Abstract: In a connection structure (A) for a manhole pipe (1) and sewer main pipe (2) in which the sewer main pipe (2) places one end at a circular opening (12) of the manhole pipe (1) through a flexible coupler (F), the flexible coupler (F) has a rubber coupler body (3). Around an inner surface of the rubber coupler body (3), there is provided a water-sealing ridge (32) with a butylene rubber layer (33) placed around an outer surface of the rubber coupler body (3). On a rear end surface of the rubber coupler body (3), has an outer flange (31) which is brought into engagement with an outer periphery of the circular opening (12) upon inserting the rubber coupler body (3) to the circular opening (12) of the manhole pipe (1). A rubber coupler cylinder (5) is provided to have a diameter-increased cylinder portion (51), a diameter-reduced cylinder portion (52) and a transitionary portion (53) connecting the diameter-increased cylinder portion (51) to the diameter-reduced cylinder portion (52).

Abstract: A duct connection assemble, whereby upon connecting a saddle flange (2a) of the joint duct (8) to the main ribbed duct (3) through the communication hole (1b), the rubber sealant (1) is interposed between the saddle flange (2a) and a circumferential area of the communication hole (1b) so that protuberances (2b) uniformly press the rubber sealant (1) through the recesses (1d) to tightly engage the saddle flange (2a) against an outer surface of the main ribbed duct (3) through rib-fitting grooves (1a) and the water sealing small projective rings (1c). The joint duct (2) is brought into an elastical engagement with the main ribbed duct (3) to achieve a good water sealing action for an extended period of time.

Abstract: In a duct connection assemble, whereby upon connecting a saddle flange 2a of the joint duct 8 to the main ribbed duct 3 through the communication hole 1b, the rubber sealant 1 is interposed between the saddle flange 2a and a circumferential area of the communication hole 1b so that protuberances 2b uniformly press the rubber sealant 1 through the recesses 1d to tightly engage the saddle flange 2a against an outer surface of the main ribbed duct 3 through rib-fitting grooves 1a and the water sealing small projective rings 1c. The joint duct 2 is brought into an elastical engagement with the main ribbed duct 3 to achieve a good water sealing action for an extended period of time.