CENTRIFUGAL PUMP.

In Fig. 1216 are shown several forms of the centrifugal pump, differing more in detail and proportion than in principle.

A shows Gwynne's centrifugal pump, which has six equidistant pallets inclined backwardly toward their outer extremities. Three of these extend from the axis, and the remainder only from the margin of the annular induction-space around the axis. The wheel rotates in a shell in the direction of the arrow, and delivers the water upward into the eduction-pipe L.

Girard's turbine elevator resembles five distinct turbines on a vertical axis, one above another, each taking the water from the one below it, and delivering it in turn to the one above it.

BC' shows the Coignard centrifugal pump, as shown at the French Exposition, 1862. A vertical section across the axis of one of these pumps is shown at B (Fig. 1216) and another section, also vertical, through the axis, at C' (same figure). Here there are two revolving-drums, g a, g a, both attached to the same axis d. They revolve in water-tight boxes, but the entrance of the water takes place from the space o, between the drums; the openings for admission being at f. The discharge takes place through an annular lateral space e e e e, into an annular cavity m m, which conducts it to the rising tube n. The tube of aspiration is 7, which communicates with the space between the drums o. form given to the pallets in this machine is spiral; they are only two in number in each drum. As in the other pumps, the form of the helices is professedly such as to make the section of passage inversely proportional to the velocity of the water at different distances from the center.

The

Andrews's centrifugal pump (D, Fig. 1216) resembles a helix or snail's shell, which forms the base of a double cone placed with its axis in a horizontal position, the space between the inner and outer cones being the chamber of the pump, and occupied by a kind of turbine-wheel shown in the detached view E (same figure). F is the stationary boss with spiral flanges 7, which give the water a twist just as it enters upon the action of the wheel, which has six vanes, as seen in the view E. a is the base of the pump, cast in one piece with the case c, to which is attached by flanges the conducting-case, composed of two parts dd, forming a spiral discharge-passage g and e; gradually enlarging to the outlet f is the stuffing-box, through which passes the driving-shaft g; this having turned in its surface at j, a series of grooves, which are accurately fitted in a Babbitt metal-box in the standard h, counteracting any tendency to end-thrust or vibration. i is the bed-plate, having cast upon it the standard h, and brackets to which the pump is secured by the flanges and base. When required to be run vertically, no bed-plate is used, but the pump is secured by the base. The base also forms a flange, to which Fig. 1217.

i

F

Centrifugal Pumps.

"that, in place of obtaining power by means of descending water, we may raise water by applying a given power." The centrifugal pump known as the "Gwynne" pump was used by Andrews and Brother in New York in 1844.

Centrifugal Pump.

is bolted the bend q of the suction-pipe, which has a foot-valve at its lower end. Motion is communicated by a belt upon the pulley p.

Fig. 1217 gives an exterior view of a centrifugal pump.

Fig. 1218 shows the centrifugal pump, with portable engine connected, as arranged for pumping out Fig. 1218

CHAFER.

a pond, or pumping from a river with a shelving bank, the dotted lines showing it as adapted for pumping out of a cistern or well. The pump is placed upon a two-wheeled carriage firmly attached to the engine when working, and driven by a band from the fly-wheel of the engine.

Cen-trip'e-tal Press. A mechanical contrivance for pressing inwardly on a radial line from all directions in the common plane.

Cen-triple-tal Pump. A pump in which the water is gathered by revolving blades or arms, and drawn to the axis from whence the discharge-tube rises.

In one form it is the exact con-
verse of the Barker mill. See Ro-
TARY PUMP.
Cen'tro-lin'e-ad.

Chaff-cut'ter. A machine for chopping or cutting long feed, such as hay, straw, or stalks, into chaff, in which condition it may be fed in a box or bag, dusted with bran or meal. An economical and compact mode of feeding. See STRAW-CUTTER. Chaff-halt'er. A lady's bridle with double reins. Chafing-dish. 1. A pan of coals to heat a dish. 2. A dish heated by lamp or jet beneath. Chaf'ing-gear. (Nautical.) Parceling or serving on ropes, to keep them from being chafed by running rigging.

Chain. 1. A device consisting of several associated links, joined end ways so as to string out in line.

The varieties of chains are numerous, and their names are derived from their (a) material, (b) structure, or (c) purpose, as,

-

a. Gold, steel, galvanized iron, etc.

b. Twisted link, flat link, etc.

c. Top-chain, curb-chain, surveyor's chain, mooring-chain, etc.

Chains in olden times had three purposes.

(1.) They were worn as emblems of investiture or badges of office, as in the cases of Joseph and Daniel, in Egypt and Babylon. The idea was preserved in Persia, and blossoms yearly in the civic ceremonies wherein London rejoices that she has found another

mayor.

(2.) For ornament. Necklaces, girdles, and anklechains were used by various nations of antiquity. Jewels were worked into the links or strung upon cords. To the chains which hung from the neck, fancy or fashion suspended cowries, mirrors, "round tires like the moon," trinkets, amulets, emblems, and scent-bottles. The Midianites, who invaded Palestine in the time of Gideon, ornamented with chains the necks of their camels. The modern uses of ornamental chains are numerous and familiar.

(3.) For confining prisoners. Before and after the time when poor Samson was blinded and then bound with fetters of brass, when David lamented Abner, and the fugitive Jedekiah, after defending his capital for two years, became a fugitive, was captured, blinded, bound with chains of brass, and carried to Babylon, chains, fetters, and manacles were the lot of captives and criminals. Peter slept "between two soldiers bound with two chains," being, no doubt, handcuffed to his guards on either side. Herod, of course, had the soldiers killed, which was the ordinary punishment of a Roman guard who allowed his prisoners to escape.

The Romans used chains with links of various patterns; circular, oval, figure-8, horse-shoe, bars with eyes, etc. These were principally of a small size and ornamental character. Their cable was of rope, as it was with us until a few decades since. Xerxes thrashed the Hellespont with chains, and then threw chains into the strait as a reminder; but the bridge he built was of rope, supported by ships, and sustaining the planks on which the host crossed. Twisted chains are mentioned by the Greek

authors.

Iron for chains is cut off with a plain chamferer; each piece is then bent, introduced, and welded. In common chains the weld is made at the small end, called the crown.

In chain cables the weld is at the side of the oval, the scarf being flatways of the link. The parts and consecutive forms are shown at i, j, k (Fig. 1222).

Curbed or twisted chains are welded in the ordinary manner and twisted afterwards; each link as

Chains with flat links are made in the fly-press. The links are cut out, of the form shown at . The holes are afterwards punched as in washers, one at a time, every blank being so held that its circular extremity touches the stops on the bed or die, which insure the centrality of the blank and punch. The two holes are thus made equidistant in all the links, and are afterwards strung together by inserting wire rivets through the holes.

The pins or rivets for the links are cut off from the length of wire in the fly-press, by a pair of cutters like wide chisels with square edges, assisted by a stop to keep the pins of one length; or by one straight cutter and an angular cutter hollowed to about 60°, or by two cutters, each hollowed to 90°. In the three cases, the wire is respectively cut from two, three, or four equidistant parts of its circum

ference.

two, or four and three, as at z, up to eight and nine links, which is sometimes used. The wires when inserted are slightly riveted at the ends.

Chains intended to catch on pins or projections on the periphery of a wheel are made two and two, as in the other figure, leaving an opening which slips over the cog.

Mr. Oldham, the engineer to the Bank of England, contrived a curved link-chain ff, adapted to work in connection with a cog-wheel g, with epicycloidal teeth.

Chains for watches, timepieces, and small machinery are too minute to be made as the ordinary flat-link chain. The slip of steel is first punched through with the rivet-holes for a number of links, by means of a punch in which two steel wires are inserted; the distance between the intended links is obtained (somewhat as in file-cutting) by resting the