A modular, constructional heating unit, useful, e.g., for the fabrication of interior partitions, is comprised of a panel member provided with at least one elongate rectilinear cavity, the longitudinal axis of such cavity being parallel to a face surface of the panel, said cavity being exteriorly communicating at one or both of its ends, and said cavity containing an electrical heating element.

BACKGROUND OF THE INVENTION 
The present addition relates to a modular heating panel or constructional 
heating unit which can be utilized simply and efficiently, especially for 
heating rooms. 
One object of the present invention is to provide a means of heating which 
displays great flexibility in use and which is highly efficient and makes 
it possible to judiciously distribute the sources or points of heat. 
A further object of the invention is to provide an easy means for producing 
heating partitions or panels while at the same time avoiding any 
obstruction of the room to be heated which is delimited or defined by said 
partitions. 
SUMMARY OF THE INVENTION 
Thus, the present invention relates to modular, constructional heating 
units, characterized in that same comprise a panel provided with at least 
one rectilinear cavity, the axis of which cavity being parallel to the 
greater face surfaces of the panel and such cavity communicating to the 
exterior of the panel at one or more of its ends, the said cavity 
containing or housing an electrical heating element. 
By the term "panel", there is intended a solid body having two large, 
parallel or essentially parallel face surfaces and having a relatively 
small thickness compared with at least one of the dimensions of the much 
larger dimensional face surfaces. The term "panel edges" is intended to 
connote the sides of a panel which are different from the larger face 
surfaces. The expression "room partition" includes both the ceiling and 
the walls. 
The panels employed in the invention can be produced from one of the 
commonly employed constructional materials, such as cement, concrete, 
baked-clay brick, plaster and combinations of these components with other 
constituents of most diverse type (agglomerates). However, in the present 
invention, plaster-based constructional units, whether the plaster be of 
natural or synthetic origin, are preferred and, indeed, define the most 
preferred embodiment of the invention. Plaster is the most suitable 
material for producing the panels according to the invention, especially 
because of the ease with which it is molded into the desired shape, even 
industrially; furthermore, plaster panels directly form partitions having 
a "finished" appearance which does not require any additional finishing 
operation.

DETAILED DESCRIPTION OF THE INVENTION 
More particularly, the constructional unit of FIG. 1 has the shape of a 
rectangular parallelepiped and thus possesses two large dimensional face 
surfaces, one of which is noted by the reference numeral 1, and 4 edges, 
two of which are noted by the reference numeral 8. Two rectilinear 
cavities, indicated as 2, are parallel to each other and parallel to the 
large dimensioned surface 1 of the panel and to two of its sides 8. These 
cavities, triangular in cross section, as shown by the base 9, have two 
sides indicated by the numeral 6. These sides, in contradistinction to the 
third, are not parallel to the large dimensioned face surfaces of the 
panel. The constructional unit is further provided with two recesses 5 
which are located at the downward ends of the cavities; these recesses are 
intended to facilitate the positioning or withdrawal of the electrical 
heating element 10. This heating element 10 consists of a strip 18 of 
flexible material, on the surface of which there are two electrically 
resistant webs; the ends of the wires 19 and 20 of these webs are provided 
with a means which allows them to be connected to a source of electrical 
energy, e.g., a simple plug. 
Being a cross section of the element of FIG. 1, FIG. 2 makes it possible to 
show more clearly the arrangement and the contents of the cavities. It is 
seen that these cavities have a face 3 which is parallel to the large 
dimensioned face surfaces 1 and 4 of the panel. This face 3 is located 
near the face surface 1 of the panel which will form or define the wall of 
the heated room; the electrical heating element has been arranged 
perpendicular to the face 3, although other arrangements can be adopted; 
this particular arrangement is especially advantageous in the case of 
radiant heating elements, since these pass virtually all of their 
radiation energy onto the reflectors 7 which, therefore, return this 
energy through the face 3 of the cavity and the face 1 of the panel. 
FIG. 3 shows, at the same time, constructional units of another type and 
the manner in which two such units are joined. FIG. 4 reflects the exact 
arrangements. These particular constructional units have the particular 
characteristic in that the recesses 13 are no longer only at the border of 
a large face surface of the panel but are in a corner, so that two 
recesses of two different but adjoining panels together form a single 
recess. A further particular characteristic of the panels shown is that 
they are formed from two plates 14 and 15; the grooves 17, which form the 
rectilinear cavities in the finished panel, are inscribed in the plate 14; 
other grooves 16, which are much smaller and in which the electrical 
heating element 10, which is not shown, is to be inserted, are also 
inscribed in the plate 15; the method of joining the two construction 
units has also not been shown, but it is quite obvious that they are 
joined or welded by any means which is known to the building industry. The 
most common method of joining two plaster panels also involves the use of 
plaster. 
Finally, FIG. 5 depicts two portions of a partition in a section of the 
room to be heated. The panels according to the invention have been placed 
only at the bottom of the partition; a skirting board conceals the various 
recesses 5 or 13; the various heating elements 10 are connected to an 
electrical circuit which is concealed by the skirting board. In the case 
of one of the partitions, the panels according to the invention are 
themselves backed by an insulating material 12 which is itself placed 
against a concrete wall, whereas, in the case of the other partition, the 
panels according to the invention form the partition in and of themselves; 
the panels according to the invention are surmounted by conventional 
plaster panels which do not possess a cavity. It should, of course, be 
understood that these arrangements are given purely by way of illustration 
and that any other variation in the arrangement of the panels can be 
adopted. 
The faces of the panels can have any possible shape, for example trapezoid, 
square or curvilinear, but are preferably rectangular. The panels can have 
markedly variable dimensions and, in the extreme case, a partition can 
consist of a single modular heating unit. However, for reasons of ease of 
handling and ease of transportation, the panels usually have relatively 
small dimensions. Of course, plaster panels of standard dimensions, such 
as panels of dimensions 50 cm.times.66 cm and having a thickness which can 
vary from 6 to 10 centimeters, can also be used. 
The panels can possess several rectilinear cavities, preferably two per 
panel, which are arranged parallel to each other; at least one of the 
cavities contains an electrical heating element. The shape of these 
rectilinear cavities is generally that of a cylinder, see FIG. 7, (or 
prism) having a circular or polygonal transverse cross section. FIG. 1 
shows a preferred variant in which the rectilinear cavities 2 have a 
triangular cross section 9. The rectilinear cavities may also have a 
rectangular cross section, see FIG. 6. 
The rectilinear cavities in the panels can have an aperture at each of 
their ends or an aperture at only one end. In the case of a single 
aperture per rectilinear cavity (this being the preferred embodiment), all 
the apertures of the cavities of the same panel open out onto the same 
edge of the panel or the same border of a large dimensional face surface 
of the panel. 
In the case of apertures at both ends, the cavities open out onto two 
opposite edges of the panel or two opposite borders of a face of a panel. 
The rectilinear cavities generally and preferably possess but a single 
aperture. 
The edge or border onto which the aperture of the said cavities open can be 
along the length or along the width of the panel. The length of the 
rectilinear cavities is typically between 50% and 95% of the dimension of 
the sides of the panel which are parallel to the cavities, but these 
values are not critical. The depth of the cavity, namely, the greatest 
dimension of the cavity perpendicular to the panel faces, can vary between 
20% and 95% of the thickness of the panel. 
According to one embodiment of the invention, the constructional units 
possess recesses 5 and 13 (FIGS. 1, 2 and 3) at the open ends of the 
rectilinear cavities. An advantage of this particular embodiment is that 
is makes it possible to introduce or withdraw the heating elements more 
easily. These recesses can have any desired shape, but most frequently 
have the shape of a parallelepiped, one face of which encloses the 
aperture of the rectilinear cavity to which the said recess corresponds. 
Each recess opens out onto at least one face of the panel (at the border) 
and also, optionally but preferably, onto the edge of the said panel, 
either on but a single side (as indicated by 5 in FIGS. 1 and 2) or on two 
adjacent sides (as indicated by 13 in FIG. 3) of the face of the said 
panel. The dimension of the recess, in the direction determined by the 
length of the rectilinear cavity, typically represents from 2% to 20% of 
the dimension of the panel parallel to this direction. The dimensions of 
the recess in the other two directions can vary widely; in simple terms, 
they must be at least equal to the corresponding dimensions of the 
aperture of the rectilinear cavity, so that the surface of the aperture is 
enclosed in a corresponding face of the recess. 
According to another embodiment of the invention, a heat-reflecting 
material or device (reflector) is placed on at least two longitudinal 
faces of each cylinder (or prism) having a polygonal base, or on part of 
the longitudinal surface of each cylinder having a circular base, which 
can form the walls of the rectilinear cavities in which the electrical 
heating elements are located. An advantage of this embodiment is that it 
permits better orientation of the heat rays emitted by the electrical 
heating element. 
This reflecting material or device is usually placed on the part of the 
cavity opposite the face of the panel which emits the heat evolved by the 
heating element. In a preferred embodiment of the invention, in which the 
rectilinear cavities have a triangular base (FIGS. 1 and 2), one 
longitudinal face 3 of the cavity is parallel to the face 1 of the panel, 
whereas the other two longitudinal faces of the cavity are covered with 
the reflecting material or device 7 which can be, for example, aluminum 
foil. 
The panels forming the constructional unit according to the invention, 
which, in their most common variant, are made of plaster, can be produced 
by molding the complete panel in a single piece, including the rectilinear 
cavities and optional recesses. It is also possible to fabricate the panel 
in two component parts. A variant of this embodiment is illustrated in 
FIG. 4. 
One of the said component parts 14 comprises the rectilinear cavity, while 
the surface of the other component part 15 then defines one of the inner 
faces of the rectilinear cavity. Furthermore, especially in the case of a 
rectilinear cavity having a triangular base, it can be of value to 
provide, in the second component part 15, a groove 16 which is parallel to 
the length of the rectilinear cavity and corresponds to the median part of 
the face of the said cavity which is formed by the second component part 
15, the other faces of the cavity being formed by a groove of suitable 
cross section 17 (V-shaped in the case of a cavity having a triangular 
base) in the first component part 14. 
The electrical heating element 10 used in the constructional units or 
modules according to the invention can consist of any type of insulated 
electrical resistance arranged on a support. The preferred electrical 
heating elements are those in which the support is sufficiently flexible 
to allow it to be introduced into a rectilinear cavity such as that 
described above; in fact, in the case of a partition such as that shown in 
FIG. 5, it is apparent that, when the electrical heating element 10 is 
flexible, it can be introduced into a recess of the type 5 or 13 through 
that part of this recess which opens onto the large dimensioned face 
surface of the panel; for an operation of this kind, it is obvious that 
the heating element 10 must be curved at the level of the recess, in order 
to be introduced into the rectilinear cavity. 
In addition to possessing this property of flexibility, electrical heating 
elements 10 are preferably used which offer all (necessary) guarantees 
from the point of view of safety, and especially of electrical insulation, 
and are capable of withstanding prolonged use; this assumes that they 
consist of an electrically insulating material having high 
heat-resistance. It is for this reason that the electrical heating 
elements which are advantageously used are those consisting of a flexible 
band of macromolecular material (polymer or polycondensate), optionally 
containing fillers, one or more electrically resistant wires being 
encrusted with or embedded in this material, so as to form a web on each 
face of the strip. 
According to a preferred embodiment of the invention, the electrical 
heating elements employed consist of: 
(a) an electrically insulating material which itself consists of the 
combination of a reinforcing filler of elongate structure with a polyimide 
resin, and 
(b) an electrical resistance element which itself consists of at least one 
web of electrically conducting and electrically resistant wires. 
Of course, the ends of these electric wires are provided with any suitable 
means for connecting same to a source of electrical power. 
These electrical heating elements 10, as defined above, can also possess 
various other characteristics. The electrical wires are thus 
advantageously covered with an electrically insulating and heat-stable 
varnish which is preferably a polyamide-imide; the electrical wires are 
also advantageously arranged in two webs, the wires of one and the same 
web being parallel to one another and the wires running parallel, or 
preferably crosswise, from one web to the other. 
Among the reinforcing fillers of elongate structure which can be used, 
there are mentioned, in particular, fillers of the flake type or fibrous 
type. As particular examples of reinforcing fillers of elongate structure, 
there are mentioned mica flake, asbestos fibers, glass or ceramic fibers, 
woven or non-woven fabrics (especially mats) of glass fibers, non-woven 
fabrics (especially felts) of asbestos fibers, or woven or non-woven 
fabrics of heat-stable synthetic fibers, for example, of an aromatic 
polyamide or of a polyamide-imide; the preferred fillers are asbestos 
fibers. 
Among the polyimide resins which can be used, there are mentioned, in 
particular, those obtained by reacting a bis-imide of an unsaturated 
dicarboxylic acid with a polyamine. Resins of this kind are described in 
greater detail in U.S. Pat. No. 3,658,764 (hereby expressly incorporated 
by reference) and in the U.S. Pat. No. Re. 29,316 (also expressly 
incorporated by reference). 
The use of such polyimides derived from bis-imides and polyamines is 
especially desirable for radiant heating elements, because these 
polyimides efficiently absorb the heat produced by the electrically 
resistant wires and then efficiently re-emit radiation at wavelengths 
suitable for heating. 
The electrical heating elements based on polyimides of this kind, and also 
the processes for their preparation, are completely described in the 
French application for certificate of addition assigned to the assignee 
hereof, filed on June 23, 1977 under number 77/20,220, hereby expressly 
incorporated by reference in its entirety and relied upon. 
The electrical wires used have a diameter which typically varies between 
0.05 and 0.8 mm and the distance between same is typically between 1 and 
10 mm. The material forming the wire can be chosen from among the metals 
or alloys which are conventionally employed for producing electrical 
resistances. Particularly valuable results have been obtained with 
nickel/chromium wire. 
As has already been stated, these electrical wires can be encrusted or 
coated with or even embedded in the electrically insulating material based 
on polyimide. The degree of encrustation is generally greater than 50%, 
and preferably greater than 80%. The term "degree of encrustation" denotes 
the proportion (measured linearly) of the diameter of the electrical wire 
which is below the surface of the electrically insulating material based 
on polyimide. 
Among the electrical heating elements such as those described above, those 
which are especially suitable for the invention are in a sufficiently 
elastic form to be able to return to their rectilinear shape when a 
bending stress is no longer applied thereto. An element of this kind, 
particularly when it is a radiant element, is preferably arranged inside 
the rectilinear cavity in the panel along a plane which is perpendicular 
to the faces of the said panel. This arrangement (shown in FIGS. 1, 2 and 
4) offers the advantage that it very greatly reduces the possibility of 
striking the electrical heating element when metal objects, such as nails, 
screws or pins, are introduced into the surface of the construction unit. 
In order to avoid any danger, even though this is rather unlikely in view 
of the arrangement of the heating element, it is possible to employ a 
variant of the invention, according to which the constructional units are 
provided with an additional safety device embedded in the surface of the 
panel, for example, an earthed metal mesh, so as to cut off the electric 
current in the event of an exceptional occurrence such as that envisaged 
above. 
The constructional heating units according to the invention can be used for 
producing heating partitions. Series of units can be juxtaposed, either 
vertically so as to form inner partitions or linings for outer walls, or 
horizontally so as to form ceilings. The most frequent use is in vertical 
partitions. FIG. 5 therefore shows an example, which is in no way 
limiting, of a vertical assembly of the constructional units. It is 
possible to combine either constructional heating units alone, or, 
uniformly or non-uniformly alternating, heating units and units which are 
identical thereto but which are not provided with a heating element, or 
also homologous units which do not possess internal cavities. In 
particular, it can be advantageous to have modular heating units, 
according to the invention, only in the bottom row of a plurality of 
constructional units, the remainder of the successive rows consisting of 
units which do not possess an electrical heating element. It is also 
possible to have modular heating units and units without an electrical 
heating element within the same row. All types of other variants in 
arrangement can easily be effected, the choice of a particular variant 
generally being dictated by considerations of installation cost, ease of 
access to the heating elements for their positioning and replacement, by 
the value of the required heating power and also by the desire to have 
uniformly or non-uniformly distributed heating at any point in the 
partition. 
For vertical partitions, it is very practical to install the constructional 
heating units in the lower part of the said partitions, the apertures of 
the rectilinear cavities in the various panels all being aligned and 
preferably being downwardly opening, and, assuming this to be the case, 
the heating elements are connected to the electricity supply at the level 
of the skirting boards, which, once they are in place, serve to conceal 
the recessess and wires. The resistances can be electrically connected in 
series or, preferably, in parallel. In FIG. 3, only some of the 
rectilinear cavities have been shown equipped with heating elements 10, 
but it is understood that as many cavities as desired can be provided with 
heating elements. In the case where it would be desired to heat both sides 
of the same partition, it is possible to orientate the reflecting material 
or device 11 in two opposite directions for the same panel, as shown in 
FIG. 5 in the case of cavities having a triangular base. It is also 
possible to alternate the orientation of the heating face from one panel 
to the other instead of alternating within the same panel. 
On the other hand, if a partition consisting of constructional units 
according to the invention is used as a lining for an outer wall or as a 
division from another room which it is not desired to be heated, it is 
possible to arrange a layer of an insulating material 12, such as those 
usually employed in the building industry, on the rear face of the panel. 
In order to further illustrate the present invention and the advantages 
thereof, the following specific example is given, it being understood that 
the same is intended only as illustrative and in nowise limitative. 
EXAMPLE 
The actual panel was made of plaster and consisted of a parallelepipedal 
base 14, of dimensions 800 mm.times.350 mm and had a thickness of 70 mm, 
and a cover 15 of dimensions 800 mm.times.350 mm and had a thickness of 70 
mm, and a cover 15 of dimensions 800 mm.times.350 mm and had a thickness 
of 30 mm. The panel was analogous to those shown in FIGS. 3 and 4. 
The base possessed two longitudinal cavities which were parallel to one 
another and parallel to the larger dimension of the base. The cross 
section of these cavities was an isosceles triangle as shown in FIG. 4, 
the base of the triangles being formed by the inner face of the cover. 
With the panel placed on the edge and the cavities having a much greater 
vertical dimension, each cavity had only one aperture located at its lower 
end and opening out onto both the edge of the base and the border of the 
front face. The cavities had a length of 600 mm, a depth (dimension 
perpendicular to the faces of the base) of 37 mm and a width (base of the 
triangular cross section of the cavities) of 75 mm. A reflector consisting 
of a 50 micron thick aluminum foil was placed on the two V-shaped faces of 
the cavities. At the bottom of the base, the apertures of the two cavities 
were concealed by a wooden skirting board having the same 350 mm width as 
the base and the cover, a height of 110 mm and a thickness of 10 mm. 
An electrical heating element was placed in each of the cavities in the 
panel. Each heating element consisted of a resistant wire made of 
nickel/chromium alloy, which had a length of 22 m and a diameter of 0.2 mm 
and was covered with a polyamide-imide varnish. This wire was encrusted on 
a support based on a polyimide and asbestos fibers (respective weight 
proportions 3/6); the polyimide was a product resulting from the 
polycondensation of 4,4'-N,N'-diphenylmethane-bis-maleimide and 
bis-(4-aminophenyl)-methane. 
For each electrical heating element 10, the electrical resistance was 800 
ohms and the power was 60 watts; the surface area was 315 cm.sup.2 and the 
power evolved was therefore 0.19 watt/cm.sup.2. 
The front surface area of the heating panel was 2,410 cm.sup.2 (surface 
area of the cover); the total power of the two construction units was 120 
watts. 
The heating density was, therefore, 500 watts per square meter of panel. 
The temperature of the front surface of the panel was 50.degree. C. at the 
level of the heating elements and 45.degree. C. over the remainder of the 
surface of the panel. 
While the invention has been described in terms of various preferred 
embodiments, the skilled artisan will appreciate that various 
modifications, substitutions, omissions, and changes may be made without 
departing from the spirit thereof. Accordingly, it is intended that the 
scope of the present invention be limited solely by the scope of the 
following claims.