JPH0449428Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a bellows tube with excellent flexibility, which is often used as a suction hose of a vacuum cleaner. Specifically, a resin tube extruded and supplied from an extruder is formed into a corrugated peripheral wall along the axial direction of the tube using blow molding means, and the corrugated peripheral wall is formed in order to reduce movement resistance of fluid such as air. The present invention relates to a flexible bellows tube in which the inner circumferential surface of the valley is formed into an oblique plane substantially parallel to the axial direction of the tube.

<Prior Art> As a conventional flexible bellows tube of this kind, one is known in which the ridges of the corrugated peripheral wall have a cross section approximately shaped like a triangular crest, and the troughs are shaped like a flat plate. . (For example, see Japanese Utility Model Application Publication No. 58-94973.) <Problems to be solved by the invention> In the conventional flexible bellows tube, the peak part, which is constantly in contact with other objects or in sliding contact, has a triangular peak shape. Therefore, there was a problem in that contact with other objects is point contact, which tends to cause local damage. Moreover, since the cross-sectional shape is a triangular mountain shape, it is difficult to secure a sufficient pressure receiving surface during blow molding.

In addition, in the conventional flexible bellows tube, the wall thickness of the trough is approximately equal in all parts in the direction of the tube axis, so when the bellows tube is bent, the tube axis at the trough The groove is bent at the center of the direction, and as this bending is repeated, the center of the valley is plastically deformed into a bent state, making it difficult to maintain the inner circumferential surface of the valley in a flat shape at all times.

Conventional bellows tubes have a shape that makes it difficult to use a blow molding method in which a softened resin tube is extruded into a mold that expands in the radial direction by extruding a softened resin tube into a mold whose inner circumferential surface is corrugated in the axial direction of the tube. It was hot. In other words, even if the inner circumferential surface of the convex portion (valley forming portion) that protrudes radially inward of the formwork is formed into a flat surface, when the tube portion corresponding to the formwork recess (peak forming portion) expands, The convex part is drawn into the concave part, and this pulling force causes the wall thickness of the tube part that forms the valley to become thinner on both sides in the tube axis direction. The shape was difficult to form into a flat shape.

The present invention solves the problems of the prior art, and aims to provide a flexible bellows tube that can withstand long-term use and that can be easily formed into a homogeneous shape during blow molding. do.

<Means for solving the problems> The flexible bellows tube of the present invention, which can achieve the above object, has a substantially uniform wall thickness throughout the tube wall except for the troughs of the uneven corrugation. The wall is thick, and the peaks of the uneven waveform are formed wide in the axial direction of the tube, and the thickness of the troughs is such that the inner circumferential surface is formed into an oblique plane substantially parallel to the axis of the tube. The outer circumferential surface is formed into a gentle arc shape that gradually becomes thicker toward the center in the axial direction of the tube and toward the outside in the radial direction.

<Function> The crest of the present invention, in which the entire other parts except the troughs are approximately uniformly thick, and the top is formed wide in the tube axis direction, has a relatively wide outer surface compared to other objects. The inner space acts as a large pressure-receiving surface during blow molding. In the trough of the present invention, the strength of the central part in the axial direction of the tube is increased,
Moreover, due to its shape, by adopting a formwork in which the axial center portion of the inner circumferential surface of the convex part of the formwork for forming the trough is recessed radially outward, the tensile strength as described in the prior art section can be improved. It acts so as to generate a force in the valley forming part that opposes the force.

<Example> An example of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a flexible bellows tube made of a corrugated synthetic resin (polyethylene or the like) having a circumferential wall formed in a spiral shape around the axial direction of the tube, consisting of peaks 1A and troughs 1B. The peak portion 1A is formed into a trapezoidal shape so that the entire thickness is approximately uniform and the peak portion is wide and flat in the axial direction of the tube, and the valley portion 1B in the corrugated peripheral wall is the inner peripheral surface 1b
is formed into an oblique plane parallel to the axis of the tube, and the outer circumferential surface is formed into a gentle arc shape that gradually becomes thicker toward the center in the axial direction of the tube toward the outside in the radial direction.

Next, a manufacturing apparatus for the flexible bellows tube 1 will be explained. In FIG. 2, two molding bands 3, 3, which are formed by connecting a plurality of half-cylindrical molding units 2 whose inner circumferential surfaces are corrugated in the axial direction so as to be relatively bendable in an endless manner in the axial direction, are connected in a predetermined manner. It is rotated to form a cylindrical mold 4 whose inner circumferential surface is corrugated along the axial direction in the path portion. A softened synthetic resin tube 6 is extruded from an extruder 5 provided at one end of the mold 4 so as to be located concentrically within the mold 4, and air is blown into the tube 6 to remove the mold 4. The tube 6 is expanded in the radial direction so as to be pressed against the inner peripheral surface of the tube 6.
The flexible bellows tube 1 is successively manufactured by deforming it along the inner circumferential surface of the mold 4. However, as shown in FIG. 3, the inner circumferential surface 2a of the spiral convex portion 2A of the forming unit 2, which protrudes radially inward to form the trough portion 1B of the bellows tube 1, is similar to the tube of the trough portion 1B. In order to project the axially intermediate portion as described above, it is formed into a gentle arcuate surface that is recessed as the axially central portion gradually moves outward in the radial direction.

As another embodiment of the present invention, a plurality of annular peaks 1A are arranged side by side at appropriate intervals in the axial direction of the tube instead of the configuration of the spiral peak 1A, so that the peripheral wall has an annular shape along the axial direction. It may also be applied to a corrugated pipe formed into a corrugated shape.

Incidentally, although reference numerals have been written in the claims section of the utility model registration for convenience of comparison with the drawings, it is not intended that the present invention be limited to the shape of the attached drawings by such entry.

<Effects of the Invention> As is already clear from the detailed description above, the flexible bellows tube of the present invention has the following effects.

(a) Since the outer surface of the peak of the bellows-like corrugation of the pipe is in wide contact with other objects, it is less susceptible to local damage unlike conventional flexible bellows pipes that have a triangular shape. This has the effect of improving the durability of the bellows tube without taking any special measures such as making it thicker.

(b) The flexible bellows tube of the present invention has a cross-sectional shape of the crest that is wider in the axial direction of the tube, so the pressure-receiving surface during blow molding is more can be widely secured,
The resin tube can be reliably aligned with the mold without increasing the molding pressure too much, and it is easy to obtain a homogeneous flexible bellows tube without molding defects.

C. The central part of the tube in the axial direction at the valley part is made thick so that the central part is difficult to bend.
Even if the bellows tube is repeatedly bent and used, the inner circumferential surface of the valley can always be kept flat, and an increase in fluid movement resistance can be prevented over a long period of time.
Even when used as a suction hose for fluid like a suction hose for a vacuum cleaner, the phenomenon that the troughs shrink and the overall length of the hose is shortened does not occur.

(d) The flexible bellows tube of the present invention has a recessing action on the formwork for forming the troughs, thereby preventing the pipe from being drawn into the recesses of the formwork for forming the ridges in the conventional technology, and improving the inner circumferential surface of the troughs. It can be formed into a substantially flat shape. Moreover, since the thick walled portion of the valley is formed into a gentle arc shape that gradually becomes thicker toward the center in the axial direction of the tube, it is not necessary to take special measures to make the mold into a complex shape. Therefore, the thick portion can be reliably formed with an extruded tube having a uniform thickness on the entire circumferential surface.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view of the flexible bellows tube of the present invention, Fig. 2 is a partially cutaway side view of the forming device, and Fig. 3 is a partially cutaway side view of the flexible bellows tube of the present invention.
The figure is a longitudinal sectional view of the main parts of the forming device and the tube of the present invention. 1...tube, 1A...peak, 1B...trough, 1b
...Inner peripheral surface of the valley, 5...Extruder.

Claims (1)

[Scope of utility model registration request] In a flexible bellows tube which is a tube formed from a resin tube supplied from an extruder 5 and whose peripheral wall is formed in a corrugated shape along the axial direction of the tube 1, the valley portion 1
The entire tube wall portion other than B is formed to have a substantially uniform thickness, the peak portion 1A is formed wide in the axial direction of the tube 1, and the inner circumferential surface 1b of the trough portion 1B is aligned with the axis of the tube 1. A flexible bellows tube is formed into an oblique plane substantially parallel to the tube 1, and its outer circumferential surface is formed into a gentle arc shape that gradually becomes thicker toward the center in the axial direction of the tube 1 toward the outside in the radial direction.