Abstract: The two endless screws (202, 203) and the four gear wheels (207, 209-307, 309) which mesh with the endless screws and with each other in pairs, have inclined teeth in opposite directions at an angle a, while the secondary gear wheels (210, 310) fixed in rotation with two respective ones of the gear wheels (209, 309) have teeth inclined at an angle b such that tan a/tan b=D1/D2, where D1 is the pitch diameter of the gear wheels and D2 is the pitch diameter of the secondary gear wheels. The secondary gear wheels (210, 310) mesh with tertiary gear wheels (213, 313) which are fixed on an intermediate shaft (315) which bears a gear wheel having straight teeth and forming part of an outlet reduction stage.

Abstract: A motor-reduction gearbox combination has the driven shaft output gear on the floor of the casing and below the driving shaft which is perpendicular to the driven shaft. The drive shaft has two multi-start corner screw portions of opposite hand and preferably of equal arithmetic pitch, to be engaged by respective pinions. Each pinion forms part of a respective double gear unit by being fixed to, or more preferably formed integrally with, a gearwheel meshing with the driven shaft output gear. For each double gear unit, the ratio of the number of teeth on the gearwheel to the number of teeth on the pinion is equal to the number of thread starts of the associated worm screw portion of the driving shaft, and in the preferred case the double gear units both have the same such ratio.

Abstract: A reduction gear comprises a parallelepiped-shaped casing containing a double worm input shaft engaging with two pinions. The input shaft has its worm portions of equal pitch magnitude but of opposite hand and the engaging pinions are one on each side of the shaft. Alternative positions are provided for the two pinions to enable the direction of rotation of the output shaft to be reversed. Each pinion carries an integral spur gear engaging a common ring gear on which the output shaft is carried. There is a square cover to the casing of the reduction gear and this cover has three bosses for use in mounting the reduction gear on a support frame.