JPH10314852A - Work tail end holding device in tensile bending device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To firmly and surely hold the tail end of a hollow work without generating slip even in case of being applied with a large tensile force in the axial direction of the work when the tail end part of the hollow work is held with a hooking structure and it is executed with tensile bending. SOLUTION: This device is composed so that both end parts of a long size hollow work W are held, the work W is pressed to a bending die while a tensile force is applied and the work W is bent. In this case, a diameter spreading step part W4 is formed on the tall end part W1 of the work W, a holding part 1 to hold the tail end part of the work is composed of an inner face holding member 2 facing to the work inner face, an outer face holding member 7 facing to the outer face of the work and on the opposite face of the inner face holding member 2 and the outer face holding member 7, step parts 6, 11 corresponding to the step part W4 are installed, the work tail end part W is faced between the inner face holding member 2 and the outer face holding member 7 and the work tail end part W1 is held with the inner face holding member 2 and the outer face holding member 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gripping device for gripping a terminal portion of a workpiece in a tension bending apparatus which pulls a workpiece against a bending mold while pressing the workpiece and bends the workpiece along the bending mold. .

[0002]

2. Description of the Related Art Tension bending in which a workpiece is pressed against a bending mold while both ends of the workpiece are stretched to bend the workpiece is described, for example, in Japanese Patent Application Laid-Open No. 59-39423, and in Japanese Utility Model Laid-Open No. 1-80214. Known as the technology. This technology grips both ends of a long workpiece,
The work is pressed against a bending mold while applying a tensile force to the work, and the work is bent into a shape along the bending mold.

[0003] In the above-mentioned tension bending work, both ends of a long work are gripped, a predetermined tensile force is applied in the axial direction of the work, the work is pressed against a bending mold, and the work is formed into a shape along the bending mold. To bend. Therefore, the workpiece is bent while applying a tensile force in the axial direction while gripping both ends of the work. Therefore, it is necessary to firmly and firmly grip both ends of the work.

[0004] In the above, unless the both ends of the work are firmly gripped, slipping occurs in the gripping portion of the work, and a predetermined tensile force cannot be applied to the work. Also, when slippage occurs, the dimensional accuracy of the tensile bending may be reduced.

[0005] In the above-mentioned tensile bending, if the work is hollow, there is no clue at the end of the work.
It is difficult to firmly hold the work terminal. Conventionally, Japanese Patent Application Laid-Open No.
No. 322825 is disclosed.

[0006]

SUMMARY OF THE INVENTION
The claw pieces are provided radially inside and outside, and are provided with inner and outer members in the form of collet chucks. The end of the hollow work is inserted between the inner and outer members having the cracked claw shape, and the pressing member facing the outer periphery of the cracked claw-shaped outer member is moved in the axial direction to reduce the diameter of the outer member. On the other hand, the diameter-expanding element faces the inside of the cracked claw cylindrical inner member and is moved in the axial direction to expand the diameter of the inner member. The structure is such that the work terminal portion is held by reducing and increasing the diameter of the inner and outer members.

In the above-mentioned technique, the gripping of the hollow work terminal portion is a holding structure in which the inner and outer members having a cracked claw shape are reduced in diameter and expanded in diameter, so that the work terminal is gripped by friction on the surface. Therefore, when a large bending force is applied to a workpiece to perform tensile bending, friction and gripping occur.
There is a possibility that the work terminal may slip. Also, in order to firmly grip the workpiece by friction, it is necessary to increase the length of the grip portion of the work terminal portion (the chucking length of the work). It may become longer, and the material yield may deteriorate.

As described above, even if the length of the gripping end portion of the workpiece is increased, the possibility of slippage cannot be eliminated because of the gripping structure by friction. Also, when a collet chuck type claw is strongly pressed between the workpiece, a large reaction force is generated, and the rigidity of the apparatus is extremely high due to the reaction force reception. To prevent deformation due to crushing of the bent part of the work in tension bending, and to perform high precision processing while properly maintaining the cross section of the bent part, it is necessary to insert a core metal into the work. preferable. When inserting such a core into the work,
According to the technique, since the expander is inserted into the cracked claw-shaped inner member and is moved in the axial direction, it is difficult to insert the core metal from the gripping portion, and the workpiece is bent using the core metal. Comes with difficulty.

The above-mentioned conventional device for gripping the end of a hollow work requires a collet chuck-type inner and outer member, a diameter reducing device for an outer member, a driving device therefor, a diameter expanding device for an inner member, a driving device therefor, and the like. There are many components and the structure is complicated.

[0010] The present invention has been made to solve the above-mentioned problems in gripping a terminal portion of a hollow work. The object of the present invention is, first, the end portion of the hollow work is gripped by a hook structure, and during tensile bending, even if a large tensile force is applied in the axial direction of the work, without causing slip, Provided is a gripping device that can reliably grip a hollow work terminal. Further, the grip length of the end portion of the work is short, and the material yield is good. Further, the present invention provides a gripping device that has a simple structure, has few components, and is simple as a whole. Further, in the tensile bending of the hollow work, when inserting the core into the work, the space for inserting the core and the rod for moving the core can be easily obtained, and the tensile bending can be easily performed using the core. It is another object of the present invention to provide a gripping device capable of performing the above-mentioned operations.

[0011]

In order to solve the above-mentioned problems, a first aspect of the present invention is to hold both ends of a long hollow work,
By applying a tensile force to the work and pressing it against a bending mold, in a tensile bending apparatus configured to perform a bending process on the work, an enlarged diameter step is formed at a terminal portion of the work, The gripping portion for gripping the terminal portion of the work is constituted by an inner surface holding member facing the inner surface of the work, and an outer surface holding member facing the outer surface of the work, and the inner surface holding member, and the opposite surface of the outer surface holding member, A step portion corresponding to the step portion is provided, a terminal portion of the work is made to face between the inner surface holding member and the outer surface holding member, and the work terminal portion is sandwiched between the inner surface holding member and the outer surface holding member. Thus, a terminal gripping device for a work in the tension bending apparatus was configured.

In the first aspect of the present invention, the hollow work terminal portion is provided with an enlarged diameter step portion, while the grip portion is formed of an inner and outer holding member having a step portion corresponding to the inner and outer surfaces of the work terminal portion. Since the inner and outer surfaces of the end portion are sandwiched between the inner and outer holding members, the hollow work end portion is formed by the corresponding steps of the inner and outer holding members, and the pressing of the inner and outer holding members is performed in the axial direction. Therefore, unlike the friction of mere pinching, the work terminal portion is firmly and reliably gripped.

The inner holding member having the step portion is fitted with the inner diameter of the work having the step portion, and the outer holding member having the corresponding step portion is pressed from the outside of the work terminal portion, and the inner and outer holding members are used. It is a structure that clamps the terminal portion, so that the mechanism for moving the inner holding member in the axial direction is unnecessary, and may be configured with a mechanism that presses the outer holding member in the radial direction. In addition, since a collet chuck mechanism is not required, the mechanism and structure of the gripping device are simple and sufficient, and an unreasonable reaction force is not applied to the outer holding member. Therefore, the entire apparatus is simplified in addition to the above.

Further, since it is not necessary to set the length of the work terminal portion to be large when gripping, there is little waste of material due to gripping, which is extremely advantageous in material yield, and is economically favorable.

According to a second aspect of the present invention, in the first aspect, the inner surface holding member is provided with a core for passing the core into the work, and a rod insertion hole for the core. According to the second aspect, the core metal needs to be inserted into the work during the tensile bending process using the core metal of the hollow work, but the axial holding mechanism of the inner holding member is not required, and the inner holding member is fixed. Since the inner holding member can be a hollow member, a space for inserting the core bar and the rod for moving the core bar can be easily obtained, and the bending and bending process can be easily performed using the core bar. Can do it.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is an explanatory view showing an example of a bending device including a gripping device according to the present invention. FIG. 2 is an enlarged cross-sectional view of the gripping device according to the first embodiment of the present invention, in an open state.
3 is a cross-sectional view of a state in which a mandrel is incorporated in the holding device, FIGS. 5 to 7 are explanatory views of a tension bending process using the mandrel, and FIG. 5 is a bending process. FIG. 6 is a diagram of a state immediately before bending, FIG. 6 is a diagram of a state where bending is started, and FIG. 7 is a diagram of a state where bending is completed.

In FIG. 2, W is a long hollow work. An enlarged diameter portion W2 is formed in a portion of the work W near the end of the terminal portion W1. A stepped portion W4 inclined so as to incline upward in the end direction is provided between the enlarged diameter portion W2 of the terminal portion W1 and a portion of the original diameter portion W3 slightly smaller than the enlarged diameter portion W2 in front of the enlarged diameter portion W2. Is formed, and the enlarged diameter portion W2 and the original diameter portion W3 are connected at the step portion W4.

In FIG. 2, reference numeral 1 denotes a holding portion for a terminal portion W2 of the work W, and the holding portion 1 includes inner and outer holding members 2 and 7. The inner holding member 2 has a cylindrical shape, and is provided with a small-diameter portion 4 on the outer periphery of the cylindrical portion 3 at the axial end portion, which is closely fitted to the inner surface of the original diameter portion W3 of the work W, and the small-diameter portion 4 is It has a predetermined length in the direction.

On the base side of the cylindrical portion 3 in the axial direction, the work W
The large-diameter portion 5 closely fits with the inner surface of the large-diameter portion W2, and the large-diameter portion 5 has a predetermined length in the axial direction. A step 6 is formed between the small diameter portion 4 and the large diameter portion 5 so as to be inclined upward in the end direction. The small diameter portion 4 and the large diameter portion 5 are connected to each other at the step 6. At the end of the large diameter portion 5, a mounting flange 2a is provided.

In FIG. 2, reference numeral 7 denotes an outer holding member, and the outer holding member 7 is provided in a pair at the top and bottom in the figure. However, three or four outer holding members 7 may be provided so as to surround the work W. The upper and lower outer holding members 7, 7 have opposite surfaces in a semicircular arc shape. The opposed inner surface 8 is provided with a projection 9 corresponding to the original diameter portion W3 of the work W and the small diameter portion 4 of the cylindrical portion 3 of the inner holding member 2.

The inner surface 8 of the outer holding member 7 is provided with a concave portion 10 corresponding to the enlarged diameter portion W2 of the work W and the large diameter portion 5 of the cylindrical portion 3 of the inner holding member 2. The step 9 and the recess 10 are connected by a step W4 of the work W and a step 11 corresponding to the step 6 of the cylindrical portion 3 of the inner holding member 2. The projection 9 and the recess 10 have a predetermined length in the axial direction.

The outer holding members 7, 7 are connected to the ends of the rods 12, 12 extending in the half body direction, respectively.
The rods 12, 12 are provided so as to extend radially outward of the work W and the inner holding member 2, and are connected to a work holding cylinder unit described later.
The outer holding members 7, 7 move up and down in FIG.

FIG. 2 shows the gripping released state, in which the work W arranged on the left side of FIG. 2 is moved to the right as shown by the arrow a, and the terminal part W1 of the work W is held on the inner holding member 2 of the gripping part 1.
To the outer circumference of The enlarged diameter portion W2 of the work W fits around the large diameter portion 5 of the cylindrical portion 3 of the inner holding member 2, and has an original diameter portion W3.
Is fitted around the small diameter portion 4 of the cylindrical portion 3.

At this time, the step portion W4 faces the step portion 6 between the large and small diameter portions 4 and 5 of the cylindrical portion 3, and the back surface of the step portion W4 of the work W faces the front surface thereof. Next, the terminal portion W1 of the work W is gripped by the gripping device 1.

The gripping of the work terminal portion W1 is separated from the cylindrical portion 3 of the inner holding member 2 up and down, and the outer holding members 7 and 4 are positioned so as not to interfere with the fitting of the work W to the inner holding member 2.
7 is moved in the direction of arrow b as shown in FIG. 3 by driving a cylinder unit (not shown). Outer holding members 7, 7
Is pressed against the upper and lower surfaces of the terminal portion W1 of the work W in a state of being fitted to the cylindrical portion 3 of the inner holding member 2.

The convex portions 9 of the outer holding members 7 contact the outer peripheral surface of the original diameter portion W3 of the work terminal portion W1, and the concave portions 10 contact the outer peripheral surface of the large diameter portion W2. 7, the original diameter portion W3 and the large diameter portion W2 of the work W are pressed against the corresponding large and small diameter portions 4 and 5 of the cylindrical portion of the inner holding member 2 so that the inner and outer holding members 2 and 7 are pressed. The work terminal unit W1 is sandwiched between them.

At this time, the steps 11, 11 of the outer holding members 7, 7
11 and the stepped portion 6 provided on the cylindrical portion 3 of the inner member 2,
The step W4 of the work terminal W1 is held in the axial direction. This state is shown in FIG. FIG. 3 shows a state where the work terminal W1 is gripped. The stepped portion W4 formed between the enlarged diameter portion W2 of the work terminal portion W1 and the original diameter portion W3 having a smaller diameter than the stepped portion W4 is formed by the stepped portions 6, 11 of the inner and outer holding members 2, 7, 7.
It is sandwiched between and is regulated in the axial direction.

The other end of the work W is also gripped in the same manner, and a tensile force is applied to the work W in the axial direction opposite to the direction indicated by arrows F and F in FIG. F,
In a state where F is applied, the work W is pressed against a bending die described later, and the work W is bent along the bending die.

The tensile force F is applied to the work W during the above-mentioned tensile bending, and the terminal W1 of the work W is held by the holding members 2, 7, 7 inside and outside the gripping device 1. W1 and the inner and outer holding members 2, 7, 7
Step portions 6, 11, 11 axially sandwich the step portion W4 of the work terminal portion W1. Therefore, the work terminal unit W
In No. 1, the step portion W4 is clamped and gripped in the radial direction, and the step portion W4 is pinched by the step portions 6, 11, 11 to be restrained in the axial direction.

Therefore, the work terminal portion W1 is also restricted in the axial direction by the inner and outer holding members 2, 7, 7 so that even if a tensile force F, F is applied to the work W, the step portions W4, 6 , 11,1
The engagement of 1 locks axial sliding. Even if a large tensile force is applied to the work W, the inner and outer holding members 2, 7, 7
Gripping of the work terminal portion W1 does not depend on a large clamping force and does not require a large clamping force.
The work terminal part W1 is gripped firmly and reliably without gripping the work terminal part W1 without depending on frictional engagement and without slippage.

FIG. 1 shows a tension bending apparatus 30 and a bending die 20. The bending die 20 includes a bending radius portion 21 and may include a bending radius portion on the left side not shown in the figure. A bending device 30 is arranged adjacent to the bending die 20,
The bending apparatus 30 includes a horizontal H-shaped frame 32 on a base 31, and upper and lower horizontal bars 32a, 32a of the frame 32.
a vertical movement cylinder units 33, 33 of the upper and lower outer holding members 7, 7 are provided at the distal end of the horizontal bar 32.
a, 32a, a pulling cylinder unit 3
4,34.

The above-mentioned inner holding member 2 is fixed to a middle portion in the height direction of the frame 32b via a mounting flange 2a. The rightward operation of the tension cylinder units 34, 34 as shown by the arrow F in FIG.
The frame 32 is pulled rightward, and the outer holding members 7, 7 are moved rightward through the cylinder units 33, 33 fixed to the frame 32 side, and the inner holding member 2 fixed to the vertical bar 32b of the frame 32. Move to perform a pulling motion in the same direction.

As described above, on the base 31, the inner and outer holding members 2, 7, 7 integrally perform the pulling operation of the work W. The base 31 moves in the direction of arrow B in FIG. 1 in an arc with the bending radius 21 as a fulcrum, and the work W is bent along the bending die while being pressed against the bending die, and is shown by a solid line in FIG. 90 ° as the bending start position
The position of E indicated by the moved imaginary line is defined as the position where the bending is completed.

Next, a description will be given of a cored bar mechanism inserted into the work W when the work W is bent. Fig. 4 shows the metal core mechanism
In detail. The main body portion of the inner holding member 2 is a cylindrical portion 3. Therefore, the cylindrical portion 3 is provided with a through hole in the axial direction, and the through hole is a core metal insertion hole 13.

Insertion hole 13 formed in inner cylindrical portion 3
Is the terminal W of the work W, as indicated by the imaginary line in FIG.
1 is coaxially communicated with the inner diameter portion W5 of the work W in a state of being fitted and set on the outer periphery of the cylindrical portion 2 as described above. The cored bar device 40 is composed of a cored bar 41 at a front end portion and a plurality of pieces 43 connected to a rear portion of the cored bar 41 via a connecting bar 42. Similarly, each other is pivoted and connected by the connecting bar 42, and the final piece 43A is connected.
Is connected to the tip of the rod 45 for mandrel position control.

A bent section 44 is constituted by the above-described core bar 41, the pieces 43,..., And the bent section 44 is bent in accordance with the bending process of the work W, and the core bar 41 is closely fitted to the inner diameter of the work W. Yes, but piece 4
3 are set to diameters that do not interfere with the inner diameter portion W5 of the workpiece W during bending of the workpiece W. The inner diameter of the insertion hole 13 of the cylindrical portion 3 of the inner holding member 2 is set to be larger than the outer diameter of the pieces 43... I do.

The base 31 has a sub table 31.
A core position controlling cylinder unit 46 is provided via a, and the rod 46a of the cylinder unit 46 is connected to the core position controlling rod 45 described above. By driving the above-described cylinder unit 46, the core metal 41 is moved within the work W along the bending process to control the position thereof, and the hollow work W is subjected to tensile bending. In FIG. 1, reference numeral 47 denotes a controller that corrects the position of the core metal 41 with respect to the amount of tension or elongation of the work W because the work W is subjected to tensile bending.

The bending apparatus 30 is moved from the start position of S to the processing end position of E in FIG. 1, and the gripping device 1, the tension cylinder unit 34,
The work W is subjected to tensile bending under the control of the core 34, the metal core 41, and the position control cylinder unit 46 thereof.

FIGS. 5 to 7 show a tension bending process, and FIG. 5 shows a state immediately before the process. The cored bar 41 is located in the bent portion W6 of the workpiece W, and starts bending as shown in FIG.
And the core 41 faces the bent portion of the bent portion W6, and retreats so as to escape from this portion.
The crush deformation of the bent portion W6 is suppressed.

FIG. 6 shows the initial state of the bending process, in which the retreating is continued with the progress of the bending of the bent portion W6, and the retreating is performed by driving the cylinder unit 46 in FIG. With the continuation of the bending process, the work W is sequentially bent in the rounded portion 2
7 is pressed along the mold surface of the bending die including 1, and finally the bent portion W6 is completely bent as shown in FIG.

As described above, the inside of the holding member 2 of the gripping device 1 is held in the position controlling rod 45 of the cored bar 41 while holding the inside and outside of the terminal portion W1 of the work W while holding it.
Can freely come and go, and the tensile bending of the hollow work W using the core metal can be performed. The rod 45 for controlling the position of the cored bar 41 and the bent portion 44 freely move back and forth inside the inner holding member 2 while the inner holding member 2 constituting the holding portion 1 holds the inner surface of the work.

As described above, while the inner holding member 2 is provided, the operation of the mandrel and the rod for controlling the position of the mandrel (for pushing and pulling the mandrel) can be performed smoothly and reliably. The operation of the gold 41 can be performed without affecting the operation of the inner holding member 2 at all. Inner and outer holding members 2,
7, 7, especially the inner holding member 2 can be realized with a simple structure without complicating the structure.

[0043]

According to the present invention, the following effects are exhibited by the above configuration. According to a first aspect of the present invention, there is provided a tension bending process in which a workpiece is bent by gripping both ends of a long hollow work and pressing the work against a bending mold while applying a tensile force to the work. In the apparatus, a terminal portion of the work is formed with an enlarged diameter step portion, and a grip portion for holding the terminal portion of the work,
An inner surface holding member facing the inner surface of the work, and an outer surface holding member facing the outer surface of the work, wherein the inner surface holding member and the outer surface holding member are provided with a step corresponding to the step of the work on a surface facing the inner surface. A terminal gripping device for a workpiece in a tension bending apparatus in which a terminal portion of the work is made to face between a holding member and an outer surface holding member, and the work terminal portion is held between the inner surface holding member and the outer surface holding member. In the tension bending apparatus, the work terminal is gripped by the step of increasing the diameter of the work, the step of the holding member inside and outside of the gripping device, and when the work is pulled, the work axial direction is engaged. , Can be gripped.

Therefore, the hollow work terminal portion is gripped in the axial direction by the corresponding steps of the work itself and the inner and outer holding members, together with the clamping of the inner and outer holding members. For this reason, unlike the simple frictional engagement of pinching, the axial gripping of the work terminal portion is significantly stronger and more reliable than the conventional frictional engagement type,
There are many advantages in tension bending of hollow materials.

The inner holding member having the step portion is fitted with the inner diameter of the work having the step portion, and the outer holding member having the corresponding step portion is pressed from the outside of the work terminal portion, and the inner and outer holding members press the work. Since the terminal portion is sandwiched, the mechanism for moving the inner holding member in the axial direction is not required, and the outer holding member need only be configured to press the outer holding member in the radial direction. Accordingly, the structure of the terminal holding device for hollow members is dramatically simplified.

Also, since the inner and outer gripping portions are divided and a collet chuck mechanism having a split claw piece structure is not required, the mechanism and structure of the gripping device are extremely simple in addition to the above. Also, no excessive reaction force is applied to the outer holding member. Therefore, the entire apparatus is simplified in addition to the above.

Furthermore, it is not necessary to set the length of the work terminal portion large in order to obtain a large frictional engagement surface when gripping the work terminal portion. For this reason, there is little wasted part of the material due to the gripping of the work terminal, which is extremely advantageous in terms of material yield, and is economically preferable.

According to a second aspect of the present invention, in the first aspect, the inner surface holding member is provided with a metal core for passing the metal core into the work and a rod insertion hole for the metal core, so that the metal core of the hollow work is used. It is necessary to insert the core metal into the work during the tension bending process, but the axial movement mechanism of the inner holding member is not required, the inner holding member is fixed, and the inner holding member is a hollow member Therefore, a space for inserting the rod for moving the metal core can be easily obtained.

Therefore, the hollow inner holding member can easily perform the bending and bending process using the core metal,
In tensile bending, it is possible to perform tensile bending with extremely excellent cross-sectional accuracy, shape accuracy, and dimensional accuracy of the bent portion of the work, and to obtain a tension bending apparatus using a core metal with a simple structure as described above. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a bending device including a gripping device according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the gripping device according to the first embodiment of the present invention, in an open state.

FIG. 3 is a diagram showing a gripping state of FIG. 2;

FIG. 4 is a cross-sectional view of a state where a core metal is incorporated in the gripping device.

5 to FIG. 7 are explanatory views of a tension bending process using a cored bar, and FIG. 5 is a diagram showing a state immediately before the bending process;

FIG. 6 is a diagram showing a state in which bending is started.

FIG. 7 is a diagram showing a state in which bending is completed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gripping device, 2 ... Inner holding member, 6 ... Step part, 7
... outer holding member, 11 ... stepped part, 13 ... insertion hole, 4
DESCRIPTION OF SYMBOLS 1 ... Core bar, 45 ... Rod for core bar position control, W ... Work, W1: Terminal part, W4 ... Step part.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideji Sato 1-10-1 Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd.

Claims (2)

[Claims] 1. A long hollow work is gripped at both ends thereof.
By applying a tensile force to the work and pressing it against a bending mold, a bending and bending apparatus configured to perform a bending process on the work, forming an enlarged diameter stepped portion at a terminal portion of the work, The gripping portion for gripping the terminal portion of the work, an inner surface holding member facing the inner surface of the work, and an outer surface holding member facing the outer surface of the work, the inner surface holding member, and the opposite surface of the outer surface holding member, Providing a step corresponding to the step of the work, the terminal of the work is made to face between the inner surface holding member and the outer surface holding member, and the work terminal is held between the inner surface holding member and the outer surface holding member. A terminal gripping device for a workpiece in a tension bending device. 2. The work in the tension bending apparatus according to claim 1, wherein the inner surface holding member is provided with a metal core for passing a metal core into the work, and a rod insertion hole for the metal core. Terminal holding device.