US2212387A - Time switch - Google Patents

Description

1940- n. G. CAMERON 2,212,387

mm swITcH Qriginal Filed Dec. 30. 1937 04) THEE/703747 Inventor-w Dofiald G.Camer-on, by Wan M76 His Attorney.

' Patented Aug. 20, 1940 UNITED STATES PATENT OFFICE TIME SWITCH Donald G. Cameron, Lynn, Mass, assignor to General Electric Company, a corporation of New York 7 Claims.

My invention relates to time switches and although not limited thereto is particularly designed for use in systems of automatic control for domestic heating apparatus.

In. the form shown the time switch employs two sets of time controlled contacts. One set determined adjustable times in a given period of time such as a 24 hour period and may thus be used to shift control from day to night thermostat and vice versa. This switch is of simple construction and operation. The lines of the circuit controlled may be connected directly to the switch contact blades'and manual means is provided to move these blades to permanently open or to permanently closed position to suspend automatic control. The other set of time controlled contacts is arranged to close a circuit for a short interval of time periodically. The number of times that this switch is closed during a 24 hour period may be adjusted and also the duration of closure may be adjusted in a novel manner This set of contacts may thus be used to momentarily start up the furnace at intervals and prevent a coal fire from going out entirely in case furnace operation isnot otherwise called for.

This application is a division of my application,

S. N. 182,539, filed December 30, 1937 and assigned to the same assignee as the present application. My prior application contains claims classifiable in class 200, subclass 39. The present application contains claims classifiable in class 200, subclass 27. Another divisional application filed concurrently herewith contains claims classifiable in class 161, subclass 1.5.

-The features of my 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 in which Fig. 1 represents a perspective, somewhat exploded vie v. of my improved 'switch and one possible way of connecting it with a furnace control system. Figs. 2 and 3 represent different positions of the cam-operated switchshown at right in Fig. -1. 7

Referring to Fig. 1, the time switch is driven by a synchronous motor indicated at I0. .The motor is connected through a speed-reducing gear train H and a friction clutch I2 to a shaft l3 so as to drive said shaft at one revolution per hour in a clockwise direction. A minute hand ll of a clock is mounted on the front end of this shaft. Concentric with shaft I3 is a hollow hour hand shaft I5 on which is mounted the hour hand I6,

and this shaft I5 is driven from shaft l3 in a clockwise direction one revolution in twelve hours through the usualbackgears ll, I8, l9 and 20. Shafts I3-and l5 have been broken away over the main time switch mechanism to more clearly expose the latter. The clock hands will cooperate is employed to open and close a circuit at prewith the usual clock dial "(not shown) to in- I dicate time.

The main time switch has its operating mechanism supported by a clock plate 2i which has been mostly broken away in the drawing. EX-

tending through this plate are bearings. 22 an i 23 for rotatively supportingcam shafts 2d and. 25. These cam shafts are driven from the hour ,is compressed between disk 35 and plate 2i.

Cam iii cooperates in a similar manner with a cam-follower 3i projecting to the rear of an adjustable dial plate 38. Shafts 2d and 25 may slide endwise in their bearings as well as rotate therein.

Cam shaft 2d together with cam plate 3D is at all times urged axially towards the front with The cam tit cooperates with a cami hand shaft it in a clockwise direction, one revolu- Y the cam plate against cam-follower finger 3t by a spring 39, which spring is also a resilient switch contact. This spring switch member has its lowl er end rigidly Sl Also, its lower end constitutes the al to which the external circuit wire may be connected. A reduced rear end portion of shaft it rests against the spring con-= tact member 39 near its upper end adjacent contact 60 so that, as shaft 24 is moved endwise to the rear or to the front bycaml 30, contact 4G is likewise moved back and forth. d

Shaft 25 likewise has reduced rea'r extension against which a spring switch contact member 4| presses. Member 4i has its upper end extending in overlapping relation and in front of contact 40 and is provided with a cooperating contact 42 on its rear face, The lower end of contact member 4! is likewise rigidly supported in a support insulating member 4! from 39 and constitutes the other line terminal 33 of the switch. The slope of the cam surfaces are such as to produce a slow, substantially uniform rearward movement of shafts 24 and 25, as these shafts are rotated ward movement of shaft is made use of to move 1 contact 42 away from contact 40 to open the switch. Dial plate 35 has time graduations over part of its periphery in order that it may be set with respect to a fixed index or pointer 43 to indicate the time when cam-follower 34 will drop over the step in cam to close the switch. In

the example given the switch is intended to close in the evening between, say 8' p. m. and midnight,

and the graduations on dial 35 will thus read from 8-12 and the indication opposite pointer 43 will designate the time as given by the clock hands when the switch will close. The opening and closing-adjustments are independent of each other. x

The switch is intended to open in the morning, say between 4 a. m. and 8 a. m. and dial .38 will have the approximate part of its periphery graduated accordingly and otherwise arranged to be set so that the switch will open at a time designated on such dial. The shape of the cam surfaces and the spacing of contacts and 42 are such that within the time setting range indicated,

the switch will remain closed at night and will remain open during the day. That is, the device may be set to close the switch as early as 8 p. m; in the evening and have it remain closed until yas late as 8 a. m. in the morning and remain open until 8 p. m. again, or, it may be set to be closed between 12 midnight and'4 a. m. and remain open the-remainder of the 24 hour period,

etc. When open, the contacts remain at about the same spacing although both contacts are gradually moved to the rear during the open and closed periods. The setting range may be extended somewhat beyond the limits indicated above but generally, for the purpose for which the switch is intended, the range given will suffice.

Associated with the switch is a manually rotatable shaft 44 having an insulated cross bar 45 at its rear end. This device is to lock the ;switch in either the closed or open position or to permit automatic operation as desired.

' The insulated cross bar 45 cooperates with fingers 45 and 41 which are integral with and extend downward from joints on the upper portions of switch members 35 and 4| which are' nearer the contacts than the joints wheretthe automatic control operates on these contact members. These fingers are'bent away from the cross bar. adjacent thereto so as to form cam surfaces and to permit of a camaction when the shaft 44 and cross bar 45 are turned by hand. In the horizontal ihtermediate or neutral position of the crossbar sho'wn,'it does not inter fere with the automatic opening and closing of the switch at contacts 40 and 42. If the cross from the end of. shaft 25 to 'close the switch inall bar be turned to the left so that its right end is raised and its leftend lowered through-an angle of about 45 degrees, finger 41 will be forced to the rear, forcing contact bar 4| to the rear away.

positions of camiill. On the other hand, if bar 45 be turned about 45 degrees clockwise from-the position shown, finger 45 contacts bar 45and relay is energized, it sets into operation a stoker :vent this, the switch mechanism shown at the upper right in Fig. l is utilized. Its function is to assur'ethat the furnace relay 50 .will be energized for a short period of time cut in the plate 2| and serves as a resilient lock to hold shaft 44 and cross bar 45 in any one of the three positions mentioned until turned to some other position by hand. 1 It is thus seen that I have devised a simple switch having few partsbut onewhich accomplishes theseveral purposes described in a reliable manner. r

I will now explain how the switch mechanism 15 thus far described may be used in a furnace control system. At 50 I h'ave shown a relay which may be termed afurnace control relay. For instance, it may be assumed that when this 2'0 motor and a draft fan to increase the heat given out by a furnace. The relay is under the control of day and night thermostats 5| and 52. It may be assumed that thermostat 5| is set so as to close its contact at 53 when the temperature drops below 70 degrees F. and to open its contact when the temperature rises to 71 degrees F. It may further be assumed that the night thermostat 52 is set so as to close its contacts at 5l-when the temperature drops below 64 degrees Fr, and to open its contacts when the temperature rises to 65 degrees F.- The time switch already described controls a transfer relay 55 which serves to transfer the control of the furnace relay 55 from the day thermostat 5| to the night thermoday thermostat 5|. at some time in the morning, depending on the setting of dial 35. To this end, relay 55 is energized from a source 55, when switch contacts 40-42 are closed. This connects furnace control relay 50 with the night thermostat 52 through the upper contacts of relay 55 and source 55. Thus, during the night time, whenever thermostat 52 calls for heat, relay 55 will be energized. During the day time, when switch contacts 4|l42 are open, relay 55 is deenergized and the furnace 'controlrelay 50 is under control of the day thermostat 5| through the lower set of contacts of relay 55. Now, it sometimes happens .when the tem- '.perature is mild, particularly when the furnace isoperating on the night thermostat, that no heat is called for by the thermostat for long periods of time. Thismay cause a coal furnace fire to go out or to so nearly so out as to fail to respond with any degree of desirability to a subsequent closing of the thermostat." To preperiodically, so as to prevent the fur'nacejflre going out under conditions where it might otherwise do so, but without producing any-great .5 amount of actual heating. To this end I have provided a pair of contacts 51 and 5B operated by the timer motoralflfto momentar energize ,5 furnace control relay 50 for afew minutes eve several hours,'the duration of closure of the con- 70 tacts and the interval between closure times both being adjustable to correspond with the several different kinds of conditions likely to be met with in practice. I r r This switch mechanism, includes acam shaft 59 driven from gear I 8 and some intermediate gears so as to operate at a rate of one revolution in three hours, for example. The cam shaft has on it several cans members, three in this instance, designated 60, SI and 62.

These cam members operate counterclockwise.-

Member 60 has two steps, member 6| three steps and member 62six steps. The steps of individual cams in each cam member are equally spaced.

The contact supporting block 63 may be slid along its supporting post 64 parallel with cam shaft 59 so as to cause the contact mechanism to be operated by any one of the three cam members that may be selected. The individual cams on all of the cam members are the same, that is the maximum and minimum radii of the steps are equal in allcases.

mechanism is opposite cam member 62, it will be operated every half hour, if opposite cam memher 6|,it will be operated every hour, and it opposite cam member 60, it will be operated every hour and .a half, but the individual operations will be similar in all cases. It is seen then that by moving the contact block 63 and the parts carried thereby along post 64, the time interval also permits the block to be rotated clockwise from the position shown in order that it may be moved endwise. The upper metal part 81 of which finger 65 is a part, is provided with'three notches 88 in its forward edge. These notches are spaced apart the distance of the cam members on camshaft 59 and serve to lock the contact block in its three operative positions with respect to the three cam members. This looking is done by causing the appropriate notch to slip over a projection 69 in the plate III. As

represented in' the drawing the block 63 and its contact mechanism is positioned in operative relation with cam 62 andhence the contact device will be operated every half hour; To adjust for operation every hour the" contact block and the parts carried thereby are rotated slightly about post, 66 in a clockwise direction until the notch in plate .6! which is engaged with the locking projection '69 is free of said projection. Then the contact block is slid along post 64 towards the front until the middle notch in plate 67 is in line with plate it and its looking extension l '89. Then the contact block is allowed to rotate counterclockwise on'post tilt under the light ten-= sion of spring 64' until the block is locked from further endwi se movement by engagement oi projection 89 in the middle notch of plate 8?. The contact finger is then aligned with cam 6| and operation of the contact device will cc?- cur once per hour.

The aontact finger arrangement is designed so that the relation between the time during which the contacts are closed and the time during which they are open during a complete cam operating cycle may be varied over a wide range in a simple manner. The lower contact finger B'I is of metal and is relatively stifl and is sufficiently short that it never engages the rotary operating "cam. This finger 51 has a contact button on its upper free end opposite 'a cooperating contact button on the lower side or contact finger 58. Contact Hence, if the contact finger 58 is also of metal, is relatively flexible and is long enough to engage with and at times to be moved by the operating cam. Contact fingers 57 and 58 have their right hand ends secured in the insulating block 63 and insulated from each other therein. The wires leading to the external circuit controlled by this contact device are connected to contact fingers 51 and 58 as indicated in Fig. 1. Above contact finger 58 is another finger II extending from block 63 out over the operating cam. Finger H is preferably of insulating material and is relatively stiff and its free end extends beyond the free endof contact finger 58 by an adjustable amount.

In the structure shown cam-follower H is an extension of a fiber strip 12 seen projecting to the rear of block 63 from beneath plate 67. Strip 12 is slotted to accommodate a screw 13. When the screw is loosened the strip 72 may be adjusted to cause its end finger H to extend a greater or less amount beyond the endof contact finger 51. It is this adjustment which determines the relative length of time on and time off of the contact device. The resilient finger 64 which engages with the under side of post 66 is suitably secured to the block 63 between plate 61' and insulating strip 12. The block 63 is free to turn on post 64 and in the operation of the contact device by the cam member there is a slight back and forth rotational movement of block 63 on post 54 as a pivot, such rocking movement however is insufilcient to raise plate 61 so as to disengage a notch 68 therein from projection 69. The extent of this rotational movement corresponds substantially to the amount by which insulating finger H is raised and lowered by engagement with the high and low parts of the cam. Thus, Fig. 2 shows the finger H in ap-' proximately its highest position and Fig. 3 shows this finger in approximately its lowest position.

The rocking movement of the contact block 63 and the parts carried thereby is thus largely controlled by the relatively slow rise of finger M by rotation of cam 62 and the sudden drop of finger ii over the step in the cam. As pointed out above, insulating finger ii and the short lower contact finger 57 are relatively stiff and hence both move up and down together with the rocking movement of block 63. The intermedi ate contact finger 53 is relatively flexible and is normally biased, as shown in Figs. 1 and 2, to close its contact on the contact of finger 51. However, when the finger 'it drops off of tl estep in the cam and contact finger 5? is lowered, the flexible contact finger he is prevented from following finger 5i downward by reason oi it striking the cam surface as shown in Fig. 3, and hence the contacts open. Thus it is seen that when the insulating contact finger 1i rests directly on the cam the contacts are closed (Figs.

l and 2) and when contact finger 58 rests on the earn the contacts are open (Fig. 3) It is further evident that when finger 58 drops oil the step in the cam the contacts close with a quiclr action and when insulating. finger it drops off the step in the earn, the contacts open with a quick action. The contacts thus open and close quickly and without hesitation which is desirable.

Now it will be seen that the time during which the contacts are closed during an operating cycle is the period between the dropping of fingers 58 and H over the same step in the cam. Also the time during which the contacts are open is the period between the dropping of finger H over one fingers H and 58. In the present embodiment step in the cam and thedropping of finger 58 over the next approaching step. in the cam. If

we make fingers H and 58 exactly the same length so that they drop over the same step together the contacts will remain open continuously. Hence, we can reduce the on period by any desired amount down to zero by decreasing the difierence between the effective lengths of ".vary the relative duration of' on and oil periods during an operating cycle by adjusting the effective length of finger 'll.]

Let us assume that this mechanism is adjusted foran' operating cycle of once per hour and that the on period is adjusted for a duration of one minute. This assures that regardless of the operation of the day and night thermostats SI and 52, the furnace control relay 5| wilbbe energized at least one minute every hour, and this will avoid the inconvenience of having the furnace go out entirely in case no heat is called for by the thermostats, but without producing any apreciable amount of heating. It

may often happen that the circuit of relay 50 will be closed at contacts 51 and 58 at a time when the relay 58 is already energized .by-one of the thermostats. This will do no harm since. the connection made by contacts 51 and 58 is -merely' a parallel connection ,to the one closed.

by the connected thermostat.

. The manual control 44 of switch contacts 48 and 42 is desirable in the application described.

' For example, when the family retires later than usual in the evening, turning switch 44 to off position assures that the temperature will be maintained by the day thermostat until switch .44 is again turned to neutral position. When the family is to'be away from home during the day time, switch 44 may be turned to on position, which will then assure the maintenance of a temperature according to the setting of the night thermostat until such time as'switch 44 is again turned to neutral position. Such use of switch 44 does not disturb the setting of dials 35 and 38 or of the thermostats or the function of the contacts 51 and 58.

It is thus seen-that I have provided afrelatively simple, yet convenient and reliable time switch for taking care of all of the time functions met with in furnace control. Although the switch is particularly suited for furnace control applications, I do not wish to limit my' invention to this particular use. '3

All of the adjustments heretofore described are made independently of each other. For example, adjustment of cam finger 34 in no way alters the result of. adjusting the number of cycles'of operation of contacts 51 and- 58 in a given 24 hour time period or the relationbetween ratio between the 24 hour time period and the y the on and of! period of contacts 51 and 58 during their cycle of operation. By making the 5 time cycles of operation of contacts 51 and 58 during such period an integer, the sequerice of operation of all contacts will remain the same in subsequent 24-hour periods for any given adjust'ment. This is not important in the application described but will be important in some process applications where a given program or sequence of operation is to be repeated on a device such as relay switch 50 under the joint control of both sets of synchronized contact mechanisms;

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention-together with the apparatus which I now consider to represent the best embodiment thereof but I. desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

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

1. In a. time switch a rotary stepped cam, a contact mechanism operated by said cam, said contact mechanism comprising a supporting block pivoted for rotation on an axis parallel to the axis of rotation of said cam and supporting a relatively stifi lower contact member extending toward but not reaching said cam; a relatively flexible intermediate contact member extending toward and reaching said cam and a relatively stiff upper cam follower member extending towards and supported by said cam, said contact members having coopeartingi contacts between them normally biased to. a closed position, the upper cam follower member extending beyond the intermediate contact member by an adjustable amount, the arrangement being such that as the cam is rotated'and the cam follower is raised and lowered thereby, the supporting block is oscillated about its pivot to raise and lower the lower contact member substantially in accordance with the rise and fall of the cam follower, and the intermediate contact member rises and falls with respect to the lower contact member to break and make contact therewith,

such contact being made when the intermediate contact member drops over a step in the cam and being broken when the cam follower drops over the same step in the cam.

2. In a time switch a contact mechanism comprising a rotary cam having a step therein, a contact block mounted for rbtation about an axis parallel to the axis'of rotation of the cam, a relatively stiff cam follower extending from said block and supportedby the periphery of the cam so as to be raised and lowered thereby to oscillate the block about its axis of rotation when the cam is rotated, a relatively flexible contact member extending from said block and resting on the cam beneath the cam followena relatively stiff contact member extending from said block beneath the relatively flexible contact member towards said cam but terminating short of the cam, cooperating contacts on'saidcontact members normally biased to a closed position and means for ing such operating, cycle depending upon the diflerence in the lengths of the cam follower and flexible contact member.

amass? 3. In a time switch, a cam shaft having a plurality of spaced cams each with a different number of similar steps therein, a rod parallel to the cam shaft, a contact block slidable along and rotatable about said rod, contact and cam follower fingers extending from said bloclr to be operated by any one of said cams depending upon the position of said block along said rod, locking means for retaining the block and its cam contacting fingers in operative relation with the selected operating cam, said contact mechanism being arranged to change the relative positions of the contact fingers and the rotary position of said block on said rod as the mechanism is operated by a cam, a pair of contacts carried by said fingers which are opened and closed by such operation and means for adjusting the relative length of certain of said fingers to vary the time of closure.

of said contacts during each such operation.

4. In a time controlled device, a cam, a movable support, a pair of control members extending therefrom, one of said control members being positioned between the second one and said cam,-

means urging said support to move in a direction to engage said control members with said cam, said members being normally engaged with each other while on a lobe of said cam and thereby assuming one control position and being disengaged from each other while the second one is on said lobe and the first one is past said lobe, said members being proportioned for the first one to pass said lobe before the second one during rotation of said cam.

5. In a time controlled device, a cam, a movable support, a pair of control members extending therefrom, means urging said support to move in a direction to engage said control members with said cam, said control members being normally engaged with each other with one of them superposed on the other one while they are on the lobe of said cam and being disengaged from each other while one of them is on said lobe and the other one is relatively past the lobe, said ried by saidsupport, said third member and the one of said 'two control members which underlies the other one making contact with each other during the time between successive passage of said control members past said lobe.

6. In a device of the class described, a plurality of cams, a switch to be actuated thereby, said switch comprising a support, an actuating arm extending therefrom and coacting with one of said earns, a switch arm extending therefrom, coacting with said cam and normally retained engaged with said actuating arm by a lobe thereon, said lobe being movable past said switch arm, whereupon prior to said lobe moving past said actuating arms, said switch arm disengages said actuating arm, said support being movable to a position where said arms coact with another of said cams, a contact arm carried by said support, and switch contacts carried by said contact arm and said switch arm and operable by said actuating and switch arms to assume one position when the switch arm is engaged with the actuating arm and another position when it is disengaged therefrom. I

T. In a device of the class described, a cam, a switch to be actuated thereby, said switch comprising a support, an actuating arm extending therefrom and coacting with said cam, a switch arm extending therefrom coacting with said cam and normally retained engaged with said actuating arm by a lobe thereon, said lobe being movable past said switch arm whereupon prior to said lobe moving past said actuating arm, said switch armdisengages said actuating arm, a. contact arm carried by said support, switch contacts carried by said contact arm and said switch arm and operable by said actuating and switch arms to assume one position when the switch arm is engaged with the actuating arm and another position when it is disengaged therefrom, and means for changing the relative positions of said arms 'to vary the time period between movement of the cam successively past the arms.

DONALD G. cAMmton.

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