Abstract:
A portico furnace includes a number of porticos ( 1 ), which are arranged parallel to one another and which define the spans of the furnace, and supports ( 2, 6 ) that are attached to the porticos ( 1 ), between which are positioned interjoists ( 3 ) that constitute the walls of the furnace. At least some of the interjoists ( 3 ) consist of a chimney block ( 4 ) with an axis that is parallel to the supports ( 2, 6 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present Application incorporates by reference and claims priority to French Application 06 08498 filed Sep. 27, 2006. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     None. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     None. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     In a general manner, this invention relates to the kilns that are used for firing products such as earthenware or ceramic products. 
     (2) Description of Related Art 
     These kilns usually come in the form of a tunnel of great length through which pass carriages bearing the products to be fired. 
     A circulation of fluid, air or any other suitable gas creates a gas stream that ensures the ventilation and the heating of the products for the purpose of their firing. The temperature, the hygrometric degree, and the displacement speed of the gas stream are continuously monitored so as to ensure a good-quality treatment of the products to be fired. In the usual manner, said gas stream enters the chamber by passing through wells or slots made in the wall of the latter, in the roof or in the lateral walls. Means, such as fans, are mounted in the ventilation circuit, usually outside of the chamber, to ensure the circulation of the gas stream. 
     The problem that arises in these chambers is tied to the fact that it is very difficult to obtain a uniform circulation of the gas stream around each of the products that are present in the chamber. 
     Numerous proposals have been made so as to improve the circulation of the gas stream by adding fans, deflectors, . . . but none have been totally satisfactory. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention aims to propose a device that is designed to cause a gas to circulate in a firing kiln, whereby said device is more particularly suited to being used in tunnel kilns, which are usually referred to as portal frame design kilns. These kilns derive their name from portal frames in the shape of inverted U&#39;s, consisting of a horizontal beam and two feet, arranged beside one another to form an external frame of the tunnel kiln that is designed to hold up the elements that constitute the chamber of the kiln. 
     The portal frames that are placed outside of the kiln, above the upper wall of the latter, consist of metal sections. 
     Supports that are designed to attach the refractory wall of the kiln are held up by said portal frames. 
     In the roof of the portal frame design kilns, suspension parts, held up by the horizontal beam of each portal frame, constitute a support that is similar to a small beam that is shaped overall like an inverted T arranged horizontally. Interjoists are positioned perpendicularly to said supports, resting on the opposite heels of two supports that are close to one another. 
     The lateral walls of the kiln are made in a similar manner by supports that are attached to the feet of the portal frames between which interjoists are positioned. 
     An insulating coating is put on the faces of the interjoists which are outside of the chamber of the kiln to reduce the losses of heat toward the outside from the useful space, or laboratory, of the kiln. 
     The suspension parts and the interjoists are made of, for example, refractory materials. 
     According to the invention, the portal frame design kiln, which is of the type comprising a number of portal frames arranged parallel to one another and defining spans of the kiln and supports that are attached to said portal frames between which interjoists that constitute the walls of the kiln are positioned, is characterized in that at least some of the interjoists consist of a chimney block which axis is parallel to said supports. 
     The kiln according to the invention is also noteworthy in that:
         Said chimney blocks are positioned beside one another in a span and constitute a transverse and/or vertical pipe extending parallel to said supports,   The pipe extends over at least a portion of the length of the supports between which it is positioned,   A transverse pipe is connected to at least one vertical pipe,   The chimney block has, viewed overall, a rectangular cross-section,   Said chimney blocks are of different types, for example chimney-block-fan, distribution chimney block, end chimney block, simple chimney block, flap chimney block, . . . .   A distribution chimney block comprises at least one seal that is arranged before an orifice,   A corner chimney block ensures the connection between a transverse pipe and a vertical pipe.       

     The invention also relates to a process for ventilation of a portal frame design kiln according to the invention, characterized in that:
         Transverse and/or vertical pipes are formed in at least some of the spans of the kiln by positioning interjoists in the form of a chimney block,   A gaseous fluid is circulated between the chamber of the kiln and said transverse and/or vertical pipes.       

     The process for ventilating a portal frame design kiln according to the invention is also noteworthy in that:
         A predetermined circulation of the gaseous fluid is obtained by selecting the chimney blocks that are designed to constitute each pipe from among a family that comprises, for example, chimney-block-fans, distribution chimney blocks, end chimney blocks, simple chimney blocks, flap chimney blocks, corner chimney blocks, . . . ,   At least some of the transverse and/or vertical pipes are connected to external fluid distribution means.       

    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The invention will be better understood using the following description that is provided by way of nonlimiting example with reference to the accompanying drawings, in which: 
         FIG. 1  is a partial cutaway view of the roof of a portal frame design kiln, limited to one span overall, 
         FIG. 2  is a view that is similar to  FIG. 1  for a portal frame design kiln in which the invention is implemented according to a first embodiment, the section being made across a chimney-block-fan, 
         FIG. 3  is a partial perspective view of a portal frame design kiln in which the invention is implemented according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , a portal frame design kiln of the known type comprises a number of metal portal frames  1  in the shape of inverted U&#39;s, consisting of a horizontal beam  11  and two feet  13 . These portal frames  1  are positioned parallel to one another and constitute an external frame of the kiln that is designed to support the elements that constitute the chamber of the kiln. 
     Two portal frames  1  that are close to one another define among them a span  10  of the kiln. 
     Each horizontal beam  11  of the portal frame holds up, by the implementation of attachment means  12 , a number of suspension parts  200  that are positioned beside one another. 
     Said suspension parts  200  constitute a horizontal support  2  that is similar to a small beam with a section in the shape of an inverted T. The sole plate  21  of such a support  2  is larger than the core  20  and, on both sides of this core  20 , forms a bearing  23  that extends longitudinally over the entire length of said support  2 . 
     Interjoists  3  that are parallelepipedic overall are positioned between two supports  2  that are close to one another by being oriented perpendicularly to said supports  2 . Said interjoists that are shown in the drawing comprise projecting edges  32  that are mounted on opposite bearings  23  of the supports  2 . 
     An insulating coating  34  covers the upper faces of the interjoists  3 . 
     According to the invention, some interjoists  3  consist of a chimney block  4  with, viewed overall, a rectangular cross-section. 
     Said chimney blocks  4  replace the interjoists  3  and are positioned in the same way as the latter, beside one another in the width of the kiln, by being mounted on the bearings  23  of the supports  2 . 
     Said chimney blocks  4  that are positioned beside one another in a span constitute a transverse pipe  45  that extends parallel to said supports  2 . 
     As could be understood, said transverse pipe  45  that is produced by the invention forms a passage in which it is possible to circulate a gaseous fluid that is intended to improve the ventilation of the parts during firing. 
     The transverse pipe  45  extends over at least a portion of the length of the supports  2  between which it is positioned; its length is defined by the number of chimney blocks  4  positioned beside one another. 
     In the embodiment shown in the drawing, the chimney blocks  4  extend completely between the cores  20  of the supports  2  and above the sole plates  21  of said supports  2  so as to propose a pipe  45  of the largest section possible. 
     According to a variant embodiment not shown in the drawing, the chimney blocks  4  comprise a lower portion that extends between the sole plates  21 . 
     Like the other elements of the roof, suspension parts  200  and interjoists  3 , the chimney blocks  4  are made of refractory material. 
     Different types of chimney blocks  4  are provided so as to fulfill various functions in the ventilation system and constitute a family of elements among which the designer of the kiln selects based on the predetermined circulation of gaseous fluid that is supposed to be obtained. 
     For example, the drawing shows a chimney-block-fan  400  in which a fan  5  is positioned, and said fan draws in or blows back the gas stream through an opening  40  of the lower face thereof that is turned toward the laboratory of the kiln, i.e., toward the space in which the products to be fired circulate. Said fan is entrained by means  50  that are shown diagrammatically in the drawing and held up by the portal frames  1  by the implementation of means  51 . Two embodiments and forms of assembly of a fan are shown in  FIGS. 2 and 3  by way of example. 
     Distribution chimney blocks  401  are visible in  FIG. 3 ; they have at least one orifice  41  in their lower face that is turned toward the laboratory of the kiln. In an embodiment that is not shown in the drawing, seals that can be controlled remotely are arranged in front of the orifices  41  of said distribution chimney blocks  401  so as to make possible the adjustment of the size of the free passage. 
     End chimney blocks  402  are also shown in the drawing; these chimney blocks  402  have an end that is closed by a transverse wall  42  that defines the end of the pipe  45 . 
     Other chimney blocks can be added to this family, for example a simple chimney block  403  that constitutes a portion of transverse pipe  45  but does not have a particular element or a flap chimney block in which a flap, optionally adjustable from the outside, makes it possible to reduce the section of the transverse pipe  45 . 
     The transverse pipe  45  that is formed by the chimney blocks  4  is used to draw in the gaseous fluid that is present in the laboratory of the kiln and to feed it back toward said laboratory at different points along said pipe. 
     The fan  5  is selected so as to draw in the gaseous fluid that is present in the laboratory through the opening  40  of the chimney-block-fan  400  and to feed it back via the openings  41  of the distribution chimney blocks  401 , or vice versa. 
     Two or more portions of transverse pipe  45  are created, if necessary, in the same span by arranging end chimney blocks  402  at suitable locations along supports  2 ; a transverse pipe  45  in two parts is shown by way of example in  FIG. 3 . 
     As can be seen in the drawing and more specifically in  FIG. 3 , the lateral walls of the kiln have a constitution that is similar to that of the roof and comprise attaching parts  600  that are attached to the feet  13  of the portal frames  1  so as to constitute the vertical supports  6  between which are positioned interjoists  3  that are identical to those used in the roof. 
     According to the invention, in a span of the kiln, a vertical pipe  46  is formed in at least one longitudinal wall of the kiln and is connected, if necessary, to the transverse pipe  45  that is arranged in the same span. 
     A vertical pipe  46  is produced in the same manner as a transverse pipe  45  according to the invention by replacing the interjoists  3  of a span by chimney blocks  4  that are selected from among the family of chimney blocks based on the gaseous fluid circulation that is to be ensured. 
     A corner chimney block  405  ensures the connection between a transverse pipe  45  and a vertical pipe  46 . 
     As could be understood, the implementation of chimney blocks  4  according to the invention makes it possible to regulate as well as possible the circulation of the gas streams around the parts to be treated by adapting the position of the openings in the transverse and/or vertical pipes. 
     Among the family of elements of chimney blocks, several distribution chimney blocks  401  whose opening or openings  41  have different sections can be proposed. 
     By way of example, openings  41  are positioned along vertical pipes  46  at selected heights so as to ensure a priority circulation of the gas streams at the load carried by the cars or at suitable zones provided in the lower spaces of said cars. 
     According to an embodiment of the invention, not shown in the drawing, the transverse pipes  45  and vertical pipes  46  are connected to external fluid distribution means and can then be used to draw off gaseous fluid that circulates in the kiln and to replace it by injecting air or any other gaseous fluid. 
     For certain types of firing, it is also possible to use these pipes for providing an injection of gaseous or solid products, etc.