The additional center ring,
E, is intended to prevent leakage through the cut in the expanded ring
and over the face of the unexpanded one, which might occur when the
rings and cylinder should become so worn that the rings, when not
expanded, should collapse and leave the surface of the cylinder. The
rivets, F, shown by the dotted lines, are placed near the cuts in the
L-rings, and are intended to hold the outside and inside rings together
at that point, and prevent any tendency on the part of the latter
to collapse and let steam under that part of the L-rings. Probably,
however, if the packing is properly constructed and adjusted in the
first instance, these devices will be unnecessary. In horizontal
cylinders the weight of the piston, if properly supported on the set
screws and gibs, will accomplish these objects, if the cuts in the
L-rings are placed near the bottom side of the cylinder. The steam
enters the annular space between the beveled edges of the spider flange
and follower and the inner periphery of the overhanging part of the
L-rings, and acts only on that part.
[Illustration: Fig.
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