US3759474A

US3759474A - Ladder jack

Info

Publication number: US3759474A
Application number: US00164563A
Authority: US
Inventors: W Narkie
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-07-21
Filing date: 1971-07-21
Publication date: 1973-09-18
Anticipated expiration: 1990-09-18

Abstract

A ladder jack consisting of a beam having a hook at one end engageable over a ladder rung and adapted to support a scaffold plank thereon, a link pivoted at one end to the opposite end of the beam, a hook at the opposite end of said link engageable over a relatively higher rung of the ladder, the link being adjustable in length to level the beam in various positions of use, and a connection joining the hook ends of the beam and link to permit limited free relative movement therebetween.

Description

United States Patent [191 Narkie Sept. 18, 1973 1 LADDER JACK [76] Inventor: Walter E. Narkie, 126 W. 5th St.,

Kansas City, Mo.

22 Filed: Jul zl, 1971 211 Appl. No.: 164,563

52 us. Cl. .Q 248/238 511 Int. Cl. F16!!! 13/00 [58] Field of Search 248/238, 309, 353, 248/354 L, 242; 287/58 R [56] References Cited UNITED STATES PATENTS 1,332,385 3/1920 Dunlap 248/238 1,107,876 8/1914 Ballard. 287/58 R 966,852 8/1910 Norton. 248/238 X 569,645 10/1896 Jones 248/238 1,042,192 10/1912 BOiiOt 248/238 328,999 10/1885 Ballman 248/238 393,512 11/1888 Long 248/238 608,629 8/1898 Wood 248/353 2,686,648 8/1954 Oehler 248/309 Primary Examiner-William H. Schultz Attorney-John A. Hamilton [5 7] ABSTRACT A ladderjack consisting of a beam having a hook at one end engageable over a ladder rung and adapted to support a scaffold plank thereon, a link pivoted at one end to the opposite end of the beam, a hook at the opposite end of said link engageable over a relatively higher rung of the ladder, the link being adjustable in length to level the beam in various positions of use, and a connection joining the hook ends of the beam and link to permit limited free relative movement therebetween.

7 Claims, 14 Drawing Figures PATENTEU SE" 8 I878 SHEET 2 [IF 2 INVENTOR. h/fer Adv/m9 E? Fig/11 1913 1 19 13 Aria/way- LADDER JACK This invention relates to new and useful improvements in ladder jacks, ladder jacks constituting brackets adapted to be mounted on ladders to support scaffolding planks. In common practice, two ladders are usually employed, each carrying a jack, with a scaffold plank extending between and supported by said two jacks. They are commonly used by painters, carpenters, and others for both interior and exterior work on buildmgs.

Among the objects of the present invention are the provision of a ladder jack of the general character described which distributes the scaffold load between two rungs of each ladder, rather than imposing the entire load on a single rung, which is freely adjustable to level the scaffold plank despite variation in the slope of the ladders, which can be positioned to dispose the scaffold plank either inside or outside of the ladder, with respect to its slope, which may be easily carried up a ladder and applied to the rungs thereof in a one-handed operation, which compensates for variations in the spacing between the rungs of the ladder, and which may be folded compactly for convenience of storage and transportation.

Other objects are simplicity and economy of construction, and efficiency, dependability, and safety of operation.

With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:

FIG. 1 is a reduced sectional view taken on line ll-I of FIG. 2, constituting a side elevationalview of a ladder jack embodying the present invention, shownoperatively applied to the outside of a ladder and supporting a scaffold plank,

FIG. 2 is an enlarged fragmentary top plan view of the parts as shown in FIG. 1,

FIG. 3 is an enlarged side elevational view of the jack link only, shown in a pivoted position assumed thereby when adjusting the length thereof,

FIG. 4 is a further enlarged fragmentary view similar to FIG. 3 but showing the link parts in locked position,

FIG. 5 is a sectional view taken on line V.-V of FIG.

FIG. 6 is a view similar to FIG. 1, but showing the jack mounted on the inner side of the ladder,

taken on line VII-VII of FIG. 1,

FIG.. 8 is an enlarged, fragmentary sectional view taken on line VIII-VIII of FIG. 1,

'FIG. 9 is a fragmentary sectional view taken on line IX-IX of FIG. 7,

FIG. 10 is a perspective view of a ladder jack of slightly modified construction, shown operatively mounted on the inner surface of a ladder,

FIGS. l1, l2, and 13 are enlarged sectional views taken respectively on lines XI-XI, XII-XII, and XIII- -XIIl of FIG. 10, and I FIG. 14 is a fragmentary sectional view taken on line XIV-'-XIV of FIG. 13.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies generally to a ladder including a pair of side rails 4 (one shown) connected at longitudinally spaced apart points by rungs 6 extending at right angles thereto. In most ladders the spacing of the rungs is generally standardized at one foot, but is subject to some manufacturing variation, and also to variation by bowing or warping of the rungs themselves. The ladder jack forming the subject matter of the present invention, in the form thereof shown in FIGS. 1-9 consists generally of a frame 8 carrying a slide 10, a beam 12, and a link 14. Frame 8 consists of two elongated rods 16 disposed in closely spaced side-by-side relation and connected rigidly at spaced apart points of their lengths by spacers 18, and adapted to lie against the rungs 6 of the ladder, longitudinally of said ladder. At their upper ends, rods 16 are spread divergently apart, and each is formed at its upper end to present a downwardly opening hook 20 adapted to be engaged over one of said rungs, as shown. Generally, said frame should be of such length as to extend past the second rung below the rung on which hooks 20 are engaged.

Slide 10 is formed of sheet metal, and is slidably mounted for free movement longitudinally along the lower portion of frame 8. It includes a base wall 22 parallel to frame rods 16 and adapted to lie against a ladder rung, and a guideway 24 through which rods 16 are inserted. Said guideway includes a center wall 26 (see FIG. 8) disposed between rods 116, which limits the movement of the slide on the rods by engagement thereof with a pair of rod spacers 18 of the frame. Also affixed to base wall 22 of the slide are a .pair of downwardly opening hook members 28 adapted to engage over the ladder rung 6 adjacent thereto, usually the second rung below that engaged by upper hooks 20. The free slidability of slide 10 on frame 8 permits the upper and lower hooks to accommodate themselves accurately to the rungs despite variations in the spacing of said rungs, since as will appear both hooks must carry a portion of the scaffold load. Also affixed to slide 10, at the side thereof opposite from hooks 28, is a planar ear 30 having formed therein a notch 32 (see FIG. 9)

which is inclined upwardly toward :its open end, in a direction away from hooks 28. A locking bar 34 is pivoted at its upper end to ear 30 above notch 32, as at 36, and normally hangs downwardly by gravity so that its lower end obstructs the exit portion of said notch (see FIG. 9

, otal about its axis therein. Lock bar 34 must be pivoted upwardly out of the way before said bolt can be inserted into said notch, but once it has been inserted, said lock bar returns by gravity to its normal locking position as shown, to prevent accidental disengagement of said bolt from said notch by shaking, vibration, lifting of the beam independently of the rest of the jack, or otherwise. The beam projects horizontally outwardly from the plane of the ladder, as shown, and is pivoted toits outer end, as by bolt 44, to the lower end of link 14, on a transverse horizontal axis. I

Link 14 consists of an upper portion 46 and a lower portion 48. Upper portion 46 consists of a pair of closely spaced apart parallel bars .50 rigidly interconnected adjacent their upper ends by a spacer 52 (see FIG. 3), and by a U-shaped connection 53, and having their extreme upper end portions bent into diverging relation and pivoted by bolts 54 to a pair of ears 56 welded respectively to frame rods 16 adjacent upper hooks 20. Lower section 48 of the link is pivoted to beam 14 at 44, and extends slidably and pivotally between bars 50 of the upper section. A keeper ring 58 encircles upper section 46 above the lower end thereof and is welded or otherwise affixed thereto. Lower section 48 extends through said keeper ring, and is provided at its upper end with a T-head 60 too large to pass through said ring, whereby the link sections are retained in assembly. Said ring is sufficiently large, however, to permit a limited degree of relative transverse pivotal movement of the link sections, as shown in FIG. 3. A bolt 62 is affixed in and extends transversely between bars 50 of upper link section 46 at the lower end thereof, said bolt being adapted to be engaged in any one of a series of notches 64 formed in the upper edge of lower link section 48, the open ends of said notches being inclined toward the lower end of the link. The effective length of the link may thus be altered at will by relatively pivoting lower link section 48 in keeper ring 58 of the upper section, as shown in FIG. 3, to free bolt 62 from the notch 64 in which it is then engaged, sliding the link sections longitudinally until bolt '62 is aligned with the notch 64 corresponding to the desired length, and again straightening the link to engage the bolt in the new notch. The inclination of the notches provides that any tensile stress in the link will hold bolt 62 securely in any notch into which it has been inserte'd. However, to prevent any possibility that the bolt could be shaken, vibrated, or otherwise accidentally disengaged from any of notches 64, there is provided also a locking ring 66 loosely encircling link 14 between keeper ring 58 and bolt 62. Said locking ring slides downwardly along the link by gravity whenever the link is straight, until it engages the head and nut of bolt 62, and in this position prevents relative pivoting of the link sections to disengage said bolt from notches 64. Said locking ring must be manually elevated along the link to a position adjacent keeper ring 58, as shown in FIG. 3, to permit relative pivoting of the link sections. The locking action thereof is entirely automatic.

In use, bolt 42 of beam 12 is first inserted in ear notch 32 of slide 10, as already described, and the jack is then carried up the ladder by a workman. This may be done easily with one hand, the jack being provided with a handle 68 welded to frame ears 56 for this purpose. Upper hooks 20 and lower hooks 28 are then engaged over appropriate rungs 6 of the ladder, as shown. Of course, as the jack is carried up the ladder, the upper and lower hooks will not be properly spaced for the rungs since slide will at that time move to its lowermost position on frame 8', said slide then engaging the lowermost frame spacer 18A (see FIG. 7), but the frame, beam and link will nonetheless be held in proper general relationship tofacilitate one-handed application of both sets of hooks to the rungs. As the hooks are applied, slide 10 will move upwardly on the frame to a position in which it is freely movable on the frame, thus insuring full weight-supporting engagement of both sets of hooks with their respective rungs.

Link 14 is then adjusted in length, as described above, to bring beam 12 into a horizontally level position. Obviously, the jack may be applied to the outer side of the ladder as shown in FIG. 1, so that beam 12 projects outwardly from the ladder, or to the inner side of the ladder as shown in FIG. 6, so that beam 12 projects inwardly from the ladder, as may be desired in any particular job as dictated by considerations of accessibility of the work area. Obviously, the FIG. I arrangement requires link 14 to be set much longer than the FIG. 6 arrangement. Also, in either case, the adjustability of the link permits levelling of beam 12 despite variations in ladder slope. Lower link section 48 could obviously be provided with as many notches 64 as might be desired. Another ladder, similarly equipped with a ladder jack, is set up in spaced relation from the first, and a scaffold plank extended between and supported by beams 12 of the two jacks.

It will be seen that the jack as shown and described has several advantageous features. It will be seen that the load carried by the inner end of beam 12 is transmitted through slide 10 directly to lower hooks 28 and the ladder rung 6 engaged thereby, while the load carried by the outer end of the beam is transmitted by link 14 to upper hooks 20 and the separate rung 6 engaged thereby. Thus the scaffold load is distributed between and carried by two ladder rungs. This represents a substantial improvement in safety and load capacity over the usual jack, which is supported by only a single ladder rung. Furthermore, this condition prevails despite possible variations in the rung spacing of the ladder, or bending or deformation of the rungs, due to the free slidability of slide 10 on frame 8. Safety of the jack is further enhanced by locking bar 34 and locking ring 66, which respectively prevent accidental disengagement of bolt 42 from notch 32, and accidental extension of link 14, either of which occurrences could cause dangerous dropping or tilting of the scaffold plank. Both locking devices operate automatically, without attention by the workman. It is not necessary to the basic operation of the jack that beam 12 be disengageable from frame 8 at all, but it does permit the entire jack to be folded into a compact space for ease and convenience of storage and transportation. The jack may be applied with equal facility to either the inner or outer surface of a ladder, and may be easily carried up a ladder and applied thereto by a single workman in a one-handed operation.

FIGS. 10-14 show a somewhat simplified modification of the structure shown in FIGS. 1-9. Its operation and construction is generally similar to those of FIGS. 1-9, corresponding parts being indicated by corresponding primed numerals. However, as clearly shown in FIG. 10, upper hooks 20' are rigidly affixed to the upper end of link 14 instead of being pivoted thereto, and lower hooks 28 are rigidly affixed to beam 12' instead of being pivoted thereto. Also, instead of the frame 8 and slide 10 shown in FIGS. 1-9 for connecting the upper and lower hooks, FIG. 10 shows a chain 72 connected at its upper end to an ear 74 welded to the upper end of link 14' and connected at its lower end by a snap fastener 76 to an eye 78 welded to beam 12 adjacent hooks 28'. Said chain serves the same general purpose as frame 8 and slide 10 in FIGS. l-9, holding the beam and link in generally proper relationship as the jack is carried up a ladder, but being of such length as to be slack as shown when the upper and lower hooks are engaged on the ladder rungs, to permit said hooks to accommodate themselves to variably spaced rungs. Here again, it is not essential that the chain be provided with detachable connection 76, and the jack can be folded for transportation or storage without it, but it does permit the jack to be assembled around a scaffold plank already in place whenever this may be desired. The detachability of beam 12 from slide serves the same purpose in FIGS. l-9. Link 14 is generally similar in structure and operation to link 14, consisting of an upper section 46' and a lower section 48' extending into slidable overlapping relation, a keeper ring 58' welded to the upper end of lower section 48' to permit relative sliding and pivotal movement between said sections, a second keeper ring 80 (not used in FIGS. ll-9) affixed to the lower end of upper section 46' and encircling lower section 48 to limit the relative pivotal movement of the sections to that amount necessary to release a bolt 62' fixed transversely in the lower end of section 46' from any of a series of longitudinally spaced notches 64' formed in lower section 48', keepers 58' and 80 also serving to retain the link sections in assembly, and a locking ring 66' loosely encircling the link between keepers 58' and 80. The length of link 14 may be adjusted substantially identically as that of link 14. The only material difference in actual operation of the species of FIGS. 10-14 from that of FIGS. ll-9 is that in FIGS. 10-14 it will be seen that in accommodating themselves to ladder rungs 6' of different spacings, upper and lower hooks and 28 must be free to pivot on said rungs. This species is therefore not well adapted for use with ladders having flat, step-like rungs instead of the rungs shown which are round in crosssectional contour. In FIGS. 1-9, on the other hand, the hooks have a fixed, non-movable relation to the rungs, and hence may be configurated to conform to rungs of any cross-sectional contour.

f While I have shown and described certain specific embodiments of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention.

What I claim as new and desire to protect by Letters Patent is:

1. A ladder jack comprising: i

a. a lower hook adapted to engage downwardly over a relatively lower ladder rung,

b. a beam connected at one end of said lower hook to extend horizontally outwardly from said ladder, transversely to the plane of said ladder, whereby it is positioned to support a scaffold plank,

c. anupper hook adaptedto engage downwardly over a relatively higher ladder rung, and I a link connected at one end to said upper hook and pivoted at its opposite end to the end of said beam remote from said ladder, on a horizontal transverse axis, said link being adjustable in length, and comprising an upper section connected to said upper hook, a lower section pivoted to said beam, said upper and lower sections extending into slidably overlapping relation, said lower section having a series of longitudinally spaced, transversely open-. ing notches formed therein, a pin fixed transversely in said upper section and engageable selectively in any of said notches, keeper means connecting said upper and lower sections at a point spaced upwardly from said pin for relative movement about an axis transverse to said link, whereby said pin may be disengaged from any of said notches, and locking means comprising a locking ring loosely encircling both sections of said link intermediate said pin and said keeper, said locking ring being movable along said link by gravity to a position adjacent said pin, whereby to prevent relative pivotal movement of said link sections and to secure said pin in one of said notches, but being manually elevatable along said link to a position adjacent said keeper, whereby to permit relative pivotal movement of said link sections.

2. A ladder jack as recited in claim 1 with the addition of connecting means joining the ends of said link and beam connected respectively to said upper and lower hooks and permitting limited free relative movement of said link and beam about their pivotal connection, whereby to maintain said link. and beam in generally normal relation for convenience in carrying the jack up a ladder and applying it thereto, and to permit said upper and lower hooks to accommodate themselves to ladders having varying spacing between rungs.

3. A ladder jack as recited in claim 2' wherein said connecting means comprises:

a. a generally vertical frame having said upper hook fixed at the upper end thereof, said link beingpivoted to said frame on a horizontal transverse axis adjacent said upper hook, and.

b. a slide movable vertically along said frame below said upper hook between fixed limits, said lower hook being affixed to said slide and said beam being pivoted to said slide on a horizontal transverse axis, said slide being disposed intermediate the limits of its movement on said frame when said upper and lower hooks engage rungs of said ladder.

4. A ladder jack as recited in claim 3 wherein said beam is detachably connected to saidslide, whereby to permit folding of said jack.

5. A ladder jack as recited in claim 3 wherein said beam is provided at the end thereof joining said slide with a fixed transverse pin, and said slide is provided with a notch inclined upwardly toward its open end for receiving said pin, and with the addition of a locking member pivoted freely to said slide above said notch and movable by gravity to a position above said beam adjacent said pin, whereby to prevent removal of said pin from said notch. y i

6. A ladder jack as recited in claim 2 wherein said upper and lower hooks are adapted to engage ladder rungs for pivotal movement thereabout, and wherein said link and beam are rigidly affixed respectively to said upper and lower hooks.

7. A ladder jack as recited in claim 6 wherein said connecting means comprises a flexible connector extending between and joining said link and said beam at points adjacent said hooks, said connector being of such length as to be slack when said hooks engage rungs of said ladder.

k 6' I 4' l

Claims

1. A ladder jack comprising: a. a lower hook adapted to engage downwardly over a relatively lower ladder rung, b. a beam connected at one end of said lower hook to extend horizontally outwardly from said ladder, transversely to the plane of said ladder, whereby it is positioned to support a scaffold plank, c. an upper hook adapted to engage downwardly over a relatively higher ladder rung, and d. a link connected at one end to said upper hook and pivoted at its opposite end to the end of said beam remote from said ladder, on a horizontal transverse axis, said link being adjustable in length, and comprising an upper section connected to said upper hook, a lower section pivoted to said beam, said upper and lower sections extending into slidably overlapping relation, said lower section having a series of longitudinally spaced, transversely opening notches formed therein, a pin fixed transversely in said upper section and engageable selectively in any of said notches, keeper means connecting said upper and lower sections at a point spaced upwardly from said pin for relative movement about an axis transverse to said link, whereby said pin may be disengaged from any of said notches, and locking means comprising a locking ring loosely encircling both sections of said link intermediate said pin and said keeper, said locking ring being movable along said link by gravity to a position adjacent said pin, whereby to prevent relative pivotal movement of said link sections and to secure said pin in one of said notches, but being manually elevatable along said link to a position adjacent said keeper, whereby to permit relative pivotal movement of said link sections.

2. A ladder jack as recited in claim 1 with the addition of connecting means joining the ends of said link and beam connected respectively to said upper and lower hooks and permitting limited free relative movement of said link and beam about their pivotal connection, whereby to maintain said link and beam in generally normal relation for convenience in carrying the jack up a ladder and applying it thereto, and to permit said upper and lower hooks to accommodate themselves to ladders having varying spacing between rungs.

3. A ladder jack as recited in claim 2 wherein said connecting means comprises: a. a generally vertical frame having said upper hook fixed at the upper end thereof, said link being pivoted to said frame on a horizontal transverse axis adjacent said upper hook, and b. a slide movable vertically along said frame below said upper hook between fixed limits, said lower hook being affixed to said slide and said beam being pivoted to said slide on a horizontal transverse axis, said slide being disposed intermediate the limits of its movement on said frame when said upper and lower hooks engage rungs oF said ladder.

4. A ladder jack as recited in claim 3 wherein said beam is detachably connected to said slide, whereby to permit folding of said jack.

5. A ladder jack as recited in claim 3 wherein said beam is provided at the end thereof joining said slide with a fixed transverse pin, and said slide is provided with a notch inclined upwardly toward its open end for receiving said pin, and with the addition of a locking member pivoted freely to said slide above said notch and movable by gravity to a position above said beam adjacent said pin, whereby to prevent removal of said pin from said notch.