US3115788A - Drive pawl for electrically wound clocks - Google Patents

Description

Dec. 31, 1963 R. SIEFERTO 3,115,788

DRIVE PAWL FOR ELECTRICALLY WOUND CLOCKS Filed June 27, 1962 2 Sheets-Sheet 1 Dec. 31, 1963 R. SIEFERT 3,115,783

DRIVE PAWL FOR ELECTRICALLY WOUND CLOCKS Filed June 27, 1962 2 Sheets-Sheet 2 United States Patent Ofiice Patented Dec. 31, 19453 3,115,733 DREVE ?AWL FQR ELEQTRHIALLY WGUND QLQQKd Roland Siefert, Schwenningen (Neckar), Germany, as-

signor to Kienzle Unrenfahriizen A.G., Schwenningen (Neckar), Germany Filed .lune 27, 1962, Ser, No. 205,579 6 (Jlaims. (Cl. 74-577) This invention relates to l2. drive pawl for electromagnetic wind-up devices for clocks or other time pieces. The drive pawl and associated ratchet wheel provide the working connection between a source of mechanical energy, such as a spring periodically stressed by a clapper armature, and the running works of the time piece. The hitherto usual drive pawls are often biased with a helical torsion spring to improve engagement with the ratchet wheel. if such a spring be strong in order to prevent a jumping out from the associated toothing there is the disadvantage during retraction, or backward motion when the pawl rides without action on the ratchet wheel, that the friction is very high. This leads to wide variations in winding torque, frequency of winding and consequent torque on the works. *In order to reduce friction, weak springs are frequently used but they have the characteristic of rather (Li .311 allowing the pawl to spring out of Working position and consequently the time piece is thrown out of time or put out of order.

Moreover simple leaf springs have been employed but they, too, also either press too strongly so that the torque required for wind-up when the pawl rides backward over the teeth becomes large or the leaf springs must be long and so lack lateral stability.

The construction of a drive pawl according to the present invention avoids the above mentioned disadvantages. The pawl itself is a resilient arm, and so the need for a helical or coil spring is eliminated which is advantageous both as to operation and to production costs.

In the accompanying drawing showing, by Way of example, two of many possible embodiments of the invention,

FIG. 1 is a perspective of a winding device with parts of a :clockworks;

FIG. 2 is a plan of a drive pawl according to the invention;

FIG. 3 is a vertical sectional view of the pawl, the section being taken substantially along the line 33 of FIG. 2 looking in the direction of the arrows of said line;

FIG. 4 is a plan of another form of the pawl, and

FIG. 5 is a vertical sectional view of the pawl of PEG. 4 the section being taken along the line 5-5 of HG. 4, looking in the direction of the arrows of said line.

The operation of a Wind-up device can be readily understood by reference to FIG. 1. An electromngnet 1i periodically attracts a clapper armature ll which strikes an eccentric cylindrical pin or 12 mounted on oscillatory disc 13 of appreciable mass. The disc is mounted on a works plate 14 for oscillation about a stub shaft so that the armature slings or turns the disc when the crank is struck. When the disc turns clockwise as shown in the drawing it stretches a tension spring 16 attached to the plate 14 and an eccentric portion of the disc. At the same time the drive pawl, generally designated 17, on thecrank 12 rides backward over theratchet wheel 18 fast on a works shaft 1). In practice, a stop pawl (not shown) is often used to prevent any backward turning of the wheel, though in some constructions this is not necessary especially if the friction of the drive pawl is kept low. When the disc reaches its limit of turning, against the tension of the spring, the drive pawl the engages the ratchet wheel so that the spring may, through 2 the pawl, drive thewheel 18 and workshaft 19 of the clockworks.

Thepawl 17 is of spr'ingy strip metal having an engagement down-turnedlip portion 24 at one end near ayoke portion 21 from which extend, in a generally opposite direction, two wide outerparallel arms 22 and anarrower tongue 23 between. Theouter end portions 24 of the arms are each cylindrically curved to embrace, side by side and coaxially, slightly more than half the circumference of thecrank pin 12.

Thetongue 23, between the arms and spaced laterally therefrom, is resiliently bent from the plane of the arms and resiliently engages the crank pin on the opposite side of the axis of pin from the major portion of the curved ends so as to provide a retaining force to increase the holding of the ends around the cylindrical pin. The pawl is secured against undue movement of thecurved ends 24 in the direction of the axis of thepin 12 by the provision of aminor chordal slot 25 in the pin in which thetongue 23 is disposed. The tongue prevents the undue movement by engagement against one or the other ofslot side walls 27 and bears resiliently against theinner edge 26 of the slot to prevent an undesired flapping of the pawl or to provide bias to hold thelip 20 in the teeth of the ratchet wheel id.

Thepin 12 oscillates about the axis of the stub shaft 15. If thepin 12 is fast on the disc, as it preferably is, theslot edge 26 turns about the stub shaft, and during oscillation of the disc, theedge 26, if the stub shaft 15 and theworks shaft 19 are coaxial, remains the same distance from the periphery of theratchet wheel 18, and the spring bias on the pawl remains constant.

However, the stub and works shafts need not be exactly coaxial and so the tension on the pawl may be made to vary according to the position of the disc, which will also affect the bias of the pawl due to gravity. Thus according to the combination of spring tension and weight the pawl may have as desired a nearly constant, as well as a distorted, bias against the ratchet wheel depending on the positions of the disc and of the axis of the said shafts. Depending on the height and slope of the ratchet wheel teeth it may be desirable to have the pawl bias against the wheel stronger, say, when the disc approaches run-down position.

By a system of gears (not shown), thepin 12 may turn relative to the disc, as the latter turns about the stub shaft, and so vary the spring tension on the pawl according to the position of the disc.

in another form of the pawl as shown as 17a in FIGS. 4 and 5 thearms 22 of FIGS. 3 and 4 are replaced byside flanges 22a at right angles to the plane of theyoke portion 21. The outer end portions of the flanges are provided with alined bearingholes 28 receiving thepin 12. In this form of the invention the tongue disposed in the slot overlies the pin and is on theouter edge 26a of the slot to cause the pawl to bear against the ratchet wheel. The pawl 17:; may be made quite rugged by the provision of a diamond shapeddimple 2% at the line of junction between the lip and yoke portion and by a weblike tie piece 3t? between the side flanges.

In either form of the invention the tongue may be sprung temporarily to permit the sliding of the pawl onto thepin 12 longitudinal thereof to register the tongue and slot, and then the tongue is allowed to engage the appropriate edge of the slot in order to cause the pawl to bear against the ratchet wheel. The slot walls prevent the tongue and pawl as a whole from unduly moving laterally.

The invention claimed is:

l. A drive pawl combination for an oscillatory windup device of an electromagnetically wound time piece, characterized by the inclusion of an oscillatory ineitia memher, a crank pin on the member, said pin having a chordal slot therein, a pawl mounted on the pin for turning slightly thereon and having a resilient tongue in the slot for tending to turn the pawl about the pin, the tongue being engageable with the side walls of the slot to limit lateral movement of the pawl, and a ratchet wheel engage able with the pawl.

2. In an electrically wound clock, an inertia member mounted for turning and a cylindrical crank pin thereon, the pin having a chordal slot therein, an elongated pawl having a yoke and lip portion at one end portion for engagement with a ratchet wheel and substantially monoplanar arms terminating at the other end as slightly more than semicylindn'cal claws partially embracing the pin on each side of the slot as bearings for the pawl, a resilient tongue fast on the yoke portion and in the slot and tensed against an edge of the slot parallel with the axis of the pin for tending to turn the pawl and claws about the pin, said tongue being adapted to engage the side walls of the slot to prevent lateral movement of the pawl on the pin, and a ratchet wheel for the pawl to engage on.

3. In an electrically wound clock, an inertia member mounted for turning and a cylindrical crank pin thereon,

the pin having a chordal slot therein, two like substantially parallel arms of strip material each having alined bearing openings at one of their end portions and receiving the pin, a yoke portion connecting the two arms at their other end portion, and a lip portion adapted to engage a ratchet wheel and integral with the yoke portion, a resilient tongue fast on the yoke portion and between the arms and tensed against the pin and lying in the slot, for tending to turn the arms about the pin and limiting motion of the arms in a direction axially along the slot.

4. In a clock as claimed inclaim 3 said tongue bearing on an edge of the slot parallel with the axis of the pin.

5. in a clock as claimed in claim 4, said arms lying in substantially a single plane to which the axis of the pin is parallel.

6. In a clock as claimed in \claim 4 said arms lying in diiierent planes to which the axis of the pin is substantially perpendicular.

Tratsch Jan. 11, 1949 Watson May 9, 1961

Claims (1)

1. A DRIVE PAWL COMBINATION FOR AN OSCILLATORY WINDUP DEVICE OF AN ELECTROMAGNETICALLY WOUND TIME PIECE, CHARACTERIZED BY THE INCLUSION OF AN OSCILLATORY INERTIA MEMBER, A CRANK PIN ON THE MEMBER, SAID PIN HAVING A CHORDAL SLOT THEREIN, A PAWL MOUNTED ON THE PIN FOR TURNING SLIGHTLY THEREON AND HAVING A RESILIENT TONGUE IN THE SLOT FOR TENDING TO TURN THE PAWL ABOUT THE PIN, THE TONGUE BEING ENGAGEABLE WITH THE SIDE WALLS OF THE SLOT TO LIMIT LATERAL MOVEMENT OF THE PAWL, AND A RATCHET WHEEL ENGAGEABLE WITH THE PAWL.

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