US2020974A - Time switch - Google Patents

Description

NOV. 12,1935. 5 w TRUESDELL 2,020,974

TIME SWITCH Filed NOV. 22, 1934 Inventxar- Francis W. Truesdell,

Hi Attorney.

Patented Nov. 12, 1935 UNITED STATES PATENT OFFICE General Electric New York Company, a corporation of Application November 22, 1934, Serial No. 754,223

3 Claims.

. My invention relates to time switches and its object is to provide a simple time switch in which both the switch-opening and switch-closing operations are performed quickly with a snap action.

In a common form of time switch, a switchactuating lever is raised and lowered by a cam having two reversely inclined steps. The cam is rotated by a timing device and the step in the cam may be adjustable to cause operation of the switch-actuating lever and the opening and closing of the switch controlled thereby at different desired times. As usually built, this simple form of time switch is subject to the difficulty that the switch operation caused by the raising of the switch-actuating lever by the cam is slow, making it difficult to set the timing thereof accurately as well as causing arcing contact conditions detrimental to the switch itself and objectionable from the standpoint of radio interference.

It is the object of my invention to overcome the above mentioned difficulty and provide a simple form of cam actuated switch mechanism which moves in both the switch-closing and switch-opening directions quickly and with a snap action. I accomplish this result by providing what may be considered as a spring-biased auxiliary cam on the switch-operating lever serving as a cam follower for the main operating cam, which cam follower when acted upon by a rise in the main operating cam, is cooked and released thereby to suddenly instead of slowly lift the switch-operating lever.

The features of the invention which are believed to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding of my invention, reference is made in the following description to the accompanying drawing showing in Fig. 1 the essential elements of a cam operated switch equipped with my invention with the switch-operating lever in a lowered position opposite a depression in the operating cam; Fig. 2 shows the relation of the parts associated with the switch-operating lever when the latter is opposite the raised portion of the cam and in its raised position; Fig. 3 represents the cocking action of the auxiliary cam mechanism occasioned by a rise in the cam just before the lever is snapped from its lower position represented in Fig. l to its upper position represented in Fig. 2; and Fig. 4 shows a detail of the auxiliary cam mechanism in perspective.

Referring now more in detail to the drawing, I have represented in Fig. 1 a time switch which,

except for the addition of an auxiliary cam member l0 thereon, is of a well known form. The device embodies a timing motor I l which may be a clock mechanism or a. small synchronous motor used for rotating the timing disc I2 in a clockwise 5 direction once in twenty-four hours through suitable speed-reducing gears here represented at 13 and M. The disc 12 has a 24-hour day time scale l5 thereon, as is customary.

For the sake of simplicity, I have shown the 0 main cam parts non-adjustable and integral with the time dial l2. These cam parts here comprise the raised portion extending about the right of the dial and the depressed portion of the periphery at the left side of the dial as viewed in Fig. 1, the two portions being separated by the steps at l6 and I1. These abrupt steps face in opposite directions. Since the dial rotates clockwise, the step It may be called a rise and the step ll a d op.

The cam operates on a switch-actuating lever l8 which is pivoted at l9 and operates on the movable member of a switch having a relatively stationary contact member 2|. In the opening and closing operations of the switch the lever l8 moves away and towards the axis of rotation of cam disc l2. The central portion of lever l8 has a circular opening 22 through which a pin 23 extends. This pin is secured to a member 24 which is pivoted on the back side of lever I8 at 25 (see Fig. 4). A spring 26 secured between the upper end of the pivoted member 24 and some stationary part of the switch structure at 21 normally resiliently biases the pivoted member 24 in the position shown in Figs. 1, 2 and 4 with the pin 23 forced against the left-hand edge of opening 22, said edge serving as a stop to limit further clockwise rotation of the member 24 about its pivot point 25 on arm IS. The pin 23 extends out over and rests against the periphery of the cam on disc l2. When the pin 23 rests against the depression in the cam, the lever I8 is in its lower position and the switch 2G-2l is closed as shown in Fig. 1. At this time, the lever l8 also rests against a stationary stop 28. When the pin rests against the raised portion of the cam, the switch is open as shown in Fig. 2.

It will be evident that when the cam disc I2 is rotated in a clockwise direction to cause the pin 23 to drop over the step l1 from the upper to the lower part of the cam, the pivoted member 24 does not rotate on its pivot and the pin 23 is held against its stop at the left edge of opening 22. Thus, for this operation, which is here a switch-closing operation, the parts func- 55 tion just as if pin 23 were an integral part of lever l8, and the cam follower maintains a definite maximum space relation between the switch-actuating lever l8 and the cam surface. Since the drop i1 is abrupt, this operation is quick, the tension in spring 26 aiding gravity to snap lever i8 down as the pin 23 rides over the drop H in the cam. The switch is, therefore, closed quickly and positively.

When the rise in the cam is rotated past the pin 23, the operation pictured in Fig. 3 takes place. The rise 15 is abrupt except that the upper corner is sloped off slightly and the pin 23 has a sharp lower corner which comes against the steep part of the rise i6. As the cam plate 12 continues to rotate in a clockwise direction, member 24 is rotated about its pivot 25 in a counter-ciockwise direction, stretching spring The lever 58 cannot move downward or towards the cam surface as it is resting against the limit stop 28 and is held against such stop by spring 26. Since the pivot point 25 does not move downward, the pin 23 must move upward as it is rotated into the cooked position represented in Fig. 2, thereby decreasing the space relation between the lever l8 and the adjacent cam surface until pin 23 is lifted over the rise, its edge clears the steep rise it, and it snaps fr m the position shown in Fig. 3 to the position shown in Fig. 2. At this instant, the member 24 rotates clockwise until stopped by pin 23 con ing against the left surface of opening 22 and in so doing wipes over the nose of the rise and produces a secondary cam action to push lever l8 upward very quickly, resulting in a quick positive opening of the switch 2l2l. The pin 23 and pivoted member 24 in which the pin is secured thus comprise a cam follower which in itself produces a secondary cam action when cocked and released as above described. This secondary cam action occurs only when the cam follower is acted upon by the rise in the main cam. At other times, the cam follower acts just as if it were an integral part of lever I8. The same spring 2E, which is used to supply the snap action of auxiliary cam 23-24, also serves to bias the switch lever 18 downward and keep the cam follower in contact with the main cam surface. The device is thus not dependent upon gravity for its operation and may be used in any angular position desired.

It will be understood that various changes may be made in the details of construction of the time switch and the manner of incorporation of my invention therein and I do not wish to be limited to the particular arrangement illustrated and described.

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

i. A time switch having rotary cam means, a timing motor for rotating said cam means, said cam means having a cam surface including abrupt rise and fall steps facing in opposite directions, a switch-actuating member movable towards and away from the axis of rotation of said cam means, a cam follower pivoted to said switch actuating member and resting upon said stepped cam surface, said cam follower comprising an auxiliary cam between said switchactuating member and said cam siuface, a stop on said switch-actuating member for limiting the rotation of said cam follower in the direction of rotation of said cam means, resilient means for biasing said cam follower against said stow means other than said cam follower for limit tates back against its stop and moves the switchactuating member away from said cam surface with a snap action.

2. In a time switch, a rotary cam member, a timing motor for rotating said cam member, a switch-actuating member movable towards and. away from the axis of rotation of said cam memher, a cam follower secured to said switch-actuating member and resting upon said cam surface, said cam follower serving to normally maintain a definite maximum space relation between said switch-actuating member and the cam surface in contact with said cam follower and to move the switch-actuating member in accordance with the contour of said cam, said cam follower, however, being movable with respect to switchactuating member in a manner to decrease the space relation between said switch-actuating member and the cam surface in contact with said cam follower, a spring for opposing such movement of said cam follower with respect to the switch-actuating member, said cam having an abrupt rise in its cam surface which, when moved against and past said cam follower, causes the aforesaid movement of the latter with respect to said switch-actuating member, and other means for preventing movement of the switchactuating member towards the cam at this time, whereby the cam follower is lifted over the rise in said cam and then quickly returns to its normal condition to quickly move the switch-actuating meml er away from said cam.

3. In a time switch, a rotary main earn, a timing motor for rotating said cam, a movable switch-operating member, a cam follower between said switch-operating member and the surface of said cam to normally move the switchactuating member in accordance with the con tour of said cam as it is rotated said cam follower, said cam flowwer comprising an auxiliary cam pivoted to said switch-actuating member, a stop on said switch-actuating member for limiting rotation of said auxiliary cam in one direction, a spring for biasing said auriilai'y cam aganst said stop, said spring also serving to bias said switch-operating member with its follower against the surface of said main carsaid main cam having an abrupt rise which,

.nen rotated in contact with and past the cam follower, causes the latter to turn on its pivot against the bias of said spring to lift the cam follower over the rise in said main cam without moving said switch-operating lever until the cam follower has cleared said rise, said auxiliary cam then returning against its stop and wiping over the nose of the rise in said main cam to quickly move the switch-actuating member away from said main cam, and means for preventing movement of the switch-actuating member towards said main cam while the cam lifted over said rise.

FRANCIS W. TRUESDELL.

follower is being

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