US3708974A

US3708974A - Pallet attracting construction

Info

Publication number: US3708974A
Application number: US00212360A
Authority: US
Inventors: M Fujimori
Original assignee: Suwa Seikosha KK
Current assignee: Suwa Seikosha KK
Priority date: 1970-12-28
Filing date: 1971-12-27
Publication date: 1973-01-09
Anticipated expiration: 1990-01-09
Also published as: DE2165083B2; GB1359743A; FR2120057B1; CH1898271A4; FR2120057A1; JPS5025188Y1; DE2165083A1; CH575621B5; DE2165083C3

Abstract

A pallet attracting construction wherein a C-shaped recess is rotatably mounted in the region of a balance bearing. A pallet having a member formed of a magnetic material secured thereto is positioned so that said member oscillates between the facing ends of said permanent magnet in an elongated hole in a support plate, the ends of said hole limiting the displacement of said pallet.

Description

O United States Patent 1191 1 1 3,708,974 Fujimori 1451 Jan. 9, 1973 [54] PALLET ATTRACTING 2,971,324 2 1961 Beyner ..58 28 1) x CONSTRUCTION 3,026,458 3/1962 Freystedtetal. ..58/23 A x 3,059,413 10/1962 Detwilel' ..58/280 InventorI Motoyuki Fllilmori, Suwa, Japan 3,122,379 3/1964 Trick etal ....-..58/28 R 3,l87,l26 6/l965 DeBarba ..58/28 R X [73] Ass'gnee' ZE;'E S Seikosha 3,611,707 10/1971 Scholz ..S8/l16 R [22] Filed: Dec. 27, 1971 Primary Examiner-R1chard B. W1lk1nson [21] PP N05 212,360 Assistant Examiner-U. Weldon AttorneyAlex Friedman et al. [30] Foreign Application Priority Data 7 Dec. 28, 1970 Ja an .;.45/l327l6 57 ABSTRACT 52 US. Cl. ..ss 2s R 74/1.5 A P1net amacfing wherein a C'ShalPed [51] Int. Cl. ..G0 4c 3/04 recess is rotatably mounted in region of a balance- [58] Field of Search.....58/7, 23 R, 23 A,- 23 D, 23 v, f A 1 having a member fi Of a 5 28 R 2 A 2 B 2 D 116 R 11 M netrc material secured thereto is POSltlOnCd S0 that 125 74/1 said member oscillates between the facing ends of said permanent magnet in an elongated hole in a support [56] References Cited plate, the ends of said hole limiting the displacement.

of said pallet. UNITED STATES PATENTS 2,061,047 11/1936 Schweitzer ..58/116 X 4 Claims, 4 Drawing Figures /6 I /4 1 'X J Y/ i /5 l I [4 K1, J/jll 11V 1- 7] /Z,/3

l l K n V PATENTEDJAM. ems 3.70374 SHEET 2 0P2 1 PALLET ATTRACTING CONSTRUCTION BACKGROUND OF THE INVENTION The present invention relates to pallet attracting constructions for incorporation in electric timepieces. In conventional mechanical timepieces, the driving torque passes through a gear train with its speed reduced, and is then appliedto an escape wheel and pallet. When the pallet stops, a turning torque is applied thereto in a predetermined direction due to the geometrical relation with the escape wheel. The pallet is brought to a standstill at fixed positions by occasional contact with a base plate or pallet supporter. This action, called attraction, prevents the pallet from contacting with the balance wheel at the vibrating seat of said balance wheel or vibrating weight, so as to eliminate the adverse affect on the accuracy of time keeping which would result should the pallet remain in contact with the balance wheel at that time.

On the other hand, in. electric. timepieces, torque is not always transmitted to an escape wheel and pallet, so that the attracting force must be applied to the pallet by some other means. In the art, such means has generally consisted of an attracting member formed of a magnetic material mounted securely to a lever portion of the pallet, said attracting member being attracted by the magnetic force of attracting magnets positioned adjacent the ends of the path of the reciprocating pivotable motion of said lever portion of said pallet at which said pallet is stopped, thereby providing an attracting force to the pallet. In another prior art embodiment, an attracting member formed of magnetic material is mounted securely to the pallet staff, and a projecting portion of said attracting member is positioned adjacentan attracting magnet mounted securely to the base frame of the watch. The attraction of said projecting portion of the attracting member to the attracting magnet'provides the attraction force when the pallet stops its reciprocating pivotable motion. Both of these prior art arrangements offer substantial disadvantages affecting time keeping accuracy, size of the structure, and the availability of a vibrograph as a means for reading time for accuracy measurement purposes.

SUMMARY OF THE INVENTION A pallet attracting construction for an electric timepiece including a balance wheel pivotably mounted on a balance bearing'for cooperation with a pivotably'mounted pallet. A C-shaped permanent magnet is rotatably mounted in the region of said balance bearing, the ends of said permanent magnet being substantially aligned with the opposed ends of a slot in the base plate of the timepiece, which base plate also serves to support said balance hearing. A member formed of magnetic material is mounted on said pallet for projecting through said slot for cooperation with the ends of said permanent magnet to provide attracting force to said pallet.

Accordingly, one object of the pallet attracting construction according to the invention is to provide an arrangement for applying attracting force to the pallet of an electric timepiece without adversely affecting the time keeping, size or other characteristics of said timepiece.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIGS. 1 and 2 are schematic plan views of two prior art ,palletattracting constructions;

FIG. 3'is a fragmentary cross-sectional view of a pallet attracting construction according to the invention;

FIG. 4 is a top plan view of the pallet attracting construction of FIG. 3.

DESCRIPTION OF THE PREFERRED 1 EMBODIMENTS Referring now to FIG. 1, the prior art pallet attracting construction depicted includes a pallet fork 4 fixedly mounted on pallet staff I, which in turn is pivotably mounted within the timepiece to permit the pivotable displacement of said pallet fork. Said pallet fork is provided with a pair of

pallet jewels

2 and 3 for cooperative engagement with the gear train of the timepiece for driving said gear train. An attracting pin 5 formed of magnetic material ismounted on the lever portion of said pallet fork, while a pair of spaced attracting magnets are mounted on opposed sides of said lever portion of said pallet fork in said timepiece. When the reciprocating swing motion of said pallet fork is stopped at the extreme ends thereof, .one of attracting magnets 6 are positioned adjacent attracting pin 5 at a fixed distance therefrom, so as to provide a magnetic attraction force to said pallet.

A second prior art pallet attracting construction is depicted in FIG. 2, wherein pallet fork 4' is fixedly mounted on pallet staff *1 ,for pivotable rotation therewith within the timepiece. Again,

jewels

2 and 3 are mounted on said pallet fork for cooperative engagement with the timepiece gear train for driving said'gear train. In this embodiment, an attracting member 7 formed of a magnetic material is mounted on pallet staff 1. Saidattracting member is formed with a pair of spaced projecting portions so that said member is, itself, in the nature of a pallet. A permanent magnet 6 is mounted in the timepiece intermediate saidprojecting portions of attracting member 7 and positioned so that when the reciprocating swing motion of pallet fork 4 is stopped, attracting magnet 6 is spaced a predetermined small interval from one of the projecting portions of attracting member 7 so as to apply magnetic attraction force to the pallet fork through said attracting member and pallet staff.

In both of the foregoing embodiments, at least one attracting magnet is positioned beneath and adjacent the pallet and the motor driving the timepiece. Said motor generally includes a balance wheel and permanent magnets which cooperate with driving coils for converting electrical energy to mechanical rotative energy for driving the timepiece by sustaining the oscillation of the balance wheel. However, when permanent magnets 6 are positioned as described above, the magnetic flux emanating therefrom combined with the leakage flux from the driving magnets of said motor or acts on balance wheels formed from magnetic material to impede the oscillation of the balance wheel. This disturbance of the vibrational period adversely affects time keeping accuracy. A further defect in these structures arises from the fact that the intensity of the magnetic moment acting on the motor and balance wheel due to permanent magnets 6 varies with variations in the relative position between said permanent magnets and the driving magnets in the motor. For this reason, variations in time keeping accuracy vary with variations in amplitude of the motor, thereby adversely affecting the isochronism of the motor and the stability of the accuracy thereof.

The magnetic coupling between the driving motor and attracting magnet 6 in the conventional timepieces is caused in part, by the constraints applied in designing said motor. The members acting on the motor are generally concentrically disposed about the balance wheel and the flux density in the magnetic circuit of the motor is generally maximum in the longitudinal direction of the movement of said balance wheel. Since the sides of the motor generally determines the thickness of the movement, the space between the respective members acting on the motor is generally minimized. In order to eliminate this magnetic coupling, a magnetism shielding member formed of magnetic material should be provided between permanent magnets 6 and the driving motor. However, such a shielding member increases the thickness of the movement, thereby reducing the marketability of the timepiece, and in particular, of Wristwatches. Further, the special materials required for the shielding member increases both material and labor costs, thereby increasing the cost of the timepiece,

A further defect in-the prior art arrangements arises from the fact that the release from attraction between the pallet and the permanent magnets is achieved by the engagement of the balance wheel against the pallet fork. The intensity of the attraction force in each direction depends on the composition of the attracting magnetic material, the attracting intensity, the material of the attracting pin or member, and the clearance between the attracting magnet and the attracting pin or member. However, it is almost impossible to vary, adjust or balance these elements in a simple manner when assembling the timepiece. This further contributes to the variations in amplitude of the oscillations of the motor, and a reduction in time keeping accuracy. Further, if the intensity of attraction is unbalanced, the impact sound produced when a roller jewel mounted on the balance wheel engages the pallet becomes unbalanced when the intensity of attraction becomes unbalanced. This produces disturbances in paper tape plots of ticktock noise so that it is impossible to read the time rate by means of vibrographs responsive to impact sound. The foregoing defect may be eliminated in the prior art arrangements only by changing the components thereof, and even this type of adjustment is difficult to accomplish and requires much time.

' pallet. While an approximate value can be obtained by using related properties such as amplitude, energy consumption of the motor and the like, this approach makes it difficult to obtain optimum conditions in the absence of the ability to make empirical manual adjustments. In addition, the prior art arrangements require a permanent magnet having a high magnetic flux, necessitating the use of a hard brittle material of increased cost and requiring greater labor.

The foregoing difficulties are eliminated by the arrangement according to the invention as depicted in FIGS. 3 and 4. In said arrangement, a bridge or plate support member 16 carries a shock absorbing bearing frame 17 which provides one of two pivotable supports for the balance wheel. Support 16 also supports one end of pallet staff 11, pallet fork 14 being fixedly mounted on said pallet staff.

A pair of pallet jewels l2 and 13 are mounted on pallet fork 14. Also mounted on said pallet fork is an attracting pin 15 formed of magnetic material, said pin being mounted on the lever portion of said pallet fork. A C-shaped attracting magnet 18 is rotatably mounted on bearing frame 17. Said permanent magnet is provided with a pair of projecting tabs to permit the rotatable positioning thereof relative to a longitudinally extending slot 19 formed in support 16. Pin 15 projects through slot 19, said attracting magnet being dimen-v sioned so that the ends 20 thereof may be selectively positioned relative to the ends of slot 19. The ends of said slot serve to limit the .pivotable oscillatory displacement of pallet fork 14 due to the engagement thereagainst of pin 15. The attraction force is applied to pin 15 by the ends 20 of attracting magnet 18 when said pin is positioned at the ends of slot 19.

In the arrangement according to the invention, attracting magnet 18.is positioned in parallel to and concentricwith the motor and balance wheel. A closed magnetic loop is defined by said attracting magnet which incorporates attracting pin 5. Further, said attracting magnet is structurally separated from the motor so that no complicated magnetic shield is required, leakage flux is decreased, and magnetic coupling between said attracting magnet and the motor is minimized. Accordingly, the adverse affect on the vibrational period of the balance wheel is diminished, and time accuracy may be stabilized. Since an additional magnet and shield member is not required, the thickness of-the movement may be minimized.

By rotatably positioning attracting magnet 8, the attraction of the pallet can be balanced and measurement of time for the purposes of adjustment can be readily performed by means of a vibrograph. Further, the measurement of the intensity of attraction of the pallet may be measured in the arrangement of FIGS. 3 and 4, so that it is possible to design the arrangement for optimum attraction, thereby further enhancing stability and accuracy of the timepiece.

Since the attracting magnet may be made larger in size than was possible with regard to the magnet 6 of the embodiments of FIGS. 1 and 2, material of relatively low magnetic flux density can be used, thereby reducing material and manufacturing costs. Since the attracting magnet is spaced from the gear train, the magnetic force thereof has no adverse affect on said gear train.

The arrangement according to the invention utilizes the ends of slot 19 to define the limits of pivotable oscillation of the pallet fork 14 by engagement by attracting pin 5. The arrangement according to the invention can also be formed utilizing a separate structure for limiting the pivotable displacement of the pallet fork, while still incorporating the arrangement accord ing to the invention of providing a rotatable attraction magnet for the adjustment of attraction force.

It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is: a i

1. A pallet attracting construction for an electric timepiece comprising a support plate; a balance wheel pivotably mounted on one side of said plate at a point thereon; a pivotably mounted pallet operatively coupled to said balance wheel fordisplacement in response to the oscillation of said balance wheel; an attracting member mounted on said pallet and projecting toward said support plate, said support plate being formed with an elongated slot therethrough for receiving said attracting member during the pivotable displacement of said pallet; and a C-shaped attracting magnet mounted for selective rotation on the side of said plate opposed from said balance wheel in the region of the point of mounting of said balance wheel, said attracting magnet and said slot being positioned so that the ends of said attracting magnet are in substantial alignment with the ends of said elongated slot for applying an attracting force to said attracting member at the extremes of pivotable displacement of said pallet.

2. A pallet attracting construction as recited in claim 1, wherein said slot is dimensioned so that the ends thereof define the outer limits of pivotable displacement of said pallet when engaged by said attracting member.

3. A pallet attracting construction as recited in claim 1, wherein said C-shaped attracting magnet is mounted so as to be positioned substantially concentric with the point of pivotable mounting of said balance wheel.

4. A pallet attracting construction as recited in claim 1, wherein said C-shaped attracting magnet is formed with at least one projecting portion for the manual selective rotation thereof to position the ends of said magnet relative to said slot.

Claims

1. A pallet attracting construction for an electric timepiece comprising a support plate; a balance wheel pivotably mounted on one side of said plate at a point thereon; a pivotably mounted pallet operatively coupled to said balance wheel for displacement in response to the oscillation of said balance wheel; an attracting member mounted on said pallet and projecting toward said support plate, said support plate being formed with an elongated slot therethrough for receiving sAid attracting member during the pivotable displacement of said pallet; and a C-shaped attracting magnet mounted for selective rotation on the side of said plate opposed from said balance wheel in the region of the point of mounting of said balance wheel, said attracting magnet and said slot being positioned so that the ends of said attracting magnet are in substantial alignment with the ends of said elongated slot for applying an attracting force to said attracting member at the extremes of pivotable displacement of said pallet.