# 装装机机械外文文献和翻译

33.1 DEFINITIONS / 33.1
33.2 TOOTH DIMENSIONS AND STANDARDS / 33.4
33.3 FORCE ANALYSIS / 33.5
33.4 FUNDAMENTAL AGMA RATING FORMULAS / 33.6
Spur gears are used to transmit rotary motion between parallel shafts. They are
cylindrical, and the teeth are straight and parallel to the axis of rotation.
The pinion is the smaller of two mating gears; the larger is called the gear or thewheel.
The pitch circle, B in Fig. 33.1, is a theoretical circle upon which all calculations arebased. The operating pitch circles of a pair of gears in mesh are tangent to each
other.毕业论文http://www.lwfree.cn/
The circular pitch, p in Fig. 33.1, is the distance, measured on the theoretical pitch
circle, from a point on one tooth to a corresponding point on an adjacent tooth. The
circular pitch is measured in inches or in millimeters. Note, in Fig. 33.1, that the circularpitch is the sum of the tooth thickness t and the width of space.原文请+QQ3249,114六.维^论,文'网
The pitch diameter, d for the pinion and D for the gear, is the diameter of the pitch
circle; it is measured in inches or in millimeters.
The module m is the ratio of the theoretical pitch diameter to the number of teeth
N. The module is the metric index of tooth sizes and is always given in millimeters.
The diametral pitch Pd is the ratio of the number of teeth on a gear to the theoretical pitch diameter. It is the index of tooth size when U.S. customary units are used and is expressed as teeth per inch.
The addendum a is the radial distance between the top land F and the pitch circle
B in Fig. 33.1. The dedendum b is the radial distance between the pitch circle B and
the root circle D in Fig. 33.1. The whole depth ht is the sum of the addendum and
dedendum.
The clearance circle C in Fig. 33.1 is tangent to the addendum circle of the mating
gear. The distance from the clearance circle to the bottom land is called the clearance c.
Backlash is the amount by which the width of a tooth space exceeds the thickness of the engaging tooth measured on the pitch circle.
Undercutting (see distance u in Fig. 33.1) occurs under certain conditions when a
small number of teeth are used in cutting a gear.
Table 33.1 lists all the relations described above. Additional terminology is shown in Fig. 33.2. Here line OP is the line of centers connecting the rotation axes of a pair2095

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