REHABILITATION DEVICE FOR A JOINT

Abstract

 The invention relates to a non-intrusive rehabilitation device (1) suitable for rehabilitating a patient's joint, the joint connecting a first extremity portion to a second extremity portion. The rehabilitation device (1) comprises first grabbing means (11), adapted to grab the first extremity portion; second grabbing means (12), adapted to grab the second extremity portion; and motion means. The motion means are adapted to move the first (11) and/or second (12) grabbing means to cause both a rotation and a translation relative movements between the first grabbing means (11) and the second grabbing means (12), thus performing a joint extension or flexion and traction.

Description

TECHNICAL FIELD

[0001] This invention belongs to the field of devices for rehabilitation of a patient's joint with restricted/reduced range of movement, caused by a traumatic injury, prolonged immobilisation or surgery. This type of devices usually forces a relative movement between two distant portions of the joint.

STATE OF THE ART

[0002] Rehabilitation devices usually comprise grabbing means for grabbing some portions of the patient's body and perform relative operations between said portions.

[0003] Several documents describe this type of devices. Documents US 9,271,864 B2, US 7,381,192 B2 and US 6,456,885 B1 show some particular examples of this type of devices, namely comprising a support, a hinge and means for causing a reciprocating bi-directional movement between the support and the hinge. Some of these devices are further adapted to provide complementary treatments, such as neuromuscular electrical stimulation, transcutaneous electrical nerve stimulation or any other action performed by electrodes, which are intended to be placed on the patient's body. These devices are good and suitable for performing known therapeutic methods.

DESCRIPTION OF THE INVENTION

[0004] The invention provides an alternative solution for problem of joint mobilisation in the rehabilitation process, by means of a non-intrusive rehabilitation device suitable for treating a patient's joint according to claim 1. Preferred embodiments of the invention are defined in dependent claims.

[0005] The treated joint connects a first extremity portion to a second extremity portion, comprising a joint rotation axis. This rehabilitation device comprises

first grabbing means, adapted to grab the first extremity portion;

second grabbing means, adapted to grab the second extremity portion; motion means;

wherein the motion means are adapted to

move the first and/or second grabbing means to cause a rotation relative movement between the first grabbing means and the second grabbing means around a rotation axis, thus performing a joint extension or flexion; and

move the first and/or second grabbing means to cause a translational relative movement between the first grabbing means and the second grabbing means, thus performing a joint traction.

[0006] This device advantageously allows performing both a rotational and translational movement between the first and second extremity portion. Further, this device is wearable, unlike the rest of actuatable rehabilitation devices, so it may be used in almost any circumstance.

[0007] In some particular embodiments, the motion means are physically attached to the first and second grabbing means.

[0008] This physical attachment provides a more reliable operation of the rehabilitation device.

[0009] In some particular embodiments, the non-intrusive rehabilitation device further comprises control means, adapted to control the movement of the motion means.

[0010] Control means provide the rehabilitation device with more flexibility and versatility, since the movements may be reproduced in a different order, depending on the patient's needs.

[0011] In some particular embodiments, the control means are adapted to allow setting of predetermined therapy parameters.

[0012] These predetermined therapy parameters may be, but not limited to: the number of repetitions, maximal interaction force, movement amplitude (maximal extension angle, maximal flexion angel, maximal length of traction), movement velocity, etc.

[0013] The movement is controlled in such manner that it maximises the therapeutic gain, while maintaining the safe operating conditions. An example of control paradigm for a session would be to perform translation movement until sufficient traction is achieved, then perform a number of repetitions of joint extension/ flexion movements. Each repetition could be such that extension is performed with higher speed until 90% of the maximal extension is reached, then with a lower speed until maximal extension is reached and then maintain the position for a specific time period, after which flexion is performed until the initial position is reached.

[0014] In some embodiments, the control parameters can be programmed by the operator, be it a therapist, patient or an informal caregiver.

[0015] In some particular embodiments, the non-intrusive rehabilitation device further comprises measuring means adapted to

measure the force of interaction between the extremity and the device;

measure the angle between the first and the second grabbing means, caused by rotation; and

measure the distance between the first and the second grabbing means, caused by translation;

send these measurements to the control means.

[0016] In these embodiments, the data acquired by the measuring means could be used to achieve a closed loop control of the device.

[0017] In some particular embodiments, the non-intrusive rehabilitation device further comprises stimulation and/or motion control means, adapted to act on the first and/or second extremity portion. In still more particular embodiments, the stimulation and/or motion control means are adapted to induce joint relaxation on the first and/or second extremity portion.

[0018] The stimulation could be used to stimulate the efferent nerves in order to produce the movement of the joint through contraction of the muscles in the targeted extremity portion, or it could be used to stimulate the afferent nerves in order to alleviate the pain.

[0019] In the embodiments where the device comprises the control means to regulate both motion and stimulation means, implementing different control paradigms. Examples of paradigms are muscle relaxation, which can extend the range of motion for the joint in question, or muscle strengthening, which increases the muscle tone of the weakened muscles.

[0020] In some particular embodiments, the motion means comprise

a first displacement means; and

a worm gear having a wheel rotation axis, the worm gear being engaged to the first displacement means;

wherein the worm gear is adapted to rotate around the wheel rotation axis and translate in a direction which is perpendicular to the wheel rotation axis, thus making the first or second grabbing means have a rotational and/or translational relative movement with respect to the second or first grabbing means.

[0021] These further elements help to perform the rotation and translation movement between the first and second extremity portions in a simple and reliable way.

[0022] In some particular embodiments, the first displacement means comprise one of a cable driven motor, a hydraulic motor, a directly coupled motor or a magnetic motor. In other embodiments, the first displacement means is a first worm screw having a first worm rotation axis, and the wheel rotation axis is perpendicular to the first worm rotation axis.

[0023] There are at least two main embodiments of this non-intrusive rehabilitation device.

[0024] In the first one, the motion means further comprises

a main cam being solidly attached to the worm gear, the main cam comprising a main cam guide;

a first, a second and a third secondary cam guides, solidly attached to the first grabbing means, each of the second and third secondary cam guides comprising a straight portion and a curved portion;

a cam follower, solidly attached to the second grabbing means, the cam follower comprising a first pin, a second pin and a third pin, the first pin being arranged to follow both the main cam guide and the first secondary cam guide, the second pin being arranged to follow the second secondary cam guide and the third pin being arranged to follow the third secondary cam guide,

in such a way that when the pins of the cam follower follow the straight portion of the secondary cam guides, the cam follower follows a straight trajectory, and when cam follower follow the curved portion of the secondary cam guides, the cam follower follows a rotatory trajectory.

[0025] In this first main embodiment, the translation and rotation of the one grabbing means in respect to the other grabbing means is achieved through a cam-follower mechanism. This solution is characterised by the fact that a single actuator can achieve the required complex movement, and by the fact than the movement trajectory is predefined and set.

[0026] In this second main embodiment of the non-intrusive rehabilitation device,

the motion means further comprises a second worm screw with a second worm rotation axis parallel to the first worm rotation axis;

the worm gear is solidly attached to the second grabbing means;

the worm gear is further engaged with the second worm screw;

in such a way that the difference between the rotation velocities of the first worm screw and the second worm screw causes the worm gear to rotate with respect to the wheel rotation axis, and the sum of the rotation velocities of the first worm screw and the second worm screw causes the worm gear to translate in a direction parallel to the first worm rotation axis.

[0027] In this second main embodiment, a worm gear is connected to two parallel, symmetrically placed worm screws connected to independent actuators. The worm gear axis is connected to the slider, parallel to the worm screws. The worm gear can rotate and/or translate depending on the movements of the two worm screws. This solution is characterised by the independent control of the two degrees of freedom (rotation and translation) resulting in an infinite number of possible trajectories.

[0028] In some particular embodiments, the non-intrusive rehabilitation device further comprises at least one stop, arranged to limit the movement of the worm gear.

[0029] In some particular embodiment of the invention, the non-intrusive rehabilitation device comprises the following elements:

a fixed base 71, comprising guide rails 72;

first grabbing means 11, attached to the fixed base 71;

a translation base 73, adapted to move along the guide rails 72 of the fixed base 71;

a first motor 74 mechanically connected to the translation base 73, being thus able to cause a translation movement of this translation base 73 with respect to the fixed base 71;

a worm gear 4 attached to the translation base 73, but free to rotate with respect to the translation base 73;

a second motor 81 mechanically connected to the worm gear 4, being thus able to cause a rotation movement of this worm gear 4 with respect to the translation base 73;

a cam follower 6 attached to the worm gear 4;

second grabbing means 12 attached to the cam follower 6.

[0030] In another inventive aspect, the invention provides a design method for a non-intrusive rehabilitation device according to the previous inventive aspect. The method comprises the following steps:

measure the patient's joint rotation axis

adapt the motion means in such a way that the rotation axis of the rotation relative movement between the first grabbing means and the second grabbing means is made coincident with the joint rotation axis.

[0031] Advantageously, this method provides the possibility that the motion means are adapted to ensure that the centre of rotation of the rotation relative movement between the first grabbing means and the second grabbing means is aligned with the physiological centre of rotation of the treated joint, throughout the entire range of the motion.

[0032] In some particular embodiments, the adaptation of the motion means comprises programming control means in a way that the control means are capable of varying the rotation axis of the rotation relative movement between the first grabbing means and the second grabbing means, either automatically or manually.

[0033] In some particular embodiments, the adaptation of the motion means comprises the designing of first, second and third secondary cam guides, in such a way that a centre of a circular portion of these first, second and third secondary cam guides is made part of the joint rotation axis.

[0034] The possibility that this cam guides are adaptable makes the non-intrusive rehabilitation device easily customizable for each patient.

[0035] In some particular embodiments, the adaptation of the motion means comprises programming control means so that first and second worm screws move according to a predetermined pattern.

[0036] In this embodiment, the control of the two degrees of freedom (translation and rotation) may be independent. Thus, the alignment of the relative movement rotation axis with the joint rotation axis can be ensured by dynamically controlling the position of the device's centre of rotation by closing the control loop through the measurement of interaction force and performing the movement in a way that minimises the non-tangential component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

Figure 1 shows a first embodiment of a rehabilitation device according to the invention.

Figures 2a to 2c show the operation of this first embodiment of a rehabilitation device.

Figure 3 shows a second embodiment of a rehabilitation device according to the invention.

Figures 4a to 4c show movement examples of a rehabilitation device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] Figures 1 and 3 show some embodiments of a non-intrusive rehabilitation device according to the invention, suitable for rehabilitating a patient's joint.

[0039] This joint is typically a knee or an elbow, and has two extremity portions: the first extremity portion (typically the upper arm or the thigh) and the second extremity portion (typically the forearm or the calf).

[0040] A rehabilitation device according to the invention is therefore intended to cause a relative movement between the first extremity portion and the second extremity portion. To achieve this goal, it has two grabbing means 11, 12, which are adapted and intended to grab the extremity portions.

[0041] This device further comprises motion means. These motion means are adapted to act on the first and/or second grabbing means 11, 12. As the grabbing means are attached, when the device is in operation, to the extremity portions of a joint, there is no need to move both grabbing means 11, 12, but only one of them. In the embodiments shown in these figures, the motion means move the second grabbing means. In different embodiments, the motion means may be arranged to move the first grabbing means instead.

[0042] The motion means are therefore adapted to move the second grabbing means to cause both a rotation relative movement and a translational relative movement between the first grabbing means and the second grabbing means.

[0043] Figure 1 shows a first embodiment of this rehabilitation device 1. In this first embodiment, the motion means comprises the following elements:

a first worm screw 31 having a first worm rotation axis 310;

a worm gear 4 having a wheel rotation axis 40, the worm gear 4 being engaged to the first worm screw 31 and the wheel rotation axis 40 being perpendicular to the first worm rotation axis 310;

a main cam 41 being solidly attached to the worm gear 4, the main cam 41 comprising a main cam guide 42;

a first 51, a second 52 and a third 53 secondary cam guides, solidly attached to the first grabbing means 11, the first 51, second 52 and third 53 secondary cam guides comprising a straight portion and a curved portion;

a cam follower 6, solidly attached to the second grabbing means 12, the cam follower 6 comprising a first pin 61, a second pin 62 and a third pin 63, the first pin 61 being arranged to follow both the main cam guide 42 and the first secondary cam guide 51, the second pin 62 being arranged to follow the second secondary cam guide 52 and the third pin 63 being arranged to follow the third secondary cam guide 53.

[0044] When the first worm screw 31 moves, the worm gear 4, which is engaged to the first worm screw 31, rotates. When the worm gear 4 rotates, the main cam 41, which is solidly attached to the worm gear 4, also rotates with the worm gear 4. As the main cam 41 comprises a main cam guide 42, the main cam guide 42 also rotates.

[0045] The secondary cam guides 51, 52, 53 do not rotate with the main cam guide 42, as the secondary cam guides 51, 52, 53 are not attached to the worm gear 4, but to the first grabbing means 11. These secondary cam guides 51, 52, 53, together with the main cam guide 42, will serve as guides for the cam follower 6 which is attached to the second grabbing means 12.

[0046] The first pin 61 of the cam follower 6 is guided by two different cam guides: the main cam guide 42, which moves, and the first secondary cam guide 51, which is fixed. Hence, the movement of the main cam guide 42 will make this first pin 61 advance along the first secondary cam guide 51 where this first pin 61 is inserted.

[0047] In this embodiment, this rehabilitation device 1 further comprises different additional aids, such as stimulation means 101 for muscle strengthening and pain management, as integral part of the rehabilitation.

[0048] The movement of the motion means is controlled by some control means. These control means control the movement velocity, duration and direction. In this embodiment, the controllable element of the rehabilitation device is the rotation of the first worm screw.

[0049] Figures 2a to 2c shows the operation of this embodiment of a rehabilitation device. Figure 2a shows the rehabilitation device 1 in a rest position, with the cam follower 6 being located at the beginning of the straight portion of the secondary cam guides. As the first, second and third secondary cam guides comprise a straight portion and a curved portion, the cam follower is forced to follow a straight trajectory and then a curved trajectory. This is shown in figures 2b and 2c. This makes the second extremity portion displace in a translational movement with respect to the first extremity portion and then a rotation movement with respect to the first extremity portion. In the movement of this embodiment of the rehabilitation device 1, as can be seen in these figures, the straight movement takes place before the curved movement. However, once the curved portion of the secondary cam guides is reached, the curved movement may be executed forwards and backwards any time it is needed.

[0050] Figure 3 shows a second embodiment of a rehabilitation device 1 according to the invention. In this second embodiment, the motion means comprises the following elements:

a first worm screw 31 having a first worm rotation axis 310 and adapted to rotate according to the right-hand rule;

a second worm screw 32 with a second worm rotation axis 320 parallel to the first worm rotation axis 310 and adapted to rotate according to the right-hand rule; and

a worm gear 4 having a wheel rotation axis 40, the worm gear 4 being engaged to the first 31 and to the second 32 worm screw and the wheel rotation axis 40 being perpendicular to the first 310 and to the second 320 worm rotation axis.

[0051] The worm gear 4 is solidly attached to the second grabbing means 12, so in this second embodiment, the movement of the second grabbing means 12 is directly achieved by moving the worm gear 4.

[0052] This embodiment is able to move the worm gear 4, and then the second grabbing means 12, with more freedom than the first embodiment, as translation and rotation movements may be communicated to the worm gear 4 in any combination with no predetermined order.

[0053] In the embodiment of this figure 3, the rehabilitation device 1 further comprises at least one stop, arranged to limit the movement of the worm gear.

[0054] The two worm screws 31, 32 which are engaged with the worm gear 4 are controlled to cause in the worm gear 4 a rotation movement, a translation movement or even a combination of such. Figures 4a to 4c show different movement examples.

[0055] As shown in figure 4a, when the two worm screws 31, 32 move in the same direction with the same velocity, the worm gear 4 is translated with no rotation, and the translation velocity is proportional to the sum of the rotation velocity of the first 31 and second 32 worm screws. The direction of the translational velocity of the worm gear 4 depends on the direction of rotational velocities of the worm screws 31, 32. If the direction of the rotational velocities of the worm screws 31, 32 is clockwise then the direction of the translational velocity of the worm gear 4 is from right to the left as shown in the figure 4a. If the direction of the rotational velocities of the worm screws 31, 32 is counter clockwise then the direction of the translational velocity of the worm gear 4 is from right to the left, opposite as what is shown in the figure 4a.

[0056] As shown in figure 4b, when the two worm screws 31, 32 move in opposite directions with the same velocity, the worm gear 4 is rotated with no translation, and the rotation velocity is proportional to the difference of the rotation velocity of first 31 and second 32 worm screws. This difference is calculated considering the sign of the movement: if they are moving with the same velocity in opposite directions, the difference will be twice the rotation velocity of one of them velocity is proportional to the difference of the rotation velocity of the first 31 and second 32 worm gears. The direction of the rotational velocity of the worm gear 4 depends on the direction of rotational velocities of the worm screws 31, 32. If the direction of the rotational velocity of the first worm screw 31 is clockwise and the direction of the rotational velocity of the second worm screw 32 is counter clockwise then the direction of the rotational velocity of the worm gear 4 is clockwise as shown in figure 4b. If the direction of the rotational velocity of the first worm screw 31 is counter clockwise and the direction of the rotational velocity of the second worm screw 32 is clockwise then the direction of the rotational velocity of the worm gear 4 is counter clockwise, opposite to what is shown in figure 4b.

[0057] When two worm screws 31, 32 move in the same direction, but with different velocities, the worm gear 4 rotates and translates. The translation velocity is proportional to the sum of the rotation velocity of the first 31 and second 32 worm screws and the rotation velocity is proportional to the difference of the rotation velocity of first 31 and second 32 worm screws.

[0058] As shown in figure 4c, when two worm screws 31, 32 move in different directions, but with different velocities, the worm gear 4 rotates and translates. The translation velocity is proportional to the sum of the rotation velocity of the first 31 and second 32 worm screws and the rotation velocity is proportional to the difference of the rotation velocity of first 31 and second 32 worm screws.

[0059] To sum up, the difference between the rotation velocities of the first worm screw and the second worm screw causes the worm gear to rotate with respect to the rotation axis, and the sum of the rotation velocities of the first worm screw and the second worm screw causes the worm gear to translate in a direction parallel to the rotation axis. As in these differences and sums the sign of the rotation velocity is considered, it is possible to move the worm gear with a wide range of rotation and translation movements.

[0060] Figure 5 shows a third embodiment of a rehabilitation device 1 according to the invention. In this third embodiment, this rehabilitation device 1 comprises the following elements:

a fixed base 71, comprising guide rails 72;

first grabbing means 11, attached to the fixed base 71;

a translation base 73, adapted to move along the guide rails 72 of the fixed base 71;

a first motor 74 mechanically connected to the translation base 73, being thus able to cause a translation movement of this translation base 73 with respect to the fixed base 71;

a worm gear 4 attached to the translation base 73, but free to rotate with respect to the translation base 73;

a second motor 81 mechanically connected to the worm gear 4, being thus able to cause a rotation movement of this worm gear 4 with respect to the translation base 73;

a cam follower 6 attached to the worm gear 4;

second grabbing means 12 attached to the cam follower 6.

[0061] In this embodiment, each separate first 74 and second 81 motor provide independent translation and rotation movements to the cam follower 6, and thus to the second grabbing means 12. In this embodiment, the first motor 74 provides translation movement to the translation base 73 by means of first pulleys 75 and a first belt 76 and the second motor 81 provides rotation movement to the worm gear 4 by means of a second pulley 82 and a second belt 83.

[0062] In this embodiment, the worm gear 4 is moved by means of the second motor 81 and a pulley 82 and belt 83 system. However, in other embodiments, this coupling between the motor and the worm gear may be made by different means, either directly or by magnetic coupling, or by cable or by any other technology which is available for the person skilled in the art. The same applies to the coupling between the first motor 74 and the translation base 73.

Claims

1. Non-intrusive rehabilitation device (1) suitable for rehabilitating a patient's joint, the joint connecting a first extremity portion to a second extremity portion, the joint comprising a joint rotation axis, the rehabilitation device (1) comprising:

first grabbing means (11), adapted to grab the first extremity portion;

second grabbing means (12), adapted to grab the second extremity portion;

motion means;

wherein the motion means are adapted to

move the first (11) and/or second (12) grabbing means to cause a rotation relative movement between the first grabbing means (11) and the second grabbing means (12) around a rotation axis, thus performing a joint extension or flexion; and

move the first (11) and/or second (12) grabbing means to cause a translational relative movement between the first grabbing means (11) and the second grabbing means (12), thus performing a joint traction.

2. Non-intrusive rehabilitation device (1) according to claim 1, wherein the motion means are physically attached to the first (11) and second (12) grabbing means.

3. Non-intrusive rehabilitation device (1) according to any of the preceding claims, further comprising control means (2), adapted to control the movement of the motion means.

4. Non-intrusive rehabilitation device (1) according to claim 3, wherein the control means are adapted to allow setting of predetermined therapy parameters.

5. Non-intrusive rehabilitation device (1) according to any of claims 3 or 4, further comprising measuring means adapted to

measure the force of interaction between the extremity and the device;

measure the angle between the first and the second grabbing means, caused by rotation; and

measure the distance between the first and the second grabbing means, caused by translation;

send these measurements to the control means.

6. Non-intrusive rehabilitation device (1) according to any of the preceding claims, further comprising stimulation and/or motion control means (101), adapted to act on the first (11) and/or second (12) extremity portion.

7. Non-intrusive rehabilitation device (1) according to claim 6, wherein the stimulation and/or motion control means are adapted to induce joint relaxation on the first (11) and/or second (12) extremity portion.

8. Non-intrusive rehabilitation device (1) according to any of the preceding claims, wherein the motion means comprise

a first displacement means

a worm gear (4) having a wheel rotation axis (40), the worm gear (4) being engaged to the first displacement means;

wherein the worm gear (4) is adapted to rotate around the wheel rotation axis (40) and translate in a direction which is perpendicular to the wheel rotation axis (40), thus making the first (11) or second (12) grabbing means have a rotational and/or translational relative movement with respect to the second (12) or first (11) grabbing means.

9. Non-intrusive rehabilitation device (1) according to claim 8, wherein the first displacement means comprise one of a cable driven motor, a hydraulic motor, a directly coupled motor or a magnetic motor.

10. Non-intrusive rehabilitation device (1) according to claim 8, wherein the first displacement means is a first worm screw (31) having a first worm rotation axis (310), and the wheel rotation axis (40) is perpendicular to the first worm rotation axis (310).

11. Non-intrusive rehabilitation device (1) according to claim 10, wherein the motion means further comprises

a main cam (41) being solidly attached to the worm gear (4), the main cam (41) comprising a main cam guide (42);

a first (51), a second (52) and a third (53) secondary cam guides, solidly attached to the first grabbing means (11), each of the second (52) and third (53) secondary cam guides comprising a straight portion and a curved portion;

a cam follower (6), solidly attached to the second grabbing means, the cam follower comprising a first pin (61), a second pin (62) and a third pin (63), the first pin (61) being arranged to follow both the main cam guide (42) and the first secondary cam guide (51), the second pin (62) being arranged to follow the second secondary cam guide (52) and the third pin (63) being arranged to follow the third secondary cam guide (53),

in such a way that when the pins (61, 62) of the cam follower (6) follow the straight portion of the secondary cam guides (51, 52), the cam follower (6) follows a straight trajectory, and when cam follower (6) follow the curved portion of the secondary cam guides (51, 52), the cam follower (6) follows a rotatory trajectory.

12. Non-intrusive rehabilitation device (1) according to claim 10, wherein

the motion means further comprises a second worm screw (32) with a second worm rotation axis (320) parallel to the first worm rotation axis;

the worm gear (4) is solidly attached to the second grabbing means (12);

the worm gear (4) is further engaged with the second worm screw (32);

in such a way that the difference between the rotation velocities of the first worm screw (31) and the second worm screw (32) causes the worm gear (4) to rotate with respect to the wheel rotation axis (40), and the sum of the rotation velocities of the first worm screw (31) and the second worm screw (32) causes the worm gear (4) to translate in a direction parallel to the first worm rotation axis (310).

13. Non-intrusive rehabilitation device (1) according to claim 12, further comprising at least one stop (7), arranged to limit the movement of the worm gear (4).

14. Method for designing a non-intrusive rehabilitation device (1) according to any of the preceding claims, wherein the method comprises the steps of

measure the patient's joint rotation axis

adapt the motion means in such a way that the rotation axis of the rotation relative movement between the first grabbing means (11) and the second grabbing means (12) is made coincident with the joint rotation axis.

15. Method according to claim 14, wherein the adaptation of the motion means comprises programming control means in a way that the control means are capable of varying the rotation axis of the rotation relative movement between the first grabbing means (11) and the second grabbing means (12), either automatically or manually.

16. Method according to claim 14, wherein the adaptation of the motion means comprises the designing of first, second and third secondary cam guides, in such a way that a centre of a circular portion of these first, second and third secondary cam guides is made part of the joint rotation axis.

17. Method according to claim 14, wherein the adaptation of the motion means comprises programming control means so that first and second worm screws move according to a predetermined pattern.

Drawing