U.S. patent application number 10/947295 was filed with the patent office on 2005-03-31 for tube pump.
This patent application is currently assigned to JAPAN SERVO CO., LTD.. Invention is credited to Shibasaki, Masanori.
Application Number | 20050069436 10/947295 |
Document ID | / |
Family ID | 34191558 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050069436 |
Kind Code |
A1 |
Shibasaki, Masanori |
March 31, 2005 |
Tube pump
Abstract
The tube pump includes a base that holds a drive shaft; a rotor
portion that rotates with the driving shaft, the rotor portion
having a pair of rollers; a casing having a U-shaped internal
surface along which an elastic tube is arranged, the casing being
mounted on the base so that the casing can slide with respect to
the base in a direction parallel to the linear portions; a cover
that is rotatably mounted on the casing; a moving mechanism
including a rack that is formed on the base and a pinion that is
fixed to the rotation shaft of the cover. The moving mechanism
moves the casing to the operating position where the roller deforms
the elastic tube when the cover closes, and the moving mechanism
moves the casing to the exchange position where the roller comes
apart from the elastic tube when the cover opens.
Inventors: |
Shibasaki, Masanori;
(Kiryu-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JAPAN SERVO CO., LTD.
Tokyo-to
JP
|
Family ID: |
34191558 |
Appl. No.: |
10/947295 |
Filed: |
September 23, 2004 |
Current U.S.
Class: |
417/476 ;
417/474 |
Current CPC
Class: |
A61M 60/279 20210101;
F04B 43/1284 20130101; A61M 60/268 20210101; A61M 60/113
20210101 |
Class at
Publication: |
417/476 ;
417/474 |
International
Class: |
F04B 043/08; F04B
043/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2003 |
JP |
2003-337150 |
Claims
What is claimed is:
1. A tube pump comprising: a base that holds a drive shaft that
connects with and is driven by a motor; a rotor portion that
rotates with said driving shaft, said rotor portion having a pair
of rollers each of which has a rotating shaft decentered from said
drive shaft; a casing having a U-shaped internal surface that
includes a semicircular portion and parallel linear portions
connected to both ends of said semicircular portion along which an
elastic tube is arranged, said casing being mounted on said base so
that said casing can slide with respect to said base in a direction
parallel to said linear portions; a cover that is rotatably mounted
on said casing at the outside of said semicircular portion, said
cover covering the portion surrounded by said internal surface at
its closing position; a moving mechanism including a rack that is
formed on said base and a pinion that is fixed to a rotation shaft
of said cover and engages with said rack, said moving mechanism
moving said casing with respect to said base to an operating
position where said roller deforms said elastic tube arranged along
said internal surface when said cover closes, and said moving
mechanism moving said casing with respect to said base to an
exchange position where said roller comes apart from said elastic
tube when said cover opens.
2. The tube pump according to claim 1, wherein said internal
surface of said casing has a step portion so that the diameter of
the semicircular portion at the side of the cover becomes larger
than the other side, and said cover has a convex rim, which can
insert inside said internal surface, is formed on said cover at the
position opposite to said step portion, whereby said step portion
and said convex rim function as a means for guiding said elastic
tube that is arranged along said internal surface.
3. The tube pump according to claim 1 or 2, further comprising: a
pair of clamp arms that is mounted on said base to hold entrance
and exit portions of said elastic tube to the pump, respectively,
the base end of each of said clamp arm being rotatably attached to
a pivot that is vertical to the axis of said drive shaft and is
parallel to said linear portions, each of said clamp arm having a
tip end that is formed to hold said elastic tube and having a small
roller at a middle portion thereof; a biasing mechanism that
applies bias pressure to said clamp arms so that said small rollers
move closer and said clamp arms release said elastic tube; and a
connecting projection that is formed on said cover to intrude
between said small rollers when said cover closes, wherein said
connecting projection of the cover intrudes between said small
rollers and separates them from each other, which rotates the clamp
arms against the bias pressure applied by the biasing mechanism
when the cover closes.
4. The tube pump according to one of claims 1 through 3, further
comprising: a permanent magnet mounted on said rotor portion at the
position opposite to the casing; and a magnetic sensor installed on
either of said casing and said base for detecting magnetic flux of
said permanent magnet to determine the rotation position of said
rotor portion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a tube pump that deforms an
elastic tube by rotating rollers to send out liquid in the elastic
tube. Especially the present invention relates to a tube pump
mounted on artificial dialysis equipment etc. that enables easy
attachment and removal of the elastic tube.
[0003] 2. Prior Art
[0004] This kind of tube pump is disclosed in Japanese unexamined
patent publication No. Hei 6-218042, for example. The tube pump
disclosed in the publication is provided with a casing body having
a semicircular internal surface, a drive shaft located at the
center of the semi-circle and a rotor portion that rotates with the
drive shaft. The rotor portion has a pair of rollers whose rotation
axes are decentered from the drive shaft. For operation, arrange an
elastic tube along the internal surface of the casing body and
rotate the rotor portion to deform the elastic tube with
compression between the internal surface and the rollers to send
liquid in the elastic tube.
[0005] Since the tube pump sends liquid by deforming the elastic
tube, the tube tends to deteriorate, which requires frequent
exchange of the tube. Further, when this kind of tube pump is used
in artificial dialysis equipment, the drawing direction of the
elastic tube may be changed to match layout of the artificial
dialysis equipment with respect to a bed of a patient or to avoid
frequently inserting shunt needles into the same arm of a patient.
However, since the elastic tube is pinched between one roller and
the internal surface of the tube pump, it takes much expense in
time and effort to exchange the tube even if the rotor portion
stops.
[0006] Therefore, the tube pump of the above publication divides
the casing body into a movable casing that forms a part of the
semicircular internal surface and a fixed casing that forms the
other portion. This enables to exchange the tube under the
condition where the roller comes apart from the elastic tube by
separating the movable casing from the fixed casing. With this
construction, the elastic tube can be easily attached and
removed.
[0007] However, since the tube pump disclosed in the above
publication divides the semicircular internal surface to which
large pressure is applied by the rotation of the rotor portion in
operation into two portions, it is difficult to keep structural
strength. Therefore, the movable and fixed casings are formed from
metal, which increases the cost of the tube pump in comparison with
that with plastic casings. Although the publication describes that
the casings may be made from plastic, if the casings having the
same structure are made from plastic, there is a high probability
that the casings break due to lack of strength in reality.
[0008] Further, the tube pump of the above publication slides the
movable casing in response to the opening and closing operations of
the casing cover. However, since the casing to which large pressure
is applied is divided as described above, a solenoid to lock the
movable casing at the position connecting to the fixed casing and a
sensor that detects the opening and closing of the cover to control
the solenoid are required, which complicates the construction of
the tube pump.
[0009] Still further, the tube pump of the publication has a pair
of tube clamp arms that hold the tube at the entrance and exit
positions of the pump. However, since the clamp arms must be
operated manually, the operation of the clamp arms for exchanging
the tube is complicated.
SUMMARY OF THE INVENTION
[0010] A first object of the present invention is to provide a tube
pump that can increase structural strength of a casing so that it
can be made from plastic with easy attachment and removal of an
elastic tube.
[0011] A second object of the present invention is to provide a
tube pump that does not require a mechanism for locking a casing at
an operating position on the precondition that a roller changes its
position in response to opening/closing of a cover between the
operating position where the roller deforms the elastic tube and an
exchange position where the roller comes apart from the elastic
tube.
[0012] A third object of the present invention is to provide a tube
pump that can automatically operate clamp arms arranged at entrance
and exit positions of the pump.
[0013] In order to achieve the first and second objects, a tube
pump of a first aspect of the present invention includes:
[0014] a base that holds a drive shaft that connects with and is
driven by a motor;
[0015] a rotor portion that rotates with the driving shaft, the
rotor portion having a pair of rollers each of which has a rotating
shaft decentered from the drive shaft;
[0016] a casing having a U-shaped internal surface that includes a
semicircular portion and parallel linear portions connected to both
ends of the semicircular portion along which an elastic tube is
arranged, the casing being mounted on the base so that the casing
can slide with respect to the base in a direction parallel to the
linear portions;
[0017] a cover that is rotatably mounted on the casing at the
outside of the semicircular portion, the cover covering the portion
surrounded by the internal surface at its closing position;
[0018] a moving mechanism including a rack that is formed on the
base and a pinion that is fixed to the rotation shaft of the cover
and engages with the rack, the moving mechanism moving the casing
with respect to the base to an operating position where the roller
deforms the elastic tube arranged along the internal surface when
the cover closes, and the moving mechanism moving the casing with
respect to the base to an exchange position where the roller comes
apart from the elastic tube when the cover opens.
[0019] With this construction, since the casing to which large
pressure is applied is not separated, the structural strength
becomes larger, which keeps the casing intact even if it is made
from plastic. Further, when an elastic tube is located along the
internal surface of the casing and the cover is closed, the
rotation of the rotor portion deforms the elastic tube between the
roller and the internal surface to send out liquid in the elastic
tube. When the cover is opened, the elastic tube can be easily
exchanged.
[0020] A step portion (a level difference portion) may be formed on
the internal surface of the casing so that the diameter of the
semicircular portion at the side of the cover becomes larger than
the other side. Further, a convex rim, which can insert inside the
internal surface, is formed on the cover at the position opposite
to the step portion. The step portion and the convex rim function
as a means for guiding the elastic tube that is arranged along the
internal surface.
[0021] In order to achieve the above-described third object, a tube
pump of a second aspect of the present invention has the following
characteristic features. That is, the base is provided with a pair
of clamp arms that hold entrance and exit portions of the elastic
tube to the pump, respectively, the base end of each clamp arm is
rotatably attached to a pivot that is vertical to the axis of the
drive shaft and is parallel to the linear portions, each clamp arm
has a tip end that is formed to hold the elastic tube and has a
small roller at a middle portion thereof. The base has a biasing
mechanism that applies bias pressure to the clamp arms so that the
small rollers move closer and the clamp arms release the elastic
tube. A connecting projection, which intrudes between the small
rollers when the cover closes, is formed on the cover.
[0022] With this construction, when the cover opens, since the tip
ends of the clamp arms release the elastic tube due to the bias
pressure applied by the biasing mechanism, the elastic tube can be
easily exchanged. When the cover closes, the connecting projection
of the cover intrudes between the small rollers and separates them
from each other, which rotates the clamp arms against the bias
pressure applied by the biasing mechanism. Therefore, the tip ends
of the clamp arms are pressed to the elastic tube and the clamp
arms hold the elastic tube.
[0023] As described above, since the elastic tube is automatically
held and released in response to the opening and closing of the
cover without manual operation of the clamp arms, the elastic tube
can be easily exchanged.
[0024] In addition, a permanent magnet may be mounted on the rotor
portion at the position opposite to the casing and a magnetic
sensor may be installed on either of the casing and the base to
determine the rotation position of the rotor portion by detecting
the magnetic flux of the permanent magnet. The output of the
magnetic sensor is used to control a motor that drives the rotor
portion. For instance, when the rotation of the rotor portion is
stopped, the motor is controlled to stop one roller at the midpoint
of the semicircular portion of the casing so that the movement of
the casing by the moving mechanism can come apart the roller from
the elastic tube. For easy exchange of the elastic tube, the roller
must come apart from the elastic tube at the exchange position. If
the rotor portion stops at the position where the roller faces the
linear portion of the internal surface, since the roller does not
come apart from the elastic tube when the cover opens, it becomes
difficult to exchange the elastic tube. Therefore, it is preferable
to predetermine the stop position and to control the motor for
driving the tube pump according to the predetermined stop
position.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0025] FIG. 1 is a perspective plan view of a tube pump of an
embodiment according to the present invention when an elastic tube
is attached to the tube pump and a cover closes;
[0026] FIG. 2 is a sectional side view of FIG. 1 along the II-II
line;
[0027] FIG. 3 is a sectional front view of FIG. 1 along the III-III
line;
[0028] FIG. 4 is a plan view of the tube pump of the embodiment
when the cover opens before the elastic tube is removed;
[0029] FIG. 5 is a plan view of the tube pump of the embodiment
when the cover opens after the elastic tube and the rotor portion
are removed;
[0030] FIG. 6 is a sectional side view of FIG. 4 along the VI-VI
line;
[0031] FIG. 7 is a sectional view of FIG. 1 along the VII-VII line
when a tube clamp mechanism holds the elastic tube;
[0032] FIG. 8 is a sectional view of FIG. 4 along the VIII-VIII
line when the tube clamp mechanism releases the elastic tube;
and
[0033] FIG. 9 is a system chart showing the entire construction of
artificial dialysis equipment that employs the tube pump of the
embodiment as a blood pump.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Hereinafter, a tube pump of an embodiment according to the
present invention will be described with reference to the drawings.
Initially, an example of the use of the tube pump of the embodiment
will be described according to FIG. 9.
[0035] FIG. 9 shows the entire construction of artificial dialysis
equipment 2 that employs the tube pump 1 of the embodiment as a
blood pump. The artificial dialysis equipment 2 is provided with
the tube pump 1, a dialyzer 3, first and second chambers 4 and 5.
The equipment 2 is incorporated in an extracorporeal circulation
path of a patient P. In addition, the reference F in FIG. 9
indicates a cover sheet put on the body of the patient P.
[0036] Blood collected from the arm of the patient P is drawn by
the tube pump 1 through the tube and is pressurized to send to the
first chamber 4. The blood that is temporally accumulated in the
first chamber 4 is sent to the dialyzer 3. The dialyzer 3 dialyzes
and filters the blood with using a dialyzate solution supplying
line 6 to remove deleterious material and excess water. The blood
after dialysis is temporally accumulated in the second chamber 5
and then is sent back to the arm of the patient P.
[0037] The construction of the above-described tube pump 1 will be
described with reference to FIG. 1 through FIG. 8. FIG. 1 through
FIG. 3 show the tube pump 1 of the embodiment when the elastic tube
C is placed and the cover closes, FIG. 1 is a perspective plan view
(the cover is illustrated by the two-dot chain line), FIG. 2 is a
sectional side view of FIG. 1 along the II-II line and FIG. 3 is a
sectional front view of FIG. 1 along the III-III line (a position
of a rotor portion is different from that in FIG. 1). FIG. 4
through FIG. 6 show the tube pump 1 of the embodiment when the
cover opens, FIG. 4 is a plan view before the elastic tube is
removed, FIG. 5 is a plan view after the elastic tube and a rotor
portion shown in FIG. 4 are removed and FIG. 6 is a sectional side
view of FIG. 4 along the VI-VI line. FIG. 7 and FIG. 8 show a tube
clamp mechanism that holds the elastic tube C at the entrance and
exit positions of the tube pump 1, FIG. 7 is a sectional view of
FIG. 1 along the VII-VII line and FIG. 8 is a sectional view of
FIG. 4 along the VIII-VIII line.
[0038] The tube pump 1 of the embodiment is provided with, as shown
in FIG. 1 and FIG. 2, a base 20 having a drive shaft 21 that is
connected to a motor 10 through a reduction gear 11, a rotor
portion 30 attached to the drive shaft 21, a casing 40 that can
slide in an arrowed X-direction in FIG. 1 with respect to the base
20 and a cover 50 that covers over the casing 40. When the drive
shaft 21 is rotated by the motor 10, the rotor portion 30 rotates
together with the drive shaft 21.
[0039] The base 20 includes a fixing portion 22 for fixing the
elastic tube C at the entrance and exit positions and a holding
portion 23 for holding the casing 40 so that the casing 40 can
slide in the X-direction. At the center of the holding portion 23,
a base opening 24 is formed for allowing the drive shaft 21 to pass
through. A bearing 21a for supporting the drive shaft 21 is
installed in the base opening 24.
[0040] The rotor portion 30 is a single unit that is
detachable/attachable to the drive shaft 21, and it consists of a
rotor body 31 having a shape of a rectangular parallelepiped to
which the drive shaft 21 is inserted, a pair of roller holders 32a,
32b attached to both sides of the rotor body 31, and a pair of
rollers 34a, 34b that are supported by the roller holders 32a, 32b
via rotating shafts 33a, 33b decentered from the drive shaft 21.
The roller holders 32a and 32b are connected to the rotor body 31
by axial pins 35a and 35b mounted on diagonal positions of the
rotor body 31 so that the roller holders 32a and 32b can pivot
about the axial pins 35a and 35b, respectively. Further, the free
ends of the respective roller holders 32a and 32b are pushed by
compression springs (not shown) in the direction that distances the
free ends from the rotor body 31.
[0041] There is a space at the center of the casing 40 for
arranging the rotor portion 30 and the elastic tube C, and a
sidewall surrounds the space from three directions. A U-shaped
internal surface 41 of the sidewall consists of a semicircular
portion 41a and a pair of linear portions 41b, 41c that are
connected to both ends of the semicircular portion 41a. The elastic
tube C is located along the internal surface 41.
[0042] Further, the casing 40 is mounted on the base 20 so that the
casing 40 can slide in the X-direction in FIG. 1, which is the
direction of the linear portions 41b, 41c, with respect to the base
20. That is, as shown in FIG. 2, FIG. 3 and FIG. 5, a projecting
edge 24a is formed along the upper edge of a base opening 24 formed
on the base 20 and a casing opening 42 is formed on the bottom of
the casing 40 to connect with the base opening 24. The casing
opening 42 is larger than the base opening 24 in the X-direction as
shown in FIG. 2 and contacts the outside of the projecting edge 24a
of the base opening 24 in a Y-direction as shown in FIG. 3. A
flange 42a is formed on the edge of the casing opening 42 and the
flange 42a, which is stepped down from the casing opening 42, is
sandwiched between the base 20 and a fixing plate 43 that is fitted
in the base opening 42. With this construction, the casing 40 can
slide in the X-direction with respect to the base 20 without
changing its position in the Y-direction and is held by the fixing
plate 43 not to be removed.
[0043] In addition, the base 20, the casing 40 and the rotor body
31 of the rotor portion 30 are made from rigid plastic. The rotor
holders 32a and 32b are made from metal or rigid plastic.
[0044] As shown in FIG. 1 and FIG. 2, the cover 50, which is made
from transparent plastic, is provided with a dome portion 51 that
covers the inside of the internal surface 41 of the casing body 40
and is fixed by screws to the rotation axis 44 that is rotatably
mounted on the one end of the casing 40. On the other end of the
cover 50, a knob 52 is formed to be handled by an operator for
closing and opening operations. The knob 52 has a connecting
projection 54 that is formed at the inside of the knob 52 towards
the casing 40 to connect with the fixing portion 22 of the base 20.
The function of the connection projection 54 will be described
below.
[0045] Next, the moving mechanism that moves the casing 40 with
respect to the base 20 will be described. As shown in FIGS. 2 and
6, a rack 25 is formed on one side of the base 20 and a pinion 45
that engages the rack 25 is fixed to a rotation shaft 44 that
rotates with the opening/closing of the cover 50. As shown in FIGS.
1 and 4, the pinions 45 are fixed to both sides of the rotation
shaft 44 and the racks 25 are formed at the corresponding
positions.
[0046] The opening/closing operations of the cover 50 rotates the
pinions 45, which changes the relative position between the pinions
45 and the racks 25 in the X-direction, sliding the casing 40 with
respect to the base 20. When the cover 50 closes as shown in FIG.
1, the casing 40 moves the roller 34b with respect to the base 20
to an operating position where the roller 34b deforms the elastic
tube C arranged along the internal surface 41. When the cover 50
opens as shown in FIG. 4, the casing 40 moves roller 34b with
respect to the base 20 to an exchange position where the roller 34b
comes apart from the elastic tube C to release the deformation.
[0047] As shown in FIG. 3, a step portion (a level difference
portion) 46 is formed on the semicircular portion 41a of the
internal surface 41 of the casing 40 so that the diameter at the
side of the cover 50 (the upper side in FIG. 3) becomes larger than
the other side (the lower side). Further, a convex rim 55, which
can insert inside the larger diameter portion of the internal
surface 41, is formed on the cover 50 at the position opposite to
the step portion 46. The step portion 46 and the convex rim 55
function as a guiding means to prevent up-and-down slippage of the
elastic tube C that is arranged along the internal surface 41.
[0048] Next, the structure of the fixing portion 22 of the base 20
will be described with reference to FIG. 7 and FIG. 8. A pair of
U-shaped grooves 22a are formed on the fixing portion 22 to guide
entrance and exit portions of the elastic tube C and a pair of
clamp arms 26a, 26b to hold the elastic tube C arranged in the
U-shaped grooves 22a are provided. The clamp arms 26a, 26b have
crank-shapes that are symmetric to each other. The base ends of the
clamp arms 26a, 26b are rotatably attached to a pivot 27 that is
vertical to the axis of the drive shaft 21 and is parallel to the
linear portions 41b, 41c of the internal surface 41. Further, the
respective clamp arms 26a, 26b have the tip ends providing circular
cutout portions to hold the elastic tube C and have small rollers
28a, 28b at middle portions. Still further, the base 20 has a pair
of coil springs 29a, 29b as a biasing mechanism that applies bias
pressure to the clamp arms 26a, 26b so that the small rollers 28a,
28b move closer and the clamp arms 26a, 26b release the elastic
tube C.
[0049] When the cover 50 opens, the tip ends of the clamp arms 26a,
26b release the elastic tube C due to the bias pressure applied by
the coil springs 29a, 29b as shown in FIG. 8. When the cover 50
closes, the connecting projection 54 of the cover 50 intrudes
between the small rollers 28a, 28b and separates them from each
other as shown in FIG. 7, which rotates the clamp arms 26a, 26b so
that the tip ends hold the elastic tube C to fix the elastic tube C
to the fixing portion 22 against the bias pressure applied by the
coil springs 29a, 29b.
[0050] In addition, a pair of permanent magnets 60 are installed at
the lower edge of the rotor body 31 at the positions indicated by
the dotted lines in FIG. 1 and FIG. 3. A rotation position sensor
61, which has a magnetic sensor such as a hall element, is mounted
on the back surface of the casing 40 in the space between the
casing 40 and the base 20. The rotation position sensor 61 is
located so that it can detect the magnetic flux of the permanent
magnets 60.
[0051] On the other hand, a permanent magnet 62 is installed on the
lower end of the clamp arm 26a and an arm position sensor 63 having
a magnetic sensor is mounted on the fixing portion 22 to detect the
magnetic flux of the permanent magnet 62.
[0052] The outputs of the sensors 61 and 63 are checked by a
controller (not shown). The output of the rotation position sensor
61 is used to detect the rotation position of the rotor portion 30
during operation of the tube pump 1. The output of the arm position
sensor 63 is used to determine whether the cover 50 opens or
closes.
[0053] Next, the function of the tube pump 1 that is constructed as
above will be described. During operation of the tube pump 1, an
operator arranges the elastic tube C along the internal surface 41
of the casing 40, closes the cover 50 and turns on a operation
switch (not shown). When the cover 50 is closed, as shown in FIG. 1
and FIG. 2, the casing 40 relatively moves leftward in the drawings
with respect to the base 20 to the operating position where the
roller 34b deforms the elastic tube C. Further, the connecting
projection 54 of the cover 50 intrudes between the small rollers
28a, 28b, which rotate the clamp arms 26a, 26b to hold the elastic
tube C to the fixing portion 22 at the entrance and exit points as
shown in FIG. 7. The controller checks the output from the arm
position sensor 63. When the controller determines that the cover
50 closes and the clamp arm 26a holds the elastic tube C, it
applies electric current to the motor 10 to rotate. The rotation of
the motor 10 is transferred via the reduction gear 11 to the drive
shaft 21, which rotates the rotor portion 30 attached to the drive
shaft 21. Assuming that the rotor portion 30 rotates in the
counterclockwise direction in FIG. 1, the roller 34a contacts the
elastic tube C when the roller 34a comes the position opposite to
the linear portion 41c of the internal surface 41. The roller 34a
revolves both on the rotating shaft 33a and around the drive shaft
21 with deforming the elastic tube C by the pressure caused by the
compression spring (not shown) arranged between the roller holder
32a and the rotor body 31. The elastic tube C is squeezed as the
roller 34a advances to the semicircular portion 41a and the linear
portion 41b, the liquid in the tube flows in the counterclockwise
direction and is pushed out to the exit side. The other roller 34b
contacts the elastic tube C just before the roller 34a comes apart
from the elastic tube C. The roller 34b sends out the liquid in the
tube in the same manner as the roller 34a. With this construction,
since the rollers 34a and 34b alternately squeeze the elastic tube
C, the tube pump 1 can continuously send out the liquid.
[0054] When an operator stops the tube pump 1, the operator turns
off the operation switch. The controller detects the output signal
from the rotation position sensor 61 and continues to apply
electric current until a predetermined time elapsed after detecting
the output signal from the rotation position sensor 61, and then
cuts the electric current. The predetermined time is an interval
from the detection of the output signal of the rotation position
sensor 61 to the arrival of the rotor portion 30 to the position
where the rollers 34a and 34b align in the X-direction as shown in
FIG. 1.
[0055] As described above, since the rotor portion 30 is controlled
so that one roller stops at the midpoint of the semicircular
portion 41a of the casing 40, the rollers 34a and 34b come apart
from the elastic tube by the movement of the moving mechanism,
which allows easy exchange of the elastic tube.
[0056] When the elastic tube C is exchanged, the operator stops the
rotation of the rotor portion 30 and open the cover 50. Opening the
cover 50 moves the casing 40 rightward in FIG. 4 and FIG. 6 with
respect to the base 20, which locates the roller 34b apart from the
elastic tube C. Further, since the connecting projection 54 of the
cover 50 gets out of the position between the small rollers 28a and
28b as shown in FIG. 8, the clamp arms 26a and 26b rotate by the
tension of the compression springs 29a and 29b, which moves the tip
ends off the elastic tube C. Under this condition, the elastic tube
C can be easily removed and exchanged.
[0057] With the above-described structure, since the casing 40 to
which large pressure is applied is not separated, the structural
strength becomes larger, which keeps the casing intact even if it
is made from plastic. Further, since the casing 40 moves and the
clamp arms 26a, 26b rotate in response to the opening/closing
operations of the cover 50, the elastic tube C can be easily
exchanged.
* * * * *