Abstract:
This invention relates generally to a juvenile belt positioning booster car seat which folds, has an adjustable back height, and has folding armrests which ships in a minimally sized carton thereby reducing shipping and warehousing costs and which has a smoother exterior surface and enclosed height adjust mechanism to prevent pinch points and protect vehicle upholstery.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates generally to a juvenile belt positioning booster car seat (booster car seat) which folds, has an adjustable back height, and has folding armrests which ships in a minimally sized carton thereby reducing shipping and warehousing costs and which has a smoother exterior surface and enclosed height adjust mechanism to prevent pinch points and protect vehicle upholstery.  
       BACKGROUND OF INVENTION  
       [0002]     The invention relates generally to a juvenile belt positioning booster car seat (booster car seat) which folds, has an adjustable back height, and has folding armrests which ships in a minimally sized carton thereby reducing shipping and warehousing costs and which has a smoother exterior surface and enclosed height adjust mechanism to prevent pinch points and protect vehicle upholstery.  
         [0003]     Passenger restraint systems in vehicles are generally well suited to properly restrain adults but not well suited to properly restrain children. Accordingly, vehicle restraint systems must be supplemented for maximum safety. For juveniles from approximately 30 to 80 or 100 pounds. This is accomplished with booster car seats. Booster car seats may be defined as supplementary child seats which rest on a vehicle seat and which utilize and properly position the vehicle&#39;s lap and shoulder belts to restrain a child occupant. These booster car seats include a seat portion which elevates the child above the vehicle&#39;s seating surface to a position in which the vehicle&#39;s shoulder belt is better positioned on the child and which also properly positions the vehicle&#39;s lap belt on the child&#39;s torso, and may include a back portion with a shoulder belt guide to further ensure proper shoulder belt position on the child. Booster seats typically also have accessory features such as armrests, height adjustments, energy absorbing foam, and upholstery which add to comfort, safety, convenience, or visual appeal.  
         [0004]     A typical booster seat configuration has, as noted, a molded plastic seat with a seating surface that raises the child above the vehicle seat and a backrest with a backrest surface. These surfaces generally have adjacent side walls that help contain and protect the child occupant. Slots or recesses in the seat side walls in the occupant&#39;s hip area receive the lap belt portion of a vehicle seat belt and direct it properly over a child&#39;s pelvis (as opposed to over the soft abdominal area and internal organs). Hooks or slots on both sides of the backrest in the shoulder area receive the shoulder belt portion of the auto seatbelt and direct it properly over the child&#39;s shoulders and away from the head and neck. The booster seat thus raises the child, provides some side protection with raise side walls, and properly positions the vehicle belts on the child&#39;s smaller body. All of these functions are important and definitive. A typical booster seat configuration usually also has armrests for occupant comfort and cup holders for convenience.  
         [0005]     Booster car seats may be constructed structurally of one piece as a rigid seat shell, as multiple pieces which are either permanently or removeably assembled, or as multiple pieces which are permanently attached and fold. Of course any accessory components such as upholstery, foam padding, armrests, or bases may be added either permanently or removeably. In all cases, structural integrity, reliability, ease and expense of manufacture, cost of distribution, and consumer appeal through comfort and ease of use are critical.  
         [0006]     Known booster seat designs suffer from several drawbacks. L-shaped one-piece booster car seats require large and expensive shipping cartons and take up a high volume of expensive shipping space. They are said to have a high “cube”. They also require considerable space for manufacturing and retail warehousing. Further, they are difficult for consumers to store or transport when not in use, say in a vehicle trunk or in a closet, because of their high volume. Multi-piece booster car seats which are assembled by a consumer (knock-down or “KD” booster car seats) can ship in small cartons but they also have drawbacks. The very fact that the consumer must do the assembly of a safety related product is a drawback. Since consumers vary in their mechanical ability, assembly may be difficult for some and there is always the possibility that a consumer will error in the assembly. In any case, most consumers would prefer not to have to assemble a product they purchase. If the booster car seat assembles permanently, it inherits the storage disadvantage of the large L-shaped seats. But if the booster car seat assembles removeably, it has the drawback that components may be lost, that tolerances and clearances necessary for easy assembly and disassembly may result in a flimsy product, and that repeated assembly may wear the assembly means.  
         [0007]     Folding booster car seats solve both the size problems of the one-piece seats and the problems of typical KD booster car seats. But, folding booster seats having raised sides on their seats and seatbacks must nest those sides to achieve an optimally compact fold and optimally high and protective sides-a desirable feature. Nesting with a side-to-side nest necessitates one component being wider than required and thus a higher volume product while nesting the upper faces of the seat sides and the front faces of the seatback sides leaves no space for an armrest unless it is outside of the folded seat—which again adds volume.  
         [0008]     Known booster seats also suffer from exposed ribs and structure which are unattractive and may damage the vehicle seat upholstery. In addition, if the booster car seats have a height adjustment mechanism, it is often exposed and may have dangerous pinch points.  
       SUMMARY OF INVENTION  
       [0009]     This invention discloses a means to have a compact folding booster car seat with its inherent compact shipping size and low shipping and storage costs, deep seat and seatback sides, and a fully functional, independently rotating armrest. This invention further discloses a means to make a stronger seatback with a smoother rear surface and a fully enclosed height adjustment mechanism.  
         [0010]     Having a folding booster car seat and one with desirable deep seat sidewalls and seatback sidewalls would seem mutually exclusive. However, booster car seats have been disclosed which fold and which nest the seat sidewalls and the back sidewalls in a side-by-side fashion (inserted nesting) and seats have been disclosed which nest the tops of seat sidewalls and the fronts of seatback sidewalls (stacked nesting). Both configurations tend to maximize both their compactness and the depth of their sidewalls.  
         [0011]     But a folding booster car seat which utilizes inserted nesting must make either the seat side walls or the seatback side walls large enough to fit over the outside exterior of the nesting component, which again introduces excess volume or reduces the size of one component to a smaller and unacceptable width. Looking at typical vehicle bucket seats it can be observed that they have seats and backs of approximately the same width. This same configuration, with seats and backs of a similar width, is also most appropriate with booster car seats and cannot be achieved with inserted nesting.  
         [0012]     Folding booster seats with stacked nesting allow similar seat and back widths. But the side face of the folded seat is filled with the seat sidewalls and the seatback sidewalls and there is no room left for an armrest. These problems (lack of space, need to pivot, and need to avoid pinch points) can be solved by moving the armrests outboard of the seat and back sidewalls. But moving the armrests outboard, again, increases the product volume and resulting shipping carton. It should be noted also that it is desirable for an armrest to fold for easy entry/exit from the booster car seat and for there to be some room between the folding armrest and the seat back side walls to prevent pinch points which might injure a child and thus, again, add to product width and hence volume.  
         [0013]     Therefore, one aspect of the present invention shows a folding booster car seat with desirable deep seat and seatback sidewalls of a similar width, and desirable folding armrests sufficiently spaced from the seatback sidewalls to prevent pinching while still allowing a compact product volume and shipping carton. This invention is achieved by utilizing consumer assembled armrests mounted to rotating intermediate armrest plates.  
         [0014]     Many booster car seats are molded single wall plastic shells with exposed rib structures on the back of their backrest surfaces or on the bottoms of their seats which interact negatively with vehicle seating surfaces by marring or damaging the vehicle upholstery. On those booster seats with adjustable headrest heights, it is common to see not only exposed ribs but also exposed adjustment mechanisms. Although some booster car seats have waffled or channeled shells with fewer exposed ribs they still generally have an unfriendly “industrial” look, exposed ribs, and exposed mechanisms. In addition to potentially marring vehicle upholstery these booster car seats have the relatively weak structure of single wall construction and the hazard of exposed mechanism susceptible to damaging the vehicle seat or causing pinch injuries.  
         [0015]     Therefore, another aspect of the present invention is to make the rear surface of the booster seat backrest as smooth as possible by minimizing the number of exposed ribs and by enclosing the headrest height adjust mechanism, and at the same time make the shell as strong as possible in the headrest area by enclosing the height adjust mechanism within a boxlike structure formed by the exterior of the headrest and an internal headrest retention plate.  
         [0016]     This folding, height adjustable booster car seat has two main components, a seat, and a backrest assembly which further includes a lower fixed back and an upper adjustable back. Additional components include cup holders, armrests, height adjustment mechanisms, fold latching mechanisms, headrest foam, and other minor but required components such as fasteners, springs, enclosures, upholstery, etc.  
         [0017]     The seat has a seating surface with left and right seat sidewalls on its respective sides, left and right hollow runners under the seating surface to support the booster car seat on a vehicle seat, a back wall connecting the left and right seat sidewalls, and left and right seat hubs at the top rear of the respective seat sidewalls which are used to secure the backrest assembly, belt path recesses used to direct a vehicle lap belt, armrest plates used to mount armrests, foam blocks used to fill the hollow runners and provide a smooth seating surface, and cup holder mounts used to mount cup holders. It also includes minor features such as pad retention hooks, label recesses, engraved text, etc.  
         [0018]     The backrest assembly includes a lower fixed back, an upper adjustable back which telescopes on the lower fixed back from a collapsed position to an extended position to accommodate various height children, a back retention panel to secure the adjustable back to the fixed back and to enclose the height adjustment mechanism, left and right adjustment latches used to facilitate adjustment of the adjustable back, a headrest foam and various facilitating parts such as screws and springs.  
         [0019]     The fixed back includes a fixed back area with a fixed back surface with left and right raised lower sides on its left and right sides, a curved top surface, a bottom edge, and a headrest support extension with left and right position teeth on parallel side walls, and left and right backrest hubs at the lower end of the left and right raised lower sides. The fixed back area has a uniform generalized cross section across its fixed back surface and it&#39;s raised lower sides. The term “generalized” is used to indicate that the cross section ignores recesses where the backrest surface drops below where it would be if continuous. This uniform cross section sweeps on a constant arc from the bottom edge of the fixed back surface to the curved top surface. A concentric offset of the fixed back surface continues on the same constant arc on the face of the headrest support extension and for the length of the headrest support extension. This offset of the fixed back surface on the headrest support extension face will allow telescoping of a similar and concentric surface defined by a similar contour and a similar and concentric sweep. The headrest support extension is thus a narrowed, offset continuation of the fixed back surface with a width, parallel side walls, a depth, and a number of position teeth cut into its parallel side walls and it extends upward to a termination surface with a hand hole clearance cut out. The headrest support extension also has a central recessed portion with a top edge. The left and right backrest hubs have a circular outer wall and are generally hollow to their outside faces except for internal ribbing detail and two raised detents.  
         [0020]     The adjustable back includes an adjustable backrest area with a backrest surface and left and right upper raised sides on its left and right edges, and a headrest area which will be described in more detail below. The exterior front contour of the adjustable backrest area is at all potential interference locations offset from the corresponding backrest area of the fixed back to allow for a nominal wall thickness of the adjustable back, for example 0.080 to 0.125 inch (2.03 to 3.18 mm), and some running clearance, for example 0.030 to 0.060 inch (0.076 to 1.52 mm). The adjustable back thus has a contour at least larger than the uniform generalized cross section of the fixed back swept on its constant arc and a matching offset generalized contour swept on the continuous arc and may telescope freely on the fixed back. It is intended that the front surface of the upper raised sides on the adjustable back actually extend substantially forward of the corresponding front surfaces of the fixed back. Thus the front surfaces of the left and right upper raised sides of the adjustable back are intended to project forward and result in deeper sidewalls. Ribs on their rearward surfaces can fill any consequently formed gaps between the rearward surfaces of the left and right upper raised sides of the adjustable back and the front surfaces of the respective raised lower sides of the fixed back down to the nominal running clearance. It can be seen that the adjustable back can telescope along the constant arc of the fixed back from a lower or collapsed position to a higher or extended position. It should be noted that all of the forward facing surfaces of the backrest area are smooth and that any reinforcing ribbing is located on its rearward facing surfaces. In other words, the backrest area is open to the back.  
         [0021]     The headrest area of the adjustable back has a central surface, left and right forward projecting surfaces connected to its respective left and right edges with gently rounded corners, and a connecting bottom surface which joins all three forming a partial box. This headrest area has a nominal thickness. The forward facing surfaces of the headrest area are interrupted by various ribs and the rearward facing sides are substantially smooth. Thus the headrest area is constructed in reverse of the backrest area in that the headrest area is open to the front and the backrest area is open to the rear. The headrest area also has a left and right curved shoulder belt path that interrupts is lower edge resulting in a narrowed center region and left and right shoulder belt hooks.  
         [0022]     The narrowed center region of the headrest area is joined to and interrupts the curved top surface of the backrest area. The connecting bottom surface of the headrest area is penetrated by an opening sized to allow passage and free up and down travel over the headrest support extension of the fixed back.  
         [0023]     The headrest area has left and right locating ribs extending forward from its central surface and spaced apart sufficiently to allow passage and running clearance of the headrest support extension of the fixed back and projecting forward sufficiently to project above the face of the headrest support extension by a nominal running clearance. These locating ribs are topped by a back retention panel which, in conjunction with the central surface, forms a structural box which will allow free up-and-down movement of the adjustable back over the headrest support extension, and will locate the adjustable back relative to the headrest support extension both front-to-rear and side-to side.  
         [0024]     The upper headrest area is also penetrated by a hand hole with peripheral walls somewhere near its top edge. The hand hole is so located vertically that when the adjustable back is in its lowest position the peripheral walls are concentric with the hand hole clearance in the backrest support extension and act as a stop to limit further downward travel of the upper back.  
         [0025]     The left and right forward projecting surfaces of the headrest area are also penetrated with lock openings which locate and allow sliding movement of left and right height locks which extend through the forward projecting surfaces from inside to outside. The left and right locating ribs are interrupted in their lengths to also allow sliding movement of left and right height locks through them.  
         [0026]     Left and right height locks are part of the backrest assembly and each slideably extends through a respective lock opening in the left and right forward projecting surface, extends inward toward the respective left and right locating ribs and terminates in locking teeth which may engage with left and right position teeth on the headrest support extension. These height locks extend beyond their respective left and right lock openings outward and terminate such that they may be pulled outward by a user. The height locks are normally spring biased inward and the locking teeth normally engage with the position teeth of the headrest support extension thus preventing upward/downward movement of the adjustable back. Pulling the height locks outward simultaneously allows free movement of the upper back, within its range of movement, by disengaging the locking teeth and position teeth. Releasing the height locks allows them to travel inward again and causes the locking teeth and the position teeth to engage in any of several possible positions of upper back travel, depending on the number and spacing of the teeth provided.  
         [0027]     A backrest retention panel is secured to several bosses on the central portion of the headrest area, nominally with screws. The backrest retention panel is thin plastic with a nominal thickness, a left to right contour which may be flat, a vertical arc which is concentric with the constant arc of the fixed back. When it is secured it forms a boxlike structure which slideably retains the headrest support extension to the headrest area of the adjustable back and makes the central portion of the upper headrest area into a stronger double-walled structure. The rearward face of the backrest retention panel has one or more tabs or raised areas which project into the recessed portion of the headrest support extension of the fixed back. These tabs are positioned such that when the adjustable back is in its maximum desirable extension they contact the lower edge of the recessed portion and prevent further vertical movement. The backrest retention panel slideably retains the left and right height locks, slideably retains the adjustable back to the headrest support extension, and strengthens the central portion of the headrest area of the adjustable back. Additionally, the backrest retention panel provides a support surface for a headrest foam part which lines the headrest area.  
         [0028]     The adjustable back also includes return hooks on the bottom lower edges of its left and right upper raised back outer walls. These return hooks slide over the corresponding outer walls of the lower raised sidewalls of the fixed back and slideably retain the two walls together.  
         [0029]     After the fixed back and the adjustable back, and all of their supporting and associated components are assembled, a semi-rigid headrest foam is added to the inside of the upper headrest area to provide a smooth and comfortable headrest surface.  
         [0030]     The seat and the backrest assembly are pivotally secured to each other on a left-to-right or common fold axis. The common fold axis on the seat is located above the seating surface and forward of the back wall of the seat and defines the axis of the seat hub. The common fold axis on the fixed back is located near the bottom edge of the fixed back and forward of the fixed back surface and defines the axis of the backrest hub. This arrangement allows the backrest assembly to pivot forward from an L-shaped position relative to the seat to a folded position more or less parallel to the seat, rotating about  105  degrees for example. The backrest assembly is selectively positioned and is retained in either position.  
         [0031]     Fold position retention is accomplished with left and right fold latching means which ideally consists of outward biased plungers mounted in the seat hubs constrained to move toward or away from the common pivot axis in a defined channel. Each biased plunger has a plunger extension which extends through an opening in an inner wall of the respective seat hub. The plunger extensions have raised areas which normally ride inside the interior of the circular outer walls of the fixed back hubs. Thus, as the backrest assembly is moved from an L-shaped position to a folded position, the raised areas on the plunger extensions nominally travel along the insides of the circular outer walls relative to the position of the backrest assembly. However, two raised detents rise above the inside of each circular outer wall, one blocking travel out of the L-shaped position and one blocking travel out of the folded position. Each raised detent has angled leading and trailing surfaces. If sufficient rotational pressure is exerted on the backrest assembly, urging it from one position to the other, the angled leading and trailing surfaces will urge the biased plungers to move away from the insides of the circular outer walls and the raised areas of the plunger extensions will ride over the raised detents and allow the backrest assembly to move to the opposite (folded or unfolded) position. The angles of the angled leading and trailing surfaces and the amount of bias on the biased plungers can be tuned to provide the desired degree of retention in the L-shaped position and in the folded position so that the booster car seat will normally retain its folded or unfolded position but can be easily change from one to the other with modest effort and no further mechanical actuation.  
         [0032]     In this booster car seat the attachment of the seat to the backrest assembly is accomplished by rotationally mating the inner faces of left and right seat hubs with outer faces of left and right backrest hubs. The hubs are rotationally secured with fasteners such as shoulder screws, rivets, or the like assembled into holes through the seat hubs and backrest hubs concentric with the common fold axis.  
         [0033]     As noted the seat and the backrest assembly each have raised sides adjacent to their seating surfaces. The seating surface and the backrest surface are about the same width and their respective raised sides are about the same width. The top surfaces of the seat sidewalls nest with the front surfaces of the backrest assembly with generally convex front-to-back curves on the front surfaces of the seat component nesting with generally concave overall form of the front surfaces of the seatback assembly when it is in its lowest position. Thus when the booster car seat is folded the collective raised sides substantially fill the sidewall area between the seating surface and the backrest surface except for nominal clearance for upholstery and spaces generated by gently rounded corners: there is no room for armrests and they must be attached to the exterior of the booster car seat where they cause an increase in carton size.  
         [0034]     Left and right armrests are attached to the exterior of the booster car seat on the outside of the collective raised sides. Although it would be ideal to have the armrests be the same width as the collective raised sides, that, again, is prevented because the collective raised sides essentially fill the space an armrest would occupy when the booster car seat is folded. In order to allow easy entry and exit from the booster car seat, the armrests fold on a common armrest axis which is ideally, but not necessarily, also the common fold axis. The armrest fold is independent of the booster car seat fold and it is limited to a given degree of rotation, rotating about 85° for example.  
         [0035]     Since the armrests are forced to be mounted to the exterior of the booster car seat they would normally force the shipping carton to be wider. This problem is solved by making the armrests consumer assembled. Thus, the booster car seat may be shipped in a smaller carton with the armrests loose in the carton and the consumer installs them. The armrests must thus be rotationally attached, limited in their travel, sturdy, easy to attach by people with limited mechanical skills and not generate pinch points.  
         [0036]     This set of complex armrest constraints is solved by mounting the armrests to intermediate left and right armrest plates which rotationally attach to the outer faces of the seat hubs ideally with the same fasteners which secure the seat and backrest assembly together. The armrest plates are limited to a specified rotation by means of rotation limiting projections on their inner faces which are stopped by the plunger guide ribs in the seat hubs. The outer faces of the armrest plates are provided with T-shaped protrusions to which the armrests slideably attach by means of C-shaped recesses on their inner faces. This armrest attachment means is made a one-time assembly by means of flexible finger on each armrest plate which rides over the top edge of each armrest C-shaped recess and then snaps into a locking position behind the top edge. Each armrest is spaced apart from its neighboring raised sidewall sufficiently to prevent pinch points. Although the invention describes mounting the armrests on the same axis as the fold, the invention is intended to encompass any mounting location on any car seat, folding or non-folding.  
         [0037]     Although the armrests describe are preferably attached with mating T-shaped keys and C-shaped keyways, many alternative attachments are possible. For example, the T-shaped keys may be any linear or circular protrusion on either the intermediate plates or armrests described mating with any corresponding linear or circular receiver on the respective mating component. As another example, the armrest may be simply attached with screws to the intermediate plates.  
         [0038]     In addition, though the armrest mounting using intermediate plates and keyway attachment has been described on a folding booster seat with an extendable back, the armrests could also be applied to a non-folding booster seat or one without an extendable back.  
         [0039]     In one aspect of the present invention, the consumer installed pivoting armrests allows a smaller more economical shipping carton, lower warehousing, and lower shipping costs.  
         [0040]     In another aspect of the invention, smooth exterior walls on the headrest and enclosed height adjustment mechanisms help prevent damage to vehicle upholstery and pinch injuries.  
         [0041]     These and other objects of the present invention will become more readily apparent from a reading of the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals indicate similar parts, and with further reference to the appended claims. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0042]      FIG. 1  is a front perspective a foldable booster car seat with an extendible backrest in its L-shaped position and showing the moveable portion of the backrest in a fully collapsed position, armrests in their usage position, and cup holders in their storage position;  
         [0043]      FIG. 2  is a side view of the booster car seat of  FIG. 1  showing the backrest in its folded or collapsed position illustrating nesting curvilinear alignment;  
         [0044]      FIG. 3  is a top view of  FIG. 2  showing one armrest removed and a phantom line of a shipping carton illustrating the need to remove the armrests of the car seat in order to fit within a standard sized shipping carton without incurring overage fees, particularly those based on courier service shipping limitations, namely girth plus length restrictions of 84 inches (213 cm);  
         [0045]      FIG. 4  is a perspective view of  FIG. 2 ;  
         [0046]      FIG. 5  is a view similar to  FIG. 4  showing one armrest removed exposing the exterior of the armrest handle hub;  
         [0047]      FIG. 6A  is a partial close-up view of  FIG. 5  showing details used for C-shaped keyway armrest attachment;  
         [0048]      FIG. 6B  is a partial close-up view showing details for an alternative embodiment for the attachment of the armrest to the plate of the car seat;  
         [0049]      FIG. 7A  is an inside perspective view of the right armrest showing attachment detail for  FIG. 6A ;  
         [0050]      FIG. 7B  is an inside perspective view of the right armrest showing attachment detail for  FIG. 6B ;  
         [0051]      FIG. 8  is a side perspective view of the armrest hub of  FIG. 6A  with the armrest attachment plate removed;  
         [0052]      FIG. 9  is a side perspective view of  FIG. 8  with the seat and associated seat hub removed;  
         [0053]      FIG. 10  is a front perspective view of the booster car seat of  FIG. 1  showing the extendible backrest in its extended position, armrests in their raised position, and cup holders in their use position;  
         [0054]      FIG. 11  is an enlarged perspective view of  FIG. 10  with the headrest foam removed showing the back retention panel;  
         [0055]      FIG. 12  is a perspective view of  FIG. 11  with the back retention panel removed to show the height adjustment mechanism;  
         [0056]      FIG. 13  is a rear perspective view of the back retention panel;  
         [0057]      FIG. 14  is a view similar to  FIG. 12  showing the moveable portion of the backrest in its fully collapsed position;  
         [0058]      FIG. 15  is an exploded assembly view of the booster car seat shown in  FIG. 1 ;  
         [0059]      FIG. 16  is a partial exploded close-up view of  FIG. 15  showing left armrest details viewed from an outside point-of-view;  
         [0060]      FIG. 17  is a partial exploded close-up view of  FIG. 15  showing right armrest details viewed from an inside point-of-view;  
         [0061]      FIG. 18  is a partial close-up view of  FIG. 14  showing the adjustable back locking detail;  
         [0062]      FIG. 19  is a perspective view of a non-folding, non-extendable back version of the car seat of  FIG. 1 ;  
         [0063]      FIG. 20  is an enlarged perspective view of the keyed intermediate plate arrangement; and  
         [0064]      FIG. 21  is an alternative armrest hub configuration to mate with the keys of  FIG. 20 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0065]     Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting the same, the figures show a foldable booster car seat with consumer assembled armrests which will ship in a reduced space and an adjustable backrest to better accommodate occupants of different heights and weights and with a smooth back surface with enclosed adjusting mechanism.  
         [0066]     As most easily seen in  FIGS. 1 and 10 , booster car seat  10  has two main components, seat component  12  and backrest assembly  14  which is further subdivided into fixed back  16  and adjustable (i.e., movable) back  18 . Additional easily seen components are left and right armrests  20 L and  20 R, headrest foam  22 , and cup holders  24 .  
         [0067]     Seat  12  has a seating surface  26  with left and right seat sidewalls  28  on its respective sides, left and right hollow runners  30  (best seen in  FIG. 15 ) under the seating surface  26  to support the booster car seat  10  on a vehicle seat (not shown). Seat component  12  further includes back wall  29  which connects left and right sidewalls  28 . Left and right seat hubs  32 L and  32 R respectively, at the top rear of sidewalls  28  are used to secure backrest assembly  14 . Belt path recesses or indentations  42  are used to direct a vehicle lap belt (not shown) across the bony pelvis of an occupant of the car seat. Seat  12  is fitted with foam blocks  58  to fill hollow runners  30  and make seating surface  26  continuous left to right across the car seat.  
         [0068]     Left and right seat sidewalls  28  have outside walls  36 , inside walls  38 , and top surface  40  and these raised curvilinear profiles are generally hollow and open to the bottom. Belt path recesses or indentations  42  form a part of top surface  40  and are located generally below armrest hubs  32 L and  32 R.  
         [0069]     As most easily seen in  FIGS. 16 and 17 , seat hubs  32 L and  32 R have outer circular walls  44  and inner faces  46  and are hollow to the outside except for reinforcing ribs  48 . Reinforcing ribs include plunger guide ribs or rails  50 . Openings  52  (illustrated in  FIG. 17 ) penetrate inner faces  46  between plunger guide ribs  50 . Seat hubs terminate in outside face or peripheral edge  54  which are interrupted by recessed detent notches  56 .  
         [0070]     Referring now to  FIGS. 10 and 15 , fixed back  16  has a fixed back area  60  which includes a fixed back surface  62  and left and right raised lower sides  64  on its respective edges and curved top surface  70 . Raised lower sides  64 , in turn, have inside walls  66 , outside walls  68  and front surfaces or edges  72 . Fixed back  16  also has headrest support extension  74  which has a front face  76  which is concentric with fixed back surface  62 , width  78  (better illustrated in  FIG. 14 ), parallel left and right side walls  80 , a termination surface  82  and a hand hole clearance  84 . A plurality (and at least three) of left and right height adjustment teeth  86  are formed into side walls  80 . Fixed back has a recessed portion  190  (see  FIG. 12 ) with a top edge  188 .  
         [0071]     As best seen in FIGS.  9  or  15 , fixed back  16  also has left and right backrest hubs  90 L and  90 R located near the bottom of raised lower sides  64  and forward of back surface  62 . These hubs have circular outer walls  92  and are hollow to the outside except for internal ribbing  94 . They additionally have raised detents  96  protruding interiorly from the internal periphery with outer faces or peripheral edge  200 . Fixed back also has left and right stand legs  98  such that folded booster car seat  10  will stand on end when in the collapsed position.  
         [0072]     Referring now again to  FIG. 15 , fixed back area  60  has a longitudinal contour defined as a constant arc  100  and shown as a phantom line and a lateral contour  102  also shown as a phantom line. Lateral contour  102  ignores any recesses  88  and may thus be considered “generalized”. Back area  60  is defined by the generalized contour of sweeping lateral contour  102  on constant arc  100 .  
         [0073]     Referring to  FIG. 12 , adjustable back  18  has an adjustable backrest area  104  and a headrest area  110 . Backrest area  104  has a backrest surface  106  and raised curvilinear sides  108  and top curved surface  114 . Raised sides  108  have inner walls  112 , outer walls  116 , and left and right front surfaces  118 . Backrest area  104  is open to the back and is a contiguous, smooth surface on its front. Headrest area  110  has central surface  120 , left and right forward projecting surfaces  122  connected with gently rounded corners  124 , and connecting bottom surface  126  forming a partial box-like structure open to the front. Headrest area  110  has a nominal generally uniform thickness. The forward facing surfaces of the headrest area  110  are interrupted by various ribs  128  and the back surfaces are substantially smooth. Headrest area  110  is constructed in reverse of the backrest area  104  in that the backrest area  104  is open to the back and can provide a smooth seating area while the headrest area is open to the front and cannot provide a smooth area absent the application of foam insert  22 .  
         [0074]     Headrest area  110  has a left and right curved shoulder belt path opening  130  that interrupts its lower edge  132  resulting in a narrowed center region and left and right shoulder belt hooks  138 . This narrowed center region is joined to and interrupts top curved surface  114 . The connecting bottom surface  126  is penetrated by an opening  136  sized to allow passage and free up-and-down movement of headrest support extension  74  of fixed back  16 .  
         [0075]     Adjustable back  18  is assembled to the fixed back with backrest surface  106  in front of and concentric with fixed back surface  62  and opening  136  is penetrated by headrest support extension  74 . Adjustable back  18  may travel between a lowest position  146  and a highest position  150  shown in  FIGS. 1 and 10  respectively.  
         [0076]     Referring again to  FIG. 12 , all areas of adjustable back area  106  are, at all potential interference locations, offset from corresponding areas of fixed back area  62  by a nominal wall thickness, for example 0.080 to 0.125 inch (2.03 to 3.18 mm), plus a nominal running clearance, for example 0.030 to 0.060 inches (0.076 to 1.52 mm). Adjustable back  18  may therefore rotationally telescope on fixed back  16 . It is intended that front surfaces  118  of upper raised sides  108  of the adjustable back area  104  actually extend further forward from corresponding top surfaces  72  of raised lower sides  64  resulting in taller upper raised sides  108  than would be required. It is also intended, as shown in  FIG. 2 , that top curved surface  118  is expanded to generally fill space available except for nominal upholstery clearance  152  and spaces  154  caused by gently rounded corners  156  when booster car seat  10  is folded.  
         [0077]     Still referring to  FIG. 12 , when adjustable back  18  is in any possible adjustment position, all areas of central surface  120  of headrest area  110  lie behind headrest support extension  74  and are separated from it by some nominal running clearance. Thus when adjustable back  18  is assembled to fixed back  16 , backrest area  106  of adjustable back  18  is in front of fixed back area  62  of fixed back  16  and headrest area  110  central surface  120  is behind headrest support extension  74 . This arrangement of components allows the smooth side of the headrest area  110  to lie on a vehicle seat back when the booster car seat is installed in a vehicle.  
         [0078]     Headrest area  110  is also penetrated by hand hole opening  140  and left and right lock openings  144  (see also  FIG. 18 ). Hand hole opening  140  penetrates central surface  120  and is surrounded by peripheral wall  142  and is located so that when adjustable back  18  is in it lowest position  146  it is concentric with hand hole clearance  84  in headrest support extension  74  and peripheral wall  142  may act as a stop to prevent adjustable back  18  from moving lower (see  FIG. 14 ). Left and right lock openings  144  penetrate respective forward projecting surfaces  122  or gently rounded corners  124  and slideably locate left and right height locks  164 .  
         [0079]     As shown in  FIG. 12 , headrest area  110  also has left and right locating ribs  150  extending forward from its central surface  120  and spaced apart sufficiently to allow passage and running clearance of headrest support extension  74  and projecting forward sufficiently to project above face  76  of headrest support extension  74  by a nominal running clearance. These locating ribs  150  are topped by a secured back retention panel  160  (see  FIG. 11 ) which in conjunction with central surface  120  forms a structural box which will allow free up-and-down movement of adjustable back  18  over the headrest support extension  74  and will locate headrest extension  74  side to side and front to back.  
         [0080]     Referring to the close-up view  FIG. 18 , left and right height locks  164  slideably assemble into respective lock openings  144 . Height locks have a lock body  166 , a guide opening  168 , and a number of lock teeth  170 . Lock springs  176  bias height locks inward by pushing on end  172  of guide opening  168  and on spring post  174  mounted to central surface  120  of headrest area  110 . Height locks  164  are guided by left and right slide ribs  178  on central surface  120 . Locating ribs  158  are interrupted to allow lock teeth  170  to engage height adjustment teeth  86  on fixed back extension  74 . Normally spring bias urges lock teeth  170  into height adjustment teeth  86  thereby fixing the position of adjustable back  18 . Ends  180  of height locks  164  extend outward beyond the outer surface of headrest area  110  (see  FIG. 3 ) and are formed so they may be grasped and pulled. Simultaneously pulling height locks  164  urges compression of lock springs  176  and disengages lock teeth  170  from height adjustment teeth  86  allowing telescoping movement of adjustable back  18 . Releasing height locks again allows springs  176  to urge lock teeth  170  to engage adjustment teeth  86  with adjustable back  18  in any of several height positions determined by the number and spacing of corresponding teeth. Height locks are further slideably located by back retention panel  160 .  
         [0081]     Referring now to  FIGS. 11 and 13 , backrest retention panel  160  is secured to adjustable back  18  preferably with screws and strengthens central surface  120  by making a double wall boxlike structure and, in addition, slideably locates headrest support extension  74  and height locks  164 . Rear surface  184  of backrest retention panel has raised protrusions  186  which are so located that when adjustable back  18  is in its highest position  150  raised protrusions  186  contact top edge  188  of recessed portion  190  of headrest support extension  74  (see  FIG. 12 ) preventing further upward movement and thus securing adjustable back  18  to fixed back  16 . Further, front surface  192  of backrest retention panel  160  serves as a mounting surface for headrest foam  22 .  
         [0082]     As can be seen in  FIG. 10 , headrest foam  22  mounts to front surface  192  of backrest retention panel  160  and provides a smooth and energy absorbing lining to headrest area  110  and is secured with hot-melt adhesive, friction, or other convenient method.  
         [0083]     Referring to  FIGS. 1 and 16 , in a preferred embodiment, seat hubs  32  share fold axis  194  with backrest hubs  90 . Seat  12  and backrest assembly  14  pivotally assemble on fold axis  194  with seat hub  32  inner faces  46  pivotally mating with outer surfaces  200  of backrest hubs  90  as shown in  FIG. 17 . Backrest assembly may pivot on fold axis  194  from a generally L-shaped usage position as shown in  FIG. 1  to a compact folded position as shown in  FIG. 2 .  
         [0084]     As may be best seen in exploded  FIG. 16  but may also be visualized by referring to  FIGS. 8, 9  and  17 , backrest assembly  14  is retained in L-shaped position or compact folded position by a fold latching means which preferably comprises outward biased plungers  208  which slideably assemble between plunger guide ribs or rails  50  in respective seat hubs  32  such that they may move toward or away from common fold axis  194 . Each plunger  208  has a plunger extension  210  which projects through respective openings  52  (see  FIG. 17 ) in inner faces  46  of seat hubs  32 . Plungers  208  are biased outward preferably by springs  216  acting on hub spring surfaces  218  and underside  220  of plunger extension  210 . Each plunger extension  210  has at least one raised area  212  which rides on inner wall  214  of backrest hubs  90 . Raised detents  96  protrude from inner wall  214  between the position raised area  212  on plunger extensions  210  occupies when backrest assembly  14  is in its L-shaped position, and the position raised area  212  on plunger extensions  210  occupies when backrest assembly  14  is in its folded position. Backrest assembly  14  is thus prevented from moving from either L-shaped position or compact folded position by rotational movement being blocked by raised detents  96 . However, exerting sufficient rotational force on backrest assembly to move it from either position will cause raised areas  212  to overcome spring bias and override raised detents  96 . The amount of force required to move backrest assembly  14  from one position to the other can be controlled by the strength of springs  216  coupled with the shape of raised detents  96  and raised areas  212 . The nominal amount of force required is great enough to prevent gravity from changing the position of the backrest assembly yet light enough to allow easy change by a consumer.  
         [0085]     Referring now primarily to  FIG. 16 , but also with reference to  FIGS. 6A and 17 , armrest plates  222  pivotally mount to seat hubs  32  with rivet  202  and washer  204  and with plate inside faces  226  mating with respective seat hub  32  outside faces  54  and rotate independently of backrest assembly  14  on common fold axis  194 . Armrest plates retain plungers  208  in seat hubs  32 . Armrest plates have raised projections  224  on plate inside faces  226  (see  FIG. 17 ). Raised projections intrude into respective hollow seat hubs  32  between guide ribs  50  and outer circular walls  44  and allow armrest plates  222  to rotate clockwise or counterclockwise until raised projections  224  contact plunger guide ribs  50 . This allowed rotation ranges from 60-120°, more preferably from 80-90°, and most preferably for example, 85°. Seat hubs  32  have sets of indented areas  56  and armrest plates  222  have sets of spring fingers  230  projecting upward from plate inside faces  226 . When armrest plates  222  are rotated clockwise to their limit of travel spring fingers  230  engage appropriately placed indented areas  56  and urge armrest plates  222  to remain in that position. When armrest plates  222  are rotated counterclockwise to their limit of travel spring fingers  230  engage appropriately placed indented areas  56  and, again, urge armrest plates to remain in that position. By applying sufficient rotational force to armrest plates  222 , spring fingers  230  can be forced out of indented areas  56  allowing armrest plates to rotate. The amount of force required to rotate armrest plates  222  out of detented position can be controlled by varying the strength, shape, and projection of spring fingers  230  and by varying the shape and depth of indented areas  56 . Armrest plates  222  have raised T-shaped protrusions  232  (see  FIG. 6A ) on their respective outside faces  234  which form flanged keys and which extend approximately % of the way across outside faces  234  and terminate in top edges  236 . Raised snap fingers  262  raise above outer faces  234  some nominal distance, and about ⅛ inch (3.18 mm) from top edges  236  of T-shaped protrusions  232  thereby making the attachment of the armrest unidirectional.  
         [0086]     As noted, seat  12  and backrest assembly  14  components fixed back  16  and adjustable back  18  have raised sides adjacent to their seating surfaces and these raised sides are about the same width. As can be seen in  FIG. 2  showing booster car seat  10  in compact folded position, the forward most extremes of backrest assembly  14  and headrest foam  22  have a generally concave form illustrated by phantom nest curve  238 . Nesting sidewalls essentially fill all space available for nesting except for nominal clearance for upholstery  152 , and corner rounding space  154  generated by gently rounded corners  156 .  
         [0087]     Armrests are a desirable feature to have on a booster car seat and ideally armrests would be installed at the same general width as raised seat sidewalls  28  of seat  12 . But as just illustrated in this booster car seat  10  that space is fully used when backrest assembly  14  is in compact folded position. Therefore, any armrests must be moved outboard of upper raised sides  108  of adjustable back  18 . It is also a desirable feature to have armrests fold for easy user access and exit from a seat. Again, any armrests must be mounted outboard of upper raised sides  108  to allow a sufficient fold for easy access and exit, but any armrests should be mounted even further outboard to prevent pinch points between any armrests and upper raised sides  108 .  
         [0088]     Now, looking at  FIG. 3 , a right armrest  20 R is shown mounted as described above and a carton size  248  is shown in phantom line. If armrests are mounted the carton size increases and carton cost and shipping and warehousing costs will increase. This problem is solved by making left and right armrests  20 L and  20 R consumer assembled.  
         [0089]     As shown in  FIGS. 6A and 7A , left and right armrests  20 L and  20 R have respective circular armrest hubs  248  with armrest axis  250  and inner faces  254  and they also have arms  252 . Armrest hubs have recessed C-shaped keyways  256  set into inner faces  254  and open to the bottom. Keyways terminate in walls  258 . Armrests are assembled by engaging respective C-shaped keyways  256  over T-shaped protrusions  232  on armrest plates  222  and pushing armrests  20  until armrest axis  250  aligns with common fold axis  194 . As armrests slide into position raised snap fingers  262  (see  FIG. 6A ) in armrest plates  222  ride over walls  258  and snap behind walls  258  locking armrests  20  in place. As illustrated in  FIGS. 6B and 7B , it is illustrated that the keys and keyways of  FIGS. 6A and 7A  may be reversed, where armrest plates  222  have C-shaped keyways  233  and armrests  20  have T-shaped protrusions  257 . It can also be easily visualized that any interlocking or male/female attachment means can replace the key / keyway attachment means illustrated.  
         [0090]     The preferred armrest attachment has been described. However, alternative attachment means may be employed. For example, looking at  FIGS. 20 and 21  it can be seen that a rotational set of protrusions would be equally effective. In  FIG. 20 , standing keys  372  on alternative intermediate plate  370  with axis  374  mates with alternative armrest  360 L, circular cutouts  364 , and rotates on armrest axis  362  (which aligns with axis  374 ) to secure armrest  360 L to intermediate plate  370 . Another alternative would be to simply screw armrest  360  to intermediate plate  370 .  
         [0091]     As illustrated in  FIG. 19 , it can be seen that the armrests  20 L and  20 R described can be assembled to alternative booster car seat  310  with seat area  320  and back area  340  in a continuous, non-folding and non-extending arrangement. The armrests  20  still mount to intermediate plates outboard of back area  340 , still pivot on axis  350 , and still provide many of the space saving packaging and rotational benefits described in the preferred embodiment.  
         [0092]     Therefore, what has been shown is a car seat and subassembly components. In one embodiment, the foldable car seat will have an extendable back with raised curvilinear sides, a seat portion having nesting raised curvilinear sides pivotally connected to the back, the seat width and the car seat back being essentially the same with a pair of oppositely attached rotatable armrests. The car seat preferably has a pair of hubs at the bottom of the extendable back, a pair of hubs at the rear of the seat, and a pair of hubs at the rear of the armrests. In a most preferred combination, the hubs will be a combination hub of the three identified individual hubs, the combination hub further containing a means for retaining the armrest in either its up or down position as well as a means for retaining the extendable back and seating surface in either its L-shaped or collapsed position. The armrests are unidirectionally attached to the hub combination by a user installer after purchase of the product and removal from its container or carton.  
         [0093]     The extendable back will have a lower fixed back portion, and an upper adjustable back portion which telescopes in relation to the fixed back portion, the upper adjustable back portion moving from at least one first collapsed position to at least one second extended position. The extendable back will additionally have a height adjustment means to secure the upper adjustable back portion into either at least a first or a second position.  
         [0094]     The foldable car seat will typically have a lowered area in the sides of the seating portion of the seat for securing an automobile lap belt to fit onto an occupant&#39;s bony pelvis.  
         [0095]     In a more generalized teaching, the foldable car seat will have a back with raised curvilinear sides, a seat portion with nesting raised curvilinear sides pivotally connected to the back, with the widths of the seat portion and the back portion being about the same. A pair of rotatable armrests are unidirectionally attached to the seat by a user installer after purchase of the product, the armrests separated by a distance across the car seat which is greater than the width dimension across the back. The car seat has a connection means for the seat and back, this connection means further having a means for retaining the back and seat in either an L-shaped or collapsed position as well as a connection means for the unidirectionally attached armrests, this connection means further having a means for retaining the armrests in either an up or a down position.  
         [0096]     In a preferred embodiment, the car seat connection means for the seat and back as well as the connection means for the armrests are on a common fold axis located above the seating surface of the seat and forward of the back wall of the back.  
         [0097]     A method is also taught in this invention for reducing the cube size of a car seat for shipping purposes when the car seat has approximately equal widths between a pair of raised curvilinear sides of the seating surface of the car seat and between a pair of raised curvilinear sides of the back of the car seat, particularly when the car seat is equipped to have a pair of rotatable armrests separated by a distance which is greater than the width between the curvilinear sides of the back. As used in the shipping industry, cube size is a combination of packaging carton length times width times height. The method employs the steps of folding said car seat along a fold axis, the axis located above the seating surface of the seat and forward of the back wall of the back, prior to insertion of said car seat into said packaging carton, with insertion of a pair of armrests into the carton. After receipt of the carton at the destination and removal of the folded seat and armrests, they are unidirectionally installed onto the car seat with a connection means which provides the installer with feedback.  
         [0098]     The unidirectional armrest installation step includes matingly engaging a T-shaped protrusion on the exterior surface of an armrest plate in a hub on the car seat, with a C-shaped channel in the interior side of the armrest. The armrest plate additionally has at least one exteriorly-facing snap finger positioned interior of a peripheral edge of the armrest plate which upon proper and complete installation will provide sensory feedback to the installer. This feedback may be visual, audio (sound) or tactile (decreased resistance).  
         [0099]     This invention has been described in detail with reference to specific embodiments thereof, including the respective best modes for carrying out each embodiment. It shall be understood that these illustrations are by way of example and not by way of limitation. Accordingly, the scope and content of the present inventions are to be defined only by the terms of the appended claims.