US3745843A

US3745843A - Motion transformer

Info

Publication number: US3745843A
Application number: US00244053A
Authority: US
Inventors: M Hetzel
Original assignee: Omega Louis Brandt and Frere SA
Current assignee: Omega Louis Brandt and Frere SA
Priority date: 1971-04-26
Filing date: 1972-04-14
Publication date: 1973-07-17
Anticipated expiration: 1990-07-17
Also published as: FR2134489A1; DE2209061A1; FR2134489B1; CH536504A; CH612671A4

Abstract

In a motion transformer for converting oscillatory to rotary motion, comprising a ratchet wheel mounted for back-and-forth oscillation on a diameter and simultaneously for rotation substantially about its center, stops for limiting the amplitude of the oscillatory motion, and pawls engaging the ratchet wheel teeth at diametrically opposite points substantially normal to the direction of oscillatory motion, shock absorbing braking members are provided on the stops in position to abut the teeth of the ratchet wheel as it approaches each end of its oscillatory path of travel to brake each oscillation gently without injury to the ratchet wheel teeth.

Description

I Umted States Patent 1 1 1111 3,745,843

Hetzel July 17, 1973 1 1 MOTION TRANSFORMER 3,127,529 3/1964 Barrett 74/575 x [75] Inventor: Max Hetzel, Bienne, Switzerland Primary Examiner-Charles J. Myhre [73] Ass1gnee: Omega Louis Brandt Et Freres S.A., Assistant Shoemaker Blame Swnzefland Attorney-Dean S. Edmonds, James W. Laist, et 111. [22] Filed: Apr. 14, 1972 (21] Appl. No.: 244,053 [57] ABSTRACT In a motion transformer for converting oscillatory to [30] Foreign Application Priorit Data rotary motion, comprising a ratchet wheel mounted for Apr. 16, 1971 Switzerland 6126/71 back'and'fmth 059mm a diameter and simuna' neously for rotation substantially about its center, stops 52 US. Cl 74/128, 74/88, 74/578, limiting the amplitude oscillatory motion 53/23 v 310/25 331/156, 74/DIG 4 pawls engaging the ratchet wheel teeth at diametrically 51 Int. Cl. F16h 27/02 Opposite P Substantially normal to the direction of [58] Field 6: Search 74/128, 88, 142, oscillamry Shock absorbing braking members 74/578, 58/23 v are provided on the stops in position to abut the teeth of the ratchet wheel as it approaches each end of its os- 5 References Cited cillatory path of travel to brake each oscillation gently UNTED STATES PATENTS without injury to the ratchet wheel teeth.

2,908,174 10/1959 Hetzel 74/578 X 8 Claims, 4 Drawing Figures memznm 1 Hm 3.745.843

FIGZ I FIG.3 FIGA MOTION TRANSFORMER RELATED APPLICATION This application describes an improvement on the motion transformer mechanism disclosed in United States application Ser. No. 88,715 now US. Pat. No. 3,691,754.

SUBJECT OF THE INVENTION This invention relates to motion transformers, espe cially for use in time pieces 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 so that it can oscillate back-and-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-and-forth oscillatory motion and pawls engaging 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 may be coupled magnetically to the drive gear in a watch or other time piece gear train.

The invention provides, in such a motion transformer,

improved shock-absorbing braking members which abut the ratchet wheel teeth as the wheel approaches each limit of its oscillatory path of travel and gently brake the motion of the wheel without injury to its teeth.

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 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 retraining 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 I 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 transformer 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, of the paws 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 general 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 only be met 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 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. 8 8 ,71 5

Detailed tests on this improved motion transformer have shown, however, that sudden braking of the translational motion of the ratchet wheel at the stops results in a permanent deformation of the tips of the ratchet teeth. This deformation, especially if it is non-uniform, has an undesirable effect on the running of the ratchet wheel.

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 time pieces, for converting oscillatory to rotary motion, comprising a ratchet wheel mounted both for oscillatory back-andforth 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 said oscillatory motion, and a pair of pawl engaging the teeth of said ratchet sheel substantially at the ends of a wheel diameter approximately normal to the direction of said oscillatory motion. In accordance with the invention, a resilient shock-absorbing braking member is secured to each of said stops in position to abut the teeth of the ratchet wheel as it approaches each end of its oscillatory path of travel, whereby the motion of the ratchet wheel at each end of its path of travel is gently braked to a stop without injury to its teeth.

In an advantageous embodiment of the invention, each resilient braking member is in the form of a thin flexible lamina secured only at one end to the fixed stop and except where so secured is spaced by a substantial gap from the stop. In another embodiment, the braking member again is a thin lamina but is attached at both ends to the fixed stop, with a substantial gap separating such lamina from the stop intermediate such attachments.

Preferably the entire assembly of ratchet wheel, stops and pawls is mounted in a liquid-tight enclosure and said enclosure is filled with a suitable damping liquid which advantageously also has lubricating properties, such as an oil of low viscosity e.g. about 1 centistolte. Such damping liquid fills the gap between each lamina and the adjoining stop and damps the movement of the flexible lamina. This arrangement makes it possible to elastically absorb the shock to which the ratchet wheel and its teeth are subjected due to the impact on the stop, and to transfer the kinetic energy of the ratchet wheel into kinetic energy of the damping liquid, which in turn is converted into heat by way of friction. This heat, in view of the given energies and the great mass of the damping fluid, can hardly be measured, and is totally insignificant insofar as operation of the device is concerned.

The cross-section of the gap between the laminae and the stops may be quadrangular, i.e. rectangular, square or trapezoidal, or it may be curvilinear. The particular shape and size of the gap may be chosen to make the damping harder or softer, or otherwise to adjust it to preselected conditions. It is also possible to adjust the size and shape of the gap in conformity to the selected frequency of oscillations since the damping liquid being pressed out of the gap must immediately afterward flow back into it. The damping effect preferably is designed in such a way as to avoid any reactive effect on the ratchet wheel.

Preferably the flexible laminae are of a hard jewel material, such as ruby, sapphire, or other stone or mineral commonly used as watch jewels, to minimize wear on these parts. Ifnot the entire lamina, then at least the portion which abuts the ratchet wheel teeth is made of such hard jewel material.

Yet another embodiment of the invention comprises a braking member in the form of a soft elastic material, such as a rubber or rubber-like synthetic resin, which is secured directly to the fixed stop and is faced where it abuts the ratchet wheel teeth with a hard deformation-resistant material such as a jewel or other stone material.

DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a schematic plan view of a motion transformer incorporating one embodiment of the invention;

FIG. 2 is a fragmentary schematic plan view of a motion transformer similar to that of FIG. l. but incorporating another embodiment of the invention;

FIG. 3 is face view of the stop assembly shown in FIG. 2; and

W6. 4! is a side view of another form of stop assembly according to the invention.

DETAlLED DESCRIPTION OF ILLUSTRATED EMBODIMENTS OF THE INVENTION ,The motion transformer shown in FIG. 1 constitutes a unitary assembly mounted in an enclosure E formed of base and cover plates joined by side members 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 batteryenergized electronic circuit, as is well understood in the electric time piece 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 double-headed arrow.

The motion transformer mechanism comprises a ratchet wheel 1 provided with ratchet teeth 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 travel in the direction of the double-headed arrow, 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 3 terminates at one end in a pawl jewel 4 which engages the ratchet wheel teeth and is fastened at its other end to the enclosure base plate. Similarly a second pawl arm 6 is provided at one end with a pawl jewel 7 which engages the ratchet wheel teeth and is attached at its other end to the enclosure base plate. The

pawl jewels

4 and 7 engage the ratchet wheel at substantially diametrically opposite positions approximately normal to the direction of oscillation of the ratchet wheel indicated by the double-headed arrow.

A pair of

stop members

9 and 14 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 counter clockwise direction in the apparatus of FIG. I as is described in detail in the above-mentioned US. application Ser. No. 88,715. Rotation of the ratchet wheel may be transmitted magnetically to a drive gear (not shown) to drive the gear train of a time piece.

in accordance with the invention, the two stops 9 and M are provided respectively with a flexible lamina II and lb. Those laminae are attached at one end only to the fixed stops by connecting

members

12 and 17 re spectively. Except at the connecting members, gaps 13 and 118 are formed between the laminae ll and 16 and the stops 9 and M. The laminae form resilient braking members which abut the teeth of the ratchet wheel as it approaches each end of its oscillatory path of travel, and they gently brake the translational motion of the ratchet wheel to a stop without injury to the ratchet teeth.

The significance of the gentle braking effect of the laminae H1 and 16 is indicated by the following: When the ratchet wheel l in its to-and-fro motion runs up against one of the stops, its teeth 2 impinge on the stop at an average pressure per unit area of the magnitude of 50 lrg/mrn (over 70,000 psi) in normal time piece (wrist watch) operation. Under such conditions the tips of the teeth are soon flattened. In order to soften and to cushion this impact, the

laminae

11 and 16, respec tively, when the teeth 2 of the ratchet wheel 1 run up against them, will yield as a flexible bar and deflect in the direction of the

stops

9 and 14, respectively.

Preferably the interior 19 of the enclosure E is filled with a damping liquid such as a low viscosity mineral oil. This liquid completely fills the sealed enclosure and in consequence fills the

gaps

13 and 18. The liquid present in these gaps will be squeezed out due to the reduced size of the gap, whereby this kinetic energy of the liquid is converted into heat due to turbulence. This heat, on account of the large volume of liquid in the space 19, is too small to be measured.

It is possible to design the gaps l3 and 18 with a suitable cross-sectional shape, for example, a quadrangular shape, e.g. square, rectangular or trapezoidal, or a round or other curvilinear shape, in such a way as to obtain optimum damping characteristics for the particular dimensions, frequencies and materials of a given mechanism. In this manner it is possible to afford maximum protection for the tips of the teeth 2 of the ratchet wheel 1 and to ensure reliable working of the motion transformer mechanis over long periods of time.

FIG. 2 shows a part of a ratchet wheel 22 with teeth 23 in a motion transformer of the same general design as that of FIG. 1. The amplitude of back-and-forth oscillatory movement of the ratchet wheel (right to left and back again as viewed in the drawing) is limited by a pair of stops, of which only one stop 25 is shown. This stop 25, shown also in FIG. 3, is fixedly mounted on the base plate of the mechanism enclosure and is provided with a lamina 27 preferably made of a hard jewel material. The lamina 27 differs from the laminae ll, 16 of FIG. 1 in that it is attached at both ends to the stop 25, advantageously by gluing at fastening points 28. In order to ensure uniform loading of the shock absorber at any time, an abuttment member 29, preferably consisting of ruby or other jewel material, is glued to the lamina 27 substantially at its mid-point. A gap between the lamina 27 and the stop 25 allows for deflection of the lamina toward the stop to gently brake the translational motion of the ratchet wheel.

A further design of a shock absorber stop in accordance with the invention is shown in FIG. 4. Here the stop 32 and an abutment member 34, the latter at least preferably made of ruby or other jewel material, are connected by an intermediate eleastic buffer 35 of rubshown) on the abutment member 34 by absorbing the kinetic energy of the impact in the buffer 35 where it is converted into strain energy and thence into frictional heat.

I claim:

1. In a motion transformer for converting oscillatory to rotary motion comprising a ratchet wheel 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 said oscillatory motion, and a pair of pawls engaging the teeth of said ratchet wheel substantially at the ends of a wheel diameter approximately normal to the direction of said oscillatory motion, the improvement comprising a resilient shock-absorbing braking member secured to each of said stops in position to abut the teeth of said ratchet wheel as it approaches each end of its oscillatory path of travel, whereby the motion of the ratchet wheel at each end of its oscillatory path of travel is gently braked to a stop without injury to the teeth.

2. A motion transformer according to claim 1 wherein each resilient braking member is a thin flexible lamina secured only at one end to the fixed stop and except where so secured is spaced by a substantial gap from said stop.

3. A motion transformer according to claim 2 wherein the assembly of ratchet wheel, stops and pawls is mounted in an enclosure and said enclosure is filled with a damping liquid which extends into the gap between each lamina and the adjoining stop and damps the movement of the flexible laminae.

4. A motion transformer according to claim 2 wherein the flexible laminae are of hard jewel material.

5. A motion transformer according to claim 1 wherein each resilient braking member is a thin flexible lamina secured at both ends of the fixed stop and except where so secured is spaced by a substantial gap from said stop.

6. A motion transformer according to claim 6 wherein each resilient braking member where it abuts the ratchet wheel comprises a hard jewel material.

7. A motion transformer according to claim 1 wherein each resilient braking member comprises a soft elastic material secured to the stop and faced where it abuts the ratchet wheel teeth with a hard deformation-resistant material.

8. A motion transformer according to claim 7 wherein the hard deformation-resistant material is a her or rubber-like synthetic resinous material. This jewel material.

buffer 35 softens the impact of the ratchet wheel (not

Claims

8. A motion transformer according to claim 7 wherein the hard deformation-resistant material is a jewel material.