Patent Application
20180185173
The present invention relates to the technical sector concerning actuating devices able to impart movements to bodies.
In the cited technical field are present various types of such actuating devices, commonly used in mechanical applications and in robotics.
In particular, the invention relates to the devices known as artificial muscles or pneumatic muscles.
In these devices, the mechanical work is not obtained from the movement of a piston in a cylinder but, conceptually, by exploiting the elastic deformation of rooms that are pressurized with air or other fluid.
The substantial difference lies in the fact that while a conventional pneumatic actuator has a ‘rigid’ behavior, that means it implements the movement only in the pre-determined mode, for example rectilinear, in an artificial muscle the behavior can vary according to the type of application and It may allow deviations of the thrust directions, or of shooting, because of external events, foreseen or unforeseen.
In the prior art document US2003/0205045A1, the artificial muscle comprises an elastic central cylindrical chamber, interposed between two head members, with the latter ones guided, for example, in the axial direction.
The side surface of said clastic central cylindrical chamber is circumscribed by an annular clastic chamber, whose internal wall is constituted by the same central chamber.
The two chambers are interconnect by a closed circuit pneumatic plant, comprising a connecting duct and a bi-directional pump.
By actuating the pump so that the fluid is removed from the cylindrical central chamber and placed in the annular chamber, a mutual approaching of the head members is obtained, that means a contraction of the artificial muscle.
By reversing the drive direction of the pump, of course, an opposite effect is obtained, with the mutual spacing of the head members, that means an extension of the artificial muscle.
The technique solution described is a relatively simple solution in terms of the operating principle, but in practice the need to have a closed circuit pneumatic system, with relative pump, determines both not negligible undesired dimensions and constructional complexity.
Similar devices are also known as McKibben muscles, in which is provided a cylindrical hollow chamber, tight, made of elastomeric material, adapted to be pressurized with air or other fluid by means of blowing, for example external.
On the outside of said hollow cylindrical chamber is coaxially disposed a braided sleeve, consisting of a first set of flexible and substantially inextensible wires, arranged each according to its own helical path of the same diameter and helix angle but different principles and by a second set of the same flexible and substantially inextensible wires, arranged according to respective helical paths symmetric to those of the above mentioned first set.
The said first and second sets of flexible wires, therefore, form the mesh of the above said sleeve, in which each of sad helical paths is inclined to a same predetermined angle with respect to the longitudinal axis of said device.
The device also comprises two rig d head members, provided at the corresponding ends of the braided sleeve, to which are attached both the head members of the respective threads and the cylindrical hollow chamber.
The rigid head members are adapted to be mechanically connected to external users means.
In an active phase of the device, the blow-in bodies bring pressure into the cylindrical hollow chamber, which interacts with the said braided sleeve: being the latter formed by inextensible threads, it can not follow in a homogeneous way the deformation undergone by the cylindrical hollow chamber, of elastic material.
From extensive studies, researches and experiments, it was found that the decisive factor to determine how the braided sleeve reacts, depends on the angle that each of the helical paths form with the longitudinal axis of said device when it is at rest; more precisely, it is seen that:
At the end of the pressuring action, the device returns to its original position.
In another prior art document, US005165323A, is described a pneumatic actuator similar to a McKibben muscle, comprising an elastic tubular clement, the ends of which are associated to two head members made of rigid material.
The elastic tubular element defines in its interior a chamber, while on the outside is wrapped in adhesion to a reinforcing mesh structure, consisting of threads of tract ion-resistant material, for example polyester, such as to be less yielding than the tubular elastic element.
The threads of the mesh, with the actuator at rest, have a predetermined angle of inclination with respect to the longitudinal axis of the actuator itself, which can be smaller than or greater than a characteristic angle, so-called of ‘stand-by’, that may have the previously indicated value.
Through a hole made in one of said head members, it is possible to pressurize the inner chamber; also in this case you get an approach or a withdrawal of the head members, that means a contraction or in extension of the actuator, in function of the angle of inclination originally established for the threads of the mesh, similarly to what previously said.
In the mentioned document it is claimed the presence of two sleeves which extend from the head members inside the chamber and telescopically mate, in order to guide the axial movement of the actuator.
Among the sleeves are shown sealing rings (O-rings) which isolate the chamber from surrounding possible losses; the volume of the chamber is reduced by the presence of the sleeves and requires a smaller air flow to be pressurized.
The drawback that most complains in the prior art devices classifiable as McKibben muscles concerns the fact that the pneumatic muscle response characteristics are laid down originally in function of the predetermined angle for the threads with respect to the longitudinal axis.
This means that a pneumatic muscle built for contraction will not stretch and vice versa, as well as a muscle that provides the angle exactly at 54.7° C. can not do other than stiffen without changing its extension.
In certain applications, where it is necessary to handle a generic user in opposite directions, therefore, we must combine two of said devices, with understandable constructive complications as well as increase of dimensions and costs.
Another drawback of the known devices concerns the fact that the predetermined angle of inclination not only determines the type of response, but also the extension or contraction stroke length, which can not be changed retrospectively.
Some researchers have experimented a technical solution to obtain actuators that could produce bi-directional movements: such solution provides an auxiliary chamber inside of the main one, adapted to be pressurized independently.
When the auxiliary chamber is not pressurized, the actuator is arranged for a shrinking movement as result of the pressurization of the main chamber; the volume occupied by the auxiliary chamber decreases request of air for the main chamber giving greater strength to the action.
When only the auxiliary chamber is pressurized, it expands axially causing a corresponding lengthening of the device.
The main drawback of this solution concerns the fact that the force exerted by the device is different in the two working conditions, with the one in extension considerably smaller than that in a contraction.
Additionally two power circuits are needed, or at least exchange valves to divert the flow of compressed air towards one or the other chamber.
All this results, inevitably, in an increase of the overall dimensions and weights.
Finally, also the limitation of other solutions in which the characteristics are predefined and not editable remains.
The object of the present invention is therefore to propose a pneumatic device for the actuation of organs, which is similar to the working principles of McKibben type artificial muscles and similar, but shaped so as to obviate the limits of the known embodiments, in particular as regards the ability to be configured at will at any time, to obtain an active phase in the contraction, or in extension or only stiffening.
An another object of the invention resides in the desire to provide a device that offers the above mentioned characteristics by means of constructive solutions at the same time simple, effective and reliable.
Still another object of the invention aims to obtain a device of compact size and regular shape, so as to be easily installed in all applications without special care.
A further object of the invention is to propose a device which can be built in series with contained costs, by using materials, machineries and equipments of common use in the industry.
These and other objects are fully achieved by a pneumatic device for the actuation of organs, in which are provided: a cylindrical hollow chamber, tight, made of elastomeric material, adapted to be pressurized with air or other fluid; a braided sleeve, coaxially disposed outside said hollow cylindrical chamber and constituted by a first set of flexible and substantially inextensible wires, arranged each one according to its own helical path of the same diameter and helix angle but different principles, and by a second set of the same flexible and substantially inextensible wires, arranged according to respective helical paths symmetric to those of the above mentioned first set, with said first and second set of flexible threads adapted to form the meshes of said net, in which each of said helical paths is inclined of a same predetermined angle with respect to the longitudinal axis of above said device; two rigid head members, provided to the corresponding ends of said braided sleeve, to which are fixed the respective ends of the mentioned wires, with the same rigid head members provided to be mechanically connected to external users means; blow in-organs, adapted to pressurize or depressurize said cylindrical hollow chamber, respectively in an active phase, or in a resting phase of the said device, in the first of which said hollow cylindrical chamber interacts with the above mentioned braided sleeve to get an extension, or a contraction, or a stiffening of the same device, respectively, if the mentioned angle of inclination of each helical path is, originally, greater than, smaller than or equal to a predetermined value, with said device comprising: adjusting means, associated with said rigid head members, adapted to modify, increasing or decreasing, the distance originally provided between the same rigid head members in said stand-by-phase of the device, so as to require a proportional and coherent variation of the angle of inclination of each helical path in said braided sleeve, such that said device, brought in its mentioned active phase, switches its response characteristics, determining for itself an axial extension, or an axial contraction, or a stiffening, respectively if, with a given distance in stand-by between the said rigid head members, the said angle of inclination is greater than, smaller than or equal to said predetermined value.
The characteristics of the invention will be made evident in the following description of preferred embodiments of the pneumatic device for the actuation of organs in the object, in accordance with the contents of the claims and with the help of the enclosed drawings, in which:
In the above listed figures, it has been indicated with reference 1, the pneumatic device for the actuating organs, object of the present invention.
The device 1 follows (he general principles of operation of the McKibben type artificial muscles and similar, of which it is said in the introduction, and provides, in an itself known manner
The blow-in bodies are adapted to pressurize or depressurize said hollow cylindrical chamber 2, respectively in an active phase K or in a stand-by phase W of the mentioned device 1, in the first of which said hollow cylindrical chamber 2 interacts with the said braided sleeve 3 to obtain an extension or a contraction, or a stiffening of the same device 1, respectively, if the mentioned angle of inclination b of each helical path is, originally, greater than, less than or equal to a predetermined value. The above mentioned predetermined value corresponds to an angle of 54.7° C. which is a theoretical limit that has been verified and experimentally validated.
According to the invention, the device 1 comprises adjusting means 5, associated to said rigid head members 4A, 4B and adapted to modify, increasing or decreasing, the distance D originally provided between the same rigid head members 4A, 4B in said phase of stand-by W of the device 1, so as to require a proportional and coherent variation of the angle of inclination b of each helical path in the above said braided sleeve 3.
In a first embodiment of the device 1, illustrated in
In a preferred constructional solution, said axial through hole 50 and the stem 51 are threaded and mutually engaged, and the mentioned operating means 53 are constituted by a rotating pawl provided in said rigid head 4A and bearing the axial threaded through hole 50.
The pawl 53 can be rotated in one direction or the other to determine the above said offsets of the corresponding rigid head 4A along the stem 51; the position reached from time to time is automatically stabilized by the above mentioned threaded coupling between the through hole 50 and the stem 51.
In the embodiment referred to in
With the rotation of the pawl 53, and the consequent variation of the distance D between the rigid head members 4A, 4B, is determined the initial value of the said angle of inclination b of each helical path, so that the device 1, brought in its mentioned active stage K, switches its response characteristics, according to the following correlations:
In a second embodiment of the device 1, illustrated in
In a preferred constructive solution, in compliance with what already provided for said first form of embodiment, the first axial through hole 50 and the first stem 51 are threaded and mutually engaged, as well as the second axial through hole 55 and the second stem 56.
The first operating means 53 are constituted by a first rotatable pawl provided in the relative rigid head 4A and bearing the first threaded axial through hole 50; similarly, the second operating means 58 are constituted by a second rotatable pawl, for example, equal to the first, provided for in the remaining rigid head 4b and bearing the second threaded axial through hole 55.
Each pawl 53, 58 can be rotated in one direction or the other, independently, to determine axial translations of the corresponding rigid head 4A, 4B with respect to the other.
The threaded couplings between the through holes 50, 55 and respective stems 51, 56 stabilize the position which is time after time achieved by each rigid head 4A, 4B.
In the embodiment of
As already explained with regard to the first embodiment, with the rotation of the first and/or of the second pawl 53, 58 and the consequent variation of the distance D between the rigid head members 4A, 4B, it is determined the initial value of the mentioned inclination angle b of each helical path, so that the device 1, taken in its mentioned active phase K, switches its response characteristics, according to the correlations previously set out.
The described second embodiment of the device 1 extends the calibration interval granted to said adjusting means 5, thereby increasing the versatility of the device 1 itself.
In a third embodiment of the device 1, illustrated in
As a constructional variant, it is possible to predict that the hollow cylindrical chamber 2 is incorporated in the sleeve 3 itself, though remaining the structural differences of the one and the other which make the first one clastic and the second one formed by substantially inextensible wires.
The corresponding adjusting means 5 comprise:
In a preferred constructive solution, in compliance with what already provided for the previous forms of embodiment, the first axial through hole 50 and the first stem 51 are threaded and mutually engaged, as well as the second axial through hole 55 and the second stem 56.
The respective first and second operating members 53, 58 are similarly constituted by a first and a second rotatable pawl provided in the relative rigid head members 4A, 4B adapted to be rotated in one direction or another, in an independent manner, to determine such axial offsets of the corresponding rigid head 4A, 4B with respect to the other.
Also in this case, the threaded couplings between the through holes 50, 55 and the respective stems 51, 56 stabilize the position reached time after time by each rigid head 4A, 4B.
The elastic member 60 inside the bellows 6 stabilizes the structure of the device 1 during the calibration operations of the angle of inclination b.
In the embodiment of
In each of the rigid head members 4A, 4B is provided a tight o ring 40 which engages the respective stem 51, 56 and prevents the compressed air to escape from the hollow cylindrical chamber 2 through the through holes 50, 55.
During the active step K of the device 1, the bellows 6 as well as the elastic member 60 are compressed or elongated in agreement with the contraction or extension of the device 1 itself.
In the figures from 5A to 7B is illustrated schematically an application with two devices 1 matched parallel, mechanically connected to a fixed upper support 70 and to a lower bar 80.
In
In
In
In
In
As it can be seen, depending on the initial adjustment of the angle b the bar 90 can be driven in two opposite directions.
In
In
The devices 1 are connected at the top to a first supporting cross 110, and at the bottom to a second supporting cross 120, for example equal to the first.
Depending on how the angles b of each device 1 are adjusted, and on the activation mode of these, it can be obtained different orientations between said supporting crosses 110, 120, similar to those granted by a ball joint, but with the application of thrust forces; it understandable how similar applications are interesting in the field of robotics and/or bio-robotics.
From the previous description emerge in the evidence the peculiar characteristics of the proposed device, which incorporates the operating principles of McKibben type artificial muscle and similar, but it introduces original construction solutions that allow it to be configured at will at any time, to obtain an active phase in the contraction, or in extension or only of stiffening.
With this important prerogative they are totally exceeded the limits of the known embodiments and it is greatly simplified any practical application of the device.
It should be highlighted how the advantageous qualities of the proposed device are obtained with techniques at the same time simple, effective and reliable which allow besides to have a compact size and regular shape.
All the constructional solutions adopted meet the requirements that allow an easy serial production of the device with contained costs, as it could be used materials, machinery and equipment of common use in the industry.
As intuitively understandable, the device can be employed in various sectors of industry, automation, robotics, bio-medical, just to name a few.
It is understood however that what above said has value of example and not limiting, therefore any modifications of detail that may be necessary to make for technical and/or functional reasons, are considered from now as remaining within the protective scope defined by the claims below.
| Number | Date | Country | Kind |
|---|---|---|---|
| ITUB20151717 | Jun 2015 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB16/53786 | 6/24/2016 | WO | 00 |
