the connecting ring 54 is fixed to some of a plurality of radial beam members 56 which make up a structure 58 in the assembly of the apparatus 10 the inner and outer rings 50 48 are located on the manifolds 26 24 and the structure 58 is lowered until the connecting ring 54 is disposed intermediate the rings 48 50 and the radial members 56 bear on the rings 48 50 a number of latches 60 are associated with some of the radial members 56 inwardly and outwardly of the connecting ring 54 an example of such latches 60 is shown in fig6 and 7 and includes an arm 62 pivotally fixed to a radial member 56 and a hook member 64 pivotally fixed to the arm 62 upwardly of the arm radial member pivot point so that as the arm 62 is moved upward the hook member 64 will seat in an opening provided in a flanged portion of the ring 50 and will draw the ring 50 and radial member 56 together so that the ring 50 is fixed relative to the structure 58 the other latches 60 for relatively fixing the rings 48 50 to the structure 58 of course are similar.