Apparatus and method for throttling a heat engine

A throttle for a heat engine having a cylinder containing a working fluid with a piston moving therein, comprising:

• a plurality of cylinder ports through a side portion of the cylinder, the cylinder ports providing fluid communication between an interior portion of the cylinder and a reservoir area when the piston is below the cylinder ports;
• a sleeve disposed around a portion of the cylinder, the sleeve having a plurality of throttle ports through it;
• a throttle collar attached to the cylinder, the throttle collar supporting the throttle sleeve;
• a throttle worm gear attached to the throttle sleeve;
• and
• a throttle control worm that engages the throttle worm gear and drives it to rotationally position the throttle sleeve about the cylinder to selectively communicate a number of the throttle ports with a number of the cylinder ports to thereby open the cylinder ports so communicated to allow a portion of the working fluid contained in the cylinder to move between the cylinder and the reservoir area through the cylinder ports to vary pressure in a portion of the cylinder above the piston.

A method of throttling a heat engine having a cylinder containing a working fluid with a piston moving therein and a reservoir area for the working fluid, the reservoir area communicating with an interior portion of the cylinder through ports in the cylinder, the method comprising the steps of:

• selectively opening ports in the cylinder to allow communication between the reservoir area and the interior portion of the cylinder above the piston when the piston is below the ports;
• venting working fluid from the interior portion of the cylinder through the open ports to the reservoir area as the piston moves up in the cylinder toward the open ports to prevent significant compression of the working fluid in the cylinder;
• and
• stopping the venting by blocking the open ports with the piston as the piston moves up past the ports to thereby resume compression of the working fluid in the cylinder,
• whereby the pressure produced during compression of the working fluid is reduced from that produced when the ports in the cylinder are closed, thereby effectively throttling the engine.