Patent Description:
Sofa support arrangements where stretched sheets provide support for a sofa seat and/or a sofa backrest are known in the prior art. They may be designed to be assembled by persons not specially trained for the task at the point of future use.

<FIG> shows such an arrangement. A sofa <NUM> frame comprises a first short-end section 104a, a second short-end section 104b and a support arrangement <NUM> comprising a first longitudinal beam <NUM>, a second longitudinal beam <NUM>, and a third longitudinal beam <NUM>, all beams running between the first short-end section 104a and the second short-end section 104b and thus carrying the load of the seat and its occupant(s) to the short-end sections 104a, 104b. A first sheet <NUM> may be stretched between the first longitudinal beam <NUM> and the second longitudinal beam <NUM> and a second sheet <NUM> may be stretched between the first longitudinal beam <NUM> and the third longitudinal beam <NUM> forming, respectively, a support for a seat and for a backrest. The seat and/or backrest may be formed by placing pillows on the sheets <NUM>, <NUM>. For stretching the sheets, there is a stretching mechanism <NUM>: the first longitudinal beam may be manually pulled and fixed with a screw <NUM>.

There is always a need to provide an improvement to such an arrangement. Further prior art is disclosed in <CIT>.

To this end, the invention provides a sofa seating furniture support arrangement for a seat or a backrest, comprising a first and a second load-carrying longitudinal beam, each being mountable to a seating furniture frame comprising one or more parts; an elastic sheet for providing support for one of the seat and the backrest; and a mechanism for stretching the elastic sheet between the first longitudinal beam and the second longitudinal beam. The mechanism comprises a stretching member pivotable on the frame around a pivot axis. The elastic sheet is, with the sofa seating furniture support arrangement in installed position, connected to the first longitudinal beam offset to said pivot axis so that the first longitudinal beam pivoting with respect to the frame, in response to an application of an external force or torque, stretches the elastic sheet, with the external force or torque working against the tension force of the elastic sheet until a point of maximum tension is reached, past which point of maximum tension the tension force facilitates further pivoting of the first longitudinal beam, acting to keep the first longitudinal beam in place in a final position.

This arrangement results in a tension mechanism that is easy to operate at the point of assembly, while still allowing for a high degree of tension in the elastic sheet, resulting in good rigidity of the support. This is turn allows for the use of the arrangement in in larger pieces of furniture than was previously possible.

In general, a large degree of elasticity is not required in the elastic sheets, i.e., their coefficient of elasticity, defined as the ratio of tension force to degree of stretching, may be rather high.

The load-carrying first longitudinal beam thus itself acting as a stretching member allows for a simple yet strong construction that still is easy to operate.

The elastic sheet is a first elastic sheet and the seating furniture support arrangement further comprises a third longitudinal beam and a second elastic sheet for providing support for the other of the seat and the backrest, where the second elastic sheet is also connected to the first longitudinal beam of the mechanism, so that the pivoting of the first longitudinal beam also stretches the second elastic sheet between the first beam and the third beam.

The seating furniture support arrangement is arranged so that the external force or torque works against the tension force of one of the first elastic sheet and the second elastic sheet up to the point of maximum tension, the other of the first elastic sheet and the second elastic sheet only being stretched with the pivoting having passed the point of maximum tension. In this way, the tension force of one of the sheets may be used to stretch the other sheet past the point of maximum tension, with less force or torque being needed to pivot the first longitudinal beam up to that point, than if both elastic sheets had been stretched at the same time.

Alternatively, the seating furniture support arrangement may be arranged so that the external force or torque works against the tension forces of both the first elastic sheet and the second elastic sheet up to the point of maximum tension. This allows for a high final degree of tension in both sheets.

The elastic sheet may, with the seating furniture support arrangement in installed position, fold around the first longitudinal beam forming a pocket, preferably being closed by a seam. This arrangement is easy to manufacture while still being durable.

The seating furniture support arrangement may further comprise a lever for applying the external force or torque for pivoting the first longitudinal beam, where the lever preferably is removable or foldable after use. This makes it easy to operate the mechanism.

The seating furniture support arrangement may further comprise a stop, against which the tension force of the elastic sheet acts through the first longitudinal beam to lock the first longitudinal beam in place in the final position.

The seating furniture support may further comprise a latch further acting to lock the first longitudinal beam in place in the final position.

Further, there is provided a piece of seating furniture comprising the seating furniture support arrangement above, and a kit for assembling a piece of seating furniture, the kit comprising the support arrangement above.

According to a further aspect, there is provided a method of assembling a piece of seating furniture as defined in claim <NUM>.

<FIG> show a seating furniture support arrangement <NUM> according to the present inventive concept. In this specific embodiment, the seating furniture support arrangement <NUM> is for a sofa <NUM>, however, the arrangement is equally suitable for other pieces of seating furniture, such as an armchair.

With reference to <FIG>, a sofa <NUM> comprises a frame comprising a first short-end section 4a, a second short-end section 4b and the support arrangement <NUM>. The support arrangement <NUM> comprises a first longitudinal beam <NUM>, a second longitudinal beam <NUM>, and a third longitudinal beam <NUM> which carry the load of the seat and its occupant(s) to the short-end sections 4a, 4b.

The first longitudinal beam <NUM>, the second longitudinal beam <NUM> and the third longitudinal beam <NUM> may be provided in a kit and mounted to the first short-end section 4a and the second short-end section 4b at the site of use of the sofa. As depicted in <FIG> they are each mounted between the first short-end section 4a and the second short-end section 4b. A first elastic sheet <NUM> is attached to the first longitudinal beam <NUM> and the second longitudinal beam <NUM> and a second elastic sheet <NUM> is attached to the first longitudinal beam <NUM> and the third longitudinal beam <NUM>.

The second longitudinal beam <NUM> and the third longitudinal beam <NUM> are fixed with respect to the first short-end section 4a and the second short-end section 4b, while the first longitudinal beam <NUM> is pivotable, through plates <NUM>, about a pivot axis running between a first pivot point P on the first short-end section 4a and a corresponding second pivot point on the second short-end section 4b. A lever <NUM>, functioning as a handle, adapted to aid pivoting of the first longitudinal beam <NUM>, is fixed to the first longitudinal beam <NUM> at a midpoint between the first short-end section 4a and the second short-end section 4b of the frame. Other locations for a lever or handle, as well at a different number of handles are equally possible, or no handle at all with an external force or torque provided through different means.

In embodiments where the stretching member is separate from the first longitudinal beam <NUM>, as discussed in conjunction with <FIG> below, the handle <NUM> or lever will be located on the stretching member. Preferably, the handle is removable, for example by being screw-mountable on the first longitudinal beam <NUM>. In that case, the lever <NUM> may be threaded as to be screw-mounted in a corresponding threaded bore in the first longitudinal beam <NUM> to be easily mountable before use and dismountable after use. Alternatively, the lever <NUM> may be foldable into or against the first longitudinal beam <NUM> after use.

Again with reference to <FIG>, a cross-sectional view of the area close to the first pivot point P shows the longitudinal beam <NUM>, the lever <NUM>, the first sheet <NUM> and the second sheet <NUM>. The sheets <NUM>, <NUM> attach to the first longitudinal beam <NUM> at an attachment point <NUM> which is rotatable with respect to the longitudinal beam <NUM>. The attachment point <NUM> is offset with respect to the pivot axis running between the first pivot point P and the second pivot point.

In the present embodiment, an elastic sheet folds around the first longitudinal beam <NUM> forming a pocket, which is closed by a seam at the attachment point <NUM>. The elastic sheet in the form of the pocket is rotatable with respect to the first longitudinal beam <NUM>. In this configuration, the first elastic sheet <NUM> and the second elastic sheet <NUM> may be part of the same elastic sheet.

A vertical, or close to vertical, plate <NUM> is fixed with respect to the first longitudinal beam <NUM> close to the first short-end section 4a of the frame. The plate has a slot <NUM> configured to interact with a stop on the first short-end section of the frame in the form of a pin <NUM>. An identical plate <NUM> configured to interact with an identical tap (not visible) in the second short-end section 4b located close to the second short-end section 4b of the frame. The plates <NUM>, and thereby the first longitudinal beam <NUM>, are pivotable around the first pivot point P and the second pivot point (not visible) respectively.

The first longitudinal beam <NUM>, the lever <NUM>, and the plates <NUM> provide a mechanism for, during assembly of the sofa, stretching the first elastic sheet <NUM> between the first longitudinal beam <NUM> and the second longitudinal beam <NUM>, and further for stretching the second elastic sheet <NUM> between the first longitudinal beam <NUM> and the third longitudinal beam <NUM>, where first longitudinal beam <NUM> functions as a stretching member for the elastic sheets, as will be described below.

In the cross-sectional view of <FIG>, a circular arc L1 shows the path traveled by the slot <NUM> of the plate <NUM> when the first longitudinal beam <NUM> pivots around the pivot point P. Similarly, a second circular arc L2 shows the path traveled by the center of the first longitudinal beam <NUM> during the same pivoting movement. Thus, since the attachment point <NUM> is offset with respect to the pivot axis running between the first pivot point P and the second pivot point, the first elastic sheet <NUM> is, with the sofa seating furniture support arrangement <NUM> in installed position, connected to the stretching member, which in this embodiment is identical to the first longitudinal beam <NUM>, in such a way that the first longitudinal beam <NUM> pivoting with respect to the frame, in response to an application of an external force or torque, stretches the first elastic sheet <NUM>. <FIG> shows the same arrangement as in <FIG> during pivoting of the first longitudinal beam <NUM>, the pivoting motion being driven by the application of an external force on the lever <NUM>, as shown with large straight arrows. During pivoting, shown with small curved arrows, the distance between the attachment point <NUM> and the second longitudinal beam <NUM> will increase, thereby starting to stretch the first elastic sheet <NUM>. The tension force of the first elastic sheet <NUM>, shown with a large straight arrow next to the first elastic sheet <NUM> in the cross-sectional view, will counteract the pivoting movement, as its leverage with respect to the pivot point P is opposite to that of the externally applied force. Thus, the external force applied to the lever <NUM> will need to work against the tension force of the first elastic sheet <NUM>. Since the attachment point <NUM> is rotatable with respect to the first longitudinal beam <NUM>, the tension force of the first elastic sheet <NUM> will cause the attachment point <NUM> to move around the first longitudinal beam <NUM> so that the stretched first elastic sheet <NUM> is perpendicular to the surface of the first longitudinal beam <NUM>. The path followed by the attachment point <NUM>, offset from the pivot point P, at this stage of pivoting will be determined by this condition.

In alternative embodiments (not shown) the attachment point <NUM> may instead be fixed with respect to the first longitudinal beam <NUM> and the plates <NUM>, i.e., to the stretching member. In this case the attachment point <NUM>, offset from the pivot point P, will during pivoting follow a circular path similar to L1 or L2.

In the shown embodiment, the first longitudinal beam <NUM> has a circular cross-section. However, other alternatives such a rectangular or elliptic cross-section are possible. The longitudinal beam <NUM> may either be fixed with respect to the plates <NUM>, resulting in an attachment point <NUM> fixed with respect to the plates <NUM>, or be pivoted at the plates <NUM> at a point offset from the first pivot points P and the second pivot point.

With the pivoting motion continuing, the external force applied to the lever <NUM> will continue to work against the tension force of the first elastic sheet <NUM>, with the length of the lever arm of the tension force with respect to the pivot point P decreasing, and the tension force increasing, until a point, i.e., position, of maximum tension force is reached, as shown in a cross-sectional view in <FIG>. Here, with the first elastic sheet <NUM> crossing the pivot point P, the lever arm of the tension force of the first elastic sheet <NUM> has been reduced to zero, thus applying no torque with respect to the pivot point P.

With further pivoting movement driven by the externally applied force on the lever <NUM>, the lever arm of the tension force of the first elastic sheet <NUM> will produce a torque around the pivot point P of opposite sign compared to the situation before the pivoting movement reached the position of maximum tension, thus resulting in a torque working in the same direction as the externally applied force on the lever <NUM>. Thus, the tension force of the first elastic sheet <NUM> will from now on facilitate the pivoting until the slot <NUM> of the plate <NUM> has reached the stop in the form of the pin <NUM>, as shown in <FIG>.

Thus, due to the attachment point <NUM> being offset from the pivot point P, the torque provided by the external force on the lever <NUM>, works against the torque provided by the tension force of the first elastic sheet <NUM> until the position maximum tension is reached, as depicted in <FIG>, past which position of maximum tension the tension force of the first elastic sheet <NUM> instead facilitates further pivoting of the first longitudinal beam <NUM>, acting to keep the stretching member in place its final position, as depicted in <FIG>.

Through the leverage made possible, the mechanism is easy to operate even when having a high tension in the elastic sheets, providing good rigidity to the support.

The elastic sheets <NUM>, <NUM> need to be elastic enough to be able to be brought to the position of maximum tension. However, in general, a large degree of elasticity is not required in the elastic sheets, i.e., their coefficient of elasticity, defined as the ratio of tension force to degree of stretching, may be rather high. For a given geometry of the stretching member, a higher coefficient of elasticity allows for a high degree of tension of the sheet, giving rigid support for the seat och backrest.

Optionally, a latch (not shown) may be provided to prevent the first longitudinal beam <NUM> from sliding back from the final position, for example due to an externally applied force.

In the embodiment shown in <FIG>, the second elastic sheet <NUM> and the distance between the attachment point <NUM> and the third longitudinal beam <NUM> are arranged so that the second elastic sheet remains slack during the pivoting movement up to the position of maximum tension (<FIG>) of the first elastic sheet <NUM>, only being stretched after that point. Thus, in this embodiment, during pivoting, the external force works against the tension force of the first elastic sheet up to the position of maximum tension, with the second elastic sheet only being stretched with the pivoting having passed the position of maximum tension. In this way, the tension force of one of the first elastic sheet <NUM> helps to stretch the second elastic sheet <NUM> past the position of maximum tension, with the effect of less external force being needed to pivot the stretching member up to that point. With both the first elastic sheet <NUM> and the second elastic sheet <NUM> being stretched, the position of the attachment point <NUM>, being rotatable around the first longitudinal beam <NUM>, will be determined by the condition that the vector sum of the tension force of the first elastic sheet <NUM> and the tension force of the second elastic sheet <NUM> is perpendicular to the surface of the first elastic beam <NUM>.

In an alternative embodiment (not shown) both the first elastic sheet <NUM> and the second elastic sheet <NUM> are stretched simultaneously up to the position of maximum tension. In that case, the position of maximum tension will be defined based on the vector sum of the tension force of the first elastic sheet <NUM> and the tension force of the second elastic sheet <NUM>. As a further alternative, there may be only one elastic sheet, either for providing support for the seat or for the backrest.

<FIG> shows an alternative embodiment, in a cross-sectional view, where the first longitudinal beam <NUM> is separate from the mechanism <NUM> for stretching the first elastic sheet <NUM> and fixed to the frame. As in the embodiments described in conjunction with <FIG> above, the elastic sheet <NUM> runs between the second longitudinal beam (not shown) and the first longitudinal beam <NUM>. However, instead from being fixed at the first longitudinal beam, it now continues to the separate stretching mechanism <NUM>. In the depicted embodiment, the first elastic sheet <NUM> lies on top of the first longitudinal beam <NUM>. However, other arrangements, such as the first elastic sheet <NUM> running through a slot or opening in the first longitudinal beam <NUM>, are equally possible. The stretching mechanism <NUM> operates according to the same principle as described above in conjunction with <FIG>. In the depicted embodiment, the first elastic sheet <NUM> attached to a cylindrical structure similar to the first longitudinal beam depicted in <FIG>, however, this structure, to which the elastic sheet <NUM>, is fixed, may in this embodiment be smaller, as it does not carry the load of, for example, an occupant of the sofa. In this embodiment, all other structures may be identical to what was described above in conjunction with <FIG>.

Finally, <FIG> shows the sofa <NUM> where the first elastic sheet <NUM> and the second elastic sheet <NUM> have been stretched according to the procedure described above. With the stretched first elastic sheet <NUM> now providing support for the seats of the sofa, pillows <NUM> may be added, as indicated with arrows, to complete the sofa seats. Likewise, with the second elastic sheet <NUM> now providing support for the backrest of the sofa, pillows <NUM> may be added to complete the backrest.

Claim 1:
A seating furniture support arrangement (<NUM>) for a seat or a backrest, comprising:
a first (<NUM>) and a second (<NUM>) load-carrying longitudinal beam, each being mountable to a seating furniture frame comprising one or more parts;
an elastic sheet (<NUM>; <NUM>) for providing support for one of said seat and said backrest; and
a mechanism for stretching said elastic sheet between said first longitudinal beam (<NUM>) and said second longitudinal beam (<NUM>),
said mechanism comprising:
said first longitudinal beam (<NUM>) pivotable on said frame around a pivot axis,
said elastic sheet (<NUM>; <NUM>), with said seating furniture support arrangement (<NUM>) in installed position, being connected to said first longitudinal beam (<NUM>) offset to said pivot axis so that said first longitudinal beam (<NUM>) pivoting with respect to said frame, in response to an application of an external force or torque, stretches said elastic sheet (<NUM>; <NUM>), said external force or torque working against the tension force of said elastic sheet (<NUM>; <NUM>) until a point of maximum tension is reached, past which point of maximum tension said tension force facilitates further pivoting of said first longitudinal beam (<NUM>), acting to keep said first longitudinal beam (<NUM>) in place in a final position,
characterized in that said elastic sheet (<NUM>; <NUM>) is a first elastic sheet (<NUM>) and said seating furniture support arrangement (<NUM>) further comprises:
a third longitudinal beam (<NUM>); and
a second elastic sheet (<NUM>) for providing support for the other of said seat and said backrest,
said second elastic sheet (<NUM>) also being connected to said first longitudinal beam (<NUM>) of said mechanism, so that said pivoting of said first longitudinal beam (<NUM>) also stretches said second elastic sheet (<NUM>) between said first beam (<NUM>) and said third longitudinal beam (<NUM>), and
wherein said external force or torque works against the tension force of one of said first elastic sheet (<NUM>) and said second elastic sheet (<NUM>) up to said point of maximum tension, the other of said first elastic sheet (<NUM>) and said second elastic sheet (<NUM>) only being stretched with said pivoting having passed said point of maximum tension.