210 



PUMP. 



Descrip- 

 tion of a 

 three-bar- 

 relled 

 pump. 

 Fig. 18. 



placed near each other. An excellent pump of this 

 kind is represented complete in Fig. 17, where MN is 

 the standard to which the machinery is fixed, AB the 

 body of the pump, CD the rising pipe from which the 

 water is received, and EF the main through which it 

 is forced. A lever handle H a', moving round a fixed 

 fulcrum/, carries the two piston rods a' v b', awb, to 

 the ends of which are attached the pistons b', b. The 

 rods vb',iv b, are made to work equably and vertically 

 by means of the wheels v, m moving between vertical 

 guides, so that though the rods aw, a' v vary their in- 

 clination to a vertical line, the piston rods v b', n> b 

 work vertically in the main barrel AB. 



When the handle H is at its lowest position, the pis- 

 ton b' is near the top of the barrel, and the piston b 

 near the bottom. There are valves in both the pis- 

 tons, and its operation is obviously similar to that of a 

 sucking pump, the power of it being doubled by the 

 use of two pistons. 



In a pump of this kind, described by M. Hachette, 

 the piston rod of the lower piston passes through a col- 

 lar of leathers in the upper piston, the piston rod being 

 in both placed a little to one side of the centre of the 

 piston. See Trait e Elemenlaire dex Machines, p. 153, 

 This contrivance is the same with that used by M. 

 Noble, in the hand pump he has made for the navy. 



14. Description of a Three-Barrelled Pump. 



The object of a three-barrelled pump is to keep up 

 a continued current of water by the action of three pis- 

 tons, one of which is at the bottom of its working bar- 

 rel, while the second is in the middle of its barrel, and 

 the third, at the top of its barrel, as shown in Fig. 18. 

 In each of the three pumps, which are similar to that 

 shown in Fig. 5, AB is the working barrel, a b the pis- 

 ton rod at the valves, and c the circular orifice or sec- 

 tion of the pipe (above D, Fig. 5) through which the 

 water is forced. The rising pipe from which the water 

 is raised is shown at EF, and m n is the suction cham- 

 ber common to all the three valves. 



Pumps of this kind were used by Mr. Smeaton, in 

 the numerous water engines which he erected at Lon- 

 don Bridge, Sheffield, and other places which required 

 to be supplied with water. When the pumps are 

 small, the barrels are generally made of brass, but when 

 they are made on a large scale, cast iron is used. Op- 

 posite to the aperture c of each barrel, there is a pro- 

 jecting neck or short pipe, covered at the end by a 

 door, through which a workman can get access, for the 

 purpose of repairing the valves. The valves used by 

 Mr. Smeaton were of iron, and shut down upon hinges 

 like a door, being covered with leather on the lower 

 side. The centre pin of the hinge was placed back 

 from the hole which the valve covers ; and it was also 

 raised above the surface of the under side of the valve, 

 so that the valve opens in some degree on that side 

 where the hinge is, as well as on the other side. Hence 

 obstructions are less liable to be detained in the valve, 

 and have less power to break its hinge. The hinge is 

 fastened to the body of the pump by a screw passing 

 through the metal into the end of the hinge. The pis- 

 ton or forcer b of each barrel consists of three metallic 

 plates, secured to the rod a b. The middle plate, 

 which is turned as true as possible, is accurately fitted 

 to the barrel, and the upper and lower plates are some- 

 what smaller. Two round pieces of leather, larger than 

 the barrel, are placed above and below the middle 



plate, and are held fast between it and the upper and Pump, 

 lower plates. When these pieces of leather are forced ** 

 into the barrels, they bend the one up and the other 

 down, round the upper and under plates, so as to form 

 two leather cups, which fit the barrel in the nicest 

 manner, and will not permit any water to pass between 

 them. When the piston b of the first barrel is raised, 

 a vacuum is produced below it, and the pressure of the 

 atmosphere forces the water up through the valve d. 

 The descent of the same piston forces open the valve 

 in the pipe at c, and drives the water up that pipe. 

 While this barrel is forcing up the water through c, 

 the next barrel is sucking it up during the ascent of its 

 piston, while the third keeps up the action in the in- 

 terval when the change of motion takes place between 

 the two. If the pistons are properly worked, by means 

 of well-adjusted cranks, they will furnish a very con- 

 stant stream of water. 



15. Description of Mr. Smeaton' s Hand-Pump fo: 

 Ships. 



This pump was invented by Mr. Smeaton in 1765, Descrip- 



and was intended to remedy a defect in all pumps used tlon , 

 A .1 i . IT Smeaton s 



at sea. As the common ship s pumps deliver the water hand-pump 



on the main deck, about 4-, 5, or 6 feet above the sur- f or sn jp s . 

 face of the sea, a quantity of power is thus unnecessa- 

 rily expended. To remedy this evil, Mr. Smeaton 

 employed horizontal wooden trunks, or pipes, which 

 carried off the water through the ship's sides at as low 

 a level as possible. One end of these pipes proceeded 

 from the upright trunk of the pump, and the other 

 was fitted into boxes, or short wooden tubes, let in 

 through the ship's side, and caulked just above the 

 load water line. " These side pipes were closely joint- 

 ed with the boxes in the ship's side at one end, and at 

 the other end into strong planks, which were bolted 

 against the sides of the pump, in order that the side 

 pipes might be got out and in without disturbing the 

 pump, which was a sucking pump with its bucket 

 worked by a lever or brake upon the deck over the 

 pump. From the top of the pump, a stand pipe was 

 carried up to the main deck, or as high as was thought 

 necessary to prevent the water reverting and running 

 back into the ship, over the top of the pump, when the 

 sea rose above the orifices of the side pipe, or when, 

 from the ship being in distress, they were under her 

 load water line. By this, even when both boxes and 

 pipes were wholly under water, it would no ways in- 

 terrupt the action of the pump, for whenever the water 

 in the stand-pipe rose above the level of the water 

 without, the pressure of the column in the stand pipe, 

 would cause it to make its way through the side-pipes, 

 so that in this case no level was lost ; and though the 

 pump was at rest, no water could revert down the 

 pump ; because there were the valves of both bucket 

 and fixed box or clack, which prevented it. The 

 working barrel was of brass, and very truly bored, the 

 bucket and fixed box being of the same construction as 

 those used in the steam-engines, and the pump rod was 

 made of greater bulk than was rtecessary, merely for 

 strength, but by way of weight, that, when the brake 

 was lifted up, the pump rod should readily descend by 

 its own weight. The brake of the pump had a branch 

 fixed on, rather obliquely at each side, so as to form 

 three handles, for four men to work at once ; they 

 stood one on each side the middle stem of the brake, 

 and one on the outside of each of the branches ; and 



