US3037580A - Self leveling step ladder attachment - Google Patents

Description

June 5, 1962 M. w. PULKIN 3,037,580

SELF LEVELING STEP LADDER ATTACHMENT 2 Sheets-Sheet 1 Filed Dec. 17, 1959 INVENTOR ATTORNEY June 5, 1962 M. w. PULKlN 3,037,580

SELF LEVELING STEP LADDER ATTACHMENT Filed Dec. 17, 1959 2 Sheets-Sheet 2 INVENTOR ATTORNEY United States Patent 3,037,580 SELF LEVELING STEP LADDER ATTACHMENT Matthew W. Pulkin, P.0. Box 158, Naranja, Fla. Filed Dec. 17, 1959, Ser. No. 860,213 1 Claim. (Cl. 182-200) This invention is a step ladder leveling attachment, being addressed to a structure involving an improvement upon the ladder construction described, illustrated and claimed in my Patent No. 2,889,099, date June 2, 1959.

An object of the invention is to provide an attachment, capable of being readily applied to step ladders now in use, of such construction as to provide automatic leveling means in order that the ladder may be solidly or firmly erected and maintained on even as well as uneven surfaces.

A further object of the invention is to provide means of simple construction in order that the attachment may be readily adapted to the back rails of the ladder without the exercise of special skill or implements, and which enables the leveling legs to have swinging movements laterally of the ladder in order to compensate for unevenness in the ground or supporting surface.

A further and particular object of the invention is to provide an attachment of the character generally set forth employing means which come automatically into play when weight is subjected to the ladder to lock the swinging leveling legs against movement whereby to stabilize the ladder throughout its use.

A still further object is to provide an attachment which is of simple construction, positive in its operations, which may be manufactured and marketed at extremely low cost, which has its several parts so constructed and assembled as to minimize the opportunity for wear, breakage or derangement, and which will adequately accomplish the purposes for which it is intended.

With the foregoing purposes in view, together with others which will appear as the description proceeds, the invention resides in the novel construction, combination and arrangement of parts, all as will be more fully described hereinafter, illustrated in the drawings, and particularly pointed out in the claim.

In the drawings:

FIG. 1 is a side elevation of a conventional step ladder illustrating an embodiment of my invention applied thereto,

FIG. 2 is a rear elevation, on an enlarged scale, of the lower end of the ladder stand and illustrating the application of my invention,

FIG. 3 is a transverse sectional view taken substantially upon line 33 of FIG. 2.

FIG. 4 is a similar view taken upon line 44 of FIG. 2.

FIG. 5 is a rear elevation of a ladder equipped with a different type of ladder stand and illustrating as applied thereto a modified form of the invention,

FIG. 6 is an enlarged transverse sectional view taken upon line 6-6 of FIG. 5, and

FIG. 7 is a similar view taken upon line 77 of FIG. 5.

Referring now more particularly to the drawings, there is illustrated a step ladder of well known form which comprises the spaced apart stiles 10 having the steps 11 disposed between and adequately secured to these stiles. The ladder stand comprises the spaced apart back rails 12 which may be parallel or substantially so, pivotally connected at their upper ends to the top portion of the ladder stiles for swinging movement as will be understood. The attachment of my invention is applicable to these back rails, whether they be of wood or metal.

The attachment comprises a leveling member consisting of spaced apart legs 13. In the present instance, these legs are made of a single length of metal tubing bent into substantially U-shape as shown and mounted for swinging 3,037,580 Patented June 5, 1962 ice movement in inverted position upon the rear of the stand. The lower ends of these legs may be equipped with feet or ferrules 14 of rubber or other material to minimize the opportunity for slippagev The legs 13 at their meeting ends or bight portion 15 have rigidly attached thereto by rivets or other means a clip plate 16 which extends downwardly from the bight portion between the said legs. This clip plate is provided with a central transverse slot for the reception of a pivot bolt 17, which bolt also passes through a clip 18 of substantially U-shaped cross section intermediate the ends of the clip. From this construction it is obvious that the clip may rock upon the clip plate.

The clip 18 is provided with a pair of openings one upon each side of the central pivotal opening thereof to receive pivot pins 19 at the inner ends of outwardly projecting arms 20 which extend in opposite directions from the clip and are secured to the back rails 12 by means of screws or other fastening elements 21. In the drawing these arms are illustrated as having several openings in longitudinal alignment in order that the arms may be adaptable to ladder stands having back rails of different widths apart.

The attachment also includes a straight flat bar 23 which is rigidly secured transversely of the stand near the lower end thereof and to the rails 12 by means of screws or other attaching means 24. It will also be observed that this bar is equipped with spaced openings 25 in order that it may be adapted to various widths of ladder stands. This bar is provided intermediate its ends or in the longitudinal center of the ladder stand with a suitable opening through which extends a bolt 26; the said bolt also passing through an arcuate slot 27 in brace plate 28 rigidly secured at its ends to the legs 13 of the brace member. The arcuate slot 27 is concentric with the pivot bolt 17. The bolt 26 is provided with spaced apart washers 29, one disposed upon each side of the brace plate 28 and the bolt is loosely held in place by lock nuts 30 to permit free swinging movement of the leg structure 13 and also to permit a certain amount of play between the brace plate 28 and the bar 23.

With the attachment applied to the back rails 12 of the stand in the manner described, it is obvious that the leveling legs may swing as a unit freely upon the pivot bolt 17. Therefore, when the ladder is placed upon an uneven surface, the attachment legs, extending slightly below the backrails 12 of the stand, will engage the sup porting surface and in the event such surface is not level, the brace will swing in order to adapt itself to this unevenness. When weight is subjected to the ladder, as by a person climbing thereon, the downward stress is borne by the legs 13 and due to the play between the spacing washers 29, a canting action will occur between these washers and the brace plate 28 to create the action of a friction brake, thus to hold the attachment legs firmly in position and against any possible opportunity for slippage. This braking action will prevail as long as the legs are subjected to weight upon the ladder. Immediately the weight is removed, the legs are free to again swing laterally upon the pivot bolt 17.

In the modification shown in FIGS. 5 to 7 inclusive, the back rails of the stand are indicated at 31 and converge downwardly from their pivotal connection with the upper part of the ladder stiles. The attachment legs 32 are similar to those shown and described in connection with the preferred embodiment of the invention, being made of suitable tubing of proper length and bent into substantially inverted U-shape, having a clip plate 33 secured to the bight portion of the legs and depending therefrom. This plate is rigidly connected to the attachment legs. This clip plate is provided with an elongated opening 34 extending in a downward direction, for the reception of a pivot bolt 35 which passes through an upper plate 35 rigidly connected at its ends to the back rails 31 above the lower ends thereof. This bolt is provided with washers 37, one disposed upon each side of the clip plate, and the bolt is provided with lock nuts 38 which loosely conmeet the plate 36 with the clip pltae 33. From this construction it is obvious that the attachment legs are capable of slight vertical movement.

The lower ends of the back rail are rigidly connected together by a bottom plate 39 through which passes bolt 40; this bolt also passing through an arcuate slot 41 in a brace plate 42 connecting the lower portions of the legs 32. The slot 41 is struck from or concentric with the bolt opening in the clip plate 33. The bolt connection between the bottom pltae 39 and the brace plate 43 is such as to permit normal free swinging movement of the attachment legs upon the pivot bolt 35.

In this form of the invention the free swinging movement of the attachment legs is the same as that described in the preferred embodiment, however, the braking or looking action is slightly different. The vertical elongated slot or opening 34 permits a certain amount of vertical play between the back rail 31 and the attachment legs so that upon the application of weight to the ladder, a canting action will occur between the clip plate 33 and the upper plate 36, thus providing a frictional binding of the pivot bolt 35 between the spaced apart washers and holding the attachment leg rigid with the back rail, which rigidity will be maintained until the ladder is relieved of its weight.

From the foregoing it is apparent that I have provided an attachment of simple construction, which may be readi- 1y applied without special skill or implements to ladders now in use, whether they be of metal or wood, and which will carry out its adjusting and locking functions automatically in order to adapt the stand to uneven surfaces.

I claim:

An attachment for a step ladder having the usual spaced apart back rails; comprising a straight fiat bar to rigidly connect the lower ends of said rails and having an opening midway its ends, an auxiliary strut comprising a pair of spaced legs united at one end and arranged in diverging relationship, a clip plate rigidly secured at one end to the meeting ends of said legs with its opposite end disposed between said legs, a second clip of substantially U-shaped cross section disposed across said clip plate having a centrally located transverse slot therein, a pivot bolt passing through said clip plate and through said slot to connect the clip in rocking as well as transverse movement with respect to said pivot bolt, a pair of arms pivoted at their outer ends respectively with said back rails, the inner ends of said arms disposed within the open ends of said second clip and pivotally connected in spaced relationship thereto, a brace plate connecting the lower ends of said legs overlying said fiat bar and having therein an arcuate slot concentric with said clip pivot, and a pivot bolt extending through said fiat bar opening and through said arcuate slot.

References Cited in the file of this patent UNITED STATES PATENTS 983,172 Sheetz Jan. 31, 1911 2,397,468 Cail Apr. 2, 1946 2,889,099 Pulkin June 2, 1959

Images