Modular frame for stretching sheet material suitable for home use in hobby activities

A modular, collapsible and adjustable rectangular frame for stretching sheet material, as for rug-tufting by a hobbyist, comprising:

• four substantially identical side bars extending along the sides of a horizontal rectangle, at least two substantially identical extension bars extending along at least two opposite sides of the rectangle, and four substantially identical legs extending downwardly from each of the sides of the rectangle, wherein:
• each bar is integrally formed of a substantially homogeneous material and comprises:
• an elongated channel member which is substantially rectangular in a vertical section transverse to the length of the bar and is formed of a top and two side walls;
• a substantially shorter bottom wall at one longitudinal end of the channel member which forms, together with the adjacent portion of the top and side walls, a connecting tunnel which is open longitudinally outwardly;
• a connecting insert extending away from the channel member at the other longitudinal end thereof, said insert being shaped and dimensioned to be received in frictional fit in said connecting tunnel;
• a longitudinally extending row of spaced bracing walls each extending transversely of the top and side walls and being integral therewith;
• a selected pair of adjacent bracing walls forming, together with the portion of the top and side walls intermediate thereto, a leg tunnel which is substantially rectangular in horizontal section;
• the side wall facing away from the frame having at its lower portion a longitudinally extending row of web-engaging projections facing away therefrom, the connecting insert of each side bar extending transversely of the length of the channel member thereof and the connecting insert of each extension bar extending along the length of the channel member thereof;
• and
• each leg is integrally formed of a substantially homogeneous material and comprises an upper tubular portion which is substantially rectangular in horizontal section and is dimensioned and shaped to be slidably received in frictional fit from below into a leg tunnel formed between the side walls of each of said channel members and two adjacent bracing walls thereof;
• wherein the frame is assembled by frictionally fitting the connecting insert of each bar into the connecting tunnel of another bar to form a rectangular frame and by frictionally fitting each leg into a leg tunnel of each side of the rectangular frame, sheet material is stretched thereon by laying the material over the frame and pulling outwardly the marginal portion thereof by a web lacing said web-engaging projections, and the lengths of any pair of opposite sides of the frame are changed by adding or subtracting extension bars.