housing means 2 in a manner to be hereinafter described an opening 27 is provided in the housing ring 26 and an opening 19 is provided in the cylindrical mounting member 18 which are larger than and aligned with the cylindrical opening 12 in the backing plate 6 through which one end of the transfer tube assembly 14 passes the transfer tube assembly 14 comprises an outer tubular member 50 with an enlarged head 52 at one end thereof the enlarged head being formed having an outer spherical surface 54 with a small conical seat 60 at its free end said spherical surface 54 having a groove therearound containing a seal member 73 the other end of the outer tubular member 50 is slightly enlarged to form an outer spherical surface 58 said spherical surface 58 having a groove therearound containing a seal member 71 contacting the inner surface of the cylindrical opening 12 an inner rod member 72 is located in the tubular member 50 with one end being threaded and having a cylindrical member 74 threadably mounted thereon with a diameter such that the cylindrical member has its periphery adjacent the inner surface of the cylindrical opening 12 cylindrical member 74 has a groove therearound containing a seal member 76 contacting the inner surface of the cylindrical opening 12 the other end of the rod 72 is threaded and has a small flange 78 extending outwardly therefrom the threaded portion of the rod 72 extends through an opening 79 in the center of.