RU1800480C - Elastic suspension for precision instrument - Google Patents

Abstract

Usage: the invention relates to precision engineering and instrumentation and can be used as a suspension for a precision instrument or test bench. The purpose of the invention is to improve operational capabilities. In order to achieve this goal, in the suspension, the joints of the elastic bands with the inner cups are made detachable. Moreover, the tapes are deprived of freedom of rotation in coaxial cups relative to their longitudinal axes by means of guides. In this case, both the inner and outer cups are rigidly connected to each other by the frame and the base. 4 ill.

Description

The invention relates to precision engineering and instrumentation and can be used as a suspension for a precision instrument or test bench.

The purpose of the invention is to increase labor productivity in the process of assembly and adjustment of the structure, to increase torsional stiffness with respect to axes lying in a plane perpendicular to the axis of rotation of the suspension, and to eliminate the influence on the measurement of the physical values of the suspension adjustment errors on the elastic elements.

Figure 1 and 2 shows the proposed suspension; Fig. 3 and 4 are diagrams for calculating the stiffness of the tape.

The suspension comprises a base 1 made in the form of a platform with two vertical struts, a frame 2, elastic supports, which are two coaxially arranged relative to each other

(internal and external) cups 3, 4 and 5, 6, interconnected by six elastic bands 7-12, offset from one another along the axis of the cups and evenly spaced in a plane perpendicular to the axis of the cups, at angles of 120 °. Along the axis of the supports between the inner 3, 4 and outer 5, 6 cups, elastic torsion bars 13 and 14 are installed, one end of which is rigidly attached to the inner cups 3 and 4, and the movable sleeves 15 and 16 are freely moved along the second end using nuts 17 and 18 The frame 2, designed to accommodate the payload, is attached to the inner cups 3 and 4, and the base 1 with its vertical posts to the outer cups 5 and 6.

The suspension is equipped with six devices for loading and moving elastic bands 7-12, made in the form of differential screw gears, the screws 19 of which

with

WITH

00

oh oh

N

00

about

rigidly fixed on the terminations of elastic tapes, moved by nuts 20 in the radial direction. The nuts 20 are threaded by external threads into the housings 21 of the tensioning devices mounted on the outer cups of the 5 and 6 supports. All six tapes have a backlash-free component of 22 in the outer cups.

In order to increase the manufacturability of the structure, reduce assembly time and reduce the error of the measured physical quantities, the suspension is equipped with detachable joints of elastic bands 7, 8, 9, 10, 11, 12 with internal cups 3, 4, made in the form of screws 23, rigidly fixed to elastic backings belts and fixing nuts 24. All six belts are also provided with guides 25 in the inner cups of the suspension. The guides 25 and 22 are designed so that the elastic bands are deprived of freedom of rotation in the coaxial cups relative to their longitudinal axes when the nuts 20 and 24 are rotated.

In this example, the guides 25 and 22 are a square sectional view. To simplify the assembly of the structure on the outer cups 5, 6, cutouts 26 are made diametrically to the loading-moving devices and coaxially with the longitudinal axes of the elastic bands. These cutouts are necessary for easy access to the nuts 24 during the assembly of the suspension.

The support is assembled as follows.

The nuts 20 are screwed onto the seals 19 together with the housings 21 of the load-transfer devices. Then the tapes with guides 25 and 22 are installed in the inner and outer cups. The nut 24 fixes the tape in the inner cups along its longitudinal axis. The head of nut 24 can be turnkey, which tightens this nut through hole 26 in the outer cup.

The suspension works as follows.

In order to create the required moment of resistance, it is necessary to expose the tapes to a tensile or compressive force, which is created by rotating the nut 20 (Fig. 2).

When this nut rotates, it is possible to twist the tape at an angle p (Fig. 3) relative to its longitudinal axis. This leads to a change in the bending stiffness H EI, and therefore to a change in the radius of curvature: it will become larger when the inner cup is rotated relative to the outer one by the same angle before twisting and after twisting the tape.

Thus, when the inner cup is rotated relative to the outer, the axis of rotation will shift by the amount of AX (Fig. 4) from the initial position, due to the different bending stiffness of the tapes, which is unacceptable in suspensions of precision instruments. The introduction of guides 22 and 25, depriving the elastic bands of freedom of rotation about their longitudinal axis, eliminates the error in adjusting the suspension, which ultimately reduces the error in physical quantities.

Example. When twisting the tape at an angle (p, the stiffness of the tape N changes (Fig.Z).

For untwisted tape Н Е у, where

.3 b at T2 the axial moment of inertia of the cross section;

E is the modulus of elasticity.

For swirling tape Н1 Е 1у:

I1 1 Y cos2 (f + lz Sin2 p - Yz y -sin2 f),

,

h h

where is lz -jo. Zy / Y z dF 0.

12F

Let's say that the tape twisted at an angle. With the following support parameters (Fig. 3, Fig. 4) L Ri + R2; a 5 L / Ri; h 1.5 m; b 20 m; RI 15-10 3 m; R2 60 About 3 m, T - preload force, / 5 3 ° angle of rotation of the inner ring relative to the outer. Then the axial moment of inertia of the cross section of the tape to twist

1u 0.5b-. Initial stiffness

H 11877 m2.

The axial moment of inertia of the cross section of the tape after twisting

1U 0.58.

Rigidity after twist

N 12296 N m2. As can be seen from the calculations, the stiffness of the tape increased.

The initial moment of the counter-action of the tape is calculated by the formula

..chaRi + tha then

MPr ----- j --------; - T / I,

with ha (+ a) -cha

SA

E C

where L Ґ; MPR 0.591 N m.

The moment of counteraction after spinning the tape

Mp 0.606 Nm.

The initial radius of curvature when the inner cup is rotated relatively outwardly / about at an angle of 1 / R MPr / N or R 2 m, a R 2.03 m.

As can be seen from the calculations, the radius of the twisted bending tape increased by 30 mm. This change will entail additional radial forces, which will ultimately lead to a displacement of the axis of rotation of the frame 2.

Thus, the proposed suspension in comparison with the prototype allows you to place the load without balancing it, quickly assemble the suspension and replace faulty elastic bands, and also eliminate errors in the suspension adjustment, which ultimately leads to more reliable measurements of physical quantities.

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5

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Claims (1)

SUMMARY OF THE INVENTION An elastic suspension for a precision device, comprising a support made in the form of two coaxially disposed cups interconnected by elastic bands uniformly spaced in a plane perpendicular to the braid of the cups and offset from one another along the axis of the cups, means for loading elastic bands, axial torsions adjustable in length, connecting the bottoms of the glasses, guides of elastic bands placed in the outer glass of the support, characterized in that, in order to improve operational capabilities It is equipped with an additional support made in the same way as the main one and placed mirrored relative to it, the elastic bands of each support are provided with additional guides in the inner cups, the joints of the elastic bands with the inner cups are detachable, with the inner cups of the main and additional supports to each other and the outer cups of the main and additional supports to each other are rigidly connected by structural elements. FIG. 3