In patent SE 466,960, a load hoist arrangement consists of a traversing device with travelling bridge and carriage. Two motors on the support structure drive cables that pull the travelling bridge in either direction.
But the design has some drawbacks. There is a need for a load hoist arrangement that supports motions in both lateral directions and not only along a line. By positioning the motors on the support structure, the design makes a relatively stable working environment. However, there are a lot of cables connecting static components with moving parts. These cables often connect to sensitive connections and couplings that will be prone to wear in this dynamic environment, risking less accurate motion control and increasing the need for maintenance. There is also a need for a load hoist arrangement that is easy and quick to install.
The invention is designed to overcome these issues and be capable of handling manually-induced accelerations, maintaining stability in the load hoist arrangement even when handling heavy goods.
Fig. 1 shows the invention. A control device 50 is arranged along a lifting cable 2 between a traverse device and load-carrying device 52. This load-carrying device is manually guidable in a three-dimensional space. A driving device controls the lateral movement of the load carrying device.
The vertical motion is not part of this patent. An industry-standard electronically-controlled balancer controls the vertical motion of the load-carrying device. A transmitter in the control device that tells the hoist to compensate for any load, so that an operator guiding the crane manually will experience a fraction of the total resistance of the load.
The driving device comprises two motors secured to carriage 3. The ends of two drag cables 21 and 21′ are secured to opposite ends of the supporting rails 5, 6 and cross at travelling bridge 4. The drag cables cross each other at the carriage so that a driving wheel unit 15 or 16 of one motor 10 or 11 works in contact with one drag element 21 or 21′.
The axle unit has two separate grooves, one for each drag cable. The combination of the two drag cable paths, each working in a different direction, locks the axle unit, providing the driving device with increased stability. The drag elements are arranged to turn in a 90 degree angle around a pulley from their anchor point to the carriage. With this arrangement, possible imperfections will be almost automatically corrected because the two drag cables working in opposition to each other.
The friction between the drag element and possible guide wheels 14, 17, axle units 18 and driving wheel units together with the drag cable path will prevent the drag cable from sliding when the driving device is in operation.
The carriage 3 is moved by actuation of the two motors 10, 11 and hence the load carrying device 52 will follow. The motors 10, 11 are capable of clockwise and counter-clockwise motion.
The motors are actuated by the movement of the load. The angle of a load-carrying element 2 is used as reference of force impact for guiding and controlling the driving device, and thus the load carrying device 52 in a lateral direction. The traverse device moves in proportion to the force manually applied by the operator. This allows a controlled movement of the load carrying device 52, relieving the operator from bearing the actual weight of the load while still being able to lift and move them.
The invented driving device is easy to manufacture and install since the carriage can be made in a standardised manner and the support structure together with the drag elements are simple to adapt to suit the location in question. Furthermore, the need for control data transmission cables is liited to a zone near the carriage. This design reduces the need for cable racks interconnecting motors and sensors.
Since it is a dynamic system, often covering a large working area, and frequently used, the risk for play in the interconnections of the control system, e.g. motors, transmitters and recording sensors, may lead to downtime and reduced productivity. Hence the invention has been designed to be less sensitive to such incidents.
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