Drilling tool and method for modifying a blind hole

Abstract

The present invention relates to a drilling tool and method for modifying a blind hole in a blade root insert of a wind turbine. The invention further relates to an apparatus and method for cleaning a blind hole. The method for modifying a blind hole comprises: removing a blade screw located in the blind hole, inserting a drilling tool into the blind hole, fixing the drilling tool in a drill, recessing the blind hole by a predetermined depth, with a maximum diameter of the end section and of the hole bottom after recessing being smaller than or equal to a diameter of the end section prior to recessing and a transition from the end section to the hole bottom being round after recessing, removing the drilling tool and the drill, mounting the blade screw in the modified blind hole.

Claims

1. Method for modifying a blind hole having a thread section, an end section following such thread section, and a hole bottom following such end section in a blade root insert of a wind turbine with a rotor blade being in mounted position, comprising: removing a blade screw located in the blind hole, inserting a drilling tool into the blind hole, fixing the drilling tool in a drill, recessing the blind hole by a predetermined depth, with a maximum diameter of the end section and of the hole bottom after recessing being smaller than or equal to a diameter of the end section prior to recessing and a transition from the end section to the hole bottom being round after recessing, with a radius of at least 2 mm, removing the drilling tool and the drill, mounting the blade screw in the modified blind hole.

2. Method according to claim 1, characterized by: cleaning the blind hole after recessing, by introducing compressed air into the area of the end section and/or hole bottom of the blind hole and sucking off air in the area of one opening of the blind hole by means of a cleaning apparatus.

3. Method according to claim 1, characterized by: checking the end section and/or hole bottom of the blind hole for possible cracks in the blade root insert prior to recessing the blind hole, which checking is to be performed by means of an eddy current test.

4. Method according to claim 1, characterized by: checking the end section and/or hole bottom of the blind hole for asperities after recessing the blind hole, with such checking to be performed by means of videoscopy.

5. Method according to claim 1, characterized by: documenting the end section and/or hole bottom of the blind hole after recessing the blind hole, wherein the documenting comprises taking photographs of the blind hole.

6. Method according to claim 1, characterized by: adjusting the predetermined depth at the drilling tool prior to recessing of the blind hole by means of an adjuster, with such adjustment to take place before the drilling tool is fixed in the drill.

7. Method according to claim 1, wherein the radius is at least 4 mm.

8. Method according to claim 1, wherein mounting the blade screw in the modified blind hole includes taking into account a maximum torque.

9. Method according to claim 1, characterized in that a crack in the blade root insert detected during inspection of the end section and/or hole bottom is closed with a welding seam, with such welding of cracks in the blade root insert to take place before recessing the blind hole.

10. Method according to claim 9, characterized in that a cooling element is arranged between the prepared welding seam and a glass-fiber reinforced plastic (GRP) bond of the rotor blade, and that a temperature is captured and documented during welding.

11. Method for modifying a plurality of blind holes in the blade root insert of the wind turbine, with the rotor blade being in mounted position: comprising: removing one part of a plurality of the blade screws located in the corresponding blind holes in the blade root insert, including removing the blade screws from every other blind hole, with the blade screws and/or blind holes having been previously numbered, modifying the blind holes from which the blade screw was removed according to the method for modifying a blind hole according to claim 1.

12. Method according to claim 11, characterized in that two adjacent blade screws of a blade stop are removed in pairs.

Description

(1) As regards the further advantages, embodiment variants, and embodiment details of said further aspects of the invention and their further developments, reference is also made to the above description of the respective apparatus features. Preferred exemplary embodiments of the invention are described based on the enclosed figures.

(2) FIG. 1 shows an exemplary embodiment of a drilling tool according to the invention;

(3) FIG. 2 shows an enlarged detail of FIG. 1;

(4) FIG. 3 shows an exemplary embodiment of a cleaning apparatus according to the invention;

(5) FIG. 4 shows a blind hole in a blade root insert with a screwed in blade screw that is to be modified;

(6) FIG. 5 shows the end of a blind hole with a screwed in blade screw that is to be modified;

(7) FIG. 6 shows the blind hole according to FIG. 5 after modification;

(8) FIG. 7 shows part of a blade root insert with a plurality of screwed in blade screws; and

(9) FIG. 8: shows the three-dimensional view of the blade screws of the rotor blade stop that are encircled in FIG. 7.

(10) The drilling tool 100 for modifying a blind hole, which is shown in FIGS. 1 and 2, comprises a drill section 110 and a handling section 120. A drill bit 130 with two main cutting edges 140 and a dead center 150 is provided at drill section 110. Minor cutting edges 160 are moreover provided at drill section 110. An external thread 121 is provided at handling section 120, to which an adjuster 170 with an internal thread is screwed. The adjuster 170 is designed as an adjusting nut with a guide band and serves to adjust the drilling depth with drilling tool 100, meaning that the penetration of the drilling tool 100 into the blind hole can be set to a predetermined depth by adjusting the adjuster 170 accordingly so as to prevent the drilling tool 100 from drilling beyond said predetermined depth. Because of the thread connection between handling section 120 and adjuster 170, the predetermined depth can be easily adjusted by rotating the adjuster 170 about the handling section 120. In addition, the depth stop sleeve serves also as a radial guide.

(11) The maximum diameter of the drill section 110 is adjusted to the blind holes to be modified such that the maximum diameter of the drill section 110 is smaller than or equal to the diameter of the end section of the blind hole prior to its modification. This way it is ensured that the drilling tool 100 will not widen the blind hole radially.

(12) To eliminate unrounded edges when recessing the blind hole, which might result in cracking, the radially outer ends 141 of the two main cutting edges 140 are rounded with a radius of 4 millimeters in the example shown in FIGS. 1 and 2. This way, one can achieve the geometry shown in FIG. 6 with a rounded transition 1010 between end section 12 and hole bottom 13.

(13) The dead center 150 of the drilling tool 100 is furthermore rounded to produce the rounded tip 1020 shown in FIG. 6 at the hole bottom 13 of the modified blind hole also after recessing.

(14) The minor cutting edges 160 are dulled and they are ground smaller in diameter to prevent the existing thread from being damaged during drill immersion.

(15) FIG. 3 shows a cleaning apparatus 200 that can be used to remove cuttings X from blind hole 1 that accumulate after the modification of said blind hole 1. To this end, the cleaning apparatus 200 shows a pneumatic pipe 210 that can be connected to a pneumatic source (which is not depicted), whose diameter is smaller than the diameter of the blind hole 1 to be cleaned. The cleaning apparatus 200 further shows a suction pipe 220 that can be connected to a vacuum source (which is not depicted), whose diameter is larger than the diameter of the blind hole 1 to be cleaned. One section of the pneumatic pipe 210 runs within the suction pipe 220, with a first end 210a of the pneumatic pipe 210 projecting beyond a first end 220a of the suction pipe 220 in longitudinal direction of the pneumatic pipe. This way, the first end 210a of the pneumatic pipe 210 can be introduced far into the blind hole 1, with the first end 220a of the suction pipe 220 remaining at the open end of the blind hole 1. A compressed air pipe 211 connects to a second end 210b of the pneumatic pipe 210, which can be used to connect the pneumatic pipe 210 to a pneumatic source (which is not depicted). The compressed air pipe 211 and pneumatic pipe 210 can be used to introduce compressed air D to the closed end of the blind hole 1, and the compressed air can then be sucked off as suction air S via the suction pipe 220 that is arranged at the opening of blind hole 1. This allows for creating an air current from the closed end of the blind hole 1 to the open end which will pick up the cuttings X and remove them from the blind hole.

(16) FIG. 4 shows a blind hole 1 in a pitch insert 30, with the end section 12 and the hole bottom 13 being emphasized by a ring. A blade screw 20 is engaged with the blind hole 1. The number 40 marks the pitch. FIG. 4 shows the blind hole 1 prior to its modification. The square, not rounded edge between the end section and the hole bottom is already visible in FIG. 4.

(17) The blade root inserts are normally made of aluminum or comprise aluminum. What is particularly preferred is an aluminum-manganese alloy, such as AlMg5.

(18) The advantage of the drilling tool and method for modifying a blind hole becomes evident, in particular, when comparing FIGS. 5 and 6: FIG. 5 shows the blind hole 1 in its original, i.e. still unmodified state. The blind hole 1 comprises a thread section 11, an end section 12 following such thread section, and a hole bottom 13 following such end section which is tapered towards the closed end of the blind hole 1. The transition in form of a square edge 1010 from end section 12 to hole bottom 13 is clearly visible. The closed end of the hole bottom 13 shows a hole bottom tip 1020.

(19) FIG. 6 shows the blind hole 1, which is depicted in FIG. 5, after modification. When comparing FIGS. 5 and 6, it becomes evident, in particular, that the end section 12 which follows thread section 11 is longer after modification, as marked by reference numbers 12 in FIG. 6. One can also see that a rounded transition 1010 with a 4-mm radius was created at the transition between the prolonged end section 12 and the newly created hole bottom 13, which was produced by the drilling tool shown in FIGS. 1 and 2 without widening the blind hole 1 radially. The hole bottom tip 1020 is also rounded due to the rounded dead center 150 of the drilling tool 100 shown in FIGS. 1 and 2. This prevents the blade root insert 30 from becoming weaker in radial direction. At the same time, the risk of cracking is clearly reduced thanks to the rounded transitions 1010.

(20) FIGS. 7 and 8 show a plurality of blade screws 20 screwed into the blind holes of a pitch insert 30. To modify a plurality of blind holes one can remove one part of all pitch screws 20 of a pitch insert 30 to make the respective blind holes accessible for modification, however without having to dismount the rotor blade. To this end, it is particularly preferred to remove every other or third blade screw 20 from the respective blind hole, to modify said blind holes and to then return the blade screws in order to then remove the blade screws from the still unmodified blind holes in a next method cycle, to subsequently modify said blind holes as well, and to then finally return the blade screws 20. Preferably, the blade screws 21 of the rotor blade stops are removed together or in pairs.

(21) Preferably, the blade screws and the blind holes are numbered before the blade screws are removed (see FIG. 8).

REFERENCE NUMBERS

(22) 1 Blind hole

(23) 11 Thread section

(24) 12, 12 End section

(25) 13, 13 Hole bottom

(26) 20 Blade screw

(27) 21 Blade screws of the rotor blade stop

(28) 30 Blade root insert

(29) 40 Pitch

(30) 100 Drilling tool

(31) 110 Drill section

(32) 120 Handling section

(33) 121 External thread

(34) 130 Drill bit

(35) 140 Main cutting edge

(36) 141 Rounded outer end

(37) 150 Dead center

(38) 160 Minor cutting edge

(39) 170 Adjuster

(40) 200 Cleaning apparatus

(41) 210 Pneumatic pipe

(42) 210a First end of the pneumatic pipe

(43) 210b Second end of the pneumatic pipe

(44) 211 Compressed air pipe

(45) 220 Suction pipe

(46) 220a First end of the suction pipe

(47) 1010 Unrounded edge

(48) 1010, 1020 Rounding

(49) 1020 Unrounded tip

(50) D Compressed air

(51) X Cuttings