Abstract:
An electric dispensing gun for dispensing two part viscous materials. The dispensing gun features a directly driven pinion/rack assembly and an optional mixing manifold for dispensing material from sausage packaging. A controller controls operation of the dispensing gun to implement dosage control and automatic power reverse features.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to viscous material dispensers and in particular to a material dispensing gun adapted to receive a disposable tubes of constituent viscous materials either in cartridge or sausage packaging that are mixed upon dispensing into a resulting adhesive or sealant material.  
         BACKGROUND OF THE INVENTION  
         [0002]    Power viscous material dispensers such as caulking guns that are driven by various power sources such as compressed air or electric motors are well known in the art. One commercially successful power caulking gun is disclosed in U.S. Pat. No. 5,775,539 to Bates et al., which is incorporated herein by reference in its entirety. The caulking gun described in the &#39;539 patent includes an electric motor that drives a piston carrying rack through a combination of planetary, bevel, and pinion gears. The electric motor is retained in a housing that protrudes from the rear of the gun and the motor shaft rotates about an axis that is parallel to the length of the piston carrying rack.  
           [0003]    Many adhesive materials are sold as two constituent materials, or parts, that are mixed together upon application to form a single adhesive material. Electric dispensing guns have been developed to dispense two part adhesives. For example, U.S. Pat. No. 6,089,407 to Gardos describes a fluid material dispensing gun for dispensing two part materials for dental use that has in-line longitudinal racks for driving a piston into each of the constituent fluids, which are then concurrently dispensed through a single orifice. This dispensing gun has racks that are driven by an electric motor through a series of bevel gears and a pinion gear that rotates about an axis perpendicular to the axis of rotation of the motor.  
         SUMMARY OF THE INVENTION  
         [0004]    A dispenser for dispensing two part viscous material. The dispenser can accept constituent materials in flexible sausage packaging or rigid cartridge form. An electric motor drives a pinion gear that is coaxial with the motor shaft. The pinion gear in turn drives two parallel spaced racks that each have a piston at a distal end for applying force to the constituent materials. The constituent materials are dispensed by the pistons through a dispensing orifice. In an embodiment that dispenses constituent materials from sausage packaging a manifold is included that directs material from each sausage to single nozzle on the dispenser.  
           [0005]    In an exemplary embodiment, the motor is mounted in the handle of the dispenser and planetary gears are interposed between the motor and the pinion to provide gear reduction in an in-line package. A control circuit controls operation of the dispenser based on preset parameters and inputs. The controller performs a dose control function by using a timer to discontinue motor operation after a preset amount of time has passed. The preset time for the dose control function can be set by the user or by the controller based on an estimated amount of material that has been dispensed as calculated by the controller. The controller uses motor voltage and current to estimate the amount of material that has been dispensed by mapping motor voltage to rack speed and motor current to material viscosity.  
           [0006]    The controller limits voltage and current to the motor to maintain dispenser functioning within preset parameters. The controller reverses the motor at the end of each application to relieve pressure on the pistons and the resulting fluid overflow. In a reload cycle, the controller may place a voltage amplifier in series with the motor to cause the motor to move the rack in a reverse direction at a relatively high speed to facilitate reloading. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a side perspective view of the novel and improved dispenser of the present invention;  
         [0008]    [0008]FIG. 2 is an enlarged and perspective view of the outlet of the present dispenser;  
         [0009]    [0009]FIG. 3 is and exploded view of the components of the dispenser at its outlet end;  
         [0010]    [0010]FIG. 4 is a view of the dispenser of FIG. 1 with the gearing enclosure removed;  
         [0011]    [0011]FIG. 5 is a perspective view of an alternative embodiment incorporating the dispensing end of the present invention; and,  
         [0012]    [0012]FIG. 6 is block diagram a of control circuit for use in an embodiment of the present dispenser. 
     
    
     DETAILED DESCRIPTION  
       [0013]    Turning now to the figures, FIG. 1 illustrates a new and improved dispensing gun  10  of the present invention. The gun  10  includes a pinion gear enclosure  12  that houses a pinion gear (shown in FIG. 4) which propels drive racks  14 ,  15 . The enclosure  12  additionally houses circuitry that controls the movement of the drive racks. The circuitry is mounted within the enclosure  12  at the location indicated by reference character  16 . The pinion gear is driven by a plurality of planetary gears (shown in FIG. 4) housed in a planetary gear enclosure  18 . The planetary gears are driven by an electrical motor located in the motor housing  20  which is supplied electrical current by battery  22 . The planetary gear housing  18  and motor housing  20  additionally are housed within a handle that is gripped by an operator during operation of the dispensing gun  10 . A portion of gear housing  18  supports a trigger  24  which activates the motor to supply power to the planetary gears and pinion gear to propel the racks  14 ,  15 . In addition, a clutch lever  26  extends through a portion of the gearing enclosure  18 . The pinion enclosure  12  also supports a dosing-speed control knob  27  that is in communication with the circuitry for controlling the movement of the racks  14 ,  15 . The racks  14 ,  15  include a plurality of teeth shown generally by reference characters  14   a ,  15   a  which engage the pinion gear to drive the racks  14 ,  15 .  
         [0014]    A cartridge holder  28  is fastened to the pinion enclosure  12  such that cartridges (shown in phantom)  30 ,  31  are aligned with the racks  14 ,  15 . The cartridge holder  28  includes a rear plate  19  that secures the cartridge holder to the gear housing  12  via two cartridge nuts  17   a ,  17   b . The rack  14  extends through the bore of nut  17   a  and the rack  15  extends through the bore of nut  17   b . Side plates  21 ,  23  extend from the rear plate  19  generally parallel to each other for the length of the cartridges  30 ,  31  and are coupled to a front plate  25 . Bottom rods  27  extend from the rear plate  19  through a front plate  25 . A dispensing unit  36  may be affixed to the front plate  25  and is further discussed below with respect to FIGS. 3 and 4.  
         [0015]    The cartridges  30 ,  31  may either resemble sausages in that each has one of parts A or B within a flexible plastic skin or rigid tubes containing the material. When the sausage type cartridges are employed, the dispensing unit  36  is attached to better accommodate the sausage type packaging of the material. However, where rigid tubes are employed, the dispensing unit  36  is removed and the standard end of the commercial two-part packaging is used in place of the dispensing unit  36 . During rigid commercial tube usage, an optional cartridge holder  37  may be employed (see FIG. 1 a ). The optional cartridge holder  37  includes a front plate  39  which has a bore  43  that provides clearance for the dispensing end of the two-part commercial tubes. Pistons  32 ,  33  are affixed to the drive end of the racks  14 ,  15  for compressing material from the cartridges  30 ,  31  as the racks  14 ,  15  are driven by the pinion gear. Additionally, the racks  14 ,  15  are coupled together by a return handle  34  located at an opposite end of the racks  14 ,  15  from the drive direction. The return handle  34  is used to pull the racks  14 ,  15  and coupled pistons  32 ,  33  out of the cartridge tubes  30 ,  31  when the tube is empty or when different tubes are desired. The return handle  34  can also act as a hanger hook for hanging the gun  10  during storage.  
         [0016]    Tuning now to FIGS. 2 and 3, the distal end of the cartridge holder is shown illustrating the dispensing unit  36 . The dispensing unit  36  includes a manifold  40  which is removably attachable to the front plate  25  of the cartridge holder  28  by locking ring  42 . Rods  29  extend through the manifold  40 , nozzle adapter  64  and locking ring  42  for securing the dispensing unit  36  to the cartridge holder  28 . The locking ring  42  selectively engages the rods  29  in arcuately curved locking slots  46  provided in the locking ring  42 . More specifically, the locking slots  46  have enlarged ends for receipt of forward ends of rods  29 . Once the enlarged ends  48  of the locking ring  42  have been telescoped over of the rods  29 , rotation of the ring in a clockwise direction brings arcuate sections of the slots  46  into circumferential grooves  50  located at the dispensing end of the rods  29 .  
         [0017]    As best seen in FIG. 3, and understood by reference to FIG. 1, the manifold  40  carries a pair of piston cups  52 ,  54  attached via a bolt through securing holes  44 . The piston cups co act with the pistons at their end of travel to provide a sealed space for the material that remains in the sausage to reduce leakage of material back into the cartridge holder. The piston cups  52 ,  54  respectively receive and carry removable piercing tubes  56 ,  58 . The piercing tubes  56 ,  58  are respectively aligned with outlet ports  60 ,  62  in the piston cups  52 ,  54 .  
         [0018]    In operation, cartridges of the A and B materials are inserted into the cartridge holder  28 , and the piston cups  52 ,  54  with their piercing tubes  56 ,  58 . The loading of the cartridges is accomplished at a time when the pistons  32  and drive racks  14  are all retracted. Once the locking ring  42  and manifold  40  are back in place, the rack  14  is advanced to press forward the pistons  32  into the forward ends of the cartridges which further press into the piston cups  52 ,  54 . As the cartridges enter the piston cups  52 ,  54  the piercing tubes  56 ,  58  pierce the respective cartridges. Motor driven advance of the rack  14  causes the material from the two cartridges to be dispensed through the manifold  40  and the nozzle adaptor  64  and, as they are dispensed to be concurrently mixed for their intended purposes. In an alternative embodiment, the nozzle adaptor  64 , the manifold  40 , the piston cups  52 ,  56 , and the piercing tubes  56 ,  58  are a single molded unit that can be removed and discarded when a new type of material is to be dispensed.  
         [0019]    Referring now to FIG. 4, a view of the pinion gear and planetary gear is shown with their respective enclosures removed. The pinion gear  72  is supported in a pinion gear housing  74 . The pinion gear  72  may be secured in the housing  74  by any means as know to those of ordinary skill in the art. The gear housing includes an extension  75  which further includes a mounting plate  77  for mounting the cartridge holder  28  (shown in FIG. 1). The gear housing  74  further includes guide depressions (not shown) which guide tracks  14  and  15  through the gear housing  74 . Tracks  14  and  15  extend through the pinion gear housing  74  in a manner such that the teeth  14   a ,  15   a  engage teeth  72   a  of the pinion gear  72 . The pinion gear  72  is coupled to a system of planetary reduction gears (generally referred to as reference character  76 ). The system  76  includes a first larger set  78  and a second small set  80  of planetary gears. The larger set  78  includes two stages of planetary gears coupled together by ring gear  82 . The smaller set  80  includes three stages of planetary gears. The planetary gear system  76  is coupled to the motor  84  through a drive shaft  86 . Further, a battery (shown in FIG. 1) supplies current to the motor  84  through conductors  88 .  
         [0020]    During operation, the motor turns the drive shaft at about 1500 rpm thus rotating the planetary gear system  76 . Each stage of the gear system reduces the drive speed at approximately a 3:1 ratio. The planetary gears of the gear system  76  operate in a manner consistent with the planetary gear system disclosed in U.S. Pat. No. 5,775,539 to Bates et al. The planetary gears are coupled between the pinion gear  72  and the drive motor such that the drive speed being imparted on the pinion gear  72  is reduced to a point suitable for driving racks  14 ,  15  for dispensing material from cartridges (shown in FIG. 1). The motor  84 , motor shaft  86 , planetary gears  76  and pinion gear  72  are located on the same axis coincident to each other which allows for a more efficient and durable dispensing system.  
         [0021]    Once the cartridges are emptied or new cartridges are desired, racks  14 ,  15  must be returned to the starting position in order to remove the cartridges. One way to return racks  14 ,  15  is through use of clutch lever  26 . Clutch lever  26  supports a plunger  90  which engages the ring gear  82 . When the lever  26  is in the locked position, the unit drives forward for normal dispensing operation. When the clutch lever  26  is in the unlocked position, the racks  14 ,  15  can be manually retracted to any position desired by the operator. The clutch and clutch lever operate in a manner consistent with FIGS. 5 and 6 of U.S. Pat. No. 5,775,539 to Bates et al.  
         [0022]    Referring now to FIG. 5, an alternative dispenser is shown incorporating the dispensing unit  36  of the present invention. The dispenser  100  includes a molded body  102 . A battery  104  is coupled to a handle portion  106  of the body  102 . The battery  104  provides energy to drive a motor within a motor portion  108  of the body  102 . A drive train, not shown, connects the output of the motor to a drive rod  110 . The drive rod  110  in turn drives a spaced and generally parallel pair of piston rods  118 ,  120 . The piston rods  118 ,  120  respectively drive a spaced pair of pistons  112 ,  114 . The piston rods  118 ,  120  and the drive rod are all connected to a return handle  122 .  
         [0023]    The pistons  112 ,  114  are respectively reciprocal within a housing  116  which is contoured to retain a pair of material cartridges, not shown. A dispensing unit  36  as previously disclosed in FIGS. 2 and 3 is coupled to the dispensing end of the body  116 .  
         [0024]    Control Circuit  
         [0025]    Referring to FIG. 6, a simplified block diagram of the control circuit  16  is shown. The control circuit controls the flow of battery voltage to the motor based on preset parameters and control algorithm logic that is stored in a controller  160 . There are four adjustable inputs to the control circuit  16 : dose control, current limit, trigger level, and voltage limit. In the described embodiment, the dose control input is set by the user via knob  29  (FIG. 1) and the current and voltage limits are internal potentiometers that are set during manufacture of the dispenser unit. However, the current and voltage limits could be made accessible to the user by placing knobs or other means on the exterior of the dispenser. The voltage limit controls the maximum speed of the motor, and correspondingly, the flow rate of the material out of the dispenser. The current limit controls the amount of force that can be applied by the pistons to prevent damage to dispenser caused by excessive forces acting within the dispenser. The control circuit  16  controls the motor supply voltage such that the motor voltage and motor current are maintained below the preset limits.  
         [0026]    The trigger level input is variable input that corresponds to an amount of displacement of the trigger that is actuated by the user to control the flow of material from the dispenser. The higher the trigger displacement, the higher the voltage that is supplied to the motor. A dose control feature is implemented using a timer circuit  162  that is activated by a signal on the trigger level input. The timer circuit signals the controller to discontinue power to the motor after an amount of time that is set by the dose control knob has passed. This feature allows a user to apply a uniform amount of material with each trigger actuation by setting the desired amount of application time and actuating the trigger until the motor stops for each application. In an alternative embodiment, if the dose control feature is actuated, the controller will supply voltage to the motor for the preset dosage time each time the trigger is actuated regardless of the length of time the trigger is actuated. The dose control feature can be disabled by turning the dose control knob  29  to an OFF position. When the dose control feature is disabled, the motor supply voltage is controlled solely by the displacement of the trigger.  
         [0027]    When the motor supply voltage is discontinued, it is desirable to relieve the pressure on the material within the dispenser to prevent continued flow out of the dispenser after the desired amount of material has been dispensed. To achieve this end, the controller  160  is in communication with an inverter circuit  164  that inverts the voltage to the motor for a preset time to cause it to reverse direction and move the racks and pistons away from the dispensing end of the dispenser. Another way to prevent unwanted flow at the end of an application cycle is to discontinue power to the motor prior to the end of the dose time limit set by the dose control knob  29  so that the continued flow becomes part of the application cycle.  
         [0028]    Prior to reloading the dispenser unit with new material cartidges or sausages, it is necessary to return the racks to the load position. As already discussed, this can be accomplished by actuating the clutch and manually pulling the racks back to the load position. The controller  160  can cause the racks to return quickly to the load position by inverting the voltage to the motor to reverse rack travel direction and placing a voltage amplifier  166  in series with the motor that boosts the supplied voltage several times to increase the speed of the racks. This reload positioning cycle can be actuated by the user via a button on the exterior of the dispenser. In another embodiment, the end of rack travel in the dispense direction can be sensed by monitoring motor current or rack position and when the end of rack travel is reached activating the rack reload positioning. In addition to reversing rack travel at increased speed to release spent cartridges, the voltage amplifier may also be activated to quicly propel the racks into engagement with a new cartridge. The voltage amplifier would be deactivated upon engagement with the cartridge, sensed by an increase in current draw or rack position.  
         [0029]    A more sophisticated dose control feature that provides an application cycle that results in a uniform amount of material being dispensed with each trigger actuation can be accomplished by programming the controller to estimate an amount of fluid that has been dispensed in any given trigger actuation by monitoring motor current, motor voltage, and time. Within the controller, the motor voltage is correlated to a rack speed and the motor current is correlated to a piston force and in turn material viscosity. The rack speed can be multiplied by the time duration to approximate an amount of material that has been dispensed. The amount of dispensed material can be compared against the desired amount that is set by the dosage control knob and this information may be used to update the time duration of the application cycle. The duration of time of the application cycle can also be continuously updated by the controller based on the estimated material viscosity (determined based on motor current) such that more viscous materials have a longer duration of time in the application cycle.  
         [0030]    Although the present invention has been described with a degree of particularity, it is the intent that the invention include all modifications and alterations from the disclosed design falling within the spirit or scope of the appended claims.