US3776050A - Motion transformer - Google Patents

Abstract

In a motion transformer for converting oscillatory to rotary motion, comprising (a) an enclosure including a base plate and a cover plate, (b) a ratchet wheel structure within the enclosure mounted for both oscillatory and rotary motion, (c) a pair of stops limiting the amplitude of such oscillatory motion, (d) a ratchet pawl and a restraining member coacting with the ratchet wheel to convert oscillatory motion thereof to unidirectional rotary motion, (e) magnetic coupling means attracting the ratchet wheel structure toward the enclosure base member, and (f) at least three and preferably four hard support members for supporting the ratchet wheel in spaced relation with the base plate, the support members, which preferably are of jewel stone or equivalent hard material, are balls firmly secured as by a press fit in openings symetrically disposed adjacent the periphery of the ratchet wheel structure. The magnetic coupling may be provided by magnetizing the ratchet wheel structure, preferably with four symetrically spaced poles coinciding substantially with the ball support members.

Description

Umted States Patent 1 [111 3,776,050 Hetzel Dec. 4, 1973 MOTION TRANSFORMER [75] Inventor: Max Hetzel, Bienne, Switzerland [57] ABSTRACT [73] Assi nee, 0m & Louis B n E Frem In a motion transformer for converting oscillatory to g S AegBienne Switzerland rotary motion, comprising (a) an enclosure including a base plate and a cover plate, (b) a ratchet wheel [22] Filed: May 25, 1972 structure within the enclosure mounted for both oscil- 21 Appl. No.: 256,994

[30] Foreign Application Priority Data June 14, 1971 Switzerland 8622/71 [52] US. Cl. 74/142, 74/DIG. 4, 58/23 AC [51] Int. Cl. Fl6h 27/02 [58] Field of Search 74/ 142, DIG. 4; 58/23 AC [56] References Cited UNITED STATES PATENTS 2,856,239 10/1958 Dacus 74/DlG. 4

Primary Examiner-Charles J. Myhre Assistant Examiner-Wesley S. Ratliff, Jr. Attorney-Dean S. Edmonds et a].

latory and rotary motion, (c) a pair of stops limiting the amplitude of such oscillatory motion, (d) a ratchet pawl and a restraining member coacting with the ratchet wheel to convert oscillatory motion thereof to unidirectional rotary motion, (e) magnetic coupling means attracting the ratchet wheel structure toward the enclosure base member, and (f) at least three and preferably four hard support members for supporting the ratchet wheel in spaced relation with the base plate, the support members, which preferably are of jewel stone or equivalent hard material, are balls firmly secured as by a press fit in openings symetrically disposed adjacent the periphery of the ratchet wheel structure. The magnetic coupling may be provided by magnetizing the ratchet wheel structure, preferably with four symetrically spaced poles coinciding substantially with the ball support members.

6 Claims, 2 Drawing Figures MOTION TRANSFORMER RELATED APPLICATION This application describes an improvement on the motion transformer mechanism disclosed in US. Pat. application Ser. No. 88,715, now abandoned.

SUBJECT OF THE INVENTION This invention relates to motion transformers, especially for use in timepieces such as wrist watches, for converting oscillatory or reciprocating motion to rotary motion. The invention pertains particularly to motion transformers comprising a ratchet wheel structure mounted in an enclosure so that itcan oscillate backand-forth through a limited path of travel and also rotate substantially about its center axis, and further comprising stops to limit the amplitude of the back-andforth oscillatory motion, and a pawl and a restraining member coacting with the ratchet wheel teeth to cause the ratchet wheel to rotate unidirectionally at a velocity determined by the frequency of the oscillations. The rotating ratchet wheel structure is coupled magnetically to the drive gear in a watch or other timepiece gear train, and is attracted by such magnetic coupling toward the base plate of the enclosure. Support members (at least three in number) are provided by which the ratchet wheel is supported on the base plate in spaced relation therewith. In accordance with the invention, these support members are hard substantially spherical balls secured, as by a press fit, in circular openings in the ratchet wheel.

Magnetic coupling of the ratchet wheel structure to the external drive gear is accomplished by magnetizing such structure, preferably to provide four poles symmetrically spaced circumferentially. These four magnetic poles advantageously coincide in location with a corresponding number of the ball support members.

BACKGROUND OF THE INVENTION A common type of electric (battery-energized) wrist watch utilizes a vibratory element which is electrically driven at a predetermined accurate (usually resonant) frequency. The vibratory back-and-forth motion of this element must be converted by a motion transformer to rotary motion by which the gear train of the time piece can be actuated. Heretofore it has been common practice to effect such motion by transformation by means of a driving pawl attached to the vibrator and aligned in the vibration direction, which pawl engages the teeth of a ratchet wheel. The pivot axis vof the latter is stationary relative to the vibrator. A restraining pawl likewise engages the teeth of the ratchet wheel to prevent reverse motion, the fixed end of this restraining pawl likewise being stationary relative to the vibrator.

The operating frequency of vibrators of the described type is usually in the range from 200 to 700 oscillations per second. The diameter of the ratchet wheel generally is about 1 to 3 mm. (0.040 to 0.120 inch). These figures alone make it apparent that the design of a reliable motion transformer for a wrist watch presents a difficult technological problem. Moreover, the effectiveness of the motion conversion must be very high, for two reasons. The first reason is that the energy consumption of a vibrator and motion transformer for small watches, must be low to be within the energy content of a battery ofa size which meets the demands of the market. The second reason is that loss of energy leads to loss of the motion transformation should the power loss exceed a certain value. In order to achieve a high efficiency of motion transformation, as well as reliability and accuracy of time keeping, very accurate adjustment of the pawls relative to the ratchet wheel, and especially strong materials of construction, are required. The adjustment of the pawls and the mounting of the ratchet wheel, in the case of motion transformers heretofore commonly used, are unfortunately subject to undesirable changes during operation, since the fastening points of vibrator, ratchet wheel rotation axis and restraining pawl are located in generally relatively far apart on the watch base plate and are subject to relative displacement by both thermal and mechanical effects.

In order for the reciprocating movement of the vibrator to serve as a synchronous motor for working control for clocks and watches it is necessary that the accurate frequency of oscillation of the vibrator be converted into equally accurate speed of rotation of the ratchet wheel. From this it follows that in a motion transformer utilizing a driving pawl attached to the vibrator and a fixedly pivoted ratchet wheel, the amplitude of the movement of the vibrator must be held constant within very narrow limits and that the positions of the pawls and the ratchet wheel relative to each other must remain unchanged within narrow limits. Such conditions can be met only with great difficulties.

Many of the difficulties in the manufacture and adjustment of motion transformers as described above have been to a considerable extent overcome by the recent development of an improved motion transformer in which the ratchet wheel, instead of being fixedly pivoted, is free to oscillate diametrically through a limited path of travel as well as to rotate. Stops at opposite ends of the path of oscillatory travel of ratchet wheel limit such travel, and pawls engaging the ratchet wheel teeth, (or at least one such pawl plus a restraining member to prevent retrograde motion of the ratchet wheel) cause the ratchet wheel to rotate unidirectionally at a rate determined by its frequency of oscillation. This entire ratchet wheel assembly in a suitable enclosure is mounted directly on or otherwise is directly connected to the vibrator so that it vibrates therewith. Since pawls and stops are mounted in close proximity on the assembly enclosure, this motion transformer is relatively insensitive to loss of adjustment due to thermal effects or mechanical shock, and its design is such that the speed of rotation of the ratchet wheel is dependent only on the frequency of oscillation of the vibrator and is essentially independent of the amplitude of such oscillation. The basic design and mode of operation of this improved motion transformer is described in greater detail in the aforesaid US. Pat. application Ser. No. 88,715, now abandoned.

It is essential, for efficient operation of this improved motion transformer, that the ratchet wheel be free to oscillate and rotate with minimum frictional losses and with minimum interferences from dust or other foreign body particles that may inadvertently be present in the ratchet wheel enclosure. The present invention provides for attainment of these ends.

STATEMENT OF THE INVENTION The invention, accordingly, is incorporated in an improved motion transformer, especially suited for use in electric vibrator-driven wrist watches and other timepieces, for converting oscillatory to "rotary'motion,

comprising anenclosure having a base plate and acover plate, a magnetized ratchet wheel structure within said enclosure mounted both for oscillatory backand-forth motion substantially on a diameter thereof'and for rotary motion substantially about its center, a pair of stops fixedly mounted for limiting the amplitude of the oscillatory motion of the ratchet wheel within the enclosure, a ratchet pawl and a restraining member (which may be a second ratchet pawl) coacting with the ratchet wheel to'convert oscillatory motion thereof to unidirectional rotary motion, said ratchet wheel being magnetically attracted toward said enclosure base member (and being magnetically coupled in driving engagement with a fixedly pivoted external wheel such as the driving gear of a timepiece gear train). At least three hard support members support the ratchet wheel in spaced relation with the base plate.

In a copending U.S. Pat. application of myself and Paul Waibel, Ser. No. 244,770, filed Apr. 17, 1972, now U.S. Pat. No. 3,744,326, a motion transformer of the character just described is disclosed, in which the support members are either in a form having a flat surface which is adhesively bonded to either the ratchet wheel structure or to the base plate, or are in the form of rolling balls confined between spaces as in aball bearing. The present invention providesan improvement on the arrangement described in said U.S. Pat. application Ser. No. 244,770 for mounting of the support members.

In accordance with this invention, the ratchet wheel structure is formed with at least three substantially circular openings adjacent its periphery, substantially symmetrically spaced about the circumference thereof. A substantially spherical ball is secured in each such opening, the balls forming the wheel support members.

Preferably the ball support members are four in number, circumferentially spaced substantially 90 apart, and are radially spaced at substantially uniform (equal) distances from the center of the ratchet wheel. Each ball may penetrate through the ratchet wheel structure and be secured in place by a friction press fit about its diameter in the opening in which it is received.

The magnetized ratchet wheel structure advantageously has four poles spaced circumferentially at substantially uniform distances (e.g. 90) apart, and on radii of the ratchet wheel structure which coincide sub stantially with the radii on which a corresponding number of ball supports are located. It is desirable, in fact, for such poles to coincide substantially with the centers of the ball support members.

The ratchet wheel structure may with advantage comprise a disc of magnetic material (e.g. platinumcobalt alloy) in which the ball support members are mounted, and a ratchet-toothed ring member secured to said disc with its ratchet-toothed periphery projecting beyond the periphery of the disc.

As described in said U.S. Pat. application Ser. No. 244,770, the ratchet wheel itself may be a permanent magnet formed of high coercivity material such as platinum-cobalt alloy, or it may be of non-magnetic material to which a permanent magnet of high coercivity material is bonded. Such permanent magnet couples the ratchet wheel within the enclosure in driving engagement with a fixed-pivot wheel (such as the dirving gear of a watch gear train) mounted outside the enclosure and likewise'made of, or having bonded to it a lamina made of, magnetic material. Such external fixedpivot wheel is mounted adjacent the base plate (which is non-magnetic) of the ratchet wheel enclosure, so that the magnetic coupling tends to hold the ratchet wheel on its supports against the base plate of the enclosure. However, shock may sometimes tend to dislodge the ratchet wheel from its bearing against the base plate,

and to prevent such dislodgement from impairing the operation of the ratchet wheel, axial deflection limiting means may be provided between the ratchet wheel and the enclosure cover plate. Such axial deflection limiting means advantageously comprise a lamina of hard material (e.g. jewel stone) secured to the cover plate in closely spaced relation to the adjacent surface of the ratchet wheel. Since such deflection limiting means is spaced from the ratchet wheel, it does not impede normal free movement of the latter, but since such spacing is close, it does not allow the ratchet wheel to be dislodged axially far enough to lose its operative engagement with the pawl, restraining member, or magnetic coupling to the external drive wheel.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view partially in cross-section, of a motion transformer according to the invention, showing one form of construction of a ratchet wheel structure within an enclosure; and

FIG. 2 is a top view of the motion transformer of FIG. 1 mounted in the enclosures.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS OF THE INVENTION The motion transformer 1 shown in FIGS. 1 and 2 constitutes a unitary assembly mounted in an enclosure formed of base plate 14 and cover plate 16 joined by side members (not shown) and hermetically sealed after assembly and adjustment. The assembly may be constructed and adjusted prior to sealing the cover plate in place. In use the assembly is mounted on a vibratory member which is caused to vibrate at a predetermined frequency by a battery-energized electronic circuit, as is well understood in the electric timepiece art. The mounting of the motion transformer of FIG. 1 on such vibratory member is such as to cause the assembly to oscillate back-and-forth in the direction indicated by the arrows 22 and 23.

The motion transformer mechanism comprises a ratchet wheel 3 provided with ratchet teeth. The ratchet wheel is not secured in place by a fixed pivot or shaft, but instead is free to oscillate within the enclosure through a limited path of back-and-forth travel in the directions indicated by the arrows 25, 26, and also to rotate substantially about its center. Oscillation of the entire motion transformer assembly by the vibratory member on which it is mounted cuases the ratchet .wheel, because of its inertia, to oscillate correspondingly within and relative to the enclosure. A first pawl arm 5 terminates at one end in a pawl jewel 6 which engages the ratchet wheel teeth and is fastened at its other end to the enclosure base plate. Similarly, a restraining member in the form of a second pawl arm 8 is provided at one end with a pawl jewel 9 which engages the ratchet wheel'teeth and is attached at its other end to the enclosure base plate. The pawl jewels 6 and 9 engage the ratchet wheel at substantially diametrically opposite positions.

A pair of stop members 11 and 12 secured fixedly to the enclosure base plate limit the maximum path of travel of the ratchet wheel in its back-and-forth oscillation. As the ratchet wheel oscillates the pawls compel rotation of the ratchet wheel (in a clockwise direction in the apparaus of FIG. 2), as is described in detail in the above-mentioned U.S. Pat. application Ser. No. 88,715, now abandoned.

The ratchet wheel 3 may be made wholly of magnetic material of high coercivity, such as platinum-cobalt alloy, which is permanently magnetized. As shown in the drawings, however, the ratchet wheel structure comprises a central disc 30 of high coercivity magnetic material about which is press-fitted a ratchet-toothed ring 24. Alternatively the ratchet wheel structure may comprise two or more laminae as described in aforesaid U.S. Pat. application Ser. No. 244,770, one of which is permanently magnetized. In any case, the ratchet wheel structure is magnetically attracted to and coupled with a fixedly pivoted magnetic wheel (not shown) which may be the drive gear of a timepiece gear train and which is mounted externally of the enclosure in parallel relation with and directly below the base plate 14. Not only does the magnetic coupling of the ratchet wheel to the external fixed pivot wheel provide for driving the latter by rotation of the former,but it also causes the ratchet wheel to be attracted toward the base plate 14 and away from the cover plate 16. Although the cover plate 16 normally is not touched by the freely. moving ratchet wheel 3, it may be provided with axial deflection limiting means as described in said application Serial No.

The ratchet wheel 3 is provided with at least three and preferably four supports 20 which are in the form of substantially spherical balls. Advantageously they are made of jewel stone, in particular sapphire or ruby, or alternatively, of hard metal, e.g. tungsten carbide.

The balls 20 are mounted in substantially circular holes 21 formed in theratchet wheel structure. These holes preferably are of such diameter that the balls 20 may be held therein by a friction press fit so that they penetrate through the ratchet wheel structure and are held in place across their diameter. They may however be held in place adhesively. In the form of apparatus shown, the holes are formed in the central disc 3a of magnetic material. The holes (and the balls pressed therein) are preferably arranged symmetrically in the ratchet wheel structure, so that. they are uniformly spaced both circumferentially and radially from the ratchet wheel center. Thus when, as preferred, four ball support members are provided, they are disposed substantially 90 apart, and substantially equidistant from the ratchet wheel center.

For optimum magnetic coupling to an external drive gear, the ratchet wheel 3 (or its magnetic component 3a) is preferably magnetized as indicated in FIG. 2 with two north poles and two south poles symmetrically spaced from the center of the structure and also symmetrically spaced circumferentially. Such magnetization may precede or follow insertion of the balls 20 in the holes 21 and mounting of the ratchet-toothed ring 24 on the magnetic disc 3a. The poles advantageously are located on or close to the radii on which the support balls are mounted; and moreover they advantageously coincide with the centers-of the support balls.

In this way optimum distribution of magnetic forces urging the ratchet wheel structure toward the base plate 14 is achieved, together with most effective driving coupling with the external magnetic drive gear.

As described in detail in the above-mentioned U.S. Pat. application Ser. No. 88,715, the entire motion transformer l is, for example, connected to a tuning fork, which imparts to it a translatory motion alternately in the direction of the arrows 22 and 23. The ratchet wheel 3, due to its inertia, will lag behind when the enclosure moves in the direction of the arrow 22, with the result that it will move relative to the enclosure in the direction of the arrow 26 until its corresponding tooth or teeth run up against the stop 12. Meanwhile the enclosure has started to move in the direction of the arrow 23, so that the ratchet wheel 3 due to its inertia now moves relative to the enclosure in the direction of the arrow 25, until the stop 1 1 acts to brake its motion. This to-and-fro oscillation of the ratchet wheel 3 in its enclosure occurs at the frequency with which the tuning form or other vibrator oscillates. During this toand-fro motion of the ratchet wheel 3 the pawl stones 6 and 9 of the pawls 5 and 8 engage the teeth of the ratchet wheel 3, whereby during movement of the ratchet wheel 3 in one direction it is pivoted on one of the pawl stones as fixed point, and during movement in the other direction the corresponding edge of the other pawl stone serves as the fixed point for the pivoting of the ratchet wheel 3, so that the ratchet wheel 3 is caused to execute a unidirectional rotary motion; that is, the back-and-forth oscillatory motion of the motion transformer assembly is converted by the action of the ratchet and pawls wheel into rotary motion of the ratchet wheel.

It is quite obvious that this rotary motion must take place with as little frictional and other losses as possible. Accordingly, the contact surface between ratchet wheel and base plate is designed as small as possible, approaching point contacts. Because the weights here involved are so small, this can be done without difficulty,for.even with nearly point contacts the contact pressures will remain exceedingly small. The ball supports 20 provide such point-like contact with the base plate.

In order to reduce to a minimum the probability that due to some foreign body (a dust particle, for example) a high resistance will be developed between the relatively moving bearing surfaces, not only are the contact surfaces kept at a minimum with respect to their number and size, but these contact surfaces are arranged in such a way that in the course of the movement of the ratchet wheel on the base plate the annular path traversed by the contact surfaces is as narrow as possible, with the result that a self-cleaning of this path is assured by the motion of the separate support members over it.

Although it is possible in principle, it is not preferred to arrange the ball support members 20 in such a way that each of them traverses a different path of travel than the others, for then the probability of a contamination impeding the free movement of the ratchet wheel will increase. Since the surface pressures exerted by the tiny bearing surfaces of the support members, as already mentioned, are exceedingly small, there is no substantial danger of a premature wear of even a vary narrow path of travel of the support members on the surface over which they slide.

The described invention makes it possible to maintain the ratchet wheel and pawls hermetically sealed and immersed in a lubricant liquid the viscosity of which need not meet any to strict requirements and may range up to centistokes. The herein described motion transformer is extremely simple. The effects of contamination and the resulting irregularities in running, wear and energy consumption are very small due to the small contact surfaces.

I claim:

'1. A motion transformer for converting oscillatory motion to rotary motion comprising an enclosure including a base plate and a cover plate, a magnetized ratchet wheel structure within said enclosure mounted both for oscillatory back-and'forth motion substantially on a diameter thereof and for rotary motion substantially about its center, a pair of stops fixedly mounted for limiting the amplitude of the oscillatory motion of the ratchet wheel within the enclosure, a ratchet pawl and a restraining member coacting with said ratchet wheel to convert oscillatory motion thereof to unidirectional rotary motion, said ratchet wheel being magnetically attracted toward said enclosure base member, and at least three hard support members supporting said ratchet wheel on an in spaced parallel relation with the base plate, characterized in that said ratchet wheel structure is formed with at least three substantially circular openings adjacent its periphery and substantially symmetrically spaced about the circumference thereof, and a substantially spherical ball is secured in each such opening, said balls forming the wheel support members.

2. A motion transformer according to claim 1 wherein said ball support members are four in number circumferentially spaced substantially apart and radialy spaced at substantially uniform distances from the center of the ratchet wheel.

3. A motion transformer according to claim 1 wherein each ball penetrates through the ratchet wheel structure and is secured in one of the circular openings by a friction press fit about its diameter.

4. A motion transformer according to claim 2 wherein the magnetized ratchet wheel structure has four poles spaced circumferentially at substantially unifonn distances apart on radii which conicide substantially with the radii on which the ball support members are mounted.

5. A motion transformer according to claim 4 wherein the magnet poles coincide substantially with the centers of the ball support members.

6. A motion transformer according to claim 1 wherein the magnetized ratchet wheel structure corn prises a disc of magnetic material in which the ball support members are mounted and a ratchet-toothed ring member secured to said disc with its ratchet-toothed periphery projecting beyond the periphery of said disc.

Claims (6)

1. A motion transformer for converting oscillatory motion to rotary motion comprising an enclosure including a base plate and a cover plate, a magnetized ratchet wheel structure within said enclosure mounted both for oscillatory back-and-forth motion substantially on a diameter thereof and for rotary motion substantially about its center, a pair of stops fixedly mounted for limiting the amplitude of the oscillatory motion of the ratchet wheel within the enclosure, a ratchet pawl and a restraining member coacting with said ratchet wheel to convert oscillatory motion thereof to unidirectional rotary motion, said ratchet wheel being magnetically attracted toward said enclosure base member, and at least three hard support members supporting said ratchet wheel on an in spaced parallel relation with the base plate, characterized in that said ratchet wheel structure is formed with at least three substantially circular openings adjacent its periphery and substantially symmetrically spaced about the circumference thereof, and a substantially spherical ball is secured in each such opening, said balls forming the wheel support members.

2. A motion transformer according to claim 1 wherein said ball support members are four in number circumferentially spaced substantially 90* apart and radialy spaced at substantially uniform distances from the center of the ratchet wheel.

3. A motion transformer according to claim 1 wherein each ball penetrates through the ratchet wheel structure and is secured in one of the circular openings by a friction press fit about its diameter.

4. A motion transformer according to claim 2 wherein the magnetized ratchet wheel structure has four poles spaced circumferentially at substantially uniform distances apart on radii which conicide substantially with the radii on which the ball support members are mounted.

5. A motion transformer according to claim 4 wherein the magnet poles coincide substantially with the centers of the ball support members.

6. A motion transformer according to claim 1 wherein the magnetized ratchet wheel structure comprises a disc of magnetic material in which the ball support members are mounted and a ratchet-toothed ring member secured to said disc with its ratchet-toothed periphery projecting beyond the periphery of said disc.

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