Spring-assisted futon frame

[0001] The present invention relates broadly to adjustable furniture, and more particularly to futon frames of a type having a seat and a back adjustable between a folded sofa position and a flat bed position.

[0002] Convertible sofa-bed frames and futon frames are known to include a seat and a back that are manually adjustable relative to one another between a folded sofa position and a flat bed position. It is intended that such furniture be operable with a mattress in place and by individuals of varying degrees of strength. Sofa-bed frames, which are typically constructed of metal and often include complex linkages for assisting in manual adjustment, are structurally and mechanically more complex than futon frames, which are constructed primarily of wood and intended to retail at a lower cost to the consumer.

[0003] Futon frames of the prior art are generally characterized by a rectangular base formed by a pair of opposing sides connected by front and rear support rails, a seat connected to each opposite side by a pivoting link and/or by a follower bearing received for travel within a guide channel formed in the associated side, and a back pivotally connected to the seat for folding along a laterally extending axis and connected to each opposite side by another pivoting link and/or follower bearing received for travel within an additional guide channel formed in the associated side. The simplicity of futon frames is an advantage that translates into relatively low cost and excellent reliability. However, a long recognized drawback of futon frames is that they are somewhat difficult to adjust and sometimes require significant exertion on the part of the adjustor, particularly in moving the seat and back from the bed position to the sofa position with a futon mattress in place.

[0004] Attempts have been made to solve this problem. For example, applicant herein has developed automatically adjustable futon frames as described in U.S. Pat. Nos. 5,790,993; 6,061,848; and 6,138,299. These automatic frames solve the problem of adjustability, but at an added cost to the consumer.

[0005] While mechanical springs are widely used in connection with metal sofa-beds and their associated linkage mechanisms, they have not been widely adopted in connection with futon frames. Applicant is aware of a self-locking futon frame disclosed at FIGS. 27 and 28 of U.S. Pat. No. 5,628,076 that employs a coil spring 186 having one end mounted to a side of the futon frame's base 12 and another end mounted to the back 22. The back 22 is connected to the base by a follower bearing riding in a guide channel 20 and by a link member having opposite ends pivotally connected to the back and to the base. Spring 186 is loaded in tension when the seat and back are in their flat bed position, such that the spring provides force to assist in moving the seat and back to their folded sofa position. This arrangement is less than ideal because spring 186 attaches to back 22, which during adjustment changes orientation from horizontal to vertical, such that the spring tends to exert force pulling the follower bearing down against the side of guide channel 20 as the back progresses toward its sofa position, thereby resulting in binding.

[0006] Therefore, it is an object of the present invention to provide a futon frame with means for assisting a user in adjustment of a seat and a back of the frame from a bed position to a sofa position.

[0007] It is another object of the present invention to provide a futon frame with the aforementioned assistance means in a simple and economical design.

[0008] It is another object of the present invention to provide a futon frame with means for assisting a user in adjustment of a seat and a back of the frame from a bed position to a sofa position, but which reduces the occurrence of binding as follower bearings associated with the back ride in guide channels formed in sides of the futon frame.

[0009] In furtherance of these and other objects, a futon frame formed in accordance with a first embodiment of the present invention comprises a pair of gas springs associated one with each opposite side of the futon frame for assisting a user in adjusting a back and seat of the frame from a bed position to a sofa position. Each gas spring has a first end pivotally mounted to an associated side of the futon frame near a front support rail that extends laterally between the opposite sides of the futon frame, and a second end pivotally connected to the seat. When the back and seat are in their flat bed position, a piston of the gas spring is forced within a cylinder of the gas spring and the seat is releasably locked in place against the urging of the spring by engagement of a detent member carried by the seat with an abutment surface that is fixed relative to the associated side.

[0010] In a second embodiment of the present invention, a pair of coil springs are used instead of gas springs. Each coil spring has a first end mounted to a lower rear portion of an associated side of the frame and a second end mounted to the seat, preferably by a bracket of the detent member. Thus, when the seat is in its bed position, the coil spring is stretched in tension and the seat is releasably locked in place against the urging of the spring by engagement of the detent member with the fixed abutment surface.

[0011] Under either embodiment, the user merely lifts the front end of the seat to disengage the detent member from the abutment surface, and the spring acts generally along the direction of a lower guide channel to assist in adjustment to the sofa position.

[0012] The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:

[0013] FIG. 1 is a perspective view of a futon frame formed in accordance with a first embodiment of the present invention, wherein a seat and a back of the futon frame are in a bed position;

[0014] FIG. 2 is a view taken generally along the line II-II in FIG. 1;

[0015] FIG. 3 is a view similar to that of FIG. 2, however showing the seat and back adjusted to a sofa position;

[0016] FIG. 4 is a view taken generally along the line IV-IV in FIG. 2;

[0017] FIG. 5 is a view comparable to FIG. 2 but showing a futon frame formed in accordance with a second embodiment of the present invention; and

[0018] FIG. 6 is a view similar to that of FIG. 5, however showing the seat and back in a sofa position.

[0019] Referring initially to FIG. 1-3 of the drawings, a futon frame formed in accordance with a first embodiment of the present invention is shown and designated broadly by the reference numeral 10. Futon frame 10 generally comprises a base 12, a back 14, and a seat 16. Base 12 includes a pair of opposing sides 18 connected by a front support rail 20 and a rear support rail 22 extending laterally between sides 18 to form a rectangular configuration. Each side 18 includes an upper guide channel 24 and a lower guide channel 26 formed therein. In the case of upper guide channel 24, it is currently preferred to form this guide channel in a plate 28 of low friction plastic material, for example PTFE or the like, and to then affix the plate to the side 18 using conventional fasteners. This preferred approach allows the plates to be manufactured by faster production methods (i.e. molding or numerically controlled machining) than can be achieved if the guide channel is milled directly into side 18, which is typically wood. Other benefits include friction reduction due to the low-friction plate material and an inherent spacer function arising from the plate thickness which brings the upper guide channel closer to back 14.

[0020] Back 14 and seat 16 are situated between sides 18 of base 12 and are hingedly connected to one another by hinge pins 30 (only one hinge pin being visible in FIG. 1) to permit the back and seat to be folded relative to one another along a laterally extending folding axis. Back 14 and seat 16 are connected to each respective side 18 by an upper follower bearing 32 carried by back 14 and received for travel within upper guide channel 24 and a lower follower bearing 34 carried by back 14 and/or seat 16 for travel within lower guide channel 26. In the embodiment shown, lower follower bearing 34 is coaxial with the folding axis and hinge pins 30, and thus the lower follower bearing is considered to be carried by both back 14 and the seat 16. As will be appreciated, back 14 and seat 16 can be adjusted between a bed position as shown in FIGS. 1 and 2 wherein the back and seat are flat and define a planar mattress-supporting framework, and a sofa position as shown in FIG. 3 wherein the back and seat are folded relative to one another such that the back is generally vertical and the seat is generally horizontal in the manner of a sofa framework.

[0021] Futon frame 10 of the first embodiment further comprises a spring 36 associated with each side 18 of frame 10 for assisting a user in the adjustment of back 14 and seat 16 from their bed position to their sofa position. More specifically, in the first embodiment, spring 36 is a gas spring having a cylinder 38 and a piston 40 received by the cylinder for axially directed movement relative thereto. A first end 42 of spring 36 is pivotally connected to base 12, while a second end 44 of spring 36 is pivotally connected to seat 16. Spring 36 acts along a linear direction and is loaded in compression during adjustment of back 14 and said seat 16 from their sofa position to their bed position. In the present embodiment, the first end 42 of spring 36 remains forward of the second end 44 throughout the entire range of adjustment motion of back 14 and seat 16, wherein forward of is determined in relationship to futon frame 10 having a front support rail 20 forward of a rear support rail 22. As an aesthetically beneficial result, spring 36 remains concealed under seat 16 at all times. A suitable gas spring for use in practicing the present invention is a high pressure gas spring manufactured by Stabilus and sold under the trademark LIFT-O-MAT and part number FVR45 0200N 051/02.

[0022] A preferred configuration for pivotally mounting spring 36 to base 12 and seat 16 is shown in greater detail in FIG. 4. In the embodiment shown, cylinder 38 includes first end 42 that is mounted to side 18 adjacent front support rail 20. Pivotal mounting is accomplished by providing a U-shaped metal bracket 46 having one leg 46A flushly fastened against side 18 by fasteners 48 and another leg 46B receiving a laterallly extending mounting bolt 50, with a bridge portion 46C of U-shaped bracket 46 being arranged flush with a surface of front support rail 20. Mounting bolt 50 receives, in succession, a washer 52, first end 42 of spring 36, a PTFE spacer 54, another washer 56, and a nut 58 to pivotally journal first end 42 on mounting bolt 50. Piston 40 includes second end 44 that is mounted to a side member 60 of seat 16 near a rear member 62 of the seat. Pivotal mounting is accomplished by providing an L-shaped metal bracket 64 having one leg 64A fastened to the underside of seat side member 60 by fasteners 66 and another leg 64B extending upward along a surface of seat side member 60 and receiving a laterally extending mounting bolt 68. Mounting bolt 68 receives, in succession, a PTFE spacer 70, second end 44, a washer 72, and a nut 74 to pivotally journal second end 44 on mounting bolt 68. Finally, a thin pad 76 of low friction material such as PTFE is provided on the top of front support rail 20 to facilitate sliding motion of seat 16 over front support rail 20 during adjustment and to prevent frictional wear.

[0023] Referring again to FIGS. 2 and 3, it will be seen that futon frame 10 further comprises a detent member 80 fixed to seat side member 60 and a cam block 82 fixed to a proximate side 18 of the futon frame. Detent member 80 includes a cylindrical pin 84 that slides upwardly along a sloped ramp surface 86 of cam block 82 during manual adjustment of back 14 and seat 16 from their sofa position to their bed position. Cam block 82 defines a vertical abutment surface 88 at its forward end that extends downward from the top of ramp surface 86, whereby pin 84 of detent member 80 drops into engagement with abutment surface 80 as seat 16 reaches its bed position. As will be understood, the engagement of detent member 80 with abutment surface 88 serves to counter the spring force provided by spring 36 that tends to return seat 16 toward its sofa position, thereby releasably locking back 14 and seat 16 in their bed position. In order to adjust back 14 and seat 16 from their bed position to their sofa position, a user need only lift the distal end of seat 16 as indicated by the arrow in FIG. 2 to disengage detent member 80 from abutment surface 88, and then push the seat rearward with the assistance of spring 36 until follower bearings 32 and 34 reach the opposite end of their respective guide channels 24 and 26 as shown in FIG. 3. Reverse adjustment from sofa to bed is carried out by pushing generally downward on the top of back 14, thereby allowing the user's own weight to work to his or her advantage as spring 36 is loaded during the adjustment.

[0024] FIGS. 5 and 6 show a futon frame 110 formed according to a second embodiment of the present invention that is similar to the first embodiment except that coil springs 136 replace the gas springs of the first embodiment for biasing seat 16 toward a sofa position. Each coil spring 136 includes a first end 142 mounted to base 12 by a metal bracket 146 located at a lower rear portion of an associated side 18, and a second end 144 mounted to seat 16. In this regard, the second embodiment differs from the first embodiment because the second end of spring 136 (that is, the end mounted to seat 16) is always forward of the first end (that is, the end mounted to base 12). In a preferred configuration, second end 144 of coil spring 136 is mounted to seat 16 using detent member 80 as a connection bracket, thereby avoiding the need for an additional mounting bracket. This preferred configuration can be realized by having pin 84 extend from both lateral sides of detent member 80, such that one portion of pin 80 engages abutment surface 88 and an opposite portion of pin 84 receives a hooked end of coil spring 136. As will be understood from FIGS. 5 and 6, spring 136 is stretched in tension when back 14 and seat 16 are in the bed position, and spring force is released during adjustment from the bed position to the sofa position.

[0025] In both the first and second embodiments, the springs are arranged to act between the base 12 and seat 16. Because the orientation of seat 16 remains primarily horizontal in both the sofa and bed positions and the line of spring action corresponds generally with the travel direction of lower guide channel 26, the present invention reduces the problem of binding associated with the prior art. Moreover, the placement of the springs (36 or 136) is primarily under seat 16 so as to keep the springs out of view.