| 摘要 |
PROBLEM TO BE SOLVED: To provide an inner form, the durability of a deforming retainer plate of which is excellent, the surface of the deforming retainer plate of which is prevented from being chapped or crapped and the deforming retainer plate of which is prevented from being forcibly pulled up and consequently broken, for manufacturing a concrete hollow product, the contracting method of the inner form and a molding form device equipped with the inner form. SOLUTION: An inner form K1 is formed substantially into a cylinder and equipped with an inner form main body 1 having a notched part 11 running along the total longitudinal length in some peripheral part, a deforming retainer plate 2, which is mounted so as to cover the notched part 11, an expanding and contracting device 3 for moving the peripheral wall part of the inner form main body 1 inwards and outwards and a sliding axis 21, which pulls the deforming retainer plate 2 inwards when the peripheral wall part of the inner form main body 1 moves inwards. The deforming retainer plate 2 is formed by a watertightly filling synthetic resin having a non-water permeability and a deformability in the gap part of the spiral belt.
|
