Heat-driven pump

Abstract: A heat-driven pump, a fluid suction porting (6) which admits liquid into a heating chamber (3) where it is heated to form bubbles within the chamber. The bubbles force fluid out of the chamber through condensation means (5) and can enter the condensation means where they condense to allow further fluid to be drawn into the pump. The bubbles are prevented from flowing through the suction porting due to capillary action in that porting. This porting includes means (12) for defining fluid passages which allow fluid to pass through into the heating chamber but prevent the bubbles from passing through due to capillary action and placing means (13) for detachably placing the fluid passage defining means in position.

Description: The present invention relates to a heat-driven pump, and particularly concerns a heat-driven pump which pumps by repeated generation and elimination of bubbles using heat. Fig. 20 illustrates a heat-driven pump disclosed in US Patent No. 4,792,283 issued to Applicant on December 20, 1988. In this, the pump 51 has a heating chamber 53 which is sunk into a heating portion 52 and communicates with a vapor-liquid exchange chamber 54 through two passages, namely a condensation tube 55 and a liquid suction port 56. The vapor-liquid exchange chamber 54 communicates with a suction tube 57 and a discharge tube 58. To allow liquid to flow only in a single direction, the suction tube 57 and the discharge tube 58 are connected to a suction side check valve 59 and a discharge side check valve 60, respectively. The upper end of the condensation tube 55 opens into the vapor-liquid chamber 54. A gap 61 is formed between the upper end of the condensation tube 55 and the lower end of the discharge tube 58 for allowing liquid to flow directly from the suction tube 57 to the discharge tube 58 through the vapor-liquid exchange chamber 54. The liquid suction port 56 is partitioned into a series of small area openings by a plurality of radially extending fins 62. The fins 62 are made of thin stainless plates, and are bonded through an adhesive or welded at regular angular intervals to the outer circumferential surface of the lower end of the condensation tube 55 as illustrated in Fig. 21. In the operation of the pump 51, the heating chamber 53 and the vapor-liquid chamber 54 are filled with liquid which flows from the suction tube 57. Bubbles are formed from the lower end of the heating chamber 53 by heating the portion 52. As a bubble grows, the interface between the bubble and liquid ascends and then reaches both the liquid suction port 56 and the lower end of the condensation tube 55. The interface is blocked at the port 56 due to capillary action caused by the fins 62, and so enters only the condensation tube 55. During this process, a volume of liquid equal to the volume of the bubble is forced out of the heating chamber 53 into the vapor-liquid chamber 54, and from there through the discharge pipe 58. When the bubble enters the condensation tube 55, it is cooled by surrounding liquid, so that it contracts and then disappears. Thus, a volume of liquid equal to the lost volume of the bubble flows from the vapor-liquid exchange chamber 54 into the heating chamber 53 through the liquid suction port 56 and the condensation tube 55. Fresh liquid, equal in volume to the liquid drawn into the heating chamber 53, flows into the vapor-liquid exchange chamber 54 through the suction tube 57. In this fashion, pumping of liquid is carried out by repeating production and elimination of bubbles using heat. To fabricate the heat-driven pump 51, it is necessary to bond or weld each of radial fins 62 to the outer circumferential surface of the lower end of the condensation tube 55, and hence it is laborious to assemble the radial fins 62. Furthermore, the fins 62 are liable to be separated from the condensation tube 55. Accordingly, it is an object of the present invention to provide a heat-driven pump of which the suction port is less laborious to fabricate and is less liable to be broken than that of the heat-driven pump according to the prior art. In the present invention, there is provided a heat-driven pump in which bubbles are formed by heating liquid introduced into a heating chamber thereby to cause fluid in the heating chamber to flow out through condensation means to a pump outlet and the bubbles are prevented from flowing through inlet or suction porting of the heating chamber by a capillary blocking action, the fluid suction porting comprising means surrounding the condensation means for defining at least one fluid passage allowing fluid to enter the heating chamber, said at least one passage preventing the passage of bubbles due to the capillary action, and placing means being provided for engagement with the fluid passage defining means to place said fluid passage defining means in said position surrounding the condensation means in a detachable manner. Examples of the invention will be described in more detail with reference to the accompanying drawings, in which: Fig. 1 is an axial sectional view of a heat-driven pump as one embodiment of the present invention, Fig. 2 is an enlarged fragmentary extended view of the fin of Fig. 1, Fig. 3 is a perspective view of the fin in Fig. 2, Fig. 4(a) is an enlarged axial sectional view of the retainer with the fin of Fig. 1, the retainer being fitted around the condensation tube, Fig. 4(b) is a bottom view of the retainer with the fin of Fig. 4(a), Fig. 4(c) is a perspective view of the retainer of Fig. 4(a), Fig. 5 is an axial sectional view of a heat-driven pump in another embodiment of the present invention, Fig. 6 is an enlarged extended view of the fin of Fig. 5, Fig. 7(a) is an enlarged perspective view of the fin of Fig. 5, Fig. 7(b) is a bottom view of the fin of Fig. 7(a), Fig. 8 is an illustration of a fluid passage defining member of a pump in yet another embodiment of the present invention, Fig. 9 is a radial sectional view of the fluid passage defining member of Fig. 8 received within its retainer, Fig. 10 illustrates the arrangement of a group of fine tubes, used in another embodiment of pump according to the present invention, with their retainer, Fig. 11 is a bottom view of the group of tubes and retainer of Fig. 10, Fig. 12 illustrates the arrangement of a pair of concentric tubes, used in another embodiment of pump according to the present invention, with their retainer, Fig. 13(a) is an axial sectional view showing the concentric tubes of Fig. 12 disposed within the retainer, Fig. 13(b) is a bottom plan view of the assembly in Fig. 13(a), Fig. 14 illustrates the arrangement of a plug, around a condensation tube, as used in a still further embodiment of the present invention, Fig. 15 is an axial sectional view of the plug and condensation tube of Fig. 14 assembled together, Fig. 16 illustrates the positioning of a fluid passage defining member around a condensation tube in another embodiment of the present invention, Fig. 17 is an axial sectional view of the fluid passage defining member and condensation tube of Fig. 16 assembled together, Fig. 18 illustrates the disposal of a mesh member within a retainer in another embodiment of the present invention, Fig. 19 is an axial sectional view of the mesh member and retainer of Fig. 18 assembled together, Fig. 20 is an axial sectional view of a known heat-driven pump, Fig. 21 is a perspective view of the fins mounted around the condensation tube of the pump of Fig. 20, Fig. 22(a) illustrates a suction port defining unit of a heat-driven pump in yet another embodiment of the present invention, Fig. 22(b) is a bottom plan view of the suction port defining unit of Fig. 22(a), and Fig. 22(c) is a perspective view of the suction port defining unit of Fig. 22(a). Referring to the drawings, several embodiments of the present invention will be described hereinafter. Fig. 1 illustrates a first embodiment of heat-driven pump according to the present invention. In this pump, a heating chamber 3, sunk into a heating portion 2, and a vapor-liquid exchange chamber 4 communicate with each other through two passages, namely a condensation tube 5 and a liquid suction port 6. The vapor-liquid exchange chamber 4 is connected to a suction tube 7 and a discharge tube 8. To cause fluid to flow only in one way, the suction tube 7 is connected to a suction-side check valve 9 and the discharge tube 8 to a discharge-side check valve 10. The condensation tube 5 is provided in an upper end portion thereof with an opening 11 for allowing part of fluid to flow directly from the suction tube 7 to the discharge tube 8 through the vapor-liquid exchange chamber 4. The liquid suction port 6 is partitioned into a series of small cross-section openings by an annular folded fin 12 formed by corrugating a substantially strip shaped metallic thin plate at fold lines 14 as shown in Fig. 2 and Fig. 3 and then by bending it to an annulus. The fold lines 14 are formed by laser beam machining, etching, etc. The fin 12 is provided at a lower edge thereof with projections 12a formed at regular intervals. As illustrated in Fig. 1 and Fig. 4(a) to 4(c), the fin 12 is placed around the condensation tube 5 at a lower end thereof, and to retain it detachably in position it is received within a retainer 13, which is fitted around the condensation tube 5 to come into contact with the bottom of the pump housing, which defines the vapor-liquid exchange chamber 4, and to cover the bottom opening of the housing. The fin 12 is held within the retainer 13 with lower projections 12a fitted into the upper end of the heating chamber 3. The retainer 13 is substantially in the shape of an inverted cup and is provided at the top thereof with four spokes which form four openings between them as shown in Fig. 4(c). The fin 12, the retainer 13 and the lower end portion of the condensation tube 5 define the liquid suction port 6. As illustrated in Fig. 4(b), the fin 12 forms a fluid passage defining means partitioning the liquid suction port 6 into many smaller chambers with triangular cross-sections (maximum width of about 1 mm in the case of stainless as fin 12 and water as liquid) for producing a capillary effect. In this heat-driven pump 1, the heating chamber 3 and the vapor-liquid exchange chamber 4 are filled with liquid which enters through the suction tube 7, and then a bubble is formed from the lower end of the chamber 3 by heating the portion 2. As the bubble grows, the interface between the bubble and the liquid ascends to both the liquid suction port 6 and the lower end of the condensation tube 5. The interface is prevented from entering the liquid suction port 6 due to the capillary action on the liquid produced by the fin 12, and hence enters only into the condensation tube 5. In this process, a volume of liquid which is equal to the growth of volume of the bubble flows out of the heating chamber 3 to the vapor-liquid exchange chamber 4. A corresponding volume of water flows out of the chamber 4 through the discharge tube 8. The bubble which has entered the condensation tube 15 is cooled and condensed by the surrounding liquid, so that it contracts and disappears. A volume of liquid which corresponds to the lost volume of the bubble thus flows from the vapor-liquid exchange chamber 4 to the heating chamber 3 through the liquid suction port 6 and the opening 11 of the condensation tube 5, and in turn this volume of fresh liquid is made up from the suction tube 7. In such a manner, pumping of liquid is achieved by repeating production and elimination of bubbles due to heat. Fig. 5 illustrates a heat-driven pump 1a which is another embodiment of the present invention, comprising a pump housing which has a reduced diameter portion at its lower end. A fin 12 is received within a space defined by both the reduced diameter portion and a lower end portion of the condensation tube 5, so that in the space there are formed a series of partitioned chambers with a substantially triangular cross-section for producing a capillary effect. The fin 12, the reduced diameter portion and the lower end portion of the condensation tube 5 define a liquid suction port 6. This embodiment obviates the retainer 13 of the pump 1, and has the same structure as the first embodiment in the other points. Fig. 6 shows a fin 15 which is a modified form of the fin of Fig. 1. The fin 15 is formed by corrugating a thin metallic strip at folds 16 and then by bending it to the form of a toothed wheel as illustrated in Fig. 7(a) and Fig. 7(b). As in the first and the second embodiments, the fin 15 is received and held within the retainer 13 or the liquid suction port 6 with lower projections 15a fitted into the heating chamber 3. The fin 15 divides the liquid suction port 6 into a series of partitioned chambers with a trapezoidal cross-section, as illustrated in Fig. 7(b), for producing a capillary action, and thereby blocks the flow of bubbles through the liquid suction port 6. The fin 15 provides partitioned chambers each of substantially the same cross-sectional shape, and hence a uniform capillary action is produced in all the chambers of the liquid suction port. A passage defining member 17 of a heat-driven pump in another embodiment is illustrated in Fig. 8 and Fig. 9, and is formed by spirally bending a thin metallic strip. The member 17 is received and secured in a retainer 19 in such a manner that claws 20a on its inner end are inserted into holes 21a of the condensation tube 18, while claws 20b on its outer end are inserted into holes 21b of the retainer 19. As shown in Fig. 9, the passage defining member 17 defines a narrow spiral section flow passage through the fluid suction port 6 within the space between the retainer 19 and the condensation tube 5, so that capillary action is produced in the port. It is thus possible to prevent bubbles formed within the heating chamber 3 from flowing out through the fluid suction port 6. The spiral passage of the suction port may be changed in width with ease by changing the number of turns of the spiral of the passage defining member 17. Fig. 10 and Fig. 11 illustrate a group of capillary tubes 22 forming fluid passage defining means of a heat-driven pump in another embodiment of the present invention, the tubes 22 being received within a retainer 23 around the lower end portion of condensation tube 5 so that the tubes are arranged parallel with the tube 5, ie. the direction of flow of liquid in the liquid suction port 6. As illustrated in Fig. 11, the liquid suction port 6 is separated into many narrow passages for producing capillary action, and thereby bubbles formed in the heating chamber 3 are blocked from flowing out through the liquid suction port 6. Fig. 12 shows a concentric tube group 24 of a heat-driven pump in yet another embodiment of the present invention, the group 24 including an inner circular tube 24a and an outer circular tube 24b fitted around the inner tube 24a. The inner circular tube 24a is larger in diameter than the condensation tube 5, and the outer circular tube 24b is smaller in diameter than retainer 25. The inner and outer tubes 24a and 24b are fitted around a lower end portion of the condensation tube 5 and are received within the retainer 25 concentrically with the condensation tube 5. The inner and outer tubes 24a and 24b are joined, for example welded or brazed, at upper edges thereof to the spokes of the retainer 25 as illustrated in Fig. 13(a). As shown in Fig. 13(b), the inner and outer tubes 24a and 24b partition the liquid suction port 6 into narrow annular gaps so that a capillary action may be produced in these gaps. Thus, bubbles are thereby prevented from flowing through the liquid suction port 6. Fig. 14 illustrates a plug 26 forming the fluid passage defining means of a heat-driven pump in another embodiment of the present invention, the plug being made of foamed material, such as a foamed metal or a foamed ceramic, having open cells. The plug 26 is fitted concentrically around the lower end of condensation tube 5, and is located at the bottom of the vapor-liquid exchange chamber 4 by clamping it between a holding ring 27 and the bottom opening of the chamber 4 leading to the heating chamber. In this example a major part of the plug 26 has a substantially frustoconical form which fits into the bottom opening. The small open cells of the plug 26 define a liquid suction port 6 for producing a capillary action, and bubbles are thereby prevented from flowing through the plug. Fig. 16 and Fig. 17 show a passage defining member 28 of a still further embodiment of the present invention in the shape of a funnel. The member 28 is partly inserted into the bottom opening of the pump housing with the narrower tubular end thereof directed downwardly, and is secured to the bottom of the vapor-liquid exchange chamber 4 by clamping a flange of the larger open end thereof between the chamber bottom and securing arms of a securing ring 29 attached around a lower end portion of the condensation tube 5. The liquid suction port 6 is divided at its opening towards the heating chamber 3 into two narrow concentric annular gaps by the passage defining member 28 to produce a capillary action blocking the flow of bubbles from the heating chamber 3, through the port 6. The inner annular gap is defined between the passage defining member 28 and a lower end portion of the condensation tube 5. The outer annular gap is formed between the passage defining member 28 and the wall at the bottom of the vapor-liquid exchange chamber 4. A mesh 30 is used in the liquid suction passage 6 of another embodiment of the present invention as illustrated in Fig. 18 and Fig. 19. The mesh 30 is made of a metal, plastic or like material. It is fitted around a lower end of the condensation tube 5, and is secured in the bottom of the housing to cover the bottom opening as shown in Fig. 19, by clamping between the periphery of the bottom opening and a circumferential shoulder of a retainer 31. The fluid suction port 6 is divided by the mesh 30 into small apertures so that a capillary action is generated to block the flowing of bubbles from the heating chamber 3 through fluid suction port 6. The strength of the capillary action is adjustable by changing the mesh size or by using a plurality of meshes. Fig. 22(a) is an illustration as to how to construct a suction port defining unit of a heat-driven pump in a still further embodiment of the present invention. An elongated metallic strip 40 is resiliently bent and placed in a meandering shape in a space defined between retainer 43 and condensation tube 45, and the opposite end portions of the strip are brought into contact with each other. The metallic strip 40 is thus received and held annularly as a whole in the retainer 43 by its own resilient restoring force, so that the strip defines a suction port in cooperation with the retainer 43 and the condensation tube 45. Fig. 22(b) and Fig. 22(c) are bottom and perspective views, respectively, of this last suction port defining unit.

Claims: A heat-driven pump in which bubbles are formed by heating liquid introduced into a heating chamber (3) thereby to cause fluid in the heating chamber to flow out through condensation means (5) to a pump outlet (8) and the bubbles are prevented from flowing through inlet or suction porting (6) of the heating chamber by a capillary blocking action, the fluid suction porting comprises fluid passage defining means (12;15;17;22;24;26;28;30) surrounding the condensation means for defining at least one fluid passage allowing fluid to enter the heating chamber, said at least one passage preventing the passage of bubbles due to the capillary action, characterised in that placing means (13;19;23;26;27;29;31) are provided for engagement with the fluid passage defining means (12;15;17;22;24;26;28;30) to place said fluid passage defining means in said position surrounding the condensation means in a detachable manner. A heat-driven pump according to claim 1 wherein the placing means (13;19;23;26;27;29;31) are located on the condensation means to engage an outlet end of the fluid passage defining means (12;15;17;22;24;26;28;30) for placing said defining means detachably in position. A heat-driven pump according to claim 1 or claim 2 wherein said placing means comprises an outer peripheral wall surrounding said passage defining means. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprising an elongate strip member (17) conformed to define a limited width spiral opening for admitting liquid and producing the capillary action. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprises an elongate strip member conformed to a series of longitudinally extending corrugations arranged in an annular manner to define a series of said passages. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprises tubes (24a,24b) are concentrically disposed within each other to define annular gaps between adjacent tubes as said passages. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprises tubes (22) arranged in parallel to define a series of said passages. A heat-driven pump as recited in claim 7 wherein said tubes are arranged side by side so as to define said passages both within the individual tubes and in the spaces between adjacent tubes. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprises a smaller open end portion of a funnel shaped fluid defining member (28) disposed with said smaller end portion directed downwardly for admitting liquid and producing the capillary action. A heat-driven pump as recited in Claim 9, wherein the condensation means comprises a condensation tube (5) around a lower end of which said funnel shaped fluid defining member (28) is placed so as to define an annular gap between the smaller open end and the lower end of the condensation tube. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprises a foamed plug member (26) having open cells providing a series of apertures for admitting liquid and producing the capillary action. A heat-driven pump as recited in any one of claims 1 to 3, wherein the fluid passage defining means comprises a mesh member (30) forming a series of apertures for admitting liquid and producing the capillary action. A heat-driven pump as recited in any one of claims 2 to 7, wherein the condensation means comprises a tube (5) having a lower end which provides a fluid passage defining member of said suction means and the fluid passage defining means (12;15;17;22;24;26;28;30) is disposed around said lower end of the condensation tube.

Inventors: OKAYASU KENJI, OKAYASU, KENJI
Applicants: OKAYASU KENJI, OKAYASU, KENJI
Application year: 1991
Main classification: F04F1
IPC codes: F04B37, F04B19, F04F1, F04F99