HEATING ELEMENTS

Abstract

A water heating element (98) is disclosed which is in the form of a tube that is open at both ends thereby to form a through passage, wherein the tube comprises a metal outer sleeve and a co-axial metal inner sleeve having an electrically insulating material in the form of ceramic beads or magnesium oxide powder therebetween with electrical resistance wires running through the insulating material. The element (98) is mounted in an inclined position in the hot water cylinder (102) with the open lower end of the element close to the bottom wall of the hot water cylinder.

Description

FIELD OF THE INVENTION

THIS INVENTION relates to heating elements specifically, but not exclusively, for heating water.

BACKGROUND TO THE INVENTION

In view of the cost of electricity, it is desirable that heating elements used to heat the water in hot water cylinders should be as efficient as possible. Desirably, the water should be raised as rapidly as possible to the temperature set on the thermostat and then the heating elements switched off

The present invention provides a heating element which enables more rapid heating to take place than is possible with heating elements that are conventionally used to heat the water in hot water cylinders.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided a heating element in the form of a hollow tube defining a passage, the passage being open at both ends so that water can flow through the tube from an inlet end of the passage to an outlet end of the passage.

Said the tube preferably comprises inner and outer shells with a resistance wire between the shells. In this form said outer shell can comprise an elongate outer metal sleeve and a cylindrical liner of electrically insulating material inside said outer metal sleeve, and the inner shell can comprise an elongate inner metal sleeve and a cylindrical sheath of electrically insulating material on the outside of said inner metal sleeve, said resistance wire being in a space between said sheath and said liner. The metal sleeves can be of copper and the liner and sheath can be of ceramic material.

End rings can be provided for closing both ends of said space in which said resistance wire is located.

In another form said tube can comprise an outer metal sleeve and an inner metal sleeve with side-by-side beads between the sleeves, each bead having a central opening through which said inner metal sleeve passes and a plurality of further openings through which the resistance wire passes.

In yet another form said tube is constituted by an elongate metal sleeve with at least one resistance wire within the sleeve and extending along it, there being electrically insulating material within the sleeve for electrically isolating said resistance wire from the sleeve, said sleeve being wound into the form of a hollow coil with a plurality of turns, said passage being bounded by the turns of the coil.

Adjacent turns of the coil preferably touch one another.

Said passage can have therein a component which reduces the area of the passage over the length of the component. Preferably said component is at one end of said passage.

According to a further aspect of the present invention there is provided a block for mounting the heater on the mounting plate of a hot water cylinder, an elongate mounting element protruding from said block, the element having a bend in it so that it has a first portion extending from said block and a second portion which is at an angle to said first portion, and a water heating structure including a resistance wire connected to said second portion of said element.

Preferably, when said first portion is horizontal, the second portion is at an angle of 30 to 60 degrees with respect to the horizontal. Said mounting element can be in the form of a tube and in a specific form said mounting element is constituted by a pair of parallel tubes.

The water heater can include a pocket for a thermostat, the pocket being externally threaded over an end portion thereof and the mounting block having an internally threaded bore through it into which said pocket can be screwed.

According to another aspect of the present invention there is provided an installation comprising, in combination, a hot water cylinder having a mounting plate and a water heater as defined in any one of the three preceding paragraphs, said block of the water heater being secured to the mounting plate with said first portion protruding into the cylinder and said second portion and said heating structure extending downwardly from said first portion towards the bottom of the cylinder.

There can be a mounting structure for the heating element, the mounting structure having a bend in it so that when the mounting structure is secured to a vertical wall of a hot water cylinder, the heating element slopes down from said wall.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:

FIG. 1 is a pictorial view of an assembled hollow heating element in accordance with the present invention;

FIG. 2 is a view similar to that of FIG. 1 but cut away to reveal the internal construction;

FIG. 3 illustrates, to a larger scale, the open end of the heating element;

FIG. 4 is a view identical to that of FIG. 1 but with components cut away to further illustrate the internal construction;

FIG. 5 illustrates the end of the heating element which is mounted on the wall of the hot water cylinder;

FIGS. 6 and 7 are pictorial views of a further embodiment of heating element according to the invention;

FIG. 8 is a diagrammatic cut away view of the heating element of FIGS. 6 and 7;

FIG. 9 is a pictorial view of a mounting for a heating element;

FIG. 10 is cut away view of another heating element;

FIG. 11 is a pictorial view of a heating element which includes a coil;

FIG. 12 is a diagrammatic representation of another heating element; and

FIG. 13 illustrates a hot water installation.

DETAILED DESCRIPTION OF THE DRAWINGS

The heating element 10 illustrated in FIG. 1 comprises a hollow tube 12 and, at one end of the tube 12, a structure 14 for mounting the heating element on the wall of a hot water cylinder (not shown).

The tube 12 comprises, see FIGS. 2 to 4, an outer shell 16 and an inner shell 18. The shell 16 comprises a cylindrical outer metal sleeve 20, preferably of copper, and a cylindrical liner 22 which is of an electrically insulating material such as a ceramic. The sleeve 20 projects beyond the liner 22 (see FIGS. 2 and 3) at both ends of the element.

The inner shell 18 comprises an inner metal sleeve 24, preferably of copper, and an outer sheath 26 of an electrically insulating material such as a ceramic. The sleeve 24 projects beyond the sheath 26 at both ends (see FIG. 3). There are flanges 28 on the outside of the sheath 26 at both ends.

The flanges 28 of the sheath 26 are in contact with the liner 22 thereby to hold the apart those parts of the liner 22 and sheath 26 which are between the flanges 28. This provides an elongate cavity for a wound resistance wire 30 which is wound onto the sheath 26 between the flanges 28.

A metal end ring 32 fits onto the sleeves 20 and 24 at the open end of the element 10 and prevents water entering the cavity which contains the resistance wire 30. The end ring 32 can be brazed to both of the sleeves 20 and 24.

An end ring 34 (see FIG. 5), similar to the end ring 32, fits onto the sleeves 20 and 24 to prevent water entering the other end of the cavity in which the wound resistance wire 30 is contained.

The ring 34 has openings 36 in it for enabling electrical leads 38 to be passed through it and connected to the resistance wire 30.

Three short copper pipes are shown at 40.

The mounting structure 14 comprises a block 42 having a cylindrical externally threaded section 44. This section screws into the mounting plate (not shown) of the hot water cylinder with the imposition of suitable water seals.

Two through bores 46, 48 in the block 42 allow the electrical leads 38 which are connected to the resistance wire 30 to pass through the block 42 and enter the bores in the ring 34. A further bore 50 in the block 42 receives a one-way valve (not shown).

At one end each pipe 40 is welded or otherwise secured to the block 42 in alignment with the bores 46, 48 and 50. The other end of each pipe 40 passes through a respective one of the openings 36 in the ring 34 and is welded or otherwise secured to the tube 12. Conveniently, the pipes 40 are secured to the sleeve 24 but they can be secured to the sleeve 20. The leads 38 pass through two of the pipes 40 and the bore 50 communicates with the pipe 40. It is also possible to secure the pipes 40 to the metal cap 34 and then secure the cap 34 to the sleeve 20. The pipes 40 form the mechanical connection between the block 42 and the tube 12.

If desired the pressure in the cavity in which the heating coil 30 is located can be increased to above atmospheric or, alternatively, the atmospheric air can be replaced by another gas such as helium using the valve in the bore 50.

In use, when current is flowing, hot water layers form on both the inner and outer metal sleeves 20 and 24. Heating of the water inside the inner metal sleeve 20 causes a flow of water through the hollow interior of the tube 12 which, as best seen in FIGS. 1 and 5, is open at both ends.

Turning now to FIGS. 6 to 8, these illustrate an embodiment which has parts in common with the embodiment of FIGS. 1 to 5. Like parts have been designated with the same reference numerals to which the suffix “1” has been added.

The liner 22 and sheath 26 are replaced by a row of what in the industry are called “beads”. Each bead, designated 52, has a central opening and a plurality of further openings which receive the resistance wires.

In the embodiment of FIGS. 6 to 8, the array of beads 52 is pushed into the outer sleeve 24.1 (from the left hand end in FIG. 8) until it encounters a ring 54 of electrically insulating material which is between the metal ring 32.1 and the beads.

A second insulating ring 56 is pushed into the sleeve 24 to insulate the resistance wires from the metal end cap 34.1.

The inner metal sleeve 24.1 is pushed into the central opening of the array of beads 52. The array of beads thus replaces the liner 22 and the sheath 26, and the beads lie between the sleeve 20.1 and the sleeve 24.1.

The mounting 58 shown in FIG. 9 includes a block 60 and an externally threaded section 62. The face of the block 60 remote from the section 62 has a groove 64 in it for receiving a sealing ring, such as a 0-ring.

The bores of the block 60 equivalent to the bores 46, 48 of the block 42 are extended by hollow bosses 66, 68 which receive plugs 70, 72 of electrically insulating material. Bores 74, 76 are provided in the plugs 70, 72. The valve referred to above as being in the bore 50 of the block 42 is shown at 78. A blind tapped bore at the centre of the block 60 is designated 80.

The mounting 58 can be used in two ways. It can be screwed into the fixed mounting plate of the hot water cylinder as described above with reference to the block 42. Alternatively the face of the block with the 0-ring groove in it can be pressed against the inside face of a removable mounting plate. A stud or bolt (not shown) is passed through a hole in the mounting plate and screwed into the tapped bore 80. This secures the mounting and hence the entire heating element to the mounting plate. The tube 12 is inserted into the interior of the hot water cylinder until the mounting plate comes into contact with the external surface of the cylinder. The mounting plate is then bolted to the cylinder.

Holes in the mounting plate permit access to the bosses 66, 68 and to the valve 78.

The heating element of this FIG. 10 has many components in common with those of the preceding Figures and where applicable like parts have been designated with the same numerals.

A component designated 82 is fitted into one end of the inner sleeve 24. The component 82 is in the form of a plug which has a cylindrical part 84 which slides into the sleeve 24 and a flange 86 which abuts the end of the sleeve 24. The bore 88 in the component 82 is of smaller diameter than the internal diameter of the sleeve 24. The component 82 thus constitutes a flow restrictor. Flow into the passageway is through the restricted bore of the component 82.

In another embodiment (not shown) the flange 86 is omitted and the cylindrical part 84 is pushed into the end of the sleeve 24. The bore in the part 84 can taper from each end to a constricted throat between the ends.

The hollow heating elements described above can be sheathed in heat insulating material. Heating then takes place substantially entirely within the passageway through the element. This causes a flow of water through the passageway that exerts an axial thrust on the heating element.

In FIG. 11 the heating element 90 initially comprises an elongate, straight copper tube 92 which has in it beads through holes in which resistance wires pass. In an alternative form the tube 92 is filled with magnesium oxide powder through which the wires pass. The powder electrically isolates the wires from the tube and from one another.

The tube 92 is then wound into the form of a coil with adjacent turns touching one another. This ensures that water in the hollow coil cannot escape between adjacent turns but must flow the full length of the coil.

In FIG. 12 the heating element is designated 98 and is connected by two hollow mounting tubes 100 to the block designated 42. Each mounting tube 100 has a bend in it so that when the block 42 is secured to the vertical mounting plate (not shown in FIG. 12) the element 98 slopes downwardly at an angle of between 30° and 60° to the horizontal. The preferred angle is between 40° and 50° with respect to horizontal and experimental work has shown that an angle of 45° with respect to horizontal gives the best results.

Cold water near the bottom of the cylinder is drawn into the hollow element 98, is heated in the sloping passage within the element 98 and emerges as a hot water stream from the upper end of the passage in the heating element, thus creating a convection flow in the cylinder.

The element 98 can be of any of the forms above with reference to FIGS. 1 to 11.

FIG. 13 shows a hot water installation comprising a thermally insulated cylinder 102, a cold water inlet 104 and a hot water outlet 106. The element 98 is mounted on the end wall 108 of the cylinder 102. The open lower end of the element 98 is close to the lowermost part of the cylinder 102. A pocket 110 is provided for receiving a thermostat.

Claims

1. A heating element in the form of a hollow tube defining a passage, the passage being open at both ends so that water can flow through the tube from an inlet end of the passage to an outlet end of the passage.

2. A heating element as claimed in claim 1, wherein the tube comprises inner and outer shells with a resistance wire between the shells.

3. A heating element as claimed in claim 2, wherein said outer shell comprises an elongate outer metal sleeve and a cylindrical liner of electrically insulating material inside said outer metal sleeve, and the inner shell comprises an elongate inner metal sleeve and a cylindrical sheath of electrically insulating material on the outside of said inner metal sleeve, said resistance wire being in a space between said sheath and said liner.

4. A heating element as claimed in claim 3, wherein the metal sleeves are of copper and the liner and sheath are of ceramic material.

5. A heating element as claimed in claim 3 and including end rings for closing both ends of said space in which said resistance wire is located.

6. A heating element as claimed in claim 1 and including, at one end of the tube, a structure for mounting the tube on the wall of a hot water cylinder, the structure including passageways for electrical leads connected to said resistance wire.

7. A heating element as claimed in claim 6, wherein said structure includes a block having bores through it, said bores constituting the passageways for said leads.

8. A heating element as claimed in claim 7, and including metal tubes secured to said block and to one or other or both of said sleeves, said leads passing through said tubes.

9. A heating element as claimed in claim 1, wherein said tube comprises an outer metal sleeve and an inner metal sleeve with side-by-side beads between the sleeves, each bead having a central opening through which said inner metal sleeve passes and a plurality of further openings through which the resistance wire passes.

10. A heating element as claimed in claim 1, wherein said tube is constituted by an elongate metal sleeve with at least one resistance wire within the sleeve and extending along it, there being electrically insulating material within the sleeve for electrically isolating said resistance wire from the sleeve, said sleeve being wound into the form of a hollow coil with a plurality of turns, said passage being bounded by the turns of the coil.

11. A heating element as claimed in claim 10, wherein adjacent turns of the coil touch one another.

12. A heating element as claimed in claim 1, in which the passage has therein a component which reduces the area of the passage over the length of the component.

13. A heating element as claimed in claim 12, wherein said component is at one end of said passage.

14. A water heater comprising a block for mounting the heater on the mounting plate of a hot water cylinder, an elongate mounting element protruding from said block, the element having a bend in it so that it has a first portion extending from said block and a second portion which is at an angle to said first portion, and a water heating structure including a resistance wire connected to said second portion of said element.

15. A water heater as claimed in claim 14, wherein, when said first portion is horizontal, the second portion is at an angle of 30 to 60 degrees with respect to the horizontal.

16. A water heater as claimed in claim 15, wherein said angle is between 40 and 50 degrees.

17. A water heater as claimed in claim 14, wherein said element is in the form of a tube.

18. A water heater as claimed in claim 14, wherein said element is constituted by a pair of parallel tubes.

19. A water heater as claimed in claim 17, wherein electrical leads extend through said tube or tubes and are connected to said resistance wire.

20. A water heater as claimed in claim 14, and including a pocket for a thermostat, the pocket being externally threaded over an end portion thereof and the mounting block having an internally threaded bore through it into which said pocket can be screwed.

21. A water heater as claimed in claim 20, wherein said pocket is above said first portion.

22. An installation comprising, in combination, a hot water cylinder having a mounting plate and a water heater as claimed in claim 14, said block of the water heater being secured to the mounting plate with said first portion protruding into the cylinder and said second portion and said heating structure extending downwardly from said first portion towards the bottom of the cylinder.

23. A heating element as claimed in claim 1 and including a mounting structure for the heating element, the mounting structure having a bend in it so that when the mounting structure is secured to a vertical wall of a hot water cylinder, the heating element slopes down from said wall.