US1620284A - Method and apparatus for changing main sheaves and cables on lift bridges - Google Patents

Description

March 8 1927.

E. A. PEARSQN METHOD AND APPARATUS FOR CHANGING MAIN SHEAVES AND CABLES 0N LIFT BRIDGES Filed July 21, 1924 Patented Mar. 8, 1927.

UNITED STATES PATENT f ERIC A. PEARSON, OF PORTLAND, OREGON.

METHOD AND APPARATUS POE CHANGING MAIN SI-EEAVES AND CABLES QN LIFT BRIDGES.

Application filed July 21, 1924. Serial No. v'727,/!f1=0.

My invention hasoforits objectthe providing of an improved means and method for repairing and replacing the main sheaves and cables of a so-called vertical lift bridge, without interfering with the operation of the lift span or with the traffic over the bridge.

The problem of accomplishing said work is especially present in the double-deck type of the vertical lift bridge. In this type the lower deck is suspcndedfrom the main deck and adapted Itobe lifted independently of the main'deck to accommodate the smaller crafts-of the river trai'iic, and is always first raised before the span on which the main deck is located is raised; the two decks being raised as a unit thereafter.

The total weight of the lifting deck and lift span of abridge of this type is approximately 1600 tons and the counter weights,

cables and sheaves will weigh approximately 990 tons each, of which there are two sets of two sheaves each located one set in each tower. The main sheaves over which sixteen two and a quarter inch cables are operated arefourteen feet in diameter and weigh approximately 32 tons each.

" The cost and investment concerned in bridges or. thistype pie-suppose heavy and continuous duty both as to water traflic and land'traffic, which cannotibe and must not i be interrupted.

A" further specific and principal object of 'myi nveiition is to provide a means and a inetho'dby which .the'said repair and replacement may be accomplished in a simple, andrrelatively economical manner, and without interfering with the operation or use of thebri'dge.

-My invention as a solution, to this problem consists in placing a temporary sheave element adjacentthe main sheave element to be repaired, and mounting a-movable girder at'each end of the lift spanbelow a fixed girderthereof, and connecting said counterweights with said movable girders by a temporary auxiliary cable element and then moving said movable girderfrom said fixed girder an interposed hydraulic power, thereby to suspend said counterweights by said temporary cable element.

' Heretofore, such similar problems, to the best of my knoivledgqhave been solvedby of absolute necessity.

constructing false work to support the lift span and the counter-weights whiclrnecjessitated putting the lift span out of operation and closing the bridge to both river and land trafiic for an indefinite time and the cost of which is prohibitiveexce 'j t in times Such method of accomplishing the replacement of the main sheaves 'ofa lift bridge is not to be considered'where contracts and industrial conditions do not permit that the continuous operation of the bridge 3 be interrupted as well as the "rulings of the .Nar Department,which 'areto the effect that navigable streams musfibe left open for water traffic at all'times.

invention and Fig. 2 shows a front elevatlon of thesame tower and illustrates the 'relative arrangement of the temp and thelift span;

The usual type of liftbridge comprises approach spansQone or morei'iii numbefl'fon orary sheaves and cables each side thelift span. The ends of th e approach spans rest on suitable "piers"wliich also support the lifting towers on which the counter-weights and lifting [deck' and "lift span are supported. l

As the method of replacing the main sheaves on either tower and (the 11ear1s'employed will be exactly the same, I will only describe the operation on onelt ower.

towersfrising from'piersfsuch as indicated at 1 upon each side of the waterway includes vertical main columns 5,"sp'aced 'inclinedcolumns .6 with struts andj'braces 7 and 8 to form a rigid structure. $a ifdftbwers are each providednear its top"with a' 'main girder 10 on which the main sheaves 11 are supported in journalf-b ealring's 12. Ma n cables 13 are operatively' mounted on sald ma n. sheaves and areconn'e'cted atone end with, thegirder'15-on the lift'spa'n and at their other ends with a counterweight 16.

Sixteen main cables 13 are operatively mounted over each of the two main sheaves 11 and are connected to the lifting girder 15 on the lift span and to the counterweight 16.

The main sheaves of a vertical lift bridge are subjected to heavy duty, and are located as before mentioned at the top of a tower 173 feet or more above low water, which height is generally required to provide clearance for all classes of vessels. The main sheaves of which there are two on each tower, are arranged parallel but spaced apart.

To more clearly bring out the difiiculties to be surmounted in replacing these sheaves, it should be understood that each sheave weighs approximately 32 tons and is fourteen feet in diameter. The weight of the lifting deck and span weighs approximately 1600 tons and each counter-weight weighs approximately 800 tons, in order to counter balance one-half the weight of the lift deck and span. With the weight of the thirtytwo two and one-quarter inch cables, sixteen of which are operated over each sheave, brings a total weight over the two sheaves to approximately 1700 tons, and the weight supported by one sheave is 850 tons.

The problems consist in raising the total weight of 1700 tons off the main sheaves, and replacing each sheave which weighs 32 tons and is fourteen feet in diameter, and is located one hundred and seventy-three feet or more in the air, without in any way interfering with the operation of the bridge.

In making repairs or replacements of said main sheaves the lifting functions of the bridge have heretofore been rendered inoperative and then thebridge becomes a source of great obstruction to trailic upon the waterway' T o avoid this obstruction and to enable a full use of the waterway during such repairs to the bridge I have devised an apparatus and a method whereby the lift span may be operated during the removal and replacement of the main sheaves or other extensive repairs to the cables or operative parts.

I first reinforce the main girder 10 upon which the sheaves 11 are supported to provide for the additional weight which it must temporarily support, and then arrange two temporary sheaves 18 adjacent each main sheave and arranged in pairs in alinement with each other and so that their outer peripheries are in vertical alinement with the outer edges of the main sheaves.

Plates 23 are provided on each side of the counter-weight 16 and a plate 22 is provided underneath the bottom of the counterweight and connected to the side plates, thus forming a frame or sling for the counterweight.

Temporary cables are then fixed to the upper ends of the plates 23 and passed over the temporary sheaves 18 and down to the lift span and connected to a temporary girder 25 which is slidably mounted between .the span cords adjacent to and below the lifting girder 15 to which the main cables are fastened.

Hydraulic jacks are then placed between the fixed lifting girder 16 and the slidable temporary girder 25, and are actuated to force the girder 15 apart from the girder 25 until the temporary cables 20 become taut and take the weight of the lift deck and span and counter-weight from off the main cables 13, and the main sheaves 11, thus leaving the cables slack. Blocks are then placed between the two girders 15 and 25 to hold them spaced apart.

At any time during the operation as when the weight of the lift span is being shifted from the main sheaves to the temporary sheaves, and either set of cables are slack, the lift span may be operated on whichever cables are taut, or in case this is not practicable, the hydraulic jacks need only be operated for not more than two minutes to bring the taut cables into the desired relation with the slack cables.

The main cables 13 may then be taken off the main sheaves 11, and the sheaves may be replaced or repaired as the case may be, by any suitable means with which those skilled in the art will be acquainted without in any way interfering with the operation of the bridge and with a very substantial saving in operating costs, time, and material.

After the repairs to the bridge are completed, such as the removal and replacement of the main sheaves, the jacks 27 are again actuated to admit of the fillers 28 being removed and the girder 25 is permitted to reapproach the girder 15 until the weight is again carried upon the main cables l i whereupon the temporary cables 20 may be removed as well as the frame from about the counterweight. I

Having described my invention, what I claim is:

1. In a lift bridge, in combination with the main sheaves, and cables supported on said sheaves having their opposite ends secured to the lift span of the bridge and a counterweight, respectively, of pairs of smaller sheaves wherefrom temporary cables are disposed in vertical alignment with said main cables, said temporary cables being connected at their opposite ends with said counterweightand lift span, a frame about said counterweight through which connec tion between the temporary cables and the counterweight is made, a slidable girder mounted below a transverse girder in said lift span to which said temporary cables are connected, and means to separate said slidable girder from said transverse girder to transfer the tension from said main cable to said temporary cables.

2. The method of changing the main cables sheaves of a lift bridge, consisting in placing a pair of temporary sheaves of smaller diameter adjacent the main sheaves to be replaced, mounting a girder at each end of the lift span in slidable relation below a transverse fixed girder thereof, securing a plurality of temporary cables to said slidable girder and to the counterweight running over said pairs of sheaves, respectively, and separating said slidable and said fixed girders to relieve the tension on the main cables whereupon the main cables may be removed.

3. In a riggers device: the combination of a pair of relatively small sheaves adapted to replace temporarily a single larger sheave; a movable girder positioned adjacent a permanent girder of the structure being operated upon; means for separating said girders; flexible members secured to said movable girder and passing over said small sheaves; and means for securing said flexible members to a counterweight.

4. In a riggers repair device: flexible hoisting members; temporarily positioned sheaves for said flexible members adjacent a permanent sheave; a cage adapted to receive a counterweight secured to said flexible members; a movable girder mounted upon the structure to be supported by the device; and means for placing the load upon said flexible members by moving said girder.

5. In a lift bridge of the character described, the method of repairing the suspending means of the counter-Weights consisting in placing a temporary sheave element adjacent the main sheave element to be repaired, mounting a movable girder at an end of the'lift span below a fixed girder thereof, connecting said counterweights with said movable girders by a temporary auxiliary cable element, and then moving said movable girder from said fixed girder by an interposed mechanical power, thereby to suspend said counterweights by said temporary cable element.

6. In a lift bridge of the character described, the method of repairing the suspending means of the counter-weights co11- sisting in placing a temporary sheave element adjacent the main sheave element to be repaired, mounting a movable girder at an end of the lift span below a fixed girder thereof, connecting said counter-weights with said movable girders by a temporary auxiliary cable element, and then moving said movable girder from said fixed girder by an interposed hydraulic power, thereby to suspend said counter-weights by said temporary cable element.

ERIC A. PEARSON.

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