GB2442438A

GB2442438A - Adjustable seat with load cell and counterbalance

Info

Publication number: GB2442438A
Application number: GB0619775A
Authority: GB
Inventors: Dominic James Robinson
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-10-06
Filing date: 2006-10-06
Publication date: 2008-04-09
Also published as: WO2008041040A1; GB0619775D0

Abstract

A seat assembly, which may be for an aircraft seat, has a substantially horizontal portion (2) supported by flange (4) mounted on an inclined support via guides (6 and 8) that slidably engage a guide rail (10). The guide rail may be located to a chassis via brackets (12 and 14). Sliding of guides (6 and 8) causes the seat portion to move with a component of vertical movement, the brackets may be attached to a first gas spring (16) which is in communication with a second gas spring (24) via conduit (34). A load cell (40) may be affixed to the horizontal portion (2) and may send a signal to control system (42) which energises an actuator (32). The actuator may drive a second gas spring and may force a second piston (28) along a bore in response to the signal from the load cell. The response may be proportionate to maintain the seat assembly at a desired height, thus acting to counterbalance the users weight and allow the user to easily adjust the seat up and down. In an alternative embodiment, see figures 7 and 8, the gas springs may be replaced by a cable and drum drive means, (50 and 52) that may be connected to the chassis and the seat base. In a further embodiment there may be a means to lock the seat in a desired position. A rack and pinion drive means may be used as an alternative to the gas springs, see figures 10 and 11.

Description

at Assemblies The present invention relates to seat assemblies and, in

particular, to seat assemblies incorporating counter-balancing systems.

In mechanised seats such as are used in premium aircraft cabins, the seat portion usually remains in the same horizontal plane while the hack and foot rest portions are lowered and raised respectively to recline the passenger. Since most of the weight of a passenger is borne by the seat portion, relatively low energy is required from the various drive mechanisms to effect the change to the back and footrest portions. The same is true for mechanisms which change the seat into a bed. Both mechanisms require a great deal of space in which to operate.

However, in a confined space, it may be preferable to lower the seat portion relative to the floor in order to make the most use of otherwise inaccessible space under the seat in front and to offer unproved comfort. This requires a change to conventional seat architecture which places the rear tie bar behind and below the rear of the fixed seat pan and the front tie bar below the front of the seat pan.

To facilitate greater knee room, it is necessary to raise the rear tie bar above knee level and to facilitate forward and downward movement of the seat, it is necessary to lower the front tie bar.

The seat mechanism can be mounted internally within a rigid outer chassis.

If the back portion is hinged to the seat portion. a coincident forward movement of the seat portion will offer a greater angle of back recline. The seat can be lowered by allowing it to fall naturally under gravity, but to return the seat to its original position, the whole weight of the passenger and seat mechanism now needs to be lifted requiring greater energy than horizontally driven systems and a larger and more resilient motor to be selected to accommodate the heaviest passengers.

In a manual lifting system, which might incorporate a ratchet drive mechanism, the occupant of the seat will be required to lift his own weight. Without gearing or spring assistance this might prove impossible and even with suitable gearing, the number of strokes of a lever or the time it might take or the force required may prove unacceptable. In powered systems gravity aids descent but raising the seat can take up to 50% longer than descent for heavier passengers.

Where spring assistance is provided of a fixed median force an occupant matching the weight of the spring force would require no energy to move the seat in either direction of travel since both he and the force of the spring would be counterbalanced in equilibrium.

However, a lighter occupant would need to work against the force of the spring to lower the seat but require no energy to raise the seat and a heavier occupant would overcome the spring force upon descent but would have to apply energy to raise the seat. Whilst the energy and forces required might be less than those without spring assistance this might also prove unacceptable.

Ideally, therefore, a counterbalance adjustable for the weight of each passenger is preferred so that the smallest and lightest motor capable of accommodating even the heaviest passenger can be specified for the primary drive mechanism.

It is an object of the invention to provide an improved seat assembly.

According to the present invention there is provided a seat assembly comprising a seat portion constrained for movement in direction having at least a component of vertical displacement, sensing means for sensing any load applied to the seat portion, counterbalancing means for providing a counterbalance force acting to displace the seat portion in a sense to oppose said load, said counterbalancing means responding to the sensing means to achieve a level of counterbalance related to the load sensed by said sensing means.

According to the present invention there is further provided a seat assembly compii sing a seat portion constrained for movement in a direction having at least a component of vertical displacement, locking means for locking the seat portion against movement in a default position. sensing means for sensing any load applied to the seat portion in the default position, counter balance means for providing a counter balance force to the seat portion to match the load sensed by the sensing means, and drive means actable when the locking means is disengaged for driving the seat portion to and from the default position.

Seat assemblies embodying the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of a seat assembly; Figures 2 to 6 are side elevations of the seat assembly of Figure 1 in different configurations; Figures 7 and 8 are side elevations of a second embodiment of a seat assembly respectively with the seat raised and the seat lowered; Figure 9 is a view similar to that shown in Figure 4 but showing the primary drive mechanism for the seat; Figures 10 and 11 show side elevations of a modification to the primary drive mechanism in different operative positions; Figure 12 shows side elevations of a conventional seat and the positions of standard tie bars; and Figure 13 shows side elevations of a modified seat incorporating a raised rear tie bar, a lowered front tie bar and a sliding seat mechanism.

The seat assembly shown in Figure 1 comprises a generally horizontal seat portion 2 having a generally vertically extending triangular support flange 4 on its underside. A pair of space guides 6 and 8 rigid with the support flange 4 slidably engage a guide rail 10 which is secured at opposite ends by a pair of brackets 12 and 14 to a chassis (not shown).

The guide rail 10 is inclined both to the horizontal and to the vertical to constrain the seat portion 2 for combined vertical and horizontal movement along a predetermined path.

A first gas spring 16 has one end secured to the bracket 14 and its opposite end secured to the support flange 4. The gas spring 16 consists of a cylindrical gas chamber 18 housing a piston 20 which moves along the chamber and a piston rod 22 which is coupled to the support flange 4 to cause displacement of, or be displaced by, the piston 20.

A second gas spring 24 consists of a cylindrical gas chamber 26 housing a piston 28 which moves along the chamber and a piston rod 30 which is coupled to an electric motorised actuator assembly 32. The cylindrical gas chamber 26 is rigid with the bracket 14. A conduit 34 provide.s communication between the two chambers 18 and 26 at ends thereof remote from their respective pistons 20 and 28.

The actuator assembly 32 comprises a body 36 rigidly secured to the chassis (not shown) and housing a telescopically extendable rod assembly consisting of a plurality of rods 38 with the outermost rod held captive by the body 36 and the innermost rod 38 coupled to the distal end of the piston 30 The actuator 32 is energisable to move the rods 38 so as to displace the piston 28 up and down the cylinder 26.

A load cell 40 mounted on or embedded in the seat 2 provides an output indicative of the weight applied to the seat. A control system 42 controls the energisation of the actuator 32 in response to the output of the load cell in a sense to maintain pressure on opposite sides of the piston 20 of the first gas spring 16 in equilibrium. Thus, as the load on the seat increases the piston 20 of the first gas spring 16 will tend to be displaced downwardly to increase the gas pressure in the cylinder I 8. However, at the same time the control system 42 will energise the actuator 32 to displace the rods 38 and so drive the piston 28 to increase the gas pressure in the cylinder 26. This increased gas pressure is communicated via the conduit 34 to the first gas spring to an extent sufficient to prevent the displacement of the piston 20. Instead of the electric actuator, other drive means could be used.

To raise and lower the seat 2 once equilibrium has been established, a primary drive mechanism is operated. The primary drive mechanism is described in connection with Figures 9 to 11 hereinafter.

In the embodiment shown in Figures 7 and 8, parts similar to those in Figure 1 are similarly referenced.

As shown, the two gas cylinders of Figure 1 are replaced by a cable and reel assembly. One end of the cable 50 is secured to the seat portion 2 while the other end of the cable 50 is secured to a reel 52 on which the cable 50 can be wound. The reel is coupled to a gear assembly 54 by a torsion spring (not shown). A motor 44 drives the gear assembly 54. The motor 44 in turn is controlled by the control system 42. The system 42 responds to the weight detected by the load cell 40 to vary the tension in the torsion spring in a sense to resist any displacement of the seat. Displacement of the seat can then be achieved by reeling in or reeling out the cable 50 from the reel until the seat has achieved its desired location. In another modification (not shown), the counter balancing means could consist of an extension or compression spring with an actuation device to vary the pre-load or pre-tension of the spring in dependence upon the load sensed.

As will be appreciated, a backrest, shown in Figure 13, is pivotally coupled to the seat to allow different angular configurations of the back rest relative to the seat portion.

In order to prevent premature temporary lowering of the seat the instant that a weight is applied, the seat portion may initially be locked in its raised position by a manual or solenoid operated bolt (not shown) which is then unlocked after the control system has responded to the output of the load cell.

The bolt may be used to lock the piston 28 in a median or default position as shown in Figure 1 so that adjustment in opposite directions for light or heavy persons is minimal.

With the system at equilibrium, preloaded for the weight of the passenger, plus if necessary an incremental amount to bear shock loads, the bolt can he withdrawn and the seat portion moved. For a middle weight occupant, the piston 28 may be set to a middle position (Figure 4). For a light occupant, piston 28 is extended (Figure 2 and 5) and for the heaviest passenger, the piston 28 is compressed (Figure 3 and 6).

As the seat portion moves along the guide rail 10 the pressure in the system increases so that a drive mechanism has to work against the counter balance mechanism to permit downward travel. On its return the increased pressure in the system aids the drive mechanism to return the seat portion to its starting position.

To raise or lower the seat portion 2 once equilibrium has been established, a manually or electrically actuated primary drive mechanism is used. Figure 9, shows an electrically actuated drive mechanism consisting of a composite motor and gear assembly having support platform 62 secured to the underside of the seat portion 2. The seat portion 2, in turn, is constrained for movement relative to the chassis for combined horizontal and vertical movement by guide rails 10. A gear 64 secured to the outer shaft of the composite motor and gear assembly 60. engages a rack 66 rigidly secured to the chassis (not shown) and inclined to both the horizontal and vertical.

Energisation of the motor 60 thus controls the primary displacement of the seat portion 2 in the vertical and horizontal direction. Should there be a power failure to the power being supplied to the motor and gear assembly 60 the seat portion 2 will be locked relative to the chassis (not shown) in its last position at the instant of power failure.

The modification shown in Figures 10 and 11 allows the seat portion 2 to return it to its original raised position relative to the chassis (not shown) in the event of power failure.

Parts in Figures 10 and 11 similar to those in the preceding Figures are similarly referenced.

In Figures 10 and 11, the rack 66 instead of being rigidly secured to the chassis has one end pivotally secured to the chassis by a pivot 68. A rod assembly 70 comprises an upper rod 72, terminating at its upper end in a button 74 and pivotally connected at its lower end to a lower rod 76. The lower end of rod 76 is pivolally connected by pivot 78 to the end of rack 66 remote from pivot 68.

The rod assembly 70 which is held captive by a housing 80 rigid with the chassis can be moved to displace the rack 66 into and out of engagement with the gear 64. A coil spring 82 encircling the rod 72 normally urges the rod assembly 70 upwardly in a sense to cause the rack 66 to engage the gear 64. A lock 84 horizontally constrained within a housing 86 rigid with the chassis comprises a locking pin 88 which slidingly engages a cavity within the button 74 to prevent rod assembly 70 from lowering to allow rack 66 to disengage from gear 64. The end of lock 84 remote from the locking pin 88 engages a push rod 90 encircled by a coil spring 92. When lock 84 is moved against the bias of spring 92 the locking pin 88 is disengaged from button 74 allowing it to be displaced manually downwardly from the position shown in Figure 10 to the position shown in Figure 11, against the bias of the spring 82. As a result the rack 66 disengages the gear 64 and so the seat portion is released from constraint and can slide upwardly to its original raised position relative to the chassis under the action of the counterbalance system. Thus, in the event of a power failure, operation of the rod assembly 70 allows the seat to return to its original raised position, but also allows the seat to be repositioned manually to any required location on its path of travel. Release of the rod assembly 70 will then lock the seat portion 2 in that location.

As will be appreciated the manual or solenoid operated bolt acts as a default locking mechanism which is automatically engaged when the seat returns to it original or default position. The lock cannot be disengaged until the counterbalance mechanism has been set or the system confirms that the weight of the passenger is less than the safe operational load of the motor. The lock has to be manually disengaged by the passenger to activate the seat mechanism each time or could be electrically disengaged when the seat mechanism is activated from its start position, provided the counterbalance status permits it.

Adjustment to the counterbalance is made when the occupant sits in the seat, such adjustment and therefore such power call (energy requirement) being made on the ground prior to take off, requiring minimal power to adjust the seat in flight or in emergency conditions, If a passenger stands up or vacates his seat, removing his weight from the load cell, the system will automatically reset to its default zero position, and will make a readjustment to the counterbalance only when a new occupant is in place.

It will be appreciated that where a plurality of such seats are used in an airliner, the load cells may communicate with a control database to provide information on the total weight of all the passengers to help manage fuel loads and to confirm the status of individual seats during take off and landing procedures.

The locking mechanism and therefore operation of the seat mechanism can be restricted or controlled by an override from the flight deck or cabin crew station. Such a facility could be used to vary the ratio of powered and static seats between economy and premium economy cabins, or to limit the length of travel of the mechanism in premium economy cabins relative to business or luxury cabins, providing an infinitely flexible, demand driven cabin layout.

The seat mechanism described (shown in Figure 3) can be accommodated within a rigid outer chassis, adjacent seats linked together by the front and rear tie bars. The rear tie bar is located at a height roughly in the region of, and behind, the waist level of the passage, allowing greater knee room for the passenger behind. The front tie bar is lowered to permit a seat mechanism to be deployed that can lower the seat pan to gain better access to the space under the seat in front. The seat and backrest portions within the shell advantageously define an included angle in the range of 1100 to 130 between them but preferably an angle of 121.50. The back rest portion guide is angled rearwardly from a vertical plane passing through the junction between the seat and hack rest portions, at an angle in the range of 2.5 to 7.5 but preferably at an angle of 50* The seat portion guide inclines downwardly from a horizontal plane passing through the same junction in the forward direction at an angle in the range of 20 to 30 but preferably 26.5 . Oaims

Claims

1. A seat assembly comprising a seat portion constrained for movement

in direction having at least a component of vertical displacement, sensing means for sensing any load applied to the seat portion, counterbalancing means for providing a counterbalance force acting to displace the seat portion in a sense to oppose the load, said counterbalancing means responding to the sensing means to achieve a level of counterbalance related to the load sensed by said sensing means.

2. An assembly according to Claim 1, wherein said seat portion is mounted by guides on a guide rail which is inclined to both the horizontal and the vertical.

3. An assembly according to Claim 1 or to Claim 2, wherein said counterbalancing means comprises a gas spring acting on said seat portion and means for varying the gas pressure in said spring in dependence upon the load sensed.

4. An assembly according to Claim 1 or to Claim 2, wherein said counterbalancing means comprises a spring acting on said seat portion and means for varying the preload or pre-tension in said spring in dependence upon the load sensed.

5. An assembly according to Claim 3, wherein said means for varying the gas pressure in said spring comprises a second gas spring in fluid communication with the first mentioned gas spring and means for varying the loading on the second gas spring to alter the gas pressure in the first mentioned gas spring in dependence upon the load sensed.

6. An assembly according to Claim 5, wherein said sensing means comprises a load cell, wherein said counterbalancing means includes an electric motor for driving said drive means and wherein said control means is responsive to the output of the load cell to control said motor accordingly. -Il-

7. An assembly according to any preceding claim, including locking means for locking said seat portion in a predetermined reference position until after said counterbalancing means have responded to the load sensed.

8. An assembly according to Claim 7, wherein said locking means comprises a solenoid operated bolt.

9. An assembly according to any preceding claim, comprising a primary diive mechanism intermediate the seat portion and counterbalancing means and operable to displace the seat portion relative to the counterbalancing means.

10. An assembly according to Claim 9, including decoupling means for decoupling the primary drive mechanism from the counterbalancing means to allow the seat portion to be manually repositioned relative to the counterbalancing means.

11. An assembly according to Claim 10, wherein the primary drive mechanism is coupled to the counterbalancing means via a rack and gear drive, wherein the rack and gear of the drive are normally bia.sed into engagement with each other, and wherein the decoupling means is operable to disengage the rack and gear from one another to effect said decoupling.

12. A seat assembly comprising a seat portion constrained for movement in a direction having at least a component of vertical displacement, locking means for locking the seat portion against movement in a default position, sensing means for sensing any load applied to the seat portion in the default position, counter balance means for providing a counter balance force to the seat portion to match the load sensed by the sensing means, and drive means actable when the locking means is disengaged for driving the seat portion to and from the default position.

13. A seat assembly according to claim 12 including means for determining when the -12-counterbalance force matches the applied load and disengaging the locking means in response thereto.

14. A seat assembly according to claim 12 including means for inhibiting the actuation of the locking means until the counterbalance force matches the load sensor.

15. A seat assembly according to any one of claims 12 to 14 including means responsive to the removal of the load on the seat portion to control the return of the seat portion to the default position and then actuate the locking means to lock the seat in the default position.

16. A seat assembly according to any one of claims 12 to 15 including override means for overriding the control of the locking means and the drive means from a remote location.

17. A seat assembly according to any preceding claim, including a back rest pivotally coupled to said seat portion and a rigid outer chassis within which said back rest and seat portion are accommodated.

18. A seat assembly substantially as hereinbefore described, with reference to Figures 1 to 6 or Figures 7 and 8 or Figures 9 to 11 or Figure 13 of the drawings.