FIELD OF THE INVENTION  
       [0001]     The present invention relates to dispensing devices for viscous product cartridges; and more particularly, to such dispensing devices having a nozzle valve.  
       BACKGROUND OF THE INVENTION  
       [0002]     Some viscous products, including for example, adhesives, caulks, and sealants, are commonly packaged in product cartridges or tubes. These tubes typically include a cardboard or plastic cylindrical body. Generally, a dispensing nozzle is located at one end of the tube and at the other end of the tube is a piston that operates as a moveable wall. These product cartridges are typically inserted into a dispensing device that includes some mechanism for exerting a force on the movable wall to push product from the product cartridge.  
         [0003]     The force exerting mechanism has traditionally been a trigger that mechanically cooperates with a shaft to drive the shaft against the movable wall. Pneumatic pressure has also been suggested as an alternative force exerting mechanism. At the end of a dispensing operation, the product within the cartridge can remain pressurized which causes product to continue to be dispensed beyond that desired by the user. Consequently, nozzle valves have been provided in such pneumatic dispensing devices to provide the user more controlled termination of product dispensing.  
         [0004]     The nozzle valve has generally been linked to a manually operated trigger that also controls the flow of the pneumatic fluid. The driving linkage between the trigger and the nozzle valve, however, has typically not been very robust. For example, product in the nozzle can begin to harden between uses such that the drive linkage is incapable of developing sufficient driving force to actuate the nozzle valve. In addition, in some instances attempts to actuate the trigger can actually cause damage to the drive linkage, making the dispensing device inoperable. Accordingly, a robust drive linkage for the nozzle valve is desirable.  
       SUMMARY OF THE INVENTION  
       [0005]     In accordance with one aspect of the present invention, a valve drive mechanism for a dispensing device that is adapted to dispense viscous product from a product cartridge having a valve associated with a dispensing passage is provided. The valve drive mechanism includes a pinion associated with the valve and adapted to move the valve between an open position and a closed position upon rotation of the pinion. A rack is associated with the pinion and adapted to rotate the pinion upon linear movement of the rack. A trigger is adapted to impart linear movement to the rack upon manual actuation of the trigger. The open position of the nozzle valve permits viscous product to flow through the dispensing passage, and the closed position of the nozzle valve prevents viscous product from flowing through the dispensing passage.  
         [0006]     In accordance with another aspect of the present invention, a device for dispensing a viscous product from a viscous product cartridge is provided. The dispensing device is adapted to be driven by a pressurized gas source. The dispensing device includes a housing adapted to retain the viscous product cartridge and to cooperate with the viscous product cartridge to form a gas enclosure separated from a product enclosure by a movable wall. A fluid passage extends from an inlet associated with the pressurized gas source to the gas enclosure to enable pressurized gas to generate a dispensing force on the movable wall. A nozzle is adapted to seal to the product cartridge and to provide a dispensing passage for the product cartridge. The nozzle has a valve body located along the dispensing passage and movable between an open position and a closed position. A pinion is associated with the valve body and adapted to move the valve body between an open position and a closed position upon rotation of the pinion. A rack is associated with the pinion and adapted to rotate the pinion upon linear movement of the rack. A trigger is adapted to impart linear movement to the rack upon manual actuation of the trigger. The open position of the valve body permits viscous product to flow through the dispensing passage, and the closed position of the valve body prevents viscous product from flowing through the dispensing passage.  
         [0007]     In accordance with yet another aspect of the present invention, a dispensing device for a viscous product includes a movable wall separating a product enclosure having a dispensing orifice from a gas enclosure. A fluid passage provides fluid communication between a pressurized gas cartridge and the gas enclosure. A nozzle is sealed to the product cartridge and provides a dispensing passage for the product cartridge. The nozzle has a valve body located along the dispensing passage and is movable between an open position and a closed position. A pinion is associated with the valve body and has a plurality of gear teeth. A rack has a plurality of cooperating gear teeth drivingly engaged with the plurality of gear teeth of the pinion and has a notch. A trigger has a drive lug drivingly engaged with the notch of the rack upon manual actuation of the trigger. Manual actuation of the trigger causes the drive lug to linearly drive the rack which causes the cooperating gear teeth of the rack and the plurality of gear teeth of the pinion to rotate the pinion and move the valve body from a closed position which prevents viscous product from flowing through the dispensing passage to an open position which permits viscous product to flow through the dispensing passage.  
         [0008]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a cross-sectional illustration of a dispensing device in accordance with one embodiment of the present invention;  
         [0011]      FIG. 2  is a cross-sectional illustration of the dispensing device similar to  FIG. 1 , but with the nozzle valve in an open position;  
         [0012]      FIG. 3  is an enlarged perspective illustration of the drive linkage of the device of  FIG. 1 ; and  
         [0013]      FIGS. 4   a ,  4   b  and  4   c  are successive fragmentary elevational illustrations of the trigger disengaging from the rack. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For example, although the drive linkage is described herein in connection with a pneumatic dispensing device for viscous product cartridges, such a drive linkage may be used with alternative dispensing devices for viscous product cartridge.  
         [0015]     As used herein, “pressurized gas cartridge” means a container that is capable of housing a material that can be dispensed from the container in the form of a pressurized gas. Thus, it is possible that the material inside the container may be, at least partially, in a form that is not gaseous. Similarly, the phrase “product cartridge” as used herein, means a container capable of housing a product for shipping and/or storage and for dispensing. Thus, the term “cartridge” does not, in itself, require any specific structural configuration. In addition, the phrase “associated with” as used herein means direct or indirect physical and/or operable connection. Thus, the phrase “associated with” does not, in itself, require direct contact.  
         [0016]     Referring to  FIGS. 1 and 2 , one preferred embodiment of a dispensing device  10  for dispensing a viscous product from a viscous product cartridge  12  is illustrated. The dispensing device  10  includes a housing  14 . The housing  14  includes an upper portion  15  that operates as a product cartridge housing component. This product cartridge housing component  15  is adapted to retain the viscous product cartridge  12 . In the illustrated embodiment, the viscous product cartridge  12  is a cylindrical tubular member having a relatively rigid cylindrical wall  16 . For example, the cylindrical wall  16  may be formed of cardboard or plastic. Such tubular cartridges  12  are commonly used in conjunction with or in association with construction adhesives, sealants and caulk.  
         [0017]     At one end of the cylindrical tubular product cartridge  12  is a dispensing orifice  18 . The dispensing orifice  18  may be provided, for example, by cutting the end of a nozzle (not seen) that is typically provided on many such commercially available viscous product cartridges  12 . In addition, it may be necessary to rupture an internal seal (not shown) at the base of the nozzle that seals the dispensing orifice  18  and is often also included in such commercially available product cartridges  12 . At the opposite end of the product cartridge  12  is a piston  20  that seals the end of the tube  12 . The piston  20  operates as a movable wall that is capable of forcing product from the product enclosure  22  through the dispensing orifice  18  as the piston  20  moves toward the dispensing orifice  18 .  
         [0018]     Although this embodiment uses product cartridges having a relatively rigid cylindrical wall  16  and a movable piston  20 , an alternative product cartridge (not shown) is made of flexible thin-film packaging material. The corresponding product cartridge housing component  15  of this alternative embodiment can optionally use a separate movable piston to dispense the product, similar to the previously described movable piston  20 . In yet another alternative embodiment, the gas enclosure can surround the flexible side walls of a squeeze tube. Commonly used squeeze tube type cartridges have a substantially cylindrical shape flexible side wall that tapers to a flat seal on one end with a dispensing orifice on an opposite end. Thus, the flexible side walls can move toward each other under external pressure within the gas enclosure to force product through the dispensing orifice. Accordingly, the separate movable piston and/or the flexible side walls provide the movable wall(s) in these alternative embodiments.  
         [0019]     Returning to the illustrated embodiment, the upper portion of the housing  14  operates as a product cartridge housing component  15 . The product cartridge housing component  15  is adapted to cooperate with the viscous product cartridge  12  to form a gas enclosure  24  separated from the product enclosure  22  by the piston wall  20 . In this embodiment, the product cartridge housing component  15  is sealed to the cylindrical outer wall  16  of the product cartridge  12  using an O-ring  26  to form a gas enclosure  24  between the housing component  15  and the product cartridge  12 . The piston  20  or movable wall separates the gas enclosure  24  from the product enclosure  22  formed inside the product cartridge  12 .  
         [0020]     A nozzle housing  30  is adapted to seal with a wall  28  of the product cartridge  12  that surrounds the dispensing orifice  18 . As indicated above, this wall  28  can be provided by trimming the end of a nozzle from a standard caulk or adhesive product cartridge  12 . A rubberized gasket  33  may be provided between the nozzle housing component  30  and the wall  28  of the product cartridge  12  to facilitate this seal. Threads  35  are provided on the nozzle housing  30  to enable threaded engagement between the wall  28  of the product cartridge  12  and the nozzle housing  30 . The threads  35  of the nozzle housing  30  can be self-threading (i.e., adapted to form cooperating threads on a smooth part of the wall  28 ) or the wall  28  can already have cooperating threads  35  formed thereon.  
         [0021]     The nozzle housing  30  includes a dispensing passage  32  which is selectively opened and closed by a valve body  34 . The valve body  34  includes a passage  37  therethrough for selective alignment with the dispensing passage  32  of the nozzle housing  30 . An annular ridge  39  on the valve body  34  cooperates with an annular groove in the nozzle housing  30  to retain the valve body  34  in the nozzle housing  30 . The lower end of the valve body  34  includes a rectangular shaped nozzle drive lug  40 . The nozzle drive lug  40  fits into a drive notch  42  of a pinion  44 . The teeth  46  of the pinion  44  cooperate with the teeth  48  of a rack  50 . In an alternative embodiment, the rack  50  can be associated with the pinion  44 , for example, through an intermediate idler gear (not seen).  
         [0022]     Referring to  FIG. 3 , the rack includes a generally cylindrical rod  52  and a flat rod  54 . The flat rod  54  of the rack  50  includes a notch  56  seen in  FIG. 4 . A lug  58  on the trigger  38  contacts against the flat rod  54  of the rack  50  at the end of the notch  56  so that the trigger  38  can drive the rack  50  forward to cooperate with the pinion  44  and rotate the valve body  34  into an open position (seen in  FIG. 2 ). Upon releasing the trigger  38 , a spring  60  biases the rack  50  to move the trigger  38  and rotate the valve body  34  into a closed position (seen in  FIG. 1 ).  
         [0023]     In an alternative embodiment (not seen), the nozzle, including the valve body and dispensing passage, may be integrally provided as part of the product cartridge, rather than as a separate part. This configuration eliminates the need to seal the dispensing orifice  18  of the product cartridge  12  to a separate nozzle housing. In contrast, the preferred embodiment described above enables re-use of the nozzle housing  38  and valve  44  assembly with multiple disposable product cartridges  12 . In addition, the embodiment described above enables the use of differently sized and/or configured nozzle housings by permitting nozzle housings to be exchanged on a product cartridge.  
         [0024]     The rack  50  and pinion  44  is capable of providing a significant amount of force to rotate the valve body  34 . Thus, this rack  50  and pinion  44  valve drive mechanism can open the valve  34 , even when product may have partially solidified in the dispensing passage  32  between uses. In order to avoid damaging the rack  50  and pinion  44  valve drive mechanism, however, an override disengagement feature is provided that operationally disengages the rack  50  and pinion  44  valve drive mechanism from the trigger  38  prior to damaging the valve  34 , the trigger  38  and/or the rack  50  and pinion  44  drive mechanism.  
         [0025]     Referring to  FIG. 4   a , the end of the notch  56  of the flat rod  54  of the rack  50  has a rounded profile that partially mates with a small undercut  62  in the drive lug  58  of the trigger  38 . Thus, during normal operation, the end of the notch  56  of the rack  50  is retained against the drive lug  58  of the trigger  38 . Referring to  FIG. 4   b , if too much force is generated between the rack  50  and the trigger  38 , the rounded end of the notch  56  of the rack  50  disengages from undercut  62  and the drive lug  58  of the trigger  38  begins to pass under the rack  50 . Referring to  FIG. 4   c , this permits the trigger  38  to rotate forward without damaging the dispensing device  10 . Upon returning the trigger  38  to its original position, the drive lug  58  will reengage with the notch  56  of the pinion  44 .  
         [0026]     As indicated above, a lower portion  64  of the housing  14  of the dispensing device  10  operates as a handle for manually grasping the dispensing device  10 . The manually actuated trigger  38  mentioned above is associated with the handle  64 . In addition, the handle provides a gas cartridge housing component  64 . A fluid passage  66  provides fluid communication between the gas enclosure  24  and an inlet  68  associated with a pressure regulator  70  located in the handle portion  64  of the housing  14 . The gas cartridge housing component  64  is adapted to retain a gas cartridge  72  in sealed fluid communication with the inlet  68 .  
         [0027]     Specifically, the inlet  68  of the fluid passage  66  includes a resilient gasket seal member (not seen). In addition, the inlet  68  can include a piercing member (not seen) to pierce an opening in the gas cartridge  72  upon sealing to the inlet  68 . The gas cartridge housing component  64  includes a screw on cap  74  associated with the gas cartridge  72 . As the cap  74  is screwed onto the remainder of the gas cartridge housing component  64 , the cap  74  pushes the gas cartridge  72  into sealing engagement with the gasket of the inlet  68 . In addition, screwing the cap  74  onto the remainder of the gas cartridge housing component  64  causes any piercing member to pierce the gas cartridge  72 . In any event, sealed fluid communication is provided between the interior of the gas cartridge  72  and the fluid passage  66 .  
         [0028]     The pressure regulator  70  reduces the pressure of the CO 2  gas flowing from the pressurized CO 2  cartridge  72  to a lower pressure level. This lower level of pressure is high enough to dispense product from the product cartridge  12  at a desirable rate. Thus, the pressure regulator  70  receives gas from the inlet  68  at a relatively high pressure from the CO 2  cartridge  72  and, after converting the gas to a reduced pressure, discharges the CO 2  gas from an outlet side of the pressure regulator  70  into the fluid passage  66  toward the gas enclosure  24 .  
         [0029]     A gas flow control valve  76  is also located along the fluid passage  66 . The gas flow control valve  76  is biased to a closed position by a spring  78 . The gas flow control valve  76  is manually actuated by the trigger  38  which moves the valve  76  to an open position as seen in  FIG. 4 . In the open position, gas is permitted to travel along the passage  66  from the pressurized CO 2  cartridge  72  and to the gas enclosure  24 . The resulting increase in gas within the gas enclosure  24  causes the pressure to increase until the piston  20  begins to move.  
         [0030]     As indicated above, the trigger  38  is also operatively connected to the nozzle valve body  34  to open the valve upon manual actuation. Thus, in this embodiment, the valve  34  of the dispensing passage  32  and the gas flow control valve  76  are simultaneously opened. As the piston  20  begins to move, a volume of the gas enclosure  24  expands reducing a volume of the product enclosure  22  and dispensing product through the dispensing orifice  18  and the dispensing passage  32 . Upon release of the trigger  38 , both the nozzle valve  34  and the gas flow control valve  76  move to their closed positions as seen in  FIGS. 1 and 3 . Thus, the product within the product enclosure  22  is maintained under pressure due to the remaining gas pressure within the gas enclosure  24 . Product does not continue to be dispensed, however, due to the valve  34  of the dispensing passage  32  being in a closed position.  
         [0031]     Two additional valve mechanisms are located within the fluid passage in this embodiment. One is a pressure release valve  80  that is additionally associated with the gas enclosure  24  and is biased to a closed position. The pressure release valve  80  may be manually moved to an open position to permit the release of pressure from the gas enclosure  24 . This release of pressure can, for example, facilitate the replacement of the viscous product cartridge  12 . A maximum pressure release valve  82  is also included in the fluid passage  66  that is designed to vent the CO 2  gas from the gas enclosure  24  should the pressure therein exceed a maximum pressure level.  
         [0032]     Operation of the dispensing device  10  described above involves locating a product cartridge  12  in the product cartridge housing component  15 . As described above, this creates a gas enclosure  24  separated from a product enclosure  22  by a moveable wall  20 . In addition, operation of the illustrated dispensing device  10  involves locating a CO 2  cartridge  72  inside the gas cartridge retaining housing component  64 . The CO 2  cartridge  72  is sealed to the inlet  68  by threading the cap  74  onto the housing  14  as discussed above. Thus, the interior of the CO 2  cartridge  72  is located in sealed fluid communication with an inlet  68  of the passage  66  by screwing on the cap  74 .  
         [0033]     Referring to  FIG. 2 , application of the product dispensing force is accomplished by manually actuating the trigger  38  which causes opening of both the nozzle valve  34  and gas flow control valve  76 . Pressurized gas from the CO 2  cartridge  72  flows through the fluid passage  66  and passes through the pressure regulator  70  where the pressure level of the gas is reduced to an operational pressure level. This pressure level is selected to affect a desirable dispensing rate without unnecessarily increasing the pressure. An adjustment mechanism (not shown) for the pressure regulator  70  can additionally be provided to enable a user to adjust the operating pressure level for different products. Typically, the desired operating pressure is between about 15 and about 75 psi to accommodate different types of sealant, caulk, and viscous products. In certain cases, it is preferred that the desired operating pressure is between about 25 and about 50 psi.  
         [0034]     The pressurized gas flows past the open gas flow control valve  76  in the fluid passage  66  and into the gas enclosure  24 . As the quantity of gas in the gas enclosure  24  increases, the gas begins to push against the piston  20 . Since the nozzle valve  34  is open the piston  20  begins to move, thereby increasing the volume of the gas enclosure  24 . Conversely, this movement of the piston  20  decreases the volume of the product enclosure  22 . Thus, product is pushed from the product enclosure  22  through the dispensing orifice  18 , and the open nozzle valve  34  in the dispensing passage  32 . Upon release of the trigger  38 , the gas flow control valve  76  closes to cause the flow of gas from the CO 2  cartridge  72  to the gas enclosure  24  to cease as seen in  FIG. 1 . In addition, the product valve  34  in the nozzle  30  closes which causes the flow of product through the dispensing passage  32  to cease.  
         [0035]     During product dispensing, the pressure of the gas within the gas enclosure  24  generates a dispensing force that is exerted on the movable piston  20  which is sufficient to move the movable piston  20  to dispense product from a dispensing orifice  18  of the product cartridge  12 .  
         [0036]     The size and configuration of the nozzle  30  also has an effect on the dispensing operation. A nozzle  30  may be selected from several alternative nozzles. The nozzles  30  can have variously sized dispensing passages  32  and/or angled or otherwise shaped tips. In order to replace a nozzle  30  that has been attached to a product cartridge  12  and used to dispense product, it is important to insure that there is not any residual pneumatic pressure in the gas enclosure  24 . Any residual pressure can be released by manually actuating the pressure release valve  80  prior to removing the nozzle  30 .  
         [0037]     The nozzle  30  and nozzle drive mechanism cooperate to insure that any residual pressure in the gas enclosure  24  has been released prior to permitting removal of the nozzle  30 . Specifically, the rectangular nozzle lug  40  is adapted to be in a plane that is substantially parallel to a plane passing through the threads  35  when the valve body  34  is in the open position. This corresponds to the rectangular nozzle lug  40  being oriented substantially perpendicular to the dispensing passage  18 , when the valve body  34  is in the open position.  
         [0038]     It should be understood that the rectangular nozzle lug  40  must be in this substantially parallel plane orientation in order for the nozzle  30  to be unscrewed from a product cartridge  12  located within the dispensing device  10 . If the rectangular nozzle lug  40  is oriented with the valve body  34  in the closed position, for example, pinion  44  will interfere with the rectangular nozzle lug  40  and prevent the nozzle housing  30  from being unscrewed. Accordingly, the nozzle valve  34  must be in the open position in order to permit removal of the nozzle housing  30 .  
         [0039]     Requiring that the nozzle valve  34  be in the open position for removal of the nozzle housing  30  serves as a reminder to vent any residual gas pressure in the gas enclosure  24 . Any meaningful residual gas pressure will cause product to be dispensed upon moving the nozzle valve  34  into the open position prior to removing the nozzle housing  30 . Thus, the user will be reminded to vent this residual pressure using pressure release valve  80  prior to attempting to remove and replace a nozzle housing  30 .  
         [0040]     Referring to  FIG. 3 , a trigger lock  84  is associated with the trigger  38  to conveniently maintain the trigger  38  (and therefore, the valve body  34 ) in the open position. This trigger lock  84  can also be used to lock the valve  34  in the open position during long dispensing operations. Thus, the trigger lock  84  can also be useful to help minimize hand fatigue during extended periods of use of the dispensing device  10 . In addition, the trigger lock  84  facilitates removal and replacement of the nozzle housing  30 , since the nozzle valve  34  must be in the open position in order to change the nozzle housing  30  as discussed above.  
         [0041]     The trigger lock  84  includes a spring  85  that biases the trigger lock  84  outwardly from the housing  14 . When the trigger  38  is in the operating position, the trigger lock  84  can be depressed and friction with the housing  14  generated by the spring  60  of the rack  50  retains the trigger  38  in the operating position. Thus, the trigger lock  84  selectively locks the trigger  38  in a position corresponding to the open position of the valve  34 . Depressing the trigger  38  again will release the friction and cause the trigger lock  84  to move outwardly under the biasing force of the spring  85 .  
         [0042]     Only a small number of the many possible alternatives are described above. Many additional modifications and alternatives beyond those described above, may be envisioned by those skilled in the art. For example, although the dispensing device is described herein as preferably being driven by pressurized CO 2  cartridges, other pressurized gas cartridges, including aerosol containers, may alternatively be used. As another example, the nozzle valve or gas flow control valve may operate independently rather than being both associated with a single trigger.  
         [0043]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
A pressurized gas cartridge drives a dispensing device for viscous product cartridges. The dispensing device and the viscous product cartridge form a gas enclosure separated from a product enclosure by a movable wall. A valve is driven by a rack and pinion valve drive mechanism between an open position and a closed position upon rotation of the pinion. The rack rotates the pinion upon linear movement thereof. A trigger is adapted to impart linear movement to the rack upon manual actuation of the trigger. The open position of the nozzle valve permits viscous product to flow through the dispensing passage, and the closed position of the nozzle valve prevents viscous product from flowing through the dispensing passage. The interface between the trigger and rack is designed to operationally disengage rather than transmit a force therebetween that is capable of damaging the device.