{"data":{"fields":"term_definition","term_definition":"
The path of the instantaneous points of contact on the surface of a gear tooth. This term has been used in the past for path of action and length of action. A study of the events in the engagement of spur gear teeth is the simplest way to examine gear tooth action. As the driving member rotates and its teeth engage with the driven member, the first point of contact is in the flank of the driver and at the tip of the driven. As rotation proceeds, succeeding points of contact proceed from the flank of the driver to the pitch circle and then outward to the tip of the driving member. On the driven member contact proceeds inward from the tip of the tooth to the pitch circle and then to the flank where the contact ceases when the next engaging pair of teeth begin contact. The summation of all the points of contact for zero load condition is the path of contact. The shape of the path of contact curve is dependent on the tooth profile curves and the general direction of the path of contact is dependent on the pressure angle. For plane involute gear tooth profiles, the path of contact is a straight line and is called line of action. The path of contact, as seen from the above description of tooth engagement, may be separated into two parts relative to the pitch circle. Considering the driving member as contact begins in the flank and proceeds to the pitch circle the action is termed approach action. Then as contact proceeds from the pitch circle outward to the tip of the tooth, the action is termed recess action. The sum of approach and recess action is the path of contact. From the above description it is noted that contact starts in the flank of the driving member; whether the driving member is the gear or pinion does not matter.<\/div>
\"ED-102b\"<\/div>
\"ED-102b\"<\/div>
\"ED-102b\"<\/div>
\"ED-102b\"<\/div>"}}