IMPROVED METHOD OF CHECKING THE RATE OF MECHANICAL CLOCKS

M. I. Kiselev, V. I. Pronyakln, and V. V. Urozhenko

UDC 681.11.031.11.089.5.002.235

In the production of mechanical clocks the quality of a finished item is checked using an acoustic method which is implemented by means of a type PPCh-7M testing instrument for the escapement.

The acoustic method has the advantages of simplicity and the possibility of checking the instantaneous rate in a closed housing. It is based technically on the use of a piezo- electric element in a primary transducer which converts the acoustic noise of an escapement into electrical signals that are utilized for the measurements.

A drawback of this checking method is that the primary transducer does not permit the use of electronic counters which are, as a rule, a component part of automated information- measuring systems.

The physical and technical reasons for the drawback are as follows: The microphone receives the sum of the vibrations for a number of equivalent oscillators (the parts of the clock mechanism) excited by a collision between the parts of the escapement. An elementary component of such a sum is a damped vibration [i]. It is not possible to predict every specific result from the addition of elementary components in an acoustic signal. The lack of repeatability in the shape of electrical pulses obtained from the piezoelectric element, the variations of their duration, and the distortion of the wavefronts rule out the use of such instruments as frequency meters to measure the acoustic signals without coarsening con- versions (the use of signal envelopes).

It is clear that flrst-hand information about the operation of a clock mechanism is contained in the variations of parameters for the movement of the structural elements (for example, of an oscillator), but the acoustic signals that accompany clock's motion are only an indirect source of this information that introduces extra distortion. It is a character- istic of the method that the primary transducer averages the incoming information, and the measuring process for instantaneous rates of clocks with the PPCh-Tm is of an indirect nature. The measuring accuracy for the instantaneous rate of clocks according to the state standards for a unique system of measurements must have the information in the form of a function for the distribution of the random-error component of a measurement (GOST 8.009-84 and GOST 8.011- 72). In view of the structural complexity of the information obtained (the acoustic signals), which arrives in the area where the microphone is applied, it is not possible to isolate the random component.

To improve the method of checking a clock's rate and obtain information regarding the vibration of the balance for diagnosing the mechanism more accurately, a promising method of direct measurements is proposed with the primary signal obtained by a photoelectric method

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Fig. i

Translated from Izmeritel'naya Tekhnika, No. 6, p. 37, June, 1987.

558 0543-1972/87/3006-0558512.50 ~ 1987 Plenum Publishing Corporation

Fig. 2

[2] which replaces the microphone with a photoelectric transducer. This method, which has a higher metrological level, is already in practical use for checking clock mechanisms [3, 4]. It is possible to employ it in the production process because the rate must also be checked before mounting the mechanism in the housing, when it is in a plastic package.

A block diagram of the proposed measuring method is shown in Fig. i. Light flux from a source I, which is directed on to the balance 2, intersects a distinctive element (for example, a spoke of the balance or a contrasting mark on its rim). Thus a modulated luminous flux is created that carries information in the form of pulses which are picked up by a photoelectric transducer 3. After amplification and conversion the signal can be passed to the input M of a type PPCh-7M instrument 4, or to an automated informatlon-measurlng system 5 to measure the instantaneous rate and the mechanical working for diagnostic purposes in an automatic mode.

It must be noted that the use of a photoelectric checking method to obtain the primary measuring signal makes it possible to utilize a type PPCh-7M instrument also after the piezo- electric element of a microphone has failed, the service life of which is considerably shorter than that of the actual instrument. Thereby measurements are provided simultaneously by the type PPCh-7M instrument and by the standard methods [5], and the use for checking the PPCh-7M instrument of a nonstandard, expensive simulator for the clock rate is avoided, being replaced by a standard pulse generator i and a frequency meter 2 in accord with the block diagram for checking shown in Fig. 2, where 3 is the PPCh-7M instrument.

The tendency towards the use of optical-physical measuring methods in the clock industry is borne out by the patents of foreign companies [6, 7] which introduce holes in the mechan- ism's housing to permit their application.

Thus the checking method we have discussed opens possibilities for automating the in- spection and processing the data for diagnostic purposes; it realizes for a PPCh-7M a pri- mary transducer with a higher metrological level, and permits it to be employed in combina- tion with other measuring facilities.

LITERATURE CITED

i. B. V. Pavlov, Acoustical Diagnosis of Mechanisms [in Russian], Mashlnostroenie, Moscow

(1971). 2. V. I. Pronyakin, Trans. of the Scientific-Research Institute of the Watch Industry, 70

(1982). 3. A. M. Kuritskii et al., Trans. of the Scientlflc-Research Institute of the Watch Indus-

try, No. 16, 15 (1974). 4. A. M. Kurltskli et al., Trans. of the Scientific-Research Institute of the Watch Indus-

try, No. 8, 81 (1971). 5. GOST 8.207-76. SSI. Direct Measurements with Repeated Observations. Methods of Pro-

cessing the Results of Observations. Basic Conditions. 6. Patent: Great Britain No. 1600409. 7. Patent: Great Britain No. 1600410.

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