Patent Description:
In particular, the invention is suitable to be used to connect an end effector (preferably a robotic hand or other prosthetic device) to a support (such as a suitably prosthetic robotic arm), thereby allowing reciprocal movement of the end effector and the support. In detail, the artificial wrist is suitable for use in the industrial or preferably prosthetic field.

Artificial wrists for the manipulation of prosthetic limbs are currently known and used to couple a prosthetic device (usually a prosthetic hand) to a robotic/human limb or a residual limb of the user, thus allowing the prosthetic device to rotate relative to the support.

Briefly, known artificial wrists provide a base element bound to the support, an element which moves relative to the base element and binds to the prosthetic device; and a hinge defining an axis of rotation between the elements and therefore between the support and the device.

An example of an artificial wrist is described in <CIT>.

In this artificial wrist the hinge consists of a cross-shaped body interposed between the base element and the movable element and provided with two pairs of arms perpendicular to each other and defining two axes of rotation for said elements; torsion springs, one for each arm, having one end integral with the base element and the other with the movable element, so as to oppose their reciprocal rotation. A second example of an artificial wrist is described in <CIT>.

The hinge of this wrist consists of a pin hinging the elements, a rack engaging the pinion so that rotation of the pinion causes translation of the rack, and springs between the rack and the base element working in opposition to the translation of the rack.

The described prior art has a few major drawbacks.

In fact, artificial wrists are equipped with complex mechanics that are difficult to achieve considering the small dimensions required by artificial wrists.

Another drawback is that artificial wrists (especially if they are prosthetic) require limited dimensions and weights to make their use practical and comfortable, but, as can be easily understood from the examples given above, they have a multiplicity of elements which impose considerable weight and large dimensions.

These drawbacks result in poor comfort of use of artificial prosthetic wrists and high manufacturing costs.

In this context, the technical task underlying the present invention is to devise an artificial wrist, which is capable of substantially obviating at least some of the above-mentioned drawbacks.

Within the scope of said technical task, a major object of the invention is to obtain a low-weight and small-sized artificial wrist.

Another major object of the invention is to provide an artificial wrist, which is low-cost and above all practical and comfortable to use.

The technical task and the specified objects are achieved by means of an artificial wrist as claimed in appended claim <NUM>. Exemplary preferred embodiments are described in the dependent claims.

The features and advantages of the invention will be clarified in the following detailed description of preferred embodiments of the invention, with reference to the accompanying drawings, in which:.

Herein, the measures, values, shapes and geometric references (such as perpendicularity and parallelism), when used with words like "about" or other similar terms such as "approximately" or "substantially", are to be understood as except for measurement errors or inaccuracies due to production and/or manufacturing errors and, above all, except for a slight divergence from the value, measure, shape or geometric reference with which it is associated. For example, these terms, if associated with a value, preferably indicate a divergence of not more than <NUM>% from said value.

Furthermore, when used, terms such as "first", "second", "higher", "lower", "main" and "secondary" do not necessarily identify an order, a priority relationship or a relative position, but can simply be used to distinguish more clearly the different components from each other.

Unless otherwise indicated, the measurements and data provided in this document are to be considered using International Standard Atmosphere ICAO (ISO <NUM>).

With reference to the Figures, the artificial wrist according to the invention is indicated as a whole by the number <NUM>.

It is suitable to be used to connect an end effector to a support, allowing at least one rotation between the end effector and the support.

The end effector is preferably a prosthetic device, and specifically a robotic hand. The support is identifiable as a suitably prosthetic robotic arm or an amputated limb.

The artificial wrist <NUM> comprises a static body <NUM> adapted to be bound to a support; a movable body <NUM> adapted to be bound to an end effector; and at least one junction block <NUM> between the static body <NUM> and the movable body <NUM> and defining an axis of rotation 4a between the static body <NUM> and the movable body <NUM>.

Preferably, the wrist <NUM> comprises a single junction block <NUM> and therefore the bodies <NUM> and <NUM> can be moved relative to each other along a single axis of rotation 4a.

The static body <NUM> defines a first, suitably barycentric longitudinal axis 2a.

The first longitudinal axis 2a is perpendicular to the axis of rotation 4a and appropriately incident to said axis of rotation 4a.

The static body <NUM> comprises first fastening means <NUM> for fastening the static body <NUM> to the support.

The movable body <NUM> defines a second, suitably barycentric longitudinal axis 3a.

The second longitudinal axis 3a is perpendicular to the axis of rotation 4a and appropriately incident to said axis of rotation 4a.

The movable body <NUM> comprises second fastening means <NUM> for fastening the movable body <NUM> to the end effector.

The fastening means <NUM> and <NUM> are known in the art.

The junction block <NUM> comprises a hinge <NUM> defining the axis of rotation 4a.

The junction block <NUM> is suitable to allow and at the same time oppose rotation between the static body <NUM> and the movable body <NUM>, suitably around the axis of rotation 4a.

It defines, for the artificial wrist <NUM>, a rest position (<FIG>) in which the resulting torque on the bodies <NUM> and <NUM> is zero and therefore the bodies <NUM> and <NUM> remain stationary relative to each other; and at least one activation position (<FIG>) in which the resulting torque on the bodies <NUM> and <NUM> is non-zero, causing mutual rotation of the bodies <NUM> and <NUM>. More specifically, in the activation position, mutual rotation of the bodies <NUM> and <NUM> results in a torque acting on the bodies <NUM> and <NUM>, which is opposite to that generating said mutual rotation and such as to bring the bodies <NUM> and <NUM> back to the rest position.

In the rest configuration, the longitudinal axes 2a and 3a are substantially parallel to each other, and specifically one is the continuation of the other.

In the one or more activation configurations, the longitudinal axes 2a and 3a are inclined to each other.

The junction block <NUM> comprises at least one cable <NUM> bound to the static body <NUM> and the movable body <NUM>; and elastic means <NUM> placing the cable <NUM> under tensile stress. Preferably, the junction block <NUM> comprises two cables <NUM>, of which a first cable <NUM> is adapted to be tensioned by mutual rotation of the bodies <NUM> and <NUM> in a first direction of rotation, and a second cable <NUM> is adapted to be tensioned by mutual rotation of the bodies <NUM> and <NUM> in a second direction opposite to the first direction of rotation.

The action of the cable <NUM> and the means <NUM> defines the aforesaid resulting torque. Each cable <NUM> has one end bound to the static body <NUM>, preferably in an integral manner. The cables <NUM> are anchored to the static body <NUM> on opposite sides with respect to the axis of rotation 4a, and specifically to the first longitudinal axis 2a.

Each cable <NUM> has the other end bound to the movable body <NUM>, suitably in a non-integral manner as hereinafter better described.

The cable <NUM> is bound to the movable body <NUM> on the opposite side of the static body <NUM>. For this purpose, the movable body <NUM> comprises a channel <NUM> for the passage of the one or more cables <NUM>.

The channel <NUM> has an axis of extension that can be perpendicular to the axis of rotation 4a. Specifically, the axis of extension of the channel <NUM> is inclined to the second longitudinal axis 3a. Alternatively, it is substantially parallel to the second axis 3a.

Preferably, the channel <NUM> comprises a first sector 32a proximal to the static body <NUM> and a second sector 32b inclined to the first sector and located on the opposite side of the first sector 32a with respect to the static body <NUM>.

The first sector 32a has a first axis of extension substantially inclined to the second longitudinal axis 3a.

The second sector 32b has a second axis of extension substantially parallel to and suitably distinct from the second longitudinal axis 3a.

The elastic means <NUM> is suitable to store energy during mutual rotation of the bodies <NUM> and <NUM> moving away from the rest position. In detail, they work in opposition to the movement of at least one cable <NUM> (due to an external torque applied to one of the bodies <NUM> and <NUM>) so as to create a torque on the bodies <NUM> and <NUM>, which is opposite and such as to bring the artificial wrist <NUM> back to the rest position.

In the rest position, the forces of the elastic means <NUM> and of the at least one cable <NUM> mainly cause two opposite and substantially equal torques, so that the resulting torque is zero and therefore such as to maintain the artificial wrist <NUM> in the rest position.

In the activation position, the forces of the elastic means <NUM> and of the at least one cable mainly cause two opposite and substantially different torques, so that the resulting torque is non-zero and therefore such as to bring the artificial wrist <NUM> back to the rest position.

The elastic means <NUM> is preloaded so that in the rest position each cable <NUM> is tensioned.

The elastic means <NUM> is interposed between the movable body <NUM> and said at least one cable <NUM> so that the transition into the activation position causes the cable <NUM> to move, thus loading the elastic means <NUM>.

They can have one end integral with the movable body <NUM> and the other end integral with the at least one cable <NUM> so that mutual rotation of the bodies <NUM> and <NUM> moving away from the rest position, which causes the cable <NUM> to move, loads the elastic means <NUM>.

The elastic means <NUM> comprises a spring, which is suitably a tension spring or specifically a compression spring. Preferably, the elastic means <NUM> is a compression spring, and the end thereof that is integral with the at least one cable <NUM> is located on the opposite side of the static body <NUM> with respect to the movable body <NUM>.

The elastic means <NUM> is preferably housed inside the channel <NUM>, which then guides the sliding of said elastic means <NUM>.

In order to integrally bind the end to the at least one cable <NUM>, the junction block <NUM> may comprise a fastening head <NUM> for fastening the cable <NUM> to the means <NUM>.

The junction block <NUM> may comprise at least one pulley <NUM> defining a groove for the sliding of the at least one cable <NUM>.

The pulley <NUM> is placed at the interface area between the bodies <NUM> and <NUM>.

Preferably, it is bound, and in detail hinged to the movable body <NUM> so as to intercept the cable <NUM> before it reaches the channel <NUM>.

Advantageously, the junction block <NUM> comprises two pulleys <NUM> alongside each other so that the sliding grooves define a duct inside which the at least one cable <NUM> slides, substantially without the possibility of coming out sideways.

The junction block <NUM> may comprise one or more guiding pins <NUM> to direct the at least one cable <NUM>.

The guiding pins <NUM> are located along the path of each cable <NUM> and define surfaces along which the cable <NUM> slides during rotation, and therefore a change in position of the artificial wrist <NUM>.

They may be bound, suitably in an integral manner, to the static body <NUM> and/or to the movable body <NUM>.

Finally, the artificial wrist <NUM> can comprise a locking member <NUM> to couple the movable body <NUM> to the static body <NUM>.

The locking member <NUM> is suitable to integrally couple the bodies <NUM> and <NUM> to each other, preventing their mutual rotation.

It is suitable to lock the artificial wrist <NUM> in one or more activation positions, preferably in the rest position.

The locking member <NUM> is known per se. It can comprise a locking member provided with a pin and two positions of stable equilibrium, and a spring presser, which can be actuated manually by a suitable lever.

The operation of the artificial wrist <NUM>, previously described in structural terms, is as follows.

Once the artificial wrist <NUM> is bound to the support (for example a robotic arm, for example a prosthetic arm, or an amputated limb) and to an end effector, such as a robotic hand, it is ready.

Initially, the artificial wrist <NUM> is in the rest position (<FIG> and <FIG>).

When an external force, for example acting on the end effector, creates a torque commanding mutual rotation of the end effector and the support around the axis of rotation 4a, the bodies <NUM> and <NUM>, i.e. the end effector and the support, mutually rotate with respect to the axis of rotation 4a moving away from the rest position.

This rotation, caused by said external force, between the bodies <NUM> and <NUM> causes one of the two cables <NUM> (for example the first cable) to be tensioned and releases this greater tension on the elastic means <NUM>. The cable <NUM> thus slides in the channel 32b and causes the elastic means <NUM> to be compressed (i.e. storage of energy).

The bodies <NUM> and <NUM> rotate relative to each other until an activation configuration is reached (<FIG>) in which the forces created by the cable <NUM> and the elastic means <NUM> generate a resulting torque counteracting that given by the external force.

It should be pointed out that during this rotation in the artificial wrist <NUM> described herein, representing one of the possible embodiments of the wrist <NUM> according to the invention, only one of the cables <NUM> (for example the first cable) is tensioned while the other cable <NUM> (for example the second cable) is released and, as shown in <FIG>, can become relaxed.

When the external force is no longer applied, the elastic means <NUM> releases the stored energy by causing a rotation opposite to the previous one and such as to bring the artificial wrist <NUM> back to the rest position.

The artificial wrist <NUM> according to the invention achieves important advantages.

In fact, the artificial wrist <NUM> has extremely simple mechanics and is therefore easy to manufacture even considering the small dimensions required.

Another advantage is that the artificial wrist <NUM>, compared to known artificial wrists, has limited dimensions and weight, thus resulting in high comfort of use and low manufacturing costs.

These advantages are due to the innovative use of cables <NUM> and elastic means <NUM> to control the rotation of the wrist <NUM>, particularly to the particular solution chosen for anchoring the cables <NUM>, and more particularly to the interposition of elastic means <NUM> between the cable <NUM> and the movable body <NUM>.

Another advantage is that the artificial wrist <NUM> allows large rotation angles (up to <NUM>° or even larger depending on the selected configuration of the wrist <NUM> according to the invention).

For example, the embodiment described above and shown in <FIG> has the same rotation angle in both directions (extension and flexion) substantially equal to <NUM>°.

The invention is susceptible of variations falling within the scope of the inventive concept as defined by the claims. In one example not falling under the scope of the claimed invention, the elastic means <NUM> and the at least one cable <NUM> may coincide and be identifiable as an elastic cable. Therefore, the junction block <NUM> may comprise at least one elastic cable, and preferably two elastic cables, one operating in the first direction of rotation, the other in the second direction of rotation.

Another possible alternative may comprise integral connection of the at least one cable <NUM> to the movable body and interposition of the elastic means <NUM> between the cable <NUM> and the static body <NUM>, and in particular the creation of a sliding duct for the elastic means <NUM> and the cable <NUM> in the static body <NUM> instead of in the movable body <NUM>.

In this context, all details are replaceable by equivalent elements, and the materials, shapes and dimensions may be any type of materials, shapes and dimensions.

Claim 1:
An artificial wrist (<NUM>) comprising:
- a static body (<NUM>) adapted to be bound to a support;
- a movable body (<NUM>) adapted to be bound to an end effector;
- a junction block (<NUM>) between said static body (<NUM>) and said movable body (<NUM>) and defining at least one axis of rotation (4a) between said static body and said movable body;
and characterised in that said junction block comprises
- at least one cable (<NUM>) having one end bound to said static body (<NUM>) and the other end to said movable body (<NUM>) so as to be moved by mutual rotation of said static body (<NUM>) and said movable body (<NUM>) around said axis of rotation (4a);
- elastic means (<NUM>) placing said cable (<NUM>) under tensile stress and working in opposition to the movement of said cable (<NUM>) so as to define a rest position in which said cable (<NUM>) and said elastic means (<NUM>) exert a zero resulting torque on said static body (<NUM>) and said movable body (<NUM>), and an activation position in which said cable (<NUM>) and elastic means (<NUM>) exert a non-zero resulting torque on said static body (<NUM>) and said movable body (<NUM>), bringing said static body (<NUM>) and said movable body (<NUM>) back to said rest position.