BACKGROUND OF THE INVENTION The present invention relates generally to a process for filtering engine exhaust and an engine exhaust filtering system. More particularly, this invention relates to an exhaust filtering system suited for use with diesel engines. As concern for the environment increases, greater attention is being given to systems for eliminating damaging discharges from internal combustion engines. In the workplace, pollution created by combustion engines threatens the health of many workers, as the carbon contained in the exhaust may be carcinogenic. The problem is especially troublesome in enclosed environments such as warehouses or factories wherein fork lifts are frequently used. Fork lifts are often operated in a cycling manner, that is, at maximum power for short spurts. At maximum power, the highest percentage of carbon is exhausted, exposing the operators to health risks. Thus, it can be seen that a system for reducing this harmful exhaust is needed. Prior filter units have generally been too expensive and difficult to service. In addition, prior filtering devices have not worked effectively during cycling when carbon exhaust is at a maximum.

The prior art, reflected by U.S. Pat. No. 3,738,089 to Brill, teaches an exhaust gas filter. Exhaust passes from the interior of a canister outward through a perforated wall and into a fiber type filter medium located between the canister and a surrounding supporting shell and exits from openings at the rear of the device. A bypass valve opens to allow a direct passage of the exhaust gases through the canister and out to the atmosphere when the engine is under maximum power conditions so that the this filter is ineffective in applications wherein the engine frequently cycles up to maximum power.

In Mizrah et al., U.S. Pat. No. 4,732,594, there is described a process for scrubbing exhaust gases from diesel engines using an open pore ceramic foam filter. This type of filter requires temperatures above 550° C, or temperatures above 400 ^° C when the filter has a catalyst coating, to regenerate the filter by combusting the soot. In many applications, the filter will not reach the high temperatures required for regeneration so that a separate heat generation device must be added, thereby making the cost prohibitive.

In addition, the prior art also teaches several types of spark arresters generally located inside of a muffler to trap carbon particles.

The present invention addresses the problems associated with filtering exhaust from internal combustion engines. It is apparent that an improved system for filtering exhaust is needed for the health and safety of vehicle operators and those working nearby. The present invention solves these problems and others associated with filtering exhaust from combustion engines.

SUMMARY OF THE INVENTION In contrast to prior art exhaust filters, the present invention uses agglomeration and diffusion before filtering exhaust gases. Both steps contribute to the greater efficiency in removing carbon from the exhaust gases. The present invention remains effective in filtering out the increased amount of carbon expelled at maximum power and is more suitable for use during cycling. According to the present invention, exhaust gases flow through an intake pipe of substantial length to promote the agglomeration of carbon particles in the exhaust gases. As the length of the intake pipe increases, the number of collisions between carbon particles and subsequent agglomerations also increases. The larger agglomerated carbon particles and the exhaust gases are then passed through a diffuser manifold in which

is located a number of diffuser chokes to add further turbulence in the flow and, therefore, further agglomeration of the carbon particles. The diffuser manifold then distributes the agglomerated carbon particles and the exhaust gases uniformly on a filter cartridge. The carbon particles are removed from the exhaust gases by the filter material, and the clean exhaust is expelled into the atmosphere.

These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, in which like reference numerals indicate corresponding elements throughout the views:

FIGURE 1 is a perspective view of an engine exhaust filtering system mounted on a forklift with the forklift counterweight removed to expose the rear of the engine compartment;

FIGURE 2 is a longitudinal sectional view of the filtering unit of the engine exhaust filtering system shown in Figure 1;

FIGURE 3 is a cross-sectional view of the filtering unit taken along section 3-3 of Figure 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows an engine exhaust filtering system, generally designated 10, attached to and drawing exhaust off a muffler 18 from the engine (not shown) . The

exhaust filtering system 10 has an agglomerating pipe 12 surrounded by a protective heat guard 14. The filtering system 10 is shown mounted on a forklift 16, however, it can be appreciated that the filtering system 10 could be used with other combustion engines as well.

The agglomerating pipe 12 leads from the muffler 18 up to a filtering unit 20 located at the upper portion of the frame of the forklift 16, so that the field of vision of an operator is not limited. The filtering unit 20 is encompassed by a filter housing 24 which in turn, is surrounded by heat guard 28 to prevent burns.

As shown in Figure 2, the agglomerating pipe 12 attaches to diffuser 30 and the end of the filter housing 24. The agglomerating pipe 12 directs the flow of the agglomerated carbon particles and the exhaust gases into an elongated diffuser manifold 36. A number of diffuser chokes 38 are spaced along the diffuser manifold 36. Each choke 38 has a reduced opening which restricts the flow along the diffuser manifold 36 to increase turbulence. The agglomerated carbon particles and exhaust gases then pass radially outward through a multiplicity of diffuser ports 39, only several of which are illustrated in Figure 2, and into cavity 31 between the diffuser 30 and the filtering unit 20, as also shown in Figure 3. In the preferred embodiment, a cylindrical filter cartridge 22 encompasses the diffuser manifold 36 and is supported by the diffuser manifold 36, as shown in Figure 2. The filter cartridge 22 has end rings 22a at the ends of cylinder filter material 22b. In the preferred embodiment, the filter cartridge 22 has an annular configuration and the filter material 22b has pleated construction, as shown in Figure 3, however, other filter configurations may be used. The filter housing 24 surrounds the filter cartridge 22. Discharge 40 in the housing 24 allows the filtered gases to pass to the atmosphere. In the preferred embodiment, the discharge 40 has a row of exit ports 42 passing the gases out.

The filter cartridge 22 engages the filter housing at the agglomerating pipe inlet end and has a removable end cap 23 at the opposite end to form a chamber 31. The removable end cap 23 is held in place by wing nut 32 engaging retention bolt 34 located on the end of the diffuser manifold 36. In the preferred embodiment, the removable end cap 23 is covered by a heat shield cap 25 which prevents workers from touching the hot surface of the removable end cap 23. The heat shield cap 25 is attached to the removable end cap 23 by a plurality of magnets 26. In addition, a security loop 27 is attached at one end to the heat shield cap 25 and at the other end to the filter housing 24 to prevent the heat shield cap 25 from being misplaced when removed during the cartridge cleaning process, as explained hereinafter.

In operation, exhaust gases containing pollutants pass from the muffler 18 to the exhaust filtering system 10 into the agglomerating pipe 12. As exhaust gases pass along the agglomerating pipe 12, turbulent flow causes the carbon particles in the gases to collide and agglomerate prior to filtering, providing for greater filtering efficiency, as the larger particles passing through filter material are easier to trap. It can be appreciated that the agglomerating pipe 12 should be made as long as is practical to achieve greater agglomeration. Turbulence and additional length for agglomeration to occur may be added by winding the agglomerating pipe 12 back and forth.

Gases pass up the agglomerating pipe 12 to the filtering unit 20 and enter the diffuser 30. The gases proceed through the diffuser manifold 36 and are directed through the diffuser chokes 38, to create turbulence and promote further agglomeration. In the preferred embodiment, the openings of the diffuser chokes 38 vary in size, with the area of these openings generally decreasing along the direction of flow to promote uniform exhaust from the diffuser manifold 36. The diffuser chokes 38 and diffuser ports 39 dispense the exhaust gases and carbon

particles uniformly throughout the chamber 31 so that the particles are distributed over the inner surface area of the filter cartridge 22.

As the gases proceed through the filter cartridge 22, agglomerated carbon particles are left on the inner surface of the filter material 22b. The clean exhaust gases then exit the filter unit 20 into the atmosphere through the exit ports 42. In the preferred embodiment, the exit ports 42 direct the gases upward and away from the vehicle operator.

Filter cartridge 22 is removable and reusable. The cartridge 22 is removed by detaching heat shield cap 25 from the end of the filter housing 24. Wing nut 32 is unscrewed from retention bolt 34 and the end cap 23 is lifted off of the end of the cartridge 22. The filter cartridge 22 can then be slid out of the filter housing 24 along the diffuser manifold 36. When the cartridge 22 is removed, vigorous agitation will loosen the carbon particles that are attached to the inside of the cartridge 22. When the particles have been removed, the cartridge 22 may be inserted back into the filter housing 24 and cleaned and reused over and over. A small amount of carbon particles may remain on the filter cartridges 22, but the filtering performance does not decrease and may actually improve. With use, filtering efficiencies as high as 99.5% have been achieved.

Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, it is to be understood that the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.