In many factories and repair shops, lifting and positioning equipment is used to move heavy objects or to remove parts to expose the underside of the vehicle or to provide easier access for repair and/or replacement of parts and assemblies. This allows a worker to inspect, repair or assemble various items with greater ease than when attempting to work through gaps or crawl spaces.
U.S. Pat. No. 7,603,734 to Connelly et al discloses a system for lifting a passenger boarding bridge for an aircraft that avoids rack fault. The system has two electromechanical screw jacks. Each motor receives a signal for adjusting the height of the tunnel selection and the system uses rotational sensors to monitor the position of the two screw jacks. Connelly does not appear to disclose a controller that monitors multiple sensors from each column to determine the position and load on the screw jacks to calculate a control signal for each of the columns.
One difficulty encountered with rotational sensors is that they can become out of phase by missing a rotation count. For example, the rotational sensor may count each rotation based on passing a optic or magnetic sensor. In many cases, some of the rotations may not be properly counted, which could lead to one column bearing a higher percentage of the overall load. Further, if the rotational sensor does not count rotations correctly, rack fault could occur.
U.S. Pat. No. 6,923,599 to Kelso discloses an in-ground lifting system for raising a building foundation. Kelso appears to show columns placed below the foundation of a building. Kelso also appears to disclose the ability to monitor the position through sensors to minimize stresses on the foundation. It does not appear that a control program monitors multiple types of sensors from each column to determine the position and/or load in order to calculate a control signal.
It is therefore desired to provide a lifting and positioning apparatus that overcomes the disadvantages of the prior art.
Vehicles such as busses, cars and rail vehicles may not provide enough space between the ground and the underside of the vehicle for access to parts or assemblies that require inspection and repair. These vehicles are often rather heavy, and lifting the vehicle or positioning various parts of the vehicle requires precise balancing and positioning of the various items. Also, the machinery used to lift or position these items undergoes a great deal of wear, and thus the maintenance and proper function of the lifting equipment itself is critical for safety concerns.
Various car hoist or drop table systems are known in the art. These systems have more than one lifting column connected to a single motor, where the rotation of the motor causes translation of a support on the column through a transmission system. The transmission system can be used to adjust the gearing to likewise adjust the speed of the support that moves along the column. For example, FIGS. 6 and 7 show a positioning apparatus having a motor 1 that is connected to transmission columns 3, 5, 7, 9. These transmission columns are connected to the motor via a drive shaft. As shown in FIG. 7, a track section 11 is connected to the transmission columns. The motor rotates the drive shaft to transmit a rotational force to each of the transmission columns 3,5,7,9. These transmission columns have a gearing system that adjusts the rotation of the screw 13, 15, 17, 19. As discussed previously, the load on the columns is often rather high, which can result in increased wear. Failure of gears within the transmission column can result in serious safety issues if failure occurs after a heavy load has been lifted above the floor.
Further, the replacement and maintenance of the transmission columns can be a skill and labor intensive process that may require specialized individuals who have been trained to repair a particular machine. The scheduling of the repair personnel can often result in a shutdown of a given machine in a way that can create bottlenecks in the repair shop or factory.
In some cases, the positioning device is designed to lift the entire vehicle for inspection and repair of the underside of the vehicle. In some cases, the positioning device is designed to be placed under a specific part or assembly of the vehicle, where the part or assembly is dropped down from the vehicle.
As an example, a rail car such as a locomotive can be rather heavy. It may be more efficient and safer to bring a wheel and axle assembly down from the engine rather than lifting the entire engine. In some cases, however, it is more appropriate to lift the entire rail car or locomotive. In other cases, the repair may only necessitate lifting a part or assembly of the rail car, for example a wheel assembly. The lifting apparatus used depends on the repair or assembly job to be completed.
The precision of the lifting process is important to balance the load and to ensure correct positioning of the columns and correct positioning of the rail car, locomotive or part or assembly thereof. The present systems and methods provide a more user friendly lifting and positioning apparatus which can likewise can aid to provide a safer working environment and reduce repair and maintenance costs.
As a further aid to safety and reliability, the position control can reduce un-necessary damage to the apparatus. Since of the mass of the item to be lifted may be relatively large, the columns can generate substantial torques and forces. If the position of the individual columns is not controlled properly, one or more of the columns could come out of alignment and bend the support structure that is connected to the columns. Thus, the failure to properly control the columns can result in damage to the structure of the lifting apparatus itself.