JPH0515936A - Device for preventing fluctuation in length under neck of work in header - Google Patents

Abstract

PURPOSE:To decrease the fluctuations in the size in the shaft part, i.e., the length under neck, of a work having a large-diameter head part at the front end of the stem part after molding. CONSTITUTION:A plunger 26 is pushed in and the volume of a hydraulic chamber 35 decreases when a moving die 5 is retreated against the energization of a hydraulic cylinder 2 by striking of a punch 16 at the time of molding, but the pressure of working fluid is kept constant by the effect of an accumulator 45 and, therefore, the energizing force does not change during the retreat of the moving die 5. The energizing force can be set at an exact value by a pressure gage and has no possibility that the energizing force changes over a long period of time. Since the oil pressure is utilized as the means for energizing the moving die 5, the energizing force can be kept always constant with high accuracy and the fluctuations in the size of the length L under the neck of the work a after molding are extremely decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hedder for cylindrically molding a shaft portion of a work having a large-diameter head formed at the front end of the shaft portion. The present invention relates to a device for preventing variation in the length, that is, the length under the neck.

[0002]

2. Description of the Related Art As one of headers for molding a shaft of a work having a large diameter head formed at the front end of the shaft into a cylindrical shape, a movable die having a molding hole formed in the front surface of a die holder. To the die holder by freely moving forward and backward with a constant stroke in the axial direction of the forming hole and biasing it forward, and fix it to the die holder with a forming pin with a smaller diameter than the forming hole inserted from the rear into the forming hole. , The front end of the shaft is fitted with the shaft of the work into the molding hole of the movable die that has been moved forward by urging, and the head of the work is engaged with the front surface of the movable die. From the stopped state, the punch is pressed to move the work together with the movable die against the urging force to push the work backward, so that the shaft of the work is pierced by the molding pin at its rear end surface. Inserted in the gap between the molding pin and the molding hole. It is used those to be formed into a predetermined under-neck length of the tubular by Rukoto.

[0003]

In the above-mentioned header, in order to make the length dimension of the shaft portion of the pressure-formed work, that is, the length under the neck, constant, the movable die is attached to the front. It is necessary that the force exerted is always constant during the retreat and that the retreating speed of the movable die when the punch is pressed is appropriate.

However, conventionally, as a means for urging the movable die forward, a method of mounting a compression coil spring on the rear side of the movable die and utilizing the elastic force thereof has been adopted.

In a conventional header using this compression coil spring, since the elastic expansion force changes due to the compression coil spring bending as the movable die moves back and forth, the biasing force must be kept constant. I can't. Further, since the spring constant of the compression coil spring has a slight variation among the individual compression coil springs, the biasing force to be set is slightly different for each movable die. Further, since the compression coil spring is unavoidably settled due to aging, the biasing force gradually decreases as it is used over a long period of time.

As described above, in the conventional header using the compression coil spring, the biasing force cannot always be kept constant, and there is a drawback in that the dimension of the neck length of the molded work is large. .. Therefore, there has been a demand for a means capable of suppressing the variation in the dimension of the length under the neck.

[0007]

As a means for solving the above problems, the present invention provides a hydraulic chamber formed in a body behind a movable die, and a plunger having a front end protruding from the body in the front-back direction. A hydraulic cylinder, which is structured so that it can be slid freely and is urged forward by the pressure of the hydraulic oil in the hydraulic chamber to be fitted, is fixed to the hydraulic cylinder. An accumulator that absorbs pressure fluctuations is connected, and the movable die is biased forward by pressing the plunger from the rear by the pressure of hydraulic oil in the hydraulic cylinder.

[0008]

According to the present invention having the above-mentioned structure, when the movable die is pushed backward against the bias of the hydraulic cylinder while forming the work by the punching pressure,
As the movable die is retracted, the plunger is pushed into the body. Even if the volume of the hydraulic chamber decreases due to the pushing of the plunger, the pressure of the hydraulic oil is kept constant because the fluctuation is absorbed by the operation of the accumulator. Therefore, the work is formed while the movable die is retracted while being constantly urged with a constant force.

Further, when the punch retracts after forming, the movable die advances to the original position before forming by the bias of the hydraulic cylinder. At this time, even if the volume of the hydraulic chamber increases as the plunger projects, the pressure of the hydraulic oil is kept constant by the operation of the accumulator.

As described in the above operation, the device of the present invention utilizes the hydraulic pressure maintained at a constant pressure as the means for urging the movable die forward. Unlike the case where the expansion force is used, the biasing force can be kept constant with high accuracy at all times during the forward and backward movement of the movable die and during long-term use. It is possible to make the movable die of the above-mentioned uniform with high accuracy. As a result, there is an effect that it is possible to suppress a slight variation in the dimension of the under-neck length of the molded work.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. A die holder 2 including a guide cylinder 3 and a rear block 4 fitted in the rear part of the guide cylinder 3 is fixed to the frame 1. In the guide cylinder 3 of the die holder 2, a movable die 5 formed by forming a molding hole 6 on the front surface is tightly fitted and freely movable in the axial direction of the molding hole 6 in the longitudinal direction. , Movable dice 5
The forward movement is prevented by bringing the front surface of the collar portion 7 formed on the outer circumference of the rear end portion into contact with the stopper 9 formed on the inner circumference of the guide cylinder 3.

The molding hole 6 of the movable die 5 is opened at the rear end surface of the movable die 5 through the accommodation hole 10.
Inside the molding hole 6, the outer diameter dimension is smaller than that of the molding hole 6, and the front end of the molding pin 15 fixed to the rear block 4 by the retainer 13 and penetrating the accommodation hole 10 forms an axis line with the molding hole 6. It is inserted in a matched state.

In front of the movable die 5, a punch 16 is reciprocally driven in a direction of approaching and separating from the movable die 5.
Are provided facing each other.

The header having the above structure is formed in the forming hole 6 of the movable die 5 projecting forward to a position where it comes into contact with the stopper 9 by the urging means described later, as shown in FIG. The shaft portion b of the work a molded in a shape in which the large diameter head c is formed at the front end of the shaft portion b is inserted, and the step portion of the head c of the work a is locked to the front surface of the movable die 5. Then, by driving the punch 16 toward the movable die 5 side from such a state, the movable die 5 is pushed rearward against the bias and the head c of the work a is moved as shown in FIG. A shallow blind hole d is formed on the front surface by pressing, and the shaft portion b of the work a is pierced by the molding pin 15 at its rear end surface so that the molding pin 15 and the molding hole 6 are formed.
It is adapted to be formed into a tubular shape by being fitted in the gap between the and.

The work a molded in this way
In the next step, a through hole reaching from the hollow e of the shaft portion b to the blind hole d is formed.

In the above-mentioned molding step, in order to reduce the variation in the dimension of the shaft portion b after molding, that is, the dimension L of the under-neck length, it is necessary that the force for urging the movable die 5 is always constant. However, the header of the present embodiment is provided with a biasing means capable of keeping the biasing force always constant with high accuracy. The structure will be described below.

A hydraulic cylinder 20 is fixed to a frame 21 behind the rear block 4 of the die holder 2. This hydraulic cylinder 20 has a body 24 formed by fixing a rod cover 22 and a head cover 23 on both front and rear ends.
A plurality of cylinders 25 are arranged and fitted at a plurality of positions concentric with the molding holes 6 of the movable die 5, and the rod cover 22 is attached to the front end of the piston 27 that slides in the cylinder 25 in the front-back direction for each cylinder 25. It has a structure in which a plunger 26 formed by fixing a rod 28 that penetrates and projects to the front is fitted.

At the front end of the rod 28 of the plunger 26, there are push rods 30 penetrating through the rear block 4 of the die holder 2 and the rear plate 29 fixed to the rear surface of the rear block 4 so as to freely slide in the front-rear direction. The rear ends are in contact with each other, and the front ends of these pushing rods 30 are brought into contact with the rear surface of the movable die 5.

Further, each cylinder 25 of the hydraulic cylinder 20
A space on the rear side of the piston 27 is connected to a hydraulic chamber 35, and these hydraulic chambers 35 are communicated with each other by a circular communication chamber 36 formed in the head cover 23. The chamber 36 has a head cover 23.
A port 37 that is open to the outer periphery of is formed.

At the port 37 of this hydraulic cylinder 20,
An operating hydraulic pressure source 42 is connected through a pipe 41 provided with an opening / closing valve 40, and the operating oil pressure-fed from the operating hydraulic pressure source 42 to the hydraulic cylinder 20 side has a pressure of By closing the opening / closing valve 40 when reaching a predetermined high value, the hydraulic chamber 35 of the hydraulic cylinder 20 and the communication chamber 36 and the portion of the pipe 41 between the opening / closing valve 40 and the port 37 are filled. I'm running.

On-off valve 40 and port 37 of this pipe 41
An accumulator 45 is connected to a position between and, and when the volume of the hydraulic chamber 35 of the hydraulic cylinder 20 changes, a corresponding operating chamber (not shown) in which nitrogen gas of a predetermined high pressure is filled in the accumulator 45. The pressure of the hydraulic oil is kept constant by changing the volume of.

Next, the operation of this embodiment will be described. The plunger 26 of the hydraulic cylinder 20 receives a force that constantly pushes the pushing rod 30 forward by the pressure of the hydraulic oil acting on the piston 27, and pushes the pushing force of the plunger 26. Therefore, the movable die 5 is biased forward.

When the work a is formed, the movable die 5 is retracted from the position shown in FIG. 1 to the position shown in FIG. 2 against the bias of the hydraulic cylinder 20 by the pressing force of the punch 16. As a result, the plunger 26 moves into the cylinder 2.
It is pushed into 5. Along with this, the volume of the hydraulic chamber 35 decreases, but at the same time, the volume of the working chamber of the accumulator 45 also decreases, so that the pressure of the working oil, that is, the urging force acting on the movable die 5 is reduced while the movable die 5 is retracted. The size is kept constant with high precision. Therefore, the dimensional accuracy of the neck length L is high in any of the formed workpieces a.

When the movable die 5 advances due to the urging of the hydraulic cylinder 20 as the punch 16 retreats after forming, the volume of the hydraulic chamber 35 increases as the plunger 26 projects. However, since the pressure of the hydraulic oil is kept constant by the operation of the accumulator 45, the magnitude of the biasing force when the movable die 5 is returned to the position shown in FIG. 1 is always constant.

In the method of urging with the hydraulic cylinder 20, the urging force during the molding process can be kept constant with high accuracy as described above, and in addition, the pressure gauge is used. The magnitude of the biasing force can be accurately set with high accuracy, and a constant biasing force can be maintained for a long period of time. Therefore, work a
The variation in the length L under the neck is extremely small.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a header before molding.

FIG. 2 is a cross-sectional view of a state after completion of molding.

[Explanation of symbols]

2: Die holder 5: Movable die 6: Forming hole 1
5: Molding pin 16: Punch 20: Hydraulic cylinder 2
4: body 26: plunger 35: hydraulic chamber 45: accumulator a: work b: shaft c: head L:
Head of neck

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B30B 1/34 A 7819-4E

Claims (1)

Claim: What is claimed is: 1. A movable die having a molding hole formed on the front surface thereof is attached to a die holder by freely advancing and retracting a predetermined stroke in the axial direction of the molding hole and urging it forward. ,
A molding pin having a diameter smaller than that of the molding hole is fixed to the die holder in a state of being inserted into the molding hole from the rear, and the shaft portion of the work having a large-diameter head formed at the front end of the shaft portion is attached to the die holder. From the state in which the head of the workpiece is locked to the front surface of the movable die while being fitted into the forming hole of the movable die moved forward by the force, the movable die is pressed by the punch. At the same time, by pushing the work backwards against the bias, the shaft of the work is fitted into the gap between the forming pin and the forming hole so that the rear end face of the forming pin is pierced. In a header so as to be formed into a tubular shape having a predetermined length below the neck, in the hydraulic chamber formed in the body behind the movable die,
A hydraulic cylinder having a structure in which a plunger having a front end protruding from the body is freely slidable in the front-rear direction and is biased forward by the pressure of hydraulic oil in the hydraulic chamber is fixedly installed, and the hydraulic pressure is fixed. The cylinder is connected with an accumulator that absorbs the pressure fluctuation of the hydraulic oil due to the protrusion and push-in of the plunger, and the pressure from the hydraulic oil of the hydraulic cylinder pushes the plunger from the rear side to move it forward of the movable die. A device for preventing variation in the neck length of a work in a header that is urged.