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 anode gel material into a battery can. In high speed battery manufacturing operations, the quantity of anode gel dispensed within the can must be accurately and quickly dispensed in a fraction of a second.

Conventional dispensing pumps typically employ an inlet receiving a supply of liquid (e. g., anode gel), 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 dispensing pump also typically includes a control valve for controlling the flow of the liquid from the inlet to the pump assembly, and from the pump assembly to the outlet nozzle. The pump assembly includes a cylinder in fluid communication with the control valve and a piston (plunger) disposed in the cylinder. The plunger is actuated linearly to control the volume within a cavity in the cylinder in which the liquid is pumped.

One example of a conventional pump assembly is disclosed in U. S. Patent Nos. 4,551, 072 and 4,545, 507, the entire disclosures of which are hereby incorporated herein by reference. The pump assembly disclosed in the aforementioned patents employs a pneumatically operated linear actuator to linearly actuate the plunger between two ends of stroke positions to effect the metering and dispensing of liquid. With the rotary valve in a fill position, the piston is pneumatically forced to a first end position to draw in liquid. With the rotary valve in a dispense position, the piston is then pneumatically forced into its second position by switching pneumatic supply and return lines.

While the conventional dispensing pumps have performed well for certain operations, a number of drawbacks exist for certain types of manufacturing operations, particularly precise high speed dispensing operations. In the conventional pneumatically operated pump assembly, the plunger is pneumatically actuated back and forth and the linear displacement of the plunger is generally controlled by hard stops on each end of the cylinder stroke, which makes it very difficult to control the dynamic movement of the piston. As a result, the pump piston may move at various speeds, since the timing is difficult to control. If the pump piston moves too fast, the liquid material is dispensed too fast which may cause overshoot at the outlet nozzle and makes it difficult to control positioning of the nozzle relative to the receiving can. If the pump piston moves too slow, poor flow of the dispensed liquid may be experienced. The pneumatic pump could short-stroke, thus, dispensing significantly less than a full desired quantity of liquid without ever knowing or detecting short-stroke defect. Also, suckback is impossible to perform with the pneumatic pump.

Accordingly, it is therefore desirable to provide for a liquid dispensing pump that provides for accurate control and timing of the liquid dispensing operation. In particular, it is desirable to provide for a pump assembly that offers controlled time movement of liquid metering and dispensing.

SUMMARY OF THE INVENTION In accordance with the teachings of the present invention, a linear actuated dispensing pump is provided which offers precise high speed and controlled metering and dispensing of liquids. The dispensing pump includes an inlet for receiving a supply of liquid, an outlet for dispensing a metered amount of liquid, and a flow control valve for controlling liquid flow between the inlet and outlet. The pump also has a cavity in communication with the control valve for receiving a metered quantity of liquid, and a plunger disposed within the cavity for controlling the quantity of liquid within the cavity. The pump further has a servo driven linear actuator for actuating the plunger within the cavity. The servo driven linear actuator includes an electric servo motor coupled to a rotational-to-linear converter for converting rotational movement of the motor to linear movement of the plunger.

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 In the drawings: FIG. 1 is a side view of a liquid dispensing pump employing a servo driven linear actuator according to the present invention; FIG. 2 is a vertical sectional view of the pump taken through the linear actuator in a first position; FIG. 3 is a vertical sectional view of the pump taken through the linear actuator in a second position; FIG. 4 is a cross-sectional view taken through lines IV-IV of FIG. 2; and FIG. 5 is a timing diagram illustrating control of the pump and rotary valve in a high speed battery manufacturing operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1-4, a liquid dispensing pump 10 is generally illustrated for repeatedly dispensing a precisely controlled quantity of liquid. The dispensing pump 10 includes an inlet 12 for receiving a supply of liquid 72. The supply of liquid 72 may include a continuous supply of a liquid that is to be dispensed in a controlled quantity via the pump 10. The liquid 72 may include any of a variety of liquids having differing viscosities. In a battery manufacturing system, the liquid 72 may include a high viscosity anode gel or a lower viscosity alkaline electrolyte solution. The dispensing pump 10 also includes an outlet nozzle 18 for dispensing the controlled quantity of liquid. Disposed between the inlet 12 and outlet nozzle 18 is a control valve 14 and a pump assembly 20.

The control valve 14 is a rotary control valve, according to one embodiment, having a cylindrical shaft of a generally cylindrical cross section and a passageway 70 formed therein. The passageway 70 provides a liquid flow path between the inlet 12 and pump assembly 20 when valve 14 is in the fill position (FIG. 2). The passageway 70 also provides a liquid flow path between the pump assembly 20 and outlet nozzle 18 when valve 14 is in the dispense position (FIG. 3). The rotary control valve 14 is actuated via a rotary valve actuator 16. According to one embodiment, the rotary valve actuator 16 may include a pneumatically operated piston having a rack and pinion connection coupling the shaft of the rotary valve 14 to the pneumatically actuated piston, as disclosed in U. S. Patent No. 4,551, 072. According to another embodiment, the rotary valve actuator 16 may include an electric motor for rotating the rotary valve 14 between the fill and dispense positions.

The pump assembly 20 includes a cylinder and piston assembly made up of a cylinder 22 and a linear actuated piston 24 disposed within the inner cavity of cylinder 22. The piston 24 operates as a plunger within cylinder 22 to draw a metered quantity of liquid 72 defined by the volume of the cavity within the interior walls of cylinder 22 when the plunger 24 is linearly moved towards its retracted position. The piston 24 further pushes the liquid out of the cavity when linearly moved to its extended position to dispense the metered amount of liquid 72. Disposed between the inner wall of cylinder 22 and piston 24 are three piston seals 27. The piston 24 has a diameter less than the interior diameter of cylinder 22 and sealingly engages seals 27 such that seals 27 prevent the passage of liquid 72 around piston 24.

The dispensing pump 10 employs a servo driven linear actuator for actuating the plunger 24 within the cavity of cylinder 22 according to the present invention. The servo driven linear actuator includes a servo driven electric motor 60 for rotating its output shaft 56 and a rotary-to-linear converter for converting rotary motion of the motor output shaft 56 to a linear actuation of piston 24. The rotary-to-linear converter as shown and described herein includes a roller screw and sliding nut assembly, according to one embodiment.

The piston 24 is fixedly connected to a rotational driven roller screw 36 via a collet 30.

Collet 30 includes a collar 28 receiving a reduced diameter end 26 of piston 24. The collar 28 is compressed and thus fixed against end 26 of piston 24 via sliding nut 32. The drive screw 36 has helical screw threads 38 formed on the outer surface thereof for threadingly engaging grooves 42 formed within nut 40. Nut 40 is fixedly connected to a supporting slide assembly 34 which, in turn, is connected to collet 30, and therefore is rigidly fixed to piston 24. Nut 40 is further connected to end member 46 for defining one end of travel position. Nut 40 is prevented from rotating and, thus, is driven linearly by screw 36. The roller screw assembly including screw 36 and nut 40 may include a"planetary roller screw"commercially available from INA Corporation or SKE. Nut 40 is prevented from rotating because it is clamped in housing 34 by clamp ring 46. Slide assembly 34 is prevented from rotating and is supported by several linear cross roller bearing assemblies 55. The linear cross roller bearing assemblies 55 are further illustrated in FIG. 4 and allow reduced friction linear movement of slide assembly 34.

The drive screw 36 translates rotary motion thereof to a linear motion of the nut 40 so as to move piston 24 linearly within cylinder 22. The drive screw 36 is rotated by way of the servo driven electric motor 60 having a rotary output shaft 56. The output shaft 56 of motor 60 is coupled to drive screw 36 via a coupler 54. A ball bearing 50 engages the base of drive screw 36. The drive screw 36 and nut 40 assembly is packaged in a self-supporting housing. The cross roller bearing assemblies 55 are used in the slide assembly 34 to prevent rotation of the nut 40 and to guide the piston 24 linearly within the self-supporting housing. Grease fittings 44 and 52 are provided to add lubricant to the assembly.

While the rotary-to-linear converter shown and described herein includes a roller screw 36 and nut 40 assembly, it should be appreciated that other rotary-to-linear converters may be employed. For example, a ball screw or the like can be substituted for the roller screw 36.

Additionally, other types of linear bearings may be employed in place of the cross roller bearing assemblies 55, including the use of guide pins (shafts) and bushings (both plain and ball).

The rotary motor 60 is a servo driven electric motor having the ability to precisely adjust the rotary position of the motor output shaft 56 and, hence, the linear movement of pump 10. The servo driven motor 60 can be continuously adjusted throughout its permitted rotational travel. One example of a servo motor 60 includes Model No. YSM103, commercially available from Giddings and Lewis. The servo motor 60 is shown as a direct current (DC) motor powered by a DC power <BR> <BR> supply 64 (e. g. , 130 volt DC supply). However, it should be appreciated that the motor 60 may be powered via any of DC or alternating current (AC) power supplies. The servo motor 60 includes an encoder 62 for sensing rotational position of the motor 60 and, hence, the motor output shaft 56.

By sensing the rotational position of the servo motor 60, the linear position of the plunger 24 can be determined.

The dispensing pump 10 is controlled by a controller 66 coupled to the servo motor 60 and rotary valve actuator 16. The controller 66 controls both the rotary valve actuator 16 and servo motor 60 to control the metering and dispensing of liquid via pump 10. The controller 66 monitors the sensed motor position signal generated by encoder 62 and processes the position signal as a feedback signal so as to determine the position of the motor and, hence, position of plunger 24.

According to one embodiment, an initial reference position of the plunger 24 may be determined by stalling out the motor 60 at its rearmost or frontmost end of travel positions. According to another embodiment, a sensor 24 may be employed to sense position of the plunger 24 or any other of the linear moving components (e. g. , collet 30), or rotary moving components (e. g. , motor output shaft 56). The sensor 30 may include an optical sensor or other position indicating sensor.

The controller 66 may include a conventional controller having a microprocessor and memory capable of processing algorithms and data to control the servo motor 60 and rotary valve actuator 16. In one embodiment, the controller 66 preferably includes a conventional microprocessor having capabilities of processing algorithms and data as described herein.

Additionally, the controller 66 has memory which 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 motor drive (controller) is Model No.

DSM015, commercially available from Giddings and Lewis. Stored within the memory and accessed/processed by the microprocessor are motor controlled algorithms for controlling the servo motor 60 and rotary valve 16. It should be appreciated that the servo motor 60 may be controlled according to known motor control routines.

In operation, the dispensing pump 10 is precisely controlled to receive and meter a precise quantity of liquid when the rotary valve actuator 16 is in a fill position as shown in FIG. 2. With the rotary valve actuator 16 in the fill position, the servo motor 60 is actuated to linearly move plunger 24 from a first extended position to a second retracted position to draw a quantity of liquid 72 into a cavity defined by the inner walls of cylinder 22. In doing so, the cavity defined by cylinder 22 is filled with a precise quantity of liquid 72.

Once the plunger 24 reaches its second retracted position and the cavity cylinder 22 is filled with liquid 72, the rotary valve actuator 16 is actuated to rotate valve 14 from the fill position to a dispense position as shown in FIG. 3. With valve 14 in the dispense position, inlet 12 is no longer in fluid communication with the cavity of cylinder 22. Instead, the cavity of cylinder 22 is in fluid communication with outlet nozzle 18. With valve 14 in the dispense position, the plunger 24 is actuated linearly from its second retracted position to its first extended position to dispense the liquid 72 from cavity 22 through the outlet nozzle 18. As seen in FIG. 3, the dispensed liquid 72 is dispensed within a container, such as battery can 74.

By employing a servo motor 60 to actuate the pump assembly of dispensing pump 10 according to the present invention, the precise metering and dispensing of liquid can be achieved in a manner that prevents or reduces overshoot and optimizes liquid flow. The use of servo motor 60 also provides continuous feedback as to piston location so short strokes are detected. Short strokes can be caused by something preventing the piston from fully completing the desired move, for example, a plugged nozzle. The servo motor 60 can further detect a piston move exceeding the profile limits (following error). The pump 10 of the present invention is particularly advantageous for use in high speed manufacturing operations where a precisely metered quantity of liquid is to be quickly dispensed repeatedly. The dispensing pump 10 is well suited for use in a high speed battery manufacturing system such as disclosed in U. S. Patent No. 6,325, 198, entitled"HIGH SPEED MANUFACTURING SYSTEM. " One example of the metering and dispensing of precise quantities of liquid achieved with the dispensing pump 10 of the present invention in accordance with a high speed battery manufacturing system is illustrated in FIG. 5. In the example shown, the battery manufacturing system performs process operations on individual articles of manufacture (batteries) in accordance with a dwell (idle) and index (moving) states. In such a system, articles of manufacture are indexed to process modules, some of which include a dispensing pump 10 to quickly dispense a precise quantity of liquid into a can during a dwell state. The indexer curve 102 shows the indexing of the manufacturing system in which articles of manufacture are in a dwell or index state.

In the example shown, a battery can is lifted onto a process module as shown by curve 104.

Once the can is substantially in the upper position, the dispensing pump 10 dispenses liquid as seen by curve 106, such as anode gel material, into the can while the can is lowered as seen by curve 104 so as to maintain a desired anode fill height. It should be appreciated that the rotary valve is switched from the fill position to the dispense position shortly before the dispensing pump 10 performs a liquid dispense operation as seen by curve 108. At the end of the dispensing cycle, the pump plunger is slightly moved back (retracted) from its first extended position so as to suck back liquid at the outermost end of the dispensing nozzle. The rotary valve is then actuated to its fill position. Once in the fill position, the linear plunger is moved to its second retracted position to draw in the next metered amount of liquid. The cycle of dispensing and filling a precise material quantity liquid is repeated at a rate sufficient to match the speed of the manufacturing system.

The dispensing pump 10 precisely controls the quantity of liquid dispensed to provide enhanced liquid dispensing operations which are particularly useful in high speed manufacturing systems. The use of the servo drive motor 60 with the dispensing pump 100 advantageously provides enhanced precise liquid dispensing, reduces maintenance cost, is available in a compact design, and allows for more precise liquid dispensing control. It should further be appreciated that the servo unit of the dispensing pump 10 can be installed as a replacement (or retrofit) to a pneumatic pump without any substantial physical changes.

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.