The present invention relates to a child seat, and particularly to a child seat for use on a child swing.  More particularly, the present invention relates to a child seat having an adjustable seat back arranged to assume several positions relative to a seat bottom of the child seat, a support structure for appending the child seat to support arms appended to a swing motor of a child swing, and a child restraint apparatus to prevent the child from inadvertently sliding off of the front edge of the child seat. 
Child seats that adjust a child's position by pivoting the seat back relative to the seat bottom are well known in the art.  For example, U.S. Pat.  No.  4,998,307 to Cone, U.S. Pat.  No.  4,762,364 to Young, U.S. Pat.  No.  4,325,578 to Borucki, U.S. Pat.  No.  3,366,294 to Stephenson, U.S. Pat.  No.  3,054,637 to Pambello, and U.S. Pat.  No.  1,876,111 to Van Guelpen all disclose child seats having seat backs that are adjustable relative to the seat bottoms. 
Further, child seats for use on child swings are widely accepted, and child swings having child seats are also well known in the art.  For example, U.S. Pat.  No.  4,807,872 to Spilman et al.,  U.S. Pat.  No.  4,325,578 to Borucki, U.S. Pat.  No.  4,323,233 to Gebhard, U.S. Pat.  No.  1,544,187 to Schroeder, U.S. Pat.  No.  1,379,566 to Holland, U.S. Pat.  No.  1,231,686 to Zuniga, U.S. Pat.  No.  648,740 to Haggard et al.,  U.S. Pat.  No.  465,275 to Kennedy et al.,  and U.S. Pat.  No.  463,863 to Johnson all disclose child swings having child seats for use on the child swings. 
What is needed is a child seat having an adjustable seat back capable of being fixed at a number of positions between a reclined position and an upright position.  Ideally, such a child seat could be formed to include a support-receiving structure for mounting the child seat to support arms appended to a swing motor.  Also, such a child seat would include a child restraint apparatus movable between an upright child-restraining position above the seat bottom and an unobtrusive child-releasing position. 
According to the present invention, a child seat is provided for a swing.  The child seat includes a seat shell having a seat bottom with a front edge and a back edge.  An adjustable seat back is pivotably appended to the back edge of the seat bottom and extends upwardly from the seat bottom.  The child seat further includes swing support-receiving structures that are arranged to receive support arms appended to a swing motor.  The support arms and the support-receiving structures cooperate to suspend the child seat above a floor.  Additionally, the child seat includes a rotatable restraint bar that is usable to restrain a child seated in the seat shell. 
The adjustable seat back is adjustable between an upright position and a reclined position.  The adjustable seat back includes a mechanism for locking the seat back in several positions relative to the seat bottom.  The locking mechanism has a peg mounted to the seat back.  The peg reciprocates between a seat back-locking position and a seat back-unlocking position.  The seat shell further includes a wall arranged to define a peg-receiving notch.  The peg-receiving notch receives the peg when the peg is in the seat back-locking position.  The peg and the peg-receiving notch cooperate to fix the seat back relative to the seat shell when the peg is received by the peg-receiving notch. 
Advantageously, the adjustable seat back is formed in a seat back shell that is pivotably appended to the seat shell.  The seat shell has a proximal end and a distal end.  The seat shell further includes two spaced-apart side edges positioned to lie between the proximal end and the distal end.  Two side arms are appended to the side edges and extend upwardly therefrom.  A first pivot axis lies in spaced-apart relation to the seat bottom adjacent to the proximal end and intersects both side arms.  A bottom surface of the seat shell includes a nesting surface adjacent to the proximal end.  The nesting surface is arranged to curve along an arc having a radius that is constant about the first pivot axis. 
The seat back shell also has a proximal end and a distal end.  The seat back shell further includes two spaced-apart side edges positioned to lie between the proximal end and the distal end.  Two side arms are appended to the side edges and extend upwardly therefrom.  A second pivot axis lies in spaced-apart relation to the seat back adjacent to the distal end and intersects both side arms.  A top surface of the seat back shell includes a mating surface adjacent to the distal end.  The mating surface is arranged to curve along an arc having a radius that is constant about the second pivot axis.  The curvature of the mating surface provides the seat back shell with a shell-receiving cavity adjacent to the distal end of the seat back shell. 
The seat back shell is rotatably appended to the seat shell.  The proximal end of the seat shell is positioned to lie in the shell-receiving cavity.  The seat shell and the seat back shell are arranged so that the first pivot axis and the second pivot axis are coincident and the nesting surface fully engages the mating surface when the seat back is in the reclined position. 
In preferred embodiments, the pivot axis lies in a transverse direction across the seat shell and the seat back shell.  Also, the child seat includes a longitudinal dimension perpendicular to the transverse direction.  As the care giver pivots the seat back shell relative to the seat shell the nesting surface slides over the mating surface.  Though the size of an overlapping area of the nesting surface and the mating surface changes as the seat back shell pivots relative to the seat shell, the nesting and mating surfaces remain in full engagement in overlapping area through the full range of movement of the seat back shell relative to the seat shell 28. 
Illustratively, an adjustable seat back in accordance with the present invention is pivotably mounted to a seat bottom included in a child seat for use on a child swing.  It is within the scope of the present invention to include such an adjustable seat back in a wide variety of child-supporting units such as car seats, high chairs, car beds, child carriers, strollers, and other types of child seats. 
Ideally, two locking mechanisms for locking the seat back relative to the seat bottom are provided with the child seat in accordance with the present invention.  One mechanism is appended to the seat shell adjacent to the first side arm and the second mechanism is appended to the seat shell adjacent to the second side arm.  Also, the pegs are preferably appended to spring assemblies which are appended to the seat back shell.  The spring assemblies urge the pegs to seat back-locking positions in which the pegs are inserted into peg-receiving notches.  Release handles, each of which is movable between a peg-inserting position and a peg-releasing position, are appended to the spring assemblies.  The release handles move the pegs from the seat back-locking positions to seat back-unlocking positions. 
When the care giver wishes to adjust the position of the seat back, the care giver grasps the child seat with both hands placing one hand on the first side arm and the other hand on the second side arm.  The release handles are arranged so that the care givers fingers will engage the release handles.  The care giver then simply squeezes the release handles to unlock the seat back-locking mechanisms, adjusts the seat back to the desired position relative to the seat bottom, and releases the release handles to lock the seat back-locking mechanisms and fix the seat back relative to the seat bottom. 
The nesting and mating surfaces of the seat shell and the seat back shell cooperate with the locking mechanisms, including the pegs appended to the seat back shell and the peg-receiving notch formed in the seat shell, to provide a child seat with an adjustable seat back.  The seat back is pivotable relative to the seat shell and can be selectively locked relative to the seat shell when the care giver allows the peg to be received by the peg-receiving notch. 
The seat shell can be formed to include more than one peg-receiving notch.  Each peg-receiving notch formed in the seat shell and positioned to receive the peg when the seat back is in a position between the upright position and the reclined position provides an additional intermediate position in which the seat back can be fixed to the seat shell.  The seat back can be arranged to be fixed is as many positions as desired between the upright position and the reclined position for which there is room to form notches in the seat shell
Construction of the child seat using a seat shell having a nesting surface and a seat back shell having a mating surface is particularly advantageous.  The mating surface and a top surface of the seat back shell adjacent to the nesting surface provide an essentially smooth and continuous seating surface for the child.  As the seat back is pivoted relative to the seat bottom, the top surface of the seat shell and the mating surface of the seat back shell continue to provide an essentially smooth and continuous seating surface.  The top surface and the mating surface are arranged so that adjustments of the seat back are essentially imperceptible underneath a child seated in the seat shell so that the only change noticed by the child is the child's change of position. 
The seat back locking mechanism cooperates with the seat shell and the seat back shell to provide a child seat that can be easily adjusted between several positions without causing discomfort or significant shifting of the child.  The seat back can be fixed in several positions relative to the seat bottom and can easily be adjusted and locked into a different position by the care giver. 
The seat shell further includes the support-receiving structure which is appended to the seat shell and is arranged to receive support arms appended to a swing motor.  The support arms and the support-receiving structure are arranged to suspend the seat above a floor. 
The seat shell and the side arms appended to the seat shell further include a bottom surface.  Each side arm includes an inner side wall, a top wall appended to a top edge of the inner side wall, and an outer side wall appended to the top wall.  The inner side wall, the top wall, and the outer side wall cooperate to define a downwardly opening U-shaped channel.  The support-receiving structure is disposed within the U-shaped channel and is appended to the bottom surface underneath the top wall. 
The support receiving structure includes a U-shaped bridge and an inverted U-shaped bracket positioned to lie in spaced-apart relation to the bridge.  The bridge and the bracket are each appended to a bottom surface of the top wall.  In preferred embodiments, a second U-shaped bridge is appended to the bottom surface of the top wall between the first bridge and the first bracket, and a second inverted U-shaped bracket is appended to the bottom surface of the top wall adjacent to the first bridge, with the first bridge positioned to lie between the second bracket and the second bridge. 
The support arms include mounting ends that are formed so that a transverse cross section of the mounting ends are non-circular.  The support-receiving structures are arranged to receive the non-circular mounting ends.  The non-circular shape of the mounting ends of the support arms cooperate with the corresponding shape of the support-receiving structures to fix the support arms and render the support arms unable to rotate relative to the seat shell. 
Illustratively, a child seat having an adjustable seat back in accordance with the present invention is intended for use on a child swing.  However, it is within the scope of the present invention to include such an adjustable seat back in a wide variety of child-supporting units such as car seats, high chairs, car beds, child carriers, strollers, and other types of child seats. 
For the reasons described above, use of the support structures of the present invention on a child seat for use on a child swing eliminates the twisting and yaw movement of the child seat and the support arms.  Typically when mounting a child seat to a swing frame structure it is necessary to improve the stability of the structure by providing an additional support member apart from the seat shell and arranged to directly connect support arms that are received on both sides of the child seat.  However, the structural stability provided by the support structures of the present invention permits mounting a child seat to a child swing without providing any member apart from the seat shell to directly connect the two mounting arms.  As a result, use of the support structures of the present invention simplifies the design and the assembly of the child seat. 
In preferred embodiments, the child seat further includes a rotatable restraint bar that is usable to restrain a child seated in the seat shell.  The restraint bar includes a post having a base, a tip, and a stop tab appended to the base.  The base of the post is mounted for rotation to the seat shell.  The base is arranged so that the tip swings easily along an arc between a child-restraining position above the seat bottom and a child-releasing position in which the stop tab engages the seat shell.  In preferred embodiments, the restraint bar is T-shaped and includes a transverse cross member having a top wall arranged to define a tray having a flat upwardly-facing top surface and a lip surrounding the perimeter of the top surface, the transverse cross member being appended to the tip of the rotatable post. 
Advantageously, a child seat for a swing is provided.  The child seat includes an adjustable seat back that is pivotably appended to the seat bottom, swing support-receiving structures that are arranged to receive support arms appended to a swing motor, and a rotatable restraint bar that is usable to restrain a child seated in the seat shell.  Consumers will appreciate the convenience and the ease of use of the various features of this child seat.  Manufacturers will likewise appreciate the ease of assembly provided by the designs of the various component elements of this child seat. 
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.