US2876462A - Convertible sofa bed - Google Patents

Description

J. MARTIN CONVERTIBLE SOFA BED- March 10, 1959 s Sheets-Shee t 1 Filed April 29. 1954 n 8 Emi -M N I. 5 mm 3 m M w m E am P m w w 5 2 m Z 1w 4 March 10, 1959 J. MARTIN 2,876,462

CONVERTIBLE SOFA BED Filed April 29. 1954 5 Sheets-Sheet 2 FIG. 3

INVENTOR JOSEPH MARTIN BY 72736, 62472072049, fifazlan, 55 f 75 ATTORNEYS March 10, 1959 J. MARTIN CONVERTIBLE SOFA BED Filed April 29. 1954 5 Sheets-Sheet 3 INVENTOR JOSEPH MARTIN BY 8 52?)267246; 7 2207227fl $224.21; f @Z TTORNEYS nit States CONVERTIBLE SOFA. BED

Joseph Martin, Bayside, N. Y., assignor to Pullman Couch Company, Chicago, Ill., acorporation of Illinois Application April-29, 1954, Serial No. 426,367

14 Glaims. (Cl. -13) This invention relates to household furniture and more particularly to a folding mechanism for a convertible sofa bed.

Convertible sofa beds as presently constructed have several major faults in that the nature of themechanism utilized toconvert them from a sofa seat toa bed necessitate the omission of important structural members commonly found in conventional sofa seats. This results in a sofa structure which lacks rigidity and strength, Furthermore, these mechanisms commonly utilize one or more pairs of legs to support the bed frame as it is being extended into bed position and retracted therefrom. Though these pairs of legs are customarily provided with wheels. or casters, they necessarily cause considerable wear of the floor covering or marring of the floor surface as they roll to and fro along the same paths with each extension or retraction of the bed frame. An additional drawback to convertible sofa beds presentlyv known is that the bed framean-d folding mechanism, when. folded within the structural frame of the sofa, require consider erable space which makes it difiicult to design sofa'seats having. pleasing proportions. tion of folded'bed frames and mechanisms in-the-prior art is such that the seat of the sofa. must. incline downwardly toward the front of the sofa rather than inclining downwardly toward the rear of thesofaas'is necessary for the greatest comfort of persons sitting ontthesofa.

I have invented a novel convertible sofa bed which overcomes these drawbacks. in a very satisfactory manner. According to my-invention, I provide a convertible sofa bed having a structuralframe including an upright back member, end members at opposite ends of the back member, and an upright transverse structural member fixed between the end members at the front thereof. lnvertibly suspended. between these end members, I provide a seat section which, when the bed frameis in the extended position, serves as the head section of the Moreover, the configuraframe and, whenthe bed frame is retracted within the I sofa, serves as the seat portion of the sofa; The bed frame also includes a back section and a foot section which are pivotally connected. Each of these latter sections is provided with a pair of castered supporting legs and are pivoted to be retractable against their respective bed frame sections.

The seat section and the back section of the bed frame are joined by. plural links which are connected, by a train of pivoted links, to the inverting mechanism of the seat section. The train oflinks and the plural links are constructed and arranged to provide determinant motion for and to support the back section ofthe ed frame independently of the legs throughout its travel into the extended or retracted position as the seat section is inverted. A train of pivotally connected links extending between the plural links joining the seat and back sections and the foot section is also adapted to provide determinant motion for and to support and guide the foot section throughout its travel between the extendedand-folded-positions Qfthe. bed frame.

The'

2,375,462 Patented Mar. 10, 1959 support of the foot section is similarly independent of thelegs which serve to support the bed frame only when the latter is in the fully extended bed position.

Each of the pairs of legs is retracted and extended by links cooperatively connecting the legs to the supporting and retracting links for the bed frame. The entire mechanism is constructed and arranged so that, beginning with the'bed frame in the extended bed position, folding ofthe legs is initiated simultaneously with the retracting action of the bed frame, thereby lifting the legs clear of the floor before they have rolled along it; The retracting action continues with the back and foot sections of the bed frame suspended by the trains of links and levers in a manner which carries every part of the frame over the transverse structural member and thereafter folds the two retracted sections within the structural frameof the sofa. In the course of retracting the bed and foot sections the seat section is completely inverted and at the end of the inversion the now forward portion of the seatsection rests on the transverse structural member atthe front of the sofa frame and the seat section slopes downwardly toward the upright back of" the structuralframe.

It-is at once apparent that I have invented a convertible sofa bed having many new and desirable features. An important one of these is the provision of a folding bed frame for a convertible sofa bed which does not depend upon the legs provided therefor during extension and retraction of' the bed frame, thereby eliminating unsightly wear of the floor covering. A further feature which stems directly from this is that this self supporting bed frame permits the inclusion of a structural member across the'front of the sofa frame, thereby adding greatly tothestrength and rigidity of furniture of this kind.

For a detailed explanation of a preferred embodiment of my invention, attention is directed to the following specification and the accompanying drawings in which:

Fig. l is a partial plan view of a convertible sofa bed;

Fig. 2' is a side elevation of the sofa bed of Fig. 1;

Fig. 3 is a side elevation of the sofa bed of Fig. 1 in a partially retracted position;

Fig. 4 is a side elevation of the sofa bed'of Fig. l in a fully retracted position.

It should be noted' that Fig. l is only a partial plan View of the sofa and extended bed frame, the portion illustratedbeing the right side when one is standing to the left" of Fig. l and is looking toward the foot of the bed frame. The left side of the frame will be understood to be identical in every respect with Fig. 1.

Referring now to Figs. 1 and 2, the sofa bed according to my'invention comprises a structural sofa frame generally indicated at 1 which includes an upright back 2; right and left end members 3 and an upright transverse structural member 4 fixed between the end members at the front thereof.

Between the end'members 3 of the structural frame, I inverti'bly suspend a seat section generally indicated at 5which is the head section of the bed frame when in the bed position shown in Fig. 2 and is the seat of the sofa when in the sofa position shown in Fig. 4'. This seat section has side rails 6 and a headboard 7 which constitute the frame of the-seat section. Additionally, I provide auxiliary side rails 8 spaced from the rails 6 and bolted thereto at opposite ends. These auxiliary rails 'atfordlocations for pivot points to be described below. The-mechanism used to invertibly suspend the seat section isa quadrilateral linkage having a first fixed link 9r secured to the end member 3 by bolts or screws 10 and a second fixed link 11 fixed to end member 3 by screws 12; These fixed links provide spaced pivot points 13* and.14 on fixed links to and 11, respectively. Ad-

ditionally, the quadrilateral linkage includes the link 15 which connects the pivot point 13 to the pivot point 16 on head section rail 6, and a J-shaped link 17 which similarly connects the pivot point 14 to a pivot point 18 on the head section rail 6. The unique shape of J-link 17 is necessitated by the fact that while the link is mounted at the point 14 which is within the upright back of the sofa frame, the link passes around the lower edge of the back and extends upwardly outside of the back as the seat section is inverted. See Fig. 3. However, the J-shaped link is not essential and may he replaced by a straight link if the proportions of the particular sofa frame so permit.

In addition to the seat section 5, the bed frame also comprises a back section generally indicated at 20 and a foot section generally indicated at 21. The back section is formed by side rails 22 and is provided at its head end as seen in Figs 1 and 2 with castered foldable legs 19 pivoted to the rails 22 at pivot points 23. The legs of the back section are rigidly joined by a transverse brace 24 which affords lateral stability. The foot section 21 is similarly formed by side rails 25 and a transverse foot rail 26 and is provided with a pair of castered foldable legs 27 pivotally connected to the rails 25 at points 55 intermediate the ends of the rails. The back and foot sections are pivotally connected together at the point 30. The back section is not pivoted directly to the seat section as is done in conventional bed frames of convertible sofa beds.

The connection between the seat section and the back section comprises a novel plural linkage including lever link 31 and tying link 32. Link 31 is pivoted to the seat section rail at intermediate point 33 and is pivoted to the back section rail at another intermediate point 34 which is spaced from point 33 along the link. For simplicity of design of the link 31 and provision of proper operating clearances, the point 34 is located on a pivot post 35 fixed to the back section rail 22. Tying link 32 of the plural linkage connecting the seat and back sections is pivotally connected to a pivot post 36 fixed to and depending from the seat section rail 6 at point 37. The other end of link 32 is pivotally connected to the hack section rail at point 23, the same point at which leg 19 is connected.

The lever link 31 of the plural linkage between the seat and back sections extends beyond point 33 toward the head rail 7 and it also extends beyond point 34 toward the foot section. Thus, it in effect constitutes a double lever, having fulcrums at the points 33 and 34. At the head end of lever 31 there is a pivot point 40 which is connected to a train of links including links 41 and 42 which have a common connection at point 43. The end of link 42 opposite point 43 is connected to J-link 17 at point 44 spaced from point 18 along J-link 17. The common pivot point 43 between levers 41 and 42 is, as I term it, a floating pivot in that there is a slot 45 cut through the auxiliary side rail 8 of the seat section and the pivot pin'for point 43 extends into this slot. Thus, the pivot point 43 has a limited sliding motion relative to the seat section. It will be readily apparent upon examination that the combination of linkages described this far is capable of supporting the seat and back sections of the bed frame when in extended position as shown in Fig. 2 independent of any other means including the legs 19 which are only utilized to support the weight of occupants of the bed and relieve the linkages of undue stresses. The legs 19 are rigidly held in the extended position by a short link 46 pivotally connected to the leg at point 47 and to the lever link 31 at a point 48 between the points 33 and 34. This short link also retractably connects the leg to the folding mechanism.

The foot section 21 of the sofa bed is extended, supported and retracted simultaneously with the seat and back sections by parallel trains of links, one of which trains also extends and retracts load bearing legs 27. As in the case of the back section, my novel folding mechanism also supports the foot section of the bed frame independently of the legs during extension and retraction of the bed frame, thus permitting the incorporation of the structurally important transverse member 4. Moreover, as previously explained, the legs are not required to roll on the floor to the detriment of the floor and its covering.

As stated above, the side rails 25 of the foot section are pivotally connected to the side rails 22 of the back section at points 30. The retracting train of the parallel trains comprises a tying link 50 connected at one end to the foot end of the lever link 31 at point 51 and at the other end to a floating pivot point 52 in slot 53 cut through the side rail 22 of the back section. Also connected at this floating pivot is an intersection link 54 which extends to a pivot point 55 intermediate the ends of foot section side rail 25. For economy in construction the pivot 55 may also be the point at which leg 27 is connected to the foot section.

The other train of the parallel trains of links actuates the folding leg 27 and comprises an intersectional link 56 and a tying link 57. These links have a common connection at a floating pivot 58 in a slot 60 cut through the foot section side rail 25. The head end of intersectional link 56 is connected to the back section side rail 22 at a point 61 between the foot end of the slot 53 and the pivot point 30, while the foot end of the tying link 57 is connected to the leg 27 at a pivot point 62 between the ends of the leg.

The operation of the mechanism of my new sofa bed can be analyzed in terms of cooperating linkages which provide the determinant motion of all sections of the bed frame and legs which is characteristic of my invention.

For the purpose of the following discussion and the claims the seat section side rail 6 and the auxiliary side rail 8 will be considered as a single element since they are fixed together and have the same motion.

Considering first the quadrilateral linkage comprising the J-link 17 and auxiliary side rail 8 pivoted at 18, the link 15 pivoted to 8 at 16, the fixed links 9 and 11 to which link 15 is pivoted at 13 and to which J-link 17 is pivoted at 14. There is formed an invertible linkage which provides determinant motion of the auxiliary side rail 8 fixed to the seat section side rail 6. Note that the auxiliary side rail 8 and the fixed links 11 and 9, effectively one link, are opposite sides of this invertible linkage. If this invertible linkage is considered alone it will be clearly seen that the seat section will move from its unfolded position as shown in Fig. 2 to its folded position as shown in Fig. 4. In doing so it will pass through the elevated and inclined position of Fig. 3.

Another. quadrilateral linkage providing determinant motion, which linkage I shall term a second four-element linkage is constituted by the auxiliary side rail 8 and the compound lever 31 pivotally connected at 33, back section side rail 22 pivotally connected to lever 31 at 34 and tying link 32 connected to side rail 22 at 23. The linkage is completed by the pivotal connection of link 32 to the pivot post 36 which depends from and is fixed to the side raii 8. Post 36 and side rail 8 effectively constitute one link of the second four-element linkage.

.It can now be seen that the second linkage has one link, namely side rail 8, which is common to the invertible linkage as well. In Fig. 3 it can be most clearly seen that the second linkage depends from the invertible linkage and is supported thereby. Back section side rail 22, being a part of this second linkage, is suspended. However, if no restraints were imposed at the pivot points 40 and 51, it can be seen in Fig. 3 that the back section side rail 22 would be free to rotate about the pivot 34 within-the scope permitted by the tying link 32.

An effective four-element linkage is utilized to coordinate the position of the side rail 22 in the second fourelement linkage with respect to the side rail 8 in the invertible four-element linkage. This effective four-element linkage comprises the following: the side rail 8 pivoted to the compound lever 31 at 33, link 41 pivoted to the compound lever 31 at point 46 and connected also to side rail 8 at the floating pivot 43. Link 42 in the train of links 41, 42 is connected at one end at the floating pivot 43 and at its opposite end to J-link 17 at pivot point 44. The effective four-element linkage is completed by J-link 17 being connected to side rail 8 at pivot point 18. Now, although there are five distinct members of this effective linkage and five pivot points which would normally result in an indeterminant five-element linkage, the provision of the floating pivot 43 connecting the train of links 41, 42 limits the freedom of motion of the floating pivot 43 to the extent of the slot 45 in the side rail 8. Such an arrangement is also known as two three-element linkages having a common sliding pair and is the equivalent of a conventional four-element linkage so far as the provision of determinate, rather than indeterminate, motion is concerned.

This effective four-element linkage is utilized to make the motion of the second four-element linkage completely dependent upon the motion of the first or invertible fourelement linkage and vice versa. Therefore, any motion imparted to this four-element linkage including the side rail 22 results in a uniquely determined motion of the side rail 8 which is a part of the invertible four-element linkage. In my new sofa bed the proportions of the various links and levers in these three linkages are made such that the side rail 8 and the side rail 22 lie in substantially the same line when the mechanism is in its extended position as seen in Fig. 2. Furthermore, these proportions are adjusted so that as the invertible linkage is moved to cause the side rail 8 to invert from its position in Fig. 2 to its position in Fig. 4 through the position shown in Fig. 3 the side rail 22 is retracted from its position in Fig. 2 downwardly into the frame of the sofa bed and thence into a vertical on-end position tothe rear of the sofa bed frame.

The foot section side rail 25 is also provided with determinant motion with respect to the seat and back sections. I accomplish this by providing another effective four-element linkage comprising the following: the back section side rail 22 is pivotally connected to the foot section side rail 25 at pivot point 39; the side rail 25 is in turn connected to link 54 at pivot point 55; the end of link 54 opposite point 55 is connected to side rail 22 and to tying link St) at the floating pivot 52; at point 51 link 50 is connected to compound lever 31; and the linkage is completed by the connection of compound lever 31 to the pivot point 34 on side rail 22. This second effective linkage is similar to the first described effective linkage in that it has five distinct links and five pivot points. Yet, with the restriction on the freedom of movement of the connection between the train of links 50, 54 at the floating pivot 52, it provides determinant motion as though it were a four-element linkage. The second eflective linkage is tied to the second four-element linkage and to the first effective four-element linkage by means of the compound lever 31 which is common to all three of the linkages. By these means the motion of all sections of the bed frame is coordinated.

By the means of these linkages l have provided a mech-' anism in which any given link has a motion which is completely determined by the motion of any other link. Having analyzed the mechanism thus far without the introduction of the legs or the linkages which control their motion, it can be seen that the bed frame comprising the seat, back and foot sections can be folded from the extended position shown in Fig. 2 through the partially retracted position in Fig. 3 into the fully retracted position as shown in Fig. 4. Moreover, it can be seen in Fig. 2 that the mechanism will maintain itself in the extended position of Fig. 2 even without the aid of legs 19 and 27 inasmuch as both. of the effective linkageshave reached the permissible extent of their motion when the frame is in the fully extended position. This is apparent from the factthat the floating pivot 43 is in the leftmost end of the slot and can travel no farther in the direction in which it is urged by the weight of the mechanism acting on the linkages. Similarly, the floating pivot 52 is in the rightmost end of the slot 53 and can travel no farther toward right, the direction in which it is urged by the weight of the mechanism acting on the linkages.

As previously stated legs 19 and 27 are provided to support the bed frame when the latter is loaded by the weight of a mattress and occupants. The extension and retraction of the legs is coordinated by linkages which also provide determinant motion. Considering first the back section legs 19, each of them is operated by a third four-element linkage which comprises the compound lever 31 pivotally connected to the back section side rail 22 at pivot point 34. The side rail 22 is pivotally connected to the leg 19 at pivot point 23 and this third four-element linkage is closed by the link 46 pivotally connected to the leg 19 at 47 and at its opposite end to the compound lever 31 at pivot point 48. It is to be noted that this third linkage has two adjacent sides in common with two adjacent sides of the second four-element linkage, namely, the compound lever 31 and the back section side rail 22. As pointed out in the earlier discussion such an arrangement makes the motion of any one link of the third linkage, for example leg 19, completely dependent upon the motion of the links in the second linkage. The result is that the motion of leg l9'is completely determined by the motion of any other link in the entire mechanism.

A third effective four-element linkage controls the motion of the foot section leg. This effective four-element linkage comprises the back section side rail 22 pivotally connected to the foot section side rail 25 to which is pivoted the leg 27 at point 55. This linkage is completed by the train of links 56, 57 having a common pivot point at the floating pivot 53. The opposite end of link 56 is pivotally connected to side rail 22 at point 61 while the opposite end of link 57 is pivotally connected to leg 27 at the point 62. This arrangement results in determinant motion for the leg 27 in the same manner as explained in connection with the effective four-element linkages previously described. It is to be noted that the side rail 22 and the side rail 25 are adjacent links in this third effective four-element linkage as well as being adjacent links in the effective four-element linkage connecting the back and foot sections.

Figs. 1 and 2 indicate generally the preferred relative spacing of the various links and side rails and also indicate the preferred locations of the pivot points to afford necessary clearances during operation. However, many other workable arrangements of the links, levers and pivot points embodying the principles of my invention will readily occur to the skilled designer.

The foregoing is a complete description of the sofa bed folding mechanism according to my invention. Operation of this mechanism is positive and simple and requires only one person to completely extend or retract the bed frame. Beginning with the bed frame in the extended bed position, conversion of the bed into a sofa is accomplished by lifting the transverse structural member 26. Initially the foot section may rotate through a small angle about the pivot point 34 before either the seat section or the back section of the bed frame begins to retract. By further lifting the foot section, however, the links and levers immediately lift the legs 19 clear of the floor and guide all of the sections of the bed frame through paths which carry them over the transverse structural member 4 at the base of the front of the end members of the sofa and into a folded position within the structural frame of the sofa. As previously pointed out, the legs 19 are completely retracted against the back section side rails early in the course of the retracting action and prior to the time that the back section passes over the structural member 4. This is clearly illustrated in Fig. 3 which shows the positions of all the components of the bed frame and folding mechanism at an inter mediate point in their travel between the extended bed position and the folded position Within the frame of the sofa.

During the folding action the seat section of the bed frame is inverted through a path which takes the seat section upward and into a position parallel with the upright back member. At the highest point in the course of travel of the seat section, the end of the seat section side rail at which pivot point 33 is located is well above the transverse structural member 4 to provide ample clearance for the passage of the back and foot sections of the bed frame into the structural frame of the sofa. As illustrated in Fig. 3, the back section and the leg 19, retracted against the back section, pass over the transverse structural member and into an on-end .position in the compartment in the back of the sofa frame as illustrated in Fig. 4.

Meanwhile, the foot section of the bed frame has been tilted upward about the pivot point 30 and in this position it moves toward the sofa frame following the back section of the bed frame. The foot section and its legs, retracted against the foot section side rails, also pass over the transverse structural member 4 and into a position substantially parallel with the floor at the bottom of the frame of the sofa. After the foot section has passed completely into the sofa frame, inversion of the seat section is completed and it settles into a position of rest with the headboard 7 of the seat section resting on the transverse structural member 4. In its position of rest, the seat section slopes downwardly at a slight angle toward the upright back of the structural frame. In this position the seat section serves as a comfortably inclined base for conventional pillows or cushions. This additional feature of my new folding mechanism stems directly from the proper proportioning of the parts which is permitted by the manner in .which the several sections are moved into the sofa frame and their relation therein.

An examination of Fig. 4 will show that a mattress may be secured to the bed frame by any suitable means and that it does not undergo any undue distortion in the course of the folding action, but is merely doubled over on itself at the completion of folding of the bed frame without requiring a sharp break at the fold. The fold occurs in that portion of the mattress secured to the back section of the bed frame.

The sofa bed folding mechanism 1 have invented is a substantial improvement over prior art mechanisms for the same purpose and makes possible the construction of strong and rigid structural frames for furniture of this kind. Moreover, the capacity of my novel sofa bed mechanism to support itself independently of its load bearing legs during extension and retraction frees it from objections to prior convertible sofa beds which caused unsightly wear of floors and their coverings.

Iclaim:

l. A convertible sofa bed comprising a structural sofa frame having an upright back and a'pair of oppositely disposed end members, a bed frame having a seat section, a back section and a foot section, each of said sections having a pair of oppositely disposed side rails, a first invertible four-element linkage in which one of said end members and one of said seat section side rails constitute opposite elements, a second four-element linkage in which one of said seat section side rails and. one of said back section side rails constitute opposite elements, means providing a first effectively determinant linkage connecting said'back and foot sections, one of said back section side rails and one of said foot section side rails constituting adjacent elements of said first effectively determinant linkage, and a means providing a second effectively determinant linkage of which one element is common to said invertible linkage, a second element is common to said second four-element linkage and a third element is common both to said invertible linkage and to said second four-element linkage, and means positively relating the motion of said first effectively determinant linkage to the motion of said second effectively determinant linkage.

2. A convertible sofa bed according to claim 1 in which said effective linkages each comprise two three-element linkages having a common sliding pair.

3. A convertible sofa bed according to claim 1 in which a link of said second effective linkage comprises an articulated link having a pivot point, and slidable means connecting said pivot point with said last-mentioned common link to provide a sliding pair.

4. A convertible sofa bed comprising a structural sofa frame having an upright back and a pair of oppositely disposed end members, a bed frame having a seat section, a back section and a foot section, each of said sections having a pair of oppositely disposed side rails, a first invertible four-element linkage in which one of said end members and one of said seat section side rails constitute opposite elements, a second four-element linkage in which one of said seat section side rails and one of said back section side rails constitute opposite elements, means providing a first effectively determinant linkage connecting said back and foot sections, one of said back section side rails and one of said foot section side rails constituting adjacent elements of said first effectively determinant linkage, and a means providing a second effectively determinant linkage of which one element is common to said invertible linkage, a second element is common to said second four element linkage and a third element is common both to said invertible linkage and to said second four element linkage, and said first and second effectively determinant linkages having a common link.

5. A convertible sofa bed according to claim 4 in which each of said effective linkages comprises two threeelement linkages having a common sliding pair.

6. A convertible sofa bed according to claim 4 in which said second effective linkage comprises a pair of elements having a pivot point and means slidably connecting said pivot point to said third common element.

7. A convertible sofa bed according to claim 4 in which said first effective linkage comprises a pair of elements having a pivot point and means slidably connecting said pivot point to another element which is common to said invertible linkage.

8. A convertible sofa bed according to claim 4 and having a supporting leg pivotally connected to each of said back section side rails and a third four-element linkage of which one of said legs and one of said back section side rails constitute two adjacent elements and of which a third element is said second element common to said second effectively determinant linkage.

9. A convertible sofa bed according to claim 4 having a supporting leg pivotally connected to said one foot section side rail and a third effective four-element linkage of which said leg and said one back section side rail constitute opposite elements.

10. A convertible sofa bed according to claim 4 hHV'. ing a supporting leg pivotally connected to said one foot section side rail and a third effectively determinant linkage of which said leg constitutes one element and two adjacent elements of said first effectively determinant linkage constitute second and third elements.

11. A convertible sofa bed according to claim 10 in which said third effectively determinant linkage comprises a pair of links connecting said one back section side rail and said leg and having a pivotal connection slidably connected to said one foot section side rail 12. A convertible sofa bed according to claim 10 in which said first and third effectively determinant linkages each comprises two three-element linkages and a common sliding pair.

13. A convertible sofa bed comprising a structural sofa frame having an upright back and a pair of end members, a foldable sectional bed frame including a seat section, a back section and a foot section, a first quadrilateral linkage of which one of said end members and said seat section are opposite links for invertibly suspending said seat section on said frame, a second quadrilateral linkage of which said seat and back sections are opposite links for determinately suspending said back section from said seat section, said back and foot sections being pivotally connected, a first determinant linkage constructed and arranged to connect said quadrilateral linkages and to restrict the motion of said back section to a uniquely determined position with respect to every position of the seat section throughout the inverting motion of the seat section, a second determinant linkage constructed and arranged to connect said foot section to said back section and to said first determinant linkage to restrict the motion of said foot section to a uniquely determined position with respect to every position of said back section throughout the inverting motion of said seat section, said second quadrilateral linkage and said first and second determinant linkages having as a I common element a compound lever which is pivotally connected at spaced points to said seat and back sections respectively and which is pivotally connected at other spaced points to elements of said first and second determinant linkages respectively, whereby the back and foot sections are suspended from said seat section independently of other external means of support throughout the folding action of said bed frame.

14. A convertible sofa bed according to claim 13 in which each of said first and second determinate linkages comprises a train of pivotally connected links and in which one end of said train of links is connected to said lever at one of said other points, the other end of said train is connected to another element of that linkage, and the pivotal connection of the links of said train is confined to linear motion with respect to one of said sections.

References Cited in the file of this patent UNITED STATES PATENTS 1,543,103 Heale June 23, 1925 1,637,797 Arton Aug. 2, 1927 2,007,988 Thomas July 16, 1935 2,197,735 Thomas Apr. 16, 1940 2,673,355 Ducrot Mar. 30, 1954 2,738,519 Thomas Mar. 20, 1956 2,755,486 Thomas July 24, 1956

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