US3472337A

US3472337A - Portable collapsible scaffold

Info

Publication number: US3472337A
Application number: US678734A
Authority: US
Inventors: George L Atchey
Original assignee: VEPED TRAFFIC CONTROLS Inc
Current assignee: VEPED TRAFFIC CONTROLS Inc
Priority date: 1967-10-27
Filing date: 1967-10-27
Publication date: 1969-10-14
Anticipated expiration: 1986-10-14

Description

OC- 14, 1969 cm L. ATCHEY 3,472,337

PORTABLE COLLAPSIBLE SCAFFOLD u Filed Oct. 27, 1967 3 Sheets-Sheet A /50 M@ 72a 5e /50 /56 a 92 IE 1 E.- E

INvErJTOR Genesi- L, rcHf-Y United States Patent O 3,472,337 PORTABLE COLLAPSIBLE SCAFFOLD George L. Atchey, Midwest City, Okla., assignor to VePed Traffic Controls, Inc., Oklahoma City, Okla., a corporation of Oklahoma Filed Oct. 27, 1967, Ser. No. 678,734 Int. Cl. E04g 1/00; E06c 5/06; A01g 19/04 U.S. Cl. 182-2 11 `Claims ABSTRACT OF THE DISCLOSURE A scaffold apparatus which can be demountably positioned in the bed of a truck, and while so positioned, can be expanded to an elevated status, or which can be similarly expanded when demounted and rested on the ground. The structure includes a horizontal base structure having a pair of substantially parallel boom elements, each pivotally secured at one end to one end portion of the base structure, and secured at their opposite ends to a substantially horizontally extending work platform. A piston and cylinder structure interconnected between the base structure and one of the booms provides power for elevating the booms and work platform. Sockets are provided on the base structure to receive the upper ends of a plurality of Outrigger jack structures, which when placed in the sockets, extend to the outside of a truck in which the scaffold apparatus is mounted and into contact with the ground. The Outrigger jacks can then be used for manually off-loading the scaffold apparatus to the ground.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to expandable work platforms and scaffolding which can be used to elevate a workman to a high work location, or folded down to a compact, inoperative status. More particularly, the invention relates to expandable scaffolding of the type which can be transported and used while mounted upon a light truck.

Brief description of the prior art A number of instances exist where it is necessary to elevate a workman above ground level in an outdoor location for the purpose of permitting the workman to make relatively rapid repairs to elevated structures, such as street lights, trolley power lines, traffic signal lamps, and the like. For this purpose, a number of special vehicles have heretofore been built which incorporate a rather massive scaffolding structure which can be elevated to selected heights, can be swiveled about so as to move the workman in a horizontal direction, and can be driven from one location to another. Many of these structures contain complicated machinery and are relatively expensive to construct and maintain. In most instances, the scaffolding or structure employed to elevate the workman cannot be easily detached or demounted from the framework of the vehicle, but rather, is made a permanent portion of the vehicle, thus rendering the vehicle incapable of other utility, and requiring that both the vehicle and scaffolding structure always be present at the same location. In other instances, equipment of the general type described has been so large in its vertical dimension that freedom of movement of the vehicle is some- 3,472,337 Patented Oct. 14, 1969 ice what restricted, and care must be exercised in traversing underpasses and tunnels having a limited vertical clearance.

Although applicant is aware of one prior proposal to demountably position an elevatable work platform on a truck, such as is depicted and described in U.S. Patent 3,283,850, this assembly does not provide any rapid and easy method for detaching the structure from the vehicle and manually lowering it to the ground.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention provides a portable collapsible scaffold which can be utilized to elevate a workman to a substantial height, either when the scaold is supported on the ground, or when it is mounted in quick detachable fashion on a relatively small, lightweight truck. The scaffold can be easily mounted on, or demounted from, a truck by a single operator, so that the entire assembly, including the truck and collapsible scaffold, can be operated by a single workman. The portable collapsible scaffold carries a self-contained power unit which permits it to be operated independently of the power plant of the truck. Moreover, when the scaffolding is folded downwardly to its collapsed or traveling position, it adds very little to the total height of the truck and consequently problems of inability to pass beneath relatively low ver tical clearance structures are seldom encountered.

Broadly described, the present invention comprises a base structure which is adapted to be secured to the bed of a truck and having a forward end portion and a rear end portion; a pair of substantially parallel, elongated boom elements each pivotally secured at one end to the rear end portions of the base structure at horizontally spaced locations for pivotation about spaced, substantially parallel, horizontal axes; a horizontally extending work platform secured to the ends of said booms opposite their ends pivotally secured to said base structure; and an extensible piston and cylinder means connected between said base structure and at least one of the booms to provide power for simultaneously elevating the booms by pivotation about said horizontal axes. A first pair of forward sockets are secured to opposite sides of the forward end portion of the base structure, and a second pair of sockets is secured to the base structure on opposite sides thereof and spaced rearwardly from the forward sockets. Outrigger jacks are provided which are engageable with the sockets secured to the base structure, and which each include a ground-contacting lower portion, and a socketentering upper portion which is horizontally offset from the ground-contacting lower portion.

In a preferred embodiment of the invention, the base structure is made with a pair of horizontally spaced parallel runners adapted to support the base structure on the flat bed of a truck, and having a plurality of securing plates connected to the runners to permit the portable scaffold structure to be secured to the truck bed by bolts. The Outrigger jacks are manually operable so that when they are engaged with the sockets provided on the base structure, a four-point support for the scaffold structure is provided, the scaffold can be elevated manually, and the truck driven out from under the scaffold to permit it to be demounted from the vehicle and lowered to the ground. A further important feature of a preferred em- Y N"at-Ellapserfrinoperatiue`p`osition.

the two booms which are provided in the scaffold structure, which nesting arrangement permits the booms to be pivoted downwardly about their horizontal pivotal axes until both extend horizontally in substantially the same plane. This permits the scaffold structure to occupy a minimum vertical dimension in its folded down or collapsed status, so that the vehicle on which it is mounted encounters no difficulty in traversing underpasses, tunnels, and the like.

From the foregoing general description of the invention, it will have become apparent that a major and important object of the invention is to provide an improved, portable, collapsible scaffold which can be easily mounted on, or demounted from, a lightweight truck so that the truck can be utilized for servicing and maintaining vertically elevated structures, and can also be used at other times in the normal fashion characteristic of lightweight trucks without impairment by the presence of the scaffolding.

An additional object of the invention is to provide a vehicle carrying elevatable scaffolding to permit a work man to be elevated to a high vertical level, which scaffolding can be folded down to a compact position in which the vertical dimension of the entire structure is only slightly greater than the distance from the ground to the top of the cab of the vehicle.

An additional object of the invention is to provide a portable collapsible scaffold which includes a selfcontained power plant, and which can be used either when mounted on a transporting vehicle or when rested upon the ground.

An additional object of the invention is to provide a portable collapsible scaffold structure which can be used with a maximum degree of safety by a workman who is elevated by the scaffold structure.

A further object of the invention is to provide a portable collapsible scaifold which automatically locks in a collapsed, compact, inoperative position.

Another object of the invention is to provide a portable collapsible scalfold structure which can be quickly and easily disassembled if it is desired to separately transport various portions of the structure from one location to the other, or to repair or replace various portions of the structure.

Another object of the invention is to provide a portable scaffold structure having a self-contained power plant, with such scaffold structure including manual jack elements which permit the scaffold structure to be loaded and off-loaded on a vehicle for purposes of transport, with such loading or off-loading being accomplished by a single person.

Another object of the invention is to provide a portable collapsible scaffold structure which is relatively inexpensive in construction, yet is of strong, durable character and possessed of a long and trouble-free operating life.

In addition to the foregoing described objects and advantages, additional objects and advantages will become apparent as the following detailed description of the invention is read in conjunction with the accompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a view in elevation of the portable collapsible scaffold of the present invention as the scaffold appears when mounted on a pickup truck in its transport or collapsed status.

FIGURE 2 is a view similar to FIGURE 1, but showing the scaffold in its elevated operative status.

FIGURE 3 is a view in elevation from the rear of a pickup truck in which the portable collapsible scaffold of the present invention is mounted, and showing the scaffold in its expanded or elevated status. Guard fences ernployed in connection with the work platform of the scaffold are shown in dashed lines to better illustrate the manner in which these guard fences are folded down t FIGURE 4 is a view in elevation from the rear of the pickup truck with the scaffold folded down to its collapsed position, and illustrating outrigger jacks positioned and connected for off-loading the scaffold from the truck.

FIGURE 5 depicts the portable collapsible scaffold of the invention as it appears after it has been off-loaded from the truck and placed upon the ground with the scaffold collapsed to a compact, inoperative status.

FIGURE 6 is a plan view of the work platform ernployed in the scaffold of the invention.

FIGURE 7 is a sectional view taken along line 7--7 of FIGURE l and illustrating the manner in which the power plant used to elevate the scaffold is mounted upon the base structure thereof.

FIGURE 8 is an enlarged detail view of a section taken along line 8-8 of FIGURE 7.

FIGURE 9 is a schematic illustration of the engine, hydraulic pump, and hydraulic piston and cylinder assembly utilized in one embodiment of the invention.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION In the following description, reference will be made to various portions of the accompanying drawings, with reference numerals associated with lead lines which have arrowheads being utilized to designate broad combinations which include several subassemblies or several elements having a unitary function in the overall operation of the scaffold of the invention. Numerals which are connected to various structural parts by plain lead lines (having no arrowheads) will be utilized to designate individual elements of structure.

Referring initially to FIGURE l of the drawings, a vehicle, typically a pickup truck 10, is shown supporting the portable collapsible scaffold of the present invention, designated generally by reference numeral 12. It should be understood, however, that one of the inventive aspects of the present disclosure is considered to be the structural combination of the portable collapsible scaffold with a vehicle of the type depicted, due to the novel and peculiar adaptability of the scaffold to the bed structure of the typical pickup truck. Thus, the truck 10 includes the usual flat, substantially horizontally extending bed 14 located to the rear of the truck cab 16 and having sideboards or side walls 18. A tailgate 20 is usually provided to provide a closure or gate extending across the rear of the bed 16 of the truck 10.

The portable collapsible scaffold 12 includes a base structure 22 comprising a pair of substantially parallel, horizontally spaced, horizontally extending runners 24 (see FIGURES 5 and 7), and four substantially parallel, vertically extending corner posts, with the rear corner posts being designated by reference numeral 26 and the forward corner posts being designated by reference numeral 28. The

corner posts

26 and 28 are each secured at their lower ends to the runners 24, and the forward corner posts 28 extend to a slightly greater height than the rear corner posts 26 for a reason hereinafter to be described. A pair of central, vertically extending posts 30 are also provided in the base structure 22 and are secured at their lower ends to the runners 24. A transverse frame member 32 interconnects the rear ends of the two runners 24, and a second transverse frame member 34 is secured between the forward ends of the runners.

A central transverse frame member 36 extends between central portions of the runners 24 at about the location therealong where the lower ends of the central, vertically extending posts 30 are connected to the runners. For purposes of reinforcement, a purality of short diagonal braces 38 extend across the corners between the runners 24 and the transverse frame members 34 and 36 (see FIGURES 3, 7 and 8), and a plurality of long diagonal braces 40 are extended between the

vertical posts

26, 28 and 30 in the manner depicted in FIGURES 1, 2 and 3. Extending between and interconnecting the upper end portions of the vertical posts 26 is an upper transverse member 42 (see FIGURES 3 and 4), and a similar upper transverse member (not visible in the drawings) interconnects the vertically extending posts 30. A transverse boom supporting bar 44 extends between the forward, vertically extending posts 28, and is secured to these posts at points spaced downwardly a short distance from their upper ends.

Secured to the outside of each of the forward, vertically extending posts 28 at locations spaced downwardly a short distance from the upper ends thereof are a pair of sockets 46 which, in the embodiment yof the invention illustrated, take the form of open ended sleeves (see FIGURES 2 and 7). Substantially identical sockets 48 are secured on the outside of the rear, vertically extending posts 26 at positions spaced downwardly from the upper ends thereof and at substantially the same level as the transverse member 42. The function of the sockets 46 and `48 will be subsequently explained in greater detail. A pair of step plates 50 are secured to the inner sides of the rear, vertically extending posts 26 at substantially the midportions thereof.

Mounted upon the base structure 22 of the portable collapsible scaifold 12 are a pair of elongated booms, hereinafter termed an outer boom 52' and an inner boom S3. The terms outer and inner are utilized in describing these booms because of the nested relationship of the booms when they are in their collapsed or inoperative positions as hereinafter further explained. The -outer boom 52 includes a plurality of elongated, longitudinal members 54 which are interconnected by transverse and

diagonal brace members

56 and 58, respectively. A plurality of horizontally extending transverse members 60 (see FIGURE 3) extend between the two uppermost longitudinal members 52 of the boom and support a ladder designated generally by reference numeral 62 and having rungs 63 as depicted in FIGURE 3. The ladder 62 provides access to a work platform 64 which extends horizontally and interconnects two ends of the

booms

52 and 53 as hereinafter explained. One end of the boom 52 is pivotally connected to the base structure 22, and specilically to the upper end portions of the rear corner posts 26 by means of a pivot bar 70, which pivot bar is journaled in a pair of pillow blocks 72 formed at the upper end of each of the corner posts 26. The pillow blocks 72 are formed so that the upper portion 72a thereof, defining approximately 180 'of the bore through the block which journals the pivot bar 70, can be removed by loosening appropriate screws or bolts employed therewith, thus permitting the boom 52 to be completely disengaged from the upper portions of the rear corner posts 26. It will be noted that the upper portion 72a of each pillow block carries a suitable grease fitting 72b (see FIGURE 5).

The boom 53 is constructed generally similarly to the boom 52 and thus includes transverse braces 80, diagonal braces 82 and transverse, horizontally extending members 84 (see FIGURE 3). It will be noted in referring to FIGURES 2 and 3 that the horizontal spacing between the pairs of longitudinal members 78 of the boom 53 is less than the horizontal spacing between the corresponding longitudinal members 54 of the boom 52 so that the boom 53 can fit within, or be nested inside of, the boom 52 when the two booms are pivoetd downwardly to the position depicted in FIGURE 1. It will further be noted that one end of the boom 53 is connected in the manner hereinafter described to the work platform 54, while the opposite end of this boom is pivotally connected to the base structure 22. Connection of the boom 53 to the base structure 22 is accomplished by the use of a pivot bar 90 to which the boom is secured and which extends through a pair of pillow blocks 92 secured to the upper ends of the central posts 30. The pillow blocks 92 are segmentally constructed similarly to the pillow blocks 72 hereinbefore described, and this construction permits the boom 53 to be detached from the base structure 22 and removed from the assembly when desired.

The Work platform 64 includes a rectangular base frame 92 which has a pair of heavy longitudinal boom attaching beams 92h positioned inwardly of the frame and connected by a pair of transverse rods 92C. The rectangular base frame 92 and the beams 92b and transverse rods 92e` support an expanded metal oor grille 94. Each of the beams 92b carries at a central position along its length, a hold-down clamp assembly 96 which functions in a manner hereinafter described. Each holddown clamp assembly 96 includes a tubular sleeve 96a which is welded to the respective beam 92h and slidingly receives a smooth bolt 96b. The bolt 9617 carries a locking toe 96C at its upper end, and a cotter key 96d at its lower end. A helical springs 96e is interposed between the key 96d and the sleeve 96a.

Pivotally connected to the base frame 92 of the work platform 64 are a plurality of guard fences. In the embodiment of the invention depicted in the accompanying drawings, the guard fences include a forward transverse guard fence 98, and a pair of side guard fences 100 and 102 (see FIGURES 2, 3 and 6). The

guard fences

98, 100 and 102 are pivotally secured to ears or lugs extending upwardly from the base frame 92 of the work platform 64, and such lugs are arranged in a manner such that the two

side guard fences

100 and 102 can lbe pivoted downwardly about horizontal axes and in the manner illustrated by the dashed lines in FIGURE 3 as can the guard fence 98.

When all of the guard fences 98, ll00 and 102 are pivoted downwardly to a horizontal collapsed and cornpact position, they appear as shown in FIGURE 4, with the

side guard fences

100 and 102 lying adjacent the base frame of the work platform 64 with the forward transverse guard fence 9S collapsed on top of the

side guard fences

100, 102. The hold-down clamp assemblies 96 are used to retain the guard fences in this collapsed position by grasping the locking toes 96C, pulling the bolts 96h upwardly against the bias of the springs 96e, and pivoting the bolts about their longitudinal axes so that the locking toes extend across and engage the top rail of the forward transverse guard fence 98.

When the guard fences have been pivoted upwardly to their working or operative position as shown in FIG- URES 2 and 3, the sliding latches 106 may be used to interlock the forward guard fence 98 with the two

side guard fences

100 and 102. In a preferred embodiment of the invention, it is also very desirable to provide a pair of back rails 107s and 107b, each of which is pivotally secured to a different one of the side guard fences, and which can be interlocked by means of a sliding sleeve 107e.

Extending downwardly from the under side of the base frame 92 of the work platform 64, and more specifically, from each of the boom attaching beams 92b are a pair of

boom attachment brackets

108 and 110. It will be noted in referring to FIGURES 2 and 3 that each of the boom attachment brackets 108 is pivotally secured through a pin 111 to the inside of the upper ends of the outer boom 52. The other boom attachment brackets 110 in each set are secured to the opposite side of the respective boom attaching beams 92b from the boom attaching brackets 110 and are secured by suitable pivot pins 112 to the outsides of the upper end of the inside boom 53. It will thus be noted that the staggered position of the

boom connecting brackets

108 and 110 relative to each other, conjunctively with the smaller transverse dimension of the inside boom 53 as compared to the outside boom 52, permit the two booms to be nested with the inside boom 53 positioned inside the outside boom 52 when both booms are lowered to a substantially horizontally extending position as shown in FIGURES 1 and 5. Moreover, the pivotal axes of the pivot pins 111 and i112 extend parallel to each other, and to the axes of the

pivot rods

42 and 90 used to connect the

booms

52 and 53 to the base structure 22 so that a parallelogram type arrangement is provided in which the base frame 92 and floor 94 of the base platform 64 are constantly maintained in a horizontal position as the

booms

52 and 53 are pivoted upwardly. It may also be pointed out here that at such time as the inner and

outer booms

53 and 52, respectively, are pivoted downwardly to their collapsed, substantially horizontal position as shown in FIGURES 1 and 5, the scaffold structure becomes locked in this position and cannot be displaced therefrom by vibration or tilting. Rather, a positive force must be applied on the outer and uppermost of the two booms in order to break this positive interlock and allow the parallelogram type motion to occur.

For the purpose of elevating the booms S2 and 53 to raise the work platform 64 to a desired height, the portable collapsible scaffold of the invention includes a selfcontained power plant which includes a prime mover, preferably a gasoline engine 118, which is supported on a suitable support plate 119 mounted on the base structure 22 of the scaffold. The support plate 119 also supports a hydraulic pump 122, which is driven by the engine 118 and supplies hydraulic power fluid through

suitable conduits

124 and 126 to a main piston and cylinder assembly designated generally by reference numeral 128, and to an auxiliary piston and cylinder assembly, designated generally be reference numeral 134), respectively (see FIGURE 2). This power plant is illustrated schematically in FIGURE 9, which also depicts a pair of flo-

w control valves

132 and 134 interposed between the hydraulic pump 122 and the piston and

cylinder assemblies

128 and 130. One of these valves, 132, may be termed the metering valve and controls the rate at which hydraulic power fluid is directed from the pump 122 into each of the piston and

cylinder assemblies

128 and 130, or is bled from these assemblies back to the pump 122. An operating valve is used for actually connecting the pump 122 hydraulically to the piston and

cylinder assemblies

128 and 130.

Referring in greater detail to the construction of the piston and cylinder assembly 128, this assembly includes an enlongated cylinder 136 which is pivotally anchored by a pivot pin 138 which extends between anchor plates 140 secured to transverse anchor beams 142. A piston 144 is located in the cylinder 136 and has secured thereto an elongated piston rod 146. The upper end of the piston rod 146 is pivotally secured by a pivot pin 148 to a pair of opposed bracket plates 150 secured to the inner boom 53. The bracket plates 150 also support a transverse cylinder base plate 152 (see FIGURE 3) upon which is mounted a short hydraulic cylinder 154 which encloses a piston 155 (see FIGURE 9) having secured thereto, and extending from the cylinder, a relatively short piston rod 156 ing from the cylinder, a relatively short piston rod 156. The free upper end of the piston rod 156 bears against one of the cross members 60 of the boom 52 when the booms are in their collapsed, nested relationship as shown in FIGURES l and 5, and functions in a manner hereinafter described for releasing the positive interlock of the booms which is developed when they are in their nested, horizontally extending positions.

For the purpose of permitting the portable collapsible scaffold structure 12 to be off-loaded from the vehicle 1t), there are provided a plurality of Outrigger jacks designated generally by reference numeral 160, and corresponding in number to the number of the

sockets

46 and 48, Each of the Outrigger jacks includes a ground-contacting plate 162 which is secured on the lower end of a threaded shaft 164 which extends upwardly into an internally threaded sleeve 166. A jack handle 168 cooperates with the threaded shaft 164 in such a way that the shaft may be further extended from the sleeve 166 in order to lift the base structure 22 of the scaffolding above the bed 14 of the truck 10 in a manner hereinafter described. At its upper end, each of the Outrigger jacks 160 carries a vertically extending, socket engaging portion 170, and this portion is set horizontally inwardly from the sleeve 166 by an angulated connecting arm 172. The length and configuration of the angulated connecting arms of the outrigeer jacks are such that the lower portions of the jacks are well clear of the sides of the vehicle 10 when the socket engaging portions 170 are positioned in their respective sockets.

OPERATION Let it be assumed, for the purposes of describing the operation of the portable collapsible scaffold of the invention, that the scaffold structure 12 is mounted on the bed 14 of the pickup truck 1t) in the manner depicted in FIGURE 1. It will be noted that the transverse dimensions of the base structure 22 of the scaffold permit it to easily fit between the side walls 18 of the bed of the truck, and the horizontally extending runners 24 allow it to rest flatly and evenly on the bed 14. The apertured securing plates 25 receive bolts which are passed through the bed 14, and these plates are utilized for bolting the scaffold to the bed of the pickup truck by means of suitable bolts, as best illustrated in FIGURE 8. The bolts may be quickly placed in position, and may be self-tapping or may require the use of nuts, as may be desired. In either event, the base structure 22 of the scaffold can be quickly detached entirely from the bed 14 of the pickup truck so that the scaffold can be off-loaded from the truck in a manner hereinfater described.

With the scaffold secured on the truck in the manner depicted in FIGURE l, the truck can be driven to a location where work is to be performed on an elevated structure, such as a telephone line, light pole, trafic light, or the like. During such transport of the scaffold to the location of the work to be performed, the

booms

52 and 53 are pivoted downwardly to the substantially horizontal, nested position which they are shown as occupying in FIGURE l of the drawings. In this position, the boom 53 is located inside the boom 52 and the work platform 64 extends substantially horizontally and in parallelism with the

booms

52 and 53. In this position, a positive interlock of the booms and work platform exists such that an upward force applied to the inner boom 53 would not alone be sufficient to cause the two booms to be pivoted about their respective horizontal pivotal axes. Rather, the result would be a greater binding action tending to prevent further upward movement of the booms, since to break away from the existing interlock, the outer and uppermost boom 52 must be moved upwardly slightly before the parallelogram-typc, expanding motion can be smoothly developed.

To the end of permitting the positive interlock to be disengaged, and the booms to pivot upwardly to the position depicted in FIGURE 2, the hydraulic piston and

cylinder assemblies

128 and 130 are provided. Both of these assemblies are actuated simultaneously by hydraulic power fluid delivered from the pump 122. As the piston rod 146 of the main piston and cylinder assembly 128 is extended, the short piston rod 156 of the auxiliary piston and cylinder assembly 136 is simultaneously extended so that both of the

booms

52 and 53 are simultaneously pivoted upwardly about their horizontal axes.

Once the interlock is disengaged by the upward movement of the upper and outer boom 52, the function of the auxiliary piston and cylinder assembly 138` is completed, and the remainder of the upward movement of the

booms

52 and 53 can be completed by the use of the main piston and cylinder assembly 128. Accordingly, extension of the piston 146 from the cylinder 136 continues until the maximum elevation of the work platform is attained. At this time, the valve 132 is closed and the

booms

52 and 53 are locked in their upraised positions. The vehicle has, of course, been steered so as to position the work platform 64 in the immediate vicinity of the structure which is to be repaired, or the location where work is to be performed by the workman.

The workman next ascends the ladder 62 which is provided on the upper side of the boom 52, using the foot supports 50 to gain access to this ladder. When the top of the ladder 62 is reached, the workman can pivot the forward and

side guard fences

98, 100 and 102 to their raised positions and interlock them by means of the sliding sleeve 106. The

bars

107a and 107b can be pivoted into alignment to complete the enclosure provided by the

guard fences

98, 100, 102 and insure the workmans safety as he stands upon the floor 94 and reaches outwardly to perform :repair ser-vices on any adjacent structure. It should be noted at this point that, in some instances, it may be desirable for the workman to open the

guard fences

98, 100, 102 to their operative positions prior to the elevation of the work platform 64 `by upward pivotation of the

booms

52 and 53. This can be easily accomplished, and the workman can stand upon the work platform 64 during the elevation thereof if this should be desired.

Upon completion of the repairs or other operations carried out by a workman standing on the work platform 64 while it is in its elevated position, this platform can be lowered to the position depicted in FIGURE 1 by pivoting the booms 52 and S3 about their horizontal pivotal axis and using the metering valve 132 to bleed hydraulic power fluid slowly out of the

pistons

136 and 154. As the power fluid is dispelled from the cylinders, the

piston rods

146 and 156 move into the respective cylinders under the weight of the booms 52 and S3 and the work platform 64. Thus, the

booms

52 and 53 will gradually be lowered to their collapsed and nested status, and the scaffold structure will again be ready for transport provided, of course, that the

guard fences

98, 100 and 102 have been pivoted downwardly to their inoperative status as depicted in FIG- URE 1.

In many instances, it is desirable to clear the bed 14 of the pickup truck 10 for other uses, such as hauling various sizes and weights of goods and commodities from one location to another. For this to be accomplished, it is, of course, necessary to remove the portable collapsible scaffold 12 from the truck. This may be very quickly and easily accomplished by a single person who may, of course, be the driver of the truck. To accomplish this, a person need merely remove the bolts which secure the securing plates 25 to the bed 14 of the vehicle 10. The Outrigger jacks 160 are then placed in position with each jack being set with its socket-engaging portion 170 in one of the

sockets

46 or 48. Thus, there are four jacks 160 located at the four corners of the base structure 22 of the scaffold 12. The operator may then pass from jack to jack and by turning each of the handles 168 on the several jacks in equal relatively small incremental amounts a number of consecutive times, the portable collapsible scaffold can be lifted from the bed 14 of the truck. If the tailgate 20 of the truck is then lowered, the truck may simply be driven out from under the runners 24 of the base structure 22 of the scaffold 12 to leave the scaffold supported in the air by the four outrigger jacks 160i. Occasionally it may be desirable to use the scaffold while it is thus supported on the jacks 160, and this may be successfully accomplished due to the sufficiency of the counterbalancing Weight afforded by the base structure 22.

It should also here be noted that by slight modification of the structure of the jacks 160 from that which is illustrated in the drawings, the entire scaffold may be com pletely lowered to the ground by consecutively turning the handles 168 of the Outrigger jacks 160 so as to shorten the jacks until the runners 24 rest upon the ground. The Outrigger jacks 160 may then be detached from engagement with the

sockets

46 and 48 so that the portable collapsible scaffold structure 12 appears as shown in FIGURE 5. In this position of the scaffold structure, it will be noted that the self-contained power plant, which includes the engine 118, the hydraulic pump 122 and the piston and

cylinder assemblies

128 and 130, is still present in its same location on the base structure 22, and can be utilized while the scaffold is rested on the ground for elevating the

booms

52 and 53. Thus, the scaffold can still be employed in the location at which it is rested upon the ground for moving the work platform 64 to a relatively high vertical level to permit access to be gained to structures upon which repairs are to be effected.

Loading of the scaffold on the vehicle and securernent on the bed thereof is achieved in precisely the reverse manner to that in which the scaffold is off-loaded from the vehicle as hereinbefore described. A single person may accomplish such loading without difficulty.

Although a preferred embodiment of the portable collapsible scaffold of the invention has been described in order to permit its construction and operation to be clearly understood by those having ordinary skill in the art, it is to be understood that various changes and modifications may be made to the depicted structure without departure from the basic principles upon which the invention is based. All changes and modifications of this type are therefore deemed to be circumscribed by the spirit and scope of the invention except as the same may be necessarily limited by the appended claims or reasonable equivalents thereof.

What is claimed is:

1. A portable, collapsible scaffold structure for mounting on a self-powered vehicle comprising:

a base structure adapted to be detachably secured to the bed of a vehicle and having a forward end portion and a rear end portion;

a pair of elongated, substantially parallel boom elements each pivotally secured at one end to the rear end portion of the base structure, said boom elements being secured to said base structure at horizontally spaced locations for pivotation about spaced, substantially parallel, horizontal axes;

a horizontally extending work platform pivotally secured to the ends of said booms opposite their ends pivotally secured to said base structure, and forming a parallelogram with said booms and base structure when said booms are pivoted upwardly from said horizontally extending position;

extensible piston and cylinder element means connected between said base structure and at least one of the booms to provide power for elevating and lowering both booms simultaneously by pivotation about said horizontal axes;

means for supplying power fluid to said piston and cylinder means mounted on said base structure;

a first plurality of sockets secured to said base structure on the opposite sides of the forward end portion thereof;

a second plurality of sockets secured to said base structure on the opposite sides of the rear end portion thereof; and

Outrigger jacks detachably engaged with said sockets, said jacks each including a ground contacting lower portion and a socket entering upper portion which is horizontally offset from the lground contacting lower portion.

2. A scaffold structure :as defined in claim 1 wherein said work platform includes a base frame connected to said boom elements;l

floor means on the base frame; and

a plurality of guard fences pivotally attached to the side edges of said base frame and each pivotal from a vertically extending position to a horizontally extending, folded down position in which said fences are in abutting contact with each other and extend parallel to each other and to said base frame.

3. A scaffold structure as defined in claim 1 and further characterized to include multi-part pillow blocks detachably connecting said booms to said base structure, whereby said booms may be quickly and easily detached from said base structure by opening said multi-part pillow blocks.

4. In combination:

a self-powered vehicle having a cab and a horizontally extending bed to the rear of the cab;

a collapsible scaffold detachably connected to said horizontally extending bed and including:

a base structure resting on, and detachably secured to, said bed, said base structure having a forward end portion adjacent said cab and a rear end portion;

a pair of elongated, substantially parallel booms each pivotally secured :at one of its ends to the rear end portion of said base structure, with said booms being attached to said base structure for pivotation about spaced, substantially parallel, horizontal pivotal axes, said booms being dimensioned so that one o-f said booms will nest inside the other boom when said booms are pivoted to a horizontally extending position of substantially coplanar alignment, said booms extending over said cab when in said nested, horizontally extending position;

a horizontally extending work platform pivotally secured to the ends of said booms opposite their ends pivotally secured to said base structure, and forming a parallelogram with said booms and base structure when said booms are pivoted upwardly fro-m said horizontally extending position;

means mounted on said base structure land drivingly connected to at least one o-f said booms for simultaneously elevating said booms by pivotation about said horizontal pivotal axes;

a first pair of sockets secured to opposite sides of the forward end portion of the base structure over opposite sides of the bed of the self-powered vehicle; and

a second pair of sockets secured to the base structure on opposite sides thereof and spaced rearwardly from said first pair of sockets.

5. The combination claimed in claim 4 wherein said booms may be pivoted downwardly about said horizontal axes until the pivotal axes at the point of connection of said work platform to said booms simultaneously pass into a common plane containing said horizontal pivotal axes whereby said booms are locked in said horizontally extending position.

6. The combination claimed in claim 4 and further characterized to include jacks slidably inserted in said sockets and extending downwardly therefrom and to the outside of the bed of said self-powered vehicle.

7. The combination claimed in claim 4 wherein said base structure includes two pairs of vertically extending posts; and

a multi-part pillow block at the upper end of each of said posts, the pillow blocks on each pair of said posts pivotally attaching one of said booms to said base structure, and said booms being detachable from said base structure when the parts of said pillow blocks are separated from each other.

8. The combination claimed in claim 4 and further characterized to include means mounted between said booms for biasing said booms apart from each other to relieve said locked status of the booms.

9. A scaffold apparatus comprising:

a base structure having a forward end portion and a rear end portion, and having a plurality of spaced, substantially horizontal runners on the lower side thereof;

a pair of elongated, substantially parallel booms each pivotally secured at one of its ends to the rear end portion of the base structure with said booms being detachably connected to said base structure for pivotation about spaced, horizontal pivotal axes, said booms extending from the po-ints of attachment to said base structure toward and over the forward end portion of said base structure, and said booms differing in their transverse dimensions so that one of said booms will nest inside the other boom when said booms are pivoted to a horizontal extending position of substantially coplanar alignment;

a rst piston and cylinder assembly connected between said base structure and the one of said booms having its horizontal pivotal axis nearest the forward end portion of said base structure for pivoting said one boom upwardly upon extension of the piston rod from the cylinder of said first piston and cylinder assembly;

a second piston and cylinder assembly mounted on said one boom between the ends thereof and including a piston rod extendable into contact with the other boom when said booms are in said nested, horizontally extending position; and

means mounted on said base structure for supplying hydraulic fluid to the cylinders of said rst and second piston and cylinder assemblies.

10. A portable, collapsible scafford structure for mounting on a self-powered vehicle comprising:

a pair of elongated, substantially parallel boom elements each pivotally secured at one end to the rear end portion of the base structure, said boom elements being secured to said base structure at horizontally spaced locations for pivotation about spaced, substantially parallel, horizontal axes, one of said boom elements having its horizontal pivotal axis forward of the horizontal pivotal axis of the other boom element and being of lesser transverse dimensioin than said other boom element, and said boom elements being dimensioned to nest in a horizontally extending position of substantially coplanar alignment;

a horizontally extending work platform pivotally secured to the ends of said booms opposite their ends pivotally secured to said base structure and forming a parallelogram with said booms and base structure when said booms are pivoted upwardly from said horizontally extending position, said horizontally extending work platform occupying a position in substantially coplanar alignment with said nested booms when said nested booms are in said horizontally extending position of coplanar alignment;

extensible piston and cylinder means connected between said base structure and at least one of the booms to provide power for elevating and lowering both booms simultaneously by pivotation about said horizontal axes;

means for supplying power fluid to said piston and cylinder means mounted on said base structure; and

means connected to the forward end portion and rear end portion of said base structure for elevating said base structure with respect to the ground to permit said self-powered vehicle to be detached and driven from under said portable collapsible scatord structure.

11. A portable, collapsible scalford structure for mounting on a self-powered vehicle comprising:

a pair of elongated, substantially paraellel boom elements each pivotally secured at one end to the rear end portion of the base structure, said boom elements being secured to said base structure at horizontally spaced locations for pivotation about spaced, substantially parallel, horizontal axes;

a horizontally extending work platform pivotally secured to the ends of said booms opposite their ends pivotally secured to said base structure;

extensible piston and cylinder means connected between said base structure and at least one of the booms to provide power for elevating and lowering both booms simultaneously by pivotation about said References Cited homomal axes.; UNITED STATES PATENTS means for supplylng power uld to said p1ston and cy1- said jacks each including a ground contacting lower 3,252,542 5/1966 Thornton et 3L 182-2 lower portion; a cylinder mounted on one of said booms; and 10 REINALDO P' MACHADO Primary Exammer a piston rod extensibly mounted in said cylinder and U Sl Cl, XR.

engageable upon extension with the other of said 182-141.63

booms for biasing said booms apart from each other. 15