Background to the Invention As mentioned above, aluminium smelting involves the breakdown of molten alumina into pure aluminium. This process emits a large amount of noxious gases which are preferably captured and removed from any air or vapour stream leaving a smelting or pot room. Aluminium smelting is associated with extreme temperatures, aggressive chemical environments, high electrical currents and voltages and is generally a highly hazardous operation.

Removing noxious gaseous by-products of aluminium smelting is generally performed by a fume extraction hood, however it is necessary to provide access through the hood for anodes which actually inject electrical current into the molten alumina. These access means provide a means of gas escape from the hood. The aggressive environment of the smelter generally precludes known sealing methods from application in a pot room, because known sealing products melt or vaporize or otherwise break down in the face of such extreme environments.

Preferred embodiments of one aspect of the present invention have application in anode clamps, as used in aluminium smelting, to clamp a carbon anode stem against an

electrical bus bar. It will be convenient to hereinafter describe one aspect of the present invention with reference to this application, however it is to be understood that this is not to be taken as limitation of the scope of the invention. That is, it is envisaged that the invention has application in many clamping and vice applications where a single turn of a bolt sets both jaws in motion towards or away from each other, such as in work benches, drawing instruments, and other clamping or vice instruments or implements.

Known tensioning devices use a bolt and nut in conjunction with an anode clamp to force an anode stem against an electrical bus bar for good electrical conductivity therebetween. The bolt has two portions, one with a left-hand thread and another with a right-hand thread and corresponding nuts threadably engaged with their respective parts.

There is generally a head disposed-at one end of the bolt, for applying a turning force to the bolt through for example a spanner.

Assembling this tensioning device currently is carried out by threadably engaging the respective threaded bolt portions with their nuts, welding the two bolt portions together and welding the head section to one end of the newly fabricated bolt. This leads to misalignment problems, strength problems, as welds are generally variable in strengths, and long assembly times difficult disassemblies and high costs.

Various aspects of the present invention seek to ameliorate one or more of the abovementioned disadvantages.

Summary of the Invention According to one aspect of the present invention there is provided a seal assembly suitable for use in reducing gas and/or liquid egress from between an anode stem and a hood in an aluminium smelting pot, the seal assembly including: a housing including one or more mounting members, the or each mounting member having an aperture therein for receiving the anode stem when in an installed position ; a seal structure which is adapted to be supported by the or each mounting member in an installed position, the seal structure including opposed spaced apart side seals and at least one end seal, the side and end seals extending into the aperture and into engagement with adjacent peripheral portions of the anode stem when in the installed position.

The seal structure may comprise one or more seal support members and one or more sealing elements operatively connected to the or each seal support members. The or each seal support member may comprise plates mounted at each edge of the recess, or may be individual plates welded together to form a single mounting plate, or, as in one preferred form, a single u-shaped mounting plate which, just as the previously mentioned plate assembly, provides mounting at each of the edges of the recess for the sealing elements.

The sealing elements may be any suitable material for such an aggressive environment as the aluminium smelting pot. In one preferred form the sealing elements are stainless steel brushes, constructed from a small diameter stainless steel dense fill wire, crimped at one end by a swaging type channel. In one embodiment the wires are 0.21 millimetres in diameter, constructed from 304 grade stainless steel, though clearly 316 grade would be suitable.

The sealing elements provide an aperture generally corresponding in shape to the anode stem. Therefore, if the anode stem is circular in cross-section, the sealing elements

provide a circular aperture through which the anode stem may pass. In one preferred form however the anode stem is square in section, thus the aperture is square in shape.

Preferably, the mounting members are plates. In one form each plate is generally flat with a deep recess cut into one edge, to form an essentially u-shaped plate. Preferably the mounting members are spaced apart vertically from each other in an installed position, in one form by a plurality of posts or threaded bolts and nuts.

The or each seal support member may be operatively connected between the mounting members in any suitable form. In one preferred form, the operative connection is via biasing means which urge the seal structure towards the recess and into engagement with the anode stem. In one form the biasing means is in the form of springs disposed between the mounting members, one spring on each side of the seal structure, one end fixed to the mounting member or other convenient point such as for example the posts.

The other end of the spring is fixed to an adjacent point on the seal support members.

The seal support member is preferably disposed generally between the mounting plates and closer to the lower plate than the upper plate when the plates are in an installed position. In one preferred embodiment tabs are provided integral with or connected to the sides and/or ends of the support member, and disposed, when installed, perpendicular to the plane of the support member. This arrangement allows selection of the vertical positioning of the support member while still allowing horizontal sliding or biasing movement by the springs.

Preferably, the vertical position of the seal elements may vary with respect to each other when installed. In one form, this may be achieved by providing a change in the location of the weld at the interface of the seal element and seal mounting members.

According to another aspect of the present invention there is provided a tensioning device for a clamp, the tensioning device including a bolt, a first nut and a second nut wherein the bolt includes a threaded shaft section having a first portion and a second

portion, the first portion having a selected cross sectional diameter and a selected thread hand, and the second portion having a larger cross sectional diameter and an opposing thread hand, the first and second nuts having internal diameters and threaded portions corresponding to the first and second portions respectively, and mounted in line with each other in the clamp, the arrangement being such that when assembling the tensioning device, the bolt approaches from one side of the clamp and nuts and the first portion can be passed through the second nut without engagement with the threads before engaging with the threads of the first nut.

The change in diameters may occur via any suitable means such as for example a ramp, step, or radius, or a combination thereof. Clearly, a step would not be ideal from the point of view of incorporating a stress concentration point, however with a suitable radius, the stress is made to pass along the shaft without large increases and discontinuities.

Therefore, in a preferred form the change in diameters occurs through a step with fillet radii to reduce the stress concentrations.

The relative length of the first and second portions may vary, depending on the application. However, in a preferred form, the relative lengths of the first and second threaded portions are equal.

A head may be provided in order to apply greater turning force to the bolt such as for example, with a spanner. In a preferred form the head is provided integral with the bolt and adjacent the second portion, remote from the first portion.

The thread on the first portion may be left hand or right hand, as long as the thread on the second portion is opposing the thread on the first portion. The threads on each portion may even be incompatible pitches, or standards, relative to each other, or even variable within each portion. For example the first portion thread may be UNC, and the second portion thread may be metric, or the threads may even vary within each portion as long as the respective nut is compatible with the varying thread.

Preferably the clamp has two jaws, each jaw being pivotally connected at a pivot point, the tensioning device connected to the jaws distal the pivot point. This may provide further mechanical advantage to the clamp.

Description of the Preferred Embodiment (s) In order to enable clearer understanding of the invention, preferred embodiments of the invention will hereinafter be described with reference to the attached drawings, and in those drawings: Figure 1 is an isometric view of a preferred embodiment of a first aspect of the present invention; Figure 2 is a plan view of the embodiment shown in Figure 1, showing hidden detail in phantom lines of a biasing means; Figure 3 is a plan view of the embodiment shown in Figures 1 and 2, with a housing removed for clarity; Figure 4 is a front elevation of the embodiment shown in Figures 1-3; Figure 5 is a section view along AA from Figure 3; Figure 6 is a section view along BB from Figure 3; Figure 7 is an isometric view of an anode clamp incorporating a tensioning device according to a preferred embodiment of a second aspect of the present invention; Figure 8 is a side elevation of the embodiment shown in Figure 7; Figure 9 is a rear elevation of the embodiment shown in Figures 7 and 8 ; Figure 10 is a front elevation of the embodiment shown in Figures 7-9;

Figure 11 is a plan view of the embodiment shown in Figures 7-10.

Referring to Figures 1-6 there is shown a preferred embodiment of a first aspect of the present invention, being a seal assembly suitable for use in creating a seal between an anode stem and a hood in an aluminium smelting pot. The seal assembly is generally indicated at 10, and includes a housing 12 including two mounting members 14,16, in the form of generally flat plates 22 and 24. The flat plates 22 and 24 are spaced apart vertically from each other in an installed position, spaced apart and operatively connected by bolts 18 and spacing nuts 20. The flat plates 22 and 24 have an aperture in the form of a deep recess cut into one edge so that generally U-shaped plates are formed. The recess 26 receives the anode stem (not shown) when in an installed position, the anode stem being,-although not shown, square in cross-section in this embodiment, the U-shape corresponding in section to the anode stem.

A seal structure 28 is provided, for reducing the amount of noxious, and other gases which may escape between the anode stem (not shown) and the hood (not shown). The seal structure 28 is generally disposed between plates 22 and 24 when in an installed position. The seal structure 28 includes a seal support member 30 comprising three plates 32,34, 36 welded together to form a u-shaped plate 38.

Tabs or flanges 40,42, 44 and 46 are provided at sides of the u-shaped plate 38 which, when deployed, are disposed generally perpendicularly to the plate 38, in order to fix the vertical position of the plate 38 between the plates 22 and 24.

The seal structure 28 further includes a seal element indicated at 50. The seal element 50 includes three brushes 52,54, 56. Each brush is in the form of a plurality of densely packed, small diameter wires 64, made from stainless steel, and crimped at one end by a swaging channel 58,60, 62. In this embodiment the wires are 0.21 millimetres in diameter and constructed from 304 grade stainless steel.

The vertical position of the brushes on the seal support structure is shown in Figures 5 and 6. Figure 5 shows the brushes 58 and 62 welded at the base corners which makes them stand higher when installed than their adjacent brush 60 which is welded mid channel to the inside recess edge of the support 34 (Figure 6).

Biasing means 70 are provided in the form of springs 72 and 74 which urge the u- shaped seals structure 28 towards the recess 26, and forcing the brushes 58,60, 62 which extend into the recess 26, into engagement with the anode stem. The outer ends of the springs are fixed to pins 76 and 78 disposed between housing plates 22 and 24. The inner ends of the springs are fixed to the outer ends of the mounting plate 34, via appropriately placed holes 80 and 82.

In operation the seal assembly 10 is mounted adjacent an anode stem (not shown) so that the anode stem is received in the recess 26, and the brushes 58, 60,62, engage with the sides of the anode stem to reduce the exit of gases through the gap between the anode stem and the hood. By engaging, it is meant that the brush wires 64 are held against the side walls of the anode stem, driving the wires 64 to bend into a small radius to ensure as many wires 64 as possible are in contact with the walls of the anode stem.

The spring loading and free floating nature of the spring support in the housing provides for engagement even when there are small variations in the dimensions of the anode stem.

Gases exiting from the pot are low in pressure, thus simple dense fill brushes reduce their egress through the gap between anode stem and hood.

Although it is common practice in patent specifications for like numerals to denote like parts, in this specification, the numerals 10, 12, 14, etc do not correspond with parts denoted by numerals 110,112, 114 respectively, etc.

Referring to Figures 7-11 there is shown a tensioning device according to a preferred embodiment of a second aspect of the present invention being a tensioning device generally indicated at 110 for use with an anode clamp 120, within which the tensioning device is assembled.

The tensioning device 110 includes a bolt 130 having a first threaded portion 132 and a second threaded portion 134 integral therewith. The first threaded portion 132 includes a left handed thread 136 and a second threaded portion 134 includes a right hand thread 138. First bolt portion 132 is smaller in diameter than the second bolt portion 134.

The change in diameters occurs over a stepped portion 162 which incorporates slight radii to reduce stress concentrations.

Further included in the tensioning assembly 110 are nuts 140 and 142 corresponding in thread and diameter to their respective bolt portions 132 and 134. The nuts are pivotally connected to their respective cross members 144 and 146, by respective pivots 148 and 150. The cross members are further pivotally connected to their respective clamp jaw assemblies 152 and 154 by respective pivot assemblies 156 and 158.

A bolt head 160 is provided integral with and adjacent the outside of the second threaded portion 134, to provide interface with spanners (not shown).

The advantages of this system are mainly seen at assembly and disassembly, however there are also advantages in operation, due to the improved alignment which comes with having a one piece bolt and head assembly.

In this regard, assembly of the tensioning device 110 into the clamp 120 generally follows these steps: The anode clamp 120 starts in a part assembled position, which includes cross members 144 and 146, and nuts 140 and 142, all pivotally connected in position. The outer end 166 of the bolt 130 is inserted into the outer end 164 of the second nut 142. Due

to the smaller diameter of the first portion 132, relative to the second nut 142, the entire first portion 132 passes wholly through the second nut 142. The second nut 142 then threadably engages with the second portion 134. The bolt 130 is then turned clockwise (when facing the direction of the arrow at 175) and the second nut 142 threads all the way to the head 160 of the bolt 130. The first portion 132 of the bolt 130 then threadably engages with the first nut 140 and the bolt 130 is turned anticlockwise (again, when facing the direction of the arrow at 175). The nuts then come together and have their maximum travel set in place. Turning the bolt 130 in one direction moves both nuts either towards or away from each other, which opens and closes the jaw assemblies 152 and 154 of the clamp 120.

Disassembly is a reversal of the assembly procedure. With known technology, the clamp must be cut apart.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word"comprise", and variations such as"comprises"or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.