DOUBLE TUBE COMPOSITE WINDING SHAFT

Abstract

A multi-bladder, expandable winding shaft with discontinuous expanding elements is provided including a shaft body made with carbon fiber composites. The shaft comprises an inner and outer tube and two types of profiles, cavity and ledge profiles. The cavity and ledge profiles can be adhesively mounted around the outer surface of the inner tube in an alternating fashion. Ledge profiles hold the expandable bladders and lug assembly. The outer tube can be created by applying layers of carbon fibers, woven or unwoven fabrics or prepregs by filament winding, roll wrapping or any other suitable method. Elongated discrete slots through the outer tube are provided along the ledge profiles. When the bladders are inflated with air, the lugs are pushed outward to engage the inner wall of the core. When deflated, an installed spring system pushes the lugs inward.

Claims

1. A shaft comprising: a first, inner tube made of a composite fiber material; a second, outer tube also made of a composite fiber material; a plurality of cavity profiles made of a composite fiber material disposed in between the inner and outer tubes; and a plurality of ledge profiles made of a composite fiber material and disposed in between the inner and outer tubes, the cavity profiles and the ledge profiles being arranged in an alternating manner, wherein one ledge profile is arranged in between two cavity profiles and one cavity profile is arranged in between two ledge profiles.

2. The shaft according to claim 1, wherein the shaft is an expandable shaft comprising: a plurality of elongated slots discontinuously distributed along the length of the outer tube; a plurality of protrusion elements, each protrusion element discontinuously positioned in one of the elongated slots; and a plurality of expandable elements located in one or more of the ledge profiles.

3. The shaft according to claim 1, wherein the composite fiber materials of the tubes and the profiles comprise one or more of glass, carbon, aramid, or graphite.

4. The shaft according to claim 1, wherein the composite fiber material comprises a matrix of a thermoset resin, including one or more of an epoxy, polyesters, phenolics, vinyl esters, bismaleimide or polyurethane.

5. The shaft according to claim 1, wherein the inner and outer tubes are made by filament winding, roll wrapping, pull-winding, resin transfer molding, vacuum assisted resin transfer molding, Seeman composite resin infusion molding process or structural reaction injection molding process.

6. The shaft according claim 1, wherein the ledge profiles and cavity profiles are made by compression molding, filament winding, pull-winding, resin transfer molding, vacuum assisted resin transfer molding, Seeman composite resin infusion molding or structural reaction injection molding.

7. The shaft according claim 2, wherein the plurality of protrusion elements and the plurality of expandable elements are arranged in the plurality of ledge profiles.

8. The shaft according to claim 7, wherein the plurality of protrusion elements are lug assemblies, each comprising a lug and a lug support.

9. The shaft according to claim 8, wherein the plurality of expandable elements are bladder assemblies, each comprising a bladder configured to be inflated with air, and a bladder support on which the bladder is disposed.

10. The shaft according to claim 9, wherein the bladder support is a single-part system and made of metal, composite, or plastics.

11. The shaft according to claim 9, wherein the bladder support is a multi-part system and made of at least two different materials having different densities.

12. The shaft according to any one of claim 9, wherein the bladder is configured to push the lug outward when the bladder inflated with air, and when deflated, an installed spring system pushes the lug inward.

13. The shaft according to claim 1, wherein one or more of the plurality of cavity profiles are hollow.

14. The shaft according to claim 1, wherein one or more of the plurality of cavity profiles comprise a stiffening bar therein.

15. The shaft according to claim 1, wherein one or more of the plurality of cavity profiles are one-part systems.

16. The shaft according to claim 1, wherein one or more of the plurality of cavity profiles are multi-part systems, comprising a top portion adhered to a bottom portion.

17. The shaft according to claim 16, wherein each of the plurality of ledge profiles is defined laterally by a wall of each adjacent cavity profile and on a base by an outer diameter of the inner tube, and further comprises a bridge element defining the top of the ledge profile.

18. The shaft according to claim 1, wherein the ledge profile comprises a curved upper surface, a curved lower surface, and parallel side walls between the curved upper surface and curved lower surface.

19. The shaft according to claim 1, wherein the composite fibers in the tubes and profiles are multi-directional.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 shows a graph of apparent flexural modulus against span-to-diameter ratio according to the prior art;

[0018] FIG. 2A shows a perspective view of a non-expanded body of a shaft according to the present application with stiffening bars;

[0019] FIG. 2B shows a cross-sectional view of the non-expanded body of a shaft according to the present application with stiffening bars;

[0020] FIG. 2C shows a perspective view of the non-expanded body of a shaft according to the present application without stiffening bars;

[0021] FIG. 2D shows a cross-sectional view of the non-expanded body of a shaft according to the present application without stiffening bars;

[0022] FIG. 3A shows a perspective view of an expanded body of a shaft according to the present application with stiffening bars;

[0023] FIG. 3B shows a cross-sectional view of the expanded body of a shaft according to the present application with stiffening bars;

[0024] FIG. 4A shows a cross-sectional view of a one-part cavity profile of a shaft according to the present application;

[0025] FIG. 4B shows a cross-sectional view of a one-part ledge profile of a shaft according to the present application;

[0026] FIGS. 5A and 5B show views of a two-part cavity profiles of a shaft according to the present application;

[0027] FIG. 6A shows an exploded view of the cross-section of the lug assembly of a shaft according to the present application;

[0028] FIG. 6B shows a lug assembly of a shaft according to the present application;

[0029] FIGS. 7 and 8 show single and multi-part bladder supports of a shaft according to the present application;

[0030] FIG. 9A-9C show views of the shaft with end journals according to the present application;

[0031] FIG. 10 shows a journal of a shaft of the present application and cross-sectional views thereof; and

[0032] FIGS. 11A-11C show cross-sectional views of a further shaft configuration according to the present application.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033] Referring to the Figures, cross-sectional views of a shaft body 100 of the present application are shown in FIGS. 2A-3B.

[0034] In the shaft body 100, three of each of a cavity profile 102 and a ledge profile 103 are arranged circumferentially on the outer surface of the inner tube 101. The outer diameter of the inner tube 101 matches with the outside smaller diameter of each cavity profile 102 and ledge profile 103. In other embodiments of the shaft body 100, more or less than three of each cavity profile 102 and ledge profile 103 can be provided. For example, in shafts having larger diameters, four or more (e.g., 4, 5, 6, 7, 8, 9, etc.) of each cavity profile 102 and ledge profile 103 can be provided.

[0035] An outer tube 109 is provided circumferentially around the cavity profiles 102 and ledge profiles 103. The outer tube 109 comprises a plurality of elongated slots along its length, in which a plurality of protrusion elements, such as lug assemblies 106 comprising lugs 108 are positioned.

[0036] The cavity profiles 102 and ledge profiles 103 can be fabricated as one or multi-part systems. In a one-part system, shown for example in FIGS. 4A and 4B, each profile covers the entire length of the shaft body 100. The cavity profiles 102 and ledge profiles 103 can each be structures mounted circumferentially on the outer surface of the inner tube 101. Such structures are elongated and hollow, excluding the components housed therein such as stiffening bars 110, lug assemblies 106, bladder support 104, and bladders 105. Alternatively, either the cavity profiles 102 or ledge profiles 103 can be formed circumferentially on the outer surface of the inner tube 101, relying in part on the walls of an adjacent cavity profile 102 or ledge profile 103, as shown for example in FIGS. 11A-11C.

[0037] The cavity profile 102 is a longitudinal structure defined by a cross-sectional profile having a curved upper surface separated from a curved lower surface with opposing wall segments connecting the upper surface and the lower surface, as shown for example in FIG. 4A. The curvature of the lower surface of the cavity profile 102 is configured to match the curvature of the outer surface of the inner tube 101. In some embodiments, the lower surface of the cavity profile 102 may be defined by the outer surface of the inner tube 101 with no separate bottom structure being provided for the cavity profile 102. The curvature of the upper surface of the cavity profile 102 is configured to match the curvature of the inner surface of the outer tube 109.

[0038] The ledge profile 103 is a longitudinal structure defined by a cross-sectional profile having a curved upper surface separated from a curved lower surface with opposing and parallel wall segments connecting the upper surface and the lower surface, as shown for example in FIG. 4B. The curvature of the lower surface of the ledge profile 103 is configured to match the curvature of the outer surface of the inner tube 101. The ledge profile 103 may comprise a plurality of elongated slots discontinuously distributed along its length, which correspond and align with the elongated slots in the outer tube 109.

[0039] In some embodiments, as shown for example in FIGS. 11A-11C, the lower surface of the ledge profile 103 may be defined by the outer surface of the inner tube 101 with no separate bottom structure being provided for the ledge profile 103. The curvature of the upper surface of the cavity ledge profile 103 is configured to match the curvature of the inner surface of the outer tube 109. The walls of the ledge profile 103 can be parallel, as shown in the Figures. In some embodiments, as shown for example in FIGS. 11A-11C, the separate wall elements are not provided for the ledge profile 103, and the walls may be defined by the adjacent walls of adjacent cavity profiles 102, which walls are parallel in forming the ledge profile 103.

[0040] FIG. 5A shows an example of a two-part cavity profile 102b. In a two-part cavity profile 102b, a top part 102c and bottom part 102d of the cavity profile 102b can be fabricated separately and then joined together with adhesive.

[0041] Alternatively, multiple longitudinal sections of a one-part cavity profile 102a can be connected via inserts 102e to cover the entire length of the shaft body 100, as shown in FIG. 5B.

[0042] FIGS. 11A-11C illustrate a configuration of the shaft body 100 in which a ledge profile 103b is formed in between the inner tube 101 and cavity profiles 102b, but without providing a discrete, elongated structure defining the ledge profile 103 as shown for example in FIGS. 2A-3B and 4B. As shown in FIG. 11A, an inner tube 101 is provided, and three cavity profile bottom parts 102d are provided, which are mounted to the inner tube 101 in a spaced apart manner, particularly an equidistantly spaced apart manner. In the configuration of FIG. 11A, stiffening bars 110 are also provided within the cavity profile bottom parts 102d. As shown in FIG. 11B, cavity profile top parts 102c are provided and affixed to the cavity profile bottom parts 102d to form cavity profiles 102b. Preferably, the cavity profile top parts 102c are dimensioned and mounted to the bottom parts 102d in such a way as to leave an upper surface exposed on each of the cavity profile bottom parts next to the top parts 102c. A plurality of bridge elements 103a are provided to cover the open spaces in between the formed cavity profiles 102b. The bridge elements 103a mount to the exposed upper surface on the cavity profile bottom parts 102d, and align with the curvature of the cavity profile top parts 102c, as shown for example in FIG. 11C. The bridge elements 103a may comprise a plurality of elongated slots discontinuously distributed along its length, which correspond and align with the elongated slots in the outer tube 109.

[0043] In the configuration of FIG. 11C, the lower surface of the ledge profile 103b is defined by the outer surface of the inner tube 101 and the walls of the ledge profile 103b are defined by the adjacent walls of adjacent cavity profiles 102b, which walls are parallel in forming the ledge profile 103b.

[0044] In the shafts of FIGS. 2A-2B and 3A-3B, inside each cavity profile 102, there may be provided a stiffening bar 110 made of CF composite. Both top and bottom surfaces of the stiffening bar 110 can be adhesively bonded to the inner walls of the cavity profile 102. Additionally or alternatively, rivets can be applied to enhance the bonding between the stiffening bar 110 and the inner walls of the cavity profile 102. The purpose of the stiffening bar 110 is to boost the overall stiffness of the shaft body 100. The stiffening bar 110 can be made of various fibers such as carbon, glass, polymers or a combination thereof, but preferably with carbon fibers. The fibers are at least partially oriented relative to the long axis of the stiffening bar 110. In other versions of the shaft body 100, stiffening bars 110 may not be necessary and the cavity profile 102 can remain hollow as shown in FIGS. 2C-2D.

[0045] A ledge profile 103 comprises therein the bladder 105, the bladder support 104, and the lug assembly 106. The bladder 105 can be made of any suitable material that is durable and flexible. When expanded by air or any other medium, the bladder 105 will radially push the lug assembly 106 outward through slots in the ledge profile 103 and outer tube 109 so that the lugs 108 can engage with the core on which web materials are wound. The ledge profile 103 may alternatively comprise other expandable elements other than a bladder 105, such as expandable hollow structures of various cross-sectional shapes such as circular, rectangular, or square.

[0046] An example of a lug assembly 106 is shown in FIGS. 6A and 6B. The lug assembly 106 comprises a lug support bar 107, female threaded standoffs 106a, lugs 108, and screws 106b, 106c, as shown in FIGS. 6A and 6B. The lug support bar 107 comprises an elongated platform upon which the lugs 108 are placed. Female threaded standoffs 106a are positioned along the length of the lug support bar 107 and are positioned therethrough. Openings are provided through the lugs 108 that are configured align with the female threaded standoffs 106a, so that the lugs 108 can be placed over the female threaded standoffs 106a and on the lug support bar 107. Screws 106b are provided for inserting through a top opening of female threaded standoffs 106a in the lugs 108, and screws 106c are provided for inserting through a bottom opening of female threaded standoffs 106a in the lugs 108, for securing the lugs 108 to the lug support bar 107. It is noted that in other embodiments, a different structure of the lug assembly 106 may be provided having different mechanisms for securing the lug 108 to the lug support bar 107. Other protrusion elements besides the lug assembly 106 described herein may be utilized, such as keys, or protrusion elements or lugs made of different shapes and materials than those shown herein.

[0047] The bladder 105 rests on a bladder support 104. The bladder support 104 can be made of plastic or fiber composite materials, and can be made as a single-part bladder support 104 or a multi-part bladder support 114, as shown in FIGS. 7 and 8, respectively. The bottom surface of the bladder support 104, 114 is curved to fit on the ledge profile 103. The top surface of the bladder support 104, 114 is flat to support the bladder 105.

[0048] In a multi-part bladder support 114, each part 114a, 114b can be two to three inches in length. However, some applications may require a different length of each part 114a, 114b. The parts 114a, 114b are then connected to each other to the required length for the bladder support 114. For example, each part 114a, 114b can have holes 114c along two sides (FIG. 8) into which rods can be inserted to hold the multiple parts 114a, 114b together. An advantage of the multi-part bladder support 114 is that one or two parts can be replaced with higher density material for balancing purposes, wherein the bladder support 114 comprises parts made of different materials. For example, if the bladder support 114 is originally made of a plastic or CF composite material that has low density, if one part is replaced by a steel that has higher density, the weight difference will serve as a balancing weight for the shaft. Alternatively, if the bladder support 104 is made as single part for the entire shaft, a metal strip of appropriate length can also be attached on the bladder support 104 for balancing purpose.

[0049] The lug support bar 107 of the lug assembly 106 is placed on top of the bladder 105. Each lug 108 is positioned in an individual slot along the length of the shaft body 100. When the bladder 105 is inflated, the lugs 108 move radially upward without any restriction to engage with the core. As shown for example in FIGS. 3A-3B. When deflated, the lugs 108 will retract back to the slot. Metal or plastic springs (not shown in the drawings) can also be used to assist the retraction.

[0050] To each end of the shaft body 100, a journal 115 can be connected, an example of which is shown in FIGS. 9A-10. In the illustrated example, an axial bore in the journal 115 is connected to the plurality of radial bores in which air channels 121, 122 are mounted to pass the air to the bladders 105. The journal 115 comprises a plurality of slots 120 arranged circumferentially around the journal 115. The slots 120 comprises a threaded hole configured to receive a screw 116 for a crimping lug 117. The slot 120 also includes a radial air channel 122, which is in communication with an axial air channel 121, as shown for example in FIG. 10. Also arranged in the slot 120 and beneath the crimping lug 117 is a bladder 118. The bladder 118 includes a bladder inlet 119 inserted into the radial air channel 122.

[0051] The shaft body 100 of the winding shaft of the present application can be made using any type of fibers, including those listed in Table 1. The matrix resins can be of various thermosets such as epoxy, polyesters, phenolics, vinyl esters, bismaleimide and polyurethane, or thermoplastics such as polyamides, polypropylene, polyether ketone, polysulfone and polyphenyle sulfide.

[0052] Comparative properties of shafts with the following dimensions are listed in Table 2: Total length: 84 inches; Body length: 72 inches; Steel journal: 2 inches OD?6 inches length (each end); and Supports distance=77 inches.

TABLE-US-00002 TABLE 2 Comparative properties of shafts Fiber Flexural tensile modulus of Shaft body modulus shaft body First critical Density Weight Specific design (MSI) (MSI) speed (rpm)*.sup.1 (lbs./in..sup.3) (lbs./in.) Modulus*.sup.2 Aluminum N/A 10 2100 0.100 0.181 100 Extrusion Carbon 92 20 3207 0.080 0.289 250 Pultrusion Shaft body 33 10 2625 0.06 0.125 167 100A Shaft body 92 25 3667 0.06 0.125 417 100B *.sup.1Calculated from the deflection under self-weight. *.sup.2Specific modulus = Modulus/Density

[0053] Body designs for the aluminum extrusion with or without carbon inside can be found in U.S. Pat. No. 5,746,387, which is incorporated by reference in its entirety. Shaft bodies 100A and 100B represent the body designs of the present application. Both shaft bodies 100A and 100B can have designs as shown in FIG. 2A or 2C. Shaft bodies 100A and 100B are differentiated by the type of fibers, as shown in Table 2. On the other hand, the difference between the designs in FIGS. 2A and 2C is that FIG. 2A does not have stiffening bar 110, unlike FIG. 2C.

[0054] As used herein, directional or positional terms such as front, rear, upper, lower, top, bottom, etc., are used for explanatory purposes and are not limiting.

[0055] As can be seen, a shaft body 100A of the present application, if made with low modulus carbon fiber, can increase the first critical speed and specific modulus by 25 and 67% respectively, while reducing the weight by about 31%, compared to aluminum extrusion itself. Further increase of the first critical speed (by 75%) and specific modulus (by 417%) is expected, if the shaft is made with higher modulus carbon fiber (shaft body 100B). Compared to the carbon-aluminum hybrid design of the prior art, shaft body 100B of the present application is expected to reduce the weight by about 43% while increasing the specific modulus by about 67%.

[0056] A prototype shaft (shaft body 100A) of the present application was made, using low modulus (33 MSI) carbon fiber. Critical speed of the prototype shaft was determined using a balancing machine (CEMB, VibraSys, Inc.). The 1.sup.st critical speed was found to be 2373 rpm which is about 90.4% of the calculated value listed in Table 2. The test results were in good agreement with the calculated values.

[0057] In summary, the expandable shaft of the present application is a multi-bladder shaft with discontinuous expanding elements. The shaft body comprises two CF composite tubes and plurality of CF composite profiles securely placed between the tubes. Some of the profiles contain assemblies of various elements that are expanded with the help of air or other media.

[0058] Although the present application describes the system in reference to expandable winding shafts, it is noted that the shafts and shaft bodies described herein can be used in other shaft applications. For example, non-expandable shafts can be provided with the structures disclosed therein, include the tube and profile features shown and described herein, but no expanding elements.

[0059] While there have been shown and described and pointed out fundamental novel features of the invention as applied to embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices and methods described may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice.