US2747704A

US2747704A - Nail-receiving beams

Info

Publication number: US2747704A
Application number: US30596A
Authority: US
Inventors: Charles B Gorey
Original assignee: National Steel Corp
Current assignee: National Steel Corp
Priority date: 1948-06-02
Filing date: 1948-06-02
Publication date: 1956-05-29
Anticipated expiration: 1973-05-29

Description

May 29, 1956 c. B. GOREY NAIL-RECEIVING BEAMS 2 Sheets-Sheet 1 Filed June 2, 1948 67.121.17.12 20 INVENTOR. CHARLES B. GOREY.

TORNEY.

I May 29, 1956 Filed June 2. 1948 C. B. GOREY NAIL-RECEIVING BEAMS 2 Sheets-Sheet 2 INVENTOR. CHARLES H. GOREY.

BY!I 2 TTORNEY.

44 V; I A

Unite rates atent 2,747,704 Patented May 29, 1956 NAE-RECEWING BEAMS Charles B. Gorey, Grosse Pointe, Mich, assignor to National Steel Corporation, a corporation of Delaware Application June 2, 1948, Serial No. 30,596

9 Claims. (Cl. 189--37) The present invention relates to metal beams, relating more particularly to beams formed from a single sheet of metal and adapted to receive and retain nails or equivalent fastening elements.

A metal beam adapted to receive and retain nails or the like is required if metal structural members are to replace traditional wooden members. One type of beam previously suggested for this purpose included a pair of channel members arranged with their webs in back-toback relation but spaced apart to provide a nail-receiving groove. Nail deforming means associated with this groove were usually provided in order to retain the nail in place. Rivets and welding have been utilized heretofore as the interconnecting means between the spaced webs but nails driven into the beam close to the points of attachment have damaged the welds or rivets thereby weakening the structure. In addition, the welds or rivets have prevented any spreading apart of the webs. Limited spreading. of this character is most desirable to permit .some give or separation of the webs to take place in response to the considerable force exerted by the nail during its deformation and to care for slight variations in nail size as well as necessary tolerances in manufacturing dimensions. Also, such spreading is desirable because the nail-receiving grooves are preferably somewhat smaller than the nail of proper size so that the nails will be gripped more satisfactorily.

Cover means interconnecting corresponding flanges of the channel members have also been proposed for interconnecting the webs. However, such cover members necessarily extend across the entrances to the nail-receiving groove so that it has been necessary heretofore to provide elongated slots therein. Such slots have seriously weakened the cover members although they have even been made of heavy material; for the narrow transverse tying pieces between the ends of successive slots serve as the only means for holding the beam together. Accordingly, such cover members have proved to be weak points in the beam structure. In addition, they have forced workmen to nail to the beam only where the slots happened to be located, which was inconvenient. When the beam was fabricated from a single sheet of metal, making the cover member integral with the side flanges, lighter gauge metal could be utilized for the entire beam, making the unifying function of the cover members more important. Consequently, the slotring of the cover members still more noticeably weakened the beam.

Co-pending application, Serial No. 15,688, filed March 18, 1948, by J. P. McMahon and B. A. Latulippe, entitled One-Piece Nail-Receiving Beams, now Patent No. 2,670,061 patented Feb. 23, 1954, describes one-piece sheet metal nail-receiving structural members having flange connecting members especially adapted for improvement by the present invention.

It is, therefore, one object of the present invention to provide an imperforate but readily puncturable flange connecting member for a metal beam without weakening 2 or otherwise adversely affecting the flange connecting member or the beam.

It is a further object of the present invention to provide a flange connection member for nailable structural members which is slightly extensible transversely under the action of nail deformation while being of suitable strength to prevent spreading of the parts of the structural memher due to normal stresses.

Another object of the present invention is to provide aflange connecting member in a nailable beam which is extensible transversely, is of suitable strength under normal load conditions and, at the same time, although imperforate, is readily penetrable by the nails.

It is still another object of the invention to provide an inexpensive metal beam of the foregoing general character which is not complicated in structure and which may be fabricated by relatively simple metal forming operations and apparatus such, for example, as a comparatively easy metal rolling procedure.

Other objects and advantages of the invention are in part obvious and will in part appear from a consideration of the following specification and appended claims, reference being had to the accompanying drawings wherein like reference numerals designate corresponding parts throughout the several views and in which:

Figure 1 is an isometric view of a one-piece I-shaped metal beam embodying one form of the invention;

Figure 2 is a view similar to Figure 1 illustrating a modification of the beam shown in Figure l;

Figure 3 is a cross-sectional view of a T-shaped beam comprising another form of the invention;

Figure 4 is a cross-sectional view illustrating still another form of the invention;

Figures 5 to 9, inclusive, are cross-sectional view illustrating various stages in a rolling procedure for forming a beam embodying the present invention; and

Figure 10 is an enlarged detail view of the depression in the metal sheet completed in the stage shown in Figure 6.

In its broader aspects, this invention pertains to a nail-receiving beam which possesses a flange connecting member having a depression provided with a thinned-out portion rendering it readily puncturable by a driven nail. The depression and the thinned-out portion are so con structed and arranged that the depression guides the nail to the desired location for driving it into the beam and the thinned-out portion causes it to enter at that location. The flange connecting members are long, flat strips interconnected by a structural member of angle shape (see

strips

17 and 18 and the angle shape 20, Figures 3 and 10), the change in angle of which supplies the extensibility of the'flange connecting member. This structure constitutes a component of the entire beam. Any tendency of the structural member to spread apart either due to the forces of nail deformation or to the stresses existing when the beam is under load, are applied to this angle element and, due to the leverage effect of the sides of the angle, are concentrated at the vertex 41. It is therefore desirable to prevent the line of material constituting the vertex of this angle element along the length of the beam from being a weak point. At the same time, it is necessary that this line of material be readily penetrable by the points of the nails driven into the beam. It has been found to be a fact that the use of heavy gauge material presents a barrier to nail penetration along this line. Applicant has developed a solution to the problems at this point which involves taking advantage of the phenomenon involved in cold reduction of metals. Decreasing the gauge of the metal along this line by a cold working operation strengthens the metal. Despite this increase in strength of the metal,

Q and contrary to all expectations, the reduction in gauge permits much easier penetration.

Referring to the drawings, and more particularly to Figure l, the beam there illustrated includes a web section shown generally at 9 and including web portions 10 and 11 which are spaced from each other transversely of the beam and which are substantially parallel. The space between the web portions 19 and 11 provides an enclosure or groove 12 for receiving nails or equivalent fastening elements in the manner explained in detail hereinafter. A longitudinally extending side flange projects outwardly from each margin of both webs 10 and 11 so that four

such side flanges

13, 14, 15 and 16 are presented. The

flanges

13 and 14 are oppositely extending and substantially coplanar as are the

flanges

15 and 16. Therefore, the

flanges

13 and 14 comprise a pair of flanges located at one side of the beam while the

flanges

15 and 16 comprise another pair of flanges located at the other side of the beam. Since each of the beams illustrated is formed from a single strip or sheet of metal, the

flanges

13, 14, 15 and 16 are integral with their associated webs 10 or 11 and are turned outwardly therefrom at substantially a right angle.

The

reference numerals

17 and 18 designate connecting or cover members. One of the cover members overlies each pair of flanges in contact with the outer surface thereof and extends across one entrance to the nailreceiving groove or space 12. The cover member 17 is associated with and attaches together the

flanges

13 and 14, while the cover member 18 is associated with and attaches together the

flanges

15 and 16. The connecting or cover

members

17 and 13 comprise reversely bent portions of the metal sheet forming the beam, which sheet is doubled back in supporting relation over a pair of the flanges. Each lateral edge of the cover member 18 is coextensive with and adjoins one of the lateral edges of the

flanges

15 and 16 and is integrally connected thereto as a result of doubling back the metal sheet. The lateral edge of the flange 14 is co-extensive with and adjoins one lateral edge of the cover member 17 and is integrally connected therewith. However, the other lateral edge of the cover 17 comprises one of the free edges of the metal strip from which the beam was formed, the other free edge of the latter comprising the free edge of the flange 13. In order to provide a unitary beam structure, the free edge portion 17a of the cover 17 is folded around the lateral edge portion of the flange 13 in the manner clearly shown on the drawings. it will be noted that the free edge portion of the cover 17 is first folded around the lateral extremity of the flange 13 and is then bent generally right angularly toward the webs 1t and 11, finally terminating inwardly of said lateral extremity. The enfolding portion of the cover member 17 embraces the edge portion of the flange 13 and is pressed against the latter.

Each of the

covers

17 and 18 is provided with a continuous, imperforate, longitudinal depression shown at 19 and 20 forming in effect a component spreadable angular structural element. Each depression has walls contacting both of the inner surfaces of the webs 16 and 11 adjacent the side flanges. The depression 19 is adjacent to the

flanges

13 and 14 while the depression 20 is adjacent to the

flanges

15 and 16. Thus, the

depressions

19 and 20 project into the nail-receiving space or groove 12. Also, the depressions 19 and Zil are medially disposed preferably extending down the longitudinal axis of the beam; preferably, the

depressions

19 and 29 are \.--shaped in crosssection with the apex 41 (Figure 10) of the V extending into the nail-receiving groove or space 12 adjacent one of the pairs of

flanges

13, 14. or 15, 16. Also, the apex 41' of the V preferably lies on the longitudinal center line of the beam and is disposed centrally of the nail-receiving space 12, from side to side.

It will be noted that the

depressions

19 and 20 maintain the webs 10 and 11 in their spaced relation since the depressions extend from the inner wall of one of the webs into contact with the inner Wall of the other web. Thus, the webs cannot come together or approach each other too closely when the beam is loaded. Furthermore, the depression 19 tends to maintain the folded relationship of the cover 17 and the flange 13 because the depression urges the flan e 13 outwardly when the beam is loaded and therefore tends to jam the lateral edge of the flange against the fold of the cover member 17, preventing the embracing fold of the cover member from opening up which is, of course, undesirable. The folded arrangement of the cover member 17 about the flange 13 and the coaction of the depression 19 in maintaining this relation is disclosed in detail and claimed in the application of J. P. McMahon and B. A. Latulippe identified hereinbefore, although this particular structure has been used in connection with the disclosed embodiment of the present invention. Unlike the structure described in the abovementioned application or in beam structures disclosed heretofore, applicant provides a thinned-out portion in the metal forming the depressions 19 and Ztl, and preferably, the bottom or apex 41' of the V-shaped depressions comprise these thinned-out portions.

The

reference numbers

21, 22, 23 and 24 designate laterally extending protuberances formed by bends in the webs 1t) and 11, which protuberances extend longitudinally along the length of the beam. These protuberances are arranged in complementary or mating pairs, one such pair comprising the protuberances 21 and 22, while the other pair comprises the

protuberances

23 and 24. Furthermore, the protuberances of each pair are substantially curvilinearly parallel and, therefore, provide a pair of lateral bends or offsets in the nail-receiving groove or space 12. However, due to the structure and arrangement of the protuberances mentioned, the offsets or bent portions of the groove 12 are substantially the same in width as the remaining portions thereof.

In Figure 2 there is illustrated a modification of the form of the invention shown in Figure 1. The principal difference between the structures shown in Figures 1 and 2 resides in the width or height of the web members 10 and 11. The structure of Figure 2 has a shortened web section 9 and comprises a so-called narrow beam sometimes employed as a stud. Due to the shortened construction of the web members of the form of the invention illustrated in Figure 2, only one pair of curvilinear protuberances 21a and 22a is provided and a single offset is presented in the nail-receiving space 12.

The form of invention particularly illustrated in Figure 3 consists of a T-shaped beam or half-stud. This T-beam possesses a pair of transversely spaced web members or

legs

25 and 26, which are generally similar to the web members 14 and 11. It will be noted that a pair of mating, curvilinear protuberances 21b and 22b is provided in the

web members

25 and 26 presenting an offset in the nail-receiving groove or space 12 in the manner previously described. However, the groove 12 is closed at one side of the beam by a reverse bend 27 which is integral with and interconnects corresponding coextending edges of the web members or

legs

25 and 26.

The structure of the side flanges and of the cover member forming a part of the T-shaped beam illustrated in Figure 3 is like that of the corresponding members of the forms of the invention illustrated in Figures 1 and 2; but only one pair of

side flanges

13 and 14 is provided. Consequently but one cover member 17 is needed. This cover member 17 possesses an edge portion which is folded about the lateral edge of the flange 13 in the way explained in detail hereinbefore. Also, a depression 19 is provided in the cover member 17, which depression projects into the nail-receiving space 12 adjacent the

side flanges

13 and 14. This depression 19 is similar in structure to the depression illustrated in Figures 1 and 2, particularly in that it is generally V-shaped in cross-section and possesses a thinned-out portion at the apex'41' of the V.

Another form of the invention is illustrated in Figure 4. This form of the invention is generally similar to the I-beam of Figure l; but only one web member 28 is provided. The side flanges 13, 14, and 16 are comparable in structure to the corresponding elements in Figure 1 as are the

cover members

17 and 18. Furthermore, each of these cover members is provided with a

depression

19 or 29 which is similar in structure to the depressions previously described, especially in that they are generally V-shaped in cross-section and possess the thinned-out portion mentioned.

The form of the invention illustrated in Figure 4 is fabricated from a single sheet or strip of metal. The

flanges

13 and 15 are first bent generally right angularly outwardly with respect to the web 28. The

covers

17 and 18 are then formed by doubling the metal upon itself in supporting relation so that the cover members are integral with the flanges. The

flanges

14 and 16 are then formed by bending the metal in the direction of the Web 28 and finally, the depending nail-guiding

elements

29 and 30 are formed by right angular bends from the

flanges

14 and 15, respectively. In this form of the invention, the web section 9 comprises the web proper 28 and the nail-guiding

elements

29 and 30. Each head portion includes one

cover member

17 or 18 and the

side flanges

13, 14, 15 or 16 associated with that cover member. A pair of complementary curvilinearly

parallel protuberances

31 and 32 is provided, the protuberance .32 being formed in the nail-guiding element 29, whereas the protuberance 31 is formed in the web 28. Therefore, a nail-receiving space 33 is provided between the nailguiding element 29 and the web 28 and this nail-receiving space possesses a laterally directed offset between the

protuberances

31 and 32 which is similar to those discussed hereinbefore. Similarly, a nail-receiving space 34 between the nail-guiding element 30 and the web 28 is provided, and possesses an offset between the mating

curvilinear protuberances

35 and 36, the formerextending from the web 28 and the latter from the nail-guiding element 30. The nail-guiding

elements

29 and 30 are preferably connected to the web 28 at their inner ends at intervals down the length of the beam to cause them to act as part of the web of the beam. Such connecting means and the

depressions

19 and 20, which extend into the nail-receiving

spaces

33 and 34, respectively, serve to maintain the nail-guiding elements and the web in their properly spaced relationship for preserving effective nail-receiving

spaces

33 and 34 under conditions of use.

In Figures 5 to 9, inclusive, there are illustratedthe principal steps in a preferred rolling procedure for forming the beam illustrated in Figure 2. This beam is formed from a single sheet or strip of metal and, according to the preferred procedure mentioned, three initial steps or passes (not shown) are involved prior to the pass illustrated in Figure 5. In these prior passes, an oifset portion or form 37 is provided in the sheet. A bend 38 is included in the offset 37 and the slightly angled flat

outer portions

39 and 40 are also provided. A bend 41 forming one side of the V-shaped depression 20 is provided by the fourth pass illustrated in Figure 5. In the pass shown in Figure 6 the V-shaped depression is completed and the bend 42 is put in the metal sheet. Suitable rolls, part of which are shown in cross-section in Figures 5 to 9, inclusive, are provided for carrying out the rolling operations or passes mentioned. In Figures 7 and 8, further metal-forming steps are illustrated. In Figure 7, it will be noted that one side 43 of the second V-shaped depression 19 is formed and this depression is completed in the pass shown in Figure 8. Also, the

angled portions

39 and 40 are further formed in the manner clearly illustrated in order to provide parts of the beams' structure as discussed in greater detail hereinafter.

It will be noted that one side of each V-shaped

depression

19 or 20 is first formed by a bending operation and the other side of the depression is thereafter formed in a succeeding pass. During the aforementioned succeeding pass,the bottom portion of the V is thinned out (see Figure 10) by having the metal of the depression squeezed to make the sheet thinner. during the rolling action in;

which the V-shaped depression is completed. Thus, the metal is cold-flowed to provide the thinned V-shaped depression. Metal is not drawn from the

edge portions

39 or 40 to provide the depression, and the bends 42 (Figure 6) and 44 (Figure 8) are instrumental in preventing such drawing. The rolls are, of course, suitably contoured .to squeeze or cold-flow the metal of the depressions in the manner explained.

In Figure 9, there is illustrated an additional step utilized in a rolling procedure for completing the fabrication of the beam shown in Figure 2. As there shown, the portions 42., 4S and 49 are bent inwardly as a unit about the point 45. This process is continued in succeeding passes until the part 42 is brought into engagement with the portion of the sheet adjacent the depression 20. As a result, the last said portion becomes the cover member 18 and the part 42 becomes the side flange 15 with the cover member overlying the flange. During the succeeding passes mentioned, the portion 39 is bent about the point 46 so that the portion 39 becomes the other cover member 17. Also, those portions of the metal sheet to the left of the point 47 (Figure 9) are bent about the point 47 to bring the bend 48 adjacent to the bend 38. Finally, the

bends

48 and 38 lie parallel with each other to form the protuberances 21 and 22, respectively. Preferably, the inner surface of the metal sheet is scored at 45 and 46 to provide a line about which the bending operations mentioned may take place and it is, of course, desirable to provide such a scored line at a pass prior to the one shown in Figure 8. For example, the scoring at 45 may be accomplished at the pass shown in Figure 6 while the scoring at 46 may be accomplished at the pass shown in Figure 7. The free edge 44 of the strip is folded about the free edge 49 to provide the folded relation of the cover 17 and flange 13 to complete the fabrication of the beam.

The cold reduction caused by the roll passes forming the thinned-out portion shown at 41 (Figure 10) coldflows and work hardens the metal of the depressions or component angular

structural elements

19 and 20. Such work hardening of plain carbon sheet steel results in increasing the tensile strength thereof markedly while also rendering the material more puncturable by a nail.

The physical properties of a typical sheet of normal-.

ized plain carbon steel before and after a rolling procedure for cold reducing the sheet are set forth for comparison in the following table:

The percentage elongation in two inches of the above sheet was reduced from about 28% to about 1% by the cold reduction and the work required to puncture it with an eight penny nail was about six foot pounds after such reduction as compared with about twelve foot pounds before the rolling operation.

It will be understood that the particular rolling operation described in detail above is given by way of illustration and not of limitation. The beams illustrated in Figures 1 to 4, inclusive, could be formed by other rolling procedures utilizing appropriately designed rolls and suitable changes in the rolling steps or passes. The sequence of the operations could be altered depending upon the design of the rolls utilized and the type of roiling operations preferred. For instance, an extra pass could be employed between the passes illustrated in Figures 7 and 8 for controlling the dimensions of the thinnedout V-shaped

depressions

19 and 20 and for restriking them to further work harden or coin them if necessary or desirable. Also, the depression 20 could be restruck at the pass shown in Figure 7 and the depression 19 could be restruck at the pass shown in Figure 9. Of course, the rolls should be suitable for thinning out the metal of the V-shaped depressions and, if rolling is not employed, such thinned-out portions should be formed by an operation effective for cold reducing the metal to work harden it in order to gain the advantages of such work hardening.

The operation of a beam embodying the present invention is simple and effective for the purpose of receiving and retaining nails and the like. At the same time, distinct advantages are secured over former beams intended for such purposes. in the first place, the

cover members

19 or 26 are stronger but are more readily puncturable due to the work hardening mentioned above and, therefore, more effectively resist excessive spreading of the webs; secondly, a nail may be placed anywhere in the depressions 19 or and is guided by the sloping walls of the depression to the line of juncture between such walls; that is, to the bottom of the depression. Since the bottom of the depression is thinned-out, the nail may be readily driven through the cover member at this point. Furthermore, the bottom of the depression not only is thinned-out but is disposed along the longitudinal center line of the beam and substantially centrally of the nail-receiving space or groove 12. Accordingly, the nail enters the beam at its center and also enters at the center of the nail-receiving groove. Consequently, the workman does not have to place the nail carefully in an aperture or slot and does not have to locate it centrally of the

depressions

19 or 20. He merely has to locate a depression and place the nail in it in order to drive the nail into the beam at the proper point.

In addition to causing the nail to enter the beam at the desired location, putting the thinned-out portion of each of the depressions 19 and 2%) at the apex 41' of its V- shaped configuration has other advantages. It permits the V-shaped depression to be formed in the metal initially without a thinned-out portion. Subsequently, the metal may be put through a roll pass for thinning out the point 41; but such a procedure would not be satisfactory, as a practical matter, unless the thinned-out portion were located at the apex 41'. Thus, the fact that the preferred location of the thinned-out portion is the apex 41 makes this procedure a feasible one. Also, it would be possible to provide the thinned-out portion initially by rolling or otherwise forming an attenuated linear thin part in a flat sheet or in a flat portion of a partially fabricated beam. In this event, the V-shaped

depressions

19 and 20 could be formed by subsequently bending the metal about the longitudinal axis of the linear thin part mentioned to produce sloping walls on each side thereof which, of course, provides a V-shaped depression having a point 41 which is thinned-out. Naturally, the bending operations required to provide a V-shaped depression by the lastmentioned procedure is facilitated by the initially formed thinned-out linear part; for the latter not only constitutes an effective line about which the metal may be bent but, at the same time, locates the thinned-out part of the resulting V-shaped depression at the point 41" thereof, as desired. It will be understood that the thinning of the metal sheet, no matter how or at what stage of the proceedings it is carried out, should be efleeted by some metal working operation resulting in work hardening the material, although applicants rolling procedure comprises a preferred way of so thinning out the sheet.

I claim:

1. An elongated structural member formed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising a web section including spaced substantially parallel nail guiding elements providing a nail receiving slot therebetween, the nail guiding elements extending substantially throughout the length of the structural member and including marginal portions forming an elongated longitudinally extending entry throat for the nail receiving slot, a pair of outwardiy extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of the nail guiding elements, the side flanges being substantially perpendicular to the nail guiding elements and extending substantially throughout the length of the structural member, a continuous cover member overlying the pair of coplanar flanges and being connected to the outer longitudinal edges of the coplanar flanges and extending substantially throughout their length, and a medially positioned continuous longitudinal imperforate depression in the cover member coextensive with the entry throat of the nail receiving slot, the depression being V-shaped in cross-section with its apex extending into the entry throat, the apex of the depression being relatively thinner than the remaining portions of the depression to render the cover member at the apex of the depression readily puncturable by a driven nail and the metal of the apex being cold-worked to increase its tensile strength by an amount sufficient to offset the decrease in strength of the apex due to the thinning thereof.

2. An elongated structural beam formed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising a web section including spaced substantially parallel nail guiding elements providing a nail receiving slot therebetween, the nail guiding elements extending substantially throughout the length of the beam and including marginal portions forming an elongated longitudinally extending entry throat for the nail receiving slot, a pair of outwardly extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of the nail guiding elements, the side flanges being substantially perpendicular to the nail guiding elements and extending substantially throughout the length of the beam, a continuous cover member overlying the pair of coplanar flanges and being connected to the outer longitudinal edges of the coplanar flanges and extending substantially throughout their length, and a medially positioned continuous longitudinal imperforate depression in the cover member coextensive with the entry throat of the nail receiving slot, the depression being V-shaped in cross-section with its apex extending into the entry throat and lying substantially on the longitudinal center of the beam, the metal of the apex of the depression being cold-worked and thinned so that the metal of the apex of the depression is relatively thinner than the metal of the other portions of the depression to render the cover member at the apex readily puncturable by a driven nail and so that the metal of the apex of the depression has increased tensile strength sufficient to offset the decrease in strength of the apex due to the thinning thereof.

3. An elongated structural member formed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising a web section including spaced substantially parallel nail guiding elements providing a nail receiving slot therebetween, nail-deforming means forming a part of the nail guiding elements for bending a nail received in the nail receiving slot, the nail guiding elements extending substantially throughout the length of the structural member and including marginal portions forming an elongated longitudinal extending entry throat for the nail receiving slot, a pair of outwardly extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of the nail' guiding elements, the side flanges being substantially perpendicular to the nail guiding elements and extending substantially throughout the length of the structural member, a continuous cover member overlying the pair of coplanar flanges and being connected to the outer longitudinal edges of the coplanar flanges and extending substantially throughout their length, and a medially positioned continuous longitudinal imperforate depression in the cover member coextensive with the entry throat of the nail receiving slot, the depression being V-shaped in cross-section with its apex extending into the entry throat, the apex of the depression being relatively thinner than the other portions of the depression to render the cover member at the apex readily puncturable by a driven nail and the metal of the apex of the depression being coldworked to increase its tensile strength by an amount sufficient to oflset the decrease in strength of the apex due to the thinning thereof.

4. An elongated beam formed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising a web section including spaced substantially parallel nail guiding elements providing a nail receiving slot therebetween, nail-deforming means forming a part of the nail guiding elements for bending'a nail received in the nail-receiving slot, the nail guiding elements extending substantially throughout the length of the beam and including marginal portions forming an elongated longitudinally extending entry throat for the nail receiving slot, a pair of outwardly extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of the nail guiding elements, the side flanges being substantially perpendicular to the nail guiding elements and extending substantially throughout the length of the beam, a continuous cover member overlying the pair of coplanar flanges and being connected to the outer longitudinal edges of the coplanar flanges and extending substantially throughout their length, and a medially positioned continuous longitudinal impeiforate depression in the cover member coextensive with the entry throat of the nail receiving slot, the depression being V-shaped in cross-section with its apex extending into the entry throat and lying substantially on the longitudinal center of the beam, the metal of the apex of the depression being cold-worked and thinned so that the metal of the apex of the depression is relatively thinner than the metal of the other portions of the depression to render the cover member at the apex readily puncturable by a driven nail and so that the metal of the apex of the depression is of increased tensile strength suflicient to oifset the decrease in strength of the apex due to the thinning thereof.

5. A beam formed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising a web section including a pair of spaced substantially parallel nail guiding elements providing a nail receiving slot therebetween, the nail guiding elements extending substantially throughout the length of the beam and including marginal portions forming an elongated longitudinally extending nail receiving slot entry throat at each end of the web section, a pair of outwardly extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of the nail guiding elements at each end of the web section, the side flanges being substantially parallel to the nail guiding elements and extending substantially throughout the length of the beam, a continuous cover member overlying each pair of coplanar side flanges and being connected to the outer longitudinal edges of the coplanar flanges and extending substantially throughout their length, and a medially positioned longitudinal imperforate depression in each of the cover members coextensive with the entry throat of a nail receiving slot, the depression being V-shaped in crosssection with its apex extending into an entry throat, the apex of the depression being relatively thinner than the remaining portions of the depression to render the cover member at the apex of the depression readily puncturable by a driven nail and the metal of the apex being coldworked to increase its tensile strength by an amount sufficient to offset the decrease in strength of the apex due to the thinning thereof.

6. An I-beam constructed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail and comprising a pair of 'beam sections each including a web portion and marginal side flanges substantially perpendicular to the web portion, the beam sections being disposed with the web portions in spaced. parallel back-to-back relation and presenting a space be-- tween the web portions dimensioned to provide a nail-- receiving groove, the metal at the juncture of the side flanges and the web portions forming an entry throat for the nail receiving groove, the side flanges being arranged. in pairs with the flanges of each pair being coplanar and extending outwardly from opposite sides of the nailreceiving groove, a cover plate overlying each pair of side flanges and being connected to the outer longitudinal edge of the side flanges and extending substantially throughout their length, and a medially positioned longitudinal imperforate depression in each cover plate, the depression being V-shaped in cross-section with its apex extending into an entry throat, the apex of the depres-- sion being relatively thinner than the other portions of the depression to render the cover plate at the apex readily puncturable by a driven nail and the metal of the apex of the depression being cold-worked to increase its metal of such thickness as to be not readly puncturable by a driven nail and comprising a pair of beam sections each including a web portion and marginal side flanges substantially perpendicular to the web portion, the beam sections being disposed with the web portions in spaced parallel back-to-back relation presenting a space between the web portions dimensioned to provide a nail-receiving groove, the metal at the juncture of the side flange and the web portions forming an entry throat for the nailreceiving groove, transversely extending rounded protuberances in the web portions arranged in substantially curvilinearparalle'l paths presenting nail-deforming means in the nail-receiving groove, the side flanges being arranged in pairs with the flanges of each pair being coplanar and extending outwardly from opposite sides of the nail-receiving groove, a cover plate overlying each pair of side flanges and being connected to the outer longitudinal edge of the side flanges and extending substantially throughout their length, and a medially positioned longitudinal imperfo-rate depression in each cover plate, each depression being V-shaped in cross-section with its apex extending into an entry throat, the apex of each depression being relatively thinner than the other portions of the depression to render the cover plate at the apex readily puncturable by a driven nail and the metal at the apex of the depression being cold-worked to increase its tensile strength by an amount suflicient to offset the decrease in strength of the apex due'to the thinning thereof.

8. A generally T-shaped beam constructed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising a pair of substantially parallel web members spaced apart to provide a nail-receiving groove therebetween, the parallel web members extending substantially throughout the length of the structural member and including marginal portions forming an elongated longitudinally extending entry throat for the nail-receiving groove, a pair of outwardly extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of the Web members, the side flanges being substantially perpendicular to the web members and extending substantially throughout the length of the beam, a continuous,

cover member overlying the pair of coplanar flanges and being connected to the outer longitudinal edges of the coplanar flanges and extending substantially throughout their length, and a medially positioned continuous longitudinal imperforate depression in the cover member coextensive therewith and lying along the entry throat of the nail receiving groove, the depression being V-shaped in cross-section with its apex extending into the entry throat, the apex of the depression being relatively thinner than the other portions of the depression to render the cover member at the apex readily puncturable by a driven nail and the metal of the apex of the depression being cold-worked to increase its tensile strength by an amount suflicient to ofiset the decrease in strength of the apex due to the thinning thereof.

9. An l-shaped elongated beam formed from a single piece of sheet metal of such thickness as to be not readily puncturable by a driven nail comprising two pairs of spaced substantially parallel nail guiding elements each providing a nail-receiving slot therebetween, web means joining the pairs of nail guiding elements, each of the nail guiding elements extending substantially throughout the length of the beam and including marginal portions forming an elongated longitudinally extending entry throat for its nail-receiving slot, a pair of outwardly extending coplanar side flanges having inner longitudinal edges joined to the marginal portions of each pair of nail guiding elements, the coplanar side flanges being substantially perpendicular to the nail guiding elements and extending substantially throughout the length of the beam, a continuous cover member overlying each pair of coplanar side flanges and connected to the outer longitudinal edges of respective coplanar flanges and extending substantially throughout their length, and a medially positioned longitudinal imperforate depression in each of the cover members coextensive therewith and lying along the entry throats of the nail receiving slots, the depression in each of the cover members being V-shaped in crossseetion with its apex extending into an entry throat and lying substantially along the longitudinal axis of the beam, the apex of each depression being relatively thinner than the other portions of the depression to render the cover member at its apex readily puncturable by a driven nail and the apex of each depression being cold-Worked to increase its tensile strength by an amount suflicient to oftset the decrease in strength of the apex due to the thinning thereof.

References Cited in the file of this patent UNITED STATES PATENTS 515,270 Zimmerman et al. Feb. 20, 1894 522,875 Bowler July 10, 1894 1,090,171 Schisler Mar. 17, 1914 1,211 1,955 Day Nov. 14, 1916 1,253,216 Day Jan. 15, 1918 1,898,925 Anderson Feb. 21, 1933 2,118,499 Durbin May 24, 1938 2,384,849 Pieri et al. Sept. 18, 1945 2,421,446 Wallis et a1. June 3, 1947 2,425,798 Hall Aug. 19, 1947 2,457,147 Hall Dec. 28, 1948 FOREIGN PATENTS 743,672 France Jan. 16, 1933