FR2709327A1 - Catalytic convertor for manually steered machine tools - Google Patents

Abstract

The invention relates to a device intended to purify the exhaust gases of two-stroke engines of manually steered machine tools, particularly motor saws, which include a catalytic convertor (1) and a silencer (muffler). In order to allow the device to be produced with a small volume and be manufactured in a technically simple manner, the catalytic convertor (1) consists of several coated metal sheets (3) which, arranged one after another, are fitted into a casing (2) forming part of the silencer. This casing (2) may either be the casing of the silencer itself or belong to the catalytic convertor metal sheets and be mounted by way of an additional casing inside the casing (30) of the silencer.

Description

Catalytic converter for manually guided machine tools
The present invention relates to a device for purifying exhaust gases from two-stroke engines of manually guided machine tools such as motor saws, which include a catalytic converter, and a silencer.

 I1 is known in the field of catalytic purification of exhaust gases, in particular as regards its application to motor vehicles, to use for the construction of a catalytic converter, simple coated metal sheets and to have these one after the other in an envelope; in this regard, reference is made to German Patent Applications respectively put to public inspection 2733640 and published 3528107.

 It is also known, as explained in the aforementioned documents, that the catalytic converter sheets have, in order to increase the turbulence of the exhaust gas stream, holes and / or recesses and elevations, for example in the form of buttons, to obtain, through increased swirling, better conversion of exhaust gases.

 It is part of the prior art to use, for catalytic converters of machine tools with two-stroke engine guided manually, such as for example motor saws or lawn mowers, a thin sheet of metal with a thickness of about 0.1 mm which is wound and housed in an envelope specially provided for this purpose and having a circular or oval section. The disadvantage of this known technique is that such a catalytic converter is relatively expensive due to the high cost of the material of the thin metal sheet. In addition, this same catalytic converter requires additional space for its mounting, which poses problems, having regard to the small dimensions of the two-stroke engines of manually-guided machine tools.

 The object of the present invention is to create a device of reduced bulk and cost which, while being fail to manufacture and technically simple to produce, has good catalytic action.

 This object is achieved, as regards a device intended to purify the exhaust gases of two-stroke engines of manually guided machine tools, such as motor saws, which comprise a catalytic converter and a silencer, according to the invention by the fact that the catalytic converter is made up of several coated catalytic converter sheets arranged one after the other and that the catalytic converter sheets are placed in an envelope forming part of the silencer.

 Thanks to the invention, a device is created which combines in itself a silencer and a catalytic converter, thus making it possible to reduce the space required and the manufacturing costs since in particular the fact of producing the catalytic converter itself in the form of individual plates makes the device less expensive and facilitates its handling.

 In an advantageous embodiment of the invention, the envelope retaining the catalytic converter sheets is the envelope of the silencer.

 In another advantageous embodiment of the invention, the catalytic converter sheets are placed in an envelope of their own and is located in the envelope of the silencer.

 In a particular embodiment of the invention, the catalytic converter sheets located in their envelope are rectangular with dimensions of approximately 48 mm by approximately 25 mm and the catalytic converter sheets (3) have a thickness of approximately 1.3 mm.

 Advantageously, the envelope where the catalytic converter sheets are located has a rectangular section and comprises, on each of its lateral sides, a cylindrical housing which forms part of said envelope and serves to receive a rod-shaped fixing member, in in particular a screw, the two housings being offset vertically with respect to each other and serving each to receive a rod-shaped fixing member, in particular a screw.

 Another advantageous characteristic of the invention consists in that the envelope of the catalytic converter is closed by closing flanges arranged laterally and which, by means of elevations and recesses in the form of pressed buttons, constitute a kind with press studs.

 According to another characteristic of the invention, the sheets of the catalytic converter have holes which may advantageously have a diameter of approximately 4.2 mm and be arranged in parallel longitudinal rows offset from one another.

 Advantageously, the catalytic converter sheets have, with a view to obtaining a swirl of the stream of exhaust gas, elevations and / or recesses, in particular bulges in the form of buttons and / or fasteners.

 The sheets of the catalytic converter can advantageously be offset with respect to each other and have a front recess by which the exhaust gases flow in cascade through the catalytic converter.

 In an advantageous embodiment of the invention, the sheets of the catalytic converter are arranged parallel to the longitudinal side of its envelope.

 Another characteristic of the invention consists in that the sheets of the catalytic converter are retained inside the envelope of the latter in their mounting position by fixing members, in particular screws, rivets or the like, which extend perpendicular to the sheets.

The invention and its important advantages and particularities are described in more detail below with the aid of exemplary embodiments shown schematically in the accompanying drawings in which
Figure 1 is a front view of a catalytic converter mounted in an envelope of its own, and shown as it can be used for manually guided machine tools
Figure 2 is a top view of the catalytic converter casing of Figure 1
FIG. 3 is a side view of the catalytic converter envelope of FIG. 1
Figure 4 is a top view of a sheet of the catalytic converter mounted therein;
Figure 5 is a front view of the catalytic converter sheet of Figure 4;
Figure 6 is a front view of the catalytic converter of Figure 1 with a partially closed front side
Figure 7 is a front view of another embodiment of a catalytic converter
FIG. 8 is a top view of a sheet mounted in the catalytic converter of FIG. 6.

 The catalytic converter shown in Figures 1 to 3 has its own envelope (2) called spray in which are placed several sheets of catalytic converter 3 superimposed in the manner of layers and along which the exhaust gases flow for purposes catalytic purification of the latter. The envelope 2, or spray, can be mounted in a silencer envelope 30 and serves to guide the exhaust gases into the silencer. It has substantially the shape of a parallelepiped with open front sides 12 and 13 (Figure 3). The casing 2 has, according to FIG. 1, advantageously a rectangular section in which several sheets of catalytic converter 3 are arranged approximately parallel to one another and at a certain distance from each other. In the longitudinal sides 31, extending parallel to the sheets 3, of the casing 2 are provided holes 27 through which the exhaust gases can exit. On the downstream side 13 is formed a recess 28.

The catalytic converter sheets 3 are retained in their mounting position inside the casing 2 by fixing members 4 extending perpendicular to the sheets 3; the fixing members 4 can be made in the form of screws, rivets or the like which protrude through corresponding holes 27 provided in the parallel longitudinal sides 31, which respectively form the top and the bottom of the casing 2, and by l 'through which the catalytic converter sheets 3 are fixedly connected to the casing 2.

 The casing 2 has on each of its two opposite longitudinal sides 21 a cylindrical housing 5 forming part of the casing 2 and produced in one piece with the latter so that the housings 5 are vertically offset relative to one another to the other. The housings 5, which are advantageously obtained by a shaping operation such as a folding of the envelope sheet, serve to receive rod-shaped fixing members such as, for example, screws by means of which the catalytic converter 1 is fixed. with its casing 2, inside the casing 30 of the silencer, advantageously directly at the outlet channel of a cylinder, so that the exhaust gases evacuated from the combustion chamber immediately flow through the catalytic converter 1.

 The envelope 2 preferably made in one piece from a sheet is closed in its joint plane by closing flanges 9 which by means of elevations and / or recesses 6, which can be obtained by stamping under the shape of pressed buttons, form a kind of press stud connection. The connecting flanges 9 advantageously follow a housing 5 on the outside of the envelope. Thanks to this type of connection, it is possible to dispense with screws, rivets or the like for closing the envelope.

 The casing 2 receiving the sheets 3 of the catalytic converter can also be the casing of the silencer itself; in this embodiment the sheets 3 of the catalytic converter are arranged directly in the casing of the silencer and retained in the casing of the silencer by means of fixing members 4. The casing of the silencer is clamped, by the intermediate of the housings 5, on the cylinder of the two-stroke engine in the region of the outlet channel.

 Catalytic converter sheets mounted directly in the silencer have larger dimensions than the casing of the catalytic converter, since the latter is larger than in the case where the catalytic converter is mounted in its own casing 2. In the two embodiments the sheets 3 of the catalytic converter are located with a reduced bulk in the envelope of the same silencer.

 As can be seen from FIG. 2, the catalytic converter 1 is traversed by the exhaust gases in the direction of the arrow 10. Therefore the surface of the sheets 3 of the catalytic converter is swept by the current of the exhaust gases. exhaust, so that the catalytic reaction intended for the purification of exhaust gases can begin.

 FIG. 4 shows, in top view, a sheet of catalytic converter 3 which is intended to be mounted in the envelope of FIGS. 1 to 3. The rectangular sheet 3 of the catalytic converter can advantageously have dimensions such as its longitudinal sides 20 are substantially supported against the inner side wall of the longitudinal sides 21 of the casing 2 and that the front sides 14 and 15 are located substantially flush with the front sides 12; 13 of the casing 2. In the embodiment shown, there remains, in the assembled state, between the longitudinal sides 20 of the sheets 3 of the catalytic converter and the longitudinal sides 21 of the casing 2 of the catalytic converter small slit which does not, however, harm the course of catalysis but can impart turbulence to the flow of exhaust gas flowing along the slit. In each sheet 3 of the catalytic converter are formed, by punching, holes 7 spaced apart in a row, several longitudinal rows being juxtaposed parallel to each other. Advantageously, the holes 7 of a longitudinal row are offset with respect to the holes 7 of a neighboring longitudinal row. The holes 7 have the effect that partial streams of exhaust gases can pass through the holes 7 to the neighboring catalytic converter sheets so as to produce turbulence of flow which results in a swirling of the stream of exhaust, thus ensuring intimate contact of the exhaust gas stream with the catalyzing surface of the catalytic converter sheet 3. The holes 27, shown in FIG. 2, in the longitudinal sides 31 of the casing 2, respectively forming an upper side and a lower side also contribute to the swirling of the exhaust gas stream. At least the holes 7 in the sheet of the catalytic converter and the holes 27 in the casing of the catalytic converter, through which the fixing members 4 extend, are coincident. Advantageously, the size of the holes in the catalytic converter sheets 3 corresponds to the size of the holes in the longitudinal sides 31 of the casing 2 of the catalytic converter.

 The sheets 3 of the catalytic converter can advantageously have elevations 11 in the form of buttons or fasteners which also produce a swirl of the exhaust gas stream. The elevations 11 can be provided either in addition to or instead of the holes 7.

 Figures 1 to 5 show a compact and space-saving catalytic converter. The sheet 3 of the catalytic converter according to Figures 4 and 5 has approximately the dimensions 48 mm x 25 mm with a thickness of about 1.3 mm. The holes 7 have a diameter of approximately 4.2 mm.

 In order to obtain that the catalytic converter sheets 3 are swept along a long flow path by the flow of exhaust gases to be purified, the flow of exhaust gases can, inside the casing 2, be deflected one or more times in the form of a waterfall. To this end, the front side 12 and the other front side 13 of the casing 2 are each advantageously closed by a front wall 17 (FIG. 6) and have respectively an inlet and outlet section 16 which extends at least on the height of the distance between two sheets of catalytic converter 3 and on the width, measured in the plane of the sheet 3, of the casing 2.

The inlet section can be offset from the outlet section 16 and this advantageously in mutually opposite walls of the envelope; the deflection of the exhaust gas stream inside the casing 2 can be produced by recesses 8 (FIG. 4) disposed frontally in the sheet of catalytic converter 3, thanks to which the exhaust gas stream at the the interior of the casing 2 is deflected, after coming into contact with the front wall 17, in the direction of the next catalytic converter sheet 3.

The recess 8 is provided, for the neighboring catalytic converter sheets 3, each time at the opposite front end, thus making it possible to obtain the deflection of the cascading flow of exhaust gas.

 Without the recesses 8 in the sheet metal 3 of the catalytic converter the exhaust gas stream is directed, under the effect of the dynamic pressure inside the envelope, through the holes 7 in the direction of the catalytic converter sheets neighbors.

 Instead of providing a recess 8, the catalytic converter sheet 3 may have a shorter extent in the longitudinal direction than that of the interior space of the envelope and be contiguous by a front side to the interior side of a front wall. respective 17. It is also possible to arrange the shortened catalytic converter sheet so that it is at an equal distance from the intake side and the outlet side, so that the exhaust gases inside the casing flows from the two front sides of a catalytic converter sheet and passes, through the recess between the front side of the sheet metal and the inner wall of the closing plate, in the direction of the catalytic converter sheet neighbor.

 On the other hand, the front face on the downstream side of the casing 2 can be completely closed by the front wall 17 and the front wall on the intake side can have a second passage section through which the stream of gas exhaust is evacuated from inside the envelope.

 Figures 7 and 8 show a catalytic converter 1 consisting of a casing 2 'and catalytic converter sheets 3, in another embodiment. In the exemplary embodiments, circular holes are shown. Other holes having a shape different from that of a circular one, such as for example slots, rectangles or the like, may also be advantageous. The envelope 2 ′ may be the envelope of the silencer itself. The sheets 3 of the catalytic converter extend parallel to the longitudinal sides 21 of the casing 2 on which the housings are formed 5. The casing of FIG. 7 has a higher construction height than that of the casing of FIG. 1 so that the catalytic converter sheets 3 can also have larger dimensions and consequently a larger surface. The catalytic converter sheet 3 according to FIG. 8 has a certain number of holes 7, which holes have in the two surface directions axes of common section 18 and 19.

 Instead of the attachment shown in Figures 1 and 7 the sheets of the catalytic converter can also be attached directly to the casing 2 which retains them; thus the sheets 3 of the catalytic converter can be welded, brazed or in another way fixed in a fixed manner in the casing 2.

Claims (12)

 1. Device intended to purify the exhaust gases of two-stroke engines, in particular of two-stroke engines of manually guided machine tools, such as engine saws, which comprise a catalytic converter (1) and a silencer (30 ), characterized in that the catalytic converter (1) consists of several coated catalytic converter sheets (3) arranged one after the other and in that the sheets 3 of the catalytic converter are arranged in an envelope (2) being part of the silencer.  2. Device according to claim 1, characterized in that the casing (2) retaining the sheets 3 of the catalytic converter is the casing of the silencer.  3. Device according to claim 1, characterized in that the sheets 3 of the catalytic converter are mounted in an envelope (2) specific to the latter and which is mounted in the envelope (30) of the silencer.  4. Device according to claim 1, characterized in that the sheets (3) of the catalytic converter are rectangular and have dimensions of approximately 48 mm by approximately 25 mm and in that the sheets (3) of the catalytic converter have a thickness about 1.3 mm.  5. Device according to any one of the preceding claims, characterized in that the casing (2) has a rectangular section and comprises on each lateral side a cylindrical housing (5) forming part of the casing (2) and serving to receiving a rod-shaped fixing member, in particular a screw, the two housings (5) being offset vertically relative to one another.  6. Device according to any one of the preceding claims, characterized in that the envelope (2) is closed by means of closing flanges (9) arranged laterally and which, by means of elevations and / or recesses (6) in the form of pressed buttons, constitute a kind of connection with press studs.  7. Device according to any one of the preceding claims, characterized in that the sheets (3) of the catalytic converter have holes (7).  8. Device according to claim 7, characterized in that the holes (7) have a diameter of about 4.2 mm and are arranged in parallel longitudinal rows which are offset from each other.  9. Device according to any one of the preceding claims, characterized in that the sheets (3) of the catalytic converter have, for the purpose of swirling the stream of exhaust gas, elevations and / or recesses, in particular buttons and / or fasteners (11).  10. Device according to any one of the preceding claims, characterized in that the sheets (3) of the catalytic converter are offset from each other and have a front recess (8) through which the exhaust gases flow cascaded through the catalytic converter.  11. Device according to any one of the preceding claims, characterized in that the sheets (3) of the catalytic converter are arranged parallel to the longitudinal side (21, 31) of the casing (2).  12. Device according to any one of the preceding claims, characterized in that the sheets (3) of the catalytic converter are retained, in their mounting position, inside the envelope (2) by fixing members. (4), in particular screws, rivets or the like, extending perpendicular to the sheets (3).