Two-position gate and sprung gate valves having a full-flow open position and a restricted-flow open position

A two-position gate valve comprising:

• a sprung gate assembly comprising:
• an endless elastic band having an inner perimeter defining an open space;
• a first gate member defining a full-flow exit and a restricted-flow exit;
• a second gate member defining a full-flow passageway having an entrance with a first area and an exit with a second area and defining a restricted-flow passageway having an entrance with a third area and an exit with a fourth area;
• wherein both the full-flow passageway and the restricted-flow passageway continuously taper from the entrance to the exit thereof, and the fourth area is smaller than the first area, the second area, and the third area, and wherein a ratio of the fourth area to the second area is in a range of 5 to 15;
• wherein the endless elastic band is sandwiched between the first and second gate members with the full-flow passageway and the restricted flow passageway received within the open space thereof;
• wherein the first and second gate members collectively define a full-open position and a restricted-flow position, without defining a closed position;
• wherein flow through the full-flow passageway is in a first direction and flow through the restricted-flow passageway is also in the first direction;
• and
• an actuator to move the gate between a full-flow position and a restricted-flow position.