Plugging the hot stuff

A lot of inventors obviously get inspiration at bathtime. David Newton of
Preston has patented (GB 2 290 467) a temperature-sensitive plug which empties a
bath if the water gets dangerously hot. The plug is made from two halves, with a
spiral spring which tries to push them apart. When the plug is cold, a
bimetallic latch of aluminium and nickel holds the plug together. But when the
water passes a threshold temperature, the latch trips to pop the plug open. And
Ronald Harris and Jenny Elphik of Hampshire want to stop baths overflowing (GB 2
319 723). They simply attach the plug to a short chain and air-filled sphere. If
the bath gets too full, the chain tightens and pulls the plug out.