GB1489289A - Gearbox - Google Patents

Abstract

1489289 Twin-screw extruder drive PLAST-UND ELASTVERARBEITUNGSMASCHINEN - KOMBINAT KARL - MARX STADT VEB 22 May 1975 [18 June 1974] 22308/75 Heading B5A [Also in Division F2] In a torque-dividing gear transmission, which may be used to drive a screw shaft of a doublescrew extruder, a driving pinion 2 secured to an input shaft 1 on a fixed axis in a gear-box 20 is meshed bilaterally with two idler wheels 7 and 9, which each mesh with another idler wheel 13, 11, respectively, and an output shaft 14, also on a fixed axis in gear-box 20, carries a pinion 15, meshed bilaterally with the two idler wheels 13 and 11, so that partial torques are transmitted to the output shaft 14 through the parallel paths formed by the two pairs of idler wheels 7, 13 and 9, 11 respectively. In one embodiment the four idler wheels 7, 9, 13 and 11 having shafts 6, 8, 12, 10, are together carried by a movable rocker frame 5, Fig. 3, which is retained in a floating relationship to the gear-box 20 by struts 24 with hinge joints 22, 23. In another embodiment, Fig. 2 (not shown), a similar rocker frame 5 is retained in a floating relationship by parallel guideways (21) in the walls of gear-box 20. In use, the frame 5 becomes subjected to reaction forces derived from the circumferential forces present at each point where idler wheels and pinions intermesh, whereby a self-adjusting displacement of frame 5 occurs, until the partial torques in the two paths become equalized. In an alternative embodiment, Fig. 1, idler wheels 9, 11 are carried on a rocker arm 3, and wheels 7, 13 are carried on a separate rocker arm 4, with arm 3 together with shaft 8 being rotatable about one fixed axis in gear-box 20, and arm 4 together with shaft 12 being rotatable about another fixed axis, while arms 3 and 4 are linked together by a strut 18 having an adjustment member 19 and hinge joints 17. In use, arm 3 is subjected to reaction forces derived from circumferential tooth forces acting on wheel 11, and arm 4 to reaction forces related to wheel 7, whereby a joint self-adjusting displacement of the arms 3 and 4 occurs, until the partial torques become equalized. The balanced nature of the output drive torque avoids asymmetric radial loading of the shaft 14, thus permitting a compact assembly in which the bearings of shafts 1 and 14 may be of small dimensions, and a second independent output shaft 16 may be located close to shaft 14, e.g. for driving a second screw shaft in a double-screw extruder.