Device comprising a fixed frame, a rotary assembly and a return mechanism
By employing short helical spring strands with guiding grooves and bends, the device maintains spring tension in compact designs, addressing the issue of premature spring loss and ensuring reliable operation beyond 250,000 cycles.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- CROUZET SA
- Filing Date
- 2026-01-19
- Publication Date
- 2026-07-30
AI Technical Summary
Existing devices with helical springs for returning rotating assemblies to a neutral position face challenges in maintaining spring tension due to spring loss, particularly in compact applications like human-machine interfaces, where space constraints and spring tilt lead to premature loss of tension.
The use of short helical spring strands with guiding grooves and strategic bends to minimize spring tilt and maintain contact with the fixed frame, combined with grooves to ensure consistent strand guidance, prevents spring loss even in compact designs.
The solution effectively maintains spring tension in compact devices, achieving over 250,000 cycles without spring loss, enhancing the reliability and durability of the return mechanism.
Smart Images
Figure EP2026051125_30072026_PF_FP_ABST
Abstract
Description
[0001] Device comprising a fixed frame, a rotating assembly and a return mechanism
[0002] [1] The invention relates to a device comprising a fixed frame, a rotating assembly and a return mechanism and a human-machine interface containing this device.
[0003] [2] Devices comprising a fixed frame, a rotating assembly and a return mechanism are used in many technical fields such as human-machine interfaces, motors or others.
[0004] [3] In these devices, the return mechanism is used to return the rotating assembly to a neutral position in the absence of external forces. For this purpose, this mechanism includes a helical spring. This helical spring has two end strands, one of which bears against the fixed frame and the other against the rotating assembly.
[0005] [4] Numerous methods of attaching the strands to the fixed frame and the rotating assembly have already been proposed to prevent spring loss. Spring loss occurs when one of the strands loses its support on the fixed frame or the rotating assembly. Without such support, the spring no longer performs its return function, and the rotating assembly is no longer automatically returned to its neutral position in the absence of external force. Typically, spring loss occurs at the end of the stroke.
[0006] [5] Thus, it has already been proposed that each of the strands have an anchoring hook. This embodiment is advantageous because the strands are then firmly attached to the fixed frame and the rotating assembly by means of these anchoring hooks. In this case, no loss of spring tension is observed after a very large number of cycles of use of this device. However, this embodiment of the return mechanism is bulky because space must be provided to attach these anchoring hooks to the fixed frame and the rotating assembly.
[0007] [6] To reduce the size of the return mechanism, it has been proposed to use end strands without anchor hooks. Such a device is described, for example, in US patent application 4828235A. Typically, in this case, each strand extends tangentially from a coil of the spring in a respective plane perpendicular to the axis of rotation. These respective planes are superimposed one above the other. In this case, the strands slide, one on a flat bearing surface of the fixed frame and the other on a flat bearing surface of the rotating assembly. When the rotating assembly is moved away from its neutral position, the strands wind around the axis of rotation. Thus, the more the rotating assembly is rotated, the shorter the strands become. Furthermore, during this movement of the rotating assembly, the spring deforms.In particular, because the end strands are located in separate planes, the spring can tilt in a way that moves the strands away from the flat bearing surfaces on the fixed frame and the rotating assembly. In this case, to prevent the spring from losing its initial tension, the strands are chosen to be sufficiently long so that, even when the rotating assembly reaches its end of travel, the length of each strand remains greater than Ds / 2, where Ds is the outside diameter of the spring coils.
[0008] [7] The prior art is also known from US9243436B2 and CN110250664A.
[0009] [8] In certain situations, it is desirable to further reduce the size of the return mechanism while avoiding, as far as possible, the loss of spring tension. These situations arise particularly with devices whose dimensions are small, such as those implemented in human-machine interfaces, for example, in aircraft piloting.
[0010] [9] The invention aims to satisfy this wish.
[0011]
[0010] The invention is set forth in the attached set of claims.
[0012]
[0011] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the drawings in which:
[0013] - Figure 1 is a partial illustration of a human-machine interface equipped with a device comprising a fixed frame, a rotating assembly, and a return mechanism; - Figure 2 is a partial cross-sectional illustration of the device in Figure 1.
[0014] - Figures 3 and 4 are illustrations, in perspective and from two different viewpoints, of the device shown in Figure 1.
[0015] - Figure 5 is a partial and enlarged illustration of the device in Figure 1; - Figure 6 is a partial and perspective illustration of a spring from the return mechanism of the device in Figure 1.
[0016] - Figures 7 and 8 are schematic and partial illustrations, in top view, of a lower end strand of the spring in Figure 6, respectively, in a neutral position and in a maximum rotated position,
[0017] - Figure 9 is a schematic and partial illustration, viewed from below, of an upper end strand in a neutral position,
[0018] - Figure 10 is a schematic illustration, in vertical section, of a lower groove of the fixed frame of the device in Figure 1.
[0019]
[0012] In this description, the terminology, conventions, and definitions of the terms used in this text are introduced in Chapter I. Detailed examples of embodiments are then described in Chapter II with reference to the figures. In Chapter III, variations of these embodiments are presented. Finally, the advantages of the different embodiments are specified in Chapter IV.
[0020]
[0013] Chapter I: Definitions, terminologies and conventions:
[0021]
[0014] In the figures, the same references are used to designate the same elements.
[0022]
[0015] In the remainder of this description, the well-known characteristics and functions of a person skilled in the art are not described in detail.
[0023]
[0016] The figures are oriented with respect to an orthogonal XYZ coordinate system, where the X and Y directions are horizontal and the Z direction is vertical. Terms such as "above", "below", "top", "bottom", "superior", "inferior" are defined with respect to the Z direction.
[0024]
[0017] The symbol “*” denotes scalar multiplication.
[0025]
[0018] In this text, a cycle of use of the device consists of moving the rotating assembly from its neutral position to its maximum rotated position and then letting the return mechanism automatically return the rotating assembly to its neutral position.
[0026]
[0019] The neutral position of a rotating assembly is the position occupied by this rotating assembly in the absence of any external stress.
[0020] The maximum rotated position of a rotating assembly is the position reached, by rotating the rotating assembly around its axis of rotation from its neutral position, when the rotating assembly is at the end of its stroke.
[0027]
[0021] In this text, when a number of usage cycles is indicated, it is an average number of usage cycles obtained by averaging the results obtained experimentally with at least five or ten copies of the same device.
[0028]
[0022] Chapter: Example of an embodiment
[0029]
[0030]
[0023] Figures 1 to 10 represent a human-machine interface 2 used to pilot an aircraft. For example, the interface 2 is a button that can be manually operated by a pilot. Thus, hereafter, the same numeral 2 is used to designate both the interface and the button. This interface 2 comprises a device 4 equipped with a fixed frame 10, a rotating assembly 12, and a return mechanism 14.
[0031]
[0024] In addition to device 4, button 2 includes a push button 16 (Fig. 1, 2) that can be moved by a finger of the pilot between a rest position, shown in Figure 1, and a pressed position. By way of illustration, when the push button 16 reaches its pressed position, this triggers the automatic execution of an action that must not be triggered accidentally. For example, this action is the firing of a missile or similar.
[0032]
[0025] The frame 10 is fixed here, without any degree of freedom, onto a pilot handle itself attached to a control panel. The handle is moved manually by the pilot to generate flight instructions for the aircraft.
[0033]
[0026] The rotating assembly 12 is here a protective flap for the push button 16. The rotating assembly 12 is rotatable about a vertical axis 18 (Fig. 1, 2) between a neutral position, shown in Figures 1 to 5, and a maximum rotated position. The rotating assembly 12 extends primarily in a horizontal plane. In the neutral position, the rotating assembly 12 covers the push button 16 so that the push button 16 cannot be moved to its depressed position by a pilot finger. In its maximum rotated position, the rotating assembly 12 no longer covers the push button 16 so that it can be moved by a pilot finger to its depressed position. Here, the rotating assembly 12 is moved, against the return mechanism 14, from its neutral position to its maximum rotated position by a pilot finger. For this purpose, device 4 includes a shaft 20 (Fig. 2) which extends along axis 18.Here, the rotating assembly 12 is fixed, without any degree of freedom, to the upper end of the shaft 20. For example, the upper end of the shaft 20 is screwed into the rotating assembly 12. The lower end of the shaft 20 is received in a through hole 22 (Fig. 2) machined in the fixed frame 10 along the axis 18. The lower end received inside the hole 22 is free to rotate about the axis 18. This lower end has a shoulder 24 which, by its shape cooperation with a shoulder 26 in the fixed frame 10, prevents any translation of the shaft 20 in the Z direction. Here, the shaft 20 is a screw, and the shoulder 24 separates the head of this screw from the shank of this screw.
[0034]
[0027] In its neutral position, the rotating assembly 12 rests on a stop provided in the fixed frame 10. In its maximum rotated position, the rotating assembly 12 rests on an end stop also provided in the fixed frame 10. To simplify the figures, these rest and end stops have not been shown. The angular travel of the rotating assembly 12 between the neutral position and the maximum rotated position is typically greater than 20° or 40°. This angular travel is less than 360° and typically less than 180°. For example, here, the angular travel of the rotating assembly 12 is equal to 90°.
[0035]
[0028] The mechanism 14 allows the rotating assembly 12 to automatically return to its neutral position in the absence of external forces. For this purpose, the mechanism 14 includes a pre-loaded helical spring 30 (Figs. 1 and 2). Here, the spring 30 has more than three or four turns and, generally, fewer than twenty or ten turns. Hereafter, the turns of the spring 30 located at the lower and upper ends of the spring 30 are called, respectively, the "lower turn" and the "upper turn" and bear, respectively, the numerical reference numerals 31a and 31b (Fig. 6). Between the upper and lower turns, there are one or more intermediate turns.
[0036]
[0029] The spring 30 also includes a lower strand 32 (Figs. 3, 5, 6, 7 and 8) which extends the lower coil 31a and an upper strand 34 (Figs. 4, 6 and 9) which extends the upper coil 31b. The strands 32 and 34 bear against vertical faces 36 (Figs. 3, 6) and 38 (Figs. 4), respectively, of the fixed frame 10 and the rotating assembly 12 in order to return the rotating assembly 12 to its neutral position in the absence of external force. Here, the vertical faces 36 and 38 are flat and each extend in a respective vertical plane. In this embodiment, in the neutral position, the faces 36 and 38 extend in respective vertical planes parallel to the Y direction and each located on a respective side of the axis 18.
[0037]
[0030] Strands 32 and 34 extend, respectively, in a lower horizontal plane 40 (Fig. 2) and in an upper horizontal plane 42 (Fig. 2). Plane 42 is located above plane 40. In this embodiment, the fixed frame 10 has a flat horizontal lower face 44 (Fig. 3, 6) that extends in plane 40 and on which the lower coil 31a rests. Face 44 forms a stop that holds the lower coil 31a above plane 40. Correspondingly, the rotating assembly 12 has a flat horizontal upper face 46 (Fig. 4) that forms a stop preventing the upper coil 31b from moving above plane 42.
[0038]
[0031] The strand 32 has a cylindrical wall 50 (Figs. 7, 8 and 10). Here, the cross-section of the wall 50 is circular. Thus, the greatest width Lr of the wall 50 in the vertical direction is equal to the diameter of this wall 50. For example, the width Lr is less than 2 mm or 1 mm. Typically, the width Lr is greater than 0.3 mm. Here, the width Lr is equal to 0.6 mm.
[0039]
[0032] The wall 50 extends from a proximal end 52 (Fig. 7) to a free distal end 54 (Fig. 7). At the end 52, in the neutral position shown in Figure 7, the wall 50 extends the coil 31a in a direction Ta that is tangent to the osculating circle centered on the axis 18 and passing through the end of the coil 31a. In other words, it is only from the end 52 that the strand 32 begins to move away from the axis 18 along the direction Ta. Under these conditions, when the rotating assembly 12 is moved from its neutral position to its maximum rotated position, this winds the strand 32 around the axis 18 so that its length decreases. This is illustrated in Figure 8, which shows the strand 32 in the maximum rotated position.
[0040]
[0033] Here, in the neutral position, the wall 50 is straight and parallel to the direction Ta from the end 52 to the end 54.
[0041]
[0034] In this embodiment, the end 54 has an elbow 56 (Fig. 7, 8). The elbow 56 is shaped so that at a point 58 (Fig. 10) of contact between this elbow 56 and the fixed frame 10, the tangent to this elbow 56 is parallel to the Y direction. Here, the elbow 56 is obtained by bending, at the end 54, the wall 50 towards the axis 18 around a vertical axis.
[0035] The strand 32 is a short strand to limit the size of the return mechanism 14. The strand 32 is a short strand because its end 54 is located, when the rotating assembly 12 is in its maximum rotated position, between two vertical planes 60 and 62 (Fig. 8). In the neutral position, planes 60 and 62 are both perpendicular to the direction Ta (Fig. 7). Plane 60 contains the axis of rotation 18. Plane 62 is tangent to the loop 31a and located on the side of plane 60 that contains the strand 32.Conversely, in this text, a strand identical to strand 32 but whose free end is located on the side of plane 62 opposite axis 18 in the maximum rotated position, is called a "long strand".
[0042]
[0036] Strand 34 is similar to strand 32. Therefore, only the differences between strand 34 and strand 32 are described in detail hereafter. The other characteristics of strand 34 are identical to those of strand 32. In particular, strand 34 has a cylindrical wall 70 (Fig. 9) extending from a proximal end 72 (Fig. 9) to a distal end 74 (Fig. 9). At the end 72, in the neutral position, the wall 70 extends the loop 31b in a direction Tb that is tangent to the osculating circle centered on the axis 18 and passes through the end of the loop 31b. In this embodiment, the direction Tb is parallel to the Y direction. Unlike strand 32, the free end 74 is without a bend.
[0043]
[0037] Here, strand 34 is also a short strand. Thus, in the maximum rotated position, the end 74 is located between two vertical planes 76 and 78 (Fig. 9). Planes 76 and 78 are both perpendicular to the direction Tb. Plane 76 contains the axis of rotation 18. Plane 78 is tangent to the loop 31b and located on the side of plane 76 that contains strand 34.
[0044]
[0038] For short strands, spring 30 loses its prime after a much smaller number of cycles than if strands 32 and 34 were long. The objective here is to achieve a number of cycles of use of the device 4 without loss of prime exceeding ten thousand or one hundred thousand cycles. To this end, the mechanism 14 has two straight grooves 82, 84 (Figs. 3 to 5) for guiding the translation of strands 32 and 34. More precisely, strand 32 slides within groove 82 and strand 34 slides within groove 84.
[0045]
[0039] The groove 82 is cut at the base of the vertical face 36. This groove 82 has: - on one side, a long, narrow opening 90 (Fig. 10) through which the elbow 56 of the strand 32 enters the interior of this groove 82, and
[0046] - on the opposite side to this opening 90, a bottom 92 (Fig. 10) on which the wall 50 of the strand 32, and more precisely the elbow 56, slides when the rotating assembly 12 is moved between its neutral position and its maximum rotated position.
[0047]
[0040] In this embodiment, the groove 82 extends along the axis formed by the intersection of the vertical plane containing the face 36 and the horizontal plane 40. Here, this axis is therefore parallel to the Y direction. Furthermore, the cross-section of the groove 82 is constant along its entire length in the Y direction. This cross-section is rectangular. Thus, the base 92 is a flat base contained in a vertical plane slightly recessed, in the X direction, from the vertical plane containing the face 36. The upper edges of the opening 90 and the base 92 are connected to each other by a flat upper wall 94 (Fig. 10) which extends in a horizontal plane. The lower edges of the opening 90 and the base 92 are connected to each other by a flat lower wall 96 (Fig. 10) which extends in the plane 40.
[0048]
[0041] The width L82 (Fig. 10) of the groove 82, in the vertical direction, is between Lr and l,l*Lr and the depth P82 (Fig. 10) of the groove 82 is greater than 0.5*Lr, where Lr is the greatest width of the wall 50. Preferably, the depth P 82 is less than or equal to 0.75*Lr.
[0049]
[0042] Here, the length of the groove 82, in the Y direction, is greater than lmax 82 -lmin 82 , Or :
[0050] - Imax 82 is equal to the length of the strand 32 when the rotating assembly 12 is in its neutral position, and
[0051] - Imin 82 is equal to the length of the strand 32 when the rotating assembly 12 is in its maximum rotated position.
[0052]
[0043] To simplify its measurement, here, the length of the strand 32 is taken to be equal to the distance between the end 54 and the plane 60. When the length of the groove 82 is greater than lmax 82 - lmin 82The groove 82 is sufficiently long so that the elbow 56 can always be located inside this groove regardless of the position of the rotating assembly 12. To achieve this, the groove 82 is positioned relative to the strand 32 so that the point 58 of contact between the fixed frame 10 and the wall 50 is always on the base 92, both in the neutral position and in the maximum rotated position. Under these conditions, regardless of the rotation of the rotating assembly 12 between its neutral position and its maximum rotated position, the end 54 of the strand 32 is always guided in translation by the groove 82.
[0053]
[0044] The vertical face 36 is away from the coils of the spring 30. In this case, in order for the strand 32 to bear against the base 92, the direction Ta is inclined with respect to the base 92. Here, the angle α between the direction Ta and the base 92 at the point of contact 58 is within the interval ]0°; 45°]. In the case of the strand 32, the angle α is greater than 0.5° and, for example, between 5° and 30°. In this case, the presence of the bend 56 helps to limit friction between the end 54 and the base 92. This therefore slows the speed at which the strand 32 digs into the base 92.
[0054]
[0045] The groove 84 performs the same function as the groove 82 but with respect to the strand 34. Thus, the groove 84 is similar to the groove 82. Therefore, only the differences between the groove 84 and the groove 82 are described in detail. The other characteristics of the groove 84 are identical to those of the groove 82. The bottom of the groove 84 is designated 102 (Fig. 9) and extends parallel to the horizontal axis formed by the intersection of the plane containing the face 38 and the plane 42. In the case of the groove 84, it is its upper wall that is contained within the plane 42. The angle α between the direction Tb and the bottom 102 of the groove 84 is here equal to 0°. In this case, in the neutral position, the cylindrical wall 70 of the strand 34 bears against the bottom 102 along its entire length.Under these conditions, given that the angle a is zero or very small, it is not necessary for the free end 74 to have a bend to limit the friction of the strand 34 against the bottom 102.
[0055]
[0046] The length of the groove 84, in the Y direction, is greater than lmax84 - lmin84, where:
[0056] - Imax 84 is equal to the length of the strand 34 when the rotating assembly 12 is in its neutral position, and
[0057] - Imin 84 is equal to the length of the strand 34 when the rotating assembly 12 is in its maximum rotated position.
[0058]
[0047] It is noted that since the lengths of the strands 32 and 34 are not necessarily equal, correspondingly the lengths of the grooves 82 and 84 are not necessarily equal. For example, here, the length of strand 34 is less than the length of strand 32, so the length of groove 84 may also be shorter than the length of groove 82.
[0048] Each of the coils of the spring 30 is wound around a spacer 110 (Figs. 2 and 6). The spacer 110 limits wear on the shaft 20 caused by friction from the coils of the spring 30. To this end, the spacer 110 is positioned between the shaft 20 and each coil of the spring 30. The spacer 110 is free to rotate on the axis 18 when a coil of the spring 30 rubs against it. Typically, the spacer 110 is made of plastic. Here, the spacer 110 has a cylindrical face with a circular cross-section, centered on the axis 18 and facing the coils of the spring 30.In the neutral position, this cylindrical face is mechanically separated from the coils of spring 30 by a clearance.
[0059]
[0049] Chapter III: Variants:
[0060]
[0050] Variants of the end strands:
[0061]
[0051] The cross-section of the wall 50 of the strand 32 is not necessarily circular. Alternatively, the cross-section of the wall 50 is rectangular and, for example, square. In this case, the width Lr of the strand 32 is equal to its height in the Z direction.
[0062]
[0052] In the neutral position, the angle between directions Ta and Tb is not necessarily less than 45°. For example, alternatively, the spring 30 is arranged so that the angle between directions Ta and Tb is close to or equal to 90°. In this case, the positions of the vertical faces 36 and 38 must be adapted accordingly so that the angle α remains less than 45° for each of the short strands.
[0063]
[0053] In a simplified embodiment, the bend 56 is omitted even if the angle α is greater than 0.5°. In this case, the friction between the strand 32 and the bottom 92 of the groove 82 is not minimized. However, even in this case, the number of operating cycles before the spring 30 loses its prime remains substantially higher than in the case where the groove 82 is omitted.
[0064]
[0054] In the neutral position, the wall 50 of the strand 32 does not necessarily extend along a straight axis. Alternatively, the wall 50 extends along a curved axis whose center of radius of curvature is located on the side of the axis 18.
[0065]
[0055] In the case where the angle a is equal to 0°, the free end 74 can still include a bend shaped as described in the case of the bend 56.
[0066]
[0056] If the angular displacement of the rotating assembly 12 is small, the free end 54 of the strand 32 can also be located between the planes 60 and 62 in the neutral position.
[0057] The positions of the strands 32 and 34 can be interchanged. Thus, alternatively, strand 32 is an upper strand and strand 34 is a lower strand.
[0067]
[0058] Alternatively, only one of the strands 32, 34 is a short strand. For example, the other strand is a long strand. In this case, the guide groove for the long strand can be omitted.
[0068]
[0059] In another embodiment, one of the strands is a short strand while the other strand has an anchoring hook that surrounds a pin of the fixed frame or rotating assembly to prevent this strand from sliding. In this case, only the short strand slides and winds around the axis 18.
[0069]
[0060] The different variants described in the case of strand 32 are also applicable to strand 34.
[0070]
[0061] Variants of the grooves:
[0071]
[0062] Alternatively, the bottom 92 of the groove 82 does not extend along a straight axis but along a curved axis whose center of radius of curvature is located on the side of the axis 18. For example, such a groove with a curved bottom is made by cutting it into the face 36 using a disk.
[0072]
[0063] Alternatively, the length of the groove 82 is less than lmax82 - lmin82. In this case, the groove 82 is positioned relative to the strand 32 so that the free end 54 is located outside the groove 82 in the neutral position of the rotating assembly 12. Then, when the rotating assembly 12 is moved towards its maximum rotated position, the strand 32 shortens and its end 54 enters the groove 82 where it slides until the maximum rotated position is reached.
[0073]
[0064] Other shapes are possible for the cross-section of the groove 82. In practice, any shape of the cross-section of the groove 82 that effectively retains the strand 32 inside this groove is acceptable. For this purpose, preferably, the lower 96 and upper 94 walls are horizontal or diverge from each other as one approaches the bottom 92 of the groove.
[0074]
[0065] In another embodiment, face 36 has a projecting rim and groove 82 is cut into this projecting rim. In this case, the projecting rim is located at the intersection between faces 36 and 44.
[0075]
[0066] All the variants described in the particular case of groove 82 also apply to groove 84.
[0076]
[0067] Other variants:
[0068] In a simplified variant, the spring 30 has only one or two turns.
[0077]
[0069] Alternatively, one or both of the vertical faces 36, 38 are not flat. For example, the faces 36, 38 may be curved. In this case, for example, the intersection of each of these faces 36, 38 with a horizontal plane is an arc of a circle centered, preferably, on the axis 18. In this case, the bottom of the grooves is also, preferably, curved, for example with the same radius of curvature as the vertical face in which this groove is cut.
[0078]
[0070] Alternatively, the spacer 110 is omitted. In this case, the diameter of the shaft 20 can be modified to be equal to the diameter of the spacer 110 at least in the section of this shaft enclosed by the coils of the spring.
[0079]
[0071] Alternatively, the shaft 20 and the spacer 110 are omitted. In this case, the pivot joint between the fixed frame 10 and the rotating assembly 12 is achieved without using a shaft extending from the fixed frame 10 to the rotating assembly 12. For example, the pivot joint is achieved using:
[0080] - a circular groove centered on axis 18 and cut into an upper face of the fixed frame 10, and
[0081] - of a circular rib fitted into an underside of the rotating assembly 12 and received by sliding inside the circular groove of the fixed frame 10.
[0082]
[0072] The fixed frame 10 is not necessarily fixed to a handle. It can also be fixed to a steering wheel or a control console.
[0083]
[0073] The device 4 described herein can be implemented in human-machine interfaces other than a button equipped with a protective cover. This device can be implemented in any human-machine interface used to control a machine or apparatus such as an aircraft. The device 4 can also be implemented in systems other than a human-machine interface, such as a motor, a circuit breaker, cockpit equipment, or a clock.
[0084]
[0074] Several of the variants described above can be combined in the same embodiment.
[0085]
[0075] Chapter IV: Advantages of the described embodiments:
[0086]
[0076] The use of a short strand reduces the size of the return mechanism. Furthermore, the presence of the groove allows for a similar number of operating cycles without spring loss to that which would be obtained with a long strand. In practice, the groove prevents the short strand from losing its contact with the fixed frame or the rotating assembly at the end of its travel. Tests were carried out on several identical copies of device 4, within manufacturing tolerances. For all of these copies, no spring loss was observed after 250,000 operating cycles. The tests were stopped after 250,000 cycles, so it is likely that no spring loss will be observed even for a number of cycles exceeding 250,000. The same tests were carried out with the same number of copies of a device identical to device 4, except that it lacks grooves 82 and 84.In this case, a loss of prime in spring 30 was observed after about a hundred cycles of use, thus confirming the effectiveness of the presence of the grooves.
[0087]
[0077] The fact that the width of the groove is between Lr and l,l*Lr and its depth is greater than 0.5*Lr, makes it possible to increase the number of cycles of use without loss of prime.
[0088]
[0078] The fact that the cross-section of the groove is rectangular also makes it possible to increase the number of cycles of use without losing prime.
[0089]
[0079] When the groove length exceeds Imax-lmin, the free end is always contained within the groove regardless of the position of the rotating assembly. This improves the robustness of the retention of the short strand in its horizontal plane and therefore increases the number of operating cycles without the spring losing its prime.
[0090]
[0080] The presence of the elbow 56 in the free end 54 of the strand 32 reduces friction between the strand 32 and the bottom 92 of the groove 82. Thus, the strand 32 does not, or hardly, dig into the groove 82, which keeps the return torque of the spring 30 practically unchanged even after a very large number of cycles of use.
[0091]
[0081] The presence of the lower bearing face 44 facilitates the assembly of the return mechanism 14. More specifically, it facilitates the positioning of the spring 30 in a position where its short strand 32 can easily be inserted into the groove 82.
[0092]
[0082] The fact that the depth P82 of the groove 82 is less than or equal to 0.75*Lr allows the bulk of the return mechanism 14 to be limited without reducing the number of cycles of use without loss of spring prime.
[0093]
[0083] The fact that the two end strands 32, 34 are short strands limits the size of the return mechanism.
[0084] The higher the number of coils in the spring, the more the coils can be inclined relative to the horizontal plane. Therefore, the presence of grooves 82, 84 for the strands 32, 34 is all the more advantageous as the number of coils in the spring increases.
Claims
Demands 1. Device comprising a fixed frame (10), a rotating assembly (12) and a return mechanism (14), in which: - the device includes a rotation axis (18), - The rotating assembly can be moved in rotation on the axis of rotation from a neutral position to a maximum rotated position reached at the end of its stroke. - the return mechanism is capable of returning the rotating assembly to its neutral position in the absence of external stress, this return mechanism comprising a helical spring (30) including: -- at least one coil (31a, 31b) which makes a complete turn around the axis of rotation, -- a first and a second end strands (32, 34) which each extend a coil of the spring, respectively, in distinct first and second planes (40, 42), the first plane (40) being perpendicular to the axis of rotation, the first strand (32) having a cylindrical wall (50) which extends, from the coil it extends, in a direction tangential (Ta) to this coil, to a free end (54), the cylindrical wall of this first strand being in sliding contact with one of the fixed frame and the rotating assembly, so that when the rotating assembly is moved from its neutral position to its maximum rotated position, this winds the first strand around the axis of rotation, characterized in that: - the first end strand is a short strand, that is to say a strand whose free end (54) is located, when the rotating assembly is in its maximum rotated position, between a third and a fourth plane (60, 62) both perpendicular to the tangential direction (Ta) of this first strand, the third plane containing the axis of rotation and the fourth plane being tangent to the coil of the spring which this strand extends and located on the side of the third plane which contains this strand, - the return mechanism (14) comprises, for each short strand, a guide groove (82, 84) in which this short strand is slidably received, this groove being cut into that of the fixed frame and of the rotating assembly on which this short strand is in sliding support.
2. Device according to claim 1, in which the width of the groove (82, 84) is between Lr and l,l*Lr and its depth is greater than 0.5*Lr, where Lr is the greatest width of the cylindrical wall of the short strand in a direction parallel to the axis of rotation.
3. A device according to any one of the preceding claims, wherein: - the groove (82, 84) has, on one side, a longitudinal opening (90) through which the short strand is introduced into this groove and, on the side opposite this longitudinal opening, a bottom (92) on which the cylindrical wall of the short strand slides when the rotating assembly is moved from its neutral position to its maximum rotated position, and - the cross-section of this groove is rectangular so that the upper edges of the long opening and the bottom are connected to each other by an upper wall (94) which extends in a plane perpendicular to the axis of rotation and the lower edges of the long opening and the bottom are connected to each other by a lower wall (96) which extends in a plane perpendicular to the axis of rotation.
4. Device according to any one of the preceding claims, wherein the length of the groove (82, 84) is greater than Imax - Imin, where: - Imax is equal to the length of the short strand when the rotating assembly is in its neutral position, and - Imin is equal to the length of the short strand when the rotating assembly is in its maximum rotated position.
5. Device according to any one of the preceding claims, wherein the free end of the short strand has a bend (56) received to slide inside the groove, this bend being shaped so that, at the point of contact (58) between the bottom and the bend, the angle between the tangent to the bottom and the tangent to the bend is zero.
6. A device according to any one of the preceding claims, wherein that of the fixed frame and the rotating assembly on which the short strand is in sliding support,17 includes a bearing face (44, 46) which extends, in the same plane as the lower wall of the groove, from the axis of rotation to the groove.
7. Device according to any one of the preceding claims, wherein the groove depth is less than or equal to 0.75*Lr.
8. A device according to any one of the preceding claims, wherein: - the second plane (42) is perpendicular to the axis of rotation, - the second strand (34) has a cylindrical wall (70) which extends, from the loop it prolongs, in a tangential direction (Tb) to this loop, to a free end (74), the cylindrical wall of the second strand is in sliding contact with the other of the fixed frame and the rotating assembly, so that when the rotating assembly is moved from its neutral position to its maximum rotated position, this also winds the second strand around the axis of rotation, and - the second strand is also a short strand.
9. Device according to any one of the preceding claims, wherein the helical spring comprises at least three turns.
10. Device according to any one of the preceding claims, wherein the device comprises a cylindrical shaft (20) which extends along the axis of rotation from the fixed frame to the rotating assembly and around which each coil of the spring is wound.
11. Human-machine interface for piloting an aircraft, in which this human-machine interface is equipped with a device (4) comprising a fixed frame (10), a rotating assembly (12) movable manually by a human being and a mechanism (14) for returning this rotating assembly to a neutral position in the absence of external stress, characterized in that the device conforms to any one of the preceding claims.