1.  Field of Invention
The present invention relates to a playyard, and more particularly to a portable playyard which can be inflated to form an air-cushioning boundary for accommodating infants or children to play therein. 
2.  Description of Related Arts
A playyard provides a safe place for infants and children to play therein.  For ease of storage, many playyards are made in portable forms.  A conventional playyard will be introduced to explain the current practice in this particular technical area.  The problems of the current practice will be discussed to establish the need of technical improvement. 
As shown in FIG.  1, a conventional playyard comprises an upper boundary frame, a lower boundary frame, and four vertical posts spacedly mounted between the upper and lower boundary frames to support a cloth boundary that a baby or a young child can dispose therein.  In order to restrict the movement of the baby within the areas, the vertical posts must be high enough that the baby cannot climb out of the playyard. 
In order to fold up the playyard, a plurality of joints and couplers are employed to interconnect the adjoining ends of the frame sections which, in turn, confine looped frames for forming a playyard frame.  Moreover, locking devices are employed to prevent folding of the adjoining frame sections.  However, accidental actuation of the locking device may occur, thereby resulting in folding of the frame sections relative to each other, which action may injure a child playing in the foldable playyard. 
Thus, in order to enhance the foldable ability of the playyard, more joints must be employed such that the playyard can be folded up in a compact unit for carriage and storage.  However, the complicated foldable frame will highly increase the manufacturing cost of the playyard and weaken the rigid structure of the frame.  Furthermore, it is a hassle for a user, such as parent, to manipulate the folding and unfolding operations of the playyard. 
Another problem of the conventional playyard is the concern of safety.  In order to provide structural strength, the boundary frames and the vertical posts are usually made of rigid materials, such as metal.  Bruises are frequently inflicted to a child due to his or her contact with the posts and joints when the child plays within the playyard.  Cuts may also happen to the child because of the sharp edges of the screws, bolts, and joints.  Therefore, a cushion layer must be additionally added into the interior of the playyard to protect the child colliding with the frame.  In addition, the additional joints, couplers, and cushion layer will substantially increase the overall weight of the playyard to reduce the portability of the playyard. 
As a result of the above-mentioned problems, what is need is portable playyard with lightweight, having a soft but substantially strong structure protecting infants and children from infliction of bruises and cuts when they play inside. 
A main object of the present invention is to provide a portable playyard which can be inflated to form an air-cushioning boundary for accommodating infants or children to play therein. 
Another object of the present invention is to provide a portable playyard, which comprises a plurality of inflatable supporters spacedly bridging the top and bottom boundary frames, wherein each of the inflatable supporters has a cross section gradually increased from the upper portion to the lower portion to provide a rigid, simple and strong structure so as to minimize the deformation of inflatable supporter, so as to prevent the playyard from being accidentally collapsed. 
Another object of the present invention is to provide a portable playyard, wherein each of the inflatable supporters is inclinedly extended from the top boundary frame to the bottom boundary frame to evenly distribute and support a downward force applied on the upper boundary frame so as to further prevent the playyard from being accidentally collapsed. 
Another object of the present invention is to provide a portable playyard, wherein each of the inflatable supporters inevitably provides an air-cushioning effect for the portable playyard so that the child is safe to accommodate in the portable playyard. 
Another object of the present invention is to provide a portable playyard, which can be quickly and easily folded into a compact unit for carriage and storage and unfolded for use.  In other words, the present invention does not require a relatively large storage space in comparison with the conventional foldable frame, so as to minimize the cost of shipping and handling of the present invention. 
Another object of the present invention is to provide a portable playyard, wherein due to the inflatable properties, the portable playyard is extremely lightweight in comparison with the conventional playyard incorporating with metal posts and joints.  In other words, the portable playyard is capable of being deflated to enhance the portability of the present invention. 
Another object of the present invention is to provide a portable playyard, wherein the folding and unfolding operations of the present invention are easy and fast by deflating and inflating the portable playyard respectively, such that an individual is able to unfold or fold up the portable playyard. 
Another object of the present invention is to provide a portable playyard, wherein no expensive or complicated structure is required to employ in the present invention in order to achieve the above mentioned objects.  Therefore, the present invention successfully provides an economic and efficient solution not only for providing a rigid configuration for the playyard but also for providing an air-cushioning effect to protect infants and children from infliction of bruises and cuts. 
Accordingly, in order to accomplish the above objects, the present invention provides a portable playyard, comprising:
a top frame defining a top opening;
a bottom frame positioning underneath the top frame;
a plurality of circular inflatable supporters spacedly bridging the top and bottom frames and defining an interior space between the top and bottom frames, wherein each of the inflatable supporters, having an air chamber, outwardly and inclinedly extended from the top frame to the bottom frame to define an interior adjacent angle and an exterior adjacent angle which is smaller than the interior adjacent angle, wherein the interior adjacent angle is defined between an interior peripheral edge of the respective inflatable supporter and the bottom frame, wherein the exterior adjacent angle is defined between an exterior peripheral edge of the respective inflatable supporter and the bottom frame, wherein a diameter of each of the inflatable supporters is gradually increased from a top portion of the inflatable supporter to a bottom portion thereof;
a boundary shelter supported by the top frame to surround the interior space and define a playyard cavity within the boundary shelter, the top frame, and the bottom frame; and
at least an air valve provided at the inflatable supporters for retaining a predetermined volume of air within the air chamber of each of the inflatable supporters. 
These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.