Buoyant body control device

A control device comprising:

• a liquid reservoir having an inlet for feeding a liquid into the reservoir, and an outlet of larger cross-sectional area than said inlet for discharging the liquid from the reservoir;
• and a buoyant body within said reservoir and movable to an upper control position and to a lower control position in response to the level of the liquid in said reservoir;
• said buoyant body including an outer surface at its bottom normally engageable with a bottom surface of the reservoir in said lower control position but movable by buoyancy away from said bottom surface of the reservoir towards said upper control position during filling of the reservoir with liquid;
• said outer surface of the buoyant body including a cavity circumscribed by a rim engageable with said bottom surface of the reservoir in said lower control position of the buoyant body to define a chamber isolated from the reservoir when the liquid is at a low level within said reservoir;
• said device further including a passageway which normally connects said chamber to a source of low pressure but which is connectible to a source of higher pressure, such that during the filling of the reservoir with the liquid, the low pressure applied to said chamber by said low pressure source normally holds the buoyant body in said lower control position until the chamber is connected by said passageway to said source of higher pressure to permit the buoyant body to move by buoyancy to said upper control position.