HUMPHREY INTERNAL-COMBUSTION PUMP 269 



rises, the exhaust valve e is shut by the sleeve f and a com- 

 bustible charge compressed in the top of the chamber 1. This 

 charge is fired, giving the working stroke ; the piston p 

 in being driven downwards first opens the exhaust valve e 

 by means of the sleeve f, then uncovers the admission valves a 

 for fresh combustible charge and is brought to rest on the 

 spring stop s. At this moment the liquid column in pipe d 

 has considerable velocity and the motion of the piston p 

 having stopped, fresh water is drawn in through the water 

 inlet valves w to follow the outwardly moving column in the 

 pipe d. After the admission valve ports are uncovered by the 

 piston, its further movement draws in a fresh combustible 

 charge through valve a and this charge lies at the bottom 

 next the piston with the hot exhaust gases above. When 

 the return movement of the column in pipe d takes place, 

 valves w close and the piston p is forced upwards by the 

 liquid, so driving out the exhaust products through valve e 

 until this valve is closed and the compression of the fresh 

 charge remaining in the chamber 1 is completed. The springs 

 m and n enable the valve e to be operated without shock. It 

 will be noted that when the exhaust valve e is forcibly opened 

 a shorter stroke and higher mean pressure can be obtained 

 than when expansion is carried to atmospheric pressure. The 

 pump is here shown of the two-cycle type but a similar 

 arrangement can be applied for the four-stroke cycle type. 



All the types of Humphrey pumps so far described have 

 their lift limited to approximately 40 ft., since this represents 

 about the mean effective pressure of the ignited expanded 

 gases during the long outward stroke ; to effect lifts higher 

 than 40 ft. Mr. Humphrey has invented what he calls an 

 " intensifier." This is practically an air cushion hydraulic ram 

 by the employment of which the lift may be increased to almost 

 any desired extent and is rendered independent of the working 

 pressures in the explosion cylinder. The idea is first to allow 

 the water column to gain velocity and then to utilise its 

 kinetic energy (a) to compress an elastic fluid, (b) to deliver 

 water under the pressure to which the elastic fluid has been 

 compressed. Fig. 6 will serve to make the cycle clear. 



a and b are the barrels of a two-barrel pump and at the 

 end of the play pipe d there are two air vessels e and f, 

 the latter being large enough to give a continuous flow at 



