US2611657A - Self-sustaining scaffold - Google Patents

Description

3 Sheets-Sheet 1 Sept. 23, 1952 E. B. BRITTIN SELF-SUSTAINING scAFFoLD File Dec. e, 1951 INVENToR B. BRITTIN` EDW ESB BRITTN SELF-SUSTAIING SCAFFOLD Sept. 23, 1952 :s sheetsL-Sheet 2 Filed Dec. 6, 1951 l 5 iNvENToR EDWARD B. BRITTm Patented Sept. 23.1952

UNITED sTATEs PATENT Edward Baylis Brittin, Washington, D. C.

Application December 6, 1951, Serial No. 260.167

This invention relates to a self-sustaining scaffold of the knockdown type wherein the main framework thereof is comprised of members formed from wood. This main framework'includes a series of'superimposed longitudinally extending members known in this art astrestle boards which are maintained in a vertically spaced relation by means of several stagesV of trestles which are well known in this art.

The invention relates more specifically to a novel form of bracing means that functions to retain all of the stagesV of the scaffold rmly bound together to form a self-sustaining unit that has a high degree of rigidity and which affords a high degree of safety to the workmen using the same.

It has been a common practice in this art to erect, more or less loosely, a series of vertically spaced trestle members and trestle boards, the lowermost' of the series being supported say directly on the ground. After the first stage of trestles has been arranged on the ground or other support, a number of trestle boards are laid across the cross boards of the trestles to permit -use thereof as a platform. To provide a platform at a higher elevation, a second stage of trestles are set up uponthe outer two trestle boardsand the more central trestle boards are removedand used to assemble the second and higher platform. Possibly, the weight of the workmen and materials such as bricks might give a little rigidity to such a scaifold but there are several elements of danger associated with the same. It is possible for the trestles to creep relatively to each other. Then if one outer side of the platform is overloaded. the upper trestles would tend to tilt inthe direction of Vthat side and, if say four to seven stages were in use, the entire structure would tend to buckle and collapse.- In some cities, an ordinance provides that such scaffolds be limited to as low as two stages hence there is little competition between the wooden and the metal scaffolds in such cities even though `.the wooden scaffold usually costs about one third as much as a metal scaold and can be erected in much less time. The danger of lateral collapse of the old form of wooden scaold is so great that it is common practice to apply long expensive wooden props or braces between the ground and the top ofA the scaffold to maintain same towards the wall being erected.

The Vmain obiectrof this invention is to provide a novel form rif-.bracing means of. the v'tension type that-.serves toflrmly bind all frame- 8 Claims. (Cl. 304-2) work members and stages together in a manner to produce a self-sustaining scaffold unit that has a maximum of rigidity and safety.

Another important object is to provide awseries of tension brace members that may be quickly placed in position and adjusted and which include quick release members of the hook' type that permits a quick knockdown of the scaffold unit. I

A further object is to provide a braced unitary scaffold that is economical to manufacture, 'that has a high degree of safety and one which may be assembled in a minimum of time.

A further object is to provide a novel'form of brace that may be applied at several similar positions in the scaiiold to produce a self-sustaining unit. L l,

A further object is to provide a scaffold that may be interchangeably arranged to 'serve as a portable unit carried by caster wheels or one to be supported directly upon a base but with the caster wheels shifted to another position.

Other objects will become apparent from the detailed description of the invention Awhich follows. j

In the accompanying drawings:

Fig. 1 is a view in front elevation of a three stage self-sustaining scaffold showing the braces in position. y

Fig. 2 is an end view of a two stage scaffold showing the braces in detail.

Fig. 3 is a view in section taken on line '3 3 ofFig. 2. "j

Fig. 4 shows a specific hook which is a part of the. brace. 'A l Fig., 5 shows in perspective a modified form of leg support or base and whichl is of the portable type. and

Fig. 6 is a view of two trestles showing the bracing. f j

Referring to the drawings in detail, Fig. il shows three stages I, 2, and 3 of a sc'aifold erected and braced according to this invention. Each trestle unit comprises the usual cross beam 4 having legs 5 that engage the brackets 6. The legs of the lowermost stage rest upon the planks 1 that. in turn, are supported directly Aupon the ground or upon a series Yof blocks' 8. Fig. 1 shows the rtrestle legsof all ` trestles asv 2 and 3 above the first stage I as being supported upon the trestle boards 9.v If elements v'I and' 9 are relatively short, several aligned planks may be used overlapped as shown in Fig. l'for the. trestle boards 9.

use and, collectively, have comprised a complete scaffold and no special brace means has been employed up to the present time. Such a scaffold is rather flimsy particularly when three or more stages are used. When a heavy load is placed upon the platform with workmen in action, its instability is evidenced by vibrations therein. If one end of the scaiold is loaded more heavily than the other end, the less loaded end becomes rather loose thereby permitting displacement of parts, these and other objections greatly increase the dangers inherent in the use of such a loose type of scaffold as compared to the metal scaold. y

Fig. 2 shows the novel brace used and its specific locations. While many brace elements are used in the structure, all ofthe braces are similar that are used to bind together adjacent superimposed trestles. most stage are provided with a specific type of base 'support and a modified form 4of brace Vmay be used therewith. In one :form of such -base support, the same 'brace is used Aas is applied thereabcve between the trestles, Vhence all braces may be interchangeable.

In -lig. 2, the braces that are :used to merely bind the base `supportplan'ks or "sleepers l cornprise a strap loop I@ `that Vis connected toa terminal eye ll by a cross bolt or pin. This eye engages a 'quick 'detachable hook l2 the Ylower end'of which is threadably engaged with a turn'- buckl'e I'3. The lower 'threaded rodof'this turn'- bucklepassesthroughtheplank 1 and is retained by -anut i4. A slipring l encircles the strap loop fora purpose tobe described.

The main vbinding braces that engage the 'cross beams of the trestles comprise eacha strap Il) and slip ring l5 'connected to a'turnbuckle as i6 which has a screw eye'or hook H that connects to thestrap l0. The hook l2 comprises a threaded'rod I8 that yforms apart ofthe turn'buckle. A second strap IS'is connected to arin'g 2a that is adapted to ngagethe hook l2and a slip ring '2i encircles the strap loop I9.

Fig. 5 shows the modified form of base support and portable sca'old. mAll braces used with Athis formare similar including the single brace 'cn-` nected tothe central portion of the basesuppor't 22. Ihese supports 22 carry planks 'lL-l that carry the scaiold load. The lower 'loop l encircles the support 22 and 'the latter 'support Serves also Vas a braceanbho'r so that these supports may be bound to the trestle stagesas a unit, in the `'position shown, vthese casters render the scaffold mobile or portable. If mobility is not desired, the transverse members V22 'may be rotated a quarter turn so that the 'fcasters'will project laterally free of the ground.

The hook l2 in Fig. 4 has apivot'ed section 25 the weight .of which is distributed so as tolc'ause or permit this section 'toV fall by gravity, -after thering 26 has beenxdisplaced upwardly, toa position shown by the `dotted lines where it "remains to 'morereadily'permt an eye ring as 2c to be engaged thereon; "Obviously, as shown, upon closure Voi 'thissection 25, the engaged ring will be raised in a mannerjto pull up on or tighten the attached loop I9 as well as the upper loop l0;

The legs of the lower- The mode of erecting the main elements ofthe or I9 is slipped over Vthis, boardand the `opposed Y loops 1'0 and l'9"`are"c`onnected, respectively, to

the eye l1 and the hook l2 that forms a unit with a turnbuckle element i6.

The function of slip links or rings l5 and 2l is important and novel in the relation shown, reference being made to Fig. 3 which shows a ring l5 that has been moved upwardly over the loop id. Such movement acts to pull the opposed sides of the loop towards each other which causes an appreciable tightening of this loop and lactually acts to cause the A'straploop to pull downwardly on a cross beam Likewise, the loop i9 will act to pull up on the opposed beam 4 when the ring 2l is moved towards this beam.

Suchcoaction of these two brace tightening forces, that is the tightening action of the hook and that due to the shortening of loops, will take Vup allslack i-n eachbrace and will actually act to pull an opposed pair of beams 4 together. Thereafter, the turnbuckle i6 is tightened and each superimposed pair of trestles will be bound together laxially with a forceup 'to 1000 pounds or more. "j

' Inmeiect, each series of superimposed 'trestles actually function as a rigid yvertical pylori or beam element suiciently rigid to 'renderi'tirne possible underany normal or A`even under an abnormal work load or lateral stress 'to cause such element to buckle. ineffect, each vvertically spaced series of trestles thus bound together functions asa built up beam Whichcould be called a back-bone andthe entire scaffold unit becomes builtup toinclude'sever'al'back-bone "elements, one for each vertical series 'o'f trestles. It should be noted, also, in Fig. 1 that all overlapped trestle 'boards 'as at 9 become "rigidly bound `t"o` gether at their adjacent ends thereby 'topreve'rt any lateral slippage 'between adjacent trestle units.

Referring to Fig. 3,`the`loop l0 'in the metallic' strap, is slid over a cross beam toits centrallpcrtion and then subjected toits tension loading; after the slip ring has been pushed towards the beam to partly close the loop. This causes the loop to cut into the wooden beam and produce rounded depressions at the corners thereof con' tacted by Athe loop. These depressions serve the useful purposeof enabling the erector to replace all loops during reassembly at the same positions before occupied by these loops, and Ano further marring occurs. y I y It will b e noted that, by use of the specific brace used and the fiat straploop connectors.' the cross beams of each trestle need not Ybe marred nor weakened by cutting or drilling. The strap Aloops are easily bent and they Amay be opened up some to permit a ready removal-from the teams When the scaffold isunloaded, after agfirst erection, there is not suiiicient weight available to force the tapered lends ofthe legs into the brackets. As shown in Figs.2 and 6, the brackets 6 are tapered along boththeir narrow and their wide sides, hence each leg must be formed at one end with corresponding tapers. With nor braces used, the structure would be wobbly, that is, too loose. However, according-tothe present invention, "when the braces are'tensio'ned,""`the tapered legends will beiorced into the brackets' and become 'securely helcltherein to permit the trestle tobe moved as a unit lfora next 1re-ase sembly. Since afterV say one or two ystages have been erectedandl properly tensionedbythebraces, when the nresuetcardsaresiid mtoiposiuonfupcn' the uppermost trestl'e cross beams, ii"`"ai:iy boaid' were to strike a cross beam, that beam and trestle would not become displaced.

A main defect of a loosely set up scaffold is that certain trestles actually shift as a job pro- -gresses and'such shifting is known as walking by the workmen thereon. It is possible for a trestle to actually slip from the supporting board 1.,However, due to brace tension, all trestles and board elements are rmly bound together and all trestle shift is prevented.

In the event that any one leg of a trestle is shorter than the other legs, a common occurrence in such scaiolds heretofore used particularly after much usage, such scaiolds become unstable. However, the force of the braces acting downwardly on the cross beams Will force any shorter leg down firmly against a supporting board 1 upon which the trestle is mounted thereby providing greater stability and preventing any relative shifting of positions of the trestles with respect to the associated longitudinally extending board elements.

In view of this disclosure, it will become obvious that the scaffold as described will possess a maximum of rigidity to withstand possible collapse. It will provide a maximum of safety, can be erected very quickly and will be economical to manufacture and maintain.

It is to be understood that the equivalents of elements shown are contemplated within the scope of the appended claims.

I claim:

l. A self-sustaining scaifold comprising a lowermost stage of spaced trestles, each trestle consisting of a transverse beam and a plurality of legs secured thereto for supporting the beam, the adjacent trestles being positioned in parallel relation, a plank element positioned upon said transverse beams adjacent each end thereof, a second stage of trestles supported upon said plank elements in a manner to position the transverse beam of each trestle in the second stage directly above and parallel to a corresponding beam of the first stage of trestles; means for binding said stages together, said means comprising a vertically extending tension brace for interconnecting each vertically spaced pair of beams; each brace comprising an adjustable coupling, said coupling including a member manually movable to vary the length of the coupling, a tension member extending from each end of the coupling, the free end of each tension member being connected to a respective transverse beam whereby the coupling may be operated to pull the pairs of opposed transverse beams together and rigidly bind together both stages of trestles. v

2. A self-sustaining scaiold comprising a first series of laterally spaced trestles, each trestle comprising a transverse beam supported by legs, said beams being positioned in a parallel relation, trestle boards positioned across said beams; a second series of laterally spaced trestles supported upon said boards, each beam in the second stage being positioned directly above a corresponding beam of the first stage; means for rigidly binding said stages together and firmly against said trestle boards; said means comprising a series of similar vertically extending tension braces, each beam of the first series being connected to a corresponding beam of the second series thereabove by one of the series of braces; each brace comprising a turnbuckle :and a tension member connected to each end of the turnbuckle, the free ends of the tension members being connected respectively to adjacent transverse beams, Iwhereby operationof the turnbuckle.fling?, tions to pull thel verticallyfspaced ,tlanverse beams towards each other to bind the stages rigidly together.

3. A scaffold as set forth in claim 2 wherein the tension membersl connected to,v the turnbuckles comprise a metallic strap loop, said loop surrounding the transverse member engaged'thereby 4. A scaold as set forth in claim 2 wherein the tension members connected to the turnbuckles comprise a metallic strap loop, said loop surrounding the transverse beam engaged thereby; a slip ring positioned to surround each strap loop and being slidable towards the adjacent transverse beam to constrict and shorten said loop thereby to take up slack in the respective brace.

5. A scaffold as set forth in claim 2 wherein the tension members connected to the turnbuckles comprise a metallic strap loop, said loop surrounding the transverse beam engaged thereby, one of said tension members having a terminal eye and being detachably connected to the turnbuckle by means of a hook, said hook comprising a shank portion connected to the turnbuckle and an arcuate load supporting finger pivoted to the free end of the shank portion, a retaining ring encircling said shank portion and being adapted to engage the free end of the finger, said finger engaging the terminal eye whereby, when the ring is disengaged from the finger, the latter is free to swing and be disengaged from the eye.

6. In a scaold as set forth in claim 2 wherein the legs of the first series of trestles are supported upon relatively wide plank members, tension rods secured to the plank members at points located between each pair of legs and substantially below each end of a respective transverse beam, tension` braces interconnecting each tension rod to the adjacent end of the respective transverse beam, and adjustable means for tightening said braces whereby the plank members are pulled upwardly to rigidly engage the legs of the first series of trestles.

7. In a scaifold as set forth in claim 2 wherein the legs of the rst series of trestles are supported on relatively wide plank members, said plank members being, in turn, supportedupon a series of transversely arranged base forming members, each base member being positioned directly below a respective transverse beam, a series of adjustable tension braces, each brace being connected at one end thereof to a transverse beam and at its other end to a base member therebelow substantially at the center thereof. adjustable means for tightening said braces whereby upon adjustment of said means, the transverse beams of the first series of trestles will be pulled downwardly to rigidly bind the scaffold to the base members.

8. In a scaffold as set forth in claim 2 wherein Y the legs of the first series of trestles are supported on relatively wide plank members, said plank members being, in turn, supported upon a series of transversely arranged base forming members, each base member being positioned directly below a respective transverse beam, a series of tension braces for binding the transverse beams oi the first series of trestles to the base members, each last named brace being connected at its upper end to a respective transverse beam and having a terminal loop connector at its lower end to be engaged around a respective base member, a series of caster wheels secured to one side ofv each base member and, in one position, being adapted to engage the ground, said terminal loop connector serving to permit the base members to

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