US3158988A - Electrical contact-magnet index system - Google Patents

Description

Dec. 1, 1964 M. s. WALMER ELECTRICAL CONTACT-MAGNET INDEX SYSTEM 2 Sheets-Sheet 1 Filed Jan. 31, 1962 INVENTOR Marlin S. Walmer,

ATTORNEYS Dec. 1, 1964 M. s. WALMER 3,153,988

ELECTRICAL CONTACT-MAGNET INDEX SYSTEM Filed Jan. 51, 1962 2 Sheets-Sheet 2 INVENTOR Marlin S. Wilma;

BY 9; btfiwm. W ATTORNEYS United States Patent 3,153,988 ELEQTEHCAL QQNTACT-ltllAGNET ENDEX SYSTEM lt larlin S. Walmer, Elizabsthtcwn, Pa, assignor to Hamilton Watch Company, Lancaster, Pan, a corporation of Pennsylvania Filed Jan. 31, T1962, Ser. No. 170,6?25 6 Claims. (Cl. 58-23) This invention relates to battery operated electric watches and more particularly relates. to an improved unitary contact and index system for such watches.

In electric wrist watches of the moving coil type which have been proposed in the commercial electric wristwatch of the assignee of this application, it has been customary to provide periodic energization of the coil by means of some type of spring-type commutating system. One such system is illustrated in assignees patent to I. A. Van Horn et al., No. 2,806,908. The proper operation of this type of contact system is absolutely essential to the successful performance of the watch, and it has been found that some criticality of adjustment exists.

In this type of electric watch, the balance wheel serves as the source of motive power and it is necessary to provide an indexing mechanism which receives power. from the oscillating movement of the balance wheel and transforms these oscillations into rotary movement in one direction. Generally speaking, this has been accomplished by means of a toothed wheel which is advanced in steps by means of a periodic contact with a jewel member carried by the balance wheel.

According to the invention disclosed and claimed in assignee's US. Patent 3,016,685, it has been found that it is possible to entirely eliminate this type of spring-type contact system and to utilize the indexing function of the balancewheel to perform the switching operation during the timethat it indexes without any requirement for the expenditure of additional energy. Because of the unique arrangement of the contactsystem, adjustment is entirely eliminated, thereby obviating the criticality previously mentioned. Fewer parts are required in that the entire spring-type contact system is done away with, thereby permitting a space reduction which makes possible a thinner watch movement. In addition to this, it is found that the contact which is obtained is more reliable than that which is possible with a spring-type contact system.

While at least one other worker in the horological field has previously proposed a combined index and contact system for an electric timepiece, the nature of that proposal was such as to make it impractical for high quality timekeeping. vide a system wherein the friction -entailed in operation was both minimized and stabilized. That is to say, the friction represented in the load which the train of the timepiece presents to the prime mover should not only be at a minimum but should also be maintained as uniform as possible during the life of the timepiece. If this latter requirement is not substantially met, the result is One reason for this was a failure to proa time iece which is erraticin o eration and inca ableof unwantedclosure of the energizing circuit at undesired instances in the operation of the system.

Even though-the-contact and index system disclosed and claimed in assignees above-mentioned copending US. application solves the foregoing problems encountered in the spring-type contact and provides the first commercially successful contact index system ever devised for an electric wrist watch, it has now been found that certain additional improvements are possible. As that system is described in the aforementioned copending application, separate and distinct contact and index wheels are used for performing the switching and indexing functions within the watch. Since both the contact and index wheels are separate units, each wheel must be made sufficiently large and strong so as to resist damage during both assembling and use of the watch. The wheels must be precisely aligned during assembly to assure that the stacked or laminated contact and index system formed when the two wheels are placed together will be within accepted tolerances. Needless to say, should the individual contact and index wheels forming the contact and index system be out of proper alignment or position, the quality of the watch would be adversely affected. The fact that each wheel is made sufficiently large to permit its handling and operation without damage results in the contact and index system being thicker than is possible with the present invention even though such a system is considerably thinnerthan the heretofore known and used spring-type contact systems.-

According to the present invention, it has been found that it is possible to retain the desired operating characteristics of the above described contact and index system while at the same time obtaining additional advantages through the unique arrangement of this invention. This goal is achieved by utilizing a contact-index system which is constructed as a single wheel made of a metal which is not only electrically conductive but is also either magnetically'hard so it can be magnetized or is magnetically soft with a sufficiently high residual induction such that it can be ferromagnetical'ly attracted to the index magnet with suificient force to properly index the watch. Because of the unique construction of the present unitary contactindex wheel, not only are fewer parts used but the adjustment or alignment of the heretofore used contact and indexing wheels is completely eliminated thus resulting in a superior system which is less expensive to manufacture, install and repair. In addition to this, the construction of the contact and index wheel as a single unit also substantially reduces the thickness of the system and gives a watch contact-index system which is thinner yet more reliable than heretofore known systems.

It is accordingly a primary object of the present invention to provide an improved contact and index system for an electric watch.

It is another object of the invention to provide an improved contact and index system for an electric watch of the type utilizing an oscillating balance staff to impart one-way motion to an index wheel wherein the energy required to advance the index wheel is also utilized to provide the periodic electric contact.

It is still another object of the invention to provide an improved contact and indexing system for an electric watch utilizing fewer parts than were heretofore found necessary.- a

' It is yet another object of the invention to provide an improved contact and indexing system for an electric watch whichutilizes a single unitary contact-index wheel for bothp'eriodically energizing the electromagnet system used to powerthe watchand for indexing the timepiece.

It is a further object of the inventionto provide an improved unitary contact-index mechanism for an electric watch wherein adjustment of the Contact system is substantially eliminated.

It-is astill further object of the present invention to "provide animproved contact-index system for an electric watch which permits a reduction in the size of the watch movement to provide a thinner watch.

It is still another "object-of the present invention to provide an improved contact-index system for an electric Watch which is susceptible to fewer failures than heretofore known like devices.

A further object of the present invention is to provide a contact-index system that is magnetized so that a more positive indexing of the watch is obtained.

It is a further object of the present invention to provide a magnetized contact-index system in which the index magnet is replaced by a magnetically soft metal index post.

A still further object of the present invention is to provide an improved electric watch which utilizes as a component part thereof a contact-index system having a unique magnetized contact-index wheel and a fixed indexing magnet.

Yet still a further object of the present invention is to provide an improved electric watch which utilizes as a component part thereof a contact-index system having a unique magnetized contact-index wheel operably associated with a fixed magnetizable material by which the wheel is properly indexed.

Yet a still further object of the present invention is to provide an improved electric watch which utilizes as a component part thereof a contact-index system having a unique ferromagnetically attracted contact-index wheel operably associated with a fixed index magnet by which the Wheel is properly indexed.

It is still a further object of the invention to provide a contact-index system which minimizes and stabilizes friction and which provides positive assurance against unwanted contact while utilizing a minimum number of parts.

It is another object and advantage of the invention to provide an improved contact-index system using a unique electric circuit which utilizes as a component part thereof an index assembly having one part in electric contact with the watch train and another part insulated from the first part but periodically connected in the energizing circuit of the Watch.

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

FIGURE 1 is a partial vertical section of an electric watch showing the unitary contact-index wheel of the present invention utilized in a contact and indexing system;

FIGURE 2 is a diagrammatical plane view showing the commencement of the index and contact cycle; and

FIGURE 3 is a diagrammatical plane view showing the termimnation of the index and contact cycle.

The same reference numerals denote the same parts throughout the several views of the drawings.

With reference to FIGURE 1, there is seen apillar plate which, in conjunction with a bridge (not shown), carries a balance staif 12. The balance staff 12 carries a balance wheel (not shown) on which there is mounted a coil of the general type shown in the aforementioned Van Horn et al. Patent No. 2,806,908. Also attached to the balance staff 12 is an index roller 14 which may cornprise a split collar of the type shown in the Van Horn et al. patent and which has friction fitted therein a semicircular jewel pin 16., A contact plate is attached to the underside of the index roller 14 by any suitable insulating adhesive 17 such as, for example, an epoxy resin. The contact plate is accurately apertured to permit the jewel pin 16 to pass therethrough. A semi-circular contact 18, such as disclosed and claimed in assignees copending US. application Serial No. 146,639, entitled Contact Index System, depends from the contact plate 20. This contact may be formed either integrally with the contact plate (such as being formed as a swaged D- pin) or permanently joined thereto, for example, by welding. The semi-circular jewel pin 16 is disposed in a back-to-back relationship with the contact 18 and may be attached thereto by any suitable adhesive. The diamas will be more fully set out hereinafter.

.4 eter of the jewel pin is preferably larger than that of the contact to provide protection against inadvertent contact being established during the backswing of the balance wheel or during possible jarring of the timepiece as is more fully explained in assignees abovementioned copending application Serial No. 146,639. A wire 24 is attached at one end to the coil and the other end is passed through a tube 25 which is carried by the roller 14. The tube 25 protects the Wire 24 and also cooperates with a finger lock (not shown) to provide motion limiting that forms no part of this invention. Electrical connection between wire 24 and the contact plate can be established in any desired manner, such as by solder 22 on the underside of the contact plate, the wire passing through an aperture in the contact plate.

The pillar plate 10 and a train bridge support the jewel bearings 32 and 34 and an index assembly which is shown generally at 36. The jewel bearings contribute to a minimization of friction in the operation of the index assembly which consists of an index pinion 38, staff and index hub 42. The staff 443 is provided with an enlarged splined end 44 which is received in a. recess 46 in the index hub 42. The spline 44 is provided to present a greater adhesive area to the epoxy resin 48 which is used to fill the recess 4d. The spline may be in the form of V-shaped grooves although it will be apparent that other spline shapes may be used as long as increased adhesive area is provided. Some type of tooth shape is preferable, however, because it provides a locking area with the adhesive. The index hub is provided with a pivot which engages a contact pad 47 preferably composed of a precious or semi-precious alloy. The contact pad 47 is carried by battery lead or spring 49 mounted below the pillar plate and secured thereto and electrically insulated therefrom in any suitable manner (not shown).

The index hub 42 carries a unique unitary contact-index wheel 50 which replaces the individual contact and index wheels usually employed in electric watches of the type described in assignees copending application Serial No. 146,639. Since the contact-index wheel 50 must serve the function of both a contact and index wheel, it must not only possess the usual mechanical properties of these Wheels such as ductility, hardness and toughness so as to resist any wear, abrasion, bending or chipping that might otherwise damage or deform the sharp teeth of the wheel either during assembling or when functioning but, the

wheel must have. acceptable electrical contact and magnetic properties as Well. These electrical cont-act properties include such characteristics as electrical conductivity, resistance to fouling, resistance to are erosion and corrosion plus other features which are normally associated with acceptable long-term and make-and-break contacts such as employed in the various contact systems described by the assignee in the patent literature. The specific magnetic properties which the wheel 50 must possess will depend to a great extent upon which embodiment of the contact-index system of this invention is to be employed However, generally, the contact-index Wheel 50 must be formed of a material which is either magnetically hard, that is, one having a high coercive force and can be permanently magnetized, or magnetically soft which means that it has a low coercive force and is thus easily magnetized by a magnetic field. An example of metals which meet the above stated requirements are, in the soft category; Permalloy, Supermendur, CoPt, nickel, Alfenol or Sendust (Fe-Al-Si); and in the hard category; CoPt and FePt. It will be noted that CoPt may be made either hard or soft. Other metals obviously could be used if they possess the aforementioned magnetic and electrical characteristics.

The contact-index wheel 50, which is best seen in FIG- URES 2 and 3, has non-symmetric teeth along its periphery. In reference to these figures, it will be seen that the teeth of the contact-index wheel 50 have undercut leadaiaaess ing edges Gil which form an angle A with a radius through the leading edge of the tooth. In a preferred embodiment, this angle is approximately 13 The lagging edge 62 of the tooth forms a much greater angle with respect to the radius through the leading edge and, in a preferred embodiment, forms an angle 18 of approximately 27. The significance of this tooth shape is to ensure, among other things, not only a better contactbut less friction be tween the teeth and the contact 18 and tomaintain these qualities .at a substantially constant uniform value as the timepiece ages, as is more fully explained in assignees copcnding application Serial No. 146,639. It is also to be noted that the tooth ends are rounded, as shown at 61, and that the teeth of the alloy contact-index wheel t) extend into the path of movement of the jewel pin 16 and contact 18 carried by the balance staff 12.

A pair of small circular metal cylinders 56 and 57, which may be either cylinders or cores having high remanence such that they can be ferromagnetically attracted or, preferably, permanent magnets, are frictionally carried by the pillar plate ltl beneath the contact-index wheel 5t? and act upon the wheel to pull the index assembly 36 downwardly so that the pivot 45 maintains constant electrical contact with the pad 47 on the battery lead 49. These cores or magnets, as the case may be, also serve a detent and drive function such as is more fully explained in assignees copending application Serial No. 146,639. Although two such cores or magnets are shown and preferred, it is to be understood that only one such element is absolutely necessary to the operation of the present invention, although the use of two or more such cores or magnets insures a more positive and balanced puildown of the pivot 45 and keeps it in firm contact with the pad 47.

In the embodiment of this invention in which the elemerits 56 and 57 are permanent index magnets and the contact-index wheel is made of a soft ferromagnetic alloy such as, for example, Permalloy, Supermcndur, CoPt or nickel so that it is ferromagnetically attracted, the operation of the contact-index system may be explained in the following manner.

As the balance staff and index roller 14 rotate in the direction of the arrow C, the semi-circular edge of the contact 18 engages the rounded tip 61 of a tooth 58. This establishes a contact to one terminal of the balance staff carried coil as follows: from the battery (not shown) to battery lead 49, contact path 47, pivot 55 of index hub 42, contact-index wheel 56 contact 18, contact plate 2d, and contact lead 24 to the coil. is grounded to the watch frame by connection to the hair-- spring so that the only moving contacts are contact-index wheel Stland contact 13.

As the balance stalf 20 and index roller .14 rotate in the direction of the arrow C, the contactls drives the index wheel against the holding force of the index magnets 5s and STuntil the index wheel reaches the. position as shown in FIGURE 3. In FIGURE 3, the contact 13,

index jewel 16 and contact-index wheel 5t) are shown.

in the position which represents the end of the contact period whereupon further movement of the balance staff and wheel in the direction of the arrow C causes termination of the contact between the tooth 5i; and thesemicircular edge of the contact 18. 1

It is to be noted that in this position (FIGURE 3), the end of the tooth 58 of the contact-index wheel Stl is closer to the center of the index magnet 5a, which has been moved radially outward by a small amountfrom the position it normally occupies in heretofore known like devices, than is the tooth 64. Because of this, the magnetic attraction of the index magnet is stronger toward tooth 58 than tooth 64 and the index magnet thereby drives the contact-index wheel 5!} in the direction of arrow D until the tooth 58 is centered over the index magnet as was the tooth 64 in FIGURE 2. it is to be understood that a similar action takes place between the index ti magnet 57 and another two teeth of the wheel 50. The contact-index wheel has thereupon been indexed one tooth position, and contact to the coil has been established by the very movement that caused indexing.

When the index roller moves in its return direction, the jewel pin 16 will completely pass by the tooth 58 of the contact wheel previously advanced on the counterclockwise rotation of the balance staff as will be seen from FIGURE 2 and the comparison of the path of movement of the jewel pin indicated at E and the position of the tooth 64. However, the jewel pin will strike the lagging edge 62 of the tooth 66 which is now in the relative position of the tooth 58 in FIGURE 2 and move it a slight amount in the counter-clockwise direction. This slight amount of movement produced by the back-swinging of the jewel pin is less than the movement of the index The other side of the coil wheel on engagement with the contact'18 during the forward swing as indicated in FIGURES 2 and 3. The annular movement of the contact-index wheel betweenthe positions shown in FIGURES 2 and 3 is sufficient to bring the tooth 58 to a position over the index magnet where the magnet draws the tooth forward. On thebackswing, however, the movement is insuflicient to cause the index magnet to advance the wheel in a counter-clockwise direction and therefore when the jewel pin clears the tooth 66, the tooth 58 merely returns to its position of rest over the magnet 56. As a result, the oscillation of the balance staff imparts a one-way rotor motion to the index wheel.

Reference to FIGURE 2 will indicate that at the moment that contact is established between the contact 18 and the tooth 58 of contact wheel 59 to energize the coil and the driving system, the arcuate phase of the contact 18 engages an arcuate portion 61 of tooth 58. As the contact 18 moves in the direction of the arrow C a roll ing and sliding action occurs at the contacting surface but the distance that contact 18 slides along the tooth 58 is maintained at a minimum. That is to say, the length of tooth edge which is subjected to a sliding action is minimized. This has been found to provide a minimum of friction and has been found to maintain the friction loss at a substantially uniform value as the timepiece ages. Such an arrangement has been found superior to a previously proposed converse arrangement wherein a contact pin establishes electrical contact with the edge 62 of the tooth and slides along that edge as electrical impulsing occurs. This latter arrangement has been found to cause pit-ting of the tooth surfaces with a resulting increase in friction that varies from tooth to tooth and nets 56-58 that is too great could cause low motion, excessive energy requirements, reduced battery life, ex-

cessive wear on the contact pin 18 plus excessive Wear on the hub and end piece. On the other hand, too weak a force would permit double indexing or possibly no indexing in that the magnetic field would fail to complete the fractional tooth advance obtained, mechanically by the contact action of the contact-index wheel, or poor electrical contact quality between. the contact pin and wheel or the pivot-contact pad interface.

5%) but to the material from which both it and the elements 5648 are constructed.

An alternate type of contact-index system can be produced which will give a strong indexing force by constructing the wheel 50 of a magnetically hard material such as CoPt or FePt, heat treating the wheel in a well known manner until the soft material is changed into a I From the above, it can be seen that careful consideration must be given not only to the design of thecontact-index wheel ensasss magnetically hard material so that it can be magnetized, and then magnetizing the contact-index wheel so as to form a permanent magnet through the face plane such that the upper face is of one polarity and the bottom face is the opposite polarity. In this type of system, the index magnets 56 and 57 can either be oriented so that they add to the attraction forces existing between them and the bottom of the wheel or they may be replaced with a circular core like element which is term-magnetically attracted by the permanent magnet contact-index wheel 50. In the former arrangement, magnetizing the wheel as a permanent magnet permits a greater magnetic attractive force to be obtained between the bottom face of the wheel and the index magnets. In the latter arrangement, it is readily seen that a portion of the watch could be used as the core elements thus completely eliminating the necessity of fitting an additional element or elements, such as those represented by elements 56 and 57, to the watch frame. The operation of these above-described contact-index systems is substantially the same as dis closed herein above with the exception that the magnetized contact-index wheel 50 would be exerting either a portion of or all of the magnetic force required to complete the indexing of the watch.

As a result of the above-described contact-index system of this invention, it is not only possible to drive a contact-index wheel of an electric watch from the oscillating motion of the balance staff which also makes electrical contact therewith, but to perform these neces sary contact and indexing steps in a simpler manner and with fewer parts being required than was heretofore thought necessary. The use of fewer parts not only insures a better watch which is susceptible to less failures, but also permits a thinner electric watch movement to be produced since an index-contact wheel of this type can be manufactured which is only approximately .005 inches thick.

In addition to the above, the assembly and adjustment heretofore necessary when a laminated or compound contact and index wheel was used has been completely eliminated thus resulting not only in a more reliable contact-index system but one which can be produced at a lower cost, thus ensuring its commercial success.

The invention may be embodied in other specific forms without departing from the spirit or essential characteris tics 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 descniption, and all changes which come within the mean ing and range of equivalency of the claims are therefore intended to be embraced therein.

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

1. A contact-indexing device for an electric watchcomprising an oscillating balance staff, a unitary toothed contact-index wheel adapted to be driven by said balance netically hard material and magnetized through its face plane.

2. A contact-indexing device according to claim 1 wherein said magnetic toothed contact-index wheel is magnetized through its face plane such that the upper face of said wheel is one polarity while the lower face of said wheel is of the opposite polarity.

3. A contact-indexing device according to claim 1 wherein said pair of indexing means are permanent indexing magnets whereby an attractive force exists between said magnetized contact-index wheel and said index magnets.

4. A contact-indexing device according to claim 1 wherein said pair of indexing means are cores formed of a material having high residual induction whereby said magnetized contact-index wheel is attracted to said pair of indexing cores. r

5. A contact-indexing device for an electric timepiece comprising ian oscillating balance staff, contact and indexing means carried by said balance staff, said means including a semi-circular electrically insulating and semicircular electrically conductive portions secured together, said insulating portion having a greater diameter than said conductive portion, an index assembly including a contact-index wheel formed from CoPt so that said wheel is both electrically conductive and magnetically soft, said contact-index wheel having teeth along its periphery which are non-symmetric relative to a radius through the outermost tip of the teeth, said teeth having leading edges which are undercut beyond a radial passing through the tips of said teeth and a lagging edge, the tips of said teeth being rounded, said tips of said teeth engaging said semi-circular electrically conductive portion of said means to establish electrical connection therewith and for advancing said wheel in one direction when said balance statf oscillates, and a pair of index magnets mounted on either side of the rotational axis of said contact-index wheel for magnetically positioning and indexing said contact-index wheel when it is advanced in said one direction.

6. A contact-indexing device for an electric watch comprising an oscillating balance staff, a permanent magnet in the form of a unitary toothed contact-index wheel adapted to be driven by said balance staff, a roller on said balance staff, index and contact means mounted on said roller and including an electrically insulating member and an electrically conducting contact, said index and contact means engaging said contact-index wheel as said balance staff oscillates to impart step by step advancement thereto in one direction, and index magnet means mounted on said watch, said index magnet means acting to attract said contact-index wheel when said contact electrically engages said contact-index wheel during at least a portion of the oscillation thereby causing said advancement, said magnetic toothed contact-index wheel being magnetized through its face plane such that the upper face of said wheel is one polarity while the lower face of said wheel is of the opposite polarity.

References Cited in the file of this patent UNITED STATES PATENTS 2,195,311 Hurst Mar. 26, 1940 2,373,429 Straurnann Apr. 10, 1945 3,016,685 Reese Jan. 16, 1962 FOREIGN PATENTS 1,107,156 Germany May 18, 1961 578,457 Germany June 14, 1933 339,582 Switzerland Aug. 31, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,158,988 December 1, 1964 Marlin S. Walmer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 69 and 70, for "copending U.S. application" read patent No. 3,016,685 column 2, lines 3 and 4, for "copending application" read patent No. 3,016,685 column 3, lines 68 and 69, strike out "copending U.S. application Serial No. 146,639, entitled "Contact Index System," depends" and insert instead U.S. Patent 3,130,537 depends column 4, lines 5 and 6, 39 and 40, and column 5, lines 12 and 27, strike out. "copending application Serial No. 3,146,639", each occurrence, and insert instead patent No. 3,130,537 column 8, line 19, strike out "a".

Signed and sealed this 15th day of June 1965.

(SEAL) Attest:

ERNEST w. SWIDER EDWARD J. BRENNER Altesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,158,988 1 December 1, 1964 Marlin S. Walmer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 69 and 70, for "copending U.S. application" read patent No. 3,016,685 column 2, lines 3 and 4, for "copending application" read H patent No. 3,016,685 column 3, lines 68 and 69, strike out 'copending U.S. application Serial No. 146,639, entitled "Contact Index System," depends" and insert instead U.S. Patent 3,130,537 depends column 4, lines 5 and 6, 39 and 40, and column 5, lines 12 and 27, strike out. "copending application Serial No. 3,146,639", each occurrence, and insert instead patent No. 3,130,537 column 8, line 19 strike out "a" Signed and sealed this 15th day of June 1965.

(SEAL) 1 Attest:

ERNEST W. SWIDER I EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. A CONTACT-INDEXING DEVICE FOR AN ELECTRIC WATCH COMPRISING AN OSCILLATING BALANCE STAFF, A UNITARY TOOTHED CONTACT-INDEX WHEEL ADAPTED TO BE DRIVEN BY SAID BALANCE STAFF, CONTACT AND INDEXING MEANS CARRIED BY SAID BALANCE STAFF, SAID MEANS ENGAGING SAID CONTACT-INDEX WHEEL AS SAID BALANCE STAFF OSCILLATES TO ADVANCE SAID CONTACTINDEX WHEEL IN ONE DIRECTION AND TO ESTABLISH PERIODIC ELECTRIC CONTACT BETWEEN SAID CONTACT-INDEX WHEEL AND SAID CONTACT MEANS, AND A PAIR OF INDEXING MEANS MOUNTED ON EITHER SIDE OF THE ROTATIONAL AXIS OF SAID CONTACTINDEX WHEEL FOR COOPERATING AXIS OF SAID WHEEL IS PROPERLY INDEXED WHEN ADVANCED IN SAID ONE DIRECTION, SAID TOOTHED CONTACT-INDEX WHEEL BEING MADE OF A MAGNETICALLY HARD MATERIAL AND MAGNETIZED THROUGH ITS FACE PLANE.

Images