Abstract:
A low cost air filter restriction indicator gauge for use in conjunction with an internal combustion engine can be achieved by both simplifying individual part configuration and reducing overall part count. More specifically, a simplified design can be achieved by utilizing a one piece base cap which includes a locking extension and reset button integral therewith. By having this part injection moldable, it is easy to fabricate and lower in cost as a complex locking pin assembly can be eliminated. Further, the low cost device can be further enhanced by providing a two color visual indicator which displays one color when the device is in its reset position and a second color when the device is in its locked or set position.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a gauge for monitoring the filtering performance of a vehicle filter. More specifically, the present invention relates to a low cost, simplified gauge for helping vehicle owners determine whether their air filter needs replacement. 
     Air filter restriction gauges are used in connection with an air filter for internal combustion engines. These devices typically sense the level of airflow restriction, and provide an indication of this restriction level by providing some type of display. When the air filter has become so loaded with contaminants that the supply of air required by the engine for its operating efficiency is not being drawn through the filter, the gauge will indicate this and thus alert the operator that the filter requires cleaning or replacement. Some existing devices will also lock themselves in various positions to provide a continuous indication as to how much useful life remains in the air filter before it should be cleaned or changed. 
     The use of a gauge to monitor the filtering ability of a vehicle&#39;s air filter is known in the art. Earlier patents in this area include U.S. Pat. No. 4,369,728, issued to Nelson on Jan. 25, 1983, and U.S. Pat. No. 4,445,456, issued to Nelson on May 1, 1984. These devices provided an incremental visual display to the users or maintenance personnel. 
     Air filter restriction indicator gauges have been available for quite some time. Initially, these indicator gauges were simply a single stage type gauge where a warning button would pop-up once a predetermined restriction level was achieved. The pop-up type gauges were not believed to be reliable and typically not trusted. The design of these gauges was complex and prone to many variations in performance. Also, this pop-up type gauge was difficult to manufacture due to the number of parts required and the intricacies of their assembly. 
     Additionally, prior art indicators have not always been easy to fully reset, sometimes resulting in a gauge that may give a false, premature signal that an air filter requires replacement. These false signals result in unnecessary filter maintenance—precisely what the gauge is intended to avoid. 
     In order to accommodate the locking features of prior indicator gauges, previous systems have required fairly involved and complex lock up mechanisms. Often these gauges comprise separate hinged locking pins which must be appropriately attached and aligned within the gauge. As expected, this has provided a manufacturing challenge to accomplish this necessary alignment. As can be easily appreciated, these types of structures also involve additional steps to assemble. 
     As most gauges have a locking feature so as to indicate that the predetermined vacuum level has been achieved, it is also necessary to provide reset capabilities. This provides additional design challenges when the lock pin is configured. More specifically, the lock pin must be accessible from the back side. Ideally, the button is depressed to unlock the mechanism. This resetting feature of previous designs which have a separate hinged locking pin structure makes the gauges more complex and costly to fabricate. 
     SUMMARY OF THE INVENTION 
     The present invention provides a more cost competitive product by dramatically simplifying the base cap design. In general, a one piece base cap is provided which includes an integral reset button and lock up extension, thus eliminating the need for a separate lock pin assembly. The part is specifically designed to be injection moldable while also providing the necessary functionality. A low cost economical restriction indicator gauge is thus provided with a lower part count and a simplified method of manufacturing. 
     The restriction indicator gauge is used in internal combustion engines for helping owners, maintenance personnel and operators determine when new air filters are required. The gauge of this invention is attached to the engine between the filter and the air intake and monitors the air pressure sign existing at that point. As is clearly understood, the pressure is likely to be a vacuum as the intake is pulling air into the engine. Once the gauge experiences a vacuum signal of a predetermined level, the gauge will “set,” thus indicating that the vacuum is undesirably high. This then provides an indication that the air filter must be changed. 
     The gauge of the present invention includes a housing which has an inlet in communication with the air intake system. Within the housing is attached a flexible diaphragm, forming an enclosed chamber inside the housing. As the flexible diaphragm is exposed to the vacuum signal, the diaphragm may be caused to move depending on the level of the vacuum. Attached to the flexible diaphragm is a sealing ring and alignment cup which help to maintain a seal between the internal chamber and the remainder of the gauge. The gauge further has a base cap which is attached to the housing such that it is on an opposite side of the diaphragm from the internal chamber. An integral locking extension in the base cap interacts with the sealing ring to provide the necessary lock up function. 
     The base cap is a single piece molded structure which is attached to the housing by a snap fit connection. This base cap includes the aforementioned lock pin extension as an integral part thereof. The integral lock pin extension eliminates the need for separate lock pin mechanisms which have been used in prior gauges. As is necessary, this lock pin extension is formed into a hinged reset button structure. As such, the reset button is easily depressed causing appropriate movement of the lock pin to unlock the gauge. 
     The hinge reset button structure of the present invention is again an integral part of the base cap. The base cap continues to be a single one-piece structure which is easily injection molded. The base cap however is specifically designed to avoid many problems typical to molded plastic parts. That is, the base cap is specifically designed to avoid the “setting” phenomena that may occur. The setting problem is avoided by specifically designing the base cap so that its hinging portion will not be permanently bent into an undesired configuration. By having the lock pin extension appropriately cooperate with other elements of the gauge, the reset button and the hinging element are held in their rest position for a majority of the time. As such, the only time the hinging element is stressed is when the gauge is reset. Consequently, it is highly unlikely that the gauge hinge will take on a set. 
     The housing additionally includes a clear window which is appropriately positioned to provide an appropriate visual indication. In operation, the vacuum signal creates forces on the flexible diaphragm. These forces can cause the flexible diaphragm to move toward the top of the housing. This causes related movement of the alignment cup and sealing ring. The alignment cup and housing window are specifically designed so that the alignment cup will become increasingly visible as it moves towards the top of the housing. Once the predetermined vacuum signal has been reached and the gauge is “set,” the alignment cup then becomes fully visible in the window. This is accomplished by having the lock pin extension interact with the sealing ring once a desired range of movement has been achieved. 
     By having the base cap be a single molded part, the parts count for the gauge is reduced. Further, the locking mechanism is greatly simplified, which provides for a product which is much easier to manufacture. 
     It is an object of the present invention to provide a low cost restriction indicator gauge having a simplified design which is easy to manufacture. 
     It is another object of the present invention to provide a reliable indicator gauge which will display indications that the gauge has experienced one or more predetermined vacuum levels at its input. This can then signal maintenance personnel that a new air filter is required. 
     It is yet another object of the present invention to provide an indicator which is highly visible to service personnel. This indicator will include brightly colored portions which are brought into view once the predetermined vacuum levels have been achieved. 
     It is a further object of the present invention to provide a simplified low cost gauge which includes a single piece molded base cap which is easily attached to the gauge. This single piece base cap includes the components necessary to provide lock up and reset capabilities to the present invention. 
     It is another object of the present invention which utilizes a single piece molded base cap which avoids the setting problem which is common to many molded parts. This allows the use of a molded plastic hinge element which will remain in its normal or natural configuration. 
     It is an additional object of the present invention to provide a lock up gauge which locks into an appropriate configuration upon experiencing a predetermined vacuum signal. The device provides one or more locking positions to display appropriate indications to the users. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further objects and advantages of the present invention can be seen by referring to the following detailed description, and the drawings in which: 
     FIG. 1 is a schematic drawing showing a simplified air intake system of an internal combustion engine; 
     FIG. 2 is a side view of the restriction indicator gauge of the present invention; 
     FIG. 3 is an exploded view showing the components of the restriction indicator gauge; 
     FIG. 4 is a cross sectional diagram of the restriction indicator gauge in its rest or reset position; 
     FIG. 5 is a partial cross sectional diagram of the restriction indicator gauge in its locked or set position; 
     FIG. 6 is a partial sectional diagram of the restriction indicator gauge illustrating the operation of the reset button; 
     FIG. 7 is a bottom view of the restriction indicator gauge with the reset cover removed; 
     FIG. 8 is a partial sectional view along section line  8 — 8  as shown in FIG. 5; 
     FIG. 9 is an enlarged partial sectional view of the restriction indicator gauge showing the connection between the housing and base cap; 
     FIGS. 10 and 11 are partial sectional diagrams showing the visual indicator feature in both the reset and set positions respectively; 
     FIGS. 12 and 13 are partial sectional diagrams showing an alternative embodiment of the visual indicator feature in the reset and set positions respectively; 
     FIG. 14 is a schematic diagram of the base cap button portion; and 
     FIG. 15 is a cutaway sectional diagram showing an alternative embodiment of the present invention having multiple locking points and a grommet tip attachment structure. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A restriction indicator gauge is useful in providing a reliable indication of an air filter&#39;s performance. By having this restriction indicator attached to the air intake system of an internal combustion engine, owners and/or maintenance personnel can have a reliable indication regarding the operating condition of their air filters. Consequently, air filters are less likely to be changed prematurely thus saving costs for the engine owners. 
     Referring to FIG. 1, there is shown a conceptual diagram of an engine&#39;s intake system. As is understood by those skilled in the art, the engine  10  draws air through a filter  12 . More specifically, air is drawn into a filter intake  14 , through filter  12 , and then on to the actual engine air intake  16 . 
     Attached to air intake  16 , downstream from filter  12 , is shown the restriction indicator gauge  20  of the present invention. Actually, two restriction indicator gauges  20  are shown in alternative locations, a first on the filter housing  22 , and a second attached to intake coupling  24 . Either location is acceptable as the same pressure or vacuum signal can be measured from either location. 
     FIG. 2 shows a side view of restriction indicator gauge  20 . As can be seen, restriction indicator gauge  20  includes a housing  30  and a coupled base cap  32 . Also shown in FIG. 2, housing  30  includes a window  33  for viewing a visual indicator. 
     Referring now to FIG. 3, the internal components making up restriction indicator gauge are shown in an exploded format. As previously mentioned, restriction indicator  20  includes housing  30  and base cap  32 . These are the two major components which form the external structure of the gauge. Further included within the gauge are a label  34 , a calibration spring  36  an indicator cup  38  (or alignment cup  38 ), a flexible diaphragm  40 , a lock ring  42 , and a reset cover  44 . In operation, indicator cup  38 , flexible diaphragm  40 , and lock ring  42  all make up a diaphragm assembly  48  which is movable within housing  30 . 
     Referring now to FIG. 4, the relationship of the various components, when assembled, can be more easily seen. FIG. 4 provides a cross sectional view of restriction indicator gauge  20  in its reset or rest position. Housing  30  has an inlet  50  at one end thereof. Inlet  50  is configured for attachment to the air intake system, and consequently allows the desired pressure or vacuum signal to enter an internal chamber  52  within housing  30 . 
     With general reference back to FIG. 1, it will be understood that there are many different ways to attach switch gauge  20  to engine air intake  16 . For example, a threaded attachment could extend outwardly from air intake  16  which would accommodate attachment of switch gauge  20  thereto. Further, a bayonet-type mount could be used which again would attach directly to air intake  16 . Generally speaking, any mechanism could be used which would physically connect switch gauge  20  so that inlet  50  is exposed to the pressure signals within the air intake  16 . 
     Housing  30  is attached to base cap  32  via a snap fitting. This snap fitting is accomplished by appropriate grooves  54  in housing  30  and related ridges  56  in base cap  32 . This snap fitting between housing  30  and base cap  32  also captures an exterior edge  58  of flexible diaphragm  40 . The interface is specifically configured to form an air tight seal between flexible diaphragm  40  and housing  30 . 
     Also attached to flexible diaphragm  40  are indicator cup  38  and lock ring  42 . An internal edge  60  of flexible diaphragm  40  is captured between lock ring  42  and indicator cup  38 . Indicator cup  38  and lock ring  42  are specifically designed to interlock with one another, and form a seal with flexible diaphragm  40 . Indicator cup  38  is configured to be within housing internal chamber  52  whereas lock ring  42  is positioned on the opposite side of flexible diaphragm  40 . Thus, lock ring  42  is not contained within internal chamber  52 . 
     Also situated within internal chamber  52  is calibration spring  36 . Calibration spring  36  is in contact with housing  30  at one end, and indicator cup  38  at another end. As is obvious from this positioning, calibration spring  36  is designed to bias indicator cup  38  away from the top of housing  30 . In FIG. 4, indicator cup  38  and lock ring  42  are positioned in their reset or rest positions. As can be seen, a lower extension  62  of lock ring  42  is in contact with base cap  32 . Diaphragm assembly  48  (again, including indicator cup  38 , flexible diaphragm  40 , and lock ring  42 ) will be held in this position by calibration spring  36  until additional forces are created to counteract the force of calibration spring  36 . 
     Base cap  32  is positioned immediately adjacent lock ring  42 , and at times, in contact therewith. Base cap  32  includes a button portion  64  and an annular outer portion  66 . A hinge element  68  connects button portion  64  and annular outer portion  66  to one another. Referring to FIG. 7, there is shown a bottom view of base cap  32  (with base cap  32  removed), where button portion  64 , annular outer portion  66 , and hinge element  68  can be more easily seen. 
     Base cap  32  also includes an integral locking extension  70  which extends upwardly from button portion  64 . Locking extension  70  is specifically configured to interact with an upper portion  72  of lock ring  42 . This upper portion  72  includes an opening or hole  74 , through which locking extension  70  extends. When diaphragm assembly  48  is in its reset position, as shown in FIG. 4, locking extension  70  extends upwardly through lock ring opening  74  and is situated immediately below indicator cup  38 . Locking extension  70  includes a ramped, notched portion  76  at an upper end thereof. This ramped, notched portion  76  will interact with lock ring  42  when lock ring  42  is moved upwardly. 
     Reset cover  44  is configured to snap into base cap  32 . Outwardly extending extensions  46  of reset cover  44  are configured to interact with lips  47  and base cap  32 . More specifically, locking tab  46  of reset cover  44  is shown to insert and interlock with structural tab  47 . Consequently, reset cover  44  is held in place immediately beneath button portion  64 . As previously mentioned, base cap  32  provides a snap fit attachment mechanism to housing  30 . Referring to FIG. 9, an enlarged portion of this joint can be seen. More specifically, outer edge  58  of flexible diaphragm  40  is shown sandwiched between base cap  32  and housing  30 . Also situated immediately adjacent the inner wall of housing  30  is shown label  34 . 
     Referring to FIG. 9, the hinging operation of the present invention is also shown. Specifically, button portion  64  of base cap  32  is shown in two positions in FIG.  9 . First, shown in cross sectional form, button portion  64  is in its natural or rest position. Alternatively, shown in phantom outline, button portion  64  has been moved to a depressed position such that a portion has rotated about hinge portion  68 . 
     As previously mentioned, the engine to which restriction indicator gauge  20  is attached creates a vacuum signal downstream from the air filter. This vacuum signal is translated to internal chamber  52  via housing inlet  50 . As internal chamber  52  is an air-tight enclosure, this vacuum signal creates a force on all walls thereof, including diaphragm assembly  48 . Because flexible diaphragm  40  is allowed to freely move, the vacuum signal creates a translational force which urges diaphragm assembly  48  upward. This translational force opposes calibration spring  52  to create a controlled movement of diaphragm assembly  48 . As the vacuum signal increases, the force also increases, thus causing compression of calibration spring  36 . 
     Referring now to FIG. 5, restriction indicator gauge  20  is shown after it has reached a predetermined vacuum signal level. The components are chosen so that this predetermined vacuum signal level will produce a very predictable range of motion for diaphragm assembly  48 . As can be seen in FIG. 5, diaphragm assembly  48  has moved to a position where it is now locked in its set or locked position. This locking is accomplished by having ramped notch  76  retain lock ring  42  in the set position. Stated alternatively, the annular surface surrounding lock ring opening  74  is in direct contact with an upper shelf portion  78  of ramp notch  76 . 
     In order to reset restriction indicator gauge  20 , the locking or holding relationship between locking extension  70  and lock ring  42  must be disturbed. To accomplish this, button portion  64  of base cap  32  is depressed, causing a related lateral movement of locking extension  70 . 
     Referring now to FIG. 6, button portion  64  is shown in its depressed orientation. More specifically, a force is applied to reset cover  44  in the direction of arrow A. This causes a hinging movement of button portion  64  about hinge element  68 . This hinging action causes locking extension  70  to move laterally, thus sliding upper shelf portion  78  out from the holding surface  80  of lock ring  42 . 
     As previously mentioned, calibration spring  36  biases diaphragm assembly  48  away from the upper portion of housing  30 . Consequently, when upper shelf portion  78  of locking extension  70  is pulled out from beneath lock ring  42 , calibration spring  36  causes motion in the direction of arrow B. Lock ring  42  can then proceed downwardly in this direction until it contacts button portion  64  (provided no counteracting vacuum signal is present in internal chamber  52 ). 
     Referring now to FIG. 14, the functional action of button portion  64  is shown. More specifically, FIG. 14 shows how button portion  64  reacts to various forces. In each case, locking extension  70  is designed to extend upwardly from the button portion  64 . This entire structure of locking extension  70  and button portion  64  is attached to annular outer portion  66  via hinge element  68 . In each case, the hinge produces a desired reaction to forces presented by various elements. 
     Referring now specifically to FIG. 14A, when a lateral force is presented to locking extension  70  in the direction shown by arrow C, button portion  64  and locking extension  70  both rotate about hinge portion  68 . This force would be presented to locking extension  70  in this manner as diaphragm assembly  48  travels upwardly. That is, as the vacuum signal within internal chamber  52  is increased, force is presented via flexible diaphragm  40  to the lock ring  42 . Lock ring  42  slides along locking extension  70  until reaching ramp notch  76 . Due to the configuration of ramp notch  76 , a lateral force is then presented to locking extension  70  in the direction of arrow C. This force produces the aforementioned desired reaction of causing button  64  (and locking extension  70 ) to rotate about hinge element  68 . 
     Referring to FIG. 14B, the reaction of button portion  64  is shown to an upward force presented from below in the direction of arrow D. Force in the direction of D represents the typical reset force which would be applied by the user to reset the restriction indicator gauge  20 . Once again, the desired rotation motion about hinge element  68  is shown. 
     Referring now to FIG. 14C, button  64  is now exposed to a downward force in the direction of arrows E. As can be seen, this downward force causes button portion  64  to be moved back to its rest position. The force in direction of E represents that force that would be presented by calibration spring  36  as it biases diaphragm assembly  48  back down into contact with button portion  64 . Specifically, this force would be presented by lock ring  42  as it contacts button portion  64 . 
     Lastly, FIG. 14D shows a force represented by arrow F in a downward direction which is applied to the top of locking extension  70 . This again moves button portion  64  back into its rest position. This force would exist when a portion of indicator cup  38  is in contact with the top of locking extension  70 . 
     As can be appreciated, the different forces presented in FIG. 14 represent those which would be typically encountered during in a normal operating cycle. 
     Referring now to FIG. 8 there shown a top cross sectional view consistent with section lines  8 — 8  of FIG.  5 . Specifically, this figure shows the top surface of lock ring  42  and lock ring opening  74  situated therein. Locking extension  70  extends at least partially through lock ring opening  74 . As can be seen by comparing FIG. 5, this sectional diagram is shown with diaphragm assembly  48  in its locked position. 
     The cooperation between base cap  32  and diaphragm assembly  48  specifically accommodates the use of a single base cap design. As is well known by those familiar with plastic moldings, a problem or complication exists when molded plastic hinges are used. That is, due to the nature of the material, the hinging element tends to take on the configuration in which it spends most of its time. For example, if a plastic part is continually forced into some shape by an external source, the plastic part will ultimately take a “set” in that configuration. In the case of base cap  32 , button portion  64  is configured to be in its natural or rest position when the hinge element  68  is not bent. However, when depressed to accomplish the reset function of restriction indicator gauge  20 , button portion  64  is depressed and hinge element  68  is bent some distance. It would be highly undesirable to have base cap  32  take on a configuration where button element  64  is maintained in its depressed position due to continuous bending of hinge element  68 . The present invention however specifically avoids this problem by appropriately configuring locking extension  70 , with lock ring  42 . 
     As has previously been described, locking extension  70  is specifically configured to extend through lock ring opening  74 . As can be seen in FIG. 4, when restriction indicator gauge  20  is in its reset configuration, locking extension  70  is contained by lock ring opening  74  such that the button portion  64  is retained or held in its rest position at almost all times. This is critical as it avoids any “setting” of the hinge element  68  in an undesired configuration. 
     Referring now to both FIGS. 5 and 8, indicator cup  38  includes a cylindrical extension  82  which substantially covers locking extension  70 . Similarly, housing  30  includes a related substantially cylindrical housing  84  aligned with indicator cup cylindrical extension  82 . Both cylindrical extension  82  and cylindrical housing  84  are coaxially aligned with one another such that movement of diaphragm assembly  48  is sufficiently contained within the restriction indicator gauge. This relationship provides proper alignment for diaphragm assembly  48 . Referring specifically to FIG. 8, this coaxial alignment can easily be seen. 
     As previously indicated, the restriction indicator gauge  20  has a visual indication of when a predetermined vacuum signal has been achieved. As shown above, this indication may simply include the existence or non-existence of indicator cup  38  in window  33 . Referring now to FIGS. 10-13, an alternative two color visual indication is shown. In this embodiment, window  33  would display a first color when the gauge is in its reset or rest position, while showing a second color once the gauge has reached its set or locked position. During transitional periods, partial viewing of either color could be obtained. 
     Referring now to FIGS. 10 and 11, there shown one structure for achieving this multicolor display feature. In the device of FIG. 10, the indicator cup  38  has been altered to accommodate a contrasting ring  90  which is seated within the previously existing indicator cup  38 . A viewing extension  92  of contrasting ring  90  is specifically configured to extend above the remainder of indicator cup  38 . 
     In this embodiment, housing  30  again has a view window  33  which could be either a clear portion of housing  30  or a clear portion of label  34 . In this embodiment, when the gauge is in its reset condition, contrasting ring  90  and specifically viewing extension  92  is positioned immediately adjacent window  33 . For example, contrasting ring  90  could be fabricated from a green colored material, consequently a green indication would be shown through window  33 . Alternatively, when restriction indicator gauge  20  has reached its set position, both indicator cup  38  and contrasting ring  90  have been moved upwardly. In this set position, the side wall of indicator cup  38  is now positioned immediately adjacent window  33 . As indicator cup  38  is colored differently from contrasting ring  90 , a different color display will be present in window  33 . Consequently, a two color display is achieved by adding contrasting ring  90 . 
     An alternative embodiment for achieving this two color display feature is shown in FIGS. 12 and 13. In this case, an indicator cup  38  substantially similar to that shown in FIGS. 3-5 is used. Additionally, a downwardly extending shield  96  is now attached to an upper portion of housing  30 . Generally, shield  96  extends a sufficient distance downward so that it can be viewed through window  33 . Consequently, when restriction indicator gauge  30  is in its set position, as shown in FIG. 12, indicator cup  38  will be positioned below window  33  and shield  96  will be exposed. When restriction indicator gauge  20  reaches its set position, however, indicator cup  38  has again been moved to a position immediately adjacent window  33 . Thus, indicator cup  38  is now seen through window  33 . Again, by fabricating indicator cup  38  and shield  96  from materials of different colors, the contrasting display capability is achieved. 
     While the above-described invention has been described as a dual position indicator (either set position or reset position), it is understood that a multi-position gauge could equally be achieved. Referring now to FIG. 15, an alternative locking extension  98  is shown. In this embodiment, multiple locking positions are shown, thus providing the gauge the ability to lock at multiple stages of its operation. 
     Those skilled in the art will further appreciate that the present invention may be embodied in other specific forms without departing from the spirit or central attributes thereof. In that the foregoing description of the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. Accordingly, the present invention is not limited to the particular embodiments which have been described in detail therein. Rather, reference should be made to the appended claims as indicative of the scope and content of the present invention.