Patent Publication Number: US-7595465-B2

Title: Device for keeping heating wires in position in a horizontal oven

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Netherlands Application No. NL 1028057, filed Jan. 18, 2005, the contents of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The invention relates to a device for keeping heating wires in position in an oven, and more particularly in a horizontal oven. 
   BACKGROUND OF THE INVENTION 
   In an electric oven, heating or incandescent wires are used in order to be able to heat the interior of the oven. The heating wires are made from a metal which is able to conduct electricity well and can be heated to the desired high temperatures without the material deforming. The heating wires have to be kept a certain distance apart so that the temperature of the oven can be kept as even as possible throughout. To this end, the heating wires are kept apart by means of spacer pieces or spacer strips. However, the hotter the heating wires become, the softer the material from which the heating wires are made will become. In a horizontal oven, where the heating wires are arranged in a helical or meandering fashion, i.e., run more or less to and fro, the heating wires will become softer as the temperature increases and, beyond a certain temperature, the risk that the wires will sag under their own weight and by the effect of gravity will increase. As a result, not only will the oven not be heated as evenly throughout as desired, but also the sagging heating wires can come into contact with materials which are in the oven. The heating wires in a horizontal oven will therefore have to be supported, especially if the wires are located at the top of the oven, so that the wires no longer sag when, due to the heating of the wires, the material from which they are made becomes so soft that they start to sag as a result of their own weight. However, care should also be taken to ensure that the heating wires are not clamped in, as the wires expand on heating and need a sufficient degree of freedom of movement as there is otherwise a great risk of the wires snapping. This is of particular importance with horizontal ovens in which semiconductor materials are treated, as the treatment in these ovens is effected at high temperatures, which may cause the heating wires which have become too soft to sag. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a device with which it is possible to arrange a heating wire in a horizontal oven in such a way that the heating wire is locked in, in such a manner that it stays in place without the wire being clamped in. An additional object is that by applying the device according to the invention, the heating wires can be installed easily and can preferably be mounted in stages, ring by ring, thereby enabling a time saving. 
   This object is achieved by a device according to the invention, in that the device consists of a bar and a number of spacer elements, each spacer element consisting of a bar-shaped part, on which a Y-shaped part is placed near the centre of the bar-shaped part, the bar-shaped part being at right angles to the plane through the Y-shaped part, and in that the V-shaped part of the Y-shaped part can partially enclose the bar, so that the spacer element is T-shaped in cross section through the bar-shaped part and the longitudinal axis of the Y-shaped part. 
   The result of these measures is that when a heating wire is fitted in an oven, the heating wire can be fitted in the oven in stages, winding by winding, in the oven while, when the heating wire has been fitted in an oven using this device, the heating wire does not have the tendency to sag by the effect of gravity when the heating wire softens as a result of an increase in the temperature. As the heating wire according to the invention is entirely enclosed by the device at a suspension point without the heating wire being clamped in, there is sufficient space around the heating wire for it to expand by the effect of the heat, yet the heating wire will roughly stay in place, as a result of which it is possible to achieve a good, even heat distribution in the oven at every temperature. 
   In one preferred embodiment of the device according to the invention, at one end of the bar-shaped part, each spacer element is provided with a transverse part which is at right angles to the bar-shaped part and runs parallel to the Y-shaped part, creating a U-shaped recess in which the heating wire can be accommodated, and the other side of the Y-shaped part and the bar-shaped part together form an L-shaped recess in which the heating wire can also be accommodated and the bar-shaped part and the spacer elements are made of ceramic material, while the one end of the bar-shaped part of a spacer element is provided with a projection in line with the bar-shaped part and a recess is provided in the other end of the bar-shaped part, so that the projection of the one spacer element can interact with the recess which is provided in the other end of the bar-shaped part of the spacer element placed against it. The result of these measures is that when a number of spacer elements according to the invention are arranged on a ceramic bar, the spacer elements together form a strong unit. Thus, once a number of spacer elements have been fitted to a ceramic bar, there is a connection between the successive spacer elements. The ceramic bar may either be solid or recess. The use of a recess bar will result in a weight-saving. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in more detail with reference to the drawing, in which: 
       FIG. 1  shows a view of a part of the heating wires of a horizontal oven suspended using a device according to the invention; 
       FIG. 2  shows a perspective view of a spacer element according to the invention; 
       FIG. 3  shows a view of a spacer element from  FIG. 4 ; 
       FIG. 4  shows a cross section through a spacer element according to the invention as illustrated in  FIG. 2  along line IV-IV from  FIG. 3 ; 
       FIG. 5  shows a cross section of another possible embodiment of a spacer element according to the invention with a ceramic bar and another two spacer elements shown by dashed lines; 
       FIG. 6  shows a cross section of another possible embodiment of a spacer element according to the invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  shows a part of a device  1  according to the invention with sections of a heating wire  2 . The device consists of a ceramic bar  3  and a number of ceramic spacer elements  4 , the sections of the heating bar  2  being enclosed between the ceramic spacer elements  4  and the ceramic bar  3 . 
     FIG. 2  shows a view of a spacer element  4  according to the invention. Each spacer element  4  consists of a bar-shaped part  5 , on which a Y-shaped part  6  is placed near the centre of the bar-shaped part  5 . The bar-shaped part  5  is at right angles to the plane through the Y-shaped part  6 . 
     FIG. 3  shows a view of the spacer element  4  from  FIG. 4 . The opening  7  delimited by the V-shaped part  8  of the Y-shaped part  6  is O-shaped, so that the V-shaped part  8  can partially enclose the ceramic bar  3 , which ceramic bar  3  is preferably cylindrical. 
     FIG. 4  shows a cross section of a spacer element  4  according to the invention as illustrated in  FIG. 2  along line IV-IV from  FIG. 3 . Near one end, the bar-shaped part  5  is provided with a transverse part  9 , which is at right angles to the bar-shaped part  5  and runs parallel to the Y-shaped part  6 , so that a U-shaped recess  10  is created which can accommodate the heating wire  2 . On the other side of the Y-shaped part  6  and the bar-shaped part  5 , an L-shaped recess  11  is created, in which the heating wire  2  can likewise be accommodated. Both the dimensions of the space delimited on one side by the ceramic bar  3  and on the other side by the U-shaped recess  10  of a spacer element  4 , and the dimensions of the space delimited on one side by the ceramic bar  3  and on the other side by the L-shaped recess  11  of a spacer element  4  and the transverse part  9  of the adjoining spacer element are chosen such that a heating wire or incandescent wire  2  has sufficient space to be able to thermally expand. The one end of the bar-shaped part  5  of the spacer element  4  is provided with a projection  12  in line with the bar-shaped part  5  and a recess  13  is provided in the other end of the bar-shaped part  5 , so that the projection of the one spacer element can interact with the recess which is provided in the other end of the bar-shaped part of the spacer element placed against it. The length of the transverse part  9  corresponds to the length of the stem of the Y-shaped part, as a result of which the transverse part  9  can rest roughly on the ceramic bar  3  when a spacer element is fitted to a ceramic bar. 
     FIG. 5  shows another possible embodiment of a spacer element  14  according to the invention with, in dashed lines, two spacer elements  14  and a ceramic bar  3 , onto which the spacer elements have been pushed. In this case, the spacer element  14  is also made up of a bar-shaped part  5 , on which a Y-shaped part  6  is also placed near the centre of the bar-shaped part  5 . The bar-shaped part  5  is at right angles to the plane through the Y-shaped part  6 . The one end of the bar-shaped part  5  of the spacer element  4  is provided with a projection  12  in line with the bar-shaped part  5  and the other end of the bar-shaped part  5  is provided with a recess  13  so that the projection of the one spacer element can interact with the recess which is provided in the other end of the bar-shaped part of a spacer element  14  placed against it. 
     FIG. 6  shows another possible embodiment of a spacer element  15  according to the invention. Near one end, the bar-shaped part  5  is provided with a transverse part  9  which is at right angles to the bar-shaped part  5  and runs parallel to the Y-shaped part  6 , thus creating a U-shaped recess  10  which can accommodate the heating wire  2 . 
   A transverse part  16  is also arranged on the other side of the Y-shaped part  6  and the bar-shaped part  5 , as a result of which a U-shaped recess  17  is created on the other side of the Y-shaped part as well, which can also accommodate the heating wire. On the other side of the transverse part  16 , an L-shaped recess  18  is created, which can also accommodate the heating wire  2 . Both the dimensions of the space delimited on one side by the ceramic bar  3  and on the other side by the U-shaped recesses  10 ,  17  of a spacer element  4 , and the dimensions of the space delimited on one side by the ceramic bar  3  and on the other side by the L-shaped recess  18  of the spacer element  15  and the transverse part  9  of the adjoining spacer element  15  are chosen such that a heating wire or incandescent wire  2  has sufficient space to be able to thermally expand. The one end of the bar-shaped part  5  of the spacer element  4  is provided with a projection  12  in line with the bar-shaped part  5 , and a recess  13  is provided in the other end of the bar-shaped part  5 , so that the projection of the one spacer element can interact with the recess which is provided in the other end of the bar-shaped part of the spacer element placed against it.