230 



Introduction to the Study of Science 



PRESS PISTON - 



VALVE FOR 



DRAINING' 



PRESS 



PUMP PISTON 



Hydraulic press. The fact that water is practically in- 

 compressible and transmits pressure equally in all directions 

 in a closed container is made use of in many ways in the in- 

 dustrial world. One of the many kinds of machines which 

 depend upon these properties of water is the hydraulic press. 



This machine is used in 

 many ways, as in baling 

 cotton, in the manufacture 

 of linoleum, in pressing 

 olives, grapes, and the like. 

 The hydraulic elevator is 

 still to be found in many 

 0*!!}^ places. The chief features 

 of the hydraulic press are 

 illustrated in Fig. 66. 



Exercise. Suppose the 

 area of the pump piston is 10 

 sq. in., and that of the press 

 piston is 100 sq. in. What will 

 a pressure of 50 Ibs. upon the 

 pump piston exert upon the 

 press piston ? The pressure is 



transmitted by water in a closed container equally and in all directions, 

 so that the 5 Ibs. pressure of each square inch of the pump piston gives 

 a pressure of 5 Ibs. to each square inch of the inner surface of the press 

 in contact with the water. The total pressure exerted upon the press 

 piston is therefore equal to 5 (pounds per sq. in.) x 100 (area of press 

 piston) or 500 pounds. How may the mechanical advantage of a 

 press be increased ? Would there be any advantage if the pistons had 

 the same area? 



95. The force pump. All pumps that have their cylinders 

 above the surface of the water supply depend upon air pressure 

 (page 15) . The lift pump delivers water without pressure. The 

 force pump delivers water with pressure. The pressure may 

 be utilized in delivering the water at a considerable distance 

 from, and height above, the cylinder. The amount of pressure 



FIG. 66. The hydraulic press. The 

 pressure on the pistons is proportional to 

 the square of the diameter. If a pressure 

 of one pound is applied to the pump pis- 

 ton, what is the total pressure transmitted 

 to the press cylinder? Scale one eighth 

 inch to one foot. 



