JPS6210672Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a test piece gripping device that is extremely useful for, for example, R-value measurement tests on test pieces.

The R value is an abbreviation of the Rankford value, which is a numerical value related to the drawing characteristics of a thin plate specimen (steel material).
It is determined by the following formula.

Here, Lo = Gauge distance of the test piece before tensioning the test piece Lt = Distance between the test piece gauges after tensioning the test piece Wo = Width of the parallel part of the test piece before tensioning the test piece Wt = Test after tensioning the test piece Width of Parallel Portion Such R value measurement has been conventionally performed based on standards because it is necessary to know the drawing characteristic value of the test piece.

By the way, the conventional R value measurement procedure is to first calculate the gauge distance Lo and the width of the parallel part of a thin steel plate test piece.
Wo is measured using a measuring instrument such as a measuring device or a micrometer, and then this test piece is held in a material testing machine and a tensile operation is performed to produce the elongation necessary for the R value. After that, remove the test piece from the material testing machine, measure the gage distance Lt after tension and the width Wt of the parallel part again using a length measuring device or micrometer, and substitute these measured values into the above formula. I am trying to find the R value.

The operation of measuring the R value in this way is complicated, but apart from the work of measuring the test piece with a measuring instrument,
The operation of gripping the test piece in the gripping mechanism of the material testing machine and the operation of removing the test piece from the gripping mechanism again complicate the R-value measurement operation.

The reason why it is necessary to perform the work of attaching and detaching the test piece, which complicates the operation, is that the R value measurement requires accurate measurement of the size of the test piece before and after the test piece is pulled, especially after the pull. This is because measurements must be performed with the tensile load on the test piece removed.

Even if the tensile mechanism is stopped after a tensile test is performed by holding a test piece in a material testing machine, the tensile load on the test piece is not removed, that is, it does not become zero, and a tensile force still acts on the test piece. If the test specimen is removed from the gripping mechanism, the tensile force is completely unloaded, but if unloading is performed without this removal, the tensile mechanism must be operated in reverse while observing the load meter until the load meter indicates a zero value. Just do it.

However, in this case, even if a small amount of compressive force is applied to the test piece, the load cell will indicate zero.
It is unclear whether accurate unloading is being carried out. However, when measuring the R value, the load must be completely unloaded, whether it is tension or compression.

The test piece gripping device in a conventional testing machine cannot measure the R value with good accuracy, and in order to improve accuracy, the test piece must be removed.

The present invention aims to completely eliminate these conventional drawbacks and provide a test specimen gripping device that is particularly useful for R-value measurement.

In other words, the gist of the present invention is a hydraulic gripping device that uses hydraulic pressure to open and close a gripping tool that grips a test specimen. ) so that only the tensile load can be removed while holding the test piece.

The embodiments shown in the drawings will be described below.

The drawing shows the tension mechanism 13, 1 for the testing machine 12.
Hydraulic gripping mechanism TC installed via 3′,
The TC' and its drive system, that is, the hydraulic operating system are mainly shown, and the testing machine 12 and the tension mechanisms 13 and 13' are shown in blocks.

First, the hydraulic system will be described. Reference numeral 1 is an oil tank, and reference numeral 3 is a hydraulic pump that is rotationally driven by a motor 2 and pumps the oil in the tank 1 under pressure. Pressure oil is supplied to the switching valve 6 via the check valve 5 and the hydraulic circuit 4. In the switching valve 6 in the illustrated state, the central valve body 6M is connected to the hydraulic circuit 4, and the hydraulic circuit 4 is connected to the hydraulic circuit 4. It is in a state of blockage.

When the valve body 6L is connected by the operation of the switching valve 6, the pressure oil (hydraulic pressure) from the hydraulic circuit 4 is transferred to the hydraulic circuit 7C for the gripping mechanisms TC, TC' to grip the test piece 18, as described later. The hydraulic circuit 7C becomes a hydraulic pressure introduction circuit and the hydraulic circuit 7P becomes a hydraulic discharge circuit. Conversely, when the valve body 6R is connected, the pressure oil (hydraulic pressure) from the hydraulic circuit 4 is transferred to the gripping mechanism TC,
TC' is sent to hydraulic circuit 7P to release the test piece. That is, the hydraulic circuit 7P serves as a hydraulic pressure introduction circuit, and the hydraulic circuit 7C serves as a hydraulic discharge circuit. 8 is a check valve interposed in the hydraulic circuit 7C for gripping, and 9 is an accumulator connected to this hydraulic circuit 7C. When the hydraulic circuit 7P serves as a hydraulic pressure introducing circuit, the hydraulic pressure becomes a pilot pressure for opening the check valve 8, and discharge from the cylinder 14 is performed by the hydraulic circuits 7C and 4.

The hydraulic pressure from the hydraulic source is guided to the gripping mechanisms TC and TC' through the hydraulic circuit as described above, and the gripping mechanism TC' has the same configuration as the TC, and the internal configuration of the gripping mechanism TC is shown below. will be explained only.

Reference numerals 17 and 17' denote gripping tools for gripping or releasing the test piece 18, which are arranged inside the frame 16, which has wedge surfaces on both sides and has a wedge surface inside. Reference numeral 19 denotes a fixing column protruding from the bottom of the hydraulic cylinder 14, and a regulating flange 20 is attached to the tip thereof, and the bottom surfaces of the gripping tools 17, 17' are joined to the right side of this flange 20. ing. Therefore, frame 1
When the frame 16 is displaced to the left, the two grippers approach each other due to the wedge action and clamp and grip the test piece 18. Conversely, when the frame 16 is displaced to the right, the two grippers 17, 17 ' are separated from each other to open the test piece 18.

The left/right displacement of frame 16 is this frame 16
This is done by moving the piston 15, which is integrated with the hydraulic cylinder 14, within the hydraulic cylinder 14 using hydraulic pressure. That is, the hydraulic pressure from the hydraulic circuit 7C is applied to the hydraulic cylinder 14.
When the specimen 18 is introduced into chamber B, the piston 15 is biased to the left and the frame 16 is displaced to the left.
is firmly gripped by gripping tools 17, 17'. When the hydraulic circuit 7P becomes a hydraulic pressure introducing circuit by the switching operation of the switching valve 6, hydraulic pressure is introduced into the A chamber of the hydraulic cylinder 14, and the frame 16 is displaced to the right.
Test piece 18 is opened.

In the present invention, in the above-described configuration, an open circuit 11 for opening the hydraulic circuit 7C to the hydraulic tank 1' is connected to the hydraulic circuit 7C on the side that becomes the hydraulic pressure introduction circuit when gripping the test piece. It is characterized by Reference numeral 10 denotes a pilot check valve interposed in this open circuit 11, which normally blocks the flow from the hydraulic circuit 7C to the hydraulic tank 1', and opens the open circuit by inputting pilot pressure through the bypass paths 22 and 22'. 11 will be opened. Pilot pressure generation control is performed by operating the switching valve 21. When the open circuit 11 is opened by the operation of the pilot check valve 10, the B of the hydraulic cylinder 14 is opened.
The hydraulic pressure in the chamber flows out into the hydraulic tank 1' and is opened, reducing the pressure to atmospheric pressure. At this time, as will be described later, the respective hydraulic circuits 7C and 7P connected to both chambers of the hydraulic cylinder are both opened to the hydraulic tank to ensure that the test piece is held in an unloaded state.

That is, since the present invention has the above-described configuration, in the tensile test of the test piece 18, the switching valve 6 is first operated to connect the valve body 6L to the hydraulic circuit 4, and the hydraulic pressure from the hydraulic source is sent to the hydraulic circuit 7C. , this hydraulic circuit 7C is used as a hydraulic pressure introduction circuit, and the hydraulic cylinder 1
Introduce it into Room B of 4. At this time, the hydraulic circuit 7P becomes a hydraulic discharge circuit. At this time, the switching valve 21 is in the state shown and no pilot pressure is generated, so the pilot check valve 10 does not operate and the hydraulic circuit 7C
is blocked. Therefore, by introducing hydraulic pressure into chamber B, the gripping tools 17, 17' firmly grip the test piece 18. The hydraulic pressure (initial pressure) in chamber B of the hydraulic cylinder 14 at this time is Pc, and the hydraulic cylinder 1
If the pressure receiving area of 4 is a, a force of Pc×a acts to bias the hydraulic cylinder 14 to the right, but this is balanced by the rigidity of the tension mechanism 13 and the hydraulic cylinder 14 itself.

Next, the switching valve 6 is set to the state shown in the figure to disconnect both hydraulic circuits 7C and 7P from the hydraulic power source. In this state, by operating the tension mechanisms 13, 13', the test piece gripping mechanisms TC, TC' connected to the tension mechanisms 13, 13' are pulled to both sides, respectively. The gripped test piece 18 is subjected to a tensile load. At this time, in chamber B of the hydraulic cylinder 14, the test piece tensile load pressure is added to the initial pressure Pc for gripping, and the pressure inside the hydraulic circuit 7C becomes considerably high. That is, if the tensile load is now W, then Pc×a≧
In the state of W, the initial pressure Pc does not change, but the load W
increases and reaches the state of Pc×a<W, since chamber B and the hydraulic circuit 7c connected to chamber B are closed, the test piece tensile load pressure is added to the initial pressure Pc of chamber B. Both sides of the above equation are balanced.
Now, if this test piece tensile load pressure is P _L (Pc +
P _L )×a=W holds true. As the load W increases, the tensile load pressure P _L of this test piece increases, and B
The oil pressure in the chamber becomes high pressure. The test is guaranteed since room A is open to the hydraulic tank. When tension is progressed in this state and elongation necessary for R-value measurement occurs, the operation of the tension mechanisms 13, 13' is stopped.

Even when the operation of the tension mechanisms 13, 13' is stopped, high pressure is applied to the hydraulic circuit 7C and chamber B of the hydraulic cylinder 14, and a constant tensile load is applied to the test piece 18. Therefore, the switching valve 6 is left in the illustrated position 6M, that is, the oil pressure source side and the oil pressure introduction circuit 7.
C and the hydraulic discharge circuit 7P are kept disconnected, the switching valve 21 is operated to generate pilot pressure, and the pilot check valve 10 is operated to drain the hydraulic pressure of the hydraulic circuit 7C to the hydraulic tank 1' and open it. Then, the piston 15 does not displace from the illustrated position where it grips the test piece 18, and the oil pressure in chamber B decreases, and chamber A is also opened to the hydraulic tank by operating the switching valve 6 to the 6M position as described above. Since the test piece 18 is held in place by the grippers 17 and 17', the hydraulic pressure has decreased, and the tensile load is completely removed from the test piece 18, leaving it in an unloaded state. By measuring the gauge length Lt and the width Wt of the parallel portion of the test piece in this state, it is possible to measure the R value.

If you wish to continue the tensile test, select the switching valve 21.
Return B to the state shown in the figure to open an open circuit, and
It is sufficient to introduce hydraulic pressure into the chamber and then start the operation of the tension mechanisms 13, 13'.

If you want to finish with R value measurement only, restore the switching valve 21, operate the switching valve 6 so that its valve body 6R is connected, send hydraulic pressure from the hydraulic source to the hydraulic circuit 7P, and connect this circuit with hydraulic pressure. Hydraulic pressure is introduced into chamber A of the hydraulic cylinder 14 as a circuit, and hydraulic pressure in chamber B is discharged using hydraulic circuit 7C as a hydraulic discharge circuit. Then, the piston 15 moves to the right and the test piece 18 is released from the test piece gripping mechanisms TC, TC'.

The switching valves 6 and 21 are electromagnetic valves in the illustrated example, and the above operations can be automatically performed by remote automatic control.

As mentioned above, the features of the present invention are as follows: the conventional hydraulic operation system, namely, the hydraulic pump 3, the hydraulic circuit 4, the switching valve 6, the hydraulic circuits 7C and 7P, and the hydraulic cylinder 14.
In this system, an open circuit 11 for opening the hydraulic circuit 7C, which serves as a hydraulic pressure introduction circuit when gripping a test piece, to a hydraulic tank is connected, and a valve that can be opened is interposed in this circuit. Various modifications other than the illustrated example are possible.

The valve for opening and closing the open circuit 11 does not need to be a pilot check valve, but may be a manually operated channel opening/closing valve. The hydraulic system is also not limited to what is illustrated. Manual switching valves can also be used.

Further, the test piece gripping device of the present invention is useful for R-value measurement, but it can also be effectively applied as a test piece gripping device for all kinds of testing machines in addition to material testing that involves breaking and testing.

As detailed above, the device of the present invention can accurately unload the tensile load while the test piece is held in the gripping mechanism, and performs R-value measurement easily and with good accuracy. Can be done. After measuring the R value,
When conducting a test, it is easy to continue the operation and can be applied to any testing machine.

[Brief explanation of the drawing]

The drawing is a diagram schematically showing the configuration of a test piece gripping device according to an embodiment of the present invention. 1, 1′...Hydraulic tank, 3...Hydraulic pump,
4...Hydraulic circuit, 6, 21...Switching valve, 7C, 7
P...Hydraulic circuit, 7C...Hydraulic pressure introduction circuit when holding the test piece, 7P...Hydraulic pressure introduction circuit when releasing the test piece, 8...
...Check valve, 10...Pilot check valve,
11...Open circuit, 12...Testing machine, 13,1
3'...Tension mechanism, 14...Hydraulic cylinder, 15
... Piston, 16 ... Frame, 17, 17'
...Gripper, 18...Test piece, 19...Fixing column,
20...Restriction flange, 22, 22'...Bypass path.

Claims (1)

[Scope of utility model registration request] Hydraulic pressure from a hydraulic source is alternately guided to both chambers of a hydraulic cylinder via a hydraulic circuit, and the piston of the hydraulic cylinder operates to open and close the gripping tool that grips the test piece, thereby gripping or releasing the test piece. In an apparatus in which a test piece gripping mechanism is connected to a test piece tensioning mechanism to perform a tensile test on a test piece gripped by the test piece gripping mechanism, the hydraulic circuit is connected to the test piece with the gripper closed. a hydraulic circuit that introduces oil pressure from a hydraulic source into one chamber of the hydraulic cylinder to grip the sample, and a hydraulic circuit that introduces oil into the other chamber of the hydraulic cylinder to open the gripper and release the test piece; means for opening only the hydraulic circuit connected to the other chamber of the hydraulic cylinder to the hydraulic tank when the respective hydraulic circuits connected to both chambers of the hydraulic cylinder are disconnected from the hydraulic source; and one of the hydraulic cylinders. A switching valve is provided to switch the introduction of hydraulic pressure to the chamber of the hydraulic cylinder and to connect it to the hydraulic power source, and when the hydraulic cylinder is disconnected, the hydraulic pressure of the hydraulic circuit connected to one chamber of the hydraulic cylinder flows out to the oil tank. circuit, and a valve interposed in the open circuit to prevent the hydraulic pressure from flowing into the hydraulic tank when hydraulic pressure is introduced for gripping the test specimen, and when the tension mechanism is inactive, the valve of the open circuit is provided. 1. A test specimen gripping device for a testing machine, characterized in that the tensile load can be unloaded while the test specimen is gripped by opening both chambers of a hydraulic cylinder to a hydraulic tank.