WO1989002565A1

WO1989002565A1 - Electrical ceiling heater panel

Info

Publication number: WO1989002565A1
Application number: PCT/NO1988/000067
Authority: WO
Inventors: Per Wesseltoft
Original assignee: Per Wesseltoft A/S
Priority date: 1987-09-14
Filing date: 1988-09-13
Publication date: 1989-03-23

Abstract

Electrical ceiling heater panel for radiant heating, comprising a relatively elongated radiant heating element (22) having a radiation emitting surface adapted to face generally downwards in the mounted position of the panel, said surface being preferably provided with longitudinal ribs (10A, 10B), at least one electrical heater element (25, 26) being in close heat conductive contact with the radiant heating element (22) and a surrounding insulated housing (5, 7, 15) having means (2, 3) for suspending the panel from a ceiling (1). The radiant heating element (22) at its longitudinal edges has engagement parts (22A, 22B) for cooperation with longitudinal edges (19A) of an element box (19) built up of sheet material and having a sufficient rigidity to keep the radiant heating element (22) in a correct position during operation. The radiant heating element can be displaced somewhat in its longitudinal direction with respect to the element box, and at each end of the element box there is provided a plate-shaped bracket (18) standing generally in a plane normal to the longitudinal direction of the panel and adapted to be somewhat resilient in this direction as well as being attached to the adjacent end of the radiant heating element (22) at the outer edges thereof.

Description

ELECTRICAL CEILING HEATER PANEL

In the principle a radiant heater panel is based on the heating of a surface to a desired temperature, so that heat radiation is emitted to the surroundings as direct radiation from the surface. As a rule it is desirable to direct the heat in certain directions, for example generally downwardly from a ceiling heater panel, which is obtained by heat insulating in other directions or by shielding against radiation in the directions in which radiant heat is not desired.

Previously there are known electrical ceiling heater panels for radiant heat comprising a relatively elongated radiant heater element consisting of a plate-shaped aluminium profile which is heated to e.g. about 300°C. The radiant heater profile is suspended in a steel enclosure and insulation is provided at the upper side so that a significant temperature difference is established between the heat emitting surface and the surfaces of the heater element facing in other directions. The electrical heater element or elements being employed is/are arranged in a close heat-conductive contact with the radiant heater element which with advantage can be provided with longitudinal ribs at its heat-emitting surface facing downwards. The ribs are favourable to, inter alia, the appearance of the whole panel.

Because of the various requirements set to such electrical heat radiation ceiling panels the design of these involves significant difficulties, among other things as a result of different heat expansion of the materials included in the structure, which can lead to undesired noise, skew and deformation in parts of the structure. In particular when employed in apartments it is of major importance that tendencies to humming and noise in such panels should be eliminated as much as possible. The relatively high temperatures which may occur mean that certain materials, e.g. aluminium profiles, to a high degree will have their mechanical strenght reduced. When there is an irregular temperature distribution over the various surfaces, there will be an uneven heat expansion with resulting skew and inner strain which can be a serious problem since the material will have its mechanical strength reduced at an elevated temperature.

As a radiant heater panel should emit as much as possible of its energy as heat radiation, it is important to have the highest possible emissivity at the same time as convection losses are prevented to the highest possible degree. At this point there is a question about structure and surface treatment of the heat emitting surface.

In order to be competitive on the market such a heater panel design must be adapted for efficient and inexpensive production, easy mounting and possible maintenance, for example by replacement of parts and so forth. In addition to the above it is therefore an object of the invention to provide a design of an electrical ceiling heater panel based upon the radiant heating principle, employing parts and components which make possible an efficient production and mounting.

Finally there is a factor which has to be taken into account, in particular when used in apartments, that the panel must not induce surrounding magnetic fields which may cause injury to people.

On the above background the invention provides solutions as defined in the claims.

In the following description the invention will be explained more thoroughly with reference to the drawings, in which:

Fig. 1 shows a cross-section of an embodiment of an electrical ceiling heater panel including structure based on this invention,

Fig. 2 shows an end portion of the panel in fig. 1 seen from below, and

Fig. 3 shows a simplified vertical section through an end portion of the panel in figs. 1 and 2, suspended from a ceiling.

A main component in the panel design shown, is a radiant heating element 22 which advantageously can consist of an extruded aluminium profile having a platelike main shape. It is very important that this aluminium profile retains its shape without any significant deformation in operation, e.g. that a flat main shape is substantially maintained even when the above mentioned high temperatures will involve strains which imply tendencies to deformation.

In order to secure the radiant heating element 22 against deformations there is provided a box-like supporting element 19 made for example of steel sheet of suitable thickness so as to attain the required rigidity. The element box 19 has side walls which terminate in inwardlay directed edges 19A adapted to co¬ operate with slits 22A facing sideways outwardly at the outer edges of the radiant heating element 22.

These co-operating inter-engaging parts of the box 19 and the radiant element 22 respectively are adapted to provide for a certain small friction between the parts, so that the radiant element 22 can perform a certain sliding movement or displacement longitudinally in relation to the element box. This is favourable for taking up uneven heat expansion in operation. Thus the aluminium profile which constitutes the radiant element 22 can expand independently of the expansion of the supporting element box 19. This box has a total lenght being equal to or somewhat larger than the length of the radiant element 22.

At each end (fig.3) the radiant element is attached to a plate- shaped bracket 18 which at its upper portion is connected to a surrounding housing by means of a screw 9. At the bottom there is shown a screw 23 joining the supporting brackets 18 to the radiant element 22, whereby the screw 23 can be screwed into each of two enlargements 22B at the innermost end of the above slit, along each of the edges of the radiant element 22. The supporting brackets 18 are made with a suitable resilience so that they can be bent against a certain natural spring effect to each side in the longitudinal direction of the panel. With an appropriately adjusted material thickness and quality in these brackets 18 the mechanical strength and rigidity of the supporting arrangement can be adjusted as desired.

A detail of significance in this connection is the bent angle portion of the bracket 18 which by the screw 9 is attached to an upper plate 7 in the surrounding outer housing, as this angle portion can be oriented in the opposite direction of what is shown in fig. 3, namely towards the end wall 15 of the surrounding housing, which makes it possible to tighten or loossen the screw 9 from below for possible replacement of the radiant element 22, and/or the associated electrical heater element. For such replacement or maintenance it is therefore not necessary to dismantle the whole panel from the ceiling 1.

The supporting element box 19 mentioned above is preferably surface treated in order to give the least possible heat radiation and it can be made mechanically very rigid since the mechanical strength can be selected by the thickness of the steel sheet from which it is made, or by the height of the box. The structure will secure that the radiant heater profile freely can move longitudinally at the same time as it is supported along its whole length, so that the desired and usually flat shape is retained during the lifetime of the panel.

In the usual manner heat insulation materials can be provided between the element box 19 and the surrounding housing as for example shown at 16 and 17 in fig. 1. Advantageously the surrounding housing can be designed with rounded corners as shown for example at 5. In fig. 3 there are shown details of the suspension of the whole panel from a ceiling 1 i.e. by means of an angular bracket 3 and a screw 2 into the ceiling. Moreover it appears from fig. 3 that the space between the box 19 and the upper plate 7 of the housing can contain electric leads 30 and a connector 31 for one or more heater elements as will be discussed more in detail below.

Centrally at the upper side 29 of the radiant element 22 there is provided a groove for receiving two electrical heater elements 25 and 26 which can be either common tube elements or bead insulated resistance elements. These lie side by side in parallel and can be so connected as to make possible power regulation of the panel. Another possibility is that the two parallel heater elements can be connected as a bifilar circuit so that outer magnetic fields from the panel will be more or less eliminated. In connection with this invention it is not strictly necessary however to employ such a double element 25/26 as the source of heat for the heating element 22.

A substantial advantage of the design consists in the manner of mounting and anchoring the heater elements 25 and 26. The groove receiving these is formed by two profile members 11 and 12 which in the finished panel generally enclose and hold the electric elements 25 and 26. One profile member 12, however, during mounting of the heater elements is pressed inwards from an initial position as shown with dotted lines at 12A, in which position both elements 25 and 26 can easily be inserted from above into the open groove. With the two elements in position the profile member is then pressed inwards from the position at 12A to the final position as shown at 12. In order to facilitate such deformation and pressing the root portion of the profile member 12A adjacent the main plane of the radiant element, can be provided with a weakening 13 running the whole length of the profile member 12. It is obvious that both the profile member 12 and the profile member 11 can be adapted to undergo such deformation for closing these members around the electric heater elements 25 and 26. The curvature of the profile members is preferably adapted to the outer and commonly circular contour of the cross section of the heater elements.

With this manner of mounting one avoids the necessity of inserting the heater elements from one end of the radiant element, which is both time-consuming and risky, because many types of heater elements may be mechanically rather vulnerable. Moreover it is of significance that such heater elements do not have an uneven tension in their mounted position, so that for example a helical wound element will have an uneven heat development for that reason. At optimum utilisation of the materials employed in the various parts of the design, such circumstances are particularly unfavourable in view of a long lifetime without problems.

The manner of mounting shown by means of the curved profile members 11 and 12 of which at least one is deformable, also implies that there is obtained a good heat conductive contact between the surface of the two heater elements 25 and 26 and the surrounding portions of the radiant element.

The various parts of the structure as discussed above to a high degree act together for providing an effecient ceiling heater panel which at a number of the points mentioned in the introduction to this description, has significant advantages compared to previously known designs. An additional feature appearing in particular from fig. 1 of the drawings, resides in the specific rib shape at the radiation emitting, downwardly facing surface of the radiant element 22. This surface has a number of ribs 27 with interstices 28, the mutual dimensional relationship of which is chosen for the purpose of obtaining a specific effect, namely to avoid undesired convectional flows of air transversally to the radiant surface. It is here to be noted that such panels are normally suspended along and parallel to the outer walls of a room, so that the natural air-flow in the room runs mainly transversally to the longitudinal direction of the panel. Strong air currents adjacent to the radiant surface of course will lead to cooling and thereby a lower temperature, which is unfavourable to the desired radiant heat emission. Thus it has been found that the height 10B of the ribs 27 in relation to the width 10A of the interstices 28, should constitute between 10 and 20% of this interstice, i.e. the spacing between adjacent ribs 27. Preferably the height 10B of the ribs is selected to be about 15% of the above spacing 10A. A suitable, .practical choice of dimensions is a rib height of about 1 mm and a spacing between adjacent ribs of about 6 mm.

Claims

1. Electrical ceiling heater panel for radiant heating, comprising a relatively elongated radiant heating element (22) having a radiation emitting surface adapted to face generally downwards in the mounted position of the panel, said surface being preferably provided with longitudinal ribs (10A, 10B), at least one electrical heater element (25, 26) being in close heat conductive contact with the radiant heating element (22) and a surrounding insulated housing (5, 7, 15) having means (2,3) for suspending the panel from a ceiling (1) , characterized in that the radiant heating element (22) at its longitudinal edges has engagement parts (22A, 22B) for co-operation with longitudinal edges (19A) of an element box (19) built up of sheet material and having a sufficient rigidity to keep the radiant heating element (22) in a correct position during operation, the radiant heating element being able to be displaced somewhat in its longitudinal direction with respect to the element box, and that at each end of the element box there is provided a plate-shaped bracket (18) standing generally in a plane normal to the longitudinal direction of the panel and adapted to be somewhat resilient in this direction as well as being attached to the adjacent end of the radiant heating element (22) at the outer edges thereof.

2. Heater panel according to claim 1 characterized in that the engagement parts of the radiant heating element (22) are in the form of transversally open slits (22A) and that the longitudinal edges (19A) of the element box (19) enter into the slits (22A).

3. Heater panel according to claim 2 characterized in that the slits (22A) have an inner enlargement (22B) being adapted to receive screws (23) for permanent connection between the ends of the radiant heating element (22) and the brackets (18).

4. Plate-shaped relatively elongated radiant heating element for use in an electrical ceiling heater panel, whereby the radiation emitting surface of the element is adapted to face generally downwards in the mounted position of the panel, said surface being preferrably provided with longitudinal ribs (10A, 10B) and the element is adapted to receive at least one electric heater element (25, 26), characterized in that preferably in the center of the radiant heating element (27) and in the longitudinal direction thereof, there is formed a. groove delimited by curved profile members (11, 12) of which at least one (12/12A) is adapted to be pressed inwards from an open position (12A) in which the electric heater element or elements (25,26) can be inserted in the groove, to a closed position (12) in which the profile members (11, 12) together substantially enclose and hold the electric heater element or elements (25, 26).

5. Radiant heater element according to claim 4 characterized in that said groove is adapted to receive two electric heating elements (25, 26) having as known per se a circular outer cross- sectional shape and lying side by side, and that the curvature of the two profile members (11, 12) at least partially corresponds to said circular cross-sectional shape of the heating elements.

6. Radiant heater element according to claims 4 and 5 characterized in that at least one (12/12A) of the profile members has a longitudinal weakening (13) at its root portion adjacent to the inner surface (29) of the radiant heating element (22), in order to facilitate said pressing to closed position (12).

7. Radiant heater element according to claims 4, 5 and 6 characterized in that the radiation emitting surface is provided with parallel ribs (27) the height (10B) of which constitutes between 10 and 20% of the spacing(lOA)between the ribs.

8. Radiant heating element according to claim 7 characterized in that the height (10B) of the ribs constitutes approximately 15% of said spacing (10A).

9. Radiant heating element according to claim 8 characterized in that the height (10B) of the ribs is about 1 mm and said spacing (10A) is approximately 6 mm.