arch head

noun Machinery.

a vertical, arc-shaped member fixed to the end of a walking beam, for supporting a chain from which a pump rod or the like is suspended in such a way as to let it rise and fall vertically.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for arch head

Historical Examples of arch head

It is divided into four lights, and the arch-head is filled with good simple tracery.
Scottish Cathedrals and Abbeys
Dugald Butler and Herbert Story