US2577172A - Commutator timing mechanism - Google Patents

Description

1951 F. B. WOESTEMEYER 7 COMMUTATOR TIMING MECHANISM Filed March 29, 1949 Fig.

Inventor; Francis B. Woestemeger,

His Attorney.

Patented Dec. 4, 1951 COMMUTATOR TIMING LIECHANISM Francis B. Woestemeyer, Schenectady, N. Y., fl8- signor to General Electric Company, a corporation of New York Application March 29, 1949, Serial No. 84,202

6 Claims.

My invention relates generally to timing mechanisms, and more particularly to a commutator timing mechanism for making electrical contacts at predetermined time intervals.

My invention finds particular application in radiosonde apparatus which is sent aloft in meteorological investigations of the upper atmosphere. Current types of radiosonde apparatus contain various instruments such as thermometers, barometers, hygrometers, and cloud moisture analysers, for measuring atmospheric conditions. The meteorological instruments, through suitable transformations, provide indications in the form of variations in magnitude of resistances. These variations in resistance are coupled into a transmitting circuit which contains a blocking oscillator, and cause the blocking rate of the oscillator to vary proportionally to the quantities being measured. The transmitted signals are recovered by suitable receiving instruments on the ground, and the conditions 'of the upper atmosphere are determined therefrom.

In order to permit the transmitter in the radiosonde to send information with regards to all of the meteorological instruments, it is feasible to employ a rapid sequence telemetering system. One such telemetering system presently in use, requires that the variations in resistance value, produced by each of the meteorological instruments, be commutated into the transmitting circuit at a rate of approximately two per second. In this system, it is essential that the various circuits be connected to the transmitter for a time interval of 480 milliseconds, with an open circuittime interval of milliseconds in between. It is necessary that both these time intervals be accurately maintained in order to permit the receiving instruments at the ground station to operate efficiently. It is also necessary that the mechanism for performing these functions operate reliably over a wide range of atmospheric conditions.

Accordingly, it is an object of my invention to provide a timing mechanism for making a series of electrical contacts at definite time intervals, said contacts to have a predetermined time duration.

Another object of my invention is to provide a clockwork type of timing mechanism for making a series of electrical contacts in which the time duration of the contact, and the time interval between contacts, are separately adjustable.

A further object of my invention is to provide a timing mechanism for making electrical contacts, in which the contacts are made with a wiping and a striking action to insure maximum reliability in the presence of icing conditions.

"For further objects and advantages, and for a better understanding of the invention, attention is now directed to the following description and accompanying drawing, and also to the appended claims in which the features of the invention believed to be novel are more particularly pointed out.

In the drawings:

Fig. l is a front elevation view of a commutator timing mechanism embodying my invention;

Fig. 2 is a side elevation view of the same mechanism, seen looking in the direction of arrow 2 in Fig. 1;

Figs. 3, 4, and 5 are detailed views of a part of the mechanism comprising the electrical commutator with which my invention is more parr ticularly concerned.

Referring to Figs. 1 and 2, the timing mechanism comprises a conventional type of gravity drive in which a drum I has wound around it a string 2 which is attached to a lifting balloon 3. The timing mechanism, along with the other instruments constituting the radiosonde, are contained in an enclosure 4 and their combined weight causes the string to unwind, thereby driving a gear 5 attached to drum I. Gear 5 is linked, by means of a pinion 6 and a gear I, to a pinion 9. Pinion 9 is mounted on, and fixed to a shaft l0, and thereby drives an escape wheel ll which has disposed on its periphery, at angles of apart, three locking teeth 13, H, and IS. The locking teeth have sloping peripheral surfaces for the purpose of providing an impulse to the pallet pins I 6 and ll, of an escape lever I8. The escape lever I 8 operates in conjunction with a pin IS on a balance wheel 20 and a hair spring 2| to constitute a well-known type of impulse escapement.

Mounted on shaft I0 is an inertia wheel 22 which carries a contactor 23. The inertia wheel rotates freely on shaft l0 and has a sloping cam surface 24 on its hub which engages with a ratchet release pin 25 on shaft ID. The inertia wheel is flexibly coupled to escape wheel II by means of a spiral spring 26, which causes it to tend to follow the rotation of the escape wheel. Located on the are described by contactor 23 as the inertia wheel 22 rotates, are six fixed contacts 28 to 33. These fixed contacts are in the form of screws having pointed conical heads. The inertia wheel 22 and its associated elements, comprising the fixed contacts, constitute the commutator.

The operation of the mechanism. leaving out of account the commutating system, is very similar to that of a gravity driven type of clock. The torques transmitted by the different gears and their directions of rotation are indicated by the adjacent curved arrows, The escape wheel H, through its loeking'teeth, is alternately re-, strained and released by means of pallet pins l6 and. I! on escape lever l8. The escape lever 'it requires three seconds ll is rocked by pin II on balance wheel 23. The moment of inertia of balance wheel 20. in combination with the stiffness in the spring 2|. is such as to cause its period of oscillation to be one second. Accordingly, the escape lever goes through a complete cycle in one second, during which cycle each pallet pin locks and releases a locking tooth on'the escape wheel. This provides two ticks per second and a rotation of the second. Accordingly, for the escape wheel and this revolution is escape wheel of 120 in one to'complete a revolution, accomplished in discrete steps of 60, half a sec- I nd or 500 milliseconds elapsing between the iniadvances at each tick, the ratchet release pin likewise advances along the sloping cam surface 24 of the hub of the inertia wheel. By the time the release pin has advanced 45, it has allowed ,knownhasagrea 45K? have to overcome static friction which. as is well magnitude than sliding friction. The mechanism can :thereby operate with a much smaller torque f rointhe spiralspring 2 than would otherwise be required. This in turn increases the range of open circuit time intervals for which the commutator can be adiusted. The required driving torque is also decreased.

My invention permits the adjustment of the time interval, between the breaking of a precedingcontact, and the making of a succeeding contact, independently of the time interval between the making of the contacts. In other words, if the interval of time during whicha contact is made is termed the closed circuit time, and the the inertia wheel to move axially to the left along shaft l0, through a distance sufiicient to disengage rotating contactor 23 from fixed contact 28. Thereupon, spiral spring 26 causes inertia wheel 22 to rotate at high speed in the same direction as the escape wheel. As inertia wheel 22 rotates, the sloping cam surface bearing against ratchet release pin causes the inertia wheel to move axially to the right along shaft I0, so. that atthe instant when the rotating contactor 23 reaches the angular position of fixed contact 23'. it is once more in a position to engage a fixed contact, thereby locking the inertia wheel.

= The sequence of events consequent upon the movement of the rotating contactor from fixed contact 28 to fixed contact 23 is more clearly illustrated inFigs. 3 to 5.

Fig. 3 shows the position of the inertia wheel 2 with its rotating contactor 23 locked against fixed contact 28. The escapewheel II is just'beginning to rotate through 60 and ratchet release pin'25 is entering the sloping cam surfacefl.

time interval required for the movin contact. after disengaging itself from a fixed contact, to. engage a succeeding one, is-called the open eircult time, my inventionpermits the independent adjustment of the closed and open circuit times- The closed circuit time is primarily'dependent upon the selection of the balance wheel and itshairspring. and can conveniently be varied by adjusting the working length of hair spring 2f? in a well-known manner. It will also be apparent that the closed circuit time of the 'various In Fig. 4. the escape wheel has rotated somewhat less than 45, and ratchet release pin 25 has point where the inertia wheel 22 has moved ax ially to the left, and the rotating contactor is barely retained by the point of'fixed contact.

contacts can be varied slightly by adjusting the- If one of the fixed coir- .tacts is-screwed in,'the ratchet release -'pin willhave to rotate through a larger angle before the-- rotating contact disengages itself. It will be ap-* fixed contact screws.

parent that such an adjustin'entwould be at the expense ofthe succeeding contact and-could affect the over-all period of the system.

The open circuit time is dependent upon the moment of inertia of wheel 22; andthe tension of hair spring 26, and can conveniently be variedby adjusting the tension of the hair spring after a well-known manner. The initial tension of hair spring 28 is large compared to the increase in'ten'sion produced as the escapejyheer fl advances to the 45 position at which wheel 22 is released. Therefore, variations in contact adjustment,- which cause the release point to vary for different contacts, have only a small effect on the open circuit time. Thus the open circuit time is completely independent of the closed circuit time. and thereby of the adadvanced along the sloping cam surface to the Fig. 5 illustrates the state of the mechanism at the instant when the rotating contactor, havingdisengaged itself from fixed contact 28, has rotated and engaged fixed contact 23.. During the process of catching up with the escape wheel, the inertia wheel has moved back to; the right along the shaft It, so that upon reaching the angular position of the fixed contact 29, rotating contactor 23 is in a position to engage it.

The inertia wheel thus advances in discrete steps. It follows the rotation of the escape wheel, but is continually interrupted by the engaging, ratchet-fashion. .of the rotating contactor with 7 one of the fixed contactors.

Itwlll be noted that theshaft I0 is rotating" as the inertia wheel 22 is sliding axially along it while being held in one angular position by contactor 23 engaging one of the fixed contacts.

This is an important structural feature, as it means that the inertia wheel need only overcome sliding friction to displace itself axially along shaft l3. Otherwise,'the inertia wheel would shown that the open circuit time is maintained at 20""milliseconds with a variation of 1-2.5 milliseconds when the ambient temperature was varied from +20 to 65 centigrade.

-M y invention also has the advantage of providing a type of contact which has-both a wiping and-a striking action. Thus the rotating contactor, during the time when it is disengaging itself from a fixed contact, provides a wiping action due to the fact that the inertia wheel.

by sliding longitudinally along its shaft, causes the. rotating contactor to slide on the point of a fixed contact. 'When the rotating contactor engages the succeeding fixed contact, it strikes with appreciable force, due to the angular veloc-. ity attained by the inertia wheeL. rims-comm nation of features insures maximum reliability-of the commutator in the presence of the icing cone. ditions frequently encountered in. the upper atmosphere.

It will be apparent, from the description already given, that it is not essential that the inertia wheel advance always in steps coinciding with those of the escape wheel. For instance, by changing the angular spread of the cam surface on the hub of the inertia wheel, it is possible to make the inertia wheel advance on every alternate step of the escape wheel. Only three fixed contacts would then be used and the contactor would advance on alternate ticks or, in other words, at intervals of 1 second time duration.

While a specific embodiment has been shown and described, it will, of course, be understood that various modifications may be made without departing from the invention. The appended claims are, therefore, intended to cover any such modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A commutator timing device comprising an escape wheel, a mechanism for driving said escape wheel, an inertia wheel carrying a rotating contactor, said inertia wheel being flexibly coupled to said escape wheel to permit relative movement in one direction, a plurality of stationary contacts for engaging said rotating contactor, and a ratchet release mechanism carried by said escape wheel for providing relative movements of said wheels in another direction to permit said moving contact to disengage itself from said fixed contacts.

2. In combination an escape wheel, a timing mechanism for driving said escape wheel by discrete steps, an inertia wheel carrying a rotating contactor, a flexible coupling between said wheels for applying a torque on said inertia wheel in the direction of rotation of said escape wheel, a plurality of stationary contacts for engaging said rotating contactor, and a ratchet release mechanism carried by said escape wheel for displacing said inertia wheel perpendicularly to the plane of said rotation for permitting said moving contact to disengage itself from a fixed contact and engage a succeeding fixed contact during said steps, whereby the time interval between the initiation of engagements of contacts is controlled substantially by said timing mechanism, and the time interval between the termination of an engagement and the initiation of a succeeding engagement is controlled by said flexible coupling.

3. A commutator timing device comprising a clockwork mechanism for driving an escape wheel through discrete angular displacements at predetermined time intervals, a supporting shaft,

said escape wheel being rigidly mounted on said shaft, an inertia wheel rotatably mounted on said shaft, a contactor mounted on said inertia wheel, a plurality of stationary contacts located in the circular path described by said contactor ina manner normally to engage said contactor, a flexible coupling between said wheels, and means on said shaft for enabling said inertia wheel and rotating contactor to slide axially to permit said contactor to disengage itself from a fixed contact when said escape wheel has advanced through a predetermined portion of said tatably mounted on said shaft, a contactor mounted on said inertia wheel, a plurality of stationary contacts located in the circular path described by said contactor in a manner normally to engage said contactor, a flexible coupling between said wheels, a sloping cam surface on the hub of said inertia wheel, a projection on said shaft for engaging said cam surface, said cam surface being shaped to allow said inertia wheel and said contactor to slide axially along said shaft during the course of said displacement, thereby permitting said contactor to disengage itself from a fixed contact and engage a succeeding fixed contact.

5. A commutator timing device comprising an escape wheel, means for applying a driving torque to said wheel, an impulse escapement for permitting said wheel to advance by discrete steps at regulated time intervals, an inertia wheel mounted co-axially, and in a manner to permit it to rotate and to slide axially, with respect to said escape wheel, a flexible coupling between said wheels, a contactor extending from the side of said inertia wheel remote from said escape wheel, a plurality of fixed contacts located in the circular path described by said contactor, a projection on said escape wheel for restraining the axial displacement of said inertia wheel to cause said contactor to engage said fixed contacts, and a cam surface on the side of said inertia wheel adjacent said escape wheel, said cam surface being shaped to allow said inertia wheel to slide axially towards said escape wheel during said steps thereby permitting said contactor to disengage itself irom a fixed contact, and engage a succeeding contact.

6. A commutator timing device comprising an escape wheel, means for applying a driving torque to said wheel, an impulse escapement for per mitting said wheel to advance by discrete steps at regulated time intervals, an inertia wheel mounted coaxially and in a manner to permit it to rotate and to slide axially with respect to said escape wheel, a flexible coupling between said wheels for applying a substantially constant torque to said inertia Wheel in the direction of rotation of said escape wheel, a contactor extending from the, side of said inertia wheel remote from said escape wheel, fixed contacts located in the circular path described by said contactor, said fixed contacts corresponding in number to the number of said steps Der revolution of said escape wheel, a projection on said escape wheel for normally restraining the axial displacement of said inertia wheel to cause said contactor to engage said fixed contacts thereby locking said inertia wheel, and a sloping cam surface on the side of said inertia wheel adjacent said escape wheel, said cam surface hearing against said projection and being shaped to allow said inertia wheel to slide axially towards said escape wheel during said steps. thereb permitting said contactor to disengage itself from a fixed contact and said coupling to drive said inertia wheel until said contactor engages a succeeding fixed contact.

FRANCIS B. WOESTEMEYER.

REFERENCES CITED UNITED STATES PATENTS Name Date Ball Feb. 14, 1933 Number

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