TECHNICAL FIELD

The present invention relates to neck adapter according to the preamble of claim 1. The invention further relates to a rock drill comprising a neck adapter and a method to corrosion protect a neck adapter.

BACKGROUND

When rock drilling, rock drill machines from which rotational power, feeding and impact energy are transferred to a drilling tool, usually under intermediate coupling of splice bars. Through a longitudinal hole in the splice bars a flush medium is supplied, for example water, to the area of the drilling tool. The flush medium has the task of partly cooling the tool and partly brings out the drill cuttings from the drilling hole. For transfer of rotation power, feeding and impact energy from the rock drilling machine to the splice bars and the drilling tool a so called a so called neck adapter is used. This neck adapter is mounted in the drilling machine and has a protruding part. The protruding part constitutes a connection end arranged to be connected with splice bars or the drilling tool. In the neck adapter a through hole is present for transfer of the flush medium from the rock drilling machine to the splice bars and the drilling tool.

The neck adapter is exposed to corrosive attacks, partly from the water used as flush medium, partly from the corrosive environments that a rock drill is located in during use and transport. The water that is available and is used as flush medium, for example when the rock drilling machine is used for mining, is often very corrosive. Corrosive attacks shorten the lifetime of a neck adapter. To corrosion protect neck adapters tests been performed with for example chroming and lacquer of neck adapters.

To coat the neck adapter with a chromium layer is partly costly but also vitiated with drawbacks since the neck adapter is exposed to hits on a specific hitting surface. From this hitting surface flakes of chromium come loose. These flakes may cause problems in the rock drilling machine. The same problem may occur with lacquered neck adapters. WO 2003/078788 A1 describes a method for corrosion protection of a neck adapter. According to the described method parts exposed to corrosion is coated by zinc phosphate, zinc manganese phosphate or manganese phosphate with a subsequent oiling or waxing. Phosphate of the neck adapter is done interior in the through hole and on a cylindrical exterior surface.

The cylindrical exterior surface on the neck adapter constitutes of a surface to which a seal in the rock drilling machine rests. It is shown that this seal is exposed to wear as a result of that the conversion layer that occurs during the phosphate process has a sharpening impact on the seal when the neck adapter rotates in the rock drilling machine. Especially the conversion layer will have a sharpening impact when corrosion starts to occur on the cylindrical surface. The conversion layer will then have a relatively rough surface. SUMMARY OF THE INVENTION

An object with the present invention is to provide a corrosion protected neck adapter that prevents at least parts of the drawbacks mentioned above.

This object is obtained according to an aspect of the invention with a neck adapter for a rock drilling machine, which neck adapter comprises an elongated body. The elongated body has an outer surface and an inner surface. The elongated body has further an end surface and a through hole extending through the elongated body between the first part of the outer surface and the end surface. The first part of the outer surface constitutes a cylindrical surface and the inner surface constitutes of a limitation surface formed by the elongated body in the through hole. At least a part of the outer surface and a part of the inner surface are provided with a corrosion protecting coating. The first part of the outer surface is provided with a first corrosion protecting coating and a second part of the outer surface and/or at least a part of the inner surface is provided with a second corrosion protecting coating. The first corrosion protecting coating constitutes a chromium layer and the second corrosion protecting coating constitutes a conversion layer. Since the first and the second corrosion protecting coating constitutes different material used on different parts of the neck adapter corrosion protecting coatings may be used with properties that is suitable for respective part of the neck adapter. For example may the first corrosion protecting coating have a smoother surface than the second corrosion protecting coating. The second corrosion protecting coating may be chosen after other criteria than surface roughness, for example the cost for coating. Thus a neck adapter that on an outer sealing surface is provided with a chromed surface, that is corrosion protected on other surfaces with a conversion layer that is relatively simple and cheap to manufacture. Accordingly, the object mentioned above is achieved.

Neck adapters are used in a rock drill to transfer rotational power, feeding and impact energy to splice bars and drilling tools. The inner surface on the neck adapter may form a through hole for through put of a flush medium. The neck adapter is suitable made of a steel material, for example hardened steel. The corrosion protecting coatings shall extend the lifetime of neck adapters when they are expose to corrosive attacks during operation, operation interruption and at transports. With coating is meant a coating on at least a part of the surface of the neck adapters that been applied on the surface in at least a process step at manufacturing of the neck adapter. For example lubricants applied for operation or mounting is to been seen as a coating in accordance with the present invention. The through hole may be used to through put of a flush medium, for example water, from the rock drilling machine to a drilling tool.

According to embodiments may the first corrosion protecting coating have a smoother surface than the second corrosion protecting coating. In this way may the first corrosion protecting coating be chosen with a surface roughness to enable a seal to rest against the first part of the outer surface without exposure to the same amount of wear as it was resting against a surface coated with the second corrosion protecting coating. The second corrosion protecting coating may be chosen by other criteria than surface roughness, for example the cost for coating.

According to embodiments may the conversion layer for example constitute a phosphate layer. According to embodiments may the conversion layer be oiled or waxed. A conversion layer as a phosphate layer is porous and its corrosion protecting properties may be improved with oiling or waxing. According to embodiments may the first coating have a surface roughness at maximum Ra 1 ,0 μιη. The first part of the outer surface constitutes thereby a suitable surface for contact surface of a seal in the rock drilling machine.

According to embodiments may the conversion layer comprise any or several of zinc phosphate, zinc manganese phosphate, or manganese phosphate.

According to embodiments may the first corrosion protecting coating have a thickness between 20 - 150 μητι. In this way may a good corrosion protection of the first part of the outer surface be obtained. In case of the first corrosion protecting coating constitutes a chromium layer may the first corrosion protecting coating have a weight per area unit within 140 - 2100 g/m ² .

According to embodiments may the second corrosion protecting coating have a thickness between 10 - 50 μΐτι, preferably about 30 μηη. In this way may a good corrosion protection of the second part of the outer surface and/or the inner surface be obtained. In case of the second corrosion protecting coating constitutes conversion layer comprising zinc phosphate, zinc manganese phosphate, or manganese phosphate may the second corrosion protecting coating have a weight per area unit within 15 - 85 g/m ² , preferably about 50 g/m ² .

With a surface coating thickness means coatings height on the neck adapter, i.e. on the material that the neck adapter is manufactured of, for example hardened steel. Coatings height is measured for example under microscope on a cross section through a neck adapter in the area of the current surface. The cross section runs perpendicular to the current surface. If the cross section through the neck adapter is done in parts this having for example a cylindrical form the cross sectional plane is in right angle to a center axis through the elongated body of the neck adapter. According to embodiments may only the first part of the outer surface be provided with the first corrosion protecting coating and the other surfaces of the neck adapter are provided with the second corrosion protecting coating. In this way may firstly the first corrosion protecting coating be applied on the neck adapter in a first process. In a second process may sedan simple the rest of the surfaces of the neck adapter be provided with the second corrosion protecting coating. When in the second process no account need to be taken to any surfaces not to be surface treated the second process is especially simple to perform. According to an aspect, the present invention also relates to a rock drill comprising a neck adapter according to any of the above mentioned aspect and/or the above mentioned embodiments.

According to embodiments the neck adapter is rotatably arranged in the rock drilling machine. The first part of the outer surface may constitute a surface for in the rock drilling machine stationary arranged sealing.

According to embodiments may the rock drilling machine be arranged to pump a liquid via a space limited by among other the sealing and the first part of the outer surface, to the through hole in the neck adapter.

According to an aspect, the present invention also relates to a method for corrosion protecting a neck adapter according to any of the above mentioned aspect and/or the above mentioned embodiments. According to the method undergoes the neck adapter firstly an electrolytic process to provide the first part of the outer surface with the first corrosion protecting coating. Thereafter undergoes the neck adapter a second process to provide the second part of the outer surface and/or the said part of the inner surface with the second corrosion protecting coating. The first process may comprise immersing of the neck adapter in a solution comprising chromium ions to coat the first part of the outer surface with a chromium layer.

According to embodiments may the second process include imposing of a solution comprising phosphor acid, and zinc ions or zinc- and manganese ions, or manganese ions on the whole neck adapter. In this way may firstly the first corrosion protecting coating be applied on the neck adapter in the first process. When the first corrosion protecting coating consists of for example of a chromium layer may in the second process simple the rest of the surfaces of the neck adapter be provided with the second corrosion protecting coating as the solution imposed in the second process do not affect the chromium layer.

Further features and advantages of the present invention emerge from the attached claims and the following detailed description. The skilled man within the area realizes that different features of the invention may be combined to create second embodiments other than the described below. This may be done without deviating from the scope of protection of the present invention defined by the attached claims.

SHORT DESCRIPTION OF FIGURES

Different approaches to the invention, including specific features and advantages, is shown from the following detailed description and the accompanying figures, in which: Fig. 1 and 2 show different views of a neck adapter according to embodiments,

Fig. 3 shows schematically a rock drill with a neck adapter according to embodiments, and

Fig. 4 shows a method for surface treatment of a neck adapter according to

embodiments.

DETAILED DESCRIPTION

The present invention will now be described more in detail with reference to the attached figures, in which examples of embodiments is shown. The invention shall not be interpreted to be limited to the examples described of embodiments. Like references in the figures refer to like elements. To simplify, well known functions and constructions will not necessarily be described in detail.

Fig. 1 and 2 show different views of a neck adapter 2 according to embodiments. The neck adapter 2 is designed to be arranged in a rock drill to transfer rotational power, feeding and impact energy from the rock drilling machine to a drilling tool via splice bars. The neck adapter 2 comprises an elongated body 4. The elongated body 4 is

substantially cylindrical and made of for example hardened steel. A center axis X extends through the lengthwise direction of elongated body 4. In one end is the neck adapter 2 provided with a driving part. The driving part comprises exterior splines 6 to enable the neck adapter 2 to be rotated in the rock drilling machine. Further, the driving part comprises a hitting surface 8 to receive and transfer momentum from the drilling machine to the drilling tool. In the second end is the neck adapter 2 provided with a fastening arrangement 10 arranged to fasten a drilling tool or a spice bar. The fastening arrangement 10 is exemplified in the form of a thread.

A through hole 12 extend through the neck adapter 2. The through hole 12 have an inlet opening inlet opening 14 arranged in a part of a cylindrical outer surface 17 at the neck adapter 2. At least a part of the cylindrical surface 17 constitutes a first part of an outer surface of the elongated body 4 and thereby the neck adapter 2. The through hole 12 have an outlet opening 16 in an end surface 18 at the neck adapter 2. The through hole 12 is arranged to lead a flush medium, for example water, from the drilling machine to the splice bars and the drilling tool. The through hole 12 is in this embodiment formed in two parts with a radial hole 13, also named flush hole, and an axial hole 15.

I Fig. 2 it is shown in addition to the neck adapter 2 also a chamber also a chamber 20 that encloses a part of the neck adapter 2. The chamber 20 is arranged about the neck adapter 2 in the area of the cylindrical surface 17. The chamber 20 is provided with an inlet tube 22. Thus may a flush medium be lead via the inlet tube 22 to the chamber 20 and from there through the neck adapter 2 via the inlet opening 14, the through hole 12 and the outlet opening 16. The chamber 20 is included in a not further shown rock drill and constitutes a space limited by among other two sealings 24, 24' and the cylindrical surface 17 at the neck adapter 2. The two sealings 24, 24' rest sealing against the neck adapter 2 and seal to the cylindrical surface 17.

Fig. 3 shows schematically a rock drilling machine 30 with a neck adapter 2 according to embodiments. The rock drilling machine 30 comprises a drilling machine 32 from which the neck adapter 2 protrude a bit. A number of splice bars 34 and a drilling tool 36 is connected with the neck adapter 2 and is rotated by the drilling machine 32. To transport drill cuttings from a drilling hole 38 drilled a flush medium is added, for example water, to the drilling tool 36 via the neck adapter 2 and the splice bars 34. The drilling machine 32 comprises a flush head 40, to which a supply conduct 42 for the flush medium connects. When comparing Fig. 2 and 3 it is apparent that the flush hole 40 comprises the chamber 20 and that the supply conduct 42 is connected to the inlet tube 22. The rock drilling machine 30 comprises a schematically shown pump 44 connected to the supply conduct 42. During operation the neck adapter 2 is rotated in the drilling machine 32 while the sealings 24, 24' seal against the cylindrical surface 17 at the neck adapter 2 so that the flush medium may be pumped via the chamber 20 and the through hole 12 in the neck adapter 2 to the drilling tool 36. The neck adapter 2 is exposed to corrosive environment i.e. during operation, at operation interruption and at transports. Especially exposed areas at the neck adapter 2 are areas in contact with the flush medium, for example on the cylindrical surface 17 in the chamber 20 and in the through hole 12. To protect the cylindrical surface 17 against corrosion is the neck adapter 2 at least in the area of the chamber 20 and the sealings 24, 24' provided with a first corrosion protecting coating in the form of a chromium layer with a thickness of about 40 μιτι. The chromium layer may also have another thickness, for example within 20 - 150 μιη. To ensure that the sealings 24, 24' have sufficient sealing function also after long operational time the chroming layer have a fine surface roughness. Except the good corrosion protection of the chromium layer, the roughness of the surface have the advantage of distribute an interval between change of the sealings 24, 24' may be kept relatively long. For example may the chromium layer have a surface roughness at highest Ra 1 ,0 μηι. In the through hole 12 and on the end surface 18 is the neck adapter 2 provided with a second corrosion protecting coating in the form of a conversion layer. Conversion layers comprise for example some or several of zinc phosphate, zinc manganese phosphate, or manganese phosphate. Such a conversion layer is porous and is suitable oiled or waxed to obtain best possible corrosion protecting properties. The conversion layer have a thickness between 10 - 50 μΐτι, preferably about 30 μητι. These thicknesses of a porous conversion layer comprising zinc phosphate, zinc manganese phosphate, or manganese phosphate corresponds to a weight per area unit, before oiling or waxing, within 15 - 85 g/m ² , preferably about 50 g/m ² .

Alternatively may the through hole 12 be partly provided with the first corrosion protecting coating in the form of a chromium layer. For example may the neck adapter 2 as a whole or in parts of the radial hole 13 be provided with a chromium layer and the resting parts of the neck adapter 2 in the through hole 12, i.e. the axial hole 15 and any resting parts of the radial hole 13, be provided with a conversion layer. According to an embodiment of the neck adapter 2 is the cylindrical surface 17 provided with a first corrosion protecting coating and the rest of the surfaces of the neck adapter 2 are provide with a second corrosion protecting coating comprising zinc phosphate, zinc manganese phosphate, and/or manganese phosphate. The other surfaces comprises i.e. outer surfaces as hitting surface 8, surface at the fastening arrangement 10, surface at the splines 16, the end surface 18 and an inner surface of the elongated body 4 in the through hole 2. The second corrosion protecting coating may easy be obtained by immersing of the neck adapter 2 in a solution comprising phosphor acid, and zinc ions or zinc- and manganese ions or manganese ions. Fig. 4 shows a method for surface treatment of a neck adapter 2 according to embodiments. The used references refer partly to details in the previous figures, especially Fig. 1 and 2. Between some of the method steps below may a second step be implemented as for example cleaning from process liquids from a previous method step.

In step 50, that is optional and depend on which surface roughness the neck adapter have after previous manufacturing step, sharpening of the cylindrical surface 17 to a surface roughness about 1 μηη is done.

In step 52 outer surfaces of the neck adapter 2 except the cylindrical surface 17 is done.

- In step 54 a first process in the form of an electrolytic coating of the cylindrical surface 17 with a first corrosion protecting coating for example a chromium layer through electrolysis in a liquid comprising chromium ions is done.

In step 56 coating of the other surfaces of the neck adapter 2 with a second corrosion protecting coating in the form of a conversion layer in a second process comprising immersing of the neck adapter 2 in a solution comprising phosphor acid, and zinc ions or zinc- and manganese ions or manganese ions.

In step 58 the conversion layered is oiled or waxed.

- A step 60 may optionally be performed and comprises polishing of the cylindrical surface with the first corrosion protecting coating. Step 60 may alternatively be performed optionally after step 54. In case of the first corrosion protecting coating is a chromium layer need before step 56 this chromium layer not be done. The skilled person within the area realizes that the embodiments described above may be combined. Even different modifications are apparent to the skilled person. For example may the surface of the elongated body be coated with the first corrosion protecting coating on other parts than the first part, i.e. may a second part of the outer surface be coated with the first corrosion protecting coating. The second part of the outer surface may then for example constitute of a surface for another seal or a seating.

Further may several parts of the inner surface be coated with the second corrosion protecting coating. When it comes to the cylindrical surface 17 may another surface roughness before and/or after coating with the first corrosion protecting coating be enough in certain cases, for example a surface roughness of maximum Ra 2,0 μΐη or of maximum Ra 3,0 μΐη. Further may flush hole 40 be more integrated in the drilling machine 32 than according to the in Fig. 3 showed embodiments. Flush hole 40 may be incorporated at sealings and driving force transferring parts in the drilling machine 32. Further may pump 44 showed in Fig. 3 alternatively be separately arranged and need thus not be part of the rock drilling machine 30. Further may solutions comprise phosphor acid, and zinc ions or zinc- and manganese ions or manganese ions for example be applied to the neck adapter through spraying instead of immersing in the solution. Further may is done not mentioned in step 52 of the method shown in Fig. 4 be obtained in several different ways. For example may two tubes be treaded over the neck adapter so the parts that not is to be coated with the first corrosion protecting coating is covered by these tubes.

Thus is the invention not limited to the embodiments described. The invention is limited only by the in the claims defined scope of protection.