Actuator with linear movement

Abstract

An actuator (10, 110) with linear movement, of the type using magnetorheological fluid, including a first section (11, 111) with a hollow member (12, 112) which develops about an axis (X) and which has, at opposite sides, a bottom (13, 113) and a head (14, 114), respectively, at least the head (14, 114) being bored for the passage of a rod (15, 115) which moves in translation with piston type means (16, 116) in the hollow member (12, 112) along the axis (X), the piston type means (16, 116) delimit at one side with the bottom (13, 113) and at the opposite side with the head (14, 114), respectively, a first chamber (17, 117) and a second chamber (18, 118) for a fluid, the first and second chambers (17, 117, 18, 118) being connected, respectively, to a first charging / discharging opening (19, 119) and to a second charging / discharging opening (20, 120) for the fluid. The actuator (10, 110) also includes a second section (21, 121) for controlling the translational movement of the rod (15, 115), the second section (21, 121) comprising a third chamber (22, 122) and a fourth chamber (23, 123) which are suitable for containing a magnetorheological fluid, and in fluid connection between them by means of at least one passage (24, 124), the second section (21, 121) being operatively connected to the first section (11, 111) by means of the rod (15, 115) in such a manner that there is induced with the translation movement thereof a variation in volume of the third and fourth chambers (22, 122, 23, 123) with a movement of the magnetorheological fluid through the at least one passage (24, 124), the second section (21, 121) being provided with electrical windings (26, 126) in the region of the at least one passage (24, 124), the electrical windings (26, 126) being suitable for generating magnetic fields for varying the sliding capacity of the magnetorheological fluid through the at least one passage (24, 124), influencing the advance speed of the rod (15, 115) during the translational movement thereof.

Description

[0001] TRANSLATION (RULE 12.3)

[0002] 14 October 2024

[0003] Actuator with linear movement

[0004] DESCRIPTION

[0005] The present invention relates to an actuator with linear movement, of pneumatic or hydraulic type.

[0006] The invention finds application especially in the industrial sector of machine tools such as presses, for example for deformation or shearing machining, in moulds or in general in machines and equipment that require the application of a linear force.

[0007] Other applications can be found, for example, in factory automation, such as for the lifting, lowering, pushing, pulling movements.

[0008] Actuators with linear movement are also known in the industry as "linear actuators" and can be of the pneumatically or hydraulically controlled type.

[0009] The use of pneumatically controlled actuators, also known as pneumatic actuators or pneumatic cylinders, is widespread due to their low cost, compact construction and the possibility, thanks to the external storage of compressed air in suitable tanks, of developing high specific power while having compact dimensions.

[0010] A single-acting pneumatic actuator typically has two chambers separated by the piston and a port with a compressed air connection, from which the compressed air is fed into one of the two chambers to push the piston in one direction. In the region of the other chamber there is a feed / discharge hole. In a double-acting actuator, compressed air is necessary for each movement direction, hence a gas connection in the region of each of the two chambers, so that both a pushing and a pulling force can be exerted on an external element connected to the actuator.

[0011] As is known, the hydraulic actuators are completely similar to pneumatic ones, replacing the compressed gas with the pressurized liquid.

[0012] Such linear actuators are not free of drawbacks, including the fact that the adjustment of the pushing force is limited to the adjustment of the pressure of the incoming fluid.

[0013] Another limitation is the difficulty of controlling the movement, especially when using a gaseous and therefore compressible fluid.

[0014] In order to control the movement of the piston, and thus its speed, it is known to couple the actuators, pneumatic and hydraulic ones, with hydraulic braking systems: the actuator drags a device on which proportional control hydraulic valves act, which possibly are in turn controlled by an electronic controller.

[0015] Such control equipment makes systems complex, cumbersome and expensive.

[0016] To date, it is also known to use actuators using magnetorheological fluids, comprising a fluid (typically mineral or synthetic oil) carrying a dispersion of metal powders which are sensitive to the magnetic field and whose shear stress depends on a viscous component typical of the carrier fluid and on a shear component proportional to the applied magnetic field, which orients the powders thereof. The activation and deactivation times of the magnetorheological behaviour at the onset of the magnetic field are a few milliseconds, thanks to the low orientation inertia of the metal powders. The fluid changes its sliding capacity to generate the required resistance when subjected to a magnetic field, which can be induced by the passage of current in cables placed in the region of a rod of the actuator.

[0017] A device using magnetorheological fluid is described in patent document SU859688, where two gas chambers are present which are separated by a first piston which moves in translation with a hollow rod on a fixed rod, the latter developing from a bottom and on which electrical windings are mounted. There is also a second piston, inside the hollow rod, which is made fixedly joined to the end of the fixed rod opposite to the end for coupling with the bottom. Two chambers for the magnetorheological fluid develop in the hollow rod, a first around the fixed rod and at one side of the second piston, a second at the opposite side of the same piston, communicating with passages in the region thereof. A compensation chamber is present in the second rod, in sequence with respect to the second chamber from which it is separated by means of a floating element.

[0018] In this solution, since the geometries of the chambers of the actuator are not symmetrical with respect to the piston that separates them, the behaviour of the magnetorheological fluid in the two directions, i.e. pushing and pulling of the actuator, is not the same, penalizing the reactivity and reliability of the device. Therefore, such devices have limitations when they are used as double-acting actuators, because it is impossible to control the return stroke of the rod with the same accuracy applicable in the pushing stroke (or vice versa).

[0019] Another drawback lies in the fact that the two chambers with different geometry make the presence of the compensation chamber indispensable, which leads to a constructive complication.

[0020] The aim of the present invention is to realize an actuator with linear movement capable of improving the prior art in one or more of the aspects indicated above.

[0021] Within this aim, an object of the invention is to realize an actuator with linear movement capable of developing a high power in both operational directions, pushing and pulling, while always ensuring an accurate control of the movement of the rod. Another object of the invention is to realize a double-acting linear actuator that has the same reliability and responsiveness for the two pushing and pulling directions.

[0022] A further object of the invention is to adjust the pushing and pulling force of the actuator without limitations due to the initial adjustment of the pressure of the fluid to be charged.

[0023] Yet another object of the invention is to provide a double-acting linear actuator whose pushing and pulling force can be modulated instant by instant.

[0024] It is also an object of the invention to realize an actuator with low costs and compact dimensions, but which at the same time is effectively controllable in speed, position and force.

[0025] This aim, as well as these and other objects, are achieved by an actuator with linear movement, as in the appended claim 1.

[0026] Said actuator is of the type using magnetorheological fluid and includes a first section with a hollow member which develops about an axis and which has, at opposite sides, a bottom and a head, respectively, at least said head being bored for the passage of a rod which moves in translation with piston type means in said hollow member along said axis, said piston type means delimit at one side with said bottom and at the opposite side with said head, respectively, a first chamber and a second chamber for a fluid, said first and second chambers are connected, respectively, to a first charging / discharging opening and to a second charging / discharging opening for the fluid.

[0027] Preferably, said actuator also includes a second section for controlling the translational movement of said rod, said second section comprising a third chamber and a fourth chamber which are suitable for containing a magnetorheological fluid and in fluid connection between them by means of at least one passage, said second section being operatively connected to said first section by means of said rod in such a manner that there is induced with the translation movement thereof a variation in volume of said third and fourth chambers with a movement of said magnetorheological fluid through said at least one passage, said second section being provided with electrical windings in the region of said at least one passage, said electrical windings being suitable for generating magnetic fields for varying the sliding capacity of said magnetorheological fluid through said at least one passage, influencing the advance speed of said rod during the translational movement thereof. In the context of the present invention, by the term "passage" is meant a circumscribed space of fluid connection between the third and fourth chambers and which can be shaped, for example, as a channel or a gap.

[0028] This passage is preferably calibrated.

[0029] The Applicant has noted that in the second section, by applying a magnetic field to the magnetorheological fluid, it is possible to increase the sliding resistance of the same fluid through the passage, which manifests itself as a resistance to the variation in volume of the third and fourth chambers and therefore to the movement of the rod. This therefore results in a control of the translation speed of the rod in the second section and consequently also in the first section for the operative connection between the two sections by means of the rod. The force of the actuator is therefore controllable without limitations due to the initial adjustment of the pressure of the gas to be charged.

[0030] Other preferred, but not exclusive, features of the invention are further defined in the dependent claims.

[0031] In one embodiment, said electrical windings comprise at least one first electrical winding and at least one second electrical winding in coils in transverse planes relative to said at least one passage.

[0032] Each winding is defined by a coil or a set of coils.

[0033] By the expression "transverse planes" is meant the planes defined by the coils themselves.

[0034] Preferably, the planes of the coils are transverse to the advance direction of the magnetorheological fluid in the passage.

[0035] In this way, the windings are able to generate magnetic fields that hit the magnetorheological fluid in a direction transverse to the advance direction of the same fluid in the passage.

[0036] Preferably, said at least one first electrical winding and said at least one second electrical winding are in coils in transverse planes relative to said axis.

[0037] Preferably in a substantially intermediate position between said at least one first electrical winding and said at least one second electrical winding there is associated at least one compensation element at least for the variations in volume of the magnetorheological fluid, said compensation element being subjected to the action of the same magnetorheological fluid which passes through said at least one passage. Preferably, said at least one first electrical winding is spaced apart from said at least one second electrical winding in the direction of said axis.

[0038] Preferably, the intermediate position is a position, in the direction of said axis, between said at least one first electrical winding and said at least one second electrical winding.

[0039] Preferably, in the presence of more than one first electrical winding and of more than one second electrical winding, the set of the first electrical windings is spaced apart from the set of second electrical windings in the direction of said axis.

[0040] Preferably, the intermediate position is a position, in the direction of said axis, between the set of the first electrical windings and the set of the second electrical windings.

[0041] Preferably, said first electrical windings in coils are spaced apart from said second electrical windings in coils in the direction of said axis, which is the direction of translation of said piston type means in said hollow member. Preferably, the intermediate position is a position, in the direction of said axis, between said first electrical windings and said second electrical windings.

[0042] By the term "associated", referred to the compensation element, is meant that it can be directly mounted in an intermediate position between the two windings or that in this position a fluid connection to the element, such as for example a pipe, can be provided.

[0043] By the expression "subjected to the action of the same magnetorheological fluid", referred to the compensation element, is meant that it can be reached by this fluid, performing its compensatory function.

[0044] In one embodiment, said at least one first electrical winding is closer to the third chamber, said at least one second electrical winding is closer to the fourth chamber. In one embodiment, the electrical windings are mounted in the region of a fixed portion of the second section.

[0045] It will be appreciated that avoiding mounting the windings on moving portions is in favour of the durability and reliability of the actuator.

[0046] The compensation element is preferably in an intermediate position between the third chamber and the fourth chamber.

[0047] The compensation element is preferably in a position that is equidistant from said third chamber and said fourth chamber.

[0048] Thanks to one or more of the above characteristics, the compensation element reacts in the passage of the fluid between the third and fourth chambers or vice versa and at least near the chamber of origin of the fluid. The Applicant has observed that this improves the control capacity of the system, because in both operative directions there are no delays in the pressurization of the chamber from which the magnetorheological fluid is pushed through the passage. In fact, the characteristics of the magnetorheological fluid, and therefore the relative force due to the shear component, can be activated at least upstream of the compensation element, preventing portion of the compressed volume, in the chamber from which the magnetorheological fluid is pushed through the passage, from occupying the volume of the compensation element, limiting the control capabilities on the system.

[0049] It will be appreciated that, thanks to the presence of two distinct electrical windings or two distinct groups of windings (first and second) and with interposition of the compensation element between the two, the actuator is able to guarantee the control of the movement of the rod both during the pushing phase and pulling phase.

[0050] In one embodiment, said at least one first electrical winding and said at least one second electrical winding can be separately supplied with electrical energy.

[0051] By the term "supplied with electrical energy" here is meant that it is possible to have the current passing through the cable of the electrical winding.

[0052] By the term "separately" is meant that it is possible to supply with electrical energy one electrical winding at a time or a group of windings at a time.

[0053] In this way it is possible to create magnetic fields only in a position more approached to the chamber of origin of the fluid, based on the phase of use of the actuator, that is, the pushing or pulling phase.

[0054] In one embodiment said compensation element comprises at least one resiliently deformable element.

[0055] In one embodiment said compensation element comprises at least one compensation device.

[0056] In one embodiment said compensation element comprises at least one compensation chamber.

[0057] In one embodiment, said compensation element is in fluid connection with said at least one passage by means of at least one respective pipe.

[0058] Said compensation device is preferably a gas or spring hydraulic accumulator.

[0059] Preferably, said compensation device is mountable at the outlet of the fluid from the pipe.

[0060] Preferably, the pipe is between the third and fourth chambers.

[0061] Said resiliently deformable element is preferably a component chosen from a resilient ring, an element made of rubber foam of the closed-cell type or a piston or a resiliently deformable membrane, which lies on a spring or on a chamber charged by gas.

[0062] In one embodiment, said at least one passage is in the form of a gap. Preferably, said gap is annular.

[0063] In one embodiment, said resiliently deformable element comprises a resilient ring which is positioned in the region of said gap.

[0064] In this way, the compensation is effective simultaneously over the entire circular area of the gap, when it is annular.

[0065] In one embodiment, said piston type means comprise a first piston and a second piston which are coaxial and spaced apart along said axis and between which said second section is present.

[0066] In one embodiment, said third and fourth chambers are successively defined inside said hollow member between said first and second pistons and separated by an intermediate portion of said hollow member which surrounds a portion of said rod.

[0067] In one embodiment, said third and fourth chambers have, in a specular manner with respect to a centre plane of said intermediate portion, areas which are identical in cross-sections relative to said axis.

[0068] The aforesaid axis is preferably perpendicular to the centre plane.

[0069] The Applicant has noted that with these identical areas it is possible to minimise the volume to be compensated for, which is thus limited to the variations due to thermal expansion and compressibility. In addition, the fact that the areas involved of the third and fourth chambers on which the fluid acts have the same geometry, favours a similar behaviour and control in pushing and pulling.

[0070] In one embodiment, said at least one passage is provided in the region of said intermediate portion, said electrical windings being mounted on said intermediate portion.

[0071] In this way, the magnetic field generated is able to modify the magnetorheological fluid by orienting the metal powders specifically in the region of the passage and the windings supplied with electrical energy.

[0072] The intermediate portion is a fixed portion of the second section.

[0073] Preferably, the compensation element is provided in the region of the intermediate portion.

[0074] In one embodiment, said intermediate portion is interposed, along said axis, between a first tubular jacket and a second tubular jacket of said hollow member.

[0075] In one embodiment, said first piston and said second piston are able to slide, in said first tubular jacket, between said bottom and said intermediate portion, and in said second tubular jacket, between said head and said intermediate portion, respectively. In one embodiment, there is present a distance between said intermediate portion and said rod, which defines said at least one passage.

[0076] In one embodiment, said intermediate portion comprises a first annular element, said compensation element is mountable in the region of said first annular element.

[0077] In one embodiment, said first annular element is closed in a sandwich-like manner between at least two second annular elements, in the region of said second annular elements there are mounted respective said at least one first electrical winding and said at least one second electrical winding.

[0078] By "at least two second annular elements" is meant that there may be more second elements in series, constituting two distinct series that close in a sandwich-like manner the first annular element. The same windings, first or second, are mounted on each element of the same series.

[0079] In one embodiment, there are present two second annular elements, on one of which there is mounted said at least one first electrical winding, on the other said at least one second electrical winding.

[0080] In one embodiment, wherein the compensation element comprises a resiliently deformable element which consists of a resilient ring, this is mounted in a corresponding internal circular groove of the first annular element, facing the passage.

[0081] In one embodiment, wherein the compensation element comprises a compensation device, this is in fluid connection with the passage preferably by means of a respective pipe that passes through the first annular element.

[0082] Preferably, the electrical windings are wound in coils on rings and retained between these and the second annular elements.

[0083] In one embodiment, said intermediate portion comprises a first portion with a bush which surrounds a portion of said rod, said electrical windings being mounted on an external side of said bush, said intermediate portion also comprises a second portion which coaxially surrounds said first portion, said at least one passage is provided between said portions.

[0084] By "external side", referred to the bush, is meant the side in the region of the curved wall with the larger diameter.

[0085] In one embodiment, there is present a distance between said first portion and said second portion which defines said at least one passage.

[0086] Preferably, said distance defines said at least one passage is in the form of a gap.

[0087] Preferably, said second portion surrounds said first portion with at least one first annular element and with at least two second annular elements which close in a sandwich-like manner said at least one first annular element.

[0088] Preferably, the bush is mounted in a fluid-tight manner around the rod. Even more preferably, by sealing means.

[0089] In this way, the magnetorheological fluid is prevented from leaking between the bush and the rod, while allowing a minimum play for the translation of the rod inside the bush.

[0090] In one embodiment, wherein the compensation element comprises a compensation device, one said at least one pipe is provided in the region of said second portion.

[0091] In one embodiment, wherein the compensation element comprises one said resiliently deformable element, this is mounted on said bush.

[0092] Preferably, the resiliently deformable element is mounted in a seat on the internal side of the bush, in the bush there being provided one said pipe for the movement of the magnetorheological fluid from the passage to the resiliently deformable element.

[0093] In one embodiment, said piston type means comprises a piston which separates said first chamber from said second chamber and said second section is provided in sequence with respect to said first section.

[0094] In one embodiment, said second section is positioned in the region of said bottom. Preferably, the second section is joined to the bottom, outside said hollow member.

[0095] In one embodiment, said bottom is bored for the passage of said rod so as to project outside said hollow member at the side opposite the side of said head in order to move in translation in said second section.

[0096] In one embodiment, said second section comprises a hollow element and a tubular element, said tubular element being received coaxially in said hollow element, wherein said third and fourth chambers can be identified in said tubular element, a further piston, fixedly joined to said rod, sliding inside said tubular element in a fluid- tight manner, said further piston separating said third chamber from said fourth chamber, wherein said at least one passage being provided between said tubular element and said hollow element.

[0097] In one embodiment, said electrical windings are mounted on an external side of said tubular element.

[0098] Preferably, they are mounted in circular grooves of the tubular element.

[0099] By "external side", referred to the tubular element, is meant the side in the region of the curved wall with the larger diameter.

[0100] In one embodiment, the tubular element and the hollow element are a fixed portion of the second section.

[0101] In one embodiment, the passage consists of a gap which can be identified between the external wall of the tubular element and the internal wall of the hollow element. Such walls are preferably curved and circular in cross-section.

[0102] In one embodiment, the hollow element has a substantially cup-shaped shape, with opening turned towards said bottom.

[0103] In one embodiment, said hollow element is passed through by said at least one pipe. In one embodiment, wherein the second section is provided in sequence with respect to the first section, the magnetorheological fluid is contained in the hollow element, which is provided in sequence with respect to the hollow member.

[0104] It will be appreciated that this allows the volumes of the third and fourth to be sized independently of the dimensions of the hollow member. In the second section it is therefore possible to work with magnetorheological fluid at higher pressures than those in the first section, limiting the volumes of the third and fourth chambers and therefore also their difference, even if the third and fourth chambers do not have the same geometry and the same cross-sectional areas.

[0105] In one embodiment there are present sensors for detecting position and speed of the rod.

[0106] In one embodiment there is present an electronic control system able to modulate the current intensity to the electrical windings.

[0107] The characteristics and advantages of the invention will become better apparent from the description of some of its preferred, but not exclusive, embodiments, illustrated by way of non-limiting example in the accompanying drawings in which:

[0108] - figure 1 illustrates a longitudinal section of the actuator according to the invention in a first embodiment thereof;

[0109] - figure 1A illustrates an enlarged portion of the actuator of figure 1;

[0110] - figure 2 illustrates a longitudinal section of the actuator according to the invention in a variant of the first embodiment;

[0111] - figure 2A illustrates an enlarged portion of the actuator of figure 2;

[0112] - figure 3 illustrates a longitudinal section of the actuator according to the invention in another variant of the first embodiment;

[0113] - figure 3A illustrates an enlarged portion of the actuator of figure 3;

[0114] - figure 4 illustrates a longitudinal section of the actuator according to the invention in a further variant of the first embodiment;

[0115] - figure 4A illustrates an enlarged portion of the actuator of figure 4; - figure 5 illustrates a longitudinal section of the actuator according to the invention in a second embodiment thereof;

[0116] - figure 6 illustrates another longitudinal section of the actuator of figure 5;

[0117] - figure 6A illustrates an enlarged portion of the actuator of figure 6;

[0118] - figure 7 illustrates a longitudinal section of the actuator according to the invention in a variant of the second embodiment;

[0119] - figure 8 illustrates another longitudinal section of the actuator of figure 7;

[0120] - figure 8A illustrates an enlarged portion of the actuator of figure 8.

[0121] With reference to figures 1 to 4, the actuator according to the invention in a first embodiment thereof is indicated overall with 10. In particular, figures 2 to 4 refer to some possible variants of the actuator of figure 1, differing in the portion reported in the respective enlargements. The enlargements are identified in all the tables of the drawings with letter A, which follows the number of the respective figures.

[0122] In a second embodiment thereof, the actuator according to the invention is indicated overall with 110 and is illustrated in figures 5 to 8. In particular, figures 7 and 8 refer to a possible variant of the actuator shown in figures 5 and 6, differing in the portion reported in the enlargements.

[0123] The features and components common to the two embodiments are described below. For the second embodiment, the numbers were preceded by 1, obtaining a numbering greater than 100.

[0124] The actuator 10, 110 is with linear movement, of the type using magnetorheological fluid and with pressurized control fluid chosen between gas and liquid depending on the applications, however connected to a pressurized source, for example a gas accumulator.

[0125] As illustrated, in both embodiments it includes a first section 11, 111 with a hollow member 12, 112 which develops about an axis X and having, at opposite sides, a bottom 13, 113 and a head 14, 114, respectively. The head is bored for the passage of a rod 15, 115 which moves in translation with piston type means 16, 116 in the hollow member 12, 112 along the axis X. The hollow member has longitudinal development.

[0126] The piston type means 16, 116 delimit at one side with the bottom 13, 113 and at the opposite side with the head 14, 114 respectively a first chamber 17, 117 and a second chamber 18, 118 for a fluid, i.e. the control fluid. By "control fluid" is meant the fluid used to fill the chambers in the pushing or pulling phases and which can be compressible or incompressible. Said first chamber 17, 117 and second chamber 18, 118 are connected to a first charging / discharging opening 19, 119 and to a second charging / discharging opening 20, 120 of the control fluid, respectively. These openings are obtained the first 19, 119 on the bottom 13, 113 the second 20, 120 on the head 14, 114.

[0127] The actuator 10, 110 can be used with single action or with double action, filling one of the two aforementioned chambers with the fluid, depending on whether a pushing phase or a pulling phase is required to the rod.

[0128] The actuator 10, 110 according to the invention also includes a second section 21, 121, for controlling the translation movement of the rod 15, 115.

[0129] The second section 21, 121 comprises a third chamber 22, 122 and a fourth chamber 23, 123 which are suitable for containing a magnetorheological fluid and in fluid connection between them by means of at least one passage 24, 124.

[0130] The enlargements show at least part of the second section of each embodiment and in the different variants. The passages 24, 124 are indicated in the enlargements.

[0131] The second section 21, 121 is operatively connected to the first section 11, 111 by means of the rod 15, 115 in such a manner that there is induced with the translation movement thereof a variation in volume of the third 22, 122 and of the fourth chamber 23, 123 with a movement of the magnetorheological fluid through the passage 24, 124.

[0132] In particular, it has the form of a gap 25, 125, preferably, but not necessarily, with constant section. In the illustrated examples, this gap has an annular shape. However, this does not exclude that it may have a different shape, for example with an open ring, or that there may be more passages, for example more gaps defined by annular sectors of gap.

[0133] The second section 21, 121 is provided with electrical windings 26, 126 in the region of the passage 24, 124 and which are suitable for generating magnetic fields to vary the sliding capacity of the magnetorheological fluid through the passage 24, 124 influencing the advance speed of the rod 15, 115 during the translational movement thereof.

[0134] The cables of the electrical windings can be run by a current that can preferably be modulated in intensity. The electrical windings are schematically represented in the figures that show the actuators as a whole, while the enlargements also show the wound electrical cables, that is, the coils that make up each winding. In a simplified manner, there are illustrated only three coils for each winding, the real number depends on technical needs. The electrical windings are mounted, in both embodiments, in the region of a fixed portion of the second section 21, 121 and which is made of a high magnetic permeability material. Also the rod 15, 115 is made of a high magnetic permeability material. By high magnetic permeability material is meant a material with ferromagnetic behaviour with high magnetic permeability values.

[0135] Such material is preferably low carbon steel, pure iron or other alloys specific for magnetic applications.

[0136] In this way the lines of force of the magnetic fields, which are shown in the enlargements and indicated with B, are not interrupted by the components of the actuator and by closing around the windings they are able to hit the magnetorheological fluid in the zone of the passage.

[0137] The electrical windings 26, 126 comprise first electrical windings 26a, 126a and second electrical windings 26b, 126b in coils in transverse planes relative to the passage, the former ones closer to the third chamber and the others closer to the fourth chamber. In an intermediate position between these, therefore also in an intermediate position between the third and fourth chambers, there is associated at least one compensation element 27, 127 at least for the variations in volume of the magnetorheological fluid. The compensation element 27, 127 is subjected to the action of the magnetorheological fluid which passes through the passage 24, 124.

[0138] In particular, the first electrical windings 26a, 126a and the second electrical windings 26b, 126b are in coils in transverse planes relative to the axis X.

[0139] The planes of the coils are also transverse to the advance direction of the magnetorheological fluid in the passage.

[0140] The first and second electrical windings 26a, 126a and 26b, 126b can be separately supplied with electrical energy. For example, only the first ones can be passed through by current, for the pushing phase of the rod, or only the second ones for the pulling phase, that is, the one with the rod retracting in the hollow member.

[0141] In the first embodiment there are present a first winding 26a and a second winding 26b, while in the second embodiment there are present two first windings 126a and two second windings 126b. This does not exclude that in other embodiments and / or variants the windings may be present in different numbers.

[0142] The first electrical winding 26 (or the set of the first electrical windings 126a) is spaced apart from the second electrical winding 26b (or from the set of the second electrical windings 126b) in the direction of the axis X, and the intermediate position is a position in the direction of the axis X between the first electrical winding 26a (or the set of the first electrical windings 126a) and the second electrical winding 26b (or the set of the second electrical windings 126b).

[0143] The compensation element 27, 127 comprises a resiliently deformable element 28 or a compensation device 28a, 128a (shown schematically) or a compensation chamber 129. The compensation element 27, 127 is in fluid connection with the passage 24, 124 by means of a respective pipe 30, 130, when it does not directly face the passage.

[0144] In a same embodiment, not illustrated, more than one compensation element and more than one type may be present.

[0145] In the actuators shown in figures 1 and 4 the compensation element 27 is a resiliently deformable element 28 which consists of a resilient ring positioned in the region of the gap 25, 125.

[0146] In the actuators shown in figures 2, 3 and 5, the compensation element 27, 127 is a compensation device 28a, 128a to be mounted outside the actuator 10, 110, at the outlet of the magnetorheological fluid from the pipe 30, 130.

[0147] This compensation device can be a gas or spring hydraulic accumulator, of the piston or membrane or bag type. Optionally, in embodiments not illustrated, it can be integrated into the actuator.

[0148] In both embodiments there are preferably sensors (not shown) for detecting the position and the speed of the rod 15, 115 and also an electronic control system able to modulate the current intensity to the electrical windings.

[0149] According to the first embodiment 10, the piston type means 16 comprise a first piston 32 and a second piston 33 which are coaxial and spaced apart along the axis X and between which the second section 21 is present.

[0150] In particular, the third and fourth chambers 22, 23 are successively defined inside the hollow member 12 between the first and second pistons 32, 33 and separated by an intermediate portion 34 of the hollow member which surrounds a portion of the rod 15.

[0151] The intermediate portion 34 is a fixed portion of the second section 21 and the electrical windings 26 are mounted on this intermediate portion 34. This intermediate portion 34 is made of a high magnetic permeability material. The passage 24 is provided in the region of the intermediate portion 34.

[0152] The third and fourth chambers 22, 23 have, in a specular manner with respect to a centre plane of the intermediate portion 34, areas which are identical in crosssections relative to the axis X. The axis X is perpendicular to the planes of such sections and to the centre plane.

[0153] The intermediate portion 34 is interposed, along the axis X, between a first tubular jacket 40 and a second tubular jacket 41 of the hollow member 12.

[0154] The first piston 32 and the second piston 33 are able to slide in the first tubular jacket 40, between the bottom 13 and the intermediate portion 34, and in the second tubular jacket 41, between the head 14 and the intermediate portion 34, respectively. In the examples of actuator 10 shown in figure 1 and figure 2, there is present a distance between the intermediate portion 34 and the rod 15, which defines the passage 24 in the form of a gap 25.

[0155] The intermediate portion 34 has an overall annular shape.

[0156] The compensation element 27 is provided in the region of the intermediate portion 34.

[0157] Still with reference to the same examples, the intermediate portion 34 comprises a first annular element 35 in the region of which the compensation element 27 can be mounted. Said first annular element 35 is closed in a sandwich-like manner between two second annular elements 36a and 36b; respective electrical windings 26 are mounted in the region of said second elements. A first electrical winding 26a is mounted on one, a second electrical winding 26b is mounted on the other. In variants not illustrated, it is possible to add series of second annular elements to install other respective electrical windings and increase the magnetorheological effect.

[0158] In the example of figure 1 the compensation element 27 comprises a resiliently deformable element which consists of the resilient ring. This is mounted in a corresponding internal circular groove 37 of the first annular element 35, directly facing the passage 24, thus the gap 25.

[0159] In the example of figure 2 the compensation element 27 consists of a compensation device 28a which is in fluid connection with the passage by means of a pipe 30 which passes through the first annular element 35.

[0160] For both examples, in the region of the second annular elements 36a, 36b there are mounted respective electrical windings, i.e. the first 26a and the second 26b. The windings are wound in coils on respective rings 38a, 38b, retained between these and the second annular elements. The second annular elements 36a, 36b have holes, respectively 39a and 39b, for the passage of the cables of the windings towards the outside of the actuator.

[0161] As visible in the enlargements, the rings 38 have a substantially U-shaped section, the cavity of which is exploited for mounting the windings and which is turned towards the internal circular wall of the second annular elements, defining a circular seat for the windings.

[0162] In the examples of actuator 10 shown in figures 3 and 4, the intermediate portion 34 comprises a first portion 42 with a bush 43 which surrounds a portion of the rod 15. The bush is the only element of the first portion. On an external side of the bush 43, there are mounted the electrical windings 26, the first 26a and the second 26b, in special circular grooves 45. The bush surrounds the rod so as to allow the translation thereof and is mounted in a fluid-tight manner around the rod, by sealing means such as ring-like gaskets 44.

[0163] In the example of figure 3 there is present a gasket 44 of a bidirectional type, so as to achieve a sealing on both sides, mounted in an intermediate position between the two windings 26a and 26b. In the example of figure 4 there is a pair of gaskets 44 of the unidirectional type on opposite portions of the resiliently deformable element 28. The gaskets 44 are mounted in corresponding internal circular grooves of the bush 43, to prevent fluid from leaking between the bush 43 and the rod 15.

[0164] The intermediate portion 34 also comprises a second portion 46 which surrounds coaxially the first portion 42. Between the two portions, there is provided the passage 24. In particular, between the first portion 42 and the second portion 46 there is present a distance which defines the passage in the form of a gap 25. The second portion 46 surrounds the first with a first annular element 35' and with two second annular elements 36a' and 36b' which close in a sandwich-like manner the first annular element 35'.

[0165] The distance is due to the radial difference between the two portions.

[0166] In the variant of figure 3, the pipe 30 is provided in the region of the second portion 46, in order to pass through the first annular element 35' up to outside, where, as a compensation element, a compensation device 28a can be connected.

[0167] In the variant of figure 4, the compensation element is a resiliently deformable element 28 which is mounted on the bush 43. In particular, in a circular seat on the internal side of the bush 43. In this case, in the bush 43 there is provided a pipe 30 for the movement of the magnetorheological fluid from the passage 24, i.e. of the gap 25, to the resiliently deformable element 28.

[0168] The cables of the windings may be carried by the circular grooves 45 to the outside by means of channels (for simplicity's sake not illustrated) which passes through both the first portion and the second portion.

[0169] In the second embodiment 110, the piston type means 116 comprises a piston 148 which separates the first chamber 117 from the second chamber 118 and the second section 121 is provided in sequence with respect to the first section 111.

[0170] The second section 121 is positioned in the region of the bottom 113, joined thereto outside the hollow member 112.

[0171] The bottom 113 is bored for the passage of the rod 115 so as to project outside the hollow member 112 at the side opposite the side of the head 114 in order to also move in translation in the second section 121, so as to make the operative connection between the two sections.

[0172] As shown in the enlargements of figures 6A and 8A, the second section 121 comprises a hollow element 149 and a tubular element 150. The tubular element 150 is received coaxially in the hollow element 149. The third chamber 122 and the fourth chamber 123 can be identified in the tubular element 150. A further piston 151, which is fixedly joined to the rod 115, slides in a fluid-tight manner inside the tubular element 150 and separates the third chamber 122 from the fourth chamber 123. Between the tubular element 150 and the hollow element 149 there is a passage 124, i.e. the gap 125. The latter can be identified between the curved external wall of the tubular element and the internal wall of the hollow element, which is curved and circular in cross-section.

[0173] The electrical windings 126 are mounted on an external side of the tubular element 150, in circular grooves 152 facing the gap 125. Two first electrical windings 126a and two second electrical windings 126b are mounted at opposite sides of an intermediate zone, with respect to the direction of the axis X. The lines of force B of the magnetic field close around a winding with direction opposite to that of the lines on the other winding of the same group.

[0174] The tubular element 150 and the hollow element 149 are a fixed portion of the second section and are both made of a high magnetic permeability material.

[0175] The hollow element 149 has a substantially cup-like shape, with opening turned towards the bottom 113, to which it is made fixedly joined by mechanical means, such as for example stud screws 153.

[0176] The hollow element 149 is passed through by the pipe 130, transversely in the region of the intermediate zone, so as to connect the gap 125 to a compensation element 127.

[0177] In the example shown with figures 5 and 6, the compensation element 127 consists of a compensation device 128a that can be installed outside the hollow element 149, at the outlet of the pipe 130. In the variant shown in figures 7 and 8, the compensation element 127 consists of a compensation chamber 129 in connection with the passage 124, i.e. with the gap 125, by means of the pipe 130. The chamber 129 is suitably provided therein with a floating element 131 which can move in translation therein as a function of the volume required for the magnetorheological fluid. In variants not illustrated, the floating element can be replaced by an elastomer membrane blocked perimetrically to the internal wall of the chamber.

[0178] The compensation chamber 129 is defined at the side opposite the side of the opening of the hollow element 149, between the bottom of the latter and a closing element 154, which is fixed to the hollow element by means of other stud screws 155.

[0179] The compensation chamber is suitable for compensating both the variations in volume of the magnetorheological fluid and the difference in volume available to the third and fourth chambers, due to the different geometries.

[0180] The operation of the actuator, according to the invention, is as follows.

[0181] With reference to the first embodiment of the actuator 10, during the pushing phase the control fluid is pushed with pressure through the first opening 19 to pressurize the first chamber 17, while the second chamber 18 is connected to the discharge by means of the second opening 20 or is at a lower pressure, causing the translation of the rod 15 out of the head 14. In a fixedly joined manner with the rod 15, the first piston 32 and the second piston 33 move in translation. Thanks to the operative connection of the first section 11 with the second section 21, the translation causes not only a variation in the volumes of the first chamber and of the second chamber 17, 18, but also a variation in the volumes of the third and fourth chambers 22, 23 with the push of the magnetorheological fluid from the third chamber 22 to the fourth 23 through the gap 25.

[0182] In this phase the windings 26 can be supplied with electrical energy. The magnetic field generated hits the magnetorheological fluid, causing the metal powders to be arranged transversely to the advance direction of the fluid itself. In particular, only the first winding 26a can be supplied with electrical energy, in such a manner as to create a pressure rise in the third chamber 22, proportional to the current that runs through the windings.

[0183] The compensation element 27, whether it is the resiliently deformable element 28 or a compensation device 28a to be connected to the outlet of the pipe 30, being interposed between the third chamber 22 and the fourth chamber 23, by expanding or compressing allows to compensate for the variations in volume of the fluid in the fourth chamber 23 due to the different thermal regimes or to the effect of the compression of the fluid in the third chamber 22, without producing response delays in the pressurization of the third chamber 22, which would happen with a compensation volume dedicated to this chamber.

[0184] During the return stroke of the rod 15, then during the pulling phase of the actuator 10, the control fluid pressurizes the second chamber 18 while the first chamber 17 is connected to the discharge by means of the first opening 19 or to a lower pressure, causing the translation with return of the rod. Following this movement, the magnetorheological fluid is pushed from the fourth chamber 23 to the third chamber 22 through the gap 25. In this phase only the second winding 26b can be supplied with electrical energy. This creates a pressure rise in the fourth chamber. The compensation element 27 makes it possible to compensate for variations in the volume of the fluid in the third chamber 22.

[0185] Since the third and fourth chambers 22, 23 have the same geometry and the same cross-sectional areas, the volume to be compensated for is minimal, so that it can be obtained even only by means of a resilient ring or other compensation devices of relatively compact dimensions compared to the compensation chambers used to date in the actuators of known type.

[0186] Both during pushing and pulling, the compensation element 27, being located downstream of the portion of fluid hit by the magnetic field, does not affect the dynamic response of the magnetorheological fluid.

[0187] During the described phases, it is possible to modulate the current to the windings and consequently the magnetic field that is established in the gap 25, obtaining a resistance force that affects the translation of the rod 15 which depends on the current that runs through the windings. A second resistance force on the rod 15 depends on the viscous resistances due to the passage of the magnetorheological fluid through the gap 25, which depends in a proportional manner on the flow velocity of the fluid through the gap itself.

[0188] By appropriately sizing the areas of the four chambers, as well as the gap 25 and the intensity and extension of the magnetic field generated and the number of windings, it is possible to modulate the resistance force due to the magnetorheological behaviour of the fluid.

[0189] With reference to the second embodiment of the actuator 110, during the pushing phase the control fluid is pushed with pressure through the first opening 119 to pressurize the first chamber 117, while the second chamber 118 is connected to the discharge by means of the second opening 120 or is at a lower pressure, causing the translation of the rod 115 out of the head 114. In a fixedly joined manner with the rod 115 not only the piston 148 that separates the first chamber 117 from the second chamber 118 moves in translation, but also the further piston 151 that separates the third chamber 122 from the fourth chamber 123 moves in translation, thanks to the operative connection of the first section 111 with the second section 121. A variation in the volumes of the third and fourth chambers 122, 123 thus occurs with the magnetorheological fluid being pushed from the third chamber 122 to the fourth 123 through the gap 125.

[0190] In this phase only the first windings 126a can be supplied with electrical energy, in such a manner as to create a pressure rise in the third chamber 122, proportional to the current that runs through the windings.

[0191] The compensation element 127 allows to compensate for the variations in volume of the fluid in the fourth chamber 123 due to the difference in section of the two chambers, to the different thermal regimes or to the effect of the compression of the fluid in the third chamber 122, without producing response delays in the pressurization of the third chamber 122, which would happen with a compensation volume dedicated to this chamber.

[0192] During the return stroke of the rod 115, thus during the pulling phase, the control fluid pressurizes the second chamber 118 while the first chamber 117 is connected to the discharge or to a lower pressure, causing the translation with return of the rod. Meanwhile, the magnetorheological fluid is pushed from the fourth chamber 123 to the third chamber 122 through the gap 125. In this phase, the second windings 126b may be supplied with electrical energy, while the others may not be fed by current. The compensation element 127, being connected with pipe 130 interposed between the two chambers, allows to compensate for the variations in volume of the fluid in the third chamber 122.

[0193] It should be noted that, regardless of the embodiment, the direction of circulation of the current in adjacent windings belonging to a same group is alternated in such a manner that the magnetic flows generated can conveniently be added.

[0194] It should be noted that, regardless of the embodiment, the actuator according to the invention works with the combination of three force components generating a resultant force on the rod: a first essentially driving force due to the pressure of the control fluid acting on the first and second chamber and two resistance force components, one of which is due to the nature of the magnetorheological behaviour of the fluid present in the chambers of the second section and modulable through the current that runs through the windings, and one due to the viscosity of the magnetorheological fluid and proportional to the flow velocity through the passage.

[0195] It should also be noted that by sizing the actuator in such a manner that the resistance force due to the magnetorheological behaviour of the fluid is conveniently greater than the force of the control fluid, it is possible to stop the device in any position.

[0196] In general, by modulating the resistance force due to the magnetorheological behaviour, it is possible to control the working speed of the actuator in both operative directions, thus ensure the control of the translation movement of the rod.

[0197] In practice, it has been found that the invention achieves the intended aim and objects by realizing an actuator with linear movement for which it is possible to guarantee a control of the movement of the rod, in speed, position and force, both during the pushing and pulling phase with the same accuracy, reliability and reactivity.

[0198] In addition, it was found that the resultant force of the actuator is adjustable instant by instant simply by modulating the magnetic field and therefore the behaviour of the magnetorheological fluid, without limitations due to the initial adjustment of the pressure of the gas to be charged.

[0199] The invention is susceptible to many modifications and variants, all falling within the same inventive concept.

Claims

CLAIMS1. An actuator (10, 110) with linear movement, of the type using magnetorheological fluid, including a first section (11, 111) with a hollow member (12, 112) which develops about an axis (X) and which has, at opposite sides, a bottom (13, 113) and a head (14, 114), respectively, at least said head (14, 114) being bored for the passage of a rod (15, 115) which moves in translation with piston type means (16, 116) in said hollow member (12, 112) along said axis (X), said piston type means (16, 116) delimit at one side with said bottom (13, 113) and at the opposite side with said head (14, 114), respectively, a first chamber (17, 117) and a second chamber (18, 118) for a fluid, said first and second chambers (17, 117, 18, 118) are connected, respectively, to a first charging / discharging opening (19, 119) and to a second charging / discharging opening (20, 120) for the fluid, said actuator (10, 110) also includes a second section (21, 121) for controlling the translational movement of said rod (15, 115), said second section (21, 121) comprising a third chamber (22, 122) and a fourth chamber (23, 123) which are suitable for containing a magnetorheological fluid, and in fluid connection between them by means of at least one passage (24, 124), said second section (21, 121) being operatively connected to said first section (11, 111) by means of said rod (15, 115) in such a manner that there is induced with the translation movement thereof a variation in volume of said third and fourth chambers (22, 122, 23, 123) with a movement of said magnetorheological fluid through said at least one passage (24, 124), said second section (21, 121) being provided with electrical windings (26, 126) in the region of said at least one passage (24, 124), said electrical windings (26, 126) being suitable for generating magnetic fields for varying the sliding capacity of said magnetorheological fluid through said at least one passage (24, 124), influencing the advance speed of said rod (15, 115) during the translational movement thereof.

2. An actuator (10, 110) according to claim 1, wherein said electrical windings (26, 126) comprise at least one first electrical winding (26a, 126a) and at least one second electrical winding (26b, 126b) in coils in transverse planes relative to said at least one passage (24, 124), in a substantially intermediate position between said at least one first electrical winding (26a, 126a) and said at least one second electrical winding (26b, 126b) there being associated at least one compensation element (27, 127) at least for the variations in volume of the magnetorheological fluid, said compensation element (27, 127) being subjected to the action of thesame magnetorheological fluid which passes through said at least one passage (24, 124).

3. An actuator (10, 110) according to claim 2, wherein said at least one first electrical winding (26a, 126a) and said at least one second electrical winding (26b, 126b) can be separately supplied with electrical energy.

4. An actuator (10, 110) according to claim 2 or claim 3, wherein said compensation element (27, 127) comprises at least one resiliently deformable element (28) and / or at least one compensation device (28a, 128a) and / or at least one compensation chamber (129).

5. An actuator (10, 110) according to one or more of the preceding claims, wherein said at least one passage (24, 124) is in the form of a gap (25, 125).

6. An actuator (10, 110) according to claim 4 and 5, wherein said resiliently deformable element (28) comprises a resilient ring which is positioned in the region of said gap (25).

7. An actuator (10, 110) according to one or more of claims 2 to 4, wherein said at least one compensation element (27, 127) is in fluid connection with said at least one passage (24, 124) by means of at least one respective pipe (30, 130).

8. An actuator (10) according to one or more of the preceding claims, wherein said piston type means (16) comprises a first piston (32) and a second piston (33) which are coaxial and spaced apart along said axis (X) and between which said second section (21) is present.

9. An actuator (10) according to claim 8, wherein said third and fourth chambers (22, 23) are successively defined inside said hollow member (12) between said first and second pistons (32, 33) and are separated by an intermediate portion (34) of said hollow member (12) which surrounds a portion of said rod (15).

10. An actuator (10) according to claim 9, wherein said third and fourth chambers (22, 23) have, in a specular manner with respect to a centre plane of said intermediate portion (34), areas which are identical in cross-sections relative to said axis (X).

11. An actuator (10) according to claim 9 or claim 10, wherein said at least one passage (24) is provided in the region of said intermediate portion (34), said electrical windings (26) being mounted on said intermediate portion (34).

12. An actuator (10) according to one or more of claims 9 to 11, wherein said intermediate portion (34) is interposed, along said axis (X), between a first tubular jacket (40) and a second tubular jacket (41) of said hollow member (12), saidfirst piston (32) and said second piston (33) are able to slide, in said first tubular jacket (40), between said bottom (13) and said intermediate portion (34) and, in said second tubular jacket (41), between said head (14) and said intermediate portion (34), respectively.

13. An actuator (10) according to one or more of claims 9 to 12, wherein there is present a distance between said intermediate portion (34) and said rod (15) which defines said at least one passage (24).

14. An actuator (10) according to one or more of claims 9 to 13 when dependent on claim 2, wherein said intermediate portion (34) comprises a first annular element (35), said compensation element (27) being mountable in the region of said first annular element (35), said first annular element (35) is closed in a sandwich-like manner between at least two second annular elements (36a, 36b), in the region of said second annular elements (36a, 36b) there are mounted respective said at least one first electrical winding (26a) and said at least one second electrical winding (26b).

15. An actuator (10) according to one or more of claims 9 to 12, wherein said intermediate portion (34) comprises a first portion (42) with a bush (43) which surrounds a portion of said rod (15), said electrical windings (26) being mounted on an external side of said bush (43), said intermediate portion (34) also comprises a second portion (46) which coaxially surrounds said first portion (42), said at least one passage (24) is provided between said portions (42, 46).

16. An actuator (110) according to one or more of claims 1 to 7, wherein said piston type means (116) comprise a piston (148) which separates said first chamber (117) from said second chamber (118) and said second section (121) is provided in sequence with respect to said first section (111).

17. An actuator (110) according to claim 16, wherein said second section (121) is positioned in the region of said bottom (113).

18. An actuator (110) according to claim 16 or claim 17, wherein said bottom (113) is bored for the passage of said rod (115) so as to project outside said hollow member (112) at the side opposite the side of said head (114) in order to move in translation in said second section (121).

19. An actuator (110) according to one or more of claims 16 to 18, wherein said second section (121) comprises a hollow element (149) and a tubular element (150), said tubular element (150) being received coaxially in said hollow element (149), wherein said third and fourth chambers (122, 123) can be identified in saidtubular element (150), a further piston (151), fixedly joined to said rod (115), sliding inside said tubular element (150) in a fluid-tight manner, said further piston (151) separating said third chamber (122) from said fourth chamber (123), wherein said at least one passage (124) being provided between said tubular element (150) and said hollow element (149).

20. An actuator (110) according to claim 19, wherein said electrical windings (126) are mounted on an external side of said tubular element (150).

21. An actuator (110) according to claim 19 or claim 20, wherein said hollow element (149) is passed through by said at least one pipe (130).

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