Air filter restriction indicating device
BACKGROUND OF THE INVENTION 
     The present invention relates to an improvement for an air filter restriction indicating device adapted for use in connection with an internal combustion engine intake air filtration system, and more particularly for an air intake filtration system used with turbo-charged diesel engines in trucks, tractors and other heavy industrial and marine applications. Such an improved device is intended to indicate when the air filter has become so loaded or clogged with contaminants that its cleaning or replacement is required and also to lock itself in various intermediate, indicating positions so as to provide a continuous indication as to how much useful life remains in the air filter before it must be cleaned or replaced. My co-pending application, Ser. No. 273,699 filed June 16, 1981 describes such an air filter restriction indicating device. 
     While the aforesaid indicating device performs its intended function admirably, experience has shown that there is a possibility that the structure used to reset the indicating device, as when, for example, the air filter has been cleaned or replaced, may be rendered ineffective when the indicating device is used in a wet, cold environment or in a particularly dusty, dirty environment. The indicating device has a housing which encloses most of its components, but a part of the resetting structure is disposed without the housing and is exposed to the environment in which the indicating device is being used. An annulus of filter material surrounds this exposed part of the resetting structure and may become inflexible and stiff because of ice forming therein or thereon or because of dirt caking on or clogging the material. If the annulus is inflexible and stiff, the resetting structure is difficult to actuate and may be rendered ineffective. To minimize this possibility, it is recommended that the indicating device be mounted so that the end of the indicating device including the exposed part of the resetting structure is in a vertically down position, i.e. faced vertically downwardly. 
     To overcome these problems, the improved indicating device of the present invention includes a novel reset structure that prevents the structure from being rendered ineffective due to dirt and/or ice clogging. The improvement in the reset structure also allows the improved device to be mounted in any position, including in a vertically up position as well as in a vertically down position. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved air filter restriction indicating device including a novel resetting structure that permits the indicating device to be used even in extremely cold, wet environments and in particularly dirty, dusty environments and that remains fully and reliably operative even when the exterior of the indicating device has become thoroughly coated or caked with ice or dirt. It is a further object of the present invention to provide an improved air filter restriction indicating device which can be reliably operated in any position, including in a vertically up position or a vertically down position, in extremely cold, wet environments or dirty, dusty environments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view in elevation showing an improved indicating device of the present invention in an operating arrangement with an internal combustion engine and air filter; 
     FIG. 2 is an enlarged, elevational view of the improved indicating device shown in FIG. 1; 
     FIG. 3 is an enlarged, vertical sectional view taken on line 3--3 of FIG. 1; 
     FIG. 4 is a view similar to FIG. 3 showing a different operating position; and 
     FIG. 5 is a partially cutaway, exploded view showing the components of the novel resetting structure of the present invention. 
     Throughout the various figures of the drawings, the same numerals will be used to designate the same parts. Moreover, when the terms &#34;up&#34;, &#34;down&#34;, &#34;upward&#34;, &#34;downward&#34;, &#34;top&#34;, &#34;bottom&#34;, &#34;right&#34;, &#34;left&#34;, &#34;right end&#34;, &#34;left end&#34; and the like are used herein, it is to be understood that these terms have reference to the structure shown in the drawings as it would appear to a person viewing the drawings. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, an air filter restriction indicating device constructed and operated in accordance with the present invention is shown generally at 12. More specifically, the indicating device 12 is shown, in FIG. 1, mounted on the side of a conventional internal combustion engine 14 and operatively connected to and in communication with an air tube 16. The air tube 16, in turn, communicates with the air flowing through the engine air intake line 18. The air line 18 permits air to flow from a conventional air filter unit 20 to the air intake portion 22 of the internal combustion engine 14. Air flowing through the air line 18, and thus in the air tube 16, is under a negative pressure or &#34;vacuum&#34; condition when the engine 14 is operating. This vacuum condition increases, i.e. the pressure of the air is reduced, as the conventional air filter element, not shown, in the filter element in the air filter unit 20 becomes increasingly dirty and ultimately clogged. 
     A rectangular mounting plate 24 may be secured to, or if desired, be an integral part of the indicating device 12 and includes cutouts 26 along each of its side edges 28. As best seen in FIG. 2, these cutouts 26 are designed to accommodate appropriate and conventional fastening means, such as bolts 30, used to secure the indicating device 12 to the engine 14 or if desired, to another fixed surface, such as an instrument panel of a vehicle. 
     Except as hereinafter noted, the structure of the indicating device 12 is described in my aforesaid application and the description in that application is incorporated herein by reference. In summary, however, device 12 comprises a substantially cylindrical housing 32, preferably molded from a suitable plastic material, and consists of an annular side wall 34 and an upper integral end wall 36. The walls 34 and 36 define a chamber 38 within the housing 32. Projecting upwardly from the end wall 36 is a central neck 40 which receives, and is secured to the lower end of the air tube 16 by means of a conventional fitting 41 (FIG. 2) and which has a central passage 42 therein for permitting communication between the air line 18 and the chamber 38. A lower integral portion 44 of the neck 40 depends from the end wall 36 into the chamber 38. A bore 46 is formed in this lower portion 44 and is coaxial with, in communication with, but has a larger diameter than the passage 42. 
     An annular, outward offset 48 is formed about the lower end or bottom of the side wall 34. This offset 48 includes an annular, right angled shoulder 50. 
     Forming and defining the lower end of the housing 32 is a cylindrical end member 52 which may be a metal stamping or made from molded plastic and which has a bottom wall 54, an integral, annular side wall 56 and an integral, annular flange 58. The outer diameter of the flange 58 is substantially equal to that of the inner diameter of the offset 48 and as shown in FIGS. 3 and 4, the flange 58 is snuggly received within the offset 48, adjacent to its shoulder 50. Conventional means, such as a snap ring 60, may be used to retain the end member 52 within the offset 48. 
     A cup-shaped diaphragm 62, formed of pliable plastic, is disposed within the housing 32. The diaphragm has a bottom wall 64 and an integral annular side wall 66 terminating in an annular flange 68. The flange 68 is positioned between the shoulder 50 and the flange 58 and is secured in that position by the snap ring 60. 
     Seated upon and either adhesively or mechanically secured to the bottom wall 64 of the diaphragm 62 is an upright, tapered cup-shaped indicating member 70 formed of rigid molded plastic. The member 70 has a bottom wall 72 overlying the bottom wall 64 of diaphragm 62 and an integral, annular, flared side wall 74 that terminates in a vertical, upper rim portion 76. This rim portion 76 may be brightly colored and may serve as readily visible indicator such that its vertical position within the chamber 38, may indicate the amount of restriction or extent of contamination of the air filter element in the unit 20. The bottom wall 72 of the member 70 has a substantially narrower width or radius than the underlying bottom wall 64 of the diaphragm 62. 
     A centrally disposed, tubular guide 78, formed as an integral part of the member 70, and extends upwardly, in the chamber 38 from the bottom wall 72 and into the bore 46. The outer diameter of the guide 78 is slightly less than the inner diameter of the bore 46 so that air may pass therebetween and so that the guide may freely slide within that bore. The guide 78 extends through a sealed, central opening in the bottom wall 64 of the diaphragm 62 and has a central coaxial bore 80 therein that opens into the lower portion 82 of the chamber 38, i.e. the portion of the chamber below the diaphragm 62. An integral, radially inwardly projecting flange 84 is formed about the bore 80, adjacent to, but spaced slightly upwardly from, the open, downwardly facing end 86 of the bore 80. The guide 78 has a length so that it cannot to be fully withdrawn from within bore 46 when the diaphragm 62 is folded in upon itself as shown in FIG. 3. 
     A coil compression spring 88 is disposed within the upper portion 90 of the chamber 38, i.e. the portion above the diaphragm 62. The spring 88 has its upper end bearing against the inner, lower side of the end wall 36 and its lower end bearing against the inner, upward facing side of the bottom wall 72 of the member 70. The spring 88 urges or biases the diaphragm 62 and member 70 toward their positions illustrated in FIG. 3. 
     The upper portion 90 of the chamber 38 is sealed from the exterior atmosphere and is in direct communication with the air in the air line 18. Thus contaminants in the atmosphere surrounding the device 12 do not affect the condition or operation of either the indicating member 70 or the spring 88. The diaphragm 62 is tightly sealed, as by a conventional snap ring 92, about the guide 78, and this seal prevents any communication between upper and lower portions 90 and 82 of the chamber 38. 
     As best illustrated in FIG. 2, vertically spaced, horizontal lines 94 may be placed on the side wall 34 of the housing 32 and may serve to provide a visual indication, together with the rim portion 76 of the member 70, of the restriction levels of the filter element in unit 20. For example, when the rim portion 76 reaches the uppermost band 96, this may be used to signify that the filter element is fully restricted and requires cleaning or replacement. The particular indicia lines, however, shown in the drawings, are merely for illustration. 
     The bottom wall 54 of the member 52 has a centrally disposed, relatively small hole 98 therein. A tubular wall 100 depends downwardly from and is integral with the bottom wall 54, with the central axis of the wall 100 being coaxial with the hole 98. Three, regularly spaced slots 102 are formed in the distal edge of the wall 100 and serve to divide the edge into three segments. 
     An elongated, molded plastic locking member 104 is disposed, intermediate its ends, within the hole 98, so that its lower projecting end 106 extends through the hole and from the chamber 38. The upper end 108 of the locking member 104 extends upwardly, into the bore 80 in guide 78 and past the flange 84. The length of the upper end 108 is such that it remains within the bore 80 and extends past the flange 84 even when the diaphragm 62 and member 70 are moved to the position shown in FIG. 4. 
     The locking member 104 has a generally cylindrical cross-section except for a flat form thereon and extending from one end to the other. A plurality of teeth or notches 110 are formed on and project from this flat adjacent to the upper end 108 and each of these teeth are adapted to engage the flange 84 when they are brought into contact with it. 
     A partial, transverse, flange 112 is integrally formed on the locking member 104, intermediate between its upper and lower ends, and extends from the member 104 in a radial direction opposite to that of the teeth 110. This flange 112 rests on the upper surface of the bottom wall 54, adjacent to the hole 98 and serves as a pivot or pivot point about which the ends of the locking member 104 may be rocked or swung through an arc about the vertical. The central axis of the locking member 104 is normally offset, i.e., disposed at an angle with respect to the vertical as illustrated in FIGS. 3 and 4, so that one of the teeth 110 is engaged in a tooth to tooth relationship, with the flange 84 on the guide 78. The normal relationship between the teeth 110 and the flange 84 is such that relative upward movement of locking member 104, with respect to the guide 78, is permitted but relative downward movement of the locking member 104, with respect to the guide is prevented due to the engagement of one of the teeth 110 with the flange 84. The distal end portion 114 of the lower end 106 of the locking member 104 has a transverse groove 116 that is generally perpendicular to the flat on the side of the locking member. Two oppositely facing flanges 118 formed on and extending from the bifurcated parts of the end portion 114, as defined by the groove 116. An annular cap 120 has a radially outwardly extending flange 122 on its lower end and has a central bore 124 therethrough adapted to receive the distal end portion 114. The cap 120 is snap-fitted over the end portion 114 and is held on the end portion 114 by cooperation between the flanges 118 and an internal partial shoulder 126 formed in the bore 124. 
     The lower facing, transverse surface of the cap 120 has a cutaway, semicircular portion 128. An integral finger 130 is formed on the outer surface of the flange 122 at a point generally perpendicular to the diameter defining or dividing the cutaway portion 128 from the remaining, semicircular portion of the flange 122. Due to the cooperation between the flanges 118 and the shoulder 126, the finger 130 is positioned on the same side of the locking member 104 as the flange 112. 
     The finger 130 extends upwardly from the flange 122 in a direction generally parallel to the axis of locking member 104. The upper, distal end of the finger 130 is spaced above the upper end of the cap 120 and with the distance between the upper end of the finger 130 and the flange 112 being slightly greater than the thickness of the bottom wall 54. 
     A coil compression spring 132 is disposed about the distal end portion 114 of the locking member 104 and extends between the bottom wall 54 and the upper facing surface of the flange 122 on the cap 120. The spring 130 urges the cap 120 against the flanges 118 and away from the bottom wall 54. 
     As best shown in FIGS. 3 and 4, the lower distal end portion 114 of the locking member 104 and the cap 120 lie slightly above a plane defined by the distal end of the depending wall 100. A generally hat-shaped, relatively flexible cover 134 is snap-fitted and held within the distal end of the wall 100. A central integral button portion 136 of the cover 134 extends downwardly from the remaining portion of the disc. The diameter of the bottom portion 126 is slightly smaller than the diameter of the cap 20. 
     An annulus 138 of conventional filter material is disposed in the annular space between the cover 134, the bottom wall 54 and the wall 100, and about the distal end portions 114 of the locking member 104. This filter annulus 138 prevents the entry of most dirt or dust particles into the lower portion 82 of the chamber 38. 
     When the disc 134 is pressed upwardly, i.e., toward the bottom wall 54, the cover 134 abuts the lower facing end surface of the cap 120. This causes the locking member 104 to pivot about the flange 112 toward the vertical, and also causes the cap 120, and the distal end portion 114 to move slightly upwardly relative to the bottom wall 54. Continued pressure on the cover 134 causes the distal end of the finger 130 to abut the bottom wall 54. This abutment, and the application of further pressure on the cover 134, assists in forcing the upper end 108 of the locking member 104 to pivot toward the vertical until the teeth 110 are swung out of engagement with the flange 84. When this occurs, the spring 88 returns the diaphragm 62 and member 70 to their positions shown in FIG. 3, provided of course, that vacuum in the upper portion 90 of the chamber 38 does not preclude such movement of the diaphragm and member. 
     Since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or central characteristics thereof, the preferred embodiment described herein is therefore to be considered in all respects as illustrative and not restrictive, the scope of my invention being indicated by the appended claims, rather than by the foregoing description.