Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H2025/204—Axial sliding means, i.e. for rotary support and axial guiding of nut or screw shaft
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H2025/2062—Arrangements for driving the actuator
  • F16H2025/2075—Coaxial drive motors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H2025/2062—Arrangements for driving the actuator
  • F16H2025/2087—Arrangements for driving the actuator using planetary gears

Definitions

• the present invention relates to a screw-nut transmission system, in particular a screw-nut transmission system intended for high-precision positioning applications, namely for applications in which the positioning accuracy is less than or equal to 50 pm, in particular less than or equal to 10 pm, for example less than or equal to 1 pm.
• the present invention relates more specifically to a screw-nut transmission system which exploits a magnetic force to cancel an angular play.
• a screw-nut transmission system includes:
• a second element arranged to rotate about an axis and cooperating with the first element such that the first element moves with a translational motion along that axis when the second element rotates.
• the nut moves by translation along the rotating screw.
• the first element is a screw and the second element a nut, it is the screw which moves by translation along its main axis when the nut rotates around the screw.
• the screw-nut system By adding balls between the first and second elements, the screw-nut system is called a "ball screw system".
• the balls allow the transmission to be carried out by rolling and not by sliding or friction, which is the case with a screw-nut system.
• P being the pitch (of the screw and/or the nut).
• the nut is the first element, which moves with a translational motion along the screw when the screw rotates around its main axis.
• the transmission system comprises a fixed envelope surrounding the nut and the screw, this envelope comprising a groove defined by sides.
• At least a portion of the nut moves with a translational motion in the groove.
• the screw-nut transmission system uses as an anti-rotation member a pin generally fixed on the nut.
• a clearance must be present between the pin and the groove.
• a conventional solution for taking up the play between the pin and the groove involves applying an angular preload using, for example, a torsion spring between the nut and the casing.
• the transmission system also comprises a rolling body guide device such as a ball bearing, to guide the movement of the nut in the groove.
• a rolling body guide device such as a ball bearing
• the preload force may vary during the travel of the nut.
• the force difference is equal to the product of the spring stiffness and its elongation. This variation may affect the positioning accuracy because of the difference in load state.
• torsion spring involves a significant force to ensure play compensation over the entire travel of the nut. This has an impact on the sizing of an actuator (e.g. a linear actuator) connected to the screw-nut transmission system, on the necessary drive torque, on the energy consumption of the system and/or on the volume used.
• an actuator e.g. a linear actuator
• Document US9273766 discloses an electric actuator comprising a ball screw mechanism for converting the rotational motion of the electric motor, into an axial linear motion of a drive shaft.
• the system may comprise a magnet on a pin and cooperating with a sensor, for example a Hall effect sensor, for the purpose of detecting the position of the shaft from the rotation angle of the pin.
• Document JP2004182063 describes a screw-nut system for an automobile, which exploits a magnetic force to prevent rotation of the nut.
• Document JP2021035311 relates to a screw-nut system. Rotation of the nut and an associated piston is avoided by exploiting a magnetic interaction between internal magnets and external magnets.
• An object of the present invention is to provide a screw-nut transmission system free from the limitations of known screw-nut transmission systems.
• Another object of the present invention is to provide a screw-nut transmission system suitable for high-precision positioning applications.
• Another object of the present invention is to propose a screw-nut transmission system which has a reduced volume compared to known systems.
• Another aim of the present invention is to propose a screw-nut transmission system which has a volume suitable for use in very compact devices, such as, for example and in a non-limiting manner, implanted devices.
• Another aim of the present invention is to propose a screw-nut transmission system in which friction is better controllable compared to known systems.
• Another aim of the invention is to propose a screw-nut transmission system which makes it possible to take up the angular play of the element which moves by translation while minimizing the energy requirement, by guaranteeing a constant state of load over the entire travel of the element which moves by translation, by ensuring a state of isostatic stress and/or having minimal impact on the volume of the system.
• the screw-nut transmission system comprises:
• the first element being a nut respectively a screw
• the second element being the screw respectively the nut
• the first element comprising a portion arranged to move with a translational movement in the groove.
• the system also comprises a first magnet connected (directly or indirectly) to this portion respectively to the fixed envelope.
• a contact surface made of ferromagnetic material and/or a second magnet is (are) connected to the fixed envelope respectively to this portion, this surface and/or this second magnet cooperating with the first magnet, so as to block any rotation of the first element.
• This solution has in particular the advantage over the prior art of a screw-nut transmission system adapted to these high-precision positioning applications. [0035] This solution also has the advantage over the prior art of having a reduced volume compared to known systems, in particular a volume suitable for use in very compact devices, such as, for example and in a non-limiting manner, implanted devices.
• the embodiment in which the first magnet is connected to the portion of the first element and the contact surface made of ferromagnetic material and/or the second magnet is (are) connected to the fixed casing has the advantage of having an even smaller volume compared to the embodiment in which the first magnet is connected to the fixed casing and the contact surface made of ferromagnetic material and/or the second magnet is (are) connected to the portion of the first element.
• the first magnet may have larger dimensions compared to the first embodiment, however this has an impact on the total diameter of the screw-nut transmission system.
• the presence of the first magnet and a surface made of ferromagnetic material and/or a second magnet makes it possible to better control friction compared to known systems.
• the screw-nut transmission system according to the invention makes it possible in all cases to compensate for the angular play of the element which moves by translation while minimizing the energy requirement, by guaranteeing a constant load state over the entire travel of the element which moves by translation, while ensuring a state of isostatic stress and/or having a minimal impact on the volume of the system.
• the screw-nut transmission system comprises a guide device for guiding the movement of the element which moves with a translational movement.
• the guide device is a rolling body guide device (rolling transmission). In this embodiment, there are balls between the screw and the nut.
• the rolling bodies are non-magnetic, for example and in a non-limiting manner they are made of ceramic.
• the rolling bodies are made of a magnetizable material, for example magnetizable steel.
• the rolling body guide device is a ball bearing.
• the rolling body guide device comprises an outer ring, at least a portion of which is arranged to roll on the contact surface made of ferromagnetic material and/or on the second magnet, or it comprises a sleeve connected to the outer ring and at least a portion of which is arranged to roll on the contact surface made of ferromagnetic material and/or on the second magnet.
• the first magnet is connected to the outer ring or the sleeve.
• the first magnet is therefore a rotating magnet, namely a magnet arranged to rotate about the axis of the rod during operation of the screw-nut transmission system.
• the portion arranged to move with a translational motion in the groove is connected to a rod (e.g. a pin, a stud, etc.) arranged to move by translation in the groove and to carry the first magnet.
• a rod e.g. a pin, a stud, etc.
• the rolling body guide device is carried by this rod.
• the guide device is a plain bearing, which is fixed and at least partially surrounds the screw and the nut (sliding transmission).
• the plain bearing may comprise the contact surface and/or the second magnet.
• the contact surface and/or the second magnet must have a low coefficient of friction, for example a coefficient of friction less than 0.15, preferably equal to 0.05.
• the groove belongs to a plane and the contact surface made of ferromagnetic material and/or the second magnet is substantially perpendicular to this plane.
• the contact surface made of ferromagnetic material and/or the second magnet has the dimension parallel to the translation direction of the first element less than 15
• the contact surface made of ferromagnetic material and/or the second magnet has a roughness (Ra) of less than 1
• the fixed casing comprises a plate, the plate comprising the ferromagnetic material contact surface and/or the second magnet, and a fixing surface for fixing the plate to the fixed casing.
• the plate is made of ferromagnetic material.
• the contact surface and/or the second magnet is perpendicular to the attachment surface.
• the first magnet is located on the casing, for example near a rolling plate which is not necessarily ferromagnetic, and a portion of the first element and/or a portion of the guide device (for example an outer ring and/or a bushing if the guide device is a ball bearing) is made of ferromagnetic material.
• the present invention also relates to a rotary stroke bearing guiding device, comprising:
• a part for example a lens connected to the first element and therefore arranged to move with a translational movement, the contact surface made of ferromagnetic material and/or the second magnet cooperating with the first magnet, in order to block any rotation of the first element and therefore any rotation of the part.
• Figure 1 illustrates a perspective view of a linear actuator comprising a screw-nut transmission system according to one embodiment of the invention, with a nut which moves with a translational movement, a rotating screw, a ball bearing and a first rotating magnet.
• Figure 2 illustrates a longitudinal section of the linear actuator of Figure 1.
• Figure 3 illustrates a detail of Figure 2.
• Figure 4 illustrates a cross-section of Figure 1.
• Figure 5 illustrates a bottom view of another linear actuator comprising a screw-nut transmission system according to another embodiment of the invention, with a nut which moves with a translational movement, a rotating screw, a ball bearing and a first non-rotating magnet.
• Figure 6 illustrates a side view of the linear actuator of Figure 5.
• Figure 7 illustrates a longitudinal section of the linear actuator of Figure 6.
• Figure 8 illustrates a cross-section of the linear actuator of Figure 7, along the A-A axis.
• Figure 9 illustrates a longitudinal section of a perspective view of another linear actuator comprising a screw-nut transmission system according to another embodiment of the invention, with a nut which moves with a translational movement, a rotating screw, a plain bearing and a first magnet which moves with a translational movement.
• Figure 10 illustrates a longitudinal section of the linear actuator of Figure 9.
• Figure 11 illustrates a longitudinal section of a perspective view of another linear actuator comprising a screw-nut transmission system according to another embodiment of the invention, with a rotating nut, a screw which moves with a translational movement, a plain bearing and a first magnet which moves with a translational movement.
• the first magnet is connected to the fixed casing and the contact surface made of ferromagnetic material is connected to the portion of the first element.
• the first magnet may be located near a rolling plate which is not necessarily ferromagnetic, and a portion of the first element and/or a portion of the guide device (for example an outer ring and/or a bushing if the guide device is a ball bearing) is made of ferromagnetic material.
• the first magnet may have larger dimensions compared to the first embodiment, however this has an impact on the total diameter of the screw-nut transmission system.
• Figure 1 illustrates a perspective view of a linear actuator 1 comprising a screw-nut transmission system according to one embodiment of the invention.
• Figure 2 illustrates a longitudinal section of the linear actuator 1 of Figure 1.
• Figure 3 illustrates a detail of Figure 2.
• Figure 4 illustrates a cross section of Figure 1.
• the screw-nut transmission system comprises a nut 10 which moves with a translational movement along a main axis X (visible for example in Figure 2) of a screw 20 which rotates around this axis X with a rotational speed given by a motor M, possibly reduced by a reducer R.
• the nut 10 is connected to a head T, which therefore also moves by translation.
• the linear actuator 1 may for example be used in a device such as for example and in a non-limiting manner an implantable device.
• Other examples include a linear actuator that can be assembled in parallel to constitute a tripod or a hexapod for positioning components such as mirrors, lenses or semiconductor wafers, or for guiding surgical tools for operations requiring high precision.
• the transmission system comprises a fixed casing 60 surrounding the nut 10 and the screw 20.
• the casing 60 is not a single piece, namely made monolithically, but it comprises several parts, including an internal part 61.
• the casing also comprises a radial force take-up part 62, the presence of which is optional.
• this part 62 is a ball cage (balls are for example visible in Figure 4) arranged to move half of the nut in the rotating screw configuration.
• the casing 60 and in particular its internal part 61, comprises a groove 90 defined by sides. A portion of the nut 10 is arranged to move with a translational movement along the axis X in this groove 90.
• the transmission system comprises a rod 30 (for example a pin or a stud) essentially perpendicular to the axis X.
• This rod 30 is integral with the nut 10, so it also moves with a translational movement along the axis X in this groove 90.
• this rod 30 is inserted into a cavity of the nut 10.
• This rod 30 makes it possible in the embodiment of figures 1 to 4 to carry the first magnet 40 and also the guide device, which in this case is a ball bearing 80.
• the first magnet 40 and/or the guide device is (are) carried directly by the portion of the nut 10 which moves in the groove 90.
• the ball bearing 80 comprises an inner ring 82 (which in this embodiment is static), an outer ring 83 (which in this embodiment is dynamic and in particular rotates about the Y axis, and rolling bodies 81 (balls in FIGS. 1 to 4) held between the outer ring 83 and the inner ring 82.
• the static ring comprises two separate and interconnected parts, in particular a core and a cone, which is generally driven onto the core and which determines the desired clearance in the bearing.
• the static ring comprises a single part, namely a core (without a cone): advantageously, the bearing may have clearance, since this is taken up by the system according to the invention.
• a cage may in certain cases be used in a known manner in order to space the rolling bodies 81 between the rings.
• the number of contact points (for example in the case where the rolling bodies are balls) or contact lines (for example in the case where the rolling bodies are rollers) of the rolling bodies with the rings may vary depending on the type of bearing.
• the bearing 80 is a deep groove bearing.
• the bearing 80 is a ball bearing with four contact points: in this case, the system according to the invention makes it possible to have a ball bearing with reduced play.
• the rolling bodies are non-magnetic or with low magnetic permeability, for example and in a non-limiting manner they are made of ceramic, which also avoids lubricating the bearing 80.
• the use of non-magnetic rolling bodies or with low magnetic permeability makes it possible to prevent any magnetization of the rolling bodies from disturbing the operation of the system according to the invention.
• the system according to the invention also operates with magnetizable rolling bodies, for example rolling bodies made of magnetizable steel.
• the ball bearing 80 comprises in this embodiment an (external) sleeve 84 connected to the outer ring 83 and therefore also rotating around the Y axis.
• the screw-nut transmission system comprises a first magnet 40 connected via the rod 30 to the portion of the nut 10 which moves in the groove 90.
• the first magnet 40 is integral with the dynamic part of the bearing 80, in particular the sleeve 84, and therefore it is also arranged to roll around the Y axis.
• the first magnet and/or the second magnet is a permanent magnet. In one embodiment, the first magnet and/or the second magnet is magnetized along the X-axis. In one embodiment, the first magnet and/or the second magnet has a substantially cylindrical shape.
• the transmission system comprises a contact surface 51 made of ferromagnetic material (for example and in a non-limiting manner made of iron, iron alloy or magnetizable steel) connected to the fixed casing 60.
• this contact surface 51 belongs to a plate 50 which is connected to the fixed casing 60, for example via one or more screws V.
• this contact surface 51 belongs directly to the fixed casing 60.
• the plate 50 and the fixed casing 60 form a single-piece part.
• this contact surface 51 cooperates with the first magnet 40, so as to block any rotation of the nut 10.
• the contact between the portion of the nut 10 which moves by translation in the groove 90 and one side of the groove 90 is an indirect contact, for example via the rod 30 and/or the guide device 80.
• the bushing 84 of the guide device 80 touches the plate 50.
• the ring 83 which can roll on the plate 50.
• the groove 90 is a clearance and is not intended to serve as a support for rolling.
• one side of the groove can be considered as a contact surface.
• At least one dynamic portion of the guide device comes into direct contact C with a portion of the contact surface 51, as for example visible in FIG. 4.
• the outer sleeve 84 therefore rolls on this contact surface 51.
• d air gap
• the magnetic attraction between the first magnet 40 and the contact surface 51 makes it possible to ensure the contact C, visible in FIG. 4, between a dynamic portion of the guide device (the outer sleeve 84 in the embodiment of FIGS. 1 to 4) and a portion of the contact surface 51.
• the adhesion force is sized to ensure this contact C under the extreme conditions required by the application of the system according to the invention (maximum load and acceleration).
• the adhesion force depends in particular on the magnetization power of the first magnet 40, the distance d and the material of the plate 51, etc.
• the adhesive force is 2.1 N.
• This force multiplied by the distance separating it from the X axis of the screw 20 must be greater than the transmissible torque during the extreme operating conditions of the system according to the invention (maximum load and acceleration).
• the contact surface made of ferromagnetic material 51 has the dimension parallel to the direction of translation of the nut 10 (therefore parallel to the axis X) less than 15 pm, preferably less than 10 pm, for example equal to 1 pm.
• the contact surface made of ferromagnetic material has a roughness (Ra) of less than 1 pm, preferably less than 0.8 pm, for example equal to 0.2 pm.
• Ra roughness
• quenching and/or grinding is (are) used to obtain this roughness.
• the plate 50 comprises not only the contact surface 51 made of ferromagnetic material but also a fixing surface 52 (visible for example in FIG. 4) for fixing the plate 50 to the fixed casing 60.
• the entire plate 50 is made of ferromagnetic material.
• the contact surface 51 is substantially perpendicular to the fixing surface 52, as visible for example in FIG. 4. In the absence of this perpendicularity, a calibration of the system according to the invention can be carried out before its use.
• Figure 5 illustrates a bottom view of another linear actuator 1 comprising a screw-nut transmission system according to another embodiment of the invention.
• Figure 6 illustrates a side view of the linear actuator 1 of Figure 5.
• Figure 7 illustrates a section longitudinal of the linear actuator 1 of figure 6.
• Figure 8 illustrates a cross-section of the linear actuator of figure 7, along the AA axis.
• the screw-nut transmission system comprises a screw 20 rotating about a main axis X of the screw (visible for example in Figure 7), with a rotation speed given by a motor M, possibly reduced by a reducer R. This rotation causes a translational movement of the nut 10 along the axis X.
• a motor M possibly reduced by a reducer R.
• This rotation causes a translational movement of the nut 10 along the axis X.
• This is a system similar to that of Figures 1 to 4, with the difference that in the embodiment of Figures 5 to 8, the first magnet 40 is non-rotating.
• the screw 20 rotates in a cavity of an intermediate part 70, which serves as a rolling surface for the ball bushing 61, 62 which takes up the radial forces and the bending force moment.
• the transmission system of Figures 5 to 8 comprises a fixed casing 60 surrounding the nut 10 and the screw 20.
• the transmission system comprises a rod 30 (for example a pin or a stud) essentially perpendicular to the screw 20 and integral with the nut 10, therefore which also moves with a translational movement along the axis X in the groove 90.
• this rod 30 is inserted into a cavity of the intermediate part 70 which is connected to the screw 20.
• This rod 30 allows in the embodiment of figures 5 to 8 to carry the first magnet 40 and also the guide device, which is in this case also a ball bearing 80.
• the guide device makes it possible to guide the movement of the portion of the nut 10 (and in the embodiment of FIGS. 5 to 8, of the rod 30 as well) in the groove 90.
• the bearing 80 is also a deep groove ball bearing.
• the ball bearing 80 comprises in this embodiment an (external) sleeve 84 connected to the outer ring 83 and therefore also rotating around the Y axis.
• the first magnet 40 is carried by the rod 30 but it is not connected to the dynamic part of the bearing. Therefore in this embodiment, the first magnet 40 is non-rotating.
• the transmission system comprises a contact surface 51 made of ferromagnetic material (for example and in a non-limiting manner made of iron, iron alloy or magnetizable steel) connected to the fixed casing 60.
• this contact surface 51 belongs to a plate 50 which is connected to the fixed casing 60, for example via one or more screws V.
• this contact surface 51 cooperates with the first magnet 40, so as to block any rotation of the nut 10.
• the contact between the portion of the nut 10 which moves by translation in the groove 90 and one side of the groove is an indirect contact, namely via the rod 30 and/or the guide device 80.
• at least one dynamic portion of the guide device comes into direct contact C with a portion of the contact surface 51, as for example visible in FIG. 8.
• d air gap
• the magnetic attraction between the first magnet 40 and the contact surface 51 makes it possible to ensure contact C between a dynamic portion of the guide device (the outer sleeve 84 in the embodiment of FIGS. 1 to 4) and a portion of the contact surface 51.
• the adhesion force is dimensioned to ensure this contact C under the extreme conditions required by the application of the system according to the invention (maximum load and acceleration).
• first non-rotating magnet 40 is not linked to the presence of a nut 10 which moves by translation.
• the first magnet rotating or not, can be placed either on the element which translates or on the casing.
• the aim is to minimize the mass of the element which translates.
• the first magnet is placed on the part which translates (on the nut subassembly for FIGS. 1 to 4 and 5 to 8; on the screw subassembly for FIG. 11).
• the guide device is a plain bearing 80'.
• the nut that moves with a translational movement
• the screw that moves with a translational movement.
• a linear actuator configuration 1 with a rotating nut is commonly referred to as a “non-captive screw actuator.”
• the nut 10 which moves with a translational movement along a main axis X (visible for example in FIG. 9) is integral with an intermediate part 70, defining a cavity which receives at least a portion of the rotating screw 20.
• the transmission system comprises a fixed casing 60 surrounding the nut 10 and the screw 20.
• the fixed casing 60 also comprises a plain bearing 80'.
• This plain bearing 80' comprises a groove 90 defined by sides. A portion of the intermediate piece 70 (or - in the absence of the intermediate piece 70 - a portion of the nut 10) is arranged to move with a translational movement along the X axis in this groove 90.
• the transmission system comprises a rod 30 (for example a pin or a stud) essentially perpendicular to the intermediate part 70 and secured to the intermediate part 70, and therefore to the nut 10, therefore which also moves with a translational movement along the axis X in this groove 90.
• this rod 30 is inserted into a cavity of the intermediate part 70.
• This rod 30 makes it possible, in the embodiment of FIGS. 9 to 10, to carry the first magnet 40.
• the guide device makes it possible to guide the movement of the rod 30 in the groove 90.
• at least a portion of the rod 30 comes into frictional contact with one side of the groove 90.
• the screw-nut transmission system comprises a first magnet 40 connected via the rod 30 to the portion of the intermediate piece 70 which moves in the groove 90.
• the first magnet 40 is non-rotatable.
• the transmission system comprises a contact surface 51 made of ferromagnetic material connected to the fixed casing 60.
• this contact surface 51 belongs to a plate 50 which is connected to the fixed casing 60, for example via one or more screws V.
• this contact surface 51 is located directly on the fixed casing 60.
• the plate 50 and the fixed casing 60 form a single piece.
• this contact surface 51 cooperates with the first magnet 40, so as to ensure contact between the rod 30 and one side of the groove, which makes it possible to block any rotation of the nut 10.
• d air gap
• the adhesion force is dimensioned to ensure this contact C' under the extreme conditions required by the application of the system according to the invention (load and maximum acceleration).
• the adhesive force depends in particular on the magnetizing power of the first magnet 40, the distance d and the material of the plate 51, etc.
• Figure 11 illustrates a longitudinal section of a perspective view of another linear actuator comprising a screw-nut transmission system according to another embodiment of the invention.
• the screw-nut transmission system comprises a nut 10 which moves with a rotational movement around a main axis X with a rotational speed given by a motor M, possibly reduced by a reducer R. (visible for example in Figure 9).
• the screw 20 moves by translation along this axis X.
• the screw 20 is secured to an intermediate part 70, defining a cavity which receives at least a portion of the screw 20.
• the transmission system comprises a fixed casing 60 surrounding the nut 10 and the screw 20.
• the casing 60 comprises a plain bearing 80' which comprises a groove 90 defined by sides.
• a portion of the intermediate piece 70 (or - in the absence of the intermediate piece 70 - a portion of the screw 20) is arranged to move with a translational movement along the X axis in this groove 90.
• the transmission system comprises a rod 30 as for the embodiments of Figures 9 to 10.
• This rod 30 makes it possible in the embodiment of Figure 11 to carry the first magnet 40.
• the guide device makes it possible to guide the movement of the rod 30 in the groove 90. In particular, at least a portion of the rod 30 comes into contact by friction with one side of the groove 90.
• the screw-nut transmission system comprises a first magnet 40 connected via the rod 30 to the portion of the intermediate piece 70 which moves in the groove 90.
• the first magnet 40 is non-rotatable.
• the transmission system comprises a contact surface 51 made of ferromagnetic material (for example and in a non-limiting manner made of iron, iron alloy or magnetizable steel) connected to the fixed casing 60.
• this contact surface 51 belongs to a plate 50 which is connected to the fixed casing 60, for example via one or more screws V.
• this contact surface 51 directly to the fixed casing 60.
• the plate 50 and the fixed casing 60 form a single piece.
• this contact surface 51 cooperates with the first magnet 40, so as to block any rotation of the screw 20.
• d air gap
• the magnetic attraction between the first magnet 40 and the contact surface 51 makes it possible to ensure direct contact between a portion of the plain bearing 80' (in this case one side of the groove 90) and a portion of the rod 30.
• the adhesive force is dimensioned to ensure this contact under the extreme conditions required by the application of the system according to the invention (maximum load and acceleration).
• the adhesive force depends in particular on the magnetization power of the first magnet 40, the distance d and the material of the plate 51, etc.
• the invention relates to a rotary stroke bearing guiding device comprising:
• a part for example a lens connected to the first element and therefore arranged to move with a translational movement, the contact surface made of ferromagnetic material cooperating with the first magnet, in order to block any rotation of the first element and therefore any rotation of the part.
• the lens must be moved linearly, but must not rotate (risk of changing the optical parameters of the lens composition).
• a magnetic play compensation according to the invention in this connection can be applied.

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• 2024
  • 2024-03-07 WO PCT/IB2024/052213 patent/WO2024189479A1/fr not_active Ceased
  • 2024-03-07 JP JP2025551164A patent/JP2026508873A/ja active Pending
  • 2024-03-07 KR KR1020257029958A patent/KR20250155549A/ko active Pending
  • 2024-03-07 EP EP24709528.4A patent/EP4662425A1/de active Pending

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