These gears are easy to manufacture and can be used in a variety of applications. Spur gear terms and concepts gears educational systems. The teeth are aligned in a direction that is parallel to the gear axis. Is the arc of the pitch circle between the beginning and the end of the engagement of a given pair of teeth. The teeth are inclined with respect to the axis of rotation, as seen in. The vocabularies for gear numerical formula and gear drawings are defined in jis b. A spur gear is one of the simplest and most common types of cylindrical gears. It is the ratio of the reference diameter of the gear divided by the number of teeth. Spur gears are used in many devices that you can see all over howstuffworks, like the electric screwdriver, dancing monster, oscillating sprinkler, windup. You can study basic gear terminology and calculation in this page. The vocabularies for gear numerical formula and gear drawings are defined in jis b 0121. Pressure line is the common normal at the point of contact of mating gears along which the driving tooth exerts force on the driven tooth.
Buchsbaum, frank, design and application of small standardized components data book 757 vol. This allows the designers to avoid undercutting of teeth and increase the thickness of the teeth only by changing the instrument relative to the wheel being processed. The geometry of a simple spur gear tooth is complex. Relationship between the involute elements determination of base tooth thickness from a known thickness and viceversa. A circle bounding the ends of the teeth, in a right section of the gear. The majority of calculations for spur gears can be applied to helical gears too. Sometimes, many spur gears are used at once to create very large gear reductions. Two of the most important parameters, often confused with each other, are the pitch diameter or thread pitch diameter.
Gear ratio is numbers of teeth of larger gear to smaller gear. Spur gears with helicoid teeth are called helical gears. Some things to know before you start how to use a compass how to use a protractor to measure angles. An involute curve is the path that the end of a string takes when it is. In this section we introduce the basic parts of spur gears cylindrical gears and dimensional calculations. Spur gears have straight teeth that run parallel to the shaft.
Calculate forces on teeth of spur gears, including impact forces associated with velocity and clearances. American standard ansi mpb steel spur gears pressure angle 1412 o s311 s312 s3 s314 s315 s316 s317 s318 s319 s320 s321 s322 s324 s325 s328 s330 s332 s336 4. Terminology the gear tooth is a component of a mechanical power transmission system that. Investigation of contact stress in spur gear using lewis equation and finite element method ashish v kadu1 and sanjay s deshmukh1 corresponding author. The design and calculation of a spur gear transmission, one of the oftenperformed mechanical engineering tasks, requires a lot of long and complicated tedious computations. Pressure angle is the angle between the pressure line and common tangent to pitch circles. Call us at 800 4911073 and ask for design support or you can email us for assistance. They consist of a cylinder or disk with teeth projecting radially. Spur gear creation american society for engineering. These applications include speed increase or reduction, torque multiplication, and enhancing accuracy for positioning systems.
Though the teeth are not straightsided but usually of special form to achieve a constant drive ratio, mainly involute but less commonly cycloidal, the edge of each tooth is straight and aligned parallel to the axis of rotation. The profile of the contact surface of spur gear teeth is in the form of an involute curve. The radial distance between the pitch circle and the top of the teeth. See figure 4 a spur gear has teeth that are uniformly spaced around the outer surface. The next loading graphic may stop or skip, but that is just because the viewer is loading. Numerous dimensional parameters define the shape of the tooth profile, determine how the gears fit together, and identify locations where forces act at the gear teeth. Spur gears or straightcut gears are the simplest type of gear. Calculate gear and gear tooth dimensions using gear pitch and the number of teeth.
Spur gears impose only radial perpendicular to axis loads on gear shafts as opposed to helical, bevel, and spiral bevel gears which impose both radial and thrust axial loads on gear shafts. This type of gear comes with two kinds of tooth profiles in accordance with the datum surface. In an involute gear, the profiles of the teeth are involutes of a circle. Determine allowable force on gear teeth, including the factors necessary due to. This can take anywhere from 10 seconds to a few minutes. They have straight teeth, and are mounted on parallel shafts. Following are the gear terminology or gear terms used in the description of gears. Spur gear terms and concepts description in order to design, build and discuss gear drive systems it is necessary to understand the terminology and concepts associated with gear systems.
They are designed to mesh with another spur gear on a parallel shaft. Each cad and any associated text, image or data is in no way sponsored by or affiliated with any company, organization or realworld item, product, or good it may purport to portray. Addendum a is the height by which a tooth projects. Cylindrical spur gears with standard profile cylindrical spur gears with corrected profile without centre distance variation with centre distance variation.
Calculate center to center distances for 2 or more gears in mesh. The involute of a circle is the spiraling curve traced by the end of an imaginary taut string unwinding itself from that stationary circle called the base circle. The computeraided design cad files and all associated content posted to this website are created, uploaded, managed and owned by third party users. Spur gear design and selection objectives apply principles learned in chapter 11 to actual design and selection of spur gear systems. A spur gear is designed to mesh with another spur gear on a parallel shaft. Contact stress analysis of spur gear for different. These gears have straight teeth and must be mounted on parallel shafts for their teeth to mesh with those of other gears. Good designers and engineers have experience and knowledge and the ability to communicate their thoughts and ideas clearly with others. The involute gear profile is the most commonly used system for gearing today, with cycloid gearing still used for some specialties such as clocks.
1511 445 1615 1162 1550 1017 54 1036 1438 1346 860 1195 737 781 1635 1619 840 1467 919 24 1515 861 1346 253 98 1424 427 73 1376 788 59 902