Simple low-cost mechanical transmission for accommodating variable loads

In a transmission, the combination of a driving input shaft, a driven output shaft, a first gear loosely mounted upon the driving input shaft and coupled thereto by a slip clutch having a predetermined torque release, a second gear carried by the driven output shaft, keyed thereto for rotation in unison, and meshing with the first gear, the first gear being larger than the second gear, thereby providing a first step-up gearing having a rotational speed increase, a third gear carried by the driving input shaft and keyed thereto for rotation in unison, and a fourth gear loosely mounted on the driven output shaft, coupled thereto through a one-way bearing, and meshing with the third gear, the third gear being smaller than the fourth gear, thereby providing a step-down gearing having a rotational speed reduction;

• such that at a relatively-light load imposed upon the driven output shaft, the slip clutch does not slip, and the drive is through the first step-up gearing while the third and fourth gears of the step-down gearing are idling;
• and such that at a relatively-heavy load imposed upon the driven output shaft, the slip clutch automatically releases at a predetermined torque, and the drive is through the third and fourth gears and the one-way bearing of the step-down gearing for reduced speed of rotation of the driven output shaft, and thereby providing increased torque for the driven output shaft to meet the demands of the relatively-heavy load.