Hand wheels and manually operated drives in assembly machines

        Some high speed assembly machines have a main driving shaft which is transferring the movement to the subassemblies through various mechanical components like cams, gears, sprocket gears, linkages and others. This shaft (usually is called the camshaft) is driven by a motor reducer, at adjustable rotating speed. The rotation speed can be adjusted at low RPM but during assembling, anti-jamming operations and machine adjustments there is a need for more “sensitive” control. Due to the nature of the movements (precise) and of the moving components, and for safety reasons it is impossible to work when the machine is driven by motor. The solution is to mount a hand wheel on the cam shaft and to have a motor reducer with a brake. During the various operations (described before) we have the brake released and then we rotating the cam shaft through the hand wheel. Through the manual rotation we have a better feeling of the machine, and we can rotate the cam shaft even with the smallest rotation angle. If the driven components of the machine produce a great resistance and it is impossible to rotate them (internal power losses), we can use a pair of spur wheels. With a pair of spur wheels we create a single stage gear reducer in order to increase the applying torque. The pinion gear and the hand wheel are mounted on a cylindrical part whilst the driven spur gear is mounted on the cam shaft. This cylindrical part is mounted by its two bushings (or bearings) on the pivot shaft. The pivot shaft is parallel to the cam shaft and at specific center distance corresponding to the pair of gears. A light compression spring constantly forces the hand wheel and the pinion to be disengaged with the driven spur gear. In other case the hand wheel will rotate when the machine is working. When we want to manually rotate the machine, we push the hand wheel in order to engage the gears, and then we rotate the hand wheel. Another basic detail of this design is the material of the spur gears. Attention, during machine operation the operator may accidentally engage the two gears, for this reason the gears must be made of non-metallic material, usually plastic (ertallon, delrin). This is necessary in order not to cause any damage to the operator and the machine. The two spur gears are easy to change although usually it is difficult to wear them out.