US2816975A - Torsion oscillator mechanical switch - Google Patents

Description

v Dec. 17, 1957 E. P. SNYDER 2,8

TORSION OSCILLATOR MECHANICAL SWITCH Filed Dec. 21, 1953 INVENTOR.

Ellery F3. Snyder WA w.

AGENT United States Patent TORSION OSCILLATOR MECHANICAL SWITCH Ellery P. Snyder, New York County, N. Y., assignor to Aviation Engineering Division, Avien-Kniclrerbocker, Inc., Woodside, N. Y.

Application December 21, 1953, Serial No. 399,266

1 Claim. (Cl. 200-92) This invention relates to mechanical switching device for electrical circuits of the commutator type having an oscillatory mechanical motion.

In electrical circuits there is frequently incorporated mechanical devices for switching circuits. Where it is desired that in a rest position of the switching apparatus a particular circuit be connected, a vibratory type device is frequently employed. In such a device an arm carrying a contact is pulled from a first position to a second position by means of an electromagnet. Upon interruption of the current the arm is returned by a spring to the first position. The most common apparatus of this type is the well known electrical bell or buzzer. However, a number of basic objections exist to the widespread use of this type of equipment, which include inability to operate at low cycling rate, poor mechanical life, unreliable characteristics of the make-and-break type of electrical circuit such as the tendency to arc. A preferred switching system utilizes a commutator. However, in order to drive a commutator at a slow rate of speed, extensive gearing between the motor and the commutator shaft is usually required.

It is an object of this invention to provide a slow speed switching means.

It is another object of this invention to provide a simple and dependable switching means.

It is still another object of this invention to provide a vibration insensitive switching apparatus.

It is an object of this invention to provide a mechanical switching arrangement which will rest in a predetermined position in the event of a motor-driving system failure.

It is another object of this invention to provide a mechanical switching arrangement utilizing a commutator operated with an oscillatory motion.

Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings:

In the drawing there is shown a pictorial view of the apparatus of this invention.

The apparatus of this invention comprises a motor 2 having a flywheel 4 and a pinion gear 6 mounted on motor shaft 8. Pinion gear 6 drives follower gear 10 which is mounted upon shaft 12, thus causing shaft 12 to turn in accordance with the motion of the motor shafts. Mounted upon shaft 12 is a switching means comprising insulated armature 14 which has a slip fit permitting a rotary motion to be carried out between armature 14 and shaft 12. Pin 16 is firmly attached to shaft 12 so that dependent on the direction of motion of shaft 12, pin 16 is caused to push either pin 18 or pin 20 which are in turn affixed to armature 14. Armature 14 is caused to rotate with shaft 12 after the pin 16 has traversed the distance between pin 18 and pin 20 thus providing a lost motion device which permits controlling the dwell rate of the armature in a particular position without further increase of gear ratio if a higher dwell period is required. Electro conductive surface 22 lCC of armature 44 is caused to oscillate between two positions, one in which it serves as a jumper or connection between brush member 24 and brush member 26. Brush member 24 is connected by suitable conductors to motor 2 while brush member 26 is connected to a source of electrical energy. Thus in one position the motor is energized and in the other position it is de-energized. With the power off, the unit is designed so that the circuit between brushes 24 and 26 is completed. Therefore, when power is applied to the unit, the motor 2 turns and causes shaft 12 to rotate resulting in the circuit between brushes 24 and 26 to be interrupted. Thus the motor is no longer energized and stops. To return the motor to the energized position, there is provided a torsion spring 30 attached to shaft 12. In moving the shaft from the energized position to the de-energized position, torsion spring 30 is contracted by the winding action of the shaft. When the motor is de-energized by the action of the switching armature 14, the spring returns the shaft to the energized position.

The flywheel provides sulficient inertia to continue the shaft rotation for a brief period so that the switch 14 rests temporarily in the de-energized motor circuit position. Shaft 12 also carries a number of commutator elements 34 which make contact with brushes 36 to provide the switching function.-

It is to be noted that in the event of the failure of power, the spring will always return the commutator shaft 12 to the same position, thus a selected commutator brush circuit is left in an operative connection.

The period of oscillation is given by:

I =total moment of inertia acting on the spring T=spring constant where:

The choice of values of the parameters is principally determined by the maximum friction of the motor and commutator and the inertia which the spring must overcome to guarantee the functioning of fail-safe feature and the switching cycle desired.

In a typical unit constructed the angle of oscillation was set at an arbitrary value of 240. The period, which is not critical, was chosen to have a nominal value of 0.5 second. The spring torque gradient sufficient to give a fail-safe uncertainty of less than :30 was chosen as 0.33 cm. per degree. The gear ratio and flywheel size were then determined to best meet packaging considerations.

The length of the motor torque cycle and its phase were then determined empirically on the basis of maintaining steady oscillation and the desired ratio of time sharing.

In carrying out the invention it is preferred to utilize the brush block and brush arrangement disclosed in my copending application No. 399,413, entitled, Brush Block filed concurrently herewith and assigned to the assignee of the present invention and which matured into Patent No. 2,700,088 on January 18, 1955.

The commutator may be designed for equal time sharing between two circuits, i. e. the on and off segments are of equal length, or for unequal time sharing. The commutator design may be greatly modified for many different circuit operations. The number of segments on a single shaft may run from 1 to 20 or even more depending on the function to be performed.

As used herein the term commutator is intended to include the segment type of contacting surface as well as the slip ring type disclosed in the accompanying drawing.

While I have disclosed what is the best mode contemplated by me for carrying out the invention it is to be understood that modifications may be made in the design without departing from the spirit of the invention as covered by the appended claim.

What I claim as new is:

The combination of an electric current motor provided with a shaft, a flywheel driven by said motor, a driver gear mounted on said motor shaft, a driven assembly comprising a follower gear engaging said driver gear and a shaft for said follower gear, a commutator rotated by said follower gear shaft brush members in contact with said commutator, means to connect an external circuit to said brush members so that said external circuit is under control of said commutator, a lost motion device actuated by said follower gear shaft, a switching means operated by said lost motion device and adapted to alternately energize and de-energize said motor, and a torsion spring wound by said motor when energized and adapted to rotate said follower gear shaft when said motor is de-energized.

References Cited in the file of this patent UNITED STATES PATENTS 129,085 Barjon July 16, 1872 1,056,739 Davis Mar. 18, 1913 1,913,826 Blosser June 13, 1933 2,205,909 Place June 25, 1940 2,222,990 Shipley Nov. 26, 1940 2,312,077 Cowles Feb. 23, 1943 2,334,447 Shaw Nov. 16, 1943 2,4(li,153 Hall et al May 28, 1946 2,514,836 Buntzman July 11, 1950

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