US20130294955A1

US20130294955A1 - Fluid transporting apparatus and fluid transporting method

Info

Publication number: US20130294955A1
Application number: US13/875,812
Authority: US
Inventors: Makoto Katase
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2012-05-02
Filing date: 2013-05-02
Publication date: 2013-11-07
Also published as: CN103382932B; JP2013231416A; JP6019718B2; CN103382932A

Abstract

A fluid transporting apparatus includes a plurality of fingers arranged along a transporting direction in which fluid is transported by a tube having elasticity, the fingers reciprocatingly moving to compress or release the tube, and a driving section configured to move the plurality of fingers in a compressing direction. The fingers move in the compressing direction and crush the tube with ends of the fingers to transport the fluid on the inside of the tube in the transporting direction. The shape of the crushed tube is restored to fill the fluid in the inside of the tube. In a releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in a releasing direction is limited to a predetermined position.

Description

BACKGROUND

1. Technical Field
The present invention relates to a fluid transporting apparatus and a fluid transporting method.
2. Related Art
A peristaltic pump is known as a fluid transporting apparatus (see, for example, U.S. Pat. No. 4,893,991 (Patent Literature 1) and Japanese Patent No. 3212315 (Patent Literature 2)). In the peristaltic pump, cams push, in order, a plurality of fingers (also referred to as pins or plungers) arranged along a tube, the tube is closed by the fingers in order, and fluid in the tube is transported.
Compression and restoration of the tube are repeated by the fingers. When the tube is deteriorated over time, a restoring ability of the tube weakens, the capacity of the tube (intratubular capacity) during the restoration decreases, and transportation accuracy decreases. Therefore, in Patent Literature 1, the cross section of the tube is maintained in an elliptical shape even during maximum expansion of the tube (when the fingers are present in a releasing position) to reduce the influence of the aged deterioration. In Patent Literature 2, the restoring force of the tube is supplemented by an elastic sleeve that surrounds the tube and the tube is restored until the tube has a circular sectional shape.
During maximum compression of the tube (when the fingers are present in a compressing position), it is necessary to completely close the tube to prevent the fluid from flowing backward. To suppress the aged deterioration without using the elastic sleeve described in Patent Literature 2, it is necessary to deform the tube even during the maximum expansion of the tube (when the fingers are present in the releasing position).
According to the configurations of Patent Literatures 1 and 2, the positions of the fingers always depend on the cams. Therefore, according to these apparatus configurations, both of the compressing position and the releasing position of the fingers are set by the cams. When both of the compressing position and the releasing position of the fingers are set by the cams in this way, it is difficult to set tolerances of the cams, the fingers, and the like.

SUMMARY

An advantage of some aspects of the invention is to provide a high accuracy fluid transporting apparatus configured to facilitate the setting of tolerances of the cams and the fingers.
An aspect of the invention is directed to a fluid transporting apparatus including: a tube having elasticity; a plurality of fingers arranged along a transporting direction in which fluid is transported by the tube, each of the fingers reciprocatingly moving in a compressing direction for compressing the tube and a releasing direction opposite to the compressing direction; and a driving section configured to move each of the plurality of fingers in the compressing direction. The fluid transporting apparatus transports, with a compressing action of the fingers moving in the compressing direction and crushing the tube with ends of the fingers, fluid on the inside of the tube in the transporting direction and fills the fluid in the inside of the tube with a releasing action of the fingers for restoring the shape of the crushed tube. In the releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in the releasing direction is limited to a predetermined position.
Other characteristics of the invention are clarified by the descriptions of this specification and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a schematic sectional view of a fluid feed pump according to a first embodiment.

FIG. 2 is an enlarged view of the vicinity of a lower side brim section in a state in which a finger is released.

FIGS. 3A and 3B are diagrams for explaining the influence of permanent distortion that occurs in a tube.

FIG. 4 is a schematic diagram showing the configuration of a fluid feed pump in a comparative example 1.

FIG. 5A is a diagram for explaining fluctuation in a fluid transportation amount of fluid transported using the fluid feed pump in the comparative example 1.

FIG. 5B is a diagram for explaining fluctuation in a fluid transportation amount of fluid transported using the fluid feed pump according to the first embodiment.

FIG. 6 is a schematic diagram showing the configuration of a fluid feed pump in a comparative example 2.

FIG. 7 is a schematic diagram showing the configuration of a fluid feed pump according to a second embodiment.

FIG. 8 is a schematic diagram showing the configuration of a fluid feed pump according to a third embodiment.

FIG. 9 is an enlarged view of the vicinity of a brim section in a state in which a finger is released.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

At least matters explained below are clarified by the descriptions of this specification and the accompanying drawings.
A fluid transporting apparatus includes: a tube having elasticity; a plurality of fingers arranged along a transporting direction in which fluid is transported by the tube, each of the fingers reciprocatingly moving in a compressing direction for compressing the tube and a releasing direction opposite to the compressing direction; and a driving section configured to move each of the plurality of fingers in the compressing direction. The fluid transporting apparatus transports, with a compressing action of the fingers moving in the compressing direction and crushing the tube with ends of the fingers, the fluid on the inside of the tube in the transporting direction and fills the fluid in the inside of the tube with a releasing action of the fingers for restoring the shape of the crushed tube. In the releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in the releasing direction is limited to a predetermined position.
With such a fluid transporting apparatus, it is easy to set tolerances of cams and the fingers for performing the compressing and releasing actions for the tube. Therefore, it is possible to highly accurately and stably transport a predetermined amount of the fluid.
In the fluid transporting apparatus, it is preferable that a clearance is present between the driving section and the fingers when the fingers move to a highest position in the releasing direction.
With such a fluid transporting apparatus, during maximum releasing of the fingers, the fingers are not affected by the cams and the like. Therefore, it is easy to transport a fixed amount of the fluid without depending on the tolerances of the cams and the fingers.
It is preferable that the fluid transporting apparatus includes a limiting section configured to limit the movement of the fingers in the releasing direction and, when the fingers perform the releasing action, upper surfaces of brim sections provided on sides of the fingers in contact with the tube are pressed by the limiting section.
With such a fluid transporting apparatus, it is possible to specify, with the limiting section, a moving position in the releasing direction of the fingers. That is, since it is easy to keep a transportation amount of the fluid constant by securing the accuracy of the limiting section, it is possible to more easily and accurately transport the fluid. The structure of the apparatus is simplified by forming the limiting section using a simple structure such as a tabular member. Therefore, it is possible to realize the fluid transporting apparatus excellent in product management and in terms of costs.
It is preferable that a crushing amount of the tube crushed when the fingers move to a highest position in releasing direction is larger than an amount of permanent distortion that occurs in the tube when the compressing action and the releasing action are repeated.
With such a fluid transporting apparatus, even when permanent distortion occurs in the tube because of repetition of a peristaltic motion of the tube, it is possible to keep an amount of the fluid filled in the tube during the releasing action constant. That is, it is possible to highly accurately and stably transport a predetermined amount of the fluid without being affected by the permanent distortion.
It is preferable that, in the releasing action, the fingers move in the releasing direction with a restoring force of restoration of the shape of the crushed tube.
With such a fluid transporting apparatus, it is possible to perform the releasing action without providing an elastic body such as a coil spring. Therefore, the configuration of the fluid transporting apparatus is further simplified. It is possible to reduce the costs of the apparatus.
A fluid transporting method includes: reciprocatingly moving, in a compressing direction for compressing a tube having elasticity and a releasing direction opposite to the compressing direction, each of a plurality of fingers arranged along a transporting direction in which fluid is transported by the tube; transporting, with a compressing action of the fingers moving in the compressing direction and crushing the tube with ends of the fingers, the fluid on the inside of the tube in the transporting direction; filling the fluid in the inside of the tube with a releasing action of the fingers for restoring the shape of the crushed tube; and limiting, in the releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in the releasing direction to a predetermined position.

First Embodiment

Basic Configuration of a Fluid Transporting Apparatus

As an example of a form of a fluid transporting apparatus used in a first embodiment, a fluid feed pump 1 that transports fluid by causing a tube to peristaltically move is explained. Representative examples of the fluid transported by the fluid feed pump 1 include water, saline, a drug solution, oil, aromatic fluid, and ink. However, it is also possible to transport other kinds of fluid having fluidity.
FIG. 1 is a schematic sectional view of the fluid feed pump 1 according to the first embodiment. The fluid feed pump 1 includes a tube 10, a tube holding section 20, a driving section 30, and a compressing section 40.
The tube 10 is formed of a circular tube-like material having elasticity. Fluid to be transported is filled on the inside of the circular tube. The tube 10 is sequentially compressed by fingers 41 a to 41 g, whereby the tube 10 performs a peristaltic motion to transport the fluid filled on the inside. In the fluid feed pump 1, the tube 10 is linearly held. The fluid feed pump 1 transports the fluid from an inlet side shown on the left side in FIG. 1 to an outlet side shown on the right side. In this specification, a direction in which the fluid is transported along the tube 10 (a direction indicated by an arrow in FIG. 1) is referred to as transporting direction.
As the material of the tube 10, a soft and elastic material such as silicon, urethane resin, or soft vinyl is suitable. The diameter (the outer diameter) of the tube 10 is about 1.0 mm. However, the diameter and the thickness of the tube 10 can be changed according to a transportation amount of the fluid.
The tube holding section 20 holds the tube 10 on the inside of the fluid feed pump 1. The tube holding section 20 in this embodiment includes a guide wall 21 and a limiting wall 25.
The guide wall 21 is a member that fixes an attachment position of the tube 10. In the fluid feed pump 1, as shown in FIG. 1, the guide wall 21 configured to support at least a lower part of the tube 10. The limiting wall 25 is a limiting section provided to be opposed to the guide wall 21 across the tube 10 and configured to limit the action of the fingers 41 a to 41 g explained below during fluid transportation. Details of the function of the limiting wall 25 are explained below.
The driving section 30 includes cams 31 a to 31 g, a rotating shaft 32, and a power section 33. Power generated by the power section 33 is transmitted to the cams 31 a to 31 g via the rotating shaft 32 to rotate each of the cams 31 a to 31 g in a direction around the rotating shaft (a rotating direction) about the rotating shaft 32.
Each of the cams 31 a to 31 g has concavities and convexities in the outer circumferential direction. The cams 31 a to 31 g push ends (upper side brim sections explained below) of the fingers 41 a to 41 g with outer circumferential sections while rotating about the rotating shaft 32 to thereby drive each of the fingers 41 a to 41 g in a downward direction. By adjusting the shape, an attachment angle, and the like of each of the cams 31 a to 31 g, it is easy to individually control the action of the fingers 41 a to 41 g during fluid transportation.
The rotating shaft 32 is attached to an output shaft of the power section 33 via a not-shown gear train. The rotating shaft 32 transmits rotation power to the cams 31 a to 31 g.
The power section 33 rotates at predetermined speed to generate the rotation power. In this embodiment, for example, a step motor M adopted in a quartz clock or the like or a piezoelectric motor including a piezoelectric element can be used as the power section 33. The motor rotates on the basis of a driving signal transmitted from a driving circuit (not shown in the figure). A predetermined driving pattern is stored in the driving circuit in advance. The driving circuit generates the driving signal on the basis of the driving pattern.
A small button battery, a dry battery, or the like is used as a driving source for the driving section 30. In the fluid feed pump 1, since a built-in power supply is adopted, an external power supply is unnecessary. Therefore, the shape of the entire apparatus is kept compact and the apparatus is excellent in portability. However, it is also possible to supply electric power from the outside to the apparatus without providing a power supply on the inside.
The compressing section 40 includes the fingers 41 a to 41 g and elastic bodies 42 a to 42 g.
The fingers 41 a to 41 g are arranged side by side in order from the upstream side to the downstream side in the transporting direction. Each of the fingers 41 a to 41 g is provided to be substantially orthogonal to the tube 10. In other words, the fingers 41 a to 41 g are provided side by side along the transporting direction such that an axial direction of the fingers 41 a to 41 g and the transporting direction of the fluid are orthogonal to each other. All the shapes of the fingers 41 a to 41 g can be the same. In this embodiment, cylindrical brim sections are provided at both ends of bar-like portions (see FIG. 1). The diameter of the brim sections is larger than the diameter of the bar-like portions. One end sides (upper side brim sections shown in FIG. 1) are arranged to be respectively set in contact with the outer circumferential portions of the cams 31 a to 31 g (however, the cams 31 a to 31 g and the brim sections do not need to be always in contact with each other). On the other hand, the other end sides (lower side brim sections shown in FIG. 1) are arranged to be set in contact with the tube 10.
The elastic bodies 42 a to 42 g are respectively provided in the bar-like portions of the fingers 41 a to 41 g. The elastic bodies 42 a to 42 g generate elastic force between the upper side brim sections of the fingers 41 a to 41 g and the limiting wall 25 and push the upper side brim sections of the fingers 41 a to 41 g to the upward side to thereby move the fingers 41 a to 41 g in the upward direction in FIG. 1. As the elastic bodies, for example, springs (coil springs) shown in the figure can be used.
Each of the fingers 41 a to 41 g is driven by the driving section 30 (the cams 31 to 31 g) and reciprocatingly moves in a direction orthogonal to the transporting direction of the fluid to thereby compress or release the tube 10. For example, in FIG. 1, when the one end side (the upper side brim section) of the finger 41 a is pushed in the downward direction by the convexity of the cam 31 a, the other end side (the lower side brim section) moves to crush the tube 10. Such an action is hereinafter referred to as “compression”. A moving direction of the finger 41 a in the action is referred to as “compressing direction”. On the other hand, as in the finger 41 e shown in FIG. 1, when the one end side (the upper side brim section) separates from the convexity of the cam 31 e, force by the finger 41 e is not applied to the tube 10. Therefore, the crushed tube 10 is about to return to the original shape. At this point, the finger 41 e moves to be pushed back in the upward direction by the elastic body 42 e. Such an action is hereinafter referred to as “release”. A moving direction of the finger 41 e in the action is referred to as “releasing direction”. That is, the “releasing direction” and the “compressing direction” are opposite directions.

Concerning a Fluid Transporting Operation of the Fluid Feed Pump 1

A fluid transporting operation of the fluid feed pump 1 is briefly explained. According to the rotation of each of the cams 31 a to 31 g of the driving section 30 at predetermined speed, the fingers 41 a to 41 g are sequentially driven from the transporting direction upstream side to the transporting direction downstream side. That is, the fingers 41 a to 41 g sequentially move in the compressing direction along the transporting direction to thereby crush the tube 10 in order from the upstream side to the downstream side in the transporting direction (a compressing action). Consequently, the tube 10 is compressed and the fluid on the inside of the tube 10 is squeezed out to the downstream side in the transporting direction.
When the fingers 41 a to 41 g moving in the compressing direction according to the rotation of the cams 31 a to 31 g separate from the convexities of the cams 31 a to 31 g, the fingers 41 a to 41 g are sequentially released from the transporting direction upstream side to the transporting direction downstream side. That is, the fingers 41 a to 41 g sequentially move in the releasing direction along the transporting direction, the tube 10 is restored in order from the upstream side to the downstream side in the transporting direction (a releasing action). At this point, the fluid flows into the inside of the tube 10 from the upstream side in the transporting direction (the inlet side shown in FIG. 1) with a restoring force of the tube 10 (the tube 10 is filled with the fluid).
The compressing action and the releasing action are repeated, whereby a peristaltic motion is generated in the tube 10. The fluid filled in the tube is transported in the transporting direction.

Concerning Details of the Releasing Action

In the releasing action of the fluid feed pump 1, when the shape of the tube 10 crushed (compressed) by the fingers 41 a to 41 g is restored, the action in the releasing direction of the fingers 41 a to 41 g is limited by the limiting wall 25.
FIG. 2 is an enlarged view of the vicinity of the lower side brim section in a state in which the finger 41 a is released. During the releasing action of the finger 41 a, when the force in the compressing direction from the cam 31 a stops acting on the finger 41 a, the finger 41 a moves in the releasing direction with the elastic force of the elastic body 42 a. When the finger 41 a moves in the releasing direction by a predetermined amount, the upper surface side of the brim section (the lower side brim section) of the finger 41 a comes into contact with the limiting wall 25 to be pressed. That is, the movement in the releasing direction of the finger 41 a during the releasing action is regulated by the limiting wall 25. In other words, the movement of the finger 41 a in the releasing direction is limited to a predetermined position.
At this point, the lower surface side of the brim section of the finger 41 a is in contact with the tube 10. Therefore, in this embodiment, a part of the tube 10 remains crushed even during maximum release of the finger 41 a. In an example shown in FIG. 2, the movement in the releasing direction of the finger 41 a is limited in a position where a space between the brim section lower end of the finger 41 a and the upper end of the tube 10 (the upper end of the tube 10, the shape of which is completely restored) is h. Consequently, even when the finger 41 a is released to a maximum degree, an upper part of the tube 10 remains crushed as shown in the figure. That is, the shape of the tube 10 is not restored to the circular shape even during the maximum release. An amount of the fluid filled in the inside of the tube 10 is also limited.
The same applies to the fingers 41 b to 41 g.
In general, in a fluid transporting apparatus that makes use of a peristaltic motion of a tube, in some case, the tube itself is deteriorated and permanent distortion occurs while the peristaltic motion is repeated. When the permanent distortion occurs in the tube, fluctuation tends to occur in a restoration amount of the tube. Therefore, fluctuation occurs in an amount of fluid filled in the inside of the tube as well to make it difficult to keep a fluid transportation amount constant.
On the other hand, in the fluid feed pump 1 according to this embodiment, a part of the tube 10 remains crushed even in a maximum release state (a state in which the fingers move to a highest position in the releasing direction). That is, a maximum amount of the fluid filled in the inside of the tube 10 is set by limiting a movement amount of the fingers during the releasing action. As explained above, in this embodiment, the sectional shape of the tube 10 is not restored to the circular shape even during the releasing action. Therefore, the capacity of the inside of the tube 10 is small compared with the capacity of the tube 10 crushed when the movement amount of the fingers 41 a to 41 g is not limited. The volume of the fluid filled in the inside is also small. Therefore, even if permanent distortion or the like occurs in the tube 10, an amount of the fluid filled in the inside is easily kept constant without being affected by the permanent distortion. It is possible to highly accurately and stably transport a predetermined amount of the fluid.
A specific example of the influence of permanent distortion that occurs in the tube is explained. FIGS. 3A and 3B are diagrams for explaining the influence of permanent distortion that occurs in the tube.
FIG. 3A is a graph showing the displacement of the tube 10 in the compressing direction and the releasing direction in a test for repeating the compressing action and the releasing action for the tube 10 while applying a predetermined load to the tube 10 using the fingers 41 a to 41 g. The displacement of the tube 10 is measured with reference to, for example, a highest position of the tube 10 (the position of the vertex of the outer circumferential portion of the tube 10) set in the horizontal direction in a no-load state. In the figure, in compression 1, compression 2, and compression 100, relations between load conditions and displacements in a first compressing action, a second compressing action, and a one hundredth compression action are respectively plotted. The same applies to the releasing action. FIG. 3B is a diagram in which the displacement of the tube 10 in a range of 0 to 300 μm in FIG. 3A is enlarged and displayed.
When a load is applied to the tube 10 by the fingers 41 a to 41 g, the tube displacement gradually increases from 0 μm and reaches 800 μm when a load of about 120 gf is applied thereto. The tube 10 is crushed and the inside of the tube 10 is closed. The load with respect to the displacement is different during the compressing action and during the releasing action in the range of 600 to 800 μm of the displacement because fixing strength by the tube 10 itself acts.
According to FIG. 3A, it is seen that the displacement of the tube 10 under the same load condition gradually increases while the compressing action and the releasing action are repeated. For example, under a loading condition of 50 gf, while a displacement in the first compression is about 650 μm, a displacement in the one hundredth compression is 680 μm. The displacement of the tube 10 increases even when the same load is applied. That is, it is seen that the tube 10 itself tends to be displaced while the peristaltic motion of the tube 10 is repeated.
Focusing on a range of 0 to 100 μm of the displacement in FIG. 3B, it can be confirmed that permanent distortion occurs in the tube 10 when the compressing action and the releasing action are repeated. For example, in the first compression, the displacement increases from 0 μm as the load increases from 0 gf. On the other hand, in the first release, a displacement of about 50 μm occurs even when the load is 0 gf. In the one hundredth release, a displacement of about 100 μm occurs when the load is 0 gf. That is, an initial displacement of about 50 to 100 μm occurs even in the no-load state (a state of load=0 gf). The initial displacement is permanent distortion of the tube 10. The initial displacement occurs when the compressing and releasing actions are performed only once as shown in FIG. 3B. Therefore, a restoration amount of the tube 10 during the releasing action is smaller than an initial tube capacity (a capacity equivalent to the inner diameter of the tube 10) by an amount of the permanent distortion. Therefore, an amount of the fluid filled in the inside of the tube 10 decreases and a transportable amount of the fluid also decreases. As a result, it is difficult to highly accurately and stably transport a fixed amount of the fluid.
On the other hand, in this embodiment, as shown in FIG. 2, a movement amount in the releasing direction of the fingers 41 a to 41 g is limited by the limiting wall 25, whereby a restoration amount of the tube 10 is limited. The movement amount in the releasing direction of the fingers 41 a to 41 g is set such that a crushing amount (a compressing amount) of the tube 10 crushed when the fingers 41 a to 41 g moves to the highest position in the releasing direction is larger than an amount of permanent distortion that occurs in the tube 10. In other words, the movement amount is set such that a decrease in the restoration amount of the tube 10 due to movement limitation on the fingers 41 a to 41 g is larger than a decrease in the restoration amount of the tube 10 due to the permanent distortion.
For example, if h is set to 200 μm in FIG. 2, even when permanent distortion of about 100 μm occurs in the tube 10, since a maximum restoration amount (a maximum expansion amount) of the tube 10 is limited to be larger than the permanent distortion, an amount of the fluid filled in the tube 10 is kept constant. Therefore, it is possible to highly accurately and stably transport a predetermined amount of the fluid without being affected by the permanent distortion of the tube 10.

COMPARATIVE EXAMPLES

As comparative examples, fluid feeding operations performed when the limiting wall 25 is not provided in a fluid feed pump are explained.

Comparative Example 1

FIG. 4 is a schematic diagram showing the configuration of a fluid feed pump in a comparative example 1. A basic apparatus configuration of the fluid feed pump is the same as the basic apparatus configuration of the fluid feed pump 1. However, in the comparative example 1, the limiting wall 25 is not provided and a movement amount in the releasing direction of the fingers is not limited during the releasing action. Therefore, the fingers move to upper limit height with an elastic force of elastic bodies. As in the fingers 41 d to 41 f shown in FIG. 4, a gap (play) is formed between the lower side brim sections and the tube 10. That is, since the brim sections of the fingers 41 d to 41 f and the tube 10 are not in contact with each other, a restoring action of the tube 10 is not limited by the action of the fingers 41 d to 41 f. Therefore, in the positions of the fingers 41 d to 41 f, the fluid is filled in the tube 10 according to a restoring force of the tube 10 irrespective of the positions of the fingers 41 d to 41 f during the maximum release.
When the compression and the release for the tube 10 is repeated in such a situation, as explained above, the restoring force of the tube 10 gradually weakens and permanent distortion occurs. As a result, fluctuation occurs in an amount of the fluid filled in the inside of the tube 10 and fluctuation tends to occur in a transportation amount of the fluid as well.
The occurrence of the fluctuation in the fluid transportation amount is specifically explained with reference to FIGS. 5A and 5B. FIG. 5A is a diagram for explaining fluctuation in the fluid transportation amount that occurs when the fluid feed pump in the comparative example 1 is used. FIG. 5B is a diagram for explaining fluctuation in the fluid transportation amount that occurs when the fluid feed pump 1 according to the first embodiment is used. The abscissa of the figures represents a rotation amount of the rotating shaft 32 (the cams 31 a to 31 g) during the fluid transporting operation and the ordinate represents the fluid transportation amount. Six kinds of plots in the figures indicate results obtained by performing tests six times using the same tube 10.
In the case of FIG. 5A (the comparative example 1), fluctuation in a flow rate increases as the rotation amount of the rotating shaft 32 increases, i.e., the peristaltic motion of the tube 10 is repeated. For example, when flow rates obtained when the peristaltic motion is performed once (near a rotation amount of 240 degrees in the figure) are compared, a difference among test flow rates in first to sixth times of the test is about 0.00021 at most. On the other hand, when flow rates obtained when the peristaltic motion is performed four times (near a rotation amount of 960 degrees in the figure) are compared, a maximum difference among test flow rates in the first to sixth times of the test is 0.00051. It is considered that such fluctuation in the flow rate occurs because permanent distortion or the like occurs according to the repetition of the peristaltic motion of the tube 10, the restoring force of the tube 10 falls, and an amount of the fluid filled in the inside of the tube 10 changes. When the peristaltic motion is repeated, the permanent distortion that occurs in the tube 10 further increases. Therefore, it is likely that the fluctuation in the fluid transportation amount also further increases. It is more difficult to perform highly accurate fluid transportation. The pump with the low fluid transportation accuracy cannot be applied to drug solution injection and the like for medical purpose.
On the other hand, in the case of FIG. 5B (the first embodiment) , even if the rotation amount of the rotating shaft 32 increases (i.e., the peristaltic motion of the tube 10 is repeated), fluctuation in the fluid transportation amount is small compared with the case of FIG. 5A. This is because, in the first embodiment, when the tube 10 is restored from the compressed state, a restoration amount is limited by the limiting wall 25, whereby an amount of the fluid filled in the inside of the tube 10 is kept constant regardless of permanent distortion that occurs in the tube 10. As a result, although a fluid transportation amount per unit time is smaller than the fluid transportation amount in the case of the comparative example 1, it is possible to realize a more highly accurate and stable transportation of a fixed amount of the fluid.

Comparative Example 2

Among methods of fixing a transportation amount of the fluid by limiting a restoration amount of the tube, a method different from the method in the first embodiment is explained as a comparative example 2. FIG. 6 is a schematic diagram showing the configuration of a fluid feed pump in the comparative example 2.
In the comparative example 2, setting positions of the rotating shaft 32 and the cams 31 a to 31 g are adjusted, whereby a movement amount of the fingers 41 a to 41 g during the releasing action is limited. Consequently, the maximum restoration amount (the maximum expansion amount) of the tube 10 is kept constant. As in the fluid feed pump 1 according to the first embodiment, it is possible to transport a fixed amount of the fluid without being affected by permanent distortion or the like.
However, in the comparative example 2, a member equivalent to the limiting wall 25 in the fluid feed pump 1 is not provided. The action of the fingers 41 a to 41 g is adjusted according to the positions of the cams 31 a to 31 g, the rotating shaft 32, and the like to adjust the maximum restoring amount of the tube 10. Specifically, the positions of the fingers 41 a to 41 g rising to the uppermost side in the releasing direction in the releasing action are determined by the cams 31 a to 31 g. In the case of FIG. 6, the position of the finger 41 f is the highest position in the releasing direction. At this point, the upper end of the finger 41 f is pressed by the cam 31 f, whereby the height of the finger 41 f is adjusted and a part of the tube 10 is compressed.
When the maximum restoration amount of the tube 10 is adjusted as in the comparative example 2, a method of adjusting accuracy and setting positions of the components such as the cams 31, the rotating shaft 32, and the fingers 41 is a problem. For example, when errors in manufacturing occur in the size of the concavities and convexities of the cams 31 a to 31 g and the length of the fingers 41 a to 41 g, even if the positions of the fingers 41 a to 41 g during the maximum release are accurately adjusted, it is likely that the positions of the lower side brim sections of the fingers 41 a to 41 g shift. When large tolerances set for straightness and cylindricity of the rotating shaft 32, likewise, it is likely that the positions of the lower side brim sections of the fingers 41 a to 41 g shift. When the positions of the lower side brim sections of the fingers 41 a to 41 g shift, fluctuation occurs in the restoration amount of the tube 10 during the maximum release. Therefore, fluctuation occurs in an amount of the fluid filled in the tube 10 as well. As a result, it is difficult to perform highly accurate and stable fluid transportation.
Therefore, in realizing highly accurate and stable fluid transportation in the comparative example 2, it is necessary to strictly manage manufacturing accuracy, assembly accuracy, and the like of the components of the driving section 30 and the compressing section 40. In particular, when accuracy in micrometer order is requested as the displacement of the tube 10 as explained in the example shown in FIGS. 3A and 3B, large costs are required for manufacturing, assembly, maintenance, and the like of the components.
On the other hand, in the fluid feed pump 1 according to the first embodiment, the positions of the fingers 41 a to 41 g during the maximum release are specified by the limiting wall 25. As a result, a gap (a clearance) is formed between the cams 31 a to 31 g and the fingers 41 a to 41 g during the maximum release. For example, when the finger 41 f is present in the highest position in the releasing direction in FIG. 1, clearance is formed between the cam 31 f and the finger 41 f. The cam 31 f and the finger 41 f are in non-contact with each other. That is, a restoration amount of the tube 10 during the maximum release is specified by the limiting wall 25 rather than by the positions of the cams 31 a to 31 g. Therefore, regions where accuracy of the components is requested are limited by the limiting wall 25 and the like. However, since the limiting wall 25 is an immovable tabular member, it is relatively easy to secure accuracy of setting positions and manufacturing accuracy. That is, it is easy to set accuracy, tolerances, and the like of the cams 31 a to 31 g and the fingers 41 a to 41 g.
Consequently, the fluid feed pump 1 according to this embodiment is excellent in terms of product management and costs compared with the comparative example 2.

Second Embodiment

In the first embodiment, in the releasing action, the elastic force is generated by the elastic bodies (the elastic bodies 42 a to 42 g shown in FIG. 1) provided in the compressing section 40 to move the fingers 41 a to 41 g in the releasing direction. However, the fingers 41 a to 41 g may be moved by other methods.
FIG. 7 is a schematic diagram showing the configuration of a fluid feed pump 2 according to a second embodiment. In the fluid feed pump 2, elastic members equivalent to the elastic bodies 42 a to 42 g in the fluid feed pump 1 are not provided. The other configurations are substantially the same as the configurations of the fluid feed pump 1.
In this embodiment, in the releasing action, the fingers 41 a to 41 g move in the releasing direction with the restoring force of the tube 10. That is, the fingers 41 a to 41 g are pushed up in the releasing direction by the force of the tube 10 crushed during the compressing action returning to the original shape. With this method, large resistance acts on the tube 10 when the tube 10 is restored from the compressed state. Therefore, the tube 10 tends to be deteriorated and permanent distortion tends to occur.
However, as in the fluid feed pump 1 according to the first embodiment, since the action in the releasing direction of the fingers 41 a to 41 g is limited by the limiting wall 25, the influence of the permanent distortion that occurs in the tube 10 less easily appears. That is, a crushing amount (a compressing amount) of the tube 10 crushed when the fingers 41 a to 41 g move to the highest position in the releasing direction is larger than an amount of the permanent distortion that occurs in the tube 10. Therefore, even when the releasing action is performed by the restoring force of the tube 10 itself, an amount of the fluid filled in the tube 10 tends to be kept constant.
Consequently, it is possible to perform highly accurate and stable fluid transportation. Further, since it is unnecessary to provide elastic bodies such as coil springs, the configuration of the fluid transporting apparatus is more simplified. As a result, it is possible to reduce costs of the apparatus.

Third Embodiment

In a fluid feed pump 3 according to a third embodiment, the tube 10 is arranged in a circumferential shape. The tube 10 is compressed and released by fingers radially provided around a rotating shaft in the center to thereby transport the fluid filled in the tube 10.

Configuration of the Fluid Feed Pump 3

FIG. 8 is a schematic diagram showing the configuration of the fluid feed pump 3 according to the third embodiment. The fluid feed pump 3 includes the tube 10, the tube holding section 20, the driving section 30, and the compressing section 40.
The tube 10 is equivalent to the tube 10 explained above in the embodiments. However, in the fluid feed pump 3, the tube 10 is retained in a circumferential shape (an arcuate shape) as shown in FIG. 8. In this embodiment, the fluid is transported in the circumferential direction along the tube 10 retained in the circumferential shape. That is, the transporting direction of the fluid is the circumferential direction.
The tube holding section 20 includes a guide wall 22 and a limiting wall 26. The guide wall 22 is a circular member shown in FIG. 8. The guide wall 22 configures a part of a casing of the fluid feed pump 3 and holds the tube 10 in a circumferential shape (an arcuate shape) in a groove on the inside of the guide wall 22 . The limiting wall 26 is a disk-like member and supports fingers 43 a to 43 g. The limiting wall 26 has a step extending along the circumferential direction in a portion where the limiting wall 26 supports the fingers 43 a to 4 3g. The action in the releasing direction of the fingers 43 a to 43 g is limited by the step. Details are explained below.
The driving section 30 includes a cam 35, a rotating shaft 36, and a not-shown power section. Power generated by the rotation of the power section is transmitted to the cam 35 via the rotating shaft 36 to rotate the cam 35 in the circumferential direction (i.e., a direction around the rotating shaft) around the rotating shaft 36 (the arc center of the tube 10). As shown in FIG. 8, the cam 35 has concavities and convexities in the outer circumferential portion. The cam 35 pushes the fingers 43 a to 43 g with the outer circumferential section while rotating to drive each of the fingers.
The compressing section 40 includes a plurality of fingers (the fingers 43 a to 43 g in FIG. 8). The fingers 43 a to 43 g are arranged side by side in a radial shape around the rotating shaft 36. Each of the fingers 43 a to 43 g is provided to be substantially orthogonal to the tube 10. All the shapes of the fingers 43 a to 43 g are the same. One end sides of the fingers 43 a to 43 g are rounded in a semispherical shape and arranged in contact with the cam 35. The other end sides of the fingers 43 a to 43 g are disk-like brim sections and arranged in contact with the tube 10 (see FIG. 8). The shape and the number of the fingers are not limited to the shape and the number explained above.
The fingers 43 a to 43 g are driven by the cam 35 of the driving section 30. The fingers 43 a to 43 g reciprocatingly move in a direction orthogonal to the transporting direction of the fluid to cause a peristaltic motion in the tube 10 and transport the fluid on the inside of the tube 10. For example, in the finger 43d shown in FIG. 8, when one end side is pushed by the convexity of the cam 35, the brim section on the other end side moves to crush the tube 10. In this embodiment, this action is referred to as “compression” and a moving direction of the finger in the action is referred to as “compressing direction”. On the other hand, in the FIG. 43 a shown in FIG. 8, when one end separates from the convexity of the cam 35, force acting in the compressing direction is not applied to the tube 10. Therefore, the crushed tube 10 is about to return to the original shape. The finger 43 a moves to be pushed back by the restoring force of the tube 10. In this embodiment, this action is referred to as “release” and a moving direction of the fingers 43 a to 43 g in the action is referred to as “releasing direction”.
In FIG. 8, the fingers 43 a to 43 g and the cam 35 are drawn as if the fingers 43 a to 43 g and the cam 35 are always in contact with each other. However, it is preferable to adopt a configuration in which a gap (a clearance) is formed between the fingers and the cam (the driving section) when the fingers move to the highest position in the releasing direction (a position closest to the rotating shaft). The configuration is adopted to specify moving positions in the releasing direction of the fingers 43 a to 43 g with the limiting wall 26 rather than the cam 35.

Concerning a Fluid Transporting Operation of the Fluid Feed Pump 3

A fluid transporting operation by the fluid feed pump 3 is basically the same as the fluid transporting operation by the fluid feed pump 1. That is, the fingers 43 a to 43 g are sequentially driven from the upstream side to the downstream side in the fluid transporting direction according to the rotation of the cam 35. The fingers 43 a to 43 g repeat the compressing action and the releasing action to cause a peristaltic motion in the tube 10 and transport the fluid on the inside of the tube 10 in the transporting direction (the circumferential direction).
At this point, the releasing action of the fingers 43 a to 43 g is limited by the limiting wall 26. FIG. 9 is an enlarged view of the vicinity of the brim section in a state in which the finger 43 a is released. During the releasing action of the finger 43a, when the force in the compressing direction from the cam 35 stops acting on the finger 43 a, the finger 43 a moves in the releasing direction (the direction of the rotating shaft 36) with the restoring force of the tube 10. When the finger 43 a moves in the releasing direction by a predetermined amount, the brim section of the finger 43 a comes into contact with the limiting wall 26. Consequently, the movement in the releasing direction of the finger 43 a is limited. In FIG. 9, the movement in the releasing direction of the finger 43 a stops in a position where a space between the brim section lower end of the finger 43 a and the upper end of the tube 10 (the upper end of the tube 10, the shape of which is completely restored) is h′. Consequently, since a part of the tube 10 is crushed, as in the embodiments explained above, it is possible to fill a fixed amount of the fluid in the inside of the tube 10 without being affected by permanent distortion. Therefore, it is possible to realize a highly accurate and stable fluid transporting operation.

Other Embodiments

The fluid transporting apparatus including the fluid feed pump that repeats the compressing and releasing actions with the fingers is explained as the embodiments. However, the embodiments are embodiments for facilitating understanding of the present invention and not for limitedly interpreting the present invention. The present invention can be altered and modified without departing from the spirit of the present invention. It goes without saying that the present invention includes equivalents thereof. In particular, an embodiment explained below is also included in the present invention.

Concerning the Driving Section

The driving section 30 explained in the embodiments explained above rotates the cams 31 or the cam 35 to sequentially drive the fingers. However, the fingers may be driven using a structure other than the cams. Concerning the actions of the fingers, the fingers may be driven using, for example, a crank mechanism as long as the actions can be realize at timing explained in this specification.
The entire disclosure of Japanese Patent Application No. 2012-105146, filed May 2, 2012, is expressly incorporated by reference herein.

Claims

What is claimed is:

1. A fluid transporting apparatus comprising:

a tube having elasticity;

a plurality of fingers arranged along a transporting direction in which fluid is transported by the tube, each of the fingers reciprocatingly moving in a compressing direction for compressing the tube and a releasing direction opposite to the compressing direction; and

a driving section configured to move each of the plurality of fingers in the compressing direction,

the fluid transporting apparatus transporting, with a compressing action of the fingers moving in the compressing direction and crushing the tube with ends of the fingers, the fluid on an inside of the tube in the transporting direction and filling the fluid in the inside of the tube with a releasing action of the fingers for restoring a shape of the crushed tube, wherein

in the releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in the releasing direction is limited to a predetermined position.

2. The fluid transporting apparatus according to claim 1, wherein a clearance is present between the driving section and the fingers when the fingers move to a highest position in the releasing direction.

3. The fluid transporting apparatus according to claim 1, further comprising a limiting section configured to limit the movement of the fingers in the releasing direction, wherein

when the fingers perform the releasing action, upper surfaces of brim sections provided on sides of the fingers in contact with the tube are pressed by the limiting section.

4. The fluid transporting apparatus according to claim 1, wherein a crushing amount of the tube crushed when the fingers move to a highest position in releasing direction is larger than an amount of permanent distortion that occurs in the tube when the compressing action and the releasing action are repeated.

5. The fluid transporting apparatus according to claim 1, wherein, in the releasing action, the fingers move in the releasing direction with a restoring force of restoration of the shape of the crushed tube.

6. A fluid transporting method comprising:

reciprocatingly moving, in a compressing direction for compressing a tube having elasticity and a releasing direction opposite to the compressing direction, each of a plurality of fingers arranged along a transporting direction in which the fluid is transported by the tube;

transporting, with a compressing action of the fingers moving in the compressing direction and crushing the tube with ends of the fingers, fluid on an inside of the tube in the transporting direction;

filling the fluid in the inside of the tube with a releasing action of the fingers for restoring a shape of the crushed tube; and

limiting, in the releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in the releasing direction to a predetermined position.