US2611429A - Time-controlled switch - Google Patents

Description

2 SHEETSSHEET l INVENTORS:

41% ATTORNEYS C G REYNARD ET AL TIME-CONTROLLED SWITCH Sept. 23, 1952 Filed Jan. 26, 1950 P 1952 c. e. REYNARD ETAL 2,611,429

TIME-CONTROLLED SWITCH Filed Jan. 26, 1950 2 SHEETS-SHEET 2 @INVEN TiJRS. %7

ATTORNE Patented Sept. 23, 1952 TIME-CONTROLLED SWITCH Chauncey Gordon Beynard and Harry L. Hart, Fort Wayne, Ind., assignors to Basic Products Corporation, Fort Wayne, Ind., a corporation of Indiana Application January 26, 1950, Serial No. 140,648

12 Claims.

This invention relates to mechanism for achieving automatically the actuation of an electric switch at a predetermined future time. More particularly, it concerns simple apparatus operable automatically to actuate an electrical circuit at a predetermined time in the future, leave the circuit actuated for a predetermined time in terval, and then de-actuate it.

Apparatus for the accomplishment of such tasks is well known in the prior art, and many useful applications have developed for such equipment. Time-controlled switches are, for example, used in the automatic control f electric ovens, for accomplishing automatic defrosting of refrigerators, for starting heating plants at predetermined hours, and many other such applications.

Prior-art apparatus of the sort under consideration has in general been quite complicated, involving trains of gears and elaborate mechanical linkage. Thestructure of the present invention, by way of contrast, accomplishes results superior to those of prior-art structures and at the same time is far simpler in mechanical structure than any of the prior-art devices.

An object of the present invention is to provide a time-controlled switch having readily accessible manual adjusting means whereby it is possible to fix a future time at which an electric switch will be opened or closed, as the case may be, and to fix accurately the duration of the interval during which the switch will be held in its opened or closed position.

Another object of our invention is to provide a time-controlled switch wherein a single, manually adjustable dial combines the functions of indicating the correct time of day and permitting selection of the future hour at which the controlled electrical circuit will be actuated.

A further object of our invention is to provide a time-controlled switch structure in which actuation of the electrical switch is accomplished by direct lever linkage from a cam follower carried by the time-of-day dial, without the interposition of gears or other mechanical expedients.

Still another object of our invention is to provide, in a time-controlled switch, adjustment means actuated by an interval-setting dial to change the conformation of the cam face engaged by the aforementioned cam follower, as a means of altering the time interval during which the electric switch remains actuated.

A still further object of our invention is to provide, in such a time-controlled switch, novel structure whereby the pivot point of the adjust 2 able cam face aforementioned is varied in position during adjustment of the interval-setting dial, whereby greatly improved sensitivity and accuracy are obtained for interval settings of small magnitude.

An additional object of our invention is to provide, in a time-controlled switch, an adjusting means for fine variation of the dimensions of the lever linkage coupling the control mechanism to the electric switch, whereby operation of the device can be set to a high order or accuracy with out necessity for extremely close manufacturing tolerances.

Other and additional objects and advantages of our invention will appear as the specification proceeds.

We have shown an illustrative embodiment of our invention in the accompanying drawing, of which Figure 1 is a view in front elevation of a time-controlled switch made according to our invention; Fig. 2, a side view, partly in section, showing the apparatus of Fig. 1 as it appears assembled in its case but with a portion of the casing cut away to reveal the internal structure; Fig. 3, a rear elevation view of the structure of Fig. 1; Fig. 4, a front elevation view of the structure of Fig. 1 removed from its casing or housing; Fig. 5, a sectional view taken along the line 5-5 of Fig. 2; Fig. 6, a view substantially similar to Fig. 5 but showing the position of the parts after the time-controlled apparatus has accomplished actuation of the electric switch; Fig. '7, a sectiona1 view taken along the line 1--'! of Fig. 2, showing the internal structure after removal of the dial-controlled interval-setting cam, the timecontrolled cam follower, and the adjustable cam co-operating therewith; Fig. 8, a fragmentary detailed view showing the electrical switch and the fine adjustment means for varying slightly the dimensions of the linkage coupling the control mechanism of the electric switch; Fig. 9, a sectional View through the center of the time-ofday dial, showing the relative positions of the various members associated therewith; Fig. 10, a sectional view through the time-of-day shaft, taken along the line Iii-10 of Fig. 9; and Fig. 11, a sectional view through the time-o-f-day shaft taken along the line I l--| l of Fig. 9.

As may be seen from Figs. 1 and 2, we prefer that our apparatus, when installed for use, be mounted n a panel or front housing 20, which may be a casting of light metal, a suitable metal stamping, or formed of molded plastic. As shown in Fig. 1, the panel 20 has a raised central portion 26;; covering the manually adjustable dials 30 and 50 which are, respectively, the time-ofday dial and the interval-setting dial. The side walls of central portion 20a are suitably slotted to allow a portion of each of the dials 30 and G to emerge externally, so as to permit easy manual setting of either of the dials.

The time-of-day dial is marked, as shown best in Fig. l, by numerals indicating the hours of the day. As will be explained in more detail ina subsequent paragraph, the time-of-day dial 3'0 rotates'once every twenty-four hours; to permit the user of the apparatus to distinguish readily between night hours and day hours, the dial may accordingly be marked as shown, with a black or dark-colored inner ring and a white or lightcolored outer ring concentric therewith. The hours from 6:00 a. m. to 6:00 p. m. are shown on the outer, while the hours from 6:00 p. m. to"

6:00 a. m. are shown on the inner, dark-colored ring. .A. viewing window 2% in panel 28 is oriented so as to show a few degrees of arc of both the light, outer ring and the dark, inner ring.

This method of marking time-of-day dials has been. employed in earlier structures of this sort and is not claimed herein as part of our invention. It will be'understood that dial 30 and dial 50 may be marked in any desired fashion, as the particular application may render appropriate.

The interval-setting dial 5!! is, in the illustrated embodiment, marked with an off position and with numbers (indicating hours) from 1 to 10, the total range from off to being 180 degrees of perimeter. Dial 50 may be viewed through a window 200 provided in panel 28; in the illustrated embodiment, window 290 is seated directly above window 2%; both. windows are Provided with an. indicator marker or arrow so as to permit accurate setting and reading of the dials.

The working parts of our apparatus are mounted on a rigid sub-panel 2|, which may be made of steel or other mechanically strong material. As may be best seen from Figs. 7 and 9, the pivots or axles for the rotating dials 30 and 533 are rigidly mounted on sub-panel 2i, the pivot for dial 3!] being denoted. 39 and that for dial 50 being denoted 53.

Dial 50 is provided, on its under side, with a cam 5! having a single flat face and an extended curved portion commencing, on the right hand side as viewed in Figs. 5 and 6, with a relatively short radius of curvature and having a gradually increasing radius of curvature the greater part of its length, finally shortening again in radius of curvature near the left-hand end of the curved face, as viewed in Figs. 5 and 6. Cam 5! is secured permanently to dial 50 by a locking screw 52, the orientation of cam 5! on dial 5G being such that the beginning of the curved face (on the right side as viewed in Figs. 5 and 6) is approximately opposite the point midway between ofi and 1 on the dial face. That is, a line drawn along the rear side of dial 50 connecting the beginning of the curved face with the center of dial 5d will, when extended beyond the center, interrupt the outer edge or dial 50 at a point midway between the markings "01? and 1. The numeral 10 on dial 50 is similarly oriented approximately opposite the point marked 10 on the curved face of cam 51 as shown in Fig. 5.

Pivot 53 is provided at its base with a circular enlarged portion 53a which serves as a pivot for a link plate 45. Plate 45, it will be noted, is of irregular shape, and it performs a very important role in the operation of our invention. t is provided with an elongated slot 54 near pivot 53a; slot 54 is arcuate with a very long radius of curvature over the greater part of its length, but it has a short end portion 54a bent rather sharply inward. toward the center of curvature at the end nearest pivot 53a; the conformation of slot 54 is best seen in Fig. 7, although it can be observed also in Figs. 3, 5, and 6.

Near the: left-hand edge of link plate 35, as viewed Fig. 7,. an extension is provided which, at its uppermost end, is bent at right angles to extend through an. aperture 2| a in sub-panel 2| to form an abutment cm, as best seen in Fig. 8. The portion of link plate 45 immediately behind abutment 45a carries a pair of parallel slots 55b, and slots 45?) are bridged at their lower ends by a cut to form a tongue. 46, which is bent slightly upward as shown in Fig. 8. An adjusting screw 4-? is threaded into asuitable aperture in link plate 45 sothat its head abuts against tongue 46, also shown best in Fig. 8. By suitable screw driver adjustment of screw 41, the stress on tongue 45 can be varied, with consequent slight variation in the position of abutment 45a. A spring-biased electric switch 40, having electrical contacts 4-! and 42, switch button 44, and actuating lever 43, is mounted on the back side of sub-panel 2-! in a position such that actuating lever 43 is normally in contact with abutment 45a. Switch 20 is oriented on sub-panel 2| so that abutment 45a, when in normal position, touches lever 43 but does not press on it hard enough to actuate switch button M.

Switch 40 may be of the normally-open or normally-closed type, or, if desired, it may be a double-pole switch. The type of switch used will, of course, depend on the application in which the time-controlled switch is to be used. The electrical switch shown in this illustrative embodiment is of the sort commonly known in the art as a microswitch.

The lowermost portion of link plate 45 is provided with a foot-like extension 450 which extends over and in large part covers a sizable aperture 210 in sub-panel 2i. Near the lower end of extension 550 is a small slot 45d, provided with rounded ends. As will be more fully explained hereinafter, slot 45d plays an important role in the operation of our invention by providing a movable or variable fulcrum for adjustable cam 35, to be more fully described.

As may be best viewed on Fig. '7, a latch member 35 is also pivoted to sub-panel 2|; latch 35 is pivoted at a point approximately identical in altitude and somewhat to the right (as viewed in Figs. 5, 6, and '7) of the pivot 39 which carries the time-of-day mechanism and time-oi-day dial 30.

An electric clock mechanism $50 is aifixed to the rear side of sub-panel 2|, and it is provided with a step-down gear train enclosed in housing 51 and operative, when clock mechanism is running, to rotate 2-toothed gear 32 at a speed of one revolution per hour. As may be seen from Figs. 2, 6, and 7, gear 32 passes through an aperture in sub-panel 2 l to the front side thereof.

As shown in Figs. 5 andB, an adjustable cam member 36, having a concave cam face along its right side is mounted above link plate 45. At its upper end cam member 36 is provided with a slidable pivot member 38a (see Fig. 3), keyed to cam member 36 by a pin 38. Pivot 38a is mounted, to slide freely within slot 5Q in link plate 55.

At the opposite end of cam member 36, a pin 8|, carried by member 36, is slidably mounted in slot 45d. A wire spring 31 is held on cam member 36 in spring seats 36a and 38b, the opposite end of spring 31 being hooked into a spring seat 35a at the right-hand end of latch member 35, as viewed in Figs. 5-9 inclusive. Spring 31 is operative, when cam 5| is presenting its fiat surface toward cam member 36, to hold pivot 33 in the end 54a of slot 54, while, under the same conditions, pin 8| occupies the lowermost end of slot 45d. Rotation of cam 5| to bring its curved surface into contact with cam member 36 shifts member 36 against the force of spring 37. The movement of member 36 as the curved face of cam 5| is progressively advanced is, first, to shift as a whole in an upward direction until pin 8| seats in the upper end of slot 45d, and thereafter to rotate clockwise on pin 8| as a pivot. Face 360 of member 36 is cut so that its leading edge engages cam follower 83 (to be described later) at the same angular position regardless of the position in slot 45d occupied by pin 8|.

We shall now describe the apparatus immediately associated with the time-of-day dial 30, a detailed showing of which appears in Fig. 9. Pivot 39 is provided with an extended annular land or shoulder 39a which rests on sub-panel 2| and serves as a base for a circular plate 34. Plate 34 is provided with a central upward extension 34a, centrally drilled to fit over pivot 39 and threaded externally at its upper end. The threaded portion of extension 34a is filed to provide two oppositely disposed fiat sides, as shown in Fig. 10.

A cam follower 83 is mounted on the under side of plate 34 near its edge, as may be best seen from Figs. 5, 6, and 9. As will be hereinafter explained in detail, cam follower 83 under certain circumstances engages cam 36 when plate 34 is rotated on pivot 39.

A bushing member 82, having an upward extension equipped with a pair of oppositely disposed axial notches, is centrally drilled to fit over extension 34a and to rest on plate 34, being separated therefrom by a thin fiber gasket (shown in Fig. 9 but not marked with a reference numeral).

A toothed gear 3| is centrally drilled to fit readily over the upward extension of bushing member 82, member 3! being separated from the upper surface of bushing 32 by a thin fiber gasket, as shown in Fig. 9. Dial 30, which may be made of plastic, fits over the upward extension of bushing 82, and is provided with a pairof inward keys 30a which fit into the aforementioned slots in bushing 82, so as to compel dial 30 and bushing 82 to maintain the same relative angular position. A friction plate H is provided with a central opening flattened along two sides to co-operate with the fiat sides of upward extension 3441, as shown in Fig. 10. Member II is separated from dial 30 by a thin fiber gasket. A spring washer '|4 fits on extension 34a over friction plate H; the assembly on upward extension 34a is secured in place by a nut 13 which engages the threaded upper portion of member 34a and holds in place all the elements mounted on extension 34a. When member 34 is fitted over pivot 39, a thumb nut 33 may be screwed into a suitable threaded aperture in the top of pivot 39, thus holding securely in place the time-of-day dial 30 and all its associated apparatus.

Toothed gear member 3| is, in the illustrated 6 embodiment, provided with forty-eight teeth, and Z-toothed gear 32 is mounted so as to engage the teeth in gear 3|. As a result, when the clock mechanism 60 is supplied with electric current, ear 3| is rotated at the rate of one revolution each twenty-four hours.

From the foregoing description of the timeof-day mechanism, it will be observed that a substantial friction coupling exists between member 34, with its cam follower 83, and the timeof-day dial 30 and the toothed gear 3|, such that under normal circumstances those elements will all rotate together. Accordingly, when gear 3| is turned by gear 32, dial 30 and plate 34 turn with it, all of said elements maintaining the same angular relationship with respect to one another. The friction coupling, however, is not positive, with the result that if substantial torque be applied, as by manual force, to dial 30 it can turn independently of either of the elements 3| and 34 which may be locked against rotation. Gear 3| is never free to turn rapidly, since the drag of gear train BI is much too great to allow rapid movement. Thus, by manually turning dial 30, the user of our apparatus can always shift the position of dial 30 to any value he pleases with respect to gear 3|.

Any time dial 30 is turned in a clockwise direction (as viewed in Figs. 1 and 4) plate 34 and cam follower 83 turn with it. Plate 34, however, is provided with a peripheral notch 34b adapted for co-operation with latch member 35. Notch 34b has a gradually slanting side which passes by latch member 35 freely when dial 3!) and member 34 are being rotated in a clockwise direction (as viewed in Figs. 1 and i). The other face of notch 341), however, is perpendicular to the circumference of member 34 so that when dial 30 is being rotated in a counter-clockwise direction (as viewed in Figs. 1 and 4) member 34 will turn with it only to that point whereat latch 35 engages notch 3412. Upon further counter-clockwise rotation of dial 30, member 34 does not turn. Thus by counter-clockwise rotation of dial 30, its angular position relative to member 34 can be set to any desired value.

Operation In discussing the operation of our invention, we shall assume that it has been installed for use, that a suitable electric power source has been connected to clock mechanism 60 by way of connecting wires 65, and that control switch 40 has been connected to the circuit whose operation is to be governed by our invention.

Let us assume, for purposes of illustration, that actuation of switch 40 is desired for a period of three hours commencing at 6:00 a. m. The duration of the switch-actuation interval is determined by a, manual settin of dial 50; in the exemplary case, dial 50 is turned manually until the numeral 3 appears below the indicator in window 200. This movement has the effect of bringing the curved face of cam 5| into engagement with the side of cam 36. When dial 50 is moved from off toward 1, the curved face of cam 5| is first brought into contact with cam 36, and the first resulting motion of cam 36 consists in moving pin 38 along the sharply bent end 54a of slot 54. This movement, as may be understood from Fig. 6, pulls pivot pin 8| at the opposite end of cam 36 away from the lower end of slot 45d and causes it, after a few degrees rotation of dial 50, to seat in the upper end of slot 45d. This seating occurs at substantially the same point at which pin 38 moves out of slot 54a and into the main slot 54. Further rotation of dial 50 causes cam to force cam 36 further to the right, as viewed in Fig. 6, pin 38 moving along slot 54 and cam 36 as a whole rotating around the upper end of slot 45d as a pivot, pin 8! being seated in the slot at that end.

As may be seen from Figs. 5 and 6, the number of degrees of arc in which cam follower 83 is pressing against the concave face of cam 36 will be governed by the position of cam 5|, and hence of dial 50.

The effect of pressure by cam follower 83 against cam 36 is to cause cam 36 and link plate 45 to swing upward around pivot 53s. This causes abutment 45a to press harder againstlever 43 and causes actuation of switch 40 by pressure on button 44. As cam follower 83 moves away from the face of cam 35, cam 3t and link plate 45 tend, under the urging of spring 31, to return to their normal positions and, as a result, the pressure on lever 43' by abutment 45a is relieved and switch 40 is de-actuated.

The calibration of interval-setting dial 50 may readily be accomplished by experimental determination; twenty-four hours of time is represented on dial 30 by 360 degrees of rotation. Thus each hour of time causes degrees rotation of dial and plate 3d. Therefore, the position of dial 50 at which cam follower 83 is in switchactuating engagement with cam for 15 degrees of rotation is the point at which the numeral l should be marked on dial 50. Similarly, switch-actuating engagement for 30 degrees of movement by cam follower 83 determines the location of the mark 2, etc. It is obviously quite desirable that the calibration of dial 50 re sult in an approximately linear scale, since the usefulness of a time-controlled switch is greatly curtailed if the scale is badly crowded at any point on the dial. We have found that by using the moving fulcrum formed by pin 8| and slot d, combined with the slot 54 having sharply bent end portion 54a, we have been able to achieve almost complete linearity of the scale on dial 50, as indicated in the illustrated embodiment by the markings of dial shown in Fig. 4. This substantially linear scale for the intervalsetting dial is one of the respects in which our invention greatly surpasses prior-art structures, and we regard it as an important part of our invention.

When the interval-setting dial 50 has been set to the proper value, the operators attention should then be directed to, setting the apparatus to accomplish switch actuation at the predetermined hourin the exemplary case, 6:00 a. In. To do this, he must adjust the relative angular position of dial 30 and cam follower 83 so that cam follower 83 comes first in contact with cam 38 when the time-of-day dial is indicating 6:00 a. m. To facilitate such an adjustment, notch 34b is placed in member 34 at that point on its circumference whereat the perpendicular face of notch 34b engages latch 35 in the same angular position as cam follower 83 first engages cam 35. Accordingly, to set the hour at which switch actuation will occur, the time-of-day dial 30 is first manually rotated in a counter-clockwise direction one complete revolution, to insure that latch 35 has seated in notch 3th, and then rotated further in counter-clockwise direction until the desired hour (in the exemplary case, 6:00 a. m.) appears below the indicator in window 2%. Dial 30 is then manually turned in clockwise direction until the correct time of day appears below the indicator in window 20?). It should be borne in mind that during this last-mentioned manual movement of dial 30 in the clockwise direction, plate 34 and cam follower 83 will move in step with dial as, since latch 35 in no way impedes movement of member 34 in the clockwise direction.

After our invention has been set in accordance with the technique Just described, time-of-day dial 33 will move slowly in clockwise direction under the impetus of clock mechanism 50. At the appointed hour (in this case, 6:00 a. m), cam follower 83 engages cam 35, applies pressurev to lever 43 via link plate 45 and abutment 55a, and switch 40 is. actuated. Switch it remains in its actuated condition for the appointed periodin the exemplary case, three hours. When the selected period has ended (that is, at 9:00 a. m. in the particular case under consideration), cam follower 83 will have been moved by clock mechanism 60 beyond the zone of pressure contact on cam 36. As a result, the pressure of abutment 45a on lever 43 is relieved and switch 48 is deactuated.

Fine adjustments in the relative orientation of abutment 45a and link plate 45 can be made by turning screw 3?, since pressure on tongue 46 causes abutment 45a to move upward as viewed in Fig. 8. This fine adjustment is valuable in the final adjustment of our invention, since it permits easy compensation for minor variations in the dimensions of parts and thus permits the mass production of timing apparatus according to our invention without requirement of excessively close manufacturing tolerances.

While we have in the present specification described in detail a single embodiment of our invention, it will be understood that many variations therein can be made by persons skilled in the art without departing from the spirit of our invention. For example, while we have shown and described a structure wherein dial 30 indicates the time of day and rotates once each twenty-four hours, in other applications it might be convenient to have dial 3B rotate at a different rate, such as once per hour. Accordingly, we do not limit ourselves to the particular embodiment of our invention herein illustrated or to any particular field of application. The scope of our invention should be determined primarily by reference to the appended claims.

We claim:

1. In combination, a cam follower, means for effecting its periodic movement through a predetermined locus at a controlled rate of speed, a cam having a curved face mounted adjacent the locus of the cam follower, a pivot for the cam, manually operable means for shifting the normal position of the. cam through a portion of the locus of the cam follower, an electrical switch, and mechanical linkage coupling the cam and the switch operative to actuate the switch responsively to engagement of the cam and cam follower, said mechanical linkage comprising manually operable means for setting to a predetermined value within a range the relative position of the switch and the cam when said cam and said cam follower are not in engagement.

2. Apparatus according .to claim 1 wherein a time indicator is provided for operation in synchronism with the cam follower movement and wherein manually operable means are provided for changing the relative phase of the time indicator and the cam follower.

3. Apparatus according to claim 1 wherein a time indicator is provided for operation in synchronism with the cam follower, manually operable means are provided for changing the relative phase of the time indicator and the cam follower, and additional means are provided for shifting the time indicator and the cam folv lower, when placed in predetermined relative phase, to cause the time indicator to show the correct time.

4. In combination, a cam follower, means for eifecting its periodic movement through a predetermined locus at a controlled rate of speed, a cam having a curved face mounted adjacent the locus of the cam follower, a link plate mounted for limited movement adjacent the cam, said link plate and cam carrying pivot means operable to permit controlled relative movement between the cam and link plate, manually operable means for shifting the relative position of the cam and link plate, said cam during a part of such relative movement occupying a portion of the locus of the cam follower, and an electrical switch mounted adjacent the link plate, said switch being oriented relative to the link plate to be actuated chronism with the cam follower movement and wherein manually operable means are provided for changing the relative phase of the time indicator and the cam follower.

6. Apparatus according to claim 4 wherein a time indicator is provided for operation in synchronism with the cam follower, manually operable means are provided for changing the relative phase of the time indicator and the cam follower, and additional means are provided for shifting the time indicator and the cam follower, when placed in predetermined relative phase, to cause the time indicator to show the correct time.

'7. Apparatus according to claim 4 wherein the link plate is provided with an extending abutment for engagement with the switch and means are provided for finely adjusting the position of the extension relative to the link plate proper for effecting precise timed relation between cam follower engagement and switch actuation.

8. Apparatus according to claim 4 wherein the link plate is provided with two slots, and the cam is held to the link plate by pins movable in said slots, the operation of said manually operable means in shifting the relative positions of the cam and link plate being to move one pin the full length of its slot while the other pin is moving through a relatively small portion of the other slot and thereupon to complete movement of the other pin through the other slot while the cam as a whole rotates on the first pin as a pivot, said first pin being then seated in the end of said first slot.

9. A time-controlled switch comprising a rigid frame, an electric switch mounted thereon, a link plate pivoted to the frame, said plate having one portion normally in engagement with said switch and operative to actuate the switch on application of super-normal pressure, a cam mounted on the link plate and having a limited range of relative movement therewith, said cam having a curved face, a time-indicator dial mounted on the frame for rotation, a timing gear carried by the frame and frictionally coupled to the timeindicator dial, clockwork mechanism for rotating the timing gear at a controlled rate for normally moving the time indicator dial in clockwise direction, a cam follower carried by the frame and frictionally coupled to the time-indicator dial, said cam follower being normally operative to traverse a predetermined locus in synchronism with rotation of said time-indicator dial, said friction coupling between the timing gear, indicator dial, and cam follower being operative to permit independent adjustment of the relative phases of both the dial and the cam follower relative to the timing gear, and an interval-setting cam mounted for rotation adjacent said firstmentioned cam and operative on rotation to move said first cam relatively to said link plate, a part of the range of movement of said first cam responsively to rotation of said interval-setting cam being within the locus of said cam follower, whereby engagement between said first cam and said cam follower raises to a super-normal value the pressure of said link plate on said switch.

10. Apparatus according to claim 9 wherein the cam follower is mounted on a plate supported coaxially of the time-indicator dial, said plate being provided with a circumferential notch, and a latch mounted on the frame adjacent the plate and operative, when the time-indicator dial is rotated in counter-clockwise direction to engage said notch and arrest counter-clockwise movement of the plate at substantially the point whereat the cam follower initially engages said first cam when the time-indicator dial is being rotated in clockwise direction.

11. Apparatus according to claim 9 wherein the link plate is provided with a modified abutment portion for pressing on the switch and wherein fine adjusting means is provided for making small changes in the'position of the abutment relative to the link plate proper for effecting precise timed relation between cam follower engagement and switch actuation.

12. Apparatus according to claim 9 wherein the link plate is provided with a pair of slots and the first cam is mounted on said link plate by pins co-operating with said slots, spring means operative between the frame and first cam being provided for holding said first cam normally in a position wherein each of said pins is held at one end of its slot, and wherein said intervalsetting cam is operative on engagement with said first cam first to move one pin to the other end of its slot while moving the second pin through only a small portion of its slot and thereafter, on further rotation of said interval-setting cam, to move said first cam in rotational movement, pivoting on said first pin, until said second pin has reached the other end of its slot.

C. GORDON REYNARD. HARRY L. HART.

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

UNITED STATES PATENTS Number Name Date 1,279,631 Abend Sept. 24, 1918 2,300,950 Lux Nov. 3, 1942 2,364,184 Baak Dec. 5, 1944

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