Connecting mechanism for a thin stainless steel pipe and a joint includes a thin stainless steel pipe in which a chevron type projection portion is formed in an outer periphery of an end portion.

Joint having an inner diameter inserting the thin stainless steel pipe and forming a male thread portion in an outer peripheral surface of an end portion, a nut having a fitting portion outwardly fitted to the thin stainless steel pipe so as to oppose to the joint on the boundary of the chevron type projection portion and having a female thread portion screwed to the male thread portion of the joint, and a packing provided between the joint and the thin stainless steel pipe wherein, a release groove is formed in a packing outer peripheral contact surface from the packing pressing surface constructing the inner side surface of the packing fitting portion of the joint to an opening end portion.

In accordance with the related art mentioned above, since it is hard to discriminate from an outer side even in a case where the female thread 8 of the nut 4 is not sufficiently fastened to the male thread 7 of the joint 2 such as a temporalfastening by a manual fastening having a weak fastening force at a time of a piping execution, this matter is often passed over at a time of inspecting a construction finish.

Further, a water leak is checked by tentatively circulating a pressure waterafter the end of the piping construction, however, since the packing 3 is closely attached to the joint 2 and the inclined surface 5b of the thin stainless steel pipe 2 even in the manual fastening stage, the water is not so leaked, so that this matteris often passed over. Due to the reason mentioned above, if the nut 4 is started to use in a state where the nut 4 is not sufficiently fastened to the joint 2, which causes a problem that the connection between the nut 4 and the joint 2 is detached, andthe water leak of the fluid such as the water flowing within the thin stainless steel pipe 1 or the like simultaneously arises, whereby a portion within a building is soiled.

This invention is made for solving the problem mentioned above, and an object of this invention is to provide a connecting mechanism for a thin stainless steel pipe and a joint which can check out a fastening failure and an insufficient fasteningat a time of a piping execution for screwing and firmly attaching a male thread portion of a joint to a female thread portion of a nut fitted to a thin stainless steel pipe, based on a leakage of a pressure water.

Accordingly, the water intruding into a spacegenerated between the packing pressing portion of the packing fitting portion projection and the packing passes through the gap corresponding to the height of the projection via the gap between the joint and the thin stainless steel pipe, thereby leakingout to the external portion from the screwed portion between the nut and the joint or the joint portion between the nut and the thin stainless steel pipe.

On the other hand, at a position at which the nut is sufficiently fastened, since the packingpressing surface of the packing fitting portion of the joint presses the packing against the joint contact surface of the nut and the inclined surface of the thin stainless steel pipe so as to stop water, the water in the thin stainless steel pipe doesnot leak out to the external portion. Further, even if a small space is generated between the packing pressing surface of the packing fitting portion and the packing and the water intrudes thereinto, the packing compressed by fastening the nut isdeformed, whereby the gap corresponding to the height of the projection is filled up with the packing. Accordingly, no water leaks out to the external portion through the gap.

As mentioned above, it is possible to securely find out the position atwhich the fastening of the nut is insufficient, by circulating the pressure water to the thin stainless steel pipe so as to specify the position at which the water leak is generated. Further, it is preferable to fasten the nut at which the water leaksout.

A description will be given below of a preferred embodiment of this invention. This invention is different from the related art in a point that a joint 2 is improved in such a manner that a water leak is generated in a case where a fastening ofa nut 4 is insufficient at a time of coupling a thin stainless steel pipe 1 via the joint 2 and a packing 3 by the nut 4. Since the other constituting elements are the same as the related art, a description thereof will be omitted by attaching the samereference numerals.