Abstract:
An electrode comprises an outer tube containing a spiral inner electrode which surrounds a rod held at its ends by fittings in the ends of the tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The invention relates to an electrode. 
     In our EP-0883700B we have described and claimed an electrode for use in electrochemical treatment of metal reinforced concrete, the electrode comprising a generally cylindrical body formed of porous material, the body having an external surface and an internal surface, a power supply conductor in use, being in electrical contact with the internal surface and with a supply of electrical current. The body wall is porous to allow ingress of gas and is preferably formed of a titanium suboxide of the formula TiO x  where is 1.55 to 1.95. 
     When electrode bodies are required to be supported at their extreme ends, in electrochemical cells, rather than being encased in concrete, it is often necessary to provide specially shaped end caps. If these are simply attached with adhesives, the adhesives often fail in the extremely aggressive electrochemical environment. If mechanical means of attachment is used, then the electrode material itself is subject to mechanical forces, which may damage the body if the material is brittle, since the wall of the body will not withstand high compressive and torsional forces when end caps are inserted. Such strains arise for example when too much force is used to tighten up nuts and can cause the body to fracture. 
     It is one object of the invention to provide an electrode having a generally tubular body and end fittings which are easy to assemble and fix in place without any major mechanical stresses being applied to the body. It is another object of the invention to provide such an electrode in which the end fittings tend to align an elongate support for the internal electrode. 
     BRIEF SUMMARY OF THE INVENTION 
     According to the invention in one aspect there is provided an electrode comprising a generally tubular body having an external surface and an internal surface, an elongate rod extending between the ends of the body and having at least one end fitting at an end of the body, a power supply conductor being present in the annulus between the rod and the inner surface and in contact with that inner surface, and in use, in connection with a power supply. 
     Preferably an end fitting in the form of a cap is present at one or both ends of the tubular body to close one or both ends, the or each cap having an inner end portion shaped to hold and contribute to the centralisation of the cap and engage the inner surface of the end portion of the body without stressing the body. Most preferably the engaging means of the inner portions comprises radially spaced apart flexible flutes or vanes. Most preferably the flutes or vanes are at an angle to the true radial direction such that once compressed the flutes or vanes will be bent in the same radial direction to farther assist the centralisation. Most preferably the flutes or vanes are sufficiently tough and flexible to provide an element of flexibility in the axis of the end cap with respect to the axis of the tubular body, thus reducing bending stresses on the body, and also allowing the use of bodies with slightly variable internal diametric tolerances. 
     It is also preferred that the inner end portions of the caps each define a socket to receive an end portion of the rod to space the two end caps at an appropriate distance to ensure that axial compressive forces are transmitted along the rod rather than along the body. Preferably, the ends of the rods are provided with a clip system in each socket so that once engaged the rod cannot be withdrawn. In this way any axial extensional forces will tend to be are borne by the rod instead of the cylindrical body. 
     Preferably, all the components of the fittings can be manufactured by injection moulding of thermoplastic polymers which is a cheap high volume method, and thus results in cost effective electrodes. 
     The body may be formed of an electrically conductive ceramic material which will tend to be brittle. The body may be inherently electrically conductive or it may be covered with a coating of such a material. 
     The tubular body may be of a suitable shape, e.g. generally cylindrical or prismatic. 
     An electrode of the invention is very versatile and may be used as an anode or a cathode in many electrochemical reactions such as:
         electrochemical water sterilisation;   electrochemical destruction of organics compounds such as pesticides and or pseudo-oestrogenic compounds in water;   electrochemical treatment of sewage;   electrochemical synthesis of fine chemicals; and   electrochlorination of water for, for instance, swimming pools.       

    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In order that the invention may be well understood it will now be described by way of example only with reference to the accompanying diagrammatic drawings, in which: 
         FIG. 1  is an exploded perspective view of one anode assembly of the invention; 
         FIG. 2  is a longitudinal sectional view of the anode of  FIG. 1 ; 
         FIG. 3A  is a perspective view of one end cap and  FIG. 3B  is an end view thereof; 
         FIG. 4  is a perspective view of an extension cap, and 
         FIG. 5  is an enlarged view of the area on  FIG. 2  marked ‘V’ and showing the end of the anode from which a wire emerges. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The anode assembly includes two elongate tubes  1 ,  1 A arranged end to end. The tube  1  is made of titanium suboxide available under the registered trade mark EBONEX. The tube  1 A is moulded of a plastics. The wall of the tube  1  is solid along its length, whereas the tube  1 A is solid save for a slot  2  at one end  3 . The tube  1  contains an elongate support rod  4  which holds two caps E 1 , E 2  in place, as will be explained below. A conductor wire  5  formed of titanium spring metal is present as a spiral about the rod  4  and has a straight tail  6  which emerges from the tube  1 A at the end  3 . This will be explained in better detail below. 
     As shown in  FIGS. 3A and 3B , the cap E 1  consists of a cylinder having two longitudinal end portions  10 ,  11 , separated by a shoulder  12 . End portion  10  is shorter than the end portion  11 . Six vanes are shown, but the number is not critical. The vanes are arranged so that they will flex in the same direction. The end portion  11  has inwardly turned reverse facing longitudinal spring tongues  15  located to be snap-engaged in slots  16  near the ends of the rod  4 . An inner partition  17  is present to separate the two end portions and an inner shoulder  18  is present in the end portion  11 , to act as an abutment for the end of the rod  4  so that the tongues  15  will align with the slots  16 . The cap E 1  is received in and engages in one end of the tube  1 . 
     The second end cap E 2 , has the same vane or fluting as E 1 , but differs in the presence of hole  19 , whereby the electrical connection wire passes through E 2 . The end portion  10  of E 2  is illustrated to be as interference fit with tube  1 A. (This joint however could be made with an adhesive or with a friction or other welding technique). Tube  1 A is present in this illustration to provide a smooth seal surface to allow the electrode to pass through the wall of the electrochemical cell, and so that the electrical connection from the power supply is outside the cell and easy to access. 
     The wire  6  passes through the end of tube  1 A through a hole, which is provided with a sealing system, such as is illustrated. Sealant can be injected into hole  2  and fill the annulus around the wire preventing any leakage of electrolyte through the end of tube  1 A. 
     The electrical connection can be made directly to the exposed end of wire  6 , but in this example, the tube  1 A is provided with a short threaded stud  25 , around which can be bent the end of the wire  5 , supported by washer  27 , to present a neat terminal for the electrical connection. 
     Typically the electrode is assembled by inserting the straight part  6  of wire  5  through hole  19  in E 2  and then pressing tube  1 A into place on E 2  with wire  5  extending through the tube  1 . Rod  4  is then placed into the socket in E 2  and engaged with the clip. An assembly tool, not shown, is then used to “wind up” the spring part of wire  5 , thus reducing its diameter such that the body  1  can be slid over it and onto the flutes of E 2  probably with a slight rotation. Because the vanes flex in the same direction, they will tend to bend and reduce the overall diameter of the cap and act as a self-centring system. The spring is then released and allowed to engage on the internal surface of tube  1 . E 1  is then pressed into place, also with a slight rotational movement until it is captured by the clip engaging into rod  4 , also with the flutes acting as a self-centring system similar to E 2 . Washer  26  is added and the wire bent around stud  25 . Finally sealant is injected into slot  2 . 
     The flutes can also accommodate tubes of different diameters, as well as some flexibility to eliminate bending stresses. 
     The support rod is positively engaged at both ends, which capture the rod and eliminates both compressive and extensive forces on the ceramic tube. 
     Because all the parts lock together mechanically, there is no need for adhesives. 
     SEQUENCE LISTING 
     Not Applicable