RU2374611C2 - Device for definition of deviations and stiffness parametres of helical compresion springs - Google Patents

Abstract

FIELD: mechanics.

SUBSTANCE: device comprises a base and a movable plate connected to each other by two parallel poles with hinges on the ends. A fixed support is set on the base and designed for setting of a tested spring on it with the spring centre line being located in the poles plane; a support which is movable in the longitudinal and transverse directions and designed for the fixation of the second end face of the tested spring is mounted on the rod of an axial loading power drive passing through the plate. The movable support is connected to the spring cross loading drive as well. The device is additionally equipped by a third pole with hinges on the ends which is also connected to the base and the plate and is equally distanced from the above poles; the hinges set on the poles ends and connecting the plate to the base are spherical ones. The device comprises also force sensors and displacement sensors.

EFFECT: expanded functionality, possibility to measure deviations by their value and direction, improved measurement accuracy.

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Description

The invention relates to measuring technique and can be used in mechanical engineering for determining longitudinal and lateral stiffness, spring withdrawal of spring suspension of vehicles, locomotives and wagons with various options for supporting the ends of the spring.

Known devices for determining the stiffness parameters of helical compression springs, containing a base with rigidly mounted guides on it and mounted on it with the possibility of axial movement along them of the upper support, equipped with clamps. To expand the range of measured characteristics, the devices are equipped with an intermediate support located between the upper support and the base, connected with the carriers that interact with power drives (Technical Report No. 4-14-74 VNITI, UDC 625.2.012.8►39.4(047.1), 1974).

The disadvantage of these devices is the following.

When determining the axial and lateral stiffnesses, the spring is loaded with the appropriate forces. Under the action of a transverse force, the spring deviates from the vertical by a certain angle φ, and its end face receives a transverse strain Δ. In this case, the spring due to bending is additionally extended by ΔН, which can be calculated by the formula

,

,

where N _p - the height of the spring under the working load.

Additional elongation ΔН will unload the spring, which will reduce the accuracy of determining axial and lateral stiffness.

The closest technical solution, selected as a prototype, is a device containing a base with guides (racks) placed on it parallel to each other, fixed and movable in the longitudinal direction of the support, between which the test spring is placed. The device has two cylindrical hinges connecting one ends of the uprights to the base, and their other ends are connected to the movable plate through two other cylindrical hinges, forming a four-link, with the possibility of lateral movement. The movable support is connected to the axial loading actuator rod, which passes through the fixed plate. Angular, linear displacements and axial force are measured by appropriate sensors (patent of the Russian Federation No. 1727012, class G01M 5/00, 1993).

However, the above device has significant disadvantages. Firstly, due to axial clearances in the bearings of the parallelogram mechanism of the strut, together with the test spring under the action of bending moments arising from its axial loading, they tilt in the direction of the bearing axis and rub against the hinge bodies during transverse spring loading. Secondly, the device does not allow to determine the "withdrawals" - the lateral displacements of the ends of the spring arising from its axial loading and due to bending moments due to the non-perpendicularity of the spring axis to the ends (construction warps) and the eccentricity of the resultant pressure forces at its ends. So, for example, for a spring with a bar diameter of 50 mm and a height (under a load of 65 kN) of 562 mm, the withdrawal reaches 45 mm. If the vector of withdrawal in the springs of the spring suspension of the locomotive will be directed in one direction, then this can lead to a rollover of the body. The moments arising during withdrawal are equal to:

M _izg1 = P _article · l and M _izg2 = P _article · N _p · sinα

where M _izg1 - bending moment arising due to the eccentricity of the resultant pressure forces at the ends of the spring;

P _article - axial static load on the spring;

l is the eccentricity of the resultant pressure forces at the ends of the spring;

M _izg2 - bending moment that occurs at the ends of the spring due to the non-perpendicularity of its axis to the ends;

N _p - spring height under load;

α is the angle of inclination of the spring with non-perpendicularity of its axis to the ends.

The objective of the invention is to expand the functionality of the device, namely to ensure the definition of discharges in size and direction and to increase the accuracy of measuring the stiffness parameters of screw compression springs.

The problem is solved in that a device for determining the discharges and stiffness parameters of screw compression springs, containing a base and a movable plate, interconnected by two parallel racks with hinges at the ends, while a fixed support is fixed on the base, designed to be installed on the test subject springs, the center line of which is in the plane of the struts, and the support movable in the longitudinal and transverse directions, designed to fix the second end of the tested spring, is mounted ana actuator rod on the axial load, transmitted through the slab; wherein the movable support is also connected with the drive of transverse loading of the spring; force sensors and displacement sensors, made with the following differences: it is additionally equipped with a third rack with hinges at the ends, also connected to the base and to the plate and equidistant from the existing racks, the hinges located at the ends of the racks and connecting the plate to the base are made spherical.

Thus, due to a new set of features, namely, three racks connected to the base and the movable plate through three pairs of spherical joints and forming a spatial parallelogram mechanism, it is possible to measure “withdrawals” both in magnitude and direction and higher measurement accuracy axial and transverse stiffness of the spring due to plane-parallel movement of the plate.

The invention is illustrated by drawings, which show the proposed device for determining discharges and stiffness parameters of screw compression springs.

Figure 1 shows a General view;

figure 2 is a side view (arrow B);

figure 3 - layout of racks and springs in the plan;

figure 4 is a variant of an intermediate support with a rigid support of the upper end of the spring;

figure 5 is a variant of an intermediate support with a hinged support of the upper end of the spring;

figure 6 - design of a fixed support for rigid support of the lower end of the spring;

figure 7 - design of a spherical hinge (section aa).

A device for determining the discharges and stiffness parameters of screw compression springs consists of a base 1 with three struts 2 mounted on it, equidistant from each other, a movable support 3 and a fixed 4. The movable support 3 has a recess for installing an intermediate support 5 made for two types of support the upper end of the spring: a) hard support (figure 4); b) articulated bearing (figure 5). The intermediate support 5 (Fig. 5) for the hinged support of the upper end of the spring is a universal hinge and consists of a spherical support 6, mounted in the recess of the movable support 3, and a guide cup 7, on the flange of which a spring 8 is mounted, mounted on a fixed support 4. The type of support of the upper end of the spring 8 is determined by the test program. The fixed support 4 (Fig. 6) consists of a guide rod 9 fixed on the base 1 in a special socket and a support cup 10 having an annular spherical protrusion 11 on the inner surface. Such a design of the fixed support 4 eliminates pinching of the guide rod 9 in the support cup 10 and does not allow the friction of the spring 8 on the support Cup 10 when it is bent during testing. The device has six spherical hinges 12 (Fig. 7), connecting one ends of the uprights 2 with the base 1, and their other ends through three other spherical hinges connected with the movable plate 13, forming a spatial parallelogram plane-parallel motion mechanism, providing the possibility of lateral displacement of the movable support 3 in the range 0-360 °, a rod 14 passes through the plate 13, on which the movable support 3 is fixed. The nut 15 is designed to fix the axial load P, which is measured by a strain gauge force sensor 16, set based on 1 and on which the fixed support 4 rests. The force Q, which moves the upper end of the spring 8, is created by a servo drive moving the supports 3 and 5 in the transverse direction. The angular and linear displacements of the ends of the spring are measured by sensors 17 and 18, mounted by brackets 19 on base 1 in the direction of the axes of the support 3. The signals of the sensors 17 and 18 are recorded by the corresponding tensometric equipment.

The device operates in four modes:

- To determine the discharges, the spring 8 is mounted on a fixed support 4 and an intermediate support 5 (Fig. 4) for rigid support of its upper end. By activating the axial loading actuator, the spring 8 is compressed to a predetermined load P, which is controlled by a force transducer of force 16. After releasing the rod 14 from the actuator of the rack 2 under the action of bending moments occurring at the ends of the spring during its axial loading, they are deflected by a certain angle α in the direction vector of the resulting bending moment, and the movable intermediate support 5 together with the upper end of the spring 8 will receive a "pull" - lateral displacement. The magnitude of the withdrawal is measured by the sensor 18, and the direction of the withdrawal vector is found by the vernier 20 (Fig. 3), established on the basis of 1. Thus, the proposed device design allows to determine the "withdrawals", which was previously impossible.

- To determine the axial stiffness, the spring 8 is installed on the supports 4 and 5 (figure 4) for hard support of its upper end. By turning on the power drive connected to the stem 14, compress the spring to the force P provided by the test program and control it by a strain gauge force transducer 16, and the axial deformation is measured by a linear displacement transducer 18. Three posts connected to the base 1 and the plate 13 with spherical hinges prevent plate distortion 13 and provide a more accurate measurement of axial stiffness.

- The transverse stiffness of the spring is found as follows. The spring 8, as in the previous modes, is loaded with the force provided for by the test program. Then, by turning on the transverse loading drive associated with the movable plate 3, the upper end of the spring 8 is shifted in the transverse direction by a certain value Δ. In this case, the posts 2 are tilted by an angle α equal to

,

,

where H _article - the height of the rack.

The transverse force Q developed by the drive is determined by the force meter included in the drive kit. When the spring 8 is tilted, its axial stiffness will decrease somewhat, which, in turn, will lead to a decrease in the axial load on the spring 8 with its axial deformation constant. The strain gauge force transducer 16 will record the load drop P, after which the inclusion of the axial load drive load the spring 8 to the required load test program P and fix it with a nut 15.

A feature of the parallelogram mechanism is that when the racks 2 are tilted, a horizontal restoring force F appears, which can be easily calculated from the equilibrium conditions of the racks 2:

F = (P-G ₁ -G ₂ -3G ₃ ) tgα,

where P is the axial force compressing the spring;

G ₁ - the weight of the movable supports 3 and 5;

G ₂ - the weight of the plate 13;

G ₃ - the weight of one rack;

α is the angle of inclination of the racks.

Obviously, the force N, which moves the end face of the spring in the transverse direction, is equal to the difference between the force Q developed by the drive and the restoring force F:

N = Q- (P-G ₁ -G ₂ -3 · G ₃ ) · tgα.

,The transverse stiffness of the spring is found by the formula

,

where Δ is the transverse shift of the upper end of the spring.

- To determine the technological errors of the shape of the spring without a gap, it is mounted on the lower support 4 and the intermediate support 5 (Fig. 5) with a hinged support of the upper end. If the tested spring is made with geometric shape deviations, then its upper end together with the guide cup 7 (Fig. 5) will receive angular and linear displacements, the value of which can be judged by the readings of the tensometric equipment to which the sensors 17 and 18 are connected.

It can be seen from the foregoing that the problem of determining the spring withdrawal vector both in magnitude and direction has been solved, and thereby the device’s functionality has been expanded; in addition, the spatial mechanism of plane-parallel motion eliminates the bias of the upper plate 13 and thereby increases the accuracy of measuring the spring stiffness parameters.

Claims (1)

A device for determining the discharges and stiffness parameters of compression screw springs, containing a base and a movable plate, interconnected by two parallel racks with hinges at the ends, while a fixed support is fixed to the base, designed to install a test spring on it, the center line of which is in the plane of the struts, and the support movable in the longitudinal and transverse directions, necessary to secure the second end of the test spring, is mounted on the rod of the axial immersion passing through the plate, the movable support is also associated with drive springs transverse load; force sensors and displacement sensors, characterized in that it is additionally equipped with a third rack with hinges at the ends, also connected to the base and the plate and equidistant from the existing racks, the hinges located at the ends of the racks and connecting the plate to the base are made spherical.

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