Abstract:
A dispenser that dispenses fluid is controlled using a feedback control system. The control system uses a positional encoder to determine the precise position of a valve contained in an actuator in order to control the dispensing of the fluid. Various motion profiles may be used to control the position of the valve. The motion profiles of the valve enable controlled variation of the amount of fluid dispensed over time and enable several specific improvements to the dispensing of sealant in the manufacture of metal and composite cans.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is based upon and claims the benefit of U.S. Provisional Patent Application Ser. No. 60/485,701 by William W. Weil, et al., entitled “Fluid Dispensing Actuator” filed Jul. 8, 2003, the entire contents of which is hereby specifically incorporated by reference for all it discloses and teaches. 
    
    
     BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The present invention generally pertains to fluid dispensing systems and more particularly to actuators that control the amount of a fluid being dispensed. 
     b. Description of the Background 
     Fluid dispensers are used in different manufacturing industries to dispense fluids, such as an adhesive, plastisol, sealant or other compounds. In the container industry, for example, it is common to apply a sealant to a can end prior to assembly. The sealant provides a proper seal between the end and a body of a can. 
     In a typical actuator, a valve is simply opened and closed to dispense a fluid. Existing electrically-controlled valves typically contain two parts: an actuator that quickly opens and closes the valve, and an adjustable stop that sets how far the valve is opened when it is actuated. The actuator that opens and closes the valve may be a solenoid, pneumatic cylinder, or other device designed to quickly open and close the valve. The adjustable stop may be moved by a stepper motor, a stepper solenoid, or by a manual adjustment. One system is described in U.S. Pat. No. 6,010,740 of Rutledge et al. entitled “Fluid Dispensing System,” which is specifically incorporated herein by reference for all that it discloses and teaches. 
     Using a solenoid to quickly open and close a valve presents some limitations. The mechanism is designed to open and close the valve as quickly as possible. Yet the mechanism has a response time that delays the opening and closing of the valve. The response time may vary due to such factors as the length of stroke. Further, the response of the valve may change with the temperature of the actuator. As the actuator heats up due to repetitive use or environmental factors, the force applied by the actuator may change, thereby changing the response of the valve. The valve itself has a rate of opening and closing that cannot be controlled. Additionally, the exact position of the valve is typically unknown during movement, increasing variability. 
     A second limitation is that there is typically no way to vary the flow rate of the liquid at any point during the period that the valve is being actuated. In some applications, such as the application of sealant during the manufacturing of cans, it may be desirable to add more sealant in one area and less in another. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages and limitations of the prior art by providing a dispenser that is capable of dispensing a fluid in a controlled manner. 
     The present invention may therefore comprise a method of applying a sealant to a can end in a controlled manner in accordance with a profile comprising: generating a profile signal that is representative of the profile; providing a dispenser that dispenses the sealant to the can end, the dispenser having a fixed portion and a moving portion that define a variable size opening through which the sealant flows through the dispenser; detecting a position of the moving portion of the dispenser with respect to the fixed portion; generating an encoder signal that is indicative the position of the moving portion; applying the profile signal and the encoder signal to a controller; generating a control signal representative of the difference between the profile signal and the encoder signal; applying the control signal to an actuator that is coupled to the moving portion that moves the moving portion in response to the control signal so that the moving portion is moved to a position that matches the profile. 
     The present invention may further comprise a device for applying sealant to a can end comprising: a valve having a fixed portion and a moving portion, the fixed portion and the moving portion defining a variable size opening that regulates the amount of the sealant that is dispensed from the valve as the moving portion is moved relative to the fixed portion; a profile signal that defines a desired movement of the moving portion of the valve; an encoder that detects a position of the moving portion and generates an encoder signal representative of the position of the moving portion; a controller that compares the encoder signal and the profile signal and generates a control signal; an actuator that moves the moving portion of the valve in response to the control signal. 
     Advantages of the present invention include the ability to dispense consistent and repeatable amounts of fluid. Further, the rate of opening and closing the valve may be varied, allowing the valve position to be changed at a desired rate. The amount of time the valve is open and the flow rate can both be more accurately controlled. The amount the valve is actually opened can be controlled to control the amount of fluid that is dispensed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG. 1  is a schematic block diagram of an embodiment of the present invention showing the various elements of the present invention. 
         FIG. 2  is a schematic illustration of an embodiment of the present invention showing a lead screw driven valve. 
         FIG. 3  is a schematic illustration of an embodiment of the present invention showing a rack and pinion driven valve. 
         FIG. 4  is a schematic illustration of an embodiment of the present invention showing the application of a fluid to a work piece. 
         FIG. 5  is a schematic illustration of an embodiment of the present invention showing the use of a spring and a voice coil driven valve. 
         FIG. 6  is a graph of the response of a rotary stepper solenoid versus a servo-stepper motor. 
         FIG. 7  is an illustration of an embodiment of a servo-motor dispenser. 
         FIG. 8  is an illustration of an embodiment of a voice coil actuated dispenser. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic block diagram  100  illustrating the basic operation of the various elements of an embodiment of the present invention. An actuator  102  is connected to a valve  104  having a moving portion and a fixed portion. The moving portion of the valve  104  is moved by the actuator  102 , and the position of the moving portion of the valve  104  is captured by an encoder  106 . The controller  108  compares the value of the encoder  106  with the desired profile  110  and adjusts the actuator  102  as necessary so that the position of the moving portion of the valve  104 , as detected by the encoder  106 , is equal to the value of the desired profile  110 . As the valve  104  opens, fluid may be dispensed in an amount in accordance with the desired profile  110  through the dispenser  112 . 
     The embodiment  100  may be used to dispense fluids in various applications for different industries. For example, in can manufacturing, the system may be used to dispense liner compound (sealant) to the can ends prior to assembly on a can body. In another example, the system may be used to dispense caulking, glue, or adhesive for various assembly tasks, wherever these materials are to be dispensed in a controlled manner. 
     The actuator  102  is a device that causes mechanical motion between the fixed portion  114  and moving portion  116  of the valve. The moving portion  116  of the valve  104  may fit together with the fixed portion  114  so that when both portions are in contact, fluid cannot flow between them. When the portions separate, a gap is created through which a fluid may flow. This gap may vary proportionately with the distance between the moving portion  116  of the valve  104 , and the fixed portion  114  of the valve  104  so that fluid flow increases as the distance between the moving portion  116  and the fixed portion  114  increases. By controlling the position of the moving portion  116  with respect to the fixed portion  114 , the size of the opening can be controlled, and thus, the amount of fluid dispensed can be controlled. 
     Various mechanical valve configurations may be used for different applications. In one example, the moving portion  116  of the valve may have a cone-shaped feature that engages a conical orifice in the fixed portion  114 . Those skilled in the arts will appreciate the various configurations of valves that may be adapted for use in the present invention, while maintaining the spirit and intent of the present invention. 
     The valve  104  may operate to control the dispensing of a pressurized fluid. The fluid may be any liquid or other compound capable of flow under pressurized conditions. Examples of compounds that may be pressurized and controlled may include adhesives, paints, sealants, caulks, soaps, gels, slurries, various flowable foodstuffs, powders, oils, curable epoxies, suspensions, plastisols, and other fluids and pastes. These materials (fluids) can be applied for any desired application. 
     The valve  104  may be mounted on various types of machines used in manufacturing lines. The valve may be part of an actuator that is moved over a work piece or may be fixedly-mounted and have a work piece presented to the actuator. 
     The encoder  106  is a measuring sensor that detects the position of the moving portion of the valve  104  with respect to the fixed portion of the valve and generates a signal representative of the position. The encoder  106  may be a linear encoder or a rotary encoder, such as a shaft encoder, and may generate an absolute or relative value. The encoder  106  may be mounted to the moving portion of the valve  104 , or may be coupled through a mechanism to the moving portion of the valve  104 . 
     The range of discrete values spanned by the encoder  106  may be proportional to the maximum size of the gap between the moving portion  116  of the valve  104  and the fixed portion  114  of the valve  104 . As the actuator  102  moves the moving portion  116  of the valve  104 , the position of the moving portion  116  of the valve  104  is detected by the encoder  106  and translated into a discrete encoder value in real time. 
     Several different types of encoders are readily available. Any type may be used with the various embodiments of the present invention. One general type of encoder  106  that may be used is a shaft encoder, which captures the rotational movement of the actuator  102 . Such an encoder may measure the full travel of the moving portion of the valve  104  in fractional or whole rotations of the encoder. A rotary encoder  106  may be mounted to a drive motor or may be separately coupled to the moving portion of the valve  104  through a rack and pinion or other mechanical linkage. 
     Another general type of encoder  106  measures linear movement. A linear encoder may optically, electrically, magnetically or mechanically sense the position of the moving portion of the valve. Mechanical detectors may be coupled directly to the moving portion of the valve  104  or may be mechanically coupled to the moving portion of the valve  104  though any type of mechanical linkage. 
     The encoder  106  may be either a digital or analog device. A digital device may return a digitized distance measurement, whereas an analog device, such as a resolver, may return analog signals that may or may not be converted to a digital equivalent. Any type of distance measurement device may be used as the encoder  106  of the present invention while keeping within the spirit and intent of the present invention. 
     The controller  108  may be a closed-loop controller that controls the actuator  102  based on the feedback of the encoder  106  by comparing the profile signal  120  with the encoder signal  122 . If a difference exists, an output control signal  118 , such as a difference signal or a control signal generated from a Proportional Integral Derivative Filter with output offset, multiple feed-forward terms, notch filters and/or compensation tables, is generated by controller  108  and applied to actuator  102 . The actuator  102  then controls the position of the moving portion  116  of the valve  104  so that the moving portion  116  follows the motion profile  110 . In this fashion, the motion of the moving portion  116  of the valve  104  may be controlled in real time using feedback from encoder  106 . Open loop systems with no feedback can also be used that generate estimated responses. Various motion profiles  110  may be used to define the desired motion of the valve. For example, the motion profile  110  may define the desired position with respect to time. In other examples, the motion profile  110  may be defined with desired velocity, force, acceleration, jerk, or other variables such as force, torque, etc., that may be used to define the desired movement of the valve. 
       FIG. 2  illustrates an embodiment  200  having a lead screw driven actuator. A servo-motor  202  is connected to a lead screw  204  that drives the moving portion  206  of the valve with respect to the fixed portion  208  of the valve. An encoder  210  is mounted directly to the moving portion  206  and/or the servo-motor  202 . The output of the encoder  210  is an encoder signal  228  that indicates the position of the moving portion  206 . The encoder signal  228  is connected to the controller  218  that controls the servo-motor  202  by comparing the profile signal  230  with the encoder signal  228 . If a difference exists, a control signal  232  is generated that can comprise any desired type of control signal, as disclosed above, by the controller  218  and applied to the servo-motor  202  so that the motion of the moving portion  206  of the valve follows the motion profile  220 . 
     The flow of the fluid  222  may be regulated by a conically shaped insert  224  that may fit into a conically shaped hole  226 . When the insert  224  and the hole  226  are seated into each other, the fluid flow  222  may be fully stopped. Various shapes and configurations of valves may be used by those skilled in the art while keeping within the spirit and intent of the present invention. 
     As indicated above, the controller  218  compares the value of the encoder  210  as represented by the encoder signal  228  with the desired profile  220 , as represented by the profile signal  230 , and adjusts the servo-motor  202  so the position of the moving portion  206  of the valve, as received by the encoder  210 , is equal to the value of the desired profile  220 . When the moving portion of the valve  206  is not touching the fixed portion of the valve  208 , fluid flow  222  is dispensed in an amount that corresponds to the desired profile  220 . 
     The servo-motor  202  may be a brushless DC motor or may be any other type of rotary actuator. For example, a rotary stepper solenoid, servo-stepper motor, AC motor, brushless DC motor, or any other type of controllable rotary actuator can be used. In some embodiments, hydraulic or pneumatic rotary actuators may be used. 
       FIG. 6  is a graph of the response  602  of a low profile linear solenoid and the response  604  of a brushless DC servo-motor, showing the change in position in thousandths of an inch versus time in ms. As shown in  FIG. 6 , the position of the device is shown in the vertical axis and the time response is shown in the horizontal axis. The low profile linear solenoid response  602  opens and closes the valve of the dispenser much quicker than the brushless DC servo-motor response  604 . The response of the voice coil actuator  502 , disclosed in more detail with respect to  FIG. 5  below, and voice coil actuator  806 , disclosed in more detail with respect to  FIG. 8  below, is similar to the low profile linear solenoid, but allows the position of the dispensing valve to be very carefully controlled. 
     In the embodiment  200 , the linear encoder  210  is directly connected to the moving portion  206  of the valve. The linear encoder  210  is capable of generating an encoder signal  228  that can be an absolute or relative signal indicating the motion of the moving portion  206 . In some embodiments, limit switches or other sensors may be used in conjunction with the linear encoder  210  as an input to the controller  218 . 
     The mechanism that incorporates the lead screw  204  illustrates how the rotary motion of the servo-motor  202  may be translated into linear motion that is more or less aligned with the axis of the motor  204 . In some embodiments, planetary gears or other speed reducers may be used by those skilled in the art to match the intended speed and other parameters of actuation of the particular embodiment as necessary. 
     The motion profile  220  may be defined in terms of the desired movement over time. For example, the motion profile may define the movement in terms of the desired position, velocity, acceleration, jerk, or other parameter with respect to time. Additionally, the embodiment may be capable of defining movement in terms of the amount of force to be exerted. In some embodiments, it may be desirable for the controller  218  to cause the motor  202  to exert a specified force between the moving portion  206  and the fixed portion  208  of the valve in order to seal the valve. 
     In some embodiments, a linear actuator may be used in place of a rotary actuator and a lead screw. A linear actuator may include a linear motor, moving coil, voice coil (all illustrated in  FIG. 5 ), variable stroke linear solenoid, or any other type of controllable actuator with a linear movement. In such embodiments, the linear actuator may be directly connected to the moving portion  206  of the valve, or may be coupled to the moving portion  206  of the valve through various mechanisms that may include various gears or linkages. 
     In some embodiments, the moving portion of the valve may cause a positive displacement of a chamber that may thereby cause the fluid to be dispensed. For example, the moving portion of the valve may cause the plunger of a syringe or other collapsible cavity to be moved such that fluid is dispensed. 
     In still other embodiments, a second encoder, such as linear direct coupled encoder  704 , that is described in more detail with respect to  FIG. 7 , may be provided on the shaft of the servo-motor  202 . The second encoder may be used to calibrate the servo-motor  202  or to perform other functions associated with controlling the motor. The output signal of the second encoder may be compared to the output signal  228  of the encoder  210  to verify proper functioning of the mechanical linkage that drives the moving portion  206  of the valve. 
       FIG. 3  is a schematic representation of an embodiment  300  of the present invention showing a rack and pinion driven valve. The valve  304  may have a moving portion  306  and a fixed portion  308  that are adapted to fit into each other and prevent any fluid flow. The rack and pinion  310  may cause the moving portion  306  of the valve to translate when the motor  302  rotates. As the moving portion of the valve  306  is moved by the rack and pinion  310 , the position and/or velocity of the moving portion  306  is captured by an encoder  312  mounted to the shaft of the motor  302  and/or an encoder mounted to the moving piece of the valve. The controller  314  compares the input from the encoder  312  with the desired profile  316  to control the motor  302 . 
     The embodiment  300  illustrates a mechanism whereby a rotational motion from the motor  302  may be translated to a linear motion of the moving portion  306  of the valve in a proportional manner. The mechanism further allows the axis of the motor  302  to be perpendicular to axis of the moving portion  306  of the valve. 
     The mechanism for translating rotational motion to linear motion may operate in a fixed ratio of angular motion to linear motion such as the rack and pinion mechanism. In other embodiments, a mechanism may be used to translate rotational motion into linear motion that may not necessarily produce a fixed ratio of movement between the rotary motion and the linear motion. As those skilled in the art will appreciate, such mechanisms may have particular advantages in specific applications. Examples of such mechanisms include a drag link mechanism, a Whitworth mechanism, a crank shaper mechanism, a scotch yoke mechanism, the many variations of the crank and slider mechanism, toggle-type mechanisms, various cam mechanisms, cable and drum mechanisms, belt and pulley mechanisms, a Watts mechanism, an Oldham coupling mechanism, various four bar linkages including the Peaucellier mechanism, and any other desired mechanism. 
     In some embodiments, the mechanism may include a lever, gear, or other speed increasing or decreasing device. For example, if the motor  302  was selected to be a low power motor, the pinion of the rack and pinion  310  may also be selected to be small such that the motor  302  has sufficient power to operate the valve. In such an example, the smaller pinion will cause the speed of the rack to be less and the speed of the embodiment will be sacrificed for the various benefits of a smaller motor. 
     In another example, a lever linkage may be used to increase the speed of movement of the moving portion  306  of the valve. In such a case, proportionally small movements of the motor  302  may cause larger movements of the moving portion  306  of the valve. 
       FIG. 4  is an illustration of an embodiment  400  of the present invention showing the application of a fluid  408  to a work piece  404 . A fluid dispensing apparatus  402  is mounted over a work piece  404  that is mounted on a mandrel  405  (yoke) which is rotated in the direction  410 . Fluid  406  is inserted into to the apparatus  402  that dispenses the fluid  408  in the form of a bead on work piece  404 . A ramp profile section  412  may be formed by the fluid dispensing apparatus  402  in a controlled manner in accordance with the desired profile specified to the controller. 
     The amount of fluid dispensed by the dispensing apparatus is critical in certain applications. As disclosed in U.S. patent application Ser. No. 10/670,176 entitled “Closure Sealant Dispenser,” filed Sep. 23, 2003 by Scott J. Woolley et al., which is based upon U.S. Provisional Application 60/412,988 entitled “Can Sealant Dispenser,” filed Sep. 23, 2002, both of which are specifically incorporated herein by reference for all that they disclose and teach, yokes that hold can lids for dispensing sealants typically have a constant rotational speed. If the rotating yoke has a constant rotational speed, can tops that are not round in shape have a peripheral area (to which the sealant is to be applied) that have a varying linear speed with respect to the dispenser. For example, an essentially rectangular or square can lid, such as may be used for canned meats, has a peripheral area in which the sealant is to be applied, that varies in rotational speed on a constant speed rotational yoke. The varying rotational speed of non-round can lids is the result of the varying radial distance from the center of the yoke. Hence, even if a dispenser is capable of quickly opening and dispensing a constant amount of fluid, the outer rounded corner portions of the can top that have a higher velocity receive less fluid. For this reason, either the speed of the yoke must be varied, or the opening of the dispenser must be controlled, to allow a constant amount of sealant to be dispensed on such non-round tops. Further, the rounded corner portions of such tops may require more sealant to be dispensed in the corners than on the straight portions of the can top to achieve an effective seal. The ability to control the size of the opening of the dispenser allows the user to control the amount of fluid dispensed by the dispenser. Since the amount of fluid dispensed may vary with the acceleration of the periphery of the can top, profiles can be provided for properly dispensing the fluid in the desired amount at various locations along the periphery of such non-round can tops. In addition, the dispensing head or mandrel may be moved in one direction to ensure proper placement of the material, as disclosed in the above identified application entitled “Closure Sealant Dispenser.” 
     The fluid of the embodiment  400  may comprise a sealant that has a thick paste or gel consistency which is otherwise described herein as a fluid. The work piece may be an item such as a can end that requires a sealant prior to assembly. Those skilled in the arts will appreciate that any type of fluid may be dispensed onto any type of work piece while keeping within the spirit and intent of the present invention. 
     As shown in  FIG. 4 , the ramp profile section  412  is created by slowly opening the valve of the fluid dispensing apparatus  402  as the mandrel  405  is rotated. By using the fluid dispensing apparatus  402 , that can be controlled to open at any desired rate, a bead of fluid that tapers from nothing to a full bead of sealant may be created. As also shown in  FIG. 4 , sealant may be continually placed on the work piece  404  until the ramp profile section  412  is underneath the fixedly-mounted fluid dispensing apparatus  402 . At such a point, the fluid dispensing apparatus  402  may slowly taper off the fluid in a profile that closely inversely matches the profile used to create the ramp profile section  412 , so as to create a uniform bead. 
     A benefit of the ramp profile section  412  is that registration on a round top is not required and low tolerances are required with respect to the starting and stopping points of the dispenser. Referring to the example illustrated in  FIG. 4 , the can end may be presented to the dispensing apparatus while the can end is rotated at a high speed. Registration of starting and stopping locations for the sealant with respect to the position of the can end may be very difficult at high speeds. The use of a ramp profile section  412  provides increased throughput of can ends on a sealant machine since a high degree of registration is not necessary, as pointed out above, as a result of the tapered nature of ramp profile section  412 . 
     The embodiment  400  may allow consistent and repeatable amounts of fluid to be dispensed to work pieces. The rate of opening and closing the valve may be varied during the dispensing process, allowing the valve position to be ramped up and down at any desired rate during the dispensing process to change the amount of fluid dispensed. 
       FIG. 5  is a schematic diagram of a voice coil actuator fluid dispenser  500  that moves the moving portion  510  of the valve with respect to the fixed portion  512  of the valve. The voice coil actuator  502  has a cylindrically shaped stationary permanent magnet that creates a stationary magnetic field within the interior of the voice coil housing. A cylindrical shell, that is capable of moving over the cylindrical permanent magnet is attached to a shaft that moves along the axis of the cylindrical magnet. The cylindrical shell has a series of coils that are wrapped around the circumference of the cylindrical shell. Application of current to the coils generates a magnetic field that interacts with the magnetic field of the cylindrical permanent magnet to cause the shell to move in a linear direction along the axis of the cylindrical magnet, thereby causing linear motion of the shaft. The amount of current applied to the coils is proportional to the force created on the shaft, and hence the movement of the shaft. Controller  516  controls the current in the voice coil actuator  502 . The force generated by the voice coil actuator  502  compresses spring  506  against a fixed element  508  of the valve. Spring  506  creates an opposing force to the voice coil  502  that changes in proportion to the amount of the distance moved. By controlling the force from the voice coil actuator  502 , the moving portion of the valve  510  follows the motion profile  504 . Those skilled in the arts will appreciate that any type of displacement resistant device such as a sealed cylinder, bladder, rubber ball, or other devices or materials that use the principle of modulus of elasticity can be used to create the opposing force created by the spring  506 . 
     The voice coil actuator  502  illustrated in  FIG. 5 , and the other actuators illustrated in other embodiments disclosed herein, can comprise a variable force actuator such as, but not by way of limitation, an electrical solenoid, a linear motor, a moving coil or a pressurized cylinder. Further, the encoders disclosed herein may be used to provide closed loop control so as to more precisely regulate the movement of the moving portion of the various valves illustrated herein. 
       FIG. 7  is an illustration of an embodiment of a servo-motor dispenser  700 . As shown in  FIG. 7  a flow control valve  702  is shown which is coupled to the fluid dispenser  703 . A linear direct coupled encoder  704  is coupled to the housing of the flow control valve  702  and directly senses the position of the flow control valve  702 . Lead screw  706  is used to control the position of the flow control valve  702  in response to the rotation of the servo-motor  708 . Rotational shaft encoder  710  also generates an encoder signal indicating the rotational position of the servo-motor shaft. In effect, the linear direct coupled converter  704  provides feedback information as to the actual position of the valve to calibrate and check the performance of the rotational shaft encoder  710 . 
       FIG. 8  illustrates another embodiment of a voice coil actuated dispenser  800 . As shown in  FIG. 8  a dispensing valve  802  is used to dispense the fluid. A linear coupling device  804  is connected to the moving portion of the dispensing value  802 . A voice coil actuator  806 , in turn, is connected to the linear coupling device  804 . Linear encoder  808  generates an electrical signal that is indicative of the position of the moving portion of the dispensing valve  802 . The control system, such as illustrated in  FIG. 1 , can be used with the embodiment illustrated in  FIG. 8 . The voice coil actuator  806  is capable of very quickly and very precisely moving the shaft of the voice coil actuator that is coupled to the linear coupling  804 . Very precise and rapid control of the size of the opening of the dispensing valve  802  can be achieved using the voice coil actuator  806 . 
     The present invention therefore provides a unique system for dispensing fluids in a controlled manner. Flow profiles can be provided to a dispenser to accurately dispense fluid in accordance with a desired profile using a dispenser that has a controlled, variable opening. Positional encoders are used to provide feedback to accurately control the flow of fluid through the dispenser in accordance with the flow profile. Accurate control of the flow profile allows accurate dispensing of fluids in applications such as the dispensing of sealant to can ends which may require different amounts of sealant on different portions of the can end. Further, accurate registration of rapidly rotating can ends is not required as a result of the flow profile that can be provided by the various embodiments of the present invention. 
     The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.