US2895660A

US2895660A - Stop hook for extension ladders

Info

Publication number: US2895660A
Application number: US583752A
Authority: US
Inventors: Thomas J O'keefe
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-05-09
Filing date: 1956-05-09
Publication date: 1959-07-21
Anticipated expiration: 1976-07-21

Description

July 21, 1959 T. J. oKEl-:FE

sToP Hoox FOR EXTENSION LADDERs Filed May 9, 1956 ATTO RN EYS United States Patent:

2,895,660 `STOP HOOK FOR EXTENSION LADDERS Thomas J. OKeefe, Bethel, Conn.

Application May 9, 1956, Serial No. 583,752 1 Claim. Y(Cl.`228'-'1v8) This invention relates to a stop hook for'extension ladders, and has for `an object to provide an improved and simplified construction of ysuch a hook which may be used without the usual omission of a rung from the section of the ladder on which the hooks are mounted.

Another object is to provide such a construction in which the adjacent rung of the top section is utilized to limit the movements of the hook.

Another object is to provide a construction in which the weight distribution of the hook andthe toggle employed therewith is such that it will function properly on a gravity principle so that no springs or 'levers are required.

With the foregoing and other objects in view, I have devised the construction illustrated in the accompanying drawing forming a part of this specification. It is, khowever, to be understood the invention is not limited to the specic details of construction and arrangement shown, but may embody `various changes and modifications within Athe scope of the invention.

In this drawing:

Fig. l is a transverse section through two rungs of the upper and lower sections of an extension ladder looking toward the inner sides of the side rails, and showing my improved stop hook in full lines in the closed or holding position and in broken lines in the open or released position; v

Fig. 2 is a partial View looking inthe same direction but showing the action of the toggle lever in displacing the hook to make it pass over the rungs of the lower section when collapsing the ladder, and

Fig. 3 is a transverse section looking toward the bottom of Fig. 1.

This improved hook is shown applied to an extension ladder of the type described specically and claimed in my copending application Serial No. 583,751, filed of even date herewith, in which the side rails and 11 of the upper and lower sections of the ladder are extruded sections of light weight metal such, for example, as aluminum and magnesium alloys, the rails of the upper and lower sections of the ladder being of the same form and section, comprising upright web 12, longitudinal upper and lower

lateral flanges

13 and 14 at the opposite edges of the web 12, and inwardly extending shorter anges and 16 at the free edges of the

anges

13 and 14 extending toward each other and spaced from and parallel to the web 12. The corresponding rails of the upper and lower section of the ladder have the lower flange 14 of the upper or top rail and the upper ange 13 of the lower .rail overlapped and interlocked, as indicated in Fig. 3, for relative longitudinal sliding movement. The

shorter llanges

15 and 16 also overlap to interlock the rails against lateral separation. The rails of the two sections are reversed with the open side of the upper rail 10 v.facing outwardly and the upper side of the lower rail 11 ffacing inwardly, and the two rails of each section are con- :nected by a series of

transverse rungs

17 and 18, nor- ;mally spaced about twelve inches apart and which are ICC preferably tubular extruded sections and -are secured at :their opposite ends to the webs 12 of the side rails by the improved fastener comprising the inner member 19 threaded into vthe end of the rail and securing screw 20, as illustrated and described in said copending application. The rungs 18 of the lower section are properly spaced from the upper flange 13 of the lower rail 11 to properly position the lower flange 14 of the upper rail, and to maintain the interlocking relation between the two rails and :permit the side rails of the upper or top section to run on the rungs 18 of the lower section, thus `eliminating the requirement of use of any supporting rollers or other additional elements.

The stop hooks 21, one only of which is shown, are lused in pairs mounted one on each side rail 10 of the upper or top section of lthe ladder, and this top section can be raised or lowered to any position on the bottom section by having the hooks engage with the desired rung 18 of the bottom section. It may also be removed fromv the bottom section to be used alone as a straight ladder.

ln the usual extension ladder one rung of the upper ladder section is omitted, leaving a gap in the ladder `where the hooks are located, providing space required for swinging of the hooks for the proper hook action. 'In the present construction the hook comprises a body k2.2 pivoted to the rail 16 by the pivot shouldered bolt 23 spacing the hook from the rail for free movement, and it is provided with an elongated slot or opening 24 embracing the adjacent rung 17 of the upper ladder section. This permits the use of a rung 17 in the upper section at this location, and thus there is no gap or skip in the rung `arrangerrlent of the top section of the ladder, and this permits the use of the .upper or top section by removing it from the lower section Vand also makes a stronger and more rigid upper or 'top section for the ladder. The Yhook has a holding notch or recess 25 in its lower side ledge to hook'over a 'rung 18 of the lower section to hold the top section in the extended position, and it has a curved cam surface 26 on its `outer edge with the exten` sion 27 to engage the rungs to swingthe hook out of the way when passing yover the rungs of the lower section when extending or lengthening the ladder. The released or .open `position of @the hook is shown .in broken lines, Fig. l, while the closed or holding position is shown in full lines. As previously indicated, the rung 17 adjacent the hook is normally omitted from the usual type of extension ladder, but in this construction the elongated opening or slot 24 is long enough to permit the hook to swing between the full line and broken line positions, the movements to these positions being limited by the opposite end walls of the opening 24 engaging the rung 17. This slot and rung will permit the hook to be swung sufficiently far to the retracted or broken line position to permit the hook and its recess 25 to readily pass the rungs 18 of the lower ladder section in extending or retracting the ladder.

A control pawl or toggle 28 is pivoted to the body portion of the hook below the recess 25 at 29, and this toggle has a weighted lower end 30 tending to hold the other arm 31 against the outer end or shoulder 32 at the outer side of the recess 25, the arm 31 being offset, as indicated, at 33, Fig. 3, to bring this arm into alignment with shoulder 32. This arm is also long enough to provide a projecting end 34 extending beyond the outer curved edge 26 of the hook member. The weighted arm 30, therefore, tends to hold the arm 31 over the open side of the, recess 25 to thus close it against entrance of a rung 18',` of the lower section, as shown in Fig. 2. However, this toggle is swingable on its pivot 29 to the dotted line position of Fig. l to remove the arm 31 from the open side of, `the recess 25 in certain operations of the stop hook, the movement of this member to the dotted line position being 3 limited by the lower or free end of the arm 30 engaging the rung 17.

This toggle or control member 31 lies over the entrance to the recess 25 when the ladder is being collapsed, as shown in Fig'. 2, to prevent the rungs 18 of the lower ladder section going into the recess 25. It will be `seen from Fig. 2 that as the rail 10 of the upper section moves downwardly, the lower edge of the arm 31 engages the rung 18 of the lower ladder section, and by action of its free end against the shoulder 32 will swing the hook to the left or broken line position of Fig. 1 and permit the lever to pass by the rung 18.

In extending the ladder, upward movement of the rail 10 of the top section will carry the curved cam edge 26 against the rung 18. This will swing the hook to the left until the projecting free end 34 of the toggle engages the rung, which will swing this toggle arm downwardly, uncovering the open side of the recess 25, and if the operator wishes to engage the hook on this rung he may do so by stopping upward movement of the top ladder section when this toggle arm has been shifted away from the entrance to the recess 2S suciently to permit the hook to swing to the right and seat the rung in this recess. If, however, it is desired to extend the ladder further the operator merely keeps on shifting the top section upwardly, which by action of the rung 18 on the arm 31 will swing it downwardly to the dotted line position of Fig. l and permit the top section to continue its upward movement until the proper rung 18 is reached for the desired extension of the ladder. In permitting downward movement of the top section from the holding position of Fig. 1, the top section is raised to remove the hook from the rung 18 and swing the arm 31 of the toggle downwardly until the rung moves past it, permitting its weighted end 30 to swing the arm 31 back to its closed position across the entrance 25, as indicated in Fig. 2, when the top ladder section may be permitted to slide downwardly and the lower edge of the arm 31 of the toggle will engage the successive rungs 18 of the lower ladder section to permit the hook to pass by these rungs without engaging them in the holding position of Fig. 1.

Thus it will be seen this hook permits the use of the normal complement of rungs in the top section of the ladder without requiring any to be omitted, and that the hook operates by action of its weight distribution without requirement of the use of springs or other devices.

The extension and retracting operations in extending and shortening the ladder mayr be done with a rope and pulley (not shown) in the well known manner.

Having thus set forth the nature of my invention, I claim:

An extension ladder comprising top and bottom relatively slidable sections each including laterally spaced side rails connected by longitudinally spaced rungs, a hook member pivotally mounted on the inner side of each top rail on a pivot adjacent to but spaced from a lower rung of the top section and each provided with an arcuate elongated opening struck about said pivot as a center and embracing said rung, each hook also provided with an open sided recess in its under side adapted to hook over a rung of the lower section in substantially the same horizontal plane as a rung of the top section to hold the top section, each hook having a curved cam edge outwardly of the recess to engage rungs of the lower section to swing the hook backwardly and allow it to pass said rungs, the movements of the hook in both directions being limited by cooperation of the opposite ends of the opening with the enclosed rung, and a control toggle pivoted to each hook including an arm adapted to lie in an inclined position across the open side of the recess to close it and have a camming action on the rungs of the lower section to swing the hook backwardly to a retracted position to permit it to pass the rungs as the top section moves downwardly on the lower section to shorten the ladder, said toggle having a free end projecting beyond the curved cam edge to engage a rung to shift the arm from the recess closing position, and the toggle including an opposite weighted end tending to hold the tirst arm in the recess closing position.

References Cited in the file of this patent UNITED STATES PATENTS 457,805 Whittington Aug. 18, 1891 827,048 Truesdell July 24, 1906 1,170,395 Beatty Feb. 1, 1916 2,388,415 John Nov. 6, 1945 FOREIGN PATENTS 14,955 Australia Oct. 26, 1933 17,883 Australia Jan. 16, 1929 154,986 Switzerland Aug. 16, 1932 928,088 France May 26, 1947