The present invention relates to a device for gripping a prebaked anode for an electrolysis cell for production of aluminium of the Hall-Heroult type and a method for operating the gripping device. Such gripping devices are used for lifting and transporting prebaked anodes and butts (worn out anodes) in various operations in a smelter plant.

In particular, the invention relates to a so-called "lifting bell" and a method for connecting/releasing same at the top end of an anode rod, and one intended use can be handling anode butts (used anodes) in a rodding shop where the butts can be transported between various stations hanging in a conveyor.

Conventionally prebaked anodes comprise an anode rod that consist of a rod or a stem of aluminium attached at its upper end to the anode beam in the superstructure of the cell by a clamping device, its other end is connected to an anode yoke, often via a bimetallic part where the yoke is made out of steel. The yoke comprises one or more studs or stubs that are integrated with bores in the top part of an anode carbon block. The connection is secured by means of cast iron poured into an annular space between the stud and the bore. The anode rods are commonly of a rectangular / square cross-section and provided with a transversal through going bore close to its top end that forms a "lifting eye".

Gripping devices for handling anodes as mentioned above are commonly attached to a lifting arrangement such as one manipulator arm arranged in a crane or Pot Tending Machine (PTM). Gripping devices complementary to this type of anode rod interface can be provided with two bolts that are entered from opposite sides of the bore. The bolts can be moved along their axis into the bore, each by an actuator. One example of this kind of device can be found in US 4,032,020 A.

US 7,850,218 B2 discloses one device for the same type of interface, where the gripping device consist of two hinged jaws each having one pin, where the jaws are moved towards each other to enter the pins in the bore formed in the top end of the anode rod. According to the present invention, it is achieved to a new lifting device that is easy to enter onto the top end of the anode rod, as it has guiding elements, it is self-locking after being lowered onto the end of the anode rod, and it is steady in use. It locks automatically, and bringing two levers apart from each other is needed to release the lifting device from the anode rod.

The gripping action can easily be carried out by an operator in a PTM due to its self-locking system. The releasing action can either be done manually, by an integrated actuator or by some external system being able to move certain parts that will release the lock.

These and further improvements and advantages can be achieved with the present invention as defined in the accompanying claims.

The invention shall be further described by examples and figures where;

Fig. 1 discloses in perspective a top part of an anode rod, with a bolt,

Fig. 2 illustrates a gripping device with locking elements, seen in perspective,

Fig. 3 illustrates a gripping device in perspective where a top of an anode rod has been introduced and push on two locking elements with a bolt, illustrates a gripping device in perspective where the bolt has passed a gap between the two locking elements,

Fig. 5 illustrates a gripping device in perspective where a top of an anode rod has been introduced and where the bolt is fixed by locking elements. The new gripping device 21 (Fig. 2) is intended to work on a design of the top end of the anode rod 1 as shown in Fig. 1. Here the top end of the anode rod is provided with a centrally arranged top-down recess 9. At each side of the recess 9 there are two legs 2, 3 having each a transversally oriented bore 4, 5, where the bores are made in-line allowing a bolt 6 to be securely fixed in the legs 2, 3. The part of the bolt accessible in the area of the recess will represent the lifting point for this anode rod. This design necessitates an amended gripping device as former mentioned gripping devices will not be compatible without modifications. In Fig. 2 some main components of a gripping device are shown, with locking elements 7, 8, guiding skirts 16, 16', releasing handlebars, and a lifting eye 100. Fig. 5 shows a gripping device 21 attached to an anode rod 1 that is provided with a recess 9 at its the top end. To enable the illustration of the function of the gripping device, some parts are cut out of in the Figure. Here only one leg 2 is shown as the other leg is removed for illustrative purposes. The Figure further shows a bolt 6 attached to the leg 2. The gripping device 21 as shown has conical guiding skirts 16, 16' that facilitates the entering of the gripping device at the top of the anode rod.

Main parts for enabling the gripping and locking action of the device are two locking elements 7, 8 pivotably arranged by respective axles (not shown) arranged in corresponding supports 9, 10. The locking elements 7, 8 are allowed to rotate upwards as the lifting device is entered onto the top end of the anode 1 , see Fig. 3 and 4. Consequently, the bolt 6 is allowed to pass through a gap formed between the locking elements 7, 8 as they are being pushed into a rotational movement upwards by the bolt 6. In Fig. 3 there is shown a gap between the locking elements 7, 8 as the anode rod with the bolt 6 enters the gripping device. In Fig. 4 the bolt has been moved so far into the gripping device that the locking elements are allowed to rotate downwards and close the gap between them.

As shown in Fig. 4, the locking elements 7, 8 can be secured or fixed in a horizontal position by abutting against supporting parts 7', 8' of the supports 9, 10, and thereby locking the lifting device to the anode rod.

As shown in Fig. 5, the supports 9, 10 including the two locking elements 7, 8 are supported in the overall frame structure 15, 15' of the gripping device 21 in a manner that allow these supports to be moved outwardly. This sliding support can be of a linear bearing type known to the skilled man (not shown).

Handles 13, 14 are connected with the respective supports 9, 10 and can be operated to release the locking function of the locking elements in case the gripping device shall be separated from the anode rod.

The function of this is that by moving the supports 9, 10 outwardly, the locking elements 7, 8 are separated by an outwardly movement forming a gap between them, thus allowing the bolt 6 to pass through the gap in a reverse action. This is not shown in the Figures but will be understood by the skilled person.

The gripping device 21 is a semi-automatic construction, which will clip on to the anode rod when lowered on to the rod or when the rod is raised in to the gripping device. Once locked in the gripping device, the rod will not be released until the mechanism is released either by manual force or by an actuator (not shown) or other means.

This gripping device can be applied either in existing rodding shops or in the electrolysis production areas where there is a need for mowing an anode assembly with the lifting crane.

The release mechanism can be modified slightly to make an operator able to release the hanger from floor level in the production area.

The gripping device has one HSE aspect as it can eliminate the need for using Polyester round sling or other lifting equipment that will require the operator to climb to the top of the anode rod to release it.