EP0470333B1

EP0470333B1 - Flexible tube for volume displacement machine

Info

Publication number: EP0470333B1
Application number: EP91106814A
Authority: EP
Inventors: Katsuo Hosokawa
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-07
Filing date: 1991-04-26
Publication date: 1997-07-09
Anticipated expiration: 2011-04-26
Also published as: DE69126746T2; EP0470333A1; DE69126746D1

Description

BACKGROUND OF THE INVENTION

The present invention relates to a flexible tube means for a volume displacement machine which can be widely used as, for example, a motor, a compressor, a pump and the like.
A volume displacement machine of the type described above is exemplified by a prime mover.
Conventional prime movers exemplified by gasoline engines and diesel engines are arranged to use gasoline or heavy oil. Therefore, an advantage can be obtained in that they can be used in the regions to which no electric power is supplied. However, a problem of noise arises since explosive noise is made at the time of inflammations. In order to overcome the above-described problem, motors are used. However, although the operative noise can be satisfactorily reduced with the conventional motors, they cannot be used in the regions in which electric power cannot easily be obtained.
Furthermore, the motors are structured too complicatedly and the overall cost cannot be reduced. Therefore, the inventor of the present invention has developed a volume displacement machine which uses a flexible tube. The above-described volume displacement machine is arranged in such a manner that a cylindrical flexible tube, which is connected to a supply port, is disposed along the inner surface of a cylindrical case. Furthermore, a rotor is concentrically disposed in the cylindrical case and rollers for abutting the tube against the above-described inner surface are provided at the end portions of the rotor. The thus arranged volume displacement machine acts in such a manner that, when compressed air is supplied into the tube through the above-described supply port, the tube abuts the rollers in the circumferential direction while being expanded. As a result, the rotor can be rotated.
If a conventional flexible tube is used, it will be bent at its bent portion to be a flat shape when it is abutted against the inner surface of the cylindrical case by the rollers. Therefore, the bent portion will be destructed due to fatigue if the flexible tube is repeatedly subjected to the bending operation and the restoring operation. As a result, a problem of unsatisfactory durability of the flexible tube arises. What is even worse, a gas leaks and thereby an energy loss takes place because the confronting surfaces of the inner bent portion of the flexible tube cannot be brought into hermetic contact with each other, that is, a gap is created.
US-A-3,508,587 discloses a tubular structural member which is adapted to withstand repeated flattening and returning into a tubular form. Even though it is not described for use in a peristaltic pump, certain embodiments disclosed therein may be capable of this use. According to one embodiment disclosed, a tubular member has a spring steel inner elastic member. However, the inner elastic member does not comprise two end portions having hollow portions and/or having a hollow portion at a central portion thereof.
Other tubular members are disclosed in US-A-4 705 464 and EP-A-0 094 580 as well as EP-A-0 325 470 and GB-1 464 894 (corresponding to NL-A-7 301 380).
With the tube members according the above prior art, the bent portion of a flexible tube is prone to be destructed due to fatigue if the flexible tube is repeatedly subjected to the bending operation and the restoring operation. Further, the confronting surfaces of the inner bent portion of the flexible tube can not be brought into hermetical contact with each other such that, when used in a pump, the pumped fluid will leak and thereby energy loss will occur.

SUMMARY OF THE INVENTION

In order to overcome the problems outlined above, it is the object of the present invention to improve the durability of a flexible tube and to prevent energy loss.
This object is achieved by the features of claim 1. Preferred embodiment of the invention are disclosed in the dependent claims.
When the above-described flexible tube is abutted against the inner surface of the cylindrical case by the rollers, it is bent at its bent portion so that it has a flat cross sectional shape. At this time, the confronting surfaces of the inner bent portion are brought into hermetically contact with each other via the elastic reinforcing member. Furthermore, the angular degree of the bent portion is restricted by the elastic reinforcing member.
Other and further objects, features and advantages of the invention will be appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1 to 10 illustrate embodiments of a volume displacement machine utilizing the flexible tube means of the present invention, where

Fig. 1 is a front elevational vertical cross sectional view;
Fig. 2 is a side elevational vertical cross sectional view;
Fig. 3 is a plan view of an expanding tube;
Fig. 4 is a cross sectional view taken along line IV-IV of Fig. 3;
Fig. 5 is a cross sectional view taken along line V-V of Fig. 3;
Fig. 6 is a cross sectional view taken along line VI-VI of Fig. 3;
Fig. 7 is a plan view of a tube according to another embodiment of the volume displacement machine;
Fig. 8 illustrates the work performed in the structure according to the first embodiment;
Fig. 9 is a front elevational view which illustrates an embodiment of a position adjustment device;
Fig. 10 is a plan view which illustrates another embodiment of the flexible tube and which corresponds to Fig. 3;
Figs. 11 to 14 illustrate the invention, where
- Fig. 11 is a vertical cross sectional view which illustrates a first embodiment;
- Fig. 12 is a cross sectional view which illustrates another state of Fig. 11;
- Fig. 13 is a vertical cross sectional view which illustrates a second embodiment and which corresponds to Fig. 11;
- Fig. 14 is a cross sectional view which illustrates another state of Fig. 13.

PREFERRED EMBODIMENTS OF THE INVENTION

A volume displacement machine will now be described with reference to Figs. 1 to 10, where the same reference numerals represent the same elements. A supply port 3 is formed in a cylindrical case 2 secured to a base 1. A flexible tube 4 is connected to the above-described supply port 3. The supply port 3 is connected to an injection pipe 5 which extends in the tangential direction of the cylindrical case 2.
As shown in Figs. 3 to 6, the flexible tube 4 is made of a flexible material such as rubber and arranged to be in the form of a tapered shape, that is, a so-called expanding type. The above-described flexible tube 4 is arranged on an inner surface 2a of the cylindrical case 2, the length L of the flexible tube 4 being determined properly to meet a requirement. The cylindrical case 2 includes a rotor 6 disposed concentrically. Four rollers 7, 8, 9 and 10 are disposed in the front portion of the rotor 6 at the same interval. Each of the above-described rollers 7 to 10 is arranged to be longer than the maximum width W of the tube 4. Furthermore, a shaft 11 of each of the rollers 7 to 10 is urged by a pre-loading spring 12 toward the above-described inner surface 2a. As a result, each of the rollers 7 to 10 presses the tube 4 toward the inner surface 2a in such a manner that the above-described tube 4 is divided into a first chamber a, a second chamber b, a third chamber c and a fourth chamber d.
Then, the operation of the above-described embodiment will now be described. When a fluid, for example, compressed air G, is supplied to the injection pipe 5, air G passes from the supply port 3 in the tangential direction so that it is introduced into the first chamber a of the tube 4.
Since the first chamber a is hermetically sealed up by the roller 7 which is being urged by the pre-loading spring 12, there is no outlet through which air G can be discharged. Therefore, the first chamber a is expanded, causing its surface to abut against the roller 7 in circumferential direction R. As a result, the above-described roller 7 moves in the circumferential direction R while hermetically sealing the first chamber a. Since the roller 7 moves while rotating, the frictional resistance of the tube 4 can be reduced. As a result, the tube 4 can be prevented from damage. When the roller 7 is rotated as described above, also the rollers 8 to 10 are rotated simultaneously.
Since the tube 4 is arranged to be in the form of the tapered shaped, volumes V of the chambers a to d are enlarged in a sequential order of the first chamber a, the second chamber b, the third chamber c and the fourth chamber d. Therefore, the pressures P1 to P4 of the chambers a to d are reduced in the sequential order of the pressure P1 of the first chamber a, the pressure P2 of the second chamber b, the pressure P3 of the third chamber c and the pressure P4 of the fourth chamber d.
Therefore, pressure difference P1 - P2 is generated between the first chamber a and the second chamber b, pressure difference P2 - P3 is generated between the second chamber b and the third chamber c, pressure difference P3 - P4 is generated between the third chamber c and the fourth chamber d. As a result, abutting force in the circumferential direction R acts on each of the rollers 7 to 10 by a level which corresponds to the pressure difference. Therefore, each of the rollers 7 to 10 rotates while sectioning the tube 4 so that the rotor 6 rotates smoothly.
When the roller 7 rotates by an angular degree of 90° in the circumferential direction as described above and thereby it is positioned on a radial line B, the roller 10 is moved to a position on a radial line A so as to hermetically seal up the first chamber a. Since the roller 8 is moved to a position on a radial line C and the roller 9 is removed from the tube 4 at this time, the third chamber c is opened so that compressed air G in the third chamber c is discharged through a discharge port 13 into the case 2. When the roller 7 is rotated by an angular degree of 180° as described above and thereby it is moved to a position on the radial line C, the roller 8 is removed from the tube 4, causing the second chamber b to be opened. Therefore, compressed air G in the second chamber b is discharged through the discharge port 13 into the case 2. When the roller 7 is further rotated by an angular degree of 90°C and thereby it is moved to a position on a radial line D, the roller 7 is removed from the tube 4, causing the first chamber a to be opened. As a result, compressed air G in the second chamber a is discharged through the discharge port 13 into the case 2.
When the above-described process is repeated, the rotor 6 rotates smoothly.
It is possible to adjust the revolving speed of the rotor 6 in a step-less manner by regulating the quantity of compressed air G to be supplied to the tube 4.
The above-described volume displacement pump is not limited to the above-made description. For example, compressed air serving as the fluid to be supplied to the supply port under pressure may be replaced by steam, water or alcohol.
Although the above-described embodiment is arranged in such a manner that the rollers 7 to 10 are abutted against the inner surface 2a of the cylindrical case 2 by the pre-loading spring 12, the embodiment is not limited to this. For example, the rollers 7 to 10 may be secured to a roller supporting plate 34 by a position adjusting device 30 as shown in Fig. 9. The position adjusting device 30 comprises an eccentric shaft 33 with a nut (omitted from illustration) disposed at the end portion of the eccentric shaft 33. Therefore, when the above-described nut is rotated in a direction designated by an arrow A, the center 37a of the shaft 37 of the roller is moved to 37b adjacent to a peripheral end 34a of the roller support plate 34 so that the roller is brought to a state 35 designated by a chain line. When the nut is rotated in the reverse direction to that in the above-described case, the center 37b of the shaft 37 of the roller is moved to 37a adjacent to the center 34b of the roller support plate 34 so that the roller is returned to the original state. As described above, the roller 37 is positioned at the predetermined position before the eccentric shaft 33 is secured to the roller support plate 34 by a fixing screw 39 so that the position of the roller 37 is maintained at the predetermined position.
Another structure may be employed which is arranged in such a manner that compressed air G is discharged outside as an alternative to the structure arranged in such a manner that the same is discharged into the case 2. In the case where the same is discharged outside, a discharge passage, which is connected to outside, is formed in the above-described case so as to be connected to the discharge port of the tube.
Furthermore, the above-described expanding type flexible tube 4 may be replaced by a straight cylindrical tube as shown in Fig. 7 or by a so-called combined type tube arranged in such a manner that the portion adjacent to the inlet port 43a of a flexible tube 43 is in the form of a straight cylindrical shape and the portion adjacent to the outlet port 43b is in the form of an expanding type.
The number of the rollers, the shape, the length and the number of the tubes and the number of the supply ports to be connected to the tube may, of course, be properly determined depending upon the type of the fluid which is employed.
Since the volume displacement machine is structured as described above, the tube is expanded when the fluid is, under pressure, introduced into the flexible tube through the supply port. As a result, the rollers are rotated in the circumferential direction, causing the rotor to be rotated. Consequently, the machine connected to the rotor is rotated.
Since the above-described volume displacement machine does not require electric power, it can be used effectively not only in the regions in which electric power can be obtained but also in the regions in which the same cannot easily be obtained.
Furthermore, since noise which will be generated during the operation of the volume displacement machine can be reduced satisfactorily in comparison to the gasoline engines and the diesel engines, the problem of the noise can be overcome.
In addition, the structure can be simplified, the overall cost can be reduced and the machine maintenance can easily be completed in comparison to the conventional structure.
Then, the work performed in the flexible tube will be described with reference to a graph about the work shown in Fig. 8. In a case of the expanding type tube (gas), although the pressure P is not changed in the first chamber a as designated by a horizontal line, the volume V increases from 0 to b'. When the second chamber b has been formed, the pressure P commences a reduction. When the third chamber c is formed, the pressure P is lowered from b to c and the volume V is enlarged from 0 to c'. When the fourth chamber d is formed, the pressure P is lowered to d and the volume V increases from 0 to d'. As a result, a work volume (energy) which corresponds to the area defined by a line passing through a, b, c, d, d' and 0 can be obtained in the case of the expanding type tube. In a case of a straight type tube (liquid), although the pressure P is not changed as designated by the horizontal line in the first chamber a because isobaric expansion takes place, the volume V is changed. Since both the pressure P and the volume V are not changed from the second chamber b to the fourth chamber d via the third chamber c, a work volume (energy) which corresponds to the area defined by a line passing through a, b, b' and 0 can be obtained in the case of the straight type tube.
Therefore, the straight type tube does not need the third chamber c and the fourth chamber d. Furthermore, no effect can be obtained from the structure as shown in Fig. 7 in which the tube is lengthened.
The volume displacement machine serves as a means for converting expanding energy of the fluid into mechanical energy, the volume displacement machine being used in a prime mover.
The volume displacement machine can be specified as, for example, A: motor utilizing a gas, B: compressor utilizing a gas, C: hydraulic power motor, D: pump.
Then, the specific examples A to D will now be described.

A: Motor utilizing a gas

A1. Rankine cycle steam motor

The volume displacement machine can be used as the output of a rankine cycle which converts steam pressure into mechanical energy. The motor of this type exhibits the following advantages in comparison to the conventional systems:

a: Energy loss due to condensation can be reduced because of the following reasons:
- a1. Each tube is made of a material having a low thermal conductivity.
- a2. The steam flows continuously in one way.
- a3. The steam does not expand at the same position as the inlet port through which the steam is introduced as in a multi-step expansion type steam engine.
- a4. A flexible adjustment can be performed in a low revolving speed range. That is, a transmission device, which is necessary for 4-cycle engines, can be eliminated from the structure.
b. An excellent volume efficiency can be obtained even if the gas fluid pressure is low because of an excellent airtightness and reduced fluid loss.
c. Excellent mechanical energy is obtainable due to a reduced resistance loss.
d. An excellent expansion efficiency can be obtainable in a structure in which an expanding type tube is employed which enables steam to discharge its expansion energy when it is transmitted from the engine.
e. Since the flexible tube exhibits an extremely simple structure and thereby its manufacturing cost can be reduced, the overall cost of the motor can be reduced.

A2. Air motor

When a gas motor is employed in a motor in which compressed air moves, for example, in a tool (drill, a nut clamping tool, a grinder, a crasher) operated by compressed air, the following advantages can be obtained in comparison to the conventional air motors:

a. A high volume efficiency can be obtained. An ordinary air motor undesirably leaks its output by 50 % since 50 % of the input passes through without relating to the mechanical power. However, the efficiency can be raised to a 90 % of the volume efficiency according to the volume displacement machine according to the present embodiment.
b. An excellent expansion efficiency can be obtained. The conventional air motor has not been designed so as to obtain the expansion energy from air. An ordinary level of 6 atmosphere possesses about 50 % of expansion energy. The fact that the above-described expansion energy is not utilized means an efficiency reduction by 50 %. The volume displacement machine according to the present embodiment is designed in such a manner that the main portion of the expansion energy can be utilized by employing the expanding type tube which enables the volume of air to be expanded two times or more. According to this structure, the expansion loss can be reduced to about 10 %.
c. In comparison to an ordinary air motor, the necessity of performing the internal lubrication can be eliminated from the volume displacement machine. This means a fact that mixture of oil into compressed air can be prevented and oil does not fly outside when air discharges. This fact has been considered important recently. In other words, the ordinary air motors are the causes of the environmental pollution, while the present volume displacement machine does not relate to the environmental pollution.
d. No expansion takes place in an oridinary air motor, causing noise to be inevitably generated when air discharges from the motor (at 6 bars). However, since air is expanded in the present volume displacement machine before air is discharged outside, noise can, of course, be eliminated. In other words, the ordinary air motors are noisy, while the present volume displacement machine is quiet.

A3. Air compressor

The present volume displacement machine can be employed as a gas compressor in place of a motor which utilizes a gas or steam. It can also be employed as the compressor of a refrigeration system. The following advantages can be obtained in comparison to the other compressors:

a. A high volume efficiency can be obtained even if the capacity is not sufficiently large.
b. The energy loss of the gas, which will take place when the heated gas is introduced into the compressor, can be prevented because the flexible tube has the low thermal conductivity.
c. It can easily be machined and thereby the manufacturing cost can be reduced.
d. In comparison to the other compressors, the present volume displacement machine does not need a lubricating operation. This fact means that the refrigerator is not contaminated by the oil deposit. Furthermore, the thermal conduction between the high temperature portions and the low temperature portions in the apparatus due to the lubricating oil can be prevented. In addition, a necessity of examining the possibility of mixture with the lubricating oil can be eliminated when a refrigerant is selected.
e. Since the present volume displacement machine does not involve a predetermined compression ratio which is established for an ordinary screw or scroll type compressors, the refrigerant system exhibits an excellent efficiency in a wide temperature range. This advantage is also exhibited with respect to piston type compressors.

C. Pump

The present volume displacement machine can be employed as a fluid pump. Schematically, it can be applied to a similar applicable range as that of the conventional pumps. It can be considered that a limit is present in a pressure level of 40 bars or less. The applicable structures are exemplified by a structure for use in a factory, a measuring motor, a water pumping up operation in a construction work, agricultural irrigation work, a circulating pump in a central heating system and the like.
The following advantages can be obtainable from the present volume displacement machine:

a. A high efficiency can be obtained.
b. The overall cost can be reduced.
c. It can be used to pump up contaminated liquid such as water with sand in a construction field.
d. A sealing means for the shaft can be eliminated from the structure. The above-described sealing means causes a jam in the conventional pumps.
e. The necessity of using valves can be eliminated.

The present invention will now be described with reference to Figs. 11 to 14. Since the operation of the volume displacement machine is the same as that according to the above-described embodiments, the description about it is omitted here. Then, only the flexible tube 4 according to the invention will be described.
As shown in Figs. 11 and 14, the flexible tube 4 is made of a flexible material such as rubber and arranged to have a cylindrical cross sectional shape, the flexible tube 4 having a wall portion 14a which has a constant thickness.
The wall portion 14a of the tube 4 has reinforcing fibers 15 which cannot be expanded/contracted, the reinforcing fibers 15 being embedded in the wall portion 14a. However, it may be omitted from the structure.
As shown in Fig. 3, the tube 4 is arranged to be in the form of a tapered shape, that is, a so-called expanding type which is expanded from the supply port 3 toward the discharge port 13. The flexible tube 4 has an elastic reinforcing member 26 on its inner surface 4a. The elastic reinforcing member 26 is, as shown in Fig. 11, arranged to have a circular arc cross sectional shape having a constant wall thickness. Two end portions 26a of the elastic reinforcing member 26 are positioned to confront bent portions 17 of the tube inner surface 4a, while each of the terminative end portions 26b is arranged to be in the form of a circular arc shape. When the process according to the above-described first embodiment is repeated, the rotor 6 smoothly rotates. During this process, the flexible tube 4 is, as shown in Fig. 1, abutted against the inner surface 2a of the cylindrical case 2 by the rollers 7, 8 and 9. As shown in Fig. 12, the bent portions 17 of the inner surface 4a of the tube 4 are bent along the terminative end portions 26b of the elastic reinforcing member 26 to form a circular arc shape while its deformation being restricted by the elastic reinforcing member 26. Furthermore, the above-described end portions 26a are brought into hermetically contact with the confronting inner surface 4a of the tube 4. Therefore, destruction of the bent portion 17 due to fatigue can be prevented and as well as the leakage through seal can be prevented.
Figs. 11 and 12 illustrate a first embodiment of the present invention arranged in such a manner that circular hollow portions 27 are formed at two end portions 26a of said elastic reinforcing member 26 having a circular arc cross sectional shape. Furthermore, each of terminative end portions 26b of the elastic reinforcing member 26 is arranged to have a semicircular cross sectional shape. As a result of the above-described arrangement of the structure of the elastic reinforcing member 26, spaces through which a gas or liquid leaks and which can easily be formed in the bent portions 17 positioned on the inner surface of the flexible tube 4 can be sealed up further perfectly since the two end portions 26a are soft and thereby they can easily be deformed when the tube 4 is folded to have a flat cross sectional shape. Figs. 13 and 14 illustrate a second embodiment of the present invention. As shown in Figs. 13 and 14, a structure may be employed which is arranged in such a manner that a hollow portion 37 is formed in the central portion of the elastic reinforcing member 36 which has a circular arc cross sectional shape. Furthermore, each of front portions 36b of the two end portions 36a of the elastic reinforcing member 36 is arranged to be in the form of a semicircular shape. When the flexible tube 4 is folded down, the cross sectional shape of the elastic reinforcing member 36 is caused to be a flat shape as shown in Fig. 14. Furthermore, the hollow portion 37, which is being compressed, is positioned at the central portion of the elastic reinforcing member 36.
The reinforcing material may be made of a material such as synthetic resin which has a small elastic force as an alternative to the rubber or the like having a large elastic force.
The invention is arranged as described above. Therefore, when the flexible tube is bent at the bent portion by the abutting force of the rollers, the angular degree of the abutment is restricted by the elastic reinforcing member. Furthermore, the elastic reinforcing member is abutted so as to be deformed while being expanded on the inner surface of. the tube. Therefore, a problem, which will taken in the conventional structures, in that the bent portion of the inner surface of the tube is bent while making an acute angle can be overcome. Furthermore, the leakage of gas or the like through the bent portion can be prevented. Consequently, the durability of the tube can be improved and energy loss can be prevented.
Although the invention has been described in its preferred form with a certain degree of particularly, it is understood that the present disclosure of the preferred form has been changed in the details of construction and the combination and arrangement of parts may be resorted to without departing from the scope of the invention as hereinafter claimed.

Claims

A flexible tube means for a volume displacement machine having a flexible tube (4) disposed along an inner surface (2a) of a cylindrical case (2) in such a manner that its end portion is connected to a supply port (3) and another end portion of the same is opened, a rotor (6) concentrically disposed in said cylindrical case (2), and rollers (7, 8, 9, 10) disposed at the front portions of said rotor (6) and act to abut said tube (4) against said inner surface (2a),
said tube means comprising:

said flexible tube (4); and

an elastic member (26, 36) disposed in at least an inner bent portion (17) of said tube (4),

wherein said two end portions (26a, 26b) of said elastic member (26) have hollow portions (27), and/or

wherein said elastic member (36) has a hollow portion (37) at the central portion thereof.
The flexible tube means according to claim 1,
wherein said flexible tube (4) comprises reinforcing fiber (15) embedded in a wall portion (14a) of said flexible tube (4); and

wherein said elastic member (26, 36, 46) disposed in at least an inner bent portion (17) of said tube (4) is an elastic reinforcing member.
The flexible tube means according to claim 1 or 2, wherein said elastic member (26, 36, 46) is arranged along the inner surface (4a) of said flexible tube (4) to have a circular arc cross sectional shape and the two end portions (26b, 36b, 46b) of said elastic member (26, 36, 46) are positioned at said inner bent portions (17).