US3791251A

US3791251A - Timepiece escapement

Info

Publication number: US3791251A
Application number: US00259863A
Authority: US
Inventors: U Pohlmann
Original assignee: Bunker Ramo Corp
Current assignee: Bunker Ramo Corp
Priority date: 1972-06-05
Filing date: 1972-06-05
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: JPS537819B2; FR2188209B1; GB1436578A; JPS4963472A; DE2328319A1; FR2188209A1; CA977164A

Abstract

An integral impulse pin and guard roller assembly is mounted adjustably on the balance wheel staff of a clockwork escapement, enabling the escapement to be put into beat easily by simply rotating the impulse pin and roller assembly on the staff to a position where the escapement operates with equal beats. The inner end of the hairspring is directly and non-adjustably attached to the staff. The impulse pin and guard roller assembly is mounted with the impulse pin more remote from the balance wheel than the roller, thus increasing the clearance between balance wheel and escapement lever, over the more conventional arrangement.

Description

United States, Patent [191 Pohlmann TIMEPIECE ESCAPEMENT [75] Inventor: Ulrich R. Pohlmann, Chicago, Ill.

[73] Assignee: Bunker Ramo Corporation, Oak

- Brook, 11].

[22] Filed: June 5, 1972 [21] Appl. No.: 259,863

[52] US. Cl. 58/116 R, 84/122 [51] Int. Cl. G04b l/00 [58] Field of Search 58/l16-R, 122, 121 R, 140, 58/117, 121 A, 28 D, 114,115, 136, 137,

[ Feb. 12, 1974 Bair [ ABSTRACT An integral impulse pin and guard roller assembly is mounted adjustably on the balance wheel staff of a clockwork escapement, enabling the escapement to be put into beat easily by simply rotating the impulse pin and roller assembly on the staff to a position where the escapement operates with equal beats. The inner end of the hairspring is directly and non-adjustably attached to the staff. The impulse pin and guard roller assemblyis mounted with the impulse pin more remote from the balance wheel than the roller, thus increasing the clearance between balance wheel and escapement lever, over the more conventional arrangement.

10 Claims, 5 Drawing Figures TIMEPIECE ESCAPEMENT BACKGROUND OF THE INVENTION This invention relates to improvements in escapement systems for clockworks, and is particularly concerned with the guard roller and impulse pin structure in such systems.

In the construction of a timepiece utilizing an escapement, placement or orientation of many of the various components comprising the system is critical. Much hand adjustment has been customary, and especially adjustment involving the positioning of the hairspring, in a rotational sense, relative to the other elements mounted on the balance staff. Such adjustments have been primarily related to putting the movement into beat, that is making the ticks equal to the tocks when the movement is in operation.

In addition to the difficulties involved in such adjustments, there have been other problems of a mechanical nature.

In prior constructions it has been conventional that the impulse pin is a separately made piece, mounted in a hole in the balance wheel or in the guard roller, and the lever pins have been separately made pieces, mounted in holes in the lever. The difficulty of making the pins themselves dimensionally uniform and free of burrs, and of making the holes uniform, smooth and free of burrs, plus the difficulty of press fitting the pins accurately in the holes, give rise tooccasional-instances where the pins, as mounted, are not parallel to their associated staffs, but lean out of alignment. This causes, at best, poor escapement action, and sometimes means that a movement assembly, in completed or nearly completed form, must be discarded, with. loss of the parts and labor which hadenteredintoit.

In some conventional movements, the guard roller is frictionally mounted on. the staff, and the balance wheel, carrying the impulse pin, is also frictionally mounted on the staff, but more tightly than the guard roller. It is necessary to align the impulse pin and the notch of the guard roller so that their center lines coincide in a plane passing through the center line of the balance staff, by assembly in tooling or fixtures which assure this coincidence between the separate parts.

In many Swiss watches, a unitary roller and pin assembly has been used, fitted on the staff in a tight and non-adjustable manner, and with the pin located between the balance wheel and the roller.

In either of the constructions just described, to put the movement in beat the hairspring must, in effect, be rotated with respect to the impulse pin and guard roller. For this reason, the inner end of the hairspring has customarily been attached to a collet which is frictionally mounted on the balance staff. To make the in beat" adjustment, the balance wheel is held, and the hairspring collet is rotated on the staff until a position is found in which the beats are equal.

It is an object of the present invention to reduce the manufacturing cost ofa movement made in the manner described as typical of the prior art, and this object is accomplished by the structural arrangement and relation of parts herein described, in which some parts are eliminated, and certain assembly and adjustment steps heretofore required are rendered unnecessary.

SUMMARY OF THE INVENTION According to my invention the guard roller and impulse pin are formed as an integral unit, which is frictionally mounted on the balance staff, tightly enough to maintain its positioning under normal operating torques, but capable of being rotated for adjustment to put the movement in beat. This permits the hair-spring to be permanently fixed to the staff, and thus eliminates 0 any need for the usual hairspring collet. The integral construction of the guard roller and impulse pin unit permits mounting of that unit on the balance staff with the impulse pin extending in an axial direction away from the balance wheel, and with the roller located axially between the balance wheel and the pin. Because the impulse pin is engaged by the lever fork, the plane of the lever is at a distance from the balance wheel such that no problems arise from interference if the balance wheel and the lever are not truly perpendicular to their respective staffs. To accommodate this reversal of the usual roller and impulse pin arrangement, the lever is made with its finger and fork reversed from the usual relation to the pallet pins. Further, the lever, finger, fork and pallet pins are preferably made as an integrally molded unit, in which all the proper relations of the respective elements are determined at the time of molding.

BRIEF DESCRIPTION OF THE DRAWING 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, in which:

FIG. 1 is a fragmentary side elevational view of a timepiece movement showing a balance wheel and escapement system embodying features of the invention;

F IG; 2 is an enlarged fragmentary sectional plan detail view taken substantially along the line II--II of FIG. I;

FIG. 3 is a fragmentary perspective view of the hairspring showing its attachment to the balance wheel staff;

FIG. 4 is a perspective view showing the combined guard roller and impulse pin; and

FIG. 5 is another perspective view of the combined impulse pin and guard roller.

Although features of the invention may be employed in any clockwork, whether of the smaller watch sizes or larger clock sizes, special advantage has been found for the invention as embodied in automobile clockworks. Automobile clocks of necessity require rugged structure capable of withstanding extremes of temperature as well as the shocks and jolts encountered in operation of the associated automobile.

A typical example of a clockwork embodying features of the invention, as represented in FIG. 1, includes spaced frame plates 10 and 11 providing suitable bearings for the journals of an escape wheel staff 12, an escape lever staff 13 and a balance wheel staff 14. Carried by the escape wheel staff 12 is a pinion 15 meshing with a gear 17 operatively coupling the associated clock movement (not shown) with the balance wheel and escape assembly. The pinion 15 is mounted adjacent to one end of the staff 12, and carried adjacent to the opposite end of the staff 12 is an escape wheel 18, controlled by an escape lever 19 mounted on the staff 13.

According to the present invention a new and improved impulse pin and guard roller means is provided on and in association with the balance wheel staff 14 and a balance wheel carried corotatably thereby. To this end a unitary molded. guard roller and impulse pin unit 21 is provided. The unit 21 may be made from any suitable moldable plastic, such as an acetal resin available commercially under the trademarks Celcon and Delrin, or it may be made by the well-known pressed powdered metal process. As best seen in FIGS. 4 and 5, the unit 21 comprises a guard roller 22'having a cylindrical perimeter with an axially extending leverreceiving notch 23 of half-moon cross section formed therein. Axially through the roller 22 extends a bore 24 which is sized to be a snug fit on the balance wheel staff 14. The fit must be sufficiently tight that the unit 21 will not move on the staff in response to the torques occurring in operation, but must permit rotational adjustment relative to the staff by application of sufficient torsional force during manufacture or repair.

At one end of the unit 21 is an impulse pin structure 28 aligned with the notch 23 in the sense that the center line of the notch, the center line of the pin structure 28, and the center line of the bore 24 all coincide in a common plane. The pin structure extends in an axial direction away from the roller 22. The alignment described is preferably provided by molding all parts of the unit 21 in one piece. This assures accuracy of orientation and alignment of the impulse pin 28 not only with respect to the axis of the unit but also with respect to the notch 23, and eliminates necessity for any subsequent adjustment.

The unitary type of construction lends itself readily to the addition of an unbalanced weight of predetermined magnitude, which, while not an essential part of the present invention, may'usefully be employed when it is desired to embody the invention of co-pending patent application serialnumber 150,586 in the'escapement. For this purpose, the unit 21 may have a disc-like balance element 25, which can be semicylindrical in general form, and which overhangs the notch 23 and is symmetrically disposed relative thereto.

In the assembly as seen in FIG. 1, the guard roller and impulse pin unit 21 is mounted on the staff 14 with the guard roller end contiguous to the balance wheel 20 and with the impulse pin 28 extending in the opposite direction from the balance wheel, that is, downwardly as viewed in FIG. 1. Assembly of the unit 21 with the staff is easily effected by an axial pressing operation with the staff received in the bore 24.

The escape lever 19 is also desirably made as a molded part, utilizing plastic, powdered metal or similar material as described above for the guard roller and impulse pin unit 21. Assembly of the lever 19 with the lever staff 13 is effected by an axial press fit wherein the staff is received in and through a hub 29 on the lever. As shown, the lever 19 is of elongated form and is pivotally mounted by means of the staff 13 adjacent to and in partially overlying relation to peripheral teeth 30 of the escape wheel 18. Thereby respective escape lever pins or pallet pins 31 integrally molded with the lever and suitably spaced and oriented in position thereon are adapted for alternate timing coaction with the successive teeth 30 in the oscillations of the lever as controlled by the balance wheel assembly.

The lever 19 has at one end a fork 32 within which the impulse pin 28 is received. The impulse pin at its outer extremity has a width appropriate to fit in the opening of the fork 32, and radially inward from the outer extremity, it has a relatively narrow part 27 which serves as a supporting or reinforcing tin, and provides clearance for the legs of the fork 32 as they swing relatively around the wider part of the pin when the lever is operating.

Also on the fork end of the lever 19 and alignedwith but axially spaced from the fork notch is a guard finger 33 which extends into the roller notch 23. As will be apparent, the particular arrangement wherein the lever 19 is adapted to be relatively closely spaced with respect to the escape wheel 18 provides for an especially compact assembly and arrangement in which the pallet pins 31 as well as the finger 33 are adapted to be molded integrally in one piece with the lever, with the pins 31 accurately formed and positioned for optimum effectiveness and without any liability of improper orientation or leaning as is frequently experienced where such pins are separately formed and attached to the lever.

Among advantages gained from the combination of the guard roller and impulse pin in a single unit which is rotatably adjustable on and relative to the balance wheel staff 14 for putting the movement in beat is that the customary hairspring 34 can be secured at its inner end directly to the balance wheel staff 14, as shown in FIG. 3. Such attachment may be effected by welding, soldering, cementing, or otherwise non-adjustably fixing the inner end of the spring to an anchor boss 35 integral with the staff. Welding may be effected by laser beam technique, if desired. Any other means for attaching the end of the hairpsring to the staff may be employed, but the customary collet can be eliminated and the hairspring placed in neutral condition, that is, without any unbalance stresses and to best advantage for isochronism of operation.

In construction, the roller and impulse pin unit 21 is pressed onto the staff 14 with a friction fit less tight than the fit of the balance wheel 20 thereon. Adjustment to place the movement in beat is then accomplished, accordingly, by holding the wheel 20 (or staff 14) and applying torque to 21 to rotate it relative to the staff 14, until a position is obtained where equal beats result.

Another advantage from the structure shown, in which the pin 28 is on the opposite end of unit 21 from the guard roller 22, is that the cooperating guard roller 22 and finger 33 are located at a position generally central of staff 14 and remote from the staff bearings. In other structures, where the roller and finger are adjacent to the shaft bearing, capillary movement or wicking of oil from the bearing to the roller results in the collection of foreign matter which interferes with proper operation. Such difficulty is obviated in a device made in accordance with the present invention.

From the foregoing it will be apparent that in comparison to prior art arrangements, the structure is simplified, in terms of the number of parts involved, and the assembly operations are simplified, both in terms of the number of steps involved, and the degree of skill required for performing them. Indeed, the present invention lends itself to the techniques of automated assembly, where the greaternumber and complexity of parts and operation steps for theprior art devices rendered such assembly out of the question. The liability of rejects and wastage is greatly reduced, accuracy of the components is enhanced, adjustment to put the movement in beat is simplified, and operating efficiency and timekeeping accuracy are improved.

By having major components, i.e., the combination guard roller and impulse pin and the escapement lever made from appropriate plastic materials, lubrication for optimum performance is not critical because the coefficient of friction of the plastic is much lower than that of metal. Of utmost value is the adjustable combination guard roller and impulse pin unit, which eliminates several machining and hand assembly operations as compared to prior arrangements, simplifies adjustment into beat, assures a high degree of accuracy with regard to the notch and impulse pin alignment, and simplifies assembly with the balance wheel staff.

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.

I claim:

1. For use in a timepiece balance wheel assembly including a balance wheel and a supporting staff:

an integrally formed guard roller-impulse pin unit,

said unit including a guard roller portion having a cylindrical perimeter provided with an axially extending notch for receiving an escape lever finger,

a disc-like balance element at one end of said roller portion, extending radially beyond said cylindrical perimeter of said roller portion adjacent to said axially extending notch,

an impulse pin on the side of said balance element opposite said roller portion, adapted to be engaged by an escape lever fork, and

an axially extending bore receptive of the staff, said unit being adjustably mounted on said staff.

2. A unit according to claim 1, having said bore dimensioned for a frictional grip on the staff sufficient to avoid operating torque displacement but enabling rotary adjustment of the unit on the staff relative to said balance wheel and shaft by the application of a torque greater than normal operating torque.

3. A unit according to claim 1, constructed from plastic material and having said bore dimensioned for frictionally gripping the staff against operating torque displacement but enabling rotary sliding adjustment of the unit on the staff relative to said balance wheel and shaft.

4. A unit according to claim 1, having said bore dimensioned for frictionally gripping the staff against operating torque displacement but enabling rotary sliding adjustment of the unit on the staff relative to said bal ance wheel and shaft, and a hairspring controlling movement of said shaft and connected thereto in a rigid non-adjustable connection.

5. In combination with a timepiece balance wheel and staff supporting the same:

a combination guard roller and impulse pin unit having a guard roller portion relatively rotatably adjustably mounted on the staff contiguous to the balance wheel and provided with a peripheral notch for receiving a guard lever finger;

a balance element at the end of said roller remote from the balance wheel and extending radially beyond said roller adjacent to said notch; and

an impulse pin structure on said balance element aligned with said notch and projecting axially away therefrom on the side of said balance element opposite from said balance wheel, and adapted to be engaged by an escape lever fork.

6. A combination according to claim 5, wherein said balance element comprises a generally semicircular platform.

7. A combination according to claim 5, wherein said impulse pin structure includes a radially inner reinforcing fin and a wider radially outer impulse pin portion.

8. A combination according to claim 5, wherein said unit comprises a molding made from plastic and provided with a bore through which the staff is engaged in frictional grip sufficient to retain the staff and unit against torsional displacement in operation in a timepiece but yieldable in response to adjustment torque for rotary adjustment of the unit relative to the staff.

9. A combination according to claim 5, including a hairspring having an end thereof permanently secured directly to an end portion of said staff.

10. A combination according to claim 9 wherein said hairspring is located on the opposite side of said balance wheel from said unit.

Claims

1. For use in a timepiece balance wheel assembly including a balance wheel and a supporting staff: an integrally formed guard roller-impulse pin unit, said unit including a guard roller portion having a cylindrical perimeter provided with an axially extending notch for receiving an escApe lever finger, a disc-like balance element at one end of said roller portion, extending radially beyond said cylindrical perimeter of said roller portion adjacent to said axially extending notch, an impulse pin on the side of said balance element opposite said roller portion, adapted to be engaged by an escape lever fork, and an axially extending bore receptive of the staff, said unit being adjustably mounted on said staff.

4. A unit according to claim 1, having said bore dimensioned for frictionally gripping the staff against operating torque displacement but enabling rotary sliding adjustment of the unit on the staff relative to said balance wheel and shaft, and a hairspring controlling movement of said shaft and connected thereto in a rigid non-adjustable connection.

5. In combination with a timepiece balance wheel and staff supporting the same: a combination guard roller and impulse pin unit having a guard roller portion relatively rotatably adjustably mounted on the staff contiguous to the balance wheel and provided with a peripheral notch for receiving a guard lever finger; a balance element at the end of said roller remote from the balance wheel and extending radially beyond said roller adjacent to said notch; and an impulse pin structure on said balance element aligned with said notch and projecting axially away therefrom on the side of said balance element opposite from said balance wheel, and adapted to be engaged by an escape lever fork.