PLASTIC CAST HYBRID SPRING ROD AND BISTABLY ABLE MECHANISM WITH SUCH A ROD

Description

TECHNICAL FIELD

[0001] The invention relates to a so-called hybrid spring-loaded connecting rod equipped with a connecting rod guide system, part of which is molded from plastic material. Such a spring-loaded connecting rod is used, in particular, as a link in opening / closing or locking mechanisms, to ensure that such a mechanism remains in place even if the control chain breaks.

[0002] The invention also relates to a mechanism having two stability positions, referred to as a bistable mechanism, in which at least one part of the mechanism is constituted by said hybrid spring connecting rod, part of whose guide system is made of plastic material. In particular, vehicle openings—aircraft, trains, ships—are intended to be actuated by such a bistable mechanism.

[0003] In the aeronautical field in particular, aircraft doors are openings operated by bistable mechanisms and adapted to occupy two stable positions - open or closed. STATE OF THE ART

[0004] Generally speaking, a connecting rod is a mechanical part with an elongated body and a joint at each end. Connecting rods are typically used to transmit and transform one movement into another, or to change its amplitude. Adding a spring to the connecting rod body allows for further transformations of the transmitted movement. The connecting rod body then consists of two tubes fitted coaxially and designed to slide within each other, forming the guide system. Such a spring-loaded connecting rod is particularly well-suited for providing a bistable function in a door / window opening / closing or locking mechanism.

[0005] More specifically, such a mechanism drives a mechanical part that can move between two stable positions: when the part is in an intermediate position between these stable positions, it is generally driven towards the nearest stable position by the spring-loaded connecting rod. As a first example, an aircraft door can have a bistable actuation mechanism where the stable positions are the extreme positions of the door, namely the closed and open positions. Under the action of this bistable mechanism, when the door is in an intermediate, partially open position, it is driven either towards its closed position or towards its open position.

[0006] According to another example also concerning aircraft doors, these may include a bistable locking mechanism equipped with a lever moving between a locking position and an unlocking position: when the lever is released between the locking position and the unlocking position, it switches to one or the other of these positions depending on the position in which it is when it is released.

[0007] Bistable mechanisms are commonly implemented using gas springs. However, the force produced by a gas spring depends on the behavior of the gas, whose physical properties, and therefore its compressive behavior, vary with temperature. In aeronautical applications, an aircraft is subjected to large temperature variations during operation—ranging from -40°C to +7°C during a single flight. Furthermore, a gas spring also incorporates a moving seal, the integrity of which can be difficult to guarantee throughout the aircraft's operational life.

[0008] To overcome the drawbacks of gas springs, metal spring-loaded connecting rods with a metallic guide system are used in bistable mechanisms. These spring-loaded rods are more reliable because their mechanical properties vary very little within the operating temperature range, and they do not present sealing problems. Such spring-loaded connecting rods with metallic guides typically feature a joint at each end to minimize the risk of wear with other components of the bistable mechanism to which these joints are attached.

[0009] Furthermore, the sliding of the tubes fitted to the connecting rod body produces undesirable friction, and the metallic materials are susceptible to corrosion. These two factors necessitate the application of coatings and / or the use of surface treatments to ensure optimal operation of the spring-loaded connecting rod and the bistable mechanism. These drawbacks increase the complexity of manufacturing and installing the spring-loaded connecting rod with a metallic guide system, as well as the weight of the bistable mechanism.

[0010] Patents CH692733, DE102012208224, and DE102011084066 disclose a spring-loaded connecting rod with metal and plastic components. In patent CH692733, the rod's shaft and sliding body are made of metal, with a plastic sleeve providing an interface between the shaft and the sliding body. In patents DE102012208224 and DE102011084066, the shaft is made of plastic, and the sliding body is made of metal. DESCRIPTION OF THE INVENTION

[0011] In order to remedy the disadvantages of the prior art described above, the invention has as its main objective to improve the manufacture and structure of a spring connecting rod as well as to create a mass-optimized bistable mechanism that is easier to install.

[0012] To achieve this, the invention provides for the production of a hybrid spring connecting rod comprising a guide system whose sliding body is molded from plastic material around a metal axis. Advantageously, this choice of material simplifies the manufacturing of the spring connecting rod, while eliminating the need for surface treatments that lengthen manufacturing time and remain susceptible to degradation over time.

[0013] More specifically, the present invention relates to a spring-loaded connecting rod having two ends and comprising: a connecting rod guide system consisting of a metal shaft and a body sliding on a zone along this metal shaft; a compression spring oriented in the direction of the metal shaft of the guide system, and two connecting members positioned each at one end of the spring connecting rod on respectively the body and the metal shaft, the connecting members having a re-engagement interface.

[0014] In this so-called hybrid metal / plastic spring connecting rod, the sliding body and connecting elements are molded in plastic, with the connecting element of the body being molded as a single piece with the sliding body of the guide system. Furthermore, each connecting element has a shoulder perpendicular to the direction of the metal axis, with the compression spring positioned in contact with these shoulders and around the guide system.

[0015] Advantageously, a hybrid spring connecting rod with a guide system featuring a plastic body sliding along a metal axis offers reduced sliding friction, enabling faster manufacturing of the metal axis and eliminating the need for friction-reducing surface treatments. Furthermore, a metal / plastic interface is relatively insensitive to temperature variations. Molding the guide system body from plastic also simplifies the manufacturing of the hybrid spring connecting rod, allowing for rapid and high-volume molding.

[0016] Another advantage is that the hybrid metal / plastic guidance system has a lower density and therefore a lower mass than an equivalent metal system, a weight reduction particularly desirable in the aeronautical industry. Indeed, a reduction in mass means either lower fuel consumption or the allocation of this weight saving to another part of the aircraft.

[0017] According to preferred forms of embodiment taken alone or in combination: The metal shaft has an angular taper on the sliding area; the taper angle is less than 5°; the metal shaft has a collar around which its connecting member is molded; the connecting member of the body has a drainage hole and the connecting member of the shaft has a positioning hole; the interface for the connecting members is open in the shape of a "U"; the sliding body of the guide system is molded and optimized according to a "lattice" structure, i.e. a lattice.

[0018] Advantageously, the angular tapering of the metal axis allows radial play which optimizes sliding with the plastic body.

[0019] Advantageously, the collar also allows the connecting element of the metal shaft to be assembled without any means of attachment or fixing.

[0020] The invention also relates to a method for manufacturing a hybrid spring connecting rod comprising a sliding body molded from plastic material around its metal axis. The manufacturing process takes place according to the following steps; machining of the metal shaft; installation of the metal shaft in a tooling comprising at least one injection mold; positioning of the metal shaft on a positioning rod in the tooling; injection of plastic material into the mold by at least two injection nozzles; extraction of the guide system from the tooling; separation of the plastic sliding body from the metal shaft; installation of the spring between the shoulders, and sliding of the plastic sliding body along the metal shaft.

[0021] Advantageously, this process allows all the components of the guidance system to be injected in a single operation, then the plastic body to be separated in order to quickly obtain a functional spring connecting rod with minimal manufacturing and installation.

[0022] Depending on certain preferred implementation methods, used alone or in combination: the machining of the metal shaft includes an angular stripping step; the collar is machined with the metal shaft; the mold includes a separating wall defining two molding volumes corresponding respectively to the sliding body and the connecting element of the shaft, each of these molding volumes being fed by an injection nozzle. PRESENTATION OF THE FIGURES

[0023] Other features and advantages of the present invention will become apparent from the following detailed embodiment, without limiting its scope, by reference to the accompanying figures which represent, respectively: there figure 1a and the figure 1b , respectively an exploded and assembled perspective view of a hybrid spring connecting rod; the figure 2 , a cross-sectional view of the metal axis illustrating the stripping; the figure 3a , a perspective view of the plastic body mold; the figure 3b , a perspective view of the plastic body of the spring connecting rod after molding, and the figure 4a , there figure 4b and the figure 4c , a cross-sectional view in plane A of the spring connecting rod guide system at three successive instants during the plastic body extraction phase from the metal shaft. DETAILED DESCRIPTION

[0024] In the figures, identical reference symbols refer to the same element as well as to the corresponding passages in the description.

[0025] THE figures 1a And 1b show a perspective view of a hybrid spring connecting rod 1, the latter being represented in an exploded view in the figure 1a and according to a view assembled in the figure 1b This spring-loaded connecting rod 1 is called hybrid because part of the connecting rod is metallic and another part is plastic.

[0026] The spring-loaded connecting rod 1 has two ends 1a and 1b and comprises: a connecting rod guide system 3, consisting of a metal shaft 4 and a plastic sliding body 5 extending over a zone C along this metal shaft 4; a compression spring 2 oriented in the direction D of the metal shaft 4 of the guide system 3, and two connecting members 6a and 6e positioned each at one of the ends 1a, 1b of the spring connecting rod 1 on, respectively, the sliding body 5 and the metal shaft 4, the connecting members 6a, 6b having a re-engagement interface 6b, 6f.

[0027] In this example, the metal shaft is made of steel and the sliding plastic body is made of polyamide 66, more commonly known as "nylon". However, any type of metal alloy (aluminum, titanium, Inconel, etc.) and any type of plastic material (polypropylene, polyethylene, polyamides, elastomers, with or without the addition of friction-optimized material such as Teflon or others, etc.) can be used.

[0028] More specifically, these interfaces 6b, 6f provide the connection at ends 1a and 1b between the hybrid spring-loaded connecting rod 1 and the other parts of the mechanism linked by this rod, an aircraft door opening / closing mechanism in the example embodiment. This connection is made by contact, the interfaces 6b, 6f being open towards the parts of the mechanism with a U-shaped opening.

[0029] In addition, the connecting member 6a positioned on the sliding body 5 is advantageously molded in one piece with the sliding body 5 which is itself molded and optimized in mass according to a lattice structure, this optimization making it possible to limit the amount of plastic injected and therefore to reduce the manufacturing time by molding.

[0030] Furthermore, since the sliding body 5 typically has a cavity 5a in which the metal shaft 4 slides, unwanted fluids from the environment can flow into it, causing malfunction of the hybrid spring-loaded connecting rod 1. To evacuate these fluids, the connecting member 6a advantageously has a drainage hole 6d. The connecting member 6d at the end of the metal shaft 4 also has an opening, in this example, a positioning hole 6h resulting from the manufacturing process described below.

[0031] Shoulders 6c and 6g on the respective connecting members 6a and 6e are visible in the exploded view. figure 1a These shoulders 6c, 6g are positioned perpendicular to the direction D of the metal axis 4, the compression spring 2 being in contact with the shoulders 6c, 6g and around the guide system 3, as shown in figure 1b .

[0032] There figure 2 Figure 4 illustrates the metal shaft. This metal shaft 4 preferably has an angular taper 4a on the sliding zone C, a taper of 2 degrees in the embodiment shown, preferably less than 5 degrees. This taper allows for smoother sliding of the sliding body 5 along the metal shaft 4, limiting the risk of jamming of the guide system 3.

[0033] Furthermore, the metal shaft 4 has a flange 4b, arranged perpendicular to the axis D, around which its connecting member 6e is molded. The flange 4b ​​eliminates the need for a connecting means between the metal shaft 4 and the connecting member 6e. This flange can be machined directly at the same time as the metal shaft 4 or be a separate part fixed to this shaft.

[0034] With reference to the figure 3a , it appears the tooling 7 used for molding in plastic material of the sliding body 5 of the guide system 3 and of the connecting elements 6a, 6e (cf. figure 1a ) of the hybrid spring connecting rod 1. In addition, the figure 3b This section details the extraction of the guide system 3 from the tooling 7 during demolding. This tooling 7 includes a press 7a that feeds the plastic material into the mold 7b using injection nozzles 7d and 7e via delivery rods 7f. The nozzles 7d and 7e are positioned and installed on the extraction rod 7g. This extraction rod 7g pushes on the plastic material and ejects the guide system 3 from the tooling 7.

[0035] In operation, the injection molding of plastic material around the metal axis of the hybrid spring connecting rod 1 proceeds according to the following steps: machining of the metal shaft 4; installation of the metal shaft 4 in the tooling 7 comprising the injection mold 7a; positioning of the metal shaft 4 on the positioning rod 7c in the tooling 7; injection of plastic material into the mold 7b through the injection nozzles 7d, 7e; extraction of the guide system 3 from the tooling 7; separation of the plastic sliding body 5 from the metal shaft 4; installation of the spring 2 between the shoulders 6c and 6g, and sliding of the plastic sliding body 5 along the metal shaft 4.

[0036] The metal shaft 4 is traditionally obtained by turning, this tooling allowing the flange 4b ​​and the angular relief 4a to be machined simultaneously. The metal shaft 4 can also be obtained by extrusion, the flange 4b ​​being manufactured separately and then assembled to the metal shaft 4 by welding or fastening.

[0037] The metal shaft 4 is then installed in the mold 7b against the positioning rod 7c. The injected plastic will therefore surround the rod 7c and during the extraction step of the guide system 3 from the tooling, the space occupied by the rod 7c is empty and creates the positioning hole 6h (cf. figure 1b Other methods of positioning the metal shaft 4 in the mold are possible, in particular by fixing the metal shaft 4 in the section that will not be covered with plastic. The rod 7c can also be removed after the metal shaft 4 has been positioned and secured. In these embodiments, no positioning hole is made, as the plastic is injected throughout the entire volume of the connecting element 6e.

[0038] Tooling 7 here comprises a single mold 7a for producing, on the one hand, the sliding body 5 with the connecting member 6a, and on the other hand, the connecting member 6e attached to the metal shaft 4 around the flange 4b. Mold 7a is therefore used to mold two distinct parts, the sliding body 5 and the metal shaft 4 with their respective connecting members, and includes a separating wall that defines and isolates two molding volumes corresponding respectively to the sliding body 5 and the connecting member 6e of the metal shaft 4. Each of these molding volumes is fed by its own injection nozzle 7d, 7e, because the separating wall prevents the flow of injected plastic from one molding volume to the other. Alternatively, tooling 7 can comprise two juxtaposed molds, each fed by an independent nozzle.

[0039] There figure 4a , figure 4b And figure 4c present cross-sectional views of the guide system 3 in a longitudinal plane A of the hybrid spring connecting rod 1 at three successive instants during the extraction phase by separation of the sliding body 5 from the metal axis 4. At the beginning of this phase, with reference to the figure 4a , the sliding body 5 and the metal shaft 4 are assembled following the injection of plastic into the mold 7b.

[0040] The metal shaft 4 is then gradually extracted from the sliding body 5 ( figure 4b This extraction is facilitated by the angular taper 4a. The mold 7b directly incorporates the drainage hole 6d: the drainage hole 6d, passing through the sliding body 5 on both sides, frees itself during the extraction of the shaft. The figure 4cThis shows the complete separation of the metal shaft 4 from the sliding body 5. The cross-sectional view of these figures allows visualization of the collar 4b as well as the connecting member 6e molded around this collar 4b. Alternatively, if the mold 7b does not incorporate the drainage hole, a drilling step for the drainage hole is then performed.

Claims

1. A metal / plastic hybrid spring connecting rod (1) having two ends (1a, 1b) and comprising: - a spring connecting rod guiding system (3) comprising a metal shaft (4) and a sliding body (5) over a zone C along said metal shaft (4); - a compression spring (2) oriented in the direction D of the metal shaft (4) of the guiding system (3), and - two connecting members (6a, 6e) each positioned at one of the ends (1a, 1b) of the spring connecting rod (1) on the sliding body (5) and the metal shaft (4) respectively, the connecting members (6a, 6e) having a load-bearing interface (6b, 6f); the spring connecting rod (1) being characterised in that the sliding body (5) and the connecting members (6a, 6e) are moulded from plastic, the connecting member (6a) of the sliding body (5) being moulded in one piece with the sliding body (5) of the guiding system (3), and in that the connecting members (6a, 6e) each comprise a shoulder (6c, 6g) perpendicular to the direction D of the metal shaft (4), the compression spring being positioned in contact with these shoulders (6c, 6g) and around the guiding system (3).

2. Hybrid spring connecting rod (1) according to claim 1, wherein the metal shaft (4) has an angular relief (4a) in the sliding zone C.

3. Hybrid spring connecting rod (1) according to claim 2, wherein the relief angle (4a) is less than 5°.

4. Hybrid spring connecting rod (1) according to any one of claims 1 to 3, wherein the metal shaft (4) comprises a flange (4b) around which its connecting member (6e) is moulded.

5. Hybrid spring connecting rod (1) according to any one of claims 1 to 4, wherein the connecting member (6a) of the sliding body (5) has a drainage hole (6d) and the connecting member (6e) of the metal shaft (4) comprises a positioning hole (6h).

6. A hybrid spring connecting rod (1) according to any one of claims 1 to 5, wherein the load-bearing interface (6b, 6f) of the connecting members (6a, 6e) is open in a 'U' shape.

7. Hybrid spring connecting rod (1) according to any one of claims 1 to 6, wherein the sliding body (5) of the guiding system (3) is moulded and optimised according to a lattice structure.

8. A method of manufacturing a hybrid spring connecting rod (1) comprising a sliding body (5) moulded from plastic material around its metal shaft (4) according to any one of the preceding claims, characterised in that the manufacture is carried out in accordance with the following steps: - machining of the metal shaft (4); - installation of the metal shaft (4) in a moulding tool (7) comprising at least one injection mould (7b); - positioning the metal shaft (4) on a positioning rod (7c) within the moulding tool (7); - injection of plastic material into the mould (7b) via at least two injection nozzles (7d, 7e); - removal of the guiding system (3) from the mould (7); - separating the plastic sliding body (5) from the metal shaft (4); - installation of the spring (2) between the shoulders (6c, 6g), and - sliding the plastic sliding body (5) along the metal shaft (4).

9. A manufacturing method according to the preceding claim, wherein the machining step of the metal shaft (4) comprises a step of creating an angular relief of less than 5 degrees.

10. A method of manufacture according to any one of claims 8 to 9, wherein the step of machining the metal shaft (4) comprises a step of machining the flange (4b).

11. A manufacturing method according to any one of claims 8 to 10, wherein the mould (7b) comprises a partition wall defining two moulding cavities corresponding respectively to the sliding body (5) and the connecting member (6e) of the metal shaft (4), each of these moulding cavities being fed by an injection nozzle (7d, 7e).