Abstract:
An anti-slosh device for attenuating oscillations of liquids in tanks caused by movement of vehicles in which the tank is located comprises an elongated flat, rectangularly, shaped, uniform thickness strip of a liquid impervious material such as polyethylene or polycarbonate which is formed into a string of arcuately curved loops. One embodiment of the device has located at opposite ends thereof spirally-shaped, quasi-helical end loops which form a figure-8 shape, and a center loop disposed obliquely between the end loops. A two-loop version of the device has two end loops but no center loop. The anti-slosh device is used to reduce the duration of undesirable oscillations induced in a liquid in a tank by placing a plurality of the devices in the interior of a tank, as by inserting a plurality of the devices through a fill tube or other access port of the tank. Non-parallel surfaces of the device function as baffles, converting large scale linear motions of liquid in a tank to small scale, energy-dissipating vortices, thus reducing the duration and amplitude of oscillations of liquid in the tank.

Description:
BACKGROUND OF THE INVENTION 
   A. Field of the Invention 
   The present invention relates to container tanks used in vehicles such as cars, trucks, planes and boats to contain liquids such as water or fuel, which are to be consumed in transit or delivered by the vehicle. More particularly, the invention relates to devices for decreasing the amplitude and duration of fluid oscillations, i.e., sloshings, of a liquid in a tank, which are induced in response to movements of a vehicle in which the tank is mounted. 
   B. Description of Background Art 
   Oscillations of a liquid such as water or fuel contained in a tank mounted in a vehicle such as a car, truck, plane or boat are induced in response to inertial accelerations of the vehicle. The natural or resonant frequency of such oscillations is an inverse function of the internal dimensions of the tank and depends to a lesser extent, upon properties of the liquid such as density and viscosity. Liquid oscillations can produce sloshing sounds which are annoying to people close to a tank, as for example, in smaller boats and personal watercraft. Moreover, in some cases, large values of linear momentum can be transferred to a tank and tank support structure as a result of oscillations of liquid contents of the tank. Such oscillations, or sloshing, can result in fatigue wear and ultimate failure of the tank mounts, and support structure. Even worse, in extreme cases, oscillations of liquid in a vehicle-mounted tank can become so large as to result in loss of steering control and even roll-over of the vehicle. Accordingly, it would be desirable to provide an effective means for damping or attenuating oscillations of fluids within tanks. One method for limiting large scale oscillations of a liquid in a tank consists of partitioning the interior of the tank into a plurality of individual cells which communicate with one another, such as by providing a plurality of baffle members within the tank interior. With this arrangement, energy of oscillating liquid in the tank is dissipated by frictional contact of the liquid with edges of intruding baffle members and/or passageways provided through the baffle members. 
   Another method for damping fluid oscillations in a tank consists of inserting into the tank through a fill port a plurality of small, hollow spheroidal shell-shaped objects made of a fluid resistant polymer. The spheroidal shells have four relatively large holes formed therethrough, including a first pair of diametrically opposed holes centered on North and South poles of the sphere, and a second pair of diametrically opposed holes centered on equatorial antipodes of the spherical shell. The devices apparently work by converting linear momentum of oscillating fluid within the tank to angular momentum of the devices and vortices within the fluid. Ultimately, dissipative viscous forces between the vortices and surrounding fluid within the tank dissipate the oscillation energy. 
   A wide variety of other techniques have been disclosed which are intended to dampen to smaller amplitudes and durations undesirable, potentially damaging fluid oscillations or sloshing of liquids contained in tanks mounted on moving vehicles. References disclosing such techniques include:
     Conway et al., U.S. Pat. No. 3,400,854, Sep. 10, 1965, Anti-Slosh Media For Fuel Tanks;   Conway et al., U.S. Pat. No. 3,349,953, Oct. 31, 1967, Anti-Slosh Media For Fuel Tanks;   Evensen et al., U.S. Pat. No. 3,443,584, May 13, 1969, Buoyant Anti-Slosh System;   Pollack, U.S. Pat. No. 3,784,050, Jan. 8, 1974, Floating Baffle System For Fuel Tanks;   Stedman et al, U.S. Pat. No. 4,764,408, Aug. 16, 1988, Foam Plastic Baffle For Fluid Containers;   Sasaki et al., U.S. Pat. No. 4,974,743, Dec. 4, 1990, Fuel Tank With Noise Suppressing Arrangement;   Spickelmire, U.S. Pat. No. 5,890,618, Apr. 6, 1999, Liquid Stabilizing Baffle System;   Behr et al., U.S. Pat. No. 6,032,347, Mar. 7, 2000, Tank And Manufacturing Method For The Same;   Evans, U.S. Pat. No. 6,062,417, May 16, 2000, Liquid Storage Tank And Baffle System;   Fenton et al., U.S. Pat. No. 6,415,942, Jul. 9, 2002, Filler Assembly For Automobile Fuel Tank;   Spickelmire et al., U.S. Pat. No. 6,547,090, Apr. 15, 2003, Liquid Stabilizing Baffle;   Bambacigno, U.S. Pat. No. 6,848,472, Feb. 1, 2005, Liquid Stabilizing Deflector Baffle;   Spickelmire et al, U.S. Patent Application No. US2002/0063133, May 30, 2002, Liquid Stabilizer;   Konja, U.S. Patent Application No. US2003/0015537, Jan. 23, 2003, Vehicle Fuel Tank With Fuel Wave Baffle;   Fenton, U.S. Patent Application No. US2004/0159663, Aug. 19, 2004, Fuel Tank And Filler Packet For Dispersing Ballistic Shock;   Krogull, U.S. Patent Application No. US2004/0173616, Sep. 9, 2004, Device For Reducing Sloshing Of Fuel In A Fuel Tank.   

   The present invention was conceived of to provide an anti-slosh device for damping oscillations of liquids contained in existing tanks of a wide variety of sizes and shapes. 
   OBJECTS OF THE INVENTION 
   An object of the present invention is to provide anti-slosh devices for damping oscillations of liquids in tanks, the devices being of an appropriate size and shape to be insertable through a fill tube or other access port into the interior of an existing tank, without requiring modification of the tank. 
   Another object of the invention is to provide an anti-slosh system which uses a plurality of anti-slosh devices that are insertable into an existing tanks of various sizes in quantities sufficient to occupy a pre-determined volume of the tank. 
   Another object of the invention is to provide an anti-slosh device which has relatively large-area flow-impeding baffle surfaces that are angled with respect to one another. 
   Another object of the invention is to provide an anti-slosh device which has a relatively large flow impeding surface area relative to the mass and volume of the device. 
   Another object of the invention is to provide an anti-slosh device which has a relatively large passageways therethrough which are effective in redirecting large scale motions of fluid in a tank to a plurality of smaller turbulent, energy dissipating paths, but which has a topology that resists interpretation or nesting of adjacent devices. 
   Another object of the device is to provide an anti-slosh device which is effective in damping oscillations of a liquid in a tank, but which displaces only a small percentage of the volume of the tank. 
   Another object of the invention is to provide an anti-slosh device which can be fabricated from a single elongated rectangularly-shaped thin sheet made of a plastic such as polycarbonate or high density polyethylene. 
   Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims. 
   It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims. 
   SUMMARY OF THE INVENTION 
   Briefly stated, the present invention comprehends a system for attenuating oscillations of a liquid such as water, gasoline, diesel fuel or the like contained in a tank, the oscillations having been induced by motions of a vehicle on which the tank is mounted. An anti-slosh system according to the present invention includes a plurality of identical anti-slosh devices that are insertable through a fill port, outlet tube or other access port into the interior of a tank, before or after the tank has been filled with a liquid. Each anti-slosh device has generally the shape of an elongated, flat, uniform thickness, rectangular strip of a fluid-impervious material such as a polycarbonate plastic, which has been formed into a plurality of non-parallel, arcuately curved loops between ends of the strip. 
   In a preferred embodiment of the invention, the flat rectangular strip is bent to form three arcuately curved, flat band loops including a pair of opposed outer end loops at opposite longitudinal ends of the device. The end loops each have a spiral shape similar to that of a single turn of a helical band, and the longitudinal pitch axes of the end loops are inclined downwards from a longitudinal connecting axis disposed through the end loops of the device. 
   A preferred embodiment of an anti-slosh device according to the present invention also includes a center flat loop which has the shape of a vertically flattened, oval ring that has a diameter similar to the diameters of the helical end loops. The center line or rotation axis of the center loop is inclined at an oblique angle, e.g., about 45°, to the longitudinal connecting axis between the end loops. 
   The anti-slosh device is preferably fabricated by fixing in place a first, starting end portion of a thin, longitudinally elongated, rectangularly-shaped strip of uniform thickness plastic material such as a polycarbonate, and bending a portion of the strip which protrudes obliquely outwardly, e.g., to the left, into a first, left end loop. The end loop has a rear half helical segment which has a forward pitch, and a front half helical segment which has a reverse pitch, thus giving the loop a spiral, quasi-helical shape. 
   The reverse pitch segment of the first end loop has an extension which protrudes obliquely inwardly and rearwardly, to the right and towards the center of the device, and crosses under the first end portion of the strip at an angle of less than 90 degrees, where it forms a first, upper loop intersection with and is secured to the underside of the starting end portion of the strip. Thus secured, a front longitudinal side edge of the extension portion of the reverse segment is positioned underneath and nearly parallel to a transverse starting edge of the starting portion of the strip. This arrangement results in the first intersection region, which is formed between a starting end portion of the strip and an underlying extension portion of the first, left helical end loop, having a generally rhomboidal shape. 
   The extension portion of the reverse segment of the first, left helical end loop is disposed obliquely to the right from the centrally located first loop intersection of the device. The extension portion then loops upwardly back to the left and thence underneath and to the right of the first intersection region, thus forming an oval ring-shaped center loop. The lower end of the center loop forms a second, bottom loop intersection region spaced below the first, upper loop intersection region. The center loop has a generally horizontally disposed major axis of larger diameter than the first end loop. 
   A lower, obliquely rightwardly angled extension portion of the large center loop continues to the right to form a second, right outer end loop similar in shape to the left outer end loop. Thus, the right outer end loop has a positive pitch rear half helical segment which protrudes obliquely rearwards and outwards from the center of the device towards the right, and a front half helical segment which has a reverse pitch. The reverse pitch front segment has an extension which protrudes obliquely inwards to the left and rearwards, i.e., towards the center of the device. The reverse pitch extension terminates in a second, finish end portion of the strip. The finish end portion also has a transverse end which is disposed perpendicularly to the parallel sides of the strip, and is inserted between a lower central portion of the center loop and the inner centrally located end portion of the reverse pitch helical half segment of the left end loop, forming therebetween a third loop intersection. 
   The four generally rhomboidly-shaped, overlapping regions of the strip located in the center of the device which form the three intersections described above are secured together by suitable means, such as a pair of rivets which extend upwards from the bottom surface of the device comprising the bottom surface of the large center loop, and emerge through the upper surface of the starting end portion of the strip. 
   The above-described construction of an anti-slosh device according to the present invention has a shape approximating that of a three-dimensional figure-8 bow, which has opposed left and right helical end loops, and an additional oval center loop which is disposed diagonally between left and right end loops of the bow, the three loops having similar diameters. All three loops protrude upwards from a flat horizontal base plane consisting of a bottom center portion of the center loop. 
   It has been found by the present inventor that anti-slosh devices shaped as described above not only provide efficient baffling action which effectively dampens oscillations of a liquid in a tank into which the devices are inserted, but also resist interpenetrating one another, or “nesting” thus enabling a small number of devices to occupy a sufficiently large percentage of the volume of the tank, e.g. one-half, to collectively provide effective dampening of liquid oscillations in the tank. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an upper front perspective view of a three-loop anti-slosh device according to the present invention. 
       FIG. 2  is an upper plan view of the device of  FIG. 1 . 
       FIG. 3  is a lower plan view of the device of  FIG. 1 . 
       FIG. 4  is a front elevation view of the device of  FIG. 1 . 
       FIG. 5  is a rear elevation view of the device of  FIG. 1 . 
       FIG. 6  is a right end elevation view of the device of  FIG. 1 . 
       FIG. 7  is a left end elevation view of the device of  FIG. 1 . 
       FIG. 8  is an upper front perspective view of a two-loop anti-slosh device according to the present invention. 
       FIG. 9  is an upper plan view of the device of  FIG. 8 . 
       FIG. 10  is a lower plan view of the device of  FIG. 8 . 
       FIG. 11  is a front elevation view of the device of  FIG. 8 . 
       FIG. 12  is a rear elevation plan view of the device of  FIG. 8 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-12  illustrate anti-slosh devices for damping oscillations of liquid in tanks, according to the present invention. 
     FIGS. 1-7  illustrate a preferred, three-loop embodiment  20  of an anti-slosh device according to the invention. As shown in those figures, anti-slosh device  20  is preferably formed of a single thin, longitudinally elongated rectangularly-shaped strip  21  which has a uniform thickness and is made of a flexible material that is resistant to degradation by liquids of the type which the device is to be immersed in, e.g., water, gasoline, diesel fuel, etc. The present inventor has found that synthetic polymers such as polycarbonate and high density polyethylene plastics are suitable materials from which to fabricate device  20 . 
   As shown in  FIGS. 1-7 , anti-slosh device  20  has a shape which can be formed by bending a thin, elongated rectangular strip  21  made of a flexible material such as a polycarbonate or high density polyethylene into a connected sequence of flat loops including a first, e.g., left, end loop  22 . Left end loop  22  has a quasi-helical shape, including a positive helix-angle, i.e., positive pitch, rear half segment  23 , which is angled obliquely outwardly, i.e., longitudinally outwards to the left and rearwardly in  FIGS. 1-3 . Left end loop  22  also has extending from rear half segment  23  thereof a negative pitch, front half segment  24  which is disposed obliquely inwardly, or to the right and rearwardly in  FIGS. 1-3 . Thus, left end loop  22  has a quasi-helical shape, which may be referred to henceforth simply as helical. 
   Device  20  also includes a second, e.g., right, quasi helical end loop  25  which forms with first end loop  22  a shape which in a lower or upper plan view approximates that of a  FIG. 8 , as shown in  FIGS. 2 and 3 . 
   Device  20  also includes a center loop  26  which has a generally oval or elliptical shape that has a horizontal major axis which is disposed obliquely with respect to a longitudinal connecting axis disposed through end loops  22 ,  25 . 
   As shown in  FIG. 2 , left end loop  22  has an outer longitudinal edge  27  and a parallel inner longitudinal edge  28 . Similarly, right end loop  25  has outer and inner parallel longitudinal edges  29 ,  30 . As is also shown in  FIG. 2 , obliquely disposed oval center loop  26  has parallel left and right obliquely disposed longitudinal edges  31 ,  32 . 
   As shown in  FIGS. 1 and 2 , the construction of anti-slosh device  20  results in a wedge-shaped left rear opening  33  being formed between inner, right-hand edge  28  of left end loop  22  and oblique left-hand edge  31  of center loop  26 . The construction of anti-slosh device  20  also includes a wedge-shaped right front opening  34  being formed between inner, left-hand edge  30  of right end loop  25 , and oblique right-hand edge  32  of center loop  26 . 
   The maximum width of each of the openings  33  and  34  is less than the width of strip  21  from which device  20  is fabricated. Thus, when a plurality of devices  20  are inserted into the interior of a tank and allowed to assume random relative orientations within the tank, the topology or geometry of the devices prevents the devices from interpentrating or nesting with each other. Three-loop anti-slosh device  20  may be fabricated from a single elongated rectangularly-shaped strip  21  cut from a thin, uniform thickness sheet of a synthetic polymer such as a high density polyethylene or polycarbonate plastic, in the following manner. 
   Referring to  FIGS. 1-7 , it may be seen that device  20  can be fabricated from strip  21  by first fixing in place a starting end portion  35  of the strip which has a first edge  36  disposed perpendicularly between front and rear longitudinal sides  37 ,  38  of the strip. A free portion of strip  21  is then payed out obliquely outwards from first edge  36  and rearwardly to form a positive-pitch, rear half-segment  23  of first, left end loop  22 . A portion  40  of strip  21  which extends rearward from the front, reverse-pitch helical half segment  24  of the left end loop  22  is then payed out obliquely inwardly, i.e., to the right and rearwardly in  FIGS. 1 ,  2  and  4 , and crossed under starting end portion  35  of strip  21  forming therewith a first, rhomboidly-shaped, top intersection  41 . An extension portion  42  of strip  21  disposed obliquely to the right from first, top intersection  41  is looped upwardly and obliquely over the top intersection, thus forming oval ring-shaped center loop  26 . A lower portion  43  of center loop  26  forms a second, bottom intersection  44  spaced below the top intersection  41 . 
   An extension  45  of lower portion  43  of oval center loop  26  protrudes obliquely rearwardly and to the right of bottom intersection  44 , and is formed into second, right helical end loop  25 . Right end loop  25  has a rear positive helix-angle half-segment  46  which protrudes obliquely rearwardly and outwardly to the right with respect to the center of device  20 , and a front negative helix-angle half-segment  47  which protrudes obliquely inwardly toward the center of the device. The front negative helix angle half segment  47  has an extension  48  which comprises the finish end portion of strip  21 . Finish end portion  48  of strip  21  has a transverse end  49  which is disposed perpendicularly between longitudinal side edges of strip  21 . 
   Finish end portion  48  of strip  21  is inserted between a portion of the strip located in the center of device  20  that comprises the finish portion of left end loop  22  and center loop  26 , and lower portion  43  of the center loop, and is secured thereto to form a third, middle intersection  50 . The four vertically stacked portions of strip  21  which form the three rhomboidly-shaped intersections as described above, are all secured together by any suitable means. In the example shown in  FIGS. 1-7 , stacked portions of strip  21  are secured together by a pair of rivets  51 ,  52 , which protrude upwardly from the bottom surface  53  of the device, through the four overlapping segments of the strip, and through the upper surface  54  of starting end portion  35  of the strip. Optionally, a third rivet  55  located between rivets  51 ,  52  is used to further secure together the four overlapping segments of strip  21 . 
   The effectiveness of anti-slosh devices  20  was tested by the following technique. 
   A plurality, i.e., 18, of identical devices  20  were each constructed from a separate 11-foot long by 8 inch wide by ⅛-inch thick high-density polyethylene (HDPE) material. Devices  20  were fabricated to have a maximum diameter of 14 inches measured between the front vertex  55  of center loop  26  and rear vertex  56  of right end loop  25 , as shown in  FIG. 2 . 
   A 300-imperial gallon, horizontally disposed cylindrical tank which had a width of 39 inches and a length of 72 inches was then filled to a level of 18 inches with water. One end of the tank was raised 8 inches, and subsequently dropped, causing water in the tank to slosh with large amplitude oscillations of up to about 1 foot. The sloshing continued for about 8.5 minutes before the amplitude of the oscillations, measured at opposite lateral ends of the tank, was reduced to less than 1 inch of vertical movement. 
   Next, 18 devices  20  of the construction described above were inserted through a 15-inch diameter fill tube opening into the interior of the tank. Each device  20  utilized a pair of stainless steel fastening bolts through the centers of the device, in place of rivets  51 ,  52 . The end of the tank was again raised 8 inches, and there was no measurable slosh. The end of the tank was then raised to a height of 26 inches, and dropped. With 18 devices  20  present in the tank, the sloshing action of amplitudes greater than 1-inch vertical movement was reduced to a duration of only about 3 seconds. 
     FIGS. 8-12  illustrate a modification  60  of anti-slosh device  20 . Modified anti-slosh device  60  has left and right end loops  62 ,  65 , shaped similarly to end loops  22 ,  25  of device  20 , but does not have a center loop. 
   As shown in  FIGS. 8-14 , two-loop anti-slosh device  60  is preferably formed from a single thin, longitudinally elongated rectangularly-shaped strip  61  made of a synthetic polymer having properties substantially the same as those described for strip  21  of three-loop anti-slosh device  20 . 
   As shown in  FIGS. 8-14 , anti-slosh device  60  has a shape which can be formed by bending a thin, elongated rectangular strip  61  made of a flexible material such as a polycarbonate or high density polyethylene into a connected sequence of flat loops including a first, e.g., left, end loop  62 . Left end loop  62  has a quasi-helical shape, including a positive helix-angle, i.e., positive pitch, rear half segment  63 , which is angled obliquely outwardly, i.e., longitudinally outwards to the left and rearwardly in  FIGS. 4-10 . Left end loop  62  also has extending from rear half segment  63  thereof a negative pitch, front half segment  64  which is disposed obliquely inwardly, or to the right and rearwardly in  FIGS. 8-10 . Thus, left end loop  62  has a quasi-helical shape, which may be referred to henceforth simply as helical. 
   Device  60  also has a second, e.g., right, quasi-helical end loop  65  which forms with first end loop  62  a shape in which a lower or upper plan view approximates that of a  FIG. 8 , as shown in  FIGS. 9 and 10 . 
   As shown in  FIG. 9 , left end loop  62  has an outer longitudinal edge  67  and a parallel inner longitudinal edge  68 . Similarly, right end loop  65  has outer and inner parallel longitudinal edges  69 ,  70 . 
   As shown in  FIGS. 11 and 12 , the construction of anti-slosh device  60  results in an opening  73  being formed between inner, right-hand edge  68  of left end loop  62  and inner, left-hand edge  70  of right end loop  65 . As shown in those figures, opening  73  has in front and rear elevation views the shape of an inverted, triangular wedge, and in three dimensions, a shape approximating that of a pie-shaped sector of a sphere. 
   As shown in  FIGS. 11 and 12 , the lateral width of opening  73  between edges  68  and  70  of left and right end loops  60 ,  65  decreases towards the bottom of device  60 , to a value less than the width of strip  61  from which device  60  is fabricated. Thus, when a plurality of devices  60  are inserted into the interior of a tank and allowed to assume random relative orientations within the tank, the topology or geometry of the devices prevent the devices from fully interpenetrating or nesting with each other. 
   Two-loop anti-slosh devices  60  may be formed by any convenient method, such as casting, injection molding, or the like. However, device  60  is preferably fabricated from a single elongated rectangularly-shaped strip  61  of a uniformly thick sheet of a synthetic polymer, such as a high-density polyethylene or polycarbinate plastic, in the following manner. 
   Referring to  FIGS. 8-14 , it may be seen that device  60  can be fabricated from strip  61  of flexible material by first fixing in place a starting end portion  75  of the strip which has a first edge  76  disposed perpendicularly between front and rear longitudinal sides  77 ,  78  of the strip. A free portion of strip  61  is then payed out obliquely outwards from first edge  76  and rearwardly to form a positive-pitch, rear half segment  63  of first, left end loop  62 . A portion  80  of strip  61  which extends rearward from the front reverse pitch helical half segment  64  of the left end loop  62  is then payed out obliquely inwardly, i.e., to the right and rearwardly in  FIGS. 8 ,  9  and  10  and crossed under starting end portion  65  of strip  61 , forming therewith a first, rhomboidly-shaped top intersection  81 . 
   Extension  80  of strip  61  is payed out obliquely rearwardly and to the right of intersection  81 , and is formed into a second, right helical end loop  65 . Right end loop  65  has a rear positive helix-angle half-segment  86  which protrudes obliquely rearwardly and outwardly to the right with respect to the center of device  60 , and a front negative helix-angle half-segment  87  which protrudes obliquely inwardly towards the center of the device. The front negative helix angle half segment  87  has an extension  88  which comprises the finish end portion of strip  61 . Finish end portion  88  of strip  61  has a transverse end  89  which is disposed perpendicularly between longitudinal side edges of strip  61 . 
   Finish end portion  88  of strip  61  is inserted between starting end portion  75  and extension  80  of the strip. The three vertically stacked portions of strip  61  which form the two rhomboidly-shaped intersections as described above, are all secured together by any suitable means. In the example shown in  FIGS. 8-14 , stacked portions of strip  61  are secured together by a pair of rivets  91 ,  92  which protrude upwardly from the bottom surface  93  of the device, through the three overlapping segments of the strip, and through the upper surface  94  of starting end portion  75  of the strip. Optionally, a third rivet  95  located between rivets  91 ,  92  is used to further secure together the three overlapping segments of strip  61 .