JP2009287945A - Extensometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extensometer capable of accurately positioning the knife edge provided to a lever at the left to right central position of a test piece. <P>SOLUTION: The clipping mechanism 12 provided to the extensometer includes a pair of arms 125 for positioning the knife edge 120 at the left to right central position of the test piece. The arms 125 are moved through a cylinder 121 while slid by a piston 122 and opened and closed accompanied by the sliding thereof to grasp and open the test piece S. Then, when the arms 125 are opened by pushing in the piston 122 against the energizing force of a compression coil 126 to stop the pushing-in of the piston 122, the piston 122 is slid by the energizing force of the compression coil 126 to close the arms 125. As a result, the knife edge 120 provided to the lever 11 is positioned at the right and left central position of the test piece and fixed so as to come into contact with the test piece. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an extensometer for measuring the elongation of a test piece in a material testing machine.

  There are non-contact type and contact type extensometers for measuring the elongation of a test piece in a material testing machine. In the contact extensometer, the upper and lower marks on the test piece are brought into contact with the knee edges provided at the tips of a pair of upper and lower arms, respectively, and the amount of opening and closing of both arms following the displacement of the marks is measured. By this, what measures the elongation of a test piece is known (for example, refer to patent documents 1).

JP 2003-240690 A

  By the way, in order to accurately measure the elongation of the test piece, it is necessary to accurately match the knitted edge of the extensometer to the left and right center position of the test piece. However, since the extensometer was attached to the left and right center position of the test piece by the operator's visual observation, when the test piece was a flat plate, the attachment position was likely to vary, and it took time to attach.

  An extensometer according to the present invention includes a pair of levers provided at predetermined intervals and having a knife edge at the tip thereof that is in contact with a test point of the test piece, a jig for fixing the pair of levers to the test piece, and a pair of levers The jig includes a pair of arms for sandwiching the test piece from the left and right, positioning the knife edge at the left and right center position of the test piece, and sliding the pair of arms. An arm holding portion that opens and closes the arm as the arm slides, and an elastic member that biases the slide operation portion toward the slide position where the arm is closed by the elastic force. With.

  According to the present invention, the knife edge provided on the lever can be accurately positioned at the left and right center position of the test piece.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an extensometer according to the present invention, and shows a schematic configuration. The extensometer 1 includes a main body 10, a pair of levers 11 provided on the main body 1, a clipping mechanism 12 attached to the tip of each lever 11, and a signal cable for outputting detection information from the main body 10 to an external device. 13. The extensometer 1 is attached to the test piece by these clipping mechanisms 12. At that time, the knife edge 120 fixed to the tip of each lever 11 is attached so as to come into contact with the test point of the test piece. The lever 11 can be opened and closed vertically, and a detector (for example, a strain gauge) for detecting the displacement of the lever 11 is provided in the main body 1.

  FIG. 2 is a view showing a state in which the extensometer 1 is attached to the test piece S set in the material testing machine 2. The upper end of the test piece S is gripped by the upper chuck 22a, the lower end of the test piece S is gripped by the lower chuck 22b, and the upper chuck 22a is fixed to the cross head 21 that moves up and down. The tensile test of the test piece S is performed by moving the test piece S. The extensometer 1 is a device for measuring the elongation of the test piece S at this time, and is attached to the test piece S by the clipping mechanism 12. that time. The knife edge 120 of the lower lever 11 is attached so as to abut the lower mark, and the knife edge 120 of the upper lever 11 is attached to the upper mark. When the test piece S extends up and down by the tensile test, the distance between the knife edges 120 changes accordingly, and the lever 11 opens, so that the displacement of the lever 11 is detected by the detector in the main body 10. The detection result is input to the control device 23 of the material testing machine 2 through the signal cable 13.

  3A and 3B are diagrams for explaining the clipping mechanism 12. FIG. 3A is a diagram in which the clipping mechanism 12 is horizontally sectioned, and FIG. 3B is a diagram in which the clipping mechanism 12 is vertically sectioned. The clipping mechanism 12 includes a cylinder 121 to which a knife edge 120 is fixed and a piston 122 that can slide within the cylinder 121. The knife edge 120 is fixed to a pedestal 123 provided on the cylinder outer wall. The piston 122 is urged downward in the figure by a compression coil spring 126. A shaft 124 is provided at the tip of the piston 122, and a corner base portion 125 b of a pair of arms 125 is fixed to the shaft 124. A grip 125 a for gripping the test piece S is formed at the tip of the arm 125.

  FIG. 4A is a view showing one of the arms 125. In the present embodiment, a piano wire is used for the arm 125, but the arm 125 is not limited to a piano wire, and may be formed of an elastic wire (thread-like member). The base 125b in the lower part of the figure is formed in a ring shape, and the gripping part 125a is formed in a shape that makes it easy to grip the test piece S. A shaft portion 125c between the grip portion 125a and the base portion 125b is formed in an arc shape. FIG. 4B is a view showing a pair of arms 125 fixed to the shaft 124. In FIG. 4B, the piston 122 and the compression coil spring 126 are not shown.

  A hole 121 a is formed in the upper end surface of the cylinder 121 in the figure. The shaft portion 125c of the arm 125 fixed to the shaft 124 of the piston 121 is exposed to the outside through the hole 121a. When the piston 122 is pushed into the cylinder 121 and the shaft 124 approaches the hole 121a as shown by a broken line, the shaft portion 125c of the arm 125 is curved as shown in FIG. 125c and the holding part 125a are greatly opened to the left and right. Note that the degree of opening of the arm 125 is limited by the shaft portion 125c coming into contact with the edge of the hole 121a.

  On the other hand, when the piston 122 is pushed down, the arm 125 is drawn into the cylinder 121. At that time, since the shaft portion 125c of the arm 125 contacts the edge of the hole 121a, the shaft portion 125c and the gripping portion 125a move in the closing direction (center direction). As shown in FIG. 3, a compression coil spring 126 is arranged between the tip of the piston 122 and the upper end surface of the cylinder 121 in the figure, so that the piston 122 is in a free state where the piston 122 is not operated. 3 is held at the lower end position in FIG.

  FIG. 5 is a diagram for explaining the operation of the clipping mechanism 12 when the extensometer 1 (see FIG. 1) is attached to the test piece S using the clipping mechanism 12. The piston 122 and the compression coil spring 126 are not shown. First, the piston 122 (see FIG. 3) is pushed in by hand to bring the arm 125 into an open state and approach the test piece S being chucked as shown in FIG. Here, it is assumed that the test piece S is a plate-like member having a rectangular cross-sectional shape. Next, when the pushing force applied to the piston 122 is weakened, the piston 122 (the shaft 124) is pushed downward by the urging force of the compression coil spring 126, and the arm 125 gradually moves into the cylinder 121 as shown in FIG. Be drawn into.

  As the arm 125 is pulled, the gripping portion 125a is closed, and the test piece S is gripped from the left and right as shown in FIG. As a result, the knife edge 120 is centered so as to be positioned at the left and right center position of the test piece S. Since the knife edge 120 is not in contact with the test piece S at this time, the piston 122 (shaft 124) is further pushed down until the knife edge 120 comes into contact with the test piece S as shown in FIG. 5D, the extensometer 1 is attached to the test piece S as shown in FIG. In FIG. 5, the test piece S is shown to move toward the cylinder 121 as the piston 122 (shaft 124) is pushed down, but actually, the chucked test piece S does not move. The cylinder 121 moves to the test piece S side.

(Second Example of Clipping Mechanism 12)
FIG. 6 is a diagram illustrating a second example of the clipping mechanism 12. Here, a description will be given centering on differences from the above-described clipping mechanism. A base (lower end) of the arm 125 is rotatably attached to a shaft 128 provided on the piston 122. That is, the inclination of each arm 125 can be changed using the axis 128 as a fulcrum. The shaft of each arm 125 protrudes to the outside of the cylinder through a hole 121a provided in the end surface of the cylinder 121, and a grip portion 125a is formed in the protruding portion. A compression coil spring 126 is provided in the cylinder 121, and the piston 122 is urged downward in the figure by the compression coil spring 126.

  FIG. 6A shows a state when the piston 122 is manually pushed. By pushing the piston 122, each arm 125 is opened. When the force applied to the piston 122 is gradually weakened and the piston 122 is moved downward in the figure, each arm 125 rotates in a closing direction with the shaft 128 as a fulcrum. When the arm 125 grips the test piece S, the extensometer 1 is centered at the left-right center position of the test piece S. As shown in FIG. 6B, when the piston 122 moves downward in the drawing until the knife edge 120 and the test piece S come into contact with each other, the extensometer 1 is fixed to the test piece S.

(Third example of the clipping mechanism 12)
FIG. 7 is a diagram illustrating a third example of the clipping mechanism 12. Here again, the description will focus on the differences from the clipping mechanism described above. In FIG. 7, the left side of the center line indicated by the alternate long and short dash line indicates a state where the piston 122 is pushed in and the arm 125 is opened, and the right side of the center line indicates a state where the test piece S is gripped by the arm 125.

  The arm 125 is connected to the piston 122 by a connecting rod 125d. The base (lower end) of the arm 125 is rotatably attached to one end of the connecting rod 125d by a shaft 128b. On the other hand, the other end of the connecting rod 125d is rotatably attached to the piston 122 by a shaft 128a. The ends of the shafts 128a and 128b protrude in the direction perpendicular to the paper surface and are fitted into cam grooves 129 formed on the inner wall of the cylinder 121. That is, the shafts 128a and 128b and the cam groove 129 constitute a cam mechanism.

  In a state where no external force is applied to the piston 122, the piston 122 is pushed out as shown in FIG. 7 by the urging force of the compression coil spring 126, and the arm 125 is closed. When attaching the extensometer 1 to the test piece S, the piston 122 is manually pushed into the cylinder 121. As a result, the shaft 128b fitted in the cam groove 129 is guided by the cam groove 129 and moves to the center side, and the base portion of the arm 125 moves to the center side, so that the arm 125 is inclined to open.

  After the arm 125 in the opened state is moved to the position of the test piece S, when the force applied to the piston 122 is gradually weakened and the piston 122 is moved downward in the figure, the shaft 128b is guided by the cam groove 129 and is centered. Move away from the side. As a result, the arm 125 closes and grips the test piece S while centering the extensometer 1 with respect to the test piece S. Even after gripping the test piece S, the piston 122 moves downward, the test piece S and the knife edge 120 come into contact with each other, and the piston 122 stops. As a result, the extensometer 1 is attached to the test piece S.

  As described above, the extensometer of the present embodiment includes a pair of arms 125 that position the knife edge 120 provided on the lever 11 at the center of the left and right sides of the test piece S. The arm 125 is slid and moved in the cylinder 121 by the piston 122, and opens and closes along with the sliding to hold and open the test piece S. The arm 125 is opened by pushing the piston 122 against the urging force of the compression coil spring 126. When the pushing of the piston 122 is stopped, the piston 122 is slid by the urging force of the compression coil spring 126 and the arm 125 is closed. As a result, the knife edge 120 provided on each lever 11 is positioned at the left and right center position of the test piece S and fixed so as to contact the test piece S. Here, the compression coil spring 126 is used as an elastic member that urges the piston 122 to push out, but a tension spring may be used instead of the compression spring, or another elastic member such as rubber may be used.

  In the above-described embodiment, a plate-shaped test piece having a rectangular cross-sectional shape has been described as an example. However, by changing the shape of the grip portion 125a, the present invention can be applied not only to a plate-shaped test piece but also to a cylindrical test piece. can do. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

It is a figure which shows one Embodiment of the extensometer by this invention. It is a figure which shows the extensometer 1 of the state attached to the test piece. It is a figure explaining the clipping mechanism 12, (a) is a horizontal sectional view, (b) is a vertical sectional view. 4A and 4B are diagrams showing details of the clipping mechanism 12, in which FIG. 4A is a view showing one of the arms 125, and FIG. 4B is a view showing a pair of arms 125 fixed to the shaft 124. It is a figure explaining operation | movement of the clipping mechanism 12, and an operation | movement procedure is shown to (a)-(d). It is a figure which shows the 2nd example of the clipping mechanism 12, (a) shows the state which opened the arm 125, (b) shows the state which hold | gripped the test piece S. It is a figure which shows the 3rd example of the clipping mechanism.

Explanation of symbols

  1: extensometer, 2: material testing machine, 10: main body, 11: lever, 12: clipping mechanism, 120: knife edge, 121: cylinder, 122: piston, 125: arm, 125a: gripping part, 126: compression coil spring , S: Test piece

Claims (3)

A pair of levers provided at a predetermined interval and having a knife edge abutting against the test point of the test piece at the tip;
A jig for fixing the pair of levers to the test piece;
A detection unit that outputs a signal according to a change in the interval between the pair of levers,
The jig is
A pair of arms for sandwiching the test piece from the left and right, and positioning a knife edge at the left and right center position of the test piece;
An arm holding unit that has a slide operation unit for sliding the pair of arms, and that opens and closes the arm as the arm slides;
An extensometer, comprising: an elastic member that urges the slide operation portion toward a slide position in which the arm is closed by an elastic force. The extensometer according to claim 1,
The extensometer, wherein the arm is formed of an elastic member, and the arm grips the test piece by an elastic force generated by deformation of the arm. The extensometer according to claim 1,
An extensometer, wherein the arm holding portion includes a cam mechanism that converts sliding movement of the arm into an opening / closing operation.

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