Abstract:
A float-type liquid level gauge assembly is provided for measuring the level of a liquid in a tank. The liquid level gauge includes a gear housing for efficiently coupling the gears and accurately assembling and aligning certain components; a movable pivot arm assembly supporting a float arm assembly; and a gear on the pivot arm assembly coupled with a pinion gear located in the gear housing. The pinion gear has a shaped passageway which accepts a similarly shaped drive shaft. A single piece magnetic cap, which defines a bore correspondingly shaped to accept the shaped drive shaft such that it will not rotate relative to the drive shaft, is installed on the drive shaft. The drive shaft and the magnetic cap each include a positioning feature, such that when the positioning feature of the drive shaft engages the positioning feature of the magnetic cap, the magnetic cap is properly aligned with a magnet in a dial assembly. A float arm with an attached float assembly can be adapted to act as both the float arm and the counterweight for counter-balancing the float assembly.

Description:
This is a Continuation-In-Part of U.S. patent application Ser. No. 09/795,233 filed Feb. 26, 2001 now U.S. Pat. No. 6,523,406. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates broadly to gauges for measuring the level of liquid in a tank; in particular, a float-type liquid level gauge for measuring the level of liquid in a tank containing a liquefied gas. More particularly, this invention relates to single piece magnetic cap with alignment feature for use with a float-type liquid level gauge. 
     BACKGROUND OF THE INVENTION 
     This invention relates generally to a liquid level gauge, and more particularly to gauges commonly used for measuring liquefied petroleum gas (LPG) type liquids. The LPG is typically stored as a liquid under pressure in a tank or cylinder. A liquid level gauge may be provided on the tank or cylinder for measuring the level of the liquid. 
     A typical gauge of this type utilizes a pivoting float arm having a float at one end and an opposing separately attached counterweight at another positioned on a opposing side of a pivot from the float. The pivoting float arm moves in response to changes in the liquid level inside the tank. As the float arm pivots, it rotates a gear assembly which turns a drive shaft located in a support arm that is connected to the float arm. The drive shaft is connected to a tank magnet which is magnetically coupled to a receiving magnet in a gauge head. As the drive shaft rotates and rotates the tank magnet, the magnetic flux of the tank magnet rotates the receiving magnet which moves an external liquid level visual indicator, such as a pointer on a dial. Examples of such gauges are disclosed in U.S. Pat. Nos. 6,089,086 and 6,041,650. 
     In assembling these gauges, it is necessary to align the tank magnet on the end of the drive shaft with a base position of the float arm so that accurate readings will be transferred to the dial assembly. It is important that when the gears connected to the drive shaft in the support arm and the gears connected to the float arm are attached, they are attached at such a position that the tank magnet is aligned to provide an accurate reading of the level of liquid in the tank. Previously, this alignment was done manually by rotating a round drive shaft until the position of the tank magnet on the drive shaft corresponded to the given location of the float arm. At that point, the drive shaft was staked to the gear, permanently attaching the gear to the drive shaft and ensuring that the alignment of the magnet did not change. Further, the magnet needs to be installed in and secured to a magnet holder or other attachment device prior to the magnet holder being secured to the drive shaft in the support arm. The extra step of assembling the magnet and the magnet holder add extra work in the installation and potentially create an opportunity for inaccuracy in alignment and incorrect readings. Additionally, attaching a separate counterweight piece to the float arm requires an additional assembly step and an accurate determination of size, weight, and positioning so as to provide the proper balance to the float arm. 
     Not surprisingly, there are problems with this assembly. Improper alignment of the magnet in the magnet holder can reduce the accuracy of the gauge. Further, it takes time to align the tank magnet to the corresponding position of the float arm. Even then, the accuracy could be compromised if the drive shaft was inadvertently turned before or while the stake is being inserted. 
     There is a continuing need for a gauge that can be assembled more efficiently and with reduced risk of error in the proper alignment of the magnet. In view of this need, this invention provides for a gauge that can be aligned in a trouble free and accurate way, allowing assembly to be more efficient. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the current invention, a linkage is provided including a pinion gear, a second gear, and a gear housing. The pinion gear, located in the passageway of the first portion of the gear housing, has a pinion gear neck and an engaging means. The second gear, rotatably attached to the second portion of the gear housing, also has engaging means which mesh with the engaging means of the pinion gear. 
     In another aspect of the current invention, a linkage is provided comprising a pinion gear, a second gear and a gear housing. In this aspect of the invention, the pinion gear has a pinion gear neck, pinion gear teeth, and a pinion gear nose. The first portion of the gear housing has a passageway for insertion of the pinion gear neck as well as an appendage, such as a support arm. The second portion of the gear housing has a slot to allow the pinion gear teeth unencumbered rotation. The second portion of the gear housing also has a notch for the pinion gear nose to rotate freely. The second gear is rotatably attached to the second portion of the gear housing and the engaging means of the second gear mesh with the teeth of the pinion gear. 
     In yet another aspect of the current invention, an apparatus for use with a liquid level gauge is provided. The apparatus comprises a pinion gear, a second gear, and a gear housing. The pinion gear neck defines a shaped passageway to accommodate a similarly shaped drive shaft. The pinion gear neck is inserted into a recess in the passageway in the gear housing. As an additional feature, the neck of the pinion gear could be longer than the recess so the pinion gear is more secure in the gear housing. A bushing could also be inserted into the passageway so as to further stabilize the pinion gear. In a further embodiment, the second gear has a nose that is inserted into a receiving passage of the gear housing as a way to rotatably attach the second gear to the gear housing. An alternative could be for the gear housing to have a nose that is inserted into a passage on the second gear. The second gear could also be adapted for use as part of a pivot arm assembly. 
     In yet another aspect of the current invention, a drive shaft assembly is presented. The drive shaft assembly comprises a drive shaft which has a positioning feature. This positioning feature limits the number of ways the drive shaft can fit into the passageway in the neck of the pinion gear. A magnet holder and a magnet are located on the end of the drive shaft opposite the end that is inserted into the pinion gear neck. 
     In a still further embodiment, a liquid level gauge is provided including a gauge head, a support arm, a gear housing, a drive shaft assembly, a pivot arm assembly, and a tank magnet. The pivot arm assembly is rotatably connected to the gear housing. The gear housing is attached to the lower end of the support arm and the gauge head is connected to the upper end of the support arm. An internal passageway for insertion of the drive shaft is located in the support arm and continues into the lower portion of the gauge head. In a further embodiment, the drive shaft can be of variable length so different length support arms can be utilized. The tank magnet is attached to the upper end of the drive shaft assembly inside the gauge head. Angular motion of the pivot arm relative to the support arm imparts rotational motion to the drive shaft via the gears, and thus to the tank magnet attached to the drive shaft. In a further embodiment, the pivot arm assembly can also include a counterweight arm and a separately attached counterweight positioned at an opposing end and on an opposing side of the pivot from the float arm and float. However, it is conceivable that the counterweight arm itself could act as the counterweight providing proper balance without need for a separately attached counterweight. 
     In yet another aspect of the invention, a single piece magnetic cap having an alignment feature to insure that the tank magnet and the dial magnet are quickly and accurately aligned in a predetermined arrangement. The magnetic cap defines a bore shaped to accept a shaped drive shaft. The magnetic cap further includes an alignment feature corresponding to an alignment feature on the shaped drive shaft. When drive shaft is properly installed within the bore of the magnetic cap, the alignment feature on the drive shaft engages the alignment feature of the magnetic cap thereby preventing rotation of the magnetic cap with respect to the drive shaft and thereby providing the predetermined alignment of the magnetic cap (tank magnet) with respect to the dial magnet. The magnetic cap is preferably molded from a ferritic material, such as ferrite powder, and a durable medium, such as nylon. The single piece magnetic cap can be quickly and inexpensively formed in any desirable shape, size, or configuration and formed to accommodate attachment to any shape or dimension shaft. The engaging portion of the drive shaft could be an engaging edge, a protrusion or a groove which would correspond to an accepting portion within the bore of the magnetic cap. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the invention and its advantages will be apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a preferred embodiment of the liquid level gauge; 
     FIG. 2 a  is a perspective view of the upper portion of the gauge head having a dial assembly; 
     FIG. 2 b  is a side view of the gauge head A portion of the gauge head is broken away to show the internal components; 
     FIG. 3 is a perspective view of a preferred embodiment of the gear housing, pinion gear, bushings, support arm and drive shaft; 
     FIG. 4 is a top view of a preferred embodiment of the pinion gear; 
     FIG. 5 is a perspective view of an alternative drive shaft, which is an extendable length drive shaft; 
     FIG. 6 is a cross-section view of the gear housing with the pinion gear, drive shaft, and alignment bushing in place; 
     FIG. 7 a  is a front view of an alternative gear housing containing a pinion pin; 
     FIG. 7 b  is a cross section of a pinion gear designed to be used with the gear housing in FIG. 7 a;    
     FIG. 7 c  is a front view of an alternative gear housing to receive a pinion gear with no pinion gear nose; 
     FIG. 7 d  is a front view of a preferred embodiment of the gear housing, including a pinion gear nose notch; 
     FIG. 8 is a perspective view of the pivot arm assembly inserted in the gear housing; 
     FIG. 9 a  is a perspective view of the front of the pivot arm assembly; 
     FIG. 9 b  is a perspective view of the back of the pivot arm assembly; 
     FIG. 10 is a perspective view of an alternate way of attaching the second gear to the gear housing; 
     FIG. 11A is a perspective view of one exemplary embodiment of a single piece molded magnetic cap; 
     FIG. 11B is a bottom view of the one exemplary embodiment shown in FIG. 11A; 
     FIG. 11C is a cross-sectional view of the one exemplary embodiment shown in FIG. 11A taken along section line  11 C— 11 C of FIG. 11A; 
     FIG. 11D is a top view of the one exemplary embodiment shown in FIG. 11A; 
     FIG. 12 is an exploded, broken, partial cutaway view of the single piece molded magnetic cap mounted to the gear assembly with alignment feature of FIG. 1; 
     FIG. 13 is a cross-sectional broken view of the single piece molded magnetic cap mounted to a drive shaft of a gear assembly and assembled with an external magnetic dial taken along section line  13 — 13  of FIG. 12; 
     FIG. 14 a  is a side view of one exemplary embodiment of the float arm and counterweight system combination; 
     FIG. 14 b  is another side view of the one exemplary embodiment of the float arm and counterweight system combination shown in FIG. 14 a;    
     FIG. 14 c  is a broken side view of the counterweight portion of the one exemplary embodiment of the float arm and counterweight system combination shown in FIG. 14 a  in an unclasped state; and 
     FIG. 14 d  is a broken side view of the counterweight portion of the one exemplary embodiment of the float arm and counterweight system combination shown in FIG. 14 a  in a clasped state. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings wherein like referenced characters designate like or corresponding parts throughout the several views, a preferred embodiment of the liquid level gauge of the present invention is illustrated along with a preferred embodiment of a molded magnet for use with a liquid level gauge. 
     Referring first to FIG. 1, liquid level gauge  20  comprises a gauge head  30 , having an upper portion  30   a  and a lower portion  30   b . The upper portion  30   a  accepts a dial assembly  32  (see FIG. 2 a ) and the lower portion  30   b  is connected to a first end  43   a  of the support arm  43 . A second end  43   b  of the support arm  43  is connected to a gear housing  50 . There is a drive shaft passageway  44  that extends from the second end  43   b  of the support arm  43 , through the first end  43   a  of the support arm  43  and into the lower portion  30   b  of gauge head  30  (see FIGS. 2 b  and  3 ). A pivot arm assembly  70  is rotatably connected to the second portion  50   b  of gear housing  50 . The pivot arm assembly  70  comprises a second gear  80  and an arm attachment portion  71 . A first end  74   a  of a float arm  74  is attached to the arm attachment portion  71 . A float  76  is attached to a second end  74   b  of the float arm  74  In a preferred embodiment, a counterweight  79  is attached to a second end  78   b  of a counterweight arm  78 . The first end  78   a  of the counterweight arm  78  is attached to the arm attachment portion  71  of the pivot arm assembly  70  It will be appreciated that the float arm  74  can be a single piece, as is known in the art. Also, as is known in the art, counterweights in some designs are not required. Thus, the illustration of a specific design with respect to the float arm is not limiting. 
     As can be seen in FIG. 2 b , there is a drive shaft passageway  44  that extends from the second end  43   b  of the support arm  43 , through the first end  43   a  of the support arm  43  and into the lower portion  30   b  of gauge head  30  (see FIGS. 2 b  and  3 ). A magnet holder  38  is attached to the second end  40   b  of the drive shaft  40 . In a preferred embodiment, the magnet holder  38  is formed integrally with the drive shaft  40 . But, the magnet holder  38  could be attached to the drive shaft  40  by any means known in the art. A tank magnet  36  is placed in the magnet holder  38 . In a preferred embodiment, the tank magnet  36  is a cylindrical magnet, but any type of magnet could be used, such as a donut magnet or a bar magnet. A receiving magnet  34  is located in the gauge head  30 . As the drive shaft  40  rotates, the tank magnet  36  rotates with the drive shaft  40 . The magnetic flux of the tank magnet  36  causes the receiving magnet  34  to rotate, which causes an indicator in the dial assembly  32  to move. In a preferred embodiment, the indicator in the dial assembly  32  is a pointer  33 , as seen in FIG. 2 a.    
     As can be seen in FIG. 3, the gear housing  50  has two portions, the first portion  50   a  and the second portion  50   b . The first portion  50   a  defines a passageway  52  located along the axis  25  shown in FIG.  3 . There is a recess  54  in the passageway  52  for insertion of a pinion gear  65 , more specifically, the pinion gear neck  68 . The pinion gear neck  68  is inserted into the recess  54  of the passageway  52  and the pinion gear teeth  66 , fit into the pinion gear tooth slot  56 . The pinion gear teeth  66  are free to revolve in the pinion gear tooth slot  56 , located in the second portion  50   b  of the gear housing  50 . The pinion gear tooth slot  56  is operatively adjacent to the recess  54 . In a preferred embodiment, the pinion gear  65  includes a pinion gear nose  67 . The pinion gear nose  67  is free to rotate in the pinion gear nose notch  58  located in the second portion  50   b  of the gear housing  50  (see FIG. 7 d ). The pinion gear nose  67  allows for easy assembly and smooth movement of the pinion gear  65 . Alternatively, as shown in FIGS. 7 a  and  7   b , the pinion gear tooth slot  56  could contain a pin  59  protruding from the pinion gear tooth slot  56  and the pinion gear  65  could have a receiving portion  59   a  for this pin. Also, in a preferred embodiment, the pinion gear neck  68  is longer than the recess  54  to further secure the pinion gear  65  in the passageway  52 . 
     In a preferred embodiment, after the pinion gear  65  is inserted into the gear housing  50 , a bushing  46  may be inserted into the passageway  52  for further stabilization of the pinion gear  65 . This bushing  46  is not required but it helps with ensuring vertical alignment of the pinion gear  65 . In a further embodiment of the bushing  46 , the bushing  46  could have an internal ledge  48  for the pinion gear neck  68  to rest upon. 
     The second end  43   b  of the support arm  43  is inserted into passageway  52  in the first portion  50   a  of gear housing  50 . The pinion gear neck  68  defines a pinion gear neck passageway  69  which is shaped to receive a similarly shaped drive shaft  40 . A top view of the pinion gear  65  is shown in FIG.  4 . The shape of the drive shaft  40  (which is a positioning feature) limits the number of ways the drive shaft  40  can be inserted into the pinion gear neck passageway  69 . In a preferred embodiment, the shape of the drive shaft  40  is square but the drive shaft  40  could be any shape which allows it to be rotated by movement of the pinion gear. Preferably, there are an even number of sides. Limiting the number of ways the drive shaft  40  can be positioned in the pinion gear neck passageway  69  is an important aspect of the invention. For example, when the drive shaft  40  is square and the gears and the magnet holder  38  are both at the correct angular position when the square shaft  40  is inserted into the pinion gear neck passageway  69 , the magnet  36  can only be oriented in two positions in the holder  38 . The magnet  36  is magnetized along its cylindrical axis with a north and south pole. This allows the assembler to quickly determine the correct orientation of the magnet  36  in the magnet holder  38  by checking the indication of the dial assembly  32  relative to the position of the float arm  74 . 
     FIG. 5 shows a drive shaft  40  which also includes a second drive shaft  41 . The second drive shaft  41  defines a passageway  42  in which the first end  40   a  of drive shaft  40  fits into. This allows for the drive shaft  40  to be extendable, thus allowing the same materials to be used with different length support arms  43 . 
     FIG. 6 shows a cross-sectional view of the pinion gear  65 , the bushing  46 , the drive shaft  40 , and the support arm  43  inserted into the gear housing  50 . FIGS. 7 a ,  7   c , and  7   d  show alternative gear housings  50 . FIG. 7 a  shows a gear housing  50  with a pinion gear pin  59  to hold the pinion gear  65  in place. FIG. 7 b  shows a cross sectional view of a pinion gear  65  that could be used with the gear housing  50  shown in FIG. 7 a . The pinion gear  65  has a receiving passageway  59   a  to receive the pinion gear pin  59 . FIG. 7 c  shows a gear housing  50  designed for a pinion gear  65  that does not have a pinion gear nose  67 . A preferred embodiment is shown in FIG. 7 d  where the gear housing  50  includes a pinion gear nose notch  58 . 
     As shown in FIG. 8, a pivot arm assembly  70  is rotatably connected to the second portion  50   b  of the gear housing  50 . The pivot arm assembly  70  comprises a second gear  80  and an arm attachment portion  71 . The pivot gear assembly  70  can be rotatably attached to the gear housing  50  in many ways. A preferred embodiment is shown in FIGS. 9 a  and  9   b  where the second gear  80  has a second gear nose  82  that is inserted into the second portion receiving passage  63  (See FIG.  3 ). FIG. 10 shows another alternative where the second gear  80  has a second gear receiving passage  83  that receives a second gear pin  84  which is located on the gear housing  50 . As shown in FIG. 3, a bushing  64  can be inserted in the second portion receiving passage  63  to further secure the pivot arm assembly  70  to the gear housing  50 . Instead of a bushing, a screw or a stake or a pin are just a few examples of alternatives that could be used. 
     When the pivot arm assembly  70 , and hence the second gear  80 , are attached to the gear housing  50 , the engaging means of the second gear  81  mesh with the engaging means of the pinion gear teeth  66 . In a preferred embodiment, the engaging means are gear teeth, but any engaging means known in the art could be used without deviating from the invention. 
     The arm attachment portion  71  of the pivot arm assembly  70  can be used to attach a float arm  74  and a float  76 . The first end  74   a  of the float arm  74  is attached to the arm attachment portion  71  and held in place by at least one fastening member  72 . A few examples of fastening members are stakes, screws, ties, clips, spring clips, pretensioned members, adhesive, as well as any means known in the art. The float  76  is attached to the second end  74   b  of the float arm  74  by any means known in the art. A float of any shape can be used without deviating from the present invention. 
     In a preferred embodiment, a counterweight arm  78  is also utilized. A first end  78   a  of the counterweight arm  78  is attached to the arm attachment portion  71 . A counterweight  79  is attached to a second end  78   b  of the counterweight arm  78 . 
     Referring to FIGS. 1 and 14 a - 14   d , in a second preferred embodiment, the counterweight arm  78  and the float arm  74  of the pivot arm assembly  70  are integrally formed as a single piece arm structure  73  with a counterweight portion  179  at one end  78   b  and a float portion  176  having a float  76  attached at an opposite end  74   b  from the counterweight portion  179 . The single piece float/counterweight arm structure  73  is preferably an elongate shaft having a pivot point  170  which is formed substantially at a position of balance of the counterweight portion  179  and the float portion  176 . The arm structure  73  preferably has a bent portion  171  positioned on the float side of the pivot point  170 . The bent portion  171  is adapted to be secured to the pivot arm assembly  70  of the liquid level gauge  20  by insertion into a similarly bent and shaped arm attachment portion  71  such that the pivot arm assembly  70  pivots about the pivot point  170  as the second gear  80  rotates. However, other designs and shapes of the arm attachment portion  71  of the pivot arm assembly  70  and thereby the corresponding bent portion  171  could be designed to perform the desired securing and pivoting operation. 
     Alternately, referring to FIGS. 14 a - 14   d , the counterweight portion  179  of the structure  73  could include a counterweight arm  78  which is extended in length and having a counterweight portion  179  which is bent back upon itself to provide the additional mass required to act as a counterweight and properly balance the pivot arm assembly  70  thereby eliminating the need for a separately attached counterweight. Hook feature  180  at an end  182  of the counterweight portion  179  allows the bent back portion of the counterweight portion  179  to be clasped back and secured onto itself just prior to installation. This design allows the extended counterweight portion  179  to be more consistent from unit to unit, prevents snagging upon installation, and provides a lead-in feature to ease assembly. While the counterweight portion  179  is shown with only one bend, any number of bends can be formed in any shape, form, or combination thereof, so long as the unit is able to fit through a tank opening. The bends can be formed by any means now know or later developed. 
     When the liquid level gauge  20  is inserted in a tank, the float  76  is partially submerged in the liquid. The float  76  is supported by the buoyant force of the liquid. As the level of the liquid within the tank changes, the float  76  and the float arm  74  can move throughout an arc until the stop surfaces  60 , located on the gear housing  50 , are reached by the stop  62  located on the second gear  80  (see FIGS. 7 a ,  7   c ,  7   d  and  9   b ). The area between the stop surfaces  60  is a keyway  61 , allowing the second gear  80  to move in a predetermined arc, relative to the gear housing  50 . The movement of the float arm  74  causes the second gear  80  of the pivot arm assembly  70  to move. This imparts rotary motion onto the pinion gear  65  which moves with the drive shaft  40 . 
     Rotation of the drive shaft  40  causes corresponding motion of the magnet  36  which is fixed to the second end  40   b  of drive shaft  40  by a magnet holder  38 . The rotation of the magnet  36  causes the magnetic field of the magnet  36  to move, causing a corresponding movement of the receiving magnet  34  and a pointer  33  to indicate the level of liquid in the tank. In a preferred embodiment, the dial assembly  32  includes a pointer  33  to indicate the level of the liquid being measured. Any visual indicator could be used without deviating from this invention. 
     One way to assemble a preferred embodiment of the liquid level gauge  20  is to insert the pinion gear  65  into the pinion recess  54  in the passageway  52  of the upper portion  50   a  of the gear housing  50 . The pinion gear teeth  66  fit into the pinion gear tooth slot  56  and the pinion gear nose  67  rests in the pinion gear nose notch  58 , both located in the second portion  50   b  of the gear housing  50 . Insert the first end  40   a  of the drive shaft  40  into the pinion gear neck passageway  69 . The tank magnet  36  is attached to the second end  40   b  of the drive shaft  40 . For further support of the pinion gear  65 , insert a bushing  46  into passageway  52 . The support arm  43  can be inserted into passageway  52  either before or after the drive shaft  40 . 
     The gauge head  30 , including the dial assembly  32  and the receiving magnet  34 , can be attached to the first end  43   a  of support arm  43  either before or after the pivot arm assembly  70 , including the second gear  80 , is rotatably attached to the second portion  50   b  of the gear housing  50 . 
     When the pivot arm assembly  70  is rotatably attached to the second portion  50   b  of the gear housing  50 , align the tank magnet  36  to one of two possible positions so the reading of the dial assembly  32  corresponds to the position of the float arm  74 . The alignment can be made by rotating the pinion gear  65  which in turn rotates the drive shaft  40 . Depending on when the gauge head  30  is attached to the support arm  43 , the alignment could be made by turning the drive shaft  40  directly. When the position of the float arm  74  corresponds to the reading on the dial assembly  32 , insert a bushing  64  into the back of the second portion  50   b  of the gear housing  50  to secure the second gear  80 , which is on the pivot arm assembly  70 . 
     While a dual-piece tank magnet  36  and magnet holder  38  assembly for use with the gear assembly for a tank liquid level gauge as described above is functional and effective, such a magnet assembly requires numerous steps to properly assemble and install. Further, the entire magnetic assembly must be properly aligned during installation in order to calibrate the tank magnet  36  with the gauge head dial magnet  38  for a correct reading to be measured by the gauge. According to another embodiment illustrated in FIGS. 11A-11D and FIGS. 12 and 13, a magnetic cap with alignment feature for use with a gear assembly is shown. The single piece magnetic cap  200  is adapted to be used with a drive shaft  40  having a shaped cross-section and/or a positioning feature  40   b , such that a magnetic portion  204  of the magnetic cap  200  is automatically properly aligned with the receiving magnet  34 , and the magnetic cap  200  is automatically properly aligned with the drive shaft  40  upon installation. 
     According to the preferred embodiment, the magnetic cap  200  is designed to be attached directly to a drive shaft  40  of a gear assembly for a tank liquid level gauge assembly  20 , such as was illustrated in FIG.  1 . The magnetic cap  200  of this embodiment, is formed as a single piece incorporating a securing portion or body portion  202 , a magnetic portion  204 , and a bearing portion  214 . Preferably, the body portion  202 , the magnetic portion  204 , and the bearing portion  214  are integrally formed as a single unit from a composite or combination of a ferrous material and a sturdy base material. However, other suitable materials may be substituted for the ferrous material. The magnetic portion  204  of the single piece magnetic cap  200  is preferably shaped as a bar or rod having a first end  206  and a second end  208 . The magnetic portion preferably extends perpendicularly to the body portion  202  with the first end  206  and second end  208  each extending equidistantly outward from the body portion  202 . The magnetic portion  204  of the single piece magnetic cap  200  is preferably polarized during formation of the molded magnetic cap such that one of the first end  206  and the second end  208  of the magnetic portion  204  has a positive magnetic charge and the other end has a negative magnetic charge. One skilled in the art would understand that other designs and arrangements could be adapted for use in this device as well For example, the shape of the body portion  202  could be identical to the shape of the magnetic portion  204  such that no visible distinction could be made between the two portions. 
     The body portion  202  of the molded magnetic cap  200  is formed defining a longitudinal bore  210  substantially centrally disposed. The shape of the longitudinal bore  210  is formed to correspond to the shape of a second end  40   b  of a drive shaft  40 , having at least one engaging edge  40   c . According to the preferred embodiment shown in FIGS. 11A-11D, an engaging groove  212  corresponding to the engaging edge  40   c  of the drive shaft  40  is also defined in the body portion  202 . When the drive shaft  40  is inserted into the bore  210 , the engaging edge  40   c  of the drive shaft  40  engages the engaging groove  212  of the body portion  202  preventing the single piece magnetic cap  200  from rotating relative to the drive shaft  40 . Alternately, the engaging edge can be a protrusion (not shown) extending either outward from the drive shaft or outward from the body portion into the bore space (not shown). Preferably, the engaging edge is provided as a result of the shape of the drive shaft, (e.g. as shown in FIGS. 11B and 12, where one of the corners of a multi-sided, e.g. square, rectangular, triangular, or other out of round cross-sectional shaped drive shaft, acts as an engaging edge). In a further alternate arrangement, the engaging edge could instead be a protrusion (not shown) extending from the body portion  202  into the bore space (not shown), and the second end  40   b  of the drive shaft  40  could be provided with a corresponding engaging groove (not shown) to accept the protrusion. In any event, when the protrusion or engaging edge is engaged with the engaging groove, the single piece magnetic cap is prevented from rotating about the drive shaft. Although prevented from rotating about the drive shaft  40 , the magnetic cap  200  can float longitudinally (up and down) on the drive shaft  40 . 
     Regardless of which piece they are on, the engaging edge or protrusion and the corresponding engaging groove described above also act as positioning features. When the engaging edge is positioned within the engaging groove, the magnetic cap (tank magnet)  200  is properly oriented and aligned with respect to the gauge dial magnet  34  of the gauge head  30  when the gauge head is ultimately installed. Preferably, as shown in FIGS. 1 and 12 and discussed above, the shaped (multi-sided) drive shaft  40  has a square or other non-circular cross-section having multiple edges, any of which could be an engaging edge depending on the particular bore configuration or depending on the particular gauge dial magnet used. Preferably, the bore  210  defined in the body portion  202  of the single piece magnetic cap  200  is similarly shaped, sized, and of sufficient depth such that the second end  40   b  of the shaped drive shaft  40  fits securely and easily within the bore  210  of the magnetic cap  200  and such that the engaging edge or edges on the drive shaft engage the engaging groove or grooves in the bore. The ability to secure the single piece magnetic cap  200  to a drive shaft  40  having an engaging edge  40   c  such that the magnetic cap  200  is precisely installed in only one or in only a limited number of orientations with respect to the drive shaft and such that the single piece magnetic cap  200  does not rotate out of alignment with the receiving magnet  34 , greatly increases the precision, accuracy, and reliability of the measurement received from the gauge and greatly reduces time and cost required for proper assembly, alignment, and calibration of the tank magnet  200  with the gauge or receiving magnet  34 . As shown in FIG. 13, the magnetic cap  200  rides within bushing  216  such that a bottom surface  200   a  of the magnetic cap  200  rests against a lip  216   a  projecting outward within a central bore  218  defined in the bushing. Further, as shown in FIGS. 11B and 13, the bearing portion  214 , which projects upward from the magnetic portion  204 , serves as an insulating contact portion of the single piece magnetic cap  200  with the gauge head  30  to prevent the magnetic portion  204  of the magnetic cap from contacting a lower surface of the gauge head and to prevent the magnetic cap from moving upwardly relative to the drive shaft. 
     In the preferred installation of the above described embodiment, the magnetic portion  204  is oriented with respect to the body portion  202  such that when the engaging edge  40   c  of the drive shaft  40  engages the engaging groove  212  of the molded magnetic cap  200 , the magnetic poles of the molded magnetic cap properly align with the magnetic poles of the receiving magnet  34  in a dial assembly. No additional installation steps or adjustments need be made in order to provide an accurate correlation with the receiving magnet  34  on a dial gauge. The single piece structure of the molded magnetic cap  200  is adapted to replace the dual piece tank magnet  36  and the tank magnet holder  38  assembly disclosed in a previous embodiment thereby improving efficiency and accuracy in the installation and calibration process. 
     Preferably, the one piece molded magnetic cap  200  is formed by injection molding a nylon material filled with a ferrite powder. More preferably, the ferrite powder is a moldable or plastic ferrite powder having a particle size and shape small enough to be used as a filler. Most preferably, the ferrite powder is one of strontium ferrite or barium ferrite. However, a rare earth ferrous powder such as NdFeB or SmCo could alternately be used. Preferably, a nylon material is used as the sturdy base material; however, other materials having similar strength, durability, and molding properties could also be used. Preferably, the single piece magnetic cap is formed by an injection molding process, with specific magnetic fields being created in desirable portions of the magnetic portion  204  during the molding process. However it is possible that the single piece magnetic cap could be formed by other methods now known or later developed. 
     There has been described and illustrated herein an embodiment of a single piece molded magnetic cap for use with a gear assembly with alignment feature. While a particular embodiment of the invention has been described, it is not intended that the invention be limited thereto, as it is intended that the invention be a broad in scope as the art will allow and that the specification be read likewise. Thus, while a molded magnetic cap having a particular shape and configuration has been disclosed and illustrated, it will be appreciated by those skilled in the art that the molded magnetic cap can be of other shapes and configurations such that a magnetic portion is formed having a positive magnetic pole and a negative magnetic pole. Likewise, while the bore and the drive shaft have been illustrated and disclosed as being of a generally square shape, it will be appreciated by those skilled in the art that the bore could be formed to fit a drive shaft having another shape which would likewise serve to prevent the molded magnetic cap once installed from rotating on the drive shaft so long as the shape of the bore corresponds to the shape of the drive shaft in such as manner to allow the drive shaft to be secured within the bore of the molded magnetic cap. Further, it is understood that the gear assembly onto which the molded magnetic cap is presented above could be different so long as the drive shaft of the gear assembly is shaped such that the improved molded magnetic cap installs in one step and is prevented from rotating freely about the drive shaft. It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from the spirit and scope as claimed.