Plastics guided spring rod and bistable mechanism comprising such a rod

Abstract

The invention relates to a spring rod (1) comprising a compression spring (4) and two guiding tubes, a male tube (2) and a female tube (3), each having a cylindrical surface, a free end and a connecting end closed by a base (2c, 3c), the tubes being joined coaxially along a main axis (X) and suitable for sliding one inside the other. In addition, the tubes are made of plastics material and the bases (2c, 3c) delimit an internal space (INT) in which the compression spring (4) is positioned, this compression spring (4) bearing against the bases (2c, 3c).

Description

[0001] DESCRIPTION

[0002] SPRING-LOADED CONNECTING ROD WITH PLASTIC GUIDE AND BISTABLE MECHANISM COMPRISING A

[0003] SUCH A CONNECTING ROD.

[0004] TECHNICAL FIELD

[0005] The invention relates to a spring rod whose guide system is made of plastic material. Such a spring rod is used as a connecting part in opening / closing or locking mechanisms in order to ensure that the mechanism remains in place even if the control chain breaks.

[0006] The invention also relates to a bistable mechanism, one of the connecting parts of which is constituted by a spring-loaded connecting rod whose guide system is made of plastic. In particular, vehicle openings - aircraft, trains, ships - are intended to be actuated by such a bistable mechanism.

[0007] In the aeronautical field in particular, the doors of an aircraft are openings operated by bistable mechanisms and adapted to occupy two stable positions - open or closed.

[0008] STATE OF THE ART

[0009] Generally speaking, a connecting rod is a mechanical part whose body is elongated and equipped with a joint at each of its ends. The connecting rod is classically used to transmit and transform a movement into another movement or to change its amplitude. The addition of a spring to the body of the connecting rod makes it possible to provide other transformations of the transmitted movement, the body of the connecting rod then being made up of two tubes fitted coaxially and adapted to slide one inside the other, forming the guidance system: such a spring connecting rod is particularly suitable for providing a "bistable" function in a mechanism.

[0010] A so-called bistable mechanism is a mechanism for driving a part between two stable positions: when the part is in an intermediate position between these stable positions, it is then driven towards one or other of these stable positions. According to a first example, an aircraft door may comprise a bistable actuating mechanism for which the stable positions are extreme positions of the door, namely in the closed position and in the open position. Under the action of this bistable mechanism, when the door is in the half-open intermediate position, it is driven either towards its closed position or towards its open position.According to another example also relating to aircraft doors, these may comprise 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 found when it is released.

[0011] Bistable mechanisms are commonly implemented using gas springs. However, the force produced by a gas spring depends on the behavior of its gas, whose physical properties and therefore compression behavior vary with temperature. However, in aeronautical applications, an aircraft is subject to large temperature variations during use - which can vary from -40°C to +70°C during a single flight. In addition, a gas spring also includes a movable seal, the sealing of which is difficult to guarantee throughout the aircraft's operating period.

[0012] To overcome the disadvantages of gas springs, spring rods with a metallic guide system are used in bistable mechanisms: in fact, spring rods are more reliable because their mechanical properties vary very little in the operating temperature range and they do not present any sealing problems. However, such spring rods with metallic guides have an articulation at each of their ends to limit the risks of wear with the other parts of the bistable mechanism to which these ball joints are connected. In addition, the sliding of the tubes fitted into the body of the rod produces undesirable friction and the metallic materials are likely to be subject to corrosion phenomena, these two factors leading to the application of coatings and / or the use of surface treatments to guarantee optimal operation of the spring rod and the bistable mechanism.These disadvantages increase the complexity of manufacturing and installation of the spring rod with metal guide system as well as the weight of the bistable mechanism.

[0013] STATEMENT OF THE INVENTION

[0014] In order to overcome the drawbacks of the state of the art set out above, the main objective of the invention is to improve the structure of a spring connecting rod and to produce a bistable mechanism which is mass-optimized and easier to install.

[0015] To do this, the invention provides for producing a spring connecting rod whose guide system is made of plastic material: this choice of material makes it possible to simplify the manufacture of the spring connecting rod, while avoiding the application of surface treatments which lengthen the manufacturing time and remain liable to deteriorate over time.

[0016] More specifically, the present invention relates to a spring connecting rod comprising a compression spring and a guide system consisting of two guide tubes, a male tube and a female tube, each having a cylindrical surface, a free end and a connecting end comprising a member for connecting to a shaft, the tubes being fitted coaxially along a main axis by their free end and adapted to slide one inside the other along their cylindrical surfaces facing each other. The tubes are made at least partially of plastic material, their connecting end being closed by a bottom having two faces perpendicular to the main axis - an internal face of each tube and an opposite external face - these bottoms delimiting an internal space and a space external to the guide system.The compression spring, which is positioned in the interior space, rests on the internal face of the bottom of each tube, while the connecting members, which are positioned in the exterior space of the guidance system, are connected to the external faces of the bottom of the tubes. Advantageously, a guidance system made of plastic material has a density and therefore a mass lower than an equivalent system made of metal, this lightening being particularly sought after in the aeronautical world: in fact, a weight saving means lower hydrocarbon consumption or the allocation of this weight saving to another part of the aircraft. In addition, the structure of the guidance system is simplified - two tubes - leading to a faster manufacturing process and a more reliable structure over time.

[0017] Advantageously also, the compression spring, positioned inside the guidance system, is thus protected from external damage such as impacts and / or risks of corrosion.

[0018] According to preferred embodiments taken alone or in combination:

[0019] - the connecting member comprises a block having a hole forming chamfers, of a suitable diameter which creates a ball joint connection with the shaft;

[0020] - the connecting member comprises a fork-shaped structure with branches extending on either side of the shaft;

[0021] - the male tube and the female tube are made in thickness, from cylindrical surfaces facing each other, in different plastic materials to reduce friction between the two tubes, the materials being chosen in particular from nylon and high density polyethylene;

[0022] - the female tube has a translational locking lip opposite a cylindrical intermediate sleeve introduced between the cylindrical surfaces of the male and female tubes;

[0023] - the intermediate sleeve is made of a sheet of polytetrafluoride ethylene known as PTFE at least 1 mm thick, cut and then shaped into a cylinder;

[0024] - the tubes have at least one circumferential groove oriented towards the other tube in which is inserted an annular stabilizing segment, preferably split, in order to facilitate its insertion, and / or made of elastic material;

[0025] - the circumferential grooves are close to the free end of the tubes;

[0026] - the segments are made of PTFE;

[0027] - the tubes are of a dimensioned length making the circumferential groove of the female tube accessible when the male tube is completely fitted into the female tube, and

[0028] - at least one drainage hole is drilled in at least one of the guide tubes.

[0029] The invention also relates to a bistable mechanism comprising at least one plastic-guided spring connecting rod in an aircraft door opening kinematics.

[0030] PRESENTATION OF FIGURES

[0031] Other characteristics and advantages of the present invention will emerge from the following reading of a detailed example of embodiment without limiting its scope, with reference to the appended figures which represent, respectively:

[0032] - figure 1a and figure 1b, a perspective view of a bistable mechanism in each of its stable positions;

[0033] - Figure 2a and Figure 2b, a front view respectively assembled and exploded of an example of a plastic-guided spring connecting rod according to the invention, used in the mechanism illustrated in Figure 1a and Figure 1b;

[0034] - figure 3 and figure 4, a side view of the plastic-guided spring connecting rod in two perpendicular orientations;

[0035] - figure 5, a sectional view of the plastic-guided spring connecting rod illustrated previously and presented here according to a first embodiment;

[0036] - Figure 6a and Figure 6b, a sectional view and an enlargement of the plastic-guided spring connecting rod illustrated in Figure 1a to Figure 4, and presented here according to a second embodiment;

[0037] - Figure 7a and Figure 7b, a sectional view and an enlargement of the plastic-guided spring connecting rod illustrated in Figure 1a to Figure 4, and presented here according to a third embodiment;

[0038] - figure 8, a diagram of the direct ball joint connection between the hole forming chamfers of the connecting rod tube connecting member and the main axis, and - figure 9, a sectional diagram of a variant of the fork connecting member.

[0039] DETAILED DESCRIPTION

[0040] In the figures, identical reference signs refer to the same element as well as to the corresponding passages of the description.

[0041] Figures 1a and 1b show an example of a bistable mechanism 7 according to the invention in its two stable positions. This bistable mechanism comprises a spring rod 1 with plastic guidance in an opening kinematics of an aircraft door (not shown). This spring rod 1 is connected by one of its ends 1a to a frame 7c belonging to the structure of the aircraft and, by its other end 1b, to a control lever 7a positionable in two stable positions illustrated respectively in Figure 1a and Figure 1b.

[0042] When an operator actuates the control lever 7a from a position illustrated in Figure 1a or Figure 1b, it rotates around its lever axis L, causing compression of the spring 4 (visible by transparency) of the spring rod 1 as well as rotation of the spring rod 1 relative to the frame 7c. In the context of a bistable mechanism, the operator will actuate the control lever 7a in order to stress the spring in compression.

[0043] When the operator releases the control lever 7a, the spring exerts its return force and drives the control lever 7a which returns to its initial position: this position is therefore a so-called stable position. If the operator continues to operate the control lever 7a, the spring rod 1 will pivot until it reaches a tilting position in which its ends 1a, 1b are aligned with the lever axis L: in this position the spring 4 is compressed. This tilting position, intermediate between the two stable positions, is said to be unstable since as soon as the spring rod 1 tilts out of this tilting position, the spring 4 does not spontaneously bring the spring rod 1 back to this tilting position. The spring 4 being compressed, it will try to relax and drive the spring rod 1 towards the stable position located on the side where the rod has tilted.By this bistable mechanism 7, the control lever 7a has two stable positions: advantageously, this control lever 7a is integral with a lever 7b also movable between two positions and actuating, in this example, the kinematics for opening an aircraft door. The positions of the lever 7b are here materialized by the stops 7d and 7e.

[0044] Figure 2a and Figure 2b show a perspective view, respectively assembled and exploded, of the spring rod 1 with plastic guide used in the previous mechanism. This spring rod 1 comprises the compression spring 4 and a guide system consisting of two guide tubes: a male tube 2 and a female tube 3. Each of the tubes 2, 3 has a cylindrical surface 2m, 3m, a free end 2a, 3a and a connecting end 2b, 3b comprising a connecting member 2f, 3f to a shaft 6a, 6b.

[0045] The male 2 and female 3 tubes are fitted coaxially along a main axis X by their free end 2a, 3a and adapted to slide one inside the other along their cylindrical surfaces 2m, 3m facing each other. In this embodiment, the connecting members 2f, 3f comprise a block having a through hole 2g, 3g and forming chamfers 2h, 3h. A drainage hole 3I is also drilled in the female tube 3: this drainage hole 3I makes it possible to evacuate fluids which can penetrate into the spring connecting rod 1 and also makes it easier to balance the air pressure between the inside and the outside of the spring connecting rod 1.

[0046] Side views of the spring rod 1 are shown in a plane A in Figure 3 and in a view perpendicular to the plane A in Figure 4. In this exemplary embodiment, the drainage hole 3I is in the plane A as it appears in Figure 4. When the spring rod 1 is mounted in the mechanism, this drainage hole 3I is positioned “vertically”, thus allowing a flow and a natural evacuation of the fluids trapped in the spring rod 1.

[0047] Figure 5 illustrates a sectional view of the spring rod 1 according to a first embodiment in which the cylindrical surfaces 2m, 3m respectively of the male tube 2 and the female tube 3 are in direct contact: these tubes 2, 3 are then made in thickness, from the cylindrical surfaces 2m, 3m facing each other, in different plastic materials, Nylon for the male tube 2 and high-density polyethylene for the female tube 3 in this example, to reduce the friction between the tubes. By limiting the friction, sliding between the tubes is facilitated: by opposing less resistance, the minimum return force of the spring 4 is reduced, thus making it possible to size a spring 4 of lesser mass. In addition, heating of the spring rod 1 is also reduced by the reduction in friction between the tubes 2 and 3.

[0048] In the context of this invention, the connecting ends 2b, 3b are closed by a base 2c, 3c having two faces perpendicular to the main axis X - an internal face 2d, 3d to each tube 2, 3 and an opposite external face 2e, 3e - these bases 2c, 3c delimiting an internal space INT and an external space EXT of the guidance system. The compression spring 4 is positioned in the internal space INT and comes to bear on the internal face 2d, 3d of the base of each tube 2, 3. The connecting members 2b, 3b are, for their part, positioned in the external space EXT of the guidance system and connected to the external faces 2e, 3e of the base of the tubes 2, 3.

[0049] The sectional view of Figure 6a shows the spring rod 1 in plane A according to a second embodiment. In this embodiment, a cylindrical intermediate sleeve 5a is introduced between the cylindrical surfaces 2m, 3m of the male 2 and female 3 tubes. An enlarged view of the intermediate sleeve 5a is also shown in Figure 6b. This intermediate sleeve 5a is made of a 1 mm thick sheet of polyethylene tetrafluoride called PTFE which is cut and then shaped into a cylinder before being inserted into the female tube 3. The female tube 3 has on its free end 3a a lip 3k for locking the cylindrical intermediate sleeve 5a in translation. This locking lip 3k closes the interstitial space between the male tube 2 and the female tube 3 in which the cylindrical intermediate sleeve 5a is located.

[0050] In this embodiment, the male tube 2 and the female tube 3 are separated by a cylindrical intermediate sleeve 5a: there is therefore no direct contact or friction between the tubes 2, 3 and they can therefore be made of the same plastic material. In addition, the drainage holes 3I are relocated to the bottom 3c of the female tube 3, the cylindrical surface 3m being completely covered by the cylindrical intermediate sleeve 5a. With reference to the sectional view of Figure 7a, a third embodiment of the spring rod 1 is illustrated. In this embodiment, two annular interposition segments 5b are inserted between the tubes 2, 3 in order to make contact between the tubes 2, 3 and implement the guidance. An enlarged view of the annular segments 5b is also shown in Figure 7b. These annular interposition segments 5b are made of PTFE. Their role is to reduce friction between the male tube 2 and the female tube 3.

[0051] In addition, each tube 2, 3 has a circumferential groove 2j, 3j oriented towards the other tube and arranged near the free end 2a, 3a of each tube. In each circumferential groove 2j, 3j is inserted an annular interposition segment 5b. These annular interposition segments 5b are sized to create an interstitial space 5c between the tubes 2, 3 which can thus be made of the same plastic material, this interstitial space 5c making it possible to overcome the friction between the tubes 2, 3. Preferably, these annular interposition segments 5b are split in order to be able to adapt their diameter and facilitate their insertion into the circumferential grooves 2j, 3j. Advantageously, these segments can be made of elastic material. They may then not be split

[0052] The tubes 2, 3 are of dimensioned length making the circumferential groove 3j of the female tube 3 accessible when the male tube 2 is completely fitted into the female tube 3 by compressing the compression spring 4 beyond its compression of the tipping point. The circumferential groove 3j thus accessible allows the installation of an annular interposition segment 5b in the circumferential groove 3j. Preferably, the compression spring 4 is compressed until the free end 2a of the male tube 2 is in contact with the bottom 3c of the female tube 3.

[0053] The diagram in Figure 8 illustrates the production of the ball joint connection of the holes 2g, 3g forming the chamfers 2h, 3h of the connecting members 2f, 3f: each through hole 2g, 3g has a diameter suitable for producing a direct ball joint connection with the shaft by the clearance allowed by the dimensions of the hole and the chamfer 2h, 3h without using an additional ball joint part. In this diagram, the shaft 6a of the male tube 2 is shown fixed and the shaft 6b of the female tube 3 is shown in two orientations permitted by the direct ball joint connection. This direct ball joint therefore allows easy mounting of the spring rod 1 as well as the gain of a degree of freedom by eliminating the need for a ball joint part.

[0054] Figure 9 shows a sectional diagram of a fork variant 2i presented here on the connecting member 2f of the male tube 2, but which can also be used on the female tube 3. This fork 2i has two branches 2n extending on either side of the shaft 6a. This variant makes it possible to obtain easy mounting of the spring connecting rod 1: the operator compresses the spring connecting rod 1 to position it and then, by releasing it, the spring locks the connecting rod in the mechanism. The fork connecting member can be combined with embodiments of the guide system comprising an intermediate sleeve or annular interposing segments.

[0055] The invention is not limited to the embodiments and implementations described and shown. Thus, the tubes can also be made of composite materials, in particular in the context of the second and third embodiments with the intermediate sleeve or the annular interposition segments. A lubricating layer can also be inserted into the tubes to reduce friction.

[0056] Also in the third embodiment, each interposing annular segment may be composed of several juxtaposed and / or spaced sections, these sections forming a partial or complete ring.

[0057] In addition, the spring can be placed in the outer space, the bottom of the tubes then being adapted to provide support for the spring.

Claims

DEMANDS 1. Spring connecting rod (1) comprising a compression spring (4) and a guide system consisting of two guide tubes, a male tube (2) and a female tube (3), each having a cylindrical surface (2m, 3m), a free end (2a, 3a) and a connecting end (2b, 3b) comprising a connecting member (2f, 3f) to a shaft (6a, 6b), the tubes (2, 3) being fitted coaxially along a principal axis (X) by their free end (2a, 3a) and adapted to slide one inside the other along their facing cylindrical surfaces (2m, 3m), the spring connecting rod (1) being characterized in that the tubes (2, 3) are made at least partially of plastic material, their connecting end (2b, 3b) being closed by a bottom (2c, 3c) having two faces perpendicular to the principal axis (X) - an inner face (2d, 3d) to each tube (2,3) and an opposite outer face (2e, 3e) - these bottoms (2c,3c) delimiting an internal space (INT) and an external space (EXT) to the guiding system, and in that the compression spring (4), which is positioned in the internal space (INT), bears against the internal face (2d, 3d) of the bottom (2c, 3c) of each tube (2, 3), while the connecting members (2f, 3f), which are positioned in the external space (EXT) of the guiding system, are connected to the external faces (2e, 3e) of the bottom (2c, 3c) of the tubes (2, 3), 2. Spring connecting rod (1) according to the preceding claim, in which the connecting member (2f, 3f) has a hole (2g, 3g) forming chamfers (2h, 3h), of a suitable diameter which makes a ball joint connection with the shaft (6a, 6b).

3. Spring connecting rod (1) according to any one of claims 1 to claim 2, wherein the connecting member (2f, 3f) comprises a forked structure (2i) whose arms (2n) extend on either side of the shaft (6a, 6b).

4. Spring connecting rod (1) according to any one of claim 1 to claim 3, wherein the male tube (2) and the female tube (3) are made in thickness, from facing cylindrical surfaces (2m, 3m), in different plastic materials, the materials being chosen in particular from nylon and high-density polyethylene.

5. Spring connecting rod (1) according to any one of claims 1 to claim 4, wherein the female tube (3) has a locking lip (3k) in translation with respect to an intercalated cylindrical sleeve (5a) introduced between the cylindrical surfaces (2m, 3m) of the male (2) and female (3) tubes.

6. Spring connecting rod (1) according to claim 5, in which the interlayer sleeve (5a) is made of a sheet of polytetrafluoride of ethylene, known as PTFE, of at least 1mm thickness, cut and then shaped into a cylinder.

7. Spring connecting rod (1) according to any one of claim 1 to claim 4, in which the tubes (2, 3) have at least one circumferential groove (2j, 3j) oriented towards the other tube (3, 2) in which is inserted an annular stabilizing segment (5b).

8. Spring connecting rod (1) according to claim 7, wherein the annular stabilizing segment (5b) is split and / or made of elastic material.

9. Spring connecting rod (1) according to any one of claims 7 to claim 8, wherein the circumferential grooves (2j, 3j) are near the free end (2a, 3a) of the tubes.

10. Spring connecting rod (1) according to any one of claims 7 to claim 9, wherein the annular stabilizing segments (5b) are made of PTFE.

11. Spring connecting rod (1) according to any one of claims 7 to claim 10, wherein the tubes (2, 3) are of dimensioned length making accessible the circumferential groove (3j) of the female tube (3) when the male tube (2) is completely fitted into the female tube (3); 12. Spring connecting rod (1) according to any one of claim 1 to claim 11, in which at least one drainage hole (3I) is drilled in at least one of the guide tubes (2, 3).

13. Bistable mechanism (7) characterized in that it comprises at least one spring-loaded connecting rod (1) with plastic guidance according to any one of the preceding claims.

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