JP2011224690A - Machining method for removing screw and machining apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining apparatus for removing a screw for promptly and reliably removing the screw even in water remotely, by reducing a swarf amount with a minimum work, while biting has occurred at a screwing part between a male screw and a female screw and thereby causing the screws to fix.SOLUTION: The machining apparatus for removing the screw is provided for removing the male screw 1 on which a head 1a and a thread part 1b are integrally formed, the thread part 1b being fixed to a member to be fasten. The apparatus includes: a vertical slit-forming means 10 for forming a vertical slit along an axis direction of the head 1a and the thread part 1b, remaining part of the head 1a; and a horizontal slit-forming means for forming a horizontal slit on a neck bottom of the head 1a and the thread part 1b vicinity of the neck bottom in the vertical slit, by turning around the axis from inside.

Description

  The present invention relates to a screw removal processing method and a removal processing device for making it possible to easily remove a male screw even in a state where the male screw and the female screw are twisted and fixed.

  Conventionally, as a method of removing the male screw and the female screw, which are fixed due to warpage, with minimal additional processing, there is a method of removing the male screw side so as not to damage the female screw as much as possible.

  Usually, a method is employed in which the male screw is removed by drilling to a diameter slightly smaller than the diameter of the female screw. Specifically, as shown in FIG. 15, the spiral of the male screw 1 is removed by performing a cutting process with a drill 2 as a cutting means in the axial direction of the male screw 1 and remaining on a female screw (not shown). It is common to carefully remove the shape (coiled) attached metal by hand. After the attached metal is removed from the female screw, the female screw is reshaped by a tap or the like so that a new male screw can be attached again. Thereby, it is possible to restore the threaded portion so as to maintain the original function while minimizing damage to the thread of the female screw. In FIG. 15, a portion of the male screw 1 cut by the drill 2 is indicated by broken line hatching.

  However, when it is difficult for the operator to access the vicinity of the work area and the work needs to be performed remotely or when it is necessary to perform in the water, work efficiency is good by applying electric discharge machining. . However, in that case, since the work area is in an underwater remote environment, it is technically difficult to perform construction with high accuracy and a slightly smaller diameter than the female thread diameter. Moreover, since the volume of the part removed by processing is large, a long processing time is required.

  When it is necessary to perform the removal work in such an environment, as shown in FIG. 16, the male screw 1 is slit in the axial direction by the electrode 3 for electric discharge machining to reduce the rigidity of the male screw 1. Then, there is a method of removing the male screw 1 by turning it. In FIG. 16, the slit processed portion by the electrode 3 in the male screw 1 is indicated by broken line hatching.

  A physical mechanism for removing the male screw 1 will be described with reference to FIG.

First, the screw can be turned in the direction of loosening, as shown in FIG. 17, due to the torque T that turns the screw in the loosening direction, the parallel component P cosθ on the thread slope of the tangential force P is caused by friction due to the axial force Ff of the screw. This is because it becomes larger than the force μFf cos θ + μP sin θ. Here, μ is a coefficient of static friction of the thread surface, Ff is an axial force applied to the thread slope, and θ is a lead angle indicating the inclination of the thread surface. That is,
Pcosθ ≧ μFfcosθ + μPsinθ
On the other hand, in the case where the screw is fixed, a frictional force (fixing force) f due to screw thread fixation is applied in addition to the frictional force due to the axial force Ff applied to the thread slope as shown in FIG. Since the tangential component force of the torque applied for this purpose cannot be applied beyond this, it cannot be loosened with respect to the female screw. That is,
Pcos θ ≦ μFf cos θ + μP sin θ + f (fixed friction force)
At that time, if the male screw is slit as described above, the male screw itself is easily deformed inward, so that the tangential fixing force f of the thread slope can be reduced. As a result, the screw surface frictional force and the sticking force due to the axial force of the screw can be reduced, so that the male screw 1 can be turned and loosened.

  By the way, as described above, even when the slot is formed on the male screw, for example, when all the screw portions (shaft portions) of the lower neck portion which is the lowermost portion of the head portion of the male screw are fixedly engaged with the female screw. Since the head of the male screw is still integrated even if the male screw is slit, the effect of facilitating the deformation of the male screw in the vicinity of the fixing portion is reduced. In particular, in the case of a large-sized screw such as the metric coarse screw M45, this problem appears remarkably, and even if the male thread is subjected to slit processing, it cannot be removed by this method alone.

  On the other hand, in the technique described in Patent Document 1, an outer end is formed on the head in a bolt configured by a shaft portion having a male screw portion formed on the outer periphery and a head portion connected to the base end of the shaft portion. There is a blind hole that is open and has an inner end that reaches the shaft portion and extends in the bolt axis direction, and a screw member that extends and deforms a portion of the shaft portion by pressing the inner end of the blind hole on the head. A threadable screw part is formed.

JP-A-6-159341

  By the way, especially when it is necessary to unscrew the screw remotely underwater, as described above, the large screw is screwed into the female screw up to the bottom of the neck, and the portion near the lower neck is the female screw. In the case of the fixed state, it is effective to make a through hole in the axial direction of the male screw by electric discharge machining to remove this, but to remove it, not slit machining, but in that case it is removed There is a problem that the amount of processing increases, the processing time and the amount of processing powder (hereinafter referred to as swarf) increase, and high-precision processing is required.

  For example, when a male screw having a nominal length of 105 mm and a thread length of 60 mm, which is a metric coarse screw M45, is fixed to the female screw, it is necessary to process a through hole with a diameter of about 30 mm on the male screw. In a simple electric discharge machining apparatus having a current capacity of about 20 A, the machining time takes about 20 hours. If it occurs during a periodic inspection related to nuclear power generation facilities and it becomes a critical path work in the entire periodic inspection process, it requires a lot of plant downtime and a lot of manpower.

  On the other hand, in the technique described in Patent Document 1, since the outer end is opened in the head and the inner end reaches the shaft portion and a blind hole extending in the bolt axis direction is formed, the axial force is increased in strength. When it is installed in water, crevice corrosion tends to occur. Further, in order to remotely screw the screw member into the blind hole, there is a problem that it takes a long working time because the positioning is extremely difficult.

  The present invention has been made to solve the above-described problems. In the state where the threaded portion of the male screw and the female screw is twisted and fixed, the amount of swarf is reduced by the minimum necessary processing. It is an object of the present invention to provide a processing method for removing a screw and a processing device for removing the same that can be quickly and surely removed even underwater.

  In order to achieve the above object, a screw removal processing method according to the present invention is a screw for removing a male screw in which a head part and a screw part are integrally formed and the screw part is fixed to a member to be tightened. The removal processing method, wherein the vertical slit forming step of forming a vertical slit along the axial direction of the head and the screw part leaving a part of the head, and after the vertical slit forming step, A transverse slit forming step for forming a transverse slit around the axis from the inside at a threaded portion near the neck of the head and in the vicinity thereof.

  The screw removal processing device according to the present invention is a screw removal processing device in which a head and a screw portion are integrally formed, and the screw portion removes a male screw fixed to a member to be tightened. A vertical slit forming means for forming a vertical slit along the axial direction of the head and the threaded portion while leaving a part of the head; and a threaded portion of the longitudinal slit at the lower part of the neck of the head and in the vicinity thereof And a horizontal slit forming means for forming a horizontal slit by turning around the axis from the inside.

  According to the present invention, when the threaded portion between the male screw and the female screw is twisted and fixed, the amount of swarf can be reduced, and processing for quick and reliable removal even underwater can be minimized. .

It is an expansion perspective view which shows the external thread which formed the vertical slit in the processing method for screw removal which concerns on this invention. It is a longitudinal cross-sectional view which shows the part which forms a vertical slit in the external thread of FIG. It is a top view which shows the part which forms a vertical slit in the external thread of FIG. It is an expansion perspective view which shows the external thread which formed the vertical slit and the horizontal slit in FIG. It is a cross-sectional view of the lower neck part in FIG. It is a longitudinal cross-sectional view of FIG. It is an elevation view which shows the electric discharge machine which forms a vertical slit in the external thread of FIG. It is a perspective view which shows the electrode which forms a vertical slit in the external thread of FIG. It is an elevation view which shows the state which attached the positioning mechanism to the electric discharge machine of FIG. It is an elevation view which shows the electric discharge machine which forms a horizontal slit in the external thread of FIG. It is a perspective view which shows the electrode which forms a horizontal slit in the external thread of FIG. It is a perspective view which shows the external thread used for the fastening of the fuel rack in the furnace installation in Example 1. FIG. 6 is a perspective view showing an electrode used in Example 2. FIG. 6 is a perspective view showing an electrode used in Example 3. FIG. It is a partial expansion perspective view which shows the processing method for the removal of the conventional screw which carries out a hole process to a male screw. It is a partial expansion perspective view which shows the processing method for the removal of the conventional screw which carries out slit processing to a male screw with a discharge electrode. It is a figure which shows the relationship between the axial force Ff and the tangential force P in a male screw.

  Embodiments and examples of a screw removal processing method and a removal processing apparatus according to the present invention will be described below with reference to the drawings.

(One embodiment)
FIG. 1 is an enlarged perspective view showing a male screw in which a vertical slit is formed in the processing method for removing a screw according to the present invention. FIG. 2 is a vertical cross-sectional view showing a portion where a vertical slit is formed in the male screw of FIG. FIG. 3 is a plan view showing a portion where a vertical slit is formed in the male screw of FIG.

  FIG. 4 is an enlarged perspective view showing a male screw formed with a vertical slit and a horizontal slit in FIG. FIG. 5 is a cross-sectional view of the lower part of the neck in FIG. 6 is a longitudinal sectional view of FIG. In addition, the same code | symbol is used and demonstrated for the component and part which are the same as or correspond to a prior art example.

  In this embodiment, after performing the vertical slit processing on the male screw, a very simple lateral slit processing is performed, and the male screw is removed by reducing the additional processing amount as much as possible by reducing the screwing force of the male screw remaining portion with respect to the female screw. To be able to. This will be specifically described below.

  As shown in FIGS. 1 to 3, a male screw 1 has a head 1a and a threaded portion 1b integrally formed, and a female thread (not shown) as a member to be tightened from the bottom of the neck to the tip of the threaded portion (shaft portion) 1b. )) And is fixed by being twisted. Here, the said neck lower part is the lowest part of the head 1a, and means the site | part in which the screw part 1b is formed continuously.

  As in the conventional example shown in FIG. 16, the male screw 1 first leaves a part of the head 1a, includes the thread of the threaded portion 1b, and is formed with a longitudinal slit (slot) 5 over the entire axial direction. The In this case, the screw thread is notched at the portion where the vertical slit 5 of the female screw is formed.

  Next, as shown in FIGS. 4 to 6, the male screw 1 is formed with a lateral slit 6 around the axis from the inside, leaving a part of the neck lower part of the head 1 a. The lateral slit 6 is not limited to the lower neck portion of the head 1a, but may be formed in the screw portion 1b in the vicinity thereof. In the following description, the neck lower part is a lowermost part of the head 1a and is a part where the threaded part 1b is continuously formed.

  Incidentally, the lateral slit 6 has a cantilever structure in which the screw portion 1b of the male screw 1 is connected to the head 1a only at the lower neck portion, and is formed at a site where the screwing force of the remaining portion of the male screw 1 with respect to the female screw is reduced. The Therefore, even if the lateral slit 6 is formed in the vicinity of the distal end portion of the screw portion 1b, the effect is small, so that it is formed in the lower neck portion of the head 1a and the screw portion 1b in the vicinity thereof.

  Thus, according to the male screw 1 of this embodiment, while leaving a part of the head 1a, including the thread of the screw part 1b, the longitudinal slit 5 is formed over the whole axial direction, and the neck of the head 1a. By forming the horizontal slit 6 around the axis from the inside while leaving a part of the lower part, since the cantilever structure is exhibited as described above, the screwing force of the remaining part of the male screw 1 with respect to the female screw is reduced, Even a highly rigid screw can be removed reliably and easily.

  Next, the structure of the processing method for screw removal according to the present embodiment will be described.

  First, a processing method for forming the vertical slit 5 in the male screw 1 will be described.

  FIG. 7 is an elevation view showing an electric discharge machine that forms a vertical slit in the male screw of FIG. FIG. 8 is a perspective view showing an electrode forming a vertical slit in the male screw of FIG. FIG. 9 is an elevational view showing a state where a positioning mechanism is attached to the electric discharge machine of FIG. 7, 9, and 10 are the same as those shown in FIGS. 1 to 6.

  As shown in FIG. 7, an electric discharge machine 10 as a vertical slit forming means includes a motor 12 installed on a base portion 11 and a ball screw connected to the output shaft of the motor 12 and rotated by driving the motor 12. A shaft 13, a ball screw nut 14 screwed into the ball screw shaft 13, a linear guide 15 for guiding the lifting and lowering operation of the ball screw nut 14, and a vertical slit forming electrode 16 attached to the ball screw nut 14. With. For example, as shown in FIG. 8, the electrode 16 is formed in a flat plate shape having a width of 45 mm, a length of 145 mm, and a thickness of 3 mm.

  In the electric discharge machine 10 configured as described above, when a power supply (not shown) is turned on, the motor 12 is driven. Then, the ball screw shaft 13 rotates, and the ball screw nut 14 descends along the linear guide 15 with the rotation.

  As a result, the electrode 16 approaches the male screw 1, leaving a part of the head 1 a on the male screw 1 as shown in FIGS. 1 to 3, including the thread of the screw part 1 b, and a width of 45 mm over the entire axial direction. Then, processing for forming the vertical slit 5 having a thickness of 3 mm is performed.

  Positioning at the time of this processing is performed using a positioning mechanism 17 shown in FIG. As shown in FIG. 9, the positioning mechanism 17 is attached to the lower part of the electric discharge machine 10 configured as described above. The positioning mechanism 17 has an insertion cap portion 18 that matches the shape of the outer peripheral portion of the head portion 1a of the male screw 1 to be removed by the electric discharge machine 10, and the insertion cap portion 18 is fitted into the head portion 1a. Thus, the electrode 16 is positioned with respect to the male screw 1.

  Then, when the electric discharge machining for forming the vertical slit 5 is completed, the ball screw shaft 13 is reversed as shown in FIG. 7, and the ball screw nut 14 is raised and returned to the original position.

  Next, a processing method for forming the lateral slit 6 in the male screw 1 will be described.

  FIG. 10 is an elevation view showing an electric discharge machine that forms a horizontal slit in the male screw of FIG. FIG. 11 is a perspective view showing an electrode forming a lateral slit in the male screw of FIG. In FIG. 10, the same portions as those in FIG.

  In FIG. 10, in the electric discharge machine 10 shown in FIG. 7, a new motor unit is attached to the mechanism for converting the motor turning drive to the vertical linear drive, and the horizontal slit can be turned by turning around the vertical axis. The electric discharge machine 20 is used as a forming means.

  Specifically, as shown in FIG. 10, a nut 21 that can be moved up and down according to the rotation of the ball screw shaft 13 is screwed onto the ball screw shaft 13 as a mechanism for converting the motor turning drive into the longitudinal linear drive. ing. A motor 22 is attached to the nut 21, and an attachment portion 24 is provided on the output shaft of the motor 22 via a speed reducer 23. A T-shaped electrode 25 is attached to the attachment portion 24. The motor 22 and the speed reducer 23 constitute the motor unit.

  As shown in FIG. 11, the T-shaped electrode 25 is provided with a rod-shaped support portion 25a having a diameter of 2 mm and a rod-shaped orthogonal portion 25b having a diameter of 1 mm and a length of 40 mm. And is formed from.

  In the electric discharge machine 20 configured as described above, the motor 12 is driven when a power supply (not shown) is turned on. Then, the ball screw shaft 13 rotates and the nut 21 descends along the linear gad 15. Then, when the T-shaped electrode 25 is inserted into the vertical slit 5 and the orthogonal part 25b reaches the lower neck of the head 1a, the motor 22 for rotation driving is driven to turn the orthogonal part 25b 180 degrees (half way). Rotate).

  That is, the orthogonal portion 25b of the electrode 25 is inserted to the lower neck portion in the male screw 1, and the orthogonal portion 25b of the electrode 25 is turned at the lower neck portion, so that the electric discharge machining is performed by half a turn around the axis. In this case, since the T-shaped electrode 25 is processed in a fan shape around the turning axis, the left and right tip portions (outer peripheral portions) of the orthogonal portion 25b are selectively worn out faster than a portion near the turning axis center. I will do it. As a result, the processed shape is not processed into a complete sectoral space, but becomes a sector as shown in FIG. 5 in which the radial direction is gradually shortened. In addition, the positioning in the case of this process is performed by the positioning mechanism 17 shown in FIG. 9 similarly to the processing method which forms the said vertical slit 5. FIG.

  As a result, the inside of the lower part of the neck of the male screw 1 is processed and removed into a fan-shaped space shape as shown in FIG. 5, and the remaining portion 6a is formed into a thin-walled cross-sectional substantially arcuate shape as shown by hatching. The contact pressure of the resulting thread surface can be significantly reduced.

  After the vertical slit 5 and the horizontal slit 6 are sequentially formed in the male screw 1 in this way, the male screw 1 is rotated and removed in a loosening direction using a dedicated screwdriver (not shown).

  Next, the operation and effect of the processing method for removing a screw according to the present embodiment will be described.

  If the lower part of the neck of the male screw 1 is screwed into the female screw, the position where the T-shaped electrode 25 is processed around the axis is a position near the inlet of the female screw. In the case of a large-diameter screw, the entrance portion of the female screw is generally subjected to a large C chamfering process. Therefore, the distal end portion of the orthogonal portion 25b of the electrode 25 that performs the above-described fan-shaped processing is the same as that of the male screw 1. Even if there is a length up to a diameter larger than the thread, the thread of the female thread is not processed.

  In this case, as shown in FIG. 5, the processed shape of the male screw 1 is that the initial processed portion is cut, but as the right and left end portions of the orthogonal portion 25 b of the electrode 25 wear down, the left and right end portions gradually inward. Since it becomes short, the connection part with the head 1a of the external thread 1, ie, the remaining part 6a, can be left. When the inside of the vicinity of the lower part of the neck of the male screw 1 is machined in this shape, when the male screw 1 is turned in the loosening direction after the machining is completed, the remaining portion 6a of the male screw 1 subjected to slit machining is inward with the axis as the center. It becomes easy to be twisted.

  Since this is added as an effect of releasing the fixation, the fixation of the male screw 1 can be released more reliably, and after the release from the fixation event, the fixed portion secondarily damages the other thread surface. It has a great effect on preventing it from occurring.

  Therefore, by processing the male screw 1 by the processing method for removing a screw according to the present embodiment and removing it, a method of releasing a fixing screw by additionally processing a large-sized through hole in the male screw 1 as in the prior art, or the male screw 1 Compared with the method of processing only the vertical slit 5, the male screw 1 is in a state where the fixing portion with the female screw is at any position of the screwed portion, and the lower part of the neck of the male screw 1 is screwed into the female screw. Even when the neck portion of the male screw 1 is bent and fixed, the remaining portion 6a of the lower portion of the male screw 1 is formed in a thin-walled cross-sectional shape as described above. Since the contact pressure on the thread surface is significantly reduced, the male screw 1 can be removed quickly and reliably.

As a reference, when a metric coarse screw M45 × L145 (including the head of a male screw) is assumed, the machining amount is 2.5 cm ³ , and the above-described male screw 1 is slit and then a through hole is formed (machining amount 100 cm ³ ), The processing time can be reduced by 97.5%.

  As described above, according to the present embodiment, when the male screw 1 and the female screw are screwed together, the thread portion is fixed and the additional processing of the screw portion for removing them is reduced as much as possible, the amount of swarf is reduced, It can be removed quickly and reliably even remotely.

  In particular, when repairing equipment related to nuclear power equipment that requires work underwater remotely, underwater electrical discharge machining is often performed to remove screws, but by applying this embodiment, machining time and machining are performed. In this case, the amount of swarf generated at the time can be minimized, and a work with high work efficiency can be performed.

  Further, according to the present embodiment, since the minimum processing of the male screw 1 is sufficient, sufficient rigidity and shape of the entire male screw necessary for turning and removing the male screw 1 after additional processing can be maintained. .

  On the other hand, when removing the lower part of the neck of the male screw 1 by another method, it is necessary to perform a continuous process from the upper part of the head 1a of the male screw 1, so that a hexagon wrench for removing after the processing is inserted. The shape of the hexagonal hole and the outer peripheral hexagonal portion of the head collapses, and additional processing of a new shape is required in order to insert a turning removal tool.

  Further, in the case of a method of machining the vertical slit a plurality of times by changing the circumferential position or a method of machining a cylindrical through hole, the shape rigidity of the head 1a of the male screw 1 is low. Even if the surface to which the wrench or spanner is applied remains, if a large torque is applied, the head 1a of the male screw 1 is damaged and cannot be removed. In this respect, according to the present embodiment, such a problem can be avoided in advance.

  Further, the T-shaped electrode 25 shown in FIG. 11 is in a state where it is difficult to eliminate the generated swarf as the machining electrode becomes deeper in the male screw 1. As a result, abnormal discharge of the electrode is likely to occur, and a machining stop event frequently occurs.

  However, in this embodiment, a very thin T-shaped electrode 25 is used. Specifically, as described above, the electrode 25 is formed of the support portion 25a having a diameter of 2 mm and the orthogonal portion 25b having a diameter of 1 mm and a length of 40 mm, so that the wear is quick. In this case, the electrode pinching event And the probability of occurrence of abnormal discharge events can be kept low. Therefore, it is possible to eliminate troublesome operations such as temporarily removing the electrode during the processing and replacing it with a new electrode.

  The T-shaped electrode 25 is designed in advance so that it is completely consumed when the horizontal slit is formed, so that the circumferential position of the orthogonal portion 25b of the electrode 25 matches the vertical slit 5 when the processing is completed. Therefore, it is possible to eliminate a highly difficult operation such as positioning and pulling out the electrode 25.

Example 1
A specific example 1 will be described below.

  The same parts as those in the above embodiment will be described using the same reference numerals. The same applies to other examples.

  In the first embodiment, as shown in FIG. 12, a slit portion 31 is processed into the male screw 30, and the electrode 25 shown in FIG. 11 can be set at the corresponding position in FIG. 6 by using the slit portion 31. , T-shaped. The electrode 25 is mainly composed of silver tungsten.

  Further, as in the above embodiment, the electric discharge machine 20 has a linear drive function for setting the T-shaped electrode 25 to the corresponding position in FIG. 6 as shown in FIG. 10 and the T-shaped electrode 25 in the vertical direction. A rotation driving function for rotating around the axis.

  Furthermore, since the T-shaped electrode 25 is designed to be completely consumed in one swiveling process (half rotation) as in the above-described embodiment, the T-shaped electrode 25 is divided into parts after the machining is completed. Positioning is performed in accordance with the circumferential position of 31, and the operation of pulling out the electrode 25 from the head 30 a of the male screw 30 is not required.

  Therefore, the rotational drive function around the longitudinal axis of this embodiment has a speed control function for electric discharge machining, but does not necessarily require a precise position control function.

  A method for removing the male screw 30 will be described below with reference to a specific example of removing the male screw 30.

  FIG. 12 is a perspective view showing a male screw 30 used for fastening a fuel rack that is an in-furnace facility of a BWR (boiling water nuclear reactor). As shown in FIG. 12, the male screw 30 is a metric coarse screw M45, and has a valley diameter of 40.1 mm and a total length including the head of 145 mm.

  First, by using the electric discharge machine 10 shown in FIG. 7 and the vertical slit (slit) electrode 16 shown in FIG. 8, the male screw 30 for fastening the fuel rack in water (not shown) is slit to a thickness of 3 mm. To do so, the electric discharge machine 10 is suspended and moved to the vicinity of the male screw 30 by remote control.

  Next, as shown in FIG. 9, the positioning mechanism 17 is attached to the lower portion of the electric discharge machine 10, and the insertion cap portion 18 is placed on the head 30 a of the male screw 30 to position the electric discharge machine 10 and the male screw 30. I do.

  After the positioning, as shown in FIG. 7, the electrode 16 is set to a position about 2 mm above the position of the head 30 a surface of the male screw 30 by the linear movement of the nut 14 by the motor 12 and the ball screw shaft 13.

  After this electrode 16 is set, electric discharge machining is started under the conditions of current 0 to 30 A and voltage 200 V ± 10% (50 Hz), and machining is performed up to a stroke of 145 mm at a machining speed of 0.2 g / min to 0.5 g / min. To do.

  The width of the slitting electrode 16 is 45 mm, the male screw 30 is completely slotted without cutting the head 30a of the male screw 30 into two left and right sides, and damage to a female screw (not shown) is minimized. Yes. Further, by setting the length of the electrode 16 to 145 mm, the slit portion 31 of 145 mm can be processed from the head 30 a of the male screw 30 to the tip of the screw portion.

  After completion of the machining of the slit portion 31, the electric discharge machine 10 is once lifted from the water, the slit machining electrode 16 and the ball screw nut 14 are removed from the electric discharge machine 10, and as shown in FIGS. 10 and 11. A ball screw nut 21 to which an electrode 25 for removing a male screw neck and a motor 22 and a speed reducer 23 are attached is attached to the electric machine 20.

  As for the positioning of the slit part 31 and the electric discharge machine 20 processed earlier, the positioning mechanism 17 is attached to the lower part of the electric discharge machine 20 in the same manner as the slitting process, and the insertion cap part 18 is attached to the male screw 30. This is done by covering the head 30a. After this positioning, the electrode 25 is set to the lower part of the neck of the male screw 30 through the slit portion 31 of the male screw 30 in the same manner as in FIG. 6 by the downward movement of the motor 12, the ball screw shaft 13 and the nut 21.

  After the electrode 25 is set on the lower part of the neck of the male screw 30, a current of 0 to 30 A and a voltage of 200 V ± 10% (50 Hz) are applied while the electrode 25 is rotated at 0.05 rpm by a motor 22 around the longitudinal axis. Then, electric discharge machining is performed, and removal of the lower part of the neck of the male screw 30 is performed at a machining speed of 0.2 g / min to 0.5 g / min.

  By using the T-shaped electrode 25 in this way, the left and right tip portions (outer peripheral portions) of the orthogonal portion 25b are selectively worn out faster than the portion close to the center of the turning axis, and the machining shape is As shown in FIG. 5, it becomes a sector shape whose radial direction becomes shorter.

  In addition, since the weight (1.9 g) of the orthogonal part 25b of the electrode 25 is smaller than the electrode weight (2.1 g) necessary for the entire processing when the electrode weight consumption cost is 13%, the orthogonal part 25b of the electrode 25 All wear out.

  After the electric discharge machining is completed, the electrode 25 is pulled out from the lower neck portion of the male screw 30 by a straight upward movement by the motor 12, the ball screw shaft 13 and the nut 21. At this time, since the orthogonal portion 25b of the electrode 25 is completely consumed by the previous processing, it is not necessary to align the orthogonal portion 25b of the electrode 25 with the slit portion 31 and can be easily pulled out. Become.

  Finally, after the electric discharge machine 20 is pulled up from the water, the male screw 30 is loosened and removed using a wrench as a screwdriver.

  As described above, according to the present embodiment, when the male screw 30 and the female screw are screwed together, the screw portion for removing them is reduced as much as possible, and the amount of swarf is reduced. It can be removed quickly and reliably even remotely.

(Example 2)
FIG. 13 is a perspective view showing electrodes used in the second embodiment.

  In the second embodiment, after machining the slit portion 31 of the male screw 30 described in the first embodiment, the neck lower portion of the male screw 30 that does not have a precise position control function with respect to the rotational drive function around the longitudinal axis in FIG. Instead of the motor 22 of the electric discharge machine 20, a servo motor and an encoder provided in the vicinity of the servo motor are attached to have a precise rotational position control function of the electrodes. These servo motors and encoders constitute rotational position control means.

  In this embodiment, since the electrode has a precise rotational position control function, an electrode 35 formed in a T shape as shown in FIG. 13 is used. As shown in FIG. 13, the electrode 35 is integrally formed with a support portion 35 a, base portions 35 b and 35 b provided in a direction orthogonal to the support portion 35 a, and these base portions 35 b and 35 b. The tip portions 35c and 35c are formed.

  Specifically, the diameter of the column portion 35a is 2 mm, the diameter of the root portions 35b and 35b is 2 mm, the length is 10 mm from the circumferential surface of the column portion 35a, and the diameter of the tip portions 35c and 35c is respectively Each extends 1 mm and 9 mm from the root portion 35b. Therefore, the space | interval of the front-end | tip part 35c and the front-end | tip part 35c is 40 mm. Therefore, the rigidity of the root portions 35b and 35b is made larger than the rigidity of the tip portions 35c and 35c.

  As described above, according to the present embodiment, since the electrode 35 has a precise rotational position control function and the positioning of the electrode 35 can be accurately performed, the shape of the root portions 35b and 35b is changed to the tip portion 35c. , 35c can be given rigidity, so that the possibility of breakage of the root portions 35b, 35b can be avoided in advance.

  In addition, since the base 35b and 35b remain after electric discharge machining because the electrode 35 has increased rigidity of the base 35b and 35b, the electrode 35 has a precise rotational position control function with respect to the rotational drive function around the vertical axis. The base portions 35b and 35b, which are T-shaped portions of 35, can be aligned with the circumferential position of the vertical slit 5, and the electrode 35 can be reliably and easily pulled out from the lower neck portion of the male screw 30.

(Example 3)
FIG. 14 is a perspective view showing electrodes used in the third embodiment.

  In the present embodiment, as shown in FIG. 14, a planar cross-shaped electrode 36 is used to form a cross-shaped slit on the male screw 30. The electrode 36 has a planar vertical width and horizontal width of 45 mm, a length of 145 mm, and a piece thickness of 3 mm.

  Thus, according to the present embodiment, by forming the cross-shaped slit using the flat cross-shaped electrode 36 on the male screw 30, the rigidity of the male screw 30 can be made smaller than that of the first embodiment. The male screw can be removed with a smaller torque after removing the lower part of the neck of the male screw 30.

  The present invention is not limited to the above-described embodiment and examples, and various modifications can be made. For example, in the third embodiment, the slit portion is formed by using the cross-shaped electrode 36. However, the present invention is not limited to this, and for example, the electrode 16 formed in the flat plate shape of the embodiment and the first embodiment is used with respect to the male screw. Then, the machining may be performed a plurality of times by changing the circumferential angle.

DESCRIPTION OF SYMBOLS 1 ... Male screw 1a ... Head 1b ... Screw part 5 ... Vertical slit 6 ... Horizontal slit 10 ... Electric discharge machine (longitudinal slit formation means)
DESCRIPTION OF SYMBOLS 11 ... Base part 12 ... Motor 16 ... Electrode 17 ... Positioning mechanism 18 ... Insertion cap part 20 ... Electric discharge machine (horizontal slit formation means)
25 ... Electrode 30 ... Male screw 31 ... Slot 35 ... Electrode 36 ... Electrode

Claims (9)

The head and the screw portion are integrally formed, and the screw portion is a processing method for removing the screw for removing the male screw fixed to the member to be tightened,
A longitudinal slit forming step for forming a longitudinal slit along the axial direction of the head and the screw part while leaving a part of the head;
After the vertical slit forming step, a horizontal slit forming step for forming a horizontal slit around the axis from the inside to the lower neck portion of the head and the screw portion in the vicinity thereof; and
A process for removing a screw, characterized by comprising: The transverse slit forming step is to form the transverse slit leaving a remaining portion having a cross-sectional arc shape;
The processing method for removing a screw according to claim 1. The vertical slit forming step is performed by electric discharge machining using a flat electrode,
The processing method for removing a screw according to claim 1. The vertical slit forming step is performed by electric discharge machining using an electrode having a support part and an orthogonal part provided in a direction orthogonal to the support part;
The processing method for removing a screw according to claim 1. A processing device for removing a screw in which a head and a screw portion are integrally formed, and the screw portion removes a male screw fixed to a member to be tightened,
A vertical slit forming means for forming a vertical slit along the axial direction of the head and the screw part, leaving a part of the head;
In the vertical slit, a horizontal slit forming means for forming a horizontal slit by turning around the axial line from the inside to the lower neck portion of the head and in the vicinity thereof,
A processing device for removing a screw, characterized by comprising: The transverse slit forming means is to form the transverse slit leaving a remaining portion having an arcuate cross section;
The processing device for removing a screw according to claim 5. The vertical slit forming means is an electric discharge machine that performs electric discharge machining with a flat electrode,
The processing device for removing a screw according to claim 5. The vertical slit forming means is an electric discharge machine that performs electric discharge machining with an electrode having a column part and an orthogonal part provided in a direction orthogonal to the column part,
The processing device for removing a screw according to claim 5. While providing rotational position control means for controlling the rotational position of the electrode,
The orthogonal part of the electrode has a larger diameter at the base part than both tip parts,
The processing device for removing a screw according to claim 8.

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