JPH0442158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for cutting a blank, and more particularly to a method for cutting a blank from a sheet mainly made of plastic.

In this specification, a sheet mainly made of plastic refers to a single sheet of plastic, a laminated sheet of different types of plastic, or a laminated sheet of plastic and metal foil, paper, etc., in which the plastic accounts for about 70% or more of the total thickness. refers to the laminated sheet that occupies Also, the sheet is usually about 1 to 20 mm thick.
Refers to a plate-like body of mm.

(Prior art) Conventionally, as a machine for cutting and punching blanks at room temperature from sheets mainly made of plastic, such as polypropylene single sheets or laminated sheets with other thermoplastic plastics, the bottom surface is uniformly flat, and the bottom surface is A punching device has been used that is equipped with a punch whose cutting edge is a corner portion of the side circumferential surface that is perpendicular to the cross section, and a die with a cavity.

Blank 1 cut and punched with such a device
As shown in FIG. 7, a relatively large burr 2 is likely to be generated along the periphery of the upper surface on the punch side. In particular, when the blank 1 is made of a laminated sheet, burrs 2 are more likely to occur than when it is a single sheet.

Therefore, from Blank 1, for example, JP-A-58-
A can-shaped plastic hollow body 3 as shown in FIG.
When forming the flange portion 4, the burr piece 2a is likely to be pushed into the upper surface of the flange portion 4. The pushed-in burr piece 2a is likely to separate from the flange portion 4 during handling or transportation, leaving a recess in its wake. Therefore, when a lid (not shown) is heat-sealed to the flange 4 after filling the hollow body 3 with the contents,
This concave portion (particularly in the case of a concave portion extending across the entire radial length and across the flange portion 4) causes a problem in that the heat seal is incomplete and the sealing performance is likely to be impaired.

Further, the cut surface of the blank 1 has an inverted trapezoid shape that slightly widens toward the side surface of the punch, and is rough. Therefore, the end surface _4a1 of the flange portion 4 of the plastic hollow body 3 is likely to have irregularities, resulting in problems such as poor texture and poor appearance.

After cutting the blank by using a blade with an acute angle cross section and an axially extending inner surface and an anvil with a flat surface, the sheet is placed on the anvil and lowered until the tip of the blade, that is, the cutting edge, reaches the anvil surface. , the above problem is unlikely to occur. However, the blade tip hits the anvil every time it cuts, causing it to spill or become dull, resulting in a short lifespan and the problem that the blade usually has to be replaced after several hundred cuts. arise.

Furthermore, from the viewpoint of the lifespan of the cutting edge, a method has been proposed in which a groove is provided in the anvil to prevent the cutting edge from coming into contact with the anvil, but in this case, a problem arises in that large burrs are formed on the blank.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method for cutting a blank from a sheet mainly made of plastic sheet, which does not generate relatively large burrs on the punched blank after cutting. shall be.

The present invention further provides a method for cutting a blank from a sheet, primarily a plastic sheet, wherein the end face of the blank after cutting is substantially perpendicular to its surface and relatively smooth. The purpose of

Another object of the present invention is to provide a method for cutting blanks from sheets, mainly plastic sheets, in which the blades for cutting the blanks have a relatively long life.

(Means for Solving the Problems) The present invention provides a method for cutting a blank from a sheet mainly made of plastic, in which a pair of opposing blades, each having an acute angle in cross section and a lobe edge portion extending on the inner surface in the axial direction, is provided. from both surfaces of the sheet,
Push the blade part leaving a small gap between the tips, and in the pushed state push the sheet portion that will become the blank inside the blade in the axial direction,
The present invention provides a method for cutting a blank, characterized in that the blank is cut from the sheet portion in the gap using the blade portion having an acute angle in cross section.

(Operation) A pair of opposing blades, each having an acute-angled cross section and a cutting edge whose inner surface extends in the axial direction, is pushed in from both surfaces of the sheet, and then the blank is cut. , there is no risk of relatively large burrs being generated.

Since the above-mentioned pushing is performed while leaving a small gap between the tips of the blade parts, the tips of the blade parts do not come into contact with each other, so that a long life of the blade can be ensured.

A pair of opposing blades, each having an acute-angled cross section and a cutting edge whose inner surface extends in the axial direction, is pushed into the sheet from both surfaces of the sheet, leaving a small gap between the tips of the blades. The side surface of the part to become the blank inside the blade is a smooth surface that is perpendicular to the surface, except for this slight gap between the sheets. Next, in the pushed-in state, push the part that will become the blank in the axial direction,
Since the sheet portion of the gap is cut by the blade section having an acute angle in cross section, the side surfaces of the cut sheet portion of the gap also become perpendicular to the surface and smooth. Therefore, a blank with all end faces vertical and smooth can be obtained.

(Example) An example will be described below with reference to the drawings.

In FIGS. 1 and 2, 11 is a sheet mainly made of plastic, for example, both outer layers are polypropylene, the center layer is an ethylene-vinyl alcohol copolymer, and the adhesive layer between each outer layer and the center layer is modified with carboxylic anhydride. It is a 5-layer laminated sheet made of polypropylene, and is fed in the horizontal direction indicated by arrow A. 12 is a blank cutting device;
13 is a device for extracting cut blanks, and is disposed downstream of the cutting device 12. .

The cutting device 12 includes a fixed blade 14 fixed to a support plate 16 and a movable blade 15 fixed to a slide 17 so as to face the fixed blade 14. The slide 17 is moved up and down by a hydraulic mechanism via a ram (not shown). The fixed blade 14 and the movable blade 15 each have a blade portion 1 with an acute angle in cross section and an inner surface (cylindrical surface in this case) extending in the axial direction (in this case vertically).
4a and 15a. The inner surface 14a ₁ which is a cylindrical surface of the blade part 14a and the inner surface 15a ₁ which is a cylindrical surface of the blade part 15a are substantially on a common virtual cylindrical surface, and the tip 14a _{2 of the blade part 14a and the inner surface 15a 1} which is a cylindrical surface of the blade part 15a are The tips 15a ₂ of 15a are opposite to each other. Inner surface 1
The diameters of 4a ₁ and of the inner surface 15a ₁ are substantially equal to the diameter of the resulting blank 18 (FIG. 6).

The cross-sectional angle θ ₁ between the inner surface 14a ₁ and the outer surface 14a ₃ of the blade portion 14a is preferably set to 30 to 50 degrees.
If it is smaller than 30 degrees, the cutting edge is likely to curl up or become partially chipped after being used many times (for example, 10,000 times), while if it is larger than 50 degrees, a large load will be required for cutting, especially when cutting plastic laminated materials. This is because when cutting a sheet, the adhesive layer tends to peel off, making cutting difficult. Similarly, the angle θ ₂ between the inner surface 15a ₁ and the outer surface 15a ₃ of the blade portion 15a
It is also preferably set at 30 to 50 degrees. Usually θ ₁ =
It is determined by θ ₂ .

Inside the fixed blade 14, a receiving member 19 is biased by a spring 20 so that its flat upper surface 19a is normally located at a slightly higher level than the tip _14a2 of the blade, and its side surface 1
It is arranged so that there is a slight gap 21 between the inner surface 9b and the inner surface _14a1 . The diameter of the receiving member 19 is
It is set slightly smaller than the diameter of the inner surface _14a1 of the blade portion 14a, preferably about 0.1 to 0.6 mm smaller.

Inside the movable blade 15, a presser member 22 is biased by a spring 23, and its flat lower surface 22a is normally held at the tip 15a ₂ of the blade portion 15a.
A short cylindrical side surface 22b extending in the axial direction and located at a slightly lower level than the blade portion 15.
It is arranged so that there is a slight gap 24 between it and the inner surface _15a1 of a. The diameter of the holding member 22 is slightly smaller than the diameter of the inner surface 15a ₁ of the blade portion 15a, therefore, the diameter of the inner surface 14a ₁ of the blade portion 14a, preferably about 0.1 to 0.6.
It is set smaller in mm. This difference is due to the pressing member 2
It is preferable that the blade be as small as possible without hitting the tip 14a 2 even if the blade ₂ descends and enters the blade portion 14a. This is to apply a large shearing force when cutting the material in the gap 37, which will be described later, to obtain a blank end face as smooth as possible.

Further, the presser member 22 is fixed to a piston rod 26 of an air cylinder 25 fixed to the slide 17, and is configured to be moved up and down by the operation of the air cylinder 25. Note that 27 is a conduit for supplying air 28 to the air cylinder.

Close to the cutting device 12, sheet supports 29 and 30 are provided upstream and downstream thereof, respectively. The upstream seat support 29 includes two lower support rods 29a ₂ each biased by a spring 29a ₁ and each support rod 29a ₂
a support plate 29a ₃ provided at the upper end of the rod, and two upper support rods 29b ₂ each biased by a spring 29b _{1 ;}
The support plate _29b3 is provided at the lower end of the support plate 29b3.
Similarly, the downstream seat support 30 also has a spring 3
It includes support rods 0a ₁ , 30b ₁ ; support rods 30a ₂ , 30b ₂ ; and support plates 30a ₃ , 30b ₃ .

The supports 29 and 30 are arranged so that the upper surfaces of the support plates 29a ₃ and 30a ₃ are normally located at the same level as the upper surface 19a of the receiving member 19, and the support plates 29b ₃ and 3
The lower surface of 0b ₃ is normally the lower surface 22a of the holding member 22.
It is constructed so that it is located at almost the same level as the Then, as will be described later, when the slide 17 is lowered and the blade parts 14a and 15a are pushed into the sheet 11, the portion 11a of the sheet 11 between the sheet supports 29 and 30, especially the blank on the receiving member 19, The portion 11b to be formed is not curved but remains flat and slightly lowered as shown in FIG. 3, so that a blank 18 of accurate dimensions can be obtained.

31 is the slide 17, therefore the movable brake 15
This is a positioning rod for setting the bottom dead center of the tip _15a2 . Lower surface 31a of positioning rod 31
When the slide 17 comes into contact with the upper surface of the support plate 16, the slide 17 reaches the bottom dead center, but at that time, the gap 37 between the tip _15a2 of the movable blade 15 and the tip _14a2 of the fixed blade 14 (FIG. 3) The height of the positioning rod 31 is determined so that the height of the positioning rod 31 is a predetermined small value h.

The blank extraction device 13 includes a support plate 16
A die 3 having a cavity 32a fixed to the
2, a punch 33 fixed to the slide 17, and a presser ring 34 surrounding the punch 33 and biased by a spring 35.

Using the above-described apparatus, cutting and extracting the blank 18 from the sheet 11 is performed in the following manner. As shown in FIG.
9 and support plates 29a ₃ and 30a ₃ , and from the position where the slide 17 is at the top dead center, the slide 17 is lowered by the operation of the hydraulic mechanism. Along with this descent, first the support plates 29b ₃ , 30
b ₃ and the presser member 22 contact the sheet 11,
Seat part 1 between seat supports 29 and 30
Press down while keeping 1a flat.

At this time, the air in the air cylinder 25 is kept open by a valve mechanism (not shown). As the slide 17 further descends, the tip 15a ₂ of the blade portion 15a comes into contact with the sheet 11, and then the blade portion 15a
is pushed into the upper surface of the sheet 11, and the pressing member 22 rises by that amount. At this time, the pushing force and the pushing force of the presser member 22 via the spring 23 push the sheet portion 11a downward, and the blade portion 14a is pushed into the lower surface of the sheet. In this way, an upper cut surface 38a and a lower cut surface 38b perpendicular to the surface of the sheet 11 are formed. As shown in FIG. 3, the lower surface 31a of the positioning rod 31 abuts against the support plate 16 with a slight gap 37 remaining between the tip 15a ₂ of the blade 15a and the tip 14a ₂ of the blade 14a. The slide 17 reaches the bottom dead center and stops descending. .

In this state, the seat portion 11b in the blade portions 14a, 15a, that is, the portion to become the blank 18, is attached to the receiving member 1 via the springs 20, 23.
9 and the holding member 22 under pressure. The seat portion 11b is connected to the outer seat portion through a gap 37.

By adjusting the balance of the bias forces of the springs 20 and 23 of the receiving member 19 and the pressing member 22, the position of the gap 37 in the sheet thickness direction can be changed. This makes it possible to determine the optimum position in the thickness direction, such as in the case of multilayer laminated sheets.

Next, due to the operation of a valve mechanism (not shown), pressurized air 28 flows into the air cylinder 25 from the conduit 27, and the air cylinder 25 is operated to operate the fourth air cylinder 28.
As shown in the figure, the presser member 22 is attached to the receiving member 19.
and a distance slightly larger than the height h of the gap 37,
For example, by lowering by 1 mm, the seat portion 11b is lowered by the above distance. The sheet portion 11b is then cut from its outer sheet portion.

A gap between the holding member 22 and the inner surface _15a1 of the blade portion 15a, and a gap between the receiving member 19 and the inner surface 14 of the blade portion 14a.
Since the gap between a ₁ is very small, the material in the gap 37 is subjected to a shear force in a direction perpendicular to the sheet surface. Therefore, a relatively smooth cut surface with substantially no burrs can be obtained. This cut surface is substantially on the same plane as the upper and lower cut surfaces 38a and 3b formed by pressing. Therefore, the end surface of the sheet portion 11b after cutting, that is, the end surface 18 of the blank 18
a is substantially perpendicular to the surface of the sheet portion 11b, and is substantially free of burrs and is relatively smooth.

The height h of the gap 37 is preferably 0.02 to 0.5 mm, more preferably 0.05 to 0.1 mm. 0.02mm
If it is smaller, the tips 14a ₂ and 15a ₂ of the blade portions will be more likely to hit each other, and the life of the blades 14 and 15 will be shortened. On the other hand, if it is larger than 0.5mm,
This is because when the holding member 22 is lowered, it becomes difficult to cut the material in the gap 37, causing burrs to occur and the fractured surface to become rough.

Next, the air in the air cylinder 25 is released, and the slide 17 is raised to the top dead center (FIG. 5). The receiving member 19 is raised to its original position by the bias force of the spring 20, and the cut sheet portion 1 is
1b, ie blank 18, also rises. The seat portion 11a between the seat supports 29 and 30 also rises to the same level as the blank 18 (that is, the level shown in FIG. 1), so that the blank 18 is raised to the same level as the seed portion 11a, as shown in FIG. The surfaces are aligned.

Next, the sheet 11 is moved in the direction A until the cut sheet portion 11b, that is, the blank 18, reaches the blank extraction device 13. Immediately, the slide 17 descends, the sheet portion around the blank 18 is pressed between the die 32 and the holding ring 34, and the blank 18 is pushed down by the punch 33 and extracted from the sheet 11, and the blank 18 is pulled out from the cavity 32.
Fall into a. At the same time, a new blank 18 is formed in the cutting device 12 in the manner described above.

The present invention is not limited to the above embodiments; for example, the slide 17 may be moved up and down by a crank mechanism.

(Effects of the Invention) The present invention eliminates the risk of relatively large burrs being generated along the surface periphery of the blank, provides a smooth blank with all end faces perpendicular to the surface, and ensures long blade life. It has the effect of being able to do it.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a system having an example of an apparatus for carrying out the method of the invention,
A drawing showing the state in which the slide is at the top dead center. Figure 2 is a plan view seen from - in Figure 1. Figure 3 is a diagram showing the state in which the slide is at the top dead center.
A partially cutaway front view showing the state in which the blade part has been pushed in by the device shown in the figure.
Fig. 5 is a partially cutaway front view showing the state in which the blank has been cut, and Fig. 5 is a partially cutaway front view showing the slide returning to the top dead center after the blank has been cut in Fig. 1 is a partially cutaway front view showing a blank being extracted by the extraction device installed in the system shown in FIG. 1, and FIG. 7 is a vertical cross-section of a main part of an example of a blank formed by the conventional method. side view,
8 is a perspective view of an exemplary flanged plastic hollow body formed from the blank of FIG. 7; FIG. 11...Sheet mainly made of plastic, 11
b... Sheet portion to be blank, 14... Fixed blade, 14a... Blade portion, 14a ₂ ... Tip, 15...
Movable blade, 15a...Blade portion, 15a ₂ ...Tip, 1
8...Blank, 37...Gap.

Claims (1)

[Claims] 1. In a method for cutting a blank from a sheet mainly made of plastic, a pair of opposing blades each having an acute-angled cross section and a blade portion whose inner surface extends in the axial direction is cut from both surfaces of the sheet by cutting the tip of the blade portion. Push it in with a small gap left in between, and in the pushed state, push the sheet part in the blade that is to become the blank in the axial direction, and separate the blade part with an acute angle in cross section from the sheet part in the gap. A blank cutting method characterized by cutting the blank.