Direct-acting

a.
  1. Acting directly, as one part upon another, without the intervention of other working parts.
    2. Direct-acting steam engine ,
    one in which motion is transmitted to the crank without the intervention of a beam or lever; -- also called direct-action steam engine.
    Direct-acting steam pump ,
    one in which the steam piston rod is directly connected with the pump rod; -- also called direct-action steam pump.