Figs. 495, 496 and 497.
The use of divided rings and bolts enables the joint to be easily disconnected at any time.
In Fig. 498 the ends of the pipes have formed on them annular ribs or projections with intermediate grooves, and over these ends a vulcanized India rubber belt is compressed by means of a metallic collar made in halves, and bolted as shown. The collar has corrugations corresponding with those on the pipes.
In the joint shown in Figs. 498b and 498c the divided ring is clamped together in a different manner from the preceding, and pipe ends are entirely plain. The clamps are provided with internal ribs and their uniting surfaces have projections and corresponding recesses to prevent misplacement, and the escape of the packing into the pipe under pressure. A packing of lead or other material placed between the pipes and the collar, and between the two halves of the collar, forms the joint by compression. In each end of the half collars there is a depression or cavity, forming together, when the two half collars are united, a box or chamber in which a piece or block of India rubber is inserted and compressed. This closes the open space left between the ends of the half rings, and prevents injury to it when the rings are drawn together.
The Bolted Ring Sleeve Joint.
In Figs. 499, 500 and 501 three separate rings are employed, and they are secured together by long bolts. The pipe ends are quite plain. Two loose collars are slid, one against the end of each collar, and next, upon one of the pipes, is slid a flat tubular ring. When the two pipes are placed end to end the ring is slid back over the joint one-half on one pipe and the other half on the other, so that the tubular ring covers the junction. By means of nut bolts the two collars are then drawn toward each other, and the annular packings thereby compressed between them and the ends of the intermediate tubular ring, and forced to expand laterally into close contact respectively with the surfaces of the two pipes forming the joint. The annular packings may be of vulcanized India rubber, and made smaller in diameter than the ends of the pipes in order that they may have a tendency to close tightly round them, or a gasket saturated with tallow or red lead in a plastic state may be employed.
In one form of the device the tubular collar has its ends enlarged so as to form sockets to receive the packing rings, and the loose collars have corresponding shoulders cast upon them to enter the sockets and press the packing rings against the pipes.
The screw joint possesses a great advantage in being perfectly and permanently steam, gas and water tight when properly made, and when the pipe and threading are of the proper kind.
It is capable of withstanding the effects of expansion and contraction, and of all kinds of strains and jars which the pipe itself can sustain, and it is extremely compact, occupying, in fact, the minimum of space in a building.
Its disadvantages are its high cost, the expense of setting up, the space required for turning the pipe and fittings, in setting up the piping, and the difficulty and expense of disconnecting for alterations or repairs.
The Flanged Screw Joint. Figs. 502 and 503 represent the first class of screw joints which we have designated as the flanged screw joint. It is intended especially for cast-iron pipe, and its principal feature consists in casting or constructing upon the spigot end of a pipe two or more threads, the inside of the socket of the pipe to which it is attached being cast with corresponding grooves. There is also a collar formed on the spigot end. The complete joint is formed by covering the spigot and socket ends of the pipe with a layer of cement or other quick-setting substance and screwing the two pipes together. By a slight turning of the pipes or either of them on their axes the connection is made. Instead of casting or otherwise permanently attaching threads upon the spigot end of the pipe, the pipe may be moulded with suitable grooves in which threads of steel or iron are afterwards placed. By using a paste of iron filings and sal ammoniac an excellent rust joint could be made by this arrangement. But the coarseness of the thread and the difficulty of insuring the cement following the thread against the friction of screwing up are defects which seem inherent in the device. It could not be relied upon to retain, at all parts of the threading, sufficient binding material to insure a perfect joint. Moreover, the joint lacks flexibility in setting up, so that the fittings could not be adjusted at different angles or to different positions with facility.
Fig. 504 shows another form of flanged screw joint, the threaded parts being on detachable sleeves. This joint might be included with equal propriety under the preceding class of sleeve joints, inasmuch as its tightness is dependent rather upon rust or other packing between the sleeve and the pipes, than upon the threading. But where the rust makes the pipe and its sleeve practically one piece, the joint becomes ultimately a true screw joint. This joint is intended either for cast iron or else for soft metal, which would allow of the ends to be slightly flanged out, as shown, to hold the threaded collars. The joint is subject to the same disadvantages as the above described screw joints, with the additional defect of the liability of the collars becoming loosened in screwing on the outer sleeve.