Abstract:
An improved oil conditioning filter, for use with an internal combustion engine, includes a mechanically active filter element and a chemically active filter element having a reactive basic conditioner therein. The reactive basic conditioner is provided to counteract acidic combustion products in lubricating oil in an internal combustion engine. In a preferred embodiment of the invention, the chemically active conditioning agent is provided in a plurality of pellets disposed within the oil filter housing. The pellets may be bonded together to form an integral porous filter element having spaces defined between the pellets thereof. The pellets are made of a mixture including a polymeric binder and the chemically active conditioning agent, in a defined weight ratio and in a narrow range of particle sizes. The chemically active filter element reacts with acids present in the oil to form a product which may be filtered out of the oil. The pellets are made either by a hot extrusion process or by a solvent process.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an oil filter apparatus for use in conjunction with an internal combustion engine. More particularly, the present invention relates to an oil filter apparatus including both a mechanically active filter element and a chemically active filter element incorporated therein. Even more particularly, the present invention relates to an oil filter of the type described, in which a chemically active filter element includes pellets formed of a basic conditioner intermixed with a polymeric binder, for counteracting acidic combustion products in engine oil.  
           [0003]    2. Description of the Background Art  
           [0004]    Many different types of fluid filters are known. Most such filters use a mechanical or ‘screening’ type of filtration, with a replaceable cartridge having a porous filter element therein.  
           [0005]    In the oil filtration art, it is well known that normal operation of an internal combustion engine, particularly a diesel engine, results in the formation of contaminants. These contaminants include, among others, soot, which is formed from incomplete combustion of the fossil fuel, and acids that result from combustion. Both of these contaminants are typically introduced into the lubricating oil during engine operation, and tend to increase oil viscosity and to generate unwanted engine deposits, leading to increased engine wear.  
           [0006]    The conventional solution to these problems has been to place various additives into lubricating oils. In order to combat soot-related problems, many conventional lubricating oils include dispersants that resist agglomeration of soot therein. These work well for a short period, but may become depleted. Additionally, due to the solubility and chemical stability limits of these dispersants in the oil, the service lives of the lubricating oil and the oil filter are less than optimal.  
           [0007]    For combating combustion acid related problems, many conventional systems include neutralizing additives known as over-based detergents. These are a source of TBN (total base number), which is a measure of the quantity of the over-based detergent in the oil. The depletion of the TBN is an important limiting factor for many internal combustion engines, and in particular for heavy-duty applications with diesel engines.  
           [0008]    In order to improve engine protection and to combat other problems, conventional lubricating oils often include one or more further additives, which may be corrosion inhibitors, antioxidants, friction modifiers, pour point depressants, detergents, viscosity index improvers, anti-wear agents, and/or extreme pressure additives. The inclusion of these further additives may be beneficial; however, with conventional methods, the amount and concentration of these additives are limited by the ability of lubricating oils to suspend these additives, as well as by the chemical stability of these additives in the oil.  
           [0009]    Other solutions have been proposed in addition to the conventional method of mixing additives with lubricating oil. For example, in order to combat the build up of sludge in oil, U.S. Pat. No. 5,478,463, issued in 1995 to Brownawell et al, and entitled Method of Reducing Sludge and Varnish Precursors in Lubricating Oil; and U.S. Pat. No. 5,042,617, issued in 1991 to Brownawell, and entitled Method of Reducing the Presence of Sludge in Lubricating Oils, each disclose an oil filter and method for reducing the amount of sludge in lubricating oil as it circulates throughout an engine. These Brownawell patents provide for the inclusion of particles in an oil filter that are oil insoluble and oil wettable, and which complex with sludge such that at least some of the sludge that these particles come into contact with is immobilized on the particles. The Brownawell &#39;617 patent discloses the inclusion of oil insoluble and oil wettable particles in an oil filter that are retained on a pelletized substrate, whereas the Brownawell &#39;463 patent discloses the inclusion of such particles that are not retained on a substrate, but are nonetheless retained in the oil filter.  
           [0010]    Another Brownawell patent, which relates to the reduction of combustion acids in lubricating oil, is U.S. Pat. No. 5,069,799 issued in 1991 and entitled Method For Rejuvenating Lubricating Oils. This Brownawell patent discloses an oil filter and method for reducing the amount of combustion acids in lubricating oil. In particular, it discloses a method of rejuvenating lubricating oil, which includes reduction of combustion acids, by serially passing the oil through first a chemically active filter media, then a physically active filter media, and finally an inactive filter media. In this &#39;799 patent, the chemically active filter media includes a strong base, to displace weak bases that have combined with combustion acids. The combustion acid and the strong base then combine to form a salt, which is then physically trapped by subsequent mechanical filter media.  
           [0011]    U.S. Pat. No. 5,225,081 to Brownawell discloses method of removing polynuclear aromatics from used lubricating oil. The method of the Brownawell &#39;081 reference involves passing oil through a staged oil filter system, which may include a chemically active filter media. The chemically active filter media is made of a composite material including particles of an active component and a and a thermoplastic binder, which are a product of a heated extrusion process. Basic conditioners are given as one example of materials suitable for use as materials usable as chemically active filter media. Activated carbon is also emphasized as a preferred component of the filter media.  
           [0012]    Some designs for multiple stage oil filters are known, such as those disclosed in U.S. Pat. Nos. 4,557,829 and 4,886,599. U.S. Pat. No. 4,886,599 to Bachmann et al. discloses a filter cartridge with sequential concentric cylindrical filter elements, for both chemical and mechanical filtration of oil contained in an oil-sealed vacuum pump.  
           [0013]    Other designs for oil filters that contain extra additives and dispense those additives into oil, over time, are disclosed in U.S. Pat. Nos. 4,075,098 and 5,552,040.  
           [0014]    A need still exists in the art for an improved oil filter having a basic conditioner incorporated therein to counteract the effects of acidic combustion products in the oil. A need also exists for an improved oil filter which could extend the useful life of engine oil, so as to allow a user to extend the time interval between oil changes in a vehicle, particularly a vehicle having a diesel engine.  
         SUMMARY OF THE INVENTION  
         [0015]    The present invention provides an improved oil filter having a basic conditioner incorporated therein. The basic conditioner is provided to counteract the effects of acidic combustion products in the oil. In a preferred embodiment of the invention, the basic conditioner is provided in the form of a plurality of pellets disposed within the oil filter housing.  
           [0016]    In a preferred embodiment of the invention, these pellets are a product of a process in which a finely divided thermoplastic binder is mixed with a granular or particulate form of a basic additive in the presence of an organic solvent. After thorough mixing, the mixture is formed into pellets, and then the solvent is evaporated from the pellets.  
           [0017]    It is an advantage of the present invention that by forming the pellets by the above-described process, a high percentage of the active basic conditioner in the pellet may be achieved.  
           [0018]    Accordingly, it is an object of the present invention to provide an improved oil filter including a pelletized basic conditioner.  
           [0019]    It is a further object of the present invention to provide a method of making an improved oil filter of the type described.  
           [0020]    For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a perspective view, partially cut away, of an oil filter in accordance with a first embodiment of the present invention;  
         [0022]    [0022]FIG. 2 is a cross-sectional view of the filter of FIG. 1;  
         [0023]    [0023]FIG. 3 is a flow chart showing a series of steps in a preferred method of forming an oil filter according to the invention;  
         [0024]    [0024]FIG. 4 is a cross-sectional view of an oil filter according to a second embodiment of the present invention;  
         [0025]    [0025]FIG. 5 is a cross-sectional view of an oil filter according to a third embodiment of the present invention;  
         [0026]    [0026]FIG. 6 is an exploded cross-sectional view of a two-part oil filter assembly according to a fourth embodiment of the present invention; and  
         [0027]    [0027]FIG. 7 is a top plan view of a supplemental cartridge, which is a component of the assembly of FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    Throughout the present specification, relative positional terms like ‘upper’, ‘lower’, ‘top’, ‘bottom’, ‘horizontal’, ‘vertical’, and the like are used to refer to the orientation of the filters shown in the drawings. These terms are used in an illustrative sense to describe the depicted embodiments, and are not meant to be limitative. It will be understood that in a specific application thereof, a filter may be installed on an engine in an orientation different from that shown in the drawings, such as inverted 180 degrees or transverse to that shown, and in such a case, the above-identified relative positional terms will no longer be accurate.  
         [0029]    Referring to FIGS. 1 and 2, there is shown an oil filter  10  according to a first preferred embodiment of this invention. The direction of oil flow, through the filter  10 , is shown by the arrows in FIG. 2, which illustrate a flow path through the filter.  
         [0030]    The oil filter  10  generally includes a hollow cylindrical housing  11  which defines a chamber  14  therein, a porous mechanically active filter element  15  within that chamber, and a chemically active filter element  16 , made up of a plurality of individual composite pellets  18 , also retained within the chamber inside the housing. A foraminous cylindrical screen or support frame  17  may, optionally, be provided within the housing  11  to supportively hold the filter elements  15 ,  16  therein. A grommet  19  or other internal sealing member is provided centrally at the base of the frame  17  to route the oil along the flow path and through the filter elements  15 ,  16 . The grommet  19  may include a flexibly resilient sealing member having an integral pressure relief valve therein, such as that disclosed in co-pending U.S. patent application Ser. No. 09/271,137, filed Mar. 17, 1999, the disclosure of which is incorporated by reference. Alternatively, the oil filter may incorporate a spring-loaded or other conventional pressure relief valve of a type known to those in the art.  
         [0031]    A base plate  20  of the housing  11  includes a plurality of inlet ports  22  formed therethrough and arranged in a circular pattern. The base plate  20  also includes a central outlet port  24 . The outlet port  24  has a plurality of female threads formed therein to allow rotatable mounting of the filter  10  on an externally threaded hollow tubular fitting on an engine block (not shown). An annular external sealing member  25  fits engagingly into a groove  26  formed at the bottom surface of the base plate, to resist oil leakage outwardly from the base of the filter.  
         [0032]    In the depicted embodiment  10  of FIGS.  1 - 2 , the mechanically active filter element  15  is a conventional cylindrical member made of accordion-pleated filter paper.  
         [0033]    The chemically active filter element  16  is also provided in the shape of a cylinder in this embodiment, and is disposed radially and coaxially within the mechanically active filter element  15 . In this first embodiment  10  the chemically active filter element  16  is located inside of, and therefore downstream of the mechanical filter element  15 , in order to allow a first mechanical filtration to take place before the chemical reaction of unwanted contaminants from the oil with the basic conditioner of the chemical filter element  16 . Placement of the chemical filter element  16  between the mechanically active filter element  15  and the frame member  17 , as shown in the first filter embodiment  10 , puts it downstream form the mechanical filter element, yet still obtains the maximum possible support from the frame member  17 . This may be helpful where the chemical filter element  16  is made up of a plurality of separate and unconnected individual pellets  18 . Alternatively, the individual pellets  18  making up the chemically active filter element  16  may be bonded together or otherwise cohesively associated with one another to form a substantially integral, yet highly porous filter element  16  capable of independently supporting itself  
         [0034]    The pellets  18  making up the chemically active filter element  16  are an important feature of the filter  10  hereof. The pellets are made with a diameter in a range of 0.1 to 3 millimeters, preferably in a range of 0.25 to 2 millimeters in order to control the intersticial spaces therebetween in the filter matrix. The size of these interstices is specifically chosen and engineered to screen out most complexes which result from a reaction between combustion acids in the filtered oil and the basic conditioner of the pellets, without substantially reducing the flow rate through the chemically active filter member  16 .  
         [0035]    The pellets are made primarily of a basic conditioner held together with a polymeric binder. Optionally, the pellets may be made exclusively of basic conditioner and binder, in order to maximize the level of active ingredient therein. The basic conditioner of the pellets is preferably a basic salt selected from the group consisting of calcium carbonate, potassium carbonate, potassium bicarbonate, aluminum dihydroxy sodium carbonate, magnesium oxide, magnesium carbonate, zinc oxide, sodium bicarbonate, sodium hydroxide, calcium hydroxide, potassium hydroxide, and mixtures thereof.  
         [0036]    The basic salt is present in the pellets in a range of 80-97 percent by weight of the total pellet weight, preferably 85-97 percent, and most preferably between 90 and 97 percent by weight of the total pellet weight, with the balance being made up by the polymeric binder. Other materials may be added to the pellets if desired.  
         [0037]    Referring now to FIG. 3, a series of steps in a first method of making a filter  10  are shown. An early step  30  in the first method hereof is to grind or shred a polymeric binder, if comminution of the binder is needed, so that it is present in a finely divided form.  
         [0038]    Preferred binders in the practice of the present invention are thermoplastics. Particularly preferred binders include polyamides, polyimides, polyesters, polyolefins, polysulfones, and mixtures thereof. If the binder may be obtained in pulverized or granular form, the step  30  of grinding or shredding the binder may be omitted.  
         [0039]    Another early step  32  in the first preferred method hereof is to grind or mill the basic conditioner for the pellets, if it is not already provided in particulate form. This step is optional, and where it is necessary, steps  30  and  32  may be performed in any order.  
         [0040]    As noted, materials usable for the basic component, in accordance with the invention, include basic salts selected from the group consisting of calcium carbonate, potassium carbonate, potassium bicarbonate, aluminum dihydroxy sodium carbonate, magnesium oxide, magnesium carbonate, zinc oxide, sodium bicarbonate, sodium hydroxide, calcium hydroxide, and mixtures thereof.  
         [0041]    Once the basic conditioner and the binder are both present in finely divided form, they must be thoroughly mixed, in the presence of a suitable solvent, during a mixing step  34 . This is done by mixing the binder into the liquid solvent, stirring, and then subsequently adding the powdered or granular base. The binder is preferred to be present in a range of 3-20 percent of the solids present, and the basic conditioner is preferred to be present in a range of 90-97 percent of the solids.  
         [0042]    Suitable solvents, which may be used in the practice of the present invention, include organic solvents, particularly volatile organic solvents. A minimum amount of solvent which will allow for complete mixing of the solids is preferred.  
         [0043]    After mixing is complete, the mixture is formed into pellets in the next step  36 . This may be done by cold extrusion or by any other suitable means known to those in the art.  
         [0044]    Once the pellets  18  are formed, the solvent is removed therefrom by evaporation in a drying step  38 , and when the pellets are dry, they are installed into the filter housing  11  in a filter assembly step  40 .  
         [0045]    Using the above-identified solvent-based first preferred method of forming the pellets according to the invention allows for up to 90-97 percent basic salt, by weight, being present in the finished pellets. This is a higher concentration of the active salt in the pellets than is possible with a pellet forming operation in which a heated mixture is extruded from a die to form a pellet. Typically using the heated extrusion method only allows for a maximum of 50-80 percent active salt, with the balance being the binder.  
         [0046]    As previously noted, if desired, the pellets may be bonded together or otherwise connected together to form a substantially integral, yet perforated and highly porous chemical filter element  16 . Where the pellets  18  are joined together in this way, the frame member  17  is not needed, and may be omitted if desired.  
         [0047]    During use, hot oil slowly flows past the basic conditioner in the chemically active filter element, and the basic salt thereof acts to counteract and neutralize acidic combustion products. This neutralization of acidic combustion products allows for a much longer useful life of additives such as, for example, dispersants and zinc dialkyldithiophosphate (ZDP), which are provided in the oil by the manufacturer. This, in turn, allows for greater intervals between oil changes than is possible without the chemically active filter element.  
         [0048]    Referring now to FIG. 4, a cross-section of an oil filter  210  in connection with a second embodiment is shown. The oil filter  210  in this embodiment generally includes a cylindrical housing  211  which defines a hollow space  214  therein, a porous mechanically active filter element  215  within that space, and a chemically active filter element  216 , made up of a plurality of individual composite pellets  218 , also retained within the hollow space inside the housing and disposed within the mechanically active filter element. As noted in connection with the first embodiment  10 , the individual pellets  218  making up the chemically active filter element  216  may be bonded together or otherwise cohesively associated with one another to form a substantially integral, yet highly porous filter element  216  capable of independently supporting itself. With the exception of the configuration and placement of the respective mechanical and chemical filter elements  215 ,  216  as specified in this section, the oil filter  210  is substantially identical to the oil filter  10  of the first embodiment, as described hereinabove.  
         [0049]    In the embodiment  210  of FIG. 4, the mechanically active filter element  215  is a conventional cylindrical member made of accordion-pleated filter paper.  
         [0050]    The chemically active filter element  216  is also provided in the shape of a cylinder in this embodiment, and is disposed radially and coaxially outside of the mechanically active filter element  215 . A foraminous cylindrical screen or support frame  217  may, optionally, be provided within the housing  211  to supportively hold the filter elements  215 ,  216  therein. In this second embodiment  210  the chemically active filter element  216  is located outside of, and therefore upstream of the mechanical filter element  215 , in order to allow chemical modification of acids or other unwanted contaminants which may be present in the oil, with the basic conditioner of the chemical filter element  216 , prior to mechanical filtration. In this second embodiment  210 , the top and bottom horizontal segments  220 ,  222  of the frame member  217  have been extended outwardly towards the outer wall of the  219  of the housing  211 , as compared to the frame member  17  from the first embodiment, to contain the pellets  218  of the chemically active filter element therebetween. However, the portion of the frame member bottom horizontal segment  222  below the chemical filter element  216  is made foraminous, as shown, to allow oil to flow freely therethrough. The vertical inner wall  224  of the frame member  217  is also necessarily foraminous to allow oil flow therethrough.  
         [0051]    Referring now to FIG. 5, an oil filter  310  in accordance with a third embodiment of the present invention is shown. With the exception of the configuration and placement of the respective mechanical and chemical filter elements  315 ,  316  and related components, and unless otherwise specified in this section, the oil filter  310  is substantially identical to the oil filter  10  of the first embodiment, as described hereinabove.  
         [0052]    The oil filter  310  in this embodiment generally includes a hollow cylindrical housing  311  which defines a chamber  314  therein, a porous mechanically active filter element  315  within that chamber, and a chemically active filter element  316 , made up of a plurality of individual composite pellets  318 , also retained within the chamber inside the housing and disposed below and before the mechanically active filter element. The pellets  318  are selected for size so as to make the best effect of the interstices therebetween. Once again, the flow path through the filter is shown by the arrows in the drawing.  
         [0053]    As noted in connection with the first embodiment  10 , the individual pellets  318  making up the chemically active filter element  316  may be bonded together or otherwise cohesively associated with one another to form a substantially integral, yet highly porous filter element  316  capable of independently supporting itself.  
         [0054]    In the embodiment  310  of FIG. 5, the mechanically active filter element  315  is a conventional cylindrical member made of accordion-pleated filter paper. A selectively foraminous cylindrical screen or support frame  317  may, optionally, be provided within the housing  311  to supportively hold the mechanically active filter element  315  therein. Also in this embodiment, porous annular upper and lower foraminous dividers  320 ,  322 , respectively, may be placed above and/or below the chemically active filter element  316  to retain the pellets  318  of the chemically active filter element therebetween. The dividers  320  or  322  may be selectively foraminous solid plates or may be mesh screens. The upper divider  320  is constructed and arranged to pass oil only to the outside surface of the mechanically active filter element  315 , so that the oil must be mechanically filtered before exiting the filter  310 .  
         [0055]    The chemically active filter element  316  is also provided in the shape of a cylinder in this embodiment, and is disposed below the mechanically active filter element  315 . In this embodiment  310  the chemically active filter element  316  is located below the mechanical filter element  315 , and therefore precedes the mechanical filter element in the flow path, in order to allow chemical modification of acids or other unwanted contaminants which may be present in the oil, with the basic conditioner of the chemically active filter element  316 , prior to mechanical filtration. This design ensures that the oil will pass completely through the chemically active filter element before it reaches the mechanically active filter element, and provides more and longer-lasting interaction between the oil and the chemically active filter element than the design of FIG. 4.  
         [0056]    Referring now to FIG. 6, an oil filter assembly  410  in accordance with a fourth embodiment of the present invention is shown. The oil filter assembly  410  in this embodiment includes two primary parts, a conventional oil filter  402  shown on top in the drawing, and a supplemental cartridge  404 , shown below the conventional filter.  
         [0057]    The conventional oil filter  402  incorporates a mechanically active filter element  415  within a cylindrical housing  411 . The conventional oil filter  402  further includes a base plate  420 , which includes a plurality of inlet ports  422  arranged in a circular pattern as well as a central outlet port  424 . The base plate  420  is provided as an integral part of the cylindrical housing  411 , and an annular sealing member  425  fits engagingly into a groove  426  formed at the bottom surface of the base plate. The outlet port  424  has a plurality of female threads formed therein to allow rotatable mounting of the filter  402  on an externally threaded hollow tubular male connector fitting  409  of the supplemental cartridge  404 .  
         [0058]    The supplemental cartridge  404  is made to rotatably and threadably attach to an externally threaded hollow tubular fitting on an engine block (not shown), and to then have the conventional filter  402  rotatably and threadably fit thereon. The supplemental cartridge  404  includes a cylindrical housing  405  having a side wall  406 , a base plate  407 , sealably connected to the bottom edge of the side wall, and a cover plate  408  sealably connected to the top edge of the side wall.  
         [0059]    The cover plate  408  has a plurality of outlet openings  412  formed therein above the chemically active filter member  416  to allow oil to flow outwardly from the supplemental cartridge  404  and then into the inlets  422  of the conventional oil filter  402 .  
         [0060]    The base plate  407  of the supplemental cartridge  404  includes a plurality of inlet ports  432 , arranged in a circular pattern, as well as a central outlet port  434 . The base plate  407  is provided as an integral part of the cylindrical housing  405 , and an annular sealing member  435  fits engagingly into a groove  436  formed at the bottom surface of the base plate. The outlet port  434  has a plurality of female threads formed therein to allow rotatable mounting of the supplemental cartridge  404  to an externally threaded hollow tubular fitting on an engine block (not shown)  
         [0061]    The hollow tubular male connector fitting  409 , which is externally threaded, is provided at the center of the cover plate  408 , and a cylindrical dividing wall member  403  is centrally disposed within the cartridge housing  405 , and forms a fluid seal at the top and bottom surfaces thereof. The cylindrical dividing wall member  403  is preferably made of an oil-tolerant elastomer.  
         [0062]    The supplemental cartridge  404  contains a chemically active filter element  416  therein. The chemically active filter element  416  is made up of a plurality of individual composite pellets  418 , retained within the hollow space inside the cartridge housing  405  and disposed radially outside of the cylindrical dividing wall member  403 .  
         [0063]    As noted in connection with the first embodiment  10 , the individual pellets  418  making up the chemically active filter element  416  may be bonded together or otherwise cohesively associated with one another to form a substantially integral, yet highly porous filter element capable of independently supporting itself.  
         [0064]    Also in this embodiment, a porous, annular lower mesh screen  419  may be placed below the chemically active filter element  416  to retain the pellets  418  of the chemically active filter element thereabove. Where used, the mesh screen  419  may rest on a transverse horizontal flange  429 , which is an integral part of the cylindrical dividing wall member  403 .  
         [0065]    When the conventional oil filter  402  is attached to the supplemental cartridge  404 , the total assembly  410  functions in a manner similar to the oil filter  310  of FIG. 5.  
         [0066]    The chemically active filter element  416  is also provided in the shape of a cylinder in this embodiment, and when the entire assembly  410  is considered as a whole, the chemically active filter element is disposed below the mechanically active filter element  415  of the conventional oil filter  402 , and therefore precedes the mechanical filter element in the flow path, in order to allow chemical modification of acids or other unwanted contaminants which may be present in the oil, with the basic conditioner of the chemically active filter element  416 , prior to mechanical filtration. This design ensures that the oil will pass completely through the chemically active filter element  416  before it reaches the mechanically active filter element  415 , and provides more and longer-lasting interaction between the oil and the chemically active filter element than the design of FIG. 4.  
         [0067]    Optionally, as shown in FIG. 7, the supplemental cartridge  404  may include a pair of hollow tubes  437 ,  438  attached to the side wall  406  thereof, which communicate with the interior of the cartridge housing  405 . Where used, these tubes  427 ,  438  are provided to allow connection of the supplemental cartridge to a heat exchanger  440  to allow cooling of the oil which passes therethrough.  
         [0068]    Although the present invention has been described herein with respect to a preferred embodiment thereof, the foregoing description is intended to be illustrative, and not restrictive. Those skilled in the art will realize that many modifications of the preferred embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention.