Patent Application
20230330491
This invention relates generally to tree climbing sticks used for climbing the trunk of a tree.
Tree climbing sticks, or simply, climbing sticks, are used by outdoor enthusiasts for scaling trees. For example, a day hunter may temporarily secure one or several climbing sticks up the trunk of the tree in order to access an elevated tree stand or platform. Such climbing sticks are designed to be portable and typically are carried into the woods by the hunter, installed on the tree to be climbed, and then removed after the day hunt. As such, climbing sticks are available in a variety of shapes and sizes geared toward portability and ease of use. Most climbing sticks include a central post (the “stick”) which extends between top and bottom ends and mounts a set of tree-engaging standoffs and foot-engaging steps at each end. A user secures the climbing stick to the tree by bracing V-shaped jaws of the standoffs against the trunk and then wrapping a line about the backside of the tree and cinching it to one or more attachment brackets fixed to the post.
The central post of a climbing stick is usually made of sturdy tubular stock, such as square steel or aluminum tubing, and the wall thickness is sufficiently thick to resist flexing of the post under the weight of a user when climbing the steps. Such robust posts, however, are heavy and some users find the weight objectionable especially when having to carry several climbing sticks into and out of the woods during a day hunt with each stick weighing several pounds.
U.S. Pat. No. 11,198,038, discloses a tree climbing stick that corresponds closely to a climbing stick sold by Tethrd, Inc. under the brand name “Tethrd One” and which is illustrated in
This prior art Tethrd One climbing stick is reported as being very light weight, with each climbing stick said to weigh less than one pound. The reduced weight is achieved in part by using thin-walled titanium alloy tubing for the post 12 and precision-machined aluminum for the standoff-step-collar components. Literature states that the alloy used for the tubing is Grade 9 TI-3 Al-2.5V aerospace seamless titanium tubing, and has been observed to have an outer diameter of about 1 inch and a wall thickness of about 0.04 inches, giving it a very high diameter-to-wall thickness ratio in the range of 25:1. It has been observed that the titanium tubing of this product, while extremely light and very hard and stiff in hand, nonetheless bends and flexes noticeably under load when a user places his or her body weight on the steps, but then recovers when the load is removed. In fact, the tube has been observed to flex elastically inward toward the tree by as much as much as 1 inch or more about midway between the top and bottom step when under load. It has also been observed that the joint connection between the collars 22 and tube ends 14, 16 can loosen after flexing, causing the steps to rock on the post 12 under load, which may give the steps a slightly unstable or wobbly feel that a user might find objectionable. It has further been observed that the degree of tilting of the step, when the right or left step is loaded, exceeds the overall bending of the tube 12, meaning that there is further localized deformation of the tube ends 14, 16 near the collars 22 beyond the overall bend in the middle of the tube 12. The tilt angle of the steps is illustrated schematically in
The dissimilar materials used for the tube and standoff-step-collar components as well as the relative thinness of the tube/thickness of the collars make the option of welding parts together extremely difficult and commercially impractical. Adhesives and bonding agents also appear not to suffice as evidenced by the loosening of the joints due to the extreme flexing of the end portions within the joint under load. Selecting a different tube (e.g., heavy-walled steel) that could withstand the bending load without flexing in the joint would not be feasible since the one-pound weight threshold would necessarily be sacrificed. The prior art approach to securing the steps on the tube in a lightweight construction is thus faced with many challenges under difficult and dynamic loading conditions, attributed in part to material selection, geometries and practical or commercial restrictions of the present feasible options.
It is an object of the present invention to provide a lightweight climbing stick that does not suffer from the deficiencies of the stick described above, and particularly improving the integrity of the tube-step joints.
A tree climbing stick assembly includes a central tubular post that extends between opposite ends and is flexible in use under a bending load. At least one step is supported on the post at a joint. At least one stabilizing member is disposed within the tubular post in position to stabilize joint by restricting inward flexing of the tubular post at the joint.
According to a preferred embodiment, the step has a mounting collar portion which engages the outer surface of the tubular post at the joint to restrict radial outward flexing of the tube wall within the joint when under a bending load. The stabilizing member is disposed within the tube opposite the collar and acts to restrict radial inward flexing of the tube wall within the joint under the bending load. The preferred combination effectively immobilizes radial movement of the tube wall within the joint and improves the tightness and integrity of the step-tube joint over time by stabilizing the tube so there is no radial flexing in the joint when bending loads are imparted on the joint by a user stepping on a right or left side of the step that is cantilevered from the post.
According to a further aspect, an improved climbing stick has a post made of lightweight, thin-walled tubing, such as titanium, aluminum, magnesium, carbon, resin fiber, or steel and has end portions which flex radially inward under a bending load. At least one step is supported on at least one of the end portions at a joint and extends from the tube in cantilevered fashion such that when a load is placed on the step it imparts a bending load to the post. The inside of the tube is reinforced by a stabilizing member disposed within the tube in position to support the tube wall against inward flexing thus stabilizing the joint under the bending load.
According to a further aspect, the stabilizing member takes the form of a rigid plug that has a hoop strength exceeding that of the wall of the tubular post so that the plug supports the wall of the tube under the bending load without the wall and plug flexing inward under the load. The rigid plug is further preferably solid in cross section along at least part of its length.
This and other features and advantages will become better understood when considered in connection with the detailed description and appended drawings, in which:
The tubing of the post 32 may be made of metal such as steel, aluminum, titanium, magnesium, etc., or it may be made of a non-metallic material such as carbon fiber tubing. It will be understood that reference to tubing materials or that of other components includes alloys of these materials, such that reference to a titanium, steel, magnesium or aluminum tube or component encompasses their alloys.
The wall thickness of the tubing 32 is selected to provide sufficient strength to the post 12 to support the weight of a user that may impart various loads and stresses on the post 32. The material selection and wall thickness of the tube 32 may also be factored by the desire to produce a light weight climbing stick 30, for example one with a total weight of 1 pound or less. These various factors may yield a tubular post 32 that is sufficiently strong to support the weight of the user, but nonetheless may elastically bend and flex under load in various ways depending on how the forces are applied. As such, it is contemplated that the wall of the tubing may be strong and stiff, but yet flexible, such that the wall of the tube may tend to flex inwardly or outwardly including at the end portions 38, 40, and the post 32 may bend and flex intermediate its ends 34, 36. Thin-walled titanium alloy tubing is such a material, including Grade 9 TA-18, Ti-3 Al-2.5V tubing which may be a preferred material. It has a very high strength-to-weight ratio relative to steel or aluminum. It is very light weight (40% lighter than steel), very strong (twice as strong as aluminum) and very durable. Even so, such thin-walled titanium tubes flex under the compression and bending loads when used as the post for a climbing stick. Thin-walled steel and aluminum may also flex, as may other materials including carbon fiber tubes. By thin-walled, it is meant that the material and wall thickness of the tube is sufficiently strong to support the weight of the user and the loads and forces applied to the tube during extended use, but with attention also to weight minimization in an effort to produce a strong but light weight climbing stick. For example, and according to a preferred embodiment, a length of Grade 9 TA-18 titanium tubing may be used having a length of about 457 mm with a nominal outer diameter of 25.4 mm and a nominal inner diameter of 24.6 mm, yielding a nominal wall thickness of about 0.9 mm.
An additional challenge with light-weight, thin-walled tubing materials, such as titanium, is that the manufacturing tolerances of commercially available product are not true to shape. In other words, round titanium tubing is typically not perfectly round and may actually be significantly out-of-round so it tends toward oval. In the above example, the 25.4 mm OD and 24.6 mm ID represent an average, when in fact there are likely irregularities or variations about the circumference. The wall thickness is generally uniform, but there may be slight variations in surface texture due to manufacturing (e.g., die lines from extrusion). Steel, aluminum and carbon fiber tubing may experience similar shape discrepancies. While various cross-sectional shapes of the post 32 are contemplated (e.g., round, square, rectangular, hexagonal, etc.) round or circular is preferred as it yields the least amount of material and lends to reduced weight and cost. The misshapen tubing tends to be generally uniform along its length, such that the end portions 38, 40 may be similarly misshapen prior to assembly with the other components to be described.
The climbing stick 30 further includes at least one step 42 preferably located adjacent one of its ends 34, 36. It is more preferred that there are at least two steps 42, 44 and that an upper one 42 of the steps is provided adjacent the upper end 34 of the post 32, and that a lower one 44 of the steps is provided adjacent the lower end 36. It is still further preferred that the upper and lower steps 42, 44 each have left and right foot pads projecting from laterally opposite sides of the post 32 and denoted in the Figures as 42a, 42b and 44a, 44b, respectively.
The climbing stick 30 further includes at least one and preferably two tree braces or standoffs 46, 48 provided adjacent the upper and lower ends 34, 36 of the post 32, respectively. The standoffs 46, 48 may be separate structures from that of the steps 42, 44 or, as illustrated, may be combined as a single structure with each of the steps 42, 44 to yield upper and lower standoff-step components 50, 52.
The at least one step 42 is provided with a mounting collar 54 for attachment to the post 12. More preferably each of the standoff-step components 50, 52 are mounted to the post via respective collars 54, 56. Still more preferably, each of the upper and lower standoff-step components 50, 52 includes as part of its unified structure the collar 54, 56, respectively, for mounting to the post 32. The unified components 50, 52, including the collar portions 54, 56 may be fabricated of a suitable light-weight material such as aluminum and may be precision machined. As illustrated, the collars 54, 56 may be disposed between and join the respective left and right foot pads 42a, 42b and 44a, 44b. The standoffs 46, 48 may each have left and right portions, denoted 46a, 46b and 48a, 48b that project from a backside of the footpads 42a, 42b and 44a, 44b, respectively, and may further engage the collars 54, 56 along their inward edge. The standoffs 46, 48 present rearward-facing jaws 58 that face away and are spaced laterally from the steps 42, 44 and post 32 to define generally V-shaped cradles or braces adjacent the ends 34, 36 of the post 32 for engaging the trunk of a tree and supporting the post 32 and steps 42, 44 and collars 54, 56 in outwardly spaced relation to the tree.
The collars 54, 56 are mounted on the end portions 38, 40 of the post 32. More specifically, the collars 54, 56 are each formed with a bore 60 for receiving the respective end portion 38, 40 into the bore 60. Even more preferably, the ID of bore 60 is dimensioned relative to the OD of the end portions 38, 40 so that the end portions 38, 40 are received with a close fit, and preferably a press fit. The bore 60 is preferably machined and is cylindrical in shape and with a profile that is preferably round in cross section. The collars 54, 56 may be the same length as the thickness of the steps 42, 44 where they join the collars 54, 56. The size of the bores 60 may further take into account the out-of-roundness of the tubing material at the end portions 38, 40 and in achieving the pressfit also reshape the wall of the tubing to conform to the round shape of the bore 60. The bore 60 may be slightly undersized relative to the nominal OD of the end portions. In the example of where the end portions have a nominal OD of about 25.4 mm, the ID of the bore 60 may be 25.3 mm, with the 0.1 mm accommodating for out-of-roundness and achieving a tight friction fit with the OD of the end portions 38, 40. A press may be used to force the collars 54, 56 onto the end portions 38, 40. Once attached, a cross pin 62 may be installed in aligned cross bores through the collars 54, 56 and end portions 38, 40 to provide added strength to the collar-tube joints including in the axial and rotational directions.
The improved climbing stick 30 further includes at least one and preferably two retention or stabilizing plugs 64 that are disposed in the open end portions 38, 40 of the post 32 as illustrated in
The plugs 64 extend axially between an insertion end 66 and an exposed end 68. The plug 64 is preferably solid in cross section over at least part of the length of the collars 54, 56 and more preferably adjacent the insertion end 66. Alternatively, the plugs 64 may be cylindrical but with walls of sufficient thickness, strength and integrity (i.e., hoop strength) to resist any inward flexing of the end portion walls 38, 40 away from the collars 54, 56 that would loosen the joint.
As illustrated in 6, 7 and 9, the plugs 64 may be formed as a separate piece from the collars 54, 56. The plugs 64 may be precision machined from aluminum or other suitable material into a cylindrical shape and may include a chamfer or taper 70 at the insertion end 66 for guidance into and along the open end portions 38, 40 of the post 32. The plugs 64 may be the same length or longer than the length of the collars 54, 56 so that they provide support to the end portions 38, 40 over the full length of the collars 54, 56.
The plugs 64 may further include a cross slot 72 that is open at the insertion end and extending toward the exposed end 68. The cross slot 72 is sized and positioned to receive the cross pin 62 into the slot 72 when the plug 54 is pressed into the respective end portion 38, 40. The slot-to-pin registration further acts to orient the face of the exposed plug end 68 in an exact rotational orientation relative to the cross pin 62. The exposed end 68 of the plug 64 is preferably solid. The exposed end 68 may reside outside of the tube ends 34, 36, but is preferably pressed to be flush or even with the ends 34, 36 so that the plugs 64 are full pressed into and even with the edges of the end portions 38, 40. Advertising indicia 74 such as a company name logo or other information may be provided on the exposed end face 68 and aligned in position relative to the cross pin 62 so that is appears in the same repeatable orientation from product to product. For example, when looking face on to the installed plug 64, the indicia 74 may extend perpendicular to the cross pin 62 or be repeatedly oriented relative to another feature of the assembly. The portions of the plug 64 that extend around and past the pin 62 firmly engage the ID of the end portion in the same manner as the solid portion of the plug 64 above the pin 62. Alternatively, the plug may be solid end-to-end and contain a cross bore instead of a slot, in which case the plug is installed before installation of the pin which is received through the aligned bores of the collar, end portion wall and plug.
The orientation of the cross pin 62 and cross bores may be arranged at any orientation relative to the axis of the steps 42, 44, such as perpendicular, as illustrated, parallel, or somewhere in between.
The climbing stick 30 further includes at least one attachment bracket 78 for engaging a rope, cable or strap for removably securing the climbing stick 30 to a tree.
A method of making the climbing stick 30 includes obtaining a length of tubular post 32 material. The collars 54, 56 of the top and bottom components 50, 52 are pressed onto top and bottom end portions 38, 40 of the post 32. The cross pins 62 are installed in the cross bores drilled through the collars 54, 56 and end portions 38, 40. The plugs 64 are pressed into the open ends 34, 36 of the end portions 38, 40 and straddle the cross pins 62 which are received into the slots 72. The plugs 64 close off the open ends of the end portions 38, 40 and support the wall of the end portions 38, 40 from flexing or moving inwardly away from the collars 54, 56.
It is contemplated that one may wish to retrofit an existing stick with the reinforcing members 64 into order to prevent loosening of the joints or to stabilize joints that have already been compromised. In such case, one would align the plugs 64 and press or lightly tap the plugs 64 into each open end portion 54, 56, which will tighten the joints and prevent inward flexing of the tube wall within the joint.
In use, a person wishing to scale a tree orients the post 32 vertically and cradles the tree in the jaws 58 of the standoffs 46, 48. The strap, rope or cable is extended around the tree and the ends cinched tight and secured to the attachment bracket 76. The user may then climb the stick 30 and repeat the process by placing and securing additional climbing sticks 30 until the desired height is achieved. The weight placed on the steps 42, 44 by the user is transferred to the collars 54, 56 and to the post 32, and the post 32 might bend and flex, but not within the upper and lower collar-plug joints, which are isolated from such flexing and stress by the tight fit of the plugs 64 and collars 54, 56 to the inside and outside of the end portion wall 38, 40. Extended use of the improved climbing stick 30 is possible without loosening of the collar-plug joints.
It is to be understood that the invention may be practiced otherwise than as specifically described while still being within the scope of the invention. The invention is defined by the appended claims.
