JPH0141478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an apparatus for cutting continuously molded tubes into desired lengths, and more specifically, in extruded tubes mainly made of plastic, it is possible to cut wrinkles and cuts after cutting. This is a method of cutting a tube without any gaps.

Traditionally, a saw is used to cut PVC resin pipes and profile extrusion molded products, and while this method is suitable for hard molded products, it is not suitable for cutting soft tubes. is not suitable.
Therefore, two main methods have been used to cut relatively soft molded products such as tubes that are mainly made of plastic. In other words, one method is a guillotine cutting method in which the blade is pressed against the molded product to cut it. In this cutting method, the molded product is crushed when the blade is pressed against it, causing the cut end of the tube to break. There is a problem in that two folds are generated in each case, and the cut surface near the folds becomes a convex surface, making it difficult to achieve perfect straightness and the cut surface is not flat. There are other problems such as difficulty in making the cut surface perpendicular to the flow direction of the tube. Another method is to make a rough cut using a guillotine method, then insert the cut tube into a mandrel, and cut the tube to a fixed length by rotating the blade or mandrel. Since it is not in-line but divided into two processes, the cutting speed is slow and a cutting allowance is required, which is wasteful as the cutting allowance is wasted. In order to increase the cutting speed, it is possible to use this method to cut several tubes at the same time, but the problem is that the length of the tube becomes longer and it is difficult to insert and eject the tube into the mandrel. In reality, it was often impossible.

As mentioned above, there are problems with conventional cutting methods, but because polyethylene tubes have almost no creases, the guillotine method has been the main method of cutting. However, recently, in order to improve barrier properties and surface properties, there has been a trend for extruded tubes to be constructed from a single layer to a multilayer structure, which has caused yet another problem. In other words, for example, in a tube with a two-layer structure in which the outer layer is made of polyamide resin and the inner layer is made of polyethylene resin, when the conventional guillotine method is used to cut the tube, when the blade is pressed against it,
When the tube is bent, the outer layer of polyamide resin stretches, but the inner layer of polyethylene resin does not. Therefore, after cutting, only the outer layer of polyamide resin remains stretched at the bent part of the product, leaving wrinkles on the product. Put it away. In particular, since the tube is continuously molded, if you try to force the tube to stop, fix it in the cutting position, and stabilize the cutting length, you have to press down on the flexible tube and bend it. , there were more and more cases where wrinkles inevitably appeared. In addition, if the tube structure includes a metal layer such as aluminum foil or a hard layer such as high-density polyethylene, not only wrinkles but also cracks will occur in these hard layers.
This also causes problems such as a decrease in gas barrier properties.

In response to the above problems, the present inventors have invented a tube cutting method that does not require an extra cutting allowance and does not cause creases or the like. That is, in a tube cutting method in which a continuously formed tube is cut in-line to a desired length, a mandrel that is movable in the flow direction of the tube being formed and has grooves in the circumferential direction is used. is inserted into the tip of the tube being formed, and by sensing the tip position of the tube, the tube and mandrel are pressed and fixed from the outside in front and back of the mandrel, and a cutting blade rotating outside the tube is inserted. By cutting the tube so that it enters the groove of the mandrel, releasing the fixation of the tube, and pulling out the tube from the mandrel by pushing out the tip of the tube,
This is a tube cutting method in which the cut tube is discharged from the line.

Hereinafter, a detailed description will be given with reference to the drawings. FIGS. 1 to 3 are simplified process diagrams of the cutting method of the present invention. First, in FIG. 2 is a groove provided in the circumferential direction of the mandrel 1, and 3 is a groove provided in the circumferential direction of the mandrel 1.
is a cutting blade rotating on the outside of the mandrel 1. The cutting blade 3 is attached to a rotating ring 4, rotated around the center of the mandrel 1, and enters the groove 2 during cutting to cut the tube to a desired length. Now, in the drawing, the tube t that is continuously formed from the left side is the mandrel 1.
When inserted, it pushes the end of the tube 5 provided outside the mandrel 1. Next, a structure is provided that senses when the cylinder 5 moves to a certain point, for example, a device in which the proximity switch 7 senses when the cylinder comes into contact with one end of the iron piece 6 for position detection. Chucks 8 and 9 which are linked to this sensing function operate to press and fix the tube t near both sides of the groove 2.
Subsequently, the cutting blade 3 approaches the tube t,
By entering the groove 2 of the mandrel 1 and making one or more revolutions on the circumference of the tube t, the tube t is cut and a tube t' of a desired length is obtained. (Figure 2). The next step is to cut the cutting blade 3 into the groove 2.
, remove chucks 8 and 9, and remove mandrel 1.
When the tube t is placed in the tube 5, the tube t with the end of the tube 5 cut off can be pulled out from the mandrel 1. Furthermore, by separating the tube 5 itself from the cutting device and moving it to the left, the tube t can be removed from the mandrel. 1 and tube 5 and the cutting device, the cut tube t' falls and is discharged from the cutting line (FIG. 3). Here, the mandrel 1 is moved to the cylinder 10 using hydraulic pressure or air, and after the cutting and discharging steps,
The cylinder 10 extends to the right and pushes the mandrel 1 back to its original position, and the tube 5 returns to its predetermined position by the spring 11 etc., and the position detecting iron piece 6 also returns to its original position, returning to the same state as in Figure 1. Become.

The present invention has the above structure, and provides a method for cutting a thin and flexible tube that does not require an extra cutting allowance and does not cause creases. This prevents double cutting by inserting the core mandrel and fixing it in a rounded state.The tube cut is perpendicular to the length direction of the tube and is flat, preventing creases and ensuring reliable cutting. It became possible to do so. Further, by moving the tube 5 together with the mandrel 1 in the flow direction of the tube, the cut tube can be discharged and the cutting speed can be increased.

Here, in order to prevent the tube from bending between the take-off machine (not shown) and the cutting device, while holding the tube t with the chucks 8 and 9, the cutting blade 3 and the chucks 8 and 9 are A cutting device consisting of the mandrel 1, tube 5, cylinder 10, etc. is moved to follow the tube forming speed, and each device is returned to its original position immediately after the tube is ejected, thereby making further cutting possible. can increase the speed of This is particularly effective when the forming speed is high, since the allowance for temporary slack between the take-off machine and the cutting device is very small when the tube is a thin-walled tube made of polyethylene or the like. Furthermore, when discharging the cut tube t from the line, more stable cutting can be achieved by forcibly discharging it with air or the like.

[Brief explanation of drawings]

The drawings show simplified process diagrams of the cutting method of the present invention; FIG. 1 shows the process before the tube is inserted into the mandrel, FIG. 2 shows the cutting process, and FIG. 3 shows the process before the tube is inserted into the mandrel. FIG. 1...Mandrel, 2...Groove, 3...Cutting blade,
4...Rotating ring, 5...Cylinder, 6...Position detecting iron piece, 7...Proximity switch, 8, 9...Chuck, 10...Cylinder, 11...Spring, t...
Tube.

Claims (1)

[Claims] 1 In a method of cutting a continuously formed tube, a mandrel that is movable in the flow direction of the tube being formed and has a groove in the circumferential direction is inserted into the tip of the tube that is being formed. By sensing the position of the tip of the tube, the tube and mandrel are pressed and fixed from the outside at the front and back of the mandrel, and the cutting blade rotating outside the tube is inserted into the groove of the mandrel to cut the tube. A tube cutting method characterized by cutting.