Dual safety-edge for an overhead door

Details Dual safety-edge for an overhead door Dual safety-edge for an overhead door

2001-08-06

2002-08-06

Redman, Jerry (Department: 3634)

Movable or removable closures

Safety means responsive to obstruction to closure

Sensing shoe on leading edge

Reexamination Certificate

active

06427382

ABSTRACT:

TECHNICAL FIELD
The invention relates to industrial doors, in particular overhead industrial doors with closure safety mechanisms.
BACKGROUND OF THE INVENTION
Overhead doors have been used for many years to secure various enclosures including manufacturing plants, warehouses, garages, and other industrial doorways. It is well known in the art to provide a safety device on the leading edge of these doors to minimize both damage to the doors and potential injury to users when the door is closing. Such safety devices are generally coupled to a door controller. If the safety device encounters an impact, a signal is transmitted to the controller. The signal causes the door to act in a prescribed manner. For example, the controller may cause the door to stop or reverse direction. It is desirable to provide a safety edge that provides multi-directional sensitivity and allows for some degree of door over-travel.
Typically, safety edges of the type found in U.S. Pat. No. 3,462,885 to Miller are employed. In particular, the safety edge in the '885 Miller patent is comprised of a resiliently compressible structure. The resilient structure includes a pair of flexible contact strips which are electrically connected to a motor. Upon deflection of the resilient structure, the contact strips engage one another and transmit an electrical signal to the motor, resulting in stoppage or reversal of the door. Alternatively, pneumatically actuated safety edges may be employed. Pneumatically actuated safety edges consist of fluid-filled chambers which are coupled to pressure sensors. The pressure sensors are responsive to pulses or changes in fluid pressure within a chamber. While both of these safety edges assist in preventing damage to the door and provide some degree of safety to the users, there exist inherent limitations in both systems.
Specifically, safety edges such as those found in the '885 Miller patent are less sensitive to impact applied perpendicular to the door body than pneumatically actuated safety edges. Furthermore, safety edges such as those in the '885 Miller patent tend to allow for only minimal door over-travel. Pneumatically actuated safety edges, on the other hand, tend to be more sensitive to impact in multiple directions. However, like the safety edges described above, conventional pneumatically actuated safety edges typically allow for limited door over-travel.
To provide a degree of over-travel, the pneumatic chamber of such a safety edge would have to be particularly large. By increasing the size of the pneumatic chamber, however, the sensitivity of the safety edge would decrease as the safety edge would require a greater impact to actuate the safety feature. Alternatively, some degree of over-travel can be obtained by attaching multiple sensors one to the other. Such a system is shown in U.S. Pat. No. 5,921,026 to Miller. The '026 Miller patent employs an adjustable height sensing edge, wherein sensors are attached one to another in order to compensate for varying door heights. The system disclosed in the '026 Miller patent, however, requires multiple connectable sensors which result in increased manufacturing costs. Moreover, there exists the possibility of failure of the connecting members used to connect the sensors of the '026 Miller patent. Accordingly, the edge in the '026 Miller patent could also result in increased maintenance and replacement, as well costs associated with such maintenance and repair.
While the safety edges discussed above have been met with a reasonable degree of success, the present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior doors of this type.
SUMMARY OF THE INVENTION
The present invention provides a safety edge for a door assembly having a door body with a bottom edge.
According to one aspect of the present invention, the safety edge is an extrudate extruded from a deformable material. The extrudate comprises a first and second chamber formed in integrated cooperative redundancy in the extrudate. The first chamber comprises a first sensor body and the second chamber comprises a second sensor body. Each sensor body is responsive to an impact.
According to another aspect of the present invention, the second sensor body is sufficiently rigid to absorb impact parallel to the safety edge without causing complete deformation of the second chamber, but sufficiently deformable to actuate the second pressure sensor upon receiving an impact perpendicular to the second sensor body.
According to yet another aspect of the present invention, a door assembly is provided in which one of the sensor bodies has a greater sensitivity to impact perpendicular to the sensor body. Likewise, the other of the sensor bodies has a greater sensitivity to impact parallel to the sensor body than the first sensor body.
According to still another aspect of the present invention, the type of the first sensor body with respect to the type of the second sensor body results in one of the sensor bodies having a greater sensitivity than the other sensor body.
Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and detailed description of the invention.


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