US3540549A

US3540549A - Foldable ladder

Info

Publication number: US3540549A
Application number: US847099A
Authority: US
Inventors: George Harvey Emmons
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-08-04
Filing date: 1969-08-04
Publication date: 1970-11-17
Anticipated expiration: 1987-11-17
Also published as: ZA705084B; FR2056514A5; NL7011544A; SE365021B; DE2034858A1; GB1270786A; BE754089A; JPS508384B1; CH519091A; CA937911A

Description

United States Patent Inventor Georgellarvey Emmons 11 S. 12th St., Marshalltown, Iowa 50158 Appl. No. 847,099 Filed Aug. 4, 1969 Patented Nov. 17, 1970 FOLDABLE LADDER 11 Claims, 11 Drawing Figs.

U.S. Cl 182/169,

1 2 172 Int. Cl E06c 1/20 Field of Search 182/ 1 69,

References Cited UNITED STATES PATENTS 4/1915 Caronia [82/172 2,652,184 9/1953 Loucks 132/172 FOREIGN PATENTS 613,324 11/1948 Great Britain 182/170 Primary ExaminerReinaldo P. Machado AnomeyMorton S. Adler ABSTRACT: A ladder having a foldable tripod supporting frame structure. The ladder component utilizes substantially parallel side pieces with connecting rungs with one of the legs of the tripod support serving as one of the ladder side pieces. The other side piece is not a ground engaging element but is operatively associated with the tripod structure so that weight forces on the ladder are appropriately distributed to the sup porting legs.

Patnted Nov. 17, 1970 I I 3,540,549

Sheet 2 012' /NV/Y70R GEORGE HAP var EMMON$ w 477'0PNEJ4 FOLDABLE LADDER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in foldable ladders and combines a ladder structure with a foldable tripod supporting frame.

2. Description of the Prior Art Foldable ladders, or step ladders as they are commonly referred to, are old and well known and include the conventional ladder structure having substantially parallel side pieces with connecting rungs to which some form of a foldable brace means of lesser sturdiness than the side pieces is hingedly attached to the top portion of the respective side pieces of the ladder so that it canbe swung out into ground engaging posi' tion. So far as is known, all such step ladders are designed so that the bottom ends of both side pieces engage the ground or supporting surface and generally the brace means also includes a pair of spaced legs. In some instances, the rear sup porting legs are converged to form a single ground engaging means as exemplified in U.S. Pat. Nos. 5,451 and 46,l05 but in addition to the ground engaging contact of'the ladder side pieces and the single point of contact of the rear leg, there is also utilized additional side leg supports.

The use of a swingable or foldable support leg for a step ladder whether having a single ground engaging arrangement or a plural ground engaging arrangement does not overcome the difficulty of using the ladder in a rigid and stable condition when both of the ladders side rails must engage the ground or support. By virtue of-the relative closeness of the side rails at the ground or support level, such ladders are quite susceptible to lateral tipping even when on a level surface and if the ground or support is not level, this susceptibility is substantially increased even though a shim or block may be placed under one ofthe side rails on the downhill side as is commonly done.

The present invention utilizes the principle of a tripod type supporting structure wherein three equally sturdy ground engaging legs can be extended or folded out from an apex frame point to provide an extremely rigid and stable frame. Such a structure, in and of itself, for example, would provide a rigid and stable support for a ladder if such ladder were to be mounted thereon without in any way engaging the ground surface. Utilizing this principle, the present invention, rather than having a separate ladder and a separate tripod frame support, has incorporated one of the tripod legs as one of the side pieces for the ladder and'by suitably associating the other side piece which is not aground engaging component, with the tripod frame structure, there is provided an extremely rigid and stable foldable ladder structure that substantially increases the safety and efficiency with which such a ladder may be used. Anadjustment means designed for use with any one of the legs is provided for use on unlevel ground and serves primarily to suitably orient the vertical plane of the ladder side pieces.

SUMMARY This invention is directed to foldable ladders and the primary object herein is to materially 'improve'the rigidity of the ladder supporting structure and to substantially increase the stability of the ladder while it is being used. This ladder incorporates a ladder component with a foldable tripod supporting structure that provides a highly stable three point ground engaging support means.

The principle of this invention is illustrated by reference to FIG. of the drawings herein which show basically a tripod frame and a separate ladder having only side rails and rungs which, if properly positioned on the tripod frame without the ladder itself engaging the ground, would provide an extremely rigid and stable support for the ladder. Such a tripod type support is a marked departure from the traditional means of supporting a step ladder because of the inherent stability of the tripod as compared with the considerably less stable support means on traditional step ladders.

The principle as illustrated in FIG. 10 is utilized in the present invention by using one leg of the tripod as one of the side rails of the ladder. The other side rail of the ladder which is required for supporting the rungs is not a ground engaging element but is designed to bear against an adjustably arrangeable brace element on the tripod frame so that weight carried by the ladder will be proportionally transmitted throughout the frame. Means are provided to prevent movement of said other side piece relative to the brace element while the ladder is folded out for use.

The side piece of the ladder which does not engage the ground is operatively associated with one of the tripod legs at two vertical spaced points near the upper and lower extremities of said side piece and a curved upper end portion of said side piece is designed to be in a vertical plane when the ladder is extended so that there is no lateral twisting of the ladder component when it is subjected to a weight lead.

A removable foot member is adapted for use with either of the legs of the tripod frame to provide an appropriate adjustment for use of this article on uneven ground and primarily such adjustment is for the purpose of properly orienting the vertical plane of the ladder rather than for shimming up one of the legs because of unevenness of the ground as is usually the case involved with the traditional step ladder when the supporting surface is not level. In this regard, such foot is provided with a bend so that the ground engaging end portion is angularly disposed to the longitudinal plane of the leg being supported and extends in a vertical plane toward the ground. Thebottom of the leg rests upon a shoulder on the vertical portion of the foot member and is suitably removably secured to such foot member.

The objects of this invention together with details of the operation outlined and the advantages of the same will be more fully described and developed in relation to the more detailed description ofthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of my new ladder in folded position,

FIG. 2 is a perspective view of this ladder in open or extended position and ready for use,

FIG. 3 is a perspective view of the lower end of one of the ladder legs showing the removable foot member attached thereto,

FIG. 4 is a perspective view of a ladder similar to but taller than the ladder in FIG. 1 and showing a second embodiment of this ladder in open position to illustrate a modified upper structure of this article,

FIG. 5 is a fragmentary perspective view of the upper portion of the ladder shown in FIG. 4 in closed position,

FIG. 6 is an enlarged perspective view taken on the line 6-6 of FIG. 4 to illustrate the latching arrangement between the leg of the ladder and the brace of the tripod frame,

FIG. 7 is a top view of the ladder shown in FIG. 1,

FIG. 8 is a top view'of the ladder shown in FIG. 4,

FIG. 9 is an enlarged perspective view of a modified arrangement for attaching one of the ladder legs to the brace of the tripod frame,

FIG. 10 is an exploded perspective view for the purpose of illustratingthe principle involved in this invention relative to a tripod supporting frame for a ladder, and

FIG. 11 is a top plan view of this ladder in open position and ready for use to illustrate the relative position of the ladder component to the tripod frame.

DESCRIPTION OF THE PREFERRED EMBODIMENTS principle involved herein, reference is first made to FIG. I0

where there is shown a rigid tripod frame with the lower ends of the respective legs in opened or spaced position and the upper ends of the tripod legs forming the apex of the triangular frame. A lower brace 12 is shown between legs l4 and 16 and a similar lower brace 18 is shown between

legs

16 and 20. An upper brace 22 extends between

legs

14 and 20. Thus illustrated, it will be appreciated that the tripod frame 10 by reason of its three ground engaging legs, provides an exceedingly stable and sturdy structure. The numeral 24 illustrates the conventional or traditional step portion of a step ladder which includes the standards or side pieces 26 and 28 of like length and the plurality of steps or rungs 30 together with a top plate 32. The usual swinging legs for the conventional step ladder are omitted in FIG. 10 since the frame 10 serves as the support. For this purpose, ladder 24, if mounted on frame 10 by any suitable means which is here illustrated by a selected arrangement of hooks 34 on the frame and complementary latch means 36 on ladder 24, would result in an extremely sturdy and for all practical purposes nontiltable or twisting ladder arrangement. For illustration, the lowermost elongated book 36 on ladder 24 would preferably engage brace 18 for proper orientation of the side pieces 26 and 28 and it will be appreciated that there would be no necessity for such side pieces to be in engagement with the ground. The advantages of this tripod frame support concept for a ladder as illustrated should be obvious and to provide a practical application for this principle, I have incorporated a ladder structure into a foldable I tripod supporting frame which I will now describe.

Reference is first made to FIGS. 1 and 2 where the step ladder shown is a relatively short ladder in the general range of six to eight feet as distinguished from the ladder shown in FIG. 4 which is in the relatively taller or higher range. The tripod frame structure for this ladder is represented by the three

leg members

38, 40 and 42 which in their open position as shown in FIG. 2 terminate at their upper ends at the apex point 44 and thus produces the considerably more stable three legged support frame that the three legged frame of the patents referred to where two of the legs are the traditional side pieces to which lateral legs are attached. No such lateral supports are required or necessary in the present ladder. Thus arranged,

legs

38, 40 and 42 would correspond respectively with the

legs

20, 16 and 14 of the illustrative tripod frame shown in FIG. 10.

For purposes of my foldable tripod frame ladder structure, the tripod leg 38 serves also as one of the side pieces for the ladder component, said component being designated generally by the numeral 46. The upper end of leg or side piece 38 is preferably fixedly attached to a short cross piece 48 and the upper end of leg 42 is pivotally attached to the other end of member 48 by any suitable means such as the pin 50 so that leg 42 may be moved toward leg 38 in its folded position as shown in FIG. I. It will be understood that the upper end of side piece 38 may be pivotally attached if desired, but this is not necessary so long as one of the

legs

38 or 42 is foldable toward and away from the other. A hinged brace means 52 connects

legs

38 and 42 for stabilizing the same when the ladder is in open position and such brace 52 would correspond generally to brace 22 shown in FIG. 10. The ladder component 46, utilizing the frame leg 38 as one of the ladder side pieces, includes the general parallel complementary side piece 54 secured in the usual ladder relationship to side piece 38 by a plurality of spaced steps or rungs 56 and including a top plate 58. As best seen in FIG. 2, side piece 54 is parallel to side piece 38 from about point 57 spaced somewhat below its upper extremities and slightly above the top rung 56 only down to point 60 which corresponds to the location of the second step 56 from the bottom of the ladder structure. At point 60, the plane'of the top edge or side of side piece 54 is provided with a sufficient bend toward its underside so that when this ladder structure is in open position, the plane of side piece 54 between point 60 and the lower extremity of such side piece, point 62, will be in a substantially vertical line relative to the ground. In this arrangement, it will be particularly noted that the lower end of side piece 54 does not engage the ground nor whatever supporting surface the ladder is on. Side piece 54 has the curved portion 63 above point 57 to its upper end that connects to the top plate 58 and such portion will be in a vertical plane when the ladder is open. Plate 58 is suitably secured to the upper end of

members

38 and 54 as shown so that weight forces on plate 58 will be directly downwardly to avoid any twisting.

Leg 40 of this ladder frame, which would correspond to leg 16 of the illustration in FIG. 10, is pivotally attached at point 64 to the upper portion of the side piece 54 by a bolt means 66. Such bolt is located relatively high on side piece 54 just above the top step 56 and from point 64, leg 40 is slightly angled so that in the open position of this ladder, the upper end 68 of leg 40 will bear against member 48 at the apex 44 of this tripod structure. The top plate 58. as best seen in FIG. 7 is provided with the slot 70 to permit the free movement of the tip end 68 of leg 40 when the ladder structure is moved to folded position as shown in FIG. 1. In the movement of leg 40 from closed to open position and for the purpose of properly orienting the ground engaging positions of the tripod frame legs, point 64 on leg 40 will move slightly away from side piece 54 as can be seen from the shape of slot 70 in FIG. 7 and to accommodate this movement, bolt 66 is provided with a suitable length for this purpose.

A foldable V-shaped brace arrangement for stabilizing

legs

38, 40 and 42 in open position corresponding to the brace elements l2 and 18 in FIG. 10 is provided by means of brace member 72 comprising the respective

elongated arms

74 and 76 which are pivotally connected in endwise relationship as at 78. The outer end of arm 74 is pivotally attached as at 80 to the lower end of leg 42 and the outer end of brace arm 76 is similarly attached as at 82 to the lower end of side piece or leg 38. Brace

arms

74 and 76 will at all times define a generally V- shape of greater or lesser degree depending upon whether the ladder is opened or closed and brace 72 is related to leg 40 in one embodiment as follows. An elongated rod 84, as perhaps best seen in FIG. 9, is secured to leg 40 so as to extend longitudinally thereon and in space relationship thereto and below point 64 as shown. An eye member 86 slidably journaled on rod 84 is secured to arm 76 of brace 72 near thepivot point 78. In the open position of this ladder, the lower end of rod 84 serves as a stop means to limit the downward movement of brace 72 so that in the open position, leg 40 will be securely braced against brace member 72. A movable paint tray 88 may be provided in any suitable manner as shown although such tray comprises no part of this invention.

Thus far described, it will be appreciated that if a weight is placed upon steps 56 of ladder component 46 when the tripod frame is opened that there would be a lateral twisting ofladder 46 toward brace element 72 in view of the fact that side piece 54 is not a ground engaging component. This would, of course, make the ladder structure unsatisfactory for use and, accordingly, such problem is overcome by providing a suitable rearwardextension on side piece '54 in the area both above and below the point on side piece 54 where it would be intersected by brace arm 76. Such extension, here designated by the numeral 90 may be in any suitable form and is here shown as a width enlargement of the lower portion of side piece 54. Any other means which would provide a rearward extending supporting edge 92, such as a rail or bar, for example, would serve the same purpose and the particular type of such extension would be a matter of choice. By reason of extension 90, edge 92 will bear against brace arm 76 when the ladder is in open position as shown in FIG. 2 and it has been determined from experiments that such point of contact is approximately at point 60 which is the second step 56 from the bottom. In this regard the vertical plane of side piece 54 between

points

60 and 62 provide a structure whereby when weight is first placed on the lowermost step 56, the weight forces are directed downwardly directly against brace 72 so that the weight forces are properly transmitted and absorbed by the tripod frame structure. Preferably, the upper end of edge 92 is provided with a shoulder 93 which is engageable with arm 76 as a precaution against edge 92 being accidentally moved out of bearing contact with such arm'. Without the directional change of the plane between

points

60 and 62 relative to the longitudinal plane of side piece 54 or, in other words, if the entirelength of piece 54 were parallel with side piece 38, a weight placed on the lowermost step 56 would result in some lateral twisting of ladder 46 even though a portion of the weight load would be taken by brace 72. Likewise, the curved portion 63 at the top of side piece 54 provides for the vertical support under top plate 58 and avoids the twisting that would occur if the upper end of member 54 continued parallel to leg 38 and a weight load were applied to plate 58 at this point.

It might also be noted that in the use of this ladder, the purpose of the upper angled upper portion of leg 40 is to permit the pivot point 64 to be as high as possible relative to side piece 54 and at the same time afford the engagement of leg end 68 with the apex end 44 of the frame structure. Such arrangement, particularly on the smaller ladder as seen in FIG. 2, has been found to provide a most adequate, stable and sturdy frame support.

With this ladder in open position, it will be seen from the top plan view in FIG. 11 that

legs

38 and 42 extend in opposite directions but in the same plane and that leg 40 forms a right angle with each of the other legs. This permits the side of the ladder represented by

legs

38 and 42 to be placed substantially flush against a building, for example, if work on such building requires the use of a ladder. In this regard, the arrangement and purpose of extension 92 as described above serves to maintain the ladder component 46 in a properly oriented position for use as seen'in FIG. 11.

While the unevenness of the ground upon which this ladder might be placed would not affect the stability of the tripod frame, it would, nevertheless, result in the disposition of the ladder component 46 at an inclination to the vertical and thus to assure that the ladder 46 can be properly oriented to the vertical for satisfactory use, I have provided a leg adjustment member 94 as illustrated in FIG. 3. Member 94 includes an elongated generally rectangular body portion 96 which is formed with an angularly extending and ground engaging lower or foot portion 98. Member 94 is designed so that body portion 96 can be removably attached to the lower ground engaging end of any one of the frame legs by any suitable means which is here illustrated by the use ofa pair of spaced removable encircling clips 100 and a bolt and wing nut 102 mounted through a hole 104 in the respective legs ofthis ladder as illustrated on leg in FIG. 2. Foot portion 98 is somewhat wider than body portion 96 to provide the shoulder 99 at the top of portion 98 on which the bottom of the ladder leg is seated and supported and by reason of the angled foot portion 98, such portion will be in a vertical plane relative to the ground when the ladder is extended so that with the attachment of leg adjustment member 94 to any one of the frame legs, any weight forces on the frame will be directed vertically toward the ground. It will thus be appreciated that member 94 serves primarily to properly orient the ladder frame and the ladder component and is not for the specific purpose of stabilizing the frame as is usually the situation in shimming traditional step ladders.

With reference now to FIGS. 46 and 8, I show this tripod frame supported ladder structure with certain modifications particularly applicable to relatively tall ladders of this type but for those elements of this article which are the same as those previously described, like numbers will be given to like parts and to the extent that modified parts correspond substantially to parts previously described, they will be given like numerals primed.

Leg 40 having the upper curved portion as described for FIG. 2 is replaced in the structure of FIG. 4 by the straight leg 40. In view of the'fact that the structure in FIG. 4 represents a relatively tall step ladder, the area of the triangle formed by the ground engaging legs will be relatively larger than in the shorter structure of FIG. 2 and by reason of this fact, the plane of intersection between leg 40' and side piece 54 will be somewhat lower than point 64 in FIG. 2 and approximately on the plane of the second step 56 from the top of the ladder. To provide a support for side piece 54 relative to leg 40', an integral depending arm 106 is provided as shown and terminates at approximately the horizontal plane of the second step 56 from the top. Such arm I06 together with the upper portion of side piece 54 provides an inverted V side piece top portion. A rigid rod 108 is secured between the lower end of arm I06 and side piece 54 at approximately the second step 56 from the to so that rod 108 is on substantially a horizontal plane. Leg 40' is pivotally and slidably journaled on rod 108 at point 64' so that in the open position of the ladder as seen in FIG. 4, the

upper end of leg 40' will be at that end of slot 70 in top plate 58' that is adjacent the apex point 44 of the tripod frame structure. The closed position of this upper portion of the ladder shown in FIG. 4 is illustrated in FIG. 5 where it will be noted that leg 40', when folded inwardly, will move on rod I08 closer to side piece 54.

With reference now to FIG. 6, I show asecond embodiment ofrelating brace 72 to leg 40 as follows. Intermediate the bottom of leg 40' and point 64' thereon, there is secured a transversely extending rod 110. A snap latch means IIZ is secured to brace arm 76 near the hinge point 78 so that as the ladder is opened for use, latch I12 will become removably locked onto rod I10 for stabilizing the tripod frame. In other respects, the ladder of FIG. 4 is similarly constructed and used as the ladder in FIG. 2.

It will be appreciated that this ladder structure is considerably more stable than traditional step ladder structures due to the relatively wide spread three legs which converge to the apex 44. The nonground engaging ladder side piece 54 is adequately and sturdily supported at two vertically spaced points on either leg 40 or leg 40 of the tripod frame such as points 64 or 64' and against brace arm 76 at element 90. The effect of this arrangement is to distribute the weight load on ladder component 46 to all of the frame legs and thus provide a greatly improved and highly efficient article for its intended purpose. This ladder is easily opened and folded and may be compactly stored or transported. Accordingly, from all of the foregoing, is thought a full understanding of the construction and operation of this invention will be bad and the advantages ofthc same will be appreciated.

Iclaim: I. A foldable ladder structure. comprising: first and second spaced elongated side pieces having respective upper and lower ends and with a plurality of longitu' dinally spaced step members disposed intermediate said side pieces and secured thereto to form a ladder component; said first side piece serving also as a first ground engaging leg of a three legged tripod frame ladder support; said second side piece being of a shorter length than said a first piece at their lower ends so that the lower end of said second side piece is free of engagement with any supporting surface for said first side piece; a second elongated ground engaging leg having an upper and lower end and pivotally secured at its upper end to the upper end of said first leg to form an apex;

a third elongated ground engaging leg having an upper and lower end and pivotally secured near its upper end to the upper end portion of said second side piece so that when the lower end of said third leg is moved outwardly, the upper end thereof will bear against said apex;

foldable brace means connected to said first and second legs and releasably lockable to said third leg when said legs are extended into a tripod shape; and

means on the lower end portion of said second side piece for engaging said brace means.

2. A ladder structure as defined in claim 1 including:

said second side piece being provided at its lower end por' tion with a sufficient bend toward its underside so that when said legs are extended into tripod shape, the plane of said second side piece below said bend is substantially perpendicular to but free of engagement with the supporting surface for said legs; the lowermost step on said ladder component being substantially planar with the lower end of said second side piece so that a weight load on said lowermost step will be directed vertically downward; and the point of engagement of said second side piece with said brace means being substantially at the plane of said bend. 3. A ladder'structure as defined in claim 1 including: a leg adjustment member comprising:

an elongated body portion having an integral angularly disposed ground engaging foot portion; and

means for detachably securing said body portion in longitudinal abutting relationship with the lower end portion of any one of said legs so that the bottom of said leg bears against said foot portion and when said legs are extended into tripod shape, the longitudinal plane of said foot portion will be perpendicular to its supporting surface.

4. A ladder structure as defined in claim 1 including:

said first and second legs when in extended position relative to each other being in the same plane; and

said third leg when extended being in a plane perpendicular to that of said first and second legs.

5. A ladder structure as defined in claim 1 including:

a top plate secured across the upper ends of said side pieces;

and

said top plate being provided with an elongated slot to provide a passageway for the upper end of said third leg when it is moved into and out of engagement with said apex.

6. A ladder structure as defined in claim 5 including: said second side piece being provided at its upper end portion with a sufficient bend-towards its upper side so that when said legs are extended into tripod shape, the longitudinal axis of said bent portion is in a substantially vertical plane when receiving any weight load on said top plate.

7. A l'oldable ladder structure, comprising:

a tripod-type frame defining first, second and third ground engaging support legs each having an upper and lower end;

means connecting the respective upper ends of said first and second legs to define the apex of said frame and at least one of said legs being pivotally associated with said apex for movement away from and toward said other legs;

said first leg also serving as the side piece for a ladder component;

a second side piece in spaced relationship to said first leg with a plurality of spaced step members disposed intermediate said side pieces and secured thereto to form a ladder component;

said second side piece terminating at a point spaced upwardly from the lower end of said first leg so that said second side piece is free of engagement with any supporting surface for said frame legs;

means pivotally connecting said third leg at its upper portion but spaced from the upper end thereof to the upper portion of said second side piece so that when the lower end of said third leg is moved outwardly, the upper end thereof will bear against said apex; a foldable brace secured to said first and second legs intermediate the upper and lower ends thereof; a pair of elongated brace arms hingedly attached together in endwise relationship to form a generally V-shaped brace; the respective outer ends of said brace being pivotally attached to the respective lower end portions of said first and second legs; means for releasably locking said third leg to said V-shaped brace when said legs are extended in tripod shape; and means on the lower end portion of said second side piece for engaging said V-shaped brace when said frame is extended. 8. A foldable ladder structure as defined in claim 7 includait] second side piece being provided at its lower end portion with a sufficient bend toward its underside so that when said legs are extended into tripod shape, the plane of said second side piece below said bend is substantially perpendicular to but free of engagement with the supporting surface for said legs; the lowermost step on said ladder component being substantially planar with the lower end of said second side piece so that a weight load on said lowermost step will be directed vertically downward; and the point of engagement of said second side piece with said brace means being substantially at the plane of said bend. 9. A ladder structure as defined in claim 7 including: a leg adjustment member comprising:

an elongated body portion having an integral angularly disposed ground engaging foot portion; and means for detachably securing said body portion in longitudinal abutting relationship with the lower end portion of any one of said legs so that the bottom of said leg bears against said foot portion and when said legs are extended into tripod shape, the longitudinal plane of said foot portion will be perpendicular to its supporting surface. 10. A ladder structure as defined in claim 7 including: a top plate secured across the upper ends ol'said side pieces;

and said top plate being provided with an elongated slot to provide a passageway for the upper end of said third leg when it is moved into and out of engagement with said apex. H. A ladder structure as defined in claim [0 including: said second side piece being provided at its upper end portion with a sufficient bend towards its upper side so that when said legs are extended into tripod shape, the longitudinal axis of said bent portion is in a substantially vertical plane when receiving any weight load on said top plate.