WO2023027620A1

WO2023027620A1 - A hydraulic cylinder arrangement and a method relating thereto

Info

Publication number: WO2023027620A1
Application number: PCT/SE2022/050729
Authority: WO
Inventors: Jonas GRANHED
Original assignee: SELDéN MAST AB
Priority date: 2021-08-26
Filing date: 2022-07-27
Publication date: 2023-03-02

Abstract

The invention relates to a hydraulic cylinder arrangement (10) comprising a cylinder (1;1A), a piston (11) movable in the cylinder (1), a piston rod (12) attached to the piston (11) and extending outwardly from the cylinder (1). When hydraulic fluid is provided under pressure, the piston (11) is retracted into the cylinder (1) housing shortening an effective total length of the hydraulic cylinder arrangement (10), when pressure is released, the piston (11) is extended increasing the effective total length of the hydraulic cylinder arrangement (10). The piston rod (12) comprises permanent markings (13) on at least one side through which can be determined how much the cylinder has been detracted and vice versa, The depth/height of the permanent markings (13) is so small that the functionality of the hydraulic cylinder is unaffected and tight sealing via an inner piston seal (8) and an outer hydraulic seal (7) is assured.

Description

Title:

A HYDRAULIC CYLINDER ARRANGEMENT AND A METHOD RELATING THERETO

TECHNICAL FIELD

The present invention relates to a hydraulic cylinder arrangement having the features of the first part of claim 1. More particularly it relates to a hydraulic tensioner used for sails on a sailing boat, most particularly to a hydraulic tensioner for a backstay adjuster of a sailing boat.

The invention also relates to a method for fabricating a hydraulic cylinder arrangement having the features of the first part of claim 15.

BACKGROUND

Hydraulic cylinder arrangements are commonly used for creating a mechanical force in a linear motion and generally comprise a cylinder or cylinder tube capped and sealed at both ends with a piston rod protruding at one end, and which, at the interior of the cylinder tube, is connected to a piston. The piston separates the internal side of the piston from the internal capped, sealed side of the cylinder. Fluid is forced into either side of the cylinder to extend or retract the piston rod, manually or electrically controlled.

The piston rod is attached to an element requiring motion and a hydraulic cylinder arrangement is applicable substantially for any application where linear application of a force is required, e.g. for and are often used in mobile applications, such as for excavators, dump trucks, loaders, graders, dozers, and for sailing boats.

In some implementations they are used for adjusting or changing the length of a tension loaded stay on a sailing boat. On a sailing boat there may be several different kinds of sails, mainsails, spinnakers, jibs, headsails, and genoas. The sails are supported by one or more masts. The sails are attached to lines or wires holding them in place and applying tension to the sails and supporting e.g. the mast. The lines, or wires, are denoted differently depending on location and function or attachment such as headstay, backstay, shrouds, sheets, halyards, etc. The mast of a sailing boat is supported by a headstay slanting toward the fore portion of the boat, and a backstay slanting toward the aft portion of the boat. The backstay is adjusted to vary the tension in the headstay and thereby e.g. control the amount of sag in the rigging when the sail is under load. Increased tension in the stays increases the compression load in the mast. Therefore hydraulic tensioners or hydraulic stay adjusters comprising a hydraulic cylinder and a piston rod are used for changing the length of a tension loaded stay on a sailboat.

It is known to use pressure gauges for determining the fluid pressure in the hydraulic cylinder as to provide an indication of e.g. backstay loading e.g. during stay or rigging adjustment.

US 3, 620,182 discloses a hydraulically actuated stay adjuster in which hydraulic fluid is forced into the interior of the hydraulic piston and cylinder, and the length of the stay adjuster can be changed to provide various stay loadings and lengths necessary for appropriate tuning of sailboat rigging which can be mechanically locked to reduce the need of constant checking and resetting due to leakage of hydraulic fluid.

US 6,543,296 discloses a method in which the force on a stay is measured by means of a strain gauge, which is arranged in a turnbuckle. The elongation measure by the strain gauge is an indication of the force that is applied to the turnbuckle. Hence, the force which occurs in a turnbuckle is measured. Larger sailing vessels, however, do not have any turnbuckles, and information about the stay itself is not provided.

W02005/075286 has as an aim to obtain a reliable indication of the behavior of the stay itself and discloses a method for monitoring the rigging of a sailing boat through which a better indication of changes in the stay itself by measuring the elongation of at least a part of the stay itself through providing the stay with an elongation measuring means comprising an optical fibre such as a glass fibre which may be integrated with or connected to the stay and which is connected to a processor. Laser pulses are generated in the optical fibre at regular time intervals by a light source, propagate through the fibre and are detected for providing a measure of the elongation of the stay. It is submitted that measuring the elongation on the stay itself gives an insight into the actual behavior of the stay. This makes it possible to detect when an elongation of such a magnitude occurs that there is a likely risk of the stay breaking in the short or long term. The measured elongation data can be converted into a force. As long as no local or permanent extension of the stay occurs, the elongation of the stay, in combination with its modulus of elasticity and cross section, can be converted to a value for the force applied to obtain information about the force which is applied to the stay during use. Transmission of measured and calculated data may take place wirelessly to an on-shore receiving unit. This is a complicated and advanced device which is not generally applicable for sailing boats, or hydraulic tensioners in general, and requires a considerable amount of specific equipment and installations. In addition, the main purpose is to be able to establish a potential risk for a stay braking.

A disadvantage, however, of all known hydraulic tensioners, particularly, but not exclusively, for hydraulic back stay tensioners, is that the tension somehow has to be measured, e.g. there is a need to establish how much force is exerted in the equipment where it is arranged, e.g. a backstay, or generally how much the piston cylinder is contracted. As referred to above, it is well known to use pressure gauges for determining the pressure. The pressure, however, then has to be converted to a force by multiplying the pressure value with the relevant cross-sectional area as is known per se.

A hydraulic tensioner may be used for several different purposes as referred to above, on sailing boats, different vehicles and vessels, on excavators, cranes etc., and sometimes access to a manometer to get information about the pressure is not straight forward due to the placement of the cylinder arrangement as such, and/or the of the manometer, due to narrow or exposed spaces preventing access etc.

Thus, there are several problems associated with having to rely on using a manometer to be able to determine the force or the extent of compression of a hydraulic cylinder.

For sailing boat backstay adjusters, e.g. when mooring, the stern will get close to the landing stage where access is difficult and unprotected leading to risks of accidents for a person desiring to read off a manometer and the manometer itself running the risk of being damaged due to getting in contact with mooring equipment etc., or while being used as a handle due to its location. For reasons as discussed above it is also known to provide hydraulic backstay tensioners without a manometer.

It is also known to use a simple ruler or a folding ruler to measure how much a hydraulic cylinder has been compressed. However, it is a rough and unprecise method, and access may also be difficult with a ruler or similar.

All known solutions for determining the hydraulic pressure in a hydraulic cylinder suffer from disadvantages, in particular when access is limited or difficult due to narrow spaces, dangerous equipment or exposed locations and in general all suffer from several disadvantages and inconveniences. In particular, in rough environments, such as on a sailing boat for example, robustness is a requirement due to exposure to dirt, salt, and corrosion.

Thus, known hydraulic cylinder arrangements, and hydraulic tensioners in particular, as discussed above all suffer from drawbacks as far as a determination of the hydraulic pressure in the cylinder, or more generally monitoring is concerned, and, so far, there are no satisfactory solutions available.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a hydraulic cylinder arrangement through which one or more of the above-mentioned problems can be overcome.

It is a particular object to provide a hydraulic cylinder arrangement the operational state of which easily can be monitored, most particularly independently of whether it being arranged in narrow spaces or in spaces which are difficult or unsafe to access.

Another object is to provide a hydraulic cylinder arrangement allowing easy and reliable determination of the operational state without introduction of complicated equipment. A particular object is to provide such a hydraulic cylinder arrangement which is robust and durable, wear resistant, and resistant to corrosion when exposed to dirt, humidity, saltwater environments. Another particular object is to provide such a hydraulic cylinder arrangement that is easy to fabricate and maintain. Particularly it is an object to provide a hydraulic cylinder arrangement for a sailing boat fulfilling one or more of the above-mentioned objects, most particularly a hydraulic tensioner, most particularly a hydraulic backstay tensioner.

Therefore, a hydraulic cylinder arrangement as initially referred to is provided having the characteristic features of the characterizing part of claim 1.

It is therefore also an object to provide a method for fabricating a hydraulic cylinder arrangement through which one or more of the above-mentioned problems can be overcome.

Therefore, a method as initially referred to is provided which has the characterizing features of claim 15.

Advantageous embodiments are given by the respective appended dependent claims.

Through the invention it has been realized that, to determine the operational state (which here refers to the current hydraulic pressure in a cylinder) it is for several implementations sufficient to determine the length or how much the piston rod has been extracted (and/or) retracted, i.e. a measure of the hydraulic pressure is not needed. Of course, in some implementation optionally a measure of the hydraulic pressure in the hydraulic cylinder (approximate, or converted and e.g. tabulated or in any other appropriate way indirectly determined) may be presented or used depending on what is needed for a particular application.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be further described, in a non-limiting manner, and with reference to the accompanying drawings, in which:

Fig. 1 is a schematic side view of a hydraulic cylinder arrangement according to the present invention according to a first embodiment,

Fig. 2 is a schematic side view of the hydraulic cylinder arrangement shown in Fig.1 with the front part of the hydraulic tensioner shown in cross-section,

Fig. 3 is a schematic view in perspective of the hydraulic cylinder arrangement shown in Fig.1, Fig. 4 is a schematic side view of a hydraulic cylinder arrangement according to the present invention according to a second embodiment,

Fig. 5 is a schematic side view of the hydraulic cylinder arrangement shown in Fig.4 with the front part of the hydraulic cylinder arrangement seen in cross-section.

Fig. 6 is a schematic view in perspective of the hydraulic cylinder arrangement shown in Fig.4.

DETAILED DESCRIPTION

Fig. 1 shows a hydraulic cylinder arrangement 10 according to a first embodiment of the present invention. In a manner known per se it comprises a cylinder 1 with a piston 11 (cf. Fig.2) to which a piston rod 12 is attached. The difference in hydraulic pressure between the two sides of the piston 11 causes the cylinder 1 to extend and retract. The piston 11 is attached to piston rod 12 e.g. by means of threads, bolts, or nuts to transfer the linear motion produced by the applied hydraulic pressure.

In the embodiment shown in Fig. l the hydraulic cylinder arrangement 10 comprises an integrated pump, i.e. a pump is integrated with the cylinder 1 for creating the hydraulic pressure in the cylinder 1. Via a pump handle 5 the pressure in the cylinder 1 can be increased/decreased moving the piston 11 in opposite directions in a known manner. The hydraulic cylinder arrangement, e.g. a so called tensioner, comprises a first, here denoted lower, terminal 2 comprising a shaft and bushings 3; how the first (or lower) terminal 2 is implemented is however not of importance for the functioning of the inventive concept of the present invention, far more it can be implemented in many different ways and therefore not will be further discussed herein. In Fig.1 also an exemplary pressure release valve 4 is shown by means of which the pressure in the cylinder 1 can be released. The cylinder arrangement 10 comprises a sealed end cap 6 (here also denoted upper end cap) with a second or upper (here) end hydraulic (outer) seal 7 (cf. Fig.2) for sealing between the piston rod 12 and the cylinder 1 at the upper (here) end and an inner or piston seal 8 (cf. Fig.2). The hydraulic cylinder arrangement may also comprise an adjustable relief valve allowing adjustment of the hydraulic pressure and for preventing overload (not shown for not being of relevance for the inventive concept. The piston rod 12 free end 15 may comprise a connecting or attachment means for connection to a means or element to be exposed to a linear motion. Since hydraulic cylinders and hydraulic tensioners and any connection means are well known in the art and can be varied in many ways, the hydraulic cylinder arrangement and its functioning will not be described in further detail.

In general, known cylinder arrangement or hydraulic tensioners are provided with a manometer fitted directly to the cylinder (or to an external pressure or power source; cf. the embodiment described with reference to Figs. 4-6). Such manometers are used to display the hydraulic pressure inside the cylinder. However, it is often difficult to read off such a manometer as discussed in the introductory part, and also the pressure needs to be converted to a force. Through the present invention it has been realized that for several particular implementations, such as e.g. for sailing boat stays, information on the hydraulic pressure, values of the hydraulic pressure, which then needs to be converted to a force, actually is not needed, and actually it is sufficient to determine how much the piston rod 12 has been extended into/retracted out of the cylinder 1.

According to the present invention it has been realized that it is easier to see on scale how much the hydraulic cylinder e.g. has been contracted (and/or extended) than to read off how much pressure the hydraulic cylinder has inside. It has also been realized that often it is of interest to easily and quickly be able to determine how much the piston rod extends. Therefore, the surface of the piston rod is marked, e.g. by engraving using a laser or equivalent, or it is etched, in order to allow a user to determine how much a hydraulic cylinder is contracted or vice versa. The marks 13 on the piston rod 12 thus indicate how much the hydraulic cylinder 1 is contracted. Alternatively, the piston rod might be provided with external markings, e.g. showing a scale to be briefly discussed further below.

In one embodiment of the invention the piston rod 12 is provided with a scale 13, in the shown embodiment with markings from 0-9, which of course merely is an example; other values, or scales can be used. As is well known, a hydraulic cylinder piston rod requires being highly ground and well-polished to allow for a safe and reliable sealing and minimize any risk of leakage of hydraulic fluid. The scale markings 13 according to the present invention are permanent, e.g. laser engraved or etched with a small depth assuring that the highly polished surface of the piston rod will be substantially unaffected. The depth of the markings may be between 0.005-0.3 mm depending on material used for the piston rod, e.g. 0.007-0.035 mm for stainless steel, and since markings with an extremely small depth are used, and such that the functionality of the hydraulic cylinder is not affected, the extremely high requirements as to tightness will be upheld, i.e. high quality sealing is still assured and leakage of hydraulic fluid is prevented.

The piston rod 12 in advantageous embodiments is made of marine grade stainless steel. The cylinder 1 may in some embodiments, naturally depending on implementation, but e.g. for marine implementations e.g. as hydraulic adjusters for backstays and vangs on sailing boats, be made of anodized aluminum. The cylinders may of course also be made of other materials, the materials discussed above being particularly advantageous for marine implementations, e.g. on sailing boats.

In Fig.2 the hydraulic cylinder arrangement 10 of Fig. 1 is shown with the upper (here) end of the cylinder 1 as a cross-sectional view such that the rear end of the piston rod 12 which is attached to the piston 11 can be seen, and also illustrating the upper end seal 7 and the piston seal 8. Features having already been discussed with reference to Fig.1 will not be further discussed.

Fig.3 is an enlarged view of the hydraulic cylinder arrangement 10 shown in Figs. 1 and 2 in perspective in order to more clearly show the scale markings 13, and also showing the pump handle 5. In other respects, features already discussed with reference to Figs. 1 and 2 will not be further discussed.

Fig. 4 shows a hydraulic cylinder arrangement, e.g. a hydraulic tensioner, 10A according to a second embodiment of the present invention. It comprises a cylinder 1 A with a piston 11 A (cf. Fig.5) attached to a piston rod 12A e.g. by means of threads, bolts, or nuts to transfer a linear motion as is well known and as also discussed above.

In the embodiment in Fig.4 the hydraulic cylinder arrangement 10A is connected to an external power source (not shown) to control the hydraulic pressure in the hydraulic cylinder by supplying the cylinder 1 A with oil through a pipe or a hose 21 A, and allowing to increase/decrease the pressure in the cylinder 1 A moving the piston 11 A in opposite directions in a known manner. The hydraulic cylinder arrangement 10A comprises a first, here lower, terminal 2 A, here comprising a fork with a head 3 A’ secured at a free end by means of a pin for connection of the hydraulic cylinder arrangement or hydraulic tensioner 10A, which however can be implemented in many different manners, also depending to which element it is to be connected, and for what implementation it is to be used, and how the first, lower, terminal 2A is implemented. How the first terminal 2 A and a second, here upper, end terminal 15 A at the outer free end of the piston rod 12A are implemented is also not part of the present invention but they can be of many different kinds, have different dimensions and be shaped and equipped with arbitrary interconnecting means in many different ways and depending on implementation not being of importance for the functioning of the inventive concept of the present invention and therefore will not be further discussed herein.

In Fig.4 the free end or second, upper, end terminal 15A of piston rod 12A connected to piston 11 A (cf. Fig.5) and protruding through a sealed end cap 6A of the cylinder 1 A is shown.

In Fig.5 the hydraulic cylinder arrangement 10A of Fig. 4 is shown with the front of the cylinder 1 A shown in cross-section such that the rear end of the piston rod 12A attached to the piston 11 A can be seen. In Fig.5 hydraulic (outer) seal 7A of sealed end cap 6A for sealing between the piston rod 12A and the cylinder 1 A at the cylinder upper end and an inner piston seal 8A are illustrated.

Features already discussed with reference to Fig.4 will not be further discussed here, and since hydraulic cylinder arrangements and hydraulic tensioners connected to an external power source are known in the art and can be implemented and varied in many ways, the hydraulic cylinder arrangement 1 A will not be further described, many variations being possible within the scope of the present invention as claimed.

Similar to the piston rod 12 described above with reference to the embodiment described with reference to Figs.1-3, also the piston rod 12A shown in Figs. 4-6 is provided with a scale 13 A, in the shown embodiment also with markings from 0-9, which of course merely is an example; other values, scales or indications can be provided. The scale markings 13 A are permanent, e.g. laser engraved or etched assuring that the highly polished surface of the piston rod 12A will be unaffected to such an extent that the functionality of the hydraulic cylinder arrangement will be unaffected, tightness will be upheld, i.e. high quality sealing is still assured and leakage is prevented, the markings having an extremely small depth as further discussed above with reference to the embodiment shown in Figs.1-3.

The piston rod 12A in advantageous embodiments is made of steel, e.g. marine grade stainless steel, or any other appropriate material depending on implementation and environment where it is to be used. The cylinder 1 A may be made of anodized aluminum. The cylinders may of course also be made of other materials, the materials discussed above being particularly advantageous for marine implementations, e.g. on sailing boats.

Fig.6 is an enlarged view of the hydraulic cylinder arrangement 10A shown in Figs. 4 and 5 in perspective mainly in order to more clearly show the scale markings 13 A. In other respects, features already discussed with reference to Figs. 4 and 5 will not be further discussed here.

In still other embodiments of the invention (not shown) the piston rod is provided with markings, e.g. a scale as discussed above which instead are printed or glued or somehow fixedly and permanently fastened onto it. As described above, markings have a small height assuring that the highly polished surface of the piston rod will be substantially unaffected. The height of the markings may be between 0.01-0.3 mm depending on marking technique and material used, e.g. 0.007-0.02 mm for stainless steel, and since markings with an extremely small height are used, and such that the functionality of the hydraulic cylinder is not affected, the extremely high requirements as to tightness will be upheld, i.e. high quality sealing is still assured and leakage of hydraulic fluid is prevented. This is particularly applicable when the piston rod remains to a large extent in a same position and wear is very low.

In a particular embodiment the hydraulic cylinder arrangement comprises a hydraulic tensioner for a sailing boat. The rig on a sailing yacht is complex and any optimum set-up changes with environment (wind and sea state). The setting of the rig is controlled by several variables but the most important is the tension of stays, therefore it is extremely advantageous to be able to, easily and quickly, see the position on a piston rod on the hydraulic tensioner (cylinder). For example, a tensioner connected to a backstay will control how a mast will bend in a longitudinal direction. If the tensioner is contracted, the mast will bend.

Backstays and vangs allowing fast and appropriate adjustment are highly important for sailing boats, both for cruising sailing boats and for racing sailing boat. Allowing appropriate tensioning of forestay, adjusting the pre-bending of a mast and controlling the power in the mainsail is important for a good control of a sailing boat, makes any boat point higher, and allows to sail faster.

A hydraulic cylinder arrangement according to the present invention can be used as any hydraulic cylinder (e.g. on a sailing yacht), or for backstay tensioners, vangs as discussed above, but also for halyard tensioners and tensioners in general. As discussed above, the cylinders may comprise an integrated pump creating the hydraulic pressure or be connected to an external source supplying a hydraulic pressure.

Most particularly the hydraulic tensioner is used for an adjustable backstay (not shown) for a sailing boat. The hydraulic cylinder arrangement 10;10A is then introduced in a segment of the stay (not shown) such that the hydraulic cylinder 1;1A is connected by means of a linked connection in any appropriate manner to a section or segment of the stay via first, lower, terminal (2;2A) whereas piston rod free end (15; 15 A) is connected to another section or segment of the stay.

In another particular embodiment the hydraulic cylinder arrangement comprises a hydraulic tensioner used for a vang (not shown) for a sailing boat.

In some embodiments additional electronic reading devices may be provided for reading off the scale. A hydraulic cylinder arrangement or tensioner for a sailing boat according to the invention in some embodiments has a long stroke allowing trying out different mast rakes. They may also in some implementations comprise a 2-speed function permitting fast tensioning until a predetermined contraction is achieved as detected by reading off the scale. Then the tensioner may be shifted down to a low speed and a reduced resistance in a handle (if provided, as shown in Figs.1-3 or on a panel (not shown) connected to the hydraulic tensioner). The level of pressure, indirectly indicated and read off through scale markings, needed to gear down is easily adjusted to suit an individual trimmer.

A hydraulic tensioner according to the invention can e.g. be for a single function or for 4- functions. It may be connected to a panel having a dual action function wherein the pump is active both when pushing and when pulling a handle. An adjustable relief valve (not shown) can be used to prevent overload. A 2-speed function permits fast tensioning until a predetermined pressure is obtained as detected by reading off the scale. Then the panel shifts down to a low speed and a reduced resistance in the handle (if provided). The level of pressure, indirectly indicated and read off through scale markings, needed to gear down can easily be adjusted to suit an individual trimmer. Such an optional panel can e.g. be connected to an electric pump station or to an external source replacing the need for manual pumping through pushing a button.

Many variations are possible.

It should be clear that in alternative embodiments the hydraulic cylinder arrangement can be used for other implementations, for vehicles, cranes, excavators etc.

It has been realized, that particularly for implementations in which the cylinder is to a large extent in a same position, the piston rod is in a substantially same position, the provisioning of markings on the piston rod according to the present invention is extremely advantageous, since wear is extremely low, as is the case e.g. when used as stays for sailing boats.

The dimensions, shape etc. of the hydraulic cylinder arrangement, the separate elements thereof, the scale markings etc. can be varied without limitation as long as the scale markings are etched, engraved or made using any other technique similarly ensuring that the functioning of the hydraulic cylinder is not affected, i.e. by the markings having a depth (or a height) sufficiently small to assure that requirements as to sealing and tightness can be upheld, preventing leakage and damages.

It is an advantage that through the present invention a hydraulic cylinder arrangement is provided which is easy to use, monitor, and, in addition, is reliable, has a long service life and is easy to fabricate.

It should be clear that the invention is not limited to the explicitly described embodiments but that it can be varied in several ways within the scope of the appended claims.

It should also be clear that the content of described embodiments freely can be varied and combined.

Claims

1. A hydraulic cylinder arrangement (10;10A) comprising a cylinder (1;1A) in a housing adapted to receive or hold a hydraulic fluid under pressure, a piston (11;11A) movable in the cylinder (1;1A) in response to hydraulic fluid being provided to the cylinder (1;1A), a piston rod (12;12A) connected to the piston (11;11A) and extending outwardly from the cylinder (1;1A), the piston

(11;11A) and cylinder (1;1A) cooperating to define a high pressure chamber arranged such that when hydraulic fluid is provided under pressure, the piston (11;11 A) is retracted into the cylinder (1;1A) housing shortening a total, effective, length of the hydraulic cylinder arrangement (10;10A), and when pressure is released, the piston (11;11A) is extended, hence increasing the total, effective, length of the hydraulic cylinder arrangement (10;10A), an inner piston seal (8;8A) and a hydraulic outer seal (7;7A) at a second outer, or upper, end of the hydraulic cylinder housing, connecting terminals (2,15;2A,15A) being provided at the first outer, or lower, end of the cylinder (1;1A) and at the free outer end (15; 15 A) of the piston rod (12;12A) respectively, c h a r a c t e r i z e d i n that the piston rod surface (12;12A) comprises at least one permanent marking (13; 13 A) or a scale on at least one side to allow determining how much the piston rod (12;12A) has been detracted and/or vice versa or if the detract! on/extended has passed a said marking by reading or monitoring the scale or the at least one marking, said at least one marking having a depth or a height which is so small or shallow/high, that the functionality of the hydraulic cylinder is unaffected and a tight sealing via the piston seal (8;8A) and the hydraulic outer seal (7;7A) is assured.

2. A hydraulic cylinder arrangement (10;) according to claim 1, c h a r a c t e r i z e d i n that it comprises at least two, or a plurality of markings or references along a longitudinal extension thereof.

3. A hydraulic cylinder arrangement (10;) according to claim 1 or 2, c h a r a c t e r i z e d i n that it comprises an integrated hydraulic pump.

4. A hydraulic cylinder arrangement (10) according to any one of claims 1-3, characterized in that it comprises a pump handle (5) for providing hydraulic fluid by means of manually actuating the pump handle (5).

5. A hydraulic cylinder arrangement (10A) according to claim 1 or 2, characterized in that it comprises a hydraulic pressure hose (21 A) and in that it is connected to an external hydraulic power source.

6. A hydraulic cylinder arrangement (10;10A) according to any one of the preceding claims, characterized in that hydraulic cylinder (1;1A) is made of Al.

7. A hydraulic cylinder arrangement (10;10A) according to any one of the preceding claims, characterized in that the piston rod (12;12A) is made of stainless steel, particularly stainless steel.

8. A hydraulic cylinder arrangement (10; 10 A) according to any one of the preceding claims, characterized in that the at least one marking (13; 13 A) is/are laser engraved or etched.

9. A hydraulic cylinder arrangement (10;10A) according to any one of the preceding claims, characterized in that the depth of the or each marking is between 0.007-0.3 mm, preferably between 0.01 and 0.05 mm, most particularly between 0.01-0.012 mm.

10. A hydraulic cylinder arrangement (10;10A) according to any one of claims 1- 7, characterized in that the at least one marking (13;13A) is/are printed, glued or attached to the piston rod in any similar manner. 16

11. A hydraulic cylinder arrangement (10; 10 A) according to 10, c h a r a c t e r i z e d i n that the height of the or each marking is between 0.007-0.3 mm, preferably between 0.01 and 0.05 mm, most particularly between 0.01-0.035 mm.

12. A hydraulic cylinder arrangement (10;10A) according to any one of claims 2-11, c h a r a c t e r i z e d i n that the markings comprise a scale with equidistant marking, e.g. from 0-10 or similar, or markings indicating a maximum and a minimum value, or an optimum value.

13. A hydraulic cylinder arrangement (10; 10 A) according to any one of the preceding claims, c h a r a c t e r i z e d i n that it comprises a hydraulic tensioner for a sailing boat such as a backstay tensioner, a halyard tensioners, the connecting terminal (15; 15 A) of the free end of piston rod (12;12A) being adapted for connection to a backstay or a forestay respectively and the first, lower, terminal (2;2A) being adapted for connection to a backstay or a headstay chain plate, or a vang or similar.

14. Use of a hydraulic cylinder arrangement (10;10A) according to any one of claims 1-13 as a backstay tensioner, a headstay tensioner, a forestay tensioner, a vang or similar on a sailing boat.

15. A method of fabricating a hydraulic cylinder arrangement (10;10A) comprising a cylinder (1;1A) in a housing adapted to receive a hydraulic fluid under pressure, a piston (11;11A) movable in the cylinder (1;1A) in response to hydraulic fluid being provided to the cylinder (1;1A), a piston rod (12;12A) connected to the piston (11;11A) and extending outwardly from the cylinder (1 ; 1 A), the piston (11 ; 11 A) and cylinder (1 ; 1 A) cooperating to define a high pressure chamber arranged such that when hydraulic fluid is provided under pressure, the piston (11;11A) is retracted into the cylinder (1;1A) housing decreasing an effective total length of cylinder arrangement, and when pressure is released, the piston (11;11A) is extended, hence increasing the effective total length of the cylinder arrangement, a piston, inner, seal (8;8A) and a hydraulic outer seal (7;7A) at a second outer, or upper, end of the hydraulic cylinder housing, connecting 17 terminals (2,15;2A,15A) being provided at first outer, or lower, end of the cylinder (1;1A) and at the free outer end of the piston rod (12;12A) respectively, c h a r a c t e r i z e d i n it comprises the step of permanently marking the piston rod (12;12A) outer surface through laser engraving, etching, printing or gluing with at least one marking or e.g. a scale or similar on at least one side of the piston rod to allow determining the how much the cylinder has been detracted and/or vice versa by reading or monitoring the scale or the at least one marking, said at least one marking having a depth or a height respectively which is so small that the functionality of the hydraulic cylinder is unaffected and tight sealing via the piston, inner, seal (8;8A) and the hydraulic outer seal (7;7A) is assured.