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) which engages with a screw (2) extending along a longitudinal axis (Ox); - a motor (3) arranged to rotate the screw (2) and bring about a linear movement of the nut (4); the actuator (1) further comprising - a single pair of return mechanisms (10, 11) comprising a first return mechanism (10) and a second return mechanism (11) which are rotatably mounted on the frame (20), the first return mechanism (10) being connected to an output (80) of the actuator (1); - a first transmission member (6) for transmitting a pulling force connected to the nut (4) by its first end (6.1) and its second end (6.2), which transmission member engages with the first return mechanism (10) and the second return mechanism (11); - an anti-rotation device (40) for preventing the nut (4) from rotating relative to the screw (2).

Description

Description Title of the invention: Cable actuator with improved compactness Technical field of the invention The invention relates to a cable jack comprising a screw / nut assembly, the nut of which is movable in translation and connected by means of cables to an element to be moved. Prior art Cable actuators are known comprising a motorized screw extending along a longitudinal axis and which is mounted on a frame. A nut cooperates with the screw and is associated with anti-rotation means so that a relative rotation of the screw and the nut causes a linear displacement of the nut. A first cable whose ends are connected to the nut makes a first loop between a first pulley and a second pulley of a first pair of pulleys. A second cable whose ends are connected to the nut makes a second loop between a third pulley and a fourth pulley of a second pair of pulleys. The first and third pulleys are generally integral in rotation with the same shaft and connected to an output of the actuator. Such a system is therefore a rotary output actuator.Conventionally, the first pair of pulleys and the second pair of pulleys are placed on either side of the screw so that the strands of the first cable which extend between the nut and the first pair of pulleys as well as the strands of the second cable which extend 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 friction on the nut and the risks of it jamming relative to the screw. However, due to the uncertainties of production, the parasitic kinematic oscillations of the nut relative to the screw, and the misalignments of the strands, this balance is not self-evident.We obtain a jack which, although having a total length close to the maximum stroke of the nut, has a significant size in width (considered in a direction parallel to the axes of rotation of the pairs of pulleys) and in height (considered in a direction orthogonal to the axes of rotation of the pulleys and to the longitudinal axis). In fact, the minimum width of such a cable jack corresponds to that of the nut and the two pulleys, when its minimum height corresponds to half the height of the nut to which is added the height of the pulleys. There are also cable jacks comprising a motorized nut mounted on a frame and which cooperates with a screw extending along a longitudinal axis. The screw has anti-rotation means so that a rotation of the nut causes a linear movement of the screw. A first cable, the ends of which are connected to the ends of the screw, makes 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 normal to the axis of rotation of the pulleys and which includes the longitudinal axis. The pulleys are positioned relative to the longitudinal axis so that it is tangent to the pulleys. Such an arrangement of the pulleys and the screw is necessary in order to generate no bending on the screw and thus limit friction and the risks of the screw jamming relative to the nut. This type of cable jack has a reduced width compared to the type of jack previously described but has a total length substantially equal to twice the maximum stroke of the jack to which is added approximately the length of the screw. The minimum height of the jack is also substantially equal to half the height of the nut to which is added the height of the pulleys. Thus, these cable actuators are still considered unsuitable for the production of very compact miniaturized actuators, even though they have particularly interesting characteristics in terms of force delivered and linearity. Presentation of the invention The object of the invention is to improve the compactness of a cable jack. For this purpose, an actuator is provided comprising a chassis, a screw / nut assembly comprising a nut cooperating with a screw extending along a longitudinal axis, a motor arranged to rotate the screw and cause a linear movement of the nut. According to the invention, the actuator also comprises a single pair of gears comprising a first gear and a second gear rotatably mounted on the chassis, the first gear being connected to an output of the actuator. A first member for transmitting a tensile force is coupled to the nut by its first end and its second end and cooperates with the first gear and the second gear. This results in a cable actuator which, using a single pair of gears, has a reduced width and also has a total length close to the maximum travel of the nut. Advantageously, the first transmission element of a traction force is a cable or a toothed belt. The compactness of the actuator is improved when the anti-rotation device comprises a carriage connected on the one hand to the nut and on the other hand to the first member for transmitting a traction force. It is possible to further improve the compactness of the actuator when the anti-rotation device comprises a mechanism for guiding a translation in a direction parallel to the longitudinal axis of the carriage relative to the chassis. Advantageously, the guide mechanism is a prismatic linear guide mechanism and / or comprises two translational guide points. 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 as well as by a second pair of cables comprising a fourth cable and a fifth cable extending on either side of the screw. The operation of the actuator is further improved when the second cable and the third cable are coupled to the nut by a first intermediate support connected to the nut by a seventh cable and an eighth cable and / or the fourth cable and the fifth cable are coupled to the nut by a second intermediate support connected to the nut by a ninth cable and a tenth cable. Indeed, this design allows tolerances in positioning and parallelism of the guide and the screw as well as the parasitic kinematic oscillations of the nut relative to the screw, which is particularly favorable to the reduction and regularity of friction. Most preferably, the actuator includes a device for tensioning the second and / or third cable. These cables being very short, they can be chosen for their strength and not for their stiffness, which can contribute to reducing the diametrical size of the nut. It is possible to increase the rigidity of the system or to increase the transmissible force when the first pulley and the second pulley have a plurality of grooves to accommodate additional actuating cables. Similarly, a toothed belt can be used instead of drive cables to increase, for example, joint travel instead of using more expensive helical cable pulleys. Other characteristics and advantages of the invention will appear on reading the following description of a particular non-limiting embodiment of the invention. Brief description of the figures [Fig. 1] Figure 1 is a schematic representation in plan and in front view of an actuator according to a first embodiment of the invention; [Fig. 2] Figure 2 is a schematic representation in plan and top view of the actuator of Figure 1; [Fig. 3] Figure 3 is a schematic representation in plan and front view of an actuator according to a second embodiment of the invention; [Fig. 4] Figure 4 is a schematic representation in plan and top view of the actuator of Figure 3; [Fig. 5] Figure 5 is a schematic representation in plan and front view of an actuator according to a third embodiment of the invention; [Fig. 6] Figure 6 is a schematic representation in plan and side view of the actuator of Figure 5. Description of the embodiments

[0001] With reference to Figure 1, the actuator of the invention, generally designated 1, comprises a frame 20 on which is mounted a bearing 21 which accommodates a screw 2 rotating about a longitudinal axis Ox. The screw 2 is a ball screw and is driven in rotation by an electric motor 3. A nut 4 cooperates with the screw 2 and comprises a ring 5 projecting radially from the nut 4.

[0002] The actuator 1 comprises a single pair of pulleys comprising a first pulley 10 mounted to rotate around a first shaft 22 secured to the chassis 20 using a first ball bearing 30 and a second pulley 11 mounted to rotate around a second shaft 23 connected to the chassis. 20 using a second ball bearing 31. A first actuating cable 6 cooperates with 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 its second end 6.2 according to methods which will be described below.

[0003] The actuator 1 comprises an anti-rotation device 40 for blocking rotation of the nut 4 relative to the screw 2. The anti-rotation device 40 comprises a carriage 41 mounted to move in translation in a direction DI parallel to the axis Ox using a guide mechanism 50. The mechanism 50 is here a prismatic linear guide which comprises a rail 51 on which a first pad 52 and a second pad 53 slide, both secured to the carriage 41.

[0004] The carriage 41 comprises a base 42 which extends substantially parallel to the longitudinal axis Ox and at the ends of which a first arm 43 and a second arm 44 project. The carriage 41 is connected to the nut 4 by a first pair of cables 60 comprising a second cable 61 and a third cable 62 extending on either side of the screw 2 as well as by a second pair of cables 70 comprising a fourth cable 71 and a fifth cable 72 extending on either side of the screw 2. As visible in FIG. 2, 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 PI passing through the nut 4 and which is normal to the screw 2. More precisely, a third end 61.1 of the cable 61 and a fourth end 62.1 of the cable 62 are crimped onto the arm 43. Symmetrically, a fifth end 71.1 of the cable 71 and a sixth end 72.1 of the cable 72 are crimped onto the arm 44.

[0005] The second cable 61, the third cable 62, the fourth cable 71 and the fifth cable 72 are crimped at their other ends to the ring 5.

[0006] As visible in Figures 1 and 2, the first cable 6 has its first end 6.1 which is crimped onto the arm 43 and extends parallel to the longitudinal axis Ox to the first pulley 10 to engage in the first groove 10.1 and make a half-turn of winding on the first pulley 10. The first cable 6 extends at the outlet of the first pulley 10 parallel to the longitudinal axis Ox to engage in the second groove 11.1 of the second pulley 11 and make a half-turn of winding there. The first cable 6 then extends 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 by crimping to the pulley 10 or even also to the pulley 11.

[0007] The first pulley 10 is integral in rotation with a finger 80 which constitutes the output of the actuator 1. The finger 80 corresponds, here, to a phalanx of a mechanized hand not shown.

[0008] In operation, under the effect of a command sent to the motor 3, a rotation of the screw 2 causes an identical rotation of the nut 4 due to the contact friction between the screw 2 and the nut 4. This movement puts tension on the first pair of cables 60 and the second pair of cables 70. The pairs of cables 60 and 70 being connected to the carriage 41 - of which only the movement along the axis Ox is authorized - the pairs of cables 60 and 70 come to exert forces opposing a rotational drive of the nut 4 by the screw 2. Thus, a rotation of the screw 2 under the action of the motor 3 causes a linear movement of the nut 4 along the longitudinal axis Ox. This movement is transmitted by the pairs of cables 60 and 70 to the carriage 41 to which the cable 6 is connected. The linear movement of the carriage 41 drives the cable 6 which causes rotation of the pulley 10 and actuation of the finger 80.

[0009] We then obtain a cable actuator 1 which has a reduced width and a total length close to the maximum stroke of the nut 4.

[0010] As visible in figure 1, the connections of the ends 6.1 and 6.2 of the first cable 6 to the carriage 41 are located below (according to the representation of figure 1) a second plane P2 orthogonal to the first plane PI and which includes the longitudinal axis Ox.

[0011]

[0012] Elements identical or analogous to those previously described will bear a numerical reference identical to this in the following description of a second embodiment of the invention.

[0013]

[0014] According to a second embodiment of the invention shown in Figures 3 and 4, a seventh end 61.2 of the second cable 61 and an eighth end 62.2 of the third cable 62 are attached to the nut 4 by a first intermediate support 90 connected to the nut 4 by a seventh cable 91 and an eighth cable 92. The first intermediate support 90 is here in the form of a ring and comprises a first bore 90.1 in which the seventh end 61.2 of the cable 61 is crimped. The first intermediate support 90 also comprises a second bore 90.2 diametrically opposite the first bore 90.1 and in which the eighth end 62.2 of the cable 62 is crimped.

[0015] The first intermediate support 90 also comprises a third bore 90.3 in which a ninth end 91.1 of the seventh cable 91 is crimped and a sixth bore 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 a seventh bore 5.1 of the ring 5 and the twelfth end 92.2 of the cable 92 is crimped in an eighth bore 5.2 of the ring 5.

[0016] Similarly, the thirteenth end 71.2 of the fourth cable 71 and the fourteenth end 72.2 of the fifth cable 72 are attached to the nut 4 by a second intermediate support 95 connected to the nut 4 by a ninth cable 96 and a tenth cable 97. The second intermediate support 95 is here in the form of a ring and includes a seventh hole 95.1 in which the thirteenth end is set 71.2 of the cable 71. The second intermediate support 95 also comprises an eighth hole 95.2 diametrically opposite the seventh hole 95.1 and in which the fourteenth end 72.2 of the cable 72 is crimped.

[0017] The second intermediate support 95 also includes a ninth drilling 95.3 in which the fifteenth end 96.1 of the ninth cable 96 is crimped and a tenth hole 95.4 in which the sixteenth end 97.1 of the tenth cable 97 is crimped.

[0018] The seventeenth end 96.2 of the cable 96 is crimped into the seventh hole 5.1 and the eighteenth end 97.2 of the tenth cable 97 is crimped into the eighth hole 5.2.

[0019] Optionally, the third end 61.1 of the cable 61 is not, here, crimped onto the arm 43 but is secured to a threaded end piece which passes through a ninth bore 43.1 of the arm 43. A knurled nut is engaged on the threaded end piece and has one of its faces which bears on the arm 43. An action on the nut makes it possible to tension the cables 61, 62, 71, 71, 71, 71, 71, 72 ...

[0020]

[0021] According to a third embodiment shown in Figures 5 and 6, the connections of the ends 6.1 and 6.2 of the first cable 6 to the carriage 41 are located above a second plane P2 orthogonal to the first plane PI and which comprises the longitudinal axis Ox. This configuration makes it possible to further reduce the size of the actuator 1 without generating parasitic forces on the screw 2 / nut 4 assembly.

[0022]

[0023] In all of the embodiments described, the cables 6, 61, 62, 71, 72, 91, 92, 96 and 97 are advantageously preloaded.

[0024]

[0025] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0026] Especially,

[0027] - although here the jack comprises a ball screw, the invention also applies to other types of screw such as for example a screw with single threads, or rollers;

[0028] - although here the first cable is attached to the nut by a crimping made in a ring secured to the nut, the invention also applies to other means of attaching a cable to the nut such as for example a crimping in a hole made in the nut, gluing or welding;

[0029] - although here the cables extend parallel to the longitudinal axis, the invention also applies to other configurations of the cables in which no section or only one section of cables extends parallel to the longitudinal axis, the rest of the cable being able to adopt any orientation relative to the longitudinal axis;

[0030] - although here all the cables of the jack are preloaded, the invention also applies to a single preloaded cable or only a fraction of the preloaded cables;

[0031] - although here the first pulley and the second pulley are pulleys with a cylindrical groove, the invention also applies to second and fourth pulleys provided with grooves of different types such as for example helical grooves;

[0032] - although here only a first cable is engaged on the first pair of pulleys, the invention also applies to a pair of pulleys which have a plurality of grooves to accommodate additional actuating cables;

[0033] - although here the first cable cooperates with the two pulleys, the invention also applies to a first cable which comprises a first strand connecting the nut (via the frame) and the first pulley, then a second strand distinct from the first which has one of its ends connected by crimping to the first pulley and the other of its ends connected by crimping to the second pulley. Finally, the first cable may comprise a third strand, one end of which is crimped onto the second pulley and the other end of which is connected to the nut (via the frame). All of the distinct strands forming a first cable which cooperates with the first and second pulleys to achieve a transmission between two connection points to the nut;

[0034] - although here the anti-rotation device comprises cables connecting the nut to a linearly guided carriage, the invention also applies to other types of anti-rotation such as for example one or more rollers integral with the nut and engaged in one or more grooves or a shaft connecting the nut with a linear guide;

[0035] - although here the actuator comprises a guide mechanism with two translational guide points, the invention also applies to a guide mechanism comprising a different number of guide points such as for example a single guide point or more than two;

[0036] - although here the guidance mechanism is a prismatic linear guidance, the invention also applies to other types of guidance of a translation such as for example one or more sliding pivots;

[0037] - although here the linear guide comprises two pads cooperating with a rail, the invention also applies to other types of linear guides, such as for example a prismatic linear guide using one or more recirculating ball pads or a linear guide comprising a recirculating ball bushing mounted on a splined shaft;

[0038] - although here the first cable is connected by crimping to the pulleys, the invention also applies to other methods of cooperation of the first cable with the pulleys such as for example a connection by friction for example using one or more dead turns of the cable around a pulley;

[0039] - although here the output of the actuator is a finger integral in rotation with the first pulley, the invention also applies to other types of output of the actuator such as for example an output integral with the first cable and which carries out a translation to obtain a linear actuator;

[0040] - although here the third end of the second cable comprises a threaded end piece cooperating with a knurled nut, the invention also applies to other types of device for tensioning the second and / or third cable such as for example a ratchet assembly of the fir tree tooth type or an eccentric roller;

[0041] - although here the actuator comprises a cable connected to the nut and cooperating with smooth pulleys, the invention also applies to other types of members for transmitting a traction force such as for example a chain, a toothed or non-toothed belt, a ribbon, a hybrid member comprising connecting rods connected by cable;

[0042] - although here the cables cooperate with pulleys, the invention also applies to other types of steering gears adapted to other types of steering organs transmission of a force such as sprockets for chains, toothed or non-toothed wheels for toothed belts, guide rollers for straps or ribbons.

Claims

CLAIMS (option a) 1. Actuator (1) comprising: - a chassis (20); - a screw (2) / nut (4) assembly comprising a nut (4) cooperating with a screw (2) extending along a longitudinal axis (Ox); - a motor (3) arranged to drive the screw (2) in rotation and cause a linear displacement of the nut (4); the actuator (1) also includes - a single pair of linkages (10, 11) comprising a first linkage (10) and a second linkage (11) mounted for rotation on the chassis (20), the first linkage (10) being connected to an output (80) of the actuator (1); - a first transmission element (6) of a traction force coupled to the nut (4) by its first end (6.1) and its second end (6.2) and which cooperates with the first linkage (10) and the second linkage (11), - an anti-rotation device (40) for blocking rotation of the nut (4) relative to the screw (2), in which the carriage (41) is connected to the nut (4) by a first pair of cables (60) comprising a second cable (61) and a third cable (62) extending on either side of the screw (2) and by a second pair of cables (70) comprising a fourth cable (71) and a fifth cable (72) extending on either side of the screw (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 (PI) passing through the nut (4) and which is normal to the screw (2).

2. Actuator (1) according to claim 1, wherein the first transmission member (6) of a traction force is a cable (6) or a toothed belt.

3. Actuator (1) according to claim 1 or 2, in which the anti-rotation device (40) comprises a carriage (41) connected on one side to the nut (4) and on the other side to the first transmission member of a traction force (6).

4. Actuator (1) according to claim 3, in which the anti-rotation device (40) includes a guidance mechanism (50) for a translation along a direction (Dl) parallel to the longitudinal axis (Ox), of the carriage (41) relative to the chassis (20).

5. Actuator (1) according to claim 4, wherein the guiding mechanism (50) is a prismatic linear guiding mechanism.

6. Actuator (1) according to any one of claims 3 to 5, wherein the guiding mechanism (50) comprises two translational guiding points.

7. Cable actuator (1) according to any one of the preceding claims, wherein the second cable (61) and the third cable (62) are attached to the nut (4) by a first intermediate support (90) connected to the nut by a seventh cable (91) and an eighth cable (92).

8. Cable actuator (1) according to any one of the preceding claims, wherein the fourth cable (71) and the fifth cable (72) are attached to the nut (4) by a second intermediate support (95) connected to the nut (4) by a ninth cable (96) and a tenth cable (97).

9. Cable actuator (1) according to any one of the preceding claims, comprising a tensioning device (7, 8) for the second cable (61) and / or the third cable 10. Cable 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 to accommodate additional traction force transmission elements.

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