Brake-equipped retracting mechanism for retractable member

In a brake-equipped retracting mechanism, rotational force of a motor is used to open a liquid crystal display device from a retracted position to an open position, a power spring is wound up in conjunction with this opening operation, and elastic restoring force thereof is used to return the liquid crystal display device from the open position to the retracted position. A rope for developing a greater or smaller tensile force in conjunction with opening and closing of the liquid crystal display device is wound around a slip clutch linked to a reducer input shaft, whereby braking force for preventing the liquid crystal display device from an abrupt return is applied to the reducer input shaft. The braking force gradually decreases as the liquid crystal display device returns to the retracted position, and the liquid crystal display device can therefore be returned at a substantially constant speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a brake-equipped retracting mechanism whereby a retractable member such as a liquid crystal display device installed in the ceiling of a passenger cabin of an aircraft or the like is swung between a retracted position and an open position.

2. Description of the Related Art

Liquid crystal display devices are installed in ceilings of passenger cabins in aircrafts or the like, and these devices are retracted horizontally in the ceiling and are opened to a substantially vertical open position when necessary. When the liquid crystal display device opens, rotational motion outputted via a motor and a reducer is converted to pivoting movement for opening the liquid crystal display device to the open position via a link mechanism. A power spring is linked to an input or output shaft of the reducer, and the power spring is designed to be wound up in conjunction with the opening movement of the liquid crystal display device. When the liquid crystal display device is retracted, the motor and reducer are disconnected by an electromagnetic clutch, and the liquid crystal display device is returned to the retracted position by restoring force of the wound-up power spring. The reason that the retracting operation should not be dependent on rotational force of the motor is because of a requirement for the liquid crystal display device to be reliably returned to a safe retracted position without relying on an electric force during emergencies.

As shown inFIG. 5(b), a liquid crystal display device1is substantially horizontal position in a retracted position1A, and is substantially vertical position in an open position1B. Therefore, as shown inFIG. 5(a), a torque T(1) that is generated by the own weight of the liquid crystal display device1and urges the device to pivot in an opening direction is greatest in the retracted position, decreases as the device pivots to the open position1B, and reaches a minimum at the vertical position. By contrast, restoring force T(18) of the power spring is lowest when the liquid crystal display device1is retracted because the power spring is wound the lowest number of times (initial winding state), and the restoring force T(18) is at a maximum when the liquid crystal display device1reaches the open position1B, because the number of windings is at a maximum. In order to return the liquid crystal display device1to the retracted position1A with the aid of the power spring, the restoring force T(18) in the initial winding state must exceed the torque T(1) in the opening direction due to the own weight of the liquid crystal display device1in the retracted position.

If restoring force of the power spring is set in this manner, the torque reaches a maximum in the open position and a return torque T(1+18) is applied, which decreases toward the retracted position. The return torque in the open position is extremely strong, which is dangerous because it causes an abrupt closure of the liquid crystal display device1. In view of this, a retracting mechanism of the liquid crystal display device1is provided with a brake mechanism for applying a brake so that the liquid crystal display device closes at an appropriate speed. Conventionally, a gear damper, which increases braking force in proportion to the speed, is used.

However, the gear damper is configured so that multiple gears are provided and frictional force is enhanced by centrifugal force, which leads to problems with complicated mechanisms and poor reliability.

SUMMARY OF THE INVENTION

A main object of the present invention is to provide a brake-equipped retracting mechanism for a retractable member such as a liquid crystal display device or the like that has a reliable and inexpensive brake mechanism with a simple structure.

In order to solve the problems described above, a brake-equipped retracting mechanism for a retractable member of the present invention has:

a retractable member that is opened from a retracted position to an open position by rotational force of a motor;

a return-spring member that undergoes greater elastic deformation in conjunction with the opening operation of the retractable member, and that returns the retractable member from the open position to the retracted position by an elastic restoring force created by the elastic deformation;

a rotational member for transmitting the rotational force of the motor and the elastic restoring force of the return-spring member to the side of the retractable member; and

a string member wound around the rotational member for restraining the rotation of the rotational member; wherein

a tensile force of the string member increases in conjunction with the opening operation of the retractable member so that rotation-restraining force acting on the rotational member is increased, while it decreases in conjunction with the closing operation of the retractable member so that the rotation-restraining force is decreased.

The rotational movement of the rotational member can be transmitted to the side of the retractable member via a link member capable of pivoting around the rotational member between a rotational position corresponding to the retracted position and a rotational position corresponding to the open position. In this case, in order to increase the tensile force of the string member in conjunction with the opening operation of the retractable member, one end of the string member may be fixed in place either directly or via a braking spring member, and the other end of the string member may be linked to the link member either directly or via the braking spring member. When the string member is pulled as the link member pivots, the amount of elastic deformation of the braking spring member increases, the tensile force acting on the string member also increases, and the rotation-restraining force on the rotational member increases as well. Specifically, braking force increases. Conversely, when the string member is slackened, the amount of elastic deformation of the braking spring member decreases, the tensile force acting on the string member also decreases, and the rotation-restraining force (braking force) on the rotational member decreases as well.

Instead of linking the braking spring member to the end of the string member, it is possible to wind a middle section of the string member around a brake drum to which the rotation-restraining force is applied by the braking spring member.

Also, part of the string member may be wound around a tension adjusting drum in order to adjust the tensile force applied to the rotational member by the braking spring member or to adjust the amount of tension or amount of slack in the string member resulting from the pivoting of the link member.

Next, a metal wire may be used as the string member, but it is preferable to use a rope made of a fluororesin with excellent durability and abrasion resistance.

Also, impregnating the string member with grease has advantages in that a specific braking force can be ensured by viscosity of the grease when the string member is slackened, variation in the tensile force of the string member over time can be reduced, and the tensile force of the string member can be easily adjusted.

A typical retracting mechanism of the present invention is configured so that the rotational force of the motor is transmitted to the rotational member via an electromagnetic clutch, and the electromagnetic clutch is cut off when the retractable member is returned to the retracted position. In a more preferred embodiment, a configuration is used in which the rotational force of the motor is transmitted to the link member via a one-way clutch for return prevention, the electromagnetic clutch, a slip clutch for overload prevention, and a reducer, and the string member is wound around an input shaft of the reducer.

The brake-equipped retracting mechanism according to the present invention is designed so that a string member is wound around the rotational member for transmitting the rotational force of the motor, and the tensile force of this string member is increased or reduced in conjunction with the movement of the retractable member. Therefore, it is possible to provide a retracting mechanism that is equipped with an extremely simple, reliable, and inexpensive brake mechanism, compared with a mechanism in which a gear damper is used to create braking force when the retractable member is stowed away.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, a brake-equipped retracting mechanism for a liquid crystal display device installed in the ceiling of a passenger cabin in an aircraft according to the present invention will be described with reference to the drawings.

FIG. 1is a general block diagram showing a brake-equipped retracting mechanism for a liquid crystal display device. A liquid crystal display device1is capable of pivoting from a horizontal retracted position1A in a ceiling2of a passenger cabin in an aircraft, as shown by the solid line, to an open position1B that is open downward by an angle of about 105 degrees, as shown by the imaginary line. A brake-equipped retracting mechanism3for the liquid crystal display device1includes a main section4, and a link mechanism6for converting rotational movement exerted from the main section4into opening and closing movement (pivoting movement) of the liquid crystal display device1around a pivot center shaft5. The link mechanism6includes, for example, a driving-side link7that is linked to a side of the main section4, a driven-side link8that is linked to a side of the pivot center shaft5of the liquid crystal display device1, and an intermediate link9that links the links7,8together and that bends at a slight angle. The liquid crystal display device1stays at the retracted position1A when the driving-side link7is in a first position7A shown by the solid line, and the liquid crystal display device1reaches the open position1B when the link pivots from the first position to a second position7B shown by the imaginary line. When the liquid crystal display device1reaches the open position1B, a screen la can be seen from a passenger seat.

FIG. 2is a diagram showing the main section4of the brake-equipped retracting mechanism3, and is a schematic block diagram of a cross section along a center axis line.FIG. 3(a) is an end view showing a rear end of the main section4,FIG. 3(b) is an end view showing a front end thereof, andFIG. 4is a cross-sectional view as seen from the direction of the arrow A inFIG. 2.

With reference to these drawings, the main section4includes a motor11on the rear side, and rotation of the motor11is transmitted via a reduction gear train12to an input side of a one-way clutch13coaxially aligned with a center axis line4aof the mechanism. The one-way clutch13, an electromagnetic clutch14, and a slip clutch15are aligned in this order coaxially with the center axis line4aof the mechanism from the rear side to the front side. An output side of the slip clutch15is linked to the rear side of an input shaft17a(rotational member) of a coaxially aligned planetary gear reducer17. A distal end17bof the input shaft17aprotrudes by a prescribed length from an end face on a distal end side of the planetary gear reducer17, and an inner end of a power spring18wound around the distal end17bin a spiral is linked thereto. An outer end of the power spring18is fixed to a cup-shaped casing18athat is fixed to a side of a mechanism frame19.

The planetary gear reducer17includes a sun gear17cfixed coaxially with the input shaft17a, an internal gear17dthat concentrically surrounds the sun gear17c, and a plurality of planetary gears17ethat are disposed between the sun gear and the internal gear and that mesh with both of the gears. The planetary gears17eare rotatably supported by a planetary carrier17f. The planetary carrier17fis fixed on the mechanism frame19, and the internal gear17dis rotatably supported by a pair of front and rear ball bearings. The internal gear17drotates in the opposite direction of the input shaft17aand outputs reduced-speed rotation. The driving-side link7of the link mechanism6is fixed to an outer peripheral surface of the internal gear17d. The driving-side link7extends parallel to the center axis line4aof the mechanism toward the distal end side, and one end of the intermediate link9is linked to the distal end thereof.

When the driving-side link7is at the first position7A shown by the solid line, the liquid crystal display device1is in the retracted position1A, and when the link reaches the second position7B shown by the imaginary line, the liquid crystal display device1reaches the open position1B. Specifically, when the motor11is driven while the liquid crystal display device1is in the retracted position1A, rotational force thereof is transmitted to the input shaft17aof the planetary gear reducer17, and its output element, namely the internal gear17d, rotates at a reduced speed. The rotational movement is converted to pivotal movement of the liquid crystal display device1via the link mechanism6, and the liquid crystal display device1begins to open toward the open position1B. Also, the power spring18is wound by the rotation of the input shaft17a. When the liquid crystal display device1reaches the open position1B, the motor11stops and the liquid crystal display device1is held at the open position1B. Here, the one-way clutch13is disposed so as to prevent a return, and the slip clutch15is disposed so as to prevent an overload.

When the liquid crystal display device1in the open position1B is closed (retracted), the electromagnetic clutch14is cut off and the link between the motor11and the gear reducer17is severed. Since the input shaft17aof the gear reducer17is linked to the power spring18, reverse rotation is started by elastic restoring force of the power spring18that is wound up when the liquid crystal display device1is open. As a result, the internal gear17dof the reducer17rotates at a reduced speed in the opposite direction, and the driving-side link7mounted thereon pivots toward the first position7A. The liquid crystal display device1therefore gradually closes toward the retracted position1A. After the liquid crystal display device1has returned to the retracted position1A, the liquid crystal display device1is held at that position by elastic force of the power spring18.

As was described with reference toFIG. 5(a), the torque T(1) that urges the liquid crystal display device1to rotate in the open direction (opening direction) due to the own weight of the liquid crystal display device1is at a maximum when the device is in a horizontal position in the retracted state, the torque reaches zero when the device is in the vertical position (pivoted by 90 degrees) before reaching the open position1B, and a small torque in the opposite direction is created when the device is at the open position1B. A return torque needed to return the liquid crystal display device1from the open position to the retracted position against the torque T(1) due to the own weight of the device ideally increases toward the retracted position1A and reaches a maximum at the retracted position1A, in which case the liquid crystal display device1can be returned to the retracted position1A by a substantially constant torque.

The return torque T(18) from the power spring18reaches a maximum at the open position1B, gradually decreases toward the retracted position1A, and reaches a minimum at the retracted position1A. A combined return torque T(1+18) from the own weight and the power spring becomes extremely strong at the open position1B. This is undesirable because the liquid crystal display device1ends up pivoting abruptly from the open position to the retracted position when the liquid crystal display device1is closed.

The retracting mechanism3includes a brake mechanism20for applying a brake to the pivoting, and the brake mechanism20of the present example includes a rope21made of a fluororesin commonly referred to as Teflon (product name), and a braking coil spring22. As can be seen fromFIG. 4, a rear end21aof the rope21is linked to the braking coil spring22, one end of which is linked to the mechanism frame19. The rope21is pulled out from this position in a stretching direction of the braking coil spring22and is placed over a rope stand23mounted on the mechanism frame19, after which the rope is wound several times around an outer peripheral surface15bof a cylindrical casing of the slip clutch15to which the input shaft17ais linked. Furthermore, the rope is pulled out from the outer peripheral surface15b, placed over the rope stand23, and then pulled out in the opposite direction. A distal end21bthereof is linked to a distal end of a linking bar24fixed to the driving-side link7.

When the driving-side link7is in the first position (when the liquid crystal display device1is in the retracted position1A), the rope21is the most loose, and therefore the braking coil spring22is the most constricted. When the driving-side link7pivots toward the second position, the rope21is pulled along with the pivoting, the braking coil spring22gradually elongates, and tensile force of the rope21increases. As a result, the rotation-restraining force (braking force) increases on a cylindrical casing15aof the slip clutch15around which the rope21is wound.

The braking force on the slip clutch15from the rope21reaches a maximum when the driving-side link7has reached the second position (when the liquid crystal display device1has reached the open position1B), as shown by a curve T(21) inFIG. 5(a). Therefore, when the liquid crystal display device1returns to the retracted position1A from the open position1B, a strong braking force acts on the reducer input shaft17afrom the slip clutch15. The braking force is thereby applied to the reducer input shaft17arotated by the elastic restoring force of the power spring18, and a rotational speed thereof is reduced. Specifically, a substantially constant torque is applied as a return torque, as shown by the curve T(1+18+21) inFIG. 5(a), and the liquid crystal display device1pivots from the open position toward the retracted position at a substantially constant speed.

Specifically, the elastic restoring force T(18) of the power spring18decreases as the liquid crystal display device1nears the retracted position1A because the power spring is gradually wound back up. Accordingly, the tension on the rope21is gradually relaxed as the liquid crystal display device1nears the retracted position1A, and therefore the braking force T(21) resulting from the tensile force of the rope21gradually decreases as well. Accordingly, when the liquid crystal display device1is retracted, the device returns to the retracted position1A at a substantially constant speed because a substantially equal return torque T(1+18+21) is applied.

Thus, in the brake-equipped retracting mechanism3of the liquid crystal display device of the present example, the rope21pulled by the coil spring22is wound around the slip clutch15linked to the reducer input shaft17a, a maximum braking force is applied to the reducer input shaft17awhen the liquid crystal display device1is in the open position, and the rope21is loosened as the device moves from the open position to the retracted position to reduce the braking force. Therefore, it is possible to provide a highly reliable retracting mechanism because a predetermined braking force can be reliably applied with an extremely simple and inexpensive configuration.

(Another Example of a Brake Mechanism)

Next, another example of a brake mechanism that can be mounted in the brake-equipped retracting mechanism3will be described.FIG. 6is a diagram showing a mechanism main section4A including a brake mechanism20A, whereinFIG. 6(a) is a schematic block diagram of a cross section along a center axis line4a,FIG. 6(b) is a cross-sectional view as seen from the direction of an arrow A, andFIG. 6(c) is an explanatory diagram of the brake mechanism. The basic configuration of the mechanism main section4A is identical to the mechanism main section4previously described, and therefore the corresponding components are denoted by the same numerals, and descriptions thereof are omitted.

The brake mechanism20A of the mechanism main section4A of the present example includes a Teflon rope31, a brake adjusting drum33equipped with a braking coil spring32, and a tension adjusting drum34. As can be seen fromFIG. 6, a rear end31aof the rope31is fixed to the mechanism frame19, from where it is pulled out to be wound around the outer peripheral surface15bof the cylindrical casing of the slip clutch15one or more times, and is then wound multiple times around the brake adjusting drum33. The rope is then pulled out from this position, wound around a small drum part34aand a large drum part34bin the tension adjusting drum34, thereafter placed over a rope stand35, and linked to a linking bar36of the driving-side link7.

The brake adjusting drum33includes a support axle33afixed to the mechanism frame19, and a drum main body33brotatably supported on a distal end of the support axle33a. The drum main body33bis fixed to a distal end of the braking coil spring32disposed around the support axle33a. A rear end of the braking coil spring32is fixed to the support axle33aor the mechanism frame19.

When the driving-side link7pivots from the first position7A to the second position7B, the rope31is pulled along with the pivoting. As a result, the section wound around the tension adjusting drum34is unwound, the braking coil spring32is wound accordingly, and tensile force of the rope31therefore increases. At the point that the driving-side link7reaches the second position7B, the tensile force acting on the rope31reaches a maximum, and therefore the braking force (rotation-restraining force) acting on the reducer input shaft17avia the slip clutch15around which the rope is wound also reaches a maximum. When the driving-side link7begins to return from the second position7B to the first position, the rope31is slackened, the braking coil spring32is wound back accordingly, and the tensile force acting on the rope31decreases. As a result, the braking force acting on the reducer input shaft17aalso decreases.

Therefore, the brake mechanism20A of the present example can function in the same manner as the brake mechanism20of the mechanism main section4previously described, and the liquid crystal display device1can be returned from the open position1B to the retracted position1A at a substantially identical speed.

Also, in the brake mechanism20A of the present example, a middle section of the rope31is wound around the tension adjusting drum34. Varying the size of the large drum part34band the like of the tension adjusting drum34makes it possible to adjust the amount of tension, the amount of slack, and the tensile force of the rope31that accompanies the pivoting of the driving-side link7. Accordingly, the braking force can be easily adjusted.

Other Embodiments

The present invention can also be applied to a brake-equipped retracting mechanism for opening a retractable member of a device other than a liquid crystal display device installed in the ceiling of a passenger cabin.

A Teflon rope was used as the rope for creating braking force in the example above, but it is also possible to use a rope, cord, wire, or other string members made from a different material.

Also, when a string member made from Teflon or another material is used, impregnating it with grease is advantageous in that a prescribed braking force can be ensured by viscosity of the grease when the string member is slackened, variation in the tensile force of the string member over time can be reduced, and the tensile force of the string member can be easily adjusted.

The following effects can also be obtained in the example above when a one-way switch is disposed concentrically on the slip clutch15. Specifically, the load on the motor from the braking force when the liquid crystal display device1is open can be reduced, and slackening resulting from paying-out of the rope for creating braking force can be prevented.