Mechanical drives are used to transmit motion, torque and power from a driver shaft to powered shaft. The driver shaft, in most the cases, is part of prime mover (such as for example electric motor, hydraulic turbine, steam turbine, etc.); while, the driven shaft is part of the machine unit. There exist four fundamental mechanical drives, namely equipment drive, belt drive, chain drive and rope drive. A gear drive is 1 engagement type rigid drive where movement and power are transmitted by means of successive engagement and disengagement of tooth of two mating gears. It really is inherently free from slip and this it provides continuous velocity ratio (positive drive). It can be used for light duty applications (such as toys, watches, etc.) aswell as for heavy duty applications (such as for example gear package of machinery, marine drive, etc.).
Driver and driven shafts may have three mutual orientations, namely (i) parallel shafts, (ii) intersecting shafts and (iii) nonparallel nonintersecting shafts. There can be found four simple types of gears and the right gear ought to be selected predicated on the mutual orientation of the driver and driven shafts. Spur gear and helical gear are applicable for parallel shafts. Bevel gear can be requested two intersecting shafts, which might not always be perpendicular. Worm gear arrangement is used for the third category (nonparallel non-intersecting shafts). Unlike spur gears that have straight teeth parallel to the gear axis, helical gears have the teeth in helical form that are cut on the pitch cylinder. Although helical gears are generally utilized for parallel shafts like spur gears, it can also be used for perpendicular but nonintersecting shafts.
Accordingly presently there are two types of helical gears-parallel and crossed. Parallel helical gears, the common one, can be used to for power transmitting between parallel shafts. Two mating parallel helical gears must have same module, same pressure position but opposite hands of helix. They offer vibration-free and quiet procedure and will transmit heavy load. On the other hand, crossed helical gears are utilized for nonintersecting but perpendicular shafts. Two mating crossed helical gears (also known as screw gears) must have same module, same pressure position and either same or reverse hand of helix. This kind of gear has application similar to worm gear; however, worm equipment is favored for steep speed reduction (1:15 to at least one 1:100), whereas crossed helical gears cannot offer quickness reduction beyond 1:2. Various differences between parallel helical equipment and crossed helical equipment receive below in desk format.