Systems, methods, and assemblies for improvement of explosion and fire resistant properties in fluid containers

Abstract

The present invention includes systems, assemblies, and methodologies for inhibiting combustion within fluid containers, enhancing the safety of such containers. One aspect includes a novel apparatus for assembling a base module of the present invention. The apparatus may include an initial stage, and intermediate stage, and a rolling stage. The initial stage is operative to receive a spool of mesh material. The intermediate stage is operative to conduct the mesh material between the initial stage and the rolling stage, as well as carry out a number of other operations associated with the present invention. The rolling stage is operative to roll the unspooled mesh material into a base module in accordance with at last one embodiment of the present invention.

Claims

1. An apparatus for producing a base module, the apparatus comprising: at least one spool of mesh; a rolling stage dimensioned and configured to unspool a predetermined length of mesh from said at least one spool of mesh into at least a first layer and a second layer of mesh; said rolling stage further dimensioned and configured to roll, concurrently, at least said first layer and said second layer into a base module; and an intermediate stage between said at least one spool of mesh and said rolling stage and comprising: (i) at least a primary carriage path for conducting said mesh to said rolling stage, and (ii) a secondary carriage path for conducting said mesh away from said rolling stage.

2. The apparatus as recited in claim 1 wherein said primary carriage path for conducting said mesh to the said rolling stage is above said secondary carriage path for conducting said mesh away from said rolling stage.

3. The apparatus as recited in claim 1 wherein said intermediate stage further comprises a cutting assembly operative to sever at least said first layer of mesh from said at least one spool of mesh.

4. The apparatus as recited in claim 1 wherein said rolling stage comprises a shaft for receiving said mesh, said shaft including a spindle lock; said spindle lock being operative in an unlocked orientation to allow said mesh to pass over said shaft.

5. The apparatus as recited in claim 4 wherein said rolling stage further comprises a motor operatively configured to drive said shaft when said spindle lock is in a locked orientation.

6. The apparatus as recited in claim 5 wherein said spindle lock is operative to hold said mesh captive against said shaft when said spindle lock is in a locked orientation.

7. An apparatus for producing a base module, the apparatus comprising: at least an initial stage, said initial stage dimensioned and configured to receive a spool of mesh material; an intermediate stage, said intermediate stage including a plurality of rollers operative to transport said mesh material from said initial stage to a rolling stage; and said rolling stage including a shaft operatively configured to roll said mesh material into the base module; wherein said intermediate stage is between said initial stage and said rolling stage and further comprises a primary carriage path and a secondary carriage path, wherein said mesh material is conducted along said primary carriage path from said initial stage to said rolling stage, and said mesh material is conducted along said secondary carriage path away from said rolling stage after passing through said rolling stage.

8. The apparatus as recited in claim 7 wherein said initial stage further comprises a spreader roller comprising a reverse-crown configuration, said spreader roller being operative to remove irregularities from said mesh material.

9. The apparatus as recited in claim 8 wherein said spreader roller is driven via a motor.

10. The apparatus as recited in claim 7 wherein said intermediate stage further comprises at least one nip roller operative to smooth deformations within said mesh material.

11. The apparatus as recited in claim 7 wherein said primary carriage path is above said secondary carriage path.

12. The apparatus as recited in claim 7 wherein said rolling stage is operatively disposable between an unspooling configuration and a rolling configuration.

13. The apparatus as recited in claim 12 wherein said shaft is operatively coupled to a spindle lock, wherein a locked configuration of said spindle lock corresponds to said rolling configuration, and an unlocked configuration of said spindle lock corresponds to said unspooling configuration.

14. The apparatus as recited in claim 7 wherein said intermediate stage further comprises a cutting assembly operative to sever said mesh material from said spool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a fuller understanding of the nature of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:

(2) FIG. 1A is a schematic depiction of two assemblies of different aspect ratios according to one embodiment of the present invention.

(3) FIG. 1B is a depiction of an assembly wrapped in a net according to one embodiment of the present invention.

(4) FIG. 2A is a schematic depiction of an apparatus for manufacturing of certain elements of the present invention.

(5) FIG. 2B is an elevation view of a portion of the apparatus disclosed in FIG. 3A.

(6) FIG. 2C is a detail view taken along line C-C of FIG. 2B.

(7) FIG. 2D is a detail view taken along line D-D of FIG. 2B FIG. 2E is a detail view taken along line E-E of FIG. 2B.

(8) FIG. 2F is a detail view of a portion of the apparatus disclosed in FIG. 2B disposed in an unspooling configuration.

(9) FIG. 2G is a detail view of a portion of the apparatus disclosed in FIG. 2B disposed in a rolling configuration.

(10) FIG. 2H is a detail view of FIG. 2F.

(11) FIG. 2I is a detail view of FIG. 2G.

(12) FIG. 3A is a schematic depiction of an apparatus for manufacturing certain elements of the present invention according to another embodiment of the present invention.

(13) FIG. 3B is a detail view of a portion of the apparatus disclosed in FIG. 3A.

(14) FIG. 4A is a side view schematic depiction of a wrapping assembly according to one embodiment of the present invention.

(15) FIG. 4B is a top view schematic depiction of a wrapping assembly according to one embodiment of the present invention.

(16) FIG. 5A is a depiction of one embodiment of the present invention deployed within a drum.

(17) FIG. 5B is a top view of a drum cluster in accordance with one embodiment of the present invention.

(18) FIG. 5C is a side view of a plurality of assemblies to be utilized as a drum cluster prior to being wrapped.

(19) FIG. 5D is a side view of a drum cluster in accordance with one embodiment of the present invention.

(20) FIG. 6A is a schematic depiction of fill material suitable for use in connection with a jerry can.

(21) FIG. 6B is a side view of a can cluster in accordance with one embodiment of the present invention.

(22) FIG. 6C is a top view of a can cluster in accordance with one embodiment of the present invention.

(23) FIG. 6D is a front view of a can cluster in accordance with one embodiment of the present invention.

(24) FIG. 6E is a rear view of a can cluster in accordance with one embodiment of the present invention.

(25) FIG. 7 is a schematic depiction of one embodiment of the present invention deployable as a mobile fuel station.

(26) FIG. 8A is a top view of a cell cluster and lattice structure in accordance with one embodiment of the present invention.

(27) FIG. 8B is a perspective view of a cell cluster and lattice structure in accordance with one embodiment of the present invention.

(28) FIG. 9A is a top view schematic depiction of a plurality of cell clusters disposed within a large volume container, namely, a tanker truck.

(29) FIG. 9B is a side view schematic depiction of a plurality of cell clusters disposed within a large volume container, namely, a tanker truck.

(30) FIG. 10A is a schematic flow chart depicting operative steps of a method according to one embodiment of the present invention.

(31) FIG. 10B is a schematic flow chart depicting operative steps of a method according to another embodiment of the present invention.

(32) Like reference numerals refer to like parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(33) An assembly 100 according to one embodiment of the present invention in depicted in FIGS. 1A and 1B. As can be seen, the assembly is constructed of a plurality of base modules 10 secured in a cylindrical configuration by a net 20. The base modules 10 are arranged along a cylindrical axis 101 to form an assembly 100.

(34) In a preferred embodiment, the base modules 10 are constructed of at least two layers of mesh 10 (but may include more or less layers) rolled into a cylindrical configuration until a desired diameter is reached. In a most preferred embodiment, a cylindrical base module 10 should have a diameter to height ratio typically (but not limited to) on the order of 0.19, i.e., diameter/height=0.19. However, this may vary as, e.g., smaller cylindrical basic modules may be utilized to increase the packing density of assemblies 100 within a container. To facilitate efficient manufacturing, the height of a basic module 10 may correspond to the width of the feed stock of mesh (as discussed below), but other manufacturing methods are envisioned (as also discussed below).

(35) With specific reference to FIG. 1B, a plurality of basic modules 10 have been arranged along a cylindrical axis 101 to form an assembly 100. Furthermore, the assembly 100 is secured with a net 20, which in the depicted embodiment is a single layer of mesh 1, which has been wrapped about the assembly 100 in overlapping fashion until all basic modules 10 within the assembly 100 are secured together. In yet further embodiments, the net 20 may be comprised of different material than the mesh 1, as long as it is suitably porous to allow fluid to flow there through. The depicted embodiment discloses a net 20 comprised of the same feed stock of mesh 1 as the basic module 10, which provides efficiencies in supply procurement and manufacturing. However, with such a net 20 material, it is necessary to overlap successive wraps of the net 20 along the length of the cylindrical axis 101 in order to sufficiently secure each basic module 10 together. If a net 20 of different material and/or dimension is utilized, it may not be necessary to provide such an overlapping configuration. By way of non-limiting example, feed stock for the net 20 material may be selected such that the width of the feed stock is approximately equal to the length of the cylindrical axis 101 of the assembly 100 and, as such, no overlapping configuration is required.

(36) As also discussed, the net 20 may be comprised of virtually any sufficiently porous material to allow fluid to flow through, while also providing sufficient structural integrity to enclose and secure the plurality of basic modules 10 into an assembly 100.

(37) As can be seen, the arrangement of basic modules 10 in a rolled, cylindrical configuration provides a certain amount of structural integrity, at least with respect to compression along the cylindrical axis 101 of each basic module and, when arranged into an assembly along such a cylindrical axis 101, the structural integrity of the assembly 100 along the cylindrical axis 101 is not compromised. Accordingly, as will be disclosed herein, when an assembly 100 is disposed within a container, a preferred embodiment of the invention calls for alignment of the cylindrical axis 101 with the normal anticipated gravitational vector of the container, i.e., the assembly 100 should be oriented substantially parallel to the direction of gravity during operation and/or storage of the container.

(38) Now turning to FIGS. 2A-2F, depicted therein is an inventive apparatus 1000 for production of base modules 10 according to one embodiment of the present invention. The depicted embodiment includes at least an initial stage 1010, an intermediate stage 1020, and a rolling stage 1030. The initial stage 1010 includes operative structuring to receive a mesh spool 1001 of mesh 1 material, with a predetermined width. The initial stage 1010 may also include a spreader roller 1011 which may also be driven by a motor 1034. In a preferred embodiment the spreader roller 1011 is of the reverse crown type, which has a larger diameter at the ends of the roller than in the middle. This configuration is operative to create a larger surface speed at the ends of the roller, which in turn will distribute tension from the center of the mesh 1 toward the edge of the mesh 1 as it passes over the roller 1011, thereby removing irregularities, such as wrinkles, from the surfaces of the mesh 1. Additionally, in embodiments where the spreader roller 1011 is driven via a motor 1034, this spreader roller 1011 will be operative to conduct the mesh 1 away from the mesh spool 1001 and toward the remaining stages of the apparatus 1000.

(39) The intermediate stage 1020 of the apparatus 1000 may include a plurality of rollers 1021, which may be configured in a nip roller configuration, and may also be comprised of a foam or other polymer material, which are operative to smooth any lateral deformations of the mesh 1. In certain embodiments, it may be desirable to employ air greasing in conjunction with any of the rollers described herein, in which air is directed between the mesh 1 and the roller to reduce the chance of slippage, deformation, and other undesirable effects. Additionally, the intermediate stage 1020 may include at least a primary carriage path 1023 and a secondary carriage path 1024. As can be seen, the mesh 1 is conducted along the primary carriage path 1023 along a region between the mesh spool 1001 and the rolling stage 1030, whereas the mesh 1 is conducted along the secondary carriage path 1024 after passing through the rolling stage 1030 and returning at least partially into the intermediate stage 1020.

(40) The rolling stage 1030 may comprise a shaft 1031, about which the mesh 1 may travel, along with a suitable number of tensioners 1036 and pretensioners 1035. With respect to FIG. 2H, a detail view of the shaft 1031, drive motor 1034, and other operative components may be seen in greater detail. According to the depicted embodiment, the mesh 1 may be guided about the shaft 1031 and allowed to return toward the intermediate stage 1020. The shaft 1031 may be operatively coupled with a spindle lock 1032, which is operative between a locked and unlocked orientation. When the spindle lock 1032 is in an unlocked orientation, as depicted in FIG. 2H, the mesh 1 is allowed to pass around the shaft 1031, but when the spindle lock 1032 is in a locked orientation, as depicted in FIG. 2I, the mesh 1 is constrained to rotate with the shaft. As such, the apparatus 1000 is operative between an unspooling configuration, as depicted in FIG. 2H, and a rolling configuration, as depicted in FIG. 2I, associated with the locked and unlocked orientation of the spindle lock 1032.

(41) More specifically, the mesh 1 of the mesh spool 1000 may be initially fed through the intermediate stage 1020, along the primary carriage path 1023 thereof, into the rolling stage 1030 and then back to the intermediate stage 1020 via the secondary carriage path 1024 until a desired length of mesh 1 is unspooled from the mesh spool 1001. This is accomplished with the spindle lock 1032 in an unlocked orientation and, accordingly, the apparatus 1000 is in an unspooling configuration. In this step, a first layer 2 and second layer 3 of mesh 1 is formed. The cutter 1022 may be used to sever the first layer 2 and second layer 3 from the mesh spool 1001. The unspooling configuration may utilize one or more motors and/or motorized shafts/rollers to conduct the mesh 1 out of the spool 1001. Then, the apparatus 1000 is converted into a rolling configuration via conversion of the spindle lock 1032 into a locked configuration. As can be seen in detail in FIGS. 2G and 2I, the first layer 2 and second layer 3 are held captive against the shaft 1031 and are both constrained to rotate with the shaft 1031, instead of passing over the shaft. As such, the first layer 2 and second layer 3 are fed into the roll that forms the base module 10.

(42) As may be seen throughout FIGS. 2H-2I, a roller 1033, which may be weighted, is disposed to rest against the mesh 1 that passes over the shaft 1031, as well as during formation of the base module 10. The roller 1033 may be pivotable such that it may move as the base module 10 grows in diameter about the shaft 1031. The roller 1033 provides a uniform lateral distribution of pressure on the mesh 1.

(43) The pretensioners 1035, tensioners 1036, roller 1033, and the motor 1034 driving the shaft 1031 may all include parameters that are adjustable to control the compactness of the base module 10 as it winds about the shaft 1031. As such, the roll density of the base module 10 may be affected via adjustment of such parameters. For a given compactness of the base module, i.e., how dense each layer of mesh 1 is rolled into the base module 10, the length of mesh 1 necessary to achieve a desired diameter may be determined and accordingly such length may be unspooled in the unspooling configuration of the apparatus 1000.

(44) In certain embodiments, it may be desirable to form a cylindrical basic module 10 of longitudinal dimension which is less than the width of the feed stock. FIGS. 3A and 3B disclose an alternative embodiment of the apparatus 1000 for the production of such a basic module 10, according to one embodiment of the present invention. Such an apparatus 1000 is capable of folding the feed stock of mesh 1 along its length, without damaging the mesh 1. The apparatus 1000 includes a folding assembly 1025 which is operative to accomplish the fold in partial stages. As such, a plurality of partial fold assemblies 1025 may be provided. In the depicted embodiment, the partial fold assemblies comprise V shaped assemblies in horizontal and vertical orientations. When the mesh 1 passes through each successive partial fold assembly 1025, the mesh is successively and progressively folded at a predetermined point along its width. An inlet hopper 1027 may be provided to gather the loosely folded mesh 1 into a more compact orientation, and a pair of finish rollers 1029, such as nip rollers, flatten the two halves of the mesh 1 against one another. In other embodiments, the invention may be operative to fold the mesh 1 at two, three, or more points along its width with successive and progressive partial fold assemblies 1025.

(45) As discussed, in a preferred embodiment, multiple base modules 10 may be combined into an assembly with a cylindrical form factor by encapsulating the base modules in a net 20, which may be comprised of mesh 1, or other suitable material such as stainless steel wire or other metal wires. An inventive wrapping assembly 2000, according to one embodiment of the present invention, is depicted in FIGS. 4A and 4B. Therein, a plurality of base modules 10 are disposed on a turn table 2010. A spool of net 20 material is disposed on a railing 2020 and is allowed to travel transversely along the length of the railing 2020. Accordingly, the net 20 material may be fed onto the base modules 10, and the turn table 2010 rotated as the net 20 material unspools and travels along the length of the railing 2020, thereby encapsulating the base modules 10 into an assembly 100. As will be disclosed further, multiple assemblies 1000 may be wrapped together to be disposed within certain types of containers to create clusters, such as drum clusters, can clusters, or cell cluster, as will be disclosed herein. In a preferred embodiment, a wrapping procedure of the present invention will include at least 4 layers about the cylindrical axis of a cluster and at least 2 layers perpendicular to the cylindrical axis of the cluster. Additionally, the wrapping assembly 2000 may be manually operative or equipped with sufficient motorized transducers to allow automated wrapping.

(46) FIGS. 5A-5D depict a plurality of assemblies 1000 disposed in various stages of a drum cluster 110 configuration, according to one embodiment of the present invention, which is suitable for packing a fuel drum-type fluid container, such as the standard 200 liter/55 gallon drums as are common in the industry. A plurality of assemblies 1000 are produced with a cylindrical axis 101 substantially equal to the height of the drum 4000 to be filled. The assemblies 1000 are compacted together in diameter approximately equal to that of the drum 4000 to be filled as well. The depicted embodiment, referred to as a drum cluster 110 may be wrapped, according to substantially the same methodology as previously disclosed, i.e., with a net 20 and placed within the drum 4000. As can be seen, a fluid transfer channel 3000 may be disposed within the drum cluster 110 and comprise a substantially hollow and porous configuration. This facilitates placement of pump lines, hoses, and other fluid conduits within the drum.

(47) Optimizing the packing density of the assemblies 1000 in a cylindrical fuel tank presents a more difficult challenge than a rectangular geometry. In a preferred embodiment, between 19 and 24 assemblies 1000, along with a fluid transfer channel 3000, are disposed within the drum 4000. The diameter of the assembly 1000 required for packing depends on the diameter of the empty tank that needs to be filled. In a preferred embodiment, the diameter of the assembly 1000 may be on the order of 20% of the drum diameter, for example, within 1% deviation. Such an arrangement produces negligible cavities for combustion and hence provides effective fire and explosion resistance.

(48) A top and side view of the packed tower cylinders are shown in FIG. 5C. For a relatively flexible assembly 1000, the volume density of the mesh 1 in the drum results in 80% or more, with the exact value dependent upon the flexibility of the assembly 1000. In order to increase the density of mesh 1 near the container surface where there exists the possibility of having larger voids, several layers of mesh pads 111 are employed near the inner surface of the drum. A completely wrapped drum cluster 110 is shown in FIG. 5D. The volume loss of the depicted drum cluster 110 is 4100 ml, which amounts to approximately 2.05% for a 200 liter fuel drum (55-gallon class).

(49) In another embodiment, with reference to FIGS. 6A and 6F, the method and apparatus of filling another type of fluid container, namely, a portable fuel container 5000 commonly referred to as a jerry can is disclosed. The scheme of packing of basic modules 10 within a portable fuel container 5000 is shown in FIG. 6A. It contains basic modules 10 in suitably sized assemblies 100, the majority of which are packed in vertical directions to fill the space within the portable fuel container 5000.

(50) However, packing solely in the vertical direction leaves considerable voids that inhibit the explosion resistant properties of the present invention. These spaces are filled with base modules 10 which are laid only in the top portion of the portable fuel container 5000 in such a way that it substantially approximates the shape of the container 5000. One of the major issues of such a container is the resistance provided by the mesh both for filling and withdrawal of fuel. In order to circumvent this problem, a fluid transfer channel 3000 is provided at one side of the can below filler cap. The diameter of the fluid transfer channel 3000 and the rate of pumping during filling is determined not only by the flow of the liquid into the tank but also by the removal of entrapped air in the meshed structure formed by the base modules 10.

(51) The plurality of assemblies 1000 may be wrapped using the nets 20 and apparatus 2000 in the manner described above. The shape thus obtained, as shown in FIG. 6B-E, referred to as a can cluster 120, fits the interior of the container 5000 and is introduced prior to welding the top of the container 5000. When the present invention is deployed according to its most preferred embodiments, the volume occupied by the mesh is less than 2% of the available volume within the jerry can.

(52) FIG. 7 discloses one embodiment of the present invention deployed in conjunction with yet another type of fluid container, namely, a mobile fuel station 6000, which typically include fuel tanks of 200 to 1000 liters in capacity, and are utilized in a variety of terrain, locations, conditions, with little to no safety precautions. In certain embodiments, a battery or solar powered fuel dispenser pump may be employed for dispensing fuel from the mobile fuel station. In the depicted embodiment, a specialized filter is inserted in the mouth of the reducer from a 50 mm butterfly valve to prevent particle suction into the pump. The tank of the mobile fuel station is filled with assemblies 1000 comprised of basic modules 10 according to the foregoing embodiments of the present invention, and may be collectively wrapped in a net 20 to form yet another cluster. The tank of the mobile fuel station may be grounded to eliminate static build up and related sparking. The main inlet of the tank is covered with a GI sheet including a fluid transfer channel that runs the length of the tank. The perforated tube facilitates decanting of fuel into the tank, while also providing space for a dip stick to measure the volume of fuel, or for sample collection.

(53) As can be seen, two different dimensions of assemblies 100 are used to fill the space of the tanks. The dimensioning of the assemblies 100 is arrived at relative to the following considerations. The assemblies 100 need not be completely rigid, but should withstand a nominal amount of deformation and distortion. A single dimension, in spite of the nominal deformation, still leaves sufficient pockets of fuel free of mesh that may support combustion. Although not the exclusive embodiment of the present invention, the use of at least two dimensions of assemblies 100 was found to optimize the packing of a rectangular fuel tank. In the preferred embodiment, the ratio of the diameter of the two sizes of assemblies 100 are 1:0.4, with exact dimensions dependent upon the size of the tank. According to this embodiment, the present invention achieves a packing density greater than 80%, with nominal distributed voids in the volume of the tank.

(54) In yet another embodiment, an inventive technique may be applied to deployment of the present invention within large containers, such as a trailered tank trucks (tankers) or railroad tank cars, intermodal tank containers, large volume stationery fuel tanks, and the like, which may also be pressurized. Such an embodiment is generally disclosed in FIGS. 8A-8B and 8A-8B.

(55) With specific reference to FIGS. 8A and 8B, a plurality of basic modules 10 (which may be of varying dimensions) are disposed within a lattice structure 140 to create a cell cluster 130. The lattice structure 140 may include vertical supports about which the basic modules 10 are disposed and/or affixed. Accordingly, in the depicted embodiment, the use of nets 20 to secure the basic modules 10 into assemblies 100 is not strictly required, but may be utilized if desired. The cell clusters may then be stacked or otherwise arranged within a large volume container, such as the tanker depicted n FIGS. 9A and 9B.

(56) With respect to FIG. 10A, a schematic of an inventive methodology 8000 according to at least one embodiment of the present invention is depicted therein. As can be seen, a first step may comprise arranging a continuous sheet of mesh into at least two layers 8010. This step may be performed substantially as discussed herein with reference to FIGS. 2A-3B and accompanying discussion.

(57) Another step of the inventive methodology may include rolling the sheet of mesh into a cylindrical form, thereby creating a base module 8020. This step may also be performed substantially as discussed herein with reference to FIGS. 2A-3B, wherein a spool of mesh is unspooled onto two separate carriage paths, substantially separated by a shaft of the rolling stage of a rolling apparatus; the sheet of mesh, after being severed from the spool, is held captive against a shaft at approximately its midpoint, and rolled into a cylindrical form.

(58) Yet another step of the inventive methodology includes the formation of assemblies from base modules. In one embodiment, this step may include arranging a plurality of base modules along a cylindrical axis and applying a net to the exterior of the plurality of base modules 8030.

(59) Another step of the inventive methodology includes disposing a plurality of assemblies within a container such that the average size of voids within the container is smaller than the quench distance of the fluid within the container 8040. As can be seen with respect to FIGS. 5A-9B this step can be accomplished in a variety of ways in regards to varying containers that are to be filled.

(60) Now turning to FIG. 10B yet another inventive methodology 900 of the present invention is depicted therein in schematic form. According to the depicted embodiment, one step of the methodology includes unspooling, from a spool of mesh, a sheet of mesh onto at least a first and second carriage path and severing the sheet of mesh from the spool 9010. Another step of the inventive methodology 9000 includes holding the sheet of mesh captive against a shaft at approximately the midpoint of the sheet 9020. Another step includes rotating the shaft such that the sheet of mesh is rolled, in two layers, into a cylindrical configuration 9030. A final step of the inventive methodology includes disposing a plurality of assemblies within a container such that the average size of voids within the container are smaller than the quench distance of the fluid within the container 9040.

(61) Since many modifications, variations and changes in detail can be made to the described preferred embodiment of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents.