Patent Publication Number: US-6215109-B1

Title: Hot melt applicator air preheater

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to hot melt adhesive application systems, and more particularly to a new and improved system or arrangement, and a method, for heating incoming air used to fiberize or determine the control pattern of the adhesive conveyed to the adhesive spray modules and dispensed therefrom. 
     BACKGROUND OF THE INVENTION 
     In connection with the spraying, dispensing, or discharge of hot melt adhesive materials, air is routed to the spray modules in order to control the particular patterns of the adhesives being dispensed. More specifically, such air is preheated so as to maintain the adhesive in its heated state such that the hot melt adhesive can properly achieve its adhesive functions. If cooled or ambient air was employed, the hot melt adhesive would experience an inappropriate amount of cooling whereby the utility of the adhesive would be lost. It has also been found to be imperative that the preheated air provided to the plurality of adhesive spray modules be uniform in temperature, density, and flow rate parameters in order to ensure uniformity of the resulting adhesive spray patterns from the adhesive spray modules. Currently, two basic air preheater design systems or arrangements are conventionally in use, however, each one of such systems or arrangements exhibits inherent operational drawbacks or disadvantages. 
     For example, as disclosed within FIG. 1, a first conventionally known and utilized system is illustrated, is generally indicated by the reference character  10 , and is seen to comprise a conduit  12  for introducing incoming air into a heater block  14  within which a plurality of heaters  16 , 16  are serially disposed. Each one of the heaters  16  may take the form of a conventional spiral tube heater which is illustrated in FIG.  5 . As seen in FIG. 5, each one of the heaters  16  comprises an outer housing  18  within which is disposed a hollow aluminum tubular member  20 . Tubular member  20  is open at a first left end portion  22  thereof, while the second op-posite right end portion thereof is closed by means of an end face or wall  24  integral with the tubular member  20 . The open end portion  22  of the tubular member  20  is provided with an external flanged portion  26  within which a O-ring type seal member  28  is disposed, and the outer peripheral surface of the tubular member  20  is provided with a helical thread or finned structure  30  which extends substantially the entire axial length of the tubular member  20  from within the vicinity of the flanged portion  26  to within the vicinity of the end face or wall  24 . An air inlet port  32  is defined within a first sidewall portion of the housing  18  at an axial position adjacent to the flanged portion  26  so as to introduce relatively cool air CAI into the housing  18 , and an air outlet port  34  is similarly defined within a second sidewall portion of the housing  18  at an axial position adjacent to the end wall or face  24  so as to permit heated air HAO to exit. It is of course to be appreciated that the helical thread or finned structure  30  cooperates with the interior peripheral surface of the housing  18  so as to in effect define a helical path or conduit along which the air is conducted from the air inlet port  32  to the air outlet port  34 . The helical path or conduit provides increased residence time for the air within the heater housing  18  whereby the air is sufficiently heated. In order to provide the heat input for the air, a cartridge type heater, not shown, is axially inserted into the open end  22  of the tubular member  20  and disposed within a heater cartridge cavity  36  defined within the tubular member  20 . 
     Returning then to the system  10  disclosed within FIG. 1, the heater block  14  also has disposed therein a temperature sensor  38  which senses the temperature of the heater block  14  and controls the energization of the heaters  16 , 16  accordingly. The heated air HAO, after exiting from the heater block  14  is conducted or distributed toward the adhesive dispensing modules  40  by means of a common conduit  42  and a plurality of branch conduits  44 , 46 , 48 , 50 . As may readily be appreciated, however, this structural system poses several operative drawbacks or disadvantages. Firstly, it is noted that due to the different distances, for example, of the conduits  44  and  50  from the common conduit  42 , relative to the distances of the conduits  46  and  48  from the common conduit  42 , non-uniform distribution of the heated air to the various conduits can occur. Secondly, due to the fact that the temperature sensor  38  is in effect embedded within the heater block  14  and is not disposed within the heated air stream, only poor or unreliable temperature control of the air stream is achieved. 
     With reference now being made to FIG. 2, a second conventionally known and utilized system is illustrated and is generally indicated by the reference character  110 . The system  110  is seen to comprise an inlet conduit  112  for introducing relatively cold ambient air into a heated block  114 . In particular, the incoming relatively cold ambient air stream  112  is initially divided or distributed into separate air streams which are conducted through branch conduits  144 ,  146 , 148 , 150 . The air streams or conduits  144 , 146 , 148 , 150  respectively pass through the heated block  114  such that the separate air streams are heated within the heated block  114 . The heated air streams are then conducted by means of the conduits  144 , 146 , 148 , 150  to the adhesive dispensing modules  140 . 
     While the system of FIG. 2 appears to have resolved the problem of dividing the heated air stream into multiple heated branched air streams and the resulting non-uniform distribution characteristics of the same, non-uniform temperature levels or gradients can nevertheless exist within the conduits  144 , 146 , 148 , 150  of the heated block  114  which can of course result in the creation of non-uniform temperature levels within, and heating of, the air streams. In addition to non-uniform fluidic transmission characteristics that may be inherent within the air stream passages defined by the conduits  144 , 146 , 148 , 150 , one of the major factors contributing to the creation of such non-uniform temperature levels within the individual air streams and conduits  144 , 146 , 148 , 150  is the embedded disposition of the single temperature sensor  138  within the heated block  114  whereby it is not possible to accurately control the temperature level within each one of the air streams passing through the conduits  144 , 146 , 148 , 150 . 
     A need therefore exists in the art for a new and improved system, and a method of operating the same, wherein the air streams supplied to the dispensing modules can be heated to a desired temperature level, wherein the temperature levels of the air streams supplied to the dispensing modules can be rendered uniform, wherein the temperature levels of the air streams supplied to the dispensing modules can be properly and accurately controlled, and wherein the air stream flow rates provided to the dispensing modules can effectively be rendered uniform. 
     OBJECTS OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus or systems for dispensing hot melt adhesives. 
     Another object of the present invention is to provide a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus for dispensing hot melt adhesive wherein the various drawbacks and operative disadvantages of the known PRIOR ART systems, as discussed hereinbefore, are effectively overcome. 
     An additional object of the present invention is to provide a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus for dispensing hot melt adhesive wherein non-uniform temperature levels, density, and flow rate parameters characteristic of the various air streams conducted to the hot melt adhesive dispensing modules are effectively eliminated. 
     A further object of the present invention is to provide a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus for dispensing hot melt adhesive wherein the air streams supplied to the hot melt adhesive dispensing modules can be heated to a desired temperature level, wherein the temperature levels of the air streams supplied to the hot melt adhesive dispensing modules can effectively be rendered uniform, wherein the temperature levels of the air streams supplied to the hot melt adhesive dispensing modules can be properly and accurately controlled, and wherein the flow rates of the air streams provided to the hot melt adhesive dispensing modules can effectively be rendered uniform. 
     SUMMARY OF THE INVENTION 
     The foregoing and other objectives are achieved in accordance with the principles and teachings of the present invention through the provision of a new and improved air preheater system, and a method of operating the same, for use in connection with the requisite supply of heated air streams to the dispensing modules of apparatus for dispensing hot melt adhesives wherein the system comprises the initial separation of the incoming ambient relatively cool air into separate air streams. The separate air streams are then individually and separately heated, and the exiting or discharged heated air streams are then recombined into a single heated air stream. In this manner, any variations in the temperature levels, density, and flow rate parameters within the individual or separate heated air streams are therefore averaged out and effectively eliminated. The single heated air stream is then conducted to a distribution manifold wherein unique structure of the distribution manifold renders uniform distribution of the separate air streams to the hot melt adhesive dispensing modules possible. In addition, in order to properly control the temperature level to which the individual air streams are initially heated, a temperature sensor is placed within the single combined air stream at a location upstream of the distribution manifold. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features, and attendant advantages of the present invention will be more fully appreciated from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views, and wherein: 
     FIG. 1 is a schematic drawing of a first embodiment of a PRIOR ART air preheater system used in connection with the supply of preheated air streams to the dispensing modules of a hot melt adhesive dispensing system; 
     FIG. 2 is a schematic drawing of a second embodiment of a PRIOR ART air preheater system used in connection with the supply of preheated air streams to the dispensing modules of a hot melt adhesive dispensing system; 
     FIG. 3 is a schematic drawing of a first embodiment of a new and improved air preheater system, constructed in accordance with the principles and teachings of the present invention, for use in connection with the supply of preheated air streams to the dispensing modules of a hot melt adhesive dispensing system; 
     FIG. 4 is an end elevational view of a second embodiment of an air preheater system, constructed in accordance with the principles and teachings of the present invention, for use in connection with the supply of preheated air streams to the dispensing modules of a hot melt adhesive dispensing system; 
     FIG. 5 is a side elevational view of a PRIOR ART spiral tube heater used within the PRIOR ART system disclosed within FIG. 1; and 
     FIG. 6 is an end elevational view of a distribution manifold used within the system of FIG. 3 so as to uniformly distribute the preheated air streams to the dispensing modules of a hot melt adhesive dispensing system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and more particularly to FIG. 3 thereof, a first embodiment of the new and improved air preheater system, constructed in accordance with the principles and teachings of the present invention, and for use in connection with the supply of preheated air streams to the dispensing modules of a hot melt adhesive dispensing system in accordance with the method of the present invention, is illustrated and is generally indicated by the reference character  210 . It is initially noted that the system  210  of the present invention is somewhat similar to the PRIOR ART systems illustrated in FIGS. 1 and 2 in that all of the systems employ some common or corresponding types of structural components. Therefore, such similar components will be designated by similar or corresponding reference characters except that the reference characters used in FIG.  3  in connection with the first embodiment of the system, and the method of operating the same, constructed in accordance with the principles and teachings of the present invention will be in the 200 series. 
     More particularly, it is seen that relatively cool ambient air is introduced into the system  210  by means of an inlet conduit  212 , and the downstream end of the inlet conduit  212  is fluidically connected to an inlet manifold  213  having a single inlet port and a plurality of outlet ports such that the incoming air stream is divided into a plurality of separated air streams. A plurality of manifold conduits  215 , 215 , 215 , 215  are fluidically connected at their upstream end portions to the inlet manifold  213  and are fluidically connected at their downstream end portions to a plurality of spiral tube heaters  216 , 216 , 216 , 216  so as to be able to respectively conduct the separated air streams to the spiral tube heaters  216 , 216 , 216 , 216 . Each one of the spiral tube heaters  216  may be of the same construction as that illustrated in FIG. 5 which was previously discussed hereinbefore. It is also noted that the particular number of spiral tube heaters  216  employed or disposed within the housing  214  for preheating the air streams is dependent upon the width or size of the hot melt adhesive applicator head, not shown, with which the hot melt adhesive dispensing modules . 240 , 240 , 240 , 240  are operatively associated. 
     The spiral tube heaters  216 , 216 , 216 , 216  are disposed within a housing  214 , and a plurality of heater conduits  217 , 217 , 217 , 217  are respectively fluidically connected at their upstream end portions to the spiral tube heaters  216 , 216 , 216 , 216  while the downstream end portion of each one of the heater conduits  217  is fluidically connected to an outlet manifold  219  having a plurality of inlet ports and a single outlet port. As a result of the provision of the heater conduits  217 , 217 , 217 , 217 , and their common fluidic connection to the single outlet manifold  219 , it is appreciated that the initially separated heated air streams, having passed through the separate spiral tube heaters  216 , 216 , 216 ,  216 , are now recombined within the outlet manifold  219 . 
     It is thus apparent that as a result of such recombination of the plurality of preheated air streams, respectively exiting the spiral tube heaters  216 , 216 , 216 , 216  and conducted or passed through the heater conduits  217 , 217 ,  217 , 217 , any temperature level, density, or flow rate parameter discrepancies, variants, or gradients existing within such air streams with respect to each other will in effect be averaged out or effectively cancelled whereby new composite temperature level, density, and flow rate parameters will be exhibited, presented, and characteristic of the new single preheated air stream exiting from the outlet manifold  219  through means of an outlet manifold conduit  221 . The single preheated air stream can then be distributed to the hot melt adhesive dispensing modules  240 , 240 , 240 , 240  whereby it can readily be appreciated that each one of the hot melt adhesive dispensing modules  240 , 240 , 240 , 240  receives a portion of the same preheated air stream such that each air stream received by a particular one of the hot melt adhesive dispensing modules  240 , 240 , 240 , 240  has substantially precisely the same temperature, density, and flow rate parameters as the air stream received by any one of the other hot melt adhesive dispensing modules  240 , 240 , 240 , 240 . 
     More particularly, the downstream end of the outlet manifold conduit  221  is fluidically connected to a distribution manifold  223  which serves to separate the single preheated air stream into a plurality of preheated air streams for conveyance to the hot melt adhesive dispensing modules  240 , 240 , 240 , 240 , and it is seen that a plurality of distribution manifold conduits  225 , 225 , 225 , 225  fluidically interconnect the distribution manifold  223  to the individual hot melt adhesive dispensing modules  240 , 240 , 240 , 240 . In order to provide for a uniform distribution of the separated preheated air streams to the individual hot melt adhesive dispensing modules  240 , 240 , 240 , 240 , the distribution manifold  223  is provided with unique structure as disclosed within FIG.  6 . 
     More specifically, the distribution manifold  223  comprises a substantially centrally located inlet port  227  which is fluidically connected to the downstream end of the outlet manifold conduit  221 , and a plurality of outlet ports  229 , 229 , 229 , 229  which are fluidically connected to the upstream ends of the distribution manifold conduits  225 , 225 ,  225 , 225 . The inlet port  227  and the outlet ports  229 , 229 ,  229 , 229  are fluidically connected to an internal chamber  231  defined within the distribution manifold  223  wherein the chamber  231  is seen to have a substantially inverted trapezoidal cross-sectional configuration comprising a relatively short longitudinal side  233  and a relatively long longitudinal side  235 . 
     The inlet port  227  is disposed adjacent to the relatively short longitudinal side  233  and the outlet ports  229 , 229 ,  229 , 229  are disposed adjacent to the relatively long longitudinal side  235 . This arrangement is critically important in that as the preheated air stream comes into the inlet port  227  of the distribution manifold  223  from the outlet manifold conduit  221 , the increasing cross-sectional configuration or volume of the chamber  231  serves to prevent any pressure drop from occurring within the air stream whereby air streams delivered to the outlet ports  229 , 229 ,  229 , 229  have substantially uniform flow properties. A baffle  237  is also provided internally within the distribution manifold chamber  231  for forcing the incoming air stream, passing through inlet port  227 , to be distributed laterally outwardly such that the air stream can be evenly distributed between the plurality of outlet ports  229 , 229 , 229 , 229  as opposed to the incoming air stream otherwise readily having the tendency to migrate directly upward above the inlet port  227  and toward the two centrally located outlet ports  229 ,  229 . 
     With reference again being made to the system  210  of the present invention as disclosed in FIG. 3, another critical feature of the present invention system  210  that should be particularly appreciated is the fact that the temperature sensor  238  is actually disposed within the single preheated air stream flowing through outlet manifold conduit  221 . In this manner, real temperature values indicative of the recombined or composite air stream can be readily determined or detected by means of the temperature sensor  238  whereby the spiral tube heaters  216 , 216 , 216 , 216  can be more accurately controlled so as to in turn accurately heat the air streams flowing therethrough and maintain the temperature of the air streams at the desired temperature level. 
     With reference lastly being made to FIG. 4, in view of the fact that, in accordance with the teachings and principles of the present invention, the temperature sensor  238  is disposed within the recombined air stream  221 , as illustrated in FIG. 3 in connection with the first embodiment of the present invention, as opposed to being disposed within the block  14  or the heated block  114  as disclosed in connection with the PRIOR ART embodiments as illustrated within FIGS. 1 and 2, a potential concern has been discussed in connection with the possible overheating of the system, and in particular with respect to the overheating of the spiral tube heaters  216 , 216 , 216 , 216  and housing  214 , under no-flow conditions, that is, when air is not being conducted through the system and yet the spiral tube heaters  216 , 216 , 216 , 216  have been energized. In order to counteract any such tendency or potential overheating of the system, an advantageous arrangement of the various components of the system has been developed and is disclosed as a second embodiment of the present invention in FIG.  4 . It is noted that the components of the system illustrated in FIG. 4, which are similar or correspond to the components of the system  210  illustrated in FIG. 3, are designated by similar or corresponding reference characters except that the reference characters are in the  300  series. 
     More particularly, the hot melt adhesive air preheating system comprising the aforenoted second embodiment of the present invention is illustrated in FIG. 4, is generally indicated by the reference character  310 , and is seen to comprise a housing  314  within which are disposed three spiral tube heaters  316 , 316 , 316 . The spiral tube heaters  316 , 316 , 316  are spaced from each other and are disposed within a substantially triangular array, and a temperature sensor  338  is disposed at the center of the triangular array of the spiral tube heaters  316 , 316 , 316  with the axes of the spiral tube heaters  316 , 316 , 316  and the temperature sensor  338  being disposed parallel to each other. It is noted that with this particular arrangement of the spiral tube heaters  316 , 316 , 316  and temperature sensor  338 , the tip portion of the temperature sensor  338  will nevertheless be disposed within the recombined air stream, not shown, in accordance with the principles and teachings of the present invention as have been fully discussed hereinbefore. 
     In addition, as a result of this particular arrangement of the spiral tube heaters  316 , 316 , 316  and the temperature sensor  338 , should the spiral tube heaters  316 ,  316 , 316  be energized under no-flow conditions, that is, when air is not flowing through the system, heat from the spiral tube heaters  316 ,  316 , 316  will in fact be conducted to, or will migrate toward, the temperature sensor  338  under convection or radiation principles whereby the energization of the spiral tube heaters  316 , 316 , 316  will be controlled at a substantially predetermined temperature level such that overheating of the system does not in fact occur. It is also to be noted that while the second embodiment of the present invention, as disclosed in FIG. 4, comprises the disposition of three spiral tube heaters  316 , 316 , 316  within the housing  314 , a greater or lesser number of spiral tube heaters can of course be employed. 
     Thus, it may be seen that in accordance with the principles and teachings of the present invention, the arrangement of the various components of the system permit individual incoming ambient air streams to be separately, individually, and independently heated, and subsequently, such separately and independently heated air streams are recombined into a single composite air stream such that any temperature, density, and flow rate differentials, variants, or gradients that previously existed within the separate or individual air streams are averaged out. The single recombined air stream is then divided into separate air streams so as to be conducted to the hot melt adhesive dispensing modules. In addition, the temperature sensor is located in the recombined composite air stream so as to accurately control the spiral tube heaters in accordance with actually sensed temperature values of the recombined composite air stream which is to be supplied to the hot melt adhesive dispensing modules. 
     Obviously, many variations and modifications of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.