Cable actuator with improved compactness

Abstract

The invention relates to an actuator (1) comprising: a frame (20); a screw (2) / nut (4) assembly comprising a nut (4) engaged with a screw (2) extending along a longitudinal axis (Ox); a motor (3) arranged to rotate the screw (2) and to cause linear movement of the nut (4); the actuator (1) further comprises: a single pair of return mechanisms (10, 11) comprising a first return mechanism (10) and a second return mechanism (11) both rotatably mounted on the frame (20), the first return mechanism (10) being connected to the output (80) of the actuator (1); a first member (6) for transmitting tension, which is connected to the nut (4) by its first end (6.1) and its second end (6.2), and which engages with a first return mechanism (10) and a second return mechanism (11), anti-rotation means (40) for preventing rotation of the nut (4) relative to the screw (2).

Description

Technical Field

[0001] The invention relates to a cable actuator comprising a screw / nut assembly, the nut of which is capable of translation and is connected to a component to be moved via a cable. Background Art

[0002] It is known that a cable actuator includes a motor-driven screw rod, which extends along the longitudinal axis and is mounted on a frame. The nut is engaged with the screw rod and is associated with an anti-rotation device so that the relative rotation of the screw rod and the nut causes the linear movement of the nut. A first cable (with both ends connected to the nut) forms a first loop between a first pulley and a second pulley of a first pair of pulleys. A second cable (with both ends connected to the nut) forms a second loop between a third pulley and a fourth pulley of a second pair of pulleys. The first pulley and the third pulley are usually constrained to rotate with the same axis and are connected to the output of the actuator. Therefore, such a system is a rotary output actuator. Conventionally, the first pair of pulleys and the second pair of pulleys are placed on either side of the screw rod so that the strands of the first cable extending between the nut and a pair of pulleys and the strands of the second cable extending between the nut and the second pair of pulleys are located in the same plane, which includes the longitudinal axis. Such an arrangement is necessary in order to balance the forces applied to the nut and limit the friction on the nut and the risk of the nut getting stuck relative to the screw rod. However, this balance is not a simple matter due to uncertainties in implementation, parasitic movement oscillations of the nut relative to the screw and misalignment of the strands. An actuator is achieved which, despite its overall length being close to the maximum stroke of the nut, has considerable dimensions in terms of width (considered in a direction parallel to the axis of rotation of the pairs of pulleys) and height (considered in a direction orthogonal to the axis of rotation and the longitudinal axis of the pulleys). This is because the maximum width of such a cable actuator corresponds to the maximum width of the nut and the two pulleys, while its minimum height corresponds to half the height of the nut, plus the height of the pulleys.

[0003] There is also a cable actuator comprising a motor-driven nut mounted on a frame and engaged with a screw extending along the longitudinal axis. The screw has an anti-rotation device so that the rotation of the nut causes a linear movement of the screw. A first cable (whose two ends are connected to the two ends of the screw) forms a loop between a first pulley and a second pulley of a first pair of pulleys. The first pulley and the second pulley are included in a plane orthogonal to the axis of rotation of the pulley and including the longitudinal axis. The pulley is positioned relative to the longitudinal axis so that the longitudinal axis is tangential to the pulley. Such an arrangement of the pulley and the screw is necessary so as not to cause bending of the screw and thus limit friction and the risk of the screw getting stuck relative to the nut. Compared with the actuator of the aforementioned type, this type of cable actuator has a reduced width, but has a total length substantially equal to twice the maximum stroke of the actuator, plus approximately the length of the screw. The minimum height of the actuator is also substantially equal to and corresponds to half the height of the nut, plus the height of the pulley.

[0004] These cable actuators are therefore still considered unsuitable for producing very compact miniaturized actuators, which have particularly advantageous properties in terms of transmitted force and linearity. Summary of the invention

[0005] It is an object of the invention to improve the compactness of a cable actuator.

[0006] For this purpose, an actuator is provided, which includes: a frame; a screw / nut assembly, which includes a nut engaged with a screw extending along a longitudinal axis; a motor, which is arranged to rotate the screw and cause a linear movement of the nut. According to the present invention, the actuator also includes: a single pair of return mechanisms, which include a first return mechanism and a second return mechanism both rotatably mounted on the frame, the first return mechanism being connected to the output of the actuator. A first member transmitting a pulling force is connected to the nut through its first end and its second end, and is engaged with the first return mechanism and the second return mechanism.

[0007] A cable actuator is then achieved that utilizes a single pair of return mechanisms, has a reduced width and yet has an overall length that approaches the maximum stroke of the nut.

[0008] Advantageously, the first member for transmitting the tensile force is a cable or a belt with notches.

[0009] The compactness of the actuator is improved when the anti-rotation device comprises a carriage which is connected firstly to the nut and secondly to the first member transmitting the tensile force.

[0010] The compactness of the actuator can be further increased when the anti-rotation device comprises a guide mechanism for guiding the translation relative to the frame in a direction parallel to the longitudinal axis of the carriage.

[0011] Advantageously, the guide is a prismatic linear guide and / or comprises two points for guiding the translation.

[0012] According to a preferred embodiment, the carriage is connected to the nut by a first pair of cables comprising a second cable and a third cable extending on either side of the screw and a second pair of cables comprising a fourth cable and a fifth cable extending on either side of the screw.

[0013] The operation of the actuator is further improved when the second and third cables are connected to the nut via the first intermediate support (connected to the nut via the seventh and eighth cables) and / or the fourth and fifth cables are connected to the nut via the second intermediate support (connected to the nut via the ninth and tenth cables). This is because such a design allows tolerance of the positioning and parallelism of the guide and the screw as well as parasitic movement oscillations of the nut relative to the screw, which is particularly advantageous for the reduction and uniformity of friction.

[0014] It is highly preferred that the actuator comprises a tensioning device for tensioning the second cable and / or the third cable.Since these cables are very short, they can be selected for their strength rather than for their stiffness, which can help to reduce the diameter size of the nut.

[0015] When the first pulley and the second pulley have a plurality of grooves for accommodating additional actuation cables, the stiffness of the system can be increased or the transmissible force can be increased.

[0016] Likewise, notched belts may be used in place of actuation cables to increase, for example, joint movement, rather than relying on pulleys with more expensive spiral cables.

[0017] Other characteristics and advantages of the invention will emerge on reading the following description of a particular non-limiting embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] [ Figure 1 ] Figure 1 is a schematic representation of a plan view and a front view of an actuator according to a first embodiment of the present invention;

[0019] [ Figure 2 ] Figure 2 yes Figure 1 Schematic representation of a plan view and a top view of an actuator;

[0020] [ Figure 3 ] Figure 3 is a schematic representation of a plan view and a front view of an actuator according to a second embodiment of the present invention;

[0021] [ Figure 4 ] Figure 4 yes Figure 3Schematic representation of a plan view and a top view of an actuator;

[0022] [ Figure 5 ] Figure 5 is a schematic representation of a plan view and a front view of an actuator according to a third embodiment of the present invention;

[0023] [ Figure 6 ] Figure 6 yes Figure 5 Schematic representation of a plan view and a side view of the actuator. DETAILED DESCRIPTION

[0024] refer to Figure 1 The actuator of the invention, generally referenced 1, comprises a frame 20 on which is mounted a bearing 21 which accommodates a screw 2 for rotation about a longitudinal axis Ox. The screw 2 is a ball screw and is rotated by an electric motor 3. A nut 4 engages the screw 2 and comprises a ring 5 protruding radially from the nut 4.

[0025] The actuator 1 comprises a single pair of pulleys comprising a first pulley 10 mounted for rotation about a first axis 22 fixed to a frame 20 by a first ball bearing 30 and a second pulley 11 mounted for rotation about a second axis 23 connected to the frame 20 by a second ball bearing 31. A first actuation cable 6 engages the first pulley 10 and the second pulley 11. The cable 6 is connected to the nut 4 at its first end 6.1 and second end 6.2 according to the method to be described below.

[0026] The actuator 1 comprises an anti-rotation device 40 for preventing the nut 4 from rotating relative to the screw 2. The anti-rotation device 40 comprises a carriage 41 mounted so as to be movable in translation in a direction D1 parallel to the axis Ox by means of a guide mechanism 50. The mechanism 50 is here a prismatic linear guide comprising a rail 51 on which slides a first slide shoe 52 and a second slide shoe 53, both fixed to the carriage 41.

[0027] The carriage 41 comprises a base 42 extending substantially parallel to the longitudinal axis Ox, and a first arm 43 and a second arm 44 protrude at both ends of the base 42. The carriage 41 is connected to the nut 4 by a first pair of cables 60 and a second pair of cables 70, the first pair of cables 60 comprising a second cable 61 and a third cable 62 extending on either side of the screw 2, and the second pair of cables 70 comprising a fourth cable 71 and a fifth cable 72 extending on either side of the screw 2. Figure 2As shown, the first pair of cables 60 and the second pair of cables 70 extend in a direction substantially parallel to the longitudinal axis, and the first pair of cables 60 and the second pair of cables are located on either side of a first plane P1 passing through the nut 4 and orthogonal to the screw 2. More precisely, the third end 61.1 of the cable 61 and the fourth end 62.1 of the cable 62 are crimped on the arm 43. Symmetrically, the fifth end 71.1 of the cable 71 and the sixth end 72.1 of the cable 72 are crimped on the arm 44.

[0028] The second cable 61 , the third cable 62 , the fourth cable 71 and the fifth cable 72 are crimped to the ring 5 at their other ends.

[0029] from Figure 1 and Figure 2 As can be seen in FIG. 4 , the first cable 6 has its first end 6.1 crimped to the arm 43 and extending parallel to the longitudinal axis Ox up to the first pulley 10 to engage in the first groove 10.1 and form a half-turn winding over the first pulley 10. The first cable 6 extends parallel to the longitudinal axis Ox at the outlet of the first pulley 10 to engage in the second groove 11.1 of the second pulley 11 and form a half-turn winding therein. The first cable 6 then extends up to the ring 5, on which the second end 6.2 of the first cable 6 is crimped. In order to limit the friction between the cable 6 and the pulleys 10 and 11, the cable 6 is preferably connected to the pulley 10 or even also to the pulley 11 by crimping.

[0030] The first pulley 10 is constrained to rotate together with a finger 80 constituting the output of the actuator 1. The finger 80 here corresponds to the knuckle of a mechanized hand not shown.

[0031] In operation, under the action of the command sent to the electric motor 3, the rotation of the screw 2 causes an equal rotation of the nut 4, due to the contact friction between the screw 2 and the nut 4. This movement tensions the first pair of cables 60 and the second pair of cables 70. These pairs of cables 60 and 70 are connected to the carriage 41 - which only allows the movement of the carriage 41 along the axis Ox - and these pairs of cables 60 and 70 exert a force opposite to the rotary drive of the nut 4 by the screw 2. Therefore, the rotation of the screw 2 under the action of the electric motor 3 causes a linear movement of the nut 4 along the longitudinal axis Ox. This movement is transmitted through these pairs of cables 60 and 70 to the carriage 41 connected to the cable 6. The linear movement of the carriage 41 drives the cable 6, which causes the rotation of the pulley 10 and the actuation of the finger 80.

[0032] A cable actuator 1 is then obtained having a reduced width and an overall length approaching the maximum stroke of the nut 4 .

[0033] As in Figure 1As can be seen in FIG. 1 , the connection between the two ends 6.1 and 6.2 of the first cable 6 and the carriage 41 is located below a second plane P2 which is orthogonal to the first plane P1 and includes the longitudinal axis Ox (according to Figure 1 ).

[0034] Elements that are the same as or similar to those described above will have the same reference numerals as in the following description of the second embodiment of the present invention.

[0035] according to Figure 3 and Figure 4 In the second embodiment of the invention shown, the second end 61.2 of the second cable 61 and the eighth end 62.2 of the third cable 62 are connected to the nut 4 via a first intermediate support 90, which is connected to the nut 4 via the seventh cable 91 and the eighth cable 92. The first intermediate support 90 is here in the form of a ring and comprises a first piercing 90.1, in which the seventh end 61.2 of the cable 61 is crimped. The first intermediate support 90 also comprises a second piercing 90.1, which is diametrically opposite to the first piercing 90.2 and in which the eighth end 62.2 of the cable 62 is crimped.

[0036] The first intermediate support 90 further comprises a third through-hole 90.3 in which the ninth end 91.1 of the seventh cable 91 is crimped, and a sixth through-hole 90.4 in which the tenth end 92.1 of the cable 92 is crimped. The eleventh end 91.2 of the cable 91 is crimped in the seventh through-hole 5.1 of the ring 5, and the twelfth end 92.2 of the cable 92 is crimped in the eighth through-hole 5.2 of the ring 5.

[0037] Similarly, the thirteenth end 71.2 of the fourth cable 71 and the fourteenth end 72.2 of the fifth cable 72 are connected to the nut 4 via a second intermediate support 95, which is connected to the nut 4 via a ninth cable 96 and a tenth cable 97. The second intermediate support 95 is here in the form of a ring and comprises a seventh through-hole 95.1, in which the thirteenth end 71.2 of the cable 71 is crimped. The second intermediate support 95 also comprises an eighth through-hole 95.1, which is diametrically opposite to the seventh through-hole 95.2, and in which the fourteenth end 72.2 of the cable 72 is crimped.

[0038] The second intermediate support 95 further comprises a ninth through hole 95.3 into which a fifteenth end 96.1 of the ninth through hole member 96 is crimped, and a tenth through hole 95.4 into which a sixteenth end 97.1 of the tenth through hole member 97 is crimped.

[0039] The seventeenth end 96.2 of the cable 96 is crimped in the seventh through-hole 5.1, and the eighteenth end 97.2 of the tenth cable 97 is crimped in the eighth through-hole 5.2.

[0040] Optionally, the third end 61.1 of the cable 61 is not crimped to the arm 43 here, but is fixed to a threaded end piece passing through a ninth through-hole 43.1 in the arm 43. A knurled nut engages on the threaded end piece and one of its faces rests on the arm 43. The action on the nut makes it possible to tension the cables 61, 62, 71, 72, 91, 92, 96 and 97.

[0041] according to Figure 5 and Figure 6 In the third embodiment shown, the connection between the two ends 6.1 and 6.2 of the first cable 6 and the carriage 41 is located above a second plane P2 that is orthogonal to the first plane P1 and includes the longitudinal axis Ox. This configuration makes it possible to further reduce the footprint of the actuator 1 without generating parasitic forces on the screw 2 / nut 4 assembly.

[0042] In all the embodiments described, the cables 6 , 61 , 62 , 71 , 72 , 91 , 92 , 96 and 97 are advantageously preloaded.

[0043] Naturally, the invention is not limited to the embodiments described but covers any variant coming within the scope of the invention as defined by the claims.

[0044] in particular,

[0045] Although the actuator here comprises a ball screw, the invention is also applicable to other types of screws, such as, for example, a screw with a simple thread, or a roller;

[0046] Although the first cable is connected to the nut by crimping performed in a ring fixed to the nut, the invention is also applicable to other ways of connecting the cable to the nut, such as, for example, crimping, gluing or welding in a perforation formed in the nut;

[0047] Although here the cable extends parallel to the longitudinal axis, the invention is also applicable to other configurations of the cable in which no section or a single section of the cable extends parallel to the longitudinal axis, the remainder of the cable being able to adopt any orientation relative to the longitudinal axis;

[0048] Although here all cables of the actuator are preloaded, the invention is also applicable to preloading a single cable or only a portion of the cables;

[0049] Although here the first and second pulleys are pulleys with cylindrical grooves, the present invention is also applicable to second and fourth pulleys provided with different types of grooves, such as, for example, spiral grooves;

[0050] Although only one cable is engaged on the first pair of pulleys here, the invention is also applicable to a pair of pulleys having multiple grooves for accommodating additional actuation cables;

[0051] Although here the first cable is engaged with two pulleys, the invention is also applicable to a first cable comprising a first strand connecting a nut (via a frame) and a first pulley, then a second strand different from the first strand, one of the two ends of the second strand being connected to the first pulley by crimping, and the other of the two ends of the second strand being connected to the second pulley by crimping. Finally, the first cable may comprise a third strand, one end of which is crimped on the second pulley and the other end of which is connected to the nut (via a frame). All the different strands form a first cable that cooperates with the first pulley and the second pulley for achieving a transmission between the two connection points with the nut;

[0052] Although the anti-rotation device here comprises a cable connecting the nut to the linearly guided carriage, the invention is also applicable to other types of anti-rotation devices, such as, for example, one or more rollers which are fixed to the nut and engage in one or more grooves or in a connecting shaft of the nut with the linear guidance;

[0053] Although here the actuator comprises a guide mechanism with two translational guide points, the invention is also applicable to a guide mechanism comprising a different number of guide points, such as, for example, a single guide point or more than two guide points;

[0054] Although the guide mechanism here is a prismatic linear guide, the invention is also applicable to other types of guides that translate, such as, for example, one or more sliding pivots;

[0055] Although the linear guide here comprises two sliding shoes engaging with a track, the invention is also applicable to other types of linear guides, such as, for example, a prismatic linear guide using one or more sliding shoes with ball recirculation or a linear guide comprising a socket with ball recirculation mounted on a slotted shaft;

[0056] Although here the first cable is connected to the pulley by crimping, the invention is also applicable to other methods for cooperation of the first cable with the pulley, such as, for example, a connection by friction, for example by one or more dead turns of the cable around the pulley;

[0057] Although here the output of the actuator is a finger constrained to rotate with the first pulley, the invention is also applicable to other types of outputs of the actuator, such as, for example, fixed to the first cable and translated to obtain the output of a linear actuator;

[0058] Although here the third end of the second cable comprises a threaded end piece engaged with a knurled nut, the present invention is also applicable to other types of devices for tensioning the second cable and / or the third cable, such as, for example, a fir tooth type snap assembly or an eccentric roller;

[0059] Although here the actuator comprises a cable connected to a nut and engaged with a smooth pulley, the invention is also applicable to other types of members for transmitting tensile forces, such as, for example, chains, belts (notched or notched), or hybrid members comprising links connected by cables;

[0060] Although the cable is engaged with a pulley here, the invention is also applicable to other types of directional return mechanisms suitable for other types of members for transmitting force, such as, for example, a pinion for a chain, a pulley for a notched belt (with or without notches), or a guide roller for a belt or tape.

Claims

1. An actuator (1), comprising: Frame (20); a screw (2) / nut (4) assembly comprising a nut (4) engaged with a screw (2) extending along a longitudinal axis (Ox); a motor (3) arranged to rotate the screw (2) and cause a linear movement of the nut (4); The actuator (1) also includes a single pair of return mechanisms (10, 11), the single pair of return mechanisms (10, 11) comprising a first return mechanism (10) and a second return mechanism (11) both rotatably mounted on the frame (20), the first return mechanism (10) being connected to an output portion (80) of the actuator (1); a first member (6) for transmitting a tensile force, the first member (6) for transmitting a tensile force being connected to the nut (4) via its first end (6.1) and its second end (6.2) and being engaged with the first return mechanism (10) and the second return mechanism (11), an anti-rotation device (40), the anti-rotation device (40) being used to prevent the nut (4) from rotating relative to the screw (2), wherein The slide (41) is connected to the nut (4) via a first pair of cables (60) and a second pair of cables (70), the first pair of cables (60) comprising a second cable (61) and a third cable (62) extending on either side of the screw rod (2), the second pair of cables (70) comprising a fourth cable (71) and a fifth cable (72) extending on either side of the screw rod (2), the first pair of cables (60) and the second pair of cables (70) extending in a direction substantially parallel to the longitudinal axis (Ox), the first pair of cables (60) and the second pair of cables (70) being located on either side of a first plane (P1) passing through the nut (4) and orthogonal to the screw rod (2).

2. The actuator (1) according to claim 1, wherein: The first component (6) for transmitting the pulling force is a cable (6) or a belt with a notch.

3. The actuator (1) according to claim 1 or 2, wherein: The anti-rotation device (40) comprises a carriage (41) which is firstly connected to the nut (4) and secondly connected to the first member (6) for transmitting the tensile force.

4. The actuator (1) according to claim 3, wherein: The anti-rotation device (40) comprises a guide structure (50) for guiding the translation of the carriage (41) relative to the frame (20) in a direction (D1) parallel to the longitudinal axis (Ox).

5. The actuator (1) according to claim 4, wherein: The guide mechanism (50) is a prismatic linear guide mechanism.

6. The actuator (1) according to any one of claims 3 to 5, wherein: The guiding mechanism (50) comprises two translation guiding points.

7. Actuator (1) according to any one of the preceding claims, wherein: The second cable (61) and the third cable (62) are connected to the nut (4) via a first intermediate support (90), and the first intermediate support (90) is connected to the nut via a seventh cable (91) and an eighth cable (92).

8. Actuator (1) according to any one of the preceding claims, wherein: The fourth cable (71) and the fifth cable (72) are connected to the nut (4) via a second intermediate support (95), and the second intermediate support (95) is connected to the nut (4) via a ninth cable (96) and a tenth cable (97).

9. Actuator (1) according to any of the preceding claims, comprising means (7, 8) for tensioning the second cable (61) and / or the third cable (62).

10. Actuator (1) according to any one of the preceding claims, wherein: The first pulley (10) and the second pulley (11) have a plurality of grooves for accommodating additional components for transmitting tension.

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