Handling: hand and hoist-line implements – Miscellaneous compound implement
Patent
1996-05-29
1998-05-19
Kramer, Dean
Handling: hand and hoist-line implements
Miscellaneous compound implement
294 641, 414627, 414730, B25J 1506, B66C 102
Patent
active
057527296
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a vacuum lifting device for lifting and manoeuvring heavy objects. The vacuum lifting device of the invention is particularly suitable for lifting slabs of material and, for convenience, the present invention will be hereinafter described with reference to the lifting of slabs. However, it will be appreciated that the device of the present invention is not to be considered to be limited to the lifting of slabs.
The production of aluminium metal is carried out in aluminium smelting cells. Each cell includes a steel shell that is lined with various refractory and carbon linings. The refractory linings of the steel shell are used to protect the shell from the high temperatures generated during operation of the cell and to provide a barrier between the steel shell and the corrosive contents of the aluminium smelting bath. Conventional practice for lining aluminium smelting cells involves placing a layer of refractory bricks on the base of the cell and subsequently adding further layers, such as cathode carbon, above the refractory bricks. Preparation of the layer of refractory bricks is a time-consuming and expensive job that requires careful laying of the bricks. Furthermore, refractory packing or refractory mortar has to be placed between each brick in order to reduce the possibility of the corrosive bath infiltrating through the refractory layer and attacking the steel shell.
In order to reduce the time required to reline an aluminium smelting cell, recent developments have involved the use of large, precast refractory slabs being placed on the floor of the cell. These refractory slabs, which may weigh between 700 to 3,000 kilograms are sized such that only a small number are required to cover the floor of the cell. This obviously reduces the number of joints in the refractory layer that have to be packed with packing or adhesive. However, the use of precast refractory slabs involves the manoeuvring of large, heavy objects into place which causes difficulties for the operators engaged in relining the cell.
It has been common for the operators to position the refractory slabs in the cell by raising the slabs with chains or hooks connected to a crane and subsequently manoeuvring the crane to place the slab in the desired position. However, this method of lifting and manoeuvring the slabs has several drawbacks, the chief one being that as either chains or hooks extend around and project from the outer periphery of the slabs, it is almost impossible to place a slab in a close fit with an adjacent slab. In order to obtain a close fit between slabs, which minimises the packing required between slabs, it has been necessary to put a slab down on the floor of the cell and subsequently have the operators move the slab sideways, for example, by the use of crowbars. Difficulties are also encountered in placement of the final slab in the cell, as this slab cannot be fitted flush into the space remaining on the floor of the cell. Consequently, the final slab partly rests on another slab until it is moved sideways by the operators and drops into place.
Vacuum lifters have been in use for a number of years and generally consist of a set of suctions cups connected to a vacuum source, the suction cups also being attached to a crane assembly to enable the cups to be raised, manoeuvred and lowered. Although they operate satisfactorily in their intended uses, known vacuum lifters do not include stringent safety features to prevent dropping of the object being lifted in the event of failure of vacuum or a suction cup. Accordingly, known vacuum lifters are not suitable for use in a plant environment, such as an aluminium smelter, due to occupational safety reasons.
It is an object of the present invention to provide a vacuum lifting device having improved safety when compared to vacuum lifters known to the applicants. In a first aspect, the present invention provides a vacuum lifting device for lifting heavy objects comprising a first set of suction cups connected to a source of vacuum, said first
REFERENCES:
patent: 2783078 (1957-02-01), Billner
patent: 3387718 (1968-06-01), Roth et al.
patent: 4828304 (1989-05-01), No et al.
patent: 5024575 (1991-06-01), Anderson
Crozier Christopher Luke
Liston Brian Joseph
Stewart Karl William
Comalco Aluminium Limited
Kramer Dean
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