Wafer container with latching mechanism for large diameter wafers
A wafer container with a latch mechanism that provides sealing for large wafer containers, such as for 450 mm wafers, accomplishes secure door closing and latching with reduced torque requirements for rotating the central rotatable cam plate. In various embodiments, a camming slot formed in the rotatable cammed plate is arcuate and defined by opposing cam surfaces which are selectively engaged by a cam follower, such as a roller, attached to a proximal end of a latch arm. The roller can include unitary axle portions that snap into the proximal end of the latch arm and is supported at both axial ends of the roller. The proximal end of the latch arm can include parallel extensions separated by a gap, and have guide in surfaces to deflect the extensions as the axle portions of the roller are forced into position thereby seating the roller at both axial ends.
1. A door latching mechanism for a wafer container, comprising:
a cammed plate including a first face, a second face opposite said first face, and an outer perimeter, said cammed plate being rotatable about a central axis that is substantially perpendicular to said first face and said second face, said cammed plate defining an arcuate camming slot that passes through said first face and said second face, said arcuate camming slot being bound by an inner perimeter having a first cam surface and a second cam surface, said second cam surface being opposite said first cam surface, wherein said first cam surface and said second cam surface define a first width and a second width, respectively, extending in a direction parallel to said central axis, said first width being greater than said second width;
a cam follower disposed within said camming slot, said cam follower being selectively engageable with said first cam surface and said second cam surface; and
a latch arm translatable along an actuation axis and including a proximal end having a first extension and a second extension, each extending in a direction parallel to said actuation axis, said first extension and said second extension extending over said outer perimeter of said cammed plate so that said first extension is adjacent said first face of said cammed plate and said second extension is adjacent said second face of said cammed plate, said cam follower being coupled to said first extension and said second extension,
wherein, when said cammed plate is rotated about said central axis in a first rotational direction, said first cam surface engages said cam follower to exert a force on said first extension and said second extension of said latch arm in a first translational direction along said actuation axis, and
wherein, when said cammed plate is rotated about said central axis in a second rotational direction that is opposite said first rotational direction, said second cam surface engages said cam follower to exert a force on said first extension and said second extension of said latch arm in second translational direction along said actuation axis, said second translational direction being opposite said first translational direction.
2. The door latching mechanism of claim 1 , wherein said first width of said first cam surface is at least two times wider and less than or equal to five times wider than said second width of said second cam surface.
3. The door latching mechanism of claim 1 , wherein said first width of said first cam surface is in a range of 4 mm to 12 mm inclusive, and said second width of said second cam surface is in a range of 1.5 mm to 3 mm inclusive.
4. The door latching mechanism of claim 1 , wherein said first width of said first cam surface is at least 1 mm wider and less than or equal to 5 mm wider than said second width of said second cam surface.
5. The door latching mechanism of claim 4 , wherein said first width of said first cam surface is about 3 mm wider than said second width of said second cam surface.
6. The door latching mechanism of claim 1 , wherein said cam follower comprises a roller that is rotatable about a rotational axis, the rotational axis being substantially parallel to said central axis.
7. The door latching mechanism of claim 6 , wherein:
said roller includes an engagement portion for selectively engaging one of said first cam surface and said second cam surface;
said arcuate camming slot is centered about an arcuate axis that lies on a rotation plane that is normal to said central axis, said arcuate camming slot defining a slot width dimension that is between said first cam surface and said second cam surface, said slot width dimension being normal to said arcuate axis on said rotation plane; and
said slot width is at least 0.25 mm greater than an outer diameter of said engagement portion of said roller and less than or equal to 1.3 times said outer diameter of said engagement portion.
8. The door latching mechanism of claim 7 , wherein said slot width less than or equal to 1.2 times said outer diameter of said engagement portion.
9. The door latching mechanism of claim 8 , wherein said slot width is less than or equal to 1.1 times said outer diameter of said engagement portion.
10. The door latching mechanism of claim 6 , wherein:
said roller includes a first face and a second face opposite said first face, said roller being rotatable about an axle, said axle having an axle diameter, said axle extending in a direction perpendicular to said first face of said roller and said second face of said roller, said roller including an engagement portion that extends radially outward from said rotational axis and having an outer diameter for engaging said first cam surface; and
said outer diameter of said engagement portion of said roller is at least 2 times greater and less than or equal to 5 times greater than said axle diameter.
11. The door latching mechanism of claim 10 , wherein said axle is in the range of 20% to 40% inclusive of the roller diameter.
12. The door latching mechanism of claim 1 , wherein a ridge extends from at least one of said first face and said second face of said cammed plate proximate said camming slot to extend said first cam surface in a direction parallel to said central axis.
13. The door latching mechanism of claim 1 , wherein said cam follower comprises a roller that is rotatable about a rotational axis, the rotational axis being substantially parallel to said central axis.
14. The door latching mechanism of claim 1 , wherein:
said roller includes a first face and a second face opposite said first face, said roller being rotatable about an axle, said axle having an axle diameter, said axle extending in a direction perpendicular to said first face of said roller and said second face of said roller, said roller including an engagement portion that extends radially outward from said rotational axis and having an outer diameter for engaging said first cam surface; and
said outer diameter of said engagement portion of said roller is at least 2 times greater and less than or equal to 5 times greater than said axle diameter.
15. The door latching mechanism of claim 14 , wherein said axle is in the range of 20% to 40% inclusive of the roller diameter.