In implementing belt or strap type restraining systems, it is sometimes necessary to provide an attachment device to make a connection between an anchoring member and the restraining belts. For instance, the commonly used shopping cart having a child seat (such as might be found at a supermarket or grocery store) may employ a belt restraining system to prevent a child from climbing out of the child seat and causing injury. The restraining system is commonly implemented using belts having opposing buckle pieces attached at an end of each belt. When the buckle pieces are engaged, the belts are fitted tightly around the child's waist, thus restraining the child from exiting the child seat. The buckle pieces can then be disengaged when it is desired to remove the child from the seat.
In order to create the restraining effect, the belts used in this system must themselves be anchored to a portion of the shopping cart in order to withstand the applied forces of the restrained object (e.g. a child). It is preferred, however, that the restraining belts of the restraining system not need to be altered in the attachment process, as this adds considerable time and cost to the manufacturing process, and may result in a weak connection. For example, it is uneconomical to stitch the restraining belts to surround an anchoring member of the shopping cart. Also, attaching a restraining belt using a hook and loop connector may result in a weak or easily removed attachment.
As a result of these deficiencies, attachment devices are generally used to accomplish the desired anchoring. Attachment devices generally allow the belts or straps of the restraining system to be anchored to the shopping cart by engaging a loop at an end of the restraining strap and by surrounding an anchoring member in the shopping cart. The attachment device creates the connection between the shopping cart and the restraining strap when an interlocking mechanism on the attachment device is engaged, causing the attachment device to completely surround the anchoring member. It is generally desirous that the attachment device provide the strongest possible connection between the shopping cart and the restraining belts or straps in order to prevent failure of the restraining system.
Attachment devices have been constructed in various forms. For example, an attachment device presently available is constructed from molded plastic and has a V-shaped surrounding member, with two opposing straight bars each attached to either end of the surrounding member. All pieces of the attachment device are solid and cylindrical. The two straight bars terminate with mating portions of an interlock mechanism, such that the straight bars may be locked together to form a connection. When connected, the straight bars form a straight belt member for engaging a loop of a restraining belt, and also thereby surround an anchoring structure within the attachment device.
Also available is an attachment device of molded plastic design, formed in approximately a D-shape. A straight bar is used as a belt member to engage a loop at the end of a restraining belt, and a D-shaped surrounding member is coupled at one end to the straight bar such that the attachment device can surround the anchoring structure. A snap interlock is provided on opposite mating ends of the surrounding member and the belt member to lock the attachment device closed once it has been engaged with the restraining strap and the anchoring member of the shopping cart. As with the previous attachment device, the members are also solid.
Difficulties may arise with these designs which can degrade their effectiveness. The straight bar typically used as a belt member is relatively inflexible, such that when a strong, sharp force is applied by the belt to the attachment device, the attachment device is prone to fracture. Also, cracks can develop in the solid members of the attachment device from other sources (for example from age, weathering, improper use, or manufacturing defects). Whatever the source, cracks can spread through the solid member when force is applied to the attachment device, eroding its resistive properties. Once a crack has extended completely through the solid member, catastrophic failure occurs, and the device must be replaced.