JP4525873B2 - Protective cap for machine tools - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention A machine tool that rotates a spindle with a tool attached to the tip and processes the workpiece with this rotating tool. When the tool holder is not mounted in the storage recess of the support pot for storing the tool holder, the storage recess of the support pot is closed so that cutting waste does not enter. Protective cap for Concerning structure.
[0002]
[Prior art]
In recent machine tools such as machining centers, as disclosed in Japanese Patent Application Laid-Open No. 10-277867, a tool storage magazine containing a large number of tool holders equipped with tools such as drills is arranged at the tip, and automatic tool change is performed. The tool holder can be exchanged between the tip end portion of the spindle of the machine tool and the tool storage magazine by a gripping device such as a pair of gripping finger bodies in the device.
[0003]
The two-surface constrained tool holder 50 used in this type of apparatus is detachable from a tapered hole opened at the tip of the main shaft, as shown in the publication, FIG. 11 (a) and FIG. 11 (b). A taper shank portion 51 is provided, and the large-diameter flange portion 52 on the proximal end side of the taper shank portion 51 has an annular concave groove portion 53 for gripping by the gripping finger body of the gripping device. The tool 54 is provided so as to protrude from the lower end of the portion 52. At the tip of the taper shank 51, a stud 55 for supporting the tool holder 50 so as not to drop off in the chuck part in a support pot as a tool storage part in the tool storage magazine or in a taper hole of the main shaft. It is protruding.
[0004]
By the way, generally, the tool holder is not set in all of the plurality of support pots in the tool storage magazine, but only the necessary type (number) of tool holders are set, and the remaining support pots do not set the tool holder. The cutting work is executed in the state. In this case, the support pot with no tool holder set Holder storage recess If the opening is left as it is for a long time, cutting waste or the like adheres to or accumulates in the support pot. Therefore, if the tool holder is to be set later, the recess of the support pot or the taper shank portion of the tool holder 50 Problems occur such as the 51 being scratched or being unable to be set properly.
[0005]
In order to eliminate this inconvenience, conventionally, as disclosed in, for example, Japanese Utility Model Publication No. 62-18354, etc., the opening of the recess of the support pot (the portion where the tapered shank portion of the tool holder fits) is provided. There has been proposed a protective cap comprising a substantially disc-shaped cap base made of a synthetic resin material or the like and a rod-like support projecting therefrom.
[0006]
In this case, when the automatic tool changer is operating normally, the tool holder removed from the tip of the main spindle is programmed not to be collected (not set) at the place of the support pot to which the protective cap is attached. .
[0007]
[Problems to be solved by the invention]
However, in the above configuration, when a tool change operation is executed due to a program error or the like of the automatic tool changer, the protective cap cannot be removed by one gripping device, while the tool holder removed from the spindle by the other gripping device is In order to operate so as to be loaded into the support pot equipped with the protective cap, the protective cap will be pushed into the support pot with the tool holder, the tool holder, the protective cap and the support pot will be damaged, There is a problem that various inconveniences such as distortion of a gripping finger body which is a gripping device occur.
[0008]
The present invention has been made to solve the above-mentioned conventional problems, and it is possible to set a protective cap in a support pot to prevent cutting waste from entering, but due to a program error or the like. It is an object of the present invention to provide a protective cap whose shape is devised so that the protective cap is removed in advance when the tool is changed.
[0009]
In order to achieve the object, the invention according to claim 1 is provided. Protective cap for machine tools Is The gripping part provided in the tool changer of the machine tool grips the annular groove formed in the flange part of the tool holder and reciprocates in the axial direction of the main axis of the machine tool, so that the tool magazine of the machine tool faces downward. A protective cap that is detachable from the storage recess instead of the tool stored in the opened storage recess, The protective cap includes a plug portion that fits into the storage recess, and the plug portion that is positioned outside the storage recess. Located below And a diameter of the plug body portion is set to be smaller than a diameter of a minimum diameter portion of the annular groove, and a diameter of the housing is set to be substantially equal to a diameter of the flange portion of the tool. When gripping when changing tools The gripping part comes into contact with the upper surface of the housing and pushes down the housing as the gripping part moves downward. It is comprised as follows.
[0010]
The invention described in claim 2 is described in claim 1. Used for machine tools Protective cap Because The plug body and the housing are integrally formed of a soft material.
[0011]
Further, the invention described in claim 3 is described in claim 1. Used for machine tools Protective cap Because The casing is connected to the plug body portion via a connecting body, and the at least casing is formed of a soft material.
[0012]
Furthermore, the invention described in claim 4 is described in any one of claims 1 to 3. Used for machine tools Protective cap Because The plug body is held and held in the storage recess. Pull stud It has a part.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment embodying the present invention will be described. 1 is a perspective view of a machine tool (machining center) with an automatic tool changer, FIG. 2 is a partially cutaway longitudinal sectional view, FIG. 3 is a plan view of a gripping device, FIG. 4 is a side view, and FIG. It is a side view of 1st Embodiment.
[0014]
As shown in FIGS. 1 and 2, in the machining center, a head stock 3 is supported by a column 2 that is fixed upright on a base 1. The headstock 3 is guided by a linear guide 4 and is moved in the vertical direction by a Z-axis feed motor 5 and a feed screw 6. A table 7 provided on the base 1 is movable in a horizontal plane direction, and a workpiece is placed and fixed on the upper surface of the table 7.
[0015]
A spindle motor 8, a spindle 9 and a rotary tool magazine 10 are mounted on the spindle stock 3. Since the spindle 9 and the tool magazine 10 have a known configuration, they will be briefly described (see FIG. 2 for an explanation of the spindle 9). The main shaft 9 has a tool mounting portion 11 on which a two-surface constraining type tool holder 50 (see FIGS. 11A and 11B) having a tool 54 mounted on the tip can be detachably held, and the tool. A tool release pin 13 is provided on the attachment portion 11 via a draw bar 12.
[0016]
The tool magazine 10 is provided with a plurality of support pots 30 that normally hold a tool holder 50 in a detachable manner and that are normally in a horizontal posture. Only the support pot 30 positioned at the lowest position rotates 90 degrees downward to take a vertical posture, and the tool can be exchanged by the gripping device 16 of the present embodiment. Selection (arrangement to the lowest position) of the tool holder 50 is performed by rotation of the magazine motor 14.
[0017]
The spindle stock 3 incorporates an automatic tool changer TC for exchanging the tool holder 50 between the tool magazine 10 and the spindle 9. The apparatus includes a tool change drive motor (hereinafter referred to as an ATC motor) 15, a swing arm type gripping device 16, and the like. The gripping device 16 according to the present embodiment includes a swing arm 16a that can be rotated horizontally around a vertical hollow main shaft 25, and a swing arm 16a that extends outward from the swing arm 16a at a symmetrical position with respect to the rotation center axis. The pair of gripping finger bodies 17a and 17b that can be opened and closed are assembled, and the tool holder 50 set on the spindle 9 and the tool magazine 10 is composed of two pairs of gripping finger bodies 17a and 17b. Exchange is performed using gripping and turning of the swing arm 16a.
[0018]
The details of the configuration of the gripping device 16 will be described later, and the outline of the mechanism that causes the movement of the gripping device 16 in the machining center will be described. As the premise, first, the configuration of the entire tool changer TC will be described with reference to FIG. A tool change drive shaft (hereinafter referred to as an ATC drive shaft) 18 of the tool changer TC is coupled to the ATC motor 15 and arranged in the vertical direction, and is rotatably supported on the upper and lower parts of the headstock 3 by bearings. Has been. The ATC drive shaft 18 is provided with four cams 21, 22, 23, and 24.
[0019]
On the other hand, on the side of the ATC drive shaft 18, a hollow main shaft 25 having a spline 25 a in the lower half and a flange at the lowermost end is arranged vertically. The hollow main shaft 25 penetrates the hole of the lower machine frame 26 of the headstock 3 in the vicinity of the lower end portion thereof, and is supported by the bush so as to be capable of rotating around the central axis and reciprocating up and down along the axis. Yes. A gripping device 16 is fixed to the lowest end of the hollow main shaft 25.
[0020]
The upper end of the hollow main shaft 25 passes through a through hole formed in the upper machine frame 28 of the main shaft base 3. Between this through hole and the hollow main shaft 25, a support member 29 and a bush can rotate. It is intervened. The support member 29 is a substantially cylindrical member. The upper part of the hollow main shaft 25 having a diameter smaller than the hole diameter is inserted into the lower part of the center hole of the support member 29. The upper part of the hollow hole of the support member 29 has a slightly smaller hole diameter than the lower part thereof, and the upper end of the arm middle shaft 31 passing through the hollow main shaft 25 is fitted and fixed using a key and a bolt 33. Yes. A gear 29 a is carved on the outer periphery of the lower end of the support member 29, and the gear 29 a meshes with the side segment gear 34. An oscillator 35 is fixed to the segment gear 34, and this follows the cam 24.
[0021]
Since the hollow main shaft 25 sandwiched between the inner peripheral surface of the support member 29 and the outer peripheral surface of the arm middle shaft 31 is not fixed to the both 29 and 31, it can rotate independently about the axis. A cylindrical member 36 having a circumferential groove is fixed near the center of the hollow main shaft 25 in the vertical direction, and the hollow main shaft 25 is moved vertically by moving the cylindrical member 36 up and down by a swing lever 40 described later. It is reciprocated. Further, the hollow main shaft 25 rotates with the rotation of the spline countershaft 37 surrounding the spline 25a below the hollow main shaft 25. The spline countershaft 37 has a follower roller 38 as a follower of the cam 21 on the upper and lower surfaces of the flange portion formed on the outer periphery thereof.
[0022]
Next, the movement of the gripping device 16 will be described in relation to the configuration of the four cams 21 to 24 provided on the ATC shaft 18. The gripping device 16 turns in the horizontal direction. This is for exchanging the tool holder 50 between the spindle 9 and the tool magazine 10. The movement is related to the parallel cam 21 provided at the lowest position of the ATC drive shaft 18. Since the movement by this is publicly known, it will be described briefly (the same applies to the movement by the cams 22 and 23 described later). The parallel cam 21 is a composite cam composed of two upper and lower plate cams, and is in contact with a follower roller 38 as a follower provided on the spline countershaft 37. Based on this configuration, the spline countershaft 37, the hollow main shaft 25, and the gripping device 16 rotate 180 degrees during one rotation of the ATC drive shaft 18.
[0023]
Further, the gripping device 16 reciprocates in the axial direction of the hollow main shaft 25. This is because the tool holder 50 is extracted from the headstock 9 or the tool magazine 10 or clamped. This movement is related to the first cylindrical groove cam 23 formed on the upper surface of the cylindrical member 39 around the ATC drive shaft 18. A contact 41 provided at the tip of the swing lever 40 engaged with the first cylindrical groove cam 23 is engaged with the circumferential groove of the columnar member 36 outside the hollow main shaft 25, and the ATC drive shaft During one rotation of 18, the hollow main shaft 25 and the gripping device 16 fixed thereto are reciprocated once in the axial direction. Further, the pair of gripping finger bodies 17a and 17b in the gripping device 16 open and close. The movement is related to the planar groove cam 24 at the upper position around the ATC drive shaft 18. Although not illustrated, the groove shape of the planar groove cam 24 is a closed ring shape, and has an arcuate large-diameter portion centered on the cam shaft, a small-diameter portion, and a connecting portion for connecting them. The gripping finger bodies 17a and 17b are in a closed state, an open state, or an open / close motion state depending on where the oscillator 35 is assembled to the large diameter portion, the small diameter portion, or the connecting portion of the rotating flat groove cam 24.
[0024]
FIG. 3 is a partially cut-away plan view of an embodiment of the gripping device 16 in the automatic tool changer, and is attached to the lower end of the hollow main shaft 25 and horizontally on both ends of both ends of the swing arm 16a. A pair of open / close pivotable gripping finger bodies 17a, 17b are pivotally supported on the pivot 40, and a tip holder (grip part) of the pair of gripping finger bodies 17a, 17b is a tool holder such as a two-surface constraining type. A substantially circular arc-shaped gripping claw portion 41 that is engaged with the concave annular groove 53 at 50 from the outer peripheral side is provided. A biasing spring 43 is fixed to a holder 42 fixed to the swing arm 16a on the passive side of the pair of gripping finger bodies 17a and 17b (the side opposite to the claw portion 41 with the pivot 40 interposed therebetween) The biasing spring 43 is configured to bias the gripping claws 41 and 41 of both gripping finger bodies 17a and 17b in the closing direction.
[0025]
Further, a cam plate 44 that rotates integrally with the arm center shaft 31 housed in the hollow main shaft 25 is disposed on the lower surface side of the swing arm 16 a, and a cam portion 44 a formed on the outer periphery of the cam plate 44. In the state where the engaging portion 45 protruding on the outer surface of the passive finger body 17a disposed near the outer periphery of the cam plate 44 is fitted, the gripping of the tip side of the pair of finger bodies 17a and 17b is performed. The nail | claw 41 and 41 are comprised so that the holding | grip attitude | position which hold | grips the tool holder 50 may be hold | maintained. Further, protrusions 46 and 46 are provided inwardly in the longitudinal middle part (near the pivot 48) of both gripping finger bodies 17a and 17b, and the cam part 44a is provided on the passive side of the one gripping finger body 17a. When it is pushed in the closing direction, it is configured to rotate so as to open the distal end side of the other finger body 17b via the projections 46, 46.
[0026]
Therefore, as shown in FIG. 2, when replacing the used tool holder 50 attached to the lower end of the main shaft 9 with a tool holder 50 detachably held in the support pot 30 in the downward posture, The annular groove 53 in the tool holder 50 is gripped by one pair of gripping finger bodies 17a and 17b in the gripping device 16. At this time, as shown in FIG. 5A, the other pair of gripping finger bodies 17 a and 17 b are formed on the annular groove 53 in the tool holder 50 in which the taper shank 51 is mounted in the housing recess 30 a of the support pot 30. Since it is in the position, when the distance between the tip portions (gripping portions) of the pair of gripping finger bodies 17a and 17b is reduced, the portion of the annular groove 53 is gripped as shown by the two-dot chain line in FIG. Thereafter, the swing arm 16a is lowered to extract both the tool holders 50, 50, and in that state, the 180-degree swing arm 16a is turned horizontally to bring the new tool holder 50 (to be used for the cutting operation) below the spindle 9. The removed tool holders 50 after replacement are respectively arranged below the support pots 30, and the swing arm 16a is raised by a predetermined amount and set at each position.
[0027]
By the way, the protective cap 57 of the present invention is mounted in advance on a place where the tool holder 50 is not mounted on an arbitrary support pot 30 of the tool magazine 10. FIG. 1 shows a first embodiment of the protective cap 57 of the present invention, and a plug part 59 in which at least the upper end part fitted so as to close the lower end part of the opening of the storage recess 30a in the support pot 30 is formed in a truncated cone shape. A large-diameter disk-shaped housing 60 integrally provided at a portion near the lower end of the outer periphery of the plug body 59, and a rod-shaped protrusion protruding upward from the upper end of the plug body 59 Pull stud These parts are made of a synthetic resin material such as hard rubber or polyacetal. The diameter of the plug body 59 is formed to be smaller than the diameter of the minimum diameter portion of the annular groove 53 in the tool holder 50, and the diameter of the housing 60 is at least larger than the diameter of the plug body 59. Preferably, it is set so as to be approximately equal to the diameter of the flange portion 52.
[0028]
This protective cap 57 is fitted in advance in the storage recess 30a of the support pot 30 in the tool magazine 10 in which the tool holder 50 is not mounted (see FIG. 7A). When the tool change program is normal, the support pot 30 to which the protective cap 57 is attached is not positioned at the lower end position of the tool magazine 10, and therefore the storage recess 30a is sealed by the protective cap 57 and cut. Debris does not enter.
[0029]
However, when the support pot 30 to which the protective cap 57 is attached is at the lower end position due to an error in the tool change program or the like, and the used tool holder 50 is fitted to the spot after being removed from the main shaft 9, As described above, the annular groove 53 in the tool holder 50 attached to the spindle 9 is gripped by one pair of gripping finger bodies 17a and 17b in the gripping device 16. At that time, when the distance between the tip portions (gripping portions) of the other pair of gripping finger bodies 17a and 17b is reduced, the gripping claw portions 41 and 41 at the distal end portion with the narrowed gap grip the plug portion 59. Since the swing arm 16a is moved downward, the housing 60 is pushed down by the gripping portions such as the pair of gripping claws 41, 41 as shown in FIG. 7B. . Then, the plug body 59 of the protective cap 57 is detached from the storage recess 30a of the support pot 30 and falls downward due to the weight of the protective cap 57, and the storage recess 30a of the support pot 30 is opened. Become. Therefore, after that, the swing arm 16a turns and the tool holder 50 removed from the main shaft 9 can be stored in the storage recess 30a of the support pot 30 without any trouble.
[0030]
Further, since all the parts (parts) of the fallen protective cap 57 are made of synthetic resin such as polyacetal and are softer than metal, the surface of the table 7 etc., which is a fall point, is not damaged. Also play. In the first embodiment, when the tool holder 50 is provided with the stud 55, the protective cap 57 is also provided. Pull stud A chuck portion (not shown) provided with a portion 61 and provided on the back side of the storage recess 30a of the support pot 30 Pull stud The part 61 can be gripped.
[0031]
FIG. 8 shows a second embodiment of the protective cap 62, an upward opening cylindrical plug body 63 that fits to close the lower end of the opening of the storage recess 30 a in the support pot 30, a bolt 64, and a nut 65. And a large-diameter housing 67 disposed via a spacer cylinder 66 as a connecting body fitted on the bolt 64. The plug body 63 is made of flexible soft rubber or a synthetic resin material, and at least a portion protruding below the housing 67 such as the head of the bolt 64 or the housing 67 is made of a synthetic resin. Also in this embodiment, as in the first embodiment, before storing the tool holder 50 removed from the spindle with respect to the support pot 30 in which the protective cap 62 is fitted due to a tool change program error or the like, As shown in FIG. 9, when the distance between the distal end portions of the other pair of gripping finger bodies 17 a and 17 b is reduced, the gripping claw portions 41 and 41 at the distal end portion where the distance is narrowed do not grip the plug body portion 63. Since it is located on the upper side of the housing 67, when the swing arm 16a is moved downward, the housing 67 is pushed down by the pair of gripping claws 41, 41 as shown in FIG. Then, the plug part 63 of the protective cap 62 is detached from the storage recess 30a of the support pot 30 and falls downward due to the weight of the protective cap 62 (see FIG. 9B). The location 30a is opened, and the same actions and effects as in the first embodiment can be achieved.
[0032]
Note that the protective cap 62 of the second embodiment corresponds to the two-surface constrained tool holder 50 of the form shown in FIG. Pull stud The taper shank 51 of the tool holder 50 has an open upper surface, and a passage 68 for supplying oil mist to the tip of the tool 54 is formed through the inner diameter of the taper shank 51. The oil mist is supplied via a draw bar 12 in the main shaft 9. In the tool holder 50 as shown in FIG. 11 through a collet by a draw bar 12 inserted so as to be movable in the axial direction in the center hole following the tapered hole of the main shaft 9. Pull stud In the case where the portion 55 is pulled in and attached, the protective cap of the present invention is also used. Pull stud Of course, it is necessary to provide a part. It goes without saying that the protective cap of the present invention can be applied to a tool holder corresponding to a tool holder of a type other than the two-surface constraining type.
[0033]
Furthermore, the gripping device according to the present invention includes, in addition to a pair of gripping finger types as shown in the drawing, a fixed gripping portion having an arc shape in plan view, and a movable gripping portion that moves far and away relative to the fixed gripping portion. In this case, any one or both of the fixed gripping portion and the movable gripping portion may be in contact with the casing of the protective cap.
[0034]
【The invention's effect】
As described in detail above, the invention according to claim 1 Protective cap for machine tools Is The gripping part provided in the tool changer of the machine tool grips the annular groove formed in the flange part of the tool holder and reciprocates in the axial direction of the main axis of the machine tool, so that the tool magazine of the machine tool faces downward. A protective cap that is detachable from the storage recess instead of the tool stored in the opened storage recess, The protective cap includes a plug portion that fits into the storage recess, and the plug portion that is positioned outside the storage recess. Located below And a diameter of the plug body portion is set to be smaller than a diameter of a minimum diameter portion of the annular groove, and a diameter of the housing is set to be substantially equal to a diameter of the flange portion of the tool. When gripping when changing tools The gripping part comes into contact with the upper surface of the housing and pushes down the housing as the gripping part moves downward. It is comprised as follows.
[0035]
If comprised in this way, since the storage recess of a support pot is normally covered with the protective cap, it can protect so that cutting waste etc. may not enter into a support pot, On the other hand, tool change by a program error etc. Sometimes the gripping part such as the gripping finger body during gripping operation is a housing in the protective cap Top surface of , And by pushing down the housing as the gripping part descends, the plug body part falls out of the support pot storage recess, so that the support pot storage recess is automatically opened. The removed tool holder can be inserted into the opened portion. Therefore, even if there is an error in the tool change program, the gripping parts such as the support pot, tool holder, and gripping finger body will not be damaged, so that problems during tool change can be resolved, and automatic machining can be continued smoothly. There is an effect.
[0036]
The invention described in claim 2 is described in claim 1. Used for machine tools Protective cap Because In addition to the action and effect of the invention according to claim 1, when the protective cap is dropped, the machine tool and the cover are integrally formed with the plug body and the casing by a soft material. Even if it collides with a workpiece, there is an effect that they can be surely prevented from being damaged.
[0037]
Further, the invention described in claim 3 is described in claim 1. Used for machine tools Protective cap Because The casing is connected to the plug body portion via a connecting body, and the at least casing is formed of a soft material. Also in this case, if the portion of the housing that is likely to collide with another object at first when the protective cap is dropped is formed of at least a soft material, it is possible to prevent the other object from being damaged.
[0038]
Furthermore, the invention described in claim 4 is described in any one of claims 1 to 3. Used for machine tools Protective cap Because The plug body is held and held in the storage recess. Pull stud It has a part. in this way Pull stud By providing the protective cap in the protective cap, in addition to the effects of the inventions of claims 1 to 3, the protective cap can be securely attached to the storage recess of the support pot, and cannot be removed carelessly. The automatic tool change operation can be executed safely and reliably.
[Brief description of the drawings]
FIG. 1 is a perspective view of a machining center.
FIG. 2 is a partially cutaway longitudinal sectional view of the automatic tool changer.
FIG. 3 is a plan view of the gripping device.
FIG. 4 is a side view of the gripping device.
5A is a side view showing a state in which a gripping finger body is brought close to a tool holder mounted on a support pot, and FIG. 5B is a side view showing a state in which the tool holder is moved down from the support pot by a gripping finger body. It is.
FIG. 6 is a side view of the protective cap of the first embodiment.
7A is a side view showing a state in which the gripping finger body is brought close to the protective cap of the first embodiment mounted on the support pot, and FIG. 7B is a protective cap from the support pot by the gripping finger body that moves downward. It is a side view of the state which removes.
FIG. 8 is a partial cross-sectional side view of a protective cap according to a second embodiment.
9A is a side view showing a state in which the gripping finger body is brought close to the protective cap of the second embodiment mounted on the support pot, and FIG. 9B is a protective cap from the support pot with the gripping finger body moving downward. It is a side view of the state which removes.
10A is a partially cutaway side view of another type of tool holder, and FIG. 10B is a cross-sectional view of a tapered shank portion.
11A is a side view of a two-surface constrained tool holder, and FIG. 11B is a plan view.
[Explanation of symbols]
9 Spindle
10 Tool magazine
16 Gripping device
16a swing arm
17a, 17b Holding finger body
30 Support pot
30a storage recess
50 Tool holder
53 Annular groove
57 Protective cap
59 Plug body
60 body
61 Pull stud Part

Claims (4)

The gripping part provided in the tool changer of the machine tool grips the annular groove formed in the flange part of the tool holder and reciprocates in the axial direction of the main axis of the machine tool, so that the tool magazine of the machine tool faces downward. A protective cap that is detachable from the storage recess instead of the tool stored in the opened storage recess,
The protective cap includes a plug portion that fits in the storage recess, and a housing that is positioned below the plug portion so as to be positioned outside the storage recess.
The diameter of the plug portion is set smaller than the diameter of the minimum diameter portion of the annular groove,
The diameter of the housing is set to be substantially equal to the diameter of the flange in the tool;
Protective cap used for a machine tool, wherein the gripping portion when gripping operation is performed at the time of tool replacement is configured to abut on the upper surface of the housing and push down the housing as the gripping portion is lowered. . The protective cap used for a machine tool according to claim 1, wherein the plug body and the housing are integrally formed of a soft material. The protective cap used for a machine tool according to claim 1, wherein the casing is connected to the plug body portion via a connecting body, and the at least casing is formed of a soft material. The protective cap used for a machine tool according to any one of claims 1 to 3, wherein the plug body portion is provided with a pull stud portion for holding and holding in the storage recess.

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