US3795101A - Electrical contact arrangement with self cleaning contact points - Google Patents

Abstract

AN ELECTROMECHANICAL REWIND DEVICE FOR CLOCK MECHANISM, IN WHICH A REWIND MOTOR SWITCH IS AUTOMATICALLY OPENED TO THE END OF EACH SPRING WINDING CYCLE BY THE THRUSTING INTO SEPARATING RELATION BETWEEN SPRING CONTACTS OF A WEDGE SEGMENT DRIVINGLY COUPLED WITH THE REWIND GEAR ASSOCIATED WITH THE POWER SPRING, AND WHEN THE SPRING IS TO BE AGAIN WOUND, A SPRING-MOTIVATED COUPLING FUNCTIONS TO RELEASE THE CONTACTSEPARATING WEDGE FROM THE SWITCH FOR CLOSING OF THE SWITCH TO REPEAT THE REWIND CYCLE. TO PREVENT UNWINDING OF THE POWER SPRING WHEN BATTERY POWER IS INSUFFICIENT FOR PROPER WINDING, A SPRING FINGER EXTENDS INTO THE PATH OF THE CONTACT-SEPARATING WEDGE, THE STRENGTH OF THE SPRING FINGER IS SO GAUGED THAT THE FORCE EXERTED BY THE POWER SPRING WILL NOT ENABLE THE WEDGE TO PASS IT, BUT THE FORCE EXERTED BY THE REWIND MOTOR WILL DO SO.

Description

United States Patent 1 91 1111 3,725,

Niznik f I j [451 Mar. 5, 1974 [54] ELECTRICALCONTACT ARRANGEMENT 7 3,474,618 10/1969 Klinck 58/41 R T SELF CLEANING CONTACT POINTS 3,521,442 7/1970 Umezawa.., 1 511/41 R [75] Inventor: Emil J. Niznik, Lake Geneva, Wis. "fi -m E ;ii Wilkinson Assistant Examiner-U. Weldon Asslgnfie- Bunker corporatwn, Oak Attorney, Agennor Firm-Frederick M1 Arbuckle 22 Filed: Dec. 8, 1971 [571 ABSTRACT Q 1 An electromechanical rewind device for clock mecha- [21] Appl' 206050 nism, in which a rewind motor switch is automatically opened at the end of each spring winding cycle by the [52] US. Cl 58/41 B, 58/46 R. t r ng o pa at g relation between p g [51] Int. Cl. G04b 3/00 1 nta o a e g seg n drivingly c p with [58] Field of Search 58/41 R, 41 A, 4] B, 46, 43 R, the rewind gear associated with the power spring, and

58/80, 80 R, 48 W, 230; 200/52, 61.19, 35 when the spring is to be again wound, a spring- R, 35 W; 185/10, 11, 14, 39, 40 motivated coupling functions to release the contact- 1v 5 separating wedge from the switch for closing of the [56] 1 References Cited switch to repeat the rewind cycle. To prevent unwind- UNITED STATES PATENTS ing of the power spring when battery power is insufficient for proper winding, a spring finger extends into 222:5 g the path of the contact-separating wedge; the strength 3,267,659 8/1966 Hancock 58/41 B 0f the Spring finger 15 gauged that the exerted.

3,276,199 10/1966 lshikawa et a1. 512/41 R b the POWer Spring will not enablevthe wedge P 3,319,414 5/1967 Schwab...; 58/41 R but the force exerted y the rewind motor will do 3,455,103 7/1969 Konno 58/41 R S0.

3 Claims, 4 Drawing Figures ELECTRICAL CONTACT ARRANGEMENT WITH SELF CLEANING CONTACT POINTS This invention relates to electromechanical rewind devices for clock mechanism and is more particularly concerned with such a device which will periodically automatically rewind a clock mechanism power spring by means of a battery-powered motor.

Prior art battery-operated clocks fall generally into two categories. One such category may be identified as of the magnetic impulse rewind type, in which the main spring of the clock is rewound to some specified extent through the action of a single coil magnetic solenoid or relay which is energized in response to the closing of a pair of normally open contacts caused to close when the mainspring has unwound to a predetermined degree. A momentary rewinding impulse produced by closing of the contacts also functions to reset the contacts after rewinding to open until the mainspring has again unwound. A particular disadvantage in such magnetic impulse battery-operated clocks is that of the annoying noise produced during the rewinding impulse, generally noticeable as an acoustical klunk.

A second category of battery-operated clocks may be classified as being of the rotary motor-driven rewind type. In such clocks, the shaft of a small rotary motor is generally coupled via a worm gear in driving relation to the periphery of a main or power spring barrel by means of a gear integral with the periphery of the barrel. In this type of clock a pair of electrical contacts which are spring-biased toward each other, in what may be termed a normally closed configuration, are kept separated from each other by means of a cam coupled to the mainspring barrel. One of the contact elements of the contacts is provided with a cam follower portion which normally engages the surface of the cam to maintain the electrical contacts separated from one another until the mainspring is to be rewound. The cam is so configurated that when the mainspring has unwound to a predetermined extent, a depression or relief in the contour of the cam permits the electrical contacts to touch one another thereby applying power to the rotary motor and rewinding the mainspring to the desired extent. A principal disadvantage in this type of rewind device is that of relatively low battery life. This is attributable to the fact that the mainspring in such clock must supply power for not only the clock movement itself, but also sufficient power to overcome the constant friction between the cam surface and the cam follower portion of the electrical contact means. In dusty environmental conditions friction between the cam follower portion of the contact means and the cam can, over a period of time, add to the energy demand upon the battery. Another problem typical of this type of clock is that of the electrical contact means having relatively short life owing to the fact that the contacts tend to bounce when the cam follower is abruptly relieved by a relief in the mainspring cam, thus permitting the contacts to snap together and bounce to an extent causing arcing and pitting of the contacts. Electrical contact life is further reduced by the arcing which is encountered between the contacts as they are slowly moved apart from one another by the slowly rising portion of the cam at the end of the rewind cycle. Further, since the rate at which the contacts are separated is a function of the battery voltage, as the battery voltage drops the speed of the motor is reduced, thereby reducing the rotational speed of the mainspring cam, hence tending to prolong any arcing that takes place and increasing the attendant pitting effect on the contacts. Furthermore, the maximum force between the electrical contacts when they are permitted to touch one another is fixed bythe characteristics of the spring metal blades to which the contacts are mounted, and any dust or oxide which develops on the surface of the contacts may eventually prevent the contacts from providing an electrical path of sufficiently low resistance to operate the motor. When the cam permits the contacts to touch one another or close the switch, the position on each contact at which it touches the other contact remains substantially the same over repeated rewind cycles, so that oxidation of the contacts at these localized positions may result in the contacts eventually failing to provide a sufficiently low electrical contact resistance to enable the rotary motor to rewind the mainspring. Considerable manufacturing cost is encountered by reason of the delicate time-consuming manual adjustment which is required at the contact elements after final assembly of the clock.

An important object of the present invention is to overcome the foregoing and other disadvantages, defects, inefficiencies, shortcomings and problems in prior art structures, and to attain important advantages and improvements in electromechanical rewind devices for clock mechanism.

Another object of the invention is to provide a new and improved electromechanical rewind device for clock mechanism having novel means for controlling operation of the motor circuit switch.

A further object of the invention is to provide new and improved switch-controlling means for electromechanical rewind devices for clock mechanism, assuring positive, rapid separation of the switch contacts.

Still another object of the invention is to provide a new and improved electromechanical rewind device for clock mechanism providing assurance of proper functioning of the switch which controls the electrical rewind motor.

Yet another object of the invention is to provide a new and improved electromechanical rewind device for clock mechanism wherein load upon the mainspring for operating the electrical rewind motor control system is greatly minimized, thus enabling use of a relatively weak spring and minimizing rewind torque so that battery life is extended.

A still further object of the invention is to provide in a new and improved control means for electromechanical clock rewind devices novel means for maintaining control switch contacts clean and in optimum electrical contact condition for efficient low voltage operation.

A yet further object of the invention is to provide novel means in an electromechanical rewind device for clock mechanism assuring freedom from false contact of the switch contacts under conditions of extreme vibration or shock.

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:

FIG. 1 is a fragmentary-elevational view of a representative electromechanical rewind device switch control means;

FIG. 2 is a fragmentary sectional detail view taken substantially along the irregular line 11-11 of FIG. 1;

FIG. 3 is a fragmentary plan view looking toward the peripheral edge of one of the switch contacts separating wedge elements; and

FIG. 4 is a fragmentary sectional detail view taken substantially along the line IV-IV of FIG. 1.

An electromechanical rewind device 5 providing a representative embodiment of the invention is constructed and arranged to function with a clock move ment 7 only a portion of which is shown in FIG. 2 and which includes some form of escapement means as is usual. Any suitable form of housing may be provided for the clock movement and associated elements, as may be suitable for the particular type and utility of the clock, such as an automobile clock. Mechanical power for operating the clock movement is provided, in this instance, by a helically wound, tubular, coiled mainspring 8 which has one end anchored to a rewind gear 9 provided with an anchor lug 10 for this purpose. Meshing with the gear 9 is a worm 11 mounted on a shaft 12 adapted to be driven by a suitable low voltage motor 13 adapted to be energized by a low voltage battery 13a. When the motor 13 is not operating and the worm 11 is therefore at standstill, the gear 9 is held stationary against turning due to spring torque.

Mounting of the rewind gear 9 is desirably freely rotatably about a tubular bearing arbor 14 having an end portion adjacent to the gear fixedly mounted on a frame panel member 15. Extending coaxially through the bearing arbor 14 is a drive shaft 17 having keyed thereto on the opposite side of the panel from the gear 9 a large diameter gear 18 meshing with a pinion 19 on the hub ofa larger gear 20 which meshes with another gear in the clockwork gear transmission.

Driving power from the wound spring 8 is transmitted to the shaft 17 through a coupling desirably provided by means of a lug or arm 21 turned inwardly from a disk plate 22 fixedly mounted corotative with the shaft 17 on a hub 23 keyed to an outer end portion of the shaft projecting outwardly from the arbor 14. At its outer end, that is the end remote from the rewind gear 9, the spring 8 is anchored to the transmission lug arm 21. Through this arrangement, as the wound spring unwinds, it drives the arm 21 and thus the hub 23 to rotate the shaft 17.

In order to minimize torque load on the motor 13 during winding of the spring and thus enable the motor and the battery to be of the most economical type, the spring 8 is constructed as light as practicable. Therefore, the spring has only limited loading capacity and requires fairly frequent rewinding to maintain constant driving torque in its power output toward the drive shaft 17. In a typical automobile clock installation, it may be desirable to rewind the spring three times in a 3 minute full rotation of the shaft 17. For this purpose, means are provided for controlling operation of the motor 13 to drive the worm 11 at suitable intermittent intervals for effecting spring rewind. To this end a switch 24 is provided for controlling an electrical circuit 25 containing the motor 13 and the battery 130. In a desirable form, the switch comprises a pair of elongated coextensive thin, narrow leaf spring contact arms 27 and 28 having respective wider mounting plate portions 29 and 30 at one of their ends secured to respectively opposite sides of an insulator bracket flange 31 which has an angular base portion 32 secured as by means of a rivet 33 and an anti-turn lug 34 to a frame member 35. Firm attachment of the base plates 29 and 30 to the bracket flange 31 may be by means of riveted lugs 37 extending from the flange 31 through respective apertures 38 in the base plate portions.

From the bracket mounting thereof, the spring switch arms 27 and 28 extend cantilever fashion with their free ends coextensively located adjacent to but suitably spaced fromthe perimeter of the hub 23 to enable switch opening means carried by the hub to operate at suitable intervals to open the switch by separating respective contact pads 39 provided on the free end portions of the switch arms by portions of the arms turned toward one another so as to be normally biased by a spring tension of the arms into engaging, switch-closing relation. In their free state, therefore, the contacts 39 close the circuit 25 to energize the motor 13 for driving the worm 11 and thus the rewind wheel 9 to wind the spring 8. To effect the limited, relatively frequent low torque rewinding of the spring 8, means are provided for opening and closing the control switch at regular intervals, herein comprising a plurality, in this instance three, identical, switch-opening, dielectric wedge elements 40 carried in equidistantly spaced projecting relation on a disk wheel 41 freely rotatably mounted on the hub 23 between a hub flange 42 and the plate 22. Mounting of the switch arms 27 and 28 is such relative to the disk wheel 41 that the wedges 40 are adapted to be driven successively into contact separating relation between the contacts 39 in rotation of the disk wheel in the same direction as rotation of the shaft 17, namely, counterclockwise as seen inFIG. 1. For this purpose the switch spring arms 27 and 28 extend toward the disk wheel 41 generally tangentially with side edges of the contact terminal portions 39 facing toward the disk wheel perimeter, and the tips of the terminals located on a radius of the wheel. For easy sliding entry of the wedge elements 40 between the contacts 39, the wedge elements are, as best seen in FIGS. 3 and 4, constructed with thin leading edges toward which side surfaces of the wedges taper. To receive the wedge elements 40 in separating relation therebetween, the contact terminals 39 are in the form of convergently related terminal portions of the spring arms 27 and 28 which are spaced apart to. a greater distance than the thickness of the wedge elements 40, and with the contacting surfaces of the contacts rounded for smoothness.

Each rewind cycle starts with the switch contacts 39 closed against one another as indicated in dash line in FIG. 2. Running of the motor 13 then drives the worm 11 to turn the rewind gear 9 in the wind-up direction which is, in FIG. ll, counterclockwise. As the wind-up gear turns, an outward tubular hub extension 43 thereon which extends in spaced relation through the spring 8 corotatively turns a disk 44 fixedly mounted on the outer end portion of the hub extension and in freely spaced relation between the outer end of the spring and the inner face of the transmission disk 22. Thereby an outwardly extending angular peripheral lug 45 on the rewind gear coupled disk 44 is driven counterclockwise within a suitable lost motion clearance gap 47 between an adjacent pair of the wedge elements 40 until in its advance the driving lug 45 engages against the opposing edge defining the gap and drives the disk wheel 41 until the wedge element which is in approaching relation to the switch arms is driven into separating relation between the contacts 39, thereby breaking the motor circuit and stopping the motor. This also halts the windup gear 9 and the driving lug 45. Continuously during rewind and in the intervals between rewind, of course, the spring 8 maintains steady driving power on the transmission arm 21.

Timing means are driven by the spring 8 for releasing the switch-opening wedge 40 from the switch arms after a suitable spring power interval. For this purpose, the disk 22 is provided with a tripping lug 48 operable in a rotary path inside the rotary path or orbit of the lug 45 and operable in the disk wheel gap 47 which is wide enough to permit the disk wheel to overrun the driving lug in respective portions of the operating cycles of the device. Thus, during the rewind cycle, the timing tripper lug 48 trails behind the more rapidly advancing rewind gear lug 45 which then comes to a halt when the switch is opened by one of the wedge elements 40. Thereupon the tripper lug 48 as advanced by spring power overtakes the rewind lug and engages the opposed shoulder of the disk wheel 41 and under spring action advances the same until the switch-opening wedge element has been driven free of the contacts 39. Thereupon the contacts close and another rewind cycle is initiated. These rewind and stop cycles continue alternately indefinitely as long as there is sufficient energy supplied by the battery 13a.

Assurance of continuously clean contact surfaces on the contact terminals 39 may be implemented by providing the contact-engaging faces of the wedge elements 40 with a suitable mildly abrasive surface such as may be provided by an abrasive material 49. Thereby as the surfaces of the wedge elements advance in contact with the contact surfaces, they wipe and effectively clean the contact interfaces or contact surfaces.

Another advantage of the device 5 is that during the entire switch off" interval false contacting, i.e. undesirable closing the contacts 39, as from shocks or vibrations is impossible by reason of the interposed dielectric wedge element 4-0 which holds the contacts positively separated.

In order to prevent the mainspring 8 from unwinding when the battery 13a expires or is disconnected, means may be provided for stopping the spring, conveniently effected by restraining the power transmission disk 22 through the disk member 41. For this purpose, a resiliently flexible, self-resetting, failsafe finger 50 is mounted to project into the path of and to be successively engaged by each of the wedge elements 40. Mounting of the finger 50 is desirably by means of a base block 51 fixedly attached in any suitable manner to the frame 35. Location of the finger 50 is such that the wedge elements 40 will engage it only while the disk 41 is propelled by the rewind gear 9, namely when the motor 13' operates in a rewind cycle under battery power. To this end, the finger 50 may extend generally parallel to the spring arms 27 and project into the orbit of the elements 40 at a point where one of the elements 40 is advanced close to the finger as the preceding wedge element 40 leaves the switch contacts 39 to complete the motor circuit. Running of the motor to rewind the spring 8 thus drives the adjacent wedge element 40 against and flexes the finger 50 aside to pass the element on toward the switch contacts, the finger 50 then snapping resiliently back to its normal intercepting position. However, should the battery have failed or be disconnected, so that the battery propelled transmission disk 22 continues driving the disk through the lug 48, upon engaging the finger 50, resilient resistance to flexible yielding by the finger will gradually stop the mechanism. To this end, of course, the resilient flexibility of the finger 50 is such that it will effectively oppose spring power of the already partially unwound spring, but will offer only moderate and easily overcome resistance to motor power supplied through the rewind gear 9 and the lug 45 without consuming any significant battery power while the affected wedge element 40 drives past the finger in normal operation.

It will be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this invention.

1 claim as my invention:

1. An electromechanical rewind device for clock mechanism including a drive shaft and a main power spring having one end drivingly connected to the shaft and its opposite end drivingly connected to a rewind wheel mounted for coaxial rotation relative to the shaft and operatively coupled with driving means of a normally idle electric motor, comprising:

means for electrically powering said motor including a source of power and electrical circuit extending therefrom to said motor through a normally-closed control switch;

switch-operating means mounted for movement relative to said switch and operative for limited interval opening of the switch;

means driven with said shaft by said spring for moving said switch-operating means in respective intervals of rotary movement of said shaft, and operative at the end of each interval to cause closure of said switch for energizing the motor to drive said rewind wheel;

means rotating with said rewind wheel and operative after a predetermined interval of motor operation to move said switch-operating means for opening said switch to stop the motor; and means preventing unwinding of said spring in the event of insufficiency of said source of power;

said switch-operating means comprising a member coaxially mounted with respect to said shaft, and having free rotation relative thereto through a limited angle, said member having a plurality of dielectric arms, each adapted to move into coacting relation with said switch, and to effect opening thereof;

said shaft having a driving extension selectively engageable with said member to drive the same corotative with the shaft,

said means rotating with said rewind wheel comprising and extension therefrom operative to drive said member in overrun relation to said driving extension from the shaft, and

said means for preventing unwinding comprising a flexible finger projecting into the orbit of travel of said arms, and operative when engaged by one of said arms to hold the member against further movement except under driving power imparted to said rewind wheel by said motor.

2. An electromechanical rewind device for clock mechanism including a drive shaft and a main power 7 8 spring having one end drivingly connected to the shaft coaxially mounted with respect to said shaft, and and its opposite end drivingly connected to a rewind having free rotation relative thereto through a wheel mounted for coaxial rotation relative to the shaft limited'angle, said member having a plurality of and operatively coupled with driving means of a dielectric arms, each adapted to move into coacty idle electric motor, Comprising: ing relation with said switch, and to effect openmeans for electrically powering said motor including ing th of; a 7 f a source of power and an electrical circuit extend- Said Shaft having a driving extension selectively ing therefrom to said motor through a normallygageable with Said member to drive the same closed control switch; 7 V rotative with the Shaft switch-operating means mounted for movement rela- 10 tive to said switch and operative for limited interval opening of the switch;

means driven with said shaft by said spring for moving said switch-operating means in respective intervals of rotary movement of said shaft, and operative at the end of each interval to cause closure of said means rotating with said rewind wheel comprising an extension therefrom operative to drive said member in overrun relation to said driving extension from the shaft, r

said switch having a pair of contacts, each yieldably mounted, normally in engagement, and

said switch for energizing the motor to drive said d rms of said member including dielectric porrewind whee]; and trons entering directly between said contacts to means rotating with said rewind wheel and operative p Said Switchafter a predetermined interval of motor operation 2 3. A rewind device according to claim 2, wherein said to move said switch-operating means for o eni g arms of said member include abrasive surfaces for wipsaid switch to stop the motor; ing said contacts. said switch-operating means comprising a member

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