Gears Drive

Automatic transmission is the most complicated component in today's automobile. Automatic transmissions contain mechanical systems, hydraulic systems, electrical systems and computer controls, all working together in perfect harmony. There is no clutch pedal and gearshift in an automatic transmission.

Bevel gear drive is a transmission which is used to drive one or more shafts which do not line up with the output shaft. It is also called bevel gear transmission. They are capable of handling heavy loads and offer higher torque. They transmit engine power smoothly onto the main clutch pulley. The bevel gear housing absorbs loading of the power band and enables the use of a short power band. Hydrostatic drive pump, hydraulic main pump and hydraulic infinitely variable length of cut-pump are flanged to a new carrier housing, adding more reliability.

Combination drive is an arrangement where a right angle gear drive is connected to the horizontal power source, providing a stand over the gear drive for mounting the vertical power source.

Combination drives are easiest to use, simplest to understand and provide high performance. They are widely used in computer industry to play and burn CDs and play DVDs. They deliver the function of two drives for a low price. They help to store move and share large amounts of data on CDs with the similar ease and convenience. They save both time and money. These drives are an asset to the mobile PC users.

Cycloidal drives combines a compact cycloidal input gear set with a slow speed helical output gear set to provide an extremely efficient, quiet and durable gearbox. It consists of high-speed shaft with eccentric bearing assembly and a slow-speed shaft assembly. It also has cycloid discs with one less lobe than the ring gear pins. The ring gear roller and pins are fixed.

The term cycloidal is derived from hypocycloidal, which is defined as the curve traced by a point on the circumference of a circle that is rotating inside the circumference of a larger fixed circle. A common example of this is the path traced by a tooth of a planetary pinion rotating inside a ring gear.

These are set of gears with three independent, rotating members with a speed and torque relationship to each other. There are two application types:

• First consists of one input and two outputs. The automobile differential is the best example here. The two outputs are connected mechanically.
• Second application has two inputs and one output. This is used to solve industrial problems when the superimposition of one motion relative to another is required, such as phase shifting on textile industry equipment.

Differential efficiency is a function of the relative speed of the three elements. As relative speed increase, the inherent losses due to basic gear efficiency, seals, and bearings also increase; thus efficiency decreases.

Epicyclic gear drive illustrates motion of a gear train consisting of a 60-tooth sun gear and arm carrying a 24-tooth planet gear riding extremely on the sun gear. Epicyclic motion is the path traced on a fixed end plate by a scribing point attached to the planet gear.

An epicyclic drive has its planet gears integrated into separately built planet assemblies. Each planet assembly includes a pin which extends through the planet gear and an antifriction bearing located between the gear and the pin. The bearing also has rolling elements organized in two rows between the inner and outer raceways. The pins have mounting ends which lie beyond the ends of the planet gear to anchor the planet assembly in a carrier. Seals fit into the planet gear and around the pin and retain grease within the bearing and prevent oil that lubricates the teeth from entering the bearing and deteriorating the grease. The bearing is set with considerable precision so the planet gear does not skew with respect to sun and ring gears with which it meshes during operation at the epicyclic drive.

This is a mechanical speed changing device, invented in 1950s, that operates on a different principle form, and has capabilities beyond the scope of, conventional speed changers. They consist of a thin ring that deflects elastically as they roll on the inside of a slightly larger rigid circular ring.

The basic elements of harmonic drive are circular spline, flexspine, and wave generator, all assembled in a normal configuration. As the wave generator rotates, it imparts a continuous motion to the flexspline. This causes meshing of the external teeth of flexspine with internal teeth of the circular spline. The meshing moves in a rolling fashion. It allows for full tooth disengagement at the two point along the minor axis of the wave generator. Flexspline has two teeth less than circular spline, so each complete revolution of the wave generator causes a two-tooth displacement of the flexspline in relation to the circular spline. This displacement is in the opposite direction. This way harmonic drive works as a speed reducer.

A helical gear drive is an improvement over straight cut spur gear because the number of teeth meshing together is increased providing more averaging of the gear errors. This is a drive with the steel helical gears close coupled to the fold rolls providing solid reliability. A positive gear drive assures no slippage between fold rolls for more consistent folds.

Helical gear drive can be single or double. In a single gear drive each shaft is always against the thrust bearings. The external axial thrust that acts on the gear shaft under load due to the friction in the tooth coupling, cannot cause momentary overloading of one helix as is the case with double helical gears. An external thrust can have some detrimental effects on a double helical gear in connection with axial compensating shift due to tooth errors.