US3785455A - Convertible ladder - Google Patents

Abstract

A convertible ladder including front and rear step sections each including side rails spanned by a plurality of steps, coupling members for selectively connecting the step sections for swinging movement from generally parallel, coextensive positions to relatively inclined positions to configure the step sections as a step ladder or connecting the step sections for generally parallel, sliding movement from coextensive positions to extended positions to configure the step sections as an extension ladder, and a support cradle mounted on the front step section for movement between a removed, inoperative position, which is rearward of the rear step section to permit relative movement of the step sections from the coextensive positions to either the inclined or the extended positions, and a support position underlying a step on the rear step section for supporting the rear step section on the front step section when the front and rear sections are extended.

Description

United States Patent [191 Waldron ,Han. 15, 1974 1 CONVERTIBLE LADDER [76] Inventor: Noel E. Waldron, Rt. No. 1, Elwell,

Mich. 48832 [22] Filed: June 29, 1972 [21] Appl. No.: 267,551

Primary Examiner-Reinaldo P M achado Attorney-John F. Learman et al [5 7] ABSTRACT A convertible ladder including front and rear step sections each including side rails spanned by a plurality of steps, coupling members for selectively connecting the step sections for swinging movement from generally parallel, coextensive positions to relatively inclined positions to configure the step sections as a step ladder or connecting the step sections for generally parallel, sliding movement from coextensive positions to extended positions to configure the step sections as an extension ladder, and a support cradle mounted on the front step section for movement between a removed, inoperative position, which is rearward of the rear step section to permit relative movement of the step sections from the coextensive positions to either the inclined or the extended positions, and a support position underlying a step on the rear step section for supporting the rear step section on the front step section when the front and rear sections are extended.

2. Qeim Qrex l li sws PATENTED JAN 1 5 i974 SHEET 10F 3 as so 34 PATENTEUJAN 1 W V 3.785.455

SHEET 3 BF 3 1 CONVERTIBLE LADDER BACKGROUND OF THE INVENTION This invention relates to a ladder, and more particularly to a convertible ladder which can be configured as either a step ladder or an extension ladder. Accordingly, it is an object of the present invention to provide a convertible ladder which can be quickly and easily converted to a step ladder or an extension ladder.

It is another object of the present invention to provide a convertible ladder which includes ladder sections that are swingable between generally parallel coextensive positions and relatively inclined positions and apparatus which will automatically move to a locking position when the ladder sections are relatively swung between coextensive positions and relatively inclined positions to lock the step sections in the relatively inclined positions.

Yet another object of the present invention is to provide a convertible ladder including a pair of step sections coupled for generally parallel movement between coextensive and extended positions and swingable support apparatus on one of the step sections for supporting the other step section when the sections are in the extended positions and being normally disposed in the path of a portion of the other step section but which is automatically moved to a removed position out of the path of the portion on the other section when the sections are being moved to extended positions.

A further object of the present invention is to provide a convertible ladder including a swingable support cradle on a front ladder section which is movable from a removed, inoperative position rearward of a rear ladder section to a support position underlying a portion of the rear ladder section to support the rear ladder section on the front ladder section when the sections are relatively longitudinally movedto extended position.

A still further object of the present invention is to provide a convertible step ladder including a cradle of the type mentioned and locking mechanism for locking the cradle in a position adjacent the rear ladder section to prevent the cradle from swinging rearwardly when the step sections are parallel.

Other objects and advantages of the present invention will become apparentas the description thereof proceeds.

SUMMARY OF THE INVENTION A ladder which can be selectively converted to an extension ladder or a step ladder comprising: front and rear step sections at least one section including a pair of laterally spaced apart rails spanned by a plurality of longitudinally spaced steps; coupling means for selectively connecting the sections for either swinging movement between adjacent, generally parallel, coextensive positions and relatively inclined positions to configure the ladder as a step ladder, or for generally parallel, longitudinal sliding movement between said coextensive positions and extended positions to configure the ladder as an extension ladder; and means for releasably supporting the rear section on the front section when the sections are in the extended positions to releasably preclude movement of the sections from the extended positions to the coextensive positions comprising: rear section support means mounted on the front section for movement between a remote inoperative position rearward of the front and rear sections, permitting the sections to be moved between the coextensive positions and either the extended positions or the relatively inclined positions, to a support position underlying a portion of the rear section when the sections are in the extended positions.

The present invention may more readily be understood by reference to the accompanying drawings in which:

FIG. 1 is a side elevational view of a ladder constructed according to the present invention, part of the side rails being broken away to illustrate more clearly the steps thereon and the position of the locking member for locking the ladder sections in the positions illustrated in FIG. 1;

FIG. 2 is a side elevational view of the ladder illustrated in FIG. 1 with the ladder sections being illustrated in adjusted, generally parallel, coextensive positions;

FIG. 3 is a side elevational view similar to FIG. 2, but illustrating the ladder sections in partially extended positions, part ofa rear ladder section side rail being broken away to illustrate more clearly the support cradle supporting the steps of the rear ladder section;

FIG. 4 is a rear elevational view of the ladder in the partially extended configuration illustrated in FIG. 3, the rear ladder section being illustrated in phantom;

FIG. 5 is a rear elevational view of the rear ladder section only;

FIG. 6 is a sectional plan view of the front ladder section only, taken along the line 6-6 of FIG. 4;

FIG. 7 is a sectional end view, taken along the line 7-7 of FIG. 4 and illustrating one of the steps on the rear ladder section supported by the cradle on the front ladder section; and

FIG. 8 is a top plan sectional view of the front ladder section only, taken along the line 88 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT A ladder constructed according to the present invention is generally designated 10 and includes a front step section, generally designated 12, and a rear step or prop section, generally designated 14. The front step section 12 includes a pair of laterally spaced, longitudinal side rails 16, spanned by a plurality of steps, generally designated 18. The side rails 16 include upper, generally parallel rail portions 16a and lower, downwardly diverging side rail portions 16b for a purpose to be described. Thesteps 18 (F IG. 1) on the front step section 12 each include a generally horizontal foot supporting section 20 having a rearward, depending terminal lip 20a and an integral, forward, depending reinforcing plate 22 which spans the rails 16 and includes a rearwardly bent rib 22a. A trapezoidal cutout 21 (FIG. 4) is provided in the lower portion of each of the plates 22 interjacent the side rails 16 to provide additional clearance for the foot of a person climbing the ladder.

The rear ladder section 14 includes a pair of generally parallel side rails 24 spanned by a plurality of steps 26, each exhibiting a generally inverted U-shaped end cross-section (see FIG. 7) and having a horizontal foot support portion 26a and a pair of depending leg por tions 26b and 26c. With the exception of the uppermost step, the steps are all longitudinally aligned and the leg portion 26c of each step is flush with the rear face 24a of the side rails 24. The uppermost step, including the leg portion 266 thereof, is set inwardly of the rear face 24a for a purpose to become apparent hereinafter.

The front and rear ladder sections 12 and 14 are coupled together for relative movement by a pair of coupling members, generally designed 28, which permit the sections 12 and 14 to be swung between the generally coextensive positions, illustrated in FIG. 2 and the relatively inclined positions, illustrated in FIG. 1. The coupling members 28 comprise a pair of vertical support plates 30 (see FIGS. 1 and 8), fixed to the upper ends of the front section side rails 16, pivotally mounting a pair of rear ladder section guides 32 by pins 33. The guides 32 include vertical side plates 34 and integral front and rear guide plates 35 and 36 which embrace the rear and front surfaces 24a and 24b, respectively, of the rear section side rails 24.

The vertical side plates 34 of the guides 30 are provided with a pair of upwardly opening notches 38 for receiving a pair of laterally outwardly extending support pins 40, provided at the upper ends of the side rails 24 on the rear ladder section 14, when the ladder sections are in the coextensive positions, illustrated in FIG. 2, and the relatively inclined positions illustrated in FIG. 1. The rear ladder section 14, which is supported on the ladder section 12 by the support pins 40, swings about the pivot pins 33 as it is moved from the position shown in FIG. 1 to the position shown in FIG. 2.

Apparatus, generally designated 42, is provided for removably locking the ladder sections 12 and 14 in the relatively inclined positions illustrated in FIG. 1 and comprises a pair of latch arms 44 (FIGS. 1 and 4), pivotally mounted on one of the front ladder section steps by pivot pins 48 and spanned by a cross member 50. The latch arms 44 include laterally inwardly turned latching hooks 52 having terminal ends 53 which ride along the rear surfaces 24a of the rear ladder section side rails 24. Recesses 54 are provided in the rear leg 26c of one of the steps 26 and the rear surfaces 24a of the side rails 24 to receive the terminal ends 53 of the latching hooks 52. The latching hooks 52 are provided with downwardly opening notches 56 which are received on the edge portions 54a of the rear leg 26c adjacent the cutouts 54.

The ladder section latching arms 44 are mounted internally of the diverging front ladder rail portions 16b and extend externally of the rear ladder section rails 24. The latching hooks 52 ride upwardly along the rear rail surfaces 24a when the sections 12 and 14 are swung apart until the ends 53 are received in the cutouts 54 and the notches 56 are received on the upper edge portions 54a of the cutouts 54. With the latching arms 44 locked in the position illustrated in FIG. 1, the ladder sections 12 and 14 cannot be swung toward and away from each other about the pivot pins 33 and thus a very safe step ladder is provided.

When the sections 12 and 14 are to be moved from the relatively inclined positions illustrated in FIG. 1, to the coextensive positions illustrated in FIG. 2, the latching arms 44 are moved upwardly from the positions illustrated in FIG. 1 so that the notches 56 are clear of the upper edge portions 54a of the notches 54 and the ladder sections 14 and 12 are swung together about the pivot pins 33. The latching arms 44 fall by gravity and the hook-shaped portions 53 ride along the rear rail surfaces 24a to return to the positions illustrated in FIG. 1.

The rear ladder section guide members 32 slidably receive the rear ladder section side rails 24 and permit the side rails 24 to slide vertically, when the sections 12 and 14 are in the parallel relation, to move between the coextensive positions, illustrated in FIG. 2, and the extended positions, illustrated in FIG. 3. A pair of guide plates 37 are also provided on the front ladder section side rails 16 below the guides 32 to assist in guiding the rear ladder section 14 as it is moved vertically between the position illustrated in FIG. 2 and the position illustrated in FIG. 3.

For supporting the rear ladder section 14, in the extended position illustrated in FIG. 3, a cradle, generally designated 60, is provided and includes a pair of support arms 62 pivotally connected to the front ladder section 12 by pivot pins 63 and spanned by an angle member 64 having a pair of laterally spaced apart, hook-shaped members 66 depending therefrom and defining upwardly opening pockets 68 for receiving the legs 260 of the steps 26 on the rear ladder section 14. The cradle supported hook members 66 are normally disposed in the path of the rear ladder section steps 26 and includes a lower camming surface 69 engageable by the steps 26 as the rear ladder section 14 is moved upwardly relative to the front ladder section 12 to cam the cradle rearwardly, from the position illustrated in solid lines in FIG. 3, to the removed position, illustrated in chain lines in FIG. 3, and permit the ladder sections to be extended. After a step 26 moves past the hook members 66, the cradle 60 will fall by gravity into the position illustrated in FIG. 3 to be disposed in the path of the rear legs 26c of the steps 26 when the ladder section 14 is lowered. The lower edge 26d (FIG. 7) of the legs 260 on one of the steps 26 is received in the cradle pockets 68 to preclude movement of the ladder section 14 from the extended position illustrated in FIG. 3 to the coextensive positions illustrated in FIG. 2. The upper ends 66b (FIG. 7) of the terminal portions 66a of the hook-shaped member 66 terminate below the underside 64a (FIGS. 4 and 8) of the angle member 64. A gap g (FIG. 4) is provided between the hook members 66 so that an individual can manually grasp the rear leg 260 between the hook members 66 and support the lower end 26d thereof above the upper terminal ends 66a of the hooks 66 and lower the leg 260 into the cradle pockets 68 without pinching an individuals hands between the steps 26 and the hook members 66.

To reconfigure the ladder as illustrated in FIG. 2, the rear ladder section 14 is moved upwardly so that the lower end 26d of the leg 26c supported on the cradle 60 is above the upper ends 66b of the cradle hooks 66 and the cradle 60 is manually swung outwardly about the pivot pins 63 to the chain line position illustrated in FIG. 3, permitting the downward movement of the ladder section 14 relative to the ladder section 12.

Apparatus, generally designated 70, is provided for locking the support cradle 60 in the position illustrated in solid lines in FIG. 3, to absolutely preclude relative swinging movement of the ladder sections 12 and 14 and comprises a pair of independent locking arms 72 pivotally mounted on the front ladder section side rails 16 by pivot pins 74. The cradle locking arms 72 include downwardly opening notches or recesses 76 which are received on the upstanding portion 64b of the angle member 64 on the cradle 60, as illustrated in FIG. 7, overlying one of the steps 26.

The upper step 26 is positioned so that the rear leg 26c thereof is set inwardly of the rear face 24a of the rear ladder section 14 out of the path of the cradle hook members 66 to preclude the depending step leg portion 260 from being received in the hook-shaped members 66 of the cradle 60 so that the free swinging movement of the cradle 60 will not be inhibited by the upper step 26. r

A support platform, generally designated 78, is provided for supporting paint buckets and the like, and includes a generally horizontal support plate 80 mounted on the flange 640 of the cradle angle member 64 by a pair of support members (not shown).

THE OPERATION The ladder will normally be stored in the configuration illustrated in FIG. 2 wherein the front and rear ladder sections 12 and 14 are generally coextensive with each other. If the ladder is to be used as a step ladder, the cradle lock members 72 are swung from the solid line positions, illustrated in FIG. 2, to the solid line positions illustrated in FIG. 1, to release the cradle 60 for free swinging movement. The rear ladder sections 14, which is supported on the front ladder section 12 by pins 40, is swung outwardly relative to the section 12 about the pivot pin 33 to the position illustrated in FIG. 1. As the rear ladder section 14 moves outwardly relative to the ladder section 12, the latching hooks 52 of the ladder section latching arms 44 ride along the rear surface 24a of the rails 24 until the hooks 52 are received in the recesses 54 after which time the latching arms 44 may drop by gravity or be manually forced downwardly so that the notches 56 in the latching arms 44 are received on the upper ends 54a of the rear step portions 260 adjacent the recesses 54.

When it is desired to return the ladder sections to their coextensive positions, illustrated in FIG. 2, the latching arms 44 are moved upwardly so that the notches 56 therein clear the upper ends 54a of the step portion 26c and the ladder section 14 is swung about the pivot pins 33 until the sections 12 and 14 are generally parallelas viewed in FIG. 2. The latching arms 44 will automatically drop under their own weight to th positions illustrated in FIG. 2.

If the ladder is to be configured as an extension ladder, the rear ladder section 14 is moved upwardly and the steps 26 engage the cam surface 69 on the underside of the cradle hooks 66 to cam them rearwardly to the removed position illustrated in chain lines in FIG. 3. As soon as the second uppermost step 26 has cleared the upper ends 66a of the cradle hooks 66, the cradle 60 will swing downwardly to the solid line position illustrated in FIG. 3, underlying the leg 26c of the second uppermost step 26. The rear ladder section 14 is then slightly lowered so that the rear leg 26c of the second uppermost step 26 is received in the recesses or pockets 68 on the hooks 66. The cradle locking members 72 are then swung from the inoperative positions illustrated in FIG. 1, to the cradle locking positions illustrated in FIG. 3, so that the notches 76 receive the flange portion 64b of the cradle angle member 64. The ladder then may be positioned against a wall or the like so that the upper ends of the side rails 24 are positioned against the wall. The ladder can, of course, be extended to a plurality of different heights and the cradle used to support any of the steps 26 with the exception of the uppermost step.

When the ladder is to be returned to the coextensive configuration illustrated in FIG. 2, the cradle locking hooks 72 are swung to the inoperative position illustrated in FIG. 1, the ladder section 14 is moved upwardly slightly so that the lower end 26d of the step leg 26c received in the cradle pockets 68 is positioned above the upper ends 6617 of the cradle hooks 66, and the support cradle 60 is swung to the chain line position illustrated in FIG. 3. The rear ladder section 14 is lowered to the position illustrated in FIG. 2 so that the rear ladder section 14 is supported by the pins 40 on the front ladder section 12. The cradle locking hooks 72 are then swung from the positions illustrated in FIG. 1 to the positions illustrated in FIG. 3 and the ladder may again be stored.

It is to be understood that the drawings and descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention, rather than as limiting the same in any way, since it is contemplated that various changes may be made in various elements to achieve like results without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

l. A ladder which can be selectively converted to either an extension ladder or a step ladder comprising:

front and rear ladder sections each including a pair of laterally spaced apart rails spanned by a plurality of longitudinally spaced steps;

coupling means connecting said ladder sections for either swinging movement between adjacent, generally parallel, coextensive positions, in which said ladder is configured as an extension ladder, and relatively inclined positions, in which said ladder is configured as a step ladder, or for generally parallel, longitudinal sliding movement between said coextensive positions and extended, generally parallel positions;

means for releasably supporting said rear ladder section on the rear face of said front ladder section when said sections are in said extended, generally parallel positions to releasably preclude movement of said sections from said extended, generally parallel positions to said coextensive, generally parallel positions comprising:

rear ladder section support means including a portion mounted on said front ladder section for movement between a removed inoperative position rearward of said front and rear sections, permitting said sections to be moved from said extended positions to said coextensive positions, and a support position underlying a portion of said rear ladder section to preclude relative movement of said ladder sections from said extended positions to said coextensive positions; and

means for removably locking said sections in said inclined positions including latch means mounted on said front section for swinging movement between a lowered position and a raised, locking position in response to said sections moving toward and away from each other between said coextensive positions and said inclined positions.

2. A ladder which can be selectively converted to either an extension ladder or a step ladder comprising:

front and rear ladder sections each including a pair of laterally spaced apart rails spanned by a plurality of longitudinally spaced steps;

coupling means connecting said ladder sections for either swinging movement between adjacent, generally parallel, coextensive positions, in which said ladder is configured as an extension ladder, and relatively inclined positions, in which said ladder is configured as a step ladder, or for generally parallel, longitudinal sliding movement between said coextensive positions and extended, generally parallel positions; and

means for releasably supporting said rear ladder section on the rear face of said front ladder section when said sections are in said extended, generally parallel positions to releasably preclude movement of said sections from said extended, generally parallel positions to said co-extensive, generally parallel positions comprising:

rear ladder section support means including a portion mounted on said front ladder section for movement between a removed inoperative position rearward of said front and rear sections, permitting said sections to be moved from said extended positions to said coextensive positions, and a support position underlying a portion of said rear ladder section to preclude relative movement of said ladder sections from said extended positions to said coextensive positions; and

latch means movable to and from a position in which it prevents said support means from moving from said support position and prevents said ladder sections from spreading.

3. The ladder as set forth in claim 2 wherein said latch means is swingably mounted on said front section to and from a position hooked over a portion of said support means when said support means is in said support position.

4. The ladder as set forth in claim 2 wherein said support means underlies the steps of said rear ladder section when said support means is in said support position.

5. The ladder as set forth in claim 2 wherein said support means includes a portion, normally in the path of a portion of said rear ladder section to prevent movement of said rear ladder section from said extended position to said coextensive position, swingable to a removed position out of said path when said rear ladder section is moving to said extended position.

6. The ladder as set forth in claim 2 wherein said rear ladder portion support means is normally disposed in the path of a portion of said rear ladder section when said rear ladder section is moving between said extended position and said coextensive position to normally preclude relative movement of said sections from said extended positions to said coextensive positions, but is movable to said removed position in response to relative movement of said sections from said coextensive positions to said extended positions.

7. The ladder set forth in claim 2 wherein said rear ladder section support means comprises cradle means swingably mounted on said front ladder section for swinging movement with said rear section when said sections are relatively moved to said inclined positions.

8. The ladder set forth in claim 2 wherein said support means comprises cradle means, normally disposed in the path of the steps on said rear ladder section for interrupting movement of said sections from said extended positions to said coextensive positions, swingable outwardly away from said sections out of the path of the steps on said rear ladder sections, to permit relative movement of said sections.

9. The ladder set forth in claim 8 wherein said support means includes clamp means swingably mounted on said front section for swinging movement to and from a locking position for selectively preventing said cradle means from swinging rearwardly away from said sections.

10. The ladder set forth in claim 9 wherein said cradle means supports the underside of one step of said rear ladder section and said clamp means overlies said one step in said locking position.

11. The ladder set forth in claim 8 wherein said support means includes means on said cradle means movable outwardly away from said sections in response to said sections being relatively moved to said extended positions.

12. The ladder set forth in claim 11 wherein said cradle means includes upwardly opening hook means for supporting the steps of said rear section on said front section, said hook means including means reacting with the steps of said rear section when said sections are relatively moved to said extended positions to move said cradle means out of said path.

13. The ladder set forth in claim 11 wherein the steps on said rear section each comprise at least one generally horizontal foot support portion and a generally vertical flange portion receivable in said cradle means.

14. The ladder set forth in claim 13 wherein the lower end of the flange portion of the uppermost step of said rear section is positioned forwardly, out of the path, of the cradle means so as not to be received by said cradle means when said sections are relatively moved.

15. The ladder set forth in claim 14 wherein said cradle means includes a pair of laterally spaced apart hook-shaped portions spanned by a cross member, the terminal ends of said hook-shaped portions terminating below the underside of said cross member when said cradle means is in the path of the steps on the rear ladder section to permit the vertical flange on a step of said rear section to be moved to a position above said hook-shaped members.

16. The ladder set forth in claim 2 including means for removably locking said sections in said inclined positions including latch means mounted on said from section for swinging movement between a lowered position and a raised locking position in response to movement of said sections toward and away from each other between said coextensive and inclined positions, and means on said rear section for receiving a portion of said latching means to removably lock said latching means in said locking position and preclude swinging movement of said sections toward and away from each other.

17. The ladder set forth in claim 16 wherein said latching means includes follower means riding on said rear ladder section for upward movement to a locking position as said sections are relatively spread to said inclined positions; said receiving means comprising recess means for receiving a portion of said latching means in said locking position.

18. A ladder comprising:

a step section including a pair of laterally spaced apart side rails spanned by a plurality of longitudinally spaced steps;

a prop section including a pair of laterally spaced apart side rails spanned by bracing members;

coupling means connecting said sections for relative swinging movement between adjacent, generally parallel positions and relatively inclined, spread positions in which said prop section will steady said step section; and

means for removably locking said sections in said spread positions including:

locking means pivotally mounted on one of said sections swingable upwardly from an inoperative position to a locking position in response to spreading of said sections; and

means on said other of said sections for releasably preventing movement of said locking means from said locking positions.

19. The ladder set forth in claim 14 wherein said pivotally mounted means includes follower means riding on the rails of said other section to and from said locking position.

20. The ladder set forth in claim 19 wherein the side rails of said step section include downwardly diverging portions, said locking means including a pair of support arms pivotally mounted on the inside portions of the side rails of said step section and extending laterally outwardly of the side rails of said prop section.

21. The ladder set forth in claim 20 wherein said portion of said locking means is disposed at the terminal end of said support means laterally inwardly of said support arms.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pate 3, 785,455 7 Dated January 15, 1974 Inventor-( N081 E. Waldron It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 7, line 48, delete. "portion"; same line, after "means" insert portion Signed and "sealed this 17th day of September 1974.

(SEAL) Attest: v

McCOY M. GIBSON JR. c. MARSHALL DANN Commissioner of Patents Attesting Officer OP P040250 (10-69) uscoMM-oc 60376-P69 U,S, GOVERNMENT PRINTING OFFICE 1 I969 0-366-334,

Claims (21)

1. A ladder which can be selectively converted to either an extension ladder or a step ladder comprising: front and rear ladder sections each including a pair of laterally spaced apart rails spanned by a plurality of longitudinally spaced steps; coupling means connecting said ladder sections for either swinging movement between adjacent, generally parallel, coextensive positions, in which said ladder is configured as an extension ladder, and relatively inclined positions, in which said ladder is configured as a step ladder, or for generally parallel, longitudinal sliding movement between said coextensive positions and extended, generally parallel positions; means for releasably supporting said rear ladder section on the rear face of said front ladder section when said sections are in said extended, generally parallel positions to releasably preclude movement of said sections from said extended, generally parallel positions to said coextensive, generally parallel positions comprising: rear ladder section support means including a portion mounted on said front ladder section for movement between a removed inoperative position rearward of said front and rear sections, permitting said sections to be moved from said extended positions to said coextensive positions, and a support position underlying a portion of said rear ladder section to preclude relative movement of said ladder sections from said extended positions to said coextensive positions; and means for removably locking said sections in said inclined positions including latch means mounted on said front section for swinging movement between a lowered position and a raised, locking position in response to said sections moving toward and away from each other between said coextensive positions and said inclined positions.

2. A ladder which can be selectively converted to either an extension ladder or a step ladder comprising: front and rear ladder sections each including a pair of laterally spaced apart rails spanned by a plurality of longitudinally spaced steps; coupling means connecting said ladder sections for either swinging movement between adjacent, generally parallel, coextensive positions, in which said ladder is configured as an extension ladder, and relatively inclined positions, in which said ladder is configured as a step ladder, or for generally parallel, longitudinal sliding movement between said coextensive positions and extended, generally parallel positions; and means for releasably supporting said rear ladder section on the rear face of said front ladder section when said sections are in said extended, generally parallel positions to releasably preclude movement of said sections from said extended, generally parallel positions to said co-extensive, generally parallel positions comprising: rear ladder section support means including a portion mounted on said front ladder section for movement between a removed inoperative position rearward of said front and rear sections, permitting said sections to be moved from said extended positions to said coextensive positions, and a support position underlying a portion of said rear ladder section to preclude relative movement of said ladder sections from said extended positions to said coextensive positions; and latch means movable to and from a position in which it prevents said support means from moving from said support position and prevents said ladder sections from spreading.

3. The ladder as set forth in claim 2 wherein said latch means is swingably mounted on said front section to and from a position hooked over a portion of said support means when said support means is in said support position.

4. The ladder as set forth in claim 2 wherein said support means underlies the steps of said rear ladder section when said support means is in said support positioN.

5. The ladder as set forth in claim 2 wherein said support means includes a portion, normally in the path of a portion of said rear ladder section to prevent movement of said rear ladder section from said extended position to said coextensive position, swingable to a removed position out of said path when said rear ladder section is moving to said extended position.

6. The ladder as set forth in claim 2 wherein said rear ladder portion support means is normally disposed in the path of a portion of said rear ladder section when said rear ladder section is moving between said extended position and said coextensive position to normally preclude relative movement of said sections from said extended positions to said coextensive positions, but is movable to said removed position in response to relative movement of said sections from said coextensive positions to said extended positions.

7. The ladder set forth in claim 2 wherein said rear ladder section support means comprises cradle means swingably mounted on said front ladder section for swinging movement with said rear section when said sections are relatively moved to said inclined positions.

8. The ladder set forth in claim 2 wherein said support means comprises cradle means, normally disposed in the path of the steps on said rear ladder section for interrupting movement of said sections from said extended positions to said coextensive positions, swingable outwardly away from said sections out of the path of the steps on said rear ladder sections, to permit relative movement of said sections.

9. The ladder set forth in claim 8 wherein said support means includes clamp means swingably mounted on said front section for swinging movement to and from a locking position for selectively preventing said cradle means from swinging rearwardly away from said sections.

10. The ladder set forth in claim 9 wherein said cradle means supports the underside of one step of said rear ladder section and said clamp means overlies said one step in said locking position.

11. The ladder set forth in claim 8 wherein said support means includes means on said cradle means movable outwardly away from said sections in response to said sections being relatively moved to said extended positions.

12. The ladder set forth in claim 11 wherein said cradle means includes upwardly opening hook means for supporting the steps of said rear section on said front section, said hook means including means reacting with the steps of said rear section when said sections are relatively moved to said extended positions to move said cradle means out of said path.

13. The ladder set forth in claim 11 wherein the steps on said rear section each comprise at least one generally horizontal foot support portion and a generally vertical flange portion receivable in said cradle means.

14. The ladder set forth in claim 13 wherein the lower end of the flange portion of the uppermost step of said rear section is positioned forwardly, out of the path, of the cradle means so as not to be received by said cradle means when said sections are relatively moved.

15. The ladder set forth in claim 14 wherein said cradle means includes a pair of laterally spaced apart hook-shaped portions spanned by a cross member, the terminal ends of said hook-shaped portions terminating below the underside of said cross member when said cradle means is in the path of the steps on the rear ladder section to permit the vertical flange on a step of said rear section to be moved to a position above said hook-shaped members.

16. The ladder set forth in claim 2 including means for removably locking said sections in said inclined positions including latch means mounted on said front section for swinging movement between a lowered position and a raised locking position in response to movement of said sections toward and away from each other between said coextensive and inclined positions, and means on said rear section for receiving a portion of said latching means to Removably lock said latching means in said locking position and preclude swinging movement of said sections toward and away from each other.

17. The ladder set forth in claim 16 wherein said latching means includes follower means riding on said rear ladder section for upward movement to a locking position as said sections are relatively spread to said inclined positions; said receiving means comprising recess means for receiving a portion of said latching means in said locking position.

18. A ladder comprising: a step section including a pair of laterally spaced apart side rails spanned by a plurality of longitudinally spaced steps; a prop section including a pair of laterally spaced apart side rails spanned by bracing members; coupling means connecting said sections for relative swinging movement between adjacent, generally parallel positions and relatively inclined, spread positions in which said prop section will steady said step section; and means for removably locking said sections in said spread positions including: locking means pivotally mounted on one of said sections swingable upwardly from an inoperative position to a locking position in response to spreading of said sections; and means on said other of said sections for releasably preventing movement of said locking means from said locking positions.

19. The ladder set forth in claim 14 wherein said pivotally mounted means includes follower means riding on the rails of said other section to and from said locking position.

20. The ladder set forth in claim 19 wherein the side rails of said step section include downwardly diverging portions, said locking means including a pair of support arms pivotally mounted on the inside portions of the side rails of said step section and extending laterally outwardly of the side rails of said prop section.

21. The ladder set forth in claim 20 wherein said portion of said locking means is disposed at the terminal end of said support means laterally inwardly of said support arms.

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