Structural joint

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to furniture and more particularly to a novel structural joint which may be economically mass produced and then rapidly assembled and permanently joined without the aid of jigs, clamps, or other tools for retaining the parts in assembled relation.

As will appear from the ensuing description, the present structural joint may utilized to join a variety of furniture parts and may be used to advantage in various articles of furniture including chairs, tables, and the like. However, the invention is particularly suited to and will be disclosed in connection with attachment of chair legs to a chair seat.

2. Prior Art

At the present state of development of the furniture manufacturing art, chairs, tables, and the like are commonly fabricated from wood and constructed of a multiplicity of separate pieces which are individually shaped by hand or machine and then joined with glue, screws, or other fastening means while the pieces are held in assembled relation with the aid of jigs or clamps. This method of fabrication is quite laborious and lends itself to only limited mass production technique. As a consequence, articles of furniture produced by the existing fabrication methods tend to be quite costly. The furniture cost increases appreciably in the event the furniture is provided with any carving, scrollwork, or other ornamental features.

FIG. 2 is a horizontal section through the chair seat showing the seat frame in top plan view;

FIG. 3 is a top plan view of the seat frame with a seat cushion supporting panel in position on the frame;

FIG. 4 is an enlarged section taken on line 4-4 in FIG. 2 illustrating a structural joint of the present invention for joining a front chair leg to the seat frame;

FIG. 5 is an enlarged section taken on line 5-5 in FIG. 2 illustrating a structural joint of the present invention for joining a rear chair leg to the seat frame;

FIG. 6 is a section taken on line 6-6 in FIG. 5;

FIG. 7 is a section taken on line 7-7 in FIG. 5;

FIG. 8 is a section taken on line 8-8 in FIG. 4 illustrating the mating complementary configuration of the parts of the structural joint for joining the front chair leg to the seat frame;

FIG. 9 is a fragmentary perspective view of the seat frame part of the structural joint illustrated in FIG. 8;

FIG. 10 is a fragmentary perspective view of the leg frame part of the structural joint illustrated in FIG. 8;

FIG. 11 is an exploded perspective view of the completed chair;

FIG. 12 is a fragmentary perspective view of one part of a structural joint of the present invention for joining the rear chair leg to the seat frame;

FIG. 13 is a fragmentary perspective view of the other part of the structural joint for joining the rear chair leg to the seat frame;

FIG. 14 is a fragmentary perspective view of an article of structural embodying a modified furniture joint according to the invention;

FIG. 15 is a section taken on line 15-15 in FIG. 14;

FIG. 16 is a fragmentary top plan view of an article of furniture embodying a further modified structural joint according to the invention;

FIG. 17 is a section taken on line 17-17 in FIG. 16; and

FIGS. 18, 19 and 20 illustrate three different male part configurations for the structural joint of FIGS. 16 and 17.

₄₀ DESCRIPTION OF THE PREFERRED EMBODIMENTS

SUMMARY OF THE INVENTION

The present invention overcomes the above drawbacks of the existing methods of furniture manufacture by providing a structural joint having mating male and female parts which may be injection molded from plastic or otherwise economically mass produced and then rapidly assembled and permanently joined with little or no tooling so as to permit an article of furniture to be mass produced at minimum cost. According to a particularly unique and important feature of the invention, the male part of the structural joint is provided with an extending coupling portion having laterally projecting attachment lugs, and the female part of the joint is formed with a longitudinally slotted socket for receiving, with a snug mating 55 fit, the coupling portion of the male part and its attachment lugs. The joint parts are shaped to interengage in such a way that mere assembly of the parts 'results in frictional retention of the same in assembled relation and positive orientation of the parts relative to one another. This permits the parts to be gQ assembled and permanently joined without the aid of jigs, clamps, or other tooling for retaining the parts in assembled relation. According to the preferred practice of the invention, the parts of the joint are injection molded from plastic and then permanently joined by solvent welding, heat welding, or gg adhesively bonding the contacting surfaces of the parts to one another. However, it will become evident as the description proceeds that the joint parts may be constructed of other suitable materials and permanently joined to one another in other ways, as by bolts, nails, or the like. 7q

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a chair embodying a number of structural joints according to the present invention for joining the chair legs to the chair seat frame; 75

FIGS. 1—13 illustrate an article of furniture 10 embodying parts 12 and 14 which are connected by structural joints constructed according to the present invention. In this instance, the furniture 10 is a chair and the furniture parts 12,14 are the chair seat frame and chair legs, respectively. As will appear presently, the frame and legs may be mass produced in various ways but are preferably molded. It will be observed that each leg 14 includes a leg member proper and a number of frame attachment lugs projecting laterally, in outwardly diverging relation, from the leg member at seat level. The frame 12 is formed with receiving sockets 16 for the legs 14. These sockets enter the undersurface of and extend upwardly through the frame. As may be readily observed in the drawings, each leg socket 16 has a central socket portion and socket slots, equal in number to the attachment lugs on its respective leg 14, extending laterally from the central socket portion. The central portion and slots of each leg socket are shaped, arranged, and dimensioned to receive with a snug mating fit the leg member and attachment lugs of the corresponding supporting leg 14.

The frame 12 and supporting legs 14 are assembled by initially longitudinally aligning the legs with their respective receiving sockets 16 and then relatively moving the frame and legs toward one another in the longitudinal directions of the legs to cause the attachment lugs on the legs to enter their respective socket slots through the lower open sides of these slots to positions wherein the lugs bottom against the upper slot walls. The slots receive the lugs with a snug mating fit which is effective to firmly retain the legs and frame in assembled relation and to positively position the legs and frame relative to one another in such a way as to permit permanent joining of the parts without the aid of jigs, clamps, or other tooling of this character. The frame and legs may be constructed of any suitable material and may be joined by any convenient

3,583,733 means, such as fasteners or an adhesive bonding agent. According to the preferred practice of the invention, however, the legs and frame are molded from plastic and are joined by solvent or heat welding their abutting surfaces to one another. The legs 14 and leg sockets 16, and particularly the attachment lugs on the legs and the lug receiving socket slots, are constructed and arranged to maintain these abutting surfaces in firm adhesive bonding contact with on another without the use of auxiliary clamping means. While the legs are shown to be solid in cross section, they may be made hollow in the manner of the chair legs disclosed in copending application Ser. No. 797,616.

Referring now in more detail to the drawings, the article of furniture 10 selected for illustration is a chair of provincial design. In this instance, the furniture frame 12 is a seat frame in the form of a generally annular frame member having inner and outer circumferential surfaces 18, 20. The frame has a rounded rear portion and front corner portions. The supporting legs 14 include a pair of front legs 22 and a pair of rear legs 24. Rear legs 24 form part of a back frame 26. The leg receiving sockets 16 in the seat frame 12 include a pair of front sockets 28 for receiving the front chair legs 22 and a pair of rear sockets 30 for receiving the rear legs 24. Front sockets 28 are located at the front corner portions, respectively, of the seat frame 12, and the rear sockets 30 are located along the rear curved portion of the seat frame. As shown best in FIGS. 5 and 16, the seat frame 12 is increased in thickness in the region of the sockets 28, 30 to provide the frame with the requisite strength and rigidity. Extending across and secured to the seat frame 12 is a seat assembly 32.

The front chair legs 22 are identical and, as already noted, each includes a leg member 34 and frame attachment lugs 36. At its upper seat level end, each front leg member 34 has a generally polygonal shape in transverse cross section which provides the leg member with three intersecting faces 38 disposed in longitudinal planes of the leg member inclined approximately at 45° relative to one another. In this instance, each front leg has three attachment lugs 36 which are located along the longitudinal center lines of and project normal to the three leg faces 38, respectively. Accordingly, the lugs diverge outwardly at approximately 45° relative to one another. As shown best in FIG. 11, each attachment lug 36 has inner and outer end portions with tapered side faces which converge in the direction of the central juncture of the end portions. The side faces of the lugs are also vertically tapered so that these faces converge in the upward direction, as shown in FIGS. 7 and 8.

The rear chair legs 24 have leg members 40 which are contoured, as shown. Each rear leg member has a generally rectangular shape in transverse cross section and mounts three frame attachment legs 42 which project from the front and two side faces, respectively, of the member. Referring to FIG. 15, it will be observed that the rear leg lugs 42 are tapered in the same fashion as the front leg lugs 36.

As shown best in FIG. 11, the front leg sockets 28 are formed in the front corner portions of the seat frame 12. Each front socket includes a central socket portion 44 and socket slots 46 extending laterally from and opening at their inner ends to the central socket portion. In this instance, the central portion 44 of each front leg socket opens longitudinally through the upper and lower surfaces of the seat frame 12 and laterally through the outer circumferential surface 20 of the frame, in a generally diagonal direction of the frame. The socket slots 46, on the other hand, open through the undersurface of the frame but are closed at their tops by upper walls 48. The depth of the slots measured along the length of the socket is substantially less than the socket length. The central portion 44 of each front leg socket 28 is shaped in transverse cross section to generally complement the contained, upper seat level portion of the corresponding front leg member 34. In this regard, it will be observed that each front leg socket has three longitudinal faces 50 which are disposed to abut the three faces 38 on the corresponding front leg member 34. The inner ends of the socket slots 46 open centrally through these socket faces, as shown. The seat frame 12 is recessed in the regions between the socket faces 50, as at 52, to lend a degree of lateral resiliency to the adjacent ends of the walls of the socket slots 46. The socket slots 46 are tapered to complement and receive with a snug mating or wedging fit the leg attachment lugs 36.

It is evident at this point that the upper ends of the front chair legs 22 and the seat frame front leg sockets 28 are shaped to permit mating engagement of the legs with the seat frame 12 by first locating the legs in longitudinal alignment with the normally lower ends of the seat frame front leg sockets 28 and then effecting relative movement of the seat frame and legs toward one another, in the longitudinal directions of the legs, in such a way as to cause the legs to enter the sockets from below. During this assembly procedure, the upper polygonal ends of the front leg members 34 enter the central front leg socket portions 44 and the front leg attachment lugs 36 enter the socket slots 46. The legs are inserted into the sockets to final positions of assembly wherein the lugs bottom against the normally upper socket walls 48. In this final position of assembly, the front leg faces 38 abut and seat flush against the seat frame socket faces 50, in the manner best illustrated in FIG. 8. The front leg attachment lugs 36 are dimensioned to have a snug fit within their respective seat frame socket slots 46. Moreover, because of the illustrated, longitudinally tapered shapes of the lugs and slots, the lugs are restrained against longitudinal movement in the slots. As a consequence, assembly of the seat frame 12 and front chair legs 22 in the manner just explained is effective to firmly secure the frame and legs to one another and to positively position the frame and legs relative to one another. In this regard, it is significant to note that the three attachment lugs 36 of each front leg 22 and their respective socket slots 46 extend in the fore and aft, lateral, and diagonal directions, respectively, of the seat frame to aid the positive positioning function of the lugs and slots. In the final position of assembly of the seat frame 12 and front legs 22, the upper ends of the legs are substantially flush with the upper surface of the frame. The exposed surface of the upper end of each leg is rounded, in the manner illustrated in FIG. 8, so that the leg protrudes slightly beyond the outer surface 20 of the frame. Since each of the legs 22 has substantial length on both sides of the lugs 36, and since each socket 44 is open on one side, the result is a cantilever support of the leg 22.

It will be seen that the rear leg sockets 30 in the seat frame 12 are generally similar to the front leg sockets 28 in that the rear sockets have central socket portions 54 and slots 56 extending laterally from and opening inwardly to the central socket portions. The central socket portions 54 open longitudinally through the upper and lower surfaces of the seat frame 12 and laterally through the rear rounded portion of the outer seat frame surface 20. These socket portions are generally rectangular in transverse cross section so as to complement the rectangular cross sections of the rear leg members 40. Similarly, the rear leg socket slots 56 have the same tapered shape as the rear leg attachment lugs 42 and are dimensioned to receive these lugs with a snug mating fit. The three slots 56 of each rear leg socket extend in the lateral and fore and aft directions, respectively, of the seat frame 12.

The seat frame 12 and the rear chair legs 24 are assembled by first laterally inserting the rear leg members 40, just above their attachment lugs 42, into the central portions 54 of the rear leg sockets 30. The seat frame 12 and the rear legs 24 are then moved relative to one another in the longitudinal directions of these legs in such a way that the rear leg attachment lugs 42 enter the rear socket slots 56 from below to a position of final assembly wherein the lugs bottom against the upper walls of the slots. The rear legs, like the front legs, are designed to have a snug mating fit in their respective seat frame sockets 40, such that assembly of the seat frame and rear legs in the manner just explained is effective to firmly attach the legs to the frame and positively position the legs rela3,583,733 tive to the frame. Thus, the frame and rear legs, like the frame and front legs, may be permanently joined without the aid of jigs, clamping means, or other tooling for locating and holding the legs relative the the frame.

The rear leg members 40 continue upwardly above seat 5 level and curve inwardly toward and join one another at their upper extremities. Extending between and joining the rear leg members, at some elevation above seat level, is a cross member 58. In the particular chair which has been selected for illustration, the inturned upper extremities of the rear leg 10 members and the crossmember 58 are provided with ornamental surface features, as shown. The joined rear leg members 40 and the crossmember 58 together constitute the back frame 26. The upper portion of this frame, above seat level, forms the back rest of the completed chair. 15

During fabrication of the chair 10, the seat frame 12, front legs 22, and back frame 26 are assembled in the manner heretofore explained and are then permanently joined. Permanentjoinder of these parts may be accomplished in various ways. As noted earlier, however, the preferred practice of the 20 invention involves molding of the seat frame, back frame, and front legs from plastic and then permanently joining these parts by sonic, solvent or heat welding.

Turning now to FIGS. 14 through 20, there are illustrated some alternative structural joint configurations according to 25 the invention. In FIGS. 14 and 15, a leg 60 of the kind disclosed in copending application Ser. No. 797,616 is secured to a frame 62. Leg 60 is rectangular in cross section and has an upper end face 64 and two adjacent sidewalls which rise above the end face to form a right angle corner flange 66. Projecting 30 perpendicularly from the two opposite sidewalls of the leg, flush with its end face 64, are a pair of attachment lugs 68. These legs taper longitudinally to an increasing thickness toward their outer ends.