Partition forming a draft-free fire barrier; and a draft-free fire barrier; and, further, methods of their operation

This invention relates to a fire barrier which includes a functional combination of at least one single-panel casement panel and a sliding panel which is connected or adjacent to it. The sliding panel, which can be automatically moved horizontally during normal operation, contains an auxiliary drive mechanism which, in an emergency, moves the sliding panel without an outside power source into the open position. The casement panel is moved simultaneously by a closing mechanism from its fixed or open position into the correct closed position to create or act as a barrier.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This present invention relates generally to a draft-free fire barrier and a 
partition that is openable and closable in the event of a fire to permit 
persons to exit an area containing a fire while still forming a draft-free 
fire barrier, in which the rotationally mounted panels or leaves or wings 
are attached to a frame or casing by means of fasteners or hinges. A 
closing mechanism which works without outside energy is attached to the 
frame around the panels and interacts with the panels, causing the panels 
to move from an open position into a closed position, thus creating a fire 
barrier or acting as a fire barrier. The closing mechanism is actuated 
when a warning signal indicating the possibility of fire in the area 
reaches the mechanism from a smoke detector. The present invention further 
relates to a method for the operation of the partition. 
2. Background Information 
Such partitions are installed in particular in public buildings, hospitals, 
hotels, factories, etc., so that when a fire breaks out, persons inside 
the building have a means of escape that also serves as a barrier to 
prevent the fire from spreading to other parts of the building. Buildings 
are divided into individual fire compartments which are separated by fire 
walls. These fire walls effectively seal one building compartment from 
another, so that any fire that breaks out in one area will not spread to 
another. Movable partitions are therefore a necessity because it would be 
impossible to seal a compartment against fire yet allow the free movement 
of occupants in and out of the room. Such partitions must then 
simultaneously meet two requirements; i.e. they must close automatically 
when a fire breaks out to complete a fire wall, and simultaneously allow 
any persons who may still be in the room at the time to leave the room 
unharmed. Therefore such partitions are located in the escape routes to 
create a safe fire-proof passage for building occupants while preventing 
the spread of fire from the room. 
Repeated attempts have been made to equip automatic sliding doors so that 
they can also be used as fire barriers or to create a fire barrier, yet 
still be permissible for use in escape routes. Building authorities and 
building regulations set very strict guidelines for the construction and 
operation of sliding doors, and current sliding doors do not fit the 
requirements to be used in fire escape routes. In the event of a fire, the 
barrier or partition, by rule, must automatically close to seal off an 
area and prevent the fire from spreading. Sliding doors can accomplish 
this task quite easily, but fail to accomplish the other requirement of 
being able to be opened by persons inside the area. Building occupants 
would therefore be trapped inside because sliding doors have neither 
handles with which a person could grasp to force open the partition, nor a 
functioning automatic opening mechanism since the power to the opening 
mechanism would have been turned off. If a person were to be able to pry 
the sliding doors open, this would create a situation where the doors 
would remain open and the fire-wall would be compromised. Therefore, 
sliding doors, as they are currently constructed and without any 
additional measures or features, cannot be used as fire barriers and 
certainly cannot be used in escape routes or as escape passages. 
By way of example, a fire door which is equipped with a fire-protection 
door leaf is described in German Patent No. 195 22 366 A1. The fire door 
described in this prior art document is made of wood, although door panels 
made of steel and filled with a suitable material such as light alloy or 
glass are also used in the form of framed doors and are generally realized 
with a glass filling when they are used as fire doors. 
Because such doors which are realized in the form of casement doors, i.e. 
the door leaf is fastened to a casing so that the door panel can swing, 
are normally left open to permit the flow of people and goods to pass 
unimpeded, such doors are equipped with a smoke detector which triggers an 
alarm and, among other things, with electric door retaining and closing 
devices, as disclosed in German Patent No. 25 31 314 A1. This type of door 
is equipped with a closing mechanism which works without outside energy. 
The door closers in question can be both top-mounted door closers and 
floor-mounted door closers. If the door in question is a two-panel door, 
there is also a closing sequence control device which guarantees that with 
door panels which generally overlap, first the fixed panel, i.e. the panel 
which is normally closed, and only then the moving panels are moved into 
the proper closed position. The electrical retaining devices make it 
possible to keep the door panels in the open position, and only when a 
fire alarm is emitted by means of the smoke detector are these door panels 
then moved into the proper closed position. 
As an alternative to the device described in the above referenced German 
Patent No. 25 31 314 A1, magnetic clamps can also be used, e.g. such as 
those which are described in the DORMA EM advertising brochure, as a 
precautionary fire protection measure. These magnetic door clamps 
simultaneously represent holding or retaining devices which hold the fire 
doors in the open position. When there is a risk of fire, the holding 
device is deactivated by a tripping device (smoke detector and control 
unit). 
The known art also discloses devices for the automatic closing of fire 
doors, on which sliding doors can be closed in response to the melting of 
an element as a result of elevated temperatures, because there are 
counterweights which move such a door into the closed position. 
An automatic sliding door with at least one door panel is described in 
German Patent No. 40 14 727 A1, whereby the sliding door is equipped with 
an additional auxiliary drive mechanism in addition to the standard drive 
mechanism. For the normal closing of the door panels, energy is fed to and 
stored in the auxiliary drive mechanism. In the event of a power failure 
or interruption of the line power, and/or in the event of a simultaneous 
interruption of the normal operation of the sliding door, this stored 
energy automatically opens the sliding door. The auxiliary drive mechanism 
thereby preferably consists of a rubber or elastic element which is 
stretched by the closing of the sliding panels and moves the panel(s) out 
of the closed position in the event of a power failure and a simultaneous 
and related separation of a coupling between the drive motor and the 
actuator device. In addition to the above-mentioned rubber element, other 
auxiliary drive mechanisms can also be used, e.g. in the form of 
compression or tension springs. 
OBJECT OF THE INVENTION 
An object of the invention is to create a partition which can also be 
operated automatically, i.e. in normal operation the partition is opened 
and closed automatically, and can be reliably closed even in the event of 
a fire, while still allowing people inside the building to pass through. 
Another object of the invention is to create a fire door which can also be 
operated automatically, i.e. in normal operation the door is opened and 
closed automatically, and can be reliably closed even in the event of a 
fire, while still allowing people inside the building to pass through. 
SUMMARY OF THE INVENTION 
The invention teaches that the objects can be accomplished by the use as a 
fire door of a combination which consists of a one-panel or two-panel 
casement or swinging or side-hung door which is certified for use as a 
fire door, and is simultaneously combined with an additional door which 
automatically moves horizontally, on which there is also an auxiliary 
drive mechanism which, in an emergency, moves the horizontally movable 
panel into the open position without outside energy. The horizontally 
movable door can be a sliding door or also a telescoping door, for 
example. 
The conventional fire doors, on which the panels are realized in the form 
of casement panels and are provided with a door retaining device, which 
can be connected to a closing mechanism, are triggered in response to a 
signal from a smoke detector by the retaining device when they are in the 
open and fixed or locked position, and are moved into the closing position 
by the closing mechanisms. The closing mechanism can, for example, be in 
the form of a door closer which can be realized in the form of a 
floor-mounted or a top-mounted door closer, or also in the form of an 
internal door closer which is installed inside the door panels. As has 
been demonstrated in practice, such fire doors are generally left in the 
open position so that they do not interfere with traffic. But to guarantee 
a draft-free environment for the persons in the area, it is desirable to 
close and open the passage automatically, without disregarding the fire 
protection requirements. Many architects have therefore long wished for 
such doors to be automated. For this reason, the present invention teaches 
the introduction of an additional door. To avoid any interference with the 
escape route, only horizontally movable doors are appropriate, because in 
an emergency, such a door must not block the escape route of the people 
leaving the building. For this reason, the automatically operating 
horizontally movable door, which is described below in the form of a 
sliding door, and which can be equipped with one or two panels, has an 
auxiliary drive mechanism, to which the necessary energy is supplied 
during the closing of the door panel. 
Although in this case two different types of doors, namely a casement door 
and a sliding door, are combined with one another to form a unit, such a 
system in its entirety must be considered a fire door. The casement panels 
of the outer door are realized in the form of a fire door, and the sliding 
door which is located inside the building is used for normal operation. 
The invention teaches that the sequence of operation of such a fire door is 
as follows: 
The smoke detector or sensor generates an alarm signal which is used to 
trigger the door retaining device, e.g. a magnetic clamp, or a device 
which is located inside a closing sequence control device. That means that 
the one-panel or multi-panel casement doors which were previously in the 
open position are moved into the normal closed position by the closing 
mechanisms to which they are connected. At the same time, however, the 
signal from the smoke detector de-energizes the drive mechanism of the 
sliding door which is normally operated automatically. The result is a 
separation by means of a coupling, such as an electric clutch, between the 
normal drive mechanism and the drive belt of the panels of the sliding 
door. Because during the closing of the sliding panel, energy is supplied 
to the auxiliary drive, which can be in the form of a rubber or 
elastomeric cable or a spring, for example, this auxiliary drive becomes 
active after the coupling has made the separation, and moves the sliding 
panel into the open position. It is thereby guaranteed that the escape 
route will remain open, whereby at the same time a fire compartment is 
closed so that as they move along the escape route, any persons who may 
still be inside the building can pass unhindered through the passage now 
left open by the horizontally movable door, and, by applying a force to 
the casement panels, they can open these panels in the direction of the 
escape route. After the people have passed through the casement door, this 
door closes automatically as a result of the closing mechanism to which it 
is connected. 
A fire door equipped in the manner described above is characterized on one 
hand by its compact size, and also by the fact that it can be retrofitted 
in existing buildings. This retrofitting can be done by suspending the 
door frame of the automatic horizontal door drive mechanism on the door 
structure above the casement doors, so that it then represents a unit with 
the specified type of control system for both doors. It is also possible 
to equip such doors with corresponding stationary side parts and transom 
lights or overhead lights. 
The above discussed embodiments of the present invention will be described 
further hereinbelow with reference to the accompanying figures. When the 
word "invention" is used in this specification, the word "invention" 
includes "inventions," that is, the plural of "invention." By stating 
"invention," the Applicants do not in any way admit that the present 
application does not include more than one patentably and non-obviously 
distinct invention, and maintains that this application may include more 
than one patentably and non-obviously distinct invention. The Applicants 
hereby assert that the disclosure of this application may include more 
than one invention, and, in the event that there is more than one 
invention, that these inventions may be patentable and non-obvious one 
with respect to the other.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The view shown in FIG. 4 can be considered to reflect the outside of a fire 
door, by way of example. The figure shows a system which is equipped with 
two casement panels 10 which are connected to a frame construction by 
means of fasteners 7. The casement panels 10 are framed laterally by 
stationary side parts 6 and transom lights 8 above them. The total passage 
width is thereby occupied by corresponding frame profiles 1, whereby glass 
panels 5 are inserted between the frame profiles 1. In the vicinity of the 
floor, there are base profiles 2, and above the casement panels 10 there 
are profiles 9. In this embodiment, the casement panels 10 are equipped 
with door closers 13 which, in the illustrated embodiment, are in the form 
of top-mounted door closers. It is also possible, however, to use 
floor-mounted door closers or spring hinges. On the profile 9, above the 
casement panels 10, there is also a closing sequence controller 12 which 
guarantees the correct closing position of the two folding casement panels 
10. A smoke detector 11 is also installed on the closing sequence 
controller 12. This smoke detector 11 can also be installed on the ceiling 
or in another exposed position. On the side frames 6, on or in the base 
profiles 2, there are retaining devices 3 which in this case are in the 
form of switchable electromagnets. The armature plates 4 which interact 
with the retaining devices 3 are each fastened to the casement panels 10. 
The retaining devices 3 can be de-energized either by manual actuation of 
the switch or by a corresponding signal from the smoke detector 11 which, 
if the casement panels 10 were previously being held in the open position, 
would mean that the casement panels 10 would then be moved into their 
normal closed position by the force of the door closers 13. 
In addition, FIG. 5 schematically illustrates one possible embodiment of 
the present invention including an example of electrical wiring 35 that 
acts as a connection between the smoke detector 11 and the retaining 
devices 3. A signal from the smoke detector 11 is transmitted through the 
wiring 35 and causes the retaining devices 3 to be de-energized and 
released from the armature plates 4, thus allowing the casement panels 10 
to move into the closed position. An exterior motion sensor 36 for 
activating the opening and closing of the sliding panels 19 is also 
illustrated. 
FIG. 1 shows only one casement panel 10 in the open position, in which the 
armature plate 4 is in contact with the retaining device 3, and the 
casement panel 10 is held in the open position by magnetic force. This 
illustration also shows the side piece 6 which is positively and 
non-positively connected to the profile 1 on a wall 14. 
FIG. 6 also shows one possible embodiment of the present invention 
including a manual actuation switch 37 and corresponding electrical wiring 
38. The actuation switch 37 represents a way by which building occupants 
can manually activate the release of the retaining device 3 in case of a 
failure of the smoke detector 11 to cause an automatic release. The wiring 
38 carries the signal from the actuation switch 37 to the retaining device 
3. FIG. 6 also shows wiring 35, as described in FIG. 5, from the retaining 
device 3 to the smoke detector 11 (not shown). 
The combination of the casement panel 10 described above with a door 18, on 
which the panels are realized in the form of sliding panels 19, is 
illustrated in FIG. 2. Between the floor 15 and the ceiling 16, the fire 
door is installed as illustrated in FIG. 4, whereby in this case, a frame 
17 of an automatic sliding door is mounted on the profile 9. The following 
description relates to this embodiment which includes a sliding door, 
although the description can also be applied analogously to a telescoping 
sliding door. The sliding door has a stationary side part 20 which is 
located behind the stationary side parts 6 of the casement panel doors 10. 
The movable sliding panel 19 is mounted by means of trucks 21, on which 
there are support rollers 22, so that the sliding panel can move inside 
the frame on a rail 33. The sliding panels 19 are driven by a drive belt 
29 by means of a drive disc 24 which is connected to a coupling (not 
shown) and a drive motor 23. The drive belt 29 is thereby guided inside 
the frame on the side opposite the motor 23 by means of a pulley 31. When 
people approach the sliding door, the door is moved into the open position 
by signals from a corresponding sensor, and is then automatically closed 
again. This closure represents a draft-free bulkhead between two rooms or 
between a room and an outdoor area. In addition to the drive belts 29, 
there is an auxiliary drive mechanism which can be in the form of a rubber 
element 30 which is fastened on one hand to the panel 19 and is reversed 
by means of a pulley 34, and on the other hand is fastened to the frame 17 
by means of a fastening point 32. The path of the rubber element 28 is 
illustrated in FIG. 3. 
The sensor signal from the smoke detector 11 therefore results in a closing 
of the casement panel 10 and simultaneously, as described above, an 
opening of the sliding panel 19. The result is a fire door which, when 
there is no fire, also represents a secure closing of the opening in the 
wall, and in the event of a fire, leaves the escape route open. 
FIG. 2 also shows that such a door 18, in this case a sliding door, can 
also be retrofitted on an existing fire door. The retrofitting 
significantly improves the ease of operation of such a system. Although 
FIG. 2 still shows a profile beam for the sliding door 18, as a result of 
the presence of the profile 9, the entire mechanism for the sliding can 
also be attached to the profile positively and non-positively. The 
invention teaches that it is possible to integrate a sliding door into a 
fire compartment. For that purpose, as shown in the embodiment illustrated 
in FIG. 4, it is not necessary to have stationary side pieces 6 or transom 
lights 8. 
FIG. 7 additionally illustrates electrical wiring 39 which carries the 
signal from the smoke detector 11 to the drive motor 23. In case of fire, 
the signal would cause the drive motor 23 to disengage and separate from 
the drive belt 29, thus allowing the auxiliary drive mechanism, which can 
be in the form of a rubber element 30, to engage and force the sliding 
panel 19 into the open position to provide a clear means of escape. 
FIG. 8 shows another possible embodiment with an interior motion sensor 40 
with wiring 41. This sensor 40 responds to the motion of approaching 
occupants and and transmits a signal through the wiring 41 to the drive 
motor 23, which causes the sliding panels 19 to open and close during 
normal operation. 
FIG. 9 illustrates schematically one possible embodiment including a 
switchable coupling 42. The switchable coupling can be realized, for 
example, in the form of an electromagnetic clutch. The switchable coupling 
connects the drive belt 29 to the drive motor 23. A signal from the smoke 
detector 11 can cause the drive motor 23 to disengage. A signal from the 
smoke detector 11 can activate or deactivate the switchable coupling 42. 
The disengaging of the drive motor 23 can also activate or deactivate the 
switchable coupling 42. The activation or deactivation of the switchable 
coupling 42 causes it to open, thus disengaging the drive belt 29 from the 
drive motor 23. The separation of the drive belt 29 from the drive motor 
23 allows the auxiliary drive mechanism to engage as described above in 
FIG. 7. 
One feature of the invention resides broadly in the fire door which has at 
least one casement panel which is rotationally mounted by means of 
fasteners or hinges, which casement panel is provided with a closing 
mechanism which works without outside energy and a door retaining device 
which can be actuated electrically by a smoke detector, which door 
retaining device, in the event of an emergency, effects a closing of the 
panel, characterized by the fact that the fire door consists of a 
functional combination of a single-panel and/or double-panel casement door 
10 and an automatic door 18 which moves horizontally and has at least one 
panel 19. 
Another feature of the invention resides broadly in the fire door 
characterized by the fact that the door 18 is a sliding door or 
telescoping door. 
Yet another feature of the invention resides broadly in the fire door 
characterized by the fact that the door 18 with its frame 17 is fastened 
to a profile 9 in the vicinity of the lintel of the casement door 10. 
Still another feature of the invention resides broadly in the fire door 
characterized by the fact that the fire door is installed in the escape 
route. 
A further feature of the invention resides broadly in the fire door 
characterized by the fact that the door 18 is provided with an auxiliary 
drive mechanism to which energy is fed during each closing movement of the 
sliding panel(s) 19 and in which the energy is stored, and when the 
coupling is de-energized, the energy of the auxiliary drive mechanism 
moves the sliding panel(s) 19 into the open position. 
Another feature of the invention resides broadly in the fire door 
characterized by the fact that the casement panel(s) 10 and the 
surrounding construction of the side piece 6 and transom light 8 are made 
of wood. 
Yet another feature of the invention resides broadly in the fire door 
characterized by the fact that the casement panel(s) 10 and the 
surrounding construction of the side piece 6 and transom light 8 are made 
of steel. 
Still another feature of the invention resides broadly in the fire door 
characterized by the fact that the casement panel(s) 10 and the 
surrounding construction consisting of the side piece 6 and transom light 
8 are made of light alloy metal. 
A further feature of the invention resides broadly in the fire door 
characterized by the fact that the casement panel(s) 10 and the 
surrounding construction consisting of the side piece 6 and the transom 
light 8 are made of glass. 
Another feature of the invention resides broadly in the method for the 
operation of a fire door characterized by the fact that in response to the 
alarm signal from the smoke detector 11, the retaining forces of the 
retaining device 3 for the stationary fixed casement panel(s) 10 are 
neutralized, and the casement panel(s) 10 are moved into the closed 
position by the energy stored in the closing mechanism 13, and 
simultaneously in response to the alarm signal from the smoke detector 11, 
the normal automatic drive of the horizontally movable door 18 is 
deactivated, and thus the energy of the auxiliary drive moves the sliding 
panel(s) 18 into the open position. 
This invention relates to a fire door in which the rotationally mounted 
panels or leaves or wings are attached to a frame or casing by means of 
fasteners or hinges, and interact with a closing mechanism which works 
without outside energy so that when a warning signal is emitted by a smoke 
detector, the door, which has its door panels in the open position, is 
moved into the closed position. The invention further relates to a method 
for the operation of a fire door. 
Such fire doors are installed in particular in public buildings, hospitals, 
hotels, factories, etc., so that when a fire breaks out, the fire can be 
prevented from spreading to other parts of the building. For that purpose, 
buildings are divided into individual fire compartments which are 
separated by fire walls. It is also necessary, however, to provide 
passages for people to move through these fire walls so that, in the event 
of a fire for example, people can leave the building as quickly as 
possible. Therefore, such fire doors must simultaneously meet two 
requirements; i.e. on one hand they must close automatically when a fire 
breaks out, but they must simultaneously allow any persons who may still 
be in the room at the time to leave the room unharmed. Therefore such fire 
doors are located in the escape routes. 
This invention relates to a fire door which consists of a functional 
combination of at least one single-panel casement door and a sliding door 
which is connected or adjacent to it. The sliding door, which can be 
automatically moved horizontally, contains an auxiliary drive mechanism 
which, in an emergency, moves the sliding door into the open position and 
simultaneously moves the casement door into the correct closed position. 
The components disclosed in the various publications, disclosed or 
incorporated by reference herein, may be used in the embodiments of the 
present invention, as well as, equivalents thereof. 
The appended drawings in their entirety, including all dimensions, 
proportions and/or shapes in at least one embodiment of the invention, are 
accurate and to scale and are hereby included by reference into this 
specification. 
All, or substantially all, of the components and methods of the various 
embodiments may be used with at least one embodiment or all of the 
embodiments, if more than one embodiment is described herein. 
All of the patents, patent applications and publications recited herein, 
and in the Declaration attached hereto, are hereby incorporated by 
reference as if set forth in their entirety herein. 
The corresponding foreign and international patent publication 
applications, namely, Federal Republic of Germany Patent Application No. 
196 51 947.0, filed on Dec. 16, 1996, having inventor Christian Hein, and 
DE-OS 196 51 947.0 and DE-PS 196 51 947.0 and International Application 
No. PCT/DE97/01759, filed on Aug. 16, 1997, as well as their published 
equivalents, and other equivalents or corresponding applications, if any, 
in corresponding cases in the Federal Republic of Germany and elsewhere, 
and the references cited in any of the documents cited herein, are hereby 
incorporated by reference as if set forth in their entirety herein. 
The details in the patents, patent applications and publications may be 
considered to be incorporable, at applicant's option, into the claims 
during prosecution as further limitations in the claims to patentably 
distinguish any amended claims from any applied prior art. 
Some examples of sliding doors which may possibly be utilized or adapted 
for use in the context of the invention may be disclosed in the following 
U.S. Pat. No. 5,383,304, issued on Jan. 1, 1995 to inventor Soley. 
Some examples of fire doors which may possibly be utilized or adapted for 
use in the context of the invention may be disclosed in the following U.S. 
Pat. No. 5,404,969, issued on Apr. 11, 1995 to inventor Hoefsloot; U.S. 
Pat. No. 5,380,053, issued on Jan. 10, 1995 to inventor Saino; U.S. Pat. 
No. 5,293,962, issued on Mar. 15, 1994 to inventor Pelvilain; U.S. Pat. 
No. 5,207,044, issued on May 4, 1993 to inventor LaSee; U.S. Pat. No. 
4,888,918, issued on Dec. 26, 1989 to inventors Green and Kreimer; and 
U.S. Pat. No. 4,799,349, issued on Jan. 24, 1989 to inventor Luckanuck. 
Some examples of door-operating mechanisms which may possibly be utilized 
or adapted for use in the context of the invention may be disclosed in the 
following U.S. Pat. No. 5,355,927, issued on Oct. 18, 1994 to inventor 
McKeon; U.S. Pat. No. 5,261,186, issued on Nov. 16, 1993 to inventor 
Saino; U.S. Pat. No. 5,082,316, issued on Jan. 21, 1992 to inventor 
Wardlaw; U.S. Pat. No. 5,072,973, issued on Dec. 17, 1991 to inventors 
Gudgel and Baker; and U.S. Pat. No. 5,044,680, issued on Sep. 3, 1991 to 
inventors Baker, Benson, and Gudgel. 
Some examples of smoke or fire detectors which may possibly be utilized or 
adapted for use in the context of the invention may be disclosed in the 
following U.S. Pat. No. 5,315,292, issued on May 24, 1994 to inventor 
Prior; U.S. Pat. No. 5,170,150, issued on Dec. 8, 1992 to inventors Austin 
and Ingrassia; and U.S. Pat. No. 5,053,754, issued on Oct. 1, 1991 to 
inventor Wong. 
Some examples of motion detectors or sensors which may possibly be utilized 
or adapted for use in the context of the invention may be disclosed in the 
following U.S. Pat. No. 5,196,826, issued on Mar. 23, 1993 to inventor 
Whiting; U.S. Pat. No. 5,142,152, issued on Jan. 2, 1991 to inventor 
Boiucaner; and U.S. Pat. No. 4,967,083, issued on Oct. 30, 1991 to 
inventors Kornbrekke and Boiucaner. 
Examples of electromagnetic clutches or couplings which may be incorporated 
in embodiments of the present invention, may be found in the following 
U.S. Pat. No. 5,396,976, issued Mar. 14, 1995 to Koitabashi; U.S. Pat. No. 
5,428,431, issued Jun. 27, 1995 to Abe et al.; and U.S. Pat. No. 
5,445,259, issued Aug. 30, 1993 to Nelson. 
Examples of electric motors which could be incorporated in embodiments of 
the present invention may be found in the following U.S. Pat. No. 
5,197,582, issued Mar. 30, 1993 to Cropley; U.S. Pat. No. 5,251,400 issued 
Oct. 12, 1993 to Schultze; U.S. Pat. No. 5,300,867 issued Apr. 5, 1994 to 
Brade et al.; U.S. Pat. No. 5,341,598, issued Aug. 30, 1994 to Reddy; and 
U.S. Pat. No. 5,374,791 issued Dec. 20, 1994 to LeMarchand. 
Examples of rotary couplings for doors which may be incorporated in 
embodiments of the present invention may be found in the following U.S. 
Pat. No. 5,386,885 issued on Feb. 2, 1995 to Bunzl et al., U.S. Pat. No. 
5,401,104, issued on Mar. 28, 1995 to Newton; U.S. Pat. No. 5,417,011, 
issued May 23, 1995 to Keszthelyi; U.S. Pat. No. 5,443,109, issued Aug. 
22, 1995 to Benthin; and U.S. Pat. No. 5,462,015, issued Jun. 1, 1994 to 
Murphy. 
Although only a few exemplary embodiments of this invention have been 
described in detail above, those skilled in the art will readily 
appreciate that many modifications are possible in the exemplary 
embodiments without materially departing from the novel teachings and 
advantages of this invention. Accordingly, all such modifications are 
intended to be included within the scope of this invention as defined in 
the following claims. In the claims, means-plus-function clause are 
intended to cover the structures described herein as performing the 
recited function and not only structural equivalents but also equivalent 
structures. 
The invention as described hereinabove in the context of the preferred 
embodiments is not to be taken as limited to all of the provided details 
thereof, since modifications and variations thereof may be made without 
departing from the spirit and scope of the invention.