US2921645A

US2921645A - Extensible ladder

Info

Publication number: US2921645A
Application number: US617846A
Authority: US
Inventors: Morrow David; Gregory Shelton Rolfe
Original assignee: Fairchild Engine and Airplane Corp
Current assignee: Fairchild Engine and Airplane Corp
Priority date: 1956-10-23
Filing date: 1956-10-23
Publication date: 1960-01-19
Anticipated expiration: 1977-01-19

Description

Jan l9, 1960 D. MORROW ET AL 2,921,645

EXTENSIBLE LADDER 2 Sheets-Sheet 1 Filed Oct. 23, 1956 INVENTORS DAVID MORROW 8| SHELTON ROLFE GREGORY ATTORNEYS Jan. 19, 1960 D. MORROW ETAL 2,921,645

EXTENSIBLE LADDER 2 Sheets-Sheet 2 Filed Oct. 23, 1956 INVENTORS DAVID MORROW 8| SHELTON ROLFE GREGORY BY M Z fhelr ATTORNEYS EXTENSIBLE LADDER David Morrow, Silver Spring, and Shelton Rolfe Gregory, Washington County, Md., assignors to Fairchild'Engine and Airplane Corporation, Hagerstown, Md., a corporation of Maryland Application October 23, 1956, Serial No. 617,846

11 Claims. (Cl. 182157) This invention relates to extensible ladders, and has particular reference to ladders of lazy tongs construction which may be folded into a compact unit for easy stowage when not in use. The application is a continuation-in-part of the copending application of Serial No. 252,688, filed October 23, 1951, now Patent No. 2,798,653, granted July 9, 1957.

The ladder of the present invention was devised to facilitate entry and exit of personnel from an elevated aircraft cabin and has proved to be admirably adapted for that purpose, although its utility is not so limited. The ladder is extended from collapsed or contracted condition in which it is stowed in the cabin or fuselage, and lowered to the ground when exit from the cabin is desired and is extended and elevated to the cabin when entry thereto is desired, thus solving a problem not otherwise susceptible of solution nith non-stowable fixed ladders or unstable rope ladders which are not attachable or detachable from the remote end thereof.

The extensible ladder of this invention comprises side members, each of which consists essentially of a primary lazy tong structure and secondary lazy tong structure superimposed thereon to brace and strengthen the former, these side members being spaced in parallel relation by rungs which lie in close proximity when the ladder is collapsed and are spaced at regular intervals vertically when the ladder is extended. Secured to the upper end of the ladder are one or more hooks for attaching the ladder to the point which is to be reached thereby. The ladder is provided with means, in the form of rigid links, which in one operative position lock the lazy tong side members in extended position to prevent them from collapsing and in another operative position permit the side members to be compactly collapsed or locked in collapsed condition for storage.

It will be seen that the collapsible ladder of this invention forms a strong and rigid structure when extended and may be handled from either end and secured safely the object to be scaled, while being capable of being retracted or collapsed from either end for compact stowage.

For a more complete understanding of the invention, reference may be had to the accompanying drawings, in which:

Figure 1 is a side view of the ladder of this invention showing the ladder in collapsed position;

Figure 2 is a front cross-section view thereof taken along the line 22 of Fig. 1 looking in the direction of the drawings;

Figure 3 is a schematic side view of the ladder locked in extended position; and

Figure 4 is a perspective view of the rigid link which locks the ladder in extended or collapsed positions.

Referring to Figure 3 of the drawings, each of the side members of the ladder comprises a primary lazy tong 11, shown in heavy lines and a secondary lazy tong 12, shown in dotted lines.

atent Patented Jan. 1 1.960.

The primary lazy tong 11 comprises a plurality of crossed bars 13 of light-weight metal, such as alloy steel, preferably channel or box-shaped in cross-section and pivoted at their center points on the reduced ends 14 of the corresponding rung 15, which preferably is tubular, although it may be a flat step extending in the common plane of corresponding opposite crossed bars 13, so as to lie horizontally when the ladder is inclined like a staircase. The rung extensions 14 may be connected by pins 14a to the inner crossed bar 13 and the outer crossed bar 13 is secured thereto by a nut 16 recessed within the channel or box-section of that crossed bar, as shown in Figure 2. The free ends of the adjacent crossed bars 13 are pivoted together by bolts 17, as shown in Figures 1 and 3.

As many such sets of crossed bars are secured together in that way as the extended length of the ladder may require, and the upper and lower free ends of the crossed bars 13 are connected by half length bars 13' and 13", respectively, the free ends of which are pivoted together on the respective upper and lower rungs 15' and 15".

Superimposed on the primary lazy tong structure 11 just described, is the secondary lazy tong structure 12, shown in dotted lines in Figure 3, and constructed essentially the same way except that it is not fitted with rungs or upper and lower half crossed bars like 13 and 13". Thus, secondary crossed bars 19 are pivoted together at their center points on bolts 20 and at their free ends to the free ends of the adjacent set, about bolts 21, with the free ends of the uppermost and lowermost secondary crossed bars 19 being pivoted at the mid-points 21' of upper and lower primary crossed bars 13. If desired, or

the rung spacing requires it, rungs like 15 may also extend between pivot points 20' on secondary structure 12, or between corresponding opposite points on either or both the primary and secondary structures 11, 12.

In addition to being pivoted at its extreme ends 21' to the primary lazy tong structure 11, the secondary lazy tong structure 12 is pivoted thereto by pivot bolts 22 at the points where the primary bars 13 cross the secondary bars 19, which is the first and third quarter points of each, as is shown particularly in Figures 1 and 3. Thus, the primary and secondary lazy tong structures 11 and 12 are pivoted together and jointly constitute the side member at each side of the ladder thus formed, whereby they supplement the strength and brace each other. Notwithstanding this double structure, the ladder may be collapsed into'the compact package shown in Figures 1 and 2, which is readily stowable in a small space within aircraft or elsewhere.

Mounting means for the ladder preferably take the form of one or more knob-like hooks such as that designated 23 and comprising a spherical enlargement on an extension 24 of the outer end of one of the upper primary cross bars 13'. The extension 24 preferably is of reduced diameter and circular in cross-section, and is curved upwardly so as to extend substantially horizontally when the ladder is fully extended. Similarly, the free end of the corresponding primary crossed bar 13 which lies parallel to the hooked upper crossed bar 13, is provided with an integral knobbed hook 25 whose reduced shank 26 also is so curved as to extend substantially horizontally when the ladder is fully extended.

The structure to be scaled with the collapsible ladde of this invention is provided with keyhole-shaped slots (not shown) into which the knobs 23 are inserted.

Where the lower end of the ladder may not rest on the reception of the lower knobs 25. It will be seen that 3 the knobs 25 lock the ladder at its lower end, thereby determining the extended length of the ladder.

In cases where the entry or hatch is on an elevated platform or floor, such as the under surface of a cabin, crew compartment orfuselage ofan aircraft, for example, the securing hooks 32 having knob-like formations 31 at the extreme ends thereof are provided for insertion into companion keyhole slots.

Where the lower end of the ladder is to rest on the ground or a suitable supporting platform, the ladder may be locked in extended position by rigid links or bars 34. A bar 34 is loosely pivoted on the outward extensions 33 (see Figure 2) of one of the lower rungs 15, in this instance the extreme lowermost rung 15". More specifically, the extensions 33 extend outwardly of the extensions 14 of the lowermost rung, and oversize holes 34a through which the extensions 33 pass afford some freedom of movement of the bar 34 relative to the extensions 33. The bar 34 may be held on the extension 33 by a cotter pin 35, as shown. Projecting outwardly from each end of the second rung from the bottom is a headed pin 36, whose head 36a is adapted to fit through the circular portion 37a of one of a plurality of keyhole slots 37 spaced along bar 34. When the ladder is extended, it is locked in extended position and held at the proper length by the slipping of the nearest keyhole slot 37 over thehead of the pin 36 and permitting the shank of the pin-to enter the narrow extended portion 37a of the slot. The security of this lock is sufficient to sustain a considerable weight on the ladder without collapse of the same, and even without requiring the upper support of the

knob formations

23 or 31 in corresponding keyhole slots. To afford a secure grip on the supporting surface, the lower ends of the locking bars 34 may be serrated, as represented by the reference numeral 39.

To extend the ladder to a desired length, the pins 36 are inserted in the appropriate keyhole slots 37, and the engagement of the lower serrated edges 39 of the extended portions 37b thereof, thereby locking the ladder in the extended position represented in Figure 3 of the drawings. When the ladder is to be collapsed for storage, the head 36:: of the pin is aligned with the wide portion 37a of the keyhole slot 37, and the bar pivoted away from the pin 36 so as to remove it from the keyhole slot. The loose fit between the hole 34a and the extension 33 makes this possible.

In order to facilitate locking the ladder in collapsed position a keyhole slot 45) may be formed in each of the links or bars 34. The keyhole slot is inverted in relation to the keyhole slots 37, and it is located in proximity to the pivot hole 34a. It is understood that, even though the ladder is collapsed, there will be some resiliency in the lazy tong linkages which will permit the ladder to be compressed somewhat more. The location of the keyhole slot 40 should be such that when the ladder is so compressed, the bar 34 will be capable of manipulation to cause the pin 36 to be engaged with the under portion 40a of the keyhole slot 40, as shown in Figures 1 and 2. Therefore, when the compressive force is removed, the resiliency of the linkages will tend to expand the ladder sufiiciently to cause the pins 36 to be received in the narrow upper ends 401) of the slots 40, thereby locking the ladder in collapsed position.

We claim: k

1. In a collapsible ladder, a pair of oppositely spaced side members each comprising a lazy tong structure of a pair of crossed bars pivoted together at their center points links or bars will cause the pins to settle into the narrow extending from said structure at a point spaced from the connecting point of said link for insertion in the said hole when the ladder is extended, the engagement of the pin with said nearest edge of the hole locking the ladder against collapse, and the removal of the pin from the hole permitting the ladder to be collapsed for storage.

2. A collapsible ladder as set forth in claim 1 includ ing a plurality of holes formed in said rigid link to permit the pin to be inserted in a selected one of said holes, the selected hole determining the extended length of the ladder. Y

3. A collapsible ladder as set forth in claim 1 wherein the rigid link is pivotally connected to said lazy tong structure and including a second hole formed in said rigid link in proximity to the pivotal connection for receiving the pin to thereby permit the ladder to be locked in collapsed position.

4. In a collapsible ladder, the combination of a pair of oppositely spaced side members each comprising a lazy tong structure of a pair of crossed bars pivoted together at their center points and pivoted at their ends to adjacent pairs of crossed bars at the ends thereof, rungs extending between corresponding points on the opposite side members, a rigid link loosely mounted at one end on a rung of said ladder and having a hole near its other end, the spacing between the mounting for the rigid link and the nearest edge of the hole determining the spacing between adjacent rungs of the ladder when the ladder is extended for use, and an extension on another rung of said ladder for insertion in said hole when the ladder is extended, the engagement of the extension with said nearest edge of the hole locking the ladder against collapse, and the removal of the extension from the hole permitting the ladder to be collapsed for storage.

5. A collapsible ladder as set forth in claim 4 wherein the pin is formed with a head and wherein the hole is wider at its upper end for receiving the head of the pin and narrower at its lower end to prevent the pin from being disengaged from the hole when the ladder is in use.

6. A collapsible ladder as set forth in claim 5 including a hole for receiving the pin when the ladder is in collapsed position to maintain the ladder locked in collapsed position.

7. A collapsible ladder as set forth in claim 6 wherein the last mentioned hole is wider at its lower end to receive the head of the pin and narrower at its upper end to permit the ladder to be locked in collapsed position.

8. In a collapsible ladder, the combination of a pair of oppositely spaced side members each comprisinga lazy tong structure of a pair of crossed bars pivoted together at their center points and pivoted at their ends to adjacent pairs of crossed bars, rungs extending between corresponding points on the opposite side members, an extension terminating in a knob serving as a mounting means for the upper end of the ladder, a rigid link loosely mounted atone end on one of the lower rungs of said ladder and having a hole spaced from said end, and a pin extending from said structure at a point spaced from the connecting point of said link for insertion in the said hole when the ladder is extended for locking the ladder against collapse.

9. A collapsible ladder comprising a pair of spaced apart, lazy tong side structures, each being extensible from a collapsed condition, rungs extending between corresponding points on the lazy tong structures, a rigid leg connected to the lowermost end of each of the lazy tong structures, whereby the distance between the ground-.

10. A collapsible ladder comprising a pair of spaced apart, lazy tong structures, each being extensible from a collapsed condition, rungs extending between corresponding parts of the lazy tong structures, a rigid bar connected to one of the lazy tong structures, a hole formed in said rigid bar and spaced apart from the connection of the rigid bar to the lazy tong structure by a distance which determines the spacing between consecutive rungs of the ladder, means carried by the lazy tong structure and engageable with said hole to lock the lazy tong structure in extended position against collapse, and a hole intermediate the connection of the rigid bar to the lazy tong structure and the above-mentioned hole, the spacing between said connection and the intermediate hole determining the spacing between consecutive rungs of the ladder in the collapsed condition.

11. A collapsible ladder comprising a pair of spaced apart, lazy tong structures, each being extensible from a collapsed condition, rungs extending between corresponding points on the lazy tong structures, a pair of rigid legs, each connected at the lower end of one of the lazy tong structures, the ground-engaging ends of the 20 legs extending beyond the lowermost rung by a fixed distance in both the extended and collapsed conditions, means defining an opening in at least one of said legs above the connection of the leg to the respective lazy tong structure, said opening being spaced from the connection by the desired spacing between consecutive rungs Of the ladder, and a detachable coupling means carried by the lazy tong structure which is insertable within said opening when the ladder is extended to lock the ladder against colapse, and removable from said hole when the ladder is to be collapsed for storage.

References Cited in the file of this patent UNITED STATES PATENTS 297,088 Root Apr. 15, 1884 772,379 Sarvela Oct. 18, 1904 874,801 Dewitz Dec. 24, 1907 1,736,878 Duvall Nov. 26, 1929 FOREIGN PATENTS 912,783 Germany June 3, 1954