U.S. patent number 3,740,173 [Application Number 05/181,052] was granted by the patent office on 1973-06-19 for peristaltic pump.
This patent grant is currently assigned to Rohe Scientific Corporation. Invention is credited to Samuel Natelson.
United States Patent |
3,740,173 |
Natelson |
June 19, 1973 |
PERISTALTIC PUMP
Abstract
A peristaltic pump wherein a roller drum is made to engage a
curved press plate, the roller drum acting on tubing passing
between the drum rollers and the press plate, the press plate has
at least two longitudinal ridges normal to the drum rollers to
prevent said drum rollers from pressing the tubing beyond its
elastic limit. A guide and resilient means are applied to the press
plate allowing the press plate freedom of movement and permitting
the press plate to adjust to the configuration of the tubing. A
flexible belt which is spring loaded covers the drum rollers to
produce a smooth peristaltic motion on the tubing.
Inventors: |
Natelson; Samuel (Chicago,
IL) |
Assignee: |
Rohe Scientific Corporation
(Santa Ana, CA)
|
Family
ID: |
22662703 |
Appl.
No.: |
05/181,052 |
Filed: |
September 16, 1971 |
Current U.S.
Class: |
417/475; 101/365;
417/477.11 |
Current CPC
Class: |
F04B
43/1284 (20130101); F04B 43/1292 (20130101) |
Current International
Class: |
F04B
43/12 (20060101); F04b 043/08 (); F04b 043/12 ();
F04b 045/06 () |
Field of
Search: |
;417/477,475,412
;308/184R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Gluck; Richard E.
Claims
I claim:
1. A peristaltic pump, comprising in combination:
a. a housing including spaced apart tube supports for holding
tubing between said supports;
b. a drum rotor member with a central drive shaft to drive said
drum rotor member disposed between said tube supports, the drive
shaft being disposed normal to tubing extending between said tube
supports, with rollers disposed around the periphery of said drum
rotor member parallel to said drive shaft so as to engage tubing
extending between said tube supports, also bearing assemblies
including a flexible inner center disposed in said housing to
support said drive shaft for rotation;
c. a floating arcuate press plate, said press plate forming a
section of a cylinder whose axis somewhat coincides with said drum
axis, the concave side of said press plate being disposed over said
drum rotor member and generally conforming to the curvature of said
drum rotor member, said press plate serving to hold tubing against
said rollers, said press plate having at least two arcuate
longitudinal ridges parallel to tubing extending between said tube
supports, said ridges preventing the tubing from being pressed
beyond its elastic limits; and,
d. extended support means disposed over said press plate and
connected to said housing, said press plate connected to said
support means by loose connecting means allowing said press plate
considerable movement up and down and from side to side over a wide
space, whereby when the drum rotor member rotates, the rollers pass
over the flexible tubing successively to drive liquid in the
flexible tubing in the same direction as the motion of the rotor,
the press plate assuming different positions so as to conform to
variations in the height and position of said rollers, the press
plate floating while being spring loaded, correcting for lack of
alignment and circularity of the drum rotor member.
2. A pump as claimed in claim 1, said ridges being substantially
along the press plate edges.
3. A pump as claimed in claim 1 wherein said loose connecting means
comprises at least one large opening in said support means, at
least one thin connecting rod extending from said press plate side
other than said concave side through said opening for substantial
up and down and side to side movement therein, and, said resilient
means being between said press plate other side and said extended
support means.
4. A peristaltic pump as claimed in claim 1, including a frame, a
flexible sheet of material covering said drum rollers so disposed
as to be between said drum rollers and tubing acted upon by said
drum rollers, and resilient means fastened to said frame holding
said sheet over said drum rollers.
5. A peristaltic pump, comprising in combination:
a. a housing including spaced apart tube supports for holding
tubing between said supports;
b. a drum rotor member with a central drive shaft to drive said
drum rotor member disposed between said tube supports, the drive
shaft being disposed normal to tubing extending between said tube
supports, with rollers disposed around the periphery of said drum
rotor member parallel to said drive shaft so as to engage tubing
extending between said tube supports, also bearing assemblies
including a flexible inner center disposed in said housing to
support said drive shaft for rotation;
c. a floating arcuate press plate, said press plate forming a
section of a cylinder whose axis somewhat coincides with said drum
axis, the concave side of said press plate being disposed over said
drum rotor member and generally conforming to the curvature of said
drum rotor member, said press plate serving to hold tubing against
said rollers; and,
d. extended support means disposed over said press plate and
connected to said housing, said press plate connected to said
support means by loose connecting means allowing said press plate
considerable movement up and down and from side to side over a wide
space, whereby when the drum rotor member rotates, the rollers pass
over the flexible tubing successively to drive liquid in the
flexible tubing in the same direction as the motion of the rotor,
the press plate assuming different positions so as to conform to
variations in the height and position of said rollers, the press
plate floating while being spring loaded, correcting for lack of
alignment and circularity of the drum rotor member.
6. A peristaltic pump, comprising in combination:
a. a housing including spaced apart tube supports for holding
tubing between said supports;
b. a drum rotor member with a central drive shaft to drive said
drum rotor member disposed between said tube supports, the drive
shaft being disposed normal to tubing extending between said tube
supports, with rollers disposed around the periphery of said drum
rotor member parallel to said drive shaft so as to engage tubing
extending between said tube supports, also bearing assemblies
disposed in said housing to support said drive shaft for
rotation;
c. a floating arcuate press plate, said press plate forming a
section of a cylinder whose axis somewhat coincides with said drum
axis, the concave side of said press plate being disposed over said
drum rotor member and generally conforming to the curvature of said
drum rotor member, said press plate serving to hold tubing against
said rollers; and,
d. extended support means disposed over said press plate and
connected to said housing, said press plate connected to said
support means by loose connecting means allowing said press plate
considerable movement up and down and from side to side over a wide
space, whereby when the drum rotor member rotates, the rollers pass
over the flexible tubing successively to drive liquid in the
flexible tubing in the same direction as the motion of the rotor,
the press plate assuming different positions so as to conform to
variations in the height and position of said rollers, the press
plate floating while being spring loaded, correcting for lack of
alignment and circularity of the drum rotor member.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a peristaltic pump, and more
particularly to a constant volume peristaltic pump.
BRIEF REVIEW OF THE PRIOR ART
The peristaltic pump has been in use for over 300 years. Some of
these pumps have been described by the present inventor in U.S.
Pat. Nos. 3,305,097; 3,450,624; 3,495,541; 3,331,665 and 3,489,525.
The advent of automatic systems of chemical analysis set up the
requirement that peristaltic pumps be developed so as to pump
fluids in a continuous manner at constant speeds for long periods
of time. While many versions of this pump were developed, only one,
where the rollers move across a flat bed, has been successful with
regard to constant volume. These pumps are expensive and difficult
to make because of the requirement that the roller milking the
tubing move on a horizontal plane. It is more economical to build
the rollers as part of a wheel, like a squirrel cage. A motor can
then drive this wheel with the mounted rollers at constant
speed.
Numerous pumps have appeared using this principle (see Natelson
U.S. Pat. No. 3,489,525, FIG. 1). None have actually been
successful except for use as a pump where constant delivery of
volume was not a requirement. Volumes are irregular and volumes
keep changing with time. In order to maintain constant volumes in a
rotary peristaltic pump certain requirements are necessary.
1. The tubes must not be subject to excessive pressure. If the
elastic limit is reached they will not return to their original
shape when the pressure is released.
2. The pressure must be adequate to seal the tube as the roller
passes over the tube to maintain forward motion.
3. It is almost impossible for rollers to be disposed in a perfect
circle. The surface on which the tube rests, and over which the
roller rolls must also be a perfect circle. In addition, the
surface and the rollers need to be aligned so that the tubing is
not caused to be distorted sideways. Some mechanism needs to be
supplied to satisfy these requirements.
4. The pressure on the tubing needs to be constant at all times and
not vary during the running of the rollers over the tubing. The
operator must automatically be able to set to the same pressure as
in the previous run if results are to be duplicated.
The present invention solves these problems in a simple fashion, so
that an inexpensive pump can be built at a low cost which will
operate on as many tubes, simultaneously, as desired (e.g. 30
tubes) keeping a constant flow continuously, over extended periods
of time.
SUMMARY OF THE INVENTION
Briefly stated the present invention contemplates an improvement in
a peristaltic pump wherein a roller drum is made to engage a curved
press plate, said roller drum acting on tubing passing between the
drum rollers and the press plate. The improvement contemplated
herein is that the press plate has at least two longitudinal ridges
normal to the drum rollers to prevent said drum rollers from
pressing the tubing beyond its elastic limit. A guide and resilient
means are applied to the press plate allowing the press plate
freedom of movement in all possible directions, thus permitting the
press plate to adjust to the configuration of the tubing.
The invention, as well as other objects and advantages thereof will
become apparent from the following detailed description when taken
together with the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 presents an overall perspective view of one version of the
assembled pump;
FIG. 2 shows a view of the pump from the side opposite to FIG. 1
with the cover removed so that the rollers can be seen in place on
the rotor shaft; the tubing is also in place, held in plastic
plates with grooves;
FIG. 3 depicts the rotor with the rollers disposed in a circular
mode so that they revolve with the rotor shaft and can also rotate
on their axles as they move across the tubing;
FIG. 4 illustrates the pump press plate from the top;
FIG. 5 is a view of the press plate from the bottom;
FIG. 6 shows the plastic supports and the mechanism for mounting
the supports on the pump housing;
FIG. 6a shows a perspective view of one of the crosspieces used
herein when turned upside down; and
FIG. 6b is a cross-sectional of the tubing in the press plate of
the pump being squeezed by a roller;
FIG. 7 shows how a spring loaded flexible belting is disposed over
the rollers to even out the pressure to the tubes being milked.
Looking first at FIG. 1, there is shown in the drawing the pump 10,
which includes a frame or housing shown as a rectangular box 12.
The pump 10 will act on plastic tubing 14 which is held in plastic
tubing support 16. Plastic tubing support 16 consists of
rectangular plastic pieces which extend along both ends of the top
of box 12. Tubing support 16 has horizontal grooves 18, the tubing
14 passing along these grooves. Thus, the plastic tubing 14 extends
across the top of box 12 and passes out of the tubing support.
Plastic or rubber stops 20 hold the tubing in place. Disposed over
the plastic tube support 16 is a metal crosspiece 22. This metal
crosspiece goes over the ends of the box and its size corresponds
to that of the plastic support. Again, over the metal crosspieces
22 are metal supports 24. These metal supports extend parallel to
the sides of the box and extend between the two metal crosspieces.
To hold the plastic tube support 16, the metal crosspieces 22 and
the metal supports 24 are threaded rods 26 at the four corners of
the box. The plastic tube support, metal crosspieces and metal
supports have apertures 26a corresponding to the location of these
threaded rods. These components are held fast by wing nuts 28. Over
the center of the box is a center crosspiece 30 held by a metal rod
32 with a flat top 34. Seen on the outside of the housing box 12 is
a drive shaft 36 with a sprocket 38 for motor drive. This drive
shaft is connected into the box by a bearing assembly 40.
In FIG. 2 the cover of box 12 is removed and one of the sides with
the input shaft 36 is rendered transparent. Also, the plastic tube
support 16 is shown with grooves 18 to hold the plastic tubing. In
the center of box 12 there is a drum 44 mounted on drive shaft 36.
Around the periphery of drum 44 are a plurality of rollers 46
disposed parallel to the cylindrical axis of the drum. The tubing
14 is curved over the rollers and the action of the rollers 46 on
the tubing 14 defines a pressing zone. Drum 44 is best seen in FIG.
3, and consists of two end plates 48 holding rollers 46, with the
main shaft 36 passing axially through the drum, the end plates are
rigidly attached to the shaft. At both ends of the main shaft 36
are bearing assemblies 40. These bearing assemblies are for roller
bearings 50. But, beside the conventional outer and inner races,
there is a flexible rubber center 52. This rubber or resilient
center is very important for reasons which will be apparent
shortly. The drive sprocket 38 is in turn driven by a chain 54, and
a motor 56 driving a sprocket 58.
Disposed over the tubes, as shown in FIGS. 4 and 5, is a press
plate 60. This press plate 60 is a section of a cylinder and will
hold the tubes against the rollers. Over the press plate 60 is the
metal support 24 held by crosspieces 22. At the center is center
crosspiece 30 shown transparent to explain the construction.
Passing through the press plate are vertical metal rods 32 with a
flat head 34. Under the center crosspiece 30 on these rods, between
the metal support 24 and the press plate 60 are springs 62. Rods 32
pass through both the center crosspiece 30 and the metal support 24
through apertures 64. These apertures 64 are quite wide allowing
considerable lateral movement of the rods 32. Looking at the press
plate from the underside, as shown in FIG. 5, there is a ridge 66
about 3/64 inch along the sides and across the center of the press
plate extending downwards. This ridge is parallel to the direction
in which the tubing will pass.
The placing of the tubing in the pump will be apparent from FIGS. 6
and 6a. The tubing 14 is stretched across the box and the plastic
tube supports 16 are placed over the tubing. These tube supports 16
have slots or grooves 18, best seen in FIG. 6a.
FIG. 7 illustrates an attachment which serves to decrease the wear
on the tubing carrying the specimen and allows a smoother action of
the pump. 70 is a 3/64 inch thick sheet of high speed belting. The
rough side faces the rollers and the smooth side is on top. This
belting wraps around the rotor and is supported on the base of the
pump housing by springs 71. As the drum 44 turns, the rollers 46
are made to rotate on their axes by contact with belting 70. When
the pump is assembled as shown in FIG. 1, the tubing will be
compressed between the belting and floating head. As the drum
rotates the rollers traverse to the underside of the belting,
lifting it and thus progressively applying pressure to the tubes
causing a smooth peristaltic action. In this version the wear is
taken mostly by the durable high speed belting, thus increasing the
life of the tubes.
The fundamental concept behind the present invention is that the
press plate 60 will float over the tubing. After lengthy studies of
the causes of pumping difficulties with peristaltic pumps, it was
found that the press plate must constantly adjust to the tubing and
must therefore float over the tubing. For this reason, apertures
26a for the end crosspieces, and aperture 64 for rod 32 at the
center crosspiece, are quite wide allowing for considerable
forward, backward, and lateral movement of the press plate.
Furthermore, the ball bearing assembly 40 has a rubber resilient
center 52, which also allows considerable movement of the drum when
pressing the press plate against the tubing. To enhance the
floating effect the press plate over the tubing is spring loaded by
springs 62 and floats freely so that it can adjust, in three
dimensions to the vagaries of the squirrel cage wheel. Two or even
four powerful springs apply adequate pressure to close the tubes as
the rollers move across them. This requires about 7 pounds per
tube, or a total of 84 pounds. The press plate over the tubes is
recessed exactly 3/64 of an inch so that the tubes can be
compressed with this thickness as a limit. This prevents the
pressure on the tubes beyond their elastic limit and assures a long
life of constant delivery from these tubes. The wall thickness of
the tubing used is 3/64 inch so that the two walls together make
6/64 inch. The design of the cover and the instrument in general is
simple so that its total cost is very inexpensive, and this
includes a 30 r.p.m. motor with a brake, capable of delivering 100
pounds per square inch pressure. This is shown in FIG. 6b, showing
the press plate 60 with the ridge 66 and the tubing 14 in
cross-section. The roller cannot compress the tubing past the 3/64
inch ridge.
OPERATION OF THE PUMP
In order to operate the pump, the tubing is placed in the slots of
two plastic supports and stretched so that the supports can be
slipped over the threaded rods as seen in FIG. 6. The pump now
appears as in FIG. 2, with the plastic tubing stretched over the
rollers. The press plate is now secured in place by slipping the
apertures at the corners of the supports of the press plate, over
the threaded rod and tightening the press plate and support in
place by means of the wing nuts. The instrument now appears as in
FIG. 1.
The wing nuts are now tightened fully so that the two crosspieces,
at the end of the press plate support, meet the plastic tube
support which acts as a stop. This compresses the springs. The
position taken each time and the tension on the springs is the same
since the top support is always necessarily tightened to the same
point where crosspiece and plastic tubing support meet flush, thus
acting as a stop.
The speed of the rotor is determined by the r.p.m. of the motor and
the ratio of the teeth on the sprocket of the rotor and the motor.
Speed may be changed by changing the motor speed or the teeth ratio
of the sprockets. This can be seen in FIG. 3. It will also be noted
in FIG. 3 that the rotor shaft is disposed on a ball bearing
support so that it rotates smoothly but is also supported on the
semi-hard rubber center support so that it has some give to it when
pressure is applied to the rotor.
When the motor is turned on, the press plate is seen to rock gently
as it takes up irregularities of the rotor, it also swivels
laterally. Thus, the rotor "floats" while being spring loaded,
correcting for the lack of alignment and circularity of the rotor.
The tubing needs to be at right angles to both the rotor and the
press plate. Any error in the location of the press plate relative
to the rotor in this regard is automatically corrected as the press
plate takes the position of least resistance. The tubes are pressed
gently but never mashed because of the protection the ridges (3/64
inch) provide. Thus the plastic tubes are compressed but not
pressed to the point beyond their elastic limit.
In running a plastic pump, the first few minutes is taken up in
stretching the tubing to a point of balance. During this period the
rate of flow increases as the tubing is compressed and resistance
to the motor decreases, the motor running faster as the load
decreases. After this point of balance is reached the pump
described will pump for many hours at constant speed.
For simplicity of demonstration, the press plate is shown tightened
down with wing nuts. In actual practice the support of the press
plate is fitted on the end with clamps similar to those which close
a valise or travel trunk. The press plate support is then placed on
the pump, and the four rods mounted on the housing are slipped
through the holes at the end as a guide. The clamps are then
tightened down on catches on the housing as one closes a valise or
travel trunk for a quick connect or disconnect, if one should so
desire.
Thus, this invention solves a problem which has been under study
for many years, namely, how to make a rotary peristaltic pump for a
plurality of tubes which will maintain constant flow in each tube.
It does this by the application of two new ideas.
1. It provides a recess in a cylinder press plate to prevent the
tubes from being over compressed. The roller actually rides on
ridges.
2. It allows the press plate to float, under constant pressure in
any of the three dimensions. It can move up, down or sway from side
to side during the running of the pump, maintaining constant
pressure on the tubes at all times. At all times the press plate
assumes the position of least resistance.
As a further aid for this purpose, the rotor rides on ball bearing
supported in stiff, but flexible rubber. This permits the rotor to
also move slightly in any direction so as to aid in assuming a
position of least friction with the press plate and aid the press
plate in taking the proper position with respect to the
rollers.
It is to be observed therefore that the present invention provides
for a peristaltic pump for delivering measured and constant amounts
of liquid per unit of time from a plurality of containers through a
plurality of flexible tubes which are stretched between two
supports. This is accomplished by means of rollers circularly
disposed around a circular drum rotor, the flexible tubes being
disposed over, in contact, and at right angle to the rollers which
are mounted so that they may rotate due to the friction as they
slide across the flexible tubes. The rotor is supported on an axle
which is in turn supported by two bearings with flexible central
support, e.g., rubber, so that it can revolve smoothly on the
shaft. The drum rotor being made to revolve at constant speed by
means of a motor drive. A press plate in the shape of a portion of
a hollow cylinder is made to press on the flexible tubes and thus
on the rollers by springs held in place by a rigid support in such
a manner that the press plate may have the capability of some
movement in any direction. The press plate is countersunk on the
concave side to provide ridges of somewhat lesser height than the
combined thickness of opposite walls of the flexible tubing so that
the flexible tubing will be closed by the rollers but never
compressed beyond its elastic limit. Thus, when the rotor rotates,
the rollers pass over the flexible tubing successively, to drive
the liquid in the flexible tubes in the same direction as the
motion of the rotor, the press plate assuming different positions
so as to conform to variations in the height and position of said
rollers, resulting in an even and constant flow of liquid in each
of the flexible tubes.
The use of a rotary design of the peristaltic pump permits (as
showin in FIG. 7) the application to a thin flexible material over
the rollers. The rollers now move within this flexible covering,
which we will now call belting for convenience. When the pump is
assembled, the tubing carrying the liquid being pumped is now
disposed between the belting and the press plate. As the pump
revolves it presses on the belting which in turn presses on the
tubing causing the liquid to flow. The scuffing of the rollers over
the tubing is eliminated and the belting takes up this wear. The
tendency of the peristaltic pump to stretch the tubes in the
forward direction is also minimized for the same reason. This
increases the life of the tubing markedly. A belting suitable for
this purpose is conventional high speed belting, 3/64 inch
thickness, which is smooth on the side contacting the tubing and
rougher on the rotor side. Thus, the rollers are induced to rotate
by the belting, which takes the wear, and not the tubing. For this
reason the tubing is not stretched forward to a great extent which
also increases its life span.
* * * * *