GB1529569A - Power drive transmission assembly - Google Patents

Abstract

1529569 Expanding pulley gear; changespeed control E F SALSBURY 19 Nov 1975 [20 Nov 1974 5 Nov 1975] 47624/75 Heading F2D In a transmission comprising two expanding pulleys interconnected by a Vee belt the transmission ratio is varied by electrically energizable means which adjusts an axially movable half of one pulley relatively to the other half. In one embodiment comprising a driving pulley F, Fig. 2, on the output shaft 12 of an internal combustion engine C coupled by a belt 14 with a spring-loaded driven pulley H, a screw-and-nut actuator 76, 66 for adjusting the movable half F-2 is controlled by a photoelectronic system which causes the adjustment to be responsive to a comparison between the speed of the driving pulley and the spacing between its two halves in order to provide substantially constant torque at the driven pulley over part of the speed range of the engine, e.g. between 5,500 and 10,500 r.p.m. Affixed to a sleeve 26 of the movable pulley half is a strip M-1 of material having a pattern, shaped to suit the engine characteristics, of generally triangular sections of light-reflecting and non-light-reflecting areas N-1, O-1, Fig. 9, and a beam from a light-emitting diode 132 is reflected by the areas N-1 on to a photoconductive transistor U. The output from the transistor is amplified at 138 and converted to square-wave form by a Schmidt trigger 140, after which the circuit divides, one branch passing through a monostable multivibrator 142 and low-pass filter 144 to deliver a voltage B related to the speed of the pulley and the other branch passing through a low-pass filter 154 and inverter 156 to deliver a voltage A related to the position of the movable pulley half. These two voltages, of opposite polarity, are fed to a summer 158 and when they do not cancel each other a signal is fed via power buffer 160 to a linear actuator X consisting of a motor which, through a belt and pulleys, one of which is shown at 80, Fig. 2, rotates the screw 76 to adjust the movable pulley half. An hydraulic telemotor may be interposed between the screw and the movable pulley half. Alternative forms of actuator employ hysteresis and eddy-current brakes. In another embodiment a pulley on the output shaft of a constant speed electric motor is controlled to vary the transmission ratio in response to a manual command, means also being provided to prevent overloading of the motor. A further embodiment functions to provide a constant output speed from a transmission driven by a variable-speed prime mover.