CHAPTER XXI 



Hydraulic Appliances Lifts and Hoists The Hydraulic Jigger Cranes Coal Tips Crane 

 Valves The Hydraulic Jack Press Forging Press Riveters Lock Gate Machinery 

 Sluice Gates Capstans Hydraulic Transmission Gear The Hydraulic Brake The 

 Hydraulic Dynamometer. 



HYDRAULIC APPLIANCES. 



ART. 197. HYDRAULIC LIFTS AND HOISTS. 



PROBABLY in the aggregate more power is used by lifts and hoists than 

 by any other class of hydraulic machinery, and for such work as this, 

 hydraulic transmission is particularly suitable. 



Several types of lift are in use, these consisting of modifications of the 

 simple direct-acting or of the suspended type. The former consists of a 

 hydraulic cylinder sunk vertically in the ground ; of length slightly 

 greater than the maximum travel of the lift ; and fitted with a ram which 

 carries the lift cage as shown in Fig. 360. l 



Pressure water is admitted below the ram, and thus raises the cage. 

 It follows that the ram, considered as a loaded column, must be of suffi- 

 ciently large sectional area to support the weight without buckling, and 

 this prevents the use of very high pressures in the ram cylinder. 



EXAMPLE. 



If the gross weight to be lifted = 2 tons. 

 pressure in cylinder = 750 Ibs. per square inch. 

 lift travel = 80 feet. 



We have the area necessary to ) 4,480 



= -,, = 6 square inches, 

 raise the weight 750 



.'. Earn diameter = 2| inches. 



a diameter which is obviously too small for a column 80 feet long, to 

 support 2 tons without buckling. 



Actually, however, the area of the ram would need to be greater than 

 this in order to overcome friction and to give the necessary acceleration 

 at starting. 



1 By kind permission of the makers. 



