Air Filter Unit

Air filter units particularly those utilized with internal combustion engines for heavy duty trucks, and the like, normally include an outer sleeve which is formed from a blank of expanded metal or perforated sheet material which in turn, is formed into a cylindrical sleeve by a complex, time-consuming operation and/or in many instances a jagged, burr-forming edge of the blank is exposed when a seam is formed in the ultimate sleeve. Such an exposed edge is susceptible to being snagged by clothing or the like or scratching or cutting the hands or arms of the installer when the filter unit is being installed on or removed from the engine or when the components of the filter unit are being assembled.

Thus, it is an object of the invention to provide an air filter unit which is of simple, inexpensive, yet sturdy construction.

It is a further object to provide an air filter unit wherein there are no exposed jagged, burr-forming edge portions.

Further and additional objects will appear from the description, accompanying drawing and appended claims.

In accordance with one embodiment of the invention, an air filter unit is provided which includes inner and outer cylindrical sleeves, a filter medium disposed between the sleeves, and a pair of end plates affixed to and overlying the corresponding ends of the sleeves and filter medium. At least the outer sleeve is formed from a blank of foraminous, relatively stiff sheet material with the periphery thereof including jagged, burr-forming peripheral portions and an elongated peripheral portion folded back upon itself to form a hem-like segment. The hem-like segment overlaps and is affixed to a jagged, burr-forming peripheral portion opposite the hem-like segment and thus, forms an elongated seam extending the length of the sleeve with the folded back portion concealed. The jagged, burr-forming peripheral portions of the blank which form the sleeve ends are concealed by the corresponding end plates. The overlapped seam-forming peripheral portion of the blank is exposed only on an interior surface of the outer sleeve.

For a more complete understanding of the invention reference is made to the drawing wherein;

FIG. 1 is a perspective side view of one embodiment of the improved air filter unit;

FIG. 2 is a perspective exploded side view of the components of the air filter unit of FIG. 1;

FIG. 3 is a perspective end view of the outer sleeve shown in FIG. 2 and showing in phantom lines the blank from which the sleeve is formed;

FIG. 4 is an enlarged fragmentary sectional view taken along line 4--4 of FIG. 3;

FIG. 5 is an enlarged fragmentary perspective view of a section of the outer sleeve and showing a portion of the seam formed therein.

Referring now to the drawing and more particularly to FIGS. 1 and 2, an improved air filter unit 10 is shown which is adapted for use on internal combustion engines for heavy duty trucks and the like. The unit is adapted to be placed within a suitable housing, not shown, which is normally located on the tractor section of a semi-trailer truck outside the hood thereof, the latter sometimes referred to as a bonnet.

As seen in FIG. 2, the unit 10 includes an inner sleeve 11; an air filter medium 12 of fiber-glass or like filtering material; an outer sleeve 13; and a pair of end plates 14, 15. The sleeves 11, 13 are preferably formed from a blank B (FIG. 3) of a foraminous material (e.g. expanded sheet metal or perforated sheet material). The periphery of the blank is initially formed of jagged, burr-forming portions. In the forming of each sleeve from the blank B, which has a rectangular or square configuration, one elongated burr-forming peripheral edge portion of the blank is folded back upon itself so as to form a hem-like segment 16. Subsequent to the hem-like segment 16 being formed, the segment and the burr-forming peripheral edge portion 17 of the blank opposite the segment are brought together in an overlapping relation so that the blank assumes a cylindrical configuration with a seam S extending the length of the sleeve see FIG. 3 and 4. It is important that the peripheral portion 17 be disposed beneath or under segment 16 and that the folded back portion 16a of the segment be concealed between the remainder of the segment and peripheral portion 17. Thus, the exposed edge 16b of the hem-like segment 16 forming the seam includes no undesirable burrs or projections. Once segment 16 and peripheral portion 17 are in proper overlapped relation, they are retained in such relation by welding W or some other suitable well known method.

The filter medium 12 is provided with a central bore 12a which is sized to frictionally accommodate the inner sleeve 11. The outer sleeve 13 is sized to frictionally accommodate the filter medium 12. The sleeves and the filter medium normally have the same lengths.

Overlying the corresponding ends of the sleeves and filter medium and affixed to the outer sleeve is a pair of end plates 14, 15. In the illustrated embodiment, the end plates are of like construction and each includes a peripheral flange 14a, 15a which is adapted to embrace and conceal the burr-forming peripheral portions forming the opposite ends of the outer sleeve 13. An inner flange 14b, 15b is provided which encompasses the opening 14c, 15c formed in each plate. The flange 14b, 15b is dimensioned so that it frictionally fits within the corresponding end of the inner sleeve 11. The peripheral flange 14a, 15a is affixed to the corresponding end of the outer sleeve by welding or some other suitable method well known in the art. Once the end plates are affixed to the outer sleeve 13, there is no jagged or burred edge portion of the sleeve blank exposed which might snag clothing or scratch or cut the arm or hands of the installer when inserting or removing the unit from the housing.

Other material besides expanded sheet metal may be utilized to form the inner and outer sleeves such as perforated sheets of metal or plastics. It is important that the material be bendable without breaking so as to form a cylinder and yet be possessed of sufficient stiffness so that the unit can be readily handled without becoming distorted. Furthermore, if desired, and depending upon the flow pattern desired through the unit, only one end plate may be provided with a center opening. The size and shape of the various components may vary from that shown and will depend upon the size and rating of the engine on which the filter unit is to be installed.

Thus, a simple, inexpensive air filter unit has been provided which is easy to manufacture and assemble and can be readily handled without injury to clothing or the hands and arms of the installer.