You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     This invention relates to an improved metal stud having a double thickness flange having novel means for remaining relatively cool when the opposite side of the wall, embodying the stud, is exposed to a fire. 
     U.S. Pat. No. 4,047,355 discloses the combination of a hole through the overlapping flange of the overlapped portion of the stud flange, to allow cooling air to enter the space between the overlapped flanges, creating a chimney effect to move the cooling air. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to modifying and improving upon this basic idea, to effectively create a second zone of cooling effects, providing cooling at the interface between the inner layer of a double thickness flange and the boards disposed adjacent thereto. 
     The invention consists essentially of a metal stud having an overlapped flange portion with a gap for air flow therebetween, dimples in the overlapped flange for spacing board away from the overlapped flange, and also, preferably, holes at spaced positions along the under flange for venting heated air from within the gap. 
     It is an object of the invention to provide an improved metal stud for resisting heat transmission in case of fire. 
     It is a further object of the invention to provide a metal stud having effectively two chimney effect cooling gaps, with provision for most effectively circulating cooling air and the cooling steam driven off from the heated gypsum boards. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages will be more readily apparent when considered in relation to the preferred embodiments of the invention as set forth in the specification and shown in the drawings in which: 
     FIG. 1 is an isometric view of a section of stud embodying the present invention. 
     FIG. 2 is an isometric view of a shaft wall embodying the stud of FIG. 1. 
     FIG. 3 is a horizontal sectional view of the wall of FIG. 2, taken along line 3--3. 
     FIG. 4 is a vertical sectional view of the wall of FIG. 2, taken along line 4--4. 
     FIG. 5 is a horizontal sectional view of wall having a modified stud in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown an elongate lightweight metal stud 10, formed from sheet metal, preferably 24 gauge galvanized steel, and formed as a one-piece unit, including a central web 12 which extends from a first side 14 of stud 10 to a second side 16. 
     First side 14 has a double thickness flange 20 and a single thickness flange 22. Double thickness flange 20 is formed from sheet metal which extends perpendicularly from the edge 23 of web 12 outwardly to a reverse fold 24 forming inner layer 26 of flange 20. The sheet metal extends from reverse fold 24 back to adjacent the edge 23 of web 12, forming outer layer 28 of flange 20. Outer layer 28 is disposed parallel to inner layer 26 with an internal gap 30 therebetween of about 0.025 inch (0.06 cm) or within a range of abut 1/16 to 1/64 inch (0.04 to 0.16 cm). 
     Inner layer 26 has a plurality of holes 32, each located with an outermost edge 34 spaced substantially inwardly from reverse fold 24, at speed positions of about four inches (10 cm) apart, and of a diameter of about 3/8 inch (1 cm) in a flange 20 width of about 3/4 inch (2 cm). Inner layer 26 also has a plurality of outwardly projecting dimples 36, disposed preferably between the holes 32 and preferably closely adjacent the holes 32. Dimples 36 project away from the internal gap 30, and form a parallel gap 37, to be discussed below relative to FIG. 2. Dimples 36 may be aligned with holes 32 or placed out of line from the line of holes 32, such as between holes 32 and the flange outer edge. 
     Single thickness flange 22 extends from outer layer 28 in the opposite direction from web edge 23 and has a width of about 3/4 inch (2 cm). At the remote edge 38 of single thickness flange 22 there is a reverse fold 40 and a short lip 42 extending back toward web edge 23. In the preferred form, a second internal gap 44 equal to internal gap 30 is provided between lip 42 and flange 22, at spaced portions. Preferably, gap 44 is formed in one inch (3 cm) unpinched sections 43 with two inch (5 cm) tightly pinched section 45 therebetween. 
     Second side 16 has a double thickness flange 46 and a single thickness flange 48. Double thickness flange 46 is formed from sheet metal which extends perpendicularly from the edge 50 of web 12 outwardly to a reverse fold 52 forming inner layer 54 of flange 46. The sheet metal extends from reverse fold 52 back to adjacent the edge 50 of web 12, forming outer layer 56 of flange 46. Outer layer 56 is disposed parallel to and tight against inner layer 54. 
     Single thickness flange 48 extends from outer layer 56 in the opposite direction from web edge 50. Flanges 46 and 48 are each about 3/4 inch (2 cm) wide. At the remote edge 58 of single thickness flange 48 there is a reverse fold 60 and a short lip 62 extending back toward web edge 50. 
     Web 12 has a plurality of small tabs 64 which are cut and folded out of the metal sheet from which web 12 is made. Tabs 64 are folded along folds 66 which extend parallel to flanges 46 and 48. Some of the tabs 64 are bent above 90 degrees out of the plane of web 12 in one direction and some are bent about 90 degrees out of the plane of web 12 in the opposite direction, with preferably every other tab 64 being in the same direction. Thus every other tab 64 is disposed in spaced parallel relation to flange 20, suitable for holding the edge of a one inch (2.5 cm) gypsum board 68 between the tabs 64 and flange 20. The alternate tabs 64 are disposed in spaced parallel relation to flange 22, suitable for holding the edge of another board 68. The forming of the tabs 64 results in forming holes 69 in web 12 which are located between the folds 66 and the stud first side 14. 
     FIGS. 2 to 4 show the boards 68 being held against the inner side of flanges 20 and 22. It will be noted that in both instances the contact of the boards 68 with flanges 20 and 22 is localized along a single narrow area, in the case of flange 20 contact being only along the tips of dimples 36, and in the case of flange 22 contact being only along the tips of unpinched sections 43 of short lip 42. Thus gap 37 and a gap 67 between pinched section 45 and board 68 are formed between most of flanges 20 and 22 and the adjacent boards 68, 68, preferably with opening dimensions of about 1/16 to 1/64 inch (0.04 to 0.16 cm). Also shown is a gypsum wallboard 70 of about 5/8 inch (11/2 cm) affixed by screws 72 to the outer face of flanges 46, 48, forming hollow wall 73. One layer of wallboard 70 or multiple layers may be used, dependent on the degree of fire retardancy sought. 
     The section of wall shown in FIG. 2 also includes a section of floor runner 74. 
     In a fire test, with the fire on the side adjacent the 5/8 inch wallboard 70, thermocouples will be placed on the opposite side of the wall in places likely to increase in temperature fastest. A thermocouple on the outer surface of the stud 10, at flange 20 or 22, will not indicate an increase in temperature as fast as in prior studs due to the novel combination of the dimples 36, the resultant gap 37 and the location of holes 32, opening into gap 37. As the stud starts to increase in temperature, air will rise in gaps 30, 37 and 44 and relatively cooler air will be drawn into gaps 30 and 44 through the bottom of the stud or lower holes 32 or gaps 67 and exhausting through holes 32 or gaps 67 higher up. Also it has been found that steam can be seen exiting from holes 32 and gaps 67 higher up, as a result of the heat of the fire driving off water of hydration in the wallboards 68 and 70. 
     Holes 32, being directed toward gap 37, causes this steam to contact the surfaces surrounding gap 37, preventing these areas from being heated above 212° F. so long as the steam continues to come from holes 32. 
     FIG. 5 shows a modified form of the invention, including a stud 90, in which holes 92 are disposed in the outer layer 28 of flange 20 and dimples 36, in the inner layer 26, form a parallel gap 37 between flange 20 and the adjacent board 68, wherein air that becomes heated will tend to rise, drawing in cooler air, to cool the flange 20 and board 68, when the opposite side of the wall is exposed to fire. 
     Having completed a detailed disclosure of the preferred embodiments of my invention, so that those skilled in the art may practice the same, I contemplate that variations may be made without departing from the essence of the invention.

Summary:
A metal stud, intended for use where the flanges on one side will be left exposed, having such exposed side flanges formed with an overlapped sheet metal portion, including an under flange and an over flange which are spaced apart to allow a cooling air flow therebetween, wherein the under flange includes means for providing a cooling flow of air or gases at the interface of the under flange and an adjacent gypsum board, which means may be a plurality of dimples in the under flange or a combination of dimples and a plurality of spaced apart holes in the under flange.