US20080257912A1

US20080257912A1 - Plug and play fluid dispensing technology

Info

Publication number: US20080257912A1
Application number: US12/082,415
Authority: US
Inventors: David T. Bach; Hui Dong
Original assignee: Scientific Products and Systems Inc
Current assignee: Scientific Products and Systems Inc
Priority date: 2007-04-17
Filing date: 2008-04-10
Publication date: 2008-10-23

Abstract

A plug and play system of fluid dispensing and auxiliary modules that use motors with integrated drivers, controllers and the capability of using an internal or external encoder where any one of several modules can be substituted into a base dispensing unit. In the case of positive displacement piston drives, a first motor can be used for the rotary valve operations and a second motor used to position the pump piston. The piston can be very accurately positioned by the second motor that can use an external linear coding system electrically coupled to the motor controller. The invention allows coordination between the two motors of a positive displacement piston system, as well as being able to work with several pump systems linked together in a liquid filling application or other application. The use of a motor system with a common user interface for different types of pump drives allows for “plug and play” capability for liquid filling and other applications. The easy changing of pump drives is often necessary because applications that use positive piston pump dispensing may need to be replaced with peristaltic or rolling diaphragm pumps if the product being dispensed is shear sensitive. The present invention allows changes of pumps with minimal difficulty.

Description

This application is related to and claims priority to U.S. Provisional patent application No. 60/923,768 filed Apr. 14, 2007. Application No. 60/923,768 is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention
The present invention relates generally to the field of precision fluid dispensing technology and more particularly to a precision pump drive suitable for working with piston positive displacement, rolling diaphragm and peristaltic pumps.
2. Description of the Prior Art
Precision fluid dispensing pumps are known in the art. U.S. Pat. No. 6,739,478 provides a disclosure of such a system. Bach et al. in that patent describe the use of stepper motors with piston positive displacement pumps to dispense micro and nano quantities of liquids. Many other types of pumps are in common use for dispensing fluids, usually in larger quantities, including rolling diaphragm and peristaltic pumps.
Motors using encoders for achieving positional accuracy are also used in numerous applications. Micro and nano stepper motors used with encoders are well known in the art. However, they generally may not be positionally accurate enough for the many different types of micro and nano quantity fluid dispensing desired. Also, when used with pumps that are less positionally accurate than piston pumps such as rotating diaphragm and peristaltic pumps, the situation becomes worse. It would be tremendously advantageous to have a pump drive system that used interpolation between motor steps to achieve high final positional accuracy as well as the ability to substitute (plug and play) different pumps and different types of pumps.
Earlier versions of the technology such as that described in U.S. Pat. No. 6,739,478 called for multiple port dual diameter piston pumps. Stepper motors were used that had electronics that could switch between resolutions. This resolution switching allowed speed of movement along with increase accuracy. Generally a linear optical encoder was used to accurately measure linear displacement. This technology could only be used with a linear piston pump. Early stepper rates ran between 15 and 18,000 stepper pulses per second. This type of speed limitation caused running of a relatively low stepper resolution of 1000 steps per revolution. Lines along the linear encoder were generally counted by an electronic counter circuit. Once the counter indicated that the piston was close to its final position, it would generate a signal that caused the motor to switch resolution to around 10,000 pulses per revolution, and then single step to the final encoder line. It would be advantageous to have a system that could make use of the much higher pulsing speeds known in the stepper motor art and that also could dispense with the need for a linear encoder in some applications.

SUMMARY OF THE INVENTION

Stepper motor driven fluid pumps have a unique advantage over pumps driven with other motor types like servo motors in that they can be used in micro- or nano-stepping modes. A micro-stepping motor combined with an encoder can provide extremely accurate positioning of the pump moving mechanism if electronics or software can be used to interpolate motor steps and set positions between encoder increments. This accurate positioning can be used or operating many different types of pumps. The present invention relates to a vary accurate stepper motor system that can be used to drive linear piston positive displacement pumps, rotating diaphragm pumps and peristaltic pumps. This system can make use of the very high stepping rates currently available in stepper motors, especially micro- and nano-stepping so that interpolated positions between encoder lines can be achieved.
The present invention uses motors with an integrated driver, controller and the capability of using an internal or external encoder to create a series of mechanical modules that can be used in a “plug and play” mode, where any one of several modules can be substituted into a base dispensing unit. In the case of positive displacement piston drives, a first motor can be used for the rotary valve operations and a second motor used to position the pump piston. The piston can be very accurately positioned by the second motor that can use an external linear coding system electrically coupled to the motor controller.
The present invention allows coordination between the two motors of a positive displacement piston system, as well as being able to work with several pump systems linked together in a liquid filling application or other application. The use of a motor system with a common user interface for different types of pump drives allows for “plug and play” capability for liquid filling applications. The easy changing of pump drives is often necessary because applications that use positive piston pump dispensing may need to be replaced with peristaltic or rolling diaphragm pumps if the product being dispensed is shear sensitive. The present invention allows changes of pumps with minimal difficulty.

DESCRIPTION OF THE FIGURES

Attention is directed to several illustrations that relate to features of the present invention:

FIG. 1 shows a block diagram of an embodiment of the present invention used with a positive displacement piston pump.

FIG. 2 shows a plug and play diving needle module.

FIG. 3 shows a plug and play screw capper module.

FIG. 4 shows a pick and place module.

FIGS. 5A-5B show an indexer module.

FIG. 6 shows a vertical pump drive module.

FIGS. 7 shows a peristaltic pump module.

FIG. 8 shows a block diagram of a multiple pump control, plug and play, system using a human interface (HMI) and programmable logic controllers (PLCs) to handle multiple pump stations.

Several drawings and illustrations have been presented to aid in understanding the present invention. The scope of the present invention is not limited to what is shown in the figures.

DESCRIPTION OF THE INVENTION

The present invention relates to advanced precision fluid dispensing systems using stepper motors with micro- and nano-stepping capability. Stepper motors can be used to both control pump piston or mechanism positions but also to control valve positioning. The use of micro-steppers allows accurate positioning between encoder lines. Motors with micro-stepping resolutions up to 51,200 steps per revolution can be used. When a 2048 line linear encoder is also used, the motor has 25 micro-steps between each encoder line.
Turning to FIG. 1, a system using two stepper motors to create a precision fluid dispensing system using a positive displacement piston pump is shown. The stepper motors used can be similar to the family of motors manufactured by Intelligent Motion System (IMS) of Marlborugh Conn. In particular, the NEMA 23 and NEMA 34 motors are preferred; however, any stepper motor is within the scope of the present invention.
FIG. 1 shows an embodiment of the present invention using two IMS NEMA motors, one with an internal encoder, and one external encoder. The internal encoder uses 110 V AC power, while the external linear encoder uses 24-72 volt DC power. The choice of power is totally up to the designer and may be changed based on the application. Any powering is within the scope of the present invention. A linear encoder like a Renishaw encoder known in the art manufactured by Renishaw of Gloucestershire, UK can be used to accurately measure linear piston displacement. Any linear encoder is within the scope of the present invention. The IMS motor can be connected to use the linear quadrature encoding with the linear encoder. External encoder data can be fed to the controller in the motor for direct processing. One of the advantages of IMS motors is that they can have built-in controllers that can be programmed from a computer using a communication link from a computer like RS-422 or other communications or network link. Once a motor controller is programmed, the programming remains, and a simple trigger signal can start the motor.
The system shown in FIG. 1 includes a linear positive displacement pump 4 on a base 7 and frame 1, and uses two different stepper motors, a first motor 2 to move the piston and a second motor 3 to rotate the rotary valves. The rotary valve motor 3 can include an internal encoder with a pulse for home position that is used to position a rotary valve to the correct position for single or multiple port pumps. The motor that provides linear motion 2 uses an external linear encoder 5. A typical design uses a 512 line encoder which represents 2048 linear positions in one revolution of the motor 2 when quadrature encoding is used. The micro-stepper motors and their associated electronics can be used for interpolated positions between encoder lines. This approach reduces costs since very high line count encoders are not required. The piston 4 in FIG. 1 is very accurately positioned with the first motor 2 that uses the external encoding system electrically coupled to the motor controller on the motor. In FIG. 1, a linear encoder like a Renishaw optical encoder can be used to feed back line position to a high speed counter located in the motor 2. When the count represents a position near the required final count position, the motor then operates in single step mode where each step is compared to an encoder line count plus any interpolated offset from the line.
It is necessary to coordinate the control of the two motors in the system of FIG. 1 as well as possibly work with several such pump systems linked together in a typical liquid filling application. As previously described, the IMS motors can be programmed by an RS422 link, and then once programmed, they are set into motion by sending a trigger signal into an I/O port 9 located on one of the motors. Motors can be daisy-chained for communications using RS-485 ports 8. Each motor can then coordinate its motion requirement with the other motor. The program for each of the motors can contain a minimal variable string of data defining the motor speed, acceleration, drip retention, and filling volume. This can be accomplished by using a personal computer, RS232 or RS422 converters and a computer program to generate the variable string. Any appropriate application software can be used. A preferred software is visual basic; however, any software system can be used.
FIGS. 2-7 show various plug and play modules that use the concepts of the present invention. FIG. 2 shows a diving needle assemble with a needle 10. A motor 11 is used to drive the needle, while an optional second motor 24 can rotate the assembly. FIG. 3 shows a screw capper module with a screw capper torque unit 12 with its own motor and a control motor 13 at the base. FIG. 4 shows a pick and place module with a rotary 14 and linear 15 motor. FIGS. 5A-5B show an indexer module with a single motor 16. FIG. 6 shows a vertical pump drive with a drive motor 25 and driven bar 26. FIG. 7 shows a peristaltic pump module. In FIG. 7, the pump 17 can be directly driven by the motor 18. The entire assembly can be mounted as a single unit 19. Communications ports 27 which can be RS-485 or RS-232 can appear on the top of the motor 18.
FIG. 8 shows a control system that uses a set of programmable logic controllers (PLCs) 21 and a human machine interface (HMI) 20 to allow control of several different pump modules 22 of different types. At least several linear pumps, several peristaltic pumps and at least one rotating diaphragm pump is shown. As before, each pump motor contains an integral motor controller for that motor. As previously stated, each motor controller contains its own software string that can set its speed, acceleration profile, drip retention and filling volume. Each module 22 can contain any of the plug and play modules previously described to perform a specific function.
The HMI 20 coupled to one or more PLCs 21 can allow coordination of the variable strings for different motors in the system as well as provide interfacing with other machines. The HMI and PLC can control the pump environment. A particular HMI can be achieved using a touch screen such as the Panasonic GT11 operating into a PLC such as the Panasonic FPX-CR14. This design has great flexibility and offers accurate smooth fluid dispensing. Numerous micro- or nano-stepper motors operating various pumps, valves or other functions can be easily incorporated. Expansion is very simple using the plug and play concept presented.
FIG. 8 shows a typical way in which various pumps can be configured to work with a common HMI 20. Each of the motors can be configured with built-in drivers and controllers with the rotary motion motors also having built-in encoders. The motors controlling linear motion each have the capability of using a linear optical encoder as an external sensor. Each of the pump drives 22 typically has a 48 volt, +5 volt and +/−12 volt power supply.
In FIG. 8, multiple drivers can be controlled in the system. One or more PLCs 21 can be used to control more than one pump drive 22 (no matter what type of pump drive, a positive displacement piston pump, a rotating diaphragm pump, a peristaltic pump or any other type of pump). The number of pump drives that can be controlled by a single PLC depends on how many I/O ports the PLC has. If the number of pump drives desired is beyond the number of I/O ports on the PLC, more PLCs can be added, or a larger PLC can be used, since PLCs come in many different sizes and capabilities. Communication among the PLCs 21 can be realized using RS232 or RS485 links (or any other type of communication or network link). Other external devices 23 like nozzles can also be plugged into the system in a similar way. In this way, the system can be expanded and integrated in a very efficient and economical way. The system can be can be configured where the RS232 or RS485 communication link connects to each unit, where each unit has a network address. That way, a single PLC can control many units.
The present invention relates to a plug and play system using micro- or nano-stepping motors to control various types of fluid dispensing pumps such as linear positive displacement piston pumps, rotating diaphragm pumps, peristaltic pumps and other pump types. The stepper motors generally have built-in integrated controllers that can be programmed. Typical micro-stepping resolution can be 51,200 steps per revolution. A linear encoder with 2048 lines can be used to provide 25 micro-steps between lines. Any other stepping resolution or encoder resolution is within the scope of the present invention. In general, the controller can calculate the number of lines needed for correct positioning, and also determine the number of steps between lines that need to be added to the move. Interpolation allows accurate positioning between encoder lines. The next move can start with the remaining interpolated steps and from that compute a new position for the next move. Typically stepping speeds can be as high as 5,000,000 steps per second. In cases where a high revolution per minute will exceed the pulse speeds, then a switching of resolution can be used to complete the move with single stepping to the final position. The use of high resolution makes ramp-slew-ramp velocity profiles very smooth with results as good as the earlier used Gaussian profiles.
Several descriptions and illustrations have been presented to aid in understanding the present invention. One of skill in the art will understand that numerous changes and variations can be made without deviating from the spirit of the invention. Each of these changes and variations is within the scope of the present invention.

Claims

1. A plug and play system of precision fluid dispensing modules comprising, in combination:

a plurality of modules, each module having a common electrical interface with each module including at least one stepper motor, said stepper motor having an internal programmed controller with said controller coupled to either an external or internal position encoder, said controller capable of being programmed to interpolate between encoder steps to allow said module to provide precision linear or rotary mechanical motion.

2. The plug and play system of claim 1 wherein each of said modules contains two stepper motors, a first stepper motor providing linear motion and a second stepper motor providing rotary motion.

3. The plug and play system of claim 2 wherein said first stepper motor drives a positive displacement piston pump.

4. The plug and play system of claim 2 wherein said second stepper motor provides rotation to select valves on a positive displacement piston pump.

5. The plug and play system of claim 1 wherein said module contains a peristaltic pump.

6. The plug and play system of claim 1 wherein said module contains a pump selected from the group consisting of positive displacement piston pump, rotating diaphragm pump and peristaltic pump.

7. The plug and play system of claim 1 further comprising a programmable logic controller (PLC) to at least command motion of said stepper motor.

8. The plug and play system of claim 7 further comprising a human machine interface (HMI) in communication with said PLC.

9. The plug and play system of claim 1 wherein said module drives one of a diving needle, screw capper, pick and place, indexer, vertical pump drive or peristaltic pump.

10. A plug and play precision fluid dispensing system comprising a plurality of modules each having a common electrical interface with each of said modules containing at least two stepper motors, a first stepper motor for providing linear motion and a second stepper motor for providing rotary motion, each of said first and second stepper motors containing an internal programmable controller, wherein said first stepper motor is connected to an external linear encoder and said second stepper motor has an internal rotary encoder, said internal controller of said first stepper motor being programmed to interpolate between steps of said external linear encoder.

11. The plug and play precision fluid dispensing system of claim 10 wherein said common electrical interface includes an RS-485 interface.

12. The plug and play precision fluid dispensing system of claim 10 wherein said first stepper motor drives a positive displacement pump.

13. The plug and play precision fluid dispensing system of claim 10 wherein said second stepper motor provides rotary motion to valves of a positive displacement pump.

14. The plug and play precision fluid dispensing system of claim 10 wherein said second stepper motor drives peristaltic pump.

15. The plug and play precision fluid dispensing system of claim 10 wherein said motor controllers are programmed by an RS-232 interface.

16. A plug and play system for precision fluid dispensing comprising:

a plurality of electrically interchangeable modules, each containing at least one stepper motor, said stepper motor having an internal controller and either an internal or an external encoder, wherein said controller can be programmed to interpolate between steps of said encoder;

a programmable logic controller (PLC) in communication with at least one of said modules;

a human machine interface (HMI) in communication with said PLC;

wherein each of said internal controllers is separately programmed, and wherein each of said internal controllers is commanded by the PLC. and wherein total system control and coordination is reported to said HMI.

17. The plug and play system for precision fluid dispensing of claim 16 wherein at least one of said modules drives a positive displacement piston pump.

18. The plug and play system for precision fluid dispensing of claim 16 wherein at least one of said modules drives a peristaltic pump.

19. The plug and play system for precision fluid dispensing of claim 16 wherein at least one of said modules drives a pump chosen from the group consisting of a positive displacement piston pump, a rotating diaphragm pump and a peristaltic pump.

20. The plug and play system for precision fluid dispensing of claim 16 wherein at least one of said modules has two stepper motors, a first stepper motor providing linear motion and using an external linear encoder and a second stepper motor providing rotary motion and using an internal rotary encoder.