Patent Publication Number: US-10772436-B2

Title: Convertible sofa bed

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application No. 62/540,068 filed on Aug. 2, 2017, the disclosure of which is incorporated herein by reference. 
    
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
     Not Applicable 
     BACKGROUND 
     The embodiments and aspects described herein relate to a sofa bed with a folding mechanism that facilitates conversion from a sofa to a bed, and vice versa. 
     Folding beds, particularly sofa beds, have been desirable in tight living spaces where utilizing a single living space for multiple purposes may be optimal to save space. However, there are various deficiencies in current folding beds, including the compromise of either giving up comfort for space or practicality for comfort in an attempt to be functional in tight spaces or multipurpose rooms. Thus, there is a need for an improved sofa bed. 
     Accordingly, there is a need in the art for a sofa bed that improves on the practicality and comfort of current sofa beds. 
     BRIEF SUMMARY 
     The various embodiments and aspects described herein address the needs discussed above, discussed below, and those that are known in the art. 
     The present disclosure is directed to a sofa bed having one or more mechanisms (e.g., a folding mechanism and a sliding mechanism) that allow the sofa bed in sofa configuration to have a backrest and seat portion so that the sofa bed can be used as a sofa, and allow the sofa bed to be traversed to a bed configuration to have a conventional mattress that stays locked in place. Additionally, a benefit of the sofa bed is that the sofa bed described herein with a standard twin or twin xl mattress does not require any sort of anchoring of a frame of the sofa bed to a wall or floor. 
     There may be a convertible sofa bed with a folding mechanism capable of traversing the sofa bed between a sofa configuration and a bed configuration. The sofa bed may have a left support member and a right support member, both configured to rest on an underlying surface, a backrest having a left end and a right end. The backrest may be horizontally disposed between the left support member and the right support member, wherein the left end is attached to the left support member and the right end is attached to the right support member. The backrest may be configured to pivot up when the sofa bed is traversed to the sofa configuration and may pivot down when the sofa bed is traversed to the bed configuration. The backrest may have a front side and a rear side. The rear side may define a bed frame. The bed frame may be engageable with a mattress. The sofa bed may further have a seat base having a left end and a right end attached to the backrest. The seat base is receptive to at least one seat cushion. 
     The folding mechanism of the sofa bed may have a left first link member rotatably attached to the left backrest end and the left support member, and a right first link member rotatably attached to the right backrest end and the right support member. The left and right first link members may push upward on the backrest when the sofa bed is in the bed configuration. The left and right first link members may be shorter than the left and right second link members. The folding mechanism may further have a left second link member rotatably attached to the left backrest end and the left support member and a right second link member rotatably attached to the right backrest end and the right support member. The pivot points of the rotatable attachment of the left and right first link members to the left and right backrest ends may be at a first height above the underlying surface and the pivot points of the rotatable attachment of the left and right second link members to the left and right backrest end may be at a second height, the first and second heights being within 3 inches of each other. The first and second heights may be equal to each other. The left and right first link members may be about 3.5 inches. The left and right second link members may be about 6.5 inches. The left and right second link members may be about twice in length than that of the left and right first link members. The left and right second link members may push downward on the backrest when the sofa bed is in the bed configuration. 
     The sofa be may further have a left front link member rotatably attached to the left backrest end and the left seat base end and a right front link member rotatably attached to the right backrest end and the right seat base end. The left and right front link members may be between about 6 inches and 18 inches. When the sofa bed is traversed to a bed configuration or a sofa configuration, the left front link member and the right front link member may be configured to rock about the seat base, and the backrest may be configured to rotate about the left link member and the right link member. The pivot points of the rotatable attachment of the left and right front link members to the left and right backrest ends may be at a first height above the underlying surface and the pivot points of the rotatable attachment of the left and right front link members to the left and right seat base ends may be at a second height, where the first height may be higher than the second height. 
     The sofa bed may further have a sliding mechanism. The sliding mechanism may have left first and second track members connecting the left seat base end to the left support member, and right first and second track members connecting the right seat base end to the right support member. The left and right track members may be parallel to each other. The left and right first and second track members may be left and right first and second rails that are receptive to left and right first and second sliding members that are slidably engageable with the left and right first and second rails. The left first and second rails may be mounted on an inner surface of the left support member and the right first and second rails may be mounted on an inner surface of the right support member. The left and right first rails and the left and right second rails may be parallel to each other and at an angle to a vertical plane. The left first and second sliding members may be mounted on the left seat base end and the right first and second sliding members may be mounted on the right seat base end. The left and right first sliding members and the left and right second sliding members may also be parallel to each other at the angle to the vertical plane. The mounting angle of the left and right first and second rails and the first and second sliding members may be between about 6 degrees to 20 degrees. The left and right first and second rails may be of equal length. Further, the sliding mechanism may be lockable with a optional stopping mechanism. The stopping mechanism may be a spring loaded latch. 
     In bed configuration, the left and right first and second link members may create a reaction force couple that counters a summation of moments created by the weight of the seat base, weight of the backrest, and a weight of a person resting on the backrest so that the sofa bed remains in the bed configuration. The left and right first link members may be vertical and parallel to the left and right second link members to lock the backrest at the bed configuration. In sofa configuration, the seat base may optionally be locked at the sofa configuration by means of a locking mechanism. Also, even without a locking mechanism, a summation of the weights of the backrest, and the mattress, may be more than the weight of the seat base so that the backrest stays in the sofa configuration as well. 
     There may further be a method of traversing a convertible sofa bed with a folding mechanism from a sofa configuration to a bed configuration. The method may include a set of steps, wherein a first step may be unlocking a lock that holds a seat base and a backrest at a sofa configuration. The lock may be unlocked by disengaging a spring loaded latch from a latch slot. A second step may be rotating a backrest having a rear side defining a bed frame to a horizontal position so that the rear side faces upwards. An application of a horizontal pulling force on the backrest, or a downward force on the seat base, may be necessary to initiate the rotation of the backrest. The rotating step may be aided by left and right front link members connecting the backrest to the seat base rocking towards the seat base and rotating the backrest and left and right first and second link members attached to the left and right backrest ends to oscillate the backrest about a left joint and a right joint that join the left and right backrest ends to the left and right second link members and a left joint and a right joint that join the left and right backrest ends to the left and right first link members until the backrest is horizontal. A third step may be lowering the seat base so that the backrest is disposed above the seat base when the sofa bed is in the bed configuration. Lowering the backrest and seat base may be assisted by a spring so that a weight of the seat base does not cause the backrest and the seat base to inadvertently and too quickly drop to the bed configuration. For example, spring (e.g., gas spring, coil spring, elastic member, . . . etc.) may be connected to the back rest and the arm rest. A fourth step may be positioning left and right first link members vertical and parallel to left and right second link members to lock the bed frame at the bed configuration. 
     As indicated above, the application of a horizontal pulling force on the backrest or a downward force on the seat base, may be necessary to initiate the rotation of the backrest. The downward force on the seat base can unlock the back rest in that the downward force on the seat base has a horizontal force component in the same direction as that as arrow. In this regard, the downward force will also move the backrest laterally in the direction of arrow and skew the link members as discussed herein to unlock the backrest. 
     Additionally, there may be a method of traversing a convertible sofa bed with a folding mechanism from a bed configuration to a sofa configuration. The method may include a set of steps, wherein a first step may be pulling a bed frame defined by a backrest laterally to orient left and right first link members to left and right second link members for unlocking the sofa bed from the bed configuration. The bed frame may be pulled until the left and right first link members are no longer at a 90-degree angle to a horizontal plane. Pulling the bed frame may involve applying a force on the bed frame that has a horizontal magnitude. A second step may be rotating the bed frame upward. Rotating the bed frame upward may involve applying a force on the bed frame that has a vertical magnitude. A third step may be raising a seat base. The seat base may be raised by sliding left and right first and second sliding members at an angle to the vertical plane along left and right first and second rails. The step of raising the seat base may be assisted by a link. Optionally, a spring may be used to help with the transition of the sofa bed to the sofa configuration. A fourth step may be locking the seat base and the backrest to a sofa configuration. The seat base may be locked by engaging a spring loaded latch with a latch slot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
         FIG. 1  is a perspective skeleton view of a sofa bed in sofa configuration. 
         FIG. 2  is a perspective skeleton view of the sofa bed shown in  FIG. 1 . having begun its conversion to bed configuration. 
         FIG. 3  is a perspective skeleton view of the sofa bed shown in  FIG. 2 . further into its conversion to bed configuration. 
         FIG. 4  is a perspective skeleton view of the sofa bed shown in  FIG. 1  in bed configuration. 
         FIG. 5  is a side view of the sofa bed shown in  FIG. 1  with a transparent right support member and in sofa configuration. 
         FIG. 6  is a side view of the sofa bed shown in  FIG. 5  about having begun its conversion to bed configuration. 
         FIG. 7  is a side view of the sofa bed shown in  FIG. 6  further into its conversion to bed configuration. 
         FIG. 8  is a side view of the sofa bed shown in  FIG. 7  further into its conversion to bed configuration. 
         FIG. 9  is a side view of the sofa bed shown in  FIG. 8  further into its conversion to bed configuration. 
         FIG. 10  is a side view of the sofa bed shown in  FIG. 9  further into its conversion to bed configuration. 
         FIG. 11  is a side view of the sofa bed shown in  FIG. 10  further into its conversion to bed configuration. 
         FIG. 12  is a side view of the sofa bed shown in  FIG. 11  further into its conversion to bed configuration. 
         FIG. 13  is a side view of the sofa bed shown in  FIG. 12  further into its conversion to bed configuration. 
         FIG. 14  is a side view of the sofa bed shown in  FIG. 13  further into its conversion to bed configuration. 
         FIG. 15  is a side view of the sofa bed shown in  FIG. 14  further into its conversion to bed configuration. 
         FIG. 16  is a side view of the sofa bed shown in  FIG. 15  in bed configuration. 
         FIG. 17  is a perspective view of a sliding mechanism of the sofa bed in bed configuration, as shown in  FIGS. 4 and 15 . 
         FIG. 18  is a perspective view of the sliding mechanism shown in  FIG. 17  of the sofa bed in sofa configuration, as shown in  FIGS. 1 and 5 . 
         FIG. 19  is a flowchart of a method of converting the sofa bed in sofa configuration (shown in  FIG. 1 ) to the bed configuration (shown in  FIG. 3 ). 
         FIG. 20  is a flowchart of a method of converting the sofa bed in bed configuration (shown in  FIG. 3 ) to the sofa configuration (shown in  FIG. 1 ). 
     
    
    
     DETAILED DESCRIPTION 
     The various aspects of the sofa bed described herein may relate to a sofa bed wherein the sofa bed is convertible between a sofa configuration and a bed configuration. In the bed configuration, the sofa bed is placed into a position where a user can lay down on a standard mattress (e.g., twin or twin xl). In the sofa configuration, the mattress is moved out of the way so that the user can sit on seat cushions. The sofa bed does not require that a frame of the sofa bed be anchored to a floor or wall. 
       FIGS. 1-4  show a perspective and skeleton view of a sofa bed  10  in sofa configuration (see  FIG. 1 ), transition configuration (see  FIGS. 2-3 ), and bed configuration (see  FIG. 4 ) resting on an underlying surface  12  with left and right support members  20 ,  22 , which may also be referred to as left and right armrests  20 ,  22 . It will be appreciated that the term “armrest” is for exemplary purposes only and not intended to be limiting. It is expressly contemplated that the sofa bed  10  may have left and right support members  20 ,  22  that are not armrests. The support members or armrests  20 ,  22  may be constructed out of one or a combination of materials commonly used in building sofa frames such as wood, artificial wood, molded plastic, aluminum and steel or any other durable, flexible, and/or resilient material. The armrests  20 ,  22  may be further padded and layered with linen fabric, corduroy, or leather depending on stylistic and comfort needs. Materials such as foam, down, feathers, fabric or a combination thereof may be utilized as padding. 
     The sofa bed  10  may have a backrest  30  (see  FIGS. 1 and 2 ), a seat base  50  (see  FIGS. 1 and 2 ), a folding mechanism  100  (see  FIG. 5 ), and a sliding mechanism  110 (see  FIG. 17 ).  FIGS. 5-16  show the folding mechanism  100 , and  FIGS. 17 and 18  show the sliding mechanism  110  in further detail and how they function, which will be discussed below. The backrest  30  and the seat base  50  may be constructed out of one or a combination of materials commonly used in building sofa frames such as wood, artificial wood, molded plastic, steel or any other durable, flexible, resilient metal. Preferably, the backrest  30  may have a width of between about 30 to 60 inches (preferably 40 inches). The seat base  50  may have a width of between about 18 to 30 inches (preferably about 24 inches). Other dimensions are also contemplated. The folding mechanism  100  and sliding mechanism  110  may be constructed out of a load bearing material such as wood, steel, plastic, metal, any material with similar mechanical properties, or a combination thereof. 
     Also shown in  FIG. 4 , the rear side  38  of the backrest  30  may include a bed frame  40 . The bed frame  40  may receive a bed. The rear side  38  may be flat wood, a wire spring grid, or incorporate other suspension arrangements known to one of ordinary skill in the art. The bed frame  40  may hold a mattress  42 . The bed frame  40  shown in  FIG. 4  is shown with side support, but that is optional. The bed frame  40  may be flat without side supports. The height of the backrest  30  may depend on the thickness of the mattress  42  held by the bed frame  40 . Preferably, the backrest  30  may have a height between about 4 to 16 inches. The bed frame  40  may have ribbed inner walls to secure the mattress  42  in place to prevent the mattress  42  from falling out of the bed frame  40  when the sofa bed  10  is in sofa configuration, and when the sofa bed  10  is being transitioned into a bed configuration. The bed frame  40  may further utilize other fastening mechanisms known in the art to hold the mattress  42  such as hooks and loops, hooks, or string ties. The mattress  42  may be one of a range of commercially available mattresses such as innerspring, memory foam, latex, or gel. The combination of type of mattress  42  and rear side  38  may be chosen by the user based on comfort, health issues, or the need to be cost-effective. The mattress  42  size may be twin xl or twin, which are standard mattress size terms used in the art. Two or more sofa beds  10 , in bed configuration may be joined side-to-side to form a queen, king, or California king size bed. 
     The length of the backrest  30  may be between about 70 inches and 90 inches, depending on the mattress size the bed frame  40  can accommodate. The seat base  50  may be suitable to put seat cushions  56  on. The seat cushions  56  may be a single piece or multiple pieces and cover the entirety of the seat base  50 , and may have padding made of foam, down, feathers, fabric or a combination thereof and may have a linen fabric, corduroy, or leather cover. The height of the seat base  50  may depend on the thickness of the seat upholstery, or cushions  56 . The length of the seat base  50  may be equal to that of the backrest  30 . The length of the seat base  50  may be between about 70 inches and 90 inches. When the sofa bed is in the bed configuration, the mattress support surface may be between about 12 and 20 inches and preferably 16 inches above the underlying surface  12 . This is so that a standard twin or twin xl size mattress may have a top surface upon which the person sleeps upon be about 20 to 32 inches (preferably about 24-27 inches) above the underlying surface  12 . 
       FIGS. 5-16  show a side view of the sofa bed  10  transitioning from a sofa, as shown in  FIG. 5 , to a bed, as shown in  FIG. 16 . These figures also illustrate how the folding mechanism  100  and the sliding mechanism  110  of  FIG. 17  facilitates the transition. Briefly, the sofa configuration may transition to a bed configuration with the user rotating the backrest  30  so that the rear side  38  faces upward and is parallel to a horizontal plane, and the seat base  50  may be lowered so that the backrest  30  is above the seat base  50 . This position is the bed configuration and is shown in  FIG. 16 . To reverse the transition, the user may pull in the direction of arrow  51  (see  FIG. 16 ) and rotate the backrest  30  upward as shown by arrow  53  in  FIG. 16  and raise the seat base  50  along with the backrest  30 . These transition processes are briefly touched on here to give context for how the folding and sliding mechanisms  100 ,  110  operate, and they will be further discussed in detail. 
     The folding mechanism  100  may be assembled on the sofa bed  10  so that a left first link member  104  and a left second link member  108  are the mirror images of a right first link member  104  and a right second link member  108  about a vertical plane normal to the seat base  50  that bisects the sofa bed  10 . The left first and second link members  104 ,  108  are identical to the right first and second link members but are located on opposite sides of each other. Reference numbers  104 ,  108  refer to both the first and second link members on the left and right sides. The left and right first link members  104  may be shorter than the left and right second link members  108 . The left and right first link members  104  are preferably of a length between 2 inches and 6 inches and most preferably about 3.5 inches, whereas the left and right second link members  108  are preferably of a length between 3 inches to 10 inches and most preferably about 6.5 inches. The link members  104 ,  108  may be made of a high strength and durable material such as steel or any another material known in the art to have adequate strength and durability. The left and right first link members  104  may be rotatably attached to the left backrest end  32  and the left armrest  20  and the right backrest end  34  and the right armrest  22 , respectively. Likewise, the left and right second link members  108  may be rotatably attached to the left backrest end  32  and the left armrest  20  and the right backrest end  34  and the right armrest  22 , respectively. The rotatable attachments on the backrest  30  may have pivot points  103   a ,  103   b ,  103   c , and the rotatable attachments on the seat base  50  may have pivot points  103   d , and the armrests  20 ,  22  may have pivot points  103   e  which may also be referred to as joints in a nonlimiting manner. These pivot points  103   a ,  103   b ,  103   c ,  103   d ,  103   e  may be in a variety of forms, such as pivot pins, rivets, and bolt and nut combinations. The pivot points  103   a  of the rotatable attachment of the left and right first link members  104  to the left and right backrest ends  32 ,  34  may be at a first height  105  above the underlying surface  12 . In the bed configuration, the first height  105  (see  FIG. 16 ) may be equal to or within 6 inches of a second height  109  (see  FIG. 16 ) above the underlying surface  12  where the pivot points  103   b  of the rotatable attachment of the left and right second link members  108  to the left and right backrest ends  32 ,  34  may be located. In the sofa configuration, the first height  105  may be higher than the second height  109  (see  FIG. 5 ). 
     As shown in  FIGS. 5-16 , in carrying out the transition from sofa configuration to bed configuration, the folding mechanism  100  may function by left and right first and second link members  104 ,  108  oscillating the backrest  30  about a left joint  103   b  and a right joint  103   b  that join the left and right backrest ends  32 ,  34  to the left and right second link members  108  and a left joint  103   a  and a right joint  103   a  that join the left and right backrest ends  32 ,  34  to the left and right first link members  104  until the backrest rear side  38  is facing upward and is parallel to the horizontal plane. The transition motion may stop when the left and right first link members  104  are parallel to the left and right second link members  108  and normal to the underlying surface  12 . All link members  104 ,  108 , and thus the backrest  30  may be at rest because the forces acting on their respective pivot points  103   a ,  103   b  may counter each other and rotational moments may be zero. For example, the moment acting on the backrest due to its combined weight, is counteracted by the reaction force couple generated by the left and right first link members  104  and the left and right second members  108 . The folding mechanism  100  is locked and the sofa bed cannot be unintentionally traversed to the sofa configuration once the sofa bed is in the bed configuration. If a user attempts to lift up on the backrest  30  without first pulling the backrest in the direction of arrow  51 , the left and right first and second link members  104 ,  108  lock up, in that they cannot be rotated. 
     The sliding mechanism  110  may be locked when the sofa bed is in the sofa configuration with a stopping mechanism  120  to further restrict movement of the link members  104 ,  108 , and thus transition of the sofa bed from the sofa configuration to the bed configuration. The sliding mechanism will be further discussed below. 
     Also in the bed configuration, the left and right first link members  104  may exert a vertical and upward pulling force on the backrest  30  due to the tension applied by the pivot points  103   a  where the first link members  104  and armrests  20 ,  22  attach together. The magnitude of this force may counter the magnitudes of all other vertical forces exerted on the backrest  30  at a downward direction. These forces may be the vertical component of the force exerted by the front link members  60 ,  62 , the weight of the backrest  30 , the downward force on the backrest  30  due to the force applied by the pivot points  103   b , where the second link members  108  and armrests  20 ,  22  attach together, and the weight of the user. Thus, the bed configuration may be in a state of static force equilibrium. This equilibrium may be further reinforced by a stopping mechanism  120  to counter the horizontal as well as the vertical component of the force transferred by the front link members  60 ,  62  on the backrest  30 . The stopping mechanism  120  may lock one, multiple, or all of the following, thereby stopping  50  and the backrest  30  from moving in all directions: the sliding mechanism  110 , the front link members  60 ,  62 , or the first and second link members  104 ,  108 . The stopping mechanism  120  may be a spring loaded latch  120  engaging with a latch slot or any other locking mechanism appreciated by those with ordinary skill in the art. There may be an upper latch slot  124   a  to allow locking at the sofa configuration and a lower latch slot  124   b  to allow locking at the bed configuration. The latch  120  may not pull out or unlock itself out of the slots  124   a ,  124   b  unless actuated by the user manually or via a control device, such as a button or a switch. The sofa bed may be locked at either the sofa configuration or bed configuration. 
     Also, as shown in  FIGS. 5 and 16  the left and right front link members  60 ,  62  may hold the seat base  50  at the desired position both in the sofa configuration and the bed configuration. The front link members  60 ,  62  may be made of a high strength and durable material such as aluminum or another material to have similar strength and durability (e.g., steel). They may preferably have a length between about 5 inches and 20 inches. The left and right front link members  60 ,  62  may be rotatably attached to the left backrest end  32  and the right seat base end  52  and the left backrest end  32  and the right seat base end  54 , respectively. The rotatable attachments may have pivot points  103   c  on the backrest  30  and pivot points  103   d  on the seat base. Pivot points  103   c  may be at a first height  64  from the underlying surface  12 , whereas pivot points  103   d  may be at a second height  66  from the underlying surface  12 . The first height  64  may be higher than the second height  66  in both sofa and bed configurations (see  FIGS. 5 and 16 ). These pivot points  103   c ,  103   d  may be in a variety of forms, such as pivot pins, rivets, and bolt and nut combinations. 
     In the sofa configuration, the left and right front link members  60 ,  62  may be static because the locking mechanism is engaged, and thus the backrest  30  may not tip over toward the bed configuration. 
     Referring now to  FIG. 17 , the sliding mechanism  110  may be employed to guide the seat base  50  up and down as the sofa bed is transitioned between the sofa and bed configurations. Although a sliding mechanism is described, other mechanisms in lieu of the sliding mechanism may be used. By way of example and not limitation, the sliding mechanism may be replaced with a profile linear bearing, a four-bar linkage, slots and grooves guiding a peg or nub, and other mechanism that limit or governs the seat base up and down as the sofa bed is transitioned between the sofa configuration and bed configuration. The up and down motion governed by the sliding mechanism or alternate mechanism may be linear or curved. 
     As mentioned above, the sliding mechanism  110  may be locked at a bottom bed configuration position and a top sofa configuration position with a stopping mechanism  120 . The sliding mechanism  110  may have left and right first track members  112 ,  116  and left and right second track members  114 ,  118  that mirror each other across the vertical plane bisecting the sofa bed  10 . The sliding mechanism  110  may have at least one track member or may have at most ten track members on each side. In the figures, two tracks are shown on each side. The two sets of track members  112 ,  116 ,  114 ,  118  described herein is only one embodiment of the invention and is not intended to be limiting in the quantity of track members that may be used in the sliding mechanism  110 . The left first and second track members  112 ,  116  may connect the left seat base end  52  to the left armrest  20 , and the right first and second track members  114 ,  118  may connect the right seat base end  54  to the right armrest  22 . First track members  112 ,  116  may be parallel to second track members  114 ,  118  and mounted on the left and right armrest inner surfaces  21 ,  23  at an angle preferably between 6 to 20 degrees to the vertical plane, and most preferably 12 degrees. However, the angle may be any acute angle to the vertical plane that would allow the seat base to travel down a trajectory to its bed configuration position without being offset with the backrest  30  for more than 3 inches at that position. This may be desirable because the seat base  50  may want to be kept tucked away as much as possible to avoid bumping into it or for stylistic reasons. The track members  112 ,  114 ,  116 ,  118  may be actuated into sliding motion with a spring. The spring may be mechanical or pneumatic. The user may convert the sofa bed  10  from one configuration to the other by exerting less energy when moving the seat base  50  either up or down by allowing the spring to bear some or all of the load. 
     The left and right first and second track members may be further split into left and right first and second rails  113   a ,  115   a ,  117   a ,  119   a  and left and right first and second sliding members  113   b ,  115   b ,  117   b ,  119   b . The left rails  113   a ,  117   a  mirror the right rails  115   a ,  119   a  along the vertical plane  20  bisecting the sofa bed  10 . The first and second rails  113   a ,  115   a ,  117   a ,  119   a  may be equal in length. The left and right first and second rails  113   a ,  115   a ,  117   a ,  119   a  may be receptive to and slidably engageable with left and right first and second sliding members  113   b ,  115   b ,  117   b ,  119   b . The left and right first and second rails  113   a ,  115   a ,  117   a ,  119   a  may be mounted on the left armrest inner surface  21  and right armrest inner surface  23 , respectively. The mounting may be so that the first and second rails  113 ,  115 ,  117 ,  119  may reach between about 7.875 inches to about 23.625 inches, preferably about 15.75 inches, high from the underlying surface  12 . The left and right first and second sliding members  113   b ,  115   b ,  117   b ,  119   b  may be mounted on the left and right seat base ends  52 ,  54 , respectively. 
       FIG. 19  shows a flowchart for a method  200  of converting the sofa bed  10  from a sofa configuration to a bed configuration. The method  200  may include a step  202  of unlocking a stopping mechanism  120  that holds the seat base  50  and the backrest  30  at the sofa configuration at both the left and right counterparts of the sliding mechanism  110 . The stopping mechanism  120  may be a spring loaded latch  120  that may be unlocked manually or with button or switch controls and may function as described above. Unlocking the spring loaded latch  120  may involve retracting the latch  120  from the upper latch slot  124   a , and thereby rendering the sliding mechanism  110  slideable. 
     The method  200  may next include a step  204  of rotating the backrest  30  until its rear side  38  defined by the bed frame  40  housing the mattress  42  faces upwards and is parallel to the horizontal plane. This is the bed configuration. To traverse the sofa bed back to the sofa configuration, a pulling force  51  on the backrest  30  may be necessary to initiate the rotation of the backrest. The pulling force  51  skews the link members  104 ,  108  so that the link members  104 , 108  can be rotated. When the link members  104 ,  108  are parallel to each other, they cannot be rotated. In this manner, the sofa bed is locked in the bed configuration even without the stopping mechanism  120 . 
     After step  204  is initiated and the back rest is being transitioned to the bed configuration, the method  200  may also include a step  206  of lowering the seat base  50  so that the backrest  30  is disposed above the seat base  50 . This step may be simultaneously executed with step  204 . Lowering the seat base  50  may be accomplished with the left and right front link members  60 ,  62 , and the sliding mechanism  110  as described above. The track members  112 ,  116 ,  114 ,  118  may be actuated into sliding motion as described above. A spring could be used to help with the lowering of the backrest and the seat base so that the sofa bed does not too quickly fall into the bed configuration. The spring may carry some of the weight of the back rest and seat base so that the back rest can be gently placed or transitioned to the bed configuration. 
     The method  200  may next include a step  208  of positioning the left and right first link members  104  vertical and parallel to the left and right second link members  108  to virtually lock the backrest  30  at the bed configuration as described above. The locking may be further reinforced by locking a stopping mechanism  120  that holds the seat base  50  and the backrest  30  at the bed configuration at both the left and right counterparts of the sliding mechanism  110 . The stopping mechanism  120  may be a spring loaded latch  120  that may be locked and may function as described above. Locking the spring loaded latch  120  may involve inserting the latch  120  to the lower latch slot  124   b , and thereby rendering the sliding mechanism  110  non-slidable. 
       FIG. 20  shows a flowchart for a method  300  of converting the sofa bed  10  from a bed configuration to a sofa configuration. The method  300  may include a step  302  of pulling a bed frame  40  defined by a backrest  30  laterally to skew left and right first link members  104  to left and right second link members  108  for unlocking the sofa bed  10  from the bed configuration to the sofa configuration. This skewed orientation of the link members  104 ,  108  may be necessary to allow link members  104 ,  108  to rotate about their pivot points  103   a ,  103   b . The user may initiate the pulling by applying a horizontal force  51  on the backrest  30 . This may involve the user standing in front of the sofa bed  10 , grabbing the bed frame  40 , and pulling the backrest  30  towards the user. The user may stop pulling when the left and right first link members  104  are skewed with respect to each other. 
     The method  300  may next include a step  304  of rotating the bed frame  40  upward in the direction of arrow  53 . This may require the user to apply a vertical force on the backrest  30 . The user may achieve this by standing in front of the sofa bed  10 , grabbing the bed frame  40 , and pulling up on the backrest  30  away from the underlying surface  12 . 
     The method  300  may next include a step  306  of raising the seat base  50 . This step may be simultaneously executed with step  304 . Raising the seat base  50  may be accomplished with the left and right front link members  60 ,  62  and the sliding mechanism  110  as described above. The backrest may be assisted toward into the upward motion with a spring as described above. The seat base may also be raised manually, without the assistance of links or springs. For example, the user can apply an upward force onto the seat base. If a stopping mechanism is included in the sofa bed, then the upward force will move the seat base upward toward the sofa configuration after disengaging the stopping mechanism. 
     The method  300  may next include a step  308  of locking the seat base  50  and the backrest  30  to a sofa configuration. This step may be executed by locking the stopping mechanism  120  at both the left and right counterparts of the sliding mechanism  110 . The stopping mechanism  120  may be a spring loaded latch  120  that may be locked and may function as described above. Locking the spring loaded latch  120  may involve inserting the latch  120  to the upper latch slot  124   a , and thereby rendering the sliding mechanism  110  non-slidable. In lieu of or in addition to the stopping mechanism, the sofa bed may be retained in the sofa configuration when the center of gravity of the back rest crosses over a rotational point of the back rest which occurs between the link members  104 ,  108 . The weight of the back rest and the distance of the center of gravity of the back rest to the center of gravity creates a moment greater than the weight of the seat base so that even without the stopping mechanism the sofa bed stays in the sofa configuration. 
     The detailed description set forth below in connection with the appended drawings is intended as a description of certain embodiments of the present disclosure and is not intended to represent the only forms that may be developed or utilized. The description sets forth the various functions in connection with the illustrated embodiments, but it is to be understood, however, that the same or equivalent functions may be accomplished by different embodiments that are also intended to be encompassed within the scope of the present disclosure. It is further understood that the use of relational terms such as “top,” “bottom,” “left,” “right,” “first,” “second,” and the like are used solely to distinguish one entity from another without necessarily requiring or implying any actual such relationship or order between such entities. Also, where used, the terms “secured,” “attached,” connected,” “mounted,” “coupled,” and the like can mean either direct or indirect attachment or contact between elements, unless stated otherwise. 
     The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including various ways of attaching the folding mechanisms to the support members. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.