US2781961A - Self-levelling stepladder - Google Patents

Description

Feb. 19, 1957 J. w. BENDICK SELF-LEVELLING STEPLADDER 3 Sheets-Sheet 1 Filed Jan. 21, 1954 INVGINTOQ, JACK w. BNDICK ATTOQNGIY.

Feb. 19, 1957 J. w. BENDICK SELF-LEVELLING STEPLADDER s Sheets-Sheet 2 Filed Jan. 21, 1954 INVGNTOK JACK w. BGNDICK ATTOKSQY 9, 1957 J. w. BENDICK 2,781,961

SELF-LEVELLING STEPLADDER Filed Jan. 21, 1954 3 Sheets-Sheet 3 I INVQNTOR/ JACK w. BCNDICK ATTo geY.

SELF-LEVELLING STEPLADDER Jack William Bendick, Winnipeg, Manitoba, Canada, as-

signor to Bendick Paul Limited, Winnipeg, Manitoba, Canada, a corporation of Manitoba Application January 21, 1954, Serial No. 405,424

Claims. (Cl. 228-29) This invention relates to stepladders and in particular to a stepladder which is constructed so that the legs will automatically conform to an uneven surface within reasonable limits, and thus provide a self-levelling stepladder. The term stepla-dder as used herein includes platform ladders, trestle ladders, ironing boards, tables and other four leg devices.

One disadvantage of stepladders which do not incorporate a self-levelling feature is that they tend to creep or walk. This comes about when the weight or force carried by the ladder is suflicient to cause the ladder to twist to make the legs conform to the uneven surface. By the term conform to the uneven surface, I mean that the four legs of the ladder are bearing against the floor, even though the floor may be uneven. The term selflevelling as used herein means the feature whereby the legs automatically adjust themselves to the uneveness of the lloor or ground upon which the ladder stands and will retain that position under load. When the ordinary ladder, i. e. one without a levelling feature, is supported on {an uneven floor the movement of the workman who is working from the ladder will cause the ladder to rock slightly alternately right and left. As the motion of the top of the ladder alternate from left to right, the legs alternately keep moving forward slightly, giving the effect of walking or creeping. A further disadvantage of a stepladder which is not levelled is that it wobbles and is therefore dangerous and unsafe.

It has already been proposed to provide stepladders with a means for adjusting the legs of the ladder to uneven surf-aces, but such self-levelling devices were rather complicated and required new adjustment every time the ladder was moved to a new surface.

The main object of the present invention is to provide a stepladder which is constructed so that the legs will automatically adjust themselves to uneven surfaces by the simple process of setting the ladder on the uneven surface or when a person stands on the ladder. Thus the self-levelling feature keeps the ladder in steady balance on the uneven surface and the steps of the ladder in a substantially horizontal plane.

Another object of the invention is to construct a stepladder having a self-levelling feature, which i simple to construct and adds little or no manufacturing cost to that of conventional ladders of better quality without such selflevelling feature.

An advantage of the self-levelling ladder, made in accordance with the present invention, is that it is free from creeping or rocking due to its specific construction.

Briefly, ladders constructed in accordance with this invention comprise front and back leg in pairs, the legs of each pair being rigidly interconnected with one another, and means for not only pivotally interconnecting the pairs of legs respectively to one another, but for also permitting the one pair of legs to cant or shift angularly in its own plane and angularly with respect to the plane of the other pair of legs whereby the floor engaging extremities of the pivot-able pair of legs'respectively are ited States Patent lowered and raised as required to provide engagement of the extremities of all four of the ladder legswith the door even though it i not truly fiat. Thus, in the preferred embodiment of the invention pivotal mounting and lateral shiftability of the ladder legs with respect to one another is provided by pin and slot interconnections through which one leg of each pair is associated either directly or indirectly with a corresponding leg of the other pair. The slots of these interconnections are angulated with respect to floor level when the ladder is open for use, the slots preferably being disposed upon corresponding angles and residing generally in alignment with one another widthwisely of the ladder, and the pins which engage the slots are slidable therein. By virtue of the angularity of the slots and slidability of the pins therein relative movement in opposite directions, both forward and rearward and upward and downward, is provided for the back legs with respect to the front legs or vice versa,and this movement of course is manifest as arelative raising of the bottom of one of the back legs and a relative lifting of the other of the back legs with respect to floor level.

Otherwise expressed the. angular disposition of the slots permits the back legs to move angularly in their own plane as an incident to the angular shifting of the plane of the back legs relative to the plane of the front legs. This movement is accomplished automatically either under the weight of the ladder alone, or whenrthe ladder is loaded, the legs thereby providing a true self-levelling function for which no manual manipulation i required. The extent of the movement depends upon the floor irregularity which is to be accommodated, the pins moving in the slots to that extent.

The self-levelling ladder constructed in accordance with this invention comprises a pair of front legs, the legs in said pair being rigidly interconnected with one another, a pair of back legs, the legs in said park being rigidly interconnected with one another, and means including pin and slot interconnection respectively pivotally associating each leg of one pair with the corresponding leg of the other pair, the slots of said pin and slot interconnections being relatively elongated, and being angulated with respect to the plane of a floor upon which said ladder is adapted to be rested when the legs are in open position, the pins of said pin and slot interconnections being slidable within said slots thereby permitting one of said pairs of legs to cant with respect to the other of said pairs of legs in accordance with irregularities in the surface of a floor upon which said ladder is rested with its legs in open position, and supplemental means for limiting the pivotal spreading apart of said pairs of leg with respect to one another.

' Other features and advantages of the present invention are set forth in the following description and the accompanying drawings in which:

Figure 1 is a side elevation of a stepladder employing the present invention.

Figure 2 is a cross sectional view on the line-22, Figure 1;

Figure 3 is a perspective view of the ladder shown in Figure 1.

Figure 4 is a rear fragmentary view of the top portion of the ladder shown in Figure 1.

Figure 5 is a fragmentary side elevation on an enlarged scale showing the top of a ladder on a larger scale than Figure 1.

Figure 6 is a cross section on the line 66,'Figure l, to show the spreader construction.

Figure 7 is a cross sectional view on the line 77, Figure 5. a

Figure 8 is a fragmentary perspective view of a stepladder showing an alternative of the construction of the spreader illustrated in Figure 6.

Figure 9 is a perspective view of the top end of a stepladder illustrating an alternative construction of the self-levelling feature.

Figure 10 is a sectional view on the line 10-10 of Figure 9.

Figure 11 is a modification of the construction shown in Figure 9.

Figure 12 is a perspective view of the top portion of the stepladder illustrating a further modification of the invention.

Figure 13 is a fragmentary vertical sectional view through the top portion of the ladder shown in Figure 12.

Referring first to the construction illustrated in Figures 1-8, the ladder includes a pair of parallel front uprights or legs 10, 10a which may be made of wood or metal, joined together by steps 25 in proper spaced apart relationship, brackets 11, 11a suitably mounted on and se cured to the upper end of the front legs 10, 1011 respectively, a top platform 12 which is secured to and supported by brackets 11, 11a. Secured to the underside of the platform and extending between the brackets is a reinforced member 31. The steps 25 are mortised into the legs 10, 10a and reinforced by metal tie rods 26 under each step. The front legs are thus formed into a rigid front leg structure. The brackets 11, 11a are constructed to project rearwardly from the legs 10, 10a respectively. The ladder is provided with spaced apart back legs 14, 15, which are formed into a rigid back leg structure by means of upper and lower horizontal cross members 16, 17 and diagonal cross members 18, 19.

One suitable type of slot and pin interconnection for connecting the front leg structure and the back leg structure to cant and pivot as hereinbefore mentioned consists of the following elements: The brackets 11, 11a are formed with slots 13, 1311 respectively, each slot being angularly disposed at approximately 25 from the horizontal. The term horizontal as used herein means a horizontal plane that is parallel to the floor or base upon which the ladder is standing or is to stand. In the construction illustrated the bottom edge of the brackets 11, 11a and the platform 12 are also disposed in a horizontal plane when the ladder is open and standing upon the floor. The angle of the slots 13, 13a may be varied within a range of between approximately 20 to 27. However the preferred angle is 25".

The upper ends of the legs 14, are provided with laterally projecting pins 20, 21 respectively, which fit into the slots 13, 13a respectively. The pins 20, 21 slide freely in the slots 13, 13a, allowing the back legs to be folded against the front legs and permitting one of said pairs of legs to cant with respect to the other of said pairs in accordance with irregularitie in the surface of the floor upon which said ladder is rested with its legs in open position. The angle is small enough so that the pin and slot interconnection automatically allows the rigid back leg structure to automatically adjust itself to the level of the floor upon which the ladder is standing and the pin and slot interconnection will be retained in the position which they assume relative to each other will support the load in the position assumed as soon as a person climbs up the ladder. In other words, the pin and slot interconnection are self-levelling under load.

' The back legs are maintained in a spread position at the correct angle relative to the front legs by a spreader A which will be more particularly described. The spread of the back legs may be varied within certain limits, depending on the wishes of the manufacturer, but it is generally more or less standard with all manufacturers to have the back legs with a pitch of about 15. The angle of the slot is approximately -27 as disclosed particularly in relation to this type of construction which has been found to be practical in the past. With the slots in the brackets, the spread of the ladder should be approximately three feet from the outside tips of the front legs at the floor level for a five foot ladder, which is about the standard distance. With the slot on the top of the back legs as hereinafter described, the distance between the front and back legs does not vary the angle of the slot in relation to the back legs as this angle is constant.

Another method of determining the angle of the slots 13, 13a is as follows: With the proper spread of the back legs, the slot can be at an angle of between and 102 relative to the back legs. The preferred angle is For a stcpladtler of generally conventional shape and size, the length of the slot can vary from 1" to 1% with a preferred length of 1 A" to 1%. The slot should be wide enough to accommodate a pin having a shank diameter of A" to with a preferred diameter of There should be sufficient clearance between the top ends of the back legs 14, 15 and the brackets 11, so that when the legs 14, 15 are at the upper and lower extremities respectively of the slots 13, 13a they will not bind in these positions. The clearance is to eliminate the friction between the back legs and the brackets so as not to restrict the free movement of the pins 20, 21, in the slots 13, 13a respectively.

Pivotally mounted between the legs 14, 15 in line with the top step 25 is a bucket rack 22. The bucket rack has parallel side members. Placed between the side members of the rack and the back legs 14, 15 are wedge shaped inserts 23, 24, which are fastened to the back of the legs 14, 15 respectively, with the narrow portion pointing upwardly. The bucket rack fits between these inserts. This permits the front end of the side members of the bucket rack, which are cut somewhat at an angle, to bear against the top step 25 when the pins 20, 21 are at opposite extremities of the slot 13, 13a respectively. it is suggested that a strip 54 (Fig. 9) be fastened to or between the top of the back of the legs to keep them suitably spaced. The spacing of the top of the legs should be such as to leave sufiicient clearance previously mentioned, between back legs and the brackets.

The member 16 is secured to the back legs at the point where the spreader A is to be fastened. This position will vary according to the size of the stepladder. The member 16, whether of metal or wood, should be stoutly fastened to the back legs. One end of the spreader is fastened to this member, and prevents the back legs from spreading more than their required amount. The diagonal members 18, 19 are suitably positioned to give lateral stability to the back legs 14, 15 and the steplaclder as a whole. The member 17 is positioned adjacent to the lower end of the legs and should be at a level, slightly below the level of one of the steps when the ladder is folded.

In detailing the construction of the stepladder it is understood that the back legs work as a rigid unit, the slots permitting movement of the legs back and forth. A backward movement raises the legs, a forward movement lowers them.

The spreader A is formed into two sections consisting of a front frame 27 and a rear frame 28 hingedly connected together at 29 to fold when the ladder is folded for storage. The front frame 27 is substantially U-shaped to form two arms which are pivotally connected to the front legs 10, 10a respectively just above the second step 25 by bolts 27a, 27b as shown. The rear frame 28 has its two sides converging towards the back legs to be pivotally connected to bracket 30 which is mounted on the member 16 centrally between the legs 14, 15. The hinge joint 29 between the front and rear frames 27, 28 should be loose enough to allow sufficient lateral play to the spreader to permit lateral movement of the back legs without strain. A tight joint will hinder the etficicnt operation of the ladder. The frames 27, 28 should be so shaped that when the ladder is folded the frames 27, 28 will nest together without binding, or interference.

For large ladders, the spreader must be considerably longer than illustrated as they are placed lower between the back and front legs. In such case the frame 28 can be considerably longer than the frame 27, but the cross member 16 between the back legs will have to be positioned somewhat below the point where the frame 27 is pivotally connected to the front legs, a suitable distance below being equal to the difference between the length of the frame 28 and the frame 27. In measuring the distance to place the cross member 16 below the pivotal point of the frame 27 on the front legs, the ladder should be folded.

In Figure 8, I have illustrated a modified form of spreader. In this connection I employ two arcuately curved members 32, 33 with the ends bent outwardly to fit in holes formed in the front and back legs respectively. A washer may be inserted over the portion of the rod protruding from the legs and the protruding end is burred to prevent washer from coming off, the arcuate members touching each other substantially centrally between the legs and are pivotally connected together by a coupling member 34 which is welded to one of the members. In addition to the primary function of keeping the legs from collapsing outwardly when the ladder is erected, the spreader has a guiding function. In order that the spreader will not prevent or interfere with the legs from adjusting themselves to an uneven floor, the spreader is constructed to allow the back legs to have the necessary lateral and up and down movement.

When a conventional ladder is placed on an uneven surface, one of the legs is out of contact with the surface and usually remains so. However, with stepladders employing the self-levelling feature herein described, the back leg which is over the low spot in the surface drops, sliding the pin on the upper end of the leg towards the low end of the slot which has the effect of dropping the leg. Simultaneously therewith, through the resulting pressure of the weight of the ladder, the pin in the upper end of the other back leg is pushed into the high end of the slot in which it rides which has the efiect of raising that leg. The design of the spreader cooperates with movement of the back legs so that when one side goes down the other goes up. When the surface is level the legs remain equally positioned somewhere along the slot.

Referring now to Figures 9, l and 11, I have therein illustrated an alternative construction of the automatic self-levelling stepladder employing a modified form of slot and pin interconnection. In that construction, there are mounted on the upper ends of the back legs 14a, 15a, leg brackets 35, 36 respectively. The brackets are made of channel iron and are secured in place by bolts 37, 38 respectively. The brackets 35, 36 extend above the top of their respective legs and each are formed with a slot 39, 39a respectively disposed at an angle which corresponds to the angle previously described in relationship to the slots 1313a. Mounted on the top ends of the front legs 100 are brackets '40, 41 respectively which are similar to the brackets 11, 11a except that the rear extensions are pierced to form a hole for receiving pivot pins 42, The legs 14a, a are connected to the brackets by means of pivot pins 42, 43 entered therethrough and through the slots 39, 39a respectively formed in the brackets 35, 36 respectively. The pivot pins are deformed so as to provide a head on each end so as to prevent the pins from leaving the slots.

The brackets 35, 3d are mounted on the ends of the legs so that the channels face outwardly with the brackets mounted on the outside of the brackets 40, 41 respectively.

The pins 42, 43 should each have a shoulder 44 to maintain proper clearance between brackets 35 and 40, and 36 and 41 respectively. Another means for ensuring this clearance may consist of a short sleeve which fits over the shank of the pins 42, 43 to lie between the brackets 35 and 40, and 36 and 41 and may be used to form the shoulder. The slots 39, 39a are disposed at an angle of leg structure.

6 92 to 105 as previously described, with a preferred angle of Figure 11 illustrates still another modification of the slot and pin interconnection between the front and back The construction shown in Figure 11 is suitable for heavy duty ladders. This figure illustrates in a fragmentary manner the modified construction but only shows the upper ends of the front and rear legs 10c and 15a and the platform 12. Since the other pair of legs are similarly constructed they are not shown. The upper end of the front leg 100 has mounted thereon a pair of brackets 50, 51 which project rearwardly from the front leg to form a channel there'between for receiving the bracket 36 mounted on the top of the back leg 15a. The back leg 15a is pivotally mounted between the brackets 50, 51 by means of the pivot pin 53 which is carried by the brackets 50, 51 and is entered through the slot 39a. A similar bracket construction is provided for connecting the leg 15a to the platform 12. This construction gives a support on both ends of the pin 53. Further rigidity may be added to the connection between the rear leg and the brackets 50, 51 by placing a sleeve around the pin 53, so that when the pin or rivet or bolt, as the case may be, is drawn up tight the sleeve keeps the side brackets in fixed spaced relationship.

Figures 12 and 13 illustrate a further modification. As both front legs and both rear legs are similar in con-. struction, the modification will be described relative to one pair of front and rear legs. In this construction the numeral 10b indicates a front leg and the numeral 14d identities the rear leg associated therewith. Mounted on the top end of the leg ltlb is a pair of spaced apart brackets 55, 56 each of which are similar to the brackets 50, 51, (Figure 11). The angularly disposed slot, for the pin 54 to ride in, is formed by two metal bands 57, 58 which are Secured to the top portion of the rear leg 14d, the bands running over the ends in the direction of the long edge. These two bands are eubstantially U-shaped and applied to the top end of the leg 14d in a superposed relationship with the uppermost end of the upper band 58 spaced above the uppermost end of band 57, both bands being parallel to each other and disposed at the same angle as the slot 13, to provide an angle slot 59 in which the pin 54 will ride. The slot 59 is disposed at the same angle as the slot 13.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. A self-levelling ladder comprising a pair of front legs rigidly interconnected to form a front leg unit, a pair of spaced apart brackets, said brackets being fixed relative to the top ends of the front legs, a pair of rear legs formed into a rigid rear leg structure, and means for piv-otally connecting the top end of the back leg structure to said brackets with a horizontal clearance between the top ends of the legs and the said brackets to permit the leg structure to can-t relative to the front leg structure in accordance with irregularities in the surface of the. floor upon which the ladder is rested with its legs in open position in addition to the movement of the back leg structure towards and away from the front legs, said means consisting of connecting members connecting each leg of one pair with the corresponding leg of the other pair, each connecting member comprising complemental parts, one part being a guideway and the other part being a bar slidably mounted in said guideway, one of said complemental parts lying in a substantially horizontal plane and the other part being disposed at a relatively small angle to the horizontal the bar of one connecting member having a movement relative to its guideway in a direction opposite to the relative movement of the other bar so that the complemental parts are self positioning and support the load in the position assumed when the four legs have adjusted their position in a vertical plane in accordance with said irregularities of the surface of the floor, and a loosely jointed spreader connecting the front and back legs to limit the spread of the legs.

2. A self-levelling ladder according to claim 1 in which the angle of the angularly disposed part is between 20-27 to the horizontal.

3. A self-levelling ladder according to claim 1 in which the guideway consists of an elongated slot formed in the bracket and disposed at a relatively small angle to the horizontal and the bar consists of a pin connected to the top end of each leg of the rear leg structure.

4. A self-levelling ladder according to claim 1 in which the guideway consists of an elongated slot formed in the bracket and disposed at an angle of approximately 20-27 to the horizontal and the 'bar consists of a pin connected to the top end of each leg of the rear leg structure.

5. A self-levelling step ladder comprising a pair of front legs, the legs in said pair being rigidly interconnected with one another, a pair of back legs, the legs in said pair being rigidly interconnected with one another, and means including pin and slot interconnections respectively pivotally connecting each leg of one pair with the corresponding leg of the other pair, said pin and slot interconnections having a horizontal clearance to permit horizontal movement of the upper ends of one pair of legs relative to the upper end of the other pair of legs, the slots of said pin and slot interconnections being relatively elongated and being disposed at a small angle with respect to the plane of a floor upon which said ladder is adapted to be rested when the legs are in open position and rising upward in a straight line from the front legs towards the back legs of the ladder the pins of said pin and slot interconnections being slidable in opposite directions relative to each other within said slots thereby permitting one of said pairs of legs to cant relative to the other of said pairs of legs in accordance with irregularities in the surface of a floor upon which said ladder is rested with its legs in open position, and spreader members for limiting the pivotal spreading apart of said pairs of legs with respect to one another, said spreader members being loosely jointed to allow sufficient play to the spreader to permit the canting movement of the back legs without strain. 6

6. A self-levelling stepladder according to claim in which the slots are at an angle of approximately from 20 to 27.

7. A self-levelling ladder comprising a pair of front legs formed into a rigid front leg structure, a pair of legs formed into a rigid back leg structure, a bracket connected to the top end of each leg of the front leg structure, means pivotally connecting each leg of the back leg structure with the bracket of the corresponding leg of the front leg structure to cause the back leg structure as a unit to cant relative to the front leg structure in accordance with the irregularities of the surface of the floor upon which the ladder stands with the legs spread apart in addition to the movement towards and away from the front leg structure, said means comprising a guide way mounted on the top end of each back leg, a bar connected to the bracket associated with the corresponding front leg and entered through and slidable in said guideway, said guideway being disposed at an angle of approximately between 95 and 102 relative to the back leg structure and having a horizontal clearance relative to the said bracket, one bar having relative movement in its guideway in a direction opposite to the movement of the other bar relative to its guideway. and spreader members for limiting the pivotal spreading apart of the said pair of legs with respect to each other, said spreader members being loosely jointed to allow sufficient play to the spreader to permit the canting movement of the back legs without strain.

8. A self-levelling stepladder comprising a pair of front legs, the legs in said pair being rigidly interconnected with one another, a pair of back legs, the legs in said pair being rigidly interconnected with one another, and means including pin and slot interconnections respectively pivotally connecting each leg of one pair with the corresponding leg of the other pair, said pin and slot interconnections having a clearance to permit movement of the upper ends of one pair of legs relative to the upper end of the other pair of legs, the slot of said pin and slot interconnections being relatively elongated, and being disposed at a small angle with respect to the plane of a floor upon which said ladder is adapted to be rested when the legs are in open position and rising upward from the front legs towards the back legs of the ladder, the pins of said pin and slot interconnection being slidcable in opposite directions relative to each other within said slots thereby permitting one of said pairs of legs to cant relative to the other of said pairs of legs in accordance with irregularities in the surface of a floor upon which said ladder is rested with its legs in open position, and spreader members for limiting the pivotal spreading apart of said pairs of legs with respect to one another, said spreader members being loosely jointed to allow sufficient play to the spreader to permit the canting movement of the back legs without strain.

9. A self-levelling ladder comprising a pair of front legs rigidly interconnected to form a front leg unit, a pair of spaced apart brackets, said brackets being fixed relative to the top ends of the front legs, a pair of rear legs formed into a rigid rear leg structure, and means for pivotally connecting the top end of the back leg structure to said brackets with a clearance between the top ends of the legs and the said brackets to permit the leg structure to cant relative to the front leg structure in accordance with irregularities in the surface of the floor upon which the ladder is rested with its legs in open position in addition to the movement of the back leg structure towards and away from the front legs, said means consisting of connecting members, each connecting member comprising complemental parts, one part being a guideway and the other part being a bar slideably mounted in said guideway, one of said complemental parts lying in a substantially horizontal plane and the other being disposed at a relatively small angle to the horizontal, the bar of one connecting member being moveable relative to its guideway in a direction opposite to the relative movement of the other bar so that the complemental parts are self-positioning and support the load in the position assumed when the four legs have adjusted their position in a vertical plane in accordance with said irregularities of the surface of the floor, and a loosely jointed spreader connecting the front and back legs to limit the spread of the legs.

10. A self-levelling ladder comprising a pair of front legs formed into a rigid front leg structure, a pair of legs formed into a rigid back leg structure, means pivotally connecting each leg of the back leg structure with the corresponding leg of the front leg structure to cause the back leg structure as a unit to cant relative to the front leg structure in accordance with the irregularities of the surface of the floor upon which the ladder stands with the legs spread apart in addition to the movement towards and away from the front leg structure, said means comprising a guideway mounted on the top end of each back leg, a bar carried by the corresponding front leg of the front leg structure and entered through and slideable in said guideway, said guideway being disposed at an angle of approximately and 102 relative to the back leg structure and having a clearance relative to the front leg structure, the bars being moveable in opposite directions in their respective guideways permitting one of said pairs of legs to cant relative to the other pair of legs, and spreader members for limiting the pivotal spreading apart of the said pair of legs with respect to each other, said spreader members being loosely jointed to allow sufficient play to the spreader to permit the canting movement of the back legs without strain.

(References on following page) 1 1 9 References Cited in the file of this patent UNITED STATES PATENTS Neill May 21, 1889 Nowick Nov. 12, 1940 5 Myers June 16, 1942 10 FOREIGN PATENTS Great Britain Oct. 31, 1951

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