GB1579951A

GB1579951A - Apparatus for pumping liquids in central heating systems

Info

Publication number: GB1579951A
Application number: GB1981977A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-05-11
Filing date: 1977-05-11
Publication date: 1980-11-26
Also published as: NL7804905A; FR2390604A1; JPS53139203A; DE2820870A1

Description

(54) APPARATUS FOR PUMPING LIQUIDS IN CENTRAL HEATING SYSTEMS (71) I, SAMUEL ALFRED ROBERTS, a British Subject, of Holwood Park Avenue, Keston Park, Farnborough, Kent, England, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to apparatus for pumping liquids in central heating systems, and is a modification or improvement of the invention forming the subject of U.K.

Patent No. 1,434,226.

It is desirable to provide pumps for circulating the liquids in small bore central heating systems, which pumps are conveniently small but powerful enough to have the required head and flow characteristics for the system.

It is also desirable that the pumps should be of the axial flow type, and preferably mounted axially, with their motors, in the pipework of the system. Such pumps generally have motors which are so large that they impede the flow of liquid in the system.

It has therefore been proposed in U.K.

Patent No. 1,434,226 to provide a pump for a central heating system comprising a tubular pump housing, a cylindrical casing disposed concentrically within the pump housing and forming an annular liquid flow passage between its outer surface and the internal surface of the pump housing, an electric induction motor housed coaxially within the cylindrical casing and adapted to run on low voltage, multi-phase, alternating current electricity supply of a frequency greater than the 50 Hertz domestic supply frequency and an axial flow impeller mounted on an output shaft of the motor. By low voltage was meant lower than domestic voltage supplies.

With such an arrangement, the use of the high frequency, low voltage supply enables the motor and the pump to be conveniently small so that they can both be located in the pipework of the system without the motor seriously impeding the flow caused by the impeller. Furthermore, the location of the motor in the pipework, where it is immersed in the liquid in the system, keeps the motor at an acceptable temperature, and reduces the effect of environmental temperature changes so as to reduce the restriction imposed on the location of the pump.

Apparatus in accordance with the present invention comprises a tubular pump housing, a cylindrical casing disposed concentrically within the pump housing and forming an annular liquid flow passage between its outer surface and the internal surface of the pump housing, an electric induction motor housed coaxially within the cylindrical casing and adapted to run on a multi-phase, alternating current electricity supply of a voltage lower than the voltage of normal domestic mains supplies and a frequency greater than the frequency of said domestic supplies, said motor having axially grooved rotor bearings so that liquid from the central heating system circulates through the central part of the motor and, mounted on the output shaft of the motor, a mixed flow impeller including vanes which are mounted on a conical or frusto-conical surface, rotation of the impeller thereby causing the vanes to impart both axial and radial components of thrust to the liquid in the system.

It has been found that such an arrangement of the impeller greatly improves the flow characteristics of the pump. The pump is more efficient, and the noise made is reduced to an even lower level than that associated with the pump of U.K. Patent No. 1,434,226. This means that the tubular pump housing need not be resiliently mounted in an inner tubular sleeve such as is described with reference to Figure 3 of the drawings accompanying U.K.

Patent No. 1,434,226. Furthermore, the pump may be constructed somewhat smaller than the pump described in that Patent.

The impeller is mounted upstream of the motor. The impeller also preferably has an inlet portion which abuts the vanes so that the vanes form channels between the inlet portion and the conical or frusto-conical surface. The inlet portion may also have a tubular part through which incoming liquid is directed.

The invention will now be further des cribed by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a pump in accordance with the invention, and Figure 2 is a view along the line 11-Il shown dotted in Figure 1.

Referring to the drawings, the pump 2 comprises a motor generally indicated at 4.

The motor includes a rotor 6 mounted for rotation on a shaft 8 located in carbon bearings 10. The motor has a stator 12 surrounding the rotor 6. The motor 4 also has a casing comprising two cup-shaped members 14 and 16 which are sealed together at their open ends by heat welding or by adhesive.

Each casing member is provided with guide vanes, two of which are indicated at 18, and these serve to hold the motor in position within an outer tubular housing 20. The housing 20 has an inlet end 22 and an outlet end 24 both of which are adapted to be connected to the pipework of a central heating system. The shaft 8 of the motor has an impeller 26 mounted at one end thereof.

The arrangement is such that, when the housing 20 is connected to the pipework and the motor is in use, the impeller 26 is rotated by the motor 4 to draw liquid into the inlet end 22 and force it into the annular space 28 defined by the outer surface of the casing 14 and 16 and the inner surface of the housing 20, as indicated by arrows A. The liquid then exits from the outer end 24 of the pump. The guide vanes 18 serve to straighten the flow of liquid, and eliminate the swirling motion of the liquid imparted thereto by the impeller 26.

The impeller 26 comprises a number of vanes 30 which are mounted on a frustoconical surface 32. The vanes are curved in such a manner that, considering their radially outer surfaces, the angle between a tangent to this outer surface and a tangent of a circle centred on the axis of the impeller is about 10 at the outer points of the vanes and about 26 at their inner points.

The impeller 26 also includes an inlet part 34 upstream of the vanes consisting of a cylindrical portion 36 which diverges toward the motor to form a frusto-conical portion 38 which abuts those edges of the vanes opposite to the ones contacting the frusto-conical surface 32. In this manner, the vanes 30 form passages between the surface 32 and the facing surface of the portion 38 and the liquid flows therethrough in a direction substantially parallel to the surface of the impeller.

The surface 32 and the facing surface of portion 38 are tapered at different angles, and the vanes 30 are corresponding sized so that they are higher at their inner ends than at their outer ends.

In operation, the liquid is forced by the vanes 30 both axially and radially of the pump 2.

The motor is powered by a multi-phase alternating current electricity supply of a voltage lower than the voltage of normal domestic supplies and a frequency greater than the frequency of said domestic supplies, and is similar to that described in U.K. Patent No. 1,434,226. The supply is connected to the stator windings via wires (not shown) passing through a water-tight grommet (also not shown) in the housing 20.

A cylindrical sleeve 40 is fixed to the inner surface of the inlet end 22 of the housing 20, around the cylindrical part 36 of the impeller 26. This sleeve acts to prevent corrosion of the inlet part 22 by the turbulent liquid which flows in this area.

The angle between the axis of the impeller and the surface 32 is desirably between about 30 and 70 , and is preferably about 65". The length of the pump 2 preferably conforms to a standard length, and this limits the permissible values of the angle, in view of the fact that as the angle increases to improve the flow caused by the impeller, the overall length of the motor 4 and impeller 26 also increases.

Liquid is allowed to enter the central part of the motor 4 via very small axial grooves in the rotor bearings 10 and a clearance between the shaft 8 and the said bearings, for cooling the motor. The axial grooves are provided in the bearings to ensure sufficient flow of liquid for adequate cooling. These grooves are small enough to preclude the passage of dirt and other foreign matter. The circulation of cooling water through this part of the motor is aided by the pressure difference between the ends of the pump, and the rotation of the rotor. Because the power supply voltage is low, no problems relating to the immersing of electrical conductors in the liquid occur.

WHAT I CLAIM IS: 1. Apparatus for pumping liquid in a central heating system comprising a tubular pump housing, a cylindrical casing disposed concentrically within the pump housing and forming an annular liquid flow passage between its outer surface and the internal surface of the pump housing, an electric induction motor housed coaxially within the cylindrical casing and adapted to run on a multi-phase, alternating current electricity supply of a voltage lower than the voltage of normal domestic supplies and a frequency greater than the frequency of said domestic supplies, said motor having axially grooved bearings so that liquid from the central heating system circulates through the central part of the motor and a pump impeller mounted on the output shaft of the motor wherein the pump impeller comprises a mixed flow impeller having vanes which are mounted on a conical or frusto-conical surface whereby rotation of the impeller causes both axial and radial components of thrust to be imparted to the liquid in the said system.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cribed by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a pump in accordance with the invention, and Figure 2 is a view along the line 11-Il shown dotted in Figure 1. Referring to the drawings, the pump 2 comprises a motor generally indicated at 4. The motor includes a rotor 6 mounted for rotation on a shaft 8 located in carbon bearings 10. The motor has a stator 12 surrounding the rotor 6. The motor 4 also has a casing comprising two cup-shaped members 14 and 16 which are sealed together at their open ends by heat welding or by adhesive. Each casing member is provided with guide vanes, two of which are indicated at 18, and these serve to hold the motor in position within an outer tubular housing 20. The housing 20 has an inlet end 22 and an outlet end 24 both of which are adapted to be connected to the pipework of a central heating system. The shaft 8 of the motor has an impeller 26 mounted at one end thereof. The arrangement is such that, when the housing 20 is connected to the pipework and the motor is in use, the impeller 26 is rotated by the motor 4 to draw liquid into the inlet end 22 and force it into the annular space 28 defined by the outer surface of the casing 14 and 16 and the inner surface of the housing 20, as indicated by arrows A. The liquid then exits from the outer end 24 of the pump. The guide vanes 18 serve to straighten the flow of liquid, and eliminate the swirling motion of the liquid imparted thereto by the impeller 26. The impeller 26 comprises a number of vanes 30 which are mounted on a frustoconical surface 32. The vanes are curved in such a manner that, considering their radially outer surfaces, the angle between a tangent to this outer surface and a tangent of a circle centred on the axis of the impeller is about 10 at the outer points of the vanes and about 26 at their inner points. The impeller 26 also includes an inlet part 34 upstream of the vanes consisting of a cylindrical portion 36 which diverges toward the motor to form a frusto-conical portion 38 which abuts those edges of the vanes opposite to the ones contacting the frusto-conical surface 32. In this manner, the vanes 30 form passages between the surface 32 and the facing surface of the portion 38 and the liquid flows therethrough in a direction substantially parallel to the surface of the impeller. The surface 32 and the facing surface of portion 38 are tapered at different angles, and the vanes 30 are corresponding sized so that they are higher at their inner ends than at their outer ends. In operation, the liquid is forced by the vanes 30 both axially and radially of the pump 2. The motor is powered by a multi-phase alternating current electricity supply of a voltage lower than the voltage of normal domestic supplies and a frequency greater than the frequency of said domestic supplies, and is similar to that described in U.K. Patent No. 1,434,226. The supply is connected to the stator windings via wires (not shown) passing through a water-tight grommet (also not shown) in the housing 20. A cylindrical sleeve 40 is fixed to the inner surface of the inlet end 22 of the housing 20, around the cylindrical part 36 of the impeller 26. This sleeve acts to prevent corrosion of the inlet part 22 by the turbulent liquid which flows in this area. The angle between the axis of the impeller and the surface 32 is desirably between about 30 and 70 , and is preferably about 65". The length of the pump 2 preferably conforms to a standard length, and this limits the permissible values of the angle, in view of the fact that as the angle increases to improve the flow caused by the impeller, the overall length of the motor 4 and impeller 26 also increases. Liquid is allowed to enter the central part of the motor 4 via very small axial grooves in the rotor bearings 10 and a clearance between the shaft 8 and the said bearings, for cooling the motor. The axial grooves are provided in the bearings to ensure sufficient flow of liquid for adequate cooling. These grooves are small enough to preclude the passage of dirt and other foreign matter. The circulation of cooling water through this part of the motor is aided by the pressure difference between the ends of the pump, and the rotation of the rotor. Because the power supply voltage is low, no problems relating to the immersing of electrical conductors in the liquid occur. WHAT I CLAIM IS:

1. Apparatus for pumping liquid in a central heating system comprising a tubular pump housing, a cylindrical casing disposed concentrically within the pump housing and forming an annular liquid flow passage between its outer surface and the internal surface of the pump housing, an electric induction motor housed coaxially within the cylindrical casing and adapted to run on a multi-phase, alternating current electricity supply of a voltage lower than the voltage of normal domestic supplies and a frequency greater than the frequency of said domestic supplies, said motor having axially grooved bearings so that liquid from the central heating system circulates through the central part of the motor and a pump impeller mounted on the output shaft of the motor wherein the pump impeller comprises a mixed flow impeller having vanes which are mounted on a conical or frusto-conical surface whereby rotation of the impeller causes both axial and radial components of thrust to be imparted to the liquid in the said system.

2. Apparatus according to Claim 1 further

comprising a respective multi-phase low voltage alternating current power supply unit which provides current to the said induction motor at a voltage less than the voltage of normal domestic mains supplies and at a frequency which is greater than the frequency of said domestic supplies.

3. Apparatus according to Claim 1 or Claim 2 wherein the said frusto-conical surface subtends an angle to the rotational axis of the impeller which is between 30 and 70".

4. Apparatus according to Claim 3 wherein the said angle is 65".

5. Apparatus according to any preceding claim wherein the said impeller vanes are curved such that considering their radially outer surfaces the angle between a tangent to this surface and a tangent of a circle centred on the axis of the impeller is about 10 at the outer points of the vanes and about 26 at their inner points.

6. Apparatus according to any preceding claim wherein the said impeller incorporates an inlet portion upstream of the vanes comprising a cylindrical tubular portion arranged coaxially with the impeller and a frustoconical annular portion which diverges from the trailing end of the said tubular portion and abuts the front edges of the vanes to thereby guide the flow of liquid over the impeller in a direction substantially parallel to the surface of the impeller.

7. Apparatus substantially as described herein with reference to the accompanying drawings.