HYDRAULIC CRANES 



1170 



all the hydraulic machines with which it is connected. Whenever the engine pumps 

 more water into the accumulator than passes direct to the hydraulic machines, tho 

 loaded plunger rises and makes room 

 in the cylinder for the surplus; but 

 when, on the other hand, the supply 

 from the engine is less, for the mo- 

 ment, than the quantity required, the 

 plunger, with its load, descends and 

 makes up the deficiency out of store. 



' The accumulator also serves as a 

 regulator to the engine; for when 

 the loaded plunger rises to a certain 

 height, it begins to close a throttle- 

 valve in the steam-pipe, so as gradu- 

 ally to reduce the speed of the engine 

 until the descent of the plunger again 

 calls for an increased production of 

 powder. 



'The introduction of the accumu- 

 lator, which took place in the year 

 1851, gave a great impulse to the ex- 

 tension of water-pressure machinery, 

 which is now either already applied, 

 or in course of being applied, to the 

 purpose of cranage throughout all 

 the great dock establishments in 

 London, as also to a considerable ex- 

 tent in Liverpool and other places. 

 I have also applied it extensively 

 to railway purposes, chiefly under the 

 direction or Mr. Brunei, who has 

 found a multitude of cases, involving 

 lifting or tractive power, in which it 

 may be made available. Most of 

 these applications are well exempli- 

 fied at the new station of the Great 

 Western Kailway Company in London, 

 where the loading and unloading of 

 trucks, the hoisting into warehouses, 

 the lifting of loaded trucks from one 

 level to another, the moving of turn-tables, and the hauling of trucks and travers- 

 ing machines are all performed, or about to be so, by means of hydraulic pressure 

 supplied by one central steam-engine with connected accumulators. Mr. Rendel also, 

 after having successfully adopted the low-pressure system to the working of the gates 

 and shuttles at Grimsby, has since applied the high -pressure, or accumulator system, 

 to the same purposes at other new docks, and a similar adaptation is being made by 

 other eminent engineers at most of the new docks now in course of construction. 



' I have also adapted hydraulic machinery to the opening and closing of swing- 

 bridges and draw-bridges of large dimensions ; and, in fact, there is scarcely any 

 mechanical operation to which human labour has been hitherto applied as a mere 

 moving power, which may not be efficiently performed by means of water-pressure 

 emanating from a steam-engine and accumulator. Even if hand-labour be retained 

 as the source of the power, the intervention of an accumulator will in many cases 

 both economise labour and increase despatch. For example, a pair of heavy dock- 

 gates requires the constant attendance of a considerable number of men, whose labous 

 is only called into action occasionally, viz., when the gates are being opened or closed. 

 Now, if an accumulator, charged by hand-pumps, were used, the labour employed 

 would be constant, instead of occasional, and the power collected in the accumulator 

 by the continuous process of pumping would be given out in a concentrated form, and 

 thus the ultimate result would be effected with fewer hands and greater despatch than 

 where manual labour is directly applied. 



' The form of pumping-engine which I generally use for charging the accumulator 

 is represented in fig. 1171. It consists of a horizontal steam-cylinder, with two force- 

 pumps connected directly with the piston. These force-pumps are supplied with 

 water from a cistern over the engine-room, into which the water discharged by the 

 cranes is generally brought back by a return-pipe, so that the water is not wasted, but 

 remains continuously in use. 



VOL. II, 3 H 



