Automatic locking device for a robot arm

Abstract

Automatic locking device for a robot arm. The present invention relates to a locking device (27) comprising: a ring (29) having a bore (43), a hub (31), rotatable relative to the ring, a plate (55), fixed to the hub (31), a rocker (33), rotatable between a locking position and a release position, a groove (35), opening onto the bore (43) and formed in the rocker or the plate, a guide ramp (37), formed on a periphery of the rocker or the plate, a pin (39), mounted in the groove to be locked between the bore and the guide ramp when the rocker is in the locking position, and a return spring (41), acting between the plate and the rocker to return the rocker to the release position. Figure for the abstract: Figure 5

Description

Title of the invention: Automatic locking device for a robot arm

[0001] The present invention relates to a locking device for a robot arm and a robot arm comprising such a locking device.

[0002] Articulated industrial robot arms are subject to gravity and, depending on their configuration, a sudden interruption of the power supply to the axis motors can cause uncontrolled movement of the arm before the motor brake is fully engaged. This problem is particularly relevant to robot arms with a vertical linear axis, since gravity applies regardless of the configuration.

[0003] KR20120107270A describes a device for blocking a vertical axis of a robot arm. The vertical movement of the arm is achieved using a screw driven by a motor via a belt. The screw is connected to a toothed wheel. A lever hinged to the frame has a roller that bears against the belt by a spring. If the belt breaks, the spring causes the lever to rotate, and a tooth on the lever locks the toothed wheel.

[0004] This solution only applies to the breakage of a transmission belt and is ineffective in the event of a sudden interruption of the motor's power supply. Furthermore, this solution does not allow the screw to be locked by limiting its rotation.

[0005] The aim of the invention is then to propose a locking device limiting the movements due to the weight of the robot arm in the event of a power outage of the motor.

[0006] To this end, the invention relates to an automatic locking device for a first and second limb of a robot arm, movable relative to each other, the locking device comprising: - a ring, provided with a bore, centered on a fixed drive axis relative to the ring and configured to be fixed to the first member, - a hub, configured to be rotated around the drive axis relative to the ring, by means of a motor belonging to the robot arm, - a plate, fixed in rotation to the hub around the drive axis, - a rocker arm, mounted on the plate and movable in rotation relative to the a plate around a rocker arm axis parallel to the motor axis and not coaxial with the motor axis, between a locking position and a release position, - a groove, formed in a first element between the rocker arm and the plate, the groove extending radially with respect to the motor axis towards the bore along a groove axis, - a guide ramp, formed at the periphery of a second element between the rocker and the plate, the second element being distinct from the first element, - a pin, which is cylindrical and extends along a pin axis parallel to the drive axis, the pin being mounted in the groove to be movable in translation along the groove axis relative to the first element when the rocker is in the release position, and to be locked between the bore and the guide ramp when the rocker is in the locking position, and

[0007] a return spring, acting between the plate and the rocker so as to apply a return force bringing the rocker back to the release position.

[0008] In the event of a power failure to the motor, the rotation of the plate relative to the crown is blocked by the movement of the pin and its locking between the bore and the guide ramp. This consequently blocks the movement of the second member relative to the first member. The return spring guarantees a triggering threshold for the locking device and ensures automatic release of the plate's rotation relative to the crown when power to the motor is restored. Furthermore, since the locking device is integrated into the hub, it can be used regardless of the mechanical transmission chosen to drive the second member relative to the first member using the motor.

[0009] According to other advantageous aspects of the invention, the locking device comprises one or more of the following features, taken individually or in all technically possible combinations: - when the direction of rotation of the hub is counterclockwise, respectively clockwise, around the drive axis relative to the crown, to drive the second member against gravity, the guide ramp is flat and the rocker moves from the release position to the locking position by rotating relative to the plate in the clockwise, respectively counterclockwise, direction around the rocker axis, relative to the plate, - the motor shaft is positioned between the rocker shaft and the groove, - the guide ramp is coplanar with a ramp plane, parallel to the axis motor and inclined relative to a radial plane containing the motor axis and the rocker axis, at an angle of 86 to 90 degrees, preferably 87 to 89 degrees and preferably even 88 degrees, - the pin is free to rotate around the pin axis when the rocker is in the release position, and the rotation of the pin around the pin axis is blocked when the rocker is in the locking position, by the interposition of the pin between the bore and the guide ramp, - when the rocker arm is in the release position, a center of inertia of the rocker arm is positioned in a radial plane containing the rocker arm axis and the motor axis, - when the rocker is in the release position, a center of inertia of an assembly, formed by the plate, the rocker, the return spring and the pin, is positioned on the motor shaft, - The first element is the rocker switch and the second element is the plate. - The first element is the plate and the second element is the rocker arm. - when the rocker arm is in the release position, the restoring force exerted by the return spring tends to bring the pin against a stop wall of the second element, - the guide ramp is a first guide ramp, a second guide ramp, symmetrical to the first guide ramp with respect to a radial plane containing the rocker arm axis and the motor shaft, is provided on the second element and when the rocker arm is in the release position, the restoring force exerted by the return spring tends to bring the pin such that the pin axis is in the radial plane, - the locking device comprises an additional rocker, carried by the plate and rotatable relative to the plate around an additional rocker axis parallel to the motor axis and non-coaxial with the motor axis, between a locking position and a release position, an additional groove, formed in a third element between the additional rocker and the plate, the additional groove extending radially relative to the motor axis towards the bore along an additional groove axis, an additional guide ramp, formed at a periphery of a fourth element between the additional rocker and the plate, the fourth element being distinct from the third element, an additional cylindrical pin, which extends along an additional pin axis, parallel to the motor axis,The additional pin is mounted in the additional groove to be movable in translation along the axis of the additional groove relative to the third element when the additional rocker is in the release position, and to be locked between the bore and the additional guide ramp when the additional rocker is in the locking position; and an additional return spring acts between the plate and the additional rocker to apply a restoring force returning the additional rocker to the release position.

[0010] The invention also relates to a robot arm comprising a first limb, a second limb movable relative to the first limb, and a device for locking as described above in which the first member is driven by the hub and the second member is fixed to the crown or the first member is fixed to the crown and the second member is driven by the hub.

[0011] According to other advantageous aspects of the invention, the robot arm comprises the following features: - the second member is free to move in translation relative to the first member along a vertical axis, - the robot arm includes a pinion fixed in rotation to the hub around the motor axis and a rack fixed to the second member, the rack being in contact with the pinion so that the rotation of the pinion around the motor axis causes a translation of the rack relative to the pinion along the vertical axis.

[0012] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0013] [Fig-1] [Fig. 1] is a front view of a robot arm on which a locking device according to a first embodiment of the invention is integrated,

[0014] [Fig. 2] [Fig. 2] is a detail view of [Fig. 1] including a local section along a vertical plane passing through a drive axis,

[0015] [Fig.3] The [Fig.3] is a detail view of the local section of the [Fig.2],

[0016] [Fig.4] Fig.4 is a front view of the locking device, a rocker being in liberation position

[0017] [Fig. 5] [Fig. 5] is a view similar to the view in [Fig. 4], the rocker being in a blocking position,

[0018] [Fig. 6] [Fig. 6] is a view similar to the view in [Fig. 3], showing a device blocking according to a second embodiment of the invention,

[0019] [Fig.7] [Fig.7] is a view similar to the view in [Fig.4], showing the device of the [Fig.6] locking mechanism in a release position,

[0020] [Fig.8] [Fig.8] is a view similar to the view in [Fig.5], showing the device of the [Fig.6] locking position,

[0021] [Fig.9] [Fig.9] is a view similar to the view in [Fig.4], showing a device blocking according to a third embodiment of the invention,

[0022] [Fig. 10] The [Fig. 10] is a cross-sectional view along plane XX of the [Fig. 9],

[0023] [Fig. 11] The [Fig. 11] is a cross-sectional view along plane XLXI of the [Fig. 9],

[0024] [Fig. 12] [Fig. 12] is a view similar to the view in [Fig. 9], the rocker being in with the locking position and an additional rocker in the release position,

[0025] [Fig. 13] [Fig. 13] is a view similar to the view in [Fig. 9], with the rocker in the release position and the additional rocker in the locking position, and

[0026] [Fig. 14] The [Fig. 14] is a view similar to the view of the [Fig.5], showing a locking device according to a fourth embodiment of the invention.

[0027] A robot arm 1 according to a first embodiment of the invention is described in [Fig. 1]. The robot arm 1 comprises a base 3, a column 5, an arm 7, a forearm 9, a flange 11 and a tool 13.

[0028] The base 3 is a first member of the robot arm 1 and is fixed relative to a horizontal plane PI on which the base 3 rests. The horizontal plane PI can be, for example, a floor surface, a workbench, or a table.

[0029] The column 5 is a second member of the robot arm 1. The column 5, when the column 5 is assembled on the robot arm 1, extends longitudinally along a vertical axis V, perpendicular to the horizontal plane PL. The column 5 is advantageously movable in translation relative to the base 3 along the vertical axis V.

[0030] The arm 7, when the arm 7 is assembled on the robot arm 1, extends parallel to the horizontal plane PL. The arm 7 is assembled, at a first end 7a, on the column 5 and is mobile in rotation relative to the column 5 around the vertical axis V.

[0031] The forearm 9, when the forearm 9 is assembled on the robot arm 1, extends parallel to the horizontal plane PL. The forearm 9 is assembled, at a first end 9a, on a second end 7b of the arm 7 and is mobile in rotation relative to the arm 7 around a first axis of rotation RI parallel to the vertical axis V.

[0032] The flange 11, when the flange 11 is assembled on the robot arm 1, extends along an axis parallel to the vertical axis V. The flange 11 is assembled, at a first end lia, on a second end 9b of the forearm 9 and is movable in rotation relative to the forearm 9 around a second axis of rotation R2 parallel to the vertical axis V.

[0033] The tool 13 is assembled to a second end 11b of the flange 11. The tool is, for example, a clamp suitable for gripping a part.

[0034] The robot arm 1 also includes a movement system 15, for moving the column 5 relative to the base 3. The movement system 15 includes a motor 17 and a mechanical transmission system 19.

[0035] The motor 17 extends along a motor axis A17 and comprises a stator 21 fixed to the base 3 and a motor shaft 23 rotating relative to the stator 21 around the motor axis A17. The motor shaft 23 is thus rotating around the motor axis A17 relative to the base 3.

[0036] Advantageously, the mechanical transmission system 19 includes a pinion 25 and a rack 26.

[0037] The pinion 25 is rotationally fixed to the motor shaft 23 around the motor axis A17. The pinion 25 has teeth 36.

[0038] The rack 26 is fixed to the column 5 and has teeth, not shown, suitable for engaging with the teeth 36 of the pinion 25 so that the rotation of the pinion 25 around the motor shaft A17 drives, via the rack 26, the vertical translation of the column 5 relative to the base 3.

[0039] The robot arm 1 also includes an automatic locking device 27 for the robot arm 1 described in figures 2 to 5.

[0040] The locking device 27 includes a ring 29, a hub 31, a rocker 33, a groove 35, a guide ramp 37, a pin 39 and a return spring 4L.

[0041] The ring 29 is provided with a bore 43 which is centered on the ring 29 and which passes through the ring 29 from one side to the other along the motor axis A17 when the ring 29 is mounted on the robot arm 1.

[0042] The bore 43 has a first internal portion 45, having a first internal diameter D1, a second internal portion 47, having a second internal diameter D2, smaller than the first internal diameter D1, and a third internal portion 49, having a third internal diameter D3, smaller than the second internal diameter D2. The decrease in diameter between the first internal diameter D1 and the second internal diameter D2 forms a first shoulder 51 belonging to the bore 43 and the decrease in diameter between the second internal diameter D2 and the third internal diameter D3 forms a second shoulder 53 belonging to the bore 43.

[0043] When the crown 29 is mounted on the robot arm 1, the crown 29 is centered on the motor shaft A17 and is fixed on the stator 21, the first internal portion 45 being turned towards the stator 21. Thus the crown 29 is fixed to the base 3.

[0044] The hub 31 is cylindrical and has an external diameter D4 that is smaller than the third internal diameter D3.

[0045] The hub 31 includes a plate 55. The plate 55 extends perpendicularly to an axis of revolution of the hub 31, which, when the hub 31 is mounted on the robot arm 1, is coaxial with the motor shaft A17. The plate 55 is a part of revolution around the motor shaft A17 when the hub 31 is mounted on the robot arm 1 and defines a second external diameter D5, larger than the first external diameter D4 and smaller than the first internal diameter DL

[0046] Advantageously, the pinion 25 is integral with the hub 31. More precisely, the pinion 25 and the hub 31 are formed from a single, monobloc piece. Alternatively, the pinion 25 may be a separate piece fixed by screws.

[0047] One end 32 of the hub 31 is mounted on the motor shaft 23 and is rotationally fixed to the motor shaft 23 about the motor axis A17. When the hub 31 is mounted on the drive shaft 23, the hub 31 is partially contained within the bore 43. More precisely, the plate 55 is contained within the first internal portion 45 of the bore 43 and the pinion 25 emerges outside the bore 43.

[0048] The locking system 27 includes a ball bearing 57, interposed between the second inner portion 47 and the hub 31 and abutted against the second shoulder 53. Thus, the hub 31 is configured to be rotated around the motor shaft A17 relative to the ring 29.

[0049] The rocker 33 has an ovoid shape, in projection in a plane perpendicular to the drive axis A17, as seen in [Fig. 4] and 5. The rocker 33 comprises a rounded base 59, a rounded portion 61, a first leg 63 and a second leg 65. The first leg 63 and the second leg 65 connect the rounded base 59 to the rounded portion 61 by defining a recess 67 between the rounded portion 61, the rounded base 59, the first leg 63 and the second leg 65.

[0050] The rounded portion 61 has a radius rl less than the first diameter DI divided by two.

[0051] The first leg 63 includes, at the junction with the rounded portion 61, an outgrowth 68 which extends into the recess 67.

[0052] The rocker arm 33 is supported by the hub 31 and is rotationally fixed to the hub 31 about the motor shaft A17. More precisely, the rocker arm is mounted on the plate 55 by means of a rocker arm shaft 69 which extends along a rocker arm axis A33 parallel to the motor shaft A17 and not coaxial with the motor shaft A17. The rocker arm shaft 69 is fixed to the plate 55 and the rounded base 59 is mounted to rotate freely on the rocker arm shaft 69. The rocker arm is thus rotationally free, relative to the hub 31, about the rocker arm axis A33 between a release position and a locking position.

[0053] The rocker 33 is positioned along the motor axis A17 between the stator 21 and the plate 55 and the end 32 of the hub 31 passes through the recess 67.

[0054] Advantageously, when the rocker 33 is in the release position, a center of inertia of the rocker 33 is positioned in a radial plane P2 containing the rocker axis A33 and the motor axis A17. Thus, the rocker 33 is insensitive to a centrifugal force acting on the rocker 33 when it is rotating about the motor axis A17. The center of inertia of the rocker is located on the side of the motor axis A17 relative to the rocker axis A33.

[0055] The return spring 41 is fixed at a first end 41a to the plate 55 and at a second end 41b to the protrusion 68. The return spring 41 acts on the plate 55 and on the rocker 33 so as to apply a return force F which tends to return the rocker 33 from the locking position to the release position.

[0056] The groove 35 is formed in a first element between the rocker arm 33 and the plate 55. In this example, the groove 35 is advantageously formed on the rocker arm 33, the rocker arm 33 thus constituting the first element. The groove 35 extends radially with respect to the drive shaft A17 towards the bore 43 along a groove axis A35. The groove 35 opens radially into the bore 43. In this example, the groove 35 passes completely through the plate 55 parallel to the drive shaft A17.

[0057] Advantageously, the motor shaft A17 is arranged between the rocker shaft A33 and the groove 35. This design makes it possible to obtain a compact locking system 27.

[0058] The guide ramp 37 is flat and formed at the periphery of a second element between the rocker arm 33 and the plate 55, the second element being distinct from the first element. In this example, the guide ramp 37 is advantageously formed at the periphery of the plate 55. The plate 55 thus constitutes the second element. The guide ramp 37 crosses the radial plane P2 and extends perpendicularly to the rocker arm axis A33 as far as the bore 43.

[0059] The guide ramp 37 is perpendicular to a radius of the plate 55. More precisely, the guide ramp 37 is coplanar with a ramp plane P3. The ramp plane P3 is parallel to the motor axis A17 and, advantageously, inclined with respect to the radial plane P2 at an angle α between 86 and 90 degrees, preferably from 87 to 90 degrees and preferably from 88 degrees.

[0060] The plate advantageously includes a stop wall 71 which extends the guide ramp 37. The stop wall 71 is parallel to the radial plane P2.

[0061] The pin 39 is cylindrical and extends along a pin axis A39 which, when the pin is mounted on the robot arm 1, is parallel to the motor axis A17. The pin is mounted in the groove 35 so that it is movable in translation along the groove axis A35 relative to the rocker 33 when the rocker 33 is in the release position and is locked between the bore 43 and the guide ramp 37 when the rocker 33 is in the locking position. The groove axis A35 is perpendicular to the rocker axis A33 and lies in the radial plane P2 when the rocker 33 is in the release position. The groove 35 guides the pin 39 between the release position and the locking position of the rocker 33.

[0062] When the robot arm 1 is in a normal operating phase, i.e. when the motor shaft 23 is rotating around the motor axis A17 clockwise relative to the ring 29, the rocker 33 is in the release position and the pin 39 is free to move along the groove 35 between the guide ramp 37 and the bore 43. The hub 31, the rocker 33 and the pin 39 are then rotating relative to the ring 29 around the motor axis A17.

[0063] Advantageously, the pin 39 is also free to rotate about the pin axis A39 when the rocker 33 is in the release position so as not to impair the rotation of the hub 31 and the rocker 33, when the robot arm 1 is in a normal operating phase and the pin 39 is in contact with the bore 43.

[0064] Advantageously, when the locking device 27 is not activated, i.e. when the rocker 33 is in the release position, the restoring force F tends to bring the pin 39 against the stop wall 71.

[0065] When the locking device 27 is not activated, the pin axis A39, the motor axis A17, and the rocker axis A33 are in the radial plane P2, and advantageously, a center of inertia of an assembly formed by the hub 31, the rocker 33, the return spring 41, and the pin 39 is positioned on the motor axis A17. This design of the locking device 27 ensures dynamic equilibrium during the normal operating phases of the robot arm 1; in other words, it guarantees that the centrifugal force acting on the rocker 33 does not trigger the locking of the locking device 27.

[0066] When the power supply to the motor 17 is interrupted, the action of gravity causes the column 5 to fall and the motor shaft 23 undergoes a strong counterclockwise acceleration A23, as shown in [Fig. 5]. Under the effect of its inertia, the rocker arm 33 then rotates from the release position to the locking position relative to the plate 55 around the rocker arm axis A33, advantageously clockwise, such that the pin 39 moves, along the groove axis A35, along the groove 35 and along the guide ramp 37 until it comes into contact with the bore 43 of the ring 29. When the rocker arm 33 is in the locking position, the plate 55 and the bore 43 clamp the pin 39, which is interposed between the bore 43 and the guide ramp. 37, and the rotation of the pawn 39 around the axis of pawn A39 is, advantageously, blocked.Thus, the pin 39 directly blocks the plate 55 relative to the ring 29, and the motor shaft 23 can no longer rotate. The fall of the column 5 of the robot arm 1 is then stopped.

[0067] When the rocker 33 moves from the release position to the locking position, the pin 39 rolls on the guide ramp 37 so that the friction forces exerted on the pin 39, which add to the restoring force F of the return spring 41, which is unfavorable to the movement of the rocker 33 from the release position to the locking position, are limited and more stable.

[0068] The inclination of the guide ramp 37 prevents the pin 39 from bouncing on the bore 43 from the locking position to the release position when the locking device 27 is activated. The inclination of the guide ramp 37 also ensures that the pin 39 is permanently wedged between the bore 43 and the plate 55.

[0069] The restoring force F of the return spring 41 is chosen according to the value of the angular acceleration at which the triggering of the locking device 27 is desired. Thus, there is an acceleration threshold for the rocker 33 to begin to to reach the locking position. This allows the motor shaft 23 to rotate up to a defined acceleration threshold in the counterclockwise direction and ensures that the plate 55 and the rocker 33 will never be locked in the clockwise direction of rotation.

[0070] To unlock the locking device 27, simply operate the motor 17 in a clockwise direction.

[0071] In an alternative, not shown, the mechanical transmission system 19 includes the pinion 25 fixed in rotation to the motor shaft 23 and a belt fixed to the column 5 and driven by the pinion 25 so that the rotation of the pinion 25 around the motor shaft A17 causes the vertical translation of the column 5 relative to the base 3 via the belt.

[0072] In an alternative, not shown, the mechanical transmission system 19 includes the pinion 25 fixed in rotation to the motor shaft 23 and a worm screw fixed to the column 5 and meshed with the pinion 25 so that the rotation of the pinion 25 around the motor shaft A17 drives the vertical translation of the column 5 relative to the base 3 via the worm screw.

[0073] More generally, the invention is applicable to a motor which would drive the column 5 in translation relative to the base 3.

[0074] In an alternative, not shown, during normal operation, the drive shaft 23 rotates counterclockwise relative to the ring gear 29. When the drive shaft 23 undergoes a strong clockwise acceleration, the rocker arm 33 moves from the release position to the locking position by rotating clockwise relative to the rocker arm axis A33.

[0075] A locking device 127, according to a second embodiment, is shown in Figures 6 to 8. The reference numerals of the locking device 127 correspond to those of the locking device 27 when the referenced element is the same. The reference numerals are increased by 100 compared to those of the locking device 27 when they designate modified elements in the locking device 127 compared to the locking device 27.

[0076] If an element is referenced on one of the figures 6 to 8 without being mentioned in the description, it corresponds to the element bearing the same reference in the first embodiment.

[0077] The locking device 127 is identical to the locking device 27 of the first embodiment, except for the characteristics described below.

[0078] The groove 135 is formed in the plate 155, and the guide ramp 137 and the stop wall 171 are formed on a periphery of the rounded portion 161 of the rocker 133. The groove 135 extends radially with respect to the drive shaft A17 towards the bore 43 along a groove axis that lies in the plane P2. The operation of the locking device 127 is analogous to the locking device 27, when the rocker 133 passes from the release position to the locking position, the pin 39 gets stuck between the bore 43 and the guide ramp 137.

[0079] A blocking device 227, according to a third embodiment, is shown in Figures 9 to 13. The reference numerals of the blocking device 227 correspond to those of the blocking device 27 when the referenced element is the same. The reference numerals are increased by 200 compared to those of the blocking device 27 when they designate modified elements in the blocking device 227 compared to the blocking device 27.

[0080] If an element is referenced on one of the figures 9 to 13 without being mentioned in the description, it corresponds to the element bearing the same reference in the first embodiment.

[0081] The locking device 227 is identical to the locking device 27 of the first embodiment, except for the characteristics described below.

[0082] The locking device 227 comprises an additional rocker 273, similar to the rocker 33, carried by the plate 255 and rotatable relative to the plate 255 about an additional rocker axis A273 parallel to the motor shaft A17 and non-coaxial with the motor shaft A17, between a locking position and a release position. The angle formed by the rocker axis A33, the motor shaft A17, and the additional rocker axis A273 is 90 degrees. The additional rocker 273 moves from the release position to the locking position in the opposite direction to the rocker 33, such that the additional rocker 273 is in the release position, or in the locking position, respectively, when the rocker 33 is in the locking position, or in the release position, respectively. Alternatively, the angle formed by the rocker shaft A33, the motor shaft A17 and the additional rocker shaft A273 could be different from 90 degrees and be, for example, equal to 180 degrees.

[0083] The locking device 227 includes an additional groove 275 formed in a third element between the additional rocker 273 and the plate 255. In this example, the additional groove 275 is formed on the additional rocker 273. The additional groove 275 extends radially with respect to the drive shaft A17 towards the bore 43 along an axis of additional groove A275 and opens into the bore 43.

[0084] The locking device 227 includes an additional guide ramp 277, formed at the periphery of a fourth element among the additional rocker 273 and the plate 255, the fourth element being distinct from the third element. In this example, the additional guide ramp 277 is formed at the periphery of the plate 255.

[0085] The locking device 227 includes an additional cylindrical pin 279, which extends along an additional pin axis A279, parallel to the drive axis A17, the additional pin 279 being mounted in the additional groove 275 to be movable in translation along the axis of the additional groove A275 relative to the additional rocker 273 when the additional rocker 273 is in the release position, and to be locked between the bore 43 and the additional guide ramp 277 when the additional rocker 273 is in the locking position.

[0086] The locking device 227 includes an additional return spring 281, acting between the plate 255 and the additional rocker 273 so as to apply a return force F2 bringing the additional rocker 273 back to the release position.

[0087] The guide ramp 37 and the additional guide ramp 277 are opposed so that, when the motor shaft undergoes a strong acceleration in one direction of rotation around the motor shaft A17, the additional rocker 273 moves into the locking position and the additional pin 279 blocks the rotation between the plate 255 and the ring 29, and that, when the motor shaft undergoes a strong acceleration in another direction of rotation around the motor shaft A17, the rocker 33 moves into the locking position and the pin 39 blocks the rotation between the plate 255 and the ring 29. Thus, the locking system 227 blocks the rotation of the plate 255 relative to the ring 29 as soon as the motor shaft 23 is subjected to a strong acceleration, regardless of the direction of rotation.The locking device 227 therefore allows the second member 5 to be locked relative to the first member 3 in both directions of rotation of the hub 31 when the angular accelerations of the hub 31 exceed a threshold which is adjustable by the choice of the return spring 41 and the additional return spring 281.

[0088] A blocking device 327, according to a fourth embodiment, is shown in [Fig. 14]. The reference numerals of the blocking device 327 correspond to those of the blocking device 27 when the referenced element is the same. The reference numerals are increased by 300 compared to those of the blocking device 27 when they designate modified elements in the blocking device 327 compared to the blocking device 27.

[0089] If an element is referenced on [Fig. 14] without being mentioned in the description, it corresponds to the element bearing the same reference in the first embodiment.

[0090] The locking device 327 is identical to the locking device 27 of the first embodiment, except for the characteristics described below.

[0091] The plate 355 includes a second guide ramp 383 symmetric to the first guide ramp 37 with respect to a radial plane P2.

[0092] The second guide ramp 327 is perpendicular to a radius of the plate 355. More precisely, the guide ramp 383 is coplanar with a ramp plane P3'. The ramp plane P3' is parallel to the motor axis A17 and, advantageously, inclined with respect to the radial plane P2 at an angle α' between 86 and 90 degrees, preferably from 87 to 90 degrees and preferably from 88 degrees.

[0093] When the rocker 333 is in the release position, the restoring force F exerted by the return spring 341 tends to bring the pin 39 such that the pin axis A39 is in the radial plane P2. The pin 39 then occupies an equilibrium position between the guide ramp 37 and the second guide ramp 383.

[0094] It is understood that the locking device 327 does not include a stop wall extending the first ramp 35. Thus the rocker 333 can rock in any direction of rotation when the motor shaft 23 is subjected to strong acceleration, regardless of the direction of rotation of the motor shaft 23, so as to wedge the pin 39 between the plate 355 and the bore 43 to block the rotation of the motor shaft 23.

[0095] The return spring 341 acts between the rocker 333 and the plate 355 in such a way as to be able to return the rocker 333 to the release position regardless of the direction of rotation of the rocker 333 relative to the plate 355.

[0096] In the embodiments of the invention described, the stator 21 is fixed to the base 3 while the rack 26 is fixed to the column 5, the invention is entirely applicable to a robot arm in which the stator is fixed to the column and the rack is fixed relative to the base.

[0097] Similarly, in the embodiments of the invention described, the motor shaft is the rotor of the electric motor, the invention is entirely applicable if the motor shaft is the output shaft of a reducer coupled to an electric motor.

[0098] Furthermore, the invention is applicable to a robot arm in which the first limb is rotationally mobile relative to the second limb. For example, it could be implemented on the forearm joint of a 6-axis industrial robot arm.

[0099] Any feature described above for one embodiment or variant is applicable to the other embodiments and variants described above, insofar as this is technically possible.

Claims

1. Demands Automatic locking device (27; 127; 227; 327) for a first limb (3) and a second limb (5) of a robot arm (1), movable relative to each other, the locking device (27; 127; 227; 327) comprising: - a ring (29), provided with a bore (43), centered on a drive shaft (A17) fixed relative to the ring (29) and configured to be fixed to the first member (3), - a hub (31), configured to be rotated around the motor shaft (A17) relative to the ring (29), by means of a motor (17) belonging to the robot arm (1), - a plate (55; 155; 255; 355), fixed in rotation to the hub (31) around the motor shaft (A17), - a rocker (33; 133; 333), carried by the plate (55; 155; 255; 355) and movable in rotation relative to the plate (55; 155; 255; 355) around a rocker axis (A33; A133) parallel to the motor axis (A17) and non-coaxial with the motor axis (A17), between a blocking position and a release position, - a groove (35; 135), formed in a first element between the rocker (33; 133) and the plate (55; 155; 255; 355), the groove (35; 135) extending radially with respect to the motor axis (A17) towards the bore (43) along a groove axis (A35), - a guide ramp (37; 137), provided at the periphery of a second element among the rocker (33; 133; 333) and the plate (55; 155; 255; 355), the second element being distinct from the first element, - a pin (39), which is cylindrical and extends along a pin axis (A39), parallel to the drive axis (A17), the pin (39) being mounted in the groove (35; 135) to be movable in translation along the groove axis (A35) relative to the first element when the rocker (33; 133; 333) is in the release position, and to be locked between the bore (43) and the guide ramp (37; 137) when the rocker (33; 133; 333) is in the locking position, and - a return spring (41; 341), acting between the plate (55; 155; 255; 355) and the rocker (33; 133; 333) so as to apply a return force (F) bringing the rocker (33; 133; 333) back to the release position.

2. Locking device (27; 127; 227; 327) according to the preceding claim, wherein, when the direction of rotation of the hub (31) is counterclockwise, respectively clockwise, around the drive shaft (A17) relative to the ring gear (29), to drive the second member (5) against gravity, the guide ramp (37; 137) is flat and the rocker (33; 133; 333) passes from the release position to the locking position by rotating relative to the plate (55; 155; 255; 355) in the clockwise, respectively counterclockwise, direction around the rocker shaft (A33; A133), relative to the plate (55; 155; 255; 355).

3. Locking device (27; 127; 227; 327) according to any one of the preceding claims, wherein the drive shaft (A17) is arranged between the rocker shaft (A33; A133) and the groove (35; 135).

4. Locking device (27; 127; 227; 327) according to any one of the preceding claims, wherein the guide ramp (37; 137) is coplanar with a ramp plane (P3), parallel to the drive shaft (A17) and inclined with respect to a radial plane (P2) containing the drive shaft (A17) and the rocker shaft (A33; A133), at an angle (a) of 86 to 90 degrees, preferably 87 to 89 degrees and more preferably 88 degrees.

5. Locking device (27; 127; 227; 327) according to any one of the preceding claims, wherein: - the pin (39) is free to rotate about the pin axis (A39) when the rocker (33; 133; 333) is in the release position, and - the rotation of the pin (39) about the pin axis (A39) is blocked when the rocker (33; 133; 333) is in the locking position, by the interposition of the pin (39) between the bore (43) and the guide ramp (37; 137).

6. A locking device (27; 127; 227; 327) according to any one of the preceding claims, wherein, when the rocker (33; 133; 333) is in the release position, a center of inertia of the rocker (33; 133; 333) is positioned in a radial plane (P2) containing the rocker axis (A33; A133) and the motor axis (A17).

7. Locking device (27; 127; 227; 327) according to any one of the preceding claims, wherein, when the rocker (33; 133; 333) is in the release position, a center of inertia of an assembly, formed by the plate (55; 155; 255; 355), the rocker (33; 133; 333), the return spring (41; 341) and the pin (39) is positioned on the drive shaft (A17).

8. Locking device (27; 227; 327) according to any one of the preceding claims, wherein the first element is the rocker (33; 333) and the second element is the plate (55; 255; 355).

9. Locking device (127) according to any one of claims 1 to 7, wherein the first element is the plate (155) and the second element is the rocker (133).

10. Locking device (27; 127; 227) according to any one of the preceding claims, wherein, when the rocker (33; 133) is in the release position, the restoring force (F) exerted by the restoring spring (41) tends to bring the pin (39) against a stop wall (71; 171) of the second element.

11. Locking device (327) according to any one of claims 1 to 9, wherein: - the guide ramp (37) is a first guide ramp, - a second guide ramp (383), symmetrical to the first guide ramp (37) with respect to a radial plane (P2) containing the rocker shaft (A33) and the drive shaft (A17), is provided on the second element (355), and - when the rocker (333) is in the release position, the restoring force (F) exerted by the return spring (41) tends to bring the pin (39) such that the pin shaft (A39) is in the radial plane (P2).

12. A locking device (227) according to any one of the preceding claims, comprising: - an additional rocker (273), carried by the plate (255) and rotatable relative to the plate (255) about an additional rocker axis (A273) parallel to the axis

13.

14. motor (A17) and non-coaxial with the motor shaft (A17), between a locked position and a released position, - an additional groove (275), formed in a third element between the additional rocker (273) and the plate (255), the additional groove (275) extending radially with respect to the drive shaft (A17) towards the bore (43) along an axis of additional groove (A275) - an additional guide ramp (277), provided at the periphery of a fourth element among the additional rocker (273) and the plate (255), the fourth element being distinct from the third element, - an additional cylindrical pin (279), extending along an additional pin axis (279), parallel to the drive axis (A17), the additional pin (279) being mounted in the additional groove (277) to be movable in translation along the additional groove axis (A275) relative to the third element when the additional rocker (273) is in the release position, and to be locked between the bore (43) and the additional guide ramp (A275) when the additional rocker (273) is in the locking position, and - an additional return spring (281), acting between the plate (255) and the additional rocker (273) so as to apply a return force (F2) bringing the additional rocker (273) back to the release position. Robot arm (1), comprising: - a first member (3), - a second member (5), movable relative to the first member (3), and - a locking device (27; 127; 227; 327) according to any one of the preceding claims in which the first member (3) is driven by the hub (31) and the second member (5) is fixed to the ring (29) or the first member (3) is fixed to the ring (29) and the second member (5) is driven by the hub (31). Robot arm (1) according to the preceding claim, wherein the second member (5) is movable in translation relative to the first member (3) along a vertical axis (V).

15. Robot arm (1) according to the preceding claim, comprising a pinion (25) rotationally fixed to the hub (31) around the motor shaft (A17) and a rack (26) fixed to the second member (5), the rack (26) being in contact with the pinion (25) so that the rotation of the pinion (25) around the motor shaft (A17) causes a translation of the rack (26) relative to the pinion (25) along the vertical axis (V).

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