Abstract:
A liquid level gauge includes a mounting head and a sensor assembly with a support tube that extends into a tank from the mounting head. A gauge rod is positioned in a support tube for selective movement out of the tank for visually determining the liquid level. A magnet is associated with the gauge rod and couples with a magnet associated with a float that slides along the support tube so that the gauge rod and float are selectively coupled together. A pair of spaced bearings are mechanically retained within the float structure with retaining rings and spaced projections located on opposite sides of each bearing. In this manner, the float slides more freely along the support tube, allowing more accurate readings while minimizing failure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/918,662 filed on Dec. 20, 2013, the disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to liquid level gauges, and more particularly to a liquid level gauge having a magnetic float that moves in response to a change in liquid level. 
         [0003]    U.S. Pat. No. 3,815,416 to Dean et al. discloses a prior art apparatus for indicating the level of liquid in a tank car. The apparatus includes a float encircling a tube extending down into the tank. The float is magnetically coupled to a gauging rod which bears indicia representing the level of liquid in the tank. The gauging rod is normally retained inside the tube via an upper cover removably secured to the tank opening. When it is desirous to check the liquid level within the tank, the cover is removed and the gauge rod is manually raised until it magnetically couples with the float. Depending on the liquid level, the length of the gauge rod extending out of the tank will change. The user can ascertain the level in the tank by the visible indicia located on the rod. The apparatus also has a mechanism for automatically visually and audibly alerting the user when the level has reached a particular level, such as a near full condition when the tank is being filled. This mechanism includes a tower and a series of reed switches mounted on the tank above the rod opening. A magnet attached to the top of the rod moves past the reed switches to serially actuate them as the tank is filled. 
         [0004]    Although such systems are adequate for their intended purpose, the sliding connection between the float and support tube can become worn, resulting in vibration or rattling between the support tube and the float when movement of the fluid in the tank may occur, such as during transportation of the tank and/or varying the fill level of the tank during use. Such interaction not only causes undesirable noise, but can lead to inaccurate measurement results and mechanical failure of the liquid level apparatus. It would therefore be desirable to overcome one or more disadvantages associated with prior art liquid level devices. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with one aspect of the invention, a liquid level gauge for determining the level of liquid within a container includes a mounting head adapted for connection to the container, and a sensor assembly adapted to extend into the container from the mounting head. The sensor assembly comprises a support tube extending downwardly from the mounting head; a gauge rod positioned in the support tube for selective movement out of the tank for visually determining the liquid level; a first magnet connected to the gauge rod; and a float assembly that slides along the support tube. The float assembly includes a float surrounding the support tube for sliding therealong in response to a change in liquid level; a second magnet for selective coupling to the first magnet so that the gauge rod and float are selectively coupled together; at least a first bearing positioned in the float and surrounding the support tube for sliding movement of the float therealong in response to change in liquid level; and at least a first support ring positioned at least adjacent to the first bearing to prevent the first bearing from becoming dislodged from the float. 
         [0006]    In accordance with a further aspect of the invention, a float assembly for use in a liquid level gauge having a vertical support tube that extends into a tank for measuring a level of liquid therein comprises a float adapted to surround the vertical support tube for sliding movement therealong in response to a change in liquid level within the tank, the float having a central axis that is adapted to be coincident with a longitudinal axis of the vertical support tube; a central tube extending through the float and being coincident with the central axis thereof, the central tube having a wall with an outer surface and an inner surface defining a central bore that is adapted to surround the support tube; first and second annular projections formed at first and second locations on the central tube, the annular projections extending generally radially inwardly from an inner surface of the central bore; first and second support rings located within the central bore and retained between the annular projections; and a first bearing having a first opening for slidably receiving the support tube and being positioned in the central bore between the first and second support rings to thereby retain the first bearing between the first and second annular projections. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The following detailed description of the preferred embodiments of the present invention will be best understood when considered in conjunction with the accompanying drawings, wherein like designations denote like elements throughout the drawings, and wherein: 
           [0008]      FIG. 1  is a sectional side view of a liquid level gauge in accordance with one exemplary embodiment of the present invention mounted in a tanker car; 
           [0009]      FIG. 2  is an isometric view of a float assembly for use with the liquid level gauge of  FIG. 1 ; 
           [0010]      FIG. 3  is an isometric sectional view of the float assembly taken along line  3 - 3  of  FIG. 2 ; 
           [0011]      FIG. 4  is an isometric exploded view of the float assembly in accordance with the invention; 
           [0012]      FIG. 5  is an isometric exploded view of a portion of a float assembly in accordance with a further embodiment of the invention; 
           [0013]      FIG. 6  is an enlarged sectional view of the complete float assembly of the  FIG. 5  embodiment; 
           [0014]      FIG. 7  is an isometric view of a float support system in accordance with the invention; and 
           [0015]      FIG. 8  is an isometric view of a dampening portion of the float support system of  FIG. 7 . 
       
    
    
       [0016]    It is noted that the drawings are intended to depict only exemplary embodiments of the invention and therefore should not be considered as limiting the scope thereof. It is further noted that the drawings are not necessarily to scale. The invention will now be described in greater detail with reference to the accompanying drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring now to the drawings, and to  FIG. 1  in particular, a liquid level gauge  10  in accordance with an exemplary embodiment of the present invention is illustrated. The liquid level gauge  10  preferably extends into a tank  12 , which may be associated with railroad tanker cars, semi-trailer tankers, large stationary storage tanks, or any other container for holding and/or transporting a liquid  14  where it is desirous to determine the level of liquid within the tank. 
         [0018]    The gauge  10  preferably includes a mounting head assembly  16  and an elongate sensing probe assembly  18  connected to the mounting head assembly  16  and extending downwardly therefrom into the tank  12 . 
         [0019]    The sensing probe assembly  18  preferably senses liquid level in a linear direction and, in accordance with one preferred embodiment of the invention, includes an outer support tube  20  with an upper end  22  that extends into the mounting head assembly  16  and a lower end  24  that terminates at a support member  26  located at or near the bottom of the tank  12 . A magnetic float assembly  28  is preferably spherically-shaped and includes a central tube  30  with a central bore  31  that is sized to receive the support tube  20  so that the float slides freely therealong. An inner gauge rod  32  is located within the outer support tube  20  and has an upper end  34  that also extends through the mounting head assembly  16  and a lower end  36  fitted with a magnet  35 . The support member  26  serves to both seal the support tube  20  from the contents of the tank  12  and provide a lower stop for the gauge rod  32  when the gauge rod is in the rest position. The outer support tube  18  and inner sensor tube  30  are preferably constructed of non-magnetic materials such as plastic, aluminum, composites, and so on. However, it will be understood that any suitable material can be used as long as the components do not interfere with selective magnetic coupling between the gauge rod  32  and the magnetic float assembly  28 . 
         [0020]    As shown in  FIG. 1 , the support member  26  can include a shank portion  25  that extends upwardly from a head portion  27  for sealing the lower end  24  of the outer support tube  20  against the ingress of the liquid  14  to be measured. 
         [0021]    If desired, an electronic sensor board (not shown) can be provided for electronically determining liquid level within the tank  12 , as described in copending provisional application No. 61/876,078 filed on Sep. 10, 2013 (now U.S. application Ser. No. 14/482,573 filed on Sep. 10, 2014, the disclosures of which are hereby incorporated by reference. 
         [0022]    Referring now to  FIGS. 2-4 , the float assembly  28  preferably includes a spherical body  44  with an upper hemispherically-shaped float portion  46  connected to a lower hemispherically-shaped float portion  48  through well-known connection means such as soldering, welding, adhesive bonding, crimping, mechanical fastening, and so on. An opening  50  is formed in the upper float portion  46  coincident with a central axis  54  thereof ( FIG. 4 ). Likewise, an opening  52  is formed in the lower float portion  48  coincident with the axis  54 . The central tube  30  has an upper end  56  connected to the upper float portion  46  coaxially with the opening  50 , and a lower end  58  connected to the lower float portion  48  coaxially with the opening  52  through well-known connection means so that the inner space  65  ( FIG. 3 ) of the spherical body  44  is hermetically sealed to prevent the unwanted ingress of fluid into the inner space. An upper annular bearing  60  is received and secured within the upper end  56  of the tube  30 . Likewise, a lower annular bearing  62  is received and secured within the lower end  58  of the tube  30 . Preferably, the central tube  30  comprises a wall  61  having a thin, circular cross section with an outer surface  63  and an inner surface  67  that defines the central bore  31 . An upper set or pair of annular projections  64 ,  66  are formed in an upper portion of the wall  61  and a lower set or pair of annular projections  68 ,  70  are formed in a lower portion of the wall  61  of the central tuber  30 . The annular projections extend radially inwardly into the bore  31  and are formed by creating annular grooves  64 ,  66 ,  68 , and  70  on the outer surface  63  of the wall  61  through roll-forming, vacuum-forming, or other known techniques. Due to the relatively thin dimension of the wall  61 , the wall is deformed inwardly to form outside annular grooves and inside annular projections, as best shown in  FIGS. 3 and 6 . 
         [0023]    In order to install the upper bearing  60 , and as best shown in  FIGS. 3 and 4 , the groove/projection or crimp  64  is formed in the upper portion of the central tube  30 . The inner diameter of the first upper annular projection  64  is less than the outer diameter of the upper annular bearing  60  such that when the bearing is inserted in the tube, it is supported by the first upper annular projection  64 . A second upper annular projection or crimp  66  is then formed in the tube  30  above the upper bearing  60  to thereby secure the upper bearing within the upper portion of the tube. Preferably, the first and second upper annular projections are similar in shape and dimension. However, it will be understood that the shape and/or dimension of the annular projections can vary without departing from the spirit and scope of the invention. 
         [0024]    Likewise, in order to install the lower bearing  62  in the tube  30 , a first lower annular groove/projection or crimp  68  is formed in the lower portion of the central tube  30 . The inner diameter of the first lower annular projection  68  is less than the outer diameter of the lower annular bearing  62  such that when the bearing is inserted in the tube, it is supported by the first lower annular projection  68 . A second lower annular groove/projection or crimp  70  is then formed in the tube  30  above the lower bearing  62  to thereby secure the lower bearing within the lower portion of the tube. 
         [0025]    The upper and lower bearings  60 ,  62  are preferably constructed of a low friction material, such as nylon, brass, PTFE, and so on, with a central bore  72  thereof surrounding the outer support tube  20  ( FIG. 1 ) and in sliding contact with, or close proximity to, the outer support tube. When softer materials are used for the bearings, such as nylon, PTFE, and so on, each bearing is preferably sandwiched between support rings  75  (shown best in  FIG. 4 ). The support rings  75  are preferably constructed of a harder material, such as metal, in order to prevent the bearings from becoming dislodged. In accordance with a preferred embodiment of the invention, the support rings are constructed of a material with spring-type properties that would allow the rings to deflect inward during assembly and then spring back and seat between the annular bearing projections. One advantage of using PTFE or other softer materials for the bearings, is that they can be pressed past one or more of the annular projections or crimps  64 ,  66 ,  68 , and/or  70 , so that all of the projections may be formed at one time with the bearings and support rings being installed after formation of the projections. 
         [0026]    A magnet assembly  74  is connected to the lower end of the central tube  30  and includes a lower cup-shaped support  76 , an annular magnet  78  received within the cup-shaped support  76 , and an upper cover  80  positioned over the magnet  78  within the support  76 . Tabs  82  are located around the perimeter of the support  76  and are bent inwardly over the upper cover  80  to thereby secure the magnet within the support  76 . The support  76  is in turn connected to the lower end of the central tube  30  by well-known connection means, such as soldering, welding, adhesive bonding, mechanical fastening, and so on. The magnet  78  can be magnetically coupled with the magnet  35  attached to the gauge rod  32  so that, when the cap  84  of the head assembly  16  is removed, the gauge rod  32  can be manually pulled upwardly until it is magnetically coupled with the float. The gauge rod  32  has a scale (not shown) so that the level of the liquid within the tank  12  can be visually observed in a well-known manner. 
         [0027]    The magnet is preferably magnetized on its outer and inner faces such that magnetic flux lines of force are directed perpendicular with respect to the longitudinal extent of the magnet and toward the center of the central tube  30  of the float  28 . However, it will be understood that the polarity of the magnets can be reversed and/or the direction of the magnetic flux can be oriented differently without departing from the spirit and scope of the invention. 
         [0028]    The components of the float assembly  28  are preferably constructed of rigid materials, such as stainless steel, aluminum or other metals, but can be constructed of other materials, such as closed-cell nitrile material, rubber, plastics, and so on, without departing from the spirit and scope of the invention. It will be understood that the shapes of the float, support tube  20 , central tube  30 , the mounting head assembly, and so on, are given by way of example only, as other suitable shapes, such as square, triangular, and so on, can be used without departing from the spirit and scope of the invention. 
         [0029]    As shown in  FIG. 1 , the mounting head assembly  16  preferably includes a cover  86  that is removably fastened to a flange  88  of a manway section  90  of the tank  12  via a plurality of bolts  92  and associated nuts  94  as shown, or through other connection means. The end cap  84  is positioned over the cover  86  and is removably connected to the outer support tube  20 . The end cap  84  has a central bore  96  that is of sufficient diameter to receive the upper end  22  of the support tube  20 . 
         [0030]    In use, when the end cap  84  is installed on the cover  86  as shown in  FIG. 1 , the gauge rod  32  is in the rest position, where the rod may or may not be magnetically coupled to the float assembly  28 . In this position, the float is free to travel along the length of the support tube  20 , but the gauge rod  32  is restrained from movement. When it is desirous to take a manual measurement of the level of liquid in the tank  12 , such as when emptying or filling the tank, the end cap  84  is removed and the gauge rod  32  is pulled out of the tank until it is magnetically coupled with the float assembly  28 . The user can then visually observe level markings (not shown) located along the length of the gauge rod to determine the liquid level within the tank  12 . The gauge rod  32  can then be magnetically decoupled from the float assembly  28  and pushed back into the support tube  20  and the end cap  84  replaced. 
         [0031]    Referring now to  FIGS. 5 and 6 , a float assembly  100  in accordance with a further embodiment of the invention is illustrated. The float assembly  100  is similar in construction to the float assembly  28  previously described, with the exception that a pair of split retaining rings  102 ,  104  are located on opposite sides of the upper annular bearing  60  and a pair of split retaining rings  106 ,  108  are located on opposite sides of the lower annular bearing  62 . The split retaining rings  102 ,  104 ,  106 , and  108  are preferably similar in construction and each includes an annular body  110  and a gap  112  to form opposing ends or fingers  114  and  116 . The annular body  110  is preferably flat and the finger  116  narrows towards the gap  112 . However, it will be understood that the annular body  110  can be of any suitable shape, and that both fingers can narrow toward the gap, or may have the same width as the annular body, or can be greater in width or of any other suitable shape without departing from the spirit and scope of the invention. Each retaining ring is constructed of a spring-like material, such as spring steel or other suitable materials, laminates, and so on, so that the ends of each retaining ring can move toward each other when a radial compression force is applied and away from each other when the compression force is removed or at least partially removed. In this manner, the retaining rings can contract in diameter during installation and removal in order to fit within the inner diameter of the central tube  30  and clear the annular projections  64 ,  66 ,  68 , and  70 . Likewise, once the retaining rings clear the annular projections during installation, the compression force can be released so that they expand against the inner surface  67  of the central tube, thereby holding the bearings in place between the pairs of annular projections. 
         [0032]    Referring now to  FIGS. 7 and 8 , an upper dampener assembly  120  is mounted on the support tube  20  at an upper end thereof and a lower dampener assembly  122  is mounted on the support tube  20  at a lower end thereof. The dampener assemblies  120 ,  122  protect the float assembly  28  or  100  from sudden impact that may occur during tank filling or transportation of a full or empty tank, as well as the potential of the float assembly to slide off the support tube during emptying or filling of the tank. It will be understood that the particular location or height of the upper and lower dampener assemblies with respect to the support tube  20  can greatly vary, and that one or both dampener assemblies can be eliminated, depending on the type of tank the liquid level gauge is installed in. 
         [0033]    Each dampener assembly is similar in construction and includes a collar  124  slidably mounted on the support tube  20 , a first spring seat  126  mounted at a fixed location with respect to the support tube  20 , a second spring seat  25  slidably mounted on the support tube  20  and located within the collar  124 , and a compression spring  128  sandwiched between the first and second spring seats  126  and  125 , respectively. slidable collar and the fixed spring seat. The compression spring  128  is preferably connected to the spring seat  126  through welding or other connection means. The collar  124  can also be fixedly connected to the spring  128  through welding or other connecting means. However, it is preferred that the spring is free-floating between the first and second spring seats to prevent damage and possible breakage of the spring and other components of the dampener assembly. This is an advantage over prior art welded components since the spring is subjected to undesired stress during operation and can break. 
         [0034]    The collar  124  is generally annular in shape with a first wall  130  that contacts the second spring seat  125  which in turn contacts the spring  128  on one side thereof. The other side of the first wall  130  faces the float assembly  28  for contact therewith. A second wall  132  extends axially away from the first wall to form a cup-shaped interior for receiving the second spring seat  125  and one end of the spring  128 . Likewise, the first and second spring seats  126 ,  125  are annular in shape with a first wall  134  that contacts the spring  128  and a second wall  136  that extends axially therefrom to form a cup-shaped interior for receiving the opposite ends of the spring  128 . 
         [0035]    It will be understood that the term “preferably” as used throughout the specification refers to one or more exemplary embodiments of the invention and therefore is not to be interpreted in any limiting sense. It will be further understood that the term “connect” and its derivatives refers to two or more parts capable of being attached together either directly or indirectly through one or more intermediate members. In addition, terms of orientation and/or position as may be used throughout the specification denote relative, rather than absolute, orientations and/or positions. 
         [0036]    It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. By way of example, the mounting head is not limited to the flange-type arrangement as shown and described but can be formed with threads or other known mounting means for connecting the gauge to the container without departing from the spirit and scope of the invention. It will be understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.