Circulation pump

An electric pump has a pump casing, a sealing plate, an impeller and a motor for driving the impeller. The pump casing has a main body. A recess is formed in the main body and with the sealing plate defines a pump chamber. A suction port is connected to the pump chamber by a suction channel and a suction passage formed in the main body. A discharge port is connected to the pump chamber by a discharge channel. The suction passage extends axially from the recess. The recess, suction passage, suction channel and discharge channel are all shaped in a manner allowing the pump casing can be molded as a monolithic structure in a single injection molding process.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Patent Application No. 201310232708.5 filed in The People's Republic of China on Jun. 13, 2013, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to pumps and, particularly, to a pump casing that can be made by a single process of plastic injection molding.

BACKGROUND OF THE INVENTION

An existing plastic pump is shown inFIG. 7, where the motor is not shown. The water inlet pipe1of the pump casing includes four sections in serial: starting section2, first middle section3, second middle section4, and end section5. The starting section2is tilted with respect to the axis of the motor. The first middle section3is substantially trapezoidal and substantially perpendicular to the axis of the motor, with the opening of smaller diameter connected to the starting section2. The second middle section4bends substantially 90 degrees. The end section5is connected to the second middle section4and is substantially parallel with the axis of the motor. Water enters the starting section2, passes through the first and second middle sections3and4, and flows into an impeller6via the end section5.

As the opening of the first middle section3having greater diameter is spaced from the starting section2, a die for producing the first middle section3cannot be extracted from the staring section2. That is to say, the starting section2and first middle section3cannot be made integrally in a single injection process. Similarly, as the second middle end5bends through a large angle, the first middle section3and the second middle section4cannot be made integrally in a single injection process. Thus, the whole pump casing cannot be made as a single piece plastic injection molding.

SUMMARY OF THE INVENTION

Hence there is a desire for a pump having a casing which is simple to manufacture.

Accordingly, in one aspect thereof, the present invention provides a pump comprising: a pump casing; a pump chamber formed in the pump casing; an impeller disposed within the pump chamber, the impeller having a plurality of vanes forming an inlet and an outlet; a sealing plate, forming one side of the pump chamber; a motor for driving the impeller; wherein the pump casing is a monolithic object comprising: a main body having a first surface, a recess in the first surface, a suction port, a suction channel, a suction passage, a discharge port, and a discharge channel; the recess forms a first opening in the first surface, the first opening is closed by the sealing pump to form the pump chamber, the recess having a second opening in a second surface opposite the first surface and a wall connecting the first surface to the second surface; the suction passage communicates with the recess via the second opening and is aligned with the inlet of the impeller; the suction port is connected to the suction passage by the suction channel; the discharge port is connected to the recess by the discharge channel which extends from a third opening formed in the wall of the recess; the diameter of wall of the recess remains the same or decreases along a direction from the first surface to the second surface; the diameter of the inner surface of the suction passage remains the same or decreases along a direction away from the recess; the inner diameter of the suction channel remains the same or decreases along a direction towards the suction passage; and the inner diameter of the discharge channel remains the same or decreases along a direction towards the recess.

Preferably, the suction channel comprises an inner surface having a top arc wall and a bottom arc wall that is closer to the recess than the top arc wall, the curvature of the top arc wall is between 0.006 and 0.01 mm−1, the curvature of the bottom arc wall is between 0.006 and 0.0085 mm−1, and an included angle α between the tangent direction of the end of the top arc wall at the suction port and a direction in which the first surface extends and an included angle β between the tangent direction of the end of the bottom arc wall at the suction port and a direction in which the first surface extends are both between 5 and 12 degrees.

Curvature is defined as 1/R where R is the radius of the curve measured in millimeters (mm).

Preferably, the curvature of the top arc wall is about 0.0071 mm−1; the included angle α is about 5 degrees; the curvature of the bottom arc wall is about 0.0070 mm−1, and the included angle β is about 8 degrees.

Preferably, the main body further comprises a spiral discharge groove in the boundary of the recess and extending from the second opening to the third opening.

Preferably, the main body further comprises a number of ribs extending from the center to the peripheral thereof.

Preferably, the main body further comprises a first ring projecting into the recess from the second opening, and the impeller further comprises a ring-shaped end surface surrounding the inlet and a second ring projecting from the end surface and surrounding the first ring, the second ring faces the first ring across a radial gap.

Preferably, a radially inner surface of the second ring is inclined at an angle θ, with respect to the axial direction of the impeller.

Preferably, the radially inner end of the end surface of the impeller extends closer to the axis of the impeller, compared to the radially inner end of the first ring.

Preferably, the end surface is inclined at an angle λ to a radial plane, such that the inner edge of the end surface is displaced towards the suction passage.

Preferably, the pump casing is a single piece plastic injection molding.

In embodiments of the present invention, due to detailed structure of the pump casing as described above, the pump casing that can be made as a single piece by a single plastic injection molding process, simplifying the manufacturing process. In some embodiments, as the second ring is arranged to surround the first ring, water is fully ducted into the impeller. This improves the efficiency of the pump.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 1 and 2, according to a preferred embodiment of the present invention, an electric pump10includes a pump casing20and a sealing plate40for sealing an opening of the pump casing20. An impeller50(shown inFIG. 4) is received in a pump chamber defined by the pump casing20and the sealing plate40. An electric motor60is connected to the sealing plate40and arranged to drive the impeller. InFIG. 2, a part of the motor has been removed to reveal that the motor has a permanent magnet rotor61.

Referring toFIGS. 3 and 4, the pump casing20includes a main body21, a suction port34, and a discharge port33. The main body21is substantially cone-shaped. A first side surface22of the main body21is substantially flat and is substantially square in the present embodiment. A second side surface23, opposing the first side surface22, is convex. A recess24is formed in the first side surface22, having a cross section in a plane perpendicular to the axis of the motor60of circular shape. The recess24creates a first opening24aon the first side surface22and is bounded by a second surface25and a wall26connecting the first side surface22to the second surface25. In a direction from the first side surface22to the second surface25, the inner diameter of the recess24becomes smaller. A suction passage27is formed in the main body21. The suction passage extends in an axial direction and communicates with the recess via a second opening27ain the second surface25. In the present embodiment, the cross section of the suction passage27is substantially circular and the inner diameter thereof becomes smaller as it moves away from the second surface25. A discharge groove28is formed in the boundary of the recess, substantially in the second surface25. The discharge groove28is spiral, extending from the suction passage27to a third opening36in the wall of the recess. According to the above description, a die for forming the recess24and the suction passage27can be removed from the first side surface22, without damage. It should be understood that in other embodiments, the inner diameter of the suction passage27can be constant. This can also fulfill the above purpose.

It should be noted that, in the present embodiment, the inner diameter becoming smaller is not necessarily limited to gradually becoming smaller, it only describes a general trend. For example, referring toFIG. 4, along a direction from the first side surface22to the second surface25, the inner diameter of a portion of the recess24can be substantially the same, such as the portion shown in block A, the inner diameter of a portion of the recess24can become smaller quickly, such as the portion shown in block B; or the inner diameter of a portion of the recess24can gradually become smaller gradually, such as the portion shown in block C. It is designed like this to match the shape of the impeller50and the sealing plate40, while at the same time allowing easy release of the molding die.

An inlet tube31is integrally formed with the main body21and includes the suction port34, the suction channel32and a suction passage opening35. The suction passage opening35is formed in the side surface of the suction passage27, allowing the suction channel to communicate or connect with the suction passage27. The inner diameter of the suction channel becomes smaller as it comes closer to the suction passage27. The suction channel is arc-shaped in the present embodiment. The discharge channel37connects the third opening36to the discharge port33. The discharge channel37is integrally formed in the main body21, opposing the inlet tube31. The third opening36is formed in the wall26of the recess24, allowing the recess24to communicate with the discharge port33. Along a direction from the discharge port to the recess24, the inner diameter of the discharge channel37becomes smaller.

According to the above description, a die for forming the inner surface32of the inlet tube31can be removed from the suction port34and a die for forming the discharge channel37can be removed from the discharge port33. It should be understood that in other embodiments, when the inner diameter of the suction channel32remains constant and the shape thereof is still arc-shape, or the suction channel32extends in a linear way and the inner diameter thereof becomes smaller as it approaches the suction passage27, the die for forming the inlet channel32can be removed from the suction port34.

Referring toFIGS. 2 and 4, the sealing plate40is circular, with a hole42formed at the center. The sealing plate40is fixed in the first opening24aof the recess24on the first surface22so as to seal the first opening24a. A shaft62of the motor60penetrates a bearing64that is fixed in the hole42. A seal (not shown) prevents water from leaking out of the pump chamber via the bearing/shaft interface. The impeller50is accommodated in the pump chamber formed by the recess24and the sealing plate40and is connected to the shaft62. The impeller50includes a first cover52, a number of vanes54extending from the first cover52, and a second cover56connected to the vanes54. The second cover56includes an opening forming the inlet58of the impeller. The suction passage27is axially aligned with the inlet58, so that water can flow into the impeller. The outer diameter of the second cover56becomes smaller along a direction away from the first cover52. The distance between the outer surface of the second cover56and the wall26of the recess24remains substantially the same.

In operation, the impeller50is driven by the motor60. Water flowing into the impeller50is expelled by the vanes through the exits (not labeled) defined by the first cover52, the second cover56, and adjacent vanes54, under centrifugal force. Water passing through the impeller50flows to the wall26of the recess24, and under the leading of the discharge groove28, the water flows in a spiral manner to the discharge port33, as shown by the dashed line inFIG. 3.

As the dies for producing the recess24and suction passage27, the suction channel32, and the discharge channel37can all be removed from the pump casing20without damage when the pump casing20has been formed, the whole pump casing20can therefore be made by a single plastic injection molding process, thereby the efficiency of manufacturing the pump casing is improved.

Preferably, the inner surface of the suction channel32includes a top arc wall32aand a bottom arc wall32b, as shown inFIG. 4, which is a sectional view taken along a plane IV-IV ofFIG. 1and defined by the axis of the motor and a radial direction of the motor on which the center line39of the suction channel32projects. The curvature of the top arc wall32ais between 0.006 and 0.01 mm−1, and the included angle α between the tangent direction of the end of the top arc wall32aof the suction channel32at the suction port34and the direction perpendicular to the axis of the motor (horizontal direction) is between 5 and 12 degrees. The curvature of the bottom arc wall32bis between 0.006 and 0.0085 mm−1, and the included angle β between the tangent direction of the end of the bottom arc wall32bof the suction channel32at the suction port34and the horizontal direction is between 5 and 12 degrees. Preferably, the curvature of the top arc wall32ais about 0.0071 mm−1, and the included angle α is about 5 degrees; the curvature of the bottom arc wall32bis about 0.0070 mm−1, and the included angle β is about 8 degrees. In this way, the axial height of the whole pump casing20is reduced.

Preferably, as shown inFIG. 5, the main body21further includes a first ring71projecting from the second surface25and surrounding the second opening27aof the recess24. The second cover56further includes a second ring72at its axial end surface that is substantially perpendicular to the axis of the motor, surrounding the inlet58. The first ring71and the second ring72are spaced from each other in the radial direction of the motor, and at least partially overlap with each other in the axial direction of the motor. As such, the second ring72surrounds the first ring71and faces the first ring across a radial air gap. In this way, water is fully ducted into the inlet58of the impeller50.

Referring toFIG. 4, during operation, part of the water thrown out of the impeller50may flow back to the inlet58of the impeller50via the space59between the outer surface of the second cover56and the wall26of the recess24. This will lower the efficiency of the pump. Thus, preferably, referring toFIG. 5, the radially inner surface of the second ring72is inclined at an angle θ towards the axial direction of the impeller. The radially outer surface of the first ring71is parallel with the radially inner surface of the second ring72. This structure eases the water at the inlet of the impeller50to flow into the space59after impact on the impeller50, the main body21, or itself. This part of water forming a resistance against that tends to running back to the impeller50via the space59, and thus the efficiency of the pump is improved. Preferably, 10°≦θ≦20°.

Preferably, referring toFIG. 6, compared to the radially inner end of the first ring71(shown by the axial dashed line), the radially inner end of the second cover56extends closer to the axis of the impeller50(or motor60as the motor and impeller are coaxially aligned). As such, when the water flows into the inlet58of the impeller50, part of the water close to the radially inner end of the second cover56will be intercepted by the end surface57of second cover56, which contributes to the quantity of water flowing into the space59and thus helps to improve the efficiency of the pump.

Preferably, as shown inFIG. 6, the end surface57of the second cover56from which the second ring72projects, in inclined at an angle λ to the direction perpendicular to the axial direction of the motor with the radially inner edge of the end surface57displaced towards the suction passage27. In this way, water entering the impeller can flow into the space59more easily. Preferably, 5°≦λ≦40°.

Preferably, referring toFIG. 1, the main body21further includes a number of ribs29on the second side surface23, extending substantially in radial directions of the motor to enhance the strength of the main body21.