Cable feed device and robot having such a device

Abstract

The invention relates to a cable feed device (1) for a robot (2), comprising: - a rotatably drivable first cable drum (8); - a rotatably mounted second cable drum (9), wherein the cable drums (8, 9) are at least indirectly connected to a first segment (4); - a deflection roller (14), which is operatively connected to a second segment (5) pivotably arranged about an axis of rotation (24) relative to the first segment (4); - a cable (6), which is wound on the deflection roller (14) and the free ends of which are each fastened to one of the cable drums (8, 9); and - a first freewheel (15) and a second freewheel (16) which are operatively connected to the deflection roller (14), wherein the first freewheel (15) moves into a coupling state when the deflection roller (15) is rotated in a first direction of rotation, wherein the second freewheel (16) moves into a coupling state when the deflection roller (14) is rotated in a second direction of rotation counter to the first direction of rotation, and wherein a cable feed drive (17) with a transmission ratio not equal to 1 is operatively arranged between the first freewheel (15) and the second segment (5) or between the second freewheel (16) and the second segment (5). The invention also relates to a robot (2) having such a cable feed device (1).

Description

[0001] rope feed device and robots with such a device

[0002] The invention relates to a cable feed device for a robot. Furthermore, the invention relates to a robot, in particular a cable-operated robot, with at least two segments arranged to pivot relative to each other, wherein at least one cable feed device is effectively arranged in the joint area of ​​the two segments.

[0003] Cable drives for cable robots transmit force from a source, such as a motor, to a load using cables. The cables can only transmit tensile forces, so two cables or a cable loop from the source to the load are required to achieve bidirectional drive. Cables under tension are laid in straight lines, but the direction of the cable and the force can be changed by using pulleys or other components. A gear ratio is achieved, for example, by using pulleys with different diameters. The cable must be kept under constant tension to prevent sagging, which would impair the rigidity of the robot joint and make robot control more difficult. However, if the tension is too high, the cable can fail prematurely. Therefore, proper cable tension is crucial.Cables or similar materials can of course be used instead of ropes.

[0004] The main problem with such cable robots, especially their drive systems, lies in the limited lifespan of the cables. During operation, the cables are subjected to fluctuating loads and wear. Longitudinal load cycles from the actuation process are superimposed on the pretension force, and bending cycles occur when the cables move over pulleys or other deflection elements. Furthermore, surface wear occurs on the pulleys or cable drums, and shear stresses are exerted on clamping elements. This causes the cable to stretch over time, which can lead to premature cable failure.

[0005] For example, CN 115621908 A describes a clamping device comprising a support, the front of which is rotatably equipped with a clamping shaft body. A transmission element is located at the left end of the front of the support and has an L-shaped structure. A reciprocating shaft body is rotatably attached to the right end of the front of the support. A handwheel is located on the lower clamping shaft body. The sliding clamping mechanism is added based on the rotational clamping; the clamping effect on the cable is ensured by the effective interaction of the two mechanisms. The two mechanisms can be operated synchronously by turning a handwheel, whereby the two mechanisms clamp the cable synchronously, thus ensuring the clamping effect on the cable.

[0006] The object of the invention is to provide a rope feed device and a robot with such a rope feed device having an improved service life. This object is achieved by the subject matter of claim 1 and by the subject matter of claim 10. Preferred embodiments can be found in the dependent claims, the description, and the figures.

[0007] A rope feeding device according to the invention for a robot comprises a rotatably driven first rope drum, a rotatably mounted second rope drum, wherein the rope drums are at least indirectly connected to a first segment, a deflection pulley which is operatively connected to a second segment which is pivotably arranged relative to the first segment about an axis of rotation, a rope which is wound on the deflection pulley and whose free ends are each attached to one of the rope drums, as well as a first freewheel and a second freewheel which are operatively connected to the deflection pulley, wherein the first freewheel enters a coupling state when the deflection pulley is rotated in a first direction of rotation, and wherein the second freewheel enters a coupling state when the deflection pulley is rotated in a second direction of rotation opposite to the first direction of rotation.and wherein a rope feed drive with a gear ratio other than 1 is effectively arranged between the first freewheel and the second segment or between the second freewheel and the second segment.

[0008] The freewheels are one-way couplings arranged in opposite directions, or with a locking effect, and each is positioned at least indirectly between the deflection pulley and the second segment. Depending on the direction of rotation of the deflection pulley, the freewheels enter either a coupled or a freewheeling state. The coupled state of the freewheel refers to the state in which the freewheel is engaged, i.e., transmits drive power between two components. Each freewheel enables the transmission of torque in one direction, while rotating or slipping freely in the opposite direction. In the coupled state, torque is transmitted from one shaft or wheel, particularly the deflection pulley, to another shaft or wheel, particularly the second segment, while in the disengaged state, no torque transmission occurs.The freewheels can be designed as friction- and / or form-locking one-way couplings or overrunning couplings.

[0009] The deflection pulley is to be understood as a rope deflection pulley. The deflection pulley is driven by the rope, which is wound at least once around the deflection pulley and connected to the rope drums. The deflection pulley is arranged axially parallel to the rope drums. The deflection pulley is, for example, arranged axially between the two freewheels. The freewheels can be arranged directly adjacent to the deflection pulley. Depending on the design of the deflection pulley, at least one of the freewheels can be arranged at least partially within the deflection pulley.

[0010] The first segment can be a first robot arm segment or a first finger segment of a robot, or be integrally connected to or attached to it. The first segment can at least partially accommodate the cable drums, the cable drums being designed such that the cable is or can be wound onto them.

[0011] The second segment can be a second robot arm segment or a second finger segment of a robot, or it can be integrally connected to or attached to it. The second segment can at least partially accommodate the freewheels and / or the deflection pulley.

[0012] A rotatable first rope drum is operatively connected to a drive that generates drive power and transmits it directly, for example via a drive shaft, or indirectly, that is, via a drive shaft and a transmission stage or the like, to the first rope drum. The deflection pulley can be set into rotational motion by the rope in a first direction of rotation or in an opposite second direction of rotation.

[0013] In this sense, the rope feed device preferably further comprises an actuator having a drive unit that is effectively connected to the first rope drum at least via a drive shaft. The drive unit can be an electric machine comprising a stator fixed to a housing and a rotor rotatably mounted thereto, which can be at least indirectly connected to the drive shaft in a rotationally fixed manner. The actuator preferably includes a transmission stage that can reduce the speed to adapt a high rotational speed of the electric machine to the speeds required for the application.

[0014] A second, rotatably mounted cable drum can be arranged on the same drive shaft as the first cable drum, but is mounted to rotate freely relative to it. The cable drums are preferably positioned axially immovably relative to each other.

[0015] By having one freewheel directly connect the deflection pulley to the second segment in the first direction of rotation, and by having the other freewheel establish a gear ratio other than one between the deflection pulley and the second segment in the second direction of rotation, a mechanism is realized that changes the rope feed required for the joint's movement in one direction by a small amount, dependent on the actual gear ratio, compared to the other direction. During a movement cycle between the first and second segments—that is, pivoting the second segment around its axis of rotation in the first direction and then pivoting it in the opposite direction—this small difference in rope length is then retrieved from the first rope drum, which can hold and provide a significantly larger amount of rope.

[0016] Preferably, the rope feed device has a rope tensioning mechanism that is operatively connected to the second rope drum. The rope tensioning mechanism pre-tensions the rope so that excess rope is always wound up. Therefore, preferably no rope or only a short length of rope is wound onto the second rope drum, particularly at the start of operation. The rope tensioning mechanism ensures that the rope is always under tension. The rope tensioning mechanism is preferably arranged coaxially with the rope drums. Preferably, the rope tensioning mechanism is arranged axially between the rope drums on the first segment. The actuator's drive shaft can pass axially through the rope tensioning mechanism.

[0017] The rope tensioning mechanism can be a spring element or the like. Unstressed rope can be supplied on the first rope drum and unwound piece by piece during each movement cycle, with a corresponding length of stressed rope being wound onto the pre-tensioned second rope drum at the other end during each movement cycle. Therefore, the rope feed device can also be understood as a rope tensioning device.

[0018] With such a rope feeding device or rope feeding and tensioning device, a slow and gradual, automatic replacement of the used, especially worn, rope with new rope segments is achieved during operation. In this way, the rope is renewed with each movement cycle over its service life before fatigue or wear of the rope has progressed to the point where it could fail.

[0019] Since the difference in cable routing between the two directions is precisely defined, this can be taken into account by an application-specific control system, such as a robot control system, ensuring that precise control of the movement of the segments relative to each other is always guaranteed or not impaired during operation.

[0020] Once the entire rope has been unwound from the first rope drum and wound onto the second, the rope can be replaced, for example, during maintenance of the robot, robot arm, or rope feeder. The direction in which the rope is unwound or wound onto the respective rope drum depends on the position of the rope feed drive on the associated freewheel, the resulting gear ratio, and the tensioning direction of the respective pre-tensioned rope drum achieved by the tensioning mechanism. Depending on the rope design, the deflection pulley can also be a belt pulley or belt roller. For the purposes of this invention, "rope" is understood to mean a traction element for transmitting tensile forces. This traction element can equally well be a cable, tape, or belt.The respective deflection pulley is used to change the direction of a tensile force, whereby, depending on the direction of rotation of the rotatable first rope drum, the second segment pivots relative to the first segment.

[0021] Preferably, the rope is a polymer cable or rope. The rope can therefore also be designed as a cable. Particularly suitable polymer cables include Dyeema, Kevlar, or similar materials. The rope exhibits high ductility with low bending stiffness.

[0022] The terms "transmission ratio not equal to 1" or "transmission ratio not equal to one" mean that the deflection pulley implements a transmission ratio different from that of a direct drive. For example, a transmission ratio greater than 1 results in a rope feed of greater than zero degrees per revolution. This rope feed is preferably a very small, linear advance of the rope during each movement cycle of the segments. Preferably, the rope feed drive has a transmission ratio greater than 0.9 and less than 1.1. More preferably, the rope feed drive has a transmission ratio greater than 0.95 and less than 1.05, more preferably greater than 0.98 and less than 1.02, and most preferably greater than 0.99 and less than 1.01. In one embodiment, the transmission ratio is greater than 0.999 and less than 1.001.

[0023] The rope feed drive is preferably designed such that an input element and an output element of the rope feed drive are arranged coaxially to each other. Intermediate gears or intermediate elements of the rope feed drive can also be arranged coaxially or parallel to the axis. The input element and the output element can each be designed as a shaft or as a gear or pulley. In particular, the input element and the output element are designed as gears of the rope feed drive. Preferably, the input element and the output element of the rope feed drive have the same direction of rotation. In other words, the input element and the output element rotate in the same direction. Thus, the rope feed drive does not reverse the direction of rotation. Intermediate gears or intermediate elements of the rope feed drive can rotate in the opposite direction.

[0024] According to one embodiment, the cable feed drive is a two-stage spur gear drive. The two-stage spur gear drive comprises an intermediate shaft with two axially adjacent gears fixed to it in a rotationally fixed manner, of which a first gear meshes with a gear operatively connected to the input element and a second gear meshes with a gear operatively connected to the output element.

[0025] The invention further relates to a robot comprising a cable feed device according to the first aspect of the invention. The cable feed device is arranged in the joint between two segments of the robot. The segments can each be configured as a robot arm segment of a robot arm or as a finger segment of a robot manipulator. The cable feed device enables improved operation of the robot with regard to its service life.

[0026] The above definitions and descriptions of technical effects, advantages and advantageous embodiments of the rope feeding device according to the first aspect of the invention also apply analogously to the robot according to the second aspect of the invention, and vice versa.

[0027] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the single figure, wherein identical or similar components are provided with the same reference numeral. The single figure shows a schematic representation of a partially depicted robot arm of a robot according to the invention with a cable feed device according to the invention.

[0028] According to the single figure, a robot arm 3 of a robot 2 (only partially shown here) is depicted in a highly schematic and simplified manner. The robot arm 3, in this example, has a first robot arm segment as the first segment 4 and a second robot arm segment as the second segment 5, which are connected to each other by a shaft 7, allowing them to pivot about a rotational axis 24. The first segment 4 is to be understood as the base link, while the second segment 5 is to be understood as the remote link. The robot 2 has a cable feed device 1, which is effectively arranged in the joint area between the two segments 4 and 5.

[0029] The rope feed device 1 comprises two rope drums 8, 9 arranged coaxially on a drive shaft 11 on the first segment 4, wherein the first rope drum 8 is rotatably driven by an actuator 10, and wherein the second rope drum 9 is rotatably arranged on the drive shaft 11 and is operatively connected to a rope tensioning mechanism 12, which is arranged axially between the rope drums 8, 9. The rope tensioning mechanism 12 can consist of a torsion spring, a one-way coupling, or other elements that can pretension a rope 6. The drive shaft 11 is arranged on the first segment 4 and is rotatably mounted to it, for example, by sliding bearings. The actuator 10 comprises a drive unit 13 designed as an electric machine and an optional transmission stage (not shown here), wherein the drive power of the drive unit 13 is consequently transmitted at least indirectly to the first rope drum 4 via the drive shaft 11.A rope 6 is wound onto the first rope drum 8. The rope leads to a deflection pulley 14 located on the second segment 5, wraps around it at least once, and then leads from there to the second rope drum 9. The rope 6 is attached to both the first rope drum 8 and the second rope drum 9. The deflection pulley 14 is operatively connected to the second segment 5.

[0030] A movement cycle of segments 4, 5, in which the second segment 5 pivots around the axis of rotation 24 relative to the first segment 4, occurs when the actuator 10 rotates the first rope drum 8 in such a way that the second segment 5 is pivoted relative to the first segment 4 in a first direction of rotation and then back in a second direction of rotation opposite to the second direction of rotation.

[0031] The deflection pulley 14 is arranged axially between two freewheels 15 and 16, with the first freewheel 15 oriented in the opposite direction to the second freewheel 16. Thus, the freewheels 15 and 16 have opposite locking directions, illustrated here by the oppositely oriented arrows in the respective freewheels 15 and 16. Accordingly, when the deflection pulley 14 rotates in a first direction, the first freewheel 15 enters a locked state, while when the deflection pulley 14 rotates in a second direction, the second freewheel 16 enters a locked state. In this case, the first freewheel 15 is directly supported on the second segment 5, while a cable feed drive 17 with a gear ratio greater than 0.9, less than 1.1, and not equal to 1 is effectively arranged between the second freewheel 16 and the second segment 5. In this case, the translation ratio is between 1 and 1.1.An input element 18 and an output element 19 of the rope feed drive 17 are arranged coaxially and rotate in the same direction. In this embodiment, the rope feed drive 17 is designed as a two-stage spur gear drive with two gears 20, 21, 22, 23 per spur gear stage. Here, the first gear 20 of the first spur gear stage is the input element 18 of the rope feed drive 17, and the second gear 23 of the second spur gear stage is the output element 19 of the rope feed drive 17.

[0032] The rope feed device 1 implements a slow and gradual automatic replacement of the rope 6 with new rope segments during the operation of the robot 2. In this way, the rope 6 is renewed before fatigue or wear of the rope 6 has progressed to the point where it could fail. At the start of operation, no rope 6 may be wound on the second rope drum 9, while the remaining rope 6 is guided over the deflection pulley 14 to the first rope drum 8, where it is wound and ready for use.

[0033] The cable feed device 1 slightly alters the cable feed required for moving the robot joint in one direction of rotation compared to the other direction. During a movement cycle of the second segment 5 relative to the first segment 4, this small difference in cable length is unwound from the first cable drum 8, which contains the unloaded cable 6. The cable tensioning mechanism 12 pre-tensions the cable 6 at the other end, so that the cable 6 is wound onto the other, second cable drum 9. Since the difference in cable feed between the two directions is precisely defined, a controller for the robot 2 or the robot arm 3 (not shown here) can take this into account and continue to precisely control the robot's movement.

[0034] In this embodiment, the two-stage spur gear drive is designed such that the number of teeth on gears 20, 21, 22, and 23 of each stage are nearly identical. For example, the first gear 20 of the first spur gear stage has 100 teeth, while the second gear 21 of the first spur gear stage has 101 teeth. The first gear 22 of the second stage also has 100 teeth, while the second gear 23 of the second spur gear stage has 99 teeth. Thus, the rope feed drive 17 has an overall gear ratio of approximately 1.0001. This results in a rope feed of approximately 0.036 degrees per revolution of the deflection pulley 14, or, in other words, 360 degrees per 9,999 revolutions of the deflection pulley 14. The linear feed is accordingly 0.016 mm per 360-degree rotation of the deflection pulley 14, assuming an exemplary pulley diameter of 50 mm. This rope feed is unwound from the first rope drum 8, simultaneously feeding the used rope.The used rope segment of the same length is wound onto the automatically pre-tensioned second rope drum 9.

[0035] During the operation of robot 2, that is, with an increasing number of movement cycles, the rope 6 is gradually replaced by new rope segments until the rope 6 is completely unwound from the first rope drum 8 and instead wound onto the circumferentially pre-tensioned rope 6. The system is designed so that the used rope 6 remains in the main power transmission path or critical load area for only a specific time, which is many times shorter than the total service life of the rope feed device 1, and thus cannot fail. The rope 6 wound onto the respective rope drum 8, 9 carries no load when it is far enough away from the loaded end, as the force is held by friction on the rope drum 8, 9.By winding the rope 6 several times around the respective rope drum 8, 9, the holding tension at the connection points of the rope 6 on the associated rope drum 8, 9 can be reduced, which further increases the service life of the rope feed device 1. See list of reference symbols.

[0036] 1 rope feed device

[0037] 2 robots

[0038] 3 robot arm

[0039] 4 First Segment

[0040] 5 Second Segment

[0041] 6 rope

[0042] 7th wave

[0043] 8 First rope drum

[0044] 9 Second rope drum

[0045] 10 Actuator

[0046] 11 Drive shaft

[0047] 12 Rope tensioning mechanism

[0048] 13 Drive unit

[0049] 14 Pulley

[0050] 15 First free run

[0051] 16 Second free run

[0052] 17 Rope feed drive

[0053] 18 Input element of the rope feed drive

[0054] 19 Output element of the rope feed drive

[0055] 20 First gear of the first stage

[0056] 21 Second gear of the first stage

[0057] 22 First gear of the second stage

[0058] 23 Second gear of the second stage

[0059] 24 Rotation axis

Claims

Patent claims 1. Rope feed device (1) for a robot (2), comprising - a rotatable first rope drum (8), - a rotatably mounted second rope drum (9), wherein the rope drums (8, 9) are at least indirectly connected to a first segment (4), - a deflection pulley (14) which is operatively connected to a second segment (5) which is arranged to pivot about an axis of rotation (24) relative to the first segment (4), - a rope (6) wound on the pulley (14) and whose free ends are each attached to one of the rope drums (8, 9), as well as - a first freewheel (15) and a second freewheel (16) which are operatively connected to the deflection pulley (14), wherein the first freewheel (15) enters a coupling state when the deflection pulley (15) is rotated in a first direction of rotation, wherein the second freewheel (16) enters a coupling state when the deflection pulley (14) is rotated in a second direction of rotation opposite to the first direction of rotation, and wherein a rope feed drive (17) with a transmission ratio other than 1 is operatively arranged between the first freewheel (15) and the second segment (5) or between the second freewheel (16) and the second segment (5).

2. Rope feed device (1 ) according to claim 1 , characterized in that the second rope drum (9) is operatively connected to a rope tensioning mechanism (12).

3. Rope feed device (1 ) according to claim 2, characterized in that the rope tensioning mechanism (12) is arranged axially between the rope drums (8, 9) on the first segment (4).

4. Rope feed device (1 ) according to one of the preceding claims, characterized by an actuator (10) comprising a drive unit (13) which is connected to the first rope drum (8) at least via a drive shaft (11 ).

5. Rope feed device (1 ) according to claim 4, characterized in that the actuator (10) comprises a transmission stage.

6. Rope feed device (1 ) according to one of the preceding claims, characterized in that an input element (18) and an output element (19) of the rope feed drive (17) are arranged coaxially.

7. Rope feed device (1 ) according to claim 6, characterized in that the input element (18) and the output element (19) of the rope feed drive (17) have the same direction of rotation.

8. Rope feed device (1 ) according to one of the preceding claims, characterized in that the rope feed drive (17) is a two-stage spur gear drive.

9. Rope feed device (1 ) according to one of the preceding claims, characterized in that the rope feed drive (17) has a transmission ratio of greater than 0.9 and less than 1 , 1.

10. Robot (2) comprising a rope feed device (1) according to one of the preceding claims.

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