Gate valve

1. A gate valve comprising:

a valve box having a communicating hole communicating with a processing chamber;

a valve plate mounted on a valve plate mounting portion at a tip end of a valve rod and accommodated in the valve box, the valve plate being configured to open and close the communicating hole by bringing a seal member into and out of contact with a periphery of the communicating hole;

a valve rod configured to displace the valve plate to a position to open and close the communicating hole;

a coupling plate coupling the valve plate and the valve rod;

an opening formed on the valve box for taking out the valve plate; and a detachable lid member configured to cover the opening, wherein

the valve plate includes a mounting hole which allows insertion of the valve plate mounting portion of the valve rod, and joint flat surfaces of the valve plate and the valve rod which are brought into press-contact with each other when coupling the valve plate and the valve rod with the coupling plate, are formed on a hole surface of the mounting hole and an outer surface of the valve plate mounting portion respectively,

the valve rod includes a depressed-shaped joint shoulder portion which allows fitting of a base-side end portion of the valve plate at a position on a base side of the valve plate mounting portion, the joint shoulder portion is formed with an inclined surface which allows abutment of a base-end-side end portion of the valve plate, the inclined surface displaces the valve plate in the direction in which the joint flat surfaces of the valve plate and the valve rod are brought into press-contact with each other by a wedge effect, and

the coupling plate couples the valve plate and the valve rod with each other in a state in which the valve plate is pressed toward a base end side of the valve plate mounting portion.

2. The gate valve according to claim 1 , wherein the inclined surface of the joint shoulder portion of the valve rod is a flat surface intersecting the joint flat surface of the valve rod at an acute angle.

3. The gate valve according to claim 2 , wherein an abutting surface parallel to the inclined surface of the joint shoulder portion of the valve rod is formed on a portion which abuts on an inclined surface of the base-end-side end portion of the valve plate.

4. The gate valve according to claim 1 , wherein an abutting surface parallel to the inclined surface of the joint shoulder portion of the valve rod is formed on a portion which abuts on an inclined surface of the base-end-side end portion of the valve plate.

5. The gate valve according to claim 4 , wherein the coupling plate includes: a first plate portion to be fixed to the valve plate and a second plate portion to be fixed to the valve plate mounting portion of the valve rod, a tip end surface of the valve plate mounting portion of the valve rod is located at a position retracted into the mounting hole with respect to a tip-side end surface of the valve plate, the first plate portion of the coupling plate is fixed to the tip-side end surface of the valve plate with a screw and the second plate portion is fixed to the tip end surface of the valve plate mounting portion with a screw, so that the valve plate is pressed toward the base end side of the valve plate mounting portion.

6. The gate valve according to claim 5 , wherein the coupling plate includes a press-contact mechanism configured to press the valve plate in the direction in which the joint flat surfaces of the valve plate and the valve rod are brought into press-contact with each other.

7. The gate valve according to claim 6 , wherein the press-contact mechanism includes an inclined portion which comes into abutment with an end portion of the valve plate mounting portion of the valve rod at an end portion of the second plate portion, and the inclined portion generates a component force in the direction in which the joint flat surfaces of the valve plate and the valve rod are brought into press-contact with each other.

8. The gate valve according to claim 7 , wherein an inclined portion parallel to the inclined portion is formed at the end portion of the valve plate mounting portion with which the inclined portion of the second plate portion comes into abutment.

9. The gate valve according to claim 6 , wherein the press-contact mechanism includes a freely bendable resilient bent portion formed at an intermediate portion of the second plate portion and a tip end engaging portion formed at a tip end portion of the second plate portion to engage the valve rod and the resilient bent portion is expanded when the second plate portion is fixed to the valve rod with a screw, whereby the joint flat surface of the valve plate and the valve rod are brought into press-contact with each other.

10. The gate valve according to claim 1 , wherein the coupling plate includes: a first plate portion to be fixed to the valve plate and a second plate portion to be fixed to the valve plate mounting portion of the valve rod, a tip end surface of the valve plate mounting portion of the valve rod is located at a position retracted into the mounting hole with respect to a tip-side end surface of the valve plate, the first plate portion of the coupling plate is fixed to the tip-side end surface of the valve plate with a screw and the second plate portion is fixed to the tip end surface of the valve plate mounting portion with a screw, so that the valve plate is pressed toward the base end side of the valve plate mounting portion.

11. The gate valve according to claim 10 , wherein the coupling plate includes a press-contact mechanism configured to press the valve plate in the direction in which the joint flat surfaces of the valve plate and the valve rod are brought into press-contact with each other.

12. The gate valve according to claim 11 , wherein the press-contact mechanism includes an inclined portion which comes into abutment with an end portion of the valve plate mounting portion of the valve rod at an end portion of the second plate portion, and the inclined portion generates a component force in the direction in which the joint flat surfaces of the valve plate and the valve rod are brought into press-contact with each other.

13. The gate valve according to claim 12 , wherein an inclined portion parallel to the inclined portion is formed at the end portion of the valve plate mounting portion with which the inclined portion of the second plate portion comes into abutment.

14. The gate valve according to claim 12 , wherein an insertion hole formed on the second plate portion of the coupling plate has a dimensional allowance absorbing a relative displacement between the second plate portions and the valve rod when fixing the second plate portions to the valve rod with the screw.

15. The gate valve according to claim 11 , wherein the press-contact mechanism includes a freely bendable resilient bent portion formed at an intermediate portion of the second plate portion and a tip end engaging portion formed at a tip end portion of the second plate portion to engage the valve rod and the resilient bent portion is expanded when the second plate portion is fixed to the valve rod with a screw, whereby the joint flat surface of the valve plate and the valve rod are brought into press-contact with each other.

16. The gate valve according to claim 15 , wherein an insertion hole formed on the second plate portion of the coupling plate has a dimensional allowance absorbing a relative displacement between the second plate portions and the valve rod when fixing the second plate portions to the valve rod with the screw.