DE2832410C2 - Measurement method for the non-contact measurement of the tensile forces of endless traction devices - Google Patents

Description

20th

The invention relates to a method for the continuous and non-contact measurement of tensile forces in the incoming and outgoing strand of endless traction devices in operation, for example on conveyor and plow chains or comparable facilities, especially in underground mining.

In an attempt to keep increasing the services in the underground area with regard to coal production increase, it has been found that the chains, for example the plow chains or the chains of the Funders, are to be seen as weak points of the operating resources.

In adaptation to the required performance and based on an unlimited shelf life Chains of a size would have to be used, which for operational and spatial reasons cannot be carried would be. For this reason, chains are used that are only designed for a limited service life.

To avoid the difficulties associated, for example, with chain tears, in particular the high costs Measurements to determine and check the chain tensile forces are to be avoided in order to avoid the loss of conveyance carried out.

A measuring magnetic tape recorder is known, as it is in the Glückauf research booklet 30/1969, No. 5, pp. 253-257 is described, the registration of measured values on difficult to access machine parts in a simple way and in particular traction means. The basic principle is conversion to a mechanical one Size in an electrical with the help of passive encoders, z. B. with strain gauges in a Wheatstone Full bridge are summarized. The recording takes place with a running in the chain strand Magnetic tape recorder. This is built into a protective housing, the shape of which corresponds to the machine to be examined or system is adapted.

The disadvantage of this measuring magnetic tape recorder is essentially that it is necessary for the Synchronism does not have a sufficiently robust drive to withstand the rough underground operation withstands. In addition, it has little storability and is unsuitable for one continuous operation.

In addition to its mechanical sensitivity, there is another serious disadvantage of the Measuring magnetic tape recorder in that it does not provide instant readings, since only after the recording and after Removal of the magnetic tape an evaluation can be carried out.

In contrast, it is the object of the invention to provide a method for measuring tensile forces, in particular on the incoming and outgoing strand of endless traction means, to create, which is the rough underground operation is adapted, which operates continuously, which enables immediate evaluation and in this way the success or failure of measures immediately through a continuous display of the tensile force values made clear

This object is achieved according to the invention in that the drive torque acting on the drive drum is measured, which is inversely proportional to the efficiency of the drive drum and proportional to the difference in the tensile forces in and expiring strand, and that the sum of the in The bearing forces acting in the conveying direction are measured, which are proportional to the sum of the tensile forces mentioned is

In the context of the invention, it is found to be advantageous that the computational determination of the the total and differential forces resulting tensile forces of the upper and lower run in the corresponding Dimension can be carried out via an evaluation unit.

Compared to the known measuring methods, the chain tensile forces can be measured with the method according to the invention continuously and, above all, without interfering with the operational sequence, at the same time on the main and auxiliary drives in the upper and lower run as well as for any length of time without strong mechanical stress on the transducers can be measured via carriers and storage both in test operation and in practical operation.

In order to measure the chain tensile forces without contact using the method according to the invention, it is necessary to first calculate the difference between the chain tensile forces F ₀ -Fu over the torque acting on the chain star, multiplied by the known efficiency of the chain / chain star.

According to Grotenhöfer, the chain / chain star efficiency results from a power balance (Diss. An KWTH Aachen 1978, p. 85)

__ ₌ (F "-F _u ) -v _K P on M _d -2n- η

(D

with the sizes

Fo chain tensile force in the upper run

Fu chain tensile force in the lower run

Vk chain speed

Md torque on the chain star

η speed of the chain star

So it is initially dependent on these five variables. The chain speed Vk is linked to the speed of the chain star π via the running circle diameter D _{LK according to the equation}

v _K = π ■ D _LK - ti.
Thus equation (1) becomes
₌ (F _O -F _U ) -D _LK I2

(2)

(3)

This corresponds to the statement in Figure 49 (Grotenhöfer) that η is independent of v% (and thus also of the speed n) For a certain chain star (with a certain running circle diameter), η only depends on the three variables F ₀ , F . and Md according to equation (3).

In Figure 50 of the above-mentioned dissertation, η is a function of the useful load Fl and the pre-tensioning force F ₁ . applied. The chain forces in the upper run F ₀ 1 nd in the η lower run F ₁₁ can be determined from the groove load F _L and the pre-tensioning force Fv according to the following considerations:

1. The force curve in the endless chain at standstill according to FIG. 1; and

2. the force curve in the endless chain when driving one chain star with F1 and braking the other chain star also with F1 and avoiding hanging chains according to FIG. 2.

The useful force Fl is equal to the difference in the chain tensile forces of the upper and lower run

F. - P - F (A \

fL - r _o - tu. (1)

The relationship between the pretensioning force F ^ and the chain _{tensile forces in the upper run F 0} and in the lower run F ₁₁ results from the fact that the length of the chain must be the same both when the chain is stationary and when it is running.

For the elongation Al of a chain results from Hooke's law

E-A

J F _K (!)

(5)

with the sizes

E modulus of elasticity of the chain

A Total chain cross-section

/ Length of the chain

Fk chain pull

I Location coordinate along the chain

F _K (s) chain tensile force at location ξ

If the chain pulling force along the chain is constant or constant in sections, the following applies instead of Equation (5)

Al

E- A

(6)

The chain elongation during standstill and during operation must be the same:

F "-21 F ₀ - I ₊ F _u

This results in
F _V = (F _O + F _u ) / 2.

From the measured quantities F ₀ and F _u , Grotenhöfer calculated the useful force Fl and the pretensioning force F, - using equations (4) and (8). Conversely, the chain tensile forces F ₀ and F _{u can be determined} from the payload Fl and the pretensioning force F _v from:

F _o = (2F _v + F ₂ ) / 2,
F _u = (2 * Fy-F ₂ ) / 2.

(9)
(10)

With the help of Figure 50 (Grotenhöfer) and the equations (9) and (10), η can also be given as a function of the chain forces F ₀ and F _u :

η = r \ (F _a Fu).

(H)

According to equation (3), only one specific value of the torque M / can be assigned to a specific combination of values tj, F ₀ and F _u. It is therefore sufficient to state the dependency according to equation (11), according to which the chain / chain star efficiency only depends on the chain tensile forces in the upper run and the lower run. This dependency is known from Grotenhöfer's dissertation or can be determined in a corresponding manner.

While planing systems and chain scraper conveyors are in operation, the torque on the chain star M and, for example, the bearing force Fweiie are measured. The relationships according to equations (3) and (11) apply:

35

and

Fw-IIe - FJ ■ D _LK n V (F ₀ , F ")

F _u ■

(12)

(13)

40

E-A E-A

E- A

These two equations allow the two unknowns F ₀ and F ₁₁ to be determined numerically, since the diameter of the pitch circle is a known quantity.
A downstream evaluation unit calculates the tensile force values in the corresponding dimension. The calculated chain pulling forces allow immediate statements to be made about the capacity utilization of the drives, about the type of laying of the conveyor, about the change in speed or, as mentioned at the beginning, about the success and failure of measures.

Furthermore, the measured chain tensile forces enable statements to be made about the chain stress in the Operation as well as a prediction of the chain service life if the appropriate damage hypotheses are known.

In addition, the measured values enable the distance between the chain star axes to be changed, which means that the Specification of a defined pre-tensioning force for planing and conveyor systems as well as the damping of system vibrations given by planing and conveyor systems

60 is.

1 sheet of drawings

Claims (1)

Claim: A method for the continuous and non-contact measurement of tensile forces in the incoming and outgoing strand of endless traction means in operation, for example in conveyor and plow chains or comparable devices, in particular in underground mining, characterized in that the drive torque (M) acting on the drive drum is measured, the inversely proportional to the efficiency (η) of the drive pulley and proportional to the difference (F _o -F _u ) of the tensile forces in the incoming and outgoing strand, and that the sum (Fwciic) of the bearing forces acting in the conveying direction is measured, which is proportional to the sum ( F ₀ + F _a ) of the tensile forces mentioned.