WO1997045595A1

WO1997045595A1 - Mobile work station

Info

Publication number: WO1997045595A1
Application number: PCT/CA1997/000355
Authority: WO
Inventors: William Watts
Original assignee: Bridge Vail International Inc
Current assignee: Bridge Vail International Inc
Priority date: 1996-05-28
Filing date: 1997-05-27
Publication date: 1997-12-04
Anticipated expiration: 1998-11-28
Also published as: AU2882497A; CA2177511A1

Abstract

A work station is disclosed comprising: a canopy (30) having a top section (45), a bottom section (41), first and second end sections (43), and first and second side sections (44) to shelter workers and to contain debris, each section being suspended between a supply means and a take-up means on a plurality of support means (14) about a structure that are mounted in a first motive means (14) on the structure to permit the canopy (30) to be repositioned from time to time, platform means (50) suspended by cables (51) on a second motive means (52) to permit a vertical degree of freedom and on a third motive means on a transverse beam for a lateral degree of freedom, each beam being mounted on a fourth motive means on the support means to permit a longitudinal degree of freedom of movement.

Description

MOBILE WORK STATION

BACKGROUND OF THE INVENTION FIELD OF ART

This invention relates to apparatus adapted to envelop successive portions of a bridge to provide a work station to shelter and support workers and equipment during maintenance or construction and to contain contaminants produced by such work from polluting the environment. More particularly, the invention relates to a mobile work station having a structure for maintaining a canopy about a portion of a bridge, scaffolding apparatus for supporting workers and equipment within the canopy and motive means for positioning the structure and canopy from time to time.

PRIOR ART Routine maintenance of bridges is necessary to prevent them from deteriorating to a point where they must be replaced. Replacement of bridges is expensive and wasteful. Routine repair is obviously more economical and sensible. Nevertheless, failures to conduct routine maintenance has left many existing bridges in extremely poor condition. Some have been closed and torn down because they are unfit for safe passage. The cause of this neglect lies partly in two fundamental impediments to routine bridge maintenance. First, it is difficult to put men and equipment up in the air on a large bridge structure, exposed to weather, without risking their safety and without interrupting traffic. Second, it is difficult to ensure that the detritus from cleaning, scraping and painting will not contaminate soil and water surrounding the bridge. The prior art discloses some equipment and methods relating to bridge maintenance but the problem of deteriorating bridges continues.

U.S. Patent 5,011,710 entitled "BRIDGE MAINTENANCE METHOD AND EQUIPMENT" dated April 30, 1991 describes a method in which surfaces of a structure are treated from a walkway within an enclosure suspended from the structure . The enclosure has a downwardly-converging cross section terminating in a vacuum conveyor for collecting and removing particles accumulating from the blasting process. The enclosure is preferably provided in modules. The vacuum conveyor removes the particulate material for transfer to conventional separating and re-cycling equipment. The enclosure and walkway are movably suspended from transverse guides secured to the structure.

U.S. Patent 4,854,419 entitled "PARTICULATE CONTAINMENT CONTROL METHOD AND PLATFORM DEVICE" dated August 08, 1989 describes a mobile containment platform method and system for sandblasting and the like used in bridge reconditioning and painting that requires removal of paint from the support structure of the bridge. The containment platform provides an entrapment envelop for spent abrasive and removed paint residue.

U.S. Patent 4,201,275 entitled "MEANS FOR THE RENOVATING AND REFURBISHING OF OVERHEAD STRUCTURES" dated May 06, 1980 describes a method for refurbishing or renovating large span overhead structures, for example the roofs of railway stations, or bridges and the like. It utilizes apparatus which comprises a plurality of runway beams suspended in spaced parallel disposition from the main ribs or framework of an overhead structure, the beams spanning a plurality of said ribs or framework and being longitudinally displaceable relative thereto, and a work platform or platforms suspended from said runway beams and being displaceable along the runway beams. Thus arranged, the overhead structure can be treated for substantially its entire length by alternately advancing the work platforms along the runway beams and the runway beams relative to the structure.

U.S. Patent 4,848,516 entitled "MOVABLE SCAFFOLD" dated July 18, 1989 describes a movable scaffold has a pair of hanger rails attached to a construction, first hanger units movably mounted on the hanger rails, beams operatively engaged with the first hanger units and laterally disposed with respect to the hanger rails, and a floor deck mounted on the beams. Second hanger units are provided for movably suspending the beams from the first hanger units.

German patent DD 241626 dated Dec.17, 1986 describes an apparatus to enable a bridge to be painted without erecting a complete scaffold, and enabling road and rail traffic to continue to use the bridge. A roller grid is used, which can be slid the whole length of the bridge. It has an upper frame with a fixed wheel and a lower frame supported by a fixed roller on the bridge structure and attached to the upper frame.

GENERAL DESCRIPTION OF THE INVENTION The present invention is a mobile work station for maintenance of a bridge having an open deck with light standards and railings, but generally without overhead trusses. The bridge will typically have supporting girders, or beams, or trusses beneath the deck and piers at regular intervals grounded into the earth below. The mobile work station has a skeleton structure, or framework, that is erected on a bridge deck in the shape of a large box framework, spanning most of the width of the deck and extending along a sufficient portion of the length of the bridge deck to define a suitable work space. The box framework is open in its lower central part to form a tunnel for traffic moving over the bridge. A canopy made up of canopy sections is raised on the box framework to enclose a work space on the bridge deck and also define rooms within the work space beside and below the bridge deck. Scaffolding within the canopy, under and beside the bridge, allows workers to access the bridge surfaces requiring maintenance. The box framework is mounted on wheels to roll to successive locations along the bridge, but has footings which alternate with the wheels, to locate the bridge at an particular spot.

The box framework includes a number of straddle frames that stand upon and straddle the deck at a corresponding number of spaced apart locations. Each straddle frame has two legs, one on each side of the bridge deck, and an overhead truss to link the legs at a sufficient height to permit the flow of traffic under the overhead truss. The straddle frames are linked together by track trusses and a suitable number of strengthening members. Each track truss connects an approximate mid-point of a leg of a straddle frame to an approximate mid-point of a leg of a next adjacent straddle frame on the same side of the bridge along the length of the box framework. Strengthening members, for example cross-pieces, link the overhead trusses of the straddle frames together. Strengthening members, for example longitudinal sections, join the top portions and the bottom portions of adjacent straddle frames along the length of the box framework.

The box framework may be mobile to move over the bridge deck or may be fixed at a location along the bridge. Each leg of the straddle frames may have wheels to support the box framework to roll along the length of the bridge deck in the mobile mode. Each leg may also have a footing to support the box framework in a fixed location on the deck. A lift means, such as a hydraulically, electrically or mechanically operated lift, may be used to transfer the box framework from the footings to the wheels or vice versa. By appropriately selecting between the mobility and fixation modes an operator may move the box framework from place to place as the during the bridge maintenance operations.

Scaffolding in the form of a platform may be hung under the bridge deck with cables hung from each side of the box framework to support workers doing maintenance work under the bridge. Typically, the platform will be wider than the bridge to extend laterally outwards of either side of the bridge to allow cables to be hung from platform booms on the box framework that protrude over the sides of the bridge. The platform booms may be fitted with winches and cables to hang the platform at a predetermined height under the bridge. The platform will have a floor and walls (the word "walls" will include railings and other suitable side enclosures) about its perimeter to ensure that workers do not fall out of it. Parts of the platform may have dividing partitions, such as rigid walls or canopy sections, to segregate work areas. The walls and partitions within the platform may have numerous floor supports to receive and hold floor sections horizontally at different heights. Thus workers can mount floor sections at different heights around the platform to work on various parts of the underside of the bridge. The floor sections may be of a standard size to permit any floor section to fit between any pair of floor supports. The platform under the bridge deck may be one large scaffold of a size determined by the size of the work station and the location or obstacles, for example piers under the bridge. The platform could also comprise a number of smaller scaffolds slung under the bridge from the box framework in locations that surround piers within the work station or otherwise provide suitable work spaces for maintenance work under the bridge. In this specification the word "platform" is used to encompass either construction, for this point is not material to the overall invention. One or more scaffolds may be provided to support workers for maintenance operations within the work station along the sides of the bridge. Preferably these scaffolds will be small cages that support a small number of workers. The cages may be hung on cables from cage booms on the box framework that protrude over the side of the bridge. The cage booms may be mounted on a track truss of the box framework to allow them to slide or roll, under control of an operator, along the track truss to change their position along the work station. Once located, a cage and may be fixed in place on the track truss by a clamp, pin, frictional engagement or other suitable fastening means. The cages may be raised or lowered with a cable using suitable winch means. In this manner the cages allow a worker to access virtually all parts of the sides of the bridge.

A canopy encloses the work space above, beside and below the bridge and continues below the platform to form one or more hoppers that lead to one or more exhaust chutes to collect and remove debris to a receptacle. The canopy not only protects the surrounding environment from the waste products of bridge maintenance, but also protects the workers and work materials, such as paint and scraping tools, from the weather conditions outside. The complete canopy is formed from a number of canopy sections. Each canopy section may be unfurled from a roll to cover a particular area of the outside surface of the work station. The rolls may be located on roll booms about the box framework and /or on the walls surrounding the platform. Canopy sections may be unfurled from the rolls to overlap other canopy sections so that, when all sections are unfurled, they completely envelop the work area. Canopy sections may be used within the work space to divide it for different types or work that might interfere with one another, for example sandblasting and painting. Some canopy sections may be temporarily connected together along their overlapping edges with canopy fasteners. Temporary canopy fastening is advantageous for assembling and disassembling the work station or to enable the canopy to be rolled up to reduce damage in a storm Some other sections may be fastened permanently, for example sewn together, to create more secure connections, for example, the hopper canopy sections under the platform may be sewn so that debris and dust cannot escape

It will be appreciated by those skilled in the art that there are many other configurations of canopy sections that might be used to enclose the work station and this invention is not limited to any particular configuration, but for the purposes of illustration one such configuration will be discussed in detail. The canopy sections of this configuration may be classified in numbered groups by their location First canopy sections depend from the walls of the platform to enclose the perimeter and the underside of the platform. The first canopy sections may be cut in appropriate tapering shapes and sewn together to form one or more hoppers hanging below the bridge to retain and direct falling debris to a receptacle. Second canopy sections extend upwardly from the platform front and back walls to fit snugly against the inside of the bridge girders, supporting structure and the underside of the bridge deck. The second canopy sections may include portions about the perimeter of the platform and within the platform area, the latter to segregate the work space into rooms within the platform. Poles and/or frames may erected on the platform to hold the second canopy sections in place. Third canopy sections extend upward from the platform front and back walls against an outside portion of the underside of the bridge structure, around the bridge deck, and upward from that outside portion of the deck to a position on the front and back portions of the box framework above the cage and the platform booms. Thus, the third canopy sections cover the work station ends above and below the deck that are not covered by the second canopy sections. Fourth canopy sections extend from the platform side walls on each side of the bridge upward to positions on the box framework above the cage booms and the platform booms to enclose the sides of the bridge and the cages within the work station. Fifth canopy sections form a roof over the cage booms, the platform booms and a portion of the legs of the straddle frames. Sixth canopy sections enclose the inside of the box framework adjacent to the flow of traffic. Other canopy sections could be used to cover the top of the straddle frames, but in a preferred embodiment disclosed hereafter the straddle frames are not covered so that the "tunnel" through the box framework is open at the top except for the overhead trusses and cross-pieces.

Each canopy section is constructed of a material suitable to shelter workers and to contain debris during bridge maintenance. It is not essential to this invention to select a suitable material for the canopy, which may depend upon the type of work being undertaken and the size and location of the work station. Some canopy sections may be rigid walls, for example it may be appropriate to have a rigid wall rather than a flexible canopy section on the inside of the box framework next to the flow of traffic or on the platform under the bridge deck.

One embodiment of this invention has the ability to avoid obstacles on the bridge deck during movement. Light standards on bridge decks, for example, present an obstacle to the advancement of the work station along the length of the bridge, particularly for the booms that protrude over the bridge sides. To avoid such obstacles, the box framework may be positioned inside the line of the light standards and other similar obstacles to advance along the deck without obstruction. The booms may be constructed with folding parts to fold in against the box framework to clear the light standards in passing. As each boom approaches a light standard, its load may be transferred to another support, its cable temporarily disconnected, and the boom folded into the box frame. Once past the light standard, the boom may be opened out to its normal position and the cable and load reattached. The canopy sections may be lowered and raised as required to pass an obstacle.

The bridge piers present an obstacle for moving the platform along under the deck. The problem is solved by lowering one side of the platform until the platform hangs outside the pier, disconnecting cables and reconnecting them as necessary as the platform moves past the pier and then elevating the platform to a horizontal position. In some cases the platform may be lowered to a vertical position and then disconnected from one side altogether to pass a pier hanging from the cables and platform booms on the other side. The description of a preferred embodiment of this invention will illustrate by example the principles of the construction and operation of this invention.

DESCRIPTION OF THE FIGURES

In the Figures that illustrate preferred embodiments of this invention: Figure 1 is a perspective view of a bridge having the box framework of this invention erected on its deck and having a platform and hoppers beneath the deck,

Figure 2 depicts the framework on a bridge enclosed in a canopy with a waste receptacle and ventilation ducts, Figure 3 is a cross sectional end view of the work station, Figure 4 is a cross sectional side view of the work station,

Figure 5 is a top view of the overhead trusses and bracing,

Figure 6 is a top sectional view of the box framework under the overhead trusses, Figure 7 is a side view of a typical straddle frame leg with wheels and footing,

Figure 8 is a detail of a wheel member,

Figure 9 is an end view detail of a typical footing,

Figure 10 is a perspective of means to elevate the canopy sections from the platform to the underside of the deck,

Figure 11 is a top view of a rod clamp,

Figure 12 is a side view of a rod clamp,

Figure 13 is a perspective of a canopy boom,

Figure 14 is a perspective of a canopy boom and a canopy section, Figure 15 is a detail of connecting canopy sections and fasteners,

Figure 16 is a side view of Figure 10 illustrating ropes for controlling canopy sections,

Figure 17 is a detail of overlapping canopy sections about the platform, Figure 18 is a side view of a cage boom,

Figure 19 is a top view of a cage boom,

Figure 20 is side view of a centre, an lower end and an upper end platform boom, and

Figure 21 is a view of the mobile work station with the platform hanging off one side while a bridge pier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention may be viewed in context of its environment in

Figures 1-3 and Figure 21. Figures 1-3 and Figure 21, show the elements of a typical bridge 1, including an open deck 2, light standards 3, railings 4, guard rail 5, girders 6, beams 7 and piers 8. Figure 1 shows a bridge 1 with a box framework 10 erected on the bridge deck 2 and a platform 50 slung beneath the deck 2. These elements form the basic internal structure of the work station upon which other elements are erected. Figure 2 shows the work station and a portion of the bridge 1 enclosed in a canopy 30. The box structure 10 shown in Figure 1 on the bridge deck 2 spans across the width and extends along a part of the length of the bridge deck 2 to form a tunnel 11 for bridge traffic. Platform 50 under the deck 2 and cages 70 beside the bridge 1 permit to workers to access bridge surfaces for maintenance. Other surfaces on the deck 2, such as the railing 4 and guard rail 5, can be reached by workers on the deck 2 within the canopy 30.

Referring to Figures 1 and 3-6, the box framework 10 comprises three straddle frames 12 that stand on and straddle the deck 2 at equally spaced intervals. Each straddle frame 12 has a leg 14 on either side of the deck 2 and an overhead truss 15 to link the legs 14 together laterally at a sufficient height to permit the flow of traffic under the overhead truss 15. The straddle frames 13 are linked together longitudinally by track trusses 16. Each track truss 16 connects an approximate mid-point of a leg 14 of one straddle frame 12 and an approximate mid-point of a leg 14 of a next adjacent straddle frame 12 along the length of the box framework 10. Strengthening members in the form of cross-pieces 17 link the overhead trusses 15 of the straddle frames 12 together on the top of the box framework 10. Strengthening members in the form of longitudinal sections 18 and 19 join the tops and the bottoms of adjacent straddle frames 12 along the length of the box framework 10. The box framework 10 is mobile, but may be fixed at any location along the bridge 1. Figures 7-9 show that each leg 14 of the straddle frames 12 has a set of wheels 20 to support the box framework 10 to roll along the length of the bridge deck 2. Each leg 14 also has a footing 22 to support the box framework 10 in a fixed location on the deck 2. A hydraulic jack 23 operates the footing 22 to permit an operator to lower the footing 22 to take the weight of the leg 14 off the wheels 20. Reversing the jack 23 retracts the footing 22 to return the support of the box framework 10 to the wheels 20. Thus, the operator may select between mobility or fixation of the box framework 10 to move or to locate the work station during the bridge maintenance operations. Further, the footings 22 are adjustable with the jack 23 to permit the operator to level the box framework 10 after it is located on the footings 22. Pin holes 24 may be provided in the sleeve 25 and the shaft 26 of the footing 22 to secure it after adjustment.

The platform 50 may be suspended under the bridge deck 2 with cables 51 hung from platform booms 52 on each side of the box framework 10. The platform 50 is wider than the bridge 1 to facilitate connection with the cables 51 hanging beside the bridge. There are six platform booms 52 on the box framework 10 to hold the platform 50 at a desired height. In one embodiment the centre platform boom 52 may be connected to a spreader rod (see Figure 1) from which two cables 51 may be dropped to the platform. The platform 50 has a permanent floor 53, front and rear walls 54 and 54', side walls 55 and 55' about its perimeter. The platform 50 also has numerous floor sections 56 that may be mounted on in floor mounts (in this embodiment rails 57) about the platform 50 to hold the floor sections 56 horizontally at different heights to permit workers to stand at suitable heights to work on various parts of the underside of the bridge. The floor sections 56 are of a standard size to permit any floor section to fit between any pair of floor supports. The floor is open grating to allow debris to pass through.

A number of cages 70 are provided to support workers within the work station along the sides of the bridge 1. The cages 70 may be hung on cables 71 from cage booms 72 mounted on a track truss 16 to permit them to slide or roll, under control of an operator, along the track truss 16 to change their longitudinal position within the work station. Once located, a cage 70 may be fixed in place on the track truss 16 by a clamp, pin or other suitable fastening means, (see the description below and Figures 18 and 19) The cages 70 may be raised or lowered with the cable 71 and suitable winch means (not shown).

The canopy 30 encloses the work space above, beside and below the bridge 1 and continues below the platform 50 to form one or more hoppers 31 that lead to one or more exhaust chutes 32 to collect and remove debris to a receptacle. The canopy 30 not only protects the surrounding environment from the waste products of bridge maintenance, but also protects the workers and work materials, such as paint and scraping tools, from the weather conditions outside. The complete canopy 30 is formed from a number of canopy sections. Most canopy sections around the front and sides of the work station are unfurled from rolls to cover a particular area of the outside surface of the work station. The canopy sections overlap adjacent canopy sections to completely envelop the work area. For the purposes of this description the canopy sections may be classified in numbered groups by their location. First canopy sections 41 depend from the walls of the platform enclosing the perimeter and the underside of the platform and to form the four hoppers 31. The first canopy sections 41 are cut in tapering shapes, drawn together and sewn to form four hoppers 31 that catch and direct falling debris to a receptacle 100. As shown on FigurelO, the first canopy sections 41 are connected to the platform 50 situated on the rails 57. This will be described further in relation to Figure 17.

Figure 10 also shows second canopy sections 42 that extend upwardly from rollers 60 in the front and rear walls 54 and 54' of the platform 50 to fit snugly about the bridge girders 6 and beams 7 and up against the underside of the bridge deck 2. For example, as illustrated in Figures 10, 11 and 12, poles 80 and cross-frames 81 may erected on the platform 50 to hold the second canopy sections 42 snugly to these underside elements. The poles 80 are fastened to the railings of the platform 50 by fasteners 85 which include collars 85a with set screw 85b to surround a pole 80 and to fix its position, clamp 85c with set screw 85d to grip the railing and a lockable hinge member 85e to fix the angle of the poles and the clamps. Figure 4 shows third canopy sections 43 that extend from rolls 61 in the front and back walls 54 and 54' of the platform 50 up the outside of the girders 6 about the bridge deck 2 and up about ten feet of the front and rear of the box framework 10 outside of the tunnel 11 to fastening bars 82 located on the box framework 10 above the cage booms 72 and the platform booms 52.

Figures 2, 3 and 14-17 show fourth canopy sections 44 that extend from rolls 62 in the platform side walls 55 and 55' up the sides of the bridge 1 to fastening bars 82 located on canopy booms 84 located about ten feet up the sides of the box framework 10 and above the cage booms 72 and the platform booms 52 to enclose the sides of the bridge 1 and the cages 70 within the work station.

Figure 2 shows fifth canopy sections 45 that form a roof about ten feet over the bridge deck 2 over the cage booms 72, the platform booms 52, the canopy booms 84 and a lower portion of the legs 14 of the straddle frames 12.

Figure 2 also shows sixth canopy sections 46 that enclose the inside of the tunnel 11 through box framework 10 adjacent to the flow of traffic.

Figure 3 shows seventh canopy sections 47 that are elevated from the platform 50 or the deck 2 within the work space to segregate sandblasting, in one room, from painting, in another room. These seventh sections may be erected from the platform 50 with poles and frames as described above and erected from the bridge deck 2 with rolls and cords and fastening bars.

Each flexible canopy section is constructed of plastic sheeting with fibre reinforcements. A rigid wall, e.g. a wooden wall, rather than a flexible canopy wall may be used within the tunnel in canopy sections 46.

As shown in Figure 15, the canopy sections may be temporarily connected together along their overlapping edges with canopy fasteners 40. Figures 14-17 show that a canopy section, e.g. 44, may be unfurled from a roller 62 and pulled up with canopy cords 91 that are looped over the fastening bars 82. The rollers 62 are fitted with a tensioning cord 92 on a pulley around the roller 62 to be pulled in opposition to cord 91 to draw the canopy section taut at the desired height. Then the cords 91 and 92 may be tied off to secure the section 44 in place. Adjacent canopy sections 44 overlap by about six inches and the rollers 62 are offset as shown for this purpose. The canopy fasteners 40 have long opposing bars and clamps to close the gap between the overlapping canopy sections.

As shown in Figures 16 and 17, the rollers 62 are set in the side wall 55 of the platform 50 and the lower canopy section 41 of the hoppers 31 are brought up and over the rollers 62 to seal the work space within. A pipe sleeve 200 and pipe 201 may be clamped along the outside of side wall 55 to help support the weight of the hoppers 31. The canopy section 41 of the hoppers 31 continues up and over the pipe sleeve 200 and the rollers 62 to seal along a top portion of the side wall 55.

The workstation of this invention may be first assembled on land in an area near the bridge 1. The box framework 10 may be assembled near an entrance to the bridge 1 and the platform 50 below the bridge 1. The three straddle frames 12 are assembled by joining the legs 14 with the overhead trusses 15. A mobile crane (not shown) is then moved out onto the bridge deck 2 where the maintenance operations are to begin. The crane raises the first straddle frame 12, and positions it across the road where it is guyed up. Similarly, the next two straddle frames 12 are lifted and guyed up into position. The straddle frames 12 are then joined with the track trusses 16, cross-pieces 17 and the strengthening members 18 and 19. The box framework 10 thus formed is leveled on its six footings 22 and secured in position with cables. Cage booms 72 are assembled to the track trusses 16 and the cages 70 are now attached with cables 71 and lowered over the side of the bridge 1 to assist in the assembly operations.

The platform 50 may be assembled under the bridge 1 with the first canopy sections 41 (previously sewn together) attached to the platform walls 54, 54' 55 and 55' to form the hoppers 31. Cables 121 from four lifting winches 120 are dropped over the side of the bridge 1 and attached to the platform 50 lying below the bridge 1. The platform 50 is then raised off the ground about 20 feet with the four hoppers 31 hanging below. The platform 50 and the canopy hoppers 31 are raised up by the lifting winches 120 to a working height under the bridge 1. Next, eight heavy cables 51 are dropped from the box framework 10 to secure the platform 50 for carrying a live load. Cables (not shown) may be dropped from the platform 50, through the hoppers 31 and chutes 32 to secure them to a debris receptacle 100.

After the internal structure is established in the bridge 1, the canopy 30 is erected around the box framework 10 and the platform 50. The canopy sections 46 at road level on the deck are first secured within the tunnel 11. The rollers containing the canopy sections 42, 43 and 44 attached to the platform 50. Canopy sections 42 are pushed up between the girders 6 to the underside of the deck 2 and secured with poles and frames to seal against the underside of the bridge. Canopy sections 43 are pulled up using winches on the large sections to cover the ends of the platform 50 outside the girders and the ends of the box framework 10. Now, all the canopy sections 44 are pulled up with cords 91 and tightened with cords 92 and fastened in place. The overlapping canopy sections are clamped with fasteners 40 to complete the closure of the workstation.

During maintenance operations, the workers may have access into the work space through four main doors 160 at road level (see Figure 2). Vent ducts 161 are brought into the workstation through access panels positioned in the platform 50.

Maintenance operations may be carried out by workers within the work space on all parts of the bridge surface requiring maintenance. The railings 4 and the guardrail 5 are fully enclosed and accessible at road level. The outside of the bridge girders 6 is accessible from the platform 50 and from the cages 70. The bottom of the girders 6, the inside lower part of the girders 6 and the under structure 7 may be accessible from floor sections 56 in the platform 50 placed at a lower level while higher portions of the inside of the girders may be accessed from the platform with raised floor sections 56 mounted on floor supports 58 on the vertical partitions (rails 57). Within the work area, canopy sections 47 may be used to partition sandblasting areas from painting areas, for example, a central canopy section 47 may be dropped through the work space so that the sandblasting can proceed on a first area of the bridge 1 while painting follows in a second area as the mobile workstation moves along the length of the bridge 1. Doors may be provided in the partitions to enable workers to move from sandblasting to painting areas.

The mobile workstation may be moved along the bridge 1 where there are no intervening obstructions by the following steps. First, the internal center walls 47 are lowered onto rollers. Next, the second canopy sections 42 between the girders, are lowered onto their rollers 60 on the platform 50. Next, the third canopy sections 43 outside the girders are lowered onto their rollers 61 about the platform 50. Next, the fourth canopy sections 44 are loosened by slacking off the cords 91 and 92 that hold these canopy sections 44 by about 1 foot of slack. Then, the platform 50 is lowered by taking the weight off the eight heavy cables 121 using the heavy lifting booms 120 and their winches to give about 1 foot of clearance. Then the six hydraulic jacks 23 in the legs 14 of the straddle frames 12 are activated to withdraw the footing 22 to put each leg 14 on the wheels 20 so that the box framework 10 is able to roll along the bridge deck 2. Next, with two horizontal winches, (not shown) the workstation is moved ahead to the next location where work is to be done. The footings 22 are then lowered by the hydraulic jacks 23 to lift the legs 14 off the wheels 20 and to level the straddle frames 12 in the new location. The platform 50 is raised and reattached to the cables 51 and the canopy sections are restored place in the reverse order to their removal.

Light standards 3 or other bridge features on the bridge deck 2 may present an obstacle to advancement of the work station along the length of the bridge 1, particularly for the platform booms 52, the cage booms 72 and the heavy lifting booms 120. To deal with such obstacles, the platform booms 52, the cage booms 72 and the heavy lifting booms 120 are constructed to permit them to be folded in against the box framework 10 to clear the light standards 3. As each successive boom approaches a light standard 3, its load is transferred to another support, its cable temporarily disconnected, and the boom folded into the box framework 10. Once past the light standard 3, the boom may be opened out to its normal position and the cable and load reattached.

Figure 13 illustrates how a canopy boom 84 is constructed to be folded into the box framework 10 while moving past obstacles. The canopy boom 84 has a fastening bar 82 hinged to the box framework 10 by arms 82a and 82b. The fastening bar 82 may be pulled up and into the box framework 10 (the position shown in dotted lines in Figure 13) by means of cord 93 powered by winch 94. The point where either of arms 82a or 82b connect to the box framework 10 may be a slot and pin connection to allow the hinge point to slide up during upward rotation but to limit the downward travel to limit the lower position of fastening bar 82.

Figures 20a and 20b illustrate top and side views of the centre platform boom 52 which holds the spreader beam. Triangular truss arms 501 and 502 are hinged by upper and lower hinge pins 503 and 504 respectively,. The arms 501 and 502 terminate at a pair of shackles 505 and 506 pierced by a hole 507 which receives a cable 51 (by means if a hook or bolted clamp - not shown) which may be attached to the platform 50. The cable 51 through both shackles 505 and 506 holds the arms 501 and 502 together in an extended position. When it is desired to fold the arms against the box frame 10, the cable 51 may be removed from the hole 507 thereby permitting the shackles 505 and 506 to separate and the arms 501 and 502 may be folded back on the hinge pin 503 and 504 to provide clearance for passing obstructions on the deck.

Figures 20c and 20d illustrate the end platform booms at either end of the box frame 10. Each end platform boom 52 has a first arm 510 and a second arm 512 which are hinged onto the box frame by hinge pins 513 and 514. Arm 510 ends in shackle 515 and arm 512 ends at shackle 516, which may be joined in abutment and pierced through by hole 517. Thus, when a cable 51 is connected through the hole 517, the shackles 516 and 517 hold the arms 510 and 512 in an extended position. By removing the cable 51 from the hole 517, the shackles 515 and 516 may be separated and the arms 510 and 512 may be folded back against the box frame 10.

Figures 20e, 20f and 20g are top, side and end views of the winch boom 120 respectively. Each such winch boom 120 comprises a first arm 520 and a second arm 522 which are hinged to the box frame by hinge pins 523 and 524. To move the work station along the bridge, first, one prepares to move the mobile station in the manner described above where there are no obstacles. The cages 70 are lowered onto the platform 50 and the cables 72 are disconnected and the cage booms 72 folded into the side of the box framework 10. The fourth canopy sections 44 on the side of the lamp standard 3 are lowered down onto their rollers 62 on the platform 50. Next, the corresponding canopy booms 84 and the fastening rods 82 are folded down on the side of the box framework 10. Then the platform boom 52 and cable 51, which is adjacent the standard 3, is disconnected from the platform 50. The lifting boom 120 adjacent the standard 3 is also folded into the box framework 10. The mobile workstation is then winched ahead so that the lifting boom 120 and the platform boom 52 clear the standard 3. Then, the lifting boom 120 and the platform boom 52 are reopened and the heavy cable 51 reconnected to the platform 50. In succession, the platform booms 52 and cables 51 are disconnected, folded in, the workstation winched ahead, the platform boom 52 reopened and reconnected to the platform 50. center heavy cable 51. Similarly, the lifting booms 120 are folded in as they approach the standard 3 and then reopened. In this manner, the mobile workstation may be advanced to the desired position. Then, the canopy sections are raised back up into position and the move is completed as a regular move.

Bridge piers 8 also present an obstacle for moving the platform 50 along under the deck 2. The problem is solved by lowering one side of the platform 50 until it hangs outside the pier, disconnecting cables and reconnecting them as necessary as the platform 50 moves past the pier 8 and then elevating the platform 50 to a horizontal position. This may be explained in greater detail with Figure 21. When moving the workstation past a bridge pier, the workstation is prepared in the same manner as a regular move. Next, all the canopy sections are lowered onto the rolls on the platform. Then, the lower platform is prepared to be hung in a vertical position. On the hinge side, i.e., the side from which the platform 50 will be hung, the weight of the platform 50 is maintained on the three heavy cables 51 (3 each side above spreader, 4 each side below spreader) and the winch cables 121 of the lifting booms 120 are attached to lifting lugs along the underside of the platform 50. On the opening side, i.e., the side which will drop, the weight is taken up by the lifting booms 120 and the three heavy cables 51 are disconnected. Then, the lifting booms 120 drop the opening side of the platform 50 until there is no weight on the winch cables 121. The winch cables 121 are then disconnected from the winches 120 and dropped to the ground, and the lifting booms 120 on the hinge side pull the platform 50 up to swing in a vertical position. Then, the mobile work station is winched forward on the bridge deck 2 to allow the platform 50 to move past the bridge pier 8 while hanging in a vertical position. Once past the bridge pier 8, the platform 50 is raised up with the following procedure. Two hand lines are dropped to the ground and attached to the two opening side winch cables 121. These cables 121 are then drawn up to their winches 120 and reconnected. Then, the two hinge side winches 120 are slackened to permit the platform 50 to be swung off vertical. Then, using the two opening side winches 120, the platform 50 is pulled back to a horizontal position. Then the platform 50 is secured in position with the heavy cables 51 and all canopy sections are refitted. The construction of the cage booms 72 that permits them to be folded into the side of the box framework 10 is illustrated in Figures 18 and 19. The cage boom 72 comprises a triangular truss section 300 terminating in a bracket 301 having a hole 302 to receive the cage cables 71. The triangular truss section 300 is hinged onto a sliding frame 305 by means of hinge pins 306. One such hinge pin 306 which pass through an upper plate 307 extending backwards from the triangular section 300 over an upper plate 308 of a sliding section 305. Two lugs 309 extending from the bottom portion of the triangular section 300 and a lug 310 extending outward from the lower part of the sliding section 305 overlap and are pierced by a hole to receive the lower pin 306. The upper plate 307 extending back from the triangular section 300 continues to overlap the upper plate 308 of the sliding section 305 to permit a second pin 311 to be inserted through plates 307 and 308 to lock the position of the triangular section 300. Removal of pin 311 permits the triangular section 300 to be folded against the track truss 16 in order to pass obstacles. When the section 300 is reopened and plate 307 is aligned with plate 308, pin 311 may be reinserted to re-fix the position of the triangular section 300. In this manner, the cage boom 72 may be folded in and out of the box framework 10.

Figures 18 and 19 also illustrate how the cage booms slide along the track truss 16. It may be seen that the sliding section 305 straddles the track truss 16 by means of plate 308. Four pads 320 frictionally engage each side of the track truss 16 when the cables 71 are attached through hole 302 to the bracket 301 thereby holding the cage boom 72 in position. When the cage boom 72 is not heavily loaded, it may be manually pushed along the track truss 6 to a new position by sliding the pads 320 along the track truss 16.

The above description of the preferred embodiments is intended to be illustrative, rather than limiting of this invention, the full scope of which may be determined by reading, as a whole, the disclosure and the claims which follow.

Claims

WHAT IS CLAIMED IS:

1. A work station comprising: a canopy having a top section, a bottom section, first and second end sections, and first and second side sections wherein each said section is constructed of a material suitable to shelter workers and to contain debris, each section being suspended between a supply means and a take-up means; a plurality of support means to suspend the supply means and take up means for said sections about a structure, said support means being mounted in a first motive means mounted on the structure to permit the canopy to be repositioned from time to time; platform means to support workers within the canopy in close proximity to surfaces of the structure, said platform means being suspended by cables connected to a second motive means to permit a vertical degree of freedom, said cables being mounted on a third motive means on a transverse beam for a lateral degree of freedom and each said beam being mounted on a fourth motive means on the support means to permit a longitudinal degree of freedom of movement.

2. A work station for a bridge comprising: a canopy having a top section, a bottom section, first and second end sections, and first and second side sections spaced apart from the bridge by a distance sufficient to permit workers to access all surfaces of the bridge, wherein each said section is constructed of a material suitable to shelter workers and to contain debris, each section being suspended between a supply means and a take-up means that permit the sections to be unfurled to construct the canopy or furled to take down the canopy; a plurality of support means to suspend the supply means and take-up means for said sections about the bridge, said support means being mounted in a first motive means mounted on the bridge to permit the canopy to be repositioned from time to time; platform means to support workers within the canopy in close A 5

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proximity to surfaces of the structure, said platform means being suspended by cables connected to a second motive means to permit a vertical degree of freedom, said cables being mounted on a third motive means on a transverse beam for a lateral degree of freedom and each said beam being mounted on a fourth motive means on the support means to permit a longitudinal degree of freedom of movement; a passage from the first end to the second end within the canopy to permit the passage of traffic during maintenance operations.

3. The work station of Claim 2 the first motive means comprises tracks positioned on the bridge within the canopy and fastened temporarily in place.

4. The work station of Claim 3 in which the track means comprises a slotted box beam and a post which moves along a slot in the box beam on an axle mounted in wheels and a guide between the wheels to maintain alignment within the box beam and a locking bolt is provided to fix the location of the wheels within the box beam.

5. The work station of Claim 4 in which anchor means and are provided on the track means to receive a cable looped about a girder and drawn tight to secure the box beam temporarily in place.

6. The work station of Claims 1 or 2 in which the supply means and the take up means are rollers mounted on an outrigger structure.

7. The work station of Claim 2 in which the workers are supported on cages, platforms and on elevator platforms wherein the cages are supported to move vertically on cables which in turn are connected to move horizontally across beams in response to controls within the cage.

8. The work station of Claim 7 in which the beams are be mounted to move horizontally along the length of the canopy and the cages are moved along the cables by means of powered pulleys and horizontally along the beam on a track and wheel means erected over a beam controlled from within the cage by control means and servo motors.

9. The work station of Claim 7 in which the cages have a floor plan cutout to fit about two vertical faces of a girder to position a worker to do maintenance work at close range on the surface of the girder.

10. The work station of Claim 7 in which the distance from the girder is determined and controlled by a positioning arm fastened to the cage by vertical arm, said positioning arm terminating at a roller which maintains rolling contact with a bridge surface and having a spring/damper unit to absorb dynamic loading.

11. The work station of Claim 2 in which the rollers are mounted overhead from supporting structures on the bridge deck on first motive means and the beams are mounted in tracks on the deck.

12. The work station of Claim 2 in which the passage is erected on the deck with walls and a roof suitable to deflect any anticipated debris and mounted on the bridge deck for longitudinal movement.

13. The work station of Claims 1, 2 or 12 in which a safety net is provided above the passage to catch falling objects or workers.