Ladder clamping device for vehicle rack

A rack which supports a ladder and which is mountable to a vehicle, said vehicle rack comprising:

• first and second pairs of first and second corner positions;
• first and second transverse frame members extending bridgingly between the first and second corner positions of the first and second pairs of corner positions, respectively;
• a first clamp mounted to the first frame member for engaging one rung of the ladder;
• a rod rotatably mounted to at least one of the corner positions between which the second frame member extends, said rod extending from said one corner position parallel to the second frame member;
• a second clamp mounted to the rod;
• handle means rigidly connected to the rod for rotating the second clamp in a first direction into engagement with another rung of the ladder or in the opposite direction out of engagement with said another rung of the ladder;
• a link proximate said one corner position and rigidly connected at a first linkage point to the rod and rotatable therewith;
• and
• spring means pivotally mounted at a second linkage point to the link and at a third linkage point to said one corner position for biasing the link in the first rotational direction when the second linkage point lies on one side of a line between the first and third linkage points and for biasing the link in the opposite rotational direction when the second linkage point lies on the other side of the line between the first and third linkage points.