Pneumatic structure of BABOT mechanism (US Patent No.4765079) Shiro Takahashi
A pneumatic structure a part or the whole of which can desirably be put in motion when the pneumatic structure is shaped into, for example, outlines of living things or the like. A spare portion having at least a pair of bending fulcra is formed on the structure main body on the opposite side to a bending direction of the structure, and a length of arc between the respective fulcra of the spare portion is made shorter than 1/2 outer circumferential length of the pneumatic structure containing a set of the respective fulcra, whereby the structure can positively be maintained in a desired state under normal conditions and bending operation thereof can be promptly effected at a large angle by means of small external force.
FIG. 1 is a schematic sectional view showing the first embodiment of the present invention;
FIGS. 2A and 2B are developments each showing the pneumatic structure of FIG. 1;
FIG. 3 is a sectional view showing a bent state of the pneumatic structure of FIG. 1;
The present invention will be described in detail hereinbelow by referring to the accompanying drawings. In the following respective Figures, it is to be noted that sewed line of a pneumatic structure is indicated by broken line. FIG. 1 is a schematic sectional view showing the first embodiment of the present invention, and FIGS. 2A and 2B are developments showing the pneumatic structure of FIG. 1 wherein FIG. 2A is a development of a main body 12, whilst FIG. 2B is a development of a spare cloth 14.
In FIG. 1, air has been supplied to the interior of a pneumatic structure 11 by a certain means (not shown) through an air hole 2A defined on a pedestal 2 along the direction of arrow Z, so that the pneumatic structure 11 is in an upright position and the outlines of which form a cylindrical shape in this case.
In FIGS. 2A and 2B, a margin to seam required for sewing the pneumatic structure 11 into a cylindrical shape is omitted. In other words, FIG. 2A is a flat layout.
In the respective Figures, the pneumatic structure 11 is composed of the main body 12 and the spare cloth 14 which are made of cloth coated with a resin or the like. An opening 13 having a length of L2 along the circumferential direction of said main body 12 as shown in FIG. 2A is defined thereon in the case when it is sewed into a cylindrical shape.
While said opening 13 is drawn in such that it is defined with a certain width in FIGS. 1 and 2 A , it is not limited thereto, but may be a mere cut notched.
The pneumatic structure 11 is formed by sewing the main body 12 into a cylindrical shape and further sewing the spare cloth 14 shown in FIG. 2 B to the opening 13 of said main body 12. The spare cloth 14 has a boat bottom-like shape and lengths of the respective sides of which, i.e., those of the arcs AD and BC as well as the sides AB and DC are determined so as to be equal to the respective sides of said opening 13, i.e., ad, bc and ab, dc. Said spare cloth 14 is sewed to the opening 13.
An end portion of the pneumatic structure 11 is secured to the pedestal 2 having the air hole 2A. Fittings 3 are fixed to a portion inside the main body 12 and substantially opposed to that on which the spare cloth 14 is sewed, and an operation cord 4 is fixed to said fittings 3.
While air is continuously supplied to the pneumatic structure 11, internal pressure thereof is kept constant, because said pneumatic structure 11 leaks air from the seam thereof.
In the first embodiment, length L2 (FIG.2A) of the opening 13 along the circumferential direction is established so as to be shorter than half of length L1 of the cylindrical outer circumference of the main body 12. As a result, said pneumatic structure 11 is erected by the above described air supply as shown in FIG. 1. In this situation, said spare cloth 14 is loose and folded in the form of bellows. In the following description, a portion folded or loosened in the case where no force is applied to the operation cord 4 will be referred to "spare portion". In this first embodiment, the spare cloth 14 corresponds to such spare portion.
When the operation cord 4 secured to the fittings 3 inside the pneumatic structure 11 is pulled along the direction of arrow Y as shown in FIG. 3, the spare cloth 14 is extended, and the pneumatic structure 11 is bent in the direction of arrow P around fulcra E at both ends of the spare cloth 14.
In this case, such volume of the pneumatic structure on the left side to which the fittings 3 are secured and cut with a plane passing through both the ends E of said spare cloth 14 and being in parallel to the central axis of said pneumatic structure 11 decreases, but on the contrary, the volume of the pneumatic structure 11 on the right side to which the spare cloth 14 is secured and cut with said plane increases by a volume derived from extension of the spare cloth 14.
Thus, a degree of reduction in volume of the pneumatic structure 11 extending over a state from before bending to after the bending becomes smaller than that in the case where no spare cloth 14 is provided, so that pressure increase inside the pneumatic structure 11 in case of bending is also comparatively efficiently suppressed.
Accordingly, when only small force is applied to the operation cord 4, the pneumatic structure 11 can be bent. As a consequence, it is also possible to make an angle for the bending comparatively large, besides such bending operation can promptly be effected. Moreover, since change in volume of the pneumatic structure 11 is little, the appearance or impression on spectators with respect to the pneumatic structure becomes also favorable.