US3798890A

US3798890A - Coil construction for electronic timepieces

Info

Publication number: US3798890A
Application number: US00319110A
Authority: US
Inventors: H Kurita; T Ota
Original assignee: Suwa Seikosha KK
Current assignee: Suwa Seikosha KK
Priority date: 1971-12-29
Filing date: 1972-12-29
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26
Also published as: GB1410520A

Abstract

An electronic timepiece provided with a pair of spaced balance wheels mounted on a common shaft and carrying a magnetic circuit including an air gap between said balance wheels is provided with a coil having a streamlined periphery, or with a coil-holding member having said streamlined periphery.

Description

United States Patent [191 Kurita et al.

[451 Mar. 26, 1974 COIL CONSTRUCTION FOR ELECTRONIC TIMEPIECES Inventors: Hirohisa Kurita, Shimosuwa-machi;

Tomio Ota, Okaya, both of Japan Assignee:

Tokyo, Japan Filed:

Appl. No.: 319,1 10

Dec. 29, 1972 Foreign Application Priority Data Dec. 29, 1971 Japan 46-001876 us. c|.. .,s gs 531(136 Int. Cl. G04c 3/04 Field of Search 58/28 R, 28 A, 107;

Kabushiki Kaisha Suwa Seikosha,

[56] References Cited UNITED STATES PATENTS 2,986,683 5/1961 Lavet et al 310/36 X 3,184,669 5/1955 Williams 310/36 X Primary ExaminerRichard B. Wilkinson Assistant Examiner-Edith Simmons Jackmon Attorney, Agent, or Firm-Blum, Moscovitz, Friedman & Kaplan [5 7] ABSTRACT An electronic timepiece provided with a pair of spaced balance wheels mounted on a common shaft and carrying a magnetic circuit including an air gap between said balance wheels is provided with a coil having a streamlined periphery, or with a coil-holding member having said streamlined periphery.

2 Claims, 7 Drawing Figures COIL CONSTRUCTION FOR ELECTRONIC TIMEPIECES BACKGROUND OF THE INVENTION This invention relates to driving and detecting coils for electronic timepieces, and in particular for electronic timepieces having a balance driven by electromagnetic force due to the cooperation of said driving coil and permanent magnets mounted on said balance.

Such electronic timepieces are generally provided with a magnetic circuit mounted on the balance having an air gap within which the coils are positioned. This construction is required to insure stable operation of the timepiece. The gap between the permanent magnets and the coils must be as small as possible, both for efficient operation and in order to provide an extremely thin timepiece. However, conventional circular coils are characterized by an isochronous error caused by air resistance due-to turbulent flow during the oscillation of the balance. The arrangement in accordance with the invention seeks to avoid this defect.

SUMMARY OF THE INVENTION Generally speaking, in accordance with the invention, an electronic timepiece is provided having a pair of balance wheels, a common shaft supporting said balance wheels in spaced relation for oscillation thereof as a unit, and a pair of permanent magnets, said permanent magnets being mounted on the opposed faces of said balance wheels with an air gap therebetween. Either a coil having a streamlined periphery or a coilholding member bearing a coil, said coil-holding member having a streamlined periphery, is mounted in said gap.

Accordingly, an object of the invention is to provide a coil structure which minimizes air resistance caused by turbulent flow, and therefore isochronous error.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is bad to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a cross sectional view of a conventional balance wheel-coil arrangement for anelectronic timepiece taken along lines 1-1 of FIG. 2;

FIG. 2 is a top plan view of the conventional balance wheel-coil arrangement of FIG. 1;

FIG. 3 is a cross sectional view of a coil structure in accordance with the invention;

FIG. '4 is a cross sectional view of a balance wheelcoil arrangement in accordance with the invention;

FIG. 5 is a cross sectionaI v-iew of a second embodiment of a balance wheel-coil arrangement in accordance with the invention taken along lines 55 of FIG. 6;

FIG. 6 is a top plan view of the balance wheel-coil arrangement of FIG. 5; and

' FIG. 7 is a graphical representation of amplitude versus isochronism for the conventional coil construction and the construction in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2, the conventional balance wheel-coil arrangement in accordance with the invention is depicted. This arrangement consists of a pair of balance wheels I mounted in spaced relation on a common shaft. A first pair of permanent magnets 2 are mounted on the under surface of the upper plate while a second pair of permanent magnets 3 are mounted on the upper surface of the lower plate. The

permanent magnets

2 and 3 are aligned in facing relation and are of a polarity such that a magnetic circuit is defined therebetween with a magnetic field passing through the gap between the facing permanent magnets. A coil structure 4. incorporating both a detecting coil and a driving coil in a single cylindrical body is mounted on a coil support 5, said coil support being mounted to the base plate (not shown) of the watch by means of a screw 6. Balancing weights 7 are also mounted on balance wheels 1 on the sides thereof opposite

permanent magnets

2 and 3.

The arrangement of FIGS. 1 and 2 is characterized by turbulent flow caused by air resistance. This in turn causes an isochronous error or positional error as shown by graph A of FIG. 7.

The arrangement in accordance with the invention for avoiding such error is depicted in FIG. 3, where it is seen that the coil structure 14 is provided with a streamlined cross section by reason of a tapered pe riphery. This arrangement substantially reduces isochronous and positional error, without regard to the orientation of the timepiece, as shown by graph B of FIG. 7. In the preferred embodiment, the periphery of the coil member has an essentially V-shaped crosssection. The coil structure of FIG. 3 is depicted mounted in a balance arrangement in FIG. 4, wherein balance wheels 11 are mounted in spaced relation on a common shaft and support permanent magnets 12 and 13 ofa construction similar to those of FIGS. 1 and 2..The coil'structure 14 is supported in the gap between said permanent magnets by a coil support 15, adapted for mounting on the watch plate by a screw 16. The streamlined periphery of coil structure 14 substantially reduces air resistance and turbulence in the region of the magnetic field. Balance weights 17 are also mounted on the balance wheels 11.

A second embodiment of the arrangement in accordance with the inventionis depicted in FIGS. 5 and 6, wherein a conventional cylindrical coil structure is mounted on a coil holder having a streamlined periphery at least in the region of the magnetic field of the

permanent magnets

22, 23 mounted on balance wheels 21. Specifically, coil structure 24 is supported by a coil support 25 adapted for mounting on the base plate of the watch by screws 26, balancing weights 27 being mounted on the balance wheels in the conventional manner. The arrangement of FIGS. 5 and 6 offers the further advantage of providing further support for the coil as well as producing the streamlined effect which reduces turbulence.

The arrangement in accordance with the invention permits the construction of a thin, movable magnettype of balance having extremely stable oscillation characteristics.

It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an electronic timepiece having a balance construction formed with a pair of balance wheels mounted in spaced relation on a common shaft for rotational oscillation, and having permanent magnet means mounted on the facing surfaces of said balance wheels to define a magnetic circuit having a gap between said permanent magnets through which magnetic flux passes, the improvement which comprises a coil construction formed with a tapered periphery, said tapered periphery of said coil construction having an essentially V-shaped cross-section, said coil construction being mounted at least in part 2. In an electronic timepiece having a balance construction formed with a pair of balance wheels mounted in spaced relation on a common shaft for rotational oscillation, and having permanent magnet means mounted on the facing surfaces of said balance wheels to define a magnetic circuit having a gap between said permanent magnets through which magnetic flux passes,- the improvement which comprises a coil assembly; and a coil support supporting said coil assembly at least in part in said gap in said magnetic circult, said coil support extending about at least the portion of the circumferential periphery of said coil assembly in said gap, the portion of said coil support extending about the portion of the periphery of said coil assembly in said gap being tapered and having an essentially V-shaped cross-section.

Claims

1. In an electronic timepiece having a balance construction formed with a pair of balance wheels mounted in spaced relation on a common shaft for rotational oscillation, and having permanent magnet means mounted on the facing surfaces of said balance wheels to define a magnetic circuit having a gap between said permanent magnets through which magnetic flux passes, the improvement which comprises a coil construction formed with a tapered periphery, said tapered periphery of said coil construction having an essentially V-shaped cross-section, said coil construction being mounted at least in part

2. In an electronic timepiece having a balance construction formed with a pair of balance wheels mounted in spaced relation on a common shaft for rotational oscillation, and having permanent magnet means mounted on the facing surfaces of said balance wheels to define a magnetic circuit having a gap between said permanent magnets through which magnetic flux passes, the improvement which comprises a coil assembly; and a coil support supporting said coil assembly at least in part in said gap in said magnetic circuit, said coil support extending about at least the portion of the circumferential periphery of said coil assembly in said gap, the portion of said coil support extending about the portion of the periphery of said coil assembly in said gap being tapered and having an essentially V-shaped cross-section.