US2294996A - Automatic band control and signal for ovens - Google Patents

Description

Sept. 8, 1942. H. o. ERGER 9 2,294,996

AUTOMATIC BAND CONTROL AND SIGNAL FOR OVENS Filed Nov. 16, 1939 5 Sheets-Sheet I Sept. 8, 1942. H. o. M ERCIER 2,294,996

AUTOMATIC BAND.CONTROL AND SIGNAL FOR OVENS Filed NOV. 16, 1939 5 Sheets-Sheet 2 lNVENTOR Sept. 1942- H. o. MERCIER 2,294,996

AUTOMATIC BAND CONTROL AND SIGNAL FOR OVENS Filed Nov. 16, 1939 5 Sheets-Sheetl 3 j. Trl l I I l ii 'llli' W a;

Patented Sept. 8, 1942 w ne :"AUTOMATKG BAND CONTROL AND SEGNAL FOR OVENS Harvey 0. Meroier, East Orange, N. J., assignor to National Biscuit Company, New York, N; Y., a corporation of New Jersey ....Applioation November 16, 1939, SerialNm. 304,757

- 9 Claims.

My invention relates-to an automatic ,band controltand signalfor ovens and isparticularly ,adapted foruse with ovens of the continuous band or conveyor types, although equallynseful with many .kinds ofendless. belts, conveyors, dryers or; similar driven. devices.

In recent years, ovens of the type having an endlessbandmr other form of continuous car- .ri r p in v runums at opposite endsof. the oven-,.have;come intoextensive. use.= These ovens .havenbeen increasedin tsize andecapacity until the drums often:are '250. to.-300 'feet..and more apart. and the-bandstwice that length. The s band commonly used is..enclosed within. a he ily. insulated housing or casingand practical construction requires that .therebe veryilittle clearance allowed. between the housing: and edges. of the band. This means that the band must be kept accurately centered .on the drums not,p er- -mitted to run or .shift to either side. I lithe band shifts very far it will .strikethe oven frame. and .cause greatidamageto one. or the other because the bands .cost thousands of dollars and. also the oven frame is very expensive,.Extensivednjury .-to either is very .costly. Even though .the drums .at thetwo ends of the. oven are-exactly cylindrical and exactly parallel and the ,band of exactly thesame length throughout its width, the band will not. always run true,on the drrums but shifts from side to side. This is because difierentparts of the band, whichmay be, 500105 SGOieetlcng. expand. unequally .dueto varying. temperature and operating. conditions within the. oven and for other.r.easons thatcannot .beleliminated- 2r always controlled. Heretofore, attempts ,have 11 been made to keep, thelband running true on the drums by purely mechanical.means, some of which are successful, but which cause considerable wear on the edges of the band becauseoi the great pressure or force that. theymustexert 4:

.to keep the. band inits central or normal position on the drums,.or.return it if, it, is, displaced.

The principal;object,, therefore, of the present invention is, touprovidegmeans that .will automatically e p. the .band running tween the drums Within allowable limits withouteny in- .jury. orappreciable wear along its edges.

Another. objectistoprovide means that will automatically return theband to central position on the drums, in case itdoes run to one t automatically chan e the alignment oithadrums soias to. cause the band, toreturn tocentral position, if it'has shiftedtoone side. Still. anotherobject is toprovide means that will automatically come into operationto shift one. ofthedrums relative tothe other byoneor more impu1ses,..at. spaced time intervals, until proper. correction has been made.

Another object is .to provide..meansfthat. will automatically change the alignment of. the drums by a slight incrementand then-pause until the effect. of the correctioncan be attained, usually by allowing for-band travel from onedrumto the other, then if .sufficientcorrection has not been made, to continue making it at spaoedintervals until the band againrunscentrally on the drums.

Another object isto provide. an electrically 0perated means that will be .oontrolledbythe position of the ovenband itself tokeep the bandrunning true on the drums.

Another object is toprovide means in the electrio control circuit. that will automaticallyv prcvent over-correction orshiftingof the drums too far out of parallel.

. Another object is to provide in a band control device a system of electriocontrol circuits that will be controlled bythe position of the band itself to operate a. mechanical means intermittently to return the band tocentral position and alsooperate anaudible or visible signal or signals at the same time.

The above and other objects andadvantages are attained by my invention, one embodiment of which I have illustrated in .the accompanying drawings wherein:

Fig, 1 is a diagram. of .the electric control circuits when. inoperative or with the band running in central position.

Fig. 2 is thesame diagram with the circuits closedas when the band has, shifted far enough to close one of the control switches.

Figs. 3 and .4 are plan and side elevations, respectively, eachpartly in section, showing the electrically operated. .mechanical means for shifting one. of the bearings of one of the drums to change. their alignment when the band is. oii

center.

Fig. 5 is a detail showing how the bearings may be adjusted. manually.

Fig. 6. is a section through an oven showing somewhat diagrammatically how the control switches may be actuated by the oven band when the band runs to. either side. of its normal or central position.

I will first describe the mechanical parts of the control. as exemplified in Figs. 3 to 6.and then the electric circuits and controls of Figs. 1 and 2 which control the operation of the mechanical parts.

Referring first to Figs. 3 and 4, I and 2 are parts of the side frame members of the oven at one end on which are mounted the bearings 3 and 3' in which the shaft 4 that supports the drum 5 is rotatably mounted. The bearings 3, 3 may be selfaligning bearings of well known construction as indicated by dotted lines in Fig. 3 or that may fit the shaft 4 with sufficient play to enable the hearing 3 to be shifted slightly without binding on the shaft. There are two of these drums 5 over which the oven band passes, one at each end of the oven. One of the bearings, as 3, at either or both ends of the oven, is slidably mounted on the frame member I. As shown in the drawings, the flanges of the bearing have slotted openings 6 engaged by bolts I which permit the bearing to have a sliding movement on the frame member. Any suitable mechanical means, such as a dovetail construction, may be used for slidably mounting the bearing. To shift the bearing back and forth I provide a screw threaded shaft or spindle 8 which engages in a screw threaded opening in a block 9 that is fixed to the oven frame adjacent the bearing 3. One end of this shaft has a collar. and is rotatably secured in a split block II! that is secured to the bearing 3. When this shaft 8 is rotating in either direction it will travel through the fixed block 9 and correspondingly shift the bearing 3 and change the position of the drum shaft 4 with respect to the drum shaft at the opposite end of the machine. Normally the two drum shafts at the two ends of the machine are parallel so that the continuous band runs uniformly over the two drums.

The shaft 8 is rotated by a reversible electric motor II, which preferably is a three phase motor, but may be any suitable kind, and is connected through a reduction gear to drive a grooved pulley or sprocket I2 that rotates on a shaft I3 journaled in a casting .I4 that is secured to the oven frame member I. The shaft I3 carries a worm I5 which meshes with a worm wheel I6 that is plined to the shaft 8 so that the shaft can slide with respect to the worm wheel. A hand wheel 22 is splined to the shaft I3 so that it can slide with respect thereto and has clutch elements 23 adapted to engage corresponding elements in the sprocket I2 so as to key the sprocket to the shaft I3. When it is desired to adjust the bearing 3 by hand, the clutch elements 23 are disengaged from sprocket I2 as shown in Fig. 5 and the shaft I3 rotated by hand until the desired adjustment is attained. In normal operation the clutch 23 engages in the sprocket I2.

The free end of the shaft 8 is connected to a swinging arm I! that may be pivoted at its lower end to the oven frame and at its free end carries a pair of adjustable stops IE, I9 that are adapted to strike the abutments or knobs 2!], 2I of a pair of limit switches R4 and L4 in the control circuit of the motor II and which normally are closed.

The amount that the bearing 3 is shifted in any i case is very slight and the limit switches and stops I9, 20 are provided as a safety means so that the motor circuit will be opened and the motor stopped before the bearing 3 can be shifted far enough, or the shaft 4 thrown far enough out of alignment to cause any damage.

The motor II is operated intermittently, when the oven band has shifted to one side or the other, to shift the bearing 3 by a series of nudges or impulses until the position of the band has been corrected. The action of the motor II is controlled by a pair of timing switches, one of which determines the length of the intervals between impulses, and the other determines the length of the impulse itself. The intervals between impulses are timed so that the band can make one complete travel through the oven before a second impulse is imparted to the motor and bearing 3. The interval between impulses will be adjusted according to the baking interval of the oven at that particular time and usually will run from three to eight minutes. The impulse itself is very short and the motor will operate only long enough to rotate the shaft I3 about two revolutions which will shift the bearing 3 about .014 of an inch in the form of the invention shown. The time interval of the impulse will usually be only from two to four seconds. In case the impulses continue in one direction so long that there is danger of shifting the bearing 3 too far, then either stop I8 or I9 will strike abutment 20 or 2| and open the switch R4 or L4, as the case may be, and stop the motor but the signals will continue to operate. When this occurs it indicates that there is something seriously wrong and no further adjustment can be made until the trouble has been corrected.

The operation of the motor II is controlled by the shifting of the band within the oven. Referring to Fig. 6, a section of the band is indicated at 24 and this band travels adjacent a pair of control switches R and L which have rollers 25, 26 adjacent the edges of the band and adapted to be engaged by the band when it shifts to either side. The roller 25, 26 are carried by levers 21, 28 pivotally mounted on brackets 29, 30 secured to the oven frame adjacent the edges of the band. The lower ends of the levers 2'1. 28 are connected to a pair of slides 3|, 32 adapted to engage the operating levers 33, 34 of the control switches R and L. I have shown the switch R on the righthand side of Fig. 6 and the switch L on the lefthand side. Switch R is connected in an electric circuit to control the operation of the motor II when the band shifts to the right and the switch L is connected in the circuit to control the operation of the motor I I when the band shifts to the left. The motor is driven in one direction when the switch R is closed and in the opposite direction when the switch L is closed.

The electric circuits for controlling the intermittent operation of the motor II and also for operating a set of visible and audible signals are shown diagrammatically in Figs. 1 and 2.

Fig. 1 shows the circuits when the band 24 is in its normal or central position.

Fig. 2 shows the circuits when the band 24 has shifted to the right so as to close the control switch R.

The operation of the automatic control will be described with reference to the diagram of Fig, 2.

Three phase current is supplied through the three wires, A, B, C and the transmission of energy to the system is controlled by a three pole switch S, which is closed when the apparatus is in operation.

When the switch S is closed the three wires A, B, C lead to a reversing switch which is of commercial construction and is housed within a metal casing for controlling the motor II. Each of the wires A, B, C has two branches, leads going from the wire A to the contacts a, a, from the wire B to the contacts b, b, and from the wire C to the contacts 0, c, of the two contactors in the reversing switch for controlling the motor II.

When the coil 35 of-the contactor- L3, shown at the left in Fig; 2,=-isenergized; aconnection is made-between the contacts a, b, c and the wires 36, Hand 38-leading*to the motor to drive it in 'one direction.

- When the coil-39 of the contactor R3; shown at the right, is energized, the circuit is completed through the contacts a, b, cwith the wires 36,

' 38 and 3'! to'drive the motor II: in the opposite direction. It is to be noted that the order of the wires 36, 31, 38 with respect to contactor R3 is difierent from their order with respectto the contacto'r L3 so as to effect a reverse driving of the motor.

To control the contactors' R3 andL3, I take a pair of leads 40, 4| from any two ofthe wires A,

B,- and C. In the diagrams, I take these leads from the contacts a, c. These two wires 40 andwhose operation is controlled by shifting of the band 24, as shown in Fig. 6. In Fig. 2 I haveshown this switch R as closed. The wire 42 continues from switch R as43 to one sideof the coil 44 of a relay RI. The wire continues from the other side of the relay coil to-one side of the coil 45 of a' relay R2 'and from there the wire 43 continues to the opposite pole of the switch R. From the switch R the circuit continues past its junction at 46 with an alarm circuit, presently to be described, down to its junction at t! with one of the relay circuits, thence on as wire 13 to the opposite pole of the switch SI.

It will thus be seen that when the =switch R is closed the coil 134 of the 'relay' RI is energized The timing switch T2 isthe long interval switch previously referred to and is automatically set or reclosed at thee'nd'of each time interval for which it has been adjusted. Thus, if it-be adjusted so as to operate the motor ll at five minute intervals then at the end of-each of these periods it is automatically closed.

The timing switch TI is the short interval switch and its opening and closing movements are controlled by the motor TM and clutch coil C so that the switch T! will remain closed for a short interval usually from two to four-seconds when the switch T2 is also closed and the relay Rl' energized. In Fig. 2', I show both of the switches TI and T2 closed.

The timing switches Tl; T2, timing motor TM,-.--

and clutch coil C are shown'only diagrammatically, the four constituting a commercial form 'of control unit that is housed within a metal box or casing indicated by the dash lines D, this-being a conventional showing of such a control unit. In a usual construction, the movable element of each timing switch Tl T2, comprises two or more cam discs mounted on a shaft driven by motor TM. The discs of eachswitch are angularlyiadjustable with respect to each other and with're specttothe shaft, so: that the crest or high :part of thecam that closes the contactmaybe. long or short, thus :holding the switch closed for a. longer or shorter intervaL. and the. closing may; occur earlierwor later during the cycle. Thus if the -cycleof switch'T2. be set for a live minuteinterval; theacam discs maybe set for a closing period of any length, as say ten seconds,'and that closing period may be made, to occur .at any time duringlthe five minute cycle. The'closed period of-switch'iT2 usually is longer andnever less than thatof TI, and TI is. set to close duringtthe closed interval'of T2. 'I'he timing switchassembly is not per se apart of my invention, but I :have. described a commercial form of such apparatus so that its use in my invention will be clearly understood.

Assuming now that the band has shifted'slight- 1y to the right of Fig. 6- so as to have'closed the control switch R; as shown in Fig. 2, the. re-

lay R! has been energized and the contact-48 "closed-through the circuit previously described.

When the contact 48 is closed, the line up to one side'of the timing motor TM is a live line comprising wire 63: from switch S, to connection- 3! 4 and thence by wire 4'! to contact-43, and wire 15 to one side of motor TM."The lead from the which will operate to close switch TI. This completes the circuit through the coil of therelay R2 and also the circuit forthe signals 49-52. '35

The circuit to the signals 49-52 will next'be described. The wire 43 leading from the source of power is connected at to a wire 53 to which one side 'of each'of the four signals is connected,

1 all in parallel. w The opposite side of each of the signals is connected to a wire 54 which extends 1 acrossand down to one side of the coil ifi of the relay'RZ and then to a connection 55 with a wire -55 which leads to one side of the timing switch Tl. From -'Ii,a wire 57 leads to the timing -switch'T2 and thence .by wire 53 to one of the poles of the switch S to which the wire 4 from the main line is connected. This completesthe circuit through the signals all of which are operated simultaneously when the relay RI is closed and the timing switches TI and T2 are closed.

'As previously described, one side of the coil ,5 of the relay R2 is connected through the switch R with the wire43 and the opposite terminal of this coil is connected to the wire 55 which is a part of the circuit for the signals when the timing switches TI and T2 are closed so that when the signals are operated the relay R2 is also energized. When this occurs the contact 59 is closed, this being in the circuit of the contactor R3 which controls the operation of the motor H in one direction. This circuit will be described next. A

- wire (5 leads from the terminal a through an automatic cut-out or overload relay 6! leading to one side of the coil 38 of the contactor R3. I From side of the limit switch R4.

the opposite side a wire 62 leads to a second overload-relayfifi from'which a wire '54 leads to one -previously described in connection with. 3

- and 4 is-normally closed and is open only when This limit switch asv that is connected to the terminal thus completing the circuit through the coil 39 of contactor R3. This energizes the coil 39, closes the contactor and connects the terminals (1', b c, with the wires 36, 33, 31 to drive the motor II in one direction. This circuit remains closed and the motor II is driven for a short interval until the switch Tl opens which breaks the circuit to the signals and also opens the circuit of the relay R2 which causes the contact 59 to open and break the circuit to the coil 39 of the contactor R3. This causes contactor R3 to open and stop the motor. Now even though the switch R. remains closed, the motor will not run again until after the elapse of the interval for which the timing switch T2 is set. The interval of the timing switch T2 usually is determined by the time which it takes the band 24 to travel the length of the oven. When the bearing 3 of the drum 6 is shifted slightly, the effect of this correction cannot be fully determined until the oven band has traveled the length of the oven. Usually a shifting of the bearing 3 for a few thousandths of an inch will be suflicient to correct the alignment of the drums and cause the band to travel back to its central or neutral position. However, if it is not fully corrected by the first nudging over of the bearing 3, and the switch R remains closed, then at the end of the proper time interval the switch T2 will again be automatically set and the motor II will run for another short interval, to nudge the bearing 3 over a little further. This will continue until the band is returned to central position and the switch R opened. In order to prevent the bearing 3 from being shifted too far by repeated nudges in one direction, I provide the limit switches R4 and L4. The switch R4 operates in conjunction with the relays RI, R2 and contactor R3. The abutment l8 previously referred to is adapted to strike the abutment when the bearing 3 is being shifted too far (by reason of the switch R being closed) and open the limit switch R4 which breaks the circuit to the motor contactor R3 so that the motor I! cannot be operated but the signals 49-52 continue to operate at intervals as controlled by the timing switch T2.

When the band 24 shifts to the left (Fig. 6) so as to close the control switch L, the relays LI, L2, and contactor L3 are energized so as to complete the circuit to the motor II and drive it in the opposite direction and also to operate the signals 49-52 as will now be described.

The wire 42 is connected at 66 to a wire 61 leading to one pole of the switch L. A wire 68 leads from the opposite terminal of the switch to one side of the coil 33 of the relay Ll. From the opposite side of this coil a wire 69 leads to one side of the coil 13 of the relay L2 from which a wire H leads to the opposite pole of the switch L. The opposite terminal of this switch L is connected to a wire 12 which is connected to the wire 53 which leads back to the switch S to complete the circuit. This energizes the relay Ll which closes the contacts !3 in a circuit which includes the timing switches Tl, T2 and relay L2 and the signals 4 352. When the relay Ll is energized, the contacts 13 are closed which leads current up to one side of the timing switch motor TM so that it is ready to operate to close the timing switch T! as soon as the timing switch T2 is reset which as previously stated is done automatically at the end of each time interval. The circuit from the relay Li comprises a wire which is connected at T4 to the wire 41 which in turn is connected to the live wire 43 from the main line. From the opposite side of the relay contact a wire 15 leads to the timing motor TM and by a wire 51 toone side of the timing switch T2. The opposite side of the timing switch is connected by wire 58 to one terminal of switch S so that the motor TM will set the switch TI as soon as T2 is closed.

When the switch TI is closed this also completes the circuit through the coil of the relay L2. As previously described, a live wire H leads to one side of the coil of relay L2 and when switch TI is closed, the circuit is completed through the wire 56, switches TI, T2 and wire 58 back to switch S and through that to wire 40 and terminal a.

Energizing relay L2 closes the contact 16 which completes the circuit of the motor control contactor L3. This circuit is as follows: The terminal c is connected with the terminal 0' which is connected by the wires 4| and 43 to the wire 41' which is connected by the wire 11 to one side of the relay contact 16. When this contact is closed, the circuit continues through wire 18 to limit switch L4 and then by wire 19 to a short wire in the motor control contactor box which in turn is connected to an overload cut-out 8| thence by wire 82 to one side of the contactor coil 35. From the opposite side of the coil, a wire 83 leads to a second overload cut-out 84 from which a wire 85 leads to the terminal a. This completes the circuit through the contactor coil 35 which is now energized and connects the terminals a, b, c, with the wires 36, 31, 38 to drive the motor I i in the direction opposite to that which it was driven when the switch R was closed. The motor now runs for a few seconds until the switch TI is opened after which it remains inactive until the band has traveled the length of the oven and then if sufficient correction has not been made the timing switch T2 will be closed and another short impulse imparted to the motor I I. This continues until suflicient correction has been made and the band returned to its normal position or until the abutment I9 strikes the abutment 2| and opens the limit switch L4.

The circuit for the signals 4952 is also completed when the timing switch TI is closed following the closing of control switch L and comprises the same wires and connections as when the control switch R is closed,

While I have shown my invention as embodied in a device for keeping an endless band and a drum running in alignment, it is equally adapted to keeping other parts of the oven or feeding and delivery conveyors running in alignment with the baking band. In some types of ovens, there are two or more bands or conveyors which receive the goods successively, each preceeding apron or band delivering the goods to the next succeeding band. It is necessary that these bands or aprons be kept accurately in alignment. It is within the contemplation of my invention, that the motor H may be connected to shift one or the other of two bands, or ne of the drums or guides over which they run to restore them to alignment in case one of the bands runs to one side.

It will also be understood that the drawings and terms used are but illustrative of the invention and are not to be construed as limitations thereon. The invention may be embodied in many other forms and can be used with many types of ovens, dryers, belts, conveyors and other apparatus. I claim as my invention all such devices and equivalents thereof-thatcome'withinthe scope of my claims.

What I claim is:

1. In a control device of the character described, thecombination with an endless band passing. around-drums spaced apart of a control switch mounted adjacenteach edge of one run of the endless band, each of said switches beingnormally open and adapted to be closed by contact with the edge of the band adjacent the switch upon lateral movement of the band toward it, means actuated upon closing of either of said switches to shift one of said drums angularly by recurring impulses until said band moves away from said closed switch, means for operating a signal intermittently upon closing of said. switch, and means for 'stopping'said impulses when said drum has been shifted angularlya predetermined distance in either direction and the operative control switch remains c1osed,.,

whereby said shifting meansbecomes inoperative and said signal continues to.operate intermit tently.

2. In a control device of the character described, the combination with an endless band passing around drums spaced apart of means for returning the band to central'position on the drums when it runs to either side comprising a shaft upon which one of the drums is mounted,- a bearing for each end of the shaft, one of said bearings being mounted to slide perpendicular to said shaft, a screw'threaded spindle connected to said bearing so'that rotation of the spindle will slide. the bearing, a reversible. electric motor con- I cuits whereby said circuits will be interrupted at I spaced time intervals when either-of said control switches is closed, and means actuated to open the operative motor circuit when said bearing has mains closed.

3. In a control device of the character described, in combination an endless band passing been shifted a pre-determined amount and .the control switch in the operative motor circuit rearound drums spaced apart, a shiftable bearing for one of said drums, a reversible motor, a pairof circuits for said motor, connections between said motor and shiftable bearing whereby said motor may shift the bearing in either direction, a contactor in each of said motor circuits that is normally open, a motor control circuit for each of said contactors, a relay operated contact in each of said motor control circuits, two control switches that are normally open, each control switch associated with one edge of said band, devices associated with each switch whereby one switch will be closed upon side shifting of the band on the drums, a timing switch connected in circuits with the relays operating the motor control circuit contacts, relay controlled contacts in said timing switch circuits, and circuits including relays operating said timing switch contacts on said control switches, whereby upon closing of either of said control switches by shifting of the band the corresponding timing switch circuit will next.

be-closed which will energize the relay. operating the motor control contact in the associated motor control circuit and close a motor circuit to drive themotorin one direction to shift the .drum. bearing and return the band to centralpositionh 4. In a control device of the character. de-

scribed, in combination an endless band passing, around drums spaced apart, a shiftablebearing.

for one of said drums, a reversible motor, -a pair of circuits for said motor, connections between. said motor and shiftable bearing whereby. said.-

motor may shiftzthe bearing in either direction,,a contactor in each of said motor circuits that is normally open, a motor control circuit for=each..

of said contactors, a relay in each of .said motor control circuits,- two control switchesthat are. normally. open, each control switch associated with one edge of said band, devices associated with each switch whereby one switch, will be closed-upon side shifting of the.bandon the, drums, a timing switch connected in circuits with. saidmotor circuit relays, relay controlled switches in'said timing switch circuits. circuits including, said, timing switch relays and controlswitches,

wherebyupon closing of either of said control switches by shifting of the band the correspond-i ing timing switch circuit will next be closed which will energize the relay in theassociated mot-org control circuit and closea motorcircuitto drive i the motor in one direction to shift the. drumbeare, ing and return the band to central position, an electrically operated signal, a circuit. for-said sig-,.. nalincluding said timing switch whereupon said signal will be operated when said timing switch l.

is closed.

5. In a control device of the ,character ,de-f,

scribed, in combination an endlesslband passing around drums spaced apart, a shiftable bearing for one ofsaid'drums, a reversible .motor, a pair;

of circuits for said motor,.connections between.

said motor and shiftable :bearin'g whereby: said, motor may shift the bearing in either direction,-.v a contactor in each of said motorcircuits thatis normally open, a motor control circuit-.foreach of;

said contactors, a relay in each of said motor con.-.v trol circuits, two control switches that. are .nor-.-.

mally. open,-.each control switch associated with. one edge of said band, devices associated with,.. each switch whereby one switch willbe;v closed.

upon side shifting of the band on the drums, .a

timing switch connected .in. circuits. with, said. motor circuit relays, relay controlled switches in,

said timing switch circuits, circuits including said timing-switch relays and control switches, where- "by upon closing of either of said control .switches 1 byshifting of the .band the corresponding timing switch circuit will next be closed which will.

energize the relay in the associated motor control circuit and close a motor circuit to drive the motor in one direction to shift the drum bearing and return the band to central position, a limit switch that is normally closed in each of said motor control circuits, and means actuated by the means which moves said shiftable bearing to open the limit switch in the closed motor control circuit when the bearing has been shifted a predetermined maximum distance.

6. In a control device for an endless band having upper and lower runs passing around drums spaced apart the combination with the endless band of a rotating drum about which the band passes, a shaft upon which the drum is mounted, a bearing for each end of the shaft, means for mounting one of said bearings so that it is slidable perpendicular to the shaft and in the direction of the length of the band, shifting means operated by lateral displacement of the band in either direction on said drum .to shift said slidable bearing by a slight increment in a direction to cause the band to return to central position, means for interrupting operation of said shifting means until the band has traveled over the drum sufficiently to determine the corrective effect of the shifting of the bearing, said interrupting means operating at recurrent intervals while the band remains displaced to restore operation of the shifting means until the cumulative effect of the recurrent shiftings of the bearing restores the band to central position, and means actuated by the shifting of the bearing for rendering said shifting means inoperative when said bearing has been shifted to a predetermined limit and the band has not been returned to central position.

'7. In a control device of the character described, the combination with a driven band having upper and lower runs passing around a rotatable drum of means for returning the band to central position on the drum when it runs to either side comprising a bearing supporting one end of the drum and mounted to slide perpendicular to the axis of the drum and parallel to the run of the band, a reversible electric motor connected to slide said bearing in either direction, two driving circuits for said motor each having a normally open switch, said driving circuits being arranged to drive the motor in opposite directions upon closing of the respective open switches; two control circuits including a common timing switch, two control switches and two limit switches; the limit switches being normally closed and one in each circuit, said control switches being one in each control circuit and positioned one adjacent each edge of the band so as to be closed by pressure of the band upon its shifting to either side, the normally open switches in the motor circuits being controlled by the respective control circuits so that when either of the control switches is closed the normally open motor circuit switch in the associated motor circuit will be closed and opened at each closing and opening of the timing switch, and means connecting the slidable bearing and the normally closed limit switches whereby the closed switch in the operative motor circuit will be opened when the hearing has been shifted a pre-determined distance to open the limit switch and the control switch in the operative control circuit remains closed.

8. In a control device of the character described, the combination with a driven band having upper and lower runs passing around a rotatable drum of means for returning the band to central position on the drum when it runs to either side comprising a bearing supporting one end of the drum and mounted to slide perpendicular to the axis of the drum and parallel to the run of the band, a reversible electric motor connected to slide said bearing in either direction, two driving circuits for said motor each having a normally open switch, said driving circuits being arranged to drive the motor in opposite directions upon closing of the respective open switches; two control circuits including a common timing switch, two control switches and two limit switches; the limit switches being normally closed and one in each circuit, said control switches being one in each control circuit and positioned one adjacent each edge of the band so as to be closed by pressure of the band upon its shifting to either side, a signal circuit included in each of said control circuits, each signal circuit including said timing switch and one of said control switches, the normally open switches in the motor circuits being controlled by the respective control circuits so that when either of the control switches is closed the normally open motor circuit switch in the associated motor circuit will be closed and opened at each closing and opening of the timing switch, and means connecting the slidable bearing and the normally closed limit switches whereby the closed switch in the operative motor circuit will be opened when the bearing has been shifted a pre-determined distance to open the limit switch and the control switch in the operative control circuit remains closed, so that the associated signal circuit will continue to be closed at each closing of the timing switch.

9. In a control device of the character described, the combination with a driven band having upper and lower runs passing around a rotatable drum of means for returning the band to central position on the drum when it runs to one side comprising a bearing supporting one end of the drum and mounted to slide perpendicular to the drum, a reversible electric motor connected to slide said bearing in either direction, a signal, motor control circuits for driving said motor, signal control circuits for operating said signal, said motor control circuits and signal circuits having a common timing switch opening and closing intermittently and common control switches, each of said control switches being adapted to be closed by shifting of the band to one side on the drum, limit switches in said motor control circuits, means for opening the limit switch in a closed motor circuit when the bearing has been shifted a pre-determined distance and the control switch is still held closed, whereby the motor will be stopped and the signal will continue to operate intermittently.

HARVEY O. MERCIER.

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