Abstract:
A self powered low oil level indicator. The device includes a dipstick extending downward from a cap, and it replaces stock oil reservoir caps on mechanical devices which have oil reservoirs and in some cases have oil fill tubes. The indicator dipstick has a first end, a second end, and a longitudinal axis. An electrical circuit is provided including electrical conductors, a battery, an indicating light, and a switch having an electrically conductive on-off element. A float configured for carriage of the electrically conductive on-off element is provided at or near the lower end of the dipstick. When the float displacement is lowered by low oil level, the electrical circuit is completed, allowing the battery to energize a warning light.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to the field of oil level gauges and indicators, and especially, to oil level gauges and indicators for power tools and equipment.  
       BACKGROUND  
       [0002]     Oil level indicators and gauges have been used for many years, and various versions have long provided their unique attributes for various tasks where it was desired to determine the oil level in a particular piece of mechanical equipment such as a motor vehicle engine. In various oil gauge designs, the use of a float has been adapted to include a way to provide an indication of low oil level to the user of the vehicle, with electrical power supplied to the gauge by the electrical system of the vehicle. And, a device which is configured to mount in the dipstick holder of an automobile was disclosed in U.S. Pat. No. 4,034,608, issued Jul. 12, 1977 to Vincent; however, that device was powered by connection to a conventional automotive electrical battery.  
         [0003]     In many mechanical devices having an oil sump, the devices are operated remotely from a convenient external electrical supply, yet the device does not generate on-board power or carry on-board battery power. One common example of such as device in everyday use is the typical push-type lawn mower. Although a magneto device is utilized to generate an electrical spark to fire many such engines, one reason for the lack of oil indicators in such devices may be the lack of an on-board electrical power supply system, so that conventional prior art oil gauges may be employed. Unfortunately, many small mechanical devices such as pumps, compressors, and engines, and particularly lawn mower engines, suffer catastrophic failure due to the lack of lubrication. Such failures could be easily prevented if the operator of the device were made aware that the device needed oil, provided that such need was brought to the operator&#39;s attention in a timely manner.  
         [0004]     Importantly, it would be a distinct and important improvement to provide an oil level indicator which is quickly and easily secured to existing mechanical devices through existing ports such as oil addition tubes. Moreover, it would be desirable to provide a design which can be quickly installed in the place of existing oil caps, thus allowing the oil level device to be easily installed yet which maintains the ease of service and oil addition. Thus, the important advantages of an oil indicating device providing such desirable features in a workable motor or engine apparatus can be readily appreciated. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0005]     In order to enable the reader to attain a more complete appreciation of the invention, and of the novel features and the advantages thereof, attention is directed to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0006]      FIG. 1  is a perspective view of a low oil level indicator as taught herein installed in a normal working position through the oil addition port in a conventional push-type lawn mower.  
         [0007]      FIG. 2  is a perspective view of an exemplary embodiment of a low oil level indicator, showing an elongated dip-stick downwardly extending from a cap, an indicator light, a battery for supply of electrical power, and a see-through cap which may be configured for retention of the battery as well as visibility of the light.  
         [0008]      FIG. 3  is a cross-sectional view of a low oil level indicator, showing the device as if installed in an oil fill tube instead of a standard oil dipstick and cover, and wherein the oil level is sufficiently high that the electrical circuit is broken by upward displacement of the float and its electrical contacts.  
         [0009]      FIG. 4  is a cross-sectional view of the low oil level indicator just set forth in  FIG. 3 , but now showing the device in operation when the oil level is low, and the electrical circuit is completed by the electrical contacts operatively connected to the float.  
         [0010]      FIG. 5  is a schematic view of a typical self contained electrical system for powering a low oil level indicator for use with such devices having no external connection to electrical power.  
         [0011]     The foregoing figures, being merely exemplary, contain various elements that may be present or omitted from actual implementations depending upon the circumstances. An attempt has been made to draw the figures in a way that illustrates at least those elements that are significant for an understanding of the various embodiments and aspects of the invention. However, various other elements of the low oil level indicator device, especially as applied for different variations and adaptations for fitting into a variety of oil fill pipes, as well as different embodiments of artistic elements such as handle design, may be utilized in order to provide a robust low oil level indicator with easy hand operated cap design.  
     
    
     DETAILED DESCRIPTION  
       [0012]     Turning now to  FIG. 1 , a mechanical device such as a lawn mower  10  having an oil sump  12  is illustrated with a low oil level indicator  14  as taught herein installed. Although the device is described with respect to use in a lawn mower, it is equally adaptable to and useful for a wide variety of mechanical devices, such as pumps, compressors, or other devices which have an oil reservoir-and are without an on-board or other nearby convenient source of electrical power. Additionally, the low oil level device as taught herein can be applied in other mechanical devices which would benefit from having an operator observable low oil level indicator independent from on-board power, including, for example, under hood application in motor vehicles, or on recreational vehicles.  
         [0013]     Details of my low oil level indicator  14  can be better appreciated by reference to  FIGS. 2 and 3 . An elongated dipstick  16  of any convenient size, such as having a width W of about 0.5 inches in one embodiment, and a thickness T of about 0.125 inches and a length L of suitable size with respect to an oil reservoir in which it is to be inserted, is provided along a longitudinal axis  18  indicated by centerline C L  in  FIG. 2 . The dipstick  16  has a first or lower end  20 , and a second or upper end  22 . The second or upper end  22  of dipstick  16  is affixed to a lower interior portion  24  of cap  26 , so that dipstick  16  extends downwardly from the cap  26 .  
         [0014]     An electrical circuit  30  is provided as indicated in  FIG. 5 . A battery  32 , indicating light  34 , and a switch  36  having an electrically conductive on-off element  38  are provided. The electrical circuit  30  includes suitable electrical conductors, such as first conductor  40  between a first pole  42  of the battery  32  and a first contact pin  44 , a second conductor  46  between second contact pin  48  and the light  34 , and a third conductor  50  between the lamp  34  and a second pole  52  of battery  32 . In conventional fashion any one of the conductors  40 ,  46 , or  50  may be provided with one or more components or sections, including for example in conductor  40 , a leaf type battery contact  54  as shown in  FIG. 2 .  
         [0015]     In one embodiment, a float  60  is configured for carriage of the electrically conductive on-off element  38  along the longitudinal axis  18  of dipstick  16 . The float  60  is operatively secured by retainers  62  and  64  at or near the first or lower end  20  of the elongated dipstick  16 , for displaceable movement between a first position  70  as shown in  FIG. 3  wherein the electrical circuit  30  is switched off, and a second position  72  as shown in  FIG. 4  wherein the electrical circuit  30  is switched on, so that light  34  is illuminated.  
         [0016]     In one embodiment as see in  FIGS. 2, 3 , and  4 , float  60  can be provided in an elongated tubular configuration having sealed generally dome shaped top and bottom ends  60   T  and  60   B , respectively, and an extension arm support  74  to secure the electrically conductive element  38  above the float  60 . In one embodiment, the extension arm support  74  and the electrically conductive element  38  may be provided integrally constructed using the same material, such as strong, stiff, conductive metallic wire. The float  60  may be manufactured in sealed hollow glass or other suitable material. When a breakable material such as glass is utilized, a caging structure defined at least in part by an elongated oval interior wall  80  in the lower portion  82  of dipstick  16 , near the bottom end  20 . For additional protection, one or more cage members  84  may be provided, which in one embodiment as indicated in  FIG. 2 , may be oriented perpendicular to the minor axis of oval interior wall  80  and affixed to dipstick  16  in a generally C-shaped configuration. Two cage members  84  on each of first  86  and second  88  sides of dipstick  16  may be provided as indicated in  FIG. 2 .  
         [0017]     In one embodiment as illustrated herein, the low oil level indicator  14  includes a cap  26  which has an upper mounting flange  90 . An at least partially transparent (to at least visible light) and preferably replaceably detachable cover  92  is provided. The cover  92  may include generally a downwardly directed mounting flange  94 . The downwardly directed mounting flange  94  is configured for secure mating engagement with the upper mounting flange  90  of cap  26 . In the embodiment indicated in  FIG. 2 , the cover  92  is generally circular with an interference fit  96  downwardly directed peripheral mounting flange, and wherein said upper mounting flange on said cap is provided in complementary shape to the interference fit cap, so that the cap and cover are secured together. Alternately, threaded construction of upwardly directed mounting flange  90  and downwardly directed mounting flanges  94  may be provided, and in such case, the cover  92  may be secured to cap  26  by threaded engagement. In any event, the provision of a replaceably detachably cover  92  which covers the battery  32  makes the battery  32  replaceable. In one embodiment, the cover  92  secures tab  54  against pole  52  of battery  32  to complete that portion of the electrical circuit  30 .  
         [0018]     As can be seen by comparison between  FIGS. 3 and 4 , the float  60  of the low oil level indicator  14  is displacebly situated along the longitudinal axis of the dipstick  16  so that the electrical circuit  30  (a) is switched off by the rise of said float  60  toward the cap  26 , such as level O H  as indicated in  FIG. 4 , and (b) is switched on by the fall of the float  60  away from the cap  26 , to a level such as level O L  as indicated in  FIG. 4 , wherein the electrically conductive on-off element  38  of the switch  36  completes electrical circuit  30  to energize the indicating light  34 . The just described mechanism is facilitated by the buoyancy of float  60  in oil  102  in oil reservoir  12 . As shown generally herein, one useful embodiment has been developed wherein the electrically conductive on-off element  38  is formed in a wire loop shape, and wherein the wire loop is sized and shaped with sufficient width  38   W  to rest on said first and second contact pins having a width therebetween of  36   W , when the float  60  level drops to a preselected position O L  indicating low level of oil  102  in a selected mechanical device, so that when loop of electrically conductive element  38  rests on the first  44  and second  48  pins, to complete the electrical circuit  30 .  
         [0019]     I have found that a useful device for light  34  is a light emitting diode. For most low oil level indicators, emission of a red light when light  34  is energized is normally appropriate.  
         [0020]     In any mechanical device, such as a lawn mower  10 , the low oil level indicator  14  must e securely affixed to the oil reservoir  12 . Many mechanical devices include an oil fill tube  110  having an upper end  112  with threaded  114  connections. In such a case, the lower flanges  116  of cap  26  are provided with threads  118  of complementary dimensions for secure mating threaded engagement.  
         [0021]     It is to be appreciated that the various aspects and embodiments of a low oil level indicator device as described herein are an important improvement in the state of the art. The low oil level indicator device is simple, robust, reliable, and useable in a variety of applications. Although only a few exemplary embodiments have been described in detail, various details are sufficiently set forth in the drawings and in the specification provided herein to enable one of ordinary skill in the art to make and use the invention(s), which need not be further described by additional writing in this detailed description.  
         [0022]     Importantly, the aspects and embodiments described and claimed herein may be modified from those shown without materially departing from the novel teachings and advantages provided by this invention, and may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the embodiments presented herein are to be considered in all respects as illustrative and not restrictive. As such, this disclosure is intended to cover the structures described herein and not only structural equivalents thereof, but also equivalent structures. Numerous modifications and variations are possible in light of the above teachings.