Many industrial and specialized facilities utilize rooms or chambers where specific environmental conditions must be closely maintained. For example, hospital surgical rooms require a sterile environment. Semi-conductor wafer fabrication facilities need to maintain clean rooms. Industrial facilities require certain temperatures which must be maintained for certain processes or to prevent product deterioration.
In all of these situations, there must be entry and exit facilities. Typically, such entry and exit facilities include doors for both vehicular and foot traffic.
Such doors are designed to swing open by pushing an object such as a forklift, gurney, or a person's hand against the door. The door must have means for being returned to the closed position without further attention.
A typical prior art approach includes a door hinge having a V-shaped cam with the apex of the "V" centered at the closed position. A follower mounted on the door rests on the V-shaped cam so that, when the door is pushed open, the follower rides up the V. When the force applied against the door is removed, gravity causes the follower to ride back down the V, thereby shutting the door.
A readily apparent disadvantage of this type of door assembly is that the door undergoes vertical motion equivalent to the rise of the cam. If the door is to be sealed, the use of a large gasket seal at the top and bottom of the doors is required. The weight of such a door rests directly on the cam and follower, rather than on a bearing which would allow for smoother and more even operation of the door.
Presently known prior art includes the following:
U.S. Pat. No. 4,080,374 to Brown PA0 U.S. Pat. No. 4,045,913 to Wright PA0 U.S. Pat. No. 1,408,302 to Kelly PA0 U.S. Pat. No. 3,059,298 to Baruch, et al. PA0 U.S. Pat. No. 1,578,328 to Lessing PA0 U.S. Pat. No. 1,556,091 to Edwards PA0 U.S. Pat. No. 2,718,026 to Slopa, et al. PA0 U.S. Pat. No. 2,747,238 to Jones, et al. PA0 U.S. Pat. No. 3,160,913 to Carey PA0 U.S. Pat. No. 1,056,171 to Henrey PA0 U.S. Pat. No. 923,400 to Ahlvin