U.S. patent application number 14/799976 was filed with the patent office on 2016-01-21 for four roller peristaltic pump.
The applicant listed for this patent is Stephen B. MAGUIRE. Invention is credited to Stephen B. MAGUIRE.
Application Number | 20160017880 14/799976 |
Document ID | / |
Family ID | 55074201 |
Filed Date | 2016-01-21 |
United States Patent
Application |
20160017880 |
Kind Code |
A1 |
MAGUIRE; Stephen B. |
January 21, 2016 |
FOUR ROLLER PERISTALTIC PUMP
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.
Inventors: |
MAGUIRE; Stephen B.; (West
Chester, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAGUIRE; Stephen B. |
West Chester |
PA |
US |
|
|
Family ID: |
55074201 |
Appl. No.: |
14/799976 |
Filed: |
July 15, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62025542 |
Jul 17, 2014 |
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Current U.S.
Class: |
417/410.3 |
Current CPC
Class: |
F04B 49/06 20130101;
F04B 49/20 20130101; F04B 17/03 20130101; F04B 43/1261 20130101;
F04B 43/1253 20130101; F04B 13/00 20130101; F04B 43/1284
20130101 |
International
Class: |
F04B 43/12 20060101
F04B043/12 |
Claims
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.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] 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
[0002] 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: [0003] 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; [0004] 2. The percentage, by weight, of
legal color to be added to each "shot"; and [0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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:
[0022] 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;
[0023] 2. The percentage, by weight, of color to be added to each
"shot"; and [0024] 3. The bulk density of the color that is to be
added , typically expressed in pounds per gallon.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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
1/5 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.
[0032] Stepper motors with gear boxes attached are more
expensive.
[0033] 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.
[0034] The speed of the outer roller set is calculated using the
following formula: [0035] C=outer diameter of the center drive
roller [0036] P=inner diameter of the pump head cavity that the
roller set is being pressed against, and is rolling against. [0037]
P/C+1=speed reduction.
[0038] Using the dimensions of one preferred embodiment of the new
pump design:
2.5/0.625+1=5
[0039] 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.
[0040] The benefit is low cost. The smaller motor costs less and
the required drive circuit costs less.
[0041] 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.
[0042] The pump of the invention drives the rollers through
friction of the center drive roller covered with urethane, pressing
into the outer rollers.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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
[0050] 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.
[0051] 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.
[0052] FIG. 3 is an exploded isometric view of the pump head,
including the stepper motor, of the four roller peristaltic pump of
the invention.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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.
[0057] FIG. 8 is a side view of the pump head identical to FIG.
4.
[0058] 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.
[0059] 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.
[0060] FIG. 11 is a schematic sectional view taken at arrows 11-11
in FIG. 10.
[0061] 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.
[0062] 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
[0063] 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.
[0064] 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.
[0065] FIG. 2 is a view of peristaltic pump 10 illustrated in FIG.
1 where pump 10 has been rotated 90.degree. 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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 (21/2) inches, the outer
diameter of the roller sleeve 22 is five-eighths (5/8) 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] 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.
[0089] 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 1/4 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 1/4 inch outer diameter tube reaches the
position indicated by dimensional arrow "J" in FIG. 9, at which the
1/4 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.
[0090] 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.)
[0091] 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.
[0092] 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.
[0093] 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.
[0094] 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.
[0095] When liquid color or another liquid is to be pumped, a
suitable tube, preferably a 1/4 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.
[0096] 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.
[0097] 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.
[0098] 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.
[0099] 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 1/4 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.
[0100] 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.
[0101] 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.
[0102] 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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] In one implementation of the invention, the peristaltic pump
is designed to pump using tubing that is 1/4 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 1/4 inch diameter
tubing having wall thickness of 1/6 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.
[0107] In the preferred implementation of the invention, the pump
head upper half has a range of vertical motion of 1/2 inch.
[0108] 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.
[0109] In the instant invention as implemented in accordance with
the drawings and this disclosure, a 1/4 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 1/4 inch
diameter tube and for many other tubes of similar size.
[0110] 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 21/2 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 5/8 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.
[0111] 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.
[0112] 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.
[0113] 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.
* * * * *