(1) Field of the Invention
This invention relates to an apparatus and a method for manufacturing a hollow synthetic resin product by inflating a parison extruded from an extruding head of an extruder in a mold, especially to an apparatus and a method optimum for manufacturing a tube-shaped synthetic resin product which is bent two- or three-dimensionally.
(2) Description of the Prior Art
A hollow synthetic resin product shown in FIGS. 1 through 3 has been disclosed in Japanese Patent Publication No. 54-15580.
As shown in FIG. 1, an extruding head 101 for extruding a parison P formed of a synthetic resin is provided at a fixed position against a base plate 110.
A mold comprises upper and lower molding portions 102 and 103. The lower molding portion 103 is provided on free bearings 105 arranged on the base plate 110, thereby moving horizontally on the free bearings 105 mechanically and/or electrically, or manually.
The lower molding portion 103 has a groove 103a, which is bent three-dimensionally, for accommodating the parison P extruded from the extruding head 101. The upper molding portion 102 has a groove 102a, which is to be opposed to the groove 103a when the upper and lower molding portions 102 and 103 are put together.
A hollow synthetic resin product manufacturing apparatus having the above construction is operated in the following manner.
As shown in FIG. 2, the lower molding portion 103 is moved to a position where an end of the groove 103a is substantially right below an end of the extruding head 101. While the parison P is extruded from the extruding head 101, the lower molding portion 103 is further moved in such a manner that the above end of the extruding head 101 follows the groove 103a, whereby the parison P is accommodated in the groove 103a.
The lower molding portion 103 is stopped when the other end of the groove 103a reaches substantially right below the above end of the extruding head 101. Then, the upper molding portion 102 is put on the lower molding portion 103, thereafter the parison P is inflated by compressed air. In this manner, a hollow synthetic resin product bent three-dimensionally such as a plastic tube is produced.
Another construction has also proposed, in which a lower molding portion is fixed and an extruding head is moved along a groove on the lower molding portion, whereby a parison P extruded from the extruding head is accommodated in the groove.
In the above conventional apparatuses, at least either of the extruding head or the lower molding portion should be moved. However, the extruding head and the lower molding portion are usually comparatively heavy and large, which makes a device for moving them inevitably complicated and large-scale. Accordingly, a hollow synthetic resin product manufacturing apparatus having the above constructions can hardly be simple and compact.
Moreover, the above-mentioned device for moving the extruding head or the molding portion is integrated therewith. Therefore, if the moving device is out of order, the whole apparatus cannot be operated until the device is repaired. This inconvenience lowers the rate of operation of the manufacturing apparatus.