{"data":{"fields":"term_definition","term_definition":"<div class=\"definition\">The contacting line on the tooth flank at any moment while a pair of gears is rolling. The contact line is the effective line or curve of contact between two engaged teeth without any rotation. The sum of all contact lines that are generated during rotation of the gears is the effective\r\ncontact pattern. The contacting line depending on the longitudinal form of the tooth can be a straight line or a curve. The direction of the contact line is defined by the helix or spiral angle of the tooth. In a straight cylindrical gear the contact line is directed parallel to the gear axis. In a helical gear the contact line is directed under an angle to the gear axis. Straight bevel gears have a straight contact line which consists of a cone element. Skew bevel gears also have a straight contact line which is inclined under an angle to the cone element. Zerol, spiral bevel and hypoid gears strictly have curved contact lines. In spiral bevel gears it is inclined to the cone element.<\/div>"}}