FIELD: mechanical engineering. SUBSTANCE: frame has connecting parts 26, defined by barriers equipped with positioning devices 34 arranged in common intermediate portion and adapted for retaining bracing members 20. Each positioning device has at least one pair of carrier surfaces 36,38 arranged to form V-shaped configuration restricting angular site with acute angle, which is adapted for receiving bracing member 20. Adjusting screw provides for gradual tightening of bracing member 20 on angular portion of barrier. EFFECT: increased efficiency and simplified construction. 8 cl, 9 dwg
