US2860702A - Timing mechanism - Google Patents

Description

Nov. 18, 1958 c, w. D LZELL 2,860,702

TIMING MECHANISM Filed larch 15, 1954 kmuuuuu "nun SWITCH CONTROL IN VENTOR Clarence WDa/zel L.

ATTORNEY United States Patent 2,860,702 TIMING MECHANISM Clarence W. Dalzell, Princeton, N. 1., assignor to Bendix Aviation Corporation, Baltimore, Md., a corporation of Delaware Application March 15, 1954, Serial No. 416,146

4 Claims. (Cl. 1611) This invention relates to timing mechanism capable of being preset to delay for a predetermined lapse of time the operation of a related machine or device, or to determine the time such machine or device remains in operation, as for example, where it is desired to cause one or more controlling switches or relays to be automatically thrown after a given lapse of time, or to condition an arming circuit, or to predetermine the length of time such switches or relays remain closed or such circuit or circuits remain energized.

An object of the invention is to provide a timer mechanism which adapts itself for fabrication from material unaffected by changes in ambient temperature andpressure and hence requires no compensating means to correct for errors which might otherwise result from such changes. 7

Another object is to provide a timer which avoids the use of escapement mechanism and hence is not susceptible to errors which are inherent in such mechanism, and which at the same time is reliable in operation.

Another object is to provide an electro-mechanical timer which operates mechanically during the actual timing operation, requiring sufficient current only to operate brake release mechanism to stop the timer, so that the mechanism, as a whole, is relatively immune to changes in the electrical power supply.

Another object is to provide a timer of the type specified which may be conveniently adjusted, set, and reset whenever such procedure is found necessary or desirable.

A further object is to generally improve and simplify, as well as render more reliable, timers of the type specitied.

Broadly stated, the foregoing objects are attained by employing a rotatable member, such as a balanced flywheel, having a predetermined moment of inertia, means for delivering a substantially constant torque to said member, and timing means responsive to a predetermined number of revolutions or angular travel of said member.

The foregoing and other objects and advantages will become apparent in view of the following description taken in conjunction with the drawings, wherein the sole figure represents schematically a timer mechanism embodying the features of the invention.

Referring to the drawing, the switches indicated at 10, 11 and 12 are representative of timing control elements, or which may be connected to a circuit to be activated or energized after a predetermined time has elapsed following the starting of the timing operation; they could extend to an arming circuit, a series of relays, or the like, and for convenience, they are hereinafter referred to as timing switches. These switches are carried by a suitable supporting frame 13, which in turn is carried by a control or setting knob 14, the latter usually being associated with a suitably calibrated dial to facilitate calibration and setting of the mechanism. The movable elements of these respective switches are of the springreturn type and are adapted to be engaged and moved into closed position by means of a series of timing cams,

2,860,702 Patented Nov. 18, 1958 as at 15, 16 and 17, adjustably secured on a shaft 18.

For exerting a driving torque on the shaft 18, a spring 19 may conveniently be employed. In the form shown, spring 19 is of the diaphragm type, but could be of any type desired having the necessary strength to carry out its intended function. An example of a suitable spring is one made of a metal alloy known as Ni-Span C, heat-treated in a manner such as to maintain its effective force constant regardless of changes in temperature. The peripheral or outer edge portion of the spring is suitably anchored against movement, as at 20, while its central or movable portion is connected by means of a link 21 and lever 22 to a shaft 23 in a manner such that when the spring delivers a power stroke, it rotates the said shaft 23 in the proper direction. Rotation is transmitted from the shaft 23 to shaft 18 by means of gear 24 and pinion 25.

A pair of limit switches are generally indicated at 26 and 27, the switch 26 comprising a relatively stationary contact member 26', and a movable contact member or arm 26", and the switch 27 having like elements 27 and 27". The contact arms 26" and 27 are mounted on rotatable shafts 28 and 29, rotation being transmitted from the shaft 18 to the shafts 28 and 29 by means of gears 30 and 31, shaft 31', worms 32 and 33, and gears 34 and 35. t

A rotatable member having a predetermined moment of inertia may conveniently take the form of a flywheel 36; it is secured on a shaft 37, which is driven from the shaft 18 by means of gear 38 and pinion 39. Preferably, the fiywheel has a high ratio of moment of inertia to inherent weight, which in the form shown is obtained by building a preponderance of weight in the peripheral portion and joining the latter to the hub through relatively light web or spoke members. Coacting with the flywheel 36 is a brake 40, here shown as of that type which when its solenoid 40 becomes energized, brake shoe 41 is retracted from braking position, said shoe being spring-actuated to braking engagement upon deenergization of said solenoid. The motor indicated at 42 is a rewind or reset motor for restoring the timer to its starting position; it is adapted to impart reverse rotation to shaft 37 through a clutch member 43, in turn adapted to engage a coacting clutch member 44, secured on the adjacent end of shaft 37. The clutch control mechanism for the member 43 is preferably of the centrifugal type, which when the motor attains a certain speed, moves said clutch member 43 into engagement with its coacting member 44.

A starting switch is indicated at 45 and a resetting switch at 46, said switches being connected to a common control member 47. The starting switch 45 is adapted to engage a pair of spaced contacts 48 and 49, while the switch 46 is adapted to engage a. single contact 50. The switch 45 is connected to the positive side of an electric circuit by means of wire 51, and when it is moved into engagement with contact 48, a circuit is completed to the contact arm 26" of switch 26 by way of wire 52; and when the said switch is moved into engagement with contact 49, a circuit is completed to the contact arm 27" of switch 27 by way of wire 53. The arm 26" of switch 26 connects byway of wire 54 with the solenoid 40 of the brake 40, the said solenoid 40' and motor 42 being connected to the ground side of the line by means of wire 55. The arm 27" of the switch 27 is connected by means of wire 56 with the input side of the motor 42; and said arm 27" also connects with contact of switch 46 by wire 57.

The relatively fixed contacts 26' and 27 of the switches 26 and 27 may be rendered adjustable with respect to the movable contacts 26" and 27" by means such as the slide rod 58, which is urged to the right by a spring 59, and at its right-hand end carries a follower 60, adapted to engage a cam 61 carried by the knob 14. The left In the position of the parts as shown in the drawing,'tne control 47 has been actuated in a direction to move the switch 45 into engagement with the contact 49 and switch? 46 into engagement withcontact 50. This is the rewind.

or resetting position, and hence when these switches were initially closed, the reset motor 42 was energized to rotate the shaft 37 in a clockwise direction as viewed from the right-hand end thereof, thereby rotating the shaft 23 and arm orlever 22.secured thereon in a direction to tension the spring 19. -When this occurred, the contact arm 27".

of switch 27 was moved clear of the contact 27, thereby opening the circuit to the motor 42, causing the latter to stop and release the clutch 43, and this action also broke the circuit to the brake solenoid 41), causing the brake to engage the flywheel 36. During the rewinding cycle, however, arm 27" remained in engagement with contact 27, so that a circuit was completed to the brake solenoid. by way of switch 45, wire 53, contact 27, arm 27 wire 57, switch 46 and wire 54, thus holding the brake in released position, until arm 27" cleared 27', whereupon the brake circuit was broken and the brake applied.

In order to preset the timing mechanism, the knob 14 is adjusted. to properly position the switches 10, 11 and 12 relative to the, cams 15, 16, and 17, and to also position the contacts 26 and 27 to obtain the proper dwell of contact arms 26" and 27". The switch control 47 may be set automatically or manually, depending upon conditions of installation. The timing cycle or operation starts when the switch is moved into engagement with contact 48 and the switch 46 is moved clear of contact 50. When this happens, the circuit is closed to the brake solenoid 40 by way of wire 52, contact arm 26 and wire 54; while at the same time the circuit to the motor 42 is opened due to the fact that the switch 46 is cleared of contact 50. The brake shoe 41 is then moved clear of the inertia or flywheel 36, whereupon the spring 19, which had previously been preloaded, becomes effective to rotate the shaft 23, and the flywheel 36 starts rotating and gradually picks up speed. The shaft 18, carrying the timing cams 15, 16 and 17, also rotates through a predetermined angular travel, depending upon the length of dwell of the contact arm 26"'on the contact 26. Following contactclosing movement of any one or more of the cams 15, 16 and 17, the contact arm'26" clears the contact 26, and the arm 27" engages the contact 27'. When this happens, the circuit to the brake solenoid 4t) is broken, whereupon the brake shoe '41 engages the flywheel 36 and stops any further motion of the timing mechanism.

To restore the timer to the starting position, the switch control member 47 is returned to its down position, bringing switches 45 and 46 into engagement with contacts 49 and 50, the position shown in the drawing.

It will be observed that the basic elements of the timer comprise the spring or constant torque motor 19 and the flywheel 36, both of which can readily be made of material immune to temperature changes. Angular acceleration is directly proportional to the force in the driving spring and indirectly proportional-to the moment ofinertia of the moving parts. The flywheel and the respective driving gears are preferably so designed as to balance through their centers of gravity, so that the moment of inertia is the controlling factor. The spring motor, when released to start the timer, exerts its initial force, which is greatest when the spring --is fully wound or tensioned, in overcoming static inertia and friction, following which, the

motive force exerted by the spring decreases with a decrease in the torque required to effect rotation of the fly is that it is unaffected by changes in the electrical power supply voltage and current, since the only electrical power required isthat necessary to operate the brake motor solenoid 45, which does not affect the actual timing operation. Also, the mechanism is not as susceptible to damage resulting from shock and vibration, as are more delicate mechanisms involving escapement and the like more or less delicate parts; and further, there are no parts which are affected by changes in altitude. By using suitable anti-friction bearings the friction component can be reduced to a minimum.

In view of the foregoing the description and the schematicillustration in the drawing, it will be obvious to those skilled in the art how to build timers in accordance with the. invention to conform to various types of installations.

What is claimed and desired to be secured by United States Letters Patent is:

1. Timing mechanism including a flywheel having a predetermined moment of inertia, a spring motor, a gear train providing a driving connection between said motor and said flywheel, at least one movable timing element having an operative connection with said flywheel for movement in predetermined ratio to rotation of the flywheel, an electric reset motor having a releasable reverse driving connection with said spring motor for tensioning the latter, a brake for holding the flywheel against movement until it is desired to start the timing cycle, said brake having a friction member and an electric solenoid for effecting release from braking position of said friction member, an electric circuit for said brake solenoid and said electric reset motor incorporating a pair of limit switches, one connected to said solenoid and the other connected to said electric reset motor, said limit switches being provided with movable contact elements adapted for movement in predetermined ratio to rotation of said flywheel to time the energization of said solenoid and said electric reset motor, said circuit also incorporating switch mechanism for effecting release of said brake to start the timing cycle and for energizing the electric reset motor to tension said spring motor following termination of the timing cycle.

2. A timer of the type specified, including a rotatable member having a predetermined moment of inertia, a spring motor adapted to deliver a driving torque to said rotatable member, at least one rotatable timing element responsive to a predetermined angular travel of said rotatable member, an electric reset motor having a releasable reverse driving connection with said spring motor to rewind or tension the latter when presetting the timer, mechanical driving means interconnecting said spring motor, said rotatable member and said timing element, an electric brake for holding said rotatable member against rotation until it is desired to start the timing cycle, an electric circuit incorporating a limit switch provided with a rotatable contact member having a driving connection with said timing mechanism and a relatively stationary contact electrically connected to said brake to automatically time the period of energization of said brake, said electrical circuit also incorporating switch mechanism for controlling the start of the timing cycle and also for energizing said reset motor to reset the timer.

3. A timer as claimed in claim 2 wherein a calibrated presetting member .is provided having an operative connection with said timing element and said limit switch.

4. Timer mechanism of the type specified including a flywheel having a predetermined moment of inertia, a spring motor, means providinga drive connection between said spring motor and flywheel, a shaft having at least one timing element connected thereto for rotation therewith, said shaft also having a drive connection with said spring motor, an electric reset motor for energizing the spring motor and resetting the timer mechanism, an electric brake for holding said flywheel against rotation and restraining the spring motor until it is desired to start the timing cycle, electric circuits for said brake and said reset motor, said brake circuit incorporating a limit switch provided with a movable contact member electrically con nected to said brake and mechanically connected to said flywheel for movement in relation thereto and a relatively stationary contact element, said movable contact coacting with said contact element to maintain the circuit to said brake in brake-release condition during a timing cycle 15 incorporating switch means effective to maintain the said reset motor ineffective during the timing cycle, and a selectively operable switch for controlling energization of the reset motor to reset the timing mechanism, said reset motor circuit also incorporating a limit switch effective to maintain the brake released during resetting of the timing mechanism and to automatically apply the brake upon completion of the resetting operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,007,177 Bevans Oct. 31, 1911 1,759,648 Kunze May 20, '1930 2,312,077 Cowles Feb. 23, 1943 2,599,858 Noon June 10, 1952

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