CATALYTIC CONVERTERS

Abstract: Protective material for a catalytic converter block comprises a pad of fibrous material in an envelope (10), wherein the envelope has its depth reduced in at least localised areas or positions by drawing together of opposing faces of the envelope, such as by stitching (16).

Description: Title: Catalytic Converters DESCRIPTION This invention concerns catalytic converters principally for motor vehicles. Catalytic converters are used for treatment of exhaust gases from motor vehicle engines to render them substantially harmless before emission to atmosphere. Treatment is by passing the exhaust gases through a chamber enclosing as porous ceramic block whose pores are coated with a suitable catalyst. The ceramic block is contained in a chamber formed from two half shells welded together at their edges, the chamber having an inlet and an outlet. The block is wrapped in fibrous material in order to insulate it from colder temperatures outside the converter, to provide sound proofing and to cushion the ceramic block against expansion and contraction of the chamber. A commonly used fibrous material is that sold under the trade name SAFFIL which is 95% alumina and provided as a low density mat. Currently two pads of fibrous material are used, one being laid in the first half shell and the other on top of the converter block when it has been laid on the first pad of fibrous material. This method -is unsatisfactory in a number of respects. Firstly, the pads do not always meet at the ends leaving unprotected areas of catalytic converter block. Secondly, the fibrous material is pre-cut and its weight adjusted to be within tolerance, but the resultant pad thickness can vary considerably even by a factor of two. That variation in thickness presents problems when putting together a catalytic converter. Proposals have been made in U.K. Patent Applications Nos. 2171180A and 2205929A for methods of wrapping ceramic blocks to facilitate fitting of same catalytic converters. These methods have proved to be acceptable in most areas but the presence of several layers of plastics material around and between layers of the fibrous material is seen as a possible source of contamination of the fibrous material that could impair its effectiveness. An object of this invention is to provide a way of installing fibrous material about catalytic converter blocks so that the above-mentioned disadvantages are overcome or at least mitigated. According to the invention it is proposed that fibrous material pads for catalytic converter blocks be provided in a preferably sealed envelope. It is further proposed that said envelope preferably has its depth reduced in at least localised areas or positions by drawing together of opposing faces of the envelope. Said drawing together of said envelope faces may be achieved in a variety of ways. For example, plastics tags such as of the type used for affixing labels to clothing and the like may be used, such tags comprising a thin flexible plastics rod with a T-bar at each end. Such tags are usually inserted by a specially designed machine. Alternatively, the opposed faces of the envelope may be stitched or tacked together either by hand or preferably by machine. Tags or stitches may be provided at discrete locations of the envelope, in an ordered pattern or randomly. Stitching or tacking may be provided in separate lines, possibly crossing over each other, or in one continuous line or indeed in any other desirable or convenient formation, particularly from production considerations. The positioning and spacing of tags or stitches may be dependent on the size of the pad of fibrous material. By selecting the positioning of tags, stitching or tacking and the tension thereof, the thickness of an envelope containing fibrous material may be controlled to within a desired range irrespective of the original thickness of the pad of fibrous material contained in the envelope. The envelopes for use in the present invention are preferably made of plastics material and may be conveniently sealed by heat sealing along edges of overlapped sheets or of a folded sheet of suitable plastics material. The plastics material itself should preferably be sufficiently strong to withstand the insertion of tags or stitches, for example without tearing. In addition, the plastics material is preferably air permeable so that the pad of fibrous material can be flexed to follow the shape of a catalytic converter half shell and/or block and be compressed by said tags or stitching. Non-woven textile material made from plastics fibres, such as polypropylene fibres, may be particularly suitable for producing envelopes for the invention. The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 shows a pad of fibrous material in an envelope; Figure 2 shows a pad of fibrous material in an envelope with a first stitch arrangement; Figure 3 shows a pad of fibrous material in an envelope with a second stitch arrangement; Figure 4 shows a pad of fibrous material in an envelope with a third stitch arrangement; Figure 5 shows, a pad of fibrous material in an envelope with a tag arrangement; and Figure 6 shows a pad of fibrous material in an envelope with a fourth stitch arrangement. Referring to Figure 1 of the accompanying drawings, a pad of fibrous material, typically SAFFIL, is enclosed in an envelope 10 of non-woven textile material made from polypropylene fibres. The envelope is formed by heat sealing together edges of overlaid sheets of the textile material with the pad of SAFFIL therebetween or by heat sealing together edges of a sheet of the textile material folded about a pad of SAFFIL. The heat sealed join is indicated at 12. Thus such enveloped pads will be used in a catalytic converter either side of a catalytic converter block for protection and sound proofing. Turning to Figure 2 of the accompanying drawings, the enveloped pad of Figure 1 is shown treated to reduce its thickness, i.e. by drawing together the opposed larger faces of the envelope. That drawing together is achieved by means of stitching 16 through the envelope. The stitching 16 is shown as a continuous line. The pad of Figure 2 being thinner is easier to install in a catalytic converter and there is less likelihood of edges thereof being trapped between half shell edges to be welded together. In Figure 3 of the accompanying drawings stitching 116 is in the form of straight lines in a crossover arrangement. In Figure 4 stitching 216 is in the form of discrete parallel lines. In Figure 5 plastics tags 316 of the type comprising a rod and T-bar ends (often used in affixing labels to clothing) are used to draw the envelope faces towards each other to compress the pad of fibrous material therein. The tags 316 are inserted using a special machine and are arranged in an orderly pattern. Finally in Figure 6 discrete stitches 416 are used arranged randomly.

Claims: CLAIMS 1. Protective material for a catalytic converter block comprising a pad of fibrous material in an envelope, wherein said envelope has its depth reduced in at least localised areas or positions by drawing together of opposing faces of said envelope. 2. Protective material as claimed in claim 1 , wherein said opposing envelope faces are drawn together by means of tags therethrough. 3. Protective material as claimed in claim 2, wherein said tags comprise a thin rod with a T-bar at each end. 4. Protective material as claimed in claim 1, wherein said opposing envelope faces are drawn together by means of stitching. 5. Protective material as claimed in claim 2, 3 or 4 , wherein said tags or said stitches are provided at discrete locations of the envelope. 6. Protective material as claimed in claim 5, wherein said tags or said stitches are arranged randomly. 7. Protective material as claimed in claim 5, wherein said tags or said stitches are arranged in an orderly pattern. 8. Protective material as claimed in claim 4, wherein said stitching is provided in separate lines. 9. Protective material as claimed in claim 8, wherein said lines cross over each other. 10. Protective material as claimed in claim 4, wherein said stitching is provided in a continuous line. 11. Protective material as claimed in any one of claims 1 to 10, wherein the envelope is of plastics material. 12. Protective material as claimed in claim 11, wherein the envelope is sealed. 13. Protective material as claimed in claim 12, wherein the envelope is formed by heat sealing together overlapping edges of plastics sheet material. 14. Protective material as claimed in any one of claims 1 to 13, wherein the envelope is of air permeable material. 15. Protective material as claimed in claim 14, wherein the air permeable material is a non-woven textile material. 16. Protective material as claimed in claim 15, wherein the non-woven textile material of plastics fibres. 17. Protective material as claimed in claim 16, wherein said plastics fibres are of polypropylene. 18. Protective material as claimed in any one of claims 1 to 17, wherein the fibrous pad is of alumina. 19. Protective material for a catalytic converter block substantially as hereinbefore described with reference to and as illustrated in any one of Figures 2 to 6 of the accompanying drawings.

Inventors: CARSON JOHN EDWARD, CARSON, JOHN, EDWARD
Applicants: FIBRE TECH LTD, FIBRE TECHNIQUES LIMITED
Application year: 1991
Main classification: F01N3
IPC codes: F01N3