What Is Gear And Its Types

 What Is The Gear And Its Types...

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque. Geared devices can change the speed, torque, and direction of a power source. Geared devices can change the speed, torque, and direction of a power source. Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine. The teeth on the two meshing gears all have the same shape. Two or more meshing gears, working in a sequence, are called a gear train or a transmission.

Function Of Gear 

1. To increase torque from the driving equipment (motor) to the driven equipment  

2. To change the speed 

3. To change the direction of the rotating shaft 

According to direction of rotation of gear 

1. External Gear :- in the case of external toothing, the teeth  are directed outwords on the circumference. while the direction of rotation charges when the two externally toothed gears are used.

2. Internal Gear :- in the case of internal gears, the teeth are directed inwards on the circumference. an internal gear wheel is sometimes simply called a ring gear the direction of rotation remains the same when pairing with a internal gear.

Types Of Gear 

1. Spur Gear 

Parallel and co-planer shafts connected by gears are called spur gears. The arrangement is called spur gearing. Spur gears have straight teeth and are parallel to the axis of the wheel. Spur gears are the most common type of gears. The advantages of spur gears are their simplicity in design, economy of manufacture and maintenance, and absence of end thrust. They impose only radial loads on the bearings. Spur gears are known as slow speed gears. If noise is not a serious design problem, spur gears can be used at almost any speed.

2. Helical Gear

Helical gears operate more smoothly and quietly compared to spur gears due to the way the teeth interact. The teeth on a helical gear cut at an angle to the face of the gear. When two of the teeth start to engage, the contact is gradual--starting at one end of the tooth and maintaining contact as the gear rotates into full engagement. The typical range of the helix angle is about 15 to 30 deg. The thrust load varies directly with the magnitude of tangent of helix angle. Helical is the most commonly used gear in transmissions. They also generate large amounts of thrust and use bearings to help support the thrust load. Helical gears can be used to adjust the rotation angle by 90 deg. when mounted on perpendicular shafts. Its normal gear ratio range is 3:2 to 10:1.

3. Bevel Gear

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.

4. Spiral Bevel Gear 

A spiral bevel gear is a bevel gear with helical teeth. The main application of this is in a vehicle differential, where the direction of drive from the drive shaft must be turned 90 degrees to drive the wheels. The helical design produces less vibration and noise than conventional straight-cut or spur-cut gear with straight teeth.

5. Hypoid Gear 

A hypoid gear is a style of spiral bevel gear whose main variance is that the mating gears' axes do not intersect. The hypoid gear is offset from the gear center, allowing unique configurations and a large diameter shaft. The teeth on a hypoid gear are helical, and the pitch surface is best described as a hyperboloid. A hypoid gear can be considered a cross between a bevel gear and a worm drive.

6. Crown Gear 

Crown gears are a particular form of bevel gear whose teeth project at right angles to the plane of the wheel; in their orientation the teeth resemble the points on a crown. A crown gear can only mesh accurately with another bevel gear, although crown gears are sometimes seen meshing with spur gears. A crown gear is also sometimes meshed with an escapement such as found in mechanical clocks.

7. worm gear 

worm gear are used to transmit power at 90 degree and where high reduction are required. the axes of worm gear shaft cross in space. the shaft of worm gear lie in parallel planes and may be skewed at any angle between zero and a right angle. in worm gear, one gear gas screw threads. due to this, worm gear are quiet, vibration free and give a smooth output. worm gear and worm gear shaft are almost invariably at right angles.

8. Herringbone gear

A herringbone gear, a specific type of double helical gear, is a special type of gear that is a side to side (not face to face) combination of two helical gears of opposite hands. From the top, each helical groove of this gear looks like the letter V, and many together form a herringbone pattern (resembling the bones of a fish such as a herring). Unlike helical gears, herringbone gears do not produce an additional axial load. Like helical gears, they have the advantage of transferring power smoothly because more than two teeth will be in mesh at any moment in time. Their advantage over the helical gears is that the side-thrust of one half is balanced by that of the other half. This means that herringbone gears can be used in torque gearboxes without requiring a substantial thrust bearing.

9. Rack And Pinion

a rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely larger radius of curvature. torque can be converted to linear force by meshing a rack moves in straight lines. such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left to right motion of the tie rod. rocks also feature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears of particular actual radii then derived from that. the rack and pinion gear type is employed in a rack railway.

10. Face Gear 

face gear transmit power at right angles in a circular motion face gears are not very common in industrial application. 

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