USRE175E - Ximprovement in truss-frames for brixges - Google Patents

Description

l UNITED STATESl PATENT OFFICE.

WILLIAM HowE, 0F WARREN, MASSACHUSETTS.

l iMPROVEMENT IN TRUSS-FRAMES FOR BRIDGES, 86C,

Specification forming part of Letters Patent No. 1,711, dated August 3, 1840 Reissue No. l 76, dated September 3, 1850.

To all whom it may concern:

Be it known that I, AWILLIAM HowE, of Warren, in the county of Worcester, in the State of Massachusetts, have invented a new and useful Improvement in the Manner of Constructing the Truss-Frames ot' Bridges and other Structures; and I do hereby declare that the following is a full, clear, and exact description of the principle or character which distinguishes it from all other things before known, and of the manner of making, constructing, and using the same, reference being had to the accompanying drawings, making part of this specification, in which- Figure 1 is a side elevation of a trussframe, and Fig. 2 a plan thereof.

The same letters indicate like parts in all the figures.

Prior to the date of my invention the trussframes of bridges were constructed with two sets of timbers-viz., posts and diagonal braces, the posts being seamed at top and bottom to the string-pieces by notching the one into the other, or by bolts passing through Athem horizontally, and with the braces either secured to the string-pieces bearing against bearingpieces or shoes lying in the angles formed by the junction of the posts and string-pieces or chords. From this mode of construction it will be seen that the4 employment of tensionrods could not be very eii'ectual in cambering the frame, as the posts would of necessity prevent the two string-pieces from being drawn nearer to one another, and in such a mode of construction the weight of the posts renders them of necessity less than useless, for they merely act as abutments to resist the thrust of the braces and to connect the upper and lower stringers, the braces having the eiect to keep the strin gers apart and to transfer, by the thrust, the weight applied at any one point along the length of the frame. I have by my improvement avoided these inconveniences and a truss-frame can be cambered with facility along any portion of its length and without weakening the stringers, and these ends I have attained with a less weight of material than byvany other mode of construction with which I am acquainted; and this consists in the employment of straining-blocks-that is, blocks that rest 'on or are slightly let into the upper surface of the bottom and under surface of the upper string-pieceS-a-gainst produced a plan by whichA which abut the ends of the timbers that are interposed between the two stringers to keep them apart, when this is combined with straining-rods that draw them together, thusA employing the interposed timbers to keep the stringers apart and the tensionrods to keep or draw them together, by which arrangement I am enabled to dispense with one set of timbers. The interposed timbers and the tension-rods may be placed at any desired angle with one another.

In the accompanying drawings, a represent s the upper, and a the lower, string-pieces, the parts ot' which each is composed being pnt together in any desired manner. These two stringers are connected together at the ends by vertical posts 2 2, and along the under surface of the top and lthe upper surface of the bottom Stringer is arranged a series of straining-blocks, 1, which are slightly let into these surfaces or otherwise retained in their appropriate places, one at top and one at bottom, for each division of the truss. The

ends of the braces that are interpos d between the two stringers to keep them apart abut against these straining-blocks, and the straining-rods 4, of iron, pass through them from top to bottom of the frame, with a head on one end and a screw-nut on the other, blocks 3 being interposed between the heads and the under surface of the bottom Stringer.

From the foregoing it will be obvious that by turning the screw-nuts on the tensionrods the two stringers will be drawn toward each other and against the ends ofthe braces or timbers interposed between the strainingblocks, so-that any part or the whole'of the frame may be cambered at' any time.

What I claim, therefore, as my invention, and desire to secure by Letters Patent in the construction of truss frames, is-

The method of uniting the upper and lower stringers without att-aching them to the interposed timbers by the combination of the straining-blocks with the timbers interposed for keeping the stringers apart and the tensionrods for drawing them together, substantially as described, whereby the camber can be regulated with facility along the whole or any portion of truss, as descri bed.

Y WILLIAM HOWE. lWitnesses:

ALEX. PORTER BROWNE, GHAS. BRowNE.

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