Abstract:
A metering device having two gears and a center plate defining a gear chamber having two major lobes to receive the gears, each of the major lobes defining a diameter and a circular segment having a perimeter extending greater than one hundred eighty degrees. The face surfaces of the first gear, the second gear and the center plate are each machined to be as precisely flat as practical and to be as precisely of equal thickness as practical. The first gear and the second gear are trued on an arbor to eliminate as much runout as practical while at the same time reducing a diameter of the first gear and the second gear to be the substantially the same or slightly larger than the diameter of the major lobes. The first gear and the second gear are press fit into the major lobes; and lapped in the major lobes.

Description:
CLAIM TO PRIORITY  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 10/794,175 which claims priority to U.S. Provisional Applications Ser. Nos. 60/452,606 entitled “Quick Change Nozzle” filed Mar. 6, 2003 and 60/454,275 entitled “Gear Pump Case” filed Mar. 13, 2003, the entire contents of the foregoing are incorporated herein by this reference.  
       RELATED APPLICATIONS  
       [0002]     This application is related to U.S. Provisional Application Ser. No. 60/452,209 filed Mar. 5, 2003 entitled “System and Process for Glazing Glass to Windows and Door Frames” and to Utility Application filed on Mar. 5, 2004, with the same title, having Attorney Doc. No. 1843.02-US-02, the entire contents of which are incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION  
       [0003]     This invention relates to dispensing viscous fluids prone to hardening, such as sealants, and more particularly relates to a metering device and nozzle for dispensing viscous fluids.  
       BACKGROUND OF THE INVENTION  
       [0004]     One of the biggest challenges in delivering viscous fluid is providing a uniform, metered flow of viscous material in applications where an interruption of the flow rate or consistency of the material delivered may lead to an unacceptable product with no avenue for remediation.  
         [0005]     A major deficiency in the prior art metering devices is fluid leaking into the interstices between the working components of the metering device. This leakage induces a deviation in operational parameters and deterioration in the viscous fluid flow.  
         [0006]     In addition, the ability to rapidly couple a nozzle to a nozzle holder body and lock it in place is an important capability, for instance, in window manufacturing machines. When dispensing viscous adhesive fluid nozzles tend to clog, foul and become coated with the fluid readily. There is no cure for this problem other than to clean the nozzle or to replace it. Once the viscous fluid begins to set or harden on or in the nozzle cleaning becomes very difficult. Generally, it is more economical to discard the nozzle and to replace with a new one. Depending on the material dispensed nozzles may require changing many times during a work shift.  
         [0007]     A typical nozzle assembly includes a female part in the form of a nozzle holder and a male part in the form of a nozzle; the reverse situation is possible as well. The female nozzle holder is connected to metering device and the metering device is connected to a fluid source, such as a tank containing sealant used in window manufacturing operations.  
         [0008]     Quick coupling devices for making a leak resistant connection between hydraulic or pneumatic components such as hoses, valves and fluid dispensing nozzles are known in the art. In a fluid dispensing environment, where the fluid dispensed is viscous and adhesive in nature, it tends to clog the nozzle apertures and gum up, adhere to and foul the associated machinery. For example, many standard fluid dispensing nozzles use a threaded connection for attachment to a nozzle holder or a fluid source. The threaded connections can gum up and stick if adhesive or viscous fluid finds its way into the threads. This can lead to the threaded fittings being difficult or impossible to disassemble, thereby significantly increasing the time required to connect and disconnect the nozzles from the dispensing machinery.  
         [0009]     The utility of quick coupling nozzles is substantially reduced in applications where viscous adhesive fluids are used and where nozzles need to be changed frequently, often within a single assembly cycle. It is difficult to repeatedly and precisely position a nozzle secured by threaded connections to dispense fluid in a preferred direction as is often required in window assembly operations. Threaded connections, by their nature, rotate.  
         [0010]     Beside threaded connections, some prior art quick disconnect nozzle assemblies require twisting and interlocking with appendages on the nozzle holder or the nozzle to hold and align the nozzle tip into a nozzle holder. Some other prior art assemblies use mechanisms with slides, ball bearings, levers and pivots to lock and position components of the nozzle assembly. These assemblies require complex manufacturing and assembly operations adding to their cost. In addition, their reliability in the field may be poor when used with viscous adhesive fluids because fluids readily infiltrate into and among the moving parts. The complex moving parts then tend to become fouled by contact with the viscous adhesive fluids.  
         [0011]     One requirement of nozzle assemblies is a fluid tight connection between the nozzle holder or fluid dispenser and the nozzle tip. This seal must be effective but additionally must be robust enough to withstand repeated connection and disconnection operations. Prior art quick disconnect nozzle assemblies with complicated seals are not practical especially if they are inaccessible, require special seating, are coated with and gummed up by the viscous liquid used in the operations and are to be inspected and replaced often. It will be apparent to those skilled in the art that this would significantly add to the cycle time and cost of manufacturing operations.  
         [0012]     Traditionally sealant applied to insulated glass window units have been silicone-based sealants. Silicone-based sealants require a curing time between several hours and several days before they achieve substantial strength. This has led to the need for large storage facilities in the window and door manufacturing industry in order to allow finished units to set for a sufficient period of time to achieve substantial curing of the sealants. Thus, recently there has been a move to change over to hot dispensed sealants. The hot applied sealants and adhesives reduce the need to store completed window and door units while the sealant cures thus reducing overhead and the overall cost of producing windows and doors.  
         [0013]     However, hot applied sealant materials tend to have high levels of abrasives and corrosive components. Hot applied sealants include substantial concentrations of silicas and other abrasive materials. Thus, the use of hot applied sealants increases the level of wear on mechanical components used to dispense them.  
       SUMMARY OF THE INVENTION  
       [0014]     It is desirable to provide a metering device that will perform consistently over an extended period of time, delivering a uniform controlled flow of viscous sealant. It is desirable that the nozzle be quickly connectable to and rapidly releasable from the nozzle holder. The ease of replacement of a nozzle can significantly affect machine utilization.  
         [0015]     In some applications, it is highly desirable that a nozzle be precisely positioned in the same orientation time after time. One skilled in the art will readily appreciate the value of having a nozzle that could be replaced quickly with precise repeatability of position.  
         [0016]     It would be desirable to have a durable metering device that has minimal leakage and a quick disconnect nozzle assembly that can be rapidly connected and disconnected and fitted onto the nozzle holder manually without the use of a tools. Preferably the nozzle assembly should provide a leak-proof connection with the fluid source that can be easily positioned in a preferred orientation. The assembly should be easily inspected, have few moving parts and easily replaceable sealing members. In addition, the nozzle assembly should allow for repeatable positioning of the nozzle.  
         [0017]     A further problem encountered with hot applied sealants is when they are subjected to high pressures, solids in the hot applied sealant mix will tend to come out of suspension. Thus it becomes important to limit the highest pressure in the system to a level lower than that at which the solids will come out of suspension. For example, if a hot applied sealant material can only be subjected to a maximum pressure of 2,500 psi and there is a pressure loss passing through the passageways of the system of 1,000 psi, this can create a major problem in maintaining high enough levels of pressure in the lowest pressure areas of the system while keeping high pressure areas below the critical pressure.  
         [0018]     Another trend seen in the adhesives industry is toward the use of two part catalyzed sealants. Two part catalyzed sealants also include high levels of abrasive and corrosive components. These qualities accelerate wear on dispensing system components. Thus, both durability and ease of maintenance are important qualities for equipment used to dispense these types of sealants.  
         [0019]     While it is desirable, in hot applied sealant systems, to maintain the fluid passage ways at a high temperature in order keep the sealants fluid, it is undesirable to expose mechanical components such as servo motors, gear boxes and actuators to high temperatures. Exposing these components to elevated temperatures tends to accelerate wear and increase the likelihood of early component failure.  
         [0020]     The present invention solves many of the above problems by providing a robust gear metering device and an easily changeable nozzle and holder assembly.  
         [0021]     The fouling resistant fluid dispensing assembly of the invention includes a metering device and a nozzle assembly. The nozzle assembly generally includes a nozzle holder including a body defining a substantially cylindrical bore. The nozzle has a cylindrical portion proportioned to be inserted into the cylindrical bore in a close fitting relationship. The nozzle holder is pierced by a passage oriented substantially perpendicular to the bore axis and passing through the cylindrical bore on a non-diametrical chord and the nozzle has a complementary passage that can be aligned with the nozzle holder passage. Once the holder passage and the nozzle passage are aligned, a retaining member proportioned to pass through the nozzle holder passage and the nozzle passage retains the nozzle in the cylindrical bore.  
         [0022]     The invention includes a gear metering device suited to delivering viscous fluids such as sealants and desiccants used in the window manufacturing industry. The metering device includes a gear metering device chamber enclosed within metering device body assembly and transfers fluid under pressure to the outlet of the metering device. A significant feature of the present invention is that the surface finish of the gear teeth and clearances between gear teeth and the walls of the metering chamber are held to tight tolerances so that pressure generated by the motion of the gears is not dissipated through leak paths in the metering chamber. Another significant feature of the present invention is the use of materials of construction and seals uniquely adapted to resist deterioration under contact with the abrasive and caustic chemicals in sealants.  
         [0023]     The invention also includes a method of producing the metering device to the close tolerances desired to minimize bypass leakage and predictably meter sealant fluids. Further the invention includes a hydraulic lock bypass port to prevent hydraulic lock between the gear teeth in order to maintain low leakage tolerances.  
         [0024]     The invention also includes a nozzle assembly capable of quick assembly and disassembly. The device comprises a nozzle holder, one end of which is coupled to the metering device or another source of fluid, such as a sealant or desiccant, under pressure and the other end of which is adapted to axially and slidably receive a first end of a nozzle. The second end of the nozzle includes a nozzle outlet from which the fluid is dispensed.  
         [0025]     The nozzle has a resilient sealing member to provide a fluid-tight seal between the nozzle holder and the body of the nozzle downstream of the sealing member. The sealing member permits rotational and sliding degrees of freedom of the nozzle with respect to the nozzle holder. Desirably the sealing member is an O-ring captured in groove on the nozzle or the holder.  
         [0026]     The nozzle holder has a chordal bore extending transverse to the nozzle axis and the nozzle has a mating chordal groove on its periphery downstream of the sealing member. In the context of this application, the term chordal refers to following the chord of a circle. When the nozzle is fully inserted into the nozzle holder body, the nozzle is rotated so that the chordal bore aligns with the chordal groove on the nozzle. A retaining pin is inserted through the chordal bore so as to extend transversely across the nozzle holder and to pass through the groove. The retaining pin fits into and seats in the chordal groove so as to axially and rotationally secure the nozzle in the nozzle holder. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0028]      FIG. 1  is a partially exploded perspective view of a gear metering device and quick-change nozzle in accordance with the present invention.  
         [0029]      FIG. 2  is an exploded view of the gear metering device in accordance with the present invention.  
         [0030]      FIG. 3  is a front view of a quick-change nozzle holder body in accordance with the invention.  
         [0031]      FIG. 4  is a side view of the quick change nozzle holder of  FIG. 3 .  
         [0032]      FIG. 5  is front view of a quick-change nozzle in accordance with the invention.  
         [0033]      FIG. 6  is a top view of a quick-change nozzle.  
         [0034]      FIG. 7  is a side view of a quick-change nozzle.  
         [0035]      FIG. 8  is a front view of a quick-change nozzle and nozzle holder assembly exemplifying a second embodiment of the present invention.  
         [0036]      FIG. 9  is a side view of a quick-change nozzle assembly.  
         [0037]      FIG. 10  is an exploded view illustrating another embodiment of the present invention.  
         [0038]      FIG. 11  is an exploded front view of another embodiment of the invention.  
         [0039]      FIG. 12  is an exploded side view of the embodiment of  FIG. 11 .  
         [0040]      FIG. 13  is an exploded top view of the embodiment of  FIG. 11 .  
         [0041]      FIG. 14  is an exploded front view of another embodiment of the invention.  
         [0042]      FIG. 15  is an exploded side view of the embodiment of  FIG. 14 .  
         [0043]      FIG. 16  is an exploded top view of the embodiment of  FIG. 14 .  
         [0044]      FIG. 17  is an exploded perspective view of a gear metering device, valve block and quick change nozzle in accordance with the present invention.  
         [0045]      FIG. 18  is perspective view of a gear metering device and valve block with interior structures of the valve block depicted in phantom.  
         [0046]      FIG. 19   a  is a perspective view of another embodiment of the valve block in accordance with the present invention.  
         [0047]      FIG. 19   b  is a plan view of the valve block depicted in  FIG.19   a.    
         [0048]      FIG. 19   c  is cross sectional view of the valve block taken along section line A-A in  FIG. 19   b.    
         [0049]      FIG. 20  is a perspective view of a center plate of the gear metering device of the present invention.  
         [0050]      FIG. 21  is an exploded perspective view of the gear metering device with some parts removed for clarity.  
         [0051]      FIG. 22  is a schematic partially exploded view of a floating head assembly in accordance with the present invention 
     
    
       [0052]     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0053]     Referring to  FIGS. 1 , viscous liquid dispenser  20  generally includes a metering device  22  and a nozzle assembly  24 . Metering device  22  is in fluid communication with nozzle assembly  24  so that viscous liquid material that leaves metering device  22  flows to and, ultimately through nozzle assembly  24 . The metering device  22  generally includes metering device body  26  and gear assembly  28 . Gear assembly  28  is enclosed within and surrounded by metering device body  26 .  
         [0054]     Referring to  FIGS. 2, 20  and  21 , metering device body  26  is generally divided into three major subcomponents, port plate  30 , center plate  32  and drive plate  34 . Each of port plate  30 , center plate  32  and drive plate  34  have a plurality of passageways, apertures and cavities machined or otherwise formed in them.  
         [0055]     Port plate  30  defines inlet  36 , a plurality of boltholes  38  and bearing cavities  40 . Inlet  36  leads to inlet passage  42  which terminates at interior inlet  44 . Thus, inlet passage  42  provides for fluid communication between inlet  36  and interior inlet  44 . Port plate  30  further defines interior outlet  36  which leads to outlet passage  48  and then to outlet  50 . Outlet passage  48  provides for fluid communication between interior outlet  46  and outlet  50 . Desirably inlet  36  and outlet  50  are threaded or otherwise adapted to receive fittings to connect them to hoses or other fluid transfer devices. Note that interior outlet  46  is shaped to include extended lobe  47  that extends toward the center of port plate  30  and is in fluid communication with outlet passage  48 .  
         [0056]     Bearing cavities  40  are desirably machined into port plate  30  and are sized and appropriately shaped to receive and support bearings  52 .  
         [0057]     Center plate  32  is a generally flat quadrilateral structure whose first surface  54  and second surface  56  are ground flat to mate with port plate  30  and drive plate  34 , respectively. Center plate  32  defines a plurality of boltholes  58  arranged in a pattern similar to bolt holes  38 . Center plate  32  also defines gear chamber  60 . Gear chamber  60  creates a multi-lobed cavity bordered by center plate  32  at its perimeter and by port plate  30  and drive plate  34  on each side. Gear chamber  60  is defined by the envelope of two intersecting major circular lobes  62  and two minor lobes  64 . Minor lobes  64  are located, generally, at the points of intersection of the circumference of each of the major circular lobes  62 . Minor lobes  64  generally correspond with the locations of interior inlet  44  and interior outlet  66  which are located symmetrically on opposite sides of gear chamber  60 . Note that the junctures  67  where major circular lobes  62  and minor lobes  64  meet are desirably slightly rounded or otherwise shaped to avoid a sharp corner. Particularly, it is desirable to machine a small flat at junctures  67  between major circular lobes  62  and minor lobes  64  as depicted in  FIG. 20   
         [0058]     Drive plate  34  corresponds in external perimeter shape to port plate  30  and center plate  32 . Drive plate  34  defines a plurality of boltholes  66  located in a pattern corresponding to bolt holes  38  and bolt holes  58 . Drive plate  34  also defines shaft passage  68  and bearing cavity  70 . Shaft passage  68  is a cylindrical bore passing all the way through drive plate  34 . Shaft passage  68  is adapted to receive sealed bearing assembly  72 . Sealed bearing assembly  72  includes vari-seal  74 , seal spacer  76 , bearing  78  and snap ring  80 . Bearing cavity  70  is a cylindrical cavity adapted to receive bearing  82 .  
         [0059]     Gear metering device assembly  84  fits into gear chamber  60 . Gear metering device assembly  84  includes drive shaft  86 , idler shaft  88 , drive gear  90  and driven gear  92 . Drive gear  90  is secured to drive shaft  86 . Driven gear  92  is secured to idler shaft  88 . Drive gear  90  and driven gear  92  are secured to drive shaft  86  and idler shaft  88 , respectively by keys  94 . Drive shaft  86  passes through sealed bearing assembly  72  and is journaled into bearings  52  which are supported by port plate  30 . Idler shaft is journaled into bearing  78  at a first end  96  and into bearing  52  at a second end  98 .  
         [0060]     Drive gear  90  and driven gear  92  are ground to be precisely flat and so as to have a thickness precisely equal to the thickness of center plate  32 . In grinding drive gear  90  and driven gear  92  it is desirable to eliminate radiused edges so that the sides of drive gear  90  and driven gear  92  are as flat as practical. Drive gear  90  and driven gear  92  should have a maximum edge break of 0.002 inches.  
         [0061]     In addition, drive gear  90  and driven gear  82  are placed on an arbor and trued to eliminate as much runout as practical. The diameter of drive gear  90  and driven gear  82  is reduced to be the same as or slightly larger than the diameter of major circular lobes  62 . Drive gear  90  and driven gear  82  are then press fit into their corresponding spaces in major circular lobes  62  and lapped in to precise fit thus providing an extremely tight seal between the perimeters of drive gear  90  and driven gear  82  and the walls of major circular lobes  62  along the entire circumference of major circular lobes  62  as well as between drive gear  90  and driven gear  82  and drive plate  34  and port plate  30 .  
         [0062]     Thus, when located in gear chamber  60 , drive gear  90  is meshed with driven gear  92  so that when drive shaft  86  is rotated, drive shaft  86  rotates drive gear  90  which in turn rotates driven gear  92  and idler shaft  88 . This rotation allows fluid to be drawn in to gear chamber  60  from inlet passage  42  and to be released out of gear chamber  60  through outlet passage  48  thereby effectively transferring fluid from inlet  36  to outlet  50 . Since a known volume of fluid is transferred with each rotation of gear metering device assembly  84  a precise amount of fluid can be delivered by counting rotations and fractions of rotations. Drive gear  90  and driven gear  92  mesh at a location directly overlying extended lobe  47 . This allows the release of fluid caught between the teeth of drive gear  90  and driven gear  82  into outlet passage  48  thus preventing hydraulic lock caused by the entrapment of incompressible fluid between drive gear  90  and driven gear  82  by the extremely tight fit between drive gear  90  and driven gear  82  and port plate  30  and drive plate  34 . Bearings  52 ,  78  and  82  serve only to keep drive shaft  86  and idler shaft  88  perpendicular so that lash in the bearings does not allow leaks.  
         [0063]     Port plate  30 , drive plate  34 , drive shaft  86  and idler shaft  88 , are constructed from D- 2  tool hardened steel with a Rockwell hardness factor in the range of 58-62. The shafts are carried by bearings, such as, for example, Torrington needle bearings and Nice needle bearings and Nice DC TN bearings supplied by Motion. Drive gear  90  and driven gear  92  are desirably constructed from brass, aluminum or steel with close tolerances maintained between drive gear  90 , driven gear  92  and the interior of gear chamber  60 . Vari-seal  74  is desirable constructed of VITON or Teflon® such as that manufactured by Vari-seal. Nozzle assembly  24  generally includes nozzle holder  100  and nozzle  102 .  
         [0064]     Referring to  FIGS. 3 and 4 , nozzle holder  100  is formed preferably by machining from a solid block of material. Nozzle holder  100  defines an inlet portion  104  and an outlet portion  106 . Inlet portion  104  is pierced by small bore  108 . Outlet portion  102  is pierced by large bore  110 . Small bore  108  and large bore  110  are preferably cylindrical and share a common axis. In other words, small bore  108  and large bore  110  are co-axial. Together small bore  108  and large bore  110  create a fluid communication passage completely through nozzle holder  100 . Referring to  FIG. 12 , arrow  112  indicates the direction of fluid flow through nozzle holder  100 .  
         [0065]     Inlet portion  104  includes threads  114 . Threads  114  as depicted in  FIG. 3  are male threads, though one skilled in the art could readily adapted nozzle holder for female threads.  
         [0066]     Outlet portion  106  includes hexagonal portion  116  and external cylindrical portion  118 . Hexagonal portion  116  is adapted to receive a standard wrench. Large bore  110  creates a cylindrical cavity  120  within outlet portion  106 . Cylindrical cavity  120  is adapted to receive nozzle  102 .  
         [0067]     A pin bore  122  pierces external cylindrical portion  118 . Pin bore  122  is located so as to pass through and intrude into cylindrical cavity  120  on a non-diametrical chord near the curved wall thereof. Pin bore  122  terminates at a first end with counterbored aperture  124  and at a second end with aperture  126 . Desirably, as seen in  FIGS. 3 and 4 , pin bore  122  passes through cylindrical cavity  120  so that the wall of pin bore  122  is approximately tangential to the wall of cylindrical cavity  120 . Pin bore  122  is adapted to receive a resilient pin  128 . The resilient pin  128  is desirably a standard cotter pin but may be another form of pin or rod.  
         [0068]     When resilient pin  128  is inserted through pin bore  122  it passes through cylindrical cavity  120  in a chord wise fashion partially blocking cylindrical cavity  120 .  
         [0069]      FIGS. 5, 6  and  7  depict a first embodiment of nozzle  102 . Conical nozzle  130  generally includes cylindrical portion  132  and frustoconical portion  134 . Conical nozzle  130  is preferably formed of a single piece of material by machining, molding or any other process known in the art. A longitudinal bore  136  pierces conical nozzle  130 . Arrow  138  demonstrates the direction of fluid flow through longitudinal bore  136 .  
         [0070]     Cylindrical portion  132  defines circumferential groove  140  and tangential groove  144 . Circumferential groove  140  is located close to inlet end  146  of cylindrical portion  132 . Circumferential groove  140  is adapted to receive a sealing member  148 . Sealing member  148  is desirably an O-ring  150  but may be another form of gasket or seal. Also located at inlet end  146  of cylindrical portion  132  is bevel  152 .  
         [0071]     Tangential groove  144  is desirably located downstream from circumferential groove  140 . Tangential groove  144  is located so that when cylindrical portion  132  is inserted into cylindrical cavity  120 , tangential groove  144  may be aligned with pin bore  122  so that resilient pin  148  may be passed through pin bore  122  while also passing through tangential groove  144 . Resilient pin  148  thus creates an interference with tangential groove  144  and holds nozzle  102  in nozzle holder  100 . The location of O-ring  150  in circumferential groove  140  allows for rotational and sliding freedom of cylindrical portion  132  within cylindrical cavity  120  until resilient pin  128  is inserted through pin bore  122  and tangential groove  124 . Upon insertion through pin bore  122 , resilient pin  128  secures nozzle  102  in cylindrical cavity  120 .  
         [0072]     Referring particularly to  FIGS. 5 and 6 , frustoconical portion  134  of conical nozzle  130  defines flat  154 . Flat  154  is desirably aligned with tangential groove  144  to provide an indication as to the position of tangential groove  144  when tangential groove  144  is inserted into cylindrical cavity  120  and thus hidden from view. Frustoconical portion  134  further defines a beveled end  156  with a smaller flattened end  158 . Desirably, nozzle holder  100  is made of brass and nozzle  102  is made of a polymer such as DELRIN® manufactured by DuPont.  
         [0073]      FIGS. 8 and 9  depict another embodiment of nozzle  102 . Shut-off tip  160  generally includes mounting portion  162  and elongate portion  164 . Fluid passage  166  passes entirely through shut-off tip  160  longitudinally.  
         [0074]     Mounting portion  162  includes hex section  168  and threaded inlet  170 . Threaded inlet  170  is internally threaded and adapted to be screwed on to a male fitting (not shown). Hex section  168  is adapted to receive a standard wrench to allow tightening onto a male fitting (not shown).  
         [0075]     Elongate portion  164  includes cylindrical portion  172  and frustoconical portion  174 . Cylindrical portion  172  is an essentially tubular structure surrounding fluid passage  166 . Frustoconical portion  174  surrounds reduced fluid passage  176 . Reduced fluid passage  176  passes through frustoconical portion and is in fluid communication with fluid passage  166 . Reduced fluid passage  176  is of smaller diameter than fluid passage  166 . Juncture  178  is formed where fluid passage  166  and reduced fluid passage  176  meet. Juncture  178  desirably is internally frustoconical and acts as a valve seat adapted to receive a valve member (not shown).  
         [0076]      FIG. 10  depicts an exemplary nozzle assembly  180  for use with shut off tip  160 . Nozzle assembly  180  generally includes fluid supply block  182 , shut off pin  184  and actuator  186 . Fluid supply block  182  is joined to actuator  186  by a plurality of fittings  188 . Shut off pin  184  includes a frustoconical pin tip  190 , actuator head  192  and elongate body  194 . Pin tip  190  is adapted to mate with juncture  178 . Actuator head  192  is adapted to be operably connected to actuator  186 . Actuator  186  is adapted to advance or retract shut off pin  184  so that pin tip  190  engages or disengages from juncture  178 , so as to prevent or allow fluid flow through shut off tip  160  as desired.  
         [0077]      FIGS. 11, 12  and  13  depict an exploded view of another embodiment of the invention. In this embodiment, nozzle holder  100  is substantially similar to that previously disclosed in  FIGS. 3 and 4 . In addition, cylindrical portion  196  is substantially similar to cylindrical portion  132  as previously described. In this embodiment, beveled end  156  is rotated ninety degrees from tangential groove  144 .  
         [0078]      FIGS. 14, 15  and  16  depict another embodiment of the invention. In this embodiment, nozzle holder  100  is substantially similar to that previously disclosed in  FIGS. 3 and 4 . In addition, cylindrical portion  196  is substantially similar to cylindrical portion  132  as previously described. Cylindrical nozzle  198  includes end plate  200  and mid plate  202 . End plate  200  is a flat plate larger in diameter than cylindrical portion  196 . In addition, outlet  204  exits generally through the center of circular end plate  200 . Mid plate  202  is positioned to abut nozzle holder  100  and is larger in diameter than cylindrical portion  196 .  
         [0079]     In addition, bore  206  is structured similarly to the bore of shut off tip  160  so that a shut off pin  184  may be advanced into bore  206  in order to allow or prevent fluid flow therethrough.  
         [0080]     Referring to  FIGS. 17 and 18 , another embodiment of the invention is depicted. In this embodiment the viscous liquid dispenser  20  incorporates a valve block  208 . In this embodiment valve block  208  is positioned directly adjacent to metering body  26 . To achieve this, metering device body  26  is ported so that inlet  210  and outlet  212  are both incorporated into port plate  214 . Thus, drive plate  216  has no external fluid ports in this embodiment.  
         [0081]     Valve block  208  defines a variety of ports and passageways. Valve block  208  is a generally rectilinear structure preferably machined out of a solid block of high strength material. Valve block defines nozzle port  218 , hose input port  220 , over pressure port  222 , pressure meter port  224  and valve port  226 . Nozzle port  218  is adapted to received nozzles  102  as described above.  
         [0082]     Hose input port  220  is threaded or otherwise adapted to receive connection to a high pressure hose (not shown), which supplies viscous material to be metered. Hose input port  220  is in direct fluid communication with over pressure port  222 , pressure meter port  224  and valve port  226 . Pressure meter port  224  is adapted to receive a pressure meter  228 , preferably of the bourdon, oil filled type. Thus, pressure meter  228  registers the pressure supplied to hose input port  220 . Thus, hose input port  220 , pressure meter port  224  and valve port  226  are all located on the upstream side of metering device  22 . Nozzle port  218  is located on the downstream side of metering device  22 , and over pressure port  222  is in fluid communication with both the upstream side and downstream side of metering device  22 .  
         [0083]     Valve port  226  is adapted to receive a poppet valve  230 . Poppet valve  230  is pneumatically actuated and generally includes valve seat  232 , pneumatic actuator  234  and plunger  236 . Poppet valve  230  is desirably sealed by a plurality of O-rings but other seals may be used as well. Over pressure port  222  is adapted to relieve over pressure relief  240 .  
         [0084]     Over pressure relief  240  generally includes stud  242 , two balls  244 , fender washer  246 , a plurality of Bellville washers  248 , sandwiched between flat washers  250  and nut  252 . Over pressure port  222  defines two cone shaped recesses  254 , one in fluid communication with the upstream side of the valve block  208 , and the other in communication with the downstream side of the valve block  208 . Balls  244  are each seated in one of cone shaped recesses  254 . Cone shaped recesses  254  straddle on either side of stud  242 . Fender washer  246  bears upon balls  244  in order to bias them into cone shaped recesses  254 . Fender washer  246  is then followed on stud  242  by a series of Bellville washers  248  interleaved with flat washers  250 . The ultimate washer on stud  242  is a flat washer  250 . The ultimate flat washer is followed by nut  252  which is tightened to bear upon the various washers and upon balls  244  in order to seal balls  244  into cone shaped recesses  254 . When pressure within valve block  208  exceeds a predetermined value, Bellville washers  248  compress allowing the relief of over pressure through cone shaped recesses  254 . This arrangement prevents the blowout of seals within valve block  208  in the event of an overpressure situation.  
         [0085]     Thus, fluid flow through valve block  208  takes the following path. Fluid enters through hose input port  220 . Hose input port  220  leads to valve port  208  where fluid meets valve plunger  236  when poppet valve  230  is in the closed position. Fluid also flows to pressure meter port  224  where pressure meter  228  provides a pressure reading. When poppet valve  230  is in the open position, fluid continues to flow through valve port  226 , to inlet  210  of metering device  22 .  
         [0086]     When metering device  22  turns to meter a desired quantity of viscous fluid, fluid continues to flow through outlet  212  and then to nozzle port  218 . Over pressure port  222  includes flow to two cone shaped recesses  254 . Fluid flow is generally prevented by the presence of balls  224  in cone shaped recesses  254 . However, if fluid pressure exceeds the biasing force provided by Bellville washers  248  on fender washer  246 , fluid may escape through cone shaped recesses  254  thus preventing damage to seals within valve block  208 .  
         [0087]     Another aspect of poppet valve  230  is depicted in  FIG. 19   a,    19   b  and  19   c.  Valve plunger  236  includes shaft  256 . In this embodiment, where shaft  256  passes through housing  258 , shaft  256  is surrounded at each end by seals  260 . The space between seals  260  and surrounding shaft  256  is filled with grease. A zerk fitting  261  is in fluid communication with the grease filled chamber. Thus, the presence of grease helps resist the force of high pressure fluid tending to seep past shaft  256 . In addition, when one of seals  260  begins to fail, viscous fluid will leak past seals  260  and begin to ooze from zerk fitting (not shown) thereby signaling that seals  260  are beginning to fail.  
         [0088]     Referring again to  FIG. 1  and to  FIGS. 19   a,    19   b,  and  19   c,  another aspect of the invention is depicted. As discussed above, more and more sealants used in industry are of the hot sealant variety. These sealants are heated for application and cool rapidly setting to their final consistency. The viscous liquid dispenser  20  of the present invention is adapted to accommodate these hot sealants. The viscous liquid dispenser  20  is structured by mass distribution to retain heat along the fluid path but to dissipate heat effectively in other areas where it is desirable to keep the viscous liquid dispenser  20  cool. For example, it is advantageous to dissipate heat effectively in areas where metering device  22  connects with pneumatic actuators, motors or gear boxes, which it is desirable to keep as cool as possible.  
         [0089]     As seen in  FIG. 1 , metering device  22  is operably connected to servo motor  262  via gear box  264 , and gear box coupling  266 . Servo motor  262  and gear box  264  are generally conventional components. Gear box coupling  266 , however, is particularly adapted to dissipate heat effectively.  
         [0090]     Gear box coupling  266  generally includes first ring  268 , second ring  270  and struts  272 . First ring  268  is adapted for connection to gear box  264 . Second ring  270  is adapted for connection to metering device  22 . One skilled in the art will readily be able to envision a large number of ways of making these connections. But, conventionally these will be done with bolts and threaded holes. Struts  272  separate first ring  268  from second ring  270 . This allows for free circulation of cooling air between first ring  268  and second ring  270 . In addition, struts  272  are widely spaced to allow for air circulation. In addition, struts  272  substantially separate first ring  268  from second ring  270 . Even further, struts  272  are perforated by multiple cooling holes  274 . Cooling holes  274  serve to reduce the thermal mass of gear box coupling  266 , to increase surface area and to allow additional air circulation in and around gear box coupling  266  to maximize cooling and thus dissipate heat rather than transmitting it to gear box s 264  and servo motor  262  where it may cause harm to these components.  
         [0091]     In another example, pneumatic actuator  234  is mounted to poppet valve  230  by valve cylinder mount  276 . As can be seen in  FIGS. 19 and 20 , valve cylinder mount  276  separates pneumatic actuator  234  substantially from valve block  208 . In addition, valve cylinder mount  276  may be pierced by cooling holes  278 . To maximize the dissipation of heat energy before it reaches pneumatic actuator  234 , potentially causing harm and increased likelihood of embodiment failure.  
         [0092]     Further yet, valve block  208  and metering device body  26  are designed to be large unitary sold metal structures in order to maximize thermal mass in this area to maintain heat in the fluid flow path. Further yet, nozzle  102  maybe formed from a highly conductive high thermal mass material, such as brass, in order to maximize thermal mass and maximize heat retention while reducing or eliminating the need to have auxiliary heaters in these structures. In another embodiment of the viscous liquid dispenser  20 , the viscous liquid dispenser  20  is supported in a floating head  280 . The floating head  280  is able to float in three axes.  
         [0093]     Referring to  FIG. 22  floating head  280  generally includes x-axis/y-axis mounting  282  and z-axis mounting  284 .  
         [0094]     X-axis/y-axis mounting  282  generally includes linear bearing members  286 ,  288  interleaved between stationary plate  290 , x-plate  292  and y-plate  294  that allow limited movement of viscous liquid dispenser  20  in the x and y-axis direction. Linear bearing members  286  interconnect x-plate  292  to stationary plate  290  so that x-plate  292  has linear freedom of motion relative to stationary plate  290  along the x-axis x. Linear bearing members  288  interconnect y-plate  294  to x-plate  292  so that y-plate  292  has linear freedom of motion relative to x-plate  292  along the y-axis y.  
         [0095]     X-axis/y-axis mounting further includes sensors  296 . Sensors  296  are desirably linear proximity sensors such as photodetectors, whisker switches or encoders. Sensors  296  are triggered by the movement of viscous liquid dispenser  20  from a centered position relative to x-axis y-axis mounting  282 . When sensors  296  are triggered by motion of viscous liquid dispenser  20  from a Zero position, sensors  296  trigger servo motors (not shown) to recenter viscous liquid dispenser  20  to a Zero position on the x-y axis.  
         [0096]     Z-axis mounting  284  generally includes a biasing mechanism  298 . Biasing mechanism  298  as depicted here includes springs  300  but may also include air springs or counterweights to compensate for the weight of floating head  280  and structures supported by floating head  280 . The weight of the floating head  280  and viscous liquid dispenser  20  are balanced by springs  300 , air springs or counterweights. The viscous liquid dispenser  20  is shock and bias loaded to a Zero position, which is a center position on the x and y axis. Sensors then sense x-y movement from the Zero point and direct servo motors to cause a readjustment of position to compensate for the drift of the Zero point. Shock and bias loading may be provided by springs  302 ,  304  bearing on blocks  306 ,  308  respectively.  
         [0097]     The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.