WO2017030475A1

WO2017030475A1 - A fluid actuator arrangement

Info

Publication number: WO2017030475A1
Application number: PCT/SE2015/050877
Authority: WO
Inventors: Magnus Landberg
Original assignee: Saab Ab
Priority date: 2015-08-18
Filing date: 2015-08-18
Publication date: 2017-02-23

Abstract

The present invention regards a fluid actuator arrangement comprising a first cylinder (3, 3') and a first piston body (5, 5') symmetrically arranged along a longitudinal axis (X), wherein the first cylinder (3, 3') exhibits a cylindrical inner peripheral surface (7), a first end (9, 10) and a second end (11, 12) forming a first cylinder interior (13); the first piston body (5, 5') comprises a first portion (21, 21') and second portion (23, 23') and a radially protruding portion (15) therebetween,the radially protruding portion (15) is slidingly arranged in the first cylinder interior (13) and protrudes outwardly towards the cylindrical inner peripheral surface (7) dividing the first cylinder interior (13) into a first cylinder chamber (17) and a second cylinder chamber (19). The first portion (21, 21')of the first piston body (5, 5´) sealingly extends through a first opening (25) of the first end (9) and the second portion (23, 23')of the first piston body (5, 5´) sealingly extends through a second opening (27) of the second end (11);and the first portion (21, 21') of the first piston body (5, 5') exhibits a larger diameter than the second portion (23, 23') of the first piston body (5, 5') and comprises an open cavity (29).

Description

A fluid actuator arrangement

TECHNICAL FIELD

The present invention relates to a fluid actuator arrangement according to the preamble of claim 1. The present invention concerns the industry using hydraulic and/or pneumatic actuators for different types of applications and also concerns the manufacture industry producing such arrangements.

The invention is not limited thereto, but can also be used for replacing electrical actuator arrangements and can be adapted for application of a wide range of different types industries.

The invention may relate to single acting fluid actuator arrangements. The present invention may also relate to fluid actuator arrangements using two or more cooperating fluid actuators coupled to a common piston rod. By controlling the pressurizing of a first cylinder chamber of a first fluid actuator for propelling the first piston body and in this connection pressurizing a piston rod engagement and disengagement means of said piston body by the fluid pressure used in the first cylinder chamber, the first piston body will clamp against the piston rod and move the piston rod relative the first cylinder in one stroke. The further motion of the piston rod is maintained by controlling the other fluid actuator in a similar way at the same time as the first fluid actuator is not pressurized for disengagement of the piston rod from the first piston body of the first fluid actuator for returning it in position for a new working stroke.

BACKGROUND ART Current fluid actuators may be bulky, especially in view of saving space in the periphery of the first cylinder and/or to save space in the axial direction.

This desire of designing less bulky fluid actuators has been known for a long time.

Hydraulic equipment in general, and hydraulic actuators especially, may be bulky for certain applications and are therefore often replaced by electric actuators. There is shown in DE 2818416 Al an arrangement having cylinders mounted in tandem for cooperating operation wherein the arrangement is designed with a dimension of the working cylinder as small as possible, but still achieving maximum force. However, the pistons in DE 2818416 Al do not protrude from the first cylinder. SUM MARY OF THE INVENTION

There is an object to provide a compact fluid actuator arrangement of the type defined in the introduction.

There is also an object to provide a compact fluid actuator arrangement including at least two cylinders (actuators) with relative small cylinder chamber volumes, wherein the first cylinders (actuators) co-operate.

There is also an object to provide a compact fluid actuator arrangement that can perform a long stroke suitable for elevator applications.

There is an object to provide a compact fluid actuator arrangement that can use a common fluid supply system for the retraction sequence in an energy efficient way.

An object is to provide a compact fluid actuator arrangement that is of low weight compared with current actuator arrangements.

A yet further object is to provide a compact fluid actuator arrangement that operates with variable speed and force using a minor fluid reservoir. There is an object to provide a compact fluid actuator arrangement, which is environmental friendly and provides clean operating environment.

An object of the present invention is to develop an energy saving compact fluid actuator arrangement providing reliable functionality.

A yet further object is to provide a compact fluid actuator arrangement that can be applied to long distance and extended piston rod members. The arrangement is preferably put into use in e.g. elevators and high bay storage arrangements having extended and relatively long piston rods. A further object is to use an arrangement in gravitation propelled applications.

This has been achieved by a fluid actuator arrangement comprising a first cylinder and a first piston body symmetrically arranged along a longitudinal axis, the first cylinder exhibits a cylindrical inner peripheral surface, a first and a second end forming a first cylinder interior; a radially protruding portion of the first piston body protrudes outwardly towards the cylindrical inner peripheral surface and divides the first cylinder interior into a first and second cylinder chamber; the first piston body comprises a first and second portion, the fluid actuator arrangement is characterized by that the first portion sealingly extends through a first opening of the first end and the second portion sealingly extends through a second opening of the second end; the first portion of the first piston body exhibits a larger diameter than the second portion of the first piston body and comprises an open cavity.

In such way is achieved that the first portion of the first piston body extending through the first opening will have a larger diameter than the second portion of the first piston body. This will make it possible to provide an open cavity centrally in the first portion along the longitudinal axis and directed away with its entrance and facing away from the first piston body.

Preferably, the open cavity is open in a direction corresponding with the direction of the working stroke of the first piston body.

In such way is achieved that the arrangement is compact and light. There is thus achieved that several cylinders can be stacked in a compact way. There is also achieved that the retraction of the not actuated (disengaged) piston body of a first cylinder into the actuated (engaged) piston body of the second cylinder can be made by using a common hydraulic power system (fluid supply).

Preferably, the open cavity is dimensioned to encompass a complementary device of the arrangement being positioned along the longitudinal axis and mounted adjacent the first piston body end.

Thereby is achieved that the open cavity entirely or partially will encompass a device positioned in line with and adjacent the first cylinder an piston body end and in position along the longitudinal axis. The device may constitute a brake apparatus, security locking device, electronic circuits, etc. Preferably, the open cavity is formed to encompass entirely or partially a member corresponding with the second portion of a second piston body of an arrangement similar to said fluid actuator arrangement and arranged in tandem with it.

This will provide a compact arrangement of alternately actuated actuators arranged in tandem (each comprising a first cylinder and a first piston body) for making a relative motion between cylinders and a common piston rod over a long distance.

Suitably, the open cavity exhibits an open direction facing away from the second portion of the first piston body in a direction along the longitudinal axis.

Suitably, the open cavity is open in an end opposite the radially protruding portion in a direction along the longitudinal axis. In such way is achieved that during a reciprocal action of the first piston body, the first portion of the first piston body alternately will encompass (entirely or partially) the device positioned adjacent the first cylinder (i.e. closer to the first portion than to the second portion of the first piston body) and along the longitudinal axis. Preferably, the respective first and second cylinder chamber is provided for coupling to a valve member of a fluid supply.

Thereby is achieved that a common fluid supply system can be used for the working stroke and the retraction stroke.

Suitably, the valve member comprises a control valve and a logic valve adapted for

operating/actuating each cylinder.

Preferably, a control unit is coupled to the control valve and logic valves.

Suitably, a first and a second piston force area (with an extension transverse to the longitudinal axis) of the radially protruding portion each being determined by the diameter of the respective first and second portion. Suitably, a first and a second piston force area of the radially protruding portion each being determined by a first diameter of the first portion and a second diameter of the second portion, wherein the first diameter is larger than the second diameter.

Preferably, the second piston force area is used for generating a working stroke and the first piston force area is used for generating a retraction stroke. The second piston force area is larger than the first piston force area.

In such way is achieved that the first piston force area can be used for a retraction sequence for retraction of the first piston body. The first piston force area is thus smaller than the second piston force area and the retraction is made quickly as the same fluid pressure is used for both first and second cylinder chamber in an energy saving manner. The same fluid supply system and pressure is thereby used. By retraction by hydraulic power systems using the same system pressure there thus is achieved small energy losses.

Suitably, a bearing member (such as bronze bearing or other bearing comprising bronze alloys and/or tin bronze and/or lead free bronze and/or copper and/or aluminium-bronze and/or carbon graphite or others) is mounted in the first opening and/or the second opening respectively acting as bearing between the first cylinder and the first portion. In such way, despite the relatively large contact area between a circumferential surface of the first portion of the first piston body and a peripheral surface of the first opening of the first cylinder, there is obtained a minimal friction between the first piston body and the first cylinder.

The friction may be further minimized by permitting a certain leakage of hydraulic fluid between the first cylinder and the first portion of the first piston body. The fluid leakage is preferably collected by an extendable and contractible cover member coupled to the first cylinder and the first portion outer end in a sealed manner. The fluid is led to the fluid supply for reuse.

Preferably, a piston rod is arranged along the longitudinal axis through the first piston body, the first cylinder and/or the piston rod being stationary, wherein the first piston body comprises a piston rod engagement and disengagement device arranged to engage or disengage the first piston body to or from the piston rod.

Suitable, the arrangement is used in an elevator apparatus or high bay storage apparatus, wherein the second piston force area limiting the second cylinder chamber faces a direction (straight and/or inclined) upwards and pressurization of the second cylinder chamber will propel the first cylinder (and elevator apparatus since the first cylinder/cylinders being attached to the elevator apparatus) in a direction upwards wherein the first piston body/piston bodies being engaged to the piston rod.

Preferably, for retraction of the first piston body, a locking device (e.g. the piston rod engagement and disengagement device) secures the first cylinder (and thus the elevator apparatus) to the piston rod while the first piston body is returned to a start position for anew pressurization of the second cylinder chamber. That is, the first piston body is returned to the start position by means of pressurization of the first cylinder chamber, whereby the pressure on the first piston force area moves the first piston body upwards to said start position.

Suitably, the piston rod engagement and disengagement device comprises a wall portion arranged adjacent the piston rod (and co-axial with the piston rod) and arranged to be inwardly expandable towards the piston rod for a clamping action and forms a hollow space adapted for direct fluid communication with the second cylinder chamber via a channel system provided in the first piston body.

In such way is achieved a simple and cost-effective arrangement for direct fluid communication between the second cylinder chamber and the hollow space of the piston rod engagement and disengagement device. That is, when the second cylinder chamber is pressurized, also the piston rod engagement and disengagement device (comprising the hollow space) will be pressurized and will engage and securely clamp around the piston rod. The pressure of the pressurized second cylinder chamber will in turn push the second end of the first cylinder along the longitudinal axis in a direction away from the engaged and secured piston body, i.e. in a direction upwardly.

Preferably, the arrangement further comprises a second cylinder and a second piston body being symmetrically arranged around said longitudinal axis and a common piston rod, the second cylinder exhibits a second cylindrical inner peripheral surface, a third and a fourth end forming a second cylinder interior, a second radially protruding portion of the second piston body protrudes outwardly towards the second cylindrical inner peripheral surface and divides the second cylinder interior into a third and fourth cylinder chamber, the second piston body comprises a third and fourth portion, the third portion sealingly extends through a third opening of the third end and the fourth portion sealingly extends through a fourth opening of the fourth end, the third portion of the second piston body exhibits a larger diameter than the fourth portion of the second piston body and comprises a second open cavity, the first cylinder according to claim 1 is positioned in tandem arrangement with the second cylinder in such way that the first portion of the first piston body forming the open cavity during use of the arrangement alternating will encompass the fourth portion of the second piston body.

Suitably, the first portion of the first piston body exhibits a larger cross-sectional (transverse to the longitudinal axis X) dimension than the second portion of the first piston body and comprises an open cavity facing away from the second portion and being directed along the longitudinal direction.

The first cylinder and piston body may be defined as a first cylinder and a first piston body. The first piston body is activated (for a first working stroke) by pressurizing the second cylinder chamber of the first cylinder, wherein the first piston body moves relative the first cylinder and towards the second piston body. Meantime, the second piston body is retracted (retraction stroke) towards its start position by pressurizing the third cylinder chamber. The second piston body thus moves to the start position by a pressure applied to the third cylinder chamber acting upon a third piston force area of the second piston body. When the second piston body is in start position, the first piston body is in position to be retracted to its start position. The second piston body is activated by pressurizing the fourth cylinder chamber of the second cylinder, wherein the second piston body moves relative the second cylinder and away from the first piston body. Meantime, the first piston body is retracted by pressurizing the first cylinder chamber and moves away from the second piston body. When the first piston body has reached its start position, the first piston body is actuated again and the procedure will be repeated. The pressurizing of the different cylinder chambers is performed by a control unit coupled to valve members, which in turn are coupled to the respective cylinder. In such way is achieved a simple and cost-effective arrangement for direct fluid communication between the second/fourth cylinder chamber and the hollow space of the respective piston rod engagement and disengagement device. That is, when the second/fourth cylinder chamber is pressurized, also the piston rod engagement and disengagement device (comprising the hollow space) will be pressurized and will engage and securely clamp around the piston rod. The pressure of the pressurized second/fourth cylinder chamber will in turn push the second end of the first cylinder away from the engaged and secured piston body, i.e. in a direction upwardly.

Suitably, the common piston rod is slidingly arranged along the longitudinal axis through the first piston body and the second piston body, the respective cylinder being stationary or the piston rod being stationary, wherein each piston body comprises a piston rod engagement and disengagement device arranged to engage or disengage the respective piston body to or from the common piston rod.

Preferably, a first and a second piston force area of a first radially protruding portion of the first piston body and a third and a fourth piston force area of a second radially protruding portion of the second piston body delimit the first cylinder chambers of the respective cylinder, the first piston force area being lesser than the second piston force area and the third piston force area being lesser than the fourth piston force area.

In such way is achieved that retraction of the piston bodies can be made in an efficient way. As the first piston force area is used for retraction of the first piston body to the starting point, its area is smaller than the second piston force area.

Suitably, the dimension of the first and third piston force area is determined so that the fluid system pressure multiplied by the piston force area always is larger than the frictional force required to overcome for moving the first piston body back to the starting point (i.e. during the retraction sequence). Hence, providing a relatively small piston force area (and thereby prepare for a larger cavity within the first portion as the diameter of the first portion is larger) will imply that energy can be saved.

Preferably, the respective piston rod engagement and disengagement device each comprises a wall portion arranged to be inwardly expandable towards the common piston rod and each forms a hollow space adapted for direct fluid communication with the respective second and fourth cylinder chamber. In such way is achieved a simple and cost-effective fluid actuator arrangement for direct fluid communication between the respective cylinder chamber and the corresponding hollow spaces of the piston rod engagement and disengagement device. That is, when the second (or fourth) cylinder chamber is pressurized, also the piston rod engagement and disengagement device (hollow space) will be pressurized and will engage and securely clamp around the common piston rod. The pressure of the pressurized second cylinder chamber will in turn force the second end of the first cylinder in a direction upward and away from the radially protruding portion of the first piston body being engaged with the common piston rod (used in e.g. an elevator or high bay storage or other lifting arrangement). Suitably, the respective first, second, third and fourth cylinder chamber is provided for connection to a valve member of a fluid supply.

In such way is achieved that a common fluid supply system can be used for the working stroke and the retraction stroke of both actuators.

Preferably, the fluid actuator arrangement comprises a plurality of cylinders and piston bodies according to any of claims 1-11 being symmetrically arranged around and along a common piston rod, each piston body comprises a piston inner wall portion arranged to be inwardly expandable towards the common piston rod and forms a hollow space (within the respective piston body) arranged for direct fluid communication with the respective cylinder chamber (second, fourth etc.).

Thereby is achieved that a simple and cost-effective fluid actuator arrangement for direct fluid communication between the "working" cylinder chamber and the hollow space (or spaces) of respective the piston rod engagement and disengagement device. That is, when the "working" cylinder chamber is pressurized, also the piston rod engagement and disengagement device (hollow space) will be pressurized and will engage and securely clamp around the piston rod. The pressure of the pressurized "working" cylinder chamber will in turn push the first cylinder, and the piston rod, in a direction along the longitudinal axis away from the engaged and secured piston body.

Suitably, the fluid actuator arrangement comprises a second piston force area of a first piston body, a fourth piston force area of a second piston body corresponding in measurement with the second piston force area, a third piston body comprises a sixth piston force area, a fourth piston body comprises an eighth piston force area, the sixth piston force area is twice as large as the second piston force area, the eighth piston force area is twice as large as the sixth force area. Preferably, the respective piston body is each mounted to a respective actuator (cylinder). That is, the first piston body is mounted in a first actuator, the second piston body is mounted in a second actuator, etc.

Suitably, the fluid actuator arrangement comprises a plurality of actuators designed accordingly the above stated.

In such way is achieved that a fast relative piston/cylinder motion can be achieved with minor stroke force.

In such way is achieved that high stroke force can be provided by using several cylinders.

In the example described above, the respective piston force area is defined as A = al - a2, wherein al is the cross-sectional area in view of the diameter of the radially protruding portion of the first piston body and a2 is the cross-sectional area in view of the diameter of the second portion of the first piston body protruding through the second opening of the second cylinder end. For reaching fast piston motion and minor force, the second piston force area (e.g. 1 area unit) is activated by alternating engagement of the first and second actuator to the common piston rod. For achieving an alternative performance of the fluid actuator arrangement, for example slow piston motion with high force, all the activators are activated. The high force may be achieved by activating all four piston force areas (e.g. 8 area units = 1 + 1 + 2 + 4, i.e. the respective piston force area of the first, second, third, fourth actuator). This implies an optimal combination of eight different piston force area units, which can be selected from required arrangement motion rate and force. Preferably, also other piston force area combinations are possible. For example 1+1+1+1+1+1 or 1+1+2+4+8+16+32 or other combinations can be used.

Alternatively, the fluid actuator arrangement comprises any number of actuators.

By controlling the total cross-sectional piston force area of the fluid actuator arrangement, the motion rate and the force of the common piston rod can be changed and optimized in an efficient way. The actual needs of operation for a certain situation can be satisfied by changing said total cross-sectional piston force area of the fluid actuator arrangement. This is due by the formula V = Q. / A and the formula F = P * A, wherein "V" is the motion rate of the piston device, "Q" is the fluid flow, "A" is the piston force area of the "working side" of the first piston body, "F" is the force of the first piston body and "?" is the pressure of the pressurized fluid. For example, by disengaging one of the piston bodies (e.g. disengaging it after acceleration) the area "A" will be decreased and the motion rate "V" will be increased at the same time as the force "F" is decreased still using the same system fluid pressure. Such mode of operation may be used when the fluid actuator arrangement is put into use in an elevator, and the elevator has finished the acceleration sequence in a direction upwardly and will maintain constant high speed.

In such way is achieved that a modular fluid actuator arrangement can be assembled from desired provisions regarding force and speed of the common piston rod relative the first cylinders - for example high force and slow speed or low force and high speed - and furthermore from the desired distance (number of strokes) the piston bodies/cylinders shall cover, braking action, precision adjustment of the piston rod/cylinders to a predetermined accurate position etc. Such modular fluid actuator arrangement can operate with less throttling compared with prior art. According to one aspect of the present invention there is provided a controlled and selected engagement and disengagement of the piston bodies to/from the common piston. This will imply flexibility and less energy losses compared with prior art at the same time as a compact arrangement is provided.

Suitably, the first and/or second opening comprises a bearing member arranged between the first piston body and the first cylinder, the bearing member comprises bronze and/or bronze alloys and/or tin bronze and/or lead free bronze and/or copper and/or aluminium-bronze and/or carbon graphite or others.

Preferably, the arrangement is used in elevator or high bay storage applications.

The definition of piston force area is that area of the piston facing the first cylinder end and extending transverse to the longitudinal axis. The first piston force area is the area defined by the outer diameter of the radially protruding portion of the first piston body minus the area defined by the outer diameter of the first portion of the first piston body. The second piston force area is the area defined by the outer diameter of the radially protruding portion of the first piston body minus the area defined by the outer diameter of the second portion of the first piston body. A piston force area may be defined as the transverse area of the piston upon which the fluid pressure within the cylinder chamber acts under pressurization of the first cylinder chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of examples with references to the

accompanying schematic drawings, of which: Figs, la to lc illustrate a first example of a fluid actuator arrangement; Figs. 2a to 2b illustrate a second example of a fluid actuator arrangement; Figs. 3a to 3c illustrate a third example of a fluid actuator arrangement; Fig. 4 illustrates a fourth example of a fluid actuator arrangement shown in a perspective view; Fig. 5 in detail illustrates a fifth example of a fluid actuator arrangement; Fig. 6 illustrates one aspect of the invention applied to an elevator;

Figs. 7a to 7g illustrate examples of the operation of a fluid actuator arrangement; and Figs. 8a and 8b illustrate a sixth example of a fluid actuator arrangement.

DETAILED DESCRIPTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein for the sake of clarity and understanding of the invention may some details of no importance be deleted from the drawings.

Fig. la schematically shows a fluid actuator arrangement 1 comprising a first cylinder 3 and a first piston body 5 symmetrically arranged along a longitudinal axis X and around a piston rod 37. The first cylinder 3 exhibits a cylindrical inner peripheral surface 7, a first 9 and a second 11 end forming a first cylinder interior 13. A radially protruding portion 15 of the first piston body 5 protrudes outwardly towards and in contact with (or adjacent to) the cylindrical inner peripheral surface 7 and divides the first cylinder interior 13 into a first 17 and second 19 cylinder chamber. The first piston body 5 comprises a first 21 and second 23 portion. The first portion 21 of the first piston body 5 sealingly extends through a first opening 25 of the first end 9 and the second portion 23 sealingly extends through a second opening 27 of the second end 11 of the first cylinder 3. The first portion 21 of the first piston body 5 exhibits a larger outer diameter than that of the second portion 23 of the first piston body 5 and comprises an open cavity 29. The open cavity 29 exhibits an open direction facing away from the second portion 23 of the first piston body 5 in a direction along the longitudinal direction of the longitudinal axis X.

The open cavity 29 is dimensioned to encompass a complementary brake 30 separately controlled by a control unit 31. The brake 30 of the fluid actuator arrangement 1 being positioned along the longitudinal axis X and mounted adjacent the first piston body 5. The open cavity 29 will thus partially encompass the brake 30 positioned adjacent the first cylinder 3 and along the longitudinal axis X. This will provide a compact arrangement. The brake 30 is thus positioned adjacent the first cylinder 3 (i.e. closer to the first portion 21 than to the second portion 23 of the first piston body 5 and along the longitudinal axis X.

The respective first 17 and second 19 cylinder chamber being coupled to a valve member 33 of a fluid supply 35. The valve member 33 comprises control valves and logic valves (not shown) for providing a reciprocal action of the first piston body 5. The first piston body 5 is slidingly arranged about the piston rod 37 along the longitudinal axis X. The piston rod 37 is arranged through the first piston body 5. The first cylinder 3 being stationary and the piston rod 37 is moved up and down. The first piston body 5 comprises a piston rod engagement and disengagement device 39 arranged to engage or disengage the first piston body 5 to or from the piston rod 37.

The piston rod engagement and disengagement device 39 comprises a wall portion 41 of the first piston body 5, which wall portion 41 is arranged adjacent an envelope surface of the piston rod 37. The wall portion 41 is arranged to be inwardly expandable towards the piston rod 37 envelope surface. Such expansion inwardly provides a clamping action between the first piston body 5 and the piston rod 37, wherein the first piston body 5 will be securely clamped on the piston rod 37. The wall portion 41 forms a hollow space 43 within the first piston body 5. The hollow space 43 is provided for direct fluid communication with the second cylinder chamber 19 via a channel system 45 provided in the first piston body 5. The hollow space 43 is coupled to the channel system 45 comprising a first opening 47 entering the hollow space 43 and a second opening 49 of the first piston body 5 entering the second cylinder chamber 19. This promotes for direct fluid communication between the second cylinder chamber 19 and the hollow space 43. The control unit 31 controls the valve member 33 to pressurize the second cylinder chamber 19 for moving the piston rod 37 relatively the first cylinder 3. The second cylinder chamber 19 is thus pressurized with a fluid pressure P (see Fig. lb) for moving the piston rod 37 in the direction of arrow A (see Fig. lb). The fluid fed into the second cylinder chamber 19 also will enter the hollow space 43 via the channel system 45. The hollow space 43 of the piston rod engagement and disengagement device 39 is formed by an inner side of the wall portion 41 and an opposite wall arranged within the first piston body 5. The hollow space 43 (or spaces) thus extends parallel with (in a direction circumferentially around and at a distance from) the envelope surface of the piston rod 37 and in a direction parallel with the longitudinal axis X (the hollow space 43 being e.g. cylindrical shaped and coaxially arranged in the first piston body 5). The mass of material forming the wall portion 41 is so flexible that the fluid pressure P will expand the mass of material of the wall portion 41 in radial direction (not shown) towards the piston rod 37 envelope surface in such manner that it is engaged with the piston rod 37. By means of the fluid pressurization of the second cylinder chamber 19 there is thus achieved that the first piston body 5 is clamped to the piston rod 37 and that the first piston body 5 and cylinder3 will be moved in relation to each other by the pressurized second cylinder chamber 19. The fluid pressurization of the hollow space 43 will instantaneously expand the wall portion 41 of the first piston body 5 for providing the engagement between the first piston body 5 and the piston rod 37 for moving the piston rod 37. When completed working stroke WS shown in Fig. lb, a retraction stroke S is performed as illustrated in Fig. lc. The control unit 31 controls the valve member 33 to pressurize the first cylinder chamber 17 for moving the first piston body 5 in the opposite direction to the working stroke WS direction. The first cylinder chamber 17 is thus pressurized with the fluid pressure P for moving the first piston body 5 in the retraction stroke RS as shown in Fig. lc. The control unit 31 (see Fig. la) controls the valve member 33 to provide the second cylinder chamber 19 with low fluid pressure (lower than the fluid pressure P) so that the piston rod engagement and disengagement device 39 during the retraction stroke RS will disengage the first piston body 5 from the piston rod 37. The control unit 31 thus controls the valve member 33 (see fig. la) to provide lower fluid pressure in the hollow space 43 directly via the second cylinder chamber 19 and the channel system 45. The lower fluid pressure in the hollow space 43 permits the flexible material mass of the wall portion 41 to "spring back" (return to original shape), wherein the first piston body 5 no longer will clamp on the piston rod 37 and will be disengaged from it.

During the reciprocal action of the first piston body 5, the first portion 21 of the first piston body 5 will alternately partially encompass the brake 30. A first PAl and a second PA2 piston force area of the radially protruding portion 15 are faced away from each other and each has an extension transverse to the longitudinal axis X. The respective area of PAl and PA2 being determined by the outer diameter Dl, D2 (See Fig. lb) of the respective first 21 and second 23 portion of the first piston body 5 and the inner diameter id (See Fig. lc) of the first cylinder interior 13.

The second piston force area PA2 is used for generating the working stroke WS and the first piston force area PAl is used for generating the retraction stroke RS as being mentioned above. The first piston force area PAl is relatively small in comparison with the second piston force area PA2 and the retraction stroke can be made in relative quick manner. This is due to that the common fluid supply 35 (see Fig. la) generating the common fluid pressure P is used for saving energy and no losses will occur. By providing the retraction by means of a common hydraulic power system using the same system pressure and saving energy there is achieved a "green technology". The brake 30 is activated in Fig. lc as a locking device for securing the piston rod 37.

Figs. 2a to 2b illustrate a further aspect of the present invention. In Fig. 2a is shown a fluid actuator arrangement 1 comprising a first cylinder 3 and a first piston body 5 symmetrically arranged along a longitudinal axis X. A radially protruding portion 15 of the first piston body 5 protrudes outwardly towards and in contact with a cylindrical inner peripheral surface 7 of the first cylinder 3 and divides the first cylinder into a first 17 and second 19 cylinder chamber as shown in Fig. 2b. The first piston body 5 comprises a first 21 and second 23 portion. The first portion 21 sealingly extends through a first end 9 of the first cylinder 3. The second portion 23 sealingly extends through a second end 11 of the first cylinder 3. The first portion 21 of the first piston body 5 exhibits a larger diameter than the second portion 23 of the first piston body 5 and comprises an open cavity 29. A respective piston rod 37 is coupled to the first piston body 5. For saving space and providing a compact fluid actuator arrangement 1, the control unit 31 is positioned within the open cavity 29. In the final moment of the working stroke WS the control unit 31 is entirely encompassed by the open cavity 29. The open cavity 29 is open in a direction corresponding with the direction of the working stroke WS.

Figs. 3a to 3c illustrate a yet further aspect of the invention. Fig. 3a shows a fluid actuator arrangement 1 comprising a first cylinder 3 and a first piston body 5 being symmetrically arranged along a longitudinal axis X. The fluid actuator arrangement 1 also comprises a second cylinder 4 and a second piston body 6 being symmetrically arranged along said longitudinal axis X and as the first piston body 5 also arranged around a common piston rod 38. The second cylinder 4 exhibits a second cylindrical inner peripheral surface 8, a third 10 and a fourth 12 end forming a second cylinder interior 14. A second radially protruding portion 16 of the second piston body 6 protrudes outwardly towards the second cylindrical inner peripheral surface 8 and divides the second cylinder interior 14 into a third 18 and fourth 20 cylinder chamber. The second piston body 6 comprises a third 22 and fourth 24 portion. The third portion 22 sealingly extends through a third opening 26 of the third end 10 and the fourth portion 24 sealingly extends through a fourth opening 28 of the fourth end 12. The third portion 22 of the second piston body 6 exhibits a larger outer diameter than the fourth portion 24 of the second piston body 6 and comprises a second open cavity 30. The first cylinder 3 is positioned in tandem arrangement with the second cylinder 4 in such way that a first portion 21 of the first piston body 5, forming a first open cavity 29, during use of the arrangement 1 alternating will encompass the fourth portion 24 of the second piston body 6. This is achieved by that the dimension (diameter) of the fourth portion 24 is smaller than the dimension (diameter) of the open cavity 29 of the first portion 21. The common piston rod 38 is slidingly arranged along the longitudinal axis X through the first piston body 5 and the second piston body 6. In this embodiment the first cylinder 3 and the second cylinder 4 are stationary arranged and the common piston rod 38 is arranged for motion. The first piston body 5 and the second piston body 6 comprise a respective piston rod engagement and disengagement device 39', 39". Each piston rod engagement and disengagement device 39', 39" being arranged to the respective piston body 5 and the second piston body 6. Each piston rod engagement and disengagement device 39', 39" is controlled to engage or disengage the respective piston body 5 and the second piston body 6 to or from the common piston rod 38. The control of the piston rod engagement and disengagement device 39', 39" of the respective piston body 5 and second piston body 6 is performed by a control unit 31 and valve member 33 (shown in Fig 3c) that alternately pressurize the respective second cylinder chamber 19 and the fourth cylinder chamber 20. The respective piston rod engagement and disengagement device 39', 39" is designed in a similar way as shown in Fig. lb. The piston rod engagement and disengagement device 39' of the first piston body 5 is in direct fluid communication with the second cylinder chamber 19. The piston rod engagement and disengagement device 39" of the second piston body 6 is in direct fluid communication with the fourth cylinder chamber 20. A hollow space (not shown) of each piston rod engagement and disengagement device 39 can thus in a controlled manner be pressurized for making a clamping action of each piston rod engagement and

disengagement device 39.

In Fig. 3c is shown the operation of the fluid actuator arrangement 1 in Fig. 3a to 3b. The control unit 31 is arranged to control the valve member 33. The valve member 33 comprises a first 51 and a second logic valve 53. The valve member 33 also comprises a control valve 55 coupled to a fluid supply 35. The control valve 55 is arranged for selecting direction of fluid flow to the respective cylinder 3 and second cylinder 4. The first logic valve 51 is arranged for selecting direction of fluid flow to the respective first 17 and second 19 cylinder chamber of the first cylinder 3. The second logic valve 51 is arranged for selecting direction of fluid flow to the respective third cylinder chamber 18 and fourth cylinder chamber 20. The selection of fluid flow controlled by the control unit 31 provides fluid pressurization in the respective cylinder chamber for actuating the working strokes WS and the retraction strokes S of the fluid actuator arrangement 1. In Fig. 3c, the first piston rod engagement and disengagement device 39' of the first piston body 5 is not engaged with the piston rod 38 for permitting the first piston body 5 to perform the retraction stroke RS. A second piston rod engagement and disengagement device 39" of the second piston body 6 is engaged with the piston rod 38 for moving the piston rod 38 during the working stroke. The second piston body 6 is thus actuated by the pressurization of the fourth cylinder chamber 20 via a channel system (not shown) in a way similar as described in connection with Fig. lb. In a next sequence the second piston body 6 is disengaged from the piston rod 38 and performs a retraction stroke at the same time as the first piston body 5 is engaged to the piston rod 38 and performs a working stroke moving the piston rod 38 a yet further distance. During this sequence (not shown) the fourth portion 24 of the second piston body 6 partly will be encompassed in the open cavity 29 of the first piston body 5. This is achieved by that the diameter D4 of the fourth portion 24 is smaller than the diameter Dl of the open cavity 29 of the first portion 21.

Fig. 4 illustrates one aspect of the invention shown in a perspective view. There is shown a fluid actuator arrangement 1 comprising a plurality of cylinders 3, 4, 4' and piston bodies 5, 6, 6'. The first cylinders 3, 4, 4' are symmetrically arranged around the common piston rod 38. Each piston body 5, 6, 6' comprises a piston inner wall portion 41 arranged to be inwardly expandable towards the common piston rod 38 for a clamping action. Each piston body 5, 6, 6' forms a hollow space 43 adapted for direct fluid communication with the respective cylinder 3, 4, 4' interior (working cylinder chamber 61', 61", 61"'). Fig. 5 shows a fluid actuator arrangement 1 comprising two cylinders 3, 3'. A respective piston rod engagement and disengagement device 39 each comprises a wall portion 41. Each wall portion 41 is arranged to be inwardly expandable towards a common piston rod 38 and forms a hollow space 43 adapted for direct fluid communication with the respective second 19 and fourth 20 cylinder chamber. A respective channel 45', 45" provides fluid communication between the respective cylinder chamber 19, 20 and the hollow space 43 of a respective first and second piston body 5', 5". A first PA1 and a second PA2 piston force area of a first radially protruding portion 15 of the first piston body 5' and a third PA3 and a fourth PA4 piston force area of a second radially protruding portion 16 of the second piston body 5" delimit the second 19 and fourth 20 cylinder chamber and also a first 17 and a third 18 cylinder chamber. A first and second opening 25, 27 each comprises a bearing member 95 arranged between the first piston body 5' and the first cylinder 3. A third and fourth opening 26, 28 each comprises a bearing member 95 arranged between the second piston body 5" and the second cylinder 3'. The bearing member 95 comprises bronze and/or bronze alloys and/or tin bronze and/or lead free bronze and/or copper and/or aluminium-bronze and/or carbon graphite or others. A portion of the first piston body 5' protruding through the first opening 25 exhibits an open cavity 29' arranged for encompassing a portion of the other piston body 5".

Fig. 6 illustrates one aspect of the invention applied to an elevator 71. The elevator 71 is moved along a piston rod 38. A fluid actuator arrangement 1 is arranged to the elevator 71 according to one aspect. The piston rod 38 is arranged through a pair of cylinders 3', 3" also shown in Figs. 7a to 7g. The respective cylinder 3', 3" is provided with a respective piston body 5', 5". Each of the piston bodies 5', 5" comprises a respective piston rod engagement and disengagement member 39', 39", each adapted for releasable engagement with the piston rod 38. In this embodiment the piston rod 38 is slidingly arranged along the longitudinal axis X through each of the piston bodies 5', 5", wherein piston rod 37 being stationary and the first cylinders move along the piston rod 37, thus propelling the elevator 71. Open cavities 29', 29" of the piston bodies 5', 5" exhibit their respective open direction downwards. The first cylinders 3', 3" are fixedly mounted to the structure of the elevator 71. The operation of the fluid actuator arrangement 1 is performed by a user 72 operating the control unit 31. Figs. 7a-7g illustrate the fluid actuator arrangement 1 mounted to a structural portion 74 of the elevator 71 in Fig. 6. The fluid actuator arrangement 1 comprises a first 3' and second 3" cylinder. In Fig. 7a is shown a first piston body 5' is mounted in the first cylinder 3' and protrudes through both ends of the first cylinder 3'. A second piston body 5" is mounted in the second cylinder 3" and protrudes through both ends of the second cylinder 3". The first 3' and second 3" cylinder and the first 5' and second 5" piston body being symmetrically arranged along a longitudinal axis X of a common piston rod 38. A first portion 2 of the first piston body 5' exhibits a larger cross-sectional dimension (transverse to the longitudinal axis X) than a second portion 23" of the second piston body 5". The first portion 2 of the first piston body 5' comprises an open cavity 29 directed towards the second piston body 5" for momentary encompassing the second portion 23" of the second piston body 5". The first piston body 5' exhibits a first piston force area PA1 determined by the dimension of the first cylinder 3' inner diameter and the outer diameter of the first portion 2 of the first piston body 5' extending through a first end 9' of the first cylinder 3'. The first piston body 5' exhibits a second piston force area PA2 determined by the dimension of the first cylinder 3' inner diameter and the outer diameter of a second portion 23' of the first piston body 5' extending through a second end 11' of the first cylinder 3'. The area of the first piston force area PA1 is lesser than that of the second piston force area PA2. The definition of the respective piston force area of the second piston body 5" corresponds with the definition of PA1 and PA2 of the first piston body 5'. In such way is achieved that the first piston force area PA1 can be used for a retraction stroke S for retraction of the respective piston body 5', 5". The first piston force area PA1 is preferably relatively small in comparison with the second piston force area PA2 and the retraction stroke is made rapidly. This is due to that the same fluid supply system and pressure being used. In Fig. 7b is shown that the retraction stroke RS of the second piston body 5" is made while the second portion 23" go into the open cavity 29. In Figs. 7c and 7d is shown changing from actuated first piston body 5' of the first cylinder 3' to the actuating of the second piston body 5" of the second cylinder 3". A respective first, second, third and fourth cylinder chamber of the fluid actuator arrangement 1 is coupled to a valve member of a fluid supply (not shown) so that controlling of the fluid flow to the respective cylinder can be performed. The retraction stroke RS and the working stroke WS of the first cylinder 3' in Fig. 7c (the first piston body 5' is engaged to the piston rod 38 by means of a first piston rod engagement and disengagement device 39' in a manner similar to that described above in e.g. Fig. 5) will shortly be completed. Note that the piston rod 38 is stationary and the first cylinders 3', 3" perform the working strokes WS. In Fig. 7d is shown that a second piston rod engagement and disengagement device 39" of the second piston body 5" is activated so that the second cylinder 3" starts a further working stroke WS. At the same time the first piston body 5' has started its retraction stroke S towards the starting point SP, which is marked in FIG. 7g. A control unit (not shown) proceeds to control a valve member (not shown) coupled to a respective first 80' and second 80" (shown in Fig. 7e) port of each cylinder 3', 3". Each port 80', 80" alternately serves as inlet port for feeding fluid from a fluid supply (not shown) system via the valve member or as outlet port for feeding fluid to a reservoir (not shown) of the fluid supply. In Fig. 7e is shown that the second port 80" of the first cylinder 3' serves as an inlet port for the fluid pressure of the system for retraction stroke RS in pressurizing the first piston force area PA1 of the first piston body 5'. At the same time the first port 80' of the second cylinder 3" serves as an inlet port for the fluid pressure of the system for working stroke WS (moving the second cylinder 3" upwards) in pressurizing the second piston force area PA2 of the second piston body 5". The second piston rod engagement and disengagement device 39" of the second piston body 5" is still activated as the first piston body 5' getting near the starting point SP as is shown in Fig. 7f. In Fig. 7g is shown that the first piston body 5' has reached the starting point SP. The control unit (not shown) controls the fluid actuator arrangement 1 to change working stroke (corresponding with WS in Fig. 7a) to the first cylinder 3' (wherein the first piston body 5' is engaged to the piston rod 38). At the same time the second piston body 5" will be retracted upward towards its starting point (not shown but similar to SP regarding its position near the second end of the first cylinder). The procedure continues until the elevator 71 has reached its destination, e.g. tenth floor of a multi-storey building (not shown).

Figs. 8a and 8b illustrate a yet further aspect of the present invention used for a high bay storage apparatus 7 . The fluid actuator arrangement 1 comprises a second piston force area A2 of a first piston body 5'. A fourth piston force area A4 of a second piston body 5" corresponds in

measurement with the second piston force area A2 of the first piston body 5'. A third piston body 5"' comprises a sixth piston force area A6. A fourth piston body 5"" comprises an eighth piston force area A8. The sixth piston force area A6 is twice as large as the second piston force area A2, the eighth piston force area A8 is twice as large as the sixth force area A6. A first piston force area Al, a third piston force area A3, a fifth piston force area A5, a seventh piston force area A7, being used for respective piston body 5', 5", 5"', 5"" retraction. In Fig. 8a is shown that the first, second, third piston bodies 5', 5", 5"' are used for a working stroke WS (i.e. the respective piston rod engagement and disengagement member 39', 39", 39"' being in engagement with a piston rod 38 of the high bay storage apparatus 7 ). This mode implies the utilisation of 4 area units. The fluid actuator arrangement 1 in total includes 8 area units. For reaching fast piston motion and minor lifting force of the high bay storage apparatus 7 , in turns, the second A2 and fourth A4 piston force area (each having 1 area unit) is activated by alternating engagement of the first 5' and second 5" piston body to the piston rod 38. For achieving an alternative performance of the fluid actuator arrangement 1, for example slow piston motion with high force, all piston bodies 5', 5", 5"', 5"" are used for engagement with the piston rod 38. The high force thus is achieved by activating all four piston force areas A2, A4, A6, A8 (e.g. 8 area units = 1 + 1 + 2 + 4). This implies an optimal combination of eight different piston force area units, which can be selected from required arrangement motion rate and force. In the Fig. 8a is shown that 4 area units are used. That is, the first, second, and third piston body 5', 5", 5"' being engaged to the piston rod 38 (and the fourth piston body 5"" is disengaged) and alternatingly as shown in Fig. 8b the fourth piston body 5"" being engaged (using 4 area units as well) to the piston rod 38 (and the first, second, and third piston body 5', 5", 5"' are disengaged).

The present invention is of course not in any way restricted to the preferred embodiments described above, but many possibilities to modifications, or combinations of the described embodiments, thereof should be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention as defined in the appended claims. One aspect involves that the fluid actuator arrangement can be adapted for momentary disengaging all pistons from the piston rod in case the piston rod propels a large mass using the kinetic energy of the mass (in a way reminding of a freewheel clutch). The valve device may comprise a logic valve of suitable type. The valve member may comprise a 5 ports/2 valve positions, so called 5/2 valve or others. The valve member may comprise a two-way valve of any type suitable for the arrangement. The manoeuvring of the valve member may be performed by means of a solenoid connected to a control unit or suitable CPU adapted for controlling the valve member and thereby the fluid actuator arrangement. The fluid actuator arrangement may be adapted for fast and high clamp force engagement of the respective piston body for providing relative motion between the first cylinder and the first piston body. Such adaptation can be made highly accurate also for acceleration of heavy loads. By manoeuvring the valve member comprising logical valves accordingly, one and same fluid actuator arrangement can perform also lower force and slow motion rate. There are different types of valve members that can be used for providing the above-mentioned aspects and other aspects. Electro-hydraulic controlled valves, other types of directly controlled electro-hydraulic logical valves, etc. The fluid actuator arrangement can be used in civil and military, manned and unmanned aircraft. The fluid actuator arrangement can be used for Leading/Trailing Edge Flap Actuators; Landing Gear Actuators; Air Brakes; Primary Servo Actuators (PSA); Electro-Hydrical Actuator (EHA) applications etc.

Claims

1. A fluid actuator arrangement comprising a first cylinder (3, 3') and a first piston body (5, 5') symmetrically arranged along a longitudinal axis (X), wherein

-the first cylinder (3, 3') exhibits a cylindrical inner peripheral surface (7), a first end (9, 10) and a second end (11, 12) forming a first cylinder interior (13);

-the first piston body (5, 5') comprises a first portion (21, 2 ) and second portion (23, 23') and a radially protruding portion (15) therebetween,

-the radially protruding portion (15) is slidingly arranged in the first cylinder interior (13) and protrudes outwardly towards the cylindrical inner peripheral surface (7) dividing the first cylinder interior (13) into a first cylinder chamber (17) and a second cylinder chamber (19), characterized in that

-the first portion (21, 2 ) of the first piston body (5, 5^') sealingly extends through a first opening (25) of the first end (9) and the second portion (23, 23') of the first piston body (5, 5^') sealingly extends through a second opening (27) of the second end (11); and

-the first portion (21, 2 ) of the first piston body (5, 5') exhibits a larger diameter than the second portion (23, 23') of the first piston body (5, 5') and comprises an open cavity (29).

2. The arrangement according to claim 1, wherein the open cavity (29) is open in an end

opposite the radially protruding portion (15) in a direction along the longitudinal axis (X).

3. The arrangement according to claim 1 or 2, wherein the open cavity (29) is formed to

encompass entirely or partially a member corresponding with the second portion (23, 23') of a second piston body (6).

4. The arrangement according to any of claim 1 to 3, wherein the respective first (17) and second (19) cylinder chamber is provided for coupling to a valve member (33) of a fluid supply (35).

5. The arrangement according to any of the preceding claims, wherein a first (PA1) and a

second (PA2) piston force area of the radially protruding portion (15) each being determined by a first diameter (Dl) of the first portion (21, 2 ) and a second diameter (D2) of the second portion (23, 23'), wherein the first diameter (Dl) is larger than the second diameter (D2).

The arrangement according to any of the preceding claims, wherein a piston rod (37) is arranged along the longitudinal axis (X) and through the first piston body (5, 5'), wherein the first cylinder (3, 3') or the piston rod (37) being stationary.

The arrangement according to any of the preceding claims, wherein the first piston body (5, 5') comprises a piston rod engagement and disengagement device (39, 39') arranged to engage or disengage the first piston body (5, 5') to or from the piston rod (37).

The arrangement according to claim 7, wherein the piston rod engagement and

disengagement device (39) comprises a wall portion (41) arranged adjacent the piston rod (37), said wall portion (41) being inwardly expandable towards the piston rod (37) for a clamping action, wherein a hollow space (43) partly is formed by the wall portion (41), wherein the hollow space (41) is arranged for direct fluid communication with the second cylinder chamber (19) via a channel system (45) provided in the first piston body (5, 5').

The arrangement according to any of the preceding claims, wherein the arrangement (1) further comprises a second cylinder (3", 4) and a second piston body (5", 6) symmetrically arranged along said longitudinal axis (X), wherein

-the second cylinder (3", 4) exhibits a second cylindrical inner peripheral surface (8), a third end (10) and a fourth end (12) forming a second cylinder interior (14);

-the second piston body (6) comprises a third (22) and fourth (24) portion and a second radially protruding portion (16) therebetween;

-the radially protruding portion (16) is arranged in the second cylinder interior (14) and protrudes outwardly towards the second cylindrical inner peripheral surface (8) dividing the second cylinder interior (14) into a third cylinder chamber (18) and a fourth cylinder chamber (20);

-the third portion (22) of the second piston body (5", 6) sealingly extends through a third opening (26) of the third end (10) and the fourth portion (24) sealingly extends through a fourth opening (28) of the fourth end (12);

-the third portion (22) of the second piston body (6) exhibits a larger diameter than the fourth portion (24) of the second piston body (6) and comprises a second open cavity (30); -the first cylinder (3) is positioned in tandem arrangement with the second cylinder (4) in such way that the first portion (21) of a first piston body (5) of the first cylinder (3) forming a first open cavity (29) during use of the arrangement (1) alternating will encompass the fourth portion (24) of the second piston body (6).

10. The arrangement according to claim 9, wherein a common piston rod (38) is arranged along the longitudinal axis (X) through the first piston body (5) and the second piston body (6), the first cylinder (3) and the second cylinder (4) being stationary or the common piston rod (38) being stationary.

11. The arrangement according to claim 9 or 10, wherein the first piston body (5) and the second piston body (6) each comprises a piston rod engagement and disengagement device (39', 39") arranged to engage or disengage the respective first piston body (5, 5') and/or the second piston body (5", 6) to or from the common piston rod (38).

12. The arrangement according to any of the claims 9 to 11, wherein a first (PA1) and a second (PA2) piston force area of a first radially protruding portion (15) of the first piston body (5) and a third (PA3) and a fourth (PA4) piston force area of a second radially protruding portion (16) of the second piston body (6) delimit the first cylinder chambers (17, 18, 19, 20) of the first and second cylinders (3, 4), the first piston force area (PA1) being smaller than the second piston force area (PA2) and the third piston force area (PA3) being smaller than the fourth piston force area (PA4).

13. The arrangement according to any of claims 9 to 12, wherein the respective piston rod

engagement and disengagement device (39, 39', 39") each comprises a wall portion (41) arranged to be inwardly expandable towards the common piston rod (38) for clamping action, wherein a respective hollow space (43) partly is formed by each wall portion (41), the respective hollow space (43) is arranged for direct fluid communication with the second cylinder chamber (19) and the fourth cylinder chamber (20) respectively.

14. The arrangement according to any of claims 9 to 13, wherein a respective first (17), second (19), third (18) and fourth (20) cylinder chamber being provided for connection to a valve member (33) of a fluid supply (35).

15. The arrangement according to any of the preceding claims, wherein the fluid actuator

arrangement (1) comprises a plurality of cylinders (3, 4, 4') and piston bodies (5, 6, 6') according to any of claims 1-14 being symmetrically arranged around a common piston rod (38), each piston body (5, 6, 6') comprises a piston inner wall portion (41) arranged to be inwardly expandable towards the common piston rod (38) and forms a hollow space (43) adapted for direct fluid communication with the respective cylinder (3, 4, 4').

16. The arrangement according to any of the preceding clams, wherein the fluid actuator

arrangement comprises a second piston force area (A2) of a first piston body (5'), a fourth piston force area (A4) of a second piston body (5") corresponding in measurement with the second piston force area (A2), a third piston body (5"') comprises a sixth piston force area (A6), a fourth piston body (5"") comprises a eighth piston force area (A8), the sixth piston force area (A6) is twice as large as the second piston force area (A2), the eighth piston force area (A8) is twice as large as the sixth force area (A6).

17. The arrangement according to any of claims 9 to 16, wherein the first and/or second opening (25, 27) comprises a bearing member (95) arranged between the first piston body (5, 5') and the first cylinder (3, 3') and/or the third and/or fourth opening (26, 28) comprises a bearing member (95) arranged between the second piston body (5") and the second cylinder (3", 4), the bearing member (95) comprises bronze and/or bronze alloys and/or tin bronze and/or lead free bronze and/or copper and/or aluminium-bronze and/or carbon graphite or others.

18. The arrangement according to any of the preceding claims, wherein the arrangement (1) is used in elevator (71) or high bay storage applications.