US2373186A - Stoker control - Google Patents

Description

April 0, 1945. sv G. ISSERSTEDT 2,373,186

STQKER CONTROL Filed March 26, 1945 2 Sheets-Sheet l sill NM swam/0 6.1551752? attorney April 1945. s G. ISSERSTEDT 2,373,186

' I STOXER CONTROL Filed March 26, 1943 2 Sheets-Sheet 2 are/r51? mowm 96 moron norm 4% tZJ/ZZL Gttorneg Patented Apr. 10, 1945 STOKER CONTROL Siegfried G. Isserstedt, Toronto, Ontario, Canada, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application March 26, 1943, Serial No. 480,675

16 Claims. The present invention relates to timing devices and particularly of the type employed in controlling stokers for operating the same suiiiciently often to prevent extinguishment of the fire under low heat requirement conditions.

In order t provide a timer for universal application to different makes of stokers, different grades of fuel, and other variable factors, it has been found desirable to provide adjustments by which the periodicity of the timed operations and their length of duration can be simply and readily adjusted.

One of the objects of the present invention is to provide a simple and durable timer, for use for example in controlling a stoker, having simplified adjusting means so arranged that many of the parts can be made of simple stalnpings.

" vision of durable and simple adjusting means for adjusting both the length and the periodicity of the timing or firing periods by merely shifting b the pivotal points of a pair of cam followers. As

a a result, such expedients as providing cover up sectors, moving cam surfaces relatively to each other, providing in effect a plurality of diiferent cams which are selectively used to operate the ,cam follower, providing separate interruption switches, or other complicated, delicate or cumbersome arrangements are all eliminated.

Other objects and advantages of the present invention will become apparent as the detailed description thereof proceeds and upon reference to the accompanying drawings, in which:

Fig. l is a showing of the essential elements of my improved mechanism with the parts adjusted ,to operate the switch once every fifteen minutes;

Fig. 2 is a detailed showing of one of the addusting-mechanisms;

Fig. 3 is a section taken on the line 3-3 of Fig. 2; Fig. 4 is a view similar to Fig. l but with the parts adjusted to operate the switch every half hour.

Fig. 5 is a view similar to Fig. l but with the parts adjusted to operate the switch once every hour, and

Fig. 6 is a diagrammatic showing of one mannor in which my invention may be utilized.

Turning now to the drawings, it might be stated that the drawings have been prepared with the view of showing, as clearly as possible, the particular configuration and shape of the fundamental parts of my invention and the manner in which they cooperate with each other as distinguished from detailed mechanical drawings of an actual device constructed in accordance with my invention, since it is believed that such a mechanical drawing would confuse rather than clarify the basic principles involved.

Turning now to Figure 1, a single base plate or supporting plate is shown at H]. In actual practice there would of course be at least two of these supporting plates so as to provide support at each end of the various shafts, journals and the like. Rotatably mounted upon the base plate I0 is a pair of cams H and i2 driven in a counter-clockwise direction by a shaft l 3 suitably journalled in the base plate In and driven in such a counterclockwise direction by any suitable timing means, such as is well known in the art, The cams II and I2 are preferably formed by stampings and are caused to rotate together as a single unit, either by being secured to each other or by being individually secured to the common shaft l3. The cam i is provided with four lobes which are exactly alike. Each lobe comprises a dwell portion M, a lifting or off portion I5, and a retracting or on portion l6.

Cooperating with the cam l I is a cam follower ll pivoted upon a pivot pin 18. The cam follower l! is shown lying in front of cam H and it supports a backwardly extending pin 13 that is adapted to ride upon the various surfaces of the cam H. The cam follower I7 is biased to rotate about a pivot E8 in a clockwise direction by any suitable means such as the spring 20 which has one of its ends secured to the cam follower I! at it and its other end secured to a suitable pin or other support 22 mounted upon the base plate l0. Clockwise rotation of cam follower ll about its pivot I8 is limited by a stop pin 23 with which the extreme right-hand end of cam follower ll cooperates. The stop pin 23 may be suitably mounted upon the base plate 10.

With the parts thus far described, upon counter-clockwise rotation of cam II, the dotted surface just to the right of follower pin [9 will engage such pin and upon continued counter-clockwise rotation of cam H the pin 19 will be raised, thus rotating cam follower I! in a counter-clockwise direction. This movement of cam follower I! will continue until the follower pin is rides up on one of the dwell surfaces Ill of the cam H. The cam follower I! will then be maintained in its raised position until the follower pin 19 rides ofi of the dwell surface l4 and begins riding down the on portion of the cam. Such downward movement of the cam follower I! will continue until the extreme right-hand end thereof engages the stop pin 23. As a result, it will be seen that the cam follower I1 is oscillated up and down four times for each revolution of cam I l. Assuming that the shaft 13 is driven at the rate of one revolution per hour (by the timing means not shown), it will be'evident that the cam follower i'l makes four complete up and down movements or reciprocations each hour. In other words, the cam follower i1 is moved upwardly to its extreme position and then moved downwardly until its right-hand end engages stop 23 once each fifteen minutes.

These up and down or reciprocating movements of the cam, follower I? may be used to operate any desired type of device. Also such operation may be direct or indirect through suitable connectin means. I. have shown the cam follower IT as operating a switch of the mercury switch type through suitable connecting linkage. For this purpose, the rightehand end of cam follower l! is provided with an operating pin 24. The pin 24 cooperates with cam surfaces, and 26 formed on two edges of one arm of a bell-crank 2'! which is in turn pivoted to the base plate Ill at 28. Suitable biasing means such as the coil spring 29 having one end secured to one of the arms of the bell crank 21, as at 3%, and its other end secured to a pin 3! carried by the base plate Ill, serves to maintain the cam surfaces 25 and 28 in engagement with the actuating pin 24. A mercury switch 32 having the usual electrodes in its left-hand In th present instance,

closed position substantially, seven minutes out of each fifteen minutes. It will be seen that upon such upward movement of pivot l8, the follower pin I9 will likewise move upwardly. As a result, the cam ll will have to turn further before one of the off portions l5 thereof engages the follower pin I9 and lifts the cam follower I! so as to move themercury switch 32 to. its off position. Similarly, upon continued rotation of the cam H, as the pin 19 starts riding down one of the on portions l6 of the cam, the mercury switch 32 will be moved to its on position more quickly since the follower pin l9 need only ride down such on portion IS a relatively short amount before the right-hand end of cam follower I! will have moved down to the switch closing position. On the other hand, if the pivot 18 be moved down to the lower end of slot 35, the mercury switch 32 will remain on for only approximately one minute out of every fifteen minutes. Such downward movement of the pivot l8 moves the cam follower i9 downwardly to a position in which adjacent I on and off surfaces l5 and [B of the cam are very end is mounted upon the other arm of the bellcrank 21-. The relation of the parts is such, as shown in Fig. 1, that when the right-hand end of cam follower I] is engaging stop pin 23, the bell-crank 27 is in such position that th mercury switch 32, is tilted to the left so that the mercury therein bridges the electrodes carried in the left-hand end of the mercury switch thereby completing an electrical circuit therethrough.

Upon movement of cam M, in a counter-clockwise direction, as one of the off surfaces l5 thereof raises the follower pin l9, the actuating pin 24 carried at the right-hand end of cam follower ll will rotate bell-crank 27 in a clockwise direction about its pivot 28 and tilt mercury the, left-hand end of cam follower I! may be adjusted in the base. plate If.) by sliding it up or down in a slot 35 provided therein. With the parts in the positions shown, the pivot i8. is placed at an intermediate point in slot 35 with the result.

that, the switch 32 will remain on or closed for substantially three and a half minutes out of every fifteen minutes. Now if the pivot I8 is moved to the upper end of the slot 35, the result will be to maintain the mercury switch 32 in close together so that there will only be a relatively short period of time during which the right-hand end of cam follower I! is sufiiciently low to permit a switch closing movement-of the mercury switch 32.

With the parts thus far described, the mercury switch 32 is closed every fifteen minutes and the length of time which it is closed may be adjusted from one minute to seven minutes simply by sifting the pivotal member is for the left-hand end of cam follower I! upwardly and downwardly within the slot 35 provided in base plate It. It will thus be seen that I have provided a, simple adjusting mechanism for varying the duration of switch closure, which mechanism eliminates the necessity of using relatively movable cam surfaces or similar complicated expedients.

The cam I2 is provided with four operating surfaces. Two of these, numered 31, are exactly alike and have relatively small radii. A third of these cam surfaces indicated at 38 has a somewhat larger radius and the fourth surface 39. has a still larger radius. Cooperating with the surfaces of cam l2, which cam might well be termed the interrupter cam, is an interrupter plate or memher All. The interrupter member 40 is pivoted upon the base plate It by a shiftable pivot, the details of which are shown in Figs. 2 and 3. Turning to these figures, it will be seen that the base plate it! is provided with a slot comprising three holes 4!, 42 and 43 which are spaced from each other and are joined together by slotted portions having a width less than the diameter of the holes 4!, s2 and 43. A screw 44. is provided with a shank having a diameter substantially equal to the width of the slots which interconnect the holes M, 52, and 43'. As shown in Fig. 2, the screw 4 is extending through. the hole 41, and likewise extends, through a spacing washer 4,5. The, end ofthe shank is provided witha reduced screw-threaded portion 46 which is'threaded into the interrupter plate .40. A cup shaped member t! is mounted on the shank between the head of the screw 44 and the base plate Ill and a coil spring has one end engaging the head of the screw and its other end engaging the bottom of the cup shaped member 4? in a manner to press, the, cup

- shaped member il against the base plate Ill. The

bottom of the cup shaped member 41 is provided with a shoulder portion 49. which snugly engages the hole. M. If it is desired to, shift, the pivotal point of the interrupter plate 40, it is onlynecessary to pull outwardly on the cup shaped member 41 against the pressure of spring 48. This removes the extension 49 from the hole, whereupon the complete assembly may be slid in the slots joining holes 4|, 42 and 43. When the desired position is reached, releasing of the cup shaped member 4! permits the spring 48 to press the extension 49 into the proper hole 42 or 43 as selected by the person adjusting the apparatus. As a result, the pivotal point for the interrupter plate may be shifted from hole 4| to hole 42,

v or to hole 43 at the option of the operator. With the parts as shown in Fig. 1, the pivotal point of the interrupter plate 48 is located in the hole 4|.

Interrupter plate 40 is further provided with an upward extension or interrupting finger which extends above stop pin 23 and which, under certain conditions, is adapted to be moved into engagement with the right-hand side of stop pin 23. With the interrupter plate 40 pivoted in hole 4| of base plate H] as shown in Fig. 1, it will be noted that the cam surfaces 31, even though of small radius, have sufficient throw to maintain the interrupter finger 55 at a point spaced to the, right from stop pin.23. Now as the cams II and I2 rotate in counter-clockwise direction, the interrupter finger 55 will never move any closer to stop pin 23, but, to the contrary, will move even further away from this stop pin since the cam surfaces 38 and 39 are each provided with a radius larger than those of the cam surfaces 31. Therefore, under these conditions of adjustment of the interrupter plate 40, no interruptions of the operation of switch 32 will take place and this switch will be operated once each fifteen minutes as heretofore explained.

Turning now to Fig. 4, the parts are shown in the same general position as in Fig. 1 except that the interrupter plate 40 has had its pivot shifted from the hole 4| in the base plate IE] to the hole 42 thereof. As a result of this shifting, as the cams and I 2 moved to the position shown and while the cam follower H was still in a somewhat raised position due to the cooperation of follower pin I9 with one of the on surfaces I6, the surfaces of cam 2 in cooperation with the new pivotal point of interrupter plate 40 permitted the same to move to such a position that the interrupter finger 55 is now engaging the stop pin 23 and extending thereabove. As a result, the extreme right-hand end of cam follower I! has had its downward movement stopped by engaging the tip of the interrupter finger 55. As a result, the

cam follower I! ha not been permitted to move to its extreme downward position. Such engagement of the right-hand end of cam follower I1 .with the upper tip of interrupter finger 55 has prevented the right-hand end of cam follower I! from moving into engagement with stop pin 23. As a result, the actuating pin 24 is engaging the cam surface 26 of the bell-crank 21 whereby the bell-crank 21 is held in such position that the mercury switch 32 is tilted to the right and the circuit therethrough is open. In other words, the interrupter plate 40 has prevented the switch 32 from moving to it closed position as such switch would have done had the pivotal point 46 of the interrupter plate 40 remained in the hole 4| instead of being shifted to the hole 42. Now as the cams II and I2 continue to rotate in counterclockwise direction, the surface 38 of cam |2 which has a larger radius than the surface. 31 will approach the cam follower portion 5| of the interrupter plate 40. As a result, the interrupter plate 40 will move toward the dotted line position, which is the position it assumes when the cam l2 has moved to the dotted line position. With the interrupter plate 40 in the dotted line position, the interrupter finger 55 has-again been moved away from the stop pin 23 and is no longer positioned under the extreme right-hand end of cam follower IT. The cam follower I! will therefore be permitted to move downwardly to its usual full extent with the result that switch 32 will move to closed position in the same manner as it did in Fig. 1. Upon further counter-clockwise rotation of cam I to an extent determined upon the setting of pivotal member l8 within slot 35, the cam follower I! will again be raised sufficiently to move mercury switch 32 to its off position. Further continued counter-clockwise movement of cams II and 12 will again present the other cam surface 31 to the cam follower portion 5| of interrupter plate 40. Therefore, as the cam follower I? again starts its succeeding downward movement, the interrupter finger 55 will again move into engagement with stop pin 23 to a position in which it is underneath the extreme right-hand end of cam follower ll. As a result, once more cam follower will not be permitted to complete its full downward movement and switch 32 will again be held in its off position. Upon further rotation of the cams and I2, cam surface 39 having the largest radius will present itself to cam follower portion 5| of interrupter plate 40 and the interrupter plate 40 will then move to a position in which interrupter finger 55 is even further to the right than shown in the dotted line position. Under these conditions, cam follower I! will of course be permitted to complete its full downward movement so that mercury switch 32 will again move to closed position.

It therefore follows, with the interrupter plate 48 pivoted in the hole 42 of base plate ID, the cam follower I1 is permitted to move downwardly to its fullest extent twice for each complete revolution of the cam Mercury switch 32 will therefore move to closed position only twice per revolution of cam II or twice an hourthat is only once each half hour instead of once each fifteen minutes as was the case in connection with Fig. 1.

Turning to Fig. 5, the pivotal point of interrupter plate 40 has nOW been moved to hole 43 in base l0. As shown in full lines, when the cam surface 38 of intermediate radius of cam I2 is presented to cam follower portion 5| of interrupter plate 40, due to the new position of the pivotal point of interrupter plate 40, interrupter finger 55 is nevertheless positioned against stoppin 23 and underneath the extreme right-hand end of cam follower ll. It follows, that upon rotation of cams l and |2 in a counter-clockwise direction, the next succeeding surface 31 of stillsmaller radius of cam I2 will likewise permit the interrupter finger 55 to move into engagement with stop pin 23 and underneath the extreme right-hand end of cam follower However, upon continued rotation and presentation of cam surface 39 of cam l2, which cam surface has the largest radius, the interrupter plate 40 will be moved to the dotted position wherein the interrupter finger 55 has been moved away from stop 'pin 23 and out from underneath-the extreme right-hand end of cam follower 17. Therefore,

during this one part of the complete revolution of cams H and 12, the cam follower H is permitted to move to its lowermost position in which the right-hand end engages stop pin 23 and the merswi'tch 32 closes. During each of the other three reciprocations of cam follower H, its downward movement is quickly stopped by the interrupted finger 55 so that the mercury switch 32 is unable to close during these three partial downward movements of the cam follower ii. In

other words, the mercury switch 32 moves to closed position but once during an hours time which is required for a complete revolution of the cam H when the interrupter 4G is pivoted in i the hole 43 of base plate H1.

It will thus be seen that I have provided a very simple means of adjusting the number of times the mercury switch 32 will be actuated to its closed position simply by changing the pivotal point of the interrupter plate 4!). With the interrupter plate 40 pivoted in hole ll as shown in Fig. 1, the mercury switch '32 is moved to closedposition four times each hour or once every fifteen minutes. With the interrupter plate 40 pivoted in the hole 42 as shown in Fig. l, the mer- 'cury switch 32 closes only twice each hour oronce every thirty minutes. With the interrupter plate 40 pivoted in the hole 43 as shown in Fig. 5,

the mercury switch 32 is permitted to move to closed position only once every hour. Regardless of the pivotal point of interrupter plate 56, the shape of the parts as shown in the drawings is so arranged that the duration of whatever number of'switch closures is allowed mercury switch 32 may be changed from 1 minute to seven be made while the parts are moving and the apparatus is in normal operation. Furthermore,

such devices as changing the relative positions of 'c'am surfaces, moving 'a cam follower bodily or sidewise so that it in effect engages a different cam than before and similar cumbersome and expensive modes of construction have been entirely eliminated in my apparatus.

7 Turning now to Fig. 6, I have shown one of the manners in which my simplified timing apparatus may be utilized. I have shown a con- "stantly energized timer motor '60 connected to l ine'wires 6! and 62 by means of wires 63 and 64. The timer motor '60 would of course be con- *nected to the shaft 13 of my timing mechanism through "any suitable gear reduction so as to drive the shaft 13 at a speed of one revolution per hour.

The system of Fig. 6 includes a room thermostat 65 of usual-construction having-contact arms -66 and 61 which sequentially engage stationary contacts 68 and :59 in the order named {upon temperature fall. The-room thetmcstat fit {controls- "energiza'tion of a relay Ill having an eper- .ating coil H and an armature l2. Armature 12 operates a'mai'ntaining switch 13 as well as load switches '14 and 15. Power for the room thermostat and relay is provided by the low voltage secondary 11 of a transformer I8 having a primary 19 connected to the line wires 61 and 62. With the parts in the position shown, the room thermostat is in its open position since the room temperature is sufliciently high. Even though the room thermostat is satisfied, however, the stoker motor will be operated periodically by the mercury switch 32 at a frequency and for a' duration of time determined by the settings of my novel timing mechanism as heretofore explained. This circuit for stoker motor 80 goes from line wire 61 through wires 81 and t2 to the mercury switch 32, then by a wire 83 to the stoker motor, and then back to the other line 62 by wire 84.

When the room temperature falls sulficiently to close both sets of room thermostat contacts, relay coil H is energized as follows: secondary 'ii, wire 85, contact X58, contact blade 65, contact 7 blade 5?, contact =69, wire 86, relay coil H, and wire 31 to the other side of secondary H. Such 'energization of relay coil H closes the switches 13, it and i5. Closure of switch it establishes a holding circuit for relay coil 1! which is independent of contact blade '6? and contact 6'9 so that the relay coil '52 will remain energized upon a first rise in temperature as is well known in the art. This holding circuit is as follows: secondary 71, wire, '85, contact '68, contact bl'adefilfi, wire 88, switch '13, wire 89, relaycoil H, and wire 8? to the other side of secondary TI. losure of switchi i energizes stoker motor '80 as follows: line 5|, wire 8!, wire 9'11, switch i l, wire 9!, Stoker motor 8i and Wire 8 to the other line wire '62. Closure of switch 15 energizes blower motor 35 as follows: line wire 6i, wire '81, wire Sill, wire '92, switch 15, wire 93, blower motor and wire 3 to the other line Wis 82. 4

When the room thermostat becomes entirely satisfied and separates contact blade 66 from contact '53 as well as contact blade 3'l'frozn contact 69., relay coil H will be deenergized and all of the switches 13. 7G and 15 will open. As a, result. stoker motor 80 and blower motor 95 will be deenergized.

While I have shown the use of separate Stoker and blower motors wherein the blower motor is only energized upon a demand for heat by the room thermostat whereas the Stoker motoris energized either upon .a demand .for heat by the room thermostat or upon closure of the fire maintaining switch 32, it is to understood that asinglemotor-could be used as is well known in the art. Likewise. while I have shown .my novel timing mechanism arranged with .adiustments of the type particularly adapted for stoker operation, his to be understood that other ranges of adjustment could. easily *beincorporated therein where it desired to use my novel timer in connection with apparatus other than .stokers. Furthermore, the reciprocatory movements of follower 1H and the interruptions thereof by the interrupter plate '40 may be utilized to control any desired type of apparatus. other than a switch, either directly or through various mechan cal connections, depending entirely upon-the use to which it is desired to put my novel timing mechanism.

While I have shown and described a preferred embodiment of my invention and its ia pplicw tion to a preferred use, as in the controlling of stokers, it is to be understood that many changes can readily be made by those skilled in the art and I therefore intend to be limited only by the scope of the appended claims.

I claim as my invention:

1. A timing mechanism, comprising, in combination, a device to be actuated periodically and repeatedly from a first position to a second position, actuating means which periodically and repeatedly moves said device from said first position to said second position upon substantially constant movement of said actuating means, movable means movable to a position to prevent actuation of said device by the actuating means, and means to control said movable means to automatically and repeatedly move it to its position in which it permits actuation of said device at a periodicity selectively less than that at which the actuating means moves to its actuating position.

2. A. timing mechanism, comprising, in combination, a device to be actuated periodically and repeatedly from a first position to a second posl tion, actuating means which periodically and repeatedly moves said device from said first position to said second position upon substantially constant movement of said actuating means, movable means movable to a position to prevent actuation of said device by the actuating means. means to control said movable means to automatically and repeatedly move it to its position in which it permits actuation of said device, and means for selectively controlling the periodicity at which said movable means is moved to its last-named position by the substantially constant movement of said actuating means.

3. The combination with a devlce'to be actuated and means for periodically and repeatedly actuating said device to a predetermined position, of means operable to prevent such actuation of said device and movable to an operative position permitting actuation of said device, abutment means for maintaining said last named means in position to prevent actuation of said device. and means to selectively place said pre venting means in said operative position during a predetermined number of times said actuating means moves to its device actuating position.

4. The combination with a device to be actuated and means for periodically and'rcpeatedly actuating said device to a predetermined position. of means operable to prevent such actuation of said device and movable to an operative position permitting actuation of said device. means to place said preventing means in said operative position during a predetermined number of times said actuatin means moves to its device actuating position. and adjustable means to determine the number of times said actuating means will be prevented from moving said device to its predetermined position in respect to the number of times it will be perm tted to move the device to said predetermined position.

5. combination with a device to be actuated and means for periodically and repeatedly actuating said device to a predetermined position, of means operable to prevent actuation of said device to said predetermined position, cam means operable to move said preventing means to permit actuation of said device, and adjustable means to determine the ratio of operation of said device to non-operation of said device by said actuating means and to selectively vary the time said means associated with one of said two last-named means to determine which portions of said cam means shall be effective to position said mov-' able member in each of its two positions.

'7. The combination with a device to be actu-' ated and means for periodically and repeatedly actuating said device to a predetermined position, of movable means movable selectively topositions preventing or permitting operation of said device by the actuating means. cam means for operating said movable means to each of its positions, adjustable means associated with one of said two last-mentioned means to var the ratio between device actuation and prevention .by said movable means, and independent means associated with the other of said two mentioned means to selectively vary the period of time said device is maintained in said predetermined position.

8. The combination with a device to be actuated and means for periodically and repeatedly actuating said device to a predetermined position, a movable member movable selectively to positions permitting or preventing actuation of said device by the actuating means, cam means for actuating said movable member, and means for bodily adjusting said movable member in respect to said cam means to vary the ratio between device actuation and prevention by said movable member.

9. The combination with a device to be actuated and means for periodically and repeatedly actuating said device to a predetermined position, a pivoted member movable selectively to positions permitting or preventing actuation of said device by the actuating means, a cam having a variable contour for moving said movable member whereby said movable member is moved back and forth variable amounts about its pivot during a single revolution of said cam, and means for shifting the pivot of said movable member to determine which portions of the variable contour of said cam shall be eiiective to move said pivoted member to one of its two aforementioned positions.

10. In a timing device, in combination, a device to be repeatedly actuated from a first posi tion to a second position, cam means associated with said device normally effective to repeatedly and periodically actuate said device to its two positions, means physically independent of said cam means to selectively vary the time said device is maintained in either of its two positions, means physically independent of said cam means but synchronized therewith to prevent actuation of said device to one of its positions at least part of the time. and adjustable means to render said last-named means effective or ineffective.

11. In combination. a device to be actuated, cam means havin a plurality of high dwells associated with said device for repeatedly actuating said device, a member physically independent of said cam means movable to positions to permit or prevent actuation of said device by certain high dwells of said cam means, and means device is maintained in said predetermined posifor simultaneously driving said cam means and for positioning said member.

12. In combination, a device to be actuated, cam means associated with said device for repeatedly actuating said device, a member physically independent of said cam means movable to positions to permit or prevent actuation of said device by said cam means, means for simultaneously driving said cam means and for positioning said member, and adjustable means to determine the number of device actuations permitted by said movable member in respect to the total number of actuations which would take place if said movable member were maintained continuously in its device actuation permitting Position. I

13. In a timing mechanism, a device to be actuated, a first cam for actuating said device, a second cam for preventing actuation of said device by said first cam, a single driving means for Both of said cams, an adjustable means to determine the ratio of device actuation to device nonactuation permitted by said second cam.

14. In a timing mechanism, in combination, a cam, a pivoted cam follower Which is oscillated by said cam upon rotation of said cam, a device actuated by said cam followenmeans for shift ing the pivot point of said cam follower to vary movement of said cam follower from actuating the amount of movement imparted to said cam follower bysaid cam, and means preventing said device.

15. In a timing mechanism, in combination, a cam, a pivoted cam follower which is oscillated by said cam upon rotation oisaid cam, a device actuated by said cam follower, a member movable to a position to prevent movement of said cam follower from actuating said device, and

means to move said member to said position at predetermined intervals correlated with the rotation of said cam to thereby prevent actuation of said device at predetermined times.

16. In a timing mechanism, in combination, a

cam, a pivoted cam followerwhich is oscillated by said cam upon rotation 'of said cam, a device actuated by said cam follower, a member movable to a position to prevent said cam follower from

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