One-piece connecting rod and production method thereof

Abstract

The present invention relates to a method of manufacturing a connecting rod (1) by filament winding, said method comprising in particular: creating an internal body (5) by manufacturing a first component (6) by winding pre-impregnated fibers (17) around a mandrel (8) and removing the mandrel; manufacturing a second part (7); providing a shoulder (12) in the second part (7); assembling the first component with the second component (7, 22); creating an external body (14) by winding pre-impregnated fibers (17), identical to those used in the manufacture of the first component (6), around said internal body (5); creating a one-piece body (18) by polymerizing the assembly formed of the internal body and of the external body; and machining a fastening (19) at one end of the one-piece body; wherein the one-piece body (18) and the first fastening element (19) are made up of a one and same composite material.

Claims

1. A method for manufacturing a connecting rod (1) by filament winding, said method comprising the following steps: providing a mandrel (8); making an inner body (5) by: manufacturing a first part (6) by winding preimpregnated fibers (17) around said mandrel (8); removing the mandrel (8); manufacturing a second part (7); providing a shoulder (12) in the second part (7); assembling the first part (6) with the second part (7, 22); making an outer body (14) by winding preimpregnated fibers (17) around said inner body (5), said preimpregnated fibers (17) being identical to those used during the manufacture of the first part (6); making a one-piece body (18) by polymerization of the assembly formed by the inner body (5) and the outer body (14); machining a first fastening element (19) at one end of the one-piece body (18); wherein the one-piece body (18) and the first fastening element (19) are made up of a one and same composite material.

2. The method according to claim 1, wherein the second part (7) is also made by winding preimpregnated fibers (17) around said mandrel (8), said preimpregnated fibers (17) being identical to those used during the manufacture of the first part (6) and the outer body (14).

3. The method according to claim 1, wherein the shoulder (12) serves as a bearing surface that abuts the first part (6) during the assembly of the first part (6) with second part (7).

4. The method according to claim 1, wherein at least the first part (6) is partially polymerized before assembly.

5. The method according to claim 1, wherein additional layers (21) of preimpregnated fibers (17) are wound on one end or both ends of the inner body (5) during the making of the outer body (14).

6. The method according to claim 1, comprising a step of machining a second fastening element (19) at the other end of the one-piece body (18).

7. The method according to claim 1, wherein the second part is an end piece (22), the shoulder (12) of the end piece (22) serving as a bearing surface that abuts the first part (6) during the assembly of the first part (6) with the end piece (22).

8. The method according to claim 1, wherein the filament winding angle is variable along the inner body (5) during the making of the outer body (14).

9. The method according to claim 1, wherein the mandrel (8) comprises a cylindrical portion (9) connected to a part with a rectangular section (11) by a connecting part (10).

10. The method of claim 6, wherein the one-piece body (18) and the first and second fastening elements (19) are made up of a one and same composite material.

11. The method of claim 1, including the step of providing a second fastening element (19) at the other end of the one-piece body (18), wherein the second fastening element (19) is made from metal, carbon or plastic material.

12. The method according to claim 1, wherein the step of manufacturing the first part (6) includes providing the first part (6) with a first part cylindrical portion having a first length; the step of manufacturing the second part (7) includes providing the second part (7) with a second part cylindrical portion having a second length; and wherein the first length is greater than the second length.

13. The method according to claim 1, wherein the step of manufacturing the first part (6) includes providing the first part (6) with a first part cylindrical portion having a first length; the step of manufacturing the second part (7) includes providing the second part (7) with a second part cylindrical portion having a second length; and wherein the second length is greater than the first length.

14. A method for manufacturing a connecting rod (1) by filament winding, said method comprising the following steps: providing a mandrel (8); making an inner body (5) by; manufacturing a first part (6) by winding preimpregnated fibers (17) around said mandrel (8); removing the mandrel (8); manufacturing a second part (7), providing a shoulder (12) in the second part (7); assembling the first part (6) with the second part (7, 22); making an outer body (14) by winding preimpregnated fibers (17) around said inner body (5), said preimpregnated fibers (17) being identical to those used during the manufacture of the first part (6); making a one-piece body (18) by polymerization of the assembly formed by the inner body (5) and the outer body (14); machining a fastening element (19) at one end of the one-piece body (18); wherein the shoulder (12) serves as a bearing surface that abuts the first part (6) during the assembly of the first part (6) with second part (7); and wherein a tube (13) is inserted into the second part (7) to form the shoulder (12), said tube (13) being manufactured via the filament winding method using preimpregnated fibers (17) identical to those used for the inner body (5) and the outer body (14).

15. A method for manufacturing a connecting rod (1) by filament winding said method comprising the following steps: providing a mandrel (8); making an inner body (5) by; manufacturing a first part (6) by winding preimpregnated fibers (17) around said mandrel (8); removing the mandrel (8); manufacturing a second part (7); providing a shoulder (12) in the second part (7); assembling the first part (6) with the second part (7, 22); making an outer body (14) by winding preimpregnated fibers (17) around said inner body (5), said preimpregnated fibers (17) being identical to those used during the manufacture of the first part (6); making a one-piece body (18) by polymerization of the assembly formed by the inner body (5) and the outer body (14); machining a fastening element (19) at one end of the one-piece body (18); wherein the shoulder (12) serves as a bearing surface that abuts the first part (6) during the assembly of the first part (6) with second part (7); wherein a tube (13) is inserted into the second part (7) to form the shoulder (12), said tube (13) being manufactured via the filament winding method using preimpregnated fibers (17) identical to those used for the inner body (5) and the outer body (14); and wherein the tube (13) is coated with a layer of resin before insertion into the second part (7), said resin being identical to that of the preimpregnated fibers used during the making of the inner (5) and outer (14) bodies.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1, already mentioned, shows a general diagram of metallic connecting rods according to the state of the art with different fastening means of the connecting rod.

(2) FIG. 2, already mentioned, shows a longitudinal section of a composite connecting rod according to the state of the art (without the fastening means).

(3) FIG. 3 shows a front view of the composite connecting rod according to the invention.

(4) FIG. 4 shows a longitudinal section of one of the component parts of the inner body of the connecting rod according to the invention and an end view of that part.

(5) FIGS. 5a and 5b respectively show a top view and a front view of a mandrel used to make the inner body of the connecting rod according to the invention.

(6) FIG. 6 illustrates the assembly of one of the component parts of the inner body of the connecting rod according to the invention with a tube to form a shoulder, as well as a half-view of the assembly.

(7) FIG. 7 shows a longitudinal section of the various component parts of the inner body of the connecting rod according to the invention after assembly.

(8) FIG. 8 illustrates the placement of bearing journals at the ends of the inner body of the connecting rod according to the invention.

(9) FIG. 9 illustrates the placement of jaws on the bearing journals of FIG. 8.

(10) FIG. 10 illustrates the filament winding step around the inner body.

(11) FIG. 11 diagrammatically shows the stack of layers of wires around the inner body with additional layers at the end of the inner body.

(12) FIG. 12 shows a longitudinal section of the inner body and the outer body of the connecting rod according to the invention before post-curing.

(13) FIGS. 13 and 14 show a longitudinal section of the single-piece body of the connecting rod according to the invention after post-curing (before and after removal of the trunnions, respectively).

(14) FIG. 15 shows a three-dimensional view of one end of the connecting rod according to the invention after machining of the fastening element.

(15) FIG. 16 shows a three-dimensional view of the continuity of the fiber between the connecting rod body and the connecting rod head.

(16) FIG. 17 shows, in two longitudinal sectional views, the assembly step, according to one alternative of the invention, of an end piece with one end of the part according to FIG. 4.

(17) FIG. 18 illustrates manufacturing the second part (7) by winding fibers around the same mandrel (8) used to manufacture the first part (6).

LEGEND

(18) (1) Connecting rod

(19) (2) Cylindrical portion of the connecting rod

(20) (3) Connecting rod head

(21) (4) Substantially conical portion

(22) (5) Inner body

(23) (6) First part

(24) (7) Second part

(25) (8) Mandrel

(26) (9) Cylindrical portion of the mandrel

(27) (10) Connecting part of the mandrel

(28) (11) Rectangular section part of the mandrel

(29) (12) Shoulder

(30) (13) Tube

(31) (14) Outer body

(32) (15) Bearing journal

(33) (16) Jaws

(34) (17) Preimpregnated fiber

(35) (18) One-piece body

(36) (19) Fastening element

(37) (20) Flat section

(38) (21) Additional layer

(39) (22) End piece

DETAILED DESCRIPTION OF THE INVENTION

(40) The present invention relates to a composite connecting rod. The composite connecting rod 1 according to the invention comprises a hollow cylindrical portion 2 connecting two connecting rod heads 3 as shown in FIG. 3. The two connecting rod heads 3 are connected to the cylindrical portion 2 by a substantially conical portion 4 with an increasing section and a thinning wall thickness from the head 3 toward the cylindrical portion 2, the substantially conical portions 4 and the cylindrical portion 2 forming the connecting rod body.

(41) According to the invention, one or both of the connecting rod heads are made in a same material as the connecting rod body and are in the form of a fastening element, for example of the fork type. The assembly of the cylindrical portion 2, the conical portions 4 and the connecting rod heads 3 then forms a one-piece connecting rod 1. One-piece means that the entire connecting rod is made in a one and same composite material without adding other materials such as glue, adhesive or glass fabric. This means that the structure is homogenous (without any discontinuity) over the entire vertical or longitudinal section of the connecting rod irrespective of the location where the cut is made. The homogenous structure has thus no joint plane, junction defect or interface defect. By extension, the phrase one-piece connecting rod will also refer to a connecting rod where only a connecting rod head is an integral part of the connecting rod and is thus made in a same material as the connecting rod body, the other head comprising an end piece positioned as described in application WO 2010/149768 A2. In that case, the fastening element may be an integral part of the attached end piece or the latter may be threaded to subsequently receive a fastening element. This alternative of the method will also be described in the present description.

(42) The method according to the invention is first illustrated below for the manufacture of a one-piece connecting rod comprising two connecting rod heads made in a same material as the connecting rod body.

(43) A first step a) consists of making an inner body, also called lost mandrel, which, as its name indicates, will be lost in the end product. The inner body is made by assembling two parts 6, 7, which in turn are made as follows. A first part 6 is made as shown in FIG. 4, using the traditional filament winding method, which consists in winding a preimpregnated fiber on a mandrel (winding not shown in the figures), consolidating it by partial polymerization and then removing the mandrel. The mandrel 8, shown in FIGS. 5a and 5b, has a cylindrical portion 9 with a shape substantially corresponding to that of the connecting rod, extended by a connecting part 10 corresponding to the substantially conical portion 4 of the connecting rod and ending with a part 11 with a rectangular section designed to make the connecting rod head in the form of a fastening element. The connecting part 10 has, on its upper and lower faces, a flat section 20 extending in three successive planes (see FIG. 5a).

(44) A second part 7 is also made by filament winding around the mandrel 8 and partially polymerized, the mandrel being removed after the partial polymerization. It will be specified that the two parts 6 and 7 may have a cylindrical portion with a variable length as needed. For example, the first part may comprise a cylindrical portion with a length greater than that of the second part.

(45) A shoulder 12 is then arranged at the cylindrical portion of the second part 7. The shoulder 12 is formed by adding a tube 13 inside the cylindrical portion until it rests against the conical portion as shown in FIG. 6, the tube having of course an outer diameter slightly smaller than the inner diameter of the cylindrical portion. According to the invention, the tube has been made beforehand using the filament winding method and partially polymerized. In order to make a one-piece body according to the invention, the preimpregnated fiber used for manufacturing the tube is the same as that used for the parts 6 and 7. Furthermore, the tube is preferably coated with a layer of resin identical to that of the preimpregnated fibers before insertion into the second part and assembly with the first part. The purpose of this coating is to avoid the formation of porosity between the parts 6 and 7 and the tube 13, thus making it possible to obtain a one-piece connecting rod according to the invention.

(46) Alternatively, the shoulder 12 can be machined into the second part 7 rather than formed via the insertion of a tube.

(47) The two parts 6, 7 are then assembled, the first part 6 resting on the shoulder 12 of the second part 7 (see FIG. 7).

(48) A second step b) consists in making an outer body 14 around the inner body 5 as shown in FIG. 12. To that end, after placing the bearing journals 15 and jaws 16 at the ends of the inner body for the assembly of the latter on the filament winding machine, the preimpregnated fiber 17 is wound on the entire inner body 5 (see FIGS. 8 to 10). According to the invention, the preimpregnated fiber used to manufacture the inner body and the outer body is the same (same fiber, same resin) so as to ultimately make a product without any discontinuity between the two bodies. In order to obtain the desired thicknesses at the connecting rod heads, additional layers 21 can be placed at the ends of the inner body 5 as shown in FIG. 11. The additional layers 21 can be placed at the connecting rod heads with a rectangular section and partially at the connecting part. By adding successive layers of fibers along the inner body, the finished outer shape of the connecting rod body as shown in FIG. 12 is obtained. In order to reinforce the mechanical properties of the obtained connecting rod, the winding angle can be modified at the ends.

(49) In a third step c), the outer body 14 and the inner body 5 are polymerized in order to obtain a one-piece body 18 where the inner and outer bodies form only one body, without any discontinuity or porosity at the interface between the two bodies (see FIGS. 13 and 14). Thus, in cross-section, it is no longer possible to differentiate the inner body from the outer body.

(50) In a fourth step d), the fastening element 19 is machined into each connecting rod head 3 and partially in the conical portion 4 (see FIG. 15). All of the crosshatched areas delimit the parts machined to ultimately form a one-piece connecting rod as previously illustrated in FIG. 3, with a fork at each end. Alternatively, only the outer areas with crosshatched areas spaced further apart may be machined, in which case another type of fastening element is made.

(51) The method for manufacturing the connecting rod as described above must be adapted when only one connecting rod head is machined to form a fastening element, the other head comprising a positioned end piece. According to this alternative, in the first step a), an end piece 22 provided with a shoulder 12 is positioned at the end with a circular section of the component part 6 (see FIG. 17). The end piece may be metallic, made from high resistance plastic material, carbon or any other material suitable for the targeted application. As already mentioned, the end piece may be threaded to later receive a fastening element or it may directly comprise a fastening element.

(52) The assembly of the part 6 with the end piece 22 forms the inner body 5 around which, in step b), the preimpregnated fiber is wound to form the outer body similarly to the method previously described. Step c) is also equivalent. In the fourth step d), the fastening element is machined as before into the only connecting rod head with a rectangular section.

(53) It will be specified that, in both alternatives of the method, the shapes of the mandrel, the connecting rod body and the connecting rod heads are provided as an illustration. The so-called cylindrical part of the connecting rod may have a section other than circular, such as oval, square, etc., the shape of the mandrel being modified consequently. The same is true for the so-called substantially conical part and the connecting rod heads with a rectangular section before machining of the fastening elements. Likewise, the connecting rod heads have been shown, after machining, in the form of a fork, but depending on the needs, they may assume other forms.

(54) According to the invention, the fibers are preferably carbon fibers and the resin must be chosen to ensure a sufficient rigidity for all of the component parts of the connecting rod before the post-curing step c). For example, it may be an epoxy resin.

(55) Advantages of the Method According to the Invention According to the present invention, the entire connecting rod, including the fastening element(s) are made with a same preimpregnated fiber. Using a same resin and a same fiber makes it possible to make a one-piece body, during post-curing in step c), which will be free of any differential thermal expansion problems. The manufacture of connecting rods incorporating the fastening elements makes it possible to reduce costs, since it is no longer necessary to position the latter during an additional step. Making a connecting rod entirely in composite material makes it possible to lighten the weight compared to a connecting rod with attached metallic end pieces. As shown in FIG. 16, the fiber is continuous between the connecting rod body and the fork. This makes it possible to improve the fatigue behavior, since when the forks are mechanically stressed, the fiber of the connecting rod body takes over the force. The method according to the invention is flexible. It makes it possible to produce a connecting rod comprising at one end a fastening element and at the other end a threaded end piece into which the fastening element is subsequently screwed. This type of connecting rod has the advantage of having a variable length (thanks to the screwing) depending on the needs and the space available within the airplane. The method according to the invention also has the advantage of making it possible to make a complex part using traditional filament winding methods, which generates low manufacturing costs. The gain lies in the implementation of the methods and the design of the connecting rod itself. The method according to the invention does not require any fusible core. This makes it possible to: reduce the manufacturing costs; manufacture connecting rods with a low diameter/length ratio without collapse and flexion of the mandrel; manufacture connecting rods with a small center distance at the forks, which may be as low as 3 mm; obtain a better surface finish inside the connecting rod and, consequently, a better reception of the signal during ultrasound examination.