Aircraft groundings resulting from inflight fan failures are a serious concern for airlines and other operators. Smoke creation and flow to aircraft cabins, due to fan failures, leads to such groundings.

Aircraft equipped with cabin air fans, experience failures resulting in the production of smoke and odor in the passenger compartment. The existing thermal protection system as used conventionally in aircraft does not respond to a smoke condition when it results from fan bearing failures and consequent fan impeller contact with the fan housing. A need exists for a solution to this problem that has the following characteristics: a) detects bearing failure prior to impeller, housing contact b) removes power to fan and is re-settable by maintenance personnel only c) capable of being installed on existing fans d) retrofitable without removing fans from aircraft e) provides a failure indication to the cockpit crew f) and may, if desired, contain or employ a built-in test system.

SUMMARY OF THE INVENTION It is a major object of the invention to provide a highly advantageous solution to the problem of air supply fan failure, due to impeller bearing failures, as for example on aircraft or other vehicles having cabins or passenger compartments, to which air is delivered. Basically, and in its method aspects, the invention includes the following:

a) detecting excessive vibration of the fan housing or frame produced prior to or in conjunction with fan rotor interference with the frame or housing causing smoke production, b) and effecting shut-down of fan rotor rotation in response to such detecting.

Another object is to provide a vibration detector apparatus, positioning and operating said detector apparatus to provide such detecting, thereby producing a signal, effecting said shut-down. The vibration threshold to be detected is typically set to be below that at which fan rotor bearing deterioration results in fan blade tip interference such as engagement with the housing bore, during high speed impeller rotation. Such interference typically leads to melting of plastic material associated with the housing or frame and consequent formation of smoke.

Yet another object is to provide a method wherein the vibration level to be detected by the detector apparatus is predetermined so as to effect fan shut- down prior to significant smoke formation resulting from rotor blade tip engagement with the housing or frame, leading to melting of plastic material associated with the housing or frame.

A further object is to provide a method as described, for remediating of smoke formation in a vehicle cabin or passenger compartment, due to ventilation fan operation.

An additional object is to provide equipment for remediating fan source production of smoke in an aircraft cabin, comprising in combination: a) first means for detecting excessive vibration of the fan housing or frame produced prior to or in conjunction with fan rotor interference with the frame or housing causing smoke production, b) and second means for effecting shut-down of fan rotor rotation in response to such detecting.

Such first means may include vibration detector apparatus positioned and operating to provide such detecting, thereby producing a signal effecting said shut-down.

An added object is to provide for support of a vibration monitor on a fan housing, and electrical connection to the power connection to the fan motor, so as not to disable such power supply.

These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which: DRAWING DESCRIPTION Fig. 1 is a schematic view of an air delivery system for use on aircraft; Fig. 2 is a schematic view of an air delivery system for use on aircraft, and in which the invention is employed; Fig. 3a is a perspective schematic view of a vibration monitor attached to a fan housing; and Fig. 3b is like Fig. 3a, but shows separate mounting of an accelerometer on the housing; Fig. 4 is a side elevation view of one type useable vibration monitor housing assembly; Fig. 5 is a top plan view of the Fig. 4 housing aircraft; and Fig. 6 is a front elevation view taken on lines 6-6 of Fig. 5.

DETAILED DESCRIPTION In Fig. 1, a fan 10 is mounted on a shaft 11 rotated by a motor 12. A bearing or bearings 13 center the shaft within a housing 14 forming a duct for fan driven air flow as at 15 to a vehicle passenger compartment, such as an aircraft cabin 16, providing ventilation. The bearing or bearings are carried as by suitable structure 17. That structure shown as within 14, but it can also be located within or in association with the motor. The bearings can also be

located within or in association with the motor. It is found that bearing wear, over time, can result in rotating shaft sideward deflection, causing corresponding sideward deflection of a fan 10. The tips 20a of rotating rotor blades 20 then can frictionally interfere with a bore 22 in the housing.

Aircraft induced vibration of dust 14 relative to shaft 11 can also produce such interference. This can result in smoke formation, as for example due to friction and heat production at a plastic bore in the housing. Melt down of plastic material due to such heat production is found to occur. Such smoke is carried at 15 to the interior of the cabin 16, in the fan produced air flow; and in the past, aircraft have been grounded due to such smoke delivery to the aircraft cabin.

In accordance with the invention, and referring to Fig. 2, vibration of the fan housing or duct 14 produced as in conjunction with bearing wear and fan rotor tip interference with the frame or housing is detected. Such vibration produced by vibration at the bearings is transmitted to the housing via bearing mounting structure 17, for example as when the bearings are located within that housing 14 or within the motor casing 12a. A vibration detector apparatus 25 is provided, and positioned and operated to detect excessive vibration of the housing or frame 14, produced as described, and which could lead to smoke production as described. Shut-down of fan rotor rotation is then effected in response to such detecting. An alternative is a reduction in fan RPM, to keep some air flowing to the cabin.

In Fig. 2, the vibration detection or monitor apparatus 25, i. e. the detector, is mounted on the housing 14, as for example at a location near the fan rotor 10, to detect vibration associated with rotor tip interference and or excessive bearing wear, as described. When a predetermined vibration threshold is detected, a signal is produced by 25, and transmitted at 26 to the motor, or to an electrical power switch associated with motor operation, to cause motor shut-down, stopping fan rotation, or reducing fan RPM, typically

before an excessive vibration level is reached that would cause smoke formation. Such shut-down can be detected, as at 27, and a signal produced at 27a indicating that repair or replacement of the fan bearing is needed.

Fig. 3a shows a detector or monitor unit 25 attached to the outer side 14a of the housing or duct 14 that delivers fan induced air flow to the cabin.

Attachment straps 33 are provided, and wrapped about the duct 14. Fig. 7 shows unit 25 as including controller 25b receiving a signal at 26 from an accelerometer. The controller operates as via 47 and relay 48 to cut-off power to the motor when detected vibrating reaches predetermined level. Fig. 3b shows an accelerometer 25e strap connected at 28 to duct 14, and sensing vibration, to produce signal 26. Connectors 29a and 29b are provided for connection between connectors 30a and 30b normally used for aircraft fan circuitry. See Fig. 7.

Fig. 4 shows a housing assembly 25c for enclosing the controller and/or the accelerometer. Strap brackets 39 are located on wall 40 of the assembly, to pass straps 33. An electrical cable 36 extends from the assembly 25c and carries an end terminal plug 25d. See Fig. 5. An elongated spiral support 34 connected to the housing at rod 34a receives and protects the cable 36 against sharp bending. Support 34 may consist of molded plastic material, and can resiliently flex or bend, to limited extent. Plug 25d is attachable to a mating plug at the motor.

The assembly 25c housing contains P. C. board 25b carrying a power supply 46, filters converters 47, and a latching device 48, LED or status indicators 49, and suitable electrical connectors. The accelerometer can be located in the same housing as the controller.

In Fig. 7, terminals 2-4 supply power to fan, and P. C. board lines 53 and 51 connect to lines 2'and 3', as shown. Lines 5'and 6'are connected to terminals 5 and 6, which are in turn connected to the thermal ON-OFF switch on the fan, the latch or relay 48 on the PC board being in series with line 5', whereby either excess bearing vibration, or overheating at the fan, result in shut-down of the fan.