Patent GB-1100943-A (GB)
Title: Variable torque fluid coupling
IPC: F16D35/02
Filed: 1965-03-12
Abstract: 1,100,943. Hydraulic couplings. SCHWITZER CORPORATION. 12 March, 1965 [18 March, 1964], No. 10495/65. Heading F2C. [Also in Division F1] In a fluid coupling for driving an engine cooling fan, wherein torque is transmitted by shear in a liquid film in a working chamber 28 formed between adjacent faces of a driving rotor 23 on an input shaft 17, and a casing 10, 11 rotatable on the shaft 17 and carrying the fan, the amount of slip is controlled by means responsive to the speed of the shaft 17 (Figs. 3, 4-not shown), or to the temperature of cooling air (Figs. 6,8-not shown), engine coolant (Fig. 7-not shown), or coupling fluid (Fig. 1 or Figs. 5, 9-not shown), which governs the distribution of fluid between the working chamber 28 and a reservoir 27 formed within the rotor 23. In Fig. 1, a bimetallic strip 36 secured at one end to the rotor 23 has at its other end a boss 33 adjacent an opening (34a), (Fig. 2-not shown) in the wall 26 of the rotor. With the strip 36 in the maximum temperature position shown, the boss lies flush with the outer surface of the wall 26. A reduction in the coupling fluid temperature causes the boss 33 to be raised into the film between the wall 26 and the plate 10 to act as an impact pump forcing fluid from the working chamber 28 into the reservoir 27, increasing the slip. A calibrated orifice 35 in the rotor allows a continuous flow from the reservoir to the working chamber, a return flow to the reservoir entering round the inner periphery of the wall 26. The outer faces of the rotor 23 have chordal slots (31, 32), (Fig. 2-not shown), and the casing 11 carries cooling fins 21. The strip 36 may alternatively be reversed, so that the boss 33 pumps fluid out of the reservoir 27 on a decrease in fluid temperature. In Figs. 3 and 4 (not shown) the bimetallic strip 36 is replaced by a spring strip (41) carrying a mass (42) intermediate its ends, so that above, or alternatively, below a predetermined rotor speed, the boss (33) is moved out to pump fluid from the working chamber into the reservoir. In Fig. 8 (not shown), a bimetallic strip (51f ) mounted externally on the casing wall (10f) acts through a piston on a spring strip (71) carrying the boss (72), to control the pumping action of the latter in accordance with external air temperature. In Fig. 6 (not shown), the arrangement of Fig. 8 is modified in that the spring strip (52) controls the opening of an aperture (53) in the wall (26d) of the rotor, and the orifice (35) is replaced by an impact pump comprising a stud (56) in a bore (54) through the wall (26d), urged against the plate (10d) by a spring (57), an aperture being provided adjacent the stud (56) through which fluid is continuously pumped into the reservoir. In Fig. 7 (not shown) a spring strip (63) carrying a boss (33e) is acted upon by a push-rod (62) moved by a temperature responsive element (66) mounted in the eye of an engine coolant impeller (68) to sense coolant temperature. In Fig. 9 (not shown) the easing (71) is rotatably supported on the rotor periphery (24g) by the film of fluid thereon, instead of being mounted on the shaft (17) by a ball bearing.