Frame assembly for modular furniture and method of assembling the same

FIELD OF THE INVENTION

[0001] The present invention relates to the field of modular, ready-to-assemble furniture, and more specifically, a frame assembly for securing together a group of modular furniture parts to form a completed furniture piece.

BACKGROUND OF THE INVENTION

[0002] Furniture pieces are typically manufactured and assembled at a factory and then shipped as a complete unit to a distributor or customer. The sections of the furniture piece are typically joined together using bolts that extend through predrilled holes in wooden or metal parts of the sections. Upholstery is used to cover the furniture sections, including the bolts and wooden or metal parts of the sections. The completed furniture piece is typically too heavy to be handled by a single individual and too large to be maneuvered through some doorways and stairwells. As a result, customers may limit the furniture that they choose to purchase or may object to additional charges required for third-party delivery of the furniture. In addition, it is difficult to efficiently pack assembled furniture pieces due to their size, shape and the fragility of the upholstered surfaces. Damage to any portion of the furniture piece typically requires the entire furniture piece to be shipped to a factory for repair.

[0003] One approach to this problem has been through the use of ready-to-assemble (RTA) furniture that provides increased options for storage, delivery and assembly of the furniture. For instance, U.S. Pat. No. 5,338,095 to Laughlin et al. discloses a furniture piece that relies on interlocking frame members to secure the modular sections together. The interlocking joints are designed to be easy to assemble. In one instance, a pair of combined wedge and parallelepiped shaped sockets <b>64</b> defined at the lower ends of a pair of vertical side members <b>72</b> of a backrest member <b>26</b> allow the backrest member to be secured to a pair of rail members <b>50</b>, as shown in FIG. 3. Despite the ease of assembly, the furniture disclosed by Laughlin, and other conventional RTA furniture, can suffer from looseness in the fit between the modular sections that results in instability. For example, a looseness in fit due to repetitive loading can result in wobble or rocking of the backrest relative to the base of the furniture piece. Laughlin attempts to solve this problem with the addition of a pair of thumbscrews <b>96</b> that secure the backrest member to respective wing portions <b>100</b> of the seat. However, a pair of unsightly flaps in the upholstery are necessary to secure the thumbscrews and the thumbscrews require the presence of the wing portions for attachment, thereby limiting aesthetic design variations.

[0004] Attempts have been made to eliminate the problem of instability through other variations in the method of assembling, or fastening, the modular pieces together. For instance, U.S. Pat. No. 5,551,757 to Glover discloses a fastening system for RTA furniture. The fastening system employs side-support rails secured to the arm sections of the seat which allow either a seat platform or a foldout bed platform to be secured within the furniture piece. A pair of hooks are mounted to a back section and the back section is connected to the side-support rails and between a pair of armrests by mounting the hooks on a pair of engagement pins of the side-support rails. The back section is further secured using hard bolts <b>88</b> that are fed through the back section and into the armrests, as shown in FIG. 2. Although the fastening system of the Glover patent increases the rigidity of the assembled back section, the back section is divided into two portions that can be disengaged to allow access for insertion of the hard bolts into the armrests. This two-piece back section is more costly to produce than a conventional sofa back section.

[0005] It would be advantageous to have a frame assembly for RTA modular furniture that allows the furniture to be quickly assembled and yet has relatively rigid construction without sacrificing aesthetic appeal. It would be further advantageous if the backrest of the furniture could be rigidly secured to the base of the furniture piece using the frame assembly without undue visible alterations in the appearance of the backrest or base of the furniture piece. It would be further advantageous if the frame assembly were adaptable to different aesthetic variations of furniture and different types of furniture, such as sleeper sofas.

SUMMARY OF THE INVENTION

[0006] The present invention addresses the above needs and achieves other advantages by providing a frame assembly for securing a plurality of modular sofa parts together into the sofa frame by producing a positive fit between one, or more, of the modular sofa parts. More particularly, the frame assembly includes a pair of tapered members attached to opposing sides of a backrest sofa part and a pair of receptacles attached to respective ones of a pair of rails, which are in turn attached to a pair of armrests. The backrest is connected between, and to, the armrests and rails by inserting each of the tapered members into a tapered slot defined by each respective receptacle. The tapered shape of the tapered members and slots produces the positive fit that has two directional components to prevent front-to-back rocking, and side-to-side rocking, of the backrest. The positive fit between each tapered member and receptacle is further strengthened using a pair of overlapping securing members each connected to a respective one of the tapered member and receptacle. The securing members may be transfixed with a hand bolt which is tightened to draw the tapered member further into the tapered slot. Further, the rails each define a plurality of holes configured to accept one of a pair of spaced drop-in supports of a spring unit, a sleeper unit, and a futon unit allowing the sofa frame to be easily upgraded or adapted as desired by the user.

[0007] In one embodiment, the frame assembly secures a plurality of modular sofa parts together into a sofa frame. The modular sofa parts include a pair of base walls, a pair of armrests and a backrest. The frame assembly includes a pair of elongate rails, a pair of receptacles and a pair of tapered members. Each of the elongate rails includes a pair of spaced bracket portions configured for attachment to a common one of the armrests. Each spaced bracket portion is further configured for attachment to a respective one of the pair of base walls. Each receptacle has a wall structure defining a tapered slot and each receptacle is attached to a respective one of the pair of elongate rails. The pair of tapered members are configured for attachment to the backrest. Each tapered member has at least one tapered outer surface receivable by a corresponding one of the pair of receptacles in a positive fit.

[0008] The frame assembly can be assembled by spacing apart the pair of elongate rails and attaching the bracket portions of the elongate rails to their respective base walls so as to space apart the base walls and secure the base walls to the elongate members. The pair of tapered members are also spaced apart and attached to the backrest. Once attached to the backrest, the tapered members are inserted into the receptacles so that each of the tapered outer surfaces is engaged with a respective tapered slot in a positive fit which rigidifies the sofa frame.

[0009] In another aspect, the pair of tapered members each include a second tapered outer surface so that the positive fit is configured to extend in multiple directions. The tapered slot defined by each wall structure may have a flattened triangular shape and the tapered outer surface of each tapered member also has a flattened triangular shape which configures the positive fit to extend in the first direction. The flattened triangular shape may also have a trapezoidal cross-section that forms a second pair of tapered surfaces which configures the positive fit to extend in a second direction. The first and second directions correspond to front-to-back, and side-to-side, motions relative to the sofa frame.

[0010] In yet another aspect, the walls structure defining the tapered slot includes at least three inner surfaces. A first inner surface has a triangular shape with a pair of vertical edges. A pair of second inner surfaces are spaced apart across the first inner surface and extend inwards from the vertical edges of the triangular shape. Each tapered member may include three of the tapered surfaces wherein each tapered surface is congruently shaped to a respective one of the at least three inner surfaces so that the positive fit extends in at least two directions.

[0011] In another embodiment, the pair of elongate rails each include a first and second overlapping channels that slidingly interfit. The first bracket is attached to the first channel and the second bracket is attached to the second channel allowing spacing between the bracket portions to be adjusted for differently sized armrests.

[0012] In another aspect, each receptacle further includes a first securing member and each tapered member includes a second securing member. The first and second securing members are configured to overlap and receive a fastener so that each tapered member can be secured to the corresponding one of the receptacles. The first securing member may be positioned on a bottom portion of the tapered member. The second securing member may be positioned on a bottom portion of the receptacle so that tightening the fastener draws the tapered member further into the receptacle thereby increasing the positive fit.

[0013] In another embodiment, each of the pair of elongate rails are configured for attachment of a pair of drop-in unit supports. The elongate rails define a plurality of holes configured to receive fasteners for attaching a respective one of the drop-in unit supports. Preferably, the drop-in unit supports support any combination of a futon, a sleeper unit or a spring unit.

[0014] In yet another embodiment, the present invention includes a positive fit assembly for rigidly securing two modular furniture pieces together in a positive fit. The positive fit assembly includes a receptacle and a tapered member. The receptacle is configured for attachment to one of the modular furniture pieces and has a triangular first wall with a pair of vertical edges, a pair of second walls and a securing member. The pair of second walls are spaced apart across the triangular first wall and each extends inwards from a respective one of the pair of vertical edges of the triangular first wall. The triangular first wall and the second walls define a tapered slot and the securing member extends laterally from the triangular first wall.

[0015] The tapered member is configured for attachment to another one of the modular furniture pieces and has a triangular first surface with a pair of vertical edges, a pair of second surfaces and a second securing member. The pair of second surfaces each extend outwardly from a respective one of the pair of vertical edges and the securing member extends laterally from the triangular first surface.

[0016] The receptacle can be attached to its modular furniture piece. The tapered member can be attached to the other one of the furniture pieces. The two furniture pieces are connected by sliding the tapered member into the tapered slot defined by the walls of the receptacle until the pair of second surfaces are flush with the pair of second walls.

[0017] The present invention has several advantages. The modular sofa parts are firmly interconnected by the frame assembly into the sofa frame, while still being easy to assemble and disassemble without tools due to the use of several hand bolts and the positive fit of the tapered members and receptacles. The modular assembly further speeds up the assembly at the plant, showroom or home and can be performed by a single person. The modular sofa parts are more efficiently shipped due to more efficient packing of the parts. The positive fit of the tapered members into the receptacles, aided by the securing members, increases stability of the backrest in at least two directions. The securing members are positioned so that they can be tightened before drop-in of the drop-in unit and do not require an unsightly access panel or hole in the upholstery. The sofa frame, and frame assembly, are easily adapted for use with a plurality of drop-in units, including a spring unit, a sleeper unit and a futon unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0019]FIG. 1 is an exploded view of one embodiment of a modular/RTA sofa including a frame support assembly of the present invention;

[0020]FIG. 2 is a sectional view of the assembled modular/RTA sofa of FIG. 1 showing an elongate rail, a receptacle and a tapered member of the frame support;

[0021]FIG. 3 is an enlarged view of the receptacle and tapered member attached to a portion of the elongate rail, as shown in FIG. 2;

[0022]FIG. 4 is a perspective view of a tapered member engaged in a receptacle of another embodiment of the present invention;

[0023]FIG. 5 is a perspective view of the tapered member and receptacle of FIG. 4, wherein the tapered member is disengaged from the receptacle; and

[0024]FIG. 6 is a cross-sectional view of the tapered member and receptacle of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

[0026] In one embodiment, the present invention includes a modular/RTA sofa assembly <b>10</b>, as shown in FIG. 1. The sofa assembly <b>10</b> includes a sofa frame <b>11</b>, a drop-in spring unit <b>12</b>, and a plurality of cushions <b>13</b>. The sofa frame <b>11</b> supports the drop-in spring unit <b>12</b>, which in turn supports the cushions <b>13</b> that provide a comfortable seating surface for a user. The sofa frame <b>11</b> includes a frame support assembly <b>14</b> that reinforces and connects several modular sofa parts preferably comprising a pair of base walls <b>15</b>, a pair of armrests <b>16</b> and a backrest <b>17</b>. The support frame assembly <b>14</b> includes a pair of elongate rails <b>20</b>, a pair of receptacles <b>40</b> and a pair of tapered members <b>60</b>. The pair of elongate rails <b>20</b> are attached to the armrests <b>16</b> and the base walls <b>15</b> to provide a box-like seating and drop-in unit <b>12</b> support area. The pair of tapered members <b>60</b> are spaced apart and attached to opposing ends of the backrest <b>17</b>. The pair of receptacles <b>40</b> are each attached near the back end of respective ones of the pair of elongate rails <b>20</b> and are configured to receive the pair of tapered members <b>60</b> therein so as to provide a relatively rigid completed sofa assembly <b>10</b>.

[0027] The pair of elongate rails <b>20</b> each include an inner channel <b>22</b>, an outer channel <b>21</b> and a pair of end brackets <b>27</b>, <b>28</b>, as shown in FIG. 2. The inner channel <b>22</b> has a continuous channel cross-section along its length, allowing the inner channel to be slidingly adjusted within the outer channel <b>21</b>. Similarly, the outer channel <b>21</b> has a continuous channel cross-section, but the outer channel cross-section is slightly oversized in comparison to the cross-section of the inner channel <b>22</b>. The slight oversize of the outer channel <b>21</b> allows the inner channel <b>22</b> to slide freely within the space defined between the outer channel <b>21</b> and the portion of the respective one of the armrests <b>16</b> to which the outer channel is attached.

[0028] The inner channel <b>21</b> defines a series of adjustment holes <b>26</b> preferably linearly spaced along the inner channel in increments of every V2 inch. The outer channel <b>22</b> defines an outer channel adjustment hole <b>32</b> which, when coincident with one of the adjustment holes <b>26</b> can be transfixed by an adjustment bolt <b>25</b>. In this manner, the length of the elongate rails <b>20</b> can be adjusted to accommodate different furniture designs. For instance, the adjustment bolt <b>25</b> can be removed from the holes <b>25</b>, <b>26</b> and the inner channel <b>22</b> slid within the outer channel <b>21</b> in half inch increments until the elongate rail <b>20</b> is long enough to span the distance between the pair of base walls <b>25</b>, or is short enough to fit between the pair of base walls <b>15</b>, if the elongate rail was originally too long. When the elongate rails <b>20</b> are each at an appropriate length, the pair of end-brackets <b>27</b>, <b>28</b> are flush with the inner faces of the pair of base walls <b>15</b> allowing them to be affixed thereto. The size of the channels <b>21</b>, <b>22</b> and the positioning of the holes can be varied, as desired. Several factors can determine the optimal size of the channels, such as the need for additional rigidity or the need to minimize weight of the furniture piece. Finer adjustments in length could be had, if desired, by spacing the adjustment holes <b>26</b> closer together, such as in ¼ inch increments.

[0029] The outer channel <b>21</b> preferably further includes a plurality of tabs <b>33</b> that extend from the edges of the outer channel at regular, spaced intervals. Each of the tabs defines an armrest connector hole <b>23</b> that can be transfixed by fasteners, such as the screws <b>34</b> shown in FIG. 2. The screws <b>34</b> firmly attach each of the outer channels <b>21</b> to their respective armrests <b>16</b>. The size and spacing of the tabs <b>33</b>, connector holes <b>23</b> and the type of fastener used can be varied depending upon such factors as the desired rigidity of the attachment, i.e., generally more and larger fasteners providing increased fixation, the desired weight and the desired ease of assembly, wherein less fasteners are generally preferred.

[0030] The outer channel <b>21</b> further defines a plurality of drop-in connector holes <b>24</b> that are positioned along the outer channel at strategic locations to allow the attachment of various drop-in unit supports. Preferably, the drop-in connector holes <b>24</b> allow the attachment of at least three drop-in unit supports, including a spring unit support <b>55</b>, a sleeper unit support <b>56</b> and a futon unit support <b>57</b>. As demonstrated by the broken lines in FIG. 3, one pair of the connector holes <b>24</b> toward the rear of the sofa frame <b>11</b> allows the attachment of the futon unit support <b>57</b>. Another pair of the connector holes <b>24</b>, allows the attachment of both the spring unit support <b>55</b> and the sleeper unit support <b>56</b>. Attachment of a spring unit support <b>57</b> to both of the elongate rails <b>20</b> provides a ledge upon which the drop-in spring unit <b>12</b> may be rested to support the weight of user. The other supports <b>56</b>, <b>57</b> also support their respective unit types, but are not described herein in further detail because their construction is known to those of skill in the art.

[0031] A first end-bracket <b>27</b> is positioned at, and attached to, the free end of the outer channel <b>21</b>, while a second end-bracket <b>28</b> is attached to the free end of the inner channel <b>22</b>. Each end bracket includes a pair of end-bracket walls <b>35</b> that share a common edge and are at right angles to each other, as shown in FIG. 3. One of the end-bracket walls <b>35</b> is configured to abut the adjacent one of the pair of armrests <b>16</b> and defines a plurality of armrest bracket holes <b>31</b>. The armrest bracket holes may be transfixed by fasteners to attach the brackets <b>27</b>, <b>28</b> to their respective adjacent armrests <b>16</b>. The other one of the end-bracket walls <b>35</b> is configured to abut the adjacent one of the pair of base walls <b>15</b> and defines a plurality of base wall slots <b>29</b>. The base wall slots are configured to be transfixed by a pair of large hand bolts <b>30</b> that connect the adjacent ones of the end-bracket walls <b>35</b> and base walls <b>15</b>. The base walls <b>15</b> may define a plurality of predrilled holes to further facilitate attachment of the hand bolts <b>15</b>. The elongated shape of the base wall slots <b>29</b> promote the easy attachment of the hand bolts <b>15</b> by allowing some initial play in the positioning of the slots coincident with the predrilled holes of the base walls <b>15</b>. As mentioned above, the spacing between the brackets <b>27</b>, <b>28</b> may be adjusted by adjusting the length of the elongate rails <b>20</b>. Such adjustment allows the respective end-bracket walls <b>35</b> to be positioned adjacent the base walls <b>15</b>.

[0032] Each of the hand bolts <b>30</b> preferably has a nob at one end for easy insertion into predrilled holes in the base walls <b>15</b> and subsequent tightening by hand. Hand bolts <b>30</b> are preferably used at the sites where attachment and detachment are likely to be performed by a consumer or during set-up in a showroom. The hand bolts could also be used in place of the other fasteners or bolts to promote adjustments by hand. Screws are preferably used in the present embodiment to secure the rails <b>20</b> to their respective armrests <b>16</b> in a more permanent manner than is available with the hand bolts <b>30</b> because detaching the rails from both the armrests and the base walls <b>15</b> is unnecessary for knockdown of the sofa assembly <b>10</b>. In an alternative embodiment, fasteners could be used to secure the rails <b>20</b> length-wise to the base walls <b>15</b> and the hand bolts used to connect the rails to the armrests <b>16</b>, which would still allow relatively easy knock-down. This may be preferable where the base walls <b>15</b> would benefit from the additional rigidity of the elongate rails <b>20</b>.

[0033] Each of the receptacles <b>40</b> includes a wall structure <b>41</b> that defines a tapered slot <b>43</b>, and a first securing member <b>44</b>, as shown in FIGS. 4, 5 and <b>6</b>. The walls structure <b>41</b> includes a first inner surface <b>45</b> and a pair of second inner surfaces <b>47</b>. The first inner surface <b>45</b> preferably is triangular in shape and includes a pair of vertical edges <b>46</b> that define a downward taper of the slot <b>43</b>. The downward taper of the slot promotes a positive fit of a respective one of the tapered members <b>60</b> into the slot in the downward direction, as will be described in more detail below. The pair of second inner surfaces <b>47</b> extend inwards from the vertical edges <b>46</b> of the first inner surface <b>45</b> and at an acute angle to the first inner surface so as to define a lateral taper of the slot <b>43</b>. Restated in a different way, the pair of second inner surfaces <b>47</b> are spaced apart across the first inner surface <b>45</b> and extend inwards from the vertical edges <b>46</b> of the triangular shape of the first inner surface. The lateral taper of the slot defined by the second inner surfaces <b>47</b> promotes a positive fit of a respective one of the tapered members <b>60</b> into the slot in the lateral direction, as will be described in more detail below.

[0034] The first inner surface <b>45</b> preferably defines a plurality of armrest holes <b>42</b>, as shown in FIG. 5, that may be transfixed by fasteners to attach the receptacles <b>40</b> to their respective armrests <b>16</b>. In the illustrated embodiment, three serially spaced holes <b>42</b> are used for a secure attachment of the inner surface <b>45</b>, and hence its one of the receptacles <b>40</b>, in a flush arrangement with a vertically oriented frame member used to construct the armrests <b>16</b>, as can be seen in FIG. 1. Attachment to the frame member reduces the likelihood of wobble, rocking or other relative displacement between the armrests <b>16</b> and their respective receptacles <b>40</b>.

[0035] The first securing member <b>44</b> extends laterally from the first inner surface <b>45</b> and includes an overlap portion <b>50</b> and a pair of securing member walls <b>49</b>, as shown in FIG. 5. The pair of walls <b>49</b> are spaced apart across the overlap portion <b>50</b> and extend upwards from the overlap portion to rigidify the securing member <b>44</b>. The overlap portion <b>50</b> extends outward from the bottom of the first inner surface <b>45</b> and defines a first securing member elongated hole <b>48</b> that is configured to receive another one of the hand bolts <b>30</b> therethrough.

[0036] The pair of receptacles <b>40</b> are preferably constructed from sheet steel that is punched, scored, or otherwise cut into a flat blank. The holes <b>42</b>, <b>48</b> are drilled into the first inner surface <b>45</b> and the overlap portion <b>50</b> while still in the shape of a blank for convenience. The second inner surfaces <b>47</b> are formed by bending strips of the sheet steel upwards and inwards at the edges <b>46</b> of, and relative to, the first inner surface <b>45</b>. The overlap portion <b>50</b> and the securing member walls <b>49</b> are bent upwards to roughly a right-angle relative to the first inner surface <b>45</b>. The securing member walls <b>49</b> are then bent inwards toward the overlap portion <b>50</b> at roughly right-angles until the edges of the member walls are in contact with the first inner surface <b>45</b>. The advantage of sheet steel is its low cost to manufacture and it relatively high strength. Other methods and materials may be used to construct the pair of receptacles <b>40</b>, however, and still achieve the same functionality.

[0037] Each of the receptacles <b>40</b> is preferably rigidly attached to the inner channel <b>22</b> of a respective one of the elongate rails <b>20</b>. In this manner, the receptacles are positioned in a spaced relationship across a seating area <b>18</b> of the sofa frame <b>11</b>. Each receptacle is preferably attached by welding the first inner surface <b>45</b> to the back edges of the channel <b>22</b> and by welding the top edges of the securing member walls <b>49</b> to the bottom wall of the inner channel. Attachment of the receptacles <b>40</b> to the rails <b>20</b> can be performed using other techniques, for instance by using rivets or other fasteners. The positioning of the receptacles <b>40</b> allows for the assembly of the backrest <b>17</b> at the back of the sofa frame <b>11</b> behind the seating area.

[0038] The pair of tapered members <b>60</b> include a wall structure <b>66</b> that defines a plurality of outer surfaces, and a second securing member <b>63</b>. The wall structure <b>66</b> defines a first outer surface <b>61</b> and a pair of second outer surfaces <b>62</b>. The first outer surface <b>61</b> is roughly the same size and shape as the tapered triangular opening defined by the top free edges of the second inner surfaces <b>47</b> of the receptacles <b>40</b>. The first outer surface <b>61</b> preferably includes a pair of vertical edges <b>67</b> and defines a plurality of backrest connector holes <b>64</b> that may be transfixed by fasteners to attach the first outer surface, and hence its respective one of the tapered members. <b>60</b>, to the side of the backrest <b>17</b>. The downward taper of the vertical edges <b>67</b> of the first outer surface <b>61</b> promotes the downward interference fit, as described in more detail below. Similar to the armrest connector holes <b>42</b> of the pair of receptacles <b>40</b>, the backrest connector holes <b>64</b> are preferably arranged coincident to a plurality of holes in a frame structure that is part of the backrest <b>17</b> in order to provide a secure fixation.

[0039] The second outer surfaces <b>62</b> extend outwards from the vertical edges <b>67</b> of the triangular shape of the first outer surface <b>61</b> and at an obtuse angle to the first outer surface. Restated, the pair of second outer surfaces <b>62</b> are spaced apart across the first outer surface <b>61</b> and extend outwards from the vertical edges <b>67</b> of the triangular shape of the first outer surface. The lateral taper defined by the second outer surfaces <b>62</b> promotes the positive fit in the lateral direction.

[0040] As mentioned above, the vertical and horizontal taper of the tapered slot <b>43</b> defined by the wall structure each of the pair of receptacles <b>40</b> which receives the roughly matching vertically and horizontally tapered surfaces of each pair of tapered members <b>60</b> ensures a horizontal and vertical positive fit. Advantageously, the horizontal and vertical components of the positive fit rigidify the connection of the backrest <b>17</b> to the remaining parts of the sofa frame <b>11</b> in both the side-to-side direction and front-to-back direction, respectively, relative to the sofa frame. Such rigidity reduces the wobble, rocking, or other displacements, that frequently occur in conventional modular, knockdown or RTA furniture. The vertical component of the taper, and the vertical positive fit, is exemplified by the flattened triangular shape of the tapered slot <b>43</b> and the tapered members <b>60</b>, as shown in FIGS. 4 and 5. FIG. 6 best illustrates the lateral, or horizontal, component of the taper and the lateral, or horizontal, positive fit by showing the trapezoidal cross-section of the tapered slot <b>43</b> and the one of the tapered members <b>60</b> received therein. It should be noted that the vertical and horizontal components of the positive fit can be accomplished using a range of tapered shapes that do not necessarily separate the various components of the positive fit into isolated surfaces, such as with a conical tapered member that is received by a conical receptacle. It should also be noted that the positive fit components are referred to as orthogonal components in a Cartesian system, but could also be referenced to other coordinate systems.

[0041] The second securing member <b>63</b> extends laterally from the first outer surface <b>61</b> and defines a hole <b>68</b> surrounded by a fixed nut <b>65</b> threaded to receive the hand bolt <b>30</b> that is extended through the first securing member hole <b>48</b>. Insertion of the hand bolt <b>30</b> through the hole <b>48</b> and the hole <b>68</b>, into the fixed nut <b>65</b> with subsequent rotation draws the respective one of the tapered members <b>60</b> further into its respective one of the receptacles <b>40</b> and thereby increases the strength of both components of the positive fit. Increasing the positive fit advantageously further reduces the likelihood of wobble or other instability of the backrest <b>17</b>. In another embodiment, illustrated in FIGS. 2 and 4-<b>6</b>, the second securing member flares outward and downward above the lateral extension so as to provide space for the inner channel <b>22</b> to pass therethrough.

[0042] The pair of tapered members <b>60</b> are preferably constructed from sheet steel cut into a flat blank, generally similar to the method of constructing the pair of receptacles <b>40</b>. The holes <b>64</b>, <b>68</b> are preferably drilled into the first outer surface <b>61</b> and the second securing member <b>63</b> while still in the shape of a blank. The second outer surfaces <b>62</b> are formed by bending strips of the sheet steel downwards at the edges <b>67</b> and away from the first outer surface <b>61</b>. The second securing member <b>63</b> is bent upwards at roughly a right angle to the first outer surface <b>61</b> and into a slightly rounded shape for additional rigidity. Other methods and materials may be used to construct the pair of receptacles <b>40</b>, however, and still achieve the same functionality.

[0043] Assembly of the sofa frame <b>11</b> using the frame support assembly <b>14</b> can be thought of as occurring in two stages. In a first stage, the more permanent fixations, typically using fasteners other than the hand bolts <b>30</b>, are performed at a factory or a store. The first stage may also be performed, typically only once, by the customer such as when the sofa <b>10</b> is shipped in mostly unassembled condition. In the first stage, the pair of elongate rails <b>20</b> are elongated or shortened by sliding the inner channel <b>22</b> within the outer channel <b>21</b> in ½ inch increments until the space between the brackets <b>27</b>, <b>28</b> match the depth of the armrests <b>16</b>. The length of the rails <b>20</b> are fixed by insertion and tightening of the adjustment bolt <b>25</b> into the adjustment hole <b>32</b> and the coincident one of the adjustment holes <b>26</b>. The rails <b>20</b> are each affixed to their respective one of the pair of armrests <b>16</b> by inserting fasteners through the armrest connector holes <b>23</b> and the armrest bracket holes <b>31</b>. The pair of tapered members <b>60</b> are spaced apart and affixed to opposite sides of the backrest <b>17</b> by inserting fasteners through the backrest connector holes <b>64</b>. Although the first stage is capable of being reversed, it is generally not as easy as undoing the second stage.

[0044] The second stage can be performed anywhere, and without tools, and is generally easier than the first stage. The second stage is ideal for a customer needing to disassemble the sofa, so that it is light enough to be carried and small enough to fit easily through doors and up stairwells, and then reassemble the sofa once it has reached its destination. The second stage is performed by spacing apart the pair of base walls <b>15</b> on opposing front and back sides of the armrests <b>16</b>. A front one of the base walls <b>15</b> is abutted against the first end-bracket <b>27</b> of each of the rails <b>20</b> and a rear one the base walls is abutted against the second end-bracket <b>28</b> of each of the rails. The base walls <b>15</b> are secured to their respective brackets by inserting pairs of the hand bolts <b>30</b> through their respective pairs of base wall slots <b>29</b> and into predrilled holes in the base walls. The pair of spring unit supports <b>55</b> (or sleeper <b>56</b>, or futon <b>57</b> supports, as desired) are attached to their respective ones of the elongate rails <b>20</b> by using the appropriately configured drop-in connector holes <b>24</b>, so that the spring unit supports are in a spaced relationship on opposing sides of the seating area of the sofa frame <b>11</b>. The drop-in spring unit <b>12</b> is dropped onto the tops of the spring unit supports <b>55</b>. The backrest <b>17</b> is joined to the rest of the sofa frame <b>11</b> by inserting the pair of tapered members <b>60</b> on either side of the backrest into the corresponding pair of receptacles <b>40</b> until the second securing member <b>63</b> overlaps the first securing member <b>44</b>. The connection of the backrest is then further secured by inserting one of the hand bolts <b>30</b> through the first securing member hole <b>48</b> of each of the pair of receptacles and tightening the bolt into the fixed nut <b>65</b> of the respective one of the pair of tapered members <b>60</b>. The seating area is prepared by placing the cushions <b>13</b> in their proper positions on the spring unit <b>12</b>. Reversing the second stage allows the sofa frame <b>11</b> to be broken into separate modular sofa parts.

[0045] It should be further noted that the positive fit characteristics of the present invention could be advantageously used to secure together other furniture pieces, and should not be considered limited to backrest attachment, or even sofas.

[0046] The present invention has several advantages. The modular sofa parts are firmly interconnected by the frame assembly <b>14</b> into the sofa frame <b>11</b>, while still being easy to assemble and disassemble without tools due to the use of several hand bolts <b>30</b> and the positive fit of the tapered members <b>60</b> and receptacles <b>40</b>. The modular assembly further speeds up the assembly at the plant, showroom or home and can be performed by a single person. The modular sofa parts are also more efficiently shipped due to more dense packing of the parts. The positive fit of the tapered members into the receptacles, aided by the securing members <b>48</b>, <b>63</b> increases stability of the backrest <b>17</b> in at least two directions. The securing members are positioned so that they can be tightened before drop-in of the drop-in unit and do not require an unsightly access panel or hole in the upholstery. The sofa frame, and frame assembly, are easily adapted for use with a plurality of drop-in units, including a spring unit, a sleeper unit and a futon unit.

[0047] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For instance, the term fastener, as used herein, is not meant to be limiting and may include such fasteners as rivets, bolts, screws, nails, with, and without washers, bolts and other fixation aids. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.