Fig. 453 shows a somewhat improved form of this joint. The most conspicuous difference between the two forms is that there is no groove in the bell, but instead the groove is made in the gasket itself as shown in the drawing. The gasket lies in a double inclined seat in the bell, and comes flush and level inside. When the forcing compound is injected the effect is to force the two wedge-shaped sections of the gasket apart, driving each into its seat firmly and solidly. The power is thus used to better advantage, it being applied to forcing the gasket into the inclined spaces between the spigot and the bell. The lead caulked bell and spigot joint, however, being radically defective in principle, a refinement in the machinery for caulking is not worth while.
The Rubber Ring Joint.
Rubber joints, or those in which rubber gaskets are used between the bell and spigot, may be made tight as long as the rubber retains its life and elasticity. The gaskets are made of vulcanized India rubber, cylindrical in section, so that they will easily roll when slipped on the end of the pipe. But to procure India rubber well cured and of good quality is difficult and costly, and the material has not been used for joints to any great extent in this country.
Fig. 454 shows this kind of joint. The spigot has a ring or shoulder on its end, and a groove just within the ring. The rubber ring is stretched over the shoulder and placed in the groove. A second shoulder collar is cast on the spigot beyond the groove, to prevent the rubber from being blown off under high pressure. The rubber ring is forced up to this shoulder when the pipes are put together.
Soft Packing Joint.
Under this heading are included all joints packed with red lead, putty, cement or other material which is plastic when applied. Joints well made with red lead may be made tight against pressure, when used in connection with the proper form of couplings as in screw-jointed pipes.
Sulphur and pitch joints have been made with a composition consisting of equal parts of these substances. This composition is used to some extent in the arts for making joints analogous to those in soil pipes.
Fig. 455 gives another form of soft packing joint. Neither of these joints is capable of withstanding the hydraulic test, however long they may be allowed to set. The joint consists of a double socket. Near one end of the pipe, and around the outside, a cupped or recessed collar is formed, which, with the continuation of the pipe, forms a socket. The joint is made by forcing the projecting inner ring of the first socket into the socket of the following length, until it butts tight against a shoulder formed inside of the small socket. The outer ring of the smaller socket then enters the larger socket, forming, with the packing, the joint.
Fig. 456 shows a third form. This joint is, however, designed more particularly for use with earthenware pipes. A tapering ring of plaster of Paris or cement is cast on the end of the spigot, by the use of carefully turned moulds. The socket end has a corresponding ring cast on its internal surface to exactly fit the ring on the spigot.
The ends of the pipe are then covered with coal tar, grease, tallow, paraffine, or other suitable varnish or lubricating material, and inserted one within the other. The joint is dependent upon the accuracy of the fit of the two ends to render it air and water tight.
Fig. 457 represents a bell and spigot joint with soft packing in which bolts are used to hold the joint together and compress the packing. A collar is slipped over the spigot end of the pipe before the spigot is inserted into the socket. Part of this collar is to enter the mouth of the socket and compress the packing therein. Any suitable means can be employed for forcing and keeping the collar against the packing. By using loose sockets and collars plain pipes may be jointed in this manner.
Fig. 458 illustrates a soft packing joint put together by threaded rings. The socket end of the pipe is cast with an external screw thread, and has an internal annular projection near its end. A nut or collar is screwed on the socket by means of a projecting rim. The spigot, covered with a packing ring, is slipped into the socket. The collar, having been previously slipped over the spigot is then screwed on the socket, and the annular projection on the collar squeezes the packing into the socket against the projecting rim.
The annular projection on the end of the spigot is intended to prevent the accidental withdrawal of the pipe from the socket. Between the packing ring and the bottom of the socket, there is sufficient space to allow the spigot a certain amount of longitudinal play.
Figs. 459, 460 and 461 represent one more soft packing joint. The object of this device is to form a plumber's joint on cast iron pipes, without caulking and without turning, threading or finishing the ends of the pipes, but using them rough as they come from the foundry. One end of the pipe has a double annular shoulder cast upon it a short distance from the end; the other end has a smaller single annular shoulder cast at the extreme end of the pipe, and at the outer edge of the shoulder a small annular projection. A ring of metal is placed on the second or outer shoulder of the end of the lower pipe to be joined, which has the double shoulder uppermost. This ring forms with the end of the pipe a triangular or wedge-shaped annular groove, which is then filled with packing in the groove, and forms the joint. The packing consists of a rust joint paste. The pipes are brought together by means of screws passing through lugs or ears on the detachable rings as shown. The contrivance allows either pipe to be turned on its axis in any direction when setting it and it forms a rigid steam tight joint when the packing hardens. This is an early device of the writer, but is too complicated, and it would be better to omit the spigot projection on the upper pipe annular ring, because then the pipes could be disconnected at any time by removing the bolts and breaking the outer ring.