Patent Publication Number: US-6988403-B2

Title: Fluid level measuring device

Description:
CROSS-REFERENCE TO RELATED PATENTS AND PATENT APPLICATIONS 
   The subject matter of the invention is related to U.S. Pat. No. 6,314,808, filed on Nov. 24, 1997, and U.S. Pat. No. 6,453,740, filed on Sep. 05, 2001; both entitled “Fluid Level Measuring Device”. The disclosure of these patents is hereby incorporated by reference. 
   The subject matter herein claims benefit under 35 U.S.C. Section 119(e) of U.S. Patent Application Ser. No. 60/326,636, filed Oct. 01, 2001, and entitled “Fluid Level Measuring Device”; the disclosure of which is hereby incorporated by reference. 

   FIELD OF THE INVENTION 
   The subject invention is directed to a device used to measure fluid levels, and more particularly, to dipsticks used to measure fluid levels by contacting an indicator at one end of the dipstick into a fluid holding compartment. 
   BACKGROUND OF THE INVENTION 
   With internal combustion engines, transmissions, and other machinery requiring fluids for lubrication and cooling, it is known to use a fluid measuring device for indicating the fluid level in a selected fluid holding compartment. Typically, the fluid measuring device is a dipstick for checking the level of fluid such as engine or transmission oil, or hydraulic fluid within one of the many fluid holding compartments in the engine, transmission, or other machine. The dipstick is normally an elongated indicator that is slidably located within a conduit or pipe attached to the engine, transmission, gear box, reservoir or machine in which a fluid level indication is desired. When the dipstick is fully inserted into the conduit, one end is immersed into the fluid. When an actual reading of the fluid level is desired, the other end of the dipstick is pulled from the conduit thereby removing the entire dipstick from the conduit to allow the user to read the fluid level from the one end. The dipstick is then reinserted into the fluid compartment once the fluid level has been checked. 
   Traditional fluid level indicator systems typically consist of a two piece system with a holding tube and a dipstick. Examples of conventional dipstick systems are disclosed in U.S. Pat. Nos. 3,371,418; 5,485,681 and 5,829,153; the disclosure of each of which is hereby incorporated by reference. The holding tubes are generally fabricated from metal tubing and require various forming operations including bending, flaring, and machining, followed by the attachment of a dipstick receptacle. In addition, the dipstick is fabricated from multiple components including a handle, washer, cap, rubber stopper, shaft assembly, and a marked spring steel shaft mechanically joined to a spring steel blade. The actual assembly of these various components involves multiple assembly operations requiring costly, time-consuming, and labor intensive manufacturing steps. Therefore, a simpler design requiring fewer parts and connections as well as less forming is desirable. 
   In addition, today&#39;s engines, transmissions, and machinery designs are smaller, more compact, and of less weight than traditional engines, transmissions, and machinery. Therefore, fluid level indicator systems must be smaller, more compact, and lighter weight. Moreover, the fluid access routes or paths through which the fluid level indicator system accesses the fluid storage compartments are becoming more complex (more twists and turns as well as longer runs), smaller, and more compact. 
   There is a need in this art for smaller and lighter weight fluid level indicator systems with improved flexibility. There is also a need for a fluid level indicator system allowing access to the fluid compartment while assuring a secure, sealed closure of the access when fluid level determinations are not being made and/or additional fluid is not being added. This sealed closure would prevent unnecessary loss of the fluids during operation as well as supply level pressurization. Moreover, a positive indication that the dipstick is securely in place is desirable. 
   SUMMARY OF THE INVENTION 
   The instant invention solves problems associated with conventional fluid level measuring systems by providing a handle associated with a dipstick that is free to swivel or rotate freely within a plastic handle. By being able to rotate (e.g., while being inserted through a non-linear tube and into an engine component), the dipstick can accommodate travel along non-linear routes without binding or being permanently deformed. 
   The fluid level measuring device includes a stationary tube assembly extending from the fluid compartment in which a dipstick is disposed. The dipstick includes a plastic handle that is joined or molded to one end of a shaft, such as a flexible spring steel wire shaft. If desired, a mold release agent can be applied upon a portion of the shaft in order to prevent the over-molded handle from permanently bonding to the shaft. A precision stamped fluid level indicator blade extends from a second end of the shaft and is preferably attached to the shaft by either die casting, spin welding, ultrasonic welding, or other bonding means, or by means of a fitting or other connector. The tube assembly is preferably made of a plastic material with an enlarged end. Lugs extend from the end and provide a bayonet interconnection between the tube and the handle assembly by twisting the handle assembly relative to the tube. The lugs can extend inwardly or outwardly depending upon the design of the handle, e.g., the handle can be inserted into an enlarged opening of the stationary tube or about the end of the stationary tube. This causes inter-engagement of the lugs with slots in the handle. An engine fitting (e.g, a steel engine fitting) extends from the tube and serves to guide the indicator blade to an appropriate location within the fluid cavity. Alternatively, the tube can include at least one O-ring or other seal that engages a protuberance/ridge defined around the tube in order to provide an interference or compression fit into a reservoir. 
   The instant invention also solves problems associated with conventional manufacturing methods by staking an engine fitting at the end of the stationary tube associated with the fluid level measuring device. The tube can be shaped or bent into a wide range of linear or non-linear configurations. Typically the tube comprises commercial grade steel. 
   A gasket acts as a pressure lock seal for sealing the handle to the enlarged end when the lugs are locked in the slots. This pressure lock seal serves to allow significant pressurization within the dipstick and oil pan or other chamber the dipstick is affixed to. The gasket can also urge the bayonet connection of the handle into a locked position relatively to the lugs on the stationary tube. 
   The bayonet interconnection in unison with the gasket supplies an actual pressurized seal thereby allowing pressurized testing of the combustion engine, transmission, or other machinery without either removal of the dipstick or attempts at sealing the dipstick. Furthermore, a sealed dipstick allows the combustion engine, transmission, or other machinery to run at the intended pressure rather than either below the intended pressure or at the intended pressure due to an adjustment. 
   The structure is manufactured from lightweight, corrosion-resistant, plastic materials such as nylon, glass-reinforced nylon, among other oil, water and temperature resistant thermoplastic materials, with the exception of the metallic shaft, attachment fitting, blade, and metal engine fitting. The metallic shaft can be fabricated from stainless steel, zinc plated, phosphated, chromated, among other metal treatments to improved corrosion resistance. The seal and locking engagement between the handle and enlarged end preferably involves a quarter-turn sealing motion with an improved sealing capability and a positive lock feature. 
   In one aspect of the invention, the fluid level indicating system is capable of being in fluid communication with the combustion engine, transmission, or other machinery to which it is affixed while maintaining a constant pressurization therein through an improved method of sealing. Specifically, a seal that is capable of maintaining several atmospheres (at least 1 to 1.5 atm.) of back pressure is desirable. The inventive seal can also serve to reduce emissions from the associated engine, e.g., reducing emissions from the dipstick tube of a diesel engine in order to satisfy environmental regulations. 
   In another aspect, the invention provides a positive engaging, yet easy to use, locking arrangement for securely locking and sealing the dipstick within or over the tube with an easy motion. It is also desirable that this sealing of the dipstick within the tube is such that the tube may be pressurized to the same back pressure as the combustion engine, transmission, or other machinery. 
   In a further aspect, the invention provides a smaller and more compact fluid level indicating system which has improved flexibility for routing of the fluid level indicator system in and around the complex design of today&#39;s engines, transmissions, and machinery. 
   The instant invention can also be employed as a kit or an assemblage in order to retrofit existing dipstick systems. When employed as a retro-fit, the inventive dipstick system provides the same advantages as if installed as an original equipment dipstick. 
   Regardless of which aspect of the invention is employed, the instant invention provides a more corrosion-resistant, lighter weight, less complex, higher precision and more cost effective fluid level indicator system. 
   Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading an understanding of the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangements of parts, certain aspects and method of which will be described in detail in this specification and illustrated in the accompanying drawings that form a part hereof. Any dimensions shown on the Figures are for illustration purposes only, and the components shown in these Figures can be employed in a wide range of dimensions and configurations. 
       FIG. 1  is a side view of the fluid level measuring device including the stationary tube assembly with a dipstick inserted therein having a handle attached to one end thereof; 
       FIG. 2  is a top view of the fluid level measuring device; 
       FIG. 3  is a partial sectional view of the fluid measuring device of  FIG. 1 ; 
       FIGS. 4 and 5  are front and side elevational views, respectively, of another preferred sealing gasket; 
       FIGS. 6 and 7  are elevational views of further preferred embodiments of grommet seals; 
       FIG. 8  is an elevational view, in partial cross-section, of the end of the dipstick assembly using the seal of  FIG. 7  received on the tube assembly; and 
       FIG. 9  is an elevational view of the end of the dipstick assembly incorporating yet another preferred grommet embodiment for sealing the end of the tube assembly. 
       FIG. 10  is an exploded side view of the fluid level measuring device including the stationary tube assembly with a dipstick wherein the dipstick handle is inserted within an expanded end of the stationary tube. 
       FIG. 11  is a side view of a shaft that is rotatably mounted within a handle. 
       FIG. 12  is an exploded side view of a fluid level measuring device that can be retrofit to replace an existing fluid level measuring assembly. 
       FIG. 13  is a side view of the fluid level measuring device including the stationary tube assembly with a dipstick inserted therein having a handle attached to one end thereof and a staked engine fitting at the other end. 
       FIG. 14  is a side view of the stationary tube assembly of  FIG. 13  and an associated staked engine fitting. 
       FIG. 15  is a side view and cross-sectional drawing of the stationary tube illustrated in  FIGS. 13 and 14 . 
       FIG. 16  is a side view and cross-sectional drawing of the engine fitting illustrated in  FIGS. 13 and 14 . 
   

   DETAILED DESCRIPTION 
   One aspect of the instant invention relates to a fluid level indicator system comprising a handle, a rotatably mounted shaft and dipstick mounted within the handle, and a stationary tube having an opening for receiving the handle. The rotatably mounted shaft can be over-molded by the plastic handle in a manner that permits the shaft to rotate (or prevents the plastic from permanently bonding to the shaft). The handle can be received within or around the stationary tube opening. 
   At least a portion of the shaft is contacted with a fluid that prohibits the over-molding plastic handle from permanently bonding to the shaft. While any suitable material can be employed, examples of suitable materials comprise commercially available injection mold release agents, oils, lubricants, among others capable of preventing a permanent bond between the shaft and over-molded plastic. One material comprises a polymeric carrier such as an acrylic, urethane or epoxy and heat expandable spheres, e.g., butane filled thermoplastic shells such as Expancels® supplied by Akzo-Nobel. The shaft is, for example, dipped into the expandable material, and during the handle plastic over molding process the heated plastic causes the material to expand thereby preventing the thermoplastic from bonding to the shaft. Any bond forming between the expandable material and the shaft can be broken by rotating the shaft. If desired, the fluid can be supplemented or replaced by using a sleeve or material that is consumed during the over-molding process. Alternatively, a roller tube or sleeve can be placed around the shaft such that the over-molding plastic bonds to the pin while allowing shaft to rotate within the tube. 
   Another aspect of the invention relates to an improved manufacturing method and resultant product wherein the stationary tube is staked onto an engine fitting (the engine fitting guides the shaft and indicator blade into a fluid reservoir such as oil, transmission fluid, among others). This method can be employed for manufacturing fluid level indicators with rotary or stationary shafts. The stationary tube can have a linear or non-linear configuration, and a wide range of lengths. Employing a staking operation to affix an engine fitting onto the stationary tube ensures a fluid tight connection while reducing assembly costs. 
   Referring now to the drawings wherein the showings are for the purposes of illustrating certain aspects of the invention only and not for purposes of limiting the invention, the overall arrangement of such aspects of the fluid level measuring device A can best be understood by reference to  FIGS. 1 ,  3 , and  8 – 10 . As illustrated therein, the fluid level measuring device A comprises a stationary tube assembly B with a dipstick assembly C removably and rotatably disposed therein. Specifically, tube assembly B is an elongated, hollow guide tube  10  with first and second spaced ends  12  and  14  having a through passage  16  that communicates with first and second openings  18  and  20  at the respective first and second ends. The tube can be fabricated from any suitable material. Examples of suitable material comprises steel, aluminum, painted steel, plastic, among others. 
   The tube assembly B further includes an enlarged diameter coupler or spout  22  attached to the first end  12  of the guide tube  10 . In one aspect, the coupler is joined to the first end  12  of the guide tube as described herein. The coupler  22  has a small diameter portion  24 , a flare or tapered transition portion  26 , and a large diameter portion  28  at its second end. The small diameter portion is closely received over the guide tube first end. The large diameter portion includes a pair of outwardly extending lugs  30 A and  30 B that form a portion of a locking assembly to be described in greater detail below. The coupler is also hollow, defining a continuous internal cavity that extends from a first or upper end  32  to a second or lower end  34 . The internal cavity is enlarged at the upper end to accommodate an interconnection between the shaft and a handle, and, if desired, to provide an orifice for receiving a spout on a fluid container, such as an oil container. For example, the spout of a standard quart of oil will fit in this enlarged upper end. Alternatively, the enlarged upper end may be dimensioned to receive a different sized oil container. It will be appreciated, however, that the enlarged upper end will eliminate use of a funnel in many instances. 
   Dipstick assembly C includes a plastic molded handle assembly  50 , an elongated relatively stiff, yet bendable shaft  52  such as the stranded wire rope illustrated in the drawings (e.g.,  FIGS. 3 ,  8  and  11 ), and a fluid level indicator blade  54 . The shaft  52  is rotatably mounted within plastic molded handle assembly  50 , e.g., the shaft  52  can rotate and flex while being inserted along the typically non-linear length of the stationary tube. The handle  50  includes gripping portion  56  connected to a hollow cylindrical base  58  by a neck  60  of reduced dimension. The gripping portion preferably has a pair of knobs  62 A and  62 B extending outwardly and obliquely from the neck  60 . The base  58 , on the other hand, has a pair of slots  64 A and  64 B defined therein. In one specific aspect, each slot extends entirely through the base sidewall and is of a generally curvilinear conformation. The slots have an opening at one end along lower edge  66  of the base and a locking seat  68  at the other end of the curvilinear slot. Each of the curvilinear slots  64 A and  64 B is defined so as to have an axial portion aligned approximately with the shaft, and likewise the tube assembly B, and positioned adjacent the lower edge  66  of the base  58 , and a generally transverse portion at the other end of the slots and in which locking seat  68  is defined. 
   The combination of slot  64 A and  64 B with lugs  30 A and  30 B defines a locking mechanism or bayonet type interconnection where lugs  30 A and  30 B slide in slots  64 A and  64 B. Axial insertion of the handle over the lugs and a quarter turn causes the handle base to slide over the coupler  22  whereby the lugs  30 A and  30 B become positively engaged in corresponding locking seats  68 . 
   Shaft  52  is associated with but not permanently joined, bonded, molded or glued, to handle assembly  50 . Shaft  52  is provided within assembly  50  in a manner that achieves a secure interconnection. Fluid level indicator blade  54  is affixed to the other end of the shaft  52  by die casting (or alternatively, by a staked attachment fitting  70  or other suitable mechanical connection). The die cast construction eliminates tolerance stack-up problems associated with prior arrangements, reduces the number of components, and provides a smooth transition fitting that does not catch in the guide tube. The indicator blade  54  is typically rounded or pointed at its free end to allow for easy insertion into the coupler  22 , through the guide tube  10 , and through engine fitting  72 . The indicator blade also includes indicia, such as shaded area  74 A and arrows  74 B and  74 C on at least one of the faces of the blade, for indicating the fluid level when dipstick assembly C is inserted fully into stationary tube assembly B that extends from the engine fitting. 
   Engine fitting  72  is compression sealed or press fit within second opening  20  of the guide tube  10 . Alternatively, the fit may be a tight seal, a threaded fitting, or other connector, or the fit may involve bonding, gluing, molding, or other means of sealably connecting. A lip  76  prevents engine fitting  72  from complete insertion into elongated guide tube  10 . The opposite end of engine fitting  72  is attached or bonded to a fluid reservoir or tank, such as found in an internal combustion engine, where it is desirous to measure the fluid level within the reservoir. In one specific aspect, this engine fitting is made of steel and has a serrated outer surface  78  (although alternatively, the outer surface may be roughened, knurled, or of other texture). 
   With the engine fitting  72  connected to a fluid reservoir and providing access for dipstick assembly C, the opposite end of stationary tube assembly B, i.e., the coupler  22 , is secured at a convenient location remote from engine fitting  72 . The elongated through passageway that connects coupler  22  and engine fitting  72  thereby provides access to the fluid in the reservoir via dipstick assembly C. Specifically, fluid level indicator blade  54  is inserted through the coupler and guide tube  10  such that the free end of blade  54  is immersed into the fluid in the reservoir. It will be appreciated that since the shaft is bendable and rotatable, the guide tube can adopt twists and turns along its route and the dipstick assembly can accommodate the tortuous path. For the blade  54  to be fully inserted, handle  56  must engage and interlock with coupler  22  and lugs  30 A and  30 B extending therefrom. Specifically, lugs  30 A and  30 B align with the open end of slot  64 A and  64 B respectively, whereby the handle is further forced over the coupler  22  resulting in lugs  30 A and  30 B following the curvilinear shape of slots  64 A and  64 B until locked in locking seats  68 . The result in the rotation by approximately 90° of the handle about the coupler  22  as lugs  30 A and  30 B move from the axial portion of the respective slots into the transverse portion and eventually the locking seat  68 . 
   A seal  80  ( FIG. 3 ) is located in the base of cavity  82 , and preferably glued, bonded or otherwise affixedly seated within the cap. The seal provides a pressure lock seal when the dipstick assembly is fully received in the guide tube. This seal has sufficient elasticity to allow compression of the seal by the coupler  22 . This bayonet type locking arrangement provides assurance that fluid level indicator blade  54  is properly positioned for accurate fluid level readings as well as providing a positive lock feature for assuring that handle  56  is locked to stationary tube assembly B. Moreover, the seal provides sufficient sealing capabilities to allow the engine, transmission, or other machinery to reach several atmospheres (preferably at least 1 to 1.5 atm.) of back pressure without leakage. In addition, when fully sealed, the seal prohibits contaminants from entering into the fluid reservoir where system integrity and reliability would be jeopardized, and prohibits unnecessary fluid loss from the assembly. When a compressible and resilient seal is employed, the seal functions to urge the handle and lugs into a locked position, e.g., locking the bayonet mechanism compresses the seal which in turn causes the seal to urge the handle into a locked position relative to the locking lugs. 
   In one aspect, the coupler  22  and guide tube  10  are fabricated from plastics while engine fitting  72  is manufactured of high heat tolerating metals or plastics. Handle  56  is typically a molded component to or in which flexible shaft  52  is directly molded, joined, pinned, or otherwise connected. The handle is dimensioned to overlie or encompass the coupler or spout in its locked position to prevent contaminants from entering the guide tube. In an alternative aspect of the invention, described below in connection with  FIG. 10 , the handle is inserted into the spout. Moreover, the use of plastics can reduce corrosive effects and provides an overall reduction in system weight. Yet another advantage of using plastic in forming a number of the components is that the system can be color-coded for ease of use by the customer. Blade  54  is fabricated from steel or other comparable metals or plastics and is attached to flexible and rotating shaft  52  by attachment fitting  70  as described above. It will be appreciated, however, that other suitable materials may be used without departing from the scope and intent of the subject invention. 
     FIGS. 4–5  illustrate another aspect of the subject invention. In this arrangement, a different configuration grommet  90  is shown. It, too is of annular construction and preferably includes a series of legs  92  disposed in generally parallel relation and extending across the entire width of the annular grommet. That is, the legs are separated by groves  94  so that the legs extend outwardly a minor dimension on the order of approximately 0.10 inch. An opposite face of the grommet  96  has a general planar conformation and fits within the base of the cavity defined by the handle. Thus, as will be appreciated, the grommet may be adhesively secured or be appreciated, the grommet may be adhesively secured or interference fit into the base of the handle and is adapted to engage against end  32  of the spout. The alternating legs and grooves on the face of the grommet that engages the end of the spout prevents a seal from being formed in this particular version, however, by forming the grommet from an elastomeric material such as neoprene, the positive locking capability described in association with the aspects of the invention illustrated in  FIGS. 1–3 ,  10  and  12  is maintained. That is, the user encounters a positive lock feel as the lugs enter the locking seats in the end of the slots. The elastomeric nature of the grommet serves as an integral portion of the locking function as the lugs  30  extend through the grooves  64 ,  66  in the handle. Engagement is made between the handle and the end of the spout. The lugs then pass the over-center position in the groove and urge the handle outwardly while maintaining the compressed relationship and ensuring a locked condition between the handle and the guide tube. 
     FIGS. 6–8  illustrate yet another version of a seal  100  that provides all of the same features and benefits of those shown and described in the earlier embodiments.  FIGS. 6 and 7  illustrate two similar grommet seals  100  so that like components will be referred to by like reference numerals with a primed suffix (′) in  FIG. 7 . The grommet has an enlarged shoulder  102  at one end that is received in the base of the handle. The shoulder has an outer diameter sufficient to engage against the axial end of the spout and perform the combined sealing and locking function as described above. In addition, a seal is formed in a radial direction with the wall of the spout by providing a circumferentially continuous sealing bead  104  ( FIG. 6 ) or pair of beads  104 ;  106  ( FIG. 7 ). In these arrangements, the sealing bead(s) is (are) integrally formed as a part of the grommet seal to reduce the number of components, eliminate additional assembly, and provide for an assembly that meets close tolerance specifications. Thus, as best illustrated in  FIG. 8 , once the handle is in the locked and scaled position, terminal end of the spout is sealed against shoulder  102 . In addition, the seal beads  104 ,  106  engage the radial inner wall of the spout to provide an enhanced seal. In these aspects or arrangements, the seals form an interference fit with the handle. Thus, the enlarged shoulder  102  is dimensioned to form an interference fit in the base of the handle in addition to being sized for engagement with the terminal end of the spout. In substantially all other respects, these arrangements are identical to the aspects described above. 
     FIG. 9  shows yet another aspect of the invention that provides both an effective seal and positive locking feature. Here, the grommet or seal  110  is integrally molded into the handle. The seal has an annular configuration that extends from the planar interior base of the handle. The seal is circumferentially continuous and has a tapered or flared radial outer face  112  that is dimensioned for sealing engagement with the spout. The tapered conformation serves the dual purpose of sealing the handle and spout, as well as providing the positive locking function described above. When the handle is in the fully locked position, the terminal end of the spout engages the integrally molded seal in the base of the cap in an axial direction and the tapered wall  112  sealingly engages the radial inner wall of the spout. 
   Referring now to  FIG. 10 ,  FIG. 10  illustrates a further aspect of the invention wherein handle  120  is inserted and lockable within opening  121  defined in expanded spout  122  on one end of tube  123 . Handle  120 , as illustrated, includes gripping knobs or areas  120 A and  120 B (handle  120  can alternatively include the gripping knobs illustrated in  FIG. 8 ). Handle  120  has the previously described bayonet connection, except that handle  120  is inserted within spout  122  and engages locking lugs (not shown) protruding inwardly from the inner surface of spout  122 . As the handle  120  is inserted into spout  122 , a recessed area (not shown) and defined within shoulder  124  engages gasket  125 . Gasket  125  is compressed against shoulder  124  and the interior base of spout  122  as handle  120  is inserted into spout  122 . As handle  120  is inserted into spout  122  curvilinear channels  126  (having one open end) defined in side-wall  127  engage inwardly protruding locking lugs on spout  122 . Locking lugs travel along channels  126  until reaching area  128  at the closed end of channels  126 . A recess  129  defined at area  128  functions to secure the locking lugs in a locked position within channels  126 . 
   Rotatable dipstick shaft  130  is carried along with handle  120  as handle  120  is inserted into spout  122 . As described above, the distal end of rotatable dipstick shaft  130  has a blade (not shown) that is employed for measuring a fluid level. Rotatable dipstick shaft  130  is free to flex and rotate as it is inserted into spout  122  and travels along tube  123 . 
   Referring now to  FIG. 11 ,  FIG. 11  illustrates a rotatable shaft  140  that is over-molded by a dipstick handle such as illustrated in  FIGS. 1–3  and  8 – 10 . The rotatable shaft  140  is normally cleaned and polished to have smooth surface thereby enhancing the ability of shaft  140  to rotate within a dipstick handle. Shaft  140  has at least two chamfered regions  141 A and  141 B. These regions enhance the molding about shaft  140  as well as prevent shaft  140  from being pulled out of a handle. These regions can have any desirable configuration such as a flatten or nail head structure, semi-circular, among other configurations that permit rotation and prevent pull-out. 
   Shaft  140  also includes chamfered region  142 . A blade (not shown) having a fluid level indicator at its distal end is connected to shaft  140  at chamfered region  142 . The attachment can be achieved by any suitable method such as die-casting, staking, riveting, welding, among other conventional methods for attaching elongated metal articles. 
   Referring now to  FIG. 12 ,  FIG. 12  illustrates a retro-fit kit that can be employed for replacing conventional dipsticks with the inventive fluid level indicator. Kit  150  comprises compression sleeve  151  having threaded area  152  and compressive fitting  153 . Kit  150  further comprises stationary tube member  154  and compression nut  155 . Stationary tube member  154  typically comprises one of the stationary tubes illustrated in  FIGS. 1 ,  3 , and  8 – 10 . The portion of compressive sleeve  151  in contact with stationary tube member  154  typically has a diamond knurled surface finish. In order to install kit  150  as a retrofit for an existing dipstick system, the existing dipstick system, which comprises the dipstick and the portion of the stationary tube contacting the existing dipstick, is removed, e.g., sawing, clipping, among other methods for cutting metal. Compressive nut  155  is slid over the existing stationary tube (after removing the original dipstick system). The stationary tube  154  including sleeve  151  are located in the stationary tube. Compressive nut  155  is contacted with threaded area  152  and tightened sufficiently to retain stationary tube  154  and sleeve  151  at a fixed position. Thereafter, the inventive dipstick system can be employed and locked into position by using the inventive bayonet connection. 
   Referring now to  FIG. 13 , shows fluid level indicator assembly  160  comprising a cap locking assembly  161  shown in  FIGS. 1–3 ,  8 – 9  and  10  or in aforementioned U.S. patent application Ser. No. 09/947,314. Cap locking assembly  161  is attached to stationary tube  162 . Stationary tube  162  is staked at  163  onto engine fitting  164 . Tube  162  and engine fitting  164  are illustrated in greater detail in  FIGS. 14–16 . 
     FIG. 14  illustrates stationary tube  162  staked onto engine fitting  164 . The end of stationary tube  162  opposite from the engine fitting  164  contains a knurled region  170 . Region  170  is provided for enhancing the bond between tube  162  and an overmolded thermoplastic material (e.g., nylon 6,6) used in forming locking cap assembly  161 . Staking region  163  can be formed by using any suitable machine such those supplied by EZ Crimp (e.g., containing 8 jaws and reducing the diameter of the stationary tube from 0.50 to about 0.475). The degree of diameter reduction and length of staking region can vary widely. 
   In one aspect of the invention, the cap assembly is connected to the stationary tube without the aforementioned over-molding process. The cap assembly can be attached via a threaded connection, contacting the interior of the stationary tube and expanding the stationary tube into contact the coupler or cap assembly, among other methods for affixing the cap assembly. 
     FIGS. 15 and 16  illustrate greater detail of tube  162  and engine fitting  164 . Tube  162  can be fabricated from any suitable material such as ASTM J525, ASTM A513 Type 1 or 2 Alloy, among other materials capable of withstanding staking. Engine fitting  164  can also be fabricated from any suitable material such as 12L or 15 ASTM Alloy A108, lead free alloys, among other suitable materials. Tube  162  can be fabricated in accordance with any suitable method. One suitable method comprises shaping or bonding the tube into a desired configuration by employing commercially available machines such as compression bending, rotary draw bending, among other apparatus. Engine fitting  164  can be shaped by any suitable method such as by a conventional screw machine operations. Engine fitting  164  can include an optional knurled region  180  for enhancing bond formed by staking at region  163 . Protuberance  181  about the exterior of engine fitting  164  is dimensioned to receive tube  162 . Engine fitting  164  is maintained at a predetermined location with respect to the engine&#39;s fluid reservoir by grooves  182  defined upon the surface of the engine fitting. Engine fitting  164  can also include protuberances or ribs  183 . Ribs  183  provide a surface that increases a bond between the engine fitting  164  and tube  162  when tube  162  is crimped or staked onto engine fitting  164 . While any suitable method such as crimping or staking can be used for connecting the engine fitting and tube, the selected method should deform the tube and provide a permanent and leak resistant bond. 
   The invention has been described with reference to certain aspects. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. For example, although the described aspects extensively use plastic as the preferred material of construction, it is understood that other materials can be used for selected components if so desired. Likewise, mere reversal of components that achieve substantially the same function and result are contemplated. For instance, the seal and locking features can be achieved by differently configured seals and/or lug and slot arrangements without departing from the present invention. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.