US3822967A - Sump pump - Google Patents

Abstract

A sump pump of especially simple, inexpensive construction employing primarily molded plastic components, other than the electrical drive motor and associated components, comprising a novel assembly of molded plastic components in which adequate motor heat dissipation is provided by a metallic heat sink arrangement, and in which novel structural features are provided including a floating drive shaft bearing arrangement and a novel carrying handle utilizing the electrical power conductors for the drive motor as a part of the handle structure.

Description

llnite 1 States atent 1 1 Cade et al. July 9, 1974 [54] SUMP PUMP 3,637,326 1/1972 Dowell 417/44 3,653,785 4 1972 1) 111 417 424 [751 Inventors: Gemge Cade; Beach; 3,685,926 23/1972 811m 417424 Fliesen, 0f Prophetstown, 111-; 3,694,110 9/1972 Guinard 417/424 Samuel R. Phillips, San Francisco,

Calif.

[73] Assignee: Houdaille Industries, Inc., Buffalo,

[22] Filed: July 21, 1972 [21] Appl. No.: 273,949

[52] US. Cl. 417/368, 417/372 [51] Int. Cl. F04b 39/06 [58] Field of Search 417/38, 422, 424, 44

[56] References Cited UNITED STATES PATENTS 3,246,186 4/1966 Schaeffer 417/422 3,307,000 2/1967 Ekey 1 417/44 3,327,144 6/1967 Double 417/422 3,556,677 1/1971 Treman .1 417/44 Primary Examiner-William L. Freeh Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson ABSTRACT A sump pump of especially simple, inexpensive con struction employing primarily molded plastic components, other than the electrical drive motor and associated components, comprising a novel assembly of molded plastic components in which adequate motor heat dissipation is provided by a metallic heat sink ar rangement, and in which novel structural features are provided including a floating drive shaft bearing arrangement and a novel carrying handle utilizing the electrical power conductors for the drive motor as a part of the handle structure.

2 Claims, 4 Drawing Figures SUMPPUMP BACKGROUND OF THE INVENTION The present invention is directed to a pump structure, more particularly a sump pump, utilizable as a submersible pump, and completely immersible in the liquid, normally water, to be pumped. In the pastsump pumps of the type herein involved have'been constructed principally of metal and to insure reasonably long life and operation many of the component parts thereof were made of bronze or other suitable metal which would more effectively resist rust and corrosive actions resulting from the immersion of the pump structure in the pumped liquid. With the attendant high cost of this type of construction, some efforts have been made in the past to reduce costs by the use of plastic in. lieu of metal components, such transition to plastic components primarily involving the substitution of plastic for metal, i.e. fabricating components of substantially the same configuration as that previously emthereon a handle member by means of which the pump may be carried and transported, with the connecting conductor cord thus forming a part of the handle structure, thereby eliminating additional handle connecting components, joints, etc.

The motor housing structure is adapted to support a suitable bearing, as for example a ball bearing which is disposed adjacent the impeller end of themotor drive shaft and adapted to maintain the adjacent end of the shaft in operable position, both radially and axially, with the bearing thus forming the shaft axial-aligning means. The opposite end of the shaft is supported in a suitable bearing, which may be a sleeve bearing, whereby the shaft is maintained in radially fixed relation with respect to the motor stator core, ect. but

floating as to axial movement of the shaft, whereby the ployed but produced from plastic materials instead of metal, and employing standard motor structures.

The present invention is directed to a pump structure of the type described which is specifically designed for fabrication, substantially completely from plastic material, with the exception of motor components necessarily of metal, and associated components required for the supply and control of electrical power to the motor.

BRIEF SUMMARY OF THE INVENTION The present invention is. directed to production of a sump pump which overcomes the problems referred to, in which substantiallyall of the components of the pump are constructed of plastic, other than the motor drive shaft, rotor, stator, field windings, bearings and necessary power cords, switches, etc. In the final assembly, only two main plastic subassemblies are employed, one involving the motor structure, etc. and the other the base and pump structure. I

The motor structure may comprise merely three' plastic components, while the base and pump assemblyv may comprise a base member, two pump halves and a cooperable pump impeller. The base unit may also form the receptacle for a pressure operable switch by means of which the motor may be controlled in dependence upon the presence or absence of liquid to be pumped.

Power is adapted to be supplied to the pump by a power cord which an end of operably'terminates at the switch receptacle, and a connecting cord which extends from the switch receptacle to the motor housing and is adapted to complete the circuit, from the switch receptacle and power cord; to the 'motor. The respective cords are suitably connected to their associated receptacle or housing in fluid-tight relation, and the connecting conductor cord is adapted to have mounted shaft is supported in axially fixed relation merely at the lower bearing, thus maintaining the impeller in substan tially axially fixed relation but permitting the main body of the shaft, and the rotor carried thereby, to shift axially in response to thermal expansion and contracform of a metallic member forming the partition wall between the interior of the motor housing and the intake chamber of the base structure. The rotor is provided with suitable fins at its lower end to promote oil circulation in the motor housing whereby an effective heat transfer will take place through the wall forming the heat sink between the oil and the water or other liquid being pumped.

BRIEF DESCRIPTION OF THE DRAWINGS power cord construction and cooperable test device.

DETAILED DESCRIPTION OF A PREFERRED I EMBODIMENT OF THE INVENTION Referring to the drawing and more particularly to FIGS. 1 and 2, the pump structure therein illustrated,

designed as a submersible type sump pump, comprises a base member 1 of suitable molded plastic adapted to contain a vortex pump 2 operatively communicating with a water discharge outlet 3 in the upper face 4 of the base unit, and likewise formed from molded plastic.

Carried by and extending upwardly from the base unit is a molded plastic motor housing, indicated generally by the numeral 5, illustrated as being constructed in two sections, an upper section 6 and a' lower section 7, with the housing being adapted to suitably support therein an electric motor, indicated generally by the numeral 8. Also extending upwardly from the base 1 and illustrated, in the present embodiment of the invention, as being integrally fonned therewith is a switch housing indicated generally by the numeral 9, adapted to receive a pressure responsive switch indicated generally by the numeral 10.

Power from a suitable power supply line is adapted to be supplied to the pump through a power cord, indicated generally by the numeral 11, which is connected to the pump structure at the switch housing 9, with power being adapted to be conducted from the power cord 11 and switch to the motor 8 through a connecting cord, indicated generally by the numeral 12, which carries a handle member 13 by means of which the pump may be manually carried.

Referring to FIGS. 2 and 3, the plastic base 1 is provided with peripheral upstanding walls 14, which with the top wall 4, are operative to form a water intake chamber 1, the lower wall of which is adapted to be defined by the surface upon which the pump may be disposed during operation, with a suitable portion of the side walls 14 being provided with openings 15 therein, illustrated as being in the form of vertically extending slots, which cooperably from the intake opening for water into the intake chamber 1 of the base.

The pump 2, disposed in the chamber 1 is illustrated as being constructed in the form of two cooperable plastic halves, a lower half and an upper half 2b which are mechanically fastened by means of screws or the like along their mating edges to form a unitary structure. The pump 2 may be of generally standard mechanical design comprising a pump casing 16, of suitable configuration, which operatively communicates with the water discharge outlet 3 through a discharge vortex 17, the free end 18 of which is suitably flanged or otherwise formed and cemented of solvent welded to the internally threaded outlet fitting l9, integrally formed on the base 1. Disposed in the central well portion 20 of the casing 16 is a molded plastic rotaty impeller 21, likewise of suitable configuration and having its central hub portion 22 rigidly secured to the adjacent end 23 of the drive shaft 24 of the motor 8. Relative rotation of the impeller and shaft is prevented by a suitable flat on the face of the shaft and complementary projection in the bore of the impeller, with the latter being retained in operative position by a lock screw 25, threaded into the end face of the motor drive shaft. The casing 16 is provided with a water inlet opening 26 disposed on the upper face of the pump casing and communicating with the water intake chamber 1 formed by the base 1. Thus, water entering the intake opening 15 may flow through the intake opening 26 of the pump and, with suitable rotation of the impeller 21, discharged through the discharge vortex 17 and discharge opening 3 for conduction through a suitable conduit threaded into the internally threaded discharge opening.

The upper wall 4 of the base 1 is provided with an opening 27 therein defined by an inset flange, upon which is supported the lower housing section 7 of the motor housing 5, the latter being secured to the base 1 by suitable means such as screws 28 passing through respective inwardly directed projections 29 on the flange 27 and cooperable enlargements 30 formed on the lower section 7, for example, four such screws being employed, generally symmetrically disposed around the axis of the opening 27, only two of which are illustrated in FIG. 3.

As clearly illustrated in FIG. 3, the respective molded plastic sections 6 and 7 of the motor housing 5 are each generally cup-shaped, the section 6 having a top wall 31 with slightly diverging side walls 32, presenting a more or less conical configuration, which is cemented or solvent welded at its lower inner peripheral surface to the adjacent exterior support peripheral surface of the side wall 33 of the lower section 7, which side wall likewise is more or less conical configuration, converging slightly towards the bottom wall thereof which is formed by a generally conically shaped heat sink plate 34. The outer peripheral edge of the plate 34 may be provided with an outwardly directed flange 35, embedded in the adjacent wall of the lower section 7, while the inner peripheral edge of the heat sink plate, defining a central circular opening, is provided with a similar flange 36, embedded in a bearing supporting ring 37. The latter is connected to adjacent side wall portions of the lower section 7 by a plurality of plastic arms 39, three such arms being employed in the construction illustrated, only two of which appear in FIG. 3, with the bearing ring 37 and arms 39 being formed integrally with and thus of the same plastic material as the side walls of the lower section 7. Thus, the plate 34 defines the lower wall of the motor housing with the outer surface of the plate being in direct contact with liquid entering the intake chamber 1'.

The lower housing section 7 may be provided with a plurality of integrally pillars or columns 40, illustrated as being three in number, (only two of which are illustrated) and may be circumferentially aligned with the reenforcing arms or ribs 39, as illustrated. Each pillar 40 is provided with a generally L-shaped notch 41 in the upper end thereof adapted to receive the adjacent end of the stator core or stack 42 of the motor 8, with the stator core being securely retained in radially fixed position by the vertically extending portions of the pillars 40 disposed adjacent the circumferential face of the core. The latter is rigidly retained in operatively fixed position by a generally cup-shaped bearing cap 43, having a top wall 44 and a cylindrical peripheral wall 45, the lower edge of which is, in effect, counterbored to form a shoulder 46 seated on the upper end face of the stator core 42, with the downwardly depending portion of the side wall 45, at the outer face of the core 42, rigidly retaining the cap in radially fixed position on the stator core. The lower section 7, core 42,.and cap 43 are secured in rigid relation by a plurality of motor mounting screws 46, two of which are adapted to be employed in the embodiment illustrated, with the screws being disposed adjacent the periphery of the core 42. The latter may be provided with longitudinally extending notches or grooves in the outer periphery thereof of a size to suitably receive the screws, with the latter being threaded into respective columns or projections, not illustrated, similar to the projections 30 formed on the lower section 7.

Rigidly carried by the drive shaft 24 is a rotor 47, co-

operable with the stator 42, which is adapted to be energized by a suitable field winding 48. The lower end of the shaft 24 is operatively supported in the bearing ring 37 by a suitable bearing, indicated generally by the numeral 49, comprising an inner race and an outer race having suitable ball bearings operatively disposed therebetween, with the inner race being rigidly secured to the end portion 23, of reduced diameter, of the drive shaft, for example by means of pressed fit, while the outer race is rigidly secured in the retaining ring 37. As illustrated, the upper end face of the inner bearing race The lower end 23 of the shaft 24 is effectively sealed with respect to the passage of fluid into or out of the motor housing by a seal, indicated generally by the reference numeral 51, comprising stationary member 52 which is rigidly mounted in the ring member 37 and provided with a lower annular end face against which a cooperable sealing ring 53 bears, the latter being supported on'the end portion 23 of the shaft 24 by a suitable snap or lock ring 54. Effective sealing between the ring 53 and the surface of the shaft portion 23 may be effected by a suitable O-ring or comparable sealing member.

The housing 5 is adapted to contain a suitable quantity of liquid coolant, as for example, a suitable oil which may also provide lubrication for the shaft bearings, with the oil being adapted to be circulated through the housing and around the core structure, etc. by vanes 55 disposed at the lower end of the rotor, the top wall 44 of the bearing cap 43 being suitably provided with a plurality of openings 56, facilitating the desired oil circulation.

As the maximum operational temperature of the motor is considerably higher than the temperatures of the liquid to be pumped by the structure, heat may be withdrawn from the coolant oil, through the metallic heat sink 34, and transferred to the water or liquid being pumped, for ultimate removal therewith. As the heat sink plate 34 is preferably of metal having a considerably higher heat conductive characteristics than the molded plastic from which the motor housing 5 is constructed, considerably improved heat dissipation is achieved.

FIG. 4 illustrates details of the switch housing and associated structure, in which the housing 9 comprises a generally cylindrical wall 57 which extends downwardly into the intake chamber 1' and is provided adjacent its lower end with an internal shoulder 58 adapted to be engaged by the annular portion of a resilient guard and ceiling member or diaphragm 59, constructed from synthetic rubber or other suitable matewater to contact the lower wall 62 of the sealing dia- 'phragm for effecting actuation of the switch 10 when the pressure on the lower wall of the switch sufficiently exceeds air pressure above the switch.

The respective ends of the connector cord 12 and the adjacent end of the power cord 11 are firmly secured in fluid-tight relation to the motor housing 5 and switch housing 9, respectively, as illustrated in FIGS. 3 and 4. Thus, the connecting cord 12 has its adjacent end extending through the lower wall of a potting well 69, the well being filled, for example, with a suitable epoxy potting material 70, and the upper end of the well being suitably closed by a cord ferrule 71. In like manner, the top wall of the switch housing 9 is provided with an inverted potting well 72, with the adjacent end of the connecting cord 12 extending through the top wall of the switch housing 9 and firmly secured in place in sealed relation by potting material 73 with a suitable cord ferrule 74 being disposed at the juncture of the cord 12 with the switchhousing. The adjacent end of the power cord 11 is secured to the switch housing 9 in the same manner as the adjacent end of the cord 12.

As illustrated in FIG. 4, the power cord 11 is of special construction and may include a vent tube 75, which communicates at its adjacent end with the interior of the switch housing 9 and at its opposite end with an air vent port 76 opening on the side wall of the connecting plug 77 of the cord 11.

rial, having a channel 60 formed in the side wall thereof of a size to snugly receive the peripheral wall portion 61 of the switch 10, thereby forming the mounting means for the switch 10 in the housing, and the same time providing an effective sealing action of the switch structure with respect to the housing side wall. The bottom face of the switch is adapted to be sealed by the horizontally extending wall 62 of the member 59 which may be provided with anupwardly extending projection 63 adapted to bear on the adjacent wall of the switch structure. The member 59 and switch 10 are adapted to be firmly retained in operative position by a generally cup-shaped switch cap, indicated generally by the numeral 64, which is secured to the base 1 by screws 65 passing through outwardly extending ears 66 formed on the cap 64, with the screws being threaded As illustrated in FIGS. 1 and 3, the handle member 13, formed from any suitable material, for example a relatively stiff synthetic rubber, is mounted directly on the connecting cord 12 and may be, for example, molded directly thereon. As the ends of the connecting cord 12 are very firmly secured to the motor housing Sand the switch housing 9, such cord may be employed as a cooperable part of the handle structure, eliminating the need for additional handle components. Referring to FIG. 2, it will be noted that the vertically extending portions of the connecting cord 12 are disposed substantially on the median line of the pump structure, so that the handle 13 may be considered symmetrically disposed with respect to the base 1 and the motor housing 5, the discharge vortex associated elements at least in part counterbalancing the portions of the switch housing and switch structure disposed at the opposite side of the handle 13.

The pressure responsive switch 10 is illustrated as being of a type responsive to pressure differentials on opposite sides thereof, i.e., closing the operative contacts thereof when the pressure at the bottom face of the switch issufficiently greater than the pressure at the top face thereof, whereby, in operation, the switch will be actuated to a closed condition when water pressure below the switch reaches a predetermined value. Consequently, testing of the switch may be effected, in the absence of water pressure below the switch, by sufficiently reducing the air pressure above the switch. This may be readily accomplished by suitably withdrawing air through the vent tube to sufficiently reduce the air pressure above the switch to effect a test actuation thereof.

FIG. 4 also illustrates a very simple device for effecting such a test of the electrical circuit of the pump. In the embodiment of the invention illustrated, the testing device, indicated generally by the numeral 78, comprises a closed hollow structure comprising two sheets of material 79a and 79b which may be of like configuration, for example circular, and sealed in fluid-tight relation along their peripheral mating edges 80, with the only air inlet and outlet comprising a hollow tube 81 firmly fastened to the sheet 79a and communicating at its inner end with the interior of the structure. The tube may be provided at its opposite end with a tapering portion 82 of a size to be suitably inserted in substantially air tight relation in the vent port 76 of the plug 77. Secured to the central portion of the sheet 79b is a manually grippable ring 83 carried by a central mounting member 84 secured in sealed relation to the sheet 79b. Thus, by effecting separating movements between the oppositely disposed walls forrned by the sheets 79a and 79b the volume of the interior of the device may be materially increased resulting in an upward flow of air through the tubular stem 81. Consequently, tests may be readily made by inserting the end of the stem 81 into the vent port 76 while the structure is in a collapsed condition as illustrated in FIG. 4, and by effecting relative separating movement between the stem 81 and the ring 83, air may be withdrawn through the vent tube 75, to sufficiently reduce the air pressure in the upper portion of the switch housing 9 to test actuate the switch 10.

Obviously, the switch 10 will normally be circuited in series with one of the line conductors, with the opposite side of the switch being operatively connected to one side of the field winding 48 through a corresponding conductor in the connecting cord 12, and the other line conductor ofthe cord 11 being directly connected with the other line conductor of the cord 12, and connected thereby to the other side of the field winding 48. The conductors 11 and 12, as well as the plug 77, are illustrated as being of three wire construction with the third wire being a ground wire which may be suitably connected to the metallic structure of the motor 8.

It will be appreciated from the above description that we have provided an exceptionally simple yet highly efficient sump pump construction particularly adapted for use as a submerged unit, in which substantially all of the main components thereof, other than the necessary metallic parts of the motor structure, may be fabricated as molded plastic components, resulting in an extremely inexpensive yet highly durable structure that is substantially uneffected by any corrosive or rusting action of the liquid being pumped.

It will also be noted that we have provided a motor structure employing a novel bearing arrangement, as well as a novel cooling arrangement. A novel handle structure is also provided making use of the electrical connecting cord as the connecting supporting structure for the handle.

Having thus described our invention it will be apparent to those skilled in the art that various immaterial modifications may be made in the same without departing from the spirit and scope of the invention.

We claim as our invention:

1. A sump pump constructed principally of molded plastic, comprising a hollow molded plastic base, forming a chamber, and having openings therein for the passage of water from the exterior into the chamber, said base having a water discharge opening therein, a pump structure disposed in said base chamber having a water inlet opening communicating with the chamber interior and a water discharge opening communicating with said discharge opening in the base, an electric motor including a drive shaft, a rotor mounted on said drive shaft, a cooperable stator core and a stator-energizing field winding, a molded plastic motor housing having a lower housing section and an upper housing section, said housing sections having adjacent mating edge portions connected in fluid-tight relation to form a closed housing, the opposite end of said lower section being mounted on said base with the bottom wall of said lower section extending across an opening in the adjacent wall of said base, said lower section being provided with means on which said stator core is seated in radially fixed relation and with the core axis disposed vertically, a bearing cap seated upon the upper end of said stator core in radially fixed relation, means operable to retain said lower section, stator core and bearing cap in axially fixed relation, said cap and the bottom wall of the lower housing section having respective aligned bearing means therein for aligning said drive shaft and rotor on the axis of said stator core, the upper bearing means carried by said cap permitting unrestricted axial movement of said shaft and the lower bearing means comprising an outer bearing race fixedly mounted on said bottom wall of the lower section, and a cooperable concentrically disposed inner bearing race fixedly mounted on said shaft with said races being operatively connected by a plurality of bearing elements operative to maintain said races in axially fixed relation, and thus support said drive shaft and rotor in operative axially fixed relation with respect to said stator core, the lower end of said drive shaft extending through said bottom wall into said chamber and through the inlet opening of said pump, an impeller mounted on the adjacent end of said shaft and rotatable therewith, seal means, disposed below said lower hearing, encircling the lower end of said shaft and comprising a stationary member carried by said bottom wall of the lower section and a cooperable member slidably and rotatably carried by said shaft and engageable with the stationary member to form a fluid seal, axially fixed means mounted on said shaft for restricting downward movement of said cooperable member thereon, and means cooperable with said restricting means and cooperable member for forming a fluid seal between the latter and said shaft, and or urging said stationary and cooperable members in operative engagement, forming a fluid seal between said shaft and said bottom wall, the latter having at least a portion thereof extending across said base opening formed from a material having greater thermal conductivity than the plastic of said lower section, forming a heat sink operatively disposed between the interior of the motor housing and the base chamber, said bearing cap being provided with the openings therein, and said drive shaft being provided, adjacent the lower end of said rotor, with a plurality of impeller blades, and a supply of liquid coolant contained within said motor housing and adapted to circulate therein by means of said impeller blades, with said heat sink being operative to conduct heat from such liquid coolant to the water being pumped.

2. A sump pump constructed principally of molded plastic, comprising a hollow molded plastic base, forming a chamber, and having openings therein for the passage of liquid from the exterior into the chamber, said base having a liquid discharge opening therein, a pump structure including an impeller, disposed in said base chamber and having a liquid inlet opening communicating with the chamber interior and a liquid discharge opening communicating with said discharge opening in the base, a closed molded plastic motor housing secured at its lower end to said base, an electric motor operatively disposed in said housing and including a drive shaft, a rotor mounted on said drive shaft, a cooperable stator core, and a stator-energizing field winding, said drive shaft extending from said housing into said chamber and having said impeller mounted thereon, said motor housing having a wall portion abutting said chamber and thus is in contact with liquid entering said chamber, said wall portion being constructed of a material having greater thermal conductivity than the plastic of said motor housing, thus forming a heat sink for the conduction of heat developed by said motor to the liquid to be pumped, said stator core and field winding being inwardly spaced with respect to said wall portion, and said top and side walls of said motor housing, said drive shaft being provided, adjacent the lower end of said rotor, with a plurality of impeller blades, and a supply of liquid coolant contained within said motor housing in direct contact with said stator core and field winding and said wall portion, and adapted to be circulated therearound in the space between the same and said housing, by means of said impeller blades, with said heat sink being operative to conduct heat directly from such liquid coolant to the water being pumped.

Claims (2)

1. A sump pump constructed principally of molded plastic, comprising a hollow molded plastic base, forming a chamber, and having openings therein for the passage of water from the exterior into the chamber, said base having a water discharge opening therein, a pump structure disposed in said base chamber having a water inlet opening communicating with the chamber interior and a water discharge opening communicating with said discharge opening in the base, an electric motor including a drive shaft, a rotor mounted on said drive shaft, a cooperable stator core and a stator-energizing field winding, a molded plastic motor housing having a lower housing section and an upper housing section, said housing sections having adjacent mating edge portions connected in fluid-tight relation to form a closed housing, the opposite end of said lower section being mounted on said base with the bottom wall of said lower section extending across an opening in the adjacent wall of said base, said lower section being provided with means on which said stator core is seated in radially fixed relation and with the core axis disposed vertically, a bearing cap seated upon the upper end of said stator core in radially fixed relation, means operable to retain said lower section, stator core and bearing cap in axially fixed relation, said cap and the bottom wall of the lower housing section having respective aligned bearing means therein for aligning said drive shaft and rotor on the axis of said stator core, the upper bearing means carried by said cap permitting unrestricted axial movement of said shaft and the lower bearing means comprising an outer bearing race fixedly mounted on said bottom wall of the lower section, and a cooperable concentrically disposed inner bearing race fixedly mounted on said shaft with said races being operatively connected by a plurality of bearing elements operative to maintain said races in axially fixed relation, and thus support said drive shaft and rotor in operative axially fixed relation with respect to said stator core, the lower end of said drive shaft extending through said bottom wall into said chamber and through the inlet opening of said pump, an impeller mounted on the adjacent end of said shaft and rotatable therewith, seal means, disposed below said lower bearing, encircling the lower end of said shaft and comprising a stationary member carried by said bottom wall of the lower section and a cooperable member slidably and rotatably carried by said shaft and engageable with the stationary member to form a fluid seal, axially fixed means mounted on said shaft for restricting downward movement of said cooperable member thereon, and means cooperable with said restricting means and cooperable member for forming a fluid seal between the latter and said shaft, and or urging said stationary and cooperable members in operative engagement, forming a fluid seal between said shaft and said bottom wall, the latter having at least a portion thereof extending across said Base opening formed from a material having greater thermal conductivity than the plastic of said lower section, forming a heat sink operatively disposed between the interior of the motor housing and the base chamber, said bearing cap being provided with the openings therein, and said drive shaft being provided, adjacent the lower end of said rotor, with a plurality of impeller blades, and a supply of liquid coolant contained within said motor housing and adapted to circulate therein by means of said impeller blades, with said heat sink being operative to conduct heat from such liquid coolant to the water being pumped.

2. A sump pump constructed principally of molded plastic, comprising a hollow molded plastic base, forming a chamber, and having openings therein for the passage of liquid from the exterior into the chamber, said base having a liquid discharge opening therein, a pump structure including an impeller, disposed in said base chamber and having a liquid inlet opening communicating with the chamber interior and a liquid discharge opening communicating with said discharge opening in the base, a closed molded plastic motor housing secured at its lower end to said base, an electric motor operatively disposed in said housing and including a drive shaft, a rotor mounted on said drive shaft, a cooperable stator core, and a stator-energizing field winding, said drive shaft extending from said housing into said chamber and having said impeller mounted thereon, said motor housing having a wall portion abutting said chamber and thus is in contact with liquid entering said chamber, said wall portion being constructed of a material having greater thermal conductivity than the plastic of said motor housing, thus forming a heat sink for the conduction of heat developed by said motor to the liquid to be pumped, said stator core and field winding being inwardly spaced with respect to said wall portion, and said top and side walls of said motor housing, said drive shaft being provided, adjacent the lower end of said rotor, with a plurality of impeller blades, and a supply of liquid coolant contained within said motor housing in direct contact with said stator core and field winding and said wall portion, and adapted to be circulated therearound in the space between the same and said housing, by means of said impeller blades, with said heat sink being operative to conduct heat directly from such liquid coolant to the water being pumped.

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