US20160017880A1

US20160017880A1 - Four roller peristaltic pump

Info

Publication number: US20160017880A1
Application number: US14/799,976
Authority: US
Inventors: Stephen B. Maguire
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-07-17
Filing date: 2015-07-15
Publication date: 2016-01-21

Abstract

A peristaltic pump for supplying liquid color to a process machine, comprising a stepper motor including an output shaft, a drive roller mounted on the output shaft, and a collection of planetary rollers positioned about and frictionally contacting driven by the output shaft, for sequentially compressing a flexible tube carrying the liquid color thereby dispensing liquid color from the tube.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This patent application claims the benefit of the priority of U.S. provisional application Ser. No. 62/025,542 entitled “Four Roller Peristaltic Pump” filed 17 Jul. 2014 in the name of Stephen B. Maguire. The priority of the '542 application is claimed under 35 USC 119 and 35 USC 120.

DESCRIPTION OF THE PRIOR ART

Known peristaltic pumps for pumping liquid color for use by a plastic processing machine, namely a molding press or an extruder, require input of a numerical setting, determined by a mathematical formula that uses three variables, namely:

- 1. The “shot” weight in grams, or extrusion rate, typically expressed as pounds per hour output by the process machine to which the legal color is to be furnished;
- 2. The percentage, by weight, of legal color to be added to each “shot”; and
- 3. The bulk density of the legal color that is to be added, typically expressed in pounds per gallon.
  Using a known prior art peristaltic pump, the operator makes the computation by applying the mathematical formula using a calculator on a cellular phone or a hand-held calculator, and enters the result as a single number into the pump.

Such prior art peristaltic pumps use DC drive gear motors and large pump heads having 3, 4, or 6 rollers for compressing the pump tube.
Tube installation in prior art peristaltic pumps is accomplished by laying the tube into a slot on the top of the pump head, and then pushing or pulling the tube under an overhanging portion of the pump head, while the pump is running, and the rollers are turning, thereby allowing the tube to “walk” into position.
Such prior art peristaltic pump designs use a motor and a gearbox to produce the torque needed to drive the rollers to squeeze the tube, thereby to effectuate the pumping.
In such prior art peristaltic pumps, bearings compress the tube. As the bearings wear and become “sloppy”, the bearings no longer press outward as far as they did when they were new. As a result, such older peristaltic pumps will eventually leak air and not draw the required vacuum. Consequently, pump accuracy is lost.
Many prior art peristaltic pump designs use a hinged door that exposes the entire face of the roller set when the door is opened. In such designs the tubing must be “walked” into place while the rollers are turning. This is not safe.

SUMMARY OF THE INVENTION

In one of its aspects, this invention provides a peristaltic pump for pumping liquid color to a process machine, where the pump preferably includes a pump head having a pump head upper half and a pump head lower half, a mounting bracket with the pump head lower half preferably being secured to the mounting bracket, and the pump head upper half preferably being vertically slidably movable towards and away from the pump head lower half along the mounting bracket. The pump preferably further includes a stepper motor including an output shaft, with a drive roller being mounted on the output shaft, and a collection of planetary rollers positioned about and preferably frictionally contactingly driven by the drive roller in the output shaft for sequentially compressing a flexible tube carrying the liquid color being compressed by the planetary rollers against the pump head upper half, thereby dispensing liquid color or other liquid from the tube.
The pump desirably further includes pump head upper half positioning pins fixedly mounted in the pump head lower half and extending upwardly therefrom, slidably residing in bores formed in the pump head upper half. The pump preferably further includes compression springs positioned about portions of the pins and extending from the pump head lower half, to bias the pump head upper half away from the pump head lower half.
The mounting bracket preferably has a flange extending transversely with the flange at least partially overlying the pump head upper half. A bolt, positioned between the mounting bracket and the pump head upper half, is preferably connected to the pump head upper half. A knob is adapted for manual rotation, with a vertical shaft connected to the knob for rotation unitarily therewith and threadedly engaging the bolt. Upon rotation of the knob in the first direction, rotation of the shaft threadedly engaging the bolt preferably causes the bolt to move away from the knob, pushing the pump head upper half downwardly along the pins and towards the pump head lower half, against bias supplied to the pump head upper half by the compression springs.
In another of its aspects, this invention provides a peristaltic pump for supplying liquid color to a process machine, where the pump preferably includes a stepper motor including an output shaft, a drive roller preferably mounted on the output shaft, and a collection of planetary rollers preferably positioned about and frictionally contactingly driven by the output shaft for sequentially compressing a flexible tube carrying liquid color, thereby dispensing liquid color from the tube.
In still another one of its aspects, this invention provides a peristaltic pump for supplying liquid color to a process machine where the pump includes a motor driving planetary rollers squeezing a tube to output pumped liquid color, and a plurality of buttons for manually entering (i) output rate in pounds per hour of product to be furnished by a process machine receiving the pumped liquid color; (ii) percentage by weight of the pumped liquid color to be added to the plastic resin material consumed by the process machine in the course of producing the plastic product; and (iii) density of the liquid color to be added. The pump further includes a plurality of video-type screens for displaying the manually entered data recited in the preceding sentence and a microprocessor for computing the amount of liquid to be dispensed using the manually entered number and speed of the motor to furnish the computed amount of liquid to be dispensed. The motor is desirably a stepper motor and the stepper motor desirably connects to the planetary rollers via a direct drive.
In still another one of its aspects, this invention provides a peristaltic pump that includes a motor driving planetary rollers squeezing a tube to output pumped liquid, a plurality of buttons for manually entering data, a plurality of display screens for visibly displaying the manually entered data and a microprocessor using the manually entered data to compute the amount of liquid to be dispensed and regulating operation of the motor to furnish the computed amount as dispensed liquid. The data are desirably output rate in pounds per hour of a process machine receiving the pumped liquid, percentage by weight of the pumped liquid to be used by the process machine, and density of the liquid.
In yet another one of its aspects, this invention provides a peristaltic pump for supplying liquid color to a process machine where the invention includes a stepper motor and a plurality of rollers frictionally contactingly driven by the stepper motor for compressing a tube carrying liquid color to dispense liquid color from the tube.
In still yet another one of its aspects, this invention provides a peristaltic pump comprising a stepper motor, a plurality of manually actuated switches for entering numbers, a plurality of screens for visually displaying the manually entered numbers, and a microprocessor using the manually entered numbers to regulate speed of the stepper motor to furnish liquid color at a preselected rate. The pump preferably includes rollers driven by the stepper motor for squeezing a tube to output pumped liquid color. The rollers are preferably frictionally driven by the stepper motor. The rollers are preferably planetary rollers. The switches are preferably push buttons or thumb wheels and may most desirably be digital thumb wheels.
The numbers provided manually to the peristaltic pump are desirably the output rate in pounds per hour of a process machine receiving the pumped liquid color, the percentage by weight of the pumped liquid color to be used by the process machine, and the density of the liquid color to be supplied.
In yet another one of its aspects, this invention provides a peristaltic pump for supplying liquid color to a process machine comprising a stepper motor, a pump head having a groove therein for receiving a liquid color tube, and plurality of rollers frictionally driven by the stepper motor for compressing the tube carrying the liquid color while in the groove to dispense liquid color from the tube. Desirably the pump head has upper and lower portions, with the upper portion being movable vertically to expose the rollers for positioning the tube thereon. The pump desirably further includes an on/off switch for controlling flow of electricity to the stepper motor and a trip for moving the on/off switch to the “off” position whenever the pump head upper portion is raised.
The pump of the invention allows direct entry by an operator or by electric connection to a systems computer of the three variables that are required to determine the amount of liquid color, namely the volume, to be dispensed. The three variables are:

- 1. The “shot” weight in grams needed to meet the required production, typically expressed as pounds per hour output by the process machine to which the liquid color is to be furnished;
- 2. The percentage, by weight, of color to be added to each “shot”; and
- 3. The bulk density of the color that is to be added , typically expressed in pounds per gallon.

The pump of the invention is a volumetric pump, without load cells for weighing. The pump meters a given volume and therefore requires the third entry to convert weight to the desired output volume. The pump of the invention uses three separate digital displays and separate entry buttons. As a result, operator errors are minimal. The three separate digital displays and separate data entry buttons allow entry of each variable directly via one of the buttons with no further calculation being required by an operator.
The pump of this invention uses a direct drive stepping motor. Stepper motors are inherently more accurately controlled than conventional motors. The pump of this invention also has a small pump head that uses only four (4) rollers.
While hinged and separable housings for liquid color peristaltic pumps are known, the pump of this invention has a housing that separates, with the top half of the pump head rising to expose the rollers, allowing clear access for the liquid-carrying flexible tube to be laid in place over the rollers, without the pump running. Lowering the top half covers the access and compresses the tube so that operation may begin.
The pump of this invention uses a “sun and planet” drive system design to drive the rollers. The motor drives a center drive roller, which is covered with a urethane sleeve that creates friction when pressed against the outer “planetary” rollers. The four outer planetary rollers are held in place to keep them positioned uniformly around the center drive roller.
In the pump of the invention, the outer planetary rollers are retained by the pump head, which has a cylindrical cavity sized to contain the rollers and hold them tightly against the inner drive roller. Preferably dimensions are such that the outer rollers are actually pressed into the center urethane sleeve, compressing the sleeve slightly at points of contact. This assures solid drive friction, which works to maintain the required radially outward force to compress the tubing as the tubing is being contacted by the planetary rollers.
The pump of this invention preferably uses a stepper motor without a gear box. For effective pumping the four roller set need only reach a rotation speed of about 1 turn per second. Speeds greater than this do not result in effective pumping so 60 RPMs is the practical limit of the planetary rollers.
Stepper motors can run much faster than this. For an example, assume that maximum speed of a stepper motor is 300 RPMs. One way to generate the required torque for a pump of this type would be to use a large stepper motor sized for the torque required and run it no faster than 60 RPMs. Another way is to use a much smaller motor, but to gear it down, so that its maximum speed of 300 RPMs can be utilized stepped down through gear reduction to the desired maximum speed of 60 RPMs. Thus by gear reduction, torque increases by a factor of 5. In this way the stepper motor can be ⅕ the size of a conventional stepper motor that would ordinarily be needed to produce the required torque specification and can still achieve the required torque.
Stepper motors with gear boxes attached are more expensive.
In the pump of the invention, a new planetary design of a center roller driving an outer set of rollers through frictional contact results in a 5 to 1 speed reduction without use of a gear box, due to the geometry designed into the pump.
The speed of the outer roller set is calculated using the following formula:

- C=outer diameter of the center drive roller
- P=inner diameter of the pump head cavity that the roller set is being pressed against, and is rolling against.
- P/C+1=speed reduction.

Using the dimensions of one preferred embodiment of the new pump design:
2.5/0.625+1=5
In this way the pump of the invention produces a 5 to 1 speed reduction and a corresponding increase in torque of 5 times the motor torque rating.
The benefit is low cost. The smaller motor costs less and the required drive circuit costs less.
Stepper motors are inherently more accurate in control then DC drives. But stepper motors have inherently less torque, unless they are large, or have gearboxes attached. The design of the pump of this invention allows a small stepper motor to do the job it otherwise could not do.
The pump of the invention drives the rollers through friction of the center drive roller covered with urethane, pressing into the outer rollers.
The outer rollers could be referred to as “compression” rollers because these rollers compress the pump tube (as is the case with all peristaltic pumps). Since the design of the inventive pump causes these rollers to be pressed outward, there must be a surface provided for the rollers to contact so the rollers are constrained to remain in a perfect circle as they turn. In the area where the tube is compressed, a groove is machined and is just wide enough to retain the tube.
The preferable tubing is 1/16 wall thickness. If compressed enough by the rollers to shut off flow, the tube would in theory be two wall thicknesses (or 0.125) thick at the point of compression. To assure that not even air will flow past such a compression point, the pump of the invention over-compresses the tube. The pump of the invention squeezes the two wall thicknesses into a space only 0.100 deep. So the groove that is machined to retain the tube is machined to 0.100 deep at least at the top dead center position and preferably throughout.
One advantage of the pump of the invention is that there are no bearings to wear out. The 0.100 compression of the tube is machined into the housing and does not change over time.
Control in the pump of the invention uses three separate sets of digital displays; each display has its own set of entry buttons, providing simpler and more intuitive operations.
The tube insertion design of the pump of the invention is an “easy to load” design, requiring that the tube simply be laid over the top of the rollers without the need to work the tube into a compression zone or groove.
Other so-called “easy load” designs use a clam shell, with the top half of the pump swinging open on a hinge point, to expose the top half of the roller set. The pump of the invention uses a sliding pump top that rises to expose the top surface of the roller set. This is safer, with less access to rotating parts. Straight vertical downward movement of the pump head upper half assures more uniform pressure against the tubing when the pump head upper half is lowered into place.
The design of the pump of the invention allows tube insertion without the rollers turning. The pump of the invention has an interlock on the drive motor to assure the motor will not run while the top half of the pump head is raised and rollers are accessible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric exterior view showing the front, the top and the left side of the four roller peristaltic pump of the invention, with the pump head visible on the left side of the housing.

FIG. 2 is an isometric exterior view showing the front, the top and the right side of the four roller peristaltic pump of the invention, with the pump having been rotated approximately 90 degrees from the position at which FIG. 1 is taken, and with a microprocessor portion of the pump, located within the housing, shown in dotted lines.

FIG. 3 is an exploded isometric view of the pump head, including the stepper motor, of the four roller peristaltic pump of the invention.

FIG. 4 is a side view of the pump head, looking forward from the rear as respecting FIG. 1, including the stepper motor, of the peristaltic pump of the invention, with the pump housing not shown to enhance drawing clarity.

FIG. 5 is a schematic partial sectional view of the pump head taken at arrows 5-5 in FIG. 4, with the pump head upper half in its fully raised position.

FIG. 6 is a side view of the pump head, looking forward from the rear as respecting FIG. 1, including the stepper motor, with the pump housing not shown to enhance drawing clarity.

FIG. 7 is a schematic partial sectional view of the pump head taken at arrow 7-7 in FIG. 6, with the pump head upper half in its fully raised position.

FIG. 8 is a side view of the pump head identical to FIG. 4.

FIG. 9 is a schematic partial sectional view of the pump head taken at arrows 9-9 in FIG. 8, with the pump head upper half in its fully lowered position.

FIG. 10 is an elevation of the pump head looking at the side of the peristaltic pump from the left in FIG. 1, with the pump head upper half in its fully lowered position; the pump housing has not been shown to enhance drawing clarity.

FIG. 11 is a schematic sectional view taken at arrows 11-11 in FIG. 10.

FIG. 12 is an elevation of the pump head looking at the side of the peristaltic pump from the left in FIG. 1, with the pump head in its fully raised position; the pump housing has not been shown to enhance drawing clarity.

FIG. 13 is a schematic sectional view taken at arrows 13-13 in FIG. 12.

DETAILED DESCRIPTION OF THE INVENTION AND BEST MODE KNOWN FOR PRACTICE THEREOF

Referring to the drawings in general and to FIG. 1 in particular, a peristaltic pump embodying the invention is indicated generally 10 and includes a housing 124 having a handle 126 connected to the top of the housing.
At the left side of the housing is a pump head indicated generally 11 which includes a pump head lower half designated generally 12, a pump head upper half designated generally 14, and a safety guard indicated generally 20 in FIG. 1. Further visible in FIG. 1 is a power indicator light 114 which illuminates when the peristaltic pump is powered and a run indicator light designated generally 116 that lights when the pump is operating and pumping fluid. Yet further illustrated in FIG. 1 are three screen displays, each designated generally 118. Associated with each screen display 118 are two buttons 120. One of buttons 120 associated with each screen display 118 is an increment button for incrementing the parameter value displayed on the associated screen 118; the second button of the two buttons 120 is a decrement button for decreasing the value displayed on the associated screen 118. Only a single pair of buttons 120, associated with one of the screen displays 118, has been numbered in FIG. 1 to enhance drawing clarity. While buttons 120 have been shown in the drawings, thumb wheels may be substituted for the buttons. Digital thumb wheels are especially desirable to be used in place of the buttons.
FIG. 2 is a view of peristaltic pump 10 illustrated in FIG. 1 where pump 10 has been rotated 90° from the position of FIG. 1. In FIG. 2 the peristaltic pump cabinet 124, handle 126, and knob 40 are shown, as are power indicator light 114, run indicator light 116, three screen displays 118, only one of which has been numbered, and pairs of increment/decrement buttons 120 for each of the screen displays, where only one of the pairs of buttons has been numbered. Further shown in FIG. 2 is an input/output connector 122 for providing connection to a microprocessor 158, located within housing 124 and shown in dotted lines, and for providing connection to a computer or other device, if data is to be provided by microprocessor 158 regarding operation of the pump. Further shown in FIG. 2 is a run/stop switch 112 and a pump on/off switch 110 to be used by an operator to power the pump or to cut off power to the pump and to signal the pump to run or to stop. A connection for an electrical power cord is provided and designated 128 in FIG. 2.
FIG. 3 shows an exploded isometric view of the pump head and the drive mechanism for the planetary roller assembly that effectuates the peristaltic pumping. A pump head is designated generally 11 and includes a pump head upper half designated generally 14 and a pump head lower half designated generally 12. A roller plate 16 serves for mounting of four cylindrical rollers, each individually designated 17 and which together with roller plate 16 constitute a planetary roller assembly designated generally 18. Rollers 17 are retained in their proper relative position respecting roller plate 16 by roller pins 19 that engage roller plate 16 and by a cylindrical surface machined into upper and lower pump head halves 14 and 12. Rollers 17 are freely rotatable about roller pins 19.
Only selected ones of rollers 17 have been numbered in the drawings, and similarly only certain ones of roller pins 19 have been numbered in the drawings, to enhance clarity of the drawing.
As shown in FIG. 3, drive hub 23 includes a shoulder portion 50 with an integral washer-like head 52 and a shaft portion 70.
Formed in pump head lower half 12 and in pump head upper half 14 are a pair of annular surfaces with the smaller annular surface designated 54, as partially shown in FIG. 3, and the larger annular surface designated 56, as also partially shown in FIG. 3.
Smaller diameter annular surface 54 in the upper and lower halves 14, 12 of pump head 11 is preferably formed such that smaller diameter annular surface 54 has a shorter length, in the axial direction, than does larger diameter annular surface 56.
Smaller diameter annular surface 54 is designed for and dimensioned to receive annular shoulder 50 of drive hub 23. Shoulder 50 and cast washer 52 are sized such that cast washer 52 of drive hub 23 cannot pass through the inner race of annular ball bearing assembly 50 in a left to right direction in FIG. 3.
Smaller diameter annular surface 54 formed in the lower and upper halves 12, 14 of pump head 11 is dimensioned to receive the outer race of annular ball bearing assembly 30. The interior race of annular ball bearing assembly 30 is sized to fit about and to receive shoulder 50 of drive hub 23. Annular ball bearing assembly 30 is held in place by roller plate 24 and screws which pass through apertures in roller plate 24 and fit into appropriate threaded bores formed in the annularly shaped, axially facing surfaces of pump head lower half 12 and pump head upper half 14. These annularly shaped axially facing surfaces define the transition between smaller diameter annular surface 54 and larger diameter annular surface 56. These annularly shaped, axially facing surfaces are not numbered in FIG. 3 to enhance the clarity of the drawing. Similarly, the screws that hold roller plate 24 in place against the annular axially facing transition surfaces are not illustrated in FIG. 3, again to enhance the clarity of the drawing.
Stepper motor 36 is held in place against facing surfaces 58, 60 of pump head upper half 14 and pump head lower half 12 by machine screws that pass through apertures 62, which are formed in the frame of stepper motor 36, and threadedly engage bores 68 in axially facing surfaces 58, 60 of upper and lower halves 14, 12 of pump head 11.
Larger diameter annular surface 56 formed in pump head lower half 12 and pump head upper half 14 define a cylindrical cavity which is sized to retain planetary rollers 17 and to hold them tightly against roller sleeve 22. The dimensions of the assembly are desirably such that planetary rollers 17 are actually pressed into roller sleeve 22, compressing sleeve 22 slightly at the points of contact as depicted in FIG. 5. This assures good drive friction as well as the required outward pressure of planetary rollers 17 to compress the pump tubing as the pump tubing is contacted by the outer cylindrically shaped surfaces of planetary rollers 17.
Roller sleeve 22 is desirably polyurethane and preferably fits tightly on the axially extended portion of drive hub 23, where the axially extended portion has been designated 70 in FIG. 3. With drive hub 23 and roller sleeve 22 transmitting power from stepper motor 36, this eliminates the need for a gear box or gears of any type. The instant design, with planetary rollers 17 being driven by drive hub 23 and roller sleeve 22 through frictional contact, allows for a 5:1 speed reduction from stepper motor 36. The 5:1 speed reduction is effectuated by the dimensions of the drive roller, namely the outer dimension of roller sleeve 22, and the inner diameter of the pump head cavity, namely the diameter of larger diameter annular surface 56 that rollers 17 are pressed against. The speed reduction is computed by forming the quotient of the diameter of the larger diameter annular surface 56 and the diameter of roller sleeve 22, and then adding the integer 1 to the result to obtain the relevant speed reduction. In a preferred implementation of the invention, the diameter of larger diameter annular surface 56 is two and one-half (2½) inches, the outer diameter of the roller sleeve 22 is five-eighths (⅝) of an inch. Forming this quotient and adding integer 1 to it yields the number “5”, which is the 5:1 speed reduction of the stepper and corresponding torque increase of five times the stepper motor torque rating.
Proper alignment of pump head upper half 14 with pump head lower half 12 is assured by dowel pins 38 that are mounted in appropriate bores formed in upwardly facing surface 72 of pump head lower half 12. Steel compression springs 32 are positioned about dowel pins 38, as illustrated in FIG. 3, to exert upward force on pump head upper half 14.
An important aspect of the invention is safety whereby stepper motor 36 is interlocked with pump head upper half 14 so that whenever pump head upper half 14 is raised and moving parts are exposed, power is cut off to stepper motor 36. This is effectuated by attachment of a pin to pump head upper half 14 where the pin is designated generally 102 in the drawings. A spring loaded safety switch 100 is provided, mounted on bracket 26 as illustrated in FIGS. 3, 11 and 13.
Pin 102 protrudes into and rides within a vertical slot 130 in mounting bracket 26, with spring loaded safety switch 100, pin 102, and slot 130 being configured such that pin 102 releases spring loaded safety switch 100 whenever pump head upper half 14 is in the raised position. When spring loaded safety switch 100 is released, power to stepper motor 36 is cut off by spring loaded safety switch 100, breaking the connection between stepper motor 36 and the power source, which will normally be conventional 115 volt power.
When knob 40 is turned and lowers pump head upper half 14 into position for pumping after a suitable tube has been placed into position on rollers 17, spring loaded safety switch 100 closes and power is once again available to stepper motor 36.
The operation and interplay of spring loaded safety switch 100 and safety pin 102 is best illustrated in FIGS. 11 and 13. In FIG. 13, which depicts the configuration of pump head 11 with pump head upper half 14 in the raised position, safety pin 102 is above and out of contact with spring loaded safety switch 100. In FIG. 11, which depicts the configuration of pump head 11 and pump head upper half 14 when pump head upper half 14 is in the lower, operating position, safety pin 102 has contacted spring loaded safety switch 100, thereby causing spring loaded safety switch 100 to break the circuit providing power to stepper motor 36, de-energizing stepper motor 36. Spring loaded safety switch 100 is partially occluded from view by safety pin 102 in FIG. 11.
Positioning of pump head upper half 14 at the extreme upper and extreme lower, or open and closed, positions is effectuated by manual rotation of knob 40. In FIG. 13, where safety pin 102 is above and out of contact with spring loaded safety switch 100, knob 40 has been rotated to allow pump head upper half 14 to rise to the “open” or the top position. A shaft 132 to which knob 40 is fixedly connected, is threadedly received by a nut 132, which is fixedly connected to a horizontal portion 134 of mounting bracket 26. Upon rotation of knob 40, shaft 132 either rises or drops, depending on the direction of rotation of knob 40, where the rising of lowering of shaft 132 is due to the engagement with nut 134.
In FIG. 4, showing pump head 11 from the rear as respecting FIG. 1, pump head upper half 14 is in its raised position due to manual rotation of knob 40 and threaded shaft 132 operating on nut 134. In the space between pump head lower half 12 and pump head upper half 14 in FIG. 4, one of the dowel pins 38 and the compression spring 32 coiled around dowel pin 38 are visible.
In FIG. 5, taken at lines and arrow 5-5 in FIG. 4, the space between the pump head lower half 12 and the pump head upper half 14, when pump head upper half 14 is in the raised position, is shown. Rollers 17 are shown as contacting roller sleeve 22, which in turn is mounted on drive hub 23, which in turn is rotated by the drive shaft of stepper motor 36. The drive shaft has been designated 138 in FIG. 5. A groove 140 is formed in the interior of pump head upper half 14 for residence therein of a suitable flexible tube carrying the fluid to be peristaltically pumped due to rotation of the planetarily arranged rollers 17.
Stepper motor drive shaft 138 rotates to turn drive hub 23 which is preferably fixedly mounted on drive shaft 138. As drive hub 23 turns with drive shaft 138, roller sleeve 22, being frictionally adhered to drive hub 23 by tight, sleeve-like fitting, contacts rollers 17 and turns rollers 17 due to the frictional contact therewith. Of course, there is no rotation of rollers 17 and no rotation of the stepper motor drive shaft 138 when pump head upper half 14 is in the position illustrated in FIG. 5 due to the interlock between pump head upper half 14 and stepper motor 36 provided by safety switch 100 and safety pin 102 as described herein.
FIG. 6 once again depicts pump head 11 as viewed from the rear of peristaltic pump 10 as illustrated in FIG. 1. In FIG. 6, as in FIG. 4, pump head upper half 14 is in its fully raised position, having been raised to that position by manual rotation of knob 40 with rotation of shaft 132 relative to nut 134 effectuating the rise of pump head upper half 14 as pushed by springs 32 that are coiled about dowel pins 38 and exert continuous upward force on pump head upper half 14.
In FIG. 7, dowel pins 38 are shown, as are compression springs 32 that are coiled about dowel pins 38. Dowel pins 38 are fixed in pump head lower half 12 by any suitable means such as press fitting, adhesive and the like. Bores 140 are formed in pump head upper half 14 for pump head upper half 14 to move slidably up and down on dowel pins 38. Annular recesses 142 are provided at the ends of bores 140 most proximate to pump head lower half 12. Recesses 142 receive springs 32 and retain springs 32 in place around dowel pins 38 as pump head upper half 14 moves up and down. Springs 32 press against blind ends of recesses 142 to exert continuous upward pressure on pump head upper half 14. In the preferred implementation of the invention, when pump head upper half 14 is raised to its maximum position away from pump head lower half 12, space between the two pump head halves is about 0.5 inches.
Further visible in FIG. 7 is annular ball bearing assembly 30, the inner race of which is not numbered and contacts shoulder 50 of drive hub 23. An extended shaft portion 144 of drive hub 23 is similarly illustrated in FIG. 7 as is stepper motor drive shaft 38 on which drive hub 23 is preferably mounted. The outer race of annular ball bearing assembly 30 rests in small diameter annular surface 54 and is preferably maintained there by a retaining half ring 146, the ends of which fit into suitable apertures. Pump head lower half 12 with retaining half ring 146 serves to retain annular ball bearing assembly 30 in position when pump head upper half is raised to the position illustrated in FIG. 7.
FIG. 8 again shows the pump head 11 as viewed looking forward from the rear of the peristaltic pump as illustrated in FIG. 1. In FIG. 8, pump head upper half 14 is in the closed position, abuttingly contacting pump head lower half 12 as illustrated. In FIG. 8, a portal opening 162 for a tube containing liquid color or other fluid material pumped by the peristaltic pump is shown. The portal opening 162 is in the form of a notch or cut-out in the portion of pump head upper half 14 that is most proximate to peristaltic pump housing 124 illustrated in FIG. 1. Portal 162 is in the form of a rectangular space having a vertical edge 148, a horizontal edge 150 and a small notched portion 152 all as designated in FIG. 8. A similar portal opening is provided in the opposite side of pump head 11, as illustrated in FIG. 12.
FIG. 9 similarly illustrates peristaltic pump head 11 with pump head upper half 14 in its lowered position ready for pumping liquid color or other liquid. In a preferred implementation of the invention, the mouth provided for entry of the pumping tube is 0.039 inches high as indicated by dimensional figure “H” in FIG. 9. When the preferred ¼ inch outer diameter tube is laid in place on rollers 17 for pumping, the position at which compression of the tube commences is indicated by dimensional arrows “I” in FIG. 9. As rollers 17 continue to rotate both individually and in a planetary fashion due to the rotation of the shaft of stepper motor 36 as transmitted to rollers 17 by drive hub 23 and roller sleeve 22, liquid in the flexible ¼ inch outer diameter tube reaches the position indicated by dimensional arrow “J” in FIG. 9, at which the ¼ inch diameter tube has been compressed to a total thickness of 1/10 inch. As rollers 17 continue to rotate individually and in a planetary fashion about an axis defined by shaft 138 of stepper motor 36, the liquid within the tube continues to be pumped though the tube and exits, while within the tube, out of the exit portal 162 defined between pump head lower half 12 and pump head upper half 14.
FIG. 9 depicts the compression of roller sleeve 22 by rollers 17 which results in outward force on rollers 17 thereby to retain rollers 17 in forceful contact with a pumping tube once a pumping tube is laid into position on rollers 17 within peristaltic pump head 11. (No pumping tube has been shown in the drawings.)
FIG. 10 is an elevation of the pump head of the invention taken looking at the pump 10 from the left side in FIG. 1. In FIG. 10, pump head 11 has been depicted with pump head upper half 14 in its lowered or closed position. Guard 20 covers pump head lower half 12 and prevents access to the moving parts of the peristaltic pump during pump operation. Note that the upper edge of guard 20, denoted 150 in FIG. 10, is the same shape and adapted for close fitting as respecting the upper edge of the path for the fluid tube defined by the machined surface 152, which is a lower extremity surface of pump head upper half 14.
A groove is machined into the facing surface of pump head upper half 14, where that facing surface is designated generally 154 in FIG. 9. The groove is to accommodate the tube when the tube is first laid into position on rollers 17 with pump head upper half 14 in the raised position and pump head upper half 14 is lowered.
FIG. 11 shows rollers 17 rotatable about roller pins 19, stepper motor 36, drive hub 23 connected to the output shaft 138 of stepper motor 36, roller sleeve 22 in concentric arrangement about a shaft portion 144 of drive hub 23 and annular ball bearing assembly 30 receiving a shoulder portion 50 of drive hub 23. FIG. 11 also depicts guard 20 and shows guard lip 148 which runs along the inner portion of guard 20, along guard upper edge 150 illustrated in FIG. 10. Guard lip 148, when guard 20 is in position as shown in FIGS. 11 and FIG. 10, precludes any access to any of the moving parts of peristaltic pump head 11 during pump operation. Note also that in FIG. 11, safety switch 100 has been actuated by contact with safety pin 102 due to downward movement of pump head upper half 14 into its lowermost position as a result of rotation of knob 40 and shaft 132. Safety switch 100, not being contacted by safety pin 102, provides electrical power to stepper motor 36 in a safe fashion since pump head upper half 14 is in the down position and guard 20 in place thereby preventing any access to the moving parts of pump head 11.
FIG. 12 is a view similar to that of FIG. 10 but with pump head upper half 14 in the raised position. In FIG. 12, the groove for entry and exit for the fluid carrying tube via portals 160, 162 as machined into pump head upper half 14 is shown as is the machined circular recess provided for retaining rollers 17 in position as planetary motion of the assembly 18 of rollers 17 proceeds.
When liquid color or another liquid is to be pumped, a suitable tube, preferably a ¼ inch outside diameter flexible tube, is connected between the supply of liquid color or other liquid to be pumped and the process machine or other equipment to which the liquid color is to be supplied. An operator then raises pump head upper half 14 by rotating knob 40 until pump head upper half 14 has reached its upper limit of travel. At this point, rollers 17 are exposed and there is clear access for the fluid-carrying tube to be laid in place over rollers 17 without having pump 10 operating. Lowering pump head upper half 14 into its lower extremity position, in contact with pump head lower half 12, covers rollers 17 and compresses the fluid-carrying tube so that operation of the pump may begin. There is no need to run the pump with the rollers turning, to allow the tube to be walked into position. Such procedure is dangerous. This procedure is prevented with the pump of the invention since the interlock between stepper motor 36 and safety switch 100 prevents motor 36 from rotating while pump head upper half 14 is in a position raised from rollers 17 so that rollers 17 are exposed.
In FIG. 12, a portion of the cylindrical cavity machined into pump head 11, specifically the portion of the cylindrical cavity machined into pump head upper half 14, is shown and designated 152. The cylindrical cavity is specifically sized and maintained to retain rollers 17 in place and to hold them tightly against roller sleeve 22 and drive hub 23. Rollers 17, in the preferred implementation of the invention, are pressed into and against urethane roller sleeve 22, compressing roller sleeve 22 at multiple points of contact, which assures solid drive friction as well as maintaining the required radially outward pressure by rollers 17 to compress the tubing that is being pressed against by the outwardly facing surfaces of the planetarily moving rollers 17.
Comparing FIGS. 12 and 10, and FIGS. 13 and 11, provides perspective on the way in which pump head 11 is constructed to provide the squeezing action on a tube carrying liquid color or other liquid to be pumped. In FIG. 11, the 1/10 inch space between the outer surface of rollers 17 and the machined surface formed at the tope dead center of pump head upper half 14 for the fluid carrying tube has been indicated as 156 in FIG. 11; this is the 1/10 inch space for the tube as indicated in FIG. 9. Comparing FIG. 11 to FIG. 13, where the pump head upper portion has been raised, surface 156 is well removed from rollers 17 to facilitate placement of the fluid carrying tube in position, lying on one or more of rollers 17.
Referring to FIGS. 9, 11, 12 and 13, in the peristaltic pump of the invention, rollers 17 are pressed outwardly against a surface 158, which is a cylindrical surface, so that the rollers are held to move in a perfect circle as the rollers move around the circle and turn about their axes. In the area of surface 158, where the fluid carrying tube is to be compressed, groove 156 is machined into surface 158. Groove 156 is machined with dimensions just wide enough to retain the desired tube.
During operation, the actual pumping of fluid through the flexible tube begins at the position indicated by dimensional letter “I” in FIG. 9, where space between the machined wall portion of pump head upper half 14 and a roller 17 is ¼ inch. As the rollers rotate in planetary fashion, counterclockwise in FIG. 9, about the axis defined by shaft 138 of stepper motor 36, and move from portal 160 to the top dead center position, space between the rollers 17 and the wall portion of pump head upper half 14 decreases (and consequently pressure in fluid within the tube increases) until the groove in which the tube lies is only 1/10 inch deep, as illustrated in FIG. 11 and as indicated by dimensional letter “J” in FIG. 9. As the rollers 17 continue moving in the planetary orientation along this portion of groove 156, the resulting increasing pressure in the fluid drives the fluid in the tube in the direction of planetary rotation until the fluid reaches the shallowest part of groove 156, at the top dead center position denoted by letter “J” in FIG. 9. As the fluid then continues to travel through the tube into an area where groove 156 is deeper, pressure on the fluid extruded by rollers 17 diminishes somewhat, but continuing planetary rotation of rollers 17 assures that the fluid is continuously squeezed through the tube, with newly squeezed fluid from the top dead center position acting as less recently squeezed fluid, resulting in a constant flow of pressurized from the peristaltic pump.
Pump operation normally begins with an operator turning knob 40 to raise pump head upper half 14 to its fully raised position. The operator then lays the flexible tube, carrying the liquid color from a supply to a process machine, across rollers 17. Once the operator has placed the flexible tube into position on rollers 17 and has lowered pump head upper half 14, by rotation of knob 40, into position, fitting tightly against pump head lower half 12 and thereby squeezing the tube that has been laid into position on rollers 17 into groove 162, the operator then plugs the peristaltic pump into a source of power using a suitable power cord and power cord receptacle 128. The operator then typically moves off/on switch 110 to the “on” position and would enter the data required for the peristaltic pump to successfully provide the required amount of liquid color at the required rate for successful molding or extrusion by an associated process machine.
Specifically, the operator, using one of the sets of buttons 120, would enter the “shot weight” in grams needed to meet the required production. He does this typically by entering a number that would have units associated with it of pounds per hour representing the output by the process machine to which the liquid color is to be furnished. As the operator enters this number using the appropriate set of buttons 120, the number as entered appears on screen 118 associated with that set of buttons 120. By toggling the buttons 120, the operator can adjust the input number indicative of pounds per hour output by the process machine until the desired value appears on the screen.
Next the operator uses a second set of buttons 120 to enter the percentage by weight of color to be added to each “shot” during operation of the extruder or other process machine, such as molding press, to which the liquid color is to be furnished.
Next, using the third set of buttons, the operator enters the density of the liquid color that is to be added. This typically would be a number having units of pounds per gallon. Once again, the number appears on the screen 118 associated with the pair of buttons 120 used by the operator to enter that number.
Next the operator presses the run button 112, whereupon, since the pump head upper half has been lowered into position and the flexible tube has been laid onto rollers 17, pumping begins. Since power has been supplied to the peristaltic pump, power indicator light 114 will be on. Once the operator presses switch 112 to commence pump operation, the run light 116 lights.
During operation, microprocessor 158 portion of peristaltic pump 10 monitors operation such as the speed of rotation of stepper motor 136 and the like and provides data as to the amount of liquid color being provided, with such data being output by microprocessor 158 via a universal coaxial input/output connector 122. Similarly, if it is desired to reprogram microprocessor 158 so that different parameters may be input for pump 10 to process different materials on different cycles at different speeds, microprocessor 158 can accordingly be reprogrammed by a connection of a suitable computer or other input device to universal input/output coaxial connector 122.
In one implementation of the invention, the peristaltic pump is designed to pump using tubing that is ¼ inch thick and has 1/16 inch wall thickness. If such tubing were compressed enough to shut off flow, the tubing would, in theory, be two wall thicknesses thick or 0.125 inches thick at the point of compression. To assure that even air will not flow past this compression point, the peristaltic pump of the invention, utilizing such ¼ inch diameter tubing having wall thickness of ⅙ inch, “over compresses” the tube. Specifically, the two wall thicknesses of the tube are squeezed into a groove only 0.1 inch deep, as indicate by dimensional arrow “J” in FIG. 9. Hence, the depth of groove 156 that is machined to retain the tube is machined to 0.1 inch deep at the top dead center position.
In the preferred implementation of the invention, the pump head upper half has a range of vertical motion of ½ inch.
In the course of design of the peristaltic pump of the invention, as with any peristaltic pump, one selects a desired pump output. In the case of the instant invention, the peristaltic pump is a volumetric pump and hence one chooses a desired volume of liquid to be output over a given time. Assuming the liquid is incompressible, which is the case with liquid color and most other liquids for which peristaltic pumps are used, once a tube size is selected with a given outer diameter and inner diameter, the inner diameter and the speed along the tube of the rollers squeezing the tube (assuming the tube is squeezed “shut” by the rollers at some point) define the volume of liquid produced per unit time.
In the instant invention as implemented in accordance with the drawings and this disclosure, a ¼ inch diameter tube was selected having 1/16 inch wall thickness. For effective pumping using this size of tube, the planetary roller set need only reach a rotation speed of about one turn per second. Based on experimentation, speed greater than this does not pump effectively. As a result, 60 revolutions per minute of the planetary four roller set is the practical design limit of the roller set for a ¼ inch diameter tube and for many other tubes of similar size.
Once the speed of the outer roller set has been selected, the pump of the invention has been designed to utilize a stepper motor. Specifically, the outer diameter of the planetary drive roller mechanism was selected to be 2½ inches. From this, an inner diameter of the pump head cavity that the rollers 17 are pressed against, namely diameter of roller sleeve 22, was selected to be ⅝ inch. When these dimensions are used, the peristaltic pump implemented according to the invention enjoys a 5:1 speed reduction as between the speed of the outer surface of the rollers 17 and the rotary speed of roller sleeve 22 which provides a corresponding increase in torque of five times the stepper motor torque rating. This allows use of a smaller stepper motor which costs less and the required drive circuitry also costs less.
While stepper motors are inherently more accurate to control than are DC drives, stepper motors inherently have less torque, unless the stepper motor is large or has a large gear box attached to it. The instant invention with the design of the peristaltic pump head disclosed herein permits a small stepper motor to be used, thereby reducing the cost of the pump substantially.
Assembly of the peristaltic pump in the preferred manifestation of the invention is effectuated essentially by aligning the components as illustrated in FIG. 3 along an axis end, inserting them into their respective pockets, apertures, and the like in accordance with ordinary mechanical assembly. Guard 20 essentially sandwiches the components of pump head 11 against mounting bracket 26, as illustrated in FIG. 1, with three screws, illustrated in FIG. 1 but not numbered, securing this assembly together. Stepper motor 36 is secured to pump head lower half 12 as described above. The mounting bracket 26 is in turn secured to housing 124 by appropriate screws which are shown in FIG. 3 but are not numbered to enhance the clarity of the drawings.
In the claims appended hereto, the term “comprising” is to be interpreted as meaning “including, but not limited to”, while the phrase “consisting of” is to be interpreted as meaning “having only and no more” and the phrase “consisting essentially of” is to be interpreted to mean the recited elements of the claim and those other items that do not materially affect the basic and novel characteristics of the claimed invention.

Claims

I claim the following:

1. A peristaltic pump for supplying liquid color to a process machine, comprising:

a. a stepper motor;

b. a plurality of rollers frictionally contactingly driven by the stepper motor, for compressing a tube carrying liquid color to dispense liquid color from the tube.

2. A peristaltic pump, comprising:

a. a stepper motor;

b. a plurality of manually actuated switches for entering numbers;

c. a plurality of screens for displaying the manually entered numbers;

d. a microprocessor using the manually entered numbers to regulate speed of the stepper motor to furnish liquid color at a preselected rate.

3. The pump of claim 2 further comprising rollers, driven by the stepper motor, for squeezing a tube to output pumped liquid color.

4. The pump of claim 3 wherein the rollers are frictionally driven by the stepper motor.

5. The pump of claim 3 wherein the rollers are planetary rollers.

6. The pump of claim 2 wherein the switches are pushbuttons.

7. The pump of claim 2 wherein the switches are thumbwheels.

8. The pump of claim 6 wherein the thumbwheels are digital thumbwheels.

9. The pump of claim 2 wherein the numbers are (i) output rate in pounds per hour of a process machine receiving the pumped liquid color; (ii) percentage by weight of the pumped liquid color to be used by the process machine; and (iii) density of the liquid color.

10. A peristaltic pump for supplying liquid color to a process machine, comprising:

a. a stepper motor;

b. a pump head having a groove therein for receiving a liquid color tube;

c. a plurality of rollers frictionally driven by the stepper motor, for compressing the tube carrying liquid color while in the groove to dispense liquid color from the tube.

11. The pump of claim 10 wherein the pump head has upper and lower portions, the upper portion being movable vertically to expose the rollers for positioning of the tube thereon.

12. The pump of claim 11 further comprising:

a. an on/off switch for controlling flow of electricity to the stepper motor;

b. a trip for moving the on/off switch to the “off” position whenever the pump head upper portion is raised.

13. The pump of claim 11 wherein the rollers are planetary rollers.

14. The pump of claim 12 wherein the rollers are planetary rollers.

15. A peristaltic pump for supplying liquid color to a process machine, comprising:

a. a stepper motor frictionally driving planetary gears squeezing a tube to output pumped liquid color;

b. a plurality of switches for manually entering (i) output rate in pounds per hour of product to be furnished by a process machine receiving the pumped liquid color; (ii) percentage by weight of the pumped liquid to be added to the materials to be consumed by the process machine in the course of producing the product; and (iii) density of the liquid color;

c. a plurality of screens for displaying the manually entered data recited in claim element “b”;

d. a microprocessor regulating speed of the stepper motor in response to the manually entered data to furnish a preselected amount of liquid color to be dispensed.

16. The pump of claim 1 wherein the rollers are planetary rollers.

17. A peristaltic pump for supplying liquid color to a process machine, comprising:

a. a stepper motor;

b. a plurality of planetary rollers frictionally driven by the stepper motor, for compressing the tube carrying liquid color while in the groove to dispense liquid color from the tube.