JPH0435787Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to a screw-driven material testing machine.

(Prior Art) There is a screw-driven material testing machine that is equipped with a screw rod and a drive nut screwed into the screw rod, and is configured so that rotation of the screw rod raises and lowers a crosshead fixed to the drive nut. This type of testing machine requires a mechanism to eliminate backlash (gap between screws) between the threaded rod and the drive nut in order to apply a continuous and smooth load to the test piece. In particular, in a testing machine that applies both a tensile load and a compressive load in the same space, such as between a crosshead and a table, it is necessary to eliminate backlash against loads in opposite directions, such as tensile and compressive loads.

In order to eliminate backlash in such contradictory load directions, there is a material testing machine equipped with a screw rod having a mechanism that can switch the direction in which backlash occurs. For example, in the device of Utility Model Application No. 56-28163 (Utility Model Application No. 57-139840), when the load is to pull the crosshead downward,
The switching nut is loosened, and the weight of the crosshead etc. presses the nut against the upper slope of the screw thread of the screw rod.

(Problem to be solved by the invention) However, in the above-mentioned known backlash removal device for a material testing machine, the nut is placed on the upper slope of the screw rod and is pressed by the weight of the crosshead, etc. Therefore, if the weight of the crosshead becomes lighter, the pressing pressure against the slope of the thread becomes weaker, and the self-aligning function of the threaded rod is reduced. For this reason, when the screw rod is started up, reversed, etc., a phenomenon occurs in which the nut is deviated from the axis of the screw rod, causing a problem in that the crosshead swings. When the crosshead shakes,
It was no longer possible to apply an accurate vertical load to the test piece, making it impossible to conduct a highly accurate test.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a pair of upper and lower nuts that are screwed into the threaded rod.
The upper nut of the pair of nuts is provided with a spring that presses upwards on the screw rod, and the lower nut is provided with a spring that presses downwards on the screw rod. Therefore, a solenoid type fixing device was provided to fix the crosshead.

(Function) Since the upper and lower nuts are strongly pressed against the threads of the threaded rod by the spring, a self-aligning effect works between the threaded rod and the upper and lower nuts, and the occurrence of backlash is suppressed. The crosshead is fixed to either an upper or lower nut by magnetic force, and moves up and down together with the fixed nut.

(Example) Fig. 1 is a sectional view showing one example of the present invention, Fig. 2 is a sectional view showing an example of the present invention.
The figure is a front view of a material testing machine incorporating this, and shows a tensile test state.

This backlash removing device 1 includes a threaded rod 3 provided in the vertical direction of a material testing machine 2, and an upper nut 4 and a lower nut 5 which are drive nuts screwed into the threaded rod 3. The upper nut 4 has a large-diameter flange 6 at its upper end, and a screw hole 7 that passes vertically through the core. Also, upper nut 4
Immediately below the collar portion 6 is a small-diameter cylindrical portion 9 into which a coil, which will be described later, is fitted. The lower nut 5 is formed in the shape of the upper nut 4 upside down, has a screw hole 10 in its core, and has a lower end connected to the collar 1.
1. Its upper part is a small diameter cylindrical part 13. Note that the screw 15 provided on the outer periphery of the screw rod 3
is a trapezoidal screw with an angle of inclination of 30 degrees.

A coil spring 17 wound around the cylindrical portions 9 and 13 is provided between the upper and lower nuts 4 and 5, and the upper and lower nuts 4 and 5
As a result, the upper nut 4 is pressed upward and the lower nut 5 is pressed downward. These upper and lower nuts 4, 5 are fitted into through holes 21 drilled at the ends of the crosshead 20, and a detent rod 23 passes through the flanges 6, 11 of both nuts 4, 5 and the crosshead 20. , 23 mutually restrict idle rotation.

An upper solenoid 25 is provided between the collar 6 of the upper nut 4 and the upper surface of the crosshead 20, and a lower solenoid 26 is provided between the collar 11 of the lower nut 5 and the lower surface of the crosshead 20.
These upper and lower solenoids 25 and 26 constitute a solenoid-type fixing device that fixes the crosshead 20 to either the upper or lower nut using magnetic force.
When the upper solenoid 25 operates, the crosshead 20 is fixed to the upper nut 4, and the lower solenoid 2
When 6 works, crosshead 20 is lower nut 5
Fixed. The upper and lower solenoids 25 and 26 are electrically connected to a solenoid switching circuit 27, which switches the drive motor controller 2 between forward and reverse rotation of the drive motor 36.
8 is connected. Then, the motor 36 is driven by a forward/reverse signal from the drive motor controller 28.
The solenoid is actuated so that the crosshead 20 is fixed to the nut on the side appropriate for the direction of rotation of the crosshead 20, that is, the direction of movement of the crosshead 20. The energization of the solenoids 25 and 26 may be manually switched without providing such a solenoid switching circuit.

Further, in the threaded joint between the upper and lower nuts 4 and 5 and the screw rod 3, the upper slope of the thread 4a of the upper nut becomes the lower slope of the thread 15 of the screw rod 3 due to the action of the coil spring 17. Also, the lower slope of the thread 5a of the lower nut is pressed against the upper slope of the screw 15. When the crosshead 20 is fixed to one of the nuts (lower nut 5 in the illustrated example), the thread pitch error amount is increased at the threaded joint between the other nut (upper nut 4 in the illustrated example) and the threaded rod 3. It is designed to allow for spinning play. The pressing force of the coil spring 17 is strong enough to cause the threaded rod 3 having a trapezoidal thread and the nuts 4, 5 to self-align along the slope of the thread. Therefore, misalignment between the screw rod 3 and the nut will not occur. Since the locking rod 23 is provided between the upper and lower nuts 4 and 5, they do not rotate independently of each other, and when the screw rod 3 rotates, the upper and lower nuts 4 and 5 move up and down at the same time. At any position of the screw rod 3, the upper and lower nuts 4,
5 and threaded rod 3 and crosshead 2
The relationship between 0 and Natsu 4 and 5 remains unchanged. In the diagram, 3
5 is a table of the testing machine, 36 is a motor, and 37 is a gear.

When applying a load to the test piece 40 using this material testing machine 2, for example, the lower solenoid 26 is energized and the crosshead 20 is fixed to the lower nut 5. In this state, the screw rod 3, lower nut 5 and crosshead 20 are connected, and the crosshead 2
Even if a downward force is applied to 0, no buckling effect (rattling, etc.) will occur. However, when a force is applied in the opposite direction, play occurs due to backlash.

When the motor 36 is started and the screw rod 3 is rotated, the upper and lower nuts 4 and 5 are rotated as one.
move upwards. In this case, screw 1 of screw rod 3
If there is a pitch error in the nut 5, the distance between the upper and lower nuts 4 and 5 will change by that error. Since there is a gap above and below the collar 11 of the upper nut 4, even if the distance between the upper and lower nuts 4 and 5 changes slightly due to pitch error of the threaded rod 3, this gap allows the change to escape. It is now possible to do so. Therefore, the crosshead 20 moves smoothly,
It is possible to apply a continuous load to the test piece without the effects of backlash. Further, since the crosshead 20 is fixed to the upper or lower nut with a self-centering effect, no wobbling of the crosshead 20 occurs. Therefore, an accurate vertical load can be applied to the test piece, improving test accuracy.
Although Figure 2 shows the tensile test condition,
It is clear that similar effects can be obtained when performing a compression test. If an upward force is applied to the crosshead 20, the upper solenoid 25 may be energized to secure the crosshead 20 to the upper nut 4.

(Effects) As is clear from the above explanation, the backlash removal device according to the present invention can eliminate the influence of backlash in any load direction by a simple switching operation, and also This resulted in an excellent product that did not cause any misalignment of the axis of the rod.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention;
FIG. 2 is a front view of the material testing machine. 1... Backlash removal device, 2... Material testing machine, 3... Screw rod, 4... Upper nut, 5...
Lower nut, 6, 11...Brim portion, 17...Coil spring, 20...Cross head, 23...Stopping rod, 25...Upper solenoid, 26...Lower solenoid.

Claims (1)

[Scope of utility model registration request] In a screw-driven material testing machine that is equipped with a screw rod and a drive nut that is screwed into the screw rod, and is configured to raise and lower a crosshead fixed to the drive nut by rotation of the screw rod, the upper and lower 1 are used as the drive nuts. In addition to providing a pair of nuts, a spring is provided to press the upper nut of the pair of nuts upwardly of the screw rod and the lower nut of the pair downwardly of the screw rod, and furthermore, the crosshead is moved by magnetic force. 1. A screw rod backlash removal device for a material testing machine, characterized in that a solenoid-type fixing device is provided that can be selectively fixed to one of the upper and lower nuts.