GB2497332A

GB2497332A - An aircraft seat actuator

Info

Publication number: GB2497332A
Application number: GB1121074.7A
Authority: GB
Inventors: Arthur Jerrett
Original assignee: ALMEC EAS Ltd
Current assignee: ALMEC EAS Ltd
Priority date: 2011-12-08
Filing date: 2011-12-08
Publication date: 2013-06-12
Also published as: GB201121074D0

Abstract

Aircraft seat actuator 1 includes light source 40 and detector 50, 60 detecting a change in light signal from the source and producing an end-of-travel signal received by a controller 8. Second aspect: A detectable member mountable on a rotatable shaft of an actuator. A sensor detects when detectable member completes a revolution and produces a signal. Third aspect: An output shaft of a linear actuator is connected to a fastener via a connecting member, which has a magnet between output shaft and fastener. A magnetic sensor is mounted on the actuator housing. Fourth aspect: An aircraft seat actuator has a position detector measuring position of an output shaft of the actuator, an ammeter measuring current drawn by the actuator, and a controller to shut-down the actuator if the current exceeds a threshold. The threshold is a function of the position of the output shaft. Fifth aspect: An aircraft seat actuator includes a gearbox having a housing constructed of polyamide. Sixth aspect: An aircraft seat linear actuator has a lead screw and nut, constructed of carbon-fibre reinforced polyamide impregnated with PTFE lubricant. Seventh aspect: An aircraft seat actuator has a gearbox with a non-circular profile for receiving an output shaft.

Description

AN AIRCRAFT SEAT ACTUATOR

This invention relates to an aircraft seat actuator.

Aircraft seats are often fitted with motorised control systems for adjusting the relative position and orientation of their constituent parts. Typically, the aircraft seat is configured to move between an upright normal' position, to either a relaxed', reclined' or sleep' position, or somewhere in between.

A conventional aircraft seat 1000 is illustrated in Figure 1. Typically, the aircraft seat 1000 is predominantly constructed out of metal, although some non-metallic materials are used, e.g. for protective covers. A control system is used for adjusting the relative position and orientation of the parts of the aircraft seat 1000. The control system comprises a control panel 1050 (including a plurality of buttons), a controller, and one or more actuators 1100 cooperating with a part of the aircraft seat 1000. The actuators 1100 are configured to move in response to operation of the button, which in turn forces the part of the aircraft seat to move. The controller may be part of the control panel 1050 or the actuators (or may be positioned elsewhere).

Figure 2 illustrates a conventional aircraft seat actuator 1100 for moving part of the aircraft seat 1000. The actuator 1100 comprises a housing 1110, a motor 1120, a gearbox 1130, a release mechanism 1140 and an output shaft 1150 (which cooperates with the part of the aircraft seat 1000). Typically, the housing 1110 is constructed out of aluminium, whilst the output shaft 1150 (including a ball screw or lead screw/nut in the case of a linear actuator) are typically constructed of steel. The lead nut may, in some circumstances, be constructed from bronze.

The motor 1120 is configured to provide drive for the output shaft 1150 when power is applied, and automatically lock the output shaft 1150 in place at all other times. The gearbox 1130 provides the necessary gearing in order to provide the required torque and speeds for any particular application. However, in applications where the motor alone provides sufficient torque, the gearbox 1130 may be omitted. The release mechanism 1140 allows the output shaft (and therefore the part of the aircraft seat) to be manipulated manually, e.g. in the event of power failure. The release mechanism 1140 may also be omitted.

It is necessary to know when the actuator 1100 (or the part of the aircraft seat 1000 with which it cooperates) has reached its end-of-travel'. The end-of-travel is the point at which the output shaft 1150 of the actuator 1100 reaches either the maximum or the minimum point of its range of motion. Alternatively, the end-of-travel may be defined as the point at which the part of the aircraft seat 1000 reaches either its maximum or minimum point in its range of motion. In the conventional aircraft seat 1000, there are three conventional devices for sensing the end-of-travel.

A first conventional end-of-travel sensor is the micro-switch'. The micro-switch is mounted on the part of the aircraft seat 1000, and is triggered when the part of the aircraft seat 1000 reaches its maximum or minimum point in its range of motion e.g. by contact with an external body. There are a number of problems with the micro-switch. Firstly, the micro-switch is mounted to the part of the aircraft seat 1000, which increases the installation time of the seat 1000, secondly, the micro-switch requires a lot of fine adjustment to ensure it triggers reliably at the correct position, and thirdly, the performance of the micro-switch degrades over time (due to, e.g. wear, fluid spills or damage from accidental physical contact) so it requires re-adjustment or replacement after installation.

A second conventional end-of-travel sensor is the magnetic switch'. The magnet is fitted to a part of the aircraft seat 1000, and a magnetic switch (such as a reed switch or Hall-Effect sensor) is positioned at each end-of-travel point (that is, the maximum and minimum points of the range of motion) such that it is triggered when the magnet (and therefore the seat 1000) is in close proximity. The magnetic sensor cooperates with the control system of the actuator 1100. There are problems with the magnetic switch. That is, it requires a magnet to be fitted to the part of the aircraft seat 1000, which increases the manufacturing or installation time of the seat.

A third conventional end-of-travel sensor is the potentiometer. The potentiometer is configured to vary its voltage output in response to movement of the output shaft 1050, and therefore also provides feedback for the position of the output shaft 1050 (another desirable feature of the conventional aircraft seat actuators 1100). However, this requires the user to calibrate the control system, such that the voltage level output at each end-of-travel point, and the dependency of the voltage level output between each end-of-travel points, is known.

Furthermore, another disadvantage of the potentiometer is that it is prone to mechanical failure (due to, for example, wear, physical damage and fluid spills).

It is also desirable to provide a form of overload protection for the conventional actuator 1000. That is, actuator motors 1120 (such as brushed DC motors) tend to increase the level of electrical current consumed as the load being driven increases. Thus, in the event the load increases due to an obstruction (e.g. the part of the aircraft seat 1000 becomes obstructed), the current increases. This may cause damage to the obstruction (which may be the seat occupant or their possessions), and may cause damage to the control system due to overloading or overheating due to the high level of current.

There are two conventional methods for providing a form of overload protection for the conventional actuator 1100. Firstly, the control system may define a threshold current level, wherein the control system shuts down power to the actuator 1000 in the event the current drawn by the actuator 1100 exceeds the threshold current level. There are problems with this first method. That is, different actuators 1100 may require very different loads depending on, e.g. the part of the aircraft seat 1000 being driven, and the mass of the occupant. Therefore, in some situations, the load placed on the obstruction may be unduly large whilst the current drawn by the actuator 1100 remains under the current limit (for example, if the occupant is a child). However, lowering the current limit to alleviate this problem results in the control system shutting down the power to the actuator 1100 inadvertently when the seat is more heavily loaded but not obstructed (so called, nuisance shut-downs').

A second conventional method of providing a form of overload protection for the conventional actuator 1100 is to detect the rate of change of current drawn by the actuator 1100. Therefore, the control system may shut down power to the actuator 1100 in the event the current drawn by the actuator 1100 exceeds a threshold rate of change. There are problems with the second conventional method. That is, it is cumbersome and time-consuming to find a suitable threshold rate, and it requires an additional means to calculate the rate of change of current (which requires extra processor power).

Furthermore, it is necessary to monitor the motor current at a high frequency (of the order of laOs of Hz) in order to detect the rate of change sufficiently quickly to prevent damage to the obstruction. The time interval between current measurements must remain constant for a particular unit and must be repeatable between units.

As noted above, aircraft seat actuators 1100 typically have a housing 1110 constructed of aluminium, have output axles (for rotary actuators) constructed out of steel, and have output screws and nuts (for linear actuators) also of steel. It is particularly important for the output screw and nut of the linear actuator to be constructed of appropriate materials, as this is critical to the strength and efficiency of the linear actuator. However, these materials are generally expensive and heavy.

It is therefore desirable to alleviate some or all of the above problems.

According to a first aspect of the invention, there is provided an aircraft seat actuator for moving a part of an aircraft seat and having an end-of-travel state, comprising a controller for controlling the actuator; a light source for producing a light signal; and a light detector for receiving the light signal, and configured to detect a change in the light signal when the actuator is at the end-of-travel state and produce an end-of-travel signal in response, wherein the controller is configured to receive the end-of-travel signal from the light detector.

Therefore, the light sensor and light detector may be embodied on the actuator and therefore combined into a single unit. This dramatically improves the installation time of the actuator to the seat, as the installer does not have to fit various parts of the actuator to different areas of the seat (e.g. fitting a magnet to an end-of-travel position on the seat) and it requires no calibration.

The light source may be configured to reflect the light signal off an object when the actuator is at the end-of-travel state, and the light detector may be arranged for receiving a reflected light signal and producing the end-of-travel signal in response. Alternatively, the light source and light detector are arranged in an optical path, and the light detector alternatively is arranged to produce an end-of-travel signal when an object interrupts the optical path.

Preferably, the light source is arranged for producing a light signal in the near infra-red range, and the light detector is arranged for receiving the light signal in the near infra-red range. Light signals in this range have excellent transmittance through dust, water and grease (which tends to build up under aircraft seats where aircraft seat actuators are typically positioned).

According to a second aspect of the invention there is provided an aircraft seat actuator for moving a part of an aircraft seat, including a rotatable shaft, comprising a first detectable member mountable on the rotatable shaft; a sensor configured to detect the first detectable member as it makes a revolution on the rotatable shaft and produce a first signal in response; and a controller, configured to receive the first signal.

Therefore, the detectable member, (e.g. a magnet) may be mounted on a rotatable shaft and the number of rotations of the shaft may be tracked. For example, the detectable member may be mounted on the motor shaft, and the number of rotations tracked, such that the current position of the output shaft may be determined with great accuracy (as the motor shaft makes a very high number of rotations compared to the output shaft). Therefore, even without calibration, the current position of the output shaft relative to a starting position may be determined. The aircraft seat actuator of the second aspect of the invention therefore uses a more accurate and more reliable method of determining the position of the shaft than the conventional aircraft seat actuator (which is more prone to mechanical failure).

Preferably, the aircraft seat actuator of the second aspect of the invention further comprises an end-of-travel detector, for detecting when the actuator has reached an end-of-travel state and for producing an end-of-travel signal, wherein the controller is configured to receive the end-of-travel signal. Therefore, the user may calibrate the system such that the controller may determine the actual position of the rotatable shaft by comparing the current position of the shaft with the position at the end-of-travel state.

The first detectable member may be a magnet and the sensor may be a magnetic sensor.

Alternatively, the first detectable member may be a light source and the sensor may be a light sensor.

Preferably, the aircraft seat actuator further comprises a second sensor and a third sensor, wherein the sensors are also configured to detect the detectable member as it makes a revolution on the rotatable shaft and produce a second signal and third signal in response respectively, and the controller is also configured to receive the second and the third signal. a

Therefore, the aircraft seat actuator may determine the direction of rotation of the rotatable shaft without referring to another parameter, e.g. the polarity of the motor.

The detectable member may be a magnet and the second and third sensors may be magnetic sensors. Alternatively, the detectable member may be a light source and the second and third sensors may be light sensors.

According to a third aspect of the invention there is provided an aircraft seat linear actuator for moving a part of an aircraft seat, having a housing including an output shaft extending therefrom, comprising a connecting member at a distal end of the output shaft; a fastener, for attachment to the part of the aircraft seat, wherein the connecting member connects the output shaft to the fastener; a magnet, positioned on the connecting member between the output shaft and the fastener; and a magnetic sensor, for detecting the magnet, mounted on the housing.

Therefore, the aircraft seat linear actuator may detect when the actuator reaches the end of travel position without using an external part. That is, the actuator may be a self-contained unit, which substantially reduces the time required to manufacture the aircraft seat, reduces the need to keep spare parts, and simplifies maintenance for the end-user.

Furthermore, by using a solid-state detector system (compared to e.g. the potentiometers used in the conventional actuators) the actuator is less prone to wear, damage or liquid spillages. The aircraft seat linear actuator is therefore substantially more reliable.

The aircraft seat linear actuator may further include an insulating member, for insulating the magnet from the connecting member, the output shaft and/or the fastener. This reduces the adverse affect of the construction materials of the actuator on the magnetic field of the magnet, thus improving the performance of the detector system.

According to a fourth aspect of the invention there is provided an aircraft seat actuator for moving a part of an aircraft seat, having an output shaft configured to move between a first end-of-travel state and a second end-of-travel state, wherein a threshold current drawn by the actuator is a function of a position of the output shaft between the first end-of-travel state and the second end-of-travel state, the actuator comprising a position detector, for detecting the position of the output shaft; a current detector, for detecting the current drawn by the actuator; and a controller, configured to shut-down the actuator if the detected current exceeds the threshold current at the detected position of the output shaft.

Therefore, in the event the output shaft or part of the aircraft seat hits an obstruction, the force applied to the obstruction does not reach an unacceptably high level before the controller shuts down the actuator (when compared to the first conventional method), whilst still not being prone to nuisance shut-downs. Furthermore, the actuator does not need to calculate the rate of change of current. The current detector may therefore take fewer current readings (compared to the second conventional method), which reduces the processing power requirements. This allows for the use of simpler, lower-cost processor and reduces the risk of an over-current being missed because of a high processor workload.

According to a fifth aspect of the invention, there is provided an aircraft seat actuator, including a gearbox having a gearbox housing, wherein the gearbox housing is constructed of polyamide. Therefore, the gearbox (and therefore the actuator) may have a lower mass than the gearbox/actuator of the prior art, whilst still maintaining a suitably high level of strength and stiffness. Furthermore, polyamide is suitable for aerospace applications as it is fungus-inert and may include additives to reduce fire and smoke risks.

The polyamide may be up to 50% glass fibre reinforced polyamide. More specifically, but not exclusively, the polyamide is around 30% glass fibre reinforced polyamide. Carbon reinforced polyamide may be used for applications requiring particularly high strength, although this material may be more expensive than the glass filled type.

According to a sixth aspect of the invention there is provided an aircraft seat linear actuator, having a lead screw and nut, wherein the nut is constructed of carbon-fibre reinforced polyamide impregnated with PTFE lubricant, and the lead screw is preferably constructed of PTFE-coated stainless steel. Therefore, the linear actuator may have an efficiency of around 80% of that of a conventional linear actuator using a steel ball-screw, but may be manufactured at a significantly lower cost and run with reduced noise.

According to a seventh aspect of the invention, there is provided an aircraft seat actuator, having a gearbox with an output stage for receiving an output shaft, wherein the output stage has a non-circular profile.

This arrangement allows the gearbox to be used in different applications. That is, the output stage of the gearbox may receive any output shaft having a complimentary non-circular profile. Thus, an output shaft for a rotary actuator may be replaced with an output shaft for a linear actuator, such that the gearbox and the actuator become a linear actuator.

The output stage may have a hexagonal profile, splined profile or other suitable non-circular profile allowing transmission of the torque. The aircraft seat actuator may further comprise an output shaft, wherein a part of the output shaft has a profile complimentary to the profile of the output stage.

Preferably, the output shaft includes fastening means, for fastening to the output stage.

Embodiments of the invention will now be described, by way of example, and with reference to the drawings in which: Figure 1 is a side view of a conventional aircraft seat, having a control panel and a plurality of actuators; Figure 2 is a schematic view of one of the plurality of actuators of Figure 1; Figure 3 is a perspective view of an aircraft seat actuator of a first embodiment of a first aspect of the present invention; Figure 4 is a perspective view of the actuator of Figure 3, at a first end-of-travel state; Figure 5 is a perspective view of the actuator of Figure 3, at a second end-of-travel state; Figure 6 is a perspective view of an aircraft seat actuator of a second embodiment of the first aspect of the present invention; Figure 7 is a perspective view of the actuator of Figure 6, at a first end-of-travel state Figure 8 is a perspective view of the actuator of Figure 6, at a second end-of-travel state; Figure 9 is a perspective view of an aircraft seat actuator of a first embodiment of a second aspect of the present invention; Figure 10 is a perspective view of a shaft of the actuator of Figure 9; Figure 11 is a perspective view of an aircraft seat actuator of a second embodiment of the second aspect of the present invention; Figure 12 is a perspective view of a shaft of the actuator of Figure 11; Figure 13 is an exploded perspective view of an aircraft seat linear actuator of an embodiment of a third aspect of the present invention; Figure 14 is a perspective view of an aircraft seat actuator of an embodiment of a fourth aspect of the present invention; Figure 15 is a graph illustrating the variation of current with respect to a position of an output shaft of the actuator of Figure 14; Figure 16 is a perspective view of an aircraft seat actuator of an embodiment of a fifth aspect of the present invention; Figure 17 is a side view of an aircraft seat linear actuator of an embodiment of a sixth aspect of the present invention; and Figure 18 is a perspective view of an aircraft seat actuator of an embodiment of a seventh aspect of the present invention.

A first embodiment of a first aspect of the present invention will now be described with reference to Figures 3 to 5. An aircraft seat actuator 1 is provided, for moving a part of an aircraft seat. In this embodiment, the actuator 1 is a linear actuator and the part of the aircraft seat is a footrest. There is also provided a control system 5, for controlling the actuator 1. The actuator 1 is configured to move between a first end-of-travel (hereinafter referred to as "ECT") point, where the footrest is substantially vertical (as shown in Figure 4), to a second EOT point, where the footrest is at an angle to the vertical (as shown in Figure 5).

The actuator 1 includes a housing 10 (containing a motor, a gearbox and a release mechanism (all not shown)) and an output shaft 20, wherein the output shaft 20 is configured to move from a first predetermined position (at the actuator's 1 first EOT, as shown in Figure 4) to a second predetermined position (at the actuator's second EOT, as shown in Figure 5).

The output shaft 20 is attached to the footrest via a clevis 30.

The control system 5 includes an UP' button 6, DOWN' button 7 and a controller 8. In this embodiment, the controller 8 is configured to cause the actuator 1 to extend the output shaft in response to a seat occupant pressing the UP button 6, and to cause the actuator 1 to contract the output shaft 20 in response to the seat occupant pressing the DOWN button 7.

The controller 8 is also configured to override the seat occupant's command (that is, to stop causing the actuator 1 to extend/contract the output shaft 20, despite the seat occupant pressing the UP or DOWN button 6, 7 respectively) in response to an FOT signal (or in response to an overload condition or detected fault state).

The actuator 1 also includes a light source 40, a first light detector 50 and a second light detector 60. In this embodiment, the light source 40 emits a light signal in the near infrared range (i.e. between 700nm-l400nm), and the first and second light detectors 50, 60 are configured to detect light in this range. Both the light source 40 and the light detectors 50, 60 are positioned on the actuator housing 10, such that they move relative to the footrest in response to a change of position thereof.

The actuator 1 is originally in a position between the first and second FOT (as shown in Figure 3). In response to the occupant's operation of the UP button, the output shaft 20 extends, causing the footrest to move towards the angled position. As shown in Figure 5, the actuator 1 reaches its second EDT (that is, the point at which the output shaft 20 reaches the second predetermined position). At this point, the light emitted from the light source 40 is reflected, e.g. off a second point of the actuator's output shaft, and is received by the second light detector 60.

In response to receiving the light from the light source 40, the second light detector 60 produces a second EOT signal, which is communicated to the controller 8. The controller 8 therefore stops causing the actuator 1 to extend the output shaft 20, overriding the seat occupant's command from the UP button 6.

When the seat occupant wishes to move the footrest back to its vertical position, he/she presses the DOWN button 7, which causes the actuator 1 to contract the output shaft 20.

When the actuator 1 reaches to its first EDT position (that is, it reaches the position shown in Figure 4), the light emitted from the light source 40 is reflected, e.g. off a first point of the actuator's output shaft, and is received by the first light detector 50. In response, the first light detector 50 produces a first EOT signal, which is communicated to the controllerS. The controller 8 therefore stops causing the actuator 1 to contract the output shaft 20, overriding the seat occupant's command from the DOWN button 7.

A second embodiment of the first aspect of the invention will now be described with reference to Figures 6 to 8.

Again, an aircraft seat actuator 101 is provided, for moving a part of an aircraft seat. There is also provided a control system 105, for controlling the actuator 101. In this embodiment, the actuator 101 is a linear actuator and the part of the aircraft seat is a footrest. The actuator 101 is configured to move between a first FOT point, where the footrest is substantially vertical (as shown in Figure 7), to a second EOT point, where the footrest is at an angle to the vertical (as shown in Figure 8).

The actuator 101 includes a housing 110 (containing a motor, a gearbox and a release mechanism (all not shown)) and an output shaft 120, wherein the output shaft 120 is configured to move from a first predetermined position (at the actuator's 101 first EOT) to a second predetermined position (at the actuator's 101 second EOT). The output shaft 120 is attached to the footrest via a clevis 130.

The control system 105 includes an UP' button 106, DOWN' button 107 and a controller 108. Again, the controller 108 is configured to cause the actuator 101 to extend the output shaft 120 in response to a seat occupant pressing the UP button 106, and to cause the actuator 101 to contract the output shaft 120 in response to the seat occupant pressing the DOWN button 107. The controller 108 is also configured to override the seat occupant's command (that is, to stop causing the actuator 101 to extend/contract the output shaft 120, despite the seat occupant pressing the UP or DOWN button 106, 107 respectively) in response to an EOT signal (or a detected fault / overload condition).

The actuator 101 also includes a first light source 140, a first light detector 150, a second light source 160 and a second light detector 170. Again, the first and second light sources 140, 160 emit alight signal in the near infrared range (i.e. between 700nm-l400nm), and the first and second light detectors 150, 170 are configured to detect light in this range.

However, in the second embodiment, the first and second light sources 140, 160 are arranged in an optical path with the first and second light detectors 150, 170 respectively.

Therefore, both light detectors 150, 170 are configured to receive a light signal when the actuator 101 is not at the first or second FOT (as shown in Figure 6) The actuator 101 is originally in a position between the first and second EOT (as shown in Figure 6). When the seat occupant presses the UP button, the controller 108 causes the actuator 101 to extend the output shaft 120 such that the footrest moves towards the angled position. As the footrest moves towards its angled position, an object moves. In this embodiment, the object is part of a seat structure, however, it could alternatively be a part of the actuator.

As shown in Figure 8, as the actuator 101 moves to the second EDT (that is, the point at which the output shaft 120 reaches the second predetermined position) the external object moves into the optical path between the second light source 160 and the second light detector 170. Therefore, the second light detector 170 no longer receives the light signal from the second light source 160.

In response to the second light detector 170 not receiving the light signal, the second light detector 170 produces a second EDT signal, which is communicated to the controller 108.

The controller 108 therefore stops causing the actuator 101 to extend the output shaft 120, overriding the seat occupant's command by pressing the UP button 106.

When the seat occupant wishes to move the footrest back to its vertical position, he/she presses the DOWN button 107, which causes the actuator 101 to contract the output shaft 120. The actuator 101 therefore moves towards the first EDT (that is, the point at which the output shaft 120 reaches the first predetermined position). As the actuator 101 reaches the first EOT, the external object moves into the optical path between the first light source 140 and the first light detector 150. Therefore, the first light detector l5Ono longer receives the light signal from the first light source 140. In response, the first light detector 1 5oproduces a first ECT signal, which is communicated to the controller 108. The controller 108 therefore stops causing the actuator 101 to contract the output shaft 120, overriding the seat occupant's command by pressing the DOWN button 107.

The skilled person will understand that the first aspect of the invention is not limited to moving a footrest. Rather, the actuator 1, 101 of the first and second embodiment may be applied to any movable part of the aircraft seat, e.g. the backrest.

The skilled person will also understand that the first aspect of the invention is not limited to linear actuators. That is, the actuator 1, 101 of the first and second embodiment may instead be a rotary actuator, and the remaining parts may be adapted accordingly.

Furthermore, the skilled person will understand that the gearbox and release mechanism are not essential parts of the first aspect of the invention.

Furthermore, the skilled person will understand that in the first embodiment of the invention, where the light signal is reflected off an object when the actuator reaches an EOT, the object may be any part of the aircraft seat, any part of an aircraft, or any part of the actuator itself.

That is, the skilled person will understand that many other arrangements for the light source/light detector are possible and the embodiment described above is merely one

example.

Also, in the second embodiment of the invention, where an object interrupts the optical path between the light source and light detector when the actuator reaches an EOT, the skilled person will understand that the external object could be any moving part of the aircraft seat, aircraft, or the actuator itself. That is, many other arrangements for the light source/light detector of the second embodiment are possible, wherein the arrangement described above is merely one example.

Furthermore, the control system is not limited to the arrangement described above. That is, whilst the UP and DOWN buttons will commonly be provided near the seat occupant for ergonomic reasons, the controller may be positioned adjacent to the buttons, on the actuator, or anywhere else on the aircraft seat.

The skilled person will also understand that the light source/light detector need not be limited to emit/receive in the range of light described above. That is, any suitable range from the electromagnetic spectrum may be used. However, the near infrared range is particularly advantageous for this invention, as it has excellent transmittance through dust and grease (which tends to build up near the actuators as they are commonly positioned under the aircraft seat). Furthermore, other detection means may be used, for example, magnetic.

The skilled person will understand that the EOT points for an actuator may be any two points along the range of motion. These two points may be determined by the installation designer, who may set up the light source/light detector accordingly such that the EOT signal is produced at those points along the range of motion.

A first embodiment of an aircraft seat actuator 201 of the second aspect of the invention will now be described with reference to Figures 9 to 10. The actuator 201 includes a housing 210, containing a motor 220 having a motor shaft 221. The housing 210 also includes a gearbox (not shown) and a release mechanism (not shown).

As shown in more detail in Figure 10, the motor shaft 221 includes a magnet 222 mounted on a circumferential edge thereof. The magnet 222 therefore rotates with the motor shaft 221. A magnetic sensor 212 is also provided, which extends from the housing 210 such that ills positioned adjacent the magnet 222 at a point along its revolution. Therefore, as the motor shaft 221 (and therefore the magnet 222) complete a revolution, the magnetic sensor 212 will detect the magnet 222, and produce a signal in response.

In this embodiment, the housing 210 further includes a controller 215 and a counter 217.

The controller 215 is configured to receive the signal from the magnetic sensor 212, and, in this embodiment, determines the direction of rotation of the motor shaft 221 by the polarity of the motor 220. The counter 217 counts the number of signals received by the controller 215, and updates a cumulative count in response (the cumulative count increases if the controller 215 receives the signal with the motor 220 in a first polarity, and the cumulative count decreases if the controller 215 receives the signal with the motor in a second polarity).

Therefore, the cumulative count is indicative of the number of revolutions of the motor shaft 221 from a starting position. Furthermore, if the motor shaft 221 drives an output shaft (not shown), the cumulative count is also indicative of the position of the output shaft. The skilled person will realise that the calculation of the position of the output shaft would be to a greater accuracy, as the motor shaft generally makes a very high number of rotations compared with output shaft.

In order to determine the actual position of the output shaft, the controller 215 and counter 217 are calibrated. That is, the motor shaft 221 drives to the first EOT point, and the counter 217 is set to a first EOT cumulative count value (preferably, zero). Then, the motor shaft 221 drives to the second EOT point, and the cumulative count is increased in response to the number of signals received by the controller 215 (which correlates with the number of revolutions of the motor shaft 221). The first ECT cumulative count value (zero) and a second FOT cumulative count (hereinafter, "D") are stored in non-volatile memory on the controller 215.

Therefore, as the cumulative count is updated as the motor shaft 221 drives between the first and second EaT, the skilled person would understand that the current position of the motor shaft 221 at any point may be calculated by using the knowledge of the updated cumulative count compared to the first and second cumulative count values.

In this embodiment, the updated cumulative count is stored in volatile memory on the controller 215.

A second embodiment of the aircraft seat actuator 301 of the second aspect of the invention will now be described with reference to Figures 11 to 12. Again, the actuator 301 includes a housing 310, containing a motor 320 having a motor shaft 321. The housing 310 also includes a gearbox (not shown) and a release mechanism (not shown).

As shown in more detail in Figure 12, the motor shaft 321 includes a magnet 322 mounted on a circumferential edge thereof. The magnet 322 therefore rotates with the motor shaft 321. A first, second and third magnetic sensor 312a, 312b, 312c are also provided, which extend from the housing 310 such that they are positioned adjacent the magnet 322 at a first, second and third point along its revolution respectively. Therefore, as the motor shaft 321 (and therefore the magnet 322) completes a revolution, the first, second and third magnetic sensors 312a, 312b, 312c will detect the magnet 322 and produce a first, second and third signal in response respectively.

Again, the housing 310 includes a controller 315 and a counter 317. The controller 315 is configured to receive the first, second and third signals from the magnetic sensors 31 2a, 31 2b, 31 2c. However, in this embodiment, the controller 315 may determine the direction of rotation of the motor shaft 321 by the order in which the first, second and third signals are received. That is, if the motor shaft 321 is rotating in a first direction, the magnetic sensors 312a, 312b, 312c will produce the signals in a first order (i.e. first signal, second signal, third signal, first signal etc.), and if the motor shaft 321 is rotating in a second direction, the magnetic sensors 312a, 312b, 312c will produce the signals in a second order (i.e. third signal, second signal, first signal, third signal etc.). Therefore, the controller 315 determines the direction of rotation according to whether it receives the first or second order of signals.

Accordingly, the counter 317 updates a cumulative count on receipt of each of the first, second and third signals, and will increase or decrease the cumulative count depending on the direction of rotation. Thus, the position of the output shaft relative to the starting position may be calculated. Furthermore, the skilled person will understand that the actual position of the output shaft may also be calculated using the calibration technique described in the first embodiment.

The skilled person will understand that number of rotations of the motor shaft 221, 321 correlates with the current position of an output shaft of the actuator 201, 301. Furthermore, the technique may also be applied to any other rotating part of the actuator 201, 301, e.g. directly on the output shaft.

In the above embodiments of the second aspect of the invention, the controller 215, 315 receives a signal from the magnet sensor 212, 312. However, the skilled person will understand that the magnet/magnetic sensor arrangement is only one possible way of counting the number of revolutions of the shaft. That is, any detectable member and corresponding sensor may be used. For example, a light source may be mounted on the shaft, and an optical sensor may produce a signal in response to a revolution of the shaft.

Furthermore, the skilled reader will understand that the second aspect of the invention may be used to command a shaft (e.g. motor, output etc.) of the actuator 201, 301 to complete a predetermined number of revolutions, such that the controller 215, 315 recognizes the number of revolutions completed and compares this to the predetermined number of revolutions. Also, the second aspect of the invention may be used to determine if two separate actuators or parts of the seat are going to collide, e.g. by comparing a position of the shaft/part of the seat associated with a first actuator to a position of the shaft/part of the seat associated with a second actuator.

The skilled person will also understand that this technique may be applied to the shaft of a rotary actuator or a linear actuator. Furthermore, the skilled person will realise that the gearbox and release mechanism are not essential parts of the second aspect of the invention.

A third aspect of the present invention will now be described with reference to Figure 13. An aircraft seat linear actuator 401 is provided. The actuator 401 includes a housing 410 (containing a motor, gearbox and release mechanism (all not shown)) and an output shaft 420. The output shaft 420 connects to a clevis 440, via a connecting rod 430. The clevis 440 fastens to a part of an aircraft seat.

A disc-shaped magnet 450, having a magnet bore 450b, is provided. In this embodiment, two insulating top-hat bushes 460, 470 (each consisting of a first and second disc, both having a central bush bore 460b, 470b) are also provided. The bore of each top-hat bush 480, 470 is configured to correspond with the diameter of the connecting rod 430.

Furthermore, the depth of the first disc of each top-hat bush 460, 470 corresponds to half the depth of the magnet 450, and the radius of the second disc of each top-hat bush 460, 470 is greater than that of the clevis 440 and the output shaft 420.

The magnet 430 and the two top-hat bushes 460, 470 are mounted on the connecting rod 430, such that the connecting rod 430 passes through the bush bores 460b, 470b of the two top-hat bushes 460, 470 (and thus also through the magnet bore 450b). The clevis 440 is screwed onto the connecting rod 430, which therefore retains the magnet 450 and the two top-hat bushes 460, 470 on the connecting rod 430. The skilled person will understand that, in this arrangement, the magnet 450 is not in direct contact with either the connecting rod 430, the output shaft 420 or the clevis 430 by virtue of the insulating top-hat bushes 460, 470.

The actuator 401 further comprises a magnetic sensor 480. In this embodiment, the magnetic sensor 480 is positioned on the housing 410. When the magnet 430 is in close proximity to the sensor 480 (i.e. when the actuator 401 reaches the end of travel) the sensor 480 is triggered and a signal sent to a controller.

The purpose of the insulating top-hat buses 460, 470 is to isolate the magnet from the clevis 440, connecting rod 430 and output shaft 420 (which are commonly made from steel, which affects the magnetic field of the magnet). However, the skilled person will realise that the top-hat bushes are not the only way of insulating the magnet from the connecting rod, the fastener and the output shaft, and that any other suitable insulating member may be used.

For example, the magnet may be enclosed in a plastic sleeve or separated by insulating washers.

Furthermore, the skilled person will understand that the magnet need not be insulated at all.

However, the insulation minimizes the attenuating affect of the construction materials of the connecting rod, fastener and output shaft on the magnetic field of the magnet. This allows the use of smaller, less powerful and less expensive magnets.

The skilled person will also realise that the gearbox and release mechanism are not essential features of the third aspect of the present invention.

An embodiment of a fourth aspect of the invention will now be described with reference to Figures 14 and 15.

An aircraft seat actuator 501 is provided, having a housing 510 (containing a motor, gearbox and a release mechanism (all not shown)) and an output shaft 520. The output shaft 520 is configured to extend between a first and second ECT point, and drives a part of an aircraft seat.

The housing 510 also includes a controller 530, a position detector 540 (such as that described in the second aspect of the invention) and a current detector (such as an ammeter) 550. The controller 530 is configured to shut-down the actuator 501 (that is, cut-off power to the motor and, where relevant apply the brake), in the event of an overload, using the method described below. The position detector 540 is configured to detect the position of the output shaft 520 between the first and second EOT point, and the current detector 550 is configured to detect the current drawn by the motor.

As shown in the graph of Figure 15, the current drawn by the actuator 501 when under a nominal load is a function of the position of the output shaft 520 between the first and second ECT (illustrated by line NOM'). From this nominal current, a threshold current may be defined (illustrated by line V'). The threshold current is therefore also a function of the position of the output shaft between the first and second EOT, but is greater than the nominal current for the same position of the output shaft 520. The controller 530 includes non-volatile memory for storing the threshold current for any position of the output shaft 520 between the first and second EOT.

The controller 530 is configured to receive the detected position of the output shaft 520 from the position detector 530, and the detected current drawn by the motor from the current detector 550. The controller 530 then compares the detected current to the threshold current for the detected position of the output shaft 520. If the detected current is less than the threshold current at that position, then the controller 530 continues to drive the actuator 501. However, if the detected current is greater than the threshold current at that position, then the controller 530 has detected an overload event, for example due to an obstruction, and shuts down the actuator 501.

The controller 530 is configured to receive the detected position of the output shaft 520 and the detected current drawn by the motor on a periodic basis. In this embodiment, the period between measurements is around 10 -20 milliseconds.

Figure 15 also shows line F, representing a constant current limit (as would be used in the first conventional method of the prior art). The difference between the actual current drawn and the limit threshold is a measure of the force applied to the obstruction. Thus, the skilled person will realise that the present invention provides an improved method in which there is a high level of safety throughout the full range of motion, despite variations in loading.

The skilled person will realise that the gearbox and release mechanism are not essential parts of the fourth aspect of the invention. The skilled person shall also realise that stopping the actuator is not the only possible course of action if the actual current exceeds the threshold level; for example, the actuator could be programmed to reverse a short distance to relieve pressure on the obstruction.

An embodiment of the fifth aspect of the present invention will now be described with reference to Figure 16.

An aircraft seat actuator 601 is provided, which includes a housing 610, having a motor (not shown), a gearbox 620, and a release mechanism (not shown). The gearbox 620 is enclosed in a gearbox housing 625.

In this embodiment, the gearbox housing 625 is constructed from 30% glass fibre reinforced polyamide. Furthermore, parts of the actuator housing 610 are coated with a conductive finish such as electrically conductive paint containing nickel, graphite or silver.

Therefore, the gearbox housing 625 has greater strength, stiffness and dimensional stability per unit mass when compared to the aluminium housings of the conventional gearbox housing. Therefore, the gearbox housing 625, and thus the aircraft seat actuator 600 may have less mass, which provides better fuel economy for an aircraft.

Furthermore, this material is suitable for aerospace interior applications as it is fungus inert.

The material also includes a flame-retardant additive (e.g. chemicals such as brominated phosphates and other commercially available halogenated or non-halogenated flame retarding agents), such that the material meets the flammability and smoke toxicity requirements for non-metallic materials of aerospace interior applications. The skilled person will understand that the choice of additive is not essential to the invention, but it must meet the regulations when in use.

The skilled person will understand that the invention is not limited to 30% glass fibre reinforced polyamide. Rather, from 0% up to 50% glass fibre reinforced polyamide provides a suitable high strength, good stiffness and dimensional stability per unit mass.

Furthermore, the skilled person will understand that the invention is not limited to the conductive finish. However, the conductive finish is preferable as it limits the electromagnetic emissions of the internal electronics, and reduces susceptibility to external electromagnetic interference. The skilled person will also understand that the release mechanism is not an essential part of the fifth aspect of the invention.

Polymer materials, being relatively soft, usually require metal inserts at points where loads are applied, such as fastener interfaces or axle seats. The use of rolling bearings (e.g. ball bearings) are used in the current embodiment of the invention, as these provide excellent running efficiency while transmitting axle reactive loads to the polymer housing over a larger surface area than would be the case using dry-sliding bushes. The skilled person will understand that the use of dry-sliding bushes is an option for mounting axles that exert minimal pressure on the housing material. Furthermore, the skilled person will understand that different materials may be employed together in different parts of the overall housing, for example the two halves of a gearbox housing may use polyamide in one part and aluminium in the other. This would allow the load-carrying part of the housing that includes the actuator mountings to be built from aluminium, while the lightly-loaded other part benefits from the weight and cost savings afforded by using polyamide material.

An embodiment of the sixth aspect of the present invention will now be described with reference to Figure 17.

A linear aircraft seat actuator 701 is provided, having a motor 710, a lead screw 720, a nut 730, and an output shaft 740.

In this embodiment, the nut 730 is constructed out of carbon-fibre reinforced polyamide impregnated with FIFE lubricant, and the lead screw 720 is constructed of PTFE-coated stainless steel. Therefore, the linear aircraft seat actuator 701 of the present invention has around 80% of the efficiency of the conventional linear aircraft seat actuator, but can be manufactured at a significantly reduced cost. Furthermore, as conventional linear aircraft seat actuators use a nut with integral ball-bearings, another benefit of the invention is that it is possible to change the lead screw 720 (such as to one with a different length) without the problem of losing ball bearings.

An embodiment of a seventh aspect of the present invention will now be described with reference to Figure 18.

An aircraft seat actuator 801 is provided, which includes a housing 810 (including a motor (not shown), a gearbox 820 and a release mechanism (not shown)). The gearbox 820 has an output stage 830 for receiving an output shaft 840. In this embodiment, the output stage 830 has a hexagonal bore, and the output shaft 840 has a first portion 840a of complimentary hexagonal profile, such that the first portion 840a of the output shaft 840 may be received by the output stage 830. Naturally, the output stage 830 and the first portion 840a of the output shaft 840 must be rigidly received such that any drive of the output stage 830 is substantially or wholly transmitted to the output shaft 840.

In this embodiment, the output shaft 840 includes a flange 840f and a nut thread 840n to secure the output shaft 840 to the output stage 830, i.e. to prevent it from axial movement.

The output shaft 840 has a second portion 840b. In this embodiment, the second portion 840b is an axle, such that the gearbox 820 may be used in a rotary actuator.

The skilled person will understand that the gearbox 820 is a modular construction, such that the output shaft 840 described above may be replaced with a different output shaft, having a first portion with an outer profile complimentary to the bore of the output stage 830 of the gearbox 820, but having a second portion having the form of a lead screw (that is, the second portion is threaded, for receiving a nut), such that the gearbox 820 may be used in a linear actuator. Therefore, the gearbox 820 may be adapted for use in both rotary and linear actuators.

The skilled person will also understand that the profile of the first portion 840a of the output shaft 840 and of the output stage 830 need rot be hexagonal. Rather, any suitable profile may be used, providing the profiles are complimentary. For example, the profile of the bore on the output stage 830 may be splined, and the profile of the first portion 840a of the output shaft 840 may be complimentary to the splined bore.

Furthermore, the skilled person will understand that the present invention is not limited to the nut thread and flange arrangement on the output shaft 840. Rather, any suitable technique for securing the output shaft 840 to the output stage 830 may be used, e.g. circlip grooves.

The skilled person will understand that it is not essential for the actuator 801 to include a release mechanism.

The skilled person will understand that any combination of features is possible, without departing from the scope of the invention, as claimed.

Claims

<claim-text>CLAIMS1. An aircraft seat actuator for moving a part of an aircraft seat and having an end-of-travel state, comprising a controller for controlling the actuator; a light source for producing a light signal; and a light detector for receiving the light signal, and configured to detect a change in the light signal when the actuator is at the end-of-travel state and produce an end-of-travel signal in response, wherein the controller is configured to receive the end-of-travel signal from the light detector.</claim-text> <claim-text>2. An aircraft seat actuator as claimed in Claim 1, wherein the light source is configured to reflect the light signal off an object when the actuator is at the end-of-travel state, and the light detector is arranged for receiving a reflected light signal and producing the end-of-travel signal in response.</claim-text> <claim-text>3. An aircraft seat actuator as claimed in Claim 1, wherein the light source and light detector are arranged in an optical path, and the light detector is arranged to produce an end-of-travel signal when an object interrupts the optical path.</claim-text> <claim-text>4. An aircraft seat actuator as claimed in any preceding claim, wherein the light source is arranged for producing a light signal in the near infra-red range, and the light detector is arranged for receiving the light signal in the near infra-red lange.</claim-text> <claim-text>5. An aircraft seat actuator for moving a part of an aircraft seat, including a rotatable shaft, comprising a detectable member mountable on the rotatable shaft; a first sensor configured to detect the detectable member as it makes a revolution on the rotatable shaft and produce a first signal in response; and a controller, configured to receive the first signal.</claim-text> <claim-text>6. An aircraft seat actuator as claimed in Claim 5, further comprising an end-of-travel detector, for detecting when the actuator has reached an end-of4ravel state and for producing an end-of-travel signal, wherein the controller is configured to receive the end-of-travel signal.</claim-text> <claim-text>7. An aircraft seat actuator as claimed in either Claim 5 or Claim 6, wherein the detectable member is a magnet and the first sensor is a magnetic sensor.</claim-text> <claim-text>8. An aircraft seat actuator as claimed in any one of Claims 5 to 7, further comprising a second sensor and a third sensor, wherein the first, second and third sensors are configured to detect the detectable member mountable as it makes a revolution on the rotatable shaft and produce a second signal and third signal in response respectively, and the controller is also configured to receive the second and the third signal.</claim-text> <claim-text>9. An aircraft seat actuator as claimed in Claim 8, wherein the detectable member is a magnet and the first, second and third sensors are magnetic sensors.</claim-text> <claim-text>10. An aircraft seat linear actuator for moving a part of an aircraft seat, having a housing including an output shaft extending therefrom, comprising a connecting member at a distal end of the output shaft; a fastener, for attachment to the part of the aircraft seat, wherein the connecting member connects the output shaft to the fastener; a magnet, positioned on the connecting member between the output shaft and the fastener; and a magnetic sensor, for detecting the magnet, mounted on the housing.</claim-text> <claim-text>11. An aircraft seat linear actuator as claimed in Claim 10, further comprising an insulating member, for insulating the magnet from the connecting member, the output shaft and/or the fastener.</claim-text> <claim-text>12. An aircraft seat actuator for moving a part of an aircraft seat, having an output shaft configured to move between a first end-of-travel state and a second end-of-travel state, wherein a threshold current drawn by the actuator is a function of a position of the output shaft between the first end-of-travel state and the second end-of-travel state, the actuator comprising a position detector, for detecting the position of the output shaft; a current detector, for detecting the current drawn by the actuator; and a controller, configured to shut-down the actuator if the detected current exceeds the threshold current at the detected position of the output shaft.</claim-text> <claim-text>13. An aircraft seat actuator, including a gearbox having a gearbox housing, wherein the gearbox housing is constructed of polyamide.</claim-text> <claim-text>14. An aircraft seat actuator as claimed in Claim 13, wherein the polyamide is up to 50% glass fibre reinforced polyamide.</claim-text> <claim-text>15. An aircraft seat actuator as claimed in Claim 13, wherein the polyamide is around 30% glass fibre reinforced polyamide.</claim-text> <claim-text>16. An aircraft seat linear actuator, having a lead screw and nut, wherein the nut is constructed of carbon-fibre reinforced polyamide impregnated with PTFE lubricant.</claim-text> <claim-text>17. An aircraft seat linear actuator as claimed in Claim 16, wherein the lead screw is constructed of FIFE-coated stainless steel.</claim-text> <claim-text>18. An aircraft seat actuator, having a gearbox with an output stage for receiving an output shaft, wherein the output stage has a non-circular profile.</claim-text> <claim-text>19. An aircraft seat actuator as claimed in Claim 18, wherein the output stage has a hexagonal profile.</claim-text> <claim-text>20. An aircraft seat actuator as claimed in Claim 18, wherein the output stage has a splined profile.</claim-text> <claim-text>21. An aircraft seat actuator as claimed in any one of Claims 18 to 20, further comprising an output shaft, wherein a part of the output shaft has a profile complimentary to the profile of the output stage.</claim-text> <claim-text>22. An aircraft seat actuator as claimed in Claim 21, wherein the output shaft is for a rotary actuator.</claim-text> <claim-text>23. An aircraft seat actuator as claimed in Claim 21, wherein the output shaft is for a linear actuator.</claim-text> <claim-text>24. An aircraft scat actuator as claimed in any one of Claims 21 to 23, wherein the output shaft includes fastening means, for fastening to the output stage.</claim-text> <claim-text>25. An aircraft seat actuator substantially as herein described with reference to and as shown in any one of Figures 3 to 18.</claim-text> <claim-text>26. An aircraft seat linear actuator substantially as herein described with reference to and as shown in any one of Figures 3 to 18.</claim-text>