JP3169154B2 - Wafer cassette elevator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer cassette elevator for raising and lowering a wafer cassette housed in a cassette chamber of a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In a conventional wafer cassette elevator, a screw rod 24 is supported on a shaft of a motor 21 via gears 22 and 23 so as to be rotatable between an upper plate 25 and a lower plate 26 as shown in FIG. I have. 27 is a guide rod fixed between the upper plate and the lower plate, 28 is a nut which engages with a screw rod, one end of which is engaged with the guide rod so as to be slidable in the vertical direction, and a support rod 29 is provided at the center. Is fixed at one end. A cassette table 30 is provided at the other end of the support bar, and is configured to mount a wafer cassette (not shown). When the motor of the wafer cassette elevator configured as described above is driven, the screw rod rotates via the gear. With the rotation of the screw rod, a nut engaged with the screw rod moves up and down along the guide rod, and moves up and down the cassette table integrally with the support rod fixed to the nut.

[0003]

However, in the prior art, as shown in FIG. 4, the mass of the cassette table 30 including the wafers in the wafer cassette and the support rod 29 is added to the nut 28 which moves the cassette table 30 up and down. The mass applied to the nut 28 acts as a moment on the threaded rod 24. For this reason, when the power supply to the motor 21 is cut off,
There is a problem that the motor holding force becomes smaller than this moment and the cassette table 30 falls.
Therefore, an object of the present invention is to dispose a non-contact type electromagnetic brake and smoothly operate the cassette table 30 that moves up and down.

In order to solve the above-mentioned problems, a wafer cassette elevator according to the present invention comprises a frame in which both sides of a rectangular upper plate and a lower plate are connected and fixed by a support, and a wafer fixed to the lower plate of the frame. Motor, a screw rod with one end attached to the rotating shaft of the motor and the other end bearing-supported by a bearing on the upper plate, a guide shaft fixed between the upper plate and the lower plate, and engaged with the screw rod at the center A lift table provided with guide nuts having sliding nuts on both sides and a guide bush sliding on the guide shaft surface, arranged on both sides of the screw rod, one end fixed to the lift table, the other end protruding from the upper plate, and a cassette table at the upper end It is characterized in that a fixed supporting arm, a brake plate having a cut groove on a plate surface attached to a rotating shaft of the motor, and an electromagnet fixed to a frame provided opposite to the plate surface are provided.

[0005]

Accordingly, since the supporting arm for supporting the cassette table is mounted on both sides of the screw bar with the screw bar interposed therebetween on the lift table which moves up and down along the screw bar by driving the motor, the mass of the lift table including the cassette table is reduced by the screw bar. The cassette table can be raised and lowered smoothly without applying a moment force to the cassette table.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partially sectional front view showing an embodiment of the present invention, FIG. 2 is a top view showing a main part, and FIG. 3 is a main part sectional view. Reference numeral 1 denotes a frame, which is provided with a rectangular upper plate 2 and a lower plate 3, which is crotch on the upper plate and the lower plate, and the side surfaces of the upper plate and the lower plate are fixed by columns 4. 5 is a guide shaft fixed to the side surfaces of the upper plate and the lower plate. Reference numeral 6 denotes a motor, in which a stator 7 is attached to a lower plate, and a screw 9 is attached to a shaft of a rotor 8.
The other end of the screw rod is supported by a bearing fixed to the upper plate surface. Reference numeral 10 denotes a lifting platform fixed at the center of the plate surface to which a nut 11 engaging with the screw rod 9 is fixed. Guide bushes 12 are attached to both sides of the lifting platform, and the guide shaft 5 is slid on the peripheral surface to move vertically. It is configured to be able to do. Numeral 13 denotes a support arm, which is provided on both sides of the screw rod and has one end fixed on a lift table, the other end protruding from the upper plate, and a cassette table 14 for mounting a wafer cassette (not shown) fixed on the upper end. Reference numeral 15 denotes an electromagnetic brake. A brake plate 16 made of a magnetic plate and provided with a plurality of cut grooves 16a on the plate surface is fixed to the screw rod 9, and an electromagnet 17 is fixed to the frame 1. This electromagnet is provided with an electromagnetic coil 19 on the legs of an iron core 18 formed in a U-shape.
And a permanent magnet 20 is attached to the end face of the leg facing the brake plate 16. The magnetic flux generated by the electromagnet 17 is
It returns to the electromagnet 17 through the brake plate 16. At this time, the brake plate 16 is held at a position where the magnetic resistance decreases. This holding force is used as a braking force. Further, a cut groove is provided in the brake plate 16 so as to change the permeance between the brake plate 16 and the electromagnet 17 arranged via the gap. The change in permeance depends on the brake plate 16
And the electromagnet 17 change several times per one revolution.
Therefore, the positional relationship between the brake plate 16 and the electromagnet 17 at which the braking force has the maximum value is several times the kerf. The brake plate is held in one of these positional relations. As a result, even if the power supply to the motor 6 is cut off, the moment force generated in the screw rod 9 by the mass applied to the nut 11 is canceled by the electromagnetic brake 15. However, the cassette table 14 can be prevented from falling. When the switch (not shown) of the motor for driving the wafer cassette elevator and the switch (not shown) of the electromagnetic brake are closed, the electromagnet is excited in a direction to cancel the magnetic flux of the permanent magnet 20 provided on the iron core leg, and the screw rod 9 is turned off. The restraint of the brake plate 16 attached to is released. The screw rod on which the brake plate is mounted rotates integrally with the rotor 9 of the motor, and the lifting platform 10 on which the nut 11 is engaged which is engaged with the screw rod.
Rises. The cassette table 14 attached to the lift table via the support arm 13 rises integrally with the lift table. In this case, the mass of the cassette table on which the wafer cassette is placed and the support arm are evenly applied to the lifting table around the nut, and the lifting table smoothly rises on the screw rod integrally with the nut,
Or descend. Now, when the motor switch and the electromagnetic brake switch are opened, the rotation of the motor stops, and the electromagnet of the electromagnetic brake is demagnetized. Prevent the rod from rotating. In the embodiment, when the motor is stopped, the magnetic flux of the permanent magnet acts on the brake plate to apply the braking force to the brake plate.However, the permanent magnet is not provided, and the electromagnet is excited to apply the braking force to the brake plate. You may. In the embodiment, one electromagnet is provided to face the brake plate, but a plurality of electromagnets may be provided. Furthermore, in the embodiment, 6 is an axial gap type pulse motor. However, according to the gist of the present invention, the present invention is not limited to this, and another type of motor may be used.

[0007]

As described above, according to the present invention, the nut engaged with the screw rod connected to the shaft of the motor is fixed to the lifting platform.
Since the support arm for supporting the cassette table is mounted on both sides of the screw bar with the screw bar in between, the mass of the lift table including the cassette table can smoothly move up and down the cassette table without applying a moment force to the screw bar. In addition, dust is not generated because the braking is performed in a non-contact manner without applying a braking force to the brake plate with a frictional force.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view showing an embodiment of the present invention.

FIG. 2 is a top view showing a main part of the present invention.

FIG. 3 is a sectional view showing a main part of the present invention.

FIG. 4 is a side view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame 2 Upper plate 3 Lower plate 4 Prop 5 Guide shaft 6 Pulse motor 9 Screw bar 10 Lifting stand 11 Nut 14 Cassette table 15 Electromagnetic brake

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/68 B65G 49/07 B66F 3/44 B66F 7/00 B66F 7/14

Claims (1)

(57) [Claims] 1. A wafer which moves up and down with a wafer cassette placed thereon
In a cassette elevator, the rectangular upper plate and lower plate
A frame body fixed by connecting both sides with pillars, and a lower plate of the frame body
Motor and one end attached to the motor shaft
A screw rod bearing the other end on the bearing of the upper plate, the upper plate and the lower plate
And the screw shaft in the center
Has a nut that engages with the guide shaft on both sides
Lifting table with guide bush
Place and fix one end to the elevator and project the other end from the upper plate.
A support arm with a cassette table fixed at one end and the motor
A brake plate having a kerf on the plate surface attached to the pivot, and a plate
And an electromagnet fixed to the frame provided facing the surface.
A wafer cassette elevator characterized by the above-mentioned.