U.S. patent number 3,758,239 [Application Number 05/210,371] was granted by the patent office on 1973-09-11 for controlled peristaltic pump.
This patent grant is currently assigned to Cskoslovenska akademie ved. Invention is credited to Jiri Hrdina.
United States Patent |
3,758,239 |
Hrdina |
September 11, 1973 |
CONTROLLED PERISTALTIC PUMP
Abstract
In peristaltic pumps, using a number of mobile occluding organs
which press a resilient hose against a support and which cause the
advance of a medium within this hose, an additional support is
provided from the limit point of occlusion up to the last contact
point with the hose. The distance of the support from the track of
the occluding organs being in inverse proportion to the required
speed of advance of the medium in this hose.
Inventors: |
Hrdina; Jiri (Praha,
CS) |
Assignee: |
Cskoslovenska akademie ved
(Praha, CS)
|
Family
ID: |
5438463 |
Appl.
No.: |
05/210,371 |
Filed: |
December 21, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Dec 23, 1970 [CS] |
|
|
8746/70 |
|
Current U.S.
Class: |
417/477.11;
417/477.14 |
Current CPC
Class: |
F04B
43/1223 (20130101) |
Current International
Class: |
F04B
43/12 (20060101); F04b 043/08 (); F04b 043/12 ();
F04b 045/06 () |
Field of
Search: |
;417/474,475,476,477 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
467,288 |
|
Jun 1937 |
|
GB |
|
1,119,170 |
|
Apr 1956 |
|
FR |
|
Primary Examiner: Smith; Al Lawrence
Assistant Examiner: Gluck; Richard E.
Claims
I claim:
1. Controlled peristaltic pump comprising at least one flexible
hose having a suction end and a discharge end for suction and
discharge, respectively, of a liquid medium, supporting means
having an active surface for supporting said hose, compressing
means disposed opposite said supporting means, movable along a
predetermined path and adapted to progressively compress said hose
against said supporting means and to generate a peristaltic pumping
effect, said supporting means including at least a first support
member substantially parallel to the path of said compressing means
and a second support member disposed next to said first member,
said second support member being adjustable with respect to the
predetermined path to selectively vary the distance from said
compressing means thereby controlling the action of said
compressing means and the discharge of said liquid medium.
2. The pump as defined in claim 1 wherein the second support member
is pivotable with respect to the first support member to meet
changing diameter and thickness requirements of hoses supported by
the supporting means.
3. The pump as defined in claim 1 wherein the second support member
is pivotable around an edge through which it contacts the first
support member and is perpendicularly adjustable to said edge.
4. The pump as defined in claim 1 wherein the second support member
is freely supported by set screws and provided with spring means
acting in an inclined direction with respect to the active surface
of the supporting means and pressing said second support member
simultaneously against the first support member and against said
set screws.
5. The pump as defined in claim 1 wherein the active surface of the
second support member of the support means forms a step at the
place of contact with the first support member of said support
means.
6. The pump as defined in claim 1 wherein said compressing means
further comprising spaced adjacent members which occlude said hose
until a last point of occlusion, and continuing to engage said hose
until a last point of contact, the distance between said last point
of occlusion and said last point of contact being substantially
equal to the spacing between said spaced adjacent members.
Description
BACKGROUND OF THE INVENTION
This invention relates to a method and to an arrangement for
regulating and programming of the discharge and suction of
periodically operating pumps, particularly peristaltic pumps.
Peristaltic pumps are particularly useful in laboratories, as they
enable a relatively simple mechanism to simultaneously generate a
stream of a medium in a large number of resilient hoses situated
side by side. Similar pumps are very suitable for operation with a
segmented stream, that is with a stream of a medium subdivided by
pistons (for instance gas pistons) into individual segments.
Peristaltic pumps have however a number of drawbacks which are at
present considered irremovable. Primarily they have a certain lack
of uniformity of the stream delivery within the so called critical
range of the pump. The critical range being defined as the area
where the occluding organ in its compression track starts to
withdraw from the hose and to release it, whereby the occlusion
ceases and the hose starts to regain, by its elasticity, its normal
shape. This condition generates irregularities of the delivered
stream which reduce the otherwise high accuracy of peristaltic
pumps.
SUMMARY OF THE INVENTION
According to this invention the occluding organ moves within a part
of its track from the marginal point of occlusion up to the last
point of contact with the hose of the pump opposite to a surface
having a longitudinal profile and the distances between individual
points from the contact point of the occluding organ change, being
reversibly proportional to the speed of advance of the stream of
the medium required by the program in the individual points of said
track.
The invention covers also an arrangement for regulating and
programming the discharge and the suction of these pumps whereby to
a fundamental supporting plate, the active surface of which has a
constant distance from the track of the contact points of the
occluding organs, an auxiliary support is joined, the individual
points of its active surface having a distance from the contact
points of the occluding organ which change being reversibly
proportional to the speed of advance of the stream of the medium,
required by the program in the individual points of said track.
The invention provides a peristaltic pump, where the irregularities
of the stream of the medium within the critical range are
eliminated and which in additon allows the adjustment of the stream
at the critical area according to a predetermined program of
control. Preferably the function of programming is to provide for
the uniform advance of the medium, but it is also possible to
achieve other conditions. For instance, it is possible to control
the stream of the medium so that it comes to a stop or even to
achieve within a short period of operation a negative speed value
(that is a movement in the opposite direction) whereby at least a
part of this negative speed together with the inlet speed of the
medium produces a resultant speed in the already segmented medium
behind the segmentation organ (the bubble generator) which is in
fact uniform even if the segmentation medium enters the pump only
within a relatively small part of a period of operation of the
pump. The term "period" covers not only subsequently following
periods within equal intervals but also a kinematic periodicity,
where for instance equal positions of individual functional
elements correspond to a certain number of revolutions of the
driving mechanism (which revolutions need not be always
uniform).
The term "programming" which will be used in the following covers
not only a control or regulation within one period of operation,
but also an extended interval of control, where for instance the
mean speed of advance of the medium, corresponding to one period,
changes to another value after the passage of the medium, either
stepwise or continuously.
DESCRIPTION OF DRAWINGS
The attached drawings show exemplary embodiments of the prior art
as well as of the present invention.
FIG. 1 is a schematic view of a peristaltic pump of known
design;
FIG. 2 a schematic view of another known design of a peristaltic
pump;
FIG. 3 is a schematic longitudinal sectional view of the active
part of a peristaltic pump adjusted according to this
invention;
FIG. 4 is a partial longitudinal sectional view of an alternative
arrangement of a peristaltic pump according to this invention;
FIG. 5 is a partial sectional view of a further modification of the
peristaltic pump according to this invention; and
FIG. 6 is a diagram schematically showing the occluding organ of a
conventional pump at full occlusion of the hose and in the course
of its subsequent release.
DESCRIPTION OF PRIOR ART
In order to enable a full understanding of the object of this
invention, two peristaltic pumps of known design will be described
first.
FIG. 1 shows one of the commonly used arrangements of peristaltic
pumps where a number of occlusion rollers 1, 2, 3, 4 are provided
either directly on arms 5 (one arm is only partly indicated in the
drawing) which arms 5 are supported on a rotating shaft 6, or
according to an alternative arrangement are supported on spring
loaded rocker levers 7, connected by bolts 8 to arms 9 fixed on
shafts 6. The rollers in the course of their movement track about
the shaft 6 and come into contact with an elastic hose 10 having an
infeed and a discharge end. The hose 10 rests on a support 11. The
arcuate shape of the support 11 insures that the rollers, within a
part of their track remain in contact with the hose 10 which is
thereby compressed so that below the individual rollers a complete
occlusion, that is a complete closing of the hose is caused. The
support 11 is urged against the rollers by an element 12 generating
pressure. In the course of rotation of the shaft 6 and thus also of
the rollers 1, 2, 3, 4 the place of occlusion advances continuously
along the hose at an angular speed corresponding to the angular
speed of the shaft 6.
FIG. 2 shows a pump of another type where the rollers 1, 2... are
supported by a roller chain 13 passing over sprocket wheels (not
shown). The hose 10 is in this case pressed against a support 14
which is along a portion indicated by A straight and parallel with
the adjacent branch of the roller chain, whereafter in part B it
recedes from the rollers.
FIG. 6 shows the operation of the pump schematically. As seen, each
occlusion organ 1,2,3, travels along a curved path 15 a portion of
which constitutes the compression track wherein the roller
compresses one portion of the wall of the hose 10 against the
opposing wall portion. The depth of compression of roller (e.g. 41)
provides an occlusion reserve C since so long as the compression is
maintained within this depth, occlusion of the hose is maintained.
During mainteneance of the occlusion reserve C the hose is
segmented by the roller forming a portion 16 behind it and a
portion 17 ahead of it and by which the media is separated. This
occlusion reserve is required to insure that a tight seal is made
between sections 16 and 17. Further, at the initial stage of
compression, the compression of the hose reduces the volume of the
hose, thus increasing the pressure of the medium in the hose
between itself and the next preceeding roller. The moving occlusion
organs thus push the medium conveying a stream of medium to the
discharge end along the path D.
The rollers, when driven along their path 15 at a constant speed,
act to impart an irregularity to the flow of medium in the conveyed
stream within the pump range which is detected at the discharge end
of the hose. This irregularity is caused by the action of the
roller when it releases from the hose during the course of each
individual compression period (a period being defined as the
distance between successive rollers). Actually, at the moment when
the occlusion roller 41 lifts in its track along the curve 15 from
the hose 10 and the roller 41 first releases the so called
occlusion reserve C, that is, as the part of one hose wall which is
pressed into the opposite one begins to recede and as soon as each
roller recedes so far that the reserve C is liquidated, (note
roller 42), the occlusion stops and the space 16 behind the roller
becomes connected with the space 17 in front of it, and the hose is
refilled with medium. The point where the occlusion stops, defined
as "limit point of occlusion" is indicated in FIG. 6 by the letter
M. In the course of the further movement of the particular roller
(position indicated by 42) along the curve 15, the medium in the
hose is no longer conveyed at a uniform speed in direction of the
arrow D. As the hose starts to expand up to the place where the
roller just leaves it (point E at position 43) the medium rushes to
fill the increasing volume reducing its forward speed. The range
between the limit point M and the contact point E is referred to as
the "critical range" and is indicated by the letter K. In the
course of release of the hose 10 suction is generated in space 17
acting against the discharge of the medium, so that the resulting
discharge is equal to the difference between the discharge movement
generated by the next succeeding roller and this suction. The
amount of medium delivered within this critical range K is
therefore reduce in dependence on this suction. Since the speed of
back flow into the tube from the discharge is directly proportional
to the speed of the rollers, the suction may even rise to such a
value that its surpasses the medium discharge speed, so that the
stream of the medium may actually be reversed and proceeds in the
opposite direction, (i.e., against the direction indicated by the
arrow D). This irregularity is very inconvenient, particularly if a
discharge having uniform proportionality is to be achieved. This
proportionality cannot be achieved with known pumps and
particularly for purposes which have hoses of different diameters.
Up till now this drawback could not be removed and it was
particularly this drawback, which caused peristaltic pumps to have
been considered to be not quite accurate. Although it is common
knowledge that their total delivery is uniform, the periodic
delivery is not and so far only the mean values of discharge are
considered in determining capacity.
Various steps have been taken in order to eliminate this
undesirable circumstance, one of which is the use of a clamp 18,
commonly called a "bar" indicated schematically in FIG. 2. The
"bar" is located between the compression track and the discharge.
The clamp 18 is adjustable with respect to a fixed support 19 and
is resiliently pressed against the support 19 to cause selected
deformation of the hose 10 up to a complete occlusion. The "bar" is
particularly used for a stream of gas such as air segmented by
pistons rather than rollers. If the bar is closed, the air or gas
compressed between the closed bar and the next approaching
occlusion roller is held until the moment when the bar is lifted
and releases the passage of the medium through the hose 10.
None of the arrangements attempted, not even the "bar," could
remove the above irregularities in delivery of the stream within
the individual periods.
It has been of course equally impossible to obtain a programmed,
that is, controlled stream of the medium within the critical range
of the peristaltic pump and thus also in the discharge conduit of
the pump.
It is therefore an object of this invention to provide a
peristaltic pump which would enable a uniform advance of the pumped
medium.
It is another object of this invention to enable an arbitrary
programming of the stream of the medium both in the suction and in
the discharge conduit.
DESCRIPTION OF PREFERRED EMBODIMENT
FIG. 3 shows one of the simplest arrangements which can be made
according to this invention. Rollers 20, 21, 22, 23 of a
peristaltic pump are arranged at mutual distances L and move along
a straight path 24 which passes over a hose 25 suitably supported
so that the rollers and hose engage in a track of corresponding
shape. The hose 25 is subsequently deformed from the place of first
contact of the individual roller with the hose which is indicated
in the drawing as being below the roller 20 which has just touched
the upper wall of the hose. This deformation corresponds to the
consecutive change along the direction of movement of the distance
between the path 24 and the support. The support consists of a base
supporting plate 26, the upper active surface 27 of which is
parallel with the path 24 and at the discharge end an auxiliary
support 28 having an upper surface 29. The auxiliary support 28 is
joined to the supporting plate 26, so that its upper surface 29 is
shaped so that its longitudinal profile at the place supporting the
hose consists of an inclined line, the individual points of which
lie at an distance d from the path 24. Preferably in the direction
of movement of the roller toward the discharge side of the pump (as
seen by the arrow) the distance d increases while in the direction
opposite thereto, that is toward the suction side, the distance d
decreases inversely proportional to the speed of the stream of the
medium required by the program at each of the individual points of
the critical range K.
In accordance with this invention, the interval of release K of one
roller is made to extend through the entire length of the discharge
stroke L of next succeeding roller. Therefore uniform discharge is
obtained.
In the simplest case wherein a uniform discharge of the medium is
required by the program, it is desirable to shape the upper active
surface 29 of the auxiliary support 28 so that the speed of the
stream is slowed to correspond for instance to the time of supply
of the bubble piston (e.g., "bar") at the segmentation point prior
to discharge. This achieves a uniform speed of the medium behind
the segmentation point. Any other shape to control speed according
to the requirements of any program is of course equally
possible.
What has been said about the discharge branch of the pump can be
obviously equally applied in the suction branch if a desired
discharge program, such as for instance a uniform suction is
required. This case is indicated in FIG. 3 where an auxiliary
support 30 is provided at the suction end, the upper surface of
which is shaped so as the meet requirements according to the
stipulated program. If no programming of suction is needed, the
auxiliary support 30 may be omitted, so that the pump will have
only a single auxiliary support at the discharge end. The converse
holds true if only suction is programmed.
FIG. 4 shows an alternative arrangement where the auxiliary support
28 is adjustable. The auxiliary support 28 rests on set screws 31
which are screwed in into the body of a supporting plate 26 and
joined at its upper active surface 29 to the corner edge 32 of the
supporting plate 26. The supporting plate 28 is pressed against the
screws 31 by the force of the spring 33 suspended between a bolt 34
on the auxiliary support 28 and a bolt 35 on the supporting plate
26. The spring 33 is preferably situated in an inclined position
with respect to the active surfaces of the supporting plate 26 and
of the auxiliary support 28 so that it is biased toward both the
auxiliary support 28 and the supporting plate 26 as well as to the
set screws 31. In this way the corner edge 32 need not be
covered.
A double arrow F (FIG. 4) indicates the length of the compression
track, which each roller has to traverse in order to eliminate the
occlusion reserve C (see FIG. 6) that is from the point where the
roller must begin to lift from compressive position up to the
place, where the occlusion ceases. From this point on, which is the
limit point M of occlusion, upt to point E, where the roller just
leaves the hose 25, the complete release of the hose is effected.
This distance, indicated by the double arrow K is the
aforementioned critical range of operation. The length of the
distance K for the same pump must be different for different
diameters of hoses, since each diameter of hose will create its own
variable suction. The uniform discharge effect of the moving
rollers will therefore be influenced by the chosen hose as well as
the distance K.
The adjustability of the auxiliary support 28 and thus also of the
length of the critical range K is rather important for modern
peristaltic pumps which may be designed to pump through a larger
number of hoses (for instance up to 28 hoses), the diameters of
each of which may be different from the other. It was impossible in
the known devices to achieve a proportionality of the discharge in
each of the different hoses. For instance in the design shown in
FIG. 2, there is no possibility of adjustment and therefore no
possibility to program, that is, control the combined effect of
discharge and suction within the critical range. This form of
control is enabled only by this invention. Thus one of the main
disadvantages of prior peristaltic pumps which had been up to now
considered irremovable has in fact been removed. That this
improvement is important is due to the fact that differences of
profiles of hoses for currently used pumps can be rather
substantial. For instance, hoses range from an internal diameter
0.127 mm up to a diameter 2.80 mm or from an external diameter of
1.56 up to a diameter 4.2 mm.
The actual development of suction within the critical range K can
be empirically determined with acceptable accuracy. Actually
delivered volumes created by deformations of hoses having different
parameters are registered. Based on the thus determined curves, it
is easy to further determine the time course of changes of
distances d that is the angle and length of the surface 9 from the
path 24 within the critical range K (see FIG. 3 and 4). By
establishing these determination of changes of discharge achieved
by the sum of the fundamental discharge effect of the peristaltic
pump in combination with the suction effect within this critical
range can be made so that they would correspond to the given
requirements of the pump program. So for instance if a perfect
uniformity of the stream is desired, or if undesirable sudden
changes of speed are to be eliminated at places both close to the
limit point M of occlusion or close to the contact point E, it is
necessary that the length of the critical range K is, as far as
possible, selected to be equal to the distance L of the occlusion
rollers. This condition is not met by any of the known peristaltic
pumps. Another important condition that has not been met by the
prior art is that the difference between the distance d at the
limit point M and the distance d at the contact point E should be
different for different profiles of hoses. It has been heretofore
impossible to achieve in practical pumps a uniform stream and even
less a controlled stream of the kind produced by the present
invention.
FIG. 5 shows another modification of this invention. The auxiliary
support 28 is in this case joined to the base supporting plate 26
so that at the place of contact of these two elements there is a
sudden drop or step indicated by the reference mark 36. In this
arrangement, the roller, for instance roller 23 advances very
quickly from a position, where it still fully occludes the hose 25
with the required reserve, to a closely adjacent point, where the
occlusion immediately stops and the hose opens. In this case the
length of the track portion F, as indicated in FIG. 4, which the
roller must traverse in order to eliminate the occlusion reserve C
(FIG. 6) is practically reduced to zero. It is obvious that this
step 36 can be achieved in the arrangement according to FIG. 4 by a
suitable adjustment of the left set screw 31 so that the auxiliary
support 28 can not only be deviated around the edge 32, but may be
also shifted perpendiculary to the edge 32.
The auxiliary support 28 can be provided either for each hose alone
or as a common support for several hoses. Of course individual
adjusting elements can be provided for an entire group of
individual hoses either of equal or different profiles.
Recently arrangements of most modern multichannel peristaltic pumps
are desired as automatic analysers, a part of which are just
peristaltic pumps, which can perform different kinds of analysis.
For this purpose wholly assembled constructional units are
provided, corresponding respectively to different possible analysis
conditions. This invention is particularly suitable for similar
cases, as it is possible to achieve with relatively simple means
the most advantageous control even if hoses of rather different
diameters are used in each. In such cases the auxiliary support 28
can form a unit in combination with the hose supporting plate 26,
so that no individual adjustment is required.
In the preceding discussion a type of a pump according to FIG. 2
has been considered, where the occlusion rollers move along a track
with a straight active branch. Everything that has been said about
this type of pump holds true for other types of peristaltic pumps,
particularly where the active part of the roller track is curved,
as for instance the circular track seen according to FIG. 1.
* * * * *