Base-clamp assembly

1. A base-clamp assembly for supporting an instrument-support apparatus having a shank extending adjacent to an equipment-mounting rail for supporting instruments relative to a patient position adjacent to the rail, the base-clamp assembly comprising:

a base;

a shank clamp for attaching the shank to the base;

a rail clamp having a first rail jaw fixedly supported relative to the base, and a second rail jaw mounted for pivoting relative to the base and opposing and movable relative to the first rail jaw, the first and second rail jaws forming a rail opening, the second rail jaw being movable between an open position in which the rail opening is sized for receiving a rail and a closed position in which the rail jaws securely hold the rail; and

an actuator assembly operable for moving the second rail jaw relative to the first rail jaw, the actuator assembly including a first force-applying element movable relative to the base and the second rail jaw, for applying a first force to the second rail jaw tending to move the second rail jaw toward the closed position, and a drive assembly manipulable for moving the first force-applying element relative to the base, wherein the drive assembly includes a frame movable relative to the base and the first force-applying element includes a roller mounted to the frame for rotation about a roller axis, the roller applying the first force to the second rail jaw.

2. A base-clamp assembly for supporting an instrument-support apparatus having a shank extending adjacent to an equipment-mounting rail for supporting instruments relative to a patient position adjacent to the rail, the base-clamp assembly comprising:

a base;

a rail clamp having a first rail jaw fixedly positioned relative to the base, a second rail jaw opposing and movable relative to the first rail jaw, and a rail-jaw axle coupling the second rail jaw to the base for pivoting the second rail jaw relative to the base, the first and second rail jaws forming a rail opening, the second rail jaw being movable between an open position in which the rail opening is sized for receiving a rail and a closed position in which the rail jaws securely hold the rail;

a shank clamp having a first shank jaw fixedly positioned relative to the base and a second shank jaw opposing and movable relative to the first shank jaw, the first and second shank jaws forming a shank opening, and the second shank jaw being movable between an open position in which the shank opening is sized for receiving a shank of the instrument-support apparatus and a closed position in which the shank jaws securely hold the shank;

an actuator assembly operable for moving the second rail jaw relative to the first rail jaw and moving the second shank jaw relative to the first shank jaw, the actuator assembly including a first force-applying element movable relative to the base and the second rail jaw for applying a first force to the second rail jaw tending to close the second rail jaw, a second force-applying element for applying a second force to the second shank jaw tending to move the second shank jaw between the open and closed positions, and a drive assembly for moving the first force-applying element relative to the second force-applying element; and

at least one bias element biasing the second shank jaw toward the open position, and

the at least one bias element, acting through the second shank jaw and the first and second force-applying elements to bias the second rail jaw toward the closed position.