US2995887A - Electric wrist watch - Google Patents

Description

Aug. 15, 1961 R. E. LE BLANC 2,

ELECTRIC WRIST WATCH Filed Dec. 51, 1956 3 Sheets-Sheet 1 INVENTOR POBEFTKZEBLf/JC ATTORNEY 1961 R. E. LE BLANC 2,995,887

ELECTRIC WRIST WATCH Filed Dec. 31, 1956 3 Sheets-Sheet 2 k\&\\\\\\&\\\\\ 42% 1 IIIIIR? lmml I """J (m My 1 mp7 1/ INVENTOR 26 1 ms Us; 7FOBEIQTEZLC gig/dc ATTORNEY Aug. 15, 1961 R. E. LE BLANC 2,995,837

ELECTRIC WRIST WATCH Filed Dec. 31, 1956 5 SheetsSheet 3 1N VENTOR Raf/er [5152 006 ATTORNEY United States Patent 2,995,887 ELECTRIC WRIST WATCH Robert E. LeBlanc, Silver Spring, Md., assignor to Hamilton Watch Company, Lancaster, Pa., a corporation of Pennsylvania Filed Dec. 31, 1956, Ser. No. 631,904 3 Claims. (Cl. 58-28) This invention relates to an electric wrist watch and more particularly relates to the source of motive power for a watch wherein the balance wheel serves as the frequency controlling element and is periodically impulsed during the passage of a magnetic field across a coil.

The limited space within the case of a wrist watch imposes stringent limitations upon both the primary electric source and the means for converting the electrical energy into mechanical energy. Further, it is obvious that the amount of electrical energy which can be built into a wrist watch size battery is limited. This require that the available electrical energy must be converted into mechanical energy as efficiently as possible so that an extended battery life can be obtained. It is also necessary that the component parts of the electric and the mechanical movement be kept to a minimum size. While many attempts have been made to solve this prob lem satisfactorily, we are not aware that any electric wrist watch has ever been successfully marketed.

In assignees copending applications Serial No. 409,934, filed February 12, 1954, now Patent No. 2,888,797, and Serial No. 578,843, filed April 17, 1956, there are disclosed electric Wrist watches utilizing stationary magnets which cooperate with coils carried by the balance wheel assembly in order to provide an impulse to the balance Wheel during each oscillation. While these arrangements have been found generally satisfactory it has been found that certain problems are presented in winding coils for the balance wheels. That is to say, absolute coil stability is difiicult to achieve, particularly under varying conditions of temperature and humidity. While others have attempted to utilize permanent magnets fixed to the balance wheel and staff assembly and moving therewith, difficulty has been encountered with these devices in that these permanent magnets produce extensive stray magnetic fields which are moved about the watch as the balance assembly oscillates. This has a marked deleterious effect upon the timekeeping characteristics of the watch, for reasons known to those skilled in the art, and among other things makes it impossible to provide satisfactory temperature compensation.

It has now been found that these stray field difficulties may be overcome and that satisfactory electric wrist watches may be produced through the use of permanent magnets carried by the balance staff assembly when these are enclosed within certain field limiting magnetic circuits. According to certain embodiments of the invention, the power obtainable from the source of motive power is greatly increased for a given current drain, so that battery life is extended or operation with a smaller battery unit is permitted.

It is accordingly a primary object of the present invention to provide an electric wrist watch operating from a self-contained battery and having a high degree of efliciency of conversion of electrical to mechanical energy.

It is another object of the invention to provide an electric wrist watch operating from a self-contained battery and having a source of permanent magnetism carried by the balance wheel assembly in a magnetic circuit which prevents extensive stray magnetic fields.

It is another object of the invention to provide an elec- Patented Aug. 15, 1961 tric wrist watch having a source of permanent magnetism carried by the balance wheel assembly in a magnetic circuit which limits stray magnetic fields and wherein such source of permanent magnetism cooperates with fixed coil means mounted adjacent the moving source of permanent magnetism.

It is still another object of the present invention to provide an electric wrist watch of the foregoing type utilizing a plurality of sources of permanent magnetism affixed to the balance staff assembly and cooperating with a plurality of coil positions to produce a higher torque than has been heretofore attainable in a source of motive power of this type.

These and further objects and advantages of the invention will become apparent upon reference to the following specification and claims and appended drawings wherein:

FIGURE 1 is a perspective view of an electric watch constructed according to one embodiment of the invention;

FIGURE 2 is a plan view of the watch shown in FIG- URE 1 taken along the line 2-2 in FIGURE 1;

FIGURE 3 is a side elevation of the watch shown in FIGURES 1 and 2;

FIGURE 4 is a partial vertical section of the watch of FIGURES 1 and 2 taken along the line 4-4 of FIG- URE 2;

FIGURE 5 is a perspective bottom view of the balance wheel assembly of a watch constructed according to another embodiment of the invention;

FIGURE 6 is a vertical section of the balance wheel assembly of a watch constructed according to still a further embodiment of the invention;

FIGURE 7 is a perspective view of the magnet, shunt and coil arrangement of the balance wheel assembly of FIGURE 6;

FIGURE 8 is a vertical section of a balance wheel assembly of a watch constructed according to still another embodiment of the invention;

FIGURE 9 is a plan view of a coil suitable for use with the balance wheel assembly construction of FIG- URE 8;

FIGURE 10 is a vertical section of a balance wheel assembly constructed according to still another embodiment of the invention;

FIGURE 11 is a plan view showing a magnet suitable for use with the balance wheel construction of FIGURE 10; and

FIGURE 12 is a diagram of the coil energizing circuit employed with the various embodiments of the present mvention.

Referring to the figures of the drawing and particularly to FIGURES 1 through 4, there is seen an electric watch 10 which, as seen from the train side in FIGURES 1 and 2, comprises a pillar plate 12 on which a balance wheel 14 is mounted by means of a balance cock 16 secured to pillar plate 12 by means of a screw 18. The balance cook 16 supports an end stone and olived jewel assembly 20 in which is journaled one end of a balance staff 22. The balance staff carries the usual hair spring 23 controlled by the conventional regulating pin 25. A roller table 27 is carried on the balance stafi 22 above the balance wheel 14 and carries a pin 29 and contact "31 for making periodic electrical contact with the contact spring arm assembly 33, described in detail in assignees copending application Serial No. 551,791, filed December 8, 1955. The contact 31 is carried by a strip 35 mounted on roller table 27 and this is connected to the balance wheel so that when the contact on contact arm 33 engages the contact 31, contact arm 33 is grounded to the watch frame to close a circuit hereinafter to be described. The balance wheel 14 consists of a rim 24 secured to a collar 26 by I means of arm 28. Counter-balancing screws 29 are carried by the ring 24 for a purpose presently to become apparent.

The pillar plate 12 is provided with a semi-cylindrical recess 38 beneath the upper half of the balance wheel 14 in FIGURE 2. This semi-cylindrical recess 38 communicates with a sector shaped recess 40 having radial walls 42 and 44 and end walls 46 and 48. The watch may be provided with a conventional train, not shown, and with a dial 50, hour hand 52, minute hand 54, and sweep second hand 56, as best seen in FIGURE 3.

Referring to FIGURES 2 and 4, the balance wheel 14 may have a synthetic resin sheet 58 cast within its rim and about collar 26 and enclosing and supported by the arms 28. For clarity of illustration, this plastic material may be and is shown herein as being transparent. Mounted in the synthetic resin sheet 58 are a pair of radially disposed (Z-shaped keepers or shunts 60 and 62. Each of these shunts is formed of a magnetic material, such as low carbon steel, and has an upper leg 64, a lower leg 66, and a connecting leg 68. The upper legs 64 are embedded in the synthetic resin sheet 58 while the lower legs carry small cylindrical magnets 70', which may be of the type described in detail in assignees copending application Serial No. 578,843, filed April 17, 1956.

Mounted on the floor 72 of sector shaped recess 40 is a mounting block 74 which supports a coil assembly 76. Coil assembly 76 consists of a sheet of synthetic resin 78 attached to the mounting block 74 by means of screws 80 and 8 2, and this synthetic resin sheet has a coil 84 embedded therein. Coil 84 is provided with a pair of radial sides 86 and 88, joined at their outermost ends by an arcuate side 90, and at their innermost ends by a side 92, as is best seen in FIGURE 2. The C-shaped keepers and the coil 84 are so arranged that the cylindrical magnets 70 underlie the radial sides 86 and 88 of the coil.

One end of the winding of coil 84 is grounded to the Watch frame, while the other end is connected to one terminal of a suitable battery 83. The other terminal of the battery 83 is connected to contact arm 33 so that when this contact arm makes contact with contact 31, a circuit is completed through the coil 84 to the battery, thereby energizing the coil and impulsing the balance wheel 14. This circuit is shown in FIGURE 12.

, With the particular shape of keeper and magnets utilized an intense magnetic field is created between the uppermost face of the magnets 70, shown in FIGURE 4, and the upper leg 64 of the keeper. Very little stray field is produced so that when the balance wheel 14 oscillates, a stray magnetic field is not moved throughout the watch. While this embodiment of the invention has been described with a contact mechanism carried by the balance wheel assembly, it will be understood by those skilled in the art that this may readily be replaced by an additional magnet carried by the balance wheel cooperating with a coil and transistor arrangement as described in detail in French No. 1,090,564, of 1954.

Referring to FIGURE there is shown another embodiment of the invention wherein a balance wheel 94 having a rim 96 is supported from a balance staff 98 by means of a collar 100 and arms 102. The balance wheel 94 is mounted in a pillar plate in a manner similar to that shown in the embodiment of the invention of FIGURES 1 through 4. It must be remembered that FIGURE 5 is a bottom view of the balance wheel and that in operative position the balance wheel is inverted.

Balance wheel 94 is provided with a segmental shaped plate of magnetic material 104 between the lowermost legs 102 and the rim 96. Because of the unsymmetrical mounting of this plate the balance wheel is also provided with suitable counter-balancing screws 106. Mounted on top of the magnetic plate 104 is a bar magnet 108 which is carried chordally within the rim 96. Imemdiately above the magnet 108 in FIGURE 5 there is provided a shunt or keeper 110 which is carried by an arm 112 at- 4 tached to a collar 114 on balance staff 98. With this arrangement, intense magnetic fields of opposite polarity are produced at the ends of the magnet 108 between the magnet and the keeper 110. The plate 104 insures that stray magnetic fields are limited. In operation, the balance wheel assembly shown in FIGURE 5 is inverted and mounted in a watch in the manner shown in FIGURES 1 and 2 so that the intense magnetic fields at the ends of the bar magnet 108 intersect the radial legs of a coil similar to coil 84. The operation of this embodiment of the watch is the same as that disclosed in connection with FIGURES 1 through 4.

Referring to FIGURE 6, there is shown another embodiment of a balance wheel assembly constructed according to the invention wherein a balance wheel 116 is supported on a balance staff 118. The balance wheel 116 consists of a rim 120, collar 122, and arms 124. The balance wheel and balance staff are mounted on a pillar plate 126 in a manner similar to that disclosed in connection with the embodiment of the invention shown in FIGURES 1 through 4. Pillar plate 126 is provided with a cylindrical recess 128 having a floor 130.

An annular channel shaped ring 132 is suspended from the underside of balance wheel 116, as best seen in FIG- URE 6, and consists of side walls 134 and 136 and a top wall 138. Attached to the innermost side wall 136 are a plurality of small cylindrical magnets 140. The channel shaped ring 132 is formed of a suitable magnetic material such a low carbon steel and forms a keeper and shield for the cylindrical magnets 1 40 to provide intense magnetic fields at the faces of these magnets with extremely limited stray magnetic field.

Mounted on the floor of recess 128 is a ring shaped coil assembly 142 which consists of a ring of synthetic resin 144 in which a zig-zag circular coil 146 is encased. The coil 1146 consists of upper arcuate sides 148, lower arcuate sides 150, and vertical sides 152, thereby forming a series of -U-shaped loops as best seen in FIGURE 7. The coil is so wound and the magnets so placed that vertical coil sides 4152 are simultaneously situated adjacent the faces of magnets 140. Adjacent magnetic fields may be either of the same or opposite polarity, depending upon the direction of current flow in the coil section adjacent each magnetic field. That is to say, where the magnetic fields are of the same polarity, the direction of current flow must be the same, and where 'the magnetic fields are of opposite polarity, the current must flow in opposite directions.

As an illustration, if it be assumed that the current in vertical leg 158 flows upwardly in FIGURE 7, then the current in the adjacent vertical leg 156 flows downwardly. If magnetic fields are provided adjacent both these legs, the polarity of the magnetic fields must be opposite. On the other hand, if magnetic fields are placed adjacent vertical legs 154 and 156, the current flow is identical and like magnetic polarity must be used. It will be apparent that a plurality of magnets may be used to provide a very high torque for the current flowing in the coil and thereby provide a very efficient source of motive power for the watch. Because of the almost complete shielding afforded by the magnetic circuit, stray magnetic fields are almost entirely eliminated. This embodiment of the invention also provides the additional feature that the clearance between the inner surface of wall 134 and the outer surface of coil assembly 142 may be made so small as to provide shock proof mounting for the balance Wheel.

Referring to FIGURES 8 and 9, there is shown still another embodiment of the invention somewhat similar to that shown in FIGURES 6 and 7, wherein a balance wheel 160 is mounted upon a balance staff 162 carried by a pillar plate 164 in manner similar to that disclosed in connection with the embodiment of the invention shown in FIGURES 1 through 4. Balance wheel 160 consists of a rim 11'66, collar 168, and supporting arms 170. Pillar plate 164 is provided with a cylindrical recess 172 having a floor 174. Suspended beneath balance wheel 160 is a channel shaped ring member 176 which consists of an upper annular leg 178, a lower annular leg 180 and a cylindrical connecting leg 182. The channel shaped ring member 176 has its upper leg 178 attached to the balance wheel 160, while its lower leg 180 carries a plurality of small cylindrical magnets 184. The channel shaped ring member 176 is formed of a suitable magnetic material such as low carbon steel and, in cooperation with the mag nets 184, produces intense magnetic fields above the faces of the magnets. Practically no stray field is produced.

Mounted on the pillar plate 164 is a washer shaped coil assembly 186, shown in detail in FIGURE 9. This coil assembly consists of a washer shaped annulus of synthetic resin 188 which encases a coil 190. The coil 190 consists of a series of inner arcuate sides 192 which are connected to a series of outer arcuate sides 194 by means of radial sides 196 thereby forming a series of U-shaped loops. The radial sides 1% are arranged to be simultaneously situated in the intense magnetic fields at the faces of magnets 184, so that when current flows through the coil the balance wheel is provided with an impulse. The polarities of the magnetic fields may be either alike or opposite, as pointed out in connection with the embodiment of the invention shown in FIGURES 6 and 7, and a large number of magnetic fields may be utilized if desired. As with the embodiment of the invention shown in FIG- URES 6 and 7, a high efficiency may be obtained with only very limited stray magnetic fields. Shock proof mounting is also possible by providing a small clearance between the inner edge of the coil assembly .186 and the cylindrical connecting leg 182.

Referring to FIGURES l and 11, there is shown still another embodiment of the invention wherein a balance wheel 198 is mounted on a balance staff 200 carried in a pillar plate 202 in a manner similar to that described in connection with the embodiment of the invention shown in FIGURES 1 through 4. The balance wheel 198 consists of a rim 204, collar 206-, and supporting arms 208. The pillar plate 202 is provided with a cylindrical recess 210 having a floor 212. Mounted on the underside of balance wheel 198 is a generally washer shaped magnet 214 having radial arms 236. This magnet may be magnetized so as to have one pole at the inner aperture 216 and an opposite pole at the outer edges 218 of arms 236, as shown in FIGURE 11.

Attached to the inner edge of this magnet is a generally U-shaped ring 220 having an inner vertical side 222, a bottom leg 224, and an outer vertical side 2 26, which is shorter than the inner vertical side 222. The generally U-shaped member 220 is formed of a suitable magnetic material, such as low carbon steel, and forms with the magnet 214 a magnetic circuit producing an intense magnetic field at the edges of the arms 236. The cutout segments 228 between arms 236 provide a negligible magnetic field at certain portions of the vertical outer leg 226.

Mounted on the pillar plate 202 is a coil assembly 230 of the same type as illustrated in FIGURE 9. With the particular magnetic field arrangement shown, this coil may take the shape shown by the broken lines 232 in FIG- URE 11. The radial portions 234 of the coil extend between the magnet 214 and lower leg 224 of U-shaped shunt member 222, so that a radial leg 234 is adjacent each arm 236 of magnet 214. The operation of this embodiment of the invention is similar to those described hereinbefore.

It will be apparent from the foregoing that according to this invention there is provided an electric wrist watch mechanism having a source of motive power possessing adequate efliciency to provide long service with a limited electrochemical energy source and which produces negligible, or at least unobjectionable stray magnetic fields. The sources of motive power disclosed are capable of simultaneously providing shock-proof mounting of the balance wheel and high efficiency driving power. According to some embodiments of the invention, the impulsing area or area of magnetic fields, may be localized in only a sector of the balance wheel. With certain embodiments of the invention, no counter-balancing is necessary and shock-proof mounting may be provided.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by the United States Letters Patent is:

1. In a battery operated electric watch, a balance wheel and staff assembly, a pair of permanent magnets carried by said assembly and having first surfaces defining the ends of a pair of intensified magnetic regions, said intensified magnetic regions spaced less than apart around said staff, shunt means having a substantially C-shaped cross section comprising a pair of substantially parallel legs joined by a connecting leg, one of said legs engaging second surfaces of said magnets, the other of said legs defining the other ends of said intensified regions, coil means stationarily mounted in said watch adjacent said assembly and having at least two spaced portions simultaneously intersecting said intensified magnetic regions, and means for periodically connecting said coil means and said battery when said spaced portions are in said intensified regions moving in a given direction so as to impart simultaneous impulses to said balance wheel from each of said intensified regions.

2. In a battery operated electric watch as set out in claim 1 wherein said parallel legs comprise circular members joined at one edge by said connecting leg which is cylindrical.

3. A watch as set out in claim 1 wherein the magnetic axes of said intensified regions are substantially parallel to said staff.

References Cited in the file of this patent UNITED STATES PATENTS 1,608,786 Fery Nov. 30, 1926 2,598,912 Held June 3, 1952 FOREIGN PATENTS 410,732 Great Britain Sept. 30, 1932

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