Mold platen, mold clamping device, injection molding device

1. A mold platen, comprising:

a mold plate to which a mold is attached;

a rear-surface plate provided opposite to the mold plate;

coupling portions configured to be coupled to respective tie rods at four corners of the mold plate and the rear-surface plate;

a cylindrical rib that is provided between the mold plate and the rear-surface plate and is located at a center part of the mold plate and the rear-surface plate;

a diagonal reinforcing rib that is provided between the mold plate and the rear-surface plate and is configured to connect the cylindrical rib and each of the coupling portions; and

a longitudinal/lateral reinforcing rib that is provided between the mold plate and the rear-surface plate and extends from the cylindrical rib toward a position between the adjacent coupling portions, wherein

a dimension L 2 of a part of the longitudinal/lateral reinforcing rib connected with the rear-surface plate is equal to or lower than 1/2 of a dimension L 1 of a part of the longitudinal/lateral reinforcing rib connected with the mold plate, or the longitudinal/lateral reinforcing rib is connected with the mold plate and the cylindrical rib but is not connected with the rear-surface plate.

2. The mold platen according to claim 1 , wherein the longitudinal/lateral reinforcing rib is smaller in thickness than the diagonal reinforcing rib.

3. The mold platen according to claim 2 , wherein the longitudinal/lateral reinforcing rib has a constant thickness from the mold plate side toward the rear-surface plate side or has a thickness reduced from the mold plate side toward the rear-surface plate side.

4. The mold platen according to claim 2 , wherein the longitudinal/lateral reinforcing rib has a constant thickness in a direction away from the cylindrical rib or has a thickness which becomes thinner with increasing distance from the cylindrical rib.

5. The mold platen according to claim 1 , wherein the longitudinal/lateral reinforcing rib is provided along a first direction of the mold platen, or is provided along the first direction of the mold platen and a direction orthogonal to the first direction.

6. The mold platen according to claim 1 , further comprising an outer peripheral reinforcing rib that is provided between the mold plate and the rear-surface plate and between the coupling portions adjacent to each other along outer peripheries of the mold plate and the rear-surface plate, wherein

the outer peripheral reinforcing rib includes an opening asymmetrical with respect to a center line between the mold plate and the rear-surface plate.

7. The mold platen according to claim 6 , wherein the opening is provided to make rigidity of the mold plate higher than rigidity of the rear-surface plate.

8. The mold platen according to claim 1 , wherein a dimension L and the dimensions L 1 and L 2 satisfy the following expressions:

L/ 2≤ L 1≤ L ; and

0≤ L 2≤ L/ 2,

where L is a dimension from an outer periphery of the cylindrical rib to an outer periphery of the mold plate along a diameter direction on outside of the cylindrical rib in the diameter direction.

9. A mold clamping device, comprising:

paired mold platens to which a mold is attached; and

a mold platen driving unit configured to move at least one of the paired mold platens forward and backward relative to the other mold platen to open/close the mold, wherein

one or both of the paired mold platens are each the mold platen according to claim 1 .

10. An injection molding device, comprising:

paired mold platens to which a mold is attached;

a mold platen driving unit configured to move at least one of the paired mold platens forward and backward relative to the other mold platen to open/close the mold; and

an injection cylinder configured to inject a molding material into a cavity of the mold, wherein

one or both of the paired mold platens are each the mold platen according to claim 1 .