WO2012105848A1

WO2012105848A1 - Hydraulic cylinder and a method for manufacturing such a cylinder

Info

Publication number: WO2012105848A1
Application number: PCT/NO2012/050011
Authority: WO
Inventors: Thomas Pettersson
Original assignee: Modular Cylinder System As
Priority date: 2011-01-31
Filing date: 2012-01-31
Publication date: 2012-08-09
Also published as: NO337662B1; NO20110166A1

Abstract

A hydraulic cylinder (100) comprises a housing (110) with a cylindrical inner surface (111). An end piece or butt (340, 341) with a cylindrical outer surface is placed in contact with the housing inner surface (111) at each end of the housing (110). The end piece or butt (340, 341) has an annular groove or slot (350, 351) along its entire circumference, and the housing wall is sealingly deformed into the annular groove or slot (350, 351).

Description

HYDRAULIC CYLINDER AND METHOD FOR MANUFACTURING

SUCH A CYLINDER

BACKGROUND

Technical Field

The present invention relates to a hydraulic cylinder and a method for manufacturing of it.

Known and related techniques

A hydraulic cylinder of the type described here is also called a linear actuator and generally consists of an outer housing with an inner cylindrical sealing surface, where a piston is arranged axially glidable / slidable and in sealing contact against the inner cylindrical sealing surface. An incompressible fluid, typically hydraulic fluid or oil, having pressure p is applied at one end of the piston and acts on a work area A. The force acting on the piston is F = p^■ A. Pressure can be applied in turns on opposite sides of the piston, which can be moved back and forth.

In the following the term rear position is used for the position where the piston is furthest inside the housing, and the total length of the piston and the housing is smallest. Similarly, front position denotes the position where the total length of the housing and the piston is greatest. The directions forward and backward show the directions towards respectively the front and the rear position, and the stroke length is defined as the distance between the piston's front and rear position in the housing.

The piston projects out of the front end of the housing and is equipped with a standard connector for attachment of different equipment that is to be moved by means of the cylinder. The rear end of the cylinder is arranged with a fastener or bracket for fastening or attachment of the cylinder. The axial mounting dimensions of the cylinder are given by the place or location where it will be mounted, which makes it often impossible to connect the hydraulic hoses to the housing end(s). A typical hydraulic cylinder has therefore one or more radially oriented fittings for the supply of hydraulic fluid.

Different hydraulic cylinders can have different stroke length. In order to reduce storage costs, it is unusual to stock all dimensions or sizes. When a cylinder gets defective, it is therefore typical to order from the supplier a new cylinder with desired stroke length. Then the supplier cuts or crops typically to a housing article with the right length, and welds or threads end caps or pieces and the radial fittings or nipples for supply of hydraulic fluid. The manufacture process takes approximately seven hours or more. Transportation time to the place where the cylinder is be used comes in addition. Threading and welding require equipment that is not normally found at the site where the cylinder is used. Welding can additionally be used in explosive or hazardous areas, such as e.g. many places on an oil or gas field or a platform for exploration and/or extraction of hydrocarbons.

The piston shall transfer a given force, and can in some applications be a solid rust- free cylinder with polished outer surface for sealing contact against the inner sealing surface. Some pistons are made of stainless steel, have a stroke length of several meters and a diameter of 30-40 cm in order to get the required bending stiffness or flexural modulus. If the outer surface of such a piston is scratched up, the cylinder can start leaking oil and thus be unable to transfer the necessary power for e.g.

heave compensation of a stroke on a typical platform used in the oil and gas industry. It is expensive, heavy and difficult to replace such a piston without occurring of new damages, and it is expensive and impractical to have a stock or store with such heavy and expensive pistons.

It is therefore an object of the present invention to reduce the time that it takes to replace a defective hydraulic cylinder. It is also an object to produce or manufacture a replacement cylinder without the use of threading or welding during installation of end pieces or butts and fittings or nipples.

It is also an object of the present invention to provide a flexural hydraulic piston that can be easily replaced on the site where it is to be used.

SUMMARY OF THE INVENTION

The present invention is based on the observation that pressing tool(s) for attachment of the hydraulic hoses to fittings or nipples on the hydraulic cylinders is(are) relatively inexpensive compared to the special threading tool(s) and welding equipment. Such pressing tools are also often already available on the site where the hydraulic cylinders are used, and their usage is associated with fewer restrictions than e.g. those for welding tools. Such a pressing tool provides a force directed radially inwards and can be equipped with pressure or press chucks or jaws fit or adapted for different hose dimensions. When the pressing tool is activated, e.g.

hydraulic, presses a press or pressure chuck or jaw radially inwards with a relatively large force. The purposes of the invention are achieved by providing the hydraulic cylinder comprising a housing with a cylindrical inner surface, an end piece or butt with a cylindrical outer surface arranged in contact with the inner surface of the housing at each end of the housing, characterized in that the end piece or butt has an annular groove along its entire circumference, and that the housing wall is sealing deformed down into the annular groove.

In another aspect the invention concerns a press chuck or jaw characterized by a group of ring segments adapted for installation or abutting or resting around a hydraulic cylinder in the circumferential direction and for applying sufficient force on the cylinder wall so that the wall is being deformed down into the annular groove in the material lying under.

In a third aspect the invention concerns a method for producing or manufacturing of a hydraulic cylinder characterized by the steps of: inserting an end piece or butt in a cylindrical end of a cylinder housing, where the end piece has a concave annular groove along the entire circumference of an outer cylindrical surface; arranging or placing a press chuck or jaw around the housing, where the press chuck or jaw comprises a group of ring segments and the press chuck or jaw defines a press or pressure element running or passing radially inwards around an inner circumference of the pressure or press chuck or jaw; setting up or installing or abutting a radially directional shoulder on the press chuck towards an axial surface of the cylinder housing, where the press or pressure element is arranged or placed radially outside the concave ring or annular groove of the end piece or butt; installing or mounting or assembling the press piece or butt in a pressing tool designed to produce or generate a force directed radially inwards; and activating the pressing tool until the cylinder housing wall is deformed into the concave ring or annular groove.

In a preferred embodiment the press or pressure element is a clamping ring that remains on the outer wall of the cylinder housing when the operation is completed. An end sleeve can be threaded onto the clamping ring in order to prevent it from expanding radially or sliding/gliding up.

The hydraulic cylinder can comprise a hollow piston, where an elongated inner part or portion is introduced or inserted. The inner portion or part transfers power or forces along the piston, and is threaded into an outer sheath or mantle, where the outer sheath has an outer cylinder surface with desired surface characteristics or qualities. The inner part or portion can, for example, have longitudinal ribs for transferring power forward from the cylinder on the piston, or it may be a wire or cable for transferring power backward from the cylinder on the piston.

Additional features of the invention are shown in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in the detailed description with reference to the

accompanying drawings, where:

Fig. 1 is a longitudinal section along the axis B-B in Fig. 3;

Fig. 2 is a cross section along the line C-C in Fig. 3;

Fig. 3 is a top view of the cylinder in Fig. 1 ;

Fig. 4 shows an open clamping ring before compression;

Fig. 5 is a section through a cylinder and a press chuck along D-D in Fig. 7;

Fig. 6 shows the press chuck and the cylinder in Fig. 5 viewed from the side;

Fig. 7 shows the press chuck and the cylinder in Fig. 5-6 seen axially from one end;

Fig. 8 shows a ring segment viewed from the side;

Fig. 9 is a perspective view of a ring segment;

Fig. 10 shows a piston rod seen from one end;

Fig. 1 1 is a longitudinal section along the line E-E in Fig. 10;

Fig. 12 shows an alternative piston rod seen from one end, corresponding to Fig. 10;

Fig. 13 is a longitudinal section along the line F-F in Fig. 12. DETAILED DESCRIPTION

Figure 1 is a longitudinal section through a hydraulic cylinder 100 according to a preferred embodiment of the invention. The cylinder consists of a housing 1 10 with an inner cylinder surface 1 1 1 . A piston 200 is axially slidably or glidably arranged or placed in sealing contact against or towards the inner cylinder surface of the housing. The piston is projecting or sticking out of the front end of the housing.

A rear end piece or cap or butt 340 has a cylindrical outer surface in contact with the inner cylinder surface 1 1 1 of the housing. The end piece 340 has an annular concave groove 350 along its entire circumference. The housing is closed at its rear end so that a part of the housing wall is deformed into the ring or annular groove 350 on the rear end piece 340. In the embodiments shown in Figure 1 a rear clamp ring 400 is used to deform the wall of the housing into the annular groove 350. The wall of the housing can alternatively be deformed down into the annular cavity of a ring-shaped or annular ridge without the use of clamping rings. See the description of Figure 5 below.

In Figure 1 a rear end sleeve 300 is threaded over the end piece 340 and the clamping ring 400, and is being held in place by a lock or counter nut 320 that is screwed on the end of the end piece 340. The counter nut 320 presses the end sleeve 300 in the direction toward the center of the cylinder. The end sleeve 300 can prevent the clamping ring 400 from expanding radially, and is therefore arranged radially outside the clamping ring 400 in Figure 1 . The end sleeve 300 has a radial bore 310 which is in fluid contact with a rear piston surface 210. Hydraulic pressure p delivered through the bore 310 acts on the rear piston surface 210 and provides a force Fi = ^■ A₂io directed forward, i.e. to the right on Figures 1 and 3. The front part of the housing is closed in a similar way by front end piece 341 , clamping ring 401 , end sleeve 301 and lock or counter nut 321 . While the rear end piece or cap 340 is a solid piece of metal, the front end piece 341 has an axially directed bore fit or adapted to the outer surface 201 of the piston. One or more seals or gaskets 342 is(are) sealed against the outer surface 201 of the piston so that the piston 200 can be moved axially in relation to the front end piece 341 without hydraulic fluid leakage between the outer surface 201 of the piston and the inner surface of the axial bore through the front end piece 341 . Hydraulic pressure p₂ delivered through a radial bore 31 1 on the end sleeve 301 acts on a front piston surface 220 and provides a force F₂ = P2 · A₂₂₀ directed backward, i.e. to the left on Figures 1 and 3. The pressures pi and p₂ can be the same pressure or different pressures. Figure 2 is a cross section along the plane C-C in Figure 1 . The figure shows that the radial bore 31 1 is in fluid connection or contact with the piston 200 through an annulus around the front end piece 341 and radially directed or oriented channels in the front end piece 341 . Figure 3 is a view of the cylinder in Figure 1 , seen towards the radial bores 310 and 31 1 .

Figure 4 shows a compression or clamping ring 400, 401 in an open state, i.e. with an open room or space. The figure is not in the same scale as Figures 1 -3. The clamping ring 400, 401 shall be clamped together around the cylinder housing and thus will get a smaller diameter. The opening is adapted to the reduced diameter so that the clamping ring will form a substantially closed torus when it is clamped in place. Figures 5-7 show a press chuck or jaw with a number of segments 510, 510a that are arranged around an end of the cylinder. The cylinder is generally shown or referred to by reference number 100, and the ring segments are being collectively referred to by reference number 510 (Figure 6). Figure 5 is a longitudinal section along D-D in Figure 7. Ring segments 510a and 51 Od are visible in the figure. The ring segment 510 has at least one installation or abutting shoulder 51 1 that is arranged or placed against the axial surface of the cylinder 100. The axial distance from the shoulder 51 1 to a groove 512 on the ring segment corresponds to the distance between the axial surface of the cylinder and at least one annular groove 350, 351 in the material under the cylinder wall. The material under the cylinder wall is represented by the end pieces or butts 340 and 341 in Figure 1 . In a first embodiment the ring segments have a groove 512 adapted to a clamping ring. Figure 8 illustrates how a compression or clamping ring 400 is located or placed in such a groove 512 in a segment 510'. The clamping ring 400 is shown in Figure 4 and is not a part of the ring segment 510'. When the press chuck is clamped radially together into the position shown in Figures 5-7, the clamping ring 400 is pressed into the cylinder wall, and the cylinder wall is deformed into an annular groove 350 in the material lying under. In this position the opening in the clamping ring 400 (or a corresponding compression ring 401 ) on Figure 4 is clamped together.

Figure 5 shows also another embodiment, where an annular ridge 513 has pressed or pushed the cylinder wall into another annular groove 351 in the material lying under. A compression or clamping ring 400, 401 and/or a ring-shaped or annular pressure ridge 513 can be used together or separately to press or push the cylinder wall down into an underlying annular groove 350, 351 . In both cases, the pressure element 400, 513 is arranged or placed axially over a ring-shaped or annular groove so that the shoulder 51 1 on the press chuck is arranged against or towards the axial surface of the cylinder 100. In a preferred embodiment a compression or clamping ring 400, 401 is used, which ring remains arranged around the cylinder housing after removing of the press chuck. In the claims the clamping ring 400, 401 and press ridge are together referred to as "press or pressure element", because they have the same function in this context.

Figure 6 shows a side view of a radially compressed press chuck, and Figure 7 shows the same press chuck as seen from one end. The fittings or nipples 520 illustrate means for attaching or fastening of the ring segments to a pressing tool (not shown). The pressing tool must be able to press or push the segments together with sufficient force so that the cylinder wall is deformed in sealing contact with a ring- shaped or annular groove 350, 351 in the material lying under. Known pressing tools for hydraulic hoses have proven suitable for this purpose. Figure 9 is a perspective view of the ring segment 510' in Figure 8.

In a preferred embodiment the press or pressure element is a compression or clamping ring 400, 401 , for example a steel ring that remains on the outer wall of the cylinder housing when the operation is completed.

In a method for using the equipment described above an end piece or butt 340 is introduced in a cylindrical end of a cylinder housing 1 10. The end piece has a concave annular groove 350, 351 along the entire circumference of an outer cylinder surface.

Then a segmented press chuck 500 is arranged around the housing. Each ring segment has a ridge adapted to the groove 351 or a groove 512 adapted to a compression or clamping ring 400, 401 . In both cases, a press or pressure element is provided in the circumferential direction, where the pressure element is directed radially inward. The axial distance between a shoulder 51 1 on the ring element 510 and the pressure element 400, 401 , 513 corresponds to the distance between an axial surface of the cylinder housing and the annular groove.

The shoulders 51 1 are so aiming at or abutting towards the axial surface.

Consequently the press or pressure element is placed radially outside the annular groove, and the wall of the cylinder housing is arranged or located between the pressure element that is directed radially inward and the concave annular groove 350, 351 in the end piece or other material lying under. The press chuck or jaw 500 must be mounted or installed or assembled in a pressing tool (not shown) before the next step, if not already installed. Each ring segment 510 has means 520 for mounting or installing in the pressing tool.

When the end piece with concave ring or annular groove, the wall of the cylinder housing and the pressure element in the press chuck are arranged as described above, the pressing tool is activated. Consequently the press or pressure element is moved radially inward until the wall of the cylinder housing is deformed into the concave ring or annular groove or slot.

An end sleeve can be threaded onto the end. This can prevent the clamping ring in the preferred embodiment described above from expanding radially.

The above can be repeated, in a similar manner, for the other end of the cylinder.

Figure 10 is a cross section through a piston rod consisting of a hollow and cylindrical outer sheath or mantle 202 and an inner part or portion 600 which is threaded into the outer sheath or jacket. The outer sheath can be manufactured of e.g. rust-free or acid-proof steel and has an outer cylinder surface 201 with desired surface characte- ristics or qualities. The cylinder surface 201 shall form sealing contact against an axial bore as described in connection with Figure 1 . The inner portion or part 600 in Figure 10 is also hollow, but corrugated along the circumferential direction. The waveform in Figure 10 and other forms, where the radius varies along the circumference, such as e.g. embodiments with other types of longitudinal ribs or ridges, give a rigid body with less mass than e.g. an equivalent solid piston rod made of rust-free (stainless) or acid-proof steel.

The inner part or portion does not need to be stainless or acid-resistant and can be made or built of any suitable material, such as e.g. steel or other metal with the desired elastic modulus and other properties or characteristics. The portion 600 can for example be extruded and cured in the same operation by choosing the right material.

If desired, the inner portion or part 600 can be attached or fastened in the outer sheath or mantle 202 in a known manner, so that the piston rod becomes a rigid shell. The effective shell thickness depends on the difference between the minimum and maximum radius along the perimeter. An inner element 600, as shown in Figure 10, can thus increase the stiffness or rigidness of the piston rod without increasing correspondingly the mass of the piston rod. Figure 1 1 shows a longitudinal section through a portion or part of the piston rod in Figure 10.

The embodiment in Figures 10 and 1 1 is suitable for transferring forces forward from the cylinder housing on the piston in Figures 1 -3. This is equivalent to a pressure pi that is supplied through the opening 310 and acts or works on the surface 210 as described in connection with Figure 1 . The forces are preferably transferred through the inner portion 600, which should be designed for this purpose. The shape of the inner portion 600 can be extruded. It is left to the specialist to choose the material and method of manufacture.

In other applications the greatest loads on the cylinder can be caused by tension or strain, i.e. forces acting from the surroundings on the piston rod, or backward from the cylinder on the piston surface. This is equivalent to a pressure pz that is supplied through the opening 31 1 and acts on the surface 220 as described in connection with Figure 1 . In such applications, the inner portion can be a cable or wire 610 as shown in Figures 12 and 13. The outer sheath 202 is equivalent to the sheath or mantle in Figures 10 and 1 1 , while the inner part is further simplified. The principle is however equal / the same. The outer sheath 202 proves desired or required hardness, rough- ness and other desired properties of the outer surface 201 , while the inner portion 600, 610 transfers power through the piston rod. There can be applications where the piston is extended with an integrated rod or bar. In such cases, at least an axial portion of the piston 200, which corresponds to the stroke length of the cylinder, has a surface 201 with surface properties that ensure sealing innstallation through the front opening of the cylinder.

In both embodiments shown in Figures 10 to 13 a piston rod is made or produced with significantly less mass than a solid bar or rod of for example stainless or acid- proof steel. By adapting the material and the design of the inner element 600, 610 it is possible to make or produce a piston rod with the same or better (higher / greater) flectional strength as a stainless steel rod, but with significantly lower mass and price. Lower mass means also that the piston rod is easier to handle, which is advantageous in many applications.

Claims

1. Hydraulic cylinder (100) comprising a housing (110) with a cylindrical inner surface (111), an end piece (340, 341) with a cylindrical outer surface placed in contact with the housing inner surface (111 ) at each end of the housing (110), characterized in that

the end piece (340, 341) comprises an annular groove (350, 351) along its entire circumference, and that the housing wall is sealingly deformed down into the annular groove (350, 351).

2. Hydraulic cylinder according to claim 1 , where a clamping ring (400, 401 ) is arranged around the wall of the housing and radially outside the annular groove (350, 351).

3. Hydraulic cylinder according to claim 1 or 2, where an end sleeve (300, 301) is arranged radially outside of the clamping ring (400, 401).

4. Press chuck or jaw (500), characterized by a group of ring segments (510, 510') adapted for installation or abutting around a hydraulic cylinder (100) in the circumferential direction and for applying sufficient force onto the cylinder wall in order to get the wall deformed down into the annular groove (350, 351) in the material lying under.

5. Press chuck according to claim 4, further adapted for attachment (520) in a pressing tool for hydraulic hoses.

6. Press chuck according to claim 4 or 5, where each ring segment (510, 510') has an abutting shoulder (511 ) and a press element (400, 401 , 513) in an axial distance from each other corresponding to the distance between an axial surface of the hydraulic cylinder (100) and the annular groove (350, 351) in the underlying material.

7. Press chuck according to claim 6, where the press element is a clamping ring (400, 401) arranged in an inner ring groove (512) in the ring segments (510, 510').

8. Method for manufacturing a hydraulic cylinder (100),

c h a r a c t e r i z e d by the following steps:

- inserting an end piece (340, 341 ) in a cylindrical end of a cylinder housing (1 10), where the end piece (340, 341 ) comprises a concave annular groove (350, 351 ) along the entire circumference of an outer cylinder surface,

- placing a press chuck or jaw (500) around the housing, where the press chuck (500) comprises a group of ring segments (510, 510') and the press chuck (500) defines a press element (400, 401 , 513) running radially inwards around an inner circumference of the press chuck,

- installing or abutting a radial directional shoulder (51 1 ) on the press chuck towards an axial surface of the cylinder housing, where the press element (400, 401 , 513) is arranged radially outside the concave annular groove (350, 351 ) of the end piece;

- installing the press chuck (500) in a pressing tool adapted for generating force directed radially inwards, and

- activating the pressing tool until the cylinder housing wall is deformed into the concave annular groove (350, 351 ).

9. Method according to claim 8, further comprising:

- removing the press chuck, and

- threading an end sleeve (300, 301 ) onto the cylinder housing end.

10. Hydraulic piston (200), c h a r a c t e r i z e d by an elongated inner portion (600, 610) inserted in an outer sheath (202) with an outer cylindrical surface (201 ), where the inner portion (600, 610) is adapted for transferring power in an axial direction of the piston, and at least a portion of the outer cylindrical surface (201 ) is adapted for pressure-sealed, axially glidable arrangement in a hydraulic cylinder housing.

1 1 . Hydraulic piston according to claim 10, where the inner portion (600) has a different radius along the circumference of a cylindrical outer sheath (202).

12. Hydraulic piston according to claim 10, where the inner portion (610) is a cable.