Thermal protection bell
A cost-effective metallic thermal protection bell, made from stamped aluminum with a frustoconical design, addresses the expense and efficiency issues of vermiculite bells by effectively dissipating thermal energy and meeting safety standards.
Patent Information
- Application Number
- FR2021005655
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-05-31
- Publication Date
- 2026-02-13
- Estimated Expiration
- 2041-05-31
AI Technical Summary
Existing thermal protection bells made from materials like vermiculite are expensive due to complex processing and high thermal conductivity, necessitating a cost-effective alternative that meets thermal insulation standards.
A metallic thermal protection bell, preferably made of aluminum, is designed with a frustoconical shape and stamped from a metallic strip, providing effective thermal protection at a lower cost while maintaining compliance with temperature standards.
The metallic bell effectively dissipates thermal energy, maintaining internal and external temperatures below safety limits, and offers improved durability and resistance to impacts compared to synthetic materials.
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Abstract
Description
Title of the invention: Thermal protection bell
[0001] The present invention relates to a thermal protection bell for protecting thermal insulation from the energy produced by a lighting device in a ceiling wall.
[0002] It is common practice to install spotlights in the walls of false ceilings, or suspended ceilings, in living or working rooms. Also, within the plenum extending between the false ceiling wall and the ceiling wall, thermal insulation such as glass wool or rock wool is generally inserted in order to save energy.
[0003] Thermal insulation materials are evolving, and it is now common practice to fill the plenum with loose-fill products, for example cellulose wadding, to a thickness of approximately 30 cm above the suspended ceiling wall. The cellulose wadding is then blown into the plenum.
[0004] Lighting fixtures typically comprise a body with a power supply end and an opposite end where the light source is installed. The lighting fixtures are mounted through an opening in the suspended ceiling wall and are adjusted so that the light source is flush with the outer surface of the suspended ceiling wall, while the power supply end protrudes into the plenum.
[0005] Lighting devices must be insulated from the thermal insulation because they generate large amounts of thermal energy which could cause it to catch fire.
[0006] To achieve this, it was conceived to implement protective bells which cover the lighting unit in the plenum on the side of its supply end.
[0007] Naturally, the choice of materials for making these bells turned to insulating materials. In other words, the choice fell on materials with the lowest possible thermal conductivity, preferably less than 10⁻¹ W / mK.
[0008] For example, it has been conceived to produce thermal protection bells made of vermiculite, a natural mineral commonly used to make high-temperature thermal insulation products.
[0009] However, vermiculite requires numerous transport and processing steps, from mineral extraction to its transformation into a workable product. Consequently, thermal protection bells made from this material are relatively expensive.
[0010] Also, a problem that arises and that the present invention aims to solve is to to provide effective thermal protection bells at a cost-effective price.
[0011] To this end, a thermal protection bell is proposed, adapted to protect thermal insulation installed above a ceiling wall from the thermal energy produced by a lighting device mounted through an opening in said ceiling wall. The protective bell has a base opposite an opening defined by a free edge. This free edge is adapted to fit against the ceiling wall around said opening, while the base extends above said opening. The bell is made of a metallic material.
[0012] Thus, a feature of the invention lies in the use of a metallic material to create the thermal protection bell. Indeed, contrary to expectations, metallic materials with a thermal conductivity greater than 10 W / mK or even 102 W / mK make it possible to create protective bells that meet current standards. In fact, according to the French standard NF DTU 45.11 Pl-1 of March 2020, the temperatures inside and outside the protective bell, when it covers a 50W 12V MR16 dichroic halogen spotlight in operation, must not exceed 150 °C and 120 °C respectively, as will be explained in more detail later in the description.
[0013] Although the thermal protection bell according to the invention is made of a metallic material, and by nature conductive of thermal energy, these temperatures are not exceeded under the conditions of the test protocol.
[0014] Moreover, since the thermal protection bell is by definition closed, one might have thought that the thermal energy produced within it would not dissipate easily and would considerably increase local temperatures, above the permitted 150 °C. This is not the case, as will be explained in the detailed description.
[0015] Furthermore, and according to a particularly advantageous embodiment of the invention, the protective bell is obtained by stamping a plate of said metallic material. In this way, it can be obtained at a cost-effective price from a strip of metallic material in a high-speed stamping press. Thus, the bells obtained in this way are produced at a very cost-effective price.
[0016] Advantageously, the metallic material used to manufacture the thermal protection bell is aluminum. This material is relatively malleable, making it easy to stamp. Although its thermal conductivity is greater than 102 W / mK, the protective bells made of aluminum meet the criteria of the aforementioned standard.
[0017] According to a particularly advantageous embodiment of the invention, the thermal protection bell has a frustoconical shape. Thus, the free edge of the bell defines the base of the frustocone, while the opposite bottom defines the apex. Such a shape allows the blown insulation, for example cellulose wadding, to be deposited in a uniform manner around the bell.
[0018] Preferably, the bell has a frustoconical shape defined by the rotation of a generatrix about an axis of rotation. Therefore, the protective bell has a conical surface of revolution that is easy to implement. For example, said generatrix is advantageously inclined to said axis of rotation at an angle between 15° and 20°.
[0019] Moreover, the thermal protection bell has a height approximately two-thirds of the diameter of said free edge. In this way, the thermal energy produced by the lighting element dissipates more easily.
[0020] Furthermore, the free edge of the bell has at least one wire passage notch. Thus, the lighting element, which extends inside the bell, is powered by a conductive wire that extends inside the bell and then through the notch to be connected to a power source.
[0021] Preferably, the free edge of the bell has a collar. In this way, the collar is adapted to lie flat against the suspended ceiling wall, inside the plenum. This feature provides a significant sealing surface, ensuring a good seal. Furthermore, it is envisaged that a bead of adhesive will be applied to the collar before it is pressed against the suspended ceiling wall to secure it.
[0022] Advantageously, said collar includes a bridge extending opposite said notch. In this way, the power supply wires can be inserted under the bridge in line with the notch. Consequently, the wires are protected from the protruding edges of the notch.
[0023] Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of example but not limitation, with reference to the accompanying drawings in which: [Fig.1] is a schematic axial cross-sectional view of the protective bell according to the invention and in situ; [Fig.2] is a schematic perspective view of the protective bell illustrated in [Fig.1]; [Fig. 3] is a schematic detail view of the object in [Fig. 2]; and, [Fig.4] is a schematic view from below of the protective bell as illustrated in [Fig.2].
[0024] Fig. 1 partially shows a false ceiling wall 10 separating the upper volume of a room 12 from a plenum 14. The false ceiling wall 10 has an external face 16, lower, opposite an internal face 18, upper.
[0025] The false ceiling panel 10 is pierced with an opening 20 to accommodate a lighting element 22. The lighting element 22 has, at one of its ends 28, a light source 24 located inside a parabolic reflector 26, and opposite, a supply end 30 to which two electrical supply wires 32, 34 are adapted to be connected.
[0026] Also, the lighting element 22 is held through the opening 20 by means of a retaining ring 36, so that one end 28 is substantially flush with the outer face 16 of the false ceiling wall 10. To this end, the retaining ring 36 has an outer diameter substantially equal to the inner diameter of the opening 20, and a retaining collar 38 adapted to bear against the edge of the opening 20 against the outer face 16. Also, the retaining ring 36 has, opposite the retaining collar 38, two diametrically opposed spring loops 40, 42 adapted to bear against the inner face 18 of the false ceiling wall 10. Thanks to the two spring loops 40, 42, the retaining ring 36 is held through the opening 20, the retaining collar 38 resting against the edge of the orifice 20.
[0027] In addition, the fixing ring 36 has a stop ring 44 located substantially opposite the stop collar 38 and retaining the lighting element 22 by means of a stop ring 46. The stop ring 44 retains the lighting element 22 at the outer edge of the parabolic reflector 26.
[0028] Thus, when the lighting element 22 is supplied with electrical current, it generates a luminous flux and also releases thermal energy. The lighting element 22 is then covered by a thermal protection bell 48 which rests against the inner face 18 of the false ceiling wall 10 around the opening 20 and beyond the two spring loops 40, 42.
[0029] We will return later in the description to the adjustment of the thermal protection bell 48.
[0030] It will first be described in detail with reference to [Fig.2] to [Fig.4].
[0031] Fig. 2 shows, in perspective from above, the thermal protection bell 48. It is made of aluminum. It is advantageously obtained by cold stamping an aluminum sheet with a thickness, for example, between 0.25 mm and 2 mm. In a preferred manufacturing method, as shown here, the aluminum sheet has a thickness of 1 mm. It should be noted that aluminum has a thermal conductivity, at 20 °C, greater than 200 W / mK.
[0032] The thermal protection bell 48 is frustoconical in shape, rotating about an axis A, and extends from a base 50 delimited by a free edge 54 to a vertex 52 closed by a bottom 55. The frustoconical shape is defined by a generatrix G inclined with respect to the axis of symmetry A at an angle between 10° and 20°. In this case, it is inclined at an angle close to 16°.
[0033] Also, the thermal protection bell 48 has a support collar 56 extending from the free edge 54. The support collar 56 defines a mean plane perpendicular to the axis of symmetry A of the thermal protection bell 48. Preferably, the support collar 56 and the bell 48 are formed together in one piece.
[0034] Advantageously, the thermal protection bell 48 has a height of 160 mm and a diameter of approximately 260 mm. Taking into account the angle of the generatrix G and the axis of symmetry A, the base 55 has a diameter of approximately 160 mm.
[0035] Also, the thermal protection bell 48 has a notch 58 and a bridge 60 provided in the support collar 56 at the notch 58.
[0036] We find in more detail on [Fig.3] the bridge 60 made in the support collar 56 with regard to the notch 58 which it extends.
[0037] The thermal protection bell 48 is shown in [Fig.4] viewed from below. It will be observed that two diametrically opposed notches 58 are provided, and that both are extended by a bridge 60.
[0038] It will be noted that these two notches 58 extended by their bridge 60 allow the passage of a two-wire power cable in particular.
[0039] Thus, the thermal protection bell 48 as shown in [Fig.1] is fitted to the false ceiling wall 10 so that the support collar 56 rests flat against the inner face 18 around the orifice 20 and the fixing ring 36. The axis of symmetry A of the protection bell 48 is then substantially coincident with the axis of symmetry of the lighting element 22.
[0040] In addition, and preferably, a bead of sealant or glue is deposited on the support collar 56 before being pressed against the inner face 18 so as to be able to secure it in a relatively airtight manner with the false ceiling wall 10.
[0041] In addition, the power supply wires 32, 34 are extended so that they can be engaged through the notches 58 and under the bridge 60 without interfering with the flat support of the support collar 56 against the inner face 18.
[0042] Also, after the protective bell 48 has been adjusted in this way, the thermal insulation, for example cellulose wadding, can then be blown and deposited loose on the inner face 18, and to a thickness of approximately 300 mm covering the protective bell 48.
[0043] In this way, the lighting element 22 is completely protected from the thermal insulation and the dust that it necessarily generates.
[0044] Furthermore, with regard to the French standard NF DTU 45.11 PI-1 of March 2020, concerning the temperatures inside and outside the protective bell 48, the precise conditions of its implementation will be described below.
[0045] To implement the aforementioned standard, a 50W 12V MR16 halogen spotlight is used dichroic as a lighting element. Furthermore, the thermal protection bell 48 is covered with 300 mm of cellulose wadding insulation. Three calibrated thermocouples are then adjusted.
[0046] A first thermocouple 62 is then fitted to the top 52 of the protective bell 48, above the bottom 55. A second thermocouple 64 is fitted at mid-height between the underside of the bottom 55 and the supply end 30 of the lighting element 22. Finally, a third thermocouple 66 is fitted laterally against the protective bell 48 at the right of the lighting element 22.
[0047] According to the standard, the test lasts 24 hours and the temperatures are measured by thermocouples 62, 64 and 66 throughout the period.
[0048] Thus, on average, the following results are obtained; the first thermocouple 62 displays a temperature of 98 °C after four hours of testing and displays this same temperature during the following 20 hours; the second thermocouple 64 displays a temperature of 117 °C after two hours of testing and this temperature is stationary during the following 22 hours; and, the third thermocouple 66 displays a temperature of 92 °C after four hours of testing, which remains constant during the following 20 hours.
[0049] Thus, unexpectedly, the internal temperature of the protective bell 48 measured by the second thermocouple 64 not only does not exceed the 150 °C required by the standard, but remains well below it at 117 °C. Moreover, the external temperature measured by the two other thermocouples 62, 66 does not exceed the 120 °C required by the standard, and remains below 100 °C.
[0050] Furthermore, it will be noted that such a protective bell 48 is more rigid than synthetic bells made of vermiculite, for example. It is therefore much more resistant to crushing and impacts.
Claims
Demands
1. Thermal protection bell (48) adapted to protect thermal insulation installed above a ceiling wall (10) from the thermal energy produced by a lighting device (22) mounted through an opening (20) made in said ceiling wall, said protection bell (48) having a bottom (55) opposite an opening delimited by a free edge (54), said free edge being able to come into contact with the ceiling wall (10) around said opening (20) while said bottom (55) extends above said opening (20); characterized in that it is made of a metallic material, and in that it has a frustoconical shape defined by the rotation of a generatrix around an axis of rotation.
2. Thermal protection bell (48) according to claim 1, characterized in that it is obtained by stamping a plate of said metallic material.
3. Thermal protection bell (48) according to claim 1 or 2, characterized in that said metallic material is aluminium.
4. Thermal protection bell (48) according to any one of claims 1 to 3, characterized in that said generator is inclined about said axis of rotation at an angle between 15° and 20°.
5. Thermal protection bell (48) according to any one of claims 1 to 4, characterized in that it has a height close to two-thirds of the diameter of said free edge (54).
6. Thermal protection bell according to any one of claims 1 to 5, characterized in that said free edge (54) has at least one wire passage notch (58).
7. Thermal protection bell according to any one of claims 1 to 6, characterized in that said free edge (54) has a collar (56).
8. Thermal protection bell according to claims 6 and 7, characterized in that said collar (56) comprises a bridge (60) extending opposite said notch (58).