JPS60227034A - Vibration removing table - Google Patents

Abstract

PURPOSE:To change natural vibration frequency without replacing an elastic body by disposing an elastic body formed in such a manner that a straight line portion is extended at least at one end of a circular-arc portion, with the straight line portion erected between a loading table and legs. CONSTITUTION:An elastic body 20 disposed between a loading table 10 and legs 15 is obtained by forming vibration-proof rubber having a suitable diameter to be U-shaped. The elastic body 20 comprises a semicircular circular-arc portion 21, and a straight line portion 22 and a straight line portion 23 which are extened from the outer peripheral edges of both ends of the circular-arc portion 21 in parallel. The elastic body 20 has the respective straight line portions 22, 23 coupled to the legs 15 and the loading table 10 by coupling members 24-27, with the circular-arc portion 21 positioned above, and with the straight line portions 22, 23 erected. The natural vibration frequency can be changed by adjusting the coupling positions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration isolating table, and in particular, it is possible to reduce the spring constant of a vibration isolating elastic body and to change the natural frequency without replacing the elastic body.

Generally, when precision instruments such as optical instruments and electron microscopes are subjected to external vibrations, relative displacement occurs inside the instrument, increasing measurement errors and causing problems such as blurred images. Anti-vibration tables are used to prevent the transmission of vibrations. As shown in FIG. 1, this type of vibration isolation table has an anti-vibration structure between a mounting table 2 on which a precision instrument 1 is placed and a table leg 4 placed on a support 5 such as a floor surface. The mounting base 1 is supported horizontally by arranging elastic bodies 3 such as vibrating rubber or coil springs at three or more locations. The smaller the spring constant of the elastic body of this vibration isolating table, the larger the amount of deflection, and therefore the lower the natural frequency that affects the external vibration transmission rate, resulting in better vibration isolation performance. Since the allowable deflection of elastic bodies is limited due to buckling deformation and durability, there is also a certain limit to the reduction in the natural frequency. According to the results of measuring the number of movements, it is 5 to 10 in the vertical direction.
Hz% in the horizontal direction is 3 to 5 Hz, and there is a problem in that it is impossible to lower the natural frequency below this value.

In addition, when it is necessary to change the natural frequency of the conventional vibration isolation table, such as when the weight of precision equipment fluctuates,
It is necessary to replace the elastic body with an elastic body having a spring constant corresponding to weight fluctuations, and disassembling and assembling the vibration isolating table requires troublesome work.

The purpose of this invention is to solve the above-mentioned problems and provide a vibration isolation table that can obtain a lower natural frequency than before and that can change the natural frequency without replacing the elastic body. do.

That is, as shown in the embodiments and drawings described later, the present invention provides an arcuate portion 21 and an arcuate portion extending from at least one end of the arcuate portion between the equipment mounting table 10 and the pedestal leg 15 placed on the support body 14. An elastic body 20 consisting of straight parts 22° 23
are arranged with the linear portions standing upright, and one linear portion 22 and the other linear portion 23 or arcuate portion 21 of the elastic body 20 are arranged.
One end of the mounting base 10 is connected to the mounting base 10 and the other end is connected to the base leg 15, and the mounting base 10 is suspended from the base leg 15 via the elastic body 20.
The distance L from the center of curvature O to the connection position of the elastic body 20 to the mounting base 10 and the connection position of the elastic body to the base leg
The present invention relates to a vibration isolation table characterized in that at least one of L1'+L2' is configured to be adjustable.

Embodiments of the present invention will be described below with reference to the drawings.

2 and 3 show an embodiment of the invention, and a second embodiment of the invention is shown in FIG.
The figure is a front view, and FIG. 3 is a plan view with a part of the mounting base removed.

In the above figure, reference numeral 10 is a mounting stand on which precision equipment (not shown) is placed. On the lower surface of this mounting stand 10, two mutually opposing guide plates 11 are suspended in the front and rear directions. It has been installed. A pair of left and right pedestals 15 are placed in parallel on a support 14 such as a floor surface.
In this case, a guide plate 16 is vertically attached to the mounting base 100 at a position opposite to the guide plate 11. The guide plate 11 of the mounting table 100 is provided with two through holes 12 at regular intervals in its height direction (see FIG. 4).
Similarly, the guide plate 16 is also provided with multiple stages of through holes 17.

The elastic body 20 placed between the mounting base 10 and the base leg 15 is formed by molding anti-vibration rubber into a U-shape having an appropriate diameter. radius of curvature R
) 21, and a straight part 22 and a straight part 23 extending in parallel from the outer peripheral edge at both ends of the circular arc part 21.
The lengths from the center of curvature 0 of 1 to the ends of the straight portions 22 and 23 are Ll + L2, respectively, and the length L2 of the straight portion 23 is longer than the length Ll of the straight portion 22. It has become.

The above elastic body 20 has a straight portion 2 with the arcuate portion 21 facing upward.
2. With 23 standing upright, one straight part 22 connects to the guide plate 16 of the pedestal 15 with a pair of connecting parts +1' 24 , 2
5, and the other straight portion 23 is connected to the mounting base 10.
The mounting base 10 is connected to the guide plate 11 by a pair of connecting members 26 and 27, and is supported horizontally by being suspended from the base legs 15 via the elastic body 20.

The structures of the connecting members 24.25 on the pedestal 15 side and the connecting members 26.27 on the mounting base 10 side are the same, so the structure and connection of the connecting members 24.25 on the pedestal 15 side are the same. The method is shown in FIG. This connecting member 24.2
A groove 30.31 having an approximately semicircular cross section having the same radius of curvature as the cross-sectional circle of the elastic body 20 is provided on the inner surface of the elastic body 5, and the straight portion 22 of the elastic body 20 is held between the groove 30. hand,
A bolt 33 passed through a bolt hole (not shown) is inserted into a through hole 17 of a guide plate 16 of the base leg 15, and a nut 34 is tightened to connect the guide plate 16.

The connecting position of the elastic body 20 shown in FIG. Information board 11
The distance from the center of curvature O of the circular arc portion 21- of the elastic body 20 to the connection position is L12. Mounting stand 1
Although the linear portion 23 on the 0 side is L12, the connecting position of each linear portion 22.23 is the same as that of each connecting member 24.23.
25; 26.degree. 27 can be changed by fastening them to the through holes 17.degree. 12 of different stages of each guide plate 16.11.

The operating procedure for changing the connection position of the linear portions 22, 23 of the elastic body 20 is as shown in FIG. 6 on the mounting platform 1o side.
27a, one of the connecting members 26a is fixed with a bolt 33a inserted into the through hole 12 of the other stage of the guide plate 11, and then the bolt 33a is inserted into the bolt hole of the other connecting member 27a 17, and the naso ) After tightening and fixing 34a, the connecting members 26 and 2' are connected to the original step position.
Remove γ.

In the vibration isolation table having the above configuration, the bending rigidity of the circular arc portion 21 and the straight portion 22 of the elastic body 20 is used to withstand the vertical load in the vertical direction, and the bending rigidity of the circular arc portion 21 and the straight portion 22 of the elastic body 20 is used to withstand the vertical load. Due to the bending rigidity of the section 21 and the oscillating action of the straight section 23, and also due to the torsional rigidity of the circular arc section 21 and the oscillating action of the straight section 23 against horizontal torsional loads, the deflection against loads in each direction is reduced. The amount is extremely sharp at 81, elastic body 2o
Even if a large amount of deflection occurs, the radius of curvature R of the circular arc portion 21
By setting the value to an appropriate value, it is possible to avoid the occurrence of local buckling deformation. Therefore, by using the elastic body of the present invention, a vibration isolating table having a much lower natural frequency than the conventional one can be obtained.

When the natural frequency of the vibration isolation table having the above configuration was actually measured, the results shown in FIGS. 7 to 9 were obtained.

The actual measurement conditions are as follows.

Weight of precision equipment Approximately 40Kp Elastic body (vibration isolating rubber) Shaft diameter 42mm Radius of curvature of arc part 7o Length of straight part L1=100+nm, L2"300
w1 Length from the center of curvature of the circular arc part to the connection position of the straight part L1' = 80ttan, L2' = 270
Fig. 7 shows the measured waveform in the vertical direction, Fig. 8 shows the measured waveform in the horizontal bending direction (left and right in Fig. 2), and Fig. 9 shows the measured waveform in the horizontal torsional direction (front-back direction in Fig. 2). (The vertical axis is amplitude, the horizontal axis is time).

As is clear from the above figure, the natural frequency fz in the vertical direction is 2.27 Hz, and the natural frequency fx in the horizontal bending direction is approximately I.
It can be seen that the natural frequency toy in the horizontal torsional direction is approximately IHz.

However, in the vibration isolation table with the above configuration, the connection position 1 of the straight portion 22.23 is from the center of curvature O of the circular arc portion 21 of the elastic body 20.
The spring characteristics of the elastic body 20 change depending on the distance L1' + L2'. Therefore, when it becomes necessary to change the natural frequency due to a change in the weight of the on-board equipment, the connection members 24 and 25 can be attached to the straight portions 22 of the elastic body 20 in the vertical direction, while the elastic body When attaching the connecting members 26 and 27 to the straight portion 23 of 20, the required natural frequency can be obtained by simply adjusting the position.

In the above embodiment, a case has been described in which the elastic body 28 is arranged with the arcuate portion 21 facing upward; however, on the contrary, it may be arranged with the arcuate portion 21 facing downward. , the straight part 23 is installed on the mounting base 10, and the straight part 2 is installed on the mounting base 10.
3, the same effect can be obtained by connecting 8
．． In addition to the one in which the arc portion 23 extends, it is also possible to use one in which the straight portion extends only from one end of the circular arc portion 21.

FIG. 10 and FIG. 11 each show an embodiment in which the shape of the elastic body of the present invention is changed.

The elastic body 20 shown in FIG. 10 is formed by molding the arcuate portion 21 into a nearly completely circular bag shape and narrowing the distance between the straight portions 22 and 23. The elastic body 20 shown in FIG. A smaller spring constant can be obtained. FIG. 11 shows the U shown in FIG.
A letter-shaped elastic body 20a.

20b are combined, and each straight part 23a.

23b are connected in series and molded into a trap shape, and an elastic body with a smaller spring constant can be obtained.

The molding material for the elastic body in each of the above embodiments is not limited to rubber, but may also be a viscoelastic material such as plastic, or reinforced rubber or reinforced plastic made by mixing reinforcing fibers with rubber, plastic, or the like.

It is preferable to use a metal material with a higher elastic modulus than the above-mentioned materials for trenches, especially vibration isolation tables for heavy loads, and elastic bodies molded from these various materials also have the same effects as described above. Effects can be obtained.

Further, this elastic body is not limited to the rod-shaped body having a circular cross section as in the above embodiments, but may have a polygonal shape, an elliptical shape, a flat shape, or the like.

As described above, the present invention provides an elastic body formed between an equipment mounting table and a pedestal leg on a support body with a straight part extending from at least one end of an arcuate part, with the straight part standing upright. The mounting base is suspended from the base legs via the straight part of the elastic body, or the straight part and one end of the circular arc part, and at least one of the connection positions with respect to the mounting base and the base legs is adjustable. There is.

Therefore, according to the present invention, due to the bending rigidity, torsional rigidity, and rocking action of the elastic body, spring characteristics with a large amount of deflection against vertical and horizontal loads are exhibited, and the natural frequency is lower than that of the conventional one. Not only does it serve as a vibration isolation table, but the natural frequency can be changed by adjusting the connection position of the elastic body, so there is no need to replace the elastic body, making it suitable for precision instruments. , a vibration isolation table that is easy to handle can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a front view of a conventional vibration isolation table, FIG. 2 is a front view showing an embodiment of the present invention, FIG. 3 is a plan view thereof, and FIG.
5 is an enlarged sectional view showing the connecting portion of the elastic body, FIG. 6 is a front view showing the procedure for adjusting the connection position of the elastic body, and FIGS. 7 to 9 are Figures 10 and 11 are actual measured waveform diagrams of the natural frequency of the vibration isolation table of the present invention, respectively.
Each figure is a partial front view showing another embodiment of the invention. In the figure, 10 is a mounting base, 14 is a support, 15 is a pedestal, and 20
is an elastic body, 21 is a circular arc portion of the elastic body, 22°23 is a straight line portion of the elastic body, 0 is the center of curvature of the circular arc portion, t, 1/, L2
' is the distance from the center of curvature of the circular arc part to the connecting position of the straight part. Patent applicant: Yokohama Rubber Co., Ltd. Figure 4

Claims (1)

[Claims] An elastic body consisting of a circular arc portion and a straight portion extending from at least one end of the circular arc portion is disposed between the equipment mounting table and the base leg placed on the support body, with the straight portion standing upright; One straight part and one end of the other straight part or arcuate part of the elastic body are connected to the mounting base, and the other is connected to the base leg, and the mounting base is suspended on the base leg via the elastic body. A vibration isolation table characterized in that at least one of the distances from the center of curvature of the circular arc portion of the elastic body to the connecting position of the elastic body to the mounting base and the connecting position of the elastic body to the base legs can be adjusted. .