EA037146B1 - Linear actuator for moving at least one closing element - Google Patents

Abstract

A linear actuator comprising at least one jacket (10) defining an axis (X) and at least one rod (20) having an end cylinder (21) tightly slidable in the at least one jacket (10) and an opposite end (22) sliding between a rest position and a working position. The end cylinder (21) divides the at least one jacket (10) into at least one first and second variable volume compartments (18', 18") fluidically independent to each other, one of them (18', 18") being fluidically insulated and under vacuum, the other (18', 18") being fluidically communicating with the outside environment. Upon the passage of the opposite end (22) from the rest position to the working position one of the compartments (18', 18") passes from a minimum volume to a maximum volume, in order to suck the at least one rod (20) automatically recalling the opposite end (22) from the working position to the rest position.

Description

(54) LINEAR ACTUATOR FOR MOVING AROUND THE MEASUREMENT OF ONE CLOSING ELEMENT (31) 102017000011597; 102017000011628 (32) 2017.02.02 (33) IT (43) 2019.11.29 (86) RSTLV2018 / 050667 (87) WO 2018/142338 2018.08.09 (71) (73) Applicant and patent owner:

IN AND TEK S.R.L. (IT) (72) Inventor:

Bucchetti Luciano (IT) (74) Representative:

Nosyreva E.L. (RU) (56) DE-U1-202005017068 DE-U1-202005001524

037146 B1

037146 Bl (57) A linear actuator comprising at least one casing (10) defining the axis (X) and at least one rod (20) having an end cylindrical part (21) capable of being displaced with a snug fit into at least one casing (10), and the opposite end (22), shifting between the rest position and the working position. The end cylindrical part (21) divides at least one casing (10) into at least one first and second cavities (18 ', 18) of variable volume, not connected by fluid with each other, while one of the cavities (18' , 18) is isolated by fluid and is under vacuum, while the other cavity (18 ', 18) is in fluid communication with the external environment. When the opposite end (22) moves from the rest position to the working position, one of the cavities (18 ', 18) changes the volume from the minimum to the maximum in order to retract at least one rod (20), automatically returning the opposite end (22) from the working position to the resting position.

The technical field to which the invention relates

The present invention mainly relates to the field of technology related to moving systems and, in particular, relates to a linear actuator.

The present invention further relates to an opening / closing system comprising such a drive.

Prior art

As you know, there are two main types of linear actuators - hydraulic or pneumatic.

In both cases, the actuator must be connected to the supply line of the working fluid, which is either oil or compressed air.

This entails an undoubted disadvantage, expressed in the need to control the working fluid, with all the associated problems. As a consequence, these types of drives are unsuitable for all kinds of non-industrial applications, such as moving a sliding door or door leaf.

Gas compression and extension springs are also known. These types of springs use a gas, mainly nitrogen, to return the stem back to its resting position after it has been pushed or pulled into a working position.

A known disadvantage of these types of springs is that over time they tend to leak, which leads to the need for periodic replacement. Moreover, since the stem opposes the gas when the stem is pushed or pulled, the gas pressure increases, and as a result, the force required to move the stem increases.

The essence of the invention

It is an object of the present invention to at least partially eliminate the aforementioned disadvantages by providing a linear actuator having the characteristics of high functionality, simplicity and low cost.

It is another object of the present invention to provide a linear actuator that always requires the same force to move the stem regardless of its position.

Another object of the present invention is to provide a linear actuator that requires minimal maintenance.

Another object of the present invention is to provide a linear actuator with a limited size.

Another object of the present invention is to provide an actuator that automatically closes / opens a door or a door leaf in an open / closed position.

It is another object of the present invention to provide a linear actuator that provides controlled movement of the cover to which it is coupled.

Another object of the present invention is to provide a linear actuator that has a minimum number of parts.

These objectives, as well as other objectives that will become more apparent in the future, are satisfied by a linear actuator in accordance with what is described, depicted and / or claimed in this document.

The linear actuator may comprise at least one casing defining an axis and at least one rod having an end cylindrical part made with the possibility of reciprocating displacement with a tight fit relative to at least one casing along the axis between the rest position and the working position ...

The end cylindrical part can divide at least one casing into at least one first and second cavities of variable volume, not connected to each other by a fluid medium, wherein one of the at least one first and second cavities of variable volume is made with the possibility of isolation and sealing, while the other of the at least one first and second cavities of variable volume can be in fluid communication with the external environment.

When the end cylindrical part moves from the rest position to the working position, one of the at least one first and second cavities of variable volume can expand to retract the end cylindrical part from the working position to the rest position by automatically returning at least one rod.

Preferably, in said linear actuator, the minimum volume of one of the at least one first and second variable volume cavities may be substantially zero, like its internal pressure.

Preferably, in said linear actuator, at least one housing may comprise one side wall and a pair of end walls, the cylindrical end piece being substantially in contact with one of the end walls in the rest position.

Preferably, in the specified linear actuator, the casing may comprise a tubular element, defining the side wall, and an end cap mutually tightly connected to the tubular element, wherein the end cap comprises one of the end walls, wherein at least one stem and a tubular element mutually configured, thus, when the end cap and the tubular element are interconnected, one of the end walls and the end cylindrical part are in mutual contact, in order to thus ensure that one of the at least one first and second cavities of variable volume is substantially under vacuum ...

Preferably, in said linear actuator, at least one rod may further comprise an end opposite to the end cylindrical part, configured to be shifted outwardly relative to at least one casing along an axis between a position closest to the at least one casing corresponding to one of the rest position and the working position of the end cylindrical part, and a position distant from at least one casing corresponding to the other from the rest position and the working position of the end cylindrical part.

Preferably, in the aforementioned linear actuator, one of the end walls can be a side wall, while the other of the end walls can be an opposite wall having a through hole for the passage of at least one rod, wherein one of the at least one first and second cavities is variable volume may contain a bottom wall, while the proximal position of the opposite end of at least one rod corresponds to the rest position of the end cylindrical part.

Preferably in the specified linear actuator in the specified other of the specified at least one first and second cavities of variable volume or from it can flow an air flow from the external environment or into it.

Preferably, in said linear actuator, when the end cylindrical part moves from said resting position to said working position, said other of said at least one first and second cavities of variable volume may decrease, releasing air into the environment when said end cylindrical part is pulled from said working position to the specified rest position, while the other of the specified at least one first and second cavities of variable volume expands by drawing in air from the external environment.

Preferably, said linear actuator may further comprise means for controlling the flow of air flowing inward / out of another of said at least one first and second variable volume cavities to control the force required to move said end cylindrical part from said resting position to said operating position, and / or to control the speed of its retraction from the specified working position to the specified resting position.

Preferably, in said linear actuator, the control means may comprise first and second lines for fluid communication with the external environment of said other of said at least one first and second cavities of variable volume;

means in the form of pipeline fittings selectively acting on one of said first and second fluid connection lines to open them upon transition of said end cylindrical part from said resting position to said operating position and close them upon return transition to force air to flow into said other of said at least one first and second cavities of variable volume through another of said first and second lines for fluid connection.

Preferably, in the aforementioned linear actuator, the control means may also comprise adjusting means acting on said other of said first and second fluid connection lines to control the cross-section of the flow channel.

Preferably, in said linear actuator, another of said first and second fluid connection lines may comprise at least one conduit, said control means comprising an adjusting screw having a control end accessible from the outside by an operator and a working end acting on said at least at least one pipeline.

In a further aspect, regardless of the configuration of the aforementioned linear actuator, a flow control unit for a working fluid may be provided in accordance with what is described, depicted and / or claimed herein.

A control unit for controlling the flow of a working fluid can be configured to be connected to a linear actuator, which can comprise at least one casing defining an axis and at least one rod having an end cylindrical part that can be shifted in a reciprocating manner with a snug fit relative to at least one casing along the axis between the resting position and the working position.

In the aforementioned flow control unit, the cylindrical end piece may divide the at least one casing into at least one first and second non-fluid cavities of variable volume. One of at least one first and second cavities of variable volume may be in fluid communication with the external environment.

The control unit may contain the first and second lines for fluid connection of one

- 2 037146 of at least one first and second cavities of variable volume with the external environment, and means in the form of pipeline fittings selectively acting on one of the first and second lines for fluid connection to open it when the end cylindrical part passes from the rest position into the working position and closing it during the reverse transition.

Thus, air can be made to flow into another of the at least one first and second cavities of variable volume through the other of the first and second fluid connection lines.

Preferably, the flow control unit described above may further comprise control means acting on said other of said first and second fluid connection lines to control the cross-section of the flow channel.

Preferably, in said flow control unit, another of said first and second fluid connection lines may comprise at least one conduit, said control means comprising an adjusting screw having a control end accessible from the outside by an operator and a working end acting on said at least one pipeline.

A linear actuator may also be provided comprising a control unit for controlling the flow of a working fluid as described above.

In particular, this linear actuator can comprise at least one casing defining an axis;

at least one rod having an end cylindrical part made with the possibility of reciprocating shift with a snug fit relative to the specified at least one casing along the specified axis between the resting position and the working position;

means for controlling the air flow flowing inward / out of said one of said at least one first and second cavities of variable volume for controlling the force required to move said end cylindrical part from said resting position to said working position and / or to control its speed retracting from the specified working position to the specified resting position;

wherein said end cylindrical part divides said at least one casing into at least one first and second cavities of variable volume that are not fluidly connected to each other, wherein one of said at least one first and second cavities of variable volume is located in fluid communication with the external environment;

wherein said control devices comprise or provide a control unit as described above.

Preferably, in an actuator comprising a control unit as described above, said one of said at least one first and one second variable volume cavities may allow air to flow from or into the external environment.

Preferably, in an actuator comprising a control unit mentioned above, upon transition of said end cylindrical part from said resting position to said operating position, said one of said at least one first and second cavities of variable volume can be reduced by bleeding air into the external environment, while upon transition of said end cylindrical part from said working position to said resting position, said one of said at least one first and second cavities of variable volume can expand by drawing in air from the external environment.

Preferably, in an actuator comprising a control unit as mentioned above, the linear actuator may have one or more of the characteristics described.

Brief description of graphic materials

Additional features and advantages of the present invention will become more apparent in view of the detailed description of some preferred, but not exclusive, embodiments of the linear actuator 1, which are shown by way of non-limiting example using the accompanying drawings, in which: FIG. 1a and 2a show schematic views of an embodiment of a system 100 for closing an opening P by means of a sliding door D movable by a preferred non-exclusive embodiment of a linear actuator 1 to the closed position of the door D and the open position of the door D, respectively;

in fig. 1b and 2b show schematic views of an embodiment of the linear actuator 1 of FIG. 1a and 2a, respectively, in the closed position of the door D and in the open position of the door D;

in fig. 3 shows an exploded view of an embodiment of the linear actuator 1 of FIG. 1a and FIG. 2a;

in fig. 4a and 4b show, respectively, sectional views of the ends 13 and 13 'of the tubular element 11 according to the linear actuator 1 embodiment of FIG. 1a and FIG. 1b in the closed position of the door D;

in fig. 5 shows a cross-sectional view of an end 13 of a tubular element 11 according to an embodiment.

- 3 037146 of the linear actuator 1 of FIG. 2a and 2b with door D open;

in fig. 6 shows a cross-sectional view of an end 13 of a tubular element 11 according to a further embodiment of a linear actuator 1 with an end 22 in a distal position;

in fig. 7 shows a cross-sectional view of an end 13 'of a tubular element 11 according to a further embodiment of the linear actuator 1 of FIG. 6 with end 22 in the proximal position;

in fig. 8a and 8b are enlarged schematic views of an embodiment of the system 100 of FIG. 1a and 2a, which show the linear actuator 1 in the closed position of the door D and the open position of the door D;

in fig. 9a and 9b show cross-sectional views of the embodiment of the linear actuator 1 shown in FIG. 8a and 8b, respectively, in the closed position D of the door and the open position D of the door.

DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS

With reference to the above figures, a linear actuator 1 is described that is capable of linear movement of any object, mechanism or system. The linear drive can act directly or indirectly by means of pulleys or auxiliary mechanisms.

In a preferred, but not exclusive, embodiment of the present invention, the linear actuator 1 can be used in the system 100 to close / open the opening P by means of a cover D movable between an open position and a closed position.

In general, the opening P can be any opening in any fixed support structure, and the cover D can be any of, for example, a door, a door leaf, a manhole cover, a hinged door, or the like. Likewise, the cover D can be moved using any motion directed directly along the shear plane or rotational about the axis of rotation.

For example, as shown in FIG. 1a and 2a, the opening P can be a passage formed in the wall W, and the cover D can be a sliding door in the plane defined by the door itself between the closed position shown in FIG. 1a and the open position shown in FIG. 2a. FIG. 1b and 2b respectively show the linear actuator 1 in positions corresponding to those in FIG. 1a and 2a.

In general, the linear actuator 1 may comprise a housing 10 defining an X-axis and a rod 20 movable therein between a reduced position, illustrated by way of example in FIG. 1b and an expanded position, exemplarily illustrated in FIG. 2b.

Even if hereinafter, the shroud 10 is described as being movable relative to the stationary rod 20, it should be understood that the opposite can also occur, i. E. the stem can move relative to the stationary casing without thus departing from the scope of protection of the appended claims.

It should also be understood that even if one stem 20 and one casing 10 are provided in the illustrated embodiments, the linear actuator 1 may comprise multiple casings and / or multiple stems as it can be connected to other actuators, such as gas springs of a known type, without deviations, therefore, from the scope of protection of the appended claims.

In any case, the movable element of the linear actuator 1, the casing 10 in the embodiment shown in the accompanying figures, can be connected to the sliding door D, while the stationary element, the rod 20 in the embodiment shown in the accompanying figures, can be attached to the wall W.

Thus, the shroud 10 will slide with the door between its open and closed positions.

For this purpose, shearing means can be provided, for example two or more carriages 110, 111, during operation, engaged with one or more rail guides 120 defining a shear direction d substantially parallel to the X-axis defined by the casing.

Advantageously, the carriages 110, 111 can be adapted to be connected to the tubular element 11 of the linear actuator 10, for example can be inserted into it with the possibility of sliding.

Thus, this results in a compact, easy to implement and functional linear actuator.

These features allow it to be contracted or lengthened, or to be a low-lying, open, C-shaped tubular member 130 that can be inserted into, or integral with, a door frame or false ceiling.

Preferably, the linear actuator profile 130 1 can be located above the sliding door D. Alternatively, it can also be located to the side of the door D or even below it, using suitable return means such as pulleys and cables.

Linear actuator 1 applicable to system 100 can be of any type. It will preferably be of the pneumatic type, for example a gas spring of a known type.

In a preferred, but not exclusive, embodiment of system 100, actuator 1 may have the characteristics described below.

- 4 037146

Even if in the rest of the description the linear actuator 1 is described as moving the sliding door D, it should be understood that the linear actuator 1 can have any application without thereby departing from the protection scope of the appended claims.

As mentioned above, in this description, the concept of a shift between the stem 20 and the housing 10 and the corresponding parts should be understood in a relative, not absolute, sense. Thus, even though the displacement of the rod 20 relative to the casing 10 is described for simplicity, it should be understood that the displacement between these portions is reciprocating and relative to each other.

In the embodiment shown in FIG. 1-5, the reduced position of FIG. 1b, corresponding to the closed position of the door D, corresponds to the rest position of the linear actuator 1, i.e. one in which the linear actuator 1 itself is not subject to external stress.

On the other hand, the expanded position of FIG. 2b, corresponding to the open position of the door D, corresponds to the operating position of the linear actuator 1, that is, one in which the linear actuator 1 is subjected to a voltage generated by the force that the user applies to the door to open it. From this position, linear actuator 1 automatically closes door D, or, equivalently, linear actuator 1 automatically returns it to the rest position.

In this embodiment, therefore, the linear actuator 1 is pulling.

Advantageously, the rod 20 may comprise a cylindrical end piece 21 and an opposite end 22, both of which can be easily displaced with a tight fit relative to each other along the X axis by means of a rod 20. The end cylindrical piece 21 will thus move between the rest position and the working position ...

The cylindrical end piece 21 can be slid to fit tightly within the casing 10 by means of a spacer 23 of a known type. The opposite end 22 is movable outwardly from the casing 10 between a position close to it corresponding to the rest position shown in FIG. 1b, and its distal position corresponding to the operating position shown in FIG. 2b.

The casing 10 may comprise a tubular element 11 defining its side wall, an end cap 12 tightly screwed on the end 13 'of the tubular element 11, and a cover element 14 tightly screwed on the other end 13 of the tubular element 11.

The stem 20 can be inserted through an opening 15 passing through the wall 14 'of the cover 14.

Advantageously, the rod 20 and the tubular element 11 may be of such mutual configuration that when the end 22 is in the proximal rest position, as shown, for example, in FIG. 1b, the bottom wall 16 of the end cap 12 contacts the end cylindrical part 21, as shown in particular in FIG. 4b.

The end cylindrical part 21 can divide the casing 10 into first and second cavities 18 ', 18 of variable volume, which are not fluidly connected to each other, i. E. cavities that are not in fluid communication with each other and between which no fluid is exchanged.

When the end 22 is in a resting position, as shown, for example in FIG. 1b, the variable volume cavity 18 'has the minimum volume, while the variable volume cavity 18 has the maximum volume, and the situation is reversed when the end 22 is in the operating position, as shown, for example, in FIG. 2b.

Since the end cap 12 is tightly screwed to the tubular element 11 and the end cylindrical part 21 is tightly inserted therein, the cavity 18 'is fluid-insulated, i. E. the fluid cannot enter or exit it.

On the other hand, since when the end 22 is in a resting position as shown, for example in FIG. 1b, the bottom wall 16 of the end cap 12 is in contact with the cylindrical end piece 21, as shown in particular in FIG. 4b, cavity 18 'is under vacuum. In this position, therefore, the volume of the cavity 18 'corresponding to its minimum volume is essentially zero, as is the pressure within it.

To this end, screwing on the end cap 12 can be carried out when the cylindrical end piece 21 is already at the end 13 'of the tubular element 11. This occurs when the end 22 is in the proximal rest position, as shown, for example in FIG. 1b. By introducing the cylindrical end piece 21 through the end 13, it is in fact possible to expel substantially all of the air from the cavity 18 ', which is then closed by the end cap 12.

Consequently, the cavity 18 'is kept under vacuum without the aid of external vacuum pumps or means.

It should be understood, however, that it is possible to place the cavity 18 'under vacuum in any way, for example by connecting it to external vacuum pumps or means, without thereby departing from the protection scope of the appended claims.

Advantageously, the cavity 18 may be in fluid communication with the external environment.

- 5 037146

Therefore, the cavity 18 can be at atmospheric pressure, that is, the pressure of the external environment.

In relation to the above, in the closed position of the door shown in FIG. 1a, the cylindrical end piece 21 remains adjacent to the bottom wall 16 of the end cap 12, and thus the end face 22 remains in the resting position closest to the casing 10.

After the user opens the sliding door D, i.e. when the end 22 passes from the rest position closest to the casing 10 to the working position farthest from it, the cavity 18 'expands, increasing in volume, up to the maximum volume, while the cavity 18 narrows, decreasing in volume, down to the minimum volume.

In doing this, the user acts on the vacuum in the cavity 18 ', which ensures that the same force is always required to open the sliding door D, regardless of its position. At the same time, the cavity 18 releases the air in it to the outside.

After the user leaves the door D in the open position, the vacuum in the cavity 18 'will retract the rod 20, automatically returning the end 22 towards the resting position close to the casing 10, returning the end cylindrical part 21 to the state of abutment against the end cover 12 and automatically closing the sliding door D. As a consequence, the cavity 18 will be filled with air from the outside.

Due to the fact that the cavity 18 'is considered empty, the linear actuator 1 ensures that the force required to open / close the door D from this position is constant.

It is also obvious that the linear actuator 1 is extremely functional and simple and economical to manufacture and assemble.

In fact, the assembly is carried out as described above: the rod 20 is introduced through the tubular element 11, the end cap 12 is screwed on the end 13 'of the latter, as described above, to obtain a cavity 18' under vacuum, and the closing element 14 is screwed in accordance with the opposite end 13 after inserting it at end 22 of rod 20 through hole 15.

Assembly is then completed by attaching the elastomeric membrane 24 to the stem 20 and inserting it into the mounting location 26, blocking the axial movement of the latter by means of a retaining ring 25, which may be, for example, a Seger ring.

Since the number of structural parts, for example, involved in movement in a reciprocating manner, is minimal, the linear actuator will require minimal maintenance and will guarantee a long service life.

The dimensions of the linear actuator 1 are minimal, making it suitable for any application such as moving sliding doors or sliding door leaves, as described in more detail below.

The simplicity of the linear actuator 1 will always guarantee automatic closing / opening of a door or leaf from an open / closed position.

In a preferred, but not exclusive, embodiment of the present invention, the cover 14 may comprise means for controlling the flow of air in / out of the variable volume cavity 18 to control the force required to open the sliding door D and its closing speed.

It should be understood that the controls can also be performed for only one of the functions described above, and in particular to control the force required to move the cylindrical element 21 from the rest position to the operating position or to control the rate of its retraction towards the closed position without retreating. therefore from the scope of protection of the appended claims.

For this purpose, in general, first and second lines can be provided to provide a fluid connection of the cavity 18 of variable volume with the external environment and means in the form of pipeline fittings acting on them.

In the embodiment shown in FIG. 1-5, the first fluid connection line may be defined by a portion of the through hole 15 and a conduit 19.

In this line for fluid connection, when the end cylindrical part 21 passes from the rest position to the operating position, the air in the cavity 18 will pass through the through hole 15, entering the pipeline 19 through the hole 19 and exiting through the outlet 19 ' ... It is obvious that when the end cylindrical part 21 is pulled from the working position to the resting position, the air will make a return path, entering through the hole 19 'to reach the expanding cavity 18.

Alternatively, the second fluid connection line may be defined by the bore 15, the mounting location 26, and the annular gap 27 between the retaining ring 25 and the stem 20.

In this line for fluid connection, when the end cylindrical part 21 passes from the resting position to the operating position, the air in the cavity 18 will reach the outlet 27 when passing through the hole 15 passing through and the installation location 26, while when retracted, 6 037146 When the end cylindrical part 21 from the working position to the resting position, the air will make a return path, entering through the annular gap 27 to reach the expanding cavity 18.

The means in the form of pipeline fittings can be determined by the installation site 26, which will act as a valve seat for axial movement of the elastomeric membrane 24, which will act as a plug for the through hole 15 when the end cylindrical part 21 is pulled from the working position to the rest position and will be supported onto the retaining ring 25 when the end cylindrical part 21 moves from the rest position to the working position, allowing in any case the passage of air.

In other words, during the opening of the sliding door D, the air in the tapering cavity 18 can pass without restriction both through the pipe 19 and through the annular gap 27, while during the closing of the sliding door D, the air will only pass through the pipe 19, reaching expanding cavity 18.

By appropriately dimensioning the above-described parts, both the force required to open the sliding door D and its closing speed can be controlled. In particular, the force required to open the sliding door D can be determined by the diameter of the end cylindrical part 21.

For the purpose of adjusting the latter, a suitable adjustment means can be provided, for example an adjusting screw 30 for adjusting the cross-section of the flow channel. Thus, it will be possible to regulate the flow of air entering the pipeline 19 through the opening 19 'when the end cylindrical part 21 is pulled from the working position to the rest position, thus adjusting the speed of return to the closed position of the sliding door D.

For this purpose, the adjusting screw 30 can have a control end 31 ', accessible from the outside by the operator, and a working end 31, acting on the pipeline 19.

It should be understood that the controls described above can be applied to any linear actuator, preferably of the pneumatic type, without thereby departing from the protection scope of the appended claims.

For example, the controls referred to above may be applied to a gas spring of a known type, or a gas spring of a known type may include these controls.

In another embodiment of the linear actuator 1, shown, for example, in FIG. 6 and 7, the rest position of end 22 may correspond to a distal position relative to its housing 10, as shown, for example, in FIGS. 6, while the operating position of the end 22 may correspond to the position closest to its casing 10, as shown, for example, in FIG. 7.

In this embodiment, the cavity 18 can be fluidly isolated and evacuated, while the cavity 18 'can be in fluid communication with the outside to remain at atmospheric pressure.

For this purpose, when the end 22 is in the rest position, the end cylindrical part 21 of the rod 20 can abut against the closing element 14, and in particular against its stop wall 14 ', while, when the end 22 is in the working position, the end cylindrical part 21 stem 20 may remain spaced from bottom wall 16 of end cap 12 to expose opening 19 of conduit 19.

Therefore, when end 22 is at rest, the volume and pressure of cavity 18 are substantially zero.

This embodiment will function in the opposite way to the embodiment shown in FIG. 1b-5, and will thus work in compression rather than tension.

After the user applies pressure to the rod 20 from the extended resting position to the reduced operating position, the cavity 18 will actually retrack the same rod, returning it to the resting position.

From what has been described above, it will be apparent that the invention meets its intended objectives.

The invention is susceptible to numerous modifications and changes, and they all fall within the inventive idea expressed in the appended claims. All parts can be replaced with other technically equivalent elements, and materials can be different as required without departing from the scope of the present invention.

Although the present invention has been described with specific reference to the accompanying drawings, the reference numbers used in the description and the claims are used to enhance the understanding of the present invention and do not limit in any way the claimed scope of protection.

Claims (9)

1. Linear drive for moving at least one cover element (D), containing - 7 037146 at least one casing (10) defining an axis (X); at least one rod (20) having an end cylindrical part (21), made with the possibility of a reciprocating shift with a snug fit relative to the specified at least one casing (10) along the specified axis (X) between the rest position and the working position ; wherein said end cylindrical part (21) divides said at least one casing (10) into at least one first and second cavity (18 ', 18) of variable volume; control means for controlling the flow of air flowing into or out of the other of said at least one first and second cavities (18 ', 18) of variable volume to control the force required to move said end cylindrical part (21) from said resting position to the specified working position or the speed of its retraction from the specified working position to the specified resting position; wherein said control means comprise first and second lines for fluid communication with the external environment of said other of said at least one first and second cavities of variable volume; means in the form of pipeline fittings selectively acting on one of said first and second fluid connection lines to open them upon transition of said end cylindrical part from said resting position to said operating position and close them upon transition back to force air to flow into said other of said at least one first and second cavities of variable volume through another of said first and second lines for fluid connection; control means containing an adjusting screw having a control end accessible from the outside by the operator, and a working end acting on the specified at least one pipeline; characterized in that said at least one first and second cavities (18 ', 18) of variable volume are not fluidly connected to each other; wherein one of the specified at least one first and one second cavities (18 ', 18) of variable volume is isolated in a fluid medium and is under vacuum, while the other of the specified at least one first and second cavities (18', 18) variable volume is in fluid communication with the external environment with the ability to draw in ambient air from the external environment or release ambient air into it; wherein when said end cylindrical part (21) moves from said resting position to said working position, said one of said at least one first and second cavities (18 ', 18) of variable volume expands so as to draw in said at least one a rod (20) for returning the specified end cylindrical part (21) from the working position to the rest position. 2. An actuator according to claim 1, characterized in that the minimum volume of said one of said at least one first and second variable volume cavities (18 ', 18) is substantially zero. 3. An actuator according to claim 1, characterized in that the pressure inside said one of said at least one first and second cavities (18 ', 18) of variable volume is substantially zero. 4. The drive according to claim 1, characterized in that said at least one casing (10) comprises a side wall (11) and a pair of end walls (14 ', 16), wherein said end cylindrical part (21) is in said position rest is essentially in contact with one of the specified end walls (14 ', 16). 5. The drive according to claim 4, characterized in that said casing comprises a tubular element (11) defining said side wall and an end cap (12) mutually tightly connected to said tubular element (11), said end cap ( 12) contains the specified one of the specified end walls (14 ', 16), while the specified at least one rod (20) and the specified tubular element (11) have such a mutual configuration that when interconnecting said end cap (12) and of said tubular element (11), said one of said end walls (14 ', 16) and said end cylindrical part (21) are in mutual contact engagement, thus ensuring that said one of said at least one first and second cavities (18 ', 18) of variable volume essentially under vacuum. 6. An actuator according to claim 4, characterized in that said at least one rod (20) further comprises an end face (22) opposite to said end cylindrical part (21), made with the possibility of sliding outwardly relative to said at least one casing ( 10) along the axis (X) between the position closest to the specified at least one casing (10) corresponding to one of the rest position and the working position of the specified end cylindrical part (21), and the position farthest from it, corresponding to another from the rest position and the working position of the specified end cylindrical part (21). 7. Drive according to claim 6, characterized in that one of said end walls (16) is lower - 8 037146 wall, while the other of the specified end walls (14 ') is the opposite wall having a through hole (15) for the passage of the specified at least one rod (20), while the specified one of the specified at least one first and the second cavities (18 ') of variable volume contains the specified lower wall (16), while the proximal position of the opposite end (22) of the specified at least one rod (20) corresponds to the rest position of the specified end cylindrical part (21). 8. Drive according to claim 1, characterized in that the air flow flows into said other of the at least one first and second cavities (18 ', 18) of variable volume from the external environment and vice versa. 9. Drive according to claim 8, characterized in that when said end cylindrical part (21) moves from said resting position to said operating position, said other of said at least one first and second cavities (18 ', 18) of variable volume decreases by releasing air into the external environment, when the specified end cylindrical part (21) is drawn from the specified operating position to the specified rest position, the other of the specified at least one first and second cavities (18 ', 18) of variable volume expands by drawing in air from the external environment ...