HUMPHREY INTERNAL-COMBUSTION PUMP 273 



venience the " pump " and the " compressor" respectively. The 

 inlet valve i for gas and air and the exhaust valve e, for burnt 

 products exist as before ; but the exhaust pipe and valve are 

 adjustable vertically so as to vary the cushion space in the top 

 of a. There is another pipe p fitted with a valve r and also 

 adjustable vertically. A reservoir x, such as an old boiler shell, 

 is connected by a flexible pipe to p. Corresponding parts are 

 fitted to the compressor ; thus/ is an air inlet valve, g an outlet 

 valve for air which is shut by the water and // a non-return valve 

 for the compressed air. The dip pipe q, with its valve s, gives 

 communication between the atmosphere and the compressor. 

 The outlet pipe and the dip pipe are vertically adjustable as in 

 the pump. Lastly, suppose the play pipe d filled with water, 



/ 



I 



H 



I 



- 



9 



D 



Fig. 7. 



then we have all the elements required for working under the 

 most varied conditions. 



The cycle can be explained by assuming that, as shown in the 

 figure, the water level is well up in a and low in c, and that a 

 compressed charge is ignited in a. Expansion occurs, driving 

 down the water in a and up in c. At first air escapes from c 

 through valve 5 but when the water reaches this valve it is shut 

 and the remaining air is trapped and suffers compression until 

 the pressure of discharge is reached, when h opens and com- 

 pressed air is delivered. Next the water reaches valve g and 

 shuts it so that no more air can escape ; the water column is then 

 brought to rest by the continued compression of the remaining 

 air, which forms a cushion. Meanwhile in chamber a expansion 

 to atmospheric pressure allows the exhaust valve e to open ; the 

 continued stroke then draws in scavenging air (the scavenging 

 valve being omitted from the figure for the sake of simplicity) but 



18 



