US56777A - Improvement in bridges - Google Patents

Description

N.PETERS. PHDTOAUTHUGRAPHER. WASHINGTON. D c,

PATENT CEEICE.

DAvID A. MITCHELL, oE cEIIcAeo, ILLInoIs.

IMPROVEM ENT IN BRIDGES.

Specication forming part of Letters Patent No. 56,777, dated July 31, 1866..

To all/whom 'it may concern Be it known that I, DAVID A. MI'rcIIELL, of Chicago, in the county of Cook, State of Illinois, have invented certain new and useful Improvements in the Construction and Mode of Operating Draws for Railroad and other Bridges; and I do hereby declare that the following is afull, clear, and exact description of the same, reference being had to the accompanying drawings, makingV a part of this speci ication, in which- Figure 1 represents a side view or elevation of the bridgestructure. Fig. 2 shows a sectional end View of the towers, the bridge, suspended draw, the truck, and supporting-braces. Fig. 3 is a broken-off section, showing a plan of the suspension frame work and collarbraces. Fig. 4 shows 'an enlarged end view of one of the collar-braces. Fig. 5 shows the top view of a movable track for connecting the draw with the stationary track. Fig. 6 represents a side view of a broken-off section, the draw passing underl the arch of the tower. Fig. 7 shows an end view of the frame-work which supports the draw whenopen. Fig. 8 is a broken-off section of a side view with the cables in the framework underneath the railway-track for the truck. Fig. 9 shows an end View of the mode of bracing the framework when the trucks on which the draw is suspended are placed and made to operate above the cables. Fig. 10 is a similar View, with truck-wheels connected together, showing the bracing outside of the frame-work. Fig. 1l shows a view of the same, with double trucks,

to which the draw is suspended. Fig. 12 shows an end section where the suspended rods are placed on both sides of the frame and cable. Fig. 13 shows the Inode of bracing the framework together, with the suspension-rods for the draw on the outside of the structure,

The object of my invention is to obviate the difficulties of bridging navigable rivers which have low banks and extended low lands on one or both sides, and, from their width and depth or the substance composing the bottom of the stream, it is impracticable to build piers or trestle-work, so that ordinarilyconstructed draws cannot easily be placed and made to operate over their channel; but by my plan of suspending the draw a railroadbridge of any length and a draw of any desired opening can be made effective without building piers in the river or near the channel.

My invention consists in hanging the drawbridge on frame-work supported by cables suspended from towers of sufcient height to allow steamers and other iloating river-craft to pass under the supporting-timbers; also, in forming a railway-track above or below the cables for trucks, from which to suspend a movable section or draw-bridge of any desired. span or opening.

My invention further consists in the construction of collar-braces which hold the suspended framework in its place, bracing it laterally and helping to equalize the strain upon the cables at all points, whether the draw is open or in its place for a train of cars to pass over; also, in the construction and mode of operating the adjustable frame and track for connecting the car-track with the track on the draw.

To enable others skilled in the art to build my suspended draw for railroad and other bridges, I will describe the construction and the arrangement of the several parts more in detail, referring to the several gures in drawings, and to the letters of reference marked thereon.

The same letters indicate the like parts in all of the gures.

The towers A A should be built of solid masonry, they having secure foundations, and elevated in one body up to a level of the grade of the road.4 Then the towers are divided and built up with two columns, A A', leaving an open space, B, between them, of sufficient width for the track and train of cars to pass between them. The open space B may be of any desired height, the columns A capped off at the top singly; or they may be arched over and so connected together at the top as to give them the greatest solidity for securing the ends of the timbers C C, which form the chord of the framework on which the entire bridge-structure is supported on the suspension-cables D D, they being `fastened and resting on the top of the towers D D', and made to extend far enough to anchor firmly to other piers or on the banks of the river.

' The upper chord of timbersV C C may be so spliced and bolted together as to present a solid mass extending the whole length of the span between the two towers. The Width of the chord C 0 should be such as to give room for the track-timbers c c to be placed in line with both edges of the chord-timbers C C, directly underneath them, leaving a narrow opening between the track-timbers c c, for the iron rods to pass, on which the draw is suspended from the trucks E E.

rIhe main towers A Amay be built at any required distance apart, and of such height as to allow the cables and all of the suspension frame-work to be placed above, out of the reach of smoke-stacks and the masts of other river-craft. All of the frame-work and braces, being supported by the cables D D, two or more in number, are held lirmly in their places by ma improved collar-braces F F, they being connected with the -cables by the stirrup-bolts ffffj'f, passing over the cables D D and vertically through the blocks b b, the timbers C C and c c, and the right-angle foot or ledge of the collar-braces e e e.

The collar-braces may be made ot' wood suitably jointed together, or they may be of cast or wrought metal, with a toot or ledge, c c, on which the chord-timber c c for the track a, a, on which the trucks EFE run, are supported, they being put on each side of the chord-timbers in pairs, with blocks of timber b b between the ends at the top and each pair held firmly together by bolts d d and boltszz, which extend through both braces just underneath the chord-tim bers C C.

rIhe truck-railway a a being placed on the ledges e e of the collar-braces F F, they are firmly heldin place by the stirrup-bolts f j' f f, which rest on the cables D D, and, passing through the timbers vertically, are secured by screw-nuts under the ledges e c.

The two chord-timbers C C may be braced and counterbraced by timbers h h, and held by the bolt-rods z' c i, so thatvery little lateral motion or vibration can be produced, and the structure may also be stayed and vibration up or down prevented by the buckle-jointed brace-rods G, fastened to the pier H, and other tension-rods J J, connecting the frame-work with the towers.

The trucks on which the draw is suspended are. mounted on a series of double-hanged carwheels, I I, they being of such dimensions that they will pass freely between the chordtimbers C C and the track t a, the two sides of the truck-frame E being coupled together by cross timbers and braces, which fall below the bottom of the collar-braces F, so that the frame-work K will pass freely under them when the truck is operated to move the draw. To the frame-work K the chain 7c k is attached for operating the draw, the chain extending over the whole length, from one tower to the other, so that the draw can be operated at either end of the bridge by a crank or Wheel, Ii.

To the truck-frame E is suspended the draw M M, which may be built mostly of timberssillsstringpieces, plates, and braces-secured rmly by iron rods m mand bolts, similar in its construction to an ordinary span of a railroad-bridge, it having cross-tics n n and the car-track N N, the draw -bridge being suspended on strong iron bars O O, and supported by angular braces P P P and crossbraces Q Q Q, so that it is prevented from yielding laterally, and will always iind its place and bring the track in a line with the stationary track when closed for a train of cars to pass over.

The draw may be so constructed as to occupy only a portion of the span between the towers, as seen in Fig. 1, and draw oft over a stationary frame-work, R' R, and track, which may be suspended from the structure above; or it may be supported on a pier, H; or, it' desirable, the draw may extend the whole length of the span between the towers and be moved off through one ot' them onto trestle-work, as seen in Fig. 6, Plate No. 2.

The draw-bridge passing over the stationary track when opened must necessarily be above it, and to connect the track when the draw is closed I make a section of the track to be raised and lowered by securing the stringpieces S S together'by cross-pieces i" o" r, on 1 which are one length or section of the iron rails, this frame being hinged to the ends of the stationary string-pieces T T, so that when let down for the draw to pass over the frame will rest on the cross-ties t t t but when the draw is closed the frame is raised up by the balance-weights U U, the cords u u passing over pulleys V until the two tracks come together; then they are rmly supported by a series of blocks, W W W, hinged to both sides of the string-pieces S, so that they will shut in under between the timbers S S and the crossties t t t, and thus iirmly support the inclined track, the hinges H H extending upon the sides of the timbers S, so as to form a support for the rails and guides to place and hold the ends of the rails in a line together. When the draw is to be opened, the hinged supports being coupled together by a connecting-rod, i/ y, are opened to a right angle, which allows the track to fall, the blocks W going in between the cross-ties t t t.

Some ofthe gures in Plate No. 2 show modifications of construction which are embraced in the principle above described, and do not require to go into a detailed explanation of theseveral parts by letters of reference.

The advantages of my mode of constructing draws for railroad and other bridges will be readily seen and understood by those familiar with sections of the country where marshy low lands extend a considerable distance from the rivers, as in the valley of the Mississippi, and many other navigable rivers in the South and West, where railroads may have to cross, and can only be bridged, unless a good and efficient draw can be built, without conflicting seriously with the commercial operations of the river. In many places the bed of the stream is quicksand, and no good foundation can be had for building cribs, piers, or driving piles for trestle-work, so that-to build ordinaryconstructed draws is wholly impracticable.

It will be readily seen that by my mode of placing the suspension work so high above the water that any ordinary sailing or steaming craft can pass under, a bridge with a draw of sufficient span can be vbuilt at-any place where'towers can be built to support the suspension.

By all of the plans heretofore known and regarded as practicable upon which draws for railroad-bridges have been built it has been necessary to build large piers in the channel ofthe stream, on which the draws are balanced current in between them that it is very difficult to steer clear of them.

By my plan and mode of construction, as above described, no piers or abutments are required, and the draw can open the entire width of the channel or river, if desired, which cannot Well be effected by any other arrangement or mode of constructing draw-bridges.

Having thus fully described my invention and improvements in the principle of constructing draws for railroad and other bridges, what l claim as new, and desire to secure by Letters Patent, is

l. Suspending the draw for bridges from trucks which run on a railway supported on frame-work by suspension-cables on towers, placed either above or below the frame-work at a height sufficient to allow steamboats and other river-craft to pass freely under the structure that supports the draw, as herein described.

2. The collar-bracesv F' F, constructed and arranged as and for the purposes specified.

3. So placing the stirrups, suspension-rods, and angular braces that. the strain upon the draw and the other portion'of the bridge'structure is equalized upon the suspension-cables, in the manner and for the purpose herein set forth.

D. A. MITCHELL.

Witnesses: A

J. B. WOODRUFF,- EDM. F. BROWN..

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