Spur gears

Gearing is single hehcal or spur gear lubrication usually is an automatic spray type. Single drives are used up to 150 kW. Kilns requiring more than 150 kW may be equipped with dual drives, i.e., two driving... 

The three most common types of cylindrical gears are shown in Fig. 29-84. Spur gears are the simplest, but they nave the disadvan-... 

Stim, Stime, /. forehead, brow front, face. Stim-. frontal, front, -flache, /. face, front, -getriebe, n. spur gear, -rad, n. spur wheel, -seite, /. front side, front, -welle, /. impact wave, bow wave. 

There are several different types of gears used in industry. Many are complex in design and manufacture and several have evolved directly from the spur gear, which is referred to as the basic gear. Types of gears are spur, helical, bevel, and worm. Table 39.1 summarizes the characteristics of each gear type. 

The spur gear is the least expensive of all gears to manufacture and is the most commonly used. It can be manufactured to close tolerances and is used to connect parallel shafts that rotate in opposite directions. It gives excellent results at moderate peripheral speeds and the tooth load produces no axial thrust. Because contact is simultaneous across the entire width of the meshing teeth, it tends to be noisy at high speeds. However, noise and wear can be minimized with proper lubrication. 

There are three main classes of spur gears external tooth, internal tooth, and rack-and-pinion. The external tooth variety shown in Figure 39.1 is the most common. Figure 39.2 illustrates an internal gear and Figure 39.3 shows a rack or straight-line spur gear. 

An internal spur gear, in combination with a standard spur-gear pinion, provides a compact drive mechanism for transmitting motion between parallel shafts that rotate in the same direction. The internal gear is a wheel that has teeth cut on the inside of its rim and the pinion is housed inside the wheel. The driving and driven members rotate in the same direction at relative speeds inversely proportional to the number of teeth. 

Helical, external Connects parallel and non-parallel shafts superior to spur gears in load-carrying capacity, quietness, and smoothness high efficiency Higher friction than spur gears, high end thrust... 

As with spur gears, the tooth size of bevel gears is established by the diametrical pitch. Because the tooth size varies along its length, measurements must be taken... 

There are several different types of gears used in industry, but the spur gear is the most commonly used. Many... 

The use of spur gears in gear pumps will produce in the discharge pulsations having a frequency equiv ent to the number of teeth on both gears multiplied by the speed of rotation. The amplitude of these disturbances is a function of tooth design. The pulsations can be reduced markedly by the use of rotors with helical teeth. This in turn introduces end thrust, which can be eliminated by the use of doublehelical or herringbone teeth. 

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