Compound spring and method for manufacturing the compound spring

Abstract

A composite spring and a method for manufacturing such a composite spring are provided. The spring includes a tube made of a fiber-reinforced composite material and having a longitudinal axis. The tube includes a first axial end having a closed shape that completely encloses the longitudinal axis, a second axial end located axially opposite the first axial end with respect to the longitudinal axis, and one or more openings formed to pass through the wall of the tube. One or more openings define the elastic member of the spring.

Description

Technical Field

[0001] Cross - reference to related applications and claim of priority

[0001] This application claims the priority of Canadian Patent Application No. 3,200,023, filed on May 19, 2023, the entire content of which is incorporated herein by reference.

[0002]

[0002] The present disclosure generally relates to composite components, and more particularly, to composite springs and associated manufacturing methods.

Background Art

[0003]

[0003] A helical spring or coil spring is a mechanical energy storage device comprising an elastic material formed in a helical shape that elastically returns to its original length when unloaded. Under compression, the spring material is torsionally stressed, where energy is stored and released upon release of the compression. When the spring is disposed between two components, the spring can absorb shock or maintain a force between the two components.

[0004]

[0004] A helical spring can be formed by winding a metal wire (e.g., a steel wire) into a coil form (e.g., a "wound helical spring"). The length of the spring may be a function of both the diameter of the spring and the number of active turns of the coil. The characteristics of a helical spring are determined by the length and diameter of the wire forming the helical spring. Helical springs can be used in a variety of applications, such as in automobiles (e.g., within vehicle suspensions or within internal combustion engines to close engine valves), recreational vehicles, power sports vehicles (e.g., all - terrain vehicles, snowmobiles, and water bikes), aerospace applications (e.g., landing gear and suspensions for airplanes and helicopters), inner - spring mattress coils, tension coils, and buckling springs for computer keyboards.

[0005]

[0005] Metal springs used in vehicle suspensions can be susceptible to corrosion, especially when exposed to road salt. Furthermore, existing manufacturing processes for wound helical springs can introduce torsion into each coil of the spring as it is wound, which can make the spring more susceptible to biasing forces on its deflection axis, potentially affecting the spring's ability to achieve true linear motion in some situations. Improvement is desired. [Overview of the project] [Means for solving the problem]

[0006]

[0006] In one embodiment, the present disclosure describes a composite spring for a vehicle suspension. The composite spring comprises a tube made of a fiber-reinforced composite material and having a longitudinal axis, the tube comprising: a first axial end having a closed shape that completely encloses the longitudinal axis; a second axial end located axially opposite the first axial end with respect to the longitudinal axis; and one or more openings formed through the wall of the tube and disposed axially between the first axial end and the second axial end, wherein a portion of the wall adjacent to one or more openings defines an elastic member of the spring.

[0007]

[0007] The elastic member may be a coil.

[0008] One or more openings can define a cellular structure, and the elastic member may be part of the cellular structure.

[0008]

[0009] One or more openings can define a honeycomb structure, and the elastic member may be part of the honeycomb structure.

[0010] The tube may have a circular radially inward profile when viewed along its longitudinal axis.

[0009]

[0011] The tube may have a circular radially outward profile when viewed along its longitudinal axis.

[0012] The tube may have a non-circular radially outward profile when viewed along its longitudinal axis.

[0010]

[0013] The pipe may have a polygonal radially outward profile when viewed along its longitudinal axis.

[0014] The tube may have a non-circular radially inward profile when viewed along its longitudinal axis.

[0011]

[0015] The tube may have a non-circular radially outward profile when viewed along its longitudinal axis.

[0016] The pipe may have a polygonal radially outward profile when viewed along its longitudinal axis.

[0012]

[0017] The closed shape may be a first closed shape. The second axial end may have a second closed shape that completely encloses the longitudinal axis.

[0018] The first axial end may be part of a first ring that completely encloses the longitudinal axis.

[0013]

[0019] The second axial end may be part of a second ring that completely encloses the longitudinal axis.

[0020] The wall of the tube may include multiple layers of laminated fibers wrapped around the longitudinal axis. The layers may be sewn together as a single unit.

[0014]

[0021] The elastic member may include a coil. The coil may have a first helical angle. The layers may be sewn together along a stitch line having a second helical angle substantially equal to the first helical angle.

[0015]

[0022] The fibers may be constructed using one method of stitching within at least one of the layers.

[0023] The walls of the tube may include pleated fiber sheets wrapped around the longitudinal axis.

[0016]

[0024] One or more pleats of the pleated sheet may be at least partially oriented radially with respect to the longitudinal axis.

[0025] The pleated fiber sheet may be a first pleated fiber sheet. The wall of the tube can include a second pleated fiber sheet that overlaps and meshes with the first pleated fiber sheet.

[0017]

[0026] The wall of the tube can include an outer non-pleated fiber sheet disposed radially outside the pleated fiber sheet and wrapped around the longitudinal axis.

[0027] The wall of the tube can include an inner non-pleated fiber sheet disposed radially inside the pleated fiber sheet and wrapped around the longitudinal axis.

[0018]

[0028] The wall of the tube can include a plurality of stitches extending through the pleated fiber sheet.

[0029] The elastic member can include a coil. The coil may have a first helix angle. The wall of the tube can include stitches along a stitch line having a second helix angle that is substantially equal to the first helix angle.

[0019]

[0030] Embodiments can include combinations of the above features.

[0031] In another aspect, the present disclosure describes a vehicle including the composite spring disclosed herein.

[0020]

[0032] In another aspect, the present disclosure describes a method of manufacturing a composite spring. The method includes: forming a tubular precursor from a fiber reinforced composite material; and utilizing a subtractive manufacturing process to form one or more openings through the wall of the tubular precursor for the purpose of defining the elastic member of the spring.

[0021]

[0033] The subtractive manufacturing process can include water jet cutting.

[0034] The step of forming the tubular precursor may include: winding a pre-impregnated pleated fiber sheet of the base material around a holder; and compression molding the pleated sheet to form the tubular precursor.

[0022]

[0035] The pleated sheet may be the first pleated fiber sheet. The method may include winding a second pre-impregnated pleated fiber sheet of the base material around the holder such that the second pleated sheet overlaps and meshes with the first pleated sheet; and integrally compression molding the first pleated sheet and the second pleated sheet to form the tubular precursor.

[0023]

[0036] At least some of the fibers in the first pleated sheet may be discontinuous and randomly oriented.

[0037] The step of forming the tubular precursor may include winding an outer non-pleated fiber sheet pre-impregnated with the base material around the holder and radially outside the pleated sheet before compression molding.

[0024]

[0038] The step of forming the tubular precursor may include winding an inner non-pleated fiber sheet pre-impregnated with the base material radially inside the pleated sheet before compression molding.

[0025]

[0039] The step of forming the tubular precursor may include: winding one or more fiber layers pre-impregnated with the base material around the holder; stitching together the one or more layers; and compression molding the one or more layers to form the tubular precursor.

[0026]

[0040] The elastic member may be a coil. The coil may have a first helical angle. The step of sewing one or more layers together may include the step of sewing one or more layers together along a stitch line having a second helical angle substantially equal to the first helical angle.

[0027]

[0041] The steps for forming a tubular precursor may include: winding one or more fiber layers, pre-impregnated with a base material, around a holder; positioning a holder having one or more layers in a mold cavity by rotating the longitudinal axis of the holder around a pivot axis that is perpendicular to the longitudinal axis of the holder; and compression molding one or more layers to form a tubular precursor.

[0028]

[0042] Embodiments may include combinations of the above features.

[0043] In another embodiment, the present disclosure describes a compression molding apparatus for forming a tubular precursor for a composite spring. The compression molding apparatus comprises: a first mold portion; a second mold portion cooperating with the first mold portion to define a mold cavity, wherein the first and second mold portions are releasable from each other to open the mold cavity; a mandrel for holding a tubular precursor wound around the mandrel inside the mold cavity, wherein the mandrel has a longitudinal axis and is pivotably connected to the second mold portion, so that the mandrel is rotatable about a pivot axis perpendicular to the longitudinal axis of the mandrel; and a heat source for heating the tubular precursor during compression molding of the tubular precursor.

[0029]

[0044] The heat source may include a heat transfer fluid. The mandrel may include passages formed within it for transporting the heat transfer fluid.

[0045] The compression molding apparatus may include a metal sleeve for holding a tubular precursor. The metal sleeve may be configured to fit onto a mandrel and to be positioned between the tubular precursor and the mandrel.

[0030]

[0046] The heat source may include a heat transfer fluid. The mandrel may include passages formed within it for carrying the heat transfer fluid. A metal sleeve may be engaged to transfer conductive heat to the mandrel.

[0031]

[0047] The compression molding apparatus may include a first mold section and a third mold section that cooperates with the second mold section to define the mold cavity. The third mold section may be movable along the longitudinal axis of the mandrel to selectively lock or release the mandrel in the compression molding position.

[0032]

[0048] Embodiments may include combinations of the above features.

[0049] In another embodiment, the disclosure describes a tubular manufacturing precursor for a composite spring, the precursor comprising a plurality of fiber layers pre-impregnated with a base material and wound around an elongated holder having a longitudinal axis, the plurality of layers being sewn together in a single unit.

[0033]

[0050] Multiple layers can be sewn together in one piece along a stitch line that has a non-zero spiral angle with respect to the longitudinal axis.

[0051] In some embodiments, at least one of the multiple layers has fibers oriented at a non-zero helical angle with respect to the longitudinal axis.

[0034]

[0052] In some embodiments, at least one of the multiple layers is pleated.

[0053] Embodiments may include combinations of the above features.

[0035]

[0054] In another embodiment, the disclosure describes a tubular manufacturing precursor for a composite spring, the precursor comprising a pleated fiber sheet pre-impregnated with a base material and wound around an elongated holder having a longitudinal axis, the pleated sheet having a plurality of pleats substantially oriented radially with respect to the longitudinal axis.

[0036]

[0055] The pleated sheet may be a first pleated sheet. The tubular manufacturing precursor may include a second pleated fiber sheet that has been pre-impregnated with a base material and wound around an elongated holder. The second pleated sheet can overlap and interlock with the first pleated sheet.

[0037]

[0056] The pleated sheet may be sandwiched between: an outer non-pleated fiber sheet, which is pre-impregnated with a base material and positioned radially outside the pleated sheet, and wound around its longitudinal axis; and an inner non-pleated fiber sheet, which is pre-impregnated with a base material and positioned radially inside the pleated sheet, and wound around its longitudinal axis.

[0038]

[0057] Embodiments may include combinations of the above features.

[0058] Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description and drawings contained herein.

[0039]

[0059] Next, refer to the attached drawings. [Brief explanation of the drawing]

[0040] [Figure 1]

[0060] This is a schematic diagram showing an automobile including the compound spring described herein. [Figure 2A]

[0061] This is a perspective view showing an example of a compound spring. [Figure 2B] This is a front view showing an example of a compound spring. [Figure 2C] This is a top view showing an example of a compound spring. [Figure 3]

[0062] Figure 3A is a perspective view showing another example of a compound spring. Figure 3B is a front view showing another example of a compound spring. Figure 3C is a top view showing another example of a compound spring. [Figure 4]

[0063] Figure 4A is a perspective view showing another example of a compound spring. Figure 4B is a front view showing another example of a compound spring. Figure 4C is a top view showing another example of a compound spring. [Figure 5]

[0064] Figure 5A is a perspective view showing another example of a compound spring. Figure 5B is a front view showing another example of a compound spring. Figure 5C is a top view showing another example of a compound spring. [Figure 6]

[0065] Figure 6A is a perspective view showing another example of a compound spring. Figure 6B is a front view showing another example of a compound spring. Figure 6C is a top view showing another example of a compound spring. [Figure 7A]

[0066] This is a perspective view showing an example of a composite spring having a diverse configuration of elastic members. [Figure 7B] This is a perspective view showing an example of a composite spring having a diverse configuration of elastic members. [Figure 7C] This is a perspective view showing an example of a composite spring having a diverse configuration of elastic members. [Figure 7D] This is a perspective view showing an example of a composite spring having a diverse configuration of elastic members. [Figure 8]

[0067] This is a flowchart showing the method for manufacturing a composite spring. [Figure 9]

[0068] This is a perspective view showing an uncured tubular precursor of an example of a compound spring. [Figure 10]

[0069] This is an enlarged view of region R1 in Figure 9, showing the tubular precursor in Figure 9, which includes multiple fiber layers that have been pre-impregnated with the base material. [Figure 11]

[0070] Figure 11A shows a pleated fiber sheet pre-impregnated with a matrix material for forming another tubular precursor.

[0071] Figure 11B shows a pleated sheet wrapped around the holder. [Figure 12]

[0072] Figure 12A is a magnified view showing region R1 for a tubular precursor of another exemplary composite spring, which includes a pleated fiber sheet pre-impregnated with a base material. Figure 12B is a magnified view showing region R1 for a tubular precursor of another exemplary composite spring, which includes a pleated fiber sheet pre-impregnated with a base material. Figure 12C is a magnified view showing region R1 for a tubular precursor of another exemplary composite spring, which includes a pleated fiber sheet pre-impregnated with a base material. [Figure 13]

[0073] Figure 13A shows the stitching process applied to the tubular precursor of a composite spring. Figure 13B shows the stitching process applied to the tubular precursor of a composite spring. Figure 13C shows the stitching process applied to the tubular precursor of a composite spring. [Figure 14]

[0074] Figure 14A is a partial front view showing the composite spring shown in Figures 2A-2C, with stitch lines indicated above it.

[0075] Figure 14B is an enlarged view showing region R3 in Figure 14A. [Figure 15]

[0076] This is a partial cross-sectional view showing a compound spring along line 15-15 in Figure 2A, with stitching visible within it. [Figure 16A]

[0077] This is a schematic axial cross-sectional view showing an exemplary apparatus for compression molding a tubular precursor, with the mold portion of the molding apparatus open. [Figure 16B]

[0078] This is a schematic axial cross-sectional view of the compression molding apparatus shown in Figure 16A, which displays the mold portion in a closed state. [Figure 16C]

[0079] This is a schematic cross-sectional view of the compression molding apparatus shown in Figure 16A, which shows the mold portion in a closed state. [Figure 17]

[0080] This is a perspective view showing a tubular precursor of a composite spring, along with the sleeve and mandrel used during the compression molding of the tubular precursor. [Figure 18A]

[0081] This is a schematic axial cross-sectional view showing another exemplary apparatus for compression molding a tubular precursor, with the mold portion of the molding apparatus open. [Figure 18B]

[0082] This is a schematic axial cross-sectional view showing the compression molding apparatus of Figure 17A, which is in a state of preparation for compression molding a tubular precursor. [Figure 18C]

[0083] This is a schematic axial cross-sectional view showing the compression molding apparatus of Figure 18A during the compression molding of a tubular precursor. [Figure 18D]

[0084] Figure 18A is a schematic axial cross-sectional view showing the compression molding apparatus after the tubular precursor has been compression molded. [Figure 19]

[0085] Figure 19A is a perspective view showing another example of a tubular precursor.

[0086] Figure 19B is a transverse cross-sectional view showing the tubular precursor of Figure 19A, illustrating the method of assembling and shaping the tubular precursor of Figure 19A. Figure 19C is a transverse cross-sectional view showing the tubular precursor of Figure 19A, illustrating the method of assembling and shaping the tubular precursor of Figure 19A. [Figure 20]

[0087] This is a perspective view showing a hardened tubular precursor after compression molding, during a subtractive manufacturing process to form an opening within the tubular precursor. [Modes for carrying out the invention]

[0041]

[0088] The following disclosure describes composite springs, precursors, methods, and apparatus for manufacturing composite springs. In some embodiments, the composite springs described herein can achieve improved corrosion resistance and reduced weight compared to other metal springs. In some embodiments, the manufacturing processes described herein can facilitate the tuning of the mechanical properties and / or shape of the composite spring. For example, the shape and size of the composite spring may be selected to tune the mechanical properties and / or spring behavior / reaction, and / or based on mounting constraints. For example, one or more axial ends of the composite spring may be shaped to facilitate the mounting of the composite spring and to facilitate the interface connection of the composite spring to the component in which the composite spring is mounted.

[0042]

[0089] In some embodiments, the composite springs described herein can exhibit a more linear compression axis because, unlike steel springs, it is not necessary to apply torsional stress to each coil during their manufacture. In some embodiments, the composite springs described herein can exhibit improved characteristics such as balance, precision, and efficiency compared to some existing springs.

[0043]

[0090] In some embodiments, the composite springs described herein can exhibit improved noise reduction and reduced transmission of road noise frequencies compared to some existing steel springs. For example, the composite springs described herein can be tuned to reduce the noise, vibration, and harshness (NVH) characteristics of a vehicle compared to existing steel springs.

[0044]

[0091] In some embodiments, the composite springs described herein can have greater visual appeal through the flexibility in selecting the shape and configuration of the elastic members and in selecting a variety of base materials (e.g., black) without the need to paint the composite springs.

[0045]

[0092] Various embodiments will be described with reference to the drawings.

[0093] The term “connection” can include both direct connection (two connected elements touching each other) and indirect connection (at least one additional element positioned between two elements). As used herein, the term “substantial” can be applied to modify any quantitative expression that may vary within acceptable limits without altering the relevant fundamental performance of the invention.

[0046]

[0094] Figure 1 shows a schematic representation of a vehicle 10 including the compound springs 12, 112, 212, 312, 412, 512, 612, 712, and 812 described herein (collectively also referred to herein as “spring 12”). The springs 12 may be part of the suspension of the vehicle 10. For example, the springs 12 may be operably mounted between the ground-engaging wheels 13 of the vehicle 10 (e.g., front or rear) and the frame / chassis of the vehicle 10. In various embodiments, the vehicle 10 may include one or more springs 12. In some embodiments, the vehicle 10 may be an automobile. In some embodiments, the vehicle 10 may be a pickup truck, a recreational vehicle, an airplane, a powersports vehicle such as an all-terrain vehicle, a snowmobile, or a motorcycle. The springs 12 may be manufactured in a wide range of shapes and sizes for a variety of applications. The use of the springs 12 in the vehicle 10 is shown as an unlimited embodiment.

[0047]

[0095] Figures 2A-2C are perspective, front, and top views of spring 12, respectively. Spring 12 may be configured as a coil spring (i.e., a helical coil spring) having one or more turns. Spring 12 may include a hollow, fenestrated, and generally tubular body made of a fiber-reinforced composite material and referred herein as a "tube 14" having a longitudinal axis LA. The tube 14 may include a first axial end 16A and a second axial end 16B located axially opposite the first axial end 16A with respect to the longitudinal axis LA. The first axial end 16A and / or the second axial end 16B may each have a closed shape that completely encloses the longitudinal axis LA. In some embodiments, the first axial end 1A and / or the second axial end 16B may each be annular bodies that completely enclose the longitudinal axis LA (for example, as shown in Figure 2C). In some embodiments, the first axial end 16A and / or the second axial end 16B may each be part of a ring that completely encloses the longitudinal axis LA. In some embodiments, the first axial end 16A and the second axial end 16B may have substantially identical shapes (e.g., mirror images of each other) and configurations. Alternatively, the first axial end 16A and the second axial end 16B may have different shapes and configurations depending on the constraints of mounting the spring 12.

[0048]

[0096] The spring 12 may include one or more openings 18 formed within the wall of the tube 14 and disposed axially between a first axial end 16A and a second axial end 16B for defining one or more elastic members 20 (hereinafter referred to singly) of the spring 12. The openings (18) may extend radially through the wall of the tube 14. In some embodiments, the elastic member 20 includes one or more wall portions adjacent to the openings 18 (e.g., between the openings 18) and is configured to facilitate axial compression and / or extension of the spring 12 along the longitudinal axis LA. In some embodiments, the elastic member 20 is a coil. In various embodiments, the coil may have a cross-sectional profile that is substantially uniform along at least a large portion of the axial length of the coil in a plane parallel to and containing the longitudinal axis LA. Alternatively, the cross-sectional profile of the coil may be non-uniform (e.g., variable) along at least a large portion of the axial length of the coil. In various embodiments, the wall thickness T2 of the spring 12 (shown in Figure 2C) may be uniform along the longitudinal axis LA, or it may vary along the longitudinal axis LA to provide a multi-rate spring. In some embodiments, the coil may have a rectangular (e.g., square) or other cross-sectional profile.

[0049]

[0097] Referring to Figure 2C, the tube 14 (and spring 12) may have a circular radially inward profile when viewed along the longitudinal axis LA. In some embodiments, the tube 14 (and spring 12) may have a circular radially outward profile when viewed along the longitudinal axis LA.

[0050]

[0098] Figures 3A-3C are perspective, front, and top views, respectively, of another exemplary composite spring 112. Spring 112 may include elements of spring 12. Similar elements are indicated using reference numerals with 100 added. Spring 112 may be configured as a coil spring. Spring 112 may include a fenestrated tube 114 made of fiber-reinforced composite material and having a longitudinal axis LA. The tube 114 may include a first axial end 116A and a second axial end 116B located axially opposite the first axial end 116A with respect to the longitudinal axis LA. Spring 112 may include one or more openings 118 formed within the tube 114 and disposed axially between the first axial end 116A and the second axial end 116B for defining one or more elastic members 120 of spring 112. The openings 118 may extend radially through the wall of the tube 114. In some embodiments, the elastic member 120 may be configured to facilitate axial compression and / or extension of the spring 112 along the longitudinal axis LA. Referring to Figure 3C, the tube 114 (and spring 112) may have a circular radially inward profile when viewed along the longitudinal axis LA. In some embodiments, the tube 114 (and spring 112) may have a non-circular radially outward profile when viewed along the longitudinal axis LA. For example, the tube 114 (and spring 112) may have a polygonal (e.g., hexagonal) radially outward profile when viewed along the longitudinal axis LA.

[0051]

[0099] Figures 4A-4C are perspective, front, and top views, respectively, of another exemplary composite spring 212. Spring 212 may include elements of spring 12. Similar elements are indicated using reference numerals with 200 added. Spring 212 may be configured as a coil spring. Spring 212 may include a fenestrated tube 214 made of fiber-reinforced composite material and having a longitudinal axis LA. The tube 214 may include a first axial end 216A and a second axial end 216B located axially opposite the first axial end 216A with respect to the longitudinal axis LA. Spring 212 may include one or more openings 218 formed within the tube 214 and disposed axially between the first axial end 216A and the second axial end 216B for defining one or more elastic members 220 of spring 212. The openings 218 may extend radially through the wall of the tube 214. In some embodiments, the elastic member 220 may be configured to facilitate axial compression and / or extension of the spring 212 along the longitudinal axis LA. Referring to Figure 4C, the tube 214 (and spring 212) may have a non-circular radially inward profile when viewed along the longitudinal axis LA. For example, the tube 214 (and spring 212) may have a polygonal (e.g., hexagonal) radially inward profile when viewed along the longitudinal axis LA. In some embodiments, the tube 214 (and spring 212) may have a non-circular radially outward profile when viewed along the longitudinal axis LA. For example, the tube 214 (and spring 212) may have a polygonal (e.g., hexagonal) radially outward profile when viewed along the longitudinal axis LA.

[0052]

[0100] Figures 5A to 5C are perspective, front, and top views, respectively, of another exemplary composite spring 312. The spring 312 may include elements of spring 12. Similar elements are indicated using reference numerals with 300 added. The spring 312 may be configured as a coil spring. The spring 312 may include a fenestrated tube 314 made of fiber-reinforced composite material and having a longitudinal axis LA. The tube 314 may include a first axial end 316A and a second axial end 316B located axially opposite the first axial end 316A with respect to the longitudinal axis LA. The spring 312 may include one or more openings 318 formed within the tube 314 and disposed axially between the first axial end 316A and the second axial end 316B for defining one or more elastic members 320 of the spring 312. The openings 318 may extend radially through the wall of the tube 314. In some embodiments, the elastic member 320 may be configured to facilitate axial compression and / or extension of the spring 312 along the longitudinal axis LA. Referring to Figure 5C, the tube 314 (and spring 312) may have a circular radially inward profile when viewed along the longitudinal axis LA. In some embodiments, the tube 314 (and spring 312) may have a non-circular radially outward profile when viewed along the longitudinal axis LA. For example, the tube 314 (and spring 312) may have a polygonal (e.g., octagonal) radially outward profile when viewed along the longitudinal axis LA.

[0053]

[0101] Figures 6A-6C are perspective, front, and top views, respectively, of another exemplary composite spring 412. The spring 412 may include elements of spring 12. Similar elements are indicated using reference numerals with 400 added. The spring 412 may be configured as a coil spring. The spring 412 may include a fenestrated tube 414 made of fiber-reinforced composite material and having a longitudinal axis LA. The tube 414 may include a first axial end 416A and a second axial end 416B located axially opposite the first axial end 416A with respect to the longitudinal axis LA. The spring 412 may include one or more openings 418 formed within the tube 414 and disposed axially between the first axial end 416A and the second axial end 416B for defining one or more elastic members 320 of the spring 412. The openings 418 may extend radially through the wall of the tube 414. In some embodiments, the elastic member 420 may be configured to facilitate axial compression and / or extension of the spring 412 along the longitudinal axis LA. Referring to Figure 4C, the tube 414 (and spring 412) may have a non-circular radially inward profile when viewed along the longitudinal axis LA. For example, the tube 414 (and spring 412) may have a polygonal (e.g., octagonal) radially inward profile when viewed along the longitudinal axis LA. In some embodiments, the tube 414 (and spring 412) may have a non-circular radially outward profile when viewed along the longitudinal axis LA. For example, the tube 414 (and spring 412) may have a polygonal (e.g., octagonal) radially outward profile when viewed along the longitudinal axis LA.

[0054]

[0102] Figure 7A is a schematic perspective view of another exemplary composite spring 512. Spring 512 may include elements of spring 12. Similar elements are indicated using reference numerals with 500 added. Spring 512 may include a fenestrated tube 514 made of fiber-reinforced composite material and having a longitudinal axis LA. Tube 514 may include a first axial end 516A and a second axial end 516B located axially opposite the first axial end 516A with respect to the longitudinal axis LA. Spring 512 may include one or more openings 518 formed within the tube 514 and disposed axially between the first axial end 516A and the second axial end 516B to define one or more elastic members 520 of spring 512. The openings 518 may extend radially through the wall of tube 514. In some embodiments, the elastic member 520 may be configured to facilitate axial compression and / or extension of the spring 512 along the longitudinal axis LA. For example, an elongated opening 518 (slot) in the circumferential direction may define the elastic member 520, which may be part of the cell structure. In various embodiments, the elastic member 520 may include one or more flexible (e.g., elongated) frame members (e.g., beams, posts).

[0055]

[0103] Figure 7B shows a schematic perspective view of another exemplary composite spring 612. Spring 612 may include elements of spring 12. Similar elements are indicated using reference numerals with 600 added. Spring 612 may include a fenestrated tube 614 made of fiber-reinforced composite material and having a longitudinal axis LA. Tube 614 may include a first axial end 616A and a second axial end 616B located axially opposite the first axial end 616A with respect to the longitudinal axis LA. Spring 612 may include one or more openings 618 formed within the tube 614 and disposed axially between the first axial end 616A and the second axial end 616B to define one or more elastic members 620 of spring 612. The openings 618 may extend radially through the wall of tube 514. In some embodiments, the elastic member 620 may be configured to facilitate axial compression and / or extension of the spring 612 along the longitudinal axis LA. For example, an axially elongated opening 618 (slot) may define the elastic member 620, which may be part of the cell structure. In various embodiments, the elastic member 620 may include one or more flexible (e.g., elongated) frame members (e.g., beams, posts).

[0056]

[0104] Figure 7C shows a schematic perspective view of another exemplary composite spring 712. Spring 712 may include elements of spring 12. Similar elements are indicated using reference numerals with 700 added. Spring 712 may include a fenestrated tube 714 made of fiber-reinforced composite material and having a longitudinal axis LA. Tube 714 may include a first axial end 716A and a second axial end 716B located axially opposite the first axial end 716A with respect to the longitudinal axis LA. Spring 712 may include one or more openings 718 formed within tube 714 and disposed axially between the first axial end 716A and the second axial end 716B to define one or more elastic members 720 of spring 712. The openings 718 may extend radially through the wall of tube 714. In some embodiments, the elastic member 720 may be configured to facilitate axial compression and / or extension of the spring 712 along the longitudinal axis LA. For example, an opening 718 may define the elastic member 720, which may be part of a cellular structure. For example, a polygonal opening 718 may define the elastic member 720, which may be part of a relatively coarse honeycomb structure. In various embodiments, the elastic member 720 may include one or more flexible (e.g., elongated) frame members (e.g., beams, posts).

[0057]

[0105] Figure 7D shows a schematic perspective view of another exemplary composite spring 812. Spring 812 may include elements of spring 12. Similar elements are indicated using reference numerals with 800 added. Spring 812 may include a fenestrated tube 814 made of fiber-reinforced composite material and having a longitudinal axis LA. Tube 814 may include a first axial end 816A and a second axial end 816B located axially opposite the first axial end 816A with respect to the longitudinal axis LA. Spring 812 may include one or more openings 818 formed within tube 814 and disposed axially between the first axial end 816A and the second axial end 816B to define one or more elastic members 820 of spring 812. The openings 818 may extend radially through the wall of tube 814. In some embodiments, the elastic member 820 may be configured to facilitate axial compression and / or extension of the spring 812 along the longitudinal axis LA. For example, an opening 818 may define the elastic member 820, which may be part of a cellular structure. For example, a polygonal opening 818 may define the elastic member 820, which may be part of a relatively coarse honeycomb structure. In various embodiments, the elastic member 820 may include one or more flexible (e.g., elongated) frame members (e.g., beams, posts).

[0058]

[0106] Figure 8 is a flowchart of a method 1000 for manufacturing a compound spring 12 or another compound spring. Method 1000 can be carried out using compression molding apparatuses 50, 150 (shown in Figures 16A-16C and 18A-18D) described below. Embodiments of spring 12 and / or apparatuses 50, 150 can be incorporated into Method 1000. In various embodiments, Method 1000 is: Forming a tubular (e.g., cylindrical, annular) precursor 24 from a fiber-reinforced composite material (Block 1002); This includes utilizing a subtractive manufacturing process to form one or more openings 18, 118, 218, 318, 418, 518, 618, 718, 818 (hereinafter collectively referred to as "openings 18") through the wall of a tubular precursor 24 in order to define the elastic members 20, 120, 220, 320, 420, 520, 620, 720, 820 of the spring 12 (hereinafter collectively referred to as "elastic members 20" of the spring 12) (block 1004).

[0059]

[0107] Aspects of Method 1000 will be described with reference to the following figures.

[0108] Figure 9 is a perspective view of exemplary uncured tubular precursors 24, 124, 224, 324 (collectively referred to herein as “precursors 24”) of spring 12. Precursors 24 may also be referred to as “blanks”. Precursors 24 may be unfinished items obtained during the process of manufacturing spring 12. For example, a precursor 24 may undergo compression molding, and then spring 12 may be obtained by using a material removal process (i.e., a subtractive process) to form an opening 18 through the wall of the precursor 24. For example, a cured precursor 24 may define the entire shape of spring 12 and may have the same longitudinal axis LA. In various embodiments, a cured precursor 24 may have the same or different wall thickness T2 (shown in Figure 15) as spring 12.

[0060]

[0109] The precursor 24 can be manufactured using appropriate composite manufacturing techniques. In various embodiments, the precursor 24 may be formed from fiber (e.g., carbon fiber or glass fiber) reinforced composite materials containing thermoplastic predicates such as homopolymers, polyoxymethylene (POM) (also known as acetal), polyacetals, and polyformaldehyde. In some embodiments, POM, sold by DuPont Chemical Company under the trademark Delrin, can exhibit suitable strength, hardness, rigidity, and stiffness, and may be suitable for low friction and dimensional stability down to low temperatures substantially close to about -40°C. In various embodiments, the precursor 24 may be formed from fiber (e.g., carbon fiber or glass fiber) reinforced composite materials containing thermosetting predicates.

[0061]

[0110] Figure 10 is an enlarged schematic view of region R1 of the precursor 24A shown in Figure 9. In some embodiments, the precursor 24A may be formed using pre-impregnated fiber layers 26 of a partially hardened matrix (also referred to herein as “prepreg”) that are integrally laminated (i.e., superimposed) and wound around a longitudinal axis LA, and then compression-molded. For example, the layers 26 may initially be supplied in sheet form, laminated, and / or wound around an elongated (e.g., cylindrical) holder such as a sleeve 130 (shown in Figure 17) or a mandrel 32 (shown in Figure 17), thereby obtaining a tubular shape. In some embodiments, each of the layers 26 may be a suitable prepreg sheet. In various embodiments, one or more layers 26 may include fibers (e.g., carbon fibers or glass fibers) that are relatively short, randomly oriented, continuous, unidirectional, and / or composed of a suitable stitching pattern.

[0062]

[0111] In some embodiments, one or more layers 26 may include a sheet molding compound (SMC) containing pre-grade carbon fibers and / or glass fibers. In various embodiments, the SMC may be a glass fiber reinforced polyester material. In some embodiments, one or more layers 26 may include a carbon fiber sheet molding compound (CF-SMC) that is ready to be molded and suitable for compression molding.

[0063]

[0112] In some embodiments, the CF-SMC may include short carbon fibers (i.e., carbon fiber tows cut from a unidirectional tape of pregreg). The length and distribution of the carbon fibers may be relatively regular, uniform, or constant. As for the matrix, the CF-SMC may include a suitable thermosetting resin, such as polyester, vinyl ester, or epoxy. In some embodiments, one or more layers 26 may include a Forged Molding Compound®, such as product number PTE130N131, and TCS-0021-18E, sold under the trademark MITSUBISHI CHEMICAL, may be suitable. The Forged Molding Compound® may be supplied in sheet form, including a carbon fiber prepreg with a random configuration of short (i.e., cut, discontinuous) fibers to aid in fluidity when molding complex shapes.

[0064]

[0113] In some embodiments, one or more layers 26 may include a carbon fiber fabric (i.e., cloth) prepreg, where the long fibers may take the form of a single stitching method, and a base material is used during manufacturing to bond the long fibers together and / or to bond the long fibers to other components. The base material may be a partially cured (e.g., B-stage material) thermosetting resin to allow for easy handling. The carbon fibers in the prepreg may be constructed (woven) in a stitching method such that two different sets of long fibers are woven together at right angles. In some embodiments, the carbon fiber fabric of the suitable prepreg may be a type of fabric sold under the trademark MITSUBISHI CHEMICAL.

[0065]

[0114] In some embodiments, one or more layers 26 may consist of carbon fibers in unidirectional (UD) tapes or sheets containing a thermosetting epoxy matrix, which are suitable for compression molding. In some embodiments, product numbers PYROFIL® 360 and PYROFIL® 361, marketed under the trademark MITSUBISHI CHEMICAL, may be suitable.

[0066]

[0115] In some embodiments, all layers 26 may be of the same type of material (e.g., a sheet) with the same fiber orientation with respect to the longitudinal axis LA. In some embodiments, all layers 26 may be of the same type of material, but some sheets may have different fiber orientations with respect to the longitudinal axis LA, depending on the desired mechanical properties of the spring 12. In some embodiments, layers 26 may include different types of prepreg sheets. For example, in some embodiments, layer 26 may be 100% CF-SMC, partial CF-SMC with some UD sheets, or 100% UD sheets, depending on the desired mechanical properties (e.g., spring constant).

[0067]

[0116] In some embodiments, the sheet defining the layer 26 may be substantially planar, flexible, and have a thickness between 2 mm and 3 mm. In some embodiments, multiple layers 26 may be required to achieve a desired pre-compression thickness T1 of the walls of the uncured precursor 24. In some embodiments, multiple layers 26 may be wound around a holder to obtain a pre-compression thickness T1 between, for example, 5 mm and 25 mm. Alternatively, a sheet of appropriate thickness may be selected to correspond to the desired pre-compression thickness T1, resulting in only a single layer 26 being required to form the precursor 24. In some situations, the prepreg sheet used to form the layer 26 may be cut to a desired shape, length, and width to facilitate winding around a holder. A non-uniform thickness T1 may be achieved through partially / cut layers 26 of varying axial lengths and / or axial positions on the uncured precursor 24.

[0068]

[0117] The precursor 24 shown may then proceed to a compression molding step. Optionally, stitching may be applied to the precursor 24 before compression molding, as described below.

[0069]

[0118] Figure 11A shows a pleated prepreg sheet 34 that can be used to form any one of the precursors 124, 224, and 324. The pleated prepreg sheet 34 may contain fibers (e.g., glass fibers or carbon fibers) and any or other suitable matrix material of any kind disclosed above (e.g., thermoplastic or thermosetting). The pleated prepreg sheet 34 can be pleated using known or other pleating equipment. For example, the pleated prepreg sheet 34 can be pleated using a servo knife pleating machine such as machine number MFM-2-S, sold under the trademark ROTH. In some embodiments, using the pleated prepreg sheet 34 to form a spring 12 can help improve the resistance of the spring 12 to torsional shear stress that it may experience during use.

[0070]

[0119] Figure 11B schematically shows a pleated prepreg sheet 34 wound around a holder such as a sleeve 130 which may be placed on a mandrel 132. Alternatively, the pleated prepreg sheet 34 may be wound directly onto the mandrel 32. In some embodiments, the pleated prepreg sheet 34 may be formed to have a thickness T1 which can substantially correspond to the pre-compression radial thickness T1 of the precursor wall 24 (shown in Figure 11B). The pleated prepreg sheet 34 may be wound over the sleeve 130 such that adjacent pleats 36 are in contact with each other. For example, the pleated prepreg sheet 34 may be wound such that the pleats 36 as a whole are relatively tightly packed. The pleated prepreg sheet 34 may be wound around the longitudinal axis LA such that the pleats 3 are substantially oriented radially with respect to the longitudinal axis LA. In some embodiments, when the pleated prepreg sheet 34 is wound around the longitudinal axis LA, both ends of the pleated prepreg sheet 34 can come into contact with each other and overlap.

[0071]

[0120] Figures 12A–12C are schematic enlarged views of region R1 in Figure 9 for precursors 124, 224, and 334, respectively. Figure 12A shows precursor 124, which represents a single pleated prepreg sheet 34 wound around a longitudinal axis LA. The faces of adjacent pleats 36 can be arranged relatively close to each other or in contact with each other.

[0072]

[0121] Figure 12B shows an embodiment in which two pleated prepreg sheets 34 are wrapped around a longitudinal axis LA. Two or more pleated prepreg sheets 34 may be laminated together to form a multilayer pleated prepreg sheet. Two pleated prepreg sheets 34 may be pleated together in a single pleating operation. Two pleated prepreg sheets 34 may be pleated and configured such that, as a result, one pleated prepreg sheet 34 overlaps the other pleated prepreg sheet 34 and the pleats 36 of the two pleated prepreg sheets 34 interlock with each other.

[0073]

[0122] The fiber orientation and type of the pleated prepreg sheet 34 can be selected to achieve desired mechanical properties. In various embodiments, the two pleated prepreg sheets 34 may have the same or different fiber orientations. In various embodiments, the two pleated prepreg sheets 34 may be substantially the same or of different types. For example, both pleated prepreg sheets 34 may be prepreg fibers arranged in different fiber orientations (stitch orientations). In some embodiments, both pleated prepreg sheets 34 may be unidirectional prepreg sheets arranged in different fiber orientations. In some embodiments, both pleated prepreg sheets 34 may be forged molding compound™ containing short (i.e., cut discontinuous) fibers that are at least partially randomly oriented and impregnated with a thermosetting resin. In some embodiments, the radially inward pleated prepreg sheet 34 may be a forged molding compound of carbon fibers containing short (i.e., cut, discontinuous) fibers that are at least partially randomly oriented and impregnated with a thermosetting resin, and the radially outward pleated prepreg sheet 34 may be prepreg fibers, in which long carbon fibers are constructed (woven) in a single stitching manner.

[0074]

[0123] Figure 12C shows an embodiment in which a single pleated prepreg sheet 34 is wound around a longitudinal axis LA and sandwiched between two or more layers 26, which may be unpleated prepreg sheets 38. In various embodiments, one or both unpleated prepreg sheets 38 may be combined with a single layer of pleated prepreg sheets 34. In some embodiments, one or both unpleated prepreg sheets 38 may be combined with two or more pleated prepreg sheets 34 in a multilayer configuration. For example, one or more inner unpleated prepreg sheets 38 may be arranged radially inward of the pleated prepreg sheets 34 and wound around the longitudinal axis LA. For example, one or more outer unpleated prepreg sheets 38 may be arranged radially outward of the pleated prepreg sheets 34 and wound around the longitudinal axis LA.

[0075]

[0124] The fiber orientation and type of the non-pleated prepreg sheet 38 can be selected to achieve desired mechanical properties. In various embodiments, the two non-pleated prepreg sheets 38 may have the same or different fiber orientations. In various embodiments, the two non-pleated prepreg sheets 38 may be substantially identical or of different types.

[0076]

[0125] Referring to Figures 12A-12C, the precursors 124, 224, and 324 shown may then proceed to the compression molding step. Optionally, stitching may be applied to precursors 124, 224, and 324 before the compression molding as described below.

[0077]

[0126] Figures 13A-13C schematically show a stitching process that can be applied to any of the spring precursors 24, 124, 224, and 324 before compression molding (i.e., in an uncured state). The stitching can be carried out by inserting a needle 40 carrying stitching thread 42 through a layer stack 26 (e.g., a prepreg sheet) to form a 3D structure. The stitching can further strengthen the final structure of the spring 12 after compression molding. In some embodiments, stitching of precursors 24, 124, 224, and 324 can facilitate improved resistance to torsional shear stress that the spring 12 may experience during use. In various embodiments, the stitching thread 42 may include, for example, carbon fiber or glass fiber. The stitching may be performed using one or more stitch patterns, such as straight stitch, triple stretch stitch, zigzag stitch, triple zigzag stitch, stretch zigzag stitch, blind hem stitch, shell tuck stitch, blanket stitch, ladder stitch, elastic overlock stitch, double overlock stitch, slant pin stitch, slant overlock stitch, feather stitch, tree stitch, fagoting stitch, honeycomb stitch, scallop stitch, and buttonhole stitch.

[0078]

[0127] The stitching may be carried out using an industrial sewing machine, such as a sewing machine sold under the trademark VETRON. The sewing machine may be a multi-axis computer numerically controlled (CNC) sewing machine capable of manipulating the precursors 24, 124, 224, and 324 relative to the needle 40 during the stitching process (e.g., rotating, advancing, indexing). The sewing machine may be a "long-arm" sewing machine. In some embodiments, the precursors 24, 124, 224, and 324 may be stitched together before compression molding, either while positioned on or away from the sleeve 130. The stitch 44 may be applied along the stitch line 46. The stitch 44 may be applied from the radially outward direction of the precursors 24, 124, 224, and 324.

[0079]

[0128] Figures 13B and 13C are exemplary cylindrical sections through the respective walls of precursors 24 and 124, cut from region R2 in Figure 13A. Referring to Figure 13B, the stitch 44 can extend through multiple layers 26 to secure the layers 26 together. In some embodiments, the stitch 44 can extend through all or part of the layer 26 so as to extend through the overall thickness T1 shown in Figures 12A–12C. Referring to Figure 13C, the stitch 44 can extend through the pleated prepreg sheet 34. In some embodiments, the stitch 44 can secure the pleats 36 of the pleated prepreg sheet 34 together.

[0080]

[0129] Figure 14A is a partial front view of the upper portion of the spring 12 shown in Figures 2A-2C, with the stitch line 46 shown above it. In some embodiments, the stitch line 46 may be oriented to maintain the integrity of the remaining stitch 44 after the material removal process that forms the opening 18. For example, in embodiments where the elastic member 20 is a coil having a first helical angle α1 with respect to the longitudinal axis LA, the stitch line 46 may also be applied in a helical pattern having a second helical angle α2 (i.e., α1 = α2) with respect to the longitudinal axis LA that may be substantially equal to the first helical angle α1. In some embodiments, this may allow the spring 12 to have a complete stitch line 46 that extends continuously around the spring 12 and is not interrupted by the opening 18.

[0081]

[0130] Figure 14B is an enlarged view of region R3 in Figure 14A to schematically show an exemplary plain weave of an outer layer 26 used in a precursor 24 used to manufacture a spring 12. In some embodiments, one or more layers 26 of the precursor 24 may be oriented according to a preferred fiber orientation α3 in order to maintain the integrity of some fibers after a material removal process that forms an opening 18. In the plain weave of Figure 14B, the fabric is oriented such that the weft 48 has a fiber orientation α3 (i.e., α1=α2=α3) where the first helical angle α1 and the second helical angle α2 with respect to the longitudinal axis LA are substantially equal. In some embodiments, this can allow the spring 12 to have complete fibers (i.e., weft 48) that extend continuously around the spring 12 and are not interrupted by the opening 18. In embodiments where layer 26 includes one or more UD sheets, some or all of such UD sheets may be oriented to have a fiber orientation α3, so that some fibers can extend continuously around the spring 12 and may not be interrupted by the opening 18. In various embodiments, the helical angle α1, the second helical angle α2, and the fiber orientation α3 may be non-zero (i.e., greater than zero). In various embodiments, the helical angle α1, the second helical angle α2, and the fiber orientation α3 may be between 10 and 30 degrees.

[0082]

[0131] Figure 15 is a partial cross-sectional view of the upper portion of spring 12 showing some of the stitches 44 located along line 15-15 in Figure 2A. In various embodiments, the stitches 44 may extend through part or all of the wall thickness T2 of spring 12. As shown in Figure 15, the elastic member 20 may have a coil configuration, where the cross-sectional profile of the coil turn may be rectangular or square.

[0083]

[0132] Figure 16A is a schematic axial cross-sectional view of an exemplary compression molding apparatus 50 (hereinafter referred to as "apparatus 50") for performing a compression molding operation on a tubular precursor 24. Apparatus 50 may include a mold comprising a first (lower) mold portion 52A and a second (upper) mold portion 52B cooperating with the first mold portion 52B to engage oppositely along a plane to define a mold cavity 54 between them. In some embodiments, the opposing surfaces of the mold portions 52A, 52B may include the longitudinal axis LA of the mandrel 32 and may be parallel to the longitudinal axis LA.

[0084]

[0133] A mandrel 32 having a precursor 24 wound around it can be inserted into the mold portions 52A and 52B, and can support the precursor 24 within the mold cavity 54. Figure 16A shows the mold portions 52A and 52B separated from each other to define an opening to the mold cavity 54. For example, the second mold portion 52B may be movable along arrow A to close the mold by moving the second mold portion 52B toward the first mold portion 52, and to open the mold by moving the second mold portion 52B toward the first mold portion 52A.

[0085]

[0134] In some embodiments, the first mold portion 52A may be fixed to a press machine, such as a V-Duo® vertical press manufactured by ENGEL® Canada Inc., to receive the mandrel 32 and the precursor 24 wound around the mandrel 32. In some embodiments, the first mold portion 52A may be considered a fixed die.

[0086]

[0135] In some embodiments, the second mold portion 52B may be removable from the press to facilitate the insertion and removal of the mandrel 32 and precursor 24 from the first mold portion 52A. In some embodiments, the second mold portion 52B may be considered a movable die.

[0087]

[0136] Furthermore, the mandrel 32 and precursor 24 may be movable along arrow A when the mold is opened. For example, opening the mold may allow the mandrel 32 and precursor 24 to be inserted into the mold by lowering them into the first mold portion 52A in preparation for compression molding. Furthermore, opening the mold may also allow the mandrel 32 and precursor 24 to be removed (released) from the mold after compression molding by raising them out of the first mold portion 52A. In some embodiments, a suitable shuttle may be provided to facilitate moving the mandrel 32 and precursor 24 into and out of the mold.

[0088]

[0137] The apparatus 50 may further include a heat source 56 for transferring heat to the precursor 24 during compression molding (i.e., thermopress) to assist in the solidification (e.g., curing) of the precursor 24. Heat H from the heat source 56 may be transferred to the precursor 24 via the mandrel 32 and / or via one of the two mold portions 52A, 52B. In some embodiments, the heat source 56 may include an electrically heated element embedded in or otherwise thermally communicating with the mold portions 52A, 52B and / or the mandrel 32. In some embodiments, the heat source 56 may include, for example, one or more heating plates engaged to transfer conductive heat to one or more mold portions 52A, 52B. In some embodiments, the heat source 56 may include a heat transfer fluid (e.g., oil, liquid water, steam) carried through one or more passages 71 formed within the mold portions 52A, 52B and / or one or more passages (not shown) within the mandrel 32. The mold parts 52A, 52B and the mandrel 32 may be made from metal materials such as steel or aluminum, or from composite materials.

[0089]

[0138] In some embodiments, the mandrel 32 may have a central rod 60 that extends substantially coaxially with the longitudinal axis LA and project axially beyond the molding surface of the mandrel 32 and, consequently, beyond the precursor 24. The rod 60 can engage by mating with one or more cooperating recesses formed in the first mold portion 52A and / or the second mold portion 52B. The rod 60 can facilitate the registration of the mandrel 32 and the precursor 24 within the mold cavity 54 to help make the wall thickness of the spring 12 reproducible and optionally uniform. The rod 60 can further facilitate the manual handling of the mandrel 32 for inserting or removing it from the first mold portion 52.

[0090]

[0139] Figure 16B is a schematic axial cross-sectional view of the apparatus 50, showing the mold portions 52A and 52B in a closed state during compression molding. The precursor 24 and the mold cavity 54 may be sized to define a compression fit when the mold portions 52A and 52B are closed together, so that the precursor 24 can occupy substantially the entirety of the mold cavity 54 after compression molding 54.

[0091]

[0140] During compression molding, pressure and heat can be applied to the precursor using mold portions 52A, 52 and a heat source 56. Compression molding can cause dissolution of the base material and / or activation of epoxy-type base materials. Mold portions 52A, 52B release air from the precursor 24 during compression molding, and as a result, the wall thickness T of the precursor 24 after compression molding can be smaller than the wall thickness before compression molding. In embodiments in which the precursor 24 includes multiple layers 26, compression molding can fuse the multiple layers 26 together, thereby forming a structure that is substantially free of knit lines.

[0092]

[0141] In some embodiments, the mandrel 32 may have an optional chamfered axial end 58, or an axial end with a reduced section to provide a thickened / reinforced region of the spring 12 suitable for certain applications and mounting constraints. In some embodiments, the mandrel 32 may be tapered in the axial direction, and as a result, the resulting spring 12 may also be tapered. In some embodiments, the radially outer surface of the mandrel 32 may be slightly tapered in the axial direction by a draft angle to facilitate the removal of the precursor 24 from the mandrel 32 by sliding the precursor 24 axially from the mandrel 32 along the longitudinal axis LA.

[0093]

[0142] Figure 16C is a schematic transverse cross-sectional view of the apparatus 50 of Figure 16A, showing mold portions 52A, 52B in a closed state during compression molding. The mold portions 52A, 52B and the mandrel 32 can define a mold cavity 54 (and the final spring 12) having desired inner and outer cross-sectional profiles, as shown in the springs 12, 112, 212, 312, 412 shown in Figures 2A-6C. In various embodiments, the mold cavity 54 may have a circular or polygonal inner cross-sectional profile. In some embodiments, the mold cavity 54 may have a circular or polygonal outer cross-sectional profile. In various embodiments, the mold cavity 54 may have an elliptical, triangular, quadrilateral, pentagonal, hexagonal, or octagonal inner and / or outer cross-sectional profiles. In some embodiments, the outer cross-sectional profile of the mold cavity 54 may correspond to the final outer cross-sectional profile of the spring 12. In some embodiments, the inner cross-sectional profile of the mold cavity 54 can correspond to the final inner cross-sectional profile of the spring 12.

[0094]

[0143] Figure 17 is a perspective view of the tubular precursor 24 of the spring 12, shown with a sleeve 130 and mandrel 132 used during the compression molding of the precursor 24. In the apparatus 50 or apparatus 150 shown in Figures 18A-18D, the uncured precursor 24 can be prepared directly on the mandrel 32 (e.g., wrapped around it) or on an optional sleeve 130. Using multiple sleeves 130 can facilitate increased production speed by allowing multiple uncured precursors 24 to be prepared simultaneously without occupying the mandrel 132 or mold. Furthermore, using sleeves 130 can facilitate mounting the uncured precursor 24 onto the mandrel 132. Once the uncured precursor 24 is prepared on the sleeve 130, the sleeve 130 can be axially slid on the mandrel 132.

[0095]

[0144] In some embodiments, such that heat H is supplied to the precursor 24 via the mandrel 132, the sleeve 130 may be made of a material having relatively high thermal conductivity (e.g., a metallic material) (e.g., an aluminum alloy). The sleeve 130 and mandrel 132 may be sized to allow relative sliding while maintaining a relatively tight fit to facilitate conductive heat transfer from the mandrel 132 to the precursor 24 through the sleeve 130. In other words, the sleeve 130 may be engaged to transfer conductive heat to the mandrel 132 when mounted on the mandrel 132.

[0096]

[0145] Figure 18A is a schematic axial cross-sectional view of another exemplary compression molding apparatus 150 for compression molding of a tubular precursor 24, where the mold portions 152A and 152B of the apparatus 150 are shown open. Apparatus 150 may include elements of apparatus 50 already described above. Similar elements are indicated using reference numerals with 100 added. Unlike apparatus 50, apparatus 150 may be configured for use with a sleeve 130, and the mandrel 132 may be pivotably connected to the second mold portion 152A, so that the mandrel 132 is rotatable about a pivot axis PA which is perpendicular to the longitudinal axis LA of the mandrel 132.

[0097]

[0146] In some embodiments, the first mold portion 152A may be fixed, and the second mold portion 152B may be movable along arrow A to open and close the mold defined by the mold portions 152A and 152B. In some embodiments, an actuator 162 may be operably connected to the second mold portion 152B to cause the second mold portion 152B to move along arrow A and to apply sufficient force when the second mold portion 152A is pushed toward the first mold portion 152A during compression molding.

[0098]

[0147] The apparatus 150 may include a third mold portion 152C that cooperates with the first mold portion 152A and the second mold portion 152B to define the mold cavity 154. The third mold portion 152C may be movable along arrow B to allow the mandrel 132 to rotate about a pivot axis PA. In some embodiments, an actuator 164 may be operably connected to the third mold portion 152C to cause the movement of the third mold portion 152C along arrow B. Once the mandrel 132 has been rotated to the compression molding position, the third mold portion 152C may be movable along the longitudinal axis LA of the mandrel 132 to selectively lock or unlock the mandrel 132 in the compression molding position. In other words, arrow B may be parallel to the longitudinal axis LA when the mandrel 132 is in the compression molding position shown in Figure 18C.

[0099]

[0148] In some embodiments, actuator 166 may be operably connected to mandrel 132 to rotate mandrel 132 about pivot axis PA along arrow C. Mandrel 132 may be pivotably connected to first mold portion 152A via pin 168 defining a pivot or hinge about pivot axis PA. Rotation of mandrel 132 along arrow C can allow mounting (i.e., fitting) sleeve 130 and uncured precursor 24 onto mandrel 132, and removing sleeve 130 and cured precursor 24 from mandrel 132 after compression molding. Mounting and removing sleeve 130 from mandrel 132 may be performed by sliding sleeve 130 against mandrel 132 along longitudinal axis LA. Actuators 162, 164, 166 may be hydraulic actuators, pneumatic actuators, or electric actuators.

[0100]

[0149] The apparatus 150 may further include a heat source 156 for transferring heat to the precursor 24 during compression molding to assist in the solidification (e.g., curing) of the precursor 24. Heat H from the heat source 156 may be transferred to the precursor 24 via the mandrel 132 and / or via one of both mold portions 152A, 152B. In some embodiments, the heat source 156 may include an electrically heated element embedded in or otherwise thermally communicating with the mold portions 152A, 152B and / or the mandrel 132. In some embodiments, the heat source 156 may include a heat transfer fluid (e.g., oil, liquid water, steam) carried through one or more passages 171 formed in the mold portions 152A, 152B and / or one or more passages 170 formed in the mandrel 132. The mandrel 132 may include a central rod 160.

[0101]

[0150] Figure 18B is a schematic axial cross-sectional view of the apparatus 150 in a state ready for compression molding of the precursor 24. The precursor 24 and sleeve 130 are mounted on the mandrel 132, which is rotated around the pivot axis PA to the compression molding position. Furthermore, the third mold portion 152C is moved to the right toward the mandrel 132.

[0102]

[0151] Figure 18C is a schematic axial cross-sectional view of the apparatus 150 in the state where the precursor 24 is being compression molded. The second mold portion 152B is lowered and pressed against the first mold portion 152A, during which time the precursor 24 is inside the mold. When pressure is applied to the precursor 24, heat H is also supplied to the precursor 24 by a heat source 156. The heat source 156 may include a heat transfer fluid circulating in passages 170 and 171.

[0103]

[0152] Figure 18D is a schematic axial cross-sectional view of the apparatus 150 after the compression molding of the precursor 24 is complete. Figure 18D shows the process of releasing the mandrel 132 from the mold. The second mold portion 152B may be moved away from the first mold portion 152A. The third mold portion 152C may be moved to the left, thereby allowing the left axial end of the mandrel 132 to rotate upward around the pivot axis PA. Once the mandrel 132 is rotated to the position shown in Figure 18A, the sleeve 130 and the precursor 24 can be slid away from the mandrel 132. The hardened precursor 24 can then be removed from the sleeve 130 by sliding the precursor 24 axially away from the sleeve 130. In some embodiments, the radially outer surface of the sleeve 130 may be slightly tapered in the axial direction by the amount of the draft angle, in order to facilitate the removal of the precursor 24 from the sleeve 130 by sliding the precursor 24 axially away from the sleeve 130 along the longitudinal axis LA.

[0104]

[0153] Figure 19A is a perspective view of another exemplary tubular precursor 424 formed from two halves referred to as thermosetting materials 476A, 476B, which are integrally compression-molded and optionally further fixed using one or more adhesive bonding patches 478A, 478B. The precursor 424 may be manufactured without using mandrels 32, 132. For example, instead of winding layer 26 around a mandrel, multiple paired prepreg thermosetting materials 476A, 476B may be prepared separately and integrally compression-molded. In some embodiments, each thermosetting material 476A, 476B may have a semi-cylindrical (e.g., U-shaped) profile of substantially constant thickness along the longitudinal axis LA. In some embodiments, the paired edges of the thermosetting materials 476A, 476B may be sealed using their respective adhesive bonding patches 478A, 478B.

[0105]

[0154] Figure 19B shows the orientation of the first thermosetting material 476A and the second thermosetting material 476B for preparation for compression molding. The first thermosetting material 476A may be placed inside the lower mold portion of the mold. The second thermosetting material 476B may then be placed on top of the first thermosetting material 476A, so that their mating surfaces are substantially aligned and matingly engaged. By arranging the first thermosetting material 476A and the second thermosetting material 476B in this way, the annular shape of the precursor 424 can be defined.

[0106]

[0155] Figure 19C shows the orientation and relative arrangement of the first thermosetting material 476A and the second thermosetting material 476B during compression molding. Prior to compression molding, the first thermosetting material 476A and the second thermosetting material 476B may be rotated within the mold about the longitudinal axis LA (e.g., 90 degrees) so that the seam between the first thermosetting material 476A and the second thermosetting material 476B coincides with the mating surface or mating line between the upper and lower mold portions. In some embodiments, the axial ends of the first thermosetting material 476A and the second thermosetting material 476B may be maintained in mating relationship by interlocking elements such as dovetails and pins. In some embodiments, the axial ends of the first thermosetting material 476A and the second thermosetting material 476B may be maintained in mating relationship by one or more adhesive bonding patches 478A, 478B.

[0107]

[0156] By utilizing non-mandrel technology, greater flexibility can be obtained in the geometric structure that can be incorporated into the precursor 424. For example, such technology allows for tapering of both axial ends of the precursor, thereby increasing the wall thickness, eliminating the need to remove the precursor 424 by sliding and separating the mandrel.

[0108]

[0157] Figure 20 is a perspective view of the hardened tubular precursor 24 after compression molding and during a subtractive manufacturing process to remove material from the precursor 24, thereby forming an opening 18 within the spring 12. In some embodiments, water jet cutting may be used to cut the opening 18 within the precursor 24. For example, a water jet cutter 72 may be programmed to follow a cutting tool path 74 that defines one or more outlines of one or more openings 18 that will be formed within the spring 12. In some embodiments, the water jet cutter 72 may be CNC controlled using a tool path obtained from a computer-aided design (CAD) of the spring 12.

[0109]

[0158] In some embodiments, the tool path 74 may be configured to create a single continuous coil as the elastic member 20. In some embodiments, the tool path 74 may be configured to create a multiple-start continuous coil, such as a continuous coil with two starts or a continuous coil with three starts. In some embodiments, the tool path 74 may be configured to create a cellular structure as described herein.

[0110]

[0159] Other subtractive manufacturing processes may be used instead of or in addition to water jet cutting. For example, other cutting (e.g., laser cutting), turning, machining (e.g., milling), etching, and grinding may be used to form the spring 12 from the hardened precursor 24. In some embodiments, the subtractive manufacturing process may be performed on a fully hardened precursor 24, thereby eliminating the need to further harden the precursor 24 after the subtractive manufacturing process. In some embodiments, one or more subtractive manufacturing processes may be used to adjust the inner and outer lateral cross-sectional profiles of the precursor 24, and / or to cut the axial length of the precursor 24, for example.

[0111]

[0160] In some situations, manufacturing time can be reduced by performing tasks in parallel. For example, by using multiple sleeves 130, the steps of winding the uncured precursor 24, performing compression forming, and performing subtractive manufacturing can be performed in parallel for different precursors 24. In some embodiments, when manufacturing tasks are performed in parallel, the total cycle time for manufacturing the spring 12 may be on the order of 2 to 3 minutes.

[0112]

[0161] The mechanical and biomechanical properties of the spring 12 can be adjusted by selecting the position and extent of the material removed from the hardened precursor 24. For example, through experimentation, simulation, and / or modeling (e.g., finite element analysis), geometric parameters of the spring 12, such as the position, orientation, thickness, and spacing of the material not lost within the spring 12, can be determined to achieve the desired properties. In the case of an elastic member 20 having a coil configuration, such geometric parameters may include, for example, the width, inner diameter, outer shape of the strip of material to be removed (e.g., having a rectangular cross-section), the spacing between adjacent turns of the coil, the number of turns, and the helical angle α1 of the turns with respect to the longitudinal axis LA.

[0113]

[0162] Therefore, as can be understood, the embodiments described and shown above are intended to be merely illustrative. The scope is indicated by the attached claims.

Claims

1. A composite spring for vehicle suspension, wherein the composite spring is A tube made from a fiber-reinforced composite material and having a longitudinal axis, wherein the tube is A first axial end having a closed shape that completely encloses the longitudinal axis, With respect to the longitudinal axis, the second axial end is located in the axial direction opposite to the first axial end, One or more openings formed to pass through the wall of the pipe and disposed in the axial direction between the first axial end and the second axial end, wherein a portion of the wall adjacent to the one or more openings defines the elastic member of the spring. Includes, pipe A composite spring equipped with [specific features / features].

2. The elastic member is a coil. The composite spring according to claim 1.

3. The one or more openings define the cellular structure, The elastic member is part of the cell structure. The composite spring according to claim 1.

4. The one or more openings define the honeycomb structure, The elastic member is part of the honeycomb structure. The composite spring according to claim 1.

5. The tube has a circular radially inward profile when viewed along the longitudinal axis. A composite spring according to any one of claims 1 to 4.

6. The tube has a circular radially outward profile when viewed along the longitudinal axis. A composite spring according to any one of claims 1 to 5.

7. The tube has a non-circular radially outward profile when viewed along the longitudinal axis. A composite spring according to any one of claims 1 to 5.

8. The tube has a polygonal radially outer profile when viewed along the longitudinal axis. The composite spring according to claim 7.

9. The tube has a non-circular radially inward profile when viewed along the longitudinal axis. A composite spring according to any one of claims 1 to 4.

10. The tube has a non-circular radially outward profile when viewed along the longitudinal axis. The composite spring according to claim 9.

11. The tube has a polygonal radially outer profile when viewed along the longitudinal axis. The composite spring according to claim 10.

12. The closed shape is the first closed shape, The second axial end has a second closed shape that completely encloses the longitudinal axis. A composite spring according to any one of claims 1 to 11.

13. The first axial end is part of a first ring that completely encloses the longitudinal axis. A composite spring according to any one of claims 1 to 12.

14. The second axial end is part of a second ring that completely encloses the longitudinal axis. The composite spring according to claim 13.

15. The wall of the pipe includes a plurality of laminated fiber layers wound around the longitudinal axis, The aforementioned layers are sewn together as a single unit. A composite spring according to any one of claims 1 to 14.

16. The elastic member is a coil or is a coil, The coil has a first helical angle, The layers are sewn together in one piece along a stitch line having a second helical angle substantially equal to the first helical angle. The composite spring according to claim 15.

17. The fibers are formed by one stitching method within at least one of the layers. The composite spring according to claim 15 or claim 16.

18. The wall of the pipe includes a pleated fiber sheet wrapped around the longitudinal axis, A composite spring according to any one of claims 1 to 14.

19. One or more pleats of the pleated sheet are at least partially oriented radially with respect to the longitudinal axis. The composite spring according to claim 18.

20. The pleated fiber sheet is the first pleated fiber sheet, The wall of the pipe includes a second pleated fiber sheet that overlaps and interlocks with the first pleated fiber sheet. A composite spring according to claim 18 or claim 19.

21. The wall of the tube includes an outer non-pleated fiber sheet disposed radially outward of the pleated fiber sheet and wound around the longitudinal axis, A composite spring according to any one of claims 18 to 20.

22. The wall of the tube includes an inner non-pleated fiber sheet disposed radially inside the pleated fiber sheet and wound around the longitudinal axis, A composite spring according to any one of claims 18 to 21.

23. The wall of the tube includes a plurality of stitches extending through the pleated fiber sheet, A composite spring according to any one of claims 18 to 22.

24. The elastic member is a coil or is a coil, The coil has a first helical angle, The wall of the tube includes a stitch along a stitch line having a second helical angle substantially equal to the first helical angle. The composite spring according to claim 23.

25. A vehicle comprising a composite spring according to any one of claims 1 to 24.

26. A method for manufacturing a compound spring, The steps include forming a tubular precursor from a fiber-reinforced composite material, A step of using a subtractive manufacturing process to form one or more openings through the wall of the tubular precursor for the purpose of defining the elastic member of the spring; including, method.

27. The aforementioned subtractive manufacturing process includes water jet cutting. The method according to claim 26.

28. The step of forming the tubular precursor is The process involves wrapping a pre-impregnated pleated fiber sheet around the holder, The steps include: compressing and molding the pleated sheet to form the tubular precursor; including, The method according to claim 26 or claim 27.

29. The pleated sheet is a first pleated fiber sheet, The method described above is A step of winding a second pleated fiber sheet, which has been pre-impregnated with the base material, around the holder, such that the second pleated sheet overlaps and interlocks with the first pleated sheet. The steps include: compressing the first pleated sheet and the second pleated sheet together to form the tubular precursor; including, The method according to claim 28.

30. At least some of the fibers in the first pleated sheet are discontinuous and randomly oriented. The method according to claim 29.

31. The step of forming the tubular precursor includes, before the compression molding, winding the outer non-pleated fiber sheet, which has been pre-impregnated with the base material, around the holder and radially outward of the pleated sheet. The method according to any one of claims 28 to 30.

32. The step of forming the tubular precursor includes, before the compression molding, winding an inner non-pleated fiber sheet, which has been pre-impregnated with the base material, radially inward around the pleated sheet. The method according to any one of claims 28 to 31.

33. The step of forming the tubular precursor is The steps include wrapping one or more pre-impregnated fiber layers around the holder, The steps of sewing together one or more of the aforementioned layers, The steps include: compressing and molding one or more layers to form the tubular precursor; including, The method according to any one of claims 26 to 32.

34. The elastic member is a coil, The coil has a first helical angle, The step of sewing one or more layers together includes the step of sewing one or more layers together along a stitch line having a second helical angle substantially equal to the first helical angle, The method according to claim 33.

35. The step of forming the tubular precursor is The steps include wrapping one or more pre-impregnated fiber layers around the holder, The steps include: positioning the holder having one or more layers in a mold cavity by rotating the longitudinal axis of the holder around a pivot axis that is perpendicular to the longitudinal axis of the holder; The steps include: compressing and molding one or more layers to form the tubular precursor; including, The method according to any one of claims 26 to 32.

36. A compression molding apparatus for forming a tubular precursor for a compound spring, wherein the compression molding apparatus is The first mold section, A second mold portion cooperating with the first mold portion to define a mold cavity, wherein the first mold portion and the second mold portion are releasable from each other in order to open the mold cavity, A mandrel for holding the tubular precursor wound around the mandrel inside the mold cavity, wherein the mandrel has a longitudinal axis and is pivotably connected to the second mold portion, so that the mandrel can rotate about a pivot axis perpendicular to the longitudinal axis of the mandrel, A heat source for heating the tubular precursor during the compression molding of the tubular precursor and A compression molding apparatus equipped with the following features.

37. The heat source includes a heat transfer fluid, The mandrel includes a passage formed therein for transporting the heat transfer fluid. The compression molding apparatus according to claim 36.

38. The tubular precursor is provided with a metal sleeve for holding it, The metal sleeve is configured to be fitted onto the mandrel and to be disposed between the tubular precursor and the mandrel. The compression molding apparatus according to claim 36 or claim 37.

39. The heat source includes a heat transfer fluid, The mandrel includes a passage formed therein for transporting the heat transfer fluid. The metal sleeve is engaged to the mandrel to transfer conductive heat. The compression molding apparatus according to claim 38.

40. The mold includes a first mold portion and a third mold portion that cooperates with the second mold portion to define the mold cavity, The third mold portion is movable along the longitudinal axis of the mandrel in order to selectively lock or release the mandrel from the compression molding position. A compression molding apparatus according to any one of claims 36 to 39.

41. A precursor for tubular manufacturing of compound springs, The precursor comprises a plurality of fiber layers that have been pre-impregnated with a base material and wound around an elongated holder having a longitudinal axis, The aforementioned multiple layers are sewn together as a single unit. A precursor for tubular manufacturing.

42. The aforementioned multiple layers are sewn together along a stitch line having a non-zero spiral angle with respect to the longitudinal axis. The tubular precursor for manufacturing according to claim 41.

43. At least one of the plurality of layers has fibers oriented at a non-zero helical angle with respect to the longitudinal axis. The tubular precursor for manufacturing according to claim 42.

44. At least one of the aforementioned multiple layers is pleated, A tubular precursor for manufacturing according to any one of claims 41 to 43.

45. A precursor for tubular manufacturing of compound springs, The precursor comprises a pleated fiber sheet that has been pre-impregnated with a base material and wound around an elongated holder having a longitudinal axis, A pleated sheet has a plurality of pleats that are substantially oriented radially with respect to the longitudinal axis. A precursor for tubular manufacturing.

46. The pleated sheet is the first pleated sheet, The tubular manufacturing precursor includes a second pleated fiber sheet that has been pre-impregnated with the base material and wrapped around the elongated holder, The second pleated sheet overlaps and interlocks with the first pleated sheet. The tubular precursor for manufacturing according to claim 45.

47. The pleated sheet mentioned above An outer non-pleated fiber sheet, which is pre-impregnated with the aforementioned base material and disposed radially outside the pleated sheet and wound around the longitudinal axis, The aforementioned base material is pre-impregnated and disposed radially inside the pleated fiber sheet, and an inner non-pleated fiber sheet is wound around the longitudinal axis. sandwiched in between, The tubular precursor for manufacturing according to claim 45 or claim 46.

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