GB2051322A - Electrical continuous flow water heater - Google Patents

Abstract

A casing 11 of plastics material has a channel 15 in which a tube 16 is centered, with an annular gap 17 therebetween. A spiral heating element 14 is disposed in the tube 16. Sealing ribs or lips 18 seal the annular gap 17 and serve to centre the tube 16 in the channel 15. The tube 16 is of a heat resistant plastics material. The arrangement and composition of the tube 16 aim to improve insulation, and reduce deposits of impurities. <IMAGE>

Description

SPECIFICATION Electrical continuous flow water heater This invention relates to an electrical continuous flow water heater, having a casing containing a channel for the passage of water, in which the channel is located an insulating tube containing an electric spiral element.

Known devices of such a type have proved often to have insufficient insulation between the heating spiral lying in the flow of water to be heated, or between the insulating tube containing the spiral, and the casing containing the channel through which water passes. Furthermore, known devices also have had the disadvantage of calcareous deposits occurring on the walls of flow channels, and especially on the walls of a tube, usually of ceramic material, which contains the heating spiral, thus causing a gradual narrowing of the flow cross-section, which eventually leads to the destruction of the device.

The present invention aims to provide, particularly but not exclusively, a continuous flow heater in which a long life may be obtained, and in which, in particular, calcareous deposits in the flow path around the heating spiral are avoided.

According to the present invention, there is provided an electrical continuous flow water heater comprising a casing, a channel in the casing, a tube of insulative, heat resistant, plastics material, disposed in the channel with an annular gap therebetween, a spiral electric heating element in the tube, and sealing means in said annular gap to centre the tube in the channel and seal said gap against water flowing through the tube, in use.

The tube is preferably of polytetrafluroroethylene or copolymers of tetrafluoroethylene and hexafluoropropylene or of polyvinylidene fluoride, which have proved to be especially suitable materials.

For a better understanding of the invention and to shown how the same way be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawing, the single figure of which illustrates an electrical continuous flow water heater.

A casing 11, of a suitable plastics material, contains an inlet channel 12 and an outlet channel 1 3 for water to be heated. The end of the inlet channel 12 opens into a channel 1 5 containing an electrical spiral heating element 14, and a tube 1 6 of a specific plastics material is inserted in the channel 1 5. The heating spiral 14 thus lies within the plastics tube 1 6, the material of the tube 1 6 being substantially non-sensitive to heat, in particular due to the fact that the tube 1 6 is arranged at a slight distance from the wall of the channel 1 5 enclosing said tube. The gap 1 7 has an additional insulating effect.For maintaining the gap and furthermore for sealing the ends of the gap, there are sealing lips or ribs 1 8 arranged at the ends of the tube 16, which, as shown, rest against the wall of the channel lying opposite to the tube 16. On the one hand, these sealing ribs or lips 18 close the gap 1 7 at both ends, and on the other hand, they centre the tube 16 within the channel 15.

It is, however, alternatively possible to arrange the sealing lips or ribs on the wall of the channel 1 5 so that the sealing ribs or lips extend out from the wall of the channel towards the tube 1 6 and also provide a centering of the tube 16 and a sealing of the gap 17.

The tube 16 is preferably of polytetrafluorethylene, or copolymers of tetrafluorethylene and hexafluoropropylene, or of polyvinylidene fluoride. This is advantageous due to the fact that tubes made of this material have an exceptionally smooth surface showing no affinity for the depositing of mineral substances, in particular lime, so that no lime can deposit on the inside of the tube.

The plastic tube 16 can be of a relatively thinwalled design without running any risk of deformation. This is due to the fact that a voltage is not applied to the spiral element 14 until water has flowed through the device, as the current is switched on by the pressure of the water.

1. An electrical continuous flow water heater comprising a casing, a channel in the casing, a tube of insulative, heat resistant, plastics material, disposed in the channel with an annular gap therebetween, a spiral electric heating element in the tube, and sealing means in said annular gap to centre the tube in the channel and seal said gap against water flowing through the tube, in use.

2. An electrical continuous flow water heater according to claim 1, wherein the tube is a thin walled tube.

3. A water heater according to claim 1 or 2, wherein said sealing means is in the form of ribs or lips.

4. A water heater according to claim 1, 2 or 3, wherein said sealing means is secured to the tube and has free edges engaging the channel.

5. A water heater according to claim 1, 2 or 3, wherein said sealing means is secured to the channel and has free edges engaging the tube.

6. A water heater according to any preceding claim, wherein said material is substantially porefree and chemically resistant.

7. A water heater according to claim 6, wherein said material comprises polytetrafluoroethylene or copolymers of tetrafluoroethylene and hexafluoropropylene.

8. A water heater according to claim 6, wherein said material comprises polyvinylidine fluoride.

9. An electrical water heater substantially as hereinbefore described with reference to the accompanying drawing.

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical continuous flow water heater This invention relates to an electrical continuous flow water heater, having a casing containing a channel for the passage of water, in which the channel is located an insulating tube containing an electric spiral element. Known devices of such a type have proved often to have insufficient insulation between the heating spiral lying in the flow of water to be heated, or between the insulating tube containing the spiral, and the casing containing the channel through which water passes. Furthermore, known devices also have had the disadvantage of calcareous deposits occurring on the walls of flow channels, and especially on the walls of a tube, usually of ceramic material, which contains the heating spiral, thus causing a gradual narrowing of the flow cross-section, which eventually leads to the destruction of the device. The present invention aims to provide, particularly but not exclusively, a continuous flow heater in which a long life may be obtained, and in which, in particular, calcareous deposits in the flow path around the heating spiral are avoided. According to the present invention, there is provided an electrical continuous flow water heater comprising a casing, a channel in the casing, a tube of insulative, heat resistant, plastics material, disposed in the channel with an annular gap therebetween, a spiral electric heating element in the tube, and sealing means in said annular gap to centre the tube in the channel and seal said gap against water flowing through the tube, in use. The tube is preferably of polytetrafluroroethylene or copolymers of tetrafluoroethylene and hexafluoropropylene or of polyvinylidene fluoride, which have proved to be especially suitable materials. For a better understanding of the invention and to shown how the same way be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawing, the single figure of which illustrates an electrical continuous flow water heater. A casing 11, of a suitable plastics material, contains an inlet channel 12 and an outlet channel 1 3 for water to be heated. The end of the inlet channel 12 opens into a channel 1 5 containing an electrical spiral heating element 14, and a tube 1 6 of a specific plastics material is inserted in the channel 1 5. The heating spiral 14 thus lies within the plastics tube 1 6, the material of the tube 1 6 being substantially non-sensitive to heat, in particular due to the fact that the tube 1 6 is arranged at a slight distance from the wall of the channel 1 5 enclosing said tube. The gap 1 7 has an additional insulating effect.For maintaining the gap and furthermore for sealing the ends of the gap, there are sealing lips or ribs 1 8 arranged at the ends of the tube 16, which, as shown, rest against the wall of the channel lying opposite to the tube 16. On the one hand, these sealing ribs or lips 18 close the gap 1 7 at both ends, and on the other hand, they centre the tube 16 within the channel 15. It is, however, alternatively possible to arrange the sealing lips or ribs on the wall of the channel 1 5 so that the sealing ribs or lips extend out from the wall of the channel towards the tube 1 6 and also provide a centering of the tube 16 and a sealing of the gap 17. The tube 16 is preferably of polytetrafluorethylene, or copolymers of tetrafluorethylene and hexafluoropropylene, or of polyvinylidene fluoride. This is advantageous due to the fact that tubes made of this material have an exceptionally smooth surface showing no affinity for the depositing of mineral substances, in particular lime, so that no lime can deposit on the inside of the tube. The plastic tube 16 can be of a relatively thinwalled design without running any risk of deformation. This is due to the fact that a voltage is not applied to the spiral element 14 until water has flowed through the device, as the current is switched on by the pressure of the water. CLAIMS

1. An electrical continuous flow water heater comprising a casing, a channel in the casing, a tube of insulative, heat resistant, plastics material, disposed in the channel with an annular gap therebetween, a spiral electric heating element in the tube, and sealing means in said annular gap to centre the tube in the channel and seal said gap against water flowing through the tube, in use.

2. An electrical continuous flow water heater according to claim 1, wherein the tube is a thin walled tube.

3. A water heater according to claim 1 or 2, wherein said sealing means is in the form of ribs or lips.

4. A water heater according to claim 1, 2 or 3, wherein said sealing means is secured to the tube and has free edges engaging the channel.

5. A water heater according to claim 1, 2 or 3, wherein said sealing means is secured to the channel and has free edges engaging the tube.

6. A water heater according to any preceding claim, wherein said material is substantially porefree and chemically resistant.

7. A water heater according to claim 6, wherein said material comprises polytetrafluoroethylene or copolymers of tetrafluoroethylene and hexafluoropropylene.

8. A water heater according to claim 6, wherein said material comprises polyvinylidine fluoride.

9. An electrical water heater substantially as hereinbefore described with reference to the accompanying drawing.