Variable speed belt drive systems

Claim 2

A variable speed belt drive system comprising a variable pitch diameter pulley (34) mounted on an input shaft (42), a variable pitch diameter pulley (30) mounted on an output shaft (40), an endless belt (38) received on said pulleys (30, 34), torque-responsive means (36) connected to the pulley (34) on the input shaft (42) to increase the effective pitch diameter of the input pulley (34) in response to an increase in load on said output pulley (30), and speed-responsive means (32) connected to the pulley (30) on the output shaft (40) to increase the effective pitch diameter of the output pulley (30) as the speed of the output shaft (40) increases.

Claim 3

A system as claimed in claim 1, wherein the system forms an accessory drive system of a motor vehicle, the input shaft (42) being connected to the engine (12) of the vehicle and the output shaft (40) being connected to an accessory.

Claim 4

A system according to claim 1 or claim 2, wherein the torque-responsive means (36) comprises a spring (126) which acts in compression to urge the pulley flanges (111, 120) of the input pulley (34) together and which acts intorsion to resist relative rotation between the pulley flanges ( lll, 120).

Claim 8

A system according to claim 1 or claim 2, wherein the torque-responsive means (36) comprises a first camming surface (106) rigidly secured to the input shaft (42), a second camming surface (116) mating with said first camming surface (106) and mounted ' for rotation with and for limited rotation relative to the input shaft (42) and being rigid with one of the flanges (111) of the input pulley (34), and a combination torsion spring and compression spring (126) connected for normally urging said one pulley flange (111) into close proximity to the other flange (120) and for torsionally preloading the said one pulley flange (111) in a direction opposite to the direction of rotation of the input shaft (42), the speed-responsive means (32) being effective to overcome the torque-responsive means (36) in response to the output shaft (40) being subjected to a normal torque load and being rotated at a speed in excess of a predetermined shifting speed at which time the first and second camming surfaces (106, 116) are effective to control rotative and axial movement of the said one pulley flange (111) relative to and away from the other pulley flange (120) against the urging of the compressive and torsional preload of the spring (126),the torque-responsive means (36) being effective to partially overcome the speed-responsive means (32) in response to the output shaft (40) being subjected to a higher than normal torque load and being rotated at a speed in excess of said shifting speed at which time the first and second camming surfaces (106, 116) are effective to control rotative and axial movement of the said one pulley flange (lll) relative to and toward the other pulley flange (120) aided by the compressive and torsional forces applied by the spring (126) and the higher frictional forces between the belt (38) and the said one pulley flange (111).