Abstract:
A reciprocating plunger-type valve mechanism or assembly, which can be utilized in conjunction with adhesive dispensing applicators to control the dispensing of adhesive compositions which are to be used in connection with the bonding, securing, or fixation of pavement markers to road pavement surfaces, is disclosed. The mechanism or assembly comprises dual shutoff locations in connection with the supply of the incoming adhesive material so as to effectively reduce the prevailing pressure upon the shutoff blade controlling the adhesive material dispensing/discharge port whereby soft pressure starts and controlled deposition quantities are enabled while the generation of residual adhesive material or splatter is avoided.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to dispensing valve mechanisms or assemblies, and more particularly to a new and improved reciprocating plunger-type dispensing valve mechanism which can be utilized in conjunction with adhesive dispensing applicators to control the dispensing of adhesive compositions which are to be used in connection with the bonding, securing, or fixation of pavement markers to road pavement surfaces. 
       BACKGROUND OF THE INVENTION 
       [0002]    Pavement markers are conventionally applied to road pavement surfaces by means of a suitable adhesive. Various adhesive dispensing mechanisms are conventionally mounted upon a road vehicle that moves along a road pavement surface upon which the pavement markers are to be applied. The adhesive material is dispensed onto a predetermined location of the road pavement surface by means of the particular adhesive dispensing mechanism or apparatus, and subsequently, a technician/operator, riding upon the road vehicle at a position directly behind the dispensing mechanism or apparatus, or another mechanism of the dispensing apparatus located upon the vehicle at a position directly behind the dispensing mechanism or apparatus, applies a pavement marker to the freshly deposited adhesive. When the adhesive cures, the pavement marker is fixedly secured or bonded to the road pavement surface. 
         [0003]    Various valve mechanisms or adhesive applicators, utilized in conjunction with pavement marker application machines, or for other purposes, are of course well known such as, for example, U.S. Pat. No. 4,887,741 which issued to Downing on Dec. 19, 1989, U.S. Pat. No. 5,888,018 which issued to Green on Mar. 30, 1999, U.S. Pat. No. 5,934,822 which issued to Green on Aug. 10, 1999, United States Patent Application Publication 2002/0139818 which was published on Oct. 3, 2002 for McGuffey, U.S. Pat. No. 7,614,529 which issued to Bolyard, Jr. et al. on Nov. 10, 2009, United States Patent Application Publication 2013/0334252 which was published on Dec. 19, 2013 for Dorman et al., and U.S. Pat. No. 8,746,501 which issued to Saine on Jun. 10, 2014. 
         [0004]    In order for an adhesive dispensing valve to be suitable for the deposition of adhesive material onto a pavement road surface so as to successfully facilitate the fixation of a pavement marker to the pavement road surface, the adhesive dispensing valve must satisfy several important operating criteria. For example, the valve needs to effectively provide the adhesive deposition with a consistent shape and thickness, such as, for example, a substantially square deposit of material of approximately four and one-half inches per side to which, for example, a four-inch square pavement marker can be adhered, and with a thickness of approximately one-eighth to one-quarter of an inch, although the particular thickness will vary depending upon the type and coarseness of the road surface to which the markers are being applied. Along these lines, it is to be noted that rough chip seal roads require a thicker deposit of adhesive than smooth concrete. 
         [0005]    In addition, the valve needs to dispense the adhesive material extremely quickly. The faster the valve can dispense the required amount of adhesive, the faster the road vehicle carrying the adhesive applicator apparatus can travel down the road, the greater the distance that can be covered within a predetermined time frame, the greater the number of pavement markers that can be applied to the pavement road surface within such timeframe, and hence, the greater the productivity per roadwork shift. For example, when the road vehicle travels at a speed of one mph (1 mph), the vehicle will travel approximately seventeen inches per second (17″/sec), and the entire adhesive dispensing cycle would then need to be accomplished within approximately two hundred sixty five milliseconds (265 ms). Alternatively, if the road vehicle travels at a speed of four mph (4 mph), the vehicle will travel approximately sixty-eight inches per second (68″/sec), and the entire adhesive dispensing cycle would then need to be accomplished within approximately sixty six milliseconds (66 ms). This rapid cycling of the dispensing of the adhesive composition by means of the applicator dispensing valve permits the applicator road vehicle to move continuously along the road pavement as opposed to being required to stop and start at each marker location in order to dispense the adhesive composition. This reduces wear and tear upon the vehicle while increasing productivity. The valve also needs to dispense the adhesive material with clean and consistent commencement and termination of the dispensing process. This reduces the generation of adhesive material tails, trailing adhesive depositions, or adhesive splatter upon the road pavement surface as the vehicle continues to move forwardly along the road pavement surface. Lastly, the valve must also exhibit good durability and serviceability so as to effectively provide a lengthy service life throughout which millions of pavement markers will be applied to the road pavement surfaces while maintenance or service operations and downtime is minimized. 
         [0006]    A need therefore exists in the art for a new and improved plunger-type dispensing valve which can be specifically used for dispensing adhesive compositions onto road pavement surfaces, wherein such dispensing valve will meet the aforenoted criteria and achieve the aforenoted objectives so as to in fact be capable of rapidly affixing pavement markers to road pavement surfaces at predetermined locations along the road pavement surfaces. 
       SUMMARY OF THE INVENTION 
       [0007]    The foregoing and other objectives are achieved in accordance with the teachings and principles of the present invention through the provision of a new and improved plunger-type dispensing valve which comprises a valve housing, and a piston-cylinder assembly disposed within a first upper section of the valve housing wherein the piston comprises a piston head and a piston rod. A lower end portion of the piston rod is fixedly connected to a first uppermost enlarged diameter portion of a valve plunger. The piston-cylinder assembly may be operated either pneumatically or hydraulically, and the combination of the piston-cylinder assembly and the valve plunger comprise the only moving part of the entire dispensing valve. The valve plunger extends vertically downwardly through a second intermediate section of the valve housing wherein a second lowermost enlarged diameter portion of the valve plunger has a valve member or shutoff blade fixedly connected thereto. The valve member or shutoff blade is adapted to operatively cooperate with, for example, a pair of oppositely disposed shutoff output plates which define an adhesive material dispensing or discharge output port within a third lowermost section of the valve housing. An adhesive material inlet supply port is fluidically connected to a first side portion of the second intermediate section of the valve housing, while an adhesive material outlet recirculation port is fluidically connected to a second side portion of the second intermediate section of the valve housing. The valve plunger is vertically reciprocable within a cylinder portion of the second intermediate section of the valve housing so as to be interposed between the adhesive material inlet supply port and the adhesive material outlet recirculation port. The valve plunger further comprises a third intermediate enlarged diameter portion interposed between the first uppermost enlarged diameter portion connected to the piston rod and the second lowermost enlarged diameter portion connected to and mounting the valve member or shutoff blade thereon. Still further, a first upper annularly configured reduced diameter portion of the valve plunger is defined between the first and third enlarged diameter portions of the valve plunger while a second lower annularly configured reduced diameter portion of the valve plunger is defined between the second and third enlarged diameter portions of the valve plunger. 
         [0008]    Accordingly, as will become more apparent hereinafter when reference is made to the accompanying drawings, when the valve plunger is disposed at its lowermost position whereby the valve member or shutoff blade is fully interposed between the pair of oppositely disposed shutoff outlet plates, or an alternatively configured valve seat, thereby defining the fact that the dispensing valve is disposed at its fully CLOSED position, the first upper annularly configured reduced diameter section of the valve plunger will effectively permit fluid communication between the adhesive material inlet supply port and the adhesive material outlet recirculation port such that the adhesive material is continuously recirculated throughout the system by means of a suitable pump operatively connected to an adhesive material reservoir or supply tank. The third intermediate enlarged diameter section of the valve plunger effectively prevents the adhesive material from flowing downwardly toward the dispensing or discharge output port, while the first uppermost enlarged diameter section of the valve plunger, in conjunction with a plunger rod seal annularly surrounding the first uppermost enlarged diameter section of the valve plunger, effectively prevents the adhesive material from flowing upwardly toward the piston-cylinder assembly. 
         [0009]    To the contrary, when the valve plunger is disposed at its uppermost position whereby the valve member or shutoff blade is fully retracted from its disposition within its valve seat or between the pair of oppositely disposed shutoff output plates, thereby defining the fact that the dispensing valve is now disposed at its fully OPEN position, the third intermediate enlarged diameter section of the valve plunger will now be interposed between the adhesive material inlet supply port and the adhesive material outlet recirculation port such that the incoming adhesive material cannot flow toward the adhesive material outlet recirculation port but can only flow downwardly, annularly around the second annular reduced diameter portion of the valve plunger, and through annular conduits leading to and fluidically connected with the dispensing valve output or discharge port. 
         [0010]    It is lastly to be noted that when the plunger valve is disposed at an intermediate TRANSITION position, that is at a position where the valve member or shutoff blade is only partially elevated and retracted away from the adhesive material dispensing valve output or discharge port, the third intermediate enlarged diameter portion of the valve plunger will be disposed directly opposite the adhesive material inlet supply port. Accordingly, all incoming fluid flow of the adhesive material is, at this point in time, blocked—all fluid flow of the adhesive material coming in from the adhesive material inlet supply port is zero, all fluid flow of the adhesive material to the adhesive material outlet recirculation port is zero, and all fluid flow of the adhesive material to the dispensing valve output or discharge port is likewise zero. This structure is extremely important in connection with the operation of the dispensing valve when the valve plunger is moved both from the fully CLOSED position to the fully OPEN position, as well as from the fully OPEN position to the fully CLOSED position, because, as will become more apparent hereinafter when reference is made to the drawings, the dispensing valve of the present invention effectively has dual shutoff locations, one at the adhesive material inlet supply port and one at the adhesive material output dispensing or discharge port. More particularly, this structure is extremely important in connection with the operation of the dispensing valve when the valve plunger is moved from the CLOSED position to the OPEN position because immediately before fluid flow is established from the adhesive material inlet supply port to the adhesive material output dispensing or discharge port, the prevailing line pressure at the adhesive material output dispensing or discharge port is minimal because the adhesive material inlet supply port, located upstream from the adhesive material output dispensing or discharge port, has been blocked or terminated by the disposition of the third intermediate enlarged diameter portion of the valve plunger being disposed directly opposite the adhesive material inlet port. This facilitates the achievement of “soft starts” or the dispensing of proper adhesive material outputs, as opposed to the deposition of excessive adhesive material outputs, because the relatively large line pressure does not immediately impact the adhesive material output dispensing or discharge port as would otherwise be the case if the relatively large line pressure was permitted to build up immediately behind the valve member or shutoff blade and to then be released when the valve member or shutoff blade is retracted so as to be moved to the fully OPEN position. 
         [0011]    Alternatively, this structure also minimizes the likelihood of the formation of any residual material or splatter being discharged from the adhesive material output dispensing or discharge port when the valve plunger is moved from the fully OPEN position to the fully CLOSED position. This is because, just as was the fact that the valve member or shutoff blade was partially retracted vertically upwardly from its fully CLOSED position before the third enlarged diameter portion of the valve plunger was likewise moved vertically upwardly a sufficient distance so as to begin to OPEN the adhesive material inlet supply port, in this opposite directional movement scenario, wherein the valve plunger is being moved downwardly from its fully OPEN position to the fully CLOSED position, the third enlarged diameter portion of the valve plunger will fully block and close off the adhesive material inlet supply port before the valve member or shutoff blade is disposed at its fully CLOSED position. Accordingly, at this point in time, the line pressure prevailing at the valve member or shutoff blade is minimized, and as the valve member or shutoff blade seats or enters the adhesive material output dispensing or discharge port and terminates at a position flush with the undersurface portions of the adjacent shutoff outlet plates, it effectively pushes or forces any residual adhesive material out from adhesive material output dispensing or discharge port such that trailing ends or splatter of the adhesive material are minimized. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Various other 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: 
           [0013]      FIG. 1  is a cross-sectional view showing the new and improved plunger-type dispensing valve at its CLOSED position at which the valve member or shutoff blade is closed with respect to its valve seat or oppositely disposed pair of shutoff output plates, a third intermediate diametrically enlarged portion of the valve plunger effectively blocks fluid flow of the adhesive material from the adhesive material inlet supply port to the valve shutoff blade and the dispensing valve discharge or output port, while a first upper annularly configured diametrically reduced portion of the valve plunger effectively provides a fluid flow path between the adhesive material inlet supply port and the adhesive material recirculation outlet port such that the adhesive material is continuously recirculated while the plunger-type dispensing valve is disposed at the CLOSED position; 
           [0014]      FIG. 2  is a cross-sectional view showing the new and improved plunger-type dispensing valve disposed at its TRANSITION position at which the valve member or shutoff blade has been moved vertically upwardly a predetermined amount from its CLOSED position with respect to its valve seat or pair of oppositely disposed shutoff output plates, while the third intermediate diametrically enlarged portion of the valve plunger has likewise been moved vertically upwardly a predetermined amount from its CLOSED position so as to now completely block the fluid flow of the adhesive material from the adhesive material input supply port to the adhesive material outlet recirculation port as well as to the valve member or shutoff blade and the dispensing valve discharge or output port; 
           [0015]      FIG. 3  is a cross-sectional view showing the new and improved plunger-type dispensing valve at its OPEN position at which the valve member or shutoff blade has been moved vertically upwardly still further from its TRANSITION position as disclosed within  FIG. 2  such that the valve member or shutoff blade is now disposed at an elevated position with respect to its valve seat or oppositely disposed pair of shutoff outlet plates whereby the valve dispensing discharge or outlet port is fully OPEN, while the third intermediate diametrically enlarged portion of the valve plunger effectively is interposed between the adhesive material inlet supply port and the adhesive material recirculation outlet port so as to effectively block any fluid flow and recirculation of the adhesive material from the adhesive material inlet supply port to the adhesive material recirculation outlet port whereby the incoming adhesive material can only be conducted toward and discharged or dispensed out from the adhesive material dispensing outlet or discharge port and not recirculated back through the recirculation portion of the system; and 
           [0016]      FIG. 4  is a cross-sectional view corresponding to  FIG. 2  but taken through a cross-sectional plane oriented 90° from the cross-sectional view of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Referring now to the drawings, and more particularly to  FIG. 1  thereof, the new and improved plunger-type dispensing valve is disclosed and is generally designated by the reference character  100 . More particularly, it is seen that the dispensing valve  100  comprises a valve housing  102  wherein the valve housing  102  effectively comprises a first uppermost section  104 , a second intermediate section  106 , and a third lowermost section  108 . A piston-cylinder assembly is disposed within the first uppermost section  104  of the valve housing  102  and is seen to comprise a piston which, in turn, comprises a piston head  110  and a piston rod  112 , the piston head  110  being vertically movable within a cylinder portion  114  of the first uppermost section  104  of the valve housing  102 . A lower end portion of the piston rod  112  is fixedly connected to a first uppermost enlarged diameter portion  116  of a valve plunger  118 . The piston-cylinder assembly may be operated either pneumatically or hydraulically wherein a pair of vertically spaced input/output ports or connectors for the incoming hydraulic fluid or compressed air are disclosed at  120 , 122 . The upper port or connector  120  is fluidically connected to the cylinder  114 , by means of a fluid conduit, not shown, such that the incoming fluid can act upon the upper surface portion of the piston head  110  so as to drive the piston vertically downwardly, while the lower port or connector  122  is fluidically connected to the cylinder  114 , by means of another fluid conduit, also not shown, such that the incoming fluid can act upon the undersurface portion of the piston head  110  so as to drive the piston vertically upwardly. Controls for routing the incoming driving fluid to the upper or lower connector  120  or  122 , and therefore to the cylinder spaces above and below the cylinder head  110  in order to drive the piston vertically downwardly or upwardly, as well as for respectively exhausting fluid from the opposite cylinder space disposed beneath or above the piston head  110 , are also not shown but are well known in the valve art. It is to be noted that a complete dispensing cycle comprises moving the piston actuator  110 , 112  and the valve plunger  118  from a CLOSED position to an OPEN position and back to the CLOSED position, as will be more fully discussed hereinafter, and that the combination of the piston-valve plunger assembly  110 , 112 , 118  comprise the only moving part of the entire dispensing valve  100 . 
         [0018]    Continuing further, it is seen that the valve plunger  118  extends vertically downwardly through the second intermediate section  106  of the valve housing  102  wherein a second lowermost enlarged diameter portion  124  of the valve plunger  118  has a valve member or shutoff blade  126  fixedly connected thereto. The valve member or shutoff blade  126  is adapted to operatively cooperate with a valve seat which, in this particular embodiment, comprises pair of oppositely disposed shutoff output plates  128 , 130  which define an adhesive material dispensing or discharge output port  132  therebetween within the third lowermost section  108  of the valve housing  102 , which can best be seen, for example, within either  FIG. 2  or  FIG. 3 . An adhesive material inlet supply port  134  is fluidically connected to a first side portion of the second intermediate section  106  of the valve housing  102 , while an adhesive material outlet recirculation port  136  is fluidically connected to a second side portion of the second intermediate section  106  of the valve housing  102 . The valve plunger  118  is vertically reciprocable within a cylinder portion  138  of the second intermediate section  106  of the valve housing  102  so as to be interposed between the adhesive material inlet supply port  134  and the adhesive material outlet recirculation port  136 . The valve plunger  118  further comprises a third intermediate enlarged diameter portion  140  interposed between the first uppermost enlarged diameter portion  116  of the valve plunger which is connected to the piston rod  112  of the piston of the piston-cylinder assembly, and the second lowermost enlarged diameter portion  124  of the valve plunger  118  which is connected to and mounting the valve member or shutoff blade  126  thereon. Still further, a first upper annularly configured reduced diameter portion  142  of the valve plunger  118  is defined between the first and third enlarged diameter portions  116 ,  124  of the valve plunger  118 , while a second lower annularly configured reduced diameter portion  144  of the valve plunger  118  is defined between the second and third enlarged diameter portions  124 , 140  of the valve plunger  118 . 
         [0019]    Accordingly, as is shown within  FIG. 1 , when the valve plunger  118  is disposed at its lowermost end position whereby the valve member or shutoff blade  126  is disposed at its lowermost position and fully interposed between the pair of oppositely disposed shutoff outlet plates  128 , 130  so as to be fully seated within the adhesive material dispensing or discharge port  132 , thereby defining the fact that the dispensing valve  100  is disposed at its fully CLOSED position, the first upper annularly configured reduced diameter section  142  of the valve plunger  118  will effectively permit fluid communication between the adhesive material inlet supply port  134  and the adhesive material outlet recirculation port  136  such that the adhesive material is continuously recirculated throughout the system by means of a suitable pump P operatively connected to an adhesive material reservoir or supply tank T. This is desirable so as to effectively ensure that the temperature and viscosity parameters of the adhesive material remain homogeneous throughout the system which, in turn, ensure precise, repeatable operations of the valve  100  and the dispensing of uniform adhesive material deposits onto the pavement road surfaces. 
         [0020]    At this time, it is also noted that the third intermediate enlarged diameter section  140  of the valve plunger  118  effectively prevents the adhesive material from flowing downwardly toward the valve member or shutoff blade  126  and the dispensing or discharge output port  132 , while the first uppermost enlarged diameter section  116  of the valve plunger  118  effectively prevents the adhesive material from flowing upwardly toward the piston-cylinder assembly. An annular seal member  145  is disposed around the first uppermost enlarged diameter section  116  of the valve plunger  118 . In this manner, it is noted that the piston-cylinder assembly, utilized for actuating or moving the valve plunger  118 , is effectively divorced or separated from the valve plunger  118  so as to effectively isolate the piston-cylinder assembly from the heat generated within the valve plunger section of the dispensing valve  100  by means of the incoming or recirculated adhesive material. Concomitantly, this separated or divorced location of the piston-cylinder assembly relative to the valve plunger  118  likewise prevents any leakage of air or hydraulic fluid from the piston-cylinder assembly into the adhesive material should a leak occur within the piston-cylinder assembly. 
         [0021]    To the contrary, when the valve plunger  118  is disposed at its uppermost end position, as can best be seen in  FIG. 3 , wherein the valve member or shutoff blade  126  has been fully retracted from its disposition between the pair of oppositely disposed shutoff output plates  128 , 130 , as well as fully retracted or unseated from its disposition within the adhesive material dispensing or discharge port  132 , thereby defining the fact that the dispensing valve  100  is now disposed at its fully OPEN position, it can be seen that the third intermediate enlarged diameter section  140  of the valve plunger  118  will now be interposed between the adhesive material inlet supply port  134  and the adhesive material outlet recirculation port  136  such that the incoming adhesive material cannot flow toward the adhesive material outlet recirculation port  136  but can only flow downwardly, annularly around the second annular reduced diameter portion  144  of the valve plunger  118 , and through annular conduits  146  which are defined within the lowermost section  108  of the valve housing  102  and which are fluidically connected with the adhesive material dispensing valve output or discharge port  132 . 
         [0022]    It is lastly to be noted that when the plunger valve  118  is disposed at an intermediate TRANSITION position, as can best be appreciated from  FIGS. 2 and 4 , that is at a position where the valve member or shutoff blade  126  has only been partially elevated and retracted away from the adhesive material dispensing valve output or discharge port  132 , the third intermediate enlarged diameter portion  140  of the valve plunger  118  will be disposed directly opposite the adhesive material inlet supply port  134 . Accordingly, all incoming fluid flow of the adhesive material is, at this point in time, blocked—all fluid flow of the adhesive material coming in from the adhesive material inlet port  134  is zero, all fluid flow of the adhesive material out to the adhesive material outlet recirculation port  136  is zero, and all fluid flow of the adhesive material to the dispensing valve output or discharge port  132  is likewise zero. This structure is extremely important in connection with the operation of the dispensing valve  100  when the valve plunger  118  is moved both from the fully CLOSED position to the fully OPEN position, as well as from the fully OPEN position to the fully CLOSED position because, as can be appreciated from the drawings and this disclosure, the dispensing valve  100  of the present invention effectively has dual shutoff locations, a first shutoff location at the adhesive material inlet supply port  134 , and a second shutoff location at the adhesive material output dispensing or discharge port  132 . 
         [0023]    More particularly, this structure is extremely important in connection with the operation of the dispensing valve  100  when the dispensing valve  100  is moved from the fully CLOSED position to the fully OPEN position because immediately before fluid flow is established from the adhesive material inlet supply port  134  to the adhesive material output dispensing or discharge port  132 , the prevailing line pressure at the adhesive material output dispensing or discharge port  132  is minimal because the adhesive material inlet supply port  134 , located upstream from the adhesive material output dispensing or discharge port  132 , has been blocked or terminated by the disposition of the third intermediate enlarged diameter portion  140  of the valve plunger  116  being disposed directly opposite the adhesive material inlet port  134 . This facilitates the achievement of “soft starts” or the dispensing of proper adhesive material outputs, as opposed to the deposition of excessive adhesive material outputs, because the relatively large line pressure does not immediately impact the adhesive material output dispensing or discharge port  132  as would otherwise be the case if the relatively large line pressure was permitted to build up immediately behind the valve member or shutoff blade  126  and to then be released when the valve member or shutoff blade  126  is retracted so as to be moved to the fully OPEN position. In connection with this structure, it is also noted that a suitable orifice or flow restrictor, not shown, can effectively be incorporated into the structure comprising the adhesive material outlet recirculation port whereby the pressure of the recirculated adhesive material can achieve a predetermined or defined pressure value which will, of course, also be the predetermined or defined pressure value of the adhesive material which is immediately available to or at the adhesive material output dispensing or discharge port when the dispensing valve  100  is disposed at its fully OPEN position. 
         [0024]    Still further, this structure also minimizes the likelihood of the formation of any residual material or splatter being discharged from the adhesive material output dispensing or discharge port  132  when the valve plunger  116  is moved from the fully OPEN position to the fully CLOSED position. This is because, just as was the case when the valve member or shutoff blade  126  was partially retracted vertically upwardly from its fully CLOSED position before the third enlarged diameter portion  140  of the valve plunger  116  was likewise moved vertically upwardly a sufficient distance so as to begin to OPEN the adhesive material inlet supply port  134 , in this opposite directional movement scenario, wherein the valve plunger  116  is being moved downwardly from its fully OPEN position to the fully CLOSED position, the third enlarged diameter portion  140  of the valve plunger  116  will fully block and close off the adhesive material inlet supply port  134  before the valve member or shutoff blade  126  is disposed at its fully CLOSED position. Accordingly, at this point in time, the line pressure prevailing at the shutoff blade  126  is minimal, and as the valve member or shutoff blade  126  enters the adhesive material output dispensing or discharge port  132  and terminates at a position flush with the undersurface portions of the adjacent shutoff outlet plates  128 , 130 , it effectively pushes or forces any residual adhesive material out from adhesive material output dispensing or discharge port  132  such that no trailing ends or splatter of the adhesive material are able to be developed. 
         [0025]    It is to be noted that the adhesive material to be utilized within the aforenoted system can either by a liquid adhesive or a heated bituminous adhesive material commonly known in the industry. As is well known, the bituminous adhesive is a solid at room temperature and must be heated to a temperature within the range of, for example, 375°-425° F. degrees for proper application. If a bituminous adhesive is being used, it is noted that the dispensing valve  100  is further provided with a first pair of oppositely disposed valve heater blocks  148 , 150  which are fixedly secured to opposite side walls of the lowermost section  108  of the valve housing  102  so as to effectively heat the adhesive material and the lowermost section  124  of the valve plunger  118 , and maintain the same heated, while a second pair of oppositely disposed valve heater blocks  149 , 151  are fixedly secured to opposite side walls of the intermediate section  106  of the valve housing  102 , as can best be seen in  FIG. 4 . In this manner, the second pair of valve heater blocks  149 , 151  also not only heat the adhesive material flowing into the system through the adhesive material inlet supply port  134 , but they also heat the intermediate section of the valve plunger  118 , and additionally serve to maintain the adhesive and the valve plunger  118  in a heated state so as to effectively prevent solidification of the adhesive material. Still further, while the aforenoted description has disclosed the operation of the dispensing valve  100  throughout its various OPEN, CLOSED, and TRANSITION stages, it is also to be noted that the dispensing valve may effectively be held at its OPEN position so as to permit purging and cleaning of, for example, the valve member or shut off blade  126  and the adhesive material output dispensing or discharge port  132  as a result of a suitable cleaning or solvent material being routed therethrough. 
         [0026]    It is lastly noted that the diametrical size of the first and second reduced diameter portions  142 , 144  of the valve plunger  118 , as well as the length of such portions, their relative axial locations along the valve plunger  118 , and their relative dispositions with respect to the adhesive material inlet supply port  134 , the adhesive material outlet recirculation port  136 , and the shutoff blade  126  can affect the OPEN and CLOSING operations and output parameters of the dispensing valve  100 . For example, the differences between the external diameters of the first and second reduced diameter portions  142 , 144  and the external diameters of the first, second, and third enlarged diameter portions  116 , 124 , 140  of the valve plunger  118  determines the effective size of the fluid flow path and therefore the volumetric output of the adhesive material being outputted or discharged from the adhesive material output dispensing or discharge port  132 . The smaller the diametrical extents of the first and second reduced diameter portions  142 , 144 , the larger the fluid flow paths for the adhesive material. The axial locations of the first and second reduced diameter portions  142 , 144  along the valve plunger  118 , relative to each other as well as with respect to the adhesive material inlet supply port  134  and the adhesive material outlet recirculation port  136 , controls the timing of the recirculation and adhesive material dispensing portions of each particular dispensing cycle as the valve plunger  118  cycles between the CLOSED, TRANSITION, OPEN, TRANSITION, and CLOSED positions as has been described hereinbefore in connection with a complete adhesive material dispensing cycle. 
         [0027]    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. 
       LIST OF REFERENCE CHARACTERS 
       [0000]    
       
           100 —Dispensing valve 
           102 —Valve housing 
           104 —Uppermost section of valve housing 
           106 —Intermediate section of valve housing 
           108 —Lowermost section of valve housing 
           110 —Piston head 
           112 —Piston rod 
           114 —Cylinder for piston head 
           116 —First uppermost enlarged diameter portion of the valve plunger 
           118 —Valve plunger 
           120 —Upper input/output port/connector for pneumatic/hydraulic fluid driving piston 
           122 —Lower input/output port/connector for pneumatic/hydraulic fluid driving piston 
           124 —Second lowermost enlarged diameter portion of the valve plunger 
           126 —Valve shutoff blade 
           128 —Shutoff outlet plate 
           130 —Shutoff outlet plate 
           132 —Adhesive material dispensing or discharge output port 
           134 —Adhesive material inlet supply port 
           136 —Adhesive material outlet recirculation port 
           138 —Cylinder portion of second intermediate housing section for valve plunger 
           140 —Third intermediate enlarged diameter portion of valve plunger 
           142 —First upper annularly configured reduced diameter portion of the valve plunger 
           144 —Second lower annularly configured reduced diameter portion of valve plunger 
           145 —Annular seal member around valve plunger 
           146 —Annular conduits within lowermost housing section 
           148 —First valve heater block 
           149 —Second valve heater block 
           150 —First valve heater block 
           151 —Second valve heater block 
         P—System pump 
         T—System reservoir/supply tank