上濟大学 Objective of This Lecture Learn to analyze power screws and to specify suitable sizes for a given application Describe the operation of a power screw and the general form of square threads,Acme threads,and buttress threads锯齿螺纹)as they are applied to power screws. Compute the torque that must be applied to a power screw to raise or lower a load Compute the efficiency of power screws Compute the power required to drive a power screw Analyze the failure modes 13 圈上我大峰 -Mawe diamete Basic Terminology3 ·Pitch,p(螺距) >Distance between adjacent thread forms measured parallel to the thread axis. ·Major Diameter,d(大径) >Largest diameter of a screw thread. ·Minor Diameter,d,(小径) >Smallest diameter of a screw thread ·Pitch Diameter,,dp(中径) >The effective diameter of the screw >Sometimes called the mean diameter,dm 1413 Objective of This Lecture Describe the operation of a power screw and the general form of square threads, Acme threads, and buttress threads（锯齿螺纹） as they are applied to power screws. Compute the torque that must be applied to a power screw to raise or lower a load Compute the efficiency of power screws Compute the power required to drive a power screw Analyze the failure modes Learn to analyze power screws and to specify suitable sizes for a given application 14 Basic Terminology3 • Pitch, p（螺距） Distance between adjacent thread forms measured parallel to the thread axis. • Major Diameter, d（大径） Largest diameter of a screw thread. • Minor Diameter, dr （小径） Smallest diameter of a screw thread • Pitch Diameter, dp（中径） The effective diameter of the screw Sometimes called the mean diameter, dm