US3608670A

US3608670A - Scaffold tender

Info

Publication number: US3608670A
Application number: US27867A
Authority: US
Inventors: James H Blake; Richard E Barber
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-04-13
Filing date: 1970-04-13
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28

Abstract

A scaffold tender for suspending a transverse work platform across the underside of highway bridges or the like. The scaffold tender comprises a wheeled framework supported on the bridge deck. A plurality of longitudinally spaced supports are mounted at each side of the framework, each support being selectively retractable in order to clear vertical abutments during movement of the framework along the bridge. The work platform is alternately suspended from one or more of the extended supports during movement of the scaffold tender. The method of traversing the bridge involves the alternate use of the supports and the movement of each support between a retracted position and an extended position as required to clear obstructions encountered in the path of movement of the framework.

Description

I United States Patent [72] Inventors Jamel H. Blake 3,145,801 8/1964 Callahan 182/63 1520 E. Capital Expreaway#220, San 3,456,756 7/1969 Price 182/63 Jose, Calif. 95121; 3,524,520 8/ 1970 Tidwell 182/36 mum Barber 6800 Enterprise Road Primary Examinr-Reinaldo Machado Attorney-Wells St. John & Roberts [211 App]. No. 27,867 [22] Filed Apr. 13, 1970 [45] Patented Sept. 28, 1971 7 ABSTRACT: A scaffold tender for suspending a transverse I 54] SCAFFOLD TENDER work platform across the underside of highway bridges or the like. The scaffold tender comprises a wheeled framework sup- 8 Claims, 12 Drawing Fig.

ported on the bridge deck. A plurality of longitudinally spaced U-S. supports are mounted at each side of the framework each 132/37, 182/142 support being selectively retractable in order to clear vertical m 8 3/10 abutments during movement of the framework along the [50] Field of Search 182/63, 36, bridge The work l tf is alternately Suspended f one 150 or more of the extended supports during movement of the 56 R t CM scaffold tender. The method of traversing the bridge involves 1 e the alternate use of the supports and the movement of each UNITED STATES PATENTS support between a retracted position and an extended position 2,669,490 2/1954 Kaufman 182/63 as required to clear obstructions encountered in the path of 2,639,950 5/1953 Wheeler 182/37 movement of the framework.

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II II H as PATENTED SEP28 I971 SHEET 1 BF 4 INVENTOR. Jun. H. BIO! Rich 5.

PATENTEUSP28|9I| 3508.670

sum 2 [IF 4 INVENTOR. James H. Blake Richard E. Barber scmou) TENDER BACKGROUND OF THIS INVENTION In the construction of bridges forhighway or other use, concrete formsare utilized on the underside of the bridge deck and these forms must be stripped after pouring of the concrete deck. The bridge structure usually includes supporting piers. In addition, substantial bridge arches are conventionally supported by a steel superstructure, suspension cables or the like, which extend upwardly from the deck at each side of the bridge. These elements comprise vertical abutments encountered in the path of movement of any overhanging apparatus mounted onthe bridge deck.

Because of the obstructions encountered by a movable scaffold tenderon the bridge deck, it has been conventional to construct stationary scafi'olding completely across such a bridge for purposes of form removal and painting. For safety, it is generally required that nets be suspended across the arch. The construction of such scaffolds and the utilization of nets imposes considerable expense on such a project, most of which can be eliminated if a scaflold could be moved across the bridge.

Prior patent disclosures have shown mobile scafi'old supports designed to clear the piers of bridges. Examples are shown in U.S. Pats. Nos. 2,669,490, 3,035,659 and 3,145,801. However, these patent disclosures indicate no effort to provide for clearance of vertical obstructions above the poured deck and would only be useful on bridges supported entirely by piers and clear of all superstructures.

SUMMARY OF THE INVENTION The scaffold tender disclosed below comprises a rigid framework having an effective width less than the width of the bridge deck and movably carried by wheels in engagement with the upper surface of the bridge deck in order that the framework may be longitudinally moved along the Means are provided on the framework for selectively fixing the framework relative to the bridge deck during stripping of forms; painting of the bridge underside, or similar working operations. A plurality of transverse supports are mounted to the framework at longitudinally spaced positions at both sides of the framework. Each support is independently mounted for selective movement relative to the framework between a retracted position located within the outside boundaries of the bridge deck to permit the framework to clear vertical obstructions and an extended position with one end of the support located outward of these boundaries to permit suspension of a platform structure from the extended end.

According to the method of this invention, a working platform beneath the deck of a bridge is supported by suspending the ends of the platform from a pair of longitudinally spaced and horizontally retractable supports movably mounted on the bridge deck. The ends of the platform are alternately suspended from horizontally retractable supports intermediate the pair of supports. Movement of the platform is permitted by retracting each support as necessary to clear obstructions and'then moving all supports as a unit along the bridge deck until a subsequent obstruction is again encountered. By alternately supporting the plafiorm from the various supports and retracting those supports not in use to suspend the platform one can work the platform across the complete length of a bridge, holding the platform at any desired position along the bridge as required for manual work at the underside of the bridge deck.

It is one object of this invention to provide a scaffold tender capable of meeting the requirements of contractors and governmental agencies concerned with the safety of men working along the undersides of a bridge deck, while providing for longitudinal movement of the scaffold tender through upright members and obstructions at the sides of the bridge deck. Another object of this invention is to provide such a scaffold tender which is adaptable to any highway bridge.

LII

These and further objects will be evident from the following disclosure of a preferred embodiment of the invention. Modifications can obviously be-made in the illustrated embodiment without deviating. from the basic concepts and objects of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational :sectional view of a preferred 'einbodiment of the invention, taken transversely through a typical bridge deck structure tothecenterline'of the bridge and the scaflold tender supported thereon;

FIG. 2 is a top view of the structure shown in FIG. 1;

FIG. 3 is a side elevational view of the structure shown in FIG. 1;

'FIG. 4 is an enlarged fragmentary sectional view taken along line 4-4 in FIG. 1;

FIG. 5 is an enlarged fragmemtarysectional view taken along line 4-5 in FIG. 2;

FIG. 6 is an enlarge fragmentary sectional view taken along line 6 -6 in FIG. 2; FIGS. 7-12 illustrate'thesteps by which the scafiold tender is moved along the bridge through fixed abutments;

FIG. 7 is a schematic-top view of the scaffold tender in a stationary working position;

FIG. 8 is a side elevation view corresponding to FIG. 7;

FIG. 9 is a top view showing retraction of one support which has cleared one of the vertical abutments;

FIG. 10 is a side elevation view corresponding to FIG. 9;

FIG. 1 1 is a schematic top view showing the repositioning of the supports after clearing the abutment; and

FIG. 12 is a side elevation view corresponding to FIG. 11.

including a concrete bridge deck 10, curb 11 and side rail 12.

For ease of illustration, the bridge structure is illustrated only to the longitudinal centerline, it being understood that the bridge structure and the scaffold apparatus are each symmetrical about this centerline.

The bridge deck 10 is typically supported by upright piers 13, one of which is shown in the background in FIG. I. The concrete deck 10 is poured along conventional stringers 14 carried by transverse girders 15. The girders 15 are interconnected at each side of the bridge by a lower truss chord which in turn is suspended by upright truss members 17 which are conventionally connected across their upper ends by an upper truss chord (not shown). In other types of bridge construction, the truss members 17 are replaced by cables which suspend the bridge between the piers at each end of an open span. In either instance, upright obstructions are located in a varying spatial arrangement along the span of the bridge deck 10. The problem solved by this disclosure is the difiiculty involved in suspending scaffolding across the underside of the bridge deck by overhanging members which project through the upright obstruction, while providing pratical means by which the supports can be worked across the bridge without dismantling the scaffold tender or the scafiolding supported thereby.

The scaffold tender comprises a framework made in two separate components. As shown, there is a rectangular side unit 18 at each transverse side of the scaffold tender. If desired, a rigid frame (not shown) may be bolted between the two side units 18 to form an integral rigid framework that extends substantially across the entire width of the bridge deck 10. when spaced as shown, units 18 provide central clearance on deck 10 for traffic or construction purposes. Each side unit 18 of this framework is supported by two sets of wheels 21, 22.

ty support the framework and relieve the weight on the wheels 21, 22 while holding the framework in a stationary position relative to the bridge deck 10. The general structure of the wheel assemblies and jacks 23 is conventional and further detail is not believed necessary to an understanding of the present invention.

Mounted at each side of the framework at an elevation above the curb 11 and rail 12 are a plurality of outwardly extensible supports. These supports include a pair of

horizontal beams

25, 26 and an inter-mediate beam 27. The

beams

25, 26 and 27 are longitudinally spaced from one another. They are mounted in a common horizontal plane and are parallel to one another. Each is movably mounted to the side unit 18 of the framework for movement between an extended position shown in FIGS. 1, 2 and 3 wherein the support protrudes outwardly beyond the upright abutrnents provided by the truss members 17, and a retracted position wherein the supports are entirely within the boundaries of the bridge deck 10.

The

beams

25 and 26 are illustrated as being l-beams movably supported between transverse channels 28 which are fixed across the top of each side unit 18 at the respective front and rear ends thereof. Transversely spaced sets of rollers 30 are journaled on the channels 28 (FIG. 4). The outside set of rollers 30 engagethe upper flange of each beam 25, while the inside set of rollers 30 engage the lower flanges to counteract the'forces exerted on the beam when in its extended position. To facilitate inward movement of the

beams

25, 26 parallel to their length, small rollers31 are provided between the channels 28. The lower beam surfaces ride along the rollers 31 during beam movement, but clear the rollers 31 when the beams are fully extended.

The wider intermediate beam 27 at each side of the scafiold tender is constructed of two spaced channels mounted back to back and separated by a connecting truss structure. Beam 27 is similarly supported by two sets of rollers 32 (FIG. and by rollers corresponding to the previously discussed rollers 31.

The suspended scaffold is shown generally in FIGS. 1, 2 and 3. It comprises a pair of scaffold slings 33 at each side of the bridge. Each end of each sling 33 is suspended by a cable 34 and bridle 35. The upper end of the cables 34 can be selectively anchored to the outer ends of the

beams

25, 26 or 27, as will be described below. Extending across the underside of the bridge deck and carried by the slings 33 are transverse planks 36 or other types of transverse work platforms. These platforms provide manual access under the bridge deck for purposes of stripping concrete forms from the underside of the deck or for painting the bridge structure, making repairs, inspections, etc.

The present method supporting the transverse working platform beneath bridge deck 10 involves the step of projecting one or

more beams

25, 26 or 27 through the upright obstructions, such as the truss members 17, and suitably suspending the slings 33 and cables 34 so as to maintain the planks 36 in a stable working condition. During use of the working platform, the framework should be fixed relative to the bridge deck by I the jacks 23 or other equivalent locking arrangements provided to hold the framework stationary relative to the deck 10. When working at considerable height, individual safety harnesses (not shown) can be utilized by workmen on the planks 36.

When it is necessary to move the working platform afforded by planks 36, those persons carrying out operations on the underside of the deck are transferred to the bridge deck 10 by a ladder or other suitable lifting device (not shown). The slings 33 are then alternately suspended by cables 34 from one or more of the

beams

25, 26 or 27 which are free to move longitudinally along the bridge deck 10 without abutting a truss member 17. Those beams 25, 26 or 27 in immediate abutting position relative to a truss member 17 are manually retracted or moved inward relative to the bridge deck 10. The framework can then be moved along the bridge deck 10 by attachment to a tractor or other vehicle (not shown) until the retracted beam has cleared the abutment. It can then be again extended and cable 34 reconnected as desired. By providing alternate suspension of the cables 34 from both

outer beams

25, 26, one

outer beam

25 or 26 and the intermediate beam 27, or from the wider intermediate beam 27, and selectively retracting and extending the

beams

25, 26 and 27 as necessary to work through the upright truss members 17, the scaffold tender can be moved in small steps across the entire length of the bridge deck 10. A winch assembly 38 on each framework side unit 18 is used to move the units in conjunction with a fixed anchor (not shown) and is alternately used to lift sling 33 during weight transfer.

The general steps by which the scaffold tender is moved are shown in FIGS. 7-12. In FIGS. 7 and 8, beams 25 are in immediate abutting position adjacent to a truss member. Cables 34 are suspended from the

outer beams

25, 26 in a working condition. The scaffold tender would be held stationary in this position during operations under the bridge deck 10. When it is desired to move the working platform, the forward cable 34 would be shifted from the beams 25 to the intermediate beams 27. This would be accomplished by connecting a substitute cable 34 between the forward end of each sling 33 and the intermediate beams 27, and then releasing the previously used cable 34. The sling 33 would remain in a horizontal position suspended between the

beams

26, 27 in the manner shown in FIG. 10.

After release of cable 34 from the beams 25 they can be retracted as shown in FIG. 9. The framework can then be moved in a forward direction as illustrated by arrow 37.

After the upright truss member 17 has been cleared, the beams 25 can again be extended as shown in FIG. 11 and cables 34 can be reconnected between sling 33 and the outer ends of beams 25 in the manner shown in FIG. 12. These steps can be repeated as necessary in order to work through any conventional pattern of truss members, cables, posts, etc., which might be encountered at the side of a bridge.

When encountering a pier at the underside of the bridge, it is necessary to either remove the planks 36 from the slings 33 or connect one end of each plank 36 to a single sling 33 and allow the planks to drop from the remaining sling 33.

Should both

beams

25, 26 be in abutment with an upright along a bridge while encountering upright obstructions having 7 variable spacing along the length of the bridge as is conventional in bridge span construction.

The apparatus illustrated is extremely versatile and adaptable to any type of concrete bridge deck or similar bridge construction. The two side units 18 are located at the respective sides of the deck and have an effective working width slightly less than the bridge deck width. They are easily transported from one location to another.

Obviously, some modifications can be made with respect to the precise details shown in the drawings and discussed above.

What is claimed is:

1. A scafiold tender for movably suspending a transverse working platform beneath the deck of a highway bridge of the like, comprising:

a framework having an effective width less than the width of said bridge deck;

said framework being movably carried by a plurality of wheels in engagement with the upper surface of the bridge deck, whereby the framework can be longitudinally moved along the bridge deck;

means on said framework for selectivity fixing the location of said framework relative to the bridge deck;

and a plurality of transverse supports mounted to said framework and longitudinally spaced from one another at both sides of the framework;

each support being independently mounted on said framework for selective movement relative to the framework between a retracted position wherein the entire support located inward of the transverse boundaries of the bridge deck and an extended position wherein one end thereof is located outward of said boundaries; and

means mounted to said one end of each support for releasably supporting a working platform extending transversely beneath the bridge deck.

2. A scaffold tender as set out in claim 1 wherein the longitudinal spacing between supports at each side of said framework is such as to permit longitudinal movement of the framework along the bridge deck while at least one of said supports is in its extended positions and received between truss members at the sides of the bridge deck.

3. A scaflold tender as set out in claim 1 wherein each support while in its extended position, is cantilevered on said framework in a horizontal transverse position.

4. A scaflold tender as set out in claim 1 wherein each support, while in its extended position, is cantilevered on said framework in a horizontal transverse position;

each support being movably guided on said framework for transverse translational movement in a direction parallel to the length of the support between its retracted and extended positions.

5. A seaflold tender as set out in claim 4 wherein each of said supports is provided with a releasable locking element operatively connected between it and said framework for selectivity securing the support relative to said framework in either its retracted or extended position.

6. A scafiold tender as set out in claim 1 wherein said framework comprises:

a pair of identical side frames having said supports mounted thereto;

said frames being symmetrically arranged at the respective sides of the bridge deck.

7. A scaffold tender as set out in claim 1 wherein each support comprises a horizontal beam movably mounted to the framework for translational motion parallel to the length of said support, said supports being parallel to one another.

8. A method of supporting a transverse working platform beneath the deck of a highway bridge of the like, comprising:

suspending the respective ends of the platform from a pair of longitudinally spaced and horizontally retractable supports mounted on the bridge deck; alternately suspending the ends of the platform from horizontally retractable supports intermediate the pair of pp retracting each support transversely relative to the bridge deck as necessary to clear obstructions at the side of the bridge deck; and

moving all supports as a unit along the bridge deck.

Claims

1. A scaffold tender for movably suspending a transverse working platform beneath the deck of a highway bridge or the like, comprising: a framework having an effective width less than the width of said bridge deck; said framework being movably carried by a plurality of wheels in engagement with the upper surface of the bridge deck, whereby the framework can be longitudinally moved along the bridge deck; means on said framework for selectivity fixing the location of said framework relative to the bridge deck; and a plurality of transverse supports mounted to said framework and longitudinally spaced from one another at both sides of the framework; each support being independently mounted on said framework for selective movement relative to the framework between a retracted position wherein the entire support located inward of the transverse boundaries of the bridge deck and an extended position wherein one end thereof is located outward of said boundaries; and means mounted to said one end of each support for releasably supporting a working platform extending transversely beneath the bridge deck.

3. A scaffold tender as set out in claim 1 wherein each support while in its extended position, is cantilevered on said framework in a horizontal transverse position.

4. A scaffold tender as set out in claim 1 wherein each support, while in its extended position, is cantilevered on said framework in a horizontal transverse position; each support being movably guided on said framework for transverse translational movement in a direction parallel to the length of the support between its retracted and extended positions.

5. A scaffold tender as set out in claim 4 wherein each of said supports is provided with a releasable locking element operatively connected between it and said framework for selectivity securing the support relative to said framework in either its retracted or extended position.

6. A scaffold tender as set out in claim 1 wherein said framework comprises: a pair of identical side frames having said supports mounted thereto; said frames being symmetrically arranged at the respective sides of the bridge deck.

8. A method of supporting a transverse working platform beneath the deck of a highway bridge of the like, comprising: suspending the respective ends of the platform from a pair of longitudinally spaced and horizontally retractable supports mounted on the bridge deck; alternately suspending the ends of the platform from horizontally retractable supports inTermediate the pair of supports; retracting each support transversely relative to the bridge deck as necessary to clear obstructions at the side of the bridge deck; and moving all supports as a unit along the bridge deck.