Abstract:
A linear and rotary actuated liquid dispensing pump is provided which offers precise high speed dispensing of liquids and easy volume adjustability. The dispensing pump includes an inlet for receiving a supply of liquid, an outlet for dispensing a metered amount of liquid, and a cavity in communication with the inlet and outlet. The pump has a plunger disposed within a cavity for controlling the amount of liquid within the cavity. The pump also has a rotary actuator for rotating the plunger, and a linear actuator for actuating the plunger linearly within the cavity to control the fill and dispensing of liquid. A controller controls the linear and rotary actuators and allows operation input to adjust variables.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/543077, filed Feb. 09, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention generally relates to pumps for dispensing a controlled quantity of liquid, and more particularly relates to a dispensing pump having a rotary and linear actuated pump/assembly for metering and dispensing a precise quantity of liquid.  
         [0003]     Liquid dispensing pumps are commonly employed in various applications to precisely dispense a measured (metered) quantity of a liquid. In electrochemical cell (battery) manufacturing operations, liquid dispensing pumps are employed to dispense a metered quantity of liquid, such as alkaline electrolyte solution containing potassium hydroxide (KOH), into a battery can. In high speed battery manufacturing operations, the quantity of alkaline electrolyte solution dispensed within the battery can must be accurately and quickly dispensed in a fraction of a second.  
         [0004]     Conventional liquid dispensing pumps typically employ an inlet receiving a supply of liquid, a pump assembly for pumping a metered quantity of the liquid, and an outlet nozzle through which the metered quantity of liquid is dispensed. The pump assembly generally includes a hollow cylinder in fluid communication with the inlet and outlet nozzle and a piston (plunger) disposed in the hollow cylinder. The plunger is actuated linearly to control the fill volume within a cavity in the cylinder into which a quantity of the liquid is drawn in and then evacuated.  
         [0005]     Some conventional liquid dispensing pumps employ a single motor to drive the plunger linearly and also to rotate the plunger valving to control the flow of liquid drawn in at the inlet and dispensed via the outlet nozzle. One example of such a pump employs an electric stepper motor driving a pump housing having a plunger, a base supporting the pump module, and a displacement adjustment mechanism that is used to change the volume of liquid dispensed via the pump. The linear motion for the plunger stroke and rotary motion for the valving is achieved by using a complex compound joint/coupling. The displacement adjustment mechanism changes the pumping volume by changing the angle of the pump housing with respect to the motor. With the motor oriented at a horizontal angle with respect to the pump housing, the pump does not dispense any liquid. The volume dispensed with the pump increases with an increase in angle between the motor and pump housing from the horizontal position. With the pump housing rotated at an angle relative to the motor, a helix motion is created which causes the piston to stroke forward and backward and to rotate, simultaneously. Thus, a single motor is able to achieve both linear and rotary motion of the plunger.  
         [0006]     The assembly employed in the aforementioned pump to effect the volume change generally causes fine adjustments to be time consuming and tedious because of the lack of precision in the adjustment mechanism. As a consequence, it is difficult to make fine volume adjustments to the pump. Additionally, adjustments of the pump to change the pumping volume are particularly difficult when the pump is mounted in confined areas where it is difficult to access the pump to adjust the displacement adjustment mechanism. The difficulties experienced with adjusting such a pump assembly can be time consuming which results in significant down time of the dispensing pump and any other associated equipment.  
         [0007]     Accordingly, it is therefore desirable to provide for a liquid dispensing pump that provides for accurate control and easy adjustment of the metered amount of liquid to be dispensed. In particular, it is desirable to provide for a liquid dispensing pump that may be quickly adjusted to control the quantity of liquid dispensed in a high speed manufacturing operation.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with the teachings of the present invention, a linear and rotary actuated pump is provided which offers precise high speed dispensing of liquids and easy adjustment of the pumping volume. The dispensing pump includes an inlet for receiving a supply of liquid, an outlet for dispensing a metered amount of liquid, and a cavity in communication with the inlet and outlet. The pump has a plunger disposed within a cavity for controlling the amount of liquid within the cavity. A rotary actuator is included for rotating the plunger. A linear actuator is included for actuating the plunger linearly within the cavity to control fill and dispensing of liquid.  
         [0009]     According to one embodiment, the linear actuator is a linear servo motor, and the rotary actuator is a rotary servo motor, both of which are controlled by a controller. The liquid dispensing pump of the present invention advantageously can be easily adjusted to dispense a selected volume of liquid by electronically programming the controller. The rotary and linear actuation of the plunger can be independently adjusted, and may be adjusted on the fly, thereby avoiding significant down time.  
         [0010]     These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     In the drawings:  
         [0012]      FIG. 1  is a perspective view of a liquid dispensing pump employing linear and rotary actuators according to the present invention;  
         [0013]      FIG. 2  is a perspective view of the pump in a refill position and illustrating the pump assembly in a partial cut-away view;  
         [0014]      FIG. 3  is a perspective view of the pump in an intermediate discharge position and illustrating the pump assembly shown in cut-away view;  
         [0015]      FIG. 4  is a perspective view of the pump in a full stroke position and illustrating the pump assembly in partial cut-away view;  
         [0016]      FIG. 5  is a cross-sectional view of the pump assembly taken through lines V-V of  FIG. 2 ;  
         [0017]      FIG. 6  is a cross-sectional view of the pump assembly taken through lines VI-VI of  FIG. 3 ;  
         [0018]      FIG. 7  is a cross-sectional view of the pump assembly taken through lines VII-VII of  FIG. 4 ; and  
         [0019]      FIG. 8  is a cam table diagram illustrating control of the rotary and linear actuation of the pump assembly.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]     Referring to  FIGS. 1-4 , a linear and rotary actuated liquid dispensing pump  10  is generally illustrated for cyclically (repeatedly) dispensing a precisely controlled quantity of liquid. The dispensing pump  10  includes an underlying base platform  12  supporting the general assembly of the pump  10 . Supported on platform  12  is an I-beam support member  14  which further supports a pump control assembly  34 . Dispensing pump  10  includes an inlet  16  for receiving a supply of liquid, and an outlet nozzle  18  for dispensing the controlled quantity of liquid. The pump control assembly  34  is disposed between the inlet  16  and the outlet nozzle  18 .  
         [0021]     The supply of liquid may include a substantially continuous supply of liquid that is to be repeatedly dispensed in periodic cycles in a controlled quantity via the dispensing pump  10 . The supply of liquid may include any of a variety of liquids having differing viscosities. In an alkaline battery manufacturing system, the liquid may include a low viscosity alkaline electrolyte solution containing potassium hydroxide (KOH). Alternately, the supply of liquid dispensed in a battery manufacturing system may include a higher viscosity liquid, such as anode gel. The dispensing pump  10  may be employed to dispense any of a variety of liquids.  
         [0022]     As seen in  FIGS. 2-7 , the pump control assembly  34  includes a plunger (piston)  36  of a generally cylindrical cross-section disposed within a hollow cylinder  28 . The hollow cylinder  28  has a closed end and defines a cavity substantially closed at one end by the plunger  36  and exposed to inlet  16  and outlet nozzle  18 . The plunger  36  is both rotated and moved linearly within cylinder  28 . The plunger  36  has a passageway  38  formed therein which provides a liquid fill volume and provide a liquid flow path between one of the inlet  16  and outlet nozzle  18 , depending on the rotational and linear position of the plunger  36 . The passageway  38  defines a full volume for receiving liquid  40  from the inlet  16  when the plunger  36  is in the refill position. When the plunger  36  is in a dispense position, the passageway  38  is in fluid communication with outlet nozzle  18  to allow the metered quantity of liquid  40  to be dispensed through outlet nozzle  18 .  
         [0023]     The liquid dispensing pump  10  employs a rotary actuator  30  in the form of a rotary servo motor, and also employs a linear actuator  20  in the form of a linear servo motor, according to the embodiment shown and described herein. The linear servo motor  20  is disposed on top of the base platform  12 . The rotary servo motor  30  is mounted on an L-shaped motor support member  26  on top of the linear servo motor  20 . Accordingly, linear actuation of the linear servo motor  20  likewise causes linear actuation of the rotary servo motor  30 .  
         [0024]     The rotary servo motor  30  has an output shaft  32  connected to the plunger  36 . Accordingly, rotation of the rotary servo motor  30  causes rotation of plunger  36  within cylinder  28 . In the embodiment shown and described herein, the rotary servo motor  20  continuously rotates plunger  36  at a substantially constant angular speed. However, speed of the rotary motor  30  may be controlled to vary the speed or turn off the motor  30 . The rotary servo motor  30  and/or its output shaft  32  may include an angular position sensor, such as an encoder, for monitoring the angular position of the output shaft  32 . Additionally, a linear position sensor may be employed to monitor the linear positioning of the output shaft  32  and corresponding plunger  36 .  
         [0025]     The rotary servo motor  30  may include a 60 mm frame brushless rotary servo motor employing a digital servo driver, such as a ServoStar CD Sercos Digital Servo Drive, commercially available from Kollmorgen. It should be appreciated that any of a number of rotary motors, both AC and DC, may be employed to rotate the plunger  36 .  
         [0026]     The linear servo motor  20  is shown as a continuous iron-core linear servo motor having a linearly actuated platform  22  mounted over a pair of magnets  24 . Platform  22  is forcibly actuated relative to magnets  24  to cause linear actuation of platform  22 . The linear servo motor  20  further includes a digital servo drive, such as a Servo Star CD Sercos Digital Servo Drive, commercially available from Kollmorgen. It should be appreciated that the linear motor  20  may be precisely adjusted to achieve a desired linear movement, according to an electronic cam table as described herein.  
         [0027]     Referring back to  FIG. 1 , the liquid dispensing pump  10  further includes a controller  50  for controlling actuation of the rotary servo motor  30  and linear servo motor  20 . The controller  50  may include a multi-axis motion controller. In the embodiment shown, the controller  50  has a microprocessor  52  and memory  54  capable of processing algorithms and data to control the rotary and linear servo motors  30  and  20 , respectively. The microprocessor  52  has sufficient capabilities to process algorithms and data as described herein. The memory  54  may include read-only memory (ROM), random access memory (RAM), flash memory, and other commercially available volatile and non-volatile memory devices. One example of a commercially available controller may include the ServoStar MC multi-axis motion controller, commercially available from Kollmorgen. Stored within memory  54  is an electronic cam table  56  for controlling the operation of the rotary and linear servo motors  30  and  20 , respectively, to effect rotating and linear motion of plunger  36  as shown in  FIG. 8  and described herein.  
         [0028]     The liquid dispensing pump  10  is operated such that the rotary servo motor  30  cyclically rotates plunger  36  into various positions through each complete  360  degrees of rotation, while linear servo motor  20  moves the plunger  36  forward and backward to cause liquid received in the inlet  16  to be drawn in during the refill motion, and discharged through outlet nozzle  18  during the discharge motion. In doing so, the plunger  36  is oriented within the passageway  38  in liquid communication with inlet  16  as shown in  FIGS. 2 and 5  when the plunger  36  is in a refill position. In this position, liquid is allowed to enter through inlet  16  into the fill volume between the plunger  36  and interior of hollow cylinder  38 . During the refill motion, the linear servo motor actuator  20  retracts the plunger  36  from within cylinder  28  so as to draw a quantity of liquid into the fill volume defined between the plunger  36  and inner walls of cylinder  28 .  
         [0029]     With the pump completely refilled at the rearmost position of plunger  36 , the linear actuator  20  reverses direction to force the liquid contained within the fill volume between plunger  36  and cylinder  38  out through outlet nozzle  18  once the plunger  36  is sufficiently rotated so that the liquid in the fill volume is in liquid communication with outlet nozzle  18 , as shown in  FIGS. 3 and 6 . In this position, the metered quantity of liquid is dispensed through the outlet nozzle  18  as shown.  
         [0030]     Following the dispensing of liquid through outlet nozzle  18 , the linear servo motor  20  and plunger  36  continue to rotate to the point where the plunger  36  reaches the full stroke position as shown in  FIGS. 4 and 7 . In this position, the outlet nozzle  18  is no longer in fluid communication with the fill volume and the pump  10  is ready to repeat the cycle of refilling and discharging liquid in a precise quantity.  
         [0031]     The controller  50  is able to control actuation of the rotary servo motor  30  and linear servo motor  20  according to a cam table  56  which is further illustrated in  FIG. 8 . As shown in the cam table  56 , the rotary servo motor  30  repeatedly rotates through a complete revolution of 0° to 360°. During one complete revolution of plunger  36 , the linear servo motor  30  is controlled by controller  50  as shown. From 0° to 10° of rotation of the rotary servo motor  30 , the linear servo motor  20  remains in a dwell position of no movement. From 10° to 180° of rotation of the rotary servo motor  30 , the linear servo motor  20  moves from its fully charged position to the fully displaced position which dispenses the liquid. With the rotary servo motor  30  at 180°, the linear servo motor  20  reverses direction and retracts itself to its fully recharged position X C  at which time the rotary servo motor  30  is at 360°. The cam table  56  is then repeatedly processed by controller  50  to provide the next fill and dispensing cycles.  
         [0032]     It should be appreciated that the position of the linear servo motor  20  may be adjusted by simply entering in a new fully charged position X C  into controller  50  via the human machine interface (HMI)  58 , which may include a personal computer, according to one embodiment. Thus, in order to change the amount of liquid dispensed with pump  10 , a new fully charged position X C  is simply entered via HMI  58  into the controller  50 . Additionally, the linear servo motor  20  may likewise be adjusted electronically, by inputting into controller  50  via HMI  58  a servo linear motor speed value. Additionally, linear servo motor  20  can be controlled to provide a periodic dwell (off) state.  
         [0033]     While a linear servo motor  20  is shown and described herein for linearly moving the plunger  36  in connection with dispensing pump  10 , it should be appreciated that other linear and rotary actuators may be employed. For example, a rotary motor coupled to a rotary-to-linear converter (e.g., roller screw and sliding nut assembly) may be employed in place of the linear servo motor  20  to linearly actuate plunger  36 . Similarly, an alternative actuator may be employed in place of the rotary servo motor  30 .  
         [0034]     The dispensing pump  10  of the present invention is able to precisely meter and dispense a quantity of liquid to provide enhanced liquid dispensing operation. The dispensing pump is easily adjustable to set the quantity of liquid to dispense, which is particularly useful in high speed manufacturing systems. For example, the dispensing pump  10  may be employed in a high speed battery manufacturing system such as disclosed in U.S. Pat. No. 6,325,198, entitled “HIGH SPEED MANUFACTURING SYSTEM.” The dispensing pump  10  may easily be adjusted to set new setpoints for each of the rotary and linear actuators  30  and  20 , respectively, as described herein.  
         [0035]     It will be understood by those who practice the invention and those skilled in the art, that various modifications and improvements may be made to the invention without departing from the spirit of the disclosed concept. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.