Expansion beam for shoring up sand guards
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United States of America Patent
Stats
-
May 27, 1986
Grant Date -
N/A
app pub date -
Nov 2, 1984
filing date -
Jun 20, 1984
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A plug of an expansion beam for shoring up sand guards is equipped with a second non-return valve. If it should happen that the head of the plug is broken off owing to, for example, a falling rock, the second non-return valve works as a safety device to prevent the expansion and contraction of the expansion beam. Thus, the shoring up function is able to be maintained.
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Family
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Cited Art Landscape
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