Drain pump

Abstract: A pump body 30 of a drain pump comprises an intake opening 42 protruded downward and a discharge opening 46 extending to the side. A vane 50 inside the pump body 30 is rotated by a motor. The vane 50 is formed so that the outer peripheral portion of large radius vanes 450 is surrounded by a cylindrical wall member 470. The height of the cylindrical wall member 470 against the height of the large radius vanes 450 to the upper rim portion 453 is set to be in a predetermined range, which effectively reduces the noise being generated.

Description: The present invention relates to a drain pump comprising a rotary vane connected to a drive shaft of a motor, and a housing for storing said rotary vane, said rotary vane comprising a shaft portion connected to said drive shaft of the motor, a plurality of plate-shaped large radius vanes mounted on said shaft portion in the radial direction, a plurality of plate-shaped small radius vanes mounted under said large radius vanes in the axial direction, a disk-shaped annular member having a hollow portion connected to the lower rim portions of said large radius vanes, and a cylindrical wall member mounted to the outer rim portion of said disk-shaped annular member for connecting the outer peripheral rim portions of said large radius vanes. 2. Description of the Prior Art When an air conditioner is driven in a cooling mode, the moisture in the air condenses and adheres to the heat exchanger of the indoor unit of the air conditioner, and the water drops to the drain vane mounted below the heat exchanger. A drain pump is equipped thereto in order to drain the water gathered in the drain vane. Priorly, many types of drain pumps were invented, the example of which is explained in the following. The example of the prior art drain pump comprises a housing having a suction opening in the lower area, an opening in the upper area and a discharge opening in the side area, and a vane mounted rotatably inside the housing. The vane is rotated by a motor fixed through a cover to the upper area of the opening of the housing. The rotary shaft of the motor is rotatably penetrated through the cover and connected to the shaft portion of the vane. A penetrating hole communicating the housing and the atmospheric air is formed on the cover. When the motor is driven to rotate the vane, the drain water stored in the drain vane is sucked in from the suction opening on the lower end of the vane, pumped up along the inner surface of the housing, and discharged to the exterior from the discharge opening of the casing. Japanese Laid-Open Patent Publication No. H9-68185 discloses a vane utilized in the above-mentioned type of drain pump. FIG. 12 is a partially cross-sectional front view showing the whole structure of the conventional drain pump. The drain pump shown as a whole by the reference number 1 comprises a motor 10, and a pump body 30 mounted through a bracket 20 below the motor 10. The bracket 20 is formed integrally with a cover 32 which constitutes the upper member of the pump housing. The cover 32 is connected to a housing 40 through a seal member 34. The housing 40 is made of plastic and comprises a suction opening 42, a pump chamber 44 and a discharge opening 46. A rotary vane 50 equipped inside the housing 40 comprises a shaft portion 52, and a plurality of plate-shaped small radius vanes 54 protruded to the diametral direction with its center positioned at the center axis of the shaft portion 52. In the drawing, the rotary vane comprises four small radius vanes 54. The shaft portion 52 protrudes through a penetrating hole 36 formed in the center area of the cover 32 toward the motor 10. A drive shaft 12 of the motor 10 is inserted to a hole formed on the shaft portion 52. A cut-water disk plate 14 is mounted to the upper surface of the shaft portion 52, which prevents the drain water spouting out of the penetrating hole 36 from reaching the motor 10. The small radius vanes 54 of the rotary vane 50 is inserted to a pipe-shaped suction opening 42 of the housing 40. A suction end 43 of the suction opening 42 is formed to have a tapered surface which reduces the inner diameter of the opening toward the opening end. The tip portion of the small radius vanes also include a tapered surface 56. Large radius vanes 60 of the rotary vane 50 is stored inside the pump chamber 44 of the housing 40. FIG. 13 is a side view of the rotary vane 50, FIG. 14 is a detailed view of portion B of FIG. 13, FIG. 15 is an upper view of the rotary vane 50, and FIGS. 16 (A), (B) and (C) each show a portion of the cross-sectional view taken at lines A-A, B-B or C-C of FIG. 15. The rotary vane 50 is equipped with a shaft portion 52, and plate-shaped large radius vanes 60 extending radially outward from the outer peripheral of the shaft portion 52. The lower rim portions of the large radius vanes 60 are formed to have a tapered shape, and the lower rim portions are connected by a disk-shaped annular member 62 having a hollow portion 63. Small radius vanes 54 are mounted under the large radius vanes 60. The large radius vanes 60 and the small radius vanes 54 are integrally formed by resin, each having four plate-shaped vanes, but the number of vanes may be selected according to design. Auxiliary vanes 68 are mounted between the large radius vanes 60. The pump head may be raised by the auxiliary vanes. A hole 53 for inserting the drive shaft of the motor is formed to the center of the shaft portion 52. The tip portions of the small radius vanes 54 are formed to have a tapered surface 56. The tilt angle of the tapered surface 56 is set, for example, to 45 degrees. A chamfer portion 57 having an arc shape toward the rotating direction is formed to the small radius vanes 54. The arc-shaped chamfer portion 57 has a radius of curvature roughly equal to the thickness of the small radius vane. By forming the chamfer portion 57, the noise generated by stirring the drain water inside the suction opening 42 is reduced, and the drain water may be pumped up to the pump chamber 44 by the rotation of the small radius vanes 54 smoothly. The outer peripheral end of the auxiliary vanes 68 and the large radius vanes 60 are connected through a cylindrical wall member 64. The cylindrical wall member 64 is formed so that its height is lower than the height to the upper rim portion of the large radius vanes 60 or the auxiliary vanes 68. Moreover, an arc-shaped chamfer 70 is formed to the inner side of the upper rim of the cylindrical wall member 64. When such cylindrical wall member 64 is used, the bubbles generated in the water by the rotation of the large radius vanes 60 may flow smoothly to the discharge opening 46, thereby reducing the collision of the bubbles to the bottom surface 35 of the cover 32, and as a result, reduces the generated noise. Even further, when the drain pump is stopped, the water returning from the discharge opening 46 to the pump chamber 44 inside the casing bumps into the cylindrical wall member 64, and by the buffer action of the cylindrical wall member 64, the bubbles are diffused gradually, and the noise caused by the return water may also be reduced. Moreover, because the arc-shaped chamfer portion 70 having a radius of curvature roughly equal to the thickness of the cylindrical wall member 64 is formed to the cylindrical wall member, the drain water provided of the energy to flow in the radial direction by the rotation of the large radius vanes 60 and the auxiliary vanes 68 will run smoothly over the upper rim portion of the cylindrical wall member 64, which also contributes to realizing low noise. The lower end of the cylindrical wall member 64 is annularly connected to an annular member 62 connecting the lower rim portions of the large radius vanes 60 and the auxiliary vanes 68. In the drawings, an example is shown where the cylindrical wall member 64 and the annular member 62 are integrally formed, but they may also be formed separately. By the annular member 62, the surface of the drain water rising from the suction opening 42 is substantially separated to upper and lower parts, which reduces the amount of water contacting the large radius vanes, and as a result, the generation of bubbles may be reduced. The inner peripheral side of the annular member 62 toward the center portion of the rotary vane is formed to have an opening 63. The lower rim of the auxiliary vanes 68 and the large radius vanes 60 are formed to have an inclined shape toward the small radius vanes 64, and the annular member 62 is formed to have a dish-like shape corresponding to such inclination. SUMMARY OF THE INVENTION According to the structure of the prior art drain pump, the noise generated when operating the drain pump may be reduced by setting the upper rim height of the cylindrical wall surface to be smaller than the upper rim height of the large radius vanes. However, there were no teachings nor consideration in the prior art regarding the way to reduce the generated noise more effectively. By continuous effort to more effectively reduce the generated noise level when operating the drain pump by forming a cylindrical wall surface having a height smaller than that of the large radius vanes, the present inventors discovered that it is most effective to set the height of the cylindrical wall surface and the height of the large radius vanes to a predetermined relation or rate. To comply with the objects of further reducing the generated noise, the drain pump according to the invention is characterized by the features of claim 1. According to the present invention, the drain pump comprises a rotary vane connected to a drive shaft of a motor, and a housing for storing said rotary vane, said rotary vane comprising a shaft portion connected to said drive shaft of the motor, a plurality of plate-shaped large radius vanes mounted on said shaft portion in the radial direction, a plurality of plate-shaped small radius vanes mounted under said large radius vanes in the axial direction, a disk-shaped annular member having a hollow portion connected to the lower rim portions of said large radius vanes, and a cylindrical wall member mounted to the outer rim portion of said disk-shaped annular member for connecting the outer peripheral rim portions of said large radius vanes, wherein the ratio of the height of said cylindrical wall member to the height of said large radius vanes is set in the range of 66 % to 83 % and wherein the upper rim portions of said large radius vanes are axially exposed from the upper rim portion of said cylindrical wall member by a distance which is radially constant. Further, the drain pump according to the present invention further comprises an auxiliary vane formed on said disk-shaped annular member in the interior of said cylindrical wall member. The drain pump according to the present invention sets the height of the cylindrical wall member to be in the range of 66% to 83% the height of the large radius vanes. This enables to effectively reduce the noise being generated when operating the drain pump. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a front view of the rotary vane of the drain pump according to the present invention; FIG. 2 is a plan view of the rotary vane of the drain pump according to the present invention; FIG. 3 is a cross-sectional view taken at line A-A of FIG. 2; FIG. 4 is a cross-sectional view taken at line D-D of FIG. 2; FIG. 5 is a cross-sectional view taken at line G-G of FIG. 2; FIG. 6 is a cross-sectional view taken at line E-E of FIG. 4; FIG. 7 is a detailed view showing area F of FIG. 1; FIG. 8 is a cross-sectional view taken at line H-H of FIG. 7; FIG. 9 is an explanatory view showing the size of the rotary vane according to the present invention; FIG. 10 is a chart of the characteristics curve showing the effect of the present invention; FIG. 11 is a chart of the characteristics curve showing the effect of the present invention; FIG. 12 is a side view showing a part in cross-section the drain pump of the prior art; FIG. 13 is a side view showing the rotary vane of FIG. 12; FIG. 14 is a detailed view showing area B of FIG. 13; FIG. 15 is an upper view of the rotary vane shown in FIG. 13; and FIG. 16 is an explanatory cross-sectional view of the rotary vane shown in FIG. 13 and FIG. 15. PREFERRED EMBODIMENT OF THE INVENTION The preferred embodiment of the drain pump according to the present invention will now be explained with reference to the accompanied drawings. In the explanation of the embodiment, the components having the same function as the components in the prior art example will be referred to by the same reference numbers. Further, the motor used in the present embodiment is the same as that used in the prior art example, so explanation regarding the motor is omitted, and only the structure of the rotary vane will be shown. FIG. 1 is a front view of one embodiment of the rotary vane of the drain pump, FIG. 2 is an upper view taken from the direction shown by arrow P of FIG. 1, FIG. 3 is a cross-sectional view taken at line A-A of FIG. 2, FIG. 4 is a cross-sectional view taken at line D-D of FIG. 2, FIG. 5 is a cross-sectional view taken at line G-G of FIG. 2, FIG. 6 is a cross-sectional view taken at line E-E of FIG. 4, FIG. 7 is a detailed view of area F shown in FIG. 1, and FIG. 8 is a cross-sectional view taken at line H-H of FIG. 7. The rotary vane 50 is formed by molding plastic, and includes a plural number of (for example, four) plate-shaped small radius vanes 410. The upper portion of the small radius vanes are connected through a tapered portion 411 to a plural number of (for example, four) large radius vanes 450. A cylindrical shaft portion 420 is formed in the center area of the large radius vanes 450, and the shaft portion 420 comprises a hole 430 with a bottom in the center area thereof. An output shaft of a motor (not shown in the drawing) is pressed into the hole 430 so as to transmit the rotary force of the motor to the rotary vane 50. The lower rim portions of the large radius vanes 450 are covered by a disk-shaped annular member 460. At the center of the annular member 460 is formed an opening 462. The outer peripheral rim of the disk-shaped annular member 460 is connected to a cylindrical wall member 470. The wall member 470 is connected to the outer rim of the large radius vanes 450, and the upper rim 472 of the cylindrical wall member 470 is formed to be lower than the upper rim 451 of the large radius vanes 450. Four auxiliary vanes 452 are mounted to the interior of the cylindrical wall member 470. Each auxiliary vane 452 is mounted between the four large radius vanes 450 so as to extend toward the direction of the opening 462 of the disk-shaped annular member 460. In the embodiment shown in FIG. 6, a rim portion 454 of the auxiliary vane facing the radially inward direction is formed to extend to a position near the opening 462 of the disk-shaped annular member 460. The height position of the upper rim 453 of the auxiliary vanes 452 is set to correspond to the height position of the upper rim 451 of the large radius vanes 450. The upper rim 451 of the large-radius vanes 450 and the upper rim 453 of the auxiliary vane 452 are positioned to be exposed above the upper rim 472 of the cylindrical wall member 470. The exposed portion contributes to secure the maximum pump head of the rotary vane. In another example, only the large radius vanes may be positioned to expose its upper rim above the wall member 470. FIGS. 7 and 8 show the shape of a tapered portion 412 formed on the bottom end of the small radius vane 410, and an arc-shaped chamfer 414 formed on the outer rim of the small radius vane 410. The vanes having the above-mentioned shape and structure which are rotatably mounted to the drain pump according to the present invention realize a light-weight rotating body. Accordingly, a drain pump having the minimum noise and vibration may be achieved. FIG. 9 is an explanatory view showing one example of the size of the rotary vane 50. The outer diameter of the rotary vane 50 may be selected to meet the required specifications of the drain pump. The present embodiment utilizes a rotary vane having an outer diameter size of 35 mm. The change in the noise level and the maximum pump head was examined when the height of the cylindrical wall member 470 was set to S, and the height of the large radius vanes 450 was set to T. Actually, experiment on the noise and the maximum pump head characteristics was performed by fixing the height T of the large radius vanes 450 to 6.0/mm, and changing the height S of the cylindrical wall member 470 from 3.5 mm to 6.0 mm by a pitch of 0.5 mm. FIG. 10 shows the experiment results performed under a rated voltage of 50 hertz, and FIG. 11 shows the result under a rated voltage of 60 hertz. In FIGS. 10 and 11, the horizontal axis shows the S/T ratio, and the vertical axis shows the noise (dB) and the no-discharge head (mm). In FIG. 10, the noise characteristics measured at the time of discharge of the drain water maintaining a pump head of 700 mm (shown by a curve connecting the Δ mark in the drawing) and at the time the discharge of the drain water maintaining a pump head of 700 mm is terminated (shown by a curve connecting the □ mark) is shown to be reduced when the S/T ratio is 4.0/6.0, while the no-discharge head characteristics shown by a curve connecting the X mark in the drawing is maintained at a high level. Such noise characteristics is also maintained at a reduced level when the S/T ratio is 4.5/6.0 and 5.0/6.0, but the no-discharge head characteristics is lowered when the S/T ratio is 5.0/6.0. FIG. 11 shows a similar chart as FIG. 10 where the no-discharge head characteristics and the noise characteristics are shown. The experiment result shows that when the S/T ratio is 4.0/6.0, the no-discharge head (shown by the curve connecting the X mark in the drawing) maintains a high level, while the noise characteristics is reduced both at the time of discharge of the drain water maintaining a pump head of 700 mm (shown by the curve connecting the Δ mark in the drawing) and at the time the discharge is terminated (shown by the curve connecting the □ mark). The noise characteristics is maintained at such level when the S/T ratio is 4.5/6.0 and 5.0/6.0, but the no-discharge head is lowered when the S/T ratio is 5.0/6.0. Accordingly, by setting the ratio of the cylindrical wall member height S to the large radius vane height T to be in the range of 4.0/6.0 through 5.0/6.0, in other words, setting the height of the cylindrical wall member so that it ranges between 66% through 83% against the height of the large radius vanes, the noise characteristics of the drain pump may be improved without lowering the no-discharge head characteristics. The case where the auxiliary vanes are formed to the rotary vane 50 was explained in the above embodiment. However, the present invention may also be applied to the case where no auxiliary vanes are formed. Moreover, the present invention may be applied to the case where the auxiliary vanes explained above are not exposed from the upper rim of the cylindrical wall member. As explained above, the drain pump according to the present invention determines the range of the height of the cylindrical wall member against the height of the large radius vanes of the rotary vane, which effectively reduces the noise level while maintaining the no-discharge head. Moreover, since there is no need to change the external form or the main components of the conventional drain pump greatly in manufacturing the drain pump according to the present invention, the present drain pump capable of reducing noise effectively may be manufactured at a low cost.

Claims: A drain pump comprising a rotary vane (50) connected to a drive shaft of a motor, and a housing for storing said rotary vane, said rotary vane comprising a shaft portion (420) connected to said drive shaft of the motor, a plurality of plate-shaped large radius vanes (450) mounted on said shaft portion (420) in the radial direction, a plurality of plate-shaped small radius vanes (410) mounted under said large radius vanes (450) in the axial direction, a disk-shaped annular member (460) having a hollow portion (462) connected to the lower rim portions of said large radius vanes (450), and a cylindrical wall member (470) mounted to the outer rim portion of said disk-shaped annular member for connecting the outer peripheral rim portions of said large radius vanes, characterized in that the ratio of the height (S) of said cylindrical wall member (470) to the height (T) of said large radius vanes (450) is set in the range of 66 % to 83 % and that the upper rim portions (451) of said large radius vanes (450) are axially exposed from the upper rim portion (472) of said cylindrical wall member (470) by a distance which is radially constant. A drain pump according to claim 1, characterized in that an auxiliary vane (452) mounted between said large radius vanes (450) is further formed on said disk-shaped annular member (460) in the interior of said cylindrical wall member (470). A drain pump according to claim 2, characterized in that the upper rim portion of said auxiliary vane (452) is exposed from the upper rim portion (472) of said cylindrical wall member (470).

Inventors: IMAI MASAYUKI, NINOMIYA TATUSHI, IMAI, MASAYUKI, NINOMIYA, TATUSHI, Imai, Masayuki, c/o Fujikoki Corporation, Ninomiya, Tatushi, c/o Fujikoki COrporation
Applicants: FUJIKOKI CORP, FUJIKOKI CORPORATION
Application year: 1999
Main classification: F04D29
IPC codes: F04D29, F24F1, F04D1