Ladder stabilization apparatus

A ladder stabilization apparatus attaches to a ladder to provide safety and stability for the ladder's user when the ladder is supported by a tree, a post, a pole, or other non-flat surface. The stabilization apparatus attaches rigidly to the ladder and uses a concavely shaped device with a knife edge, multiple teeth, or rubber gasket to grip the tree, post, or pole, thereby securing the top of the ladder to the non-flat surface. When not in use, the concavely shaped gripper plate can be removed and attached to the ladder in a flat storage position, allowing the ladder to be used against typical flat surfaces.

DETAILED DESCRIPTION OF THE INVENTION One embodiment of the present invention is depicted in FIGS. 1 through 7 C and is generally denoted by reference number 10 . The depicted embodiment represents the best mode, known at present, for practicing the invention. A variety of other embodiments could certainly be imagined by one skilled in the art, using the same general design and achieving similar objectives. FIG. 1 is an exploded assembly, showing examples of components of one embodiment of the present invention. Gripper plate B makes contact with a tree, pole, or other object against which a ladder L is to be positioned. Mounting plate A can be used to secure gripper plate B to the ladder L, although some embodiments of the invention comprise a gripper plate or similar gripper device attached directly to the ladder. In one embodiment of the invention, angle block C attaches either to the mounting plate or directly to the ladder L. Angle block C or a similar device enables the attachment of gripper plate B essentially in a flat position against the ladder, providing a convenient means for storing gripper plate B, and allowing mounting plate A or other mounting hardware to remain attached to the ladder for later use. In the illustrated embodiment of the present invention, fasteners can be used to rigidly attach angle block C to mounting plate A, although angle block C might also be permanently attached to mounting plate A by welding, or could be part of mounting plate A itself, fabricated as one piece. A set of U-bolts 3 and associated wing nuts 4 are used in one embodiment of the present invention to secure mounting plate A to the ladder, and a corresponding set of U-bolt clamps D provide a firm, stable surface against which a set of wing nuts or other fastening hardware can provide secure attachment. In the depicted embodiment, a pair of threaded knobs 1 secure gripper plate B to mounting hardware, for example to mounting plate A as illustrated. A set of shear pins 2 , dowels, or similar hardware can be used to fix the position of gripper hardware in relation to mounting hardware, to prevent slippage, and to resist forces applied to the ladder or applied to the gripper in a direction essentially perpendicular to the pins. The pair of threaded knobs 1 provides a means to secure a gripper device to mounting hardware, for example by pulling gripper plate B down snug against mounting plate A. An additional safety device, such as strap 6 (see FIGS. 7A, 7B , and 7 C), or a cord, or a cable, can be attached to the ladder or to other components of the present invention and secured to the tree or pole to provide redundant means for stabilization. In the embodiment of the present invention depicted in FIG. 1 , mounting plate A is rigidly attached to the uppermost step S of a ladder L by a set of U-bolts 3 , passing through mounting plate A and U-bolt clamps D, and secured by wing nuts 4 . Mounting plate A has an optional pair of flanges A 1 , one at each end, which slip over the legs (L 1 and L 2 ) of the ladder L for added security. An embodiment without optional flanges A 1 , is illustrated in FIG. 4B . Conversely, an embodiment is also envisioned (not shown) in which flanges A 1 allow clamped attachment solely to the legs (L 1 and L 2 ) of the ladder L, fastened securely enough so that U-bolts 3 and other hardware are not required. Such an embodiment would make attachment to a rung of the ladder unnecessary. Referring back to FIG. 1 , Gripper plate B is rigidly attached to mounting plate A, using shear pins 2 which pass through aligned holes B 2 and A 2 in gripper plate B and mounting plate A, respectively. Gripper plate B is further secured by threaded knobs 1 , which pass through optional slots B 1 , in gripper plate B, providing adjustable (fore and aft) positioning of gripper plate B, and then mate with aligned, threaded holes A 4 in mounting plate A. Threaded knobs 1 consist of threaded fasteners equipped with knobs which allow them to be tightened and loosened for assembly and disassembly by hand. Angle block C rigidly attaches to mounting plate A by bolting or other mechanical attachment technique, and provides a surface C 1 parallel to the length of the ladder. Parallel surface C 1 provided by angle block C is drilled and tapped so that gripper plate B, when removed from mounting plate A, can be rigidly attached to angle block C in a position flat against the ladder, convenient for storage when not in use. In a prescribed storage position (see FIG. 5C ), gripper plate B is attached to angle block C using threaded knobs 1 , the same threaded knobs 1 otherwise used to attach gripper plate B to mounting plate A when gripper plate B is in its functional position. Safety strap 6 (See FIGS. 7A, 7B , and 7 C) attaches to eyebolts, other attachment hardware, or strap attachment holes A 6 at each end of mounting plate A, and passes around the tree or pole against which the ladder leans, in order to further secure the ladder. Also in the illustrated embodiment of the present invention (see FIGS. 7 A-C), string or light cable (not shown) can be attached from one end of each shear pin 2 to small drilled holes in the mounting plate A to prevent shear pins 2 from being dropped when not in functional position. All components of the apparatus depicted in FIG. 1 , with the exception of the string or cable and the safety strap, are preferably fabricated from a suitable structural, corrosion-resistant material such as stainless steel, aluminum, composite, or high-strength plastic. Referring now to FIG. 2 , one embodiment of a gripper plate B is depicted. In the depicted embodiment, the gripper plate B is shown as a flat plate of appropriate material with a section (B 3 ) designed to engage a tree, a post, a pole, or other non-flat object against which a ladder may lean. In the illustrated embodiment of the present invention, a substantially V-shaped cut-out B 3 is designed such that a tree may fit into the V-shaped region, preventing the ladder from moving from its position against the tree. In the depiction, the substantially V-shaped region is lined with either a knife-edge (not shown), which may cut into the surface of a tree, or a plurality of teeth B 4 (as shown), which may bite into (i.e. grip) the surface of a tree. One practiced in the art will recognize that a variety of geometries might be substituted for the V-shaped cut-out B 3 . For example, a substantially circular, elliptical, or parabolic curve might provide an appropriate concave shape to engage and to help grip a non-flat surface securely. Elliptical or parabolic curves, like the V-shaped cut-out B3, may actually grip the tree or pole more firmly, as the weight of the ladder user causes the tree to become more securely pressed into the decreasing curvature. Also, aside from the flat gripper plate, one skilled in the art could envision trusses, boxes, or other structures, other than flat plates, which might support a concave shape capable of engaging with a tree or pole. Additionally, as depicted in FIG. 3A, a rubber friction-producing boot 3 A might be attached to the gripper plate B to provide friction with the tree or pole. A rubber friction-producing boot may be fabricated as an integral part of the gripper hardware for any application, or it might be used as an add-on component specifically when a ladder is leaned against a metal pole or other surface not conducive to gripping by teeth or knife-edges. Referring back to FIG. 2, a gripper plate B or other gripper hardware may be equipped with slots B 1 through which threaded knobs or fasteners might pass, to allow the gripper to be fixed at varying positions with respect to the ladder; for example, if the ladder user prefers to be closer to, or farther from, the surface against which the ladder leans. A set of holes B 2 may be provided also, to allow the use of one or more shear pins 2 to help secure the gripper plate B in position. Referring back to FIG. 3A, a boot 3 A may be fabricated from rubber or other friction-producing material, such that its curvature (or other geometry) matches that of gripper plate B (e.g. B 3 of FIG. 2 ). As illustrated, boot 3 A may be molded or machined with a V-shaped cross-section to enable it to fit over the biting or gripping edge of a gripper plate B. A rubber boot like the one depicted may be used to enhance the gripping ability of a gripper plate in operation against a tree or wooden pole, or it might be used specifically to create function against harder surfaces, such as metal poles. A rubber boot may also be made an integral part of the gripper hardware, as opposed to being a add-on component. For example, although FIG. 3B depicts a U-shaped cross section of boot 3 A assembled over the teeth B 4 of gripper plate B, a rubber boot can be permanently molded to the curved edge of a gripper plate for use solely in conjunction with metal poles. Referring now to FIGS. 4A and 4B , a mounting plate A is depicted. Although a gripper plate B can be fabricated to mount directly to a ladder, a mounting plate A can be attached rigidly to the ladder, and a gripper plate B then attached rigidly to the mounting plate A. In the illustrated embodiment of the present invention, mounting plate A is depicted as a flat plate of structural material with cut-out areas A 5 in optional flanges A 1 , allowing the passage of a typical pair of ladder legs. ( FIG. 4B illustrates an embodiment of a mounting plate A 0 without optional flanges.) The ladder leg cut-outs A 5 in flanges A 1 (of FIG. 4A ) should be of such spacing and dimensions that the mounting plate A can be slipped over the legs of most commercially available ladders. The depiction also shows that a mounting plate A may include means for fixing the mounting plate A in place, for example clearance holes A 3 , through which U-bolts may pass in order to secure the mounting plate A to the uppermost step of the ladder. A mounting plate A may also include means for rigidly attaching gripping hardware, such as gripper plate B. The FIG. 4A illustration shows a pattern of drilled and reamed holes A 2 and a pattern of tapped holes A 4 , which may allow a combination of shear pins 2 and threaded fasteners or threaded knobs 1 , respectively, to rigidly attach a gripper plate B to a mounting plate A. One skilled in the art can readily envision a variety of other methods by which mounting hardware might attach to a ladder and to a gripping apparatus. In addition, other features might be added to any of the above designs. For example in FIG. 4 A, the illustrated embodiment of the present invention includes strap holes A 6 allowing the attachment of a safety strap 6 (see FIGS. 7A, 7B , and 7 C), to provide redundant security in holding a ladder against a tree or pole. An indentation N may also be fabricated into the surface of a gripper plate B (see FIG. 2 ), to allow the placement of tools or other hardware. The present embodiment of angle block C, gripper plate B, or mounting plate A can also include holes through which one end of a set of strings or cords may be secured, the other ends attached to the shear pins 2 to prevent them from being dropped from the ladder. Additionally, FIG. 5C shows that means may be provided for gripper plate B to be attached to mounting plate A in a storage position when not in use. Likewise, FIG. 5D shows gripper plate B attached to mounting plate A so that the gripper plate is stored on the opposite or lower side (i.e. tree or pole side) of the ladder L. One skilled in the art of mechanical design can envision a variety of storage assemblies enabling the normal use of the ladder against flat surfaces while gripper plate B is not in use. The safety advantages to gripper plate storage out of the way of possible interference with the user's foot access to ladder rungs is clearly understood to the user of a ladder. Referring to FIG. 5 A, an angled bevel C 1 with tapped holes C 2 allows the attachment of angle block C to which gripper plate B can be mounted in a position flat against the ladder. In the illustrated embodiment (see FIGS. 5A, 5C and 5 D), a 15-degree bevel may be used in order to accommodate the typical angle of most ladder steps. When mounting plate A is rigidly attached to the flat side of a typical ladder step, it typically will be oriented at an angle of about 15 degrees off the perpendicular to the ladder's length. An approximately 15-degree bevel on mounting plate A allows a gripper plate B to attach at the correct angle to facilitate flat storage attachment against the ladder. Referring back to FIG. 4B, a bevel A 5 may be cut directly into mounting plate A 0 (or A) to allow attachment of a gripper plate B in storage position. Alternatively, angle block C may be attached to mounting plate A or A 0 , and gripper plate B attached to angle block C. Referring again to FIG. 5 A, one embodiment of angle block C is depicted. Angle block C fabricated for use in the illustrated embodiment of the present invention may be made from appropriate structural materials, and sized to essentially span the width of mounting plate A. Angle block C may contain clearance holes C 3 through which fasteners, such as cap screws, may rigidly attach angle block C to mounting plate A. Those practiced in the art may envision other embodiments, such as mounting plate A machined such that angle block C is an integral part of mounting plate A, or an embodiment in which angle block C is welded to mounting plate A. Regardless of its method of attachment, angle block C provides a surface (see bevel C 1 ) upon which gripper plate B, or other hardware, may be attached. In the illustrated embodiment of FIG. 5 A, angle block C has a beveled edge which provides a surface (bevel C 1 ) parallel to the ladder length, so that hardware such as gripper plate B may be rigidly attached in a storage position parallel to the ladder, e.g. flat against the ladder (see FIG. 5A ). The illustration of FIG. 5A depicts a 15-degree bevel C 1 which corresponds to the angle formed by the steps of essentially most commercially available ladders, in relation to a line perpendicular to the ladder length. Tapped holes C 2 in angle block C can correspond to a similar hole pattern in gripper plate B, such that gripper plate B may be attached to the angle block C, for example for convenient storage. Referring to FIG. 6 , one embodiment of a U-bolt clamp D is depicted, which may assist in enabling the rigid attachment of mounting plate A to a ladder. In the embodiment illustrated in FIG. 1, a set of wing nuts 4 tighten against a corresponding set of U-bolt clamps D to enable a set of U-bolts 3 to rigidly attach a mounting plate A to the uppermost step S of a ladder. The set of U-bolts 3 may comprise as few as one U-bolt, although at least two would be preferable. The illustration of FIG. 6 depicts a U-bolt clamp D of sufficient dimension to span the width of a U-bolt 3 , having a hole pattern D 1 matching the dimensions of the threaded ends of the U-bolt 3 . A U-bolt clamp D should be of sufficient thickness, and fabricated from appropriate material, to serve in essentially the same function as a washer, providing a hard surface against which a wing nut 4 or other nut might tighten, and protecting any mounting plate A or other hardware underneath the U-bolt clamp D from wear or deformation. In other embodiments, one might substitute other hardware, such as flat washers, for U-bolt clamps. Referring now to FIGS. 7A, 7B , and 7 C, procedures are depicted for assembling the present invention for use with a ladder, and top views are illustrated for three configurations of the assembly. In FIG. 7 A, the present invention is shown securing a ladder against a tree T. FIG. 7B depicts its use against a wooden pole W. FIG. 7C shows the present invention used against a metal pole M, with the rubber boot 3 A in place to provide a frictional engagement between gripper plate B and the pole M. In all three configurations, a safety strap 6 is in place to reinforce secure attachment to the tree or pole. The top views also illustrate the relationship between the slots B 1 and threaded knobs 1 , and shear pin holes A 2 , as they may be coordinated to set a ladder in its position with respect to a tree or pole. When assembled as described in this specification, the present invention provides a means for safely securing a ladder supported by a tree, a post, a pole, or other non-flat surface. As soon as the ladder is leaned against the tree, engaging the gripper plate with the surface of the tree, the present invention becomes functionally effective. As the operator of the ladder climbs upwardly, the gripper plate becomes even more securely engaged, due to the force applied by the operator's weight. The subject invention is simple in assembly, structurally sound, and has no moving parts, thereby minimizing possible modes of failure or malfunction. Further to the structural integrity and functional stability of the present invention, the security provided by the apparatus is redundantly ensured when the operator tightens the safety strap around the tree. The present invention therefore provides the means to use a ladder in an otherwise precarious circumstance (i.e. without a firm, flat surface against which to lean the ladder). Additionally, the design allows the gripper plate to be removed conveniently when not required, and stored flatly against the ladder while the ladder is used in more inherently stable applications against typical flat surfaces. In conclusion, the descriptions of the present invention represent the invention in its preferred embodiment. It should be clearly understood that additional changes in the details, materials, assembly procedure, and arrangement of parts may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Although the invention has been described relative to a specific embodiment, there are numerous variations that will be readily apparent to those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.