Horology: time measuring systems or devices – Cases – With movement securing means
Patent
1980-04-11
1983-04-05
Roskoski, Bernard
Horology: time measuring systems or devices
Cases
With movement securing means
368318, 368220, G04B 3700
Patent
active
043789579
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to electronic wristwatches having a stepping motor and an analog type of indication, and more particularly it relates to the reduction gear of an electronic wristwatch having a stepping motor and a sweep second.
DESCRIPTION OF THE PRIOR ART
There is known a reduction gear of an electronic wristwatch, /cf. a prospectus No. 850 avialable from Citizen Watch Co Ltd for wristwatch model 85XX/, comprising three concentric output shafts adapted to rotate at different speeds, one of these shafts being adapted to make one full revolution per hour and having mounted threron a friction wheel, the shafts being drivingly connected through gear wheels with one another and with a stepping motor, and a bridge coordinated relative to a plate and secured thereon by threaded means. One of the three concentric shafts carries the second hand, another shaft carries the minute hand, and the third shaft carries the hour hand.
The shaft adapted to make one revolution per hour has one of its bearings arranged in the frame plate while its other bearing is mounted in an auxiliary bridge accommodated in a counterbore provided in the plate on that side thereof which faces the main bridge of the reduction gear. The incorporation of the auxiliary bridge inadvertently results in an increased height of the reduction gear, and, hence, of the entire movement of the timepiece, which is contrary to the present-day trend in making watches of the type being described. The additional counterbore in the plate complicates the manufacture of the plate, and the use of the auxiliary bridge further complicates the assembling of the reduction gear, on account of the necessity of positioning and securing an extra part. Furthermore, the friction torque is produced by two pairs of perpendicular surfaces which are not relatively adjustable, which also substantially complicates the assembling and adjustment of the reduction gear.
There is further known a reduction gear of an electronic wristwatch with analog type of indication, (cf. FRG application No. p 2003045 9-31 published on Jan. 23, 1970, Int. Class G04 C 3/00) comprising three concentric output shafts adapted to rotate at different speeds, of which one shaft is provided with a bearing press-fitted in a bore in the plate and adapted to make one revolution per hour, this shaft carrying a friction wheel; the three shafts being drivingly connected with one another and with the shaft of a stepping motor through gear wheels. The framework of the reduction gear includes a bridge coordindated with respect to the plate and secured thereon by threaded means.
In this known reduction gear the shaft adapted to make one revolution per minute is the last one in the drive chain, which necessitates an additional friction member without which normal operation of the reduction gear is practically impossible. The incorporation of this friction member which is permanently under load adversely affects the efficiency of the reduction gear. Another important feature of this reduction gear is that its gear wheels between the shafts making, respectively, one revolution per hour and one revolution per minute are accommodated in counterbores on both sides of the plate. Consequently, the plate is of a complex configuration, which means that it is labour-consuming to manufacture, and also that it complicates the automation of the process of assembling the reduction gear. Moreover, as the shaft making one revolution per minute has only one bearing, the operation of setting thereon the second hand also becomes complicated.
The closest one to the reduction gear of the present invention is a reduction gear of electronic wristwatch having a stepping motor and a sweep second, disclosed in French application No. 2108200 Cl 04C 3/00. This reduction gear comprises three concentric output shafts adapted to rotate at different speeds, one of the shafts being provided with a bearing in the form of a supporting bush press-fitted in a bore in the plate, this shaft making one revolution per ho
REFERENCES:
patent: 3888073 (1975-06-01), Kurita
patent: 3916614 (1975-11-01), Takatsuki
Kruglov Gennady A.
Malkin Daniel D.
Peredkov Boris A.
Simbirtsev Alexei V.
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