US2034380A

US2034380A - Car roof

Info

Publication number: US2034380A
Application number: US33042A
Authority: US
Inventors: Bonsall Charles David
Original assignee: PH Murphy Co
Current assignee: PH Murphy Co
Priority date: 1935-07-25
Filing date: 1935-07-25
Publication date: 1936-03-17
Anticipated expiration: 1953-03-17

Description

March 1936. Q DBONSALL 2,034,380

CAR ROOF Filed July 25, 1935 2 Sheets-Sheet l l T l I I i l A NVE/V702:

.xi/5 rrokuens.

arch w36 c. D. BONSALL 2,034,380

CAR ROOF Filed July 25, 1955 2 Sheecs-Sheel 2 f/LS HTTOR/VEYS.

Patented Mar. 17, 1936 STAEES PATENT @Fii CAR ROOF Application July 25, 1935, Serial No. 33,042

Claims.

This invention relates to car roofs of the type wherein metal roof sheets are secured to metal carlines whose ends rest on the side plates of the car. Such carlines act as beams and hereto- 5 fore it has been the practice to make them by rolling or by pressing homogeneous metal sheets into a cross-sectional and area that will enable them to carry their vertical load. It has been the practice to design such carlines so that the neutral axis thereof is midway between the top and botto-ir thereof and to rivet theretothe overlapping margins of the roof sheets resting thereon. The object oi the present invention is to provide a car roof wherein much lighter carlines can be used than have heretofore been used in roofs ci the same strength. 'TheV invention consists principally in securing the sheets to the carlines by welds of metal of high compressive strength, the cross-section of the carline and of the weld metal being such that the neutral axis of the structure is below the geometrical center lines oi the carlines and the unit fiber stress on the weld metal is higher than the unit ber stress at the bottom of the carlines; It also consists in the carlines and in the combinations of parts hereinafter described and claimed.

In the accompanying drawings, wherein like reference numerals refer to like parts wherever they occur,

Fig. l is a plan view of apart of a car roof embodying my invention, with parts oi the roof sheets broken away,

Fig. 2 is a cross-sectional View on the line 2 2 of Fig. l,

Fig. 3 is a sectional View longitudinally of the roof but crosswise oi the carline on the line 3-3 of Fig. i,

Figs. i and la sectional views showing an old construction in comparison with the present invention, with numerical data for the comparison, and

Figs. 5 and 5a, G and 6a, 7 and 7a., 8 and 8a., 9 and 9a, and i@ losy are comparative views, the vertically alined views at the left illustrating old types of carlines and sheets and the vertically alined views at the right showing the manner of modifying them coniormabiy to my invention.

According to the present invention, the car roof comprises metal carlines l whose ends rest upon and are secured to the side plates 2 oi the car. Metal roof sheets 3 extend from side plate to side plate with their margins overlapping the carlines but with the margins of adjacent sheets spaced apart. The sheets are secured to the carlines by welds 4 of alloy steel or other metal of (Cl. 10S-5) high compressive strength that ll the spaces between adjacent sheets.

My oarline is so designed that the neutral axis thereof is considerably below vthe geometrical center line of the carline; in fact, it is so far below such geometrical center line that, although the neutral axis of the assembled structure is raised by the metal of the weld and marginal portions of the roof sheets, such neutral axis will still be below the geometricai center line of the carline. By this arrangement, the unit iiber stress on the weld metal is considerably higher than the unit fiber stress on the lower portion of the carline. Accordingly the strength of the structure may be increased even though its weight is decreased, as will appear from the comparison oi a specic example of the old construction illustrated in Fig, 4 with the new construction illustrated in Fig. 4a.

Fig. 4 represents an A. R. A. standard carline la made of a sheet of low carbon steel, of a compressive strength of about 25,009 pounds per square inch, and of a thickness of of an inch, pressed into the form of an inverted channel with an overall depth oi 3 inches, an inside width of 11/2 inches and with side flanges da which are 3A, of an inch wide and extend outwardly at the bottom of the carline. Roof sheets of an inch thick overlap each other 3A, of an inch and are secured by rivets 6 through such iap to the carline. In the new construction illustrated in Fig. 4a, the overall depth or" the cariine i and the interior width of the channel are the same as before, namely, 3 inches in depth and 11/2 inches sheet of low carbon steel only 1/8 oi an inch in thickness and its side franges t are eachl%,inches wide. The roof sheets are of the same thickness as before but, instead lapping, they are spaced l inch apart and the space is illed with a weld or" alloy steel having a compressive strength of about 90,000 pounds per square inch. From the dimensions stated it ioliovs that the cross sectional area and consequently the weight of the new carline construction, including the weld and one-quarter inch of the adjacent roof sheets, is 24 percent less than the corresponding parts of the old construction.

Further comparing the design of Figs. 4 and 4a, it is noted that although the neutral axis of the old carline alone shown in Fig. 4 is midway between the top and the bottom thereof, that is, 1.5 inches below its upper surface, the neutral axis is raised by the riveting of the sheets to the carline to a point that is only 1.3672 inches below Ybelow the upper surface of the top sheet.

the top surface of the carline or 1.5547 inches On the other hand, the neutral axis of the assembly incorporating the carline illustrated in Fig. 4a is 1.5271 inches below the top surface. It follows that the section modulus of the old construction of Fig. 4 is 1.2910 and that the section modulus of the new construction of Fig. 4a is 1.0428, which is 19.4 percent less than in the old construction. It follows that, for the same load, the stress in the compression region of the new construction is 19.4 percent higher than in the old construction, but such increased stress is well within the capacity of the weld metal.

Summarizing the comparison of the old construction of Fig. 4 with the new construction of Fig. 4a., the new construction is 24.4 percent lighter and 24 percent stronger than the old.

While I have described my invention as applied to carlines of inverted channel shape, it is equally applicable to carlines of other shapes. Heretofore, it has been the practice to design such carlines with their upper and lower chords of equal cross-sectional area and consequently with their neutral axes midway between the top and bottom thereof. According to the present invention, the cross-sectional area of the lowerV chord is considerably larger than that of the upper chord and the neutral axis of the new carline is so far below the geometrical center line thereof that, if the weld metal of high compressive strength is applied to the top thereof, the neutral aXis of the assembly will still be low enough to put such weld metal under greater unit stress than would be practicable with metal of less compressive strength. For instance, Fig. 5 represents a riveted construction using a Z- shaped carline A of pressed metal of even thickness and with its upper and lower flanges or chords of even width; in comparison therewith in Fig. 5a is shown my welded construction that uses a lighter Z-shaped carline A whose lower flange is widened out to increase the cross-sectional area thereof and thereby lower its neutral axis.

In Fig. 6, an old rolled metal carline B of Z- shape section is shown in comparison with a new lighter roller carline B (Fig. 6a) of Z-shape section whose lower iiange or chord is of greater thickness than in the old section.

Fig. 7 compares an old inverted Channel shaped Vcarline C with a new inverted channel shaped carline C (Fig. 7a) of lighter weight but with thick bottom ilanges.

Fig. 8a illustrates the invention as applied to channel shaped carlines D with lateral top flanges, the new carline D being of less total weight than the old carline of Fig. 8 and of uniform thickness but the bottom thereof being wider than in the old construction.

Fig. 9 sho-ws an old pressed metal carline E consisting of a Vertical web portion and top and bottom anges of equal width in comparison with the lighter new carline E (Fig. 9a) of similar shape but with its bottom flange considerably widened.

Fig. 10 illustrates a rolled carline F of channel shape set with its web vertical in comparison with a lighter rolled carline F' (Fig. 10a) of similar shape except that the lower flange or chord thereof is considerably thickened.

What I claim is:

Y1. A car roof comprising metal carlines that have an upper chord and a lower chord and a vertical web connecting said chords, roof sheets with their side margins spaced apart and resting on the carlines, and welds of metal of high'compression strength uniting adjacent sheets to the underlying carline, the total cross-sectional area of the metal in the lower chord of the carline being substantially greater than the sum of the area of the metal in the upper chord thereof plus the area of the weld, whereby the unit stress on the weld metal is more than the unit stress on the metal in the lower chord.

2. A car roof comprising inverted channel shaped carlines with wide lateral flanges of greater sectional area than the tops of the carlines, roof sheets with their side margins spaced apart and resting on the carlines, and welds of metal of high compression strength uniting adjacent sheets together and to the underlying carline, the total cross-sectional area of the metal in the flanges of a carline being substantially greater than the sum of the area of the metal in the top thereof plus the area of the weld, whereby the unit stress on the weld metal is more than the unit stress on the ange metal.

3. A car roof comprising pressed metal carlines, roof sheets with their side margins spaced apart and resting on the carlines, and welds of metal of high compression strength uniting adjacent sheets together and to the underlying carline, the total cross-sectional area of the metal in the lower chord of a carline being substantially greater than the sum of the area of the metal in the top thereof plus the area of the Weld, whereby the unit stress on the weld metal is more than the unit stress on the metal of the lower chord.

4. A car roof comprising Z-shaped carlines, roof sheets with their side margins spaced apart and resting on the carlines, and welds of metal of high compression strength uniting adjacent sheets together and to the underlying carline, the total cross-sectional area of the metal in the lower chord of a carline being substantially greater than the sum of the area of the metal in the top thereof plus the area of the weld, whereby the unit stress on the weld metal is more than the unit stress on the metal of the lower chord.

5. A car roof comprising pressed metal carlines that have an upper chord and a lower chord that is considerably wider than the upper chord and a vertical web connecting said chords, roof sheets with their side margins spaced apart and resting on the carlines, and welds of metal of high compression strength uniting adjacent sheets to the underlying carline, the total crosssectional area of the metal in the lower chord of the carline being substantially greater than the sum of the area of the metal in the upper chord thereof plus the area of the weld, ywhereby the unit stress on the weld metal is more than the unit stress on the metal in the lower chord.

CHARLES DAVID BONSALL.

CAD