US3744327A

US3744327A - Motion transformer

Info

Publication number: US3744327A
Application number: US00246580A
Authority: US
Inventors: M Hetzel
Original assignee: Omega Louis Brandt and Frere SA
Current assignee: Omega Louis Brandt and Frere SA
Priority date: 1971-05-05
Filing date: 1972-04-24
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10
Also published as: CH668871A4; FR2135202B1; DE2210390A1; FR2135202A1; CH537037A

Abstract

In a motion transformer for converting oscillatory to rotary motion, comprising (a) an enclosure including a base plate, a cover plate, and side members, all of which are substantially rigid, (b) a ratchet wheel 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 coacting with the ratchet wheel and a restraining member preventing retrograde rotation thereof to convert oscillatory motion thereof to uni-directional rotary motion, and (e) a liquid filling the space in said enclosure, a variable volume sealing chamber is bonded to the enclosure so as to hermetically seal the liquid in the enclosure and yet yield to thermal expansion and contraction of said liquid. The side members of the enclosure are preferably configured to fit in closely spaced relation about the ratchet wheel, to minimize the volume of the chamber within the enclosure.

Description

United States Patent [191 Hetzel [451 July 10, 1973 MOTION TRANSFORMER Primary Examiner-Charles J v M hre A E F o Sh y k z l ssistant xammer oema er [75] Inventor Max Hetze Blame Swltzerland AItrne vDean S. Edmonds, James W. Laist et al. [73] Assignee: Omega Louis Brandt Et Freres, S.A.,

Bienne, Switzerland q [57] ABSTRACT [22] Filed: Apr. 24, 1972 In a motion transformer for converting oscillatory to PP N03 246,580 rotary motion, comprising (a) an enclosure including a base plate, a cover plate, and side members, all of [30] Foreign Applicatio priority Data which are substantially rigid, (b) a ratchet wheel within Ma 5 1971 Switzerland 6688/71, the enclosure mounted for both oscillatory and rotary y motion, (0) a pair of stops limiting the amplitude of [52] U S C] 74,128 58/23 D 58/23 TF such oscillatory motion, (d) a ratchet pawl coacting 58 V 43 92/60 310/25 331/156 with the ratchet wheel and a restraining member preventing retrograde rotation thereof to convert oscillatory motion thereof to uni-directional rotary motion, and (e) a liquid filling the space in said enclosure, a variable volume sealing chamber is bonded to the enclosure so as to hermetically seal the liquid in the enclosure and yet yield to thermal expansion and contrac- [56] References cued tion of said liquid. The side members of the enclosure UNITED STATES PATENTS are preferably configured to fit in closely spaced rela- 2,856,239 l0/ 1958 Dacus 74/DlG. 4 tion about the ratchet wheel, to minimize the volume 3,216,198 BIOOlCSHU X of the chamber the enclosure 3,691,754 9/1972 Hetzel 74/88 X 10 Claims, 3 Drawing Figures 22 23 1 1s 12 ii- 7 KA/V/Al 1 'r /z x \R 1 5? T I L\\l l\\)\\\\\\\\\' I r'\\/ K ///V l// /V, X //,L// V/ I) I I l I 1:9 2s 20 u.

Patented July 10, 1973 3,744,327

FIG.3 3 32 MOTION TRANSFORMER RELATED APPLICATION This application describes an improvement of the motion transformer mechanism disclosed in U.S. application Ser. No. 88,715 now U.S. Pat. No. 3,691,754.

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 mounted in an enclosure so that it can oscillate back-and-forth through a limited path of travel and alsorotate substantially about its center axis, and further comprising stops to limit the amplitude of the back-and-forth oscillatory motion, and a pawl and coacting with the ratchet-wheel teeth and a restraining member to prevent retrograde rotation thereof to cause the ratchet wheel to rotate unidirectionally at a velocity determined by the frequency of the oscillations. The rotating ratchet wheel 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. The enclosure is filled with a liquid such as a low viscosity, e.g., one centistoke, lubricating oil.

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 timepiece can be actuated. Heretofore it has been common practice to effect such motion 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 of 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 of a size which meets the demands of the market. The second reason is that loss of energy leads to destruction 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 stong 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 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 the 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. application Ser. No. 88,715.

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. For this reason it is desirable to fill the ratchet wheel enclosure with a suitable lowviscosity liquid, such as a light oil of, say, one centistoke viscosity. Experience with this improved motion transformer has shown, however, that special provision must be made to compensate for the effects of temperature. Since the coefficient of expansion of the materials forming the enclosure is in general many times smaller than that of the liquid filling it, provision must be made to accommodate the differential in thermal expansion.

STATEMENT OF THE INVENTION The invention, accordingly, relates to a motion transformer for converting oscillatory motion to rotary motion comprising an enclosure including a base plate, a cover plate, and side members, all of which are subthereof to convert oscillatory motion of the ratchet wheel to unidirectional rotary motion, and a liquid filling the space in said enclosure about said ratchet wheel, stops, pawl and restraining member. The invention provides, in such a motion transformer, a variable volume sealing chamber bonded to the enclosure in communication with and hermetically sealing the liquid in the enclosure, while yielding to thermal expansion and contraction of such liquid.

In one advantageous embodiment of the invention, the variable volume sealing chamber is formed by a yieldable diaphragm bonded to the enclosure and defining an expansion chamber communicating with the interior of the enclosure. In another advantageous embodiment, the variable volume sealing chamber comprises a bellows bonded to the enclosure and defining an expansion chamber communicating with the interior of the enclosure. In either case the diaphragm, or bellows, preferably is bonded to the exterior of the cover plate and the variable volume expansion chamber defined thereby communicates with the interior of the ratchet wheel enclosure through one or more openings in the cover plate.

Preferably the volume of the ratchet wheel enclosure, and hence the volume of liquid which it contains, is made as small as possible by configuring the side members of the enclosure to fit in closely spaced relation about the ratchet wheel. Thus the side members may be configured to form a substantially cylindrical enclosure chamber only slightly larger in diameter than required to accommodate oscillatory motion of the ratchet wheel. Such side members may further define a substantially tangential channel to receive the ratchet pawl; and when the restraining member is itself a second pawl, they may define a second tangential channel to receive it also. The side members further may be formed with additional channels in which the stops are received and fixed in proper spaced relation relative to the ratchet wheel. Such design makes it possible to use two substantially identically configured side members which can be bonded together and to the base and cover plates to form a hermetically sealed enclosure (except for openings communicating with the variable volume chamber) and at the same time to facilitate accurate alignment of stops, pawls and ratchet wheel.

DESCRIPTION OF THE DRAWINGS 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 2 (FIG. 2) and hermetically sealed after assembly and adjustment. In use the assembly is mounted on a vibratory member which is caused to vibrate at a predetermined frequency by a batteryenergized 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 (fragmentarily indicated at 17 in FIG. 2). 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 causes 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, approximately perpendicularly to the direction of oscillation of the ratchet wheel.

A pair of

stop members

11 and 12 secured in channels 13 in the side members 2 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 apparatus of FIG. 2), as is described in detail in the above-mentioned US. application Ser. No. 88,715 now US. Pat. No. 3,691,754.

As is apparent from FIG. 2, the side members 2 are configured so as to provide a generally cylindrical chamber 19 the walls of which are closely spaced relative to the ratchet wheel 3 and allow only slightly more than enough space for the latter to execute its oscillatory motion between the stops l1 and 12. Thus the volume of the chamber 19 is minimized. Further to minimize this volume, the

pawl arms

5 and 8 are received in narrow channels or boxes formed in the side members 2 and extending tangentially from the main cylindrical portion of the chamber 19.

In the apparatus of FIG. 2 the two side members 2 are of identical configuration and abut along projections of the center lines of the tangential channels in which the

pawl arms

5 and 8 are received. When these side members are bonded together (by an adhesive, for example) where they abut, and are bonded to the base plate 14 and cover plate 16 they form a hermetically sealed chamber 19 except for the provision of openings 32 which provide for communication with a variable volume sealing chamber.

As can be seen in FIGS. 1 and 2 the chamber 19 is of minimum dimensions to adapt it to the dimensions of the ratchet wheel 3 and the

pawls

5 and 8. In order to ensure low constant resistance to motion of the ratchet wheel, the chamber 19 is entirely filled with a liquid such as a low viscosity lubricating oil. This minimum volume of the chamber 19 is important in order to reduce to a minimum the effect of volume changes of the liquid which are caused by temperature changes and which may exceed by a power of ten those of the solid parts forming the chamber 19 (i.e., the side members 2 and the base and cover plates 14 and 16).

In order to avoid both high strain on the rigid enclosure of the ratchet wheel 3 when the temperature increases and to prevent bubble formation when the temperature drops, the apparatus of FIG. 1 includes a discshaped diaphragm 30 which is sealed exteriorly to the periphery of the cover plate 16. A variable volume expansion chamber 31 thereby is formed between this diaphragm 30 and the cover plate 16; and this expansion chamber communicates with the ratchet wheel enclosure chamber 19 by way of openings 32. The solid-line profile of the diaphragm 30 shows its central position when both the enclosure chamber 19 and expansion chamber 31 are completely filled with the liquid at a normal temperature (say atmospheric temperature), while the dash-and-dot line shows the diaphragm at a raised temperature, e.g., up to 50 or 60 C. When the temperature falls, e.g., to l C, then the expansion chamber is reduced to the diaphragm position indicated by the dashed line.

Instead of a disc-shaped diaphragm, a bellows 34 with a relatively rigid end closure 36, as shown in FIG. 3, may define the expansion chamber. In case of temperature changes the bellows move up and down, as indicated in FIG. 3 by the solid line and the dash-and-dot line. Here again the interior of the expansion chamber within the bellows and the enclosure chamber 19 are filled with liquid, and communicate through openings 32 in the cover plate, to the upper surface of which the bellows is adhesively bonded.

Other forms of variable volume chambers to accommodate expansion and contraction of the liquid filling the chamber 19 may be provided. For example, a flexible rubber-elastic closure may be applied over the openings 32, or a rigid-walled chamber containing a compressible and expansible member may be provided to accommodate expansion and contraction of the liquid. Instead of closing the expansion chamber with a flexible solid member such as the diaphragm 30 or the bellows 34, it may be closed with an immiscible liquid or other flowable material of high viscosity which follows the liquid level in the expansion chamber and is retained in place by adhesion or surface tension.

The ratchet wheel 3 is made of magnetic material of high coercivity, such as platinum-cobalt alloy, and is permanently magnetized. Thereby it 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, the cover plate is provided with means to limit axial deflection of the ratchet wheel away from the base plate. Such means is in the form of a disc 18 which preferably, like the base plate 14 and the cover plate 16, is made of a hard non-magnetic material such as jewel stone, e.g., ruby, and which, since it is ground to a lamina, is transparent.

The ratchet wheel 3 is provided with three or more supports 20, mounted at equi-angular positions, which may be glued or cemented to the wheel 3. These supports 20, having the shape of spherical segments or hemispheres, likewise are made of jewel stone, in particular ruby, or alternatively, of hard metal, e.g., tungsten carbide. Three supports 20 of this type advantageously are provided, thus ensuring a reliable and neat mounting of the ratchet wheel 3 on the base 14.

FIG. 1 also shows by way of the

arrows

22 and 23 the directions in which the vibrator imparts back-and-forth oscillation to the entire motion transformer l.

Arrows

25 and 26 show the direction of the oscillatory movement of the ratchet wheel 3 relative to its enclosure, a movement which depends on the inertia of the ratchet wheel 3 and which is controlled by the

pawls

5 and 8 with

pawl stones

6 and 9, and by the

stop members

11 and 12, in such a way that the ratchet wheel is made to rotate in one direction (clockwise, as viewed in FIG. 2).

As described in detail in the above-mentioned application Serial No. 88,715 now US. Pat. No. 3,691,754, the entire motion transformer 1 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 11 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 fork or other vibrator oscillates. During this to-and-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 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.

In a liquid-filled motion transformer constructed in accordance with the invention, expansion of this liquid, due to temperature changes, will have little effect on the walls of the chamber 19. Without the variable volume chamber provided by the invention, and depending on the temperature at which the chamber 19 is entirely filled with liquid, an internal pressure could develop in the chamber, with increasing temperature, of sufficient magnitude to burst the enclosing walls of the chamber. On the other hand, a decreasing temperature could lead to such' a contraction of the liquid as to create a bubble which, if sufficiently large, might cause the mass of liquid in the chamber 19 to at least partially oscillate along with the ratchet wheel, resulting in increased friction loss and higher current consumption by the timepiece; and it might even impair proper functioning of the motion transformer in converting reciprocating movement to rotary motion of controlled velocity. For these reasons the provision of the expansion space in connection with the design of the ratchet wheel enclosure, and the shape of the enclosure chamber, are of substantial importance.

I claim:

1. In a motion transformer for converting oscillatory motion to rotary motion comprising an enclosure including a base plate, a cover plate, and side members, all of which are substantially rigid, a ratchet wheel 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 coacting with said ratchet wheel and a restraining member preventing retrograde rotation thereof to convert oscillatory motion of said ratchet wheel to unidirectional rotary motion, and a liquid filling the interior of said chamber about said ratchet wheel, stops, pawl and restraining member, the improvement comprising a variable volume sealing chamber bonded to said enclosure in communication with and hermetically sealing said liquid in the enclosure while yielding to thermal expansion and contraction of said liquid.

2. A motion transformer according to claim 1 wherein the variable-volume sealing chamber is formed by a yieldable diaphragm bonded to said enclosure and defining an expansion chamber communicating with the interior of said enclosure.

3. A motion transformer according to claim 1 wherein the variable volume sealing chamber comprises a bellows bonded to said enclosure and defining an expansion chamber communicating with the interior of said enclosure.

4. A motion transformer according to claim 2 wherein the diaphragm is bonded to the exterior of the cover plate and the expansion chamber defined thereby communicates with the interior of the enclosure through at least one opening in the cover plate.

5. A motion transformer according to claim 3 wherein the bellows is bonded to the exterior of the cover plate and the interior thereof communicates with the interior of the enclosure through at least one opening in the cover plate.

6. A motion transformer according to claim I wherein the side members of the enclosure are configured to fit in closely spaced relation about the ratchet wheel and thereby to minimize the volume of the enclosure interior.

7. A motion transformer according to claim 6 wherein the side members are configured to form a substantially cylindrical enclosure chamber only slightly larger in diameter than required to accommodate oscillatory motion of the ratchet wheel and to define at least one substantially tangential channel to receive the ratchet pawl.

8. A motion transformer according to claim 7 wherein the restraining member is a second pawl and the side members define a second substantially tangential channel to receive said second pawl.

9. A motion transformer according to claim 6 wherein the side members are formed with channels in which the stops are received and fixed in proper spaced relation relative to the ratchet wheel.

10. A motion transformer according to claim 6 wherein two substantially identically configured side members are bonded together and to the base and cover plates to form the enclosures.

Claims

6. A motion transformer according to claim 1 wherein the side members of the enclosure are configured to fit in closely spaced relation about the ratchet wheel and thereby to minimize the volume of the enclosure interior.