Patent Description:
Patent Literature <NUM> discloses an example of a drainage pump of the related art. The drainage pump in Patent Literature <NUM> includes a housing, and an impeller housed in the housing. The housing includes a suction pipe extending in an up-and-down direction. The suction pipe includes a suction port facing downward. The suction port is disposed at the lower end of the suction pipe. Patent Literature <NUM> discloses an example of a drainage pump comprising a housing, an impeller housed in the housing and a motor with a drive shaft connected to the impeller, wherein the housing includes a suction pipe in a cylindrical shape extending in an up-and-down direction, and wherein the suction pipe includes a suction port facing downward.

The drainage pump suctions up, through the suction port, drain water collected in a drain pan. However, the drainage pump cannot suction up all the drain water in the drain pan because a gap should be left between the suction port and the drain pan. Consequently, the drain water remains in the drain pan, and slime may be formed in the drain water.

In view of this, it is an object of the present invention to provide a drainage pump capable of reducing the amount of the drain water remaining in the drain pan. Solution to Problem.

The inventors of the present invention focused on a suction pipe of a drainage pump. The inventors found that surface tension raises drain water from its water surface to the lower end of the suction pipe, and the position of the water surface of the drain water remaining in a drain pan is lower than the lower end of the suction pipe when the drainage pump cannot suction up any more drain water from the drain pan in a drainage operation to discharge the drain water, i.e., when the drain water is suctioned up and retained in a housing of the drainage pump without falling (hereinafter referred to as "balanced state"). Therefore, the inventors made an intensive study of the shape of the suction pipe and came up with the present invention.

To solve the problem described above, a drainage pump according to the present invention includes a housing, an impeller housed in the housing, and a motor with a drive shaft connected to the impeller. The housing includes a suction pipe in a cylindrical shape extending in an up-and-down direction. The suction pipe includes a suction port facing downward and a concave surface in an annular shape around the suction port. The suction port and the concave surface are disposed at a lower end of the suction pipe.

In the present invention, a width at the lower end of the suction pipe in a radial direction (thickness of the suction pipe) is preferably greater than or equal to <NUM> and less than or equal to <NUM>.

The drainage pump according to the present invention includes the suction pipe in the cylindrical shape extending in the up-and-down direction. The suction pipe includes the suction port facing downward and the concave surface in the annular shape around the suction port. The suction port and the concave surface are disposed at the lower end of the suction pipe. As a result, the drain water can be raised to a higher position due to increased surface tension acting on the drain water by the concave surface of the drainage pump. Therefore, the drainage pump can suction up the drain water to further lower the position of the water surface of the drain water in the drain pan and effectively reduce the amount of the drain water remaining in the drain pan.

Hereinafter, a drainage pump according to an embodiment of the present invention is described with reference to <FIG> and <FIG>.

<FIG> illustrates the drainage pump according to the embodiment of the present invention. <FIG> is a sectional view of the drainage pump. In <FIG>, only a housing and a motor case are illustrated in section. <FIG> illustrates a suction pipe in a bottom view. <FIG> is an enlarged sectional view of the lower end of the suction pipe of the drainage pump in <FIG>.

The drainage pump according to the embodiment discharges outside, for example, drain water collected in a drain pan of an indoor unit of an air conditioner. Usage of the drainage pump is not limited to discharging the drain water. The drainage pump may be used for suctioning up or discharging various liquids in containers.

As illustrated in <FIG>, a drainage pump <NUM> according to an embodiment of the present invention includes a housing <NUM>, an impeller <NUM>, a motor <NUM>, and a motor case <NUM>. The housing <NUM>, the impeller <NUM>, and the motor case <NUM> are made of synthetic resin.

The housing <NUM> includes a main body <NUM> in a substantially inverted truncated conical shape. A suction pipe <NUM> extends downward from the main body <NUM>. The suction pipe <NUM> has a cylindrical shape extending linearly in an up-and-down direction. The suction pipe <NUM> has a suction port 12a facing downward. The suction port 12a is disposed at a lower end 12c of the suction pipe <NUM>. The suction pipe <NUM> has a concave surface 12b in a circular annular shape. The concave surface 12b is disposed at the lower end 12c of the suction pipe <NUM>. The concave surface 12b is around the suction port 12a. A discharge pipe <NUM> extends from the main body <NUM> in a lateral direction. The discharge pipe <NUM> has a discharge port 13a facing the lateral direction. The discharge pipe <NUM> has a cylindrical shape extending linearly in the lateral direction. Alternatively, the discharge pipe <NUM> may have an arc shape or be substantially L-shaped, with the discharge port 13a facing upward. The suction pipe <NUM> and the discharge pipe <NUM> are connected to a pump chamber <NUM> inside the main body <NUM>.

An outer diameter D of the lower end 12c of the suction pipe <NUM> is preferably greater than or equal to <NUM> and less than or equal to <NUM>. A width RT at the lower end of the suction pipe <NUM> in the radial direction (thickness of the suction pipe <NUM>) is preferably greater than or equal to <NUM> and less than or equal to <NUM>. The width RT is also the width of the concave surface 12b. If the outer diameter D is less than <NUM>, the width of the concave surface 12b cannot be obtained enough, and a height H of a portion Wa of drain water W raised from a water surface Ws by surface tension is small. If the outer diameter D is greater than <NUM>, the suction pipe <NUM> is in contact with a water collection basin for drain water provided in the drain pan. With the outer diameter D greater than or equal to <NUM> and less than or equal to <NUM> in the drainage pump <NUM>, the height H of the portion Wa of the drain water W is obtained enough by the surface tension, and the suction pipe <NUM> is inhibited from being in contact with the water collection basin of the drain pan. Consequently, the drain water W remaining in the drain pan can be effectively reduced. If the width RT in the drainage pump is less than <NUM>, high surface tension by the concave surface 12b cannot be obtained. If the width RT in the drainage pump is greater than <NUM>, the outer diameter D is large, and the suction pipe <NUM> may be in contact with the water collection basin as above.

The impeller <NUM> includes a shaft portion <NUM>, a large-diameter blade portion <NUM>, and a small-diameter blade portion <NUM>. The shaft portion <NUM> has a circular columnar shape. The large-diameter blade portion <NUM> has a plurality of large-diameter blades (not illustrated) in a flat plate shape extending radially from the shaft portion <NUM>. The large-diameter blade portion <NUM> has a ring 22a in a cylindrical shape connecting the tip ends of the large-diameter blades and a lower plate 22b in an annular shape of which the outer peripheral edge is connected to the lower end of the ring 22a. The large-diameter blade portion <NUM> is disposed in the pump chamber <NUM>. The small-diameter blade portion <NUM> has a plurality of small-diameter blades 23a in a flat plate shape. The small-diameter blades 23a extend downward from the lower ends of the large-diameter blades through the inside of the lower plate 22b. The small-diameter blade portion <NUM> is disposed in the suction pipe <NUM>.

The motor <NUM> is disposed above the housing <NUM>. The motor <NUM> has a motor body <NUM> and a drive shaft <NUM> extending downward from the motor body <NUM>. The drive shaft <NUM> is connected to the shaft portion <NUM> of the impeller <NUM>.

The motor case <NUM> is mounted to the housing <NUM> by a snap-fit mechanism. The motor case <NUM> has a lower case <NUM> and an upper case <NUM>.

The lower case <NUM> has a bottom wall portion <NUM>, a peripheral wall portion <NUM>, and a motor support portion <NUM>.

The bottom wall portion <NUM> has a circular plate shape. The bottom wall portion <NUM> closes an upper end opening of the main body <NUM> of the housing <NUM>. The bottom wall portion <NUM> defines the pump chamber <NUM> together with the main body <NUM>. A shaft hole 51a is provided in the center of the bottom wall portion <NUM>. The shaft portion <NUM> of the impeller <NUM> is disposed in the shaft hole 51a.

The peripheral wall portion <NUM> has a cylindrical shape. The lower end of the peripheral wall portion <NUM> is connected to the bottom wall portion <NUM>. The peripheral wall portion <NUM> extends upward from the bottom wall portion <NUM>. The motor support portion <NUM> is connected to the upper end of the peripheral wall portion <NUM>.

The upper case <NUM> is mounted to the motor support portion <NUM> by a snap-fit mechanism. The upper case <NUM> covers an upper part of the motor <NUM>. The motor case <NUM> houses the motor <NUM> in a space between the motor support portion <NUM> and the upper case <NUM>. Parts of wires or others of the motor <NUM> are disposed outside the motor case <NUM>.

As described above, the drainage pump <NUM> according to the embodiment includes the suction pipe <NUM> in the cylindrical shape extending in the up-and-down direction. The suction pipe <NUM> includes the suction port 12a facing downward and the concave surface 12b in the annular shape around the suction port 12a. The suction port 12a and the concave surface 12b are disposed at the lower end 12c of the suction pipe <NUM>. As a result, the drainage pump <NUM> can raise the drain water W to a higher position by the surface tension. Therefore, the drainage pump <NUM> can suction up the drain water W to further lower the position of the water surface of the drain water in the drain pan and effectively reduce the amount of the drain water W remaining in the drain pan.

The embodiment of the present invention is described above. The present invention, however, is not limited to the embodiment. Embodiments obtained by appropriately adding, removing, or modifying components according to the embodiment described above by a person skilled in the art, and an embodiment obtained by appropriately combining features of the embodiment are included in the scope of the present invention as long as they have the gist of the present invention.

The inventors verified the effects of the present invention by measuring the position of the water surface of the drain water relative to the lower end of the suction pipe in the balanced state using Example <NUM> according to the present invention and Comparative examples <NUM> and <NUM>.

Example <NUM> has the same configuration as the drainage pump <NUM> described above. In Example <NUM>, the outer diameter D of the lower end of the suction pipe is <NUM>. The suction pipe has the concave surface in the circular annular shape around the suction port. The width RT at the lower end of the suction pipe in the radial direction is <NUM>.

In Comparative example <NUM>, the outer diameter D and the width RT at the lower end of the suction pipe are the same as those of Example <NUM>. However, Comparative example <NUM> differs from Example <NUM> in that the suction pipe has a flat surface in a circular annular shape around the suction port. Comparative example <NUM> has the same configuration as Example <NUM> except the suction pipe.

In Comparative example <NUM>, the outer diameter D of the lower end of the suction pipe is <NUM>. The suction pipe has a flat surface in a circular annular shape around the suction port. Additionally, the width RT at the lower end of the suction pipe of Comparative example <NUM> in the radial direction is <NUM> and is narrower than that of Comparative example <NUM>. Comparative example <NUM> has the same configuration as Example <NUM> except the suction pipe.

The inventors used Example <NUM> and Comparative examples <NUM> and <NUM> to discharge the drain water W from the drain pan and measured the position of the water surface of the drain water W in the drain pan relative to the lower end of the suction pipe when the drainage pump was in the balanced state. The inventors measured the position of the water surface three times for each of Example <NUM> and Comparative examples <NUM> and <NUM> and calculated average values. Table <NUM> shows suction pipe configurations and measurement results of Example <NUM> and Comparative examples <NUM> and <NUM>. <FIG> shows the measurement results. <FIG> is a graph showing the positions of the water surfaces (average value) relative to the lower end of the suction pipe in the balanced state.

The measurement results of Comparative examples <NUM> and <NUM> show that increasing the width of the flat surface around the suction port allows the position of the water surface of the drain water in the drain pan to be lower. Additionally, the measurement results of Example <NUM> and Comparative example <NUM> show that changing the shape around the suction port from the flat surface to the concave surface allows the position of the water surface of the drain water in the drain pan to be further lower. In other words, a drainage pump with a concave surface in a circular annular shape around its suction port can lower the position of the water surface of the drain water in the drain pan compared to a drainage pump with a flat surface in a circular annular shape around its suction port.

This shows that the effects of the present invention are also evident in the verification of using actual drainage pumps.

Claim 1:
A drainage pump (<NUM>) comprising:
a housing (<NUM>);
an impeller (<NUM>) housed in the housing (<NUM>); and
a motor (<NUM>) with a drive shaft (<NUM>) connected to the impeller (<NUM>),
wherein the housing (<NUM>) includes a suction pipe (<NUM>) in a cylindrical shape extending in an up-and-down direction,
characterized in that the suction pipe (<NUM>) includes a suction port (12a) facing downward and a concave surface (12b) in an annular shape around the suction port (12a), the suction port (12a) and the concave surface (12b) being disposed at a lower end of the suction pipe (<NUM>).