In the groove in the leaden ring temporary sheet iron discs, formed in two parts and held together by hooks, are then placed. The two coupling rings are then pushed against the disc, which by resisting allows of and facilitates the junction, at the same time preventing the groove from being flattened' or closed. The junction being completed, the disc is removed and the outer hoop is placed over the whole, and cement is put in the empty spaces between the coupling rings and the pipes beyond the lead ring.
The groove in the leaden ring is designed for the purpose of giving a certain flexibility to the joint, and allowing of expansion and contraction of the pipes, and I introduce it on account of its ingenuity and to illustrate the pains taken in the effort to overcome the destructive effect on lead packing by expansion and contraction.
The method here tried is ineffective, and the joint is open to all the objections of the ordinary lead caulked bell and spigot joint.
Figs. 486 and 487 represent a sleeve joint in which rubber is used for packing. A hollow cylinder or shell is constructed of brass or iron, and has belts cast upon it for additional strength. The ends are bevelled or inclined inwards towards the pipe, so as to contract the opening for the insertion of the pipe, and to form recesses into which are forced annular conical India-rubber rings or other similar packings. These rings or packings are so formed that when internal pressure is applied they press against the contracted ends of the cylinder to give rigidity to the joint, but when flexibility is desired, the webs are omitted. Fig. 488 shows one side of a pipe having a cold lead packing ring. The pipe is shown partly in elevation and the packing and clamping rings in section. The ends of the pipes are here provided With slight enlargements or collars. A strip of lead, shaped to fit the enlarged ends, and having a central rib underneath to project into a space left between the ends of the pipes, is lapped around so as to embrace the ends of the pipes. A circular band or collar is then tightened round the lead by a "press collar," and finally all is secured by binding rings. The ends of the pipes abut against the central rib of the lead and prevent shifting of the packing when the binding rings are driven on. These rings are formed to fit the outer surface of the pipe, in order that their binding pressure may be equally distributed.
Fig. 489 shows a sleeve joint in which the ends of the pipe are grooved or corrugated and connected by means of a lead ring compressed into the corrugations. This lead ring is of double conical form externally, and has at the middle of its length an internal annular rib which forms an abutment for the ends of the pipes to be coupled. The joint is completed by forcing over the opposite ends of the leaden sleeve conical clamping rings, which, when driven home by means of a hammer or cramp, will compress the lead into the annular grooves. Collars, brackets or ears may be cast on the pipes at some little distance from the ends, to prevent injury to the joint or pipe in ramming the earth about it when it is used under ground.
In all these lead packed joints the same weakness is inherent. They fail under expansion and contraction of the pipes, the corrugations forming no more protection in restraining this force than a rope of sand.
Figs. 490 and 491 show a sleeve joint in which a rubber band is used for packing, secured by means of an elastic metallic strap. The India-rubber in a broad band is made to embrace the two ends of the pipes. Over the band is then placed a metallic strap, which is drawn together by means of screws or wedges. The tightening of the strap forces the India-rubber band into a number of annular grooves with which the strap or ends of the pipe are furnished.
Figs. 492 and 493 show a joint similar to the last, except that a small bead is formed on the ends of the pipes, and the sleeve is bevelled, or wider on one side than on the other, to enable the pipes to be connected on an angle. The edges of the metallic collar used to compress and hold the rubber packing sleeve are turned down, as shown, so as to bring the packing close down over the beads. The collar is strained on by means of a bolt and nut, in the same manner with that in the joint preceding.
Fig. 494 shows a sleeve joint for cement or melted lead packing. A movable or shifting sleeve or jacket is placed over the ends of the pipes, and has openings for the introduction of the packing. ' The ends of the pipes are grooved, and corresponding grooves are cast on the inside of the sleeve. These are intended to protect the pipes from longitudinal movement. The joint is bulky and expensive.
Divided Ring Sleeve Joint.
Figs. 495, 496 and 497 represent a sleeve joint connected by means of half rings bolted together. The general principle of this consists in lapping soft leaden or metallic packing round the meeting ends of the pipes, and forcing this packing into intimate contact with the surface of a screw clip or hinged collar, the pipe ends externally, and the packing internally, having annular grooves and ribs, which respectively bed the ribs on the pipes into the grooves in the packing, and vice versa, when the hinged collar or clip is temporarily closed around them by a screw. The collar is afterwards removed, and a hoop of wrought iron, conical internally, is driven on over the lead. Instead of using the lead alone, India rubber may be used in connection therewith; the lead packing may be made conical, to correspond with the collar and hoop, and the annular grooves and ribs on the pipe ends may, of course, have an endless variety of shapes.