Robotic Mechanisms – BEVEL Gears 51035
This class of gears includes the most common straight and spiral bevel gears as well as miter and hypoid gears.
Bevel & Miter Gears Properties: a gear having teeth cut on the body, perpendicular to the axis of rotation
» Gear teeth are placed conically on the body
» Miter is a special type of bevel gear, whose dimensions are identical to its mating part (equal size gears)
» Designed to transmit motion & power between right angle shafts (90°, intersecting), which rotates in the opposite direction
» Durable & ideal for high load applications
» Plastic, brass, steel, & aluminum are the materials generally used for manufacturing
» Hand drills, printers, automobiles, locomotives, elevators & blowers are just a few everyday machines where bevel gears are used
» Bevel gears are also used in machine tools, material handlers, conveyors, cooling towers, power plants, rotorcrafts & marine applications
Note: in order for bevel gears and miter gears to work together (mesh) they must have the same diametral pitch (pitch), pressure angle (PA) & face width
STRAIGHT BEVEL GEARS
Straight bevel gears are the simplest bevel gears. Their straight teeth produce instantaneous line contact when they mate. These gears provide moderate torque transmission, but they are not as smooth running or quiet as spiral bevel gears because the straight teeth engage with full-line contact. They permit medium load capacity.
A bevel gear is shaped like a right circular cone with most of its tip cut off. When two bevel gears mesh, their imaginary vertices must occupy the same point. Their shaft axes also intersect at this point, forming an arbitrary non-straight angle between the shafts. The angle between the shafts can be anything except zero or 180 degrees. Bevel gears with equal numbers of teeth and shaft axes at 90 degrees are called miter gears.
SPIRAL BEVEL GEARS
Spiral bevel gears have curved oblique teeth. The spiral angle of curvature with respect to the gear axis permits substantial tooth overlap. Consequently, the teeth engage gradually and at least two teeth are in contact at the same time. These gears have lower tooth loading than straight bevel gears and they can turn up to 8 times faster. They permit high load capacity.
Miter gears are mating bevel gears with equal numbers of teeth used between rotating input and output shafts with axes that are 90° apart.
Hypoid gears are helical bevel gears used when the axes of the two shafts are perpendicular but do not intersect. They are commonly used to connect driveshafts to rear axles of automobiles, and are often incorrectly called spiral gearing.
Hypoid gears resemble spiral bevel gears except the shaft axes do not intersect. The pitch surfaces appear conical but, to compensate for the offset shaft, are in fact hyperboloids of revolution. Hypoid gears are almost always designed to operate with shafts at 90 degrees. Depending on which side the shaft is offset to, relative to the angling of the teeth, contact between hypoid gear teeth may be even smoother and more gradual than with spiral bevel gear teeth. Also, the pinion can be designed with fewer teeth than a spiral bevel pinion, with the result that gear ratios of 60:1 and higher are feasible using a single set of hypoid gears. This style of gear is most commonly found driving mechanical differentials; which are normally straight cut bevel gears; in motor vehicle axles.
Bevel Gears TECHNICAL DETAILS
Download This PDF – 51035-Bevel-Gears-Technical-Details.pdf
BEVEL GEAR VIDEOS
Spiral Bevel Gear
How Differential Gears Work – Basic Principles
An excellent tutorial from the 1930’s on the principles and development of the Differential Gear. Fast Forward to 1:50 if you want to skip the intro.
Car Differential With BEVEL GEARS
Bevel Gear Coupling