Pipe connecting assembly and method for joining two lengths of pipe by a press-fit connection

In combination with at least two adjacent lengths of metal pipe of the type wherein the lengths of pipe are conventionally welded together generally horizontally, end-to-end, at a pipelaying site in both trenching pipelaying and in trenchless pipelaying, an improvement eliminating the welding of the lengths of pipe at the pipelaying site in order to join the lengths of pipe, the improvement comprising:

• the two adjacent coaxial lengths of metal pipe have cylindrical exterior surfaces with substantially equal exterior diameters and the two adjacent lengths of metal pipe have cylindrical interior surfaces with substantially equal interior diameters;
• one of the two adjacent lengths of metal pipe has a tubular male connector provided on one end of the one length of pipe, the tubular male connector has a center axis and extends coaxially from the one length of pipe to a distal end of the male connector, the male connector has a cylindrical interior surface with an interior diameter substantially equal to the interior diameters of the two lengths of pipe, the male connector has a cylindrical exterior surface with an exterior diameter substantially equal to the exterior diameters of the two lengths of pipe, the exterior surface of the male connector has an annular end wall formed therein spaced axially from the distal end of the male connector, the annular end wall extends radially from the exterior surface of the male connector toward the center axis of the male connector and is perpendicular to the center axis, extending axially from the annular end wall to the distal end of the male connector the exterior surface is formed with a plurality of sequences of four exterior surface configurations, each sequence including a flat annular surface that extends parallel to the male connector center axis, then a flat annular wall that extends radially outwardly from the flat annular surface perpendicular to the connector center axis, then a flat annular ridge that extends from the flat annular wall substantially parallel to the connector center axis, and then a tapered annular ridge that extends from the flat annular ridge and tapers toward the connector center axis, and then the sequence of surface configurations repeats for each sequence of the plurality of sequences, and the plurality of sequences end at a flat annular end surface at the distal end of the male connector, the flat annular end surface having the smallest exterior diameter on the male connector;
• a second of the two adjacent lengths of metal pipe has a tubular female connector provided on one end of the second length of pipe, the tubular female connector has a center axis and extends coaxially from the second length of pipe to a distal end of the female connector, the female connector has a cylindrical interior surface with an interior diameter substantially equal to the interior diameters of the two lengths of pipe, the female connector has a cylindrical exterior surface with an exterior diameter substantially equal to the exterior diameters of the two lengths of pipe, the interior surface of the female connector has an annular end wall formed therein spaced axially from the distal end of the female connector, the annular end wall extends radially from the interior surface of the female connector away from the center axis of the female connector and is substantially perpendicular to the center axis, extending axially from the annular end wall toward the distal end of the female connector is a flat interior annular surface that extends substantially parallel to the female connector center axis, and extending axially from the flat annular surface to the distal end of the female connector the interior surface is formed with a plurality of sequences of four interior surface configurations, each sequence including a tapered annular surface that tapers away from the center axis of the female connector, then a flat annular surface that extends from the tapered annular surface parallel to the female connector center axis, then a flat annular wall that extends radially inwardly from the flat annular surface perpendicular to the female connector center axis, and then a flat annular ridge that extends from the flat annular wall parallel to the female connector center axis, and then the sequence of interior surface configurations repeats for each sequence of the plurality of sequences, and the plurality of sequences end at the distal end of the female connector;
• wherein,
• the male connector is inserted into the female connector forming a press-fit connection between the two adjacent lengths of metal pipe that is capable of transmitting axially directed forces across the press-fit connection.

A method of pipelaying by connecting two lengths of steel pipe without welding the pipe, the method comprising:

• forming first and second tubular members of steel with each member having opposite ends and each member having cylindrical exterior and interior surfaces with diameters that are the same as exterior and interior diameters of the steel pipe to be connected;
• forming a tubular male connector on one end of the first tubular member with the male connector having an exterior surface with a plurality of annular ridges and flat surfaces formed thereon;
• welding an end of the first tubular member opposite the male connector to an end of one of the two lengths of steel pipe;
• forming a tubular female connector on one end of the second tubular member with the female connector having an interior surface with a plurality of annular ridges and flat surfaces formed thereon;
• welding an end of the second tubular member opposite the female connector to an end of a second of the two lengths of steel pipe;
• press fitting the male connector into the female connector and thereby joining the two lengths of steel pipe together;
• and
• using a male push ring that is configured to pass inside the female connector and engage the one end of the second tubular member to exert a pushing force on the second tubular member without damaging the female connector.