l^^ BULLETIN 173, U. S. NATIONAL MUSEUM 



as a gas intake valve and ignition valve. The drop valve is the ex- 

 haust valve, and the governor acts on the gas throttle valve. The cycle 

 is the Otto, or 4-stroke. 



OTTO AND CROSSLEY GAS ENGINE, 1877 



U.S.N.M. no. 308695 ; original patent model ; transferred from the United States 

 Patent Office, not illustrated. 



This model was submitted with the application for the patent is- 

 sued to Nicolaus A. Otto, of Deutz, Germany, and Francis W. and 

 William J. Crossley, of Manchester, England, October 23, 1877, no. 

 19G473. 



The gas engine described is designed to effect a gradual combustion 

 of the charge by the use of a weak mixture in the cylinder. In order 

 that the mixture would not ignite too slowly a strong or explosive 

 mixture was introduced into a separate but connecting chamber and 

 ignited in the conventional way. The flame issuing with some force 

 from the chamber into the cylinder effected a sufficiently rapid igni- 

 tion of the weak charge. 



The inventors also describe a means of raising the pressure on the 

 cavity of the slide valve carrying the burning ignition charge in a 

 flame ignition engine, high enough to equal the compression pressure 

 within the cylinder of the engine. 



MULTIPLE-PISTON GAS ENGINE, 1879 



U.S.N.M. no. 30S726 ; original patent model ; transferred from the United States 

 Patent Office ; not illustrated. 



This model was submitted with the application for the patent 

 issued to Wilhelm Wittig and Wilhelm Hees, of Hanover, Prussia, 

 March 25, 1879, no. 213539. 



This model shows an engine with a vertical cylinder open at both 

 ends. Within the cylinder are two pistons, so connected to the same 

 crankshaft that they move in unison in and out from the midpoint 

 of the cylinder, alternately traveling apart and then approaching 

 each other at the midpoint. The intake and exhaust valves are the 

 poppet type. Ignition is effected by a flame timed by a slide valve. 



The engine works on the 4-stroke cycle. As the pistons travel away 

 from the midpoint of the cylinder the combustible mixture of air 

 and gas is drawn into the space between them. When the pistons 

 come together on the next stroke the charge is compressed and when 

 near the end of the stroke ignited. Combustion drives the pistons 

 to the ends of the cylinders, performing work, and the spent gases 

 are expelled on the next instroke of the piston. 



