US2326002A - Control of fuel feeding devices - Google Patents

Description

CONTROL OF FUEL FEEDING DEVCES Filed Jan. 2, 1941 2 Sheets-Sheet l f|15 11 f g5 l 'X E I3 3 6 lol INVENTOR j BYAlbr .ono\.14- L my d 22A/2.

ATTORNEY Aug. 3, 1943.

A. E. BAAK CONTROL OF FUEL FEED-ING DEVICES Filed Jan. 2, 1941 2 Sheets-Sheet 2 LVI/ ATTORNEY Patented Aug. 3, 1943 UNITED STATES PA'IENT- OFFICE CONTROL F FUEL FEEDING DEVICES Albert E. Baak, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a' corporation of Delaware Application January 2, 1941, Serial No. 372,783

9 Claims.

This invention is concerned with the control of fuel feeding devices, principally stokers and is particularly directed to improvements in automatic systems for controlling stokers in response to temperature and time and to improvements in timing apparatus adapted for use in such systems.

It is common practice to control stokers by means of a space thermostat and a timing device,- the latter serving to intermittently operate the stoker for fire maintaining purposes during mild weather. The control arrangement is usually electrical, comprising circuits controlled by contact mechanism operated by the timing device and by the space thermostat. l

The object of my invention is to provide an improved electrical system for controlling a stoker by a thermostat and a timer, the improvements residing in part in arrangements whereby control from the timer and adjustment of the timed operation are simplified so as to reduce the cost of manufacture and enable operators to adjust the controls with greater facility.

Another object of my invention is to provide an improved arrangement for controlling a relay by means of a timer wherein the contacts which cause energizaton of the relay need not be snap acting and the length of the energized period of therelay may be adjusted merely by adjusting a screw.

Another object is to provide an improved heat actuated device for producing rotary motion of a timing device. 1

Another object is to provide an improved heat motor for a timer having an expansible and contractible heat responsive element andarrangements whereby the element rotates a member about a sha-ft both when the element cools and when it heats.

Another object is to provide a device as set forth in the foregoing object wherein the heat motor is located within the rotary member.

Figure l is a partly diagrammatic view of a stoker control system embodying my invention showing the details of the heat motor actuated timer.

Figure 2 is a plan view of the timer cam.

Figure 3 is a view of a completely assembled control unit, embodying the timing mechanism," relay and transformers.

Figure 4 is a view of an unassembled part of the timing mechanism.

Figure 5 is a View similar to Figure 4 showing parts of the timing mechanism more completely assembled.

Figure 6 is a detail of the contacting mechanism, and

Figure '7 is a view of a modified form of heat motor.

Referring to Figure 1 of the drawings, numeral I 0 designates a stoker which may be of any known type and which forms part of a fuel burning device which may be any of various known forms. The controls for the stoker 1nclude a relay II having a winding I2, the armature of which is connected to movable switch blades I3 and I4 having electrical contacts l5 and I6, the switch blades moving to the left when the winding I2 is energized bringing their contacts into engagement with fixed electrical contacts I1 and I8 respectively. Numeral 2l designates a space thermostat of a known type comprising a circular bimetal element 22 to which is attached two switch blades 23 and 24 movable to the left by the bimetal element into engagement with fixed electrical contacts 25 and 26 respectively. The bimetal element 22 contracts upon a drop in temperature, its free end then moving in a direction to move the blades 23 and 24 to the left, the blade 24 engaging contact 26 at a predetermined temperature which may be 72, for example, and the blade 23 engaging the contact 25 at a, predetermined lower temperature which may be one or two degrees lower, for example, this lower temperature may be 70. Power for operation of the relay II is supplied by a stepdown transformer 29 having a primary winding 30 and a secondary Winding 3 I, the primary winding having a greater I number of turns than the secondary winding.

- Power is supplied to the transformer 29 through wires 32 and 33 which may be connected to any suitable power source.

The relay II may also be controlled by a time operated contacting mechanism which is designated generally by the numeral 35; the details of the time mechanism will presently be described. In connecton with the timing mechanism 35, there is provided a second transformer 36 having a primary winding 31 and a secondary winding 38, the primary winding having the greater number of turns. Numerals 39 and 4U designate line conductors whereby power is supplied to the stoker and to the transformer 36. The circuits ofthe stoker and the transformer 36 will presently be described,

My invention contemplates the manufacture of designates the casing of the control unit or device. The transformers 29 and 36 are shown suitably mounted on a panel 43 within the casing 42, which panel has brackets 44 and 45 which are i disposed between suitable ears on a -side wall of the casing 42 and which are fastened nto the side wall of the casing 42 by bolts as shown. The

. relay I I of Figure 1 may be of the hinge type, as

shown in Figure 3, and is also mounted on the panel 43 on the side of the casing 42 opposite the transformers. In this type of relay the two pairs need not be described in further detail. At the upper part of the casing 42, as seen in Figure 3, adjacent the opposite sides are bracket members 46 and 41 which are secured to the bottom of the casing and which have openings through which electrical leads may be carried to the interior of the casing. Numeral 48 designates a terminal panel having a bracket 49 which is secured to the bottom of the casing 42, as shown, for holding the panel 48in place. The panel 48 has a number of electrical terminals, as shown, formed by screws whereby the necessary wining connections can be made. Between the transformers and the relay is mounted a generally rectangular casing 50 which houses the timing unit or mechanism of Figure 1. The casing 59 has 'anges 5| and 52 which are secured to the panel 43 by screws 53 and 54. Certain adjustments for the timing mechanism are provided which may be made from the outside of the casing 56, and these adjustments will presently be described.

Referring back to Figure 1, the timing mechanism comprises a cylindrical member 51 having substantial depth, -as shown, and the upper 'face of which is constructed so as to form a cam. The member 51 has a portion 58 at the upper part which is of smaller diameter, and it is carried on a shaft 59 which protrude's through the casing 50, as shown in Figures l and 3. The upper face of the member 51 has four dwells 62, 63, 64 and 65, as may be best'seen on the plan view of the cam member 51 shown in Figure 2. The dwells 62 and 64 are diametrically opposed, and thesedwells are of the same radial and angular extent.

'I'hey are spaced from the yperiphery of the member 51. The dwells have a gradual rise from the face of the member 51, and they have abruptv drop-offs at 61 'and 68. At the drop-offs 61 and 68 there are small depressions in the face of the cam, 69 Aand 19 respectively, which areof relatively small angular extent. The dwells 63 and 65 are diametrically opposed and Ialso vhave a gradual rise with abrupt drop-oils at 1I and 12. The dwells 63 and 65 are similar except that the dwell 63 is of slightly greater radial extent than the dwells 62 and 64, and the dwell 65 is of slightly greater radial extent than the dwell 63, and the dwell 65 extending all the way to the periphery of the member 51. At the drop-oils 1i and 12 are depressions 13 and 14 respectively in the face of the member 51, these depressions being of the same radial extent as the dwells 63 and 65 and being of Arelatively 'short angularextent.

From the foregoing, it will be understood that the cam member 5 1 is wholly within the casing 58 (which is shown more or less diagrammatically in Figure l) with the shaft 59 protruding from,

the casing 50 so that it may be manually rotated, 75

the shaft 59 having the deslgnationmanua adjacent it on the casing 50 as shown in-Figure'.

The cam member 51 is normally rotated ina counter-clockwise direction by a heat actuated device or heat motor designated generally at 11, which heat motor is mounted on a panel 18. The panel 18 has the same dimensions las the casing 50 including its flanges, and the panel'18 is'positioned between the iianges 5l and 52 `and the panel 43 with the screws 53 and 54 securing the parts inassembled relationship, the' heat motor 11, as will now appear, is inside of the cam member 51 which of course, as has been pointed out above, is within the casing 50. 'i y g Referring now to the heat motor 11, numeral 19 designates an arbor carried onv the panel. 18 and rotatably mounted on the arbor 19 isa member having a downwardly extending arm 8| and an upwardly extending arm 82. Numeral 8f3 designates a normally xed arm member pivotally carried on the arbor 19 but having ascrew 83a attached thereto which extends through an arcuate slot 84 in the panel 18 which screwcarspiral isthen coiled into a second spiral as shown.

This arrangement of the bimetal makes il'rpossi'- ble to have a relatively large amount of bimetal arranged in a small and compact space, the amount of bimetal being suicient to provide a relatively large amount of movement when the bimetal expands and contracts in response to temperature changes. This particular arrangement of bimetal expands and contracts in. re-

spense to temperature changes along a straight line in the direction of its axis. v At the end of arm 82 is attached a nger 81 which engages lthe interior of the skirtl formed by the cam member 51, the interior surface of the skirt being grooved or serrated as shown in Figf ure 1. Numeral 88 designates an angular-arm pivoted on a xed pivot 89 and also pivoted to'an ear on the member 86 by means of a pivot 98. At

the end ofA the arm 88 is a linger 9| similar to the` finger- 81 vwhich also forms a pawl engagingthe interior grooved surface of the skirt, formedfby .the member 51. Numeral A designates a flexible Iblade, the lowerend of which is attachedv to ,the member 82 and the upper end of which carriesl a contact 96, the upper end being slightlyA spaced from the arm 82. Attached to the upper'endo'f blade 95 is an angular member 91 which extends through an opening in arm 82 and which-has'a downwardly extending projection adapted toengage the arm 82 and limit the extent to which the blade 95 may be iiexed away from the arm- 82. Numeral 98 designates a contact carried at the end of a contact screw 99 which extends through a bracket member |00 which isfsuita'bly secured to the panel v18. The contact screw 99 is disposed between .the legs of a permanent magnet Ii which is attached to the bracket |00 by means of a clamp |62 and a screw |03. The member 91.

forms an armature, and when it is broughttoa position adjacent the legs of the magnet IOI it is attracted by the iield of the magnet and the contacts 96 and 98 are brought together, with a tion shown in Figure 1, the element 86 is cold and is therefore in its contracted position with the legs 82 and 88 spaced relatively far apart, the contacts 96 and 98 just having been snapped into engagement. Engagement of the contacts completes a circuit for transformer 36 as follows: from line conductor 39, through wire |01, primary 31 of transformer 36, Wire |08, arm 8|, member 80, blade 95, contacts 96 and 98, bracket |00, and wire |08 back to line conductor 40. Completion rotates the angular arm 88 in a clockwise direction about its pivot 89 so that this arm moves towardsthe arm .82 with the pawf 9| sliding over the serrations on the inner surface of the skirt of member 51. The contacts 96and 98 stay in engagement with each other until the arm 82 engages the downwardly extending projection of member 91, and when this occurs, further leftward movement of arm 82 pulls the flexible blade 95v to the left so as to disengage the contacts 9,6 and 98 interrupting the circuit of transformer 36. When the circuit of transformer'36 is thus interrupted, winding 38 is deenergized and heating of element 86 discontinues and it begins to cool and contract. Member 80 is now rotated in a clockwise direction and angular arm 88 is now rotated in a counter-clockwise direction, the arms 82 and 88 moving away from each other. Pawl 9| now engages the serrations on the inner surface of member 51 rotating it again in a counter-clockwise direction and pawl 81 slides over the serrations. The arms 82 and 88 continue moving away from each other until contact 96is snapped into engagement with contact 98 with the parts again in the position shown in Figure l wherein the circuit of transformer 36 is completed. It is to be noted that flexible blade 95 provides some freedom of relative movement between arm 82` and contact 96, that is, lost motion, so that considerable movement of arm 82 is required to effect opening and closing of contacts 96 and 98. By reason of the flexible blade 95, arms 82 and 88 can move with a smooth back and forth motion inasmuch as they are free from the effect of the snap'action with which contact 96 is operated.

From the foregoing, it is to be seen that the arms 88 and 82 alternately move toward and away from each other so as to walk around the inner surface of the member 51 so as to rotate it substantially uniformly and continuously in a counter-clockwise direction. By loosening the screw which extends through the slot 84, the position of arm 83 may be adjusted and such adjustment of course adjusts the position of element 86 and the actuator arms 82 and 88. If arm 83 is adjusted to the right, it is to be Iseen that arm 82 is adjustedin a counter-clockwise direction bringtacts. n the other hand, if arm 83 is adjusted length of the steps taken by the legs, 82 and 88 is adjusted by adjusting the position of arm .l0 of this circuit energizes the transformer which 8 3. Thus by adjusting the positionof arm 83, the length of time required for the member 51 to make one complete revolution may be adjusted.

Arm 83 is so adjusted that normally the memberA 51 makes one complete revolution per hour.

Within the casing is acam follower arrangement and a contacting mechanism operated thereby. The outer side of casing 50 forms an adjustment or control panel, and on the inner surface of Vthis side of the casing 50 is carried a plate to which is attached the cam follower. The control panel formed by the outer side of casing 50 may be best seen on Figure 3 and the mechanism carried o n the inner surface of the casing 50 as may best be seen in Figure 1. Nu- -meral ||4 designates a pin having a relatively large "head, the slot ||3 engaging the pin ||4 so as to be guided thereby. At the end of each of legs and ||2 are three small spaced apertures, and cooperating with the apertures in each leg are small bossesv ||5 and ||6 raised from the surface of the inner side of'the control panel of casing 50. These bosses ||5 and 6 are adapted to fit into the apertures in the legs and ||2 of plate ||0 so as 4to hold the plate I I0 in any one of three different positions. Numerals I|9 designates a screw attached to the plate ||0 which extends through a slot |20 in thejcontrol panel of casing 50. There are indicia adjacent the slot |20, as may be seen on Figure 3, the purpose of which will be explained presently. The screw 9 may be manually grasped and moved up or down in the slot |20, as seen on Figure 3, so as to movev the plate 0 into any one of its three positions with the vbosses ||5 and |6 engaged in one of their associated apertures in the legs and ||2.

The plate v| I0 has two downwardly extending legs |22 and |23.Y At the lower end of lthese legs,

there are openings, and engaged in these openings are projections at the ends of a V-shaped member |24 which forms the cam follower. The engagement of the member |24 with the legs |22 and |23 permits pivotal movement of the cam follower. The position of the cam follower with respect to the cam in the casing 50 is best shown .in Figure ,1. The cam follower has an extending portion |25 lying, in the same plane, and this portion has two projecting portions |26 and |21 lying in a perpendicular plane (see Figure 1).

cause arm 82 to engage the downwardly extending projection of member 91 for opening the con- The projection |26 rides on the cam member 51. The projection |21 of the cam follower |24 nor- Vmally bears against an abutment |28 formed at opening in the side wall of the casing adjacent a pair of ears |32 and |33 extending outwardly from the side of the casing 50. The shoulders are pivoted to the ears by means of a, pin |34, as shown on Figures 3 and 5, whereby7V the member |29 may move pivotally about the'pin |34, that is in the manner of a hinge. |29 is normally biased about its pivot away from the control panel of casingl 50 by a coiled spring as may be seen on Figure 6. 'Ihe member |29 has a medial rib |35 and the abutmentl |28 forms part of a broader rib |36, there being rectangular recesses or depressions on opposite sides of rib |36. Numeral |31 (see Figure 6) designates a flexible contact blade, the right end of which is attached to the member |29 in the recess at one side of rib |36. At its free end, blade |31 carries electrical contacts |39 and |39. The blade 31 has an ear |40 for attaching an electrical lead thereto. Numeral |4| designates a U-shaped contact bracket which is attached to the member |29 by rivets or the like as may be best seen on Figure 5. The member |4I` has a leg |42 which is flexible, the entire bracket |4| being made of flexible material. At its end the leg |42 carries a contact |43 which is adjacent and cooperable with the contact 39. The member |4 has a leg |48 which carries a contact |44 at its end which is hidden by the cam follower on Figure but which may be seen on Figure 1. The contact |44 cooperates with a contact |45 on the end of a contact screw |46 (see Figure 1) which -is carried at the end of a contact bracket |41 which is suitably secured to a side of the casing 50. There are rigid backing members interposed between each of the legs |42 and |48 and the member |29, and one of these may be seen at |50 on Figure 6. The member |4| has an ear |5| for attaching an electrical lead thereto.

The contact |39 at the end of blade 31 cooperates with a contact |53 (see Figures 1 and 6) carried at the end of a contact bracket 54 which is suitably secured to a side of the casingl 50. Numeral .|55 designates a rotatable member Member which is rotatable by a screw |56 which extends through the control panel of casing and which is rotatable from outside of the casing. The memberv comprises a disk portion |51, part of which is of slightly greater radius than the other part whereby shoulders are formed, as seen on Figure 4, and these shoulders cooperate with a stop |56 so as to limit rotation of the member.` |55 by the screw |56. The portion |51 has numbered graduations on its face from 2 to '7 and these graduations are visible through a-slot |60 in the control panel of casing 50.. As will be explained hereinafter the screw |56 is an adjustment for adjusting the length of time that the stoker is automatically operated by the timing mechanism for purposes ,of maintaining the re. The member |55 hasv a circular rib |6|, the edge r of which forms a gradually rising surface, the rib |6| forming a cam which bears against a' shoulder |62 on the contact bracket |54; thus by rotating the member 55 by means of the screw |56, the rib |6| moves the bracket |54 so as to adjust the position of contact |53. By thus adjusting the position of contact |53, the period of time that .contacts |53 and |38 are kept engaged is varied, pas will presently be described.

Reference is now made particularly to Figure 1 wherein the relative positions of the cam, the cam follower and the contacting mechanism within the casing 50 are shown. Theprojection |26 of the cam follower |24 rides on the cam 51 adjacent its periphery, and as the cam rotates,

one or more of the dwells on the cam lift the left end 0f the camv follower |24 rotating it slightly causing the projection |21 which bears against abutment |28 to move the member |29 in a counter-clockwise direction, as seen on Figure 6. that is to move the contacts |43 and |44 upwardly, as seen on Figure 1. When the screw ||9 is moved downwardly in slot |20 to the end of the slot (this would be leftward movement of screw |9 as seen on Figure 1), the end of the cam follower |24 and projection |26 are very close to the edge of cam 51 so that under the circumstances the prois, there is then only one contacting operation and consequently only one timed operation of the stoker per hour as will presently appear, lthe screw ||9 being adjacent the graduation marked 60 (the graduations adjacent slot |20 indicating minutes of time) on the control panel of casing 50. When the screw ||9 is movedto a mid position in slot |20, the cam follower has its left end moved toward the center of the cam sufficiently so that projection |26 will miss the dwells 62 and 64 but both of the dwells .63 and 65 will be effective. There will now be two contacting operations per hour produced by the timing mechanism, the screw I|9 being adjacent the graduation vmarked 30 on the control panel of casing 50. When the screw ||9 is moved to the upper end of the slot |20, as seen in Figure 3, that is to the right as seen in Figure 1, the left end of cam follower |24 is moved towards the center of the cam sufdciently so that the projection |26 will now not miss any of the dwellsand consequently there will be four contacting operations per hour, the screw ||9 now being adjacent the graduation marked |5 on the control panel of casing 50.

The contacts |44 and |45 are normally in engagement, and when the end of the cam follower is raised by one oi the gradually rising dwells causing the end of member 29 to be lifted, the leg |48 exes, contacts |44 and |45 remaining in engagement, and contact |38 is brought into engagement with contact |53. This will happen when the projection |26 is at a predetermined position on one of the gradually rising dwells,4

and as the end of member |29 continues to be lifted, upward movement of leg |42 will move -"i contact |43 into engagement .with contact |39.

- now be described. Whenever the space temperature falls to '10 so as to bring both blades 23 and 24 into engagement with their associated contacts, the relay is energized through the following circuit: from secondary 3| of transformer 29 through wire |10, contact 26,' thermostatic blade 24, element 22, blade 23, contact 25, wire |1|, wire |12, contact bracket |4|; contacts |44 and |45, contact screw |46, contact bracket |41, wire |13, relay'winding I2 and wire |14 back to secondary 3|. Energization of winding I2 causes blades |3 and |4 to move to the left bringing their associated contacts into engagement. Engagement of contacts |5 and |1 produces a maintaining circuit for the relay II as follows: from secondary 3| of transformer 29 through Wire |10, contact 26, blade 24, element 22, wire |15, wire |16, blade |3, contacts I5 and l1, wire |11, wire |12, contact bracket |4|, contacts |44 and |45, contact screw |46, contact bracket |41, wire |13, Winding I2 and wire |14 back to secondary 3|. It will be seen that the maintaining circuit is independent of the therlmostatic contact 25 so that after the relay has been energized, it will remain energized until the temperature rises to a value of '12 at which blade 24 disengages from contact 26. It should be noted also that both the original energizing circuit and the maintaining circuit for relay extend through the contacts |44 and |45, which as pointed out above, are normally closed, and which I prefer to refer to as auxiliary contacts. When the contacts I6 and I8 are engaged a circuit for the stoker l is completed as follows: from line conductor 39 to wire |80, through contacts |8 and I6, blade |4, wire |8|, through the stoker and wire |82 back to line conductor 40. The stoker will be kept in operationv until the temperature has risen to '12 so as to cause both of the thermostatic contacts to be disengaged.

The heat motor driven mechanism operates continuously so as to keep the cam 51 constantly rotating in a counter-clockwise direction one revolution per hour. When heat requirements are relatively low so that the thermostat does not often cause operation of the Stoker, the stoker must be intermittently operated by the timing mechanism to prevent the fire from going out. With the screw |9 in the mid position of slot |20 as shown on Figure 3, the projection |26 at the end of the cam follower |24 is in such a position as to make the dwells 63 and 65 effective so as to produce two automatic timed operations of the stoker per hour. Thus when the end of the cam follower is raised by one of the dwells 63 or 65, the end of member |29 will be raised and contacts |38 and |53 will first be brought into engagement. these contacts are brought into engagement, but when the end of member |29 is further raised and contacts |39 and |43 are brought into env gagement, a circuit for the relay will be completed as follows: from secondary winding 3|,-

through wire |84, contact bracket |54, contacts |53 and |38, blade |31, contacts |39 and |43, contact bracket |4|, contacts |44 and |45, contact t screw |46, contact bracket |41, wire 13, winding |2 and wire |14 back to secondary 3|. The relay will now be energized and engagement of contacts I and |1 will complete a maintaining circuit for the relay as follows: from secondary winding 3 I, through wire |84, contact bracket 54, contacts |53 and |38, blade |31, ear |40, wire |81, Wire |16, blade I3, contacts I5 and |1, Wire |11, wire |12, contact bracket |4I, contacts |44 and |45, contact screw |46, contact bracket |41, wire |13, winding |2 and wire |14 back to transformer secondary 3|. It will be seen from the immediately foregoing, that the maintaining circuit is independent of the contacts |39 and |43. From the description previously made, it will be remembered that when the left end of member |29 is raised, contacts |53 and-|38 are first brought into engagement but the relay is not energized until contacts |43 and |39 are brought into engagement. `Thus as soon as the relay is ener- No circuits will be completed when gized, a maintaining circuit is formed through contacts |53 and |38 which will be relatively firmly engaged at the time, and this circuit is independent of the contacts |43 and |39 which at the time are not yet firmly engaged inasmuch as the projection |26 rises only gradually on the gradually rising cam dwells. By reasonof the maintaining circuit through the firmly closed contacts, sparking is prevented at the other contacts which are not immediately firmly engaged when the relay is energized. This contacting arrangement for eliminating sparking and conse- 'quent deterioration of the contacts is a. feature of my invention. f

After the relay has been energized by the timing mechanism, the stoker is operated in the same manner as previously described. When the relay* has been so energized, it remains energized until the projection |26 drops off the cam dwell which lifted it for operating the contacting mechanism. All of the timer contacts remain in engagement until the projection |26 drops off the cam dwell. For instance, if the cam follower was lifted by the dwell 65, when the cam has rotated suiliciently, the projection |26 will drop in to the depression 14 for opening the contacts and deenergizing the relay as will presently be described. As has previously been pointed out, the relay will be energized when the projection |26 is at a predetermined position on one of the cam dwells, for instance, on dwell 65, and this position will be determined by the adjustment of the contact bracket |54 as determined by the position of member |51. After the relay has been so energized, a predetermined number of minutes will expire during which the cam 51 will continue rotating until the cam follower, that is projection |26, drops in to a depression, for instance the depression 14. The parts are so arranged and adjusted that the said number of minutes will be the number appearing through the slot of the control panel of casing 50 opposite the index marker. In other words, the number of minutes during which the relay is kept energized by the timing mechanism is determined by the adjustment of screw |56, and the desired number of minutes can be set opposite the index marker on the control panel and visible through the slot |60.

When the projection |26 drops oi the drop-off of dwell into the depression 14, the end of member |29 is allowed to move downwardly to a position lower than normal inasmuch as the depression 14 is lower than the normal atface of member 51. When the end of member |29 is allowed to move to the lower than normal position, the bracket |4| is moved downwardly enough to cause contacts |53 and |38 to disengage, to cause contacts |39 and |43 to disengage and also to cause disengagement of the normally closed auxiliary contacts |44 and |45. The contacts |44 and |45 remain open only.for a very short time While the projection |26 is in the depression 14 (or in a similar depression). As soon as the cam has rotated sufficiently to bring the projection I 26 back up on the normal at face of the cam, the contacting mechanism is returned toits normal position as seen in Figure l, wherein the auxiliary contacts |44 and |45 are closed. The purpose of opening the auxiliary contacts `after each timed operation of the stoker is to pretimed operation, blade 24 of the thermostat 2| may be in engagement with contact 26, and while this position of the thermostat is not onecalling for stoker operation, if the relay has been energized, the thermostatic maintaining circuit through contact 26 would keep the relay in energized position unless this maintaining circuit were interrupted by disengaging contacts l44-and |45. Thus after there has been a timed operation of the stoker, the relay will be positively deenergized and will only be reenergized by the thermostat if both blades of the thermostat are engaging their associated contacts. If during a timed operation of the Stoker the space temperature should fall sufficiently to cause both therlmostatic blades to engage their associated contacts, at the endof the timed operation the relay will be deenergized as described but will be reenergized in response to the normal thermostatic demand as soon as the projection |26 of the cam follower has passed the depression at the dropoff of the dwell to reclose the auxiliary contacts.

From the foregoing, it should now be recognized by those skilled in the art that I have provided a very compact, inexpensive and Aeiiicient control instrument embodying a timing unit occupying a minimum'of space but still offering great facility, ease and simplicity of adjustment of the timing operation. The timing unit itself `is driven by a heat motor which may be very cheaply made but which still provides a suitable rangev of adjustment ofthe timing and which produces uniform and accurate timing operation.y

a nature .that they may all be made from a single small panel lying in a single plane, the cam shaft also being so positioned that it may be manually rotated by grasping its end lwhich extends through the control panel as described. The memberV 51y ofcourse is freely rotatable in a vcounterclockwise direction, there being nothing to restrain its rotation in this manner.Y 'I'he manifold advantages and utility of my invention shouldbe apparent to'those skilled in the art from the foregoing.v

-.Referring to Figure 7 of the drawings, I have shownV a slightly modified form of heat motor for driving the timing mechanism. In Figure 7, the

l* .heat `motor is mounted on a panel 18j, the same asin Figure 1, andthe rotary member 51 is the same as that of Figure 1. In the present embodiment, there are two bimetal elements 200 and 20| which are rigidly mounted in the position shown, being attached to brackets 202 and 203 respectively. The heating element 204 which l is preferably insulated is carried on the bimetal element 200 and one end of the heating element is connected to the element 200 while the other end is connected to the source of power.v At its.

,'upper end the element 200 carries an arm or finger 205 which forms a ,pawl engaging the serrations on the innerv surfacel of the skirt of member 51. At its upper end, the element 20| carriesa similar nger206 forming a pawl also engaging the-inner surface of member 51. Numeral 201 1designates a contact carried at the upper end of element 200, and numeral 208 designates a contact carried at the upper end of element I. When the heating element 204 is energized to heat the bimetal elements, the element 200 warps to the left and the element 20| warps to the right. When the elements cool, they Warp toward each other so as to bring the ` contacts 201 and 208 together. v With the parts in the position shown, the heating element 204 has been deenergized so vas to allow the elements 200 and 20| to cool so that they have warped toward each other bringing the contacts 201 and 208 together. A circuit for the heating element 204 is now completed throughV 7 the heating element, the bimetai. element 20o,

contacts 201 and 208, the bimetal element 20| and the bracket 203, which is also connected to the source of power. The heating element 204 being insulated, as long as it is energized its temperature rises .as the heat therein accumulates.v

The heat causes the bimetal elements 200 and 20| to warp away from each other, element 200 -the heater during the time it is energized causes the bimetal elements to continue to warp to some extent after the contacts are opened. When the accumulated heat has been sufliciently dissipated so as to permit the bimetal elements to begin to cool, they warp toward each other with the pawl 206 now rotating the member 51 in a counter-clockwise direction and the pawl 205 sliding over the serrations. When the bimetal elements 'have cooled sufliciently, the parts again assume the position shown in Figure 7 and the cycle is repeated. It is to be seen therefore that the arms or pawls 205 and 206 walk around the inner surface of member 51 similarly to the operation of the previous embodiment.

The forms of my invention which I have disthe art which fall Within the spirit and scope of l the invention. 'Ihe invention therefore is to be limited not by my disclosure but only by the claims appended hereto.

I claim as my invention;- 1. In apparatus of the character described,.in

- combination, an automatic stoker, control means for the stoker comprising a relay, means controlling the relay comprising contacting mechanism, a timing device capable of producing uniform cycling operation of the contacting mechanism, said timing device comprising a rotatable element, means forming a cam having gradually rising dwells, a cam follower associated with said cam, said mechanism having two pairs of electrical contacts operated by said follower so arranged that the two pairs of contacts are engaged sequentially as the follower rises on a dwell, circuit means whereby the last to close of said pairs of contacts energizes said relay and whereby a maintaining circuit for said relay is formed through the `other pair of contacts, manual means for adjusting at least one of said contacts for varying the position of the cam follower with respect to a; dwell at which the con-' tacts close to energize the relay and to thereby vary the period of time the relay is energized, actuating means for uniformly rotating the said rotary element comprising an arm having a. pawl adapted to engage the element, a. second arm having a pawl adapted to vengage said element,

heat responsive means for actuating said arms,

means whereby said heat responsive means a1- ternately heats and cools so as to cause it to expand and contract, and means whereby said heat responsive means actuates said arms so as to cause one pawl to move the element in a given direction when the heat responsive means expands and to cause the other pawlto move the as the follower rises on a dwell, manual means for adjusting one of said contacts whereby the point on a dwell at which at least one pair of contacts closes may be varied, a relay controlled by said contacts, circuit means whereby the last to close of said pairs of contacts energizes said relay and whereby a maintaining circuit for the relay is formed through the other pair of said contacts, means including a thermostat ofthe type having two pairs of contacts which close in sequence for controlling said relay, circuit means whereby a maintaining circuit for said relay may be formed through the first to close of said lpairs of contacts of the thermostat, means includving an additional pair of contacts actuatable by said cam, said lastpair of contacts being nor- `mally closed and connected in circuit with said relay and said cam having a contour such that said last means opens said additional contacts for a relatively short interval of time when said follower is at a position on the cam to deenergize the relay, opening4 of said additional contacts interrupting the maintaining circuit of said thermostat.

3. In apparatus of the character described, in combination, means forming a circular cam having gradually rising dwells which rise from the normal surface of the cam, said dwells having abrupt drop-offs, and said cam having' depressions in its normal surface of relatively small circumferential extent at the drop-offs, cam follower means associated with the cam, means .forming electrical contacts operated by said cam follower means, a relay and circuit means whereby the relay may be energized by said contacts,

the arrangement being such that the contacts close when the cam follower means are on a dwell and open when the cam follower means drop off a dwell, and additional normally closed contact means operated by said cam follower means for interrupting the relay circuit when the cam follower means drops into one of said depressions.

4. In apparatus of the character described, in combination, means comprising an automatic stoker, means for controlling ,the stoker including a relay, timing mechanism for controlling the relay comprising means forming a circular cam having gradually rising dwells which rise from the normal surface of the cam, said dwells having abrupt drop-offs, and said cam having depressions in its normal surface of relatively small circumferential extent at the drop-offs, cam follower means associated with the cam, means forming electrical contacts operated by said cam follower means, circuit means whereby the relay may be energized by said contacts, the arrangement being such that the contacts close when the cam follower means are on a dwell and open when the cam follower means drop off a dwell, means comprising a space thermostat ofthe type having two pairs of contacts which close sequentially, and circuit means whereby the thermostat may also control the relay, the relay being adapted to form a maintaining circuit for itself through the first to close of the thermostatic contacts when the relay is energized, and additional normally closed contact means operated by said cam follower means for interrupting the relay circuits when the cam follower means drops into one of said depressions, said last mentioned contact means preventing the relay from remaining energized through the thermostatic maintaining circuit after the relay has been initially energized by the timing mechanism.

5. In apparatus of the character described, in combination, an automatic stoker, control means for the Stoker comprising a relay, means contro-lling the relay comprising contacting mechanism, a timing device capable of producing uniform cycling operation of the contacting mechanism, said timing device comprising a rotatable element, actuating means for the element located therewithin comprising an arm having a pawl adapted to engage said element, a second arm having a pawl adapted to engage said element, heat responsive means for actuating said arms, means whereby said heat responsive means alternately heats and cools so as to cause it to expand and contract, and means whereby said heat responsive means actuates said arms so as to cause one pawl to move the element in a given direction when the heat responsive means expands and to cause the other pawl to move the element in said given direction when the heat responsive means contracts, said timing device comprising means forming a circular cam having gradually rising dwells which rise from the normal surface of the cam, said dwells having abrupt drop-offs, and said cam having depressions in its normal surface of relatively small circumferential extent at the drop-offs, cam follower means associated with the cam, means forming electrical contacts "operated by said cam follower means, circuit means whereby said relay is controlled by said electrical contacts, the arrangement being such that the contacts close when the cam follower means are on a dwell and open when the cam follower means `drops off a dwell,

means comprising a space thermostat of the type having two pairs of electrical contacts which close in sequence, circuit means whereby the thermostat also controls the relay, the relay being adapted to form a. maintaining circuit for itself extending through the first to close of said thermostatic contacts when the relay is energized, and additional normally closed contact means operated by said cam follower means for interrupting the relayv circuit when the cam follower means drops into one of said depressions, said last mentioned contact means operating to prevent the relay from remaining energized through 1 the thermostatic maintaining circuitwhen thev initially energized by the` timinga asaaooa a l within lthe casing and having a plurality of cirv cularly arranged cam surfaces of substantially element, actuating means for the element located therewithin comprising an arm having a pawladapted to engagesaid element, 'a'second element having a pawl adapted to engagel said element, heat responsive means for ac'tuatingsaidarm, means whereby said heat responsive means alternately heats and cools so as to cause itto expand and contract, and means whereby said heat'responsive means actuates said arm so as to cause one pawl to move the element in a given direction when the heat responsive means expands and to cause the other pawl to move the element in said given direction when the heat responsive meansA contracts,said timing device" including means forming a circular camhaving gradually' rising dwells which rise fr om'the norits normal surface of relatively small circunfferential extent at .the .drop-offs, cam4 follower means associated withthe cam, said mechanism having-two pairs of electrical contacts operated by said cam follower so arranged that vthe two .mal surface of the cam, said dwells having abrupt f drop-offs, and saidcam having depressions in vuniform angular extent but of different radial width, a cam follower within said casing and engaging said cam, means for causing relative rotation of said cam and cam follower, a switch comprising a pair of contacts one of which is normally fixed and the other of which is associated with said cam follower so as to be movable thereby into and out of engagement with the normally fixed contact, means for moving said cam follower radially of said cam to vary the frequency with which said cam follower and movable contact are actuated without varying the length of time the contacts are engaged, and means extending outside of said casing for adjusting the spacing of said normally fixed contact with respect to said normally movable contact tovvary the length of time that said contacts are engaged.

8. In a timing switch, a casing, a circular cam within the casing and having a plurality of circularly arranged cam surfaces of substantially uniform 'angular extent but of diierent radial widtha cam follower within said casing and engaging said cam, means for causing relative rotation of said cam and cam follower, a switch asso-A ciated with said cam follower and-movable there-- by into and out of contact making position, means pairs of contacts are engaged sequentially as the follower rises on a dwell, circuit means whereby the last to close of said pairs of contacts energizes said'relay and whereby a maintaining circuit for s'aid relay is formed through the other pair of contacts, manual means for adjusting at `least one of said contacts for varying the position ofthe cam follower with respect to a dwell at which the contacts close tov energize the relay and to thereby vary the period of time the relay is energized, means including a space thermostat of the type having two pairs of contacts which close in sequence and circuit means whereby the thermostat also controls the relay, said relay being adapted to form a maintaining circuit through the first to close of the thermostatic contacts when the relay is energized, and additional normally closed contact means operated by said cam follower means for interrupting the relay circuit when the cam follower means drops l' into one of said depressions, said last mentioned contact means operating to prevent the relay from remaining energized through the'thermo. static maintaining circuit when the relay has been initially energized by the timing device.

7. In a timing switch, a casing, a circular cam extending outside of said casing for moving said cam follower radially of said cam to vary the frequency with which said cam follower and switch are actuated without varying the-length of timethe switch is in its contact making position, and .further means extending outside of said casing to adjust the movement'of said switch necessary to move it to contact making position thereby to vary the length of time that said switch is in contact making position when moved to that position by said cam follower.

9. In a timing switch, a casing, a v circular cam within the casing and having a plurality of circularly arranged cam surfaces of substantially uniform angular extent but of different radial width, a cam follower within said casing and engaging said cam, means for causing relative rotation of said cam and cam follower, a switch associated with said cam follower and movable thereby into and out of contact making position, means extending outside of said casing for movingsaidcam follower away from and closer ,to

ALBERT E. BAAK.

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