FR2808962A1 - Heating unit, for laboratory samples, includes electric element in double-walled rectangular base with electric control at safe distance - Google Patents

Abstract

Heating plate has base (1) providing rectangular casing (2) with control panel (3) attached to one side. Casing has a double wall (4) and base panel, and has a top opening. Two skins of each wall are spaced apart with air space in between, and slots at the top allowing circulation of air. Each corner includes a tubular support (8) with a foot (12) at the base, and a cap (14) on top. Base is made of synthetic material such as a plastic with glass fibre reinforcement. A grill (18) with a set of part-circular slots forms an upper surface to the casing, covering a resistance heating element controlled by the external control panel. The resistance heating element is formed as a spiral, with the active part of the element being mounted above a reflective bowl.

Description

The present invention relates to a heating device which can be used in particular in laboratories for heating the contents of a flask, a beaker, a test tube, or burning materials kept close to said device.

A heater of this type generally comprises a base to which is fixed a heating resistor connected to an electric control module.

Heating devices are known in which the base is formed from a metal housing including the heating resistor and the control module. A cowling of metallic grids is sometimes added around the bolt box at a distance from it in order to avoid any contact of an operator with the box, the temperature of which rises during the operation of the heating resistor.

Heating apparatuses are also known in which the base comprises a metal housing which receives the control module and is surmounted by an enclosure also metallic receiving the resistance. The enclosure is surrounded by a perforated protective metal fairing preventing any contact of an operator with the walls of the enclosure, the temperature of which rises during the operation of the heating resistor.

In these heating devices, all the elements extending near the heating resistance undergo a rise in temperature during the operation thereof. This results in an overall heating of the device which makes it necessary to thermally isolate the electrical control module in order to avoid deterioration thereof caused by excessive heating or to resort to the manufacture thereof of components relatively expensive resistant to the temperatures involved.

In addition, the housing itself also undergoes a temperature rise such that the operator risks being burned by touching it, making it compulsory to provide means (rollover or fairing) preventing accidental contact of the operator with The box. The heaters thus produced are relatively expensive because of the large number of parts making them up.

An object of the present invention is to provide a heater of simple structure and ensuring thermal protection both of the material surrounding the heating resistor and of the operators brought to use 1 heater.

In order to achieve this goal, there is provided, according to the invention, a heating device comprising a base to which is fixed a heating resistor connected to an electrical control module, the base being made of synthetic material and comprising an enclosure for receiving the resistor and a console which is laterally offset from the enclosure and receives the control module, the enclosure being delimited by double side walls and a bottom defining an upper opening in which a tray extends, the double - side walls having upper and lower air circulation openings and the bottom and the tray being perforated, and the resistance comprising an active part received in a reflecting bowl fixed under the tray.

Thus, the reflective bowl channels the heat given off by the resistance to the plate and isolates the heating resistance from the rest of the enclosure. This makes it possible to obtain inside the enclosure a volume of air which is not heated directly by the resistor limiting the rise in temperature thereof. This volume forms an insulating layer which limits the dissipation of heat energy towards the side walls and the bottom of the enclosure to channel it towards the object to be heated. In addition, the double-walls also make it possible to maintain between the walls opposite each double-wall an insulating layer of air limiting the heating of the outermost walls of the enclosure. The days of the bottom and the tray and the openings of the side double-walls make it possible to create an air circulation by natural convection which contributes to limit the heating of the peripheral part of the enclosure. The use of a synthetic material makes it possible to limit the transfer of heat by conduction between the internal walls and the external walls of the double walls. In addition, it is possible to further limit this flow of heat by arranging the lower and upper openings in the parts extending between the internal and external walls of the double walls. Finally, the lateral offset of the console relative to the enclosure makes it possible to further limit the amount of heat received by the control module.

According to a particular embodiment, the side double walls are connected two by two by uprights.

Advantageously then, at least one of the uprights is hollow and receives a ballast, and preferably, this upright has one end fixed in a removable manner and provided with means for wedging the ballast in the upright. This makes it possible to weigh down the base in synthetic material in order to limit the risks of an accidental overturning or tilting thereof.

Preferably, the heating device comprises bracing means arranged for, when two heating devices are stacked one on the other, keep apart the bottom of the upper device and the tray of the lower device. After use, it is then possible to stack the heaters on top of each other even if the resistors and the trays thereof are not yet cooled.

In the aforementioned particular embodiment, the uprights comprise parts projecting vertically relative to the plate and / or the bottom to form the bracing means.

More preferably, the device comprises means for centering it on a heating device of the same type when it is stacked on the latter. This improves the stability of a stack of heaters according to the invention.

In the aforementioned embodiment, the uprights have opposite ends provided with homologous centering means intended to cooperate with corresponding means of a heating device placed immediately on or under the heating device in question when these are superimposed, and advantageously, the lower ends of the uprights are provided with non-slip nipples and the upper ends of the uprights include recesses shaped to receive the nipples of a heating appliance of the same type superimposed on the heating appliance in question.

According to a particular characteristic, the heating apparatus comprises a barrier fixed to the enclosure around the upper opening thereof. Access to the plate and to the heating resistance are thus prevented when a container is placed on said plate.

According to another particular characteristic, the heating appliance comprises a handle integral with the desk opposite the enclosure, and preferably the handle formed by a recess formed under the desk. Transporting the heater is thus easy.

Other characteristics and advantages of the invention will emerge on reading the following description of a particular, non-limiting embodiment of the invention.

Reference will be made to the appended drawings, among which - FIG. 1 is a perspective view from above of a heater according to the invention, FIG. 2 is a view similar to the figure of the heater after removal of the plate and of the resistor, FIG. 3 is a bottom perspective view of the heating appliance, - FIG. 4 is a partial sectional view along plane IV of FIG. 1 of the heating appliance, - Figure 5 is a partial sectional view along the plane V of Figure 1 of the heater.

With reference to the figures, the heating device according to the invention comprises a base generally designated at 1 comprising an enclosure and a console respectively bearing the general references 2 and 3. The base 1 is made of synthetic material such as a material plastic loaded for example with reinforcing fibers. The base is for example obtained by injecting a corresponding resin into a mold.

The enclosure 2 is delimited by double side walls 4 and a bottom 5 defining an upper opening 6.

Each side double-wall 4 comprises an internal wall 4a and an external wall 4b spaced from one another and connected at their upper edge by a wall portion 4c in which slots 7 are formed.

The side double-walls 4 are here four in number, arranged in a square and connected two by two by uprights 8 which are integral with the vertical edges of the internal walls 4a and external 4b of the side double-walls 4.

The lower edges of the internal and external walls 4a and 4b of each side double-wall 4 are free relative to each other so that they define a single opening 9.

The bottom 5 is integral with the lower edges of the internal walls 4a. The bottom 5 is provided with a plurality of slots 11 in the form of slots, some of which extend astride the bottom 5 and the lower part of the internal walls 4a. Each upright 8 is tubular in shape and has a lower end 12 which projects slightly downwards relative to the bottom 5 and to the external walls 4b and is provided with a stud 13 of non-slip material such as an elastomer, and a upper end 14 which projects in relation to the plane of the opening 6 and has a recess 15 of shape corresponding to that of the stud 13.

A ballast 16 is housed inside each upright 8. The ballast 16 is for example made of metal. The upper end 14 is removably mounted on the upright 8 for example by snap-fastening (the end 14 could also be fixed by screwing or any other removable fixing method) and comprises a bevelled tongue 17 which is inserted between the ballast 16 and the peripheral wall of the upright 8 to wedge the ballast 16 inside this upright by pressing it against the peripheral wall opposite the tongue 17.

An openwork plate forming a grid 18 extends in the upper opening 6. The grid 18 is fixed by inserting its corners in a slot 19 left between each upright 8 and the corresponding end 14.

Barriers 20 extend around the upper opening 6 in a raised manner with respect to the grid 18. The barriers 20 have their ends fixed to the ends 14 of the uprights 8.

A guardrail 21 on horseback has its ends fixed to the upper ends 14 of the uprights 8 opposite the desk 3 to extend above the upper opening 6 and the grid 18.

The console 3 is offset laterally with respect to the enclosure and forms a housing for an electrical control module 22 of a heating resistor 23 extending in the enclosure 2. This control module is of the known type and comprises for example a member for regulating the temperature of the heating resistor such as a thermostat and a supply member capable of being connected to the mains. The console 3 can be made in one piece with the enclosure 2 or be snapped onto one of the external walls 4b thereof (the console 3 can also be screwed or fixed by any other means ensuring a removable or irremovable assembly). Perforations 28 (visible in FIG. 3) can be made in the console 3 so as to ensure ventilation of the control module 22. It will be noted that the lateral offset of the console makes it possible to limit the risk of projection onto the electrical control module d 'A liquid being heated and, the console being provided with non-slip feet 29, to have a support polygon of the base 1 having large dimensions, which improves the stability thereof.

The heating resistor 23 comprises an active part 24 in the form of a spiral which is received in a reflecting bowl 25 fixed under the grid and an inactive part 26 crossing the bottom of the reflecting bowl cooking the double side wall 4 adjacent console 3 to be connected by pins 30 to the control module 22 disposed in the console 23 (Figure 4). It will be noted that the passage hole of the resistor 23 in the bowl 25 is of dimensions greater than the transverse dimensions of the resistor 23 so as to allow that the liquid initially contained in the container to be heated and which would have been spilled can escape from the bowl reflecting towards the bottom 5 of the enclosure 2 where lights 11 will allow it to flow outwards.

In operation, the reflective bowl returns the heat given off by the resistance upwards towards the grid 18 and the element to be heated. The volume of air between the internal walls 4a, the bottom 5 and the grid 18 provides thermal insulation limiting the transfer of heat to the side double walls 4 and bottom 5.

Furthermore, the volume of air extending between the internal 4a and external 4b walls of the lateral double walls 4 also provides a thermal insulation function.

The openings 7 made in the upper portion 4c and the openings 9 in the side double-walls 4, the openings 11 in the lower parts of the internal walls 4a and in the bottom 5, and on the days the grid 18 allow air circulation by natural convection which make unnecessary the use of forced ventilation and help maintain a relatively low temperature at the outer walls 4b of the double side walls 4 and the desk 3. In addition, the heater resting on the pins 13 the feet 29, the lower ends 12 of the uprights 8 projecting make it possible to raise the bottom 5 relative to the surface supporting the heating appliance and to leave a space between this surface and lower part of the external walls 4b, which favors air circulation.

It is further noted that, due to the openings 7 formed in the wall portion 4c of the side double-walls 4, the internal and external walls 4a, 4b are connected to each other by a small amount of material, which limits heat transfer by conduction from the inner wall 4a to the outer wall 4b.

When not in use, heaters can be stacked on top of each other. The pins 13 of the lower ends 12 of one of the heaters are then received in the recesses 15 of the ends 14 of the heater located immediately below the heater in question. When the heaters are stacked on top of each other, the projection height of the upper and lower ends 12, 14 of the uprights defines a minimum bracing distance ensuring that the heat which would be released by a heating resistor 23 not yet completely cooled would not risk damaging the bottom 5 of the heater above 1 heater in question.

To facilitate the transport of the heating appliance, a handle 27 is formed by a recess provided under the desks near an edge thereof opposite the enclosure 2.

Of course, the invention is not limited to the embodiment described and it is possible to make variant embodiments without departing from the scope of the invention as defined by the claims.

In particular, the base can take other forms. We can thus have a cylindrical enclosure, a triangular console ...

Claims (2)

1. Heating appliance comprising a base (1) to which a heating resistor (23) is attached connected to an electrical control module (22), characterized in that the base is made of synthetic material and comprises an enclosure (2) for receive the resistor and a console (3) which is offset laterally with respect to the enclosure and receives the control module, in that the enclosure is delimited by double side walls (4) and a bottom (5) defining a upper opening (6) in which a plate (18) extends, the double side walls having upper and lower openings (7, 9) for air circulation and the bottom and the plate being perforated, and in that the resistor comprises an active part (24) received in a reflecting bowl (25) fixed under the plate (18). 2. Heating device according to claim 1, characterized in that the side double-walls (4) are connected two by two by uprights (8). . Heating device according to claim 2, characterized in that at least one of the uprights (8) is hollow and receives a ballast (16). 4. Heating device according to claim 3, characterized in that this upright (8) has one end (14) which is detachably fixed and is provided with means (17) for wedging ballast (14) in the upright. 5. A heating appliance according to any one of claims 1 to 4, characterized in that it comprises bracing means (12, 14) arranged for, when two heating appliances are stacked one on the other, keep the bottom (5) of the upper appliance and the plate (18) of the lower appliance apart. 6. Heating appliance according to claim 5 taken in dependence on any one of claims 2 to 4, characterized in that the uprights (8) comprise parts (12, 14) projecting vertically relative to the plate (18) and / or at the bottom (5) to form the bracing means. 7. Heating device according to any one of the preceding claims, characterized in that it comprises means for centering it (13, 15) on a heating device of the same type when it is stacked on the latter. 8 Heating appliance according to claim 7 taken in dependence on any one of claims 2 to 6, characterized in that the uprights (8) have opposite ends (12, 14) provided with homologous centering means (13, 15 ) intended to cooperate with corresponding means (15, 13) of a heating device placed immediately on or under the heating device in question when these two devices are stacked. 9. Heating appliance according to claim 8, characterized in that the lower ends (12) of the uprights (8) are provided with non-slip pins (13) and in that the upper ends (14) of the uprights () include recesses (15) shaped to receive the pins (13) of a heater of the same type superimposed on the heater in question. 10. Heating device according to any one of the preceding claims, characterized in that it comprises a barrier (20) fixed on the enclosure (2) around the upper opening (6) thereof. 11. Heating device according to any one of the preceding claims, characterized in that '1 comprises a handle (27) integral with the desk (3) opposite the enclosure (2). 12. Heating device according to claim 11, characterized in that the handle is formed by a recess (27) formed under the console (3).