Retaining structure for frames of multi-electrode electrolysis apparatus
United States Patent Weltin et al. Apr. 1, 1975 [54] RETAINING STRUCTURE FOR FRAMES 0F 542,358 l/1942 United Kingdom 204/256 MULTI-ELECTRODE ELECTROLYSIS APPARATUS Primary E.\&#39;aminer.lohn H. Mack [75] Inventors: Carl Weltin; Horst Pomiczinski, Assistant E.\&#39;aminerW. 1. Solomon both of Leverkusen, Germany Attorney, Agent, or FirmBurgess, Dinklage &amp; [73] Assignee: Bayer Aktiengesellschaft, Sprung Leverkusen, Germany [2]] Appl. No.: 354,033  
  In an apparatus suitable for the electrolysis of hydrochloric acid and alkali metal chlorides and comprising [30] Forelg Apphcat&#39;on Pnomy Data a plurality of current-conducting electrodes, a plural- May 9, 1972 Germany 2222637 ity of frames respectively carrying the electrodes, means for holding said frames together in an assembly, Cl 6 204/254, 20 and means for passing an electric current through said 8, 204/286 assembled electrodes, the improvement which com- [51] Int. Cl B01k 3/00 rises pin securing each electrode against movement Field of Search relative to its frame by extending into aligned recesses 286 in the electrode and frame, a plurality of elastic insulating seals between adjacent frames to allow limited References Cited movement upon expansion, a pair of spaced end plates UNITED STATES PATENTS provided with aligned apertures, a bolt extending 2.075 688 3/1937 Zdansky 204/256 through each Pair of aligned aPerwres and resilient 2143.793 1 1939 Nicdcrrcither.. 204 254 means On each bolt forcing Sflld end Plates together 3287.251 11/1966 Horne ct a] 204/268 x against the g g of said elastic insulating Seals t0 3.402.1l7 9/1968 Evans 204/268 constitute said assembly. 3.778.362 l2/l973 Wicchcrs ct al. 204/254 FOREIGN PATENTS OR APPLICATIONS 2 Claims, 3 Drawing Figures 398.02! 9/1933 United Kingdom 204/268 A r i We 9 g 10 o 9 77b 4 1 F4 1 I i L! PATENTEUAPR H975 BQYSfiAO sum 2 or 3 FIG. 2  
 RETAINING STRUCTURE FOR FRAMES OF MULTI-ELECTRODE ELECTROLYSIS APPARATUS This invention relates to an apparatus in which the electrically insulated holding frames of an electrolysis unit (electrolyzer) are connected particularly favorably to the electrodes, preferably electrode plates.  
  It is known that current-conducting electrode plates can be cemented into frames consisting of an insulating plastic material. Unfortunately, serious disadvantages are involved in connecting the holding frame of an electrolysis unit (electrolyzer) to the electrodes in this way. Electrolysis can frequently be interrupted because, in view of the temperature differences which occur, cracks and hence leaks can be developed in the cement through the different coefficients of expansion of the plastic material and electrode material.  
  A second known form of connection between the holding frame and the electrodes is the so-called interlocking joint, in which the holding frame and the electrode are joined by tongue and groove. However ajoint of this kind needs room in which to expand at elevated electrolysis temperatures which, in the event of a reduction in temperature, can result in leaks and the overflow of liquid from one chamber into the other.  
  One of the objects of the present invention is to obviate the disadvantages of conventional methods and to provide a suitable connection between the holding frame and electrode plates which consist of different materials. More particularly, the object of the invention is to provide an apparatus in which the disadvantages referred to above do not occur in the event of fluctuations in temperature of the kind which inevitably occur during the start up and run down of the electrolysis apparatus. In addition, the apparatus according to the invention is intended to allow the use of materials which, although hitherto regarded as suitable in regard to their behavior with respect to acids to be electrolyzed and other reactive substances, have never been able to be cemented to the electrodes plates in conventional apparatus on account of their high coefficient of expansion.  
  In accordance with the present invention there is pro vided an apparatus suitable for the electrolysis of hydrochloric acid and alkali metal chlorides and comprising a plurality of current-conducting electrodes, a plurality of frames respectively carrying the elctrodes, means for holding said frames together in an assembly, and means for passing an electric current through said I with corresponding faces of its frame, said frame and assembled electrodes. The apparatus includes elastic insulating seals separating a frame and its electrode from its adjacent frames and electrodes, said frame holding means including a resilient mounting, whereby said frame holding means will resiliently be displaced upon expansion of said electrodes.  
  Advantageously, the frame holding means comprises a pair of spaced end plates provided with aligned apertures, a bolt extending through each pair of aligned apertures, and resilient means on each bolt forcing said end plates together against the urging of said elastic insulating seals to constitute said assembly. At least one end of each bolt is threaded and carries a threaded nut, the resilient means comprising a coiled spring which is compressed between the nut and end plate.  
  In accordance with a further aspect of the invention each electrode has parallel faces substantially flush electrode being provided with aligned recesses extending parallel to the faces but spaced therefrom, the assembly including a pluralityof pins respectively in a pair of said aligned recesses whereby each electrode and its framev will move together in direction perpendicular to the faces.  
  In the force-locking joint according to the invention between the electrodes and the electrolyzer frame surrouning them, the electrode plates, anodes as well as cathodes, are neither cemented in nor interlocked, but instead are held resiliently between the electrolyzer frames by the retaining bolts of the electrolyzer.  
  The apparatus according to the invention is suitable for electrolysis in aqueous medium, for example for the electrolysis of hydrochloric acid and alkali metal chlorides. These electrolysis processes can be carried out particularly favorably by the diaphragm process using so-called bipolar electrodes in the apparatus according to the invention. The electrodes are preferably carbon electrodes.  
  The invention will be further described with reference to the accompanying drawings wherein:  
  FIG. 1 is a schematic longitudinal section through an apparatus with the electrodes shown in elevation; and FIG. 2 is an enlarged view of a portion of FIG. 1.  
  FIG. 3 is a cross-sectional view (section A B of FIG. 1).  
  Referring now more particularly to the drawings, as seen in FIG. 1, the electrolyzer consists of any number of individual frames 1, 8, 10, 11, 12 and electrodes 2, the cathode of the preceding cell 3 being the anode for the following cell 4 (bipolar electrode), etc. Diaphragms 7 are used to separate the anode compartments 5 from the cathode compartments 6. Retaining bolts 9 press the frame 8 against the frame 10, the frame 11 against the frame 12, etc. The electrodes between the frames are held in position through elastic seals 13, the transverse expansion of the materials being elastically absorbed by the retaining bolts 9. The frames can expand or contract perpendicularly to any extend without any negative effect upon the joint between the holding frames and the electrodes in the range of temperatures which occur. To facilitate assembly of the electrodes, plastic pins 14 which fit into corresponding aligned recesses 15 in the electrodes are introduced into the individual frames of the electrolyzer both on top and beneath. The electrode plates are thus prevented from dropping out of the frame during assembly. However, the pins must have enough room .for movement in the aforementioned recesses to provide them with the necessary clearance, even in the operative state, for example at 80C.  
  Threaded bolts 9 pass through aligned apertures in a pair of end plates 16a, 16b holding all the frames together, threaded nuts 17a, 1712 being positioned on the bolt ends and compressing resilient springs 18a, 18b which work against the elastic seals.  
  The advantages of the apparatus according to the invention are that the formation of cracks in the cement is now avoided so that the electrode plates cannot become loose, and that the frames can readily be replaced without destroying the electrode plates.  
  It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation and that various modifications and changes may be made without departing from the spirit and scope of the present invention.  
 What is claimed is:  
  1. In an apparatus suitable for the electrolysis of hydrochloric acid and alkali metal chlorides and comprising a plurality of current-conducting electrodes having parallel faces, a plurality of frames respectively carrying the electrodes, means for holding said frames together in an assembly, and means for passing an electric current through said assembled electrodes, the improvement which comprises providing each frame and electrode with an aligned pin and recess extending parallel to the faces but spaced therefrom, whereby each trode-and-frame units.