US20987A - Bearing-block osi tbuss-bridges - Google Patents

Description

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ALBERT D. BRIGGS, OF SPRINGFIELD, MASSACHUSETTS.

BEARING-BLOCK 0F TRUSS-BRIDGES.

Ressued September l2, 1865, No. 2,070.

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.Be it known that I, ALBERT D. Braces, of Springfield, in the county of Hampden and State of Massachusetts, have invented cer tain new and useful Improvements in Truss- Frames Jfor Bridges and other Structures; and I do hereby declare that the following is a full, clear, and exact description ot' the same, reference being had to the accompanying drawings, making part of this specification, in which- Figure l is a side elevation of a truss frame, constructed according to my invention. Fig. 2 is a side view of a section of the same on an enlarged scale. Fig. 3 is a perspective View of a section of the same truss frame. Fig. i is a perspective view of part of the lower chord or stringer showing the manner of placing packing keys or blocks between the chord-sticks and between the bearing blocks of the braces, which constitute one part of my invention.

Similar letters of reference indicate corresponding parts in the several figures.

This invention consists in a certain method of increasing the bearing surface for the bearing blocks against which the braces abut in truss frames.

To enable others skilled in the art to use my invention, I will proceed to describe the manner in which it is applied to practice.

A, A, is the top chord or Stringer, and B B, the bottom chord or Stringer; these I usually make each of three or more pieces or sticks of timber, which sticks are kept apart by means of keys c, c, which pass vertically through the openings in the chords,1 into which they are notched for the purpose of keeping the chord sticks from slipping past each other. Upon the upper side of the bottom chord and the under side of the top are placed bearing blocks or angle pieces (Z, (Z, against which the main braces Zr, Zr, which are arranged in pairs, and the counter braces z', c', which are arranged singly, abut. These braces forming the panels of the bridge are so arranged that the bearing blocks (Z, (Z, of the top chord are in vertical planes which pass through or 'near the centers of the spaces between the bearing blocks of the bottom chord, and that the bearing blocks of the bottom chord are in vertical planes which pass through or near the centers of the spaces between the bearing blocks of the bottom chord, which makes the panels of or nearly of the form of a series of isosceles triangles. The tension rods f, f, by which the straining up of the frame is effected and regulated are double, having the counter braces z', i, arranged between them. These rods are screwed at each end, and tted with nuts, and they pass through the bearing blocks (Z, (Z, and through the bearing keys, (which will be presently described,) and through bearing blocks or angle pieces c, e, above the top and below the bottom chord, and their nuts are screwed up against the outside bearing blocks or angle pieces e, e, as shown at s, s, in Figs. l, 2 and 3. Between each pair of main braces 7c, Za, (excepting the end pairs where it is not necessary), there is a counter tension rod o, 0, which, like the tension rods f, f, pass through the bearing blocks (Z, and e, and are screwed at their ends and tted with nuts which screw up against the outer bearing blocks c, e, as represented at m, m, in Figs. l and 2. When the tension rods f, f, are screwed np with the braces 7c, 7u, and counterbraces z', z', in their proper places to keep the chords apart, and the counter tension rods o, o, tightened up to prevent vertical vibration, a truss frame is formed which cannot be materially affected by the passing of a variable load which is within its capacity to sustain.

The method of increasing the bearing surface for the bearing blocks (Z, and e, is as follows: I make the said bearing blocks to eX- tend beyond the sides of the chords, as shown at g, g, in Figs. 3 and t, and between the corresponding bearing blocks (Z, e, (Z, e, of each chord I fit blocks Zi, L, and blocks or keys c, c, of hard wood to keep the bearing blocks apart and prevent the crushing of the chord timbers by the screwing up of the nuts of the tension rods; the blocks Zt, ZL, being placed between the ends of the bearing blocks, which extend beyond the sides of the chords, and a block or key c, beingfitted tightly into each opening between the chord sticks. The tension rods f, f, pass through the above described blocks 0', c. The bearing blocks e, e, of the lower chord, with the exception of those at the ends of thel frame,

-are held up to their places by the tension and counter tension rods, but the bearing blocks next the ends of the frame are supported by the holsters or corbels n, n, which project laterally beyond the sides of the chord sticks for the purpose of sustaining the blocks h, h, at the points of bearing over the abutments and piers.

The wooden blocks c', c, and h, h, are intended to have substantially the same effect as the metallic sockets which constitute part of the subject of Wm. Howes patent, of 1846, viz, to prevent the crushing of the soft timber of the chords by the bearing blocks; but the said blocks c, c', and h, 7L, are also intended to ob-viate some of the objections to the use of the said metallic sockets, which may be briefly enumerated as ollowsz-lst, the cost of the heavy cast iron bearing blocks with the sockets attached; 2nd, the liability to breakage; 3rd, the socket must be of a certain length, and as the timber is usually framed in an unseasoned state, the chords must in framing therefore be left so deep that they will when seasoned correspond with the depth of the socket, or 'if they are out to the depth of the socket when framed, the timber shrinks away from the casting, and leaves a loose joint which is prejudicial to the durability of the structure. My method of providing for a bearing surface for the blocks d, e, by the employment of the blocks h, h, and c', c', obviates all the above difculties, and said blocks serve to keep the bearing blocks from crushing the chords in a manner ar more effective than the iron sockets, as the blocks c, c, can be fitted tightly between the chord sticks while the truss is being framed; and by making said blocks c', o', entirely fill up the spaces between the chord sticks, and providing blocks h, h, outside of the chords a very much greater amount of bearing surface for the bearing blocks cl, e, is obtained than is provided for by the cast iron sockets; and it is this characteristic that constitutes the important feature of this part of my invent-ion, and makes it not merely a substitute of wood for iron.

I do not claim, separately, any of the parts of the truss Jframe, but

What I claim as my invention and desire to secure by Letters Patent, is

The method of increasing the bearing surfaces for the bearing blocks d, d, e, e, by the employment of the combination of blocks or keys c', c', and blocks 71 h; the former being tightly litted between the chord sticks and the said bearing blocks, and the latter between the ends of said bearing blocks, outside ot the chord sticks, substantially as described.

ALBERT D. BRIGGS.

Witnesses R. F. HAwKINs, J. B. HARRIS.

[FIRST PRINTED 1911.]

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