P. T. LARGE.

REINFO G BAR FOR oouonmn CONSTRUCTION.

LIGATION FILED APR. 5. 1907.

93 1 ,320. Patented Aug. 17, 1909.

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NORTH TONAWANDA, NEW YORK, ASSIGNOR TO BUFFALO STEEL COMPANY, OF TONAWANDA, NEW YORK.

REINFORCING-ZBAR FOR CGNCRETE CONSTRUCTION.

Specification of Letters Patent.

' Patentedhug. 17, 1909.-

Application filed April 5; 1907. Serial No. 366,515.

- and State of New York, have invented a new and'nseful Improvement in Reinforcing- Bars for Concrete Construction, of whichthe following is a specification.

This invent-ion relates to improvement-s in reinforcing bars for concrete construe tion,'and more particularly to that class of bars which are commonly known as twisted bars.

Twisted bars of square crosssection have long been used, The corners of these bars form sharp helical edges which wind' about the bar while the sides or surfaces of the bar between the corners remain fiat. It has been found that these sharp or wedge-like helical edges and the intervening flat surfaces do not form a firm and continuous union with the concrete when embedded therein for the reason that the concrete tends to shrink away from the flat surfaces and. the sharp corners vor edges of the bar tend to cleave the concrete, causing it to crack.

"he object of this invention is toovercome these objections byconstructing a twisted reinforcing bar provided with helical ribs or ridges having broad or rounded peaks instead of sharp or wedge-like edges, and in. which there are no flat sides or surfaces between the ridges. Such a bar, when en'ibedd'ed in the concrete, forms ainore intiinate and continuous union therewith and does not tendlto cleave the concrete nor perinit any movementthereof independent of the bar. Moreover, in twisting square bars, the corners of the bar which. form the helical.

ridges, being a greater distance from the length of the bar as is desirable for the best results." Around bar, on the other hand, owing to the uniform distance of all parts of the surface metal from its center, can be twisted to a much greater degree without rupturing such surface metal. It is, therefore, a further object of this invention to employ in the place of the twisted square bars heretofore used, a twisted round bar provided with suitable helical ribs or ridges. Inasmuch as the twisting of such a round bar does nottend to diminish its strength and-as it has no sharp edges or corners to be ruptured thereby, the bar can be twisted to the extent necessary to give the desired angle or pitch to the helical ridges.

lnthe accompanying drawings: Figure 1 represents a perspective view of a section of' a reinforcing-bar embodying the invention. Fig. 2 is a cross-section of the same. Fig. 3 is a perspective view of the bar before the same is twisted. Fig. 4 is a cross-section of atwisted barof slightly modified form.

Like letters of reference refer to like parts in the several figures.

A represents a reinforcing bar which is round in cr0ss-sect-ion,-as will appearfrom Fig. 2, and is provided at suitable intervals upon its surface'with helicalribs or ridges a a separated by convex portions a a of such surface. The ribs or ridges, shown in Figs. 13, are substantially semicircular in cross-section, which is preferable, but they could also be of somewhat different cross sectional shape, for instance, as shown in Fig. 41-, in which the edges are of substantially rectangular cross-section. The ridges .in both bars have broad and'niore or less flat peaks ascontradistinguished from 1' rp or wedge-like peaks. In the drawing our of these ribs or ridges are shown, but it is obvious that a greater or less number could be used, dependingupon the size of the-bar and the nature of the work for which it is intended. In making these bars, the bar with the straight longitudinal ribs or ridges, shown in Fig. 3, is produced by rolling be- ;t-wecn suitable rolls forming'a pass of a shape corresponding to the cross-sectional shape of the bar. This bar is then twisted, preferably while hot, in a. well known main ner. By thus rolling the bar in a substantially circular pass it acepii-rcs the additional strength and elasticity of a round bar, and by forming the ribs therein in the same operation the bar with its ribs can be produced cheaply as the common square bar.

The sides or surfaces 0. a ofthe bar be tween the ribs instead of being flat, as in twisted square bars, are convexed. As the concrete will the more firmly adhere to such convexed surfaces, a close union between the its'len th; the said bar being otherwise free bar and the concrete is thus obtained. of surface irregularities, every eripheral I claim as my invention i portion of the bar being substantia 1y convex.

A reinforcing bar for concrete which com- Witness my hand, this 29th day of March, 5 prises a round bar having a plurality of 1907/ y longitudinal ribs of uniform cross-section PRESTON T LARGE spaced about the bar, said bar being subsequently twisted, whereby said ribs are made ,Witnesses:

to extend'continuously and in the same di- J. G. Josnrii, 10 i'ection, helically of the bar and throughout FRED R. LARGE.