Abstract:
A two stage air filter restriction indicating device communicates with the supply of air passing from an air filter to the air intake of an engine. The amount of vacuum required by the engine to supply air is directly indicative of the amount of blockage in the air filtering system. The gauge or air filter restriction indicating device monitors this vacuum level and provides signals at an output indicating whether a predetermined vacuum level has been achieved. In one configuration, the gauge locks into this configuration and maintains its output, even when the engine is shut off. Alternatively, the gauge of the present invention automatically resets, thus not requiring a manual reset of the gauge.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a mechanical filter gauge for determining the filtering capability of a vehicle filter. Specifically, the present invention relates to a mechanical gauge for measuring the functionality of a vehicle&#39;s air filter and providing a related electrical signal at an output. 
     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 then indicate the level of restriction by locking itself in position. 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 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 a visual display to the users or maintenance personnel. They did not have provisions to output an electrical signal indicative of the gauge&#39;s status. 
     By including an electrical component to the gauge, an indicator light within the cab of the vehicle can be added. The electrical component can simply be a switch which opens or closes when predetermined conditions are met. A dashboard indicator light could then be switched appropriately. However, the signal in the vehicle and the gauge near the engine would not always agree with each other using these prior art devices. Further, the dashboard light would not always remain on until the filter was serviced and the gauge reset. Also, as disclosed, these switches were relatively expensive to manufacture and assemble. The dashboard light signal could sometimes light before the gauge actually reached “redline,” or the point at which the air filter required replacement. Further, the dashboard light signal could flicker or not remain lit after the gauge had reached redline. The mere presence of the gauge and dashboard indicator will in most cases cause the driver of the vehicle to rely on the signal being given. However, if a signal is unclear, or gives a false indication that the filter is not yet in need of replacement, serious engine damage could result. 
     Once a clean and predictable signal could be developed as an output from the gauge, this signal could also be input to a computer control system or system controller to coordinate many functions. For example, this could provide an indication of an engine&#39;s operating conditions. 
     As mentioned above, several 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 once a predetermined restriction level was achieved. These gauges were phased out in favor of the incremental type gauges. The pop-up type gauges were not believed to be reliable and typically not trusted. The incremental type gauges would display an indication of the amount of filter left, thus would provide more reliable and believable information to the users. However, again as mentioned, none of these incremental gauges included reliable switching indicators which could be used to generate displays or to feed a system controller. If input to the system controller, even a single stage gauge is valuable as this provides meaningful information to the controller. Further, even a gauge which does not lock after predetermined levels nor requires manual resetting is provided, beneficial information can be measured and tracked. 
     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. This may in turn result in unnecessary filter maintenance. 
     SUMMARY OF THE INVENTION 
     The switch gauge of the present invention measures the performance of the filter and signals when the air filter of an internal combustion engine requires servicing or replacement. The measurement is accomplished by monitoring the vacuum in the air intake system of the vehicle. The level of vacuum achieved during engine operation is indicative of the air filter&#39;s condition. The device can gradually sense the status of the filter, from a clean condition to a dirty filter condition. 
     In the filter gauge of the present invention, a vacuum level of a predetermined level has been reached, a switch within the internal sensing chamber of the gauge is actuated. The switch can either be maintained or locked in this on position, even after the engine has been shut off, or the switch can be released at engine shut off. Stated alternatively, in a first configuration, the gauge of the present invention locks in a “set” condition after the predetermined level of vacuum has been achieved. When this lock takes place, the switch is maintained in a closed configuration. Alternatively, in another embodiment, the switch is only actuated when the engine is operating at the predetermined vacuum level. When the engine is subsequently shut off, the switch changes its condition. In each of these cases, the information can be used to alert the user, or to provide valuable control information to a system controller. 
     An object of the invention is to provide a gauge for indicating that an air filter for a vehicle with an internal combustion engine requires replacement. 
     It is a further object of the invention to provide such a gauge that is easily reset after each filter change. 
     It is another object of the present invention to provide a device which produces a signal indicative of whether or not a predetermined vacuum level has been achieved. This signal can then be used to alert the user that the filter must be replaced. This information can be provided to the user either via a warning light placed on the dash, or through an overall control system which monitors and coordinates the operations of the vehicle. 
     It is an additional object of the present invention to provide a device which produces a signal indicating when the engine is operating at a predetermined level of restriction in the air filter. This signal will maintain a certain condition as long as the engine is running and the predetermined vacuum level is maintained. When the engine is shut off, or the vacuum level is no longer above the predetermined amount, the signal will then change states, indicating that this operating condition no longer exists for whichever reason. These signals are easily transmitted to a overall engine controller system. 
     It is a further object of the present invention to provide a system which produces a constant signal once a predetermined vacuum level has been achieved. This signal will then remain the same until it is reset either manually or via a coordinated computer control reset. 
     It is yet another object of the present invention to provide a device which will produce both a visual and electrical indication that a predetermined vacuum level has been achieved. By placing a window in the housing, and appropriately configuring an indicator device, the visual indication is achieved. The visual indicator will not be seen when the device is below the predetermined level, however the indicator will be seen when the predetermined vacuum level has been achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent from the following detailed description and from the appended drawings, where like numbers have been used to describe like parts throughout the several views, in which: 
     FIG. 1 is a schematic view of an air intake system for an internal combustion engine incorporating the switch gauge of the present invention; 
     FIG. 2 is a perspective view of the switch gauge of the present invention; 
     FIG. 3 is an exploded view of the switch gauge illustrated in FIG. 2; 
     FIG. 4 is a vertical section view of the switch gauge taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is a partial section view similar to FIG. 4, showing the lockpin in the locking position; 
     FIG. 6 is a partial section view showing a top view of the locking pin and switching terminal; 
     FIG. 7 is a perspective view of one switching assembly used in the present invention; 
     FIG. 8 is a side view of the switching assembly shown in FIG. 7; 
     FIG. 9 is a side view of one alternative configuration for the switching assembly; 
     FIG. 10 is a vertical section view of a second embodiment of the present invention, again taken along  4 — 4  of FIG. 2; 
     FIG. 11 is again a vertical section view of the alternative embodiment of the present invention taken along  4 — 4  of FIG. 2 with the cup assembly shown in a second position; 
     FIG. 12 is a perspective view of an alternative embodiment of the switching assembly; 
     FIG. 13 is a partial side view of the switching assembly shown in FIG. 12 while in its closed position showing a normally closed switch; 
     FIG. 14 is a partial view, similar to that shown in FIG. 13, with the switching assembly in its open position; 
     FIG. 15 is a partial cross-sectional view showing an additional embodiment of the present invention which includes a visual indicator; 
     FIG. 16 is a top view of an alternative configuration for a switching assembly; 
     FIG. 17 is a perspective view of the alternative switch assembly shown in FIG. 17; and 
     FIG. 18 is a side view of the alternative switching assembly and lock pin. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to the drawings, and in particular to FIG. 2, a switch gauge of the present invention is generally indicated by reference numeral  10 . Switch gauge  10  includes a housing  12 , and a base cap  14 . Housing  12  includes a preferably generally cylindrical attachment member  20  for attachment to air intake system  22  of a vehicle&#39;s internal combustion engine, preferably via a tube  24 , as shown in FIG.  1 . 
     Referring to FIG. 1, switch gauge  10  is shown schematically attached to a vehicle&#39;s air intake system  22 , and also electrically attached to a control system  26 . Control system  26  and switch gauge  10  are both powered by a power source  28 , preferably the vehicle&#39;s battery. Control system  26  may include a light  29  mounted on the dashboard of the vehicle to provide an indicator to the driver of the vehicle. Other indicators, or combinations of indicators, such as a buzzer, a voice message, or a text message, could also be used to achieve the same result. 
     Control system  26  may include a computerized controller for operating many different functions in a vehicle. It is understood that an indicator light alone could be connected to the switch output to provide appropriate indications to the user. Alternatively, a sophisticated system monitoring device for coordinating and operating many functions of the engine and vehicle could also be used. 
     Referring to FIGS. 3 and 4, the switch gauge  10  includes a lockpin  32  pivotally attached to and projecting outwardly from base cap  14 . A base portion  34  of lockpin  32  is coupled to a reset coupling  36 , which in turn is actuated by a flexible reset cover  38 . A reset spring  40  bears against base cap  14  to bias reset coupling  36  away from base cap  14 . Additionally, reset spring  40  ensures appropriate alignment for necessary contact between reset cover  38  and base portion  34  of lockpin  32 . Reset Spring also holds lockpin  32  in position such that base portion  34  extends through base cap  14  while the remainder extends upwardly from base cap  14 . Reset coupling  36  includes a bearing surface  44  which reset spring  40  bears against. It is preferred that base portion  34  of lockpin  32  include a groove along a portion of the diameter thereof (not shown) to permit compression thereof when bring attached to reset button  36 . Many other attachment mechanisms could also be used, including press fits, threads, glue, etc. Base portion  34  also includes a flat surface  46  which bears against a mating flat inner surface  48  on reset coupling  36  to insure proper positioning of the two components relative to one another. During assembly, it is also preferable to apply a small amount of adhesive to ensure the permanent retention of base portion  34  within the opening of reset button  36 . 
     Switch gauge  10  also includes a flexible diaphragm  30  which is attached to a lock ring or sealing ring  52  and an alignment cup  54 . As can be seen, lock ring  52  is attached to one side of diaphragm  30  whereas an alignment cup  54  is attached to the other side. This attachment mechanism causes flexible diaphragm  30  to be sandwiched between these two elements (alignment cup  54  and locking ring  52 ). A diaphragm assembly  60  is thus created which includes lock ring  52 , flexible diaphragm  30 , and alignment cup  54 . As such, an airtight seal is created between these elements, thus not allowing air to pass through this interface. Similarly, diaphragm  30  is sandwiched between housing  12  and base cap  14 . Again, this seal is designed to be air tight. Through these various seals, an internal chamber  64  is created within switch gauge  10 . This internal chamber  64 , generally existing beneath housing  12 , is in communication with gauge input  16 , however is isolated from the remainder of the gauge. This allows switch gauge  10  to measure the vacuum signal presented at input  16  and maintain a closed system. 
     Lockpin  32  has an upper portion  56  which is configured to extend through an opening  58  in lock ring  52 . The relationship of these elements accommodates proper operation between multiple positions of the diaphragm assembly  60 . 
     A calibration spring  62  bears against the upper, interior surface of housing  12  on one end, and against alignment cup  54  on the other. Attachment member  20  of housing  12  engages tube  24 , which in turn intersects air intake  22 , which carries air from the air filter  23  to the engine (not shown). 
     With general reference back to FIG. 1, it will be understood that there are many different ways to attach switch gauge  10  to engine air intake  22 . For example, a threaded attachment could extend outwardly from air intake  22  which would accommodate attachment of switch gauge  10  thereto. Further, a bayonet-type mount could be used which again would attach directly to air intake  22 . Generally speaking, any mechanism could be used which would physically connect switch gauge  10  so that input  16  is exposed to the pressure signals within the air intake  22 . 
     As the air filter in the air intake system  22  becomes dirty from extended use, the amount of air allowed to pass through it decreases, although the vehicle&#39;s internal combustion engine continues to draw air at a steady rate. As the amount of air passing through the filter decreases, there is a corresponding decrease in the air pressure and a resulting vacuum in air intake system  22 . This vacuum is communicated through attachment member  20  and the corresponding inner chamber  64  within housing  12 . As this vacuum increases, the negative air pressure gradually overcomes the force of calibration spring  62 , and alignment cup  54  is drawn upwards, or toward attachment member  20 . As alignment cup  54  is drawing toward attachment member  20 , the edge of lock ring opening  58  engages an upper portion  56  of lockpin  32 . Thus, even after the vehicle&#39;s engine is turned off, diaphragm assembly  60  is maintained in its prior position. 
     While still referring to FIGS. 3 and 4, switch gauge  10  further includes an electrical contact or switch assembly  70  which is configured to interact with lock pin  32 . Shown along in FIG. 7 is switch assembly  70  which includes a base contact  72  and a leaf contact  74 . Both base contact  72  and leaf contact  74  are attached to base cap  14  at a position which is adjacent a lever portion  76  of lock pin  32 . As can be seen in FIG. 4, base contact  72  is configured to follow the internal dimensions of base cap  14 . Leaf contact  74  includes a resiliently deformable member  74  which is held in a cooperating position relative to base contact  72 . More specifically, resiliently deformable member, or leaf contact  74  includes a lever arm portion  78 , which is situated at an angle to the plane of base contact  72 . As can be appreciated, this lever portion is specifically designed to cooperate with base contact  72  to accomplish the desired switching action. 
     Base contact  72  and leaf contact  74  can be configured as a normally open switch or a normally closed switch. In a normally open configuration, lever portion  78  of leaf contact  74  is held slightly above base contact  72 . When desired to have the switch closed, lever portion  78  is depressed, thus creating contact with base contact  72 . Alternatively, in a normally closed configuration, as shown in FIG. 9 base contact  72  includes an extension  80  which extends above the planar surface of base contact  72 . Extension  80  is configured to interact with lever arm  78  such that contact between those two elements is maintained when lever arm  78  is in its normal position. Subsequently, when lever arm  78  is depressed, contact between extension  80  and lever arm  78  is broken, thus opening a circuit between those two elements. 
     A more complete view of switch assembly  70  in its normally open configuration can be seen by referring to FIGS. 7 and 8. As can be seen, both base contact  72  and leaf contact  74  both include alignment holes  82  along with mounting tabs  84 . Each of these elements interact with structures on the internal surface of base cap  14  to accommodate proper alignment and mounting. For example, posts are molded on the interior surface of base cap  14  which pass through alignment holes  82 . Further, mounting structures are included in base cap  14  which occupy the space created by mounting tabs  84 . To secure both base contact  72  and leaf contact  74  to base cap  14 , these mounting structures are simply deformed to hold these contacts in place. As can be appreciated, multiple methods or structures for attachment could be used including adhesives, glues, screws, tacks, rivets, etc. 
     Referring now to FIG. 6, a top view of switch assembly  70  is shown after installation in base cap  14 . As previously mentioned, base cap  14  includes alignment pins  86  which are configured to be inserted into alignment holes  82 . Base cap  14  also includes attachment pins  88  which are configured to interact with a slot created between mounting tabs  84  and the remainder of the respective contact (base contact  72  or leaf contact  74 ). To attach base contact  72  and leaf contact  74  to base cap  14 , attachment pins  88  are simply deformed to surround and cover the associated contact. Prior to their deformation, attachment pins  88  and alignment pins  86  are configured substantially the same. 
     Also shown in FIG. 6 is lock pin  32 . As can be seen, lock pin  32  is situated in a central recessed  90  within base contact  72 . As will be later described, this allows lock pin  32  to have its appropriate range of motion. Lever portion  76  of lock pin  32  is specifically aligned to extend above leaf contact lever portion  78 . This alignment allows lock pin  32  to appropriately carry out the switching function of the present invention. 
     Alternative configurations for the switch assembly can easily be used. Shown in FIGS. 16 through 18 is a modified switch assembly  140  which operates substantially similarly to that previously described. Once again, modified switch assembly  140  includes a base contact  142  and a spring contact  144 . Attached to spring contact  144  is a leaf spring or switch blade  146  which cooperates with other elements of switch gauge  10  to perform the desired switching function. Base contact  142  further includes a switch projection  148  which provides a contact point for switch blade  146 . As is obvious from viewing the figures, physical contact between switch blade  146  and switch projection  148  will provide electrical continuity between base contact  142  and spring contact  144 . 
     As can be seen, base contact  142  has a connection pin  150  on one side thereof. Similarly, spring contact  144  has a connection pin  152  extending from one side thereof. A pin housing  154  is utilized to appropriately hold and align both connection pins  150  and  152 . Both base contact  142  and spring contact  144  also have holding tabs  156  and  158  extending outwardly opposite the respective connection pin  152  and  154 . 
     Referring now specifically to FIG. 16, the cooperation of holding tabs  156  and  158  with a pair of attachment structures  160  within base cap  14  can be seen. More specifically, attachment structures  160  are configured to have an internal slot (not shown) into which holding tabs  156  and  158  are positioned. These internal slots are configured to completely surround holding tabs  156  and  158  and appropriately position entire modified switch assembly  140 . As previously mentioned, pin housing  154  attaches and holds connection pins  150  and  152  at the other end of base contact  142  and spring contact  144 . 
     In FIG. 18, the attachment mechanism between pin housing  154  and base cap  14  can be seen. Pin housing  154  is designed to be inserted into an opening in base cap  14  and attached thereto. Thus, the combination of pin housing  154  and attachment structures  160  hold the entire modified switch assembly  140  in place. Pin housing  154  includes a locking tab  162  which cooperates with base cap  14  to provide secure attachment of connector pins  150  and  152 . That is, locking tab snaps into an appropriate recess in base cap  14  to retain pin housing  154  in place. This is important as it accomodates the attachment of an electrical connector to the appropriate connection pins. 
     As with the earlier described switch assembly, modified switch assembly  140  cooperates with lock pin  32  to provide appropriate switching. As can be seen in FIGS. 16 and 18, lock pin  32  is again appropriately aligned to have a lever portion  76  extend directly above switch blade  146 . When lock pin  32  is moved to its locked position, lever portion  76  will contact switch blade  146 , thus causing closure of switch assembly  140 . More specifically, causing contact between switch blade  146  and switch contact  148 . As will be recognized, many different configurations for the actual switch assembly are possible depending upon mounting requirements, etc. Generally speaking, the switch assembly is simply required to interact with lock pin  32  in order to mechanically close a switching element. 
     Referring again to FIG. 4, switch gauge  10  is shown in its initial condition or reset condition. More specifically, this reset condition is the state of the gauge when no pressure or vacuum signal has been applied at the gauge input  16 . In this condition, calibration spring  62  biases diaphragm assembly  60  away from housing  12 . When in this reset condition, diaphragm assembly  60  (and specifically lock ring  52 ) contacts an internal portion of base cap  14 . Also, lock ring  52  retains upper portion  56  of lock pin  32  in a central opening. This retention of lock pin  32  in lock ring opening  58  maintains the lock pin in its desired position. More specifically, lock pin lever portion  76  is held above leaf contact lever portion  78 . Consequently, the switch formed between leaf contact  74  and base contact  72  is kept open. 
     As mentioned above, lock gauge  10  is connected to the air intake system of an internal combustion engine. This connection causes internal chamber  64  to be subjected to a vacuum signal. As the air filter of the internal combustion engine becomes dirty and clogged, a higher level vacuum signal is created. This vacuum signal, present in internal chamber  64 , will interact with diaphragm assembly  60  to create forces which will oppose calibration spring  62 . More specifically, alignment cup  54  will be drawn towards housing  12 , thus compressing calibration spring  62 . 
     Switch gauge  10  of the present invention is specifically configured to cause the switches to change state once a predetermined vacuum signal has been experienced. This function is accomplished by the appropriate configuration of lock pin  32  in conjunction with calibration spring  62 . (Naturally, other factors will affect the operation of switch gauge  10  such as diaphragm size, lock ring design, etc. All of these elements must cooperate appropriately to achieve the desired function.) 
     Referring again to FIG. 4, it can be seen that some movement of diaphragm assembly  60  will simply cause lock ring  52  to slide along lock pin upper portion  56 . However, at some vacuum level, lock ring  52  will move to a point where lock pin upper portion  56  is no longer contained within lock ring opening  58 . 
     Referring now to FIG. 5, the lower portion of switch gauge  10  is shown in its set condition. This is representative of the situation where the switch gauge has experienced vacuum signals in its internal chamber  64  which were above the predetermined level. Specifically, lock ring  52  has been moved to a position where lock pin upper portion  56  is no longer contained within lock ring opening  58 . When lock pin  32  is no longer contained in lock ring opening  58 , reset spring  40  urges lock pin out of alignment with lock ring opening  58 . This moves lock pin  32  into contacting relationship with a number of different elements, including lock ring  52 . Consequently lock  52  ring is no longer allowed to move back towards the reset condition. Additionally, lever portion  76  of lock pin  32  has now engaged with leaf contact lever portion  78  of switch assembly  70 . This movement causes the base contact  72  and leaf contact  74  to be electrically connected to one another. As these two elements form the electrical switching portion of lock gauge  10 , this corresponds to the closure of an electrical switch when the predetermined vacuum level has been achieved. 
     Once switch gauge  10  has reached the set condition, the device must be physically reset in order for it to return to its reset condition. This reset action is achieved by depressing flexible reset cover  38 , thus causing the flat portion of reset cover  38  to interact with lock pin  32 . This interaction will cause lock pin  32  to move back into alignment with lock ring opening  58 . Once lock pin  32  is again aligned with lock pin opening  58 , calibration spring  62  urges the diaphragm assembly  60  back to its reset position. This also causes leaf contact  74  and base contact  72  to be separated from one another, thus opening the electrical switch portion of switch gauge  10 . 
     As previously mentioned, switch assembly  70  of the present invention can be configured in either a normally open or normally closed configuration. The previous discussion has generally related to the normally open configuration as is shown in FIGS. 4-8. Referring to FIG. 9, there is shown the switch assembly  70  in its normally closed configuration. This alternative switch assembly  70  is also shown as an alternative configuration in the exploded view of FIG.  3 . This alternative switch assembly  70  includes a base contact  72 , leaf contact  74  and leaf contact lever portion  78 . In the normally closed configuration however, extension  80  is included as part of base contact  72 . When assembled in base cap  14 , extension  80  is configured to extend above leaf contact lever portion  78 . During a normal condition these two elements will be in contact with one another. Subsequently, when switch gauge  80  reaches its set condition, lever portion  76  will urge leaf contact lever portion  78  away from extension  80 . As leaf contact lever portion  78  and extension  80  create the electrical switching portion of switch assembly  70 , this motion causes the switch to open. 
     Switch assembly  70 , whether in the normally opened or normally closed configuration, includes a pair of connector pins  92  on one end. These connector pins are configured to extend to a connector portion  94  of switch gauge  10 . Connector pins  92  can then be attached to an electrical connector (not shown) for carrying the switching signal away from switch gauge  10 . 
     Referring to FIG. 5, as the air filter becomes dirty, further reducing air flow through the air intake system, calibration spring  62  gradually becomes increasingly compressed. Compression of calibration spring  62  causes alignment cup  54  to be drawn closer to attachment member  20 , until upper end of lockpin  32  no longer extends into central opening  58  of lock ring  52 . Then, as illustrated in FIG. 5, upper end  56  of lockpin  32  no longer extends through central opening  58  of lock ring  52 . Rather lock pin upper  56  is moved to a new position which is no longer aligned with opening  58 . 
     Referring now to FIGS. 10 and 11, there is shown an alternative embodiment of the present invention. This embodiment is similar to that previously discussed, however is designed to operate differently. That is, this embodiment of the present invention produces a first signal when the measured vacuum level is below a predetermined level and produces a second signal when the measured vacuum level is above a predetermined level. However, each time the engine is shut down and the vacuum signal no longer exists, the gauge is brought back to its original condition and the first signal is again produced. Stated alternatively, the gauge of this alternative embodiment does not have a locking or manual reset feature. 
     Referring specifically to FIGS. 10 and 11, switch gauge  10  includes housing  12  and base cap  14 . Switch gauge  10  further includes an input  16  which is configured for connection to the engine air intake system. Switch gauge  10  also has a cup assembly similar to that discussed above. That is, within switch gauge  10  there is situated an alignment cup  54 , diaphragm  30  and a lock ring  98 . There also exists a calibration spring  62  for biasing diaphragm assembly  60  away from housing  12 . By comparing FIG. 10 with FIG. 4, it can be seen that in this alternative embodiment, lock pin  32  has been eliminated. As this embodiment does not include a locking or manual reset feature, lock pin  32  is no longer needed. Consequently, lock ring  98  is also configured differently. 
     Base cap  14 , again has a switch assembly  100  attached thereto. In this embodiment of the invention, lock ring  98  and switch assembly  100  are specifically designed to cooperate with one another to provide the desired electrical switching signals. 
     Referring to FIG. 12, there is shown a perspective view of switch assembly  100 . Again, switch assembly  100  includes a base contact member  102  and a leaf contact member  104 . Both base contact member  102  and leaf contact member  104  are designed for attachment to base cap  14  while also for providing the appropriate electrical switching functions. Switch assembly  100  further includes a leaf spring member  106  which is connected to leaf contact  104 . 
     To accommodate attachment to base cap  14 , both base contact member  102  and leaf contact member  104  include alignment holes  108  and mounting tabs  110 . As discussed above, these alignment holes  108  and mounting tabs  110  are configured to interact with alignment pins  86  and attachment pins  88 , respectively, of base cap  14 . As is shown, base contact member  102  includes a step up configuration designed to follow the contour of base cap  14 . Referring to FIGS. 13 and 14, this relationship is shown in partial cross-sectional view. 
     As can be seen by referring to the figures, FIG. 10 shows the lock ring  98  in a first position while FIG. 11 shows lock ring  98  in a second position. The position shown in FIG. 10 is the initial position or position that the lock ring is situated when no vacuum signal is present. Once a vacuum signal is applied at input  16 , internal chamber  64  will also be subjected to this vacuum signal. Initially, this will not have a significant effect on switch gauge  10 . As discussed above, internal chamber  64  is sealed off by diaphragm  30  and diaphragm assembly  60 . Thus, a vacuum signal present in internal chamber  64  will produce a force on diaphragm  30  and diaphragm assembly  60 . This force is applied against calibration spring  62  and at some level will produce movement of diaphragm assembly  60 . Calibration spring  62  is configured to allow movement at a predetermined vacuum signal level. (It is understood that calibration  62  operates in conjunction with the configuration of diaphragm  30  and diaphragm assembly  60  and these elements together produce this desired result.) Once this predetermined vacuum signal level is reached, diaphragm assembly  60  and specifically locking ring  98  are moved to the position shown in FIG.  11 . 
     Referring again to FIGS. 13 and 14, lock ring  98  is shown in both its initial position (FIG. 13) and its second position (FIG.  14 ). The movement of lock ring  98  has a related effect on switch assembly  100 . When lock ring  98  is in its first or initial position, calibration spring  62  biases an extending edge  112  of lock ring  98  to contact leaf spring  106 . This causes leaf spring  106  to contact a switching pin  114  which is electrically connected to base contact member  102 . Again, leaf spring  106  is attached to leaf contact member  104  (not shown in FIGS.  13  and  14 ), thus electrical connection is made between base contact member  102  and leaf contact member  104 . 
     Alternatively, when lock ring  98  is moved to its second position, extension  112  no longer contacts leaf spring  106 . Further, contact between switch pin  114  and leaf spring  106  no longer exists. Thus electrical connection between base contact member  102  and leaf contact member  104  is no longer present. 
     Again referring to FIG. 12, both base contact member  102  and leaf contact member  104  have extending connector pins  92  which are configured to extend partially out of base cap  14 . Thus, these connector pins  92  can be electrically connected to other elements. 
     As outlined above, this second embodiment produces a non-locking version of switch gauge  10 . Many identical concepts are shown between this embodiment and the first embodiment described. However, all elements providing related locking and manual reset do not exist. 
     Referring now to FIG. 15, there is shown an additional modification of the present invention which provides an additional visual indication. Specifically, switch gauge  10  has been slightly modified to provide a visual indication that the predetermined vacuum level has been achieved. This visual indication is in addition to the electrical signal that is being provided. In this case, housing  12  has been slightly modified to include a view window  120 . This view window includes a clear portion in the housing through which portions of the internal structure can be seen. 
     Additionally, alignment cup  54  has been slightly altered to include an indicator extension  122 . Indicator extension  122  is specifically configured so as to not interfere with diaphragm  30  while also being located in close proximity to an inner wall  124  of housing  12 . In FIG.  15 (B), switch gauge  10  is shown in its set position, thus diaphragm assembly  60  has been extended to an upper location within housing  12 . In this upper location, indicator extension  122  is positioned immediately adjacent to view window  120 . By manufacturing cup  54  so that indicator extension  122  is a noticeable color, this indicator extension will be readily apparent to the user. This provides the desired visual indication, in addition to the electrical signal indications previously discussed. Preferably, the indicator extension  122  would be brightly colored including red, orange, florescent green, or some other highly visible color. 
     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 in 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.