US2487154A

US2487154A - Time switch

Info

Publication number: US2487154A
Application number: US661020A
Authority: US
Inventors: Tom C Lloyd
Original assignee: ROBINS AND MYERS Inc
Current assignee: ROBINS AND MYERS Inc
Priority date: 1946-04-10
Filing date: 1946-04-10
Publication date: 1949-11-08
Anticipated expiration: 1966-11-08

Description

Nov 8, 1949 c, LLOYD 2,487,154

TIME SWITCH Filed April 10. 1946 2 Sheets-Sheet l Kg r l Ike, 6,

12 12 5 i T 11v VEN TOR.

25M C Lam a.

ATTQEN EVE.

Nov. 8, 1949 T. c. LLOYD TIME SWITCH Filed April 10 1946 2 Sheets-Sheet 2 s u n T .6 INVENTOR. & J 75M 5:11am.

ATTORNEYS.

Patented Nov. 8, 1949 TIME SWITCH tion of Ohio Lloyd, Springfield, Ohio, assignor to Rob- & Myers, Inc., Springfield, Ohio, as corpora- Appllcation April 10, 1946, Serial No. 661,020

My invention relates to time switches which can be set to open or close an electric circuit after a selected interval of time.

The usual structure of this character embodies a small synchronous motor with connections in the way of gearing and cams to operate the switch element. In older days a spring controlled escapement mechanism or time clock has been used for this purpose. These structures are satisfactory but too expensive for many devices. For example, with a small domestic electric fan when it is desired to cut off current therefrom after a given interval of time, the time switch is almost as costly as the fan itself.

One of my objects is to provide a time switch device which can be purchased on the market independently of any piece of electrical equipment and simply plugged into the receptacle from which the device derives its electric current supply, whereupon the supply cord to the device can be plugged into the time switch mechanism. Such a device can simply be removed from its plugged in connections, and the device plugged back into the wall receptacle when no timing is required. When inexpensive, the householder may provide himself with several of these devices for various uses when and if called for and readily shift them from place to place.

Another object of my invention is to provide a very inexpensive, 'but yet sufiiciently reliable time switch device to serve the above purpose. For the timing element I provide a bimetallic strip and a small heating coil. I use the bimetallic strip to actuate step by step a device which is settable by manipulation for elapsed time, and in connection with establishing periodic heating and cooling of the bimetallic strip I have evolved a mechanical arrangement whereby when an actuating stroke of the strip has been completed there is a quick break in the heating circuit, and thereafter when the strip has cooled there is a quick make of the heating circuit.

So far as I am advised there has, in the past been no mechanical arrangement for periodic heating and cooling of a bimetallic strip acting as an interrupter, where the amount of movement of the strip to break circuit through its heater has been other than very slight, or where a quick break and make was established. According to my invention I employ a long stroke for the bimetallic element and in addition provide for a quick make and break.

In the form of my invention principally illutrated in the drawings as exemplary of the invention I have not shown the use of any means to 3 Claims. (Cl. 172-126) 2 compensate for ambient temperature. In other words, since the actuating element for the master switch in the device is a piece of bimetallic material, the initial conformation may become distorted in a very warm room. differently than in a cold room, and if there is no compensation for the location of the switch tripping point and latching point there are conditions wherein the initial step of movement in a very hot location may be shorter than normal and even extreme conditions when the device will not operate. I have illustrated modifications which provide for such compensation, but under all ordinary conditions the device illustrated will operate with sufllcient accuracy to take care of opening a heating or fan circuit or the like within a few percent of the required elapsed time for which the device .is set.

In the drawings Figures 1, 2, 3, and 4 are diagrams showing the various positions of the timing devic during a single cycle of heating and permitting the bimetallic element to cool down.

Figure 5 is a front elevation of the device with the lid removed.

Figure 6 is a section on the line 6, 8 of Figure 5 with the lid in place.

Figure 7 is a perspective of the device.

Figure 8 is a wiring diagram.

Figures 9 and 10 are detailed diagrams showing compensation provisions for the device already illustrated.

The diagrams of Figures 1 through 4-constltute the meat of the invention, the details of construction of the exemplary structure are preferable, but not essential. Neither is it essential that the bimetallic element or elements used in the device should 'be of straight line construction since they could be spirals, if desired. Referring then to said diagrams, the switch operating device is in the form of a toothed disc, the problem being to advance it step by step with lapse of time, using a thermostatic means for that purpose.

The disc I is provided with teeth 2 proportioned for the distance through which the thermostatic element is intended to move. The number of teeth (for any one thermostat being accomplished by changing the size of the disc) is selected to provide for the total time lapse through which the disc is to move. A switch operating point is indicated at 3 whereby the disc will operate a desired switch to open or close the same. Connected across the circuit controlled by the switch is a resilient contact finger 4 which rides on the oothed edge of the disc, which in the diagram accuse is pulled step by step counterclockwise, and can be set by manually imparting a counterclockwise movement during which the contact finger 4 will ratchet over the face of the disc. The bimetallic strip is connected to a heater coil 8 and thence to the other branch of the circuit to be controlled, and will bow downwardly .(in the diagram) when heated. This pulls down on a pawl or hook ended arm 1 secured to the end of the strip which arm like the finger engages the toothed edge of the disc. When the thermostatic element pulls down on the arm I, the toothed wheel is pulled down. In Figure 2 is illustrated an"intermediate position. In this position it will be noted that the teeth of the disc act to keep the contact finger 4 against the hooked end 8 of the arm I.

Finally the bimetallic strip will reach the bowed position which represents the time lag desired and pre-arranged, whereupon the disc will have been turned a full step and the contact finger 4 will snap over the ledge of the next tooth, as shown in Figure 3.

This will break the by-pass circuit through th contact finger i through the hooked shaped arm 7 and through the heater coil 8 to the other branch of the circuit and cut all current from the heater 6 for the strip.

The strip will then start to cool down, and it will be noted that the break caused by the snapping over of the contact finger will be a quick break, without sparking etc. The cooling bimetallic strip will begin to straighten up again causing the hooked end of the arm to travel up along the toothed disc which is held against retrograde movement by the contact finger ii. The intermediate position is shown at Figure 4;, but the control point for the main switch which is operated by the disc will remain in the position which it took in the diagram oi" Figure 3.

Finally when the strip has stra'ghtened it will be back to the position of Figure 1 whereupon the hooked end will snap in over the tooth, make a quick contact with the contact finger, and reestablish the circuit through the finger, hooked arm, bimetallic strip and heater coil, thus, initiating a new cycle.

The elapsed time for the switch control will then be a factor of the period that it takes for the strip to bow down and cool again to more straightened position. The disc w.ll be calibrated according to this time, and by setting the point 3 by manipulation of the disc, the elapsed time when it will reach a position of operation of the main switch can be set.

Now, if it is desired to compensate for ambient heat, it will be possible readily to mount the support for the contact finger 3 and a bimetallic strip 9 as indicated in the diagram of Figure l which will respond only to the ambient temperature.

-It will also be possible to change the location of the point 3 by means of a bimetallic strip or coil. When this is not done the device may vary slightly in its operation during the initial stroke, but for general use these compensations are not required.

Turning now to the wiring diagram Figure 8, the input to the main circuit is at 9 and iii, the main switch to be controlled is at ii, the bypass in which the heater and thermostatically operated element is located is indicated at i2, and a device using the current of the main circuit is shown at I 3. When switch H is opened, it will out out the thermostatic circuit.

The views in Figures 5 and 6 are larger than the device will ordinarily be. A simple construction as shown embodies a molded case It, and a molded lid i5 to be attached to the case by screws I8. The top wall of the case is cut away as at H, and a lip I8 is formed on the lid to fit into said cut away space except at its inner end, with the result of leaving a slot through which the dial oi the toothed wheel will project. Molded integral with the case is a pad 19 for mounting the bimetallic element and heater coil, and pad 20 for mounting the contact finger, and pair of posts connected by a reenforcing web as indicated generally at 2i on which to mount the two switch arms, and a round stud 22 on which the toothed wheel and dial are located.

The toothed wheel as indicated at 23 is merely set over the stud 22. The dial element 26 of this wheel is in the form of an integral flange (when desired for cheapness). The lid and theswitch contacts hold the wheel in place.

Mounted on the posts at 2i are the two switch arms 25 and 26. The arm 26 is connected by wire 21 which passes into the flexible cable casing 28. This cable has a forked plug 28a on the end for introduction into an electric outlet receptacle. The other wire 29 in this casing passes from the cable casing across the top of the case Ht where it is connected with the contact finger to be described. From this contact, finger a wire extends tothe fitting 36 designed for reception of a pronged plug which will be on the cable attached to the electrical device which is to be operated from the main circuit of the system. The other side of this fitting is connected by wire 3! to the other switch arm 25.

The switch arm 25 is relatively rigid, and the switch arm 25 is resilient and tends to hug the face of the toothed disc. On the face of the disc is located a cam rib 32, preferably integral which has a gap at 33. When the disc is moved to position where the gap 33 is opposite the overlapping tips of the two switch arms, the arm 25 will drop away from the arm 25 thus opening a circuit between the two arms. When ths circuit is opened the current is disconnected from the entire apparatus until the toothed disc is manually moved again, which is done by fingering the projecting edge of the dial. At all other points the rib 32 will hold the contacts together. The dial will be calibrated on its edge, as indicated at St, and preferably a zero point will be formed by a projection 35 on the lip of the cover plate.

The thermostat is formed of a bimetallic strip 5 mounted on the pad 99. this bimetallic strip car-= rying the heater coil 39. A connector rivet 38 in the tip of the bimetallic strip serves to mount the hooked wheel operating arm on the bimetallic strip, as will be noted. A flexible connection to connects the switch arm 25 to the heater coil. The other end of the heater coil is connected to the fixed end of strip 5.

Referring now to the hooked arm. As shown at i it extends up from the tip of the bimetallic strip 5 where its hooked end 8 engages in the teeth of the toothed disc. By its natural resilience the end of the arm tends to engage the toothed portion of the disc. The contact finger i mounted on pad 20 resiliently engages the teeth of the disc also.

The operation of the device will be apparent from the previous discussion of the diagrams.

As shown in the views of Figures 9 and 10, it will be readily possible to compensate for ambient heat in connection with the device now described, if greater accuracy is required. Thus, as shown be shifted by mounting the arms 25 and 26 on a 1 rocker held on one of the mounting studs 2|. This rocker is not secured to the other stud, but merely rests upon it, and the rocker 5| is pivoted to the first stud. A bimetallic strip 52 engages a forked end of the rocker 5i, and under the infiuence of ambient heat will shift the locus of the tips of the two arms clockwise as indicated by small arrows on Figure 9.

In Figure is shown a mounting plate 54, which may be placed back of the toothed wheel on its mounting stud. This plate will pivot on the mounting stud 22 and is controlled in its position thereon by means of a bimetallic strip 55. The mounting plate 56 for the two switch arms 25 and 26 will be placed on this plate, and the mounting pad for the contact finger, as indicated at 5'! will also be mounted on this plate.

The efiect of ambient temperature on the bimetallic strip 55 will then shift the initial position of both the contact finger and the switch points to correspond with the initial position of the tip of the bimetallic strip 8.

It will be evident that various modes of compensation may be provided for, but with a bimetallic strip 5 selected for small movements within the practical range of room temperatures, it will not be necessary to do so except for conditions where great accuracy is required.

I have illustrated only devices where a circuit is opened by the thermostatically actuated wheel. It will be apparent that the wheel could be employed to make a circuit instead of to break it, without change except for the cam. It might be desirable where a circuit is to be closed to use the disc also for opening the heater circuit when the point has been reached that closes the main circuit. Illustrations of wiring diagrams etc. for these simple modifications will not be required.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a time switch a toothed wheel having means operated thereby to actuate an electrical switch, a bimetallic element and heater therefor, an arm on the bimetallic element having a hooked end to engage the teeth of said wheel, a resilient fixed pawl for engaging the teeth of said wheel, said fixed pawl located to lie between said hooked end and the the teeth of the wheel, the fixed pawl and hooked end having faces which are in contact with each other when the bimetallic element is cool, electrical connections for the heater established by said contact, the bimetallic element arranged to move the arm so as to pull the toothed wheel around in the direction not opposed by the fixed resilient pawl, whereby when the wheel has been pulled far enough for the fixed resilient pawl to snap over a tooth of the wheel, electrical connections to the heater will be broken causing the bimetallic element to cool, and the hooked end of the arm to move along the periphery of the toothed wheel until it snaps over the same tooth thus reestablishing electrical connections.

2. In a time switch a toothed wheel having means operated thereby to actuate an electrical switch, a bimetallic element and heater therefor, an arm on th bimetallic element having an end to engage the teeth of said wheel, a resilient fixed pawl for engaging the teeth of said wheel, said fixed pawl located to lie between said arm end and the teeth of the wheel, the fixed pawl and arm end having faces which are in contact with each other when the bimetallic element is cool, electrical connections for the heater established by said contact, the bimetallic element arranged to move the arm so as to move the toothed wheel around in the direction not opposed by the fixed resilient pawl, whereby when the wheel has been moved far enough for the fixed resilient pawl to snap over a tooth of the wheel, electrical connections to the heater will be broken causing the bimetallic element to cool, and the end of the arm to move along the periphery of the toothed wheel until it snaps over the same tooth thus reestablishing electrical connections.

3. In a time switch a toothed wheel having means operated thereby to actuate an electric switch, a heat responsive element and heater therefor, an arm associated with said heat responsive element and having an end to engage the teeth of said wheel, a resilient fixed pawl for engaging the teeth of said wheel, said fixed pawl located to lie between said arm and and the teeth of the wheel, the fixed pawl and arm end having faces which are in contact with each other when the heat responsive element is cool, electrical connections for the heater established by said contact, the heat responsive element arranged to move the arm so as to move the toothed wheel around in the direction not opposed by the first resilient pawl, whereby when the wheel has been moved far enough for the fixed resilient pawl to snap over a tooth of the wheel, electrical connections to the heater will be broken causing the heat responsive element to cool, and the end of the arm to move along the periphery of the toothed wheel until it snaps over the same tooth thus reestablishing electrical connections.

TOM C. LLOYD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,275,780 Spurr Aug. 13. 1918 1,780,302 Koch et a1 Nov. 4, 1930 2,066,145 Fink Dec. 29, 1936 2,355,041 Baak Aug. 8, 1944 2,417,368 Little Mar. 11, 1947