from The Century Dictionary and Cyclopedia
- n. A flat plate forming part of the seat of a valve, usually the contact portion, so that it can be renewed on wear or leakage without discarding or re-finishing the entire casting.
- n. A plate fitting over the end of the casing of a cylindrical valve, serving to guide the valve and close the opening.
- n. A plate covering an opening into a valve-chest. Usually called a bonnet.
Sorry, no etymologies found.
The motor being a single acting one, a single valve-plate suffices.