Horology: time measuring systems or devices – Chronological – With mechanical or electromechanical driven display
Reexamination Certificate
1999-04-22
2001-12-11
Hirshfeld, Andrew H. (Department: 2859)
Horology: time measuring systems or devices
Chronological
With mechanical or electromechanical driven display
C368S047000, C368S080000, C368S181000, C368S250000
Reexamination Certificate
active
06330207
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a timepiece including a clockwork movement, provided with an analogue display and at least one wheel and pinion fixed in rotation to a rotating indicator or display means of said analogue display, and a device for detecting, at least one reference angular position of said wheel and pinion, this detection device including a magnetic or capacitive sensor.
More particularly, the invention concerns a device for detecting at least one reference angular position of a toothed wheel of the gear train of a clockwork movement.
Those skilled in the art know optical devices for detecting at least one reference angular wheel position belonging to a gear train of a clockwork movement. All these optical detection devices are relatively complex. They require a light source and a light receiver at a distance from said source. The mounting operations of an optical detection device are often difficult given the precise adjustment necessary between the light source, the receiver and the wheel or wheels associated with this device. Within the scope of the present invention, it is therefore proposed to avoid any optical system for detecting the position of a wheel in a clockwork movement.
A system for detecting the position of coaxial wheels respectively associated with coaxial hands of a clockwork movement is known from the English abstract of International Patent Application No. WO 97/45705 (corresponding to U.S. Pat. No. 6,038,523—Akahane et al). On each solid or full toothed wheel are arranged several discrete portions of a hard thin magnetic film which define an identification pattern for a contactless magnetic sensor. Each of the wheels whose the angular position is able to be detected is associated with its own magnetic sensor. The amplitude of the signal detected by these magnetic sensors varies according to whether they are situated in front of segment of magnetic material or not, as is shown in
FIGS. 3 and 4
of this International Patent Application. The detection system proposed in this document is disadvantageous because each wheel associated with a magnetic sensor has to be provided with distinct segments or portions of a solid film made of magnetic material arranged on one face of the toothed wheel. The manufacturing cost of the wheels is thus increased and the arrangement of the identification pattern is provided on a solid or full plate of the toothed wheel, which can be inconvenient for the working of the clockwork movement. The plates of the wheels are thus formed of at least two different materials, namely the material forming the base of the plate of the wheel and the magnetic material arranged at the surface of the base.
SUMMARY OF THE INVENTION
One object of the present invention is to overcome the aforementioned drawbacks by providing a timepiece including a contactless device for detecting the angular position of at least one reference semi-axis of a wheel which is of simple construction and which involves minimum complication of the clockwork movement.
The present invention therefore concerns a timepiece including:
a clockwork movement provided with an analogue display and including at least one wheel fixed in rotation to a rotating indicator of analogue display, this wheel including a plate with a toothing defined by its external edge and a shaft perpendicular to said plate;
a device for detecting the angular position of at least one reference geometric semi-axis of said wheel, this device including a magnetic or capacitive sensor provided with a detection element;
said plate of the wheel being formed by a material a variation in whose presence above or below the detection element of the sensor generates a variation in at least one parameter or one variable of said sensor on which a measuring signal provided by the latter depends. Said plate has at least one opening situated in the intermediate region thereof between a central hole, provided for the passage of said shaft, and said toothing. This opening is used to define said at least one reference geometric semi-axis. The sensor is arranged in relation to the wheel so that its detection element is at least partially above or below said opening in at least one given angular position of said wheel.
As a result of the aforementioned features of the invention, the wheel associated with the contactless sensor can have a plate formed of a single material, conventional for wheels of a clockwork movement, in particular an electrically conductive metal such as brass.
The plate of the wheel associated with the detection device does not have to be formed of a permanently magnetised material, nor to carry magnetised elements with the selected type of contactless sensor.
As will be understood better with reference to the description hereinafter, the invention allows at least one reference geometrical semi-axis of a wheel formed in a conventional manner with appropriate machining of the plate of such wheel, in particular of said at least one opening.
By way of example for the electronic circuit of the magnetic or capacitive sensor provided within the scope of the present invention, reference will be made to European Patent No. 0746100 which discloses an inductive or capacitive proximity sensor and which is incorporated by reference into the present description.
According to a particular embodiment of the invention, the reference geometric semi-axis of the wheel starts perpendicularly from time geometric axis of rotation of said wheel and passes through the geometric centre of said opening.
Thus, a single opening provided in the plate of the wheel allows the detection device according to the invention to determine the angular position of the wheel. Machining of an opening in a wheel plate is a very cheap operation, which is moreover, already provided in certain wheels in order to limit the weight of the wheel and also the cost of materials. Thus, the present invention does not generate any complication for the conventional clockwork movement to allow detection of the angular position of a wheel.
According to another particular embodiment, the plate of said wheel associated with the detection device has, in its intermediate region, at least one opening and a radial arm, the median direction of this arm defining a reference geometric semi-axis of the wheel whose angular position can be detected by the detection device according to the invention.
Thus, within the scope of the present invention, the angular position of a wheel can be determined by a radial and median direction of an opening or an arm, in particular in the shape of an annular section. Moreover, as will be described hereinafter, it is also possible in the case of the present invention to define a reference geometric semi-axis of a wheel by a transition between an opening and a material portion of the plate of said wheel, the type of sensor provided in a preferred embodiment of the present invention allowing detection of such a transition when this transition allows a particular radial direction of the wheel to be defined.
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Born Jean-Jacques
Farine Pierre-Andre
Passeraub Philippe
Asulab S.A.
Goodwin Jeanne-Marguerite
Hirshfeld Andrew H.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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