US1302302A - Bascule-bridge. - Google Patents

Description

T. E. BROWN.

BASCULE BRIDGE. APPLICATION FILED IIov. I3. I916.

I; I1 Patented JI 29, I919.

3 SHEETS-SHEET I.

T. E. BROWN.

' BASCULE BRIDGE.

APPLHJATION FILED NOV. 13.

3 SHEETS-SHEET 2.

T. E. BROWN.

BASCULE BRIDGE.

APPLICATION FILED ov. 13. 1916.

Patented Apr. 29, 191-9.

3 SHEETSSHEET 3- ED ere momnsie; rnown, on- NEW roan, n. it.

mascara- Barnes.

' b all whom timed/concern:

Be it knownv that I, T OMAS E. Brown,

acitizen of the United States, and a resident of the borough of Manhattan, city of New York, in the county of, New,.1York' and.

State of New York, have-invented certain new and useful Improvements in Ba'scule- Bridges, of which the following is a specification. M

bascule bridges. 1 r

The simplest form of a bascule bridge is the ordinary heel counterbalanced trunnion type, and this form is usually adopted when the height of the bridge above the water is I suflicient to admitof its use. In. many situa-' tions, however, the height is insuflicient for the'heel' of the bridge and counterebalance to clear the water or tops of the piers, and

in such cases the span must be made longer in proportion to the width of the Waterway and a watertight pit must be provided into which theheel of the bridge and counter balance may descend. The expense of construction in such cases becomes, very great,

and therefore the more complicated and un-.

sightly types, with towers and counterweights above the roadway, are usually resorted to.

Cases frequently occur where the height.

above water is not suificie'nt for a simple heel balanced bridge of ordinary type, wlthout "watertight pits, and yet' where the use of unsightly towers and counterweights would be very objectionable. In' ordinary heel-.

counter-balanced trunnion bridges 'it'is necessary to so dispose the counterbalance-that the center of gravity of the entire moving mass will coincide with the center of thetrunnion or pivot and this usually" reqmres:

the placingof a considerable portion of the counter-balance above the bridge deck, to

the detriment of the appearance of the struc-i i coincidence of the center of gravity and the ture; and .it is therefore an objectof my invention to produce a heel balanced trunnion bridge, suitable for such cases. in which pivot is unnecessary and wherein no countor-balance need to be placed above the deck of the bridge, and by which also the use of watertight pits or unsightly towers is entirely avoided. 'f a To accomplish this, I prefer to partially Specification of Letters Patent.

Patented Apr-.29, M1 19 Application filed November 1a, 1916.. Serial no. 131,174.

balance the bridgeby heel counter-balance,

i. 6. heavy material placed in the heel of the bridge, using as muchheel counter-balance as the. height, above water will conveniently permit, and complete the balance of structure and connected to the moving span V k V by a flexible connection pivotally attached This invention r'elates'to improvements in v to said counterweightandca'rried around and supported by a curved member on said moving span of such curvature that the heel horizontal line through its pivot and-need not descend below its pivot, andI so shape and place the curved member supporting the counterweight connection that it'continually nection, during motion of the bridge, and

simultaneously varies the lever arm'sof'said connection about the pivot of the bridge and the pivot of the counterweight in a proper relationship to effect the balance'of the bridge in all its positions, and this I am enabled to do, under these novel conditions,

" bymeans of a method discovered by me and fully described hereinafter, but not herein claimed.

My construction is especially useful when concrete is used-for counter-balance, which is now the'general practice, as, on account. of ts great bulk, concrete counterbalance 1s changes the angular position of said convery clumsy and unsightly when placed above the bridge deck.

Referring to the drawings which accompany the specification to aid the description:

- Figure 1 is a side view of a bridge according to my construction.

Fig. 2 is a diagram explanatory of'the method of laying out the curve of balance.

Fig. 3 shows aspecial case, and Fig. 4. is a view showing a truss bridge with the counterweight placed above the deck level.

, Similar letters of reference .refer to simi larparts in all the figures.

Y Referring to Fig. 1, B is a bascule bridge, P the pivot or trunnion above which it rotates. A, A ,A are piers and D a portion the parts described will in genera be dupli venient position on some fixed part of the structure, as the pier A.

C is a counterweight connection pivotally attached at a convenient point E on said arm K and also attached at a point I on said bridge B at or near said pivot 'P.

Said connection C passes around and ,is supported by the curve F. Said curve F forms a part of and rotates with said bridge B, and is of such form as to cause said weight W to move in a manner to complete the balance of'said bridge B in all its positions, as is hereinafter explained in connection with Fig. 2.

The point G. g. is the position of the center of gravity of the combined weights of-the bridge B and heel counterbalance H. Said centerof gravity may bebrought, by adjustment of the amount of the counterbalance H, to as near to the pivot P as is convenient, and hereinafter we will for brevity use the term bridge as referring to the total mass, including the counterbalance ll, rotating about the pivot P. G is the center of gravity or center of mass of the counterweight W, which we will refer to hereinafter as the center G to avoid confusion with the center of gravity G. g. of the bridge. R and R, are respectively the fixed and movable portions of the roadway or bridge floo and Z is the break in the floor between them, which, as well as the heel counterbalance H, should be preferably so located as to clear the top of pier A, when the bridge is in a vertical position.

It will be understood that the description refers to one side of the bridge ,onl and that cated on the other side of the bridge, but the heel counterbalance H and the counterweight W may extend clear across the bridge if desired.

The counterweight connection C may be of wire rope, chains or any other suitable construction, but I prefer to make it in part of a series of pivoted links as indicated on the drawings.

The bridge may be operated in any suitable manner,-but I prefer to use a gear segment M secured to the bridge and meshing with a pinion Non shaft 0, supported on a fixed part of the structure; and shaft 0 Inav be rotated by any suitable gearing and power.

When said pinion N is rotated in the direction the reverse of the hands of a clock,

.ieoaaaa the free end of said bridge til rises and the heel end descends, the connection C unwraps froin saidcurve F and the said arm K and weight W descend, and when said pinion N is rotated in the opposite direction said bridge B descends and said weight W rises.

Analytical solution of thg curve F is too complicated for practical use and the curve as also do the lever arms of said connection both about the pivot of the bridge and the pivot of the counterweight, and therefore 1' resort to the principle ofvirtual work in order to lay out saidcurves. The use of this principle gives great latitude in the choice of position of the various parts and greatly assists in the design of the bridge, as the limitation usually deemed necessary of making theangular motion of the arm K and weight W equal to the angular motion ofthe bridge is entirely avoided. In order that a movable bridge shall be balancedin all its positions, it is only necessary that for every position of the movement of the bridge the work of the parts which rise shall be equaled by the work of the parts which descend, i. 'e. the total work must equal zero. Hence when the. center of gravity of the bridge G. g.

rises any vertical distance it, and the center G of the weight "W falls a vertical distance h, then,'if B and W are used to represent the respective weights of the bridge and the weight W, the relation required for balance is that Bit-l-VWL' :0. Any mechanism whatsoever connecting the weight W to bridge B, which will maintain this relationship, will cause the bridge to be balanced in all its positions, and it is an object of this inven tion to produce such a mechanism. e

It may be stated as a broad principle that motion of any point on the counterweight connection (such as E, Fig. 1) can be determoaeoa work, then the-curve of motion of this point relatively "to the bridge can be traced and a member which is the evolute of the curve so traced will effect the balance of thebrid'ge 'in all its positions.

The following graphic-method is an ap- I plication of-this principle the'position of the center of gravity, C. y.

of thebridge including the heel I counter-- balance H, and the total Weight corresponding to said center of gravity, 1 swing an are through C.fgj. with the pivot Pas a center, 15

'of the bridge, and longer necessary to bring said G. g. vertically'over the pivot P,

making said, are equal to the angular motion whether-the bridge may move so faror not, as said vertical position .10=-.of portant in. the construction of the-curve as willbe explained hereinafter; i

' I divide this are into. a convenient number' ofparts thus'gobtaining the positions 2, 3,4, etc., of C. 9., and includingthe vertical position 10]" of G. gf I then draw a horizontal line G. g.la throu glifthe primary position 1 of C. y.- and vertical lines to said horizontal 'line'frorn the other positions, 2,3,4, "etc;

I Then-said vertical lines 71?, it, hf, etc.' represent the vertical-heights through which the g". of the'brid'ge moves in reaching its successive positions, and? the 'Work'of' the bridge'in attaining said successive positions,

will'be its total Weight B, multiplied bythe heights 71, h?*-, etc. said-heights may be' scaled from the] drawing, or may be cal culated' trigonometrically.

Having chose a suitable amountfor the weight-VV, WhichI prefer to' determine by dividing: the work ofthe bridge in rising to its highest position byv the height the I said weight maybe conveniently allowed' to descend, I. divide the work of .the bridge for its various positions.'1,'2,' and 3, etc, by

the-Weight of the, WeightW,fin accordance withthe generalfequation given above and so determine the corresponding vertical disan are through said center Gr-froni the pivot L" as a center,and the intersections-ofthis; arc with said hor zontal lmes glve the var-1g.

ousrequired positions g2, g3, 94, etc, of said 2, 3,4, etc of G. g. Havingselecteda convenient point. E for the attachment, of the counter-weight connection C'to the arm. K, I. swing an arc through said point E from L- g. is imbrid'ge itself, which also has moved. vI then draw arcs through said pointse2yc3, e4,- etc, from'the pivot P as a center, and lay off- 7 on said arcs, but in the reversedirection,v 1' Referring to Fig. 2', having determined distances corresponding-to the angular motions of thebridge and thus obtain-a series of points f3,,f4, etc, which are the relative positions ofthe point E, with respect to the bridge itself, said bridge B being considered as fixed in position.

Ef2, f3, f4, etc., lie in a curve of cycloidal form relativelyto the pivot P, ofthe bridge.

. It Willbe found that said series of points Choosing the point'fl0 which corresponds to the position 10 of the bridge, when-its center of gravity G. 'g. is vertically above the-pivot, inwhich position the moment of the bridge aroundits pivot P is equal to zero, and therefore the moment of the coun- ,terweight connection C around saidpivot inust also be equal-t0 zero, and therefore the line of pull of said connection G must pass through the pivot 'P, we draw vthe lino"- f10P,-which is the relative position of-the connection C forthis position of the bridge and is a tangent to the .curve F. The line f10P,-, is the length of the connection C, measured from the point f.-1O to-thepivot P, and as obviously said connection C must .be of constant length, the length from the- -pivot P. to each of the points E, f2, f3, etc, measuring around the curve]? must be con.- stant and equal to the len 3th of the said line P flO, and therefore the curve F is the 'evolute of the curve E, f2, f3+f10, and therefore by drawing normals in the usual manner to said latter curvewe obtain a series of lines t1, t2, 223, etc, which areitam gents toijsaid curve F, and by;d'rawing'a cur-ve tosaidtangents, we obtain the re quired curve FQ Y The-correctness of the curve F so found is of course dependent upon the number of tances through whichthe center. G of-said weight W must descend order to balance the bridge. I then draw horizontallines'atsaiddistances h'2-7r3, h'L below the primary positionof said center G, and 1 then swing I positions taken, theiscaleof the drawing. and the ca're with whichthegraphic processesare performed; and I prefer to check the correctness ofythe-"positions of thevaridescribed, and therefore the'teusions in the. center G, corresponding With-the positionsconnection in its'various positions can now be readily computed in the usual manner.

curveas constructed on-the bridge must allow for the thickness of said connection. In the usual design of bridges as described,

the center of gravity G. g. of the bridge sufficiently long section of curve tangent to said line P, flO and reversed in position to the curve F may be used.

In Fig. 1 the connection C is shown a composed of numerous links and the curve F is continuous. This is necessary when great accuracy of balance is required, but in many" cases a sufficiently accurate balance for practical purposes can be obtained by using a few long'links as shown in Fig. 3, by a, r, s, and in Fig. 4 by a, o, w. In such cases the curve F. need not be continuous, but may preferably consist of short segments at and supporting the joints of said connection as shown in Fig. 3. In small bridges a practical balance may often be attained with a single link, and the curve F may be then considered as of such small radius as to be the equivalent of a simple pivot or pin.

Cases occasionally occur where, on account of very limited vertical height, or on account of the necessary size of the weight W, we can not conveniently place the said weight W entirely beneath the floor of I the bridge B, as is shown in Fig. 1, and in such casesthe top of the weight W may be placed at the floor level as shown in Fig. 3, and extend across the bridge and form a part of the bridge floor when in normal position.

The distribution of counter-balance between the heel of the bridge and the counterweight W depends on the conditions of each particular case, and it will often be desirable to place all the counter-balance in the weight W and none in the heel'of the bridge, as indicated in Fig. 3.

With the construction shown in Figs. 1

and 3, suitable locks are necessary to hold the bridge in its lowered position. These are well known in the art and are not specifically part of this invention, and are therefore not shown in said figures.

My invention is not limited to cases where the counter-balancing devices are placed below the bridge deck, though especially valuable in such cases, for the weight W, arm

K and its pivot L may be placed above said deck and the invention may be applied to an ordinary truss bridge as shown in Fig. 4. In such cases, (see Fig. a) I prefer to place the pivot P at the extreme end of the bridge, and to make the weight W sumaoaaoa ciently heavy to completely balance the es bridge. The drawings show single leaf bridges only, but it will be understood that this invention applies equally well to double leaf bridges.

'By referring to the drawings, it will be noted that the angular movements of the counterweight W are not equal to the angular movements of the bridge, and that the total angular motion of the counterweight issubstantially less than the total angular motion of the bridge, and that the moments of the counterweight about its pivotare not pivot. The method herein described enables the form of the curve F'to be determined under these conditions, and is specially useful in the cases shown where the counterweight and its path are above the horizontal line through the counterweight pivot.

@bviously the tensional connection may be pivotally connected to the moving span and the curved supporting member placed on the counterwelght, the curved member is thenthe evolute of the curve formed by the span end of the tensional connection when rotated about the counterweight, considered as fixed, but this arrangement usually produces awkward structures of no great practical value.

Nowhaving described my improvements, 1 claim as my invention.

'1. In abascule bridge, the combination of a pivotedbridge, a counterweight pivoted to a fixed support at a point lower than said counterweight, a tensional connection. from said counterweight to said bridge and means having a curved surface supporting said connection to vary the lever arms of said connection about the pivot of said bridge and the pivot of said counterweight to efiect the balance of said bridge in all its positions, substantially as described.

2. In a bascule bridge, the combination of a pivoted span, a counterweight, an arm carrying said counterweight and pivoted to a fixed support at a point lower than said counterweight, a tensional connection from counterweight, an arm carrying said coun terweight and pivoted to a fixed support, a tensional connection from said arm to said span and means having a curved surface supporting said connection and varying the lever arms of said connection about the pivot equal to the moments of the bridge about its of saiL span and the pivot of said eeunter- Weight to balance said span in all its positions, the lever arm of said counterweight ab0ur, its pivot increasing as the lever arm 5 of said span about its pivot decreases, substantially ae cleserfleefl.

Signed at New York city, in the county 01? New York, arfl State of New York, this 11th day 011 November, A. D. 1916.

THKJMA$ BRUWN.

Witnesses;

Parmrserp N. Harms.

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