JP2002107276A - Holding device of test piece for torsion test - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a holding device capable of keeping a holding force even if the diameter of a test piece is contracted during a torsion test. SOLUTION: This holding device for nipping and holding the test piece 4 from three sides by three grip jaws 3 by displacing the grip jaws 3 by the operation of a screw feeding mechanism, a disc spring S is interposed between the pressing rod 8 and bolt 5 of the screw feeding mechanism. The grip jaws 3 are allowed to abut on the test piece 4 in the state where the disc spring S is compressed. When the diameter of the test piece 4 is contracted, the grip jaws 3 follow it by the elastic force of the compressed disc spring S to keep the holding force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material testing machine for performing a torsional test of a test piece such as a round bar or the like, and to a gripping device for the test piece.

[0002]

2. Description of the Related Art In a material testing machine for performing this kind of torsion test, gripping teeth to be held are designed to prevent rotation of the test piece due to a rotational force applied to the test piece around its axis. It is necessary to grasp from the surroundings. For this purpose, a conventional gripping apparatus employs a method of gripping three test teeth 3 from three sides around a test piece 4 as shown in FIG. The gripping teeth 3 are arranged at intervals of 120 degrees, and each advance and retreat with respect to the test piece 4 by reciprocating on the principle of a screw feed mechanism.

More specifically, reference numeral 1 denotes a frame which is fixedly installed on a frame or the like of a material testing machine (not shown) for performing a torsional test with a frame. In a normal torsional test, the test piece 4 has its axis centered in the horizontal direction. In this case, the lower part of the illustrated frame 1 is fixedly installed on the machine base of the tester.

[0004] As shown in the figure, the frame 1 has a substantially equilateral triangular frame body, and gripping teeth 3 are arranged on each side of the frame via a guide table 2. The corresponding surface (gripping surface) of each gripping tooth 3 to the test piece 4 is formed with a certain inclination angle with respect to each inner side of the frame 1, and therefore, each gripping tooth 3
Moves in the direction of the arrow to approach the test piece 4 and firmly grip the test piece 4. This movement is driven by a screw feed mechanism. That is, a nut 10 is provided in the lower right corner of the frame 1, and a bolt 5 is screwed into the nut 10. Further, a pressing rod 8 is connected to the inner end of the frame 1 of the bolt 5, and the pressing rod 8 is locked to the gripping teeth 3 via a locking tool 9.

In the above configuration, the operating section 5 of the bolt 5
By rotating S with a fastening handle (not shown), the gripping teeth 3 are displaced in the direction of the arrow via the pressing rod 8, and the test piece 4 is gripped. The other two bolts 6 and 7 are screwed into screw holes provided directly in the frame 1, and are screwed by rotation, and the three bolts 5, 6 and 7 are actuated to rotate three bolts. The test piece 4 is pinched and gripped from three directions by the displacement of the gripping teeth 3. Setting the number of the gripping teeth 3 to three has a gripping force that can withstand a torsional test, is the simplest in structure, and is practical.
In the torsion test, a torque is applied to the test piece 4, but the gripping teeth 3 from these three directions surely hold the test piece 4.

[0006]

In the torsion test, various materials are subjected to a torsion test. In particular, in the case of a test piece 4 having a large amount of torsion, the diameter of the test piece 4 becomes thinner as the test progresses. 3, the holding force of the test piece 4 is weakened, and the test piece 4 may be turned by the load torque. In this state, a torsional test cannot be performed. Alternatively, when the torsion test is performed in a high or low temperature atmosphere, the test piece 4 may be deformed by the influence of the temperature. In this case, too, the gripping teeth 3 cannot grip the test piece 4, and the torsion test may be performed. Nothing happens. An object of the present invention is to provide a device for gripping a test piece for a torsional test which solves such a problem.

[0007]

SUMMARY OF THE INVENTION The present invention provides a torsion test specimen gripping apparatus provided by the present invention.
In a screw feed mechanism for moving grip teeth forward and backward with respect to a test piece, a compression spring material is interposed between the pressing rod connecting the grip teeth to the screw feed mechanism and the grip teeth. The compression spring material is interposed by compressing and deforming the spring material to generate elasticity. When the diameter of the test piece is reduced by the intervention, the gripping teeth are pushed by the elasticity of the compression spring material. Following displacement, the grip of the test piece is maintained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a gripping device for a torsional test specimen provided by the present invention will be described with reference to the embodiment shown in FIG. In FIG. 1, components and configurations indicated by the same reference numerals as those in FIG. 5 are the same as those in FIG. 5, and their functions are also the same as those in FIG.

The gripping device according to the present invention is characterized in that a disc spring S is interposed in the pressing rod 8 as is clear from FIG. That is, specifically, the bolt 5P, which is the main body of the screw feed mechanism, has a tubular shape as shown in the figure, and a control rod 11 whose tip is connected to the pressing rod 8 is inserted inward. . The control rod 11 has its tip inserted into the inside of the pressing rod 8 and fixed with a pin P, and the large-diameter portion 11T at the other end is located in the recess 5K of the bolt 5P. There is a certain distance between the large diameter part 11T and the concave part 5K to allow the control rod 11 to be displaced to the left by a certain amount.

In such a configuration, two sets of disc springs S are interposed between the pressing rod 8 and the tip of the bolt 5P. That is, four disc springs S are interposed. The other bolts 6P and 7P also have a tubular shape as shown in FIG. 1, and the control rod 11 is inserted therethrough. As in the case of the bolt 5P, the pressing rod 12 is engaged with the tip of the control rod 11, and the pressing rod 12 and each bolt 6 are connected.
A disc spring S is interposed between P and 7P.

Since the gripping device of the present invention is configured as described above, when the test piece 4 is set as shown in FIG. 1 and the bolts 5P, 6P and 7P are rotated, the operation of each screw feed mechanism is started. As a result, each gripping tooth 3 is displaced in the direction of the arrow via the bolts 5P, 6P, 7P and the respective pressing rods 8, 12. Due to this displacement, the inclined surface of each gripping tooth 3 approaches and comes into contact with the test piece 4. Then, the test piece 4 is gripped.

In this case, even if each gripping tooth 3 comes into contact with the test piece 4, the screw feed mechanism is further operated to set the bolts 5P, 6
P and 7P are further screwed into the frame 1. Then
Although the gripping teeth 3 do not displace, the bolts 5P, 6P, 7
The disc spring S is deformed (compressed) by the inward displacement of P to form a compression spring member. FIG. 1 shows this state.
Therefore, the gripper 3 is moved by the elasticity of the compression spring member.
Is constantly urged, and the gripping force of the test piece 4 is urged.

Since the gripping device according to the present invention is configured as described above, it functions as shown in FIGS. 2 and 3 when the test piece 4 is reduced and deformed in the course of the torsion test.
That is, FIG. 2 is an enlarged view of the screw feed mechanism in the same state as FIG. 1, and shows a state where the disc spring S is compressed, that is, a state before the start of the torsion test or before the test. Then, as the torsion test progresses and the diameter of the test piece 4 is reduced as shown in FIG. 3, a gap tends to be formed between the test piece 4 and the slope of the gripping tooth 3. However, the gripping teeth 3 are immediately pressed by the elasticity of the gripping teeth 3 due to the interposition of the disc spring S, and the gripping teeth 3 are displaced to follow the change of the test piece 4 and continue to grip the test piece 4. The same is true for temperature changes.

Although the features of the gripping device provided by the present invention are as described above, the present invention is not limited to the above and illustrated examples, but may include various modifications. First,
The portion where the disc spring S is interposed so as to generate a compression spring is described. However, the portion is not limited to only between the pressing rod 8 and the bolt 5P. For example, as shown in FIG. 4, it can be interposed between the pressing rod 13 and the gripping teeth 3. In this modification, the tip of the pressing rod 13 is a flat surface,
The locking member 14 is large enough to accommodate the disc spring S. FIG. 4 shows a state where the disc spring S is compressed,
When the test piece 4 shrinks and changes in this state, the elasticity of the compressed disc spring S is exerted, and the grip of the test piece 4 is maintained as in the embodiment of FIG.

In the embodiment shown in FIG. 1, the bolt 5P
Although the example in which the disc spring S is interposed between the pressure rod 8 and the pressing rod 8 has been described, the method of interposing an elastic material on the operating rod of the screw feed mechanism such as the bolt and the pressing rod is not limited to that shown in FIG. It is also conceivable to interpose an elastic material in the middle of the rod 8 itself. Further, the elastic material described above is not limited to the disc spring S alone, and a coiled spring may be interposed. However, in this gripping device, it is necessary to allow a certain amount of follow-up displacement and to have a large elasticity, so that elastic materials such as rubber materials are inappropriate and should be spring materials.

Further, in the illustrated example, each screw feed mechanism is provided to individually displace each gripping tooth 3, but the rotation drive system of each bolt is connected by a bevel gear, a transmission rod or the like, and
By driving only one of the rotary units to rotate, each screw feed mechanism can be driven in synchronization.

[0017]

As described above, the gripping device for a torsion test specimen provided by the present invention is as described above, so that the gripping teeth can always follow the deformation of the specimen during the torsion test and maintain the gripping force. it can. Therefore, it is possible to prevent a situation where the test specimen cannot be slid during the torsion test.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a torsion test specimen gripping device according to the present invention.

FIG. 2 is an enlarged view of a main part of a gripping device for a torsion test specimen according to the present invention.

FIG. 3 is a view showing an operation state of the torsion test specimen gripping device according to the present invention.

FIG. 4 is a view showing a modified example of the torsion test specimen gripping device according to the present invention.

FIG. 5 is a diagram showing a configuration of a conventional torsion test specimen gripping device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Frame 2 ... Guide stand 3 ... Gripping tooth 4 ... Test piece 5, 6, 7 ... Bolt 5P, 6P, 7P ... Bolt 8, 12, 13 ... Pressing rod 9 ... Locking tool 10 ... Nut 11 ... Control rod S … Belleville spring

Claims (2)

[Claims] The present invention comprises: gripping teeth for gripping a test piece to be subjected to a torsion test from three sides; and respective screw feed mechanisms for moving the respective gripping teeth forward and backward with respect to the test piece. The gripping teeth are connected to the distal end of an operating rod that reciprocates by the operation, and the test strip is gripped by each gripping tooth by the operation of a screw feed mechanism. A gripping device for a test piece for a torsion test, wherein a gripping device is provided. 2. The apparatus according to claim 1, further comprising: gripping teeth for gripping the test piece to be subjected to the torsion test from three sides, and a screw feed mechanism for moving the gripping teeth forward and backward with respect to the test piece. The gripping teeth are connected to the tip of an operating rod that reciprocates by the operation, and the gripping device of the test piece is configured such that the test piece is gripped by each gripping tooth by the operation of the screw feed mechanism. A torsion test specimen gripping device, comprising a compression spring material interposed between teeth.