Patent Application
20160230792
The present invention relates generally to the mechanical fastening of materials and more particularly to mechanical fastening of materials where one of the materials to be joined is a barbed sheet textured with raised and pointed barbs.
Short, press-in fasteners suffer from low pull-out strength as exemplified in the extreme by a thumbtack pressed into foam. This is because such fasteners rely solely on the friction created by the shank spreading apart the substrate.
Screw-in fasteners on the other hand provide much greater pull-out strength but require more time and effort to rotate the screw into the substrate. The increase in pull-out strength is achieved due to the fact that substrate material is trapped or captured between the threads of the screw while the substrate material remains contiguous with the surrounding substrate material. The result is that considerably more force is required to pull out a screw out as compared to a press-in fastener.
The present invention provides a textured sheet of ductile material with barbs extending from a face of the sheet of ductile material. Some or all of the barbs are self-locking barbs. Each self-locking barb is curved so that one side is convex and an opposite side is concave, and a thrust line that is perpendicular to the face of the sheet of ductile material lies entirely within each self-locking barb. As a result, when a self-locking barb is pushed (or pressed) into a substrate, the self-locking barb deflects, increasing the concavity of the concave side of the self-locking barb while the self-locking barb fully penetrates into the substrate so that the textured sheet of ductile material is bound to the substrate with a portion of the substrate material above an end portion of the self-locking barb, thereby providing pull-out resistance.
Some or all of the self-locking barbs may be coated with hard particulate material. Preferably all of the self-locking barbs are coated with hard particulate material. The hard particulate material may be abrasive grains adhered to the barbs. For example, the hard particulate material may include sand, aluminum oxide, silicon carbide, garnet or emery.
The invention also provides a textured sheet of ductile material with barbs extending from a face of the sheet of ductile material, where a portion of the textured sheet is curved so that the textured face in the curved portion of the sheet is concave. The textured sheet can then be bonded to a substrate by pressing the textured face of the sheet into the substrate, causing the curved portion of the sheet to flatten as the barbs are penetrating the substrate so that lateral force is applied to the barbs in the curved portion of the sheet and at least some of the barbs in the curved portion of the sheet deflect while they are entering the substrate. As a result, a portion of the substrate material is above end portions of at least some of the barbs, thereby providing pull-out resistance. There may be multiple such curved portions of the textured sheet.
The invention also provides a method of attaching a sheet of barbed material to a substrate. The sheet of barbed material has a textured face with barbs extending from the face. The substrate is made of a barb-penetrable material and has a substantially flat face. In this method, a portion of the sheet of barbed material is positioned to be proximate to the substrate so that the portion of the sheet of barbed material is curved away from the substantially flat face of the substrate. In this position, the textured face of the portion of the sheet of barbed material is not parallel to the substantially flat face of the substrate and the barbs on the portion of the sheet of barbed material are proximate to the flat face of the substrate. Then the portion of the sheet of barbed material is pressed into the substrate while the sheet of barbed material is being rotated so that the barbed face of the portion of the sheet of barbed material becomes parallel to the substantially flat face of the substrate when the barbs in the portion of the sheet of barbed material are fully embedded in the substrate. The rotation of the sheet of barbed material causes the barbs to deflect as they enter the substrate so that portions of the substrate material are above end portions of at least some, and preferably all, of the barbs in the portion of the sheet of barbed material, thereby providing pull-out resistance.
The pressing of the portion of the sheet of barbed material into the substrate may be performed by a roller. Some or all of the barbs in the portion of the sheet of barbed material may be self-locking barbs. Each self-locking barb is curved so that one side is convex and an opposite side is concave, and a thrust line that is perpendicular to the textured face of the sheet of ductile material lies entirely within each of the self-locking barbs. When each of the self-locking barbs is pressed into a substrate, the self-locking barb deflects, increasing the concavity of the concave side of the self-locking barb while the self-locking barb fully penetrates into the substrate.
The invention also provides a laminate made from a sheet of ductile material and a substrate. The sheet of ductile material has barbs extending from a face of the sheet of ductile material. The sheet of ductile material is mated to a substrate by some or all of the barbs of the sheet of ductile material being embedded in the substrate so that for each of a plurality of the embedded barbs, a portion of the substrate is above an end portion of the embedded barb, thereby providing pull-out resistance. Some or all of the embedded barbs may be self-locking barbs such that each self-locking barb is curved so that one side is convex and an opposite side is concave. In such embodiments, prior to the sheet of ductile material and the substrate being mated, a thrust line that is perpendicular to the face of the sheet of ductile material lies entirely within the self-locking barb and when the self-locking barb is pressed into the substrate, the self-locking barb deflects, increasing the concavity of the concave side of the self-locking barb while the self-locking barb fully penetrates into the substrate.
The invention provides textured sheets of a ductile material, such as metal (e.g. steel), with multiple “self-locking barbs” on a face of the sheet of ductile material. The textured sheets are adapted, as described herein, to be used in the formation of laminates where a layer of a substrate material, such as hard foam or wood, is pressed against the textured face with the self-locking barbs which are configured so that the barbs penetrate the substrate and lock the two layers together in a laminate.
The barbs are made to self-lock in a substrate to increase pull-out resistance by the deflection of at least some of the barbs while they are entering the substrate. In one embodiment the shape of the barbs is optimized to ensure straight-in entry after which the design of the barb generates unequal forces causing its path into the substrate to deflect from a straight path. A capture zone is thereby created to lock or trap the barb in the substrate.
Optionally, the barbed sheet may be curved before mating with the substrate, causing the barbs to angularly fan out from perpendicular before they enter the substrate, and then, as they enter, they are forced to transition back to perpendicular causing them to deflect and self-lock.
Adding secondary material to the barbs can also be used to deflect them and cause self-locking.
As used herein, “barb” and “piercing member” describe any type of nail-like or pin-like structure, or hooked structure, raised from the surface of a material by carving, gouging, planing or scraping its surface, such as is described in Canadian patent numbers 1,330,521, 1,337,622, and 2,127,339 and in Canadian patent application number 2,778,455, all of which are hereby incorporated in their entirety herein by reference. The use of such textured materials to form laminates is described in Canadian patent application numbers 2,778,455, 2,821,897 and 2,855,378, and U.S. patent application Ser. Nos. 14/532,739 and 14/533,218, all of which are hereby incorporated in their entirety herein by reference.
Certain forms of barbed materials are available from Nucap Industries of Toronto Canada.
In
Examples of suitable substrates for use, for example, with metal or steel barbed sheet material include wood, particle board, hard foam and other such “expanded” or “composite” substrates, and pliant materials such as softer plastics and metals. In order to be “suitable”, the substrate material should “give way” to a deflecting barb as the barb penetrates it.
In
a, show another self-locking embodiment where the barbed sheet material 1 is provided with wavy ends 1a that effectively shorten its length so that it ends at point 20a rather than point 20b as it would if it were flat. Barbs 3d (
A rigid pressure plate A positioned above the barbed material has a recess with side clearance C to hold an elastomer pad B. Barbs 3 under the pad B are first pressed into the substrate 30 as the elastomeric pad B is compressed and squash-flows sideways into clearances C. Further downward travel brings the end portions of the rigid plate A against the wavy ends 1a of the barbed material, which are gradually pressed flat as the pad B is further compressed. This flattening causes lateral movement of the barbs 3d as they simultaneously enter the substrate 30. The effect of the two movements, downward and lateral, causes deflection of the barbs 3d. That is, the barbed material 1 with waved ends 1a starts out shorter and becomes marginally longer while the barbs 3d are entering the substrate 30 and creating capture zones 40, resulting in the desired self-locking action.
In
The hard particulate material 50 may be, for example, sand, aluminum oxide, silicon carbide, garnet, emery and the like.
In should be noted that in some methods of making laminates as described herein, where a barbed sheet is locked to a substrate by having curved barbs embedded in the substrate with a capture zone of substrate above them to add pull out resistance, while the laminate is being formed, the substrate may be “torn” by lateral movement of the barb shank near the base of the barb caused by lateral forces on the sheet of material. In such cases, it is preferred that the substrate be selected to be a resilient material so that it will, at least in part and preferably mostly, return into the space temporarily created by the tearing so that some of the substrate is above the barb in the region of tearing. This is not an issue in methods where the locking is predominantly achieved by deflection of the barb by lateral forces acting on the barb shanks, for example as the formation methods shown in
It should be understood that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are only examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention as will be evident to those skilled in the art. That is, persons skilled in the art will appreciate and understand that such modifications and variations are, or will be, possible to utilize and carry out the teachings of the invention described herein.
Where, in this document, a list of one or more items is prefaced by the expression “such as” or “including”, is followed by the abbreviation “etc.”, or is prefaced or followed by the expression “for example”, or “e.g.”, this is done to expressly convey and emphasize that the list is not exhaustive, irrespective of the length of the list. The absence of such an expression, or another similar expression, is in no way intended to imply that a list is exhaustive. Unless otherwise expressly stated or clearly implied, such lists shall be read to include all comparable or equivalent variations of the listed item(s), and alternatives to the item(s), in the list that a skilled person would understand would be suitable for the purpose that the one or more items are listed.
The words “comprises” and “comprising”, when used in this specification and the claims, are to used to specify the presence of stated features, elements, integers, steps or components, and do not preclude, nor imply the necessity for, the presence or addition of one or more other features, elements, integers, steps, components or groups thereof.
The scope of the claims that follow is not limited by the embodiments set forth in the description. The claims should be given the broadest purposive construction consistent with the description and figures as a whole.
