Kiln with displaceable frames for the firing of manufactured articles

The kiln with displaceable frames, designed to contain also manufactured articles of considerable mass avoiding any direct contact between them and the motor rollers which causes thickenings, is provided with a formation of short transverse, non-through, rollers (22), distributed in two opposite rows to define at least one plate of transport, said rollers extending in an overhanging manner towards the inside of the lateral walls of the kiln; a loading frame (28), rectangular or square, constituted by a pair of stringers (29) connected rotationally to the internal ends of said rollers and interconnected by transverse elements (30) for supporting the manufactured articles to be treated, is introduced into the kiln and guided by lateral surfaces; the kiln is used in industries in which drying or firing of manufactured articles, for instance ceramic articles such as sanitary apparatus, is made.

FIELD OF THE INVENTION 
The invention relates to a kiln with displaceable frames for the firing of 
manufactured articles, that is to say a kiln in which the material to be 
fired, or to be treated thermally somehow, is loaded onto frames which are 
rendered movable inside the kiln itself. 
BACKGROUND OF THE DISCLOSURE 
The state of the art comprises, for the firing or the drying of 
manufactured articles which are mainly made of ceramic material, so-called 
tunnel kilns, in which the products to be subjected to heat treatment are 
loaded onto containers made of refractory material on board trolleys which 
pass through the kiln, the firing cycle of the material taking place at 
predetermined times and rates. It also comprises kilns in which the 
material is loaded onto motorised transverse rollers which cross the kiln 
for the transport of the same material in the longitudinal direction, the 
external ends of each roller being rotatably supported close to the 
lateral walls of this kiln. 
DE 35 15 856 discloses a tunnel kiln having two opposite rows of transport 
rollers which pass through the opposite side walls of the kiln; the 
internal ends of said rollers being equipped with wheels lying on the 
floor of the kiln, in order to support and transport in a longitudinal 
direction a pair of longitudinal beams hold between flanges protruding 
circumferentially from said wheels; said longitudinal beams supporting a 
number of cross members in order to constitute a loading frame for the 
items to be treated in the kiln. 
Moreover, in the tunnel kilns, considerable thermal power is used for the 
heating of the trolley, with a consequent reduction of the relative 
thermal efficiency; furthermore, each trolley, which consists of an 
expensive metal structure covered in refractory material, needs frequent 
maintenance operations with regard on the one hand to the restoration of 
the covering, which tends to break up as a result of the thermal shocks 
and of the inevitable knocks during movement, and on the other hand to the 
necessity of frequent greasing of the hubs of the wheels, to avoid their 
deterioration and the consequent seizing. 
As far as the rollers are concerned, these become encrusted through contact 
with the wet and/or green glaze material, causing obstacles to the flow of 
the material, with possible harmful moving across and thickening of this 
towards the walls, avoidable only by means of periodic thorough cleaning 
of the rollers, to be carried out by the previous extraction of the same 
through the walls of the kiln, which, employing considerable labour, 
necessitates large spaces for manoeuvring at the side of the kiln and 
great financial outlay, the latter also being contributed to by the 
breaking of rollers which occurs during the cleaning phase, especially in 
the case of rollers of considerable length which have modest carrying 
capacity. 
Another disadvantage, in the case of manufactured articles which are short 
in relation to the interval of the rollers, derives from the need to 
support them by the interposition of plates which are subject to harmful 
deviations in trajectory, particularly in the case of encrusted rollers. 
Furthermore, the width of the kiln is limited by the maximum length which 
can be assigned to the rollers; this latter, which is currently not 
greater than 3.4 m, does not in fact permit the firing of products of 
large dimensions, which, however, is desirable. 
In the kiln according to DE 35 15 856 the wheels fastened at the internal 
ends of each roller rotate in contact with the floor of the kiln thus 
generating a frictional tangential force resulting in a lateral bending 
stress and a torsion stress on each roller and in an increase of drive 
torque for each roller; particularly when heavy items are to be conveyed. 
Furthermore, the sliding friction between the wheels and the floor of the 
kiln causes a considerable loss of energy and a rapid wearing of the floor 
of the kiln in the contact areas between the floor and the wheels, which 
can result in an unbalanced distribution of the loads on the rollers due 
to a misalignment of the axes thereof. 
This state of the art is susceptible to considerable improvements with 
regard to the possibility of avoiding the disadvantages indicated above. 
What has been stated above gives rise to the need for a solution to the 
technical problem of obtaining a kiln for the firing or the drying of 
manufactured articles, in particular of ceramic material, which are also 
of considerable mass and dimensions, which kiln permits considerable 
reductions in consumption, waste and maintenance, in order to achieve a 
great reduction in costs, such a kiln also having to allow both the method 
of firing manufactured articles by continuous unidirectional passing 
through, and that by alternating or intermittent flow; the mechanical 
wearing of the floor of the kiln being also eliminated. 
SUMMARY OF THE INVENTION 
The invention solves the abovementioned technical problem by adopting a 
kiln comprising an external support structure, an insulating shell for the 
internal walls of the kiln, a plurality of gas burners arranged at the 
bottom and at the top in relation to the product to be fired, there being 
provided short transverse, non-through, transport rollers which are 
motorised and distributed in two opposite rows to define in each case, in 
the totality of the upper generating lines, at least one plane of 
transport, with the rollers of each row extending in an overhanging manner 
from the outside towards the inside of the kiln, through the lateral walls 
of the latter, at least sufficiently to pass through them, a rectangular 
or square loading frame, which has sides which consist of at least a pair 
of coplanar longitudinal stringers, between which are inserted transverse 
elements for supporting, directly or by means of refractory supports, the 
manufactured articles to be treated, being introduced into the kiln, with 
the lower surfaces of these stringers simultaneously connected 
rotationally to the internal ends, of reduced diameter or otherwise, of at 
least two opposite pairs of said short transport rollers, and the external 
lateral surfaces of the pair of longitudinal stringers being inserted 
between vertical guides. 
The advantages achieved by this invention are the possibility of firing 
manufactured articles of considerable dimensions also, the useful width of 
the kiln being independent of the length of the rollers, a reduction in 
the percentage of waste, a considerable reduction in consumption and in 
maintenance operations, the possibility of increasing the interval between 
the short transverse transport rollers, independently of the longitudinal 
dimensions of the manufactured articles to be fired also, with a 
consequent reduction in costs, a considerable increase in productivity, in 
the case also of manufactured articles of dimensions which are not great, 
and a drastic reduction in the space necessary at the sides of the kiln 
for the extraction of said rollers; elimination of the mechanical wearing 
of the floor of the kiln; considerable reduction of the energy required by 
the roller drive means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Numeral 1 indicates the external tubular support framework of the kiln 
according to the invention; 2 indicates the transverse clearance of the 
kiln; 3 indicates the material being fired, said kiln being covered at the 
bottom, in the event of use for temperatures in the region of 1300.degree. 
C., with insulating blocks 4; 5 indicates a pair of walls consisting of 
insulating bricks, to cover the lower lateral parts of the kiln, a 
corresponding pair of external insulating layers 6 made of fibroceramic 
material being provided externally to said pair of walls; 7 indicates a 
similar layer made of fibroceramic material for covering the upper portion 
of the lateral walls of the kiln in relation to the plane of transport A 
of the manufactured articles; 8 indicates the crown of the kiln, which 
consists of insulating elements and is suspended by means of tie rods 9 
from the upper crosspieces 10 of the framework 1; 11 indicates the intake 
pipe for the fuel gas relative to the supply of each burner 12; 13 
indicates the relevant upper supply pipe for primary air, derived from the 
upper longitudinal duct 13'; 14 indicates a corresponding lower supply 
pipe for air, derived from the lower longitudinal duct 14'; 15 (FIG. 4) 
indicates the motor for the movement of a group of short transverse 
transport rollers, which is coupled to a first speed reducer 16, with axes 
at right angles, the opposite longitudinal output shafts 17 of which 
operate a series of reducers 18 at right angles, provided with output 
pinions 19 which move the chain 20 along each side of the kiln; 21 (FIG. 
3) indicates the external end pinion for the movement of each short 
transverse, non-through, transport roller 22, operated by the chain 20, 
the internal end 22' of said roller being of reduced diameter in order to 
constitute, in the region of the reduction in diameter, a longitudinal 
vertical guide; 23 indicates the shaft of the pinion 21, which is 
rotatably coupled to the external support 24 which is fixed to the 
external side member 25 which is integral with the framework 1, the 
internal end of the shaft 23 being provided with a spring-coupling for its 
insertion into the corresponding external end of the short transverse 
transport roller 22; 26 indicates the cantilever support of each said 
roller, installed on the relevant, more internal side member 27; 27' 
indicates a series of horizontal crosspieces external to the lateral walls 
of the kiln, extending between these latter and the uprights of the 
framework 1 in order to hold up the side members 25 and 27; 28 indicates 
the rectangular or square displaceable loading frame, advantageously made 
of silicon carbide, on which the manufactured articles 3 to be fired are 
arranged; P (FIG. 4) indicates the interval between the axes of the short 
transverse transport rollers 22, the speeds of rotation of these latter 
being controlled by electric or electronic devices, for example so-called 
encoders, which synchronise the angular velocities of the motors 15; 29 
indicates a pair of longitudinal stringers interconnected by crosspieces 
30 which are separated from one another according to intervals D which 
depend upon the dimensions of the manufactured articles to be treated; 31 
indicates support plates which can be used for the manufactured articles, 
in particular in the case of these being of small size, and rest on the 
crosspieces 30 of one of the loading frames 28; 32 (FIG. 7) indicates the 
internal end, of the same diameter, of the short transverse transport 
roller 22, in the alternative which provides a groove 33 for guiding and 
accommodating the stringer 29 of the loading frame 28, which groove is 
obtained by reduction of the diameter towards said end; 34 (FIG. 8) 
indicates the end without any reduction of the diameter of each of the 
short transverse transport rollers 22, when the displacement guide of the 
loading frame 28 is obtained by means of a pair of parapets 35 made of 
refractory material, said parapets having a series of holes 36 for the 
passage of said rollers through them; 37 (FIG. 9) indicates the internal 
chamber of the kiln in the case in which, in addition to the lower plane A 
for loading the manufactured articles, a second, upper plane B is 
provided; 38 indicates the insulating covering layer of the walls of the 
kiln, comprised between said loading planes A and B, which is 
advantageously made of refractory material, the distribution of the short 
transverse transport rollers 22 in relation to the upper loading plane, 
the motorisation, the mechanical transmission and the members for 
controlling the speed of rotation being entirely similar to those provided 
for the lower loading plane; 39 (FIG. 10) indicates transverse pipes for 
suction of the products of combustion; 40 indicates the door for access to 
the kiln, covered with insulating or fibroceramic material, in the case of 
a kiln for intermittent firing; 41 indicates the end wall of this kiln, 
similarly covered with insulating material. 
Functioning, in the case of FIGS. 1 to 9, takes place in the following 
manner: the manufactured articles 3 are loaded onto the frames 28 which 
are continuously drawn along by friction by the transverse rollers 22 and 
admitted to the chamber 2 of the kiln, in which they generally undergo an 
initial preheating followed by the firing and cooling phases, to exit at 
the end opposite that of entry; in the case of FIG. 10, however, the 
manufactured articles, which are introduced into the kiln through the door 
40 of the entry section upon loading onto the frames 28 which are drawn 
inside the firing chamber by the short transverse rollers 22, remain 
inside the kiln for the entire duration of the cycle; when firing is 
completed, the direction of rotation of said short rollers is reversed, 
thus bringing about the exit of the loading frames. 
In practice, the materials, the dimensions and the executive details can be 
different from those indicated, but technically equivalent to these, 
without for this reason leaving the legal scope of the present invention.