Abstract:
A system for actuating an indicator in response to a depth change in a liquid that is confined to a container comprises a housing, a float constrained to vertical movement in response to changes in liquid depth in the container, an actuator connected to the housing and arranged to move in response to vertical movement of the float, and a coupler mechanism mounted between the actuator and the housing and arranged to transfer movement of the actuator to the indicator.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to the measurement of the quantity of liquid in a container, vessel, barrel, drum, or the like. More particularly this invention relates to an improved liquid level measurement device having a float drive mechanism that includes a magnetic coupler arranged to activate an indicator pointer to indicate the liquid level in a container or the like. 
   DESCRIPTION OF PRIOR ART 
   There are many instances in which it is essential or desirable to be able to measure the level of liquid in a container, barrel, or the like, and in that manner determine the volume or quantity of liquid in the container. For example, numerous companies, business, shops, institutions and other organizations either transporting, storing or dispersing of liquid products, find it convenient to introduce chemicals, lubricants and fuels directly from shipping containers, i.e., drums, barrels, into their processes. This saves time and expense of having additional large bulk storage tanks and equipment to transfer the contents of the bulk storage tanks to the smaller containers. Drums are used throughout the world to transport, store, distribute, and dispense a variety of liquid products. For example, manufacturing firms use individual drums or an entire rack or rows of racks in their manufacturing processes. Material handling dealers and suppliers of chemical products package and distribute their liquid products in drums. In addition, farms, construction sites, schools, machine shops, printing firms, military, government, and numerous other organizations find the use of containers a useful way of handing their liquid products requirements. 
   A frequently used device for measuring the liquid contents of drums and or containers is a liquid level detector. There are a number of devices in the market place that serve this purpose. One of these devices is the standard sight gauge consisting of a metal pipe with a glass window to view of the level of liquid. The viewing glass has a gauge registered to the nearest gallon. In addition, the device is equipped with a threaded fitting on one end to fit a standard ¾-inch threaded bunghole and to accommodate a faucet on the other end. The sight gauge devices suffer from a number of deficiencies that make them unsatisfactory for extended-life measuring purposes. For example, the device is not equipped with a pressure relief valve for drum venting purposes and must rely on a separate device to provide this capability. The glass view port is subject to fogging due to condensation and discolorization and lacks the convenience of a large dial for easy, at a glance reading in increments of gallons or liters. Also the external mounting design lends itself to damage through mishandling and breakage. 
   Another device in use in the measurement of drums, small tanks and containers is a self-contained unit with a magnet-equipped float that moves with the liquid level along the unit stem, inside the storage container. A liquid level readout is obtained by simply removing the protective cap at the top of the unit and lifting the calibrated indicator (within the unit) until magnetic interlock with the float is felt. The indicator is then lowered back inside the unit for storage and is protected by the screw cap when not in use. This unit suffers from a number of deficiencies, namely it is cumbersome to use, provides readouts in inches only, does not provide at-a-glance check of drum contents, and is not applicable to stack drum racks, and is restrictive in use in confined storage spaces were the drum must be moved to an open floor space to be used. This unit is not equipped with a built in pressure relief valve capability. 
   The wood dipstick is another method for measurement of container liquid levels but at best gives an approximate measurement of liquid levels. This approach is dependent upon the residual liquid wet-line to indicate the liquid level in the container. The wet line is subjected to “splashing” and evaporation when exposed to air or to the elements, which distorts the accuracy of the measurement, and leads to approximate readings at best The gauge on the typical wood stick is not refined and therefore lacks accuracy and provides approximate measurements at best. The stamped painted gauge on the stick is subject to ware and fads in time. In addition, the wood construction of the stick leads to splintering and breakage over time. 
   Another device used to measure liquid levels within containers is a drum gauge that is confined to upright mounted drums. The device consists of an indicator with a plastic housing with an attached flexible rod, the top of which is affixed with a washer used as a pointer. The indicator is screwed into the drum bunghole for mounting to the drum. The indicator is inscribed with a scale calibrated in gallons, liters and inches. As float moves up or down with changing liquid levels the indicator rod with the attached washer pointer registers against the scale. As in the instance of the sight gauge device, the plastic indicator housing containing the imprinted scale is subject to the corrosive effects of fumes venting from the container into the indicator housing. In addition, the plastic housing is subject to fogging. These two conditions contribute to reduce visibility in viewing the readout of liquid levels and shorten the useful life of the device. In addition; the device tends not to deploy in a full drum condition because when the float and associated rod contact the liquid the unit extends in a horizontal direction and thus contacts the side of the drum making installation difficult and time consuming. 
   SUMMARY OF THE INVENTION 
   The liquid level measurement device according to the invention includes an indicator having a 360° rotational movement for mounting on a drum, a tank or a container for providing a visual reading related to the level of the liquid in the container. The rotational feature of the indicator accommodates the movement of the indicator to permit upright viewing rather than requiring changing the position of the container. The liquid level measurement device has a frame section that is threaded mounted in the container&#39;s bunghole. The indicator is then snapped-on or snapped off the housing and frame section completing the installation. The frame has a buoyant float adapted for floating on the surface of the liquid in the container. In a preferred embodiment the liquid level measurement device has a 270° fractional turn helix as a driver for an attached magnetic coupling, which together with a matching magnetic coupling contained in the indicator comprises a magnetic coupler. The magnetic coupler provides the capability of providing a sealed environment to convey the level of liquid in a container by the use of magnetics, which eliminates the requirements for the conventional shaft, and bearing combination, which prevents a sealed environment. The frame section has two guide bars that engage the float and prevent the float from having a rotational motion instead of the desired linear motion as the float moves in an upward or downward direction on the fractional turn helix. 
   A ball joint connects the housing and frame sections together and allow the frame section to seek the local vertical of the container. The ball joint contains a retainer pin and slot arrangement to prevent a rotational movement between the frame section and the housing section that would otherwise occur with the float movement. A flexible shaft is used in conjunction with the ball joint to accommodate the rotational movement of the frame section. The indicator provides for a snap-on/snap-off feature that facilitates the removal of the indicator from the container to accommodate safety, material-handling, storage, shipping requirements and permit liquid level readings for multiple containers with a single indicator. The use of one indicator to measure multiple container contents also protects against cross contamination between differing liquid products. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front elevation view of an embodiment of the present invention mounted for use on a vertically oriented container; 
       FIG. 2  is a top plan view of the embodiment of the invention of  FIG. 1 ; 
       FIG. 3  is are a side elevation, fragmentary view of the measuring device of  FIG. 1  threadedly mounted an opening in the top of a container of liquid; 
       FIG. 4  is an elevation view of an indicator dial face; 
       FIG. 5  is a front elevation view of the present invention as mounted for use in the vertical mode showing the self-alignment feature of the device in a distorted container, 
       FIG. 6  shows the invention used in a container that is on a surface that is not level; 
       FIG. 7  is a cross-sectional view of the present invention; 
       FIG. 8  is a fragmented view of guide rods and a fractional turn helix seated on a base plate; 
       FIG. 9  is a perspective view showing a float and portions of the guide rods; 
       FIGS. 10-12  a illustrate a ball joint that may be used to connect the frame section to a housing; and 
       FIG. 13  illustrates a magnetic coupling that may be used to transmit rotational movement of the helix to an indicator dial to show liquid depth; and 
       FIGS. 14-15  illustrate features of a vent assembly that may be included in the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning now to the drawings and particularly to  FIG. 1 , a container  20  is depicted for illustrative purposes as being located on a level surface  22  and partially filled with a liquid  24 . A liquid level measurement device  26  according to the invention is mounted to the container  20 . It is a primary purpose of the liquid level measurement device  26  to measure the depth of the liquid  24  from which (knowing the tank geometry) the volume of liquid  24  in the container  20  can be determined. 
   Referring to  FIG. 2 , the container  20  typically has openings  28  and  30  provided in a lid  32  for adding or dispensing liquids. The openings  28  and  30  typically are threaded and have diameters of 0.75 inch and 2 inches respectively. As shown in  FIG. 3 , the liquid level measurement device  26  has a first threaded coupling  34  and a second threaded coupling  36  that may be used to mount the liquid level measurement device  26  in the openings  28  or  30 , respectively. When the coupling  34  is engaged in the 0.75 inch diameter opening  28 , the outer end of the coupling  36  is adjacent the portion of the lid  32  surrounding the opening  28 . When the coupling  36  is engaged in the opening  30 , the coupling  34  extends into the container  20 , and a flange  38  that is connected to the coupling  36  is adjacent the portion of the lid  32  surrounding the opening  30 . 
   The liquid level measurement device  26  according to the invention may be advantageously employed for measuring liquids of great variety in tanks. It is considered within the sprit of this invention to make the measurement device small-sized for uses such as measuring liquid depth in drums, barrels, jumbo, rectangular shop tanks, oval shaped tanks for shop, home heating generators and numerous other applications. Therefore, for the convenience of description of the invention, it is described in connection with measuring the depth (and thus amount) of liquids stored and dispensed in such containers. 
   The liquid level measurement device  26  is an elongated structure having an overall length such that it extends to a location near the bottom end  40  of the container  20 . Differing containers have varying lengths, and to conform to this requirement the frame section along with the fractional turn helix and the guide bars can be modified to conform to differing dimensions of the containers involved. As shown in  FIGS. 1 and 7 , the liquid level measurement device  26  comprises an indicator  42 , a housing  44  and a frame section  46 . The frame section  46  is pivotally suspended from the housing  44 . The frame section  46  includes a pair of guide rods  48  and  50 , a fractional turn helix  52 , a ball joint  82  and a float  54 . 
   The frame  46  includes an upper plate  56  and a baseplate  58  with the guide bars  48  and  50  arranged to extend between them. The fractional turn helix  52  has a bottom projection  60  that extends into a recess  62  in the baseplate  58 . The upper end of the fractional turn helix  52  is connected to a flexible shaft  64  that is in turn connected to a rod  65 . The fractional turn helix  52  is suspended between the guide bars  48  and  50 . The lower ends of the guide bars  48  and  50  are fastened to outer edge portions  66  and  68  of the baseplate  58 . The upper ends of the guide bars  48  and  50  are connected to the upper plate  56 . The fractional turn helix  52  is suspended centrally between the guide bars  48  and  50  with the upper end of the fractional turn helix  52  extending through a passage  70  in the upper plate  56 . 
   The float  54  preferably is formed as a cylinder and preferably has a rectangular central passage  72  extending therethrough. A pair of circular passages  74  and  76  is formed near opposite side portions of the float  54 . The float  54  is mounted in the frame so that the guide bars  48  and  50  extend through the passages  74  and  76  and the fractional turn helix  52  extends through the passage  72 . The guide bars  48  and  50  are parallel so that the float  54  is constrained to linear movement up and down as the liquid level changes in the container. The fractional turn helix  52  can be rotated about the vertical axis. As the height of the float  54  changes, the rectangular cross section fractional turn helix  52  engages the surfaces of the rectangular central passage, which produces a torque on the fractional turn helix  52 . The liquid level measurement device  26  is calibrated so that the angular orientation of the fractional turn helix  52  as it rotates about the vertical axis indicates the liquid level in the container  20 . 
   The upper plate  56  is connected to a spacer  80 , which is connected to a ball joint assembly  82 . The spacer  80  and the ball joint assembly  82  have longitudinal passages  84  and  86 , respectively, arranged so that the flexible shaft  64  passes therethrough. The ball joint assembly  82  has a threaded coupling  88  that is connected to the housing  44  to support the weight of the guide rods  48  and  50  and the helix  52 . 
   The ball joint assembly  82  includes a ball member  90  pivotally mounted in a slotted and partially threaded housing  92 . As shown in  FIGS. 7 ,  9  and  10 , the ball member  90  includes a slot  94 . A pin  96  extends from the housing  92  into the slot  94  to prevent the ball joint assembly from rotating about its longitudinal axis while allowing it to pivot so that the guide rods  48  and  50  always are suspended in a vertical orientation inside the container  20 . 
   As the device  26  is inserted and secured to the container  20  by threading into the selected container hole, the liquid level measurement device  26 , as a pendulous system, self aligns seeking the local vertical to adjust for any small angle in any two-plane container orientation (FIGS.  5  and  6 ). As the frame  46  is inserted into the container  20  the float  54  tends to seek the level of the liquid  24  contained therein. 
   The rod  65  is connected to a first magnetic assembly  98  to support it in a cavity  100  in the housing  44 . A second magnetic assembly  102  is mounted in the cavity  100 A by a rod  104  that is rotatably mounted in the housing  44 . As shown in  FIG. 13 , the first magnetic assembly  98  preferably comprises a pair of magnets  106  and  108  mounted in a dielectric disk  110  with opposite poles being adjacent an end of the disk  110 . The second magnetic assembly  102  preferably comprises a pair of magnets  114  and  116  mounted in a dielectric disk  118  with opposite poles being adjacent an end  120 . The magnetic assemblies  98  and  102  are arranged so that magnets of opposite polarity face one another. Because the magnetic poles of opposite polarity attract one another, they automatically align and remain in alignment as the helix  52  and the rod  65  rotate in response to changes in the liquid level. 
   A first bevel gear  122  is affixed to an upper end of the rod  124 . A second bevel gear  126  is engaged with the first bevel gear  122  and arranged to rotate a pointer  128  in response to rotation of the rod  124 . 
   The magnet assemblies  98  and  102  are arranged so that they are attracted to one another such that rotation of the first magnet assembly  98  causes rotation of the second magnet assembly  102 . 
   The employment of the magnetic coupler approach makes possible another embodiment of the present invention. As shown in  FIG. 7 , the indicator  42  is arranged to be snap-fit on the housing  46 . A spring  130  is mounted in a cavity  132  in the housing  44 . A plunger  134  is fastened to the spring  130 . The housing  44  has a base that includes a circumferential groove arranged to receive the plunger when sufficient force is used to urge the indicator  42  toward the housing  44 . The snap-fit mounting arrangement allows the indicator  42  to turn 360°, making possible the repositioning of the indicator  42  rather than the cumbersome movement of a heavy container. The indicator  42  can be easily removed from one container and attached to another. This embodiment of the invention permits multiple measurements of similar configured containers with a single indicator in addition to protecting the indicator from damage through miss handling and damage from material handling equipment. In the event that the container is positioned in a protective cabinet or the like, the indicator can be removed for clearance purposes. 
   When the indicator  42  is removed, from the housing  44 , the first magnetic  98  assembly remains in the position it was in while the indicator was attached if no liquid is removed from the container  20 . If the liquid is removed, magnetic assembly  98  will so indicate. The angular position of the first magnetic assembly  98  is a function only of the liquid level. When the indicator  42  is reattached to the housing  46 , the second magnetic assembly returns to its previous or changed angular position to indicate the liquid level. 
   In addition, this use of a magnetic coupler provides a sealed environment between the contents of the container and the outer environment and eliminates the need for conventional shafts and prevents the associated leakage of fumes and liquid that can contaminate instrument components and the environment. The magnetic coupler feature also provides for the means for the snap on snap off feature of the indicator that permits the removal of the indicator from the device with out the need to remove the entire device from the container or the like. This feature also accommodates the multiple readings of numerous containers with a single indicator and hence avoiding contamination of liquid products. Another feature of the device is the use of the flexible spring shaft  65  in conjunction with ball joint assembly  82  to accommodate the free axial movement of the frame section  46  of the device and assures a continual alignment with the vertical. 
   The invention includes a venting system  136  shown in FIG.  7 . The housing  44  includes a passage  137  that allows pressurized gasses to flow between the housing  44  and the indicator assembly. The indicator assembly  42  includes an airflow valve  138 , a plunger pin  140  and a locator pin  142 . When the locator pin  142  is seated in a corresponding hole in the housing  44 , the plunger pin  140  seats in a hole in the housing  44 . As the connection of the indicator assembly  42  and the housing  44  occurs, the plunger pin  140  compresses a spring  150  with its associated ball seal to open a vent hole  148 . The venting action passes through a vent passage  152  to a pressure release assembly  154  that includes a piston  156 , a spring  158  and a cap  160 . As the venting pressure impacts the piston  156 , the spring  158  contracts to force the piston  156  to an open position, which relieves the pressure in the container  20 . The vent system  136  may be manually opened by pulling outward on the cap  160  and then turning it to lock it in its open position. 
   Although the present invention described in connection with a preferred embodiment it is to be understood that modifications within the scope of the invention may occur to those skilled in the appertaining art.