Abstract: Each of the semi-circular coupling segments has pipe fastening parts. One pipe fastening part has a protrusion to be in contact with the side surface of the circumferential groove of one pipe nearer to the end of the pipe in one of the end sections thereof with respect to a circumferential direction, and a protrusion to be in contact with the side surface of the circumferential groove of the pipe farther from the end of the pipe in the other end section thereof with respect to the circumferential direction. The other pipe fastening part has a protrusion to be in contact with the side surface of the circumferential groove of the pipe farther from the end of the pipe in one of the end sections thereof with respect to the circumferential direction, and a protrusion to be in contact with the side surface of the circumferential groove of the pipe nearer to the end of the pipe in the other end section thereof with respect to the circumferential direction.

Abstract: A pipe is assembled from sections of a liner pipe formed of a moulded glass reinforced plastics material (GRP). A sleeve, also of moulded GRP, sealingly surrounds the joint between the sections. An outer pipe of polymer concrete is formed in sections on the liner pipe sections to surround the latter together with the sleeve. The sections have a packer provided between adjacent ends, and the joint is offset from the joint between the liner pipe sections. The GRP of the liner pipe can withstand high chemical concentrations in toxic sewage, the sleeve preventing seepage of sewage and being able to withstand chemical attach by any passing through the inner joint. The polymer concrete enables the pipe to withstand jacking forces, and is also resistant to chemical attack from a basically saline surrounding soil.

Abstract: Disclosed is a new bow nock device for use with a conventional release aid for extending the useful life of a bowstring by eliminating wear caused by the release aid and additionally for improving accuracy by aligning an arrow directly in front of the release aid to maintain the arrow at a 90.degree. angle relative the longitudinal axis of the bow during the entire arrow release process. The bow nock device comprises a U-shaped member attachable to the bowstring for gripping by the release aid and for positioning a nocked end of the arrow between the ends thereof. The U-shaped member has a bowstring receiving groove formed on each end, each groove having a flared mouth for preventing bowstring chafing, and internal facing protrusions co-pending with the end of the arrow for stabilizing the same. Two fastening plates, attached to the U-shaped member with flat head machine screws, hold the bowstring within the bowstring receiving grooves whereby clampedly retaining the bowstring within the grooves.