US3565211A

US3565211A - Extension ladder rung lock

Info

Publication number: US3565211A
Application number: US879035A
Authority: US
Inventors: Edward H Le Blanc
Original assignee: Larson Manufacturing Co
Current assignee: AMERICAN FOREST PRODUCTS COMPANY A CALIF LP; Larson Manufacturing Co
Priority date: 1969-11-24
Filing date: 1969-11-24
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A retractable rung lock for an extension ladder in which a pivotal lock body is normally positioned to engage simultaneously adjacent rungs on relatively movable ladder sections. To permit selective extension and retraction of the ladder sections a camming latch is operatively engaged with the lock body. The latch is longitudinally and pivotally movable on a mounting bracket to effect retraction of the lock body during extension or retraction of the ladder sections. The latch member and lock body are normally spring urged to their respective extended positions.

Description

United States Patent [72] Inventor [2]] Appl. No.

[22] Filed [45] Patented [73] Assignee Edward H. Le Blauc Redwood City, Calif. 879,035

Nov. 24, 1969 Feb. 23,1971

Larson Manufacturing, Inc. Santa Clara, Calif.

[54] EXTENSION LADDER RUNG LOCK 15 Claims, 9 Drawing Figs.

[52] U.S. Cl...

501 FieldofSearch.....................................:::::::

References Cited UNITED STATES PATENTS 1,045,165. 11/1912 Moulton 3,502,l73 3/1970 Arnold 3,502,175 3/1970 Bullock Primary Examiner-Reinaldo P. Machado Attorney-Flehr, Hohbach, Test, Albritton & Herbert EXTENSION LADDER RUNG LOCK BACKGROUND OF THE INVENTION tion to a retracted position to permit selective extension or retraction of the ladder sections relative to each other.

2. Description of the Prior Art Wooden and metal extension ladders have been used for many years and various lock mechanisms have been devised for retaining movable ladder sections in predetermined extended positions relative to each other. The lock mechanism of the present invention possesses the important safety feature of engaging aligned rungs of two ladder sections simultaneously to insure safe utilization thereof and to preclude accidental release of the lock mechanism. Additionally, the lock mechanism of this invention operates positively and automatically in response to movement of the ladder sections relative to each other to permit selective adjustment of the ladder sections to predetermined extended positions without requiring manual manipulation of any of the components of the lock SUMMARY OF THE INVENTION This invention relates generally to an improved extension ladder rung lock. More particularly this invention relates to an automatically operable rung lock mechanism in which secure engagement of aligned side-by-side rungs of movable ladder sections is insured. Still more particularly, this invention relates to a lock mechanism comprising a minimum number of components including a pivotally retractable lock body and longitudinally slidable and pivotal camming latch member for actuating the lock body during retraction or extension of two ladder sections relative to each other.

This invention solves problems encountered with rung locks heretofore in that it insures secure locking engagement of the lock mechanism with aligned side-by-side rungs of two ladder sections yet it permits easy ready disengagement of the lock mechanism from one of such aligned rungs so that the ladder may be selectively and easily extended or retracted relative to a given position automatically and without requiring any manual manipulation of the components of the lock mechanism. The improved features of this invention are embodied in a mechanism having a minimum number of operative parts which are normally urged to their operative position by spring means effectively positioned in conjunction therewith.

From the foregoing it should be understood that objects of this invention include the provision of an improved extension ladder rung lock mechanism requiring few operative components; the provision of such a lock mechanism which is safe, efficient and automatically operable in response to extension or retraction of ladder sections relative to each other; the provision of a rung lock mechanism incorporating therein a pivotal lock body. and a longitudinally slidable and pivotal latch member which operates the lock body automatically during extension or retraction of two ladder sections relative to each other; and the provision of a rung lock mechanism which requires minimum maintenance and which is easy to install upon conventional ladder sections.

These and other objects of this inventionwill become apparent from a study of the following disclosure in which reference is directed to the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of a ladder showing the subject rung lock mechanism, in duplicate, in conjunction with two relatively movable ladder sections.

FIG. 2 is a side elevational view, Partly in section, taken in the plane of line 2-2 of FIG. 1 showing details of the lock mechanism.

FIG. 3 is a vertical sectional .view through the lock mechanism taken in the plane of line 3-3 of FIG. 2.

FIGS. 4 through 6 are sequential side elevational views showing the sequence of operation of the lock mechanism when the ladder sections are being extended.

FIGS. 7 through 9 aresequentia1- side elevational views showing the sequence of operation of the lock mechanism when the ladder sections are being retracted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS and 2, the lock mechanism of this invention is shown employed in conjunction with a'conventional extension ladder, of wood or metal, with light weight aluminum, magnesium, or like metal being preferred for the structural components of the ladder. In that regard, the ladder comprises two slidably interconnected sections 1 and 2, each of which comprises a pair of spaced

parallel side rails

3 and 4,

and 5 and 6, respectively, between which extend and are secured a series of vertically spaced rungs. The rungs of ladder section 1 are designated 7 and the rungs of ladder section 2 are designated 8.

It will be understood that ladder section 1 in the embodiment illustrated is intended to rest upon the ground or other supporting surface with section 2 being supported by section 1 and being longitudinally slidable relative thereto during extension or retraction of the ladder in the manner to be described. In that regard, means for operatively interconnecting the ladder sections, such as a series of spaced guide brackets 9, are secured to the side rails of ladder section I and engage the side rails of section 2 to maintain the ladder sections together during extension or retraction thereof. Other equivalent means may be substituted for the guide brackets 9 if preferred, in accord with procedures well known in the ladder art.

The rung lock mechanism of this invention, generally designated 11 in FIG. 1, preferably is secured to the

opposite side rails

5 and 6 of the movable ladder sections 2 for maintaining the ladder sections in any preselected position of extension or retraction chosen in accordance with the use to which the ladder is to be put. While a lock mechanism of this invention could be utilized along only one side rail of ladder section 2, duplicate lock mechanisms are preferred to provide maximum safety. Such lock mechanisms thus act in concert with each other to perform the intended locking function.

Hereinafter reference is directed to that lock mechanism 11 which is secured to side rail 5 of ladder section 1 but it will be understood that the lock mechanism secured to the other side rail 6 corresponds in construction to the mechanism to be described.

Referring to FIGS. 2 and 3, it will be noted that the respective side rails of the ladder sections preferable are shallow channel shaped in cross section in accordance with accepted ladder construction techniques. Desirably the

rungs

7 and 8 of the ladder sections are generally triangular in cross-sectional configuration and include flat

upper surfaces

12 and 13 on the

respective rungs

7 and 8 which are generally coplanar to provide maximum comfort for a person standing on the ladder when the ladder sections are oriented in a predetermined extended position.

Secured to the base 15 of channel-shaped side rail of the movable ladder section 2 is an inverted hook-shaped mounting bracket 16. The bracket is secured in place in any suitable fashion such as by bolting, riveting or welding. In the embodiment illustrated two or more spaced rivets 17 extend through holes provided in the side rail 5 and in a flat base portion 18 of the bracket secured in face-to-face relationship with the base ofthe side rail 5 as best seen in FIG. 3.

Bracket 16 includes an offset shoulder portion 19 which extends generally normal to the surface of the base 15 of side rail 5 and the bracket terminates in a generally vertically extending hook-shaped mounting portion 21 which extends generally parallel to the base of the side rail. Mounting portion 21 is provided with a cutout section as best seen in H0. 2 which is contoured to conform closely with a portion of the periphery of a triangular rung 8 of the movable ladder section 2. The mounting bracket is secured to the movable ladder section so that the mounting portion of the bracket is in close contacting relationship with rung 8.

The mounting bracket 16 defines means for supporting the remaining components of the lock mechanism in operative engagement on the movable ladder section 2. Such other components include means normally extending transversely of the ladder side rails for simultaneously engaging

aligned rungs

7 and 8 of the respective ladder sections in the form of an elongated pivotal lock body 22, and also means for effecting selective retraction of the pivotal lock body 22 relative to such aligned rungs so that the ladder sections may be extended or retracted selectively as will be described. This latter mentioned means comprises an elongated movable camming latch member generally designated 23 which is normally positioned to extend longitudinally of the ladder side rails between aligned

rungs

7 and 8 of the ladder sections when the ladder sections are positioned in a predetermined orientation.

Means for mounting the pivotal lock body and the movable camming latch on the bracket 16 comprises a headed pin 26 which extends through mounting portion 21 of the bracket and through the lock body 22 and camming latch 23, as best seen in FIG. 3. Opposite ends of the pin are provided with enlarged heads 27 which prevent separation of the components of the lock mechanism assembly.

Latch member 23 is generally U-shaped in cross section and is defined by a pair of generally

parallel legs

28 and 29 connected by a central bight portion 31. At one end thereof, the latch is defined by a generally hook-shaped nose portion 32 having a recess 33 thereat for the purpose to be described. At its other end the latch member is defined by a rounded camming surface 33. The parallel legs of the latch member are formed with aligned elongated slots 34 therein through which pivot pin 26 extends.

As best seen in FIG. 3, the latch member straddles mounting portion 21 of bracket 16 and is generally longitudinally slidable relative thereto due to the pin and slot interengagement noted. The latch is also pivotal within limits on pin 26. intermediate its ends the latch is provided with an exterior rounded camming surface 36 which is selectively engageable during operation of the lock mechanism with the respective rungs 7 of ladder section 1.

The pivotal lock body also is generally U-shaped in cross section and is defined by a pair of spaced legs 37 and 38 interconnected by a central bight portion 39.

Opposite ends

41 and 42 of the lock body are rounded and an opening 43 is provided through each of the legs of the lock body centrally of its ends to accommodate the pivot pin 26 therethrough. Between the pivot pin and the

respective ends

41 and 42, the legs of the lock body are formed with generally planar aligned

edges

44 and 46 respectively. Such edges are adapted to engage in surface to surface contact with the upper

flat surfaces

12 and 13 of the

rungs

7 and 8 of the ladder section when such rungs are aligned with each other in the manner seen in FIG. 2.

As will be described hereinafter, the rounded end 41 of the lock body is adapted to be received within the recess 33 of the latch member under certain conditions during operation of the lock mechanism as the ladder sections are being extended and retracted.

Means preferably are provided for urging the lock body and the latch to their extended positions from which positions the lock body and latch may be selectively retracted during operation of the latch upon retraction or extension of the ladder sections relative to each other.

The means for urging the latch to its extended position comprises a torsion spring 51 coiled about a mounting pin 52 secured to the upright mounting portion 21 of bracket 16. One end 53 of the torsion spring 5] is engaged with the shoulder portion 19 of the bracket. The other end of the spring is bent to extend laterally of the mounting portion 21 of the bracket and includes an end portion 54 which projects through the bracket mounting portion so as to be operatively engageable with a portion of the camming latch 23. In that regard, spring end 54 engages an edge portion 55 of leg 28 of the latch and normally urges the latch in a clockwise direction as viewed in FIG. 2 toward its extended position in which it contacts rungs 7 of ladder section 1. Retraction of the latch relative to the mounting bracket is permitted by depressing end 54 of spring 51. Such spring end'is movable within a generally arcuate slot 56 formed in the mounting portion 21 of the bracket as seen in FIG. 2 so that such depression may be effected.

It should be understood that when the lock mechanism is in the position shown in FIG. 2 with the lock body 22 engaged with aligned

rungs

7 and 8 of the adjacent ladder sections, retraction of the ladder sections relative to each other is positively precluded. However, upon upward movement of the movable ladder section 2 relative to the ground engaging ladder section 1, retraction of the lock body and the latch may be effected to permit further extension of the ladder or selective retraction thereofin the manner to be described.

in the embodiment shown, guide means preferably is provided between the mounting bracket 16 and latch 23 to facilitate longitudinal sliding movement of the latch relative to the bracket during operation of the lock mechanism. Such guide means includes a flange section 61 bent to extend generally normally relative to the plane of the mounting portion 21 of the bracket as seen in FIGS. 2 and 3. Such guide flange engages the edge portion 55 of leg 28 of the latch along its upper extent and cooperates with the projecting end 54 of spring 51 engaged with such edge portion of leg 28 intermediate the opposite ends of the latch to facilitate movement of the latch.

The aforementioned means for normally urging the lock body and latch toward their respective extended positions further includes a spring member operatively connected between the mounting bracket and the lock body. This spring member comprises a coil spring 62 secured at one of its ends by a mounting pin 64 to the upper end ofthe mounting portion 21 of the bracket and its other end by a mounting pin 63 to the lock body adjacent its curved end 41. Upon counterclockwise pivotal movement, when permitted, of the lock body from the position shown in FIG. 2, spring 62 is extended so that when pivotal forces exerted on the lock body are released, such spring returns the lock body to the extended position shown in FIG. 2.

As noted previously, latch 23 straddles the mounting portion 21 of bracket 16 and such mounting portion, as seen in FIG. 2, is provided with a cutout section 66 adjacent its point of juncture with shoulder portion 19 of the bracket. Such cutout portion is provided to accommodate leg 29 of the latch when the latch is pivoted in a counterclockwise direction upon engagement thereof with a rung 7 of ladder section 1 during extension or retraction of the ladder as will be described.

Operation of the lock mechanism during extension of the ladder will first be described with respect to H65. 4 through 6, taken in conjunction with FlG. 2. When it is desired to extend the ladder sections from the position shown in FIG. 2, the movable ladder section 2 is drawn upwardly in any known fashion, such as by a rope and pulley mechanism (not shown) of the type commonly employed in extension ladders.

Such upward movement of ladder section 2 will draw latch 23 upwardly therewith so that the camming surface 36 thereof is urged inwardly by rung 7 against the urging of torsion spring 54 to effect some counterclockwise rotation of the latch about the axis of pivot pin 26. Such inward urging motion by rung 7 is accomplished when torsion spring end 54 is moved within the slot 56 provided in the mounting bracket. Clearance of the latch relative to rung 7 of the fixed ladder section during upward movement of ladder section 2 is shown in FIG. .5.

During such upward movement, the lock body 22 is free to pivot in a counterclockwise direction but normally the same will remain in its extended position shown in FIGS until the same comes in contact with a rung 7 of ladder section 1 which is located above the rung with which it had previously been engaged. Upon the lock body striking such upper rung 7, the lock body is pivoted in a counterclockwise direction to the position generally shown in FIG. 6 in which position it straddles and substantially covers the camming latch. To permit the latch and the lock body to pass between the generally aligned rungs as shown in FIG. 6, counterclockwise rotation of the latch and the lock body as a unit is effected in response to the urging of the upper rung 7 against the outer surface of the lock body. Such counterclockwise rotation'is permitted by furthertorsional movement of the end 54 of the torsion spring in slot 56 as seen in FIG. 6.

It should be understood that, asladder section 2 continues to move upwardly from the FIG. 6 position, end 41 of the lock body will clear the upper rung 7"and,upon such clearance being effected, coil spring 62 will pivot' the lock body in a clockwise direction to its extended position in which it lies transversely of the two rungs 7 andBLBy limiting the upward movement of ladder section 2 relative to ladder section 1 as the lock body clears rung 7, and by then allowing the ladder section 2 to reverse its direction, the lock body may beengaged with both rungs in the orientation illustrated in FIG. 2

Operation of the lock mechanism during retraction of the ladder sections relative to each'other is shown in FIGS. 7

through 9. Starting with the lock mechanism in the locked position shown in FIG. 2, it is first necessary to raise movable ladder section 2 upwardly relative to ladder sectionjl to bring the camming latch 23 above rung 7, in the manner previously described, to the position shown in FIG. 7. Upon the camming latch reaching that position, it is merely necessary to allow the movable ladder section to move downwardly under the effects of gravity until the hook-shaped nose portion 32 of the latch strikes the rung 7 with which the lock body was previously engaged. Upon such contact being made, rung 7 temporarily precludes downward movement of the latch, although downward movement of ladder section 2 continues. Thus, the latch is moved longitudinally upwardly relative to the downwardly moving ladder section 2 with the pivot pin 26 sliding within the slot 34 of the latch.

Such longitudinal sliding movement of'the latch causes the upper camming end 33 thereof to slide along the interior of the lock body and to cause the lock body to pivot in a counterclockwise direction to the position shown in FIG. 8. Such counterclockwise movement brings end 41 of the lock body into position within the recess 33 of the nose portion of the latch, in which position such nose portion is oriented to clear downward movement of ladder section 2. It should be understood that when pivot pin 26 has reached the end of slot 34 'in the latch, continued resistance to downward movement thereof by rung 7 will cause the latch to pivot inwardly against the urging of the torsion spring 51. Thus, the nose portion of the latch pivots inwardly in a counterclockwise direction and carries therewith the retracted lock body. Upon such pivotal continues, the lock body and latch will pass by rung 7 and upon the same clearing that rung, spring 62 will urge the lock body to its extended position and spring 51 will urge the latch the rung generally as shown in FIG. 8 in response to continued to its extended position. In such positions, the components are again oriented generally as shown in FIG. 7 and are positioned to engage and clear the next lower rung in the same fashion as just described. The sequence of selective retraction and extension of the lock body and latch is repeated until the ladder sections are lowered to the position desired.

In the foregoing manner, the lock mechanism may be automatically and selectively engaged with any two aligned rungs of two extensible ladder sections without requiring any manual manipulation of any components of the lock mechanism.

Having thus made a full disclosure'of the improved lock mechanism of thisinvention, reference is directed to the appended claims for the scope of protection to be afforded thereto.

Iclaim: v

I. For use in an extension ladder which includes two slidably interconnected sections with spaced rungs on each, lock mechanism comprising:

A. a mounting bracket to be secured to one of said ladder sections adjacent a predetermined rung thereon;

B. a retractable lock body pivotally mounted on said bracket adapted to engage simultaneously said rung on said one ladder section and a rung on the other of said ladder sections when such rungs are aligned with each other; and I C. a retractable camming latchoperatively engaged with said lock body and mounted on said bracket for limited longitudinal and pivotal movement relative thereto;

l. said camming latch being positioned to pass between aligned rungs on said ladder sections during extension and retraction of said ladder sections relative to each other for actuating said lock body during such extension and retraction.

2. The lock mechanism of claiml in which said camming latch further includes;

2. a recessed nose section within which a portion of said lock body is receivable during retraction of saidrladder sections relative to each other.

3. The lock mechanism ofclaim 2 which further includes:

D. spring means normally urging saidcamming latch to an extended position relative to said bracket in which position said nose section is engageable with rungs of said other ladder section and urged by such rungs to a retracted position against the effects of said spring means during retraction of said laddersections'irelative to each other.

4. The lock mechanism of claim 1 which further includes:

D. spring means normally urging said lock body to an extended position in which the same is engageable with adjjacent aligned rungs of said ladder sections.

5. The lock mechanism of claim 3 in which said camming latch further includesi 3. an elongated slot extending generally longitudinally thereof, and in which said lock mechanism further includes;

E. a mounting pin extending through said bracket, said lock body and said slot in said camming latch, whereby said lock body may be pivotally retracted by said camming latch in response to longitudinal sliding movement of said latch relative to said pivot pin.

6. The lock mechanism of claim 1 which further includes:

D. spring means interposed between said bracket and said latch and said lock body for normally urging both of the latter to their respective extended positions.

7. The lock mechanism of claim 6 in which said spring means includes:

l. a torsion spring mounted on said bracket and having an end thereof engaged with an edge portion of said latch normally urging said latch towards its extended position.

8. An extension ladder including:

A. two slidable interconnected ladder sections each of which comprises:

. spaced parallel side rails, and

2. a series of spaced rungs extending between and secured to said side rails; and

B. a rung lock mechanism secured to one of said ladder sections for movement therewith during extension or retraction of said ladder sections relative to each other comprising:

2. 3. a lock body pivotally mounted on said pin for movea mounting bracket secured to said one ladder section adjacent a predetermined rung of such section; a mounting pin extending through said bracket;

ment between an extended position, in which said body is oriented to simultaneously engage said rung on said one ladder section and an aligned rung on said other ladder section, and a retracted position, in which said lock body is oriented to pass between such aligned rungs;

a retractable camming latch mounted on said pin for limited pivotal and longitudinal movement between an extended position, in which said latch is engageable with rungs of said other ladder section when such sections are bring retracted, and a retracted position, in which said latch may pass between aligned rungs of such ladder sections when such sections are being retracted; and

spring means normally urging said latch toward said extended position.

9. The ladder of claim 8 in which said latch includes;

a. a hook shaped nose portion having a recess therein in which an end of said lock body is receivable when said lock body and said latch are in their respective retracted positions, whereby said lock body is held out of interfering engagement with the rungs of said other ladder section during retraction of said ladder sections relative to each other.

10. The ladder of claim 8 which further includes: 6. spring means normally urging said lock body toward its extended position.

11. The ladder of claim 8 in which said latch is generally U- shaped in cross section and straddles said bracket, and in which said lock body is generally U-shaped in cross section and straddles said latch.

12. The ladder of claim 8 in which said spring means includes:

a. a torsion spring mounted on said bracket having an end thereof engaged with an edge portion of said latch, said spring being actuated by said latch upon engagement thereof with a rung of said other ladder section to permit retraction of said latch so that said latch may pass between aligned rungs of said ladder sections.

13. The ladder of claim 9 in which said latch further includes;

b. a rounded camming surface at the end thereof opposite from said hook shaped portion which is engageable with said lock body and urges such body toward its retracted position in response to longitudinal movement of said latch on said pin toward its retracted position in response to engagement thereof with a rung of said other ladder section.

14. The ladder of claim 11 in which said latch includes:

a. a rounded camming surface at an end thereof which is engaged with the interior of said lock body and urges such body toward its retracted position in response to longitudinal movement of said latch on said pin toward its retracted position in response to engagement thereof with a rung of said other ladder section.

15. The ladder of claim 8 in which said latch includes a. an elongated slot therein through which said pin extends so that said latch may move along said pin between its extended and retracted positions.

Claims

1. For use in an extension ladder which includes two slidably interconnected sections with spaced rungs on each, lock mechanism comprising: A. a mounting bracket to be secured to one of said ladder sections adjacent a predetermined rung thereon; B. a retractable lock body pivotally mounted on said bracket adapted to engage simultaneously said rung on said one ladder section and a rung on the other of said ladder sections when such rungs are aligned with each other; and C. a retractable camming latch operatively engaged with said lock body and mounted on said bracket for limited longitudinal and pivotal movement relative thereto; 1. said camming latch being positioned to pass between aligned rungs on said ladder sections during extension and retraction of said ladder sections relative to each other for actuating said lock body during such extension and retraction.

2. The lock mechanism of claim 1 in which said camming latch further includes;

2. a recessed nose section within which a portion of said lock body is receivaBle during retraction of said ladder sections relative to each other.

2. a mounting pin extending through said bracket;

2. a series of spaced rungs extending between and secured to said side rails; and B. a rung lock mechanism secured to one of said ladder sections for movement therewith during extension or retraction of said ladder sections relative to each other comprising:

3. a lock body pivotally mounted on said pin for movement between an extended position, in which said body is oriented to simultaneously engage said rung on said one ladder section and an aligned rung on said other ladder section, and a retracted position, in which said lock body is oriented to pass between such aligned rungs;

3. The lock mechanism of claim 2 which further includes: D. spring means normally urging said camming latch to an extended position relative to said bracket in which position said nose section is engageable with rungs of said other ladder section and urged by such rungs to a retracted position against the effects of said spring means during retraction of said ladder sections relative to each other.

3. an elongated slot extending generally longitudinally thereof, and in which said lock mechanism further includes; E. a mounting pin extending through said bracket, said lock body and said slot in said camming latch, whereby said lock body may be pivotally retracted by said camming latch in response to longitudinal sliding movement of said latch relative to said pivot pin.

4. The lock mechanism of claim 1 which further includes: D. spring means normally urging said lock body to an extended position in which the same is engageable with adjacent aligned rungs of said ladder sections.

4. a retractable camming latch mounted on said pin for limited pivotal and longitudinal movement between an extended position, in which said latch is engageable with rungs of said other ladder section when such sections are bring retracted, and a retracted position, in which said latch may pass between aligned rungs of such ladder sections when such sections are being retracted; and

5. spring means normally urging said latch toward said extended position.

5. The lock mechanism of claim 3 in which said camming latch further includes:

6. The lock mechanism of claim 1 which further includes: D. spring means interposed between said bracket and said latch and said lock body for normally urging both of the latter to their respective extended positions.

7. The lock mechanism of claim 6 in which said spring means includes:

8. An extension ladder including: A. two slidable interconnected ladder sections each of which comprises:

9. The ladder of claim 8 in which said latch includes; a. a hook shaped nose portion having a recess therein in which an end of said lock body is receivable when said lock body and said latch are in their respective retracted positions, whereby said lock body is held out of interfering engagement with the rungs of said other ladder section during retraction of said ladder sections relative to each other.

11. The ladder of claim 8 in which said latch is generally U-shaped in cross section and straddles said bracket, and in which said lock body is generally U-shaped in cross section and straddles said latch.

12. The ladder of claim 8 in which said spring means includes: a. a torsion spring mounted on said bracket having an end thereof engaged with an edGe portion of said latch, said spring being actuated by said latch upon engagement thereof with a rung of said other ladder section to permit retraction of said latch so that said latch may pass between aligned rungs of said ladder sections.

13. The ladder of claim 9 in which said latch further includes; b. a rounded camming surface at the end thereof opposite from said hook shaped portion which is engageable with said lock body and urges such body toward its retracted position in response to longitudinal movement of said latch on said pin toward its retracted position in response to engagement thereof with a rung of said other ladder section.

14. The ladder of claim 11 in which said latch includes: a. a rounded camming surface at an end thereof which is engaged with the interior of said lock body and urges such body toward its retracted position in response to longitudinal movement of said latch on said pin toward its retracted position in response to engagement thereof with a rung of said other ladder section.