US2596521A - Stepladder - Google Patents

Description

May 13, 1952 J. B. BELL 2,596,521

STEPLADDER v Filed May 7, 1949 2 SHEETS-Sl-EET 1 May 13, 1952 J. B. BELL 2,596,521

STEPLADDER Filed May '7, 1949 2 SHEETS-SHEET 2 INVENTOR A oma P3642 Patented May 13, 1952 UNITED STATES PATENT OFFICE STEPLADDER Jerome B. Bell, Wallingford, Pa.

Application May 7, 1949, Serial No. 92,035

4 Claims.

The present invention relates to step ladders.

A purpose of the invention is to permit a step ladder to fold into a comparatively flat form and occupy a minimum of space in folded position, while at the same time having ample depth of step when the ladder is opened up, thus providing security and safety of tread on the ladder.

A further purpose is to provide a step positioning bar pivotally connected to the individual lower steps and below the top step, and preferably to make such bar extend parallel with the front rails.

A further purpose is to employ an interlocking system of upper and lower limiting bars interconnected by an intermediate limiting bar to limit the opening of the rails in opening position.

A further purpose is to make the distance be tween the pivots of the upper and lower limiting bars on the front rail the same as the distance between the pivot of the lower limiting bars on the front rail and the pivot of the intermediate limiting bar on the lower limiting bars.

A further purpose is to make the length of the intermediate limiting bar between its pivots the same as the distance between the pivot of the upper limiting bars on the front rail and the pivot connection between the upper limiting bars and with the intermediate limiting bars.

A further purpose is to locate a stop on the lower limiting bars toward the back rail with respect to the pivotal connections between the lower limiting bars and the intermediate limiting bar.

A further purpose is to locate a stop adjacent the pivot of the upper limiting bars on the back rail.

Further purposes appear in the specification and in the claims.

Figure 1 is a perspective mainly from the front showing the ladder of the invention in open position.

Figure 2 is a perspective partly from the rear showing the open ladder, with a portion of the top step broken away to illustrate the step positioning bar.

Figure 3 is a section of Figure 1 on the line Figure 4 is a fragmentary end elevation of the folded ladder showing the limiting bars in folded position.

Figure 5 is a fragmentary section corresponding to Figure 3 but showing the folded ladder.

Figure 6 is a fragmentary perspective of the rear rail showing the limiting bars and the pivotal connection thereto.

Figure 7 is a transverse perspective through one of the rails showing a variation in the manner of pivoting the limiting bars.

Figure 8 is a fragmentary end elevation of the ladder of the invention, showing a variation in the pivot support for the rear rails, with th ladder open.

Figure 9 is a view corresponding to Figure 8, with the ladder folded.

Describing in illustration but not in limitation and referring to the drawings:

In the prior art step ladders, where it is desired to make the ladder fold into a very compact form, the tendency has been to use very narrow steps which are uncomfortable and unsafe for the user. By the present invention comparatively wide or deep steps are used, while at the same time the ladder is enabled to fold into a very compact form.

The single limiting bar construction employed in the prior art has in some cases failed to provide adequate limitation when open, resulting in accidents due to unexpected collapse of the ladder when the user has been subjected to some unexpected force incident to the work he has been doing. By the present invention a double system of interconnected limiting bars is employed, which is much less likely to become dislodged and is much less subject to the danger of breakage.

The ladder of the invention comprises front rails 20, rear rails 2|, a top step 22 and lower steps 23 and 24.

The rails are suitably made of any desirable material, such as wood, or metal, but preferably comprise metallic channel or box sections as shown. The rails conveniently have cushion feet 25 at the bottom, suitably of rubber. The rails are desirably diverged outwardly at 26 to provide wide spacing at the feet for greater stability.

The steps may desirably be formed of any suitable material, such as wood or metal. metal stampings being desirable. Any suitable antifriction or roughening surface may be used on the steps. The top step carries beneath it brackets 21 at each end, suitably attached to the step, which pivotally interconnect with the front rails at 28 and with the back rails at 30.

The back rails are cross braced by bars 3| suitably cross connected at the middle for greater strength.

Each of the lower steps 23 and 24 is pivotally connected at 32 at its ends with the front rails, pivot brackets 33 on the steps desirably making the connections. It will be evident that the shorter the brackets 33 and the closer the pivots 32 to the top of each step, the flatter will be the fold of the ladder and the more nearly flush will be the folded position of the steps with respect to the frontrails. The step 24 below the bend 26 in the rails has diagonal ends 54 to conform to the rails in folding.

At the rear of each of the lower steps pivotal connection is made at 34, suitably through a pivot bracket 35 with astep positioning rail 36 which extendsbehind'the steps and makes pivotal connection beneath the top steps at 31 suitably on a pivot bracket 38 secured to the bottom of the top step. The positioning bar 3'5 as shown in Figures 3 and preferably remains at all times parallel with the front rails 20, so thatthe steps, the front rails and the step positioningrbarimake a parallelogram.

The improved limiting bar construction at the rails comprises lower limiting bars 40 and 4| pivotally interconnected .at 42. A slot 43 suitably in1the upper-portion .of the bar M receives a stop 44 on the endof-bar lfl to limit the-motion of :the .lower limiting barsdfl and M downward. Thelower limiting bar Allis pivotally interconnected with the front .rail .at 45 while the lower limiting bar 4| is pivotally interconnected with the back rail at 46. In open position the lower limiting bars can "desirably be approximately horizontaLlocated however above the point 26 at which the rails diverge.

Above the-lowerlimiting .bars upper limiting bars A! and 48 .extend across between the rails, being pivotally interconnected at '50 near the middle. The upper limiting .bar 41 is pivotally connected to :the frontrailat 28 and the upper limiting bar 48 is-pivotally connected to the back rail at 51,:suitably by a stud stop extending out sufiiciently to prevent the lower-limiting bars in folded position from.movingbeyond the upper limiting bars as best seeninlFigure 6. To pre- 7 vent interference the lower limiting bars are desirablyspaced out from the rails as by washers 52 while the .upper .limiting bars are positioned closer to the rails as shownin Figure 6. Thus a slight overlapping of the bars is possible in folded position.

The upper .andlower'limiting bars are interconnected by .an intermediate limiting bar 52 pivoted at one end'to the lower limiting bars at 53 and pivoted at the other end to the upper limiting bars at 50, the point where the upper limiting'bars pivot to one another. The pivot 53 is preferably located on the side toward the front rail of the pivotal connection "E2 between the lower limiting bars. In open position the intermediate "limitingbar '52 is inclined off the vertical as shown, tending to prevent the possibility that verticals components of torsional forces normally encountered in the ladder could cause the limiting bars .to break and thus .permit the :ladder to fold at a time which is notintended. v s

.It has been found very desirable to employ a certain relation of lengths,-creating a trapezoidal character 7011 the front and also on the back portion of the limiting bars. The distance between the pivotal connection of the lower limiting bars with the front rail "and the pivotal connection 26 of the upper limiting bars with the front rail should equal the distance between the pivotal connection 45 of the lower limiting bars and the .front rail and the pivotal connection 53 between the intermediate limiting bar and the lower limiting bars.

the'two lower limiting'barsextend in prolongation of one another and almost horizontal, while the two upper limiting bars extend in prolongation-.of one another and sharply inclined toward the rear, the intermediate relating bar being in- -'clined-'si'milarly to the front rails. The lock between theslot 43 and the stop 44 prevents the "limiting'bars'from travelling beyond this straight position.

While the embodiments shown illustrate limiting' lear-s-on both sides of the ladder, and illustrate-a lsingle step positioning bar, it will be evident that theinvention is not limited to use of any particular number of sets of limiting bars, nor to the use-of a-single step positioning bar as distinguished from a plurality of step positioning bars-as :desired.

'The detail as to how the pivotal connection is to'be made to the steps, and whether-the pivots are carried-clearacross from one tothe'other of the steps'or are individual-on each side-is not to 'be regarded as vital in the invention. It has been found thatadvantage can be obtained by pivoting the limiting bars-on the front and back rails insid the channel sections 'of the rails, as indicated by pivo 55 in Figure '7. By carrying the pivots -55 of Figure 7 clear across the channel and locating washers 5! around the pivots, the functionof the stop 5| in theform of Figures 1 to Binclusiveis performedbythe vrashersEl.

Asshown inFigures 8 and 9, the top step can fold flatter if theipivotal connection between the top step and the rear rails is carried farther below thetops tep' err-brackets 21 than the pivotal connection between the top step and the front rails on brackets 1 The additional length of bracket 2 l'should correspond-to the depth of the front rail section.

In operation it will be understood that in closing the ladder from the open position as shown, the user should grasp the lower limiting bars near thecenter and cause the limiting bars to break upward at their pivots %2, at the same time of course causing a similar deflection in the upper limiting barsdue to the pressure transmitted upward through the intermediate limiting bars 52. At the same time the front and back rails are pivoted toward one another, cau's'ing'the ladder to fold. The step positioning bar'iit automatically swings the lower steps into the .positions shown in Figures 4 and 5, thus producing 'a very compact folded ladder. When the ladder reaches its fully folded position, the pin 5| prevents thelimiting bars from moving too far.

To open the ladder it is merely necessary to pull the rails apartthe step positioning bar automatically positioning the lower steps in the correct position when the rails are fully open. To assure that the limiting bars are fully locked, the user should press down on the middle of the limiting bars on both sides to insure that the stops M engageri n theslots #3.

In view of my invention and disclosure variations and modifications to meet individual whim or particular needwill doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a step ladder, front and back rails, a top step pivotally connecting th front and back rails, lower limiting bars extending between one front rail and the adjoining back rail, pivotally connected to the respective rails and to one another, upper limiting bars extending across between the same front and back rails, pivotally connected to those front and back rails at points above the lower limiting bars and pivotally connected to one another and an intermediate limiting bar extending across between the upper and lower limiting bars and pivotally connected to the upper and lower limiting bars.

2. In a step ladder, front and back rails, a top step pivotally connecting the front and back rails, lower limiting bars extending between one front rail and the adjoining back rail, pivotally connected to the respective rails and to one another, upper limiting bars extending across between the same front and back rails, pivotally connected to the front and back rails at points above the lower limiting bars and pivotally connected to one another and an intermediate limiting bar extending across between the upper and lower limiting bars, pivotally connected to the lower limiting bars, and pivotally connected to the upper limiting bars where they pivotally connect to one another, the distance between the pivotal connection of the lower limiting bars to the front rail and to the intermediate limiting bar, and the distance between the pivotal connections at the ends of the intermediate limiting bars being the same, and the distance between the pivotal connection of the upper limiting bars with the front rail and with the intermediate limiting bar being the same as the distance between the pivotal connections of the intermediate limiting bar.

3. In a step ladder, front and back rails, a top step pivotally connected to the rails, lower limiting bars extending across between a front rail and its adjoining back rail, pivotally connected to the front and back rails and pivotally connected to one another, stop means limiting the motion of the lower limiting bars downward beyond the straight extension position, upper limiting bars extending across between the same front and back rails, pivotally connected to the rails above the pivotal connections of the lower limiting bars and pivotally connected to one another and an intermediate limiting bar pivotally connected to the lower limiting bars and pivotally connected to the upper limiting bars where they pivotally connect with one another, the upper limiting bars extending in prolongation of one another and the lower limiting bars extending in prolongation of one another when the ladder is fully open, the distance between the pivotal connections of the upper and lower limiting bars to the front rail being the same as the distance between the pivotal connection of the lower limiting bars to the front rail and to the intermediate limiting bar and the distance between the pivotal connections of the intermediate limiting bar with the upper and lower limiting bars being the same as the distance between the pivotal connection of the upper limiting bars with the front rail and with one another.

4. In a step ladder, front and back rails, a top step pivotally connected to the rails, lower limiting bars extending across between a front rail and its adjoining back rail, pivotally connected to the front and back rails and pivotally connected to one another, stop means limiting the motion of the lower limiting bars downward beyond the straight extension position, upper limiting bars extending across between the same front and back rails, pivotally connected to the rails above the pivotal connections of the lower limiting bars and pivotally connected to one another, a stop adjacent the pivot of the upper limiting bars on the back rail, and an intermediate limiting bar pivotally connected to the lower limiting bars and pivotally connected to the upper limiting bars where they pivotally connect with one another, the upper limiting bars extending in prolongation of one another and the lower limiting bars extending in prolongation of one another whe the ladder is fully open, the distance between the pivotal connections of the upper and lower limiting bars to the front rail being the same as the distance between the pivotal connection of the lower limitin bars to the front rail and to the intermediate limiting bar and the distance between the pivotal connection of the intermediate limiting bar with the upper and lower limiting bars being the same as the distance between the pivotal connection of the upper limiting bars with the front rail and with one another.

JEROME B. BELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 421,843 Teal Feb. 18, 1880 2,136,354 Welsh Nov. ll, 1938 2,160,124 Cast May 30, 1939 2,230,015 Rich Jan. 28, 1941 FOREIGN PATENTS Number Country Date 26,333 Great Britain 1904

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