Plug and play fluid dispensing technology
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.
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.
BACKGROUND1. 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 INVENTIONStepper 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.
Attention is directed to several illustrations that relate to features of the present invention:
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 INVENTIONThe 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
The system shown in
It is necessary to coordinate the control of the two motors in the system of
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.
In
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.
Type: Application
Filed: Apr 10, 2008
Publication Date: Oct 23, 2008
Inventors: David T. Bach (Bear, DE), Hui Dong (Columbia, MD)
Application Number: 12/082,415