WO1997020706A1

WO1997020706A1 - Seat recliner adjustment mechanism

Info

Publication number: WO1997020706A1
Application number: PCT/AU1996/000770
Authority: WO
Inventors: John Francis Carrig; Matthew Alan Cope; Morris Taylor Murray; Mark Paul Spataro; Martin Raymond Young
Original assignee: Henderson's Industries Pty. Ltd.
Priority date: 1995-12-01
Filing date: 1996-11-29
Publication date: 1997-06-12
Also published as: AUPN690995A0

Abstract

The adjustment mechanism, for a chair or seat, provides an adjustable coupling between a respective rigid side plate for a base and seat-back at one side of the seat. The mechanism includes an elongate shaft adapted to be mounted along a pivot axis with one end of the shaft extending through aligned openings of the side plates. An adjustment member engaged with the shaft enables an occupant of the seat to apply a force to rotate the shaft on the pivot axis. A coupling arrangement through which the one end of the shaft extends, includes a first coupling means carried by one of the side plates and comprises a circumferential array of first gear means defined by the one plate around the shaft. The coupling arrangement also includes a second coupling means comprising a coupling member which defines a through bore in which the shaft extends, and which has at one end a circumferential array of second gear means disposed around the shaft and complementary to the gear means of the first coupling means. Also resilient biasing means is operable to bias the second coupling means axially along the shaft, away from a retracted or disengaged position in which the first and second gear means are out of meshing engagement, to an advanced or engaged position in which the first and second gear means are in meshing engagement. The coupling member is engaged with the other one of the side plates, at least when the coupling member is in its advanced position, whereby rotation of the coupling member is substantially precluded. The coupling member is engaged with the shaft by engagement means acting directly therebetween whereby, on rotation of the shaft in at least one direction, the engagement means is operable to move the coupling member to the retracted position, enabling adjustment of the inclination of the side plate of the seat-back relative to the side plate of the base.

Description

SEAT RECLINER ADJUSTMENT MECHANISM

This invention relates to an improved mechanism enabling adjustment of the inclination of the back-rest of a seat or chair

At least with the front seats of vehicles, in particular for the driver's seat, it is necessary that the inclination of the back-rest is able to be adjusted This is to enable the occupant of a vehicle seat to be able to adjust the seat for maximum comfort and, in the case of a driver's seat, to position the driver in an ergonomically appropriate position for access to the controls of a vehicle Also, in the case of a two-door vehicle having front and rear seats, the front seats may need to be adapted to enable forward tilting of a front seat back-rest to enable rear seat passenger access

The mechanism provided by the invention is particularly well suited for back-rest adjustment of motor vehicle seats and, for ease of description, the invention is detailed herein primarily with reference to that application However, it is to be understood that the invention also is suitable for use with other forms of vehicle seats, as well as non-vehicular seats and chairs

The adjustment mechanism according to the invention is for use with a seat having a base on which an occupant is supportable, and a back-rest (or squab) which is pivotably secured in relation to the base, so as to be adjustable in fore-and-aft directions, for variation of its inclination relative to the base by pivoting on a transverse pivot axis The mechanism of the invention is adapted to be integrated into the seat so as to provide at least part of a pivotable coupling arrangement by which the back-rest is secured in relation to the base of the seat A wide variety of mechanisms have been proposed for enabling adjustment of the back-rest of a vehicle seat One such mechanism is disclosed in United States patent 5516198, issued on 14 May 1996 to Yokoyama The device of USP5516198 utilises first and second gear elements which mesh together to retain the seat-back at a given inclination One of the gear elements is able to be drawn out of meshing engagement, to enable relative rotation between the elements, for adjusting the seat back to a new inclination In this regard, the device of USP5516198 is somewhat similar to the mechanism of the present invention. However, the device of USP5516198 is relatively complex in terms of the number of components required, and in terms of the working relationship between those components.

As a consequence, the device of USP5516198 is relatively expensive. Also it is less amenable to manufacture in a compact form enabling its use within the space constraints applicable to a vehicle seat recliner device while still being sufficiently robust to enable it to withstand impact loadings experienced in the event of a vehicle collision.

According to the invention there is provided an adjustment mechanism, for a chair or seat having a seat base and also having a back-rest which is pivotally secured in relation to the seat base so as to be adjustable in fore-to-aft directions relative to the seat base on a transverse pivot axis; wherein the mechanism provides an adjustable coupling between a respective rigid side plate for the seat base and seat-back at one side of the seat and includes: (a) an elongate shaft adapted to be mounted in relation to the seat base so as to be disposed along the pivot axis with one end of the shaft extending through aligned openings of the side plates at the one side of the seat;

(b) an adjustment member engaged with the shaft by which an occupant of the seat is able to apply a force to rotate the shaft on the pivot axis;

(c) a coupling arrangement through which the one end of the shaft extends, the coupling arrangement including:

(i) a first coupling means carried by one of the side plates and comprising a circumferential array of first gear means defined by the one plate around its opening and around the shaft; and

(ii) a second coupling means comprising a coupling member defining a through bore in which the shaft extends, the coupling member having at one end thereof a circumferential array of second gear means which is disposed around the shaft and is complementary to the gear means of the first coupling means; and

(d) resilient biasing means operable to bias the second coupling means axially along the shaft, away from a retracted or disengaged position in which the first and second gear means are out of meshing engagement, to an advanced or engaged position in which the first and second gear means are in meshing engagement; wherein the coupling member of the second coupling means is engaged with the other one of the side plates, at least when the coupling member is in its advanced position, whereby rotation of the coupling member is substantially precluded; and wherein the coupling member of the second coupling means is engaged with the shaft by engagement means acting directly therebetween whereby, on rotation of the shaft in at least one direction, the engagement means is operable to move the coupling member axially along the shaft, from the advanced position to the retracted position, and thereby enable adjustment of the inclination of the side plate of the seat back relative to the side plate of the seat base.

The mechanism of the invention avoids the complexity of the arrangement of USP5516198 in that it has a minimal number of parts. The mechanism of the invention therefore is both amendable to manufacture in an economical, compact form, while it also is easier to install and disassemble.

Also, allowing for space constraints generally applicable to vehicle seats, in particular, the components of the mechanism of the invention are better suited to manufacture in a robust form, enabling the construction of its main components from weight-saving light alloys such as of aluminium, magnesium or zinc or, at least in the case of the coupling member of the second coupling means, enabling construction from a suitable engineering plastics material.

In the arrangement of USP5116198 there is a shaft. However, this essentially is a passive component which carries other components and it is fixed to either the seat back side frame or the seat base side frame. In contrast, the shaft of the mechanism of the invention is an active component which transmits an applied rotational force, and thereby causes axial movement of the coupling component of the second coupling means along the shaft. The arrangement of USP5116198 necessitates three concentric cylindrical components, of which the innermost one is the shaft, with these components being secured in an adjustable assembly by a pin extending through opposed longitudinal slots of the shaft, diametrically opposed holes in the intermediate component, and opposed inclined helical slots of the outer component. The shaft is fixed to one of the respective side frames of the seat- back and seat base, with the intermediate component meshing with the other one of those side frames. Thus, in the event of an impact loading on the seat- back, such as in a vehicle collision, the loading is transmitted to the seat base side frame via the pin and those concentric components, in particular the shaft and the intermediate component. There accordingly is a risk of failure of the pin or one of the components, while the concentric arrangement is not conducive to the system being sufficiently robust to withstand such impact loadings. In contrast, while the mechanism of the present invention has a concentric relationship between the coupling member of the second coupling means and the shaft, it is only that coupling member which directly engages the two side frames and which essentially needs to be able to transmit impact loadings between the sides frames. The more simple arrangement of the invention readily is able to accommodate a coupling member which is sufficiently robust for this purpose. in one form of the invention, the one end of the shaft projects through both of the seat base and seat-back side frames and has mounted thereon an adjustment member by which an occupant of a seat having the mechanism is able to apply a force manually, to rotate the shaft on the pivot axis. This arrangement is particularly suitable as the shaft needs to be rotatable in one, or in either, direction through only part of a revolution. However, the mechanism can, if required, by adapted for use of a power drive for rotating the shaft. The first coupling means, as a consequence of being carried by one of the side plates, is fixed axially with respect to the shaft. However, with the second coupling means in its retracted position, the first coupling means where carried by the seat-back side plate can rotate with pivoting of that plate. As indicated, the coupling member comprising the second coupling means is movable axially along the shaft between its advanced and retracted positions. For ease of further reference, the first and second coupling means hereinafter are distinguished as a "fixed" and "movable" coupling member, respectively. Each coupling member preferably has a continuous circumferential array of gear means which is disposed around the shaft and by which the coupling members are able to interlock in a plurality of relative circumferential positions The fixed coupling member may be defined by, or adapted to be secured to, the seat back-rest so as to be rotatable relative to the shaft by pivoting of the back-rest in the fore-and-aft directions Alternatively, the fixed coupling member may be defined by, or adapted to be secured to, the seat base so as to be fixed relative to the seat base The movable coupling member is engaged by the shaft so as to be adjustable therealong, in response to rotation of the shaft, so as to be movable from the advanced position, in which its gear means is interlocked or meshed with the gear means of the fixed coupling means, and the retracted position in which the respective engagement means are moved out of interlocking or meshing relationship

The engagement between the movable coupling member and the shaft is such that rotation of the latter causes movement of the movable coupling member along the pivot axis A number of arrangements enable this In one arrangement, one of the movable coupling member and the shaft defines a cam surface which is engaged by a cam follower surface of the other one of the shaft and the movable member Thus, the shaft may have a lateral cam follower projection, with the projection which is engaged by a cam surface which is defined by the movable coupling member and which extends obliquely or part helically around the pivot axis Alternatively, the shaft may have a raised shoulder which defines a cam surface facing axially towards the movable coupling member and extending obliquely or part helically with respect to the pivot axis, with the movable coupling member having either a projection, or defining a complementary oblique or part helical surface, which engages the cam surface defined by the shoulder In each case, the biasing means acts to retain the engagement between the movable coupling member and the shaft

The engagement between the movable coupling member and the shaft may be such that the coupling member is made captive on the shaft That is, the arrangement may be such that the shaft is rotatable relative to the movable coupling member, and the coupling member is movable along shaft, substantially only to the extent necessary for the movable coupling member to move between its advanced and retracted positions. Where the movable coupling member is made captive on the shaft, this may be by means of a lateral projection or pin on the shaft being received in an oblique or part helical groove or slot defined by the movable coupling member. Conversely, the shaft may define an oblique or part helical slot or groove into which a lateral projection or pin on the movable coupling member extends.

The circumferential arrays of gear means, by which the coupling members are able to interlock or mesh, can take a variety of forms. In a first arrangement, the movable coupling member may have a cylindrical body portion which defines the bore through which the shaft extends, with the fixed coupling means defined by a cylindrical hub. In that first arrangement, the body portion of the movable member may have gear means comprising a circumferential array of external splines which are substantially parallel with the shaft, with the hub of the fixed member having gear means comprising a complementary circumferential array of internal splines. The arrangement is such that, with the movable member in its advanced position, the splines of each array mesh together such that the movable coupling member is secured against rotation relative to the fixed coupling member and the plate by which the latter is carried. The arrangement also is such that, on movement of the movable coupling member to its retracted position, its splines are moved out of engagement with the splines of the fixed member and the movable member then is able to rotate relative to the fixed member. Of course, a seat-back side plate with which the fixed member is integral or secured either is prevented from pivoting or is able to pivot, on the pivot axis, depending respectively on whether the movable member is in its advanced or retracted position.

In a second arrangement, somewhat analogous to the first arrangement, the gear means again comprise external splines on the movable coupling member and internal splines on the fixed coupling member. However, whereas the splines are parallel to the shaft in the first arrangement, they flare radially and longitudinally of the shaft in the second arrangement. Thus, the movable member has a frusto-conical external surface on which its circumferential array of splines is disposed, while the fixed member has a frusto-conical internal surface on which its complementary circumferential array of splines is disposed. In the first and second arrangements, the relationship between the coupling members is such that the movable member, when in its advanced position, is at least partially within the fixed coupling member. A third arrangement enables this relationship, if required, but does not necessitate it. In the third arrangement, each coupling member has a respective annular engagement surface which is axially opposed to the other coupling member, with each engagement surface having thereon gear means comprising a complementary and similar, circumferential array of teeth which project axially, that is, longitudinally with respect to the elongate member. Thus, with the movable member in its advanced position, the engagement surfaces are relatively closely adjacent and the teeth of each array mesh together to secure the movable member against rotation relative to the fixed member. Similarly, with the movable member in its retracted position, the engagement surfaces are more widely spaced, with the arrays of teeth out of meshing engagement and the movable member able to rotate relative to the fixed member.

As indicated above the fixed coupling member is carried by the side plate for one of the seat base and the seat-back. Thus, when the movable coupling member is in its advanced position, such that its gear means meshes with the gear means of the fixed coupling member, the movable member is held relative to the plate carrying the fixed coupling member. However, this is not sufficient in itself to hold the side plate for the seat-back in a given inclination and, hence, fixed against pivoting on the transverse axis relative to the side plate for the seat base. As indicated above, at least when the movable coupling member is in its advanced position, it also is engaged with the side plate of the other one of the seat base and the seat back, that is, the side plate not carrying the fixed coupling member. This engagement with the other side plate obtains at least while the movable member is in its advanced position, but may be retained during movement of movable member to and while in its retracted position. The engagement between the movable member and the other plate may be, and most preferably is, direct engagement, an arrangement which is in marked contrast to operation of the recliner device disclosed is USP 5516198.

As will be appreciated, the arrangement of the present invention is such that a single component, namely the movable coupling member, is able to act directly between the two side plates while the seat-back side plate is to be held at a given inclination. Thus one sufficiently robust component is able to withstand forces or loadings acting between the side plates.

There is a number of arrangements by which the movable coupling member is able to suitably engage the other side plate. In a first of these, the movable member has its gear means at or adjacent to one end and, at or towards its other end, it has a portion such as of circular cross-section which projects through an opening of the other side plate. The projecting portion has at least one tooth which, with the movable member in its advanced position, is axially received in a recess defined by the other side plate and thereby precludes rotation of the movable member relative to the other side plate. Conversely, the projecting portion may define at least one recess in which, with the movable member in its advanced position, a tooth of the other side plate is axially received, again to preclude such relative rotation. In each case, location of the tooth in the recess may be retained, if required, when the movable member is in its retracted position, although this is not necessary. Also, in each case, there preferably is a circumferential array of teeth and recesses, while the recesses may comprise gaps between a similar array of teeth.

In a second arrangement by which the movable member is able to engage the other side plate, a portion of the movable member extends into or through an opening defined by the other plate. The portion of the movable member is of non-circular cross-section, that is, in a section at right angles to the shaft. The opening of the other side plate also is non-circular, preferably complementary to that of the portion of the movable member, and such that the movable member is held against rotation relative to the other side plate.

The one of the side plates which carries the fixed coupling member may have that member formed integrally therewith. Alternatively, the fixed coupling member may be defined by a separate component which is secured to the one side plate. Similarly, the movable member may engage with a section of the other side plate which is formed integrally therewith, or with a section which is secured to the other side plate. The mechanism preferably includes biasing means which acts to rotate the movable coupling member in one direction when that coupling member is in its retracted position. Particularly with use of the mechanism for adjustment of the seat-back of a vehicle seat, the direction is such as to pivot the seat-back in a forwards position, such that the seat-back extends over the base of the seat. The biasing may comprise a torsion spring or bar which is coupled at one end to the movable member and which, at its other end, is connected to an anchor point of the mechanism or is adapted to securement to an anchor point of the seat base or of a mounting for the seat base. Altematively, the biasing means may comprise a helical spring through which the shaft extends and which is connected to the movable member at one end and to the shaft or such fixed anchor point at its other end. In a further alternative the biasing means may be a helical spring directly connected between the back seat and base. However, other types of springs, such as a clock spring type, can be used.

The shaft may comprise a bar or tube of circular cross-section. Where this is the case, the movable coupling member of the coupling arrangement preferably defines a cylindrical bore through which the shaft extends, such that the movable coupling member is slidable on the shaft in movement between the advanced and retracted positions. At least in part, the bore may be defined by a sleeve portion of the movable coupling member. Where this is the case, the movable member may be engaged with the shaft at its sleeve portion, for movement between its advanced and retracted positions.

In one form of the invention, the shaft is adapted such that it has a respective end portion adjacent to each side of the seat when disposed along the pivot axis. In that form, the mechanism is able to provide the sole means by which the back-rest is secured. Also, a respective coupling arrangement may be provided at each end portion of the shaft, such that the shaft is common to each coupling arrangement. Where respective coupling arrangements are provided, the movable coupling members may be oppositely movable to the respective retracted position for each of them.

In order that the invention can be more readily understood, description now is directed to the accompanying drawings, in which: Figure 1 is a front elevation, showing a mechanism according to a first embodiment of the invention;

Figure 2 is a part sectional view, showing detail of the mechanism of Figure 1 in a first condition;

Figure 3 corresponds to Figure 2, but shows the mechanism in a second condition;

Figure 4 corresponds to Figures 2 and 3, but shows the components thereof in an exploded view;

Figure 5 corresponds to Figure 2, but shows detail of a mechanism according to a second embodiment of the invention; Figure 6 shows a partial, exploded perspective view of components of the mechanism of Figure 5 as viewed from the right hand side in the view of Figure 5;

Figure 7 corresponds to Figure 4, but shows detail of a mechanism according to a third embodiment of the invention; Figure 8 corresponds to Figure 7, but shows components thereof partly assembled;

Figure 9 corresponds to Figure 2, but shows detail of a mechanism according to a fourth embodiment of the invention;

Figure 10 is a perspective view of a component of the mechanism of Figure 9, and

Figure 11 is a part transverse sectional view of the component of Figure 10, showing its peripheral configuration.

With reference to Figure 1 , the mechanism 10 shown therein is illustrated partially in an in use relationship for a vehicle seat. Thus, in Figure 1 , the body of a vehicle is represented simply by a section of its floor pan P. The base of a seat is represented by a parallel pair of side plates B which are vertically disposed and extend in fore-to-aft directions perpendicular to the view of Figure 1. The seat-back or squab of the seat is represented by side plates S which also are vertically disposed and which are interconnected by a horizontal bar S'.

The lower edge of each plate B of the seat base defines a rail R which forms part of a rail assembly A by which the seat as a whole can be adjusted to a required position in the fore-to-aft directions. However, this is not the form of adjustment to which the invention relates, and the rails R and their assemblies

A can take a variety of different forms.

The seat-back is mounted on the base by a pivotal connection between the lower end of each plate S and the rearward end of a respective side plate B. The connection is provided by mechanism 10 and enables the seat-back to pivot in fore-to-aft directions on lateral pivot axis X-X. Thus, the inclination of the seat-back relative to the base of the seat is able to be varied over a required range, by reversible pivoting on axis X-X, such as through an angle of about 170°. The actual range can be chosen to suit a particular application, but is such that it enables the seat-back to be positioned in an upright position, such as to provide back support for an occupant. However, from such upright position, the seat-back can be pivotable rearwardly to a reclining position (in which it may extend rearwardly of and substantially parallel with the seat base) or forwardly over the seat base to a storage or rear seat access position (in which it may engage the top surface of the seat base).

Mechanism 10 has a horizontally disposed shaft 12 which has its longitudinal axis co-incident with axis X-X. Each end of shaft 12 extends through a respective interconnection between a side plate B and a side plate S and, at each such interconnection, mechanism 12 has a respective coupling arrangement 14. Also, on one end of shaft 12, outwardly from an interconnection between plates B and S and an associated arrangement 14, there is secured a handwheel 15 by which shaft 12 can be manually rotated.

Figure 2 to 4 show detail of the left hand coupling arrangement 14 of Figure 1. The right hand arrangement 14 of Figure 1 is the same, but in the reverse end for end orientation. As shown Figures 2 to 4, the arrangements 14 have a first coupling member 16 and a second coupling member 18. For reasons which will become apparent, members 16 and 18 are hereinafter referred to as respectively being fixed and movable.

The fixed coupling member 16, as shown, is defined by an upper part of a respective plate B o the seat base. Member 16 includes a cylindrical sleeve portion or boss 20 which projects outwardly from the plate B and defines a bore 22. Within the thickness of the plate B and seen most clearly in Figure 4, bore 22 is continued by a frusto-conical portion 24 which tapers inwardly and a smaller diameter bore portion 26 which opens at the inner surface of plate B. Shaft 12 extends substantially co-axially through boss 20 and the continuation of its bore 22 provided by portions 24 and 26. Around the circumference of frusto-conical portion 24, fixed coupling 16 has a circumferential array of radially and longitudinally extending internal splines 30.

As indicated, the fixed coupling member 16 is shown as defined by, or integral with, the plate B. However, it could alternatively comprise a separate component which is secured to plate B, such as by welding, bolts or a clamping device.

The movable coupling member 18 is of overall circular cross-section and defines a longitudinal bore 32 therethrough. An end portion of shaft 12 extends through bore 32, and the diameter of bore 32 is such that member 18 is a neat sliding fit on shaft 12.

Member 18 has an intermediate body 34, a smaller diameter cylindrical sleeve 36 at its inner end, and a larger diameter boss 38 at its outer end. Each of body 34, sleeve 36 and boss 38 defines a respective part of and is substantially symmetrical around, bore 32. Over part of the length of body 34 adjacent to sleeve 36, body 34 has a frusto-conical portion 40 which tapers to the diameter of sleeve 36. Also, at portion 40, member 18 has a circumferential array of radially and longitudinally extending external splines 42.

The coupling arrangement 14 is such that movable member 18 is able to be received onto shaft 12, and partly within bore 22 of fixed member 16. When so received, sleeve 36 projects through and inwardly beyond portion 26 of bore 22, with body 34 received in bore 22 and its portion 40 and splines 42 adjacent to portion 24 and splines 30 of fixed member 16. The portion 24 of member 16 is complementary to portion 40 of member 18, such that the respective arrays of splines 30 and 42 are able to mesh to lock member 18 against rotation relative to member 16.

The movable coupling member 18 is engaged with shaft 12 so as to be movable longitudinally of shaft 12 with rotation of the latter. The arrangement is such that member 18 is movable from an innermost or advanced position shown in Figure 2, in which splines 30 and 42 are meshed, and an outermost or retracted position shown in Figure 3 in which splines 30 and 42 are out of meshing engagement. Thus, when in its retracted position, movable coupling member 18 is able to rotate relative to fixed coupling member 16.

The engagement of movable member 18 with shaft 12 is by each of diametrically opposite lateral pins 44 secured in shaft 12 locating in a respective slot 46 formed in sleeve 36. While only one slot 46 is directly visible in the drawings, the form of the second one is shown in broken outline in Figure 2 and, as is evident from this, the two slots 46 are laterally in line but oppositely inclined. Also, each slot 46 is oblique with respect to the axial extent of sleeve 36 or extends along part of a revolution of a respective helix. The resultant engagement is such that, with member 18 in its advance position as shown in Figure 2, rotation of shaft 12 in a clock-wise direction as viewed from the left hand side of Figure 2 results in the outer edge 46a of each slot 46 being engaged by the respective pin 44, causing member 18 to move outwardly along shaft 12 to its retracted position. In relation to Figure 1 , the arrangement is such that this rotation of shaft 12 causes opposite movement of the member 18 of each coupling arrangement 14. With movement of member 18 towards its retracted position, its movement is solely along shaft 12, by relative rotation of shaft 12, until the splines 42 move out of meshing engagement with splines 30. Member 12 then is able to rotate relative to member 16. However, when or shortly after this stage is reached, each pin 44 is located at the outer end of the respective slot. Thus, member 18 is constrained against further movement along shaft 12 and any further rotation of the latter causes corresponding rotation of member 18. As shown most clearly in Figures 2 to 4, each seat-back plate S defines an opening 48 at its lower end by which it is journalled on boss 20. The periphery of opening 48 has a groove 50 formed therein, while a similar groove 52 is formed around the outer surface of boss 20. A plurality of roller, ball or taper bearings 54 are contained by the grooves 52 and 54 and facilitate pivotal movement of plate S on boss 20, around axis X-X.

Projecting outwardly from each plate S, around its opening 48, there is a circumferential array of teeth 56. The arrangement is such that the teeth 56 are axially opposed to boss 38 of the respective movable coupling member 18. Also, each boss 38 is provided with an inwardly projecting circumferential array of similar teeth 58 which are adapted to mesh with teeth 56 when member 18 is in its advanced position. Thus, with each member 18 in its advanced position, not only is each member 18 precluded from rotating relative to its member 16 due to meshing of splines 30 and 42, but also each plate S is prevented from rotating on boss 20 by its teeth 56 meshing with teeth 58. Conversely, when each member 18 is in its retracted position, it can rotate relative to its member 16 and plates S can pivot on the respective boss 20 due to splines 30 and 42 and teeth 56 and 58 being out of respective meshing engagement.

The distance along shaft 12 that each member 18 needs to move from its advanced position for splines 30 and 42 to move out of meshing relationship may be the same as, slightly more than or slightly less than, the distance to be moved by each member 18 for teeth 56 and 58 to move out of meshing relationship. However, it is preferred that splines 30 and 42 move out of meshing relation slightly in advance of teeth 56 and 58 doing so. Thus, on movement of each member 18 from its retracted position to its advanced position, teeth 56 and 58 will commence to mesh slightly in advance of splines 30 and 42. This enables teeth 56 and 58 to be configured so as to facilitate their meshing, such as by the teeth 56, 58 having tapered side walls at which they engage circumferentially, to thereby facilitate meshing of splines 30, 42. Figure 1 shows a helical spring 60 is provided around shaft 12. Spring

60 is preset in torsion and tension and, at each end, it is attached to the inner end of the movable coupling member 18 of a respective coupling arrangement 14. The spring 60 thus acts to bias the members 18 resiliently towards the advanced position for each.

As also shown in Figure 1 , mechanism 10 further includes a torsion bar or spring 62. As seen in Figure 1 , the torsion spring 62 has one end coupled to the plate B adjacent one end of shaft 12, and its other end connected to the plate S at a point above the other end of shaft 12. The spring 62 acts to provide a force tending to pivot the plates S forwardly over the seat base. However, with the movable members 18 in their advanced positions, this force is resisted by the meshing of splines 30 and 42, the meshing of teeth 56 and 58. The force also is resisted by the action of spring 60 in retaining members 18 in the advanced position.

When it is required to alter the inclination of the seat-back, by pivoting of its plates S, handwheel 15 is manually rotated in a direction resulting in rotation of shaft 12 in a direction in which its pins 44 act to move the members 18 from the advanced position to the retracted position, against the bias of spring 60. When members are in their retracted positions, teeth 56 and 58 are out of meshing relationship, and plates S (and hence the seat-back) are able to pivot on axis X-X. Torsion spring 62 is able to act to pivot plates S forwardly and, if this is the required direction of movement of the seat-back, the seat-back is allowed to pivot to a required new position. However, if the new position required is rearwardly of an initial position, it can be achieved by pushing the seat-back rearwardly against the force generated by spring 62. Throughout the forward or rearward pivoting, handwheel 15 is manually retained on its rotated position, and then released when the required new position is attained. The handwheel 15 then is released, enabling each member 18 to return to its advanced position under the action of spring 60. The seat-back and its plates S then are secured in the required new position.

With the seat-back and its plates S in the new position, teeth 56 and 58 again mesh, with splines 30 and 42 also again meshing. However, teeth 56 and 58 will have meshed in new relative circumferential positions, due to rotation of teeth 56 with plates S. Splines 30 and 42 are likely to be meshed in the same positions as for the initial position for plates S although minor, inconsequential variation in this can occur.

In the embodiment of Figures 5 and 6, plates B and S and axis X-X are identified as in Figures 1 to 4. Also the same reference numerals plus 100 are used in so far as there is relevant correspondence in components with those of the embodiment of Figures 1 to 4.

In the mechanism 110 of Figures 5 and 6, the overall arrangement is as shown in Figure 1. The differences principally reside in the connection between plates B and S, and in the form of the coupling arrangements 114 and its coupling members 116 and 118. Description therefore will be limited to matters of difference.

In mechanism 110, the fixed coupling member 116 is defined by the lower end of plate S of the seat-back, rather than integral with or connected to the plate B of the base of the seat. However, rather than being integral with plate S, member 116 could be secured there to by welding, bolts or a clamp device. In either case, the member 116 is fixed against movement longitudinally of shaft 112, but it is rotatable relative to shaft 112 with pivoting of its plate S and the seat-back around shaft 112 and pivot axis X-X.

The member 116 includes an externally cylindrical sleeve or boss 120 which projects outwardly from its plate S and defines a bore 122 of square cross-section. Adjacent and within the thickness of plate S, bore 122 is continued by a frusto-conical portion 124 which tapers inwardly and a smaller diameter bore portion 126 which opens at the inner surface of plate S. Shaft 112 extends substantially co-axially through boss 120 and the continuation of its bore 122 provided by portions 124 and 126. Around the circumference of frusto-conical portion 124, coupling 116 has a circumferential array of radially and longitudinally extending internal splines 130.

The movable coupling member 118 is engaged with shaft 112 in the same manner as described in relation to Figures 1 to 4 for member 18 and shaft 12. Thus, member 118 is of overall circular cross-section over the main part of its length and defines a bore 132 therethrough. Also, shaft 112 extends through bore 132 with a neat sliding fit therein with member 118, while pins 144 of shaft 112 locate in oblique slots 146 of sleeve 136 of member 118. Again, the engagement of pins 144 in slots 146 causes member 118 to move longitudinally along shaft 112 with rotation of the latter. Rotation of shaft 112 is by manual rotation of handle 115 fitted to the outer end of shaft 112. Beyond the outer end of its sleeve 136, member 118 has a body 134 of larger diameter, with body 134 integral with sleeve 136 by a frusto-conical portion 140. Beyond sleeve 136, the diameter of bore 132 increases in portion 140 to a maximum in body 134 at portion 141. Also, at portion 140, member 118 has a circumferential array of radially and longitudinally extending external splines 142. With member 118 in its advanced position in member 116, splines 130 and 142 mesh such that relative rotation between members 116 and 118 is prevented. However, with member 118 in its advanced position, the end of its body 134 projects beyond boss 120 of member 116.

Members 116 and 118 are retained in co-axial relationship with each other and with shaft 112 by provision of a cover 63 which is secured to seat base side plate B. As viewed from the left of Figure 5, cover 63 is of rectangular form as shown in Figure 6, and has a main body 65 and a depending flange 67. The body 65 of cover 63 is recessed at its inner face to define a cavity 69 therein. A peripheral wall 70 of body 65, which defines cavity 69, is stepped to define a shoulder 7 . Outwardly from step 71 , cavity 69 is square cross-section such that boss 120 of plate S is neatly received therein and is journalled for pivoting on axis X-X, relative to plate B. Also, inwardly from step 71 , cavity 69 is of square section, and slidably receives portion 141 of member 118 therein. Thus, as cover 63 is secured to plate B, member 118 is held by cover 63 against rotation on axis X-X and shaft 112, and is movable from its advanced or engaged position to its retracted or disengaged position, against the bias of spring 75.

Cover 63 is fitted over the outer end of coupling arrangement 114 such that boss 120 abuts the shoulder 71 and is journalled in cavity 69 by peripheral wall 70. The depth of cavity 69 inwardly of shoulder 71 is such that member 118 has sufficient clearance to move outwardly from its advanced or engaged position, shown in Figure 5, to its retracted or disengaged position. Cover 63 is secured to base plate B at its flange 67 to thereby retain its body 65 over the outer end of arrangement 114. The inner face of flange 67 is provided with recesses 72, while plate B is provided with corresponding ribs 73 each of which fits into a respective recess 72. Bolts 74 inserted through openings 74a in flange 67 engage in plate B to secure cover 63 thereto.

In the seat base, there is a plate B at each side and these are secured in a fixed lateral relationship. Similarly two plates S of the seat-back are fixed in spaced relationship, such as by at least one bar S' as shown in Figure 1. Thus, with a cover 63 similarly secured to each plate B and receiving a respective coupling arrangement 114 in its cavity 69, the mechanism 110 secures the seat-back in relation to the seat base.

Operation with mechanism 110 will be readily understood from the description of the mechanism 10 of Figures 1 to 4. However, whereas mechanism 10 has a spring 60 which biases the movable member 18 of each coupling arrangement 14 to its advanced position, mechanism 110 has a respective helical spring 75 for each movable member 118. As shown in Figure 5, spring 75 extends around shaft 112, within cavity 69, and is compressed between cover 63 and member 118, so as to resiliently bias the latter to its advanced position. Rotation of shaft 112, by manually turning lever 115, causes member 118 to move outwardly to its retracted position in which its splines 142 are out of meshing engagement with splines 130 of member 116. Thus, the inclination of plate S and hence the seat-back is able to be changed to a new position, by pivoting of plate S and rotation of boss 120 in cover 63. With release of lever 115, spring 75 returns member 118 to its advanced position, with meshing of splines 130 and 142, to lock plate S and hence the seat-back at a new position of inclination relative to the seat base and plate B.

The embodiment of Figures 7 and 8 is a simplified form of that shown in Figures 1 to 4, and corresponding parts are identified by the same reference numerals primed. Also, the shaft corresponding to shaft 12 of Figures 1 to 4 is not shown in Figures 7 and 8 but is of the same form in mechanism 10'. Also, the shaft of mechanism 10' has a manually movable member, such as handwheel 15 as in Figures 1 to 4 or a lever 115 as in Figures 5 and 6. Mechanism 10' of Figures 7 and 8 differs from mechanism 10 of Figures 1 to 4 principally in that plate S has an outwardly projecting sleeve 76. Also, a square-section bore 78 defined by sleeve 76 provides a continuation of opening 48' in plate S . While bore 78 is of square section, opening 48' is circular such that, with plates S and B assembled together, cylindrical boss 20' is a neat fit in opening 48' and plate S thus is journalled on boss 20'. Boss 38' of member 18' also is of square-section and is a neat sliding fit in bore 78 of sleeve 76. The length of sleeve 76 is such that boss 38' of member 18' is substantially fully received in bore 78 with member 18' in its advanced position, but also such that boss 38' is partly within bore 78 with member 18' in its retracted position. The engagement of boss 38' in sleeve 76 is such that member 18' is axially movable, but non-rotatable, in bore 78.

While bore 78 and boss 38' are described as being of square-section, they maybe of other convenient section, precluding rotation of member 18' in bore 78.

The embodiment of Figures 9 to 11 will be understood from the description of Figures 1 to 4. Corresponding parts have the same reference numerals as in Figures 1 to 4, plus 200, and description is limited to features of difference. In mechanism 210 of Figures 9 to 11 , member 216 is defined by plate S but again could be a separate component secured to plate S. As shown in Figure 9, plate S has an inwardly projecting annular flange 79 which defines a short bore 81 providing a continuation of the opening 248 in plate S. Within opening 248 and bore 81 , member 216 has a circumferential array of longitudinally extending internal splines 230 which are substantially parallel to shaft 212. Also, as shown most clearly in Figure 11 , mechanism 210 has a modified form of movable coupling member 218.

In mechanism 210, coupling member 218 has an intermediate body 234, a smaller diameter cylindrical sleeve 236 at the inner end of body 234, and an outer end portion 238 of square cross-section. Shaft 212 extends through bore 232 of member 218, and is engaged with member 218 by opposite lateral pins 244 each locating in a respective oblique slot 246 formed in sleeve 236. Around the circumference of its body 234, member 218 has a circumferential array of external splines 242 which are longitudinally extending. Splines 242 are parallel to bore 232 and, hence, to shaft 212 and are complementary to splines 230 of coupling member 216. The end portion 238 of member 218 is received in a square opening 83 through an upper rear section of seat base side plate B. The end portion 238 is a neat fit in opening 83. The square form of end portion 238 and opening 83 precludes rotation of member 218 relative so plate B, but enables member 218 to move longitudinally along shaft 212 between a retracted or disengaged position as shown in Figure 9 and an advanced or engaged position.

Shaft 212 projects through member 218 so as to extend outwardly beyond plate 13, and has handwheel 215 secured to its outer end. Member 218 is movable to its retracted position with rotation of handwheel 215, in a clockwise direction as wheel 215 is view from the left of Figure 9, and consequential rotation of shaft 212, by engagement of each of pins 244 in a respective slot 246. When member 218 is in the retracted position as shown, splines 230 and 242 are slightly longitudinally spaced and out of meshing engagement, and plate S and hence the seat-back of which it forms part is able to be pivoted on axis X-X to a new position of inclination. Also, with splines 230 and 242 out of engagement, end portion 238 of member 218 is fully accommodated in opening 83 of plate B and an outer flange 84 around the perimeter of opening 83. When handwheel 215 is released, member 218 returns to its advanced position under the action of spring 260, to achieve meshing engagement between splines 230 and 242. When member 218 is in its advanced position, end portion 238 is partially accommodated in opening 83 and due to this member 218 is constrained against rotation relative to plate B.

Also the engagement of splines 230 and 242 with member 218 in its advanced position locks plate S and hence the seat-back in a new position of inclination.

Figure 11 shows a convenient cross-sectional form for splines 242, with splines 230 being of complementary form. However, to facilitate meshing engagement of splines 230 and 242, the circumferential side walls of each spline 230, at an outer end portion thereof, preferably taper inwardly while the circumferential side walls of each spline 242, at an inner end portion thereof, also taper inwardly.

As shown in Figure 9, spring 260 is tensioned by having its outer end secured in a groove 85 at the inner end of sleeve 236 of member 218 and its inner end secured to a pin 86 which is inserted in shaft 212 at a location spaced member 218 when the latter is in its advanced position. Thus spring 260 acts to return member to its advanced position. Also, where mechanism 210 is provided with a coupling arrangement 214 at each end of shaft 212, rather than only a single arrangement 214 at only one end of shaft 212, a respective spring 260 is provided for the member 218 of each arrangement 214, or a single spring is used as in Figures 1 to 4.

The mechanism of the invention has a number of practical advantages. One of these is that the mechanism is simple to operate. Thus, for example, compared with mechanisms which require continuous rotation of a handwheel during forward or rearward pivoting of a seat-back to rotate a helically threaded shaft or the like, rotation of the shaft of the present invention need be only through a part of a revolution. Also, rotation of the shaft is in the same direction for both forward and rearward pivoting of the seat-back, and requires manual application of a relatively low level of torque. A further advantage of the mechanism of the invention is that its components can be made of a wide variety of materials. This is of particular importance where the mechanism is to be used in a motor vehicle, as vehicle manufacturers need to be able to minimise weight of such mechanisms and other vehicle components. In this regard, the mechanism of the invention is well suited to manufacture of its components from light alloys, such as of aluminium, magnesium or zinc, by simple casting operations necessitating little if any machining. Also, the components can be made of suitable plastics materials, such as by injection moulding.

A number of modifications are possible in the embodiments described with reference to the drawings. Thus, while mechanism 10 has a coupling arrangement 14 at each end of shaft 12 (as is intended to be understood in relation to mechanisms 110, 10' and 210), there is a need to have a coupling arrangement at only one end of the shaft. In such case, there may for example, be a simple, conventional coupling at the other end of the shaft, such as by the shaft being journalled in overlapping portions of side plates B and S at that other end. Also, the shaft need not extend fully across the width of a seat, with those overlapping portions being pivotally connected on axis X-X other than by the shaft.

Also, in the illustrated embodiments, the movable coupling members are movable to their retracted position by rotation of the shaft in only one direction. An attempt at rotation of the shaft in the other direction is resisted by the movable member being unable to move away from the retracted position, beyond the advanced position. However, it is possible for the engagement between the or each movable member to be such that the movable member can move, from its advanced position to its retracted position, by rotation of the shaft in either direction. Thus, in the mechanism 10 of Figures 1 to 4, for example, the pins 44 could each locate in a slot having two oppositely inclined oblique arms, with the pin locating at a junction between the arms with the movable member in its advanced position and moving into one or other of the arms, depending on the direction of rotation of the shaft, to move the movable member to its retracted position. In the illustrated embodiments, the handwheel or lever by which the shaft is rotated is shown as mounted on the shaft. If required the handwheel or lever can provide indirect manual drive, by being coupled to the shaft via a gear or gear train.

Also, while the movable member in each embodiment moves, with rotation of its shaft, in one direction, the arrangement can be reversed such that movement is in the opposite direction.

Finally, it is to be understood that various further alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.

Claims

Claims:

1. According to the invention there is provided an adjustment mechanism, for a chair or seat having a base and also having a back-rest which is pivotally secured in relation to the base so as to be adjustable in fore-to-aft directions relative to the bench portion on a transverse pivot axis; wherein the mechanism provides an adjustable coupling between a respective rigid side plate for the base and seat-back at one side of the seat and includes:

(a) an elongate shaft adapted to be mounted in relation to the base so as to be disposed along the pivot axis with one end of the shaft extending through alinged openings of the side plates at the one side of the seat;

(c) a coupling arrangement through which the one end of the shaft extends, the coupling arrangement including: (i) a first coupling means carried by one of the side plates and comprising a circumferential array of first gear means defined by the one plate around its opening and around the shaft; and

(d) resilient biasing means operable to bias the second coupling means axially along the shaft, away from a retracted or disengaged position in which the first and second gear means are out of meshing engagement, to an advanced or engaged position in which the first and second gear means are in meshing engagement; wherein the coupling member of the second coupling means is engaged with the other one of the side plates, at least when the coupling member is in its advanced position, whereby rotation of the coupling member is substantially precluded; and wherein the coupling member of the second coupling means is engaged with the shaft by engagement means acting directly therebetween whereby, on rotation of the shaft in at least one direction, the engagement means is operable to move the coupling member axially along the shaft, from the advanced position to the retracted positon and thereby enable adjustment of the inclination of the side plate of the seat back relative to the side plate of the bench portion.

2. The mechanism of claim 1 , wherein the one end of the shaft projects through both the base side frame and the seat-back side frame and has mounted thereon an adjustement member by which an occupant of a seat having the mechanism is able to apply a force manually, to rotate the shaft on the pivot axis.

3. The mechanism of claim 1 or claim 2, wherein the first coupling means is carried by the seat-back side plate whereby it can rotate around the shaft with pivoting of the seat-back plate but is fixed axially with respect to the shaft.

4. The mechanism of claim 1 or claim 2, wherein the first coupling means is carried by the base side plate whereby it is fixed axially relative to the shaft and is non-rotatable.

5. The mechanism of any one of claims 1 to 4, wherein one of the shaft and the coupling member comprising the second coupling means defines a cam surface which is engaged by a cam follower of the other one of the shaft and said coupling member, whereby rotation of the shaft causes axial movement of the coupling member therealong, from the advanced position of the retracted position.

6. The mechanism of claim 5, wherein the shaft has a lateral cam follower projection and the coupling member defines the cam surface, with the cam surface extending obliquely or part helically around the pivot axis.

7. The mechanism of claim 5, wherein the shaft has a raised shoulder which defines the cam surface, with the cam surface facing axiallly towards the coupling member and extending obliquely or part helically around the pivot axis, and wherein the coupling member defines a cam follower surface which engages the cam surface.

8. The mechanism of any one of claims 5 to 7, wherein the coupling member is made captive on the shaft, by engagement of the cam follower with the cam surface.

9. The mechanism of claim 8, wherein the cam surface is defined by a side wall of an oblique or part helical groove or slot formed in the one of the shaft and the coupling member, and the cam follower comprises a projection or pin extending laterally from the other of the shaft and coupling member to locate in the groove or slot.

10. The mechanism of any one of claims 1 to 9, wherein the first gear means comprises a circumferential array of internal splines and the second gear means comprises a circumferential array of external splines which are complementary to the splines of the first gear means.

11. The mechanism of claim 10, wherein the splines of each gear means extend flare radically and longitudinally with respect to the shaft on a frusto- conical surface of the respective coupling means.

12. The mechanism of claim 10, wherein the coupling member comprising the second coupling means has a cylindrical body which defines at least part of the bore through which the shaft extends, with the array of external splines of the second coupling means of extending substantially parallel to the shaft along an external surface of the cylindrical body; and wherein the first coupling means is defined by a cylindrical hub, with the internal splines of the first coupling means extending substantially parallel to the shaft on an internal surface of the hub.

13. The mechanism of any one of claims 1 to 9, wherein each coupling means has a respective annular engagement surface which is axially opposed to the other coupling means, and wherein the gear means of each coupling means comprises a circumferential array of axially projecting gear teeth.

14. The mechanism of any one of claims 1 to 13, wherein the coupling member is engaged with the other side plate, at least when the coupling member is in its advanced position, by a tooth on the coupling member locating axially in a recess defined by the other side plate.

15. The mechanism of any one of claims 1 to 13, wherein the coupling member is engaged with the other side plate, at least when the coupling member is in its advanced position, by a tooth on the side plate locating axially in a recess defined by the coupling member.

16. The mechanism according to calim 14 or claim 15, whrein said tooth is one of a circumferential array of teeth, and the recess is one of a circumferential array of recesses defined between an array of teeth.

17. The mechanism according to any one of claims 14 to 16, wherein the coupling member extends through an opening defined by the other side plate and is engaged with the other side plate at a surface thereof remote from the one side plate.

18. The mechanism according to any one of claims 1 to 13, wherein the coupling member, when in its advanced position, extends from the one side plates towards the other side plate, and wherein the coupling member has an end portion by which it is engaged with the other side plate, said end portion being of non-circular form and locating in an opening or recess of the other side plate which engages the end portion to thereby prevent rotation of the coupling member relative to the other side plate.

19. A mechanism according to any one of claims 1 to 18, wherein the coupling member comprising the second coupling means is of rigid unitary construction whereby, when the coupling member is in its advanced position, the coupling member is adapted to suitable for providing the load transmitting means acting directly between the plates.