WO2000057755A1

WO2000057755A1 - Convertible sofa

Info

Publication number: WO2000057755A1
Application number: PCT/GB2000/000681
Authority: WO
Inventors: Alan F. J. Hookway
Original assignee: Hookway Consultancy Limited
Priority date: 1999-03-26
Filing date: 2000-02-25
Publication date: 2000-10-05
Also published as: GB9906930D0

Abstract

The invention provides a sofa convertible into bunk beds, which comprises a lower frame (1) adapted to support a mattress (15) and serving the dual purpose of forming the seat of the sofa and the lower bunk bed; an upper frame (3) also adapted to support a mattress (17) and movable between a first position in which it is substantially vertical and forms the back of the sofa, and a second position in which it is substantially horizontal and forms the upper bunk bed, a pair of upright front members (8) fixed in position in front of, or to the front of the sides, of the lower frame; a pair of linking members (5) attached to the top of the upright members in such a manner that they can be moved, from a first position, in which they point backward and constitute the arms of the sofa; to an upright position in which they engage with and may be locked to the upper frame to form the front supports to the upper bunk.

Description

CONVERTIBLE SOFA

This invention relates to a convertible sofa. More particularly, this invention relates to a sofa that is convertible between a first form, in which it is useable as a conventional sofa, and a second form, in which it is useable as a pair of bunk beds.

As is well known, there are a large number of so-called sofa beds on the market, that is articles of furniture that can be changed from one form, in which they can be used as a conventional sofa, to a second form, in which they are opened out to constitute a double bed.

Conventional sofa beds have the disadvantages that:

• they require, of necessity, the same amount of floor space as a double bed, a considerable problem when a room has limited floor space;

• they can be awkward to convert, often requiring the repositioning of other occasional furniture;

• they are frequently uncomfortable to sleep on, due to the difficulty of joining the mattresses together;

• they can be an inappropriate form of bedding for those who are forced to share;

• they often require different coverings when used as a bed as opposed to a sofa; and • they are rarely a sightly piece of furniture.

The present invention overcomes these disadvantages, and provides an article of furniture which is useable as a sofa, and which converts into a form in which there is provision for two people to sleep one above the other, as in a pair of bunk beds. This provides accommodation for two sleepers, while economising on floor space by virtue of occupying no more space than a conventional sofa.

The method of construction is such that the entire piece of furniture can be easily assembled from its component parts, which may thus be packaged as a "Flat Pack" for self-assembly.

Various attempts have been made to produce articles of Furniture that may be used either for seating or as bunk structures with upper levels. GB-A-543208, GB-A- 1028036, WO 87-07487, US-A- 4051564, US-A-4555821 and US-A-4592101 all show structures that potentially fulfil these functions. Some of them provide sofas with backboards that can be swung up to provide an upper bunk. Such usually have either complex folding mechanisms or removable parts to provide at least a part of the support for the upper bunk.

One embodiment of this invention provides a sofa convertible into a pair of bunk beds which comprises a base frame having two upright sides which are linked by a front cross member and upper and lower rear cross members; a pair of rear legs attached to the support frame sides: a lower frame being adapted to support a mattress and movable, from a first position where it forms the seat of the sofa and rests on the base frame lower rear cross member, to a second position where it is substantially horizontal and forms the lower bunk bed; an upper frame also adapted to support a mattress, movable between a first position in which it is slanted to the vertical and forms the back of the sofa, and a second position in which it is substantially horizontal and forms the upper bunk bed; a pair of upright front members fixed to the front of the sides of the base frame; a pair of linking members attached to the top of the upright members in such a manner that they can be moved from a first position in which they point backward and constitute the arms of the sofa, to a second, substantially vertical, position in which they form the front supports to the upper bunk; a pair of pins attached to the inside of the free ends of the linking members, which are arranged to slide in slots formed in guide plates attached to the ends of the upper frame and engage with the curved ends or spurs formed in the slots to prevent rotation of the linking members when configured either as the front supports of the upper bunk or the arms of the sofa respectively, but allowing the pins to slide in the slots as the upper frame and linking members are rotated between their first and second positions, the upper frame being sufficiently flexible to allow the pins attached to the linking members to engage with either the curved ends or spurs formed in the slot in the guide plates; a backboard attached to the rear of the lower frame and, by hinges, to the underside of the upper frame, such that by rotation of the upper frame from its first position to its second position the lower frame is also rotated from its first to its second position; and a pair of spring loaded arm lifters, arranged to overcome the weight of the linking members at the start of their rotation from their first to their second position.

Another embodiment of this invention provides a sofa convertible into bunk beds, which in a preferred form comprises a lower frame being adapted to support a mattress and serving the dual purpose of forming the seat of the sofa and the lower bunk bed; an upper frame also adapted to support a mattress and movable, preferably by rotation about hinges, between a first position in which it is upright and forms the back of the sofa; and a second position in which it is substantially horizontal and forms the upper bunk bed, it being possible to flex the upper frame to allow the linking members to engage with it as described below; a pair of upright front members fixed in position in front of, or to the front of the sides, of the base frame; a pair of linking members attached, preferably by a hinge, to the top of the upright members in such a manner that they can be moved from a first, substantially-horizontal position, in which they point backward and constitute the arms of the sofa, to a second position wherein they do not interfere with the lower frame when moved between its first and second position, and a third, substantially vertical, position in which they engage with and may be locked to the upper frame in its second position to form the front supports to the upper bunk.

The invention will be further described with reference to the accompanying Drawings in which: Fig 1 is a cross-sectioned end elevation of a sofa according to the invention along the line l-l ' of Fig 3; Fig 2 is a partial cross section, along the line ll-ll ^' of Fig 3, showing the attachment of the upper frame, and mattress, to the rear frame; Fig 3 is a plan view of the sofa when configured as a sofa; Fig 4 is a front elevation of the sofa when configured as bunk beds; Fig 5 is a partial sectional view of the upper end of a linking member and the upper frame; Figs 6a and b are, respectively, a cross-section along the line Ill-Ill ^' of Fig 6b and a side view of a linkage between an upright member and a linking member; Figs 7a, b and c are respectively a plan view, a front elevation and an end elevation of an optional guard-rail assembly; Figs 8 and 9 are respective cutting means for lower and upper mattress covers; Fig 10 is an end view of a second embodiment of the invention;

Fig 11 is an end elevation showing another preferred embodiment of the invention configured as a sofa; Figs 12a and 12b are rear elevations of the embodiment of Fig 11 , Fig 12a showing the item configured as a pair of bunks whilst Fig 12b showing it in the sofa configuration; Fig 13 is a partial section along the line V-V of Fig 12a in which the bunk configuration is shown in ghost form; and Fig 14 is a partial detail section along the line IV-IV of Fig 13 through a slotted guide plate. In the Drawings, the following reference numerals are employed:

1 Lower Frame 21 Hooks

2 Central Legs 22 Spring

3 Upper Frame 23 Flap Seam

3a Detail of engagement pin 24 Corner Seam

3b Ball Catch 25 Mitre Seam

4 Rear Frame 26 Velcro^(TM) Strip

5 Linking Members

5a Locking Attachments 31 Endplate

6 Upper Locking Bolt 32 Front Cross Member

7 Bolts through Lower Frame 32a Hinges

8 Upright Members 33 Upper Rear Cross Member

9 Support Bar 34 Lower Rear Cross Member

10 Bolts through Upper Frame 35 Rear Legs

11 Stop Bar 36 Upright Members

12 Stretcher Bars 37 Linking Members

13 Guard-rail assembly 38 Hinge 13a Guard-rail 39 Upholstered Plates 13b Support 40 Upper Frame 13c Clip 41 Lower Frame

14 Lower Locking Bolt 42 Hinges

15 Lower Mattress 43 Batten and Hinges

15a Lower Mattress Cover 44 Backboard

16 Integral Hinge 45 End Boards

17 Upper Mattress 46 Arm Lifting Attachments 17a Upper Mattress Cover 47 Pins 17b Flap 48 Slots

18 Hinge in Upper Frame 48a Curved Slot End

19 Hinge Pin tube 48b Curved Slot Spur

20 End Caps 49 Guide Plates

A, B & C Arrows showing operational rotation l-r Position of section through Linking Member.

■ I — 11" Position of partial section through Upper Frame. lll-lir Position of section through integral hinge.

IV- IV Position of partial section through pin and guide plate. V-V Position of section immediately behind end board.

Referring now to Figures 1 to 10 of the Drawings, which are of an embodiment fashioned in wood with material covered foam mattresses supported on longitudinal and transverse webbing (not shown) stretched across the frames in a woven pattern, they show a lower frame [1] supported on legs [2], an upper frame [3], in first and second positions, a rear frame [4], and a linking member [5] movable between first [A], second [B] and third [C] positions.

In the first position, the linking members act as armrests when the invention is being employed as a sofa. From this first position they are swung up, past the vertical, to their second position where they do not foul the upper frame when it, in turn, is swung up into the horizontal for use as a bunk. The linking members are then returned to the vertical, their third position, where they engage with and are locked to the upper frame.

In another embodiment, the upper and lower frames may be attached directly or indirectly to a convenient wall or partition by omitting the rear frame [4]. The embodiments provide either a free-standing piece of furniture or a space saving fixture.

As shown more clearly in Fig 5, the linking members engage with the upper frame preferably by means of a pair of short pins [3a], protruding from the lower surface of the frame, entering bores formed into the ends of the linking members thus preventing lateral movement of the linking members. To protect the edges of the bores flanged collets are let into each bore where they are retained by virtue of a push fit. Once engaged, vertical movement of the frame is prevented by sliding catches [6], attached to the frame and operating in a plane substantially at right angles to the centrelines of the pins, entering bores drilled in the linking members. A drilled metal plate screwed over the holes protects the bores into which the pin of the catch engages.

In order to provide a rigid stop for the linking members, when they are in their first position, and a step up to the upper bunk bed, when they are in their third position, each linking member may be provided with a locking attachment [5a] adjacent to the hinge between it and an upright member [8] such that, when the linking member is in its first position, the attachment is parallel to, and in the same plane as, the upright member. When in their first positions the linking members can be latched in position by a lockable sliding bolt located between the back of the upright members and the lower mattress.

Other methods of locking the linking members to the upright members and upper frame and engaging said members with the upper frame can be employed, especially if the members are constructed in another material.

By using catches, which provide a means of being locked in their engaged position, differing levels of security can be provided to prevent the conversion to or from a sofa. Several forms of latch are commercially available ranging from child proof, to being locked by means of a key. A similar attachment near the top of the linking member when in its third position may be provided to allow the fore-aft position, or width, of the upper frame in relation to the lower frame, to be varied to provide differing ratios between the width of the seat and the height of the back of the invention when configured as a sofa.

Both said attachments may be permanently affixed to, form part of or be implicit in the shaping of the linking members.

By variation of the position of the hinge between, and the length of, the upright and linking members, the height of the arms, above the seat, and rake of the top frame, when in its first position, may be adjusted.

In a variation of the invention, the linking members can be detached from the upright members and reattached in either the first or third position, obviating the necessity of the hinge between the members.

The mattress may be attached to the upper frame to prevent the mattress falling forward when the upper frame is in its first position.

Fig 1 of the Drawings shows both positions of the upper frame and all three positions of the linking members with the second position of the upper frame and the second and third positions of the linking member being shown in dotted outline. Also shown are bolts [7] for connecting the lower frame [1] to the upright members [8] and rear frame [4]. Preferably, each join is made with a pair of bolts to retain the upright members and rear frame in the vertical. Similarly, the rear frame [4] is bolted to the hinged support bar [9] of the upper frame, each joint being made with one bolt whose head [10] can be seen. The recesses cut into the bottom of the upper frame to accommodate the end of the bolt, nut and washer are not illustrated in this figure. A stop bar [11] is attached to the rear of the bottom of the upper frame which, by being larger than the support bar in the dimension by which both come between the upper frame and rear frames, prevents the upper frame rotating downward to the vertical and results in the rake of the upper frame mattress, and the local compression of the mattress by the linking members.

Other methods such as press-fit clips may be employed whereby the upright members and rear frame members may be attached to the lower frame and upper frame support bar. The central legs [2] and stretcher bars [12] below the lower frame [1] and the stretcher bars behind the upper frame are drawn. These are attached to the respective frames. In this embodiment the attachment is by screws (not shown), one screw being employed at each end of the stretcher bars and two on each of the central legs. The optional guard-rails [13] are shown accommodated, in their storage position where they are retained in position by being flexed over the stretcher bars. The sliding bolt [14] used to secure the linking member in its first position is located between the upright member [8] and the lower frame mattress [15]. This bolt is of the cranked type and lies flat against the upright member when disengaged. Local distortion of the lower frame mattress is necessary to operate this locking mechanism.

It should be noted that the upper frame [3] differs from the lower frame [2] in that it has a stop bar [11] attached behind the bottom longitudinal member, a support bar attached by hinges [18] recessed into the back of the top longitudinal member (see Figs 2 and 3), counterbored recesses to accommodate the ends of the bolts, nuts and washers which attach the support bar to the rear frame, wall or partition, and are drilled to accept screws for attaching the central legs and to provide bolt holes to attach the upright members and rear frame.

The stop bar [11] prevents the upper frame rotating fully downward to the vertical by coming into contact with the rear frame, wall or partition, thus giving the sofa back a slight backward rake whilst the support bar, which has the same thickness as the upright and linking members, locates the rear of the upper frame in front of that of the lower frame such that the linking members are vertical when engaged with the bottom of the front longitudinal member of the upper frame in its second position.

The position of the hinge [16] between the upright and linking members, and the length of the linking members is such that the linking members protrude backwards from the rear of the upright members by a distance equal to the distance from the front of the mattress [17] attached to the upper frame and the back of the upright members assuming the upper frame is allowed to rotate downwards to the vertical. Due to the limitation placed on the rotation of the upper frame, the linking members deform the upper frame mattress and help to keep it in position in the sofa configuration. When in their first position [A], the linking members may be latched in position by a lockable sliding bolt located between the back of the upright members and the lower mattress and engaging with a socket provided in the linking member. The sliding bolt operates in a plane substantially at right angles to the axis of the hinge connecting the upright and linking members and thus prevents rotation of the linking member around the axis of the hinge. This bolt may also be locked in its engaged position.

Fig 2 is a detailed cross-section ll-ll ^' on Figure 3 of the upper frame and top of the rear frame with the upper frame in its first position. It shows the upper part of the upper frame [3] along with the upper part of the rear frame [4] to illustrate the position of the hinges [18] between the rear longitudinal member of the upper frame and the support bar [9], the upper frame mattress [17] and a flap [17b] attached to the upper frame mattress cover and the position of a Velcro^tm strip [26] by which the flap is attached to the longitudinal member. This will be described in more detail below.

Fig 3 is a plan view configured as a sofa. The positions of the cross-sections l-l ^' and ll-ll ^' illustrated in Figs 1 and 2 are shown and also illustrate the arrangement of the hinges [18] between the support bar and the rest of the upper frame. These are substantial hinges and are illustrated as metal hinges recessed into the frame and support bar and secured by screws (not shown). Cutouts are shown in the flap [17b] which secures the mattress to the upper frame. These cutouts allow the rear guard rail to be attached to the upper frame if required.

To facilitate assembly, the hinges between the upper frame and the support bar may be of the removable pin type, the upper frame and support bar being relieved to facilitate insertion and removal of the hinge pin.

Fig 4 is a front elevation, drawn with the linking members [5] shown in their third position and the upper frame [3] in its second position: that is when configured as a pair of bunk beds.

The stop bar [11], affixed below the front of the upper frame, is drawn with a cut-away to reveal the otherwise hidden metal hinges [18], support bar [11] and tubular stretcher bars [12]. The dotted line indicates the extent of this cut away. Also shown are the positions of sliding bolts [6] attached to the ends of the stop bar. By the operation of these bolts, the linking members are secured, upright, in their third position. Central legs [2] are shown below the lower frame [1]. These are provided to accommodate the additional weight, which may be expected when used as a sofa, without increasing the dimensions of the longitudinal members of the lower frame. The position of the integrated hinges [16] between the upright and linking members is also shown.

The upright members [8] and rear frame [4] extend downward past the lower frame [1] by equal amounts to provide the outer legs, which combined with the central legs [2], act to provide the sofa bunk with a rigid frame. Given reasonably accurate construction and a reasonably level and preferably carpeted floor, the inherent flexibility of the construction ensures that all six feet remain in contact with the floor.

As the rectangles formed between the central legs, lower frame, outer legs and floor, are pinned by the screwed and glued joint between the central legs and lower frame, frictional forces between the floor and outer legs help retain the uprights in a vertical position.

Fig 5 illustrates how the linking members [5] engage with the upper frame [3] by means of a pair of short but substantial pins [3a]. The pins protrude from the lower surface of the frame and enter sockets formed into the ends of the linking members thus preventing lateral and rotational movement of the linking members. Once the pins are engaged in the sockets the vertical movement of the upper frame is prevented by sliding catches [6], which operate in a plane substantially at right angles to the centreline of the pin.

The engagement pins [3a] are implemented as large gauge screws with their heads removed. The sockets are simply holes drilled in the free end of the linking members. To protect the edges of these holes, a flanged collet, normally used for positioning shelves in a bookcase, is let into the hole where it is retained by virtue of a push fit. The sliding catches consist of sliding bolts [6], attached to the front of the upper frame stop bar, which enter holes drilled in the linking members. A drilled metal plate screwed over the holes protects the holes into which the pins of the catches engage. The catches are locked in position by the rotation of the handle attached to each bolt by which it can be slid between the engaged and free position. Figs 6a and 6b are enlarged details of hinge [16] and present an end elevation (Fig 6b) and section through the hinge (Fig 6a) as indicated by Ill-Ill ^' on figure 6b.

Fig 6a shows a tube [19] inserted through the holes bored through the ends of the upright [8] and linking [9] members thereby forming a hinge pin; end caps [20] set into counter-bored recesses; and an arrangement of hooks [21] and a spring [22], passing through the hinge pin, by which the end caps are retained in position.

It can be seen from Fig 6b that the relieving of the material adjacent to the hinge allows the linking member to rotate through a larger angle, e.g. 90° to its first position and is limited to rotation through a smaller angle e.g. 60° to its second position, which is sufficient to allow the upper frame to be rotated without fouling.

Figs 7a, b and c illustrate an optional guard-rail assembly [13]. This comprises a longitudinal rail [13a] screwed and glued to three upright supports [13b], each having a metal clip [13c], also attached by screws. The screws are not shown. The longitudinal rail is substantially the same length as the upper frame mattress [17] and the supports are arranged such that the clips fit between the upper frame's transverse webbing strips.

Fig 7c shows a partial section through the upper frame [3] over mattress [17] and longitudinal member and illustrates how the guard-rail [13] is clipped in place using metal clips attached to the upright supports. The enlarged inset shows how the clips may be retained in position by spring loaded roller or ball catches [3b] let into the longitudinal member.

Figs 8 and 9 are cutting plans for the lower [15a] and upper frame mattress covers [17a] respectively and in which seams and folds are shown as dashed lines. The upper frame mattress [17a] cover includes an additional panel [17b] which folds over itself to form the flap by which it is preferably fitted by a Velcro^tm strip to the upper frame. The cutouts resulting from the holes cut in this panel allow the rear guard-rail to be clipped to the upper frame.

The seam [23] (upper frame mattress cover only) is sown to form the joining flap with the material right side out and the flaps around the cutouts and at the ends being sown under. After the flaps on the outer edges are sown under. The seam [24] and corresponding seams at each comer are then sown with the flaps inside. This forms the corners of the cover. Finally the mitre joins [25] are then sown, again with the flaps on the inside. This forms the envelope into which the mattress can be stuffed.

Conversion from a sofa according to this embodiment into a pair of bunks is achieved as follows: 1 The linking members [5], currently configured as the sofa arms in their first position, are unlocked from the upright members by operation of the cranked sliding bolts between the rear of the upright members and the lower frame mattress. When retracted, the cranked bolt can be rotated to lie flat against the back of the upright member.

2 The linking members are rotated through the vertical to their second position where they are clear of the rotating upper frame.

3 The upper frame [3] is rotated from its first position, in which it forms the rear of the sofa to a position slightly above its second position where it forms the upper bunk.

4 While holding the upper frame, in the position described in Step 3, one of the linking members [5] is rotated back to its third, substantially vertical position and the upper frame is lowered such that the pin [3a] engages with the socket at the top of the linking member. The upper frame is then locked to this linking member by the operation of the sliding bolt [6].

5 The upper frame is flexed to allow the operation described in Step 4 to be repeated for the other linking member.

Conversion from a pair of bunk beds to a sofa is essentially a reversal of the steps described above.

When configured as a bunk, the mattresses may be removed by lifting them off in turn. Before lifting off the upper mattress the two halves of the Velcro™ strip must be separated. Once the mattresses have been removed, their covers can be removed for cleaning.

When the sofa is first supplied, as a flat pack, it may be assembled as follows.

1. Screw and glue the central legs to the lower frame with the long countersunk screws and glue provided. Wipe any excess glue off with a damp cloth. 2. Screw the stretcher bars into position on both the upper and lower frames with the round- headed screws provided.

3. Stretch the two sets of ten webbing strips across the width of the frame. This is best done by standing the frames on a long edge and inserting the webbing clips into the lower slot before stretching them to insert in the upper slot. A mallet may be helpful to drive them home. 4. Weave and stretch the two sets of four longitudinal webbing strips into place in similar manner. 5. Attach the sliding bolts and striker plates in position using the short counter sunk screws provided. 6. Assemble the linking and upright member hinges by inserting the hinge tubes and attaching the springs and hooks to the end caps using the hook tool provided. Note that when assembled, they are handed with the striker plates on the inside of the linking members. 7. Loosely attach the upright and rear frame members with the bolts nuts and washers provided. 8. Put the mattresses in their covers. 9 Attach the hinges to the upper frame longitudinal members and support bar with the medium sized counter sunk screws provided. 10. Place a mattress on the lower frame.

11. Place the Upper frame on the lower frame mattress and insert the remaining bolts through the rear frame members and support bar.

12. Lift the upper frame to the vertical and attach, loosely, the washers and screws to the bolts inserted through the support bar. 13. Remove the mattress from the lower frame.

14. Engage the linking members with the upper frame and lock into position.

15. Ensuring the rear frame and upright members are square to the frames tighten all nuts and bolts.

16. Finally place the mattresses in position and engage the Velcro^tm strips on the upper frame mattress.

Fig 10 illustrates another embodiment of the invention using a smaller upper frame, and configuring the loop [5a] attached to linking arm [5] slightly differently. One end of the loop being used as an offset attachment to support the upper frame [3] indirectly.

This configuration produces a sofa with a less exaggerated ratio of back height to seat depth, at the expense of a narrower upper bunk and less headroom between upper and lower bunks. In this configuration, the second position [B] of the linking members needs only to be about 15° from the vertical. In other embodiments, both frames can be provided with slats, springs or a thin board to support the respective mattresses which may be manufactured from and covered in different materials.

A further embodiment of the invention is illustrated in Figs 11 to 14. This further embodiment comprises a support frame to which are attached a pair of upright members, upper and lower frames and a pair of sprung loaded arm lifters.

The support frame comprises an endplate [31], a front cross member [32], upper [33] and lower rear cross members [34] and rear legs [35]. The upright members [36], which provide the front legs, are attached on the outside of the support frame endplates [31].

The upper and lower frames [40, 41] are substantially rectangular frames, arranged to support upholstered mattresses, which serve as the mattresses of the bunks and as the cushioned seat and back of the sofa. In the version the upper frame is narrower than the lower frame, and the upper mattress is thinner than the lower. In other embodiments these ratios may vary by a slight variation in the geometry.

Linking members [37] are attached to the top of the upright members by a hinge [38], in this case formed into the ends of the upright and linking members themselves, allowing the linking members to rotate backwards from their vertical position, in which they form the front supports for the upper frame when configured as the upper bunk, through the horizontal to the position in which they form the arms of the sofa.

Preferably, the linking members carry plates [39] that extend beyond the hinge and to which upholstered pads are attached so as to form cushioned pads when configured as the sofa arms. These are provided purely for user comfort.

The lower frame [41] is attached by hinges [32a] to the front cross member [32] of the support frame, and rests on the lower support frame rear cross member [34] when configured as the seat of the sofa, but can be raised to the horizontal when configured as the lower bunk. The upper frame [40] is attached by hinges [42] to the support frame upper rear cross member [33] such that it can rotate from above the horizontal, through the horizontal, where it forms the upper bunk, downwards to form the rear of the sofa.

Both upper and lower frames are mounted so that they can rotate within the two end plates of the support frame.

A backboard [44] is attached to the rear of the lower frame and, via a batten and hinges [43] to the upper frame. The hinges [43] being attached to the upper frame in a position such that, as the upper frame is raised from the position in which it forms the rear of the sofa to the horizontal, where it forms the upper bunk, the rear of the lower frame is lifted from its lower position, where it forms the sofa seat, to its upper position, where it forms the lower bunk. To accommodate the lower frame being restricted in its downward rotation by the support frame lower rear cross member [34], the backboard [44] is constructed of a material of moderate flexibility. As well as linking the upper and lower frames, the backboard gives lateral stability to the structure.

As will be seen from Figs 13 and 14, the linking members [37] are connected to the upper frame via pins [47], attached to the linking members, which are constrained to move in slots [48] formed in guide plates [49] attached to the ends of the upper frame. The slots [48] are shaped such that as the upper frame is lifted from its position as the sofa back, the pins attached to the linking members are forced to travel along the slot, rotating the linking members from their position as the arms of the sofa upwards to a point where the loss of mechanical advantage requires them to be pulled forward raising the upper frame above the horizontal, until the curve [48a] in the end of the slot allows the upper frame to rotate back down to the horizontal, at which point the pin is constrained with the linking members in their vertical position.

In order that they are constrained at their lower position when forming the arms of the sofa, the pins enter curved spurs [48b] in the slots, formed in the guide plate, thus preventing rotation of the linking members.

To assist the initial upward rotation of the linking members from the position where they disengage from the spurs [48b] in the slot [48], where the mechanical advantage offered by the upward vector of the force exerted between the guide plates and the pins is low, spring loaded, arm lifting attachments [46] are attached to the end plates of the support frame which engage with the free ends of the linking members. The force exerted by these springs is sufficient to overcome the weight of the linking members [37] until they have rotated to a point where sufficient mechanical advantage is obtained from the force exerted between the guide plates and pins that they can be raised by the rotation of the upper frame alone.

Lifting the upper frame [40] from the horizontal allows the pins to disengage from the curved ends of the slots and, under their own weight the linking members begin rotating backwards. The upper frame is then allowed to rotate downwards until the linking members engage with the sprung loaded arm lifters. Each arm is then depressed until the upper frame is at the point where it can be pushed backwards to engage the pins in the spurs formed in the guide plates preventing further rotation of the linking members.

The upper frame is constructed in such a manner that it will twist slightly along its length enabling the linking members to be moved individually when the attached pins are to be engaged in the curved ends or spurs formed in the slots in the guide plates.

For aesthetic reasons, the upper frame has end boards [45] attached over part of the guide plates and lying in substantially the same plane as the endplates of the support frame, such that when configured as a sofa the end boards and endplates are aligned and hide the guide plates. These end boards are shaped to allow the pins attached to the linking members to engage in the end curves and spurs formed in the slots in the guide plates.

As illustrated in Figure 14, the pins [47] attached to the linking members are shaped such that they are of a greater diameter either side of the slots [48] in the guide plate [49]. The guide plates are slotted on to the pins before attaching the guide plates to the upper frame. The heads of the pins can then run along a groove formed in the upper frame behind the guide plates, as the sofa is converted into a pair of bunks and vice versa.

Claims

1. A sofa convertible into bunk beds which comprises a lower frame [1] being adapted to support a mattress [15] and serving the dual purpose of forming the seat of the sofa and the lower bunk bed; an upper frame [3] also adapted to support a mattress [17] and movable between a first position in which it is substantially vertical and forms the back of the sofa, and a second position in which it is substantially horizontal and forms the upper bunk bed, a pair of upright front members [8] fixed in position in front of, or to the front of the sides, of the lower frame; a pair of linking members [5] attached to the top of the upright members in such a manner that they can be moved, from a first, substantially-horizontal position, in which they point backward and constitute the arms of the sofa; to a second position wherein they do not interfere with the lower frame when moved between its first and second position, and a third substantially vertical position in which they engage with and may be locked to the upper frame in its second position to form the front supports to the upper bunk.

2. A sofa convertible into a pair of bunk beds which comprises a base frame having two upright sides which are linked by a front cross member and upper and lower rear cross members, a pair of rear legs attached to the support frame sides; a lower frame being adapted to support a mattress and movable, from a first position where it forms the seat of the sofa and rests on the base frame lower rear cross member, to a second position where it is substantial horizontal and forms the lower bunk bed, an upper frame also adapted to support a mattress, movable between a first position in which it is slanted to the vertical and forms the back of the sofa, and a second position in which it is substantially horizontal and forms the upper bunk bed; a pair of upright front members fixed to the front of the sides of the base frame; a pair of linking members attached to the top of the upright members in such a manner that they can be moved from a first position in which they point backward and constitute the arms of the sofa, to a second, substantially vertical, position in which they form the front supports to the upper bunk; a pair of pins, attached to the inside of the free ends of the linking members, which are arranged to slide in slots formed in guide plates attached to the ends of the upper frame and engage with the curved ends or spurs formed in the slots to prevent rotation of the linking members when configured either as the front supports of the upper bunk or the arms of the sofa respectively, but allowing the pins to slide in the slots as the upper frame and linking members are rotated between their first and second positions, the upper frame being sufficiently flexible to allow the pins attached to the linking members to engage with the curved ends and spurs formed in the slot in the guide plates; a backboard attached to the rear of the lower frame and, by hinges, to the underside of the upper frame, such that by rotation of the upper frame from its first position to its second position the lower frame is also rotated from its first to its second position, a pair of spring loaded arm lifters, arranged to overcome the weight of the linking members at the start of their rotation from their first to their second position.

3. A sofa as claimed in Claim 1 or 2 wherein the linking members are attached to the upright members by hinges [16].

4. A sofa as claimed in Claim 1 wherein the linking members can be detached from the upright members and reattached in either their first or third positions.

5. A sofa as claimed in any of Claims 1 , 3 and 4 wherein the upper frame [3] is supported above the lower frame [1] by a rear frame [4] to which they are both attached.

6. A sofa as claimed in any of Claims 1 to 4 wherein both frames [1 , 3] are adapted or may be modified for attachment directly or indirectly to a wall or partition.

7. A sofa as claimed in any of Claims 1 , 2 and 6 wherein the upper frame [3] is provided with detachable guard rails [13].

8. A sofa as claimed in any one of the preceding Claims wherein the linking members [5] are provided with locking attachments [5a] providing a step when the linking members are in the third position.

9. A sofa as claimed in any one of Claims 1 , and 3 to 8 wherein the upper frame [3] is provided with downwardly projecting pins [3a] engaging with corresponding bores in the upper ends of the linking members when the latter is held upright in its third position.

10. A sofa as claimed in any one of Claims 1 to 9 wherein the upper frame [3] when in its second position is supported on a limb of the locking attachment [5a].

11. A sofa as claimed in Claim 1 and substantially as hereinbefore described.