Patent Publication Number: US-2005132946-A1

Title: Repeatable fluid indicator assembly

Description:
TECHNICAL FIELD  
      The present invention relates to indicator assemblies used to measure fluid levels, and in particular to an oil level indicator assembly for motor vehicle engines and transmissions.  
     BACKGROUND OF THE INVENTION  
      Indicator sticks for checking the level of fluids in an operational environment, for example, engine oil within a vehicle engine or transmission oil within a transmission, are removably disposed within an indicator tube. The indicator sticks are typically a single narrow strip of steel with a proximate end and a distal end. The proximate end has a handle by which the indicator stick is inserted into and removed from the indicator tube, and a seal, which provides a retaining force for the indicator stick. The seal of the indicator tube serves as a stop for the indicator stick, limiting the travel of the indicator stick into a fluid sump. The distal end is immersed in the fluid sump holding fluid whose level is being checked and extends into the fluid without contacting any positive stop. The distal end has marks intended to indicate such things as indicating a full level of fluid and a low level of the fluid. Locations of the marks are dependent on the nominal values for the lengths of the indicator stick and the indicator tube, respectively, the point of contact between the indicator stick and the indicator tube, the relative location of the indicator tube to the engine or transmission block with which the indicator tube is associated, and the relative location of the engine block to a fluid sump. Any variations of these values from their nominal values can produce indicator stick readings that do not accurately reflect the true fluid level in the fluid sump.  
      However, the design of fluid indicator assemblies have inherent variances due to dimensional tolerances that must be added to the nominal values. Tolerance values increase as the number of components in a system increase and as the complexity between the interaction of the components increases. For example, with an engine oil indicator assembly, tolerances must be accounted from the point of contact between the indicator stick and the indicator tube to the fluid level indication marking on the indicator stick, and from the point of contact between the indicator stick and the indicator tube to where the indicator tube contacts the engine block. Moreover, tolerance must be added to the length of the indicator stick to take into consideration any bends in the indicator tube, the dimensions of the mating components such as an engine block, the dimensions of any gaskets associated with the mating components and the distance from the bottom of the gasket to the bottom of the fluid sump. Since these tolerances are cumulative, the positioning relationship between the indicator stick and the surface of the fluid is subject to a great amount of variation. Thus, conventional fluid indicator assemblies do not accurately and consistently read the proper fluid levels within the fluid sump. As a result, fluid levels may be overfilled or underfilled, depending upon the inaccurate reading of the indicator stick.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a fluid indicator assembly comprising an indicator tube having an upper portion and a lower portion. A stop associated with the indicator tube is defined by the transition from the upper portion to the lower portion of the indicator tube. An indicator stick is removably disposed within the indicator tube. The indicator stick has an upper portion and a lower portion. A stop associated with the indicator stick is defined by the transition from the upper portion to the lower portion of the indicator stick. The stop in the indicator tube and the stop in the indicator stick are proximate a fluid sump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
       FIG. 1  is a side view of a fluid indicator assembly in an engine according to the present invention within an engine.  
       FIG. 2  is a side view of the fluid indicator assembly according to the present invention.  
       FIG. 2A  is a cross-sectional view of the fluid indicator assembly taken along line  2 A- 2 A according to the present invention.  
       FIG. 2B  is a cross-sectional view of an alternate embodiment of the fluid indicator assembly taken along line  2 A- 2 A according to the present invention.  
       FIG. 3  is an exploded side view of two stop features of the fluid indicator assembly according to the present invention shown by the encircled region of  FIG. 2 .  
       FIG. 4  is an exploded side view of alternate stop features of the fluid indicator assembly according to the present invention.  
       FIG. 5  is an exploded side view of further alternate stop features of the fluid indicator assembly according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to the Figures, a fluid indicator assembly  10  is generally shown installed within an operable environment, such as a vehicle engine block  12 . The fluid indicator assembly  10  measures the fluid level, shown as a dashed line X, of a fluid  14  within a fluid sump  16 . The fluid indicator assembly  10  includes an indicator stick  18  and an indicator tube  20 . The indicator stick  18  is removably disposed within the indicator tube  20 . The indicator stick  18  is a flexible material, such as a flexible blade, cable, or the like, and is substantially linear prior to being inserted into the indicator tube  20 . Preferably, the indicator stick  18  is made from a flexible metal. While the fluid indicator assembly  10  of the present invention is directed towards measuring the fluid level of engine oil, it should be noted that the present invention may be practiced to measure the fluid level of other fluids in a vehicle, for example, the transmission fluid level of a transmission.  
      The indicator stick  18  includes an upper portion  22  and a lower portion  24 . The upper portion  22  includes a means for removal of the indicator stick  18  from the indicator tube  20  adjacent a proximate end  21 . As illustrated in  FIG. 2 , the means for removal of the indicator stick  18  is a handle  26 . The upper portion  22  further includes a seal  28  adjacent handle  26 . When indicator stick  18  is properly disposed within indicator tube  20 , seal  28  engages the interior of indicator tube  20  and provides a retaining force against indicator tube  20 . Additionally, seal  28  restricts the exit of fluid  14  from the indicator tube  20  by a lip  28   a  that sealingly engages the outer periphery of indicator tube  20 . It should be noted that while seal  28  and lip  28   a  sealingly engage indicator tube  20 , seal  28  and lip  28   a  do not limit the travel of indicator stick  18  within indicator tube  20 , in contrast to the teachings of the prior art. The lower portion  24  further includes markings indicating such things as a full level of fluid F and a low level of fluid L within the fluid sump  16 . Lower portion  24  terminates at a distal end  23  that is intended to contact fluid  14  within fluid sump  16 .  
      As best illustrated in  FIGS. 3-5 , upper portion  22  of indicator stick  18  has a diameter or a width A and lower portion  24  has a diameter or a width B. Width A is greater than width B. The transition between upper portion  22  and lower portion  24  defines a stop feature  25  of indicator stick  18 . As best shown in the illustrations, stop feature  25  is proximate the fluid sump  16 . In the embodiment of  FIG. 3 , the transition from upper portion  22  to lower portion  24  is in the form of a step, or a square geometry, or the like. Alternatively, the transition from dimension A to dimension B may be more gradual. As illustrated in  FIG. 4 , upper portion  22  gradually tapers at an angle into lower portion  24 . In a further alternative embodiment, the transition from upper portion  22  to lower portion  24  may be more fluid.  FIG. 5  illustrates the transition from upper portion  22  flowing continuously into lower portion  24 . It should be noted that  FIGS. 3-5  are for purposes of illustration only, and stop feature  25  of indicator stick  18  may be of any desired configuration so long as dimension A of upper portion  22  is greater than dimension B of lower portion  24 .  
      Indicator tube  20  receives indicator stick- 18 . Typically, indicator stick  18  is a flat bar and indicator tube  20  is a hollow cylindrical tube, best shown in the cross section illustrated in  FIG. 2A . However, indicator stick  18  and indicator tube  20  may have complementary geometries, as illustrated in  FIG. 2B . It can be appreciated that indicator stick  18  and indicator tube  20  may be of any desired geometry so long as indicator tube  20  is able to receive indicator stick  18 .  
      Indicator tube  20  has an upper portion  30  and a lower portion  32 . There are S-bends  34  in the indicator tube  20 , both in upper portion  30  and in lower portion  32 . During insertion, indicator stick  18  conforms to bends  34  in indicator tube  20 . The bends  34  aid in centering the indicator stick  18  relative to the indicator tube  20 .  
      Upper portion  30  of indicator tube  20  has an internal diameter or width D that is greater than a corresponding internal diameter or width d of lower portion  34 . Width D is greater than width A while width d is greater than width B. A stop feature  36  is defined by the transition between upper portion  30  and lower portion  32 . As with stop feature  25 , stop feature  36  of indicator tube  20  is also proximate the fluid sump  16 . As illustrated in  FIGS. 3-5 , stop feature  36  of indicator tube  20  generally follows the geometry of stop feature  25  of indicator stick  18 . Accordingly, there may be a substantially sharp transition, a gradual tapering or a generally fluid transition between upper portion  30  and lower portion  34  of indicator tube  20 . When indicator stick  18  is inserted into indicator tube  20 , stop feature  25  of indicator stick  18  engages stop feature  36  of indicator tube  20 . The interaction between stop feature  25  of indicator stick  18  and stop feature  36  of indicator tube  20  provides a point of contact between indicator stick  18  and indicator tube  20  that is proximate to fluid  14  in the fluid sump  16 . It should be noted that stop features  25  and  36  may be of any desired shape, so long as stop features  25  and  36  have complimentary geometries that provide engagement to limit the travel of the indicator stick  18  into fluid sump  16 . As stated above, it should be noted that when indicator stick  18  is properly disposed within indicator tube  20 , seal  28  and lip  28   a  do not prohibit stop features  25  and  36  from engaging. In essence, the engagement of stop features  25  and  36  limit the travel of indicator stick  18  within indicator tube  20 .  
      The fluid indicator assembly  10  of the present invention has advantages over conventional fluid indicator assemblies. For example, fluid indicator assembly  10  has a reduced tolerance stack up because (i) the number of components that comprise the tolerance stack up is reduced and (ii) the complexity of the interaction between different components is minimized. Specifically, the fluid indicator assembly  10  of the present invention does not have to include additional tolerance values for the interaction between the S-bends  34  of the indication tube  20  and the corresponding bends in the indicator stick  18 . Also, any tolerance associated with the interaction between seal  28  and indicator tube  20  is not included in the tolerance stack up because the point of contact between indicator stick  18  and indicator tube  20  is proximate fluid sump  16 . Thus, indicator stick  18 , indicator tube  20  and seal  28  have a reduced effect in the tolerance stack up of the present invention. Therefore, the fluid indicator assembly  10  more accurately measures the true level of fluid and the. repeatability and corresponding accuracy of the fluid level readings of fluid indicator assembly  10  is greater than with conventional fluid indicator assemblies.  
      It should be understood that the aforementioned and other various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.