Low-friction two-way fluid actuator assembly

Abstract

A two-way fluid actuator assembly (100) comprising: a first cylinder-piston device (10) comprising a first cylinder (12) and a first piston (11) sliding inside said first cylinder (12) along a first axis (PA), forming a first variable-volume chamber (14) between said first cylinder (12) and said first piston (11) as a function of a relative position between said first cylinder (12) and said first piston (11), a first rolling-diaphragm fluid-tight element (13) between said first cylinder (12) and said first piston (11); a first hydraulic pipe (8) having a first end communicating with said first variable-volume chamber (14); a second cylinder-piston device ((2200)) comprising a second cylinder (22) and a second piston (21) sliding inside said second cylinder (22) along a second axis (SA), forming a second variable-volume chamber (24) between said second cylinder (22) and said second piston (21) as a function of a relative position between said second cylinder (22) and said second piston (21), a second rolling-diaphragm fluid-tight element (23) between said second cylinder (22) and said second piston (21); a second hydraulic pipe (9) having a first end communicating with said second variable-volume chamber (24); a linear actuator device (5) comprising a translating element (1) arranged to translate along a translation axis (T) wherein the remaining movements of said translating element (1) are prevented, a rotating element (2) arranged to rotate about said translation axis (T) constrained in all remaining movements, wherein the translating element (1) and the rotating element (2) are engaged with each other by means of a helical kinematic couple, the linear actuator device (5) comprising an electric motor (3) connected to said rotating element (2) to rotate said rotating element (2), wherein said first cylinder-piston device (10) and said second cylinder-piston device (20) are connected to said translating element (1) on opposite sides with respect to the translation direction (T) so that a translation of said translating element (1) corresponds to a compression of one of said first variable-volume chamber (14) and said second variable-volume chamber (24) and a simultaneous expansion of the other of said first variable-volume chamber (14) and said second variable-volume chamber (24).

Description

"LOW- FRICTION TWO-WAY FLUID ACTUATOR ASSEMBLY"DESCRIPTIONField of the invention

[0001] The present invention relates to a two-way fluid actuator assembly with high precision and very low friction, in particular for operating a remote actuated assembly connected to the actuator assembly by means of two fluid pipes . Moreover, the present invention relates to a remote actuation system comprising such an actuator assembly .Background art

[0002] In the automation field, in particular for the motion actuation of articulated mechanism j oints , such as a robot , for example , a solution i s often adopted whereby the j oint actuators are placed in remote positions with respect to the j oints themselves .

[0003] A known implementation uses a system of cables diverted by pulleys , which connect the actuation system to the aforesaid j oint , and which are conveniently integrated into the structure of the articulated mechanism .

[0004] Sheathed cable transmission systems are also known .

[0005] Such devices are not free from defects ; indeed, the sheathed cables have poor mechanical transmission quality with high friction and backlash; the systems basedon cables and pulleys have very good transmission quality but are very complex because they require the fabrication of high-precision, high-quality mechanical components . Moreover, they are limited in terms of design flexibility because they can only be ef fectively applied to relatively simple kinematic mechanisms .

[0006] In particular, none of these solutions suggests a transmission system which has the highest mechanical quality possible in terms of low friction and backlash, and avoids the need to integrate mechanical components of high accuracy and mechanical quality .

[0007] Hydrostatic transmission systems designed to overcome the problems of complexity, flexibility, friction and si ze introduced by the remote actuation systems mentioned above are also known .

[0008] However, the known hydrostatic transmission systems do not allow achieving the performance required in the robotics industry of high compactness , light weight , ef ficiency, and high torque , being practically uncapable of implementing the operating principle of frictionless hydrostatic transmissions .

[0009] Therefore , the need is felt to provide a compact , lightweight two-way fluid actuator assembly with high- precision and very low- friction so as to obtain an equal and opposite displacement for the two hydraulic cylinders ,so as to obviate, at least partially, the drawbacks complained of above with reference to the prior art. Summary of the invention

[0010] It is the object of the present invention to devise and provide a fluid actuator assembly which allows meeting the aforesaid needs and at least partially obviating the drawbacks complained of above with reference to the prior art.

[0011] In particular, it is the task of the present invention to provide a two-way fluid actuator assembly which allows transmitting the mechanical torque generated by an actuator placed far from the joint, in a proximal position, onto the joints of an articulated mechanism placed in a distal position, e.g., the joints of a robot.

[0012] It is another object of the present invention to provide a two-way actuator assembly capable of simultaneously moving two cylinder-piston systems which use rolling diaphragms, so as to actuate an actuated system remotely located and hydraulically connected to such a cylinder-piston systems.

[0013] It is a further object of the present invention to provide a two-way fluid actuator assembly which exhibits high mechanical transparency, i.e., high efficiency, low backlash, low friction, and specifically virtually zero static friction.

[0014] It is another obj ect of the present invention to provide a two-way actuator assembly capable of actuating mechanisms , and in particular robots , with a high stability of control of both position and force / torque , which can achieve high motion speeds , which are back-drivable per se , i . e . , which make retrograde motion possible , so as to interact safely with the surrounding environment , and the position and output force / torque of which are controllable in a precise manner without necessarily requiring the use of additional force or pressure sensors mounted in a distal position .

[0015] An important advantage produced by the invention lies in allowing the assembly of the first and second cylinder-piston systems at the two ends of the same translating element ; this solutions , which has the advantage of being compact and low-weight , is enabled by the flexibility of the diaphragms , which allow l imiting the internal forces generated in the presence of minor misalignments , or non-perfect concentricity, of the cylinder and piston during their relative motion due to small and realistically unavoidable assembly or manufacturing imperfections . This allows the entire assembly, consisting of screw / nut + first cylinder-piston device + second cylinder-piston device , to have highly low friction even without resorting to solutions the correctoperation of which would only be ensured by means of high construction accuracy / tolerances ( of concentricity / coaxiality ) of the mechanical parts . In conclusion, beside preventing losses and friction, the rolling diaphragms also act as an intrinsic yielding decoupling and / or centering element of the sliding axes of the involved elements .

[0016] These and further obj ects and advantages are achieved by a two-way fluid actuator assembly, as well as by a remote actuation system, as well as by a robotic arm, according to the independent claims .

[0017] Advantageously, the two-way fluid actuator assembly according to the invention is compact in si ze and with high precision and very low friction, capable of simultaneously actuating two hydraulic cylinders using only one electric actuator so as to achieve an equal and opposite displacement for the two hydraulic cylinders .

[0018] The use of a fluid with a low modulus of compressibility as the transmission medium makes the transmission rigid and allows power transmission over wide frequency bands .

[0019] The two-way fluid actuator assembly thus allows controlling the pressure of the fluid contained in the hydraulic pipe connected, or in the hydraulic pipes connected, to the actuated assembly only bycontrolling / measuring the torque generated by an electric motor, without necessarily requiring the use of additional sensors or components .

[0020] The main design choices which respond to the need to actuate the two said hydraulic cylinders by moving volumes of fluid with high precision and low friction consist in :A) employing an actuator assembly which uses a single electric actuator of the rotational type which allows delivering torques , and controlling its position in an accurate manner ;B ) employing a translating element / rotating element pair arranged in series with the two said pistons , which allows :1 ) trans forming the rotary motion of said electric actuator into linear motion of the two pistons ; 2 ) setting a ratio between cylinder stroke and motor rotations (below referred to as the gear ratio ) which can be chosen at the design stage based on the choice of the pitch of the translating / rotating element ;C ) employing rolling-diaphragm cylinders to contain and move the fluid inside the hydraulic pipes ; indeed, by employing rolling-diaphragm cylinders , the following advantages are achieved : 1 ) fluid leakages are prevented,2 ) sliding friction and wear are l imited, and 3 ) the system formed is made tolerant to the minor misalignments whichcan be generated when coaxially arranging the three moving elements ( two said hydraulic cylinders and said translating element-rotating element ) .

[0021] These choices allow obtaining a system having the aforesaid features of low friction, ef ficiency, and transparency .

[0022] Further obj ects , solutions , and advantages are present in the embodiments described below and claimed in the dependent claims .Brief description of the drawings

[0023] The invention will be disclosed below through the description of embodiments thereof , given by way of non-limiting example , with reference to the accompanying drawings , in which :

[0024] - figure 1 shows a diagrammatic view of a two- way fluid actuator assembly according to the invention, having fixed pistons and cylinders moved by a translating screw actuated by the rotation of a nut rotated by a motor, in which the screw cannot rotate and the nut cannot translate , and in which the pistons subj ect the screw to tensile loads only;

[0025] - figure 2 shows a tensile load diagram of the translating element , in particular the screw, highlighting how, i f a misalignment of the translation axis with respect to the sliding axes of the first and second cylinder-pistondevices occurs , the moment of the tensile forces applies an action which tends to restore the alignment of the axes ;

[0026] - figure 3 shows a diagrammatic view of an embodiment of the two-way fluid actuator assembly according to the invention, in which the cylinders are fixed and the pi stons are movable , and also in which the screw translates while the nut rotates , and the pistons subj ect the screw to tensile loads only;

[0027] - figure 4 shows a diagrammatic view of an embodiment of the actuator assembly according to the invention, in which the cylinders are movable and the pistons are fixed and in which the screw translates while the nut rotates , and in which the cylinders subj ect the screw to compressive loads only;

[0028] - figure 5 shows a diagrammatic view of an embodiment of the actuator assembly according to the invention, in which the cylinders are fixed and the pistons are movable , and in which the screw translates while the nut rotates , and the pistons subj ect the screw to compressive loads only;

[0029] - figure 6 shows an embodiment of a remote actuation system according to the invention, having an actuated device of the translation type ;

[0030] - figure 7 shows an embodiment of a remote actuation system according to the invention, in which theactuated device is rotary and has a driven pulley and a flexible transmission member wound on the pulley, and having each end fixed to a respective one of the third cylinder-piston device and the fourth cylinder-piston device ;

[0031] - figure 8 shows a diagrammatic view of the remote actuation system in figure 7 in which the linear motions of the third cylinder-piston device and the fourth cylinder-piston device are connected to the rotary actuated element by means of a toothed coupling mechanism, e . g . , of the rack-and-pinion type , or friction-rolling type ;

[0032] - figure 9 shows a diagrammatic view of the remote actuation system in figure 7 , in which the linear motions of the third cylinder-piston device and the fourth cylinder-piston device are connected to the rotary actuated element by means of an articulated pantograph mechanism;

[0033] - figure 10 shows a diagrammatic example of a robotic arm, having for example two degrees of freedom, e . g . , two rotary actuated j oints , in which such rotary actuated j oints are associated with two respective remote actuation systems , such as that in figure 8 , for example ;

[0034] - figure 11 shows an embodiment of a two-way fluid actuator assembly such as that in figure 1 ,comprising a rotation prevention device for the translating element , comprising an arm and a fixed sliding rail ;

[0035] - figure 12 shows an embodiment of an example of implementation of a rotation prevention device such as that in figure 11 , in which the arm integral with the translating element comprises two linear sliding elements , and the rail comprises two linear bearings ;

[0036] - figure 13 shows an embodiment of an example of implementation of a rotation prevention device such as that in figure 11 , in which the arm integral with the translating element comprises two linear bearings , while the rail comprises two linear sliding elements ;

[0037] - figure 14 shows an embodiment of an example of implementation of a rotation prevention device such as that in figure 11 , in which the arm integral with the translating element comprises a linear rail , and the rail comprises a sliding shoe ;

[0038] - figure 15 shows an embodiment of an example of implementation of a rotation prevention device such as that in figure 11 , in which the arm integral with the translating element comprises two wheels engaged in two slots of the rail ;

[0039] - figure 16 shows an embodiment of an example of implementation of a rotation prevention device such asthat in figure 11 , in which the arm integral with the translating element is connected to the fixed rail by means of a planar articulated kinematic mechanism which allows translating the translating element but constrains the rotations thereof about axes parallel to the translation axis ;

[0040] - figure 17 shows a diagrammatic view of a possible solution for transmitting motion between the electric motor and the rotating element , comprising a flexible belt or closed-chain transmission member ;

[0041] - figure 18 shows a diagrammatic view of a possible solution for transmitting motion between the motor and the rotating element , comprising a gear wheel coupling;

[0042] - figure 19 shows a diagrammatic view of a possible solution of direct transmission of motion between the rotor of the torque motor and the rotating element ;

[0043] - figure 20 shows a diagrammatic view of the two-way fluid actuator assembly in figure 1 , comprising two flexible coupling devices serving the function of allowing a misalignment of the screw / nut translation axis T and cylinder / piston element axes PA and SA;

[0044] - figure 21 shows a three-dimensional view of an example of a two-dimensional f luid actuator assembly corresponding to the diagrammatic view in figure 1 ,comprising a torque motor, a mechanical transmission between the motor and the nut , such as that in figure 19 , and two flexible coupling devices , such as those in figure 20 ;

[0045] - figure 22 shows a three-dimensional view of an example of a two-way fluid actuator assembly corresponding to the diagrammatic view in figure 27 , a mechanical belt transmission of rotational motion between the motor and the rotating element , in particular the screw, as in figure 17 , and having a rotation prevention device of the rotation of the translating element , in particular the nut , such as that shown in figure 12 ;

[0046] - figure 23 shows another view according to a di f ferent angle of the fluid actuator assembly in figure 22 ;

[0047] - figure 24 shows a diagrammatic view of a two- way fluid actuator assembly such as that in figure 11 , in which each of the first and second cylinder-piston devices is broken down into two equal and mutually integral cylinder-piston devices ;

[0048] - figure 25 shows a three-dimensional view of an example of a two-way fluid actuator assembly corresponding to the diagrammatic view in figure 24 , having dual cylinder-piston assemblies , a torque motor such as that shown in figure 19 , and a rotation prevention device suchas that shown in figure 13 ;

[0049] - figure 26 shows the embodiment of the actuator assembly in figure 25 , in which an outer tubular cover element was removed to allow observing the internal elements ;

[0050] - figure 27 shows a diagrammatic view of an embodiment of the present invention, alternative to that in figure 1 , in which the translating element is the nut , instead of the screw, and the rotating element is the screw, instead of the nut .

[0051] - figure 28 shows a diagrammatic view of an embodiment of the present invention, alternative to that in figure 1 and figure 20 , in which the axes PA and SA are not aligned with the axis T and the piston-cylinder systems are connected to the translating element through flexible coupling devices and combined with diversion systems 18 and 28 .Description of preferred embodiments

[0052] With reference to the figures , a two-way fluid actuator assembly according to the invention is indicated by reference numeral 100 .

[0053] The two-way fluid actuator assembly 100 comprises a first cylinder-piston device 10 and a second cylinder-piston device 20 .

[0054] The first cylinder-piston device 10 comprises afirst cylinder 12 and a first piston 11 sliding inside said first cylinder 12 along a first axis PA, forming a first variable-volume chamber 14 between said first cylinder 12 and said first piston 11 as a function of a relative position between said first cylinder 12 and said first piston 11 , a first rolling-diaphragm fluid-tight element 13 between said first cylinder 12 and said first piston 11 .

[0055] The second cylinder-piston device 20 comprises a second cylinder 22 and a second piston 21 sliding inside said second cylinder 22 along a second axis SA, forming a second variable-volume chamber 24 between said second cylinder 22 and said second piston 21 as a function of a relative position between said second cylinder 22 and said second piston 21 , a second rolling-diaphragm fluid-tight element 23 between said second cylinder 22 and said second piston 21 .

[0056] The two-way fluid actuator assembly 100 further comprises a first hydraulic pipe 8 having a first end communicating with said first variable-volume chamber 14 and a second hydraulic pipe 9 having a first end communicating with said second variable-volume chamber 24 .

[0057] The two-way fluid actuator assembly 100 further comprises a linear actuator device 5 comprising a translating element 1 arranged to translate along atranslation axis T where the remaining movements of said translating element 1 are prevented, a rotating element 2 arranged to rotate about said translation axis T constrained in all remaining movements , where the translating element 1 and the rotating element 2 are engaged with each other by means of a helical kinematic couple .

[0058] The linear actuator device 5 comprises an electric motor 3 connected to said rotating element 2 to rotate said rotating element 2 . Various connection possibilities and mechanical transmissions will be shown below .

[0059] The first cylinder-piston device 10 and the second cylinder-piston device 20 are connected to said translating element 1 on opposite sides with respect to the translation direction T so that a translation of said translating element 1 corresponds to a compression of one of said first variable-volume chamber 14 and said second variable-volume chamber 24 and a simultaneous expansion of the other of said first variable-volume chamber 14 and said second variable-volume chamber 24 .

[0060] According to an embodiment , both pistons 11 , 21 or both cylinders 12 , 22 of said first cylinder-piston device 10 and said second cylinder-piston device 20 are connected to said translating element 1 , on opposite sidesof said translating element 1, so that a translation of said translating element 1 corresponds to equal and opposite displacements of said pistons 11, 21 or said cylinders 12, 22.

[0061] According to an embodiment, said first cylinderpiston device 10 and said second cylinder-piston device 20 are dimensionally equal to each other.

[0062] Therefore, if a first and a second cylinderpiston system of equal size are chosen, the resultant force on the screw - and thus also on the balls - is zero in the resting condition, i.e., if the torque delivered by the motor is zero, despite the fluid pressure in the cylinderpiston systems being greater than zero.

[0063] According to an embodiment, the first axis PA and the second axis SA are coaxial, or parallel, to the translation axis T.

[0064] In reality, this axis arrangement is an optimal or nominal arrangement, however, the presence of the flexible coupling devices described below in some embodiments also has the benefit of ensuring low friction in real-world conditions, even if the construction of the device would lead to deviations from coaxiality or parallelism conditions.

[0065] According to an embodiment, shown in figures 1, 4, 6, 7, 10, 11, 20, 27, 28, for example, the first piston11 and the second piston 12 are fixed, and said first cylinder 12 and said second cylinder 22 are movable and connected to said translating element 1 by means of a first connection element 15 and a second connection element 25 , respectively .

[0066] Among the configurations involving said fixed first piston 11 and said second pi ston 21 , according to an embodiment , shown in figures 1 , 6 , 7 , 10 , 11 , 20 , 27 , 28 , for example , said first piston 11 is interposed between said first variable volume chamber 14 and said translating element 1 , and said second piston 21 is interposed between said second variable volume chamber 24 and said translating element 1 .

[0067] In this configuration, the cylinders subj ect the translating element 1 to tensile loads only, mitigating any j amming or unfavorable loading conditions which could occur in a configuration in which the ends of translating element 1 are compressed / pushed by the cylinder-piston systems against the rotating element 2 .

[0068] According to an embodiment , shown in figures 3 , 5 , for example , the first cylinder 12 and the second cylinder 22 are fixed, and said first piston 11 and said second piston 12 are movable and connected to said first translating element 1 by means of a first connection element 15 and a second connection element 25 ,respectively .

[0069] Among the configurations involving said fixed first cylinder 12 and second cylinder 22 , according to an embodiment , shown in figure 3 , for example , said first variable-volume chamber 14 is interposed between said first piston 11 and said translating element 1 and said second variable-volume chamber 24 is interposed between said second piston 21 and said translating element 1 .

[0070] In this configuration, the pistons subj ect the translating element 1 to tensile loads only, mitigating any j amming or unfavorable loading conditions which might occur in a configuration in which the ends of translating element 1 are compressed / pushed by the cylinder-piston systems against the rotating element 2 .

[0071] According to an embodiment , the second hydraulic pipe 8 communicates with said first variable-volume chamber 14 through a first fluid passage 16 which passes through said first piston 11 and said first rolling membrane fluid-tight element 13 .

[0072] According to an embodiment , the second hydraulic pipe 9 communicates with said second variable-volume chamber 24 through a second fluid passage 26 passing through said second piston 21 and said second rolling membrane fluid-tight element 23 .

[0073] According to an embodiment , said f irst variable-volume chamber 14 and said second variable-volume chamber24 have cross sections of equal area causing the volume change of said first variable-volume chamber 14 to be equal and opposite to a corresponding volume change of said second variable-volume chamber 24 .

[0074] According to an embodiment , the two-way fluid actuator assembly 100 comprises a first flexible coupling device 17 interposed between said translating element 1 and said first cylinder-piston device 10 and a second flexible coupling device 27 interposed between said translating element 1 and said second cylinder-piston device 20 , said first flexible coupling device 17 and said second flexible coupling device 27 are configured to allow the operation of the system in the presence of possible misalignments between said first axis PA, said second axis SA, and said translation axis T .

[0075] In particular, the presence of such flexible coupling devices allows , in the case of minor misalignments of the axes T , PA and SA, enabling the translating element 1 and the two cylinder-piston devices 10 , 20 to translate freely while mitigating the ef fects of such a misalignment . Therefore , even in the presence of misalignments caused by design imperfections in the device , no constraining reactions are produced, and the actuator assembly continues to ensure a very low- friction operation .

[0076] Moreover, the use of flexible coupling devices allows reducing / limiting the strength of the bond reaction forces / torques generated during the linear motion of the translating element due to slight misalignments of said axes .

[0077] According to an embodiment , the first flexible coupling device 17 and said second flexible coupling device 27 are inextensible , or substantially inextensible , along said translation axis T and yielding in directions perpendicular to said translation axis T .

[0078] According to an embodiment , the first flexible coupling device 17 and said second flexible coupling device 27 comprise at least one flexible cable or at least one flexible belt .

[0079] According to an embodiment , the first flexible coupling device 17 and said second flexible coupling device 27 comprise at least one flexible cable or at least one flexible belt diverted by diversion systems 18 and 28 .

[0080] According to an embodiment , the translating element 1 is a screw and said rotating element 2 is a nut coupled to said screw 1 by screwing .

[0081] According to an embodiment , the two-way fluid actuator assembly 100 comprises a rotation prevention device 51 associated with said translating element 1 , which allows the translation of the translating element 1 alongthe translation axis T and prevents the rotation thereof about the translation axis T .

[0082] According to an embodiment , the rotation prevention device 51 comprises an arm 52 integral with said translating element 1 slidingly coupled to a fixed sliding rail 53 parallel to said translation axis T .

[0083] According to an embodiment , the linear actuator device 5 comprises a mechanical motion transmission 4 connected to , and interposed between, said electric motor 3 and said rotating element 2 , so as to apply a rotation about said translation axis T to said rotating element 2 .

[0084] According to an embodiment , the mechanical motion transmission 4 comprises a closed-belt element 4 ' wrapped around a pulley coaxial and integral with said rotating element 2 and a drive wheel integral with a drive shaft of said electric motor 3 .

[0085] According to an embodiment , the mechanical motion transmission 4 is a gear wheel transmission .

[0086] According to an embodiment , the electric motor 3 is a torque motor comprising an annular stator and an annular rotor coaxial with said annular stator, where said rotating element 2 is coaxial with, and placed within, said annular rotor, and rotationally connected by means of said mechanical motion transmission 4 , which is interposed radially between said annular rotor and said nut .

[0087] The radial loads on the rotating elements, which would be generated when using the other types of motion transmission 4 shown, further limiting frictions, are thus drastically reduced.

[0088] Moreover, there are obtained a significant compactness of the device, a reduction in mass since the frame of motor 3 and the frame supporting the rotating element 2 can be the same element, and no radial forces are created on the motor and the rotating element.

[0089] Possible alternatives to obtain such a transmission consist in using conventional gears, such as planetary or harmonic drive gears, for example, in combination with flexible bodies to transform rotary motion into linear motion of the hydraulic cylinders.

[0090] However, such a solution would involve some disadvantages that would compromise one or more requirements of the implementation system.

[0091] For example, the planetary gears, as well as any other toothed wheel gear, are highly bulky, heavy and introduce a large amount of friction when designed to have low backlash.

[0092] Harmonic drive gears, despite being light and compact, are complex, allow implementing only very high reduction ratios, achieve moderate efficiency, and in retrograde motion operation mode also have rather highfriction .

[0093] Possible other systems that can be used to implement such a transmission are toothed belts or pinionrack pairs, which however offer a smaller range of transmission ratio, for reasons related to lower limits of the drive pulley or motor pinion radius.

[0094] The actuator assembly, being capable of moving a desired volume of fluid with high precision, having a completely lossless and / or frictionless actuation and transmission system, is capable of controlling the position of the joints of an articulated system by controlling only the position of the motor, which can thus be assumed to be the same as that of the joint, without necessarily requiring the use of additional elements, e.g., valves or sensors, e.g., rotation sensors mounted on the joints of the articulated system.

[0095] Since the robot has no sensors on board, it can be used in environments with features that are critical and / or hostile to sensor reliability and longevity.

[0096] According to another embodiment, shown in figure 27, for example, the rotating element 2 is a screw and the translating element 1 is a nut coupled to said screw 2 by screwing .

[0097] This embodiment differs from those described above only in that the rotating element 2 is the screw,instead of the nut , and the translating element 1 is the nut , instead of the screw .

[0098] This embodiment can comprise any one of the features described above .

[0099] According to another aspect of the present invention, the aforesaid obj ects and advantages are achieved by a remote actuation system comprising a two-way fluid actuator assembly 100 according to the features described above and an actuated assembly 200 .

[0100] The actuated assembly 200 comprises a third cylinder-piston device 30 comprising a third cylinder 32 and a third piston 31 sliding inside said third cylinder 32 along a third axis TA, forming a third variable-volume chamber 34 between said third cylinder 32 and said third piston 31 as a function of a relative position between said third cylinder 32 and said third piston 31 , a third rolling-diaphragm fluid-tight element 33 between said third cylinder 32 and said third piston 31 , where said first hydraulic pipe 8 has a second end communicating with said third variable-volume chamber 34 .

[0101] Moreover, the actuated assembly 200 comprises a fourth cylinder-piston device 40 comprising a fourth cylinder 42 and a fourth piston 41 sliding inside said fourth cylinder 42 along a fourth axis QA, forming a fourth variable-volume chamber 44 between said fourth cylinder 42and said fourth piston 41 as a function of a relative position between said fourth cylinder 42 and said fourth piston 41 , a fourth rolling-diaphragm fluid-tight element 43 between said fourth cylinder 42 and said fourth piston 41 , where said second hydraulic pipe 9 has a second end communicating with said fourth variable-volume chamber 44 .

[0102] Moreover, the actuated assembly 200 comprises an actuated device 50 , connected to said third cylinderpiston device 30 and said fourth cylinder-piston device 40 so that said actuated device is moved by a combined action of said third cylinder-piston device 30 and said fourth cylinder-piston device 40 .

[0103] A true low- friction remote motion actuation is thus implemented between the actuation source , represented by motor 3 , and the actuated element 50 . The two transmission channels , in particular the pipes 8 and 9 , can cross long distances and bend according to any geometry .

[0104] According to an embodiment , the actuated device 50 is interposed between said third cylinder-piston device 30 and said fourth cylinder-piston device 40 and exhibits a translating movement along a sliding direction S parallel to , or coincident with, said third axis TA and said fourth axis QA.

[0105] The same advantages discussed for the partrelated to the actuator assembly are achieved : a low- friction transmission is achieved i f also in this case the cylinder-piston devices generate tensile loads on the actuated element 50 .

[0106] According to an embodiment , the actuated device 50 exhibits a rotary movement and comprises a pulley 55 driven to rotate about a motion output axis 54 by means of a flexible transmission member 56 wrapped around said pulley 55 and connected to said third cylinder-piston device 30 and said fourth cylinder-piston device 40 .

[0107] A remote rotary motion implementation can thus be achieved, which is useful in speci fic settings such as the actuation of robot j oints .

[0108] According to an embodiment , the actuated device 50 exhibits a rotary movement and comprises a wheel 58 driven to rotate about a motion output axis 57 by means of a toothed pinion-rack type coupl ing with respect to two rigid translating elements 59 , 60 connected to said third cylinder-piston device 30 and said fourth cylinder-piston device 40 , respectively .

[0109] This alternative works equivalently to the belt transmission, and is applicable to settings where the belt use can be limiting and / or prevented due to environmental conditions , quantity of the transmitted torques , or required rotation range .

[0110] According to an embodiment , the actuated device50 exhibits a rotary movement about a motion output axis 61 and comprises an articulated mechanism 62 connected to said motion output axis 61 and said third cylinder-piston device 30 and said fourth cylinder-piston device 40 .

[0111] According to another aspect of the present invention, the aforesaid obj ects and advantages are achieved by a robotic arm 400 having at least two actuated j oints 70 , 80 , where each of said at least two actuated j oints 70 , 80 is associated with a respective remote actuation system 300 having the features described above .

[0112] Those skilled in the art may make changes and adaptations to the embodiments of the device described above or may replace elements with others which are functionally equivalent in order to meet contingent needs without departing from the scope of the following claims . Each of the features described as belonging to a possible embodiment can be made irrespective of the other embodiments described .-k 'k 'kList of reference signs1 translating element2 rotating element3 electric motor4 mechanical motion transmission5 linear actuator device6 movable rotation prevention device7 fixed abutment element8 first hydraulic pipe9 second hydraulic pipe10 first cylinder-piston device11 first piston12 first cylinder13 first rolling-diaphragm fluid-tight element14 first variable-volume chamber15 first connection element16 first fluid passage17 first flexible coupling device20 second cylinder-piston device21 second piston22 second cylinder23 second rolling-diaphragm fluid-tight element24 second variable-volume chamber25 second connection element26 second fluid passagesecond flexible coupling device , 28 diversion system third cylinder-piston device third piston third cylinder third rolling-diaphragm fluid-tight element third variable-volume chamber fourth cylinder-piston device fourth piston fourth cylinder fourth rolling-diaphragm fluid-tight element fourth variable-volume chamber actuated device rotation prevention device arm fixed sliding rail motion output axis pulley flexible transmission member motion output axis driven wheel , 60 rigid translating elements motion output axis articulated mechanism 0 two-way fluid actuator assembly200 actuated assembly300 remote actuation systemPA first axisSA second axisTA third axisQA fourth axisT translation axis

Claims

CLAIMS1. A two-way fluid actuator assembly (100) comprising:- a first cylinder-piston device (10) comprising a first cylinder (12) and a first piston (11) sliding inside said first cylinder (12) along a first axis (PA) , forming a first variable-volume chamber (14) between said first cylinder (12) and said first piston (11) as a function of a relative position between said first cylinder (12) and said first piston (11) , a first rolling-diaphragm fluid- tight element (13) between said first cylinder (12) and said first piston (11) ; a first hydraulic pipe (8) having a first end communicating with said first variable-volume chamber (14) ;- a second cylinder-piston device (20) comprising a second cylinder (22) and a second piston (21) sliding inside said second cylinder (22) along a second axis (SA) , forming a second variable-volume chamber (24) between said second cylinder (22) and said second piston (21) as a function of a relative position between said second cylinder (22) and said second piston (21) , a second rolling-diaphragm fluid- tight element (23) between said second cylinder (22) and said second piston (21) ; a second hydraulic pipe (9) having a first end communicating with said second variable-volume chamber- a linear actuator device (5) comprising a translating element (1) arranged to translate along a translation axis (T) wherein the remaining movements of said translating element (1) are prevented, a rotating element (2) arranged to rotate about said translation axis (T) constrained in all remaining movements, wherein the translating element (1) and the rotating element (2) are engaged with each other by means of a helical kinematic couple, the linear actuator device (5) comprising an electric motor (3) connected to said rotating element (2) to rotate said rotating element (2) ,- wherein said first cylinder-piston device (10) and said second cylinder-piston device (20) are connected to said translating element (1) on opposite sides with respect to the translation direction (T) so that a translation of said translating element (1) corresponds to a compression of one of said first variable-volume chamber (14) and said second variable-volume chamber (24) and a simultaneous expansion of the other of said first variable-volume chamber (14) and said second variable-volume chamber (24) .

2. A two-way fluid actuator assembly (100) according to claim 1, wherein both pistons (11, 21) or both cylinders (12, 22) of said first cylinder-piston device (10) and said second cylinder-piston device (20) are connected tosaid translating element (1) , on opposite sides of said translating element (1) , so that a translation of said translating element (1) corresponds to equal and opposite displacements of said pistons (11, 21) or said cylinders (12, 22) .

3. A two-way fluid actuator assembly (100) according to at least one preceding claim, wherein said first cylinderpiston device (10) and said second cylinder-piston device (20) are dimensionally equal to each other.

4. A two-way fluid actuator assembly (100) according to at least one preceding claim, wherein said first axis (PA) and said second axis (SA) are coaxial with, or parallel to, said translation axis (T) .

5. A two-way fluid actuator assembly (100) according to at least one preceding claim, wherein said first piston (11) and said second piston (21) are fixed, and wherein said first cylinder (12) and said second cylinder (22) are movable and connected to said translating element (1) by means of a first connection element (15) and a second connection element (25) , respectively.

6. A two-way fluid actuator assembly (100) according to claim 5, wherein said first piston (11) is interposed between said first variable-volume chamber (14) and said translating element (1) , and wherein said second piston(21) is interposed between said second variable-volumechamber (24) and said translating element (1) .

7. A two-way fluid actuator assembly (100) according to claim 5, wherein said first variable-volume chamber (14) is interposed between said first piston (11) and said translating element (1) , and wherein said second variablevolume chamber (24) is interposed between said second piston (21) and said translating element (1) .

8. A two-way fluid actuator assembly (100) according to claim 6 or 7, wherein said first hydraulic pipe (8) communicates with said first variable-volume chamber (14) through a first fluid passage (16) which crosses said first piston (11) and said first rolling-diaphragm fluid-tight element (13) , and wherein said second hydraulic pipe (9) communicates with said second variable-volume chamber (24) through a second fluid passage (26) which crosses said second piston (21) and said second rolling-diaphragm fluid-tight element (23) .

9. A two-way fluid actuator assembly (100) according to claim 1, wherein said first cylinder (12) and said second cylinder (22) are fixed, and wherein said first piston (11) and said second piston (21) are movable and connected to said translating element (1) by means of a first connection element (15) and a second connection element (25) , respectively.

10. A two-way fluid actuator assembly (100) according toclaim 9, wherein said first variable-volume chamber (14) is interposed between said first piston (11) and said translating element (1) and wherein said second variablevolume chamber (24) is interposed between said second piston (21) and said translating element (1) .

11. A two-way fluid actuator assembly (100) according to claim 9, wherein said first piston (11) is interposed between said first variable-volume chamber (14) and said translating element (1) , and wherein said second piston (21) is interposed between said second variable-volume chamber (24) and said translating element (1) .

12. A two-way fluid actuator assembly (100) according to claim 1, wherein each change in volume of said first variable-volume chamber (14) is equal and opposite to a corresponding change in volume of said second variablevolume chamber (24) .

13. A two-way fluid actuator assembly (100) according to claim 1 comprising a first flexible coupling device (17) interposed between said translating element (1) and said first cylinder-piston device (10) and a second flexible coupling device (27) interposed between said translating element (1) and said second cylinder-piston device (20) , said first flexible coupling device (17) and said second flexible coupling device (27) being configured to allow the operation of the actuator assembly in the presence ofpossible minor misalignments between said first axis (PA) and said second axis (SA) with respect to said translation axis (T) .

14. A two-way fluid actuator assembly (100) according to claim 13, wherein said first flexible coupling device (17) and said second flexible coupling device (27) are inextensible, or substantially inextensible, along said translation axis (T) and yielding in directions perpendicular to said translation axis (T) .

15. A two-way fluid actuator assembly (100) according to claim 13 or 14, wherein said first flexible coupling device (17) and said second flexible coupling device (27) comprise at least one flexible cable or at least one flexible belt.

16. A two-way fluid actuator assembly (100) according to at least one of the preceding claims, comprising a rotation prevention device (51) associated with said translating element (1) , which allows the translation of the translating element (1) along the translation axis (T) and prevents the rotation thereof about the translation axis (T) .

17. A two-way fluid actuator assembly (100) according to claim 16, wherein said rotation prevention device (51) comprises an arm (52) integral with said translating element (1) slidingly coupled to a fixed sliding rail (53) parallel to said translation axis (T) .

18. A two-way fluid actuator assembly (100) according to claim 1, wherein said linear actuator device (5) comprises a mechanical motion transmission (4) connected to, and interposed between, said electric motor (3) and said rotating element (2) , so as to apply a rotation about said translation axis (T) to said rotating element (2) .

19. A two-way fluid actuator assembly (100) according to claim 18, wherein said mechanical motion transmission (4) comprises a closed belt or closed chain element (4' ) wrapped around a pulley coaxial and integral with said rotating element (2) and a drive wheel integral with a drive shaft of said electric motor (3) .

20. A two-way fluid actuator assembly (100) according to claim 18, wherein said mechanical motion transmission (4) is a gear wheel transmission.

21. A two-way fluid actuator assembly (100) according to claim 18, wherein said electric motor (3) is a torque motor comprising an annular stator and an annular rotor coaxial with said annular stator, wherein said rotating element (2) is coaxial with said annular rotor and said mechanical motion transmission (4) .

22. A two-way fluid actuator assembly (100) according to claim 1, wherein said translating element (1) is a screw and said rotating element (2) is a nut mutually coupled by means of a helical kinematic couple.

23. A two-way fluid actuator assembly (100) according to claim 1, wherein said rotating element (2) is a screw and said translating element (1) is a nut mutually coupled by means of a helical kinematic couple.

24. A remote actuation system comprising a two-way fluid actuator assembly (100) according to at least one of the preceding claims and an actuated assembly (200) , wherein said actuated assembly comprises:- a third cylinder-piston device (30) comprising a third cylinder (32) and a third piston (31) sliding inside said third cylinder (32) along a third axis (TA) , forming a third variable-volume chamber (34) between said third cylinder (32) and said third piston (31) as a function of a relative position between said third cylinder (32) and said third piston (31) , a third rolling-diaphragm fluid- tight element (33) between said third cylinder (32) and said third piston (31) , wherein said first hydraulic pipe (8) has a second end communicating with said third variable-volume chamber (34) ;- a fourth cylinder-piston device (40) comprising a fourth cylinder (42) and a fourth piston (41) sliding inside said fourth cylinder (42) along a fourth axis (QA) , forming a fourth variable-volume chamber (44) between said fourth cylinder (42) and said fourth piston (41) as a function of a relative position between said fourth cylinder (42) andsaid fourth piston (41) , a fourth rolling-diaphragm fluid- tight element (43) between said fourth cylinder (42) and said fourth piston (41) , wherein said second hydraulic pipe (9) has a second end communicating with said fourth variable-volume chamber (44) ; an actuated device (50) , connected to said third cylinder-piston device (30) and said fourth cylinderpiston device (40) so that said actuated device is moved by a combined action of said third cylinder-piston device (30) and said fourth cylinder-piston device (40) .

25. A remote actuation system according to claim 24, wherein said actuated device (50) is interposed between said third cylinder-piston device (30) and said fourth cylinder-piston device (40) and exhibits a translating movement along a sliding direction (S) parallel to, or coincident with, said third axis (TA) and said fourth axis (QA) .

26. A remote actuation system according to claim 25, wherein said actuated device (50) exhibits a rotary movement and comprises a pulley (55) driven to rotate about a motion output axis (54) by means of a flexible transmission member (56) wrapped around said pulley (55) and connected to said third cylinder-piston device (30) and said fourth cylinder-piston device (40) .

27. A remote actuation system according to claim 25,wherein said actuated device (50) exhibits a rotary movement and comprises a wheel (58) driven to rotate about a motion output axis (57) by means of a toothed pinionrack type coupling with respect to two rigid translating elements (59, 60) connected to said third cylinder-piston device (30) and said fourth cylinder-piston device (40) , respectively .

28. A remote actuation system according to claim 25, wherein said actuated device (50) exhibits a rotary movement about a motion output axis (61) and comprises an articulated mechanism (62) connected to said motion output axis (61) and said third cylinder-piston device (30) and said fourth cylinder-piston device (40) .

29. A robotic arm (400) having at least two actuated joints (70, 80) , wherein each of said at least two actuated joints (70, 80) is associated with a respective remote actuation system (300) according to at least one of claims 24 to 28.

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