Actuator

An actuator has a rotatable input member coupled to a drive member such that rotation of the rotatable input member under an input load causes rotation of the drive member on a first axis. The drive member is coupled to a driven member such that rotation of the drive member causes rotation of the driven member on a second axis which is laterally offset from the first axis. A coupling between the drive member and the driven member is arranged to provide a rotational reduction from the drive member to the driven member. The driven member is arranged for connection to a wire of a Bowden cable having a sleeve seatable in relation to a housing for the actuator such that rotation of the driven member causes extension or retraction of the cable. The braking means exerts a braking load on a braking surface of the actuator which is fixed relative to the housing and the braking means is arranged for cooperation with the drive member such that when a backdriving load is exerted through the Bowden cable wire to the driven member, tending to cause the driven member to rotate the drive member, the drive member cooperates with the braking means to increase the braking load to resist rotation of the drive member.

FIELD OF THE INVENTION

This invention relates to an actuator which is suited for the actuation of lumbar supports employed in vehicle seats, such as in aircraft, waterborne vehicles and land vehicles. It will be convenient to describe the invention in relation to its use as a lumbar support actuator, but it should be appreciated that an actuator according to the invention could be employed in other fields.

BACKGROUND OF THE INVENTION

It is well known to provide adjustable lumbar supports in vehicle seats. Various different forms of adjustable lumbar supports exist and variation occurs both in the lumbar supports themselves and in the actuators that enable lumbar support adjustment.

Some manual actuators for lumbar supports include a rotatable knob which can be rotated both clockwise and anti-clockwise, in order to increase or decrease the extent of lumbar support. In some forms of this type of actuator, the mechanism of the actuator includes a braking function, to brake the actuator against backdriving from an adjusted position. The force applied to rotate the knob must be large enough both to overcome the braking load, as well as to perform the lumbar support adjustment. Because of this, the knob can be difficult to rotate. That difficulty can be accentuated as the knob is usually located in a confined position, such as on the side of the seat back, between the seat and the vehicle door frame.

Some lumbar support actuators are bulky, which can limit the seat designs with which they can be used. Also, many actuators require several revolutions of the knob to adjust the lumbar support between extreme positions.

SUMMARY OF THE INVENTION

Some embodiments of the present invention provide an improved actuator which is simple and easy to produce.

According to the one embodiment of the present invention, there is provided an actuator including a housing and, within the housing: a rotatable input member; a drive member; a driven member; and braking means, wherein the rotatable input member is coupled to the drive member such that rotation of the rotatable input member under an input load causes rotation of the drive member on a first axis. The drive member is coupled to the driven member such that rotation of the drive member causes rotation of the driven member on a second axis which is laterally offset from the first axis, and the coupling between the drive member and the driven member is arranged to provide a rotational reduction from the drive member to the driven member. The driven member is arranged for connection to a wire of a Bowden cable having a sleeve seatable in relation to the housing such that rotation of the driven member causes extension or retraction of the wire. The braking means exerts a braking load on a braking surface of the actuator which is fixed relative to the housing and the braking means is arranged for cooperation with the drive member, the cooperation being such that when a backdriving load is exerted through the Bowden cable wire to the driven member, tending to cause the driven member to rotate the drive member, the drive member cooperates with the braking means to increase the braking load to resist rotation of the drive member.

An actuator according to some embodiments of the present invention advantageously can be assembled with relatively few parts. Thus the cost of an actuator according to the invention can be lowered by virtue of lesser components and greater ease of assembly. Also, the ease of actuation of the actuator according to the invention is able to be improved.

In some embodiments of the invention, both the drive member and the rotatable input member are arranged for cooperation with the braking means. The cooperation between the rotatable input member and the braking means is such that upon an input load being applied to the rotatable input member, the braking load exerted on the braking surface is reduced. The resistance to rotation of the rotatable input under an input load is reduced so that a reduced effort to rotate the rotatable input is achieved, compared to the effort required if the braking load exerted by the braking means was not reduced. This reduction of the braking load is important when the actuator is to be employed for lumbar support adjustment and is awkward to access, as the ease with which the rotatable input can be rotated is an important characteristic.

The braking means can be a suitable brake or clutch arrangement in which the braking load can be increased under a backdriving load, so that unintended adjustment is avoided. In one form, the braking means comprises a curved spring. The spring can be a penannular band, or it can be a coil spring which preferably comprises two or more turns. The spring will be manufactured of spring metal, which can resiliently adjust to expand or contract its radius of curvature.

A braking means in the form of a resilient penannular band, or in the form of a coil spring, preferably defines spaced-apart turned end portions. The arrangement is such that, upon rotation of the drive member when a backdriving load is experienced, the drive member cooperates with one of the spring end portions depending on the direction of rotation of the drive member. In this arrangement, the cooperation between the drive member and the end portions is such as to cause the band or spring to increase its radius of curvature and thus to increase the braking load against the braking surface. Preferably the end portions extend inwardly from the braking surface for engagement by the drive member.

The drive member is preferably coupled to the driven member by a geared coupling, most preferably by a spur gear coupling. The drive member may include a first spur gear coaxially with the rotatable input such as a toothed spindle which extends coaxially from the rotatable input for meshing engagement with a gear portion of the driven member. The driven member can include a fully circular second spur gear although, in one preferred form of the invention, the driven member has a part circular second spur gear. In that form, the part circular spur gear may extend through an arc of about 120°. The arcuate extent of the second spur gear on the driven member is related to the extent of travel which is required between the wire and sleeve of a Bowden cable and therefore the spur gear can extend arcuately a lesser or greater amount than 120°, such as from 100° to 140°.

A helical gear arrangement could alternatively be employed, particularly if noise and backlash are to be minimised. Still alternatively, a geared connection could be replaced with a belt and pulley connection, for example one using a toothed belt operable between sprockets.

The drive member preferably has three portions, comprising a first portion for coupling to the rotatable input member, a second portion for coupling to the driven member and a third portion which is disposed between the first and second portions, for cooperation with the braking means. In some embodiments of the invention, the first, second and third portions have a common axis and that the third portion is a generally circular disc having major surfaces normal to the common axis. In this form of drive member, an abutment means can extend from one major surface of the disc for cooperation with the braking means, such as at a peripheral edge of the disc. The abutment means preferably extends beyond the outer periphery of the disc.

The abutment means can define a pair of abutment surfaces which face generally away from each other and which are spaced from each other circumferentially of the disc and are arranged to be positioned between inwardly extending end portions of a spring forming the braking means. The circumferential spacing between the abutment surfaces and a respective inwardly extending spring end portions, in a rest position of the drive member, should be small. This is so that only a small amount of rotation of the drive member under a backdriving load, will result in one of the abutment surfaces engaging one of the spring end portions to cause the spring to flex and increase its radius of curvature and thereby to increase the braking load against the braking surface for resisting the backdriving load.

The rotatable input member can also include abutment means which defines a pair of circumferentially spaced abutment surfaces which face circumferentially towards each other and between which the abutment means of the drive members is receivable. By this arrangement, each spring end portion is positioned between two opposing abutment surfaces each of which is defined by a respective abutment means. Accordingly, when an input load is applied to the input member, one of the abutment surfaces of the input member will engage one of the spaced-apart end portions of the spring, to contract the radius of curvature of the spring and thereby to reduce the braking load against the braking surface. The abutment faces of the rotatable input member can likewise be positioned close to the spring end portions, for the same reason that only a small rotation of the rotatable input member will bring an abutment surface into engagement with the one spring end portion to contract the spring.

The close spacing of the opposing abutment surfaces of the respective abutment means of the drive member and the rotation input member thus results in only a small rotational movement of either of the drive member or the rotational input member for engagement of the spring portion end to be achieved. In some embodiments of the invention, the rotational movement is not more than 4° to 10°, and in some embodiments from 4° to 6°.

It should be appreciated, that expansion or contraction of the radius of curvature of the spring is dependent on the load applied to the actuator. An input load will drive the input member to engage the spring in a manner which causes the spring to flex to reduce its radius of curvature, while a backdriving load will cause the drive member to engage the spring in a manner which causes the spring to flex to expand its radius of curvature.

It is not necessary that the braking load be completely reduced to allow the rotatable input and the drive member to rotate under an input load. In some instances, it may be desired that the reduction in the braking load be as large as possible, but it may be acceptable for a small residual braking load to be maintained in the spring so that the spring slips against the braking surface upon rotation of the rotatable input member under the influence of an input load.

Optionally, the actuator includes stop means to stop rotation of the rotatable input member after a predetermined amount of rotation in either direction. For example, the rotation could be terminated at each of extreme positions for a full range of required lumbar support adjustment. In the preferred arrangement, the rotatable input member is rotatable through about two revolutions thereof in achieving that full range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows an assembled actuator10, whileFIG. 2is an exploded view of actuator10, showing individual components. The actuator10has a housing11which includes an upper housing part12and a lower housing part13. The housing parts12and13connect together by interconnection of snaplock tabs12aof part12into receiving tabs13aof part13.

The actuator10includes a manually rotatable handle or knob14(shown partly broken away inFIG. 1) and, within housing11, a spring brake15, a rotatable input member16, a drive member17and a driven member18. Apart from the handle14and the spring brake15, each of these parts is illustrated separately in two views inFIGS. 3 to 7.

The upper housing12includes a cylindrical portion20which accommodates a hollow, upper splined extension21of the rotatable input member16. The splined extension21of the input member16is spaced from the internal wall22of the cylindrical portion20so that an internally splined, inner sleeve14aof the actuating knob14can be inserted into the cylindrical portion20and engage the splined extension21. Thus, by manual rotation of knob14, input member16is rotatable.

The spring brake15is a coil spring, and each end portion15aand15bof the spring15is bent to extend inwardly. The spring15has a diameter sufficient to fit around a surface24of an upstanding part annular wall25of the input member16. The spring15is arranged so that the end portions15aand15bextend inwardly in front of a radial surface of a respective abutment26and27(FIG. 6) at each end of the wall25. The input member16includes a flange28around wall25to support the spring15.

The input member16defines, on an underside thereof, a recess30within the depth of flange28and in which a portion of the drive member17is received. The configuration of the input member16is such that a circular disc31of the drive member17is a loose rotatable fit within the recess30. Moreover the circumferential gap G between the end faces26and27of the input member16is more than sufficient to accommodate an abutment32on disc31of the drive member17, with each of end abutment surfaces33and34of the abutment32being opposed to but closely spaced apart from the end surfaces26and27, respectively, so that each spring end portion15aand15bcan be loosely positioned between a respective one of opposed surface pairs26,33and27,34.

The drive member17has a spindle35. The spindle35is accommodated within a bore36formed in the splined end21of the input member16and thereby enables accommodation of the disc31within the recess30. The drive member17thus nests coaxially with the input member16.

Projecting from the major face of the disc31remote from the spindle35, drive member17has a splined shaft37. The shaft37extends coaxially with the spindle35and the shaft37is arranged for toothed engagement with a spur gear38formed on the driven member18. The driven member18defines a bore40in which is received a boss41which projects from the inner surface42of the upper housing part12. The lower end of boss41is recessed at41aso as to locate on annular bead41bof lower housing part13when housing parts12and13are connected together. The driven member18is driven to rotate about the axis X-X of boss41upon rotation of the drive member17. The driven member18further includes a slotted opening43to receive a barrel44affixed to the end of an actuating wire46of a Bowden cable47. The driven member18further includes a cable groove48which extends on either side of the opening43, to enable wire46to extend in a selected one of opposite directions.

FIG. 8is a view of the upper housing part12which is provided to illustrate the arrangement of the input member16and the drive member17(both depicted as projections and shown in broken outline), specifically in respect of their interaction with the spring15. InFIG. 8, the spring15is shown accommodated within an annular recess50defined by housing part12. The resilience of spring is such that it is biased to expand into frictional engagement with the peripheral wall52of the recess50. Thus, the natural radius of curvature of the spring15must be reduced for the spring to be accommodated in the recess50.

With the spring15accommodated within the recess50, the spring end portion15ais positioned respectively between opposed surfaces26,33, with spring end portion15bpositioned between opposed surfaces27,34. In each case, the respective opposed surfaces are slightly spaced from engagement with the respective spring end portions15aand15b.

With the parts of actuator10assembled together, driven member18is retained on boss41and rotatable on axis X-X of boss41. Also, drive member17is nested in input member16, with its spindle35received in bore36of extension21of input member16, with disc31of drive member21located in recess30of input member16and with abutment32between surfaces26and27of member16. The extension21of member16is located coaxially within cylindrical portion20of upper part12of housing11, and then inner sleeve14aof knob14is received in portion20and makes a splined coupling with extension21. The spring15is located around surface24of wall25of input member16, with its ends15aand15blocated between the opposing respective surfaces as depicted inFIG. 8. The bias of spring15generated by its resilience, and the need to reduce the radius of curvature of spring15in order for it to be received in recess50results in spring15frictionally engaging peripheral wall52of recess50. Thus, knob14, input member16, drive member17and spring15have a common axis Y-Y through portion20, with axis Y-Y substantially parallel to and laterally offset from axis X-X. The offset is such that teeth defined by splined shaft37mesh with the teeth of gear38on the driven member18. As will be appreciated, the extension21and wall24of input member16, as well as the spindle35, disc31and shaft37of drive member17all are rotatable on axis Y-Y.

When it is required to secure an end of Bowden cable to actuator10, it first is appropriate to determine to which of the opposite sides of actuator10the Bowden cable47is to extend. Assuming that this is as shown inFIG. 7, the driven member18is rotated anti-clockwise, as it is viewed in that figure, to locate opening43in line with a corresponding opening54of upper part12of housing11, to locate the barrel44of the wire46of Bowen cable47in opening43of member18. With the barrel44secured, the wire46of cable47then is able to drop down into the slot43aof opening43and into slot54aof opening54of housing part12a. The member18as viewed inFIG. 7then is able to be rotated clockwise to draw the wire longitudinally from sleeve56of cable47, along groove44, with the end of sleeve56seating against the side of housing11.

The operation of the actuator10is as follows. If it is desired to adjust a lumbar support to which the actuator10is connected by a Bowden cable which extends from the driven member18, rotational input load is applied to the input member16, specifically to the splined end21by knob14. That input load, applied in either a clockwise or an anti-clockwise direction, causes the input member16to rotate. For the purposes of illustration, it will be assumed that the input load imparts a clockwise rotation to the input member16. Thus, the end surface27of the input member16will move into engagement with the spring end portion15b. Continued rotation of the input member16will cause the spring end portion15bto shift in the same direction of rotation. The spring15will not itself initially commence rotation, because it is in frictional engagement with the peripheral wall52of the recess50. However, by shifting the spring end portion15bin the direction of rotation, there will be a reduction in the frictional load between the spring15and the recess wall52due to movement of end portion15btightening the coil of spring15and thereby reducing its radius of curvature. Thus, there will be a reduction in the resistance to rotation of spring15relative to the recess50, so that the effort required to rotate the input member16is lower than if it was necessary for the input load to also overcome the full frictional load between the spring15and the recess wall52.

Continued rotation of the input member16will further shift the spring end portion15bto further maintain the reduction in the frictional load between spring15and the recess wall52. Also, the continued rotation will shift the end27of the input member16toward the facing abutment surface34of the drive member17. The arrangement can be such that the surfaces27and34abut, or that the surfaces27and34do not abut, but instead that they sandwich the spring end portion15bbetween them. Whichever arrangement is employed, continued rotation will cause the spring15to slip against the recess wall52and the drive member17to rotate. As a consequence, the meshing spur gears comprising splined shaft37of member17and gear38of member18, will cause the driven member18to rotate anti-clockwise. The driven member18thus will cause the wire46of the Bowden cable47to thereby move longitudinally to retract into sleeve56the Bowden cable. The input member16can continue to be rotated until the lumbar support has been properly adjusted and further rotation is then discontinued.

Once the desired adjustment has been made to the lumbar support, the present invention is adapted to resist backdriving load through the Bowden cable wire46. A backdriving load may occur simply because the lumbar support has a natural tendency to return to a preadjusted or relaxed condition, or it may be that pressure applied by the vehicle occupant, by sitting in the vehicle seat, causes the lumbar support to impart a backdriving load through the wire46to the driven member18. Thus the tendency under a backdriving load is for the driven member18to rotate clockwise and that would allow the cable wire46to shift from its previously set position and the lumbar support would be adjusted unintentionally. However, the actuator10prevents rotation of the driven member18under a backdriving load up to a limit beyond loads encountered in normal use with a lumbar support. That prevention occurs by spring15braking the drive member17against rotating under a backdriving load that acts on the driven member18.

Assuming that a backdriving load applied to the driven member18causes it to rotate clockwise relative to its orientation inFIG. 7, the tendency will be for the drive member17to rotate anti-clockwise. Thus, the abutment32will also rotate in an anti-clockwise direction and that will cause the abutment surface34of the abutment32to engage the spring end portion15bof the spring15. Continued anti-clockwise rotation of the drive member17will cause opposite movement of the spring15to that described above for an input load which rotates the input member16clockwise. That is, the abutment32will expand the spring15into more firm engagement with the recess wall52of the recess50within which the spring15is disposed. That more firm engagement brakes the drive member17against rotation and, because the drive member and driven member18are coupled together, rotation of the driven member18is also resisted.

One advantage found in some embodiments of the invention is that the direction of the input load to the input member16in either clockwise or anti-clockwise direction, will cause a reduction in the braking load between the spring15and the recess wall52, because in either direction, one of the spring end portions15aand15bwill be engaged by a respective end surface26and27of the input member16. Likewise, a backdriving load will be resisted regardless of whether that load influences the driven member18to rotate in a clockwise or anti-clockwise direction, because in either direction of rotation, the abutment32of the drive member17will engage one of the spring end portions15aand15b, and that engagement in either direction will cause an increased braking load to be applied by the spring15to the recess wall52.

It will be appreciated that an input load which is applied to the input member16to drive the driven member18to retract a cable connected thereto, will have to be sufficient to overcome any residual backdriving load that already is present in the Bowden cable47. Advantageously, the invention provides for a geared reduction between the drive member17and the driven member18, so that the input load is multiplied through to the driven member18. Moreover, the invention can employ a gear arrangement of very high efficiency, in contrast to prior art lumbar support actuators in which resistance to backdriving is provided by low efficiency screw mechanisms. In that form of prior art actuator, the input load must be sufficient to overcome the braking load in such a screw mechanism and this can significantly increase the input load which is required to be applied. In some embodiments of the invention, a spur gear arrangement between members17and18provides a reduction of about 6:1.

The outer surface20aof the cylindrical portion20of upper housing12includes a raised, arcuate bead59which is arranged to cooperate with a circumferential groove14cformed in the interior surface of outer cylindrical skirt14bof a knob14. The recess is intended to receive the bead59to locate the knob14over the portion20. The knob14further includes a bore having splines14d, defined within inner sleeve14a, which is complementary to the splines of the splined end21, so that rotation of the knob14causes rotation of the input member16.

In the assembled form of the actuator10shown inFIG. 1, a compact actuator is provided. Moreover, the geared coupling between the drive member17and the driven member18can be arranged so that only two turns of the drive member17are required for full rotational travel of the driven member18. This compares very favorably with other known actuators, in which up to five turns are required.

The gear ratio of about 6:1 between members17and18assist in enabling about two turns of the drive member to achieve sufficient rotational travel of the driven member. In this regard, sufficient travel means travel which is sufficient to provide a required range of relative longitudinal movement between wire46and sleeve56of Bowden cable47. The form of driven member18assists in these regards since, as shown inFIGS. 7 and 7(a), the slotted opening43in the driven member18is located symmetrically with respect to the arcuate extent of spur gear38. Also, the centre of opening43is spaced beyond the centre of curvature of gear38by a distance greater than the radius of gear38, such as by an amount of 10 to 20%, in some embodiments about 15%, of the radius of gear38. Also, with respect to the axis X-X, the radius of groove48varies from a maximum greater than the radius of gear38to a minimum less than the radius of gear38. The maximum radius of groove48is through the centre of opening43, while the minimum radius is 120° to each side of the centre of opening43. This variation in the radius of groove48is to create variation in the rate of cable traverse with respect to the rate of input rotation. The arrangement causes the cable to travel more quickly at minimum cable extension and less quickly as it approaches maximum cable extension to achieve a more uniform rate of adjustment, such as of a lumbar support.

It is to be noted that actuator10is able to receive the Bowden cable47from either of two directions, obviating the need for left and right hand versions of the actuator. Thus, upper housing part12, in addition to having opening54, has a second slotted opening60which has a slot60a. The openings54and60are symmetrically disposed at opposite sides of housing11, and cable47is able to connect to actuator10via either of openings54and60.

The embodiments in accordance with the invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the above description.