Abstract: Disclosed is a polar crane supported by a rail and having a bridge and a bridge-supporting end truck at each end of the bridge. Each end truck has, for either direction of revolving bridge motion, a leading wheel contacting the rail. In the improvement, the leading wheel of each end truck has a single flange and the flange is inward of the rail. Skewed crane "lock-up" is thereby substantially prevented. A related method for modifying a polar crane includes raising the first end truck away from the rail, removing a two-flange wheel (the leading wheel) from the first end truck and installing a one-flange wheel in place thereof.

Abstract: An overhead traveling crane adapted to be supported on a pair of spaced apart, generally parallel first and second rails, the crane comprising a frame having opposite first and second ends, a first drive wheel which is rotatably mounted on the first end of the frame and which is adapted to roll along the first rail, a first idler wheel which is rotatably mounted on the first end of the frame and which is adapted to roll along the first rail, a second drive wheel which is rotatably mounted on the second end of the frame and which is adapted to roll along the second rail, a second idler wheel which is rotatably mounted on the second end of the frame and which is adapted to roll along the second rail, a first motor mounted on the frame and drivingly connected to the first drive wheel, a second motor mounted on the frame and drivingly connected to the second drive wheel, an idler shaft connecting the idler wheels such that the idler wheels rotate at the same speed, a hoist moveable along the frame in a direction

Abstract: A skew correcting apparatus for a crane having drive wheels traveling on spaced apart rails which are independently driven. Each one of the drive wheels has an axially extending single diameter cylindrical surface and first and second axially spaced apart radially extending circumferential flanges. The spacing distance of the first flange of each of the first and second wheels is such that, when the crane is in one of the skewed positions the first flange of the leading wheel in the direction of travel engages the faced outer side of the rail head and the engagement of the second flange of the lagging one of the wheels with the inner rail side which it faces is minimized. Each rail head has a shoulder surface including a radius defining a cross-sectional shoulder curvature. The first flange of each one of the wheels also includes a circumferential flange juncture surface adjoining the cylindrical surface.

Abstract: A skew correcting apparatus for a crane supported on spaced apart generally parallel rails by a plurality of wheels including a drive wheel traveling on each of the parallel rails. The drive wheels traveling on the spaced apart rails are driven such that they rotate at the same speed. One of the drive wheels has an axially extending single diameter cylindrical surface engaging the top side of the rail head and a radially extending circumferential flange facing the inner side of the rail head. In one of the skewed positions of the crane, one of the wheels lags the other of the wheels and is subject to high levels of skew force such that the flange of the lagging wheel and the inner side of the rail head it faces engage each other. Each one of the wheels also includes a flange juncture surface joining the cylindrical surface of the flange of each wheel.

Abstract: A drive for a traveling bridge crane including a bridge having a width spanning two parallel spaced apart rails and opposite ends located at one of the rails. A first pair of wheels comprising first and second wheels are respectively mounted at the opposite ends of the bridge and each of the first and second wheels engage a different one of the rails. A second pair of wheels comprising third and fourth wheels are also mounted at the opposite ends of the bridge and each engage a different one of the rails. The crane travels along the rails on the first and second pair of wheels in a position generally parallel to the rails. The crane is subject to unbalanced wheel rotating forces causing the crane to frequently attempt to skew. First and second drive mechanisms are respectively connected to the first and second wheels of the first pair of wheels for rotating the first and second wheels independently of each other. A third drive mechanism is connected to both of the third and fourth wheels.

Abstract: A skew correction apparatus for a crane traveling on generally parallel spaced apart rails and having a drive wheel on each rail rotatably driven at the same speed. The drive wheels each have center cylindrical portions riding on a rail head and inside and outside flanges facing the sides of the rail head and having a larger diameter than the diameter of the center portion. The clearance distance between the inside flange of each drive wheel and the rail side it faces is smaller than the clearance distance between the outside flange and the rail side the outside flange faces. Thus, if the drive wheels and thereby the crane become skewed, only the inside drive wheel flanges will engage the rail sides. The lagging wheel of the skewed wheels will rotate against the rail side on the larger flange diameter of the wheel and tend to ride up on the rail side.