Sliding doors typically move horizontally or vertically and parallel to the wall to which they are attached along a track system. In some applications, the door may move away from the wall on a track system once it has cleared the opening as in an overhead door or a vertical door that is tilted out from the wall. The door panel may be manually or automatically moved from its blocking position to an unblocking position. Some door openings may use multiple leaves to cover the opening. In horizontal applications, the leaves will move in opposite directions to clear the opening more quickly. In some instances, the amount of overhead track required to extend beyond the door opening is reduced by having the door panel vertically divided into a number of over-lapped, vertically-separated leaves that take up less horizontal space when moved to the unblocking position.
Cold storage lockers are often accessed through a door opening closed by a sliding door. The panels for this purpose are typically transparent vinyl sheets, minimally insulated flexible panels or foam filled rigid panels. The transparent vinyl sheets are selected to reduce the likelihood of damage to the door. In particular, such doors are used in an institutional (e.g., warehouse) setting wherein palletized cargo is moved in and out of a cold storage locker by forklift. Since this panel is transparent, it also allows forklift operators to see what is on the other side of the door before it is opened. Although providing damage resistance, these types of panels have a very low insulation value and are too flexible to provide an effective air seal between the environments on either side of the opening. Because of the properties of the material, the transparent vinyl sheets may develop a warp that prevents a good seal. Air pressure differentials will cause leakage due to the lack of a compressive seal between the door panels and the door frame. This will allow a significant amount of warm moist air to enter the cold storage locker and/or refrigerated air to be lost into an unrefrigerated space. Consequently, such door systems are less efficient to operate and can lead to ice accumulation in the cold storage locker.
Rigid door panels are often used, especially in the United States, in order to reduce the operating costs of a cold storage locker. The rigid panel provides a consistent surface to seal to the door frame. The thickness of the rigid door panel is selected to provide a specific amount of insulation. Since the panel is rigid, a constraint can be applied to the edges that are parallel to the direction of travel to seal the door against the gasket the full width of the panel perpendicular to the direction of travel. On a horizontal sliding door, the constraint is a floor-mounted device that presses against the door when it is closed. Typically, these devices are rollers that are bolted to the floor and, since they are rigidly mounted, they can be damaged or broken when the door is impacted and/or they cause damage to the panel during an impact. Elimination of the need for these items would reduce the amount of damage to a rigid panel during an impact. Rigid door panels do provide very good environmental separation; however, the panels become susceptible to differential air pressure defeating the air seal.
Vertical sliding doors, similar to the familiar residential garage door, are supported on both vertical sides. However, these doors can also suffer to a degree from a poor seal at the top lateral and/or bottom lateral edges, especially for a wide doorway. It would be desirable to also provide a way to urge these non-tracked edges into sealing contact with the door front.
Attempts have been made to provide a damage resistant door panel for a sliding door system that also provides sufficient insulation. Resilient door panels have been suggested which have sufficient thickness to insulate like a rigid door panel, but yield to a degree when impacted by a forklift. While the panel itself achieves a degree of insulation, the insulation capability of the overall door system suffers from poor sealing between panels and poor sealing between a panel and the door frame. The stiffness of each door panel is much less than that of a rigid panel so sealing across the full gasket width perpendicular to the direction of travel is very difficult.
Thus, approaches to seal the door known in rigid doors are not applicable. In U.S. Pat. No. 3,039,153, a shank is projected from the door frame that has a head that engages a medial slot in a plate attached to a sliding door panel. This binder assembly is disclosed as for maintaining a close seal for a fire door that slides close to the door frame. However, the binding assembly resides within the sealing area of the door frame and the door panel, forcing some spacing therebetween that must be overcome by other sealing components. Moreover, the binder assembly is incapable of overcoming any significant spacing of the door panel from the door frame. However, for a refrigerated door intended to translate quickly and to reduce damage due to impact, it is not desirable that the door panel necessarily translate closely to the door frame to allow engagement of such a binder assembly. Thus, such a planar binding assembly may not reliably engage upon door closure.
Consequently, a significant need exists for an improved sealing system for sliding doors that maintains a good air seal to the door frame. It would be desirable in some instances that the improved sealing system be releasable and easily resets. This will minimize damage of rigid panels and will improve the seal of flexible panels.