Tube pump
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.
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1. Field of the Invention
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.
2. Prior Art
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.
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.
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.
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.
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.
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 INVENTIONA 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.
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.
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.
In order to achieve the first and second objects, a tube pump of a first aspect of the present invention includes:
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- a base that holds a drive shaft that connects with and is driven by a motor;
- 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;
- 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;
- 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;
- 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.
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.
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.
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.
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.
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.
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
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
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.
The construction of the above-described tube pump 1 will be described with reference to
The tube pump 1 of the embodiment is provided with, as shown in
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.
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.
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.
Further, the casing 40 is mounted on the base 20 so that the casing 40 can slide in the X-direction in
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.
As shown in
Next, the moving mechanism that moves the casing 40 with respect to the base 20 will be described. As shown in
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
As shown in
Next, the structure of the fixing portion 22 of the base 20 will be described with reference to
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
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
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.
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.
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
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
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.
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
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.
Claims
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.
Type: Application
Filed: Sep 23, 2004
Publication Date: Mar 31, 2005
Applicant: JAPAN SERVO CO., LTD. (Tokyo-to)
Inventor: Masanori Shibasaki (Kiryu-shi)
Application Number: 10/947,295