| http://www.w3.org/ns/prov#value | - The control valve 144, which may be of any suitable type, has a casing 156 with a chamber 158 and a sliding valve 160 therein (FIG. 4), as well as conduits 162, 164 and 166, of which conduit 162 connects the valve chamber 158 with a source of fluid under pressure, such as compressed air, for instance, while the conduits 164 and 166 connect the valve chamber 158 with the rear and front ends, respec
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