direct-acting

[dih-rekt-ak-ting, dahy-]

adjective

(of a steam pump) having the steam pistons connected directly to the pump pistons without a crankshaft or flywheel.

Origin of direct-acting

First recorded in 1855–60

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

Direct-acting compressors are liable to center when doing work at slow speed.
Scientific American Supplement, No. 799, April 25, 1891
Various
Fishers carriages were driven by direct-acting engines, one cylinder on each side of the smoke-box.
Automobile Biographies
Lyman Horace Weeks
Ricketts later engines had spur wheels; but his last engines were direct-acting.
Automobile Biographies
Lyman Horace Weeks
Each was fitted with a Blake, horizontal, direct-acting, vacuum pump.
Transactions of the American Society of Civil Engineers, Vol. LXVIII, Sept. 1910
B. H. M. Hewett
It was worked by a pair of direct-acting engines, coupled to the crank shaft.
Automobile Biographies
Lyman Horace Weeks