Note: Descriptions are shown in the official language in which they were submitted.
The present invention rela~es to a space heating element
comprising a ceramic shaped body which is provided on the side
facing away from the side visible from the space to be heated,
with a heating conductor extending across its surface in the
form of an electrically resistive coating.
Elements serving the purpose of space heating are
generally provided in the form of ribbed or panel
radiators below window openings so that the air of the
room which hey heat rises above the window openings,
thereby producing a curtain of wann air in front of the
window opening. In the case of radiators set up against
walls as well, there is a movement of air from the floor
to the ceiling of the room being heated, whereby the
heat radiated by the radiator into the room plays only
a small part.
Conventional radiant elements proper which are provided
in rooms have a radiating area which is very limited
locally,and work at high temperatures.
The prior art further includes floor heating, by which
heating coils containing a liquid heat transfer medium,
or else electric heating conductors, are provided in the
floor pavement or beneath the uppermost floor covering.
Floor heating is relatlvely troublesome and expensive
to install, however, and requires relatively complicated
control means.
There thus exists a need to form elements of design for
the periphery of the room itself in such a way that they
can perform singly, in groups or in the form of the en-
,' ~
_ 2
tire Deriphery of ~he room or a substantial part t~ereof,~he functlon of heating the room or a part o~ the room
periphery to be heated or kept warm.
¦ S Examples of such elements of design for the periphery of
rooms are ceramic shaped bodies such as tiles, w~ich ac~
as floor or wall lining ~iles for designing ~he walls or
the floor or ceiling of private rooms, stores and offices,
but also of sanitary rooms, gymnasiums and indoor swim-
ming pools. Such ceramic shaped bodies may also be
shaped bricks for lining swimming pools, etc.
.. ..
A ~hlet issued by Canespa KG, 3005 Hemmingen-Westerfeld,
Gutenbergstrasse 13, in 1975 already reveals a wireless
heating system called "Canespa Therm" (trade mark), in which
a heating varnish layer is provided as an electrically
resistive coating on the back of shaped bodies, in fact of
ceramic tiles. This heating varnish layer is covered by a
polyurethane foam body. This system did not find wide
acceptance, however, since there was repeatedly overheating
locally, resulting in harmful complications which even led
to danger for persons and objects.
The prior art also includes an electrical space heating
device according to DE-A 14 40 971, comprising a carrier
with a large smooth surface and a thin hea~ing conductor
extending across ~his surface and adhering directly there-
to. The earrier consists of an earthenware or vitreous
fused silica tile. This tile is provided on its side
facing away from the visible side with a thin, adhesive,
imetallic heat conducting coating extending across the
surface and formed by precipitating a chemical solution,
or bears on this side an adhesive heat conducting coating
consisting of a very thin aluminum layer.
~t is necessary in the case of such a space heating de-
vice to provide spacing means between the tile and the
~ 3 --
ca~ie~ fac:e which hears it, whlch ~n ~u~ o~
a take-up for ~he alr o~ the roam beh~d the ~pac2 heat-
lng de~rice wit:h all the dlsadv~ntages descr~bed abo~7e
whlch ha~re already been observed in the case o~ othe~
5 space heatir~g devices. Further;n~re, the metallic re-
s~sti~re layers used have a relatively low resistance
value and re~ e high electrical pow~r ko obtain a
suf icient ther~aal yield .
10 DE-A 19 ~4 202 an~ the non prepublished DE-A 33 Z5 204
disclose a s~Leet-liX~ el ectrical heating ap~aratus
haYing a sheet~ ce carrier which takes up a heating
element, in whic~ the heating element is ~or~ed as
a thin layer of elec~rically conductive material wh' ch
1; is applied to one surface of the carrie-. Even if the
elec~_ically c~ncu~ti~e material consists wholly or
partially of s~iconductor material, as described in
DE-A 33 25 204, no success can be achleved therewith
because the laye-s cannot ~e produce~ in a reproducible
Z0 manner with r~s?ec~ to their elect~ical r~sistance when
made of such material. The heating a?paratus therefore
exhibit heatin~ ca?acities which diffe_ from piece to
piece.
25 The invention is directed to the problem of providing a space
heating element which supplies a high thermal yield while
re~uiring little elec rical power, is capable of being used as
an element of design for the periphery of the room and may be
installed in such a manner that no channels are formed which
~ight force air currents to circulate in the room to be heated,
but is also reproducible at will, i.e. exhibits the desired
heating capacit~ from piece to piece.
- 3a -~
In accordance with the present invention there is
provided a space heating elerr,ent comprising a ceramic shaped
body which is provided on one side with an electrically
resistive layer made of a material comprising non-metallic
particles which have a large specific area, which are
sufficiently electrically conductive, and which do not
substantially alter their electrical conductivity at the higher
temperatures of operation of the element, wherein the
electrically resistive layer is provided on the side facing away
from the visible side of the shaped ceramic body and that the
particles are embedded in a carrier substance which is not
electrically conductive, or is only poorly electrically
conductive, so that the resistive layer exhibits uniform
electrical and thermal conductivity.
Also in accordance with the invention there is provided
an electrical space heating element comprising:
a ceramic tile body having a visible side and an
opposite side which faces away from said visible side;
a polyester cover layer;
an adhesive bonding said polyester cover layer to said
opposite side of said ceramic tile body;
a non-metallic electrically resistive layer disposed
along the surface of said cover layer which faces away from said
visible side of said ceramic tile body, said non-metallic
electrically resistive layer being divided into at least two
spatially separated areas, each of said spatially separated
areas being separated from each other spatially separated area
adjacent thereto by a separation space;
low resistance contacting means electrically contacting
each of said at least two spatially separated areas in at least
two different spatially separated locations; and
a polyester bottom layer disposed over said cover layer
and enclosing said electrically resistive layer therebetween,
said bottom and said cover layers having a plurality of
perforations provided therethrough along each of said separation
spaces.
- 3b -
Further in accordance with the invention there is
provided an electrical space heatiny element coMprising:
a ceramic tile bo~y having a visible side which faces
the space to be heated and an opposite side which faces away
from the space to be heated;
an electrically resistive glaze applied to said
opposite side, said electrically resistive glaze being embedded
with non-metallic electrically conductive particles such that
the electrieal resistance of said electrically resistive glaze
is substantially constant as a function of its temperature; and
low resistance contacting means for electrically
contacting said electrically resistive glaze in at least two
spatially separated areas.
Further in accordance with the invention there is
provided an electrical space heating element comprising:
a ceramic tile body having a visible side which faces a
space to be heated and an opposite side which faces away from
the space to be heated;
an electrically resistive adhesive applied to said
opposite side of said ceramic tile body, said electrically
resistive adhesive having non-metallic electrically conductive
particles embedded therein to give it a predetermined resistance
value; and
means for making electrical contact with said
eleetrieally resistive adhesive along opposite ends of said
eeramie tile body.
~ 4 w
. .
The non-metallic particles whlch have a large speciflc
area, are electrically conductive and do not substan
tially alter their electrical conductivity at higher
temperaturesO are preferably made of graphite and
S carbon black, or mixtures thereof.
According to the present invention it is possible to provide a
space heating element in the form of a radiant element a
multiplicity of which may be used to cover an entire wall,
ceiling or floor area, for example, the thermal radiation being
even or divided up as desired. The heating can be achieved
without significant circulation of the air in the room, and an
even feeling of well-being can be achieved in the room at a
substantially lower room temperature, which leads to a
i5 considerable energy saving.
.
Since the heating elements are exactly reproducible
with regard to their heating capacity, they can be
- 20 produced in predetermined heating capacity classes.
Thus, any desired distribution of the thermal radiation
from the lined surface is possible.
Any local faults in the electrically resistive coating have no
material effect on the heating capacity. At most, there is a
slight local reduction in the heating capacity, but no complete
interruption thereof, and there is no local overheating.
The electrically resistive coating may consist of a layer
made of non-ageing synthetic resin with an electrically
conductive admixture such as an admixture of pure
graphite, and have a construction such that the layer
exhibits a resistance value which is necessary in accord-
ance with the required electrical power. The resistancevalue may be set to values of a few Q up to several kn,
B~3
-- 5 --
which is effected by altering the percentage of the
electrically conductive admixture of the resistive
coating and/or altering the layer thickness. The layer
thickness is usually between 10 and 50 ~.
In the case of a tile which is 100 cm x 100 cm, the
the electrical power consumption is approx. 100 W, for
example; in the case of a 60 x 60 tile it is approx. 30 W.
The term "non-ageing" refers in the case of the inven-
tively selected layer to stability under continuous
stress up to approx. 100C.
In an alternative embodiment of the invention, the
electrically resistive coating consists of an electrical-
ly resistive film comprising a polyester cover layer, a
conductive intermediate layer provided with supply lines
and removal lines, e.g. a graphite and/or carbon black
layer,as a resistive layer, and a bottom layer of poly-
ester. Such resistive films are known per se. Thesupply lines and removal lines leading to the resistive
layer are generally designed in the form of copper bands.
However, the problem of using such resistive films in
connection with the solution to the problem on which
the invention is based is that polyester layers adhere
poorly to the resistive layer so that it is not assured
with sufficient certainty that the shaped body, e.g. a
ceramic tile, provided on the side facing away from the
visible side with such a resistive film, will adhere
to the place of attachment, even if an adhesive is used
which adheres, for example, to plastered walling and
the back of the shaped body and to the polyester layers.
On the other hand, the use of polyester is recommended
as the material for the cover and bottom layers, because
polyester is very non-ageing. The problem which occurs
when polyester material is used for the cover and bottom
- 6
- lay~rs of the resistive film may be solved, howéver, l~
the resistive layex, in accordance with a modified em-
bodiment of the invention, is divided up across its sur-
face, leaving areas not covered thereby, the divided
S areas communlcating with each other electrically
and local perforations o~ the resistive film beiNg pro-
vided in the areas not covered by the resistive layer.
An adhesive may be used for this purpose which sticks
only to plastered surfaces ~nd ceramic surfaces, but
not, or not well, to a polyester surface, bçcause the
resistive film is perforated locally, e.g. punched
through and attached to the side of the ceramic body
facing away from the visible side thereof by means of
the adhesive which is exposed in the perforated areas
or pervades them at least partially. When a ceramic
shaped body of such a design is stuck to a plastered
layer, etc., by aid of a conventional adhesive as used
for sticking ceramic shaped bodies to wall surfaces, etc.,
the adhesion takes place via the adhesive which is ex-
posed in the perforatiohs or emerges therefrom, so that
the ceramic shaped body is attached to the base intended
to receive it in a manner which is only local but is suf-
ficient if the perforation pattern is correctly dimensioned.
It is particularly advantageous to provide the electrically
resistive coating ln the form of a resistive glaze. This
glaze i5 applied to the shaped body after it is haked, and
fixed by baking the shaped body once again. A glaze must
be selected whose melting point is not higher than 750C.
Glazes with higher melting points have proved to be un
suitable.
It is already disclosed in DE-A 19 24 202 to provide an
electrically conductive glaze on the visible side of
ceramic shaped bodies , but this glaze only serves the
_ 7 _
purpose of removing static electricity, i.e. it is so
highly resistive that it i5 not suitable for heating
purposes.
A further possibility consists in designing the adhesive
for fixing the ceramic shaped body to the carrier base,
as an electrical resistor itself. It is then possible
to use two different types of adhesive, the adhesive ad-
jacent to the shaped body being made of electrically re-
sistive material while the adhesive lying against thebase is an electrically insulating adhesive. The adhe-
sives exhibit substantially the same thermal expansion
properties and chemical compatibility, so that it is
particularly simple to attach the electrically resistive
ceramic shaped body in this manner.
The material for the electrically conductive resistive
layex may be one which, when sub~ected to electric cur-
rent, exhibits a temperature response such thatthe current
absorption of the material decreases greatly as the tem-
perature rises.
It is stated in DE-A 33 25 204 in connection with the
use of semiconductors as a conductive material for a
heating element, that semiconductors in particular ex-
hibit a desirable negative temperature coefficient, but
this is opposed by the statements in Rompp according to
which the conductivity of semiconductors usually increases
greatly as the temperature rises.
The contacting of the electrically resistive coating
takes place expediently by means of contacting elements
arranged symmetrically on the electrically resistive
layer. Thus, the contacting elements may be arranged
on square or rectangular tiles, for example, along two
edges of the tile facing away from one another, in the
form of con~ac~l~g band~ th~ tlle ls a c~r~mle
ha~iAg a ~lie~ struc~ure on ~he bac~, ~he contack~ng
ele~ent3 are exped~ently arranged i~ ~h~ cha~ lo
cated at the edges ~acing away ~o~ each other betw~en
5 . th~ rldges limiting thes~ channels.
,
It~ls possible sn the basis of:an embadiment the ~r.
~e~tion to finely adjus~ the resistance values o~ elec-
tically resisti~e layers ln such space heating elements
to desired values subs2~uently as well.
; This is effected ~n accordance with this ~mbodim~nt by
reducing the layer t~ickness of khe resisti~e layer or
heatins the resistive layer ln order to ~ncrease lts
15 resistance value.
~o increa3e the resistance value of the resistive
layer, the layer thickness of the resistive layer
can be reduced by sandblas'cing, electroerosion,
brushing off, etc., or else the resistive layer i~
heated from the outside, for example by subjecting
it to flames or radiation. It is also possible to
conduct electric current of considerably yreater
power than during normal operation through the
resi-qtive layer. ~his alters the struc~ure of the
resi~tive layer in such a wa~ that its resistance
value is increased.
The invention will be bet~er understood with
reference to the drawings in which:
Figure 1 is a rear view o~ a preferred embodiment
o~ a space heating element according to the pre~ent
invention in the form a tile having an electrically
resistive layer and contacting elements;
Figure 2 is a cross-section of an al~ernative
embodi~ent of a space heating element according to
the present invention in the form o~ a tile having
a relief structure on the back;
3 i9 a ~oe view of an embodiraent of a c~ra~c
hea~ g elem~n ln the ~orm o~ a til~ and ha~ing an
electrically re~istive ~llm applied thereto
. Figure 4 i a partial sectlonal view of khe
embodiment o~ the ceramic heating element 3hown in
Fiyure 3, at an enlarged scale and
Figure 5 is a cross-sec~ional view of a ~eramic
tile with a resistive layer shown schema~ically to
illu~ra~e a technique for changing the resistance
o~ ~he resistive layer.
In Fig. 1 number 1 refers to a space heating ele~nt in general,
here in the for~ of a tile, an ~lectrically resis~ive
layer being located on its bacX 2. Numbers 3 and 4 re~
fer to contacting elements which are stuck ~o the elec-
trically resistive layer or attached thereto in another
manner. Numbers S and 6 re~er to the current supply
lines.
Fig. 2 shows a cross-section of a space heating element
which exists here in the form of a tile with a relief
structure on the back 21. This back 21 exhibi~s ridges
22 and grooves 23. On the back o~ this tile, i.el on
the side on which the ridges and grooves a~e located,
an electrically conductive adhesive 24 is provided, for
exa~ple. A conductor 27 is provided in a groove 26
adjacent to edge 25 of the tile. Adhesive 24 is of
course an electrically resistive adhesive, l.e. a
material which is conducti~re but conducts so poorly
that the electrical energy conducted thereinto ls
converted into thermal enersy.
In Fig. 3 number 31 refers to a ~e heating el~t in gen~x~,
which, as shown in Fig. 4, exhibits a tile 41, an ad-
hesi~e layer 42 and a resistive film 43. ~he resistive
filn consists o~ a polyester cover layer 46 con~ected
~ -- 10 --
- via adhesive layer 42 to the side 45 facing away from
the visible slde 44 of tile 41, further of graphite and/or
carbon black intermediate layers 43a, 43b, 43c as re-
sistive layers each provided at the edge with supply
lines and removal lines in the fc rm of copper bands
32 to 37 with current supply lines 38 (Fig. 3), and fi-
nally of a polyester bottom layer 48 which is stuck to
the supporting surface 49, e.g. plastered walling, via
an adhesive layer 50. Resistive film 43 contains three
webs 43a, 43b, 43c of resistive layer material in the
embodiment shown, but may of course also have a greater
structure.
Between webs 43a and 43b, and 43b and 43c there are
areas 51 and 52 (Fig. 3) in which no resisti~e layer
material is present. However, web 43a borders on area
51 via conduction band 36. Similarly, web 43c borders
on area 52 via conduction band 33 while web 43b borders
on each side on areas 51 and 52 via conduction bands
34 and 35. In areas 51 and 52, in which layers 46 and
48 are superjacent, there are perforations 53 through
which the adhesive extends out of the layer and communi-
cates with the adhesive from layer 50 on supporting sur-
face 49. The individual conduction bands may be intercon-
nected in any manner one chooses. The single tile 31
may also be replaced by three subtiles each assigned
accordingly to webs 43a, 43b and 43c.
The possible design of the conductive intermediate
layer or resistive layer in a form in which its area
is divided up leaving areas not covered thereby,
may involve, for example, a meander-shaped
arrangement of the resistive layer or a division there-
of into several sublayers in the form of bands, surface
elements, etc., which extend across the surface but are
electrically connected to each other or are to be con-
- 11 -
nected to each other subsequently. The seleetion of
the eorresponding pattern depends on the local data
and/or the teehnical requirements.
In Fig. 5 number 91 indicates a ceramic tile on which
a resistive layer 92 is provided. The thickness in
whieh this resistive coating 92 is applied is reduced
using a suitable means, e.g. sandblasting, electro-
erosion, brushing off, etc. In the embodiment shown
this is effected using a brush 93 which rotates, for
example, so that the thickness of application is re-
dueed to the desired thickness as indicated in area
94. This also reduces the conductivity of this layer,
i.e. the surfaee resistance inereases. In this manner
fine adjustment of the resistance value of layer 92 is
possible.
