JPS62287953A - Pallet changer for machine tool - Google Patents

Abstract

PURPOSE:To enable a straight moving actuator to generate the action of turning and torsion, by providing a pallet gripper rotary turning device such that a pallet gripper turns 180 deg. by a turning mechanism simultaneously rotates 90 deg. by a rotary mechanism. CONSTITUTION:A saddle 48 is horizontally moved by actuating an actuator 64, and a vertical gripper 42B reaches a position where it grips a pallet B. If the pallet B is gripped by the gripper 42B, a work table 26 retracts from a head 22. In this way, the pallet B, placed in a condition that it is gripped by the gripper 42B, is detached from a machine tool. Next the actuator 180 deg. turns a pallet clamping arm 41 about a horizontal fixed shaft while 90 deg. rotates both grippers 42A, 42B about the axial center of a gripper shaft through this shaft. Thus the pallet is replaced with each other, further a new pallet is mounted by advancing the work table 26.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a pallet changer for a machine tool, particularly between a pallet magazine disposed in front of the machine tool and the machine tool. A machine tool that performs pallet exchange by twisting the direction of the work placement surface of the pallet between the horizontal exchange position on the magazine and the horizontal attachment position on the pallet attachment part of the machine tool. Regarding the palette changer.

[Conventional technology]

A pallet changer that automatically exchanges a pallet with a workpiece mounted thereon and a pallet 7) on a work table of a machine tool with a processed workpiece mounted thereon is a pallet changer that automatically exchanges a pallet with a workpiece mounted thereon and a pallet 7) on a work table of a machine tool with a machined workpiece mounted thereon. A number of systems have already been proposed in which automatic pallet exchange is performed by transferring the pallet to and from a table while maintaining its horizontal position.

JP-A No. 56-9153 discloses an example of such a conventional pallet changer, in which a pinion is rotated using the rotational movement of a machine table of a machine tool, and a carriage rack that is constantly engaged with the pinion is moved in the X direction. The carriage of the pallet changer is moved in the X direction by
This disclosure discloses a configuration in which pallets are carried in and out of a carriage of a pallet changer by movement in the Z direction of a column in which a special tool for changing pallets is attached to a spindle of a machine tool. In addition, Utility Model Application Publication No. 57-157441 has a configuration in which a pallet placed on a cart that is arranged in an oval shape on the side of a machine table and is guided by a rail is carried into and out of the machine table using a hydraulic cylinder. Disclosed.

Furthermore, Japanese Patent Application Laid-Open No. 60-16742 filed by the same applicant as the present applicant
No. 0 discloses a pallet changer that simultaneously grips a pallet on a pallet stand and a pallet on a work table with two pairs of gripping arms, and can automatically exchange the pallets with each other by rotating them 180 degrees.

The above is a conventional technique for automatically exchanging pallets in a horizontal plane, but it is similar to the technique for automatically exchanging pallets between a work table with a vertical mounting surface of a machine tool and a horizontal pallet stand. As a technique beyond that, there is, for example, Japanese Patent Application Laid-Open No. 107839/1983.

This discloses a technology for a handling robot that mutually exchanges workpieces between the vertical workpiece mounting surface of a chuck of a lathe and a workpiece magazine adjacent to the lathe in which workpieces are placed horizontally. Two hands are provided at the tip of the robot arm, one of which grips a new workpiece and waits at a standby position. When a workpiece exchange command is issued, the robot arm first swings toward the chuck, and
The processed workpiece mounted on the chuck is gripped by the other empty node. The entire robot arm then tilts to the right to remove the machined work from the chuck, and then only the hand rotates 180 degrees to direct the new work toward the chuck. The entire robot arm moves to the left and attaches a new workpiece to the chuck. Next, the robot arm swings upward into a vertical position, and then swings 90 degrees toward the workpiece table. Next, the robot arm descends and places the work into the work magazine. Then, the robot arm rises, the work magazine indexes the next work, the robot arm descends, grasps the next work, swings 90 degrees to the standby position, and moves to the next work in an upward vertical position. Wait until a replacement order is issued.

This handling robot has two actuators for two types of oscillations to perform the above-mentioned operations.
Hand part 180: 1 piece for same city reuse, 1 piece for left and right movement
A total of 5 pieces are required: 1 piece and 1 piece for raising and lowering.

[Problem that the invention seeks to solve]

In order to mutually exchange the two, the aforementioned lathe work handling robot may be applied, but this requires a large number of actuators. This poses a problem in that not only the structure becomes complicated, but also the drive control device becomes large-scale and the control method becomes complicated.

Therefore, the purpose of the present invention is to solve these problems.
It is an object of the present invention to provide a compact and inexpensive pallet changer that requires few actuators and can exchange two pallets that are twisted by 90 degrees with respect to each other by a translational movement and one rotational movement.

[Means for solving problems]

In view of the above-mentioned objects of the invention, the present invention provides a pallet changer that automatically exchanges pallets between a machine tool and a pallet magazine disposed in front of the machine tool while rotating and moving the pallets. a changer saddle that is movable back and forth along a fixed path provided on the changer saddle, and a changer saddle that is provided on the changer saddle so as to be pivotable around a horizontal axis, the changer saddle being provided with a pallet exchange position of the pallet magazine and a pallet mounting portion of the machine tool. A swing arm that swings at a predetermined angle between a gripping device, the swinging arm being a driving node, the changer saddle being a fixed node, and the housing of the gripping device being a horizontally movable node, and parallel to the swinging arm, both ends are pinned to the changer saddle and the bouncing of the gripping device. a parallel link mechanism that uses a connected rod as a driven joint to move the pallet gripped by the gripping device in a horizontal state between the pallet magazine and the machine tool side; and a parallel link mechanism provided in the gripping device and the pair of pallet grips. A rotation mechanism that rotates the pair of pallet grippers around a first axis in a horizontal direction that connects the center of the brim with each other, and a rotation mechanism that rotates the pair of pallet grippers around a second axis that is orthogonal to the first axis. and a pallet gripper rotation device that rotates the pair of pallet grippers by 180 degrees by the rotation mechanism and 90 degrees by the rotation mechanism at the same time. To provide a pallet changer for a machine tool configured so that a pallet horizontally placed at a pallet exchange position and a pallet horizontally mounted on a pallet mounting part of the machine tool can be mutually rotated and replaced.

(Function) According to the above means according to the present invention, a pair of pallet grippers can simultaneously rotate 180 degrees around two orthogonal axes.
Since 0 degree rotation is possible, two pallets that are twisted 90 degrees to each other can be exchanged by a translational movement and one rotational movement.

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the accompanying drawings.

〔Example〕

FIG. 1 is a schematic front view showing a pallet changer according to the present invention together with a pallet magazine and a machine tool, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is along the arrow line [-I[[
FIG. 4 is a cross-sectional view taken along the arrow line IV-IV in FIG. 3, and FIG. 5 is an explanatory diagram of the operation of the pallet changer according to the present invention.

Referring first to FIG. 1, a pallet changer 40 according to the present invention is disposed on a changer base 18 installed between a pallet magazine 10 and a machine tool 20. As shown in FIG. A pallet A to which a workpiece a is attached is placed on a pallet stand 12 of the pallet magazine 10 so that the pallet surface is horizontal. The machine tool 20 also includes a column section 24 having a spindle head 28 and a bed section 22 on which a work table 26 is mounted.A rotary table 30 is attached to the work table 26. On the side surface (parallel to the plane of the paper in FIG. 1), a pallet B carrying a processed workpiece b is attached to the pallet mounting portion 29 so that the pallet surface is perpendicular.

The pallet changer 40 that automatically exchanges the pallet B carrying the work b and the pallet A carrying the work a includes a housing 44 and a pallet gripping arm 41.
A gripping device is provided, and a pallet gripper (hereinafter referred to as gripper) 42A for gripping pallet A and a gripper 42B for gripping pallet B are provided at both ends of a pallet gripping arm 41 of the gripping device, respectively. They are arranged horizontally and vertically with their axes twisted by 90 degrees. Note that a turning device for turning both grippers 42A and 42B will be described later. The pallet gripping arm 41 is supported by the housing 44 via the turning device. On the other hand, two guideways 46 are disposed on the changer base 18 in a direction that connects the pallet stand 12 for pallet exchange of the pallet magazine 10 and the pallet mounting portion of the machine tool 20. Hagonoi Guideway 46
A changer saddle 48 is mounted to be slidable along. A horizontal shaft 50 is provided at the upper part of the saddle 48, and between the horizontal shaft 50 and a housing shaft 51 provided horizontally on the housing 44, the two wheels 50,
A swinging arm 52 is pivotally attached to the saddle 51, and the upper part of the saddle 48 is a fixed joint, and the fixed joint, the swinging arm 52, and the housing 44 are combined to form a parallel link mechanism. A rod 54 is disposed parallel to the swing arm 52 and is connected to the upper part of the saddle 48 and the housing 44 with a pin.

The swinging arm 52 is rotatable about the horizontal axis 50.
An arm 58 is provided on the segment gear 56 disposed so as to mesh with the gear 49 fixed to the segment gear 56 , and a connecting member 59 is attached to the tip of the arm 58 via a pin 63 . Further, a hydraulic reciprocating actuator (second cylinder) 60 is fixed to the saddle 48, and the reciprocating movement of the actuator 60 is transmitted to the connecting member 59 via a pin 65 at the tip of the piston. As a result of this reciprocating motion, the arm 58 is given a rocking motion, and the segment gear 56 can be rotated forward and backward (rotated) around a pin (another horizontal shaft) 620 fixed to the saddle 48. This rotation of the segment gear 56 is transmitted to the gear 49, causing the swing arm 52 to swing. At this time, since the swing arm 52 constitutes a parallel link mechanism together with the rod 54 and the housing 44 as described above,
The pallet gripping arm 41 supported by the housing 44 via a fixed shaft 78 (FIG. 3), which will be described later, swings while maintaining a horizontal state. Note that the stroke of the reciprocating actuator 60 is determined by an appropriate spacing (not shown), and in this embodiment, the horizontal height of the pallet gripping arm 41 is the same as the pallet mounting position of the machine tool 20 after swinging. The stroke is set so as to oscillate to position P1.

The gripper 42B holds the pallet gripping arm 41, which has oscillatedly moved to the same height position P1, to the machine tool 20.
It is necessary to move the pallet B to the position P2 where it is to be gripped. Therefore, the saddle 48 is linearly moved along the guideway 46 by a saddle reciprocating actuator (first cylinder) 64 fixedly supported by the cylinder support 19 of the base 18. In this case as well, the stroke of the actuator 64 is set by a suitable stopper.

FIG. 2 is a plan view showing the pallet changer 40, pallet magazine 10, and machine tool 20 according to the present invention, the outline of which has been explained above. A plurality of pallets loaded with workpieces are mounted on the pallet magazine, and in this figure, a desired pallet is transported to the pallet exchange position PO by the command control unit (not shown), and the gripper 4
The figure shows a state in which a desired pallet A is gripped by 2A. The fact that the gripper 42A has completed gripping the pallet I-A is detected by a dog and a limit switch (not shown). Further, the work table 26 of the machine tool 20 is horizontally movable in the axial direction (X direction) of the mounting portion 29 of the pallet 7).

Next, FIG. 3 shows the gripping device in a sectional view taken along the line of arrow mm in FIG. 1, and mainly shows the pallet gripping arm 41 and the turning device inside the housing 44. First, the turning mechanism of the turning device will be explained.

As the rack 70 moves in the vertical direction (perpendicular to the plane of the paper in FIG. 3), the pinion 72 meshing with the rack 70
rotates, and the T-shaped cylinder body 76, which is integrally fixed to the pinion 72 via a key 74, rotates. The T-shaped cylinder 76 and the pinion 72 are fixed to the housing 44 horizontally (parallel to the plane of FIG. 80 and is pivoted between the housing 44 and another bushing 82 .

Next, the rotation mechanism of the rotation device will be explained. The T-shaped cylinder body 7
6 supports a gripper shaft 84 so as to be rotatable around its axis (first axis), and the axis is parallel to the horizontal fixed axis 7.
It is perpendicular to and at the same height as the axis of No. 8 (second center). Further, a gripper 42A and a gripper 42B are fixed to both ends of the glyph/shaft 84 so that their gripping axes are twisted 90 degrees with respect to each other. Further, the tip of the horizontal fixed shaft 78 inside the T-shaped cylinder 76 and the gripper shaft 8
A sun gear 86 and a planetary gear 88, which are bevel gears, are fixed to the outer periphery at appropriate axial positions of the gripper shaft 84 so as to mesh with each other.
6 and is rotatable around the axis of the gripper shaft 84 via a bush 90. Further, the sun gear 8
6 is fixed to the horizontal fixed shaft 78 and therefore does not rotate.

Note that the number of teeth of the sun gear 86 and the number of teeth of the planetary gear 88 are set at a ratio of 1:2.

By reciprocating the rack 70 in a manner to be described later, the pallet gripping arm 41 is rotated around the horizontal fixed shaft 78 via the pinion 72 and the T-shaped cylinder 76. In this case, the planet gear 88 rotates around the axis of the gripper shaft 84 while revolving around the sun gear 86 fixed to the horizontal fixed shaft 78, but as described above, the number of teeth of the sun gear 86 and the planet gear Since the ratio of 88 teeth is 1:2, the ratio of the angle of revolution to the angle of rotation is 2:1. For example, the pallet gripping arm 41 is rotated once around the axis of the horizontal fixed shaft 78.
When the pallet gripping arm 4
1 rotates (rotates) 90 degrees around the axis of the gripper shaft 84.

In this embodiment, since the fixed shaft 78 was provided in the horizontal direction as the second axis, the pallet gripping arm 41 rotated 180 degrees in the vertical plane around the horizontal fixed shaft 78. Here, it is assumed that the gripper shaft 84, which is the first axis, remains horizontal, and the fixed shaft, which is the second axis, is provided vertically, and the sun gear 86 is attached to the vertical fixed axis so as to mesh with the planetary gear 88. . Of course, the pinion 72, the T-shaped cylinder 76, etc. are also provided around this vertical fixed axis, and the rack 70 is also provided so as to reciprocate in the horizontal direction. Then, the pallet gripping arm 41 rotates 180 degrees in a horizontal plane around the vertical fixed axis. In this case as well, both grippers 42A and 42B can perform a 90 degree torsional rotation with respect to each other at the same time as the 180 degree rotation and rotation. Therefore, if the second axis is orthogonal to the horizontally provided first axis, the same action and effect will be achieved whether the second axis is in the horizontal or vertical direction.

FIG. 4 is a longitudinal sectional view including the rack 70 and pinion 72 taken along the arrow line IV-TV in FIG. Pistons 94a and 94b are inserted into the cylinder 96, and a rack 70 guided by a guide 92 is disposed between the pistons 94a and 94b.

The piston 94a is pushed up by pressure oil supplied from the lower pressure oil supply port 98a under suitable control means, thereby pushing up the rack 70. At this time, the rack 7
The pinion 72, which is engaged with the pinion 0, is driven to rotate.

Also, under the above-mentioned appropriate control means, the upper pressure oil supply port 9
The piston 9'4 is moved by pressure oil supplied from 8b.
b is pushed down, pushing the rack 70 downward.

As a result, the pinion 72 is driven to rotate in a direction opposite to the aforementioned direction of rotation. In this way, the pallet gripping arms 41 are pivoted in opposite directions.

The length of the cylinder 96 is the same as that of each piston 94a or 94b.
The stroke is set to correspond to the rotation of the pallet gripping arm 41 by 180 degrees.

When manufacturing such a cylinder with a long stroke, it is generally ground from both ends to form a single cylinder bore. In this case, due to machining accuracy issues, the entire cylinder bore is
The bore is not aligned with the axial center, and some axial misalignment inevitably occurs. When a long rack that also serves as a piston is inserted into such a cylinder bore, the piston (rack) becomes distorted as it reciprocates, resulting in the cylinder being used in a state where it does not slide smoothly. This causes wear between the piston and cylinder, and eventually a phenomenon called "galling" occurs in which the piston becomes clogged with wear particles and stops moving.

In this embodiment, in order to solve this problem, two short pistons are used.
A rack slightly smaller than the cylinder bore is disposed between them and guided by a dovetail 93 of a guide 92. When the shaft moves upward, it is operated by the lower piston, and when it moves downward, it is operated by the upper piston. In other words, the two pistons reciprocate only within the cylinder bore, each of which has a single axis, so they are not twisted, and "galling" can be prevented.

The operation of the pallet changer according to the present invention having the above configuration will be explained with reference to FIG. 5 as well as FIGS. 1 to 4. FIG. 5 (δ) shows a state in which the pallet changer 40 has been moved by the saddle reciprocating actuator 64 from its retracted position to the position where it grips the pallet 7) A of the pallet magazine IO. In this state, the gripper 42A in the horizontal state grips the pallet A, and when the dog and limit switch detect the completion of gripping, the reciprocating actuator 60 is activated, and the pallet gripping arm 41 moves in translation while maintaining the horizontal state, and A stopper stops the pallet gripping arm 41 at a position P1 where the horizontal height is the same as the pallet mounting position of the machine tool 20. (
bl illustrates this state.

Next, the saddle reciprocating actuator 64 is actuated to horizontally move the saddle 48, and the vertical gripper 42B reaches a position P2 where it grips the pallet B vertically attached to the machine tool 20. When the pallet B is gripped by the gripper 42B, the work table 26 is moved to the bed 2.
2 in the "X" direction shown in FIG. 2 (direction toward the back side of the paper in FIG. 1). In this way, the pare throat B is removed from the machine tool while being gripped by the gripper 42B.

(C1 indicates this state.

Next, the rack 70 is moved from top to bottom by hydraulic pressure, and this operation causes the pallet gripping arm 41 to rotate 180 degrees counterclockwise around the horizontal fixed shaft 78, and
Both grippers 42A and 42B are connected via the gripper shaft 84.
is rotated (rotated) by 90 degrees around the axis of the gripper shaft 84. In this way, pallets A and B are exchanged with each other, and this state is shown at Tdl. Further, from this state, the work table 26 moves forward (from the back side of the paper in FIG. 1 to the front side) and a new pallet 8 is attached. (dl
This also shows this condition.

After attaching a new pallet A to the low-return table 30 of the machine tool, the pallet changer 40 is moved again using the saddle reciprocating actuator 64 while holding the pallet-sol I-B.
Return to the pallet magazine 10 side. This state is shown in (e).

Next, the pallet magazine 1 is held by the reciprocating actuator 60 while holding the pallet gripping arm 41 in a horizontal state.
Pallet B is placed on the pallet stand 12 of 0. (fl
indicates this state.

Finally, the pallet changer 40 is moved to its retracted position using the reciprocating actuator 64, and the rack 7
0 from the bottom to the top, rotate the pallet/throat gripping arm 41 clockwise 180 degrees, so that the gripper 42A faces the pallet magazine 10 side, the gripper 42B faces the machine tool 20 side, and then picks up the next pallet. Prepare for exchange.

This state is shown in (g).

〔Effect of the invention〕

As is clear from the above description, it is possible to simultaneously generate a 180-degree rotation of the pallet gripping arm and a 90-degree torsional rotation of the two grippers by one operation of one linear actuator.

Two linear actuators are provided for transporting pallets between the pallet magazine and the machine tool. Furthermore, the attachment and detachment of pallets to and from the low-level table on the machine tool utilizes the X-direction feeding function originally possessed by the machine tool. Therefore, the pallet changer of the present invention is
With only three actuators, a pallet placed vertically on a pallet magazine and a pallet mounted horizontally and vertically on a rotary table of a machine tool can be mutually exchanged. In other words, the structure is compact, the control method is simple, and an inexpensive pallet changer can be provided.

In addition, a rack sandwiched between two pistons that move linearly in a cylinder is used as a linear actuator that rotates the pallet gripping arm 180 degrees and twists the two grippers of the same color by 90 degrees. There is no galling of the piston due to misalignment errors between the top and bottom of the cylinder during long strokes, which inevitably occurs, and smooth and reliable rotation of the pallet gripping arm can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view showing a pallet changer according to the present invention together with a pallet magazine and a machine tool, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a gripping device taken along arrow line mm in FIG. 1. An enlarged sectional view of FIG. 4 is taken along the arrow line IV in FIG.
-rV sectional view, and FIG. 5 is an explanatory diagram of the operation of the pallet changer according to the present invention. 10... Pallet magazine, 12... Pallet stand,
18... Changer base, 19... Cylinder support stand, 20... Machine tool, 2
2...Bed part, 24...Column part, 2
6...Work table, 28...Spindle head, 29.
...Pallet mounting part, 30...Row grip table, 40...Pallet changer, 41...Pallet gripping arm, 42A, 42B...Pallet gripper, 44...
・Housing, 46...Guideway, 48
...Changer saddle, 49...Gear, 50...
Horizontal axis, 52... Swing arm, 54...
Rod, 56...Segment gear, 58
...Arm, 59...Connection material, 60.
... Reciprocating actuator, 62... Pin (other horizontal axis), 64... Reciprocating actuator for saddle, 70...
Rack, 72...Pinion, 76...
T-shaped cylinder, 78...horizontal fixed shaft, 84...
Gripper shaft, 86... Sun gear, 88... Planet gear, 92... Guide, 94a, 94b.
...Piston, 96...Cylinder, 98a, 98
b...Pressure oil supply port.

Claims (1)

[Scope of Claims] 1. In a pallet changer that automatically exchanges pallets while rotating them between a machine tool and a pallet magazine placed in front of the machine tool, a fixed portion provided between the machine tool and the pallet magazine a changer saddle that is reciprocally movable along a path; and a changer saddle that is pivotable about a horizontal axis provided on the changer saddle to move between a pallet exchange position of the pallet magazine and a pallet mounting portion of the machine tool. A gripping device comprising a swinging arm that swings over a predetermined angle, and a pair of pallet grippers having gripping axes twisted by 90 degrees on both sides of a housing pin-coupled to the tip of the swinging arm. , wherein the swinging arm is a driving section, the changer saddle is a fixed section, and the housing of the gripping device is a horizontally moving section, and the rod is parallel to the swinging arm and has both ends pin-coupled to the changer saddle and the housing of the gripping device. a parallel link mechanism that moves the pallet gripped by the gripping device in a horizontal state between the pallet magazine and the machine tool side using the driven joint as a driven joint;
a rotation mechanism that is provided in the gripping device and rotates the pair of pallet grippers around a first axis in a horizontal direction that connects the centers of the pair of pallet grippers; and a second axis that is perpendicular to the first axis. and a pallet gripper rotation device that rotates the pair of pallet grippers by 180 degrees by the rotation mechanism and 90 degrees by the rotation mechanism at the same time. A pallet changer for a machine tool, wherein a pallet placed horizontally at a pallet exchange position of the pallet magazine and a pallet horizontally mounted on a pallet mounting portion of the machine tool can be mutually rotated and exchanged. . 2. The changer saddle is reciprocated by a first cylinder along a guideway that is installed between the machine tool and the pallet changer, is provided on the changer base, and forms the constant path. A pallet changer for the machine tool according to item 1. 3. The swing arm is meshed with a gear that rotates forward and backward around another horizontal axis parallel to the horizontal axis axis in accordance with the operation of a second cylinder provided in the changer saddle. Claim 1 or 2, which is operated by a swinging mechanism configured by providing a gear at the rear end of the swinging arm concentrically with the horizontal axis axis. Pallet changer for the machine tools listed. 4. The pallet gripper turning device includes a cylindrical body in which the turning mechanism of the turning device can turn around the second axis concentrically with the second axis, and a rack and pinion mechanism that drives the cylindrical body to turn. a rotation shaft, the rotation mechanism of the rotation device being rotatably supported by the cylindrical body, having the first axis as the axis and having the pair of pallet grippers fixed to both ends; and the gripping device. a non-rotating sun gear consisting of a bevel gear fixed concentrically to the second axis with respect to the housing forming the horizontally moving node; and a bevel gear meshing with the sun gear and fixed concentrically to the rotating shaft. The machine tool according to any one of claims 1 to 3, comprising a planetary gear made of a gear, and a ratio of the number of teeth between the sun gear and the planetary gear is 1:2. palette changer. 5. The rack and pinion mechanism reciprocates within a cylinder provided in the housing of the gripping device using fluid pressure.
a rack that is sandwiched between the two pistons from both sides and reciprocated;
A pinion that rotates integrally with the cylindrical body around the axis, and a rack guide that is provided in the cylinder and guides the rack so as to maintain uniform meshing with the pinion over the entire stroke. A pallet changer for a machine tool according to scope 4.