74(3 



HYDEAULICS AND ITS APPLICATIONS 



cylinder D is in communication with an auxiliary low pressure supply, 

 through the pipe (7, and a downward pressure on the annulus at E is 

 thus produced, which, together with the weight of this ram, produces a 



pressure in the cylinder F 

 sufficiently great to balance 

 any required proportion of 

 the weight of the lift ram 

 and cage. The total pressure 

 transmitted to the water in 

 the cylinder F is then the 

 sum of the weight of the ram 

 B and of the pressures on E 

 and on ram B, the former 

 performing the balancing, and 

 the latter lifting the load. 



A suitable area of lift ram 

 being assigned, the external 

 diameter of B is calculated so 

 as to give the required inten- 

 sity of pressure in the cylinder 



F. The lift cylinder is sup- 

 plied from F through the pipe 



G. On the down stroke of 

 the lift, the ram B rises, the 

 balance water is returned to 

 its own supply tank, and the 

 only water rejected is that 

 originally filling the high- 

 pressure ram B. In a lift of 

 this type mentioned by Mr. 

 Ellington, the lift ram was 

 4J inches diameter, the lift 

 carrying 7 cwts. with a 70 feet 

 rise. The volume of pressure 

 water at 700 Ibs. per square 

 inch was 10J gallons per trip, 



as against 43 gallons when working direct-acting and without the balance 

 cylinder. 



It will be observed that as the balance ram falls, the pressure on the 

 annulus E increases, due to the increasing head to which it is subjected, 



FIG. 363. Suspended Hoist, 



