Planer Reversible Motor with Rack and Worm
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Planer Reversible Motor with Rack and Worm
Planer Reversible Motor with Rack and Worm - This system is commonly used on modern planers as it provides a wider range of table speeds and a better control. Most planers are driven direct by a coupled motor in place of the old method of open and crossed belt drive.
The reciprocating motion of the planer table is obtained by driving through a worm on to a rack attached to the length of the underside of the table (Fig.). The reversal of the drive for cutting and return strokes is obtained in most cases, by reversing the motor itself either by field or phase changing.
Reversible Motor Drive with Rack and Worm Arrangement
| A - Driving Motor | E - Worm shaft entering machine bed at an angle | I - Worm |
| B - Flexible Coupling | F - Table | J - Bed of Machine |
| C - Worm | G - Table Rack | K - Worm wheel |
| D - Column | H - Shaft supported in bearing both sides of worm | L - Box shown broken to expose drive |
The main driving motor may be fed with a variable voltage ,direct current of reversible polarity from a special motorgenerator set which forms part of the equipment of the planer.
Special types of motors and control gear are incorporated to ensure a rapid but controlled reversal, as well as a steady acceleration which is necessary in order to avoid a sudden impact upon the tools as they commence their cut.
The operation of the control unit is effected and timed automatically by a mechanism actuated by the table traverse. In one mechanism, the trip cams are carried on the table itself and are set to actuate the switch gear through a rocking lever. Trips are mounted on one side of the planer table with a gap between them equal to the stroke length.
At the end of each stroke the trip operates the switch which causes the driving motor to rotate in the opposite direction thereby causing the planer table to reverse.
Another tripping arrangement employs the principle of attaching the trips to a circular flange whose revolving movement synchronises with the longitudinal motion of the table.
As compared to mechanically belt driven planers, electrical drive has certain definite advantages large number of cutting and return speeds can be obtained higher return speeds are possible and the control is quick accurate and more responsive.
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