Patent Page: Mery Explosive Engine

Check out this antique patent from California for a double-acting engine featuring a single piston.

| August/September 2020

Top-down view of the cylinder in Michael Lawrence Mery’s 1895 patent for the Mery Explosive Engine. The double-acting engine featured two igniter/intake valve chests (D), one at each end of the cylinder. Fresh air drawn in via a purge valve (L3) cleared out the exhaust manifold and kept exhaust gases from drawing back into the cylinder.

“The object of my invention is to provide a double-acting explosive engine, simple in its construction of parts, efficient and accurate in its explosions, and capable of easy and perfect adjustment.”

So wrote Michael Lawrence Mery of Chico, California, in his patent application submitted Feb. 7, 1895. On July 23, a little more than four months later, Mery was awarded patent number 543,157 for his Mery Explosive Engine. Constructed in some measure along steam engine principles in common use at the time, the Mery is a double-acting engine featuring a single piston. Like a double-acting steam engine, the Mery utilizes a crosshead with a connecting rod running forward to a single cylinder and an another connecting rod running from the crosshead to the crankshaft. The connecting rod running into the cylinder passes through a water-cooled packing gland and then to the piston. But that’s where the Mery’s similarity to a steam engine, or any other engine, stops.

Its similarities to steam engine layout notwithstanding, the Mery is unlike any other engine in the annals of stationary engine design. Igniter fired, the Mery utilized its own governing system that combined speed-controlled volume governing with hit-and-miss load control. The intake valves were atmospheric and the exhaust valves were actuated by a rocking lever driven off the crankshaft. Another rocking lever, also driven off the crankshaft, actuated the igniters. To allow timing adjustment, the igniter rocking lever was mounted on an eccentric, which could be adjusted to alter the pivotal center of the rocking lever.

To control intake volume, bell crank levers acted upon by a governor engaged a stop on the intake valve stems, limiting the total stroke of the intake valves to control fuel/air volume. At their contact point with the valve stems, the bell cranks had graduated stops (see Fig. 5) to effect differing levels of valve opening. Below governed speed, the bell cranks were out of action and the intake valves were free to fully open. As the governor latched in, valve lift was impeded in steps, thereby limiting the amount of fuel/air drawn into the cylinders. For further fine tuning, the stops on the intake valve were adjustable.

Bell crank (Q, Fig. 5) with graduated stops limited intake valve lift. A pendulum (P, Fig. 6) lifted levers with pawls (O) to hold the exhaust valves open.


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