protruding into said housing, alternating and interdigitating inner and outer blades, which are axially slidably and non-rotatably connected to the shaft and to the housing, respectively, annular expanding springs, which extend between adjacent inner blades or outer blades, and an annular piston, which is sealed in the housing and axially displaceable therein and is operable from the outside and arranged to act on the blades in order to change the blade spacing. In order to increase the range in which the blade spacing can be controlled and possibly to permit the coupling to be used as a clutch coupling, the volume of the viscous liquid which is contained in the housing equals the total volume of the free spaces in the housing outside the outer periphery of the inner blades when the piston is in the position which corresponds to the largest blade spacing.