US3502175A

US3502175A - Cammed compression locking device for extension ladders

Info

Publication number: US3502175A
Application number: US787758A
Authority: US
Inventors: Robert E Bullock
Original assignee: CROFT METAL PRODUCTS Inc
Current assignee: CROFT METAL PRODUCTS Inc
Priority date: 1968-12-30
Filing date: 1968-12-30
Publication date: 1970-03-24
Anticipated expiration: 1987-03-24

Description

March 24, 1970 R. E. BULLOCK 3,502,175

CAMMED COMPRESSING LOCKING DEVICE FOR EXTENSION LADDERS Filed Dec. 30, 1968 2 Sheets-Sheet 1 INVENTOR ROBERT E. BULLOCK ATTORNEYS March 24, 1970 v B O 3,502,175

CAMMED COMPRESSING LOCKING DEVICE FOR EXTENSION LADDERS Filed Dec. 30, 1968 2 Sheets-Sheet 2 INVENTOR ROBERT E. BULLOCK BY f'M ATTORNEYS United States Patent M 3,502,175 CAMMED COMPRESSION LOCKING DEVICE FOR EXTENSION LADDERS Robert E. Bullock, McComb, Miss., assignor to Croft Metal Products, Inc., McComb, Miss., a corporation of Mississippi Filed Dec. 30, 1968, Ser. No. 787,758 Int. Cl. E06c 7/06 US. Cl. 182211 8 'Claims ABSTRACT OF THE DISCLOSURE The latching mechanism for holding the sections of an extension ladder in an extension position is pivoted for movement about a vertical axis confined within the narrow space afforded between the adjacent edges of the steps of the sections, the steps being of wide tread configuration of approximately the width of the side rails of the ladder. A latching plate is pivoted along one edge on this axis and has a depending extension which carries the camming paddle for swinging the latching plate aside upon relative descent of the ladder sections.

BACKGROUND OF THE INVENTION One of the advantages of metal ladder construction is the ease with which wide tread steps, as opposed to rungs, may be employed. Aside from the user comfort involved with wide tread steps, they also oifer the possibility for increased rigidity of the structure as a whole inasmuch as the wide tread may form part of a step construction of great rigidity and, as well, the existence of a wide, flat tread offers the possibility of using a latching device which distributes the bearing pressure over a relatively large area.

Previous constructions of this type have not, however, utilized the inherent possibilities above described, particularly in the area of latch mechanism construction. Conventional types of latch constructions have required serious weakening of the step structure in orderto operate successfully or have imposed highly localized and distortion-producing bearing pressures on that step engaged by the latches.

BRIEF SUMMARY OF THE INVENTION With the present invention, wide tread step construction having approximately the width of the side rails, thus leaving only a narrow clearance space between the adjacent edges of the steps of the ladder sections, may be employed while using latch mechanism which bears upon the step treads and distributes the bearing pressures over a substantial if not complete transverse extent thereof. To achieve this, the latching plate is pivoted along a vertical edge thereof about an axis confined within the stated clearance space and which axis is therefore disposed very close to the adjacent edge of the step upon which the latching plate bears. The lower edge of the latching plate bears completely or substantially completely across the tread at a position very close to the side rail, thus establishing a very robust and effective bearing support for the supported ladder section. To cam the latching plate aside when the ladder is extended, the remote side of the latching plate is suitably constructed to produce the requisite moment arm about the pivot axis. To cam the latching plate aside when the ladder is retracted, a camming paddle is provided at the lower end of a stem or depending projection of the latching plate. The stem extends substantially along the pivot axis so as to operate within the clearance space and the camming paddle is pivoted about a horizontal axis projecting laterally from the stem and is resiliently supported Patented Mar. 24, 1970 to lie horizontally in spaced relation below the latching plate. Upon descent of the ladder section carrying it, the camming paddle swings upwardly to strike the stem and thus arrest its upward swing, whereafter it exerts a moment arm upon the stem to swing the latching plate aside to clear the step with which the camming paddle is engaged.

BRIEF DESCRIPTION OF THE DRAWING FIGURES DETAILED DESCRIPTION OF THE INVENTION The general construction of an illustrative embodiment of the invention may be seen in FIGURE 1 wherein the ladder 10 will be evident as of the extension type having two

ladder sections

12 and 14, each comprising a pair of side rails and interconnecting steps. Thus, the ladder section 12 comprises the side rails 16 and 18 and a series of steps 20 while the ladder section 14 comprises the

side rails

22 and 24 and a series of steps 26. As may be seen better in FIGURE 3, the side rails 16 and 18 are provided with web portions 28 having smooth inner side faces and with inner and

outer flange portions

30 and 32 lending structural rigidity to the side rails. Similarly, the

side rails

22 and 24 include the web portions 34 having smooth inner side faces and the inner and

outer flanges

36 and 38. The

inner flanges

30 and 36 of the side rails of the two sections are in contact and are slidably interconnected by any suitable tongueand-groove structure, thus further lending structural rigidity to the assembly while also establishing the requisite guided, slidable connection between the sections.

FIGURE 3 also illustrates the fact that the steps are of widths approximately equal to the widths of the side rails to thus establish as comfortable and safe a tread as possible, leaving only a narrow clearance space 40 between the

adjacent edges

42 and 44 of the steps of the two

ladder sections

12 and 14. FIGURE 1 as well as FIGURE 3 serves to show that the latching mechanism is located so as to position the steps of the overlapping portions of the ladder sections in substantial alignment and, as shown in FIGURE 1, the latching mechanism is associated with the lowermost step 20 of the extensible ladder section 12.

In FIGURE 1, one latching mechanism is indicated therein by the reference character 46 but it will of course be understood that a mirror-image mechanism is located at a position opposite thereto. The constructions of these latching mechanisms may be appreciated from FIGURES 2 and 3 wherein it will be seen that a generally Z-shaped bracket is provided in each case, the base portion 50 thereof being secured by suitable fasteners 52 to the inner face of the web 28 of the associated side rail 16 or 18-, with the offset portion 54 serving to position the flange 56 so as to clear the side rail flange 30. A hinge plate 58 is secured to the flange 56 and carries a pintle 40 and establishing a pivot axis for the latching plate 62 which extends parallel to the

side rails

16 and 22. The 62 which extends parallel to the side rails 16- and 22. The vertical side edge portion 64 of the latching plate 62 receives the pin 60 as within the portions 66 (see also 3 FIGURE 4) between respective pairs of which the portions 68 of the hinge plate 58 are located.

A section of the pintle pin is exposed between the hinge regions and a suitable torsion spring 70 is received thereon, its opposite ends 72 and 74 bearing against the latching plate 62 and the hinge plate 58 normally urging the former to the position shown in FIGURES 2, 3 and 4. The lower edge of the latching plate is bent to form a bearing foot 76 which, in the operative position, bears upon the tread of one of the steps 26 commencing at the edge 44 thereof to extend substantially completely across the step.

A feature of the invention is the fact that the pivot axis established by the pin 69 is very close to the steps 26 and is also oriented to allow the bearing foot 76 of the latching plate to bear upon the step at a position very close to the side rail 22 or, in the case of the counterpart to the latching mechanism shown in FIGURE 3, very close to the side rail 24. These relationships are fundamentally important since they first of all impose a minimal moment arm upon the hinge structure, they distribute the bearing loads over large areas of the steps 26, and they place the bearing loads on the steps at points of maximum structural rigidity so that the least likelihood of structural damage or permanent deformation of the steps is assured.

The latching plate 62 may be twisted as shown so that it presents an outer or free edge portion 80 which, as shown in FIGURE 5, is adapted to engage the successive steps 26 of the ladder section 14 and cam the latching plate aside to clear them. As is usual, when the ladder has been extended the desired amount, the ladder section 12 is released as soon as the latching plate 62 has cleared the desired step, whereupon the parts will assume the position of FIGURE 3 due to the return action of the spring 70.

In order to retract the ladder, the latching plate 62 is provided, substantially as an extension of its vertical edge 64, with a depending stem 82 which is located within the clearance space and which may be suitably reinforced as by the plate 84 but which, in any case, lies very close to or upon an extension of the pivot axis established by the pin 60. This allows the stem 82 to be of a width nearly as large as the width of the clearance space while still allowing the stem to rotate without interference, it being appreciated that the latching plate and its stem 82 rotate together.

A bracket 86 is carried by the stem 82 and projects laterally therefrom substantially at a right angle to the foot 76 of the latching plate and this bracket is hinged to the camming paddle 88 by means of the pintle pin 90, the paddle 88 normally being held in horizontal position in underlying relation to the latching plate by means of the torsion spring 92 whose

opposite ends

94 and 96 bear against the outer faces of the bracket 86 and the paddle 88 to support the weight of the latter.

The main body 98 of the paddle is in one plane whereas the side edge portion 100 thereof is bent to lie substantially in a vertical plane. The vertical edge portion 100 includes a heel portion 102 which is adapted to be swung into abutting relation with the stem 82, as is shown in FIGURE 4, when the ladder is retracted and the paddle strikes a step 26 and is swung thereby about its pivot 90. Since the paddle may swing no further about its pivot 90 and since the engagement between the main body 98' of the paddle and the step 26 is offset from the vertical pivot axis of pin 60, a moment arm is exerted upon the latching plate and its stem to swing the latching plate aside to clear the step 26.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While the presently illustrative embodiments of the invention are given for the purpose of disclosure, numerous changes in the details of construction and arrangement of parts may be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. An extension ladder comprising a pair of ladder sections slidably connected together,

each section comprising parallel side rails and a plurality of steps fixed at spaced intervals along said ladder sections,

latch means carried by one of said ladder sections to hold the ladder in an extension position, said latch means comprising a latch plate pivotally connected along one side thereof to said one section about an axis extending longitudinally with respect to said side rails for movement between a latching position, in which it projects outwardly from said one ladder section to engage over and rest upon a step of the other section, and a cammed position in which it is rotated approximately about its pivot axis to clear the steps of the other ladder section and lie between said ladder sections, and

means for camming said latch plate to its cammed position during descent of said one ladder section.

2. The extension ladder according to claim 1 wherein the last mentioned means comprises a camming paddle, said latch plate having a depending stem, and said camming paddle being carried by said stem.

3. The extension ladder as defined in claim 2 wherein said camming paddle is pivotally secured to said stern about a generally horizontal axis, said camming paddle having one side portion adapted to abut said stem and an opposite side portion to rotate said stem about said pivot axis.

4. The extension ladder according to claim 3 wherein said stem is substantially aligned with said pivot axis.

5. The extension ladder as defined in claim 4 including spring means normally holding said camming paddle in horizontal position.

6. The extension ladder as defined in claim 5 wherein said steps are wide tread steps having a flat tread portion of a width approximating the width of said side rails.

7. In an extension ladder of the type having a pair of ladder sections, each comprising a pair of parallel side rails and a plurality of wide tread steps fixed at spaced intervals along said ladder sections, the corresponding side rails of the two ladder sections being directly slidable against each other and interconnected by tongue-andgroove means and each of said steps having a flat tread portion of a width approximating the width of said side rails whereby only a narrow space is left between the adjacent edges of the steps of one ladder section and the steps of the other ladder section, the improvement comprising:

latch means carried by one ladder section to hold the ladder in an extension position with the steps of the overlapping portions of the two ladder sections disposed in alignment, said latch means including a latch plate having a vertical side edge portion pivoted to said one ladder section about an axis contained between said narrow space and extending parallel to the longitudinal direction of the ladder, said latch plate having a bottom edge substantially coplanar with the tread portion of a lower step of said one section, said bottom edge being adapted to overlie and rest upon the tread portions of the steps of the other ladder section whereby to hold the steps of the overlapping portions of the ladder sections in alignment as aforesaid, said latch plate having a depending stem portion dimensioned to be accommodated in said narrow space and projecting downwardly from the latch plate within the confines of said narrow space substantially in alignment with said pivot axis, said stem having a laterally projecting bracket disposed below said lower step, a camming paddle pivoted on said bracket about a generally horizontal axis extending in the direction of projection of said bracket from said stem, spring means normally holding said camming paddle in substantially horizontal position underlying said latching plate, said camming paddle having a portion on one side thereof adapted hold the ladder in an extension position, said latch means including a latch plate pivotally connected along one side thereof to said one section about an axis extending longitudinally with respect to said side rails for movement between a matching position, in

to abut said stem when said camming paddle is 5 which it projects outwardly from said one ladder pivoted upwardly incidental to engagement thereof section to extend over and rest upon a step of said with a step of said other ladder section during descent other section, and a cammed position, in which it is of said one ladder section and presenting, in that rotated approximately 90 about its pivot axis to position, a portion adapted to exert a turning moment 10 clear the steps of said other ladder section, and spring on said stem to swing said latching plate aside in r means for urging said latch plate toward its latching sponse to further descent of said one ladder section position, said latch plate defining a first camming to clear said step of the other ladder section, and said surface for intermittently moving said latch plate latching plate having a portion spaced from said to its cammed position as said latched plate passes vertical edge thereof for swinging said latching plate 15 said steps of said other ladder section during ascent aside in response to engagement thereof with a step of said one ladder section, and

means for camming said latch plate to its cammed posi of said other ladder section upon ascending rnovetion during descent of said one ladder section.

ment of said one ladder section. 8. An extension ladder comprising a pair of ladder sections slidably connected together, 20

each section comprising parallel side rails and a plurality of steps fixed at spaced intervals along said ladder sections, latch means carried by one of said ladder sections to References Cited UNITED STATES PATENTS 434,176 8/1890 Crafts 182209 REINALDO P. MACHADO, Primary Examiner