US2712758A - Escapement mechanism - Google Patents

Description

July 12, 1955 R. G. scHAAF, JR 2,712,758

ESCAPEMENT MECHANISM Filed Nov. 2, 1948 ZNVENTOR.

HTTOFZNEY naiss mouth ileach, N. I., assigner n, N. Y., a

Application 2, 1943, No. 57,930

This invention relates to timing mechanisms or the like and more particularly to escapemcnt mechanisms and motion transmitting means associated therewith, including means for supporting rotatable parts or such and other mechanisms.

One of the objects of the present invention is to provide novel structural features in a clock or other timing mechanism whereby operational noises are appreciably reduced.

Another object or" the invention is to improve .known types of timing mechanisms in such a manor as to insure more accurate and uniform operation for longer periods of time.

A further object is to provide novel simplied mounting means for a rota t e shaft, such as the escapernent wheel device, whereby stabilization ot the axis ot rotation is assured and undesirable movement thereof is eliminated,

A still further object is to provide means for mounting a rotatable shalt in a novel manner to automatically obtain optimum braking ecct while at the same time providing improved lubrication facil es which materially increase the dry-out time period.

Still another object is to provide an escapement mechanism wherein the noise level is materially reduced by constructing parts, which are subjected to impact, from materials not heretofore used in such mechanisms.

Another object is to provide novel means for rotatably supporting a shaft whereby torsional resistance is reduced to desired minimum, and whereby wear is reduced and automatically compensated.

The above and further obiects and novel features of the present invention will more fully appear `from the following detailed description when the same is read in conection with the accompanying drawings. lt is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention, reference for this latter purpose bein had primarily to the appended claims.

ln the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. l is a top plan view, partly in section with parts removed, of an electrically actuated timing device embodying one form or the present invention, the sectio being taken substantially on line of 2, and the electrical connections to a source of energy being shown diagrammatically;

Fig. 2 is a front elevation of the device shown in Fig. l;

Fig. 3 is an enlarged detail view of the balance wheel assembly embodied in said device; and

Fig. is a still further enlarged detail view, partly in section and witlI parts broken away, of one end of the escapement wheel shaft and the mounting bracket there for.

Although the present invention may be incorporated in other types of devices and particularly in various other types of escapement mechanisms for timing devices, the

single embodiment illustrated in the drawhgs, by way of example, is shown in the form or" an elec ic elo-cl; of the type employed in automobiles and the like, the same being adapted for operation by electrical e.. ergy from a storage battery. The noise created by the average timing devices, although not great when compared with other types of normal noises, is of sufficient magnitude and of such a nature as to be most annoying and nerve-racking. For example, the engines or" modern automobiles have been so perfected that the noise emanating from a clock mounted on the instrument panel can be heard by occupants of the car even when the engine is ruiming. l have round that a substantial part of this noise results from the operatic-n ot the cscapement mechanism, and it is accordingly a purpose of this invention to improve that mechsin with a view to reducing the noise level thereof.

The clock in conjunction with which the invention is l"lustrated comprises a balance wheel staff 5 journalled at its opposite ends in jewelled bearings (not shown) suitably mounted in plates e and 7. The latter are secured together in superposed spaced relation by two pillars 8, each having one end thereof secured to plate o and the opposite end extending through plate 7 and being externally threaded to receive a nut 9.

Oscillatory motion of staff 5 is effected in part by a hair spring lll having one end secured to the stad and the other end anchored in stud il which is fixed to and depends from plate 7. Motion is imparted to stai-t` 5 and energy is stored in hair spring l@ by electromagnetic means which includes a balance wheel l2 of magnetic material, such as iron, mounted on the Staifor rotation therewith. As shown, the balance wheel comprises three circumferentially spaced pallets i3. A pair of oppositely disposed pole pieces or shoes i4 and l5 are arranged adjacent the path of movement of pallets i3, and the connected ends thereof constitute a core on which a coil i6 is wound. Pole pieces 14 and i5 are provided with openings through which pillars S extend and are rigidly held in proper position relative to armature .l2 through the medium of Spacers l? which surround the pillars between the pole pieces and plate 7. The connected pole pieces and l5, together with the armature l2, constitute a path for magnetic ilux created by variable current Flow through the winding of coil lo. Upon energization of the coil, balance wheel l2 will be urged in one direction of rotation or the other, depending upon the position at that time of pallets 13 with respect to the pole shoes 14 Secured to the armature l2 and extending downwardly therefrom, as viewed in Figs. 2 and 3 of the drawings, is a contact pin lo which is adapted to close an electrical circuit by making contact with the free end portion of a resilient Contact linger constituted by flat spring 19, the other end of which is anchored to a post 2t) which is in turn secured to and electrically connected with a conducting strip 2l. latter is insulated from plate o and secured thereto by a screw 22 that extends upwardly through said plate and strip 2l and has a nut 23 threaded on the upper end thereof. interposed between strip 2li and nut 23 is a tubular resistor 24 which, as will hereinafter appear, is electively connected in shunt with the winding of coil 16. Means are also provided for insulating the screw or bolt 22 from plate 6 and resistor 24. Strip 2i, and hence contact spring 19, is connecte to one end of coil i6 by means of a con` ductor 25, the end portion of tween strip 2l and resistor 24. resistor is connected to the other end of the winding of coil 16 by means of a conductor 26, the terminal of which is interposed between the resistor and nut 23.

One terminal of a source of electrical energy, such as battery 253, may be connected to terminal 22 by means of a conductor 27, and the other terminal of the source which is interposed be- The other end of the may be connected by a conductor 29 to a terminal post 30 secured to plate 6, which may be regarded as, and is in normal practice, a so-called ground connection. The electrical circuit through the winding of coil 16 may thus be traced from battery 28, through ground or conductor 29, terminal post 3G, plate 6, pillars 8, plate 7, stud 11, hair spring 1t), staff 5, armature 12, contact pin 1S, Contact spring 19, post 2i), strip 21, conductor 25, the winding of coil 16, conductor 26, terminal 22, and conductor 27 to the other terminal of battery 28. The resistor 24, being connected between the terminals of conductors 25 and 2n, is connected in shunt with the winding of coil 26 and is effective to prevent the contacts 18, 19 against burning and corrosion during long use.

When the clock is stopped, the balance wheel or armature 12 is caused by hair spring 19 to assume the position shown in Fig. l. with contact pin 15 in engagement with contact finger 19. `For the purpose of starting the clock, a manually operated conductor (not shown) may be provided for momentarily connecting plate 7 directly to post 20 so that the coil 16 may be momentarily subjected to the maximum energy of the battery. During energization of the coil in this manner, the magnetic flux across pole pieces 1e and 15 is effective to cause the armature 12 to move, let us say, in a clockwise direction as viewed in Pig. l. This initial movement of the armature contracts hair spring 1u and causes contact pin 1S to move out of engagement with contact spring 19, thereby interrupting the circuit through coil 16. With the circuit deenergized, armature 12 is free to rotate in a counter-clockwise direction under the inuence of the energy stored in contracted hair spring 1t). Upon return of wheel 34 to its initial position, the electrical circuit is again closed through contacts 18, 19 and coil 16 is again energized, whereupon armature 12, having been carried past its central position by momentum, is magnetically attracted in a counter-clockwise direction, thereby expandmg hair spring 1lb beyond its neutral position and again moving contact pin 18 out of contact spring 19. Coil 16 is thus again deenergized and the armature is caused to rotate in a clockwise direction by the energy of expanded hair spring 1d. This cycle of operation is periodically repeated as long as the battery is connected across the terminals 22 and 30, thereby sustaining the oscillatory movement of the armature or balance wheel 12 and staff 5.

The oscillatory movement of shaft 5 may be transposed in a known manner through an escapement mechanism into uni-directional motion of a gear train which actuates the hands of a clock or other time-indicating means. In the form shown, the escapement mechanism comprises a member 31 (Fig. 3) secured to staff S for movement therewith, said member being provided with axially spaced, radially extending discs which form a channel and which are interrupted and bent to form two oppositely inclined cams 32 and 33. The latter are effective in a known manner to alternately engage successive teeth on an escapement pinion or wheel 34 during oscillation of staff 5 to impart intermittent uni-directional movement to said wheel.

Upon movement of staff 5 in a clockwise direction,

as viewed in Fig. l, cam 32 engages a tooth on wheel 34 and moves the latter downwardly into the channel between the discs on member 31. Upon subsequent counter-clockwise rotation of the staff, as explained above, cam 33 engages the same tooth and rotates wheel 34 further in the same direction, and thereby moves the next tooth on the wheel into position for engagement by cam 32 and the cycle is repeated.

It will be seen that escapement wheel 34 is stationary at the moment of each impact between a cam 32 or 33 and a tooth on the wheel. Additionally, the cam is moving at its maximum velocity at the moment of each impact. The kinetic energy of each impact is thus relatively high and is accordingly the cause of an appreciable lll part of the noise of operation. A large portion of such noise is eliminated in the present novel construction wherein the mass of the escapement wheel is materially reduced Without adversely affecting the efficiency of operation or the operating life of the parts. lt has heretofore been the universal practice to construct the escapement wheel of brass or similar resonant metals having a relatively high specific gravity and good sound transmission qualities. In the novel structure comprehended by this invention, wheel 34 is made of a plastic, such as nylon, Lucite, Bakelite, or the like, or lighter metals, such as aluminum and magnesium alloys, all of which have a considerably lower specific gravity than brass and are relatively inert to sound transmission. Another advantage in using plastic Wheels is that the same may be molded, whereas the metal wheels must be cut.

The present invention also contemplates novel means for mounting a rotatable shaft, such as the shaft on which wheel 34 is secured, to thereby substantially eliminate undesirable radial and axial movements thereof to insure uniform dead-beat escapement action and to provide long life lubrication while automatically effecting the desired optimum braking, thereby eliminating the necessity for a separate braking means. In the form r shown, the worm shaft 35 on which wheel 34 is mounted has a cone-shaped tip (Fig. 4) at each end thereof for engagement with a pair of supporting brackets 45 and 46. The former of these, as shown, is a rigid right-angle bracket and is rigidly secured by rivets or other suitable means to the upper surface of plate 6, as viewed in Fig. 2.

Bracket 46 is made of a rather thin gauge spring metal, such as spring phosphor bronze, and may be either rigidly or adjustably secured to the surface of plate 6. As illustrated, bracket 46 is piveted on said plate at 47 and the base thereof is slotted to receive a set screw 43 adapted to hold the same in a variety of adjusted positions around the vertical pivot 47.

The resilient upstanding portion of bracket 46 is provided with a bore or opening i9 therethrough (Fig. 4), the diameter of which is just large enough to receive the tip end of shaft 35. Preferably, this hole terminates in a slight chamfer to serve as a bearing seat and provide suitable annular surface contact for the conical end of the shaft. The upstanding portion of rigid bracket 45 may be similarly bored and chamfered in axial alignment with bore 49 for receiving and supporting the other end of shaft 3S which is also preferably cone-shaped. The unlled portions of the bores in the brackets serve as oil reservoirs wherein a supply of oil which will last for a considerable period of operation may be held by capillary action.

With the shaft mounting above described, the elimination of undesirable end play and radial movement of the Shaft and the provision of automatic braking against reverse movement of the shaft are attained by placing the upstanding spring arm of bracket 46 under an initial tension toward shaft 3S. Adjustment of this tension or pressure may be effected by slightly bending said spring arm at its juncture with the base of the bracket, or by adjusting the entire bracket about pivot 47. Proferably, tne bracket is so constructed and positioned that the upstanding portion thereof will be substantially vertical when the installation is complete with the proper pressure being exerted thereby endwise upon shaft 35. Since the braking pressure is applied at a comparatively small radius,

it will be observed that quite a wide variation of the end pressure is permissible without adversely affecting the braking torque. Essentially constant braking effort is thus assured without the necessity for critical or sensitive adjustments by the operator. Thus, when the parts have been properly adjusted in the factory during initial assembly, the pressure, and hence the braking torque, will remain sufficiently constant for an indefinite period of operation. The spring support for the shaft also compensates automatically for wear at the journals which in prior constructions resulted in a loosening of the escapement wheel shaft and hence erratic operation thereof.

In the structure illustrated, the uni-directional, interhke carried by fore known and now in commercial use.

Although only a single embodiment of the invention has been illustrated in the accompanying drawings by way of example, it is to be expressly understood that the same is not limited thereto.

Gand 7. The

3. In apparatus of the class described, a shaft having said cone-shaped ends, the latter and the same angularity relative to the axis of the shaft and the dimensions of the parts being such that the conical entrance to each bore makes annular surface contact with a cone-shaped against the other support to thereby effect a on the shaft.

4. An escapement a cone-shaped end of shaft out of contact at right angles to each other.

6. Apparatus as defined in claim 2 wherein said support is resilient and is biased to apply continuous, axially directed pressure against said shaft.

References Cited in the le of this patent UNITED STATES PATENTS 613,178 Unz Oct. 25, 1898 687,776 Pain Dec. 3, 1901 1,371,654 Walmsley Mar. 15, 1921 1,508,824 Schramm Sept. 16, 1924 1,950,243 House Mar. 6, 1934 1,965,762 Battegay July 10, 1934 1,972,461 Reiner Sept. 4, 1934 1,991,839 Favre-Bulle Feb. 19, 1935 2,266,015 Fink Dec. 16, 1941 2,377,276 Sperry et al May 29, 1945 2,420,827 Kennedy May 20, 1947 2,531,966 Berge Nov. 28, 1950 FOREIGN PATENTS 403,267 Great Britain Dec. 21, 1933 346,752 Italy Mar. 5, 1937

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