#quickreturnmechanism #planer #specialmachines
Planer Quick Return Mechanisms:
To move the planer table faster during the return stroke, the following quick return mechanisms are used.
1. Belt drive
2. Electric drive
3. Hydraulic drive
Belt drive:
 This drive is used for smaller planers. An electric motor is used to drive a countershaft, it is placed under the table.
 The shaft has two larger pulleys of the same diameter and one smaller pulley. The open belt is connected to one pulley and the cross belt is connected to another pulley.
 The driving pinion is fitted to the one end of the shaft. One of the smaller pulley and one larger pulley is keyed to the shaft. They are called fast pulleys.
 The other two pulleys rotate freely on the shaft. They are called loose pulleys.
 Driving shaft speed can be reduced by using a speed reduction gearbox. The driving pinion meshes with the rack provided at the bottom of the table.
 The table reciprocates when the pinion rotates. The position of the open belt and cross belt is changed by a belt shifter.
 During the return stroke, the cross belt is connected to the larger loose pulley and the open belt is connected to the smaller fast pulleys.
 At the end of the return stroke, the trip dog pushes the belt shifter and both the belts are shifted to the right. Now cross belt connects the larger fast pulley and the open belt connects the smaller loose pulley.
 Next, the drive is transmitted to the main shaft through the cross belt on the larger fast pulley. Due to this, the direction of rotation of the main shaft is reversed.
 Due to the larger diameter of the pulley, the speed of the main shaft is reduced. So, that the table moves slowly during the cutting stroke.
 Both the belts are shifted to the previous position by another trip dog at the end of the cutting stroke. Thus the return stroke and cutting stroke are obtained successively.