JPH0628676Y2 - Material gripping device for material testing machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a test piece gripping device for a material testing machine, and more particularly to a test piece gripping device for a material testing machine in which the test piece is a coil spring.

[Prior Art] Generally, in a fatigue test of a coil spring, hooks 2 and 2 are formed at both ends of a coil spring body 1 as shown in FIG. 2, and the hooks 2 and 2 are attached to upper and lower pull rods 3 and 3 of a material testing machine. After pulling on one of the grippers 4, 4, one pull rod 3 is fixed and the other pull rod 3 is driven in the direction of the arrow by an actuator to apply tensile / compressive repetitive stress.

[Problems to be Solved by the Invention] However, in the above-described conventional coil spring material test, it is necessary to form the hook 2 on the coil spring body 1 for gripping the coil spring test piece. The boundary portion 1a between the coil spring main body 1 and the hook 2 has a small radius of curvature, so that stress concentration in bending and torsion occurs in the fatigue test, causing breakage, and there is a problem that the fatigue true value of the coil spring cannot be obtained. In order to reduce this stress concentration, the hook requires special processing, which causes an increase in cost.

Further, if the hook 2 is not aligned with the axial center of the coil spring body 1, eccentric stress is generated when a load is applied, and the measurement accuracy is significantly reduced. Therefore, it is necessary to align the hook 2 with the axial center of the coil spring main body 1, which requires high-precision spring processing, and in this case also causes an increase in cost.

Therefore, an object of the present invention is to provide a test piece gripping device for a material testing machine that can securely grip a coil spring test piece without a hook.

[Means for Solving the Problems] In order to achieve this object, the present invention is a test piece gripping device of a material testing machine for gripping a coil spring test piece. A test piece fixing body having a joining part to be joined and a nut part extending from this joining part, and a male screw part that can be loosely screwed into the nut part and has a screw pitch and a diameter substantially equal to the pitch and the diameter of the coil spring test piece. The test piece fixing body and the support shaft are screwed together with the coil spring test piece being sandwiched between the nut portion and the male screw portion, and by the screwing, It holds the coil spring test piece.

The test piece fixing body is preferably coupled to the mounting body such that the central axis of the nut portion substantially coincides with the axial center of the pull rod, and the mounting body is arranged in the axial direction with respect to the pull rod. It is preferably screwed to the pull rod so that the mounting position can be adjusted.

Further, the mounting body has a shaft portion attached to the pull rod at one end and a flange portion formed at the other end of the shaft portion, and has a guide hole extending in the axial direction. Preferably has a through hole that is detachably coupled to the flange portion and communicates with the guide hole, and the support shaft has the through hole and a guide portion that is inserted into the guide hole.

[Operation] The test piece gripping device is attached to the pull rod by the attachment body, and the coil spring test piece is fixed by being screwed with the nut portion of the test piece fixing body and the male screw portion of the support shaft sandwiching the coil spring test piece. To do. In this way, the coil spring having no hook can be gripped, and stress concentration and eccentric stress caused by the hook can be avoided and highly accurate measurement can be performed.

When the length of the coil spring is different, it can be dealt with by adjusting the mounting position of the mounting body with respect to the pull rod.

Since the central axis of the nut portion substantially coincides with the axial center of the pull rod, the axial center of the coil spring test piece also substantially coincides with the axial center of the pull rod, and the occurrence of eccentric stress can be further reduced.

By inserting the guide portion of the support shaft into the through hole of the test piece fixing body and the guide hole of the attachment body, the axis of the support shaft can be easily aligned with the axis of the pull rod.

[Embodiment] An embodiment of the test piece gripping device of the material testing machine according to the present invention will be described below with reference to FIG. 1 in which the same parts as those in FIG.

In FIG. 1, the test piece gripping device 5 attached to the pull rod 3 is roughly composed of an attachment body 6, a test piece fixing body 7, and a support shaft 8. This mounting body 6 is a male screw 9
It is composed of a shaft portion 9 in which a is formed and a flange portion 10. A guide hole 11 opened in the flange portion 10 is bored in the mounting body 6, and the guide hole 11 extends through the flange portion 10 in the axial direction to the middle of the shaft portion 9, and
It is set so as to substantially coincide with the axis of the pull rod 3.

The test piece fixing body 7 is composed of a joint portion 13 detachably joined to the flange portion 10 by a plurality of bolts 12 and a bag-shaped nut portion 14 extending from the joint portion 13. A through hole 15 is bored in the joint portion 13, and the through hole 15 corresponds to the guide hole 11 when the joint portion 13 is joined to the flange portion 10. The female screw portion of the nut portion 14 has a pitch and a diameter which are substantially equal to the pitch P and the diameter D of the coil spring test piece 1, respectively.

The support shaft 8 has a male screw portion 16 at one end and a guide portion 17 at the other end. The male screw portion 16 also has a pitch and a diameter which are substantially equal to the pitch P and the diameter D of the coil spring test piece 1, respectively, and can be screwed with the nut portion 14 with the coil spring 1 interposed between the female screw of the nut portion 14 and the female screw. Thus, the pitch and diameter are defined. The nut portion 14 and the male screw portion 16 fix the coil spring 1 between them by screwing with the coil spring sandwiched therebetween. The guide portion 17 is defined so as to be positioned inside the through hole 15 and the guide hole 11 in a state where the male screw portion 16 is screwed into the nut portion 14.

The gripping device at the other end of the coil spring test piece 1 has the same structure as described above.

The grip of the coil spring test piece 1 by the test piece gripping device 5 is performed as follows.

The attachment body 6 is attached by screwing the male screw of the shaft portion 9 into the pull rod 3. At this time, the axial mounting position of the mounting body 6 with respect to the pull rod 3 is adjusted according to the length of the coil spring test piece 1. After the coil spring test piece 1 is screwed into the trough of the male screw portion 16 of the support shaft 8, the fixed body 7 is inserted through the guide portion 17 of the support shaft 8 and the coil spring test piece 1 is inserted.
It is screwed to the male screw portion 16 that is screwed. As a result, the coil spring test piece 1 is fixed between the fixed body 7 and the support shaft 8.

With the fixed body 7 and the support shaft 8 with the coil spring test piece 1 sandwiched therebetween, the guide portion 17 of the support shaft 8 is inserted into the guide hole 11 of the mounting body 6 so that the central axis of the support shaft 8 is substantially aligned with the axial center of the pull rod 3. Match. In this state, the fixing portion 7 and the support shaft 8 are fixed to the mounting body 6 by fixing the coupling portion 13 to the flange portion 10 with the bolt 12. Since the axis of the support shaft 8 is substantially aligned with the axis of the pull rod 3, the axis of the coil spring test piece 1 is also aligned with the axis of the pull rod 3.

After gripping the coil spring test piece 3 in this way, a fatigue test is performed.

[Effects of the Invention] As is apparent from the above description, according to the present invention, the coil spring test piece is screwed with the nut part of the test piece fixing body and the male screw part of the support shaft in a state in which the coil spring test piece is interposed. Therefore, the coil spring having no hook can be securely held, and the stress concentration and the eccentric stress due to the existence of the hook can be suppressed, and the accuracy of the material test can be improved.

If the fixed body of the test piece is connected to the mounting body so that the central axis of the nut part is substantially aligned with the axial center of the pull rod, the axial center of the coil spring test piece is also approximately aligned with the axial center of the pull rod, and eccentric stress is further generated. It can be reduced.

If the mounting body is constructed so that the mounting position in the axial direction can be adjusted with respect to the pull rod, coil spring test pieces of various lengths can be easily accommodated.

Further, the guide body is provided with a guide hole, the support shaft is provided with a guide portion, and the guide portion is inserted into the guide hole, whereby the axis of the coil spring test piece can be easily aligned with the axis of the pull rod. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a test piece gripping device of a material testing machine according to the present invention, and FIG. 2 is a front view showing a test piece gripping device of a conventional material testing machine. 1 ... Coil spring body, 3 ... Pull rod, 5 ... Test piece gripping device, 6 ... Mounting body, 7 ... Test piece fixed body, 8 ...
... Support shaft, 9 ... Shaft part, 10 ... Flange part, 11 ...
Guide hole, 13 ... coupling part, 14 ... nut part, 15 ...
Through hole, 16 ... Male part, 17 ... Guide part.

Claims (1)

[Scope of utility model registration request] 1. A test piece gripping device for a material testing machine for gripping a coil spring test piece, comprising: an attachment body attached to a pull rod; a coupling portion coupled to the attachment body; and a nut portion extending from the coupling portion. The test piece fixing body, and the support shaft having a male screw portion loosely screwed into the nut portion and having a screw pitch and diameter substantially equal to the pitch and diameter of the coil spring test piece. The support shaft is screwed in a state where the coil spring test piece is sandwiched between the nut portion and the male screw portion, and the coil spring test piece is gripped by this screwing. Machine test piece gripping device.