U.S. patent application number 11/129235 was filed with the patent office on 2005-11-17 for bench top pump.
Invention is credited to Baker, Rodney W., Grayson, Keith.
Application Number | 20050254972 11/129235 |
Document ID | / |
Family ID | 35309598 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050254972 |
Kind Code |
A1 |
Baker, Rodney W. ; et
al. |
November 17, 2005 |
Bench top pump
Abstract
A modular, expandable, no-tools pump assembly having precise
computer control for controlling dispensing volumes and flow
characteristics of the dispensed fluid.
Inventors: |
Baker, Rodney W.;
(Westminster, MD) ; Grayson, Keith; (Taneytown,
MD) |
Correspondence
Address: |
WHITEFORD, TAYLOR & PRESTON, LLP
ATTN: GREGORY M STONE
SEVEN SAINT PAUL STREET
BALTIMORE
MD
21202-1626
US
|
Family ID: |
35309598 |
Appl. No.: |
11/129235 |
Filed: |
May 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60571327 |
May 14, 2004 |
|
|
|
Current U.S.
Class: |
417/415 ;
417/437 |
Current CPC
Class: |
F04B 9/02 20130101; F04B
17/03 20130101 |
Class at
Publication: |
417/415 ;
417/437 |
International
Class: |
F04B 017/00; F04B
001/00 |
Claims
What is claimed is:
1. A drive unit, comprising: a housing; a hollow drive rod; a
motor; a screw member extending through said hollow drive rod and
operationally attached to said motor; and an internally threaded
drive member attached to said drive rod and operationally attached
to said screw member such that rotation of said screw member causes
linear displacement of said drive rod.
2. The drive unit according to claim 1, further comprising: at
least one guide member mounted to the front of said housing, said
at least one guide member having a central bore therein to allow
said drive rod to pass therethrough.
3. The drive unit according to claim 2, said at least one guide
member further comprising: a low friction seal member to form a
seal around said drive rod.
4. The drive unit according to claim 1, further comprising: a drive
plate attached to an end of said drive rod.
5. The drive unit according to claim 4, further comprising: a guide
plate rigidly attached to said drive plate; a plurality of guide
rods connected to said housing, said guide plate having a plurality
of channels to enable said plurality of guide rods to pass
therethrough.
6. The drive unit according to claim 5, wherein said drive member
is rigidly attached to said drive plate, said guide plate, and said
drive rod through a trantourque, said trantourque comprising: an
inner race; a plurality of outer races; and a plurality of
fasteners; wherein said inner race is tapered on its upper outside
half; said plurality of fasteners enables tightening of said drive
rod to said guide plate, such that said fasteners draw said inner
race into said plurality of outer races to engage said guide plate
and engage said inner race to said drive rod.
7. The drive unit according to claim 1, wherein said drive member
comprises a ball nut.
8. The drive unit according to claim 1, wherein said screw member
is operationally connected to said motor by a pulley system.
9. The drive unit according to claim 1, wherein said motor
comprises a high precision servomotor.
10. The drive unit according to claim 1, further comprising a
controller to operate said motor.
11. A fluid product delivery system, comprising: a housing; a
hollow drive rod; a motor; a screw member extending through said
hollow drive rod and operationally attached to said motor; an
internally threaded drive member attached to said drive rod and
operationally attached to said screw member such that rotation of
said screw member causes linear displacement of said drive rod; and
a piston assembly operationally attached to said drive rod, wherein
linear displacement of said drive rod causes linear displacement of
said piston.
12. The fluid product delivery system according to claim 11,
further comprising: at least one guide member mounted to the front
of said housing, said at least one guide member having a central
bore therein to allow said drive rod to pass therethrough.
13. The fluid product delivery system according to claim 12, said
at least one guide member further comprising: a low friction seal
member to form a seal around said drive rod.
14. The fluid product delivery system according to claim 11,
further comprising: a drive plate attached to an end of said drive
rod.
15. The fluid product delivery system according to claim 14,
further comprising: a guide plate rigidly attached to said drive
plate; a plurality of guide rods connected to said housing, said
guide plate having a plurality of channels to enable said plurality
of guide rods to pass therethrough.
16. The fluid product delivery system according to claim 15,
wherein said drive member is rigidly attached to said drive plate,
said guide plate, and said drive rod through a trantourque, said
trantourque comprising: an inner race; a plurality of outer races;
and a plurality of fasteners; wherein said inner race is tapered on
its upper outside half; said plurality of fasteners enables
tightening of said drive rod to said guide plate, such that said
fasteners draw said inner race into said plurality of outer races
to engage said guide plate and engage said inner race to said drive
rod.
17. The fluid product delivery system according to claim 11,
wherein said drive member comprises a ball nut.
18. The fluid product delivery system according to claim 11, said
piston assembly further comprising: a pump enclosure releasably
mounted to said housing and a pump selected from the group
consisting of: piston pumps; and diaphragm pumps.
19. The fluid product delivery system according to claim 18,
wherein said pump enclosure comprises a modular component enabling
quick-connect assembly to said enclosure.
20. The fluid product delivery system according to claim 11,
further comprising a controller to operate said motor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims benefit of
copending and co-owned U.S. Provisional Patent Application Ser. No.
60/571,327 entitled "Bench Top Pump," filed with the U.S. Patent
and Trademark Office on May 14, 2004 by the inventors herein, the
specification of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] This invention relates to fluid dispensing apparatus, and
more particularly to a modular, expandable, no-tools pump assembly
having precise computer control for regulating dispensing volumes
and flow characteristics of the dispensed fluid.
SUMMARY OF THE INVENTION
[0004] Disclosed is a modular product delivery system capable of
dispensing aqueous materials of various viscosities. The pump
assembly described herein is capable of dispensing fluids with
extremely high accuracy, in turn enabling a wider range of fill
volumes to be satisfied for a given pump size. The modular
construction enables a single drive unit to be used with pump
assemblies of varying sizes and configurations, valves of various
sizes and configurations, and even a variety of automated actuating
systems. The pump assembly described herein in suitable for use in
automatic, semi-automatic, and stand-alone operations. A
programmable controller is provided, allowing a user to input at
least dispense volumes and dispense profiles through a user
interface giving control of the product flow characteristics and
process functions. Quick-connect fasteners interconnect the modular
components of the assembly, such that no tools are required for
cleanup and there are no married pump parts. All parts for a given
pump size are interchangeable with any other pump of the same size.
The pump assembly may be manufactured from a variety of materials,
thus making it compatible with a wide range of products. Moreover,
the controller of the pump assembly is preferably capable of
working numerous peripheral devices.
[0005] The various features of novelty that characterize the
invention will be pointed out with particularity in the claims of
this application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The above and other features, aspects, and advantages of the
present invention are considered in more detail, in relation to the
following description of embodiments thereof shown in the
accompanying drawings, in which:
[0007] FIG. 1 is an exemplary drive unit for a fluid product
delivery system according to a first embodiment of the present
invention.
[0008] FIG. 2 is an elevational side view of a drive assembly
according to a first embodiment of the present invention.
[0009] FIG. 2(a) is an elevational end view of a drive assembly
according to a first embodiment of the present invention.
[0010] FIG. 3 shows a piston pump assembly according to the present
invention.
[0011] FIG. 4 shows a diaphragm pump assembly according to the
present invention.
DETAILED DESCRIPTION
[0012] The invention summarized above and defined by the enumerated
claims may be better understood by referring to the following
description, which should be read in conjunction with the
accompanying drawings. This description of an embodiment, set out
below to enable one to build and use an implementation of the
invention, is not intended to limit the invention, but to serve as
a particular example thereof. Those skilled in the art should
appreciate that they may readily use the conception and specific
embodiments disclosed as a basis for modifying or designing other
methods and systems for carrying out the same purposes of the
present invention. Those skilled in the art should also realize
that such equivalent assemblies do not depart from the spirit and
scope of the invention in its broadest form.
[0013] As shown in the front, top, and side sectional views of FIG.
1, an exemplary drive unit for a fluid product delivery system
according to a first embodiment of the invention includes a pump
housing 10, a linearly extending drive rod 20 configured for
generally horizontal movement out of and into housing 10, and a
programmable controller 30 in communication with a drive motor 40,
the drive motor 40 being mechanically connected to drive rod 20
through a drive assembly so as to execute linear displacement of
drive rod 20 as desired.
[0014] As shown more particularly in the cross-sectional view of
FIG. 2, drive rod 20 comprises a rigid, hollow shaft extending
between a drive plate 21 and a front face 11 of housing 10. In FIG.
2, drive rod 20 is particularly depicted at a rear-most "home"
position. Extending through drive rod 20 is a screw member 50
rotatably mounted within housing 10. A rear end of screw member 50
is attached to a drive pulley 60, such that rotation of drive
pulley 60 in turn causes rotation of screw member 50. Positioned to
ride along screw member 50 is internally threaded drive member 51,
preferably in the form of a ball nut. As will be explained, the
angular orientation of drive member 51 is fixed with regard to
housing 10, such that rotation of screw member 50 causes linear
displacement of drive member 51 along screw member 50 in a
direction determined by the direction of rotation of screw member
50.
[0015] A guide member 70 is mounted to front face 11 of housing 10,
and is provided a central bore therein allowing drive rod 20 to
pass therethrough. As the position of guide member 70 is fixed with
regard to front face 11 of housing 10, it provides a guide for the
front end of drive rod 20 as it moves linearly into and out of
housing 10. A seal member 71 is provided external to guide member
70 positioned within a circular groove in the front face of
faceplate 75. Seal member 71, preferably in the form of a spring
loaded cup seal, has an inner diameter and an outer diameter with a
thickness corresponding to a groove in front face 11. The inner
diameter of seal member 71 is such that it forms a closed circle
around drive rod 20 closing off any path that liquid could pass by
seal member 71, serving to prevent residual liquid from entering
housing 10 through front face 11 during cleanup. The outer diameter
of seal member 71 fits tightly in the groove of front face 11, thus
securing seal member 71 so that linear movement of drive rod 20
does not displace seal member 71. A spring located between the
inner and outer diameter of seal member 71 adds additional squeeze
pressure against the inner diameter of seal member 71. The seal
member 71 is preferably made of Teflon, creating a low friction
surface allowing drive rod 20 virtually unrestricted linear
movement while maintaining a liquid tight seal.
[0016] Referring to both FIGS. 2 and 2a, drive plate 21 is rigidly
affixed to a guide plate 22. Guide plate 22 is provided a plurality
of channels through which guide rods 23 pass. Guide rods 23 are
likewise rigidly connected to housing 10, preferably via threaded
connectors or similarly fashioned fasteners 23a joining a front end
of guide rods 23 to front face 11, and back end of guide rods 23 to
a support plate 25 positioned near the back of drive unit enclosure
10. Optionally, a bearing 23b may be provided in each such channel
surrounding the respective guide rod 23 to assist linear movement
of guide plate 22 along guide rods 23. Screw member 50 likewise
extends through support plate 25, and is likewise optionally
supported therein by one or more bearings 50a.
[0017] Guide plate 22 and guide rods 23 help assure precise,
strictly linear movement of drive rod 20 out of and into housing 10
when motor 40 is actuated. Drive member 51 is rigidly attached to
drive plate 21, guide plate 22, and drive rod 20 through trantorque
17. The trantorque 17 is comprised of 5 pieces, nut 202, inner race
201 and 3 outer races 200. The nut 202 has a hexagonal outer form
to accept a standard English wrench. The hex allows for tightening
in order to secure the drive rod 20 to guide plate 22. The nut 202
has internal thread and the inner race 201 has mating external
threads. The inner race 201 is also tapered on the upper outside
half such that rotating the nut 202, while engaged with the threads
of the inner race 201, pulls the inner race 201 up towards the top
of nut 202, forcing the taper to move inside the 3 outer races 200.
As the taper contacts outer races 200, they are forced outward,
against guide plate 22. The inner race 201 has slots to allow for
compressing as the outer races 200 engage the guide plate 22. When
the outer races 200 engage the guide plate 22, it compresses the
inner race 201 thus engaging the drive rod 20. The nut 202 is
continually rotated until inner race 201 and outer races 200 fill
the gap between the drive rod 20 and guide plate 22. The taper on
the inner race 201 creates a locking force keeping the nut 202 from
rotating. With the nut 202 tightened and all gap removed between
the drive rod 20 and guide plate 22, the drive rod 20 is secured to
the guide plate allowing no independent movement. Because drive
member 51, drive plate 21, guide plate 22, and drive rod 20 are
thus all rigidly affixed to one another, they form a unitary block
structure that moves as a single unit upon rotation of screw member
50, which eliminates the risk of slippage and associated
inadvertent and unwanted displacement of drive rod 20. Rotation of
screw member 50 in even miniscule increments causes an associated,
minute linear displacement of drive plate 21 and drive rod 20, thus
allowing greater control of displacement of a piston external to
the drive unit, and thus greater control over dispensed volumes.
With no mechanical inefficiencies in the connection point from the
drive rod 20 to the drive member 51, the linear movement of the
drive rod 20 with respect to the drive member is calculatingly
repeatable.
[0018] In order to rotate screw member 50, motor 40 is preferably
utilized to rotate a first drive pulley 45. First drive pulley 45
is operatively connected to drive pulley 60 through a drive chain
member, such as drive belt 46. Optionally, drive pulleys 45 and 60
may be provided in sizes customized for a particularly desired
dispensing configuration to deliver the optimum power for products
being dispensed. Further, to ensure micro control of the linear
displacement of drive rod 20, and thus of the volume to be
dispensed, motor 40 preferably comprises a high precision
servomotor. By way of example only, and not by way of limitation,
motor 40 may comprise an Allen Bradley type Y series motor.
Notably, any servo motor that can be given an analog or digital
signal, interpret the signal into an angular displacement, and,
through means of an encoder or resolver, monitor and compare the
angular displacement against the input signal thus confirming that
the position the motor was commanded to go to is in fact the
position it has reached, will suffice, provided the resolution of
the angular position and the encoder/resolver meet the precision
required by the system.
[0019] As particularly shown in FIG. 2, drive rod 20 is preferably
equipped with a threaded stud 24 at the end that extends outside of
housing 10. As will be discussed in greater detail below, threaded
stud 24 is configured to receive an internally threaded piston
member for use in a modular cylinder assembly for use with the
aforementioned drive unit.
[0020] Mounted to front face 11 of housing 10 is a faceplate 75
through which drive rod 20 extends and travels during its linear
displacement. While not particularly shown in FIG. 2, faceplate 75
is preferably provided a plurality of externally facing threaded
bores for receiving threaded members used to attach modular
components to the exterior of housing 10, as will be described.
[0021] Referring again to FIG. 1, a position sensor 80 is mounted
at a fixed position within drive housing 10 so as to establish a
"home" reference position for the piston rod. By way of example
only and not by way of limitation, position sensor 80 may comprise
a proximity switch model AE1-AP-4F from Automation Direct. For
instance, position sensor 80 may be mounted immediately adjacent
the path of travel of guide plate 22 so as to detect the presence
of guide plate 22 when it reaches its predetermined home position.
As guide plate 22 is rigidly attached to drive rod 20, such home
position of guide plate 22 likewise indicates home position of
drive rod 20, and thus of a piston attached to drive rod 20
external to housing 10. A second sensor of the same type described
above may be mounted at the full travel position of guide plate 22.
This sensor may be used to initiate a stop condition should the
guide plate 22 travel past its stop limit position.
[0022] A significant advantage of the construction of the fluid
product delivery system of the instant invention is its modular
construction enabling the quick-connect assembly and disassembly of
pump members from the drive unit. Such quick connect assembly and
disassembly provides a pump construction having no married parts,
thus easing adaptability to various pumping requirements and easing
maintenance by allowing separate pump cylinder, piston, and valve
assemblies to be quickly removed for cleaning, maintenance, and
replacement.
[0023] As shown in FIG. 3, a preferably machined cylinder 100 is
provided. Cylinder 100 is preferably machined to allow, if
required, the ability to modify the dimensions of the pump for
custom fit applications and/or future enhancements. The base of
cylinder 100 is preferably provided a skirt 110 having a plurality
of boreholes 111 extending therethrough. Skirt 110 is sized so as
to fit on face plate 75 mounted to front face 11 of housing 10,
with bore holes 111 aligned with threaded bores on the external
surface of face plate 75. A plurality of hand-tightening screws
(not shown) are provided, the threaded shafts of which extend
through bore holes 111 in skirt 110 and into the threaded bores on
the external surface of face plate 75, such that mere hand
tightening of such screws is sufficient to clamp cylinder 100 to
drive housing 10. Cylinder 100 is provided an internal chamber 120
through which a preferably multilayer piston 130 travels. Piston
130 is provided a central threaded bore configured to receive
threaded post 24 on the end of drive rod 20. The layers of piston
130 preferably comprise multiple layers of rubber and plastic so as
to allow easy assembly and cleaning as well as an ability to accept
various types of seal materials so that the seals will be
compatible with the product being dispensed. A generally cup-shaped
cap 140 is provided on an outside end of cylinder 100. Cap 140 is
provided at least two boreholes 141 to allow fluid access into and
out of cylinder 100 when fully assembled. Preferably press-fit into
boreholes 141 are channel members 150. Press fit is preferred so
that no other type of material comes in contact with the channel
members 150 and cap 140, providing purity at the connection point.
However, the channel members 150 may be welded and chemically
treated to an acceptable purity level. The latter welding and
treatment process though, increases the number of operations
required to fabricate the cap 140 making it more costly. Attached
to channel members 150 are fluid inlet and outlet connectors 142
and 143, respectively. One-directional valves of typical
construction, such as those manufactured by Intellitech, part #
200-00000009, utilizing umbrella style seals that open in the
direction of applied pressure, are preferably situated on each
inlet and outlet so as to allow one directional flow of fluid into
and out of internal chamber 120.
[0024] As mentioned above, an important advantage of such assembly
is its modular construction. Using a single drive unit, cylinders
having various diameters but a uniform skirt 110 may be provided
for different pumping applications. Likewise, different caps 140
may be provided. Channel members 150 and inlet and outlet
connectors 142 and 143, respectively, of varying geometries may be
provided to suit particular dispensing needs. As the system is
modular in construction and enables quick connect and disconnect of
such components, the system may be readily adapted to varying
dispensing requirements. To effect such quick connect and
disconnect function, manually operable quick connect clamps 160 are
provided, for example, clamps commercially available from VNE as
type 102-HDC-.50, to attach cap 140 to cylinder 100, and to connect
each of inlet connector 142 and outlet connector 143 to their
respective channel members 150. Preferably, compressible sealing
members, such as O-ring seals 165, are provided at the connection
point between cap 140 and cylinder 100, and between each inlet and
outlet connector 142 and 143 and their respective channel members
150.
[0025] As an alternative to the piston pump shown in FIG. 3, a
diaphragm pump assembly may likewise be provided as shown in FIG.
4. Once again, a piston 130 is provided having a threaded opening
configured to receive threaded stud member 24. A flexible diaphragm
assembly of traditional construction (shown generally at 170) is
provided, mounted between cap 140 and cylinder 100. Such diaphragm
pump assembly is particularly advantageous in pumping applications
in which particulate is not acceptable in the product being
dispensed. The diaphragm is moved back and forth by a piston 130
located outside the product contact area of the diaphragm. The
diaphragm does not rub against the walls of the cylinder 100 or the
cap 140, thus eliminating friction that could cause particles to
separate from the diaphragm and mix with the product. As with the
assembly of FIG. 3, the base of cylinder 100 is preferably provided
a skirt 110 having a plurality of bore holes 111 extending
therethrough. Skirt 110 is again sized so as to fit on face plate
75 mounted to outside face 11 of housing 10, with bore holes 111
aligned with threaded bores on the external surface of face plate
75. A plurality of hand-tightening screws (not shown) are provided,
the threaded shafts of which extend through bore holes 111 in skirt
110 and into the threaded bores on the external surface of face
plate 75, such that mere hand tightening of such screws is
sufficient to clamp cylinder 100 to drive housing 10. Once again,
cap 140 is provided at least two channel members 150 to allow fluid
access into and out of cylinder 100. Attached to channel members
150 are fluid inlet and outlet connectors 142 and 143,
respectively. One-directional valves of typical construction are
again preferably situated on each inlet and outlet so as to allow
one directional flow of fluid into and out of internal chamber 120.
The diaphragm pump assembly likewise maintains the above-described
quick connect and quick disconnect functionality, including
manually operable quick connect clamps 160 to attach cap 140 to
cylinder 100, and to connect each of inlet connector 142 and outlet
connector 143 to their respective channel members 150. Once again,
compressible sealing members, such as O-ring seals 165, are
preferably provided at the connection point between cap 140 and
cylinder 100, and between each inlet and outlet connector 142 and
143 and their respective channel members 150.
[0026] The above-described construction has been found to provide
significant benefit over prior known dispensing apparatuses, in
that it provides for a modular assembly lacking married pump parts
that complicate even routine maintenance. The modular structure
described above with quick connect clamps allows the system to be
readily adapted to particularly dispensing operations, and enables
easy disassembly of components that come in contact with the
working fluid to ease maintenance. Further, the linear ball screw
drive construction provides for significantly improved control over
linear displacement of the piston external to the pump housing
10.
[0027] Of course, in order to move drive rod 20 to any extent,
servomotor 40 must be operated to rotate screw member 50.
Programmable controller 30 is provided to precisely control such
activation.
[0028] More particularly, the controller 30 allows a user to
program instructions to the motor 40 to control fluid intake and
fluid discharge entirely independent of one another, thus providing
the user unlimited ability to control the flow characteristics of
the product being dispensed, and more particularly allowing the
user to customize such operation for the particular delivery system
and collection device in use. For both intake and discharge, a user
may input a desired acceleration value (i.e., the acceleration of
piston 130 as it travels through cylinder 100), a desired
deceleration value, and a velocity value for when the piston is at
speed. In addition to these values, an operator is likewise
prompted to input pump size, dispense volume, and optionally other
parameters that may affect motion or overall cycle of the piston
130. An appropriate scaling factor is applied to the parameters
input by the user to translate the desired dispensing volumes and
acceleration, deceleration, and velocity settings to specific
instructions configured for driving the motor, based upon the screw
pitch of screw member 50, the gear ratio between the motor 40 and
the screw member 50, and the amount of fluid that will be displaced
by a given linear movement of the piston 130 as a result of a given
rotation of screw member 50 (as determined by the geometry of the
modular components attached to the drive housing 10). Of course,
such scaling factor is a matter of geometry, and thus the
particular value of such scaling factor may be readily determined
once based on the geometry of the above-described elements.
[0029] In some embodiments, programmable controller 30 may comprise
a touch sensitive key pad, as illustrated. In some embodiments, the
controller 30 may comprise a remote personal computer having data
storage capability to record information concerning operation of
the drive unit and attached pump components.
[0030] Such programmable control of motor 40 enables precise
control of dispensing volumes and of overall flow characteristics
of the fluid being dispensed. For instance, if a product delivery
system is located below the pump described herein, an operator may
adjust acceleration, velocity, and deceleration on the intake
stroke to accommodate for the need to pull product into the pump.
Likewise, if the product is located above the pump, an operator may
again adjust acceleration, velocity, and deceleration on the intake
stroke to compensate for the resulting in-feed pressure. Similarly,
a user may vary discharge fluid flow characteristics based on the
container into which the fluid is to be dispensed. For instance, if
a container has a wide base that funnels down to a narrow neck and
opening area, the user may reduce velocity and deceleration as the
product enters the neck, thus reducing the opportunity of overflow
of the product.
[0031] Again, each of the flow characteristics input by the user
may effect actual movement of the piston 130 by translating those
characteristics into a drive signal that is sent to motor 40. Given
the pitch of screw member 50, the gear ratio between motor 40 and
screw member 50, and the resolution of a motor feedback device
(i.e., any device capable of generating an accurate electronic
pulse representing a distance mark that can be interpreted by the
controller), the exact displacement of drive rod 20 may be
determined for a given rotation of the motor 40. More particularly,
such control is accomplished by an encoder mounted to the motor. An
encoder sends out pulses as it rotates. Depending on the resolution
of the encoder, i.e., the number of pulse segments per revolution,
one may determine the angular position of the motor shaft by
dividing one revolution by the encoder resolution. For example,
assuming an encoder has a resolution of 1000, one revolution of the
motor feeds back 1000 pulses or counts. If the ball nut of drive
member 51 has a 10 mm pitch, and the belt drive has a 1 to 1 ratio,
then for every revolution, or 1000 pulses, the piston rod mounted
to the drive member 51 will move 10 mm, thus enabling exact
determination of the displacement of drive rod 20 for a given motor
rotation. By controlling motor 40, displacement of drive rod 20,
and thus of piston 130, is likewise controlled. Based, in turn, on
the geometry of the pump housing (cylinder 100, cap 140, etc.), a
user may readily determine the precise volume of fluid that will be
dispensed for a given angular displacement of motor 40 (and ensuing
linear displacement of drive rod 20). Based on this mathematical
analysis, an appropriate scaling factor, as discussed above, may
readily be determined for varying pump configurations. By providing
a control system that adapts dispensing characteristics based upon
geometry of the drive and pump elements and the desired fluid flow
characteristics of the product to be dispensed, a user may
accurately determine and control the volume dispensed by a pump and
maintain a repeatable accuracy level, and likewise utilize a single
pump assembly for dispensing products of highly varying viscosities
and other characteristics.
[0032] By way of example, in order to dispense protein product, it
is typically desirable to begin moving product slowly, keep it
moving at a steady velocity, and slow it down to a controlled stop,
so as to keep the shear effect on the fluid at an acceptable
minimum and thus prevent damage to the protein in the fluid. Using
a system in accordance with the instant invention, during intake,
fluid is pulled into chamber 120 until the stroke of drive rod 20
stops. The rearward movement of drive rod 20, and resulting
rearward movement of piston 130 within chamber 120, creates a
vacuum in the fluid tubing causing the fluid to begin moving in the
direction of the vacuum source. If such intake proceeds too
quickly, the shear forces created by so moving the fluid could
damage the protein material and cause the fluid to cavitate, in
turn leaving holes in the fluid path and causing an inaccurate
amount of fluid to accumulate in the pump chamber, resulting in an
inaccurate volume of fluid being dispensed. A user may, through
controller 30, input an appropriate acceleration that will
gradually begin moving the fluid, thereby reducing the shear effect
and cavitation. The user may also input a velocity value to
maintain a constant flow rate once the fluid starts moving. As the
pump reaches the end of its intake cycle, it is desirable not to
abruptly stop the fluid motion, as this will also affect the shear
properties of the fluid being dispensed. Moreover, because the flow
path changes as the product enters the pump chamber 120, it is
again desirable to change the rate of flow to decrease the shear
effect. Accordingly, the user may also input a deceleration value
to slow the flow of fluid as it enters pump chamber 120, until
piston 130 stops its intake stroke. With regard to dispensing such
a protein product, it remains desirable to start moving the fluid
slowly as it is dispensed from chamber 120, keep it moving at a
steady velocity, and slow it down to a controlled stop, so as to
keep the shear effect on the fluid at an acceptable minimum so as
to not damage protein in the fluid. Moreover, excessive speed in
dispensing fluid from chamber 120 may result in the fluid hitting
the collection container with enough force to splash out of the
container, in turn causing an inaccurate fill, as well as spilled
product. The user is prompted, before beginning the dispensing
operation, to input an acceptable acceleration that will gradually
begin moving the fluid, thereby reducing the shear effect and
dispensing force. The user likewise inputs a velocity value to
establish a constant flow rate during dispensing of the fluid.
Still further, the user may input a deceleration value such that,
as the piston reaches the end of its discharge cycle, it does not
abruptly stop the fluid motion and result in excess shear stress on
the fluid. Such versatility and control of fluid flow
characteristics enables a single system constructed pursuant to the
invention herein to be used for dispensing fluids of highly varied
viscosities without requiring substitution of the pump or drive
assembly.
[0033] The invention has been described with references to a
preferred embodiment. While specific values, relationships,
materials and steps have been set forth for purposes of describing
concepts of the invention, it will be appreciated by persons
skilled in the art that numerous variations and/or modifications
may be made to the invention as shown in the specific embodiments
without departing from the spirit or scope of the basic concepts
and operating principles of the invention as broadly described. It
should be recognized that, in the light of the above teachings,
those skilled in the art can modify those specifics without
departing from the invention taught herein. Having now fully set
forth the preferred embodiments and certain modifications of the
concept underlying the present invention, various other embodiments
as well as certain variations and modifications of the embodiments
herein shown and described will obviously occur to those skilled in
the art upon becoming familiar with such underlying concept. It is
intended to include all such modifications, alternatives and other
embodiments insofar as they come within the scope of the appended
claims or equivalents thereof. It should be understood, therefore,
that the invention may be practiced otherwise than as specifically
set forth herein. Consequently, the present embodiments are to be
considered in all respects as illustrative and not restrictive.
* * * * *