Industrial door system responsive to an impact

Abstract
An impact sensing system for a powered roll-up door combines an electrical switch and a breakaway coupling. To avoid damage or injury resulting from the door's roll-up curtain accidentally closing upon an obstacle or something striking the curtain, the breakaway coupling responds to such a collision by breaking away, which releases a lower portion of the curtain from between its two vertical guide tracks. Each breakaway coupling includes a set of electrical contacts that make or break in response to the coupling breaking away. When the curtain's lower portion becomes effectively derailed from its guide track, the electrical contacts disable continued operation of the door to prevent the door's drive motor from jamming the curtain. In some embodiments, the breakaway coupling is releasably held together by way of magnetic attraction between two coupling segments, with one electrical contact on each segment to comprise one set of functional contacts.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The subject invention generally pertains to industrial doors having a pliable door curtain, and more specifically to a system responsive to a door impact.




2. Description of Related Art




Industrial doors in which the door itself is made of pliable material such as fabric are used in a variety of applications, typically for the purpose of separating areas within a building, or closing off building doorways that lead outside. Examples of such pliable doors are planar doors, overhead-storing doors, concertina doors and roll-up doors. Planar doors include frame members on which the fabric comprising the door is disposed. This plane of material is then movable between a doorway blocking position and a storage position, wherein the plane of material and associated frame members are disposed above the doorway. The frame typically includes extensions extending past either side of the door, and which are receivable within guide tracks to guide the door through its vertical movement. These extensions may include wheels or trolleys. An overhead-storing door is similar in that the fabric door is maintained on frame members and is movable between doorway blocking and storage positions. In this door, however, the storage position is overhead, as in a typical garage door. Accordingly, the guide members associated with such a door will curve between the vertical and horizontal. A concertina door includes a fabric panel supported by spaced-apart ribs or stays that are guided for movement along a track. As the ribs travel along the track, the fabric panel folds and unfolds between the ribs to respectively open and close the door. A typical roll-up door comprises a roll-up panel or fabric curtain that is wound about a roller journalled for rotation above the doorway. To close the door, the roller pays out the curtain as two vertical tracks disposed along either side edge of the doorway guide the side edges of the curtain generally along a vertical plane across the doorway. The rotation of the roller is reversed to open the door. Roll-up doors are typically either powered open and closed, or are powered open and allowed to fall closed by gravity. As the invention herein is envisioned for use primarily with roll-up doors, it will be described with reference thereto. However, the invention may also be used in combination with other such pliable industrial doors.




Some roll-up doors have a rigid leading edge provided by a rigid or semi-rigid bar disposed along a lower portion of the curtain. The rigidity of the bar helps keep the curtain within the side tracks and helps the curtain resist wind and other air pressure differentials that may develop across opposite sides of the door.




Other roll-up doors, however, have a curtain with a relatively soft leading edge. To help keep such a curtain within its guide tracks, as well as keep the curtain taut and square to the doorway, opposite ends of the bottom portion of the curtain can be held in tension by two opposing carriages or trolleys that are constrained to travel along the tracks: one in each track. However, the door's lower leading edge does not necessarily have to be held in tension, especially when the door is not subject to significant pressure differentials.




Industrial doors are commonly installed in warehouses, where the doors are very susceptible to being struck by forklifts or other vehicles. To protect the door and the vehicle from damage and to protect personnel in the vicinity of the collision from injury, often some type of breakaway or compliant feature is added to the door. For a door having a rigid reinforcing bar along its leading edge, the bar may be provided with sufficient flexibility and resilience to safely pop out of its track when struck. Alternatively, a hard edge door may have its bottom bar connected at either end to carriages engageable with the tracks such that the bottom bar breaks away from the carriages for an impact. Doors having a relatively soft leading edge may have sufficient flexibility to absorb an impact, or a bottom portion of the door's curtain can be coupled to its two guide carriages by way of a breakaway coupling. The coupling releases the curtain from the carriage upon being subjected to a predetermined breakaway force, thereby limiting the impact force to a predetermined safe level. More information on break away couplings can be found in U.S. Pat. No. 5,638,883, which is specifically incorporated by reference herein.




A collision can also occur when a door accidentally closes upon an obstacle in its path, such as an object or a person. To protect the door and obstacle from damage or injury, often some type of switch is installed generally along the lower portion of the door to detect when an obstacle has been encountered. An example of such a switch would be an elongated bumper switch, tape-switch or some other elongated switch extending along the lower, leading edge of the roll-up panel. In reaction to sensing the obstacle upon impact, a set of electrical contacts of the switch typically close to stop or reverse the motor that drives roller.




However, switches are impractical for use on a door having a relatively soft leading edge, because the normal flexing of the door curtain could trip the switch prematurely. This can happen regardless of whether the soft leading edge of the curtain is held taut or left relatively loose. Therefore, some doors with a soft leading edge instead include a switch with closed biased contacts that are held open by the tension in the leading edge of the curtain. When an impact forces the leading edge of the curtain to break away from its guide tracks, the resulting release of tension within the curtain allows the switch's contacts to close, The closed contacts provide a signal that can be conveyed to the door's control circuit or an alarm circuit by way of a wire or battery powered radio transmission. Alternatively, a sensing mechanism may be associated with the guide carriages or trolleys associated with the soft edge. This sensing mechanism has a first state when the breakaway connection to the leading edge is intact, and a second state upon breakaway. This change to this second state is detected to stop or reverse the door.




In hard edged doors with a tape switch or other elongated switch, such elongated switches are typically inserted into a sheath attached to the curtain or incorporated within the curtain itself to allow a more durable or suitable sealing member to be installed just below the switch. This allows the very bottom or leading edge of the roll-up panel to be provided with a more compliant sealing material that can effectively conform to seal against the floor beneath the doorway when the door is closed. However, installing switches in such a manner, makes them rather inaccessible for servicing. Serviceability is particularly important, as the switch itself, being disposed along the lower portion of the roll-up panel, places the switch's electrical contacts and other electrical parts in a vulnerable position where they are subject to repeated impacts that could eventually damage the switch.




Further, when such a switch is used on a door having a breakaway coupling, wiring connecting the switch to a terminal associated with the motor's control needs to accommodate the separation of the coupling. That is often accomplished by running a separate coiled wire (i.e., multi-conductor cable) along the outside of the track and extending the wire from the terminal to the switch. Such a wire is usually coiled so it can stretch to accommodate the up and down motion of the door panel as well as the motion of the panel upon breaking away from its carriage. However, an exposed coiled wire can be unsightly, especially when it becomes permanently stretched out from use and begins to sag. As the wire sags, it becomes prone to snagging adjacent parts of the door or other items nearby.




SUMMARY OF THE INVENTION




In order to more effectively synthesize a safety switch with a breakaway coupling of a roll-up door, there is provided a breakaway coupling that includes at least one electrical contact that remains coupled to a guide carriage of the door even after the coupling disengages the door's roll-up panel from the carriage.




This eliminates the need for externally running a separate coiled or otherwise flexible wire out to the roll-up panel.




It also positions the electrical contacts of the switch at a more serviceable location and at a location that is beyond the impact-vulnerable central portion of the roll-up panel's leading edge.




In some embodiments, the electrical contacts of the switch are an integral part of the breakaway coupling itself, which is relatively more rugged than the small delicate electrical contacts of a conventional electrical switch.




By integrating a safety switch with an omni-directional breakaway coupling, the switch also becomes omni-directional in that it is responsive to an impact from any direction.




There is also provided an impact detection system wherein the sensing circuit includes a conductor that extends across the width of the doorway. For normal door operation, the conductor conducts electricity as part of the sensing circuit. For an impact, however, the conductor is no longer a conductive part of the circuit. This change can be detected and interpreted as an impact having occurred.




There is also provided a breakaway coupling wherein a member associated with a door guide track (e.g., a trolley or guide carriage) and a conductor are in electrical, conductive contact for normal door operation, and are not in conductive contact for a breakaway condition.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a front view of one embodiment with a cut-away portion showing a breakaway coupling.





FIG. 2

is a cross-sectional top view taken along line


2





2


of

FIG. 1

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 3

is the same view as

FIG. 1

, but with one of the breakaway couplings disengaged.





FIG. 4

is a cross-sectional top view taken along line


4





4


of

FIG. 3

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 5

is a front view of another embodiment with a cut-away portion showing a breakaway coupling.





FIG. 6

is a cross-sectional top view taken along line


6





6


of

FIG. 5

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 7

is the same view as

FIG. 5

, but with one of the breakaway couplings disengaged.





FIG. 8

is a cross-sectional top view taken along line


8





8


of

FIG. 7

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 9

is a front view of another embodiment with a cut-away portion showing a breakaway coupling.





FIG. 10

is a cross-sectional top view taken along line


10





10


of

FIG. 9

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 11

is the same view as

FIG. 9

, but with both of the breakaway couplings disengaged.





FIG. 12

is a cross-sectional top view taken along line


12





12


of

FIG. 11

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 13

is a front view of another embodiment with a cut-away portion showing a breakaway coupling.





FIG. 14

is a cross-sectional top view taken along line


14





14


of

FIG. 13

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 15

is the same view as

FIG. 13

, but with one of the breakaway couplings disengaged.





FIG. 16

is a cross-sectional top view taken along line


16





16


of

FIG. 15

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 17

is a front view of another embodiment with a cut-away portion showing a breakaway coupling.





FIG. 18

is a cross-sectional top view taken along line


18





18


of

FIG. 17

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 19

is the same view as

FIG. 17

, but with one of the breakaway couplings disengaged.





FIG. 20

is a cross-sectional top view taken along line


20





20


of

FIG. 19

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 21

is a front view of another embodiment with a cut-away portion showing a breakaway coupling.





FIG. 22

is a cross-sectional top view taken along line


22





22


of

FIG. 21

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity.





FIG. 23

is the same view as

FIG. 21

, but with one of the breakaway couplings disengaged.





FIG. 24

is a cross-sectional top view taken along line


24





24


of

FIG. 23

, but with the roll-up panel and wiring leading to the breakaway coupling omitted for clarity. .











DESCRIPTION OF THE PREFERRED EMBODIMENT




To provide a more durable and readily accessible elongated switch for use along a lower portion of a roll-up door panel releasably held by a breakaway coupling, the embodiment of

FIGS. 1-4

detects electrical continuity through the coupling itself. Referring to

FIG. 1

, a roll-up door


10


includes a pair of vertically extending members such as vertical side frames


12


that supports a roller


14


upon which a flexible roll-up panel, such as a fabric curtain


16


, is wound and unwound to respectively open and close the door. In this example, a motor drive unit


18


drives roller


14


to feed panel


16


up and down as vertical slits


20


in frame


12


guide side edges


22


of curtain


16


generally along a vertical plane across the doorway. A lower portion


24


of curtain


16


includes a compliant sealing member


26


at the very bottom or leading edge


28


of the curtain to ensure that the curtain seals against the floor when door


10


is closed.




To help keep curtain


16


within slits


20


, as well as help keep curtain


16


taut and square to the doorway under normal operation, and yet still release curtain


16


in the event of a collision, two breakaway couplings


32


releasably couple opposite ends


34


and


36


of lower portion


24


to two opposing carriages


38


or trolleys. In its broadest sense, only one breakaway coupling


32


is needed, but two is preferred. In some embodiments, curtain


16


is kept relatively taut by couplings


32


pulling an elongated member


56


, such as a steel cable, in tension. Other examples of elongated member


56


include, but are not limited to, a fabric strap or an integral fabric portion of curtain


16


itself. However, it should be noted that if desired, the leading edge of curtain


16


could be left relatively loose by not applying tension to member


56


. In such a case, member


56


would first be forced into tension by exertion of an external force upon the door as could by created by a collision.




To protect a door in the event of a collision, a breakaway feature can be provided by a variety of structures. For example, in this exemplary embodiment, breakaway couplings


32


are attached to first members such as carriages


38


that include rollers


40


attached to a bracket


42


. Rollers


40


and bracket


42


conform to the shape of frame


12


(see

FIG. 2

) to constrain carriage


38


to travel along tracks


44


, as door


10


opens and closes. In this example, tracks


44


are provided by the contour of frames


12


. Each breakaway coupling


32


includes an inner coupling member


46


that releasably engages an outer coupling member


48


to provide a breakaway connection therebetween. Under normal door operation, couplings


32


remain intact, i.e., their coupling members


46


and


48


remain connected to each other and move together. However, in the event of a collision creating a force sufficient to disconnect either breakaway coupling


32


, allowing independent relative movement between the members, the resulting separation of coupling members


46


and


48


protects the rest of the door (especially curtains


16


) from damage. A disconnectable coupling or breakaway connection can be provided by any one of a wide variety of available mechanisms including, but not limited to, various fittings that mechanically snap together and apart. However, in some preferred embodiments, the disconnectable joint is provided by magnetic attraction between coupling members


46


and


48


. Of course, breakaway couplings may also be provided between trolleys and the rigid bars associated with hard edge doors. The teachings herein are intended to apply to such hard edge doors as well as the soft edge doors specifically described.




In this example, each outer coupling member


48


includes a magnet


50


, while each inner coupling member


46


is of a material that is attracted to magnet


50


(e.g., a ferromagnetic material, such as iron or an iron alloy). Magnet


50


is pivotally connected to bracket


42


by way of a hinge


52


that includes a torsional spring


54


that biases the position of magnet


50


generally away from the center of the doorway and towards side frame


12


. A similar arrangement is provided at both the right and left side of the doorway. Elongated member


56


connects the two inner coupling members


46


to each other. In this example, the elongated member is a conductor in the form of an electrically conductive steel cable


56


that runs through an elongated aperture


58


extending horizontally across curtain


16


.




Under normal operation, cable


56


is kept taut across the width of the doorway by a face


60


of each inner coupling member


46


being magnetically clamped to the magnet


50


of its respective outer coupling member


48


. However, when a collision occurs (i.e., the door strikes an obstacle or something strikes the door) that deflects cable


56


with sufficient force to overcome the magnetic attraction of either breakaway coupling


32


, the two halves of the coupling will separate, as shown near the left side of

FIGS. 3 and 4

. Note that outer coupling member


48


being restrained by side frame


12


enhances this action. When this occurs, usually part of the curtain pulls out of slit


20


as well. Also, for the magnet


50


that breaks away, the spring loaded hinge


52


urges the magnet to swing back and magnetically cling to the side of frame


12


, which prevents the disengaged trolley


38


from slamming to the floor. Further details of the construction, operation and various alternate embodiments of a magnetic breakaway coupling are disclosed in U.S. Pat. No. 5,638,883, which has already been incorporated by reference herein.




As outer coupling member


48


alternately engages and separates from inner coupling member


46


, their mating surfaces,


62


and


60


, respectively, can serve as electrical contacts of a switch, i.e., a device whose electrical conductivity changes in response to an action. The switch can be used to convey or interrupt an electrical signal in reaction to the breakaway coupling separating. The electrical signal, in turn, can be used to activate an alarm or inhibit continued normal operation of the door, until the separated coupling and the rest of the door are returned to normal, i.e., each coupling is connected and curtain


16


is properly within slits


20


. For the breakaway system of

FIGS. 1-4

, disabling the operation of door


10


can be carried out by any one of a variety of circuits. In

FIG. 1

, for example, an electrical power source


64


(e.g., 24 VAC) delivers current in series through a coil


66


of a relay


68


, a wire


70


, electrically conductive bracket


42


, electrically conductive hinge


52


, the left outer coupling member


48


(being electrically conductive itself), the left inner coupling member


46


(also being electrically conductive and while engaging magnet


50


), cable


56


(or a conductive wire parallel thereto in the case of a nonconductive elongated member), the right inner coupling member


46


, the right outer coupling member


48


(while engaging the right inner coupling member


46


), right hinge


52


, right bracket


42


and a wire


76


. Wire


76


leads back to power source


64


to complete a sensing circuit


78


when both breakaway couplings


32


are intact. The completed circuit energizes coil


66


to close relay contacts


80


to be used as desired. For example, in some embodiment, relay contacts


80


enable a motor control circuit


82


, such as a conventional reversing motor starter that controls the operation of motor


18


. When either coupling


32


breaks away, its corresponding coupling halves


46


and


48


, which in this example serve as electrical contacts, separate to interrupt the continuity of sensing circuit


78


. When this happens, coil


66


de-energizes to open relay contacts


80


, which in turn disables motor control circuit


82


to stop motor


18


. Stopping motor


18


avoids jamming the door and damaging curtain


16


by preventing roller


14


from attempting to forcibly raise or lower a curtain that is uncoupled from one or both of its carriages


38


. However, it should be appreciated by those skilled in the art, that sensing circuit


78


could be independent of the operation of motor control circuit


82


. For example, circuit


78


could be used simply to activate an audible or visual alarm, or increment a counter that indicates how often door


10


has been subjected to an impact that caused it to break away.




The system shown in

FIGS. 1-4

thus senses the exertion of a force above a predetermined magnitude on the curtain. To achieve this, sensing circuit


78


is included, and a conductor (cable


56


) forms a part of the circuit and extends across the width of the doorway. For normal door operation when no force above the predetermined magnitude is exerted thereon, the conductor is an electrically conductive part of the sensing circuit. When a force above the curtain magnitude is exerted on the curtain, however, the conductor no longer forms a conductive part of the circuit. Here, this is due to the fact that the coupling members separate, electrically isolating the conductor from the remainder of the circuit.




For the exemplary embodiment just described, it should be appreciated by those skilled in the art, that the wiring diagram of sensing circuit


78


and motor control


82


are schematically illustrated in

FIGS. 1 and 3

. Much of the circuit and curtain


16


are omitted in

FIGS. 2 and 4

to more clearly show other components of the breakaway system. In

FIGS. 1 and 3

, a simple loop


84


is shown to depict that wires


70


and


76


flex within a flexible cable carrier (e.g., a Model 06-10-028, of IGUS, Inc. from Providence, R.I.) disposed within frame


12


to follow the vertical movement of carriages


38


along tracks


44


. However, the actual path along which the wires are laid; the actual positions of the circuit components; and the actual location of where the wiring connects to the components, including carriage


38


and coupling


32


, can vary widely depending on personal preference and design details of the specific roll-up door to which the breakaway system is applied. In some embodiments, for example, cable


56


can be replaced by a non-conductive fabric strap with an electrical wire connected parallel thereto that electrically couples the two inner coupling members to each other.




In some embodiments, some components such as bracket


42


and hinge


52


are relied upon as electrical conductors in lieu of wires or jumpers, such as optional redundant jumper wires


72


and


74


. However, when doing so, some precautions need to be taken. For example, when bracket


42


is relied upon as an electrical conductor to complete sensing circuit


78


, bracket


42


should be electrically insulated from side frame


12


. This can be done by maintaining an air gap


86


between bracket


42


and frame


12


as shown in

FIGS. 2 and 4

, or by using various electrically resistive plastic bearing pads and rollers to keep the conductive parts of bracket


42


from contacting frame


12


(i.e., shorting out). Jumper wires


72


and


74


are shown as optional conductors to complete circuit


78


in an embodiment where bracket


42


and hinge


52


are not relied upon to conduct electrical current.




If desired, a circuit breaker or resettable fuse (e.g., a Model MF-R020, of Bourns, Inc. of Riverside Calif.) can be used to protect circuit


78


in the event of an electrical short or current overload. This is particularly important, as magnet


50


short circuits circuit


78


to a grounded frame


12


whenever coupling


32


associated with the magnet breaks away. It should be further noted that while the conductor in this embodiment, which extends across the width of the doorway and selectively either forms or does not form a conductive part of the sensing circuit, is carried on the door curtain, this need not be so. Rather, the conductor could extend across the width of the doorway at other locations and still perform its conducting/non-conducting function.




The embodiment of

FIGS. 5-8

is similar to the one just described, however, cable


56


is replaced by a two-conductor cable


88


. And each breakaway coupling


90


and


92


has two sets of electrical contacts for a total of eight contacts


94




a-h


with contacts


94




d


and


94




e


sharing a common node at magnet


50


. Contacts


94




a


and


94




h


are respectively provided by separate magnets


96


and


98


that are electrically conductive, but are insulated from hinge


52


and carriage


38


by way of a nonconductive shim


100


. Each inner coupling member


108


and


112


includes an electrically nonconductive core


101


that electrically separates its respective contacts


94




b


and


94




g


(coupling member


108


) and contacts


94




c


and


94




f


(coupling member


112


). This arrangement allows wires


102


and


104


to share a common cable carrier disposed inside just one side frame


12


(e.g., the left or right side of the doorway).




Referring to

FIG. 5

, under normal door operation, power source


64


delivers current in series through coil


66


, wire


104


, magnet


96


, a first contact


94




a


of a left outer coupling member


106


, a second contact


94




b


of a left inner coupling member


108


, a first wire


110


of cable


88


, a third contact


94




c


of a right inner coupling member


112


, a fourth contact


94




d


of a right outer coupling member


114


, magnet


50


, a fifth contact


94




e


, a sixth contact


94




f


, a second wire


116


of cable


88


, a seventh contact


94




g


of left inner coupling member


108


, magnet


98


, and wire


102


. Wire


102


leads back to power source


64


to complete a sensing circuit


119


when both breakaway couplings


90


and


92


are intact. The completed circuit energies coil


66


to close relay contacts


80


, which enable the operation of motor


18


to open or close the door.




When either coupling


90


or


92


breaks away in reaction to a collision, its corresponding coupling halves separate to interrupt the continuity of sensing circuit


119


. If coupling


92


on the right breaks away, as shown in

FIGS. 7 and 8

, contact


94




c


and


94




f


separate from the combined contacts


94




d


and


94




e


that are disposed on the face of magnet


50


. If coupling


90


on the left breaks away, contacts


94




a


and


94




b


separate, and so do contacts


94




g


and


94




h


. If either coupling


90


or


92


separates, the continuity of circuit


119


is interrupted to disable the operation of motor


82


, thus stopping the opening or closing of the door. The door is reset to normal operation by placing curtain


16


back into slits


20


and reconnecting the two halves of each breakaway coupling


90


and


92


that may have separated.




Although inner coupling halves


108


and


112


are shown connected to each other by cable


88


, in some embodiments, another elongated member such as a fabric strap or an integral portion of the door curtain itself extends across the width of curtain


16


and generally parallel to cable


88


to hold the two halves


108


and


112


together, which thus relieves the tension in wires


110


and


116


of cable


88


.




In a similar embodiment, shown in

FIGS. 9-12

, contacts


94




c,d,e,f


of

FIGS. 5 and 7

are replaced by an electrical switch


118


. Switch


118


is disposed on a right inner coupling member


120


of a breakaway coupling


122


and includes open biased contacts


124


and


126


that are held closed during normal operation of the door. Magnet


50


of outer coupling member


114


at the right side of the door magnetically clings to ferromagnetic blocks


128


that are on inner coupling member


120


. As magnet


50


magnetically clamps against blocks


128


, magnet


50


also depresses a switch actuator


130


that closes contacts


124


and


126


of switch


118


. When closed, contacts


124


and


126


provide electrical continuity between wires


110


and


116


. That continuity was previously provided by contacts


94




c, d, e, f


of the embodiment of

FIGS. 5-8

. When coupling


122


breaks away, as shown in

FIGS. 11 and 12

, actuator


130


returns to its normally extended position to open contacts


124


and


126


(i.e., break their continuity). This interrupts the current to relay


68


to activate an alarm, or disable motor


18


to stop the door.




The left breakaway coupling


90


of

FIGS. 9-12

is the same as the one in the embodiment of

FIGS. 5-8

. It might also be noted that in

FIGS. 11 and 12

, both breakaway couplings


90


and


122


are shown in their uncoupled state, as this could actually occur in some collisions.




In some applications, it might be beneficial to eliminate the need to extend an electrical conductor across the width of the door curtain. This is accomplished in the embodiment of

FIGS. 13-16

, wherein both breakaway couplings


131


are basically the same, and their outer coupling halves


106


are the same as the left outer one of

FIGS. 9-12

. Each outer coupling member


106


includes a pair of spaced-apart magnets


96


and


98


that are electrically insulated from the rest of the coupling member by way of electrically nonconductive shim


100


between hinge


52


and magnets


96


and


98


. Each pair of magnets


96


and


98


provide a corresponding pair of electrical contacts:


132


and


134


on the left and


136


and


138


on the right. Each pair of contacts are shorted out (i.e., electrically connected to each other) by an inner coupling member


46


, which is the same as those used in the embodiment of

FIGS. 1-4

. However, the two inner coupling halves


46


are connected to each other by an elongated member


140


that does not need to be electrically conductive, such as for example, a cable, strap, or an integral portion of the door curtain itself.




During normal door operation, power supply


64


delivers current in series through relay


68


, wire


104


, contacts


132


, left inner coupling member


46


, contacts


134


, a second wire


142


that leads up and over to the right breakaway coupling


131


, contacts


138


, right inner coupling member


46


, contacts


136


and wire


144


. Wire


144


leads back to power supply


64


to complete a sensing circuit


147


that energizes relay


68


to enable motor


18


to open or close the door.




When either of couplings


131


are forced to break away, the separation of an inner coupling member


46


from its corresponding outer coupling member


106


opens contacts


132


and


134


or


136


and


138


, accordingly. In the example shown in

FIGS. 15 and 16

, the left breakaway coupling


131


separates to interrupt the continuity of circuit


147


, which de-energizes relay


68


to disable the normal operation of the door. The door is returned to normal operation by placing curtain


16


back into slits


20


and reconnecting the two halves of the left breakaway coupling


131


.




Another breakaway system that eliminates the need for extending an electrical conductor across the width of the door curtain is shown in

FIG. 17-20

. In this example, switch


118


(described earlier in reference to

FIGS. 9-12

) is attached to each outer coupling member


148


of breakaway couplings


150


. Each switch


118


is disposed within or adjacent a magnet


152


with the switch's actuator


130


depressed by an inner coupling member


146


that is magnetically drawn up against magnet


152


, as shown in

FIGS. 17

and


18


. The two inner coupling halves


146


are connected to each other by elongated member


140


that does not need to be electrically conductive, such as for example, a cable, strap, or an integral portion of the door curtain itself.




During normal operation of the door, current from power supply


64


passes in series through relay


68


, a wire


154


, closed contacts


124


and


126


on the left breakaway coupling, a wire


156


, closed contacts


124


and


126


on the right breakaway coupling, and back to power supply


64


through a wire


158


to complete the continuity of a sensing circuit


160


. This energizes relay


68


to enable motor


18


to open or close the door.




When either of couplings


159


are forced to break away, the separation of an inner coupling member


146


from its corresponding outer coupling member


148


allows the switch actuator


130


associated with the separated coupling to open its contacts


124


and


126


. In the example shown in

FIGS. 19 and 20

, the left breakaway coupling


150


separates to interrupt the continuity of circuit


160


, which de-energizes relay


68


to disable the normal operation of the door. The door is returned to normal operation by placing curtain


16


back into slits


20


and reconnecting the two halves of the left breakaway coupling


150


.





FIGS. 21-24

illustrate another embodiment of a breakaway system that is very similar to the embodiment of

FIG. 17-20

. However, instead of switches


118


with normally open contacts held closed, the breakaway system employs switches


162


that have normally closed contacts. One switch


162


on a left breakaway coupling


164


has contacts


166


and


168


, and another switch


162


on the right breakaway coupling


164


has contacts


170


and


172


. Each breakaway coupling includes a magnet


174


on an outer coupling member


176


that magnetically clings to inner coupling member


146


. The two inner coupling halves


146


are connected to each other by elongated member


140


that does not need to be electrically conductive, such as the examples mentioned earlier.




During normal operation of the door, current from power supply


64


passes in series through relay


68


, a wire


178


, normally closed contacts


166


and


168


on the left breakaway coupling, a wire


180


, normally closed contacts


170


and


172


on the right breakaway coupling, and back to power supply


64


through a wire


182


to complete the continuity of a sensing circuit


184


. This energizes relay


68


to enable motor


18


to open or close the door.




When a coupling


164


breaks away, for example, the left breakaway coupling


164


of

FIGS. 23 and 24

, the coupling's spring-loaded hinge


52


swings its magnet


174


and its adjacent switch


162


up against the side of frame


12


. The side of frame


12


depresses the switch's actuator


130


to open contacts


166


and


168


, which interrupts the continuity of circuit


184


. This, in turn, de-energizes relay


68


to disable the normal operation of the door. Although frame


12


is the structure that actuates switch


162


as hinge


52


moves the switch, the actuation could be carried out by a variety of other structures in the vicinity, including but not limited to the hinge itself. The door is returned to normal operation by placing curtain


16


back into slits


20


and reconnecting the two halves of the left breakaway coupling


164


.




Although the invention is described with respect to preferred embodiments, modifications thereto will be apparent to those skilled in the art. For example, in providing a breakaway coupling that includes two coupling halves that are magnetically attracted to each other, either coupling member could be the magnet with the other coupling member being of a material attracted to the magnet. Also, one coupling member could be an integral component or extension of carriage


38


itself. For instance, it is well within the scope of the invention to eliminate hinge


52


and provide an inner coupling member with a magnet that clings directly to bracket


42


of carriage


38


. In such a case, the portion of bracket


42


that engages the magnet would serve as the outer coupling member. Since other modifications will be apparent to those skilled in the art, the scope of the invention is to be determined by reference to the claims, which follow.



Claims
  • 1. A system responsive to a force above a certain magnitude, the system comprising:a door that is moveable, during a normal operation of the door, between an open position and a closed position relative to a doorway opening having a width; and a sensing circuit adapted to sense the force exceeding the certain magnitude and being exerted on the door, and including a conductor which is in a conductive state during the normal operation of the door to provide the sensing circuit with an electrically conductive path that extends substantially across the width of the doorway opening to conduct current substantially across the width of the doorway opening and which changes to a nonconductive state in response to the force exceeding the certain magnitude.
  • 2. The system of claim 1, further comprising a vertically-extending member disposed adjacent a lateral edge that at least partially defines the doorway opening, and a first member associated with the vertically extending member, wherein the conductor is releasably coupled to the first member such that the conductor and the vertically-extending member have a coupled state and an uncoupled state, wherein the conductor and the first member are in the coupled state during the normal operation of the door to place the conductor and first member in electrically conductive contact with each other, and wherein the conductor and the first member are otherwise in the uncoupled state to electrically separate the conductor from the first member.
  • 3. The system of claim 2, wherein at least one of the conductor and the first member includes a magnet.
  • 4. The system of claim 2, wherein the conductor and the first member comprise a first set of electrical contacts that is connected electrically in series with a second set of electrical contacts that are provided by the conductor and a second member associated with a second vertically-extending member disposed along an opposite lateral edge of the doorway opening.
  • 5. A door including a system responsive to a force above a certain magnitude being exerted on the door, wherein during a normal operation of the door, the door is moveable between an open position and a closed position relative to a doorway opening at least partially defined by a lateral edge, and comprising in combination:a vertically-extending member disposed adjacent to the lateral edge of the doorway opening; a first member associated with the vertically-extending member; a door panel capable of movement between the open position and the closed position; a sensing circuit adapted to sense the force exceeding the certain magnitude; and including a conductor releasably coupled to the first member such that the conductor and the first member have a coupled state and an uncoupled state, wherein the conductor and the first member are in the coupled state and move together during the normal operation of the door to place the conductor and first member in electrically conductive contact with each other such that current is conducted through the coupled conductor and the first member, and wherein the conductor and the first member are otherwise in the uncoupled state wherein they are capable of independent relative movement to electrically separate the conductor from the first member.
  • 6. The door including the system of claim 5, wherein the conductor and the first member comprise a first set of electrical contacts that is connected electrically in series with a second set of electrical contacts that are provided by the conductor and a second member associated with a second vertically-extending member disposed along an opposite lateral edge of the doorway opening.
  • 7. A method of controlling an electrical current used to signal the separation of a breakaway coupling that selectively couples and uncouples a roll-up panel to a carriage, wherein the carriage travels along a track to help guide the roll-up panel, comprising:conveying the electrical current through the breakaway coupling; uncoupling the roll-up panel from the carriage by way of the breakaway coupling; and sensing the interruption of the electrical current through the breakaway coupling upon uncoupling the roll-up panel from the carriage.
  • 8. The method of claim 7, further comprising urging the breakaway coupling to couple the roll-up panel to the carriage by way of magnetic attraction.
  • 9. The method of claim 7, further comprising conveying the electrical current in series through the breakaway coupling and a second breakaway coupling, wherein the breakaway coupling and the second breakaway coupling are disposed at opposite ends of the roll-up panel.
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