Gear is a kind of meshing mechanical parts with teeth. It is widely used in mechanical transmission and even in the whole machinery industry and daily life. The application of gear has a long history, and it is also an indispensable important part in the machinery industry.

The working principle of rack and pinion is objective

The working principle of the rack and pinion is to change the rotary motion of the gear into the reciprocating linear motion of the rack, or the reciprocating linear motion of the rack into the rotary motion of the gear.

Gear classification

Parallel shaft gear & Spur gear & rack 

Spur gear

A cylindrical gear whose tooth line is parallel to the axis line. Because it is easy to process, it is widely used in power transmission

Rack

A straight toothed strip gear meshed with a spur gear. It can be regarded as a special case when the pitch diameter of spur gear becomes infinite.

Internal gear & helical gear 

Internal gear

A gear that is meshed with a spur gear and has teeth machined on the inside of the ring. It is mainly used in planetary gear rotating mechanism and gear coupling

Helical gear

Cylindrical gear with helical tooth line. It is widely used because it is stronger than spur gear and runs smoothly. Axial thrust is generated during transmission.

Helical rack & herringbone gear

Various Classification and Function of rack and pinion 1

Helical rack

A strip gear that meshes with a helical gear. It is equivalent to the case when the pitch diameter of helical gear becomes infinite.

Herringbone gear

The tooth line is composed of two helical gears of left and right rotation. It has the advantage of not producing thrust in the axial direction.

Straight bevel gear

Various Classification and Function of rack and pinion 2

Straight bevel gear

A bevel gear in which the generatrix of the tooth line and pitch cone line are consistent. In bevel gear, it belongs to the type which is easy to manufacture

Spiral bevel gear & zero degree bevel gear

Various Classification and Function of rack and pinion 3

Spiral bevel gear

The tooth line is a curve bevel gear with spiral angle. Although compared with the straight bevel gear, it is more difficult to make, but it is also widely used as a gear with high strength and low noise.

Zero degree bevel gear

Curved bevel teeth with zero helix angle

Zero degree bevel gear

Spiral bevel gear with zero helix angle. Because it has the characteristics of both straight and curved bevel gears, the force on the tooth surface is the same as that of the straight bevel gear.

Staggered shaft gear

Cylindrical worm pair & staggered helical gear

Various Classification and Function of rack and pinion 4

Cylindrical worm pair

Other special gears

Drum worm pair & hypoid gear

Various Classification and Function of rack and pinion 5

Face gear

Various Classification and Function of rack and pinion 6

Face gear

It can be meshed with spur or helical gears. Drive between the straight axis and the staggered shaft.

pinion and rack

The rack and pinion mechanism is composed of gears and racks. We have a detailed explanation of gears in front of them. The rack is divided into straight rack and helical rack. The tooth profile of rack is straight line rather than involute, which is equivalent to cylindrical gear with infinite dividing circle radius.

Main features of rack

Because the rack tooth profile is straight line, each point on the tooth profile has the same pressure angle, which is equal to the inclination angle of the tooth profile. This angle is called the tooth profile angle, and the standard value is 20 °.

Any straight line parallel to the addendum has the same pitch and modulus.

The straight line parallel to the tooth top line and the tooth thickness equal to the width of the tooth space is called the dividing line (center line), which is the reference line for calculating the rack size.

Application range of rack and pinion drive

1. Suitable for fast and accurate positioning mechanism

2. It is suitable for CNC machine tools, machining centers, cutting machines and welding machines with heavy load, high precision, high rigidity, high speed and long stroke

3. It is suitable for fast transplanting machine of factory automation, industrial robot arm grabbing mechanism, etc

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