Abstract:
A rocking chair whose rocking action is achieved solely through a linkage mechanism rather than rocking cams conventionally employed. The chair includes upholstered seat, backrest and armrests which are united in a one-piece structure mounted on a fixed base by means of the linkage mechanism. In the preferred embodiment, the base is provided with a swivel enabling the chair to swivel about a vertical axis. The linkage mechanism allows it to be mounted within the seat frame into a compact space which permits low seat styling and yet, the linkage mechanism is concealed and still functions to provide stable rocking as well as gliding action.

Description:
BACKGROUND OF INVENTION 
     Various types of rocking chairs have, of course, existed for many years. One type utilizes cams or cam surfaces rockable on the floor or a platform such as in a platform rocker. Another type rocks about a fixed axis such as is in a so-called &#34;rocker-box&#34; chair. In yet another type of rocking chair, the chair is suspended from swing arms located externally of the sides of the chair. It is this general category of chair to which the present invention is directed. 
     OBJECTS OF INVENTION 
     It is an object of the present invention to provide an improved rocking chair that may be upholstered and designed to meet present-day styling requirements including low seat styling. 
     It is a further object of the present invention to provide such a chair as described above that will also provide comfortable and stable rocking and gliding action. 
     A further object of the present invention is to provide a rocking chair that utilizes a linkage mechanism to achieve rocking and gliding action and yet the linkage mechanism is totally concealed within the chair below the seat without sacrificing safety or styling requirements. Included herein is such a chair that may be designed with low-seat styling unimpaired by the linkage mechanism incorporated therein. 
     A still further object of the present invention is to provide a novel and improved linkage mechanism that may be incorporated in an upholstered chair to provide rocking action. 
     SUMMARY OF INVENTION 
     In summary, the rocking chair of the present invention includes a seat, armrest and backrest structure mounted on a fixed base by a linkage mechanism. The latter includes a seat link fixed to the seat frame along the side rail thereof, a stationary base link fixed on the base at a location above the seat link, and a pair of swing arms pivoted at their opposite ends to the seat and base links. The distance between the swing arm pivots on the seat frame is less than the distance between the pivots on the base link and these distances are designed with ratios within a predetermined range to provide safe and effective rocking and gliding action. The seat, armrest and back structure may be upholstered as desired and furthermore, the linkage mechanism may be designed in a compact size allowing lowseat styling in accordance with prevailing tastes. 
    
    
     DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following more detailed description taken in conjunction with the attached drawings in which: 
     FIG. 1 is a perspective view of a rocking chair embodying the present invention with the upholstered portions thereof shown in phantom lines; 
     FIG. 2 is a cross-sectional side view of the chair with a part of the backrest broken away; 
     FIG. 3 is a diagrammatic side view of the chair shown in a rearwardly rocked position; and 
     FIG. 4 is a view similar to FIG. 3 but with the chair shown in a forwardly rocked position. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings in detail, there is shown for illustrative purposes only, a rocking chair embodying the present invention. Referring to FIG. 2, the basic parts of the chair include a seat 12, backrest 14 and armrests 16 which, in the specific embodiment, are united together as one structure. In accordance with the invention, this structure is mounted on a base generally designated 18 by means of a novel and improved linkage mechanism generally designated 10 which allows the chair to rock as well as glide relative to the base 18. In the specific embodiment, base 18 includes a swivel generally designated 20 (see FIG. 2) for also providing swiveling motion of the chair about a vertical axis relative to the base. Swivel 20 may include any conventional or other suitable structure such as, for example, upper and lower plates 24 and 26 mounted about a central swivel pin 28 with ball bearings and races generally designated 30 formed between the swivel plates 24 and 26 in typical fashion. The lower swivel plate 24 is fixed to the underlying base structure 18 to be stationary while the upper swivel plate 26 is rotatable about the axis of the swivel pin 28 relative to the lower plate 24 and underlying base structure 18. Although base 18 in the specific embodiment shown includes a plurality of spider legs 22 radiating outwardly from a central area, it will be appreciated that any other suitable base structure may be employed. 
     Referring now to FIG. 2, seat 12 may have any suitable or conventional frame construction including, for example, side rails 32 (one shown) interconnected by a front rail 34 and a back rail 36 which is also secured against a backrest frame including a rail 38 as shown in FIG. 2. The frame parts just mentioned may be made from wood, as shown, or any other suitable material. Additionally, any conventional seat springs such as designated 39 may be employed. It is preferred that the chair parts be upholstered such as shown for illustrative purposes only in the drawings, so that the linkage mechanism 10, to be described below, will be completely concealed within the chair. Additionally, in accordance with the invention, the chair may be designed to possess a relatively low-seat styling meaning that the seat is positioned from floor within a certain minimum range. The chair, of course, may also include a seat cushion illustrated at 12a in FIG. 1 and moreover, the chair may include T-cushion styling where the front ends of seat cushion 12 are positioned beyond the front of armrests 16. 
     Referring now to FIGS. 1 and 2, linkage mechanism 10 in the preferred embodiment includes a pair of base links 40 fixed relative to the base as will be described, and a pair of seat links 41 fixed respectively to the opposite side rails 32 of the seat frame, preferably on the inner sides thereof. As clearly shown in FIG. 1, seat links 41 are formed as right-angle members so that they may be secured by fasteners through the base thereof and into the bottom surface of seat side rails 32 as best shown in FIG. 2. 
     The base links 40 are located above the seat links 41 and fixed relative to the base 18 by means of extension members generally designated 42 which, in the specific embodiment shown, are plate members extending in opposite vertical planes from the upper swivel plate 26 to which they are attached by cross members 44, the latter being shown as angle-shaped to provide legs for securing the same to the extensions 42 and swivel plate 26. It will thus be seen that the base links are united with the upper swivel plate 26 to be rotatable about the axis of the swivel pin 28 relative to the lower swivel plate 24 and its associated base structure 22. 
     Seat 12 is suspended from base links 40 by means of swing arms 50, 52, whose opposite ends are mounted for pivotal or rotational movement to the base link and seat link 41; there being, of course, two pairs of links 50 and 52 mounted to the base links 40 and seat links 41 on opposite sides of the chair. Swing link 50 which, relatively speaking, is pivotally interconnected at the rear end portions of the seat and base links and may be termed a &#34;rear swing link&#34;, is pivoted at joint 54 to the base link and at joint 58 to the seat link. The front swing link 52 is pivoted at joint 56 to the base link and at joint 59 to the seat link. In order to provide a minimal tolerance in the pivot joints, it is preferred that they be formed by ball joints rather than pivot pins or rivets conventionally employed in chair linkage mechanisms. This minimizes, if not avoids, undesired noise and bump during motion of the chair that would otherwise be caused by the slack attendant conventional pivot pin joints presently in used in chair mechanisms. 
     In the preferred embodiment, the swing arms 50, 52 on opposite sides of the chair are interconnected by bars 62 and 60 to integrate the swing arms as well as to reinforce the same against side-sway. In the specific embodiment shown, the upper ends of swing arms 50 and 52 are provided with inwardly projecting flanges to which the bars 60 and 62 are fixed in any suitable fashion. 
     In order to provide rocking action of the seat relative to the base as opposed to purely translatory motion, it is necessary that the distance between the upper pivots 54 and 56 be greater than the distance between the lower pivots 58, 59. It will thus be seen that one occupying the chair may rock the seat and back structure to and fro relative to the base 22 by virtue of the swinging movement of swing arms 50, 52 relative to the seat and base structures. This is illustrated in FIGS. 3 and 4. Moreover, through the use of the swing arms 50, 52, the seat structure also is displaced in the horizontal direction relative to the fixed base as the former undergoes rocking motion along a relatively large arc. This gives a pleasing gliding sensation reminiscent of that produced by porch gliders. In order to allow the seat height of the chair to be designed within a limited range, the distance between the upper pivot joints 54, 56 and lower pivot joints 58, 59 (or the distance between the base and seat links 40, 41 in the specific embodiment) must also be kept within a limited range; however, it was discovered that such limitations could excessively magnify the leverage of the chair and the occupant&#39;s momentum during rocking of the chair to produce an unstable condition. In accordance with the invention, it was discovered that the ratio of the distance between the upper pivots 54 and 56 and the distance between the lower pivots 58 and 59 must be such as to be capable of producing a certain obtuse triangle among the four-bar linkage 40, 41, 50 and 52 if the chair were rocked to its rear while being vacant of any occupant. For conventional chair sizes and styling, this triangle which is shown in dotted lines in FIG. 3, must have an angle &#34;a&#34; of at least six degrees (6°) but no greater than sixteen degrees (16°). It has been found that with such specifications, the chair may be easily rocked by the occupant with comfortable gliding action and yet, the occupant&#39;s weight will serve to resist any excessive rocking action so as to provide a safe chair. At the same time, the linkage mechanism is fully concealed within the chair without sacrificing low-seat styling requirements or other present-day design criteria. Indeed, the chair of the present invention may take its place in any living or sitting room. 
     Although the present invention has been illustrated in a chair incorporating a swivel, it will be apparent that the invention may be incorporated in chairs without a swivel. Furthermore, the invention may be incorporated in chairs where the backrest is movable relative to the seat or in other action chairs such as recliner chairs.