Patent Grant
8635994
The field of the present invention relates to archery bows. In particular, multilayer composite limbs are disclosed herein for an archery bow.
Examples of conventional multilayer limbs for archery bows are disclosed in some of the following references. Examples of multilayer beams or leaf springs of somewhat analogous construction are disclosed in some other of the following references.
U.S. Pat. No. 2,665,678 entitled “Composite archery bow” issued Jan. 12, 1954 to Bear;
U.S. Pat. No. 2,815,015 entitled “Archery bow” issued Dec. 3, 1957 to De Giacomo;
U.S. Pat. No. 2,894,503 entitled “Archery bow” issued Jul. 14, 1959 to Pierson et al;
U.S. Pat. No. 4,712,533 entitled “High-speed bow limbs” issued Dec. 15, 1987 to Cruise;
U.S. Pat. No. 5,087,503 entitled “Composite constant stress beam with gradient fiber distribution” issued Feb. 11, 1992 to Meatto et al;
U.S. Pat. No. 5,194,111 entitled “Composite constant stress beam with gradient fiber distribution” issued Mar. 16, 1993 to Meatto et al;
U.S. Pat. No. 6,012,709 entitled “Hybrid leaf spring and suspension system for supporting an axle of a vehicle” issued Jan. 11, 2000 to Meatto et al; and
U.S. Pat. No. 6,679,487 entitled “Hybrid leaf spring with reinforced bond lines” issued Jan. 20, 2004 to Meatto et al.
An archery bow comprises a central riser, first and second bow limbs, and a draw cable. The first and second bow limbs are attached to the riser. The draw cable is coupled to the first and second bow limbs and arranged so that pulling the draw cable to draw the bow causes the first and second bow limbs to bend toward one another. Each of the first and second bow limbs comprises a multilayer composite structure having a compression layer, a tension layer, and an intermediate layer between the compression and tension layers. Each of said layers comprises corresponding fibers embedded in a corresponding polymer matrix. The first and second bow limbs are arranged on the bow so that drawing the bow causes each limb to bend toward its corresponding compression layer. The compression and tension layers each have a respective elastic modulus smaller than an elastic modulus of the intermediate layer. A method comprises attaching the first and second bow limbs to the riser and coupling the draw cable to the limbs. Another method can further comprise forming each bow limb by embedding the corresponding fibers of each layer in the corresponding polymer matrix, and curing the corresponding polymer matrix.
Objects and advantages pertaining to archery bow limbs may become apparent upon referring to the exemplary embodiments illustrated in the drawings and disclosed in the following written description or appended claims.
The embodiments shown in the Figures are exemplary, and should not be construed as limiting the scope of the present disclosure or appended claims.
Exemplary compound archery bows 10 are illustrated in
In the exemplary bow 10 of
The exemplary bow 10 of
As shown in the example of
When a bow limb bends as a bow is drawn, strain energy is stored in the bent limb. The strain imposed by bending the bow limb is tensile on one surface of the limb and compressive on the opposite surface of the limb; there is a surface within the limb (referred to as the neutral surface) along which there is no compressive or tensile strain. The strain energy density of the bent bow limb is therefore concentrated at the limb surfaces, particularly if the limb has a substantially uniform elastic modulus.
The multilayer composite bow limb 14 is constructed so that the elastic modulus is larger in the intermediate layer 130 than in the compression layer 110 or the tension layer 120. The distribution of strain energy is therefore shifted away from the limb surfaces and toward the intermediate layer 130. That shift can enable a variety adaptations of the multilayer composite bow limb's characteristics to achieve differing performance goals. In one example, using a stiffer (i.e., higher modulus) material for intermediate layer 130 can enable larger overall strain energy to be stored for a given amount of bending of the bow limb, without increasing the strain at the surfaces of the limb (and the corresponding increased likelihood of structural failure of the limb at one of its surfaces). Conversely, a given overall amount of strain energy can be stored while reducing the strain at the surfaces of the limb. In another example, multilayer limbs that are smaller (e.g., thinner or shorter) than single-modulus limbs can be employed to store the same overall strain energy without commensurately increasing surface strain. Conversely, more overall strain energy can be stored without increasing the size of the limb or the strain energy at the limb surfaces. Smaller limbs offer various advantages, e.g., less mass and inertia, better dynamic response, higher natural resonance frequencies, or more readily achieved vibrational damping.
In an example of a multilayer composite bow limb 14, the following elastic moduli of the layers can be employed (1 Mpsi≡106 pounds per square inch). The elastic modulus of the compression layer 110 can typically be between about 3 Mpsi and about 10 Mpsi, preferably between about 4.5 Mpsi and about 7 Mpsi; the elastic modulus of the intermediate layer 130 can typically be between about 6 Mpsi and about 25 Mpsi, preferably between about 6 Mpsi and about 15 Mpsi; the elastic modulus of the tension layer 120 can typically be between about 3 Mpsi and about 10 Mpsi, preferably, between about 4.5 Mpsi and about 7 Mpsi.
In some examples of multilayer composite bow limbs 14, differing fibers or differing polymer matrix materials can be employed among the compression (110), intermediate (130), and tension (120) layers. For example, carbon fibers can be employed in the intermediate layer 130, while glass fibers can be employed in the compression layer 110 and the tension layer 120, with all three layers including epoxy polymer matrix material. Any suitable matrix material can be employed. Examples include but are not limited to epoxies, polyurethanes, polyesters, or polyvinyl esters. The carbon fiber intermediate layer 130 exhibits a larger elastic modulus (i.e., greater stiffness) than the glass fiber compression and tension layers 110 and 120. Any suitable fiber material can be employed. Examples include but are not limited to boron fiber, aramid fiber, polyester fiber, silica fiber, basalt fiber, liquid crystal polymer fiber, glass fiber, carbon fiber, or nanotubes. Instead of, or in addition to, employing differing fiber materials among the three layers of bow limb 14, differing polymer matrix materials can be employed among the three layers of bow limb 14. Any suitable combination of fiber material and/or polymer matrix material can be employed to achieve a desired combination of elastic moduli among the compression, intermediate, and tension layers of the multilayer composite bow limb 14.
In other examples of multilayer composite bow limbs 14, the differing elastic moduli of the compression, tension, and intermediate layers can be achieved by employing the same fiber material and polymer matrix material in all three layers, but employing a weight percentage of the fibers in the composite material of the intermediate layer 130 that is higher than that of the compression or tension layers 110 or 120. The higher weight percent of fibers in the intermediate layer 130 yields a corresponding elastic modulus of the intermediate layer 130 that is larger than that of the compression or tension layers 110 or 120. Differing weight percent of fibers can be combined with differing matrix materials or differing fiber materials.
In another example of a multilayer composite bow limb 14, the following compositions of the layers can be employed. The weight percent of fibers in the compression layer 110 can typically be between about 40% and about 75%, preferably between about 65% and about 75%; the weight percent of fibers in the intermediate layer 130 can typically be between about 40% and about 85%, preferably between about 55% and about 65%; the weight percent of fibers in the tension layer can typically be between about 40% and about 75%, preferably between about 65% and about 75%.
In another example of a multilayer composite bow limb 14, the following thicknesses of the layers can be employed over at least an intermediate portion of the length of each bow limb. The compression layer 110 can typically be between about 0.03 inches thick and about 0.15 inches thick; the intermediate layer 130 can typically be between about 0.03 inches thick and about 0.50 inches thick; the tension layer 120 can typically be between about 0.03 inches thick and about 0.15 inches thick.
In a particular example, compression layer 110 comprises about 70% glass fibers in an epoxy matrix (modulus of about 5.8 Mpsi) about 0.12 inches thick, intermediate layer 130 comprises about 60% carbon fibers in an epoxy matrix (modulus of about 14 Mpsi) about 0.06 inches thick, and tension layer 120 comprises about 70% glass fibers in an epoxy matrix (modulus of about 6.8 Mpsi) about 0.04 inches thick. In this example the intermediate layer 130 increases in thickness to about 0.17 inches at the riser end of the limb 14 and to about 0.25 inches at the cable end of the limb 14. The increased thickness accommodates attachment of limb 14 to the riser 12 and attachment of draw cable 20 to bow limb 14 (directly or using a pulley member rotatably mounted on limb 14). Any suitable, necessary, or desired thicknesses of the layers 110/120/130, or any suitable, necessary, or desired variation of those thicknesses along the length of limb 14, can be employed.
In some examples of a multilayer composite bow limb 14, over at least an intermediate portion of the length of each bow limb, the compression layer 120 and the tension layer 120 have the same elastic modulus and have the same thickness (as in
In other examples of a multilayer composite bow limb 14, any one or more of the compression, tension, or intermediate layers 110, 120, or 130 can itself comprise multiple sublayers having differing elastic moduli. In the example of
Each multilayer composite bow limb 14 can comprise a single limb member (as in the top view of
A method for constructing an archery bow comprises attaching the bow limbs 14 to the riser 12, and coupling the draw cable 20 to the bow limbs 14 in any of the arrangements described above.
The method can further comprise forming each bow limb by embedding the corresponding fibers of each layer or sublayer in the corresponding polymer matrix, and curing the corresponding polymer matrix. In some exemplary methods, fibers can be embedded in the corresponding polymer matrix material for each of the multiple layers or sublayers, those layers or sublayers can be arranged in any of the ways described above, and the polymer matrix material of each of those layers or sublayers can then be cured simultaneously. In other exemplary embodiments, each layer or sublayer can individually have its polymer matrix material cured with its fibers embedded therein, and the layers or sublayers thus formed can then be secured together using an appropriate adhesive or bonding agent. In still other exemplary methods, a combination of the foregoing methods can be employed, with some sets of layers or sublayers cured together and then adhered or bonded to other layers, sublayers, or sets thereof.
It is intended that equivalents of the disclosed exemplary embodiments and methods shall fall within the scope of the present disclosure or appended claims. It is intended that the disclosed exemplary embodiments and methods, and equivalents thereof, may be modified while remaining within the scope of the present disclosure or appended claims.
For purposes of the present disclosure and appended claims, the conjunction “or” is to be construed inclusively (e.g., “a dog or a cat” would be interpreted as “a dog, or a cat, or both”; e.g., “a dog, a cat, or a mouse” would be interpreted as “a dog, or a cat, or a mouse, or any two, or all three”), unless: (i) it is explicitly stated otherwise, e.g., by use of “either . . . or”, “only one of . . . ”, or similar language; or (ii) two or more of the listed alternatives are mutually exclusive within the particular context, in which case “or” would encompass only those combinations involving non-mutually-exclusive alternatives. For purposes of the present disclosure or appended claims, the words “comprising,” “including,” “having,” and variants thereof shall be construed as open ended terminology, with the same meaning as if the phrase “at least” were appended after each instance thereof.
In the appended claims, if the provisions of 35 USC §112 ¶ 6 are desired to be invoked in an apparatus claim, then the word “means” will appear in that apparatus claim. If those provisions are desired to be invoked in a method claim, the words “a step for” will appear in that method claim. Conversely, if the words “means” or “a step for” do not appear in a claim, then the provisions of 35 USC §112 ¶ 6 are not intended to be invoked for that claim.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2665678 | Bear | Jan 1954 | A |
| 2815015 | De Giacomo | Dec 1957 | A |
| 2894503 | Pierson et al. | Jul 1959 | A |
| 3492368 | Coover, Jr. et al. | Jan 1970 | A |
| 3558423 | Rossetti, Jr. | Jan 1971 | A |
| 3850156 | Eicholtz | Nov 1974 | A |
| 4474851 | Urry | Oct 1984 | A |
| 4712533 | Cruise | Dec 1987 | A |
| 4954127 | Kira | Sep 1990 | A |
| 5087503 | Meatto et al. | Feb 1992 | A |
| 5194111 | Meatto et al. | Mar 1993 | A |
| 6012709 | Meatto et al. | Jan 2000 | A |
| 6679487 | Meatto et al. | Jan 2004 | B2 |
| 20040007223 | Adcock | Jan 2004 | A1 |
| 20070007689 | Pilpel | Jan 2007 | A1 |
| 20070163559 | Simonds | Jul 2007 | A1 |
| 20080072887 | Park | Mar 2008 | A1 |
| Entry |
|---|
| M.com E-glass Fibre. |
| Clemson University—nylon fiber facts. |
