US3537545A - Positioning device for elevated structures - Google Patents

Description

United States Patent [72] Invento s Jill wlllli H I 1 3,114,433 12/1963 Downs 182/37 RFD 02, Hiram, 30141; 3,251,435 5/1966 Fisher 182/142 gm RFD Dw'hsvme Primary Examiner-Reinaldo P. Macl ado [2" App]. 769.835 Attorney-Newton, Hopluns & Ormsby [22] Filed Oct. 23,1968

[45 l muted 1970 ABSTRACT: A positioning device for use with elevated structures and a method of using the same. The apparatus includes a boom attachable to the top of the structure and rotatable [54] DEVICE FOR ELEVATED about the centerline of the structure. Power means is provided for rotatin the boom about the centerline of the structure and no can, to 1mm; Figs. 8 means is provided on the outer extendlng end of the boom for [52] US- /1 suspending a workman's platform therefrom. The invention 1 142 also includes a workmans platform selectively suspendable [$1 ht. E04: 3/10 from the extending end of the boom for supporting a workman [50] Field of Search 182/ l4, l3, thereon and is provided with a power means for selectively I p 1.2, 1 37 raising and lowering the workman's platform with respect to the extending end of the boom to give the workman access to [56] the exterior of the structure. Control means is provided on the UNITED STATES P TENTS workmans platform for selectively controlling the raising and 1,101,839 6/1914 Elvestrom 182/37 lowering of the workmans platform with "Spec! the 1,421,609 7/1922 3m gt 182/37 L extending end of the boom and for selectively controlling the 6/1963 Reinhardt..l 182/12 W movement of the boom about the centerline of the structure.

Sheet 1 of 3 v /38 INVENTORS JAMES E.W|LLI5 REFFORD LLEGGETT BY fawn-4y ATTORNEYS Patented Nov. 3, 1970 Sheet 7 3 INVENTORS JAMES E. WILLIS REFFORD L.LEGGETT POSITIONING DEVICE FOR ELEVATED. STRUCTURES The method of the invention includes the steps of climbing an elevated structure while carrying a cable attached to a powered workmans platform, securing the cable to the center of the top of the structure, attaching a powered boom to said platform, activating said platform to cause said platform to take up said cable and raise said platform and said boom to the top of said structure, deactivating said platform when it reaches the top of said structure, securing one end of the boom to the center of said structure after releasing said boom from said platform, and attaching said cable of said platform to the other end of said boom. Alternatively, the cable of the workmans platform may be first attached above the catwalk of the structure, the platform and boom raised to the catwalk, the cable reattached to the topof the structure, and then the platform and boom raised to the top. The method also includes slidably connecting said platform to said structure to control the sidewise direction of movement of said platform as said platform is raised and lowered with respect to said boom.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a positioning device for elevated structures and a method of using same, and is more particularly concerned with a powered workmans platform which moves the workman around the structure and moves the workman up and down along the exterior of the structure and the method of using same.

2. Discussion of the Prior Art Normally, elevated structures such as water tanks must be periodically sandblasted and repainted to prevent corrosion of the material of the structure. In order to do this, some means must be available for positioning a workman about the exterior surface of the structure so that he can sandblast and repaint the same. Presently this task is performed using ropefalls and a boatswains chair. With this rigging, the workman usually makes drops straight down the side of the structure, painting or sandblasting as much of an area as can be reached by swinging to theleft or right in the boatswains chair. Each time the worker reaches the ground he must climb to the top of the structure, move his rig to the next location which he wishes to work, and then have someone pull the boatswains chair back up to him'so that he can work down the structure again. ln the process of swinging out to reach horizontal beams and wind brace rods, the worker is usually in a strenuous, awkward and uncomfortable position requiring professional skill and endurance to adequately perform the work. The biggest drawback to the presently used rigging apparatus and methods for refinishing elevated structures is the fact that the worker expends more effort and skill in getting to the work area than the actual labor involved in the sandblasting or painting opera- 7 tion. Therefore, the amount of work that can be performed by the worker is limited by the amount of exhaustive labor he must exert in climbing the structure, swinging the boatswains chair to the work area, and clinging to the structure at his work area.

Moreover, the boatswains chair is usually raised and lowered by the workman manually through a block and tackle,

which causes the worker to tire quickly when he is working on a rather high elevated structure. Also, the workman in the boatswains chair must support the sandblasting and painting hoses which he uses to clean and paint the structure. Since these hoses are of the high pressure type, they are so heavy that the workman has great difficulty in supporting the same, thereby expending unnecessary energy not required for the actual work performed on the elevated structure. On relatively high structures, the sandblasting hose is generally so heavy that it must be raised and lowered by separate block and tackle and manually manipulated by a crew on the ground. This increases the size of the ground crew which must be used with the present rigging methods for refinishing elevated structures.

SUMMARY OF THE INVENTION These and other problems and disadvantages associated with prior art positioning devices and methods for elevated structures are overcome by the invention disclosed herein in that the workman only has to climb up the structure once and climb down the structure once when using the invention. Moreover, the workman can move circumferentially about the structure and up and down with respect to the structure without having to waste time tying and untying a cable and can also sandblast or paint the structure while moving along on his platform. Moreover, the workman can raise the materials that he needs to work by attaching the same to the platform as it is movedup and down the structure, thereby eliminating a major part of the ground crew normally associated with prior art devices and methods.

The apparatus of the invention includes generally a powered boom attached to the center of the top of the structure and movable around the periphery of the structure and a powered workmans platform moveable up and down the side of the structure with respect to the end of the powered boom. The powered boom is selectively extendable to compensate for the different sizes of structures and includes a wheel assenibly which is selectively driven around the structure by a driving unit to move the boom circumferentially about the structure. The workmans platform is suspended from the extending end of the boom and carries a powered winch assembly for moving the platform up and down the side of the structure with respect to the boom. A first switch means is carried by the workmans platform for controlling the driving unit associated with the boom and a second switch means is carried by the workmans platform for selectively controlling the powered winch assembly of the workmans platform. The winch assembly associated with the workmans platform is effective to carry materials and implements therewith up and down the side of the structure so that the workman on the platform or workmen on the ground do not have to support the weight of the same.

The method of the invention includes the steps of securing the cable of the powered workmans platform to the center of the top of the elevated structure while the platform itself rests on the ground, attaching the powered boom to the platform, activating the platform so that the platform raises itself and the boomto the top of the structure, attaching one end of the boom to the center of the top of the structure, and detaching the cable of the platform from the structure and reattaching it to the other end of the boom. The method also includes slidably connecting the platform to the structure to control the direction of movement of the platform as it moves up and down with respect to the boom.

These and other features and advantages of the invention will become more apparent upon consideration of the following specification and accompanying drawings wherein like characters of reference designate corresponding parts throughout and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an elevated structure showing the invention positioned thereon;

FIG. 2 is a perspective view of the powered boom of the invention;

FIG. 3 is an exploded perspective view of the workmans platform of the invention;

FIG. 4 is a longitudinal cross section view of the powered FIG. 8 is a schematic diagram of the electrical circuit associated with the invention' for selectively controlling the same;

FIG. 9 is a perspective view of the second embodiment of the invention; and v FIG. 10 is a schematic diagram of the electrical circuit associated with the second embodiment of the invention.

These FIGS. and the following detailed description disclose specific embodiments of the invention; however, the inventive concept is not limited thereto since it may be embodied in other forms.

' DESCRIPTION or ILLUSTRATIVE EMBODIMENTS Referring to FIGS. 18,- it will be seen that the fir-st embodiment of the invention comprises generally a powered boom 10 secured to the center X of the top T of an elevated structure S, here shown as a water tank, and a workmans platform 11 suspended from the extending end of the boom 10. The boom 10 moves circumferentially about the structure S and the workmans platform 11 ascends and descends along the side of the structure S so that the workman carried on the platform 11 may selectively engage the structure S for repair ing and refinishing the same.

Referring more particularly to FIGS. 2 and 4, the powered boom 10 comprises generally an elongate support tube 12 having a passage 15 therethrough, an extension shaft 14 slidably received in the passage 15, a driving means 16 slidably carried along the support tube 12 for driving the boom 10 circumferentially about the structure S, and a hanger assembly 1 l8 slidably carried along the support tube 12 at its extending 4 The bottom of the journal 34 associated with the stanchion 31 is provided with a mounting plate 42 which mounts the driving unit 28 under the support tube 12.

The driving unit 28 comprises a drive motor 44 and a rightangle gear reducer 45 as seen in FIG. 2. The drive motor 44 is connected to'the gearreducer 45 as seen in FIG. 2. The drive motor 44 is connected to the gear reducer 45 so that rotation of the drive motor 44 causes rotation of the output shaft 46 of end for suspending the platform 11 therefrom. The driving 7 means 16 selectively moves the boom 10 circumferentially about the structure S and the hanger assembly 18 extends over the edge of the structure S to support the platform 11 therebelow.

* Referring particularly to FIG. 4, the support tube 12 carries a pair of locking bolts 20 which engage the extension shaft 14 and fix the extension shaft with respect to the support tube 12. The end of the extension shaft'14 extending toward the center X of the structure S is provided with an attaching lug 22 to be connected to the center X of the structure S in conventional manner by a cable 24. The cable 24 is best seen in FIG. 1.

The driving means 16 includes an inverted U-shaped positioning frame 25, a driving'wheel 26, a driving unit 28, and a drive chain 29 operativelyconnecting the driving wheel 26 with the driving unit 28 for rotation of the driving wheel 26 about the support tube 12. The positioning frame 25 includes apair of upstanding stanchions 30 and 31, the stanchion 30 being positioned on the rightside of the driving wheel 26 as seen in FIG. 4 and the stanchion 31 being positioned on the left side of the driving wheel 26 as seen in FIG. 4. The upper ends of the stanchions 30 and 31 are joined by a cross brace 32 and the lower depending ends of the stanchions 30 and 31 define apertures 34 therethrough having a diameter sufficient to slidably receive the support tube 12 therethrough. Journals 35 are attached to the lower depending ends of the stanchions 30 and 3,1 and slidably extend around the support tube 12 to assist in maintaining the stanchions 30-and 31 perpendicular to the support tube 12. Lock bolts 36 threadedly extend through journals 35 to selectively engage the support tube 12 and lock the positioning frame 25 in position at any selected point along the length of the support tube 12.

The driving wheel 26 is rotatable about an axis coinciding with the centerline of the tube 12 and includes a hub 38 defining a passage 39 therethrou'gh'sufficient in diameter to be slidably received over the support tube 12. The hub 38 is positioned between and in abutment with the journals 34 attached to the stanchions 30 and 31. The hub 38 mounts a conventional tire 40 thereon so that the tire 40 is freely rotatable with respect to the support tube 12 and between the stanchions 30 and 31. A drive sprocket 41 is fixedly attached about the hub 38 at one end thereof for attachment to the drive chain 29.

the gear reducer 45. A sprocket 48 is mounted on the extending end of the output shaft 46 and in vertical alignment with the drive sprocket 41 on the hub 38, and the chain 29 connects the sprockets 41 and 48 so that when the motor 44 is rotating, the driving wheel 26 will also be rotated. It is to be understood that the drive motor 44 is a reversible motor so that the driving wheel 26 may be selectively rotated clockwise or counterclockwise to drive the boom 10 about the structure S. The drive motor 44 may be an electric motor or an air motor or any other conventional motor, the motor 44 here shown being an electric motor.

The hanger assembly 16 comprises a U-shaped bracket 50 having journals 51 attached to the upper ends of thelegs 52 thereof. The journals 51 each define a passage therethroug h effective to slidably receive the support tube 12 therethrough. Lock bolt 54 threadedly extends through the journal 51 to selectively engage the support tube 12 and lock the mounting bracket 50 at any point therealong. The mounting bracket 50 is generally mounted on that end of the support tube 12 extending past the positioning frame 25 and a stabilizer plate 55 is pinned to the lower portion of the mounting bracket 50. The stabilizer plate 55 is provided with a clevis 56 at the lower 'end thereof for attachment to the platform 11. It is understood that the stabilizer plate 55 may always hang vertically when in use regardless of the angle defined by the support tube 12. A plurality of additional apertures 57 are provided through the bracket 50 to adjust the position of the stabilizer plate 55.

To distribute the forces applied to the support tube 12, a lug 58 is provided onone of the journals 51 and a lug 59 is provided at the inwardly extending end of the support tube 12. A cable 60 provided with a turnbuckle 61 extends between the lugs 58 and 59. The cable 60 extends over the positioning frame 25 through a pair of eyelets 62. When the turnbuckle 60 is properly manipulated, the forces applied to the support tube 12 will be exerted not only along the hub 38 but also along the journals 34. Further, the.cable 60 prevents the support tube 12 from bending. I

The driving unit 28 is mounted under the support tube 12 so that the center of gravity thereof lies directly under the support tube 12 to prevent the boom 10 from tilting about the centerline of the'support tube 12 when it is in position on the structure S; The positioning frame 25 and the driving wheel 26 are movable along the support tube 12 to reduce the tendency of the boom 10 to pivot about the driving wheel 26 to a minimum.

Referring more particularly to FIGS. 3, 5 and 6, the workmans platform 11 comprises generally a seat 100, a guide assembly 101 and a winch assembly 102. The winch assembly 102 has a cable Cextending upwardly therefrom through the 7 guide assembly 101 and attached to the boom 10 through the ing a generally rectangular configuration and defining an opening 108 at one end thereof through which the cable C extends from the winch assembly 102. A U-shaped carriage member 109 having the upper extending ends of its legs 110 attached to the. underside of the support plate 106 are positioned at each end thereof. The carriage members 109 serve to strengthen the support plate 106 and positions the winch as sembly 102 above the ground when the platform 11 is resting thereon. A pair of: crossed auxiliary braces 112 extend between the depending portions of the carriage members 109 to strengthen same. A connecting ring 114 circles the braces 112 at the point where they cross and serve as an attaching point for equipment to be suspended below the platform 11 or as an attaching point to hang the platform llupside down and use the same as a winch.

The guide assembly 101 is pyramidal in shape, and includes a tie rod 115 pivotaily connected to one corner of the top of the support plate 106 and a tie rod 116 pivotally connected to the support plate 106 at the opposite corner thereof. The tie rods 115 and 116 extend upwardly from the right end of the support plate 106 as seen in FIG. 5. A tie rod 118 and a tie rod 119 extend upwardly from the opposite corners of the support plate 106 from the left side thereof as seen in FIG. 5. The tie rods 115, 116, 118 and 119 extend upwardly and inwardly toward each other to join a guide member 120 spaced above and over the center of the support platform 106i Reinforcing struts 121 extend between the upper portions of the tie rods and the guide member 120 to reinforce the same. The tie rods 115 and 116 are attached to the support plate 106 through mounting brackets 107. The rods 115 and 116 have bent end portions 117 slidably received through the brackets 107. The bent end portions 117 can be removed from the brackets 107 by forcing the rods 115 and 116 apart. When the end portions 117 are removed from the brackets 107, the guide assembly 101 can be pivoted over in horizontal alignment with the seat 100 to reduce the overall height of the platform 11.

The guide member 120 is hollow and defines a passage, 122 therethrough through which the cable C passes as it leaves the winch assembly 102 and travels upwardly to be engaged by the clevis 56. A guide roller 124 is rotatably carried in the guide member 120 adjacent the passage 122 for directing the cable C as it passes through the passage 122. The guide roller 124 is freely rotatable with respect to the guide member 120 so that, as the cable C passes thereby, the guide roller 124 rotates to prevent the cable C from wearing. A safety belt 8 maybe attached to the guide assembly 101 as shown in FIG. 5 to assist in keeping the workman on the sent 100.

The winch assembly 102 includes a driving unit 122. a winch sheave 124, and a drive chain 125 operatlvely connecting the driving unit 122 and the winch sheave 124 so that the driving unit 122 may selectively rotate the winch sheave 124. The cable C is attached to the winch sheave 124 so that, as the same is rotated, the cable C will be taken up on the sheave 124 or let out therefrom to raise and lower the workmans plat form 11 with respect to the boom 10. The winch sheave 124 is carried on an axle 126 as best seen in FIG. 6. The axle 126 is rotatably mounted at each end thereof in a bearing 128 carried by the legs 110 of the left carriage member 109 as seen in H0. 5. The axle 126 is provided with adrive sprocket 129 which is connected to the chain 125 for selectively rotating the axle 126. The winch sheave 124 includes a disc-shaped side wall 130 at each end thereof for retaining the cable C. A connecting pin 131 fixes the sheave 124 with respect to the axle 126 and also serves to attach the cable C to the sheave 124 so that it will be wound therearound or released therefrom as the sheave 124 is rotated.

The driving unit 122 includes a motor 132 operativeiy connected to a right angle gear reducer 134 so that the motor 132 rotates the output shaft 135 of the gear reducer 134. A driving sprocket 136 is mounted on the extending end of the output shaft 135 of the gear reducer 134 and is operatively' connected to the chain 125 so that rotation of the motor 132 rotates the driving sprocket 136 and the sheave 124 through the chain 125.

The motor 132 is equipped with an automatic brake 138 so that, when the motor 132 is not energized, the automatic brake 130 automatically locks the shaft of the motor to prevent the sheave 124 from releasing the cable C therefrom. it will thus be seen that theworkman may selectively energize the motor 132 to ascend or descend adjacent the elevated structure S. When he arrives at the desired location, he can deenergize the motor 132 and the platform 11 will remain in place. The motor 132 is a reversible motor so that the sheave 124 can be selectively driven in either direction to raise or lower the platform 11'. The particular motor 132 shown is an electric motor; however, it is to be understood that other type driving motors may be used to perform the same function.

A seat cushion 140 is provided on the upper surface of the support plate 106 between the tie rods 115, 116, 118 and 119 so that the workman may sit thereon and be supported by the safety belt B as the platform 11 ascends and descends the elevated structure S. For connecting auxiliary power tools that the workman on the platform 11 may need to perform his work on the structure S, an electrical outlet box 141 is provided just under the support platform 106 so that the workman can easily and conveniently connect the power tools thereto and use the same while sitting on the platform 11.

Referring more specifically to FIG. 8, the control circuit 142 is connected to a 110 volt source normally provided at the base of the elevated structure S to provide a common ground wire 144 and a common hot wire 145. The motor 44 is connected between ground wire 144 and hot wire 145 through the switch 104. The switch 104 is a conventional three-position switch which has an off position, a first position in which a circuit is completed through that portion of the motor 44 so that the motor 44 rotates in a first direction, and a second position in which a circuit is completed through that portion of motor 44 so that the motor 44 rotates in the opposite direction. In this manner, the direction of movement of the boom 10 circumferentially about the structure S can be selectively controlled depending on which position the workman places the switch 104.

in like manner, the motor 132 is connected between the hot wire 145 and the ground wire 144 through the switch 105. The switch 105, like the switch 104, is a three-position switch having an off position, a first position which connects the wires 145 and 144 with that portion of the circuitry of the motor 132 and causes the motor 132 to rotate in a first direction, and a second position in which the switch 105 connects the hot wire 145 and the ground wire 144 to that portion of the motor 132 and causes the motor 132 to rotate in the opposite direction. in this manner, the workman can control the ascension and descension of the platform 11 carrying the workman therewith adjacent the elevated structure S. It will be noted that the motors 44 and 132 are connected between the 'hot wire 145 and the ground wire 144 parallel to each other so that they are independently operatable with respect to each other. The outlet box 141 is also connected between the hot wire 145 and the ground wire 144 and parallel with the motors 44 and 132 so that power will always be supplied to any power tools that the workman connects to the box 141. By maintaining each part of the circuit 142 independent of the other parts thereof, the workman can independently control the movement of the boom 10 and the movement of the platform 11.

Referring to FIG. 7, an attachment 146 isillustrated which allows the invention to be used adjacent an elevated structure having a catwalk 148 therearound. The catwalks 148 are normally present when refinishing a water tank. The attachment 146 is a U-shaped member having an attaching lug 149 at the extending end of one leg thereof and an attaching lug 150 at the extending of the other leg thereof. The space between the legs of the attachment 146 is sufficient to fit around the catwalk 148 and the attachment 146 is turned on its side to be used. in use, the lug 149 is connected to the extending and of the boom 10 by a fixed length of cable and the cable C associatedwith the workmans platform 11 is connected to the attaching lug 150. This positions the workmans platform 11 under the catwalk 148 adjacent the structure S.

Referring more particularly to FIGS. 9 and 10, a means is provided for adapting the apparatus of the invention to provide a platform extension 200 on which several workmen may stand at the same time and be moved circumferentially about the elevated structure S and up and down with respect to the structure S. The attachment comprises generally a slave boom 210 operatively connected to the power boom Ill and a slave workmans platform 211 operatively connected to the workman's platform 11. The platform extension 2% extends between the workmans platforms 11 and 211 so that several workmen may stand thereon.

More specifically, the slave boom 21b is identical in construction to the boom 10 except that the driving unit 28 and drive chain 29 have been eliminated. The slave boom 21% is connected to the center C of the elevated structure S in the same manner as the boom 10 and extends radially outward therefrom over the edge of the elevated structure. Connecting struts 212 connect the booms 214) and 10 so that both extend radially outward from the center of the elevated structure S. The workman's platform 11 is suspended from the end of the boom 10 while the workmans platform 211 is suspended from the end ofboom 210.

The workman's platform 11 is provided with a power transfer connection 214 and a complementary power transfer connection 215 is provided on the workmans platform 211. These connections are best seen in H6. iii. A coaxial cable connector 216 connects the connectors 2M and 21 .5. The workmans platform 211 is provided with a switch 204 which corresponds to the switch we of the platform 11 and is connected to the motor 44 in parallel with the switch 1%. Therefore, the motor td may be activated from eitherplatform ill or platform 231i to selectively move the booms 1 B and 210 circumferentially about the structure S.

Platform 211 includes a drive motor 232 corresponding to the drive motor 132 in the platform 11. Platform 211 also includes a switch 205 which corresponds to the switch 105 on the platform 11. The cable 216 connects switch 105 to both motors 132 and 232 and connects switch 2&5 to both motors 132 and 232 in parallel with switch 105. it will be seen that activation of either switch 105 or 205 will activate motors 132 and 232 simultaneously to selectively raise or lower the workmans platforms .11 and 211 and the platform extension 200. Also, it will be seen that an outlet box 24R is provided on the workmans platform Zll for attachment of power tools thereto.

METHOD OF INSTALLATION AND OPERATION Referring more particularly to FIG. 1, the power cable to the workmans platform 11 is'connected to the 110 volt power source at the base of elevated structure S, and the power boom it) is connected to the workmans platform 11 as it sits on the ground by securing it to the connecting ring 114 on the platform 11. A sufficient length of cable C is let out from the workmans platform 11 to reach to the top of the elevated structure S and the workman climbs the structure 5 and attaches the cable C to the center of the structure S. Another workman on the ground then activates switch 105, thereby causing the winch assembly 102 to raise the workmans platform 11 and the power boom ll) connected thereto up to the top of the structure S. The workman on top of the structure 5 then opens switch 105 to stop the winch assembly 102 from operating, disconnects the power boom ill from the platform 11, and attaches the boom to the center of the top of the elevated structure S with the cable 24 connecting the attaching lug 22 with the structure S. The power boom lll extends radially outward from the center of the structure S and the tire 40 of the driving wheel 26 rests on top of the structure 5.

Alternately, the cable C may be first attached to the structure S above the catwalk 148, if there is one, and the boom 10 and platform 11 first raised to the catwalk M3 by manipulating the switch 105. The workman on the catwalk M8 then lays the boom 10 and platform 11 on the catwalk 148 and reattaches the cable C to the center of the top of the structure S. He then manipulates switch 105 to raise the platform 11 and boom 10 to the top of the structure and attaches the boom 10 as set forth above.

The workman then moves the driving means 16 along the support tube 12 until the proper position is achieved for balancing the power boom llle then screws the lock bolts 36 into place to lock the driving means 16 with respect to the support tube l2.

The workman then disconnects the cable C from the top of the structure 5 and reattaches the cable C to the clevis 56. The workman gets into-the workmans platform ill and manipulates switches 1M and 3105 to selectively lower himself to the ground to pick up equipment with which he will work on the elevated structure and starts to work on the structure When the workman desires to ascend or descend beside the elevated structure S, he merely manipulates the switch 1% to do so. When the workman desires to move circumferentially about the structure S, he simply manipulates the switch lltl to do so. In this manner, almost every point on the elevated structure S can be covered without the workman having to leave the workman s platform ll if there is a catwalk 1413 around the structure S, the workman simply attaches the cable C of the platform lit to the attaching lug 150 of the attachment i465 and attaches the other lug 149 of the attachment 146 to the clevis 56 using a length of cable to cause the attachment 146 to extend out and around the catwalk M8. if the workman desires to move further under the elevated structure S for standpipes and the like normally associated with water tanks, then a workman on the catwalk 148 may disconnect the cable C when the platform ll is resting on the ground and reconnect the cable C to the support structure extending under the structure S and let the cable drop down adjacent the standpipe. The workman on the ground then gets back in the platform 11 and manipulates the switch to raise and lower himself adjacent the standpipe. After this is completed, the workman then lowers himselfback to the ground and the workman on the catwalk MS reattaches the cable C to the lug 150 or to the clevis as.

The slave boom 21th and the workmans platform 211 may be attached to the elevated structure S in a manner similar to that set forth hereinabove for the power boom ill and the workmans platform 211. After the slave boom 210 and the power boom 10 are attached to the structure 8, the workman on top of the structure then connects the connecting strut 212 between the booms 210 and it) so as to'properly position them. The connecting strut 212 may be adjustable so that the distance between the extending ends of the booms 210 and 10 may be selectively determined. The platform extension 260 is then placed between the platforms 11 and 211, and the workman can stand thereon and operate the platforms Ill and Zll simultaneously to raise and lower the workman along the side of the structure by manipulating switches 105 or 205. The workman can also manipulate the switch 104 or 204 to move the entire assembly circumferentially about the elevated structure S.

The motors 44 and 132 are powerful enough for the workman to attach all of the equipment and supplies he needs to the platform 11 by using the connecting ring 114 and carry the equipment and supplies to the desired location on the structure S without having to manually lift it. This leaves the workman free to use all of his energies in the most effective manner.

While specific embodiments of the invention have been described herein, modifications, substitutions and equivalents may be used without departing from the inventive concept as set forth by the appended claims.

We claim:

1. A positioning device for use by a workman on elevated structures comprising:

a power boom connectable to the center of the top of the structure and extending radially from the center over the edge of the structure for movement circumferentially about the structure, said boom including a hollow support tube, and hanger means carried by the extending end of said support tube; and

9 a first power means for moving said boom circumferentially about said structure, said power means including a frame journaled about said support tube for slidable movement therealong, means for selectively fixing said frame with respect to said tube, a driving wheel rotatably carried around said support tube within said frame for slidable movement along said tube as said frameis moved, said wheel adapted to roll along the structure to move said boom circumferentially about the structure, and a first driving unit secured to said frame and drivingly connected to said wheel for rotating said wheel and moving Y said boom circumferentially about the structure. h 2. The positioning device as set forth in claim 1 further includingi i i a workmans platform for supporting form including a frame. a winch assembly carried by frame, a cable connecting said winch sssernblyto said hunger means, second power menns for selectively driving said winch assembly to effect tslteup and release of i said cable to raise and lower said platform, and first control means for selectively controlling said first and second power means. p

3. The positioning device as set forth in claim 2 wherein said platform further includesguide means for orienting said platform with respect to said cable.

4. A positioning device as set forth in claim 2 further including a slave boom connectable to the center of the top of the structure andconnected to said power boom for movement therewith and' a slave workmans platform suspended therefrom adjacent the structure, said slave workmans platform including third power',means for raising and lowering said slave platform and wherein said first control means is a workman, said platoperatively connected tosalid third power means for selectively controlling said first, second and third power means 5. The positioning device of claim 4 further including second control means carriedby said slave workmans platform for selectively controlling said first, second and third power means.

6. The positioning device of claim 5 wherein each of said first and second control means includes first switch means for said selectively controlling said first power means and second 4 switch means for simultaneously controlling said second and third power means. i r

7. A method of installing a powered boom having means for moving the boom circumferentially about an elevated structure and a powered worltman's platform suspended from the boom by a cable and havingmeans for raising and lowering the platform including the steps of:

attaching the cable of the workman's platform to the center of the top of the structure;

attaching one end of the boom to the platform;

energizing the means on the platform to raise the platform and the boom to the top of the structure;

detaching the boom from the platform and securing one end of the boom to the center of the top of the structure so that the means for moving the boom is properly positioned on the structure; and

detaching the cable of the platform from the center of the top of the structure and reattaching the cable to that end of the boom extending over the edge of the structure.

8. A positioning device for use by a workman on elevated structures comprising: I l

a boom connectable to the center of the top of the structure and extending radially from the center over the edge of the structure for movement clrcumferentlully about the structure, ssid boom including a hollow support tube, an extension shaft slldably receivable in said hollow support tube,,mcans for selectively fixing said shaft with respect to said support tube, and hanger means adjustably carried by the extending end of said support tube;

a first power means for moving said boom circumferentially about said structure, said power means including an inverted, U-shaped frame journaled about said support tube for slidable movement therealong and extending upwardly therefrom, means for selectively fixing said frame with respect to said tube, a driving wheel rotatably carried around saidsupport tube between the depending legs of said frame for slidable movement along said tube as said frame is moved, said wheelhaving a tire which rolls along the structure to move said boom circumferentially about the structure, and a first driving unit secured to said frame and driving connected to said wheel for rotating said wheel and moving said boom circumferentially about the structure;

a workmans platform for supporting the workman suspended from said hanger means, said platform including a horizontally positioned support plate, a U-shaped carriage member depending from each end of said support plate a pair of crossed auxilliary braces secured between the depending ends of said carriage members, and a cushion carried on top of said support plate; a guide assembly pivotally mounted on said support plate and extending upwardly therefrom, said guide assembly including a plurality of tie rods attached to each corner of said support plate and extending inwardly and upwardly from said plate, a guide member centered over and spaced above said support plate and attached to the upper extending ends of said 'tie rods, said guide member defining a passage therethrough, and a guide roller rotatably mounted in said guide member adjacent said passage; a winch assembly carried beneath said platform for moving said platform with respect to said boom, said winch assembly including a winch sheave rotatably mounted by one of said carriage members, a cable attached to said sheave, extending through said passage through said guide member and in contact with said roller, and attached to said hanger means on said boom, a second driving unit carried by said support plate and operatively connected to said which sheave for selectively rotating said sheave to take up and release said cable thereon, said second driving unit including an automatic brake for arresting movement of said sheave unless said driving unit is rotating same; a first switch means carried by said support plate for controlling said first driving unit; and second switch means curried by said support plate for controlling said second driving unit.

9. A method of installing a powered boom having a wheel for moving the boom circumferentially about an elevated structure having a catwalk therearound and a powered workmans platform suspendable from the boom including the steps of:

attaching the cable of the workmans platform to the structure above the catwalk;

attaching one end of the boom to the platform;

energizing the platform to raise the platform and boom to the catwalk;

laying the boom and platform on the catwalk;

detaching the cable from above the catwalk and reattaching the cable to the center of the top of the structure;

again energizing the platform to raise the platform and boom to the top of the structure;

attaching one end of the boom to the center of the top of the structure so that the wheel rests on top of the structure and moves the boom circumferentially about the structure; and

detaching the cable from the structure and reattaching the cable to that end of the boom extending over the edge of the structure.

10. A boom for attachment to the center of the top of an elevated structure and for suspending a workman therefrom comprising:

an elongate hollow tubular support tube;

an extension member slidably received in one end of said support tube for extending theeffective length of said support tube;

means for selectively fixing the relative position of said extension in said support tube;

said structure when said wheel rests on said structure;

a hanger assembly slidably carried by said support tube for suspending the workman therefrom;

means for fixing said hanger assembly with respect to said support tube;

cable means connecting each end of said support tube and said positioning frame for distributing the forces exerted on said support tube and for increasing the rigidity of said support tube; and

remote switch means for controlling said driving unit.

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