Hydraulic lash assembly and valvetrain implementing same

An expander for use within a heat recovery system, the expander comprising:

• a housing defining:
• an inlet configured to receive a supercritical fluid;
• and
• a receiving chamber configured to receive the supercritical fluid from the inlet;
• a valve configured to transition between a closed orientation in which the inlet and the receiving chamber are fluidly decoupled, and an open orientation in which the inlet and the receiving chamber are fluidly coupled;
• and
• a hydraulic lash assembly disposed in the housing, the hydraulic lash assembly comprising:
• a first arm configured to transition the valve between the closed orientation and the open orientation, the first arm including an engagement surface configured to receive a driving force from a cam so as to cause the valve to transition to the open orientation for a predetermined period of time;
• and
• a second arm configured to receive a holding force from an actuator, the second arm including a protruding pivot member coupled to the first arm so as to displace the first arm based on the holding force,
• wherein the first arm and the second arm form a lever arrangement in which the protruding pivot member underlies and supports the first arm so as to enable rotational movement of the first arm independently from the second arm when transitioning the valve to the open orientation based on the driving.