Abstract:
The invention described herein generally pertains to temperature-indicating foam gun nozzles and/or at least one temperature-indicating hose which employs at least one thermochromic material disposed within said foam gun nozzle and/or hoses.

Description:
TECHNICAL FIELD  
       [0001]    The invention described herein pertains generally to temperature-indicating foam gun nozzles and hoses. 
       BACKGROUND OF THE INVENTION 
       [0002]    This invention is particularly suited for in-situ applications of liquid chemicals mixed and dispensed as a spray or a foam and more specifically, to in-situ application of polyurethane foam or froth and the measurement of the temperature of the chemicals used therewith. In-situ applications for polyurethane foam have continued to increase in recent years extending the application of polyurethane foam beyond its traditional uses in the packaging, insulation and molding fields. For example, polyurethane foam is being used with increasing frequency as a sealant in the building trades for sealing spaces between windows and door frames and the like and as an adhesive for gluing flooring, roof tiles, and the like. 
         [0003]    Polyurethane foam for in-situ applications is typically supplied as a “one-component” froth foam or a “two-component” froth foam in portable containers hand carried and dispensed by the operator through either a valve or a gun. However, the chemical reactions producing the polyurethane froth foam in a “one-component” polyurethane foam is significantly different than the chemical reactions producing a polyurethane froth foam in a “two-component” polyurethane foam. Because the reactions are different, the dispensing of the chemicals for a two-component polyurethane foam involves different and additional concepts and concerns than that present in the dispensing apparatus for a “one-component” polyurethane froth foam. 
         [0004]    A “one-component” foam generally means that both the resin and the isocyanate used in the foam formulation are supplied in a single pressurized container and dispensed from the container through a valve or a gun attached to the container. When the chemicals leave the valve, a reaction with moisture in the air produces a polyurethane froth or foam. Thus, the design concerns related to an apparatus for dispensing one-component polyurethane foam essentially concerns the operating characteristics of how the one-component polyurethane foam is throttled or metered from the pressurized container. While one-component guns can variably meter the polyurethane froth, they are typically used in caulk/glue applications where an adhesive or caulk bead is determined by the nozzle configuration. Post drip is a major concern in such applications as well as the dispensing gun not clogging because of reaction of the one component formulation with air (moisture) within the gun. To address or at least partially address such problems, a needle valve seat is typically applied as close to the dispensing point by a metering rod arrangement which can be pulled back for cleaning. While metering can occur at the needle valve seat, the seat is primarily for shut-off to prevent post drip; and depending on gun dimensioning, metering may principally occur at the gun opening. 
         [0005]    In contrast, a “two-component” froth foam means that one principal foam component is supplied in one pressurized container, typically the “A” container (i.e., polymeric isocyanate, fluorocarbons, etc.) while the other principal foam component is supplied in a second pressurized container, typically the “B” container (i.e., polyols, catalysts, flame retardants, fluorocarbons, etc.). 
         [0006]    In a two-component polyurethane foam, the “A” and “B” components form the foam or froth, when they are mixed in the gun. Of course, chemical reactions with moisture in the air will also occur with a two-component polyurethane foam after dispensing, but the principal reaction forming the polyurethane foam occurs when the “A” and “B” components are mixed, or contact one another in the dispensing gun. The dispensing apparatus for a two-component polyurethane foam application has to thus address not only the metering design concerns present in a one-component dispensing apparatus, but also the mixing requirements of a two-component polyurethane foam. 
         [0007]    Further, a “frothing” characteristic of the foam (foam assumes consistency resembling shaving cream) is enhanced by the fluorocarbon (or similar) component, which is present in the “A” and “B” components. This fluorocarbon component is a compressed gas which exits in its liquid state under pressure and changes to it gaseous state when the liquid is dispensed into a lower pressure ambient environment, such as when the liquid components exit the gun and enter the nozzle. 
         [0008]    While polyurethane foam is well known, the formulation varies considerably depending on application. In particular, while the polyols and isocyanates are typically kept separate in the “B” and “A” containers, other chemicals in the formulation may be placed in either container with the result that the weight or viscosity of the liquids in each container varies as well as the ratios at which the “A” and “B” components are to be mixed. In the dispensing gun applications which relate to this invention, the “A” and “B” formulations are such that the mixing ratios are generally kept equal so that the “A” and “B” containers are the same size. However, the weight, more importantly the viscosity, of the liquids in the containers invariably vary from one another. To adjust for viscosity variation between “A” and “B” chemical formulations, the “A” and “B” containers are charged (typically with an inert gas,) at different pressures to achieve equal flow rates. The metering valves in a two-component gun, therefore, have to meter different liquids at different pressures at a precise ratio under varying flow rates. For this reason (among others), some dispensing guns have a design where each metering rod/valve is separately adjustable against a separate spring to compensate not only for ratio variations in different formulations but also viscosity variations between the components. The typical two-component dispensing gun in use today can be viewed as two separate one-component dispensing guns in a common housing discharging their components into a mixing chamber or nozzle. In practice, often the gun operator adjusts the ratio settings to improve gun “performance” with poor results. To counteract this adverse result, the ratio adjustment then has to be “hidden” within the gun, or the design has to be such that the ratio setting is “fixed” in the gun for specific formulations. The gun cost is increased in either event and “fixing” the ratio setting to a specific formulation prevents interchangeability of the dispensing gun. 
         [0009]    Besides the ratio control which distinguishes two-component dispensing guns from one-component dispensing guns, a concern which affects all two-component gun designs (not present in one-component dispensing guns) is known in the trade as “cross-over”. Generally, “cross-over” means that one of the components of the foam (“A” or “B”) has crossed over into the dispensing mechanism in the dispensing gun for the other component (“B” or “A”). Cross-over may occur when the pressure variation between the “A” and “B” cylinders becomes significant. Variation can become significant when the foam formulation initially calls for the “A” and “B” containers to be at high differential charge pressures and the containers have discharged a majority of their components. (The containers are accumulators which inherently vary the pressure as the contents of the container are used.) To overcome this problem, it is known to equip the guns with conventional one-way valves, such as a poppet valve (or other similarly acting device). While necessary, the dispensing gun&#39;s cost is increased. 
         [0010]    Somewhat related to cross-over and affecting the operation of a two-component gun is the design of the nozzle. The nozzle is a throw away item detachably mounted to the gun nose. Nozzle design is important for cross-over and metering considerations in that the nozzle directs the “A” and “B” components to a static mixer in the gun. 
         [0011]    A still further characteristic distinguishing two-component from one-component gun designs resides in the clogging tendencies of two-component guns. Because the foam foaming reaction commences when the “A” and “B” components contact one another, it is clear that, once the gun is used, the static mixer will clog with polyurethane foam or froth formed within the mixer. This is why the nozzles, which contain the static mixer, are designed are throw away items. In practice, the foam does not instantaneously form within the nozzle upon cessation of metering to the point where the nozzles have to be discarded. Some time must elapse. This is a function of the formulation itself, the design of the static mixer and, all things being equal, the design of the nozzle. 
         [0012]    The dispensing gun of the present invention is particularly suited for use in two-component polyurethane foam “kits” typically sold to the building or construction trade. Typically, the kit contains two pressurized “A” and “B” cylinders of about 7.5 inches in diameter which are pressurized anywhere between 150-250 psi, a pair of hoses for connection to the cylinders and a dispensing gun, all of which are packaged in a container constructed to house and carry the components to the site where the foam is to be applied. When the chemicals in the “A” and “B” containers are depleted, the kit is sometimes discarded or the containers can be recycled. The dispensing gun may or may not be replaced. Since the dispensing gun is included in the kit, kit cost considerations dictate that the dispensing gun be relatively inexpensive. Typically, the dispensing gun is made from plastic with minimal usage of machined parts. 
         [0013]    The dispensing guns cited and to which this invention relates are additionally characterized and distinguished from other types of multi-component dispensing guns in that they are, “airless” and do not contain provisions for cleaning the gun. That is, a number of dispensing or metering guns or apparatus, particularly those used in high volume foam applications, are equipped or provided with a means or mechanism to introduce air or a solvent for cleaning or clearing the passages in the gun. The use of the term “airless” as used in this patent and the claims hereof means that the dispensing apparatus is not provided with an external, cleaning or purging mechanism. 
         [0014]    While the two-component dispensing guns discussed above function in a commercially acceptable manner, it is becoming increasingly clear as the number of in-situ applications for polyurethane foam increase, that the range or the ability of the dispensing gun to function for all such applications has to be improved. As a general example, the dispensing gun design has to be able to throttle or meter a fine bead of polyurethane froth in a sealant application where the kit is sold to seal spaces around window frames, door frames, and the like in the building trade. In contrast, where the kit is sold to form insulation, an ability to meter or flow a high volume flow of chemicals is required. Still yet, in an adhesive application, liquid spray patterns of various widths and thickness are required. While the “A” and “B” components for each of these applications are specially formulated and differ from one another, one dispensing gun for all such applications involving different formulations of the chemicals is needed. 
         [0015]    At least one recurring quality issue facing the disposable polyurethane foam kit industry is the inability of end-users to effectively assess the core chemical temperature of the liquid and gas contents contained therein. Two important functions are often negatively impacted: achievement of maximum foam kit yield on the job site, and proper chemical cure of the “A” &amp; “B” components. 
         [0016]    Maximum yield is highly desired by purchasers of polyurethane foam kit products. If the chemicals are too cold for optimum use, the “B”-side viscosity increases, which in turn distorts the 1:1 ratio (by weight) required for proper yield. Lower-than-advertised yields carry significant economical consequences for the contractor. 
         [0017]    Proper chemical cure (on-ratio ˜1:1) is also critical to achieving maximum physical properties. It ensures that the cured foam meets building code specifications, e.g. fire ratings. In addition, a complete, on-ratio cure is critical for the health and safety of foam kit operators and building occupants. Again, cold chemical temperatures (below recommended) can create off-ratio foam, with the resulting incomplete chemical cure. 
         [0018]    At least one important variable impacting the above issues is the core chemical temperature of the liquid/gas contents of the foam kit. The core chemical temperature of a kit before use must meet the manufacturer&#39;s recommended temperature, usually ˜75° F.-85° F., in order to meet the objectives of maximum yield and proper (complete) chemical cure. However, end-users typically do not condition the kits long enough at the recommended temperature. For example, kits stored in an unconditioned warehouse or insulation truck in the winter months may have a core chemical temperature of only ˜40° F. If dispensed without being conditioned for a sufficient amount of time, the result is foam of very poor physical quality and appearance. Also, improper chemical cure will most likely occur (unbalanced ratio of “A” to “B” chemical, which is typically 1:1 by weight). This “off-ratio” foam becomes a liability for the reasons mentioned above. It can take up to 48 hours to condition cylinders to the recommended chemical temperature, a recommendation often ignored by end-users. 
         [0019]    The industry has long searched for an effective, economical way to allow end-users to gauge the core chemical temperature of a kit with a reasonable degree of qualitative accuracy before applying the foam. This invention utilizes thermochromism in both the nozzle and the hoses associated with the “A” and “B” chemicals to determine when the temperature of the chemicals falls within the acceptable use range, based upon the color change of the nozzle or hose due to a change in temperature of the flowing chemical. 
       SUMMARY OF THE INVENTION 
       [0020]    In accordance with the present invention, there is provided a frothable foam, the application temperature of which can be easily measured. 
         [0021]    It is yet another aspect of the invention to provide 
         [0022]    The above and other aspects of the invention are achieved by 
         [0023]    These and other objects of this invention will be evident when viewed in light of the drawings, detailed description and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawing which form a part hereof, and wherein: 
           [0025]      FIGS. 1 &amp; 2  are perspective views of the dispensing gun; 
           [0026]      FIG. 3  is a section view of the dispensing gun of the present invention taken generally along line  3 - 3  of  FIG. 1 ; 
           [0027]      FIG. 4  is a section view of the dispensing gun of the present invention taken generally along line  4 - 4  of  FIG. 2 ; 
           [0028]      FIGS. 5 &amp; 6  are perspective views of the nozzle; 
           [0029]      FIG. 7  is an exploded view of the nozzle shown in  FIGS. 5 &amp; 6 ; 
           [0030]      FIG. 8  is a front view of the back plate used in the nozzle; 
           [0031]      FIG. 9  is a section view of the back plate taken generally along the lines designated  9 - 9  of  FIG. 8 ; 
           [0032]      FIG. 10  is a top view of the back plate; 
           [0033]      FIG. 11  is a front view of the one-way valve; 
           [0034]      FIG. 12  is a cross-section view of the one-way valve of  FIG. 11  taken along line  12 - 12  of  FIG. 11 ; 
           [0035]      FIGS. 13A ,  138 , &amp;  13 C are schematic elevation views illustrating various positions of the metering rod in the valve seat of the gun; 
           [0036]      FIGS. 14A &amp; 148  are schematic partially sectioned views indicating the position of the metering rod and trigger during operation of the dispensing gun of the present invention; 
           [0037]      FIG. 15  is a schematic section view of an alternative embodiment of the nozzle of the present invention; 
           [0038]      FIG. 16  is a section view of the nozzle taken along lines  16 - 16  of  FIG. 15 ; 
           [0039]      FIG. 17  is an elevation view of the handle and trigger portions of the dispensing gun showing grooves for the lock tab of the dispensing gun; and, 
           [0040]      FIG. 18  is a front view of the nose surface of the dispensing gun of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    The best mode for carrying out the invention will now be described for the purposes of illustrating the best mode known to the applicant at the time of the filing of this patent application. The examples and figures are illustrative only and not meant to limit the invention, which is measured by the scope and spirit of the claims. 
         [0042]    The invention relates to, as shown in perspective views in  FIGS. 1 &amp; 2 , an airless (as that term is previously defined) two-component dispensing gun  10 . Dispensing gun  10  may be viewed as comprising a one-piece gun body  12  (which includes components to be described) to which is detachably secured a disposable nozzle  13 . In the preferred embodiment, the gun is molded from polypropylene and the nozzle is molded from an ABS (Acrylonitrile-Butadiene-Styrene) plastic. While one of the objects of the invention is to provide an inexpensive dispensing gun achieved in part by molding gun body  12  and nozzle  13  from plastic, the invention in its broader sense is not limited to a dispensing gun molded from the particular plastics specified nor, in fact, is the invention limited to a dispensing gun manufactured from plastic. 
         [0043]    Gun body  12  may be further defined as having integral portions including a longitudinally-extending valve portion  15  to which nozzle  13  is connected and terminating at a longitudinally-extending trigger portion  16 , in turn, terminating at a longitudinally-extending spring portion  17  from which transversely extends a handle portion  18 . Within gun body housing  12  is a pair of hose openings  22 ,  23 , canted as shown, to which the “A” and “B” hoses (not shown) are attached, respectively, by conventional quick connect couplings or retaining mechanisms. Dispensing gun  10  is also provided with a trigger  20  extending within trigger body portion  16 . It should be appreciated that when the operator grasps dispensing gun  10  about handle  18  for finger actuation of trigger  20 , that the position of hose openings  22 ,  23  is such that the kit hoses will drape over the operator&#39;s forearm which surprisingly is preferred over other conventional hose attachment positions on the dispensing gun. For example, if the hose connections were attached to the handle bottom, it is possible for the hoses to become entangled with the operator&#39;s feet. If the hoses are attached to the rear end of the gun, the hoses rest on the operator&#39;s wrist. If the hoses are conventionally attached to the top of the gun, they can drape on either side of the gun and distort the pistol feel of the gun. Canting hose openings  22 ,  23  is thus believed to provide some ergonomic benefit while contributing to the improved performance of dispensing gun  10  as described below. 
         [0044]    Referring now to  FIGS. 3 &amp; 4 , dispensing gun  10  is shown in vertical and horizontal cross-section views, respectively, to best illustrate the overall relationship of the gun components. In gun body valve portion  15 , there is formed a pair of parallel, open ended, laterally displaced and straight dispensing passages  25 ,  26  which are identical to one another so that a description of one dispensing passage such as a dispensing passage  25  for component “A” will apply to the other dispensing passage  26 . Within each dispensing passage is placed a longitudinally-extending metering rod  28  and the metering rod for dispensing the “A” component in passage  25  is not shown in  FIG. 4  for drawing clarity. Metering rod  28  will be defined in further detail below but generally has tip section  29  at one end terminating in an intermediate sealing section  30 , in turn, terminating at a yoke collar section  31  at the opposite end of metering rod  28 . Metering rod sections  29 ,  30  and  31  are cylindrical in the preferred embodiment but conceptually could be tubular. Each metering rod  28  has a pair of grooves  33  for an O-ring seal (not shown) to prevent the liquid component in dispensing passage  25  or  26  from escaping out end opening  34  in each dispensing passage  25 ,  26  through which intermediate sealing section  30  extends. The opposite end opening of each dispensing passage  25 ,  26  is formed as an especially configured valve seat  35  which will be explained in further detail below. 
         [0045]    For consistency in terminology, when describing dispensing gun  10 , “longitudinal” will refer to the direction of the dispensing gun along the long axis of dispensing passage  25 ,  26  of metering rods  28 , i.e., x-x plane; “transverse” will refer to the direction of the gun along the long axis of handle portion  18 , i.e., z-z plane; and, “laterally” will refer to the direction of the gun such as the distance spanning the spacing between dispensing passages  25 ,  26 , i.e., the y-y plane. 
         [0046]    Within valve body portion  15  are two laterally spaced and straight feed passages  37  in fluid communication at one end with a hose opening  22  or  23  and at the opposite end with a dispensing passage  25  or  26  at a position in a dispensing passage adjacent valve seat  35 . Feed passage  37  extends along an axis  38  which forms an acute angle of about 20° with dispensing passage  25  or  26 , preferably extending not greater than about 30°. The arrangement of feed passages  37 , dispensing passages  25 ,  26  and metering rods  28  is believed to alleviate or reduce turbulent flow of the liquid components through dispensing gun  10 . 
         [0047]    Referring still to  FIGS. 3 &amp; 4 , trigger  20  has a yoke crossbar portion  40  with a pair of elongated metering rod openings  41  formed therein through which intermediate sealing section  30  of each metering rod extends. Extending transversely from yoke crossbar portion  40  of trigger  20  in the direction of handle  18  is a recessed trigger lever  44 . Transversely extending from the opposite side of yoke crossbar portion  40  is a rounded trigger pivot portion  45 . Trigger pivot portion  45  fits within a U-shaped trigger recess  47  formed within trigger body portion  16 . Trigger pivot portion  45  is not pinned or journaled within U-shaped recess  47  and can be viewed as floating. Movement of trigger lever  44  causes trigger pivot  45  to pivot within trigger recess  47  moving yoke crossbar  40  into contact with yoke collar section  31  of each metering rod  28  in a manner which causes metering of the “A” and “B” liquid components as will be described further below. 
         [0048]    Within spring body portion  17  of dispensing gun  10 , which is open ended, is positioned, a single spring  50 . Spring  50  is compressed between an inner spring retainer  51  and an outer spring retainer  52  which perhaps, as best shown in  FIG. 4 , has a bayonet clip which snaps into openings in spring body portion  17 . Inner spring retainer  51  has a pair of tubular projections  53  extending therefrom which fit within openings formed in the rear surface of yoke collar section  31 . The design of inner spring retainer  51  thus provides a form of alignment assuring equal travel of each metering rod  28  in dispensing passages  25 ,  26 . In conventional, two-component dispensing guns in commercial use, separate springs are provided for each metering rod (perhaps to provide different spring forces for each metering rod). As noted in the Background, the polyurethane foam or froth components under discussion are formulated to provide equal ratios of the “A” and “B” components. When separate springs are used, it is possible for one spring to set when compared to the other spring, tending to result in an off ratio dispensing gun. Two-component dispensing gun  10  of the present invention avoids this concern by using a single spring in combination with inner spring retainer  51  and yoke crossbar  40  of trigger  20  to assure that movement of trigger  20  will result in equal movement of both metering rods  28  in dispensing passages  25 ,  26 . Equal ratio metering is mechanically forced and the single spring  50  exerts a constant force on both metering rods  28  so that binding within metering rod openings  41  of trigger crossbar portion  40  does not occur. 
         [0049]    Dispensing gun  10  is easily assembled. Trigger  20  is inserted into gun body  12  such that trigger pivot portion  45  is within trigger recess  47 . Each metering rod  28  is then inserted through spring body portion  17  into its dispensing passage  25  or  26 . Inner spring retainer  51  is then inserted within spring body portion  17 . Spring  50  is then inserted and compressed when outer spring retainer  52  is snapped by the bayonet clips into spring body portion  17 . 
         [0050]    Referring now to  FIGS. 5 ,  6  &amp;  7 , nozzle  13  has an outlet tip section or outlet tip  58 , a mixing chamber section or a mixing chamber  59  and an inlet chamber section or inlet chamber  60 . Nozzle  13  is molded so that each section,  58 ,  59 ,  60  is an integral part of nozzle  13 . However, dispensing tip  58  can be separately molded and threaded into mixing chamber  59  to permit a variety of differently shaped dispensing tips  58  to be fitted to nozzle  13 . Alternatively, different tips may be threaded onto or into dispensing tip  58 . Different gun application may require different spray patterns other than the conical spray pattern which will be produced through nozzle tip opening  62  provided in dispensing tip  58  of nozzle  13  shown in  FIGS. 5-7 . Making outlet tip  58  detachable from mixing chamber  59  such as by a threaded engagement, allows for a variety of spray patterns. Within mixing chamber  59 , which is cylindrical, is a conventional static mixer (illustrated schematically in part as reference numeral  63  in  FIG. 15 ). 
         [0051]    Nozzle design is essential to the proper functioning of any two-component dispensing gun. In accordance with the invention, inlet chamber  60  introduces the “A” and “B” components to static mixer  63  in a somewhat non-turbulent manner and with only minimal contact between the “A” and “B” components so that static mixer  63  can effectively perform its mixing function. More particularly, the shape, construction and relationship of inlet chamber  60  relative to dispensing passages  25 ,  26  and relative to mixing chamber  59  is important. Perhaps as best shown in  FIGS. 15 &amp; 18 , to which reference should be had, dispensing passages  25 ,  26  exit valve gun portion  15  at a flat nose surface  65  in valve body portion  15 . Flat nose surface  65  is defined by an edge from which an edge lip  66  protrudes. Edge lip  66 , in the preferred embodiment, is defined by two identical, laterally spaced semi-circular edge portions  67 ,  68  connected to one another by laterally extending straight edge portions  69 ,  70  transversely spaced from one another. Alternatively, and somewhat conceptually preferable, edge lip  66  could be circular. 
         [0052]    Longitudinally-extending from nose surface  65  and concentric with semi-circular edge lip portion  67 ,  68  are a pair of valve seat protrusions  72 ,  73  forming or continuing the metering tip valve seats of dispensing passages  25 ,  26  respectively. Each valve seat protrusion  72 ,  73  has a flat end surface  74  through which a central valve seat opening  75  extends. Valve seat opening is the minor diameter of a frustoconical surface which defines valve seat  35  in the preferred embodiment. 
         [0053]    Referring again to  FIGS. 5 ,  6  &amp;  7 , inlet chamber  60  of nozzle  13  has a collar section  76  extending from its entrance end which is in the shape of nose edge and fits within nozzle edge lip  66 . Extending laterally and transversely from the bottom portion of collar section  76  is a positioning tab  78 . When nozzle  13  is applied to dispensing gun  10 , positioning tab  78  fits within a nozzle recess  79  best shown as extending between dash lines in  FIG. 18  and shown in cross-section in  FIG. 3 . Extending transversely upward from collar section  76  is a latch  80  which has a lock surface  81  adapted to engage a snap ledge  82  longitudinally-extending from nose edge lip  66  in the rearward direction perhaps as best shown in  FIG. 3 . To apply, the gun operator grasps nozzle  13  by its outlet tip  58  and mixing chamber  59  and inserts positioning tab  78  into nozzle recess  79 . At this point, nozzle  13  will be at a slight downward angle relative to gun nose surface  65 . As the remaining portion of collar section  76  is brought within edge lip  66 , positioning tab  78  will rotate within nozzle recess  79  so that snap ledge  82  will snap into locking engagement with lock surface  81 . To remove nozzle  13 , the gun operator depresses latch tip  83  formed in latch  80  to unseat lock surface  81  on snap ledge  82 . Nozzle  13  can then be rotated so that positioning tab  78  can be lifted from nozzle recess  79 . The latch mechanism described in the preferred embodiment is particularly preferred because the rigidity of latch  80  can be designed in combination with the lever force exerted by the operator to achieve desired sealing of nozzle  13  to gun body  12 . However, other arrangements which will produce desired sealing can be employed. In particular, collar section  76  of nozzle  13  and edge lip  66  of gun nose surface  65  can be made circular and provided with a mason jar lid type thread. The pitch of the thread can be established to produce the desired sealing in less than 360° of rotation. Still another mechanism for attaching nozzle  13  to gun body  12  would be to simply provide the nozzle with opposing bayonet clips which would snap into recesses or clip holders foamed into gun body  12  adjacent nose surface  65  or vice-versa. Thus, in its broader sense, the invention contemplates attaching nozzle  13  to gun body  12  in a sealing manner either through pivoting such as shown by latch  80 , or by rotation such as by a threaded connection or by a straight, snap in connection such as achieved by bayonet type clips. 
         [0054]    Referring now to  FIGS. 7 ,  8 ,  9  &amp;  10 , backplate  85  having an edge configuration similar to collar section  76  is permanently affixed to collar section  76  of nozzle  13 . Backplate  85  is “glued” to nozzle collar section  76  and is sealed thereto about its entire periphery. Because nozzle  13 , in the preferred embodiment, is an ABS plastic, it lends itself to “solvent welding” with a variety of common solvents. Backplate  85  has a forward surface  86  and a rearward surface  87  shaped as shown to provide a pair of cup shaped recesses  88  opening to nozzle face surface  65 . At the base of each cup shaped recess  88  is a valve extension opening  89  and a sealing rib  90  extends from the base of cup shaped recess  88  circumscribing valve seat extension opening  89 . Sealing rib  90  thus contacts flat end surface  74  of each valve seat protrusion when nozzle  13  is latched to gun body  12 . Because the plastic composition of nozzle  13  has a different hardness than the plastic composition of body  12 , a deformation will occur between sealing lip  90  and flat end surface  74  with the positive lock nozzle arrangement described above. In the preferred embodiment, nozzle  13  is harder than the plastic of gun body  12  so that sealing lip  70  will deform flat end surface  74  to effect sealing of nozzle  13  to gun body  12 . However, the deformation from sealing is not beyond the memory of the plastic so that permanent set is not experienced in the gun body and any number of nozzles can be repeatedly sealed to gun body  12 . Nozzle sealing conventionally occurs in commercial applications by means of conventional O-rings and like resilient seals. 
         [0055]    Referring now to  FIGS. 7 ,  8 ,  11  &amp;  12 , a resilient strip  92  of flexible material such as any number of plastics (ABS is used in the preferred embodiment) or natural or synthetic rubber or similar elastomers is secured to rear surface  87  of backplate  85  by an attachment portion  93  wedged into centrally positioned attachment recess  94  formed in backplate  85  and opening to rearward surface  87  thereof. Resilient strip  92  as best shown in  FIG. 4  extends over to cover valve seat extension openings  89 . Resilient strip  92  acts as a flapper valve to prevent crossover. When dispensing gun  10  is operated, pressure of the “A” and “B” liquid components will force resilient strip  92  to flex away from valve seat extension openings  89  to a flex position such as shown by the dash lines in  FIG. 15 . Should one of the components significantly drop in pressure, so that the pressure in nozzle inlet chamber  60  is greater than the pressure in one of the dispensing passages  25 ,  26 , the resilient strip  92  will cover that dispensing passage&#39;s valve seat extension opening  89 . This provides an effective one way valve positively sealing dispensing passages  25  and  26  in the event a cross-over condition occurs. Preferably, a single resilient strip  92  as shown is utilized. However, each valve seat extension opening  89  can be provided with its own separate resilient strip of material  92 . It must be noted that the flexibility of resilient strip  92  is a design variable. It is believed that resilient strip  92  aids in the fine metering characteristics of dispensing gun  10 . As already noted, dispensing gun  10  is provided with a plurality of nozzles  13  having various outlet tip  58  configurations suitable for specific applications. In those applications requiring a small bead of polyurethane foam to be applied such as in a window frame sealant application, a nozzle having a relatively long outlet tip  58  with a narrow opening  62  is provided with a stiffer resilient strip  92  then that which may be provided in a universal nozzle provided with the kit. Still further, there are applications where full flow of the gun is required. For example, mining applications which use polyurethane foam to seal shaft “doors” or “bulkheads” in mine shafts in the event of a fire require the dispensing gun to meter the components at very high dispensing rates. In such applications, nozzle  13  would be supplied without resilient strip  92 . 
         [0056]    The choice of flexibility or rigidity of resilient strip  92  is believed to be a factor also with respect to “post” drip which is foam dripping from outlet tip  58  when dispensing gun  10  is stopped. To some extent post drip is inherent and will always occur because the components within static mixer of mixing chamber began to react and force the foam from outlet tip  58 . It is believed that, depending on the rigidity of resilient strip  92 , a seal can be additionally maintained at valve seat extension opening  89 . The rigidity of resilient strip  92  has to be balanced against gun performance so that full flow performance is not adversely affected. However, to the extent resilient material  92  snaps back into contact with valve seat extension opening  89 , some additional sealing assistance in alleviating post drip may be present. 
         [0057]    Referring still to  FIGS. 5 ,  6  &amp;  7 , it can be seen that the cross-sectional area of nozzle  13  at its entrance end, i.e., collar  76  is greater than the cross-sectional area of inlet chamber  60  at its exit end, i.e., the intersection with mixing chamber  59 . The nozzle wall forming inlet chamber  60  has semi-circular portions  96  corresponding to nose edge surfaces  67 ,  68  which take the shape of truncated cones as the nozzle extends from its entrance to its exit end. Similarly, the wall forming nozzle chamber  60  also has top and bottom flat portions  97  corresponding to nose straight edge surfaces  69 ,  70  which assume a triangular shape as inlet chamber  60  transitions from its entrance to its exit end. Generally speaking, inlet chamber  60  is in the shape of a funnel or a truncated cone. This configuration is believed to result in a somewhat smooth flow of the “A” and “B” liquid components into mixing chamber  59  as they travel through inlet chamber  60  after exiting valve seat extension openings  89 . That is, significant mixing or contact of the “A” and “B” components does not occur white components are flowing through inlet chamber  60 . In this regard, reference can be had to  FIG. 15  in which it can be seen that the flexure of resilient strip  92  will direct components “A” and “B” away from one another towards semi-circular portions  96  of inlet chamber  60 . It is, of course, understood that some quantity of the “A” and “B” components will contact one another at the center of inlet chamber  60 . It is not believed that the contact is detrimental to the gun operation because the flow within inlet chamber  60  is somewhat non-turbulent. Contact at the nozzle center will thus occur at a somewhat laminar flow condition while the components are directed into static mixer  63 . Further, there may be some benefit to a slight mixing contact just prior to entering mixing chamber  59 . The geometry of the centrally positioned valve seat protrusions  72 ,  73 , within nozzle inlet chamber  60  which is frustoconical in combination with resilient strip  92  provides a generally smooth, somewhat, non-turbulent flow of the “A” and “B” components, maintained somewhat separately, to the inlet of static mixer  63 . The flow does not experience any impingement against corners or dead end against any flat wall surfaces. Thus, the non-turbulent type flow of the “A” and “B” components within gun body  12  is carried through nozzle  13 . 
         [0058]    It is to be appreciated that the interaction between the “A” and “B” components within nozzle  13  are complex. Further, the words “laminar” and “turbulent” are not used herein in their strict, classical sense but are used in a relative sense. Inlet chamber  60  is believed to be relatively “quiescent”. 
         [0059]      FIGS. 15 &amp; 16  illustrate an alternative embodiment to nozzle  13  which can be utilized for applications requiring fine metering of the “A” and “B” components. In the alternative embodiment illustrated, a central wall  99  is provided. Central wall  99  extends from static mixer  63  to a distance short of resilient strip  92  so as not to affect flexure of resilient strip  92 . While wall  99  could be a flat, straight wall, it is preferred that the wall be curved such as shown in  FIG. 16  providing two truncated cone “A” and “B” component passage ways  100 ,  101  in nozzle inlet chamber  60 . Truncated cone passageways  100 ,  101  positively assure generally non-turbulent liquid component flow until the components reach static mixer  63 , which as noted above, enhance the metering characteristics of dispensing gun  10 . While wall  99  does not divide the nozzle into two separate compartments as in the known prior art nozzles, wall  99  serves to maintain the components separate at the inlet of mixing chamber  59 . The funneling nature of nozzle inlet chamber  60  is enhanced. While tests have not been conducted, some improvement in the “clogging” time is expected, and where the wall is curved, the possible adverse effects at very high flow may be somewhat alleviated. 
         [0060]    Referring now to  FIGS. 13A ,  138 , &amp;  13 C, tip section  29  of each metering rod  28  has a cylindrical tip portion  104  at its end terminating in a truncated cone or frustoconical portion  105  which in turn terminates in a larger cylindrical portion  106  which intersects with intermediate sealing section  30 . Metering tip section  29  as thus defined is conventional and is traditionally used in one-component dispensing guns and also used in two-component guns, although, when used in two-component guns, the metering tip has been used in combination with other valves. 
         [0061]    Valve seat  35  is a frustoconical or truncated cone seat. Both frustoconical valve seat  35  and truncated cone metering rod portion  105  form the same angle with longitudinal centerline  109  of each dispensing passage  25 ,  26  designated by reference arrow “A” in  FIG. 138 . For reasons which will be discussed, truncated cone angle A is not to exceed about 10°. Frustoconical valve seat  35  reduces to a minimum at valve seat opening  75  in flat end surface  74  designated by reference letter B in  FIG. 13C  which is the minor diameter of the frustoconical surface forming valve seat  35 . Diameter B is slightly larger than the outside diameter of cylindrical tip portion  104 . In the preferred embodiment of the invention, valve seat extension opening  89  is cylindrical and has a diameter indicated by reference letter C in  FIG. 13C  which is equal to or greater than diameter B. However, in an alternative embodiment of the invention, diameter C is less than diameter B (but still greater than metering rod cylindrical tip portion  104 ) and can extend for some slight distance (i.e., ⅛″ to ¼″) into valve seat  35  before the valve seat assumes its conical configuration. 
         [0062]    Each dispensing passage  25 ,  26  is sealed when truncated cone portion  105  of metering rod  28  seats against frustoconical valve seat  35  as shown in  FIG. 13A . When metering rod  28  initially is pulled rearward in dispensing passage  25  or  26 , the annular clearance space which exists between cylindrical tip portion  104  and valve seat extension opening  89  can function as the metering orifice and remains relatively constant until nozzle tip portion  104  exits valve seat extension opening  89  such as shown in  FIG. 138 . When metering rod  28  is retracted to positions as shown in  FIGS. 138 &amp; 13C , metering occurs at the distance or clearance (i.e., orifice) between the end of metering tip portion  104  and frustoconical valve seat  35 , generally in the annular space occupied by dot-dash lines  110  in  FIGS. 138 &amp; 13C  (technically dot-dash lines are perpendicular to frustoconical valve seat  35 ). Specifically, the smallest (diametrical) opening, whether in valve seat extension opening  89  (designated by reference letter “C” in  FIG. 13C ) or in frustoconical valve seat  35  (designated by reference letter “B” in  FIG. 13C ) is larger in area than the clearance between cylindrical tip portion  104  and frustoconical valve seat  35  lying generally along dot-dash line  110  throughout the travel of metering rod  28  (between full open and close portions of trigger lever  44 ). If valve seat extension opening “C”  89  is sized significantly larger than the minimum diametrical opening of frustoconical valve seat  75 , (reference letter “B”), variable metering will occur once cylindrical tip  104  clears “B”. If, in an alternative embodiment of the invention, valve seat extension opening “C”  89 , (and the extension of “C” into the frustoconical valve seat  35 ) is sized smaller than the minor diameter of frustoconical valve seat  35  (i.e., the frusto-conical surface thereof), a somewhat constant “fine” metering of the components will occur until the end of cylindrical tip portion  104  reaches the frustoconical surface of frustoconical valve seat  35 . 
         [0063]    Dimensionally the areas of cylindrical tip portion  104 , the truncated cone angle of metering rod  28  and frustoconical valve seat  35  (reference letter “A” less than  1020 ), and the minor diameter of frustoconical valve seat  35  (reference letter “B”) are selected so that the minimum annular clearance between cylindrical tip portion  104  and frustoconical valve seat  35  at the fully retracted position of metering rod  28 , i.e., full open, is equal to or less than the minimum diametrical opening  75  of frustoconical valve seat  35 , i.e., reference letter “B”. In the preferred embodiment, the fully open portion of dispensing gun  10  establishes an orifice between metering rod cylindrical tip portion  104  and frustoconical valve seat  35  of about 94-96% of the area of valve seat opening  75 , defined, in the preferred embodiment as the minor diameter of frustoconical valve seat  35 . This relationship allows variable metering of the gun throughout its travel range. In all cases, metering rod tip portion  104  is within the frustoconical surface of frustoconical valve seat  35  and functions as the orifice. Valve seat extension opening  89 , in the preferred embodiment, is sized greater than minimum frustoconical diameter “B”. In the alternative embodiment, the diameter of valve seat extension opening “C” is sized equal to or less than minimum frustoconical diametrical opening “B” for generally constant fine metering of the gun over an initial travel. In both embodiments, variable progressive metering occurs when cylindrical tip portion  104  is within the frustoconical surface of valve seat  35 . 
         [0064]    Dispensing gun  10  of the present invention exhibits excellent metering characteristics throughout its range of travel. Without wishing to be bound by any theory of operation, it is believed the arrangement described is especially advantageous for polyurethane foam in which chemical components, such as fluorocarbons, expand from a liquid to a gaseous state at defined pressures for a given temperature. In particular, a pressure gradient exists about the variable orifice which, as defined, is the minimum distance between the frustoconical surface of frustoconical valve seat  35  and cylindrical tip portion  104  of metering rod  28 . As the orifice opens the gradient expands increasing the distance whereat state change of the chemical occurs. This result, in turn, increases the backpressure exerted by the components on the orifice as the gun is increasingly opened. This increase in backpressure is believed to partially account for the improved metering of dispensing gun  10  especially at higher flow conditions. Thus, dispensing gun  10  of the present invention is able to dispense the components at slow flow rates and controllably meter the components at high or full rates at the limits of the gun&#39;s travel. 
         [0065]    It should be noted that the length of cylindrical tip portion  104  is not especially significant, about  1 / 8 ″ in the preferred embodiment. While most dispensing guns employ some form of a pivot arm arrangement for the gun&#39;s trigger, and the travel of any pivoting lever can be increased by increasing the lever length, there is a limit to the lever length and it is desirable to provide some form of increased motion for the gun&#39;s trigger when fine metering of the “A” and “B” components is desired, whether the fine metering is progressively variable as in the preferred embodiment or constant for a fixed travel length as in the alternative embodiment. 
         [0066]    Referring now to  FIGS. 14A &amp; 148 , there is shown a pivoting arrangement used in dispensing gun  10  which provides increased travel of trigger  20  to enhance fine metering of dispensing gun  10  while also providing increased control of dispensing gun  10  at full flow conditions. Trigger body portion  16  as noted has a U-shaped trigger recess  47  formed therein. Trigger pivot portion  45  of trigger  20  simply fits within U-shaped recess  47  and because the curved portion of trigger pivot  45  is a sharper radius than that of trigger recess  47  there is some translational movement of trigger  20  when trigger lever  44  is moved such as shown when comparing the relative trigger positions of  FIGS. 14A &amp; 148 . Thus, trigger pivot  45  is not fixed in the sense of being pinned or journaled within a fixed pivot. While spring  50  will maintain the curved surfaces together in rolling contact there will be some translation which is believed to assist in lever travel at the travel limits. Yoke crossbar portion  40  of trigger  20  at its intersection with elongated metering rod opening  41 , makes a line contact  112  with yoke collar section  31  of metering rod  28 . Yoke collar section  31  of metering rod  28  has a flat spring base surface  114  at its end, i.e., the end of metering rod  28 , and an annular surface  115  at the intersection of intermediate sealing section  30  with yoke collar section  31 . Annular surface  115  is chamfered (as a straight line) or curved or formed as a compound curve such as the S-shaped curve shown in  FIGS. 14A &amp; 148 , to provide a camming surface for crossbar line contact  112 . Forming annular surface  115  as a camming surface allows increased motion of trigger lever  44  at the limits of longitudinal travel of metering rod  28 . The increased motion allows for better operator control and gun feel for fine and full open metering applications. 
         [0067]    Referring now to  FIGS. 1 ,  3  &amp;  17  (in which handle body portion  18  has been “sliced” to better illustrate the invention) trigger lever  44  is formed with a trigger lever recess  117  which faces or opens to handle body portion  18 . Within trigger lever recess  117  is lock tab  120  which at one end has ears  121  snapped into openings formed in trigger lever  44  so that lock tab  120  is pivotal into and out of trigger lever recess  117 . Handle body portion  18  has its surface which faces trigger lever  44  in the form of a curve or arc indicated by dot-dash line  121  in  FIG. 17  from which a series of indentations forming grooves are formed. In particular, one groove is formed as a locking groove  122  into which lock tab  120  is positioned as shown in  FIGS. 1-3  and at which trigger  20  is locked to render the gun inoperable. In accordance, however, with the fine metering aspects of the invention, additional grooves  123  and  124  are also provided which allow some motion of trigger lever  44  until locking tab seats in the groove. In accordance with the preferred embodiment, grooves  123 ,  124  provide a fixed stop corresponding to a fixed orifice size between cylindrical tip portion  104  of metering rod  28  and frustoconical valve seat  35 . In accordance with the alternative embodiment, (smaller orifice “C”) very fine metering groove  123  establishes a generally constant, very fine metering stop. In order to provide positive placement of lock tab  120 , bumps or protrusions  125  can be formed within trigger lever recess  117  at which lock tab  120  assumes a pivoted position engaging the intended locking groove. 
         [0068]    Referring back to  FIG. 5 , the ability to determine the chemical temperature as it exits the “A” and “B” cylinders through respective “A” and “B” flexible plastic hoses (not shown) or the ability to determine the chemical temperature as it enters and/or exits disposable nozzle  13  is effected either by having a thermochromic material contained within the plastic used to mold disposable nozzle  13  or to fabricate the flexible plastic hoses. Still another approach involves affixing label  130  either permanently using a permanent adhesive or non-permanently, using a pressure-sensitive adhesive (the label optionally having thermochromic text or thermochromic graphic material printed thereupon) which changes in one instance from colored (below the recommended use temperature, illustrated by the text “Cold” in the figure), to colorless or a different color when the chemicals have transferred a sufficient amount of heat to the nozzle or label. 
         [0069]    Thermochromism is typically implemented via one of two common approaches: liquid crystals and leuco dyes. Liquid crystals are used in precision applications, as their responses can be engineered to accurate temperatures, but their color range is limited by their principle of operation. Leuco dyes allow wider range of colors to be used, but their response temperatures are more difficult to set with accuracy. 
         [0070]    Some liquid crystals are capable of displaying different colors at different temperatures. This change is dependent on selective reflection of certain wavelengths by the crystalline structure of the material, as it changes between the low-temperature crystalline phase, through anisotropic chiral or twisted nematic phase, to the high-temperature isotropic liquid phase. Only the nematic mesophase has thermochromic properties. This restricts the effective temperature range of the material. 
         [0071]    The twisted nematic phase has the molecules oriented in layers with regularly changing orientation, which gives them periodic spacing. The light passing through the crystal undergoes Bragg diffraction on these layers, and the wavelength with the greatest constructive interference is reflected back, which is perceived as a spectral color. A change in the crystal temperature can result in a change of spacing between the layers and therefore in the reflected wavelength. The color of the thermochromic liquid crystal can therefore continuously range from non-reflective (black) through the spectral colors to black again, depending on the temperature. Typically, the high temperature state will reflect blue-violet, while the low-temperature state will reflect red-orange. Since blue is a shorter wavelength than red, this indicates that the distance of layer spacing is reduced by heating through the liquid-crystal state. 
         [0072]    Some such materials are cholesteryl nonanoate or cyanobiphenyls. Liquid crystals used in dyes and inks often come microencapsulated, in the form of suspension. Liquid crystals are used in applications where the color change has to be accurately defined. 
         [0073]    Thermochromic dyes are based on mixtures of leuco dyes with suitable other chemicals, displaying a color change (usually between the colorless leuco form and the colored form) in dependence on temperature. The dyes are rarely applied on materials directly; they are usually in the form of microcapsules with the mixture sealed inside. An illustrative example would include microcapsules with crystal violet lactone, weak acid, and a dissociable salt dissolved in dodecanol; when the solvent is solid, the dye exists in its lactone leuco form, while when the solvent melts, the salt dissociates, the pH inside the microcapsule lowers, the dye becomes protonated, its lactone ring opens, and its absorption spectrum shifts drastically, therefore it becomes deeply violet. In this case the apparent thermochromism is in fact halochromism. 
         [0074]    The dyes most commonly used are spirolactones, fluorans, spiropyrans, and fulgides. The weak acids include bisphenol A, parabens, 1,2,3-triazole derivates, and 4-hydroxycoumarin and act as proton donors, changing the dye molecule between its leuco form and its protonated colored form; stronger acids would make the change irreversible. 
         [0075]    Leuco dyes have less accurate temperature response than liquid crystals. They are suitable for general indicators of approximate temperature. They are usually used in combination with some other pigment, producing a color change between the color of the base pigment and the color of the pigment combined with the color of the non-leuco form of the leuco dye. Organic leuco dyes are available for temperature ranges between about 23° F. (−5° C.) and about 140° F. (60° C.), in wide range of colors. The color change usually happens in about a 5.4° F. (3° C.) interval. 
         [0076]    The size of the microcapsules typically ranges between 3-5 μm (over 10 times larger than regular pigment particles), which requires some adjustments to printing and manufacturing processes. 
         [0077]    Thermochromic paints use liquid crystals or leuco dye technology. After absorbing a certain amount of light or heat, the crystalline or molecular structure of the pigment reversibly changes in such a way that it absorbs and emits light at a different wavelength than at lower temperatures. 
         [0078]    The thermochromic dyes contained either within or affixed upon either the disposable nozzle or hoses may be configured to change the color of the composition in various ways. For example, in one embodiment, once the composition reaches a selected temperature, the composition may change from a base color to a white color or a clear color. In another embodiment, a pigment or dye that does not change color based on temperature may be present for providing a base color. The thermochromic dyes, on the other hand, can be included in order to change the composition from the base color to at least one other color. 
         [0079]    In one particular embodiment, the plurality of thermochromic dyes are configured to cause the cleansing composition to change color over a temperature range of at least about 3° C., such as at least about 5° C., once the composition is heated to a selected temperature. For example, multiple thermochromic dyes may be present within the cleansing composition so that the dyes change color as the composition gradually increases in temperature. For instance, in one embodiment, a first thermochromic dye may be present that changes color at a temperature of from about 23° C. to about 28° C. and a second thermochromic dye may be present that changes color at a temperature of from about 27° C. to about 32° C. If desired, a third thermochromic dye may also be present that changes color at a temperature of from about 31° C. to about 36° C. In this manner, the cleansing composition changes color at the selected temperature and then continues to change color in a stepwise manner as the temperature of the composition continues to increase. It should be understood that the above temperature ranges are for exemplary and illustrative purposes only. 
         [0080]    Any thermochromic substance that undergoes a color change at the desired temperature may generally be employed in the present disclosure. For example, liquid crystals may be employed as a thermochromic substance in some embodiments. The wavelength of light (“color”) reflected by liquid crystals depends in part on the pitch of the helical structure of the liquid crystal molecules. Because the length of this pitch varies with temperature, the color of the liquid crystals is also a function of temperature. One particular type of liquid crystal that may be used in the present disclosure is a liquid crystal cholesterol derivative. Exemplary liquid crystal cholesterol derivatives may include alkanoic and aralkanoic acid esters of cholesterol, alkyl esters of cholesterol carbonate, cholesterol chloride, cholesterol bromide, cholesterol acetate, cholesterol oleate, cholesterol caprylate, cholesterol oleyl-carbonate, and so forth. Other suitable liquid crystal compositions are possible and contemplated within the scope of the invention. 
         [0081]    In addition to liquid crystals, another suitable thermochromic substance that may be employed in the present disclosure is a composition that includes a proton accepting chromogen (“Lewis base”) and a solvent. The melting point of the solvent controls the temperature at which the chromogen will change color. More specifically, at a temperature below the melting point of the solvent, the chromogen generally possesses a first color (e.g., red). When the solvent is heated to its melting temperature, the chromogen may become protonated or deprotonated, thereby resulting in a shift of the absorption maxima. The nature of the color change depends on a variety of factors, including the type of proton-accepting chromogen utilized and the presence of any additional temperature-insensitive chromogens. Regardless, the color change is typically reversible. 
         [0082]    Although not required, the proton-accepting chromogen is typically an organic dye, such as a leuco dye. In solution, the protonated form of the leuco dye predominates at acidic pH levels (e.g., pH of about 4 or less). When the solution is made more alkaline through deprotonation, however, a color change occurs. Of course, the position of this equilibrium may be shifted with temperature when other components are present. Suitable and non-limiting examples of leuco dyes for use in the present disclosure may include, for instance, phthalides; phthalanes; substituted phthalides or phthalanes, such as triphenylmethane phthalides, triphenylmethanes, or diphenylmethanes; acyl-leucomethylene blue compounds; fluoranes; indolylphthalides, spiropyranes; cumarins; and so forth. Exemplary fluoranes include, for instance, 3,3′-dimethoxyfluorane, 3,6-dimethoxyfluorane, 3,6-di-butoxyfluorane, 3-chloro-6-phenylamino-flourane, 3-diethylamino-6-dimethylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, and 3-diethyl-7,8-benzofluorane, 3,3′-bis-(p-dimethyl-aminophenyl)-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylamino-fluorane, 3-diethylamino-7-phenyl-aminofluorane, and 2-anilino-3-methyl-6-diethylamino-fluorane. Likewise, exemplary phthalides include 3,3′,3″-tris(p-dimethylamino-phenyl)phthalide, 3,3′-bis(p-dimethyl-aminophenyl)phthalide, 3,3-bis(p-diethylamino-phenyl)-6-dimethylamino-phthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, and 3-(4-diethylamino-2-methyl)phenyl-3-(1,2-dimethylindol-3-yl)phthalide. 
         [0083]    Although any solvent for the thermochromic dye may generally be employed in the present disclosure, it is typically desired that the solvent have a low volatility. For example, the solvent may have a boiling point of about 150° C. or higher, and in some embodiments, from about 170° C. to 280° C. Likewise, the melting temperature of the solvent is also typically from about 25° C. to about 40° C., and in some embodiments, from about 30° C. to about 37° C. Examples of suitable solvents may include saturated or unsaturated alcohols containing about 6 to 30 carbon atoms, such as octyl alcohol, dodecyl alcohol, lauryl alcohol, cetyl alcohol, myristyl alcohol, stearyl alcohol, behenyl alcohol, geraniol, etc.; esters of saturated or unsaturated alcohols containing about 6 to 30 carbon atoms, such as butyl stearate, methyl stearate, lauryl laurate, lauryl stearate, stearyl laurate, methyl myristate, decyl myristate, lauryl myristate, butyl stearate, lauryl palmitate, decyl palmitate, palmitic acid glyceride, etc.; azomethines, such as benzylideneaniline, benzylidenelaurylamide, o-methoxybenzylidene laurylamine, benzylidene p-toluidine, p-cumylbenzylidene, etc.; amides, such as acetamide, stearamide, etc.; and so forth. 
         [0084]    The thermochromic composition may also include a proton-donating agent (also referred to as a “color developer”) to facilitate the reversibility of the color change. Such proton-donating agents may include, for instance, phenols, azoles, organic acids, esters of organic acids, and salts of organic acids. Exemplary phenols may include phenylphenol, bisphenol A, cresol, resorcinol, chlorolucinol, b-naphthol, 1,5-dihydroxynaphthalene, pyrocatechol, pyrogallol, trimer of p-chlorophenol-formaldehyde condensate, etc. Exemplary azoles may include benzotriaoles, such as 5-chlorobenzotriazole, 4-laurylaminosulfobenzotriazole, 5-butylbenzotriazole, dibenzotriazole, 2-oxybenzotriazole, 5-ethoxycarbonylbenzotriazole, etc.; imidazoles, such as oxybenzimidazole, etc.; tetrazoles; and so forth. Exemplary organic acids may include aromatic carboxylic acids, such as salicylic acid, methylenebissalicylic acid, resorcylic acid, gallic acid, benzoic acid, p-oxybenzoic acid, pyromellitic acid, b-naphthoic acid, tannic acid, toluic acid, trimellitic acid, phthalic acid, terephthalic acid, anthranilic acid, etc.; aliphatic carboxylic acids, such as stearic acid, 1,2-hydroxystearic acid, tartaric acid, citric acid, oxalic acid, lauric acid, etc.; and so forth. Exemplary esters may include alkyl esters of aromatic carboxylic acids in which the alkyl moiety has 1 to 6 carbon atoms, such as butyl gallate, ethyl p-hydroxybenzoate, methyl salicylate, etc. 
         [0085]    The amount of the proton-accepting chromogen employed may generally vary, but is typically from about 2 wt. % to about 20 wt. %, and in some embodiments, from about 5 to about 15 wt. % of the thermochromic substance. Likewise, the proton-donating agent may constitute from about 5 to about 40 wt. %, and in some embodiments, from about 10 wt. % to about 30 wt. % of the thermochromic substance. In addition, the solvent may constitute from about 50 wt. % to about 95 wt. %, and in some embodiments, from about 65 wt. % to about 85 wt. % of the thermochromic composition. 
         [0086]    Regardless of the particular thermochromic substance employed, it may be microencapsulated to enhance the stability of the substance during processing. For example, the thermochromic substance may be mixed with a thermosetting resin according to any conventional method, such as interfacial polymerization, in-situ polymerization, etc. The thermosetting resin may include, for example, polyester resins, polyurethane resins, melamine resins, epoxy resins, diallyl phthalate resins, vinylester resins, and so forth. The resulting mixture may then be granulated and optionally coated with a hydrophilic macromolecular compound, such as alginic acid and salts thereof, carrageenan, pectin, gelatin and the like, semisynthetic macromolecular compounds such as methylcellulose, cationized starch, carboxymethylcellulose, carboxymethylated starch, vinyl polymers (e.g., polyvinyl alcohol), polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, maleic acid copolymers, and so forth. The resulting thermochromic microcapsules typically have a size of from about 1 to about 50 micrometers, and in some embodiments, from about 3 to about 15 micrometers. Various other microencapsulation techniques may also be used. 
         [0087]    Thermochromic dyes are commercially available from various sources. In one embodiment, for instance, thermochromic dyes marketed by Chromadic creations, Hamilton, Ontario and sold under the trade name SpectraBurst Thermochromic Polypropylene. 
         [0088]    The thermochromic dyes can be present in the composition in an amount sufficient to have a visual effect on the color of the composition. The amount or concentration of the dyes can also be increased or decreased depending upon the desired intensity of any color. In general, the thermochromic dyes may be present in the composition in an amount from about 0.01% by weight to about 9% by weight, such as from about 0.1% by weight to about 3% by weight. For instance, in one particular embodiment, the thermochromic dyes may be present in an amount from about 0.3% to about 1.5% by weight. 
         [0089]    As described above, thermochromic dyes typically change from a specific color to clear at a certain temperature, e.g., dark blue below 60° F. to transparent or translucent above 60° F. If desired, other pigments or dyes can be added to the composition in order to provide a background color that remains constant independent of the temperature of the composition. By adding other pigments or dyes in combination with the thermochromic dyes to the composition, the thermochromic dyes can provide a color change at certain temperatures rather than just a loss of color should the thermochromic dye become clear. For instance, a non-thermochromic pigment, such as a yellow pigment, may be used in conjunction with a plurality of thermochromic dyes, such as a red dye and a blue dye. When all combined together, the cleansing composition may have a dark color. As the composition is increased in temperature, the red thermochromic dye may turn clear changing the color to a green shade (a combination of yellow and blue). As the temperature further increases, the blue thermochromic dye turns clear causing the composition to turn yellow. 
         [0090]    It should be understood, that all different sorts of thermochromic dyes and non-thermochromic pigments and dyes may be combined in order to produce a composition having a desired base color and one that undergoes desired color changes. The color changes, for instance, can be somewhat dramatic and fanciful. For instance, in one embodiment, the composition may change from green to yellow to red. 
         [0091]    In an alternative embodiment, however, the composition can contain different thermochromic dyes all having the same color. As the temperature of the composition is increased, however, the shade or intensity of the color can change. For instance, the composition can change from a vibrant blue to a light blue to a clear color. 
         [0092]    In addition to the above, it should be understood that many alterations and permutations are possible. Any of a variety of colors and shades can be mixed in order to undergo color changes as a function of temperature. 
         [0093]    The best mode for carrying out the invention has been described for purposes of illustrating the best mode known to the applicant at the time. The examples are illustrative only and not meant to limit the invention, as measured by the scope and merit of the claims. The invention has been described with reference to preferred and alternate embodiments. Obviously, modifications and alterations will occur to others upon the reading and understanding of the specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.