JPS633695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in cutting knives for cold-formed coil springs.

There are two methods for manufacturing coil springs: cold forming and hot forming. To manufacture coil springs made of thin wire rods with a wire rod diameter of approximately 6 to 8 mm or less, a cold forming method is used in which wire rods that have been given high strength are cold-formed into a coil shape. When the diameter becomes larger than the above, it becomes difficult to cold-form a high-strength wire rod, so the wire material is heated to make it easily plastically deformed and then formed into a coil shape. A hot forming method is used to heat-treat the spring to give it high strength and make it into a coil spring. The cutting knife according to the present invention is used for cutting the end of a high-strength wire wound into a coil when manufactured by the above-mentioned cold forming method.

By the way, a cutting tool and a cutting mechanism conventionally used in a coil spring automatic cold forming machine will be explained with reference to FIGS. 1a and 1b.

Figure 1a shows the cutting tool and its positional relationship.
The cutting tool consists of a combination of a cutting knife, designated 1', and a cutting mandrel, designated 2. The cutting knife 1' is a rather elongated prismatic body with a substantially square cross section, and has a knife edge 11' at one end, which is a very narrow surface that is substantially perpendicular to one side surface 1'a of the cylindrical body. and a tapered portion 12' having a predetermined clearance angle α (for example, 20 degrees) with respect to the surface of the knife edge 11', and a blade portion is formed with the one side surface 1'a as a blade surface. The other end of the cutting knife 1' extends over a predetermined length as shown in FIG. It is fixedly attached to the cutting carriage 3 using a tightening tool. The above-mentioned tightening tool includes a cutting knife holder 4 having a protrusion 41 at one end for pressing the cutting knife 1', a screw hole bored approximately in the longitudinal center of the cutting knife holder 4, and a cutting carriage. A headless bolt 5a and a nut 5b are screwed into the screw holes 7 drilled in the cutting knife holder 4 to fix the cutting knife holder 4 to the cutting carriage 3, and a headless bolt 5a and a nut 5b are screwed into the screw holes 7 drilled in the cutting knife holder 4 to fix the cutting knife holder 4 to the cutting carriage 3. A headed bolt that is screwed into a threaded hole and presses the end face of the cutting carriage 3 with its tip to generate a pressing force on the protrusion 41 in the direction of the cutting knife 1 using the headless bolt 5a as a fulcrum. It consists of a nut 6a and a nut 6b. Since the cutting carriage 3 is configured to be driven in the vertical direction, the cutting knife 1' fixed to the cutting carriage 3 can be displaced as the cutting carriage 3 moves up and down. be.
The cutting mandrel 2 is a semi-cylindrical body whose diameter is the same as or slightly smaller than the inner diameter of the wound coil. It is set to be able to move left and right. As shown in FIG. 1a, the side surface 2a of the cutting mandrel 2 and the blade surface 1'a of the cutting knife 1' are included in parallel planes separated by a predetermined gap determined by the strength of the wire to be cut. At the same time, the forward position of the cutting mandrel 2 is such that its tip end face 21 is within the final winding part of the coil C formed by a forming mechanism (not shown), and the vertical displacement line and the end face at approximately the center in the width direction of the cutting knife 1'. The specifications are set so that 21 and 21 are parallel to each other.

When cutting the wire rod W ₁ at the end of the winding with the above cutting tool and cutting mechanism, the cutting mandrel 2 with its arc-shaped side surface facing the line of sight is advanced from right to left according to arrow R, Insert it into the final winding part of coil C whose axial direction is horizontal. In this state, the wire rod W ₁ above the final winding portion and the upper peripheral side of the cutting mandrel 2 are in a positional relationship in which they are almost inscribed. Then, the cutting carriage 3 is rapidly driven, and the cutting knife 1' is impulsively displaced from above to below in accordance with the arrow S to a position slightly below the upper circumferential line of the cutting mandrel 2. wire
W ₁ is supported on the semi-cylindrical upper periphery of the cutting mandrel 2 on the viewing direction side, and an impact force is applied to the non-supported side by the knife edge 11' of the cutting knife 1', so that it is cut.

Normally, compression coil springs are tightly wound at the start and end of the winding. Therefore, when the wire W ₁ is cut by the cutting knife 1' and the cutting mandrel 2, the left side in the width direction of the knife edge 11' of the cutting knife 1', which is displaced downward, cuts the winding part following the last winding part of the coil C. It also contacts the upper periphery of the constituent wire _W2 . However, since the winding part is not supported by the cutting mandrel 2, if the diameter of the wire used is small or the ratio of the coil diameter to the wire diameter is large, the impact of the knife edge 11' will be absorbed by the wire W.
Wire _W2 is not affected by impact contact because it absorbs it by its own elasticity and elastic deformation in the radial direction of the coil, and even if the wire diameter is about 5 to 8 mm, it will not be affected. However, in the past, only very few dents were visible and were not considered to be a major problem.

However, in recent years, efforts have been made to improve the strength of coil springs, and the strength of wire rods with diameters of about 5 to 8 mm has been made even higher than in the past. In addition, the rigidity of the wire rod itself has increased, and the impact of the knife edge 11' that comes into contact with the uncut portion during impact cutting cannot be sufficiently absorbed, and deep dents are often left behind. Furthermore, the development of large-diameter, high-strength wire rods with excellent cold formability has progressed, and wire rods with a diameter of about 9 to 16 mm can now be coiled by cold forming. The rigidity of the coil in the radial direction has further increased, and there is a possibility that the scratches made on the uncut portion of the wire _W2 during cutting may become deep enough to become a fatal defect for the coil.

The present invention has been made to solve the above-mentioned problems, and is a cold-formed coil spring that can cut a high-strength wire rod at a predetermined cut portion without damaging the uncut wire rod, and can ensure a long service life. The present invention provides a cutting knife for use in cutting machines.

The cutting knife for cold-formed coil springs of the present invention and its usage will be explained with reference to FIGS. 2 and 3. FIG. 2 is a perspective view showing the entire configuration of the cutting knife 1, and the blade portion at one end of the cutting knife 1 is configured to have double-edged edges, which is different from the conventional knife. That is, it is composed of knife edges 11a and 11b facing oppositely to each other, and tapered portions 12a and 12b each having a predetermined clearance angle α, with the center of the width direction of opposing side surfaces 1a and 1b serving as a boundary. Therefore, the opposing sides 1a and 1b
The surfaces in contact with the knife edges 11a and 11b respectively serve as blade surfaces.

A side surface 1 that does not form a blade surface near the center and is spaced apart from the opposite end of the blade portion of the cutting knife 1 by a predetermined distance.
Shallow grooves 8 perpendicular to the longitudinal direction are cut in each of c and 1d. The grooves 8, 8 arise from extremely large reaction forces when the two sets of bolts and nuts 5a, 5b and 6a, 6b, which tighten the conventional cutting knife 1' using the cutting knife holder 4, cut the high-strength wire material. The cutting knife holder 4 will loosen in a short time due to vibration, and using a double nut or washer to prevent this is ineffective.
This is provided in order to fit the protrusion 41 therein and prevent it from becoming loose.

Figures 3a and 3b show the positional relationship when cutting the wire _W1 located at the end of the winding of the coil C using the cutting knife 1 of the present invention having the above configuration. The cutting mandrel 2 is in a position advanced to the last turn within the coil C. On the other hand, the cutting knife 1 is positioned such that the center in its width direction is on a surface including the tip end surface 21 of the cutting mandrel 2. Therefore, in this state, the wire W ₁ is sandwiched between the upper side line of the cutting mandrel 2 and the knife edge 11a of the cutting knife 1, as shown in FIG.
The wire W ₂ faces the tapered portion 12b continuous with the knife edge 11b of the cutting knife 1, and is therefore wider than the gap where the wire W ₁ faces the knife edge 11a.
In the above positional relationship, the cutting carriage 3 is rapidly driven to displace the cutting knife 1 downward.
As a result, the wire _W1 is cut by the impulsive pressing force of the knife edge 11a while being supported on the upper side periphery of the cutting mandrel 2. On the other hand, since the gap between the wire rod W ₂ and the tapered portion 12b disposed opposite thereto is wide, the cutting knife 1 is displaced downward and starts cutting the wire rod W ₁ at the initial cutting point where there is less resistance. No strong impact,
Furthermore, even if the tapered portion 12b comes into contact due to the relationship between the degree of downward displacement and the diameter of the wire at the point when the cutting of the wire W ₁ has progressed, the contact occurs because the knife edge 11a is cutting the high-strength wire W ₁ . The impact force is weakened from the initial stage of cutting, and since it is a surface contact, the impact is sufficiently absorbed by the elasticity of the wire itself and the elastic deformation of the winding part in the radial direction, and the wire W ₂ does not leave impact marks, much less scratches. In addition, even if the high-strength wire rod is cut by repeating the cutting process many times, the protrusion 41 of the cutting knife holder 4 is fitted into the groove 41 of the cutting knife 1, so that the resistance of the high-strength wire rod W is reduced during cutting. The cutting knife 1 is not tightened due to the vibration in the vertical direction caused by the resulting repulsive force, and can withstand continuous use for a long time.

The effects of using the cutting knife according to the present invention are as follows: (1) It is possible to cut the wire at the end of the coil winding without damaging the uncut wire at all, so there are no defects in the manufactured cold-formed coil spring. (2) The impact force caused by the downward displacement of the cutting knife is concentrated on half the width of the cutting knife and is stronger than before, so the cutting force increases; (3) Moreover, the cutting process (4) Furthermore, the area to be polished when reshaping the blade is reduced when wear or chipping occurs due to repeated steps, reducing the time for reshaping and reducing the loss of polishing margin. (5) Since the cutting knife can be attached to the cutting carrier upside down and the other knife edge can be used, it is possible to double the number of cutting cycles of the cutting knife. Since there is no loosening of the cutting knife, the time required to correct the loosening is saved compared to when using a conventional cutting knife, making it possible to cut more efficiently.

[Brief explanation of the drawing]

Figure 1a is a perspective view showing the shape of the blade of a conventional cutting knife and the shape of a cutting mandrel, as well as the positional relationship between the two, and Figure 1b is a diagram of a cutting mechanism for explaining the drawbacks of conventional cutting knives. 2 is a front view, FIG. 2 is a perspective view showing the structure of the cutting knife of the present invention, and FIGS. 3a and 3b are a front view and a partial side view, respectively, of a cutting mechanism to which the cutting knife of the present invention is attached. 1... Cutting knife, 1a, 1b... Blade surface, 11a,
11b...knife edge, 12a, 12b...tapered portion, 2...cutting mandrel, 3...cutting carriage, 4...cutting knife holder, 41...protrusion,
8...Groove, C...Coil spring, α...Predetermined clearance angle of tapered part, _W1 ...High strength wire material at the end of winding.

Claims (1)

[Scope of Claims] 1. In a knife for cutting the winding end of a high-strength wire material formed into a coil, the blade portions of the knife are arranged in opposite directions with the center of the width of each opposing side surface as the border. A cutting device for a cold-formed coil spring, comprising a knife edge and a tapered portion having a predetermined relief angle continuous with each of the knife edges, and each surface of the opposing side surfaces in contact with the knife edge is a blade surface. knife. 2. In a prismatic knife that cuts the winding end of a coiled high-strength wire rod that is fixed to the cutting holder via the protrusion of the cutting knife holder that is tightened to the cutting carrier with a tightening tool, one of the knives The blade portion at the end is composed of knife edges that are oriented in opposite directions with respect to the widthwise center of each of the opposing side surfaces, and a tapered portion that has a predetermined clearance angle and continues to each of the knife edges, Each surface in contact with the knife edge is a blade surface, and a shallow groove in the width direction into which the protrusion of the cutting knife holder can be inserted is formed on each side that is different from the side surface where the blade surface is formed and is spaced apart from the other end by a predetermined distance toward the center. A cutting knife for cold-formed coil springs, characterized in that the cutting knife is formed into a cold-formed coil spring.