Patent Description:
As known, exoskeletons are applied to aid a person in movement, such as in the rehabilitation of a patient, or in the manufacturing industry, to help operators lift or move heavy loads, or to hold arms raised for long periods of time.

Elastic load-balancing mechanisms, in which the movement of an element that is rotated is counterbalanced by the elastic force of a spring under tension, are known in the art. See, for example, patent publications <CIT>, <CIT>, <CIT>.

With exoskeletons, the need is felt to leave plenty freedom of movement to the wearer, not only relative to the limb involved in rehabilitation or the execution of certain movements, but to the whole body.

<CIT> discloses a mechanism for elastically balancing loads applied to the exoskeleton the mechanism comprising: a rigid connection element, a lever, one flexible traction element and at least one compression spring. Other mechanisms for elastically balancing loads are known from <CIT>, <CIT>, <CIT>, and <CIT>.

Thus, the present invention aims to provide an exoskeleton of the type specified above, primarily addressing the problem of constructing an elastic mechanism, incorporated in the exoskeleton, having as compact of dimensions as possible, while still being able to be loaded elastically and to return an adequate elastic force to the user. An additional object of the invention is to obtain a robust and mechanically simple balancing mechanism.

The above and other objects and advantages are fully achieved according to the present invention by an exoskeleton having the features defined in the appended independent claim <NUM>. Preferred embodiments are specified in the dependent claims, the content of which is to be understood as an integral part of the description that follows.

In summary, the invention is based on the idea of equipping an exoskeleton with a compensating mechanism that, due to the presence of a lever, allows the use of a very stiff compression spring able to return a particularly high intensity force while occupying a small footprint.

According to one aspect, the invention provides an exoskeleton comprising a mechanism for elastically balancing loads applied to the exoskeleton, where the mechanism comprises:.

Further features and advantages of this invention will become clear from the detailed description that follows, given purely by way of non-limiting example with reference to the accompanying drawings, in which:.

Referring initially to <FIG>, the number <NUM> designates an exoskeleton, applied in this example to a user's shoulder to move integrally therewith. Reference to this possible field of application should in no way be interpreted as limiting. Those skilled in the art will recognize that the principle of operation of the balancing mechanism disclosed herein is applicable both to rehabilitative exoskeletons other than the one in <FIG> and applicable to other parts of the human body, and to exoskeletons that may be used in fields other than biomedical engineering, such as in the manufacturing industry.

The exoskeleton <NUM> comprises a mechanism <NUM> for elastically balancing loads applied to the exoskeleton. The mechanism <NUM> comprises a connection element <NUM> and a housing <NUM> mutually pivoted about a first axis of oscillation <NUM>, in this example a horizontally oriented axis. The connection element <NUM> and the housing <NUM> are two rigid elements that may be attached to two additional elements of the exoskeleton, respectively. In the present example, the housing <NUM> is attached to a proximal part <NUM> of the exoskeleton, while the connection element <NUM> is attached to a distal element <NUM> of the exoskeleton, which follows the movements of the user's body, in this example, the movements of the user's shoulder.

In the embodiment shown in the drawings, the connection element <NUM> comprises a plate portion <NUM> with holes <NUM> for attaching to the movable element <NUM> of the exoskeleton, and two lugs <NUM> supporting an axis <NUM> arranged along the first axis of oscillation <NUM>. One end <NUM> of the housing <NUM> is hinged to the axis <NUM>. For attachment to the exoskeleton, the housing <NUM> has attachment means <NUM>, in this example in the form of a bushing (<FIG>).

According to an embodiment, an eccentric element or cam <NUM> is rotationally integral to the connection element <NUM> around the first axis of oscillation <NUM>. Preferably, as in the example shown, there are two eccentric elements (or cams) <NUM>, <NUM> spaced along the axis of oscillation <NUM>. Each eccentric element <NUM>, <NUM> has a radially outer eccentric surface <NUM> and a securing point <NUM> where a first end <NUM> of a respective flexible and elastically inextensible traction element <NUM>, <NUM> is attached to be rotationally integral with the connection element <NUM> about the first axis of oscillation.

At least one lever <NUM>, preferably two parallel levers <NUM>, <NUM>, is rotatably mounted on the housing <NUM> about a second axis of oscillation <NUM> parallel to the first axis of oscillation <NUM>. The levers <NUM>, <NUM> are hinged to the housing at their first ends <NUM> at the second axis of oscillation, and each has a second end <NUM> secured to a respective second end <NUM> of the two traction elements <NUM>, <NUM>.

The traction elements <NUM>, <NUM> may comprise chains or cables or other flexible and inextensible bodies.

Preferably, as in the illustrated embodiment, each traction element <NUM>, <NUM> incorporates a respective adjusting device <NUM>, in this example, a threaded adjusting device, for adjusting the length of the respective traction element.

The housing comprises at least one elastic element in the form of a compression spring <NUM>, elastically compressed between a base <NUM> integral with the housing and arranged on the side of the first axis of oscillation <NUM>, and a head <NUM> movable along the housing arranged farthest from the first axis of oscillation <NUM> and nearest to the second axis of oscillation <NUM>, and acting in a thrust relationship against an intermediate portion <NUM> of the lever or of each lever <NUM>, <NUM>, at an intermediate position between the second axis of oscillation <NUM> and the second end <NUM> of the levers <NUM>, <NUM>.

The head <NUM> may appropriately rest on the lever <NUM>, <NUM> and act against it in a thrust relationship without being articulately connected thereto.

Two or more parallel and cooperating compression springs <NUM> may be provided, acting in a thrust relationship against the levers <NUM>, <NUM>. The elastic force of compression springs <NUM> tensions the traction elements <NUM>, <NUM>. The adjusting devices <NUM> allow the preload of the compression spring or springs <NUM> to be adjusted.

Preferably, as shown in <FIG> and <FIG> the compression spring <NUM> is accommodated within the housing <NUM> and is guided within it in its compression and extension movements.

Preferably, as illustrated in the example of <FIG>, the mechanism <NUM> comprises two or more levers <NUM>, <NUM> and a corresponding number of said traction elements <NUM>, <NUM>, each associated with a respective lever and lying in parallel planes, perpendicular to the axes of oscillation <NUM>, <NUM>.

The operation of the mechanism <NUM> is as follows. Starting from an initial or rest position (<FIG> and <FIG>), the compression spring <NUM> is distended or at most subjected to a preload determined by the calibration of the adjusting device <NUM>. When a movement imparted by the user to the exoskeleton causes a rotation of the distal part <NUM> of the exoskeleton (<FIG>), the resulting relative rotation between the connection element <NUM> and the housing <NUM> about the first axis of oscillation <NUM> also puts the cam <NUM> into rotation, which, by means of the traction elements <NUM>, <NUM>, pulls the lever <NUM>, <NUM> toward the first axis of oscillation, further compressing the spring <NUM>. The reaction of the spring generates about the first axis of oscillation an equal and opposite torque to that produced by the load. The torque generated varies with the angle of rotation of the load due to the different compression of the spring and the particular profile of the radially outer surface <NUM> of the cams <NUM>, <NUM>.

As may be appreciated, the mechanism <NUM> has a very compact configuration due to the presence of a lever combined with a compression spring. With respect to a conventional direct connection between the spring and the flexible element, characteristic of current state-of-the-art systems, the introduction of levers <NUM>, <NUM> enables:.

The compression springs may be very short; since they are not subject to elongation (but rather to shortening, being compression springs), there is no need to provide dedicated spaces in the exoskeleton to allow for their temporary elongation during the operation phase; this results in a further reduction in bulk. The spring, in fact, is the element that most affects the overall size of a mechanism of this type; therefore, the possibility of using stiff springs with a reduced stroke ensures a remarkable compactness of the mechanism.

Preferably, the profile of the radially external surfaces <NUM> of the cam(s) <NUM>, <NUM> is made so that the product of the distance from the axis of rotation <NUM> of the tangential force and said force, generated by the action of the spring <NUM> on the lever <NUM>, is increasing equivalently to the torque to be balanced. In fact, the torque to be balanced, which is equal to the weight of the moving part of the exoskeleton times the horizontal distance of its center of gravity from the axis of rotation, increases with the inclination of the moving part of the exoskeleton with respect to the vertical axis in a manner directly proportional to the sine of the angle of inclination.

According to a preferred embodiment, the radially outer and eccentric surfaces <NUM> are shaped so that they have a greater radial distance from the first axis of oscillation <NUM> in their part farthest from the levers <NUM>, <NUM> and a smaller radial distance in their part closest to the levers <NUM>, <NUM>. The securing points <NUM> of the traction elements <NUM>, <NUM> to the cams <NUM>, <NUM> are located in the parts of the cams where the radial distance of the outer surfaces <NUM> from the first axis of oscillation <NUM> is greatest. The traction elements <NUM>, <NUM>, winding on the radially outer surfaces of the cams, act tangentially to the first axis of rotation of the cams, always ensuring the required torque as the spring compresses.

According to the prior art, a direct connection between the spring and the element that winds on the cam forces the use of a spring with useful travel at least equal to the entire perimeter of the cam. This results in a long spring, which increases the bulk. The free length of the spring strongly conditions the axial dimension of the system, which is the preponderant and most difficult one to limit. According to one aspect of the present invention, by instead exploiting the lever ratio at the same cam perimeter, the required travel of the spring is reduced; therefore, springs with higher stiffness and smaller travel, i.e., shorter, may be used.

An advantage related to the parallelism between the axis of the compression spring <NUM> and the traction element <NUM>, <NUM> will also be appreciated: if, as in the present state of the art, the line of action of the spring and that of the element that winds on the cam may not be arranged parallel and close together, the dimension perpendicular to the axes of action of the flexible element is greatly affected. In contrast, the mechanism described here arranges all the elements on extremely close parallel straight lines, so that the transverse dimension of the device is little larger than the footprint of the individual elements.

The described system finds its application whenever it is necessary to balance a load free to rotate about a non-barycentric axis while minimizing the size of the mechanism.

Claim 1:
An exoskeleton (<NUM>) comprising a mechanism (<NUM>) for elastically balancing loads applied to the exoskeleton, the mechanism (<NUM>) comprising:
a rigid connection element (<NUM>) and a rigid housing (<NUM>) mutually pivoted to one another about a first axis of oscillation (<NUM>) and attachable to respective relatively rotatable parts (<NUM>, <NUM>) of the exoskeleton;
at least one lever (<NUM>, <NUM>) rotatably mounted to the housing (<NUM>) about a second axis of oscillation (<NUM>) parallel to the first axis of oscillation (<NUM>);
at least one flexible traction element (<NUM>, <NUM>) having a first end (<NUM>) rotationally secured to the connection element (<NUM>) with respect to the first axis of oscillation (<NUM>) and a second end (<NUM>) secured to said lever (<NUM>, <NUM>) at a securing point (<NUM>) spaced from the second axis of oscillation (<NUM>);
at least one compression spring (<NUM>) elastically compressed between a base (<NUM>) integral with the housing (<NUM>) and arranged on the side of the first axis of oscillation (<NUM>), and a head (<NUM>) movable along the housing and farther from the first axis of oscillation (<NUM>) and closer to the second axis of oscillation (<NUM>), the head (<NUM>) acting in a thrust relationship, away from the first axis of oscillation, against a portion (<NUM>) of the lever (<NUM>, <NUM>) intermediately between the second axis of oscillation (<NUM>) and the securing point (<NUM>) to the second end (<NUM>) of the traction element (<NUM>, <NUM>).