JP3868086B2 - Method for producing synthetic resin hollow coil spring - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a hollow coil spring made of synthetic resin used as a coil spring.
[0002]
[Prior art]
Conventionally, metal springs have been widely used as coil springs. However, since metal spiral bodies are prone to rust and corrosion, synthetic resin coil springs have come to be desired. In order to satisfy the demand, the inventors have also developed a method for producing a synthetic resin spiral body as described in, for example, Japanese Patent Publication No. 64-4900. In this method of manufacturing a synthetic resin helical body, a synthetic resin linear material having a circular cross section in a semi-molten state is wound around the outer peripheral surface of a molded rotating shaft body in the axial direction while being spirally wound at a desired pitch. In addition, it is characterized in that it is cured during its movement.
[0003]
[Problems to be solved by the invention]
However, when a synthetic resin linear material in a semi-molten state is wound around the rotating shaft for molding, the synthetic resin linear material may be deformed into a flat shape due to the winding force. Not only is it difficult to manufacture, but if a large diameter coil spring is manufactured using a thick wire material, the material cost will rise and it will be uneconomical, and the weight will increase and there will be a problem with handling. A point is created. In addition, in order to reduce the weight of the product and obtain a large-diameter coil spring, a hollow semi-molten resin pipe can be spirally wound around a molding rotary shaft while being extruded instead of a linear material. Although it is conceivable, the larger the diameter of the semi-molten resin pipe, there is a problem that the cross section easily deforms into a flat shape when it is wound around the rotating shaft body for molding and cannot be commercialized.
[0004]
On the other hand, when a ready-made hard synthetic resin tube is spirally wound around a rotating shaft for molding, a large-diameter coil spring can be obtained without flattening the cross section as described above. When the synthetic resin tube is wound around the rotating shaft body for molding, the synthetic resin tube body tries to expand its diameter by its elastic restoring force, and therefore slip occurs between the rotating shaft body for molding and the shaft center. Even if the synthetic resin tube wound around the molding rotating shaft is pressed from the outside against the molding rotating shaft by the pressing roller, it is molded even if it is moved in the axial direction. When it is detached from the rotary shaft body for use, there is a problem that a springback occurs and the product cannot be produced.
[0005]
The present invention has been made in view of such problems, and an object of the present invention is to provide a method for producing a hollow coil spring made of a synthetic resin capable of efficiently and reliably producing a coil spring having a hollow cross section. .
[0006]
[Means for solving the problems]
In order to achieve the above object, a synthetic resin hollow coil spring manufacturing method according to claim 1 of the present invention is a semi-molten synthetic material extruded from a molding die into a flexible ready-made rigid synthetic resin bellows tube. A semi-molten synthetic resin-coated tube body is formed by coating a resin pipe body, and the semi-molten synthetic resin-coated tube body is continuously supplied to the molding rotary shaft body to obtain an outer peripheral surface of the molding rotary shaft body. The semi-molten synthetic resin-coated tube is cured while being spirally wound and moved in the length direction of the molding rotary shaft according to the rotation of the molding rotary shaft.
[0007]
[Action]
When extruding a semi-molten synthetic resin pipe body from a molding die of an extruder, this hard synthetic resin bellows is fed into the pipe body so as to insert a ready-made hard synthetic resin bellows pipe having a hollow inside. the tube with a predetermined pitch in the molding rotary shaft on the body while forming a semi-molten synthetic resin cladding body coated with synthetic resin pipe in a semi-molten state wound helically. At this time, the semi-molten synthetic resin cladding body interior and along which the circular cross section of the holding and rigid synthetic resin bellows tube by hard synthetic resin bellows tube of ready-made to the molding rotary shaft on as its core The semi-molten synthetic resin pipe, which is a covering portion, is wound spirally while being bent and deformed to form an uncured spiral body.
[0008]
Then, the uncured helical body moves in the axial direction according to the rotation of the molding rotating shaft, and the semi-molten synthetic resin pipe body of the covering is cured during the movement. By causing the coating portion to be in close contact with the molding rotary shaft body, the inner peripheral surface of the cured spiral body attempts to reduce the diameter by the rotation of the molding rotary shaft body. It is fixed to the outer peripheral surface of the mold and smoothly moves in the axial direction according to the rotation of the molding rotary shaft body without slipping, and the uncovered spiral body is surely placed on the molding rotary shaft body. It can be spirally wound.
[0009]
Thus, when the helical body having the coating portion hardened on the molding rotary shaft body is fed out from the molding rotary shaft body, the hard coating portion prevents the internal hard synthetic resin bellows tube from springing back. A hollow coil spring having a certain diameter can be obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A specific embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, an extrusion molding machine 2 is disposed on one side of a rear end portion (base end portion) of a rotary shaft 1 for molding, A semi-molten synthetic resin pipe body 4 having an annular cross section having a constant diameter is extruded from the molding die 3 of the extrusion molding machine 2 and the outer diameter of the semi-molten synthetic resin pipe is from the back side into the extrusion molding machine 2. The hollow tube body made of a ready-made hard synthetic resin bellows tube 5 having a diameter smaller than the outer diameter of 4 and having a flexibility equal to or slightly larger than the inner diameter is continuously supplied and extruded from the molding die 3. A semi-molten synthetic resin-coated tube body in which the pre-made hard synthetic resin bellows tube 5 is inserted into the semi-molten synthetic resin pipe 4 and the semi-molten synthetic resin pipe 4 serves as a covering portion of the core body. While forming A, it is supplied toward the rotating shaft 1 for molding.
[0011]
At the time of forming the semi-molten synthetic resin-coated tube A, when the hard synthetic resin bellows tube 5 is inserted into the semi-molten synthetic resin pipe 4 in the molding die 3, the semi-molten synthetic resin pipe 4 As shown in FIG. 2, the inner layer portion is in a state of being filled in the concave portion of the hard synthetic resin bellows tube 5 bent in a continuous uneven shape in the length direction. That is, the outer peripheral surface of the semi-molten synthetic resin pipe 4 has the same diameter over its entire length, but its thickness is thick at the concave portion of the ready-made hard synthetic resin bellows tube 5 and thinly covered at the convex portion. .
[0012]
The semi-molten synthetic resin-coated tube body A is formed of a hard synthetic resin bellows tube 5 made of a hard resin, which has a core body formed on the molding rotary shaft 1 from one side with respect to the molding rotary shaft 1. A hollow spiral body A1 in which the covering portion is uncured is formed by being wound spirally at a predetermined pitch while being curved. At this time, since the ready-made hard synthetic resin hollow tube forming the core body is composed of a flexible bellows tube, the semi-molten synthetic resin-coated tube body A is formed while being held in an annular cross section. It can be easily bent and wound in the circumferential direction on the rotating shaft 1. The molding rotary shaft 1 is configured to rotate in the direction of winding the semi-molten synthetic resin-coated tube A and move the wound hollow spiral body A1 in the axial direction, as will be described later. is doing.
[0013]
In this way, the semi-molten synthetic resin-coated tube body A is spirally wound around the molding rotary shaft body 1 to form the hollow spiral body A1 whose coating portion is uncured and the molding rotary shaft body 1 The hollow helical body A1 is moved forward in the axial direction of the molding rotary shaft 1 in accordance with the rotation of the semi-molten synthetic resin pipe 4 forming the covering portion of the hollow helical body A1 during the movement. When cured, a hollow coil spring A2 is obtained in which the synthetic resin pipe 4 is integrally fixed to the outer peripheral surface of a ready-made hard synthetic resin bellows pipe 5 that is spirally curved.
[0014]
When the semi-molten synthetic resin pipe 4 is cured, the ready-made hard synthetic resin bellows pipe 5 which is the core is formed by the hardened synthetic resin pipe covering the hard synthetic resin bellows pipe 5 to form a rotating shaft. The hollow coil is fixed in a state of spiral winding with a constant diameter along the outer peripheral surface of 1 and does not expand the entire hollow coil spring A2 by the elastic restoring force of the hard synthetic resin bellows tube 5, and the covering portion is hardened. The inner circumferential surface of the spring A2 is in close contact with the molding rotary shaft 1.
[0015]
Therefore, the hollow coil spring A2 is rotated in the direction of tightening the molding rotary shaft 1 by the rotation of the molding rotary shaft 1, that is, while being integrally rotated with the molding rotary shaft 1 while being attracted in the diameter reducing direction. Since it advances on the rotating shaft 1 and draws the subsequent spiral body A1 whose coating portion is uncured by the advancement, the semi-molten synthetic resin-coated tube body A is extruded through the uncured spiral body A1. While being drawn out from the machine 2, it can be continuously spirally wound on the rotary shaft 1 for molding. When the covering portion of the spiral body A1 is cured, a pressing roller is formed that positively presses the spiral body immediately after the curing, that is, the inner peripheral surface of the coil spring A2 on the molding rotating shaft 1. You may arrange | position in the outer peripheral side of the rotary shaft body 1 for a use.
[0016]
In this way, a hollow coil in which the ready-made hard synthetic resin bellows tube 5 as the core is fixed with a constant diameter by curing the semi-molten synthetic resin pipe 4 as the covering portion on the rotating shaft 1 for molding. The spring A2 can be formed and the flexibility of the hard synthetic resin bellows tube 5 is lost by the coating resin made of the synthetic resin pipe 4 integrally cured on the outer peripheral surface of the hard synthetic resin bellows tube 5. A coil spring A2 that exhibits a predetermined spring force is formed. The coil spring A2 is fed forward from the front end of the molding rotary shaft 1 and is cut by a cutter (not shown) each time a desired length is fed. A hollow coil spring having a predetermined diameter and having a predetermined length that does not cause a spring back by being cut is obtained.
[0017]
In the above embodiment, the bellows tube 5 is used as a ready-made synthetic resin tube inserted into the semi-molten synthetic resin pipe 4, but it is possible to use a bellows tube as shown in FIG. Any synthetic resin hollow tube 5 ′ having flexibility and shape retention may be used. Also, as the semi-molten synthetic resin pipe 4 extruded from the molding die 3 and the ready-made rigid synthetic resin pipe body inserted into the semi-molten synthetic resin pipe 4, suitable materials such as hard vinyl chloride, polyethylene, and polypropylene are used. Any material made of hard synthetic resin may be used. In this case, as described above, when the ready-made hard synthetic resin bellows tube 5 is used, the inner layer portion of the semi-molten synthetic resin pipe 4 is cured in the concave portion bent into the continuous irregular shape of the bellows tube. Therefore, even if the hard synthetic resin bellows tube 5 and the semi-molten synthetic resin pipe 4 are made of a synthetic resin that is difficult to adhere to each other, an integrated hollow coil spring A2 can be formed.
[0018]
As shown in FIG. 1, the synthetic resin hollow coil spring manufacturing apparatus has a plurality of molding rotary shafts 11 arranged at regular intervals on a virtual cylinder in a machine frame 10 incorporating a rotation drive mechanism. The base end (rear end) of the molding rotary shaft 1 configured as described above is rotatably supported, and each molding rotary shaft 11 has the same angle and angle as to the axis of the virtual cylinder. The semi-molten synthetic resin-coated tube A supplied onto the molding rotary shaft 1 is wound at a predetermined helical pitch by rotating these molding rotary shafts 11 in the same direction at the same time. The wound helical body A1 is configured to move in the axial direction of the molding rotary shaft 1.
[0019]
Each of the molding rotary shafts 11 constituting the molding rotary shaft body 1 is rotatably supported by a bearing 13 whose base end portion is movably arranged in the radial direction on the machine frame 10 via a universal joint 12. In addition, it is connected to gears 23 of meshing gears that are simultaneously rotated in the same direction by a drive motor 16 through a short shaft 15 having a universal joint 14 disposed in the machine frame. Further, a support shaft 17 is arranged at the axis of the virtual cylinder so that the base end portion of the support shaft 17 is supported by the machine frame 10, and a screw mechanism is provided between the base end portion and the front end portion of the support shaft 17. Sliding pieces 19 and 20 that can be moved in the front-rear direction by operating 18 are fitted, and the base end bearing 13 of each molding rotary shaft 11 and the rear sliding piece 19 are connected by a connecting rod 21. At the same time, the tip bearing portion and the front sliding piece 20 are similarly connected by a connecting rod 22. The front sliding piece 20 is configured to be rotatable and fixed around the support shaft 17.
[0020]
With this configuration, when the front and rear sliding pieces 19 and 20 are moved back and forth on the support shaft 17 by rotating the screw mechanism 18, all the rotating shafts for molding are connected via the connecting rods 21 and 22. 11 moves in the radial direction to change the diameter of the molding rotary shaft 1 (the virtual cylinder) to be larger or smaller, and therefore the diameter of the synthetic resin hollow coil spring A2 to be manufactured can be changed. Further, when the front sliding piece 20 is rotated by a desired angle around the support shaft 17, the inclination angle changes in the circumferential direction from the proximal end side to the distal end side of each molding rotary shaft 11, and the composite to be manufactured The helical pitch of the resin hollow coil spring A2 can be changed.
[0021]
In addition, according to this manufacturing apparatus, a synthetic resin hollow coil spring having a diameter of 1 meter or more can be easily manufactured. The hollow coil spring may be appropriately changed in diameter and thickness of the semi-molten synthetic resin pipe 4 and the hard synthetic resin bellows pipe 5 according to its diameter, strength, elasticity, and the like.
[0022]
Further, without using the manufacturing apparatus as described above, for example, a plurality of long rollers that rotate in the spiral feed direction are arranged at predetermined intervals in the circumferential direction on the peripheral surface of a shaft body having a constant diameter. The semi-molten synthetic resin-coated tube A may be spirally wound on a long roller, or the semi-molten synthetic resin-coated tube A may be spirally wound on the rotating shaft while moving the rotating shaft in the axial direction. A hollow coil spring may be formed by winding.
[0023]
【The invention's effect】
As described above, according to the method for producing a hollow coil spring made of a synthetic resin of the present invention, a semi-molten synthetic resin pipe body extruded from a molding die is coated on a flexible hard synthetic resin bellows pipe having flexibility. To form a semi-molten synthetic resin-coated tube body, continuously supply the semi-molten synthetic resin-coated tube body to the molding rotary shaft body, and spirally wrap the outer peripheral surface of the molding rotary shaft body. Since the semi-molten synthetic resin-coated tube is cured while moving in the length direction of the molding rotary shaft according to the rotation of the molding rotary shaft, When spirally wound around a molding rotary shaft body, it can be spirally wound with high accuracy while the cross section is securely held in an annular shape by an already- made hard synthetic resin bellows tube , and further, the molding rotary shaft Move on the body While constant by curing the synthetic resin pipe semi-molten state covering the hard synthetic resin bellows tube, with the interior of the ready-made hard synthetic resin bellows tube is blocked from attempting to spring back It can be fixed as a synthetic resin hollow coil spring having a diameter.
[0024]
In this way, a synthetic resin coil spring having a hollow interior can be accurately manufactured, and the diameter of the rotary shaft body for molding and a ready-made hard synthetic resin constituting a semi-molten synthetic resin-coated tube according to the diameter By changing the diameter and wall thickness of the bellows tube and the semi-molten synthetic resin pipe, it is possible to efficiently produce a synthetic resin hollow coil spring having a large diameter of 50 cm or more. Since it is hollow, material costs can be saved, and it is lightweight and easy to handle, and can be used in various applications as a large-diameter synthetic resin hollow coil spring that does not cause rust or corrosion. Is.
[0025]
Further, since the above-described flexible hard synthetic resin tube body having flexibility is a bellows tube, a semi-molten synthetic resin-coated tube body obtained by coating this hard synthetic resin bellows tube with a semi-molten synthetic resin pipe. In a state where the flexibility is good and the cross-sectional shape is maintained, spiral winding around the rotary shaft for molding can be easily and efficiently performed. When hardened, the hardened synthetic resin pipe and the ready-made hard synthetic resin bellows tube are integrated so that the flexibility of the hard synthetic resin bellows tube disappears, and a synthetic resin hollow coil that exhibits the desired spring force A spring can be obtained.
[Brief description of the drawings]
FIG. 1 is a simplified vertical side view of a state where a synthetic resin hollow spiral body is manufactured,
FIG. 2 is a partially cutaway perspective view of a semi-molten synthetic resin-coated tube,
FIG. 3 is a perspective view of a part of a semi-molten synthetic resin-coated tube having another structure;
FIG. 4 is a side view of a part of the obtained hollow coil spring.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotary shaft body for shaping | molding 2 Extruder 3 Molding die 4 Semi-molten synthetic resin pipe 5 Hard synthetic resin bellows pipe A Semi-molten synthetic resin coated pipe body
A2 Synthetic resin hollow coil spring

Claims (1)

A semi-molten synthetic resin-coated tube body is formed by coating a semi-molten synthetic resin pipe body that is extruded from a molding die on a flexible hard synthetic resin bellows pipe that has flexibility. The tube body is continuously supplied to the molding rotary shaft body, spirally wound around the outer peripheral surface of the molding rotary shaft body, and moved in the length direction of the molding rotary shaft body according to the rotation of the molding rotary shaft body. A method for producing a synthetic resin hollow coil spring characterized by curing a semi-molten synthetic resin-coated tube body.

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