Patent Description:
In an aluminum factory a very important part of the production process are the anodes. Anodes are used in the electrolysis processes, whereas they are being used up in this process. Thus, for each ton of aluminum approx. <NUM> of anode material is being consumed. Generally, these anodes are made from carbon and pitch. When they are produced in a first step, they are transported by conveyors to a storage area, where they are handled by anode stacking cranes, putting the anodes in storage. Next, the anodes are taken out of storage by the anode stacking crane, taken to a conveying system that transports them to the baking furnace where they are handled by a different crane, the furnace tending assembly. Subsequently, the anodes are baked in the furnace, where they get their required properties, taken from the furnace and placed on a conveyor system that takes them again to a storage where they are taken again by an anode stacking crane and placed in storage. Next, the anodes are taken out of storage and placed on a conveyor that takes them to a rodding shop where a rod is attached and they can be used in the electrolysis process.

Both, the anode stacking crane and the furnace tending assembly have either mechanically (e.g., by gravity) or hydraulically operated clamping members, e.g., gripping jaws, described exemplary in <CIT>, <CIT>, <CIT>, and <CIT>. In case of mechanical operated gripping jaws, according to e.g., <CIT>, on both types of cranes, the clamping force to the anode is provided by a lever mechanism using the weight of the parts of the gripping mechanism and the anode to create enough clamping force so that the anode stays grabbed and can get lifted. Further known hoisting apparatuses are described in <CIT> and <CIT>.

<CIT> discloses a hoisting apparatus according to the preamble of claim <NUM> and describes that a lever mechanism is assigned to each clamping jaw, each lever mechanism having angle levers pivotably connected to the lower frame. A first straight lever is running between and pivotably connected to a clamping jaw and to a first lever arm of the angle lever, and a second straight lever is running between and pivotably connected to an upper frame and to a second lever arm of said angle lever. Thereby, the straight levers are pivotably connected to the respective lever arms of the angle levers in such a way, that a first angle between the first straight lever and the first lever arm of the angle lever and a second angle between the second straight lever and the second lever arm of said angle lever each increase upon moving the upper frame apart from the lower frame and each decrease upon moving the upper frame closer to the lower frame in the lifting direction respectively.

All conventional gravity-based mechanisms have the drawback, that the clamping force varies over the full stroke of the gripping jaws, due to the construction of the conventional lever mechanisms. The clamping force is highest at the maximum distance of the gripping jaws and reduces as the distance between the gripping jaws gets smaller. This clamping force reduction or variation therefore limits the different sizes of the anodes that can be handled by the gripping jaws, as a minimum clamping force is required to be able to lift the anodes. This is an issue as aluminum smelters tend to increase their anode dimensions with each new extension of the factory, while the existing part of the factory keeps using anodes with smaller dimensions requiring the anode stacking cranes and the furnace tending assemblies to handle different types of anodes with different dimensions.

Accordingly, it is the object of the present invention to provide a hoisting apparatus, which allows a hoisting of a load, in particular an anode as used in a furnace for the production of aluminum, in a flexible and secure way.

This object is achieved by a hoisting apparatus according to the features of claim <NUM>. Preferred embodiments are referred to in the subclaims.

Thus, according to the invention, the clamping force to the anode is provided by lever mechanisms that are assigned to each of both clamping jaws, whereas each lever mechanism is preferably constructed identical and contains.

This construction of the lever mechanisms allows a load to be grabbed by the clamping jaws with a nearly constant clamping force, nearly independent of the size or the dimension of the load, as these lever mechanisms are able to provide a certain clamping force to the load, e.g., the anodes, that does not vary over the stroke of the clamping jaws. Thus, when moving an upper frame of the hoisting apparatus relative to a lower frame, that contains the gripping jaws, each movably connected to the lower frame by a parallelogram linkage, each lever mechanism causes the gripping jaws to move closer together or to move apart from each other in a uniform and controlled manner. As such, the hoisting apparatus may be part of an anode stacking crane for putting anodes in or out of storage and/or a furnace tending assembly for handling the anodes in the baking furnace.

According to the invention, the straight levers of each lever mechanism are pivotably connected to the respective lever arms of said angle levers in such a way, that a first angle between the first straight lever and the first lever arm of said angle lever and a second angle between the second straight lever and the second lever arm of said angle lever each increase upon moving the upper frame apart from the lower frame and each decrease upon moving the upper frame closer to the lower frame in the lifting direction respectively. Consequently, the clamping force amount provided by the second straight lever in conjunction with the second lever arm of the respective lever mechanism is behaving contrary to the clamping force amount provided by the first straight lever and the first lever arm of the respective lever mechanism. Thus, these clamping force amounts can advantageously compensate each other, if the first angle and the second angle increase or decrease in a similar amount upon moving the upper frame against the lower frame. This can ensure a nearly constant clamping force over the full stroke of the clamping jaws.

According to another aspect of the invention, a first lever-length of the first lever arm of said angle lever pivotably connected to the first straight lever is different from a second lever-length of the second lever arm of said angle lever pivotably connected to the second straight lever, whereas the first lever-length is preferably smaller than the second lever-length. This ensures, that the clamping force amount provided by the weight of all the elements carried by the upper frame is increased, due to the principles of a mechanical lever. This can be combined with the mechanical construction of the overall lever mechanism to set a certain clamping force needed to grab the load for lifting. To enhance this effect, the first straight lever, pivotably connected to the shorter first lever arm, is also shorter than the second straight lever, pivotably connected to the longer second lever arm. Preferably, this is done in such a way that the ratio between the first lever-length of said first lever arm and the length of said first straight lever is equal to the ratio between the second lever-length of said second lever arm and the length of said second straight lever.

According to a further aspect of the invention, each parallelogram linkage contains linking members arranged in parallel, each running between a first shaft on the lower frame and second shaft on the respective gripping jaw, pivotably connecting the respective linking member thereto, thus allowing each clamping jaw to uniformly move into the gripping direction.

To operatively connect the gripping jaws to the upper frame by means of the lever mechanisms, the first straight lever of the respective lever mechanism is pivotably connected to the second shaft on the respective gripping jaw or to any of the linking members of the respective parallelogram linkage. This allows an easy and flexible connection between both to set or ensure a certain constant clamping force as described.

According to a further aspect of the invention, the upper frame can be immovably connected to the lower frame in a locked state preventing the gripping jaws to move against each other in the gripping direction. Thus, the hoisting apparatus can be locked, e.g., in case the load is released and the gripping jaws should be lifted without grabbing the anode. Instead, any other locking mechanism can be used that is able to prevent the gripping jaws to move against each other in the gripping direction.

According to another aspect of the invention, at least one of the parallelogram linkages, the first straight levers, the second straight levers, the lower frame, the upper frame or the gripping jaws are composed or arranged in pairs. Thus, the mechanical construction can be strengthened, by using pairs of levers or crossbars, as a distortion or twisting of said elements can be prevented.

Features and advantages of the present invention will become apparent upon reading of the following detailed description along with the accompanied drawings, wherein:.

<FIG> shows a hoisting apparatus <NUM> having a substantially horizontal aligned lower frame <NUM> or yoke containing movable clamping members, e.g., gripping jaws <NUM>, <NUM>, on each side and an upper frame <NUM> that can be moved relative to the lower frame <NUM>. The upper frame <NUM> is connected to a lifting means, e.g., a motor (not shown), suitable to lift a load <NUM> that is grabbed using the gripping jaws <NUM>, <NUM>. For example, the upper frame <NUM> can be connected to the lifting means by wire ropes or rope sheaves. In this embodiment, the frames <NUM>, <NUM> each consists of u-shaped crossbars arranged in parallel or in pairs (s.

Preferably, the load <NUM> is an anode (or a plurality of anodes) as used in a furnace for producing aluminum. As such, the hoisting apparatus <NUM> may be part of an anode stacking crane to put or pick new or baked anodes into or out of a storage, or a furnace tending assembly, which handles the anodes in the area of the baking furnace, where the anodes get their properties required for the subsequent electrolysis process.

With reference to <FIG>, the respective gripping jaws <NUM>, <NUM> are each connected to the lower frame <NUM> by means of a parallelogram linkage <NUM>, <NUM>. Each parallelogram linkage <NUM>, <NUM> contains linking members <NUM> running between first shafts <NUM> on the lower frame <NUM> and second shafts <NUM> on a horizontal arm 3a, 4a of the gripping jaws <NUM>, <NUM>. The parallelogram linkages <NUM>, <NUM> ensure that the gripping jaws <NUM>, <NUM> can be solely moved essentially in a gripping direction D1 (horizontal direction). As can be seen in the perspective view of <FIG>, each gripping jaw <NUM>, <NUM> is connected to the lower frame <NUM> by two parallelogram linkages <NUM>, <NUM> that are arranged in parallel or in pairs.

To couple the movement of both gripping jaws <NUM>, <NUM>, each parallelogram linkage <NUM>, <NUM> or each gripping jaw <NUM>, <NUM> is connected to the upper frame <NUM> by an additional lever mechanism 9a, 9b. If the upper frame <NUM> is moved against the lower frame <NUM> in a lifting direction D2 (vertical direction) the lever mechanisms 9a, 9b transfer this movement into both parallelogram linkages <NUM>, <NUM> or gripping jaws <NUM>, <NUM>. As both lever mechanisms 9a, 9b are designed identical, each parallelogram linkage <NUM>, <NUM> or gripping jaw <NUM>, <NUM> is affected in the same way, thus, moving both clamping jaws <NUM>, <NUM> in a uniform manner when moving the upper frame <NUM> up or down against the lower frame <NUM>. Thus, upon raising the upper frame <NUM> against the lower frame <NUM>, e.g., by actuating the lifting means, the clamping jaws <NUM>, <NUM> are uniformly moved closer together and upon lowering the upper frame <NUM> against the lower frame <NUM>, the clamping jaws <NUM>, <NUM> are uniformly moved apart from each other.

If (upon raising the upper frame <NUM>) both clamping jaws <NUM>, <NUM> come into contact with the load <NUM> in a grabbed state, a clamping force F is acting on the load <NUM>, whereas said clamping force F is, in particular, dependent on the weight of all the elements carried by the upper frame <NUM>, namely the load <NUM> as well as the parallelogram linkages <NUM>, <NUM>, the lever mechanisms 9a, 9b and the lower frame <NUM>. According to the invention, the clamping force F is further affected by the special construction of the lever mechanisms 9a, 9b, as described hereinafter.

In contrast to the parallelogram linkages <NUM>, <NUM> said lever mechanisms 9a, 9b are not arranged in pairs in the shown embodiment, as can be seen in the perspective view of <FIG>. Each lever mechanism 9a, 9b is positioned between the respective pair of parallelogram linkages <NUM>, <NUM>, whereas each lever mechanism 9a, 9b contains a pair of first straight levers <NUM>, an angle lever <NUM> having first and second lever arms 14a, 14b, and a pair of second straight levers <NUM>.

The first straight levers <NUM> are pivotably connected to the respective parallelogram linkage <NUM>, <NUM> or the respective gripping jaws <NUM>, <NUM>, e.g., to one of the second shafts <NUM> connecting the respective pair of linking members <NUM> to the respective horizontal arms 3a, 4a of the gripping jaws <NUM>, <NUM>. The other ends of the first straight levers <NUM> are each pivotably connected to said first lever arm 14a of the respective angle lever <NUM> by a third shaft <NUM>. Further, said angle lever <NUM> is pivotably connected to the lower frame <NUM> at a pivot point <NUM>. Starting from said pivot point <NUM>, said second lever arm 14b of the angle lever <NUM> is extending to said pair of second straight levers <NUM> of the respective lever mechanism 9a, 9b, whereas a fourth shaft <NUM> pivotably connects the second lever arm 14b to the pair of second straight levers <NUM> at one end. At the other end said pair of second straight levers <NUM> are pivotable connected to the upper frame <NUM> by a fifth shaft <NUM>.

This mechanical construction of the lever mechanisms 9a, 9b coupled to the parallelogram linkages <NUM>, <NUM> or the gripping jaws <NUM>, <NUM> allows the clamping force F (in the gripping direction D1) to be almost constant over the full stroke of the clamping jaws <NUM>, <NUM>. Accordingly, a nearly constant clamping force F acting on the load <NUM> can be provided independent of a dimension A of the load <NUM> to be grabbed. This can be achieved as follows:.

Firstly, due to the ratio between a first lever-length L1 of the first lever arm 14a of said angle lever <NUM> (distance between the pivot point <NUM> and the third shaft <NUM>) and a second lever-length L2 of the second lever arm 14b of said angle lever <NUM> (distance between the pivot point <NUM> and the fourth shaft <NUM>) the clamping force amount provided by the weight of all the elements carried by the upper frame <NUM> is increased. This is further ensured by the fact that a ratio between the first lever-length L1 of said first lever arm 14a and a length of said first straight lever <NUM> is equal to the ratio between the second lever-length L2 of said second lever arm 14b and a length of said second straight lever <NUM> (L1/length of first straight lever <NUM> = L2/length of second straight lever <NUM>).

Further, when lifting the upper frame <NUM> against the lower frame <NUM> to move the clamping jaws <NUM>, <NUM> closer together, a second angle β between the pair of second straight levers <NUM> and the second lever arm 14b of said angle lever <NUM> becomes larger (s. <FIG> and <FIG>, <FIG>). Consequently, the moment acting around pivot point <NUM> of the angle lever <NUM> is reduced, thus, the clamping force amount provided by the pair of second straight levers <NUM> in conjunction with the second lever arm 14b is also reduced. Further, when lifting the upper frame <NUM> against the lower frame <NUM> to move the clamping jaws <NUM>, <NUM> closer together, a first angle α between the pair of first straight levers <NUM> and the first lever arm 14a of said angle lever <NUM> also becomes larger. As the first angle α increases the clamping force amount provided by the pair of first straight levers <NUM> in conjunction with the first lever arm 14a also increases.

The three levers <NUM>, <NUM> and <NUM> of the lever mechanisms 9a, 9b are arranged in such a way, that the first angle α and the second angle β increase in a similar amount, when the upper frame <NUM> is lifted against the lower frame <NUM> to move the clamping jaws <NUM>, <NUM> closer together. Thus, the reduced clamping force amount provided by the pair of second straight levers <NUM> and the second lever arm 14b is equally compensated by the increased clamping force amount provided by the first straight levers <NUM> and the first lever arm 14a. This ensures a nearly constant clamping force F over the full stroke of the clamping jaws <NUM>, <NUM>, whereas this clamping force can be set by the ratio between the first lever-length L1 of the first lever arm 14a and a second lever-length L2 of the second lever arm 14b.

Claim 1:
Hoisting apparatus (<NUM>) for gripping and lifting a load (<NUM>), e.g., an anode, comprising,
- a horizontally aligned lower frame (<NUM>) containing movable gripping jaws (<NUM>, <NUM>) at each side, each connected to the lower frame (<NUM>) by a parallelogram linkage (<NUM>, <NUM>) of said hoisting apparatus (<NUM>) to allow said clamping jaws (<NUM>, <NUM>) to move into a gripping direction (D1), and
- an upper frame (<NUM>) that can be moved relative to the lower frame (<NUM>) in an unlocked state, whereas the upper frame (<NUM>) is operatively connected to each gripping jaw (<NUM>, <NUM>) by a lever mechanism (9a, 9b) in such a way, that a movement of the upper frame (<NUM>) against the lower frame (<NUM>) into a lifting direction (D2) causes the gripping jaws (<NUM>, <NUM>) to move closer together or to move apart from each other to release or to grip a load (<NUM>) with a certain clamping force (F),
wherein a lever mechanism (9a, 9b) is assigned to each clamping jaw (<NUM>, <NUM>), whereas each lever mechanism (9a, 9b) contains
- an angle lever (<NUM>) having two lever arms (14a, 14b) originating from a pivot point (<NUM>) of said angle lever (<NUM>) into different directions, whereas the angle lever (<NUM>) is pivotably connected to the lower frame (<NUM>) at a pivot point (<NUM>),
- a first straight lever (<NUM>) running between and pivotably connected to the assigned clamping jaw (<NUM>, <NUM>) and to a first lever arm (14a) of said angle lever (<NUM>), and
- a second straight lever (<NUM>) running between and pivotably connected to the upper frame (<NUM>) and to a second lever arm (14b) of said angle lever (<NUM>)
wherein the first and second straight levers (<NUM>, <NUM>) of each lever mechanism (9a, 9b) are pivotably connected to the respective lever arms (14a, 14b) of said angle levers (<NUM>) in such a way, that a first angle (α) between the first straight lever (<NUM>) and the first lever arm (14a) of said angle lever (<NUM>) and a second angle (β) between the second straight lever (<NUM>) and the second lever arm (14b) of said angle lever (<NUM>) each increase upon moving the upper frame (<NUM>) apart from the lower frame (<NUM>) and each decrease upon moving the upper frame (<NUM>) closer to the lower frame (<NUM>) in the lifting direction (D2) respectively,
characterized in that,
the first angle (α) and the second angle (β) increase in a similar amount upon moving the upper frame (<NUM>) against the lower frame (<NUM>).