Cable tensioning device and robot having such a cable tensioning device

Abstract

The invention relates to a cable tensioning device (1), comprising a first deflecting roller (2), on which a first cable (3) is wound, a second deflecting roller (4) which is arranged coaxially with respect to the first deflecting roller (2) and on which a second cable (5) is wound, and a ratchet mechanism (6), comprising a preloading element (7) for axially preloading the first deflecting roller (2) in the direction of the second deflecting roller (4), a first spur toothing system (8) which is arranged on the first deflecting roller (2), and a second spur toothing system (9) which is arranged on the second deflecting roller (3), wherein, in the non-actuated state of the cable tensioning device (1), the spur toothing systems (8, 9) are in engagement with one another as a result of an axial preloading force of the preloading element (7), in such a way that a relative rotation of the deflecting rollers (2, 4) in a first rotational direction (10) is prevented and a relative rotation of the deflecting rollers (2, 4) in a second rotational direction (11), opposed to the first rotational direction, is released, wherein, if at least one of the deflecting rollers (2, 4) is actuated with an actuating force, exceeding a limit value, in the second rotational direction (11), the spur toothing systems (8, 9) slide on one another and, as a result, the first deflecting roller (2) moves relative to the second deflecting roller (4) counter to the axial preloading force of the preloading element (7), in order to release an adjustment of a rotational position of the deflecting rollers relative to one another.

Description

[0001] Rope tensioning device and robot with such a rope tensioning device

[0002] The invention relates to a cable tensioning device. Furthermore, the invention relates to a robot, in particular a cable-pulling robot, with at least one such cable tensioning device.

[0003] CN 115621908 A discloses a tensioning device comprising a support, the front of which is rotatably provided with a tensioning shaft body. A transmission part is arranged at the left end of the front of the support, and the transmission part has an L-shaped structure. A swinging shaft body is rotatably mounted at the right end of the front of the support. A handwheel is arranged on the lower tensioning shaft body. The sliding tensioning mechanism is added based on the rotary tensioning; the tensioning effect of the cable is ensured by the rational cooperation of the two mechanisms. The two mechanisms can be operated synchronously by turning a handwheel, whereby the two mechanisms tension the cable synchronously, ensuring the tensioning effect of the cable.

[0004] In the case of cable robots, it can happen that cables connected to components, in particular end effectors or the like, lose tension during operation, which in turn can lead to errors in the operation of the end effector.

[0005] The object of the invention is to provide a rope tensioning device and a robot with such a rope tensioning device that enables simple tensioning of the respective rope to be tensioned and can maintain the tension within the rope for as long as possible. This object is achieved by the subject matter of patent claim 1 and by the subject matter of patent claim 10. Preferred embodiments can be found in the dependent claims, the description, and the figures. A rope tensioning device according to the invention comprises a first deflection pulley, on which a first rope is wound, a second deflection pulley arranged coaxially to the first deflection pulley, on which a second rope is wound, and a ratchet mechanism having a pretensioning element for axially pretensioning the first deflection pulley in the direction of the second deflection pulley.a first spur gear arranged on the first deflection pulley and a second spur gear arranged on the second deflection pulley, wherein the spur gears engage with one another in the unactuated state of the cable tensioning device as a result of an axial pretensioning force of the pretensioning element, such that a relative rotation of the deflection pulleys in a first direction of rotation is prevented and a relative rotation of the deflection pulleys in a second direction of rotation opposite thereto is permitted, wherein, when at least one of the deflection pulleys is actuated in the second direction of rotation with an actuating force exceeding a limit value, the spur gears slide against one another and thereby displace the first deflection pulley relative to the second deflection pulley counter to the axial pretensioning force of the pretensioning element, in order to enable an adjustment of a rotational position of the deflection pulleys relative to one another.

[0006] By adjusting the rotational position of the pulleys, the first and / or second rope can be tensioned, depending on which pulley is actuated or rotated around its rotational axis in the second direction. A rotational position refers to the position of a rotating object, i.e., the respective pulley, relative to another, optionally rotating object. It can be the angular position of a rotating object, such as the position of the respective pulley on a shaft on which it is rotatably mounted.

[0007] The first cable is configured to be connected, starting from the first pulley, to a first component to be driven, such as a robot arm segment or an end effector of a robot. The second cable is configured to be connected, starting from the second pulley, to a second component to be driven, such as the same or a different robot arm segment or the same or a different end effector of the robot. Thus, two cable branches are provided on the cable tensioning device, whereby one or both of the cables can be tensioned.

[0008] The deflection pulleys are to be understood as rope deflection pulleys. Depending on the design of the rope, the deflection pulleys can also be designed as belt pulleys or belt rollers. For the purposes of the invention, a rope is understood to be a traction device for transmitting tensile forces. The traction device can equally well be a band or belt. The respective deflection pulley is used to change the direction of a tensile force and optionally to reduce tension at a connection point of the rope to the associated roller. The respective deflection pulley is rotatably mounted. The respective deflection pulley can be driven in rotation or can be rotated manually by a user, in particular by means of an actuating tool, in the second direction of rotation. Rotation in the first direction of rotation is blocked due to the design of the spur gearing. The deflection pulleys mesh with each other in the initial or unactuated state.Depending on the direction of rotation, the pulleys can mesh with each other at their front teeth or separate from each other.

[0009] A ratchet mechanism is a mechanism that enables a unidirectional rotation of one pulley relative to the other. The mechanism consists of two spur gear teeth and a preload element that keeps the spur gear teeth engaged in the initial state. The spur gear teeth can be complementary. The spur gear teeth are designed in the form of a sawtooth pattern, which is designed to always prevent relative rotation of the pulleys in the first direction of rotation and to permit relative rotation of the pulleys in the second direction of rotation depending on the torque.The shape of the toothing, in particular the angle of the ramps of the individual teeth, has a direct influence on the actuating force required to make the spur gears slide. Rotation of the deflection pulleys causes a longitudinal displacement of the first deflection pulley due to the pitch angle of the ramp-shaped teeth. As the respective deflection pulley progresses, a tooth of one spur gear slides from one tooth gap to the next, thereby adjusting the rotational position. The steeper the angle of the ramp-shaped teeth in relation to a longitudinal axis of the deflection pulleys, the greater the actuating force required to tension the respective cable and the greater the number of achievable steps per revolution of the respective deflection pulley.

[0010] The teeth of the spur gears initially mesh with each other as a result of the axial preload of the preload element, i.e., when the device is not actuated. The spur gears are designed in such a way that a positive locking mechanism is present, preventing the respective deflection pulley from rotating in the first direction of rotation. In the first direction of rotation of the deflection pulleys, the shape of the spur gears creates a positive locking mechanism, preventing the respective deflection pulley from rotating in the first direction of rotation. This prevents the respective deflection pulley from rotating backward after tensioning, which would otherwise cause the tension in the taut cable to be lost.

[0011] When the respective deflection pulley is actuated or rotated in the opposite second direction of rotation, the first deflection pulley is moved axially opposite to the second deflection pulley as the spur gear teeth slide against each other. This causes the deflection pulleys to rotate relative to each other. In the second direction of rotation of the respective deflection pulley, relative rotation of the deflection pulleys is only possible if a torque introduced into the respective deflection pulley exceeds the pretensioning force of the pretensioning element and the friction between the spur gear teeth, so that the spur gear teeth slide against each other and the deflection pulleys can rotate gradually relative to each other. In this way, the respective cable of the actuated deflection pulley can be tensioned gradually and as required, while at the same time preventing the actuated deflection pulley from turning back in the first direction of rotation, with the associated slackening of the respective cable.The tensioning of the respective rope can thus be carried out safely and in relatively small steps.

[0012] Depending on the pre-tensioning force of the pre-tensioning element and the design of the spur gear teeth, a limit value is defined for an actuating force for actuating the respective deflection pulley in the second direction of rotation, which limit value must be overcome in order to initiate a rope tensioning process of the respective rope.

[0013] With such a device, the rope can be tensioned easily and safely, and the tension can be maintained for longer. It is also convenient and intuitive for the user.

[0014] Preferably, the preload element is a compression spring. It is conceivable to provide several preload elements connected in parallel and / or in series. The type and design of the preload element depends on the required preload force and the existing structure of the spur gear teeth.

[0015] If the operation of the respective deflection pulley is stopped or the applied torque falls below the limit value, the spur gears engage again so that relative rotation in both directions is blocked.

[0016] Preferably, the respective rope is a polymer cable. Thus, the rope is designed as a cable. Dyeema, Kevlar, or similar materials are particularly suitable as polymer cables. Such a cable exhibits high ductility and low flexural rigidity.

[0017] In a further development of the invention, the cable tensioning device comprises a shaft on which the deflection pulleys are rotatably mounted, and on which at least one of the deflection pulleys, in particular the first deflection pulley, is arranged for axial displacement. The shaft holds the deflection pulleys coaxially to one another and enables axial movement of the spring-loaded first deflection pulley relative to the other second deflection pulley during coupling or decoupling. The shaft defines the rotational axis of the deflection pulleys. The shaft can be accommodated and mounted in a housing.

[0018] According to one embodiment, means for receiving an operating tool are arranged on each of the pulleys. The means can, for example, be designed with a hexagonal geometry, for example, to be operated using an open-end wrench or the like. When adjusting the cable tension, two wrenches can be used to perform the rotational movement of both pulleys, with the wrenches being operated in opposite directions to tension both cables simultaneously. Alternatively, one wrench can be held by the user, thus serving as a counterweight, while the other wrench can be used to operate the corresponding pulley in the second direction of rotation.

[0019] Preferably, one end of the first rope is attached to the first pulley. Alternatively or additionally, one end of the second rope is attached to the second pulley. The respective pulley is at least half-wrapped by the associated rope. Depending on the type of attachment of the ropes to the associated pulley, the rope lengths decrease or increase during the tensioning process. Therefore, the proposed rope tensioning device makes it easier for the user to adjust the rope tension.

[0020] Preferably, the respective pulley is wrapped several times by the associated rope. This allows for secure winding of the rope on the respective pulley. The respective rope is wound helically on the associated pulley. The pulley can therefore be designed in the form of a rope drum. Accordingly, the respective pulley has a specific axial length and its position is more stable than with other known rope tensioning devices. Therefore, the respective rope is not affected by the movement of the pulleys.

[0021] By winding each rope several turns around the pulley, the holding tension at the connection points of the respective rope on the corresponding pulley can also be reduced, which further increases the service life of the tensioning device and keeps the tension of the respective rope essentially constant for longer.

[0022] In a further development, the pulleys are designed identically. This allows the cable tensioning device to be manufactured more simply and cost-effectively. One advantage of this is that if a tooth gap of the first spur gear is designed to complement a tooth of the second spur gear, and vice versa, the spur gears of the ratchet mechanism effectively mesh with each other.

[0023] The invention further relates to a robot comprising a cable tensioning device according to one of the preceding claims. The cables can be operatively connected to a joint of a robot arm of the robot in order to pivot a first robot arm segment relative to a second robot arm segment, or vice versa. The cable tensioning device can be arranged on the first or second robot arm segment. The cable tensioning device according to the first aspect of the invention makes cable-connected robot arms more robust for industrial use.

[0024] The above definitions as well as explanations of technical effects, advantages and advantageous embodiments of the cable tensioning device according to the first aspect of the invention also apply mutatis mutandis to the robot according to the second aspect of the invention, and vice versa.

[0025] Further measures improving the invention are described in more detail below together with the description of a preferred embodiment of the invention with reference to the figures, wherein identical or similar components are provided with the same reference numerals.

[0026] Figure 1 is a schematic representation of a partially illustrated robot according to the invention with a rope tensioning device,

[0027] Figure 2 is a schematic view of the cable tensioning device according to the invention according to Figure 1,

[0028] Figure 3 is a schematic perspective view of the - only partially shown - rope tensioning device according to Figure 2 during a tensioning process of a rope to be tensioned, and Figure 4 is a highly simplified side view of a deflection pulley and an end effector of the robot to illustrate the tensioning process of the rope to be tensioned.

[0029] According to Figure 1, a robot arm 14 of a robot 13—only partially shown here—is shown in a highly schematic and simplified manner. The robot 13 has a cable tensioning device 1. In this example, the robot arm 14 has a first robot arm segment 15 and a second robot arm segment 16, which are pivotably connected to one another via a joint 17. The joint 17 drives the first robot arm segment 15 around the second robot arm segment 16.

[0030] The cable tensioning device 1 is attached to the second robot arm segment 16 to tension cables 3, 5 of the robot arm 14. The cable tensioning device 1 is described in detail with reference to Figures 2 to 4. However, the structure of the joint 17 is not described in detail here.

[0031] The cable tensioning device 1 comprises a first deflection pulley 2 designed as a drum, on which a first cable 3 is wound over several turns, and a second deflection pulley 4 arranged coaxially to the first deflection pulley 2 and also designed as a drum, on which a second cable 5 is wound over several turns. The respective cable 3, 5 is a polymer cable that can be operatively connected to an associated robot arm segment 15, 16. Each cable 3, 5 is wound several times around the associated deflection pulley 2, 4. One end of the first cable 3 is attached to a first connection point 18 on the first deflection pulley 2. One end of the second cable 4 is attached to a second connection point 19 on the second deflection pulley 5. Figure 2 shows that the cables 3, 5 are wound in opposite directions around the associated deflection pulley 2, 4.

[0032] The deflection pulleys 2, 4 are rotatably mounted on a shaft 12, with the first deflection pulley 2 also being axially displaceable thereon and being axially preloaded by a preload element 7 designed as a compression spring. The deflection pulleys 2, 4 are identical in design, with the deflection pulleys 2, 4 being mounted on the shaft 12 such that the spur gear teeth 8, 9 face towards one another. The preload element 7 for axially preloading the first deflection pulley 2 in the direction of the second deflection pulley 4 is part of a ratchet mechanism 6, which further has a first spur gear tooth 8 arranged on the end face of the first deflection pulley 2 and a second spur gear tooth 9 arranged on the end face of the second deflection pulley 3.

[0033] The spring preload force of the preload element 7 acts permanently on the first deflection pulley 2, such that the spur gear teeth 8, 9 are already in engagement with one another when the cable tensioning device 1 or the ratchet mechanism 6 is not actuated. This prevents a relative rotation of the deflection pulleys 2, 4 in a first direction of rotation 10 and thus an unwanted drop in tension of the respective cable 3, 5. When the cable tensioning device 1 is not actuated, a relative rotation of the deflection pulleys 2, 4 in an opposite second direction of rotation 11 is also prevented, since the preload element 7, due to the preload force in combination with a pitch angle of the teeth of the spur gear teeth 8, 9, keeps the first deflection pulley 2 in engagement with the second deflection pulley 4.

[0034] Figures 2 and 3 show that, on a section of the deflection pulleys 2, 4, means for receiving an actuating tool W1, W2 are formed on an outer circumference, specifically in the form of a hexagonal circumference 20. According to Figure 3, the actuating tools W1, W2 are open-end wrenches with an inner geometry complementary to the outer geometry of the deflection pulleys 2, 4. The cable tensioning device 1 and the actuating tools W1, W2 can therefore be part of a separate tensioning system. For the sake of simplicity, only the deflection pulleys 2, 4 with the actuating tools W1, W2 are shown in Figure 3.

[0035] If an actuating force is generated with one or both actuating tools W1, W2 or a torque is transmitted to the associated deflection pulley 2, 4, which is large enough to realize a sliding of the teeth of the spur gears 8, 9 and at the same time to axially displace the first deflection pulley 2 against the preload force of the preload element 7, a rotative position of the first deflection pulley 2 relative to the second deflection pulley 4, and vice versa, can be set. In other words, when at least one of the deflection pulleys 2, 4 is actuated in the second direction of rotation 11 with an actuating force exceeding a limit value, the spur gear teeth 8, 9 slide against one another, whereby the first deflection pulley 2 is displaced relative to the second deflection pulley 4 against the axial pretensioning force of the pretensioning element 7, so that the deflection pulleys 2, 4 can be positioned tooth by tooth relative to one another in order to tension the respective cable 3, 5.

[0036] Accordingly, when tensioning of the first cable 3 is required, the first deflection pulley 2 can be actuated in the corresponding second rotational direction 11 by means of the first actuating tool W1, while the second deflection pulley 4 is held in place or remains rotationally fixed by means of the second actuating tool W2. Similarly, when the second cable 5 needs to be tensioned, the second deflection pulley 4 can be actuated in the corresponding second rotational direction 11 by means of the second actuating tool W2, while the first deflection pulley 2 is held in place or remains rotationally fixed by means of the first actuating tool W1. Simultaneous actuation of the deflection pulleys 2, 4 in the respective second rotational direction 11 is also conceivable, so that both cables 3, 5 are tensioned simultaneously.

[0037] The illustration in Figure 4 is intended to illustrate rope stretching by means of the rope tensioning device 1. The first deflection pulley 2 and the first rope 3 are shown as examples, with the first rope 3 wound on the first deflection pulley 2 on the one hand and fastened to a component, here an end effector E or the like on the other hand. Assuming that the end effector E is completely fixed, i.e., arranged in a rotationally fixed manner, and that the first deflection pulley 2 rotates, the rope 3 is wound more tightly onto the first deflection pulley 2 when the first deflection pulley 2 rotates counterclockwise. Accordingly, a distance between points A and B would be longer than the original distance a. Neglecting any slippage between the first rope 3 and the first deflection pulley 2, the rope stretch of the first rope 3 in this situation is calculated as

[0038] AAB = mar where r corresponds to a radius of the first pulley 2, ma to a rotation angle with a=2n7n and n to a number of teeth of the first spur gear 8. Adjusting the variables m and r influences the achievable rope elongation.

[0039] In order to reduce the tension within the respective rope 3, 5, in particular at the connection points 18, 19, the ropes 3, 5 are wound several times around the associated deflection pulley 2, 4, as can be seen in Figure 2, which increases the frictional force between the ropes 3, 5 and the deflection pulleys 2, 4. The more often the rope 3, 5 is wound around the deflection pulley 2, 4, the lower the tension at the connection point 18, 19 of the respective rope 3, 5 to the associated deflection pulley 2, 4. It has been shown that the tension at the connection point of the respective rope 3, 5 to the associated deflection pulley 2, 4 is reduced by 50% if the rope 3, 5 is simply wound around the associated deflection pulley 2, 4. Starting with just three turns, depending on the load on the respective rope 3, 5, the load tension at the connection point 18, 19 can be virtually eliminated. With such a rope tensioning device 1, the rope tension can also be maintained for a significantly longer period of time.

[0040] List of reference symbols

[0041] 1 rope tensioning device

[0042] 2 First pulley

[0043] 3 First rope

[0044] 4 Second pulley

[0045] 5 Second rope

[0046] 6 ratchet mechanism

[0047] 7 Preload element

[0048] 8 First spur gears

[0049] 9 Second spur gears

[0050] 10 First direction of rotation

[0051] 11 Second direction of rotation

[0052] 12 Wave

[0053] 13 robots

[0054] 14 Robot arm

[0055] 15 First robot arm segment

[0056] 16 Second robot arm segment

[0057] 17 joint

[0058] 18 First connection point

[0059] 19 Second connection point

[0060] 20 Hexagon circumference a distance

[0061] A point

[0062] B point

[0063] E End effector

[0064] R Radius

[0065] W1 First operating tool

[0066] W2 Second operating tool

Claims

Patent claims 1. Rope tensioning device (1 ), comprising - a first pulley (2) on which a first rope (3) is wound, - a second deflection pulley (4) arranged coaxially to the first deflection pulley (2), on which a second rope (5) is wound, and - a ratchet mechanism (6) comprising a pre-tensioning element (7) for axially pre-tensioning the first deflection pulley (2) in the direction of the second deflection pulley (4), a first spur gear (8) arranged on the first deflection pulley (2) and a second spur gear (9) arranged on the second deflection pulley (3), wherein the spur gears (8, 9) engage with one another in the unactuated state of the cable tensioning device (1) as a result of an axial pre-tensioning force of the pre-tensioning element (7), such that a relative rotation of the deflection pulleys (2, 4) in a first direction of rotation (10) is prevented and a relative rotation of the deflection pulleys (2, 4) in a second direction of rotation (11) opposite thereto is permitted, wherein, when at least one of the deflection pulleys (2, 4) is actuated in the second direction of rotation (11) with an actuating force exceeding a limit value, the spur gears (8,9) slide against each other and thereby displace the first deflection roller (2) relative to the second deflection roller (4) against the axial pretensioning force of the pretensioning element (7) in order to release an adjustment of a rotational position of the deflection rollers relative to each other.

2. Cable tensioning device (1) according to claim 1, characterized in that the respective cable (3, 5) is a polymer cable.

3. Cable tensioning device (1) according to claim 1 or claim 2, characterized by a shaft (12) on which the deflection rollers (2, 4) are rotatably mounted and on which at least one of the deflection rollers (2, 4) is arranged to be axially displaceable.

4. Cable tensioning device (1) according to one of the preceding claims, characterized in that means for receiving an actuating tool (W1, W2) are arranged on the deflection rollers (2, 4).

5. Cable tensioning device (1) according to one of the preceding claims, characterized in that one end of the first cable (3) is fastened to the first deflection pulley (2).

6. Cable tensioning device (1) according to one of the preceding claims, characterized in that one end of the second cable (4) is fastened to the second deflection pulley (5).

7. Cable tensioning device (1) according to one of the preceding claims, characterized in that the pretensioning element (7) is a compression spring.

8. Cable tensioning device (1) according to one of the preceding claims, characterized in that the deflection rollers (2, 4) are of identical design.

9. Cable tensioning device (1) according to one of the preceding claims, characterized in that the respective deflection roller (2, 4) is wound several times by the associated cable (3, 5).

10. Robot (13) comprising a cable tensioning device (1) according to one of the preceding claims.

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