Abstract:
A float-type liquid level gauge assembly  20  is provided for measuring the level of a liquid, such as liquefied petroleum gases, in a tank. The liquid level gauge  20  includes a gear housing  50  which provides for an efficient way to couple gears together as well as to accurately assemble and align the components of a liquid level gauge. The liquid level gauge  20  includes a movable pivot arm assembly  70  supporting a float arm assembly  74.  A gear on the pivot arm assembly  70  is coupled with a pinion gear  65  located in the gear housing  50.  The pinion gear  65  has a shaped passageway  69  which accepts a similarly shaped drive shaft  40  which has a magnet  36  at one end. The magnet  36  extends into a passageway  44  on the lower side  30   b  of a gauge head  30  so as to be magnetically coupled to a level indicating dial assembly  32  provided on the upper side  30   a  of the gauge head  30.  The shaped drive shaft  40  only allows for a limited number of ways the drive shaft  40  will fit into the pinion gear passageway  69,  thus allowing efficient alignment of the magnet  36  with the level indicating dial  32.

Description:
TECHNICAL FIELD OF THE INVENTION  
         [0001]    This invention relates 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.  
         BACKGROUND OF THE INVENTION  
         [0002]    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.  
           [0003]    A typical gauge of this type utilizes a pivoting float arm which 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, which is 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.  
           [0004]    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.  
           [0005]    Not surprisingly, there are problems with this assembly. 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 inserted.  
           [0006]    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  
         [0007]    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.  
           [0008]    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.  
           [0009]    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.  
           [0010]    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.  
           [0011]    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 counterweight.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    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:  
         [0013]    [0013]FIG. 1 is a perspective view of a preferred embodiment of the liquid level gauge;  
         [0014]    [0014]FIG. 2 a  is a perspective view of the upper portion of the gauge head having a dial assembly;  
         [0015]    [0015]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;  
         [0016]    [0016]FIG. 3 is a perspective view of a preferred embodiment of the gear housing, pinion gear, bushings, support arm and drive shaft;  
         [0017]    [0017]FIG. 4 is a top view of a preferred embodiment of the pinion gear;  
         [0018]    [0018]FIG. 5 is a perspective view of an alternative drive shaft, which is an extendable length drive shaft;  
         [0019]    [0019]FIG. 6 is a cross-section view of the gear housing with the pinion gear, drive shaft, and alignment bushing in place;  
         [0020]    [0020]FIG. 7 a  is a front view of an alternative gear housing containing a pinion pin;  
         [0021]    [0021]FIG. 7 b  is a cross section of a pinion gear designed to be used with the gear housing in FIG. 7 a;    
         [0022]    [0022]FIG. 7 c  is a front view of an alternative gear housing to receive a pinion gear with no pinion gear nose;  
         [0023]    [0023]FIG. 7 d  is a front view of a preferred embodiment of the gear housing, including a pinion gear nose notch;  
         [0024]    [0024]FIG. 8 is a perspective view of the pivot arm assembly inserted in the gear housing;  
         [0025]    [0025]FIG. 9 a  is a perspective view of the front of the pivot arm assembly;  
         [0026]    [0026]FIG. 9 b  is a perspective view of the back of the pivot arm assembly; and  
         [0027]    [0027]FIG. 10 is a perspective view of an alternate way of attaching the second gear to the gear housing.  
     
    
     DETAILED DESCRIPTION  
       [0028]    Referring now to the drawings wherein like referenced characters designate like or corresponding parts throughout several views, a preferred embodiment of the liquid level gauge of the present invention is illustrated.  
         [0029]    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.  
         [0030]    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.    
         [0031]    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 .  
         [0032]    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.  
         [0033]    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 .  
         [0034]    [0034]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 .  
         [0035]    [0035]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 .  
         [0036]    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.  
         [0037]    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.  
         [0038]    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, 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 . A float of any shape can be used without deviating from the present invention. In a preferred embodiment, a counterweight arm  78  is also attached. The first end  78   a  of the counterweight arm  78  is attached to the arm attachment portion  71 . A counterweight  79  is attached to the second end  78   b  of the counterweight arm  78 . The float arm and the counterweight are not essential to the invention.  
         [0039]    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 .  
         [0040]    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.  
         [0041]    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 .  
         [0042]    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 .  
         [0043]    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 .